JPH09293888A - Manufacture of thin-film silicon solar battery and formation resist mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin-film silicon solar battery with a high yield, which can increase an accuracy in a via hole pattern by forming closed patterns of openings in surface of a thin-film silicon layer at equal intervals by overlapping a plurality of open resist patterns of openings. SOLUTION: Through a first screen printing process, a resist pattern 16 having linear opening is formed on the surface of a thin-film polycrystalline silicon layer 3 (step(a)). Through a second screen printing process, a resist pattern 17 having linear openings is formed perpendicularly to the resist pattern 16 (step(b)). The openings of the resist patterns 16 and 17 are overlapped with each other, thereby forming a via hole pattern having a closed pattern of openings 19 arranged at equal intervals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor solar cell, and more particularly to a screen printing method capable of accurately forming a desired pattern by screen printing a resist when manufacturing a solar cell structure.

[0002]

2. Description of the Related Art FIGS. 3A to 3E show, for example, "A NOVE
L FABRICATION TECHNIQUE FOR LOW COST THIN FILM PO-
LYCRYSTALLINE SILICON SOLAR CELLS "(Technical Dig
est of7th Internatio-nal Photovoltaic Science and
Engineering Conference, Nov.22-26 / 1993, pp.243-24
4, M. Deguchi et.al), which is a process cross-sectional view showing a conventional method for manufacturing a solar cell, and FIG. 3A is a cross-sectional view showing a formation state of a via hole, and FIG. FIG. 3B is a sectional view showing a partially etched state of the silicon oxide film.
3C is a cross-sectional view showing a state where the thin film polycrystalline silicon is separated from the substrate, and FIG. 3D is a cross-sectional view showing a state where the thin film polycrystalline silicon is attached to the glass substrate. Each of e) is a cross-sectional view showing the structure of the solar cell. In FIG. 3, thin film silicon with expanded crystal grains is formed on the insulating film by external heat treatment,
A method of manufacturing a solar cell using the thin film silicon layer as a power generation layer is disclosed.

According to this method of manufacturing a solar cell, a silicon oxide film (Si) as an insulating film is formed on the silicon substrate 1.
O ₂ ) is formed, polysilicon is formed on it, and the polysilicon is formed into a thin film polycrystalline silicon 3 having expanded crystal grains by a melt recrystallization method or the like. And
A via hole pattern is formed on the thin film polycrystalline silicon 3 by screen printing of a resist. After that, the thin film polycrystalline silicon 3 is etched using an acid or alkaline etching solution. Therefore, the thin film polycrystalline silicon 3 is etched from the opening portion of the via hole pattern, and the via hole 4 is formed as shown in FIG.
Is formed. Here, when the via holes 4 are provided at a pitch of 2 mm with respect to the semiconductor layer of 10 cm square, approximately 2500 via holes 4 are formed. Then, after removing the resist, the silicon oxide film 2 exposed in the via hole 4 is partially etched by immersing it in hydrofluoric acid (HF). After that, by performing thermal diffusion of phosphorus or the like, as shown in FIG.
Are formed on the surface layer of the thin film polycrystalline silicon 3. Then, the silicon oxide film 2 is removed by immersing in hydrofluoric acid, and the thin film polycrystalline silicon 3 is separated from the silicon substrate 1 as shown in FIG. The separation of the thin film polycrystalline silicon 3 is carried out by completely removing the silicon oxide film 2 by etching. Then, as shown in FIG. 3D, the thin film polycrystalline silicon 3 is attached to the glass substrate 6 using the transparent silicone resin 7. Finally, the p-electrode 8 and the n-electrode 9 are formed on the thin film polycrystalline silicon 3 to complete the solar cell having the structure shown in FIG. In this solar cell, the incident light 10 causes the glass substrate 6
It is incident from and power is generated.

Now, in the solar cell manufactured by such a basic flow, as shown in FIG. 3 (c), it is particularly important to surely separate the silicon substrate 1 and the thin film polycrystalline silicon 3 from each other. Becomes In order to realize this, it is necessary to accurately form the via hole 4. The reason is that, as described above, the number of via holes 4 is as many as 2500, and if there is a hole that does not penetrate even one of them, the silicon substrate 1 and the thin film polycrystalline silicon 3
It becomes impossible to separate from. Secondly, if the hole size is too large, it leads to a loss of the light receiving area of the solar cell. In order to solve the second point, it is desirable that the via hole 4 be formed in a round or quadrangular shape of, for example, about 200 to 300 μm.

