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Publication numberUS20060070884 A1
Publication typeApplication
Application numberUS 11/245,912
Publication dateApr 6, 2006
Filing dateOct 6, 2005
Priority dateOct 6, 2004
Publication number11245912, 245912, US 2006/0070884 A1, US 2006/070884 A1, US 20060070884 A1, US 20060070884A1, US 2006070884 A1, US 2006070884A1, US-A1-20060070884, US-A1-2006070884, US2006/0070884A1, US2006/070884A1, US20060070884 A1, US20060070884A1, US2006070884 A1, US2006070884A1
InventorsKazutaka Momoi, Kazutaka Yanaqita, Nobuhiko Sato
Original AssigneeKazutaka Momoi, Kazutaka Yanaqita, Nobuhiko Sato
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrochemical processing apparatus and method
US 20060070884 A1
Abstract
A processing apparatus electrochemically processes part of a first surface of a member having the first surface and a second surface. The processing apparatus includes a support which supports the member to expose the first surface, a first electrode which is arranged to oppose a first portion of the first surface, a second electrode which is arranged to oppose a second portion of the first surface, a third electrode which applies a potential to the member from a second surface side, and a processing bath to fill a space defined by the first and second electrodes and the member with a processing liquid.
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Claims(9)
1. A processing apparatus for electrochemically partially processing a first surface of a member having the first surface and a second surface, the apparatus comprising:
a support which supports the member to expose the first surface;
a first electrode which is arranged to oppose a first portion of the first surface;
a second electrode which is arranged to oppose a second portion of the first surface;
a third electrode which applies a potential to the member from a second surface side; and
a processing bath to fill a space defined by said first and second electrodes and the member with a processing liquid.
2. The apparatus according to claim 1, wherein said first and second electrodes are arranged such that a distance between said second electrode and the second portion of the first surface is smaller than that between said first electrode and the first portion of the first surface.
3. The apparatus according to claim 1, further comprising a power supply which provides a potential to said first, second, and third electrodes, wherein said power supply is configured to decrease an electric field intensity between said second and third electrodes to be lower than that between said first and third electrodes.
4. The apparatus according to claim 1, wherein the first portion comprises a region to be electrochemically processed, and the second portion comprises a region not to be electrochemically processed.
5. The apparatus according to claim 1, wherein said first and second electrodes are arranged at such positions not to be in contact with the member.
6. The apparatus according to claim 1, wherein the member is supported to expose the first surface entirely.
7. A processing method of electrochemically processing part of a first surface of a member having the first surface and a second surface, the method comprising:
a step of arranging the member such that a first electrode opposes a first portion of the first surface, that a second electrode opposes a second portion of the first surface, and that a third electrode applies a potential to the member from a second surface side; and
a step of processing the member while applying a potential to the first, second, and third electrodes.
8. The method according to claim 7, wherein the first and second surfaces are processed with different chemical liquids.
9. A method of manufacturing a member having first and second surfaces, the method comprising:
a step of arranging the member such that a first electrode opposes a first portion of the first surface, that a second electrode opposes a second portion of the first surface, and that a third electrode applies a potential to the member from a second surface side; and
a step of electrochemically processing the member while applying a potential to the first, second, and third electrodes.
Description
FIELD OF THE INVENTION

The present invention relates to a processing apparatus for a member and a processing method and, more particularly, to a processing apparatus and processing method which electrochemically process part of the first surface of a member having the first and second surfaces.

BACKGROUND OF THE INVENTION

Methods for obtaining a substrate which has been subjected to a target process in only the processing-target region of its entire surface can be roughly divided into two methods. According to the first method, the entire surface of the substrate is subjected to a target process, and after that the non-processing-target region of the entire surface is removed by etching or cutting. According to the second method, only the processing-target region of the entire surface is subjected to a target process, while the non-processing-target region is not processed.

