JPH0562603B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing cyclized polyisoprene, and more particularly to a method for producing high-quality cyclized polyisoprene, which is suitable as a raw material for rubber-based photoresists, by an economical process. Prior Art As a rubber-based photoresist, a reduced product of natural rubber is conventionally known. However, cyclized natural rubber contains many impurities such as dust, gel, and metal ions, and must be purified before it can be used as an IC photoresist. On the other hand, polyisoprene, which has almost the same structure as natural rubber, contains less dust and has a constant quality, making it suitable as a raw material for cyclized rubber.
However, in order to produce cyclized polyisoprene using polyisoprene as a raw material, mastication of polyisoprene, dissolution in a solvent, cyclization reaction, reaction termination,
Many steps such as washing with water and purification are required, and impurities that degrade the performance of the photoresist are mixed in during the mastication process, causing problems both economically and in terms of quality. As a method for solving this problem, a method has been disclosed in which isoprene monomer is polymerized using an organometallic compound and then cyclized using a Friedel-Crafts catalyst (Japanese Patent Application Laid-open No. 15504/1983). Although this method has the advantage of a simple process since there is no step of dissolving polyisoprene, it has the following serious drawbacks. That is, unreacted isoprene after polymerization or isoamylene accompanying isoprene reacts with the solvent during the cyclization reaction to form a high-boiling compound (hereinafter referred to as high-boiling impurity). The high-boiling impurity is an evaporated substance having a higher boiling point than the solvent, and when the solvent is evaporated from the cyclized polyisoprene solution, it evaporates later than the solvent. This causes a problem in that pinholes occur frequently on the coating film when cyclized polyisoprene is coated on a semiconductor wafer. Problems to be Solved by the Invention As a result of intensive research in order to solve the above-mentioned drawbacks, the present inventor has found that if, after polymerizing isoprene, unreacted isoprene and isoamylene accompanying isoprene are removed, a cyclization reaction is carried out. The present inventors have discovered that cyclized polyisoprene, which causes fewer pinholes when formed into a coating film, can be stably produced, leading to the completion of the present invention. Means for Solving the Problems Thus, according to the present invention, when producing cyclized polyisoprene by solution polymerizing isoprene using an organometallic compound and cyclizing the obtained polyisoprene with an acid catalyst, , using an aromatic hydrocarbon as a polymerization solvent, and after completing the solution polymerization, removing unreacted isoprene and/or isoamylene until it becomes 0.5 parts by weight or less per 100 parts by weight of polyisoprene, and then carrying out a cyclization reaction. Provided is a method for producing cyclized polyisoprene characterized by the following. The solvent used in the polymerization and cyclization reaction of isoprene is a known solvent capable of selectively obtaining cis-1,4-addition polymers of isoprene, including aromatic carbonization solvents such as benzene, toluene, xylene, ethylbenzene, and mixtures thereof. Hydrogen solvents can be used. Generally, those having a higher boiling point than isoprene and isoamylene are preferred, and aromatic hydrocarbons such as benzene, toluene, and xylene used as resist solvents are preferred. The organometallic compound used in the step of polymerizing the isoprene monomer is a living polymerization initiator, and a typical example thereof is the general formula RM (R represents an alkyl, aryl, or aralkyl group, and M represents lithium, sodium, potassium, or cesium). ), specifically, n-
Examples include butyllithium, sodium naphthalene, sodium anthracene, sodium biphenyl, phenylisopropyl potassium, α-methylstyrene quadruple potassium, and the like. Preferably n-
Butyllithium. Polymerization of isoprene is carried out as follows. First, isoprene monomer is dissolved in a sufficiently dehydrated solvent. The monomer concentration is not particularly limited, but depending on the viscosity of the reaction solution and the ease of stirring, it should be between 2 and 2.
