JPH0358104B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a positive resist material for high-energy beam lithography and a method for forming a fine resist pattern using the same. Conventionally, photoresists using visible light or near ultraviolet light have been used as pattern forming materials in technical fields such as masking and semiconductor manufacturing, and such resists have been sufficient to form openings on the order of several μm. However, in recent years, as electronic components have become lighter and larger in capacity, patterns have become finer, and it has become necessary to have openings on the order of several μm or less, particularly 1 μm or less. In order to form such fine patterns on the order of several μm or submicron, conventional photoresist materials cannot be used. Resist materials have been developed that utilize this technology, and it has become possible to form fine patterns on the submicron order. One of the most widely used resist materials is polymethacrylate (hereinafter referred to as PMMA). Although PMMA has extremely high resolution, it has low sensitivity (for example, 1300 mJ/cm ² for Mo L-ray, which is a soft X-ray,
(1×10 ⁻⁴ C/cm ² ) for electron beams, and therefore requires a long time to form a pattern. In addition, attempts have been made to use certain polyfluoroalkyl methacrylates as resist materials for high-energy rays (Japanese Patent Publication No. 55-24088
Although these resist materials have improved sensitivity, which is a drawback of PMMA, when developing certain types of substrates such as silicon, the developer may penetrate between the resist pattern and the resist pattern. The pattern may peel off or the pattern may float, resulting in poor adhesion, such as a pattern on the substrate obtained by etching becoming larger than the predetermined size, resulting in a decrease in precision. Sometimes. Such defects may not be fully recovered even by post-baking. As a result of intensive research to overcome the drawbacks of these conventional resist materials, the inventors found that the general formula () (In the formula, R ₁ represents a divalent hydrocarbon group having 1 to 6 carbon atoms, and R _f represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. fluoroalkyl methacrylate represented by ) and the general formula (): (In the formula, R ₂ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a methyl group). It has been found that this resist material is extremely excellent as a positive resist material for forming fine patterns, having high resolution and excellent adhesion. Specific examples of the compound represented by the general formula () include those represented by the following chemical formula. CH ₂ =C(CH ₃ )COOCH ₂ CF ₂ CHF ₂ CH ₂ =C(CH ₃ )COOCH ₂ CF ₂ CF ₂ CF ₂ CHF ₂ CH ₂ =C(CH ₃ )COOCH ₂ CH ₂ CF ₂ CF ₂ CF ₃ CH ₂ =C(CH ₃ )COOCH ₂ CH ₂ (CF ₂ CF ₂ ) ₂ CF _3General formula in the copolymer according to the present invention ( ) The ratio (molar ratio) of the compound represented by formula () to the compound represented by general formula () is 60:40~
It is preferable to set it to 99.9:0.1, especially 80:20 to 99.9:0.1. The adhesion of the copolymer is expressed by the general formula ()
As the proportion of the compound represented by is increased, the improvement is improved, but the sensitivity and resolution are conversely reduced. Within the above ratio range, the sensitivity and resolution do not deteriorate to the extent that they become a practical problem, and the adhesion is also within a sufficient range. In addition, the weight average molecular weight is 10000~
20,000,000, preferably 50,000 to 1,000,000 is used. The higher the molecular weight, the greater the difference in solubility in a solvent between the irradiated part and the non-irradiated part with the high-energy rays, resulting in improved sensitivity and resolution. The copolymer used in the present invention can be produced by bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. of the compound represented by the general formula () and the compound represented by the general formula () in the presence of a conventional polymerization catalyst. This can be carried out by copolymerization using any polymerization method. The degree of polymerization can be adjusted by changing the amount of polymerization catalyst added, reaction temperature, etc. A method for forming a resist film of the copolymer on the substrate can be performed by a general resist film forming method. That is, the copolymer is dissolved in a solvent such as an aliphatic ketone, an aliphatic alcohol, an aliphatic ester, an aliphatic ether, an aromatic hydrocarbon, an alicyclic ketone, a halogenated hydrocarbon, or a mixture thereof to prepare a resist solution. A resist film can be formed by coating the resist solution onto a substrate using a spin coater or the like, and then completely evaporating the solvent by air drying, heating drying, or the like. The substrate that can be used is not particularly limited, and various substrates such as a chrome mask substrate, silicon, silicon oxide, silicate glass, silicon titanium, aluminum, titanium, and gold can be used in the present invention, and any of the substrates can be used in the present invention. The resist film obtained by this method shows high adhesion. A fine resist pattern can be formed by irradiating the resist film with high-energy rays to draw a pattern and then developing it using a developer. As the high-energy beam used for pattern drawing, an electron beam, ultraviolet rays of 300 nm or less, deep ultraviolet rays, or X-rays can be used. The developing solution is a solvent in which the dissolution rate of the resist film made of the above-mentioned copolymer is significantly different between the part whose molecular weight has been reduced by irradiation with high-energy rays and the originally high-molecular-weight part which has not been irradiated with high-energy rays. used. Such solvents include (A) one or more alcohols having 2 to 8 carbon atoms, or (B) ketones such as methyl ethyl ketone and methyl isobutyl ketone, and alkyl groups having 1 to 8 carbon atoms. An organic solvent selected from the group consisting of an alkyl cellosolve in which the number of carbon atoms in the alkyl group is 1 to 5 and an alkyl carcanate in which the number of carbon atoms in the alkyl group is 1 to 5.
