JPH05232704A - Positive type resist material - Google Patents

Abstract

PURPOSE:To provide a positive type resist material for exposure with high energy ray, which is equipped with high sensitivity, high resolution, and excellent process adaptability. CONSTITUTION:A positive type resist is formed which is sensitive for high energy beam and can be developed with an alkaline aqueous solution containing three components, i.e., (A) a resin of such a structure that part of each hydroxyl radical of polyhydroxystylene is substituted by t-butoxycarbonyl oxy radical, (B) dissolution inhibitor, and (C) acid generating agent, wherein (A) is composed of two or more types of resin having different rate of substitution while (B) contains one or more t-butoxycarbonyl oxy radicals in one molecule and is prepared under such conditions with its weight proportion that 0.01<=B<=0.40, 0.005<=<=0.15, 0.55<=A, A+B+C=1. It may also be accepted that polyhydroxy stylene is added. The resultant presents excellent dimensional controllability, is embodied in a simple system, and favorable for fine processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to deep ultraviolet rays, electron beams and X-rays.
The present invention relates to a positive resist material having high sensitivity to high energy rays such as rays and capable of forming a pattern by developing with an alkaline aqueous solution and suitable for a fine processing technique.

[0002]

2. Description of the Related Art As LSIs become more highly integrated and operate at higher speeds, finer pattern rules are required. In photoexposure, which is currently used as a general-purpose technique, an essential factor is derived from the wavelength of the light source. The limit of resolution is approaching. g line (43
6 nm) or i-line (365 nm) as a light source, the pattern rule of about 0.5 μm is the limit, and the integration degree of the LSI manufactured using this is 1
Up to 6 Mbit DRAM. However, the trial manufacture of LSI has already reached this stage, and the development of further miniaturization technology is urgently needed. Against this background, far-ultraviolet lithography is promising as a next-generation microfabrication technology. Deep-UV lithography is capable of processing 0.3 μm or less, and when a resist having a small light absorption is used, it is possible to form a pattern having a side wall that is nearly vertical to the substrate. Moreover, since the patterns can be transferred at one time, it is advantageous in terms of throughput over electron beam lithography. In recent years, a high-intensity KrF excimer laser is used as a light source for far-ultraviolet rays, and a resist material having low light absorption and high sensitivity is required for use as a mass production technique. Recently developed,
Chemical amplification with acid as catalyst
Resist material for performing the above (for example, Liu et al., Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.), Volume B6, Volume 37).
Page 9 (1988)] has excellent characteristics that it has sensitivity equal to or higher than that of a conventional high-sensitivity resist, high resolution, and high dry etching resistance. Therefore, it is a particularly promising resist material for deep ultraviolet lithography. As a negative resist, Shipley has already commercialized a three-component chemically amplified resist (trade name SAL601ER7) consisting of a novolak resin, a melamine compound and an acid generator. However, no chemically amplified positive resist has been commercialized yet. In the LSI manufacturing process, wiring and gate formation can be handled with a negative resist, but contact holes can be easily fogged by using a negative resist, so fine processing is difficult.
Positive resists are much more suitable. Therefore, a high-performance positive resist is strongly demanded. Previously, Ito et al.
-PB protected with butoxycarbonyl group (tBoc group)
We are developing a positive chemically amplified resist by adding an acid generator to a resin called OCST. However, the acid generator used contains antimony as a metal component [References: Polymers in Electronics, ACS Symposium Series (Polymers in Electronics, ACS
Symposium Series) 242nd (American Chemical Society, Washington DC. 1984), p. 11]. To avoid contamination of the substrate, metal components in the resist material are generally disliked. Therefore, the PBOCST resist is not preferable in the process. Ueno et al. Have announced a deep-UV positive resist containing poly (p-styreneoxytetrahydropyranyl) as a main component and an acid generator added (reference: 36th Association of Applied Physics Association Related Lecture, 198).
9 years, 1p-k-7). However, according to the study by the present inventors, this material system was easy to undergo positive-negative inversion with respect to far ultraviolet rays, electron beams and X-rays. In the case of the two-component positive resist including the resin in which the OH group is protected by the protective group and the acid generator as described above, in order to be dissolved in the developing solution,
Many protecting groups need to be cleaved. At that time, there is a high possibility of causing a change in film thickness, stress in the film, generation of bubbles, and the like. As the chemically amplified positive resist, a three-component system with more differentiated functions, that is, an alkali-soluble resin,
Since the material system consisting of the dissolution inhibitor and the acid generator requires a smaller amount of the dissolution inhibitor in which the acid should be decomposed, it is possible to further reduce the film thickness change and bubble generation as described above. Yes, it is presumed to be more useful for precise microfabrication. As a three-component positive resist, Hoechst has developed a resist material-RAY / PF-for an X-ray lithography in which an acetal compound is added to a novolac resin as a dissolution inhibitor and an acid generator is further added. Since RAY / PF performs chemical amplification at room temperature, the resist sensitivity remarkably depends on the standing time after X-ray exposure. In practical use, it is presumed that the pattern dimension controllability is difficult because it is difficult to constantly and strictly control the time between the exposure and development steps. Further, there is a problem that the light absorption at the exposure wavelength (248 nm) of the KrF excimer laser is large. In general, post-exposure baking (PEB) is often required for chemical amplification. Although the resist process step is increased by one step as compared with a material system in which chemical amplification is performed at room temperature, the control of the resist characteristics is easier because the time control between exposure and development is loose. In addition, in a system in which hydrolysis is performed in the chemical amplification process, water is required for the hydrolysis reaction, and therefore it is necessary that the resist material contains water. In general, an organic solvent that is immiscible with water, such as ethoxyethyl acetate, is often used as a coating solvent for the resist material, and the resist resin itself is often a material that is not easily compatible with water. It is not preferable to mix a predetermined amount of water with such a material system, and even if it is possible to mix it, the components to be controlled increase, so that the system becomes more complicated and is not preferable. .. On the other hand, tBoc
The group decomposition reaction proceeds with the two components of the tBoc group and the acid that is the catalyst, and does not require water as the third component.
The reaction is simple and convenient for use in chemical amplification. It is known that many of the compounds converted to tBoc have the effect of inhibiting the solubility of the novolak resin, and the tBoc group is useful for expressing the ability to inhibit dissolution. Schlegel et al. Have announced a three-component positive resist consisting of a novolak resin, a bisphenol A tBoc-ized dissolution inhibitor, and pyrogallol methanesulfonate (Spring 1990, 37th Association for Applied Physics Association Lecture 28p-ZE-4). Schwalm et al. Have developed bis (pt-butoxycarbonyloxyphenyl) iodonium hexafluoroantimonate as a material combining a dissolution inhibitor and an acid generator [Polymer for microelectronics (Polymer for microelectronics Microelectronics) (Tokyo,
1989), session A38]. This is mixed with novolac resin to form a deep UV positive resist. However, this material system is not practically preferable because it contains a metal and the novolak resin absorbs a large amount of light. Kumada et al. Used a resin obtained by substituting a part of polyhydroxystyrene, which has low light absorption, with a tBoc group as a base polymer, and added a dissolution inhibitor and an acid generator to make it a positive resist for deep UV rays (40th Polymer Debate 2H-01,199
1, Okayama). However, this material has a large molecular weight distribution of polyhydroxystyrene and uses one type of resin having a substitution ratio of tBoc group, so that the defocus margin becomes small in the pattern of 0.3 μm or less in KrF lithography. was there. In addition, the conventional chemically amplified positive resist has a drawback that the pattern tends to be overhanged when formed by deep ultraviolet rays, electron beams or X-rays. This is presumably because the solubility of the resist surface is reduced [Reference; K. G. Thion (K.
G. Chiong) et al., Journal of Vacuum Science and Technology, Volume B7, (6), p. 1771 (1989)]. The overhang shape makes pattern size control difficult and impairs dimensional controllability even during substrate processing using dry etching. Also, since the lower part of the pattern is thin, it is easy to cause the pattern to collapse.

