JPH0721055B2 - Copolymer of Sulfur Dioxide and Nuclear Substituted Styrene Derivative - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel copolymer of sulfur dioxide and a styrene derivative. More specifically, it relates to the copolymer which is sensitive to light, electron beams or X-rays, has a high resolution and is excellent in dry etching resistance, and is useful as a resist material. If you specify the wavelength of light,
It is suitable when using deep UV light of 300 nm.

[0002]

2. Description of the Related Art In recent years, the degree of integration of semiconductor elements and integrated circuits has been remarkably improved, and accordingly, the demand for fine processing by a lithography technique has become stricter year by year. In order to meet this requirement, there is a demand for the development of a resist material having high sensitivity, high resolution, and resistance to dry etching, which is sensitive in the deep ultraviolet region. Various proposals have already been made to meet this requirement, and poly (pt- is a chemically amplified resist as a highly sensitive resist.
butoxycarbonyloxystyrene) USP 4,491,628 Jan 1,1985
And poly (pt-butoxycarbonyloxystyrene sulfone) EP 33
0,386 (priority US 160,368) is known.

Conventional chemically amplified positive resists such as p
oly (pt-butoxycarbonyloxystyrene), poly (pt-butoxy
A resist containing a hydroxystyrene derivative such as carbonyloxystyrene sulfone) as a structural unit is exposed to light, and polyhydroxystyrene produced by deprotection by an acid generated by baking after exposure is usually used at the time of development, TMAH (tetramethylammonium human oxide). ) A positive image is formed by developing with an aqueous solution, but at this time, there is a problem in that the unexposed portion is partially dissolved to cause film reduction or the pattern becomes thin and peels from the substrate.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The inventors of the present invention have conducted diligent research to find a resist material which does not have the drawbacks possessed by the conventional chemically amplified positive type resist as described above.
As a result, a binary copolymer of sulfur dioxide represented by the following (formula 3) and a specific nuclear-substituted styrene derivative or a sulfur dioxide represented by (formula 4) and the specific two types of nuclear-substituted styrene derivatives It was found that a terpolymer can solve the above-mentioned problems, and the present invention was completed based on this finding. That is, the copolymer of the present invention solves the above-mentioned problems of the known art, has an excellent ability to inhibit dissolution against alkali, and when used as a resist, causes film loss in unexposed areas during TMAH development. Almost no generation occurs, and the adhesiveness with the substrate is excellent, and even if no special substrate treatment is performed, peeling does not occur, and a submicron fine pattern can be easily obtained.

As is clear from the above description, the objects of the present invention are as follows. That is, the first is to provide a novel copolymer, and the second is a copolymer which is useful as a resist material sensitive to light, electron beams or X-rays, which has high sensitivity, high resolution and excellent dry etching resistance. It is to provide a coalesce. No. 3 has an excellent ability to prevent dissolution against alkali, hardly causes film loss during alkali development, and has excellent substrate adhesion, so that submicron fine patterns can be easily obtained without any special substrate treatment. It is to provide a resist material that can be used.
The present invention is a copolymer of sulfur dioxide and a styrene derivative, and by using the monomer of the present application, that is, an alkylated styrene derivative as a structural unit of the copolymer, the solubility resistance of the copolymer to alkali is improved and a resist is obtained. Enabled the practical application of.

[0006]

The present invention includes the following (1).
To (3). (1) 1 to 50 mol% of a structural unit represented by —SO ₂ — and 50 to 99 mol% of a nuclear-substituted styrene derivative represented by the following (formula 1) as a structural unit, and is a linear compound and has a number average. A binary copolymer of sulfur dioxide having a molecular weight of 2.00 to 2.000.00 and having the following structural formula (formula 3) and a nucleus-substituted styrene derivative.

[Chemical 6] Here, R ¹ and R ² are H at the meta position, an alkyl group having 1 to 4 carbon atoms or [Si (CH ₃ ) ₂ ] _y CH ₃ , and y is an integer of 1 to 3. Further, R ¹ and R ² may be the same or different. R ³ is in para position (CH ₂ )
m, m = 0 or m = 1 to 3 represents an alkylene group,
X represents OH, a tertiary butoxy group or a tertiary butoxycarbonyloxy group. However, the case where R ¹ and R ² are H and m = 0 is excluded.

