KR100240823B1 - Photoresist composition - Google Patents

Abstract

The present invention is a copolymer of a styrene monomer containing a hydroxy styrene and an alkali insoluble group or a terpolymer of a styrene monomer and an acrylic monomer containing a hydroxy styrene and an alkali insoluble group as a matrix resin and 4,4'-bis- [4-Vinyloxyethoxy (4-methoxyphenyl)] The present invention relates to a two-component photoresist composition containing a sulfonium methanesulfonate-based cross-linking photoacid generator. The photoresist composition of the present invention can increase the efficiency of the process application by lowering the high temperature insolubilization temperature during soft baking.

Description

Photoresist composition

The present invention relates to a two-component photoresist composition. More specifically, the present invention is a copolymer of styrene styrene and styrene having an insoluble group in an alkaline developer or a terpolymer of styrene styrene and an acrylic monomer having an insoluble group in an alkaline developer as a matrix resin, and 4,4'-bis. -[4-vinyloxyethoxy (4-methoxyphenyl)] The present invention relates to a two-component photoresist composition containing a sulfonium methanesulfonate-based cross-linking photoacid generator.

Photoresist is a polymer material that acts as a resist to form a fine pattern on a substrate when subjected to exposure, development, etching, etc. during semiconductor ultrafine processing. During exposure, light sources are classified according to wavelength range from G-ray (436 nm) to I-ray (365 nm), KrF excimer laser (248 nm), and ArF excimer laser (193 nm). . As a main source of determining fine line width, a conventional I-line short wavelength KrF excimer laser or far ultraviolet (DUV) (248 nm) is mainly used.

In the conventional photoresist for I-ray (365 nm), a combination of novolak and diazo compound was used, but novolak resin has a high light absorption in the short wavelength region. Since the early days, a new concept of chemical-amplification resists has been developed.

Resists used in KrF excimer lasers or far ultraviolet rays are typically chemically amplified and their compositions consist of alkali soluble resins, photoacid generators, crosslinkers, dissolution inhibitors and the like. IBM's ESCAP, well known as a two-component positive photoresist composition, consists of a superacid generator of poly (t-butyloxycarbonyloxy) styrene and triphenylsulfonium salts (US 4,491,628). In order to improve the resolution, a three-component resist composition in which a dissolution inhibitor is added to an alkali-soluble resin and a photoacid generator has also been developed (JP 5,094,017, US 5,342,734, US 5,362,607).

Most recently, SUCCESS, a new composition resist composition containing a dissolution inhibiting photoacid generator in an alkali soluble resin, was developed by BASF (EP 337258A2). A dissolution inhibiting photoacid generator (PAG) refers to a compound integrating the functions of a dissolution inhibitor and an acid generator in the same molecule. This function serves to suppress dissolution for the alkali-soluble resin, but also has a function of promoting the dissolution promoting effect on the alkali-soluble resin by destroying the protecting group in the same molecule by an acid generated by light itself. Such a system is known to have a relatively high sensitivity and resolution, but results in residual film loss after development due to physical interaction between the resin and the acid generator.

On the other hand, a new type of resist composition containing a vinyl ether group in the side chain of the phenol resin has been developed (Chem. Mater, 1993, 5, 1315). It is a composition which chemically bonds vinyl ether groups directly to a polymer and separately contains a photoacid generator. The decrosslinking mechanism of this system is dependent on the acid catalyst mechanism by photoacid generated acid. However, the acid generator produces photodegradation and hydrophobic substances to suppress the dissolution of the exposed part, so that the sensitivity is weak. Especially, when triphenylsulfonium triflate is used as the acid generator, the acid generator exhibits a sensitivity of 100 mJ / cm ² or more in the KrF excimer laser. There are disadvantages.

As described above, a lot of development of photoacid generators, which are essential elements of the 248 nm resist, has been made mainly, and onium salts such as sulfonium and iodonium salts are known (US 4,760,013, US 5,397,680, EP 615163A1, EP 337258A2, JP 05,134,414, JP). 05,255,240). In recent years, it is compatibility in resists. Due to the problem of acid diffusion, the development of nonionic organic photoacid generators has been actively conducted (EP 330386A, EP 388343A0, JP 0,291,832, US 5,191,069). Meanwhile, a crosslinking type vinyl ether is substituted with a photoacid generator 4,4'-bis- [4-vinyloxyethoxy (4-methoxyphenyl) sulfonium methanesulfonate which generates super acid like conventionally known onium salts. The results of the research and development of a new concept of photoresist (Society of Plastics Engineering; 11th International Conference Photopolymers 1997), which are used as cross-linked groups rather than protecting groups, are also known. However, the photoresist incorporating the photoacid generator using the cross-linked vinyl ether showed problems such as high cost and low yield due to high temperature soft baking conditions for insolubilization during soft baking. In addition, there is a problem that the transmittance is reduced due to the use of an excess amount of photoacid generator (2 mol% or more).