Here, a method of forming the via hole 4 will be described with reference to FIG. 4A is a plan view showing a state in which a resist is screen-printed on the surface of the thin film polycrystalline silicon, and FIG. 4B is a IVB of FIG. 4A.
4B is a cross-sectional view taken along the line IVB, and FIG. 4C is a cross-sectional view showing the formation state of the via holes. First,
As shown in FIG. 4B, the stainless wire printing mask is constructed by embedding a mesh body made of stainless wires 14 in a mask emulsion 15, and removing unnecessary portions of the mask emulsion 15 to form dots. Mask Emulsion 1
A mask pattern in which a plurality of 5 are arranged at equal intervals is formed. Then, by screen printing, as shown in FIGS. 4A and 4B, a resist pattern 11 formed by arranging dot-shaped openings, which are closed patterns, in a lattice pattern on the surface of the thin film polycrystalline silicon 3. To form. Then, the resist is hardened, and the thin film polycrystalline silicon 3 exposed in the opening of the resist pattern 11 is etched by an etching solution. Then, as shown in FIG. 4C, the resist pattern 11 is formed on the thin film polycrystalline silicon 3.
The via hole 4 is formed in the shape of the opening.

[0006]

As described above, according to the conventional method for manufacturing a solar cell, the resist pattern 11 is formed by arranging dot-shaped openings, which are closed patterns, on the surface of the thin film polycrystalline silicon 3 in a grid pattern. Is formed by screen printing once. At this time, the resist is (a) and (b) in FIG.
It will flow into the opening as indicated by the arrow (leveling). The leveled resist 12 reduces the size of the opening, so that the opening diameter varies in an unstable manner. Then, the opening shape 13 after printing becomes a rounded and irregular shape. For example, when a 200-mesh print mask is used and printing is performed with a thermosetting resist ink having a viscosity of 500 poise, the leveling amount becomes 100 μm, which is an extremely large value. Moreover, when the number of times of printing was repeated in this state, the opening of the resist pattern 11 was almost crushed after several times of printing. This is because the leveled resist 12 adheres to the mask emulsion 15 of the print mask and is transferred to the surface of the thin film polycrystalline silicon 3 during the next printing. Therefore, it is necessary to wipe off the resist adhering to the mask emulsion 15 of the print mask each time printing is performed. In order to improve this, it was considered to use a resist with a higher viscosity, but the above situation was not improved, and the printed pattern was faint, and as a result, it was necessary to adjust the resist viscosity. It turns out that you can't. That is, continuous printing is practically impossible with the conventional method. Thus, in the conventional method,
There was a problem that a via hole pattern of a fixed size could not be stably formed and a solar cell could not be manufactured with a high yield.

The present invention has been made to solve the above problems, and improves the method of forming a via hole pattern by screen printing, increases the accuracy of the via hole pattern, and produces solar cells with a high yield. An object of the present invention is to obtain a method of manufacturing a thin film silicon solar cell that can be manufactured. Another object of the present invention is to provide a resist mask forming method capable of highly accurately forming a resist mask in which the openings of the closed pattern are arranged at equal intervals while suppressing the leveling of the resist in the openings of the closed pattern.

[0008]

A method of manufacturing a thin film silicon solar cell according to the first aspect of the present invention comprises forming thin film silicon on an insulating film formed on a substrate, and forming a resist via on the surface of the thin film silicon. After forming a hole pattern and performing etching processing on the thin film silicon to form a plurality of via holes at equal intervals, the insulating film is removed by etching through the via holes to separate the thin film silicon from the substrate to separate solar cells. In the method for manufacturing a thin-film silicon solar cell used as a power generation layer, a resist pattern having an opening of an open pattern on the surface of the thin film silicon on the insulating film is continuously screen-printed several times, and the opening of the opening of the resist pattern is By forming a plurality of closed pattern openings at equal intervals on the surface of the thin-film silicon by superposition, a via hole pattern is formed. Those were Unishi.

The method of manufacturing a thin film silicon solar cell according to the second aspect of the present invention is the method of manufacturing the thin film silicon solar cell according to the first aspect of the present invention, wherein the resist pattern in which the openings of the open pattern are formed in a linear pattern is used. The via-hole pattern is formed by screen-printing a plurality of times so that the patterns are in different directions.

