JP2000012465A - Formation of silicon film and manufacture of solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a silicon film and a solar battery which are excellent in characteristics by arranging a silicon film formation body so that its film formation surface is in opposition to a gas blow out opening whose size is the same as an area of a film formation surface of a silicon film formation body or exceeding it. SOLUTION: A bottom part and a ceiling part inside a film formation chamber 1 are provided with a lower heater 2 and an upper heater 3, respectively and a container 4 for storing liquid raw material A is installed on the lower heater 2. An opening area of an upper opening 4a of the container 4 is sized equivalent to or larger than an area of a film formation surface of a glass substrate B. A gas blow out opening is composed of the upper opening 4a. The glass substrate B which is subjected to face-down bonding to the upper heater 3 is mounted along a parallel direction to an opening surface of the upper opening 4a of the container 4 arranged therebelow, and the glass substrate B is thereby arranged in opposition to the container 4 and is covered with the upper opening 4a of the container 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention mainly relates to an LSI,
The present invention relates to a method for forming a silicon film used as a thin film transistor, a solar cell, and a photoconductor, and a method for manufacturing a solar cell.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a polycrystalline silicon film or an amorphous silicon film, SiH ₄ or Si ₂ H _{6 is used.}
CVD (Chemical Vapor) using silane gas such as
Deposition), plasma CVD, photo-CVD and the like are used. That is, these deposition methods are methods in which a silane gas is decomposed by thermal energy, electric energy, or light energy such that silane gas as a source gas is decomposed to form a silicon deposition film on a silicon film formation object. In general, thermal CV is used for polycrystalline silicon film.
For the D method and the amorphous silicon film, the plasma CVD method is widely used and commercialized.

However, these methods have the following disadvantages. That is, in the plasma CVD method, it is difficult to control the plasma, and there are problems in physical properties of the amorphous silicon film such as deterioration of film quality due to collision of charged particles, deterioration of interface state in a device, and the like.
A complicated and expensive device such as a high-frequency generator has been required.

In the light CVD method, since light from a light source is introduced through a transmission window, a part of silicon generated by photolysis adheres to the inside of the transmission window and absorbs irradiation light, and as a result, reacts with the reaction gas. Irradiating light intensity was significantly reduced.

In the thermal CVD method, when an amorphous silicon film is formed, if monosilane (SiH ₄ ) is used as a raw material gas, the substrate temperature needs to be raised to a high temperature of 600 to 650 ° C., and structural defects in the film are reduced. The amount of bonded hydrogen to be compensated was extremely small, and the characteristics of the film were not good.

As a first method capable of solving these disadvantages, there is a thermal CVD method using a high-order silane gas. As this method, conventionally, a high-order silane gas is thermally decomposed at a pressure higher than the atmospheric pressure. Method (for example, Japanese Patent Publication No. 4-620)
No. 73), a method of thermally decomposing a cyclic silane gas (for example, Japanese Patent Publication No. 5-469), a method of using a branched silane gas (for example, Japanese Patent Application Laid-Open No. 60-26665), and a method of using a higher-order silane gas of trisilane or higher. Heat C below 480 ° C
A method of performing VD (for example, Japanese Patent Publication No. 5-56852) has been proposed.

As a second method capable of solving such a problem, conventionally, a liquid compound to be a silicon film is applied on a silicon film forming body and thermally decomposed, instead of a gas phase reaction. A method of forming a silicon film has been proposed (for example, Japanese Patent Application Laid-Open Nos. 7-267621 and 9-2
No. 37927).

[0008]

However, the first method (the thermal CVD method using higher order silane) is particularly difficult because the source gas is introduced from outside the chamber via a blowing nozzle. There is a problem that a uniform silicon film having a uniform thickness cannot be obtained on an area substrate.

In the second method (a method of forming a silicon film by thermal decomposition of a coated liquid compound), a considerable amount of the liquid compound evaporates in a process until a silicon film is formed. There has been a problem that the utilization efficiency of the silicon film raw material is poor, and the production cost is accordingly reduced. Further, when the liquid compound is applied in a state of being dissolved in a solvent, there is a problem that the silicon film is contaminated by impurities other than the doping agent contained in the solvent.

Therefore, an object of the present invention is to solve these problems and to produce a silicon film and a solar cell having excellent characteristics at a low cost.

[0011]

The present invention achieves the above-mentioned object by the following means.

According to the first aspect of the invention, the silicon film-forming body has its film-forming surface facing a gas outlet having a size equal to or larger than the area of the film-forming surface of the silicon film-forming body. Arranging, and blowing a gas mainly composed of higher order silane from the gas outlet toward the film forming surface, and decomposing the blown gas on the film forming surface to form a silicon film. It has the feature of being included, and thereby has the following operation.
That is, the gas is decomposed in a state where the gas is uniformly and uniformly sprayed on the film forming surface, and the thickness of the formed silicon film becomes uniform regardless of the size of the film forming area.

