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Publication numberUS20050051432 A1
Publication typeApplication
Application numberUS 10/498,042
PCT numberPCT/JP2002/012973
Publication dateMar 10, 2005
Filing dateDec 11, 2002
Priority dateDec 13, 2001
Also published asEP1453991A1, EP1453991A4, WO2003054255A1
Publication number10498042, 498042, PCT/2002/12973, PCT/JP/2/012973, PCT/JP/2/12973, PCT/JP/2002/012973, PCT/JP/2002/12973, PCT/JP2/012973, PCT/JP2/12973, PCT/JP2002/012973, PCT/JP2002/12973, PCT/JP2002012973, PCT/JP200212973, PCT/JP2012973, PCT/JP212973, US 2005/0051432 A1, US 2005/051432 A1, US 20050051432 A1, US 20050051432A1, US 2005051432 A1, US 2005051432A1, US-A1-20050051432, US-A1-2005051432, US2005/0051432A1, US2005/051432A1, US20050051432 A1, US20050051432A1, US2005051432 A1, US2005051432A1
InventorsMitsuhiko Shirakashi, Masayuki Kumekawa, Hozumi Yasuda, Itsuki Kobata
Original AssigneeMitsuhiko Shirakashi, Masayuki Kumekawa, Hozumi Yasuda, Itsuki Kobata
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrolytic processing apparatus and method
US 20050051432 A1
Abstract
There is provided an electrolytic processing apparatus and method that can effect processing of a workpiece with high processing precision and can produce an intended form of processed workpiece with high accuracy of form. The electrolytic processing apparatus includes: a processing electrode which can come close to a workpiece; a feeding electrode for feeding electricity to the workpiece; an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode; a fluid supply section for supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode; and a power source for supplying an electric power between the processing electrode and the feeding electrode while arbitrarily controlling at least one of a voltage and an electric current.
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Claims(21)
1. An electrolytic processing apparatus, comprising:
a processing electrode which can come close to or in contact with a workpiece;
a feeding electrode for feeding electricity to the workpiece;
an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode;
a fluid supply section for supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and
a power source for supplying an electric power between the processing electrode and the feeding electrode while arbitrarily controlling at least one of a voltage and an electric current.
2. The electrolytic processing apparatus according to claim 1, wherein the power source supplies a constant voltage between the processing electrode and the feeding electrode.
3. The electrolytic processing apparatus according to claim 1, wherein the power source supplies an electric power between the processing electrode and the feeding electrode, while changing at last one of the voltage and the electric current with time.
4. The electrolytic processing apparatus according to claim 1, wherein the power source supplies constant voltages or constant electric currents with changing values sequentially between the processing electrode and the feeding electrode.
5. The electrolytic processing apparatus according to claim 1, wherein the power source supplies a constant electric current and a constant voltage sequentially between the processing electrode and the feeding electrode.
6. The electrolytic processing apparatus according to claim 1, wherein the power source first supplies constant electric currents with changing values sequentially, and then supplies constant voltages with changing values sequentially between the processing electrode and the feeding electrode.
7. An electrolytic processing method, comprising:
providing a processing electrode, a feeding electrode and an ion exchanger disposed in at least one of the space between a workpiece and the processing electrode and the space between the workpiece and the feeding electrode;
allowing the processing electrode to be close to or in contact with the workpiece while feeding electricity from the feeding electrode to the workpiece;
supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and
supplying an electric power between the processing electrode and the feeding electrode while arbitrarily controlling at least one of a voltage and an electric current.
8. The electrolytic processing method according to claim 7, wherein a constant voltage is supplied between the processing electrode and the feeding electrode.
9. The electrolytic processing method according to claim 7, wherein the power source applies an electric power between the processing electrode and the feeding electrode, while at least one of the voltage and the electric current changing with time.
10. The electrolytic processing method according to claim 7, wherein the power source applies constant voltages or constant electric currents with changing values sequentially between the processing electrode and the feeding electrode.
11. The electrolytic processing method according to claim 7, wherein the power source applies a constant current and a constant voltage sequentially between the processing electrode and the feeding electrode.
12. An electrolytic processing apparatus, comprising:
a processing electrode which can come close to or in contact with a workpiece;
a feeding electrode for feeding electricity to the workpiece;
an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode;
a fluid supply section for supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and
an electricity amount integrator for measuring the integrated amount of an electricity supplied between the processing electrode and the feeding electrode.
13. An electrolytic processing method, comprising:
providing a processing electrode, a feeding electrode and an ion exchanger disposed in at least one of the space between a workpiece and the processing electrode and the space between the workpiece and the feeding electrode;
allowing the processing electrode to be close to or in contact with the workpiece while feeding electricity from the feeding electrode to the workpiece;
supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and
measuring the integrated amount of an electricity supplied between the processing electrode and the feeding electrode, and detecting the progress of processing of the workpiece and/or the end point of processing based on the measured integrated amount of electricity.
14. An electrolytic processing apparatus, comprising:
a holder for detachably holding a workpiece;
a processing electrode that can come close to or into contact with the workpiece held by the holder;
a feeding electrode for feeding electricity to the workpiece held by the holder;
an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode;
a fluid supply section for supplying a fluid between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present;
a power source for supplying an electric power between the processing electrode and the feeding electrode while controlling at least one of a voltage and an electric current;
a drive section for allowing the workpiece held by the holder and the processing electrode to make a relative movement; and
a numerical controller for effecting a numerical control of the drive section and the power source.
15. The electrolytic processing apparatus according to claim 14, further comprising an electricity amount monitor for monitoring and measuring the amount of electricity during the progress of processing.
16. The electrolytic processing apparatus according to claim 14, wherein the numerical controller controls the power source according to the coordinate difference between coordinate data on a measured form of the workpiece as measured before processing and coordinate data on an intended form of the workpiece after processing.
17. The electrolytic processing apparatus according to claim 14, wherein the numerical controller controls the power source according to the coordinate difference between coordinate data on a measured form of the workpiece as measured during the progress of processing and coordinate data on an intended form of the workpiece after processing.
18. The electrolytic processing apparatus according to claim 15, wherein the numerical controller determines the end point of processing based on a measured value obtained in the electricity amount monitor.
19. An electrolytic processing method, comprising:
providing a processing electrode, a feeding electrode and an ion exchanger disposed in at least one of the space between a workpiece held by a holder and the processing electrode and the space between the workpiece and the feeding electrode;
allowing the processing electrode to be close to or in contact with the workpiece held by the holder while feeding electricity from the feeding electrode to the workpiece;
supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present;
supplying an electric power between the processing electrode and the feeding electrode while numerically controlling at least one of a voltage and an electric current by an numerical controller; and
allowing the workpiece held by the holder and the processing electrode to make a relative movement while numerically controlling the movement by the numerical controller.
20. The electrolytic processing method according to claim 19, comprising:
measuring the form of the workpiece before processing;
inputting coordinate data on the measured form and on an intended form after processing of the workpiece to the numerical controller; and
supplying an electric power between the processing electrode and the feeding electrode while controlling at least one of a voltage and an electric current according to the coordinate difference between the measured form and the intended form.
21. The electrolytic processing method according to claim 19, comprising:
measuring the form of the workpiece during the progress of processing;
inputting coordinate data on the measured form and on an intended form after processing of the workpiece to the numerical controller; and
supplying an electric current between the processing electrode and the feeding electrode while controlling at least one of a voltage and an electric current according to the coordinate difference between the measured form and the intended form.
Description
TECHNICAL FIELD

This invention relates to an electrolytic processing apparatus and method, and more particularly to an electrolytic processing apparatus and method useful for processing a conductive material present in the surface of a substrate, especially a semiconductor wafer, or for removing impurities adhering to the surface of a substrate.

BACKGROUND ART

In recent years, instead of using aluminum or aluminum alloys as a material for forming interconnection circuits on a substrate such as a semiconductor wafer, there is an eminent movement towards using copper (Cu) which has a low electric resistivity and high electromigration resistance. Copper interconnects are generally formed by filling copper into fine recesses formed in the surface of a substrate. There are known various techniques for forming such copper interconnects, including CVD, sputtering, and plating. According to any such technique, a copper film is formed in the substantially entire surface of a substrate, followed by removal of unnecessary copper by chemical mechanical polishing (CMP).

FIGS. 1A through 1C illustrate, in sequence of process steps, an example of forming such a substrate W having copper interconnects. As shown in FIG. 1A, an insulating film 2, such as an oxide film of SiO2 or a film of low-k material, is deposited on a conductive layer la in which semiconductor devices are formed, which is formed on a semiconductor base 1. A contact hole 3 and a trench 4 for interconnects are formed in the insulating film 2 by the lithography/etching technique. Thereafter, a barrier layer 5 of TaN or the like is formed on the entire surface, and a seed layer 7 as an electric supply layer for electroplating is formed on the barrier layer 5.

Then, as shown in FIG. 1B, copper plating is performed onto the surface of the substrate W to fill the contact hole 3 and the trench 4 with copper and, at the same time, deposit a copper film 6 on the insulating film 2. Thereafter, the copper film 6 and the barrier layer 5 on the insulating film 2 are removed by chemical mechanical polishing (CMP) so as to make the surface of the copper film 6 filled in the contact hole 3 and the trench 4 for interconnects and the surface of the insulating film 2 lie substantially on the same plane. An interconnection composed of the copper film 6 as shown in FIG. 1C is thus formed.

Components in various types of equipments have recently become finer and have required higher accuracy. As sub-micro manufacturing technology has commonly been used, the properties of materials are largely influenced by the processing method. Under these circumstances, in such a conventional machining method that a desired portion in a workpiece is physically destroyed and removed from the surface thereof by a tool, a large number of defects may be produced to deteriorate the properties of the workpiece. Therefore, it becomes important to perform processing without deteriorating the properties of the materials.

Some processing methods, such as chemical polishing, electrolytic processing, and electrolytic polishing, have been developed in order to solve this problem. In contrast with the conventional physical processing, these methods perform removal processing or the like through chemical dissolution reaction. Therefore, these methods do not suffer from defects, such as formation of an altered layer and dislocation, due to plastic deformation, so that processing can be performed without deteriorating the properties of the materials.

