JP2000349066A - Method for producing semiconductor substrate and solar cell and anodizing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor substrate and a thin-film crystal solar cell having good characteristics with less cracks and cracks efficiently and to provide a mass-produced high-quality semiconductor substrate and a method of manufacturing a solar cell. is there. SOLUTION: In a method for manufacturing a semiconductor substrate and a solar cell obtained by peeling a thin film crystalline semiconductor layer formed on a first substrate and transferring it to a second substrate, a method for manufacturing a semiconductor device in a peripheral portion of the first substrate is described. A method for manufacturing a semiconductor substrate and a solar cell, wherein the thin film crystalline semiconductor layer is removed by etching by electrolytic polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor substrate and a solar cell, and an anodizing apparatus suitable for forming the same. More particularly, the present invention relates to a semiconductor substrate and a solar cell having a thin film crystal laminated on a low-cost substrate. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Solar cells have been widely studied as power sources that are system-connected to driving energy sources of various devices and commercial power.

[0003] For a solar cell, it is desired that an element can be formed on a low-cost substrate from the viewpoint of cost. On the other hand, silicon is generally used as a semiconductor constituting a solar cell. Above all, from the viewpoint of efficiency of converting light energy into electromotive force, that is, photoelectric conversion efficiency, single crystal silicon is the best, but from the viewpoint of large area and low cost, amorphous silicon is considered to be advantageous. I have. In recent years, the use of polycrystalline silicon has been studied for the purpose of obtaining low cost comparable to amorphous silicon and high energy conversion efficiency comparable to single crystal.

[0004] However, in the method conventionally proposed for such a single crystal or polycrystalline silicon, since a bulk crystal is sliced into a plate-like substrate, its thickness is reduced to 0.3 m.
m or less. Therefore, the substrate has a thickness greater than necessary to sufficiently absorb the light amount,
Effective utilization of materials was not sufficient. That is, in order to reduce the cost, it is necessary to further reduce the thickness. Recently, a method of forming a silicon sheet by a spin method in which molten silicon droplets are poured into a mold has been proposed, but the thickness is at least about 0.1 mm to 0.2 mm, which is necessary for light absorption as crystalline silicon. Sufficient film thickness (20 μm
(.About.50 .mu.m).

[0005]

In order to achieve high energy conversion efficiency and low cost, a thin film epitaxial layer grown on a single crystal silicon substrate is separated (peeled) from the substrate and used for a solar cell. Attempts to achieve have been proposed (Milncs, AG and Feu).
cht, D .; L, "Peeled Film Tech
nology Solar Cells ”, IEEE P
photovoltaic Specialist Co
mference, p. 338, 1975).

However, according to this method, the SiG is placed between the single crystal silicon serving as the substrate and the grown epitaxial layer.
It is necessary to insert the intermediate layer e and perform heteroepitaxial growth, and then selectively melt this intermediate layer to peel off the grown layer. In general, when heteroepitaxial growth is performed, defects are likely to be induced at the growth interface because of different lattice constants. In addition, it cannot be said that it is advantageous in terms of process cost in that different materials are used.

A method disclosed in US Pat. No. 4,816,420, that is, a sheet-like crystal is formed on a crystal substrate by a selective epitaxial growth and a lateral growth method through a mask material and then separated from the substrate. It has been shown that a thin-film crystalline solar cell can be obtained by the method for manufacturing a solar cell characterized in that:

However, in this method, the openings provided in the mask material are linear. To separate a sheet-like crystal grown by selective epitaxial growth and lateral growth from the line seed, it is necessary to form the crystal. When the shape of the line seed is larger than a certain size because the film is mechanically peeled by using the cleavage, the ground contact area with the substrate increases, so that the sheet crystal is damaged during the peeling. In particular, when increasing the area of a solar cell, the above-described method is practically difficult if the line length is several mm to several cm or more, no matter how narrow the line width is (actually around 1 μm). Becomes

In view of the above, a porous silicon layer is formed on the surface of a silicon wafer by anodization and then separated, and the separated porous layer is fixed on a metal substrate to form an epitaxial layer on the porous layer. It has been shown that a thin-film crystal solar cell having good characteristics can be manufactured by using the thin film crystal solar cell formed by using the thin film crystal solar cell (JP-A-6-45622). However, also in this method, since the metal substrate is exposed to a high-temperature process, there remains a problem that impurities are mixed in the epitaxial layer and characteristics are limited.

On the other hand, there has been disclosed a method in which an epitaxial growth layer is formed on a porous silicon layer, and then the porous silicon layer is broken to separate the epitaxial layer and transfer it to another substrate. (JP-A-7-30288)
No. 9). Furthermore, a method of forming a thin-film crystal solar cell on a plastic substrate by the same method has been disclosed (JP-A-8-213645). Japanese Patent Laid-Open No. Hei 10-23 discloses a technique for transferring an epitaxial layer onto a film by applying a certain force by utilizing the flexibility of the film.
No. 3352.

In these cases, for example, when an external force is applied in the direction of peeling as shown in FIG. After reaching the porous layer, it was necessary to separate at the porous layer. In addition, even when there is no epitaxial layer as shown in FIG. 8, when an external force is applied in the peeling direction, it is necessary to break the porous layer surface in the same manner and reach a dangerous portion in the porous layer. In any case, due to the impact at the time of rupture in the peripheral portion, the rupture did not follow the ideal separation line indicated by 707 or 807, and fine cracks or cracks were sometimes formed in the epitaxial layer. Also, instead of applying a direct external force such as pulling, the internal force (internal stress) in the porous layer or the epitaxial layer or between these and the substrate, heat from the outside, ultrasonic waves, electromagnetic waves, centrifugal force, etc. In the case of peeling by applying force indirectly to the dangerous part in the porous layer using energy such as force, when the peripheral part of the base inhibits smooth separation and cracks and cracks occur as described above was there.

Such cracks and cracks not only make it difficult to handle in the subsequent steps, but also extend to the central part, greatly affecting the characteristics and yield of devices such as solar cells. Affect.

An object of the present invention is to provide a method of manufacturing a semiconductor substrate on which a device having good characteristics can be formed.

Another object of the present invention is to provide a high-performance semiconductor device which can be mass-produced by forming a thin-film crystalline semiconductor layer on a film substrate.

Still another object of the present invention is to provide an inexpensive solar cell by separating an epitaxial layer formed on a crystal substrate to obtain a solar cell and reusing the crystal substrate.

[0016]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and has been completed as a result of intensive studies by the present inventors to achieve the above object. The present invention relates to a method for manufacturing a substrate and a solar cell and an anodizing apparatus suitable for forming the same.

That is, a method of manufacturing a semiconductor substrate according to the present invention is directed to a method of manufacturing a semiconductor substrate obtained by peeling a thin film crystalline semiconductor layer formed on a first substrate and transferring it onto a second substrate. A method of manufacturing a semiconductor substrate in which the thin-film crystal semiconductor layer in the peripheral portion of the first substrate is removed by etching by electrolytic polishing, and a peeling layer is provided between the first substrate and the thin-film crystal semiconductor layer; This is a method of manufacturing a semiconductor substrate in which only a thin film crystalline semiconductor layer, only a peeling layer, or a thin film crystalline semiconductor layer and a peeling layer are removed at a peripheral portion of one substrate.

Another method of manufacturing a semiconductor substrate according to the present invention is a method of manufacturing a semiconductor substrate using a thin-film crystalline semiconductor layer, wherein (1) anodizing at least the main surface of the first substrate to form a porous substrate. Forming a porous layer, (2) forming a semiconductor layer on the porous material, and (3) removing a semiconductor layer in a peripheral portion of the first base by electrolytic polishing by etching. (4) a step of bonding a second substrate to the surface of the semiconductor layer; and (5) the semiconductor layer and the first substrate are separated and transferred to the second substrate via the porous layer. And (6) treating the surface of the first substrate after the peeling and repeating the steps (1) to (5) again.

