JPH07263340A - Manufacture of polycrystalline semiconductor film - Google Patents

Abstract

PURPOSE:To provide a polycrystalline semiconductor film manufacturing method in which a polycrystalline semiconductor film composed of large crystal grains is formed by heat-treating amorphous semiconductor films in a short heat- treating time. CONSTITUTION:A polycrystalline semiconductor film is obtained by heat-treating an amorphous semiconductor film 2 doped with a conductivity type determining impurity at a specific concentration and an intrinsic amorphous semiconductor film 3 while the films 2 and 3 are brought into contact with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polycrystalline semiconductor film used as a semiconductor layer in a switching element such as a thin film transistor, a photoelectric conversion layer in a photovoltaic device such as an optical sensor or a solar cell, and the like. It is a thing.

[0002]

2. Description of the Related Art As a method of manufacturing this polycrystalline semiconductor film, L
Performing heater heating or heat treatment with laser light on a semiconductor once formed in an amorphous state by a so-called direct formation method in which a polycrystalline semiconductor film is directly formed by a PCVD method or an APCVD method, or a plasma CVD method. The so-called recrystallization method is generally used in which the polycrystal semiconductor film is obtained by recrystallizing the polycrystal semiconductor.

The recrystallization method is characterized in that a polycrystalline semiconductor film can be formed at a relatively low temperature as compared with the direct formation method, and in particular, it is used for polycrystallizing an amorphous silicon film doped with phosphorus. 600 ℃ when used as starting material
A polycrystalline semiconductor film composed of large crystal grains has been obtained even in the following low temperature region (JP-A-2-94625).

As another method for producing a polycrystalline semiconductor film by this recrystallization method, an amorphous semiconductor containing phosphorus and an intrinsic amorphous semiconductor are heat-treated in contact with each other, and It has been confirmed that a polycrystalline semiconductor film having large crystal grains at a low temperature can be obtained (JP-A-4-8).
8642).

The lowering of the heat treatment temperature required for such recrystallization due to phosphorus causes the amorphous semiconductor containing phosphorus to function as a nucleus for polycrystallization. This is because polycrystallization proceeds at a relatively low temperature.
As a result, a polycrystalline semiconductor film having large crystal grains can be obtained.

[0006]

However, in these recrystallization methods, a polycrystalline semiconductor film composed of large crystal grains can be obtained at a relatively low temperature as compared with other forming methods.
Considering the device characteristics using this, it is not possible to obtain sufficient characteristics. Furthermore, in order for polycrystallization to proceed sufficiently in the manufacturing process, heat treatment must be performed for an extremely long time such as 10 hours to 100 hours, resulting in a problem of extremely poor productivity.

The present invention provides a method for manufacturing a polycrystalline semiconductor film, which can shorten the time required for heat treatment and can make the crystal grains contained in the film very large. It is in.

[0008]

A feature of the method for producing a polycrystalline semiconductor film of the present invention is that an amorphous semiconductor film doped with a predetermined amount of a conductivity type determining impurity and a semiconductor film are in contact with each other. A method of manufacturing a polycrystalline semiconductor film, which polycrystallizes these semiconductor films by applying heat treatment,
The predetermined amount is characterized in that it is set to such an amount that polycrystallization from the amorphous semiconductor film can rapidly proceed,
In addition, a predetermined amount of the amorphous semiconductor film doped at a concentration of 1 × 10 ²⁰ cm ⁻³ or more and an intrinsic amorphous semiconductor film may be polycrystallized by heat treatment in a contact state. Furthermore, the conductivity determining impurity is 1 × 10 ²⁰ cm
^A heat treatment in contact with an amorphous semiconductor film doped at a concentration of ^-3 or more and an amorphous semiconductor film having a conductivity lower than the concentration and having the same conductivity type or a different conductivity type as the conductivity type. It is to polycrystallize by applying.

Furthermore, a polycrystalline semiconductor film is used as a semiconductor in contact with the amorphous semiconductor film doped with the predetermined amount.

[0010]

According to the manufacturing method of the present invention, an amorphous semiconductor film containing a conductivity determining impurity having a concentration of 1 × 10 ²⁰ cm ⁻³ or more,
Since the intrinsic amorphous semiconductor film is polycrystallized by heat treatment in a contact state, or an amorphous semiconductor film doped with a conductivity type determining impurity at a concentration of 1 × 10 ²⁰ cm ⁻³ or more. , A concentration lower than the above-mentioned concentration, and an amorphous semiconductor film of the same conductivity type or different conductivity type as the conductivity type is polycrystallized by heat treatment in a contact state. Compared with the recrystallization method by
A polycrystalline semiconductor film composed of crystal grains having an extremely large grain size can be obtained.

