JPH06273935A - Resin material - Google Patents

Abstract

PURPOSE:To enhance sensitivity, resolution, process aptitude, and practicability by dissolving a specified base resin, an onium salt, and a dissolution inhibitor having an acid-instable group in an organic solvent. CONSTITUTION:This resist material comprises the base resin represented by formula I, the onium salt as an acid-generator, and further, when the dissolution inhibitor containing the acid-instable group is added, an amount of the inhibitor to be decomposed by the acid can be reduced, thus permitting change of film thickness and bubbling to be reduced, and fine precise fabrication to be favored, and the obtained resist material to be adapted to production of ultrafine LSI. In formula I, each of R<1>, R<3>, and R<5> is H or methyl; R<2> is t-butyl, or methoxymethyl, tetrahydropyranyl, or trialkylsilyl; R<4> is lower alkoxy, such as methoxy or ethoxy; and m+n+k=1.

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 which is particularly suitable as a fine pattern forming material for manufacturing 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 along with this, miniaturization of wiring patterns requires a submicron rule.

Therefore, the wavelength of the light source for lithography is shifting from the ultraviolet region to the far ultraviolet region toward the short wavelength side, which is more advantageous for fine patterning. Also, LS
Dry etching by RF plasma is the mainstream of the etching process in the manufacturing process.

In such a lithographic technique, the resist material used is required to have photosensitivity and transparency with respect to the wavelength used and dry etching resistance.

Photolithography under these conditions,
In particular, as a resist used for g-line or i-line lithography, an aromatic resin such as a novolac resin is preferably used from the viewpoints of light transmittance with respect to the wavelength of light used and plasma etching resistance. It

However, the light source intensity of the far ultraviolet light such as the mercury emission line and the KrF or ArF excimer laser light having a wavelength shorter than that of the g-line or the i-line is larger than the intensity of the g-line or the i-line light source. Therefore, when using these far-ultraviolet rays for photolithography, sufficient exposure sensitivity cannot be obtained for conventional resist materials used as g-line and i-line resists. There is a problem that the light transmittance for light is lowered, and therefore a new type of resist material has been desired.

Therefore, a chemical amplification type resist has been studied as an alternative to the conventional type resist material. For example, in Japanese Patent Laid-Open No. 59-45439, there is a branch which is unstable to acid and which exists repeatedly. A resist composition containing p-tert-butoxycarbonyloxy-α-methylstyrene, which is one of the polymers having a group, and a photopolymerization initiator that generates an acid when exposed to radiant light, for example, a diaryl iodonium salt In this resist material, when exposed to far-ultraviolet light, the diaryl iodonium salt decomposes to generate an acid, and the p-tert-butoxycarbonyl group of p-tert-butoxycarbonyloxy-α-methylstyrene is converted by this acid. Cleavage yields a polar group.

Therefore, the exposed region or the unexposed region can be dissolved with a base or a non-polar solvent to obtain a desired pattern.

Further, in Japanese Patent Application Laid-Open No. 62-115440, 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 has been proposed, which can obtain good resolution by the reaction mechanism similar to that of JP-A-59-45439.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 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 butoxy group-containing resin and an acid generator, and Japanese Patent Application Laid-Open No. 4-212158 discloses methyl group, isopropyl group, tert-butyl group, tetrahydropyranyl group, trimethylsilyl group-containing polyhydroxy. A two-component resist material composed of styrene and an acid generator has been proposed.

However, the polymers which are the main components of these known resist materials are all obtained by the usual radical polymerization or cationic polymerization of monomers. In this case, the molecular weight distribution of the polymer should be taken into consideration. The resulting polymer has a broad and non-uniform molecular weight distribution. Further, according to the study of the present inventors, as a conventionally proposed chemical amplification type base polymer, a part of the hydroxyl groups of hydroxystyrene is converted to a tert-butoxycarbonyloxy group (hereinafter, t
A resin substituted with -Boc group) has been proposed, but this resin has very poor thermal stability and is easily t-Bo.
There is a problem that the c group is eliminated.

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

As described above, the chemically-amplified positive resists proposed hitherto have many problems, and it is still difficult to put them to practical use.