25% is preferred, particularly preferably 3-20%. The amount of catalyst is calculated so as to have a target molecular weight (usually 50,000 to 400,000), taking into account the amount of catalyst-deactivating components. Further, the polymerization temperature is not particularly limited, but is preferably room temperature to 100°C from the viewpoint of economy and operability. As long as the temperature is within this range, it is not necessary to keep the temperature constant during the polymerization, and it may be changed. The polymerization time is preferably a time sufficient for 99% or more of the monomers to react, and is usually 10 minutes to 5 hours. After the polymerization reaction is completed, a polymerization terminator is generally added to prevent ultrahigh molecular weight reactions such as coupling of the living polymer. As a stopper,
2,6-di-tert-butyl-4-methylphenol, 4-tert-butylcatechol, 2,6-di-
tert-butylhydroxytoluene, 2,2'-methinebis(4-methyl-6-tert-butylphenol), 1,1-bis(4-hydroxyphenyl)
Phenol compounds such as cyclohexane, p,
Amine compounds such as p′diaminodiphenylmethane, phenyl-β-naphthylamine, di-p-methoxydiphenylamine, diphenylethylenediamine, sulfide compounds, phosphite compounds, alcohols, ketones, or water are used, but cyclization Any material may be used as long as it does not inhibit the reaction. The polyisoprene solution obtained by such an operation contains a small amount of unreacted isoprene and a hydrocarbon having 5 carbon atoms such as isoamylene contained as an impurity in the isoprene monomer. If the cyclization reaction is carried out while containing such hydrocarbons, high boiling point impurities will be produced as by-products. In the present invention, it is necessary to remove such hydrocarbons to an amount of 0.5 parts by weight or less per 100 parts by weight of polyisoprene before the cyclization reaction. As a removal method,
An excellent method is to use the polyisoprene solution as it is, or to add a solvent and then evaporate the solvent. The temperature is not particularly limited, but it is set to 0 for economical reasons.
-100°C is preferred and the pressure is 5-1500 Torr. When evaporating a hydrocarbon having 5 carbon atoms, it is convenient for operation to distill out a part of the solvent along with the evaporation. By removing the remaining isoprene monomer in this way, it is possible to suppress the production of high-boiling point impurities during the cyclization reaction, and therefore, it is possible to suppress the formation of high-boiling point impurities during the cyclization reaction. The occurrence of pinholes can be significantly reduced. During the cyclization reaction, the polyisoprene concentration in the polyisoprene solution subjected to the above treatment is usually 1 to 1.
Adjust to 20%. If it is lower than 1%, productivity is poor;
On the other hand, if it is higher than 20%, gel formation will occur significantly and the quality of the product will deteriorate. The concentration is adjusted by adjusting the amount of solvent that accompanies the evaporation of unreacted isoprene and/or isoamylene after isoprene polymerization, or by adjusting the amount of new solvent added. Acid catalysts for the cyclization reaction include Friedel-Crafts catalysts such as tin tetrachloride, titanium tetrachloride, ferric chloride, boron trifluoride ether complexes;
Examples include sulfuric acid, sulfonic acid compounds such as benzenesulfonic acid, p-toluenesulfonic acid, and methanesulfonic acid, phosphorus compounds such as phosphorus pentachloride and phosphorus oxychloride, and trichloroacetic acid. Particularly preferred are sulfonic acid compounds. In either case, the amount of catalyst used is 1 to 15 parts by weight per 100 parts by weight of polyisoprene. If it is less than 1 part by weight, the reaction rate is slow and impractical. Moreover, if the amount is more than 15 parts by weight, gel formation may occur, which is unfavorable in terms of quality. There are no particular restrictions on the reaction temperature, but it is usually room temperature to 120℃.
