JP2003054931A - Method for forming polycrystalline silicon film and composition therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a polycrystalline silicon film on a substrate by a simple operation and apparatus, and to provide a composition therefor. SOLUTION: The composition contains a specified nickel compound. The polycrystalline silicon film can be formed by using the above composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of polycrystallizing amorphous silicon and a method of forming polycrystalline silicon,
And a composition for use therein.

[0002]

2. Description of the Related Art As a method for producing a polycrystalline silicon film for use in a solar cell or the like, a thermal CVD method (J. Vac. Sci.
Technology. 14: 1082 (1977
Etc.) or by plasma CVD method (Soli
d State Com. Vol. 17, p. 1193 (197)
The mainstream method is to first form an amorphous silicon film by (5 years), etc.) and then convert it to a polycrystalline silicon film by laser annealing, hydrogen plasma treatment, or the like. In the formation of a silicon film using such a CVD method, since a gas phase reaction is used, silicon particles are generated in the gas phase, and the production yield is low due to contamination of the device and the generation of foreign matter. Therefore, it is difficult to obtain a film having a uniform film thickness on a substrate having an uneven surface, productivity is low due to a low film formation speed, and a complicated and expensive high-frequency generator or vacuum device in the plasma CVD method is used. There were problems such as necessity, and further improvement was awaited.

In recent years, a method has been reported in which, when converting amorphous silicon into polycrystalline silicon, a thin film of a dissimilar metal or metal silicide is provided on the surface of amorphous silicon and heat treatment is performed. For example, J. Appl. Ph
y. , 69 , 6394 (1991), J. Appl. P
hy. , 70 , 5153 (1991), JPn. J. A
ppl. Phys. , Part 1, 29 , 729 (1
990), J. Appl. Phy. , 87 , 609 (2
000) and the like, it is reported that a thin film layer of aluminum, copper, nickel or the like may be provided on amorphous silicon and heat-treated at about 500 ° C. to convert it to polycrystalline silicon. However, according to this method, the heat treatment requires a relatively high temperature, so that there is a drawback that the usable material of the substrate is limited.
Since the VD method is adopted, it also has the above-mentioned problems. Further, in recent years, it has been reported that NiSi ₂ can be attached to a part of the surface of amorphous silicon and heat-treated at about 380 ° C. to convert it to polycrystalline silicon. According to this method, it is possible to polycrystallize at a relatively low temperature, so that there is a large degree of freedom in the material of the substrate that can be used, but since the CVD method is still required when forming amorphous silicon, it has the same problem. There is.

By the way, when a polycrystalline silicon film is used for a solar cell, it preferably has a (220) crystal plane on the surface. However, the polycrystalline silicon formed by the above-mentioned method has a (111) plane as the main component, and it has not been possible to selectively form a (220) plane. There is a demand for a technique capable of forming a polycrystalline silicon film having a (220) plane on its surface, which can be suitably used for a solar cell, by a simple method.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a CV
Unlike a method that requires a complicated and expensive vacuum-type apparatus such as the D method or the sputtering method, a method of forming a polycrystalline silicon film having a (220) surface on the substrate by a simple operation or apparatus, and It is to provide a composition therefor.

According to the present invention, firstly, the above objects are at least one compound selected from the following formulas (1) to (3): Ni (CO) ₄ . ． ． (1) Ni (CO) ₃ (SiF ₃ ) ₂ . ． ． _{(2) Ni (CO) (} PF 3) 3. ． ． (3) and a solvent are contained, and it is achieved by the composition (henceforth a "1st composition" may be used.) For polycrystallizing amorphous silicon.

Secondly, the above objects are expressed by the following formulas (1) to (3).
At least one compound selected from the group consisting of Ni (C
O) ₄ . ． ． (1) Ni (CO) ₃ (SiF ₃ ) ₂ . ． ． _{(2) Ni (CO) (} PF 3) 3. ． ． (3) and compounds represented by the following formula (4) Si _n R _m . ． ． (4) (wherein, plural R's each independently represent a hydrogen atom, an alkyl group, a phenyl group or a halogen atom, and n is 3
It is the above integer, and m is an integer of n to 2n + 2. )
It is achieved by a composition containing (hereinafter sometimes referred to as “second composition”).

