JP2000031066A - Method for forming silicon film and manufacture of solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a silicon film on a substrate under the condition where silane is uniformly doped from an inner part to an outer part, by using specified high-order silane formed of a first process to a third process in a liquid form. SOLUTION: A gate bulb 3 is set in an open state and a coating room 1 and a film forming room 2 are vacuum-exhausted. Helium is introduced to the film forming room 2 through a gas supply line 8. High-order silane expressed by SiH2n+2 or SinH2n ((n) is the integer of 3<=n<=7) is dissolved in the additive of phosphine in a first process. Then, high-order silane containing the additive is dropped on a glass substrate 9 on a spin coater 4 through a high-order silane supply line 6, and the whole face of the glass substrate 9 is coated lay silane with the rotation of the spin coater 4 in a second process. The temperature of high-order silane containing additive on the glass substrate 9 is raised to 35 deg.C with the temperature inclination of 100 deg.C, the temperature of the substrate is held for thirty minutes and a silicon film having an n-type conduction type is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a silicon film used for an LSI, a thin film transistor, a photoreceptor, a solar cell and the like, and a method for manufacturing a solar cell.

[0002]

2. Description of the Related Art Conventionally, a polycrystalline silicon film (hereinafter referred to as "poly-
Si film ". ) Or amorphous silicon film (hereinafter referred to as “a-
Si film ". As a method for forming (a), a thermal CVD (Chemical Vapor Deposition) method using a silane gas, a plasma CVD method, an optical CVD method, or the like is used. In general, a thermal CVD method is used for a poly-Si film, and an a- For the Si film, the plasma CVD method is widely used and industrialized.

As a CVD method using a higher silane gas, a method of thermally decomposing a higher silane gas under a pressure higher than the atmospheric pressure (for example, Japanese Patent Publication No. 4-62073), a method of thermally decomposing a cyclic silane gas (for example, , Tokuho 5-469
Japanese Patent Application Laid-Open No. 5-56852), a method using a branched silane gas (for example, Japanese Unexamined Patent Publication No. 60-26665), and a method for performing thermal CVD at a temperature of 480 ° C. or lower with a higher-order silane gas of trisilane or more (for example, Japanese Patent Publication No. 5-56852). Etc. have been proposed.

[0004] However, these CVD methods use aS
It is a manufacturing method suitable for the i-film, and cannot be said to be a manufacturing method sufficiently suitable for the poly-Si film. Furthermore, in these CVD methods, 1. Since a gas phase reaction is used, particles are generated in a gas phase, which causes problems such as contamination of an apparatus and a decrease in the yield of a device.
2. Since the raw material is used in the gaseous state, it is difficult to obtain a film having good step coverage on a substrate having an uneven surface. 3. The film formation speed is low and the throughput is low.
4. An expensive high-vacuum apparatus is required. 5. In particular, the plasma CVD method has a disadvantage that a complicated and expensive apparatus such as a high-frequency generator is required.

Therefore, in order to avoid these problems,
Conventionally, a production method using a higher-order silane in a liquid state instead of a gas phase reaction (for example, JP-A-7-267621)
Has been proposed. The outline of this manufacturing method is as follows.
That is, after applying the higher order silane on the substrate in a liquid state, by raising the temperature of the substrate, the higher order silane is subjected to a decomposition reaction within the coating film through a heat history including a temperature increasing process including a temperature increasing process, Thus, a silicon film is to be formed on a substrate.

[0006]

However, in a method of forming a silicon film in which high order silane is applied on a substrate in a liquid state, it is difficult to manufacture electronic devices such as photoelectric conversion devices such as LSIs, thin film transistors, and solar cells. A poly-Si film having an essential p-type or n-type conductivity,
That is, an impurity-doped poly-Si film could not be formed.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a silicon film suitable for forming an impurity-doped silicon film (poly-Si film, a-Si film). An object of the present invention is to provide a forming method and a method for manufacturing a solar cell.

[0008]

Means for Solving the Problems The present invention comprises the following first to third steps, the general formula Si _n H _{2n + 2} or Si _n H
This is a method for forming a silicon film using a higher order silane represented by _2n (n is an integer of 3 ≦ n ≦ 7) in a liquid state. The first step is a step of adding an additive containing an atom belonging to Group 3 or 5 of the periodic table to the higher order silane to obtain an additive-containing higher order silane. The second step is a step of applying the additive-containing higher silane obtained in the first step on a substrate. Third
The step is a step of forming a silicon film containing an atom belonging to Group 3 or 5 of the periodic table by a decomposition reaction of the additive-containing higher silane applied to the substrate in the second step.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for forming a silicon film according to an embodiment of the present invention will be described. The step of forming the silicon film includes the following first to third steps.

