KR950000702B1 - Process for preparation of n-t-butoxycarbonylmaleimid and stylene derivatives copolymer - Google Patents

Abstract

The copolymer, useful for a heat-resistant positive resist image, of N-t-butoxycarbonyl maleimide and styrene deriv. is produced by radical polycondensing an N-t-butoxycarbonyl maleimide monomer and a styrene deriv. with a radical initiator. The styrene deriv. is pref. styrene, p-acetoxystyrene, p-methylstyrene, p-t-butoxycarbonyloxystyrene, p-trimethylsillylstyrene or p- chlorinated styrene. The resist image is formed by spin-coating a soln. obtd. by dissolving the copolymer and an onium salt in a chlorobenzene on the silicon wafer, prebaking, ultra-violet exposing and postbaking the coated wafer, and developing it with a developing liquor i.e. trimethylammonium hydroxy soln., anisole, toluene, methylisobutyl ketone or chloroform.

Description

Method for preparing copolymer of N-t-butoxycarbonylmaleimide and styrene derivative and method for forming heat resistant positive resist image using copolymer of N-t-butoxycarbonylmaleimide and styrene derivative

The present invention utilizes a method for preparing a copolymer of styrene derivatives with Nt-butoxycarbonylmaleamide (hereinafter referred to as t-BOCMI) and a new monomer, and using radiation-sensitive radiation of the copolymer. A method of forming a heat resistant resist image with high sensitivity and high resolution in a highly integrated semiconductor and electronic device micromachining process.

In order to achieve high sensitivity in the micromachining process, in recent years, the chemical amplification (chenicalapplification) resist has been greatly spotlighted, thereby increasing the sensitivity of the conventional positive novolak-based photoresist by more than 100 times. A chemically amplified resist is a resist system 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.

That is, when the photoacid generator is exposed to light or irradiated with high energy radiation of X-rays or electron beams, a strong positive asset, bronsted acid, is formed, and the action of the acid causes the main chain or condensation of the matrix polymer to react and decompose. Or crosslinking, or the polarity of the polymer is greatly changed, so that the solubility increases or decreases for a given developer, thereby producing a fine image of the irradiated portion.

Onium salts are generally known as photoacid generators, and various ammonium salts, sulfonium salts, and the like, and organic sulfonic acid esters have recently been reported.

As the acid-reactive matrix polymer, a polymer having a carboxylic acid or a phenol functional group having a side chain protected with t-butyl ester, carbonate, t-butoxy or t-butoxycarbonyl (t-BOC) group is used. BOC protecting groups are known to be the best in terms of sensitivity.

The acid-reactive polymer is soluble in the organic solvent before the reaction with the protected state or acid, but the polarity is greatly changed in the structure of the polymer in the acid-reacted and de-removed state, thereby changing to an aqueous alkali solution. On the other hand, in today's advanced microlithography, high resolution is achieved through an automated process, where a fine image of a resist is 200 ° C. in a pattern transfer by plasma dry etching. It is required to have heat resistance from the above. In addition, to achieve submicron resolution, the irradiated wavelength is shorter in the ultraviolet rays of G-ray (436nm), I-ray (365nm) of ultraviolet rays (deep UV. Technological advances are moving towards shorter wavelengths of 248nm for the KrF excimer laser.

Therefore, light absorption of the resist should be appropriate in the far ultraviolet, especially in the excimer laser wavelength range.

Currently, the basic matrix polymer of the positive type photoresist used for microfabrication is an aqueous alkali solution developable novolak resin, and the novolak resin has a low glass transition temperature of 100 ° C. to 150 ° C. or lower. It is known that deformation of the microscopic image may occur, and the light absorption in the far ultraviolet region is too high to be suitable for achieving a resolution of 0.5 mu m or less.

As a resist material satisfying such high sensitivity, high resolution, and heat resistance, a polymer having a maleimide structure containing a t-BOC protecting group has come into the spotlight.

Turner, Ahn and Willson published poly (t-BOC-oxyphenylmaleimide / styrene), P (t-BOCPMI / ^st ), which had a glass transition temperature of about 235 ° C after deprotection. It has been reported that t-BOC protected maleimide-styrene copolymer (P (MI / St) -t-BOC) with heat resistance of sensitivity can be used as an far ultraviolet resist.