A third object of the present invention is to thirdly coat the first or second composition on amorphous silicon,
This is achieved by a method of polycrystallizing amorphous silicon, which is characterized by heat treatment. Further, the object of the present invention is fourthly achieved by a method for forming polycrystalline silicon, which is characterized in that the second composition is applied onto a substrate and then heat-treated. Hereinafter, each component of the composition of the present invention will be described in detail.

First Composition The first composition of the present invention comprises at least one compound selected from the following formulas (1) to (3): Ni (CO) ₄ . ． ． (1) Ni (CO) ₃ (SiF ₃ ) ₂ . ． ． _{(2) Ni (CO) (} PF 3) 3. ． ． (3) and a solvent are contained. Above (1)
Methods for synthesizing the compound of formula (3) are known. The compound of the formula (1) can be obtained, for example, by Inorg. Synth., 2 , 234 (1946), Z.
It can be synthesized according to Anorg. Allg. Chem., 269 , 308 (1952) and the like. The compound of the formula (2) can be prepared according to, for example, Or
g. Metal. Chem. , 259 , 337 (198
3) and the like. Compounds of formula (3) are described, for example, by Inorg. Chem. , 4 , 651
(1965) and the like. The compounds (1) to (3) may be used alone or in combination of two or more.

The solvent used in the first composition of the present invention may be any solvent as long as it dissolves the compounds of the above formulas (1) to (3) and does not substantially react with them. Although not limited, for example, n-pentane, n-hexane, n-heptane, n-octane, decane, cyclopentane, benzene, toluene, xylene, durene, indene, tetrahydronaphthalene, decahydronaphthalene, squalane, and other aliphatic compounds. Hydrocarbon solvent or aromatic hydrocarbon type solvent; diethyl ether, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ether Ether solvents such as ether, tetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, p-dioxane, tetrahydrofuran; and propylene carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, dimethyl sulfoxide, chloride Mention may be made of polar solvents such as methylene and chloroform. Of these, aromatic hydrocarbon solvents are preferable from the viewpoint of stability of the solution, and benzene, toluene, xylene, and durene are particularly preferable. These solvents are
They can be used alone or as a mixture of two or more kinds.

In the first composition of the present invention, the above formulas (1) to (1) to
The content of the compound represented by (3) can be an appropriate value depending on the desired film thickness and purpose, but is usually 0.00
001-1.0% by weight, preferably 0.0001-0.
It can be 5% by weight, particularly preferably 0.0005 to 0.1% by weight.

Second Composition The second composition of the present invention comprises at least one compound selected from the following formulas (1) to (3): Ni (CO) ₄ . ． ． (1) Ni (CO) ₃ (SiF ₃ ) ₂ . ． ． _{(2) Ni (CO) (} PF 3) 3. ． ． (3) and compounds represented by the following formula (4) Si _n R _m . ． ． (4) (wherein, plural R's each independently represent a hydrogen atom, an alkyl group, a phenyl group or a halogen atom, and n is 3
It is the above integer, and m is an integer of n to 2n + 2. )
Contains.

The compounds represented by the above formulas (1) to (3) are the same as the above-mentioned first composition. Formula (4) above
When there are a plurality of R's, they are each independently a hydrogen atom, an alkyl group, a phenyl group or a halogen atom. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group,
sec-butyl group, t-butyl group, n-pentyl group, i
-Pentyl group, neopentyl group, n-hexyl group, cyclohexyl group, n-heptyl group, n-octyl group, n-
Preferable ones are alkyl groups having 1 to 10 carbon atoms such as nonyl group and n-decyl group. n
Is an integer of 3 or more, and m is an integer of n to 2n + 2. n is preferably 3 to 8, and particularly preferably 3 to
It is 6.