According to a second aspect of the present invention, there is provided the method of forming a silicon film according to the first aspect, wherein the gas has a general formula of Si _n H _{2n + 2} or Si _n H _2n (n is an integer of 3 ≦ n ≦ 7). It is characterized in that it is a vapor of a higher order silane represented by the following formula, and has the following effects. That is, since impurities are hardly contained in the gas, contamination of the silicon film by these impurities hardly occurs.

According to a third aspect of the present invention, after a liquid material mainly composed of higher order silane is applied to the film forming surface of the first silicon film forming body, the second silicon film forming body is coated with a second raw material. Arranging the silicon film forming bodies with their film forming surfaces opposed to each other, and forming a silicon film on the first silicon film forming body by a decomposition reaction of the liquid raw material, and a liquid generated by the decomposition reaction Forming a silicon film by decomposing the vaporized material as a raw material on the film forming surface of the second silicon film forming body, thereby having the following effects. In other words, the decomposition of the applied liquid material and the decomposition of the vaporized liquid material generated with the liquid material allow a silicon film to be simultaneously formed on the first and second silicon film formation bodies.

According to a fourth aspect of the present invention, in the method of forming a silicon film according to the third aspect, the liquid raw material is a compound represented by the general formula: Si _n H
_{2n + 2} or Si _n H _2n (n is an integer of 3 ≦ n ≦ 7), and is characterized in that it is a liquid of a higher order silane.
This has the following effect. That is, since almost no impurities are contained in the liquid material, contamination of the silicon film by these impurities hardly occurs.

According to a fifth aspect of the present invention, in the method of forming a silicon film according to any one of the first to fourth aspects, an additive for giving a desired conductivity type to the high order silane is added to a vaporized atmosphere of the liquid material. This has the following effects. That is, a desired conductivity type can be imparted to the formed silicon film.

According to a sixth aspect of the present invention, at least one of the semiconductor layers constituting the solar cell is formed by the method of forming a silicon film according to any one of the first to fifth aspects. Has the following effects.
That is, the above-described functions of claims 1 to 5 can be exerted at the time of manufacturing the solar cell.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

The high order silane which is a main component of the liquid material in the present invention is represented by the general formula Si _n H _{2n + 2} or Si _n H _2n (n is 3
.Ltoreq.n.ltoreq.7), and these higher silanes are made into a liquid state and contained in a liquid raw material. As an example of such a higher silane, trisilane [Si ₃ H
₈ ], tetrasilane [Si ₄ H ₁₀ ], pentasilane [Si ₅
H ₁₂ ], hexasilane [Si ₆ H ₁₄ ], heptasilane [S
i ₇ H ₁₆ ], cyclotrisilane [Si ₃ H ₆ ], cyclotetrasilane [Si ₄ H ₈ ], cyclopentasilane [Si
₅ H ₁₀ ], cyclohexasilane [Si ₆ H ₁₂ ], cycloheptasilane [Si ₇ H ₁₄ ] and the like, and isomers thereof. In addition, the higher silane referred to in the present invention includes the above compounds themselves as well as various mixtures thereof.

Examples of the material for the substrate as the silicon film forming body and the material introduction container include semiconductor materials such as silicon, and materials such as glass, metal, ceramics, and heat-resistant polymers.

The method of forming a silicon film according to the present invention is as follows.

First Method The first method includes the following steps.

In the first step, first, a container having an opening (which serves as a gas blowing port) having an opening area (corresponding to a sprayed area of the vaporized material) equal to or larger than the area of the substrate surface is prepared. This container is placed in the film forming chamber.
Then, the substrate, which is the silicon film forming body, is carried into the film forming chamber, and the substrate is arranged such that the film forming surface faces the opening of the container.

In the second step, the substrate is heated to a temperature (for example, 350 ° C.) suitable for performing the thermal CVD, and the temperature of the liquid source is raised to the boiling point of the higher order silane.
Then, the higher-order silane component is vaporized from the liquid raw material by the temperature raising process of the liquid raw material, and the vaporized substance is blown out from the opening of the container and sprayed on the substrate. At this time, the substrate is heated CV
D is heated to a temperature suitable for performing D (for example, 350 ° C.). Therefore, silicon is deposited by a thermal CVD method using a vapor as a raw material, and a silicon film is formed on the film forming surface of the substrate.

According to this method, the substrate is arranged so that the film-forming surface thereof faces the opening of the container whose opening area is equal to or larger than the area of the substrate surface.
Since the vapor is sprayed evenly on the substrate along the direction substantially perpendicular to the film forming surface of the substrate, the thickness of the silicon film becomes uniform.

Second Method As described in the first method, after a higher silane component is vaporized by raising the temperature of a liquid raw material to a temperature higher than its boiling point, a silicon film is formed on a substrate by a thermal CVD method. However, it is also possible to form a silicon film by applying a liquid source to a substrate and then subjecting the substrate to a temperature raising process to cause a decomposition reaction of higher silane in the applied liquid source to form a silicon film.

