JP2953252B2 - Resist material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemically amplified resist material particularly suitable as a material for forming a fine pattern for the manufacture of VLSI.

[0002]

2. Description of the Related Art In recent years,
With the development of LSI technology, the number of bits of memory integrated in an IC chip has entered the order of megabits, and with this, sub-micron rules are required for finer wiring patterns.

For this reason, the wavelength of the light source for lithography is shifting from the ultraviolet region to the far ultraviolet region to the shorter wavelength side in order to be more advantageous for fine patterning. Also, LS
In the etching process in the I manufacturing process, dry etching using RF plasma is mainly used.

In such a lithography technique, a resist material to be used is required to have photosensitivity and transparency to a wavelength to be used, dry etching resistance, and the like.

Under these conditions, photolithography,
In particular, as a resist used in g-line or i-line lithography, an aromatic resin such as a novolak resin is preferably used from the viewpoint of light transmittance with respect to the wavelength of light used, plasma etching resistance, and the like. You.

However, the light source intensity of far ultraviolet light such as mercury emission line and KrF or ArF excimer laser light having a wavelength shorter than that of the g-line or i-line is different from that of the g-line or i-line light source. When utilizing such deep ultraviolet light for photolithography, sufficient exposure sensitivity cannot be obtained with respect to a conventional resist material used as a g-line or i-line resist. There are problems such as a decrease in light transmittance with respect to light, and thus a new type of resist material has been desired.

Therefore, a chemically amplified resist has been studied as an alternative to the conventional resist material. For example, in Japanese Patent Application Laid-Open No. 59-45439, an acid-unstable and recurring branched resist is proposed. Proposes a resist composition comprising p-tert-butoxycarbonyloxy-α-methylstyrene, which is one of polymers having a group, and a photopolymerization initiator that generates an acid when exposed to radiation, for example, a diaryliodonium salt. In this resist material, when exposed to deep ultraviolet light, the diaryliodonium salt is decomposed to generate an acid, and the p-tert-butoxycarbonyl group of p-tert-butoxycarbonyloxy-α-methylstyrene is converted to the acid by this acid. Cleavage produces a polar group.

Accordingly, a desired pattern can be obtained by dissolving the thus exposed or unexposed area with a base or a non-polar solvent.

Japanese Patent Application Laid-Open No. Sho 62-115440 discloses that, for example, poly-4-tert-butoxy-α-methylstyrene is dissolved in diglyme together with di (tert-butylphenyl) iodonium trifluoromethanesulfonate and then exposed to far ultraviolet light. Exposure is proposed, and a good resolution can be obtained by the same reaction mechanism as in the above-mentioned JP-A-59-45439.

On the other hand, Japanese Patent Application Laid-Open No. Sho 62-115440 proposes a resist material comprising poly-4-tert-butoxystyrene and an acid generator. Tert in the molecule
-Proposal of a two-component resist material comprising a resin having a butoxy group and an acid generator; Japanese Patent Application Laid-Open No. 4-212258 discloses a polyhydroxy resin containing a methyl group, an isopropyl group, a tert-butyl group, a tetrahydropyranyl group and a trimethylsilyl group. A two-component resist material comprising styrene and an acid generator has been proposed.

However, the polymer which is a main component of these known resist materials is obtained by subjecting a monomer to ordinary radical polymerization or cationic polymerization. In this case, in particular, consideration should be given to the molecular weight distribution of the polymer. The resulting polymer has a broad and non-uniform molecular weight distribution. According to the study of the present inventors, a part of the hydroxyl group of hydroxystyrene is replaced with a tert-butoxycarbonyloxy group (hereinafter referred to as t-type) as a conventionally proposed chemically amplified base polymer.
(Referred to as —Boc group), but this resin has very poor thermal stability and is easily t-Boc.
There was a problem that the c group was eliminated.

According to the study of the present inventors, a two-component positive resist comprising a resin in which the OH group of hydroxystyrene is protected with a protecting group and an acid generator as described above dissolves in a developing solution. To do so, it is necessary to decompose many protecting groups. At that time, there is a high possibility that a change in the film thickness, stress in the film, generation of bubbles, or the like is caused.

As described above, the conventionally proposed chemically amplified positive resist has many problems, and it is still difficult to put it to practical use.