[0014]

Means and Actions for Solving the Problems The present inventors have
As a result of earnest studies on a highly practical chemically amplified resist material having high sensitivity, high resolution, and excellent process adaptability, a resin represented by the following rational formula (1) was used as a base resin. When a dissolution inhibitor containing an acid labile group is added together with the compound as an acid generator, the amount of the dissolution inhibitor that the acid needs to decompose is small, so that film thickness changes and bubbles The present invention has been completed on the basis of the finding that it can be generated less, is advantageous for precise microfabrication, and is very effective as a resist material for VLSI.

[0015]

[Chemical 2](However, R¹, R³, R^FiveIs a hydrogen atom or a methyl group, R²
Is tert-butyl group, methoxymethyl group, tetrahydr
A lopyranyl group or a trialkylsilyl group is replaced by R^FourIs met
A lower alkyloxy group such as an oxy group or an ethoxy group, or
It represents a hydrogen atom, and m + n + k = 1. )

The present invention will be described in more detail below. The resist composition of the present invention comprises the polymer of the above formula (1) as a base resin (A), an onium salt (B), and an acid labile group-containing soluble material. It is a chemical amplification type in which three components of the inhibitor (C) are dissolved in an organic solvent.

Here, the polymer of the above formula (1) includes, for example, a monomer such as p-methoxystyrene, p-methoxy-α-methylstyrene, p-ethoxystyrene, p-ethoxy-α-methylstyrene and p-methoxystyrene. 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 treated with an acid to form a tert-butoxy group alone. It can be obtained by cutting partially and selectively.

[0018]

[Chemical 3]

As the polymerization method for obtaining the copolymer of the above formula (2), radical polymerization, cationic polymerization, anionic polymerization or the like can be adopted.

After obtaining the copolymer of the formula (2) by such a polymerization method, if necessary, the reaction mixture in the polymer is precipitated and washed with, for example, methanol, followed by purification and drying. Can be separated. Usually, the copolymer after the reaction contains unreacted substances, by-products and the like as impurities.
When used as a resist in the production of I or the like, these impurities may adversely affect the wafer production process, and therefore it is preferable to sufficiently perform the purification treatment.

Furthermore, since the molecular weight distribution of the polymer of the above-mentioned rational formula (1) greatly influences the resist characteristics, it is necessary to control the molecular weight distribution. As this method, for example, the copolymer of the formula (2) is used by fractionation. It is preferable to adjust the molecular weight distribution in the range of 1.0 to 1.4 by a method such as removing low molecular weight substances.

The copolymer of formula (2) was then prepared.
R with acid² Partial and selective cleavage of only the ether bond of
When a polymer represented by the rational formula (1) is obtained,
The cleavage reaction of the tert-butoxy group is performed by dioxane or aceto
Solvent such as benzene, acetonitrile, benzene or a mixture of these
After dissolving in a mixed solvent, hydrochloric acid, hydrobromic acid, paratoluene
Acids such as sulfonic acid pyridinium salt and trifluoroacetic acid
It can be easily performed by dropping. Desorption degree
The compatibility depends on the acid used, but in the case of hydrochloric acid, for example.
In the case of the tert-butoxy group,
It can be adjusted by appropriately selecting in the range of 2.0 times.
is there. The residual ratio of tert-butoxy group, that is, m value is
0.05 to 0.5 in terms of image quality, residual film rate, and pattern shape
Range, preferably 0.1 to 0.3.
And are preferred.

In this case, n is 0.01 to 0.3, especially 0.02 to 0.2, and k is 0.4 to 0.99, especially 0.
It is preferably from 7 to 0.9.

The resist material of the present invention contains the polymer of the above formula (1) as a main component, but this 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. This acid generator generates a strong acid by 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 to form a hydroxyl group, whereby an alkali-soluble polymer can be obtained.

[0026]

[Chemical 4]

The following are examples of onium salt cationic photoinitiators, and further, JP-A-59-59
-45439, 62-115440, JP-A-1-.
The onium salt cationic photoinitiators disclosed in 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 to these, and the acid can be generated by light irradiation. Any substance can be used.

[0028]

[Chemical 5]

The amount of the above-mentioned onium salt is 0.1 to 15% (weight%, the same applies hereinafter) of the entire resist material, especially 0.1.
It is preferably 5 to 5%. If it is less than 0.5%, positive resist characteristics are exhibited, but the sensitivity is low. When the content of the acid generator increases, the resist sensitivity tends to increase, and even if it exceeds 15%, it shows a positive type property, but further increase in the sensitivity cannot be expected due to the increase in the content, and it is expensive. The increase of low molecular weight components in the resist lowers the mechanical strength of the resist film, etc., so that the content is preferably 15% or less.

