JPH05235391A - Thin film solar cell and its manufacture and manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To avoid damages to a graphite sheet substrate and to heat the substrate with a high heating efficiency by heating the substrate by high-frequency direct heating. CONSTITUTION:A graphite sheet substrate 1 fed into a thin film forming chamber 2 is heated by an induction heating source 3. Since induction heating does not allow the direct contact of terminals as by electrothermal heating with a substrate, deformation and peeling of the surface of the graphite substrate can be prevented. Heating failure caused by a poor contact of electrothermal terminal with the substrate and temperature irregularity caused by a partial flow of current do not occur, and heating of uniform temperature distribution can be made; therefore, the film thickness of a semiconductor thin film formed on the substrate can be made uniform. Since induction heating causes no decrease in heating efficiency by gloss of the substrate surface, but heating of only the conductive substrate, efficient heating can be attained. The graphite sheet can be thinned very much, so that heating can be attained by a small power source capacitance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film solar cell and a method for manufacturing the same, and in particular, the manufacturing process of the thin film solar cell using a graphite sheet or the like as a substrate can be facilitated and its performance and reliability can be improved. The present invention relates to a thin film solar cell structure and a manufacturing method capable of reducing manufacturing cost.

[0002]

2. Description of the Related Art FIG. 43 is a perspective view showing the structure of an example of a thin film solar cell that performs photoelectric conversion in a Si thin film formed on a substrate. In the figure, 200 is a substrate, which includes a pn junction and generates electricity. The active layer 201 that contributes to is disposed on the substrate 200. The antireflection film 202 is disposed on the active layer 201. An upper electrode composed of a grid electrode 203a that collects the photocurrent generated in the active layer 201 and a bus electrode 203b that collects the current collected by the grid electrode 203a in one place is provided on the antireflection film 202, and the lower electrode 204 is the substrate. 200 is provided on the back surface.

In such a thin-film solar cell, the active layer 201 that contributes to power generation is as thin as several tens of microns, and the film itself cannot be mechanically self-supported, so some substrate is required. Conditions are required. First, the thin film must be mechanically supported and strong enough to be self-supported by the substrate itself. Secondly, since the Si thin film active layer is formed on the substrate 200 by thermal CVD or the like, heat resistance is required to withstand the process temperature (about 1000 ° C.) at the time of the film formation. Thirdly, since the substrate itself also serves as the lower electrode, conductivity is required. However, a thin-film solar cell can be manufactured even if it has no conductivity, but in that case, it is necessary to take out the lower electrode from the side by inserting a conductive film on the substrate or by making it an integrated type. The thin film solar cell structure becomes complicated. Fourthly, the substrate itself does not have to contribute to power generation, but merely needs to play a role of supporting the active layer. Therefore, it is desirable to use a material of a low cost as possible and to manufacture it by a low cost method.

As a substrate satisfying these conditions to some extent, for example, L. L. Paper by Dr. Kazmerski (LLKa
zmerski ； 14th IEEE Photovoltaic Specialists Confe
As described in rence (PVSC14) p.281 (1980)), substrates such as iron, graphite plates and metal grade Si have been studied. Among them, the iron or metal-grade Si substrate contains a large amount of impurities such as Fe that deteriorate the solar cell characteristics even in a small amount, and there is a possibility that these impurities may be mixed in the active layer.
It seems that it is not very suitable as a substrate for thin film solar cells. Therefore, as satisfying the requirements for the above-mentioned substrate, Kazmerski states in the above-mentioned paper that the graphite plate is suitable at this stage.

FIG. 44 shows, for example, T.M. L. Published by Chu et al. (TLChu et al .; J. Electrochem. Soc. 123, p. 10
6 (1976)) is a cross-sectional view showing the structure of a conventional thin-film solar cell using a graphite plate as a substrate. This thin-film solar cell has a structure similar to that shown in FIG. 43, and FIG. 44 is a diagram corresponding to a part of the AA cross section of FIG. 43.
In the figure, reference numeral 205 denotes a conductive substrate made of a sintered and molded graphite plate, which is an active layer 20 of a polycrystalline Si thin film.
6 is arranged on the substrate 205, and the antireflection film 207 is arranged on the active layer 206. The upper electrode 208 is provided on the antireflection film 207, and the lower electrode 209 is provided on the back surface of the substrate 205.

Next, a manufacturing process of a conventional thin film solar cell using a graphite plate as a substrate will be described. The graphite plate is produced by charging graphite powder obtained from anthracite, coke, or the like into a mold, sintering it at a high temperature of about 3000 ° C., taking it out from the mold, and flattening the surface by polishing.

The graphite plate thus produced is set in a CVD apparatus, and silane (SiH ₄ ) or (trichlorosilane) SiHC1 ₃ gas is flowed, and this gas is heated to 100%.
Decomposes at a high temperature of about 0 ° C., and on the graphite plate 205,
A polycrystal Si film to be the active layer 206 is formed with a thickness of several tens of microns. Since the Si thin film immediately after being formed has a small crystal grain size, in some cases, polycrystalline Si may be melted and recrystallized by laser irradiation or lamp heating to increase the crystal grain size. After the film formation, a pn junction is formed in the active layer 206 by impurity diffusion or ion implantation. Also, this pn junction is
During the formation of the active layer by mixing the doping gas by CVD,
By changing the type of dopant on the way,
Further, it can also be formed by forming a microcrystalline film having a conductivity type opposite to that of the active layer on the active layer using a plasma CVD apparatus.

After forming the pn junction, an antireflection film 207 is formed by sputtering or the like. As the antireflection film, when the lateral conductivity of the film is low as in the case where a microcrystalline film is formed to form a pn junction, the ITO (I
n ₂ O ₃ : SnO ₂ ), SnO ₂ or ZnO is used, and a silicon nitride film (Si ₃ N ₄ ) is used when the lateral conductivity of the Si film is high and a transparent electrode is not required.
An insulating film such as is used. Next, the antireflection film 207
An upper electrode 208 is formed on top. The upper electrode is mainly a silver electrode and is formed by screen printing or vapor deposition.

By the way, such a thin film solar cell using a graphite plate as a substrate has the following problems. That is, the graphite plate is manufactured through a complicated manual process in which a graphite powder material is charged into a mold, sintered at an ultrahigh temperature of 2000 to 3000 ° C., taken out of the mold, and then flattened by polishing the surface. To be done. Therefore, the graphite powder, which is a raw material, is inexpensive but requires a high-temperature process, resulting in high manufacturing cost. Further, since it is necessary to charge and take out the mold, continuous production is difficult.

Even if the surface of the conventional graphite plate is flattened by polishing, irregularities of about several microns remain and electrical leakage occurs when the active layer is thin.
FIG. 45 is an enlarged cross-sectional view of the surface portion of the conventional graphite plate (the surface of the substrate 205 in FIG. 44 which is in contact with the active layer 206), and 210 is graphite powder. As shown in the figure, the surface of the conventional graphite plate was a surface with severe irregularities of several microns. Further, the conventional graphite plate has a small light reflectance, and it is difficult for the light passing through the active layer to be reflected on the back surface of the active layer, that is, the surface of the substrate, so that sunlight cannot be effectively used. In addition, the conventional graphite plate is porous,
It absorbs water from the back surface of the substrate during long-term use and deteriorates the active layer.
Also, since the graphite plate is not flexible, it is not possible to continuously flow the substrate like the roll-to-roll method so that it cannot be continuously manufactured. Must be produced,
Mass production is difficult.

On the other hand, when the active layer is an amorphous film, 3
Since the film can be formed by a low temperature process of 00 ° C or lower, continuous production was performed using a sheet-shaped heat-resistant plastic. Since the substrate easily absorbs moisture, there is a problem in moisture resistance.

FIG. 46 shows a method of manufacturing a thin-film solar cell disclosed in, for example, Japanese Patent Laid-Open No. 53-44192 by Bernhard Outheal. In the figure, 211
Is a graphite sheet substrate, 212 and 213 are rollers for feeding the substrate, 214 is an active layer film forming chamber, 215 is a grain size expanding chamber, 216 is a pn junction forming chamber, 217 is an active layer film forming chamber 214. The raw material gas inlet 218 for introducing the raw material gas for is for a gas outlet. Further, reference numeral 219 denotes a power supply for electric heating for generating a current for heating the substrate, 22
Reference numeral 0 is an electric heating terminal which contacts the graphite sheet substrate. Reference numeral 221 is a heating lamp, and 222 is a cutter for cutting the substrate.

Next, a conventional method for manufacturing a thin film solar cell will be described. Roll the graphite sheet substrate 211 to the roller 21.
In step 2, it is sent to the active layer film forming chamber 214. Active layer deposition chamber 21
A raw material gas for forming an active layer made of a Si thin film, such as silane or dichlorosilane, is introduced from the raw material gas introduction port 217 of No. 4. The graphite sheet substrate 211 is in contact with the energization heating terminal 220, and the current supplied from the energization heating power source 219 flows through the substrate, so that the graphite sheet substrate 211 is heated. Since the raw material gas introduced from the raw material gas inlet 217 is filled in the active layer film forming chamber 214, the raw material gas is decomposed by heating the substrate, and polycrystalline Si which is the active layer is formed on the graphite sheet substrate 211. To be done. The gas after the decomposition reaction and the raw material gas remaining without being decomposed are exhausted from the gas exhaust port 218.

The graphite sheet substrate 211 on which the polycrystalline Si thin film is formed is sent by a roller and further moved to the next grain size expansion chamber 215. In the particle size expansion chamber 215, by heating the substrate by energization and heating by the lamp 221,
Polycrystalline Si is melted and recrystallized to increase the grain size. p
In the n-junction forming chamber 216, a pn junction is formed by impurity diffusion or the like in the Si thin film whose grain size has been expanded. After that, the substrate 211 is cut into a predetermined length by the cutter 222.

In this conventional example, a graphite sheet is used as a substrate satisfying the above-mentioned conditions for the substrate of the thin-film solar cell, that is, mechanical support of the thin film, high temperature heat resistance, conductivity, and low cost. Graphite sheets have hitherto been used as heat-resistant gaskets, packings, heat insulating materials for nuclear reactors, and the like. The characteristics of the graphite sheet and the manufacturing method will be described below.

FIG. 47 is a diagram showing a crystal structure of graphite which is a raw material used for the graphite sheet.
The raw material is naturally occurring scaly graphite, and the crystal structure has a structure in which a layer 223 in which carbon atoms are arranged in a plane and six carbon rings are stacked is laminated. Although the carbon bond in the same plane is strong, the bond between the faces 223 is van der Waals force, so the bond force is weak and the cleavage can be easily performed in layers. This crystal structure is microscopically similar to that of conventional graphite powder, but scaly graphite has larger crystals than graphite powder, and if it is particularly large, it is composed of a large lump of crystals of about several mm.

FIG. 48 is a diagram showing a method for producing a graphite sheet, in which 224 is expanded graphite and 225 is a roller. When scaly graphite is acid-treated with a mixed solution of NH ₄ OH and H ₂ SO ₄ and the acid is heated and evaporated at about 300 ° C., the scaly graphite foams and becomes cotton-like and expands in volume. As shown in the figure, a graphite sheet 226 can be continuously formed by pressure-molding the expanded graphite 224 with a roller 225 at room temperature. It is considered that each of the crystals can be formed by simply applying a pressure without performing a high-temperature treatment, because each crystal size is large.

The graphite sheet thus manufactured has the following features. That is, by forming a roll, a crystal structure or a layered structure elongated in the surface direction of the substrate is laminated in the thickness direction of the substrate. Even if this is not roll formation, if it is formed by compression from one direction, it will have a structure with such anisotropy. Since the internal structure has anisotropy, thermal conductivity and electrical conductivity become anisotropic in the plane direction and the thickness direction. Moreover, the graphite sheet formed by compression at room temperature is flexible and has a very smooth surface. Further, when forming a roll, the surface shape of the substrate depends on the surface shape of the roller. Therefore, a substrate having a smooth surface shape can be produced by molding with a roller having a smooth surface shape.

FIG. 49 is an enlarged sectional view of the surface portion of the graphite sheet. As shown in the figure, the layered structure of the graphite sheet has a structure in which one layer or a plurality of layers 227 in which the crystal structure of FIG. 47 is spread is laminated. Therefore, even if there is a large undulation of several mm to several cm due to the flexibility of the substrate itself, there are few sharp irregularities on the surface unless the surface is physically scratched, and in principle at the atomic level. Very flat.

Moreover, since the layer structure is parallel to the substrate surface direction, the water absorption and inhalation properties from the substrate end face are large, but the permeability in the direction perpendicular to the surface is small, and even if moisture is supplied from the substrate back surface. Even if it does, the permeation resistance is large and the active layer is hardly adversely affected. Furthermore, since the layer structure of the substrate is parallel to the plane direction, the reflectance is higher than that of a normal graphite plate having no anisotropy. This is probably because, in the crystal structure of FIG. 47, the light reflectance in the vertical direction is higher than the light reflectance in the horizontal direction with respect to the planar crystal structure of graphite.

In the manufacturing method of FIG. 46, by using the graphite sheet having such characteristics as the substrate, it is possible to continuously mass-produce thin film solar cells of high efficiency and high reliability.

FIG. 51 is a schematic sectional view showing an example of a conventional structure of a solar cell using a crystalline silicon thin film on a substrate containing carbon as a main component. In the figure, 23
0 is a substrate containing carbon as a main component. Silicon layer 231
Are disposed on the substrate 230, and the emitter layer 232 is provided on the surface of the silicon layer 231. A metal electrode 233 is provided on the surface of the emitter layer 232.

The substrate 230 is mainly composed of carbon,
It is possible to use a carbonaceous or graphite molded pair or the above-mentioned sheet graphite. The advantage of using the substrate 230 containing carbon as a main component is that carbon itself is a material that can withstand a high temperature of about 3000 ° C. as long as it is in a reducing atmosphere, so that it is necessary to form a crystalline silicon thin film on this. That it can sufficiently withstand a temperature (1000 to 1500 ° C.) as a supporting substrate, has good conductivity, and can function as a back electrode of a solar cell;
Since it is an element that is abundant on the earth, it can withstand a large amount of production, can form a strong chemical bond with silicon, and can obtain sufficient adhesion strength as a supporting substrate for a silicon film.

A silicon layer 231 is formed on the substrate 230 by, for example, the CVD method (chemical vapor deposition method) or the like. The silicon layer 231 is, for example, p-type. The silicon layer formed by the CVD method becomes polycrystalline silicon at a forming temperature of about 600 or more, but the crystal grain size of the polycrystalline silicon thus obtained is at most about 1 μm, which is a good performance when a solar cell is constructed. In order to obtain the above, the formed polycrystalline silicon can be once melted and recrystallized on the substrate 230 to increase the crystal grain size. This makes it possible to easily obtain the silicon layer 231 having a crystal grain size that is at least twice the layer thickness.

Further, an emitter layer of a conductivity type (n type in this case) opposite to that of the silicon layer 231 is formed on the surface of the silicon layer 231 by means such as impurity diffusion to form a pn junction. After that, a transparent conductive film, an antireflection film, or the like is provided (not shown) if necessary, and a metal electrode 233 is provided to form a solar cell.

In the above solar cell, the silicon layer 2
Since 31 is directly formed on the substrate 230 containing carbon as a main component, impurities slightly contained in the substrate 230,
That is, calcium, iron, aluminum, sulfur, etc. are diffused and mixed into the silicon layer 231 during the high temperature process for forming the silicon layer 231 or the emitter layer 232. If these impurities are mixed in the silicon layer 231, the characteristics of the silicon layer 231 as a semiconductor are impaired, and as a result, a solar cell with good performance cannot be obtained.

As a method for solving this problem, a structure as shown in FIG. 52 can be considered. In this example, the substrate 230
And a silicon layer 231 are provided with a silicon oxide film 234. When the entire surface of the substrate 230 is covered with the silicon oxide film 234, electrical connection between the silicon layer 231 and the substrate 230 is not made. Two
31 is in contact.

However, even in this case, although the silicon oxide film 234 functions as an impurity diffusion barrier from the substrate 230, the opening 235 of the silicon oxide film 234 is formed.
At a portion where the substrate 230 and the silicon layer 231 are in contact with each other,
Eventually, a phenomenon similar to that in the structure of FIG. 51 occurs, and impurities of the substrate 230 pass through this portion and the silicon layer 231 is removed.
Spread to. Further, in the structure of FIG. 51, since the silicon layer 231 and the substrate 230 containing carbon as a main component are strongly bonded to each other, sufficient adhesion strength can be obtained. However, in the structure of FIG. 234 is placed, and the adhesion between carbon and the silicon oxide film 234 is weak, so that the silicon layer 231 is easily peeled off from the substrate 230, the structure is easily broken, the yield is poor, and the sufficient yield is obtained. It has the drawback of not being reliable.