The compound represented by the above formula (4) is a chain,
It can be annular or cage-shaped. Among the compounds represented by the above formula (4), compounds in which all R are hydrogen atoms are preferably used. As such a compound, a chain compound represented by the formula Si _n H _{2n + 2} , a compound represented by the formula Si
A cyclic compound represented by _n H _2n and a cage compound represented by the formula Si _n H _n are preferably used. Particularly preferred are cyclic compounds of the formula _Si n _{H 2n.} In addition, "cage-like" means a thing including a Prisman skeleton, a Cuban skeleton, a pentagonal prism skeleton, and the like. N in the above formula is an integer of 3 or more, preferably 3 to 8, and particularly preferably 3 to 6. Among the compounds represented by the above formula (4), cyclopentasilane, silylcyclopentasilane, and cyclohexasilane can be particularly preferable.

In the second composition of the present invention, the above formulas (1) to (1) to
The addition amount of at least one compound among the compounds represented by (3) can be appropriately set depending on the purpose of use of the second composition of the present invention. When the second composition of the present invention is used for polycrystallizing amorphous silicon, the above formula (1) to
The addition amount of at least one compound among the compounds represented by (3) is usually 0.0001 to 10% by weight based on the total amount of the compounds represented by the above formula (4), and preferably It is 0.001 to 5% by weight, and particularly preferably 0.1.
002 to 1% by weight. On the other hand, when the second composition of the present invention is used to form polycrystalline silicon on a substrate, the addition amount of at least one compound selected from the compounds represented by the above formulas (1) to (3) Is usually 0.0001 to 10% by weight, preferably 0.001 to 5% by weight, based on the total amount of the compound represented by the formula (4).
It is particularly preferably 0.002 to 1% by weight.

The second composition of the present invention may contain a solvent similar to those exemplified in the first composition.
When the second composition of the present invention contains a solvent, the sum of at least one compound of the compounds represented by the above formulas (1) to (3) and the compound represented by the above formula (4). The proportion of the amount in the solution is usually 0.01% by weight or more,
It is preferably 0.05 to 80% by weight, more preferably 0.1 to 50% by weight.

Next, a method for polycrystallizing amorphous silicon using the first or second composition of the present invention will be described. When the amorphous silicon is polycrystallized by the method of the present invention, the amorphous silicon is preferably in the form of a film formed on a substrate. The substrate used at this time is not particularly limited. The substrate on which the coating film is formed may be flat or non-planar with steps, and the form thereof is not particularly limited. When the oxidation treatment of the coating film of the polysilane compound is performed by heat treatment, the material of the substrate is preferably one that can withstand the treatment temperature. Specific examples of the material of such a substrate include glass, metal, plastic, and ceramics. As the glass, for example, quartz glass, borosilicate glass, soda glass, lead glass, lanthanum glass, etc. can be used.
As the metal, for example, gold, silver, copper, nickel, silicon, aluminum, iron and stainless steel can be used. As the plastic, for example, polyimide, polyether sulfone, norbornene ring-opening polymer and hydrogenated product thereof can be used. Furthermore, the shape of these substrates is not particularly limited to a lump shape, a plate shape, a film shape, or the like.

An appropriate method can be used to form amorphous silicon on the substrate. For example, plasma CV
A method such as the D method may be used, or WO00 / 58409.
It may be formed from a composition in the form of a solution by the method described in JP-A No. The thickness of the amorphous silicon film may be an appropriate value depending on the purpose, but is usually 0.01.
˜20 μm, preferably 0.02 to 10 μm, more preferably 0.03 to 5 μm.

