JPH07196743A - Radiation-sensitive material and method for forming pattern - Google Patents

Abstract

PURPOSE:To obtain the subject material comprising the copolymer of an adamantyl methacrylate with a specific vinylic monomer, useful for lithography using an excimer laser, etc., as a light-exposing source, excellent in transparency and etching durability, having high sensitivity, and not peeled. CONSTITUTION:This material comprises the copolymer of an adamantyl methacrylate (derivative) of the formula (R1, R2 are each H, methyl) preferably in an amount of 40-70mol.% with a vinylic monomer whose alpha-position is substituted with an electron-attracting group (e.g. methyl alpha-chloroacrylate, ethyl alpha-cyanoacrylate).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation sensitive material and a pattern forming method using the radiation sensitive material. In recent years, the integration of semiconductor integrated circuits has advanced, and LSI and LSI have been put into practical use. With the high integration and miniaturization of such elements, the minimum line width in the microfabrication technology is in the submicron or half-micron region. , And there is a tendency for further miniaturization.

To form a fine pattern in the fine processing technology, a resist is coated on a substrate on which a thin film is formed, and after selective exposure, development is performed to form a resist pattern, and this is used as a mask for dry etching. Then, it is essential to use a lithography (photolithography) technique for obtaining a thin film pattern by dissolving and removing the resist after that. At first, ultraviolet rays were used as an exposure light source used in this lithography technique, but with the miniaturization of patterns, the wavelength has been shortened, and far ultraviolet rays, electron beams, X-rays, etc. are used as light sources. became.

Therefore, a resist material having high resolution, high sensitivity, and excellent dry etching resistance is required especially in response to a new lithography technique using an electron beam.

[0004]

2. Description of the Related Art Regarding positive resists for electron beams, a chemically amplified resist is being developed as a resist that can easily achieve high sensitivity (H.Ito and CG Willson, ACS
Symp.Ser.242,1-13,1984 and many others), stable performance cannot be obtained due to the formation of the surface insolubilized layer and PED. In particular, it is remarkable in a positive resist, and its practical application is difficult.

Therefore, the present inventors have proposed an α-methylstyrene copolymer as a positive resist for electron beams (see JP-A-63-137227). Since this copolymer has a styrene skeleton, it is excellent in dry etching, is decomposed by electron beam irradiation, and is patterned by utilizing the difference in solubility depending on the molecular weight. However, although this α-methylstyrene copolymer has obtained a practical sensitivity, it is necessary to further increase the sensitivity in view of throughput. This kind of high sensitivity can be achieved by using a strong developing solution, but there is a limit because it causes film slippage in the unexposed area and a decrease in resolution, so the resin itself must be added to achieve higher sensitivity. It is necessary to change to polymers with higher degradation efficiency.

[0006]

As described above, the resist composed of α-methylstyrene copolymer developed as a positive resist for electron beam must also have higher sensitivity in order to improve the throughput. There were challenges. Therefore, the present invention is used in lithography using an excimer laser or an electron beam as an exposure source, not only excellent transparency and etching resistance, but also a highly sensitive radiation-sensitive material with less peeling and a pattern using the radiation-sensitive material. An object is to provide a forming method.

[0007]

[Means for Solving the Problems]

[0008]

[Chemical 2] (Wherein each of R1 and R2 represents a hydrogen atom or a methyl group), and a copolymer containing adamantyl methacrylate or a derivative thereof and a vinyl monomer in which the α-position is substituted with an electron-withdrawing group. Is achieved by the radiation-sensitive material.

In the radiation-sensitive material described above, the unit structure having an adamantyl group in the copolymer is preferably 40 to 70 mol%. The monomer to be copolymerized with adamantyl methacrylate or a derivative thereof is a vinyl monomer having an electron-withdrawing group at the α-position. For example, methyl α-chloroacrylate,
α-chloro acrylate, α-chloro acrylate, α-chloro acrylate, α-chloro acrylate 2,2,2-trifluoroethyl, α-bromo acrylate, α-bromo acrylate, α -Isopropyl bromoacrylate, α-promoacrylic acid, α
-Methyl trifmethylloroacrylate, ethyl α-trifluoromethylacrylate, isopropyl α-trifluoromethylacrylate, 2,2,2-trifluoroethyl α-trifmethylloroacrylate, itaconic acid, dimethyl itaconate, Monomethyl itaconate, α-chloroacrylonitrile, fumaronitrile, glutaronitrile, α-
Examples thereof include methyl cyanoacrylate and ethyl α-cyanoacrylate, but are not limited to these monomers.

