JPH06123970A - Positive resist material - Google Patents

Abstract

PURPOSE:To provide a positive resist material for a high energy ray having high sensitivity, high resolution and excellent process adaptability which has not been realized in a conventional material. CONSTITUTION:This positive resist material contains poly(hydroxystyrene) resin (a) in which t-butoxycarbonyl group is substituted for hydrogen atoms in a part of hydroxyl groups, dissolution preventing agent (b), and onium salt (c) with weight proportion of 0.55<=a, 0.07<=b<=0.40 and 0.005<=c<=0.15 satisfying a+b+c=1. This resist material can be developed with an alkali aq. soln. and reacts to high energy rays. The dissolution preventing agent (b) is a t-butylester compd. of cholic acid or deoxycholic acid. The onium salt (c) is expressed by general formula (R)nAM, wherein R is an aromatic or substd. aromatic group, and each R may be the same or different, A is sulfonium or iodonium, M is p toluenesulfonate group or trifluoromethane sulfonate group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive resist material, and in particular, it has a high sensitivity to high-energy rays such as deep ultraviolet rays, electron beams and X-rays, and can be developed with an alkaline aqueous solution. The present invention relates to a positive resist material suitable for processing.

[0002]

2. Description of the Related Art Conventionally, with the high integration and high speed of LSIs (high-density integrated circuits), miniaturization of pattern rules has been demanded, but light emitted from a light source used in a normal optical exposure technique is required. Has a long wavelength and is not a single wavelength, so there is a limit to the miniaturization of the pattern rule. Therefore, g-rays (wavelength 436 nm) or i-rays (wavelength 365 nm) emitted from an ultra-high pressure mercury lamp are also used as a light source.

However, even in this case, about 0.5 μm
The pattern rule of resolution is the limit, and L that can be produced
SI has a degree of integration of about 16 Mbit DRAM. Therefore, in recent years, far-ultraviolet lithography, which uses far-ultraviolet rays as a light source and has a shorter wavelength than g-line and i-line, is regarded as promising.

According to deep ultraviolet lithography, it is 0.1
It is also possible to form a pattern rule of up to 0.3 μm, and when a resist material having low light absorption is used,
It is possible to form a pattern having a side wall that is nearly vertical to the substrate, and it is also possible to transfer the pattern at once, so that the pattern formation processing efficiency (throughput) is higher than that of lithography using an electron beam. Excellent in high points. Moreover, in recent years, high-intensity K
Since the use of the rF excimer laser has become possible, it is necessary to use a highly sensitive resist material from the viewpoint of mass-producing LSI using the light source.

Therefore, in recent years, a chemically amplified resist material has been developed which has sensitivity equal to or higher than that of the conventional high-sensitivity resist material, and which has high resolution and high dry etching resistance and which is produced by using an acid as a catalyst (for example, Ryu (Liu)
Et al., Journal of Vacuum Science and Technology (J. Vac. Techno.), Volume B6, page 379, 1988, Already Shipley (S.
hipley) has commercialized a chemically amplified negative resist material (SAL601ER7: trade name of Shipley), which is composed of three components of a novolac resin, a melamine compound and an acid generator. However, LSI
When the negative resist material is used in the manufacturing process of 1., it is easy to form the wiring and the gate portion, but there is a drawback that it is difficult to form the contact hole that requires fine processing. It was

Further, when a chemically amplified positive type resist material which has been proposed hitherto is used as it is for pattern formation by deep ultraviolet rays, electron beams or X-rays, the solubility of the resist surface is lowered and development is carried out. Since the subsequent pattern is likely to be overhanged, it becomes difficult to control the pattern size, which not only impairs dimensional controllability during substrate processing using dry etching, but also causes the pattern to collapse. It had the drawback of being easy [K.G.C.
(Hiong) et al., Journal of Vacuum Science and Technology, Volume B7, (6), p. 1771, 1989]. Therefore, it has been strongly desired to revise a high-performance, chemically-amplified positive resist material that does not have such a defect.

In response to this demand, Ito et al. Added an onium salt to a resin called poly (butoxycarbonyloxystyrene) (referred to as PBOCST) in which the OH group of polyhydroxystyrene was protected with t-butoxycarbonyl group. Proposes a chemically amplified positive resist material (Polymers in Electronics, ACS symposium series [Polymer
s in Electronics, ACS sym
242 (Posium Series) (American Chemical Society, Washington DC. 1984), p. 11].