The method for manufacturing a thin-film silicon solar cell according to the third aspect of the present invention is the method of manufacturing the thin-film silicon solar cell according to the first aspect, wherein the resist pattern in which the openings of the open pattern are formed in a linear pattern is used. The via-hole pattern is formed by screen-printing twice so that the patterns are orthogonal to each other.

Further, the method of forming a resist mask according to the fourth aspect of the present invention is a method of forming a resist mask in which openings of a closed pattern are arranged at equal intervals, and a resist pattern having openings of an open pattern is continuously formed. Then, a plurality of screens are printed, and the openings of the open pattern of the resist pattern are overlapped with each other to form the openings of the closed pattern arranged at equal intervals.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1. 1 (a) to 1 (d) are process charts for explaining a via hole forming process in the method for manufacturing a thin film silicon solar cell according to the first embodiment of the present invention, and FIG. FIG. 1B is a plan view showing a state where a first resist pattern is formed on the surface of crystalline silicon, and FIG. 1B is a plan view showing a state where a second resist pattern is formed on the surface of thin film polycrystalline silicon. 3 (c)
1B is a sectional view taken along line IC-IC in FIG. 1B, and FIG. 1D is a sectional view showing a state in which a via hole is formed in the thin film polycrystalline silicon. The invention of the present application resides in the screen printing process for forming a resist mask having a via hole pattern, and the process before and after the screen printing process related to the method for manufacturing a solar cell is shown in FIG. Since it is the same as that of (e) to (e), the description thereof is omitted here.

In the first embodiment, a stainless wire printing mask in which the mask emulsion is formed to have a linear opening is used. First, the first screen printing is performed using this stainless wire printing mask, and as shown in FIG. 1A, a linear opening having an open pattern is formed on the surface of the thin film polycrystalline silicon 3. The first resist pattern 16 is formed. Then, the resist is temporarily cured. After that, a second screen printing is performed using this stainless wire printing mask,
As shown in FIG. 1B, the thin film polycrystalline silicon 3
A second resist pattern 17 having a linear opening, which is an open pattern, is formed on the surface of. At this time, in the second screen printing, the linear opening of the second resist pattern 17 is changed to the first resist pattern 1.
The positional relationship between the stainless-steel wire print mask and the silicon substrate 1 is set so as to be orthogonal to the linear opening portion of 6. If the first and second resist patterns 16 and 17 are, for example, a pattern in which linear openings having a width of 300 μm are arranged at a pitch of 2 mm,
A resist pattern 1 is formed on the surface of the thin film polycrystalline silicon 3.
300 constructed by stacking 6 and 17 openings
A resist mask is formed in which openings 19 having a closed pattern of squares of μm are arranged in a grid pattern at a pitch of 2 mm. Then, after curing the resist, the thin film polycrystalline silicon 3 exposed in the opening 19 is etched with an etching solution,
As shown in FIG. 1D, the thin film polycrystalline silicon 3
A via hole 20 is formed in the shape of the opening 19.

The results of an experimental examination of the hole pattern formation state according to the first embodiment will be described below. The material, mesh size and resist of the printing mask used are the same as those in the prior art. Results of the experiment, 1
The leveling amount of the leveled resist 18 in the second and second resist patterns 16 and 17 is 50.
The leveling amount (1
The result was very small compared with the case of (00 μm). It is considered that this is because the resist patterns 16 and 17 are formed in a linear opening, that is, an open pattern. That is, the resist pattern 11 in the conventional technique has a dot-shaped opening, that is, a closed pattern, and the resist flows from the periphery into the opening, and the leveling amount increases. On the other hand, resist pattern 1
In Nos. 6 and 17, the opening is formed as an open pattern to prevent the resist from flowing into the opening from the periphery during printing. Further, the printing was performed 100 times continuously, but the leveling amount of the resist 18 hardly changed, and the opening 1
It was possible to stably form the hole pattern of 9 in which the variation in the opening diameter was suppressed. In addition, the via hole 20 produced by etching has no defect such as a deformed shape or non-penetration.
The variation was suppressed to ± 50 μm or less with respect to the m-square target value.