Therefore, the present inventors have applied to hydroxystyrene and alkaline developer instead of polyhydroxystyrene homopolymers conventionally used to solve the problems caused by the high temperature soft baking condition and the inefficiency of the process application and the use of excess photoacid generator. The use of copolymers or terpolymers of monomers containing insoluble groups as matrix resins has led to the development of photoresist compositions containing bi-crosslinking photoacid generators.

The technical problem to be achieved by the present invention is to provide a photoresist composition suitable for low temperature soft baking conditions by using a copolymer or terpolymer of hydroxystyrene and a monomer containing an alkali insoluble group.

Another technical problem to be achieved by the present invention is to provide a photoresist composition which significantly improves the transmittance by using a relatively small amount of photoacid generator.

Another technical problem to be achieved by the present invention is to lower the soft baking temperature by using a copolymer having a low glass transition temperature to facilitate the practical application.

1 is a graph showing ultraviolet spectra for photoresists prepared according to Example 4 and Comparative Example 2. FIG.

The present invention is a copolymer of a styrene-based monomer comprising a hydroxy styrene and an alkali insoluble group represented by the formula (1) or a terpolymer of a styrene-based monomer and an acrylic monomer comprising a hydroxy styrene and an alkali insoluble group represented by the formula (2) To a matrix resin and to a photoresist composition containing a photoacid generator represented by the following formula (3):

In Formula 1, R ₁ and R ₂ are H or C ₁ -C ₁₀ alkyl, X is H, C _1-5 alkoxy or C _2-5 alkyl, m: n is 5-9: 5-1, It is preferable that it is 8-9: 2-1.

In Formula 2, R ₁ and R ₂ are H or C _1-10 alkyl, Y is C _1-5 alkoxy, a: b: c is 5-8: 0.5-2.5: 0.5-2.5, and 8: 1 : 1 is preferable.

In Formula 3, A is Cl, CH ₃ SO ₃ or CF ₃ SO ₃ , B is-(CH) _k -OCH = CH ₂ and k is an integer of 0 to 5, C is H or CH ₃ , D Is H or C _1-6 alkyl.

The photoresist composition of the present invention consists of a styrenic copolymer or terpolymer and a bi-crosslinking photoacid generator, each of which is described in detail below.

The copolymer is a copolymer of hydroxy styrene represented by Chemical Formula 1 and a styrene-based monomer including a group insoluble in an alkaline developer and polymerized with a monomer ratio of 5-9: 5-1 and polymerized with 8-9: 2-1. It is desirable to be. As such styrene monomer, tert-butyloxycarbonyl styrene is preferably used.

The terpolymer is a terpolymer of a styrene-based monomer and an acryl-based monomer containing a group insoluble in hydroxystyrene and an alkaline developer represented by Chemical Formula 2 and polymerized with a monomer ratio of 5-8.5: 0.5-2.5: 0.5-2.5. It is preferable to superpose | polymerize to 8: 1: 1.

Styrene-based monomers that may be preferably used include tert-butyloxycarbonyl styrene, and the acrylic monomers preferably include tert-butyloxycarbonyl groups.

The terpolymer used as the matrix resin of the photoresist composition of the present invention preferably has a weight average molecular weight of 5,000 to 20,000 and more preferably 9,500.

While the glass transition temperature of the polyhydroxystyrene homopolymer used in the past was 180 ° C., the copolymer containing monomers containing an alkali insoluble group can be lowered to 100 to 130 ° C., and the terpolymer may be 90 to 110 ° C. It can be lowered to ℃. Therefore, the soft baking temperature is much reduced, thereby increasing the efficiency of the process application.

In addition, the acidity caused by hydroxystyrene and the activation energy decrease during soft baking, so that acid-labile groups such as tert-butyloxycarbonyl groups are easily deprotected to other comonomers, and the reaction with the crosslinking photoacid generator used in the present invention. Chemical bonds with deprotected moieties react more strongly than hydroxystyrene homopolymers, which requires a relatively small amount of photoacid generator, greatly improving the permeability degradation problem caused by the use of excess photoacid generator (20%). Double effect).