[Chemical 7] Here, the meanings of R ¹ , R ² , R ³ and X are the same as in the case of (Formula 1), p is an arbitrary integer from 1 to 99, and n is 1
It is an integer of 0 or more and 10,000 or less. (2) 1 to 50 mol% of a structural unit represented by —SO ₂ —, 15 to 98 mol% of a nucleus-substituted styrene derivative represented by the following (formula 1) and 1 to 84 mol% of the following (formula 2) A linear compound having a number average molecular weight of 2,000 to 2,000, which is a structural unit of the nuclear-substituted styrene derivative shown below.
A terpolymer of sulfur dioxide having a structural formula of (Formula 4) below at 000 and a nucleus-substituted styrene derivative.

[Chemical 8] Here, R ¹ and R ² are H at the meta position, an alkyl group having 1 to 4 carbon atoms or [Si (CH ₃ ) ₂ ] _y CH ₃ , and y is an integer of 1 to 3. Further, R ¹ and R ² may be the same or different. R ³ is in para position (CH ₂ )
m, m = 0 or m = 1 to 3 represents an alkylene group,
X represents OH, a tertiary butoxy group or a tertiary butoxycarbonyloxy group. However, the case where R ¹ and R ² are H and m = 0 is excluded.

[Chemical 9] Here, X represents OH, a tertiary butoxy group or a tertiary butoxycarbonyloxy group.

[Chemical 10] Here, the meanings of R ¹ , R ² , R ³ and X are the same as in the case of (Formula 1), p and q are 1 to 10, and l and m are the molar fractions of the copolymer. Corresponding, l is 15-9
9 mol%, m is 1 to 85 mol%, (p + q) is 50 to 9
It is 9 mol%, and each structural unit is irregularly distributed in the copolymer to form the main chain of the copolymer. n is 5
It is an integer not less than 5,000. (3) A resist material containing the copolymer according to (1) or (2) as an active ingredient.

The structure and effects of the present invention will be described in detail below. The binary copolymer of sulfur dioxide and the nucleus-substituted styrene derivative of the present invention is represented by (Formula 3).

[Chemical 11] Here, R ¹ and R ² are H, CH ₃ , CH ₂ C in the meta position.
H _3, isopropyl, tert-butyl, etc. C1-C
4 alkyl group or [Si (CH ₃ ) ₂ ] _y CH ₃ and y represents 1 to 3. R ¹ and R ² may be the same or different. R ³ is in para position (CH ₂ ) m, m = 0
Represents the alkylene group of ~ 3. X represents OH, tertiary butoxy or tertiary butoxycarbonyloxy. However, the case where R ¹ and R ² are H and m = 0 is excluded. p represents the molar ratio of the nucleus-substituted styrene derivative and SO _2, and represents an arbitrary value of 1 to 99. When p is 1, it represents an alternating copolymer.

The terpolymer of sulfur dioxide and the nucleus-substituted styrene derivative of the present invention is represented by the formula (4).

[Chemical 12] Here, R ¹ , R ² , R ³ and X are the same as in the case of (Equation 3).

Specific examples of the nucleus-substituted styrene derivative according to the present invention include the following formula (1): m, m-dimethyl-p-hydroxystyrene m-methyl-p-tert-butoxystyrene m-tert-butyl-p -Tert-butoxystyrene m-methyl-p-tert-butoxycarbonyloxystyrene m-trimethylsilyl-p-tert-butoxystyrene m-trimethylsilyl-p-tert-butoxycarbonyloxystyrene p-tert-butoxycarbonioxymethylstyrene p -Tert-butoxycarbonioxyethylstyrene p-tert-butoxyethylstyrene and the like.

As an example of the formula (2), p-hydroxystyrene, p-tert-butoxystyrene, p-tert-butoxycarbonyloxystyrene and the like can be mentioned. The object of the present invention can be achieved by including at least 15 mol% of the structural unit represented by the formula (1) in the copolymer.