First Step The higher order silane used in the present embodiment has a general formula of Si _n H _{2n + 2}
Alternatively, it is represented by Si _n H _2n (n is an integer of 3 ≦ n ≦ 7). Specifically, trisilane [Si ₃ H ₈ ], tetrasilane [Si ₄ H ₁₀ ], pentasilane [Si ₅ H ₁₂ ], hexasilane [Si ₆ H ₁₄ ], heptasilane [Si ₇ H ₁₆ ],
Cyclotrisilane [Si ₃ H ₆ ], cyclotetrasilane [Si ₄ H ₈ ], cyclopentasilane [Si ₅ H ₁₀ ], cyclohexasilane [Si ₆ H ₁₂ ], cycloheptasilane [S
i ₇ H ₁₄ ] and the isomers thereof. The higher order silane referred to in the present invention includes not only the above-mentioned compound itself, various mixtures thereof, but also, when forming a silicon film from the higher order silane, affecting the physical properties of the silicon film at the time of manufacturing or the silicon film. Includes those dissolved in various solvents without. In addition, when the higher order silane is formed from the compound itself and various mixtures, a step of dissolving the higher order silane in various solvents is not required, and impurities are mixed into the higher order silane from the solvent side. There is an advantage that the possibility of inconvenience can be reduced to zero.

On the other hand, those suitable for the additives to be added to the higher order silane (substances contained in the higher order silane as a source of the dopant source) include boron [B], aluminum [Al], gallium [Ga], Indium [In],
Substances (compounds, etc.) containing Group 3 atoms of the periodic table, such as thallium [Tl], or phosphorus [P], arsenic [A
s], antimony [Sb], bismuth [Bi], and the like (compounds and the like) containing atoms of Group 5 of the periodic table.

Specific examples of these additives 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 ], pentaphorane [B ₅ H ₉ ], hexaborane [B ₆ H ₁₀ ], decaborane [B ₁₀ H ₁₄ ], trimethylboron [B (C
H _{3) 3],} triethyl boron _{[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 ], diphosphine [P ₂ H ₄ ], trimethylphosphine [(CH ₃ ) ₃ P], and triethylphosphine [P (C ₂ H). ₅ ) ₃ ], triphenylphosphine [P
(C ₆ H ₅ ) ₃ ], arsine [AsH ₃ ], trimethylarsine [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.

[0013] Then, after making the above-mentioned high order silane into a liquid state, the above additive is dissolved in advance, or
Alternatively, it is added immediately before coating on the substrate. As a method of adding (mixing) these additives to the liquid higher silane, the following method can be mentioned. That is,
Pressure is applied as the additives are added to the higher order silane.
Further, an additive is added to the higher order silane just before the application of the higher order silane. Alternatively, a solution in which an additive is dissolved in an organic solvent in advance may be prepared, and this solution may be added to the higher order silane immediately before the application of the higher order silane. In addition, the concept of immediately before application here means that, in other words, the liquid higher-order silane to which the additive is added is immediately applied to the substrate without a time interval. , A time interval that does not have much time delay.

By setting the timing of adding the additive to the higher order silane immediately before coating, it becomes possible to dope while maintaining a uniform state with good reproducibility and to adjust the doping amount as necessary. There is an advantage that it becomes possible.

The organic solvents in which the above additives can be dissolved include the following first and second solvents. The first solvent is
C _m H _n (m is an integer of 4 ≦ m ≦ 16, n is 10 ≦ n ≦ 34
), Saturated hydrocarbons, unsaturated hydrocarbons, or aromatics. The second solvent is C _x H _y O
_z (x is 2 ≦ x ≦ 16, y is 6 ≦ y ≦ 34, z is 1 ≦ z
<3) alcohols, ethers, or a mixed solvent thereof. Specific examples of these first and second solvents include butane, pentane, hexane, heptane, benzene, toluene, xylene, ethylbenzene,
Cumene, butylbenzene, styrene, cyclohexane,
Methyl cyclohexane, ethanol, pentanol, butanol, dimethyl ether, methyl ethyl ether,
Examples include diethyl ether, dioxane, trioxane, tetrahydrofuran, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, glycerin ether, and acetal.

Second step Then, the higher order silane to which the above additive is added is applied in a liquid state on the substrate. Examples of the substrate in the present invention include a substrate made of a material such as a semiconductor material such as silicon, glass, metal, ceramics, and a heat-resistant polymer. In addition, as a method of applying the liquid higher silane to the substrate, 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. A spinner having a spinner rotation speed of 100 to 10000 rpm, preferably 300 to 6 rpm, is used for applying a high-order silane to a substrate in a liquid state using a generally used spin coating method.
000 rpm.