To polycrystallize amorphous silicon by the method of the present invention, the above-mentioned first or second composition of the present invention is applied onto the above-mentioned amorphous silicon by, for example, a spray method, a roll coating method, a curtain coating method or a spin coating method. The film thickness is preferably 0.% by an appropriate method such as a coating method, a screen printing method, an offset printing method and an inkjet method.
00001 to 1.0 μm, particularly preferably 0.0001
It is applied so as to be about 0.1 μm. When the composition contains a solvent, the above film thickness should be understood as the film thickness after removal of the solvent. The film forming process is preferably performed in a non-oxidizing atmosphere. In order to realize such an atmosphere, an atmosphere that does not substantially contain an oxidizing substance such as oxygen or carbon dioxide may be used. Specifically, nitrogen, hydrogen, a rare gas, or a mixed gas thereof may be used. Atmosphere can be preferably used.

After forming a coating film of the composition of the present invention on amorphous silicon, the amorphous silicon film is converted into a polycrystalline silicon film by heat treatment in an appropriate atmosphere. The above heat treatment is preferably carried out in a non-oxidizing atmosphere, usually in an argon atmosphere or in argon containing hydrogen. The processing temperature is 200 to 1
About 000 ° C, preferably about 200-850 ° C,
More preferably, it is about 300 ° C to 500 ° C. The heat treatment time is usually 1 to 180 minutes, preferably 5 to 120 minutes.

Next, a method of forming polycrystalline silicon on a substrate by using the second composition of the present invention will be described. The second composition of the invention is applied onto a substrate, for example by spraying,
Roll coating method, curtain coating method, spin coating method,
The film thickness is preferably 0.00 by an appropriate method such as a screen printing method, an offset printing method and an inkjet method.
5 to 10 μm, particularly preferably 0.01 to 5 μm. When the composition contains a solvent, the above film thickness should be understood as the film thickness after removal of the solvent. The same substrate as described above can be used. The film forming process is preferably performed in a non-oxidizing atmosphere. Such an atmosphere can be realized as described above.

In order to form a coating film of the second composition of the present invention on the substrate with good adhesion and high density, light irradiation treatment may be performed at least once before and after coating. preferable. In such light irradiation treatment, in addition to visible light, ultraviolet light, far ultraviolet light, low-pressure or high-pressure mercury lamp, deuterium lamp, discharge light of rare gas such as argon, krypton, xenon, YAG laser, argon laser, etc. , Carbon dioxide laser, XeF, XeCl,
An excimer laser such as XeBr, KrF, KrCl, ArF, or ArCl can be used as a light source. These light sources are generally 10 to 5000 W
The output of is used, but usually 100-1000W
Is enough. The wavelength of these light sources is not particularly limited as long as the polysilane compound in the composition or the coating film absorbs even a little, but 170 nm to 600 nm is preferable. The temperature during the light irradiation treatment is usually room temperature to 300 ° C.
And the processing time is about 0.1 to 30 minutes. It is preferable that these light irradiation treatments are performed in a non-oxidizing atmosphere similar to the film forming step of the polysilane compound.

The second aspect of the present invention formed as described above
The coating film of the composition of 1 is converted into a polycrystalline silicon film by heat treatment in an appropriate atmosphere. The coating film of the composition of the present invention formed as described above is preferably in a non-oxidizing atmosphere, usually in an argon atmosphere or argon containing hydrogen at about 100 to 1000 ° C., preferably 20 ° C.
0 to 850 ° C, more preferably 300 ° C to 50
It is heat-treated at about 0 ° C. to obtain a polycrystalline silicon film.

According to the method of the present invention, the polycrystalline silicon film is formed as described above. The method of the present invention can form a dense polycrystalline silicon film regardless of the area or shape of the substrate, and can be suitably used for manufacturing a device that requires high reliability. Further, the method of the present invention is low in cost because an expensive device such as a vacuum device is unnecessary. Further, the polycrystalline silicon film formed by the method of the present invention has a main surface of (220) plane, and can be suitably used for manufacturing a solar cell.

