JPH08334901A - Chemical amplification positive resist material - Google Patents

Abstract

PURPOSE: To obtain a resist material having high sensitivity and high resolution, excellent in applicability to a process and ensuring improved shelf stability by incorporating polysiloxane having terminal silanol groups each protected with a trimethylsilyl group and represented by a specified formula and an acid generating agent. CONSTITUTION: This resist material contains polysiloxane having terminal silanol groups each protected with a trimethylsilyl group and represented by the formula and an acid generating agent. The polysiloxane is obtd., e.g., as follows; p-methoxybenzyltrichlorosilane is hydrolyzed, a condensation product of the resultant hydrolyzate is further thermally condensed, the silanol groups of the resultant polysiloxane are trimethylsilylated with trimethylsilyl iodide, trimethylsilyl groups are substd. for methyl groups of methoxy groups, phenolic hydroxyl groups are produced by hydrolysis, a part of hydrogen atoms of the hydroxyl groups are trimethylsilylated, hydrogen atoms of the remaining silanol groups are trimethylsilylated and acid-unstable groups are substd. for a part of the remaining phenolic hydroxyl groups.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a high sensitivity to high energy rays such as deep ultraviolet rays, electron beams, and X-rays,
The present invention relates to a chemically amplified positive type resist material suitable for a fine processing technique, which can form a resist pattern by developing with an alkaline aqueous solution.

[0002]

2. Description of the Related Art LSI to be Solved
With the higher integration and higher speed, the finer pattern rule is required, and far-ultraviolet lithography is expected as a next-generation fine processing technology. Far-ultraviolet lithography can also process 0.3-0.4 μm,
When a resist material having low light absorption is used, it becomes possible to form a pattern having a side wall that is nearly vertical to the substrate. In addition, since the patterns can be transferred at one time, it is more advantageous than electron beam lithography in terms of throughput. In recent years, a technique using a high-intensity KrF excimer laser as a light source for far-ultraviolet rays has been attracting attention, and its light absorption is low in order to be used as a mass production technique.
There is a demand for a highly sensitive resist material.

From such a point, chemical amplification (chemical amplifier) has recently been developed using an acid as a catalyst.
resist material [eg Liu (Li
u) et al., Journal of Vacuum Science
And Technology (J. Vac. Sci. Tech.
nol. ), B6, 379 (1988)],
This resist material is particularly promising for deep-UV lithography because it has sensitivity equal to or higher than that of conventional high-sensitivity resist material, and has high resolution and high dry etching resistance.

In this case, as a negative resist material, Shipley has already commercialized a three-component chemically amplified resist material (trade name: SAL601ER7) consisting of a novolac resin, a melamine compound and an acid generator. However, no chemically amplified positive resist material has been commercialized yet. Here, in the manufacturing process of an LSI, wiring and gate formation can be handled with a negative resist material, but contact holes are difficult to finely process because a fog is likely to occur if a negative resist material is used. Resist materials are much more suitable.

Therefore, a high-performance positive resist material has been strongly demanded. Conventionally, Ito et al. Have protected P from a hydroxy group of polyhydroxystyrene with a tert-butoxycarbonyl group (tert-BOC group).
We are developing a positive-type chemically amplified resist material in which an onium salt is added to a resin called BOCST.

However, the onium salt used here is
Contains antimony as a metal component [Reference: Polymers in Electronics, ACS Symposium
Series (Polymers in Electron
ics, ACS Symposium Series)
242nd Meeting (American Chemical Society, Washington DC. 198)
4), page 11], the metal component in the resist material is generally disliked from the viewpoint of avoiding contamination of the substrate. In that respect, the PBOCST resist material is preferable in the process. is not.

On the other hand, Ueno et al. Have announced a deep-UV positive resist material containing poly (p-styreneoxytetrahydropyranyl) as a main component and an acid generator (reference;
The 36th Joint Lecture Meeting of Japan Society of Applied Physics, 1989, 1
pk-7), this chemically amplified resist material is known to have high sensitivity and high resolution. However, forming a fine pattern with a high aspect ratio with high precision is not possible because of the mechanical strength of the pattern. It was difficult.

As described above, a large number of chemically amplified resist materials containing novolac resin or polyhydroxystyrene as a base polymer and having sensitivity to deep ultraviolet rays, electron beams and X-rays have been published so far. And
At present, it is difficult to put it into practical use due to the problems of substrate step, the problem of standing wave due to light reflection from the substrate, and the problem of difficulty in forming a pattern with a high aspect ratio.

By the way, the two-layer resist method is generally excellent for forming a pattern with a high aspect ratio on a stepped substrate. In order to carry out alkali development using polysiloxane in the two-layer resist method, polysiloxane having a hydrophilic group such as a hydroxyl group or a carboxyl group is required.
A hydroxyl group (silanol group) directly bonded to a silicon atom remains in this polysiloxane, and the silanol group causes a cross-linking reaction by an acid, so that it is difficult to apply it to a chemically amplified positive resist material.

As a stable alkali-soluble polysiloxane, there is polyhydroxybenzylsilsesquioxane, and a material in which a part of its hydroxyl groups is protected by a tert-BOC group is a chemically amplified type in combination with an acid generator. It is known to be a silicone-based positive resist material (SPIE Vol. 1925 (1993) 37.
7), an example of using an alkali-soluble polysiloxane as a base polymer, and a method for synthesizing an alkali-soluble polysiloxane are described in JP-A-6-118651 and JP-A-6-6-1.
No. 84311 and Japanese Patent Publication No. 5-58446.