More specifically, according to the first method, the entire surface of the substrate is subjected to an electrochemical process such as plating or a chemical process. After that, part of the processed region is removed by etching or cutting to leave an unprocessed region. For example, after the entire surface of the substrate is plated, a protective film is formed to cover only a region on which a plated layer should be left. The substrate is then immersed in a solution that dissolves the plating material, so that a processed region and unprocessed region can be formed on the substrate surface. This method has a drawback in that a removing process such as etching or cutting is indispensable, so that the number of steps increases to increase the cost. If the process for the processing-target region progresses in the direction of depth of the substrate as in a chemical process, the removing step for forming an unprocessed region undesirably forms a step on the substrate surface.

According to the second method, a protective film is formed in advance to cover the non-processing-target region of the substrate surface, or a member is brought into contact with the substrate surface, to divide a processing-target region and the non-processing-target region, and after that a process is performed. Regarding the chemical process, “Volker Lehmann, Electrochemistry of Silicon, WILEY-VCH, Germany, 2002, pp. 107-108.” describes a method of forming an oxide film or nitride film on the substrate surface in advance and a method of applying a resist to the substrate surface in advance.

With the method of forming a protective film, how to remove the protective film after the process becomes an issue. In the method of applying a resist film, the residual resist can be removed by a stripping liquid such as acetone or a heated sulfuric-acid-based solution. The resist or stripping liquid, however, remains in the pores of a porous layer formed by the chemical process, and may be burned or evaporate in a later annealing process. Then, an evaporated substance may corrode the chamber or attach to the substrate surface to increase the number of foreign substances, or cause impurity contamination in the later step.

To bring the member into contact with the substrate surface, the processing-target region and non-processing-target region may be divided by using seal member such as an O-ring. With this method, when the seal member comes into contact with the substrate, foreign substances can undesirably attach to the substrate. In particular, a powerful cleaning method to remove the foreign substances cannot be applied to a porous layer or plated layer that can be formed by anodizing. This is because cleaning can damage the porous layer or plated layer. Thus, the foreign substances which have attached as the seal member comes into contact are undesirably carried to the next process. Also, as the seal member comes into contact with the substrate, it can damage the substrate.

When a seal member is used, if the seal is insufficient, sometimes a processing liquid can enter the non-processing-target region by capillarity. As the size of the semiconductor substrate or liquid crystal panel increases, the region to be sealed also becomes large, and the problem of defective sealing becomes more conspicuous. As the process is repeated, the function of the seal member such as an O-ring degrades due to wear or a chemical change.

According to the method disclosed in Japanese Patent Laid-Open No. 2002-246364, a mask is arranged to oppose the processing-target region of a wafer. A processing liquid is supplied to the gap between the processing-target region and mask by the capillary action to process the processing-target region. This method provides one solution for the problem of foreign substances attaching to the substrate and the problem of damage to the substrate.

According to the method described in Japanese Patent Laid-Open No. 2002-246364, since the processing liquid is supplied to the gap between the processing-target region and mask by using the capillary action, the gap must be inevitably sufficiently small. Therefore, the supply amount of the processing liquid is limited, and sometimes the processing liquid accordingly degrades during the process. Such a small gap makes it difficult to circulate the processing liquid and is thus inappropriate for uniformly processing the processing-target region. When this method is applied to cleaning, the foreign substances removed by cleaning attach to the substrate again at a high possibility. Therefore, the actual application of the method described in Japanese Patent Laid-Open No. 2002-246364 is supposed to be limited to simple ones such as coating removal.

SUMMARY OF THE INVENTION

The present invention has been made on the basis of the above situation, and has as its object to provide a novel technique which electrochemically processes part of a member to form a processed region and unprocessed region.

More specifically, it is an object of the present invention to provide a technique to form a member having a processed region which is processed more uniformly.

According to the first aspect of the present invention, there is provided a processing apparatus for electrochemically partially processing a first surface of a member having the first surface and a second surface, comprising a support which supports the member to expose the first surface, a first electrode which is arranged to oppose a first portion of the first surface, a second electrode which is arranged to oppose a second portion of the first surface, a third electrode which applies a potential to the member from a second surface side, and a processing bath to fill a space defined by the first and second electrodes and member with a processing liquid.