The reason why the adhesion between carbon and the silicon oxide film 234 is weak is explained as follows. That is, carbon reduces silicon oxide at high temperature to become carbon dioxide and volatilizes. Therefore, at the interface between the substrate 230 containing carbon as a main component and the silicon oxide film 234, this reaction occurs during the high temperature process for forming the silicon layer 231 or the emitter layer 232, and the substrate 230 and the silicon oxide film 23.
The chemical bond with 4 is not formed, and as a result, it depends only on the physical attachment form, and only weak adhesive force is obtained. By the way, in the case of silicon and a silicon oxide film, a chemical bond is established between them, so that a much stronger adhesive force can be obtained than in the case of carbon and a silicon oxide film.

The insertion of the silicon oxide film 234 in the solar cell shown in FIG. 52 has another purpose. Since it exists as a dielectric layer on the substrate side of the silicon layer 231, the difference in the refractive index between the silicon layer 231 and
This is to reflect the light that has entered the solar cell and transmitted without being absorbed by the silicon layer 231, and guide it to the silicon layer 231 again. The effect of reflection on the back surface of the silicon layer 231 is that the substrate 230 is in direct contact with the silicon layer 231.
The presence of the silicon oxide film 234 is larger than the case of 1.

However, by inserting the silicon oxide film 234, the silicon layer 231 and the silicon oxide film 234 are inserted.
Although the reflection between the two is improved, below the silicon oxide film 234 is the substrate 230 containing carbon as a main component.
Since 0 is black and absorbs light, there is little reflection from the substrate 230, and the effect of improving the back surface reflection due to the insertion of the silicon oxide film 234 is not great. That is, the effect of improving the performance of the solar cell is small.

Further, in order to form the solar cell having the structure shown in FIG. 52, it is necessary to provide an opening in the silicon oxide film provided on the substrate 230 containing carbon as a main component. Usually, for patterning a silicon oxide film, a method of coating with a resist according to a predetermined pattern and performing dry or wet etching is used. However, not only when wet etching is used but also when dry etching is used, the wet process cannot be eliminated at all as long as the resist is used.

However, since the substrate 230 contains carbon as a main component, it is generally porous and has a considerable water absorption property. Therefore, once the wet process is performed, there is a problem that the water absorbed by the substrate 230 at that time is not easily removed, which adversely affects the subsequent steps and impairs the reliability of the solar cell.

56 to 58 are cross-sectional views showing structures of various conventional solar cells having an uneven structure. FIG. 56 shows a crystalline solar cell, FIG. 57 shows an amorphous Si solar cell, and FIG. 58 shows a thin film solar cell. Show. In the figure, 2 is a polycrystalline Si thin film, 3 is a grid electrode, 4 is single crystal Si, 5 is a glass substrate, 6 is a transparent electrode, 7 is amorphous Si, 8 is a back electrode, and 9 is a heat-resistant substrate.

Next, the manufacturing method and operation of each of the above conventional solar cells will be described. In the crystalline solar cell shown in FIG. 56, an uneven shape as shown in the figure is formed on the surface of a Si (100) single crystal wafer 240 by anisotropic etching using potassium hydroxide (KOH) or the like. Anisotropic etching forms such a shape because an uneven shape having a triangular structure is formed. Next, impurities are diffused from the surface of the wafer thus treated to form a pn junction 241, and then a grid electrode 242 is formed. Further, in order to improve the efficiency of the solar cell, an antireflection film is formed on the surface of the wafer having an uneven shape, or impurities are diffused on the back surface of the wafer so that BS
An F (Back Surface Field) may be formed (neither is shown). In the solar cell of FIG. 56, the light 243 is incident on the crystal 240 from the surface having the uneven shape.
The incident light is photoelectrically converted in the crystal 240 and is extracted from the grid electrode 242 and a back surface electrode (not shown) provided on the back surface of the crystal 240. Here, in this solar cell, due to the uneven shape of the incident surface, the light reflected by the surface can also be made incident on the wafer as indicated by the arrow 244, and the reduction of the incident light due to the light reflection on the surface is small. In addition, the photoelectric conversion efficiency becomes high.

Next, the case of the amorphous Si solar cell shown in FIG. 57 will be described. First, the transparent electrode 246 is formed on the glass substrate 245. This transparent electrode 246 is Sn
It is produced by sputtering, vapor deposition, CVD, coating or the like of O ₂ , ZnO, ITO (In ₂ O ₃ : SnO ₂ ) or the like, and the uneven shape can be produced by selecting the film forming conditions. An amorphous Si film 247 is formed on the transparent electrode 246 having an uneven structure by plasma CVD or the like. Further, a film of Al or Ti / Ag is formed to form the back electrode 248.
To form. In the solar cell configured in this way,
Sunlight enters from the glass surface 245, and electric power is taken out by the transparent electrode 246 and the back surface electrode 248. In the case of this amorphous solar cell, since the transparent electrode 246 has a concavo-convex structure, the angle of incident sunlight is bent, and the distance traveled in the active layer becomes long, so more light is absorbed and the solar cell The conversion efficiency of is improved.

Next, the case of the thin film solar cell shown in FIG. 58 will be described. A concavo-convex structure is formed on the heat resistant substrate 250 made of a heat resistant material such as alumina or conductive ceramic by mechanical cutting. And this substrate 25
A thin polycrystalline Si thin film 251 is formed on the surface of 0, a pn junction 252 is formed by diffusing impurities, and then a grid electrode 253 is formed. In the case of a thin-film solar cell having an uneven structure obtained in this way, since the surface has an uneven structure as in the solar cell of FIG. Will be done. Further, when the light is reflected at the interface between the active layer and the heat-resistant substrate 250, the reflection angle changes, so that the distance traveled by the light in the active layer becomes long and the efficiency of the solar cell is increased.

FIG. 59 shows, for example, Solar Cells, 29 (1
990), pp. 257 to 266, which is a solar cell manufactured by using a semiconductor thin film and shows a conventional method for manufacturing a thin film solar cell, which is finally separated from a substrate and used. In the figure, 260 is a p-type silicon single crystal substrate, and 261 is V formed on the surface of the substrate 260.
V-shaped stripe groove, 262 is an n-type silicon crystal layer epitaxially grown on the substrate 260, 263 is a stripe-shaped groove formed on the surface of the n-type silicon crystal layer 262,
64 is a glass substrate adhered to the silicon crystal layer 262.

Next, the manufacturing process will be described. First, a plurality of V-shaped stripe grooves 261 are formed on the p-type silicon single crystal substrate 260 shown in FIG. 59 (a) by anisotropic etching, as shown in FIG. 59 (b). Next stripe stripe 2
As shown in FIG. 59 (c), an n-type silicon layer 262 having a low impurity concentration is epitaxially grown on the substrate 260 on which 61 is formed. Then, after the surface of the silicon layer 262 is planarized by polishing as needed, the silicon layer 262 is
By anisotropic etching, a plurality of V-shaped stripe grooves 263 are formed in the direction perpendicular to the stripe grooves 261 on the surface as shown in FIG. 59 (d). After this, the silicon layer 2
A pn junction is formed on the surface of 62, and the silicon layer 2
A protective film and an electrode are formed on the surface of 62. Next, in FIG.
As shown in (e), the glass substrate 26 is formed on the silicon layer 262.
Bond 4 together. The glass substrate 264 and the adhesive agent for adhering the glass substrate 264 are made of a material that is not etched in the subsequent etching process. Then, by using the selective etching technique, as shown in FIG. 59 (f), the silicon single crystal substrate 2
The cell is completed by removing 60 by etching and forming a protective film and an electrode on the back surface side of the silicon layer 262.

FIG. 60 (a) shows, for example, the public utility model sho 60
2 is a cross-sectional structure of a conventional solar cell module disclosed in Japanese Patent Laid-Open No. 194355. In the figure, 270 is a solar cell substrate made of, for example, single crystal or polycrystalline Si, 27
1a is an upper metal electrode for collecting a current generated by light, 271b is a lower metal electrode serving as a counter electrode, 27a
Reference numeral 3 is a lead wire whose one end is fixed to the upper electrode 271a of one solar battery cell and the other end is fixed to the lower electrode 271b of another solar battery cell by solder 273 or the like to electrically connect the solar battery cells to each other. There is a plurality of solar cells connected in this way and the surface glass 2 is filled with the filling resin 274.
It is sealed between 75 and the back material 275.

FIG. 60 (b) shows an example of a module structure of a thin film solar cell formed on a conductive substrate. In the figure, 280 is a conductive substrate, and 281 is a semiconductor thin film formed on it. A power generation layer 282a, an upper metal electrode 282a provided on the power generation layer 281, and a lower electrode lead portion 282b. The lead wire 283 has one end fixed to the upper electrode 282a of one solar cell and the other end fixed to the lower electrode 282b of another solar cell by solder 284 or the like as in the case of FIG. Electrically connect the battery cells. The plurality of solar cells connected in this way are sealed between the front surface glass 286 and the back surface material 287 by the filling resin 285.

Next, the operation of this conventional solar cell module will be described. The electrons and holes generated in the solar cell substrate 270 that received the light are separated into the front surface (upper) side and the back surface (lower) side by the internal electric field existing in the solar cell base 270, and the upper electrode 271a and the back electrode 271b are separated. It is collected in and is taken out as a current to the outside. For example, when the solar cell substrate 270 is made of silicon, the operating voltage at which the maximum output is obtained is about 0.5 V per cell, so in a normal power module, several to several tens of cells are connected in series. Connected to. Therefore, the upper metal electrode 27
The lead wire 272 fixed to the 1a by the solder 273 is extended and arranged on the back side of the adjacent cell, and fixed to the part of the lower metal electrode 271b of the adjacent cell by the solder 273 to realize the series connection. In this way, the plurality of solar cells connected to each other are integrally sealed by the resin 274, the surface glass 275, and the back surface material 276 and used as a power solar cell module.

In recent years, as low-cost solar cells, solar cells in which a thin-film power generation layer is formed on various low-priced substrates have been actively studied. In the case of the thin film solar cell formed on the conductive substrate 280 shown in FIG. 60 (b), the lower connection electrode 282b is formed on a part of the back surface of the conductive substrate 280 to connect the cells in series. Then, the lead wire 283 fixed to the upper electrode 282a of the adjacent cell by the solder 284 is soldered to the lower connection electrode 282b to establish the connection.

As a method of connecting solar cells in series,
Many proposals other than the above have been proposed, and examples thereof will be shown below. FIG. 61 shows a composite solar cell element disclosed in JP-A-59-3980. As shown in FIG. 61 (a), the front surface electrode 291a of one solar battery cell 290 and the back surface electrode 291b of the adjacent cell are soldered or a conductive adhesive or the like 2
The cells are adhered at 92, and the cells are stacked in a tile shape as shown in FIG. 61 (b) to realize the series connection. This structure can be connected in series in a compact manner in a simple process, but stress is likely to be applied to the adhesive part, and although it can be used as a power source for consumer equipment composed of a ru, it uses a large area cell of about 10 cm square. It could not be applied to the module for reliability.

An integrated amorphous solar cell is a typical example of another series connection method. FIG. 62 shows JP-A-61
FIG. 4 is a cross-sectional structural diagram of an integrated amorphous silicon solar cell disclosed in Japanese Patent Publication No. 54681/1990. In this solar cell,
As shown in the figure, the transparent conductive film 30 is formed on the insulating substrate 300.
1, the amorphous Si layer 302 and the metal electrode 303 are sequentially formed while being separated into predetermined regions, so that the upper electrode is connected to the lower electrode of the adjacent unit cell, and monolithically connected in series on the same substrate. realizable. However, at present, as a method for separating unit cells, lithography using ordinary photoresist,
Alternatively, laser patterning is used, which is an obstacle to realizing low cost because the process is complicated. From the above background, the structure adopting the connection method shown in FIG. 60 is currently generally used as the mainstream of solar cell modules for electric power.

[0046]

In the conventional method for manufacturing a thin film solar cell using a graphite sheet substrate shown in FIG. 46, an active layer is formed by lamp heating or electric heating. In the case of lamp heating, there is a problem that polycrystalline Si is deposited on the inner wall of the film forming chamber because the entire film forming chamber is heated, and it takes time for maintenance. Compared with the above, there is a problem that the surface is glossy and the light reflectance is large, so that the light for heating is reflected and the heating cannot be effectively performed. In addition, in the case of heating by energization, there are problems that the energizing terminals do not come into contact with the graphite sheet substrate well, or the temperature unevenness occurs on the substrate due to partial current flow. In addition, since the graphite sheet is very soft,
As shown in FIG.
There is a problem that the contact portion 228 with 20 is deformed or peeled off.

Further, since the graphite sheet substrate is soft and flexible, when thin film polycrystalline silicon is formed on the substrate by the CVD method, the expansion coefficient of silicon 237 and graphite 236 are different as shown in FIG. There is a problem in that it becomes curved and becomes a major obstacle in the subsequent process. Especially when grain size expansion is performed, the crystal surface is not evenly heated and only a part of the substrate can be grain size expanded. There is a problem that only a small substrate can be used. This is a big problem not only in the case of continuous production using a band-shaped graphite sheet as shown in FIG. 46 but also in the case of single-wafer production using a graphite sheet.

Although this is not limited to the manufacturing method shown in FIG. 46, in the conventional thin film forming process, the raw material gas is introduced and exhausted to the outside until it is all decomposed, so that the raw material gas is used efficiently. There was a problem that I could not do it. This is a major problem that obstructs the important advantage of thin-film solar cells that the amount of semiconductors used is reduced and the cost is reduced. Further, in the manufacturing method of FIG. 46, a film forming chamber for flowing a raw material gas is required for forming a thin film, the size of the apparatus becomes large, and maintenance of the film forming chamber is required, which causes a cost increase. There was a point. Also, when expanding the grain size of thin-film polycrystalline silicon on a graphite sheet substrate by zone melting,
In the manufacturing method of FIG. 46, there is a problem that polycrystalline Si aggregates into an island shape due to the above-described bending of the substrate or the like, and Si vapor evaporates from the surface portion to contaminate the grain size expansion chamber. was there.

By the way, in the thin film solar cell, in addition to the one using a graphite plate or a graphite sheet as its supporting substrate, as shown in FIG. 54, metal grade silicon (MG) is used.
-Si) 350 may be used as a substrate. FIG. 54
351 is a silicon thin film, 352 is an emitter layer formed on the surface of the thin film by impurity diffusion, and 353 is an upper grid electrode. The MG-Si substrate is cheaper than high-purity crystalline silicon, and is not curved due to the film formation of the thin film polycrystalline silicon on the substrate. Since the temperature is increased to near the melting point of silicon (1414 ° C.) when the grain size is expanded, 2% is added to the MG-Si substrate 350 as shown in FIG.
To some extent iron (Fe), aluminum (Al),
There is a problem in that impurities 354 such as gallium (Ga) are collectively ejected from the surface and destroy the active layer.

Further, the thin film solar cell using the conventional graphite-based substrate is, as described with reference to FIGS. 51 and 52,
Impurities cannot be avoided from the substrate into the silicon layer, back reflection from the substrate cannot be used effectively, and the adhesion between the silicon layer and the substrate is weak, resulting in excellent performance and high reliability. However, it is difficult to obtain the solar cell.

Further, a solar cell using a crystalline silicon wafer, an amorphous solar cell, and a thin-film solar cell each having a concavo-convex structure capable of effectively utilizing incident light are configured as shown in FIGS. Since the concavo-convex structure can be formed by chemical treatment when a crystalline silicon wafer is used as the substrate, and can be formed by changing the film forming condition of the transparent electrode in the case of an amorphous solar cell,
Although it can be formed relatively easily, in the case of a thin film solar cell equipped with an active layer obtained by processing polycrystalline silicon at a high temperature, such a method cannot be used and a substrate with excellent heat resistance can be used. There is a problem that it is not possible to easily fabricate the concavo-convex structure because it is only mechanically cut or processed by a laser or the like, and it is difficult to reduce the cost which is an important point in the thin film solar cell.

Also, a conventional thin film semiconductor device, in particular a thin film solar cell, in which a semiconductor thin film is formed on a substrate and which uses this semiconductor thin film as an active layer, is used in a form in which the thin film is finally separated from the substrate. The manufactured product is manufactured as shown in FIG. 59, and the process is carried out in a single-wafer process on a wafer-by-wafer basis, resulting in a problem of poor mass productivity.

In addition, a conventional solar cell module in which a plurality of solar cells are electrically connected is generally shown in FIG.
The electrical connection between each solar cell is extended so that the lead wire soldered to the upper electrode of the solar cell reaches part of the lower electrode of the adjacent solar cell. Then, the method of connecting there is taken. However, in this connection method, the upper electrode 27 of each cell is
A step of soldering a lead wire 272 that has been subjected to L-shaped processing twice on 1a, each cell at a predetermined position, that is, the end of the lead wire of one cell is part of the back surface electrode of the adjacent cell. It requires a step of arranging in a position where they come into contact with each other, a step of fixing the whole body and inverting it so that the back surface of the cell faces upward, and a step of making a soldering connection between the lower electrode of the cell and the lead wire. In addition, the interconnection process between cells becomes complicated, and automation of this process is very difficult. Further, in the conventional interconnection method of cells formed on a conductive substrate shown in FIG. 60 (b),
In addition to the complexity of the steps described above, it is necessary to form the lower electrode 282b for connection on a part of the back surface of the conductive substrate, and the adhesion strength between the conductive substrate 280 and the lower electrode 282b, the lower electrode 282b and the leads. The soldering strength with the wire 283 was not sufficient, and there was a problem in reliability.

