JPH0245509A - Fluorine-containing polyacrylic acid derivative - Google Patents

Abstract

PURPOSE:To provide the subject polymer causing the decomposition of the main thereof by the irradiation of radiations and useful as a highly sensitive resist material by copolymerizing alpha-trifluoromethyl acrylate containing fluorine atoms and a benzene ring in the ester portion thereof with a copolymerizable monomer. CONSTITUTION:(A) alpha-Trifluoromethyl acrylate (e.g., 2-phenyl hexafluoroisopropyl alpha-trifluoromethylacrylate) containing fluorine atoms and a benzene ring in the ester portion thereof is copolymerized with (B) a monomer (e.g., methyl acrylate) having a double bond copolymerizable therewith to provide the objective polymer of formula I [A is a structural unit derived from the monomer having the copolymerizable double bond; R is a group of formula II (R1 and R2 are H or fluorine-substituted methyl; Y1-Y5 are H, lower alkyl or F; m is a positive integer; n is 0 or a positive integer) or formula III].

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a polyacrylic ester containing fluorine and benzene rings that can be used as a resist material sensitive to radiation such as electron beams, deep ultraviolet rays, and X-rays. The present invention relates to a derivative and a method of forming a pattern using the polyacrylic acid ester derivative.

[Prior Art] Polymethyl methacrylate (hereinafter abbreviated as PMMA) is well known as an electron beam positive resist. PMM
Although A has high resolution, it has low sensitivity and poor dry etching resistance. In addition, for the purpose of increasing sensitivity, (
Polymers of esters of meth)acrylic acid or its derivatives with mono- or polyfluoroalkanols are used as positive resists for pattern formation by electron beams etc. 60-2
Similar to PMMA, dry etching resistance is insufficient. Although polyphenyl methacrylate has improved dry etching resistance compared to PMMA, its sensitivity is as low as that of PMMA. Further, active research and development is being carried out on positive resists that have excellent dry etching resistance and high sensitivity, but resists with sufficient performance, such as poor resolution, have not yet been developed.

[Problem to be solved by the invention] In recent years, various polymers containing halogens such as fluorine have been studied and used for various purposes by taking advantage of their properties. Due to its high sensitivity, it is attracting attention as a resist material. however,
Although the recent trend toward miniaturization has shifted to dry processes, it still has the drawback of insufficient dry etching resistance as a resist material.

Furthermore, the current situation is that positive resists having dry etching resistance lack sensitivity, and that attempts to achieve high sensitivity result in poor resolution.

The present invention has been made from the above-mentioned viewpoint, and its purpose is to obtain a positive resist material that has particularly improved dry etching resistance, high sensitivity, and high resolution.

[Means for Solving the Problems] The present inventors have conducted extensive research based on the above background, and have completed the present invention.

That is, the present invention relates to the general formula (1) (where A represents a structural unit derived from a monomer having a copolymerizable double bond, R represents, and R1 and R
2 represents hydrogen or a fluorine-substituted methyl group, but does not become hydrogen at the same time: Y, ~Y5 represents hydrogen, a lower alkyl group, or fluorine: m is an integer of 1E, n is 0 or a positive integer, 07m is 0 to 2, preferably θ to 1), a resist material comprising this fluorine-containing polyacrylic acid derivative, and a resist material containing this fluorine a-polyacrylic acid derivative. The present invention provides a method for forming a resist pattern used as a resist pattern.

The fluorine-containing polyacrylic acid derivative of the present invention is an α-substituted acrylic acid ester polymer containing a trifluoromethyl group at the α-position and a fluorine atom and a benzene ring at the ester moiety.

The fluorine-containing polyacrylic ester derivative of the present invention can be obtained by polymerizing the corresponding acrylic ester monomer. The lower alkyl group as a substituent on the benzene ring is preferably an alkyl group having 1 to 5 carbon atoms, such as a methyl group or an ethyl group.

Examples of the fluorine-containing acrylic acid ester monomer of the present invention include α-trifluoromethylacrylic acid 1-phenyl-2,2,2-1-lifluoroethyl ester, α-trifluoromethylacrylic acid 2-phenyl- Hexafluoroisopropyl ester, α-trifluoromethylacrylic acid 1-pentafluorophenyl-2,2,2-)lifluoroethyl ester, α-trifluoromethylacrylic acid 2-pentafluorophenyl-hexafluoroisopropyl ester, α -trifluoromethylacrylic acid 1-p-fluorophenyl-2゜2.2-)lifluoroethyl ester, α-trifluoromethylacrylic acid 2-p-fluorophenyl-hexafluoroisopropyl ester, α-trifluoromethyl Examples include acrylic acid pentafluorophenyl ester.

The fluorine-containing acrylic ester monomer of the present invention can be produced, for example, by the following method.