According to a preferred embodiment of the present invention, preferably, the first and second electrodes are arranged such that a distance between the second electrode and the second portion of the first surface is smaller than that between the first electrode and the first portion of the first surface.

According to another preferred embodiment of the present invention, the processing apparatus can further comprise a power supply which provides a potential to the first, second, and third electrodes. The power supply is preferably configured to decrease an electric field intensity between the second and third electrodes to be lower than that between the first and third electrodes.

According to still another preferred embodiment of the present invention, the first portion comprises a region to be electrochemically processed, and the second portion comprises a region not to be electrochemically processed.

According to still another preferred embodiment of the present invention, preferably, the first and second electrodes are arranged at such positions not to be in contact with the member.

According to the second aspect of the present invention, there is provided a processing method of electrochemically processing part of a first surface of a member having the first surface and a second surface, comprising a step of arranging the member such that a first electrode opposes a first portion of the first surface, that a second electrode opposes a second portion of the first surface, and that a third electrode applies a potential to the member from a second surface side, and a step of processing the member while applying a potential to the first, second, and third electrodes.

According to the present invention, there is provided a novel technique for electrochemically processing part of a member to form a processed region and unprocessed region and, more particularly, a technique to form a member having a processed region which is processed more uniformly.

According to the third aspect of the present invention, there is provided a method of manufacturing a member having first and second surfaces, comprising a step of arranging the member such that a first electrode opposes a first portion of the first surface, that a second electrode opposes a second portion of the first surface, and that a third electrode applies a potential to the member from a second surface side, and a step of electrochemically processing the member while applying a potential to the first, second, and third electrodes.

Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a view showing the structure of a processing apparatus according to the first embodiment of the present invention; and

FIG. 2 is a view showing the structure of a processing apparatus according to the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a view showing the structure of a processing apparatus according to the first embodiment of the present invention. A processing apparatus 100 shown in FIG. 1 is configured to electrochemically process part of a first surface 10 a of a substrate (e.g., a silicon substrate) 10 which serves as a member having the first surface 10 a and a second surface 10 b. An example of the electrochemical process can include a chemical process, plating, and electrolytic oxidation.

The processing apparatus 100 has a support 140 which supports the member 10 to expose its first surface 10 a, a first electrode (main electrode) 115 which is arranged to oppose a first portion 10 a 1 of the first surface 10 a, a second electrode (auxiliary electrode) 125 which is arranged to oppose a second portion 10 a 2 of the first surface 10 a, a third electrode 150 which applies a potential to the member 10 from the second surface 10 b side, and a processing bath 160 which serves to fill the space defined by the first electrode 115, second electrode 125, and member 10 with a processing liquid 135.

The above structure preferably has such a layout that the support 140 supports the member 10 by coming into contact with a portion of the member 10 other than the first surface 10 a, and that the first surface 10 a is entirely in contact with the processing liquid 135.

For example, the support 140 can be formed as a chucking pad which chucks the second surface 10 b of the member 10 with a negative pressure. The support 140 can have a ring-like shape and be arranged to oppose the second electrode 125.

The first portion 10 a 1 is a processing-target portion or region to be processed with the processing liquid 135, and the second portion 10 a 2 is a non-processing-target portion or region not to be processed with the liquid 135. Desirably, the non-processing-target region is not processed at all. However, sometimes it will do as far as the non-processing-target region is processed with a lower degree than the processing-target region is.

In the example shown in FIG. 1, the first portion 10 a 1 has a circular shape while the second portion 10 a 2 has a ring-like shape.

The distance between the second electrode 125 and member 10 (or third electrode 150) is smaller than that between the first electrode 115 and member 10 (or third electrode 150). In order to improve the controllability of separation of the region to be processed and the region not to be processed, the distance between the second electrode 125 and the first surface 10 a of the member 10 is preferably 1 mm or less, and more preferably 0.2 mm or less.