Third Step Next, the additive-containing high order silane applied to the substrate is subjected to a decomposition reaction to form a silicon film doped with impurities derived from the additive. The conditions for the decomposition reaction are not particularly limited, and a reaction by heating or a method by irradiation with ultraviolet light, an electron beam, or the like is possible. Preferably, a method by heating is used, and specific examples thereof are described in, for example, JP-A-7-267621. According to these methods, the thickness of the obtained silicon film is 2 nm.
It can be freely selected in the range of about 50 μm.

The above second and third steps (a step of applying the liquid-state higher silane to the substrate and a step of decomposing the higher silane).
When performing the above, the working atmosphere is preferably as follows. That is, in a gaseous atmosphere composed of a gas containing an atom belonging to the same Group 3 or 5 of the periodic table as the additive contained in the higher order silane, or in a gaseous atmosphere composed of a mixed gas of this gas and an inert gas. In the above, it is preferable to perform the above steps.

Such an atmosphere is provided for the following reasons. That is, in the step of applying the additive-containing higher silane in a liquid state, it is inevitable that a part of the additive is released to the outside from the applied higher silane film. Further, in the step of forming a silicon film on a substrate by decomposing the applied higher silane, it is inevitable that a part of the additive is released to the outside of the higher silane film. Therefore, the doping amount finally added to the silicon film decreases due to the release of such an additive. With respect to such a decrease in the additive, it is only necessary to supplement the atoms serving as the dopant source from the outside by the amount of the additive released from the higher order silane. In view of this, in the present invention,
Atmospheric gas is used as a replenishment source for the dopant source,
For this purpose, a substance having the same atom belonging to Group 3 or 5 of the periodic table as the additive mixed with the higher order silane is added to the atmospheric gas. Thereby, the dopant source can be supplemented from the atmospheric gas, and the doping amount in the silicon film does not decrease. However, in order to uniformly dope impurities into the silicon film, it is preferable that the doughant source be covered with an additive that is directly mixed with the higher order silane. Therefore, the concentration of the substance added to the atmosphere gas is preferably Is preferably as small as possible.

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 an atom belonging to Group 3 of the periodic table formed by the method of forming a silicon film according to the above-described embodiment is used as a p-layer,
A silicon film containing an element of Group V of the periodic table formed by the method of the above-described embodiment is defined as an n-layer, and a silicon film formed in the same manner as described above from higher-order silane containing no impurities is defined as an i-layer. It is laminated on a substrate with electrodes (electrodes are unnecessary if the substrate is conductive), and electrodes are formed thereon.

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 higher silane to which an additive containing an atom belonging to Group 3 of the periodic table such as boron is added is prepared, and the higher silane is applied to the transparent electrode film in a liquid state. Further, the applied high order silane is decomposed by subjecting the glass substrate to a treatment such as a heat treatment, whereby a p-type a-Si layer (belonging to Group 3 of the periodic table) is formed on the transparent electrode film. (A silicon film doped with atomic impurities).

Next, a high-order silane to which no impurities are added is prepared, and this high-order silane is converted to a p-type a-Si in a liquid state.
Apply on layer. Further, by applying a treatment such as a heat treatment to the glass substrate, the applied high order silane is decomposed to form an i-type a-Si layer on the p-type a-Si layer.

Further, a high-order silane to which an additive containing an atom belonging to Group 5 of the periodic table such as phosphorus is added is prepared, and the high-order silane is coated in a liquid state on the i-type a-Si layer. I do. Then, the high-order silane applied by subjecting the glass substrate to heat treatment or the like is caused to undergo a decomposition reaction, whereby an n-type a-Si layer (fifth periodic table No. 5) is formed on the i-type a-Si layer.
(A silicon film doped with an impurity consisting of atoms belonging to group III).

Next, an electrode made of silver (Ag) or the like is connected to an n-type a-Si
By forming on the layer, an amorphous silicon solar cell is completed.

In the case of manufacturing a crystalline solar cell, a high-order silane to which an additive containing an atom belonging to Group 5 of the periodic table such as phosphorus is added is prepared, and this high-order silane is prepared in a liquid state. It is applied on the surface of a p-type crystal Si substrate. Then, the applied high-order silane 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 on the p-type crystal Si substrate. (A silicon film doped with an impurity composed of Group V 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.