Therefore, in the second method, a silicon film is formed on a plurality of substrates at once by including the following steps.

In the first step, the above-described first substrate is formed on the film formation surface of one of the pair of substrates (the first substrate) having the same size, the first substrate and the second substrate. After applying the same liquid material as in the above method, these substrates are housed in a film forming chamber with their film forming surfaces facing each other.

In the second step, the first substrate is heated to a temperature higher than the temperature at which the applied liquid raw material is thermally decomposed, and the second substrate is heated to a temperature (for example, 350 ° C.) suitable for performing thermal CVD. Heat. Thus, the higher order silane in the applied liquid raw material is decomposed, and a silicon film is formed on the first substrate by the decomposed higher order silane.

On the other hand, when the high order silane is decomposed, the high order silane which is vaporized is sprayed on the second substrate which is arranged opposite to the high order silane. Since the second substrate is heated to a temperature (for example, 350 ° C.) suitable for performing thermal CVD, silicon deposition by the thermal CVD method using the sprayed vapor as a raw material is performed on the second substrate. As a result, a silicon film is formed.

According to this method, a silicon film can be formed on the first and second substrates at a time, so that the throughput is increased and the utilization efficiency of the liquid material is also increased. On the second substrate side on which a silicon film is formed by thermal CVD using a vaporized substance, the vaporized substance is sprayed while the entire surface on which the film is formed is covered with the first substrate. As a result, the same effect as in the first method, in which the spraying of the vaporized material becomes uniform and the thickness of the silicon film formed by thermal CVD becomes uniform, can be achieved.

The shape (thickness, etc.) of the silicon film formed on the first substrate (liquid material coated substrate) and the shape (thickness, etc.) of the silicon film formed on the second substrate are different from each other. In order to equalize, the application amount of the liquid raw material, the separation distance of the substrate,
The parameters such as the temperature increase temperature, the temperature increase time, and the pressure of the atmosphere gas may be appropriately controlled, and such control is related to the volume and shape of the film forming chamber. Therefore, it is only necessary to perform various experiments in advance for each film forming chamber and set the above-described parameters to achieve a desired film thickness.

As a method for applying the liquid material,
Although there are a spin coating method, a dip coating method, a spray coating method, a bar coating method, a curtain coating method and the like, there is no particular limitation.

In the first and second methods described above,
As liquid material, the general formula Si _n H _{2n + 2} or Si _n H _{2n (n}
If the liquid itself of the higher order silane represented by 3 ≦ n ≦ 7 (including a mixture of isomers and different higher order silanes) is used, no impurities are contained in the liquid raw material, Contamination of the silicon film by these impurities hardly occurs.

In the case where a conductivity type is imparted to the silicon film formed by the first and second methods described above, the following method may be used. That is, when imparting a p-type conductivity type,
Boron [B], Aluminum [Al], Gallium [G
a], indium [In], and thallium [Tl] may be added to the film-forming atmosphere. When an n-type conductivity type is to be provided, a compound containing a Group 5 atom of the periodic table, such as phosphorus [P], arsenic [As], antimony [Sb], bismuth [Bi], is added to the film forming atmosphere. What is necessary is just to add.

Specific examples of these compounds are as follows. That is, substances containing atoms of Group 3 of the periodic table include diborane [B ₂ H ₆ ] and tetraborane [B ₄
H ₁₀ ], pentaborane [B ₅ H ₉ ], hexaborane [B ₆
H ₁₀ ], decaborane [B ₁₀ H ₁₄ ], trimethylboron [B (CH ₃ ) ₃ ], triethylboron [B (C
₂ H _{5) 3],} triphenyl boron _{[B (C 6 H 5)} 3] , and the like. Examples of the substance containing an atom belonging to Group 5 of the periodic table include phosphine [PH ₃ ] and diphosphine [P ₂
H _4], trimethylphosphine _{[P (CH 3) 3]} , triethyl phosphine _{[P (C 2 H 5)} 3], triphenylphosphine _{[P (C 6 H 5)} 3], arsine [AsH _3], trimethyl arsine [As (CH ₃ ) ₃ ], triethylarsine [As (C ₂ H ₅ ) ₃ ], triphenylarsine [As
(C ₆ H ₅ ) ₃ ], stibine [SbH ₃ ], trimethylstibine [Sb (CH ₃ ) ₃ ], triethylstibine [Sb (C
₂ H ₅ ) ₃ ], triphenylstibine [Sb (C ₆ H ₅ ) ₃ ]
And the like.

Although the amount of the compound serving as a dopant source to the semiconductor material depends on the required impurity concentration of the semiconductor thin film to be formed, generally, the number of impurity atoms relative to the total number of silicon atoms in the liquid material is reduced. The amount which becomes about 0.1 to 10% is preferable.

Next, an example of a method for manufacturing a solar cell using the method for forming a silicon film of the present invention will be described.