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

The content of the dissolution inhibitor is preferably 5 to 40% of the total resist material. If it is less than 5%, the dissolution inhibiting effect is small, and if it exceeds 40%, the mechanical strength and heat resistance of the resist,
There are cases where the resolution is reduced.

The resist material is usually the above-mentioned components (A) to (C).
Is used as a resist by dissolving it in an amount of several times as much as the total amount of the organic solvent, which is capable of sufficiently dissolving the resist component containing the polymer of the formula (1) of the present invention as the main component, and A material that allows the resist film to spread uniformly is selected. 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, butyl lactate and the like. To be These organic solvents may be used alone or in combination of two or more.

The method of using the resist material, the method of irradiating the light and the like can be carried out by adopting a known lithography technique. Particularly, the resist material of the present invention is 254 to 193n.
It is most suitable for fine patterning with m far 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 eliminating the OR ² group to obtain the polymer represented by the formula (1). You can By using the resin designed in this way as the main component, sufficient exposure sensitivity to ultraviolet light and far ultraviolet light can be obtained, and the light intensity does not decrease, and moreover, during the wafer manufacturing process. Since it does not cause a decrease in the degree of vacuum in the vacuum process of, the induction of contamination of the process atmosphere, a slow dissolution rate of the polymer, etc.
Instability of patterning is eliminated. Therefore, the resist material of the present invention is suitable as a resist material used for manufacturing a VLSI or the like.

[0035]

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

[Synthesis Example 1] 2. In a 500 ml flask.
4 g of 2,2'-azobisisobutyl nitrile, 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, and the mixture was stirred at 90 ° C. for 6 minutes. 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 16500 and the molecular weight distribution (M _w / M _n ) was 1.6.
7, the yield was 72%. The polymer was further dissolved in a benzene / methanol-based solvent and fractionated.
The polymer thus fractionated was dried again to obtain a polymer A of the following rational formula having a weight average molecular weight of 14500 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 each peak derived from —O—CH ₃ was observed at 3.1 ppm (m ′: n = 0.9: 0.1).

[0037]

[Chemical 6]

[Synthesis Example 2] In the same manner as in Synthesis Example 1, p-tetrahydropyranyloctystyrene and p-methoxystyrene were radical-polymerized and then fractionated to give a weight molecular weight of 16500 and a molecular weight distribution of 1.25. Polymer B of the formula was obtained (m ′: n = 0.95: 0.05).

[0039]

[Chemical 7]

[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 in methylstyrene and 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 as described above.
When mixed kinds of monomers were added and polymerized for 1 hour,
It exhibited a red color. Then, methanol was added to terminate the polymerization. The reaction mixture was poured into methanol to precipitate the obtained polymer, which was then separated and dried to obtain 48 g of white polymer C. When the obtained polymer was analyzed by GPC,
It was a narrowly dispersed polymer having a weight average molecular weight of 15,000 and a molecular weight distribution of 1.03. Moreover, from ¹ H-NMR analysis, 4.8
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]

[Chemical 8]

[Synthesis Example 4] P-Trimethylsiloxystyrene and p-methoxystyrene (equimolar mixture) were used in Synthesis Example 1
Benzene was used as a reaction solvent in the same manner as in (1) above to perform radical polymerization, followed by washing with methanol, precipitation and drying.
0 g of white polymer D was obtained. This was a polymer having a weight average molecular weight of 13500 and a molecular weight distribution of 1.25 as measured by GPC (polystyrene conversion) (m ′: n = 0.9: 0.
1).

[0043]

[Chemical 9]

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

[0045]

[Table 1] The obtained resins E to H are represented by the following rational formula.

[0046]

[Chemical 10]

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

[0048]

[Chemical 11]

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

Also, Kr which is far ultraviolet rays instead of electron beams
The D ₀ sensitivity when evaluated by F excimer laser light (wavelength 248 nm) was 10 mJ / cm ² .

0.26 in KrF excimer laser exposure
The line & space pattern of μm and the line & space of 0.25 μm were 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 F sensitivity was comparable to that of Example 1, and it was possible to form a pattern having vertical sidewalls by KrF exposure.

