JPH0358102B2 - - 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, so high-energy rays such as far ultraviolet rays with shorter wavelengths, X-rays, and electron beams are 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 polymethyl methacrylate (hereinafter referred to as PMMA). Although PMMA has extremely high resolution, it has low sensitivity (for example, 1300 mJ/L for Mo L-ray, which is a soft X-ray).
cm ² , 1×10 ^-4 C/cm ² for electron beam), therefore,
It takes 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. Problems caused by poor adhesion, such as peeling off or lifting of the pattern, resulting in the dimensions of the pattern on the substrate obtained by etching becoming larger than the specified dimensions, resulting in a decrease in precision. There is a point. In some cases, such defects cannot be sufficiently recovered even by post-baking. The present inventors have conducted intensive research to overcome the drawbacks of these conventional resist materials, and as a result, the general formula (): (In the formula, R ₁ represents a group in which at least one methyl group is substituted with a halogen atom, a halogen atom, or a hydrogen atom, and R ₂ represents a 2 having 1 to 6 carbon atoms.
a valent hydrocarbon group, _Rf represents an alkyl group having 1 to 15 carbon atoms substituted with at least one hydrogen atom) and a fluoroalkyl acrylate represented by the general formula (): (In the formula, R ₃ represents a hydrogen atom, a methyl group, or an ethyl group) A copolymer obtained by copolymerizing acrylic acids has high sensitivity and resolution, and has excellent adhesion. It has been found that this material is extremely excellent as a positive resist material for forming fine patterns. 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. Further, the copolymer has a weight average molecular weight of 10,000 to 2,000,000, preferably 50,000 to 1,000,000.
range is used. As the molecular weight becomes higher, the difference in dissolution rate in the solvent between the irradiated part and the non-irradiated part becomes larger, and the sensitivity and resolution improve. 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 conventional methods such as changing the amount of polymerization catalyst added and the reaction temperature. 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 nitride, aluminum, titanium, and gold can be used in the present invention, and the present invention can be applied to any of the substrates. 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 a mixture of two or more alcohols having 2 to 8 carbon atoms; or (B) () one or more alcohols having 2 to 8 carbon atoms. Examples include a mixture consisting of a mixture and () a mixture of one or more hydrocarbons having 5 to 11 carbon atoms, or water. Among (B), the preferred ones are:
() is isopropyl alcohol or normal propyl alcohol, () is hexane,
Heptane, octane, nonane, benzene, cyclohexane or water. Furthermore, the hydrocarbons referred to in parentheses in (B) include aliphatic hydrocarbons and aromatic hydrocarbons. 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, Examples, and Comparative Examples, but the present invention is not limited to these Examples. Reference Example 1 0.1 part of hydroquinone dimethyl ether was added as a polymerization inhibitor to 12 parts of methacrylic acid chloride (parts by weight, same below) and 60 parts of 2,2,3,4,4,4-hexafluorobutyl alcohol,
Heated at 90-100°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 (97.1 mol%) of HFBMA, 1 part (2.9 mol%) of methacrylic acid (hereinafter referred to as MA) and azobisisobutyronitrile (hereinafter referred to as AIBN
After adding and mixing 0.1 part of 100% acetate (20%) and then degassing, the mixture was copolymerized at 60° C. for 24 hours.
Acetone was added to the reaction product mixture to make a homogeneous solution, and then petroleum ether was added to precipitate it, yielding 68 parts of a copolymer. Analysis of this copolymer by pyrolysis gas chromatography revealed that the monomer unit of MA was
It was confirmed that the content was 3.0 mol%, and copolymerization occurred at approximately the charging ratio. Intrinsic viscosity [η] determined at 35℃ using this copolymer as a methyl ethyl ketone solution
was 1.13. The weight average molecular weight determined by gel permeation chromatography is approximately
It was 1100000. Reference Examples 2 to 4 Using 100 parts of a monomer mixture of HFBMA and MA in the proportions shown in Table 1, the amount of AIBN used was
A copolymer was obtained by carrying out an experiment in the same manner as in Reference Example 1, except that the procedures were as shown in the table. Table 1 shows the intrinsic viscosity and weight average molecular weight of the obtained copolymer, which were measured in the same manner as in Reference Example 1.