As described above, according to the first embodiment,
Since the first and second resist patterns 16 and 17 having the linear openings, which are open patterns, are screen-printed so as to be orthogonal to each other, a resist mask having a via hole pattern is formed. Since the leveling of 17 can be suppressed, a via hole pattern of a certain size can be stably formed, a solar cell can be manufactured with a high yield, and further, a via hole pattern can be formed by two screen printing steps. Productivity can be improved. Further, the leveling of the resist patterns 16 and 17 is small, the number of times of continuous printing of the print mask can be increased, and the productivity can be improved.

Embodiment 2 In the first embodiment, the pattern printing is performed on the flat surface. However, in this type of solar cell, in order to improve the characteristics, a pyramid-shaped uneven surface (height: several μm to 10 μm) generally called texture is often provided to reduce the surface reflectance. In the second embodiment, as shown in FIGS. 2A to 2D, pattern printing is performed on a pyramidal surface. 2A is a sectional view of a substrate on which thin film polycrystalline silicon is formed, FIG. 2B is a sectional view of a substrate on which a second resist pattern is formed, and FIG. FIG. 4D is a cross-sectional view of the substrate on which the via holes are formed by etching, and FIG. 4D is a perspective view of the substrate with the resist removed.

In the second embodiment, the above-mentioned first embodiment is used.
Similarly, a stainless wire printing mask in which the mask emulsion is formed so as to have a linear opening is used. First, the first screen printing is performed using this stainless wire printing mask, and the surface shown in FIG. 2 (a) is a linear pattern having an open pattern on the surface of the thin film polycrystalline silicon 21 formed in the texture structure. Forming a first resist pattern having an opening of. Then, the resist is temporarily cured. After that, a second screen printing is performed using this stainless wire printing mask,
As shown in FIG. 2B, the thin film polycrystalline silicon 2
1 having a linear opening which is an open pattern on the surface of 2
The resist pattern 22 for the first time is formed. Therefore, on the surface of the thin film polycrystalline silicon 21, the opening portions 23 having a closed pattern formed by overlapping the opening portions of the first and second resist patterns are arranged in a lattice pattern. Then, the resist is cured. At this time, 2
In the screen printing of the second time, the printing mask made of stainless wire and the silicon substrate 1 are so arranged that the linear opening of the resist pattern 22 of the second time is orthogonal to the linear opening of the resist pattern of the first time. The positional relationship is set. Then, using the etching solution, the opening 2
Etching the thin film polycrystalline silicon 21 exposed to 3
As shown in FIG. 2C, the thin film polycrystalline silicon 2
A via hole 24 is formed in the shape of the opening 23. Then, the resist is removed, and as shown in FIG. 2D, the thin film polycrystalline silicon 21 in which the via holes 24 are formed is obtained.

In the second embodiment, the first embodiment described above is used.
As a result of experimentally examining the formation state of the hole pattern in the same manner as described above, the same result as that of the first embodiment was obtained,
It could be sufficiently applied to the surface of the thin film polycrystalline silicon 21 having the texture structure. In the case of the conventional method in which the resist pattern 11 in which a plurality of closed pattern openings are arranged in a dot pattern is formed on the surface of the thin film polycrystalline silicon 21 by one screen printing, continuous printing cannot be performed at all.

In each of the above-described embodiments, resist patterns having linear openings which are open patterns are formed so as to be orthogonal to each other by two printing steps, and the openings having closed patterns are arranged in a grid pattern. However, the printing process is not limited to two times, and is not limited to two.
A resist pattern having linear openings may be formed by inclining by a predetermined angle by a printing process more than once to form a resist mask in which a plurality of closed pattern openings are arranged in a grid pattern. For example, if the resist pattern is 1
When printing is performed three times while inclining by 20 °, a resist mask in which a plurality of hexagonal openings are arranged in a grid pattern can be obtained. Further, in each of the above embodiments, the resist pattern having a linear opening is formed, but the opening of the resist pattern is not limited to the linear opening shape, and may be an open pattern. For example, it may have a gentle wavy opening shape. Further, in each of the above-mentioned embodiments, the via holes formed in the thin film polycrystalline silicon are assumed to be arranged in a lattice shape, but the arrangement of the via holes is not limited to this, and the via holes are equally spaced. May be arranged, for example, an array corresponding to each vertex position of the honeycomb structure or an array corresponding to each vertex position of an equilateral triangle.