That is, the synthesis of the polysiloxane having the main skeleton as the base polymer can be carried out by a general hydrolysis method in which a solution of chlorosilane having a protected phenolic hydroxyl group is added to water. In the above-mentioned publication, as a method for synthesizing polysiloxane, a methyl group is used for protecting a phenolic hydroxyl group, and for example, p-methoxybenzyldichlorosilane is hydrolyzed to obtain p-methoxybenzylsilsesquioxane, and then methyl is used. A method of leaving the group is shown.

More specifically, the method described in Japanese Patent Publication No. 5-58446 is to hydrolyze chlorosilane and then perform condensation in the presence of an alkali. In this case, the active silanol group is Since a large amount remains in the siloxane, the condensation reaction proceeds even after the reaction is completed, and reproducibility in synthesis cannot be obtained.

In Japanese Unexamined Patent Publication (Kokai) No. 6-184311, a method of reacting a methyl group with boron tribromide and then hydrolyzing it is adopted as a method for removing the methyl group protected with a phenolic hydroxyl group. However, in this method, the reaction operation is complicated because it is difficult to handle the reagent boron tribromide and the reaction temperature must be extremely low. Further, according to the study by the present inventors, the polysiloxane obtained by this method cannot be used as a resist material when it is prepared as a resist material because a large amount of particles are generated during storage of the resist solution. Therefore, there is a problem that storage stability is extremely poor.

In Japanese Patent Laid-Open No. 6-118651, it is suitable that the condensation reaction of polysiloxane is carried out under reduced pressure and thermal condensation under a neutral condition. It is described that the methyl group can be easily eliminated by reacting the protected methyl group with trimethylsilyl iodide and then performing hydrolysis. Specifically, for example, p-methoxybenzylchlorosilane in which a phenolic hydroxyl group is protected with a methyl group is hydrolyzed, the obtained polysiloxane is thermally condensed under reduced pressure, and then reacted with trimethylsilyl iodide, and then, An alkali-soluble polysiloxane is obtained by hydrolysis. However, even the polysiloxane obtained by this method cannot obtain sufficient storage stability when prepared as a resist material.

The present invention has been made in view of the above circumstances, and has high sensitivity, high resolution, excellent process applicability, and excellent storage stability, and is particularly suitable as a two-layer resist material. It is an object to provide a chemically amplified silicone-based positive resist material used.

[0016]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of various studies conducted by the present inventors to achieve the above object, the polysiloxane (A) represented by the following composition formula (1) was obtained.
That a resist material having excellent storage stability can be obtained by using as a base polymer of the resist material,
In particular, when an onium salt represented by the following general formula (6) is used as an acid generator (B) that decomposes to generate an acid by the action of irradiation radiation, it can be developed with an alkaline aqueous solution and has high sensitivity and high sensitivity. It has been found that a chemically amplified silicone-based positive resist material is obtained which is particularly excellent in resolution and process applicability as well as in storage stability, and is particularly suitable for use as an upper layer material of the two-layer resist method. It was

[0017]

Embedded image (R) _m JM (6) (wherein R represents the same or different aromatic group or substituted aromatic group, J represents sulfonium or iodonium, and M represents a toluene sulfonate group or trifluoromethane sulfone group. Represents a phonate group, and m is 2 or 3.)

That is, as described above, when the alkali-soluble polysiloxane obtained by the conventional synthesis method is used as the base polymer of the resist material, a large amount of particles are generated during the storage of the resist solution, and it is used as the resist material. There is a problem that you can not do it. Therefore, the inventors of the present invention have investigated the cause, and found that a large amount of silanol groups remain in the polysiloxane obtained by the above-mentioned method by ²⁹ Si-NMR analysis, and this remains. It has been found that silanol groups are condensed during storage of the resist material to form a gel and appear as particles. For example, the above-mentioned JP-A-6-1186.
The alkali-soluble polysiloxane obtained by the synthesis method described in Japanese Patent Publication No. 51 has relatively good storage stability when prepared as a resist material as compared with other synthesis methods. It was confirmed by ²⁹ Si-NMR that silanol groups remained in the siloxane. That is, the residual silanol groups in the polysiloxane are trimethylsilylated by trimethylsilyl iodide, but the reaction is not sufficient, and a considerable amount of silanol groups still remain in the alkali-soluble polysiloxane, so that the storage stability as a resist material is high. Is not enough.

Therefore, the present inventors have studied various synthetic methods for reducing the residual silanol groups at the polysiloxane end that deteriorate the storage stability when an alkali-soluble polysiloxane is prepared as a resist material, and have a storage stability. As a result of further diligent studies on an excellent alkali-soluble polysiloxane, it was found that an alkali-soluble polysiloxane having a residual silanol group significantly reduced as compared with the above conventional method can be obtained.

