JP2002198546A - Formation method for solar cell element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a complicated formation method for a solar cell and to provide a formation method for a solar cell element whose characteristic can be enhanced. SOLUTION: In the formation method for the solar cell element, a region displaying an opposite conductivity is formed near the surface of a semiconductor substrate displaying one conductivity, and electrodes are formed on both main face sides of the semiconductor substrate. The region displaying the opposite conductivity is formed near the surface of the semiconductor substrate, the region displaying the opposite conductivity on one main face side of the semiconductor substrate is cut from a region displaying the opposite conductivity on the other main face side, a specific region on one main face side and a specific region on the other main face side of the semiconductor substrate are coated with a silver paste, and another region on the other main face side is coated with an aluminum paste so as to be fired. As a result, the electrodes are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a solar cell element.

[0002]

2. Description of the Related Art A typical manufacturing process of a conventional silicon solar cell is shown in FIG. First, a P-type semiconductor substrate 1 is prepared as shown in FIG. Then, as shown in FIG. 5B, the semiconductor substrate 1 is subjected to a heat treatment in an N-type impurity atmosphere to diffuse the N-type impurity to a predetermined depth over the entire surface near the surface of the semiconductor substrate 1, thereby providing an N-type diffusion layer. Form 2

[0005] Next, as shown in FIG.
The PN junction is separated by removing other portions except for one main surface side. Then, as shown in FIG. 5D, an aluminum paste is applied to the back surface of the semiconductor substrate 1 by screen printing or the like, and the aluminum paste is baked.
Is diffused in the vicinity of the back surface of the substrate to form a BSF layer 6 containing a high concentration of P-type impurities. Next, the alloy layer remaining on the back side of the semiconductor substrate 1 is removed.

Next, as shown in FIG. 5E, an antireflection film 3 is formed on the surface of the semiconductor substrate 1 by a CVD apparatus or the like. Then, a silver paste is screen-printed on each of the front and back surfaces of the semiconductor substrate 1 and baked, whereby FIG.
As shown in (f), the collecting electrodes 4 and 5 are formed, and finally the surfaces of the collecting electrodes 4 and 5 are covered with a solder layer (not shown). Thereby, a solar cell can be obtained. At this time, the back surface electrode 5 may be partially formed as shown in FIG. 6A, or may be formed on the entire back surface as shown in FIG. 6B.

[0005]

However, in this conventional method for forming a solar cell element, the PN is removed by removing the remaining portion except for the diffusion layer 2 on the main surface side of the semiconductor substrate 1.
After the separation, an aluminum paste is screen-printed and baked on the back surface side of the semiconductor substrate 1, the residue of the aluminum paste is removed by an etching method or the like, and a silver paste is screen-printed and baked. Since the back surface electrode 5 is formed on the back surface side of the substrate 1, there is a problem in that the removal of the diffusion layer 2 and the formation of the BSF layer 6 and the back surface electrode 5 are complicated, and it takes a long time to manufacture a solar cell.

Conventionally, PN separation has been performed by leaving only the diffusion layer 2 on one main surface side of the semiconductor substrate 1 and removing other portions. Also, as another method, P
Even if N separation is performed, in the case of a silver electrode, it is necessary to remove the diffusion layer 2 on the back surface before forming the electrode. As another method, in the case of PN separation by blast, a silver electrode could not be formed unless the BSF layer 6 was formed on the diffusion layer 2.

The present invention has been made in view of such problems of the prior art, and provides a method of forming a solar electronic element which can simplify a complicated method of manufacturing a solar cell and improve characteristics. The purpose is to do.

[0008]

According to a first aspect of the present invention, there is provided a method for forming a solar cell element, wherein a region having an opposite conductivity type is formed near a surface of a semiconductor substrate having one conductivity type. In the method for forming a solar cell element in which electrodes are formed on both main surfaces of the semiconductor substrate, after forming a region having the opposite conductivity type near the surface of the semiconductor substrate, the semiconductor substrate is inverted on one main surface side. The region exhibiting the conductivity type is separated from the region exhibiting the opposite conductivity type on the other main surface side, and a silver paste is applied to a specific region on one main surface side and another main surface side of the semiconductor substrate, and the other The electrode is formed by applying and baking an aluminum paste to another specific region on the main surface side.

In the method for forming a solar cell element, a polycrystalline silicon substrate can be used as the semiconductor substrate.

In the method for forming a solar cell element, the region having the opposite conductivity type on one main surface of the semiconductor substrate and the region having the opposite conductivity type on the other main surface are separated from each other by the other main surface. It is desirable to divide by forming a groove near the peripheral edge on the surface side.

In the method for forming a solar cell element, the groove is formed by a sand blast method, a laser processing method, a dicing method,
Alternatively, it can be formed by any of the etching methods.