Furthermore, according to the manufacturing method of the present invention, the time required for recrystallization can be shortened.

[0012]

FIG. 1 is an element structure diagram for each step for explaining a first embodiment of a method for producing a polycrystalline semiconductor film according to the present invention. In the first step shown in FIG. An amorphous semiconductor film (2) containing a conductivity-determining impurity is formed on a substrate (1) which is made of an insulating material or made of a metal such as tungsten, titanium or stainless. In this embodiment, the amorphous semiconductor film (2) is formed by plasma CVD.
An amorphous silicon film formed by the method is used, and phosphorus is contained as the conductivity type determining impurity.

The starting material for recrystallization in the present invention is not limited to the amorphous silicon film, and amorphous germanium, amorphous silicon germanium, etc. may be used, and the formation method thereof is the vapor deposition method, Either a sputtering method or ion plating may be used.

In addition to phosphorus, the conductivity type determining impurity may be a dopant such as boron, antimony, aluminum, gallium, indium, or arsenic.

Table 1 shows the conditions for forming the amorphous silicon film used in the examples.

[0016]

[Table 1]

Next, in the second step shown in FIG. 3B, the intrinsic amorphous semiconductor film (3), specifically, the amorphous semiconductor film (3), which is a starting material, is formed on the surface of the amorphous semiconductor film (2). An intrinsic amorphous silicon film is formed in a film thickness range of 100Å to 100 μm to make a contact state between the amorphous semiconductor (2) and the amorphous semiconductor (3).

In this embodiment, an intrinsic amorphous semiconductor film is used.
(3) was laminated on the amorphous semiconductor film (2), but instead of this, from the concentration of the amorphous semiconductor film (2) which is the same conductivity type as the conductivity determining impurity and is the starting material Alternatively, a low concentration doped amorphous semiconductor film may be stacked. Specifically, this low concentration is in the range of 1 × 10 ¹⁹ cm ⁻³ or less, and the reason for using such a low concentration doped amorphous semiconductor film is that it is higher than that. If so, the amorphous semiconductor (3) will start to crystallize earlier than the amorphous semiconductor film (2) as the starting material, and the desired polycrystallization cannot be performed. Is.

Further, an amorphous semiconductor film of a different conductivity type may be used in place of the amorphous semiconductor film of the same conductivity type doped with a low concentration. In such a case, after the heat treatment step described later, the amorphous semiconductor film (2) and the amorphous semiconductor film
In the film of the polycrystalline semiconductor film obtained from the laminate of (3),
It will include a pn junction.

Next, in the third step shown in FIG.
(1) The amorphous semiconductor film (2) and the amorphous semiconductor film (3) formed on the laminated body are heated at 400 to 700 ° C. in vacuum or in an atmosphere of an inert gas such as nitrogen or argon. Heat treatment of.

By performing this heat treatment, the substrate (1)
In the laminated body of the amorphous semiconductor film above, polycrystallization progresses from the amorphous semiconductor film (2) containing the conductivity determining impurity, and thus the amorphous semiconductor film on the semiconductor film (2). Polycrystallization will progress to (3).

In particular, according to the manufacturing method of the present invention, the use of a semiconductor film containing a conductivity-determining impurity in a predetermined concentration or more as a starting material results in a polycrystal having large crystal grains that cannot be obtained by conventional methods. The semiconductor film (4) can be obtained.

Further, in the present invention, the semiconductor film formed on the starting material amorphous semiconductor (2) is not limited to the amorphous semiconductor, and a polycrystalline semiconductor film may be used. In such a case, even when a film with poor film quality is formed by the thermal CVD method, the plasma CVD method, or the vapor deposition method, the amorphous semiconductor film (2) which is the starting material for the base is used. By polycrystallizing, the polycrystalline semiconductor film having the poor film quality can be made a good polycrystalline semiconductor film.

