KR0148622B1 - The copolymer of n-(tert-butyloxycarbonyloxy)maleimide and styrene derivative and its processing method - Google Patents

Abstract

N- (tertiary-butyloxycarbonyloxy) maleimide (t-BOCOMI) and styrene derivative (X-St) with the unit of N- (tertiary-oxyoxyylyl) maleimide Copolymer and

Wherein X-St is styrene, p-methylstyrene, p-acetoxystyrene, p-styrene chloride, p-methyl chloride styrene, p-hydroxystyrene, p-tertiary-butoxycarbonyloxystyrene, p-trimethyl Silylstyrene and n is 20-1000.

Method for preparing N- (tertary-butyloxycarbonyloxy) maleimide and styrene derivative in dioxane and polymerizing by adding a radical polymerization initiator .

Description

Copolymer using N- (tertiary-butyloxycarbonyloxy) maleimide and its preparation method

According to the present invention, a tert-butyloxycarbonyl (hereinafter referred to as t-BOC) group, which is easy to be decomposed by acid or heat and is advantageous for protecting and deprotecting N-hydroxy groups, is represented by N-hydroxymaleimide ( N- (tert-butyloxycarbonyloxy) maleimide (hereinafter referred to as t-BOCOMI) introduced into N-hydroxymaleimide (hereinafter referred to as HONI) as a monomer The present invention relates to a copolymer usable as a heat resistant chemically amplified resist and a method for producing the same. The t-BOCOMI monomer and its preparation method are described in detail in the patent application specification filed simultaneously with the present application.

As a characteristic of the maleimide compound, a functional group can be easily introduced to the N-position of the maleimide, and various functional maleimide polymers can be synthesized using the N-substituted maleimide monomer. Electron deficient maleimide monomers exhibit high reactivity during radical copolymerization with electron rich monomers such as styrene derivatives, and thus have high polymer conversion, and the resulting polymers are used in various fields because of their excellent heat resistance.

In particular, when introducing a protecting group that can be easily deprotected by acid or heat as an N-substituent, the polymer having such a maleimide unit exhibits a significant difference in solubility due to a large polarity change before and after deprotection. It can be applied as a material. For example, the inventors have found that maleimide N-substituted with a t-BOC group and a tert-butoxy protecting group, namely N- (tertiary-butoxycarbonyl) maleimide (t-BOCMI) and N- (tertiary- Butoxy) maleimide (t-BUOMI) was newly synthesized, and a copolymer was synthesized using this as a monomer and its resist properties were investigated. The results of this study are described in detail in Korean Patent No. 70225 (1994) and in pending patent applications (application nos. 91-10272, 92-3539, 92-3540).

Since the protecting groups are easily deprotected in the presence of acid in the amount of catalyst, the deprotection reaction occurs in series, and the reaction is amplified. Therefore, the polymer using the maleimide monomer substituted with such a protecting group not only exhibits high sensitivity chemical amplification but also has high heat resistance, low light absorption in the deep UV (200-300 nm) region, and good film forming ability. Because of its characteristics, the application of the ultra-high density semiconductor (VLSI) as a microfabrication resist material is very large. As a representative example of a chemically amplified resist using deprotection of the polymer side chain, poly (t-BOC-styrene) or P (t-BOCSt) that protects a phenol group is well known. P (t-BOCSt) is deprotected at 100 ℃ or lower after exposure in the presence of a photoacid generator (PAG), so it has a high resolution of 10mJ / cm ^{2 and} a high resolution, developable alkaline aqueous solution. Used as a resist material (US Pat. No. 4,491,628 Jan 1985).

The present invention relates to a polymer for chemically amplified resists having high sensitivity, high resolution, and heat resistance as described above, and a method of manufacturing the same.

In the present invention, using the t-BOCOMI monomer and styrene derivative (X-St) to prepare a copolymer P (t-BOCOMI / X-St) having the following chemical mainly.

In the formula, X-St represents a styrene derivative and X represents a substituent such as hydrogen, methyl, acetoxy, chlorine, methyl chloride, hydroxy, t-BOC-oxy, trimethylsilyl and the like.

Synthesis of P (t-BOCOMI / X-St) was carried out according to the conventional radical polymerization method using a radical polymerization initiator.

T-BOCOMI and styrene derivatives were dissolved in dioxane in a 1: 1 molar ratio, and the copolymer was synthesized at a high conversion rate of about 80% or more in a relatively short polymerization time of less than 3 hours at 55 ° C, and the amount of initiator or solvent used was It was possible to adjust the molecular weight.

Polymerization according to the present invention was confirmed that the proton nuclear magnetic resonance analysis and elemental analysis has an alternating structure containing t-BOCOMI and styrene derivative in a 1: 1 molar ratio. In particular, in the P (t-BOCOMI / X-St) copolymer, the deprotection temperature of the t-BOC group was confirmed to be around 110 ° C by differential scanning calorimetry (DSC). This deprotection temperature is much lower than that of other t-BOC-protected maleimide polymers (up to about 150 ° C.), which has been published so far, so that better sensitivity can be expected when used as a resist material. Heating this polymer in the presence of acid results in thermal acidolysis of the t-BOC group resulting in a lower deprotection temperature. For example, copolymer P (t-BOCOMI / St) is 10% P-toluenesulfonic acid. Was deprotected at a very low temperature of about 60 ° C. in the presence of.