The method for manufacturing a solar cell according to the present invention is characterized in that the thin film crystalline semiconductor layer formed on the first substrate is peeled off and transferred onto a second substrate, A method for manufacturing a solar cell in which the thin film crystal semiconductor layer in the peripheral portion of the base is removed by etching by electrolytic polishing, and a peeling layer between the first base and the thin film crystal semiconductor layer, wherein the first This is a method for manufacturing a solar cell in which only a thin film crystalline semiconductor layer, only a peeling layer, or a thin film crystalline semiconductor layer and a peeling layer are removed at a peripheral portion of a base.

Another method of manufacturing a solar cell according to the present invention is a method of manufacturing a solar cell using a thin-film crystalline semiconductor layer, wherein (1) anodizing at least the main surface of the first substrate to form a porous film. Forming a porous layer, (2) forming a semiconductor layer on the porous material, and (3) removing a semiconductor layer in a peripheral portion of the first base by electrolytic polishing by etching. (4) a step of forming a surface antireflection layer of a porous layer on the surface of the semiconductor layer other than the peripheral portion of the first substrate; and (5) a step of bonding a second substrate to the surface of the semiconductor layer. (6) a step of separating the semiconductor layer and the first base via the porous layer and transferring the separated semiconductor layer and the first base to the second base; and (7) treating the surface of the first base after the separation. And repeating the steps (1) to (6) again. That.

Further, the anodizing apparatus according to the present invention further comprises a first electrode in contact with the back surface of the substrate at a peripheral portion of the substrate to be anodized, and a second electrode supporting the first electrode with the substrate interposed therebetween. An anodizing apparatus comprising an electrode, wherein the first electrode and the second electrode have substantially the same shape.

In another anodizing apparatus of the present invention, a first electrode in contact with the back surface of a base is provided at a peripheral portion of the base to be anodized, and a first electrode facing the first electrode with the base interposed therebetween. In the remaining base region excluding the peripheral portion, including a second electrode, a third electrode in contact with the back surface of the base, and a fourth electrode facing the third electrode across the base, An anodizing apparatus in which the first electrode and the second electrode, and the third electrode and the fourth electrode have substantially the same shape.

Further, the method of manufacturing a semiconductor substrate and a solar cell according to the present invention is a method of manufacturing a thin film semiconductor substrate and a solar cell in which a thin film crystalline semiconductor layer is peeled into an arbitrary shape by electrolytic polishing etching.

According to the method for manufacturing a semiconductor substrate and a solar cell of the present invention, after forming a thin film semiconductor layer on a porous layer,
By removing part or all of the thin film semiconductor layer and the porous layer to the periphery of the separation region before bonding to the supporting substrate to be transferred, the film can be directly formed in the porous layer (the interface with the substrate or the semiconductor layer). ) Can be efficiently applied to the parts that are easy to separate, so that the thin film semiconductor layer can be separated without destruction such as cracking or cracking, and a thin film semiconductor substrate or a solar cell with excellent characteristics and good yield can be obtained. Can be.

[0025]

Embodiments of the present invention will be described below in detail.

(Embodiment 1) As an example of an embodiment according to the present invention, a method for manufacturing a semiconductor substrate will be described with reference to FIG.

As shown in FIG. 1A, B (boron) is first introduced into the surface layer of the silicon single crystal substrate 101 by thermal diffusion, ion implantation, or mixing during wafer preparation. By anodizing the single crystal substrate having the surface layer 102 of p ⁺ in, for example, an HF solution, p
^{+ The} surface layer 102 is made porous to form a porous layer 103 (FIG. 1B). At this time, after a certain period of time has elapsed at the low current level, the structure in the porous layer is preliminarily changed in density by making the porous layer porous by rapidly raising the current level to a high current level and shortening the time. This makes it easier to separate the silicon layer 104 from the silicon single crystal substrate 101 later.

Next, a silicon layer 104 is formed on the porous surface layer 103 by, for example, a thermal CVD method (FIG. 1C). At this time, the p ^- type (or n ^- type) of the silicon layer can be controlled by mixing a small amount of dopant during the formation of the silicon layer 104.

The silicon single crystal substrate 101 is attached to a predetermined position in the anodizing apparatus shown in FIG.
4 is opposed to the negative electrode 504 in the HF solution.
At this time, the negative electrode 504 has substantially the same shape as the positive electrode 505 that is in contact with the back surface of the silicon single crystal substrate 101, and extends along the periphery of the silicon single crystal substrate 101, for example, as shown in FIG.
It has a band-like ring or polygonal shape. A current is passed between the electrodes to perform etching in an electrolytic polishing mode, and the silicon layer 1 around the silicon single crystal substrate 101 is etched.
04 or a part or all of the silicon layer 104 and the porous layer 103 is removed. In this case, depending on the separation strength of the porous layer, only the silicon layer 104 and the silicon layer 1
04 and a part of the porous layer 103 or the silicon layer 104
And removal of the entire porous layer can be selected.

Further, as shown in FIG.
04 does not completely cover the porous layer 103 and the porous layer 1
When 03 is exposed on the surface of the substrate 101, part or all of the exposed porous layer 103 is removed (FIG. 1D).

After an oxide film 106 is formed on the surface of the silicon layer 104, the support substrate 105 is bonded to the oxide film 106, placed in a heat treatment furnace (not shown), and heated.
05 and the silicon single crystal substrate 101 (FIG. 1
(E)).

Next, a force is applied between the support substrate 105 and the silicon single crystal substrate 101 in a direction in which they are separated from each other.
Separation occurs at the portion of the porous layer 103 (FIG. 1F).

The porous layer 103a remaining on the silicon layer 104 separated from the silicon single crystal substrate is selectively removed. An ordinary silicon etchant, a hydrofluoric acid that is a selective etchant for porous silicon, a mixed solution of at least one of alcohol and hydrogen peroxide added to hydrofluoric acid, or a buffered hydrofluoric acid or Electroless wet chemical etching of porous silicon only using a mixture of buffered hydrofluoric acid and at least one of alcohol and hydrogen peroxide, or at least one of alkaline solutions such as KOH, NaOH, and hydrazine (See FIG. 1).
(G)). The support substrate to which the silicon layer has been transferred may be used as it is as a semiconductor substrate, or the silicon layer may be transferred again to a third substrate suitable for a product as occasion demands.

In the silicon single crystal substrate 101, the porous layer 103b remaining on the surface is removed in the same manner as described above, and if necessary, if the surface flatness is unacceptably rough. After surface flattening (Fig. 1
(H)), it is again subjected to the step of FIG.

(Embodiment 2) As an example of another embodiment according to the present invention, a method of manufacturing a thin film crystal solar cell is shown in FIG.
This will be described with reference to FIG.

As shown in FIG. First, B (boron) is introduced into the surface layer of the silicon single crystal substrate 201 by thermal diffusion, ion implantation, or infiltration during wafer preparation. By anodizing the single crystal substrate having the surface layer 202 of p ⁺ in, for example, an HF solution, p
^{+ The} surface layer 202 is made porous to form a porous layer 203 (FIG. 2B). At this time, after a certain period of time has elapsed at the low current level, the structure in the porous layer is preliminarily changed in density by making the porous layer porous by rapidly raising the current level to a high current level and shortening the time. Is possible,
Thus, the silicon layer 204 can be easily separated from the silicon single crystal substrate 201 later.

