JPH06342212A - Resist for forming fine pattern and fine pattern forming method - Google Patents

Abstract

PURPOSE:To provide a resist for forming a fine pattern causing little dimensional change to a resist pattern, transmitting ArF excimer laser light and less expensive than the conventional resist. CONSTITUTION:A two-component material consisting of a high molecular compd. represented by the formula and an acid generating agent is used as the objective resist. In the formula, each of R1-R6 is H, alkoxycarbonyl, alkyl, alkoxyalkyl, alkylsilyl, tetrahydropyranyl, alkoxycarbonylmethyl or hydroxypropyl.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine pattern forming method for producing a semiconductor device or an integrated circuit device and a fine pattern forming material used in the forming method.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of ICs or LSIs, pattern formation is performed by photolithography using ultraviolet rays. On the other hand, along with the miniaturization of semiconductor devices, the use of short-wavelength light sources as ultraviolet light sources has been promoted.

When a short-wavelength light source is used for photolithography, a chemically amplified resist which has high sensitivity and high resolution has been developed as a resist to be used (eg, O.NALAMASU et al., Pr.
oc. SPIE, Vol. 1262, P.I. 32 (199
0)). The chemically amplified resist is a multi-component substance containing an acid generator that generates an acid when irradiated with radiation and a compound that reacts with the acid. As a polymer compound that reacts with an acid, for example, a polymer compound having a structure such as [Chemical Formula 2] is known.

[0004]

[Chemical 2]

Here, R is an alkoxycarbonyl group, an alkyl group, an alkoxyalkyl group, an alkylsilyl group,
A tetrahydropyranyl group, an alkoxycarbonylmethyl group or the like, which easily causes a decomposition reaction with an acid. As described above, the conventional chemically amplified resist is mainly composed of a polymer compound having a low absorptance of light in a short wavelength region such as a polyvinylphenol derivative.

Therefore, the chemically amplified resist has high sensitivity and excellent resolution because the transparency of the resist is increased and the reaction of the resist proceeds by a chain reaction by an acid catalyst. Therefore, the chemically amplified resist is regarded as a promising material for forming a fine pattern using a short wavelength light source.

[0007]

However, the conventional chemically amplified resist has the following problems.

The first problem is that it is necessary to perform heat treatment on the exposed resist film in order to cause the decomposition reaction, and if the exposed resist film is left until the start of the heat treatment. That is, the shape and dimensions of the resist pattern change depending on the environment during the leaving period.

Normally, in the manufacturing process of ICs and the like, 25 to 50 semiconductor substrates per lot are continuously processed in each process. The time required for exposure varies depending on the performance of the stepper, the number of exposure shots or the amount of exposure, but currently 2 to 4 minutes per sheet is required for exposure. On the other hand, the time required for heat treatment is usually 1 to 2 minutes per sheet. 25 lots per lot, exposure time 2 minutes, heat treatment time 1
Considering the case of minutes, the time required from the completion of exposure to the start of heat treatment is about 50 minutes for the first semiconductor substrate, 2
It takes about 25 minutes for the fifth semiconductor substrate, and there is a difference of about 25 minutes between the first semiconductor substrate and the 25th semiconductor substrate in the same lot. This difference in processing time has a great influence on the size of the resist pattern, and it depends on the performance of the resist. However, in the case of a resist pattern of the rule of 0.3 μm, the dimensional fluctuation of the resist pattern is 10% or more of the size of the resist pattern. There are many.

Further, when it takes time from the completion of the exposure to the start of the heat treatment, the dimensional variation of the resist pattern varies among lots.

The dimensional variation of the resist pattern as described above is mainly due to the fact that the basic substance in the atmosphere neutralizes the acid generated from the acid generator, so that the dimensional variation occurs on the surface of the resist pattern. And a dimensional difference also occurs between the top surface portion and the bottom surface portion of the resist pattern. This phenomenon makes it difficult to control the dimensions of the resist pattern.

Therefore, as disclosed in Japanese Patent Laid-Open No. 5-29212, a method of forming a film on a resist film has been proposed in order to avoid the influence of the atmosphere.

However, the method of forming a film on the resist film has a problem that the process is complicated and the cost is increased.

The second problem is that the conventional chemically amplified resist cannot be used as a light source for the next-generation pattern exposure.