It is ℃. The reaction pressure is also not particularly limited, but it is generally carried out at normal pressure. After the cyclization reaction reaches a predetermined cyclization rate, the cyclization reaction is generally stopped by adding water to the reaction system and stirring well to transfer the acid catalyst to the water side. The cyclization rate is
It can be measured by IR analysis, NMR analysis, changes in refractive index and viscosity, etc. After allowing the reaction system to stand still, the water layer and oil layer are separated. If the acid catalyst in the oil layer is to be more completely removed, water is further added and stirred, and after standing still, the aqueous layer is separated. Thereafter, if a trace amount of water in the oil layer is to be further removed, separation using a centrifuge or distillation is performed to obtain a cyclized polyisoprene solution. Through such a cyclization reaction, a cyclized polyisoprene substantially free of high-boiling impurities can be produced. Stabilizers, sensitizers, photosensitizers, antihalation agents, and the like are appropriately added to the cyclized polyisoprene solution obtained according to the present invention, and after precision filtration, it is used for uses such as photoresists. Effects of the Invention Thus, according to the present invention, cyclized polyisoprene containing no high-boiling impurities can be stably produced in a simpler process than in conventional production methods. Therefore, by using this cyclized polyisoprene, a photoresist with fewer pinholes can be obtained. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that the percentages in the examples are based on weight unless otherwise specified. Example 1 After thoroughly drying the inside of an autoclave with a capacity of 5 and thoroughly replacing the air with dry nitrogen, 1500 g of dry purified xylene and dry purified isoprene (purity
99.2%, the rest is isoamylene) 200g,
After mixing well, the moisture content in the system was measured and found to be 2.1 ppm. Next, 3.9 ml of a solution of n-butyllithium in n-hexane having a concentration of 0.3 mol/h was added to initiate polymerization. Reaction temperature ranges from 30℃ to 85℃
It was between ℃ and ℃. 60 minutes after the start of the reaction, 3 g of a 10% xylene solution of 2,6-di-tert-butylhydroxytoluene was added to stop the polymerization. 99% of the isoprene was converted to polyisoprene.
Furthermore, gas chromatography analysis confirmed that 1.0 parts by weight of unreacted isoprene and 0.8 parts by weight of isoamylene were present in the solution based on 100 parts by weight of polyisoprene. Next, in order to remove unreacted monomers, 1400 g of dry purified xylene was charged into the reaction system, and the gas layer of the autoclave was connected to a vacuum pump via a cooler to maintain the temperature inside the autoclave.
The temperature was 80°C and the pressure was 50 Torr. After distilling off 100 g of a mixture of unreacted isoprene and isoamylene and xylene, the pressure inside the autoclave was brought to normal pressure with dry nitrogen. No isoprene or isoamylene was observed in the polyisoprene solution. Next, after the temperature inside the autoclave was set to 80° C., 80 g of a xylene solution of p-toluenesulfonic acid having a concentration of 9% was added to carry out a cyclization reaction. 200
After a minute, add 600ml of distilled water and stir well.
The mixture was allowed to stand still, and the aqueous layer was extracted into the system. Plus distilled water
600 ml was added and water was separated by the same operation.
After repeating such water washing, water in the oil layer was removed using a centrifuge. after that,
The oil layer is returned to the autoclave at a temperature of 80℃ and a pressure of
Evaporate 1500g of xine under reduced pressure of 50Torr,
A solution of cyclized polyisoprene was obtained. When the amount of residual double bonds in the obtained cyclized polyisoprene was measured by nuclear magnetic resonance spectroscopy, it was found that
It was 24%. Furthermore, when the cyclized polyisoprene solution was analyzed by gas chromatography, no high boiling point impurities were observed. Next, to 1000 g of the cyclized polyisoprene solution, 4 g of 2,6-bis(4'-azidobenzal)methylcyclohexanone was added as a photocrosslinking agent, and 2,2'-methylenebis(4'-methyl-6-
Add 1.25g of tert-butylphenol to 0.22μ
A photoresist composition was prepared through precision filtration using a microfilter. A silicon oxide layer with a thickness of 4,000 Å was spin-coated onto a silicon wafer using a conventional method, and a temperature of 85°C was applied for 20 minutes.
It was prebaked for 1 minute to form a photoresist film with a thickness of 1 μm. This was exposed to light for a predetermined period of time three times the sensitivity using a mask aligner equipped with a 200W high-pressure mercury lamp through a photomask drawn with a test pattern, and then exposed to a developer containing n-heptane as its main component.
