KR940010966B1 - Process for producing n-tertiary-butoxy maleimide copolymer - Google Patents

Abstract

The N-tert-butoxymaleimide/styrene copolymer is produced by radical- copolymerizing N-tert-butoxymaleimide monomer and styrene derivative in the presence of a radical copolymerization initiator i.e. benzoyl peroxide or azobis (isobutylonitrile). The styrene derivative is pref. styrene, p-acetoxy styrene, p-methyl styrene, p-chloro styrene, m-chloromethyl styrene, p-tert- butoxycarbonyloxy styrene or p-trimethylsilyl styrene. The copolymer is used as a microlithographic resist having a high radiation-sensibility, resolution and heat resistance.

Description

[Name of invention]

N-tertiary-butoxymaleimide copolymer production method

Detailed description of the invention

The present invention relates to a method for producing a copolymer of N-tertiary-butoxymaleimide (hereinafter referred to as t-BuOMI), which is a new monomer.

In order to achieve high sensitivity in the lithography process of semiconductor manufacturing, in recent years, chemical amplification resists have been greatly spotlighted, thereby increasing the sensitivity of the conventional positive novolak-based photoresist by more than 100 times. It turns out that. The chemically amplified resist is a resist type using a photoacid generator (hereinafter referred to as PAG), and is made by mixing PAG with a matrix polymer having a structure sensitive to acid.

In other words, when the photoacid generator is exposed to light or irradiated with high energy radiation such as X-rays or electron beams, a strong proton acid, Bronsted Acid, is formed, and the action of the generated acid reacts to decompose or crosslink the main or side chains of the matrix polymer. , Or the polarity of the polymer is greatly changed, so that the solubility of the irradiated portion with respect to the developer is increased or decreased, thereby producing a fine image.

As photoacid generators, onium salts, which generate acids by the action of light and radiation, are generally known. Representatively, there are various ammonium salts, oxonium salts, and sulfonium salts. Reported.

As the acid reactive matrix polymer, polymers having carboxylic acid or phenol functional groups having side chains protected with t-butyl ester, t-butyl carbonate and t-butoxy or t-butoxy carbonyl (t-BOC) groups are usefully used. Among the side chain protecting groups, t-BOC protecting group is known to be the best in terms of sensitivity. Acid-reactive polymers are soluble in a protected state or in an organic solvent before reacting with an acid, but in a state in which they are deprotected by reacting with an acid, the polarity is greatly changed in the structure of the polymer, thereby changing to an aqueous alkali solution.

On the other hand, submicron microlithography, which produces microscopic images of less than 1 μm, requires an image transfer process by plasma dry etching in order to achieve high resolution. At this time, the heat resistance of the resist fine image is required to be 200 ° C or more.

Also, in order to achieve submicron resolution, the irradiation wavelength is shorter in ultraviolet G-ray (436nm), I-ray (365nm) or deeper UV (wavelength 200-300nm) or more advantageously. The technique using the short wavelength of 248 nm of the high output KrF excimer laser is highly important. Therefore, light absorption of the resist should be appropriate in the far ultraviolet, especially in the excimer laser wavelength region of 248 nm.

Currently, the basic matrix polymer of the positive type photoresist used in micromachining is an aqueous alkali solution developable novolak resin, and the novolak resin has a low glass transition temperature of 100 ° C. to 150 ° C., resulting in plasma etching or ion implantation. During the process, the microscopic image of the resist may be deformed by heat, and the light absorption in the far-ultraviolet region is so high that it is not suitable for achieving a high resolution of 0.5 mu m or less.

The present invention is a conventional radical copolymerization reaction of t-BuOMI, styrene, styrene derivatives and other monomers with t-butoxy protecting group-containing maleimide polymers as a new micro-resisting material that satisfies such high sensitivity, high resolution, and heat resistance. It is related with the method of manufacturing efficiently.

As a resist material that satisfies high sensitivity, high resolution, and heat resistance, a polymer having a maleimide structure containing a t-BOC protecting group is very useful, and the researchers have already used a t-BOC protecting group containing a maleimide polymer as a new t-BOC protecting monomer. There is a patent application relating to a method of preparing using -butoxycarbonylmaleimide (abbreviated t-BOCMI) and to use it as a resist (patent applications 10272 and 10273 in 1991). The above-described t-BOC protecting group-containing maleimide polymer is capable of forming a fine image of heat resistance with high sensitivity, but since it has a slightly lower decomposition temperature of 150 ° C, this study supplements this point, but has a high decomposition temperature of 200 ° C or higher. Invented a maleimide polymer protected with age.

