JPH11174670A - Resist material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemically amplifying positive-type resist, eliminating T-shapes and film reduction in a resist pattern and capable of forming a rectangular resist pattern with good repeatability. SOLUTION: A chemically amplifying positive-type resist of this invention is characterized in that its molecular structure has basic functional groups and contains an acid-producing agent P 101 (particularly, a sulfanilic acid imide compound, and specifically, a sulfanilic acid phthalimide, a sulfanilic acid naphtalimide, or a sulfanilic acid succinimide compound) for producing amphoteric ions by exposure, and an acid A 106 produced after the exposure efficiently forms basic functional groups and ion pairs A 107. Therefore, the acid A 106 is not deactivated by a basic substance B 108 derived from the atmosphere, and resultantly, environment-resisting performance of the resist is improved, a rectangular resist pattern is obtained, and both focal depth and dimensional accuracy can be improved by more than 7%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resist material used in a lithography step in manufacturing a semiconductor device. In particular, the present invention relates to a resist material having excellent withdrawal resistance (also referred to as “environmental resistance performance”) when a photoresist film formed on a semiconductor substrate is withdrawn after pattern exposure, and furthermore, has a high resolution and focus. The present invention relates to a chemically amplified resist material which is excellent in depth and dimensional accuracy and enables high integration of device patterns.

[0002]

2. Description of the Related Art A resist material used in a lithography process at the time of manufacturing a semiconductor device is described as follows. A photoresist film formed on a semiconductor substrate is exposed through a reticle or a mask on which a desired semiconductor integrated circuit pattern is drawn. Post exposure bake processing (PostExposure bake processing,
(Hereinafter, referred to as “PEB treatment”) and then developing with a developer to form a rectangular resist pattern ”.

The main technology of the exposure technology in the conventional lithography process is that a g-line (436 n
This is an exposure technique in which an exposure apparatus using m) or i-line (365 nm) is combined with a novolak resist. However, with the increase in integration of LSI devices, lithography using excimer laser light (248 nm, 193 nm), which is far ultraviolet light that is advantageous for making resist patterns finer, has become necessary.

When a conventional novolak-based resist is used as a resist to be combined with an exposure apparatus using the excimer laser light as an exposure light source, light absorption is large, a good resist shape cannot be obtained, and the sensitivity of the novolak-based resist is high. Was low. Therefore, as a resist combined with an exposure apparatus using an excimer laser beam as an exposure light source, it is necessary to greatly increase the sensitivity of the resist.

[0005] To overcome this situation, a chemically amplified resist has been proposed. The chemically amplified resists are roughly classified into (1) positive type and (2) negative type.

The chemically amplified positive resist of the above (1) is:
For example, polyhydroxy resin soluble in alkaline developer
a resin protected with a protecting group such as a tert-butyloxycarbonyl group and an acid generator, and the protecting group is removed by a catalytic reaction of an acid generated from the acid generator upon exposure;
The exposed portion becomes soluble in the alkaline developer. Therefore, the exposed portion is dissolved by the alkali developing treatment, and the unexposed portion remains to form a resist pattern. On the other hand, the chemically amplified negative resist of the above (2) comprises, for example, three components of a polyhydroxy resin soluble in an alkali developer, a melamine crosslinking agent, and an acid generator, and the acid generated from the acid generator upon exposure. The cross-linking reaction between the polyhydroxy resin and the melamine cross-linking agent is promoted by the catalytic reaction, and the exposed portion becomes insoluble in the alkaline developer. Therefore, by the alkali developing treatment, the unexposed portion is dissolved, and the exposed portion remains to form a resist pattern.

As described above, in the chemically amplified resist, since the dissolution selectivity of the resin is changed by the catalytic sensitization reaction of the acid generated from the acid generator, higher sensitivity is realized as compared with the conventional novolak resist. be able to.