The outline of the production method is as follows. That is, a silicon film containing Group 3 atoms of the periodic table formed by the above-described first or second method is used as a p-layer, and a silicon film containing Group 5 atoms of the periodic table formed by the same method is used. n
A silicon film formed in the same manner as described above from a high-order silane containing no impurities as an i-layer is laminated on a substrate provided with electrodes (electrodes are not required when the substrate is conductive). Make electrodes.

The details of the production method are as follows. That is, to manufacture an amorphous silicon solar cell on a glass substrate, first, a transparent conductive film such as SnO ₂ is formed on the glass substrate. Then, a liquid material mainly composed of higher order silane to which an additive containing an atom belonging to Group 3 of the periodic table, such as boron, is applied onto the transparent electrode film. Further, the applied liquid raw material is subjected to a decomposition reaction by subjecting the glass substrate to heat treatment or the like, whereby a p-type a-Si layer (atom belonging to Group 3 of the periodic table) is formed on the transparent electrode film. (A silicon film doped with an impurity composed of).

Next, a liquid material mainly composed of higher silane to which no impurities are added is prepared, and this liquid material is
Apply on the mold a-Si layer. Further, by applying a treatment such as a heat treatment to the glass substrate, the applied liquid raw material undergoes a decomposition reaction to form an i-type a-Si layer on the p-type a-Si layer.

Further, a liquid material mainly composed of higher silane to which an additive containing an atom belonging to Group 5 of the periodic table, such as phosphorus, is prepared, and this liquid material is i-type a-Si.
Apply on layer. Then, the applied liquid raw material is subjected to a decomposition reaction by subjecting the glass substrate to heat treatment or the like, whereby an n-type a-Si layer (atom belonging to Group 5 of the periodic table) is formed on the i-type a-Si layer. (A silicon film doped with an impurity composed of).

Next, a back electrode made of silver (Ag) or the like is n-type a-
An amorphous silicon solar cell is completed by forming it on the Si layer.

In the case of manufacturing a crystalline solar cell, a liquid material mainly composed of higher silane to which an additive containing an atom belonging to Group 5 of the periodic table such as phosphorus is added is prepared.
This liquid material is applied on the surface of the p-type crystal Si substrate. Then, the applied liquid raw material is subjected to a decomposition reaction by subjecting the p-type crystal Si substrate to a treatment such as a heat treatment, thereby forming an n-type poly-Si layer (fifth element in the periodic table 5) on the p-type crystal Si substrate. (A silicon film doped with an impurity composed of group atoms).

Next, Ti / Pd / Ag is formed on the n-type poly-Si layer.
By forming an Al electrode on the back surface of the p-type crystal Si substrate while forming the electrode, a crystalline solar cell is completed.

[0046] Example Next, an example of the present invention. In each of the examples described below, about 25% of tetrasilane was used as the liquid material.
wt.%, pentasilane about 40 wt.%, hexasilane about 20
A liquid material A composed of a mixture containing wt.% and about 15 wt.% heptasilane was used, and a silicon film was formed on a glass substrate using the liquid material A.

Example 1 In this example, an apparatus 100 shown in FIG. 1 was used as an experimental apparatus. This apparatus 100 has a film forming chamber 1. A lower heater 2 and an upper heater 3 are provided at the bottom and the ceiling in the film forming chamber 1, respectively. The heaters 2 and 3 have a planar shape and are arranged to face each other. A container 4 for storing the liquid raw material A is mounted on the lower heater 2. The container 4 has a shallow wide-mouthed shape with an open upper end, and is made of, for example, quartz. The opening area of the upper opening 4a of the container 4 is set to be equal to or larger than the area of the film forming surface of the glass substrate B. In the first embodiment, the upper opening 4a
Constitutes a gas outlet.

A mounting surface 3a is formed on the bottom surface of the upper heater 3, and a glass substrate B is mounted on the mounting surface 3a. Therefore, the glass substrate B surface-mounted on the upper heater 3 is mounted along a direction parallel to the opening surface of the upper opening 4a of the container 4 disposed below the glass substrate B. The container 4 is disposed so as to be opposed to the container 4 and is covered by the upper opening 4 a of the container 4.

A liquid material supply line 5 is introduced into the film forming chamber 1. The liquid raw material supply line 5 has an outer end connected to the liquid raw material supply source 6, while an inner end facing the upper opening 4 a of the container 4, and the liquid raw material A stored in the liquid raw material supply source 6. The liquid is supplied to the container 4 through the liquid material supply line 5.

An atmosphere gas supply line 8 is introduced into the film forming chamber 1, and an atmosphere gas (here, helium gas) is supplied from the atmosphere gas supply source 9 to the film formation chamber 1 through the atmosphere gas supply line 8. It is supposed to be.

An exhaust line 11 communicates with the film forming chamber 1, and the film forming chamber 1 is evacuated and evacuated by operating a vacuum evacuation device 12 through the vacuum evacuation line 11. .