The distance between the first electrode 115 and member 10 can be determined within a range where the above conditions are satisfied, and is preferably 5 mm or more. When the first electrode 115 and member 10 are spaced apart from each other by a certain distance in this manner, the degrees of freedom of movement of the processing liquid 135, and a reaction gas if it is generated by the process, on the first portion 10 a 1 can be increased. To increase the degrees of freedom of the processing liquid 135 or reaction gas on the first portion 10 a 1 contributes to the uniform process of the first portion 10 a 1. In order to process the first portion 10 a 1 more uniformly, preferably, a circulation system is formed to circulate the processing liquid, so that a fresh processing liquid 135 is constantly supplied to the first portion 10 a. Circulation of the processing liquid is also effective in removing the reaction gas from the first portion 10 a 1.

In the structure in which the second electrode 125 is in contact with the processing liquid 135, the second electrode 125 is preferably made of a material inactive to the processing liquid 135. When the processing apparatus 100 is to be applied to a chemical process, the second electrode 125 is preferably made of a material, e.g., a diamond electrode, graphite, or SiC, which is inactive to a chemical processing liquid (e.g., a liquid containing hydrogen fluoride). The second electrode 125 may be covered with a protective member made of a material inactive to the processing liquid 135.

Typically, the boundary between the first and second portions 10 a 1 and 10 a 2 can be located near the intermediate portion between the end (outer end in FIG. 1) of the first electrode 115 and the end (inner end in FIG. 1) of the second electrode 125.

The third electrode 150 can be arranged to oppose the first electrode 115 through the member 10 as a processing target. The third electrode 150 may be arranged to be in direct contact with the second surface lob of the member 10 (in this case, the third electrode 150 can also serve as a support which supports the member 10), or to provide a potential to the member 10 from the second surface 10 b side through a conductive liquid (electrolytic liquid).

The processing bath 160 can be formed of, e.g., a bottom member 105 which supports the third electrode 150 and support 140; an intermediate wall 106, and a top wall 110. The intermediate wall 106 and top wall 110 may be connected with an adhesive or the like, or separably connected by connecting elements such as bolts. The bottom member 105 and intermediate wall 106 can be separably connected by connecting elements such as bolts through a seal member such as an O-ring 145.

When the member 10 as the processing target is to be arranged on the support 140 of the processing apparatus 100 or be unloaded from the processing apparatus 100, typically, the bottom member 105 is removed from the intermediate wall 106. If a high throughput is required, for example, an openable/closeable access port is preferably formed in the side portion of the processing bath 160, so that the member 10 can be loaded in and unloaded from the processing apparatus 100 through the access port.

The processing apparatus 100 can further include a power supply 170 which provides a potential to the first, second, and third electrodes 115, 125, and 150. The power supply 170 is configured or adjusted to decrease the electric field intensity between the second and third electrodes 125 and 150 to be lower than that between the first and third electrodes 115 and 150. The power supply 170 can include a DC power supply 120 which provides a potential difference between the first and second electrodes 115 and 150 and a circuit 130 which provides a potential to the second electrode 125. The circuit 130 can be a circuit that makes the second and third electrodes 125 and 150 equipotential, a circuit that provides a potential difference between the second and third electrodes 125 and 150, or a resistor. When a resistor is arranged between the second and third electrodes 125 and 150, the current flowing between the first and second electrodes 115 and 125 can be limited.

As described above, when the second electrode 125 is arranged to oppose the second portion 10 a 2, the electric field intensity between the second and third electrodes 125 and 150 can be controlled to be lower than that between the first and third electrodes 115 and 150 by using the second electrode 125. When the distance between the second electrode 125 and member 10 is decreased to be smaller than that between the first electrode 115 and member 10, supply of the reaction species to the second portion 10 a 2 is limited. More specifically, the current flowing through the second portion 10 a 2 can be controlled to be smaller than that flowing through the first portion 10 a 1. As the supply of the reaction species to the second portion 10 a 2 is limited, electrochemical reaction in the second portion 10 a 2 is more suppressed than in the first portion 10 a 1. As a result, the first portion 10 a 1 can be processed with a higher degree than the second portion 10 a 2 is to provide a difference between the first and second portions 10 a 1 and 10 a 2.

