JP2011026638A - Anodization apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anodization apparatus capable of preventing the contamination to a substrate to be treated during anodization for forming a porous layer on a semiconductor wafer with a simple process to efficiently form the high grade porous layer. <P>SOLUTION: This invention relates to the anodization apparatus having the porous layer formed on the substrate to be treated which is arranged in an electrolyte solution by passing current between electrodes of an anode and a cathode in the electrolyte solution, wherein the electrode has a structure that at least metallic electrode member is covered with a non-metallic electrode member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an anodizing apparatus used when forming a porous layer on a semiconductor wafer.

  As a method of manufacturing a thin film semiconductor device used for an IC card or the like, a porous layer is formed on the surface of a semiconductor wafer, a semiconductor film serving as an element formation region is formed on the surface of the porous layer, and the semiconductor film is formed on the semiconductor film. There is a method of forming a thin film semiconductor device by peeling off a porous layer after forming an element.

  According to this method, in order to reduce the film thickness by peeling, it is necessary to remove the back side of the semiconductor wafer after forming the element (the side opposite to the side on which the device is manufactured) by grinding / polishing as in the past. As a result, there is little material loss, and wastes such as shavings can be reduced, resulting in an environmental advantage. Furthermore, since the number of wafers to be used can be reduced by reusing the peeled semiconductor wafer, there is a great expectation that the manufacturing cost can be reduced.

When forming a porous layer on such a semiconductor wafer, an anodizing apparatus is used from the viewpoint of easy control of manufacturing cost and porosity.
The porous layer formation using the anodizing apparatus is performed by, for example, immersing the substrate to be processed and the anode and cathode electrodes in a tank filled with an electrolyte solution, and applying a current between both electrodes. The substrate is anodized to form a porous layer. As an electrode used at this time, a platinum electrode is usually used.

In such an anodizing apparatus, the metal electrode as described above is in contact with the electrolyte solution in which the substrate to be treated is immersed or is in contact, and the electrode may be in direct contact with the substrate to be energized. There was a problem that the processing substrate was contaminated with metal. Further, there has been a demand for an apparatus that can efficiently form a porous layer having a uniform in-plane distribution in order to perform uniform peeling at low cost after device formation.
For the problem of contamination as described above, Patent Document 1 discloses that the electrolyte solution does not stay on the substrate surface by performing anodization while continuously supplying the electrolyte solution to the substrate surface. An anodizing device that can reduce contamination is disclosed.

JP 2000-12537 A

  However, since the above-described apparatus has a structure and the like different from those conventionally used, there is a problem that it is necessary to newly manufacture a dedicated apparatus and the cost is increased.

  The present invention has been made in view of the above problems, and during anodization for forming a porous layer on a semiconductor wafer, contamination of the substrate to be processed can be prevented by a simple method, An object of the present invention is to provide an anodizing apparatus capable of efficiently forming a high-quality porous layer.

  In order to achieve the above object, the present invention is an anodic oxidation apparatus for forming a porous layer on a substrate to be processed disposed in an electrolyte solution by energizing at least between an anode electrode and a cathode electrode in the electrolyte solution. The electrode has a structure in which at least a metal electrode member is covered with a non-metal electrode member.

Thus, in the anodizing apparatus, if the metal electrode member is an electrode covered with a non-metal electrode member, it is easy to dissolve the metal impurities in the electrolyte solution and contaminate the substrate to be processed. Can be effectively prevented. Further, since the metal electrode member is provided on the inner side, the electrolyte solution and the substrate to be processed can be energized uniformly with little loss of current, so that the formation efficiency of the porous layer is good. For this reason, when the electrode is brought into surface contact with the substrate, a porous layer having a uniform in-plane can be efficiently formed while preventing contamination. In addition, even when the electrode is brought into contact with the substrate to be processed, the substrate is hardly damaged because of contact with the non-metallic electrode member. Furthermore, the device of the present invention can be constructed at low cost because it is only necessary to replace the electrode with respect to the conventional device.
As described above, according to the anodizing apparatus of the present invention, it is possible to efficiently form an in-plane porous layer efficiently and at low cost while preventing contamination of the substrate.