The copolymer of the present invention can be obtained by a known radical polymerization method or redox polymerization method. That is, the monomers (1 to 2 types) shown in (Formula 1) and (Formula 2) and the reaction initiator (azobisisobutyronitrile, tert-butylhydroperoxide, di-
(tert-butyl hydroperoxide, etc.) in a pressure resistant reactor, degassed in a vacuum line, add a predetermined amount of sulfur dioxide dried with diphosphorus pentoxide, sufficiently stir to form a uniform solution, and then predetermined temperature Polymerize for a time. The composition, molecular weight, and molecular weight distribution of the copolymer obtained will vary depending on the composition of sulfur dioxide and the monomer, the type and amount of the reaction initiator, the type and amount of the polymerization solvent, the polymerization temperature and the time, and the like. For example, in the case of obtaining an alternating copolymer in which the molar ratio of the nucleus-substituted styrene derivative and SO ₂ is 1, the polymerization temperature is preferably −50 ° C. or lower.

The characteristics of the sulfur dioxide copolymer are as follows:
Although it is difficult to obtain a high molecular weight product by homopolymerization of the monomer represented by (Formula 1), it is relatively easy to copolymerize with the bulky monomer represented by (Formula 1) by copolymerization with sulfur dioxide. This is the point where a molecular weight product is obtained. Generally, it can be said that the high molecular weight polymer is superior in performance as a positive resist. Regarding the copolymer composition, (formula 1)
The ratio of the monomer unit to the sulfone unit shown in 1) is related to the sensitivity of the positive resist, and the performance as an electron beam resist becomes higher as the ratio becomes closer to an alternating copolymer having a ratio of 1: 1.

The copolymer thus obtained is dissolved in a dissolving solvent (preferably methyl cellosolve acetate, cyclohexanone) (preferably 5 to 20 wt% concentration), and if necessary, an acid generator (preferably onium salt). (Triphenylsulfonium salt, diphenyliodonium salt) is added to the copolymer in an amount of 3 to 12 wt% to form a uniform solution, which is then filtered with a filter of 0.5 μm or less. The solution is hereinafter referred to as a resist solution. The resist solution thus obtained is applied onto a silicon wafer with a spin coater and prebaked to obtain a test plate (hereinafter referred to as a resist film or film). The film thickness is 0.2-
2.0 μm is preferable.

A far ultraviolet ray (hereinafter referred to as deepUV or DUV), an electron beam (hereinafter referred to as EB), an X-ray exposure is performed through a mask having a pattern drawn on the film thus obtained, and post-baking (hereinafter referred to as PEB) is performed.
(Direct writing in the case of electron beam exposure) The film thus obtained is immersed in a developing solution for development. When an alkaline aqueous solution (preferably tetramethylammonium hydroxide aqueous solution (hereinafter referred to as TMAH)) is used as a developing solution, a positive image in which an exposed portion is dissolved is formed, and when an organic solvent is used in a developing solution, a negative image in which an unexposed portion is dissolved Is obtained.

The present invention will be described below with reference to examples. Example 1 Para-ter distilled into a 100 ml pressure-resistant glass reaction tube.
t-Butoxycarbonyloxyethylstyrene 10.0
g and tert-butyl hydroperoxide (3 mol toluene solution) (0.14 ml) were added and mixed, and the mixture was degassed in vacuo. It was then cooled with dry ice / acetone and the reaction tube was dried over phosphorous pentoxide with sulfur dioxide (at -10 ° C) 10.5.
ml was added in a vacuum line and mixed well. This reaction tube was placed in a low temperature constant temperature bath of -50 ° C and reacted for 20 hours.
After the passage of time, unreacted sulfur dioxide was removed and the reaction tube was opened. A small amount of acetone was added to the reaction solution remaining in the tube to make a homogeneous solution, and the homogeneous solution was poured into a large amount of methanol with stirring to precipitate a white polymer. The polymer was collected on a glass filter, washed with methanol, and dried under reduced pressure for 24 hours. In this way 3.1 g of polymer was obtained. This polymer was found to be a para-tert-butoxycarbonyloxyethylstyrenesulfone copolymer by IR spectrum analysis, and the polymer composition was found to have a para-tert-butoxycarbonyloxyethylstyrene unit content of 48 mol% and a sulfone unit content of 52% by sulfone unit. It was found to be an alternating copolymer having a molar ratio of about 1: 1. Further, the molecular weight of this polymer is the number average molecular weight (Mn) = in terms of polystyrene by GPC analysis.
The dispersion was 154,000 and the dispersity (d) was 1.8.