Hereinafter, a process for forming an amorphous silicon film on a glass substrate B using the apparatus 100 will be described. First, a glass substrate B (here, a glass substrate having a size of 20 cm × 20 cm, which is an example of a large substrate) is surface-mounted on the upper heater 3, and then the film forming chamber 1 is sealed. 1 is evacuated to 10 ⁻⁷ torr by the evacuation device 12. After exhausting under reduced pressure, an atmosphere gas is supplied from the atmosphere gas supply source 9 into the film forming chamber 1 and the internal pressure in the film forming chamber 1 is reduced to 10 kP.
Introduce until a. Next, the liquid raw material A is supplied from the liquid raw material supply source 6 to the container 4 in the film forming chamber 1. Liquid raw material A
Is supplied until the container 4 is almost completely filled.

In this state, the upper heater 3 is operated to heat the glass substrate B to 350 ° C., which is a temperature suitable for thermal CVD, and the temperature is maintained. Simultaneously with or after the heating of the glass substrate B, the lower heater 2 is operated to raise the temperature of the liquid raw material A in the container 4 to 200 ° C., which is a temperature higher than its boiling point, and maintain the liquid temperature. . Then, the liquid temperature raw material A is vaporized, and the vaporized substance is transferred to the upper opening 4.
The liquid is sprayed onto the glass substrate B disposed above the container 4 via a. At this time, since the glass substrate B is maintained at a temperature (350 ° C.) suitable for depositing amorphous silicon by the thermal CVD method by the upper heater 3, the vaporized substance to be sprayed is heated by the thermal CVD. Is deposited on the surface of the substrate as an amorphous silicon film. The thickness of the amorphous silicon film can be controlled, for example, by adjusting the deposition time. Here, the deposition time was set until the average thickness of the amorphous silicon film reached 1.22 μm.

When the change in thickness of the amorphous silicon film (average film thickness: 1.22 μm) formed on the glass substrate B in the plane was measured, the maximum film thickness was 1.32.
μm, the minimum film thickness is 1.14 μm, and the standard deviation is 0.0
It was confirmed that the amorphous silicon film had a uniform film thickness of 6.

[Comparative Example] As a comparative example of Example 1, the following manufacturing method was performed. That is, in this comparative example, an apparatus 200 shown in FIG. 2 was used as an experimental apparatus. The apparatus 200 includes a film forming chamber 1, an upper heater 3 for mounting a glass substrate B, a liquid source supply line 5, a liquid source supply source 6, an atmosphere gas introduction line 8, an atmosphere gas supply source 9, and an exhaust gas. Line 11 and decompression exhaust device 12
Is similar to the apparatus 100 used in the first embodiment, but differs in the following points. That is, the apparatus 200 includes the raw material vaporizing section 13 and the vaporized substance ejecting section 14. The raw material vaporizing section 13 is provided outside the film forming chamber 1, and vaporizes the liquid raw material A supplied from the liquid raw material supply source 6 by heating the vaporized liquid raw material A, and supplies the vaporized material to the vaporizing section ejection section 14. are doing. The vapor discharge section 14 is provided in the film forming chamber 1 and is arranged to face the upper heater 3. The vaporized material ejecting section 14 supplies the vaporized material to the upper heater 3.
It has a spout 14a spouting toward the side. A plurality of spouts 14a are provided.

Hereinafter, a process of forming an amorphous silicon film on a glass substrate B using the apparatus 200 will be described. First, a glass substrate B (here, a glass substrate having a size of 20 cm × 20 cm similar to that in Example 1) was surface-mounted on the upper heater 3, and then the film forming chamber 1 was sealed. 1 is evacuated to 10 ⁻⁷ torr by the evacuation device 12. After exhausting under reduced pressure, an atmosphere gas is supplied from the atmosphere gas supply source 9 into the film forming chamber 1 and the internal pressure in the film forming chamber 1 is reduced to 10 kPa
Introduce until it becomes.

In this state, the upper heater 3 is operated to heat the glass substrate B to 350 ° C., which is a temperature suitable for thermal CVD, and the temperature is maintained. Simultaneously with or after the heating of the glass substrate B, the liquid raw material A is supplied from the liquid raw material supply source 6 to the raw material vaporizing section 13, where the liquid raw material A is vaporized.
a, and is sprayed onto the glass substrate B disposed above the vaporized material ejection section 14. At this time, since the glass substrate B is maintained at a temperature (350 ° C.) suitable for the deposition of amorphous silicon by the thermal CVD method by the upper heater 3, the vaporized substance to be sprayed is exposed to the surface of the glass substrate B by the thermal CVD. Is deposited as an amorphous silicon film. The thickness of the amorphous silicon film can be controlled, for example, by adjusting the deposition time. Here, the deposition time was set until the thickness of the silicon film became 1.30 μm on average.

When the in-plane change in the thickness of the amorphous silicon film (average film thickness: 1.30 μm) thus formed on the glass substrate B was measured, the maximum film thickness was 1.47.
μm, the minimum film thickness is 1.16 μm, and the standard deviation is 0.1 μm.
It was 10.