[0014]

Means and Action for Solving the Problems The present inventors have
As a result of intensive studies on a chemically amplified resist material having high sensitivity, high resolution, excellent process adaptability, and high practicability, it is represented by the following descriptive formula (1) and has a molecular weight distribution of 1.0 to 1.0.
When a resin of 1.4 is used as a base resin, an onium salt is added to the resin as an acid generator, and a dissolution inhibitor containing an acid labile group is further added. Since the amount can be small, the change in film thickness and the generation of bubbles can be reduced as compared with the conventional method, which is advantageous for precise fine processing, and is very effective as a resist material for VLSI. The present invention has been accomplished.

[0015]

Embedded image (However, R ¹ , R ³ and R ⁵ represent a hydrogen atom or a methyl group, and R ²
Represents a tert-butyl group, a methoxymethyl group, a tetrahydropyranyl group or a trialkylsilyl group; R ⁴ represents a lower alkyloxy group or a hydrogen atom;
0.3, n is 0.01 to 0.3, k is 0.4 to 0.9, and m + n + k = 1. )

Hereinafter, the present invention will be described in more detail. The resist composition of the present invention comprises a polymer represented by the above formula (1) as a base resin (A), an onium salt (B) and a solution containing an acid labile group. It is a chemically amplified type obtained by dissolving three components of the inhibitor (C) in an organic solvent.

Here, the polymer of the above formula (1) is composed of a monomer such as p-methoxystyrene, p-methoxy-α-methylstyrene, p-ethoxystyrene, p-ethoxy-α-methylstyrene and the like. tert-butoxystyrene, p-tetrahydropyranyloxystyrene,
After copolymerizing a mixture of monomers such as p-trimethylsiloxystyrene and p-methoxymethoxystyrene to obtain a copolymer of the following formula (2), the polymer of the formula (2) is acid-terminated to form only a tert-butoxy group. It can be obtained by partially and selectively cutting.

[0018]

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Incidentally, as a polymerization method for obtaining the copolymer of the above formula (2), methods such as radical polymerization, cationic polymerization and anionic polymerization can be adopted.

After the copolymer of the formula (2) is obtained by such a polymerization method, if necessary, the reaction mixture in the polymer is precipitated by using, for example, methanol, washed, and dried to purify and purify the copolymer. Can be released. Usually, the copolymer after the reaction contains unreacted substances, by-products, etc. as impurities.
When used as a resist in the manufacture of I and the like, the impurities may have an adverse effect on the wafer manufacturing process.

Further, since the molecular weight distribution of the polymer of the above formula (1) has a great influence on the resist properties, it is necessary to control the molecular weight distribution. It is preferable to adjust the molecular weight distribution to a range of 1.0 to 1.4 by a method such as removing low molecular weight substances.

Next, when the copolymer represented by the formula (2) is partially and selectively cleaved only with the adjusted acid at the ether bond of R ² to obtain a polymer represented by the formula (1), -Butoxy group cleavage reaction is dissolved in a solvent such as dioxane, acetone, acetonitrile, benzene or a mixed solvent thereof, and then an acid such as hydrochloric acid, hydrobromic acid, pyridinium salt of paratoluenesulfonic acid, trifluoroacetic acid or the like is added dropwise. This can be easily performed. Although the degree of elimination varies depending on the acid used, for example, in the case of hydrochloric acid, 0.1 to 0.1 mol per mol of tert-butoxy group is used.
It can be adjusted by appropriately selecting a range of 2.0 times. The residual ratio of the tert-butoxy group, that is, the m value is 0.05 to 0.3 from the viewpoint of resolution, remaining film ratio, and pattern shape.
, Preferably in the range of 0.1 to 0.3.

In this case, n is 0.01 to 0.3, especially 0.02 to 0.2, and k is 0.4 to 0.9, especially 0.7.
０．９0.9 is preferred.

The resist material of the present invention contains a polymer represented by the above formula (1) as a main component. The resist material contains an acid generator which generates an acid upon irradiation with light, and an acid labile group. The dissolution inhibitor is dissolved in an organic solvent.