The introduction of the maleimide structure into the matrix polymer greatly improves the heat resistance, and the matrix polymer containing maleimide has low light absorption in the KrF excimer laser region, which is very suitable for resist applications.

However, the above two maleimide-styrene polymers are not directly polymerized from t-BOC-containing monomers, but because t-BOC protecting groups are introduced into the polymer by reaction of the polymer, there is a problem in controlling the resist polymer structure completely.

That is, the t-BOC protecting group-containing polymer P (MI / St) -t-BOC introduced the t-BOC protecting group by chemical reaction to the copolymer P (MI / St) of maleimide (MI) and styrene (St). .

Since P- (MI / St) -t-BOC starts pyrolysis of t-BOC groups at 115 ° C, problems arise in the process, and at this low temperature, de-protection of t-BOO protecting groups occurs at t-BOC It is due to the incomplete protection reaction in the polymer reaction process to introduce the protecting group. The present invention uses a t-BOC protecting group-containing polymer to efficiently produce a new t-BOC protecting monomer, t-BOCMI, styrene and styrene conductor, and other monomers by a conventional radical copolymer reaction, and uses them as a resist material.

The copolymer prepared in the present invention, unlike the synthesis by the polymer reaction described above, is completely bonded to the t-BOC protecting group in the maleimide structure, which is advantageous for the preparation of the polymer and the structure control.

In the present invention, a copolymer with a representative styrene derivative containing t-BOCMI has the following general formula (I).

In the formula, X is an alkyl group such as hydrogen, methyl or ethyl, and a silicon-containing group such as acetoxy, chlorine, methyl chloride, hydroxyl, t-BOC-oxy and trimethylsilyl, trimethylsilmethyl and the like. The copolymer of t-BOCMI and styrene derivative (XSt) of substituent X is represented by P (t-BOCMI / XSt). The radical copolymerization reaction of the t-BOCMI monomer is carried out according to a conventional polymerization method using a radical polymerization initiator. It proceeds with a high conversion of t-BOCMI of various styrene derivatives (expressed as XSt) or methyl methacrylate (MMA) monomers, and especially in the copolymerization of styrene derivatives XSt and t-BOCMI synthesized by the amount of radical initiator and solvent used. Control of the molecular weight of the polymer is possible. Copolymerization of t-BOCMI with various styrene derivatives was carried out in a 1: 1 molar ratio, and the synthesized copolymer had an alternating structure by carbon-13 and proton nuclear magnetic resonance spectroscopy.

It is well known that 1: 1 copolymers are produced when styrene derivatives, the former monomers of t-BOCMI, which are electron-deficient monomers, are copolymerized.

Representative styrene and alternating copolymers of t-BOCMI poly (t-butoxycarbonylmaleimide / styrene) and P (t-BOCMI / St) copolymers synthesized in the present invention are thermogravimetric analysis (TGA) up to 130 ° C. Stable and above 150 ° C, rapid deprotection of the t-butoxycarbonyl (t-BOC) group occurred, resulting in a 33% weight loss corresponding to 2-methylpropene and carbon dioxide evolution, resulting in P (t- It can be seen that BOCMI / St) has superior thermal properties than conventional P (MI / St) -t-BOC polymers synthesized by polymer reaction.

P (t-BOCMI / St) showed the endothermic phenomenon corresponding to deprotection of t-BOC group at 152 ° C in the first measurement observed at room temperature to 200 ° C. After cooling the same deprotected sample to room temperature, the glass transition temperature was 245 ° C in the second measurement observed while raising the temperature again, and decomposition started at 400 ° C. In the present invention, all of the t-BOC protective copolymers drawn by the polymerization of t-BOCMI and styrene derivatives and other monomers show good film-forming ability. In particular, the synthesized P (t-BOCMI / XSt) is chloroform, dioxane, It was very well soluble in organic solvents such as tetrahydrofuran and chlorobenzene, while the deprotected polymer was well soluble in aqueous alkali solution such as caustic soda and ammonium salt and insoluble in most organic solvents. The excellent image forming ability by the selective phenomenon was confirmed before and after.

Table 1 summarizes the change in solubility following deprotection of representative P (t-BOCMI / St) copolymers. In addition, t-BOC group deprotection of this polymer was observed at 100 ° C. or lower in the presence of an organic acid, and its application as a chemically amplified resist was confirmed by ordinary microscopic image experiments.