A KrF excimer laser with a wavelength of 248 nm has been developed as a light source that can comply with the rule of 0.35 μm to 0.25 μm, instead of the conventional g-line or i-line utilizing the emission line of mercury. By the way, the conventional chemically amplified resist has higher transparency to deep ultraviolet rays than a resist made of novolac resin (a conventional resist that is not a chemically amplified resist), and can be used for pattern formation by a 248 nm KrF excimer laser. However,
It is considered that the practical resolution is 0.25 μm at the limit according to the exposure with the ordinary KrF excimer laser, and therefore, as a next-generation light source, the development of a shorter wavelength 192 nm ArF excimer laser is underway.

However, in the conventional chemically amplified resist, the polymer compound contains a polyvinylphenol derivative, and since the polymer compound contains an aromatic ring, it has high dry etching resistance equivalent to that of a resist made of a novolac resin. On the other hand, on the other hand, since the polymer compound contains an aromatic ring, its transparency to deep ultraviolet rays is low. According to the conventional chemically amplified resist, the resist film with a film thickness of 1 μm is 7 with respect to the KrF excimer laser light.
A transmittance close to 0% can be obtained, but a shorter wavelength of 19
The 2 nm ArF excimer laser light is hardly transmitted. Therefore, the conventional chemically amplified resist containing a polyvinylphenol derivative as a main component cannot be used as a resist for ArF excimer laser.

The third problem is that the conventional chemically amplified resist is expensive because it takes time to synthesize a polymer compound as shown in [Chemical formula 2].

The present invention solves the above problems all at once, has a small dimensional variation of the resist pattern, allows the ArF excimer laser light having a wavelength of 192 nm to pass therethrough, and is a cheaper resist for forming a fine pattern than a conventional chemically amplified resist. It is an object to provide a material and a fine pattern forming method.

[0019]

In order to achieve the above-mentioned object, the present invention is such that instead of a polymer compound containing an aromatic ring, a cellulose skeleton is contained in the main chain and the main chain is cleaved by an acid. A polymer compound is used.

The resist for forming a fine pattern according to the present invention comprises a polymer compound containing a cellulose skeleton in the main chain and causing the main chain to be cleaved by an acid, and an acid generator which generates an acid when irradiated with radiation. It is a multi-component substance containing.

The above polymer compound is represented by the following [Chemical Formula 3].

[0022]

[Chemical 3] However, R _{1 to} R ₆ are a hydrogen atom, an alkoxycarbonyl group, an alkyl group, an alkoxyalkyl group, an alkylsilyl group, a tetrahydropyranyl group, an alkoxycarbonylmethyl group, a hydroxypropyl group, a haloalkyl group, a phenyl group, a substituted phenyl group. It is one of the groups.

Examples of the polymer compound include methyl cellulose (R _{1 to} R ₆ are hydrogen atoms or methyl groups), ethyl cellulose (R _{1 to} R ₆ are hydrogen atoms or ethyl groups), hydroxypropylmethyl cellulose. (R _{1 to} R ₆ are hydrogen atoms, methyl groups or hydroxypropyl groups) and the like.

The high molecular compound used as the matrix polymer is originally insoluble in the developer,
The main chain containing the cellulose skeleton must be one that has a low molecular weight and becomes soluble in a developing solution by being cleaved by an acid.

Generally, as the developing solution, a conventionally used organic alkaline aqueous solution, an organic solvent such as methyl isobutyl ketone or isopropyl alcohol, or a mixed solvent of the organic solvents can be used.

The polymer compound represented by [Chemical Formula 3] is insoluble in a developing solution when the average molecular weight is 10,000 or more, and is soluble in the developing solution when it is an oligomer having an average molecular weight of 1,000 or less.

Therefore, the polymer compound represented by [Chemical Formula 3] is used as a matrix polymer, and a resist containing an acid generator that generates an acid when the matrix polymer is irradiated with radiation is coated on a semiconductor substrate. To form a resist film, and after exposing the resist film, the resist film is developed with an organic developer. By doing so, the exposed portion of the resist film becomes soluble in the developer because the polymer compound has a low molecular weight due to the acid generated from the acid generator, and the unexposed portion is the polymer compound. Insoluble in developer due to its large molecular weight.

Since the above decomposition reaction proceeds at room temperature, heat treatment after exposure is not required, so that a positive resist pattern having stable dimensions can be obtained.