At this time, the anode and cathode electrodes are immersed in the electrolyte solution, and at least a portion of the electrode immersed in the electrolyte solution is covered with the nonmetallic electrode member. It is preferable to have a structure.
Thus, if at least the portion immersed in the electrolyte solution is covered with the non-metallic electrode member, the metal electrode member does not come into direct contact with the electrolyte solution, and thus more reliably prevents metal contamination of the substrate. be able to.

At this time, it is preferable that the electrode of the anode has a substrate holding mechanism that holds the substrate to be processed by bringing the nonmetallic electrode member of the anode into surface contact with the back surface of the substrate to be processed.
If it has such a substrate holding mechanism, when the substrate is held, it comes into surface contact with the electrode, and the current is uniformly supplied in the substrate surface, so that the porous layer is formed more uniformly and efficiently in the surface. be able to.

At this time, the metal electrode member of the anode electrode having the substrate holding mechanism preferably has a size corresponding to the entire back surface of the substrate to be processed to be held.
With a metal electrode member having such a size, uniform energization can be more reliably performed on the entire surface of the substrate to be processed, and thus a uniform in-plane porous layer can be formed more efficiently.

The metal electrode member may be made of copper, aluminum, or platinum.
Any of the above can be used as the material of the metal electrode member of the electrode of the anodizing apparatus of the present invention.

It is preferable that the non-metallic electrode member is made of silicon, carbon, or conductive resin.
The material of the non-metallic electrode member of the electrode of the anodizing apparatus of the present invention is preferably any of the above because it has resistance to an HF solution used as an electrolyte solution and allows a good current to pass therethrough.

  As described above, according to the anodizing apparatus of the present invention, when a porous layer is formed on a semiconductor wafer, contamination of the substrate can be prevented by a simple method, and even when an electrode is brought into contact with the substrate. Contamination does not occur and an in-plane uniform porous layer can be formed efficiently at low cost.

It is (a) schematic sectional drawing and (b) schematic side view which show an example of the embodiment of the anode of the anodizing apparatus of this invention. It is a schematic sectional drawing which shows an example of the embodiment of the anodizing apparatus of this invention. It is a block diagram which shows the other example of the embodiment of the anodizing apparatus of this invention. It is a block diagram which shows the other example of the embodiment of the anodizing apparatus of this invention. It is explanatory drawing for demonstrating the connection part of the conducting wire from a power supply at the time of using a to-be-processed substrate as an electrode, and a board | substrate. It is a graph which shows the platinum density | concentration in the wafer after an anodizing process measured in the Example and the comparative example, and the un-processed wafer. It is a graph which shows the in-plane distribution of the thickness of the porous layer formed in the wafer after the process measured in the Example. It is a graph which shows in-plane distribution of the thickness of the porous layer formed in the wafer after the process measured in the comparative example.

  Conventionally, as an electrode of an anodizing apparatus for forming a porous layer on a semiconductor wafer, a platinum electrode having resistance to an HF solution used as an electrolyte solution has been used. However, there has been a problem that the electrolyte solution is contaminated by immersing a metal electrode such as a platinum electrode, and the substrate is also contaminated by the metal. In addition, in an apparatus configured to flow an electric current by directly contacting an electrode to the substrate to be processed, if the electrode is brought into contact with the entire back surface of the substrate, the metal contamination is large and the substrate is likely to be damaged. Reduced scratches and direct contamination on the substrate. However, the present inventors have found that in this case, the in-plane distribution of the formed porous layer is deteriorated and the efficiency of forming the porous layer is also deteriorated.

In response to the above problems, when a non-metallic electrode such as carbon is simply used, the resistance is higher than that of the metal electrode, resulting in a large current loss. Also, the current to the substrate to be treated and the electrolyte solution is reduced. Since the flow becomes non-uniform, it is difficult to adjust the thickness and in-plane distribution of the porous layer.
Therefore, the present inventors have solved the problem of metal contamination and the in-plane distribution of the porous layer at the same time by making the electrode of the anodizing device cover the metal electrode member with a non-metal electrode member. The present invention has been completed by finding out what can be done.

