JPH09237927A - Semiconductor film forming method and solar cell manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a Si or Ge semiconductor film having a large area by selecting a semiconductor material from among compds. expressed by specified formulae. SOLUTION: A semiconductor material is selected from among compds. given by formulae I, II (M is Si or Ge, R1 selected among H and alkyls having 2C or more and beta H), III, IV (X is halogen atom, n is 4 or higher integer, a is 1 or 1) V (R2 is substituted group given by VII nonsubstituted alkyl group, R3 is H atom, 1-15C substituted group, R4 is 1-15C substituted group) VI (R5 is 1-15C substituted group) to form a semiconductor thin film. This soln. is coated and thermally decomposed to form a Si film having a large area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel semiconductor thin film forming method and a solar cell manufacturing method using this method.

[0002]

2. Description of the Related Art Conventionally, as a method for forming a semiconductor thin film made of silicon or germanium which is a group IV element, a vapor deposition method, a sputtering method, an ion plating method,
A vapor phase growth method such as a CVD method is used. But,
Since all of these methods use a depressurized environment, a hydrogen furnace environment, etc. during film formation, it is essential to use a highly airtight reaction vessel, and to form a uniform semiconductor thin film on a large-area substrate. Was difficult. Therefore, there is a limit to manufacturing applied products having a semiconductor thin film, for example, solar cells having an area larger than that of conventional ones by one digit or more.

Therefore, it has been considered to use a wet coating method as one of the methods for forming a large-area semiconductor thin film. For example, Japanese Patent Laid-Open No. 4-119996 discloses a method of forming a silicon thin film by coating a compound such as octasilacubane as a silicon source on a substrate and thermally decomposing the silicon source compound. This method is considered to be advantageous for easily forming a silicon thin film on a large-area substrate without requiring large-scale and expensive manufacturing equipment such as a vacuum chamber.

However, the compounds such as octasilacubane described in this publication are often unstable to oxygen, and are easily oxidized and modified in air. Further, these compounds often have low solubility in a solvent, and it is difficult to form a uniform thin film.

Further, in consideration of application to solar cells and the like, it is necessary to form a silicon thin film doped with p-type or n-type impurities. However, conventionally, since a silicon thin film is formed by thermal decomposition and then impurities are doped by thermal diffusion or ion implantation, a large-scale apparatus is required, and the process is complicated.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for easily forming a large area semiconductor thin film made of silicon or germanium, and a method for producing a large area solar cell using this method. To provide.

[0007]

A method for forming a semiconductor thin film of the present invention is a method for forming a semiconductor thin film by applying a solution of a semiconductor raw material onto a substrate and then thermally decomposing it to release the semiconductor. Semiconductor raw materials are represented by the general formulas (I) and (II)

[0008]

[Chemical 6] (In the formula, M is selected from the group consisting of silicon and germanium, and R ¹ is each independently hydrogen, an alkyl group having hydrogen at the β-position and having 2 or more carbon atoms, and a phenyl group;
It is selected from the group consisting of silyl groups. ), Compounds represented by general formulas (III) and (IV)

[0009]

Embedded image (In the formula, M is selected from the group consisting of silicon and germanium, X is a halogen atom, n is an integer of 4 or more, a
Is 1 or 2. ) A compound represented by the general formula (V)

[0010]

Embedded image (In the formula, each R ² is independently selected from the group consisting of a substituted or unsubstituted alkyl group, aryl group and aralkyl group represented by the following formula.)

[0011]

Embedded image (In the formula, R ³ is independently a hydrogen atom or a carbon number 1
To substituted or unsubstituted alkyl group having 6 to 15 carbon atoms
5 substituted or unsubstituted aryl groups and 7 to 7 carbon atoms
Selected from the group consisting of 15 substituted or unsubstituted aralkyl groups, R ⁴ is a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, and 7 to 15 carbon atoms. Selected from the group consisting of substituted or unsubstituted aralkyl groups. ), A compound represented by
And general formula (VI)

[0012]

Embedded image (In the formula, each R ⁵ is independently a group consisting of a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms, an aryl group, and an aralkyl group, and a substituted or unsubstituted silyl group having 1 to 5 silicon atoms. Selected from the group consisting of compounds represented by

The method of forming a semiconductor thin film having a predetermined conductivity type in the present invention is a method of forming a semiconductor raw material selected from the group consisting of the compounds represented by the general formulas (I) to (VI) in a p-type or n-type solution. A dopant source that gives a conductivity type of a type is added and applied on a substrate, and then thermally decomposed to release a semiconductor containing impurities of a predetermined conductivity type.

Another method of forming a semiconductor thin film having a predetermined conductivity type in the present invention is to apply a solution of a semiconductor raw material selected from the group consisting of the compounds represented by the general formulas (I) to (VI) on a substrate. And then thermally decomposed in an atmosphere containing a dopant source giving a p-type or n-type conductivity to release a semiconductor containing impurities of a predetermined conductivity type.