[0003]

As described above,
Many chemically amplified positive resists based on novolac resin or polyhydroxystyrene, which have sensitivity to deep ultraviolet rays, electron beams and X-rays, have been published, but all of them have problems. At present, it is still difficult to put it into practical use. It is an object of the present invention to provide a positive resist material for high energy beam exposure, which is superior in sensitivity, resolution, and process applicability to the prior art.

[0004]

The present invention will be described in brief. The present invention relates to a positive resist material, in which a part of hydroxyl groups of polyhydroxystyrene is t-butoxycarbonyloxy (hereinafter referred to as tBoc-O-). Abbreviated as a group), a high-energy-ray-sensitive positive resist capable of being developed with an alkaline aqueous solution, which contains a resin (A) substituted with a group, a dissolution inhibitor (B), and an acid generator (C). Resin (A) in which a part of hydroxyl groups of polyhydroxystyrene is substituted with tBoc-O- group is composed of two or more kinds of resins having different substitution rates, and the dissolution inhibitor (B) is 1 in 1 molecule.
Containing at least tBoc-O- groups and having a weight fraction of 0.0
1 ≦ B ≦ 0.40, 0.005 ≦ C ≦ 0.15, 0.5
It is characterized in that 5 ≦ A and A + B + C = 1.

The acid generator (C) has the following general formula (formula 1).

[0006]

[Chemical formula 1] (R) _n AM

(In the formula, R may be the same or different and represents an aromatic group or a substituted aromatic group, A is sulfonium or iodonium, M is trifluoromethanesulfonate ( ⁺ -O ₃ SCF ₃ ), hexafluorophosphate) ( ⁺ -PF ₆ ), hexafluoroantimonate ( ^+-
SbF ₆ ), hexafluoroarsenate ( ⁺ -As
Shows the F _6). Further, an onium salt represented by n is a positive integer of 2 or 3, or an acid generator such as halogenated methyltriazine, tetrabromobisphenol A, a dinitrobenzyl ester compound, and pyrogallol methanesulfonate can be used. Solubility, reactivity (sensitivity), acid diffusion (resolution), ease of production, resin for solvents suitable for coating resist such as ethyl cellosolve acetate, ethyl lactate, 1-methoxy-2-propanol, etc. The optimum acid generator is selected based on the compatibility with and the like.

