JP2936957B2 - 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 a light source for lithography is shifting to a single wavelength side from an ultraviolet region to a far ultraviolet region so as 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 g
As a resist used for lithography for lines and i-lines, an aromatic resin such as a novolak resin is preferably used from the viewpoint of light transmittance with respect to the wavelength of light to be used and resistance to plasma etching.

However, the intensity of the light source of far ultraviolet light such as mercury emission line and KrF or ArF excimer laser light having a single wavelength than that of the g-line or i-line is larger than 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 material has been studied as a substitute for the conventional resist material. For example, Japanese Unexamined Patent Publication No. Sho 59-45439 discloses a resist material which is unstable with respect to acid. A resist composition comprising p-tert-butoxycarbonyloxy-α-methylstyrene, which is one of polymers having a branched group, and a photopolymerization initiator which generates an acid when exposed to radiation, for example, a diaryliodonium salt. In this resist material, when exposed to far 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 Cleavage with an acid produces a polar group.

Accordingly, a desired pattern can be obtained by dissolving the thus exposed or unexposed area with a base or a nonpolar 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.

Japanese Patent Application Laid-Open No. 62-115440 also proposes a resist material comprising poly-4-tert-butoxystyrene and an acid generator. The publication proposes a two-component resist material comprising a resin having a tert-butoxy group in the molecule and an acid generator.
No. 258 discloses a methyl group, an isopropyl group, and tert.
A two-component resist material comprising a polyhydroxystyrene containing a -butyl group, a tetrahydropyranyl group and a trimethylsilyl group and an acid generator has been proposed.

[0010] However, according to the study of the present inventors,
As a chemically-amplified base polymer conventionally proposed, a part of the hydroxyl group of hydroxystyrene is replaced with a tert-butoxycarbonyloxy group (hereinafter referred to as a t-Boc group).
Is very poor in thermal stability, and easily replaced with t-
There was a problem that the Boc group was eliminated. According to the study of the present inventors, in a two-component positive resist material composed of an acid generator and a resin in which the OH group of hydroxystyrene is protected with a protecting group as described above, the resin is dissolved 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 material has many problems, and it is still difficult to put it to practical use.

[0012]

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 practicality, a resin represented by the following formula (I) was used as a base resin, and an onium salt was used. Is added as an acid generator, and when a dissolution inhibitor containing an acid labile group is further added, the change in film thickness and generation of bubbles can be reduced as compared with the prior art, which is advantageous for precise fine processing. And super L
It has been found that it is very effective as a resist material for SI.

[0013]

Embedded image(However, R¹And R^ThreeIs a hydrogen atom or a methyl group, R^Two Is t
tert-butyl group, m + n = 1. )

In this case, by using a narrowly dispersed polymer having a molecular weight distribution _Mw / _Mn of 1.0 to 1.4 as the base resin of the above formula (I), the resolution is remarkably increased,
It has been found that the excimer laser light exhibits excellent resolution even at a level of 0.4 μm or less.

That is, although the base resin of the above formula (I) is known as a main component of the resist material, any of the polymers which are the main components of the known resist material can be obtained by subjecting a monomer to ordinary radical polymerization or cationic polymerization. In this case, the molecular weight distribution of the polymer is not controlled, and no particular consideration is given to the molecular weight distribution of the polymer, and the obtained polymer has a broad and non-uniform molecular weight distribution. Become.

However, the present inventors have found that these polymers having a polydispersity cannot sufficiently cope with excimer laser light, so that resolution is increased and an ultra-fine pattern is provided by excimer laser light exposure. It has been found that it is effective to set the molecular weight distribution M _w / M _n of the base resin of the above formula (I) in the range of 1.0 to 1.4.

By using such a polymer having a narrow molecular weight distribution, a resin having excellent heat resistance can be obtained.
Further, by using the resin thus designed as a main component, a sufficient exposure sensitivity to ultraviolet light or far ultraviolet light can be obtained, and the light intensity does not decrease. Since there is no reduction in the degree of vacuum in the middle vacuum process, no contamination of the process atmosphere, no slowing down of the dissolution rate of the polymer, etc., the instability of patterning is eliminated and the resist material used for the manufacture of VLSI etc. It has been found that the present invention is suitable for the present invention, and has led to the present invention.

Accordingly, the present invention, (A) the above formula (I) the molecular weight distribution M _w / M _n is the base resin is 1.0 to 1.4 of, (B) an onium salt, (C) acid labile Provided is a chemically amplified resist material containing a dissolution inhibitor containing a group.

Hereinafter, the present invention will be described in more detail. The main component of the chemically amplified resist material of the present invention (component (A))
Is a polymer represented by the following descriptive formula (I).

[0020]

Embedded image(However, R¹And R^ThreeIs a hydrogen atom or a methyl group, R^Two Is t
tert-butyl group, m + n = 1. )

Here, the molecular weight distribution M _w / M _n of the polymer of the formula (I) is obtained from the viewpoint of increasing the resolution.
The range is from 0 to 1.4, preferably from 1.0 to 1.3. When the molecular weight distribution exceeds 1.4, the resolution tends to be significantly reduced.