Next, a second embodiment of the present invention is shown in FIG. The figure shows the structure of the laminated body before the heat treatment step of the first embodiment, and the same reference numerals as those in FIG. 1 are given the same reference numerals in the figure. The difference from FIG. 1 of the figure is that the amorphous semiconductor film (2) containing the conductivity determining impurities of a predetermined concentration or more is not formed on the entire surface of the substrate (1) but is formed in an island shape, and is formed next. In addition, the amorphous semiconductor film (3) is formed so as to cover the surface of the amorphous semiconductor film (2) and the exposed surface of the substrate (1).

Even in the case of such a structure, polycrystallization proceeds from the amorphous semiconductor film (2) which is the base as in the first embodiment, and both the amorphous semiconductor film (3) and Polycrystal. That is, the polycrystallization that progresses from the island-shaped amorphous semiconductor film (3) also proceeds across the straits of the islands, and eventually the amorphous semiconductor (3) between the islands. It can be polycrystallized. However, if the strait between the islands is too large, the progress of polycrystallization will be poor, so it is preferable to set it to 100 μm or less at most.

FIG. 3 shows the time required for crystallization of the portion of the amorphous semiconductor film (2) containing the conductivity determining impurities as a function of the concentration of the conductivity determining impurities when the manufacturing method of the present invention is used. It is shown as. According to this, when the concentration of the impurities contained in the amorphous semiconductor film (2) as the starting material is 1 × 10 ²⁰ cm ⁻³ or more, the time required for crystallization is drastically shortened. I understand.

This means that, according to the present invention, the progress of crystallization of the amorphous semiconductor film (2) as a starting material progresses remarkably as compared with the conventional one.
(2) It also promotes the crystallization of the intrinsic or low-concentration doped amorphous semiconductor film (3), which results in crystallization of the laminate. The heat treatment time can also be shortened.

Next, the grain size of the crystal grains of the polycrystalline semiconductor film obtained by the manufacturing method of the present invention and the concentration of the conductivity determining impurities contained in the starting amorphous semiconductor film (2). FIG. 4 is a characteristic diagram showing the relationship with

According to this, the impurity concentration is 1 × 10.
It can be seen that when it is ²⁰ cm ⁻³ or more, the size of the crystal grains contained in the polycrystalline semiconductor film increases dramatically. This means that the number of crystal grains contained in one polycrystalline semiconductor region can be reduced, and consequently the inclusion of grain boundaries that deteriorate the film characteristics can be reduced, and a high-quality polycrystalline semiconductor film can be obtained. Will be obtained.

Next, the case where the polycrystalline semiconductor film obtained by the manufacturing method of the present invention is used as a photoelectric conversion layer of a photovoltaic device will be described.

FIG. 5 is a cross-sectional view of the element structure of the photovoltaic device, and (51) in the figure serves as a supporting substrate of the photovoltaic device and is made of titanium, tungsten, or the like which also functions as an electrode. (52) is a polycrystalline semiconductor film formed on the substrate (51) by the method described above, and the semiconductor film uses phosphorus as the conductivity type determining impurity. On the surface of the polycrystalline semiconductor film (52), a conductivity type determining impurity such as boron is ion-implanted, thermally diffused, or p-type amorphous semiconductor film is formed to form a p-type semiconductor film. The formation of p-type polycrystalline semiconductor film (53).

As a result, at the interface between the polycrystalline semiconductor films (52) and (53), a pn junction is included in the film. Reference numeral (54) is the other electrode formed on the polycrystalline semiconductor film (53), which is an aluminum film or a silver film formed by a vapor deposition method or a plating method.

In particular, in this photovoltaic device, the polycrystalline semiconductor film having large crystal grains obtained by the manufacturing method of the present invention can be used, and the substrate (51) side is doped with the above-mentioned starting material. Since a highly doped polycrystalline semiconductor film based on an amorphous semiconductor is arranged, good contact characteristics can be secured between the polycrystalline semiconductor film and the metal substrate. Become.

In addition, the high-concentration region of this polycrystalline semiconductor has a BSF (Back Surface Field) structure as a solar cell structure.
d) Since it also functions as a semiconductor layer as a structure, it contributes to further improvement of photovoltaic characteristics.

In the present invention, the heat treatment step is
Although the present invention is not limited to this, the present invention is not limited to this. For example, by irradiating the stacked body of the semiconductor films with light energy by a laser in the above-described contact state, a high quality multi-layer structure is obtained. A crystalline semiconductor film can be obtained.