However, in a chemically amplified resist,
When the optical contrast decreases near the resolution limit, the dimensional uniformity decreases, and furthermore, there is a disadvantage that resist scum is easily generated. As a method of solving this problem, a method of adding a basic substance to the resist to neutralize a part of the generated acid to improve the resist shape (hereinafter referred to as a “first conventional method”) has been conventionally used. It has been proposed (Japanese Patent Laid-Open No. 5-1273).
No. 69).

Further, in the chemically amplified resist, since the acid generated at the time of exposure is diffused into the unexposed portion, a desired resist pattern cannot be obtained, and the resolution, the depth of focus, and the dimensional accuracy are reduced. Was. As a method of solving this problem, a method of adding a specific compound (that is, a compound that neutralizes an acid and decomposes or reduces the neutralizing power of an acid by irradiation with actinic radiation) to a photosensitive composition (hereinafter referred to as “second compound”). Conventional method ”) has been proposed (JP-A-6-2661).
No. 00).

[0010]

However, when the above chemically amplified resist is withdrawn after the exposure, the acid generated at the time of the exposure is neutralized by the basic substance in the atmosphere on the resist surface and deactivated. However, a desired rectangular resist pattern cannot be obtained, and the resolution, the depth of focus, and the dimensional accuracy are reduced. In particular, when a fine pattern is formed, the deterioration of the shape of the resist pattern, the resolving power, and the decrease in the depth of focus due to the poor withdrawal resistance after exposure are remarkable. Therefore, it has been desired to improve the withstand resistance (environmental resistance) of the resist material.

With reference to FIGS. 3 and 4, a description will be given of the withstand resistance after exposure when the conventional chemically amplified resist is used. FIG. 3 shows the case of using the chemically amplified resist of the first conventional method (the resist obtained by adding a basic substance to the resist: “shown as a basic compound“ Q ”301) in the drawing”). It is a process order sectional view consisting of process AD. FIG. 4 is a sectional view showing a resist pattern shape obtained by using a chemically amplified resist including the first conventional method.

When the chemically amplified resist of the first conventional method is used, first, as shown in step A of FIG. 3, a "basic compound" Q "301 and an acid generator" P "302 (Not shown) added to the silicon substrate 304
Form on top. Next, as shown in FIG. 3B, the resist film 303 is exposed to light using an excimer laser beam 305 through a mask 306, whereby an acid “A” 307 is generated from the acid generator “P” 302.

Subsequently, as shown in FIG. 3C, a part of the generated acid “A” 307 forms a conjugate “AQ” 308 with the basic compound “Q” 301. (However, the acid generator “P” 302
In the system where the basic compound "Q" 301 is added, all the generated acids "A" 307 are not neutralized by the basic compound "Q" 301. Then, as shown in FIG. 3 step D, the basic compound “Q”
Acid "A" 307 which did not form conjugate "AQ" 308 with 301
Is neutralized and deactivated by the atmosphere-derived basic substance “B” 309 during the withdrawal after exposure (see “Deactivated acid“ AB ”310” in the figure).

By the way, the deactivation of the acid "A" 307 by the basic substance "B" 309 derived from the atmosphere during the withdrawal is particularly remarkable on the exposed resist surface. Therefore, even if such a resist film 303 is heated by the PEB process, the change in the dissolution selectivity of the resin due to the catalytic sensitization reaction of the acid does not progress on the exposed surface of the resist, and when this is developed with an alkali developing solution, In addition, a problem arises in that a desired rectangular resist pattern cannot be obtained.

Particularly, in a chemically amplified positive resist, the deprotection reaction does not proceed on the resist surface.
There is a problem that if the substrate is pulled for one hour or more, a T-top (T-shaped) resist pattern as shown in FIG. 4 is obtained.

Further, regarding the formation of a fine pattern, the deterioration of the resist pattern shape, the resolving power, and the depth of focus due to the poor withdrawal resistance are remarkable.
Improvement in resisting resistance (environmental resistance) of resist materials has been strongly desired.