As an attempt to solve the problems in the conventional example shown in FIG. 60, there is one disclosed in Japanese Patent Laid-Open No. 3-22574, which connects the solar cells by screws. However, there is a problem that the process is complicated, such as a screw hole needs to be opened in the substrate, and the substrate supporting the power generation layer is made of metal, so that the power generation layer having excellent characteristics cannot be formed.

The present invention has been made in order to solve the above problems, and has a high performance in a simple manufacturing process.
The object is to obtain a thin film solar cell with high reliability and low cost, and further to provide a method for manufacturing the thin film solar cell. Another object of the present invention is to finally obtain a semiconductor device manufacturing method capable of continuously manufacturing a thin film semiconductor device used in a form in which a thin film is separated from a substrate. Further, the present invention comprises a solar cell module in which a plurality of solar cells are interconnected to each other, and the interconnection is easy, and the mechanical strength of the connection is excellent and the thin film solar cell is highly reliable and the production thereof. Aim to get a way.

[0056]

In the method of manufacturing a thin film solar cell according to the present invention, the substrate is heated by high frequency direct heating in the step of forming a thin film on the graphite sheet substrate.

Further, in the method for manufacturing a thin film solar cell according to the present invention, a belt-shaped graphite sheet substrate is sequentially fed into the reaction chamber, a thin film active layer is formed on the substrate, and then a film is formed on the substrate. A cap layer made of a silicon oxide film or a silicon nitride film is formed on a thin film semiconductor, and the thin film semiconductor is melted and recrystallized in a state of covering the cap layer to expand the crystal grain size of the active layer. is there.

Further, in the method for manufacturing a thin film solar cell according to the present invention, two graphite sheet substrates are adhered to each other in such a state that the first main surfaces thereof face each other and overlap each other, and in this adhered state, the above-mentioned two substrates are adhered. A semiconductor thin film to be an active layer is formed on each of the second main surfaces, and after the thin film forming step, the substrates in a close contact state are separated into two substrates. Further, in the method for manufacturing a thin film solar cell according to the present invention, a graphite sheet formed by roll molding is subjected to a curing treatment at 1000 several hundreds of degrees Celsius, and then a semiconductor thin film to be an active layer is formed on a substrate. Is.

Further, in the method for manufacturing a thin film solar cell according to the present invention, a graphite sheet formed by roll forming is annealed in an HCl atmosphere at 3000 ° C. or higher, and then a semiconductor thin film to be an active layer is formed on the substrate. It is formed. Further, the method for manufacturing a thin-film solar cell according to the present invention is such that two graphite sheet substrates are overlapped with their first main surfaces facing each other, and a space is formed between the two overlapped substrates. Partial contact is made, and a raw material gas is caused to flow into the space to form a thin film on each of the first main surfaces of the two substrates.

Further, in the method for manufacturing a thin film solar cell according to the present invention, the distance from the raw material gas inlet port to the exhaust port of the film forming chamber for forming a thin film to be an active layer on the substrate is determined by the raw material gas flow rate and the flow velocity. Based on the decomposition rate and the decomposition rate, a thin film is formed in a film forming chamber set to a length such that most of the introduced source gas is decomposed before reaching the exhaust port. Further, the method for manufacturing a thin-film solar cell according to the present invention is a film-forming chamber provided with a means that does not allow only raw material gas components to permeate the exhaust port of the film-forming chamber for forming a thin film to be an active layer on a substrate. A thin film is formed.

In the thin film solar cell according to the present invention, a support base having high mechanical strength is fixed to the surface of the graphite sheet substrate opposite to the surface on which the thin film is formed. Further, the method for manufacturing a thin-film solar cell according to the present invention is such that a graphite sheet substrate is fixed using a frame made of carbon or ceramic so that tension is applied to the graphite sheet substrate, and the graphite sheet substrate is activated on the substrate in this state. The semiconductor thin film to be a layer is formed.

Further, in the method for manufacturing a thin-film solar cell according to the present invention, a graphite sheet substrate is arranged on a mold having a recess along the shape of the recess, and the recess covered with the graphite sheet has a metal grade. After heating in a state of being filled with silicon powder, it is cooled, and the metal-grade silicon powder is melted and solidified to form a heat-resistant substrate in which the metal-grade silicon substrate is fixed to the back surface of the graphite sheet substrate. A semiconductor thin film to be an active layer is formed on the surface of a sheet substrate.

In the thin-film solar cell according to the present invention, a first silicon layer, an insulating layer having openings of a predetermined pattern, and a second silicon layer are laminated in this order on a substrate containing carbon as a main component. It was done. Further, a method of manufacturing a thin film solar cell according to the present invention comprises a step of forming a first silicon layer on a substrate containing carbon as a main component, and an opening of a predetermined pattern on the first silicon layer. And a step of forming a second silicon layer on the insulating layer so as to be in contact with the first silicon layer in the opening, and particularly, the first step After an amorphous silicon layer is formed on the silicon layer, an insulating layer is formed on the amorphous silicon layer, laser irradiation is performed in a predetermined pattern, and the amorphous silicon layer in the laser irradiation region is an upper layer. The insulating layer is pierced and ruptured to form openings of a predetermined pattern in the insulating layer.

Further, the thin film solar cell according to the present invention has a semiconductor thin film formed on a graphite sheet substrate having an uneven structure on the surface. Further, in the method for manufacturing a semiconductor device according to the present invention, a step of forming a semiconductor film on a strip-shaped first substrate, a step of forming a pn junction in the semiconductor film, and a step of forming a semiconductor film in the semiconductor film Including the step of adhering the second substrate and the step of separating the semiconductor film from the first substrate, and the steps are continuously performed while sequentially moving the first substrate in the length direction thereof. It was done like this.

The thin-film solar cell according to the present invention, which constitutes a solar cell module, uses cells formed on a substrate made of a conductive material whose hardness is lower than that of the lead wire material, and uses a connecting lead wire. The cells are interconnected by partially penetrating or penetrating a part of the substrate of the adjacent cells. Further, in the method for manufacturing a semiconductor device according to the present invention, the tip of the lead wire arranged on the front surface side is bent, and the tip of the bent portion is brought into contact with and pressed at a predetermined position of the substrate of the adjacent cell. Thus, the tip portion of the lead wire is made to penetrate or enter a part of the substrate.

[0066]

In the present invention, since the graphite sheet substrate is heated by direct heating with high frequency, the substrate can be heated with high heating efficiency without damaging the substrate. In the present invention, the thin-film semiconductor formed on the graphite sheet substrate is covered with a cap layer made of a silicon oxide film or a silicon nitride film, and the thin-film semiconductor is melted and recrystallized to form a crystal grain size of the active layer. Therefore, the thin film layer does not form an island shape, and the contamination of the reaction chamber due to evaporation of the thin film layer can be prevented.

Further, in the present invention, two graphite sheet substrates are adhered to each other in a state where the first main surfaces thereof face each other and overlap each other.
Since a semiconductor thin film to be an active layer is formed on the main surface of the substrate and the substrate in a close contact state is separated into two substrates after the thin film forming step, stress caused by the difference in expansion coefficient between graphite and the semiconductor is generated. The two sides are offset to each other, and the substrate can be prevented from being bent. This makes it possible to facilitate the post-process and double the number of productions per unit time, thereby improving the productivity.

Further, in the present invention, since the graphite sheet formed by roll forming is cured at 1000 to several hundreds of degrees Celsius, the semiconductor thin film to be the active layer is formed on the substrate. It is possible to reduce the curvature of the substrate due to the stress generated by the difference in expansion coefficient between the substrate and the substrate. Further, in the present invention, the graphite sheet formed by roll forming is heated at 3000 ° C. in an HCl atmosphere.
Since the semiconductor thin film to be the active layer is formed on the substrate after performing the above annealing to reduce the impurities in the substrate, a high performance thin film solar cell can be manufactured.

Further, in the present invention, two graphite sheet substrates are overlapped with their first main surfaces facing each other,
In addition, the two overlapping substrates are partially brought into close contact with each other so that a space is formed between them.
Since the thin film is formed on each of the first main surfaces of the substrates, the reaction chamber for forming the thin film can be eliminated. Also,
In the present invention, the distance from the source gas introduction port to the exhaust port of the film forming chamber for forming a thin film to be an active layer on the substrate is
Based on the flow rate, flow rate, and decomposition rate of the raw material gas, most of the introduced raw material gas is activated in the film formation chamber or on the substrate set so that it is decomposed before reaching the exhaust port. Since the thin film is formed in the film forming chamber in which a means that does not allow only the raw material gas component to pass through is provided at the exhaust port of the film forming chamber for forming the thin film to be a layer, the use efficiency of the raw material gas can be improved.

Further, according to the present invention, since the supporting base having high mechanical strength is fixed to the surface of the graphite sheet substrate opposite to the surface on which the thin film is formed, the thin film solar cell using the graphite sheet substrate. The mechanical strength of can be improved. Further, in the present invention, the graphite sheet substrate is fixed to the graphite sheet substrate by applying tension to the graphite sheet substrate using a frame body made of carbon or ceramic, and in this state, a semiconductor thin film to be an active layer is formed on the substrate. By doing so, it is possible to prevent the substrate from being bent due to the stress generated due to the difference in expansion coefficient between the graphite and the semiconductor, and it is possible to facilitate the grain size expansion step.

Further, in the present invention, a graphite sheet substrate is placed on a mold having a depression along the shape of the depression, and the depression covered with the graphite sheet is filled with metallurgical grade silicon powder. After heating and cooling, the metal-grade silicon powder is melted and solidified to form a heat-resistant substrate in which the metal-grade silicon substrate is fixed to the back surface of the graphite sheet substrate, and an active layer is formed on the surface of the graphite sheet substrate of the heat-resistant substrate. Since the semiconductor thin film to be formed is formed, a thin film solar cell having high mechanical strength can be easily manufactured.

Further, in the present invention, a predetermined pattern is formed on the substrate containing carbon as a main component, the first silicon layer provided on the substrate, and the first silicon layer provided on the first silicon layer. Since the insulating layer having the opening and the second silicon layer provided on the insulating layer so as to contact the first silicon layer at the opening are provided,
By the silicon layer of, the substrate containing carbon as the main component and the insulating layer are firmly bonded, and the one having strong mechanical strength can be realized.
Moreover, since the second silicon layer and the substrate do not directly contact each other,
The influence of diffusion and mixing of impurities can be suppressed, and since the insulating layer is arranged on the silicon layer, the back reflection of light can be effectively used.

Further, according to the present invention, after the first silicon layer is formed on the substrate containing carbon as a main component, the first silicon layer is formed.
An insulating layer having openings of a predetermined pattern is formed on the silicon layer, and a second silicon layer is formed on the insulating layer so as to contact the first silicon layer at the opening. Therefore, a thin film solar cell having high performance and high reliability can be easily manufactured. In addition, in particular, after forming an amorphous silicon layer on the first silicon layer, an insulating layer is formed on the amorphous silicon layer, and laser irradiation is performed corresponding to a predetermined pattern, When the amorphous silicon layer pierces and ruptures the upper insulating layer to form an opening having a predetermined pattern in the insulating layer, a wet process can be unnecessary for forming the opening, and the performance of the solar cell can be improved. It can be further improved.

Further, in the present invention, since the semiconductor thin film is formed on the graphite sheet substrate having the uneven structure on the surface, a high performance thin film solar cell can be realized by an easy process. Further, in the present invention, the first strip-shaped shape
A step of forming a semiconductor film on the substrate, a step of forming a pn junction in the semiconductor film, a step of adhering a second substrate to the semiconductor film, and a step of removing the semiconductor film from the first substrate. And a step of separating the first substrate, the steps are continuously performed while sequentially moving the first substrate in the length direction thereof, and thus the thin film semiconductor device is finally used in a state of being separated from the substrate. Can be mass-produced continuously.

Further, in the present invention, in a solar cell module, a cell formed on a substrate made of a conductive material having a hardness lower than that of a lead wire is used, and one end of a connecting lead wire is used. Since the cells are interconnected by penetrating or penetrating into a part of the substrate of the adjacent cells, a solar cell module having excellent mechanical strength of the connecting section can be constructed easily. Further, according to the present invention, the tip of the lead wire is bent by bending the tip of the lead wire disposed on the front surface side and abutting the tip of the bent portion at a predetermined position of the substrate of the adjacent cell to apply pressure. Since it is made to penetrate or invade a part of the substrate, it is possible to obtain a solar cell module for electric power with high throughput in a very simple process.

[0076]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a substrate heating method in a method of manufacturing a thin film solar cell according to a first embodiment of the present invention. In the figure, 1 is a graphite sheet used as a conductive type substrate of a thin film solar cell. Reference numeral 2 is a thin film forming chamber for forming a semiconductor thin film on the graphite sheet substrate 1, 4 is a raw material gas inlet for introducing a raw material gas for semiconductor film formation into the thin film forming chamber 2, and 5 is a thin film forming chamber 2 It is the exhaust port. An induction heating source 3 is arranged inside the thin film forming chamber 2.

As shown by the arrow in FIG. 1, the graphite sheet substrate 1 fed into the thin film forming chamber 2 is heated by the induction heating source 3. In the induction heating, the terminals do not come into direct contact with the substrate unlike the electric heating, so that the deformation and peeling of the graphite sheet substrate surface can be prevented. Further, since heating can be performed with a uniform temperature distribution without heating failure due to poor contact of the current-carrying terminals with the substrate and temperature unevenness due to partial current flow, the semiconductor formed on the substrate can be heated. The thickness of the thin film can be made uniform. In lamp heating, since the surface of the graphite sheet substrate is glossy, the heating efficiency is poor due to the reflection of lamp light on the substrate surface, and since the entire reaction chamber is heated, silicon accumulates on the wall of the reaction chamber. However, induction heating does not lower the heating efficiency due to the gloss of the substrate surface, and only the conductive substrate is heated, so efficient heating can be performed and the reaction chamber wall surface Maintenance such as silicon removal is also unnecessary.

Dielectric heating has been performed on the sintered carbon plate so far. However, since the sintered carbon plate is fragile and the thickness of the substrate cannot be reduced, a heating source having a large power supply capacity is required, and the efficiency is not necessarily improved. It was not a good heating method. Since the graphite sheet can be made very thin, it can be heated with a small power source capacity, and the heating by induction heating is extremely efficient.

FIG. 2 is a diagram for explaining a thin film forming step and a grain size increasing step in the method of manufacturing a thin film solar cell according to the second embodiment of the present invention. In the figure, the same reference numerals as in FIG. 1 designate the same or corresponding parts, 6 is a cap layer deposition chamber, and 7 is a cap layer deposition chamber.
Is a thermal CVD apparatus disposed inside the cap layer deposition chamber 6,
8 is a particle size expansion chamber. Further, 10 is a thin film Si layer formed in the thin film forming chamber 2 on the graphite sheet substrate 1,
Reference numeral 15 is a cap layer formed on the thin film Si layer 10 in the cap layer forming chamber 6.

The graphite sheet substrate 1 sent to the thin film forming chamber 2 is heated by the induction heating source 3, and the raw material gas introduced from the raw material gas inlet 4 is decomposed by the heat of the substrate 1 to form a polycrystal on the substrate 1. The Si thin film 10 is formed. Si
The substrate 1 on which the thin film 10 is formed is then subjected to a cap layer deposition chamber 6
Sent to. In the cap layer deposition chamber 6, a thermal CVD device 7
Thus, the cap layer 15 is formed on the Si thin film 10. As for the cap layer 15, the polycrystalline Si layer 10 is the grain size expansion chamber 8
The thin film is pressed so that it does not become an island shape when melted by the method of expanding the grain size. The cap layer is composed of an oxide film, a nitride film, or a laminated film thereof. The grain size enlargement using the cap layer has been used for grain size enlargement of the thin film polycrystalline silicon on the crystalline silicon substrate. This is more important because it may be deformed by the stress of polycrystalline silicon. In this way, the cap layer is formed and further moved to the next grain size expansion chamber 8. In the grain size expansion chamber 8, polycrystalline S is produced by induction heating.
i is melted and the particle size is expanded.

FIG. 3 is a diagram showing a method of manufacturing a thin film solar cell according to a third embodiment of the present invention.
The same reference numerals as those in FIG. 2 indicate the same or corresponding parts. Reference numeral 20 denotes a cap layer removing chamber which is provided with a dry etching device 21 therein and removes the cap layer used in the grain size increasing step by dry etching. Reference numeral 22 denotes a pn junction forming chamber which has a thermal diffusion device 23 therein and which forms a pn junction in the Si thin film on the substrate 1 by thermal diffusion of impurities. 24 is equipped with a sputter device 25 inside thereof,
This is an antireflection film forming chamber for forming an antireflection film on a Si thin film on which an n-junction is formed. Reference numeral 26 is a surface electrode forming chamber in which a sputtering device 27 is provided and a surface electrode is formed by sputtering. Reference numeral 29 denotes a scaly graphite which has been acid-treated for purification and foaming, and 30 denotes a graphite sheet forming roller which press-molds the scaly graphite 29 to produce the graphite sheet substrate 1. 31 is a roller 30
It is a stacking / feeding roller that stacks two graphite sheet substrates 1 formed in 1 above, pressurizes them into close contact, and sends the stacked graphite sheet substrates 1 to a continuous reaction chamber. 32 is sent out from the reaction chamber,
It is a winding roller that winds each of the two original substrates 1 separated.