That is, first, for example, p-methoxybenzyltrichlorosilane is hydrolyzed, and the hydrolyzed condensate is further thermally condensed to obtain a polysiloxane having a repeating unit represented by the following general formula (2). By reacting trimethylsilyl iodide, the terminal silanol group of the polysiloxane main chain is protected with a trimethylsilyl group, and the methyl group protected with a phenolic hydroxyl group is also substituted with a trimethylsilyl group (3).
The polysiloxane composed of the repeating unit represented by the formula (4) is hydrolyzed to form a phenolic hydroxyl group, and the polysiloxane composed of the repeating unit represented by the following general formula (4) is represented by the following reaction formula. Is re-trimethylsilylated with hexamethyldisilazane or trimethylsilyl chloride to replace the residual silanol group and a part of the phenolic hydroxyl group generated by hydrolysis with a trimethylsilyl group.
It has been found that an alkali-soluble polysiloxane composed of the repeating units represented by a) and (5b), in which the residual silanol group is remarkably reduced as compared with the alkali-soluble polysiloxane obtained by the conventional method, can be obtained.

[0021]

[Chemical 6] (In the formula, Me, a, and n have the same meanings as above.)

Here, in the above-described method for synthesizing soluble polysiloxane, an alkali-soluble polysiloxane obtained by reacting a methyl group protected with a phenolic hydroxyl group with boron tribromide and then hydrolyzing the same. (JP-A-6-184311) Alkali-soluble polysiloxane obtained by reacting a methyl group protected with a phenolic hydroxyl group with trimethylsilyl iodide, followed by hydrolysis (JP-A-6-11
No. 8651) To hydrolyze p-methoxybenzyltrichlorosilane and the like, and perform thermal condensation, trimethylsilylation is performed for the purpose of protecting the residual silanol group, and trimethylsilylation of the methyl group for which the phenolic hydroxyl group is protected. Was reacted with trimethylsilyl iodide and then hydrolyzed, and then some of the residual silanol groups and phenolic hydroxyl groups were converted to hexamethyldisilazane or Me ₃ SiCl.
When the alkali-soluble polysiloxane (reaction formula above) obtained by re-trimethylsilylation in (3) was analyzed by ²⁹ Si-NMR, it was found that the residual silanol groups were the smallest, and the following were the largest. Further, when the above-mentioned three kinds of alkali-soluble polysiloxanes were protected with acid labile groups such as tert-butoxycarbonyl group and used as a base polymer of a resist material, the polymer of was found to be most excellent in storage stability. did. That is, by using the polysiloxane (A) represented by the above composition formula (1) obtained by the above method according to the present invention as a base polymer of a resist material, its storage stability becomes extremely excellent. They found out the present invention and made the present invention.

Therefore, the present invention is characterized by containing the polysiloxane (A) represented by the above composition formula (1) in which the terminal silanol group of the polysiloxane is protected by a trimethylsilyl group, and the acid generator (B). The chemically amplified positive resist material, particularly polysiloxane (A), has a weight average molecular weight of 5,000 to 50,000, and the silanol group of the polysiloxane composed of the repeating unit represented by the general formula (2) is replaced with trimethylsilyl. Along with trimethylsilylation with iodide, the methyl group of the methoxy group is replaced with a trimethylsilyl group, and then hydrolyzed to form a phenolic hydroxyl group, which is then hydrogenated with hexamethyldisilazane or trimethylsilyl chloride. Some of the atoms are trimethylsilylated and the remaining silano By substituting a part of the remaining phenolic hydroxyl group of the polysiloxane consisting of the repeating units represented by the above general formulas (5a) and (5b) obtained by trimethylsilylating the hydrogen atom of the alkyl group with an acid labile group. Provided is a chemically amplified positive resist composition, which is obtained, in which the acid generator (B) is an onium salt represented by the above general formula (6) and which optionally contains a dissolution inhibitor (C).

The present invention will be described in more detail below. The chemically amplified positive resist composition of the present invention contains polysiloxane (A) as an alkali-soluble resin, and the polysiloxane (A) and the acid generator (B) are used. Not only can it be used as a two-component resist material consisting of (1) and (3), but it can also be used as a three-component resist material to which a dissolution inhibitor (C) is added, if necessary. Here, the polysiloxane (A) of the present invention is represented by the following composition formula (1), and the terminal silanol group is blocked with a trimethylsilyl group.

[0025]

[Chemical 7]

Here, the acid labile group represented by Q is an acid labile group other than a trimethylsilyl group, such as a tert-butyl group, a tert-butoxycarbonyl group, and a tert-group.
Butoxycarbonylmethyl group and the like, especially ter
A t-butoxycarbonyl group is preferred.

A is 0.001≤a≤0.05, and this OSiMe ₃ blocks the end of the polysiloxane (A).

[0028]

Embedded image

That is, the polysiloxane (A) can be represented by the following formula (1 ').

[0030]

[Chemical 9] In this formula (1 ′), p, q and r are p ≧ 0, q> 0,
r> 0, but q / (p + q + r) is 0.05 to 0.
5, especially 0.1 to 0.3 is preferred. The polysiloxane (A) has a small absorption for the KrF excimer laser, but when q / (p + q + r) is less than 0.05, the dissolution inhibiting effect is small, so that it is necessary to add an inhibitor. . On the other hand, when q / (p + q + r) is more than 0.5, the solubility in an alkaline aqueous solution is extremely lowered, so that an inhibitor is not necessary, but the sensitivity of a commonly used developer is extremely lowered. There are cases.