On the other hand, in the second conventional method, a part of the acid generated at the time of exposure is diffused to the unexposed part. To neutralize the acid diffused to the unexposed part, "acid And a compound which decomposes or degrades the neutralizing power of acid upon irradiation with actinic radiation "to the photosensitive composition. That is, in the unexposed part, the diffused acid is neutralized by this compound, and in the exposed part, this compound is
It does not react with the acid generated in the exposed area because it is decomposed by the irradiation of actinic radiation or the neutralizing power of the acid decreases. Therefore, even with the configuration of the second conventional method, the drawback that the acid deactivation of the exposed portion due to the atmosphere-derived basic substance is not prevented during the post-exposure withdrawal described above. Have.

(Purpose of the Invention) The present invention has been made in view of the above problems and disadvantages, and has the following objects. To provide a resist material that suppresses formation of a surface insolubilized layer due to acid deactivation and prevents a resist pattern after development from becoming a T-shape. Third, by providing a resist material that prevents the reduction, by providing the resist material intended in the first and second, a rectangular resist pattern can be obtained, resolution, It is an object of the present invention to provide a resist material capable of improving focus, depth, and dimensional accuracy and enabling high integration of a device pattern.

[0019]

The resist material according to the present invention is intended to improve the shape of a chemically amplified resist and improve environmental resistance performance. The resist material has a basic functional group in a molecular structure and is amphoteric by exposure. An acid generator that generates ions (claim 1); the acid generator is a sulfanilic imide compound (claim 2); and the sulfanilic imide compound has the following chemical formula:
(1) to (3), a sulfanilic acid phthalimide, a sulfanilic acid naphthalimide, or a sulfanilic acid succinimide compound (claims 3, 4, and 5). Thus, the first to third objective resist materials are provided.

[0020]

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[0021]

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[0022]

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The resist material according to the present invention may further comprise: (1) the acid generator or the sulfanilic imide compound is contained in an amount of 1 to 15% (% by weight based on resin) (Claim 6); Is a chemically amplified positive resin, and is a t-BOC protected polyhydroxystyrene resin or a t-BOC protected polymethyl methacrylate resin (Claim 7), According to the present invention, the first to third resist materials are provided.

[0024]

In the present invention, by using an acid generator having a basic functional group in the molecular structure and generating an amphoteric ion upon exposure, the acid generated after the exposure can be converted into the basic functional group in the molecular structure. Since the group and ion pair (amphoteric ion) are formed efficiently, the acid is not deactivated by the basic substance derived from the atmosphere during the post-exposure storage, and as a result, the environmental resistance performance of the resist is improved, A rectangular resist pattern is obtained.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. FIG.
FIG. 3 is a view for explaining an embodiment of the present invention, and shows “steps A to E” when a chemically amplified resist according to the present invention is used.
It is a process order sectional view consisting of. FIG. 2 is a sectional view showing the shape of a rectangular resist pattern obtained by using the chemically amplified resist according to the present invention.

In the embodiment of the present invention, a chemically amplified resist containing a basic functional group in the molecular structure and containing an acid generator that generates amphoteric ions upon exposure is used. As shown in Step A, a resist film 102 comprising an acid generator “P” 101 having a basic functional group in the molecular structure and generating an acid upon irradiation with actinic radiation and a resin (not shown) is formed. Is formed on the silicon substrate 103. next,
As shown in FIG. 1B, the resist film 102 is exposed by an excimer laser beam 104 through a mask 105. In the region of the resist film 102 exposed to the excimer laser beam 104, the acid “A” 1 having a basic functional group is removed from the acid generator “P” 101.
06 occurs.

Then, as shown in step C of FIG. 1, the generated acid “A” 106 forms an ion pair “ ₊ A ⁻ ” 107 in the molecule together with the basic functional group in the molecular structure. The formed ion pair “ ₊ A ⁻ ” 107 is neutralized by the basic substance “B” 108 derived from the atmosphere during the withdrawal as shown in Step D in FIG. 1 and does not become deactivated.