Example 2 11.4 g of distilled meta-methyl-para-tert-butoxystyrene and 28 mg of azobisisobutyronitrile (AIBN) were added to a 100 ml pressure-resistant glass reaction tube, mixed and deaerated under vacuum. Then, it was cooled with dry ice / acetone, and 5.4 ml of sulfur dioxide (at -10 ° C) dried with phosphorous pentoxide was added to the reaction tube through a vacuum line and mixed well. This reaction tube was placed in a constant temperature bath at 60 ° C. and reacted for 5 hours. After the passage of time, the reaction tube was cooled to room temperature, unreacted sulfur dioxide was removed, and then the reaction tube was opened. A small amount of acetone was added to the reaction solution remaining in the tube to make a homogeneous solution, and the homogeneous solution was poured into a large amount of methanol with stirring to precipitate a white polymer. The polymer was collected on a glass filter, washed with methanol, and dried under reduced pressure for 24 hours. In this way 4.8 g of polymer was obtained. This polymer was a meta-methyl-para-tert-butoxystyrene sulfone (2: 1) copolymer by IR spectrum analysis and elemental analysis, and the molecular weight of this polymer was the number average molecular weight (Mn by polystyrene conversion by GPC analysis). ) = 267,000 and polydispersity (d) = 1.4.

Example 3 7.3 g of meta-trimethylsilyl-para-tert-butoxycarbonyloxystyrene, 5.5 g of para-tert-butoxycarbonyloxystyrene and tert-butyl hydroperoxide (3) distilled in a 100 ml pressure-resistant glass reaction tube. 0.16 ml of a molar toluene solution) was added and mixed, and the mixture was deaerated under vacuum. Then, it was cooled with dry ice / acetone, and 11.0 ml of sulfur dioxide (at -10 ° C) dried with diphosphorus pentoxide was added to the reaction tube through a vacuum line,
Mixed well. This reaction tube was placed in a low temperature constant temperature bath of -60 ° C and reacted for 8 hours. After the passage of time, unreacted sulfur dioxide was removed and the reaction tube was opened. A small amount of acetone was added to the reaction solution remaining in the tube to make a homogeneous solution, and the homogeneous solution was poured into a large amount of methanol with stirring to precipitate a white polymer. The polymer was collected on a glass filter, washed with methanol, and dried under reduced pressure for 24 hours. Thus 2.8 g of polymer was obtained. This polymer is a terpolymer of meta-trimethylsilyl-para-tert-butoxycarbonyloxystyrene / para-tert-butoxycarbonyloxystyrene / sulfone according to IR spectrum analysis and elemental analysis. The content of -tert-butoxycarbonyloxystyrene unit was 23 mol%, the content of para-tert-butoxycarbonyloxystyrene unit was 28 mol%, and the sulfone unit was 49 mol%. Further, the molecular weight of this polymer was a polystyrene reduced value by GPC analysis and was number average molecular weight (Mn) = 194,000 and dispersity (d) = 3.2.

Example 4 The polymer obtained in Example 1 was dissolved in cyclohexanone to form a 10.0% solution, which was filtered through a 0.2 μm filter. This solution was spin-coated on a silicon wafer at a rotation speed of 3500 rpm for 30 seconds, and prebaked on a hot plate at 105 ° C. for 2 minutes. The film thickness after prebaking was 0.3 μm. Accelerating voltage of 20
The exposure amount was changed by kv, electron beam irradiation was performed, and then baking was performed on a hot plate at 110 ° C. for 30 seconds. The wafer was immersion developed in 1.5% TMAH for 30 seconds and rinsed with distilled water for 60 seconds. The residual film of each pattern thus obtained was measured with a stylus profilometer, and the exposure dose (decomposition sensitivity) of the portion where the residual film was completely removed was determined. As a result, a value of ²⁰ μC / cm ² was obtained. Was obtained. In addition, there was almost no film loss in the unexposed portion.