Further, in the method of forming a solar cell, the semiconductor substrate may include a region having the opposite conductivity type on one main surface side and a region having the opposite conductivity type on the other main surface side. Alternatively, the region may be divided by removing a region having the opposite conductivity type.

Further, in the method for forming a solar cell element,
The region having the opposite conductivity type on the side surface of the semiconductor substrate can be removed by any of sandblasting, laser processing, dicing, plasma etching, or wet etching.

In the above-described method for forming a solar cell element, a silver paste is applied to a specific area to which a lead wire on the other main surface of the semiconductor substrate is connected, and a large area on the other main surface other than the specific area is applied. The electrode is formed by applying an aluminum paste to another specific region occupying the portion and simultaneously firing the aluminum paste.

With the above structure, a groove is formed in the vicinity of the peripheral portion on the other main surface side of the semiconductor substrate 1 to perform PN separation, or PN separation is performed by etching the side surface portion, and a silver paste is applied. In addition, by applying and baking an aluminum paste, a composite electrode of silver and aluminum is formed, and the aluminum electrode has a BSF effect and the BSF layer and the electrode can be formed simultaneously without losing the shape of the diffusion layer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a diagram showing a method for forming a solar cell element according to claim 1.

First, as shown in FIG. 1A, a semiconductor substrate 1 exhibiting one conductivity type, for example, a P-type is prepared. As the semiconductor substrate 1, various semiconductor substrates such as a silicon substrate and a gallium arsenide substrate can be used, but a polycrystalline silicon substrate is advantageous in terms of manufacturing cost. Then, as shown in FIG. 1B, the semiconductor substrate 1 is subjected to a heat treatment in an atmosphere of a reverse conductivity type, for example, an N-type impurity, so that N The region 2 having the opposite conductivity type is formed by diffusing the type impurity.

Next, as shown in FIG. 1C, an anti-reflection film 3 made of silicon nitride (SiN _x ) having a thickness of about 800 ° is formed on the surface of the semiconductor substrate 1 by a plasma CVD method or the like.
To form

Next, the region 2 having the opposite conductivity type on one main surface side of the semiconductor substrate 1 and the other main surface side is divided. A region 2 of opposite conductivity type on one main surface side of the semiconductor substrate 1 and the other main surface side
Is formed by providing a groove 2a in the vicinity of the peripheral portion on the other main surface side of the semiconductor substrate by any of sandblasting, laser processing, dicing, and etching. Examples of the etching method include a reactive ion etching (RIE) method and a chemical etching method using a mixed solution of hydrofluoric acid and nitric acid. Alternatively, by printing and firing a paste containing glass as a main component, the opposite conductivity type region 2 on one main surface side of the semiconductor substrate 1 and the other main surface side may be separated.

The order of the step of forming the antireflection film 3 and the step of separating the reverse conductivity type region 2 does not matter. The position and shape of the separation groove 2a are not limited as long as the opposite conductivity type region 2 can be completely completely electrically separated between the one main surface side and the other main surface side of the semiconductor substrate 1. Alternatively, as shown in FIG. 2D, the region 2 having the opposite conductivity type may be separated from the side surface of the semiconductor substrate 1. Even in this separation, for example, a plasma etching method,
Sand blast method, laser processing method, dicing method, R
The IE method or the like is used. 3 (c) and FIG.
As shown in (d), the anti-reflection film 3 may be formed after separating the opposite conductivity type region 2 on the side surface of the semiconductor substrate 1.

Next, as shown in FIGS. 1 (d) and 4 (a), a silver paste 5 (5a) is applied to specific regions on one main surface side and the other main surface side of the semiconductor substrate 1. An electrode is formed by applying aluminum paste 5 (5b) to another specific region on the other main surface side and firing at a temperature of about 700 ° C. The printing of the aluminum paste 5b on the other main surface side of the semiconductor substrate 1 is performed by a screen printing method, a spin coating method, or the like. The electrode 4 on one main surface side may be a method of screen-printing and baking a silver paste on an insulating film (anti-reflection film 3) called fire-through, or opening the insulating film (anti-reflection film 3) in advance. Alternatively, a method in which a silver paste is printed thereon and fired may be used.

The electrode 5 on the other main surface side of the semiconductor substrate 1 (5
a and 5b), as shown in FIG.
To form. This silver may or may not contain aluminum. The shape of the silver paste 5a at this time is not limited to the shape of FIG. 4A, and may be divided as shown in FIG. 4B, for example. The order of applying the aluminum paste 5b and the silver paste 5a may be any order. Also, in FIGS. 4A and 4B, the application area of the aluminum paste 5b is larger than the application area of the silver paste 5a. However, if the BSF effect is not expected, the application area of the silver paste 5a is increased. It may be.