Since the above-mentioned polymer compound does not contain a conjugated double bond such as an aromatic ring, the resist of the present invention has high transparency to deep ultraviolet rays. Therefore, the pattern can be transferred into the resist film without impairing the contrast of light. Further, since the above-mentioned polymer compound contains a cyclic structure in the main chain, it has sufficient dry etching resistance and has a selection ratio similar to that of a conventional chemically amplified resist.

Further, since the above-mentioned polymer compound uses a natural polymer cellulose as a skeleton, it is easy to synthesize, so that the cost of the chemically amplified resist can be reduced.

Since the cellulose skeleton contains many hydroxyl groups,
The resist is soluble in an alkaline aqueous solution, but if a part or all of the hydroxyl groups of the cellulose skeleton are replaced with protective groups, the resist becomes insoluble in the alkaline aqueous solution.

For example, R _{1 to} R ₆ in [Chemical formula 3] are
If a hydrogen atom, an alkoxycarbonyl group, an alkyl group, an alkoxyalkyl group, an alkylsilyl group, a tetrahydropyranyl group, an alkoxycarbonylmethyl group or a hydroxypropyl group is used, the polymer compound only undergoes main chain cleavage by an acid. However, like the conventional chemically amplified resist, the protective group is decomposed. Therefore, such a high molecular compound is used as a matrix polymer,
A resist film containing an acid generator that generates an acid when the matrix polymer is irradiated with radiation is applied on a semiconductor substrate to form a resist film, and the resist film is exposed, and then the resist film is formed. A positive resist pattern can be formed by developing with an alkaline aqueous solution. When the exposed resist film is heat-treated before development, decomposition of the protective group is promoted.

The resist pattern formed by such a resist has a feature that the main chain is cleaved and the protective group is decomposed by the acid at the same time, so that the solubility contrast is large and the resolution is high.

Examples of acid generators that generate an acid when irradiated with radiation include halogenated organic compounds, onium salts, and sulfonic acid esters. Examples of the halogenated organic compound include 1,1-bis [p-chlorophenyl] -2,2,2-trichloroethane, 1,1-bis [p-methoxyphenyl] -2,2,2-trichloroethane, 1, 1-bis [p-chlorophenyl] -2,2-
Examples include dichloroethane and 2-chloro-6- (trichloromethyl) pyridine. Examples of the Ounim salt include a triphenylsulfonium salt and a diphenyliodonium salt. As sulfonic acid ester,
2,6-dinitrobenzyl tosylate, o-nitrobenzyl tosylate, pyrogallol trimesylate and the like can be mentioned.

These compounds generate an acid when irradiated with radiation. The cellulose derivative, which is the matrix polymer, causes the decomposition reaction shown in [Chemical Formula 4] by the generated acid.

[0036]

[Chemical 4]

By the progress of such a decomposition reaction, the main chain of the cellulose derivative is cleaved, that is, the molecular weight of the polymer compound is reduced. That is, in the ether bond (glycoside bond) of the main chain, hydrolysis is promoted by the acid generated from the acid generator and water in the resist or in the atmosphere to lower the molecular weight and form a hydroxyl group. At this time, since the acid acts as a catalyst, one proton causes a plurality of decomposition reactions as in the conventional chemically amplified resist, so that the resist according to the present invention has high sensitivity. The polymer compound becomes soluble in an alkaline aqueous solution due to the hydroxyl group formed by the above hydrolysis.
Also, the solubility of the polymer compound is improved even if the polymer compound has a low molecular weight.

At the same time as the above decomposition reaction, the reaction of [Chemical formula 5] proceeds to form a hydroxyl group, and the polymer compound is converted into an alkali-soluble substance.

[0039]

[Chemical 5]

That is, an acid is generated from the acid generator by irradiation with radiation, and this acid promotes the cleavage of the main chain of cellulose and the decomposition of the protective group to change the solubility of the polymer, so that the resist is alkaline developed. It becomes soluble in the liquid. Since the resist having a cellulose skeleton is originally insoluble in an alkaline developing solution, the unexposed area is not dissolved in the alkaline developing solution, and the exposed area has a lower molecular weight and formation of a hydroxyl group. Dissolve in. Therefore, a positive resist pattern can be formed easily and accurately.

The radiation used for exposure includes ultraviolet rays, far ultraviolet rays, electron beams or X-rays, and has a wavelength of 190.
Examples of far ultraviolet rays of nm to 250 nm include KrF excimer laser and ArF excimer laser.