A processing method, which makes use of a catalytic reaction of the ion exchanger and carries out processing in ultrapure water, has been developed as electrolytic processing. FIG. 2 illustrates the principle of this electrolytic processing. FIG. 2 shows the ionic state when an ion exchanger 12 a mounted on a processing electrode 14 and an ion exchanger 12 b mounted on a feeding electrode 16 are brought into contact with or close to a surface of a workpiece 10, while a voltage is applied via a power source 17 between the processing electrode 14 and the feeding electrode 16, and a liquid 18, e.g. ultrapure water, is supplied from a liquid supply section 19 between the processing electrode 14, the feeding electrode 16 and the workpiece 10. In the case of this electrolytic processing, water molecules 20 in the liquid 18 such as ultrapure water are dissociated efficiently by using the ion exchangers 12 a, 12 b into hydroxide ions 22 and hydrogen ions 24. The hydroxide ions 22 thus produced, for example, are carried, by the electric field between the workpiece 10 and the processing electrode 14 and by the flow of the liquid 18, to the surface of the workpiece 10 opposite to the processing electrode 14 whereby the density of the hydroxide ions 22 in the vicinity of the workpiece 10 is enhanced, and the hydroxide ions 22 are reacted with the atoms 10 a of the workpiece 10. The reaction product 26 produced by this reaction is dissolved in the liquid 18, and removed from the workpiece 10 by the flow of the liquid 18 along the surface of the workpiece 10. Removal processing of the surface of the workpiece 10 is thus effected.

In carrying out electrolytic processing of a workpiece by disposing an ion exchanger between the workpiece and at least one of a processing electrode and a feeding electrode, as described above, it has generally been difficult to control the processing rate and the end point of processing.

When the electrolytic processing is carried out while controlling the electric current supplied between the processing electrode and the feeding electrode at a constant value, the processing rate, in principle, becomes constant so that the processing area of the workpiece does not change, whereby control of the processing rate during the processing is made with ease. Moreover, since in this case the integrated amount of electricity can be calculated with ease, it is easy to determine the processing amount and the end point of processing.

If the processing area changes, however, the processing rate also changes. In this regard, as shown in FIGS. 3A through 3D, when a copper film 6, embedded in interconnect trenches 4 formed in the surface of a substrate W, is polished by electrolytic processing under a constant electric current, a barrier layer 5 composed of an insulator becomes exposed on the surface of the substrate W with the progress of polishing. When the barrier layer 5 becomes exposed on the surface of the substrate W, the processing area decreases dependent on the line/space ratio and the interconnect pattern density, causing a rapid rise in the processing rate.

Further, when removing an electrically conductive film, such as the copper film 6, as a to-be-processed material in the surface of a substrate W, the electric resistance of the conductive film increases with a decrease in the film thickness. Accordingly, when electrolytic processing is carried out under a controlled constant electric current, the voltage applied between the processing electrode and the feeding electrode increases with a degree in the film thickness. The rate of the increase of voltage becomes larger as the processing approaches the end point when the interconnect pattern becomes exposed. FIG. 4 shows a change (increase) with time in the voltage applied in electrolytic processing as carried out under a controlled constant electric current. As shown in FIG. 4, the larger the current density is, the larger is the rate of increase in voltage. The increase in voltage is because the applied voltage is in inverse proportion to the film thickness of copper film. In the case where the voltage rapidly rises, control of the end point of processing is effected with difficulty. In addition, an excessive rise in applied voltage can give rise to dielectric breakdown (so-called discharge) of ultrapure water, causing a physical damage to the workpiece.

On the other hand, when the electrolytic processing is carried out while controlling the voltage applied between the processing electrode and the feeding electrode at a constant value, the processing rate decreases rapidly with a rapid decrease in the processing area. In this regard, as shown in FIGS. 5A through 5D, when a copper film 6, embedded in interconnect trenches 4 formed in the surface of a substrate W, is polished by electrolytic processing under a constant voltage, a barrier layer 5 composed of an insulator becomes exposed on the surface of the substrate W with the progress of polishing. When the barrier layer 5 is exposed on the surface of the substrate W, the processing area decreases and the electric current becomes hard to flow, resulting in a rapid decrease in the processing rate. Further, a conductive film, such as the copper film 6, increases its electric resistance with a decrease in the film thickness, and the electric current value decrease with the increase in electric resistance. The degree of the decrease in current value becomes smaller as the processing approaches the end point. FIG. 6 shows a change with time in the electric current in electrolytic processing as carried out under a controlled constant voltage. A change in the processing rate is therefore small near the end point of processing. Accordingly, as compared to the case of controlling an electric current at a constant value, it is easier to securely terminate the processing at the end point.

As described above, however, when carrying out electrolytic processing by supplying a constant voltage between the processing electrode and the feeding electrode, the electric current changes with time. The processing rate also changes with the change in electric current, making it difficult to control the processing rate during processing.

Further, with the electrolytic processing of an electrically conductive material carried out by using an ion exchanger in the above-described manner, it is not possible to directly apply thereto a numerical control mechanism generally employed in conventional mechanical processing. In this regard, an electrolytic processing method utilizes a chemical interaction between OH ions and the atoms of a workpiece. Accordingly, the processing phenomenon occurs even when a workpiece and a tool (electrode) is not in contact with each other. Electrolytic processing is thus differentiated in the processing principle from mechanical processing in which processing is effected by physical destruction of a workpiece. More specifically, in a common mechanical processing, processing is effected by allowing a workpiece and a tool, which are in contact with each other, to make a relative movement so as to physically destruct the workpiece. The progress of processing may be stopped by releasing the contact between the workpiece and the tool e.g. when an intended processing amount is reached. The processing does not progress any more even when the tool passes over the surface of the workpiece. On the other, according to the electrolytic processing method which utilizes a chemical interaction between the reaction species and a workpiece, as described above, the processing phenomenon occurs when the amount of the reaction species reaches a certain level, even when the tool (electrode) is not in contact with the workpiece. Accordingly, the processing phenomenon inevitably occurs when the tool (electrode) passes over the surface of a portion of the workpiece in which a predetermined amount of processing has been effected.

Accordingly, in order to perform processing of an electrically conductive material with a high processing precision that follows an intended form of a processed workpiece, by the electrolytic processing method utilizing the chemical interaction between the reaction species and the workpiece, such a control system is needed that does not simply control the contact state (position of tool) between the workpiece and the tool as is the case of mechanical processing, but also control the chemical interaction between the reaction species, such as OH ions, and the atoms of the workpiece.

DISCLOSURE OF INVENTION

The present invention has been made in view of the above situation in the background art. It is therefore an object of the present invention to provide an electrolytic processing apparatus and method that can carry out a uniform processing without suffering from a rapid change in the processing rate.

It is also an object of the present invention to provide an electrolytic processing apparatus and method that can effect processing of a workpiece, having in the surface an electrically conductive material as a to-be-processed material, with high processing precision and can produce an intended form of processed workpiece with high accuracy of form.

In order to achieve the above object, the present invention provides an electrolytic processing apparatus, comprising: a processing electrode which can come close to or in contact with a workpiece; a feeding electrode for feeding electricity to the workpiece; an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode; a fluid supply section for supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and a power source for supplying an electric power between the processing electrode and the feeding electrode while arbitrarily controlling at least one of a voltage and an electric current.

In electrolytic processing, the processing rate is high as the electric current supplied between a feeding electrode and a processing electrode is large (the processing rate is low as the electric current is small). Further, when the voltage supplied between the feeding electrode and the processing electrode is raised, the electric current flowing between the feeding electrode and processing electrode becomes larger and, as a result, the processing rate becomes higher. Thus, by arbitrarily controlling, for example by changing with time, at least one of the voltage and electric current supplied between a processing electrode and a feeding electrode, it becomes possible to optimize the processing rate according to the stage (situation) of processing.

In the above electrolytic processing apparatus, the power source may supply a constant voltage between the processing electrode and the feeding electrode, or change at least one of the voltage and the electric current with time.

The power source may supply constant voltages or constant electric currents with changing values sequentially between the processing electrode and the feeding electrode. Thus, for example, electrolytic processing may be carried out by supplying a high electric current or a high voltage between the processing electrode and the feeding electrode until the processing comes near to the end point, e.g. until an interconnect pattern becomes exposed, thereby earning the processing rate, and supplying a low electric current or a low voltage when the processing comes near to the endpoint to thereby drop the processing rate, thereby preventing the so-called over-etching.

The power source may supply a constant electric current and a constant voltage sequentially between the processing electrode and the feeding electrode. For example, electrolytic processing may be carried out under a controlled constant electric current in the stage of processing when there is no change in the processing area of a workpiece, thereby making the processing rate constant and facilitating control of the processing rate. When the processing comes near to the end point when the processing area rapidly decreases, electrolytic processing may be carried out under a constant voltage so as to facilitate control of the processing rate near the end point.

The power source may first supply constant electric currents with changing values sequentially, and then supply constant voltages with changing values sequentially between the processing electrode and the feeding electrode. This makes it possible to first change stepwise the processing rate in electrolytic processing as carried out under sequential constant electric currents and then change stepwise the processing rate in electrolytic processing as carried out under sequential constant voltages.

Further, the power source may continuously change the voltage or the electric current with time. This makes it possible to carry out electrolytic processing at a desired processing rate according to the stage (situation) of processing.

The present invention provides an electrolytic processing method, comprising: providing a processing electrode, a feeding electrode and an ion exchanger disposed in at least one of the space between a workpiece and the processing electrode and the space between the workpiece and the feeding electrode; allowing the processing electrode to be close to or in contact with the workpiece while feeding electricity from the feeding electrode to the workpiece; supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and supplying an electric power between the processing electrode and the feeding electrode while arbitrarily controlling at least one of a voltage and an electric current.

The present invention also provides electrolytic processing apparatus, comprising: a processing electrode which can come close to or in contact with a workpiece; a feeding electrode for feeding electricity to the workpiece; an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode; a fluid supply section for supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and an electricity amount integrator for measuring the integrated amount of an electricity supplied between the processing electrode and the feeding electrode.