[0023]

Examples of the present invention will be described below. As shown in FIG. 1A, a semiconductor substrate is 15 cm square and 0.3 m thick.
A P-type silicon substrate having a specific resistance of 1.5 Ω · cm was prepared. Then, as shown in FIG. 1 (b), a thermal diffusion method using phosphorus oxychloride (POCl ₃ ) as a diffusion source to a depth of 0.5
A μm N-type diffusion layer was formed.

Next, an antireflection film of silicon nitride is formed on the front surface by plasma CVD at a thickness of 800 °, and on the back surface, an injection nozzle is applied at an angle of 80 ° to the semiconductor substrate. Is directly injected, and FIG. 1 (c)
An N-type diffusion layer separation part was formed as shown in FIG.

Finally, a silver paste and an aluminum paste are screen-printed on the back surface in the pattern shown in FIG.
After forming electrodes on both surfaces of the silicon substrate by baking, the substrate was immersed in a 200 ° C. solder bath and pulled up to cover the electrode surface with a solder layer to produce a solar cell.

The solar cell obtained by the method of the present invention and FIG.
Table 1 shows electrical characteristics of a solar cell obtained by a conventional manufacturing method in which a BSF layer is formed by etching the other so that one main surface side of the diffusion layer remains as shown in FIG.

[0027]

[Table 1]

As shown in Table 1, the conversion efficiency (Effi) was 14.20% in the conventional method, but was 14.97% in the product of the present invention, and a solar cell with high conversion efficiency was obtained. Can be.

[0029]

As described above, according to the method for forming a solar cell element according to the first aspect, after forming a region having the opposite conductivity type near the surface of the semiconductor substrate having the one conductivity type, the semiconductor substrate is formed. A region having the opposite conductivity type on one main surface side and a region having the opposite conductivity type on the other main surface side are separated from each other, and a silver paste is applied to one main surface side of the semiconductor substrate and a specific region on the other main surface side. Is applied, and an aluminum paste is applied to another specific region on the other main surface side and baked to form the electrode, so that the manufacturing process of the solar cell element can be simplified and the characteristics can be improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a view for explaining steps of a method for forming a solar cell element according to the present invention.

FIG. 2 is a view for explaining another step of the method for forming a solar cell element according to the present invention.

FIG. 3 is a view for explaining another step of the method for forming a solar cell element according to the present invention.

FIG. 4 is a view showing the shape of an electrode on another main surface side of the solar electronic element formed by the forming method of the present invention.

FIG. 5 is a view for explaining steps of a conventional method for forming a solar cell element.

FIG. 6 is a view showing a structure of a conventional solar cell element.

[Explanation of symbols]

1 ... semiconductor substrate, 2 ... reverse conductivity type region (N-type region), 3 ... antireflection film, 4 ... one main surface side ... P. (BS) Electrodes of other principal surfaces, 6... P ⁺ (BS
F) Layer

Claims (7)

[Claims] 1. A method for forming a solar cell element, comprising: forming a region having an opposite conductivity type near a surface of a semiconductor substrate having one conductivity type; and forming electrodes on both main surfaces of the semiconductor substrate. After forming a region having the opposite conductivity type near the surface of the semiconductor substrate, the region having the opposite conductivity type on one main surface side of the semiconductor substrate is separated from the region having the opposite conductivity type on the other main surface side. Forming the electrodes by applying a silver paste to a specific region on one main surface side and another main surface side of the substrate, and applying and firing an aluminum paste to another specific region on the other main surface side; A method for forming a solar cell element. 2. The method according to claim 1, wherein the semiconductor substrate is a polycrystalline silicon substrate. 3. A region having the opposite conductivity type on one main surface side of the semiconductor substrate and a region having the opposite conductivity type on the other main surface side,
The method for forming a solar cell element according to claim 1, wherein the semiconductor substrate is divided by forming a groove near a peripheral portion on the other main surface side of the semiconductor substrate. 4. The method for forming a solar cell element according to claim 3, wherein the groove is formed by any one of a sandblast method, a laser processing method, a dicing method, and an etching method. 5. A semiconductor device according to claim 1, wherein the semiconductor substrate has a region on the one principal surface side having the opposite conductivity type and a region on the other principal surface having the opposite conductivity type.
The method for forming a solar cell element according to claim 1, wherein the side surface of the semiconductor substrate is divided by removing a region having a reverse conductivity type. 6. The semiconductor device according to claim 1, wherein a region of the side surface of the semiconductor substrate having an opposite conductivity type is removed by one of a sandblasting method, a laser processing method, a dicing method, a plasma etching method, and a wet etching method. 5
3. The method for forming a solar cell element according to item 1. 7. A silver paste is applied to a specific region to which a lead wire on the other main surface side of the semiconductor substrate is connected,
2. The solar cell element according to claim 1, wherein the electrode is formed by applying an aluminum paste to another specific region occupying most of the main surface other than the specific region and firing the same at the same time. 3. Formation method.