[0042]

【Example】

(First Embodiment) A fine pattern forming material and a fine pattern forming method according to the first embodiment of the present invention will be described below.
A description will be given with reference to the drawings.

An acid generator consisting of 1.0 g of 1,1-bis [p-chlorophenyl] -2,2,2-trichloroethane and 15 g of a polymer compound represented by [Chemical Formula 6] were dissolved in an ethyl cellosolve acetate solution. To obtain a mixture. The mixture was gently stirred at a temperature of 25 ° C. for 60 minutes, and the insoluble material was filtered off to give a uniform solution.

[0044]

[Chemical 6]

As shown in FIG. 1 (a), the above solution was dropped onto a semiconductor substrate 11 made of silicon, and 2000 r
Spin coating was performed for 1 minute at pm. Then, the semiconductor substrate 11 is baked at a temperature of 90 ° C. for 20 minutes to form a resist film 12 having a film thickness of 1.0 μm.
Got

Next, the reticle 13 is formed on the resist film 12.
Through a radiation 14 made of a KrF excimer laser having a NA of 0.45 through a developing solution made of isopropyl alcohol for 1 minute.
A resist pattern 12p as shown in FIG. 1 (b) was obtained.

Resist pattern 12 thus obtained
The maximum resolution of p was 0.2 μm line and space, and its sensitivity was 25 mJ / cm ² , and it was confirmed that a fine resist pattern of high resolution could be obtained with high sensitivity.

The resist pattern exposed with the same exposure dose did not change in pattern size and shape when developed immediately after exposure or after being left for 30 minutes and then developed.

As described above, according to the first embodiment, since the two-component substance containing the acid generator and the main polymer composed of the cellulose derivative is used as the resist for the KrF excimer laser, it has high sensitivity and high sensitivity. A fine positive resist pattern having a resolution can be stably formed.

Although the two-component system of the main polymer and the acid generator is used in the first embodiment, the same effect can be obtained even if additives such as a dissolution accelerator or a dissolution inhibitor are added.

(Second Embodiment) A fine pattern forming material and a fine pattern forming method according to a second embodiment of the present invention will be described below.

An acid generator consisting of 0.5 g of pyrogallol trimesylate and 15 g of a polymer compound represented by [Chemical Formula 7] were dissolved in a cellosolve acetate solution to obtain a mixture.

[0053]

[Chemical 7]

This mixture is treated at a temperature of 25 ° C. with 60
After gently stirring for 1 minute, the insoluble material was filtered off to obtain a uniform solution. Then, the above solution was dropped on a silicon substrate and spin-coated at 2000 rpm for 1 minute. This semiconductor substrate has a temperature of 90 ° C.
Baking was performed for 0 minutes to obtain a resist film having a film thickness of 1.0 μm.

Next, after drawing with an electron beam with an accelerating voltage of 50 kV, this resist was developed with an organic alkali aqueous solution for 1 minute, and an accurate and fine positive resist pattern was obtained.

The resist pattern thus obtained had a maximum resolution of 0.15 μm line and space and a sensitivity of 3 μC / cm ² , and a high resolution fine resist pattern was obtained.

As described above, according to the second embodiment, by using a two-component system substance containing an acid generator and a main polymer composed of a cellulose derivative as an electron beam resist, a high-sensitivity and high-resolution fine pattern can be obtained. It is possible to stably form a positive resist pattern.

It should be noted that after pattern drawing, it is 100 before development.
Even if the resist film was heat-treated at a temperature of about ° C, the same effect was obtained.

[0059]

According to the resist for forming a fine pattern according to the first aspect of the present invention, a polymer compound containing a cellulose skeleton in the main chain and the main chain being cleaved by an acid, and an acid generated when irradiated with radiation. Since it contains an acid generator that
Since the main chain containing the cellulose skeleton is cleaved and decomposed by the acid generated from the acid generator, and this decomposition reaction occurs at room temperature, there is no need for heat treatment for promoting the decomposition reaction as in the conventional case. Therefore, the problem of dimensional variation of the resist pattern with the lapse of time from the exposure to the heat treatment does not occur, and the process can be simplified.

Further, since the polymer compound constituting the resist for forming a fine pattern according to the invention of claim 1 has a cyclic structure in the main chain, it has sufficient dry etching resistance and is the same as the conventional chemically amplified resist. It has some selectivity.