The present invention also provides electrolytic processing method, comprising: providing a processing electrode, a feeding electrode and an ion exchanger disposed in at least one of the space between a workpiece and the processing electrode and the space between the workpiece and the feeding electrode; allowing the processing electrode to be close to or in contact with the workpiece while feeding electricity from the feeding electrode to the workpiece; supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; and measuring the integrated amount of an electricity supplied between the processing electrode and the feeding electrode, and detecting the progress of processing of the workpiece and/or the end point of processing based on the measured integrated amount of electricity.

The present invention provides another electrolytic processing apparatus, comprising: a holder for detachably holding a workpiece; a processing electrode that can come close to or into contact with the workpiece held by the holder; a feeding electrode for feeding electricity to the workpiece held by the holder; an ion exchanger disposed in at least one of the space between the workpiece and the processing electrode and the space between the workpiece and the feeding electrode; a fluid supply section for supplying a fluid between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; a power source for supplying an electric power between the processing electrode and the feeding electrode while controlling at least one of a voltage and an electric current; a drive section for allowing the workpiece held by the holder and the processing electrode to make a relative movement; and a numerical controller for effecting a numerical control of the drive section and the power source.

According to this electrolytic processing apparatus, a current value data (or a voltage date), which is determined according to a predetermined processing time as well as a processing amount corresponding to the coordinate difference between the form of a workpiece before processing and an intended form of the workpiece after processing, or the coordinate difference between the form of a workpiece during the progress of processing and an intended form of the workpiece after processing, is inputted to the numerical controller. Based on the input data, the numerical controller numerically controls the electric current (or voltage) supplied from the power source to between the processing electrode and the feeding electrode. The thus controlled electrolytic processing can produce the intended form of processed workpiece with high accuracy of form.

The above control is based on the fact that in electrolytic processing as carried out for a predetermined processing time and by processing a workpiece by a processing electrode disposed opposite to the workpiece, the processing amount depends on the processing rate and therefore on the value of the electric current (or voltage) supplied between the processing electrode and the feeding electrode. In this regard, in such an electrolytic processing, the processing rate is high as the value of the electric current supplied between the processing electrode and the feeding electrode is large. Further, as a higher voltage is applied between the processing electrode and the feeding electrode, a larger current flows between the processing electrode and the feeding electrode, and consequently the processing rate becomes higher. The processing amount is determined by the product of the processing rate and the processing time.

The apparatus may further comprise an electricity amount monitor for monitoring and measuring the amount of electricity during the progress of processing. As described above, in electrolytic processing as carried out under a fixed-processing time condition, the processing amount depends on the value of the electric current (voltage) supplied between a processing electrode and a feeding electrode. Accordingly, the processing amount can be determined by monitoring and measuring the amount of electricity supplied between the processing electrode and the feeding electrode.

The numerical controller may control the power source according to the coordinate difference between coordinate data on a measured form of the workpiece as measured before processing and coordinate data on an intended form of the workpiece after processing. Alternatively, the numerical controller may control the power source according to the coordinate difference between coordinate data on a measured form of the workpiece as measured during the progress of processing and coordinate date on the intended form of the workpiece.

The numerical controller determines the end point of processing e.g. based on a measured value obtained in the electricity amount monitor. By thus determining the end point of processing, utilizing the correlation between the processing amount and the amount of electricity, by monitoring and measuring the amount of electricity supplied during processing, it becomes possible to produce an intended form of processed workpiece with high accuracy-of form.

The present invention provides another electrolytic processing method, comprising: providing a processing electrode, a feeding electrode and an ion exchanger disposed in at least one of the space between a workpiece held by a holder and the processing electrode and the space between the workpiece and the feeding electrode; allowing the processing electrode to be close to or in contact with the workpiece held by the holder while feeding electricity from the feeding electrode to the workpiece; supplying a fluid to the space between the workpiece and at least one of the processing electrode and the feeding electrode, in which the ion exchanger is present; supplying an electric power between the processing electrode and the feeding electrode while numerically controlling at least one of a voltage and an electric current by an numerical controller; and allowing the workpiece held by the holder and the processing electrode to make a relative movement while numerically controlling the movement by the numerical controller.

The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrates preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A through 1C are diagrams illustrating, in sequence of process steps, an example of the formation of copper interconnects;

FIG. 2 is a diagram illustrating the principle of electrolytic processing as carried out by using an ion exchanger;

FIGS. 3A through 3D are diagrams illustrating a change in the processing rate in electrolytic processing as carried out under a controlled constant electric current;

FIG. 4 is a graph showing a change with time in the voltage applied in electrolytic processing as carried out under a controlled constant electric current;

FIGS. 5A through 5D are diagrams illustrating a change in the processing rate in electrolytic processing as carried out under a controlled constant voltage;

FIG. 6 is a graph showing a change with time in the electric current in electrolytic processing as carried out under a controlled constant voltage;

FIG. 7 is a longitudinal sectional front view of an electrolytic processing apparatus according to an embodiment of the present invention;

FIG. 8 is a plan view of the apparatus of FIG. 7;

FIG. 9 is a graph showing an example of voltage and electric current supplied between a processing electrode and a feeding electrode;

FIG. 10 is a graph showing another example of voltage and electric current supplied between a processing electrode and a feeding electrode;

FIG. 11 is a graph showing still another example of voltage and electric current supplied between a processing electrode and a feeding electrode;

FIG. 12 is a graph showing still another example of voltage and electric current supplied between a processing electrode and a feeding electrode;

FIG. 13 is a graph showing still another example of voltage and electric current supplied between a processing electrode and a feeding electrode;

FIG. 14 is a graph showing still another example of voltage and electric current supplied between a processing electrode and a feeding electrode;

FIG. 15 is a graph showing still another example of voltage and electric current supplied between a processing electrode and a feeding electrode;

FIG. 16 is a longitudinal sectional front view of an electrolytic processing apparatus according to another embodiment of the present invention;

FIG. 17 is a plan view of the apparatus of FIG. 16;

FIG. 18 is a longitudinal sectional front view of an electrolytic processing apparatus according to still another embodiment of the present invention;

FIG. 19 is a plan view of the apparatus of FIG. 18;

FIG. 20 is a longitudinal sectional front view of an electrolytic processing apparatus according to still another embodiment of the present invention;

FIG. 21 is a plan view of the apparatus of FIG. 20;

FIG. 22 is a longitudinal sectional front view of an electrolytic processing apparatus according to still another embodiment of the present invention;

FIG. 23 is a diagram illustrating the relationship between the pre-processing form and an intended post-processing form of a workpiece;

FIG. 24 is a block diagram illustrating an example of numerical control by the electrolytic processing apparatus of FIG. 22;

FIG. 25 is a block diagram illustrating another example of numerical control by the electrolytic processing apparatus of FIG. 22; and

FIG. 26 is a longitudinal sectional front view of an electrolytic processing apparatus according to still another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will now be described with reference to the drawings. Though the below-described embodiments refer to application to electrolytic processing apparatuses (electrolytic polishing apparatuses) which use a substrate as a workpiece to be processed and remove (polish) copper formed on the surface of the substrate, the present invention is of course applicable to other workpiece, and to other electrolytic processing.

FIGS. 7 and 8 show an electrolytic processing apparatus 36 according to an embodiment of the present invention. This electrolytic processing apparatus 36 includes a substrate holder 46, supported at the free end of a pivot arm 44 that can pivot horizontally, for attracting and holding the substrate W with its front surface facing downward (so-called “face-down” manner), and, positioned beneath the substrate holder 46, a disc-shaped electrode section 48 made of an insulating material. The electrode section 48 has, embedded therein, fan-shaped processing electrodes. 50 and feeding electrodes 52 that are disposed alternately with their surfaces (upper faces) exposed. A film-like ion exchanger 56 is mounted on the upper surface of the electrode section 48 so as to cover the surfaces of the processing electrodes 50 and the feeding electrodes 52.

This embodiment uses, merely as an example of the electrode section 48 having the processing electrodes 50 and the feeding electrodes 52, such one that has a diameter more than twice than that of the substrate W so that the entire surface of the substrate W may undergo electrolytic processing.

The pivot arm 44, which moves up and down via a ball screw 62 by the actuation of a motor 60 for vertical movement, is connected to the upper end of a pivot shaft 66 that rotates by the actuation of a motor 64 for pivoting. The substrate holder 46 is connected to a motor 68 for rotation that is mounted on the free end of the pivot arm 44, and is allowed to rotate by the actuation of the motor 68 for rotation.

The electrode section 48 is connected directly to a hollow motor 70, and is allowed to rotate by the actuation of the hollow motor 70. A through-hole 48 a as a pure water supply section for supplying pure water, preferably ultrapure water, is formed in the central portion of the electrode section 48. The through-hole 48 a is connected to a pure water supply pipe 72 that vertically extends inside the hollow motor 70. Pure water or ultrapure water is supplied through the through-hole 48 a, and via the ion exchanger 56, is supplied to the entire processing surface of the substrate W. A plurality of through-holes 48 a, each connected to the pure water supply pipe 72, may be provided to facilitate the processing liquid reaching over the entire processing surface of the substrate W.

Further, a pure water nozzle 74 as a pure water supply section for supplying pure water or ultrapure water, extending in the radial direction of the electrode section 48 and having a plurality of supply ports, is disposed above the electrode section 48. Pure water or ultrapure water is thus supplied to the surface of the substrate W from above and beneath the substrate W. Pure water herein refers to a water having an electric conductivity of not more than 10 μS/cm, and ultrapure water refers to a water having an electric conductivity of not more than 0.1 μS/cm. Instead of pure water, a liquid having an electric conductivity of not more than 500 μS/cm or any electrolytic solution may be used. The electric conductivity of the present invention refers herein to that at 25° C., 1 atm. By supplying such a liquid during processing, the instability factors of processing, such as process products and dissolved gases, can be removed, and processing can be effected uniformly with good reproducibility.

