JP2001253706A - Silylcyclopentasilane and application thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new silane compound useful as a radical polymerization initiator of cyclopentasilane and vinyl monomer. SOLUTION: Silylcyclopentasilane is provided and is used as the radical polymeraization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel compound, monosilylcyclopentasilane, and its use.

[0002]

2. Description of the Related Art Conventionally, as a method of forming an amorphous silicon film or a polysilicon film, thermal CVD (Chemical Vapor D) of monosilane gas or disilane gas is used.
(e.g., deposition), plasma CVD, optical CVD, and the like.
(J. Vac. Sci. Technology., Vol. 14, 1)
082 (1977)), and amorphous silicon is manufactured by plasma CVD (Solid State C).
om., Vol. 17, p. 1193 (1975)), and is used for manufacturing liquid crystal display devices having thin film transistors, solar cells, and the like.

However, in the formation of a silicon film by the CVD method, further improvements have been awaited in the following points in terms of process. Since a gas phase reaction is used, silicon particles are generated in the gas phase, so that the production yield due to contamination of the apparatus and generation of foreign matter is low. Since the raw material is gaseous, it is difficult to obtain a substrate with a uniform thickness on a substrate having an uneven surface. Low productivity due to slow film formation rate. The plasma CVD method requires a complicated and expensive high-frequency generator or vacuum device. In addition, in terms of material, since gaseous silicon hydride having high toxicity and reactivity is used, not only is there a difficulty in handling, but since it is gaseous, a closed vacuum device is required. In general, these devices are large-scale and not only expensive, but also consume a large amount of energy in a vacuum system or a plasma system, which leads to an increase in product cost.

In recent years, a method of applying liquid silicon hydride without using a vacuum system has been proposed. JP-A-1-29661 discloses a method of forming a silicon-based thin film by liquefying and adsorbing a gaseous raw material on a cooled substrate and reacting it with chemically active atomic hydrogen. However, there are the following problems. Since silicon hydride as a raw material is continuously vaporized and cooled, not only a complicated apparatus is required, but also it is difficult to control the film thickness. Also, Japanese Patent Application Laid-Open No. 7-267621 discloses a method of applying low molecular weight liquid silicon hydride to a substrate. However, this method has a drawback in handling because the system is unstable. Since it is in a liquid state, it is difficult to obtain a uniform film thickness when applied to a large-area substrate.

On the other hand, an example of a solid silicon hydride polymer is reported in British Patent GB-2077710A, but it cannot be formed into a film by coating because it is insoluble in a solvent. Further, Japanese Patent Application Laid-Open No. 9-237927 discloses a method of applying a polysilane solution on a substrate and thermally decomposing the silicon film to release a silicon film for the purpose of manufacturing a solar cell. However, in the case of a silicon compound containing carbon, a large amount of carbon remains as an impurity in thermal decomposition or photolysis by ultraviolet irradiation, so that it is difficult to obtain an amorphous or polycrystalline silicon film having excellent electric characteristics. Further, JP-A-60-24261 discloses the following formula:

[0006]