It was developed by immersion for 1 minute and rinsed with acetic acid n-butyl ester for 1 minute. Then, after post-baking at a temperature of 160°C for 20 minutes, fluorine/ammonium fluoride 3.6
%/18% buffered fluoric acid at an etching rate of 550 Å/min at a temperature of 20°C for 6 times as long as the silicon oxide film while gently shaking the film up and down. After washing for 5 minutes and air drying with clean nitrogen, pinholes were measured using an optical microscope at 200x magnification. As a result, the number of pinholes per unit area (1 cm ² ) was 3.0 pinholes/cm ² as the average value of 5 measurements. For comparison, cyclization and purification were carried out in the same manner as in Example 1, except that 1300 g of dry purified xylene was added to the system after termination of polymerization, and the vacuum distillation operation to remove unreacted monomers was not performed. A cyclized polyisoprene solution was produced by concentrating the solution, which was used as a photoresist, and the number of pinholes generated was counted. As a result, in the cyclized polyisoprene solution, reaction products from the reaction of isoprene or/and isoamylene with xylene are present in the cyclized polyisoprene solution.
Approximately 2.3 parts by weight per 100 parts by weight was also observed. Further, the number of pinholes generated was 149.1 pinholes/cm ² as the average value of 5 measurements. In order to further confirm the effects of the present invention, the amount of unreacted monomer was quantified using the photoresist of the present invention example and the photoresist of the comparative example obtained above. In other words, apply the photoresist using the same operation as above.
One wafer coated to a thickness of 1 μm and one wafer prebaked in the same manner were prepared. 2 mg of photoresist remaining on the wafer was scraped off, dissolved in xylene, and heated at a temperature in the range of 80 to 300°C. was measured by gas chromatography. The results are 1st and 2nd
(Comparative example) and FIGS. 3 and 4 (Example of the present invention). In the resist of the comparative example in which unreacted monomers were not removed, the distillation time of gas chromatography was 8 minutes or more.
There is a large amount of reaction products between isoprene and/or isoamylene and the solvent xylene, which are shown by the peak at 10 minutes (Figure 1), but most of them evaporate and disappear after prebaking. I understand (Figure 2). On the other hand, in the case of the photoresist according to the present invention obtained by removing unreacted monomers, the amount of reaction products is small (Figure 3), and it can be seen that they evaporate and disappear after prebaking (Figure 4). figure). From the above, it can be seen that the side reaction products greatly influence the generation of pinholes in the resist film, and by removing them, the number of pinholes generated can be significantly reduced. Example 2 The pinhole density was measured in the same manner as in Example 1, except that the amount of unreacted monomer distilled off was changed to change the amount of unreacted monomer remaining in the polyisoprene before cyclization. The results are shown in the table below.

[Table] Parts by Weight As is clear from these results, the remaining amount of unreacted monomer is related to the number of pinholes, and it is particularly desirable that the amount of unreacted monomer is 0.5 parts by weight or less.

[Brief explanation of the drawing]

Figures 1 and 2 are gas chromatography of the photoresist obtained in the comparative example of Example 1 (Figure 2 is after prebaking), and Figures 3 and 4 are the gas chromatography of the photoresist obtained in the comparative example of Example 1. Gas chromatography of the obtained photoresist (FIG. 4 is after prebaking). The horizontal axis of each figure is the distillation time (in minutes).

Claims (1)

[Claims] 1. When producing cyclized polyisoprene by solution polymerizing isoprene using an organometallic compound and cyclizing the obtained polyisoprene with an acid catalyst, an aromatic hydrocarbon is used as a polymerization solvent, and solution polymerization is performed. After completion of the reaction, unreacted isoprene and/or isoamylene is removed until the amount becomes 0.5 parts by weight or less per 100 parts by weight of polyisoprene, and then a cyclization reaction is carried out.