According to this embodiment, a plurality of fan-shaped electrode plates 76 are disposed in the electrode section 48 in the circumference direction, and the cathode and anode of a power source 80 are alternately connected, via a slip ring 78, to the electrode plates 76. The electrode plates 76 connected to the cathode of the power source 80 become the processing electrodes 50 and the electrode plates 76 connected to the anode of the power source 80 become the feeding electrodes 52. This applies to processing of e.g. copper, because electrolytic processing of copper proceeds on the cathode side. Depending upon a material to be processed, the cathode side can be a feeding electrode and the anode side can be a processing electrode. More specifically, when the material to be processed is copper, molybdenum, iron or the like, electrolytic processing proceeds on the cathode side, and therefore the electrode plates 76 connected to the cathode of the power source 80 should be the processing electrodes 50 and the electrode plates 76 connected to the anode should be the feeding electrodes 52. In the case of aluminum, silicon or the like, on the other hand, electrolytic processing proceeds on the anode side. Accordingly, the electrode plates connected to the anode of the power source should be the processing electrodes and the electrode plates connected to the cathode should be the feeding electrodes.

By thus disposing the processing electrodes 50 and the feeding electrodes 52 separately and alternately in the circumferential direction of the electrode section 48, fixed feeding portions to supply electricity to a conductive film (portion to be processed) of the substrate is not needed, and processing can be effected to the entire surface of the substrate. Further, be changing the positive and negative in a pulse manner, an electrolysis product can be dissolved and the flatness of the processed surface can be enhanced by the multiplex repetition of processing.

With respect to the processing electrode 50 and the feeding electrode 52, oxidation or dissolution thereof due to an electrolytic reaction is generally a problem. In view of this, it is preferred to use, as a base material of the feeding electrode 52, carbon, a noble metal that is relatively inactive, a conductive oxide or a conductive ceramics, rather than a metal or metal compound widely used for electrodes. A noble metal-based electrode may, for example, be one obtained by plating or coating platinum or iridium onto a titanium electrode, and then sintering the coated electrode at a high temperature to stabilize and strengthen the electrode. Ceramics products are generally obtained by heat-treating inorganic raw materials, and ceramics products having various properties are produced from various raw materials including oxides, carbides and nitrides of metals and nonmetals. Among them there are ceramics having an electric conductivity. When an electrode is oxidized, the value of the electric resistance generally increases to cause an increase of applied voltage. However, by protecting the surface of an electrode with a non-oxidative material such as platinum or with a conductive oxide such as an iridium oxide, the decrease of electric conductivity due to oxidation of the base material of an electrode can be prevented.

The ion exchanger 56 may be a nonwoven fabric which has an anion-exchange group or a cation-exchange group. A cation exchanger preferably carries a strongly acidic cation-exchange group (sulfonic acid group) ; however, a cation exchanger carrying a weakly acidic cation-exchange group (carboxyl group) may also be used. Though an anion exchanger preferably carries a strongly basic anion-exchange group (quaternary ammonium group), an anion exchanger carrying a weakly basic anion-exchange group (tertiary or lower amino group) may also be used.

The nonwoven fabric carrying a strongly basic anion-exchange group can be prepared by, for example, the following method: A polyolefin nonwoven fabric having a fiber diameter of 20-50 μm and a porosity of about 90% is subjected to the so-called radiation graft polymerization, comprising γ-ray irradiation onto the nonwoven fabric and the subsequent graft polymerization, thereby introducing graft chains; and the graft chains thus introduced are then aminated to introduce quaternary ammonium groups thereinto. The capacity of the ion-exchange groups introduced can be determined by the amount of the graft chains introduced. The graft polymerization may be conducted by the use of a monomer such as acrylic acid, styrene, glicidyl methacrylate, sodium styrenesulfonate or chloromethylstyrene. The amount of the graft chains can be controlled by adjusting the monomer concentration, the reaction temperature and the reaction time. Thus, the degree of grafting, i.e. the ratio of the weight of the nonwoven fabric after graft polymerization to the weight of the nonwoven fabric before graft polymerization, can be made 500% at its maximum. Consequently, the capacity of the ion-exchange groups introduced after graft polymerization can be made 5 meq/g at its maximum.

The nonwoven fabric carrying a strongly acidic cation-exchange group can be prepared by the following method: As in the case of the nonwoven fabric carrying a strongly basic anion-exchange group, a polyolefin nonwoven fabric having a fiber diameter of 20-50 μm and a porosity of about 90% is subjected to the so-called radiation graft polymerization comprising γ-ray irradiation onto the nonwoven fabric and the subsequent graft polymerization, thereby introducing graft chains; and the graft chains thus introduced are then treated with a heated sulfuric acid to introduce sulfonic acid groups thereinto. If the graft chains are treated with a heated phosphoric acid, phosphate groups can be introduced. The degree of grafting can reach 500% at its maximum, and the capacity of the ion-exchange groups thus introduced after graft polymerization can reach 5 meq/g at its maximum.

The base material of the ion exchanger 56 may be a polyolefin such as polyethylene or polypropylene, or any other organic polymer. Further, besides the form of a nonwoven fabric, the ion-exchanger may be in the form of a woven fabric, a sheet, a porous material, net or short fibers, etc.

When polyethylene or polypropylene is used as the base material, graft polymerization can be effected by first irradiating radioactive rays (γ-rays or electron beam) onto the base material (pre-irradiation) to thereby generate a radical, and then reacting the radical with a monomer, whereby uniform graft chains with few impurities can be obtained. When an organic polymer other than polyolefin is used as the base material, on the other hand, radical polymerization can be effected by impregnating the base material with a monomer and irradiating radio active rays (γ-rays, electron beam or UV-rays) onto the base material (simultaneous irradiation). Though this method fails to provide uniform graft chains, it is applicable to a wide variety of base materials.

By using as the ion exchanger 56 a nonwoven fabric having an anion-exchange group or a cation-exchange group, it becomes possible that pure water or ultrapure water, or a liquid such as an electrolytic solution can freely move within the nonwoven fabric and easily arrive at the active points in the nonwoven fabric having a catalytic activity for water dissociation, so that many water molecules are dissociated into hydrogen ions and hydroxide ions. Further, by the movement of pure water or ultrapure water, or a liquid such as an electrolytic solution, the hydroxide ions produced by the water dissociation can be efficiently carried to the surface of the processing electrodes 50, whereby a high electric current can be obtained even with a low voltage applied.

When the ion exchanger 56 has only one of anion-exchange group and cation-exchange group, a limitation is imposed on electrolytically processible materials and, in addition, impurities are likely to form due to the polarity. In order to solve this problem, the ion exchanger 56 may have such a structure wherein anion-exchangers having an anion-exchange group and cation-exchangers having a cation-exchange group are concentrically disposed to constitute an integral structure. The anion exchangers and the cation exchangers may be superimposed on the surface, to be processed, of a substrate. It may also be possible to make the anion-exchangers and the cation-exchangers each in the shape of a fan, and dispose them alternately. Alternatively, the ion exchanger 56 may carry both of an anion-exchange group and a cation-exchange group per se. Such an ion exchanger may include an amphoteric ion exchanger in which anion-exchange groups and cation-exchange groups are distributed randomly, a bipolar ion exchanger in which anion-exchange groups and cation-exchange groups are present in layers, and a mosaic ion exchanger in which portions containing anion-exchange groups and portions containing cation-exchange groups are present in parallel in the thickness direction. Incidentally, it is of course possible to selectively use, as the ion exchange 56, one having an anion-exchange group or one having a cation-exchange group according to the material to be processed.

The electrolytic processing apparatus 36 is provided with a controller 100 that controls the power source 80 so as to allow the power source 80 to arbitrarily control at least one of the voltage and the electric current supplied from the power source 80 to between the processing electrodes 50 and the feeding electrodes 52. The electrolytic processing apparatus 36 is also provided with an electricity amount integrator (coulomb meter) 102 which is connected to a wire extending from the cathode of the power source 80 to detect the current value, determines the amount of electricity by the product of the current value and the processing time, and integrates the amount of electricity to thereby determine the total amount of electricity used. An output signal from the electricity amount integrator 102 is inputted to the controller 100, and an output signal from the controller 100 is inputted to the power source 80.

Further, according to this embodiment, wires extending from the cathode and the anode of the power source 80 are connected to the controller 100, and an output signal from the controller 100 is inputted to the motor 60 for vertical movement, whereby the electric current supplied between the processing electrodes 50 and the feeding electrodes 52 can be controlled at a constant value. When controlling the electric current supplied between the processing electrodes 50 and the feeding electrodes 52 at a constant value, the current value of the electric current being supplied between the processing electrodes 50 and the feeding electrodes 52 is measured from the wire extending from the cathode of the power source 80. When the current value is lowered, for example, the motor 60 for vertical movement is driven to lower the substrate holder 46 so as to reduce the distance between the substrate W and the processing electrodes 50 and feeding electrodes 52, thereby controlling the electric current at a constant value.

Further, as shown in FIG. 8, a regeneration section 84 for regenerating the ion exchanger 56 is provided. The regeneration section 84 comprises a pivot arm 86 having a structure substantially similar to the pivot arm 44 that holds the substrate holder 46 and positioned at the opposite side to the pivot arm 44 across the electrode section 48, and a regeneration head 88 held by the pivot arm 86 at the free end thereof. In operation, the reverse electric potential to that for processing is given to the ion exchanger 56 from the power source 80 (see FIG. 7), thereby promoting dissolution of extraneous matter such as copper adhering to the ion exchanger 56. The regeneration of the ion exchanger 56 during processing can thus be effected. The regenerated ion exchanger 56 is rinsed by pure water or ultrapure water supplied to the upper surface of the electrode section 48.

Next, electrolytic processing by the electrolytic processing apparatus 36 will be described.

First, a substrate W, e.g. a substrate W as shown in FIG. 1B which has in its surface a copper film 6 as a conductor film (portion to be processed), is attracted and held by the substrate holder 46 of the electrolytic processing apparatus 36, and the substrate holder 46 is moved by the pivot arm 44 to a processing position right above the electrode section 48. The substrate holder 46 is then lowered by the actuation of the motor 60 for vertical movement, so that the substrate W held by the substrate holder 46 contacts or gets close to the surface of the ion exchanger 56 mounted on the upper surface of the electrode section 48.

