JPH05267163A - Polycrystalline semiconductor film formation method and photovoltaic device using the film - Google Patents

Abstract

PURPOSE:To provide a formation method which is capable of forming a polycrystalline semiconductor film which provides larger crystal sizes and a high carrier mobility. CONSTITUTION:An intrinsic amorphous semiconductor film 2 and a amorphous semiconductor film 3 of one conductivity tape are formed on an uneven substrate 1 in this order. Then, they are heat-treated so that the impurities contained in the amorphous semiconductor film 3 may be diffused in the intrinsic amorphous semiconductor film 2 and further crystallized, thereby forming a polycrystalline semiconductor film 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a polycrystalline semiconductor film and a photovoltaic device using the film.

[0002]

2. Description of the Related Art In a photovoltaic device composed of a polycrystalline semiconductor film, an increase in the crystal grain size in the polycrystalline semiconductor film and an improvement in carrier mobility in the film improve the photoelectric conversion efficiency. Is an essential condition of. A typical example of such a polycrystalline semiconductor film is a polycrystalline silicon film.

Conventionally, a so-called solid phase growth method has been adopted as a method for forming the polycrystalline silicon film. As a conventional solid-phase growth method, as shown in FIG. 6, an amorphous silicon 11 doped with impurities is formed on a substrate 1 having an uneven surface, and an intrinsic non-crystalline silicon 11 is formed on the amorphous silicon 11. Amorphous silicon 2 is formed. Then, the amorphous silicon is heat-treated to be crystallized while the impurities are diffused to the intrinsic amorphous silicon layer, and the polycrystalline silicon film 10 of one conductivity type is transformed to be formed. is there.

[0004]

According to the above method, although a polycrystalline silicon film having a crystal grain size of a certain size can be obtained, the nuclei generated by the impurity-doped amorphous silicon layer located in the lower layer are obtained. There is a problem that the number is large and the crystal grain size and carrier mobility are still insufficient.

Therefore, an object of the present invention is to provide a method capable of forming a polycrystalline semiconductor film having a larger crystal grain size and high carrier mobility.

[0006]

According to the method of forming a polycrystalline semiconductor film of the present invention, an intrinsic amorphous semiconductor film and a one-conductivity type amorphous semiconductor film are formed in this order on a substrate having an uneven surface. And then crystallize while diffusing the impurities contained in the one conductivity type amorphous semiconductor film into the intrinsic amorphous semiconductor film to form a polycrystalline semiconductor film. To do.

In the photovoltaic device of the present invention, an amorphous semiconductor in which an intrinsic amorphous semiconductor and an amorphous semiconductor of one conductivity type are formed in this order on a substrate having irregularities on its surface is subjected to heat treatment. A polycrystalline semiconductor film of one conductivity type formed by applying is provided.

[0008]

According to the present invention, the impurity layer is located above the intrinsic semiconductor for doping the intrinsic semiconductor. Therefore, the center of nucleation depends on the unevenness of the substrate, the number of nuclei generated decreases corresponding to the unevenness of the substrate, and a large crystal grain size can be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an element structure diagram for each manufacturing step for explaining a method for forming a polycrystalline semiconductor film according to the present invention, in which silicon is used as a material.

First, an intrinsic amorphous silicon film 2 is formed by a conventionally known plasma CVD method on a substrate 1 having an uneven surface of 0.3 μm to several tens of μm on its surface. The substrate 1 may be either conductive or insulating, but a translucent insulating substrate was used in the examples.

As the method of manufacturing the uneven shape, for example, the surface itself of the translucent insulating substrate is processed by chemical or physical etching, or Sn is formed on the surface of the substrate.
O ₂ film and ITO (Indium Tin Oxide)
For example, by forming a conductive film such as a film or an insulating film such as a SiO ₂ film or a Si ₃ N ₄ film, the uneven shape provided on the surface of these films is used.

As the formation conditions by the plasma CVD method, 10 cc / min of silane gas was used as a reaction gas, the degree of vacuum during discharge was 11 Pa, and the discharge power was 15 W. The substrate temperature is 350 ° C.

After forming the intrinsic amorphous silicon film 2, a phosphorus-doped n-type amorphous silicon layer 3 is formed. This formation may be similarly performed by the plasma CVD method. The formation conditions of this plasma CVD method were as follows: silane gas of 10 cc / min mixed with phosphine (1% concentration of hydrogen diluted) of 5 cc / min was used, the discharge vacuum was 11 Pa, and the discharge power was 15
Formed with W. The substrate temperature is 350 ° C.

Next, the intrinsic amorphous silicon film and the substrate 1 having the n-type amorphous silicon film 3 formed thereon are placed in an electric furnace at a temperature of 600 ° C. to 700 ° C. for 3 to 7 hours. Heat treatment of. This n-type impurity of the n-type amorphous silicon layer, i.e. phosphorus is diffused to an intrinsic amorphous silicon layer, and these amorphous silicon film is transformed into polycrystalline silicon, n ^- -type polycrystalline Silicon 20 is formed.