As is apparent from this comparative example, in Example 1, the standard deviation of the film thickness was 0.06, and the film thickness was uniform as compared with the comparative example having a standard deviation of 0.10. That was confirmed. This seems to be due to the following reasons. That is, in the first embodiment, the upper opening 4a
That is, the vaporized material is sprayed from the upper opening 4a of the container 4 having a size equal to or greater than the area of the film forming surface of the glass substrate B toward the glass substrate B, Vapors are uniformly and uniformly deposited on the glass substrate. On the other hand, in the comparative example, since the vaporized material is sprayed toward the glass substrate B from the plurality of ejection ports 14a, the spraying is slightly non-uniform on the glass substrate B. It seems that the film thickness is not uniform.

Example 2 In this example, an apparatus 300 shown in FIG. 3 was used as an experimental apparatus. This device 300
Has a film forming chamber 20 and a coating chamber 21 arranged in parallel with each other. The film forming chamber 20 and the coating chamber 21 are partitioned by a gate valve 22 so as to be openable and closable. A lower heater 23 and an upper heater 24 are provided at the bottom and the ceiling in the film forming chamber 20, respectively. These heaters 23, 2
Numerals 4 are planar and arranged to face each other. The upper heater 24 is provided with a driving device 24b for adjusting the distance between the upper heater 24 and the lower heater 23.

Mounting surfaces 23a and 24a are formed on the facing surfaces of the heaters 23 and 24, respectively. Glass substrates B1 and B2 are mounted on the mounting surfaces 23a and 24a, respectively. I have. Therefore, heater 2
The glass substrates B1 and B2, which are respectively provided on the substrates 3 and 24, are arranged to face each other in a direction parallel to each other.

The coating chamber 21 accommodates a coating device (such as a spin coater) 25. Further, a liquid material supply line 26 is introduced into the coating chamber 21. The liquid source supply line 26 has an outer end connected to the liquid source supply source 27 and an inner end connected to the substrate mounting surface 25 a of the coating apparatus 25.
And the liquid raw material A stored in the liquid raw material supply source 6 is dropped on the substrate mounting surface 25a of the coating apparatus 25 via the liquid raw material supply line 5. .

The film forming chamber 20 has an atmosphere gas introduction line 2
The atmosphere gas supply line 29 supplies an atmosphere gas (here, helium gas) from the atmosphere gas supply source 29 to the film forming chamber 20.

Exhaust lines 30A and 30B communicate with the film forming chamber 20 and the coating chamber 21, respectively. The film forming chamber 20 and the coating chamber 21 are connected to the vacuum evacuation unit 31 through the vacuum evacuation lines 30A and 30B. The evacuation is performed by the operation.

Hereinafter, a process of forming an amorphous silicon film on a glass substrate B using the apparatus 300 will be described. First, the first glass substrate B1 (here, 20 cm, which is an example of a large substrate) is placed on the substrate mounting surface 25a of the coating device 25.
A glass substrate having a size of × 20 cm) and a second glass substrate B2 (having the same size as the first glass substrate B1) on the mounting surface 24a of the upper heater 24. After wearing, the film forming chamber 20 and the coating chamber 21 are sealed (the gate valve 22 is kept open).
Evacuate to 0 ^-7 torr. After evacuation and evacuation, the film forming chamber 2
0 and an atmosphere gas are introduced from the atmosphere gas supply source 29 into the coating chamber 21 until the room pressure becomes 10 kPa. Next, the liquid raw material A is dropped from the liquid raw material supply line 26 onto the first glass substrate B1 on the substrate mounting surface 25a, and the liquid raw material A is uniformly coated on the entire surface of the first glass substrate B1 by the coating device 25. .

In this state, the upper heater 24 is operated to heat the second glass substrate B2 to 350 ° C., which is a temperature suitable for depositing amorphous silicon by the thermal CVD method, and the temperature is maintained. Then, the first glass substrate B1 (with the liquid raw material A applied) is removed from the coating device 25, transported to the film forming chamber 20, placed on the placement surface 23a of the lower heater 23, and the gate valve 22 is closed. I do. At this time, the upper heater 24 is driven by the driving device 24b so that the first glass substrate B1 can be mounted on the lower heater 23.
To the standby position. After the first glass substrate B1 is mounted on the lower heater 23, the upper heater 24 is again lowered by the driving device 24b to the position where the two glass substrates B1 and B2 are in the normal film forming position.

After the first glass substrate B1 is carried into the film forming chamber 20 and the gate valve 22 is closed, the lower heater 2 is operated to raise the first glass substrate B1 at a rate of 200 ° C./min. At 350 ° C. to maintain the substrate temperature. Then, the liquid material (higher order silane) applied to the first glass substrate B1 is decomposed, and an amorphous silicon film is formed on the first glass substrate B1 by the decomposed higher order silane. On the other hand, when the high order silane is decomposed, the high order silane which is vaporized is sprayed on the second glass substrate B2 disposed opposite to the high order silane. The second glass substrate B2 has a temperature (for example, 3 ° C.) suitable for forming an amorphous silicon film by thermal CVD.
(50 ° C.), the second glass substrate B2
In this case, amorphous silicon is deposited by a thermal CVD method using the sprayed vapor as a raw material, and an amorphous silicon film is formed.