Conventionally, the most practical acid generator for chemically amplified resist acid is said to be an aromatic sulfonium salt (reference: Okawa, et al., 37th Association of Applied Physics Association Related Lecture Meeting, 28p-PD-2, 1990). However, some acid generators were effective against electron beams and X-rays but had low solubility on the resist bottom surface in KrF lithography and were difficult to separate into patterns. It is presumed that this is due to the dissolution inhibiting effect of the acid generator itself. Therefore, it is necessary to select an optimum acid generator depending on the energy ray used for exposure. The inventors of the present invention are organic acid generators, which have a high solubility in a resist coating solvent, and are acid generators in a positive resist material composed of a polyhydroxystyrene resin, a tBoc dissolution inhibitor and an acid generator. as,
In (Chemical Formula 1), it was found that a compound having a phenyl group having a substituent such as a methoxy group in R exhibits good properties.

The content of (Chemical Formula 1) in the resist of the present invention is preferably 0.5 to 15 wt%. If it is less than 0.5%, positive resist characteristics are exhibited, but the sensitivity is low. As the content of the acid generator increased, the resist sensitivity tended to increase and the contrast (γ) improved. Even if it exceeds 15%, it shows positive type resist characteristics, but further increase in sensitivity due to increase in content cannot be expected, (Chemical formula 1) is an expensive reagent, and increase in low molecular components in the resist It is preferable that the content of (Chemical Formula 1) is 15% or less because the mechanical strength of the resist film is lowered. The resist material according to the present invention using (Chemical Formula 1) essentially contains at least one tBoc-O- group in one molecule as a dissolution inhibitor. The content of dissolution inhibitor is 1 to 40 wt.
% Is good. If it is less than 1%, the dissolution inhibiting effect is small, and 40%
If it is more, the mechanical strength and heat resistance of the resist will be reduced. The tBoc compound as a dissolution inhibitor for a positive resist, which has been conventionally announced, is almost the only material obtained by converting the OH group of bisphenol A to tBoc. However, as a result of diligent studies, the present inventors have found that even those obtained by converting phloroglucin, tetrahydroxybenzophenone and the like into tBoc are useful as dissolution inhibitors.

When a novolac resin is used as the base resin, there is a problem that absorption by KrF laser light is large, so it was decided to use polyhydroxystyrene, which has small absorption, but the dissolution inhibitory effect when a dissolution inhibitor is added. Is small. This is because polyhydroxystyrene has a high solubility, and in order to control the solubility, a part of the hydroxyl groups is tBo.
Substitution with the c group gave a dissolution inhibiting effect of one digit or more. However, when the resin (A) substituted with tBoc-O-styrene group is used as one type of resin, when a line & space pattern of 0.30 μm or less is formed by KrF lithography with a thickness of 1 μm, it is separated at the bottom surface of the pattern. In order to resolve, there is a problem that the width of the pattern surface becomes small or film loss occurs. That is, the pattern shape becomes a triangle, which causes a reduction in the process margin.

In order to address this problem, the inventors of the present invention have earnestly studied the improvement of the dissolution rate ratio between the exposed portion and the unexposed portion, and as a result, one resin having a constant substitution rate of tBoc-O-styrene was used alone. It was discovered that a larger dissolution rate ratio can be obtained by mixing two or more kinds of resins having different substitution rates than those used in. The reason for this is presumed to be that the unexposed portion has a large dissolution inhibiting effect due to the influence of the resin having a high substitution rate, and the exposed portion has a large dissolution promoting effect due to the influence of the resin having a low substitution rate. This phenomenon is presumed to be a problem peculiar to this resin.

By the method of mixing two or more kinds of resins having different substitution rates according to the present invention, a line & space pattern of 0.25 μm or less can be formed by KrF lithography with a resist thickness of 1 μm almost perpendicular to the substrate. did it. In addition, the defocus margin is 0.3 μm, and the line and space pattern is 1.5 μm, which is practically no problem. When one resin with a constant replacement rate is used alone, the defocus margin is 0.3 μm
The space pattern was only 0.5 μm. From this, it can be seen that the present invention significantly improved the process margin.

The advantage of mixing two or more kinds of resins having different substitution rates of tBoc is that the alkali solubility of the resin can be easily controlled in addition to the above. When the resin is used alone, the alkali solubility of the resin is uniquely determined by the substitution ratio of tBoc.
It is necessary to accurately control the oc substitution rate. However, since the substitution rate greatly changes depending on the manufacturing conditions and the manufacturing scale, it is very difficult to manufacture it with the accuracy required for the resist material for forming a fine pattern. In the case of the present invention, it can be easily controlled by controlling the compounding ratio of two resins having different substitution rates.

