JPS62150345A - Pattern forming method - Google Patents

Abstract

PURPOSE:To obtain a resist material high in sensitivity to electron beams and X-rays, also in resolution, and durable against dry etching by using a polymer composed of F-containing repeating units. CONSTITUTION:The resist material to be used is the polymer composed of the F-containing repeating units each represented by formula (1) in which each of R1 and R2 is H or optionally substituted alkyl. It is preferred for the resist material to have the molecular weight of about nX10<3>-nX10<6>, (n) being 1-9. If it is below the lower limit, the mechanical strength and heat resistance of the film to be formed are deteriorated, and if above the upper limit, the resist solution is made too high in viscosity to control the film thickness, and be difficult in processability.

Description

Detailed Description of the Invention [Field of the Invention] The present invention provides high sensitivity and high resolution to high energy rays such as electron beams or X-rays by using a fluorine atom-containing polymer as a resist material. The present invention relates to a method for forming a positive-type resist pattern having the same properties and good dry etching resistance.

[Prior art]

In recent years, semiconductor integrated circuits have become denser and more highly integrated, and we are now in an era where the degree of integration is 1 Mbit or more, and it has become necessary to form patterns of the 1 μm rule or even smaller. Along with this, lithography techniques using electron beams, X-rays, etc. are attracting attention and are being put into practical use. The performance of the resist material used in this process is that it is highly sensitive to electron beams and X-rays, that the resolution of the formed pattern is excellent, and that a dry process is required for microfabrication. To be advantageous, it is necessary to have dry etching resistance.

In order to satisfy high resolution, positive resist materials are more advantageous than negative resist materials, and the development of excellent positive resist materials is active.

Polymethyl methacrylate (hereinafter abbreviated as PMMA) is well known as a positive resist material. PMM
Although A has high resolution, sensitivity is low and dry etching resistance is poor.゛Also, to improve sensitivity,
Polymers in which the methyl ester moiety of PMMA is changed to a fluorine-containing alkyl ester and polymers in which the methyl group directly connected to the main chain of PMMA is changed to an electron-withdrawing group such as a halogen have been synthesized. Etching resistance is insufficient. Although polyphenyl methacrylate has improved dry etching resistance compared to PMMAIC, its sensitivity to electron beams and X-rays is as low as PMMA.

[Problems to be solved by the present invention]

Therefore, there is a need to provide a material that has high sensitivity and resolution to electron beams and X@ and has dry etching resistance as a practical positive type resist material for use in microfabrication at the submicron level.

[Detailed description of the invention]

The inventors of the present invention conducted extensive research in search of a positive resist material that has high sensitivity, high resolution, and excellent dry etching resistance. As a result, they discovered that a polymer containing a fluorine atom and having a special chemical structure containing a benzene ring has excellent performance, leading to the present invention.

That is, the present invention provides general formula (1) % formula % (R11RR* ” + alkyl group, substituted alkyl group)
The present invention relates to a pattern forming method characterized in that a fluorine atom-containing polymer composed of repeating units represented by is used as a resist material.

The fluorine atom-containing polymer consisting of repeating units represented by the above general formula (1), which is the resist material of the present invention, has the general formula (
2) (R1* R1: H+ alkyl group, substituted alkyl group)
It can be obtained by homopolymerizing α-trifluoromethylacrylic acid ester represented by

α-Trifluoromethylacrylic acid ester can be produced, for example, by the following method.

That is, by reacting α-trifluoromethylacrylate potassium with α-substituted pendyl bromide, or
α-Trifluoromethylacrylic acid chloride is synthesized by reacting α-trifluoromethylacrylic acid with a chlorinating agent such as thionyl chloride, phosphorus pentachloride, oxalyl chloride, or a mixture of phosphorous oxychloride and dimethylformamide, and then By reacting the compound with α-substituted pendyl alcohol in the presence of a base, the desired α
-Trifluoromethylacrylic acid ester can be synthesized.

Homopolymerization of α-trifluoromethylacrylic acid ester does not have radical polymerizability, so ionic polymerization, particularly anionic polymerization, is effective. Pyridine as a catalyst, t-
Using butoxylithium, t-butoxypotassium, etc., in an organic solvent such as toluene or tetrahydrofuran,
The polymer is obtained by polymerization under heating at 100°C.

The resist material according to the present invention preferably has a molecular weight in the range of several thousand to several million. If the molecular weight is less than several thousand, the mechanical strength and heat resistance of the formed film will be poor. Moreover, if it is more than several million, the viscosity of the resist material solution becomes too high, making it difficult to control the film thickness and making it difficult to handle.

The coating solvent for the resist material according to the present invention is not particularly limited as long as it can dissolve the polymer and form a uniform film, and examples thereof include xylene, toluene, benzene, tetrahydrofuran, ethyl cellosolve, and the like.

As the developer, for example, a mixed solvent of the above-mentioned solvent and alcohol.

A mixed solvent of an ester or ketone solvent and an alcohol and an alkaline aqueous solution can be used. coating,
Other methods such as brebake, exposure, development, etc. can be carried out according to conventional methods.

〔Effect of the invention〕

In the resist material of the present invention, when irradiated with electron beams, X-rays, etc., a main chain collapse reaction occurs and carboxylic acid is generated, and the solubility of the irradiated area in the solvent changes and improves significantly compared to the non-irradiated area. do.

Furthermore, the resist material of the present invention has excellent dry etching resistance. These effects are presumed to be due to the special structure of the polymer, in which the molecule contains a trifluoromethyl group and a benzene ring.