Further, r, which indicates the introduction ratio of the trimethylsilyl group to the phenolic hydroxyl group in the polysiloxane (A), is such that r / (p + q + r) is 0.05 to 0.5, particularly 0.1 to 0.2. Preferably there is. The introduction amount of the trimethylsilyl group can be adjusted by the reaction amount of the trimethylsilylating agent with respect to the polysiloxane composed of the repeating unit of the following general formula (4), and r / (p + q +
When r) is less than 0.05, the remaining silanol groups cannot be sufficiently protected, and the storage stability of the prepared resist material may not be improved in some cases.
If (p + q + r) exceeds 0.5, the sensitivity of the resist material may be reduced.

The polysiloxane (A) has a weight average molecular weight of 5,000 to 50,000, particularly 5,000 to 1
It is preferably 10,000. If it is less than 5,000, the desired plasma resistance may not be obtained, or the dissolution inhibitory effect in an alkaline aqueous solution may be low, which is 50,000.
If it exceeds, it may be difficult to dissolve in a general-purpose resist solvent.

The polysiloxane (A) can be obtained by the following synthetic method. First, a polysiloxane having a repeating unit represented by the following general formula (2) obtained by hydrolyzing p-methoxybenzylsiloxane or the like and further thermally condensing the hydrolyzed condensate is treated with a silanol group at the end of its main chain. For the trimethylsilylation of the protected and phenolic hydroxyl group-protected methyl group, it is reacted with trisilyl iodide to produce an organopolysiloxane comprising a repeating unit represented by the following general formula (3). In the trimethylsilylation reaction, the polysiloxane is dissolved in an organic solvent such as acetonitrile, trimethylsilyl iodide is dropped into the organic solvent, the reaction temperature is 20 to 30 ° C., and the reaction time is 8 to 10 hours. Is preferred.

Then, hydrolysis is carried out to eliminate the trimethylsilyl group protecting the phenolic hydroxyl group to generate a phenolic hydroxyl group, thereby obtaining a polysiloxane having a repeating unit represented by the following general formula (4). Here, as the hydrolysis conditions, known conditions for desilylation can be adopted, and for example, under water cooling, while paying attention to heat generation, 30 to 30 can be adopted.
Water is added at a temperature of 45 ° C.

Further, the polysiloxane having the repeating unit of the following general formula (4) is re-trimethylsilylated to obtain a polysiloxane having the repeating unit of the following general formulas (5a) and (5b). In this case, for trimethylsilylation, it is preferable to dissolve a polysiloxane composed of the repeating unit of the following general formula (4) in an organic solvent such as toluene and use hexamethyldisilazane as a silylating agent at a reaction temperature of 0 ° C to room temperature. The reaction time is preferably 2 to 5 hours. In this method, since by-product ammonia does not remain in the reaction system after trimethylsilylation, it is possible to carry out purification by stripping the reaction solvent under reduced pressure after the reaction, and it is possible to easily carry out the desired trimethylsilylation. There is. It should be noted that, after being dissolved in an organic solvent, it is also possible to carry out trimethylsilylation by reacting with trimethylsilyl chloride in the presence of a base, but it may be difficult to remove the resulting hydrochloride salt. As a method of dissolving and separating, since hydrolysis of a trimethylsilyl group may occur and a silanol group may be generated again in the polymer, it is recommended to use the method using hexamethyldisilazane described above.
The amount of the trimethylsilyl group introduced into the phenolic hydroxyl group by this re-trimethylsilylation can be controlled by selecting the reaction conditions and charging the amount of the silylating agent such as hexamethyldisilazane.

Further, the following method can be used to replace the phenolic hydroxyl group of the polysiloxane with an acid labile group.

For example, tert-butoxycarbonylation can be easily carried out by reacting with di-tert-butyl dicarbonate in a pyridine solution, and tert-butoxycarbonylmethyloxylation can be carried out by tert-butoxycarbonylmethylation. -The reaction with butyl bromoacetate in the presence of a base and tert-butoxylation is carried out by reacting with tert-butyl alcohol in the presence of trifluoroacetic anhydride.

[0038]

[Chemical 10] (In the formula, R, Me, Q, a, p, q, r, and n have the same meanings as above.)

In this reaction formula, the above formula (2)
In the reaction of the polysiloxane of formula (3) with trimethylsilyl iodide, not all of the terminal silanol groups of the polysiloxane of formula (2) are protected by trimethylsilyl groups, and in addition, in the hydrolysis of the polysiloxane of formula (4), The trimethylsilyl group at the end of the polysiloxane chain was deprotected, though very slightly, and the following formula (4
The compound consisting of the unit of a) remains in the compound (4).

[0040]

[Chemical 11] (In the formula, a and n have the same meanings as above.)

According to the above reaction formula, the residual silanol group obtained by trimethylsilylation with hexamethyldisilazane or trimethylsilyl chloride is surely protected by the trimethylsilyl group. Therefore, in the compound consisting of the units of the formulas (5a) and (5b), Is substantially free of residual silanol groups, and thus the polysiloxane (A) of formula (1) obtained therefrom is also substantially free of residual silanol groups.

Here, it is very difficult to quantify the amount of residual silanol groups of the polymer comprising the unit of the above formula (4a), and it is difficult to quantitatively protect only the residual silanol groups with trimethylsilyl groups.