That is, potassium α-trifluoromethylacrylate and α
- by reacting with substituted benzyl bromide, or by reacting α-trifluoromethylacrylic acid with a mixture of thionyl chloride, phosphorus pentachloride, oxalyl chloride, phosphorus oxychloride and a solvent such as dimethylformamide as a chlorinating agent. By reacting the compound with alcohol or its alkali salt or phenol or its alkali salt corresponding to the ester to be prepared, α-trifluoromethylacrylic acid chloride is synthesized. Can synthesize esters. Further, purification can be performed by vacuum distillation or column separation.

In the case of homopolymerization, the α-trifluoromethylacrylic acid ester monomer of the present invention is polymerized by an ionic polymerization method, particularly an anionic polymerization method, since the compound does not have radical polymerizability. As a catalyst, pyridine, tert
-butoxylithium, tert-butoxypotassium, etc. in an organic solvent such as toluene, tetrahydrofuran, etc.
By performing polymerization at a reaction temperature of -80°C to 100°C, an α-trifluoromethylacrylic acid ester polymer is obtained. Further, in the case of copolymerization, synthesis can be performed by ionic polymerization or radical polymerization. In addition, the degree of polymerization is preferably 20 to 20,000.

Examples of copolymerizable monomers include acrylic esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, methyl methacrylate, and 2-methacrylate.
Hydroxyethyl, methacrylic acid esters such as glycidyl methacrylate, α-methyl chloroacrylate, α-
Phenyl chloroacrylate, α-trifluoroethyl chloroacrylate, 1-phenyl α-chloroacrylate
α- such as 2,2,2-trifluoroethyl, 2-phenyl-hexafluoroisopropyl α-chloroacrylate, etc.
α-Trifluoromethyl such as chloroacrylic acid esters, methyl α-trifluoromethylacrylate, phenyl α-trifluoromethylacrylate, benzyl α-trifluoromethylacrylate, trifluoroethyl α-trifluoromethylacrylate, etc. acrylic esters,
α-cyanoacrylic esters such as ethyl α-cyanoacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid; acid amides such as acrylamide, methacrylamide, and N-phenylmethacrylamide;
Vinyl esters such as vinyl acetate and vinyl propionate, aromatic vinyls such as styrene and α-methylstyrene,
Acrylonitrile, methacrylonitrile, etc. can be mentioned.

[Function] The fluorine-containing polyacrylic acid ester derivative of the present invention can be used as a resist material to form a resist pattern by electron beam drawing, etc., and has radiation sensitivity,
Excellent resolution and dry etching resistance.

There are no particular limitations on the method of using the fluorine-containing polyacrylic acid ester derivative of the present invention to form a resist pattern by electron beam drawing or the like (it can be carried out according to a conventional method).

When using the fluorine-containing polyacrylic acid ester derivative of the present invention as a resist material, the coating solvent is not particularly limited as long as it can dissolve the polymer and form a uniform film, such as xylene, toluene, benzene, etc. ,
Tetrahydrofuran, ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate
and 1,4-bis(trifluoromethyl)benzene. The amount used is a conventional amount, for example, about 5 to about 3 fluorine-containing polyacrylic acid ester derivatives of the present invention.
0%, solvent about 95 to about 70%.

As the developer, for example, a mixed solvent of the above-mentioned solvents and alcohol, or a mixed solvent of ester or ketone solvent and alcohol can be used. Other methods such as coating, pre-baking, exposure, and development can be carried out by conventional methods.

[Example] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

In addition, the electron beam sensitivity test in Examples was conducted by the following method.

Spin code the polymeric 1,4-bis(trifluoromethyl)benzene or ethylene glycol monoethyl ether acetate solution onto a chrome mask blank (two layers of chromium oxide/chromium) to obtain a 0.5 μm coating film. Ta. After prebaking at 200° C. for 30 minutes, desired portions of the coating film were irradiated with an electron beam at an acceleration voltage of 20 KV at various doses. Next, development was performed using a dipping method at 24° C. to selectively remove the irradiated areas. Sensitivity and resolution were evaluated from a sensitivity curve diagram depicting the relationship between dose and residual film thickness after development.

Here, the sensitivity (hereinafter referred to as S value) is indicated by the value of the irradiation amount at which the residual film thickness becomes zero. In addition, the resolution (hereinafter γ
(referred to as the value) is expressed by the equation j og (S/D i) l-' (1) where the irradiation dose at the point where the film thickness begins to decrease on the tangent line corresponding to the S value of the sensitivity curve is Di. The larger the value, the higher the resolution.

The dry etching resistance test was performed using dry etching equipment D.
Resistance to reactive sputtering by CF4 gas was observed using EM-451 model (manufactured by Nikkei Anelva Co., Ltd.).

Example 1 6.0 g of α-trifluoromethylacrylic acid 1-phenyl-2,2,2-trifluoroethyl ester was added to a vacuum-degassed flask, and the mixture was cooled with dry ice-methanol. 0.05 d of pyridine was added to this, and the flask was left standing at -20°C. After 40 hours of reaction, 5.0 mi of methanol was added. After dissolving the reaction product in tetrahydrofuran, the polymer was precipitated in methanol, filtered and dried to obtain 3.25 g of poly-α-trifluoromethylacrylic acid 1-phenyl-2,2°2-trifluoroethyl ester. I got it.

