JPH07239558A - Developer and pattern forming method - Google Patents

Abstract

PURPOSE:To provide a pattern forming method using a positive type resist material for exposure with high energy beams excellent in applicability to a process. CONSTITUTION:One or more kinds of crosslinking agents selected from among hexamethylolmelamine, phenylenediamine and xylylene glycol are added to a developer contg. tetraalkylammonium hydroxide to obtain the objective developer used for a chemical amplification type positive resist material. A pattern of a chemical amplification type positive resist contg. a polyhydroxystyrene deriv. is formed through a heat treating process after exposure, a developing process using a developer obtd. by adding a crosslinking agent to an aq. alkali soln. and a deihydrating and baking process. Irradiation with far UV may be carried out after the development or development with only an aq. alkali soln. and processing with a soln. contg. a crosslinking agent may be carried out. The deformation of the formed pattern during etching can be inhibited.

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 pattern formation method of a chemically amplified positive resist material which has high sensitivity to high energy rays such as rays and develops with an alkaline aqueous solution.

[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 technology, an essential factor is 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 16M.
Up to bit DRAM equivalent. 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 0.3-0.4μ
It is also possible to process m, and when a resist having small light absorption is used, it is 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 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 using acid as a catalyst
n) resist material (eg, Liu et al.,
Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.), Vol. B6, page 379 (1988)] has a sensitivity equal to or higher than that of conventional high-sensitivity resists and has high resolution. It also has excellent dry etching resistance. Therefore, it is a particularly promising resist material for deep ultraviolet lithography. As a negative resist, Shipley Co., Ltd. used a three-component chemically amplified resist (trade name: SAL601ER) consisting of a novolac resin, a melamine compound and an acid generator.
7) has already been commercialized. However, no chemically amplified positive resist has been commercialized yet. Negative resist can be used for wiring and gate formation in the LSI manufacturing process, but contact holes are difficult to finely process using a negative resist, so fine processing is difficult, and positive resist is much more suitable. ing. Therefore, a high-performance positive resist is strongly demanded. Traditionally, Ito et al.
We are developing a positive chemically amplified resist by adding an onium salt to a resin called PBOCST in which the H group is protected by a t-butoxycarbonyl group (tBoc group). However, the onium salt used contains antimony as a metal component [Reference: Polymers Thin Electronics, A
CS Symposium Series (Polymers in Electro
nics, ACS Symposium Series) 242 (American Chemical Society, Washington DC. 1984), page 11]. To avoid contamination of the substrate, metal components in the resist material are generally disliked. Therefore, PBOCST resist is not preferable in terms of process. Also, tBO
In the C-based positive resist, the tBOC group is decomposed into an isobutene gas and a carbon dioxide gas in the etching step after pattern formation, and therefore, there is a high possibility that pattern deformation due to film thickness change or volume contraction occurs. In general, a novolac resin photoresist undergoes a cross-linking reaction by post-baking or ultraviolet curing after forming a resist pattern, so that the heat resistance of the pattern is improved. Since the resist using the polyhydroxystyrene derivative as the base polymer is less likely to be crosslinked even by post-baking or UV curing,
Pattern deformation occurs. This pattern deformation differs depending on the pattern shape, and the larger the pattern, the larger the deformation. It is presumed that the above-mentioned film thickness change and volume contraction pose a serious problem for precise fine processing. Further, there is a problem that a resist using a polyhydroxystyrene derivative as a base resin has lower peeling resistance in an aqueous hydrofluoric acid solution than a novolak resin photoresist.

[0003]

As described above,
A chemically amplified resist containing a polyhydroxystyrene derivative has the advantages of high sensitivity and high resolution in deep ultraviolet, electron beam and X-ray lithography, but has the problem of large pattern deformation in the process after pattern formation. However, it is still difficult to put it into practical use. An object of the present invention is to provide a pattern forming method of a positive resist material for high energy beam exposure, which is superior in process applicability and is superior to the prior art.

[0004]

The present invention will be described in brief. The first invention of the present invention relates to a developer, and in a developer used for a chemically amplified positive resist material,
One or more cross-linking agents selected from hexamethylol melamine, phenylenediamine, and xylylene glycol are added to a developer containing tetraalkylammonium hydroxide. A second invention of the present invention relates to a pattern forming method,
A pattern forming method used for a chemically amplified positive resist containing a polyhydroxystyrene derivative, characterized by including a step of heat treatment after exposure, a step of developing with a developer containing a crosslinking agent added to an alkaline aqueous solution, and a step of dehydration baking. And A third invention of the present invention is an invention relating to another pattern forming method, wherein in the pattern forming method of the present invention, a step of performing heat treatment after exposure, a step of developing with a developing solution containing a crosslinking agent added to an alkaline aqueous solution, And a step of performing a heat treatment after irradiation with deep ultraviolet rays. Further, the fourth invention of the present invention relates to another pattern forming method, wherein in the pattern forming method of the present invention, a step of heat treatment after exposure, a step of developing with an alkaline aqueous solution, a dipping treatment in a solution containing a crosslinking agent And a step of dehydration baking are included. Furthermore, the fifth invention of the present invention relates to another pattern forming method, wherein in the pattern forming method of the present invention, a step of heat treatment after exposure, a step of developing with an alkaline aqueous solution, a solution containing a crosslinking agent and a strong acid is used. The method is characterized by including a step of dipping treatment in and a step of dehydration baking.