Next, a silicon layer 204 is formed on the porous surface layer 203 by, for example, a thermal CVD method (FIG. 2C). At this time, it is possible to control the silicon layer to be p ^- type (or n ^- type) by mixing a small amount of dopant when forming the silicon layer 204.
A p ⁺ layer (or n ⁺ layer) 205 on the silicon layer 204
Is formed by plasma CVD or by increasing the amount of dopant at the end of the formation of the silicon layer 204 (FIG. 2D).

The silicon single crystal substrate 201 is mounted at a predetermined position in the anodizing apparatus shown in FIG.
4 and 205 are opposed to the negative electrode 504 in the HF solution. At this time, the negative electrode 504 has substantially the same shape as the positive electrode 505 in contact with the back surface of the silicon single crystal substrate 201, and extends along the periphery of the silicon single crystal substrate 201.
For example, it has a band-like ring or polygonal shape as shown in FIG. Etching is performed in an electrolytic polishing mode by passing a current between the electrodes, and silicon layers 204 and 205 or silicon layers 204 and 20 around the silicon single crystal substrate 201 are etched.
5 and part or all of the porous layer 203 are removed. In this case, any one of the silicon layers 204 and 205, a part of the silicon layers 204 and 205 and the porous layer 203, or the removal of the silicon layers 204 and 205 and the entire porous layer is performed according to the separation strength of the porous layer. You can choose.

Further, as shown in FIG.
When the porous layers 203 and 04 and 205 do not completely cover the porous layer 203 and are exposed on the surface of the silicon single crystal substrate 201, a part or all of the exposed porous layer 203 is removed. Removal is performed (FIG. 2E).

A polymer film substrate 206 on which a silver paste is printed in advance as a back electrode 207 is closely attached to the silicon single crystal substrate 201 on the side where the silicon layers 204 and 205 are formed, and an oven (not shown) ) And heated to fix the polymer film substrate 206 and the silicon single crystal substrate 201 (FIG. 2F).

Next, a force is applied between the polymer film substrate 206 and the silicon single crystal substrate 201 in a direction to separate them from each other. That is, the two are gradually peeled off from the edge of the silicon single crystal substrate 201 by utilizing the flexibility of the polymer film, and separated at the porous layer 203 (FIG. 2).
(G)).

The porous layer 203a remaining on the silicon layer 204 separated from the silicon single crystal substrate is selectively removed. Normal silicon etchant, hydrofluoric acid, which is a selective etchant for porous silicon, or a mixture of hydrofluoric acid and at least one of alcohol and hydrogen peroxide, or buffered hydrofluoric acid or buffered Electroless wet chemical etching of only porous silicon is performed using at least one of a mixture of hydrofluoric acid and at least one of alcohol and hydrogen peroxide or an alkaline solution such as KOH, NaOH, or hydrazine.

The silicon layer 204 from which the porous layer has been removed
N on the surface by plasma CVD ⁺(P⁺) Layer 208
Formed, and a transparent conductive layer that also serves as a surface anti-reflection layer
The film (ITO) 209 and the grid-like current collecting electrode 210
Vacuum evaporation is performed to form a solar cell (FIG. 2 (h)).

In the silicon single crystal substrate 201, the porous layer 203b remaining on the surface is removed in the same manner as described above, and if necessary, if the surface flatness is unacceptably rough, After performing surface flattening (Fig. 2
(I)) is again provided to the step of FIG.

(Embodiment 3) As a further embodiment of the present invention, a method of manufacturing a thin-film crystal solar cell will be described with reference to FIG.

As shown in FIG. 3A, B (boron) is first introduced into the surface layer of the silicon single crystal substrate 301 by thermal diffusion, ion implantation, or mixing during wafer preparation. By anodizing the single crystal substrate having the surface layer 302 of p ⁺ in, for example, an HF solution, p
^{+ The} surface layer 302 is made porous to form a porous layer 303 (FIG. 3B). At this time, after a certain period of time has elapsed at the low current level, the structure in the porous layer is preliminarily provided with sparse and dense changes by increasing the current level to a high current level and shortening the time to form a porous layer. This allows the silicon layer 304 to be later
01 can be easily separated.

Next, a silicon layer 304 is formed on the porous surface layer 303 by, for example, a thermal CVD method (FIG. 3C). At this time, the p ^- type (or n ^- type) of the silicon layer can be controlled by mixing a small amount of dopant during the formation of the silicon layer 304.
An n ⁺ layer (or p ⁺ layer) 305 on the silicon layer 304
Is formed by plasma CVD or by changing the type and amount of dopant at the end of the formation of the silicon layer 304 (FIG. 3D).

The silicon single crystal substrate 301 is attached to a predetermined position in the anodizing apparatus shown in FIG.
4 and 305 face the negative electrodes 604 and 606 in the HF solution. At this time, the negative electrodes 604 and 606
Has substantially the same shape as the positive electrodes 605 and 607 that are in contact with the back surface of the silicon single crystal substrate 301, and the electrodes 604 and 605 extend along the peripheral portion of the silicon single crystal substrate 301, for example, as shown in FIG. The electrodes 606 and 607 are located inside the electrodes 604 and 605, respectively, in a region other than the peripheral portion of the silicon single crystal substrate 301. For example, as shown in FIG. It has a polygonal shape.

A relatively high current is applied between the electrodes 604 and 605 to perform etching in the electrolytic polishing mode, and the silicon layers 304 and 3 around the silicon single crystal substrate 301 are etched.
05 or silicon layers 304 and 305 and porous layer 3
03 is partially or entirely removed. In this case, only the silicon layers 304 and 305, a part of the silicon layers 304 and 305 and the porous layer 303, or the silicon layers 304 and 305 and the porous layer 303 depending on the separation strength of the porous layer.
Either of the total removals can be selected.

Further, as shown in FIG.
When the porous layer 303 is not completely covered with the layers 04 and 305 and the porous layer 303 is exposed on the surface of the substrate 301, part or all of the exposed porous layer 303 is removed. . A relatively low current is passed between the electrodes 604 and 605 to perform normal anodization, and the silicon single crystal substrate 3
The thin porous layer 309 is formed on the surface of the silicon layer 304 other than the peripheral region of No. 01 to form an anti-reflection layer (FIG. 3).
(E)). At this time, the step of removing the peripheral silicon layer and the porous layer and the step of forming the porous layer on the surface of the silicon layer other than the peripheral region may be performed simultaneously or separately.

The grid electrode 31 is provided on the surface of the porous layer 309.
After forming the polymer film substrate 0, the polymer film substrate 306 is attached to the side of the silicon single crystal substrate 301 on which the silicon layers 304 and 305 are formed with an adhesive 307, and is heated in an oven (not shown). The molecular film substrate 306 and the silicon single crystal substrate 301 are fixed (FIG. 3
(F)).

Next, the fixed transparent polymer film substrate 306 and the silicon single crystal substrate 301 are put in a water tank and ultrasonic waves are applied (not shown). Thus, the silicon layer 304 is separated from the silicon single crystal substrate at the portion of the porous layer 303 (FIG. 3G).

The porous layer 303a remaining on the back surface of the silicon layer 304 peeled from the silicon single crystal substrate is selectively removed. Normal silicon etchant, hydrofluoric acid as a selective etchant for porous silicon, or a mixture of hydrofluoric acid and at least one of alcohol and hydrogen peroxide, or buffered hydrofluoric acid or buffer Electroless wet chemical etching of only porous silicon is performed by using at least one of a mixed solution obtained by adding at least one of alcohol and hydrogen peroxide solution to dihydrofluoric acid, or an alkaline solution such as KOH, NaOH, and hydrazine. .

The silicon layer 304 from which the porous layer has been removed
P on the back side by plasma CVD ⁺(N⁺) Layer 308
Formed and vacuum-deposited the back electrode 311 to form a solar cell
(FIG. 3 (h)). At this time, if necessary, the back electrode 311
In contact with another support substrate (metal substrate) via conductive adhesive
It may be pasted.

