JP2001100400A - Resist composition and pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resist composition which retains high sensitivity and high resolution peculiar to a chemical amplification type resist, has stability through a pattern forming process and gives a fine resist pattern having a rectangular cross-section and to provide a pattern forming method. SOLUTION: A quencher compound which generates a weak acid is added to a chemical amplification type resist composition to obtain the objective resist composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resist composition and a method for forming a pattern using the resist composition.

[0002]

2. Description of the Related Art In recent years, with miniaturization of semiconductor devices, miniaturization of resist patterns has been required. Among the conventional resists, the composition of a resist composition called a chemically amplified resist is composed of three components: 1) a resin protected by a dissolution inhibiting group, 2) a photoacid generator, and 3) a quencher that inhibits acid diffusion. It is configured. In particular, examples of the quencher compound include those disclosed in, for example, JP-A-7-146558. It has been conventionally known to use basic compounds such as quaternary ammonium salts and nitrogen-containing saccharide compounds.

In order to achieve a finer resist pattern in a chemically amplified resist, it is necessary to control the diffusion length of the acid generated from the photoacid generator by adjusting the components of the resist composition. . That is, in the surface layer of the resist film using the chemically amplified resist, a phenomenon occurs in which the acid in the surface layer is deactivated due to the basic substance contained in the atmosphere. When the acid in the surface layer is deactivated, the resist pattern is not resolved, and a poorly soluble layer is generated on the surface, and the cross-sectional shape of the pattern becomes elongated. Therefore, in order to replace the deactivated acid, the amount of the photoacid generator to be added is further increased. However, if the photoacid generator is added too much, the diffusion length of the acid becomes too long, and the resist pattern becomes tapered. Therefore, in order to control the diffusion of the acid, a quencher is added to control the diffusion length. A desired resist pattern can be obtained by adding an appropriate amount of quencher.

As described above, in order to obtain a desired resist pattern, it is necessary to strictly control the type and amount of each component of the resist composition.

In order to form a finer pattern, it is necessary to control the diffusion length of acid to be shorter, and it is necessary to increase the amount of quencher. However, with the increase in the amount of the quencher, the sensitivity of the chemically amplified resist decreases, and a problem arises that the required exposure amount increases and the productivity decreases.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a resist composition and a pattern forming method capable of obtaining a fine pattern without lowering the sensitivity of the resist composition. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention provides a polymer comprising at least (a) a polymer in which an alkali-soluble group of an alkali-soluble polymer is protected by a dissolution inhibiting group which is dissociated by an acid; and (b) a compound capable of generating an acid upon exposure to light. When,
And (c) a quencher compound that generates a weak acid.

The present invention also provides a step of forming a resist film containing the resist composition as a main component on a substrate, a step of subjecting the resist film to pattern exposure, and a step of cleaning the exposed resist film. And a step of developing the resist film after baking using an alkaline solution.

In the resist composition of the present invention, since the component (c) further enhances the compatibility between the polymer of the component (a) and the compound of the component (b), occurrence of phase separation in a film state is prevented. Is done. In addition, since component (c) significantly increases the dissolution rate of the film in an exposed portion in an alkaline solution,
The formation of the hardly-solubilized layer on the surface is suppressed, and the contrast of the exposed part and the unexposed part is improved.

Therefore, the resist composition of the present invention maintains the high sensitivity and high resolution characteristic of a chemically amplified resist, is stable throughout the pattern forming process, and provides a fine rectangular cross section pattern.

Further, a sparse pattern and a dense pattern can be resolved at the same exposure regardless of the resist pattern density.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The resist composition according to the present invention comprises:
At least (a) a polymer in which an alkali-soluble group of an alkali-soluble polymer is protected by a dissolution inhibiting group that dissociates with an acid, (b) a compound that generates an acid upon exposure, and (c) a quencher compound that generates a weak acid. It contains.

The components (a) to (c) will be described below.