[Table] Reference example 5 2,2,3,3-tetrafluoro-1,1-dimethylpropyl methacrylate (4FiPMA)
An experiment was carried out in the same manner as in Reference Example 1, except that 100 parts of a monomer mixture consisting of 97.3 mol% MA and 2.7 mol% MA was used to obtain a copolymer. The intrinsic viscosity [η] of the obtained copolymer was measured in the same manner as in Reference Example 1 and was 1.12. Reference example 6 97.1 mol% of HFBMA and 2.9 mol% of acrylic acid
A copolymer was obtained by carrying out an experiment in the same manner as in Reference Example 1, except that 100 parts of a monomer mixture consisting of mol % was used. The intrinsic viscosity [η] of the obtained copolymer was measured in the same manner as in Reference Example 1 and was 0.89. Example 1 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 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 solvent was evaporated by heating for 30 minutes, and then cooled to room temperature to form a resist film. Next, using an ERE-302 electron beam lithography system (manufactured by Elionix Co., Ltd.), each sample having the resist film was applied at an accelerating voltage of 20 kV (current density: 1×
10 ^-9 A/cm ² ) electron beam was applied stepwise for irradiation time of 0.08 seconds (electron dose 2.9 x 10 ^-7 C/cm ² ) to 125 seconds (electron dose 2.9 x 10 ^-4 C/cm ² ). I irradiated several points and drew it. These samples were mixed with isopropyl alcohol-n-heptane mixed solvent (volume ratio 25:
10) for 90 seconds to develop the resist pattern. This material was immediately washed by immersion in normal heptane at 23° C. for 60 seconds, and then dried. 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)). Figure 1 shows the electron beam irradiation time (seconds) and the remaining film thickness (μ
A characteristic diagram showing the relationship of m) is shown. From FIG. 1, it can be seen that the resist has a sensitivity of 1.9×10 ⁻⁶ C/cm ² and a γ value of 1.4. Next, lines and spaces of 2, 3, and 5 μm were drawn using an electron beam of 1.9×10 ^-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. Examples 2 to 7 Experiments were conducted in the same manner as in Example 1, except that the copolymer, developer, and cleaning solution were replaced with those shown in Table 2. Table 2 shows the sensitivity, γ value, and adhesion of each resist film obtained. In Table 2, the adhesion of the resist film was measured using an electron beam with an irradiation dose corresponding to the sensitivity of each resist film.
The resist pattern was drawn at 3 and 5 μm, developed and washed with each developer and cleaning solution, and then dried, and the resulting resist pattern was observed and evaluated using an optical microscope at 400x magnification. is as follows. ×: Peeling was observed in any part. △: Any slight lifting was observed. ○: In both cases, complete adhesion was observed. Comparative Example 1 Instead of the copolymer obtained in Reference Example 1
Using a homologous polymer of HFBMA ([η] 0.8, weight average molecular weight approximately 800000), the film thickness of the resist film was 0.5μ.
Example 1, except that the coating was carried out so that it became m, and the developing solution and cleaning solution were replaced with those shown in Table 2.
The experiment was conducted in the same manner. Table 2 shows the sensitivity, γ value, and adhesion of the resist film obtained.

[Table] Reference example 7 Methyl methacrylate (hereinafter referred to as MMA)
22 parts (25 mol%) of methacrylic acid and 0.1 part of AIBN were added to 78 parts (75 mol%) and mixed, and after degassing, this mixture was copolymerized 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 83 parts of the polymer. The resulting polymer was dissolved in dimethylformamide and analyzed by neutralization titration with potassium hydroxide, which confirmed that it contained 25 mol% of methacrylic acid monomer units and was copolymerized at approximately the same charging ratio. did. The intrinsic viscosity [η] of this copolymer was determined at 35°C as a solution in methyl ethyl ketone.
It was 1.1. In addition, the weight average molecular weight determined by gel permeation chromatography is approximately
It was 600,000. Reference Example 8 0.1 part of AIBN was added to 100 parts of MMA and mixed. After degassing, this 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] of the obtained polymer was determined to be 1.0 at 35°C as a solution in methyl ethyl ketone.
Furthermore, the weight average molecular weight determined by gel permeation chromatography was approximately 500,000. Example 8 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 thickness of the film is increased by spin coating the resist solution onto a silicon wafer.