Examples include a mixture of a species or two or more species and one or two or more alcohols having 3 to 8 carbon atoms. Among (B), preferred are methyl isobutyl ketone, methyl cellosolve, ethyl cellulosolve, methyl cellosolve acetate or ethyl cellosolve acetate, and () is isopropyl alcohol or normal propyl alcohol. The mixing ratio of the solvents listed in () and the solvents listed in () of (B) can be appropriately selected and determined depending on the molecular weight of the copolymer and the desired sensitivity. Further, the developing temperature and time may be appropriately determined depending on the type of developer and the molecular weight of the copolymer. Finally, the desired fine resist pattern is formed by drying and baking the irradiated object after development. Next, the present invention will be explained in more detail with reference to reference examples and examples, but the present invention is not limited only to these examples. Reference Example 1 0.1 part of hydroquinone dimethyl ether as a polymerization inhibitor was added to 12 parts of methacrylic acid chloride (parts by weight, same hereinafter) and 60 parts of 2,2,3,4,4,4-hexafluorobutyl alcohol, and 90 parts of hydroquinone dimethyl ether was added as a polymerization inhibitor.
Heated at ~100°C for 3 hours. The reaction product mixture was distilled to obtain 15 parts of 2,2,3,4,4,4-hexafluorobutyl methacrylate (hereinafter referred to as HFBMA) (boiling point: 60-63°C/20mmHg). Next, 99 parts (97.8 mol) of HFBMA was added to methyl α-
Cyanoacrylate (hereinafter referred to as CN-MA)
1 part (2.2 mol parts) and 0.1 part of azobisisobutyronitrile (hereinafter referred to as AIBN) were added and mixed, and after degassing, this mixture was copolymerized at 70°C for 24 hours. Acetone was added to the reaction product mixture to make a homogeneous solution, and then petroleum ether was added for precipitation to obtain 87 parts of a copolymer. As a result of analysis by pyrolysis gas chromatography, this copolymer was confirmed to contain 2.1 mol% of CN-MA monomer units, and was copolymerized at approximately the purchasing ratio. The intrinsic viscosity (η) of this copolymer determined as a methyl ethyl ketone solution at 35°C was 1.39.The weight average molecular weight determined by gel vermi-ation chromatography was approximately 120,000.Example 1 A uniform resist solution was prepared by adding 46 parts of methyl isobutyl ketone to 4 parts of the copolymer obtained in Reference Example 1.The resist solution was spin-coated onto a silicon wafer until the film thickness was 0.8μ.
coated so that it becomes m, and then heated at 140℃
The solution was heated for 30 minutes to evaporate the solution, and then cooled to room temperature to form a resist film. Next, using a CRE-302 electron beam lithography system (manufactured by Elionix Co., Ltd.), each sample with the resist film was applied at an accelerating voltage of 20 KV (current: 1 × 10 ^-9 A).
electron beam for 0.08 seconds each (electron dose 1.9×
10 ^-9 C/cm ² ) to 125 seconds (electronic dose 2.9×10 ^-4 C/
cm ² ) and was drawn by irradiating several points. 23 of these samples
The resist pattern was developed by immersion in a mixed solvent of methyl isobutyl ketone and isopropanol (volume ratio 1.5:98.5) for 90 seconds. This thing immediately
Washed by soaking in isopropanol at 23°C for 60 seconds. The remaining film thickness of the resist film of the resist pattern obtained in the above manner was measured using a film thickness measuring device (Talystep (manufactured by Bobson, UK)). FIG. 1 shows a characteristic diagram showing the relationship between irradiation time (seconds) and residual film thickness (μm). From FIG. 1, it can be seen that the resist has a sensitivity of 1.20×10 ⁻⁶ C/cm ² and a γ value of 4.05. Next, lines and spaces of 2, 3, and 5 μm were drawn using an electron beam of 1.20×10 ⁻⁶ C/cm ² , and the resulting resist pattern was similarly developed, washed, and dried, and the resulting resist pattern was observed under a 400x optical microscope. Adhesion was evaluated. As a result, it was observed that both patterns were completely adhered to each other. Reference Example 2 The experiment was carried out in the same manner as in Example 1, except that 95 parts of 2,2,3,3-hexafluoro-1,1-dimethylpropyl methacrylate and 5 parts of ethyl α-cyanoacrylate were used as raw material monomers. I got a polymer. Example 2 An experiment was conducted in the same manner as in Example 1, except that the copolymer used was replaced with that obtained in Reference Example 2, and the developer was replaced with a mixed solvent of methyl cellosolve acetate and isopropyl alcohol (volume ratio 15:85). Summer. As a result, the sensitivity was 1.6×10 ^-5 C/cm ² and the γ value was 2.5.