[0025]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Synthesis Example 1 (Synthesis of Ni (CO) ₃ (SiF ₃ ) ₂ ) In a 200 mL eggplant flask, 6.4 g of nickel (0.1 g) was added.
1 g / atm), toluene 40 g (0.44 mol),
68.1 g (0.4 mol) of hexafluorodisilane was weighed and cooled to -196 ° C for 2 hours. The deposited reddish brown solid was heated and melted, excess toluene and hexafluorodisilane were removed under reduced pressure, and the obtained black powder was washed twice with 40 ml of toluene. Further, the mixture was filtered under nitrogen to obtain a pale yellow filtrate. The solvent of the pale yellow solution was removed under reduced pressure to obtain 0.2 g of a pale yellow solid. The melting point of this product was 95 ° C., and ¹ H-NMR measured in a deuterated chloroform solvent showed peaks at 2.5 (s, 3H) and 6.8 ppm (s, 5H), and the product had (η ⁶ − It was shown to be C ₆ H ₅ CH ₃ ) Ni (SiF ₃ ) ₂ . Then, 0.05 g of (η ⁶ -C ₆ H ₅ CH
₃ ) Ni (SiF ₃ ) ₂ was weighed in a 100 mL 2-necked eggplant flask, the container was replaced with carbon monoxide to fill the container, and the mixture was reacted under atmospheric pressure for 1 hour. Further, toluene produced as a by-product was removed under reduced pressure to obtain a white product. The IR spectrum of the product showed absorption of stretching vibration of C = O at 2100 cm ^-1 , indicating that the product was Ni (CO) ₃ (SiF ₃ ) ₂ .

Synthesis Example 2 (Synthesis of cyclosilane) Install a thermometer, condenser, dropping funnel and stirring device.
Argon gas in a 4-liter flask with a capacity of 2 L attached
After replacement with 1.5 L of dry tetrahydrofuran
Charge 27.4g of lithium metal and bubble with argon gas.
I ringed. Add to this solution agitating under ice-cooling while stirring.
Add 500 g of phenyldichlorosilane from the dropping funnel.
It was The reaction was continued until the lithium metal disappeared completely.
After that, the reaction mixture is poured into ice water to precipitate the reaction product.
It was The precipitate was filtered off, washed well with water, and then washed with cyclone.
Washing with hexane gave 208 g of product. This product
When analyzed by high performance liquid chromatography,
Phenyl cyclopentasilane and undecaphenyl cyclo
Hexasilane mixture with a mixing ratio of 10/1 (weight
Ratio). Then, add 3 L of the frass, replaced with argon.
190 g of the above product and 2000 mL of toluene
Then, add 15 g of aluminum chloride and add hydrogen chloride gas.
Introduced.¹H-NMR replaces phenyl group with chlorine
After confirming that the chlorine atom was
1 equivalent of lithium aluminum hydride for each
In addition, reduction reaction was performed. Aluminization generated by reaction
Silane compound 16 reduced by removing compound
g was obtained. This one is²⁹Si-NMR, IR spectrum
Tol and gas chromatographic analysis₅
H₁₀And Si₆H ₁₂In a mixture (10/1 by weight)
I knew there was something.

Example 1 Formation of amorphous silicon 4 g of the cyclosilane obtained in Synthesis Example 1 above was mixed with toluene 1
Membrane of 0.2 micrometer dissolved in 0 g
Prepare a coating solution of cyclosilane by filtering with an ilter,
On a quartz substrate by dip coating in an argon atmosphere
A coating film of cyclosilane was formed on. About coated substrate,
After evaporating the solvent in an argon atmosphere, at 5O 0 C 5
Heat for minutes to form a silicon film with metallic luster on the substrate
did. The film thickness of this silicon film was 1500Å. This
When the ESCA spectrum of the silicon film of
A peak was observed at 99 eV. This peak is 2p of Si
Be assigned to orbit. In addition, the Raman scattering scan of this silicon film
The vector must be 100% amorphous silicon.
showed that. Conversion of amorphous silicon to polycrystalline silicon In a 300 mL eggplant-shaped flask in which nitrogen was replaced,
Synthesized Ni (CO) _Three(SiF_Three)_Two  10 mg
After dissolving in 200 mL of Ruen, 0.05 μm men
Filtered with a blanc filter and Ni (CO)_Three(Si
F_Three)_TwoA solution was prepared. Amorpha produced above
Ni (CO) on silicon dioxide under nitrogen_Three(Si
F_Three)_TwoSpin coating the solution to form a 5Å film thickness
did. Then, it was baked at 450 ° C. for 1 hour. In this way
The Raman scattering spectrum of the obtained silicon film is 520c.
m^-1Shows a sharp peak in the
It was shown that the silicon was converted to polycrystalline silicon.

