JPH0557289B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a high purity phenyl silicone ladder polymer. More specifically, the present invention relates to a method for producing a high-purity phenyl silicone ladder polymer that can be suitably used as a protective film for semiconductors, an interlayer insulating film, etc. [Prior art] Phenyl silicone ladder polymer has been well known as a heat-resistant polymer, and several manufacturing methods have already been proposed (Japanese Patent Publication No.
Publication No. 15989, Japanese Patent Publication No. 59-111197, Japanese Patent Publication No. 1987-111197
50-111198, JP-A-50-111199, and JP-A-57-18729). According to these manufacturing methods, phenyl silicone ladder polymer is produced by hydrolyzing phenyltrichlorosilane in an organic solvent, washing the hydrolyzate with water, and removing a large amount of hydrogen chloride generated during hydrolysis. After that, the hydrolyzate (weight average molecular weight: about 2000) is recovered, and then a dehydration condensation reaction is carried out using a nucleophilic reagent at high temperature in an organic solvent. However, the produced phenyl silicone ladder polymer contains a large amount of impurities and by-products. This is because the molecular weight is increased in a state close to the solid phase (Tokuko Sho).
40-15989, JP-A-50-111197, JP-A-50-111198), using large amounts of catalysts such as carbodiimide (see JP-A-57-18729), etc. This is because the product was manufactured under conditions that made it difficult to remove by-products. That is, phenyl silicone ladder polymers obtained by conventional manufacturing methods were not developed for application to electronic devices. [Problems to be Solved by the Invention] Therefore, in view of the problems of the prior art as described above, the present inventors have conducted extensive research to solve the problems, and as a result, have developed an organic solvent solution of phenyltrichlorosilane. Ultrapure water is added dropwise to perform hydrolysis, and the resulting hydrolyzate is washed with ultrapure water to remove the generated hydrogen chloride. Next, a small amount of nucleophilic reagent is added to this solution. A heating dehydration condensation reaction is carried out under stirring to increase the molecular weight, and after the reaction is complete, the reaction solution is dropped into methanol for the electronics industry and the reaction product is recovered as a precipitate. The present inventors have discovered that a high purity phenyl silicone ladder polymer can be obtained which can be suitably used for insulating films, etc., and have completed the present invention. [Means for Solving the Problems] That is, the present invention provides sodium, potassium,
The content of iron, copper, lead and chlorine is 1ppm or less, and the content of uranium and sodium is 1ppm or less.
General formula () that is less than or equal to 1 ppb: (wherein n is an integer from 7 to 1600) [Example] According to the production method of the present invention, the content of each of sodium, potassium, iron, copper, lead, and chlorine is 1 ppm or less, and the content of each of uranium and thorium is 1 ppm or less.
General formula () that is less than or equal to 1 ppb: The high purity phenyl silicone ladder polymer represented by (wherein n is an integer of 7 to 16) is,
Dissolve phenyltrichlorosilane in an organic solvent,
It can be obtained by adding ultrapure water dropwise to hydrolyze the phenyltrichlorosilane under cooling, and then washing with ultrapure water. The phenyltrichlorosilane used in the present invention is preferably purified by distillation in advance under reduced pressure in a nitrogen stream. Since purified phenyltrichlorosilane is easily hydrolyzed by moisture in the air and generates hydrogen chloride to become silica, it is preferable to handle it in such a way that it is not exposed to humid air. The phenyltrichlorosilane is first dissolved in an organic solvent. There is no particular limitation on the concentration of the phenyltrichlorosilane in the organic solvent solution, but usually the concentration of the obtained prepolymer in the organic solvent solution is 0.1 to 0.3 g/
It is preferable to adjust the amount to ml. If the concentration of such a prepolymer is less than 0.1 g/ml, the polymerization reaction rate is slow and the obtained prepolymer has a low molecular weight. If the concentration exceeds 0.3 g/ml, the heat generated during hydrolysis cannot be effectively dissipated, resulting in a partial increase in the polymerization rate, and the hydrolysis Organic solvent solutions tend to gel. As the organic solvent, a non-aqueous organic solvent capable of dissolving hydrolysis is used. Specific examples of such organic solvents include ketones such as methyl isobutyl ketone and methyl ethyl ketone; ethers such as diethyl ether and isopropyl ether; and aromatic hydrocarbons such as xylene, toluene, and benzene. In this case, high-purity chemicals for the electronics industry (ELSS grade) are preferred. Next, ultrapure water is dropped into an organic solvent solution in which phenyltrichlorosilane is dissolved in an organic solvent.