Next, a given voltage or electric current, which is changed with time, is applied from the power source 80 between the processing electrodes 50 and the feeding electrodes 52, while the substrate holder 46 and the electrode section 48 are rotated. At the same time, pure water or ultrapure water is supplied, through the through-hole 48 a, from beneath the electrode section 48 to the upper surface thereof, and simultaneously, pure water or ultrapure water is supplied, through the pure water nozzle 74, from above the electrode section 48 to the upper surface thereof, thereby filling pure water or ultrapure water into the space between the processing and feeding electrodes 50, 52 and the substrate W. Thereby, electrolytic processing of the conductor film (copper film 6) formed on the substrate W is effected by hydrogen ions or hydroxide ions produced in the ion exchanger 56. According to the above electrolytic processing apparatus 36, a large amount of hydrogen ions or hydroxide ions can be produced by allowing pure water or ultrapure water to flow within the ion exchanger 56, and the large amount of such ions can be supplied to the surface of the substrate W, whereby the electrolytic processing can be conducted efficiently.

More specifically, by allowing pure water or ultrapure water to flow within the ion exchanger 56, a sufficient amount of water can be supplied to a functional group (sulfonic acid group in the case of an ion exchanger carrying a strongly acidic cation-exchange group) thereby to increase the amount of dissociated water molecules, and the process product (including a gas) formed by the reaction between the conductor film (copper film 6) and hydroxide ions (or OH radicals) can be removed by the flow of water, whereby the processing efficiency can be enhanced. The flow of pure water or ultrapure water is thus necessary, and the flow of water should desirably be constant and uniform. The constancy and uniformity of the flow of water leads to constancy and uniformity in the supply of ions and the removal of the process product, which in turn leads to constancy and uniformity in the processing.

During the electrolytic processing, at least one of the electric current and the voltage supplied from the power source 80 to between the processing electrodes 50 and the feeding electrodes 52 is changed with time. Examples thereof are now described with reference to FIGS. 9 through 15.

FIG. 9 shows an example of supplying constant voltages with stepwise decreasing values between the processing electrodes 50 and the feeding electrodes 52. More specifically, at the initial stage of processing, a high constant voltage V1 is supplied between the processing electrodes 50 and the feeding electrodes 52. When the amount of electricity (the shaded area in FIG. 9 and also in the following figures), determined by the product of the current value and the processing time, reaches a predetermined value (at time t1), a constant voltage V2 lower than the voltage V1 is supplied between the processing electrodes 50 and the feeding electrodes 52. When the integrated amount of electricity reaches a predetermined value (at time t2), a constant voltage V3 lower than the voltage V2 is supplied between the processing electrodes 50 and the feeding electrodes 52. Further, when the integrated amount of electricity reaches a predetermined value (at time t3), a constant voltage V4 lower than the voltage V3 is supplied between the processing electrodes 50 and the feeding electrodes 52. The processing is terminated when the integrated amount of electricity reaches a predetermined value (at time t4), i.e. at the end point of processing.

By thus carrying out electrolytic processing while supplying a high constant voltage at the initial stage of processing and then supplying lower constant voltages with stepwise decreasing values as the processing reaches the end point to between the processing electrodes 50 and the feeding electrodes 52, it becomes possible to earn the processing rate at the initial stage of processing and prevent the so-called over-etching.

Though in this example constant voltages with stepwise decreasing values are supplied between the processing electrodes 50 and the feeding electrodes 52, it is also possible to supply constant electric currents with stepwise decreasing values between the processing electrodes 50 and the feeding electrodes 52.

FIG. 10 shows an example of first supplying constant electric currents with changed values sequentially and then supplying constant voltages with changed values sequentially between the processing electrodes 50 and the feeding electrodes 52, in particular first supplying constant electric currents with stepwise (two steps in FIG. 10) decreasing values and then supplying constant voltages with stepwise (two steps in FIG. 10) decreasing values between the processing electrodes 50 and the feeding electrodes 52. More specifically, at the initial stage of processing, a high constant current I1 is supplied between the processing electrodes 50 and the feeding electrodes 52. When the amount of electricity, determined by the product of the current value and the processing time, reaches a predetermined value (at time t5), a constant current I2 lower than the current I1 is supplied between the processing electrodes 50 and the feeding electrodes 52. When the integrated amount of electricity reaches a predetermined value (at time t6), a constant voltage V5 is supplied between the processing electrodes 50 and the feeding electrodes 52. Further, when the integrated amount of electricity reaches a predetermined value (at time t7), a constant voltage V6 lower than the voltage V5 is supplied between the processing electrodes 50 and the feeding electrodes 52. The processing is terminated when the integrated amount of electricity reaches a predetermined value (at time t8), i.e. at the end point of processing.

Such a control of voltage and electric current makes it possible to first change stepwise the processing rate in electrolytic processing as carried out under controlled constant electric currents and then change stepwise the processing rate in electrolytic processing as carried out under controlled constant voltages. Further, it becomes possible to carry out electrolytic processing under sequential constant electric currents in the stage of processing when there is no change in the processing area of a workpiece, thereby sequentially making the processing rate constant and facilitating control of the processing rate, and then carry out electrolytic processing under sequential constant voltages when the processing comes near to the end point when the processing area rapidly decreases, thereby facilitating control of the processing rate near the end point.

Though in the example of FIG. 10 constant electric currents with changed values are supplied in the plurality of steps and then constant voltages with changed values are supplied also in the plurality of steps, it is possible to first carry out processing by supplying a constant electric current for a certain time without changing the value (constant current processing), and then carry out processing by supplying a constant voltage for a certain time without changing the value (constant voltage processing). It is also possible to repeat the constant current processing/constant voltage processing cycle a plurality of times. Further, it is also possible to first supply a constant electric current without changing the value and then supply constant voltages with stepwise changing values in a plurality of steps, or adversely, first supply constant electric currents with stepwise changing values in a plurality of steps and then supply a constant voltage without changing the value.

FIG. 11 shows an example of first supplying a constant voltage between the processing electrodes 50 and the feeding electrodes 52, and then gradually decreasing the voltage supplied between the processing electrodes 50 and the feeding electrodes 52. More specifically, a high constant voltage V7 is first supplied between the processing electrodes 50 and the feeding electrodes 52. When the amount of electricity, determined by the product of the current value and the processing time, reaches a predetermined value (at time t9), the voltage supplied between the processing electrodes 50 and the feeding electrodes 52 is gradually lowered. The processing is terminated when the integrated amount of electricity reaches a predetermined value.(at time t10), i.e. at the end point of processing.

By thus supplying a constant voltage at the initial stage of processing and then gradually decreasing the voltage with the progress of processing, it becomes possible to earn the processing rate at the initial stage of processing, and then gradually decrease the processing rate as the processing approaches the end point, thereby preventing the so-called over-etching.

FIG. 12 shows an example of first supplying a constant electric current between the processing electrodes 50 and the feeding electrodes 52, and then gradually decreasing the electric current supplied between the processing electrodes 50 and the feeding electrodes 52. More specifically, a high constant current I3 is first supplied between the processing electrodes 50 and the feeding electrodes 52. When the amount of electricity, determined by the product of the current value and the processing time, reaches a predetermined value (at time t11), the electric current supplied between the processing electrodes 50 and the feeding electrodes 52 is gradually lowered. The processing is terminated when the integrated amount of electricity reaches a predetermined value (at time t12), i.e. at the end point of processing.

Also with this manner of controlling electric current, it is possible to earn the processing rate and prevent over-etching as described above.

FIG. 13 shows an example of first supplying a constant electric current between the processing electrodes 50 and the feeding electrodes 52, then gradually decreasing the electric current supplied between the processing electrodes 50 and the feeding electrodes 52, and lastly supplying a constant low voltage between the processing electrodes 50 and the feeding electrodes 52 near the end point of processing. More specifically, a high constant current I4 is first supplied between the processing electrodes 50 and the feeding electrodes 52. When the amount of electricity, determined by the product of the current value and the processing time, reaches a predetermined value (at time t13), the electric current supplied between the processing electrodes 50 and the feeding electrodes 52 is gradually lowered. When the integrated amount of electricity reaches a predetermined amount (at time t14), a constant low voltage V8 is supplied between the processing electrodes 50 and the feeding electrodes 52. The processing is terminated when the integrated amount of electricity reaches a predetermined value (at time t15), i.e. at the end point of processing. This control method can facilitate control of the processing rate near the end point of processing.

FIG. 14 shows an example of gradually and linearly decreasing the voltage or electric current supplied between the processing electrodes 50 and the feeding electrodes 52. More specifically, with respect to electric current I, the electric current is gradually lowered along the line I=I0−at (I0: initial value, a: proportionality constant). With respect to voltage V, the voltage is gradually lowered along the line V=V0−bt (V0: initial value, b: proportionality constant). The processing is terminated when the integrated amount reaches a predetermined value (at time t16), i.e. at the end point of processing. This control method makes it possible to decrease the processing rate gradually over the entire processing process.

FIG. 15 shows an example of continuously changing the voltage or electric current supplied between the processing electrodes 50 and the feeding electrodes 52 along an arbitrary curve. More specifically, with respect to electric current I, the electric current is changed along an arbitrarily set curve: I=f(t). With respect to voltage V, the voltage is changed along an arbitrarily set curve: V=f(t). The processing is terminated when the integrated amount of electricity reaches a predetermined value (at time t17), i.e. at the end point of processing. This control method makes it possible to arbitrarily set the processing rate over the entire processing process.

After completion of the electrolytic processing, the power source 80 is disconnected from the processing electrodes 50 and feeding electrodes 52, the rotations of the substrate holder 46 and of the electrode section 48 are stopped. Thereafter, the substrate holder 46 is raised, and processed substrate W is transferred to next process.

This embodiment shows the case of supplying pure water, preferably ultrapure water, to the space between the electrode section 48 and the substrate W. The use of pure water or ultrapure water containing no electrolyte upon electrolytic processing can prevent extra impurities such as an electrolyte from adhering to and remaining on the surface of the substrate W. Further, copper ions or the like dissolved during electrolytic processing are immediately caught by the ion exchanger 56 through the ion-exchange reaction. This can prevent the dissolved copper ions or the like from re-precipitating on the other portions of the substrate W, or from being oxidized to become fine particles which contaminate the surface of the substrate W.