The substitution rate of tBoc can be from 0 to 100%, and the substitution rate and the mixing rate can be selected according to the alkali concentration of the developer. When a commonly used developer is used, the substitution rate of tBoc is preferably 50% or less. When a resin having a substitution rate of more than 50% is used, the solubility in an alkaline aqueous solution is extremely reduced.
The poorly soluble layer is formed on the surface, and the resist pattern shape is likely to be a so-called T-top. This T-top pattern can be used for lift-off. However, when the substitution rate is 70% or more, the sensitivity of a commonly used developing solution is extremely lowered.

The weight average molecular weight of the polyhydroxystyrene is preferably 10,000 or more from the viewpoint of the heat resistance of the formed resist pattern, but the one obtained by radical polymerization has a large molecular weight distribution and is therefore soluble in an alkaline aqueous solution. Includes difficult and high molecular weights, which cause tailing after pattern formation. Therefore, it is advantageous for highly accurate pattern formation that the molecular weight is large and the molecular weight distribution is as small as possible. In the present invention, when polyhydroxystyrene obtained by living polymerization (molecular weight: 14,000, molecular weight distribution: 1.1) was used, a 0.2 μm line & space pattern could be accurately formed by electron beam drawing without trailing. .. Moreover, regarding heat resistance, pattern deformation was not observed even after baking at 150 ° C. for 10 minutes. The polymer having a molecular weight of 12,000 obtained by radical polymerization had a molecular weight distribution of 3.0, and a pattern tail was observed even in a 0.5 μm line & space pattern.

The method for obtaining a polymer having such a narrow molecular weight distribution is generally a method of narrowing the molecular weight by separating a polymer having a broad molecular weight distribution polymerized by a radical polymerization method or the like according to the degree of polymerization by fractionation treatment, and living A method in which the molecular weight is regulated by the polymerization method can be mentioned, but the former fractionation method complicates the process and lowers the yield. Therefore, the living polymerization method is preferably used. However, in the para-hydroxystyrene polymer of the present invention, if the para-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 does not proceed. For this purpose, a method is used in which a monomer having a protective group for protecting a hydroxyl group is subjected to living polymerization, and the protective group is eliminated after the polymerization to obtain the target parahydroxystyrene polymer. Examples of these protecting groups include a tertiary butyl group, a dimethylphenylcarbinyldimethylsilyl group, a tBoc group, a tetrahydropyranyl group, and a tertiary butyldimethylsilyl group.

More specifically, the narrow-dispersion polyhydroxystyrene, which is the base resin of the resist material of the present invention, has, for example, a structural formula (Formula 2) or a structural formula (Formula 3).

[0018]

[Chemical 2]

[0019]

[Chemical 3]

It is obtained by subjecting the monomer represented by the formula (1) to living polymerization, and then eliminating the dimethylphenylcarbinyldimethylsilyl group in the structural formula (Formula 2) and the t-butyl group in the structural formula (Formula 3). A polymerization initiator is used for living polymerization of the above monomers, and an organometallic compound is used as the polymerization initiator. For example, n-butyllithium, s
Organic alkali metals such as ec-butyllithium, t-butyllithium, sodium naphthalene, sodium anthracene, sodium α-methylstyrene tetrameride, cumyl potassium, cumyl cesium and the like can be mentioned.

Living polymerization of the above monomers generally involves
It is carried out in an organic solvent. The organic solvent used in this case is an aromatic hydrocarbon, a cyclic ether or an aliphatic hydrocarbon solvent, and specific examples thereof include benzene, toluene, tetrahydrofuran, dioxane, tetrahydropyran, dimethoxyethane and n-hexane. , Cyclohexane and the like. These organic solvents may be used alone or in combination of two or more. The concentration of the monomer in the polymerization is 1 to 50% by weight, especially 1 to
30 wt% is preferable, and the reaction is carried out by stirring under high vacuum or in an atmosphere of an inert gas such as argon or nitrogen.
The reaction temperature can be freely selected from −100 ° C. to the boiling point temperature of the organic solvent used. Particularly, tetrahydrofuran solvent is preferably −78 ° C. to 0 ° C., and benzene solvent is preferably room temperature. Polymerization is usually carried out for about 10 minutes to 7 hours, whereby only vinyl groups selectively react and polymerize to form the following structural formulas (chemical formula 4) and structural formula (chemical formula 3). Then, a polymer represented by the following structural formula (Formula 5) is obtained.

[0022]

[Chemical 4]

[0023]

[Chemical 5]

After that, for example, a terminating agent such as methanol, water or methyl bromide is added to the reaction system to stop the reaction. Further, the obtained reaction mixed solution can be purified and isolated by precipitating with a suitable solvent such as methanol, washing and drying. The polymer compound thus obtained is monodisperse in terms of molecular weight distribution (1.00 <Mw
/Mn≦1.50).

The yield of the polymer is almost 100% based on the monomer used in the reaction, and the molecular weight of this polymer is easily calculated from the weight of the monomer used and the number of moles (number of molecules) of the polymerization initiator. it can. The number average molecular weight (Mn) can be determined by measurement using a membrane osmometer, and the molecular weight distribution is evaluated by gel permeation chromatography (GPC), and the obtained polymer is the target polymer. You can evaluate whether or not.

