JPH0422957A - Ionizing radiation ray sensitive material and pattern forming method - Google Patents

Abstract

PURPOSE:To improve the sensitivity and resolution of a resist by forming the above photosensitive material so as to have substituents which generate an acid when irradiated with ionizing radiation rays and specific substituents which are hydrolyzed by the acid generated by the substituents and are thereby changed in polarization in one molecule. CONSTITUTION:This photosensitive material has either or both of at least >=1 kinds of the substituents which generate the acid when irradiated with the ionizing radiation rays and the the substituents which are hydrolyzed by the acid generated by the substituents and are thereby changed in polarization and are expressed by -COOL or -OL in one molecule. In the formula, L denotes any one of -CR1R2R3, -NR1R2, -SiR1R2R3, -PR1R2R3R4 and at least two of R1>R2>R3>R4 are 1 to 12C alkyl group, phenyl group, or a phenyl group in which a part or the whole of the hydrogen is substed. with a methyl group or ethyl group. The ionizing radiation sensitive resist which is excellent in both sensitivity and resolution is put into practicable use in this way.

Description

[Detailed Description of the Invention] [Summary] Regarding the method of forming fine patterns, the aim is to put into practical use an IT-separating radiation resist with excellent sensitivity and resolution. Ionizing radiation characterized by having one or both of at least one type of substituent that occurs and a substituent represented by -COOL or -OL that changes polarity by being hydrolyzed by the acid generated by the substituent. Constitutes a photosensitive material. Here, L is -CRIR,R,, -NR1)b+-5I JR
J3. -PR is any one of RIRzRJa, and at least two of RI, Rz, Rs, and Ra are an alkyl group or phenyl group having 1 to 12 carbon atoms.

or a phenyl group in which part or all of the hydrogen is substituted with a methyl group or an ethyl group, or a substituent that generates an acid upon irradiation with t-separating radiation is a halogen group, a halogenated alkyl group, or a polyhalogenated alkyl group. It is.

[Industrial application field]

The present invention provides an ionizing radiation-sensitive material with excellent sensitivity and resolution,
This invention relates to a pattern forming method using this.

Semiconductor integrated circuits have become more integrated and LSI and VLSI have been put into practical use, and the minimum line width of the wiring patterns used in these circuits is about 0.7μ, but further miniaturization is expected in the future. There is a tendency.

For this reason, thin film formation technology, photolithography (photolithography or electron beam lithography), ion implantation technology, etc. are used to form semiconductor integrated circuits.

That is, regarding the formation of fine patterns, a resist is coated on a substrate to be processed on which a thin film has been formed, selective exposure is performed, and then development is performed to create a resist pattern. Dry etching is performed using this as a mask, and then the resist is removed. A photolithography technique is used to obtain a thin film pattern by dissolving and removing the film.

In order to accurately form fine patterns, it is a prerequisite that the resist has good sensitivity and resolution.

[Conventional technology]

As mentioned above, it is necessary to use a resist material with high resolution to form fine patterns, and high sensitivity is also required to increase productivity (throughput).

Recently, chemically amplified resists have been attracting attention as a resist that simultaneously satisfies these two conditions.

Here, chemically amplified resist is a general term for resists that contain an acid generator in the resist composition and utilize the catalytic action of the generated acid.

This type of resist causes reactions such as decomposition and crosslinking of many polymer molecules due to the catalytic action of a small amount of acid generated from an acid generator when irradiated with ionizing radiation.
Generally sensitive.

Further, since the acid diffusion distance itself is as small as about 5 nn+, the resolution is excellent.

Chemically amplified resists having such excellent properties can be divided into the following four types in terms of composition.

(1) A negative resist consisting of an alkali-soluble resin, a crosslinked network, and an acid generator, (2) A positive resist consisting of an alkali-soluble resin, a dissolution inhibitor, and an acid generator, (3) an alkali-insoluble resin, and (4) a positive resist consisting of an alkali-soluble resin and an acid generator; and (4) a positive resist consisting of an alkali-soluble resin and an acid generator. There are also many other types depending on the developing method and the type of ionizing radiation to which they are sensitive.

However, all of these chemically amplified resists require an acid generator to be added to the resist.

Currently used acid generators include onium salts, nitrobenzyl tosylate, and various halogen organic substances, each of which is used appropriately.

However, in order to add these acid generators into the resist, it is necessary to consider their solubility in organic solvents.