When fabricating a crystalline / amorphous hybrid solar cell, a higher silane to which an additive containing an atom belonging to Group 5 of the periodic table such as phosphorus is added is prepared, and this higher silane is prepared. It is applied in a liquid state on the surface of the p-type crystal Si substrate. Then, the applied high order silane is subjected to a decomposition reaction by subjecting the p-type crystal Si substrate to a treatment such as a heat treatment, whereby the n-type poly
Forming an Si layer (a silicon film doped with an impurity comprising an atom belonging to Group 5 of the periodic table);

Next, a high-order silane to which an additive containing an atom belonging to Group 3 of the periodic table, such as boron, is prepared, and this high-order silane is placed in a liquid state on the n-type poly-Si layer. Apply. Then, the applied high order silane is decomposed by subjecting the p-type crystal Si substrate to a treatment such as a heat treatment, thereby forming a p-type a-Si layer (periodic rule) on the n-type poly-Si layer. (A silicon film doped with an impurity consisting of atoms belonging to Table 3).

Next, a high-order silane to which no impurities are added is prepared, and this high-order silane is converted to a p-type a-Si in a liquid state.
Apply on layer. Then, by applying a treatment such as heat treatment to the p-type crystal Si substrate, the applied higher order silane is decomposed and reacted, thereby forming an i-type a-Si layer on the p-type a-Si layer. I do.

Further, a higher silane to which an additive containing an atom belonging to Group 5 of the periodic table such as phosphorus is added is prepared, and the higher silane is coated in a liquid state on the i-type a-Si layer. I do. Then, the applied high-order silane is subjected to a decomposition reaction by subjecting the p-type crystal substrate to a treatment such as a heat treatment, whereby the n-type a-Si layer (the fifth element in the periodic table) is formed on the i-type a-Si layer.
(A silicon layer doped with an impurity consisting of atoms belonging to a group).

Next, an electrode of Ag or the like is formed on the n-type a-Si layer, and an Al electrode is formed on the back surface of the p-type crystal Si substrate, thereby completing the crystal / amorphous hybrid solar cell.

[0033] Examples will be specifically described by way of examples the invention.

Example 1 In this example, the apparatus shown in FIG. 1 was used as an experimental apparatus. This apparatus includes a coating chamber 1
And the film forming chamber 2 are arranged in parallel so as to communicate with each other, and a gate valve 3 is provided between the coating chamber 1 and the film forming chamber 2. A spin coater 4 is provided in the coating chamber 1, and a heater 5 is provided in the film forming chamber 2. The coating chamber 1 is connected to a supply line 6 for supplying liquid higher silane to the coating chamber 1 and an exhaust line 7A for exhausting gas in the coating chamber 1. Is a gas supply line 8 for supplying an atmosphere gas to the film forming chamber 2 and an exhaust line 7B for exhausting exhaust gas in the film forming chamber 2.
And are connected.

In the present embodiment, a mixture of 15 wt% of tetrasilane, 50 wt% of pentasilane, 30 wt% of hexasilane, and 5 wt% of heptasilane was used as the higher order silane as the material of the silicon film. Furthermore, 80 mg of phosphine is added as an additive to such a higher silane.
Was added. At the time of addition, the higher order silane 3
After applying a pressure of 5 MPa to 0 cc and sealing the inside of the cylinder under high pressure, phosphine was added to the higher order silane by dissolving the phosphine in the higher order silane in a liquid state, and stored in the cylinder.

Using the high order silane containing the additive as described above, a silicon film was formed by the above-described apparatus in the following procedure.

First, the gate valve 3 is opened,
The coating chamber 1 and the film forming chamber 2 are evacuated to 2 × 10 ⁻⁴ Pa. Then, 30 helium is supplied through the gas supply line 8.
After introducing into the film forming chamber 2 up to kPa, 1.5 cc of high order silane in which an additive (phosphine) is dissolved is dropped in a liquid state through the high order silane supply line 6 onto the glass substrate 9 on the spin coater 4. . Then, the dropped high-order silane in a liquid state is uniformly applied to the entire surface of the glass substrate 9 by rotating the spin coater 4.

Next, by introducing phosphine (gas) into the atmosphere in the coating chamber 1 and the film forming chamber 2 from the gas supply line 8, the inside of the coating chamber 1 and the film forming chamber 2 is pressurized to 150 kPa. Then, in this state, the glass substrate 9 is moved onto the heater 5 and the gate valve 3 is closed. After that, the glass substrate 9 is moved at a temperature gradient of 100 ° C./min.
After the temperature was raised to 0 ° C., a silicon film having an n-type conductivity was formed to a thickness of 220 nm on the glass substrate 9 while maintaining the substrate temperature for 30 minutes. The silicon film thus formed is an amorphous silicon film (a-Si film).