Copolymer P (t-BuOMI-X-St) prepared from t-BuOMI and styrene derivatives of the present invention has the following chemical structure (I).

In the formula, X-St represents a styrene derivative and X represents an alkyl group such as hydrogen, methyl and ethyl, and a polar group such as acetoxy, chlorine, methyl chloride, hydroxyl, t-BOC-oxy, and a silicon-containing group such as trimethylsilyl. The t-BuOMI monomer is polymerized according to a conventional radical polymerization method using a radical polymerization initiator to prepare a homopolymer and a copolymer.

t-BuOMI is polymerized at high conversion rates with styrene derivative (X-St) or methyl methacrylate (MMA) monomers, especially in the copolymerization of styrene derivative X-St with t-BuOMI by the amount of solvent and the radiator initiator used. Molecular weight control of the synthesized polymer is possible. The copolymer synthesized in the present invention was identified as an alternating structure of carbon-13 and proton nuclear magnetic resonance analysis with a chemical structure of 1: 1 mole ratio. It is well known that 1: 1 alternating copolymers are produced when t-BuOMI, an electron-deficient monomer, and X-St, a monomer rich in electrons, are copolymerized. In addition, the P (t-BuOMI / St) alternating copolymer exhibited high transparency in the far ultraviolet region (200-300 nm wavelength) because the absorbance was lower than 0.2 for a 1 μm thick film.

The alternating copolymer poly (t-butoxymaleimide / styrene) of t-BuOMI and styrene, a representative copolymer prepared in the present invention, is stable up to 280 ° C. in thermogravimetric analysis (TGA) Above 280 ° C, rapid deprotection of t-butyl (t-Bu) groups occurred, resulting in a 21% weight loss, corresponding to the occurrence of 2-methylpropene, resulting in P (t-BuOMI / St) Excellent thermal properties with very high pyrolysis temperature. In differential scanning thermal analysis (DSC), P (t-BuOMI / St) showed endothermic phenomena corresponding to deprotection of t-Bu groups at 283 ° C in the first measurement observed at room temperature to 300 ° C. After cooling the same protected sample to room temperature, the glass transition temperature was 245 ° C. in the second measurement observed while raising the temperature again, and the polymer main chain began to decompose at 340 ° C. As described above, the copolymer P (t-BuOMI / X-St) of t-BuOMI referred to in the present invention generates 2-methylpropene by deprotection of t-Bu groups at a high temperature of 250 ° C. or higher, and deprotection. The copolymer P (HOMI / X-St) of the obtained N-hydroxymaleimide (HOMI) structure had a glass transition temperature of 245 ° C or higher.

The t-Bu protected maleimide copolymers prepared by the polymerization of t-BuOMI and styrene derivatives and other monomers in the present invention all exhibited excellent film forming ability. Typically, P (t-BuOMI / St) was very well soluble in organic solvents such as chloroform, dioxane, tetrahydrofuran and chlorobenzene, while the deprotected polymer was well soluble in alkaline aqueous solutions such as caustic soda and ammonium salts. It was found to be insoluble in organic solvents, so that excellent image forming ability by selective development was observed before and after deprotection of t-Bu group.

The solubility change according to representative P (t-BuOMI / St) deprotection in the protective maleimide copolymer in the present invention is summarized in Table 1. In addition, t-Bu group deprotection of this polymer film in the presence of an organic acid was observed at 150 ° C. or lower and ordinary microimage formation experiments were conducted to confirm its applicability as a highly sensitive chemically amplified resist.

Pyrolysis behavior analysis, a polymer that is an important feature of the present invention, was carried out using a DuPont Model 910 DSC and Model 951 TGA at a temperature increase rate of 10 ° C. under nitrogen gas. The inherent solution viscosity of the produced polymer was measured with a glass viscous tube at 25 ° C. with a dioxane solution concentration of 0.20 g / dl. Some embodiments of the present invention are described in detail below, but these examples do not limit the scope of the present invention.