The reason why ultrapure water is added dropwise in the present invention is that if ultrapure water is added all at once, a large amount of heat of hydrolysis will be generated. Therefore, when adding ultrapure water dropwise, it is desirable to cool the organic solvent solution while stirring it. Here, the ultrapure water refers to pure water with a resistivity of 16 MΩ·cm or more after removing impurities as much as possible. The amount of ultrapure water added is preferably 3 to 30 parts by mole per 1 part by mole of phenyltrichlorosilane in order to sufficiently progress the hydrolysis of phenyltrichlorosilane. If the amount of ultrapure water added is less than 3 mol parts, unreacted phenyltrichlorosilane may remain, and if it exceeds 30 mol parts, the effect will be commensurate with the added amount. Not only is it difficult to remove, but it also tends to hinder hydrolysis. When cooling the organic solvent solution, the temperature of the organic solvent solution is preferably adjusted to -10 to 20°C. If the temperature is lower than -10°C, the dropped ultrapure water tends to solidify or the hydrolysis reaction slows down, and if it exceeds 20°C, the reaction speed increases and heat generation becomes intense. Therefore, the structure of the resulting prepolymer tends to be irregular. In addition, after dropping the ultrapure water, it is preferable to continue stirring for another 2 hours in order to complete the hydrolysis reaction. After the reaction is completed, the reaction solution is separated into two phases: an organic solvent phase and an aqueous phase. Next, the lower aqueous phase is removed using, for example, a separatory funnel, and the organic solvent phase containing the prepolymer is recovered. The recovered organic solvent phase is then washed with ultrapure water, but the present invention is not limited to such a washing method, and various known methods may be employed. One example is a method in which an organic solvent phase is mixed with the same volume of the ultrapure water, stirred or shaken, and then the organic solvent phase is drawn out. When such a cleaning method is adopted, by repeating the above-described cleaning operation three or more times, sodium ions, potassium ions, and chlorine ions generated in large amounts in the prepolymer can be easily removed. It is thought that the reason why these impurities are removed is that the obtained prepolymer has a ladder-like structure and impurities are difficult to be incorporated into the molecules. In addition,
Since the prepolymer has a small molecular weight and cannot be recovered by a conventional precipitation method using an appropriate solvent, it is preferable to distill the solvent off to dryness and recover it as a powder. Thus, the above general formula () has a degree of polymerization (n) of 7 to 16, in which each content of sodium, potassium, iron, copper, lead, and hydrogen chloride is 1 ppm or less, and each content of uranium and thorium is 1 ppb or less. A high purity phenyl silicone ladder polymer is recovered. In addition, in the general formula (), the degree of polymerization (n) is
17 to 1600, the organic solvent phase containing the prepolymer is transferred to a quartz glass flask equipped with, for example, a fluoropolymer stirring bar, a reflux condenser, and a Dane-Stark trap; It can be obtained by adding a nucleophilic reagent into the flask, heating it to cause dehydration condensation, and purifying the resulting high molecular weight product by a dissolution and reprecipitation method. Examples of the nucleophilic reagent include hydroxides of K, Na, Cs, and the like. Preferably, ELSS grade potassium hydroxide, sodium hydroxide, etc. are used. Preferably, the amount of the nucleophile is 0.05 to 5% by weight based on the prepolymer. If the amount of the nucleophilic reagent is less than 0.05% by weight, the catalytic activity decreases and the reaction rate of the prepolymer decreases, and if it exceeds 5% by weight, the siloxane bond will dissociate due to the presence of the nucleophilic reagent. has a tendency to preferentially not increase the molecular weight, and furthermore, the nucleophilic reagent remains as an impurity. In addition, when using a high molecular weight, high purity phenyl silicone ladder polymer with a degree of polymerization of 350 or higher, the amount of catalyst is