Example 5 1 g of the polymer obtained in Example 1 and 0.05 g of triphenylsulfonium triflate were dissolved in 10 ml of cyclohexanone, and the solution was filtered through a 0.2 μm Teflon filter. This solution was spin-coated on a silicon wafer at a rotation speed of 2500 rpm for 30 seconds, and prebaked at 105 ° C. for 2 minutes on a hot plate. The film thickness at this time was 0.5 μm. A deep UV exposure is performed by passing a mask through this and changing the exposure amount (using a Ushio 500W Xe-Hg lamp as a light source, using Canon PLA-520 and cold mirror CM250 as an illumination system), and then 110 on a hot plate. Baking was performed at 30 ° C. for 30 seconds. The wafer in 30% TMAH at 30%
Immersion development was performed for 2 seconds, and rinsed with distilled water for 60 seconds. The respective patterns thus obtained were observed with a microscope and the optimum exposure dose (decomposition sensitivity) and the resolution were determined from the resolution, and a value of sensitivity of 10 mJ / cm ² and a resolution of 0.4 μm was obtained. . In addition, there was almost no film loss in the unexposed portion.

Example 6 The same resist solution as in Example 5 was spin-coated on a silicon wafer at a rotation speed of 1500 rpm for 30 seconds, and prebaked on a hot plate at 105 ° C. for 2 minutes. The film thickness at this time was 0.95 μm. This was subjected to Deep UV exposure in the same manner as in Example 5, and then on a hot plate.
Baking was performed at 10 ° C. for 30 seconds. The wafer was immersion developed for 60 seconds in a solvent of dichloromethane: cyclohexanone = 1: 1 and rinsed for 60 seconds with isopropanol.
(In this case, the unexposed portion is dissolved and removed by the developer to give a negative image.) The residual film of each pattern thus obtained is measured with a stylus meter and the residual film is saturated to a substantially constant value. When the exposure amount (negative sensitivity) was determined, a value of 20 mJ / cm ² was obtained.

Comparative Example 1 In the same manner as in Example 2, 10.6 g of para-tert-butoxystyrene, 26 mg of AIBN and sulfur dioxide (-
(10 ° C.) and 5.4 ml gave 4.3 g of para-tert-butoxystyrene sulfone (2: 1) copolymer.
The molecular weight of this polymer is number average molecular weight (Mn) = 24.
It was 3,000 and the degree of dispersion (d) was 1.5. Then, in the same manner as in Example 5, 1 g of the polymer obtained here and 0.0
5 g of triphenylsulfonium triflate and 10
A resist solution was prepared by dissolving it in ml of cyclohexanone. This solution was added to hexamethyldisilazane (hereinafter HMDS
2700 rpm on the processed silicon wafer
Spin coating at rpm for 30 seconds, 1 on hot plate
Prebaking was performed at 05 ° C. for 2 minutes to obtain a film having a thickness of 0.8 μm. DUV exposure was performed in the same manner as in Example 5, and 1
After baking at 10 ° C. for 30 seconds, the wafer was 1.
Immersion development was carried out for 30 seconds in 5% TMAH and rinsed with distilled water for 60 seconds. As a result, the sensitivity is about 10 mJ / cm
² was good, but the resolution was poor because peeling occurred in a pattern of 1.0 μm or less. The film loss in the unexposed portion was 8%.