In the method for manufacturing a solar cell of the present invention, two or more layers of semiconductor thin film having any one of i-type, p-type and n-type conductivity is provided between a pair of electrodes to form a semiconductor junction. When forming an i-type semiconductor thin film in manufacturing a solar cell, a solution of a semiconductor raw material selected from the group consisting of compounds represented by the general formulas (I) to (VI) is applied onto a substrate. When a p-type or n-type semiconductor thin film is formed by employing a step of thermally decomposing and then releasing the semiconductor, a compound represented by the general formula (I) to (VI) is used. From the group consisting of compounds represented by the above general formulas (I) to (VI), a dopant source that gives a predetermined conductivity type is added to a solution of a semiconductor raw material to be selected and applied on a substrate and then thermally decomposed. A solution of the selected semiconductor raw material was applied onto the substrate A step of liberating a semiconductor containing an impurity giving a predetermined conductivity type by thermally decomposing in a atmosphere containing a dopant source giving a predetermined conductivity type to a semiconductor having two or more layers. It forms a thin film.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, as the substrate material, a semiconductor such as silicon, glass, glass having a transparent electrode, metal,
Any material selected from ceramics, heat resistant polymers and the like can be used.

The compound used as a semiconductor raw material in the present invention will be described. Formula (I) or (I
The compound represented by I) is a silane-based or germane-based compound having a one-dimensional chain or cyclic structure. These compounds may be copolymers or may be used as a mixture. In the present invention, a compound that is solid at room temperature and soluble in an organic solvent is used. In order to satisfy such conditions, for example, in a polymer having a one-dimensional chain structure, the degree of polymerization n is preferably 3 or more and 10000 or less, and more preferably 5 to 30.

Specific examples of the compound represented by formula (I) or (II) are shown below. Although only one-dimensional chain polysilane is shown below, it is needless to say that cyclic polysilane may be used or polygermane in which silicon is replaced with germanium.

[0019]

Embedded image

[0020]

Embedded image

The compound represented by the general formula (III) or (IV) is a halide of silicon or / and germanium. These halides have a weight average molecular weight of 500 in order to satisfy the condition of being soluble in an organic solvent.
It is preferably 100,000. If the molecular weight is small, it will volatilize from the substrate before thermal decomposition, so that it is difficult to form a good film. When the molecular weight is within the above range, the vapor pressure at the thermal decomposition temperature is relatively low, and the volatilization from the substrate can be ignored. If the molecular weight is too large, the solubility in a solvent decreases, making it difficult to apply it to a substrate.

The silane compound represented by the general formula (V) is solid at room temperature, is soluble in an organic solvent, and has high stability against oxidation. The silylene compound represented by the general formula (VI) is solid at room temperature and soluble in an organic solvent,
High stability against oxidation.

General formulas (I) used in the present invention
Since the compound represented by (VI) is soluble in an organic solvent,
A uniform coating film can be formed by coating on a substrate having a large area of a flat surface or a curved surface by an arbitrary coating method such as dipping, spin coating or spray coating. The thickness of the coating film is preferably several tens nm. The device used in this coating step can be arbitrarily selected according to the size of the substrate. Further, as for the coating device, it is sufficient if it is possible to prevent mixing of air, and a large-scale pressure reducing device having high airtightness as in the case of the vapor phase growth method is not necessary.

In the present invention, the coating film of the compound applied on the substrate is heated to a temperature around its melting point in a predetermined atmosphere, for example, an inert gas atmosphere or a reducing atmosphere such as hydrogen to evaporate the solvent. Then, a thermal decomposition reaction is caused to release silicon and / or germanium to form a semiconductor thin film. The pressure of the atmosphere may be around normal pressure (1 atm). Further, the reaction product is preferably removed by exhausting. The heating means is not particularly limited, a general electric furnace may be used, or infrared rays may be irradiated as in the rapid thermal annealing method,
Laser annealing may be performed. The specific thermal decomposition temperature depends on the compound. For example, in the case of the compounds represented by the general formulas (I) and (II), 200 to 700
It is preferable to carry out the thermal decomposition at a temperature of 300 to 650 ° C. In the case of the compounds represented by the general formulas (III) and (IV), thermal decomposition occurs in the range of about 250 ° C to about 1300 ° C, but it is preferable to carry out thermal decomposition at 300 to 500 ° C. In the case of the compounds represented by the general formulas (V) and (VI), it is preferable to carry out the thermal decomposition at 300 to 700 ° C. The heating rate is set to about 5 ° C./min. A reaction time of 10 minutes to 10 hours is sufficient. However, in some cases, the temperature may not be raised and the thermal decomposition may be performed at a constant temperature.

By this thermal decomposition reaction, the elimination reaction of the substituent introduced into the side chain of the semiconductor raw material occurs. For example,
A β-elimination reaction occurs in a compound having an alkyl group having hydrogen at β-position and having 2 or more carbon atoms, and a radical elimination occurs in a compound having a phenyl group. By such a thermal decomposition reaction, a polycrystalline thin film of silicon or germanium can be formed. In addition, an amorphous thin film can be formed by lowering the thermal decomposition temperature in combination with decomposition by ultraviolet irradiation. These thin films contain some hydrogen in addition to the group IV element.

A solution of a mixture of a silane compound and a germane compound or a solution of a copolymer having a repeating unit of silane and a repeating unit of germane is applied and thermally decomposed to mix silicon and germanium. It is also possible to form a semiconductor thin film. The former method is preferable for controlling the composition of silicon and germanium.