Therefore, in order to sufficiently protect the residual silanol groups, it is necessary to carry out the reaction with an excess of trimethylsilylating agent, so that some of the phenolic hydroxyl groups are necessarily trimethylsilylated. By the way, when the phenolic hydroxyl group was substituted with a trimethylsilyl group as in the above formula (1), it was confirmed that the resist material using this as a base polymer exhibits extremely high storage stability.
When a polysiloxane having a phenolic hydroxyl group protected by a trimethylsilyl group is used as a base polymer of a resist material, the trimethylsilyl group is similar to an acid labile group such as a tert-butoxycarbonyl group in the resist film. Since it is deprotected by the acid generated from the acid generator upon exposure, there is no problem in the resolution of the resist film. Here, if the phenolic hydroxyl group is not protected with a trimethylsilyl group but is protected only with an acid labile group or the like, it is protected in order to exert the same storage stability effect as in the case of combination with a trimethylsilyl group. It is necessary to increase the proportion of phenolic hydroxyl groups, which causes a decrease in sensitivity and a decrease in resolution when prepared as a resist material. Further, when a tetrahydropyranyl group is used in place of the trimethylsilyl group, it is difficult to remove the deprotection group in the exposed portion of the resist, so that the sensitivity and resolution of the resist material decrease. On the other hand, when a part of the phenolic hydroxyl group is protected with only a trimethylsilyl group, it is difficult to improve the resolution of the resist material and it is necessary to introduce an acid labile group. Therefore,
As a base polymer that is very easy to manufacture, has extremely high storage stability as a resist material, and is excellent in its sensitivity and resolution, a part of the phenolic hydroxyl group represented by the above formula (1) is a trimethylsilyl group and an acid labile group. It has been found that group-protected soluble polysiloxanes are effective.

The compounding amount of the polysiloxane (A) in the resist material of the present invention is 55% with respect to the total amount of the material excluding the solvent in any of the three-component system and the two-component system.
Above (wt%, same below), especially above 80% is suitable. If the blending amount is less than 55%, the coating properties of the resist solution may be poor, or the strength of the resist film may be poor.

The resist material of the present invention comprises an acid generator (B).
It is preferable to use an onium salt represented by the following general formula (6). (R) _m JM (6) (wherein R represents the same or different aromatic group or substituted aromatic group, J represents sulfonium or iodonium, and M represents a toluene sulfonate group or trifluoromethane sulfone group. Represents a phonate group, and m is 2 or 3.)

That is, as an acid generator which decomposes to high energy rays such as deep ultraviolet rays, electron beams and X-rays to generate an acid, an oxime sulfonic acid derivative, a 2,6-dinitrobenzyl sulfonic acid derivative, Examples thereof include naphthoquinone-4-sulfonic acid derivative, 2,4-bistrichloromethyl-6-allyl-1,3,5-triazine derivative, α, α′-bisallylsulfonyldiazomethane and the like. However, when the polysiloxane (A) of the present invention is used as a base polymer, it may not be possible to obtain a highly sensitive resist material with these acid generators (B), which is represented by the general formula (6). Onium salts are preferably used.

In the above formula (6), R is specifically a tert-butoxyphenyl group, a tert-butoxycarbonyloxyphenyl group, a tert-butoxycarbonylmethoxyphenyl group, a tetrahydropyranyloxyphenyl group, a trimethylsiloxyphenyl group. And the like. Among these, a tert-butoxyphenyl group, a tert-butoxycarbonyloxyphenyl group or a tert-butoxycarbonylmethoxyphenyl group is preferable, and the onium salt in the present invention is at least R of the above formula (6). It is desirable that one is these groups.

Here, as an example of the onium salt represented by the above general formula (6), generally (C ₆ H ₅ ) ₂ I ⁺ -O ₃ SC is used.
_{F 3, (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 S
_{(C 6 H 4) CH 3} , (tert- butyl _{-C 6 H 4) 2 I +} -
O ₃ SCF ₃ , (C ₆ H ₅ ) (MeOC ₆ H ₅ ) I ⁺ -O ₃ S
(C ₆ H ₄₎ CH ₃ and the like are known. However, these acid generators have a drawback that they have low solubility in ethyl cellosolve acetate, ethyl lactate, ethoxy-2-propanol and the like, which are widely used as a suitable solvent when applied as a resist solution. Therefore, it may be difficult to mix an appropriate amount into the resist material. Further, even if it has a high solubility in a solvent, it has a poor compatibility with the polysiloxane (A) of the present invention, so that it is difficult to form a good resist film, or heat treatment is performed after light irradiation. Some acid generators have the drawback that sensitivity change and pattern shape change with time easily occur. Particularly in the case of an acid generator having a poor compatibility with the polysiloxane (A), distribution may occur in the resist film and an overhang may be observed on the pattern surface. In a chemically amplified resist material, such a phenomenon often occurs because the acid is deactivated on the surface of the resist film or the acid generator is lost on the surface.

Therefore, by using the onium salt in which at least one R in the general formula (6) is substituted with a tert-butoxyphenyl group or the like, it is easily dissolved in the commonly used resist solvent, and Not only the compatibility with the polysiloxane (A) is good, but also the solubility after exposure is excellent, and the resist pattern can be formed perpendicular to the substrate. That is, since the onium salt produces a phenolic hydroxyl group or a carboxylic acid during exposure and heat treatment due to its tert-butoxyphenyl group and the like, the solubility after exposure is improved. Therefore, onium salts generally have a dissolution inhibiting effect, but these onium salts have a dissolution promoting effect after exposure. Therefore, the difference in dissolution rate before and after the exposure can be increased, and it is preferably used. The larger the number of R substituted with the acid labile group, the better the solubility of the onium salt.