Component (a) The polymer in which the alkali-soluble group of the alkali-soluble polymer which is the component (a) is protected by a dissolution inhibiting group which is dissociated by an acid is used as a base polymer. A compound in which a soluble group, for example, a phenolic hydroxyl group, a carboxyl group, or the like is protected by an acid-labile group (dissolution inhibiting group) to suppress its alkali affinity. Such a polymer is substantially insoluble in an alkali solution in an unexposed state, but the acid generated from the component (b) upon exposure decomposes the dissolution inhibiting group, and the alkali contained in the base polymer. Since the soluble group is regenerated, the compound changes to a compound exhibiting alkali solubility.

The molecular weight of the polymer is preferably from about 1,000 to 1,000,000 from the viewpoint of improving heat resistance.

As the polymer of the component (a), preferably, an ether or ester using an alkali-soluble polymer having a phenol skeleton as a base polymer, specifically, a phenolic hydroxyl group of a polymer having a phenol skeleton is converted into a suitable ether A compound protected by treatment with an agent or an esterifying agent and etherification or esterification can be used.

Incidentally, in the polymer which has been treated with the appropriate etherifying agent or esterifying agent and etherified or esterified, all the phenolic hydroxyl groups in the base polymer remain partially unprotected. Therefore, this polymer is substantially a copolymer comprising a monomer unit into which an ether or an ester is introduced, and a monomer unit having a phenolic hydroxyl group.

As the polymer of the component (a), a compound represented by the following formula (1) is particularly preferred because of its high resolution.

Embedded image Component (b) As the compound that generates an acid upon exposure as the component (b), known compounds and mixtures, for example, onium salts, organic halogen compounds, orthoquinonediazide sulfonic acid chloride, sulfonic acid esters and the like can be used. The organic halogen compound is a compound that forms hydrohalic acid. For example, US Pat.
2, U.S. Pat. No. 3,536,489, U.S. Pat.
9778 and German Offenlegungsschrift No. 2243621.
And those disclosed in US Pat. Other photoacid generators other than those described above include, for example, JP-A-54-74728.
JP-A-55-24113, JP-A-55-7774
No. 2, JP-A-60-3626, JP-A-60-1385
39, JP-A-56-17345, and JP-A-50-
Compounds disclosed in JP-A-36209 are disclosed.

Preferably, a super strong acid compound represented by a triflate compound such as diphenyliodonium trifluoromethanesulfonate and trifluoromethanesulfonic acid (p-tert-butoxyphenyl) is exemplified.

The amount of component (b) is preferably in the range of about 0.01 to 50% by weight, more preferably 0.1 to 30% by weight, based on the total solid components of the resist composition. If the amount of the component (b) is less than 0.01% by weight, it may be difficult to obtain sufficient photosensitive characteristics. 50
If the content is more than 10% by weight, it may be difficult to obtain uniform photosensitive characteristics, or a residue may be generated upon removal after pattern formation.

Component (c) The acid generated from the quencher compound that generates a weak acid, which is the component (c), is that (b) the compound that generates an acid upon exposure is a weaker acid than the acid generated upon exposure. It is desirable to increase the resolution performance during pattern formation.

The component (c) is preferably a compound having a cyclic skeleton and containing at least one nitrogen atom in the cyclic skeleton in order to keep the transmittance of the resist film constant. The compound has a 5-membered ring or more cyclic skeleton as a cyclic skeleton, and a compound in which a carbon atom of part or all of the cyclic skeleton is replaced with a nitrogen atom is particularly desirable.

Specific examples of the cyclic skeleton containing a nitrogen atom include those shown below.

Embedded image The component (c) is preferably at least one compound selected from the above-mentioned condensed polycyclic compounds having a cyclic skeleton containing a nitrogen atom. (B) The compound capable of generating an acid upon exposure can sufficiently quench the acid generated upon exposure. Desirable for ching.

Further, it is desirable that the component (c) is a compound having a substituent which is dissociated by at least one or more strong acids in order to sufficiently generate a weak acid.

As the substituent, for example, tertiary butoxycarbonyl or tertiary butyl ester is preferable because it has an effect of keeping a resist shape in a rectangular shape when a resist pattern is formed.

Specific examples of the component (c) of the present invention include the following compounds.