Next, the manufacturing process of the thin film solar cell according to this embodiment will be described. The graphite sheet substrate 1 is manufactured by press-molding scaly graphite 29 purified and foamed by acid treatment with a roller 30. In this embodiment, two graphite sheet substrates 1 are superposed as shown in the figure,
It is delivered to the reaction chamber in a state in which it is brought into close contact by being pressed by the roller 31. Graphite sheets can be easily adhered while maintaining airtightness simply by applying pressure. A very large pressure is required for complete adhesion, but by selecting an appropriate pressure, it is possible to bond them with such strength that they can be easily peeled off in a later step. In the thin film forming chamber 2, silane (SiH ₄ ) or dichlorosilane (SiH ₂ C)
A raw material gas such as l ₂ ) is introduced from the raw material gas inlet. The graphite sheet substrate 1 sent into the reaction chamber is directly heated to about 1000 ° C. by the dielectric heating power source 3. Heated graphite sheet substrate 1 because the source gas is full
The gas is decomposed above, and polycrystalline Si, which is an active layer, is formed on the substrate. Here, in this embodiment, since the Si thin films are formed on both surfaces of the two substrates 1 bonded together, the stress between the thin film and the substrate cancels each other out, and the graphite sheet substrate as shown in FIG. Deformation can be suppressed.

The graphite sheet substrate on which the polycrystalline Si thin film is formed is sent to the cap layer forming chamber 6, where heat C is applied.
A cap layer made of an oxide film, a nitride film, or a laminated film thereof is formed by the VD method or the like. After the cap layer is formed, the substrate 1 is sent to the grain size enlargement chamber 8 where the polycrystalline Si is melted by induction heating and recrystallized to enlarge the grain size. After this, the substrate 1 is placed in the cap layer removal chamber 2
0, where the cap layer is removed by dry etching.

Next, the graphite sheet substrate 1 is sent to the pn junction forming chamber 22. Here, a pn junction is formed in the Si thin film by thermal diffusion of impurities. Thereafter, the substrate 1 is sent to the antireflection film forming chamber 24, where the antireflection film is formed by sputtering, and the substrate 1 is sent to the upper electrode forming chamber 26, where the upper electrode is formed by sputtering. . The substrate 1 sent out from the reaction chamber is separated into the original two sheets, and each is wound up by the winding roll 32. Here, since the two graphite sheets are originally press-molded separately from each other and adhered by applying a light pressure of about 100 g to 1 kg / cm ² , the bonding force of the adhered surfaces is relatively small. Since it is small, it can be easily separated by tearing along the contact surface.

In this embodiment, two graphite sheet substrates are adhered to each other in such a state that one main surface thereof faces each other and overlaps with each other, and in this contact state, S is formed on each of the other main surfaces of the two substrates.
Since the i thin film is formed, the stress caused by the difference in the coefficient of thermal expansion between the thin film and the substrate cancels out on both sides, and the substrate can be prevented from being curved, whereby the subsequent steps can be easily performed. Further, since the solar cells are simultaneously formed on the two substrates, the productivity can be doubled.

In the above-mentioned embodiment, although the substrate is manufactured with flexibility, it is curved to some extent even if the substrate is heated to 1000s of hundreds of degrees Celsius or more and cured before the film forming process. Can be prevented and the step of increasing the particle size can be facilitated. In this case, the completed solar cells are not wound into a roll but are cut sequentially.

Further, in the above embodiment, it is premised that the graphite sheet just molded by the roller is used, but after the substrate is molded by the roller, the substrate is annealed in an HCl atmosphere at about 3000 ° C. Impurity concentration can be purified, and performance deterioration due to the inclusion of impurities in the thin film can be prevented.

In order to continuously form a semiconductor thin film on a belt-shaped graphite sheet substrate while flowing it, a reaction chamber for flowing a raw material gas to form a film is required, which requires a large-scale manufacturing apparatus and maintenance. Etc. are also complicated. FIG. 4 (a) is a diagram showing a method for manufacturing a thin film solar cell according to a fourth embodiment of the present invention, which does not require a reaction chamber. In the figure, reference numeral 35 is a stacking roller that stacks and feeds two graphite sheet substrates 1 together, and 36 is an edge holding roller that holds down both edges of the stacked graphite sheet substrates 1 to bring them into close contact. Reference numeral 38 is a raw material gas supply nozzle that abuts the edge portion of the superposed graphite sheet substrates 1 while rotating and supplies the raw material gas to a reaction space 39 formed between the two graphite sheet substrates. Reference numeral 37 denotes a gas supply unit pressing roller that presses both sides of the position where the raw material gas supply nozzle 38 of the graphite sheet substrate 1 abuts. 4 (b) is a top view of the raw material gas supply section, and FIG. 4 (c) is a sectional view taken along line CC of FIG. 4 (b).

The two graphite sheet substrates 1 are superposed by the superposing roller 35 and sent out. Both edge portions of the sent-out substrate 1 are pressed and brought into close contact with each other by an edge pressing roller 36. As described in the third embodiment, the graphite sheet can be easily adhered while maintaining airtightness only by applying pressure. A very large pressure is required for complete adhesion, but by selecting an appropriate pressure, it is possible to bond them with airtightness, and further to facilitate peeling in a later step. In addition, since the graphite sheet has flexibility, a space can be created in the two laminated sheets and the original flat plate can be formed again after the solar cell manufacturing process is completed.

The substrate 1 is heated from above and below by a heater or the like (not shown). Substrate 1 sent in this state
By injecting the raw material gas from the edge portion of the raw material gas by the raw material gas supply nozzle 38, a reaction space filled with the raw material gas is formed in the central portion in the width direction of the substrate 1, and the raw material gas is decomposed inside the reaction space to form an inner surface of the space 39. A semiconductor thin film is formed on. Exhaust from the reaction space 39 may be performed by bringing a disk-shaped exhaust nozzle having the same configuration as the raw material gas supply nozzle into contact with the edge portion. Since the thin film is already formed on the inner surface of the reaction space 39, the pressing of the substrate in the width direction at the terminal end of the reaction space 39 needs to be performed with a minute pressure so as not to damage it. After forming the semiconductor thin film in this manner, the two graphite sheet substrates 1 are separated, and the thin film solar cell is completed through the subsequent steps, that is, the step of expanding the grain size, forming the pn junction, and the like.

As described above, in this embodiment, the two graphite sheet substrates are superposed so that their main surfaces are opposed to each other, and the edges are closely contacted so that a space is formed between the two superposed substrates. Then, since the raw material gas is caused to flow into this space to form the semiconductor thin film on each one main surface of the above-mentioned two substrates, the reaction chamber can be eliminated. In the above embodiment, 2
Although it has been described that the grain size expansion is performed after separating the graphite sheet substrates, a second reaction space different from the reaction space for forming the thin film is formed, and the cap layer is formed in the second reaction space. It is also possible to form a film and further form another third reaction space, and perform melt recrystallization of the thin film in this third reaction space to expand the grain size.

By the way, the thin film formation reaction chamber used in the conventional method of continuously forming a semiconductor thin film on the surface of a substrate while flowing a strip-shaped substrate is provided with a source gas introduction port at one end and at the other end. Exhaust ports are provided, but the length between them is several tens of centimeters to 1 meter,
This is not long enough for the raw material gas introduced from the inlet to be completely decomposed before flowing to the exhaust outlet, and therefore the raw material gas was exhausted without being effectively used. Specifically, when the length of the reaction chamber is about 1 meter, only about 10% of the introduced source gas that decomposes and contributes to film formation is used, and the rest is unused. It was being exhausted from the exhaust port. This is a serious problem in terms of cost, and effective use of the raw material gas is a key to reducing the cost of the thin film solar cell. FIG. 5 is a view showing a method of manufacturing a thin film solar cell according to a fifth embodiment of the present invention, which enables effective use of raw material gas, and in the drawing, 40 is a thin film forming chamber. Reference numeral 41 denotes a belt-shaped substrate, for example, a graphite sheet substrate, on the surface of which a semiconductor thin film is formed in the thin film forming chamber 40, which is sequentially moved in the arrow direction in the drawing. The substrate 41 is directly heated by the dielectric heating source 3. The raw material gas 42 is introduced into the reaction chamber through the raw material gas inlet 4, and flows in the reaction chamber while being decomposed by the heat of the substrate 41. Reference numeral 43 is a carrier gas after the raw material gas is decomposed and a component that contributes to film formation is used, and the carrier gas is exhausted from the exhaust port 5 to the outside of the reaction chamber. Here, in this embodiment, the length between the source gas introduction port 4 and the exhaust port 5, that is, the length L ₁ of the reaction chamber in which the source gas flows is almost all decomposed while the source gas reaches the exhaust port. The length is set as described. Such a length can be set based on the flow rate of the raw material gas to be introduced, the decomposition rate, and the like. For example, length L
_{When 1 is set} to about 10 meters, about 60% of the total raw material gas is decomposed and contributes to film formation, and the use efficiency can be significantly improved.

FIG. 6 is a view showing a method of manufacturing a thin film solar cell according to a sixth embodiment of the present invention, which is another example capable of effectively utilizing the raw material gas, and in the figure, the same reference numerals as those in FIG. Are the same or corresponding parts. The exhaust port 5 of the thin film forming chamber 44 of this embodiment is provided with a film, for example, a platinum film 45, which does not allow only undecomposed raw material gas to pass therethrough. For this reason, the carrier gas after the raw material gas is decomposed and the component contributing to film formation is used is exhausted from the exhaust port 5, and the raw material gas that has flowed through the reaction chamber and reached the exhaust port without being decomposed reaches the platinum film 45. To remain in the reaction chamber as indicated by arrow 46. In this way, in this embodiment, since the unused raw material gas is not exhausted, the use efficiency of the raw material gas can be improved. In this embodiment, the semiconductor thin film is continuously formed on the surface of the substrate while flowing the belt-shaped substrate. However, this is also applicable to a structure in which film formation is performed in a single wafer unit. It goes without saying that you can do it.

FIG. 7 is a sectional view showing a thin film solar cell according to the seventh embodiment of the present invention. In the figure, 51 is a flexible graphite sheet substrate. The polycrystalline silicon thin film 52 is arranged on the substrate 51, the antireflection film 53 is arranged on the silicon thin film 52, and the upper electrode 54 is arranged on the antireflection film 53. Further, 50 is a support base made of an inexpensive metal plate which is adhered and fired on the back surface of the graphite sheet substrate 51 with silver paste or aluminum paste.

FIG. 8 is a sectional view showing a thin film solar cell according to the eighth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 7 denote the same or corresponding portions, and 55 denotes a support base provided on the back surface of the graphite sheet substrate 51 and made of metal grade silicon (MG-Si) having a thickness of 300 microns or more.

A thin film solar cell using a graphite sheet as a substrate is insufficient in mechanical holding of the semiconductor thin film as an active layer because the graphite sheet has flexibility. In addition, in the manufacturing process, the graphite sheet substrate and the semiconductor thin film are curved due to the difference in expansion coefficient between them as shown in FIG. 53, which makes it very difficult to enlarge the crystal grain size in the subsequent process. On the other hand, as a substrate, a metal plate or MG
-Using a Si substrate improves the strength of mechanical holding,
There is a problem that impurities in the substrate are mixed into the thin film when the thin film is formed and the performance is remarkably deteriorated, or the active layer is destroyed by jetting of the impurity as shown in FIG.

In the thin-film solar cell of the seventh embodiment, an inexpensive metal plate is adhered and fired on the back surface of a graphite sheet substrate having a semiconductor thin film formed on the surface thereof with a metal paste, and in the eighth embodiment. In the thin film solar cell, MG-Si is arranged on the back surface of a graphite sheet substrate having a semiconductor thin film formed on the surface thereof. As a result of this,
In the thin film solar cell of the eighth embodiment, the mechanical holding strength of the semiconductor thin film in the thin film solar cell using the graphite sheet as the substrate is greatly improved.

Next, a method of manufacturing the thin film solar cell shown in FIGS. 7 and 8 will be described. First, an example of a method of manufacturing the thin film solar cell of FIG. 7 will be described with reference to FIGS. FIG. 9 is a diagram showing a step of fitting the graphite sheet substrate 57 into the frame body, in which 56 is an outer frame body sandwiching the flexible graphite sheet 57, 58 is an inner frame body similarly sandwiching the flexible graphite sheet 57, 5
Reference numeral 9 denotes a heat equalizing plate which is fitted inside the inner frame 58 so that the graphite sheet 57 is entirely in contact with one main surface thereof. These outer frame body 56, inner frame body 58, and heat equalizing plate 5
All of 9 are made of carbon or ceramic.

First, the graphite sheet substrate 57 bent in advance according to the size of the outer periphery of the inner frame body 58 is sandwiched between the outer frame body 56 and the inner frame body 58, fixed by applying tension of tension, and further soaked. By fitting the plate 59 inside the inner frame 58, as shown in FIG. 10, a substrate whose one main surface is partially covered with the graphite sheet 57 is completed. 11 is shown in FIG.
FIG. 11 is a process drawing in a BB cross section in FIG. 10 showing a process after the state shown in FIG. The substrate in the state of FIG. 11 (a) is C
The polycrystal Si thin film 60 is formed on the graphite sheet substrate 57 by several tens of microns in a VD apparatus. At this time, since the flexible graphite sheet is pressed by the outer frame body 56 and the inner frame body 58, the flexible graphite sheet does not bend and the step of increasing the crystal grain size by melting and recrystallization of polycrystalline Si can be easily performed. You can After the grain size increasing step, impurity diffusion or ion implantation is performed on the Si thin film 60 to form a pn junction. This pn junction can also be formed by mixing the doping gas by CVD and switching the type of dopant midway during the formation of the active layer. The pn junction can also be formed by forming a microcrystalline film having a conductivity type opposite to that of the active layer on the Si thin film 60 by the plasma CVD method. After forming the pn junction,
The antireflection film 61 is formed by a sputtering method or the like. As the antireflection film, when the lateral conductivity of the Si thin film 60 is low, ITO (In ₂ O ₃ : Sn) also serving as an electrode is used.
If a transparent conductive film such as O ₂ ), SnO ₂ or ZnO is used and the lateral conductivity of the Si thin film is high and a transparent electrode is not required, an insulating film such as a silicon nitride film (Si ₃ N ₄ ) is used. Used. FIG. 11B shows a state where the antireflection film 61 is formed. After that, an upper electrode (grid electrode) 86 is formed on the antireflection film 61 (not shown). A silver electrode is mainly used for the upper electrode and is formed by screen printing or vapor deposition. Next, as shown in FIG. 11C, the flexible graphite sheet 57 is attached to the outer frame body 5.
While holding 6 and the inner frame 58, remove the soaking plate 59, and attach an inexpensive metal plate 62 of the same size as the soaking plate 59 with silver paste or aluminum paste as shown in FIG. 11 (d). , Bake. Finally, the outer frame body 56 and the inner frame body 58 are removed to complete the thin film solar cell.

In the above embodiment, the one using the heat equalizing plate 59 has been described, but the flexible graphite sheet 57 is sandwiched between the outer frame body 56 and the inner frame body 58, and the surface of the substrate 57 opposite to that in the above embodiment is used. That is, the Si thin film, the antireflection film, and the upper electrode may be formed inside the inner frame 58, and the metal plate 62 may be attached to the surface opposite to the surface on which these are formed.

FIG. 12 shows the outer frame body 5 used in the above manufacturing method.
6 and the inner frame 58 to form a polycrystalline S over a large area.
It is a figure which shows the method of forming an i thin film. In this method, the flexible graphite sheet 57 serves as a packing (gasket) of the CVD apparatus, and the outer periphery thereof is fixed by the outer frame body 56 and the inner frame body 58. 63 is a bell jar of a CVD apparatus. Board 57
Is heated by the induction heating source 3. The raw material gas is introduced into the reaction chamber through the raw material gas introduction port, decomposed on the substrate, and a thin film is formed on the substrate 57. 5 is an exhaust port. After the thin film is formed in this manner, the thin film solar cell is subjected to the grain size expanding step, the pn junction forming step, the antireflection film forming step, the upper electrode forming step, and the metal plate attaching / baking step, as described above. Is completed.

Next, an example of a method of manufacturing the thin film solar cell of FIG. 8 will be described with reference to FIG. FIG. 13 is a diagram showing a method of forming an MG-Si supporting substrate and fixing it to a graphite sheet, in which 64 is boron nitride (B).
N) mold. As shown in the figure, the mold 64 has a two-step recess, and the graphite sheet 65 is arranged in close contact with the inner wall of the mold along the shape of the recess.
The metal grade Si powder 67 fills the deep recess of the mold 64, and the BN lid 66 is arranged so as to cover the deep recess filled with the metal grade Si powder 67.