As compared to a case wherein the second electrode 125 is not provided, with the presence of the second electrode 125, the electric line of force which passes through the first portion 10 a 1 as the processing-target region can be uniformed, so that the process in the first portion 10 a 1 is uniformed.

A method of processing the member 10 such as a substrate by using the processing apparatus 100 will be described. First, the member 10 is supported by the support 140. In this case, in the processing apparatus 100 having the structure shown in FIG. 1, with the bottom member 105 being removed from the intermediate wall 106, the member 10 is aligned with a predetermined position on the bottom member 105, and is supported by the support 140 with negative pressure chucking or the like. Subsequently, the bottom member 105 is connected to the lower portion of the intermediate wall 106 by a connecting element (not shown). Thus, the processing bath 160 including the bottom member 105, intermediate wall 106, and top wall 110 is formed. Then, the processing liquid 135 is injected in the processing bath 160 to fill the space defined by the first electrode 115, second electrode 125, and member 10 with the processing liquid 135.

Then, the power supply 170 provides a potential to the first, second, and third electrodes 115, 125, and 150 to electrochemically process the member 10. The power supply 170 is configured or adjusted to decrease the electric field intensity between the second and third electrodes 125 and 150 to be lower than that between the first and third electrodes 115 and 150. An example of the electrochemical process can include a chemical process, plating, and anodizing.

After a prescribed period of time elapses, the power supply 170 is stopped to end the electrochemical process. The processing liquid 135 is discharged from the processing bath 160, and the member 10 is unloaded from the processing bath 160. In the processing apparatus 100 having the structure shown in FIG. 1, with the third electrode 150 being removed from the intermediate wall 106, the member 10 may be unloaded from the support 140.

A member with an electrochemically processed surface can be manufactured in this manner.

An example in which the surface (first surface) of a semiconductor substrate is to be anodized by using the processing apparatus 100 will be described.

The processing apparatus 100 was prepared. The semiconductor substrate as the processing-target member 10 was supported by the support 140 in accordance with the procedure described above, and part (the first portion) of the surface (first surface) of the semiconductor substrate was anodized.

The conditions for anodize were as follows:

    • Semiconductor substrate; p+ silicon substrate with a resistivity of 16 mΩ•cm
    • Chemical processing liquid; HF:IPA=42.5:9.2 (wt. %) (prepared by mixing hydrofluoric acid and IPA)
    • Depth of chemical processing liquid; 20 mm from the surface of the semiconductor substrate
    • Current Conditions (cathode=first electrode 115, anode=third electrode 150); 5.12 A, 210 sec

The distance between the semiconductor substrate and first electrode, the distance between the semiconductor substrate and second electrode, and the potential difference between the semiconductor substrate and second electrode were set as follows:

    • Distance between semiconductor substrate (region within the radius of 90 mm from the center) and first electrode; 20 mm
    • Distance between semiconductor substrate (region outside the radius of 90 mm to the outermost circumference); 1 mm
    • Potential difference between semiconductor substrate and second electrode; 0 (equipotential)

The semiconductor substrate was processed under the above conditions, and the result was compared to a case wherein the second electrode (auxiliary electrode) was not provided. In the case wherein the second electrode (auxiliary electrode) was provided, variations in current density in the second portion (the region opposed to the second electrode) 10 a 2 of the semiconductor substrate could be decreased by one order of magnitude. Thus, the thickness of the anodized layer (porous layer) could be decreased to 1/10 or less when compared to the case wherein the second electrode (auxiliary electrode) was not provided.

The electric field intensity distribution was analyzed by numerical simulation. It was confirmed that when the second electrode (auxiliary electrode) was provided, variations in current density in the region where the second electrode (auxiliary electrode) was provided could be suppressed to 1/10 or less when compared to the case wherein the second electrode was not provided.

