JPS648811B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel high energy ray resist material. More specifically, the present invention relates to a high-energy ray resist material comprising a fluorine-containing copolymer having specific fluoroalkyl vinyl ether units and maleic acid unsaturated alkyl ester units. In the manufacturing of semiconductor components such as those found in large-scale integrated circuits (LSI), a photosensitive polymer material called photoresist has traditionally been used to process fine patterns. Precision is now required. In such high-precision microfabrication, it is said that it is necessary to use ultraviolet light, soft X-rays, electron beams, etc. as high-energy rays with short wavelengths in order to avoid a decrease in resolution due to diffraction effects. Therefore, there is an urgent need to develop polymer resist materials that are highly sensitive to these high-energy rays and can form fine patterns with good resolution. An object of the present invention is to provide a high-energy ray resist material that can satisfy the above-mentioned conditions, and the object is to provide a high-energy ray resist material that satisfies the above-mentioned conditions. (wherein, X is H, F or

[Formula], m is an integer of 1 to 10, and n is an integer of 1 or 2 It has been found that this can be achieved by using a fluorine-containing copolymer having a structure in which units in which unsaturated bonds are cleaved are alternately repeated. That is, the fluorine-containing copolymer is exposed to ultraviolet light, soft
It has photosensitivity to high-energy beams such as beams and electron beams, and has high sensitivity and resolution, making it ideal as a resist material for high-energy beams. The fluorine-containing copolymer used in the present invention is a novel polymer. That is, the general formula F(CF ₂ ) _p
Fluoroalkyl vinyl ethers represented by CH ₂ OCH=CH ₂ (wherein p is an integer from 1 to 11) have been known for a long time, and for example,
No. 739731 describes a method for producing the fluoroalkyl vinyl ethers, the production of homopolymers thereof, and the production of copolymers of various fluoroalkyl vinyl ethers; It is also described that it can be copolymerized with vinyl monomers such as and diene monomers such as isoprene and butadiene. Further, US Pat. No. 2,991,278 describes a copolymer of CF ₃ CH ₂ OCH=CH ₂ and a haloolefin such as tetrafluoroethylene or vinyl chloride. However, little is known about copolymers of fluoroalkyl vinyl ethers and α,β-unsaturated dicarboxylic acids such as maleic acid and maleic anhydride or derivatives thereof. The fluorine- _containing copolymer used in the present invention has, _{for example} , _the general formula ( ₎ : )
It is produced by reacting a copolymer of fluoroalkyl vinyl ether (hereinafter referred to as FVE) and maleic anhydride with an unsaturated alcohol to esterify it. The FVE was obtained by the method described in British Patent No. 739731, as shown in the following formula: X(CF ₂ ) _n (CH ₂ ) _o OH+CH ₃ COOCH= _{CH 2 →} (CH ₂ ) _o OCH=CH ₂ +CH ₃ COOH It can be synthesized by reacting a fluoroalkanol and vinyl acetate in the presence of a mercury catalyst. In addition, the fluoroalkanol used here where X is H is mCF ₂ = CF ₂ + CH ₃ OH→H (CF ₂ CF ₂ ) _n CH ₂ OH as shown in the following formula. Synthesized by telomerization of fluoroethylene,
is F, as shown in the following formula: C ₃ F ₇ COOH→C ₃ F ₇ COOCH ₃ →C ₃ F ₇ CH ₂ OH Synthesized by reduction with (LiAlH ₄ ). Furthermore, X