It was hot. Also, the adhesion was very good. Reference example 3 Methyl methacrylate (hereinafter referred to as MMA)
2.4 parts (2.2 mol%) of methyl α-cyanoacrylate and 0.1 part of AIBN were added to 97.6 parts (97.8 mol%), mixed, and then degassed.
Copolymerization was carried out at 60°C for 24 hours. Acetone was added to the reaction product to make a homogeneous solution, which was then poured into petroleum ether, and the precipitated polymer was collected and vacuum dried to obtain 87 parts of the polymer. The intrinsic viscosity [η] of this copolymer determined as a methyl ethyl ketone solution at 35° C. was 1.0. Furthermore, the weight average molecular weight determined by gel permeation chromatography was approximately 500,000. Reference Example 4 0.1 part of AIBN was added to 100 parts of MMA, mixed, and then degassed, and the mixture was polymerized at 60° C. for 24 hours. Acetone was added to the reaction product to make a homogeneous solution, which was then poured into petroleum ether, and the precipitated polymer was collected and vacuum dried to obtain 90 parts of the polymer. The intrinsic viscosity [η] determined at 35° C. of the resulting polymer as a methyl ethyl ketone solution was 1.0.
Furthermore, the weight average molecular weight determined by gel permeation chromatography was approximately 500,000. Example 3 46 parts of methyl isobutyl ketone was added to 4 parts of the copolymer obtained in Reference Example 1 to prepare a uniform resist solution. The resist solution is applied onto a silicon wafer by spin coating to reduce the thickness of the film.
Coating to 0.8μm, then 140μm
The solution was evaporated by pre-paking at 30° C. for 30 minutes, and then cooled to room temperature to form a resist film. Next, using the same electron beam irradiation device as in Example 1, 400 square patterns with sides of 1.0 μm, 2.0 μm, 3.0 μm, and 5.0 μm were each made at an electron beam irradiation dose of 1.2×10 ^-6 C/cm ² . Electron beam lithography is performed to form individual particles, and then a mixed solution of methyl isobutyl ketone/isopropanol (volume ratio 1.5:
98.5) for 90 seconds (23℃), rinsed (60 seconds in normal heptane at 23℃), dried, and observed with an optical microscope to determine the survival rate of each pattern size (( When the number of remaining patterns/400)×100) was calculated, all the patterns remained, giving a survival rate of 100%. Comparative Examples 1 to 3 10 parts of the polymer shown in Table 1 was dissolved in 90 parts of ethyl cellosolve acetate to make a homogeneous solution, and then coated on a silicon wafer to a thickness of approximately 1 μm, and pretreated at 200°C for 30 minutes. Perform baking;
A resist film with a thickness of 0.8 μm was obtained. An experiment was conducted in the same manner as in Example 3, except that the developer (development conditions were 23°C for 120 seconds) and rinse solution were replaced with those shown in Table 1. I asked for The results are shown in Table 1.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between electron beam irradiation time and residual film thickness.

Claims (1)

[Claims] 1 General formula (): (In the formula, R ₁ represents a divalent hydrocarbon group having 1 to 6 carbon atoms, and R _f represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. fluoroalkyl methacrylate represented by ) and the general formula (): A resist material made of a copolymer with α-cyanoacrylate represented by the formula (wherein R ₂ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms). 2 The molar ratio of the fluoroalkyl methacrylate represented by the general formula () to the α-cyanoacrylate represented by the general formula () is 60:40.
The resist material according to claim 1, comprising a copolymer having a ratio of 99.9:0.1. 3 The molar ratio of the fluoroalkyl methacrylate represented by the general formula () to the α-cyanoacrylate represented by the general formula () is 80:20.
The resist material according to claim 1, comprising a copolymer having a ratio of 99.9:0.1. 4 General formula (): (In the formula, R ₁ represents a divalent hydrocarbon group having 1 to 6 carbon atoms, and R _f represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. fluoroalkyl methacrylate represented by ) and the general formula (): (In the formula, R ₂ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.) A resist film made of a copolymer obtained by copolymerizing α-cyanoacrylate represented by A method for forming a fine resist pattern, which is characterized in that it is then developed. 5 The development is an alcohol having 2 to 8 carbon atoms.
5. The method for forming a fine resist pattern according to claim 4, wherein the method is carried out using a species or a mixture of two or more species as a developer. 6. The development is carried out using ketones such as methyl ethyl ketone and methyl isobutyl ketone, alkyl cellosolves in which the alkyl group has 1 to 5 carbon atoms, and alkyl groups in which the alkyl group has 1 to 5 carbon atoms and the alkanate group has 1 to 5 carbon atoms. A mixture consisting of one or more organic solvents selected from the group consisting of 5 alkyl cellosolves and one or more alcohols having 3 to 8 carbon atoms as a developer. A method for forming a fine resist pattern according to claim 4. 7. Claim 4, wherein the development is carried out using a mixture of methyl isobutyl ketone, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, or ethyl cellosolve acetate and isopropyl alcohol or n-propyl alcohol as a developer. A method for forming fine resist patterns.