Further, the above-mentioned problem is that a resist is formed by using the radiation-sensitive material described above, the resist is applied onto a substrate, prebaking is performed, and the resist on the substrate is selectively exposed to radiation. After that, post-baking is performed, and the resist on the substrate is developed to form a predetermined resist pattern, which is achieved by a pattern forming method.

[0011]

The present invention has the general formula

[0012]

[Chemical 3] (Wherein R 1 and R 2 each represent a hydrogen atom or a methyl group), and a radiation-sensitive material comprising a copolymer containing adamantyl methacrylate or a derivative thereof and a vinyl monomer in which the α-position is substituted with an electron-withdrawing group. Since the polymer consisting of adamantyl methacrylate or its derivative has an α-methyl substituted acrylic structure, it is decomposed by electron beam irradiation. The cleavage efficiency of a molecular chain having an α-methyl substituted acrylic structure is 10 times or more that of an α-methylstyrene structure. Further, despite having higher cleavage efficiency than α-methylstyrene polymer, the polymer comprising adamantyl methacrylate or its derivative has a dry etching resistance comparable to that of α-methylstyrene polymer. On the other hand, an acrylic polymer in which the α-position is substituted with an electron withdrawing group such as halogen or cyano is very easy to decompose by electron beam irradiation. Therefore, practical sensitivity can be obtained even in the case of a copolymer with α-methylstyrene having a low cleavage efficiency. Therefore, in order to further improve the decomposition efficiency and achieve high sensitivity, a copolymer of adamantyl methacrylate or a derivative thereof and an acrylic acid ester substituted with an electron-withdrawing group was used.

Here, the unit structure having an adamantyl group in this copolymer is preferably 40 to 70 mol% because the composition ratio of adamantyl methacrylate or its derivative is less than 40 to 70 mol%. This is because the etching resistance is inferior, and conversely, if the etching resistance is high, the sensitivity decreases.

[0014]

【Example】

[Example 1] Adamantyl methacrylate monomer and α-
Methyl chloroacrylate monomer was charged at a ratio of 2: 1 to prepare a 0.5 mol / l 1,4-dioxane solution,
AIBN was added at 10 mol% as an initiator. Then, it heated at the temperature of 80 degreeC for about 8 hours. After heating, it was precipitated in a large amount of methanol for purification. As a result,

[0015]

[Chemical 4] , Composition ratio 53:47, weight average molecular weight 570
00 copolymer was obtained. Next, the polymer thus synthesized was dissolved in cyclohexanone to prepare a 10 wt% resist solution. This solution was applied on a Si wafer to a thickness of 0.5 μm by spin coating, and the temperature was adjusted to 20 ° C. in an oven.
Prebaking was performed at 0 ° C. for 20 minutes.

The Si wafer thus obtained was selectively exposed using an electron beam exposure apparatus with an accelerating voltage of 20 KV.
After that, xylene / IPA (volume ratio 3: 1
Development was performed for 5 minutes using the mixed solution of (1). The threshold energy Eth of the exposure energy at this time was 3 μC / cm ^2, and L & S having a width of 0.4 μm was resolved. [Comparative example 1]

[0017]

[Chemical 5] A 1: 1 copolymer of α-methylstyrene and α-methyl chloroacrylate (weight average molecular weight 560
A 12 wt% o-dichlorobenzene solution of 00) was prepared as a resist solution. This solution was applied on a Si wafer to a thickness of 0.5 μm by spin coating, and prebaked at a temperature of 200 ° C. for 20 minutes in an oven. The Si wafer thus obtained was selectively exposed using an electron beam exposure apparatus with an acceleration voltage of 20 KV. Then, it was developed with xylene for 20 minutes. The threshold energy Eth of the exposure energy at this time was 10 μC / cm ² . Example 2 3,5-Dimethyladamantyl Methacrylate Monomer and α-Trifluoromethyl Acrylate 2,2
2-trifluoroethyl monomer and 1: 3, 8m
An ol / l 1,4-dioxane solution was prepared, and 1 mol% of AIBN was added as an initiator. Then, polymerization was carried out at a temperature of 80 ° C. for about 3.5 hours. After the polymerization was completed, the product was purified by precipitating it in a large amount of methanol.

