JPS61209438A - Resist - Google Patents

Abstract

PURPOSE:To obtain a resist pattern of very high contrast with X-rays having <5Angstrom dominant wavelength such as X-rays from palladium as an X-ray source by specifying the structure and mol.wt. of a polymer having a high halogen content. CONSTITUTION:A resist for forming a latent image by irradiation with X-rays having <5Angstrom dominant wavelength is made of a polymer having repeating structural units represented by formula (I) and repeating structural units represented by formula (II), 10-40wt% total halogen content and 8,000-1,500,000 number average mol.wt. expressed in terms of standard polystyrene. The pre ferred number of the repeating structural units represented by the formula (I) is 50-95%, especially 45-95% of the number of all the repeating structural units in the polymer, and the preferred number of the repeating structural units represented by the formula (II) is 5-50%, especially 5-45% of the number of all the repeating structural units in the polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a negative resist applied to lithography using X-rays of a specific wavelength.

2. Description of the Related Art In the manufacturing process of semiconductor integrated circuits, resist is considered to be an important factor that influences the degree of integration and productivity of semiconductor integrated circuits. In recent years, as the degree of integration of semiconductor integrated circuits has tended to increase, the conventional method of forming a resist image by exposing it to ultraviolet rays and developing it, and then wet-etching the substrate other than the resist image area, has changed. A shift is now being made to a method in which a resist image is formed using ionizing radiation as a radiation source, which causes less reduction in resolution due to diffraction phenomena, and is then etched by dry etching using plasma etching or reactive ion etching. With these changes in technology, electron beams, long-distance external beams, X-rays, and the like are being considered as radiation sources.

However, when electron beams are used, a decrease in resolution due to diffraction phenomena is not a problem, but since patterns are drawn over a large area by scanning a narrowly focused electron beam, productivity is poor when mass producing semiconductor circuits. There is a drawback.

On the other hand, with far ultraviolet rays, there is no problem in productivity since it can be exposed all at once, but since the wavelength is at most about 250 nm, there is a problem in that there is a limit in resolution due to the phenomenon of light diffraction.

However, xNa has the advantage that it has a short wavelength of 0.1 to 100 degrees and can be exposed all at once.

Conventionally, polyglycidyl methacrylate has been known as a resist for X-ray irradiation, but it has many drawbacks such as low sensitivity due to low X-ray absorption efficiency and lack of dry etching resistance. are doing.

Therefore, in recent years, it has been proposed to employ polymers of vinyl aromatic compounds having halogenated alkyl groups as X-ray resists.

Problems to be Solved by the Invention An object of the present invention is to optimize a resist made of a polymer of a vinyl aromatic compound having a halogenated alkyl group, thereby improving lithography using X-rays with a dominant wavelength of less than 5. It is an object of the present invention to provide a resist that has high sensitivity and contrast to X-rays, can form a fine resist image with high precision, and has high resistance to dry etching when applied to.

A means for solving the problems, that is, the present invention, is based on the following general formula (I) (wherein A r l represents an aromatic hydrocarbon group having a haloalkyl group, and R represents a hydrogen atom or an alkyl group). and a repeating structural unit represented by the following general formula (II) (wherein, Ar" represents an aromatic hydrocarbon group, and R is the same as in general formula (I)). However, the total halogen content is 10 to 40% by weight, and the number average molecular weight in terms of standard polystyrene (hereinafter simply referred to as "number average molecular weight") is 8.000 to 1,500. The present invention provides a resist for forming a latent image by irradiating xvA with a dominant wavelength of less than 5, characterized by being made of an OOO polymer.

In the repeating structural unit represented by general formula (1), A
Examples of the aromatic hydrocarbon group having a haloalkyl group represented by r' include (here, R' represents a haloalkyl group having 1 to 4 carbon atoms,
n represents an integer of 1 to 3. ), and the alkyl group for R is, for example, a methyl group.