An example of the acid generator is an onium salt cationic photoinitiator. The acid generator generates a strong acid upon irradiation with light, and the onium salt in the resist film is decomposed by a wafer stepper or the like. The generated strong acid cleaves the OR ² group of the polymer of the formula (1) of the present invention, and converts it into a hydroxyl group, whereby an alkali-soluble polymer can be obtained.

[0026]

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The following are examples of the onium salt cationic photoinitiator.
-45439, 62-115440, JP-A-1-
The onium salt cationic photoinitiator disclosed in Japanese Patent No. 300250, U.S. Pat. No. 4,537,854 and the like can also be used, but the onium salt used in the present invention is not limited thereto. Any substance that generates

[0028]

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The amount of the above-mentioned onium salt is 0.1 to 15% (% by weight, the same applies hereinafter) of the whole resist material, particularly 0.1 to 15%.
It is preferable to set it to 5 to 5%. If it is less than 0.5%, positive resist characteristics are exhibited, but sensitivity is low. When the content of the acid generator increases, the resist sensitivity tends to increase, and even when the content is more than 15%, a positive type characteristic is exhibited. The content of the low molecular component in the resist is preferably adjusted to 15% or less by decreasing the mechanical strength of the resist film.

The present resist is prepared by mixing a dissolution inhibitor containing an acid labile group. Examples of such a dissolution inhibitor include an OH group of bisphenol A, a tert-butoxy group and a tert-butoxy group. A compound in which one or more -butoxycarbonyloxy groups (t-Boc groups) are substituted is preferably used.

The amount of the dissolution inhibitor is preferably 5 to 40% of the whole resist material. If it is less than 5%, the dissolution inhibiting effect is small, and if it is more than 40%, the mechanical strength and heat resistance of the resist,
The resolution may decrease.

The resist material is usually composed of the above components (A) to (C)
Is used as a resist after being dissolved in an organic solvent in an amount several times the total amount of the above. As the organic solvent, a resist component mainly comprising the polymer of the formula (1) of the present invention can be sufficiently dissolved, and The resist is selected such that the resist film spreads uniformly. Specific examples include butyl acetate, xylene, acetone, cellosolve acetate, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, ethyl lactate, methyl lactate, propyl lactate, and butyl lactate. Can be One of these organic solvents may be used alone, or two or more thereof may be used in combination.

The method of using the resist material, the method of irradiating light, and the like can be performed by using a known lithography technique. In particular, the resist material of the present invention has a thickness of 254 to 193n.
It is most suitable for fine patterning with m deep ultraviolet light.

According to the present invention, a resin having excellent heat resistance can be obtained by obtaining a polymer having a narrow molecular weight distribution and then partially removing an OR ² group to obtain a polymer represented by the following formula (1). Can be. By using the resin thus designed as a main component, sufficient exposure sensitivity to ultraviolet light or far ultraviolet light can be obtained, and the light intensity does not decrease. In the vacuum process, there is no decrease in the degree of vacuum, no contamination of the process atmosphere, no slowing down of the polymer dissolution rate, etc.
The instability of patterning is eliminated. For this reason, the resist material of the present invention is suitable as a resist material used in the manufacture of VLSI and the like.

[0035]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Synthesis Example 1]
4 g of 2,2'-azobisisobutylnitrile, 63.
After charging 3 g (0.36 mol) of p-tert-butoxystyrene and 6.6 g (0.04 mol) of p-methoxystyrene and 120 ml of benzene, the flask was purged with nitrogen. Polymerized for hours. The obtained polymer was washed with methanol and then dried. When this polymer was analyzed by GPC, the weight average molecular weight (M _w ) was 16,500, and the molecular weight distribution (M _w / M _n ) was 1.6.
In 7, the yield was 72%. The polymer was further dissolved in a benzene / methanol solvent and fractionated.
The polymer thus fractionated was dried again to obtain a polymer A having the following exponential formula having a weight average molecular weight of 14,500 and a molecular weight distribution of 1.30. When this polymer was analyzed by ¹ H-NMR, a peak derived from a tert-butyl group was observed at 1.5 ppm, and respective peaks derived from —O—CH ₃ were observed at 3.1 ppm (m ′: n = 0.9: 0.1).