Measurement of the pyrolysis behavior of the polymer, which is an important characteristic of the present invention, was carried out using a DuPont 910 DSC and Model 951 TGA at a temperature rising rate of 10 ° C. under nitrogen gas.

The solution viscosity of the polymer was measured at 25 ° C. with a concentration of dioxane solution of 0.20 g / dl in a glass viscosity tube. Some embodiments of the present invention are described in detail below, but these examples do not limit the present invention.

Reference Example: Synthesis method of t-BOCMI monomer (patent pending)

According to the Diels-Alder reaction, 25.0 g (0.26 mol) of maleimide, 28.0 g (0.41 mol) of furan, and 100 ml of toluene were refluxed for 24 hours. The reaction was cooled to room temperature, filtered and dried to give 42.0 g (99% yield) of 3.6-epoxy-1, 2, 3, 6-tetrahydrotalimide and used for the next reaction without further purification. Take 42.0 g (0.26 mol) of 3, 6-epoxy-1, 2, 3, -tetrahydrophthalimide, dissolve in 300 ml of dimethyl sulfoxide (DMSO), and add 35.0 g (0.31 mol) of tasium t-butoxide in powder form. After stirring at room temperature for 30 minutes, di-t-butyldicarbate 0.0 g (0.28 mol) was added and reacted for 2 hours.

The reactant was poured into cooled distilled water, precipitated, filtered and dried to give N- (t-butoxycarbonyl) -3, 6-epoxy-1, 2, 3, 6-tetrahydrophthalamide containing t-BOC as a white powder. 55.0 g (81% yield) were obtained. Take 10.0 g of N- (t-butoxycarbonyl) -3, 6-epoxy-1, 2, 3,6-tetrahydrophthalimide, dissolve in 100 ml of toluene and reflux for 1.5 hours in 110 ℃ -125 ℃ oil bath. It was.

Toluene was evaporated under reduced pressure, and the obtained solid was recrystallized from a solvent of toluene and hexane (volume ratio of 1: 10) to obtain 6.7 g of high purity t-BOCMI (yield 90%). The melting point of t-BOCMI was observed at 62 ° C, and proton spectroscopy confirmed two protopes of double sum (6.70ppm) and nine fronts of t-BOC group (1.60ppm) as single peaks. 2980 cm equivalent to t-butyl in infrared spectroscopy^-One1800, 1760, 1720 cm equivalent to imides and esters²of The belt was confirmed.

In the carbon-13 proton spectroscopy, the carbon of the t-butyl group was found to be 85.24 ppm, the carbon of the olefin was 135.83 ppm, the carbon of the ester was 145.88 ppm, and the ketone carbon of the maleimide was 166.22 ppm.

Example 1

Homopolymer Preparation of t-BOCMI

A copolymer of 0.98 g (5 mmol) of monomer t-BOCMI and 12.10 g (35% conversion) of a radical polymerization initiator benzoyl peroxide (BPO) was obtained. The viscosity measured was 0.24 dl / g.

Example 2

Preparation of Alternating Copolymer P (t-BOCMI / St) of t-BOCMI and Styrene

15.8 g (80 mmol) of the radical initiator AIBN 1.1 g (6.4 mmol) was added to the polymerization vessel, dissolved in 40 ml of dioxane, and then polymerized at 55 ° C. in an oil bath under nitrogen stream for 5 hours.

After the polymerization reaction, the mixture was diluted with dioxane, precipitated in about 5 L of methanol, and recovered to obtain a copolymer of 21.4 g (89% conversion).

The carbon and proton spectroscopic paths were found to have a 1: 1 alternation structure, and thermal analysis reduced the weight of 33% corresponding to the deprotection of t-BOCMI from 150 ° C to 160 ° C. The measured viscosity was 0.95 dl / g.

Example 3

Manufacture copolymer P (t-BOCMI / XSt) of BOCMI and styrene derivative (XSt)

P-methylstyrene (MeSt), p-acetoxystyrene (AcOSt), p-styrene chloride (ClSt), m-methyl chloride (ClCH ₁ St), pt-BOC-oxy as monomer t-BOCMI and styrene derivative XSt Styrene (t-BOCSt), p-trimethylsilylstyrene (SiSt), and p-trimethylsilylmethylstyrene (SiCH ₁ St) were subjected to the same procedure as described in Example 3, with the molar ratio of monomers 1: 1. The copolymerization result of -BOCMI and each XSt monomer was shown in Table 2.