An apparatus for carrying out the method of the present invention as described above is schematically shown in FIGS. As shown in FIG. 1 (a), the substrate 1 is placed in a coating device 3 having a nozzle 4, and a nitrogen gas atmosphere is provided to prevent atmospheric air from entering the coating device 3. The raw material solution is sprayed and applied on the substrate 1. In this case, the amount of the solution applied on the substrate 1 can be controlled by appropriately setting the nozzle shape and the spraying time. Next, FIG.
As shown in (b), the substrate 1 coated with the semiconductor raw material solution is placed in a hydrogen furnace 5, and the substrate 1 is heated by a heater 6 in a reducing gas atmosphere mainly containing hydrogen to thermally decompose the semiconductor raw material. Then, the semiconductor thin film 2 is formed on the substrate 1. As the heater 6, an infrared heater, a resistance heater or the like can be used.

As shown in FIG. 2, the substrate 1 is placed in the hydrogen furnace 5, the solution of the semiconductor raw material is directly sprayed from the nozzle 4 onto the substrate 1 to apply the solution onto the substrate 1, and the substrate 1 is heated by the heater 6. However, a semiconductor thin film can be formed by thermally decomposing the semiconductor raw material.

FIG. 3 shows an apparatus for continuously manufacturing semiconductor thin films using a flexible substrate. The flexible substrate 1 is supplied from the supply roll 11 and immersed in the semiconductor raw material solution 8 in the raw material container 7.
The substrate 1 is sent to the hydrogen furnace 5 by the feed rolls 12, 12. The semiconductor raw material is thermally decomposed by being heated by the heater 6 in the hydrogen furnace 5 to form a semiconductor thin film on the substrate 1. Then, the substrate 1 is wound on the winding roll 13. Thus, the semiconductor thin film can be continuously formed on the flexible substrate.

In the present invention, it is also possible to form a semiconductor thin film of a predetermined conductivity type by using a dopant source which gives a p-type or n-type conductivity type. As the method, the following two methods can be used. That is, (1) a dopant source for imparting p-type or n-type conductivity is added to a solution of a semiconductor raw material selected from the group consisting of compounds represented by formulas (I) to (VI), and After coating, thermal decomposition to liberate a semiconductor containing impurities of a predetermined conductivity type, and (2) general formula (I)
To (VI), a solution of a semiconductor raw material selected from the group consisting of compounds represented by (VI) is coated on a substrate, and then thermally decomposed in an atmosphere containing a dopant source that gives a p-type or n-type conductivity. This is a method of releasing a semiconductor containing impurities of a predetermined conductivity type. The equipment and reaction conditions for carrying out these methods may be similar to those described above.

In these methods, boron (B) is generally used as the p-type impurity, and phosphorus (P), arsenic (As) or antimony (Sb) is used as the n-type impurity. In the method (1), an alkylated impurity element or a compound having a bond between the impurity element and Si in the molecule is used as a dopant source. In the method of (2),
As the dopant source, an alkylated impurity element, a compound having a bond between the impurity element and Si in the molecule, or a hydride of the impurity element is used. The amount of the dopant source added to the semiconductor raw material depends on the impurity concentration required for the semiconductor thin film to be formed, but generally the number of impurity element atoms is 0.1 to 10% of the total number of silicon atoms in the raw material. It is preferable.

Examples of alkylated p-type impurities include BPh ₃ , BMePh ₂ and B (t-Bu) ₃ . Compounds having a bond between p-type impurities and Si include B (SiMe ₃ ) ₃ and PhB (SiMe ₃ )
₂ , Cl ₂ B (SiMe ₃ ) and the like. Examples of hydrides of p-type impurities include diborane.

Examples of alkylated n-type impurities include PPh ₃ , PMePh ₂ , P (t-Bu) ₃ and AsP.
_{h 3, AsMePh 2, As (} t-Bu) 3, SbPh
₃ , SbMePh ₂ , Sb (t-Bu) _{3, and the} like. Examples of compounds having a bond between n-type impurities and Si include P (SiMe ₃ ) ₃ , PhP (SiMe ₃ ) ₂ and C.
l ₂ P (SiMe ₃ ), As (SiMe ₃ ) ₃ , PhA
s (SiMe ₃ ) ₂ , Cl ₂ As (SiMe ₃ ) Sb
(SiMe ₃ ) ₃ , PhSb (SiMe ₃ ) ₂ , Cl ₂
Such as Sb (SiMe _3), and the like. Examples of the hydride of the n-type impurity include phosphine and arsine.

Of the above dopant sources, especially B-Si
Compound having bond or P (As or Sb) -S
When compounds having i-bonds are used, the amount of C incorporated into the semiconductor thin film to be formed can be suppressed because the bonds between impurities and C are small in these compounds.
The electrical characteristics of the semiconductor thin film can be improved.

When a compound having a B-Si bond or a compound having a P (As or Sb) -Si bond is used as a dopant source, octasilacubane represented by the following general formula is used as a silicon source compound. It can also be used.

[0036]

Embedded image Specific examples of the substituent R ⁶ include those shown below.

