US 3852181 A
Apparatus for coating substrate members by sputtering comprises a sputtering chamber having two circular cylindrical tubes of insulating material connected together in axial alignment by a metal ring carrying sputtering electrodes and connections for the sputtering voltage, a source of sputtering gas, and a source of coolant. Vacuum-tight ports are provided at both ends of the sputtering chamber, with means for heating, in a vacuum, the substrates to be coated prior to their admission into the sputtering chamber, and means for cooling such substrates, in a vacuum, prior to their removal into the atmosphere. The substrates are transported through the sputtering chamber by means of a conveyor device. The apparatus provides for the rapid manufacture of thin-layer electrical circuits formed by sputtering metallic material on the insulating substrates.
Description (OCR text may contain errors)
Unite States Cirltler et a1.
tet 11 1 Dec. 3, 1974 1 CONTINUOUS CATHODE SPUTTERING SYSTEM  Assignee: Siemens Aktiengesellschaft,
Berlin-Munich, Germany 22 Filed: Oct.30, 1973 21 Appl. No.: 411,088
 Foreign Application Priority Data Continuous Parallel-Plate RF Sputtering System, by
Byrne et al., IBM Technical Disclosure Bulletin, vol.
13, No. 4, September 1970, pp. 1034-1036.
Practical Design Aspects of a Continuous Vacuum RF Sputtering Machine, by Williams et al., The Journal of Vacuum Science and Technology, Aug. 13, 1969, pages 278-281.
Primary Examiner-John H. Mack Assistant Examiner-Wayne A. Langel Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson 5 7] ABSTRACT Apparatus for coating substrate members by sputtering comprises a sputtering chamber having two circular cylindrical tubes of insulating material connected together in axial alignment by a metal ring carrying sputtering electrodes and connections for the sputtering voltage, a source of sputtering gas, and a source of coolant. Vacuum-tight ports are provided at both ends of the sputtering chamber, with means for heating, in a vacuum, the substrates to be coated prior to their admission into the sputtering chamber, and means for cooling such substrates, in a vacuum, prior to their removal into the atmosphere. The substrates are transported through the sputtering chamber by means of a conveyor device. The apparatus provides for the rapid manufacture of thin-layer electrical circuits formed by sputtering metallic material on the insulating substrates. I
15 Claims, 3 Drawing Figures l CONTINUOUS CATI-IODE SPUTTERING SYSTEM BACKGROUND 1. Field of the Invention The present invention relates to a sputtering coating apparatus and, more particularly, to such an apparatus with means for providing a continuous flow of substrate members, so that the apparatus operates in a continuous manner.
2. The Prior Art It is known that thin metallic layers can be produced by means of cathode sputtering within a controlled gas environment, and it is known that the sputtering process is enhanced by an auxiliary discharge which tends to form ions within the controlled gas environment. The auxiliary discharge is sustained by means of a coil placed around the periphery of the container, adjacent the anode, so that a so-called ring discharge is produced through the high-frequency electromagnetic field created by operation of the coil. With the controlled gas environment partially ionized, the discharge supplies the ions which are necessary for the sputtering, and the ions are accelerated toward the cathode within the container. Such apparatus is illustrated and described in German Pat. No. 1,122,801.
Devices are also known in which the sputtering takes place with a ring discharge in a chamber which is permeated with a high-frequency electromagnetic field with the electrodes enveloping the chamber and with means for cooling the electrodes. Such apparatus is illustrated in German Pat. No. 1,515,311.
Other arrangements are illustrated in German Pat. No. 1,690,688, in which a d.c. or low-frequency alternating magnetic field is employed, in addition to the high-frequency electromagnetic field. This field may be aligned in parallel or perpendicular to the highfrequency magnetic field, as shown in German Pat. No. 1,690,689.
SUMMARY OF THE PRESENT INVENTION A principal object of the present invention is to provide an apparatus in which the process may be carried out in a continuous manner.
A further object of the present invention is to provide such apparatus in which an even thickness layer is produced over the entire surface of the substrate.
A further object of the present invention is to provide such apparatus in which the substrate is maintained generally in vertical orientation during coating.
A further object of the present invention is to provide apparatus for accommodating thermal expansion and contraction of the assembly during heating and cooling.
Another object of the present invention is to provide an apparatus having a large surface cylindrical anode encircling the interior of the sputtering chamber, such anode serving as a getter surface for undesired components of the sputtering gas.
Another object of the present invention is to provide a sputtering assembly in which rod-shaped cathodes are employed.
A further object of the present invention is to provide a mechanism by which the amount of sputtering is relatively constant throughout the sputtering chamber.