Here, di-t-butyl ether, methyl isobutyl ketone, etc. are used as resist solvents.
These acid generators have low solubility in the above-mentioned solvents, and it is difficult to dissolve them in the required amount.

Now, a characteristic of chemically amplified resists is that a large amount of reaction occurs with a small amount of generated acid, but in reality, sufficient sensitivity cannot be obtained if the amount of acid generator added is small.

Further, the added acid generator becomes a residue together with the acid after irradiation with ionizing radiation.

Therefore, in order to remove this, it is necessary to perform another cleaning process after development, which increases the number of steps and also impairs the pattern shape.

Note that if the residue is highly volatile, it is not necessarily necessary to remove it using a solvent, but in that case, problems such as the volatile residue contaminating the stepper used during exposure occur.

For these reasons, there are many problems that need to be solved in use.

[Problem to be solved by the invention]

As mentioned above, the acid generators constituting chemically amplified resists, which have been attracting attention recently, have low solubility in solvents and are difficult to dissolve to the required amount, and acid generators that remain as residues are difficult to dissolve. In order to remove the agent, it is necessary to wash with a solvent other than the developer, but there are problems such as the pattern shape being damaged by this washing, and improvements are needed.

[Means to solve the problem]

The above-mentioned problem is that one molecule contains at least one type of substituent that generates an acid when irradiated with ionizing radiation, and the following (1) or (2) that changes polarity by being hydrolyzed by the acid generated by this substituent. ) This problem can be solved by constructing an ionizing radiation-sensitive material characterized by having one or both of the substituents represented by the following.

Here, -COOL...(1
)OL...(2) However, L is -CRIRZR31-N RIRz, -5i
Any one of RIR2R3P RIR2R3R4, and the least of RI, R2, R3, and R4 (both of which are an alkyl group having 1 to 12 carbon atoms, a phenyl group, or a part or all of hydrogen is methyl) It is a phenyl group substituted with an ethyl group.

Also,! A substituent that generates an acid upon irradiation with dissociative radiation is
It is any one of a halogen group, a halogenated alkyl group, and a polyhalogenated alkyl group.

[Function] To date, no literature has been published or a patent application has been filed regarding a resist material in which the base resin itself contains a portion corresponding to an acid generator.

Furthermore, although some polymer sensitizers that generate acid are known, there are no polymer sensitizers that are known to decompose themselves with acid.

The present invention has a part in the base resin itself that generates acid when irradiated with ionizing radiation, and a part whose polarity changes when hydrolyzed by this acid, and this resin is used as a photosensitive material to form a resist. It consists of

That is, the base resin contains at least one type of substituent selected from a halogen group, a halogenated alkyl group, and a polyhalogenated alkyl group, and the halogen is removed in the form of a radical by irradiation with ionizing radiation. Hydrogen is extracted from the remaining solvent and becomes hydrogen halide.

Next, this hydrogen halide is in the same base resin, C00L...(1)-
OL...attacks the substituent shown in (2).

As a result, the portion indicated by L in formulas (1) and (2) is removed by hydrolysis and becomes a carboxyl group or a phenol group, resulting in a significant change in polarity.

Therefore, alkaline development results in a positive resist, while organic solvent development using a nonpolar solvent such as methyl isobutyl ketone (abbreviated as MIBK) results in a negative resist.

In this case, since the acid generator is chemically bonded to the resin, there is no need to consider the solubility of the acid generator if a solvent with high solubility for the resin is selected.

Furthermore, even after the acid is generated, there is no residue other than the resin, so the stepper will not be contaminated.

R1 included in the formulas (1) and (2) above
) As for Rz and Rz-Ra, as long as at least two of them are an alkyl group having several months to 12 carbon atoms, a phenyl group, or a phenyl group in which some of the hydrogens are completely substituted with a methyl group or an ethyl group, Even if all the substituents are the same,
It does not matter if only one substituent is different or all substituents are different.

The reason why it is limited to at least two is that if at least two or more are not present, hydrolysis is difficult to occur even when attacked by hydrogen halide.

Further, the reason why the number of carbon atoms in the alkyl group is limited to 1 to 12 is that if the volume of the alkyl group is too large, hydrogen halide will not be able to approach it and the reaction will not occur (steric hindrance).

Now, when using a resin as a resist, it is preferable to have a benzene nucleus in the polymer in order to have sufficient dry etching resistance. desirable.