[0028] Example _{2 Ni (CO) 3 (SiF} 3) 2 / cyclosilanes synthesized _Ni in Preparation Synthesis Example 1 composition _{(CO) 3 (SiF 3)} 2 5
90 mg of 0 mg and 10 g of cyclosilane synthesized in Synthesis Example 2
g of toluene and then filtered through a 0.2 μm membrane filter to obtain Ni (CO) ₃ (S
A mixed solution of iF ₃ ) ₂ and cyclosilane was prepared. Formation of Polycrystalline Silicon The mixed solution of Ni (CO) ₃ (SiF ₃ ) ₂ and cyclosilane prepared above was applied to a quartz substrate by spin coating under an argon atmosphere. With respect to the coated substrate, after evaporating the solvent in an argon atmosphere, the coated substrate was heated at 450 ° C. for 1 hour to form a silicon film having a metallic luster on the substrate. The thickness of this silicon film was 1.0 μm. When the ESCA spectrum of this silicon film was measured, S
A peak assigned to the 2p orbital of i was observed at 99 eV. The Raman scattering spectrum of this silicon film is 5
A sharp peak was shown at 20 cm ⁻¹ , indicating that a polycrystalline silicon film was formed.

[0029]

According to the present invention, unlike a method such as a CVD method or a sputtering method which requires a complicated and expensive vacuum system apparatus, a polycrystalline silicon film is formed on a substrate by a simple operation or apparatus. Methods and compositions therefor are provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hitoshi Kato             2-11-21 Tsukiji, Chuo-ku, Tokyo J             Within SRL Co., Ltd. F term (reference) 4G072 AA01 BB09 BB12 GG03 HH01                       HH33 JJ34 NN01 UU02                 4J038 AA011 HA131 PB09                 5F051 AA03 CB13 CB24 CB29

Claims (6)

[Claims] 1. At least one compound selected from the following formulas (1) to (3), Ni (CO) ₄ . ． ． (1) Ni (CO) ₃ (SiF ₃ ) ₂ . ． ． _{(2) Ni (CO) (} PF 3) 3. ． ． A composition for polycrystallizing amorphous silicon, which contains (3) and a solvent. 2. At least one compound selected from the following formulas (1) to (3), Ni (CO) ₄ . ． ． (1) Ni (CO) ₃ (SiF ₃ ) ₂ . ． ． _{(2) Ni (CO) (} PF 3) 3. ． ． (3) and compounds represented by the following formula (4) Si _n R _m . ． ． (4) (wherein, plural R's each independently represent a hydrogen atom, an alkyl group, a phenyl group or a halogen atom, and n is 3
It is the above integer, and m is an integer of n to 2n + 2. )
A composition containing: 3. The composition according to claim 2, wherein the composition is for use in polycrystallizing amorphous silicon. 4. The composition according to claim 2, wherein the composition is for forming polycrystalline silicon on a substrate.
The composition according to. 5. A method for polycrystallizing amorphous silicon, which comprises coating the composition according to claim 1 on amorphous silicon and then heat treating the composition. 6. A method for forming polycrystalline silicon, which comprises applying the composition according to claim 4 onto a substrate and then performing a heat treatment.