Furthermore, in the repeating structural unit represented by the general formula (■), A r ! Examples of the aromatic hydrocarbon group represented by (herein, R2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is the same as in general formula (1)) can be mentioned.

Examples of the halogen atom constituting the haloalkyl group represented by R1 include a chlorine atom, a bromine atom, an iodine atom, and an elemental fluorine. Specific examples of such haloalkyl groups include a methyl chloride group, a methyl bromide group, and an iodine atom. Methyl chloride group, Methyl fluoride group, Ethyl chloride group, Propyl chloride group, Butyl chloride group, Methyl dichloride group, Methyl tribromide group, Methyl diiodide group, Ethyl dichloride group, Ethyl tribromide group, Examples include propyl chloride, propyl dibromide, butyl dichloride, methyl trichloride, methyl tribromide, ethyl trichloride, and ethyl tribromide.

Particularly preferred aromatic hydrocarbon groups having a haloalkyl group represented by Ar include methylphenyl chloride group, methylphenyl fluoride group, methylphenyl bromide group, methylphenyl iodide group, methylnaphthyl chloride group, and methylphenyl bromide group. Methylnaphthyl group, methylnaphthyl fluoride group, methylnaphthyl iodide group, ethylphenyl chloride group, ethylphenyl fluoride group, ethylphenyl bromide group, ethylphenyl iodide group, ethylnaphthyl fluoride group, ethylphenyl chloride group, Ethylnaphthyl bromide group, ethylnaphthyl iodide group, propylphenyl chloride group, propylphenyl fluoride group, propylphenyl bromide group, propylnaphthyl chloride group, propylnaphthyl fluoride group,
Examples include propylnaphthyl iodide, methylphenyl tribromide, methylphenyl dichloride, chloromethyltolyl, methyltolyl fluoride, methyltolyl bromide, methyltolyl iodide, and most preferably 0 -lm
- or p-chloromethylphenyl group, 0-lm- or p-bromomethylphenyl! , 2-(l-chloromethyl)naphthyl group, 2-(3-chloromethyl)naphthyl group, 1-(2-chloromethyl)naphthyl group or 1-
(4-chloromethyl)naphthyl group.

The repeating structural unit represented by the general formula (1) preferably accounts for 50 to 95 of the total number of repeating structural units in the polymer.
%, particularly preferably 45 to 95%; if it is less than 50%, the total halogen content will be low and the sensitivity to X-rays will be reduced, while if it exceeds 95%, the total halogen content will be too high and the contrast after development will be reduced. I come to do it.

Next, in the repeating structural unit represented by the general formula (n), the alkyl group represented by Rz is usually represented by the general formula (n).
It has the same number of carbon atoms as R' in 1), specifically methyl group, ethyl group, n-propyl group, 1
so-propyl group, n-butyl group, 5ec-butyl group,
Examples include tert-butyl group, in particular Ar
It is preferable that 2 is a phenyl group, a naphthyl group, a cumenyl group, a butylphenyl group, a methylnaphthyl group, an ethylnaphthyl group, a propylnaphthyl group or a butylnaphthyl group, and most preferably a phenyl group, a naphthyl group or a tolyl group.

The repeating structural unit represented by general formula (II) preferably accounts for 5 to 50%, particularly preferably 5 to 45%, of the total number of repeating structural units in the polymer. If it is less than 5%, the number of repeating structural units represented by general formula (1) becomes too large, and the total halogen content tends to increase too much.
The number of alkyl groups represented by R2 decreases, and a crosslinking reaction due to hydrogen atom abstraction from the alkyl group becomes difficult to occur during X-ray irradiation. On the other hand, if it exceeds 50%, the general formula (r)
This is not preferable since the number of repeating structural units represented by is reduced.