Examples of the onium salt in which at least one R of the general formula (6) is substituted with an acid labile group include the onium salts represented by the following structural formulas. In addition,
In the following structural formula, t-BuO is a tert-butoxy group, THPO is a tetrahydropyranyloxyphenyl group, Tf is a trifluoromethanesulfonate group, Ts
Represents a toluene sulfonate group.

[0051]

[Chemical 12]

The amount of the onium salt compounded in the resist material of the present invention is 0.5 with respect to the total amount of the material excluding the solvent.
-15%, especially 1-10% is suitable. If it is less than 0.5%, positive resist characteristics are exhibited, but the sensitivity is low. When the content of the acid generator is increased, the resist sensitivity tends to be higher and the contrast (γ) is improved, but when it exceeds 15%, positive resist characteristics are exhibited, but the content is further increased. Further improvement in sensitivity cannot be expected, onium salt is an expensive reagent, increase in low molecular weight components in the resist material lowers the mechanical strength of the resist film, and also lowers oxygen plasma resistance. Therefore, the blending amount of the onium salt (B) is preferably 15% or less.

The resist material of the present invention is also suitable as a three-component system containing a dissolution inhibitor (C),
The dissolution inhibitor (C) may be either a low molecular weight compound or a high molecular compound as long as it has one or more acid labile groups in the molecule, and it can be used for known positive resists. Dissolution inhibitors can be used. Here, examples of the acid labile group include the same groups as R in the general formula (6). Examples of such a dissolution inhibitor (C) include a compound obtained by converting the hydroxyl group of bisphenol A into tert-BOC, and a compound obtained by converting phloroglucin, tetrahydroxybenzophenone and the like into tert-BOC.

The content of the dissolution inhibitor (C) in the resist composition of the present invention is preferably 40% or less, particularly 10 to 30% based on the total amount of the material excluding the solvent.
When it exceeds 40%, the oxygen plasma resistance of the resist film is remarkably lowered, and it cannot be used as a material for the two-layer resist method.

The resist material of the present invention comprises the polysiloxane (A) and the acid generator (B), or (A),
Each of the components (B) and the dissolution inhibitor (C) is used by being dissolved in an organic solvent. The organic solvent at this time is preferably one in which each component is sufficiently dissolved and the resist film is uniformly spread, and specifically, butyl acetate, xylene, acetone, cellosolve acetate, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether. , Diethylene glycol monoethyl ether, ethylene glycol monoethyl ether, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, ethyl lactate, methyl lactate, propyl lactate, butyl lactate, and the like,
Among these, ethyl lactate, butyl acetate and diethylene glycol monoethyl ether are particularly preferably used.
These organic solvents may be used alone or in combination of two or more. It should be noted that the amount of the organic solvent blended is preferably several times the total weight of the components (A), (B), or (A) to (C).

Other additives may be added to the resist material of the present invention as long as the effects of the present invention are not impaired.

As a method of forming a pattern using the resist material of the present invention, a usual method can be adopted, and for example, it can be performed as follows.

First, a thick organic polymer layer is formed as a lower resist film on a silicon substrate. Here, a novolac resin-based positive photoresist material can be used as the material of the lower layer resist film, and after applying this on the substrate,
Hard bake at 200 ° C. for 1 hour. Thereby, intermixing with the resist material of the present invention can be prevented. After forming the lower layer resist film, the solution of the resist material of the present invention is spin-coated thereon, prebaked, and irradiated with a high energy ray. At this time, the acid generator (B) decomposes to generate an acid. PEB (Post E
xposure Bake) decomposes an acid labile group such as a tert-BOC group using an acid as a catalyst,
The dissolution inhibitory effect disappears. Then, by developing with an alkaline aqueous solution and rinsing with water, a positive resist pattern can be formed on the lower resist film.

[0059]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Prior to the description of Examples and Comparative Examples, examples of synthesizing polysiloxane used as a base polymer will be shown.

[Synthesis Example 1] Synthesis of p-methoxybenzylsilsesquioxane 600 ml of water was charged into a reaction vessel, and 283.5 g of p-methoxybenzyltrichlorosilane was stirred at 30 ° C.
A mixed solution of (1 mol) and 300 ml of toluene was added dropwise over 2 hours for hydrolysis. Then, the aqueous layer was removed by liquid separation operation, and the solvent was distilled off from the organic layer by an evaporator. The concentrated liquid was heated under reduced pressure at 200 ° C. for 2 hours to carry out a polymerization reaction. Acetonitrile 20 was added to the obtained polymer.
0 g was added and dissolved to obtain a solution of p-methoxybenzylsilsesquioxane.

[Synthesis Example 2] Synthesis of p-hydroxybenzylsilsesquioxane- 1 To the solution obtained in Synthesis Example 1, 240 g of trimethylsilyl iodide was added dropwise at 60 ° C or lower and reacted at 60 ° C for 10 hours. . After completion of the reaction, 200 g of water was added for hydrolysis, and then decanting was performed to obtain a polymer layer. The polymer layer was vacuum dried to obtain 165 g of p-hydroxybenzylsilsesquioxane. When the molecular weight of this polymer was measured by GPC (gel permeation chromatography), it was Mw = 3,000 in terms of polystyrene. In addition, ²⁹ Si-NMR
In this analysis, a peak attributed to the SiOH group was observed at -62 ppm.