The silicon single crystal substrate 301 has the porous layer 303b remaining on the surface removed in the same manner as described above, and if necessary, when the surface flatness is unacceptably rough. After the surface is flattened (Fig. 3
(I)) is again provided to the step of FIG.

As described above, according to the present invention, after the thin film semiconductor layer is formed on the porous layer, the thin film semiconductor layer and the porous layer around the separation area before being bonded to the supporting substrate to be transferred. By removing, the force can be efficiently applied directly to the easily separated portion in the porous layer (including the interface with the base and the semiconductor layer), so that the thin film semiconductor layer is not affected by cracks and cracks. Separation can be achieved, and a thin film semiconductor substrate having excellent characteristics and good yield can be obtained.

Further, according to the present invention, after the thin film semiconductor layer is formed on the porous layer, the thin film semiconductor layer and the porous layer around the separation area are removed before the thin film semiconductor layer is bonded to the transfer base. By forming an anti-reflection layer on the surface of the thin-film semiconductor layer in the area to be separated, the thin-film semiconductor layer on which the anti-reflection layer has been formed without cracks and cracks in the peripheral portion can be separated, and the process can be performed. It is possible to obtain a thin film semiconductor substrate having excellent simplified characteristics.

The hydrofluoric acid solution is used in the anodization method for forming the porous layer serving as the separation layer used in the present invention.
When the F concentration is 10% by weight or more, it can be made porous. The amount of current to flow during anodization is appropriately determined depending on the HF concentration, the desired thickness of the porous layer, the state of the surface of the porous layer, and the like, but is approximately several mA / cm ² to several tens mA /
A range of cm ² is appropriate. By changing the current level in the middle, it is possible to provide a change in density in the structure in the porous layer, and it is easy to separate the porous structure into two or more layers.

By adding an alcohol such as ethyl alcohol to the HF solution, bubbles of the reaction gas generated during anodization can be instantaneously removed from the reaction surface without stirring, and porous silicon can be formed uniformly and efficiently. can do. The amount of the alcohol to be added is appropriately determined depending on the HF concentration, the desired thickness of the porous layer or the surface state of the porous layer, and it is particularly necessary to carefully determine that the HF concentration does not become too low.

Further, in the anodization apparatus used in the present invention for forming an anti-reflection layer on the surface of a semiconductor layer other than the peripheral portion by etching the semiconductor layer in the peripheral portion, there is provided a method for forming an anti-reflection layer between the peripheral portion removing electrodes. The power applied between the electrodes is
It is preferable that each is controlled independently. As the electrode shape, a shape conforming to the shape of the substrate to be processed as shown in FIGS. 9 and 10 is preferably used, and the electrode for forming the antireflection layer is arranged so as to be inside the electrode for removing the peripheral portion. Preferably. In some cases, for example, the shape of a square as shown in FIG. 11 and FIG. 12 may be used as an electrode for removing a peripheral portion, and the shape substantially corresponding to the square may be used as an anti-reflection layer. It can also be used for electrodes.
By using such an electrode shape, a square semiconductor layer can be separated from a round wafer-shaped substrate. Although there is no particular limitation on the anode side as the electrode material, it is preferable that the cathode side be resistant to acids such as HF, and platinum is optimally used.

In order to increase the independence of the current control between the electrode for removing the peripheral portion and the electrode for forming the anti-reflection layer, an isolator (cross-sectional shape is shown in FIG. (According to the electrode).

The distance between the substrate to be processed and the electrode on the cathode side is not particularly specified, but the electrode for removing the peripheral portion is arranged at a position as close to the substrate as possible for the purpose of reducing the loss since a relatively high current flows. In addition, it is preferable that the distance between the electrodes is shorter than that of the anti-reflection layer forming electrode, but any distance may be used for the anti-reflection layer forming electrode (see FIGS. 4 to 6).

The conditions for setting the electrolytic polishing mode for etching the semiconductor layer and the porous layer in the peripheral portion are as follows. When silicon is etched using a hydrofluoric acid solution, the HF concentration is 20% by weight or less. Is possible. For the dilution of HF, an electrical conductivity imparting agent such as an alcohol such as ethyl alcohol, water, an acid or a salt thereof can be used. The amount of current flowing at this time is appropriately determined depending on the HF concentration.
The approximate range of 10mA / cm ² ~100mA / cm ² is appropriate.

In the present invention, the crystal growth method used for forming the silicon layer on the porous layer includes thermal CVD, LPC
There are a VD method, a sputtering method, a plasma CVD method, a photo CVD method, a liquid phase growth method, and the like. For example, thermal CVD, LPCV
Source gases used in the case of a vapor phase growth method such as a D method, a plasma CVD method, or a photo CVD method include SiH ₂ Cl ₂ ,
SiCl ₄ , SiHCl ₃ , SiH ₄ , Si ₂ H ₆ , SiH ₂
Representative examples include silanes such as F ₂ and Si ₂ F ₆ and halogenated silanes.

In addition, hydrogen (H ₂ ) is added to the above-mentioned raw material gas in order to obtain a reducing atmosphere for promoting crystal growth as a carrier gas. The ratio of the amount of the raw material gas to the amount of hydrogen is appropriately determined as desired depending on the forming method, the type of the raw material gas, and the forming conditions, and preferably 1:10 to 1: 1000 (introduction flow ratio). More preferably, the ratio is set to 1:20 to 1: 800.

When liquid phase growth is used, silicon is dissolved in a solvent such as Ga, In, Sb, Bi, Sn, etc. in an H ₂ or N ₂ atmosphere, and the solvent is gradually cooled or a temperature difference is caused in the solvent. To perform epitaxial growth.

The temperature and the pressure in the epitaxial growth method used in the present invention vary depending on the forming method and the kind of the raw material (gas) to be used, but the temperature is, for example, silicon growth by a normal thermal CVD method. In this case, the temperature is suitably from about 800 ° C. to 1250 ° C., and more preferably from 850 ° C. to 1200 ° C. In the case of the liquid phase growth method, depending on the kind of the solvent, when the silicon is grown using Sn or In as the solvent, 600 is used.
It is desirable that the temperature be controlled at from 10 ° C to 1050 ° C. Plasma C
In a low-temperature process such as the VD method, the temperature is generally 200 ° C. to 600 ° C., more preferably, 200 ° C. to 500 ° C.

Similarly, the pressure is generally about 10 ^-2 Torr.
~ 760 Torr is appropriate, and more preferably 10 ^-1.
A range of Torr to 760 Torr is desirable.

In the method of the present invention, the substrate on which the thin-film crystalline semiconductor layer is transferred may be any rigid or flexible substrate. For example, silicon wafer, S
Examples include a US plate, a glass plate, a plastic or resin film, and the like. As the resin film material, a polymer film or the like is suitably used, and typical examples thereof include a polyimide film, EVA (ethylene vinyl acetate), and Tefzel.

In the method of the present invention, as a method of bonding the substrate and the thin film crystalline semiconductor layer, a conductive metal paste such as a copper paste or a silver paste, and a glass frit mixed with the conductive metal paste. It is preferable to use a method in which an adhesive or an epoxy-based adhesive is inserted between the two to make them adhere to each other, and then baked and fixed. In this case, the metal such as copper or silver after sintering also functions as a back surface electrode and a back surface reflection layer. In the case of a substrate such as a polymer film, the substrate and the thin film crystalline semiconductor layer are brought into close contact with each other (in this case, a back electrode is previously formed on the surface of the thin film crystalline semiconductor layer) to reach the softening point of the film substrate. The two may be fixed by increasing the temperature.