Other repeating structural units that can form a polymer together with the repeating structural units represented by general formulas (1) and (If) include ethyl (meth)acrylate unit, (
Nisterurium (meth)acrylate units such as butyl meth)acrylate units and glycidyl (meth)acrylate units;
Aromatic vinyl compound units other than those mentioned above such as 2-vinylpyridine units and 4-vinylpyridine units, conjugated diene compound units such as butadiene units and isoprene units, unsaturated ethylene compound units such as maleic anhydride units and vinyl acetate units. I can give an example.

For sensitivity to X-rays and resistance to dry etching, these repeating structural units preferably account for less than 50%, especially less than 20%, of the total number of repeating structural units in the copolymer.

The total halogen content in the polymer in the resist of the present invention is 10 to 40% by weight, preferably 14 to 40% by weight. If the total halogen content is less than 10% by weight, XL
The absorption efficiency for A decreases, and on the other hand, if it exceeds 25% by weight, the contrast decreases and when fine resist patterns are formed, undeveloped areas and bridges occur between patterns, resulting in a decrease in resolution.

Regarding the molecular weight of the polymer in the resist of the present invention, a higher molecular weight is preferable in order to maintain the performance of high sensitivity to X-rays, whereas a lower molecular weight is preferable from the viewpoint of handling for forming a coating film as a resist. is preferred. The number average molecular weight range that satisfies these two contradictory requirements is 8.000 to 1.
,500,000, particularly preferably 10,000 to 1
,000,000. If the number average molecular weight is less than 8,000, the sensitivity to X-rays is low;
When it exceeds 0, swelling during development increases and the resolution of the formed resist pattern decreases.

Furthermore, the molecular weight distribution of the polymer in the resist of the present invention (
Weight average molecular weight/number average molecular weight is preferably 1.5 or less, particularly preferably 1.3 or less, and even more preferably 1.1.
This further improves the resolution.

As mentioned above, the polymer constituting the resist of the present invention is
The polymer has a specific amount of repeating structural units represented by the general formulas (I) and (n), has a high halogen content, and has a specific molecular weight. is 3 or more and less than 5 people
It is highly sensitive to lines and can produce good contrast after development. As described above, the resist of the present invention is for X-rays with a wavelength of less than 5 Å, and even if the resist of the present invention is applied to X-rays of 5 Å or more, it is a resist with particularly high sensitivity and high contrast to X-rays. Must not be.

The polymer used in the resist of the present invention is, for example, the following (1
) or (2).

(1) Monomer represented by general formula (1) (wherein R is the same as in general formula (1), R3-R7 are the same or different and represent a hydrogen atom, an alkyl group, a haloalkyl group, R3 -R7 is a haloalkyl group) and a monomer represented by general formula (IV) (wherein R is the same as in general formula (1), R11 to R'
1 is the same or different and is a hydrogen atom or an alkyl group. ) can be obtained by polymerizing monomers containing the monomers shown.

In the above general formula, examples of the monomer represented by general formula (II[) include O-chloromethylstyrene, m-
Chloromethylstyrene, p-chloromethylstyrene, 0
-chloromethyl-α-methylstyrene, m-chloromethyl-α-methylstyrene, p-chloromethyl-α-methylstyrene, 0-chloromethyl-p-methylstyrene,
p-chloromethyl-〇-methylstyrene, 0-bromomethylstyrene, m-bromomethylstyrene, p-bromomethylstyrene, m-chloroethylstyrene, m-chloroethyl-α-methylstyrene, p-chloropropylstyrene, p -chloropropyl-α-methylstyrene, 4
-chloromethyl-1-vinylnaphthalene, 2-chloromethyl-1-vinylnaphthalene, 5-chloromethyl-1-
Examples include vinylnaphthalene and 1-chloromethyl-2-vinylnaphthalene, and two or more of these may be used in combination.

Further, examples of the monomer represented by the general formula (IV) include 0-methylstyrene, m-methylstyrene, p-methylstyrene, 0-ethylstyrene, m-ethylstyrene, p-ethylstyrene, m- Propylstyrene, p-
Methoxystyrene, α.

m-dimethylstyrene, 2,4-dimethylstyrene, p
-methoxystyrene, p-methyl-α-methylstyrene, p-ethyl-α-methylstyrene, styrene, α-vinylnaphthalene, β-vinylnaphthalene, etc., and two or more of these monomers are used in combination You may.