In this substrate manufacturing method, the graphite sheet 65 is preliminarily bent so as to be in close contact with the inner wall of the mold. This is placed in a mold 64 and the depression is filled with metal grade Si powder 67. In this state, the lid 66 is heated and heated to melt the metal-grade Si powder, and then cooled and solidified. As a result, as shown in FIG. 13B, the MG-Si supporting base 68 is formed, and the graphite sheet 65 is fixed to the supporting base 68. After that, this is taken out of the mold, and the unnecessary graphite sheet around the periphery is cut off to complete a heat-resistant substrate in which the graphite sheet is fixed to the MG-Si supporting substrate.

The thin film solar cell shown in FIG. 8 is manufactured using the heat resistant substrate thus formed. The heat-resistant substrate in which the graphite sheet is fixed to the MG-Si supporting base is the graphite sheet substrate 51 and MG-S in FIG.
This corresponds to the i support base 55. This is set in the CVD device and SiH ₄ or SiHCl ₃ gas is flown,
This gas is decomposed at a high temperature of about 1000 ° C., and a polycrystalline Si thin film 52 serving as an active layer is formed on the graphite sheet substrate 51.
To form a film of several tens of microns. At this time, since the graphite sheet substrate 51 is fixed to the MG-Si supporting base 55, the graphite sheet substrate 51 does not bend due to the stress due to the difference in expansion coefficient between graphite and silicon, and the crystal grain size due to the melt recrystallization of polycrystalline Si. Can be easily performed.
After the grain size increasing step, impurity diffusion or ion implantation is performed on the Si thin film 52 to form a pn junction. This pn junction is CV
It can also be formed by mixing the doping gas in D and forming the active layer during film formation, and switching the type of dopant midway. In addition, the Si thin film 52 is formed by the plasma CVD method.
The pn junction can also be formed by forming a microcrystalline film having a conductivity type opposite to that of the active layer thereon. After forming the pn junction, an antireflection film 53 is formed by a sputtering method or the like. As the antireflection film, when the lateral conductivity of the Si thin film 52 is low, ITO (In ₂ O ₃ : S) which also serves as an electrode is used.
nO ₂ ), SnO ₂ or ZnO is used, and when a Si thin film has high lateral conductivity and a transparent electrode is not required, an insulating film such as a silicon nitride film (Si ₃ N ₄ ) is used. Used. After that, an upper electrode (grid electrode) 54 is formed on the antireflection film 53. A silver electrode is mainly used for the upper electrode and is formed by screen printing or vapor deposition. In this way, the thin film solar cell shown in FIG. 8 is completed.

In the above example, by the template forming method,
A graphite sheet was formed on a MG-Si supporting substrate to form a heat-resistant substrate, which was prepared by sandwiching a graphite sheet 57 between an outer frame body 56 and an inner frame body 58 shown in FIG. 9 as shown in FIG. The metal grade silicon layer 71 may be formed by the plasma spraying method while the tensile tension is applied to 57. In FIG. 14, 6
Reference numeral 9 is a material ejection nozzle of the plasma spraying apparatus, and 70 is a molten metal grade silicon. Here, it is possible to form the MG-Si supporting substrate with a uniform thickness on the surface of the graphite sheet 57 by moving the nozzle in the direction of the arrow in the figure.

The ninth embodiment of the present invention will be described below with reference to the drawings. FIG. 15 is a schematic sectional view showing the structure of the solar cell according to the ninth embodiment of the present invention. In the figure, 72
Is a substrate whose main component is carbon. First silicon layer 7
3 is disposed on the substrate 72, and the insulating layer 74 is disposed on the first silicon layer 73. Openings 78 are provided at predetermined locations in the insulating layer 74. The second silicon layer 75 is disposed on the insulating layer 74 and contacts the first silicon layer 73 at the opening 78. The emitter layer 76 is the second silicon layer 75.
Formed on the surface of. The metal electrode 77 is arranged on the emitter layer 76.

Next, the structure of the embodiment shown in FIG. 15 will be described in order along with the manufacturing process for manufacturing the structure. Board 7
2 is a substrate containing carbon as a main component, which is similar to that described in the conventional example, and has mechanical support for the silicon layers 73 and 75,
It functions as one electrode of the solar cell. The first silicon layer 73 is formed on the substrate 72 by, for example, the CVD method. The specific resistance of the first silicon layer 73 depends on the output current of the solar cell.
It is only necessary to be low enough not to hinder the flow through the substrate 3 through the thickness direction into the substrate 72. For example, when the thickness of the first silicon layer 73 is 1 μm, the specific resistance of the first silicon layer 73 is set to be 0.01 Ω · cm ² or less in the thickness direction per unit area. It is sufficient to set it to 100 Ω · cm or less. However, as described later, it is desirable that the resistivity of the first silicon layer be as low as possible.
When the first silicon layer 73 is a p-type, the first silicon layer 73 having a low specific resistance can be obtained by mixing a large amount of a gas containing boron into the source gas during formation.

Next, the insulating layer 74 is formed on the first silicon layer 73 by, eg, CVD method. Insulating layer 74
The openings are provided in a predetermined pattern. this is,
First, the insulating layer 74 may be provided on the entire surface of the first silicon layer 73, and the insulating layer 74 may be partially removed only at the place where the opening is to be provided. As the insulating layer 74, a silicon oxide film, a silicon nitride film, or a laminated film of these can be used. Although only one silicon oxide film may be used as the insulating layer 74 in order to serve as a barrier against diffusion of impurities from the substrate 72 and to function as a back surface reflection layer, if a silicon nitride film or a laminated film with the silicon nitride film is used, it will be described later. At the time of the melt recrystallization of the silicon layer described below, the familiarity between the insulating layer 74 and the silicon layer is improved, and the melt recrystallization can be performed more effectively.

Furthermore, a second silicon layer 75 is further formed on this.
Are formed by the CVD method or the like. Second silicon layer 75
Is a main power generation region of the solar cell, and is formed to have a thickness of about 5 μm to 30 μm. When the first silicon layer 73 is p-type, the second silicon layer 75 is also p-type. The specific resistance of the second silicon layer 75 is preferably about 1 Ω · cm. CVD
Since the crystal grain size of the second silicon layer 75 does not exceed 1 μm at most when formed by the method,
If the characteristics of the obtained solar cell are insufficient as they are, once the second silicon layer 75 is melted and recrystallized, the crystal grain size can be increased, and the second silicon layer 75 can be easily doubled in layer thickness. The above crystal grain size can be obtained. During the melt recrystallization, as shown in FIG. 16, the second silicon layer 7
It is necessary to cover the surface of 5 with a cap film 79 made of a silicon oxide film or the like. After the recrystallization, the cap film is removed. When performing the melt recrystallization of the second silicon layer 75, it is necessary to perform the first re-crystallization before forming the second silicon layer.
The silicon layer 73 may be melted and recrystallized first. In this case, since the first silicon layer 73 is in contact with the substrate 72 containing carbon as a main component, the first silicon layer 73 is well compatible with the substrate 72 during melt recrystallization, and is easily large. A silicon layer having a crystal grain size can be used.
Then, on this, when the second silicon layer 75 is melted and recrystallized, the portion where the second silicon layer 75 is in contact with the first silicon layer 73 in the opening provided in the insulating layer 74. Then, since the second silicon layer 75 is recrystallized while being drawn into the crystal orientation of the first silicon layer 73, the crystal grain size of the second silicon layer 75 after recrystallization is also large. Alternatively, when the second silicon layer 75 is melted and recrystallized, even if the first silicon layer 73 is also melted and recrystallized at the same time, the first silicon layer 73 becomes familiar with the substrate 72 and has a large grain size. If the first silicon layer 73 is solidified first, the second silicon layer 75 is also solidified while being drawn into the second silicon layer 75, so that the above effect can be obtained similarly.
Thus, obtaining a silicon layer having a large grain size is very advantageous in improving the performance of the solar cell.

On the surface of the second silicon layer 75 thus formed, the emitter layer 7 is formed by means such as impurity diffusion or film formation of a microcrystalline silicon film, an amorphous silicon film or the like.
6 is formed. The emitter layer 76 is the second silicon layer 75.
The conductivity type opposite to that is used to form a pn junction. Furthermore, if necessary, a transparent conductive film, an antireflection film, or the like is provided on the surface (not shown), and a metal electrode 77 is provided to form a solar cell.

In the solar cell constructed as described above, the second silicon layer 7 functioning as a main power generation region is formed.
5 and the substrate 72, an insulating layer 74 acting as a barrier against diffusion of impurities is interposed, and the first silicon layer 73 is also in contact with the opening of the insulating layer 74, and is in direct contact with the substrate 72. Therefore, it is possible to avoid the adverse effect of the diffusion and mixing of impurities from the substrate 72, which is seen in the conventional example.

Since the insulating layer 74 is formed on the silicon layer and not directly on the substrate 72 containing carbon as a main component, the insulating layer 74 is not formed on the substrate as shown in the conventional example. The problem that the adhesive force is weak and peels easily is solved. Further, even when attention is paid to the function of the insulating layer 74 as a back surface reflection film, in addition to the reflection due to the difference in refractive index between the second silicon layer 75, which is the main power generation layer, and the insulating layer 74, there is no conventional example. First silicon layer 73
Since the reflection due to the difference in refractive index between the insulating layer 74 and the insulating layer 74 can be utilized, the effect of the back surface reflection is greatly improved as a whole. FIG. 17 is a graph showing this, and FIG. 17 (a) shows the reflectance with respect to wavelength when the silicon oxide film is directly formed on the substrate containing carbon as the main component as in the conventional example of FIG. FIG. 17 (b) is also a plot of the reflectance when a silicon oxide film is formed on crystalline silicon. The vertical axis scale of FIG. 17 (a) is shown in FIG.
Note that it is one-twentieth that of (b), and it is understood that the reflectivity is significantly improved by changing the material under the silicon oxide film from the substrate whose main component is carbon to the silicon layer. To be done.

Further, as described above, the first silicon layer 7
When the second silicon layer 75 of the same conductivity type is formed thereon by making 3 as low as possible, a so-called high-low junction is formed at the opening of the insulating layer 74. It works as a BSF (Back Surface Field) and contributes to effective collection of carriers generated during operation as a solar cell. This is an effect not seen in the conventional example and is effective in improving the performance of the solar cell.

FIG. 18 is a sectional process drawing showing another manufacturing method for manufacturing the solar cell of FIG. The description was made according to the manufacturing method. The example which further improved this manufacturing method is shown. A first silicon layer 73 is formed on the substrate 72 containing carbon as the main component shown in FIG. 18A by, for example, the CVD method as shown in FIG. 18B. Then the first
When the insulating layer 74 is formed on the silicon layer 73 by the CVD method or the like, first, the surface of the first silicon layer 73 is covered with the amorphous silicon layer 80, and then the insulating layer 74 is provided. The amorphous silicon layer 80 is formed by plasma CVD, for example. After this, as indicated by the arrow 81 in FIG.
A laser beam such as an argon laser is applied to a portion of the insulating layer 74 where the opening is to be provided. The insulating layer 74 is generally transparent and absorbs little laser beam, so
Patterning with a laser beam is difficult by itself, but
In this case, the irradiated laser beam is absorbed by the amorphous silicon layer 80 and heats this portion. A portion of the heated amorphous silicon layer 80 crushes and ruptures the insulating layer 74, whereby an opening 82 is formed in the insulating layer 74 (FIG. 18D). On top of this, a second silicon layer 75,
When the emitter layer 76 and the metal electrode 77 are sequentially formed, FIG.
A solar cell having the structure shown in is obtained.

According to this method, the patterning of the insulating layer 74 can be realized without using any wet process. Therefore, performance deterioration due to moisture absorption of the substrate can be prevented, and a solar cell with excellent performance can be manufactured. Note that the amorphous silicon layer 80 is crystallized by a high temperature process such as a step of forming the second silicon layer 75 and a step of forming the emitter layer 76 and integrated with the first silicon layer 73. The introduction of layer 80 has no adverse effect on the performance of the solar cell.

FIG. 19 is a sectional view showing the structure of a thin film solar cell according to the tenth embodiment of the present invention. In the figure, 8
3 is a graphite sheet substrate having an uneven structure.
The polycrystalline silicon thin film 84 is arranged on the substrate 83, and the antireflection film 85 is arranged on the polycrystalline silicon thin film 84.
A grid electrode 86 is arranged at a predetermined position on the antireflection film 85.

FIG. 20 is a diagram showing a method for producing the graphite sheet substrate 83 having the concavo-convex structure shown in FIG. 19. In the diagram, 88 is a graphite material obtained by acid treatment of scaly graphite to be purified / foamed, and 87 is A graphite sheet forming roller for press-molding this graphite material 88 to produce a graphite sheet substrate 89. As shown in FIG.
When press-molding is performed, the graphite sheet 89 thus formed also has an uneven structure because the surface of the roller 87 has an uneven shape. Note that in the substrate manufacturing method of FIG. 20, the graphite sheet 89 having the concavo-convex structure is directly manufactured from the raw material, but as shown in FIG. 21, the graphite sheet 90 already flat is passed through the roller. As a result, the graphite sheet 89 having an uneven structure
You may form as. In addition, FIG.
In the example shown in FIG. 1, both the upper and lower rollers 87 have an uneven structure, but the shape of the rollers may be changed so that the uneven structure is formed only on the surface on which the polycrystalline Si thin film is formed.
Further, as shown in FIG. 22, the graphite sheet 90 is
By pressing a Si (100) wafer with an uneven structure formed by anisotropic etching, Si can be easily
A graphite sheet substrate having the same shape as the (100) concavo-convex structure can be produced.

A process of manufacturing the thin film solar cell shown in FIG. 19 will be described. The graphite sheet substrate 83 having the concavo-convex structure manufactured as described above is set in the CVD apparatus, and silane (SiH ₄ ) or silane trichloride (SiHC 1 ₃ ) which is a raw material gas of the silicon thin film is flown into the reaction chamber. , Decomposes these gases at a high temperature of about 1000 ° C,
A polycrystalline Si thin film 84 to be an active layer is formed on the substrate 83 by the number 1
A film of 0 micron is formed. Here, during crystal growth, boron (B) or the like is doped as a p-type impurity. Since the Si thin film just formed has a small crystal grain size, in some cases, polycrystalline Si may be melted and recrystallized by laser irradiation or lamp heating to increase the crystal grain size. After the film formation, impurity diffusion and ion implantation are performed on this active layer to form a pn junction. Here, for example, phosphorus (P) is used as an impurity when the pn junction is formed by diffusion. That is, flowing phosphoryl chloride (POCl ₃ ) into the reaction tube,
Gas phase diffusion may be performed at 700 to 800 ° C. Arsenic (As), for example, is used as an ion source when forming a pn junction by ion implantation. Also, this pn junction is CV
It can also be formed by mixing the doping gas in D and forming the active layer during film formation, and switching the type of dopant midway. In addition, the active layer 84 is formed by the plasma CVD device.
The pn junction can also be formed by forming a microcrystalline film having a conductivity type opposite to that of the active layer thereon.

After forming the pn junction, an antireflection film 85 is formed by a sputtering method or the like. As the antireflection film, an electrode is used when the semiconductor layer 84 is an amorphous semiconductor layer or when the lateral conductivity of the film is low, such as when a microcrystalline film is formed to form a pn junction. Combined ITO (In ₂ O
₃ : SnO ₂ ), SnO ₂ , ZnO, or other transparent conductive film is used. If the lateral conductivity of the Si film is high and a transparent electrode is not required, a silicon nitride film (Si ₃ N ₄ ) or other insulating film is used. Membranes are used. When the Si ₃ N ₄ film is used, the thickness of the antireflection film may be 700 to 800 angstroms when the center wavelength of incident light is 6000 angstroms. Next, an upper electrode (grid electrode) 86 is formed on the antireflection film 3. A silver electrode is mainly used for the upper electrode and is formed by screen printing or vapor deposition. The upper electrode 86 is formed directly on the semiconductor layer 84 before the antireflection film 85 is formed, and thereafter, the upper electrode 8 is formed.
The antireflection film 85 may be formed so as to cover 6. In this case, it is necessary to electrically connect the plurality of solar cells after removing the antireflection film 85 on the bus electrodes.

The thin-film solar cell shown in FIG. 19 is manufactured as described above, but in this embodiment, the concavo-convex structure of the graphite sheet substrate 83 is extremely easily formed as shown in FIGS. 20, 21 and 22. Therefore, the cost of the thin film solar cell can be reduced. Further, as shown in FIGS. 20 and 21, in the case of manufacturing with a roller, a desired uneven shape can be formed by changing the roller shape.
In the case of the solar cell using the single crystal Si substrate of FIG. 56 shown in the conventional example, anisotropic etching was performed by chemical treatment, so that only a concavo-convex structure with a certain angle was obtained, but in the present example, Since the concavo-convex structure can be freely changed depending on the shape of the roller processed as described above, a solar cell having an optimum angle and shape with less reflection can be manufactured. According to the method of FIGS. 20 and 21, the graphite sheet can be continuously manufactured by the roll-to-roll method, but it goes without saying that a normal single-wafer manufacturing is also possible.