The thickness of the amorphous silicon film can be controlled, for example, by adjusting the deposition time. here,
The deposition time was set until the thickness of the amorphous silicon film on the side of the first glass substrate B1 became 0.30 μm on average.

Thus, the first and second glass substrates B
When the thickness of the amorphous silicon film formed on the first and second glass substrates B2 was measured, the average thickness of the amorphous silicon film on the first glass substrate B1 side was 0.30 μm.
The average thickness of the amorphous silicon film on the side of the second glass substrate B3 was 0.32 μm, and it was confirmed that both amorphous silicon films had substantially the same thickness.

In this embodiment, an amorphous silicon film can be formed on the first and second glass substrates B1 and B2 at once, so that the throughput is increased and the utilization efficiency of the liquid raw material is also increased. In addition, heat C using vaporized material
VD forming an amorphous silicon film
On the glass substrate B2 side, the vaporized material is sprayed while the entire surface on which the film is formed is covered with the first glass substrate B1. As a result, the spraying of the vaporized material becomes uniform, so that the film thickness of the amorphous silicon film formed by thermal CVD is also made uniform.

Example 3 In this example, an amorphous silicon film was formed on a glass substrate B in the same manner as in Example 1 by using the apparatus 100 shown in FIG. 1 as an experimental apparatus. The difference from the first embodiment is that a mixed gas of phosphine (which will be a doping reagent) and hydrogen is stored in an atmosphere gas supply source 9 and this mixed gas is supplied through an atmosphere gas introduction line 8 to a film forming chamber. 1 and a film was formed in the atmosphere of the mixed gas.

With the above manufacturing method, the glass substrate B
It was confirmed that an n-type doped amorphous silicon film having an average film thickness of 1.20 μm was formed thereon.

Example 4 In this example, an amorphous silicon film was formed on a glass substrate B in the same manner as in Example 1 by using the apparatus 100 shown in FIG. 1 as an experimental apparatus. The difference from the first embodiment is that a mixed gas of diborane (to be a doping reagent) and hydrogen is stored in an atmosphere gas supply source 9, and this mixed gas is supplied through an atmosphere gas introduction line 8 to a film forming chamber. 1 and a film was formed in the atmosphere of the mixed gas.

With the above-described manufacturing method, the glass substrate B
It was confirmed that an amorphous silicon film doped with p-type and having an average film thickness of 1.25 μm was formed thereon.

Example 5 In this example, an amorphous silicon film was formed on a glass substrate B in the same manner as in Example 2 using the apparatus 300 shown in FIG. 3 as an experimental apparatus. The difference from the third embodiment is that a mixed gas of diborane (to be a doping reagent) and hydrogen is stored in an atmosphere gas supply source 29, and this mixed gas is supplied to the film forming chamber through an atmosphere gas introduction line 28. 20 and coating chamber 21
To form a film in the atmosphere of the mixed gas.

According to such a manufacturing method, the first and second glass substrates B1 and B2 each have an average film thickness of 0.3.
It was confirmed that p-type doped amorphous silicon films of 0 μm (on the first glass substrate B1 side) and 0.32 μm (on the second glass substrate B2 side) were formed.

[Embodiment 6] In this embodiment, the apparatus 100 shown in FIG.
The solar cell shown in FIG. 4 was produced by sequentially carrying out the same method as in 3 and 4. Here, a glass substrate B3 on which a transparent electrode film (SnO ₂ ) 40 was previously formed was used as the silicon film forming body.

First, by performing the same method as that of the fourth embodiment on the glass substrate B3, a 20 nm-thick p-type amorphous silicon film (P-type -Si layer) 41 is formed. Next, by performing the same method as that of the first embodiment on the glass substrate B3, the i-type amorphous silicon film (i
A mold a-Si layer) 42 is formed. Next, the glass substrate B3
By performing the same method as in Example 3 for
On the i-type amorphous silicon film 42, an n-type amorphous silicon film (n-type a-Si layer) 43 having a thickness of 20 nm is formed. After the n-type amorphous silicon film 43 is formed, the glass substrate B3 is taken out of the apparatus 100, and a back electrode 44 made of silver is formed on the n-type amorphous silicon film 43 by a resistance heating vacuum evaporation apparatus (not shown). By doing so, an amorphous silicon solar cell is completed.

As a result of examining the characteristics of this solar cell, it was confirmed that the conversion efficiency was 6.5%, and characteristics comparable to those of a conventional amorphous silicon solar cell could be obtained.

In the above-described Embodiment 6, the present invention was implemented in a solar cell. However, the present invention can be implemented not only in a solar cell but also in other photoelectric conversion devices. Needless to say, the present invention can be similarly applied to electronic devices such as LSIs and thin film transistors.