From the above, the resist material of the present invention can be used for optical application parts,
It can be seen that it is effective as a resist material for forming fine patterns in magnetic pulp elements, semiconductor preparation, etc.

〔Example〕

The present invention will be explained in more detail with reference to Examples below. However, the present invention is not limited to these.

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

A xylene or methyl ethyl ketone solution of the resist material was coated onto a silicon wafer to obtain a coating film of 1 μm. Prebaking was performed at 125° C. for 25 minutes, and desired portions of the coating film were irradiated with an electron beam at an accelerating voltage of 20 KV at various doses. Next, isoamyl acetate/isopropyl alcohol mixed solvent or organic alkaline developer (Silapray).

M? -312) 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 (r
The value) indicates the S value of the sensitivity curve, and the larger the value, the higher the resolution.

[For details, refer to "Currently Applied Technology of Fluorine Compounds," NMC, published April 24, 1980, pages 169-140.] The dry etching resistance test was carried out using dry etching equipment D.
Resistance to reactive sputtering by CF4 gas was observed using EM-451 model (manufactured by Nichiden Anelpa).

Example 1 In a vacuum degassed flask, α-trifluoromethylacrylic acid benzyl ester 5. ．． 5f was taken and cooled with dry ice-methanol.

Pyridine α05d was added to this, and the flask was heated to -20°C.
It was left undisturbed. After a few minutes the solution became a pale yellow viscous liquid. Subsequently, after reacting at -20°C for 40 hours, 5.0 ml of methanol was added. After dissolving the reaction product in benzene, the polymer was precipitated in methanol, filtered and dried to obtain poly-α-trifluoromethylacrylic acid benzyl ester. As a result of GPC measurement, the weight average molecular weight was 9.7 x 10' in terms of polystyrene.

Next, an electron beam sensitivity test was conducted, and when isoamyl acetate/isopropyl alcohol was used as a developer, a positive type pattern was formed with an S value and an r value of 60 μC/C-91.1, respectively.

Further, when a dry etching resistance test against reactive sputtering using CF4 gas was conducted, the etching rate was 70 QA/min. Comparison and L-t”
The etching speed of silicon substrate is 1500A/min.
Met. In the case of polymethyl methacrylate, the etching rate was 1700 A/min.

Example 2 1α-trifluoromethyl acrylic and benzyl ester &3t were placed in a vacuum degassed flask and cooled with dry ice-methanol.

To this, 80 rI of anhydrous THF solution of potassium t-butoxy
After adding Ll (containing 44 x 10-' moles of potassium t-butoxy), the flask was stirred at -20°C for 7 days,
After the reaction, 5-Od of methanol was added. After dissolving the reaction product in benzene, the polymer was precipitated in methanol, filtered and dried to obtain poly-α-trifluoromethylacrylic acid benzyl ester. As a result of GPC measurement, the weight average molecular weight is &4x10' in terms of polystyrene.
Met.

Next, we conducted an electron beam sensitivity test and found that when isoamyl acetate/isopropyl alcohol was used as the developer,
The S value and r value are each 12μC7cm”.

A positive type pattern of 2.4 was formed.

Example 3 In a vacuum degassed flask, α-trifluoromethylacrylic acid cumyl ester 5. The mixture was taken off and cooled using dry ice-methanol. After adding 80 ml of an anhydrous THF solution of t-butoxypotassium (containing &4xlO-' moles of t-butoxypotassium), the flask was stirred at -20°C for 7 days, and after the reaction, 5.0ml of methanol was added.
0- added. After dissolving the reaction product in benzene, the polymer was precipitated in methanol, filtered, and dried.
Polyα-trifluoromethylacrylic acid cumyl ester was obtained. As a result of GPC measurement, the weight average molecular weight was 5.4xlO' in terms of polystyrene.

Next, an electron beam sensitivity test was conducted, and it was found that when isoamyl acetate/isopropyl alcohol was used as the developer, the S value and r value were 10 μ (37 cm), respectively.
Z, 1, and when an organic alkali aqueous solution is used as the developer, the S value and r value are each 6 μQ/cya.
”, a positive type pattern with L8 was formed.

Further, when a dry etching resistance test against reactive sputtering using CF4 gas was conducted, the etching rate was 650 Vmin.

Example 4 4.9 tons of α-trifluoromethylacrylic fi2,2.2-)refluoro-1-phenylethyl ester was placed in a vacuum-degassed flask and cooled with dry ice-methanol. To this, 80 mj of anhydrous THF solution of t-butoxypotassium (6.4 mj of t-butoxypotassium
After adding X10-' moles), the flask was
℃, stirred for 7 days, and after reaction, added 5.0 rnl of methanol.
Added. After dissolving the reaction product in benzene, the polymer was precipitated in methanol, filtered and dried to obtain polyα-trifluoromethylacrylic acid2. λ2-trifluoro 1-phenylethyl ester was obtained. As a result of GPC measurement, the weight average molecular weight is 3 x 1 in terms of polystyrene.
It was 0S.

Next, an electron beam sensitivity test was conducted, and when isoamyl acetate/isopropyl alcohol was used as the developer, the S value and r value were 8 μQ/cm, respectively! .

A positive type pattern of 2.5 was formed.

Claims (1)

[Claims] (1) A pattern forming method characterized by using a fluorine atom-containing polymer composed of repeating units represented by general formula (1) as a resist material. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) (R_1, R_2; H, alkyl group, substituted alkyl group)