However, since the above-mentioned onium salt contains antimony as a metal component, it has a drawback of contaminating the substrate. In addition, Ueno et al.
Styreneoxytetrahydropyranyl) as the main component,
A positive type resist material for deep ultraviolet rays obtained by adding an acid generator to this has been proposed (36th Joint Lecture Meeting of Japan Society of Applied Physics, 1989, 1p-k-7). However,
The positive resist material has a drawback that it is easy to invert from a positive type to a negative type with respect to deep ultraviolet rays, electron beams or X-rays.

In addition to the above-mentioned drawbacks, the two-component positive resist composition comprising a resin in which an OH group is protected by a protective group and an acid generator as described above, is further dissolved in a developing solution. Needs to cleave many protecting groups, so LS
In the manufacturing process of I, there was a drawback that the film thickness of the resist was changed and stress and bubbles were easily generated in the film. Therefore, a three-component positive resist material comprising an alkali-soluble resin, a dissolution inhibitor and an acid generator has been developed as a chemically amplified positive resist material that has improved the drawbacks of the above two-component positive resist material. ing.

As such a three-component positive resist material, a resist material (RA containing a novolak resin, an acetal compound as a dissolution inhibitor and an acid generator) is added.
Y / PF resist material: Hoechst) has been developed for X-ray lithography.

However, since this resist material undergoes chemical amplification at room temperature, the resist sensitivity remarkably depends on the time from X-ray exposure to development. Therefore, it is necessary to control the time strictly at all times, but it is difficult to control the time, so that the dimension of the pattern cannot be stabilized, and the absorption of the KrF excimer laser light (wavelength 248 nm) is not possible. Due to its large size, it has a drawback that it is unsuitable for use in lithography using the laser.

By the way, in general, for chemical amplification,
Heat treatment is often required after exposure. In this case, although the number of steps is increased as compared with the case of a resist material which is chemically amplified at room temperature, it is not necessary to strictly control the time from exposure to development, so that the resist characteristics are stable. . In addition, in the case of a system in which hydrolysis is performed in the process of performing chemical amplification, water is required for hydrolysis, so it is necessary to include water in the resist material.

However, as the solvent used when the resist material is applied to the substrate, an organic solvent such as ethoxyethyl acetate which is generally insoluble in water is often used, and the resin itself used as the resist material is also compatible with water. Since many of them do not dissolve, it is difficult to contain water in the resist material, and even if it is contained, the control of the water becomes complicated.

On the other hand, in the decomposition reaction of the t-butoxycarbonyloxy group, the reaction proceeds with the two components of the t-butoxycarbonyloxy group and the acid which is the catalyst and does not require water, so that chemical amplification is performed. It is suitable for Further, since many compounds having a t-butoxycarbonyloxy group have an effect of inhibiting the solubility of the novolak resin, it is known that the t-butoxycarbonyloxy group has a dissolution inhibiting effect on the novolak resin. Has been.

From such a viewpoint, Schlegel (Sch
legel) is a novolac resin, bisphenol A
Has proposed a three-component positive resist material consisting of a dissolution inhibitor having a t-butoxycarbonyl group introduced therein and pyrogallol methanesulfonic acid ester (Spring Lee, 1990, 37th Annual Meeting of the Japan Society of Applied Physics, 28p-
ZE-4). However, in this case, it is difficult to put it into practical use because the light absorption of the novolac resin is large.

Further, Schwarm et al. Have developed bis (pt-butoxycarbonyloxyphenyl) iodonium hexafluoroantimonate as a material that serves as both a dissolution inhibitor and an acid generator [Polymer Fore Microelectronics
r for Microelectronics), Tokyo, 1989, Session A38], and proposes a positive resist material for deep ultraviolet rays in which this is mixed with a novolac resin. However, the above-mentioned positive resist material has a drawback that it is difficult to put into practical use because the novolak resin has a large light absorption and contains a metal.

[0017]

Therefore, as a result of intensive studies to solve the drawbacks of the conventional chemically amplified positive resist materials for high energy rays, the present inventors have found that a specific resin, a dissolution inhibitor, and an onium are used. The inventors have found that by combining a salt, a positive resist material for high energy rays having unprecedentedly high sensitivity, high resolution, and excellent process suitability can be produced, and arrived at the present invention. Therefore, an object of the present invention is to provide unprecedented high sensitivity, high resolution,
Another object of the present invention is to provide a positive resist material for high energy rays having excellent process suitability.