Further, the dimethylphenylcarbinyldimethylsilyl group of the above-mentioned structural formula (Formula 4) or the t-butyl group of the structural formula (Formula 5) is eliminated to give the following structural formula (Formula 6).

[0027]

[Chemical 6]

Polyhydroistystyrene having a phenol residue structural unit represented by can be obtained.

The ether bond cleavage reaction is carried out using dioxane,
It can be easily carried out by dropping an acid such as hydrochloric acid or hydrobromic acid in a mixed solvent of acetone, acetonitrile, benzene or the like. During these reactions, the main chain of the polymer is not cleaved and the crosslinking reaction between the molecules does not occur, so that monodisperse polyhydroxystyrene having a narrow molecular weight distribution can be easily obtained. In addition, tBo of OH group
Cylation is a method of protecting functional groups that is often used in peptide synthesis, and can be easily performed by reacting with di-t-butyl dicarbonate in a pyridine solution.

Pattern formation using the resist of the present invention can be carried out as follows. The resist solution is spin-coated on the substrate and prebaked. Irradiate with high energy rays. At this time, the acid generator decomposes to generate an acid. By performing PEB, tBoc can be catalyzed by acid
The group decomposes and the dissolution inhibiting effect disappears. A positive type pattern is obtained by developing with an alkaline aqueous solution and rinsing with water. In the resist material of the present invention, polyhydroxystyrene may be added to the above materials.

The synthetic examples of the raw materials used in the present invention are shown below, but the invention is not limited thereto.

Synthesis Example 1 Synthesis of Narrowly Dispersed Polyhydroxystyrene In a reactor, equimolar amount of dimethylphenylcarbinyldimethylchlorosilane was added to p-vinylphenol, and in the presence of imidazole in a dimethylformamide solvent at room temperature for 6 hours. It was made to react. The product was distilled under reduced pressure to obtain p-vinylphenoxydimethylphenylcarbinyldimethylsilane in a yield of 70%. This p-vinylphenoxydimethylphenylcarbinyldimethylsilane is 130 ° C /
It had a boiling point of 0.1 mmHg. In order to remove impurities such as water from the above monomers, purification was performed using a purification agent such as CaH ₂ or sodium benzophenone, and distillation was performed. Polymerization was carried out by charging 550 ml of tetrahydrofuran as a solvent and 8.5 × 10 ⁻⁴ mol of n-butyllithium as a polymerization initiator in a 1-liter flask, and then adding -7 to this mixed solution.
When 30 g of p-vinylphenoxydimethylphenylcarbinyldimethylsilane diluted with 50 ml of tetrahydrofuran at 8 ° C. was added and polymerized for 1 hour, the solution turned red. Polymerization was completed by adding methanol to the reaction solution. The reaction mixture is then poured into methanol and the polymer obtained is precipitated, then separated, dried and dried to 24.5.
g of a white polymer was obtained. ¹ H-NMR of the obtained polymer
Was measured to obtain the results shown in Table 1 below.

[0033]

TABLE 1 TABLE 1 ¹ H-NMR 0.0 ppm: reference (S, 6H, O-Si -CH 3) 1~2ppm: ( broad, 6H, Si-C-CH 3) 1~2ppm: ( broad, _{3H, CH 2, -CH) 6~7ppm} : ( broad, 5H, Si-C-C 6 H 5) 6~7ppm: ( broad, 4H, C ₆ H ₅₎

From ¹ H-NMR, it was confirmed that the dimethylphenylcarbinyldimethylsilyl group bonded to the ether had an active end remaining unreacted, and only the vinyl group in the styrene portion was reacted.

Next, 20 g of the obtained poly (p-vinylphenoxydimethylphenylcarbinyldimethylsilane) was dissolved in 250 ml of acetone, a small amount of concentrated hydrochloric acid was added at 60 ° C., and the mixture was stirred for 6 hours and poured into water to precipitate the polymer. It was washed and dried to obtain 8 g of polymer. The number average molecular weight of the obtained polymer was 1.4 × 10 ⁻⁴ g / mol. G
The PC elution curve confirmed that the polymer was highly monodisperse as shown in FIG. 1, and had a molecular weight distribution of 1.10. Note that FIG. 1 shows time (minutes, horizontal axis) and intensity (vertical axis).
It is a figure which shows the relationship with. Furthermore, since no peak derived from a dimethylphenylcarbinyldimethylsilyl group was observed from ¹ H-NMR, it was confirmed that the obtained polymer was polyhydroxystyrene having a narrow molecular weight distribution.