Second Embodiment

FIG. 2 is a view showing the structure of a processing apparatus according to the second embodiment of the present invention. A processing apparatus 200 shown in FIG. 2 is configured to electrochemically process part of a first surface 10 a of a substrate (e.g., a silicon substrate) 10 which serves as a member having the first surface 10 a and a second surface 10 b. An example of the electrochemical process can include a chemical process, plating, and electrolytic oxidation.

The processing apparatus 200 has a support 205 which supports the member 10 to expose its first surface 10 a, a first electrode (main electrode) 215 which is arranged to oppose a first portion 10 a 1 of the first surface 10 a, a second electrode (auxiliary electrode) 240 which is arranged to oppose a second portion 10 a 2 of the first surface 10 a, a third electrode 220 which is arranged to oppose the second surface 10 b so as to apply a potential to the member 10 from the second surface 10 b side, and a processing bath 260 to fill the space defined by the first electrode 215, second electrode 240, and member 10 with a processing liquid 230 and to fill the space between the member 10 and third electrode 220 with an electrolytic liquid 235.

In this manner, when necessary, the chemical liquid (processing liquid, electrolytic liquid, and the like) can be changed between the first surface 10 a side and second portion 10 a 2 side of the member 10.

The second electrode 240 is supported by an electrode support member 245. Typically, the electrode support member 245 can have a ring-like shape.

For example, the support 205 is formed as a chucking pad having a chucking groove 206, and supports the member 10 by negative pressure suction. The support 205 typically has a ring-like shape. The region (opening) inside the ring-like shape preferably has an area equal to or smaller than that of the first portion 10 a 1 of the member 10. Then, the electric line of force which should pass through the first portion 10 a 1 can be prevented from spreading to the outer second portion 10 a 2 side.

The first portion 10 a 1 is a portion to be processed with the processing liquid 230 (processing-target region), and the second portion 10 a 2 is a portion not to be processed with the processing liquid 230 (non-processing-target region). Desirably, the non-processing-target region is not processed at all. However, sometimes it will do as far as the non-processing-target region is processed with a lower degree than the processing-target region is. In the example shown in FIG. 2, the first portion 10 a 1 has a circular shape while the second portion 10 a 2 has a ring-like shape.

The distance between the second electrode 240 (electrode support member 245) and member 10 is smaller than that between the first electrode 215 and member 10. In order to improve the controllability of separation of the processing-target region (processed region) and non-processing-target region (unprocessed region), the distance between the second electrode 240 and the first surface 10 a of the member 10 is preferably 1 mm or less, and more preferably 0.2 mm or less. The second electrode 240 is preferably made of a material inactive to the processing liquid.

The distance between the first electrode 215 and member 10 can be determined within a range where the above conditions are satisfied, and is preferably 5 mm or more. When the first electrode 215 and member 10 are spaced apart from each other by a certain distance in this manner, the degrees of freedom of movement of the processing liquid 230 on the first portion 10 a 1 can be increased. If a reaction gas is generated by the process, the degrees of freedom of movement of the reaction gas can be increased. To increase the degrees of freedom of the processing liquid 230 or reaction gas on the first portion 10 a 1 contributes to the uniform process of the first portion 10 a 1. In order to process the first portion 10 a 1 more uniformly, preferably, a circulation system is formed to circulate the processing liquid, so that a fresh processing liquid 230 is constantly supplied to the first portion 10 a. Circulation of the processing liquid is also effective in removing the reaction gas from the first portion 10 a 1.

The processing apparatus 200 can further include a power supply 270 which provides a potential to the first, second, and third electrodes 215, 240, and 220. The power supply 270 is configured or adjusted to decrease the electric field intensity between the second and third electrodes 240 and 220 to be lower than that between the first and third electrodes 215 and 220. The power supply 270 can include a DC power supply 225 which provides a potential difference between the first and second electrodes 215 and 220 and a circuit 250 which provides a potential to the second electrode 240. The circuit 250 can be a circuit that makes the second and third electrodes 240 and 220 equipotential, a circuit that provides a potential difference between the second and third electrodes 240 and 220, or a resistor. When a resistor is arranged between the second and third electrodes 240 and 220, the current flowing between the first and second electrodes 215 and 240 can be limited.