[0018]

The above objects of the present invention are as follows.
A poly (hydroxystyrene) resin a in which some of the hydrogen atoms of the hydroxyl groups are replaced with t-butoxycarbonyl groups, a dissolution inhibitor b, and an onium salt c are added in a weight fraction of 0.55 ≦.
a, 0.07 ≦ b ≦ 0.40, 0.005 ≦ c ≦ 0.1
5 and a so that a + b + c = 1, and
A positive resist material which can be developed with an aqueous alkaline solution and is sensitive to high energy rays, wherein the dissolution inhibitor b is a t-butyl ester compound of cholic acid or deoxycholic acid, and the onium salt c Is an onium salt represented by the general formula (R) n AM. R in the above general formula is an aromatic group or a substituted aromatic group, and each R may be the same or different. A is sulfonium or iodonium, and M is p-toluenesulfonate group or trifluoromethanesulfonate group.

Specific examples of the onium salt include (C _{6
^{H 5) 3 S + - O}} 3 SCF 3, (C 6 H 5 SC 6 H 4)
_{(C 6 H 5) 2 S} + - O 3 SCF 3, (C 6 H 5) 2 I + -
O ₃ SCF ₃ , (CH ₃ OC ₆ H ₄ ) (C ₆ H ₅ ) ₂ I
⁺ - _{O 3} SCF 3 and _{[(CH 3) 3 ─C 6 H} 5 ] ₂ I + ^-
An onium salt having a trifluoromethanesulfonate group represented by O ₃ SCF ₃ , or a trifluoromethanesulfonate group in these substituted with a p-toluenesulfonate group [eg (C ₆ H ₅ ) ₃ S ^+- O ₃
SC ₆ H ₄ CH ₃ , (C ₆ H ₅ SC ₆ H ₄ ) (C
^{_{6 H 5) 2 S + -}} O 3 SC 6 H 4 CH 3, (C 6 H 5) 2
I ⁺ -O ₃ SC ₆ H ₄ CH ₃ , (CH ₃ OC ₆ H ₄ ) (C
^{_{6 H 5) 2 I + -}} O 3 SC 6 H 4 CH 3 and [(CH _3)
3 ─C ₆ H _{5] ^{2 I + - O 3 SC 6}} H 4 CH 3) onium salt] and the like, each having represented p─ toluenesulfonate group and the like.

Generally, the onium salt used in the positive type resist material is diglyme, ethyl cellosolve acetate, ethyl lactate or methoxy-2 used at the time of coating.
--Good solubility in a solvent such as propanol, good compatibility with the resin (base polymer) and dissolution inhibitor used, and the exposed portion when exposing the resist coated substrate It is preferably one that does not invert to a negative type before completely dissolved.

From the viewpoint of such solubility and compatibility,
Although the positive resist material using the para-toluenesulfonate-based onium salt is superior to the one using the trifluoromethanesulfonate-based onium salt,
From the viewpoint of the sensitivity of the resist material, the one using a trifluoromethanesulfonate system is superior. On the other hand, those using trifluoromethanesulfonate-based ones are easily inverted to a negative type.

From the above viewpoints, among the above-mentioned onium salts c, as the onium salt c used with the resin a, diphenyl (p-methoxyphenyl) sulfonium trifluoromethanesulfonate and phenyl (p-methoxyphenyl) iodonium trifluoromethanesulfonate are used. , Diphenyl (p-thiophenoxyphenyl) sulfonium-p-toluenesulfonate, diphenyl (p-
Methoxyphenyl) sulfonium-p-toluenesulfonate and phenyl (p-methoxyphenyl) iodonium-p-toluenesulfonate are preferred.

The onium salt c is crystalline, can be easily purified by recrystallization, and has excellent solubility in a solvent for resist coating such as diglyme. The content of the onium salt in the resist material is preferably in the range of 0.5 to 15% by weight. If the content is less than 0.5% by weight, the sensitivity of the resist material cannot be improved, and if it is 15% by weight or more, the cost of the resist material increases and the mechanical strength of the resist film decreases.