In addition, in order to obtain sufficient resolution, the molecular weight should be 50o, o
In order to obtain sufficient sensitivity, it is desirable that the molecular weight be 2,000 or more.

In addition, in order to have sufficient acid generating ability, the number of halogen-containing substituents must be 10% or more and 80% or less of the number of carbosyl groups and phenol groups shown in formulas (1) and (2). is desirable.

The reason for this is that if it is less than 10%, it does not show sufficient acid generation ability, and if it is more than 80%, a large amount of acid can be produced.
This is because the absolute number of carbosyl groups and phenol groups is small, so there is little change in polarity, which prevents development.

〔Example〕

Example 1: Allyl chloride and paratertiary butoxystyrene (abbreviated as P
TBST) at a molar ratio of 1:1 and radical copolymerization using azobisisobutyronitrile as an initiator (3)
A polymer shown in the formula was synthesized.

However, m and n are positive integers, the weight average molecular weight of this polymer is 1.3 XIO', and the degree of dispersion is 2.5.

After dissolving 1 g of this polymer in 4 g of methyl isobutyl ketone, a resist solution prepared by filtering through a 0.2 μm membrane filter was applied onto a Si wafer to a thickness of 0.7 μm to prepare a sample for exposure.

When the electron beam sensitivity of this sample was measured, it was found that the exposure amount when the residual film rate was 50% was 8 μC/cmz.

Furthermore, a substantially rectangular pattern of 0.3 μm line and space could be resolved.

Next, the above sample was irradiated with soft X-rays having a wavelength of 4.4 to examine sensitivity and resolution.

As a result, the sensitivity was approximately 30 mJ/cmz, and the resolution was 0.4 μI line and space, which is the minimum line width of an X-ray mask.

Furthermore, when an alkaline developer (MP-312, Schiffbray) was used for development, a positive image was obtained, and when development was performed using an organic solvent CMIBK, a negative image was obtained.

In addition, since the electron beam sensitivity of polyPTBST having a similar molecular weight is about 500 μC/cn+2, which is low sensitivity, it can be said that the high sensitivity of this polymer is due to the chemical amplification effect.

Example 2: The hydroxyl group of 286-bis(bromomethyl)-4-vinylphenol was blocked with a trimethylsilyl group using an alkali catalyst (pyridine).

Thereafter, by performing living anionic polymerization using n-butyllithium as an initiator, a polymer shown in formula (4) was produced.

This polymer has a weight average molecular weight of 1.5 XIO' and a dispersity of 1.2.

This polymer Ig was dissolved in 4 g of methyl isobutyl ketone, and a resist solution prepared by filtering through a 0.2 μm membrane filter was applied onto a Si wafer to a thickness of 0.7 μm to prepare a sample for exposure.

When we measured the electron beam sensitivity and X-ray sensitivity of this sample, the electron beam sensitivity was 6 μC/cm", and the X-ray sensitivity was 3
2mJ/cm”, resolution is 0°4μ for both electron beam and X-ray.
m lines and spaces were resolved with good shape.

[Effects of the Invention] By carrying out the present invention, it becomes possible to put into practical use a resist that is sensitive to ionizing radiation and has excellent sensitivity and resolution.

Claims (3)

[Claims] (1) At least one type of substituent that generates an acid when irradiated with ionizing radiation in one molecule, and the following (1) that changes polarity by being hydrolyzed by the acid generated by the substituent.
An ionizing radiation-sensitive material having one or both of the substituents represented by (2) or (2). -COOL...(1) -OL...(2) However, L is -CR_1R_2R_3, -NR_1R_2
, -SiR_1R_2R_3, -PR_1R_2R_3
Any one of R_4, and R_1, R_2
, R_3, and R_4, at least two have carbon atoms of 1 to
12 alkyl groups, phenyl groups, or phenyl groups in which part or all of the hydrogen atoms are substituted with methyl or ethyl groups. (2) An ionizing radiation-sensitive material, wherein the substituent that generates an acid upon irradiation with ionizing radiation according to claim 1 is any one of a halogen group, a halogenated alkyl group, and a polyhalogenated alkyl group. (3) A pattern forming method comprising forming a resist using the photosensitive material according to claim 1, selectively exposing a substrate coated with the resist to ionizing radiation, and then developing to form a resist pattern. .