JP2001168356A - Method of manufacturing solar cell - Google Patents

Abstract

(57) [Problem] To provide a photovoltaic cell having a texture structure on a light receiving surface and a flat pn junction surface, is expensive. [MEANS FOR SOLVING PROBLEMS] To solve the above problems, the present invention provides:
Doping an impurity of a second conductivity type on a light receiving surface side of a semiconductor substrate of a first conductivity type to form a polycrystalline silicon layer; and oxidizing the polycrystalline silicon layer to generate a silicon oxide film; And a step of removing the silicon oxide film on the polycrystalline silicon layer.

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 solar cell for converting light energy into electric energy.

[0002]

2. Description of the Related Art Conventionally, a solar cell has been known as an element for converting light energy into electric energy.

FIG. 4 shows a general cell structure of a solar cell, according to which a solar cell comprises a single-crystal silicon substrate 401, an n-type diffusion layer 402, and a light-receiving surface electrode 404.
, A back electrode 403, and an antireflection film 405.

[0004] However, the above solar cell structure has
Since the junction between the p-type single crystal silicon substrate 401 and the n-type diffusion layer 402 has an uneven shape (hereinafter referred to as a texture structure), the area of the junction, that is, the so-called pn junction area does not use this structure. It is about 1.5 to 2.0 times larger than the case. This allows the saturation current density to be p
The saturation current obtained by integrating with the area of the n-junction becomes large as compared with the case where the structure is not used, and thus the open-circuit voltage is reduced.

In order to solve the above problem, the junction between the crystalline silicon substrate 401 and the n-type diffusion layer 402 is flat, and the light-receiving surface side of the n-type diffusion layer 402 has a textured photoelectric conversion element (solar cell). ) Is disclosed in JP-A-5-9512.
No. 4 discloses this.

FIG. 3 is a sectional view showing the structure of the photoelectric conversion element. The photoelectric conversion element is a single crystal p-type semiconductor substrate 301, an n-type semiconductor layer 302, and an antireflection film made of a silicon oxide film. 303 and a high concentration p + type impurity region 3
4, the back side electrode 305, and the light receiving surface electrode 306.

[0007]

However, in the above-mentioned photoelectric conversion element, in order to form the n-type semiconductor layer 302 by epitaxial growth, the p-type semiconductor substrate 301 must be formed.
Needs to be single-crystal silicon, which is unsuitable for cost reduction.

Further, a shallow pn junction surface is required between the p-type semiconductor substrate 301 and the n-type semiconductor layer 302. When a texture structure is formed on the surface of the n-type semiconductor layer 302 by selective etching, a uniform pn junction is formed. There is a problem that it is difficult to control the amount of etching to obtain the junction depth. This is the same when the n-type semiconductor layer 302 is formed by using the thermal diffusion method.

[0009]

According to the present invention, in order to solve the above-mentioned problems, a polycrystalline silicon layer is formed on a light-receiving surface side of a semiconductor substrate of a first conductivity type by doping impurities of a second conductivity type. And a step of oxidizing the polycrystalline silicon layer to form a silicon oxide film, and a step of removing the silicon oxide film on the polycrystalline silicon layer.

A solar cell manufactured by this method can be manufactured at low cost because polycrystalline silicon can be used for a semiconductor substrate.

[0011] The present invention also provides a method for manufacturing a solar cell, characterized in that in the step of forming the polycrystalline silicon layer, an amorphous silicon layer is formed and then a polycrystalline silicon layer is formed. The solar cell produced by this method has large crystal grains and good electrical characteristics.

Further, according to the present invention, in the step of oxidizing the polycrystalline silicon layer to form a silicon oxide film, the height of the irregularities on the polycrystalline silicon layer can be easily controlled by adjusting the oxidation time. Become.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a solar cell according to the present invention, showing the structure thereof. As shown in FIG. 1, a solar cell according to the present invention comprises a polycrystalline p-type silicon substrate 101, a polycrystalline silicon layer 102, and a p-electrode 104.
, An n-electrode 105, and an antireflection film 106.