Example 2 In this example, the apparatus shown in FIG. 2 was used as an experimental apparatus. This apparatus basically has the same configuration as that of the first embodiment, and the same or similar parts are denoted by the same reference numerals and description thereof will be omitted. This apparatus is characterized by a supply configuration of the additive-containing high order silane in a liquid state. That is, the apparatus includes a supply line 10 for a high-order silane in a liquid state, a supply line 11 for an additive in a liquid state, and a gas supply line 12.
The three supply lines 10, 11,
12 is merged into one tube, and the merged tube 13 is connected to the coating chamber 1. The joining pipe 13 is connected to the coating chamber 1 by piping downward from above the coating chamber 1, and the middle part thereof is bent twice in an S-shape. Confluence pipe 1
A liquid stirring device (small stirrer) 14 is provided in the lower bent portion 13a of the bent portion 3.

The higher order silanes were the same as in Example 1 (tetrasilane 15 wt%, pentasilane 50 wt%,
A mixture of 30 wt% of hexasilane and 5 wt% of heptasilane) was used. Further, diphosphine was used as an additive.

A silicon film was formed by the above-described apparatus using the high-order silane and the additive having the above-described structure in the following procedure.

First, the gate valve 3 is opened,
The coating chamber 1 and the film forming chamber 2 are evacuated to 2 × 10 ⁻⁴ Pa. Then, after injecting helium gas to 60 kPa into the film forming chamber 2 and the coating chamber 1 through the gas supply line 8,
1.5 cc of high order silane is supplied to the high order silane supply line 10 and 4.0 mg of the additive (diphosphine) is supplied to the additive supply line 11. Both the higher order silane and the diphosphine are supplied in a liquid state, and after the supply, stay at the lower bent portion 13a of the merging pipe 13. Therefore, the liquid high-order silane and the liquid diphosphine which are in a liquid state are sufficiently stirred and mixed by the liquid stirring device 14. After sufficient stirring and mixing of the high order silane and diphosphine, the phosphine gas is supplied to the gas supply line 12 so that the high order silane (containing diphosphine) in the liquid state retained in the lower bent portion 13a is removed. It is extruded into the coating chamber 1 and dropped on the glass substrate 9. Then, the dropped high-order silane in a liquid state is uniformly applied to the entire surface of the glass substrate 9 by rotating the spin coater 4.

Next, a phosphine gas is introduced into the coating chamber 1 and the film forming chamber 2 through the gas supply lines 12 and 8 for 15 minutes.
The glass substrate 9 was heated to 350 ° C. at a temperature gradient of 100 ° C./min while maintaining the pressure at 0 kPa, and then maintained at a substrate temperature for 30 minutes to form a 220 nm-thick silicon film having an n-type conductivity on the glass substrate 9. A film is formed. The silicon film thus formed is an amorphous silicon film (a-
(Si film).

Example 3 A silicon film was formed by using the same high-order silane and additives as in Example 2, and using the same apparatus. However, the heating condition of the glass substrate 9 coated with the liquid higher silane (containing an additive) is different from that of the second embodiment. That is, the temperature of the glass substrate 9 coated with the liquid-state high order silane is raised to 700 ° C. at a temperature gradient of 100 ° C. per minute, and then the substrate temperature is maintained for 10 minutes and the n-type conductive type is placed on the glass substrate 9. Having a thickness of 340
nm of a silicon film was formed. The silicon film thus formed is a polysilicon film (poly-Si film).

Example 4 This example is basically the same as in Example 1, except that diborane was used instead of phosphine as an additive. Then, after applying a pressure of 5 MPa to 30 cc of the liquid higher silane, 250 mg of diborane in a gas state was sealed in a cylinder at a high pressure and stored. And the additive (diborane) as above
Example 1 using a high-order silane in a liquid state containing
A silicon film having a p-type conductivity and a thickness of 220 nm was formed on the glass substrate 9 in the same manner as described above. The silicon film thus formed is an amorphous silicon film (a-Si film).

Example 5 This example is similar to Example 2 except that 20 mg of hexaborane was used instead of diphosphine as an additive and diborane was used instead of phosphine as a substance to be added to the atmosphere. A 210-nm-thick silicon film having a p-type conductivity was formed on the substrate 9. The silicon film thus formed is an amorphous silicon film (a-Si film).

[Embodiment 6] In this embodiment, a silicon film is formed on a glass substrate 9 by the same manufacturing method as in Embodiment 5, but a glass substrate 9 on which high order silane is applied in a liquid state is used.
Are slightly different from those in Example 5. That is, after raising the temperature to 700 ° C. with a temperature gradient of 100 ° C. per minute, and holding the substrate temperature for 10 minutes, a 340 nm-thick silicon film having a p-type conductivity type is formed on the glass substrate 9. did. The silicon film thus formed is a polysilicon film (poly-Si film).

[Example 7] In this example, as an additive,
It is characterized in that an additive dissolved in a solvent in advance is used. The same high-order silane as in Example 2 was used, and the apparatus used in Example 2 was used. Further, a substance containing the same atom as the dopant source contained in the additive is mixed in the atmosphere.
Hereinafter, details of the manufacturing method will be described.