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(Where n is 3, 4 or 5;
Is a H or SiH ₃ ) gaseous atmosphere of a cyclic silane compound and a halogen compound, which is formed in a deposition chamber in which the support is disposed, and heat energy is applied to these compounds to form silicon on the support. A method for forming a silicon deposited film by thermal CVD for forming a deposited film containing atoms is disclosed. In the above publication, the cyclic silane compound represented by the above formula is specifically disclosed by five kinds of chemical structural formulas. However, with respect to these cyclic compounds, not only the identification data of the compounds but also their production methods are not described in the publication. On the other hand, with respect to the method for producing polysilane, it can be produced by using the monomers having the respective structural units as raw materials, for example, by the following method.
(A) A method of dehalogenating polycondensation of halosilanes in the presence of an alkali metal in an amount equivalent to a halogen atom (so-called “Kipping method”, J. Am. Chem. Soc., 1
10, 124 (1988), Macromole
cures, 23, 3423 (1990)); (b)
A method of subjecting halosilanes to dehalogen condensation polymerization by electrode reduction (J. Chem. Soc., Chem. Commun.,
1161 (1990), J. Chem. Soc., Ch.
em. Commun., 897 (1992));
(C) A method of subjecting hydrosilanes to dehydrocondensation polymerization in the presence of a metal catalyst (JP-A-4-334551):
(D) A method by anionic polymerization of disilene cross-linked with biphenyl or the like (Macromolecules, 23
Volume, 4494 (1990)). (E) After synthesizing a cyclic silicon compound substituted with a phenyl group or an alkyl group by the above method, a known method (for example, Z. anorg.a
Chem., 459, p. 123 (1979)) to obtain a hydro-substituted or halogen-substituted product. These halogenated cyclosilane compounds can be prepared by known methods (for example, Mh. Chem. Vol. 106,
503, 1975), (Z. Anorg. All)
g. Chem. Vol. 621, p. 1517, 1995), (J. Chem. Soc., Chem. Commu).
n., p. 777, 1984). As described above, polysilane is generally synthesized by a polycondensation reaction, but a step of purifying the synthesized polymer is necessary because polycondensation produces a salt or the like as a by-product. Recently, Macromolecules (Macromole)
cules, 27, 2360, 1994)
It is disclosed that phenyl nanomethylcyclopentasilane 1 undergoes anionic ring-opening polymerization to produce poly (phenyl nanomethylpentasilanylene) 2. Unlike the above-mentioned polycondensation reaction, this ring-opening polyaddition reaction of a cyclic monomer has no by-product, and is an excellent method for synthesizing high-purity polysilane. Such ring-opening addition polymerization is particularly preferable in applications requiring high purity such as electronic materials. However, in the above-mentioned monomers, carbon atoms such as methyl group and phenyl group are bonded to silicon atoms, and even if such polysilane is thermally decomposed, only polycarbosilane with carbon incorporated is generated, and silicon for semiconductor Can not get.

[0008]

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[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel compound, silylcyclopentasilane, composed of only silicon atoms and hydrogen atoms. Another object of the present invention is to provide a use of silylcyclopentasilane as a radical polymerization initiator. Still another object of the present invention is to allow silylcyclopentasilane to undergo radical ring-opening addition polymerization of cyclopentasilane, and to be capable of deriving a high-purity, solvent-soluble polysilane without by-producing a salt or the like. An object of the present invention is to provide a use of silylcyclopentasilane, which is composed of only atoms and hydrogen atoms, and can be easily derived into metal silicon for a semiconductor by thermal decomposition or photolysis.
Still other objects and advantages of the present invention will become apparent from the following description.

[0010]

According to the present invention, the above objects and advantages of the present invention are firstly achieved by the following formula:

[0011]

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This is achieved by the silylcyclopentasilane represented by the formula:

The above objects and advantages of the present invention are, second,
This is achieved by using silylcyclopentasilane as a radical initiator for the ring-opening addition polymerization of cyclopentasilane. Thirdly, the above objects and advantages of the present invention are achieved by the use of silylcyclopentasilane as a radical initiator for ring-opening addition polymerization of cyclopentasilane.

A method for synthesizing the silylcyclopentasilane of the present invention will be described. Regarding a method for synthesizing a silylcyclopentasilane skeleton, J. Organomet. Chem., 197
Five years, vol. 100, p. 127 reported that skeletal rearrangement to trimethylsilylnonamethylcyclopentasilane by treatment of dodecamethylcyclohexasilane with an aluminum chloride catalyst was reported. It has been reported that rearrangement to a silylcyclopentasilane skeleton is stable. However, the silylcyclopentasilane skeleton has all substituents of a methyl group, and no hydrogen-substituted product has been reported. It is known that polysilane having a carbon atom such as a methyl group in silicon is converted into carbosilane in which carbon is incorporated by a dehydrogenation reaction by thermal decomposition, and cannot be converted into metal silicon of a semiconductor.

As a method for converting a phenyl group bonded to a silicon atom into a chlorine atom or a hydrogen atom, known methods (for example, Mh. Chem., Vol. 106, p. 503, 1
975), (Z. Anorg. Allg. Chem.
621, p. 1517, 1995), (J.C.
Chem. Soc., Chem. Commun., 777, 19
1984).