In the present invention, as a method for separating the semiconductor layer other than the peripheral portion, a method in which a mechanical external force is directly applied between the substrates to separate the semiconductor layer at the release layer, a method for separating the semiconductor layer or the release layer, or the method for separating the semiconductor layer or the release layer from the substrate. Force (internal stress)
Alternatively, there is a method of indirectly applying a force to a dangerous portion in the peeling layer using energy such as heat, an ultrasonic wave, an electromagnetic wave, or a centrifugal force from the outside to perform separation.

In the solar cell of the present invention, the surface of the semiconductor layer can be subjected to texture processing for the purpose of reducing the reflected light of the incident light. In the case of silicon, hydrazine or Na
This is performed using OH, KOH, or the like. The height of the pyramid of the texture to be formed is suitably in the range of several μm to several tens μm.

[0073]

Hereinafter, the formation of a desired solar cell by carrying out the method of the present invention will be described in more detail, but the present invention is not limited to these examples.

Example 1 In this example, a semiconductor substrate is formed by transferring a single crystal silicon layer onto a glass substrate by the process shown in FIG.

A p ⁺ layer was formed on the surface layer of the 5-inch silicon wafer 101 by performing thermal diffusion of boron at 1200 ° C. using BCl ₃ as a thermal diffusion source to obtain a diffusion layer 102 having a thickness of about 3 μm ( FIG. 1 (a). This surface layer 102 is p
^The anodized wafer was anodized in an HF + C ₂ H ₅ OH solution under the conditions shown in Table 1 to form a porous layer 103 on the wafer (FIG. 1B). At this time, 8 mA / cm ²
After the formation at a low current of 2.5 minutes, the current level was gradually increased, and the formation was completed when the current reached 35 mA / cm ² in 30 seconds. The thickness of the porous layer 103 was about 3 μm in total.

[0076]

[Table 1]

As a result, the structure in the porous layer can be changed in density in advance, and the silicon layer 104 can be easily separated from the wafer 101 later.

Next, a silicon layer 104 having a thickness of 0.5 μm was formed on the porous surface layer 103 by a thermal CVD method (FIG. 1C). At this time, the periphery of the wafer is covered with the silicon layer 10 on the porous layer 103 as in the case of FIG.
4 was covered.

The wafer 101 was mounted at a predetermined position in the anodizing apparatus shown in FIG. 5, and was arranged so that the silicon layer 104 faced the negative electrode 504 in the HF solution. At this time,
The negative electrode 504 was substantially the same shape as the positive electrode 505 in contact with the back surface of the wafer 101, and was a band-like ring along the periphery of the wafer 101 (see FIG. 9). In a HF + H ₂ O solution (HF: C ₂ H ₅ OH: H ₂ O = 1: 1: 6), a current of 120 mA / cm ² is passed between the electrodes to perform etching in an electropolishing mode, and the peripheral portion of the wafer 101 is etched. 10. The total depth of the silicon layer 104 and the porous layer 103 is 10.
5 μm removal was performed (FIG. 1D).

After an oxide film 106 having a thickness of 0.1 μm is formed on the surface of the silicon layer 104 at 450 ° C. by a normal pressure CVD apparatus, the glass substrate 105 is bonded to the oxide film 106, and the resultant is placed in a heat treatment furnace (not shown). It was then heated at 1150 ° C. to fix the glass substrate 105 and the wafer 101 (FIG. 1E).

Next, a force is applied between the glass substrate 105 and the wafer 101 in a direction in which the glass substrate 105 and the wafer 101 are separated from each other, so that the porous layer 1
Separation was performed at the part No. 03 (FIG. 1 (f)). No cracks or cracks were found around the silicon layer thus separated.

The porous layer 103a remaining on the silicon layer 104 separated from the wafer was selectively removed with a mixed solution of HF + H ₂ O to obtain an SOI substrate (FIG. 1 (g)).

The wafer 101 is formed by removing the porous layer 103b remaining on the surface in the same manner as described above, and if necessary, if the surface flatness is unacceptably rough, such as polishing. The surface was flattened (Fig. 1
(H)).

By repeating the above steps using the reclaimed wafer thus obtained, a plurality of semiconductor (SOI) substrates having a high-quality semiconductor layer were obtained.

(Embodiment 2) In this embodiment, a solar cell is formed by transferring a thin film single crystal silicon layer to a polyimide film by the process shown in FIG.

A p ⁺ layer was formed on the surface layer of the 5-inch silicon wafer 201 by performing thermal diffusion of boron at 1200 ° C. using BCl ₃ as a thermal diffusion source to obtain a diffusion layer 202 having a thickness of about 3 μm ( FIG. 2 (a)). This surface layer 202 is p
^The anodized wafer was anodized in an HF + C ₂ H ₅ OH solution under the conditions shown in Table 2 to form a porous layer 203 on the wafer (FIG. 2B). At this time, after forming at a low current of 8 mA / cm ² for 10 minutes, the current level was raised to 30
Electric current was applied at mA / cm ² for 1 minute. The total thickness of the porous layer 203 was about 13 μm.

[0087]

[Table 2]

Next, on the surface of the porous silicon layer 203, I
Epitaxial growth was performed with a slider type liquid phase growth apparatus using n as a solvent under the formation conditions shown in Table 3 to make the thickness of the silicon layer 204 30 μm. At this time, a very small amount of boron (0.1 pp with respect to the amount of dissolved silicon)
m to several ppm) to make the growth silicon layer 204 p ^- type, and after the growth is completed, another In melt containing a large amount of boron (to the amount of silicon dissolved) is further deposited on the growth silicon layer. P ⁺ layer 2 using several hundred ppm or more)
05 was formed with a thickness of 1 μm (FIGS. 2C and 2D). At this time, the periphery of the wafer is In due to the jig for mounting the substrate.
Since it does not come into contact with the solvent, the silicon layer 2
04 did not completely cover the porous layer 203, and the porous layer 203 was exposed on the surface of the substrate 201.

[0089]

[Table 3]

The wafer 201 is mounted at a predetermined position in the anodizing apparatus shown in FIG.
Is arranged so as to face the negative electrode 504 in the HF solution. At this time, the negative electrode 504 was substantially the same shape as the positive electrode 505 in contact with the back surface of the wafer 201, and was a band-like ring along the periphery of the wafer 201 (see FIG. 9).

HF + H ₂ O solution (HF: C ₂ H ₅ OH: H ₂
O = 1: 1: 6), a current of 170 mA / cm ² was passed between the electrodes to perform etching in an electropolishing mode, and the entire porous layer 203 (13 μm in thickness) around the wafer 201 was etched.
m) was removed (FIG. 2E).

A polyimide film 206 having a thickness of 50 μm
Silver paste 207 by screen printing on one side of
The wafer was coated with a thickness of ３０30 μm, and this surface was closely attached to the surface of the p ⁺ silicon layer 205 of the above-mentioned wafer.

In this state, the silver paste was sintered at 360 ° C. for 20 minutes while being opened, and the polyimide film 206 and the wafer 201 were fixed together (FIG. 2F).

The surface of the non-bonded side of the wafer is fixed to the fixed polyimide film 206 and wafer 201 with a vacuum chuck (not shown), and a force is applied from one end of the polyimide film 206. By using the flexibility of the polyimide film, both are gradually peeled off from the edge of the wafer to perform peeling. In this manner, the silicon layers 204 and 205 are separated from the wafer 201 and transferred onto the polyimide film 206. (Figure 2
(G)). No cracks or cracks were found around the silicon layer thus separated.

Silicon layer 2 separated from silicon wafer
The porous layer 203a remaining on the substrate 04 is made of HF + H ₂ O ₂
Selective etching was performed while stirring with a mixed solution of + H ₂ O.
The silicon layer remained without being etched, and only the porous layer was completely removed.