Comparative Example 2 In the same manner as in Example 1, 10.0 g of para-tert-butoxycarbonyloxystyrene and tert-butyl hydroperoxide (3 mol toluene solution) 0.15 m were used.
and 12 ml of sulfur dioxide (at -10 ° C) and more para-t.
2.7 g of an ert-butoxycarbonyloxystyrene sulfone (1: 1) alternating copolymer was obtained. The polymer had a number average molecular weight (Mn) of 200,000 and a dispersity (d) of 2.5. In the same manner as in Example 5, 1 g of the polymer obtained here and 0.05 g of triphenylsulfonium triflate were dissolved in 10 ml of cyclohexanone to prepare a resist solution. This solution is HMDS
Spin treatment is performed on the treated silicon wafer at a rotation speed of 1800 rpm for 30 seconds, and then is applied on a hot plate at 105 ° C. for 2 seconds.
It was pre-baked for a minute to obtain a film having a film thickness of 0.8 μm. DUV exposure is carried out as in Example 5, then 3 hours at 110 ° C.
After baking for 0 seconds, the wafer is 1.5% TM
Immersion development was carried out in AH for 30 seconds and rinsed with distilled water for 60 seconds. As a result, the sensitivity was good at about 10 mJ / cm ² , but peeling occurred in the pattern having a resolution of 1.0 μm or less, which was not good. The film loss in the unexposed portion was 12%.

[Brief description of drawings]

FIG. 1 is an infrared absorption spectrum diagram of a binary copolymer according to the present invention.

FIG. 2 is an infrared absorption spectrum diagram of the terpolymer according to the present invention.

Continuation of front page (56) Reference JP 62-215628 (JP, A) JP 63-10634 (JP, A) JP 1-131246 (JP, A) JP 63-319 (JP , A)

Claims (3)

[Claims] 1. A linear compound comprising 1 to 50 mol% of a structural unit represented by —SO ₂ — and 50 to 99 mol% of a nuclear-substituted styrene derivative represented by the following (formula 1) as a structural unit. A binary copolymer of sulfur dioxide having a number average molecular weight of 2,000 to 2,000,000 and a structural formula (formula 3) below and a nucleus-substituted styrene derivative. [Chemical 1] Here, R ¹ and R ² are H at the meta position, an alkyl group having 1 to 4 carbon atoms or [Si (CH ₃ ) ₂ ] _y CH ₃ , and y is an integer of 1 to 3. Further, R ¹ and R ² may be the same or different. R ³ is in para position (CH ₂ )
m represents an alkylene group of m = 0 or m = 1 to 3,
X represents OH, a tertiary-butoxy group or a tertiary-butoxycarbonyloxy group. However, the case where R ¹ and R ² are H and m = 0 is excluded. [Chemical 2] Here, the meanings of R ¹ , R ² , R ³ and X are the same as in the case of (Formula 1), p is an arbitrary integer from 1 to 99, and n is 1
It is an integer of 0 or more and 10,000 or less. 2. A structural unit represented by 1 to 50 mol% of --SO _2- , 15 to 98 mol% of a nucleus-substituted styrene derivative represented by the following (formula 1) and 1 to 84 mol% of the following (formula 2 ) Is a linear compound having a number average molecular weight of 2,000 to
A terpolymer of sulfur dioxide having a structural formula of the following (formula 4) at 2,000,000 and a nucleus-substituted styrene derivative. [Chemical 3] Here, R ¹ and R ² are H at the meta position, an alkyl group having 1 to 4 carbon atoms or [Si (CH ₃ ) ₂ ] _y CH ₃ , and y is an integer of 1 to 3. Further, R ¹ and R ² may be the same or different. R ³ is in para position (CH ₂ )
m represents an alkylene group of m = 0 or m = 1 to 3,
X represents OH, a tertiary-butoxy group or a tertiary-butoxycarbonyloxy group. However, the case where R ¹ and R ² are H and m = 0 is excluded. [Chemical 4] Here, X represents OH, a tertiary butoxy group or a tertiary butoxycarbonyloxy group. [Chemical 5] Here, the meanings of R ¹ , R ² , R ³ and X are the same as in the case of (Formula 1), p and q are 1 to 10, and l and m are the molar fractions of the copolymer. Corresponding, l is 15-9
9 mol%, m is 1 to 85 mol%, (p + q) is 50 to 9
It is 9 mol%, and each structural unit is irregularly distributed in the copolymer to form the main chain of the copolymer. n is 5
It is an integer not less than 5,000. 3. A resist material containing the copolymer according to claim 1 or 2 as an active ingredient.