Reference Example

[Synthesis method of t-BuOMI monomer]

Maleic anhydride and furan were refluxed in a toluene solution to synthesize 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, and methanol solution of hydroxyl amine and 3,6-epoxy-1 N-hydroxy-3,6-epoxy-1,2,3,6-tetrahydrophthalimide was synthesized by reacting 2,3,6-tetrahydrophthalic anhydride in a yield of 81%. N-hydroxy-3,6-epoxy-1,2,3,6-tetrahydrophthalimide was placed in a pressure reactor and reacted with isobutylene at 110 ° C. for 8 days under sulfuric acid catalytic conditions. The solvent was evaporated under reduced pressure at to prepare N- (t-butoxy) -3,6-epoxy-1,2,3,6-tetrahydrophthalimide with a yield of 82%. 10.4 g of N- (t-butoxy) -3,6-epoxy-1,2,3,6-tetrahydrophthalimide was taken and pyrolyzed in an oil bath at 145 ° C. for 2 hours to obtain a high purity of the desired monomer t-BuOMI. 5.6 g (yield 75%) was prepared.

The produced t-BuOMI has a melting point of 92 ℃ and its chemical structure was confirmed by infrared spectroscopy, nuclear magnetic resonance analysis, and elemental analysis.

Example 1

[Preparation of homopolymer of t-BuOMI]

To the monomer t-BuOMI 1.7 g (10 mmol) was added 27.0 mg (0.10 mmol) of the radical polymerization initiator Dicumyl peroxide (DCP), placed in a glass tube ampoule for polymerization, and then polymerized at 110 ° C for 3 hours. The polymerization reaction was poured into methanol to precipitate the polymer and recovered and dried to obtain 0.9 g (56% conversion) of homopolymer poly (t-BuOMI) and P (t-BuOMI). The intrinsic viscosity measured by a glass viscous tube at 25 ° C. by dissolving P (t-BuOMI) in dioxane was 0.23 dl / g.

Example 2

[Manufacture of Alternate Copolymer P (t-BuOMI / St) of t-BuOMI and Styrene]

3.0 g (18 mmol) of t-BuOMI monomer and 1.9 g (18 mmol) of styrene (St), 0.3 g (6 mol%) of dioxane and radical initiator N, N'-azobis (isobutyronitrile) (AIBN) 20 ml was added and polymerized in a 55 degreeC oil bath under nitrogen stream for 5 hours.

After the polymerization reaction, the reaction mixture was diluted in 10 ml of dioxane, poured into 2 L of methanol to precipitate a copolymer, and dried to obtain 4.2 g (86% conversion) of P (t-BuOMI / St) copolymer. The copolymer was identified to have a 1: 1 alternating structure as a result of carbon-13 and proton nuclear magnetic resonance analysis, and a thermal analysis showed a 21% weight loss corresponding to deprotection of t-butyl group at 283 ° C.

Intrinsic viscosity was found to be 0.53 dl / g. When P (t-BuOMI / St) was deprotected, an alternating copolymer of P (HOMI / St) was obtained. The glass transition temperature of P (HOMI / St) was found to be 245 ° C.

Example 3

[Preparation of copolymer P (t-BuOMI / X-St) of t-BuOMI and styrene derivative]

The monomer t-BuOMI was converted into styrene derivative (X-St), p-methyl styrene (MeSt), p-acetoxy styrene (AcOSt), p-styrene chloride (ClSt), m-methyl chloride (ClCH ₂ St), pt And copolymerized with -BOC-oxystyrene (t-BOCSt) and p-trimethylsilylstyrene (SiSt) in a molar ratio of 1: 1. The copolymerization results of t-BuOMI and X-St monomers were carried out in the same manner as in Example 2, and are shown in Table 2.

Example 4

[Manufacture of copolymer P (t-BuOMI / MMA) of t-BuOMI and MMA]

Table 2 shows the results of copolymerization of t-BuOMI and methyl methacrylate (MMA) as in Example 2.

Example 5

[Manufacture of copolymer P (t-BuOMI / PMI) of t-BuOMI and N-phenylmaleimide (PMI)]

Table 2 shows the results of copolymerization of t-BuOMI and PMI in the same manner as in Example 2.