Preferably it is 0.1 to 1% by weight. Next, the prepolymer is dehydrated and condensed under reflux in the organic solvent phase to which the nucleophilic reagent is added. At this time, the reflux time is preferably 1 hour or more. If the reflux time is shorter than 1 hour, the reaction may not proceed much. In this way, a phenyl silicone ladder polymer represented by the general formula () having a degree of polymerization (n) of 17 to 1,600 is obtained. The degree of polymerization (n) of the polymer is adjusted by appropriately selecting the types and amounts of the solvent and catalyst, and the condensation reaction time. Note that the obtained phenyl silicone ladder polymer contains a trace amount of a nucleophilic reagent as an impurity, so it is purified by a dissolution and reprecipitation method. The dissolution and reprecipitation method is a purification method in which a solution in which a solute containing impurities is dissolved in a good solvent is gradually dropped into a poor solvent to cause reprecipitation. As the good solvent, an ether solvent is used in the present invention. A typical example of such a good solvent is tetrahydrofuran. Note that the good solvent is preferably distilled in advance and then filtered through a filter with an opening diameter of 0.5 μm. Examples of the poor solvent in the present invention include alcohol-based solvents. A typical example of such a poor solvent is methyl alcohol. In addition,
As the poor solvent, it is desirable to use a highly pure ELSS grade solvent. The good solvent is added to the reaction solution containing the phenyl silicone ladder polymer so that the concentration of the phenyl silicone ladder polymer is 2 to 8% by weight. If the concentration of the phenyl silicone ladder polymer is less than 2% by weight, the phenyl silicone ladder polymer will not re-precipitate and will be difficult to purify, and if it exceeds 8% by weight, the concentration will be too high. Nucleophilic reagents tend to be incorporated between molecules, making it difficult to purify by reprecipitation. Next, the reaction solution containing the phenyl silicone ladder polymer to which the good solvent has been added is gradually dropped into the poor solvent. The poor solvent is preferably added in such a manner that the amount of the poor solvent dissolved is 5 to 20 times the amount of the reaction solution. If the amount of the poor solvent dissolved is less than 5 times, it will be difficult to remove impurity ions, and if it exceeds 20 times, the solvent will be wasted.
Note that the reason why the poor solvent is gradually added dropwise is to efficiently remove impurity ions. The phenyl silicone ladder polymer thus precipitated and recovered by addition to the poor solvent is further dissolved in a good solvent in the same manner as described above, and then added dropwise to the poor solvent to be recovered as a precipitate. When this purification operation is repeated 3 to 5 times, the content of the nucleophilic reagent becomes 1 ppm or less. Thus, the nuclear content of sodium, potassium, iron, lead, and hydrogen chloride is 1 ppm or less, the content of each of uranium and thorium is 1 ppb or less, and the degree of polymerization (n) is 17 to 100, and is represented by the above general formula (). A high purity phenyl silicone ladder polymer is obtained. Next, the method for producing a high purity phenyl silicone ladder polymer of the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples. Examples 1 to 7 Phenyltrichlorosilane as a raw material was distilled at a temperature of 81 to 82°C under a reduced pressure of 15 mmHg in a nitrogen stream.
A solution of 317.4 g of distilled phenyltrichlorosilane and the amount of ELSS grade solvent shown in Table 1 was transferred to a 2-volume, 4-necked flask equipped with a dropping funnel, a thermometer, and a stir bar. It was cooled to the indicated temperature (hydrolysis temperature). Next, ultrapure water in the amount shown in Table 1 was gradually added dropwise over 1 to 3 hours while stirring and cooling to maintain the temperature. At this time, hydrogen chloride was generated violently. After the dropwise addition was completed, stirring was further continued for 2 hours to complete the hydrolysis reaction. This prepolymer solution was transferred to a separatory funnel and allowed to stand to separate the prepolymer solution into two layers. Next, the lower aqueous layer containing a large amount of hydrogen chloride was removed, the organic layer containing the prepolymer was collected, and the same volume of ultrapure water as the organic layer was added to the organic layer and washed by shaking. After repeating this washing operation five times, the amount of impurities contained in the washed prepolymer was analyzed using an ion chromatography analyzer (manufactured by Yokogawa Hokushin Electric Co., Ltd., product number: IC-500). The content of chlorine ions in the prepolymers obtained in Examples 1 to 7 was all 1.