As the dissolution inhibitor b, from the viewpoint of preventing the pattern from inverting from the positive type to the negative type, t-butylcholate or t-butylcholate which is a t-butyl ester compound of cholic acid or deoxycholic acid. Deoxycholate is preferred. The content of the dissolution inhibitor b in the resist material is preferably in the range of 7-40% by weight. If the content is less than 7% by weight, the dissolution inhibiting effect is small, and if it is 40% by weight or more, the mechanical strength and heat resistance of the resist film are lowered.

Polyhydroxystyrene resin a in which hydrogen atoms of some hydroxyl groups are substituted with t-butoxycarbonyl groups
The substitution ratio of t-butoxycarbonyl group is 10 to
Those in the range of 50 mol% are preferable. When the substitution rate is 50 mol% or more, the solubility in an alkaline aqueous solution is lowered, so that the sensitivity of the resist material is lowered when the development is carried out using a commonly used developing solution. On the other hand, when the substitution rate is 10 mol% or less, the dissolution inhibiting effect is small.

The weight average molecular weight of the polyhydroxystyrene used is from the viewpoint of obtaining a heat resistant resist film.
The molecular weight distribution is preferably 10,000 or more, and the molecular weight distribution is preferably monodisperse from the viewpoint of forming a highly accurate pattern. When polyhydroxystyrene having a wide molecular weight distribution, such as that obtained by radical polymerization, is used, the resist material will also have a large molecular weight that is difficult to dissolve in an aqueous alkaline solution. It may cause hem pulling. Therefore, it is preferable to use monodisperse polyhydroxystyrene as obtained by living polymerization.

By the way, in the present invention, a resist material using polyhydroxystyrene obtained by living polymerization (for example, one having an average molecular weight of 10,000 and a molecular weight distribution of 1.1) is used, and a resist material of 0.2 μm is used. When the pattern of the line and the space is formed, it is possible to form the pattern with good precision without the hem. Moreover, even if the pattern thus obtained is baked at 150 ° C. for 10 minutes, no deformation is observed in the pattern and the heat resistance is sufficient.

On the other hand, a resist material using polyhydroxystyrene obtained by radical polymerization (for example, one having an average molecular weight of 12,000 and a molecular weight distribution of 3.0) was used to obtain a line of 0.5 μm. When the space pattern is formed, the heat resistance of the pattern is almost the same, but since the hem is visible, a resolution of 0.2 μm cannot be obtained.

The monodispersity means that the molecular weight distribution is Mw / Mn.
= 1.05 to 1.50. However, M
w is the weight average molecular weight of the polymer, and Mn is the number average molecular weight. In the case of living polymerization, the weight average molecular weight can be easily calculated by calculating from the weight of the monomer and the number of moles of the initiator, or by using the light scattering method. Moreover, the number average molecular weight is easily measured using a membrane osmometer.

The molecular weight distribution can be evaluated by gel permeation chromatography (GPC), and the molecular structure is infrared absorption (IR) spectrum or ¹ H.
-It can be easily confirmed by the NMR spectrum. The first method for obtaining a monodisperse polymer is as follows:
A method of fractionating a polymer having a wide molecular weight distribution, which is obtained by a radical polymerization method, and a method of obtaining a monodisperse polymer from the beginning by a living polymerization method are mentioned, but the step of monodispersion is simple. Therefore, it is preferable to adopt the living polymerization method.

Even if the p-hydroxystyrene monomer is subjected to living polymerization as it is, the hydroxyl group of the monomer reacts with the polymerization initiator, so that the polymerization is not started.
Therefore, a method is used in which a monomer introduced with a protective group for protecting the hydroxyl group is subjected to living polymerization and then the protective group is eliminated to obtain the target parahydroxystyrene. Examples of the protective group used include a tertiary butyl group, a dimethylphenylcarbylmethylsilyl group, a tertiary butoxycarbonyl group, a tetrahydropyranyl group, and a tertiary butyldimethylsilyl group.

For example, it can be easily obtained by subjecting a monomer represented by the following Chemical Formula 1 or Chemical Formula 2 to living anionic polymerization and then eliminating the dimethylphenylcarbyldimethylsilyl group or t-butyl group.