Elemental analysis values: C: 48.0%, H: 2.8%, F: 3
It showed 8.8%.

The ffi Q average molecular weight is 1.5% in terms of polystyrene as a result of c p cap + constant. It was I x 10'.

Next, an electron beam sensitivity test was conducted, and when developing for 3 minutes using methyl isobutyl ketone/isopropyl alcohol as the developer, the S value and γ value were each 10.
A positive type pattern with μC/(4,3,6) was formed.

Further, when a dry etching resistance test was conducted against reactive ion etching using CF4 gas, the etching rate was 1900 A/min. As a comparison,
Etching speed of polymethyl methacrylate is 230OA
/min.

Example 2 7.0 g of α-trifluoromethylacrylic acid 2-phenyl-hexafluoroisopropyl ester was added to a vacuum-degassed flask, and the mixture was cooled with dry ice-methanol. 0.05 d of pyridine was added to this, and the flask was left standing at -20°C. After 50 hours of reaction, 5.0 mj of methanol was added. After dissolving the reaction product in tetrahydrofuran, the polymer was precipitated in methanol, filtered, and dried to obtain 3.80 g of polyα-trifluoromethylacrylic acid 2-phenyl-hexafluoroisopropyl ester.

Elemental analysis values: C, 42.3%, H, 1.8%, F; 4
It showed 7.0%.

As a result of G P CaP1 constant, the weight average molecular weight was 2.5×10' in terms of polystyrene.

Next, an electron beam sensitivity test was conducted, and when development was performed for 3 minutes using 1,4-bis(trifluoromethyl)benzene/isopropyl alcohol as the developer, the S value and γ value were 6.0 μC each. A positive type pattern with /cj, 3.1 was formed.

Further, when a dry etching resistance test was conducted against reactive ion etching using CF4 gas, the etching rate was 1980 A/min.

Example 3 In a vacuum degassed flask, 10.0 g α-trifluoromethylacrylic acid pentafluorophenyl ester
was added and cooled with dry ice-methanol.

To this, anhydrous THF solution of tert-butoxypotassium 4
0mj! (tert-butquine potassium lXl0-3
After the addition of the mol. After 7 days of reaction, 5.0 g of methanol was added.

After dissolving the reaction product in tetrahydrofuran, the polymer was precipitated in methanol, filtered and dried to obtain polyα
8.5 g of -trifluoromethylacrylic acid pentafluorophenyl ester was obtained.

Elemental analysis values showed C: 39.6%, F: 49.1%.

As a result of GPC Δ-j determination, the weight average molecular weight was 5.8×105 in terms of polystyrene.

Next, an electron beam sensitivity test was conducted, and when development was performed for 3 minutes using 1,4-bis(trifluoromethyl)benzene/isopropyl alcohol as the developer, the S value and γ value were 7 μC/cd, respectively. , 2.6, a positive type pattern was formed.

Further, when a dry etching resistance test against reactive ion etching using CF4 gas was conducted, the etching rate was 1950 A/min.

[Effect of the invention] The fluorine-containing polyacrylic acid ester derivative of the present invention has the following properties:
It is an acrylic ester polymer containing a trifluoromethyl group at the α-position, a fluorine atom, and a benzene ring in the ester moiety, and when irradiated with radiation such as electron beams, far ultraviolet rays, or X-rays, it causes a main chain collapse reaction and is exposed to The irradiated area has greatly improved solubility in the solvent compared to the non-irradiated area.

Polymethyl methacrylate and polyphenyl methacrylate also undergo main chain collapse due to these radiations, but the fluorine-containing polyacrylic ester derivative of the present invention
Because fluorine is introduced into the - position and the ester part,
It is easy to cause a disintegration reaction, and as a result, sensitivity is improved.

Further, the fluorine-containing polyacrylic acid ester derivative of the present invention has excellent dry etching resistance because it contains a benzene ring.

Claims (2)

[Claims] (1) General formula (I) ▲Mathematical formulas, chemical formulas, tables, etc.▼(I) (However, A indicates a constitutional unit derived from a monomer having a copolymerizable double bond, and R is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ , where R_1 and R_2 represent hydrogen or fluorine-substituted methyl groups, but do not become hydrogen at the same time; Y_1 to Y_5
represents hydrogen, a lower alkyl group, or fluorine; m represents a positive integer, n represents 0 or a positive integer, and n/m is 0 to 2, preferably 0 to 1). Acrylic acid derivative. (2) A resist material composition comprising the fluorine-containing polyacrylic acid derivative according to claim (1). (3) A method for forming a resist pattern, characterized in that the fluorine-containing polyacrylic acid derivative according to claim (1) is used as a resist material.