FIG. 2 shows a manufacturing process of the solar cell. Hereinafter, the manufacturing process will be described with reference to FIG.

First, as shown in FIG. 2A, the surface of the p-type silicon substrate 101 is washed with hydrofluoric acid of about 1%, and a silane gas or a disilane gas is deposited at a film forming temperature of about 600 to 650 ° C. in a low pressure CVD apparatus. Is thermally decomposed. afterwards,
By mixing phosphorus trioxide or the like on the light receiving surface side and doping with impurities such as phosphorus, the polycrystalline silicon layer 102 made of crystal grains is formed. Note that these crystal grains are actually generated at random positions with random sizes, but in FIG. 2A, to schematically show the crystal grains, columnar crystals of the same size are used. The grains are shown arranged at equal intervals. In addition, in the step of FIG. 2A, when the film formation temperature is set at 500 ° C. or lower, an amorphous silicon layer is formed, and thereafter, the amorphous silicon layer is grown in a nitrogen atmosphere at about 620 ° C. The polycrystalline silicon layer 10
2 are formed. In this case, a polycrystalline silicon layer having larger crystal grains than the former method can be formed.

Thereafter, as shown in FIG. 2B, a silicon oxide film 103 is formed by steam oxidation.

Next, as shown in FIG. 2C, the silicon oxide film 103 on the surface of the p-type silicon substrate 101 and the surface of the polycrystalline silicon layer 102 is removed by immersing the substrate in hydrofluoric acid of about 10%. . Thereafter, the crystal boundaries on the polycrystalline silicon surface on the light-receiving surface side are exposed, and the diameter is 0.03-1.
An uneven surface of about 0 μm is formed. Here, the height of the irregularities on the polycrystalline silicon surface can be controlled by the oxidation time. Note that the oxidation time for forming the uneven surface of the desired height is slower than the film formation time by the conventional selective etching used for forming the texture structure, so that the adjustment is easy. .

Next, as shown in FIG. 2D, a comb-shaped n-electrode 105 is formed on the light-receiving surface, an anti-reflection film 106 is formed thereon, and the p-electrode 104 is evacuated on the back surface. By forming by a vapor deposition method or the like, the solar cell according to the present invention is completed.

The present invention provides a BSR (Back Surface Reflect) which is effective for use in space solar cells.
BSF (Back Surf) in which a high-concentration p-type diffusion layer is formed on the back surface side of the substrate other than the solar cell having the (or) structure.
ace Field) structure and a solar cell having a partial BSF structure in which a p-type diffusion layer is partially formed. Further, the present invention can be applied to a terrestrial solar cell.

[0021]

As described above, according to the present invention, p
Since a solar cell having a flat n-junction surface and a texture structure on the light-receiving surface can be manufactured using a polycrystalline silicon substrate, the cost can be reduced.
Further, since the height of the irregularities of the texture structure can be adjusted by the oxidation time, the control is easy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a solar cell according to the present invention.

FIG. 2 is a diagram illustrating a manufacturing process of a solar battery cell according to the present invention.

FIG. 3 is a cross-sectional view of a conventional photoelectric conversion element.

FIG. 4 is a view showing a manufacturing process of a conventional solar cell.

[Explanation of symbols]

 Reference Signs List 101 p-type silicon substrate 102 polycrystalline silicon layer 103 silicon oxide film 104 p-electrode 105 n-electrode 106 anti-reflection film

Claims (2)

[Claims] 1. A light-receiving surface side of a semiconductor substrate of a first conductivity type,
Doping an impurity of a second conductivity type to form a polycrystalline silicon layer, oxidizing the polycrystalline silicon layer to form a silicon oxide film, and forming the silicon oxide film on the polycrystalline silicon layer. And a step of removing the solar cell. 2. The method according to claim 1, wherein in the step of forming the polycrystalline silicon layer, a polycrystalline silicon layer is formed after forming an amorphous silicon layer.