Another object of the present invention is to provide such a sputtering assembly, with means for generating a low-frequency magnetic field axially aligned within the sputtering chamber, to guide electrons within the chamber into spiral paths, to increase the current between the cathode and anode, and to permit a reduction in the pressure of the inert gas atmosphere within the chamber.
A further object of the present invention is to provide a mechanism for minimizing variations in thickness of the coating over the surface of the substrate.
A further object of the present invention is to provide a sputtering system employing a cylindrical cathode arrangement, with means for establishing a magnetic field intensity along the length of the electrode in such a way as to produce a uniform coating thickness.
A further object of the present invention is to provide a sputtering apparatus having a heating chamber adjacent the sputtering chamber and a means to minimize sputtering in the heating chamber.
These and other objects and advantages of the present invention will become manifest upon an examination of the following description and the accompanying drawings.
In one embodiment of the present invention, there is provided a sputtering chamber formed of two glass cylinders joined in axial alignment bya metal ring, said ring providing connections to the exterior of said sputtering chamber for connection to a source of sputtering gas and to a source of coolant and to a sputtering voltage, means provided at each end of said sputtering chamber for introducing a continuous series of carriers supporting substrate members, said sputtering chamber including an electrode array comprising a cylindrical cathode and a disk-like anode, and including means surrounding said insulating tubes for producing a highfrequency electromagnetic field within said chamber, and means for producing'a low-frequency magnetic field within said sputtering chamber inaxial alignment with the glass cylinders.-
BRIEF DESCRIPTION OF THE DRAWINGS Reference will now be made to the accompanying drawings, in which:
FIG. 1 is a side elevation, partly in cross-sectiom'of apparatus illustrating an illustrative embodiment of the present invention;
FIG. 2 is a transverse cross section of the apparatus illustrated in FIG. 1, taken in the plane II-II; and
FIG. 3 is a transverse cross section of a carrier supporting a plurality of substrate members, which carrier is employed in the apparatus illustrated in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an illustrative embodiment of the present invention. The sputtering chamber 5 is comprised of a pair of glass tubes 51 joined in axial arrangement by means of a metal connector 6. The connector 6 supports a flow of coolant by means of a pair of conduits l4, and provides a connection 15 between the electrodes inside the sputtering chamber 5 and a source of d.c. voltage. In addition, a flow of sputtering gas is supplied to the interior of the sputtering chamber through a conduit 16, which is preferably equipped with a valve adapted to open or close the conduit 16, and provides a certain gas throughput.
An inlet chamber 1 is provided, through which sub strate members are adapted to pass on their way from outside the apparatus into the interior of the sputtering outer door (not shown), which is closed after a carrier supporting one or more substrate members is inserted into the inlet chamber 1. The chamber 1 is then evacuated by means of a vacuum pump attached to the chamber 1 by a conduit 2. Preferably, the inlet chamber 1 is evacuated to a pressure of approximately 10* Torr. Following suchevacuation, it is flushed with a gas mixture which corresponds to the sputtering gas, to minimize as much as possible the presence of gases other than sputtering gas.
A gate (not shown) interconnects the chamber 1 with a heating chamber 3, and the gate is adapted to be opened to permit introduction of a carrier supporting the substrate members into the chamber 3 from the chamber 1. The chamber 3 is previously evacuated by means of a vacuum pump secured thereto by a conduit 2, so that there is no pressure differential between the chambers 1 and 2 while the gate therebetween is open. The heating chamber 3 is connected to an end of one of the glass tubes 51 by means of a metal bellows 4,
which bellows is adapted to expand or contract in an axial direction in accordance with the thermal expansion and contraction of the components of the apparatus.
A pair of highfrequency coils 12 surround the tubes 51, and the ends of the coils 12 are connected to a source of high-frequency current so that a plasma of ionized gas is created and maintained within the interior of the chamber 5. An end plate 17 facilitates making a vacuum-tight connection between the chambers 3 and 5.
A cooling chamber 8 is provided at the outlet end of the sputtering chamber 5, and a metal bellows 4 is provided at that end to interconnect a tube 51 to the chamber 8'. The chamber 8 is normally evacuated by means of a vacuum pump connected thereto by a conduit 2, and the chamber 8 is constructed in similar fashion to the heating chamber 3. It is connected by means of a gateto an outlet chamber 10, which is constructed in the identical manner described in connection with the inlet-chamber 1. The outlet chamber 10 is also evacuated by means of a vacuum pump connected thereto. by a conduit 2, and is provided with a door (not shown) which may be opened in order to withdraw the carriers and the substrate members from the chamber 10.