Synthesis Example 3 (Comparative Example) Synthesis of p-hydroxybenzylsilsesquioxane-2 The polymer obtained in Synthesis Example 1 was dissolved by adding 200 g of methylene chloride instead of acetonitrile. This solution is
The mixture was cooled to 80 ° C., and a solution of 250 g (1 mol) of boron tribromide in 600 ml of methylene chloride was gradually stirred for 10 minutes.
It dripped over time. After completion of the dropping, the mixture was aged at -80 ° C for 2 hours, gradually returned to room temperature, and further aged overnight. After the reaction was completed, 1 liter of water was added with stirring to separate the organic layer. The organic layer was washed with water until the washing water became neutral, the solvent was removed, the residue was dissolved in methanol and then added into water to obtain a white precipitate. The precipitate was vacuum dried to obtain 134 g of p-hydroxybenzylsilsesquioxane. The molecular weight of this polymer was measured by GPC (gel permeation chromatography), and was found to be M in terms of polystyrene.
It was w = 2,900. Further, in the ²⁹ Si-NMR analysis, a peak attributable to the SiOH group was observed at −62 ppm, and the peak of this SiOH group was compared with the peak size of the silsesquioxane at −70 ppm. It was found to be present in a larger amount than the obtained p-hydroxybenzylsilsesquioxane.

[Synthesis Example 4] Trimethyi of p-hydroxybenzylsilsesquioxane
The p- hydroxybenzyl silsesquioxane 159.2g obtained in Rushiriru of Synthesis Example 2 was dissolved in toluene 400 ml,
Hexamethyldisilazane (22.3 g, 0.17 mol) was added, and the mixture was refluxed for 3 hours. After that, toluene was removed by stripping under reduced pressure, and the residue was vacuum dried.
22.4 g of a trimethylsilylated polymer of hydroxybenzylsilsesquioxane was obtained. ¹ H-NM
In the R analysis, the introduction rate of the trimethylsilyl group was determined from the peak of the phenyl group at 6 to 7 ppm and the peak of the trimethylsilyl group at 0 ppm, and it was about 10%. In addition, in the analysis of ²⁹ Si-NMR, it is -62 ppm.
No peak due to the SiOH group of -70p
Only the peak of pm silsesquioxane was observed.

[Synthesis Example 5]Tert-Butoxyl of the polymer obtained in Synthesis Example 4
Bonyl (tert-BOC) conversion 25 g of the polymer obtained in Synthesis Example 4 was added to 250 g of pyridine.
And di-tert-dicarbonate with stirring at 45 ° C.
6.85 g of butyl (0.031 mol, relative to the hydroxyl group
Equivalent to about 20 mol%) was added. Gas is added at the same time
Occurred, but N ₂The reaction was carried out for 1.5 hours in an air stream. reaction
After stripping the liquid pyridine, methanol 100m
dissolved in 5 l of water and added dropwise to 5 l of water to give a white precipitate.
Obtained. The precipitate was washed with water 5 times, filtered,
When vacuum dried at 40 ° C or lower, tert-butoxy
Carbonylated p-hydroxybenzylsilsesqui
25 g of oxane was obtained.¹H-NMR analysis
The peak of phenyl group at 6-7ppm and 1-2ppm
Of the tert-butyl group and methylene peak of
The tert-BOC conversion rate was calculated to be 19.6%.
It was.

[Synthesis Example 6] (Comparative Example) tert-butoxycal of the polymer obtained in Synthesis Example 2
In Boniru (tert-BOC) Synthetic Example 5 The same procedure was carried out tert- butoxycarbonyl of the polymer obtained in Synthesis Example 2.

[Synthesis Example 7] (Comparative Example) tert-butoxycal of the polymer obtained in Synthesis Example 3
In Boniru (tert-BOC) Synthetic Example 5 The same procedure was carried out tert- butoxycarbonyl of the polymer obtained in Synthesis Example 3.

Example 1 Base Resin (Synthesis Example 5) 96 parts by weight Tri (p-tert-butoxyphenyl) sulfonium triflate 4 parts by weight N-methylpyrrolidone 0.4 parts by weight 1-ethoxy-2- A resist solution consisting of 600 parts by weight of propanol was prepared and filtered using a 0.1 μm filter.

Next, this resist solution was spin-coated on a silicon substrate at 2,000 rpm and prebaked on a hot plate at 85 ° C. for 1 minute. At this time, the film thickness was 0.4 μm. After drawing with a KrF excimer laser or an electron beam with an accelerating voltage of 30 kV, PEB was performed at 85 ° C. for 2 minutes. Development was carried out for 1 minute with a 2.4% aqueous solution of tetramethylammonium hydroxide (TMAH), followed by rinsing with water for 30 seconds.

The resist film thus obtained showed positive type characteristics and the D ₀ sensitivity was 4.5 μC / cm ² . KrF excimer laser (wavelength 2)
48 nm) has an Eth sensitivity of 10 mJ / c.
m ² . The base resin used here showed a dissolution rate of 35 nm / s in the developing solution. The resist film had a dissolution rate of about 1.5 nm / s in the unexposed area and a dissolution rate of 40 nm / s in the exposed area after PEB.