3.5 g of decaborane was previously added to benzene 100c
Dissolve in c and keep the additive solution. And
The gate valve 3 is opened, the coating chamber 1 and the film forming chamber 2 are evacuated to 2 × 10 ⁻⁴ Pa, and helium gas is introduced from the gas supply lines 12 and 8 to 60 kPa, and then prepared in advance. 0.3cc of the above additive solution
Is injected into the additive supply line 11, and 1.5 cc of the high order silane in a liquid state is further injected into the high order silane supply line 10. By sufficiently stirring and mixing the injected additive solution and the liquid-state high-order silane with the liquid stirrer 14 at the lower bent portion 13a of the joining pipe 13, by supplying helium gas to the gas supply line 12, Higher order silane (containing an additive) in a liquid state remaining in the lower bent portion 13 a is extruded into the coating chamber 1 and coated on the glass substrate 9.

Next, the temperature of the coating chamber 1 and the film forming chamber 2 is raised to 90 ° C. while evacuating, thereby removing benzene contained in the additive solution by evaporation. After the benzene is completely removed, diborane gas is introduced into the coating chamber 1 and the film forming chamber 2 from the gas supply lines 12 and 8 up to 150 kPa. Then, the glass substrate 9 is heated at 350 ° C. at a temperature gradient of 100 ° C./min.
Raise the temperature to Further, while maintaining the substrate temperature for 30 minutes, a 230 nm-thick film having a p-type conductivity is formed on the glass substrate 9.
m of silicon film was formed. The silicon film thus formed is an amorphous silicon film (a-Si film)
Becomes

[Embodiment 8] In this embodiment, a silicon film is formed by the same method and apparatus as in Embodiment 1, but is characterized by the structure of the atmosphere in the coating chamber 1 and the film forming chamber 2. is there. That is, in Example 1, a substance containing the same atom as the dopant source (atom) contained in the additive is contained, but in this example, such a substance is not contained in the atmosphere. There is a feature in this point. This will be described below.

With the gate pulse 3 opened, helium gas 6 is supplied from the gas supply line 8 to the coating chamber 1 and the film forming chamber 2.
Introduce up to 0 kPa. Then, the same high order silane as that of Example 1 (containing additives) through the high order silane supply line 6
Is applied on the glass substrate 9 in a liquid state. Further, helium gas is introduced again from the gas supply line 8 to pressurize the inside of the coating chamber 1 and the film forming chamber 2 to 200 kPa. In this atmosphere, the temperature is raised to 350 ° C. at a temperature gradient of 100 ° C./min, and the substrate temperature is maintained for 30 minutes, whereby the glass substrate 9 is heated.
A 210-nm-thick silicon film having an n-type conductivity was formed thereon. The silicon film thus formed is
As in the first embodiment, the amorphous silicon film (a-Si
Film).

Embodiment 9 In this embodiment, an apparatus shown in FIG. 3 was used as an experimental apparatus. This device is basically
A low-pressure mercury lamp 15 for irradiating light having a wavelength of 400 nm or less above the heater 5 is similar to the apparatus shown in FIG.
2 has a feature not found in the apparatus of FIG. A silicon film was formed on the glass substrate 9 under the same conditions as in Example 2 except for the device configuration and the conditions of the higher order silane and the additives.

That is, after the high order silane containing the additive is applied in a liquid state onto the glass substrate 9 by rotating the spin coater 4, the coating chamber 1 and the film forming chamber 2 are supplied through the gas supply lines 12 and 8. While maintaining the pressure at 150 kPa by introducing a phosphine gas into the
The temperature was raised to 350 ° C. with a temperature gradient of ° C., and the substrate temperature was maintained for 30 minutes. In the present embodiment, at the time of such a heat treatment, the glass substrate 9 is irradiated with light having a wavelength of 400 nm or less from the low-pressure mercury lamp 15 to the glass substrate 9 being heated to form a 220 nm-thick silicon film having an n-type conductivity. A film was formed. The silicon film thus formed is an amorphous silicon film (a-Si film).

The above is an embodiment in which a silicon film doped with an impurity is formed on the glass substrate 9. Next, examples of various solar cell manufacturing methods will be described.

Example 10 In this example, the apparatus shown in FIG. 2 was used as an experimental apparatus, and a glass substrate 20 on which a SnO ₂ film (transparent conductive film) was formed was used as a substrate.
An amorphous silicon solar cell was manufactured. As shown in FIG. 4, the amorphous silicon solar cell has a SnO ₂ film 21, a p-type a-Si film 22 and an i-type film 22 on a glass substrate 20.
The n-type a-Si film 23 and the n-type a-Si film 24 are sequentially laminated and formed, and an Ag electrode 25 is formed on the n-type a-Si film 24.