Embedded image Such compounds include, for example, tert-butoxycarbonyl,
Contains a substituent dissociated by a strong acid such as tertiary butyl ester. This substituent is easily decomposed by the strong acid generated from the component (b) upon exposure to light to generate a weak acid such as carboxylic acid or carbonic acid. .

The amount of component (c) is preferably in the range of about 0.01 to 70% by weight, more preferably 0.1 to 50% by weight, based on all solid components of the resist composition.
If the compounding amount of the component (c) is less than 0.01% by weight, shallowness occurs after the development treatment, and the difference in the dissolution rate of the exposed part and the unexposed part in the resist film in the alkaline solution becomes small, and Image performance may be reduced.

In the resist composition of the present invention, a surfactant as a coating modifier, a dye as an antireflection agent, and the like may be further added, if necessary, in addition to the above-mentioned essential components. .

The resist composition of the present invention is prepared by dissolving the above-mentioned essential components (a) to (c) and, if necessary, other additives in a suitable organic solvent, followed by filtration. Can be done.

As the organic solvent used here, for example,
Ketone solvents such as cyclohexanone, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve,
Ethyl cellosolve acetate, butyl cellosolve, cellosolve solvents such as butyl cellosolve acetate, ethyl acetate, butyl acetate, isoamyl acetate, ethyl lactate, ester solvent such as methyl lactate, N-methyl-2-pyrrolidone, dimethylformamide, Dimethylacetamide, dimethylsulfoxide and the like can be mentioned. Also,
These solvents may contain an appropriate amount of an aliphatic alcohol such as xylene, toluene, or isopropyl alcohol.

Next, a process for forming a resist pattern using the resist composition of the present invention will be described.

First, a solution of the resist composition is applied on a substrate by a spin coating method or dipping.
Thereafter, drying is preferably performed at 70 to 140 ° C. to form a photosensitive resin layer (resist film) containing the resist composition as a main component.

As the substrate used here, a silicon wafer, a silicon wafer having steps on the surface on which various insulating films, electrodes, and wirings are formed, a blank mask, GaAs,
An Ill-V group compound semiconductor wafer such as A1GaAs can be used.

Next, pattern exposure is performed on the resist film. At this time, in the exposed portion of the resist film, acid is generated from (b) of the resist composition. Light sources for such exposure include, for example, i-line, h-line, g-line of a low-pressure mercury lamp, xenon lamp light, various ultraviolet rays such as DeepUV such as KrF or ArF excimer laser, X-ray, electron beam, and γ.
Lines, ion beams, etc. may be used.

As a specific method of pattern exposure, when ultraviolet rays and X-rays are used, selective exposure is performed on the resist film via a predetermined master pattern. On the other hand, when an electron beam, an ion beam, or the like is used, the radiation is scanned without using a mask, and pattern exposure is performed directly on the resist film. In order to improve the resolution by lowering the dissolution rate of the unexposed portion, fog exposure may be performed by exposing the entire resist film while heating the pattern exposed portion.

Subsequently, the exposed resist film is subjected to a heat treatment (baking) by using a hot plate, an open or by irradiating infrared rays or the like. By such baking, in the exposed portion of the resist film, the acid generated at the time of exposure diffuses and acts on the polymer of component (a) to decompose the introduced protective group and regenerate the alkali-soluble group. The baking temperature is preferably 200 ° C. or less, more preferably 70 ° C.
Set within the range of ~ 140 ° C. If the temperature is lower than 50 ° C., the acid generated from the component (b) may not be able to react sufficiently with the component (a). Excessive decomposition and curing may occur.

Next, the exposed portion of the resist film is selectively dissolved and removed by subjecting the baked resist film to development processing using an alkaline solution according to a dipping method, a spray method, or the like, to obtain a desired pattern. Here, as the alkaline solution used as the developer, for example, potassium hydroxide,
An inorganic alkali solution such as an aqueous solution of sodium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, or the like, an aqueous solution of tetramethylammonium hydroxy, an aqueous solution of trimethylhydroxyethylammonium hydroxy (TMAH), or an alcohol, a surfactant, etc. And those added.

The substrate and the resist film (resist pattern) after the development process are subjected to a rinsing process using water or the like, and further dried.