The process of forming a positive pattern using the photoresist photosensitive composition of the present invention is as follows. In the case of the copolymer of styrene monomer containing hydroxy styrene and alkali insoluble group, it is mixed with 2-5 mol% of a cross-linking photoacid generator, and the terpolymer of styrene monomer and acrylic monomer containing hydroxy styrene and alkali insoluble group is used. In this case, 1-5 mol% of a crosslinked photoacid generator is mixed. Then, the mixture is dissolved in propylene glycol methyl ether acetate or cyclohexanone, filtered to 0.2 μm to remove impurities, and then spin-coated on a 6 inch silicon wafer. At this time, the rotational speed was 1,000 to 2500 rpm, and the resist film thickness was maintained at 6,000 to 7,000 Pa. The coated wafer is subjected to an electrothermal treatment at about 50 to 120 캜. At this time, the thermal crosslinking reaction between the hydroxyl group of the alkali-soluble resin and the acid generator vinyloxy group occurs in the resist, and the resist is insolubilized. The energy interval is 0.5 to 5 mJ and is exposed in stages, and the post-exposure heat treatment is varied from room temperature to 170 ° C. The development is a 50-second puddle, 40-second spray on NMD-3 (2.38 wt% TMAH solution) and washed with ultrapure water. During the development process, the exposed portion is insoluble in the aqueous alkali solution because it is decomposed by the generated acid and solubilized in the alkaline developer, while the unexposed portion remains in the state of crosslinking insolubility. Therefore, it shows a positive pattern with high sensitivity and high resolution.

The invention will be apparent from the following examples which are intended to be illustrative and not intended to limit the scope of the appended claims.

Example

Polymers and photoacid generators used in the following Examples and Comparative Examples were synthesized as follows.

Hydroxystyrene / tert-butyloxycarbonylstyrene copolymer

600 ml of purified toluene was added to a 1 L flask, and 0.05 g of 2,2'-azobisbutylonitrile was added to the monomer of 1 g of styrene and 10 g of tert-butyloxycarbonylstyrene as an initiator. After 24 hours of reaction at room temperature, precipitated and dried in methanol. The polymer was added to 500 ml of methanol, and 10 ml of concentrated hydrochloric acid was added thereto. The reaction was carried out at 80 ° C for 24 hours, and then deprotected hydroxystyrene / tert-butyloxycarbonylstyrene was added. The copolymer was prepared while changing the monomer ratio (5-9: 4-1) of the polymer.

Hydroxystyrene / tert-butyloxycarbonylstyrene / tert-butyloxycarbonylacrylate terpolymer

Into a 1 L flask, 600 ml of purified toluene was added, followed by 10 g of p-hydroxystyrene, 0.3 g of tert-butyloxycarbonylstyrene and 1 g of tert-butyloxycarbonylacrylate as initiators. 0.03 g of 2,2'-azobisbutyronitrile (AIBN) was added thereto, reacted at 80 ° C. for 48 hours, precipitated in methanol, dried, and the polymer was put in 1000 ml of methanol, and washed three times to obtain a polymer. Terpolymer by changing the monomer ratio (5-8.0: 0.5-2.5: 0.5-2.5) of hydroxystyrene / tert-butyloxycarbonylstyrene / tert-butyloxycarbonylacrylate terpolymer in the same manner as described above Was prepared.

Hydroxystyrene homopolymer

Into a 1 L flask, 700 ml of toluene was added as a solvent, and 20 g of tert-butyloxycarbonyl styrene monomer was added together with 0.01 g of 2,2'-azobisisobutyronitrile of 0.01 g of an initiator and reacted at 80 ° C for 12 hours. After precipitated and dried in methanol, the polymer was added to 500 ml of methanol, and 10 ml of concentrated hydrochloric acid was added thereto, followed by reaction at 80 ° C. for 24 hours to obtain a deprotected hydroxystyrene homopolymer.

Photoacid Synthesis

Synthesis of the photoacid generator used in the photoresist of the present invention was synthesized as shown in (Society of Plastics Engineering; 11th International Conference Photopolymers 1997). That is, 1 mol of di- (4-hydroxyphenyl) -4-methoxy phenyl sulfonium methane-sulfonate, 2.2 mol of vinyl-2-chloroethyl ether, and 2.2 mol of NaOH were added to 1000 ml of DMSO, followed by 70 minutes for 4 hours. The reaction was maintained while maintaining a temperature between ˜110 ° C. NaCl and DMSO used as a solvent were removed, dissolved in 1000mL of a solvent such as MC or chloroform, and then 1000mL of water dissolved in 1 mol of NaOTf was mixed and stirred for 10 hours. After separation of the non-water solution layer and vacuum drying, bis (4-vinyloxyepoxy-phenyl) -4-methoxyphenyl sulfonium triflate was obtained as a sticky liquid, which was subjected to column chromatography to increase purity. Purification by bis [4-vinyloxy-epoxy phenyl (4-methoxyphenyl)] sulfonium triflate yielded at least 99% pure yield 75%.