The concentration was about 1000 ppm after the first washing, and less than 1 ppm after the third washing. Moreover, the potassium ion concentration also decreased with the number of washings, and after the third washing, it became less than 1 ppm. Next, the weight average molecular weight of each prepolymer obtained in Examples 1 to 7 was measured by gel permeation chromatography (manufactured by JASCO Corporation, product number: TRI-
ROTAR-VI). The result is the first
Shown in the table. In addition, the impurity content of the prepolymer after washing three times is as shown in Table 1, with each content of sodium, potassium, iron, copper, lead, and chlorine being 1 ppm or less, and the content of uranium and thorium, which are radioactive elements. The amount was less than 1 ppb. Next, the structure of each prepolymer obtained in Examples 1 to 7 was analyzed using infrared analysis (manufactured by JASCO Corporation: FT/IR-
111 type), a double peak of siloxane bonds was observed near 1100 cm ^-1 (Journal of Polymer Science (published in 1963), C
(Vol. 1, p. 83), these prepolymers all have the general formula (): It was confirmed that the compound has a structure represented by the following formula (where n represents an integer). Next, the thermal decomposition onset temperature of the prepolymers obtained in each example was investigated based on the following method. The results are also listed in Table 1. (Thermal decomposition start temperature) The prepolymer obtained in air was heated at a heating rate of 10° C./min using a thermobalance, weight change was examined, and the weight loss start temperature was taken as the pyrolysis start temperature. Comparative Examples 1 to 4 Phenyltrichlorosilane was hydrolyzed in the same manner as in Examples 1 to 7, except that the formulations and hydrolysis temperatures were as shown in Table 1. In Comparative Examples 1 and 2, the reaction rate was very slow and the molecular weight was low, so that the solutions did not undergo phase separation after the reaction was stopped and could not be purified by washing. In Comparative Examples 3 and 4, the reaction solution gelled because the reaction rate was fast. Comparative Example 5 105.8 g of purified phenyltrichlorosilane was dissolved in 200 c.c. of xylene and then placed in a dropping funnel. Next, ultrapure water 1 was added and the temperature was 10°C.
The xylene solution of phenyltrichlorosilane was added dropwise from the dropping funnel into a four-necked flask cooled to 100 mL with stirring to effect hydrolysis. Note that it took 4 hours to complete the dropping. The reaction solution was transferred to a separatory funnel, and the organic layer was taken out and washed three times with ultrapure water until it became neutral. Thereafter, xylene was removed and the product was dried under reduced pressure. Next, the concentration of impurities contained in the obtained powder was examined by atomic absorption spectrometry. The results are shown in Table 1.

[Table] Examples 8 to 21 In Examples 1 to 7, the type of solvent and the amount used, the amount of ultrapure water used, the molar ratio of ultrapure water and phenyltrichlorosilane, the hydrolysis temperature, and the produced prepolymer A solution containing a highly pure prepolymer was prepared in the same manner as in Examples 1 to 7, except that the concentration in the solution was adjusted to the values shown in Table 2. Next, the obtained solution containing the high-purity prepolymer was transferred to a 2-volume, 4-neck flask made of quartz glass equipped with a fluororesin stirring rod, a Dane-Stark trap, and a thermometer. Next, dissolve potassium hydroxide in methanol (ELSS grade) at a concentration of 0.1g/
ml of KOH solution as a catalyst was added to a four-necked flask in the amount shown in Table 2 relative to the prepolymer.
The reaction was carried out under reflux for the heating times shown in Table 2.
The amount of water removed during this period was approximately 20 ml, which was distilled off in approximately 1 hour. Next, after the reaction solution was allowed to cool, purified tetrahydrofuran was added so that the content of the polymer component became the concentration shown in Table 2, and the mixture was thoroughly stirred and dissolved. Alcohol (ELSS grade) was added dropwise to collect the precipitate of high molecular weight phenyl silicone ladder polymer. After drying the precipitate, the same tetrahydrofuran as above was added to obtain a tetrahydrofuran solution having the same concentration as above, and the solution was dropped into methyl alcohol again to precipitate, and the phenyl silicone ladder polymer was recovered. This operation was repeated four times. The molecular weight of the high molecular weight phenyl silicone ladder polymer synthesized in this way was determined by gel permeation chromatography (manufactured by JASCO Corporation).
The concentration of sodium ions, potassium ions, iron ions, ions, and lead ions was measured using an atomic absorption spectrometer (manufactured by Seiko Electronics Co., Ltd., model SAS-760), and the chloride ion concentration was measured using Ion chromatography (Yokogawa Hokushin Electric Co., Ltd.)