  Hereinafter, the anodizing apparatus of the present invention will be described in detail as an example of an embodiment with reference to the drawings. However, the present invention is not limited to this.

  The anodizing apparatus of the present invention is an anodizing apparatus for forming a porous layer on a substrate to be processed disposed in an electrolyte solution by energizing between an anode and a cathode in the electrolyte solution, and the electrode is at least a metal The electrode member has a structure covered with a nonmetallic electrode member.

  Thus, in the anodizing apparatus, if the metal electrode member is an electrode covered with a non-metal electrode member, it is easy to dissolve the metal impurities in the electrolyte solution and contaminate the substrate to be processed. Can be effectively prevented. Further, since the metal electrode member is provided on the inner side, the electrolyte solution and the substrate to be processed can be energized uniformly with little loss of current, so that the formation efficiency of the porous layer is good. For this reason, when the electrode is brought into surface contact with the substrate, a porous layer having a uniform in-plane can be efficiently formed while preventing contamination. In addition, even when the electrode is brought into contact with the substrate to be processed, the substrate is hardly damaged because of contact with the non-metallic electrode member. Furthermore, the device of the present invention can be constructed at low cost because it is only necessary to replace the electrode with respect to the conventional device. Therefore, the anodizing treatment can be performed at a low cost.

In the anodizing apparatus, when the anode and cathode electrodes are immersed in the electrolyte solution, the electrode for the anodizing apparatus of the present invention has at least a portion immersed in the electrolyte solution. It is preferable to have a structure covered with a non-metallic electrode member.
Thus, if at least the portion immersed in the electrolyte solution is covered with the non-metallic electrode member, the metal electrode member does not come into contact with the electrolyte solution, so that metal contamination of the substrate can be prevented more reliably. .

Moreover, it is preferable that the anode of the anodizing apparatus of the present invention has a substrate holding mechanism that holds the substrate to be processed by bringing the nonmetallic electrode member of the anode into surface contact with the back surface of the substrate to be processed.
If it has such a substrate holding mechanism, when the substrate is held, it can come into surface contact with the electrode and the current can be evenly supplied in the substrate surface, so that the porous layer can be formed more uniformly in the surface. .

At this time, the metal electrode member of the anode electrode having the substrate holding mechanism preferably has a size corresponding to the entire back surface of the substrate to be processed to be held.
With a metal electrode member having such a size, uniform energization can be more reliably performed on the entire surface of the substrate to be processed, so that an in-plane uniform porous layer can be more reliably formed.

  Moreover, it does not specifically limit as a material of the metal electrode member of the electrode of this invention, Although any thing can be used, it can be set as either copper, aluminum, or platinum. These materials are widely used as electrode materials.

The material of the non-metallic electrode member of the electrode of the present invention is preferably any of silicon, carbon, and conductive resin.
The material of the non-metallic electrode member of the electrode of the anodizing apparatus of the present invention is preferably any of the above because it has resistance to HF solution or the like and can pass current well. Further, it is difficult for impurities to be deteriorated in electrical characteristics with respect to the substrate to be processed. In particular, when the electrode is brought into contact with the substrate, damage to the substrate can be more reliably prevented if the nonmetallic electrode member is a conductive resin.