[0020]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the invention, thin film silicon is formed on the insulating film formed on the substrate, a via hole pattern of a resist is formed on the surface of the thin film silicon, and the thin film silicon is subjected to etching treatment. After forming a plurality of via holes at equal intervals, in the method of manufacturing a thin film silicon solar cell used as a power generation layer of a solar cell by separating the thin film silicon from the substrate by etching away the insulating film through the via hole, A resist pattern having an open pattern opening on the surface of the insulating film is screen-printed multiple times in succession, and the closed pattern opening is formed by superimposing the open pattern openings of the resist pattern on the surface of the thin film silicon. Since a plurality of via hole patterns are formed at equal intervals on the surface, the leveling amount of the resist pattern Less possible, the via hole pattern of variations of the opening diameter is suppressed in the opening of the closed pattern can be stably formed, a manufacturing method of thin-film silicon solar cell capable of manufacturing method of thin-film silicon solar cell at a high yield is obtained.

According to the second invention, the first
In the invention, the resist pattern in which the openings of the open pattern are formed in a linear pattern is screen-printed a plurality of times so that the linear patterns are in different directions to form a via hole pattern. Therefore, the leveling amount of the resist pattern can be reduced, and the variation in the opening diameter of the opening of the closed pattern forming the via hole pattern can be suppressed.

According to the third invention, the first
In the invention, since the resist pattern in which the opening of the open pattern is formed in a linear pattern is screen-printed twice so that the linear patterns are orthogonal to each other, a via hole pattern is formed. Further, the leveling amount of the resist pattern can be reduced, the variation in the opening diameter of the opening of the closed pattern forming the via hole pattern can be suppressed, the number of screen printing can be reduced, and the productivity can be improved.

According to the fourth aspect of the invention, in the method of forming a resist mask in which the openings of the closed pattern are arranged at equal intervals, the resist pattern having the openings of the open pattern is continuously screened a plurality of times. Since the openings of the open pattern of the resist pattern are printed and overlapped so that the openings of the closed pattern are arranged at equal intervals, the leveling amount of the resist pattern can be reduced and the opening of the closed pattern can be reduced. A method of forming a resist mask in which variations in the opening diameter are suppressed and a highly accurate resist mask can be stably formed can be obtained.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating a via hole forming process in a method of manufacturing a thin film silicon solar cell according to a first embodiment of the present invention.

FIG. 2 is a process diagram illustrating a via hole forming process in the method of manufacturing a thin film silicon solar cell according to the second embodiment of the present invention.

FIG. 3 is a process diagram illustrating a conventional method for manufacturing a solar cell.

FIG. 4 is a process diagram illustrating a via hole forming process in a conventional method for manufacturing a solar cell.

[Explanation of symbols]

1 Silicon Substrate (Substrate), 2 Silicon Oxide Film (Insulating Film), 3, 21 Thin Film Polycrystalline Silicon (Thin Film Silicon), 16, 17, 22 Resist Pattern, 20, 2
4 via holes.

Claims (4)

[Claims] 1. A thin film silicon is formed on an insulating film formed on a substrate, a via hole pattern of a resist is formed on the surface of the thin film silicon, and the thin film silicon is subjected to an etching treatment to form via holes at equal intervals. In the method for manufacturing a thin film silicon solar cell used as a power generation layer of a solar cell by separating the thin film silicon from the substrate by etching and removing the insulating film through the via hole, A resist pattern having an opening of an open pattern on the surface of the thin film silicon is continuously screen-printed a plurality of times, and an opening of a closed pattern is formed by superposing the openings of the open pattern of the resist pattern. A thin film shield characterized in that a plurality of via holes are formed on the surface at equal intervals. Recon solar cell manufacturing method. 2. A via hole pattern is formed by screen-printing a resist pattern in which an opening of an open pattern is formed in a linear pattern a plurality of times so that the linear patterns have different directions. The method for manufacturing a thin-film silicon solar cell according to claim 1, wherein 3. A via hole pattern is formed by screen-printing a resist pattern in which an opening of an open pattern is formed in a linear pattern twice so that the linear patterns are orthogonal to each other. The method for manufacturing a thin-film silicon solar cell according to claim 1, wherein 4. A method of forming a resist mask in which openings of a closed pattern are arranged at equal intervals, wherein a resist pattern having openings of an open pattern is continuously screen-printed a plurality of times to open the resist pattern. A method of forming a resist mask, characterized in that the openings of the closed pattern are arranged at equal intervals by overlapping the openings of the pattern.