In each of the embodiments described above, the present invention has been described by exemplifying a method of forming an amorphous silicon film as a silicon film. However, the present invention is not limited to this. It goes without saying that the same method can be applied to the method of forming a silicon film.

In the first embodiment described above, as an example of the gas outlet, the upper opening 4a of the wide-mouthed container 4 having a shallow depth with an open upper end is used as the gas outlet. It is needless to say that the material is not limited to such a material, and may be any material having a size equal to or greater than the area of the film forming surface of the silicon film forming body. Absent.

[0083]

As described above, according to the present invention, the following effects can be obtained.

According to the first aspect, the vaporized material can be uniformly and uniformly sprayed on the film forming surface. Therefore, the thickness of the silicon film to be formed is made uniform irrespective of the size of the film area to be formed, whereby the yield rate of the large silicon film-formed body is improved, and the cost can be reduced accordingly. Was.

According to the second aspect, since almost no impurities are contained in the liquid raw material, contamination of the silicon film by these impurities hardly occurs, and the electrical characteristics of the silicon film are improved accordingly.

According to the third aspect, the decomposition of the applied liquid raw material and the accompanying vaporization of the liquid raw material enable the simultaneous formation of the silicon film on the first and second silicon film forming bodies. As a result, the throughput at the time of production is increased, the utilization efficiency of the liquid raw material is improved, and the cost is reduced.

According to the fourth aspect, since almost no impurities are contained in the liquid material, contamination of the silicon film by these impurities hardly occurs, and the electrical characteristics of the silicon film are improved accordingly.

According to the present invention, a desired conductivity type can be imparted to a silicon film to be formed, and various electronic components (solar cells) requiring a silicon film having a conductivity type can be provided. The invention can be put into practice.

According to the sixth aspect, the functions and effects of the first to fifth aspects described above can be exerted at the time of manufacturing the solar cell, so that the electric characteristics of the solar cell can be improved and the cost can be reduced. become.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of an apparatus used in Example 1 of the present invention.

FIG. 2 is a sectional view showing a structure of an apparatus used in a comparative example of the present invention.

FIG. 3 is a cross-sectional view illustrating a structure of an apparatus used in Example 2 of the present invention.

FIG. 4 is a cross-sectional view showing a structure of a solar cell embodying the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Film-forming chamber 2 Lower heater 3 Upper heater 4 Container 4a Upper opening 20 Film-forming chamber 21 Coating chamber 23 Lower heater 24 Upper heater 25 Coating device 40 Transparent electrode film 41 p-type amorphous silicon film 42 i-type amorphous silicon film 43 n-type Amorphous silicon film A Liquid raw material B Glass substrate B1 First glass substrate B2 Second
Glass substrate

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masafumi Shimizu 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F-term (reference) 4G072 AA01 AA02 BB09 BB13 FF01 FF02 FF04 FF07 GG03 HH03 JJ25 JJ44 LL11 LL13 MM01 NN21 RR01 UU02 4K030 AA05 BA29 BA30 BA55 BA56 BB05 CA01 CA05 CA06 CA07 CA17 HA15 KA23 KA25 LA16 5F045 AA06 AB03 AB04 AC01 AC19 AD07 AE23 AF03 AF07 AF10 BB02 BB08 BB14 CA13 DA52 CA05 A05 CA05 A05

Claims (6)

[Claims] 1. A step of arranging a silicon film formation object with its film formation surface facing a gas outlet having a size equal to or larger than the area of the film formation surface of the silicon film formation object. Spraying a gas containing high order silane as a main component from the gas outlet toward the film forming surface, and decomposing the sprayed gas on the film forming surface to form a silicon film. A method for forming a silicon film. 2. The method for forming a silicon film according to claim 1, wherein the gas is a general formula of Si _n H _{2n + 2} or Si _n H _2n (n is 3
≦ n ≦ 7 (an integer of 7). 3. A liquid material mainly composed of higher silane is applied to a film formation surface of a first silicon film formation object, and then a second silicon film is applied to the first silicon film formation object. Arranging the film-forming bodies with their film-forming surfaces facing each other; forming a silicon film on the first silicon film-forming body by the decomposition reaction of the liquid raw material, Forming a silicon film by decomposing the vaporized material on the film formation surface of the second silicon film formation object. A method for forming a silicon film. 4. The method for forming a silicon film according to claim 3, wherein the liquid source is a general formula of Si _n H _{2n + 2} or Si _n H _2n (n
Wherein n is an integer of 3 ≦ n ≦ 7). 5. The method for forming a silicon film according to claim 1, wherein an additive that gives a desired conductivity type to said higher order silane is added to a film forming atmosphere. A method for forming a silicon film. 6. Each of the semiconductor layers constituting the solar cell,
A method for manufacturing a solar cell, wherein at least one layer is formed by the method for forming a silicon film according to claim 1.