Here, the anodizing apparatus of the present invention will be described more specifically with reference to FIGS. 1A is a schematic sectional view showing an example of an embodiment of an anode of an anodizing apparatus of the present invention, and FIG. 1B is a schematic side view thereof. FIG. 2 is a schematic view showing an example of an embodiment of the anodizing apparatus of the present invention using the anode shown in FIG.
As shown in FIG. 1, the anode 1a of the electrode for an anodic oxidation apparatus of the present invention uses, for example, a silicon single crystal as the nonmetallic electrode member 11, and the silicon single crystal substrate in which the metal electrode member 10 is the nonmetallic electrode member 11. The structure is sandwiched between and covered. Here, as a substrate holding mechanism of the anode 1a, the substrate to be processed W can be fitted into a concave portion having a shape corresponding to the substrate to be processed W as shown in FIG. It has become. Since the area of the internal metal electrode member 10 is larger than that of the substrate to be processed W, the entire surface of the substrate W can be energized uniformly, and the metal electrode member 10 is connected to a connection portion 15 with a lead wire from a power source located above. . As the material of the connection portion 15, the same material as that of the metal electrode member 10 can be used. Here, the shape of the metal electrode member 10 is not particularly limited, and may be a circular shape, a lattice shape, or the like. Further, when a silicon single crystal is used as the non-metallic electrode member 11, a desired porous layer is formed on the substrate to be processed by using a P-type or N-type silicon single crystal having a resistivity of several tens of mΩcm to several tens of Ωcm. can do.

The anodizing apparatus 2 of the present invention shown in FIG. 2 has the anode 1a and the cathode 1b shown in FIG. 1 fixed to the carrier 12 in the tank 13, and the substrate W to be processed is completely immersed. Until the tank 13 is filled with an electrolyte solution 14 such as an HF solution. As the cathode 1b, a cathode having the same structure as the above-described anode 1a, but having no recess for holding the substrate can be used. This eliminates metal contamination from the cathode. The material of the carrier 12 and the tank 13 is not particularly limited as long as the material has resistance to the electrolyte solution. For example, a fluororesin, a vinyl chloride resin, or the like can be used.
As shown in FIG. 2, the electrodes are arranged, and the connection portion 15 of both the anode 1 a and the cathode 1 b is connected to a power source and a current flows, so that the substrate is directed to the cathode side of the substrate W held on the anode. A porous layer is formed on the surface.

Here, the anodic oxidation apparatus of the present invention is not limited to the apparatus having the structure shown in FIGS. 1 and 2, and for example, an anodic oxidation having a structure as shown in FIGS. 3 (a), (b), (c) and FIG. It can be a device.
The anodic oxidation apparatus shown in FIG. 3A has a structure in which the anode 1a and the cathode 1b are immersed in the electrolyte solution 14, and the anode 1a and the substrate W to be processed are brought into direct contact with each other to pass a current. This structure is the same as that shown in FIGS. In this case, it is preferable to use the electrode of the present invention having a structure in which at least the anode 1a is covered with a non-metallic electrode member. More preferably, both electrodes are electrodes according to the present invention.

  In the structure of FIG. 3A, the substrate W itself can be used as the anode 1a, and the electrode of the present invention can be used only for the cathode 1b. In this case, the upper part of the substrate to be processed W is connected to a lead wire from the power source. As a connection method at this time, for example, as shown in FIG. 5, the upper portion of the substrate W to be processed and the metal connection member 20 are sandwiched between the silicon members 21 from both sides, and a protective rubber 22 is wound around the silicon member 21. The protective rubber 22 also serves to protect the metal connecting member 20 from contact with the electrolyte solution.

  Next, the anodizing apparatus shown in FIG. 3B fixes the substrate to be processed W and the tank placed on the anode 1a through the O-ring 16, and the cathode 1b in the electrolyte solution 14 as the substrate to be processed. This is a structure arranged to face W. In the anodic oxidation apparatus having such a structure, since the anode 1a does not contact the electrolyte solution, it is possible to cover only the surface in contact with the substrate W to be processed with a nonmetallic electrode member. On the other hand, since the cathode 1b is immersed in an electrolyte solution, an electrode in which the metal electrode member of the present invention is covered with a nonmetal electrode member is used.

