JPH0590159A - Production of polycrystalline semiconductor film - Google Patents

Abstract

PURPOSE:To obtain a polycrystalline silicon semiconductor film having uniform crystalline grains by periodically providing recesses on a board, securing fine powder of silicon to the recesses, forming amorphous silicon thereon and heating to crystallize it. CONSTITUTION:A glass board 1 is first coated with resist 2 to form a predetermined pattern. The board 1 is etched, and the resist is further removed to form recesses. The recesses are provided like crosses of a 'go' board (or a checkerboard) in a matrix state of a predetermined interval. Then, fine powder of silicon having substantially the same size as the recesses is dissolved in organic solvent, the board 1 is coated with the solution, and the solvent is evaporated by heat to secure the powder to the recesses. Here, an amorphous silicon semiconductor film is formed on the board. Thus, a polycrystalline silicon semiconductor film having uniform crystalline grains can be obtained.

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 having a uniform crystal grain size, which is produced in a controlled crystal grain size. It can be used for a semiconductor device such as a conversion device and a thin film transistor.

[0002]

[Prior Art]

Conventionally, as a method of producing a polycrystalline semiconductor film, for example, in the case of silicon, a method of obtaining a bulk polycrystalline silicon semiconductor by liquid phase growth from a molten silicon core using polycrystalline silicon, A method for obtaining a polycrystalline silicon semiconductor by solid-phase growth by heating an amorphous silicon semiconductor film formed by a vapor phase chemical reaction method or the like, and further an amorphous silicon semiconductor formed on a glass substrate or the like. A method of obtaining a polycrystalline silicon semiconductor film by performing laser irradiation on the film is known.

In particular, a method of forming an amorphous semiconductor film on a glass substrate or the like by a vapor phase chemical reaction method and crystallizing the amorphous semiconductor film by heating (called a solid phase growth method) is In view of low cost and large area, application to solar cells, TFTs (thin film transistors), etc. has been vigorously studied.

[0005]

However, the polycrystalline silicon semiconductor film obtained by the conventional solid phase growth has a problem that it is difficult to control the number of nuclei generated and the crystal grain size. In particular, the presence of defects and the presence of impurities due to the nonuniform particle size have been problems.

[0006]

According to the present invention, in order to control the number of crystal nuclei generated and the crystal grain size, a fine silicon powder is provided on a substrate provided with recesses having substantially the same size as the fine silicon powder. A step of applying the above, a step of sintering the fine powder of silicon applied on the substrate, a step of forming an amorphous silicon semiconductor film after the step, and a heating after the step. And a step of crystallizing the amorphous silicon semiconductor film.

In the above structure of the present invention, as the substrate, a glass substrate, a monocrystalline or polycrystalline silicon wafer, and an insulating or semiconductor substrate can be used.

Providing a recess having substantially the same size as the fine silicon powder on the substrate means that the size of the recessed portion of the recess is approximately matched with the size of the fine silicon powder (diameter of the fine powder). Is.

An object of the present invention is to form a polycrystalline silicon film by growing crystal grains of silicon using fine powder of silicon as a crystal nucleus. Therefore, in the structure of the present invention, fine silicon powder serving as crystal nuclei is fixed on the substrate, and then an amorphous silicon semiconductor film is formed by a vapor phase chemical reaction method or the like, and the amorphous silicon semiconductor film is formed at about 550 to 800 degrees. It is crystallized by heating at temperature.

The size of the crystal grain size to be produced can be controlled by controlling the size and interval of the recesses provided on the substrate and the size of the fine silicon powder. In this case, of course, it is important to use fine silicon powder having crystallinity (preferably single crystal). This is because crystals grow using this fine powder as crystal nuclei.

The grain size of the crystal in this specification indicates the size of the crystal seen from the upper surface direction of the substrate. It is known that the thin film-like polycrystalline silicon semiconductor film formed on the substrate as in the structure of the present invention grows in a column shape,
In this specification, the portion corresponding to the diameter of the column of the columnar crystal is defined as the grain size. The size of the fine powder of silicon is defined as the diameter of the fine powder.