Further, since the polymer compound constituting the resist for forming a fine pattern according to the invention of claim 1 does not contain a conjugated double bond such as an aromatic ring, the resist film has a high transmittance for short wavelength radiation. A pattern can be transferred in the resist film without impairing the contrast of light, and the resist film also transmits ArF excimer laser light of a short wavelength, so that it can be used as a light source for next-generation pattern exposure. .

Therefore, according to the resist for forming a fine pattern according to the first aspect of the present invention, it is possible to easily and stably obtain a fine resist pattern having an accurate and high resolution and a high aspect ratio.

Furthermore, since cellulose as a main raw material is widely present in nature, it is easier to synthesize a polymer compound containing a cellulose skeleton in the main chain, as compared with a conventional chemically amplified resist. The fine pattern forming resist according to (2) can be manufactured at low cost.

According to the resist for forming a fine pattern of the second aspect of the present invention, since the polymer compound is insoluble in the alkaline aqueous solution, the alkaline aqueous solution can be used as the developing solution.

According to the resist for forming a fine pattern according to the invention of claim 3, in the polymer compound, not only the main chain is cleaved by the acid, but also the protective group is decomposed similarly to the conventional chemically amplified resist. Therefore, since the solubility contrast of the resist is large, it is possible to form a resist pattern having a high resolution.

According to the fine pattern forming method of the fourth aspect of the present invention, for the same reason as the explanation for the fine pattern forming resist of the first aspect of the present invention, the fine resist pattern is accurate, has a high resolution, and has a high aspect ratio. Can be obtained easily and stably.

According to the fine pattern forming method of the fifth aspect of the present invention, since the resist film is irradiated with deep ultraviolet rays having a wavelength of 190 to 250 nm, a resist pattern having high resolution can be obtained.

According to the fine pattern forming method of the sixth aspect of the present invention, since the resist film is irradiated with the ArF excimer laser, a resist pattern having extremely high resolution can be obtained.

According to the fine pattern forming method of the seventh aspect of the present invention, it is possible to perform development using an alkaline aqueous solution.

According to the fine pattern forming method of the eighth aspect of the invention, the decomposition of the protective group of the polymer compound constituting the resist is promoted.

[Brief description of drawings]

1A and 1B are cross-sectional views showing respective steps of a fine pattern forming method according to a first embodiment of the present invention.

[Explanation of symbols]

 11 semiconductor substrate 12 resist film 13 reticle 14 radiation

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/312 D 7352-4M

Claims (8)

[Claims] 1. A fine pattern formation comprising a polymer compound containing a cellulose skeleton in the main chain and the main chain being cleaved by an acid, and an acid generator that generates an acid when irradiated with radiation. Resist. 2. The polymer compound is insoluble in an alkaline aqueous solution because at least a part of hydroxyl groups of the cellulose skeleton is substituted with a protecting group. Resist for fine pattern formation. 3. The resist for forming a fine pattern according to claim 1, wherein the polymer compound is represented by [Chemical Formula 1]. [Chemical 1] (However, R _{1 to} R ₆ are any of a hydrogen atom, an alkoxycarbonyl group, an alkyl group, an alkoxyalkyl group, an alkylsilyl group, a tetrahydropyranyl group, an alkoxycarbonylmethyl group, or a hydroxypropyl group.) 4. A polymer compound comprising a cellulose skeleton in a main chain on a semiconductor substrate, the main chain being cleaved by an acid,
A first step of forming a resist film by applying a resist containing an acid generator that generates an acid when irradiated with radiation; and irradiating the resist film with radiation to perform pattern exposure A second step of decomposing the cellulose skeleton by the acid generated from the acid generator by irradiation of the compound to lower the molecular weight of the polymer compound in the exposed region of the resist film, and developing the resist film with a developing solution. By developing
And a third step of forming a positive resist pattern. 5. The method for forming a fine pattern according to claim 4, wherein the radiation in the second step is deep ultraviolet rays having a wavelength of 190 nm to 250 nm. 6. The radiation in the second step is ArF.
The fine pattern forming method according to claim 4, which is an excimer laser. 7. The polymer compound in the first step is insoluble in an alkaline aqueous solution by substituting at least a part of hydroxyl groups of the cellulose skeleton with a protecting group, The developer in the step (1) is an alkaline aqueous solution.
The method for forming a fine pattern as described in. 8. The step of applying the resist on the semiconductor substrate to form a resist film in the first step includes the step of heating the resist applied on the semiconductor substrate. The fine pattern forming method according to claim 4.