Subsequently, as shown in step E of FIG. 1, during the PEB treatment after the withdrawal, the ion pair “ ₊ A ⁻ ” 10 is heated by heating.
7 becomes acid active and generates proton “H ⁺ ” 109. Since the generated proton “H ⁺ ” 109 induces a deprotection reaction in the exposed area, even if it is left for more than one hour, the rectangular resist pattern shape as shown in FIG. can get.

As the resist material according to the present invention, in order to improve the shape of a chemically amplified resist and improve environmental resistance,
It has a basic functional group in the molecular structure, and contains an `` acid generator '' that generates amphoteric ions upon exposure, but the acid generator has a molecular weight of 100 to 1,000. The amount of the acid generator is preferably 1 to 15% by weight relative to the resin.

In the embodiment of the present invention, when the addition amount of the acid generator is optimized within the range of 1 to 15% by weight to the resin so that the optimum shape can be obtained for each resist, the depth of focus can be improved.
The dimensional accuracy can be improved by 7% or more. In particular, the effect is great for forming a fine pattern, and a rectangular photoresist pattern can be formed with good reproducibility.

[0031]

Next, examples of the present invention will be described together with comparative examples.
Although the present invention will be described in detail, the present invention is not limited to the following embodiments, and various changes and modifications can be made without departing from the above-described “items specifying the present invention”. It is.

(Example 1) The chemically amplified resist of this Example 1 is: t-BOC protected polyhydroxystyrene resin (tert-
A polyhydroxystyrene resin protected with a butyloxycarbonyl group) and as an acid generator, a sulfanilic acid phthalimide represented by the following chemical formula (1) (having a basic functional group in the molecular structure: resin The ratio is 5% by weight).

[0033]

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Using this chemically amplified resist, a resist film was formed on a wafer and exposed with a KrF excimer laser stepper through a mask or reticle on which a desired semiconductor integrated circuit pattern was drawn. After leaving for 1 hour in an atmosphere having an ammonia concentration of 10 ppb, PEB treatment and development with a 2.38% aqueous solution of TMAH (tetramethylammonium hydroxide) gave a rectangular resist pattern as shown in FIG.

COMPARATIVE EXAMPLE 1 For comparison, a chemically amplified resist composed of a t-BOC protected polyhydroxystyrene resin and benzenesulfonic acid phthalimide (resin ratio: 5%) represented by the following chemical formula (4) was used. When a resist pattern was formed through the same steps as in Example 1, a T-top shape as shown in FIG. 4 was obtained. The compound represented by the following chemical formula (4) is benzenesulfonic acid phthalimide used in Comparative Example 1 and functioning as an acid generator.
A compound having no basic functional group in the molecular structure.

[0036]

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(Example 2) The chemically amplified resist of Example 2 is composed of t-BOC protected polyhydroxystyrene resin (tert-
A polyhydroxystyrene resin protected with a butyloxycarbonyl group); and as an acid generator, naphthalimide sulfanilate represented by the following chemical formula (2) (having a basic functional group in the molecular structure: resin The ratio is 5% by weight).

[0038]

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Using this chemically amplified resist, a resist film is formed on a wafer, exposed through a mask or reticle on which a desired semiconductor integrated circuit pattern is drawn, using a KrF excimer laser stepper, and subjected to an atmosphere having an ammonia concentration of 10 ppb for one hour. After the substrate was left inside, it was subjected to PEB treatment and developed with a 2.38% TMAH aqueous solution. As a result, a rectangular resist pattern as shown in FIG. 2 was obtained.

Comparative Example 2 For comparison, a chemically amplified resist comprising a t-BOC protected polyhydroxystyrene resin and naphthalimide benzenesulfonate (resin ratio 5%) represented by the following chemical formula (5) was used. When a resist pattern was formed through the same steps as in Example 2, a T-top shape as shown in FIG. 4 was obtained. The compound represented by the following chemical formula (5) is naphthalimide benzenesulfonate which functions as an acid generator and is used in Comparative Example 2 and has no basic functional group in the molecular structure. .