The present inventors conceived to convert the silicon-bonded phenyl group of dodecaphenylcyclohexasilane into a hydrogen atom, treated with an aluminum chloride catalyst as a Lewis acid, rearranged the skeleton, and subsequently chlorided. By introducing hydrogen gas to perform chlorination and further reducing this with lithium aluminum hydride, all the phenyl group substituents of the cyclohexasilane skeleton are converted to hydrogen atoms, and at the same time, converted to the silylcyclopentasilane skeleton. Rearrangement was successful, and silylcyclopentasilane comprising only silicon atoms and hydrogen atoms of the present invention was successfully developed.

The silylcyclopentasilane comprising only silicon and hydrogen atoms according to the present invention has a chemical property capable of undergoing radical ring-opening addition polymerization of cyclopentasilane comprising only silicon and hydrogen atoms to convert it into a solvent-soluble polysilane. Was found to have. The polysilane solution thus obtained has good coatability and can form a good polysilane film on the substrate, and the polysilane film can be converted to a metallic silicon film by a dehydrogenation reaction by thermal decomposition or photolysis.

The silylcyclopentasilane of the present invention can be used as a radical polymerization initiator for cyclopentasilane. That is, even if cyclopentasilane alone is dissolved in a hydrocarbon solvent such as toluene, and the solution is heated to about the boiling point of the solvent, the polymerization reaction does not proceed. On the other hand, cyclopentasilane and a small amount thereof, for example, about 1% by weight of monosilylcyclopentasilane are similarly dissolved in a hydrocarbon solvent such as toluene so that the polymerization reaction of cyclopentasilane proceeds smoothly. Become. This is presumed to be due to a mechanism in which the silyl group (SiH ₃ ) of monosilylcyclopentasilane is radically cleaved and the generated radical initiates polymerization of cyclopentasilane. When monosilylcyclopentasilane is used as a radical polymerization initiator of cyclopentasilane, it is preferably 0.01 to 30 parts by weight, more preferably 0.5 to 20 parts by weight, based on 100 parts by weight of cyclopentasilane.
Used in parts by weight.

A polymer of cyclopentasilane with silylcyclopentasilane, which is a target compound of the present invention, can be easily synthesized by the following method. For example, diphenyldichlorosilane is cyclized with magnesium or metal lithium in tetrahydrofuran to produce decaphenylcyclopentasilane and dodecaphenylcyclohexasilane, and then the mixture is treated with aluminum chloride in toluene and subsequently hydrogen chloride By treating with gas and then with lithium aluminum hydride and silica gel, cyclopentasilane can be produced from decaphenylcyclopentasilane and silylcyclopentasilane with skeleton rearrangement from dodecaphenylcyclohexasilane. . By heating the solution of this mixture of silylcyclopentasilane and cyclopentasilane, a solvent-soluble polysilane solution is obtained.

The polysilane solution synthesized in this manner can form a polysilane film by a coating method. As a coating method, a method such as a spin coating method, a roll coating method, a curtain coating method, a dip coating method, a spray method, and an ink jet method can be used. The application is generally performed at a temperature above room temperature. If the temperature is lower than room temperature, the solubility of the silicon compound may be reduced and the silicon compound may be partially deposited.
The application is preferably performed in an atmosphere of an inert gas such as nitrogen, helium, or argon. Further, a mixture containing a reducing gas such as hydrogen as necessary is preferable. When the spin coating method is used, the rotation speed of the spinner is determined by the thickness of the thin film to be formed and the composition of the coating solution, but is generally 100 to 5000 rpm, preferably 300 to
3000 rpm is used. After the application, a heat treatment is performed to remove the solvent. The heating temperature varies depending on the type of solvent used and the boiling point, but is usually 100 ° C to 200 ° C.
It is. The atmosphere is the same as the above coating process, nitrogen, helium,
It is preferable to carry out in an inert gas such as argon.