Specifically, as a method of controlling the crystal grain size, the size of the concave portion provided on the surface of the substrate is changed to obtain crystal grains according to the size. In this case, of course, the condition is that the size of the recess that becomes the crystal nucleus is smaller than the size of the recess. Further, the size of the crystal grain size can be changed by changing the size of the fine powder of silicon that becomes the crystal nuclei.

In addition, there are cases where fine silicon powders serving as crystal nuclei are bonded to each other to form a polycrystalline silicon semiconductor film. In this case, the size of the fine powders and the size of the crystal grain size are almost the same. Of course, since the crystal grows in a granular form, it is still the case that the fine powder of silicon grows as a crystal nucleus.

Obtaining a polycrystalline silicon semiconductor film in a state where crystal grains are uniform is important for a solar cell which requires uniform film quality over a large area. By arranging crystals of large grain size, a polycrystalline silicon semiconductor film having the best electric characteristics can be obtained. This is because there are lattice defects and impurities that adversely affect the electrical characteristics of the semiconductor at the grain boundaries of the crystal, that is, the boundaries between the crystal grains, and they are homogeneous to minimize the effects of these lattice defects and impurities. This is because the ratio of the area of this grain boundary can be minimized by arranging the crystals of large grain size.

[0015]

[Embodiment 1] In this embodiment, as shown in FIG. 1, recesses provided at intervals of 10 .mu.m.
The convex portions having a width of 10 μm and provided at intervals of μm are provided on the substrate. It can also be said that unevenness is provided on the substrate at intervals of 10 μm. The manufacturing process will be described below.

In this example, a Corning 7059 glass substrate (hereinafter referred to as a glass substrate) was used as the substrate.

First, a resist 2 (which may be a positive type or a negative type) is applied on the glass substrate 1 and a known photolithography process is performed to form a pattern as shown in FIG. 1 on the glass substrate. Then, the glass substrate 1 is removed by chemically etching it.
1 μm to 2 μm In this embodiment, etching is performed to a depth of about 0.3 μm. Then, the resist is removed to form a recess.

FIG. 1 shows a cross-sectional view of the substrate viewed from the cross-sectional direction, but the cross-sectional view viewed from a direction different from this cross-section by 90 ° is also the same as FIG. In other words, this concave portion is provided like a grid pattern.
The recesses are provided in a matrix at intervals of 0 mμ.

The depth formed in the above process is about 0.3 μm.
On a glass substrate having m recesses, fine powder of silicon having a size of about 10 μm was dissolved in an organic solvent and applied. And 3
The fine powder of silicon was fixed (fixed) on the glass substrate by blowing off the organic solvent at 00 ° C. for 1 hour. In this way, the fine silicon powder could be placed in the recesses provided on the glass substrate.

Next, an amorphous silicon semiconductor film having a thickness of 10 μm was formed on the glass substrate, in which fine silicon powder was placed in the recesses in the above step, by the plasma vapor phase reaction method. The film forming conditions are atmosphere SiH ₄ (flow rate 10 to 100 sccm) substrate temperature 100 to 400 degrees, film forming pressure 0.01 to 1.00 Torr high frequency power (13.56 MHz) 10 to 80 W.

The amorphous silicon semiconductor film formed by the above process was heated at a temperature of 600 ° C. for 24 hours to cause solid phase growth of crystals to form a polycrystalline silicon semiconductor film on a glass substrate. This solid-phase growth, that is, the heating process for crystallizing amorphous silicon can be performed in the temperature range of 550 to 800 ° C., and the heating time is 2 hours to 96 hours depending on the film forming conditions such as film thickness. It is possible within a time range.

When the polycrystalline silicon semiconductor film produced in this example was observed by a cross-sectional SEM photograph, the grain size of the crystal was about 10 μm, and a polycrystalline silicon semiconductor film with uniform crystal grains could be obtained. It was

[Embodiment 2] In this embodiment, the same crystal growth method as in Embodiment 1 is used, and the PI is applied from the substrate side.
A photoelectric conversion device having an N structure, that is, a solar cell is manufactured.