Synthesis Example 2 Synthesis of Narrowly Dispersed Polyhydroxystyrene The raw material pt-butoxystyrene monomer was dehydrated and purified in the same manner as in Synthesis Example 1. Polymerization was carried out in a 2-liter flask using tetrahydrofuran 1500 m as a solvent.
1 and an initiator n-butyllithium 4 × 10 ⁻³ mol were charged. When 80 g of pt-butoxystyrene diluted with 50 ml of tetrahydrofuran was added to the mixed solution at −78 ° C. and the mixture was polymerized for 2 hours, the solution turned red. After confirming that the desired polymerization was reached, methanol was added to the reaction solution to terminate the polymerization reaction. Next, the reaction mixture was poured into methanol to precipitate the obtained polymer, which was then separated and dried to obtain 80 g of a white polymer.
^{From the 1} H-NMR measurement result, the active end remained without reacting with the t-butyl group bonded to the ether, and
It was confirmed that only the vinyl group in the styrene portion had reacted.

Next, 12 g of the obtained poly (pt-butoxystyrene) was dissolved in 250 ml of acetone, a small amount of concentrated hydrochloric acid was added at 60 ° C., the mixture was stirred for 6 hours, and then poured into water to precipitate the polymer, which was washed, After drying, 8 g of polymer was obtained.
The number average molecular weight of the obtained polymer was 1.4 × 10 ⁻⁴ g /
It was mol. The GPC elution curve is as shown in FIG. 2, and it was confirmed that the polymer was extremely highly monodisperse, and the molecular weight distribution was 1.08. 2 is a diagram showing the relationship between time (minutes, horizontal axis) and intensity (vertical axis).
Further, since no peak derived from a tert-butyl group was observed from ¹ H-NMR, it was confirmed that the obtained polymer was polyhydroxystyrene having a narrow molecular weight distribution.

Synthesis Example 3 tBoc Conversion of Polyhydroxystyrene 5 g of polyhydroxystyrene obtained by the living polymerization of Synthesis Example 1 was dissolved in 40 ml of pyridine, and 1 g of di-t-butyl dicarbonate (about 1 g) was added while stirring at 45 ° C. 20 mol
%)Added. A gas is generated at the same time as the addition, but the reaction is carried out for 1 hour in a N ₂ stream. The reaction solution is added dropwise to 1 liter of water containing 20 g of concentrated hydrochloric acid to obtain a white precipitate. After filtration, the precipitate was dissolved in 50 ml of acetone and added dropwise to 1 liter of water. After filtering the precipitate, it was vacuum dried at 40 ° C. or lower. As a result of obtaining the introduction rate of tBoc using the peak of the OH group of 8 ppm in ¹ H-NMR, the result was 19.6%. Di-t-dicarbonate for polyhydroxystyrene
By increasing the addition amount of butyl, the introduction rate of tBoc can be controlled.

[0039]

EXAMPLES The present invention will be described in the following examples, but the present invention is not limited to these examples.

Example 1 Resins having a tBoc conversion ratio of 20% and 40% obtained in Synthesis Example 3 were mixed and their solubility in an alkali developing solution [tetramethylammonium hydroxide (TMAH) 2.4% aqueous solution] was improved. It was measured. FIG. 3 shows the dissolution rate when a resin having a tBoc conversion rate of 40% was added to a resin having a tBoc conversion rate of 20%. That is, FIG. 3 shows tBo for 20% tBoc.
It is a graph showing the relationship between the composition (%, horizontal axis) of c40% and the dissolution rate (Å / s, vertical axis). tBoc rate 40%
The rate of alkali dissolution decreased with the increase in the amount of resin. When both are mixed in a ratio of 1 to 1, the tBoc ratio is approximately 30%.
It was found that the rate of dissolution of alkali was the same as that of the resin of Example 1, and the rate of dissolution could be controlled by the mixing ratio. Even when three or more kinds of resins having different tBoc conversion rates were mixed, the dissolution rate could be controlled by the mixing ratio in the same manner.

Example 2 Base resin (mixing ratio 1: 1 in Example 1) 81 parts by weight Dissolution inhibitor [2,2-bis {p- (tBoc-O-) phenyl} propane] 14 parts by weight Acid generator [Diphenyl (p-methoxyphenyl) sulfonium trifluoromethanesulfonate] 5 parts by weight A solvent solution of 400 parts by weight of solvent (ethoxyethyl acetate) was spin-coated on a silicon substrate at 2000 rpm for 1 minute at 85 ° C on a hot plate. Prebaked. The film thickness was 0.7 μm. After drawing with a KrF excimer laser or an electron beam with an acceleration voltage of 30 kV, PEB was performed at 85 ° C. for 2 minutes. 2.4% T
It was developed with an aqueous solution of MAH for 1 minute and rinsed with water for 30 seconds. Shows positive characteristics and Do sensitivity of 6 μC / cm ²
Met. Do when evaluated with KrF excimer laser light (wavelength 248 nm) which is far ultraviolet rays instead of electron beams
The sensitivity was 24 mJ / cm ² . When PEB was carried out at 85 ° C. for 5 minutes, the electron beam sensitivity was 4.5 μC / cm ² .