[0037]

Embedded image

Of these substituents, octasilacubane having a trimethylsilyl group (Me ₃ Si-) is particularly preferable because it has good solubility in an organic solvent. Furthermore, in the present invention, a large-area solar cell can be manufactured by using the method for forming a semiconductor thin film as described above. That is, since the solar cell has a structure in which two or more semiconductor thin films having any one of i-type, p-type, and n-type conductivity are provided between a pair of electrodes to form a semiconductor junction, the method described above is used. By repeatedly forming two or more semiconductor thin films, pn, pin, ip, in
It is possible to realize a semiconductor junction such as.

When a solar cell is manufactured by the method of the present invention, for example, by connecting a plurality of sets of a raw material container and a hydrogen furnace as shown in FIG. 3, a multilayer semiconductor thin film is laminated in a consistent continuous process. The film can be formed, which is advantageous for manufacturing a large-area solar cell.

As described above, in the present invention, the solution of the semiconductor raw material is first applied, and then the semiconductor is released by thermal decomposition, so that a uniform semiconductor thin film can be formed even if the substrate has a large area. A large area solar cell can be manufactured using such a method.

Although the method of the present invention was developed mainly for the production of solar cells, it has a large area of amorphous silicon T.
It is clear that it is also effective for manufacturing FT. Further, since the method of the present invention can be applied to a substrate having a curved surface, it can be expected to be applied to other fields.

[0042]

Embodiments of the present invention will be described below. Example 1 Dichlorosilane was dissolved in tetrahydrofuran, metallic lithium was added, and polymerization was performed under predetermined polymerization conditions to obtain-(Si.
H _{2) n} - is synthesized one-dimensional chain polysilane represented by, precipitated as a solid. The one-dimensional chain polysilane obtained is
It was a mixture of polysilanes with n = 5-15. This polysilane is solid at room temperature and dissolves in an organic solvent such as xylene.

A solution of this polysilane dissolved in xylene was applied onto a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, xylene was evaporated, and polysilane was thermally decomposed at 650 ° C. to release silicon. As a result, it was confirmed that a thin film of polycrystalline silicon was formed on the substrate.

Further, when hydrogen was flowed at a flow rate of ² m ² / min and the pressure was set to 1 atm, and the thermal decomposition temperature was lowered to 350 ° C. by using a KrF excimer laser and irradiating ultraviolet rays at an output of 10 J. It was confirmed that can form a thin film of amorphous silicon.

Next, as a result of performing a step of releasing silicon by thermal decomposition in a hydrogen atmosphere containing diborane after the same coating step as described above, it was confirmed that a p-type silicon thin film could be formed. In addition, as a result of performing a step of releasing silicon by thermal decomposition in a hydrogen atmosphere containing arsine after the coating step similar to the above, it was confirmed that an n-type silicon thin film can be formed. Note that phosphine may be used instead of arsine.

Further, the solar cell shown in FIG. 4 was manufactured by utilizing the above-described method of forming a silicon thin film. In FIG. 4, a transparent electrode 22 made of tin oxide (SnO ₂ ) or indium tin oxide (ITO) is provided on a glass substrate 21.
Are formed. By repeating the process of applying a polysilane solution on the transparent electrode 22 so that a part of the transparent electrode 22 is exposed and thermally decomposing it, a p-type amorphous silicon layer 23 having a thickness of 0.1 μm and a thickness of 0. An undoped (i-type) amorphous silicon layer 24 having a thickness of 5 μm and an n-type amorphous silicon layer 25 having a thickness of 0.1 μm are sequentially stacked. Further, an aluminum electrode 26 is formed on the n-type amorphous silicon layer 25, and an aluminum electrode 27 is formed on the exposed transparent electrode 22.

The photovoltaic efficiency of the obtained solar cell was measured to obtain the conversion efficiency, which was 7.8%, which is comparable to the conventional amorphous silicon solar cell. confirmed.

Example 2 To a reaction vessel filled with Ar was added 1 L of toluene, and 2.2 mol of finely cut metallic Na was added thereto. 1
A solution obtained by diluting a mixed solution of mol of diethyldichlorosilane and 0.05 mol of triethylchlorosilane with 100 mL of toluene was added dropwise to the reaction vessel over 1 hour. At this time, the dropping rate was controlled so that the reaction temperature did not exceed 100 ° C. 2 hours after dropping
The reaction was carried out at 110 ° C. Then, the unreacted metal was treated with ethanol, and then the one-dimensional chain polysilane was precipitated in ethanol. This polysilane - (SiEt _{2) n} -
And the molecular weight was about 3000.

A solution of this polysilane dissolved in xylene was applied onto a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, xylene was evaporated, and polysilane was thermally decomposed at 450 ° C. to release silicon. As a result, it was confirmed that a thin film of polycrystalline silicon was formed on the substrate.

When hydrogen is flown at a flow rate of ² m ² / min, the pressure is set to 1 atm, and the thermal decomposition temperature is lowered to 350 ° C. by using a KrF excimer laser and irradiating ultraviolet rays at an output of 10 J. It was confirmed that can form a thin film of amorphous silicon.