Example 1

Bis [4-vinyloxy-ethoxyphenyl (4-methoxyphenyl)] sulfonium triflate 2 as a hydroxy styrene / tert-butyloxycarbonyl styrene (monomer ratio 9: 1) copolymer and di-crosslinking photoacid generator The mol% was dissolved in a propylene glycol methyl ether acetate solvent to make a solvent, followed by spin coating, followed by thermal crosslinking at 130 ° C. for 90 seconds. Stepwise exposure was performed from 5 mJ to 53 mJ at 0.5 intervals, and post-exposure heat treatment was performed at 160 ° C. for 90 seconds each. After the development, the result was confirmed by a scanning electron microscope (SEM), and 40 mJ exposure was carried out to obtain a fine pattern of 0.56 μm.

Example 2

Bis [4-vinyloxy-ethoxyphenyl (4-methoxyphenyl)] sulfonium triflate 2 as a hydroxystyrene / tert-butyloxycarbonyl styrene (monomer ratio 8.5: 1.5) copolymer and a bicrosslinked photoacid generator The mol% was dissolved in propylene glycol methyl ether acetate solvent to make a solution, spin coated, and then thermally crosslinked at 110 ° C. for 60 seconds.

From 5mJ to 1mJ interval up to 53mJ and post-exposure heat treatment was performed at 120 ℃ for 90 seconds each. As a result of confirming with the scanning electron microscope (SEM) after image development, it exposed by 15mJ and obtained the fine pattern of 0.34 micrometer.

Example 3

2 mol% of hydroxystyrene / tert-butyloxycarbonylstyrene (monomer ratio 8: 2) and bis [4-vinyloxy-ethoxyphenyl (4-methoxyphenyl)] sulfonium triflate as a bi-crosslinking photoacid generator Was dissolved in propylene glycol methyl ether acetate to form a solution, spin coated, and then thermally crosslinked at 90 ° C. for 60 seconds. After the development, the result was confirmed with a scanning electron microscope (SEM) to obtain 48 mJ exposure to obtain a fine pattern of 0.60 μm.

Example 4

Hydroxystyrene / tert-butyloxycarbonyl styrene / tert-butyloxycarbonyl acrylate having a weight average molecular weight of 9,500 (monomer ratio 8: 1: 1) and bis [4-vinyloxy-e as a bi-crosslinking photoacid generator 0.5 mol% of oxyphenyl (4-methoxyphenyl)] sulfonium triflate was dissolved in a propylene glycol methyl ether acetate solvent to make a solution, followed by spin coating, followed by thermal crosslinking at 110 ° C. for 90 seconds. Exposure was performed stepwise from 5 mJ to 53 mJ at 0.5 intervals, and post-exposure heat treatment was performed at 160 ° C. for 90 seconds each. After the development, scanning electron microscopy (SEM) confirmed that the micropattern of 0.46μm was obtained by 30mJ exposure, and the ultraviolet (248nm) transmittance was 51%.

Example 5

Hydroxystyrene / tert-butyloxycarbonyl styrene / tert-butyloxycarbonyl acrylate (monomer ratio 9: 0.5: 0.5) having a weight average molecular weight of 10,000 and bis [4-vinyloxy-e as a bi-crosslinking photoacid generator 0.5 mol% of methoxyphenyl (4-methoxyphenyl)] sulfonium triflate was dissolved in a propylene glycol methyl ether acetate solvent to make a solution, followed by spin coating and thermal crosslinking at 110 ° C. for 60 seconds. From 5mJ to 1mJ interval up to 53mJ and post-exposure heat treatment was performed at 120 ℃ for 90 seconds each. As a result of the post-development scanning electron microscopy (SEM), the micro pattern of 0.34μm was obtained by 15mJ exposure, and the transmittance of ultraviolet (248nm) was 58%.