[0037]

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[Synthesis Example 2] After p-tetrahydropyranyloxystyrene and p-methoxystyrene were radically polymerized in the same manner as in Synthesis Example 1, fractionation treatment was carried out to give the following compounds having a weight molecular weight of 16,500 and a molecular weight distribution of 1.25. Polymer B of the formula was obtained (m ': n = 0.95: 0.05).

[0039]

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[Synthesis Example 3] p-methoxymethoxy-α-
Distillation was performed using a purifying agent such as CaH ₂ or sodium benzophenone to remove impurities such as water between the methylstyrene and the p-methoxystyrene monomer. Next, 550 ml of tetrahydrofuran as a solvent and 3.3 × 10 ⁻⁴ mol of n-butyllithium as a polymerization initiator were charged into a 1-liter flask, and then cooled to −78 ° C. This solution was then purified by the method described above.
After adding one kind of mixed monomer and polymerizing for 1 hour,
It was red. Then, methanol was added to terminate the polymerization. The reaction mixture was poured into methanol to precipitate the obtained polymer, which was separated and dried to obtain 48 g of a white polymer C. When the obtained polymer was analyzed by GPC,
The polymer was a narrow-dispersion polymer having a weight average molecular weight of 15,000 and a molecular weight distribution of 1.03. From ¹ H-NMR analysis, 4.8 was obtained.
ppm to -O-CH ₂ -O- derived peaks, 3.1Pp
Each peak derived from -O-CH ₃ was observed in m (m ': n = 0.95 : 0.05).

[0041]

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[Synthesis Example 4] Synthesis Example 1 of P-trimethylsiloxystyrene and p-methoxystyrene (equimolar mixture)
Using benzene as the reaction solvent in the same manner as described above, radical polymerization is carried out, followed by washing with methanol, precipitation and drying, followed by drying.
0 g of a white polymer D was obtained. This was a polymer having a weight average molecular weight of 13,500 and a molecular weight distribution of 1.25 by GPC (in terms of polystyrene) (m ′: n = 0.9: 0.
1).

[0043]

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Next, 40 g of each of the polymers A to D obtained in the above Synthesis Examples 1 to 4 was charged into a 500 ml flask, and then dissolved in 200 ml of acetone. Thereafter, a partial elimination reaction was performed on the flask using an acid in an amount shown in Table 1 below, and the flask was cooled. After the obtained polymer was washed with water and dried, the remaining amounts of t-butyl group, methoxymethyl group, tetrahydropyranyl group and trimethylsilyl group were analyzed by ¹ H-NMR. Table 1 shows the results.

[0045]

[Table 1] In addition, the obtained resins E to H are represented by the following descriptive formulas.

[0046]

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Example 1 Polymer E obtained in the above example
(Poly-p-tert-butoxystyrene, polyp-methoxystyrene, polyhydroxystyrene copolymer)
9.6 g of a compound of the following formula (i) as an acid generator in an amount of 0.1 g.
48 g, (2,2-bis [p- (t-
Butoxycarbonyloxy) phenyl] propane 1.9
After dissolving 2 g in 66 g of diethylene glycol dimethyl ether, the solution was filtered through a 0.2 μm filter to prepare a resist solution.

[0048]

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This resist solution was applied on a silicon substrate for 20 minutes.
Spin-coated at 00 rpm and 10 on a hot plate
Prebaked at 0 ° C for 2 minutes. The thickness was 0.95 μm. After drawing with an electron beam with an acceleration voltage of 30 kv, 85 ° C
PEB (post-exposure bake) for 90 seconds. Development was carried out with a 2.4% aqueous solution of tetramethylammonium hydroxide (TMAH) for 1 minute, followed by rinsing with water for 30 seconds. It shows positive-type characteristics and has a D ₀ sensitivity of 5 μC /
cm ² .

Further, Kr, which is far ultraviolet light instead of an electron beam,
D ₀ sensitivity as assessed by the F excimer laser beam (wavelength 248 nm) was 10 mJ / cm ^2.

0.26 for KrF excimer laser exposure
A μm line and space pattern was resolved, and a 0.25 μm line and space was resolved by electron beam exposure.

Example 2 A resist solution was prepared and evaluated in the same manner as in Example 1 except that Polymer F was used. As a result, the electron beam sensitivity was 6.3 μC / cm ² , Kr
The F sensitivity was 20 mJ / cm ² , and it was confirmed that the film had the same resolution as that of Example 1. By KrF exposure, a pattern having vertical side walls could be formed.