The surface of the silicon layer on the obtained polyimide film was cleaned by lightly etching with a hydrofluoric / nitric acid-based etchant, and then the surface of the silicon layer was coated on the silicon layer by a normal plasma CVD apparatus as shown in Table 4. Under the conditions shown, n-type μc-S
An i-layer was deposited at 200 °. At this time, the dark conductivity of the μc-Si layer was ５5 S / cm.

[0097]

[Table 4]

Finally, an EB (Elect) is formed on the μc-Si layer.
ITO transparent conductive film (82) by evaporation (tro Beam).
nm / collecting electrode Ti / Pd / Ag (400 nm / 200
nm / 1 μm)) to form a solar cell (FIG. 2).
(H)).

The thus obtained thin-film single-crystal silicon solar cell on polyimide had an AM1.5 (100 m
W / cm ²⁾ was measured for the I-V characteristic under irradiation with light, open-circuit voltage 0.59V in cell area 6 cm ^2, short-circuit photocurrent 33 mA / cm ^2, a fill factor 0.78, the energy conversion efficiency 15. 2% was obtained.

The porous layer remaining on the silicon wafer after peeling was also removed by etching in the same manner as described above, and a smooth surface was obtained (FIG. 2 (i)). By repeating the above-mentioned steps using the reclaimed wafer thus obtained, a plurality of thin-film single-crystal solar cells having a high-quality semiconductor layer were obtained.

(Embodiment 3) In this embodiment, a solar cell is formed by transferring a polycrystalline silicon layer to a Tefzel film (transparent film) by the process shown in FIG.

The surface of a square (square) polycrystalline silicon wafer 301 having a thickness of 500 μm was coated with BCl ₃ as a heat diffusion source.
By performing thermal diffusion of boron at a temperature of 200 ° C., the p ⁺ layer 30 is formed.
2 was obtained to obtain a diffusion layer having a thickness of about 3 μm (FIG. 3).
(A)). Next, anodization was performed in an HF solution under the conditions shown in Table 5 to form a porous silicon layer 303 on the wafer (FIG. 3B). That is, formation was first performed at a low current of 5 mA / cm ² for 2.5 minutes, and then the current level was slowly increased. When formation reached 32 mA / cm ² in 30 seconds, formation was completed.

[0103]

[Table 5]

Crystal growth was carried out on the surface of the porous silicon layer by a normal thermal CVD apparatus under the conditions shown in Table 6, and the thickness of the silicon layer (polycrystal) was reduced to about 30 μm.

[0105]

[Table 6]

At this time, the amount of B ₂ H ₆ was reduced to 0. Several pp
The growth silicon layer is made to be p ⁻ -type with m to several ppm, and at the end of the growth, PH ₃ is replaced with B ₂ H ₆ by several hundreds p.
By adding about pm, an n ⁺ layer 305 was formed to a thickness of 0.2 μm to form a junction. (FIGS. 3C and 3D).

At this time, the periphery of the wafer was in a state where the silicon layer 304 covered the porous layer 303 as in the case of FIG.

The wafer 301 is mounted at a predetermined position in the anodizing apparatus shown in FIG.
Is opposed to the negative electrodes 604 and 606 in the HF solution. At this time, the negative electrodes 604 and 606 are
01 is substantially the same shape as the positive electrodes 605 and 607 that are in contact with the back surface of the wafer 01, and the electrodes 604 and 605 form a band-shaped square (square) shape along the periphery of the wafer 301 (see FIG. 9). Electrodes 606 and 607 are on wafer 3
01, the electrodes 604 and 6
05 and has a square (square) shape (see FIG. 10).

HF + H ₂ O solution (HF: C ₂ H ₅ OH: H ₂
O = 1: 1: 6) between electrodes 604 and 605
Etching is performed in an electrolytic polishing mode by passing a current of mA / cm ² , and the silicon layer 304 around the wafer 301 is etched.
305 and the entire porous layer 303 were removed. Also, a current of 8 mA / cm ² is applied between the electrodes 604 and 605 to perform normal anodization, and a thin porous layer 309 is formed on the surface of the silicon layer 304 other than the peripheral region of the wafer 301 by 90 μm.
Then, an anti-reflection layer was formed (FIG. 3E).

After the formation, EB is formed on the antireflection layer 309.
ITO transparent conductive film (82 nm) by vapor deposition (not shown)
/ Collecting electrode (Ti / Pd / Ag (400nm / 200n
m / 1 μm)) 310 to form a solar cell structure in advance, and then apply a transparent adhesive 307 to one side of the Tefzel film 306 having a thickness of 80 μm to a thickness of 10 to 30 μm. The transparent conductive film / current collecting electrode surface was closely adhered and bonded (FIG. 3 (f)).

When the adhesive has hardened sufficiently, the surface of the non-adhered side of the wafer against the fixed Tefzel film 306 and wafer 301 is vacuum chucked (not shown).
, And a force is applied from one end of the Tefzel film 306, and the two are gradually peeled off from the edge of the wafer 301 by using the flexibility of the Tefzel film.
Perform eeling. Thus, the silicon layer 304
And 305 were peeled off from the wafer and transferred onto a Tefzel film (FIG. 3 (g)). No cracks or cracks were found around the silicon layer thus separated.

The porous layer 303a remaining on the silicon layer 304 peeled from the polycrystalline silicon wafer 301 is
Selective etching was performed while stirring a 1% by weight KOH solution. The silicon layer 304 remained without being etched much, and the porous layer was completely removed.

On the back surface of the silicon layer 304 on the obtained Tefzel film, p was applied by plasma CVD under the conditions shown in Table 7.
A mold μc-Si layer 308 was deposited at 500 °. At this time, the dark conductivity of the μc-Si layer was １1 S / cm.

[0114]

[Table 7]

Further, Al was formed to a thickness of 0.1 μm as a back electrode 311 by a sputtering method, and was further pasted on a SUS substrate (not shown) as a support substrate via a conductive adhesive to obtain a solar cell ( (FIG. 3 (h)).

The thin-film polycrystalline silicon solar cell on Tefzel obtained in this manner was subjected to AM1.5 (100 mW / cm ² ) light irradiation from the Tefzel film side.
As a result of measuring the -V characteristics, the open area voltage was 0.59 V and the short-circuit photocurrent was 33.5 mA / c in a cell area of 6 cm ^2.
m ² , fill factor 0.78, energy conversion efficiency 1
5.4% was obtained.

Further, the porous layer remaining on the silicon wafer after peeling was also removed by etching in the same manner as described above, and a smooth surface was obtained (FIG. 3 (h)). By repeating the above steps using the reclaimed wafer thus obtained, a plurality of thin-film polycrystalline solar cells having high-quality semiconductor layers were obtained.

(Embodiment 4) In this embodiment, the shape shown in FIGS. 11 and 12 in which a square is cut through the disk is used as an electrode for removing a peripheral portion, and the shape substantially corresponding to the cut-out square is used. FIG. 2 shows a process of forming a solar cell by separating a square semiconductor layer from a round wafer-like substrate by using the electrode for forming an anti-reflection layer.

In the same manner as in Examples 1 to 3, an 8-inch silicon
BCl on the surface layer of the wafer 201_ThreeAs a heat diffusion source
Thermal diffusion of boron at a temperature of 200 ° C.⁺Form a layer
As a result, a diffusion layer 202 having a thickness of about 3 μm was obtained (FIG. 2).
(A)). This surface layer 202 is p⁺The wafer that became
HF + C_TwoH_FiveAnodization was performed in an OH solution under the conditions shown in Table 2.
The porous layer 203 was formed on the wafer (see FIG. 2).
(B)). At this time, 8 mA / cm ^Two10 at low current
After forming for 30 minutes, the current level is increased to 30 mA / cm^Two
For 1 minute. The total thickness of the porous layer 203 is about 1
It was 3 μm.