Ultrapure water has a high resistivity, and therefore an electric current is hard to flow therethrough. A lowering of the electric resistance is made by shortening a distance between the electrode and the workpiece, or interposing the ion exchanger between the electrode and the workpiece. Further, an electrolytic solution, when used in combination with electrolytic solutions, can further lower the electric resistance and reduce the power consumption. When electrolytic processing is conducted by using an electrolytic solution, the portion of a workpiece that undergoes processing ranges over a slightly wider area than the area of the processing electrode. In the case of the combined use of ultrapure water and the ion exchanger, on the other hand, since almost no electric current flows through ultrapure water, electric processing is effected only within the area of a workpiece that is equal to the area of the processing electrode and the ion exchanger.

It is possible to use, instead of pure water or ultrapure water, an electrolytic solution obtained by adding an electrolyte to pure water or ultrapure water. The use of such an electrolytic solution can further lower the electric resistance and reduce the power consumption. A solution of a neutral salt such as NaCl or Na2SO4, a solution of an acid such as HCl or H2SO4, or a solution of an alkali such as ammonia, may be used as the electrolytic solution, and these solutions may be selectively used according to the properties of the workpiece. When the electrolytic solution is used, it is preferred to provide a slight interspace between the substrate W and the ion exchanger 56 so that they are not in contact with each other.

Further, it is also possible to use, instead of pure water or ultrapure water, a liquid obtained by adding a surfactant or the like to pure water or ultrapure water, and having an electric conductivity of not more than 500 μS/cm, preferably not more than 50 μS/cm, more preferably not more than 0.1 μS/cm (resistivity of not less than 10 MΩ·cm). Due to the presence of a surfactant in pure water or ultrapure water, the liquid can form a layer, which functions to inhibit ion migration evenly, at the interface between the substrate W and the ion exchanger 56, thereby moderating concentration of ion exchange (metal dissolution) to enhance the flatness of the processed surface. The surfactant concentration is desirably not more than 100 ppm.

According to the embodiment, the processing rate can be considerably enhanced by interposing the ion exchanger 56 between the substrate W and the processing and feeding electrodes 50, 52. In this regard, electrochemical processing using ultrapure water is effected by a chemical interaction between hydroxide ions in ultrapure water and a material to be processed. However, the amount of the hydroxide ions acting as reactant in ultrapure water is as small as 10−7 mol/L under normal temperature and pressure conditions, so that the removal processing efficiency can decrease due to reactions (such as an oxide film-forming reaction) other than the reaction for removal processing. It is therefore necessary to increase hydroxide ions in order to conduct removal processing efficiently. A method for increasing hydroxide ions is to promote the dissociation reaction of ultrapure water by using a catalytic material, and an ion exchanger can be effectively used as such a catalytic material. More specifically, the activation energy relating to water-molecule dissociation reaction is lowered by the interaction between functional groups in an ion exchanger and water molecules, whereby the dissociation of water is promoted to thereby enhance the processing rate.

Further, according to this embodiment, the ion exchanger 56 is brought into contact with or close to the substrate W upon electrolytic processing. When the ion exchanger 56 is positioned close to the substrate W, though depending on the distance therebetween, the electric resistance is large to some degree and, therefore, a somewhat large voltage is necessary to provide a requisite electric current density. However, on the other hand, because of the non-contact relation, it is easy to form flow of pure water or ultrapure water along the surface of the substrate W, whereby the reaction product produced on the substrate surface can be efficiently removed. In the case where the ion exchanger 56 is brought into contact with the substrate W, the electric resistance becomes very small and therefore only a small voltage needs to be applied, whereby the power consumption can be reduced.

If a voltage is raised to increase the current density in order to enhance the processing rate, an electric discharge can occur when the electric resistance between the electrode and the substrate (workpiece to be processed) is large. The occurrence of electric discharge causes pitching on the surface of the workpiece, thus failing to form an even and flat processed surface. To the contrary, since the electric resistance is very small when the ion exchanger 56 is in contact with the substrate W, the occurrence of an electric discharge can be avoided.

When electrolytic processing of copper is conducted by using, as the ion exchanger 56, an ion exchanger having a cation-exchange group, the ion-exchange group of the ion exchanger (cation exchanger) 56 is saturated with copper after the processing, whereby the processing efficiency of the next processing is lowered. When electrolytic processing of copper is conducted by using, as the ion exchanger 56, an ion exchanger having an anion-exchange group, fine particles of a copper oxide can be produced and adhere to the surface of the ion exchanger (anion exchanger) 56, which particles can contaminate the surface of a next substrate to be processed.

In operation, in order to obviate such drawbacks, the reverse electric potential to that for processing is given to the ion exchanger 56 from the power source 80, thereby promoting dissolution of extraneous matter such as copper adhering to the ion exchanger 56 via regeneration head 88. The regeneration of the ion exchanger 56 during processing can thus be effected. The regenerated ion exchanger 56 is rinsed by pure water or ultrapure water supplied to the upper surface of the electrode section 48.

FIGS. 16 and 17 show an electrolytic processing apparatus 36 b according to another embodiment of the present invention. In this electrolytic processing apparatus 36 b, the rotational center O1 of the electrode section 48 is distant from the rotational center O2 of the substrate holder 46 by a distance d; and the electrode section 48 rotates about the rotational center O1 and the substrate holder 46 rotates about the rotational center O2. Further, the processing electrodes 50 and the feeding electrodes 52 are connected to the power source 80 via the slip ring 78. Further according to this embodiment, the electrode section 48 is designed to have a diameter which is larger than the diameter of the substrate holder 46 to such a degree that when the electrode section 48 rotates about the rotational center O1 and the substrate holder rotates about the rotational center O2, the electrode section 48 covers the entire surface of the substrate W held by the substrate holder 46.

According to the electrolytic processing apparatus 36 b, electrolytic processing of the surface of the substrate W is carried out by rotating the substrate W via the substrate holder 46 and, at the same, rotating the electrode section 48 by the actuation of the hollow motor 70, while supplying pure water or ultrapure water to the upper surface of the electrode section 48 and applying a given voltage between the processing electrodes 50 and the feeding electrodes 52.

The electrode section 48 or substrate holder 46 may be made orbit movement such as scroll movement or reciprocation instead of rotation.

FIGS. 18 and 19 show an electrolytic processing apparatus 36 d according to still another embodiment of the present invention. In this electrolytic processing apparatus 36 d, the positional relationship between the substrate holder 46 and the electrode section 48 in the preceding embodiments is reversed, and the substrate W is held with its front surface facing upward (so-called “face-up” manner) so that electrolytic processing is conducted to the upper surface of the substrate. Thus, the substrate holder 46 is disposed beneath the electrode section 48, holds the substrate W with its front surface facing upward, and rotates about its own axis by the actuation of the motor 68 for rotation. On the other hand, the electrode section 48, which has the processing electrodes 50 and the feeding electrodes 52 that are covered with the ion exchanger 56 is disposed above the substrate holder 46, is held with its front surface downward by the pivot arm 44 at the free end thereof, and rotates about its own axis by the actuation of the hollow motor 70. Further, wires extending from the power source 80 pass through a hollow portion formed in the pivot shaft 66 and reach the slip ring 78, and further pass through the hollow portion of the hollow motor 70 and reach the processing electrodes 50 and the feeding electrodes 52 to apply a voltage therebetween.

Pure water or ultrapure water is supplied from the pure water supply pipe 72, via the through-hole 48 a formed in the central portion of the electrode section 48, to the front surface (upper surface) of the substrate W.

A regeneration section 92 for regenerating the ion exchanger 56 mounted on the electrode section 48 is disposed beside the substrate holder 46. The regeneration section 92 includes a regeneration tank 94 filled with e.g. a dilute acid solution. In operation, the electrode section 48 is moved by the pivot arm 44 to a position right above the regeneration tank 94, and is then lowered so that at least the ion exchanger 56 of the electrode section 48 is immersed in the acid solution in the regeneration tank 94. Thereafter, the reverse electric potential to that for processing is given to the electrode plates 76, i.e. by connecting the processing electrodes 50 to the anode of the power source 80 and connecting the feeding electrodes 52 to the cathode of the power source 80, thereby promoting dissolution of extraneous matter such as copper adhering to the ion exchanger 56 to thereby regenerate the ion exchanger 56. The regenerated ion exchanger 56 is rinsed by e.g. ultrapure water.

Further according to this embodiment, the electrode section 48 is designed to have a sufficiently larger diameter than that of the substrate W held by the substrate holder 46. Electrolytic processing of the surface of the substrate W is conducted by lowering the electrode section 48 so that the ion exchanger 56 contacts or gets close to the substrate W held by the substrate holder 46, then rotating the substrate holder 46 and the electrode section 48 and, at the same time, pivoting the pivot arm 44 to move the electrode section 48 along the upper surface of the substrate W, while supplying pure water or ultrapure water to the upper surface of the substrate and applying a given voltage between the processing electrodes 50 and the feeding electrodes 52.

FIGS. 20 and 21 show an electrolytic processing apparatus 36e according to still another embodiment of the present invention. This electrolytic processing apparatus 36 e employs, as the electrode section 48, such one that has a sufficiently smaller diameter than that of the substrate W held by the substrate holder 46 so that the surface of the substrate may not be entirely covered with the electrode section 48. In this embodiment, the ion exchanger 56 is of a three-layer structure (lamination) consisting of a pair of strongly acidic cation-exchange fibers 56 a, 56 b and a strongly acidic cation-exchange membrane 56 c interposed between the fibers 56 a, 56 b. The ion exchanger (laminate) 56 has a good water permeability and a high hardness and, in addition, the exposed surface (lower surface) to be opposed to the substrate W has a good smoothness. Other construction is the same as shown in FIGS. 18 and 19. The construction of the ion exchanger 56 may be arranged such that the ion-exchange membrane is used for the exposed surface and the laminate of the ion-exchange fibers is arranged above the exposed ion-exchange membrane.