TABLE 1

Example: ++; Well recording, +; record, - ; Insoluble

* P (t-BuOMI / St); Alternating copolymer of t-BuOMI and styrene molar ratio 1: 1 structure.

* * P (HOMI / St); An alternating copolymer of a molar ratio 1: 1 structure of HOMI and styrene obtained by deprotecting a t-butyl group in copolymer P (t-BuOMI / St).

^# TMAH: Tetramethylammonium Hydroxide (Me ₄ NOH)

TABLE 2

* Comonomer: St is styrene; t-BuOMI is pt-BOC-oxystyrene; SiSt is p-trimethylsilyl styrene; AcOSt is p-acetoxy styrene, MeSt is p-methyl styrene; ClSt is p-styrene chloride; ClCH ₂ St is m-methyl chloride; MMA is methyl methacrylate; PMI stands for N-phenylmaleimide.

* * M / S: ratio of total monomer weight to dioxane solvent volume in molar ratio 1: 1 (g / ml)

* ηinh: Intrinsic viscosity measured, 0.20 dl / g of polymer dissolved in dioxane, measured with a glass viscosity tube at 25 ° C.

Example 6

[Resist Solution Preparation and Positive Micro Image Formation Method]

P (t-BuOMI / St) was dissolved in cyclohexanone at 10.0% to 30.0% by weight, and the onium salt and the eutectic acid, which are photoacid generators, were mixed at 5.0 to 30.0% by weight with respect to the resist polymer and filtered through an ultra fine filter. A chemically amplified resist solution was made. Next, a thin thin film having a thickness of about 1.0 μm was prepared by spin coating on a silicon wafer.

The sample wafer is prebaked for 1 to 3 minutes in a 110 ° C. oven, exposed using an ultraviolet ray apparatus or an excimer laser exposure apparatus, and after heat exposure for 1 to 3 minutes in a 100 to 110 ° C. oven. post exposure-baking: PEB) and then submerged in a 2.38 weight% aqueous solution of trimethylammonium hydroxide (TMAH) for 3 minutes to form a positive resist image of submicron.

Example 7

[Heat resistant negative micro image forming method]

The resist solution (Example 6) was spin-coated in the same manner, subjected to far ultraviolet light exposure, and then subjected to post-exposure heat treatment (PEB). The negative image formed by immersion and development for 3 minutes using the organic solvent anisole as a developing solution was formed, and the image showed heat resistance of 200 degreeC or more.

Example 8

[Fine image formation method using electron beam]

In Example 6, when the electron beam was irradiated and developed in the same manner, the same positive resist image as in Example 6 was formed, and the negative resist fine image developed in the method of Example 7 was formed.

Example 9

[General resist micro image formation method]

As the polymer, a copolymer of P (t-BuOMI / X-St) prepared in Examples 3, 4, and 5 was used, and as the photoacid generator, the conventional onium salt and organic sulfonic acid were used. Ester and cyclohexanone are used as solvents to prepare a resist solution. Chlorobenzene, 2-ethoxyethyl acetate (cellosolve acetate), dioxane, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethyl lactate, etc. The same results were obtained using a conventional solvent for preparing a resist solution and using TMAH as an alkaline developer and using an aqueous solution of caustic soda.

Claims (3)

A method for producing N-t-butoxymaleimide homopolymer, wherein the N-tert-butoxymaleimide monomer is heated and radically polymerized in the presence of dicumylperoxide. Of Nt-butoxymaleimide and styrene derivatives which are radically copolymerized with an N-tertoxy-butoxymaleimide monomer and a styrene derivative (X-St) in the presence of a radical initiator such as benzoyl peroxide and azobis (isobutyronitrile). Method for producing copolymer P (t-BuOMI / X-St) having a molar ratio of 1: 1. 3. The styrene derivative (X-St) according to claim 2, wherein the styrene derivative (X-St) is styrene, p-acetoxystyrene, p-methylstyrene, p-chloride chloride, m-methyl chloride, pt-butoxycarbonyloxystyrene, p-trimethyl A method for producing copolymer P (t-BuOMI / X-St) of silt styrene, Nt-butoxymaleimide, and a styrene derivative.