The polysilane film thus obtained can be converted to a metal silicon film by a dehydrogenation reaction by heat treatment or light treatment. In the case of heat treatment, the reached temperature is generally about 550 ° C
At the following temperatures, an amorphous silicon film is obtained, and at higher temperatures, a polycrystalline silicon film is obtained. When it is desired to obtain an amorphous silicon film, the temperature is preferably 300 ° C. to 550 ° C.
° C, more preferably 350 ° C to 500 ° C.
If the ultimate temperature is lower than 300 ° C., thermal decomposition of the silicon compound does not sufficiently proceed, and a silicon film having a sufficient thickness may not be formed. The atmosphere for the heat treatment is preferably an atmosphere containing an inert gas such as nitrogen, helium, or argon, or a reducing gas such as hydrogen. Also,
In the case of light treatment, the light source used is a low-pressure or high-pressure mercury lamp, deuterium lamp or argon,
In addition to discharge light of rare gases such as krypton and xenon, YAG
Laser, argon laser, carbon dioxide laser, Xe
F, XeCl, XeBr, KrF, KrCl, ArF,
An excimer laser such as ArCl can be used as a light source. These light sources include 10-5,
000W output is preferable, and 100 ~ 1,000
W is more preferred. The wavelength of these light sources is not particularly limited as long as it absorbs silicon compounds to some extent, but is preferably 170 nm to 600 nm. The use of laser light is particularly preferable in terms of conversion efficiency to a silicon film. The temperature during these light treatments is usually about room temperature, and the atmosphere is preferably in the above-mentioned inert gas, but can be appropriately selected according to the purpose.

The silylcyclopentasilane of the present invention can be used not only as a radical polymerization initiator of cyclopentasilane, but also as a vinyl monomer radical initiator. In this case, since a vinyl polymer having a silicon atom at the terminal of the polymer molecule is obtained, it is possible to derive a block or random copolymer of such a vinyl polymer and a silicone-based polymer.

Examples of the above vinyl monomer include styrene, α-methylstyrene, o-vinyltoluene, m-
Vinyltoluene, p-vinyltoluene, p-chlorostyrene, o-methoxystyrene, m-methoxystyrene,
aromatic vinyl compounds such as p-methoxystyrene; methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, i-propyl acrylate, i-propyl methacrylate, n-butyl acrylate, n- Butyl methacrylate, i-butyl acrylate, i-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, t-
Butyl acrylate, t-butyl methacrylate, 2-
Acrylates or methacrylates such as hydroxyethyl acrylate and 2-hydroxyethyl methacrylate; and aliphatic conjugated dienes such as 1,3-butadiene, isoprene and chloroprene can be mentioned.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 (1) After replacing the inside of a 2-L four-necked flask equipped with a thermometer, a condenser, a dropping funnel and a stirrer with argon gas, 1.5 L of dry tetrahydrofuran and lithium metal 27 were removed. 0.4 g was charged, and the mixture was bubbled with argon gas. To this suspension, 500 g of diphenyldichlorosilane was added from a dropping funnel while stirring under ice cooling. After the reaction was continued until lithium metal completely disappeared, the reaction mixture was poured into ice water to precipitate a reaction product. The precipitate was separated by filtration, washed well with water, and then washed with cyclohexane. The crude product was recrystallized from ethyl acetate to obtain 216 g of undecaphenylcyclohexasilane. The structure of this is TOF-
Confirmed by MS, NMR and IR. Next, 100 g of this dodecaphenylcyclohexasilane and 1000 ml of toluene were charged into a 2 L flask, and 50 ml of aluminum chloride was added.
g, and the mixture was stirred at room temperature for 5 hours in an argon gas atmosphere, and then hydrogen chloride gas was introduced until the phenyl group disappeared. The product obtained in this reaction is ²⁹ Si-NM
The R and IR spectra indicated that the product was dodecachlorocyclohexasilane. Next, 42 g of lithium aluminum hydride was added to 500 ml of diethyl ether.
The above reaction mixture was slowly added to the liquid that had become turbid, and stirring was continued at room temperature for 12 hours. The reaction mixture was filtered to obtain a colorless and transparent silylcyclopentasilane solution.

(2) The obtained silylcyclopentasilane is an oil at room temperature and its infrared absorption spectrum is shown in FIG.
Shown in It is composed solely of silicon and hydrogen atoms and has a relatively simple infrared spectrum of 2125 cm ^-1.
A sharp peak attributable to stretching vibration of silicon-hydrogen bond is observed, and peaks at 985 cm ^-1 and 863 cm ^{-1 due} to stretching vibration of silicon-silicon are observed. Also,
The mass spectrum is shown in FIG. A molecular ion peak is observed at m / e = 180, which indicates that the molecular weight is 180. In addition, a peak at m / e = 148 was strongly detected, and this peak was attributed to a fragment in which one monosilane (SiH ₄ ) was eliminated from the silylcyclopentasilane molecule.
Further, the peak at m / e = 116 is assigned to a fragment in which two monosilanes are eliminated from the silylcyclopentasilane molecule.

The chemical properties of silylcyclopentasilane include hydrocarbon solvents such as benzene, toluene, xylene, hexane, cyclohexane, indane and decahydronaphthalene; ether solvents such as diethyl ether, tetrahydrofuran, monoglyme and diglyme;
It is easily soluble in ordinary organic solvents such as ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone, and can be dissolved at any ratio.

As described above, silylcyclopentasilane is a colorless and transparent oily substance at room temperature and is very stable in an inert atmosphere such as argon or nitrogen. Converted to siloxane structure. Further, when silylcyclopentasilane is exposed to heat of 300 ° C. or more in an inert atmosphere, a dehydrogenation reaction occurs and is converted into amorphous metal silicon. Further, this silylcyclopentasilane generates a radical by a heat treatment at about 100 ° C., and can be converted into a solvent-soluble polysilane through radical ring-opening polymerization of the cyclopentasilane. Further, radical polymerizable monomers such as ordinary vinyl compounds such as acrylic compounds can also be polymerized.

Gas chromatography of silylcyclopentasilane and cyclopentasilane was carried out using Chr as a carrier.
Omosorb W (60-80 mesh) was obtained by using silicone-based OV-17 (5%) as a liquid phase and developing with helium gas at 120 ° C. (see FIGS. 5 and 6).

Example 2 After replacing the inside of a three-neck flask with a capacity of 2 L equipped with a thermometer, a condenser and a stirrer with argon gas, 1.5 L of dry tetrahydrofuran and 3.8 g of lithium metal were charged. Bubbling was performed with argon gas. Among them, the method of Hengge et al. (J. Organ
Omet. Chem., 1981, 212, 155
Octaphenylcyclobutanesilane 1
By adding 00 g and stirring at room temperature for 5 hours, a dianion in which octaphenylcyclobutasilane was opened was generated. While stirring the dark brown dianion solution at room temperature, 50 g of triphenylsilyldichlorosilane was added and reacted. The reaction mixture was poured into 2 liters of ice water to precipitate the product. The product is filtered, washed with water, further washed with cyclohexane, and dried under reduced pressure to obtain triphenyloctaphenylcyclopentasilane 10
8 g were obtained. 50 g of triphenyloctaphenylcyclopentasilane thus obtained was dissolved in 500 ml of toluene, 5 g of anhydrous aluminum chloride was added, and hydrogen chloride gas was reacted until the phenyl group disappeared. Next, the reaction product solution was added to a solution of 20 g of lithium aluminum hydride in 100 ml of diethyl ether and stirred at room temperature for 12 hours. The reaction mixture was treated with silica gel and concentrated to obtain a colorless and transparent oil. Its IR and MS spectra were consistent with the product of Example 1 above.

Reference Example 1 50 g of decaphenylcyclopentasilane and 500 ml of toluene were charged into a two-liter four-necked flask equipped with a thermometer, a condenser and a stirrer. 5 g of anhydrous aluminum chloride was added to this reaction solution, and hydrogen chloride gas was further reacted at room temperature for 5 hours. NM of reaction system
The disappearance of the phenyl group was confirmed by R. Next, this reaction mixture was added to a separately prepared solution of 20 g of lithium aluminum hydride in 100 ml of diethyl ether and stirred at room temperature for 12 hours. The reaction mixture was treated with silica gel and concentrated to obtain cyclopentasilane as a colorless and transparent oil. FIG. 3 shows the IR spectrum and FIG. 4 shows the MS spectrum.