Next, epitaxial growth was carried out on the surface of the porous silicon layer 203 by a normal thermal CVD apparatus under the conditions shown in Table 6 to reduce the thickness of the silicon layer 204 (single crystal) to about 3
It was set to 0 μm. At this time, the amount of B ₂ H ₆ was reduced to 0. Number p
The growth silicon layer was made to be p ⁺ type with about pm to several ppm, and at the end of the growth, B ₂ H ₆ was increased to about several hundred ppm or more to form the p ⁺ layer 205 with a thickness of 1 μm (FIG. 2 (c), (a)). At this time, the periphery of the wafer is shown in FIG.
The silicon layer 204 is formed on the porous layer 203 as in the case of
Was covered.

The wafer 201 is mounted at a predetermined position in the anodizing apparatus shown in FIG.
Was made to face the negative electrodes 604 and 606 in the HF solution. At this time, the negative electrodes 604 and 606 have substantially the same shape as the positive electrodes 605 and 607, respectively, which are in contact with the back surface of the wafer 201, and the electrodes 604 and 605 are square in the disk along the periphery of the wafer 201. The electrodes 606 and 607 are formed in a region other than the peripheral portion of the wafer 201, respectively.
4 and 605, and have a shape substantially equivalent to a hollow square (see FIG. 12).

HF + H ₂ O solution (HF: C ₂ H ₅ OH: H ₂
O = 1: 1: 6) between electrodes 604 and 605
Etching is performed in an electrolytic polishing mode by passing a current of mA / cm ² , and a silicon layer 204 around the wafer 201 is removed.
205 and the entire porous layer 203 were removed. A normal anodization is performed by applying a current of 6 mA / cm ² between the electrodes 604 and 605, and a thin porous layer 209 is formed on the surface of the silicon layer 204 except for the peripheral region of the wafer 201.
Then, an anti-reflection layer was formed (FIG. 2E).

A polyimide film 206 having a thickness of 50 μm
Silver paste 207 by screen printing on one side of
The wafer was coated with a thickness of ３０30 μm, and this surface was closely attached to the surface of the p ⁺ silicon layer 205 of the above-mentioned wafer. In this state, the silver paste was baked at 360 ° C. for 20 minutes in an oven, and the polyimide film 206 and the wafer 201 were fixed (FIG. 2F).

The fixed polyimide film 206 and wafer 201 were irradiated with ultrasonic energy in a water bath. For example, when irradiated with 25 KHz and 650 W ultrasonic waves, the silicon layer was separated from the wafer at the porous layer portion. Thus, the silicon layer 2 of about 125 mm square is
04 and 205 were peeled off from the 8-inch round wafer 201 and transferred onto the polyimide film 206 (FIG. 2).
(G)). No cracks or cracks were found around the silicon layer thus separated.

The silicon layer 2 peeled off from the silicon wafer
The porous layer 203a remaining on the substrate 04 is made of HF + H ₂ O ₂
Selective etching was performed while stirring with a mixed solution of + H ₂ O.
The silicon layer remained without being etched, and only the porous layer was completely removed.

After the surface of the silicon layer on the obtained polyimide film was cleaned by light etching with a hydrofluoric / nitric acid-based etching solution, the surface of the silicon layer was subjected to cleaning using a conventional plasma CVD apparatus as shown in Table 4. Under the conditions shown, n-type μc-S
An i-layer was deposited at 200 °. At this time, the dark conductivity of the μc-Si layer was ５5 S / cm.

Finally, an ITO transparent conductive film (82 nm) collector electrode (Ti / Pd / Ti) was formed on the μc-Si layer by EB evaporation.
Ag (400 nm / 200 nm / 1 μm)) was formed to obtain a solar cell (FIG. 2 (h)).

The thus obtained thin-film single-crystal silicon solar cell on polyimide had an AM1.5 (100 m
W / cm ²⁾ was measured for the I-V characteristic under irradiation with light, open-circuit voltage 0.60V in cell area 6 cm ^2, short-circuit photocurrent 33 mA / cm ^2, a fill factor 0.79, the energy conversion efficiency 15. 6% was obtained.

Further, the porous layer remaining on the silicon wafer after peeling was also removed by etching in the same manner as described above, and a smooth surface was obtained (FIG. 2 (i)). By repeating the above steps using the reclaimed wafer thus obtained, a plurality of thin-film single-crystal solar cells having a high-quality semiconductor layer were obtained.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the above-described example, a case where a square semiconductor layer is separated from a round wafer-shaped substrate to form a solar cell has been described, but the shapes of the electrode for removing the peripheral portion and the electrode for forming the anti-reflection layer are arbitrary. Thus, it is possible to separate a semiconductor layer of any shape from a substrate of any shape.

Further, in each of the above embodiments, the porous layer is used as the release layer. Can be treated in exactly the same manner as described above for the semiconductor substrate formed as a release layer. For example, specifically, H ions are implanted into the surface of the crystalline Si substrate under the conditions of 20 KeV and 5 × 10 ¹⁶ cm ⁻² to form a critical layer at a depth of 0.1 μm from the Si surface.
After a silicon layer is formed thereon by a thermal CVD method in the same manner as in the first embodiment, peripheral removal and peeling may be performed in the same manner as in the process of FIG.

[0132]

As described above, according to the present invention,
A semiconductor substrate and a thin-film crystal solar cell having good characteristics with less cracks and cracks can be efficiently obtained, and thereby a high-quality semiconductor substrate and a solar cell with mass productivity can be provided to the market. . Further, according to the present invention, a thin film crystal solar cell having good characteristics can be formed by a simple process, and an inexpensive solar cell can be manufactured.
Further, according to the present invention, a semiconductor substrate and a thin-film crystal solar cell having an arbitrary shape can be easily formed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for manufacturing a semiconductor substrate according to the present invention.

FIG. 2 is a diagram illustrating a method for manufacturing a solar cell according to the present invention.

FIG. 3 is a diagram illustrating a method for manufacturing a solar cell according to the present invention.

FIG. 4 is a diagram illustrating the structure of the anodizing apparatus of the present invention.

FIG. 5 is a diagram illustrating the structure of the anodizing apparatus of the present invention.

FIG. 6 is a diagram illustrating the structure of the anodizing apparatus of the present invention.

FIG. 7 is a diagram illustrating a state in which cracks and cracks enter the epitaxial layer during peeling.

FIG. 8 is a diagram illustrating a state in which cracks and cracks enter the epitaxial layer during peeling.

FIG. 9 is a diagram showing an example of a shape of an electrode for removing a peripheral portion used in the anodizing apparatus of the present invention.

FIG. 10 is a view showing an example of the shape of an anti-reflection layer forming electrode used in the anodizing apparatus of the present invention.

FIG. 11 is a view showing an example of a shape of an electrode for removing a peripheral portion used in the anodizing apparatus of the present invention.

FIG. 12 is a view showing an example of the shape of an anti-reflection layer forming electrode used in the anodizing apparatus of the present invention.