As a polymerization initiator for polymerizing these monomers,
For example, radical polymerization initiators such as 4,4'-azobisisobutyronitrile, benzoyl peroxide, and lauroyl peroxide can be used.

The amount of radical polymerization initiator used is usually monomer 1, O
The amount is 0.01 to 10 parts by weight relative to 0 parts by weight. Also,
Polymerization solvents include aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and tetralin, alicyclic hydrocarbons such as cyclohexane and decalin, hexane,
Aliphatic hydrocarbons such as heptane and octane, or mixtures thereof are preferably used. These polymerization solvents are usually used so that the monomer concentration is 1 to 50% by weight. The polymerization temperature is not particularly limited, but in view of the economic efficiency of the reaction, it is generally above room temperature, and the upper limit is below the boiling point of the solvent. Suitable polymerization temperature is 40°C to 100°C
It is.

(2) Monomer represented by general formula (IV) and styrene, α
- It can be obtained by polymerizing a monomer mixture containing methylstyrene, vinylnaphthalene, α-methylvinylnaphthalene, etc., and then haloalkylating the benzene ring of the resulting polymer.

As a polymerization initiator for polymerizing these monomers,
Anionic polymerization initiators such as charge transfer complexes such as lithium naphthalene, sodium naphthalene, potassium naphthalene, organometallic compounds such as n-butyllithium, 5ec-butyllithium, benzylpotassium, cumylpotassium, diethylzinc, dibutylmagnesium;
The same radical polymerization initiator as in the method of ) can be used. The amount of anionic polymerization initiator used is usually 1 monomer
The amount of the radical polymerization initiator is 2 x 10-' to 5 x 10-2 mol per mole, and the amount of the radical polymerization initiator used is the same as in the method (1). Also, the polymerization solvent and polymerization temperature (1)
The same solvents and temperatures as in the method can be mentioned.

In order to haloalkylate the polymer, the polymer is treated with chloromethyl methyl ether, chloromethyl ethyl ether, etc. in the presence of a free sol Tarafluor catalyst such as boron trifluoride, zinc chloride, tetrachloride, titanium tetrachloride, etc. Haloalkylation is carried out using a haloalkyl ether, and then a halogen exchange reaction is carried out using potassium bromide, potassium iodide, sodium bromide, sodium iodide, etc. in the presence of a quaternary ammonium salt or phosphonium salt, if necessary.

The haloalkyl ether used in haloalkylation can also be used as a solvent for the reaction system, and is usually used so that the concentration of the polymer is 1 to 50% by weight. that time,
It may be diluted with a solvent that is inert towards haloalkylation. Further, the amount of the free sol fluorine catalyst used is generally 0.01 to 1 mole per mole of monomer units constituting the polymer. Further, the temperature during the haloalkylation reaction is preferably -10 to 40°C.

After the haloalkylation is completed, the catalyst is usually decomposed to stop the reaction, and a common method for this is to add water to the reaction system. When adding water to the reaction system, water can be mixed with an organic solvent such as dioxane before being added.

Examples of monomers copolymerizable with the above monomers in methods (1) and (2) include (meth)ethyl acrylate, butyl (meth)acrylate, glycidyl (meth)acrylate, etc. meth)acrylic acid ester, 2-
Examples include aromatic vinyl compounds other than those mentioned above such as vinylpyridine and 4-vinylpyridine, conjugated diene compounds such as butadiene and isoprene, and unsaturated ethylene compounds such as maleic anhydride and vinyl acetate.