[Chemical 1]

[Chemical 2]

In the above living anionic polymerization, it is preferable to use an organometallic compound as a polymerization initiator. Preferred organometallic compounds include, for example, n-butyllithium, sec-butyllithium, tert-butyllithium, sodium naphthalene, anthracene sodium, α-methylstyrenetetramage sodium,
Examples thereof include organic alkali metal compounds such as cumyl potassium and cumyl cesium.

Living anionic polymerization is preferably carried out in an organic solvent. The organic solvent used in this case is a solvent such as aromatic hydrocarbon, cyclic ether, and aliphatic hydrocarbon, and specific examples thereof include, for example, benzene, toluene, tetrahydrofuran, dioxane, tetrahydropyran, dimethoxyethane, n-. Hexane, cyclohexane and the like can be mentioned.

These organic solvents may be used alone or as a mixture, but tetrahydrofuran is particularly preferably used. Monomer concentration during polymerization is 1
Appropriately ˜50 wt%, especially 1˜30 wt%, and the reaction is preferably carried out under high vacuum or in an atmosphere of an inert gas such as argon or nitrogen with stirring.

The reaction temperature can be arbitrarily selected in the range of -100 ° C to the boiling temperature of the organic solvent used. Especially when a tetrahydrofuran solvent is used
It is preferable to carry out the reaction at 78 ° C to 0 ° C and at room temperature when a benzene solvent is used. By carrying out the reaction for about 10 minutes to 7 hours under the above conditions, only the vinyl group selectively reacts and polymerizes to obtain a polymer represented by the following chemical formula 3 or chemical formula 4.

[0037]

[Chemical 3]

[Chemical 4]

When the desired degree of polymerization is reached, a polymerization reaction terminator such as methanol, water, methyl bromide, etc. is added to the reaction system to stop the polymerization reaction, thereby obtaining a living polymer having a desired molecular weight. be able to. Further, the living polymer can be purified and isolated by precipitating the obtained reaction mixture with an appropriate solvent (for example, methanol), washing and drying.

In the polymerization reaction, the monomer content is 100%.
The reaction yields a living polymer of about 10
It is 0%. Therefore, the molecular weight of the living polymer obtained can be appropriately adjusted by adjusting the amount of the monomer used and the number of moles of the reaction initiator. The molecular weight distribution of the living polymer thus obtained is monodisperse (Mw / Mn = 1.05 to 1.50).

Further, by cleaving the ether bond of the dimethylphenylcarbyldimethylsilyl group or t-butyl group of the polymer represented by the chemical formula 3 or 4, the poly (p-hydroxystyrene) represented by the following chemical formula 5 is obtained. ) Can be obtained.

[Chemical 5]

The above reaction for cleaving the ether bond is carried out by dissolving the polymer represented by Chemical formula 3 or Chemical formula 4 in a solvent such as dioxane, acetone, acetonitrile, benzene or a mixed solvent thereof, and then adding hydrochloric acid or hydrobromic acid. Alternatively, it can be easily carried out by adding an acid such as paratoluenesulfonic acid pyridinium salt dropwise. In the above reaction,
The resulting poly (p-hydroxystyrene) is monodisperse because the polymer backbone is not cleaved and no intermolecular crosslinking reactions occur.

Regarding the hydroxyl group of poly (hydroxystyrene), substituting its hydrogen atom with a t-butoxycarbonyl group is a method of protecting a functional group generally used in peptide synthesis, that is, poly (hydroxystyrene) in a pyridine solution. It is easily achieved by reacting styrene) with di-t-butyl dicarbonate.

Pattern formation on a substrate using the resist material of the present invention can be easily performed by the following method. That is, a resist material solution is spin-coated on a substrate and then pre-baked to obtain a coated substrate.

When the obtained coated substrate is irradiated with a high energy ray, the acid generator in the coated film decomposes to produce an acid.
Next, when the substrate is exposed to heat and then subjected to heat treatment, the t-butoxycarbonyloxy group is decomposed by using the generated acid as a catalyst and the dissolution inhibiting effect of the resist disappears, whereby a substrate on which a latent image is formed is obtained. Then, the substrate having the latent image is developed with an alkaline aqueous solution and washed with water to form a positive pattern. Next, a method for synthesizing the monodisperse poly (hydroxystyrene) that can be used in the present invention will be described.