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

[0054]

[Chemical 12]

Example 4 A resist was prepared using the same acid generator and dissolution inhibitor as in Example 3 except that the polymer H was used, and the resist was coated on a wafer and then exposed to light (40 mJ / excimer stepper). cm ² ), PEB was performed at 90 ° C. for 90 seconds, and the film was developed with 2.38% TMAH. 0.2
A pattern with vertical sidewalls of 6 μm lines and spaces was resolved.

Example 5 Polymer G, an acid generator containing t-
A resist was prepared and evaluated in the same manner except that butyl iodonium triflate was used. It was possible to form a fine pattern almost the same as in Example 4.

Comparative Example A solution prepared by dissolving 0.40 g of 2,2-azobisisobutylnitrile in 20 g of p-tert-butoxystyrene monomer using 20 ml of toluene as a solvent was reacted at 70 ° C. for 5 hours in a nitrogen atmosphere. did. The produced polymer is washed with methanol and then dried to obtain poly-t.
14 g of ert-butoxystyrene was obtained. This is G
Weight average molecular weight (M _w ) of 9000, dispersity (M _w /
_Mn ) was 1.90. Then, this polymer is added to 15%
Partial desorption was carried out with hydrochloric acid water (3.0 times mol) for 6 hours. The degree of desorption was 100%. Then, it was washed, dried, and dissolved in 100 ml of pyridine, and this solution was diluted with di-tert-
A t-Boc reaction was carried out using dicarbonate. t-B
The oc ratio was 20 mol% from the NMR measurement results.

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

[0059]

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

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[Procedure amendment]

[Submission date] February 9, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

Next, when the copolymer of the formula (2) is partially and selectively cleaved with an adjusted acid only in the ether bond of R ² to obtain the polymer of the formula (1), this tert is used. -For the butoxy group cleavage reaction, the compound 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, p-toluenesulfonic acid pyridinium salt or trifluoroacetic acid is added dropwise. This can be done easily. Although the degree of elimination varies depending on the acid used, for example, in the case of hydrochloric acid, it is 0.1 to the number of moles of the tert-butoxy group.
It can be adjusted by appropriately selecting in the range of 2.0 times. The residual ratio of the tert-butoxy group, that is, the m value is 0.05 to 0.3 in terms of resolution, residual film ratio, and pattern shape.
It is preferable to adjust to the range, preferably 0.1 to 0.2 .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

In this case, n is 0.01 to 0.3, in particular 0.01 to 0.1 , k is 0.4 to 0.94 , and especially 0.
It is preferably from 7 to 0.89 .

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0057

[Correction method] Change

[Correction content]

[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 in a nitrogen atmosphere. The produced polymer was washed with methanol and then dried to obtain 14 g of poly-tert-butoxystyrene. This product had a weight average molecular weight (M _w ) of 9,000 and a dispersity (M _w / M _n ) of 1.
It was 90. Next, this polymer was partially desorbed with 15% hydrochloric acid water (3.0 times mol) for 6 hours. Desorption degree is 1
It was 00%. Then, it is washed, dried, and dissolved in 100 ml of pyridine, and this solution is diluted with di-tert- butoxide.
A t-Boc reaction was carried out using sidicarbonate . t-
The Boc-conversion rate was 20 mol% based on the NMR measurement results.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H01L 21/027 (72) Inventor Kenichi Ito 28-1 Nishifukushima, Nishikufukushima, Kubiki-mura, Nakakubiki-gun, Niigata Prefecture Shin-Etsu Chemical Industry Co., Ltd.

Claims (2)

[Claims] 1. The following rational formula (1):(However, R¹, R³, R^FiveIs a hydrogen atom or a methyl group, R²
Is tert-butyl group, methoxymethyl group, tetrahydr
A lopyranyl group or a trialkylsilyl group is replaced by R^FourIs low
Represents an alkyloxy group or a hydrogen atom, m + n + k = 1
Is. ) Base resin (A) represented by
Dissolution inhibitor containing salt (B) and an acid labile group
(C) dissolved in an organic solvent
Amplification-type resist material. 2. The resist material according to claim 1, wherein a narrow-dispersion polymer in which the molecular weight distribution of the base resin of the rational formula (1) is 1.0 to 1.4 is used.