In the above-described process, in order to further improve the heat resistance of the resist pattern, the resin component (polymer of component (a)) in the resist pattern is gradually heated after the development process by heating the substrate. Step baking such as cross-linking, Deep U while heating
Deep UV for irradiating V light to crosslink the resin component (polymer of component (a)) in the resist pattern
Processing such as curing can also be performed.

Further, in order to improve the contrast with the unexposed portion of the resist film, before or after exposure, the resist film is immersed in a low-concentration alkaline solution, and then developed using a higher-concentration alkaline solution. You may do it. In this case, instead of a low-concentration alkaline solution, the resist is immersed in amines such as triethylamine, triethanolamine, and hexamethyldisilazane, or the resist film exposed to these amines is heat-treated as necessary. You can also.

[0041]

(Example 1) 70% by weight of a polymer in which a dissolution inhibiting group capable of dissociating with an acid is introduced into a part of a side chain made of polyvinylphenol as a component (a), and (b) a compound capable of generating an acid upon exposure A resist composition obtained by adding (c) 5% by weight of tert-butoxycarbonyltriazole as a quencher compound that generates a weak acid to a composition comprising 25% by weight of an onium salt compound as Apply using
After drying at 30 ° C. for 1 minute, a resist film having a thickness of 0.2 to 1.0 μm was formed. Subsequently, K
Exposure was performed with an rF excimer laser light source. Next, the exposed resist film is heated on a hot plate at 130 ° C. for 1 minute and then heated, and then subjected to a TMAH aqueous solution (TMAH 2.38).
%) To form a resist pattern. The sensitivity and resolution at this time are 155 μC / cm ² ,
It was 0.175 μm. As a result of observing the cross-sectional shape of the formed resist pattern by SEM, the pattern contrast was good, the wall angle was increased, and the pattern shape was dramatically improved.

(Comparative Example 1) A resist pattern was formed in the same manner as in Example 1 except that the component (c) was not added, using the same resist composition as in Example 1. The sensitivity and resolution at this time were 130 μC / cm ² , 0.25
μm. As a result of observing the cross-sectional shape of the formed resist pattern by SEM, the wall angle was lower and the pattern shape was worse than that of the pattern shape obtained in Example 1.

Comparative Example 2 A resist pattern was formed in the same manner as in Example 1 except that the imidazole compound was added in an amount of 5% by weight instead of the component (c). The sensitivity and resolution at this time are 200 μC / cm ² and 0.2 μC.
m. The cross-sectional shape of the formed resist pattern is S
As a result of observation by EM, as compared with the pattern shape obtained in Example 1, the wall angle was lower and the pattern shape was worse.

[0044]

The resist composition of the present invention maintains the high sensitivity and high resolution characteristic of a chemically amplified resist, is stable throughout the pattern formation process, and provides a resist pattern having a fine rectangular cross section.

Further, according to the pattern forming method of the present invention, a fine pattern can be formed without increasing the exposure amount of the resist (decrease in sensitivity).

Claims (6)

[Claims] 1. A polymer in which at least (a) an alkali-soluble group of an alkali-soluble polymer is protected by a dissolution inhibiting group dissociated by an acid, (b) a compound which generates an acid upon exposure, and (c) a weak acid. And a quencher compound. 2. The method according to claim 1, wherein (c) the acid which generates the quencher compound which generates a weak acid is (b) the compound which generates an acid by exposure is an acid which is weaker than the acid which is generated by exposure. 2. The resist composition according to 1. 3. The resist composition according to claim 1, wherein (c) the quencher compound that generates a weak acid is a compound having a cyclic skeleton and containing a nitrogen atom in the cyclic skeleton. 4. The method according to claim 1, wherein the (c) quencher compound that generates a weak acid is at least one compound selected from a condensed polycyclic compound having a cyclic skeleton containing a nitrogen atom. Resist composition. 5. The resist composition according to claim 1, wherein (c) the quencher compound that generates a weak acid is a compound having a substituent that dissociates with at least one or more strong acids. 6. A step of forming a resist film mainly comprising the resist composition according to claim 1 on a substrate, a step of subjecting the resist film to pattern exposure, and baking the exposed resist film. And a step of developing the resist film after baking using an alkaline solution.