Both'of the tubes 51 are identical in construction so that no further description of the right half of the chamber 5 is necessary, it being the same as the left half which has been described.
An electrode 52 surrounds the interior of the sputtering chamber 5. The electrode 52 is in the form of a hollow circular cylinder, and two additional electrodes 54 and 56, both of which are disk-shaped, are disposed at one axial end thereof. The electrode 52 is provided with a plurality of slots 57, which prevent screening of the high-frequency magnetic field developed by the coils 12. The electrodes 54 and the parts of electrodes 52 which are opposite to the substrate surfaces are connected as cathode. The electrodes 56 and the parts of electrodes 52 which are placed below and above the substrates are connected as anode. The electrode arrangement employing the disk-shaped electrodes 54 and 56 improves the sputtering operation at the ends of the sputtering chamber 5, so that a generally constant thickness of coating is applied, even at the ends of the chamber 5. A rectangularly shaped window 9 (best shown in FIG. 2) is provided in theend plates 17 and in the electrodes 54 and 56 to accommodate introduction of the carrier supporting the substrate members, and the clearance provided by such window is preferably as little as possible to enhance a choke or throttling effect in the region of the window 9. This substantially prevents passage of gas molecules from the heating chamber 3, which may be contaminated with residual gas molecules entering from the inlet chamber 1 into the chamber 5. In addition, the chamber 3 is maintained at a lower pressure than the chamber 5, also to minimize contamination. This is assured by the continued evacuation of the chamber 3 by the conduit 2, while gas is introduced into the chamber via the conduit 16.
A coil 13 is provided at each end of the'sputtering chamber 5, and the ends of both coils l3 are connected to a source of low-frequency a.c. voltage, so that a lowfrequency alternating field is created which permeates the sputtering chamber 5 in an axial direction.
FIG. 2 illustrates one of the glass tubes 51 in cross section, and the coil 12 which surrounds such tube. The window 9 is illustrated in-the electrode 54, and the larger disk-shaped electrode 56 is also illustrated; For reasons of clarity, the transport mechanism by which substrate members are carried is not illustrated in FIG. 2.
The electrode 52 is provided with four equally spaced slots 57, as illustrated in FIG. 2. The slots 57 prevent the screening of the electromagnetic field which is created by the coil 12. Instead of sputtering from the cathode parts of the electrode 52, a number of rods 53 forming the sputtering cathode may be provided in spaced-apartrelationship, parallel to the axis .of the sputtering chamber, and they are'arranged at a relatively short distance inwardly from the cylindrical anode 52. Viewed from the position of the substrate to be coated, the electrodes 53 extend through an arc of about 135, indicated in FIG. 2 by the angle a. The rods 53 are spaced apart by a distance of approximately three times the diameter of the rods.
The electrode 52 is preferably water cooled, by means of a plurality of water carrying tubes 55. The tubes 55 are in contact with the exterior surface of the electrode 52, in heat-conducting relationship therewith.
A cross section of the transport or conveyor arrangement is illustrated in FIG. 3. A carrier 11 is provided with a roller at its upper end, which is trapped by two elongate rods supported by a bracket 70, the roller 110 being adapted to roll longitudinally relative to the rods. The lower end of the carrier 11 is trapped between two rods supported by another bracket 70. The carrier 11' and the substrate members 20, which are secured thereto, are maintained in a general vertical can conveniently be introduced into the chamber and extracted from the outlet chamber without difficulty.
The-sputtering gas, introduced into the chamber 5 through the conduit 16, is preferably an inert gas such as argon.
The sputtering electrodes 53 are mounted by brackets (not shown) on the interior of the metal connector 6, and are connected to a suitable source of voltage through the terminal 15. The rod shaped elements 53 are easily replaced when necessary simply by disassembling the connector from one of the glass cylinders 51, or by removing one or both of the end plates 17. The voltage source applied to the terminal is preferably pulsating d.c., derived from a single phase ac voltage source by means of a full wave bridge-type diode rectifier or the like. The auxiliary coils 13 are preferably connected to a source of low-frequency ac. current,
preferably at about 50 Hz. The field generated by the coils 13 causes electrons to move in spiral paths, causing an increase in the current between the cathode and anode electrodes. The use of the coils 13 also permits operation with a lower pressure within the chamber. The a.c. current is preferably in phase with the pulsating d.c. applied to the terminal 15, so that the most cooperative relation between the electric field, created by the electrodes 53, and the magnetic field, created by the coils 13, can be maintained. This is'most effectively accomplished by employing the same single phase a.c. source for both the coils 13 and the electrodes 53, although in the latter case, a rectifier is employed to furnish the required pulsating d.c. When the electrodes 53 and the coils 13 are energized in the manner described above, heating of the substrate members by electron bombardment is minimized, since electrons tend to be deflected by the magnetic field, and the in-phase ac. current applied to the coils l3 prevents any variation in thickness in the coating which might otherwise result.