It was also confirmed that a p-type or n-type silicon thin film can be formed by using the same method as in Example 1. Further, as a result of repeating these methods and forming an np junction by laminating the n-type silicon thin film and the p-type silicon thin film, it was confirmed that the photovoltaic characteristics were exhibited.

The substituent R is --CH (CH ₃ ) ₂ ,-
_{C (CH 3) 3, -C} (CH 3) Ph 2 or -C (C
Good results were also obtained when using polysilane which was H ₃ ) (cyclopropyl) ₂ .

Example 3 As a compound serving as a silicon source,-(SiEtPh) _n-
The one-dimensional chain polysilane represented by the formula (molecular weight about 5000) was used. This polysilane is solid at room temperature and dissolves in an organic solvent such as xylene.

A solution of this polysilane dissolved in xylene was applied onto a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, xylene was evaporated, and polysilane was thermally decomposed at 450 ° C. to release silicon. As a result, it was confirmed that a thin film of polycrystalline silicon was formed on the substrate.

When hydrogen was flowed at a flow rate of ² m ² / min, the pressure was set to 1 atm, and the thermal decomposition temperature was lowered to 370 ° C. by using a KrF excimer laser and irradiating ultraviolet rays at an output of 10 J. It was confirmed that can form a thin film of amorphous silicon.

It was also confirmed that a p-type or n-type silicon thin film can be formed by using the same method as in Example 1. Further, by repeatedly applying the method for forming a silicon thin film as described above, a multi-layered silicon thin film was formed and the solar cell shown in FIG. 5 was produced. In FIG. 5, the molybdenum electrode 3 is provided on the stainless steel substrate 31.
2 are formed. On this molybdenum electrode 32,
A p-type amorphous silicon layer 33 having a thickness of 0.1 μm, an i-type amorphous silicon layer 34 having a thickness of 0.4 μm, and a p-type amorphous silicon layer 35 having a thickness of 0.1 μm are sequentially formed. Further, an ITO electrode 36 and an aluminum electrode 37 are sequentially formed on the p-type amorphous silicon layer 35.

The photovoltaic efficiency of the obtained solar cell was measured to obtain the conversion efficiency, which was 8.3%, which is comparable to that of the conventional amorphous silicon solar cell. confirmed.

Example 4 As a compound serving as a silicon source (Si (t-Bu) ₂ ).
A cyclic polysilane represented by _n (n is 3 or 4) was used. This cyclic polysilane is a solid at room temperature and dissolves in an organic solvent such as toluene.

A solution of this cyclic polysilane dissolved in toluene was applied on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, toluene was evaporated, and cyclic polysilane was thermally decomposed at 430 ° C. to release silicon. As a result, it was confirmed that a thin film of polycrystalline silicon was formed on the substrate.

When hydrogen was flowed at a flow rate of ² m ² / min, the pressure was set to 1 atm, and the thermal decomposition temperature was lowered to 350 ° C. by using a KrF excimer laser and irradiating ultraviolet rays at an output of 10 J. It was confirmed that can form a thin film of amorphous silicon.

It was also confirmed that a p-type or n-type silicon thin film can be formed by using the same method as in Example 1. Further, by repeatedly applying the method for forming a silicon thin film as described above, a multi-layered silicon thin film was formed, and the solar cell shown in FIG. 6 was produced. In FIG. 6, a SiO ₂ film 42 and a Si ₃ N ₄ film 43 are sequentially laminated on an alumina substrate 41. This Si ₃
On the N ₄ film 43, a boron-added p-type polycrystalline silicon layer 44 having a thickness of 10 μm is formed. By performing phosphorus diffusion on the p-type polycrystalline silicon layer 44, the n-type diffusion layer 4 is formed.
5 are formed. An ITO electrode 46 is formed on the n-type diffusion layer 45. Further, an aluminum electrode 47 is formed on the p-type polycrystalline silicon layer 44 exposed after the mesa etching. Solar cell characteristics were also observed in this element.

Example 5 As a compound serving as a germanium source,-(GeEt ₂ ) _n
One-dimensional polygermane represented by- (molecular weight of about 300
0) or cyclic polygermane was used. These compounds are solid at room temperature and are soluble in organic solvents such as xylene.

A solution of these polygermanes dissolved in xylene was applied on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, xylene was evaporated, and polygermane was thermally decomposed at 550 ° C. to release germanium. As a result, it was confirmed that a polycrystalline germanium thin film was formed on the substrate.

In addition, when hydrogen was flowed at a flow rate of ² m ² / min, the pressure was set to 1 atm, and the thermal decomposition temperature was lowered to 200 ° C. by using a KrF excimer laser and irradiating ultraviolet rays at an output of 10 J. It was confirmed that can form a thin film of amorphous germanium.

Example 6 One-dimensional chain polysilane represented by-(SiH ₂ ) _n- (molecular weight about 1000) or cyclic polysilane was used as a compound serving as a silicon source, and-(GeH ₂ ) _n was prepared as a compound serving as a germanium source. One-dimensional chain polygermane (molecular weight about 1000) represented by-or cyclic polygermane was used. These compounds are solid at room temperature and are soluble in organic solvents such as xylene.