Synthesis Example 1 Into a monodisperse poly (p-hydroxystyrene) synthesis reactor, charge dimethylformamide as a solvent together with imidazole, add p-hydroxystyrene and dimethylphenylcarbyldimethylchlorosilane in an equimolar amount thereto, and react at room temperature for 6 hours. Let The obtained reaction product was distilled under reduced pressure to obtain p-vinylphenoxydimethylphenylcarbyldimethylsilane (monomer) having a boiling point of 130 ° C. under a pressure of 0.1 mmHg in a yield of 70%. The monomer obtained as described above was converted into CaH ₂
After further distilling in the presence of, the product was purified using sodium benzophenone to obtain a monomer from which impurities such as water were removed.

Poly (p-vinylphenoxydimethylphen )
Synthesis of Nylcarbyldimethylsilane) In a 1-liter flask, 550 ml of tetrahydrofuran as a solvent and 8.5 × 10 ⁻⁴ mol of n-butyllithium as a polymerization initiator were charged, and the mixture was cooled to −78 ° C. When 30 g of the p-vinylphenoxydimethylphenylcarbyldimethylsilane monomer (dissolved in 50 ml of tetrahydrofuran and cooled to −78 ° C.) was added and the living polymerization reaction was carried out for 1 hour, the solution turned red. .

After confirming that the desired degree of polymerization has been reached,
Methanol was added to the reaction solution to terminate the living polymerization reaction. Next, the obtained reaction mixture was poured into methanol to precipitate the polymer, which was separated and dried to obtain 24.5 g of a white polymer. ¹ H-NMR of the obtained polymer was measured, and the results are shown in Table 1. In the polymer, only the vinyl group in the styrene portion was reacted, and the active end was reacted with the dimethylphenylcarbyldimethylsilyl group. It was confirmed to be poly (p-vinylphenoxydimethylphenylcarbyldimethylsilane) which remained without any treatment.

[0048]

[Table 1] The number average molecular weight measured by the membrane osmometry is 1
It was 1,000 g / mol.

Synthesis of poly (p-hydroxystyrene) 20 g of the synthesized poly (p-vinylphenoxydimethylphenylcarbyldimethylsilane ) was added to 250 ml of acetone.
, A small amount of hydrochloric acid was added at 60 ° C., and the mixture was stirred for 6 hours. Then, the solution was poured into water to precipitate a polymer, which was washed, separated and dried to obtain 8 g of a polymer. The molecular weight distribution (Mw / of the polymer obtained from the GPC elution curve (FIG. 1))
Mn) was 1.10, and it was confirmed that the monodispersity of the polymer was extremely high.

Further, in the ¹ H-NMR spectrum of the obtained polymer, the peak derived from the dimethylphenylcarbyldimethylsilyl group disappeared. From these results, it was confirmed that the obtained polymer was monodisperse poly (p-hydroxystyrene). The number average molecular weight of the obtained polymer by the membrane osmometry is 1.
It was 4 × 10 ⁴ g / mol.

Synthesis Example 2 Synthesis of monodisperse poly (p-hydroxystyrene) Synthesis of poly (pt-butoxystyrene) In a 2 liter flask, 1,500 ml of tetrahydrofuran as a solvent and n-butyllithium 4 × 10 ⁻ as a polymerization initiator. Charge ³ mol and cool to -78 ° C.
Then, it was distilled in the presence of CaH ₂ and then purified using sodium benzophenone to remove impurities such as water.
-T-Butoxystyrene monomer 80 g (dissolved in 50 ml of tetrahydrofuran and cooled to -78 ° C)
Was added and the living polymerization reaction was carried out for 2 hours to obtain 80 g of a white polymer in the same manner as in Synthesis Example 1.

When the ¹ H-NMR of the obtained polymer was measured, it was found that only the vinyl group in the styrene portion of the obtained polymer was reacted and the t-butyl group bonded to the ether was reacted with the active terminal. It was confirmed to be poly (pt-butoxystyrene), which was left without any treatment.

Synthesis of poly (p-hydroxystyrene ) 12 g of poly (pt-butoxystyrene) synthesized as described above was dissolved in 250 ml of acetone, and a small amount of hydrochloric acid was added at 60 ° C. and stirred for 8 hours. The solution was poured into water to precipitate a polymer, which was washed, separated and dried to obtain 8 g of a polymer. The molecular weight distribution (Mw / Mn) of the polymer obtained from the GPC elution curve (FIG. 2) is 1.08,
It was confirmed that the monodispersity of the polymer was extremely high.
In the ¹ H-NMR spectrum of the obtained polymer, the peak derived from t-butyl group disappeared.