Briefly describing the present invention, the present invention relates to a developer for a positive resist material and a method for pattern formation, wherein a crosslinking agent is diffused in a pattern during pattern formation or after pattern formation, and a subsequent heat treatment. Is characterized by causing crosslinking in the base resin.

If the base resin is crosslinked and the pattern can be made strong, the pattern deformation can be prevented even if the tBOC group is decomposed, but the polyhydroxystyrene-based resist is difficult to crosslink. Therefore, it is necessary to add a crosslinking agent. However, when a cross-linking agent is added to the resist material, in the case of a positive resist, there is a problem that the cross-linking reaction by the cross-linking agent affects the positive-type decomposition reaction. Therefore, the crosslinking agent must be introduced into the pattern during pattern formation or after pattern formation. The present inventors have found an effective method for introducing a cross-linking agent into a pattern, and have completed the present invention.

One of the important effects of the present invention is to add a cross-linking agent to the developing solution, and the pattern swells during development and the cross-linking agent diffuses therein. Then, dehydration baking is carried out at a temperature low enough not to decompose the tBOC group to cause cross-linking of polyhydroxystyrene. When deep UV irradiation is performed before dehydration baking, an acid is generated, so that decomposition and crosslinking of tBOC occur simultaneously. In this case, the volumetric shrinkage is large, but the crosslinking density is high, so that the heat resistance is further improved. The other is to immerse in a solution containing a cross-linking agent after pattern formation to diffuse the cross-linking agent in the pattern. After that, baking is performed at a low temperature at which decomposition of the tBOC group does not occur to cause crosslinking. At this time, by adding a strong acid, the acid diffuses in the same manner as the crosslinking agent, and at the same time as the crosslinking, tB
OC decomposition occurs. Therefore, the same effect as irradiation with deep ultraviolet rays before dehydration baking can be expected.

Of the tetraalkylammonium hydroxides, an aqueous solution of tetramethylammonium hydroxide is generally used as the developing solution, and water-soluble hexamethylolmelamine, phenylenediamine, benzenedicarboxylic acid, benzenedisulfonic acid is used as the crosslinking agent. Polyfunctional compounds such as and xylylene glycol were effective. The addition amount of the cross-linking agent can be changed from 0.5 to 15% by weight, but it needs to be sufficiently controlled because it changes the alkali concentration of the developer. That is, in the case of an acidic cross-linking agent, the developing speed becomes slower, so it is necessary to increase the developing time. On the contrary, in the case of a basic cross-linking agent, the developing speed becomes faster, so that it is necessary to shorten the developing time.

When the immersion treatment is carried out after the pattern formation, it is necessary to use an aqueous solution which does not dissolve the pattern or a non-polar organic solvent such as chlorobenzene or xylene as the immersion solution. Alcohol and ketone solvents cannot be used because they dissolve the pattern. In the case of an aqueous solution, the above water-soluble polyfunctional compound can be used. When using an organic solvent such as chlorobenzene, a polyfunctional epoxy compound can be used as a crosslinking agent. Trifluoroacetic acid, trifluoromethanesulfonic acid, or paratoluenesulfonic acid can be used as a strong acid that serves as a catalyst for the crosslinking reaction. The amount of the cross-linking agent added can be larger than that in the case of the developer, but
If it is 0% or more, there is a problem that the resist pattern is partially dissolved in the solution, so it is necessary to suppress it to less than that. By increasing the temperature of the treatment liquid, diffusion of the acid and the cross-linking agent into the pattern can be promoted.

After forming a pattern with tBOC type chemically amplified resist, dehydration baking was performed on a hot plate at 100 ° C. for 2 minutes. When the sample is baked at 120 ° C. or higher, the pattern of 1 μm or less hardly changes,
A pattern having a size of 100 μm or more shrinks, so that the pattern edge recedes. In particular, when the temperature is 140 ° C. or higher, this change amount becomes large, and a recession of 5 μm or more occurs. On the other hand, it was confirmed that before the dehydration bake, the pattern was reinforced by dipping the pattern in the above-mentioned treatment liquid to diffuse the crosslinking agent to crosslink the resist polymer, and thus the pattern deformation was small and could be used in the LSI process. The pattern deformation can be reduced below the softening temperature of the base polymer, but when polyhydroxystyrene is used as the base polymer, the pattern deformation can be suppressed up to 180 ° C.

[0011]

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

Example 1 Resin in which a part of the hydroxyl groups of polyhydroxystyrene was converted to tBOC 80.6 parts by weight 3,3-bis [p- (t-butoxycarbonyloxy) phenyl] butanoic acid t-butyl ester 14 parts by weight Part Bis (pt-butylphenyl) iodonium trifluoromethanesulfonate 5 parts by weight Diglyme (solvent) 400 parts by weight of a resist solution on a silicon substrate at 3000 rpm
Spin coating was performed and prebaked at 100 ° C. for 1 minute on a hot plate. The film thickness was 0.9 μm.