Coating to 0.8μm, then 140μm
C. for 30 minutes to evaporate the solvent, and then cooled to room temperature to form a resist film. Next, using the same electron beam irradiation equipment 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 formed at an electron beam irradiation dose of 2.5×10 ^-6 C/cm ² . Electron beam lithography is performed to form individual particles, and then the isopropyl alcohol/n-heptane mixed solution (volume ratio 25:10) is used.
(23℃), rinsed (60 seconds in n-heptane at 23℃), dried, and observed with an optical microscope to determine the survival rate ((residual When the number of patterns that had been removed/400) x 100) was calculated, all the patterns remained, giving a survival rate of 100%. Examples 9 to 13 Experiments were conducted in the same manner as in Example 8, except that the copolymer, developer, rinse solution, and electron beam irradiation amount were changed to those shown in Table 3. The survival rate for each pattern was determined. The results are shown in Table 3. Comparative Example 2 Using the homologous polymer of HFBMA used in Comparative Example 1 ([η] 0.8, weight average molecular weight approximately 800000),
A homogeneous solution was prepared by adding 46 parts of methyl isobutyl ketone to 4 parts of this polymer. The resist solution was coated onto a silicon wafer by spin coating to a film thickness of 0.8 μm, and then prebaked at 140°C for 30 minutes to evaporate the solvent, cooled to room temperature, and coated with the resist solution. A film was formed. Next, an experiment was conducted in the same manner as in Example 8, except that the developer, rinse solution, and electron beam irradiation amount were changed to those listed in Table 3, and the survival rate for each pattern of each size was determined. The results are shown in Table 3. Comparative Examples 3 to 4 10 parts of the polymer shown in Table 3 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. The experiment was conducted in the same manner as in Example 8, except that the developer (development conditions were 23°C for 120 seconds) and rinse liquid were replaced with those shown in Table 3. I asked for The results are shown in Table 3.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the electron beam irradiation time and the remaining film thickness in the resist film obtained in Example 1.

Claims (1)

[Claims] 1 General formula (): (In the formula, R ₁ represents a methyl group, R ₂ has 1 carbon number
Represents a divalent hydrocarbon group having ~6 atoms, R _f
represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is replaced with a fluorine atom) and a fluoroalkyl acrylate represented by the general formula (): (In the formula, R ₃ represents a hydrogen atom, a methyl group, or an ethyl group.) A resist material made of a copolymer with an acrylic acid. 2 The molar ratio of the fluoroalkyl acrylate represented by the general formula () to the acrylic acid represented by the general formula () is 60:40 to 99.9:0.1.
The resist material according to claim 1, comprising a copolymer. 3 The molar ratio of the fluoroalkyl acrylate represented by the general formula () to the acrylic acid represented by the general formula () is 80:20 to 99.9:0.1.
The resist material according to claim 1, comprising a copolymer. 4 The weight average molecular weight of the copolymer is from 10,000 to
20000000. The resist material according to claim 1, 2 or 3. 5 The weight average molecular weight of the copolymer is 50,000 to 50,000.
10000000. The resist material according to claim 1, 2 or 3. 6 General formula (): (In the formula, R ₁ represents a methyl group, R ₂ has 1 carbon number
Represents a divalent hydrocarbon group having ~6 atoms, R _f
represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is replaced with a fluorine atom) and a fluoroalkyl acrylate represented by the general formula (): (In the formula, R ₃ represents a hydrogen atom, a methyl group, or an ethyl group.) A resist film made of a copolymer obtained by copolymerizing acrylic acids represented by R 3 is irradiated with high-energy rays and then developed. Features a method for forming fine resist patterns. 7. The developing agent is an alcohol having 2 to 8 carbon atoms.
7. The method for forming a fine resist pattern according to claim 6, wherein the method is carried out using a species or a mixture of two or more species as a developer. 8. A mixture in which the development is made of () one or a mixture of two or more alcohols having 2 to 8 carbon atoms and () a mixture of one or more hydrocarbons having 5 to 11 carbon atoms or water. 7. A method for forming a fine resist pattern according to claim 6, which is carried out using as a developer. 9 The development is performed using () isopropyl alcohol or n-propyl alcohol and () hexane, heptane, octane, nonane,
7. The method for forming a fine resist pattern according to claim 6, wherein the method is carried out using a mixture of benzene, cyclohexane, or water as a developer.