FIG. 4 compares the exposure-residual film characteristics of a resist of a resin having a tBoc conversion ratio of 30% with a KrF excimer laser as an example of using this embodiment and the base resin alone. That is, FIG. 4 is a graph showing the relationship between the exposure dose (mJ / cm ² , horizontal axis) and the residual film rate (vertical axis). Sensitivity is 47
mJ / cm 2 times from ² to 24 mJ / cm ^2, gamma value was improved from 4 to 11 3 times or more. As a result of continuous evaluation of resolution, when a resin having a tBoc conversion ratio of 30% was used alone, it was not possible to achieve a resolution of a line and space pattern of 0.3 μm, but in the present example, a 0.25 μm line was obtained. & Space patterns and hole patterns were resolved, and patterns with vertical side walls were formed. The defocus margin at 0.30 μm could be 1.2 μm. Further, 0.2 μm was resolved by electron beam drawing and X-ray exposure. From this, it was found that the resin-mixed type material was superior in the resolution to the resist material using the resin alone.

Example 3 Base resin tBoc conversion rate 20% 20 parts by weight tBoc conversion rate 30% 41 parts by weight tBoc conversion rate 40% 20 parts by weight 2,2-bis [p- (tBoc-O-) phenyl] propane 14 A resist solution containing 5 parts by weight of diphenyl (p-methoxyphenyl) sulfonium trifluoromethanesulfonate and 400 parts by weight of ethoxyethyl acetate was prepared, and the KrF resist characteristics were evaluated by the same method as in Example 2. This embodiment and tBoc
Exposure with a resist using a resin with a conversion rate of 30% alone-
The result of comparison of the residual film characteristics is shown in FIG. That is, FIG.
Is a graph showing the relationship between exposure amount (mJ / cm ² , horizontal axis) and residual film rate (vertical axis). It can be seen that, as in the case of Example 2, the sensitivity is higher than that when the resin is used alone, and the γ value can be increased. The pattern shape and resolution were the same as in Example 2.

Example 4 Using resins with different tBoc conversion rates and mixing ratios, Kr
As a result of examining the composition ratio for obtaining the resist sensitivity by the F excimer laser similar to that in Example 2, the results are shown in Table 2. When polyhydroxystyrene having a tBoc conversion rate of 50% or less was used, a pattern of 0.30 μm or less could be formed vertically to the substrate, but when a tBoc conversion rate of 60% or more was used, a width of 0.3 μm was obtained. The pattern shape of "No." became a so-called T-top shape with a "mushroom" on the head. This T-top pattern was effective for lift-off. By changing the tBoc conversion rate and the mixing ratio,
The pattern shape can be freely changed from rectangular to T-top.

[0045]

[Table 2]

Examples 5 to 8 The KrF resist characteristics were evaluated in the same manner as in Example 2 by using the resin in which the mixing ratio of the base resin in Example 2 was changed to 1: 1 and the mixing ratio was changed. The results obtained are shown in Table 3. If the tBoc ratio is 40%, the solubility tends to decrease and the sensitivity tends to decrease. Conversely, tBo
When the c-conversion rate is 20%, the sensitivity increases, but the amount of film loss increases. Therefore, in Example 8, the upper part of the fine pattern had a rounded shape. Further, Example 5 has a so-called T-top pattern shape. This T-top pattern was effective for lift-off. tBoc
A T-top shape can be obtained by extremely increasing the rate of conversion of 40%. That is, the pattern shape can be freely controlled by the mixing ratio.

[0047]

[Table 3]

Example 9 A resist prepared by adding polyhydroxystyrene to the resist solution of Example 2 in an amount of 10% by weight based on the base resin was used.
The KrF resist characteristics were evaluated in the same manner as in Example 2. The sensitivity was 20 mJ / cm ^2, which was higher than that in Example 2, and the film reduction amount was 0.02 μm, which was unchanged. It is presumed that since the polyhydroxystyrene has good solubility, the sensitivity was high and the film loss was suppressed by the dissolution inhibiting effect of tBoc of 40%.

Examples 10 to 12 Dissolution inhibitors in Example 2, 2,2-bis [p- (tB
oc-O-) phenyl] propane instead of 1,3,5-
Tris (tBoc-O-) benzene (Example 10), poly [p- (tBoc-O-) styrene] having a molecular weight of 2500 (Example 11), a high molecular weight obtained by converting the OH group of a novolac resin having a molecular weight of 2000 to tBoc. Using the molecular dissolution inhibitor (Example 12), the resist properties were evaluated in the same manner as in Example 2. In Example 10, the electron beam sensitivity was 6.6 μC / cm ² and the KrF sensitivity was 30 mJ / cm ² . It was confirmed by KrF exposure and electron beam drawing that the resolution was comparable to that of Example 2, and a pattern having vertical sidewalls could be formed by KrF exposure. However, in Examples 11 and 12, the high-molecular-weight dissolution inhibitor has a much higher dissolution-inhibiting ability than the low-molecular-weight dissolution inhibitor, so that the solubility is low and the sensitivity in both 2.4% TMAH aqueous solution is KrF. It was 1000 mJ / cm ² with an excimer laser.