Next, in the anodic oxidation apparatus shown in FIG. 3C, the substrate W to be processed is disposed between the anode 1a and the cathode 1b, and the substrate W is attached to the O-ring 16 so that the electrolyte solution cannot move to the opposite side. It is a structure fixed via. In this case, both electrodes 1a and 1b are electrodes for the anodizing device of the present invention.
In addition, the substrates to be processed W can be arranged side by side as shown in FIG. 4 so that a large number of substrates to be processed W can be processed with the same structure.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Examples and comparative examples)
With the anodizing apparatus having the structure shown in FIG. 3A, a porous layer was formed for each of four silicon wafers in the example and the comparative example. The electrodes used in the examples were platinum as a metal electrode member for both the anode and the cathode, and silicon as a non-metal electrode member, and the electrodes of the present invention shown in FIGS. In the comparative example, a platinum electrode was used for both the anode and the cathode without using a non-metal electrode member, and the anode platinum electrode was brought into point contact at a position 60 mm above the center of the silicon wafer to be processed.
The silicon wafer to be processed in the examples and comparative examples was a PW (Polished Wafer) having a diameter of 6 inches (15 cm) and p + (0.01 to 0.02 Ωcm).

As anodizing conditions, treatment was performed in an electrolyte solution (HF: EtOH (ethanol): H ₂ O = 1: 1: 1) at a current of 1.7 A and 720 sec.
The thickness of the porous layer formed by the above processing is 5 locations in total, 37.5 (-37.5) mm and 60.0 (-60.0) mm in the wafer center position (0.0) and in the vertical direction. Measured with The measurement results are shown in FIG. 7 (Example) and FIG. 8 (Comparative example).
Moreover, the platinum concentration in the processed wafer was measured by the total dissolution method. For reference, the platinum concentration in an untreated wafer that was not anodized with four silicon wafers under the same conditions was measured by the total dissolution method. The measurement results are shown in FIG.

As can be seen from FIGS. 7 and 8, although the anodization was performed under the same conditions, the thickness of the formed porous layer was more than twice as large in the example as compared with the comparative example. This is thought to be because the current density per unit area of the example could be increased compared to the comparative example. Further, as shown in FIG. 7, the in-plane distribution of the porous layer is good in the example, and in the comparative example shown in FIG. 8, the porous material at the position where the electrode of the wafer is in point contact (60 mm from the wafer center). The layer became extremely thick compared to the other positions, and the in-plane distribution deteriorated.
Further, as shown in FIG. 6, in the comparative example, the platinum concentration in the wafer becomes high, and in the example, it is equivalent to the untreated wafer, and it is understood that no contamination is caused by the process in the example.

  From the above, it was found that the anodizing apparatus of the present invention can efficiently form a porous layer having a uniform in-plane surface while preventing metal contamination.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

DESCRIPTION OF SYMBOLS 1a ... Anode, 1b ... Cathode, 2 ... Anodizing apparatus, 10 ... Metal electrode member,
11 ... Non-metallic electrode member, 12 ... Carrier, 13 ... Tank,
14 ... electrolyte solution, 15 ... connection part, 16 ... O-ring,
20 ... Metal connecting member, 21 ... Silicon member, 22 ... Protective rubber,
W: Substrate to be processed.

Claims (6)

  An anodic oxidation apparatus for forming a porous layer on a substrate to be processed disposed in an electrolyte solution by energizing at least between an anode electrode and a cathode electrode in the electrolyte solution, wherein the electrode has at least a metal electrode member An anodizing device having a structure covered with a metal electrode member.   The anode and cathode electrodes are immersed in an electrolyte solution, and the electrode has a structure in which at least a portion of the electrode immersed in the electrolyte solution is covered with the nonmetallic electrode member. The anodizing device according to claim 1, wherein the anodizing device is provided.   2. The substrate according to claim 1, wherein the anode electrode has a substrate holding mechanism for holding the substrate to be processed by bringing the non-metallic electrode member of the anode into surface contact with the back surface of the substrate to be processed. Item 3. The anodizing apparatus according to Item 2.   4. The anodizing apparatus according to claim 3, wherein the metal electrode member of the anode electrode having the substrate holding mechanism has a size corresponding to the entire back surface of the substrate to be processed.   The material of the said metal electrode member is copper, aluminum, or platinum, The anodizing apparatus as described in any one of Claim 1 thru | or 4 characterized by the above-mentioned.   The anodizing apparatus according to any one of claims 1 to 5, wherein a material of the non-metallic electrode member is any one of silicon, carbon, and conductive resin.

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