Further, in this embodiment, as the higher order silane,
The same material as in Example 1 (a mixture of 15 wt% of tetrasilane, 50 wt% of pentasilane, 30 wt% of hexasilane, and 5 wt% of heptasilane) was used. Hexaborane as in Example 5 and diphosphine as in Example 2 were used as additives.

First, SnO ₂ of the glass substrate 20 was prepared in the same manner as in Example 5 using hexaborane as an additive.
A p-type a-Si layer 22 is formed on the film 21 to a thickness of 10 nm. Next, the i-type a-type layer is formed on the p-type a-Si layer 22 by a similar method using a liquid-state higher silane containing no additive.
-The Si layer 23 is formed to a thickness of 390 nm. Next, an n-type a-Si layer 24 is formed to a thickness of 35 nm on the i-type a-Si layer 23 in the same manner as in Example 2 using a liquid-state higher silane containing diphosphine. Moreover,
The glass substrate 20 was taken out of the apparatus, and an Ag electrode 25 was formed on the n-type a-Si layer 20 using the inside of a resistance heating vacuum evaporation apparatus to obtain an amorphous silicon solar cell.

[Embodiment 11] In this embodiment, an apparatus shown in FIG. 2 was used as an experimental apparatus, and a p-type crystal S was used as a substrate.
Using the i-substrate, a crystalline / amorphous hybrid solar cell was produced. As shown in FIG. 5, a crystalline / amorphous hybrid solar cell is a p-type crystalline Si substrate 3
0, an n-type poly-Si film 31, a p-type a-Si film 32,
An i-type a-Si film 33 and an n-type a-Si film 34 are sequentially laminated, and the Ag electrode 3 is formed on the n-type a-Si film 34.
5 is provided on the back surface of the p-type crystalline Si substrate 30 with an Al electrode 36.
Are formed respectively.

In this embodiment, the higher order silane is
The same material as in Example 1 (a mixture of 15 wt% of tetrasilane, 50 wt% of pentasilane, 30 wt% of hexasilane, and 5 wt% of heptasilane) was used. Hexaborane as in Example 5 and diphosphine as in Example 2 were used as additives.

First, an n-type poly-Si film 3 is formed on a p-type crystal Si substrate 30 in the same manner as in Example 3 by using the same liquid silane containing diphosphine as in Example 3.
1 is formed to a thickness of 30 μm. Next, a p-type a-Si film is formed on the n-type poly-Si film 31 in the same manner as in Example 6 by using a liquid-state higher silane containing hexaborane.
The film 32 is formed to a thickness of 12 nm. Next, an i-type a-Si film 33 is formed on the p-type a-Si film 32 by a similar method using higher-order silane in a liquid state containing no additive.
The film is formed to a thickness of nm. Next, an n-type a-Si film 34 is formed on the i-type a-Si film 33 by a method similar to that in Example 2 using liquid-state higher silane containing diphosphine.
The film is formed to a thickness of nm. Thereafter, the p-type crystal Si substrate 30
Was taken out of the apparatus, and n was obtained using a resistance heating vacuum evaporation apparatus.
An Ag electrode 35 is formed on the type a-Si film 34, and then the p-type crystal Si substrate 30 is formed using the same resistance heating vacuum deposition apparatus.
An Al electrode 36 was formed on the back surface of the device to obtain a crystalline / amorphous hybrid solar cell.

The physical properties such as photoconductivity (AM 1.5, irradiation of 100 mW / cm ² ), dark conductivity, and optical gap of the films formed in Examples 1 to 9 were measured. Summarized. Further, Table 2 summarizes the IV characteristics of the solar cells manufactured according to Examples 10 and 11.

[0063]

[Table 1]

[0064]

[Table 2]

As is clear from these measurement data,
The silicon film and the solar cell manufactured by the method of the present invention are:
It can be seen that good characteristics are exhibited regardless of whether the film has the a-Si film or the poly-Si film.

Embodiment 1 where there is a difference only in the atmosphere
Comparing Example 8 with Example 8, it can be seen that Example 1 is superior by one digit in the data of photoconductivity and dark conductivity. This is due to the following reasons.

That is, when a part of the additive is released from the coating film to the outside, the amount of doping added to the silicon film is reduced, and the electrical characteristics of the formed silicon film are slightly deteriorated. Occurs. In Example 8,
No measures are taken against such a decrease in the doping amount. On the other hand, in the first embodiment, a countermeasure of adding a substance containing the same atoms as the dopant source to the atmosphere is taken against such a decrease in the dopant source, thereby releasing the dopant from the coating film to the outside. The dopant source to be
Supplement from outside (atmosphere). Therefore, the characteristics of the first embodiment are superior to the characteristics of the eighth embodiment because of such measures.