Examples 13 to 15 Instead of the acid generator diphenyl (p-methoxyphenyl) sulfonium trifluoromethanesulfonate in Example 2, bis (pt-butylphenyl) iodonium trifluoromethanesulfonate (Example 13),
Pyrogallol methanesulfonate (Example 1
4) and phenyl (p-methoxyphenyl) iodonium trifluoromethanesulfonate (Example 15) were used to evaluate the resist characteristics in the same manner as in Example 2.
The sensitivity to the KrF excimer laser is 24 m in the second embodiment.
Although it was J / cm ² , in Examples 14 and 15, both were 20 mJ.
/ Cm ² and the resolution was 0.25 μm. However, in Example 13, the sensitivity was 20 mJ / cm ² , but the resolution was only up to 0.30 μm. It is presumed that this is because the effect of inhibiting dissolution of bis (pt-butylphenyl) iodonium trifluoromethanesulfonate is large. 0.2 μm could be dissolved by electron beam and X-ray.

Examples 16 to 23 The dissolution inhibitor 2,2-bis [p- (tB in Example 2
oc-O-) phenyl] propane instead of Tables 4 and 5
The resist characteristics were evaluated by a KrF excimer laser using the dissolution inhibitor of. The resolution was 0.25 μm in both patterns.

[0052]

[Table 4]

[0053]

[Table 5]

Examples 24 to 29 Base resin in Example 2, dissolution inhibitor [2,2-bis {p- (tBoc-O-) phenyl} propane], acid generator [diphenyl (p-methoxyphenyl) sulfonium] Table 6 shows the results of examining the KrF resist characteristics in the same manner as in Example 2 except that the resist solution containing trifluoromethanesulfonate] was used and the proportion of each component was changed. Basically, PEB is performed at 85 ° C. for 2 minutes, and development is 2.
It was performed for 1 minute using a 4% TMAH aqueous solution. The resolution was 0.25 μm in both patterns.

[0055]

[Table 6]

Example 30 The narrowly dispersed polyhydroxystyrene obtained in Synthesis Example 2 was subjected to tBoc conversion in Synthesis Example 3 to synthesize a resin having a tBoc conversion rate of 20% and 40%. Using a resin obtained by mixing these two resins in a ratio of 1: 1 as a base resin, a resist solution having the same composition as in Example 2 was prepared, and KrF resist characteristics were evaluated by the same method as in Example 2. Sensitivity is 36mJ / cm ²
The sensitivity was lower than that of Example 2 but no difference in resolution was observed.

[0057]

The positive resist obtained by the present invention is sensitive to high energy rays and is excellent in sensitivity, resolution and plasma etching resistance. Moreover, the heat resistance of the resist pattern is excellent. Further, since two or more kinds of resins having different solubilities are mixed as the base resin, it is possible to form a pattern with a width of 0.25 μm by KrF excimer laser lithography, and it is possible to increase the defocus margin. Moreover, it does not easily overhang and has excellent dimensional controllability. Since PEB is required in the chemical amplification process, the dependency of the resist characteristics after exposure over time is small, and the system is simpler because water is not required in the chemical amplification process. From these, it is particularly useful for fine processing with electron beams or deep ultraviolet rays. Especially KrF
Since the absorption at the exposure wavelength of the excimer laser is small, there is a feature that it is possible to easily form a fine pattern perpendicular to the substrate.

[Brief description of drawings]

FIG. 1 is a diagram showing a GPC elution curve of narrowly dispersed polyhydroxystyrene.

FIG. 2 is a diagram showing a GPC elution curve of another narrowly dispersed polyhydroxystyrene.

FIG. 3 shows a resin having a tBoc conversion rate of 20% and a tBoc conversion rate of 40%.
It is a figure which shows the relationship between the amount of addition and the dissolution rate at the time of adding the resin of%.

FIG. 4 is a resin having a tBoc conversion rate of 20% and a tBoc conversion rate of 40%.
It is a figure which shows the exposure-residual film | membrane characteristic by a KrF excimer laser when what mixed the resin of 1% with 1: 1 was made into a base resin.

FIG. 5: Resin with tBoc conversion rate of 20%, tBoc conversion rate of 30
FIG. 3 is a diagram showing exposure-residual film characteristics by a KrF excimer laser when a mixture of three kinds of resins having a% and a tBoc conversion rate of 40% is used as a base resin.

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Claims (2)

[Claims] 1. An alkali containing three components of a resin (A) in which a part of hydroxyl groups of polyhydroxystyrene is substituted with a t-butoxycarbonyloxy group, a dissolution inhibitor (B), and an acid generator (C). In a high-energy-ray-sensitive positive resist that can be developed with an aqueous solution, the resin (A) in which a part of the hydroxyl groups of the polyhydroxystyrene is replaced with a t-butoxycarbonyloxy group is composed of two or more kinds of resins having different substitution rates. The dissolution inhibitor (B) is 1 in one molecule.
Containing at least t-butoxycarbonyloxy groups and having a weight fraction of 0.01 ≦ B ≦ 0.40, 0.005 ≦ C ≦
A resist material, wherein 0.15, 0.55 ≦ A, and A + B + C = 1. 2. A resist material obtained by adding polyhydroxystyrene to the resist material according to claim 1.