[Formula] is synthesized from a fluoroalkyl iodide derived from hexafluoropropylene, as shown in the following formula. The FVE represented by the general formula () used in the production of the copolymer used in the present invention is a fluoroalkyl vinyl ether with n=1 or 2 produced by the method described above, and those with m>10 are Fluoroalkyl vinyl ether with m=1 to 10 is used in the production of the copolymer used in the present invention because it is solid at room temperature and has a high boiling point, making it difficult to handle in terms of synthesis or purification. A copolymer of FVE and maleic anhydride can be obtained by copolymerizing both monomers in the presence of a radical polymerization initiator.
Both emulsification and solution polymerization can be carried out. The radical polymerization initiator used in copolymerization may be any initiator that is soluble in the monomer mixture or a mixture of them and a solvent, and in the case of emulsion polymerization, an initiator that is soluble in water. Examples thereof include azo compounds such as azobisisobutyronitrile, peroxides such as diisopropyl peroxydicarbonate, and ammonium persulfate. The thus obtained copolymer of FVE and maleic anhydride was found to have an alternating structure in which FVE units and maleic anhydride units were alternately repeated in a 1:1 ratio, as determined by elemental analysis and nuclear magnetic resonance (NMR) measurements. It turned out to be a copolymer. The fluorine-containing copolymer used in the present invention is the FVE
It is obtained by reacting a copolymer of maleic anhydride and maleic anhydride with an unsaturated alcohol, and this reaction is shown, for example, by the following formula. In addition, in the following formula, R is an unsaturated alkyl group. Examples of the unsaturated alcohol include allyl alcohol, crotyl alcohol, and propargyl alcohol. The fluorine-containing copolymer thus obtained is a colorless to pale yellow amorphous solid polymer that dissolves in polar solvents such as acetone and chloroform.
-Not soluble in non-polar solvents such as hexane. In order to form a polymer film pattern from the fluorine-containing copolymer, a film of the copolymer is formed on a substrate, and then high-energy rays such as ultraviolet light, soft X-rays, and electron beams are irradiated with arbitrary radiation. After irradiating the shape and insolubilizing the irradiated area by crosslinking, the irradiated area can be left on the substrate as a polymer coating pattern by treating it with a developer that can elute and remove the coating on the non-irradiated area. . That is, a solution of a fluorine-containing copolymer is applied to a substrate such as a silicon wafer in a conventional manner, dried to form a film, and then a suitable mask is placed over the solution and high-energy rays are irradiated. Then, by processing with a developer, the irradiated portions become insolubilized and the least irradiated portions are removed, forming a desired fine pattern. Next, the present invention will be explained with reference to Examples. In addition, below, % is weight %. Example 1 91.6 g (0.2 mol) of H(CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ and 19.6 g (0.2 mol) of maleic anhydride in 200 ml
After adding 0.03 g of azobisisobutyronitrile to the glass ampoule, the inside of the ampoule was degassed and melt-sealed. The ampoule was submerged in a water bath at 65° C. and occasionally shaken while heating, so that the maleic anhydride was dissolved and the mixture became uniform. After 24 hours, the contents were poured into 1 part of benzene to yield a white solid. After drying this at 30°C, it was dissolved in 350ml of acetone and poured into the benzene from Step 3 again. The separated polymer was dried under reduced pressure at 80°C to obtain 93g of a white polymer. Elemental analysis of this polymer revealed that F
= 54.1%, H = 1.41%, C = 31.6%, and from the results of nuclear magnetic resonance (NMR) analysis, H
(CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ and maleic anhydride were found to be a 1:1 alternating copolymer.
In addition, the viscosity of this copolymer (viscosity in methyl ethyl ketone at 25°C) was measured [η]
= 0.61. When 10 g of the copolymer was refluxed in allyl alcohol for 5 hours to convert the acid anhydride group into a semi-allylic ester, it became soluble in allyl alcohol.
After cooling this solution, it was poured into n-hexane to precipitate the reaction product. This was dried in a vacuum dryer to obtain about 8 g of a semiallylic ester of the copolymer. Figures 1 and 2 show the infrared absorption spectra of a copolymer of H(CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ and maleic anhydride and a half-allylic ester thereof made with allyl alcohol, respectively. . The absorption of carboxylic acid at around 1730 cm ^-1 is observed even before semi-allyl esterification because some of the acid anhydride groups are absorbed by trace amounts of moisture in the polymerization system or by moisture in the air during storage of the copolymer. It is thought that the ring has been opened.
After semi-allylic esterification, the absorption by the acid anhydride groups observed at 1800 cm ^-1 and 1860 cm ^-1 disappeared, indicating that the acid anhydride groups were semi-allylic esterified. The semi-allylic ester of the copolymer of H(CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ and maleic anhydride obtained above was dissolved in methyl ethyl ketone to make a 10% solution,
When this was applied onto a silicon wafer by spin coating and heated under reduced pressure at 60°C for 15 minutes, a uniform film with a thickness of approximately 0.42 μm was formed.
This is followed by soft X-rays (molybdenum target, 16kV,
After irradiation (operating at 200 mA), development is performed using a mixed solvent of dioxane and benzene at a volume ratio of 2:3. While the non-irradiated areas are dissolved and removed, the irradiated areas are insolubilized by the cross-linking reaction of allyl groups and are not deposited on the wafer. I stayed behind. At this time, the remaining film ratio [(film thickness remaining in the irradiated area after development processing)/(original film thickness)] against the soft X-ray irradiation amount was blotted and the third
As shown in the figure. The sensitivity was approximately 60 mJ/cm ² when taking the irradiation dose at 50% residual film rate. The above sensitivity was measured using a commercially available electron beam resist material, a copolymer of glycidyl acrylate and ethyl acrylate (manufactured by Mead Chemical Co., trade name:
The sensitivity is comparable to that of Copolymer). In addition,
The γ value (Figure 4 shows the irradiation characteristics and γ value =
(logEo/Ei) ^-1 ) is 1.5 and the γ value of the copolymer of glycidyl acrylate and ethyl acrylate is 1.2 [LFThompson, JP
Ballantyne and EDFeit, J.Vac.Sci.Technol.
Vol.12, p.1280 (1975)]. Example 2 H (CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ obtained in Example 1
A coating film was formed on a silicon substrate in the same manner as in Example 1 using a semi-allylic ester of a copolymer of 1 and maleic anhydride. This was irradiated with soft X-rays through a pattern mask using gold as a soft X-ray absorbing material in the same manner as in Example 1, and then developed with a solvent of dioxane and benzene in a volume ratio of 1:1 to form a pattern on the mask. When transferred onto a film, a resolution of approximately 1 μm was obtained. Example 3 H (CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ obtained in Example 1
A coating film of 0.6 μm was formed on a silicon substrate in the same manner as in Example 1 using a semi-allylic ester of a copolymer of 1 and maleic anhydride. On the other hand, a chrome hard mask formed on a quartz substrate with a minimum line width of 1 μm was brought into close contact with the silicon wafer on which the film was formed, and 37 mJ/cm ² of short wavelength ultraviolet light from a deuterium discharge tube was irradiated through the mask. When developed with a solvent containing dioxane and benzene in a volume ratio of 1:1, a minute pattern with a minimum line width of 1 μm and a thickness of 0.32 μm was formed faithfully to the mask pattern. Example 4 H (CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ obtained in Example 1
A solution prepared by dissolving 2 g of a semi-allylic ester of a copolymer of maleic anhydride and 0.03 g of benzoyl peroxide in acetone was coated on an aluminum plate, dried at 50°C for 30 minutes, and then heated at 120°C. After heating for 10 minutes, a uniform film was formed. When the aluminum plate coated with this film was placed 20 cm away from a 2kW high-pressure mercury lamp and exposed to ultraviolet light for 15 minutes, a coating was obtained that swelled in acetone but did not dissolve or peel.