[0036]

According to the manufacturing method of the present invention, an amorphous semiconductor film containing a conductivity type determining impurity of a predetermined concentration and an intrinsic amorphous semiconductor film are heat-treated in a contact state to be polycrystallized. Therefore, the conductivity determining impurity is 1 × 1
An amorphous semiconductor film doped at a concentration of 0 ²⁰ cm ⁻³ or higher, and an amorphous semiconductor film having a concentration lower than the above concentration and having the same conductivity type as the conductivity type or a different conductivity type; Since polycrystallization is performed by performing heat treatment in a contact state, it is possible to obtain a polycrystal semiconductor film composed of crystal grains having an extremely large grain size as compared with the conventional recrystallization method by heat treatment. Become.

Further, a high-quality polycrystalline semiconductor film can be obtained by heat-treating the amorphous semiconductor film, which has been subjected to a predetermined doping, in contact with the polycrystalline semiconductor film.

Furthermore, according to the manufacturing method of the present invention, the time required for recrystallization can be shortened.

[Brief description of drawings]

FIG. 1 is a sectional view of a device structure for each step of a first embodiment for explaining a method for manufacturing a polycrystalline semiconductor film according to the present invention.

FIG. 2 is a sectional view of the element structure for each step of the second embodiment for explaining the method for manufacturing a polycrystalline semiconductor film according to the present invention.

FIG. 3 is a characteristic diagram showing the time required for crystallization with respect to the concentration of conductivity type determining impurities in the method for producing a polycrystalline semiconductor film of the present invention.

FIG. 4 is a characteristic diagram showing the crystal grain size of the obtained polycrystalline semiconductor film with respect to the concentration of the conductivity type determining impurity in the method for producing a polycrystalline semiconductor film of the present invention.

FIG. 5 is an element structure cross-sectional view of a photovoltaic device using a polycrystalline semiconductor film formed by the method for producing a polycrystalline semiconductor film of the present invention as a photoelectric conversion layer.

[Explanation of symbols]

(1) ... Substrate (2) ... Metal or metal salt (3) ... Amorphous silicon film (3) '... Thin film polycrystalline silicon

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[Procedure amendment]

[Submission date] June 15, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

FIG. 5 is a cross-sectional view of the element structure of the photovoltaic device, and (51) in the figure serves as a supporting substrate of the photovoltaic device and is made of titanium, tungsten, or the like which also functions as an electrode. (52) is a polycrystalline semiconductor film formed on the substrate (51) by the method described above, and the semiconductor film uses phosphorus as the conductivity type determining impurity. On the surface of the polycrystalline semiconductor film (52), a conductivity type determining impurity such as boron is ion-implanted, thermally diffused, or p-type amorphous semiconductor film is formed to form a p-type semiconductor film. the formation, p-type semi-conductor film (53) is formed.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

As a result, the polycrystalline semiconductor film (52) and the p-type half
At the interface of the conductor film (53), a pn junction is included in the film. (54) is the other electrode formed on the p-type semiconductor film (53), which is an aluminum film or a silver film formed by a vapor deposition method or a plating method.

Claims (4)

[Claims] 1. A method for producing a polycrystalline semiconductor film, which comprises polycrystallizing an amorphous semiconductor film doped with a predetermined amount of a conductivity determining impurity and a semiconductor film by heat treatment in contact with each other. A method for producing a polycrystalline semiconductor film, wherein the predetermined amount is set to an amount at which polycrystallization from the amorphous semiconductor film rapidly progresses. 2. An amorphous semiconductor film doped with a conductivity-determining impurity at a concentration of 1 × 10 ²⁰ cm ⁻³ or more and an intrinsic amorphous semiconductor film are heat-treated in contact with each other to form a polycrystalline film. A method of manufacturing a polycrystalline semiconductor film, characterized by: 3. An amorphous semiconductor film doped with a conductivity type determining impurity at a concentration of 1 × 10 ²⁰ cm ⁻³ or more, and a conductivity type which is lower than the concentration and is the same conductivity type as or different from the conductivity type. And a type amorphous semiconductor film are subjected to heat treatment in a contact state so as to be polycrystallized. 4. An amorphous semiconductor film doped with a conductivity determining impurity at a concentration of 1 × 10 ²⁰ cm ⁻³ or more and a polycrystalline semiconductor film are polycrystallized by heat treatment in a contact state. A method for manufacturing a polycrystalline semiconductor film, comprising: