KR100343552B1 - A method of preparing for polymethylsilsesquioxane copolymer with well dispersed dimethysiloxane unit - Google Patents

Abstract

The present invention relates to a method for producing a polymethylsilsesquioxane copolymer containing uniformly dispersed dimethylsiloxane, and more particularly, to a heat treatment of a mixed solution of methyltrialkoxysilane and dimethyldialkoxysilane in a specific molar ratio. After obtaining a ligand exchange-reacted alkoxysilane compound, and then sol-gel reaction using a mixed solvent of THF and toluene and neutralized with ammonia water, each of the dimethylsiloxane molecules were dispersed uniformly at the molecular level in the methylsiloxane skeleton. A method for producing a polymethylsilsesquioxane copolymer.

The copolymer prepared by the method of the present invention has a high heat resistance and is expected to be flexible due to an increase in the content of methyl groups, and thus requires a very low dielectric constant value through a spin on glass (SOG) and chemical mechanical polishing (CMP) process. It can be used as the base material of the interlayer insulating film material.

Description

A method of preparing for polymethylsilsesquioxane copolymer with well dispersed dimethysiloxane unit}

The present invention relates to a method for producing a polymethylsilsesquioxane copolymer containing uniformly dispersed dimethylsiloxane, and more particularly, to a heat treatment of a mixed solution of methyltrialkoxysilane and dimethyldialkoxysilane in a specific molar ratio. After obtaining a ligand exchange-reacted alkoxysilane compound, and then sol-gel reaction using a mixed solvent of THF and toluene and neutralized with ammonia water, each of the dimethylsiloxane molecules were dispersed uniformly at the molecular level in the methylsiloxane skeleton. A method for producing a polymethylsilsesquioxane copolymer.

The copolymer prepared by the method of the present invention has a high heat resistance and is expected to be flexible due to an increase in the content of methyl groups, and thus requires a very low dielectric constant value through a spin on glass (SOG) and chemical mechanical polishing (CMP) process. It can be used as the base material of the interlayer insulating film material.

Low-k interlayer materials have been attracting attention along with copper conductors having excellent electrical conductivity as materials necessary for minimizing signal delay and interference due to capacitance of insulating materials in high integrated semiconductor wiring. In particular, in semiconductor designs with a circuit width of 0.18 μm or less, the introduction of aluminum wiring, copper wiring in silicon oxide (SiO ₂ ) insulating films, and low dielectric constant interlayer insulating materials of dielectric constant 3 or less for high speed and low power consumption. This is inevitable.

One of the materials considered as such a low dielectric constant interlayer insulating film is polymethylsilsesquioxane, in which nanopores are easily introduced. However, due to the brittleness of the polymethylsilsesquioxane, there is a possibility that fine cracks occur during the semiconductor manufacturing process.

In general, silicon oxide is also known to be very brittle material. According to the reference of silicon chemistry, the introduction of organic methyl group instead of oxygen in (SiO ₄ ) _n bonded structure has been reported to increase the flexibility. However, although methylsilsesquioxane having one methyl group bonded to silicon has a slight increase in flexibility compared to silicon oxide, there is a risk of microcracks due to external forces that may be received during semiconductor manufacturing processes including CMP and heat treatment processes. Still remains. In order to prevent this, it is necessary to include a methyl group further with respect to a silicone group.

One such method is a method of introducing a copolymer of dimethylsiloxane into methylsilsesquioxane and copolymerizing it, and various methods have been studied.

First, Japanese Patent No. Hei 2-279779 has attempted to add flexibility by adding dimethyldisiloxane to methyl sesquioxane, in which the methylsiloxane oligomer and dimethyl oligomer are simply mixed with an organic solvent in a coating solution. Is preparing. However, the method has a problem in heat resistance because the dimethyl siloxane is not bonded to the methyl siloxane at the molecular level, and there is a problem to use as a low-k substrate having a heat treatment process of 400 ° C. or higher.

As another method, a sol-gel method is used in which two starting materials are mixed and hydrolyzed at a predetermined ratio, followed by condensation polymerization to copolymerize two different alkoxysilanes. However, the method has a limitation in synthesizing a copolymer in a form in which the starting materials are very uniformly bonded to each other due to the difference in hydrolysis of the starting materials. For example, in the case of a copolymer obtained by mixing sol-gel method with methyltrimethoxysilane and dimethyldimethoxysilane in a predetermined ratio, there is a difference in the hydrolysis rate of the two starting materials with respect to water. Since the siloxane groups are not uniformly dispersed and bound, the dimethylsiloxane groups are rearranged by thermal energy at a high temperature of 300 ° C. or higher, thereby partially producing a tetramer or octamer-type ring compound and causing thermal decomposition.

In addition, Japanese Patent Laid-Open No. 9-324051 discloses a method of washing an acid with water by first removing THF used as a solvent after copolymer synthesis and then adding toluene. However, the process is a multi-step process, not only requires the use of a large amount of water to wash the acid, but also requires a long time to separate the water layer and the toluene layer.

Accordingly, the present inventors have tried to solve the problem of thermal decomposition of a part by the generation of fine cracks and the formation of cyclic compounds of the conventional polymethylsilsesquioxane. As a result, the problem of fine cracks is solved by copolymerizing dimethylsiloxane to methylsiloxane in a constant ratio, thereby adding flexibility of the polymethylsilsesquioxane base material, and minimizing the difference in hydrolysis rate with respect to water. Starting materials having different ligands were heat-treated before and after 100 ° C. to prepare a mixture of alkoxysilane compounds in which ligands were exchanged with each other (see FIG. 1). The novel and unique method of synthesizing coalescing has been realized to complete the present invention. In addition, in the process of removing the acid used as a catalyst for the sol-gel reaction after the copolymer synthesis, a very simple process of neutralizing with ammonia water in advance and washing with direct addition of water to the mixed solvent and a method of removing the acid with a small amount of water are also invented. Was done.

Accordingly, it is an object of the present invention to provide a method for preparing a polymethylsilsesquioxane copolymer in which chemical bonds between methylsiloxane and dimethylsiloxane are bonded very uniformly at a molecular level, which is excellent in heat resistance and expected flexibility.

FIG. 1 shows a ²⁹ Si NMR spectrum showing a reaction product in which methyltriethoxysilane and dimethyldimethoxysilane were heat-treated at 100 ° C. for 24 hours to exchange ligands.

Figure 2 shows a ²⁹ Si NMR spectrum of the polymethylsilsesquioxane copolymer according to the present invention,

Figure 3 shows the TG-IR at 350 ℃ of the polymethylsilsesquioxane copolymer according to the present invention.

The present invention provides a method for producing a polymethylsilsesquioxane copolymer in which a dimethylsiloxane group is partially introduced,

A process for preparing a ligand-exchanged alkoxysilane compound by heat-treating a mixed solution of methyltrialkoxysilane: dimethyldialkoxysilane in a molar ratio of 0.95: 0.05 to 0.70: 0.30 at a temperature of 70 to 150 ° C:

Performing a sol-gel reaction of the ligand exchanged alkoxysilane compound with water and an acid under a condition of 0 to 60 ° C. in a mixed organic solvent of tetrahydrofuran and toluene; And,

The method for producing a polymethylsilsesquioxane copolymer comprising a process of neutralizing the sol-gel reacted mixed solution to pH 6-7 by adding ammonia water.

In another aspect, the present invention is characterized by a polymethylsilsesquioxane copolymer prepared by the above method in which dimethylsiloxane is dispersed in one single unit in the methylsiloxane skeleton.

The present invention will be described in more detail as follows.

The present invention introduces a dimethylsiloxane group to methylsilsesquioxane for the purpose of improving the brittleness of polymethylsilsesquioxane (PMSSQ) to give flexibility, so that the methylsilsesquioxane and dimethylsiloxane groups are very uniform at the molecular level. The present invention relates to a method for preparing a polymethylsilsesquioxane copolymer which is bound together.

In particular, the present invention has a very high uniformity of the reaction product, there is no pyrolysis product even in the heat treatment of 200 ℃ or more, and unlike the conventional synthesis of THF and toluene in a separate step, the THF and toluene mixed with an organic solvent As a result, it has the characteristic of simplifying the process of removing the acid after synthesis of the copolymer.

Polymethylsilsesquioxane copolymer according to the present invention having the above characteristics can be represented by the following formula (1).

(CH ₃ ) _{1 + x} Si (O _nx ) (OH) _3-nx

In Chemical Formula 1, x is 0.05 to 0.3, and n is 0 to 3.

The polymethylsilsesquioxane copolymer represented by Chemical Formula 1 according to the present invention will be described in more detail based on the preparation method.

In the first process, silane compounds having different ligands are mixed in a constant molar ratio, and then heat-treated at a temperature of about 100 ° C. to carry out a ligand exchange reaction to prepare an alkoxysilane compound.

As the silane compound having different ligands used in the present invention, a mixed solution of methyltrialkoxysilane: dimethyldiakoxysilane having a molar ratio of 0.95: 0.05 to 0.70: 0.30 is used. In this case, when the mixing molar ratio of the starting materials is lower than the range, there is a problem in flexibility to improve brittleness, and when the range exceeds the range, there is a problem in that the heat resistance is low. As said methyltrialkoxysilane, what was chosen from methyltriethoxysilane, methyltrimethoxysilane, and methyltripropoxysilane is used. As the dimethyl dialkoxysilane, one selected from dimethyldimethoxysilane and dimethyldiethoxysilane is used.

When explaining the ligand exchange reaction according to the present invention in more detail, the silicon oil bath maintained in 70 ~ 150 ℃, more preferably 90 ~ 130 ℃ put the mixed solution used as the starting material in a thick glass tube to withstand pressure The alkoxysilane compound may be obtained by heat treatment in a bath for 5 to 40 hours, more preferably 10 to 25 hours, so that an exchange reaction occurs between two different ligands. At this time, when the heat treatment temperature is out of the range, there is a problem that the ligand exchange reaction between two different materials does not occur sufficiently.

In the second process, the alkoxysilane compound obtained in the above process is hydrolyzed and subjected to condensation polymerization to obtain a copolymer by a sol-gel method.

In the present invention, the alkoxysilane compound is added to an organic solvent in which tetrahydrofuran (THF) and toluene are mixed, followed by sol-gel reaction by adding water for hydrolysis reaction and acid as a hydrolysis and polycondensation reaction catalyst. Coalescing can be obtained.

The composition of the mixed solvent used in the present invention is 2-15 mol times, more preferably 4-10 mol times, THF relative to 1 mol of the ligand exchange-reacted starting material, and toluene is further added to the ligand-exchanged start. It was added to 2-15 mol times, more preferably 4-10 mol times with respect to 1 mol of raw materials, and it mixed so that it might become a mixed solvent which THF and toluene mixed. Then, water for the hydrolysis reaction is added at 1 to 4 mol times, more preferably 1.5 to 3.5 mol times with respect to 1 mol of the ligand exchanged starting material, and the acid used as a catalyst for the hydrolysis and polycondensation reaction is used. 0.001 to 0.1 mole times, more preferably 0.01 to 0.08 mole times, based on 1 mole of the ligand-exchanged starting material, and then 3 to 30 hours at 0 to 60 ° C, more preferably 10 to 40 ° C, more preferably 5 The sol-gel reaction is carried out for 20 hours. In this case, as the acid used as a catalyst in the present invention, an organic acid or an inorganic acid such as hydrochloric acid and nitric acid is used, more preferably nitric acid.

The final process is to complete the present invention by neutralizing the copolymer obtained in the above process, removing impurities and obtaining a final reaction product.

That is, the reaction solution is neutralized to pH 6-7 by adding ammonia water, the neutralized reaction solution is transferred to a separatory funnel and the ion exchanged water is doubled in a volume ratio to the reaction solution, shaken vigorously, and left to stand. The water is removed to wash the neutralized salt. Then, the trace amount of water dissolved in the upper organic solvent layer is dried. Then, the organic solvent layer was filtered in a filtration funnel, transferred to a 1-neck round flask, and the organic solvent was removed by distillation under reduced pressure to obtain a resin or a solid reaction product. The gel reaction catalyst can be more simply removed to obtain a stable polymethylsilsesquioxane copolymer.

As described above, the polysesquioxane copolymer according to the present invention is excellent in heat resistance because dimethylsiloxane is uniformly dispersed in methylsiloxane at the molecular level. In addition, an increase in the CH ₃ / Si ratio of the formula (1), that is, an increase in the content of dimethylsiloxane is expected to increase the flexibility accordingly.

Hereinafter, the present invention will be described in more detail based on the following examples. The following examples are merely illustrative of the present invention, and the present invention is not limited by the examples.

Example 1

36.02 g of methyltriethoxysilane and 2.53 g of dimethyldimethoxysilane are weighed into a 40 ml thick wall-glass tube and immersed in a silicon oil bath maintained at about 100 ° C. Kept for hours. The solution was transferred to a 1 L round flask, and 113.6 ml of THF and 149.1 ml of toluene were added thereto, and 10.02 g of ion-exchanged water and 1.05 g of 60% nitric acid were added thereto, followed by copolymerization with stirring at room temperature for 15 hours. 0.83 ml of a 20% ammonia solution was added to the copolymerized solution to neutralize the pH to 6-7. The neutralized reaction solution was transferred to a 1 L separatory funnel, and 500 ml of ion-exchanged water was added thereto, followed by vigorous shaking, followed by standing. After about 5 minutes, the water layer of the lower layer was removed from the two layers separated by the organic layer and the water layer, and about 20 g of MgSO ₄ powder was added to the upper layer and shaken vigorously to remove trace water. The solid phase dispersed in the organic layer was removed by filtration with No. 5 filter of Whatman filter paper, and the filtered organic layer was transferred to a 1 L round neck flask and the organic solvent was removed by vacuum distillation at a pressure of about 10 torr and the reaction product was recovered. At this time, about 14.8 g of a reaction product was obtained, and the average molecular weight was 1343 as a result of GPC analysis. At this time, the methyl triethoxysilane and dimethyldimethoxysilane was heat-treated at 100 ℃ for 24 hours to show the ²⁹ Si NMR spectrum for the ligand-exchanged reaction product is shown in Figure 1, generated through such ligand exchange reaction The ²⁹ Si NMR spectrum of the polymethylsilsesquioxane copolymer obtained is shown in FIG. 2. In addition, TG-IR at 350 ° C. of the prepared polymethylsilsesquioxane copolymer is shown in FIG. 3.

Example 2

Were obtained and are the reaction product was 13.7 g and the same procedure as example 1 except the starting raw material was used to form the silane methyl trimethoxy silane and dimethyl-die, was a result of GPC analysis-average molecular weight 1210.

Comparative example

36.02 g of methyltriethoxysilane and 2.53 g of dimethyldimethoxysilane are weighed into a 1 L round flask, and 113.6 ml of THF and 149.1 ml of toluene are added without heat treatment, and 10.02 g of ion-exchanged water and 1.05 g of 60% nitric acid are added thereto. The copolymerization reaction was carried out with stirring for 15 hours. Since the process is the same as in Example 1, it takes a long time to separate the water layer and the organic layer to remove the water in the lower layer after about 30 minutes. The reaction product thus obtained was 13.4 g, and the average molecular weight measured by GPC was 864.

Test Example

Take a part of the reaction product prepared in Examples 1 and 2 and Comparative Example, add a THF solution to dissolve the content of the reaction product to 50% by weight, and after coating the slide glass with a thickness of about 0.5 mm and maintained at 100 ℃ Heat treatment was performed in the oven for about 1 hour. After peeling off the film-form product generated after the heat treatment was recovered and confirmed the presence of pyrolysis products according to the temperature from room temperature to 500 ℃ by TG-IR, the results are shown in Table 1 below.

According to the said Table 1, in the copolymer manufactured in Examples 1-2, the decomposition product except water was not detected from the normal temperature to the temperature of 500 degreeC. On the other hand, in the case of the comparative example, a compound in the form of a ring such as octamethylcyclotetrasiloxane was detected continuously with temperature.

As described above, the polymethylsilsesquioxane copolymer in which dimethylsiloxane is uniformly dispersed at the molecular level according to the present invention is selected from starting materials having different ligands and heat treated in advance, and then undergoes a ligand exchange reaction to water. By minimizing the difference in the rate of hydrolysis, a high homogeneous copolymer can be obtained, and thus, excellent heat resistance and flexibility by increasing the content of methyl groups in silicon atoms (Si) are expected. ) Can be used as an interlayer material.

Claims (5)

In the method for producing a polymethylsilsesquioxane copolymer in which dimethylsiloxane groups are partially introduced, A process for preparing a ligand-exchanged alkoxysilane compound by heat-treating a mixed solution of methyltrialkoxysilane: dimethyldialkoxysilane in a molar ratio of 0.95: 0.05 to 0.70: 0.30 at a temperature of 70 to 150 ° C: Performing a sol-gel reaction of the ligand exchanged alkoxysilane compound with water and an acid under a condition of 0 to 60 ° C. in a mixed organic solvent of tetrahydrofuran and toluene; And, Method for producing a polymethylsilsesquioxane copolymer comprising a uniformly dispersed dimethylsiloxane, characterized in that the step of neutralizing the pH to 6-7 by adding ammonia water to the sol-gel reaction solution. 2. The polymethylsilsesqui of claim 1, wherein the methyltrialkoxysilane is selected from methyltriethoxysilane, methyltrimethoxysilane and methyltripropoxysilane. Method for preparing the oxane copolymer. The polymethylsilsesquioxane copolymer comprising uniformly dispersed dimethylsiloxane according to claim 1, wherein the dimethyl dialkoxysilane is selected from dimethyldimethoxysilane and dimethyldiethoxysilane. Manufacturing method. The method of claim 1, wherein the acid is an organic acid or an inorganic acid. The method of producing a polymethylsilsesquioxane copolymer comprising uniformly dispersed dimethylsiloxane. A polymethylsilsesquioxane copolymer comprising uniformly dispersed dimethylsiloxane prepared by the method of claim 1, wherein dimethylsiloxane is dispersed and bonded to one methyl unit in a methylsiloxane skeleton.