From these results, the polymer obtained was
Poly (p-hydroxystyrene) with extremely high monodispersity
Was confirmed. The number average molecular weight of the obtained polymer measured by the membrane osmometry was 5 × 10 ⁴ g / mol.

Synthesis Example 3 T-Butoxy to poly (p-hydroxystyrene)
Into a reaction vessel for introducing a carbonyl group, 40 ml of pyridine was charged, 5 g of poly (p-hydroxystyrene) synthesized in Synthesis Example 1 was added and dissolved, and di-tert-butyl dicarbonate 1 was added at 45 ° C. with stirring.
g (about 22 mol%) was added, and the mixture was reacted in a nitrogen stream for 1 hour. A gas was generated at the same time when di-t-butyl dicarbonate was added.

The resulting reaction solution was dropped into 1 liter of an aqueous solution containing 20 g of concentrated hydrochloric acid to precipitate a polymer,
Filtration gave a white product. The obtained product was dissolved in 50 ml of acetone, dropped into 1 liter of water to precipitate the polymer, which was then filtered and dried under vacuum at 40 ° C. or lower to introduce poly (p-butoxy) carbonyl group.
-Hydroxystyrene) was obtained.

Obtained poly (p-hydroxystyrene)
From the area ratio of the aliphatic protons to the aromatic protons in the ¹ H-NMR spectrum of, the introduction rate of t-butoxycarbonyl group to poly (p-hydroxystyrene) was 1
It was confirmed to be 9.6%.

[0058]

INDUSTRIAL APPLICABILITY The positive resist composition of the present invention has high sensitivity to high energy rays, particularly to deep ultraviolet rays having a short wavelength (KrF excimer laser, etc.), and
It is a resist material suitable for fine processing of substrates used for LSI and the like because it absorbs little deep ultraviolet rays. Further, the positive resist composition of the present invention does not contain a metal element, has little time dependence after exposure, and does not require water in the chemical amplification process. It is a positive resist material that is extremely suitable for processing processes.

[0059]

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.
In addition, as the base resin in the examples, t obtained in Synthesis Example 3 was used.
A polyhydroxystyrene resin having an introduction rate of butoxycarbonyl groups of 20 mol% was used.

Example 1. Base resin 81 parts by weight t-butyl cholate (dissolution inhibitor) 14 parts by weight Diphenyl (p-methoxyphenyl) sulfonium trifluoromethanesulfonate 5 parts by weight Ethoxyethyl acetate 400 parts by weight A resist solution mixed with 2 parts on a silicone substrate. , 0
Spin coating at 00 rpm and 85 on hot plate
Pre-bake at ℃ for 1 minute, the resist film thickness is 0.7
A resist-coated substrate of μm was obtained.

After drawing on the coated side of the obtained coated substrate with a KrF excimer laser (wavelength 248 nm), heat treatment was performed at 85 ° C. for 2 minutes. Then, development was carried out for 1 minute using an aqueous solution of tetramethylammonium hydroxide (TMAH) 2.4% by weight, followed by washing with water for 30 seconds to obtain a silicone substrate (pattern substrate) on which patterns were formed.
The pattern of the obtained substrate showed positive characteristics, and the D ₀ sensitivity of the resist film was 25 mJ / cm ² . Also, Kr
When an electron beam of 30 kv is used instead of the F excimer laser, the electron beam sensitivity of the resist film is 3.0 μC / cm.
^{Was 2} . Further, the electron beam sensitivity was 2.5 μC / cm ² when the heat treatment after drawing was performed at 85 ° C. for 5 minutes.

When the KrF excimer laser was used, the obtained patterns had line and space patterns and hole patterns each having a resolution of 0.25 μm and had vertical sidewalls. The resolution of the pattern when using an electron beam was 0.2 μm.
The dissolution rate of the base resin used in the developer before pre-baking was measured to be 70 nm / sec, and the dissolution rate of the resin after pre-baking was
It was 0.5 nm / sec and 7 nm / sec after the heat treatment in the exposed area. It has been found that the addition of the dissolution inhibitor reduces the dissolution rate of the base resin by a factor of 140.