The coils 13 are spaced apart along the axis of the assembly by a distance greater than the radius of either coil. Thus, the spacing exceeds that of so-called l-lelmholtz coils. When so spaced, the magnitude of the magnetic field is somewhat less in the centerof the chamber 5 than at the ends, which contributes to a uniform thickness of coating applied during the sputtering process.
The use of the disk-like electrodes 54 and 56 also contributes to an evenness of the coating throughout the chamber 5. Preferably the diameter of the cathode 54 is half that of the anode cylinder 52, while the disk 56 is approximately the same diameter as the anode 52.
The use of the choke windows 9 permits higher pressure inside the chamber 5 than in the heating and cooling chambers 3 and 8 The pressure in the chamber 5 is preferably on the order of l0"Torr, while that in the heating and cooling chambers is about lO' Torr. The use of the window 9 also results in improved operation by tending to smooth disturbances produced by diffusion pump which is connected to the conduits 2.
Apparatus has now been described by which substrate members may be uniformly coated by sputtering in a virtually continuous manner, which brings about a great increase in the speed and efficiency of this process. In addition, sputtered layers are extremely uniform and do not vary in thickness.
It will be evident that others skilled in the art may make additions and modifications in the apparatus as disclosed herein, without departing from the essential features of novelty thereof, which areintended to be defined and secured by the appended claims.
When several layers of coating are to be applied, a plurality of the sputtering chambers 5 may be connected together, so the substrate members pass sequentially through all of them.
What is claimed is:
1. Coating apparatus comprising an input chamber, a heating chamber, a sputtering chamber, a cooling chamber, and an output chamber, means for connecting said chambers in series to permit a substrate member to be transported sequentially therethrough, said sputtering chamber comprising two cylindrical tubes formed of insulating material interconnected in axially aligned relationship by a metal connector, means for supporting a plurality of electrodes on said ring in position to envelop said chamber internally thereof, means on said ring for establishing a connection between at least one of said electrodes and a source of d.c. voltage, means for evacuating said sputtering chamber,-means for introducing a gas into said sputtering chamber, a high frequency coil surrounding said sputtering chamber, and a transport means mounted centrally within 4. Apparatus according to claim 2, including means for applying a pulsating d.c. voltage to electrodes within said sputtering chamber, and means for applying an ac. current to said coils which is in phase with said pulsating d.c. voltage.
5. Apparatus according to claim 2, wherein the distance between said auxiliary coils exceeds the radius of said coils.
6. Apparatus according to claim 1, wherein said electrodes enveloping the sputtering chamber comprise two circular cylindrical shell members, one of said members serving as the anode and the other as the cathode, said cathode shell covering an angle of approximately relative to the axis of the chamber.
7. Apparatus according to claim 6, including a diskshaped cathode electrode arranged at an end of said sputtering chamber, the diameter of said cathode disk being approximately half the diameter of said anode shell.
8. Apparatus according to claim 1, wherein said transport means comprises a plurality of carriers supported for axial movement within said sputtering chamber, each of said carriers being adapted to support two pairs of substrate members in back-to-back relationship.
9. Apparatus according to claim 8, wherein each of said carriers comprises a roller, a substrate member supporting member, and a depending arm, said roller supporting said carrier and said arm maintaining said carrier in a generally vertical orientation.
10. Apparatus accordingto claim 1, wherein said electrodes comprise a circular cylindrical shell connected as the anode of the sputtering system, and a plurality of rods spaced inwardly a small distance from said anode and covering an angle of approximately 135 relative to the axis of the chamber.
11. Apparatus according to claim 10, wherein the distance between the cathode rods corresponds to approximately three times the diameter of each of said rods.
12. Apparatus according to claim 1, including a pair of metal bellows for interconnecting said sputtering chamber with said heating and cooling chambers, to compensate for thermal expansion and contraction.
13. Apparatus according to claim 1, including means mounted on said metal connector for supporting a conduit for introducing an inert gas into said sputtering chamber.
14. Apparatus according to claim 1, including a choke window interconnecting each end of said sputtering chamber with the heating chamber and the cooling chamber, respectively, said means for evacuating said chamber being connected with said heating and cooling chambers.
15. Apparatus according to claim 1, includingmeans for connecting a plurality of said sputtering chambers in series with each other, whereby several coatings can be successively applied to said substrates.