In this embodiment, an amorphous semiconductor serving as a back electrode is prepared by adding an impurity imparting N-type conductivity to a Corning 7059 glass substrate at a high concentration, and a non-type semiconductor having N-type conductivity is formed thereon. A single crystal semiconductor film, an i-type intrinsic or substantially intrinsic (meaning that no impurities are artificially added) amorphous silicon semiconductor film, and an amorphous semiconductor film having a p-type conductivity type Are laminated and heated at a temperature of 600 ° C. for 24 hours to be polycrystallized.

When crystal nuclei are grown from the glass substrate surface as in the structure of the present invention, the crystals grow in a columnar shape as described above. Therefore, as described above, semiconductor layers having a conductivity type different from NIP are laminated. Also, the entire layer can be crystallized. That is, the crystal generated from the fine powder of silicon as crystal nuclei at the interface between the substrate and the N layer grows in columnar shape continuously with the I layer and the P layer.

The back electrode and NIP in this embodiment will be described below.
The manufacturing conditions of the amorphous silicon semiconductor of each layer are shown below. The conditions for forming the N ⁺ layer to be the electrode are as follows: atmosphere SiH ₄ (flow rate 50 sccm) (P
H ₃ 1000 ppm added) substrate temperature 100 to 400 degrees deposition pressure 0.01~1.00Torr frequency power 10~80W (13.56MHz), was deposited to a thickness of 7000 Å.

The N layer is formed under the following conditions: atmosphere SiH ₄ (50 sccm) (PH ₃
Addition of 10 ppm) Substrate temperature 100 to 400 degrees Film forming pressure 0.01 to 1.00 Torr High frequency power 10 to 80 W (13.56 MHz), and a film having a thickness of 500 Å was formed.

The film forming conditions for the I layer are as follows: atmosphere SiH ₄ (10 to 100 sccm) substrate temperature 100 to 400 ° C. film forming pressure 0.01 to 1.00 Torr high frequency power 10 to 80 W (13.56 MHz) at 10 μm. The film was formed to a thickness.

The P layer is formed under the following conditions: atmosphere SiH ₄ (50 sccm) (B ₂ H
₆ 10 ppm added) Substrate temperature 100 to 400 degrees Film forming pressure 0.01 to 1.00 Torr High frequency power 10 to 80 W (13.56 MHz), and film was formed to a thickness of 500 Å.

After that, crystallization was performed by heating in an N ₂ atmosphere at a temperature of 600 ° C. for 24 hours. The heating for this crystallization can be carried out at a temperature of 450 to 800 degrees, preferably 550 to 700 degrees.

By adopting the structure as in this example, a solar cell using a polycrystalline semiconductor film having a uniform crystal grain size could be obtained.

[0032]

According to the structure of the present invention, concave portions are periodically provided in the substrate, fine silicon powder is fixed to the concave portions, and amorphous silicon is deposited on the fine particles and crystallized by heating. A polycrystalline silicon semiconductor film having a uniform crystal grain size could be obtained. The polycrystalline silicon semiconductor film obtained by adopting the structure of the present invention is a semiconductor layer of a solar cell, a channel forming region of a thin film transistor, a source and a drain region,
It can be applied to other semiconductor devices.

In the above description, silicon has been described as an example, but a semiconductor other than silicon can be used. The method for depositing the amorphous semiconductor is not limited to the plasma CVD method, and other CVD method, sputtering method, or the like may be used.

[Brief description of drawings]

FIG. 1 shows a substrate processing step in a first embodiment using the configuration of the present invention.

[Explanation of symbols]

 1 glass substrate 2 resist

Claims (1)

[Claims] 1. A step of coating fine silicon powder on a substrate and then sintering, a step of forming an amorphous semiconductor film after the step, and a step of forming the amorphous semiconductor film after the step. And a step of heating for polycrystallization, wherein a recess having a size substantially the same as that of the fine powder of silicon is formed in the substrate. And a method for manufacturing a polycrystalline semiconductor film.