By making the ion exchanger 56 a multi-layer structure consisting of laminated layers of ion-exchange materials, such as a nonwoven fabric, a woven fabric and a porous membrane, it is possible to increase the total ion exchange capacity of the ion exchanger 56, whereby formation of an oxide, for example, in removal (polishing) processing of copper, can be restrained to thereby avoid the oxide adversely affecting the processing rate. In this regard, when the total ion exchange capacity of an ion exchanger 56 is smaller than the amount of copper ions taken in the ion exchanger 56 during removal processing, the oxide should inevitably be formed on the surface or in the inside of the ion exchanger 56, which adversely affects the processing rate. Thus, the formation of the oxide is governed by the ion exchange capacity of an ion exchanger, and copper ions exceeding the capacity should become the oxide. The formation of an oxide can thus be effectively restrained by using, as the ion exchanger 56, a multi-layer ion exchanger composed of laminated layers of ion-exchange materials which has enhanced total ion exchange capacity.

According to the embodiments described hereinabove, uniform processing of e.g. an electrically conductive material can be carried out without suffering from a rapid change in the processing rate even when an insulating material for forming interconnects becomes exposed on the processing surface.

FIG. 22 is a longitudinal sectional front view of an electrolytic processing apparatus according to still another embodiment of the present invention. This electrolytic processing apparatus includes a substrate holder 130 for attracting and holding the substrate W with its front surface facing upward (so-called “face-up” manner), and an electrode head 138 having a disc-shaped electrode section 136 made of an insulating material. The electrode section 136 has, embedded therein, fan-shaped processing electrodes 132 and feeding electrodes 134 that are disposed alternately with their surfaces (lower faces) exposed. The electrode head 138 is positioned above the substrate holder 130. An ion exchanger 140 consisting of laminated layers (lamination) is mounted on the lower surface of the electrode section 136 so as to cover the surfaces of the processing electrodes 132 and the feeding electrodes 134.

The substrate holder 130 is connected directly to the upper end of a motor shaft 144 of the motor 142 as a first drive section for making the relative movement between the substrate W held by the substrate holder 130 and the processing electrodes 132, and is allowed to rotate with the substrate W by the actuation of the motor (first drive section) 142 in such a state that the substrate holder 130 holds the substrate W.

The electrode head 138 is connected downwardly to the free end of a pivot arm 146 which can pivot horizontally. The base portion of the pivot arm 146 is connected to the upper end of a hollow pivot shaft 152 which moves vertically via a ball screw 150 by the actuation of a motor 148 for vertical movement. A motor 154, as a second drive section for making the relative movement between the substrate W held by the substrate holder 130 and the processing electrodes 132, is positioned beside the pivot arm 152, and allows to move vertically with the pivot arm 152. A timing belt 156 is engaged between the pivot arm 152 and the motor (second drive section) 154 so that the pivot arm 152 and the pivot arm 146 pivots (rotates) integrally by the actuation of the motor (second drive section) 154.

The electrode head 138 is connected directly to a hollow motor 160 as a third drive section for making the relative movement between the substrate W held by the substrate holder 130 and the processing electrodes 132 so as to rotate by the actuation of the hollow motor (third drive section) 160.

In this embodiment, the ion exchanger 140 is of a three-layer structure (lamination) consisting of a pair of strongly acidic cation-exchange fibers 162 a, 162 b and a strongly acidic cation-exchange membrane 162 c interposed between the fibers 162 a, 162 b. The ion exchanger (laminate) 140 has a good water permeability and a high hardness and, in addition, the exposed surface (upper surface) to be opposed to the substrate W has a good smoothness.

Each of the laminated layers 162 a, 162 b and 162 c of the ion exchanger 140 preferably carries a strongly acidic cation-exchange group (sulfonic acid group), however, an ion exchanger carrying a weakly acidic cation-exchange group (carboxyl group), an ion exchanger carrying a strongly basic anion-exchange group (quaternary ammonium group), or an ion exchanger carrying a weakly basic anion-exchange group (tertiary or lower amino group) may be used.

By using each of the laminated layers 162 a, 162 b and 162 c of the ion exchanger 140 made of a nonwoven fabric, which liquid can flows therethough, having an anion-exchange group or a cation-exchange group, it becomes possible that the ion-exchange reaction between ions in the liquid and the ion-exchange group of the ion exchanger can be easily taken place.

The ion exchanger 140 should preferably have “water permeability and water-absorbing properties”. Further, it is desirable that at least the material to be opposed to the workpiece have a high hardness and good surface smoothness. For example, a commercially-available foamed polyurethane “IC 1000” (manufactured by Rodel, Inc.), generally employed as a pad for CMP, is hard and excellent in wear resistance. By providing a number of through-holes, this product can be used as a material for the ion exchanger 140. It is possible to provide holes in a resin plate, thereby making the plate water-permeable for use in the ion exchanger 140. It is of course desirable that the resin have “water-absorbing properties”.

A pure water nozzle 170 as a pure water supply section for supplying liquid, such as pure water or ultrapure water, to between the substrate W held by the substrate-holder 130 and electrode head 138 positioned below, is disposed above the electrode holder 130. Pure water or ultrapure water is thus supplied to the ion exchanger 140.

The electrolytic processing apparatus is provided with a numerical controller 172 for effecting numerical control of the drive sections, i.e. the motor (first drive section) 142, the motor (second drive section) 154 and the motor (third drive section) 160, which allow the substrate W held by the substrate holder 130 and the processing electrodes 132, facing each other, to make a relative movement. The motors (drive sections) 142, 154 and 160 are thus numerically controllable servomotors, and their rotation angles and rotational speeds are numerically controlled by an output signal from the numerical controller 172. According to this embodiment, the motor 148 for vertical movement also is a servomotor, and is numerically controlled by an output signal from the numeral controller 172.

The electrolytic processing apparatus is also provided with an electricity amount monitor 174 which is connected to a wire extending from a power source 168 to monitor and measure the amount of electricity during the progress of processing. According to this embodiment, the electricity monitor 174 comprises an electricity amount integrator (coulomb meter) which determines the amount of electricity by the product of the current value of the electric current, supplied from the power source 168, and the processing time, and integrates the amount of electricity to thereby determine the total amount of electricity used. An output signal from the electricity monitor 174 is inputted to the numerical controller 172.

According to this embodiment, during electrolytic processing carried out for a predetermined time, the numeral controller 172 numerically controls: the rotational speed of the substrate W, held by the substrate holder 130, via the motor (first drive section) 142; the speed of the horizontal movement of the electrode head 138, by pivoting of the pivot arm 146, via the motor (second drive section) 154; the rotational speed of the electrode head 138 via the motor (third drive section) 160; and the relative movement speed between the substrate W and the electrode head 138. Further, in the electrolytic processing, an electric power is supplied between the processing electrodes 132 and the feeding electrodes 134 while controlling at least one of the electric current and the voltage.

An example of the numerical control will now be described with reference to FIGS. 23 and 24. First, as shown in FIG. 23, the form of a workpiece before processing is measured. Specifically, various coordinate points of the pre-processing form are measured in a X-Y-Z coordinate system (in which the Z axis is orthogonal to the X-Y plane as a datum plane). The measured pre-processing form data is inputted to the numerical controller 172. Further, with respect to a coordinate point (x, y, Z1) of the pre-processing form, the corresponding coordinate point (x, y, Z2) of an intended post-processing form is also inputted as intended form data to the numerical controller 172. In addition, unit processing form data e.g. on voltage dependence of processing rate, i.e. the relationship between processing rate and voltage applied between the processing electrodes 132 and the feeding electrodes 134, and data on the relative speed between the processing electrodes 132 and the workpiece W are inputted to the numerical controller 172 in advance or at an arbitrary time.

When electrolytic processing is carried out for a controlled fixed processing time under control of the relative movement speed between the processing electrodes 132 and the workpiece W, the processing amount depends on the processing rate, and therefore on the voltage (or current value) applied between the processing electrodes 132 and the feeding electrodes 134. Accordingly, in the case of fixing the processing time, i.e. a period of time during which the workpiece W and the processing electrodes 132 are in face-to-face positions and the electrolytic processing phenomenon occurs (residence time), numerical control only of the voltage (or current value) applied between the processing electrodes 132 and the feeding electrodes 134 can produce an intended form of processed workpiece with high accuracy of form.

Thus, according to this embodiment, a processing amount Z1-Z2 in the Z direction is determined at each coordinate point based on the data inputted in the numerical controller 172. Based on the processing amount Z1-Z2 the voltage (or current value) to be applied between the processing electrodes 132 and the feeding electrodes 134 is determined for each coordinate point, and the signal is inputted to the power source 168 so as to numerically control the voltage (or current value) applied from the power source 168 to between the processing electrodes 132 and the feeding electrodes 134.

Next, electrolytic processing by this electrolytic processing apparatus will be described.

First, a substrate W. e.g. a substrate W as shown in FIG. 1B which has in its surface a copper film 6 as a conductor film (portion to be processed), is attracted and held by the substrate holder 130, and the electrode head 138 is moved by the pivot arm 146 to a processing position right above the substrate W held by the substrate holder 130. The electrode head 138 is then lowered by the actuation of the motor 148 for vertical movement; so that the ion exchanger 140 mounted on the lower surface of the electrode section 136 of the electrode head 138 contacts or gets close to the upper surface of the substrate W held by the substrate holder 130.

Next, an electric power is applied from the power source 168 to between the processing electrodes 132 and the feeding electrodes 134, while at least one of the voltage and the current value being controlled, and the substrate holder 130 and the electrode head 130 are rotated. Further, the pivot arm 146 is pivoted to move the electrode head 138 horizontally. At the same time, pure water or ultrapure water is supplied, from above the electrode substrate holder 130 to between the substrate W and the electrode head 138, thereby filling pure water or ultrapure water into the space between the processing and feeding electrodes 132, 134 and the substrate W. Thereby, electrolytic processing of the conductor film (copper film 6) formed on the substrate W is effected by hydrogen ions or hydroxide ions produced in the ion exchanger 140.

More specifically, pure water or ultrapure water is dissociated into OH ions and H+ ions with the aid of a catalytic reaction in the ion exchanger 140. The OH ions transfer the electric charges in the vicinity of the copper film 6 and become OH radicals. The OH radicals are reacted with the copper film 6 of the substrate W to thereby effect removal (polishing) processing of the film. In order to shut off H2 gas generated at the feeding electrodes 134, a gas-impermeable ion membrane may be used as the strongly acidic cation-exchange membrane 162 c. The H2 gas is thus shut off, and is discharged out by the flow of pure water or ultrapure water produced by the rotation of the electrode section 136.