In Embodiments 10 and 11 described above, the present invention was implemented in various solar cells. However, the present invention can be implemented not only in solar cells but also in other photoelectric conversion devices. It can be implemented similarly,
Needless to say, the present invention can be similarly applied to an electronic device such as an LSI and a thin film transistor.

In each of the above-described embodiments, an atmosphere in which a gas containing the same atoms as the additives is mixed with an inert gas is used. It goes without saying that the present invention can be carried out even in an atmosphere of a substance containing atoms.

[0070]

According to the present invention, a silicon film having characteristics that can be used as a device is not deposited from a gas phase on a substrate heated and held at a constant temperature by a conventional CVD method or the like, but a dopant is used. After applying a high order silane to which a source additive is added in a liquid state on a substrate, the additive-containing high order silane is subjected to a decomposition reaction, and the Si film is uniformly doped from inside and outside to form a Si film on the substrate. Could be fabricated on top. As a result, the cost of the device can be reduced, and the range of application has been widened. Moreover, such an effect is
The same effect can be obtained regardless of whether the film has the a-Si film or the poly-Si film.

Further, by performing such a step in an atmosphere containing a dopant source, it becomes possible to form a doped Si film having further excellent characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view of a silicon film forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a silicon film forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a silicon film forming apparatus according to a ninth embodiment of the present invention.

FIG. 4 is a cross-sectional view of an amorphous silicon solar cell capable of implementing the present invention.

FIG. 5 is a cross-sectional view of a crystalline / amorphous hybrid solar cell capable of implementing the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Coating chamber 2 Film-forming chamber 3 Gate valve 4 Spin coater 5 Heater 6 Higher silane supply line 7A Exhaust line 7B Exhaust line 8 Gas supply line 9 Glass substrate 10 Higher silane supply line 11 Additive supply line 12 Gas supply line DESCRIPTION OF SYMBOLS 13 Confluence pipe 13a Lower bent part 14 Liquid stirring device 15 Low-pressure mercury lamp 20 Glass substrate 21 Sn
O ₂ film 22 p-type a-Si film 23 i
Type a-Si film 24 n-type a-Si film 25 Ag
Electrode 30 p-type crystal Si substrate 31 n
Type poly-Si film 32 p-type a-Si film 33 i
Type a-Si film 34 n-type a-Si film 35 Ag
Electrode 36 Al electrode

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Keiichi Fukuyama 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Akira Sakawaki 5-1 Yawata Kaigan-dori, Ichihara-shi, Chiba Prefecture Showa Denko HD Research and Development Center Co., Ltd. (72) Inventor Kotaro Yano 1-1-1 Onodai, Midori-ku, Chiba City, Chiba Prefecture Showa Denko KK Research Institute (72) Inventor Yutaka Tachibana 1505 Shimokage Mori, Chichibu City, Saitama Prefecture Showa F term in Chichibu Research Laboratory, Electric Works Co., Ltd. (Reference) 4G072 AA01 AA02 BB09 BB12 BB13 FF01 FF02 FF04 FF07 GG03 HH03 JJ25 JJ45 LL11 LL13 MM01 NN21 RR01 UU02 5F045 AB03 AB04 AC01 AC19 AF03 A07 CA03 DA05

Claims (6)

[Claims] 1. A high-order silane represented by the general formula Si _n H _{2n + 2} or Si _n H _2n (n is an integer of 3 ≦ n ≦ 7) comprising the following first to third steps: Method of forming a silicon film used in a state. First step: a step of adding an additive containing an atom belonging to Group 3 or 5 of the periodic table to the higher order silane to obtain an additive-containing higher order silane. Second step A step of applying the additive-containing higher silane obtained in the first step on a substrate. Third Step A step of forming a silicon film containing an atom belonging to Group 3 or 5 of the periodic table by a decomposition reaction of the additive-containing higher silane applied to the substrate in the second step. 2. The method of forming a silicon film according to claim 1, wherein the third step is performed under an atmosphere of a substance containing the same atoms as the additives, or an inert gas. A method of forming a silicon film in an atmosphere of a mixed gas of 3. The method for forming a silicon film according to claim 1, wherein a pressure is applied when the additive is added to the higher order silane in the first step. Forming method. 4. The method for forming a silicon film according to claim 1, wherein the additive is mixed with the higher order silane immediately before the application of the higher order silane in the first step. A method for forming a silicon film. 5. The method for forming a silicon film according to claim 1, wherein in the first step, a solution in which the additive is previously dissolved in an organic solvent is prepared, and then a high-order silane is applied. A method of forming a silicon film, wherein the solution and the higher silane are mixed immediately before. 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.