In the formula (I), m + n = 1, but from the viewpoints of the remaining film ratio, the resolution, the pattern shape, etc., m is 0.05 to 0.5, preferably 0.1 to 0.5. 3, more preferably in the range of 0.12 to 0.25.

The above-mentioned polymer is obtained, for example, by polymerizing a monomer of p-tert-butoxystyrene or p-tert-butoxy-α-methylstyrene to obtain poly-p-tert-butoxystyrene.
It can be obtained by obtaining butoxystyrene or poly-p-tert-butoxy-α-methylstyrene and then partially removing some of the ether bonds of the polymer.
Here, the polymerization can be performed by a method such as radical polymerization, cationic polymerization, or anionic polymerization. Next, the obtained polymer can be further purified and isolated as necessary by precipitating the reaction mixture in the polymer using, for example, methanol, washing and drying. Usually, the polymer after the reaction contains unreacted substances, by-products, and the like as impurities. When a resist material containing the polymer is used as a resist for manufacturing an ultra-large LSI or the like, the impurities are produced in a wafer. It is preferable that the purification treatment is sufficiently performed, since this may adversely affect the process. Furthermore, since the molecular weight distribution of the obtained polymer greatly affects the resist properties,
It is preferable to control the molecular weight distribution, and as this method, the molecular weight distribution can be adjusted to a range of 1.0 to 1.4 by, for example, removing low molecular weight substances by fractionation.

Next, the ether bond of the obtained polymer is partially cleaved with an acid to obtain a polymer represented by the formula (I). In this case, the ether bond cleavage reaction is dissolved in a solvent such as dioxane, acetone, acetonitrile, or benzene or a mixed solvent thereof, and then hydrochloric acid,
Hydrobromic acid, pyridinium p-toluenesulfonate,
It can be easily carried out by dropping an acid such as trifluoroacetic acid. Although the degree of elimination varies depending on the acid used, for example, in the case of hydrochloric acid, it can be adjusted by appropriately selecting the molar number of the ether bond in the range of 0.1 to 2 times. It is preferable that the residual ratio of the ether bond, that is, the m value is adjusted in the range of 0.05 to 0.5, preferably in the range of 0.1 to 0.3, more preferably in the range of 0.12 to 0.25. .

Next, the onium salt of the component (B) is an acid generator that generates an acid upon irradiation with light, and the strong acid generated by the decomposition of the onium salt in the resist film by a wafer stepper or the like is represented by the above formula ( The tert-butoxy group of the polymer of I) is cleaved to a hydroxyl group as described below to render the polymer of formula (I) alkali-soluble.

[0026]

Embedded image

Examples of such an onium salt cationic photoinitiator include compounds represented by the following formulas. Further, JP-A-59-45439 and JP-A-62-115440.
No. JP-A-1-300250, U.S. Pat.
Onium salt cationic photoinitiators disclosed in No. 7854 and the like can also be used, but are not limited thereto, and may be any substance capable of generating an acid upon irradiation with light.

[0028]

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The amount of the above-mentioned onium salt cationic photoinitiator is preferably 0.1 to 15% (% by weight, the same applies hereinafter), particularly preferably 0.5 to 1% of the whole resist material.
If it is less than 0.1%, positive resist characteristics are exhibited, but sensitivity is low. On the other hand, 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 15% or less by decreasing the mechanical strength of the resist film.

The resist material of the present invention includes the above (A),
In addition to the component (B), a dissolution inhibitor containing an acid labile group is mixed as the component (C). As such a dissolution inhibitor, for example, a compound in which one or more OH groups of bisphenol A are substituted with a tert-butoxy group or a tert-butoxycarbonyloxy group (t-Boc group) is used. As other examples, the following dissolution inhibitors are exemplified. Particularly, from the viewpoint of resolution, it is preferable that at least one of the acid labile groups is a tert-butoxycarbonyloxy group.

[0031]

Embedded image

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 used as a resist material by dissolving it in an organic solvent several times the amount of the resist material. As the organic solvent, a resist component mainly comprising the polymer of the present invention can be sufficiently dissolved. Those which can be formed and which spread the resist film uniformly are selected. Specifically, butyl acetate, xylene, acetone, cellosolve acetate,
Examples thereof include 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. These organic solvents may be used alone or in a combination of two or more.

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.

[0035]

The positive resist material 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.

[0036]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. Prior to the description of Examples and Comparative Examples, a synthesis example of a base resin will be described.

[Synthesis Example] 2.4 in a 500 ml flask
g of 2,2'-azobisisobutylnitrile, 60 g of p-tert-butoxystyrene, 120 ml of benzene
, And the mixture in the flask is replaced with nitrogen.
Polymerized at 7 ° C. for 7 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 17000, and the molecular weight distribution (M _w / M _n ) was 2.01. The yield was 70%.