A case will be described hereinafter wherein a silicon substrate as the member 10 is to be anodized by using the processing apparatus 200. When the first surface side of the silicon substrate is to be anodized, the first electrode 215 serves as the cathode and the third electrode 220 serves as the anode. Regarding the materials of the electrodes, particularly of the anode, a material is preferable that has a lower ionization tendency than silicon and makes an electrode which is not dissolved by electrode reaction. For example, platinum is preferably used to form the cathode, and platinum or low-resistivity silicon is preferably used to form the anode.

The processing liquid 230 is injected between the member 10 and first electrode (cathode) 215, and the electrolytic liquid (conductive solution) 235 is injected between the silicon substrate 10 and third electrode (anode) 220.

As the processing liquid 230, for example, one which is identical to that (HF:IPA=42.5:9.2 (wt. %)) of the example of the first embodiment can be used, and selected freely in accordance with a chemically processed target layer (porous layer). The electrolytic liquid 235 may be identical to the chemical processing liquid 230, or selected arbitrarily from conductive materials. For example, when a low-resistivity silicon substrate is to be employed as the third electrode (anode) 220, if a chemical processing liquid is used as the electrolytic liquid 235, the surface of the third electrode 220 is also undesirably processed chemically. To prevent this, preferably, the concentration of the hydrofluoric acid (HF) is decreased, and the process is performed under such conditions that no porous layer is formed on the surface of the third electrode 220.

The electrode support member 245 which supports the second electrode 240 can have a ring-like shape. The inner edge of the ring-shaped electrode support member 245 substantially coincides with the boundary between the region to be processed (processed region) and region not to be processed (unprocessed region). The second electrode 240 is preferably made of a material, e.g., a diamond electrode, graphite, or SiC, which is inactive to the chemical processing liquid 230. The second electrode 240 may be covered with a protective member made of a material inactive to the processing liquid 240. The distance between the second electrode 240 (electrode support member 245) and the first surface 10 a of the member 10 is preferably 1 mm or less, and more preferably 0.2 mm or less.

As described above, when the second electrode 240 is arranged to oppose the second portion 10 a 2, the electric field intensity between the second and third electrodes 240 and 220 can be controlled to be lower than that between the first and third electrodes 215 and 220. When the distance between the second electrode 240 and member 10 is decreased to be smaller than that between the first electrode 215 and member 10, supply of the reaction species to the second portion 10 a 2 is limited. More specifically, the current flowing through the second portion 10 a 2 can be controlled to be smaller than that flowing through the first portion 10 a 1. As the supply of the reaction species to the second portion 10 a 2 is limited, electrochemical reaction in the second portion 10 a 2 is more suppressed than in the first portion 10 a 1. As a result, the first portion 10 a 1 can be processed with a higher degree than the second portion 10 a 2 is to provide a difference between the first and second portions 10 a 1 and 10 a 2.

As compared to a case wherein the second electrode 240 is not provided, with the presence of the second electrode 240, the electric line of force which passes through the first portion 10 a 1 as the processing-target region can be uniformed, so that the process in the first portion 10 a 1 is uniformed.

As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.

CLAIM OF PRIORITY

This application claims priority from Japanese Patent Application No. 2004-294272 filed on Oct. 6, 2004, the entire contents of which are hereby incorporated by reference herein.

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Classifications
U.S. Classification205/118
International ClassificationC25D5/02
Cooperative ClassificationC25D5/02, C25D17/10, C25D11/02
European ClassificationC25D5/02, C25D11/02, C25D17/10
Legal Events
DateCodeEventDescription
Oct 6, 2005ASAssignment
Owner name: CANON KABUSHIKI KAISHA, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MOMOI, KAZUTAKA;YANAGITA, KAZUTAKA;SATO, NOBUHIKO;REEL/FRAME:017075/0226;SIGNING DATES FROM 20050926 TO 20050927