Solutions of these polysilanes and polygermanes independently dissolved in xylene were coated on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil at a predetermined mixing ratio. These substrates were put in a hydrogen furnace, xylene was evaporated, and polysilane and polygermane were thermally decomposed at 650 ° C. to release silicon and germanium. As a result, it was confirmed that a polycrystalline silicon-germanium thin film corresponding to the raw material molar ratio was formed on the substrate.

When hydrogen was flowed at a flow rate of ² m ² / min, the pressure was set to 1 atm, and the thermal decomposition temperature was lowered to 350 ° C. by using a KrF excimer laser and irradiating ultraviolet rays at an output of 10 J. Is amorphous silicon
It was confirmed that a germanium thin film could be formed.

As a result of stacking a Si thin film and a SiGe mixed thin film by combining the above-described methods and adding a donor and an acceptor to each layer to form an np junction, it was revealed that solar cell characteristics are exhibited. .

Example 7 One-dimensional chain polysilane represented by-(SiHPh) _n- as a compound serving as a silicon source (molecular weight about 12000),
And P (SiMe
₃ ) ₃ was used. A toluene solution of a mixture of these compounds was spin-coated on a quartz substrate and then vacuum dried at 70 ° C. for 1 hour. Then, the raw material was thermally decomposed by heating at 300 ° C. for 1 hour and at 700 ° C. for 1 hour under a mixed air flow of argon and hydrogen. As a result, a phosphorus-doped silicon thin film was formed.

Example 8 As a halide serving as a silicon source, Si ₅ Cl ₁₂ which is one of compounds called perchlorosilane was used.
This compound has a melting point of 345 ° C. and is soluble in organic solvents such as petroleum ether.

This solution of Si ₅ Cl ₁₂ dissolved in petroleum ether was coated on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace to evaporate petroleum ether and thermally decompose Si ₅ Cl ₁₂ at 450 ° C. to release silicon. As a result, it was confirmed that a thin film of amorphous silicon was formed on the substrate. It was also confirmed that a polycrystalline silicon thin film can be formed by increasing the heating temperature.

Next, as a result of carrying out the step of releasing silicon by thermal decomposition in the hydrogen atmosphere containing diborane after the coating step similar to the above, it was confirmed that a p-type silicon thin film could be formed. In addition, as a result of performing a step of releasing silicon by thermal decomposition in a hydrogen atmosphere containing arsine after the coating step similar to the above, it was confirmed that an n-type silicon thin film can be formed. Note that phosphine may be used instead of arsine.

Further, the solar cell shown in FIG. 4 was manufactured by utilizing the above-described method for forming a silicon thin film. The conversion efficiency of the obtained solar cell was measured by measuring the photovoltaic power, and the result was 8.5%. It was confirmed that the conversion efficiency was comparable to that of the conventional amorphous silicon solar cell. .

Example 9 Si ₆ Cl ₁₄ was used as a halide serving as a silicon source. This compound has a melting point of 320 ° C. and is soluble in an organic solvent such as petroleum ether.

This solution of Si ₆ Cl ₁₄ dissolved in petroleum ether was applied on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, the petroleum ether was evaporated, and Si ₆ Cl ₁₄ was thermally decomposed at 440 ° C. to release silicon. As a result, it was confirmed that a thin film of amorphous silicon was formed on the substrate. It was also confirmed that a polycrystalline silicon thin film can be formed by increasing the heating temperature.

It was also confirmed that a p-type or n-type silicon thin film could be formed by using the same method as in Example 8. Further, as a result of repeating these methods and forming an np junction by laminating the n-type silicon thin film and the p-type silicon thin film, it was confirmed that the photovoltaic characteristics were exhibited.

Example 10 The same Si ₅ Cl _{12 as} that used in Example 8 was used as a halide serving as a silicon source. This Si ₅ Cl
₁₂ was applied to a silicon substrate, a quartz substrate, a glass substrate or a stainless foil by mechanical operation at a temperature near the melting point. These substrates were placed in a hydrogen furnace to evaporate petroleum ether and thermally decompose Si ₅ Cl ₁₂ at 450 ° C. to release silicon. As a result, it was confirmed that a thin film of amorphous silicon was formed on the substrate. It was also confirmed that a polycrystalline silicon thin film can be formed by increasing the heating temperature.

It was also confirmed that a p-type or n-type silicon thin film could be formed by using the same method as in Example 8. Further, by repeatedly applying the method for forming a silicon thin film as described above, a multi-layered silicon thin film was formed and the solar cell shown in FIG. 5 was produced. The conversion efficiency of the obtained solar cell was measured by measuring the photovoltaic power, and as a result, it was confirmed that the conversion efficiency was 14%, which was comparable to that of the conventional amorphous silicon solar cell.

Example 11 The same Si ₆ Cl ₁₄ as used in Example 9 was used as a halide serving as a silicon source. This Si ₆ Cl
₁₄ was applied on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil by a mechanical operation at a temperature near the melting point. These substrates were placed in a hydrogen furnace, the petroleum ether was evaporated, and Si ₆ Cl ₁₄ was thermally decomposed at 440 ° C. to release silicon. As a result, it was confirmed that a thin film of amorphous silicon was formed on the substrate. It was also confirmed that a polycrystalline silicon thin film can be formed by increasing the heating temperature.