In advance of or during processing, the pre-processing form data or in-processing form data during processing, the unit processing form data, and the data of the relative movement of the processing electrodes and the workpiece are inputted to the numerical controller 172. Electrolytic processing is carried out for a predetermined time while numerically controlling: the rotational speed of the substrate W, held by the substrate holder 130, via the motor (first drive section) 142; the speed of the horizontal movement of the electrode head 138, by pivoting of the pivot arm 146, via the motor (second drive section) 154, the rotational speed of the electrode head 138 via the motor (third drive section) 160; and the relative movement speed between the workpiece W and the electrode head 138. In the electrolytic processing, an electric power is supplied between the processing electrodes 132 and the feeding electrodes 134 while controlling at least one of the electric current and the voltage. The electrolytic processing can produce an intended form of processed workpiece with high accuracy of form.

During the electrolytic processing, the amount of electricity supplied from the power source 168 to between the processing electrodes 132 and the feeding electrodes 134 is monitored and measured by the electricity amount monitor 174. Thus, the amount of electricity is determined by the product of the current value of the electric current supplied from the power source 168 and the processing time. The amount of electricity is integrated to determine the total amount of electricity used. In electrolytic processing as carried out for a fixed processing time, the processing amount depends on the value of the electric current (or voltage) supplied between the processing electrodes 132 and the feeding electrodes 134. Accordingly, the processing amount can be determined by monitoring and measuring the amount of electricity. The processing is terminated when the integrated amount of electricity reaches a predetermined value, i.e. at the end point of processing. By thus determining the end point of processing, utilizing the correlation between the processing amount and the amount of electricity, by monitoring and measuring the amount of electricity supplied during the processing, it becomes possible to produce an intended form of processed workpiece with high accuracy of form.

After completion of the electrolytic processing, the power source 168 is disconnected, the rotation of the substrate holder 130 and the electrode head 138 are stopped, and pivoting of the pivot arm 146 is stopped. Thereafter, the electrode head 138 is raised, and processed substrate W held by the substrate holder 130 is transferred to next process.

According to this embodiment, a relative step operation can be carried out optionally. Thus, the motor 142 for rotating the substrate holder 130 for holding the substrate (workpiece) W is mounted on the upper surface of a X-Y table (first drive section) 178 having an X stage 176 a that moves in the X direction by the actuation of a motor 175 a, and a Y stage 176 b that moves in the Y direction by the actuation of a motor 175 b. The motors 175 a, 175 b are numerically controllable servomotors, and their rotation angles and rotational speeds are numerically controlled by an output signal from the numerical controller 172.

An example of the numerical control for carrying out the step operation will now be described with reference to FIG. 25 First, as illustrated in FIG. 23, the form of the workpiece W before processing is measured by measuring various coordinate points of the pre-processing form in a X-Y-Z coordinate system (in which the Z axis is orthogonal to the X-Y plane as a datum plane). The measured pre-processing form data is inputted to the numerical controller 172. Further, with respect to a coordinate point (x, y, Z1) of the pre-processing form, the corresponding coordinate point (x. y, Z2) of an intended post-processing form is also inputted to the numerical controller 172. In addition, unit processing form data, e.g. on voltage dependence of processing rate, and data on a period of time during which the workpiece faces the processing electrodes are inputted to the numerical controller 172 in advance or at an arbitrary time.

According to this embodiment, a processing amount Z1-Z2 in the Z direction is determined at each coordinate point based on the data inputted in the numerical controller 172. Based on the processing amount Z1-Z2, the voltage (or current value) to be applied between the processing electrodes 132 and the feeding electrodes 134 is determined for each coordinate point, and the signal is inputted to the power source 168 so as to numerically control the voltage (or current value) applied from the power source 168 to between the processing electrodes 132 and the feeding electrodes 134 while supplying an electric power therebetween.

According to this embodiment, e.g. a substrate W as shown in FIG. 1B, having copper film 6 as a conductive film (to-be-processed portion) in the surface, is attracted and held by the substrate holder 130. The ion exchanger 140 mounted on the processing electrodes 132 is brought close to or into contact with the surface of the substrate W. Electrolytic processing is then carried out by supplying an electric power between the processing electrodes 132 and the feeding electrodes 134 while controlling the voltage (or electric current) by the numerical controller 172 and rotating the electrode head 138.

During the electrolytic processing, a step operation, which makes a repetition of movement and stop of the substrate W in the X or Y direction, is carried out. For this operation, as described above, the pre-processing form data, the intended form data, the unit processing form data and the workpiece-electrodes face-to-face time data are inputted to the numerical controller 172 in advance, thereby numerically controlling: the rotation of the electrode head 138 via the motor 160; the movement of the X-Y table (fourth drive section) 178 via the motors 175 a, 175 b; and the voltage (or electric current) applied between the processing electrodes 132 and the feeding electrodes 134 via the power source 168. Thus, the processing time, i.e. the time during which the electrode head 138 faces a given portion of the substrate to carry out electrolytic processing of the portion, is controlled by respectively controlling the motor 160 and the motors 175 a, 175 b of the X-Y table 178, thereby carrying out the electrolytic processing for a predetermined time. During the electrolytic processing, the voltage (or electric current) applied between the processing electrodes 132 and the feeding electrodes 134 is numerically controlled. Such an electric processing can produce the intended form of processed substrate with high accuracy of form.

The “relative step operation” herein refers to a operation which allows either one or both of the X-Y table and the processing electrodes 132 to move or make a relative movement so that the processing electrodes 132 makes a repetition of a certain-distance movement and stop over the substrate W.

FIG. 26 shows an -electrolytic processing apparatus according to still another embodiment of the present invention. The electrolytic processing apparatus has a ring-shaped contact holding plate 180 at the periphery of the upper surface of the substrate holder 130. A plurality of inwardly-protruding contacts 182 as feeding electrodes are mounted at a given pitch to the contact holding plate 180. Further, the electrode head 138 is provided with a processing electrode. 184 instead of the electrode section 136 used in the embodiment of FIG. 22. The processing electrode 184 is connected to the cathode of the power source 168 via a slip ring 186, and the contacts (feeding electrodes) 182 are connected to the anode of the power source 168. The other construction is the same as the apparatus shown in FIG. 22.

According to this embodiment, when a substrate W is held by the substrate holder 130, the contacts (feeding electrodes) 182 contact the copper layer 6 as a to-be-processed material, deposited on the surface of the substrate W as shown in FIG. 1B. Electrolytic processing can be carried in the same manner as in the preceding embodiment. Thus, the electrode head 138 is lowered, and an electric power is applied from the power source 168 to between the processing electrode 184 and the contacts (feeding electrodes) 182 while numerically controlling at least one of the voltage or the electric current. At the same time, the substrate holder 130 and the electrode head 138 are rotated, while the pivot arm 146 is pivoted to move the electrode head 138 horizontally, or the electrode head 138 is rotated, while the substrate W held by the substrate holder 130 is allowed to make a repetition of a movement and stop, i.e. a step movement, via the X-Y table 178. At the same time, pure water or ultrapure water is supplied from the pure water nozzle 170 to between the substrate W and the processing electrode 184. Electrolytic processing of the conductive film (copper film 6) of the substrate W is thus effected.

In advance of the electrolytic processing, as with the processing embodiment, the pre-processing form data, the intended form data, the unit processing form data, etc. are inputted to the numerical controller 172 so as to control the processing time, i.e. a period of time during which the substrate Wand the processing electrode 184 are in face-to-face positions, so that the electrolytic processing phenomenon occurs (residence time), at a predetermined time and, at the same, numerically control the voltage (or electric current) applied between the processing electrode 184 and the contacts (feeding electrodes) 182. The electrolytic processing carried out under such a control can produce an intended form of processed substrate W with high accuracy of form.

The control of the voltage applied between the processing electrode 184 and the contacts (feeding electrodes) 182 makes use of the fact that as the voltage is increased, the electric current flowing between the processing electrode and the feeding electrode becomes larger and the processing rate becomes higher in proportion thereto, and vice versa.

The measurement of the form of a workpiece may be carried out not only before processing but also at any time during processing any number of times. In this connection, there is a case where the actual processing time becomes different from a predetermined processing time. The difference can lead to a lowered accuracy of form of the resulting processed workpiece. Such a lowering of accuracy may be eliminated or reduced by effecting in-processing measurement of the workpiece as many times as possible. Thus, an increased number of in-processing measurements can generally enhance the processing precision.

According to the embodiments described hereinabove, an electric current value data (or a voltage data), which is determined according to a predetermined processing time as well as a processing amount corresponding to the coordinate difference between the form of a workpiece before processing and an intended form the workpiece after processing or the coordinate difference between the form of a workpiece during the progress of processing and an intended form of the workpiece after processing, is inputted to the numerical controller Based on the inputted data, the numerical controller numerically controls the electric current (or voltage) supplied from a power source to between a processing electrode and a feeding electrode. The thus controlled electrolytic processing can produce an intended form of processed workpiece with high accuracy of form.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

The present application is based on the International Application PCT/JP02/01545, filed Feb. 21, 2002, the entire disclosure of which is hereby incorporated by reference.

Industrial Applicability

This invention relates to an electrolytic processing apparatus and method useful for processing a conductive material present in the surface of a substrate, especially a semiconductor wafer, or for removing impurities adhering to the surface of a substrate.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7476303Aug 10, 2004Jan 13, 2009Ebara CorporationElectrolytic processing apparatus and electrolytic processing method
WO2007035408A1 *Sep 15, 2006Mar 29, 2007Applied Materials IncMethod for stabilized polishing process
Classifications
U.S. Classification205/81
International ClassificationB23H3/02, C25F7/00, C25F3/00, H01L21/321, B23H5/08
Cooperative ClassificationH01L21/32125, C25F3/00, C25F7/00, B23H3/02, B23H5/08
European ClassificationB23H3/02, C25F7/00, B23H5/08, C25F3/00
Legal Events
DateCodeEventDescription
Oct 14, 2004ASAssignment
Owner name: EBARA CORPORATION, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SHIRAKASHI, MITSUHIKO;KUMEKAWA, MASAYUKI;YASUDA, HOZUMI;AND OTHERS;REEL/FRAME:015883/0277
Effective date: 20040701