[Brief explanation of drawings]

Figure 1 shows the infrared absorption spectrum of a copolymer of H(CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ and maleic anhydride.
Figure 2 shows an infrared absorption spectrum of a semi-allylic ester of a copolymer of H(CF ₂ CF ₂ ) ₄ CH ₂ OCH=CH ₂ and maleic anhydride;
(CF ₂ CF ₂ ) ₄ CH ₂ OCH=Characteristic curve obtained when a semi-allylic ester of a copolymer of CH ₂ and maleic anhydride is irradiated with soft X-rays. Figure 4 shows the energy ray irradiation characteristics. It is a graph showing the relationship with γ value = [logEo/Ei] ^-1 .

Claims (1)

[Claims] 1 General formula (): (wherein, X is H, F or [Formula], m is an integer of 1 to 10, and n is an integer of 1 or 2) and a maleic acid unsaturated alkyl ester A high-energy ray resist material comprising a fluorine-containing copolymer having a structure in which units in the form of cleaved carbon-carbon unsaturated bonds in the maleic acid group moiety are alternately repeated. 2. A copolymer in which the fluorine-containing copolymer has a structure in which fluoroalkyl vinyl ether units represented by the general formula () and units in which the carbon-carbon unsaturated bond of maleic anhydride is cleaved are alternately repeated. 2. The high-energy ray resist material according to claim 1, which is a reaction product of a combination and an unsaturated alcohol.