It was also confirmed that a p-type or n-type silicon thin film could be formed by using the same method as in Example 8. Further, by repeatedly applying the method for forming a silicon thin film as described above, a multi-layered silicon thin film was formed, and the solar cell shown in FIG. 6 was produced. Solar cell characteristics were also observed in this element.

Example 12 Ge ₅ Cl ₁₂ was used as a halide serving as a germanium source.
Was used. This compound is soluble in organic solvents such as petroleum ether. This solution of Ge ₅ Cl ₁₂ dissolved in petroleum ether was applied on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, the petroleum ether was evaporated, and further Ge ₅ Cl ₁₂ was thermally decomposed at 400 ° C. to liberate germanium. As a result, it was confirmed that a polycrystalline germanium thin film was formed on the substrate. It was also confirmed that when the thermal decomposition temperature was lowered by applying ultraviolet irradiation, a thin film of amorphous germanium could be formed.

Example 13 Si ₅ Br ₁₂ was used as a halide serving as a silicon source. This Si ₅ Br ₁₂ was applied on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil by a mechanical operation at a temperature near the melting point. These substrates were placed in a hydrogen furnace to evaporate petroleum ether and thermally decompose Si ₅ Br ₁₂ at 440 ° C. to release silicon. As a result, it was confirmed that a thin film of amorphous silicon was formed on the substrate. It was also confirmed that a polycrystalline silicon thin film can be formed by increasing the heating temperature.

It was also confirmed that a p-type or n-type silicon thin film can be formed by using the same method as in Example 8. Further, by repeatedly applying the method for forming a silicon thin film as described above, a multi-layered silicon thin film was formed, and the solar cell shown in FIG. 6 was produced. Solar cell characteristics were also observed in this element.

Example 14 As a silicon source, a solution of a silane compound represented by the following chemical formula in xylene was coated on a silicon substrate, a quartz substrate, a glass substrate or a stainless foil. These substrates were placed in a hydrogen furnace, xylene was evaporated, and the silane compound was thermally decomposed at 650 ° C. to release silicon. As a result, it was confirmed that a thin film of polycrystalline silicon was formed on the substrate.

[0085]

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In addition, when hydrogen was flowed at a flow rate of ² m ² / min and the pressure was set to 1 atm, and the thermal decomposition temperature was lowered to 350 ° C. by using a KrF excimer laser and irradiating ultraviolet rays at an output of 10 J. It was confirmed that can form a thin film of amorphous silicon.

Next, it was confirmed that a p-type silicon thin film could be formed as a result of carrying out the step of liberating silicon by thermal decomposition in the hydrogen atmosphere containing diborane after the coating step similar to the above. In addition, as a result of performing a step of releasing silicon by thermal decomposition in a hydrogen atmosphere containing arsine after the coating step similar to the above, it was confirmed that an n-type silicon thin film can be formed. Note that phosphine may be used instead of arsine.

Further, the solar cell shown in FIG. 4 was manufactured by utilizing the above-described method for forming a silicon thin film. The conversion efficiency of the obtained solar cell was measured by measuring the photovoltaic power, and the result was 8.5%. It was confirmed that the conversion efficiency was comparable to that of the conventional amorphous silicon solar cell. .

Similarly, the solar cell shown in FIG. 5 was produced.
The conversion efficiency of the obtained solar cell was measured by measuring the photovoltaic power, and as a result, it was 8.3%, which confirmed that the conversion efficiency was comparable to that of the conventional amorphous silicon solar cell. .

Similarly, the solar cell shown in FIG. 6 was prepared.
Solar cell characteristics were also observed in this element. Example 15 A silylene compound represented by the following chemical formula was used as a silicon source compound, and P (SiMe ₃ ) ₃ was used as an n-type impurity source compound. After spin coating a toluene solution of a mixture of these compounds on a quartz substrate,
It was vacuum dried at 70 ° C. for 1 hour. Then, under a mixed air flow of argon and hydrogen, at 300 ° C for 1 hour, 600 ° C
It was heated for 1 hour to thermally decompose the raw material. As a result, a phosphorus-doped silicon thin film was formed.

[0091]

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Example 16 An octasilacubane compound having a trimethylsilyl group (TMS) represented by the following chemical formula as a silicon source compound and P as an n-type impurity source compound
(SiMe ₃ ) ₃ was used. After a toluene solution of a mixture of these compounds was spin-coated on a quartz substrate, 70
It was vacuum dried at ℃ for 1 hour. Then, under a mixed air flow of argon and hydrogen, the temperature is 300 ° C. for 1 hour, and the temperature is 600 ° C. for 1 hour.
The raw material was pyrolyzed by heating for a time. As a result, a phosphorus-doped silicon thin film was formed.

[0093]

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[0094]

As described above in detail, according to the method of the present invention, a semiconductor thin film composed of a large area of silicon or germanium can be obtained by adopting two steps of applying a solution of a semiconductor raw material and pyrolyzing. Can be easily formed, and a large area solar cell can be manufactured by utilizing this method.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a schematic diagram showing another example of an apparatus for carrying out the method of the present invention.