Example 6

Hydroxystyrene / tert-butyloxycarbonylstyrene / tert-butyloxycarbonyl acrylate (monomer ratio 7: 1.5: 1.5) having a weight average molecular weight of 11,000 and bis [4-vinyloxy-e as a bi-crosslinking photoacid generator 0.5 mol% of methoxyphenyl (4-methoxyphenyl)] sulfonium triflate was dissolved in a propylene glycol methyl ether acetate solvent, spin-coated, and thermally crosslinked at 90 ° C. for 60 seconds. After the development, scanning electron microscopy (SEM) confirmed that the micropattern of 0.60μm was obtained by 48mJ exposure, and the transmittance of ultraviolet (248nm) was 55%.

Comparative Example 1

After dissolving hydroxystyrene homopolymer and 2 mol% of bis [4-vinyloxy-ethoxyphenyl (4-methoxyphenyl)] sulfonium triflate as a bi-crosslinking photoacid generator in a propylene glycol methyl ether acetate solution to make a solution After spin coating, thermal crosslinking at 130 ° C. for 90 seconds was not crosslinked and crosslinking was performed at a temperature of 170 ° C. or higher after the soft baking condition was changed.

Comparative Example 2

A hydroxystyrene homopolymer having a weight average molecular weight of 9,700 and 0.5 mol% of bis [4-vinyloxy-ethoxyphenyl (4-methoxyphenyl)] sulfonium triflate as a bi-crosslinking photoacid generator were dissolved in propylene glycol methyl ether acetate. After dissolving in a solution to spin coating and thermally crosslinked at 130 ℃ for 90 seconds, but not cross-linking, cross-linking was carried out at a temperature of more than 180 ℃ after changing the soft baking conditions, and the ultraviolet (248nm) transmittance was measured 31%.

Comparative Example 3

A hydroxystyrene homopolymer having a weight average molecular weight of 10,000 and 0.5 mol% of bis [4-vinyloxy-ethoxyphenyl (4-methoxyphenyl)] sulfonium triflate as a bi-crosslinking photoacid generator were dissolved in propylene glycol methyl ether acetate. After dissolving in a solution to spin coating and thermal crosslinking at 130 ℃ for 90 seconds, but not cross-linking, cross-linking was carried out at a temperature of more than 180 ℃ after changing the soft baking conditions, and the transmittance of UV (248nm) was 35%.

The photoresist composition of the present invention is suitable for low temperature soft baking conditions by using a copolymer or terpolymer of polyhydroxystyrene and a monomer containing an alkali insoluble group, and improves permeability by using a relatively small amount of photoacid generator. Significantly improved and the use of a low glass transition temperature of the copolymer lowers the soft baking temperature has the effect of the invention easy to apply in the actual process.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (7)

A photoresist composition comprising a styrene-based copolymer represented by the following formula (1) and 1 to 30% by weight of a bi-crosslinked photoacid generator represented by the following formula (3): Formula 1 R in Formula 1_OneAnd R₂H or C_1-10Alkyl, X is H, C_1-5 Alkoxy or C_2-5Alkyl and the ratio of m: n is 5-9: 5-1; Formula 3 In Formula 3, A is Cl, CH ₃ SO ₃ or CF ₃ SO ₃ , B is-(CH) _k -OCH = CH ₂ and k is an integer of 0 to 5, C is H or CH ₃ , D Is H or C _1-6 alkyl. The photoresist composition of claim 1, wherein the monomer ratio m: n of Formula 1 is 8-9: 2-1. The photoresist composition of claim 1, wherein the styrene copolymer is a hydroxy styrene / tert-butyloxycarbonyl styrene copolymer. A photoresist composition comprising a styrenic terpolymer represented by the following Chemical Formula 2 and 1 to 20% by weight of a bi-crosslinking photoacid generator represented by the following Chemical Formula 3: Formula 2 In Formula 2 R ₁ and R ₂ is H or C _1-10 alkyl, Y is a C _1-5 alkoxy group, a: b: c is 5-8: 0.5 to 2.5: 0.5 to 2.5 Im; Formula 3 In Formula 3, A is Cl, CH ₃ SO ₃ or CF ₃ SO ₃ , B is-(CH) _k -OCH = CH ₂ and k is an integer of 0 to 5, C is H or CH ₃ , D Is H or C _1-6 alkyl. The photoresist composition of claim 4, wherein the ratio of the monomer ratio a: b: c of Chemical Formula 2 is 8: 1: 1. The photoresist composition of claim 4, wherein the terpolymer is hydroxystyrene / tert-butyloxycarbonylstyrene / tert-butyloxycarbonyl acrylate terpolymer. The photoresist composition of claim 4, wherein the weight average molecular weight of the terpolymer is 5,000 to 20,000.