(manufactured by IC-500), which contains the radioactive element uranium,
Thorium content was measured using a spectrofluorometer (Hitachi, Ltd.)
Co., Ltd., model number: MPF-4). The results are shown in Table 2. Next, when the structure of each polymer obtained in Examples 8 to 18 was investigated by infrared spectroscopy, a double peak of siloxane bond was observed near 1100 cm ^-1 , so all of these polymers had the general formula (): It was confirmed that the compound has a structure represented by the following formula (where n represents an integer). As can be seen from Table 2, a highly pure phenyl silicone ladder polymer was obtained. In addition, the impurity ion concentration decreased as the number of reprecipitations increased. Furthermore, the thermal decomposition onset temperature of the obtained phenyl silicone ladder polymer was investigated in the same manner as in Example 1. Comparative Examples 6 to 8 Type of solvent and amount used, amount of ultrapure water used, molar ratio of ultrapure water and phenyltrichlorosilane, hydrolysis temperature, concentration of produced prepolymer in solution, amount of catalyst, heating A phenyl silicone ladder polymer was obtained in the same manner as in Example 8, except that the time and the content of the polymer in the good solvent were adjusted as shown in Table 2. In Comparative Example 6, the amount of catalyst was too large, so decomposition of the main chain proceeded, the molecular weight of the polymer decreased, and the added catalyst could not be removed sufficiently. In Comparative Example 7, since the solution concentration at the time of solution reprecipitation was dilute, the precipitate only became cloudy and no polymer could be recovered. In addition, in Comparative Example 8, the solution concentration was high, so a sufficient purification effect could not be obtained.
As shown in Table 2, the added catalyst could not be removed sufficiently. Comparative Example 9 Fluorine was added by adding 10 g of the low molecular weight siloxane polymer obtained in Comparative Example 5, 10 g of xylene, and 1 ml of a potassium hydroxide solution with a concentration of 0.1 g/ml, which was prepared by dissolving potassium hydroxide in methanol (ELSS grade) as a catalyst. The resin was transferred to a four-necked quartz glass flask equipped with a stirring rod, a reflux condenser, and a thermometer, and reacted under reflux for 3 hours. After the reaction was completed, the silicone polymer was recovered in the same manner as in Example 8, and purified by repeating reprecipitation four times. The concentration of impurities contained in the obtained polymer was examined in the same manner as in Example 8. The results are shown in Table 2.

【table】

[Table] From the results in Tables 1 and 2, according to the production method of the present invention, sodium, potassium, chlorine, iron,
It can be seen that a phenyl silicone ladder polymer of high purity can be obtained with extremely low content of impurities such as copper, uranium and thorium. [Effects of the Invention] As described above, according to the production method of the present invention, an extremely high purity phenyl silicone ladder polymer can be easily produced, and furthermore, the obtained high purity phenyl silicone ladder polymer of the present invention has excellent properties. Since it has heat resistance, it can be suitably used for interlayer insulating films, etc., and therefore has the effect of contributing to improving the reliability of semiconductor devices.

Claims (1)

[Claims] 1. Phenyltrichlorosilane is dissolved in an organic solvent so that the concentration of the resulting prepolymer is 0.1 to 0.3 g/ml, and ultrapure water is added dropwise to the solution at -10 to 20°C. After hydrolyzing phenyltrichlorosilane, it is washed with ultrapure water.The content of sodium, potassium, iron, copper, lead and chlorine is 1ppm or less, and the content of uranium and thorium is 1ppm or less. General formula () that is less than or equal to 1 ppb: (wherein n represents an integer of 7 to 16) A method for producing a high purity phenyl silicone ladder polymer. 2 Dissolve phenyltrichlorosilane in an organic solvent so that the concentration of the resulting prepolymer is 0.1 to 0.3 g/ml, and add dropwise ultrapure water to hydrate the phenyltrichlorosilane at -10 to 20°C. After decomposition, the organic solvent phase is washed with ultrapure water, a nucleophile is added to the organic solvent phase, and the hydrolyzate is dehydrated and condensed by heating, and the resulting high molecular weight product is dissolved and reprecipitated. The general formula () has a content of each of sodium, potassium, iron, copper, lead, and chlorine of 1 ppm or less, and a content of uranium and thorium of 1 ppb or less: (wherein n represents an integer of 17 to 1600) A method for producing a high purity phenyl silicone ladder polymer.