Example 4

Copolymer Preparation of t-BOCMI MMA

The copolymerization of t-BOCMI and methyl methacrylate (MMI) was carried out in the same manner as in Example 3, as shown in Table 2.

Example 5

Copolymer Preparation of t-BOCMI and N-phenylmaleimide (PhMI)

The copolymerization of t-BOCMI and PhMI was carried out in the same manner as in Example 3, and the results were as shown in Table 2.

[Table 1] Deprotection of P (t-BOCMI / ST) copolymer

Example: ++: Recorded, +; record - ; Insoluble

* P (t-BOCMI / St): Copolymer of the molar ratio 1: 1 structure of t-BOCMI and styrene.

** P (MI / St): Copolymer of mole ratio 1: 1 structure of styrene of maleimide obtained by deprotecting t-BOC group from P (t-BOCMI / St) copolymer

* TMAH: Tetramethylammonium Hydroxide

Table 2 Copolymerization Results of t-BOCMI

* Comonomer: St is styrene; AcOSt is p-acetoxy styrene; MeST is p-methylstyrene; ClSt is p-styrene chloride; ClCH ₂ St is m-methyl chloride; BOCSt is pt-butoxycarbonyloxystyrene; SiSt is p-trimethylsilyl styrene; SiCH ₂ St is p-trimethylsilylmethylstyrene; MMA is methacrylmethyl; PhMI is N-phenylmaleimide.

** Volume ratio of dioxane solvent to total weight of monomers used in M / S: molar ratio 1: 1.

* ninh: intrinsic viscosity measurement, dioxane solution concentration 0.20g / dl, 25 ℃ solution.

Example 6

Resist Solution Preparation and Positive Micro Image Formation Method

Dissolve P (t-BOCMI / St) in chlorobenzene at 10.0% to 20.0% by weight, and mix the photoacid generator onium salt and organic sulfonic acid at 5.0 to 20.0% by weight with respect to the resist polymer to form a chemically amplified resist solution. Spin coating was performed on the wafer to prepare a thin film having a thickness of about 1.0 μm.

The sample wafer was prebaked in a 110 ° C. oven for 3 to 10 minutes, postexposurebaked (PEB) in a 100 to 110 ° C. oven for 1 to 3 minutes after exposure to ultraviolet light, and then trimethammonium hydroxide ( TMAH) Submerged in 2.38 weight% aqueous solution for 3 minutes, the submicron resist image was formed.

Example 7

Heat-resistant negative image forming method

The resist solution (Example 6) was spin-coated in the same direction, exposed to ultraviolet light and then subjected to post-exposure heat treatment (PEB). After immersion for 3 minutes using an organic solvent, anisole, as a developing solution, a negative image was formed and exhibited heat resistance of 200 ° C. or higher.

Example 8

Resist Micro Image Formation Method

In Examples 6 and 7, photoacid generators include conventional onium salts and organic sulfonic acid esters, and cyclohexanone and 2-ethoxyethyl acetate (cellosolve acetate), including chlorobenzene, as a solvent used for preparing a resist solution. Conventional solvents for preparing resist solutions, such as dioxane and methyl isobutyl ketone, were used. The same result was obtained when using TMAH and alkaline caustic aqueous solution as alkaline developing solution.

Claims (4)

A copolymer of Nt-butoxycarbonylmaleimide monomer and a styrene derivative by radical copolymerization of Nt-butoxycarbonylmaleimide and a styrene derivative in which the molar ratio of Nt-butoxycarbonylmaleimide and styrene derivative is 1: 1. Manufacturing method The styrene derivative according to claim 1, wherein the styrene derivative is styrene, P-acetoxystyrene, P-methylstyrene, P-styrene chloride, m-methyl chloride, Pt-butoxycarbonyloxystyrene, P-trimethylsilylmethylstyrene, P A method for producing a copolymer of -Nt-butoxycarbonylmaleimide, which is -trimethylsilylstyrene, and a styrene derivative. A spin-coated solution of a copolymer of Nt-butoxycarbonylmaleimide and a styrene derivative and an onium salt in chlorobenzene was spin-coated on a silicon wafer, followed by prebaking, post-heat treatment, and development. Positive resist image forming method. 4. The method of claim 3, wherein the developer is an aqueous solution of trimethylammonium hydroxide, anisole, toluene, methyl isobutyl ketone, and chloroform.