JPH01231315A - Device for manufacturing crystal semiconductor thin-film - Google Patents

Abstract

PURPOSE:To form a thin-film as a material for a solar cell of a high conversion-efficiency at a film formation rate higher than that of a plasma CVD method, by spraying an amorphous semiconductor particulate generated by a chemical reaction against a substrate, on which the film is shaped, on a belt, which is penetrated through a circumferential wall and moved, in a reaction chamber with an exhaust port, depositing the particulate and irradiating the substrate on the belt with laser beams. CONSTITUTION:A torch 2 is projected into a reaction chamber 1, and there is an endless belt 3 penetrated through a wall from the outside of the reaction chamber by two driving rolls 4, moved from the left to the right in the reaction chamber and projected outside the reaction chamber again in the lower section of the torch 2. A raw material gas composed of a monosilane derivative is introduced from an introducing pipe 61 and an addition gas for combustion from an introducing pipe 62 to the torch 2, and blown out of the torch 2. Amorphous silicon particulates are formed by a chemical reaction by these gases while a particulate flow 8 is sprayed against a substrate 7, on which a film is shaped, positioned on the belt 3 by gas pressure, and an amorphous silicon particulate layer is deposited on the substrate 7. When the particulate silicon layer is irradiated with layer beams 5, amorphous silicon is crystallized, and the crystal silicon thin-film is formed onto the substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for manufacturing a crystalline semiconductor thin film used as a photoelectric conversion layer of a solar cell, for example.

[Conventional technology]

Conventionally, low-cost solar cells have used amorphous silicon thin films that can be easily formed using a plasma CVD apparatus that utilizes glow discharge plasma. Amorphous silicon thin film is
In an evacuated reaction chamber, a high-frequency electric field is applied between a substrate mounting support with a built-in heater and a counter electrode to decompose the raw material gas mainly consisting of monosilane into a plasma state. A film is formed on a substrate heated to 300°C.

[Problem to be solved by the invention]

However, the rate of formation of an amorphous silicon thin film in the above apparatus is only a few people per second, and the throughput cannot be easily increased, and the basic vacuum level of the reaction chamber is about 10-'Torr. Because of this requirement, it is necessary to provide a vacuum evacuation system, and the equipment cost of the device also increases, so there is a problem that it is difficult to expect much reduction in the manufacturing cost of amorphous solar cells.

On the other hand, solar cells using amorphous silicon have a drawback of lower conversion efficiency than solar cells using single crystal or polycrystalline silicon.

However, ribbon crystals, film crystals, and other methods have been developed as methods for forming thin crystals in order to lower the material cost of single-crystal silicon, but it is difficult to achieve large-area applications, and polycrystalline silicon thin films cannot be obtained at low manufacturing costs. do not have.

The problem of the present invention is to utilize the above-mentioned drawbacks to improve plasma CV
The object of the present invention is to provide an apparatus capable of producing a crystalline semiconductor thin film, which is expected to be used as a material for high conversion efficiency solar cells, at a film formation rate higher than that of the D method.

[Means to solve the problem]

In order to solve the above problems, the apparatus of the present invention includes a belt that is movable through a peripheral wall of a reaction chamber having an exhaust port, and an amorphous crystal produced by a chemical reaction toward a substrate on which a film is formed on the belt. The system is equipped with a reaction torch that sprays fine semiconductor particles and a laser oscillator that irradiates a laser beam onto the substrate on the belt on which the fine particles are deposited.

[Effect]

The deposition rate of amorphous semiconductor particles caused by chemical reactions is much higher than the deposition rate by plasma CVD method.
When the substrate advances with the belt and enters the laser beam irradiation area, the amorphous particles instantaneously crystallize, resulting in a high sloop7)
A semiconductor crystal thin film can be continuously formed using this method.

〔Example〕

FIG. 1 shows an embodiment of the invention, in which a torch 2 projects into a reaction chamber l. Below the torch 2, there is an endless belt 3 that is moved by two drive rolls 4 from outside the reaction chamber through the wall, moves from left to right in the figure within the reaction chamber, and exits again to the outside of the reaction chamber. The laser beam 5 is placed on the belt 3 from below the torch 2 in the traveling direction, that is, on the right side in the figure.
A laser oscillator 51. outside the reaction chamber is used to irradiate the laser oscillator 51. An entrance window 52 in the reaction chamber wall and a mirror 53 inside the reaction chamber are provided. A raw material gas consisting of monosilane (SiH4) or a monosilane derivative such as 5IC71 is introduced into the torch 2 through an inlet pipe 61, and an additional gas for combustion such as C7□ or H2 is introduced through an inlet pipe 62 and blown out from the torch 2. These gases generate amorphous silicon fine particles of one order of magnitude through a chemical reaction, and the gas pressure blows a fine particle stream 8 toward the substrate 7 placed on the belt 3 to form particles on the substrate 7. A layer of amorphous silicon particles is deposited on the wafer. Since unreacted gas is exhausted from the exhaust port 9 by gas pressure, a vacuum exhaust system is not required. CO! When irradiated with a laser beam 5 such as a laser or NdjYAG laser, the amorphous silicon is crystallized at a temperature of about 1000° C., and crystalline silicon yIW 14 is formed on the base Fi, 7. 5IHa as raw material gas
0~11005cc, additional gas, ;t, (Jl 200~
600SCCM 'a I
j x = Si + 2 When the chemical reaction of HC7 is caused, the deposition rate of amorphous silicon particles is 0.1 per minute.
~5-, which is about 100 times faster than conventional plasma CVD.Normally, in order to obtain a film thickness of 5000 mm, the belt movement speed is about 20 1/min. The laser beam 5 is irradiated in a pulsed manner in a direction perpendicular to the moving direction of the belt 3. It was more effective to irradiate with a beam diameter of 0.1 Tsuru and slightly defocused. 'BzHb in raw material gas
or B Cf 3, or PH3 or P(J,
It goes without saying that a p- or n-type semiconductor thin film can be formed by mixing doping gases such as
A pn junction type solar cell can be formed by using a glass plate as a substrate, depositing a Sn0g film as a transparent electrode in advance, and then sequentially stacking a p-type film and an n-type film. Furthermore, by changing the source gas and additional gas, crystal thin films of elemental semiconductors or compound semiconductors other than silicon can also be formed. Further, it is also possible to make the belt serve as a substrate by using an end belt. Although it is possible to heat the substrate at a thermal temperature outside the reaction chamber without laser irradiation to turn the amorphous fine particle layer into a crystalline thin film, the throughput becomes low and this is not practical.

[Effects of the Invention] According to the present invention, semiconductor fine particles produced by a chemical reaction are supported on a belt from a torch, are blown toward a substrate and deposited, are moved by the belt, and are made into a crystalline thin film by irradiation with a laser beam. Since a crystalline semiconductor thin film can be obtained at a higher deposition rate than an amorphous semiconductor thin film using a plasma CVD apparatus, it can be applied to the production of low-cost solar cells with high conversion efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention. 1: reaction chamber, 2: torch, 3: belt, 5: laser beam, 51
: laser oscillator, 61; source gas introduction pipe, 62: additional gas introduction pipe, 7: film-forming substrate, 8: amorphous Si fine particle flow,
92 exhaust port. Figure 1

Claims (1)

[Claims] (1) A belt that is movable through the peripheral wall of the reaction chamber having an exhaust port, a reaction torch that sprays amorphous semiconductor particles generated by a chemical reaction toward the substrate on which the film is to be formed, and A crystalline semiconductor thin film manufacturing apparatus characterized by comprising a laser oscillator that irradiates a laser beam onto a deposited substrate on a belt.