Further, although the case where the polycrystalline Si film is used as the active layer is shown in the above embodiment, the active layer used for the amorphous solar cell such as amorphous silicon or amorphous silicon germanium, or CuInSe.
Any material such as ₂ can be used as the active layer of the solar cell. Up until now, heat-resistant plastic films have been used as the substrate for flexible film-shaped amorphous solar cells, but because they are superior in heat resistance to plastics, amorphous films can be formed under a wide range of film formation conditions. Become.

The eleventh embodiment of the present invention will be described below with reference to the drawings. FIG. 23 is a schematic view showing a method for manufacturing a semiconductor device according to an eleventh embodiment of the present invention, in which 92 is a strip-shaped first substrate. 93 is a step of forming a semiconductor film on the first substrate 92, 94 is a step of forming a pn junction on the semiconductor film formed on the substrate 92, and 95 is a second step on the semiconductor film on which the pn junction is formed. A step of adhering the substrate, 96 is a step of separating the semiconductor film to which the second substrate is adhered from the first substrate 92. Here, as the first substrate, a substrate having flexibility and withstanding a high temperature process such as semiconductor film formation, such as carbon cloth or carbon sheet, is used.

Next, the manufacturing process will be described. In FIG. 23, the first substrate 92 sequentially moves in the direction of the arrow in the figure, and steps 93 to 96 are sequentially performed. Hereinafter, each step will be specifically described. FIG. 24 is a diagram showing an example of an apparatus for forming a semiconductor film according to the present embodiment, in which 97 is a processing chamber, 98 is a heater for heating a substrate 92,
99 is a source gas inlet for introducing a source gas for semiconductor film formation into the processing chamber 97, 100 is an exhaust port of the processing chamber 97, 1
01 is a preparatory chamber provided at the entrance and the exit of the processing chamber 97, 1
Reference numeral 02 denotes a gas which flows into the auxiliary chamber 101 so that the gas inside the processing chamber 97 does not mix with the atmosphere outside the processing chamber.
Reference numeral 1 denotes a gas introduction port, and 103 denotes an exhaust port of the auxiliary chamber 101.

In FIG. 24, passing through the spare chamber 101,
The first substrate 92 sent into the processing chamber 97 is connected to the heater 98.
To heat. A semiconductor film is formed by decomposing a gas (silane or the like), which is a raw material for forming a semiconductor film, introduced into the processing chamber through the raw material gas introduction port 99 and depositing it on the first substrate 92. The arrows in the figure indicate the flow of the introduced gas. The source gas introduction port 99 is provided at the end of the processing chamber 97, but a semiconductor film having a uniform thickness can be formed on the substrate 92 by performing film formation while gradually moving the substrate 92. It is possible.

FIG. 25 is a view showing another example of the apparatus for forming a semiconductor film in this embodiment, and in FIG.
4 is the same or corresponding part, and 104 is the first
It is an electrode for heating the substrate 92. The carbon cloth and the carbon sheet are conductive, and the substrate itself generates heat when an electric current is applied. In the apparatus shown in FIG. 25, the electrode 104 is brought into contact with the substrate 92, and a current is passed through the substrate 92 to directly heat the substrate. The other structure is the same as that of the apparatus shown in FIG.

The semiconductor film is formed on the first substrate 92 as described above. Since the semiconductor film formed in this way has a polycrystalline structure, it is necessary to melt the melted film in order to improve the performance of the device. It is desirable to use a crystallization technique to increase the crystal grain size of the semiconductor film and single crystallize it. 26 is shown in FIG.
FIG. 26 is a diagram showing an example of an apparatus for melting and recrystallizing a semiconductor film formed on the first substrate 92 by the apparatus of FIG. 4 or FIG. 25, etc., in which the same symbols as in FIG. There is a strip heater 105 made of carbon or the like. In FIG. 26, the substrate 92 sent to the processing chamber 97 is heated by the heater 98, and the semiconductor film on the substrate 92 is further heated by the strip heater 105 to partially melt. In the example shown in the figure, the strip heater 105 is fixed, and the molten portion moves as the substrate 92 moves, whereby zone melting recrystallization is performed. After moving the substrate 92 into the processing chamber, the movement of the substrate is stopped,
The strip heater 105 may be moved while the substrate is stopped.

By the way, when a smooth surface such as a carbon sheet is used as the first substrate, the substrate 9
2 It is easy to form a semiconductor film directly on the surface,
When the surface is not smooth like carbon cloth, it is difficult to directly form a semiconductor film on the surface of the substrate 92, and therefore the surface of the substrate 92 needs to be smooth before the semiconductor film is formed. As this method, a separation film such as a silicon oxide film may be first formed on the surface of the substrate 92 before forming a semiconductor so as to fill the holes on the surface of the substrate 92. FIG. 27 is a diagram showing an example of an apparatus for forming a separation film on the first substrate 92 before forming a semiconductor film. In the figure, the same reference numerals as those in FIG. 24 denote the same or corresponding parts.
In FIG. 27, the first substrate 92 sent to the processing chamber 97.
Is heated by the heater 98. For example, silane and oxygen are flown from the source gas introduction port 99 to form a silicon oxide film on the first substrate 92.

Further, in the case of performing the melt recrystallization of the semiconductor film described above, in order to obtain a good quality recrystallized film, the melt recrystallization is performed with the semiconductor film covered with a cap film such as a silicon oxide film. However, in such a case, the apparatus shown in FIG. 27 is provided between the semiconductor film forming apparatus shown in FIGS. 24 and 25 and the apparatus for performing melt recrystallization shown in FIG. 26 so that a silicon oxide film or the like is formed on the semiconductor film. A cap film may be formed. Further, the removal of the cap film after the completion of the melt recrystallization is performed by the device shown in FIG. In FIG. 28, 106 is an etching solution nozzle. What is melted and recrystallized by the apparatus shown in FIG. 26 is sent into the processing chamber 97 of the apparatus shown in FIG. 28, and hydrofluoric acid or the like is jetted from the nozzle 106 to dissolve and remove the cap film on the semiconductor film. ..

Next, the step of forming a pn junction in the semiconductor film formed as described above will be described. FIG. 29
2 is a diagram showing an example of an apparatus for forming a pn junction in a semiconductor film formed on a first substrate 92, and in FIG.
The same symbols as 4 are the same or corresponding parts. The processing chamber 97 is heated by a heater 98 from the outside and constitutes a tubular furnace. Gas serving as a diffusion source is introduced from the gas introduction port 99. The first substrate 92 having a semiconductor film formed on its surface is sent to the processing chamber 97, a gas serving as a diffusion source is caused to flow through the gas introduction port 99, and is heated by a heater 98, so that impurities are thermally diffused in the semiconductor film. To form a pn junction. Here again, the introduction port 99 for introducing the impurity gas is provided at the end portion of the processing chamber 97, but the diffusion condition is made uniform at each position in the movement direction by performing diffusion while gradually moving the substrate 92. It is possible to form a diffusion region having a uniform depth and impurity concentration.

FIG. 30 is a diagram showing another example of an apparatus for forming a pn junction in a semiconductor film formed on the first substrate 92. In the figure, the same symbols as in FIG. 24 are the same or corresponding parts. , 107 is a high frequency generator, and 108 is a ground. In this device, a high frequency is applied to an electrode provided at the source gas introduction port to generate plasma, the introduced gas is decomposed, and an amorphous or amorphous film is formed on the semiconductor film formed on the first substrate 92. A pn junction is formed by depositing a microcrystalline film.

After the pn junction is formed in the semiconductor film in this way, a second substrate is bonded onto the semiconductor film. As a device for bonding the second substrate, a general robot hand or the like can be used. As the second substrate and the adhesive, those having resistance to the etching solution used in the subsequent separation step 96 are used.

Next, the step of separating the semiconductor film to which the second substrate is bonded from the first substrate will be described. FIG. 31 is a diagram showing an example of an apparatus for separating the semiconductor film from the first substrate 92, and etching for injecting an etching solution toward the back surface of the first substrate 92 sent to the lower portion of the processing chamber 97. A liquid nozzle 110 is provided. In FIG. 31, the first substrate 92 is sent into the processing chamber 97, and an etching solution is sprayed from the back surface side of the first substrate 92 to the portion where the semiconductor film to which the second substrate 109 is bonded is formed, so that etching is performed. The liquid permeates the first substrate 92. Then, the semiconductor film, which is sent out from the processing chamber 97 and easily peeled off by the etching solution, together with the second substrate 109, is supplied to the first substrate 92.
Separate from. The apparatus shown in FIG. 31 is suitable for the case where the first substrate 92 is a material such as carbon cloth, through which the etching liquid easily penetrates from the back surface.

FIG. 32 is a diagram showing another example of the device for separating the semiconductor film from the first substrate 92.
This is suitable for the case where a substrate such as a carbon sheet, which is less likely to allow the etching solution to penetrate from the back surface, is used as the substrate 92. In the figure, the first substrate 9 is placed in the processing chamber 97.
A roller 113 for separating 2 from the semiconductor film and sending it in different directions is provided. Reference numeral 111 is a roller for carrying the semiconductor film separated from the first substrate 92 together with the second substrate 109. In FIG. 32, the first substrate 92 is sent into the processing chamber 97, and the first substrate 92 is moved by the roller 113.
While curving the substrate, an etching solution is sprayed from the nozzle 112 between the first substrate 92 and the semiconductor film, so that the semiconductor film and the first film are separated from each other.
The substrate 92 is separated. The semiconductor film separated from the first substrate 92 together with the second substrate 109 is carried out of the processing chamber 97 by the roller 111.

After being separated from the first substrate 92 in this manner, a protective film and an electrode are formed on the surface of the semiconductor film. In addition,
When it is necessary to form an electrode or the like on the side of the semiconductor film that is to be bonded to the second substrate, the process is performed between the pn junction forming step 94 and the second substrate bonding step 95. As a method of moving the first substrate 92, a general roll-to-roll method as shown in FIG. 33A can be used, and in the present embodiment, the first substrate is repeatedly used. Therefore, it is also possible to use a belt conveyor system as shown in FIG. 33 (b).

As described above, in this embodiment, the step of forming the semiconductor film on the first substrate while moving the strip-shaped first substrate in the longitudinal direction, and the step of forming the pn junction on the semiconductor film. Since the step of adhering the second substrate to the semiconductor film and the step of separating the semiconductor film from the first substrate are sequentially performed, thin-film solar battery cells and the like can be continuously mass-produced. .. Further, by using a carbon substrate as the first substrate, high-temperature processing becomes possible, and a high quality device can be manufactured.

Although the semiconductor film forming process is performed by thermal CVD in the above embodiment, it may be performed by plasma CVD. In this case, as the film forming apparatus, one having the same structure as the apparatus shown in FIG. 30 may be used. In addition, in the above-mentioned embodiment, the production of the thin film solar cell is described. However, the thin film formed semiconductor layer has a pn junction, and this semiconductor layer is bonded to a substrate different from the substrate on which the semiconductor layer is grown. It goes without saying that the present invention can be applied to the manufacture of general semiconductor devices having a structure to be used later.

FIG. 34 is a diagram showing a thin film solar cell according to the twelfth embodiment of the present invention. The thin film solar cell of this embodiment is constructed by connecting a plurality of solar battery cells to each other. FIG. 34 (a) is a perspective view thereof, and FIG. 34 (b) is a sectional view thereof. In the figure, 114 has a thickness of 0.1 to 0.5 mm, for example.
Is a conductive substrate made of sheet-shaped graphite or a thin metal plate such as Al. The power generation layer 115 is the substrate 114
It is arranged on the upper side and is composed of, for example, an amorphous Si-based alloy material, a polycrystalline thin film Si, or a compound layer of C ₂ Te, CuInSe _2, or the like. Reference numeral 116 denotes a surface electrode formed on the power generation layer 115 in an appropriate pattern shape, for example, A
The main component is g. The surface electrode 116 is shown in FIG.
As shown in part (c), it comprises a grid portion 116a and a bus portion 116b.

In order to minimize the resistance loss when the current collected by the surface electrode is taken out to the outside, for example, the width is 1 m.
Lead wire 1 is a copper ribbon wire with a thickness of about m and a thickness of about 100 μm.
A part of the front surface electrode 116, that is, the bus portion 116b
Soldered on. This copper ribbon wire is often tin or solder coated. In this embodiment, the power generation layer 115 is formed by exposing a part of the substrate without covering the entire surface of the conductive substrate 115, and the tip of the lead wire penetrates the substrate at the exposed portion of the substrate. Fixed. It is more effective to further bend the tip end portion of the lead wire protruding through as shown in the figure in order to increase the strength of the connection portion. Here, when a graphite sheet having a crystal structure oriented parallel to the substrate surface is used as the conductive substrate 115, it is very easy to penetrate the lead wire into the substrate, and good electrical contact can be obtained. Was given.

Further, in the conventional interconnection method between cells, when the lead wire on the front surface side of the cell is arranged on the back surface side of the adjacent cell, the lead wire is attached to the back surface of the cell itself or the conductive substrate. The cells must not come into contact with each other, and for that reason, it is necessary to secure a space between cells to be arrayed by about 2 to 3 mm.
However, in this embodiment, the lead wire 117 does not have to be wrapped around the back surface of the adjacent cell and is not L-shaped, so the lead wire does not come into contact with the back surface of the cell or the substrate. Therefore, in principle, it becomes possible to limit the cell-to-cell spacing infinitely, and it is possible to increase the filling efficiency of the cells in the module and obtain a high output. Practically, an interval between cells of about 0.5 mm is suitable.

In the structure shown in FIG. 34, the conductive substrate 114 is used.
Although the exposed area is wide, it is obvious that the power generation layer 115 can be formed on the entire surface of the other area while leaving the through portion for interconnection. In addition, although the solar cells are arranged on a plane in the above-mentioned embodiment, when a flexible material such as sheet-shaped graphite is used as the conductive substrate 114, it is shown in FIG. As described above, a part of the substrates of the adjacent cells may be overlapped with the edge part of the cell, and the tip part of the lead wire may be penetrated into the upper substrate at this part for connection. At this time, as shown in the figure, by providing the cutout portion 118 in a portion other than the through portion of the substrate 114 to be overlapped, it is possible to generate power also in the power generation layer 115 in the region below the cutout portion 118 and improve power generation efficiency. You can

Also in the case shown in FIG. 35, the effective area contributing to the power generation can be increased by using the power generation layer formed in the area where the substrates are overlapped with each other except the connection portion. Further, a connection method as shown in FIG. 36 is also possible as a modification of this embodiment. That is, the tip of the lead wire on the upper part of the cell is placed around the back surface of the adjacent cell by double L-shape processing, and the lead wire is penetrated from the back surface side to the front surface side of the substrate for interconnection. You may do it. However, in this case, the lead wire may come into contact with the back surface of its own cell or the substrate, so that the inter-cell spacing needs to be widened to some extent.

34 to 36 show a structure in which a plurality of solar cells are connected in series, that is, a method of connecting the tip of a lead wire soldered to the upper electrode of the cell to the substrate of the adjacent cell. It can also be applied as a parallel connection method of cells. That is, as shown in FIG. 37, the conductive substrates of the cells adjacent to each other may be connected to each other using the substrate connecting lead wire 119.

Further, FIG. 38 is a diagram showing a structure for taking out the electrode at the final end to the outside in the thin film solar cell module of this embodiment. In the figure, 120 is a lead wire for taking out electrodes in parallel from the substrate side of the cells arranged in two rows. FIG. 39 is a diagram showing a state in which a plurality of cells are sealed with a filling resin 122 between the front surface glass 123 and the back surface material 124, and corresponds to a DD cross section of FIG. 38.
Since the back surface material 124 is made of a metal such as Al, in order to prevent a short circuit between the back surface material 124 and the lead wire 120, the electrode extraction portion insulator 1 made of insulating rubber or the like is provided in the electrode extraction portion.
21 is provided. By connecting a plurality of columns of cells in parallel with the lead wire 120 in this manner, a high power thin film solar cell can be constructed.

Next, a method of implementing inter-cell interconnection according to the present invention will be described. FIG. 40 is a diagram showing a specific method for making electrical connection by making the tip of the lead wire 117 penetrate into the conductive substrate of the adjacent cell in the process of manufacturing the thin film solar cell of FIG. In the figure, the same reference numerals as those in FIG. 34 denote the same or corresponding parts. First, the cells are set on the pedestal 125 such that the tips of the lead wires 117 soldered on the upper electrodes 116 of the respective cells protrude from the ends of the cell pedestal 125 by a predetermined length. Next, fix the position where the length of the lead wire that should be bent is left,
After fixing at 26, the piston 127 is lowered as shown in FIG. 40 (a), and the tip end portion of the lead wire is bent as shown in FIG. 40 (b). Next, this cell and the cell to be connected are set on the cell array table 128, and the crimping jig 129 is arranged on the lead wire bent in the above-described step as shown in FIG. 40 (c). Next, when the crimping jig 129 is lowered, as shown in FIG. 40 (d), the lead wire tip portion penetrates the substrate 114 having a hardness lower than that of the lead wire material.
At this time, as shown in an enlarged view of FIG. 40 (e), a lead wire guide groove 130 is provided on the surface of the cell array base 128 immediately below the penetrating portion, so that the tip of the lead wire penetrating the substrate is The part is further bent along the guide groove 130 as shown in FIG. 40 (f). Through such a series of steps, interconnection between the cells of the thin film solar cell shown in FIG. 34 is performed.