P (t-BOCOMI / X-St) is generally well soluble in general organic solvents and insoluble in aqueous alkali solutions, but deprotected polymers are insoluble in organic solvents, while they are soluble in alkaline aqueous solutions. Therefore, after the photoresist is mixed with P (t-BOCOMI / X-St) to prepare a resist thin film, it is exposed through a photomask and post-exposure baking (PEB) at an appropriate temperature. Since deprotection occurs and the solubility is changed, a fine image can be obtained by developing with an organic solvent or an aqueous alkali solution.

As another feature of P (t-BOCOMI / X-St) of the present invention, the polymer obtained by removing the protecting group has a high glass transition temperature of 200 ° C. or higher, thus being a step during the ultra-fine processing process of semiconductors. It satisfies the important physical properties that must be stable at 200 ° C. or higher in the resist image of a resist in a dry etching process.

In addition, in order to achieve a resolution of 0.5 μm or less, the light absorption of the resist should be appropriate without being high in the far ultraviolet region having a short wavelength or more advantageously in the wavelength of 248 nm of a high-output fluoride krypton excimer laser. The polymer containing the t-BOCOMI monomer prepared in the present invention is expected to be very suitable for use as a resist reacting to ultraviolet rays and radiation because the light absorption is very low at 0.3 / µm or less at 250 nm.

Hereinafter, the present invention will be described in detail with reference to several examples. However, these examples do not limit the present invention.

Example 1

Preparation of T-BOCOMI Styrene Shift Copolymer P- (t-BOCOMI / St) In a polymerization vessel, 4,46 g (20.9 mmol) of t-BOCOMI and 2.13 g (20.4 mmol) of styrene (St), radical initiators N, N ′-133 mg (2 mol%) of azoisobutyronitrile (AIBN) and 13 ml of dioxane were added thereto, and the mixture was polymerized in an oil bath at 50 ° C. under nitrogen stream for 2 hours. After the polymerization reaction, the reaction mixture was diluted with a small amount of dioxane, poured into 1 liter of methanol, precipitated, dried, and filtered to obtain 5.47 g (83% conversion) of P (t-BOCOMI / St) copolymer. The preparation of copolymer P (t-BOCOMI / X-St) of t-BOCOMI and styrene derivatives was carried out in a similar manner.

This copolymer was found to be 1: 1 alternating structure in the proton nuclear magnetic resonance and elemental analysis. The thermogravimetric analysis showed a 31% mass loss corresponding to the deprotection of t-BOC groups in the range of 90-120 ° C. It became. When the copolymer P (t-BOCOMI / St) was deprotected, an alternating copolymer of P (HOMI / St) was obtained. The glass transition temperature of P (HOMI / St) was found to be 260 ° C. Copolymer P (t-BOCOMI / St) before deprotection is well soluble in common organic solvents such as chloroform, anisole, 2-ethoxyethyl acetate, cyclohexanone, while it is insoluble in aqueous solution of Almaly but deprotected copolymer. P (HOMI / St) was well soaked in aqueous alkali solution and insoluble in the above-mentioned organic solvent.

Example 2

Preparation of Resist Solution and Formation of Heat Resistant Positive Microimage Dissolve P (t-BOCOMI / St) in cyclohexanone at 1 to 30% by weight, and combine onium salt, an inorganic photoacid generator, at 1 to 20% by weight with respect to the resist polymer Filtration with a fine filter produced a chemically amplified resist solution. Next, a thin film having a thickness of about 1 μm was prepared by rotating coating on a silicon wafer.

The sample wafer was pre-baked for 1 to 3 minutes on a 60 ° C. hot plate, exposed using an ultraviolet ray device, and then heat treated for 1 to 3 minutes on a hot plate at a certain temperature in the range of 50 to 70 ° C. A positive resist image was formed when the trimethylammonium hydroxide (TMAH) 2.38 weight% immersion was developed.

Example 3

Heat-resistant negative micro-image forming method The resist solution (Example 2) is spin-coated in the same manner, exposed to far ultraviolet rays and then subjected to post-heat treatment (PEB). The negative image formed by immersion and development using the organic solvent anisole as a developing solution was formed.

Claims (2)

N- (tertiary-butyloxycarbonyloxy) maleimide (t-BOCOMI) and styrene derivative (X-St) with the unit of N- (tertiary-butyloxycarbonyloxy) maleimide Copolymer. Wherein X-St is styrene, p-methylstyrene, p-acetoxystyrene, p-styrene chloride, p-methyl chloride, p-hydroxystyrene, p-tertiary-buroxycarbonyloxycitrene, p- Trimethylsilylstyrene and n is 20-1000. A method for producing an N-tertiary-butyloxycarbonyloxymaleimide-styrene derivative copolymer wherein N- (tertiary-butyloxycarbonyloxy) maleimide and styrene derivative are dissolved in dioxane and polymerized by adding a radical polymerization initiator.