[0041]

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Example 3 The chemically amplified resist of Example 3 was: t-BOC protected polymethyl methacrylate resin (tert-
A polymethyl methacrylic acid resin protected with a butyloxycarbonyl group) and, as an acid generator, a sulfanilic acid succinimide compound represented by the following chemical formula (3) (having a basic functional group in the molecular structure: (5% by weight with respect to the resin).

[0043]

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Using this chemically amplified resist, a resist film is formed on a wafer, and is exposed with an ArF excimer laser stepper through a mask or reticle on which a desired semiconductor integrated circuit pattern is drawn, and is exposed to an atmosphere having an ammonia concentration of 10 ppb for one hour. After PEB treatment,
When developed with a 2.38% TMAH aqueous solution, a rectangular resist pattern as shown in FIG. 2 was obtained.

Comparative Example 3 For comparison, a chemically amplified resist comprising a t-BOC protected polyhydroxystyrene resin and a benzenesulfonic acid succinimide compound represented by the following chemical formula (6) (resin ratio: 5%) was used. Then, a resist pattern was formed through the same steps as in Example 3 above. As a result, a T-top shape as shown in FIG. 4 was obtained.

[0046]

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In the above Examples 1 to 3, the resin in the resist material is a chemically amplified positive type resin and t-
BOC protected polyhydroxystyrene resin or tB
Although an example in which an OC-protected polymethyl methacrylate resin is used has been described, the resist material according to the present invention is not limited to such a chemically amplified positive-type resin, and may be used for a chemically amplified negative-type resin. And the present invention is also included in the present invention.

[0048]

As described in detail above, the present invention relates to an acid generator (especially a sulfanilic imide compound, specifically a sulfanilic imide compound, which has a basic functional group in its molecular structure and generates an amphoteric ion upon exposure to light). , Sulfanilic acid phthalimide, sulfanilic acid naphthalimide, sulfanilic acid succinimide compound), and a pattern forming method using the resist material comprises:
It is possible to almost completely eliminate the T-shape of the resist pattern and the film loss, and obtain a rectangular resist pattern. Further, according to the present invention, resolution, focus, depth, and dimensional accuracy are improved, and high integration of device patterns can be achieved.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment of the present invention, wherein “steps A to A” when a chemically amplified resist according to the present invention is used;
It is a process order sectional view consisting of E ".

FIG. 2 is a cross-sectional view showing the shape of a rectangular resist pattern obtained using the chemically amplified resist according to the present invention.

FIG. 3 is a sectional view in the order of steps including steps A to D when a chemically amplified resist according to a first conventional method is used.

FIG. 4 is a sectional view showing a resist pattern shape obtained by using a chemically amplified resist including the first conventional method.

[Explanation of symbols]

101, 302 Acid generator “P” 102, 303 Resist film 103, 304 Silicon substrate 104, 305 Excimer laser beam 105, 306 Mask 106, 307 Acid “A” 107 − Ion pair “ ₊ A ⁻ ” 108, 309 Atmosphere Basic substance "B" derived from 109-proton "H ⁺ " -301 Basic compound "Q" -308 Conjugate "AQ" -310 Inactivated acid "AB"

Claims (7)

[Claims] 1. A resist material having a basic functional group in the molecular structure and containing an acid generator that generates amphoteric ions upon exposure. 2. The resist material according to claim 1, wherein the acid generator is a sulfanilic imide compound. 3. The resist material according to claim 2, wherein the sulfanilic imide compound is a sulfanilic phthalimide represented by the following chemical formula (1). Embedded image 4. The resist material according to claim 2, wherein the sulfanilic imide compound is a naphthalimide sulfanilate represented by the following chemical formula (2). Embedded image 5. The resist material according to claim 2, wherein the sulfanilic imide compound is a sulfanilic succinimide compound represented by the following chemical formula (3). Embedded image 6. The resist material according to claim 1, wherein the acid generator or the sulfanilic imide compound contains 1 to 15% (based on resin weight%). 7. The resin in the resist material is a chemically amplified positive resin, and is a t-BOC protected polyhydroxystyrene resin or a t-BOC protected polymethyl methacrylate resin. The resist material according to claim 1.