Example 3 A resist was prepared in the same manner as in Example 1 except that the polymer G and the acid generator used were onium salts represented by the following formula (ii). PEB at 90 ° C for 90
Seconds. As a result, it was confirmed that the composition exhibited positive-type characteristics. The electron beam sensitivity was 6.5 μC / cm ² . This resist also had good film loss of about 2% with respect to the developing conditions of Example 1, and resolved 0.22 μm line & space.
On the other hand, it was also evaluated by KrF excimer laser exposure,
A 0.27 μm line & space was resolved.

[0054]

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Example 4 A resist was prepared using the same acid generator and dissolution inhibitor as used in Example 3 except that Polymer H was used. The resist was applied to a wafer, and exposed with an excimer stepper (40 mJ / cm ²⁾ and, PEB was carried out for 90 seconds at 90 ° C., and developed with 2.38% TMAH. 0.2
A pattern with vertical side walls of 6 μm line & space was resolved.

Example 5 Polymer G and acid generator were t-
A resist was prepared and evaluated in the same manner except that butyl iodonium triflate was used. A fine pattern almost similar to that of Example 4 could be formed.

[0057]

Comparative Example 20 g of p using 20 ml of toluene as a solvent
A solution of 0.40 g of 2,2-azobisisobutylnitrile dissolved in -tert-butoxystyrene monomer was reacted at 70 ° C. for 5 hours under a nitrogen atmosphere. The resulting polymer was washed with methanol and dried to obtain 14 g of poly-tert-butoxystyrene. This was measured by GPC with a weight average molecular weight ( _Mw ) of 9000 and a dispersity ( _Mw / _Mn ) of 1.
90. Next, this polymer was partially desorbed with 15% aqueous hydrochloric acid (3.0-fold mol) for 6 hours. Desorption degree is 1
00%. Then, it is washed, dried, further dissolved in 100 ml of pyridine, and this solution is added with di-tert- butoxy.
A t-Boc-forming reaction was performed using sidicarbonate . t-
The Boc conversion was 20 mol% from the result of NMR measurement.

A resist was prepared using this polymer, the acid generator, dissolution inhibitor and solvent used in Example 1. Exposure was performed using a KrF excimer stepper in the same manner as in Example 1. The obtained pattern was resolved up to 0.4 μm, but fine patterns smaller than 0.4 μm could not be resolved.

[0059]

The positive resist obtained according to the present invention is sensitive to high energy rays and has excellent sensitivity, resolution and plasma etching resistance. Moreover, the heat resistance of the resist pattern is excellent. Further, the pattern is unlikely to be overhanging, and has excellent dimensional controllability. Due to these characteristics, the absorption at the exposure wavelength of the KrF excimer laser is small, so that a fine pattern perpendicular to the substrate can be easily formed.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumasa Maruyama 28-1 Nishifukushima, Kazagi-mura, Nakakubijo-gun, Niigata Pref. Shin-Etsu Chemical Co., Ltd. 28-1 Nishifukushima, Mura Dai-Shin Shin-Etsu Chemical Co., Ltd. Synthetic Technology Laboratory (56) References JP-A-6-167811 (JP, A) JP-A-5-265214 (JP, A) JP-A 5-204157 ( JP, A) JP-A-6-43651 (JP, A) JP-A-4-211258 (JP, A) JP-A-3-107165 (JP, A) JP-A-2-1777031 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G03F 7/039 G03F 7/004 G03F 7/029 G03F 7/033

Claims (1)

(57) [Claims] 1. The following chemical formula (1) (However, R ¹ , R ³ and R ⁵ represent a hydrogen atom or a methyl group, and R ²
Represents a tert-butyl group, a methoxymethyl group, a tetrahydropyranyl group or a trialkylsilyl group; R ⁴ represents a lower alkyloxy group or a hydrogen atom;
0.3, n is 0.01 to 0.3, k is 0.4 to 0.9, and m + n + k = 1. A) a base resin (A) having a molecular weight distribution of 1.0 to 1.4, an onium salt (B), and a dissolution inhibitor (C) containing an acid labile group, A chemically amplified resist material characterized by being dissolved in water.