After drawing on the resist film with an electron beam having an accelerating voltage of 30 kV, PEB was performed on a hot plate at 75 ° C.
I went. Subsequently, development was carried out for 1 minute using a developer obtained by adding 3% by weight of hexamethylolmelamine to an aqueous solution of 2.0% tetramethylammonium hydroxide (TMAH), and rinsed with water for 1 minute. Shows positive characteristics,
The Do sensitivity was ² μC / cm ² . When hexamethylolmelamine is not added, it is 4 μC / cm ² , and the addition of a crosslinking agent provides high sensitivity. By cross-linking the obtained resist pattern by dehydration baking at 100 ° C., it was confirmed that pattern deformation did not occur even at 140 ° C. baking.

Examples 2 and 3 Instead of the cross-linking agent hexamethylolmelamine of Example 1,
The pattern deformation was evaluated in the same manner as in Example 1 using the crosslinking agents shown in Table 1 below. In each case, it was confirmed that pattern deformation did not occur at 140 ° C.

[0015]

[Table 1]

Examples 4 to 8 After exposure and PEB in the same manner as in Example 1, 2.0% by weight
It was developed with an aqueous TMAH solution for 1 minute. The obtained pattern was immersed in an aqueous solution containing 5% by weight of the crosslinking agent shown in Table 2 for 1 minute, and then the pattern was crosslinked by dehydration baking.
In this case, since the crosslinking agent concentration is higher than in Examples 1 to 3,
It was confirmed that the crosslink density was high and that pattern deformation did not occur even when baked at 160 ° C.

[0017]

[Table 2]

Examples 9-11 Trifluoroacetic acid (Example 9), trifluoromethanesulfonic acid (Example 10), and paratoluenesulfonic acid (Example 11), which serve as catalysts, were added to the treatment liquids of Examples 4-8. Pattern deformation was evaluated in the same manner as in Examples 4 to 8 using the treatment liquid added in an amount of wt%. It was confirmed that the strong acid of the catalyst diffused into the pattern at the same time as the cross-linking agent, so that the cross-linking reaction was complete and there was no pattern deformation even when baked at 180 ° C.

Example 12 A 5 wt% solution of chlorobenzene was prepared using Epon 815 (manufactured by Wako) as a crosslinking agent. The patterns obtained in the same manner as in Examples 4 to 8 were immersed in the solution for 1 minute, and the pattern deformation was evaluated. It was confirmed that there was no deformation even when baked at 140 ° C.

Example 13 In Examples 4 to 8, the liquid temperature in the immersion treatment was 80 ° C.
When, the diffusion of the crosslinking agent into the pattern and the crosslinking reaction were promoted. Therefore, the obtained resist pattern is 100
It was confirmed that the cross-linking by dehydration baking at ℃ did not cause pattern deformation even by baking at 180 ℃.

Example 14 Far-ultraviolet rays were irradiated before dehydration baking in Example 1. Subsequent dehydration baking resulted in 10% volume shrinkage, but heat resistance of 200 ° C. or higher was recognized. Also,
The resistance to peeling from the substrate in an aqueous hydrofluoric acid solution was improved.

[0022]

The pattern forming method of the present invention is based on tBOC.
In the pattern formation of the chemically amplified resist, the cross-linking agent is diffused in the pattern and cross-linked with the base resin, so that the pattern deformation during etching can be suppressed. This method enables highly precise etching and has excellent dimensional controllability, and is useful for fine processing of semiconductor integrated circuits. In addition, the peeling resistance to the hydrofluoric acid aqueous solution was significantly improved.

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Claims (5)

[Claims] 1. A developer used for a chemically amplified positive resist material, wherein hexamethylolmelamine is added to a developer containing tetraalkylammonium hydroxide.
A developer comprising one or more cross-linking agents selected from phenylenediamine and xylylene glycol. 2. A pattern forming method used for a chemically amplified positive resist containing a polyhydroxystyrene derivative, which comprises a step of heat treatment after exposure, a step of developing with a developer containing a crosslinking agent added to an alkaline aqueous solution, and a step of dehydration baking. A pattern forming method comprising: 3. A pattern forming method used for a chemically amplified positive resist containing a polyhydroxystyrene derivative, a step of performing a heat treatment after exposure, a step of developing with a developer containing a crosslinking agent added to an alkaline aqueous solution, and a heat treatment after irradiation with deep ultraviolet rays. A method for forming a pattern, which comprises the step of: 4. A pattern forming method used for a chemically amplified positive resist containing a polyhydroxystyrene derivative, a step of heat treatment after exposure, a step of developing with an alkaline aqueous solution, a step of immersion treatment in a solution containing a crosslinking agent, and a dehydration bake. A method for forming a pattern, which comprises the step of: 5. A pattern forming method used for a chemically amplified positive resist containing a polyhydroxystyrene derivative, a step of heat treatment after exposure, a step of developing with an alkaline aqueous solution, a step of dipping treatment in a solution containing a crosslinking agent and a strong acid,
And a pattern forming method including a step of dehydration baking.