[Explanation of symbols]

101, 201, 301, 401, 501, 601 Semiconductor substrate 102, 202, 302 p ⁺ diffusion layer 103, 103a, 103b, 203, 203a, 20
3b, 303, 303a, 303b, 703, 803
Porous layer 104, 204, 304, 704, 804 Semiconductor layer 205, 305 P ⁺ layer (or n ⁺ layer) 208, 308 n ⁺ layer (or p ⁺ layer) 209, 309 Antireflection layer 210, 310 Collector electrode 311 Back electrode 207, 307 Conductive paste 106 Oxide film 105, 206, 306, 708, 808 Support substrate 705, 805 Porous surface smooth layer 706, 806 Crack or crack 707, 807 Ideal separation line 402, 502, 602 Liquid 403, 503, 603 Chemical conversion layer 404, 504, 604 Peripheral part removing electrode (cathode) 405, 505, 605 Peripheral part removing electrode (anode) 406, 606 Antireflection layer forming electrode (cathode) 407, 607 Reflection Electrode for preventing layer formation (anode) 408, 508, 608 Sealing material 409, 509, 609 Substrate holder 410, 411, 510, 610, 611 electrode 412 isolator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Iwa ▲ saki ▼ Yukiko 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kiyofumi Sakaguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo No. F term in Canon Inc. (reference) 5F043 AA09 BB01 DD14 DD30 GG10 5F051 CB21 GA04 GA05 GA06 GA11 GA20

Claims (37)

[Claims] 1. A method of manufacturing a semiconductor substrate obtained by peeling a thin-film crystalline semiconductor layer formed on a first substrate and transferring it onto a second substrate, wherein the thin film on the periphery of the first substrate is provided. A method for manufacturing a semiconductor substrate, wherein a crystalline semiconductor layer is removed by etching by electrolytic polishing. 2. A peeling layer is provided between the first base and the thin-film crystalline semiconductor layer, and only a thin-film crystalline semiconductor layer, only a peeling layer, or a thin-film crystalline semiconductor layer is formed around the first base. The method for manufacturing a semiconductor substrate according to claim 1, wherein the release layer is removed. 3. The method according to claim 2, wherein the release layer is made of a porous material. 4. The method according to claim 2, wherein the release layer is made of two or more layers of porous material. 5. The method according to claim 2, wherein the release layer is formed by ion implantation. 6. A method of manufacturing a semiconductor substrate using a thin-film crystalline semiconductor layer, comprising: (1) forming a porous layer by anodizing at least the main surface of the first substrate; A step of forming a semiconductor layer on a porous body; (3) a step of removing a semiconductor layer in a peripheral portion of the first base by electrolytic polishing; and (4) a step of forming a second base on a surface of the semiconductor layer. (5) a step of separating the semiconductor layer and the first substrate via the porous layer and transferring the separated semiconductor layer and the first substrate to the second substrate; and (6) a first step after the separation. Treating the surface of the substrate and repeating steps (1) to (5) again. 7. The method according to claim 6, wherein in the step (3), the semiconductor layer at the peripheral portion and the porous layer immediately below the semiconductor layer are continuously removed.
3. The method for manufacturing a semiconductor substrate according to item 1. 8. The method according to claim 6, wherein the first substrate is silicon. 9. The method according to claim 6, wherein the first substrate is a single crystal.
9. The method for producing a semiconductor substrate according to any one of items 1 to 8. 10. The method according to claim 6, wherein a semiconductor junction is formed in the semiconductor layer in the step (2). 11. The method according to claim 6, further comprising, between the steps (4) and (5), a step of forming a semiconductor junction on the surface of the semiconductor layer transferred onto the second substrate. A method for manufacturing a semiconductor substrate according to any one of the above. 12. The second substrate is a flexible film, and the semiconductor layer is separated at the porous layer by applying a force to the film in a direction in which the film is peeled from the first substrate. A method for manufacturing a semiconductor substrate according to claim 6. 13. The method according to claim 12, wherein the film is made of a resinous film. 14. A method for manufacturing a solar cell obtained by peeling a thin-film crystalline semiconductor layer formed on a first base and transferring it onto a second base, wherein the thin film at the periphery of the first base is provided. A method for manufacturing a solar cell, comprising removing a crystalline semiconductor layer by etching by electrolytic polishing. 15. The method for manufacturing a solar cell according to claim 14, wherein a release layer exists between the first base and the thin-film crystalline semiconductor layer. 16. The method according to claim 1, wherein the release layer is made of a porous material.
6. The method for manufacturing a solar cell according to 5. 17. The method for manufacturing a solar cell according to claim 15, wherein the release layer is composed of two or more porous layers. 18. The method according to claim 15, wherein the release layer is formed by ion implantation. 19. A method for manufacturing a solar cell using a thin-film crystalline semiconductor layer, comprising: (1) forming a porous layer by anodizing at least the main surface of the first base; A step of forming a semiconductor layer on the porous body; (3) a step of removing the semiconductor layer at the peripheral portion of the first base by electrolytic polishing; and (4) a semiconductor other than the peripheral portion of the first base. A step of forming a surface antireflection layer of a porous layer on the surface of the layer; (5) a step of bonding a second substrate to the surface of the semiconductor layer; and (6) the semiconductor layer via the porous layer. (7) separating the first substrate from the first substrate and transferring the separated substrate to the second substrate; and (7) treating the surface of the first substrate after the separation and repeating the above (1) to (6) again. And a method for manufacturing a solar cell. 20. The method for manufacturing a solar cell according to claim 19, wherein in the step (3), the peripheral semiconductor layer and the porous layer immediately below the peripheral semiconductor layer are continuously removed. 21. The method according to claim 19, wherein the first substrate is silicon. 22. The method for manufacturing a solar cell according to claim 19, wherein the first base is a single crystal. 23. The step of removing the semiconductor layer and the porous layer at the peripheral portion of the first base and the step of forming a surface antireflection layer on the surface of the semiconductor layer other than the peripheral portion of the first base are performed simultaneously. A method for manufacturing a solar cell according to claim 19. 24. The step of removing the semiconductor layer and the porous layer at the periphery of the first base and the step of forming a surface antireflection layer on the surface of the semiconductor layer other than the periphery of the first base are performed in the same manner. The method for producing a solar cell according to claim 19, wherein the method is performed in an anodizing tank. 25. The method for manufacturing a solar cell according to claim 19, wherein in the step (2), a semiconductor junction is formed in the semiconductor layer. 26. The method according to claim 19, further comprising the step of forming a semiconductor bond on the surface of the semiconductor layer transferred onto the second substrate between the steps (4) and (5).
The method for producing a solar cell according to any one of the above. 27. The second substrate is a flexible film, and the semiconductor layer is separated at the porous layer by applying a force in a direction in which the film is peeled from the first substrate to the film. A method for manufacturing a solar cell according to any one of claims 19 to 26. 28. The method for manufacturing a solar cell according to claim 27, wherein the film is made of a resinous film. 29. A peripheral part of the base to be anodized, comprising: a first electrode in contact with the back side of the base; and a second electrode opposed to the first electrode with the base interposed therebetween. An anodizing apparatus wherein the electrode and the second electrode have substantially the same shape. 30. The anodizing apparatus according to claim 29, wherein the first and second electrode shapes are a band-shaped ring or a band-shaped polygon. 31. The second electrode is platinum.
Anodizing apparatus according to claim 9. 32. A peripheral portion of a base to be anodized, comprising: a first electrode in contact with a back side of the base; and a second electrode opposed to the first electrode with the base therebetween. In the remaining substrate region except for, a third electrode in contact with the back side of the substrate, a fourth electrode facing the third electrode across the substrate, the first electrode and the second electrode The third electrode and the fourth electrode each have substantially the same shape. 33. The anodizing apparatus according to claim 32, wherein the first and second electrode shapes are a band-shaped ring or a band-shaped polygon. 34. The anodizing apparatus according to claim 32, wherein the third and fourth electrode shapes are disks or polygons. 35. The anodizing apparatus according to claim 32, wherein the distance between the first and second electrodes is shorter than the distance between the third and fourth electrodes. 36. The method of manufacturing a semiconductor substrate according to claim 1, wherein the thin film crystalline semiconductor layer is separated into an arbitrary shape by electrolytic polishing etching. 37. The method for manufacturing a solar cell according to claim 14, wherein the thin film crystalline semiconductor layer is peeled into an arbitrary shape by electrolytic polishing etching.