The grain size of the n ^-- type polycrystalline silicon film 20 obtained in this embodiment is 8 to 10 μm.

On the other hand, as shown in FIG. 6, after the n-type amorphous silicon 11 is formed on the substrate 1 and the intrinsic amorphous silicon 2 is formed thereon, the polycrystalline silicon film is formed by solid phase growth. In the case of the conventional one having a diameter of 10, the particle diameter is 4 to 6 μm.
Therefore, it can be seen that the product according to the present invention has grown significantly.

In the above embodiment, the case where the n ^-- type polycrystalline silicon film is formed has been described. However, the formation is exactly the same even when the p ^-- type polycrystalline silicon film other than the n ^-- type is formed. You can In this case, a p-type amorphous silicon layer doped with p-type impurities may be stacked on the intrinsic amorphous silicon, and then heat treatment may be performed to perform solid phase growth.

A photovoltaic device using the polycrystalline silicon film thus obtained is shown in FIGS. 2 and 3. In FIG. 2, the intrinsic amorphous silicon layer 3 is formed on the n ⁻ type polycrystalline silicon 20 formed by the above method, and the p type amorphous silicon layer 4 is further formed thereon. To form a joint.

In FIG. 3, the junction is formed by forming the p-type polycrystalline silicon 5 on the n ^-- type polycrystalline silicon 20 formed by the above method.

Data of a photovoltaic device using the thus obtained polycrystalline silicon film are shown in FIGS. 4 and 5.
In FIG. 4, a polycrystalline silicon film (A) according to the present invention, a conventional polycrystalline silicon film (B) shown in FIG. 6 and a polycrystalline silicon film formed in the same manner as in the method shown in FIG. The relationship between each carrier concentration and carrier dependence with C) is shown. In the figure, what is shown by the solid line is according to the present invention, the one-dot chain line is the conventional one using the uneven substrate, and the dotted line is the conventional one using the flat substrate. It can be seen from FIG. 4 that the polycrystalline silicon film of the present invention has a much improved carrier mobility as compared with the conventional one.

FIG. 5 is a characteristic diagram of collection efficiency which is an optical characteristic of the photovoltaic device using the polycrystalline silicon film according to the present invention and the conventional example, and A is the photovoltaic efficiency using the polycrystalline silicon according to the present invention. Device B is a photovoltaic device using polycrystalline silicon formed by a conventional method, and C is a photovoltaic device using polycrystalline silicon formed by a conventional method using a conventional flat substrate. As is clear from FIG. 5, the photovoltaic device according to the present invention has further improved collection efficiency in the long wavelength region as compared with the conventional photovoltaic device.

[0022]

As described above, according to the present invention, an intrinsic amorphous semiconductor and a one-conductivity type amorphous semiconductor are formed in this order on a substrate having an uneven surface, and this is heat treated. The polycrystalline semiconductor film thus formed has a large grain size and a large carrier mobility. A photovoltaic device having a polycrystalline semiconductor film formed by this method has high photoelectric conversion efficiency.

[Brief description of drawings]

FIG. 1 is an element structure diagram for each manufacturing step for explaining a method for forming a polycrystalline semiconductor film according to the present invention.

FIG. 2 is a schematic view showing a photovoltaic device using a polycrystalline silicon film according to the present invention.

FIG. 3 is a schematic view showing a photovoltaic device using a polycrystalline silicon film according to the present invention.

FIG. 4 is a characteristic diagram showing a relationship between carrier concentration and carrier dependence of a polycrystalline silicon film according to the present invention and a conventional polycrystalline silicon film.

FIG. 5 is a collection efficiency characteristic diagram of photovoltaic devices using the polycrystalline silicon film of the present invention and the conventional example.

FIG. 6 is an element structure diagram for each manufacturing step for explaining a conventional method for forming a polycrystalline semiconductor film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Intrinsic amorphous silicon film 3 n-type amorphous silicon film 20 n ^- type polycrystalline silicon 10 n ^- type polycrystalline silicon 11 n-type amorphous silicon film

Claims (2)

[Claims] 1. An intrinsic amorphous semiconductor film and a one-conductivity type amorphous semiconductor film are formed in this order on a substrate having an uneven surface, and then heat treated to form the one-conductivity type amorphous film. A method for forming a polycrystalline semiconductor film, which comprises forming a polycrystalline semiconductor film by crystallization while diffusing impurities contained in the semiconductor film into an intrinsic amorphous semiconductor film. 2. An intrinsic amorphous semiconductor and an amorphous semiconductor of one conductivity type are formed by subjecting an amorphous semiconductor formed in this order to heat treatment on a substrate having an uneven surface. A photovoltaic device comprising a polycrystalline semiconductor film of one conductivity type.