Example 3 One of the silylcyclopentasilanes obtained in Example 1 above
10 g of a 0% toluene solution and 90 g of a 10% toluene solution of cyclopentasilane obtained in Reference Example 1 were mixed. FIG. 5 shows a gas chromatogram of the solution immediately after mixing.
FIG. 6 shows a gas chromatogram of a toluene solution of cyclopentasilane for comparison. After the mixed solution was stirred at 50 ° C. for 12 hours in an argon atmosphere, a gas chromatogram was measured again. As a result, neither a cyclopentasilane peak nor a silylcyclopentasilane peak was observed, and a ring-opening polymerized high boiling polysilane was obtained. It turned out that it was converted to. This solution was spin-coated at 2,000 rpm on a glass substrate in an argon atmosphere to obtain a colorless and transparent polysilane film. This polysilane film is 500
When calcined at ℃, a silicon film having a metallic luster was obtained. When the thickness of the silicon film was measured by an alpha step, it was 1,500 angstroms. Further, when the ESCA of this silicon film was measured, only a peak derived from Si _2p was observed at 99 eV, and no other peak was observed. FIG. 7 shows the Raman spectrum of this silicon film. As a result of analysis by waveform separation, Raman lines are attributed to the TO phonon around 480 cm ^-1 is also Raman lines attributable to LO phonons around 420 cm ^-1 is in the vicinity of further 320 cm ^-1 L
Raman line attributed to A phonon was observed, and 100%
It was an amorphous silicon film.

Example 4 After replacing the inside of a three-necked flask equipped with a thermometer, a condenser, and a stirrer with a 200 ml capacity with argon gas, 80 g of toluene and 20 g of methyl methacrylate monomer were charged. 0.1 g of the silylcyclopentasilane obtained in
Stirred for hours. 1,000 ml of methanol was added to the reaction mixture.
To precipitate the polymer. This was filtered and dried under reduced pressure to obtain 11.5 g of polymethyl methacrylate. This is dissolved in tetrahydrofuran and GP
When the molecular weight was measured by C, the weight average molecular weight in terms of polystyrene was 45,000.

Example 5 In Example 3, the silylcyclopentasilane obtained in Example 1 was replaced with the silylcyclopentasilane obtained in Example 2 to convert it to a high boiling polysilane.
Otherwise, a polysilane film and a metallic silicon film were formed in the same manner as in Example 3. These analysis results were exactly the same as in Example 3.

Comparative Example 1 In Example 4, 0.1 g of silylcyclopentasilane was used.
In place of the cyclopentasilane obtained in Reference Example 1,
The polymerization of methyl methacrylate was attempted in the same manner as in Example 4 except that 1 g was used, but the polymerization reaction did not proceed, and the reaction mixture was poured into methanol, but no precipitate was obtained.

[Brief description of the drawings]

FIG. 1 is an infrared absorption spectrum of silylcyclopentasilane.

FIG. 2 is a mass spectrum diagram of silylcyclopentasilane.

FIG. 3 is an infrared absorption spectrum diagram of cyclopentasilane.

FIG. 4 is a mass spectrum diagram of cyclopentasilane.

FIG. 5 is a GLC (gas chromatogram) of a toluene solution of a mixture of cyclopentasilane and silylcyclopentasilane (weight ratio: 9/1).

FIG. 6: GLC of a toluene solution of cyclopentasilane
(Gas chromatogram).

FIG. 7 is a Raman spectrum diagram of a silicon film.

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Claims (3)

[Claims] [Claim 1] The following formula: A silylcyclopentasilane represented by the formula: 2. Use of silylcyclopentasilane as a radical initiator for ring-opening polymerization of cyclopentasilane. 3. Use of a silylcyclopentasilane as a polymerization initiator for a vinyl monomer.