[0018]

[Chemical 6] Composition ratio 58:42, weight average molecular weight 300
A copolymer having a dispersity of 00 and a dispersity of 1.9 was obtained. Next, the polymer thus synthesized is dissolved in cyclohexanone to obtain 12 wt.
% Resist solution was prepared. This solution was applied on a Si wafer to a thickness of 0.5 μm by spin coating, and prebaked at a temperature of 200 ° C. for 20 minutes in an oven.
The Si wafer thus obtained was selectively exposed using an electron beam exposure apparatus with an acceleration voltage of 20 KV. Then, it was developed with isoamyl acetate for 5 minutes. The threshold energy Eth of the exposure energy at this time was 1 μC / cm ² , and the resolution was 0.45 μm wide L & S. [Example 3] 3,5-dimethyladamantyl methacrylate monomer and α-trifluoromethylacrylic acid were mixed with 1: 5.
The mixture was charged with 3 to prepare an 8 mol / l 1,4-dioxane solution, and 1 mol% of BPO was added as an initiator. Then, polymerization was carried out at a temperature of 80 ° C. for about 5 hours. After the polymerization was completed, the product was purified by precipitation in a large amount of diethyl ether.

[0019]

[Chemical 7] , Composition ratio 51:49, weight average molecular weight 230
A copolymer having a dispersity of 00 and a dispersity of 2.1 was obtained. Next, the polymer thus synthesized was dissolved in ethyl cellosolve to obtain 12 wt.
% Resist solution was prepared. This solution was applied on a Si wafer to a thickness of 0.5 μm by spin coating, and prebaked at a temperature of 170 ° C. for 20 minutes in an oven.
The Si wafer thus obtained was selectively exposed using an electron beam exposure apparatus with an acceleration voltage of 20 KV. Then, it was developed with ethyl acetate for 5 minutes. At this time, the threshold energy Eth of the exposure energy was 1.6 μC / cm ² , and the resolution was L & S with a width of 0.5 μm. Example 4 Similar results were obtained even when 3,5-dimethyladamantyl methacrylate was used instead of adamantyl methacrylate in Example 1 above. Example 5 Adamantyl Methacrylate Monomer and α-
1: 1 with methyl cyanoacrylate monomer and 1
Mol / l benzene solution, AIBN as the initiator
Was added in an amount of 5 mol%. Then, the polymerization was carried out at a temperature of 80 ° C. for about 8 hours. After completion of the polymerization, the product was purified by precipitation in a large amount of methanol. Thus,

[0020]

[Chemical 8] The composition ratio is 50:50 and the weight average molecular weight is 120.
000 and a dispersity of 1.8 were obtained. Next, the polymer thus synthesized was dissolved in cyclohexanone to obtain 9 wt.
% Resist solution was prepared. This solution was applied on a Si wafer to a thickness of 0.5 μm by spin coating, and prebaked at a temperature of 200 ° C. for 20 minutes in an oven.
The Si wafer thus obtained was selectively exposed using an electron beam exposure apparatus with an acceleration voltage of 20 KV. Then, it was developed with methyl ethyl ketone for 3 minutes. The threshold energy Eth of the exposure energy at this time is 4 μC / cm ² ,
An L & S pattern having a resolution of 0.4 μm was obtained. Example 6 Similar results were obtained when 3,5-dimethyladamantyl methacrylate was used instead of adamantyl methacrylate in Example 5 above.

[0021]

As described above, according to the present invention, the general formula

[0022]

[Chemical 9] (Wherein R 1 and R 2 each represent a hydrogen atom or a methyl group), and a radiation-sensitive material comprising a copolymer containing adamantyl methacrylate or a derivative thereof and a vinyl monomer in which the α-position is substituted with an electron-withdrawing group. By virtue of this, since this polymer has an α-methyl-substituted acrylic structure, it is decomposed by electron beam irradiation, has dry etching resistance, and practical sensitivity can be obtained.

Thus, in lithography using an electron beam as an exposure source, not only excellent transparency and etching resistance but also a highly sensitive radiation-sensitive material with less peeling, and pattern formation using the radiation-sensitive material. A method can be provided and can greatly contribute to highly accurate pattern formation.

Claims (3)

[Claims] 1. A general formula: (Wherein each of R1 and R2 represents a hydrogen atom or a methyl group), and a copolymer containing adamantyl methacrylate or a derivative thereof and a vinyl monomer in which the α-position is substituted with an electron-withdrawing group. Radiation sensitive material. 2. The radiation-sensitive material according to claim 1, wherein the unit structure having an adamantyl group in the copolymer is 40 to 70 mol%. 3. A resist is formed using the radiation-sensitive material according to claim 1 or 2, and the resist is applied onto a substrate and then prebaked to selectively expose the resist on the substrate to radiation. After the exposure, post-baking is performed, and the resist on the substrate is developed to form a predetermined resist pattern.