The cells can be connected to each other by the above method, but in order to further reduce the contact resistance at the connection portion, the conductive paste 131 is spread on the lead-through portion as shown in FIG. You may keep it. As a result, not only the contact resistance at the connection portion can be reduced, but also the connection strength can be improved.

Further, in these examples, the structure in which the tip of the lead wire completely penetrates the substrate to be connected is shown.
As shown in FIG. 42, it is also possible to connect by a type in which the tip of the lead wire penetrates into the substrate. In this case, it is effective to form the tip of the lead wire 117 with a hook 132 for preventing the return as shown in FIG. 42 (a).

As described above, in the twelfth embodiment, a conductive material having a hardness lower than that of the lead wire for interconnection such as a graphite sheet is used as the substrate of the thin film solar cell, and solder is applied on the upper electrode of the solar cell. By crimping the tip end of the attached lead wire for interconnection from the direction perpendicular to the substrate surface of the adjacent cell, the lead wire penetrates the substrate or penetrates into the substrate halfway. Since the cells are fixed to the substrate and the cells are interconnected, a simple and high mechanical strength connection can be realized.

[0148]

As described above, according to the present invention, since the graphite sheet substrate is heated by direct heating with high frequency, the substrate can be heated with high heating efficiency without damaging the substrate. There is.

Further, according to the present invention, the thin film semiconductor formed on the graphite sheet substrate is covered with a cap layer made of a silicon oxide film or a silicon nitride film, and the thin film semiconductor is melted and recrystallized to form an active layer. Since the crystal grain size is increased, the thin film layer does not form an island shape, and the contamination of the reaction chamber due to evaporation of the thin film layer can be prevented.

Further, according to the present invention, two graphite sheet substrates are adhered to each other in such a state that the first main surfaces thereof face each other and overlap each other, and in this adhered state, each of the second main substrates of the two substrates is adhered. Since a semiconductor thin film to be an active layer is formed on the surface and the substrate in a close contact state is separated into two substrates after the thin film forming process, stress caused by the difference in expansion coefficient between graphite and the semiconductor is generated on both sides. Offset, preventing the board from bending,
This makes it easy to perform the post process, and
The number of productions per unit time can be doubled, which has the effect of improving productivity.

According to the present invention, the graphite sheet formed by roll forming is hardened at 1000's of several hundreds of degrees Celsius, and then the semiconductor thin film to be the active layer is formed on the substrate. This has the effect of reducing the curvature of the substrate due to the stress generated due to the difference in expansion coefficient from the semiconductor. Further, according to the present invention, the graphite sheet formed by roll forming is used in an HCl atmosphere for 30 days.
Since the semiconductor thin film to be the active layer is formed on the substrate after the impurities in the substrate are reduced by annealing at 00 ° C. or higher, there is an effect that a high performance thin film solar cell can be manufactured.

Further, according to the present invention, two graphite sheet substrates are partially overlapped so that their first main surfaces face each other and a space is formed between the two substrates. Since the raw material gas is brought into close contact and the raw material gas is caused to flow into the space to form a thin film on each of the first main surfaces of the two substrates, there is an effect that a reaction chamber for forming the thin film is unnecessary.

Further, according to the present invention, the distance from the raw material gas introduction port to the exhaust port of the film forming chamber for forming a thin film which becomes an active layer on the substrate is determined based on the raw material gas flow rate, the flow velocity and the decomposition rate. And a film forming chamber in which a thin film to be an active layer is formed on a substrate in a film forming chamber in which most of the introduced source gas is decomposed before reaching the exhaust port. Since the thin film is formed in the film forming chamber in which a means for preventing only the raw material gas component from permeating is provided at the exhaust port, the use efficiency of the raw material gas can be improved.

Further, according to the present invention, since the supporting base having high mechanical strength is fixed to the surface of the graphite sheet substrate opposite to the surface on which the thin film is formed, the thin film solar cell using the graphite sheet substrate is formed. This has the effect of improving the mechanical strength of the battery. Further, according to the present invention, the graphite sheet substrate is fixed so that tension is applied to the graphite sheet substrate using a frame body made of carbon or ceramic, and in this state, a semiconductor thin film to be an active layer is formed on the substrate. Since it is formed, it is possible to prevent the substrate from being bent due to the stress generated due to the difference in expansion coefficient between graphite and the semiconductor, and it is possible to facilitate the grain size increasing process.

Further, according to the present invention, the graphite sheet substrate is placed on the mold having the depression along the shape of the depression, and the depression covered with the graphite sheet is filled with the metallurgical grade silicon powder. Then, the metal-grade silicon powder is melted and solidified to form a heat-resistant substrate in which a metal-grade silicon substrate is fixed to the back surface of the graphite sheet substrate, and the heat-resistant substrate is activated on the surface of the graphite sheet substrate. Since the semiconductor thin film serving as the layer is formed, there is an effect that a thin film solar cell having high mechanical strength can be easily manufactured.

Further, according to the present invention, a predetermined pattern formed on the substrate containing carbon as a main component, the first silicon layer provided on the substrate, and the predetermined pattern provided on the first silicon layer. Since the insulating layer having the opening and the second silicon layer provided on the insulating layer so as to contact the first silicon layer at the opening are provided, the first silicon layer is formed. By virtue of the strong bond between the substrate containing carbon as a main component and the insulating layer, a strong mechanical strength can be realized, and since the second silicon layer and the substrate do not come into direct contact with each other, the influence of the diffusion and mixing of impurities is reduced. The effect is that it can be suppressed, and since the insulating layer is arranged on the silicon layer, the back reflection of light can be effectively used.

Further, according to the present invention, after forming the first silicon layer on the substrate containing carbon as a main component, the insulating layer having openings of a predetermined pattern is formed on the first silicon layer. Further, since the second silicon layer is formed on the insulating layer so as to be in contact with the first silicon layer in the opening, a thin film solar cell having high performance and high reliability can be easily manufactured. effective. In addition, in particular, after forming an amorphous silicon layer on the first silicon layer, an insulating layer is formed on the amorphous silicon layer, laser irradiation is performed corresponding to a predetermined pattern, and the laser irradiation is performed on the laser irradiation region. When the amorphous silicon layer pierces and ruptures the upper insulating layer to form an opening having a predetermined pattern in the insulating layer, a wet process can be unnecessary for forming the opening, and the performance of the solar cell can be improved. There is an effect that it can be further improved.

Further, according to the present invention, since the semiconductor thin film is formed on the graphite sheet substrate having the uneven structure on the surface, there is an effect that a high performance thin film solar cell can be realized by an easy process. Further, according to the present invention, the step of forming a semiconductor film on the strip-shaped first substrate, the step of forming a pn junction in the semiconductor film, and the step of adhering the second substrate to the semiconductor film. And a step of separating the semiconductor film from the first substrate, and the steps are continuously performed while sequentially moving the first substrate in the length direction thereof. Finally, it is possible to continuously mass-produce the thin film semiconductor device used in a state of being separated from the substrate.

Further, according to the present invention, in a solar cell module constituting a cell, a cell formed on a substrate made of a conductive material having a hardness lower than that of a lead wire is used, and the tip of the connecting lead wire is A part of the substrate of the adjacent cell is penetrated or invaded so that the cells are interconnected, so that a solar cell module with excellent mechanical strength of the connection part can be easily constructed. effective.

Further, according to the present invention, the tip of the lead wire arranged on the front surface side is bent, and the tip of the bent portion is brought into contact with a predetermined position of the substrate of the adjacent cell to pressurize the lead wire. Since the tip of the device is made to penetrate or invade a part of the substrate, there is an effect that a solar cell module for electric power can be obtained with high throughput in a very simple process.

[Brief description of drawings]

FIG. 1 is a diagram showing a substrate heating method in a method of manufacturing a thin film solar cell according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a grain size expansion method in the method of manufacturing a thin film solar cell according to the second embodiment of the present invention.

FIG. 3 is a diagram showing a method for manufacturing a thin film solar cell according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a method for manufacturing a thin film solar cell according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a structure of a thin film forming chamber used in a method of manufacturing a thin film solar cell according to a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a thin film forming chamber used in a method of manufacturing a thin film solar cell according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view showing a structure of a thin film solar cell according to a seventh embodiment of the present invention.

FIG. 8 is a sectional view showing a structure of a thin film solar cell according to an eighth embodiment of the present invention.

9 is a diagram for explaining an example of a method for manufacturing the thin film solar cell of FIG.

10 is a diagram for explaining an example of a method for manufacturing the thin film solar cell of FIG.

FIG. 11 is a diagram illustrating an example of a method for manufacturing the thin film solar cell of FIG. 7.

12 is a diagram for explaining another example of the method for manufacturing the thin-film solar cell of FIG.

13 is a diagram for explaining an example of a method for manufacturing the thin film solar cell of FIG.

14 is a diagram for explaining another example of the method for manufacturing the thin-film solar cell of FIG.

FIG. 15 is a sectional view showing the structure of a thin film solar cell according to a ninth embodiment of the present invention.

16 is a manufacturing process of the thin film solar cell of FIG.
FIG. 6 is a cross-sectional view showing a method for increasing the crystal grain size of the silicon layer.

FIG. 17 is a diagram for explaining that the back surface reflection effect can be more effectively utilized in the thin film solar cell of FIG. 15 than in the conventional case.

FIG. 18 is a sectional process diagram for explaining the manufacturing method for the thin-film solar cell in FIG.

FIG. 19 is a sectional view showing a structure of a thin film solar cell according to a tenth embodiment of the present invention.

FIG. 20 is a diagram showing an example of a method for producing a graphite sheet substrate having an uneven structure on its surface.

FIG. 21 is a diagram showing another example of a method for producing a graphite sheet substrate having an uneven structure on the surface.

FIG. 22 is a diagram showing still another example of the method for producing the graphite sheet substrate having the uneven structure on the surface.

FIG. 23 is a schematic view showing a method of manufacturing a thin film semiconductor device according to an eleventh embodiment of the present invention.

FIG. 24 is a diagram showing an example of an apparatus for performing a semiconductor film forming step in a method of manufacturing a thin film semiconductor device according to an eleventh embodiment of the present invention.

FIG. 25 is a diagram showing another example of an apparatus for performing a semiconductor film forming step in the method of manufacturing a thin film semiconductor device according to the eleventh embodiment of the present invention.

FIG. 26 is a diagram showing an example of an apparatus for melting and recrystallizing a semiconductor film after a semiconductor film forming step in a method for manufacturing a thin film semiconductor device according to an eleventh embodiment of the present invention.

FIG. 27 is a diagram showing an example of an apparatus for forming a separation film on a substrate before a semiconductor film forming step in a method for manufacturing a thin film semiconductor device according to an eleventh embodiment of the present invention.

FIG. 28 is a view showing a method of removing a protective film formed on a semiconductor surface during melting and recrystallization after a semiconductor film forming step in a method for manufacturing a thin film semiconductor device according to an eleventh embodiment of the present invention. It is a figure which shows an example of an apparatus.

FIG. 29 is a diagram showing an example of an apparatus for performing a pn junction forming step in the method of manufacturing a thin film semiconductor device according to the eleventh embodiment of the present invention.

FIG. 30 is a diagram showing another example of an apparatus for performing a pn junction forming step in the method of manufacturing a thin film semiconductor device according to the eleventh embodiment of the present invention.

FIG. 31 is a diagram showing an example of an apparatus for performing a substrate separating step in a method of manufacturing a thin film semiconductor device according to an eleventh embodiment of the present invention.

FIG. 32 is a diagram showing another example of an apparatus for performing the substrate separating step in the method of manufacturing a thin film semiconductor device according to the eleventh embodiment of the present invention.

FIG. 33 is a diagram showing an example of a first substrate carrying mechanism in the method of manufacturing a thin film semiconductor device according to the eleventh embodiment of the present invention.

FIG. 34 is a diagram showing a thin film solar cell according to a twelfth embodiment of the present invention.

FIG. 35 is a diagram showing a modification of the thin-film solar cell according to the twelfth embodiment of the present invention.

FIG. 36 is a diagram showing a modification of the thin-film solar cell according to the twelfth embodiment of the present invention.

FIG. 37 is a diagram showing a parallel connection method of cells in a thin film solar cell according to a twelfth embodiment of the present invention.

FIG. 38 is a diagram showing a method of extracting electrodes in the thin-film solar cell according to the twelfth embodiment of the present invention.

FIG. 39 is a view corresponding to a section taken along line DD of FIG. 38.

40 is a diagram showing a method of connecting cells of the thin-film solar cell of FIG. 34.

FIG. 41 is a diagram showing a modification of the thin-film solar cell according to the twelfth embodiment of the present invention.

FIG. 42 is a diagram showing a modification of the thin-film solar cell according to the twelfth embodiment of the present invention.

FIG. 43 is a perspective view showing a configuration of a thin film solar cell.

FIG. 44 is a cross-sectional view showing the structure of a conventional thin film solar cell using a graphite plate as a substrate.

FIG. 45 is a diagram showing a surface structure of a graphite plate.

FIG. 46 is a schematic diagram showing a conventional method for manufacturing a thin film solar cell using a graphite sheet as a substrate.

FIG. 47 is a diagram showing a crystal structure of graphite.

FIG. 48 is a schematic diagram showing a method for manufacturing a graphite sheet.

FIG. 49 is a diagram showing a surface structure of a graphite sheet.

FIG. 50 is a diagram for explaining a problem in the manufacturing method of FIG. 46.

FIG. 51 is a cross-sectional view showing the structure of a conventional thin film solar cell using a substrate containing carbon as a main component.

FIG. 52 is a cross-sectional view showing the structure of another conventional thin-film solar cell using a substrate containing carbon as a main component.

FIG. 53 is a schematic diagram for explaining a problem when a thin film is formed on a graphite sheet.

FIG. 54 is a cross-sectional view showing a structure of a conventional thin film solar cell using metallurgical grade silicon as a substrate.

FIG. 55 is a schematic diagram for explaining a problem in a conventional thin film solar cell using metallurgical grade silicon as a substrate.

FIG. 56 is a diagram showing an example of a conventional solar cell using crystalline silicon.

FIG. 57 is a diagram showing an example of a conventional amorphous solar cell.

FIG. 58 is a diagram showing a conventional thin-film solar cell having a thin film on a substrate having an uneven structure on its surface.

FIG. 59 is a diagram showing a conventional method for manufacturing a thin film semiconductor device, which is used in a state where it is finally separated from a substrate.

FIG. 60 is a diagram showing an example of a conventional solar cell module.

FIG. 61 is a diagram showing another example of a conventional solar cell module.