Example 2. A resist solution was prepared in the same manner as in Example 1 except that t-butyl deoxycholate was used instead of t-butyl cholate used in Example 1, and a pattern substrate was prepared and evaluated. As a result, KrF
The excimer laser sensitivity was 30 mJ / cm ² , and the electron beam sensitivity was 3.6 μC / cm ² . The dissolution rate before exposure was about 0.5 nm / sec. It was also confirmed that when the KrF excimer laser was used, it was possible to form a pattern having vertical sidewalls, and the performances regarding resolution and the like were the same as in the case of Example 1.

Examples 3 to 15. A resist solution was prepared in the same manner as in Example 1 except that the onium salts shown in Table 2 were used instead of the diphenyl (p-methoxyphenyl) sulfonium trifluoromethanesulfonate used in Example 1, and a pattern substrate was prepared. The resist characteristics in the case where the electron beam was produced and the electron beam was used were evaluated in the same manner as in Example 1.

The results are shown in Table 2. The trifluoromethanesulfonate system had higher sensitivity than the tosylate system, but in the case of the tosylate system, the sensitivity could be improved without lowering the resolution by increasing the heat treatment temperature after drawing. . Regarding the resolution, it was confirmed that a resolution of 0.2 μm could be obtained in any case.

Examples 16 to 29 Diphenyl (p- used as the onium salt in Example 1)
The resist characteristics when a KrF excimer laser was used were evaluated in exactly the same manner as in Example 1 except that the onium salts shown in Table 3 were used instead of methoxyphenyl) sulfonium trifluoromethanesulfonate. The results are shown in Table 3, and the sensitivity of the trifluoromethanesulfonate system was higher than that of the tosylate system as in the case of the electron beam. Regarding the resolution, it was confirmed that a resolution of 0.25 μm could be obtained in any case.

Examples 30 to 35 Using base resin, t-butyl cholate (dissolution inhibitor) and phenyl (p-methoxyphenyl) iodonium tosylate (onium salt), the component fractions were changed as shown in Table 4. Other than that, a resist solution was prepared in the same manner as in Example 1, a pattern substrate was prepared, and the resist characteristics when a KrF excimer laser was used were evaluated. The results are as shown in Table 4. The heat treatment after exposure is 2 at 85 ° C.
Development was carried out for 1 minute, and development was carried out for 1 minute using a 2.4% TMAH aqueous solution. In either case, a 0.25 μm pattern could be resolved.

[0068]

[Table 2]

[0069]

[Table 3]

[0070]

[Table 4]

[Brief description of drawings]

FIG. 1 is a GPC elution curve of the polymer synthesized in Synthesis Example 1.

FIG. 2 is a GPC elution curve of the polymer synthesized in Synthesis Example 2.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location G03F 7/029 H01L 21/027 (72) Inventor Tomoaki Tomoaki 3 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa 2-1 Shin-Etsu Chemical Industry Co., Ltd. Corporate Research Center (72) Inventor Minoru Takamizawa 3-2-1 Sakado, Takatsu-ku, Kawasaki City, Kanagawa Shin-Etsu Chemical Co., Ltd. Corporate Research Center (72) Inventor Keijun Tanaka Nihon Telegraph and Telephone Corporation 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo (72) Inventor Yoshio Kawai 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor, Masato Matsuda 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A poly (hydroxystyrene) in which hydrogen atoms of some hydroxyl groups are substituted with t-butoxycarbonyl groups.
The resin a, the dissolution inhibitor b, and the onium salt c are added in a weight fraction of 0.55 ≦ a, 0.07 ≦ b ≦ 0.40, 0.00, respectively.
A positive resist material which is contained so that 5 ≦ c ≦ 0.15 and a + b + c = 1 and which can be developed with an aqueous alkaline solution and is sensitive to high energy rays, wherein the dissolution inhibitor b is a call. Acid or deoxycholic acid t-butyl ester compound, and the onium salt c is an onium salt represented by the general formula (R) n AM; , R are aromatic groups or substituted aromatic groups, and each R may be the same or different. A is sulfonium or iodonium, and M is p-toluenesulfonate group or trifluoromethanesulfonate group. 2. The positive resist material according to claim 1, wherein the poly (hydroxystyrene) is a monodisperse poly (hydroxystyrene) obtained by a living polymerization reaction.