FIG. 3 is a schematic diagram showing still another example of an apparatus for carrying out the method of the present invention.

FIG. 4 is a sectional view showing an example of a solar cell manufactured in an example of the present invention.

FIG. 5 is a cross-sectional view showing another example of the solar cell manufactured in the example of the present invention.

FIG. 6 is a cross-sectional view showing still another example of the solar cell manufactured in the example of the present invention.

[Explanation of Codes] 1 ... Substrate 2 ... Semiconductor thin film 3 ... Coating device 4 ... Nozzle 5 ... Hydrogen furnace 6 ... Heater 7 ... Raw material container 8 ... Semiconductor raw material solution 11 ... Supply roll 12 ... Feed roll 13 ... Winding roll 21 ... Glass substrate 22 ... Transparent electrode 23 ... P type amorphous silicon layer 24 ... Undoped (i type) amorphous silicon layer 25 ... N type amorphous silicon layer 26 ... Aluminum electrode 27 ... Aluminum electrode 31 ... Stainless substrate 32 ... Molybdenum electrode 33 ... P type Amorphous silicon layer 34 ... i-type amorphous silicon layer 35 ... p-type amorphous silicon layer 36 ... ITO electrode 37 ... Aluminum electrode 41 ... Alumina substrate 42 ... SiO ₂ film 43 ... Si ₃ N ₄ film 44 ... P-type polycrystalline silicon layer 45 ... n-type diffusion layer 46 ... ITO electrode 47 ... aluminum Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Kamata No. 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Within the Corporate Research and Development Center, Toshiba Corporation (72) Kenji Sano Komukai-shiba, Saiwai-ku, Kawasaki-shi, Kanagawa Town No. 1 Toshiba Corporation Research & Development Center

Claims (4)

[Claims] 1. A method for forming a semiconductor thin film by applying a solution of a semiconductor raw material onto a substrate and then thermally decomposing it to form a semiconductor thin film, wherein the semiconductor raw material is represented by the general formulas (I) and (II). [Chemical 1] (In the formula, M is selected from the group consisting of silicon and germanium, and R ¹ is each independently hydrogen, an alkyl group having hydrogen at the β-position and having 2 or more carbon atoms, and a phenyl group;
It is selected from the group consisting of silyl groups. ), Compounds represented by general formulas (III) and (VI) (In the formula, M is selected from the group consisting of silicon and germanium, X is a halogen atom, n is an integer of 4 or more, a
Is 1 or 2. ), A compound represented by the general formula (V): (In the formula, each R ² is independently selected from the group consisting of a substituted or unsubstituted alkyl group, aryl group and aralkyl group represented by the following formula.) (In the formula, R ³ is independently a hydrogen atom or a carbon number 1
To substituted or unsubstituted alkyl group having 6 to 15 carbon atoms
5 substituted or unsubstituted aryl groups and 7 to 7 carbon atoms
Selected from the group consisting of 15 substituted or unsubstituted aralkyl groups, R ⁴ is a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, and 7 to 15 carbon atoms. Selected from the group consisting of substituted or unsubstituted aralkyl groups. ), A compound represented by
And the general formula (VI): (In the formula, each R ⁵ is independently a group consisting of a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms, an aryl group, and an aralkyl group, and a substituted or unsubstituted silyl group having 1 to 5 silicon atoms. The method for forming a semiconductor thin film is characterized by being selected from the group consisting of compounds represented by 2. On a substrate, a dopant source for imparting p-type or n-type conductivity is added to a solution of a semiconductor raw material selected from the group consisting of compounds represented by the general formulas (I) to (VI). A method for forming a semiconductor thin film, characterized in that after being applied to a substrate, it is thermally decomposed to release a semiconductor containing impurities of a predetermined conductivity type. 3. A dopant which gives a p-type or n-type conductivity after a solution of a semiconductor raw material selected from the group consisting of compounds represented by the general formulas (I) to (VI) is applied on a substrate. A method for forming a semiconductor thin film, which comprises thermally decomposing in a source-containing atmosphere to release a semiconductor containing impurities of a predetermined conductivity type. 4. When manufacturing a solar cell in which two or more layers of semiconductor thin films having any one of i-type, p-type, and n-type conductivity are provided between a pair of electrodes to form a semiconductor junction, i In the case of forming a semiconductor thin film of the type, a solution of a semiconductor raw material selected from the group consisting of the compounds represented by the general formulas (I) to (VI) is applied and then thermally decomposed to release the semiconductor. When a p-type or n-type semiconductor thin film is formed by adopting the steps, a solution of a semiconductor raw material selected from the group consisting of the compounds represented by the general formulas (I) to (VI) has a predetermined conductivity type. Is added to the substrate by adding a dopant source that gives
To (VI), a solution of a semiconductor raw material selected from the group consisting of compounds represented by the formula (VI) is applied on a substrate and then thermally decomposed in an atmosphere containing a dopant source that gives a predetermined conductivity type, thereby obtaining a predetermined conductivity type. A method of manufacturing a solar cell, characterized in that a step of liberating a semiconductor containing an impurity that gives an impurity is adopted, and these steps are repeated to form a semiconductor thin film having two or more layers.