FIG. 62 is a diagram showing another example of a conventional solar cell module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Graphite sheet 2 Thin film forming chamber 3 Induction heating source 4 Raw material gas inlet 5 Gas exhaust port 6 Cap layer film forming chamber 8 Particle size expanding chamber 20 Cap layer removing chamber 22 pn junction forming chamber 24 Antireflection film forming chamber 26 Upper electrode Forming chamber 35 Stacking roller 36 Edge pressing roller 37 Gas supply unit pressing roller 38 Reaction gas supply nozzle 39 Reaction space 45 Platinum film 50 Inexpensive metal plate 51 Graphite sheet substrate 55 Metallic grade silicon substrate 56 Outer frame 58 Inner frame 59 soaking plate 63 bell jar 64 mold 66 lid 67 metal grade silicon powder 69 plasma injection nozzle 70 molten metal grade silicon 72 substrate 73 first silicon layer 74 insulating layer 75 second silicon layer 76 emitter layer 78 opening 92 first Substrate 93 Step of forming semiconductor film 94 pn junction Forming to step 95 second step 114 a conductive substrate 115 generator layer 116 upper electrode 117 leads to separate step 96 semiconductor film to bond the substrate from the first substrate

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[Procedure amendment]

[Submission date] June 4, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 23

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

FIG. 48 is a diagram showing a method for producing a graphite sheet, in which 224 is expanded graphite and 225 is a roller. Scale graphite with H ₂ SO ₄
When acid treatment is performed with a mixed solution of HNO ₃ and the acid is heated and evaporated at about 300 ° C., scaly graphite foams and becomes cotton-like and expands in volume. As shown in the figure, a graphite sheet 226 can be continuously formed by pressure-molding the expanded graphite 224 with a roller 225 at room temperature. It is considered that each of the crystals can be formed by simply applying a pressure without performing a high-temperature treatment, because each crystal size is large.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

56 to 58 are cross-sectional views showing structures of various conventional solar cells having an uneven structure. FIG. 56 shows a crystalline solar cell, FIG. 57 shows an amorphous Si solar cell, and FIG. 58 shows a thin film solar cell. Show. In the figure, 251 is polycrystalline Si
Thin film, 242 , 253 are grid electrodes, 240 is single crystal Si, 245 is a glass substrate, 246 is a transparent electrode, 247
Is amorphous Si, 248 is a back electrode, and 250 is a heat-resistant substrate.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0122

[Correction method] Change

[Correction content]

The eleventh embodiment of the present invention will be described below with reference to the drawings. FIG. 23 is a schematic view showing a method for manufacturing a semiconductor device according to an eleventh embodiment of the present invention, in which 92 is a strip-shaped first substrate. 93 is a step of forming a semiconductor film on the first substrate 92, 94 is a step of forming a pn junction on the semiconductor film formed on the substrate 92, and 95 is a second substrate on the semiconductor film on which the pn junction is formed. Step 96 is a step of separating the semiconductor film, to which the second substrate is adhered, from the first substrate 92. Here, as the first substrate, a substrate having flexibility and withstanding a high temperature process such as semiconductor film formation, such as carbon cloth or carbon sheet, is used.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0123

[Correction method] Change

[Correction content]

Next, the manufacturing process will be described. In FIG. 23, the first substrate 92 sequentially moves in the direction of the arrow in the figure, and steps 93 to 96 are sequentially performed. Hereinafter, each step will be specifically described. FIG. 24 is a diagram showing an example of an apparatus for forming a semiconductor film in the present embodiment, in which 97 is a processing chamber, 98 is a heater for heating a substrate 92,
99 is a source gas inlet for introducing a source gas for semiconductor film formation into the processing chamber 97, 100 is an exhaust port of the processing chamber 97, 1
01 is a preparatory chamber provided at the entrance and the exit of the processing chamber 97, 1
Reference numeral 02 denotes a gas which flows into the auxiliary chamber 101 so that the gas inside the processing chamber 97 does not mix with the atmosphere outside the processing chamber.
Reference numeral 1 denotes a gas introduction port, and 103 denotes an exhaust port of the auxiliary chamber 101.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0125

[Correction method] Change

[Correction content]

FIG. 25 is a view showing another example of an apparatus for forming a semiconductor film in this embodiment, and in FIG.
4 is the same or corresponding part, and 104 is the first
It is an electrode for heating the substrate 92. The carbon cloth and the carbon sheet are conductive, and the substrate itself generates heat when an electric current is applied. In the apparatus shown in FIG. 25, the electrode 104 is brought into contact with the substrate 92, and a current is passed through the substrate 92 to directly heat the substrate. The other structure is the same as that of the apparatus shown in FIG. Also, in the above example, decomposition of the source gas
Although the case of forming a semiconductor film by using
For example, the molten semiconductor material is directly formed on the first substrate 92 in a film form.
Even if the semiconductor film is formed by spreading
good.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0126

[Correction method] Change

[Correction content]

The semiconductor film is formed on the first substrate 92 as described above. Since the semiconductor film formed in this way has a polycrystalline structure, it is necessary to melt the melted film in order to improve the performance of the device. It is desirable to use a crystallization technique to increase the crystal grain size of the semiconductor film and single crystallize it. 26 is shown in FIG.
FIG. 26 is a diagram showing an example of an apparatus for melting and recrystallizing a semiconductor film formed on the first substrate 92 by the apparatus of FIG. 4 or FIG. 25, etc., in which the same symbols as in FIG. There is a strip heater 105 made of carbon or the like. In FIG. 26, the substrate 92 sent to the processing chamber 97 is heated by the heater 98, and the semiconductor film on the substrate 92 is further heated by the strip heater 105 to partially melt. In the example shown in the figure, the strip heater 105 is fixed, and the substrate of the melting portion is moved as the substrate 92 moves.
The upper position moves, which results in zone melt recrystallization. The substrate 92 may be moved within the processing chamber by a certain length , the movement of the substrate may be stopped, and the strip heater 105 may be moved while the substrate is stopped.

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[Name of item to be corrected] 0127

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By the way, when a smooth surface such as a carbon sheet is used as the first substrate, the substrate 9
2 It is easy to form a semiconductor film directly on the surface,
If the surface is not smooth like carbon cloth, it is difficult to form the semiconductor film directly on the surface of the substrate 92, and therefore the surface of the substrate 92 needs to be smooth before the formation of the semiconductor film . This method includes a substrate 92
Before forming a semiconductor film on the surface, a separation film such as a silicon oxide film may be first formed to fill the holes on the surface of the substrate 92. FIG. 27 is a view showing an example of an apparatus for forming a separation film on the first substrate 92 before forming a semiconductor film,
In the figure, the same reference numerals as those in FIG. 24 denote the same or corresponding parts. In FIG. 27, the first substrate 92 sent to the processing chamber 97 is heated by the heater 98. Raw material gas inlet 99
For example, silane and oxygen are flown to form a silicon oxide film on the first substrate 92.

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After being separated from the first substrate 92 in this manner, a protective film and an electrode are formed on the surface of the semiconductor film. above
In the embodiment, when separating the semiconductor film from the first substrate 92,
In addition, the case where the first substrate 92 is not destroyed is described.
However, the separation of the semiconductor film and the first substrate is, for example, the first substrate.
Do not burn the plate or remove it by dissolving it in a solvent.
How to achieve by eliminating the first substrate
May be. However, in this case, the first substrate 92 is repeated.
Re-use of the first substrate is required for
It Note that when it is necessary to form an electrode or the like on the surface of the semiconductor film which is attached to the second substrate, the step is performed between the pn junction formation step 94 and the second substrate attachment step 95. As a method of moving the first substrate 92, a general roll-to-roll method as shown in FIG. 33A can be used, and in the present embodiment, the first substrate is repeatedly used. Therefore, it is also possible to use a belt conveyor system as shown in FIG. 33 (b).

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Although the semiconductor film forming process is performed by thermal CVD in the above embodiment, it may be performed by plasma CVD. In this case, as the film forming apparatus, one having the same structure as the apparatus shown in FIG. 30 may be used. Further, in the above embodiment, the first substrate is
Step 2 of forming a semiconductor film, forming a pn junction in the semiconductor film
Step 3 of forming, attaching the second substrate to the semiconductor film
4 and step 5 of separating the semiconductor film from the first substrate
I explained each of them with specific examples.
Each of the implementation means is not limited to those described,
It is clear that other methods will produce the same effect.
Yes, and is included in the concept claimed by the present invention. It
Luo, in the above embodiment has been described that the production of thin-film solar cells, pn in the semiconductor film which is a thin film formed
It goes without saying that the present invention can be applied to the manufacture of general semiconductor devices having a structure in which the semiconductor film has a junction and is bonded to a substrate different from the substrate on which the semiconductor film is formed .

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[Explanation of symbols] 1 graphite sheet 2 thin film forming chamber 3 induction heating source 4 raw material gas inlet port 5 gas exhaust port 6 cap layer film forming chamber 8 grain size expanding chamber 20 cap layer removing chamber 22 pn junction forming chamber 24 antireflection film Forming chamber 26 Upper electrode forming chamber 35 Stacking roller 36 Edge pressing roller 37 Gas supply pressing roller 38 Reactive gas supply nozzle 39 Reaction space 45 Platinum film 50 Inexpensive metal plate 51 Graphite sheet substrate 55 Metal grade silicon substrate 56 Outer frame Body 58 Inner frame 59 Uniform heat plate 63 Belger 64 Mold 66 Lid 67 Metallurgical grade silicon powder 69 Plasma injection nozzle 70 Molten metal grade silicon 72 Substrate 73 First silicon layer 74 Insulating layer 75 Second silicon layer 76 Emitter layer 78 Industrial performing formation of the opening 92 the first substrate 93 semiconductor film 94 pn junction to form a step 95 second step 96 for bonding the substrate of the semiconductor film is separated from the first substrate step 114 a conductive substrate 115 generator layer 116 upper electrode 117 leads

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[Figure 4]

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FIG. 23

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 3-359749 (32) Priority date Hei 3 (1991) December 26 (33) Priority claim country Japan (JP) (72) Inventor Exit Mikio 4-1-1 Mizuhara, Itami City, Hyogo Prefecture Mitsubishi Electric Corp. Optical & Microwave Device Research Center

Claims (27)

[Claims] 1. A thin film having a thin-film active layer on a substrate, which is made of scaly graphite and has a sheet-like graphite having a crystal structure or a layer structure having anisotropy in the plane direction and the thickness direction of the substrate. In the method for manufacturing a solar cell, the method for manufacturing a thin film solar cell is characterized in that in the step of forming a thin film on the substrate, the substrate is heated by direct heating with high frequency. 2. A method for manufacturing a thin-film solar cell, wherein a strip-shaped graphite sheet substrate is sequentially fed into a reaction chamber, and a thin-film solar cell having a thin-film active layer is continuously formed on the substrate. A step of forming a cap layer made of a silicon oxide film or a silicon nitride film on the filmed thin film semiconductor, and melting and recrystallizing the thin film semiconductor in a state of covering the cap layer to expand the crystal grain size of the active layer. A method of manufacturing a thin-film solar cell, comprising: 3. A thin film having a thin-film active layer on a substrate, which is made of scaly graphite and has a sheet-like graphite whose crystal structure or layer structure has anisotropy in the plane direction and the thickness direction of the substrate. In the method for manufacturing a solar cell, a step of closely adhering two graphite sheet substrates in a state where their first main surfaces face each other and overlap each other; 1. A method of manufacturing a thin-film solar cell, comprising the steps of: forming a semiconductor thin film to be an active layer, and separating the adhered substrate into two substrates after the thin-film forming step. 4. A thin film having a thin film-like active layer on a substrate made of scaly graphite, which is a sheet-like graphite having a crystal structure or a layer structure having anisotropy in the plane direction and the thickness direction of the substrate. In a method for manufacturing a solar cell, a graphite sheet formed by roll molding is used.
A method for producing a thin film solar cell, which comprises forming a semiconductor thin film to be an active layer on a substrate after a curing treatment at 0 to several hundreds of degrees Celsius. 5. A thin film having a thin film-like active layer on a substrate made of scaly graphite as a raw material and made of sheet-like graphite having a crystal structure or a layer structure having anisotropy in the plane direction and the thickness direction of the substrate. In a method of manufacturing a solar cell, a graphite sheet formed by roll forming is treated with HCl.
A method of manufacturing a thin-film solar cell, comprising forming a semiconductor thin film to be an active layer on a substrate after annealing at 3000 ° C. or higher in an atmosphere. 6. A thin film having a thin-film active layer on a substrate, which is made of scaly graphite and has a sheet-like graphite having a crystal structure or a layer structure having anisotropy in the plane direction and the thickness direction of the substrate. In the method for manufacturing a solar cell, a step of partially adhering two graphite sheet substrates such that their first main surfaces are opposed to each other and a space is formed between the two overlapping substrates. , A source gas is caused to flow into the space, and each of the first of the two substrates is
And a step of forming a thin film on the main surface of the thin film solar cell. 7. A method for producing a thin-film solar cell, in which a strip-shaped graphite sheet substrate is sequentially fed into a reaction chamber to continuously form a thin-film solar cell having a thin-film active layer on the substrate. The distance from the raw material gas inlet to the exhaust outlet of the film forming chamber for depositing a thin film to form a layer is based on the raw material gas flow rate, flow velocity, and decomposition rate until most of the introduced raw material gas reaches the exhaust outlet. A method of manufacturing a thin-film solar cell, which comprises forming a thin film in a film-forming chamber set to have a length such that the thin-film solar cell is decomposed. 8. A method of manufacturing a thin film solar cell having a thin film active layer on a substrate, comprising: an exhaust port of a film forming chamber for forming a thin film to be an active layer on the substrate; A method of manufacturing a thin film solar cell, comprising forming a thin film in a film forming chamber provided with a means that does not allow only a raw material gas component to pass therethrough. 9. A thin film solar cell having a semiconductor thin film as an active layer on one main surface of a graphite sheet substrate, comprising a support base having high mechanical strength fixed to the other main surface of the graphite sheet substrate. A thin-film solar cell characterized in that 10. The thin-film solar cell according to claim 9, wherein the supporting base is made of an inexpensive metal plate, and is bonded and fired on the main surface of the graphite sheet with a metal paste. 11. The thin film solar cell according to claim 9, wherein the supporting substrate is made of a metal-grade silicon substrate. 12. A thin film having a thin film-like active layer on a substrate, which is made of scaly graphite and has a sheet-like graphite whose crystal structure or layer structure has anisotropy in the plane direction and the thickness direction of the substrate. In the method of manufacturing a solar cell, a step of fixing a graphite sheet substrate using a frame body made of carbon or ceramic so that tension is applied to the graphite sheet substrate, and the graphite sheet substrate is placed on the substrate while the tension is applied. And a step of forming a semiconductor thin film to be an active layer, the method of manufacturing a thin film solar cell. 13. A step of adhering and firing an inexpensive metal plate with a metal paste on the surface of the graphite sheet substrate opposite to the surface on which the semiconductor thin film is formed after the step of forming the semiconductor thin film. The method for manufacturing a thin film solar cell according to claim 12. 14. A step of forming a metallurgical grade silicon layer by plasma spraying on the surface of the graphite sheet substrate opposite to the surface on which the semiconductor thin film is formed, prior to the step of forming the semiconductor thin film as the active layer. 13. The method for manufacturing a thin film solar cell according to claim 12. 15. A thin film having a thin film-like active layer on a substrate made of scaly graphite as a raw material, and made of sheet-like graphite having a crystal structure or a layer structure having anisotropy in the plane direction and the thickness direction of the substrate. In the method for manufacturing a solar cell, a graphite sheet substrate is placed on a mold having a depression along the shape of the depression, and the depression covered with the graphite sheet is heated in a state of being filled with a metal-grade silicon powder and then cooled. Then, a step of melting and solidifying the metal-grade silicon powder to form a heat-resistant substrate having a metal-grade silicon substrate fixed to the back surface of the graphite sheet substrate, and forming an active layer on the surface of the graphite sheet substrate of the heat-resistant substrate. And a step of forming a semiconductor thin film. 16. A substrate containing carbon as a main component, a first silicon layer provided on the substrate, and an insulating layer provided on the first silicon layer and having an opening of a predetermined pattern. And a second silicon layer provided on the insulating layer so as to be in contact with the first silicon layer at the opening, and a thin film solar cell. 17. A step of forming a first silicon layer on a substrate containing carbon as a main component, a step of forming an insulating layer having openings of a predetermined pattern on the first silicon layer, A method of manufacturing a thin-film solar cell, comprising the step of forming a second silicon layer on the insulating layer so as to contact the first silicon layer at the opening. 18. The amorphous silicon layer is provided on the first silicon layer after the first silicon layer is formed in the step of forming the first silicon layer, and the amorphous layer is formed in the step of forming the insulating layer. 18. The method for manufacturing a solar cell according to claim 17, wherein a pattern is formed on the insulating layer by irradiating a laser beam on a place where an opening is to be formed on the entire surface of the quality silicon layer. 19. A thin film solar cell in which a polycrystalline silicon thin film layer serving as an active layer is formed on a heat resistant substrate, wherein a graphite sheet having an uneven structure is used as the heat resistant substrate. 20. A method of manufacturing a thin-film solar cell, comprising: a step of forming a graphite sheet substrate having an uneven structure on its surface; and a step of forming an active layer made of a polycrystalline silicon thin film on the substrate. .. 21. The production of a thin film solar cell according to claim 20, wherein a graphite sheet substrate having an uneven structure is formed by pressing scaly graphite purified and foamed by an acid treatment with a roller having an uneven surface. Method. 22. The method for producing a thin film solar cell according to claim 20, wherein a graphite sheet substrate having an uneven structure is formed by pressing a flat graphite sheet with a roller having an uneven surface. 23. A step of forming a semiconductor film on a strip-shaped first substrate, a step of forming a pn junction in the semiconductor film, and a step of adhering a second substrate to the semiconductor film. And a step of separating the semiconductor film from the first substrate, wherein the steps are continuously performed while sequentially moving the first substrate in the length direction thereof. Production method. 24. A solar battery cell having a thin film semiconductor layer formed on a conductive substrate is connected to a current collecting metal lead wire arranged on the surface side thereof and an adjacent substrate of the thin film solar battery cell. Thus, in a thin-film solar cell having a structure in which a plurality of solar cells are connected, a part of the metal lead wire is penetrated or penetrated into a part of a substrate of an adjacent cell to make a connection. And thin-film solar cells. 25. The thin film solar cell according to claim 24, wherein the conductive substrate is a graphite sheet. 26. The thin film solar cell according to claim 24, wherein the conductive substrate is made of aluminum. 27. A solar cell having a thin film semiconductor layer formed on a conductive substrate is connected to a current collecting metal lead wire arranged on the surface side thereof and a substrate of the thin film solar cell adjacent thereto. In the method of manufacturing a thin-film solar cell having a structure in which a plurality of solar cells are connected by bending the tip of the lead wire arranged on the surface side, and at a predetermined position of the substrate of the adjacent cells And a step of bringing the tip of the bent portion into contact with each other to pressurize the bent portion.