The polymer was further dissolved in a benzene / methanol solvent and fractionated. The polymer fractionated in this manner was dried again to give a weight average molecular weight of 150.
Thus, 29 g of poly-p-tert-butoxystyrene having a molecular weight distribution of 1.35 was obtained (Polymer A).

Further, p-ter is prepared in the same manner as described above.
After radical polymerization of t-butoxy-α-methylstyrene, fractionation treatment is performed to obtain a weight molecular weight of 1600 and a molecular weight distribution of 1.
A p-tert-butoxy-α-methylstyrene polymer of 30 was obtained (Polymer B).

Next, 50 g of the obtained polymer A or B was charged into a 500 ml flask, and 200 ml of acetone was added.
l. Thereafter, the temperature was raised to 60 ° C., and the amount of the acid shown in Table 1 below was dropped into this flask over about 1 hour to perform a partial desorption reaction for 6 hours. Then, the flask was cooled. After the obtained polymer is washed with water and dried, FT
The degree of desorption was analyzed by -IR. The desorption degree was 151
An absorption peak derived from a phenyl group at 2 cm ^-1 and 897 cm ^-1
Was determined from the absorbance ratio of the absorption peak derived from the t-butyl group.

[0041]

[Table 1]

Example 1 The resin C obtained in the above synthesis example
9.6 g of (poly-tert-butoxystyrene-polyhydroxystyrene), 0.48 g of the compound of the following formula (1) as an acid generator, and (2,2-bis [p- (t-butoxycarbonyl) as a dissolution inhibitor Using 1.92 g of [oxy) phenyl] propane, these were dissolved in 66 g of diethylene glycol dimethyl ether, and this solution was filtered through a 0.2 μm filter to prepare a resist solution.

[0043]

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The resist solution was applied on a silicone substrate
Spin coating at 000 rpm and 1 on hot plate
Prebaked at 00 ° C for 2 minutes. The thickness was 0.8 μm.

After drawing with an electron beam having an acceleration voltage of 30 kv,
PEB (PostExposure B at 85 ° C. for 90 seconds)
ake). 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. As a result, positive characteristics were exhibited, and the D ₀ sensitivity was 7 μC / cm ² .

Further, instead of the electron beam, Kr
D ₀ sensitivity as assessed by the F excimer laser beam (wavelength 248 nm) was 24 mJ / cm ^2.

0.28 in KrF excimer laser exposure
A line and space pattern of μm was resolved, and a line and space of 0.22 μm 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 resin D (poly-tert-butoxystyrene-polyhydroxystyrene) was used instead of resin C. As a result, the electron beam sensitivity was 8.4.
μC / cm ² , KrF sensitivity was 28 mJ / cm ² , and it was confirmed that the sample had the same resolution as that of Example 1.
It was also confirmed that a pattern having vertical side walls could be formed by KrF exposure.

Example 3 Example 1 was repeated except that the resin E (poly-tert-butoxy-α-methylstyrene-polyhydroxystyrene) and an onium salt represented by the following formula (2) were used as the acid generator. Similarly, a resist was prepared.

[0050]

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As a result of performing PEB at 90 ° C. for 90 seconds, it was confirmed that the film 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 lines and spaces. On the other hand, evaluation was also made by KrF excimer laser exposure, and 0.28 μ lines and spaces were resolved.

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. I let it.
The resulting polymer was washed with methanol and dried, and
14 g of tert-butoxystyrene were obtained. This one is G
The weight average molecular weight (M _w ) of the PC was 9,000, and the degree of dispersion (M _w /
_Mn ) 1.90. Next, 15% of this polymer was used.
The mixture was partially desorbed with hydrochloric acid (3.0-fold mol) for 6 hours. The degree of elimination was 100%. Next, after washing and drying, the resultant was further dissolved in 100 ml of pyridine.
A t-Boc reaction was performed using t-butyl-dicarbonate. The t-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. As a result, the obtained pattern was resolved up to 0.4 μm, but a fine pattern smaller than 0.4 μm could not be resolved.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenichi Ito 28-1 Nishifukushima, Kazagi-mura, Nakakushiro-gun, Niigata Pref. Shin-Etsu Chemical Co., Ltd. 28-1 Nishi-Fukushima, Shinjuku-mura, 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-4-21258 (JP, A) JP-A-3-223858 (JP, A) JP-A-2-1777031 (JP, A) JP Hei 4-195138 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03F 7/039

Claims (1)

(57) [Claims] 1. The following chemical formula (I): (However, R ¹ and R ³ are a hydrogen atom or a methyl group, and R ² is t
tert-butyl group, m + n = 1. ), Comprising a base resin having a molecular weight distribution M _w / M _n of 1.0 to 1.4, an onium salt, and a dissolution inhibitor containing an acid labile group. Amplification type resist material.