Additives such as stabilizers can be added to the resist of the present invention. Examples of stabilizers include hydroquinone, methoxyphenol, pt-butylcatechol, 2.2'
- hydroxyaromatic compounds such as methylenebis(6-t-butyl-4-ethylphenol), benzoquinone,
Quinones such as p-toluquinone and p-xyloquinone, amines such as phenyl-α-naphthylamine, p,p'-diphenylphenylenediamine, dilaurylthiodipropionate, 4,4-thiobis(6-t-butyl- 3
2-(3,5-di-t-butyl-4-hydroxyanilino)-4,6-bis(N- Examples include sulfur compounds such as octylthio)-δ-triazine. The amount of these additions is usually 0.3
It is about 5 to 5% by weight.

The X-ray resist of the present invention is usually handled in the form of a solution in a petroleum fraction such as xylene, ethylbenzene, toluene, etc., a chlorinated solvent such as trichloroethane, tetrachloroethane, or a polar solvent such as methyl isobutyl ketone or cellosolve acetate. In this case, the resist concentration is
- Although it cannot be generally specified, it is determined depending on the film thickness when applied, and is generally used as a 5 to 30% by weight solution.

Example Next, the present invention will be explained in more detail with reference to Examples.

Example 1 The inside of a glass ampoule with an internal volume of 100 mn was replaced with nitrogen,
15.3 g of cyclohexane under nitrogen flow.

11.8 g of p-methylstyrene, 15.6 g of p-chloromethylstyrene and 0.0 g of azobisisobutyronitrile.
01g was added and the ampoule was sealed.

The ampoule was then immersed in a hot water bath and shaken.

After shaking for 12 hours, it was taken out and the polymerization rate was measured and found to be 60%.

This reaction solution was poured into methanol containing 2,6-di-t-butyl-p-cresol, and the polymer was recovered.
It was dried under reduced pressure at ℃ for 16 hours. The number average molecular weight of the thus obtained polymer measured by gel permeation chromatography (hereinafter referred to as rGPCJ) was 20×10′, and the molecular weight distribution was 2.5.

Determination of the chlorine content of the polymer obtained above 1
It was 4.3%. In addition, when the IH nuclear magnetic resonance spectrum (hereinafter simply referred to as r'H-NMRJ) of the obtained polymer was obtained, absorption of protons of the methyl chloride group attached to the aromatic ring was observed at δ = 4.5 ppn+. It was found that the proportions of p-chloromethylstyrene repeating structural units and p-methylstyrene repeating structural units in all repeating structural units were 55% and 45%, respectively.

The product obtained above was dissolved in xylene to make a solution with a solid content concentration of 8.8% by weight, and this solution was
Spin coating onto a silicon wafer with a thermally oxidized layer of
After heat treatment in a circulating clean oven at 90° C. for 30 minutes, the film thickness was measured, and it was found that a coating film of 098 μm was formed on the wafer. This wafer was exposed to X-rays (main wavelength: Lα, 4.4
After irradiation through a 0.7 μm mask using an irradiation device, the film was developed with cellosolve acetate for 1 minute, and rinsed with a mixed solution of methyl ethyl ketone/isopropanol (1:1) for 1 minute.

As a result, with irradiation energy of 55 mJ/cd, 0.8μ
It was found that the pattern of m can be resolved faithfully to the mask.

Furthermore, this pattern is etched using CF as an etching gas using a parallel plate type dry etching device.

10, (9515 volume ratio) using mixed gas, output 100
When dry etching resistance was investigated by processing with W and a gas pressure of 10 Pa, the etching rate of the resist was 0.35 times that of polymethyl methacrylate, and good dry etching resistance results were obtained. Ta.

Comparative Example 1 9.4 g of p-methylstyrene and 3.1 g of p-chloromethylstyrene were polymerized in the same manner as in Example 1. 1
After shaking for 2 hours, it was taken out and the polymerization rate was measured and found to be 65%.

The number average molecular weight was determined in the same manner as in Example 1.
It was 21 x 10'. It was also found that the chlorine content was 5.1% by weight, and the proportions of p-chloromethylstyrene repeating structural units and p-methylstyrene repeating structural units among all repeating structural units were 18% and 82%, respectively. Ta.