With KrF excimer laser exposure, 0.2
A 5 μm line & space pattern and a hole pattern were resolved, and a pattern having side walls perpendicular to the substrate was formed. In electron beam writing, the resolution was 0.1 μm.

When the storage stability of the resist solution was examined, the number of particles of 0.3 μm or larger in the solution prepared as a resist solution and immediately after filtration was 10 particles / ml. The numbers of particles in each solution after storage at room temperature for 1 month and 2 months were 20 particles / ml and 24 particles / ml, respectively, and it was confirmed that the number of particles in the resist solution hardly changed. Further, the resist characteristics such as sensitivity and resolution of the resist film when the resist solution after storage was used did not change.

Comparative Example 1 Example 1 except that the polymer obtained in Synthetic Example 6 was used in place of the polymer in Example 1.
A resist solution was prepared in the same manner as in.

Immediately after preparation as a resist solution, the same resist characteristics as the resist film of Example 1 were exhibited, but after storage at room temperature for 1 month, the number of particles of 0.3 μm or more in the solution was 3, Over 000 cells / ml. When the resist film formed by this resist solution is exposed by the KrF excimer laser, the Eth sensitivity is 13 mJ / cm ^2.
And it was possible to resolve only up to a pattern of 0.35 μm. Further, the number of particles stored for 2 months increased so much that the particles could not be measured.

Comparative Example 2 Example 1 was repeated except that the polymer obtained in Synthesis Example 7 was used in place of the polymer used in Example 1.
A resist solution was prepared in the same manner as in.

Immediately after preparation as a resist solution, the same resist characteristics as the resist film of Example 1 were exhibited, but when stored at room temperature for 1 month, the number of particles increased to such an extent that the particles could not be measured. did.

[Example 2] OFPR800 (manufactured by Tokyo Ohka Co., Ltd.) as a lower resist film having a thickness of 2 μm was formed on a silicon wafer.
To a thickness of 100 ° C. and heated at 200 ° C. for 1 hour to cure. The resist solution of Example 1 was applied onto the lower resist film in a thickness of about 0.4 μm in the same manner as above, and prebaked. The pattern was formed on the lower resist film by exposing and developing with an electron beam or a KrF excimer laser in the same manner as in Example 1.

After that, etching was performed with a parallel plate type sputter etching apparatus using oxygen gas as an etchant gas. The etching rate of the lower resist film is 150 nm /
However, the resist film having the composition of Example 1 had a thickness of 2.5 nm / min or less. By etching for 15 minutes, the lower resist film of the portion of Example 1 not covered with the resist film completely disappeared, and a two-layer resist pattern having a thickness of 2 μm or more was formed. A pattern of 0.25 μm was formed by KrF excimer laser exposure and a pattern of 0.1 μm was formed by electron beam exposure with a high aspect ratio.
The etching conditions are shown below. Gas flow rate: 50 SCCM, gas pressure: 1.3 Pa rf power: 50 W, dc bias: 450 V

[0078]

The chemically amplified positive resist composition of the present invention is sensitive to high energy rays and is excellent in sensitivity, resolution, PEB delay stability and oxygen plasma etching resistance. Therefore, the two-layer resist film obtained by applying the resist material of the present invention on the lower resist film has a feature that a fine pattern can be formed with a high aspect ratio. Therefore, it is particularly useful for fine processing with electron beams or deep ultraviolet rays. Further, since the chemically amplified positive resist composition of the present invention has a small absorption particularly at the exposure wavelength of the KrF excimer laser, it has a feature that a fine resist pattern which is perpendicular to the substrate can be easily formed.

Claims (6)

[Claims] 1. A chemical amplification comprising a polysiloxane (A) represented by the following composition formula (1) in which a terminal silanol group of the polysiloxane is protected by a trimethylsilyl group, and an acid generator (B). Positive resist material. R (OSiMe ₃ ) _a SiO _{(3-a) / 2} (1) embedded image 2. [Chemical formula 2] 3. The weight average molecular weight of the polysiloxane (A) is 5,000 to 50,000.
The chemically amplified positive type resist material described. 4. The polysiloxane (A) has the following general formula (2): (In the formula, Me, a, and n have the same meanings as described above.) The silanol group of the polysiloxane consisting of the repeating unit is trimethylsilylated with trimethylsilyl iodide, and the methyl group of the methoxy group is trimethylsilyl group. To produce a phenolic hydroxyl group by hydrolysis, and then hexamethyldisilazane or trimethylsilyl chloride is used to trimethylsilylate a part of the hydrogen atoms of the phenolic hydroxyl group and the remaining hydrogen atoms of the silanol group. By trimethylsilylation of the following general formulas (5a) and (5b) (In the formula, Me, a, and n have the same meanings as described above.) By substituting a part or all of the remaining phenolic hydroxyl group of the polysiloxane composed of the repeating unit with an acid labile group, Claim 1, which is obtained
The chemically amplified positive resist material as described in 2 or 3. 5. The chemically amplified positive resist composition according to claim 1, wherein the acid generator (B) is an onium salt represented by the following general formula (6). (R) _m JM (6) (wherein R represents the same or different aromatic group or substituted aromatic group, J represents sulfonium or iodonium, and M represents a toluene sulfonate group or trifluoromethane sulfone group. Represents a phonate group, and m is 2 or 3.) 6. The chemically amplified positive resist composition according to claim 1, which contains a dissolution inhibitor (C).