Using the polymer obtained above, a coating film was formed on a silicon wafer under the same conditions as in Example 1, and when irradiated with XvA using palladium as a radiation source, the result was 160 mJ/c+aO
We were finally able to resolve a 1.0 μm pattern using the X-ray irradiation energy.

Example 2 A magnetic stirrer was placed in a four-eye round bottom flask with an internal volume of 21,
The system was replaced with nitrogen, and 320% of cyclohexane was added under a nitrogen stream.
After adding g and 31.2 g of styrene to make the system a homogeneous solution, the internal temperature was maintained at 60°C. Next, 015 ml of a 0.50 mol/l cyclohexane solution of n-butyllithium was added to this solution under a nitrogen stream to initiate polymerization.

The polymerization rate reached 99% after 60 minutes. The reaction solution was poured into methanol to recover the polymer, which was dried under reduced pressure at 40° C. for 16 hours.

14.0 g of the polymer thus obtained and 144 ml of chloromethyl methyl ether were placed in a 1 liter round bottom flask purged with nitrogen, and stirred with a magnetic stirrer to form a uniform solution.

Next, put it in a water bath and stir while keeping the internal temperature at 0℃ for 2 hours.
．． 0 mol/l tin tetrachloride solution in chloromethyl methyl ether for 15 minutes.6. '1 drop of Im was added. Furthermore, 120
After continuing stirring for a minute, 50 ml of a mixed solution of dioxane/water = 1/1 (volume ratio) was added to stop the reaction.

Next, the reaction solution was poured into methanol to recover the polymer, which was further washed with methanol and dried under reduced pressure at 40° C. for 16 hours. The number average molecular weight of the thus obtained polymer measured by GPC was 30×10′, and the molecular weight distribution was 1.2. In addition, the obtained polymer's
When H-NMR was analyzed, there was no change in the peak derived from the hydrogen of the methine group around δ = 1.8 ppm observed in the raw material polymer, and the peak derived from the hydrogen of the methine group around δ = 4.5 ppm was observed. A new peak derived from hydrogen was observed. This revealed that a chloromethyl group was introduced into the benzene ring of the polymer. -I H-NM
When R was analyzed and the chloromethylation rate of the benzene ring of the polymer was measured, it was 62%.

Using the polymer obtained above, a coating film was formed on a silicon wafer under the same conditions as in Example 1, and irradiated with X-rays using palladium as a radiation source.
A 0.6 μm resist pattern was resolved faithfully to the mask with an irradiation energy of .

When the resist etching rate of this pattern was examined in the same manner as in Example 1, the etching rate was 0.36 times that of polymethyl methacrylate, and good dry etching resistance was obtained.

Effects of the Invention The resist of the present invention has a high halogen content and, in combination with its specific structure and molecular weight, can be used for X-rays with a dominant wavelength in the range of less than 5, such as palladium (Lα; 4.4), X using rhodium (Lα; 4.6 people) as an X-ray source
It insolubilizes against lines with high sensitivity like conventional resists,
Moreover, it is possible to obtain a resist pattern with extremely superior contrast compared to conventional resist patterns.

Therefore, the present invention can provide a resist that is highly sensitive, highly resistant to dry etching, has significantly improved resolution, and provides a resist pattern with excellent contrast.

Claims (1)

[Claims] (1) The following general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・・・・・(
I ) (wherein, Ar^1 represents an aromatic hydrocarbon group having a haloalkyl group, and R represents a hydrogen atom or an alkyl group), and the following general formula (I
I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・・・・(
II) (In the formula, Ar^2 represents an aromatic hydrocarbon group, and R is the same as in general formula (I).) It has a repeating structural unit represented by the formula (I), and has a total halogen content of 10 to 40% by weight. and
Standard polystyrene equivalent number average molecular weight is 8,000 to 1,
500,000. A resist for forming a latent image by irradiating X-rays with a dominant wavelength of less than 5 Å.