JPH0733879A - Binary copolymer composed of sulfur dioxide and vinyl compound - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer useful as a positive-type resist material decomposable in high sensitivity by electron rays, etc., and having excellent dry-etching resistance by introducing a vinyl compound unit having aromatic ring to a poly(olefin-sulfone). CONSTITUTION:This copolymer expressed by the formula I [R<5> is H, Cl, OCOCH3, OH, ClCH2 or group of the formula II (R<6> is CH3, C2H5 or C3H7); group of the formula III is monocyclic or polycyclic aromatic ring; (p) is sequence length and is 1-10] and having a weight-average molecular weight of 1,000-1,000,000 is composed of 30-50mol% of the structural unit of the formula IV and 50-70mol% of a vinyl compound (excluding nucleus-substituted trialkylsilylstyrene) as a structural unit.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel binary copolymer composed of sulfur dioxide and a vinyl compound. For more details,
The present invention relates to the above binary copolymer as an active ingredient of a new resist material which is a positive type which is highly sensitively decomposed by an electron beam or X-ray and is excellent in dry etching resistance.

[0002]

2. Description of the Related Art The progress of LSIs in recent years has been remarkable, and high performance is also required for resist materials used for fine processing of LSIs. The high performance means having high sensitivity and high resolution with respect to light, electron beams and X-rays. In the LSI technology field, more recently, a method of performing dry etching instead of chemical etching in the microfabrication stage has become mainstream, and the resist material is also required to have dry etching resistance. became. By the way, as a conventional polymer material for positive resist, a copolymer of sulfur dioxide and an olefin, a polymer of a methyl methacrylate group, etc. are known (Kiyotake Naraoka, "Precision and fine processing of electronics", General Electronics Publisher Showa 5
8 years). However, many positive resist materials
Unable to withstand plasma irradiation. Therefore, chemical etching is commonly used despite the drawbacks mentioned above. However, the mainstream of the substrate etching method is now shifting to etching by the plasma irradiation method because of its excellent resolution, reproducibility and throughput. Therefore, there is an urgent need to develop a positive resist having excellent plasma resistance.

[0003]

DISCLOSURE OF THE INVENTION As a result of intensive studies to improve the above-mentioned problems, the present inventors have found that poly (olefin-
By introducing a vinyl compound unit having an aromatic ring into (sulfone), it is possible to impart dry etching resistance without deteriorating the property of poly (olefin-sulfone) having high sensitivity to electron beam exposure. Heading, completed the present invention. As is clear from the above description, an object of the present invention is to provide a novel copolymer in which a vinyl compound unit having an aromatic ring is introduced into poly (olefin-sulfone) (however,
In the case where the silicon-containing vinyl compound is a nucleus-substituted trialkylsilylstyrene in the copolymer, the present inventors previously invented it and filed it as Japanese Patent Application No. 61-51,638).

[0004]

Means for Solving the Problems The present invention includes the following (1) to
It consists of (3). (1) a. It is shown by the following formula (1),

[Chemical 9]

[Chemical 10] (Here, R ⁶ = CH ₃ , C ₂ H ₅ , and C ₃ H ₇ are represented)

[Chemical 11] (Where R ⁵ = H, Cl, OCOCH ₃ , OH, ClC
H ₂ is represented by Chemical formula 10. Chemical formula 11 represents a monocyclic or polycyclic aromatic ring. Also, p represents the sequence length and represents 1 to 10).

[Chemical 12] b. 30 to 50 mol% of the structural unit represented by Chemical formula 12 and 5
A binary copolymer having 0 to 70 mol% of a vinyl compound (excluding nucleus-substituted trialkylsilylstyrene) as a structural unit and having a weight average molecular weight of 1,000 to 1,000,000. (2) The above (1), wherein the vinyl compound is any compound selected from chlorostyrene, chloromethylstyrene, acetoxystyrene or hydroxystyrene.
The binary copolymer according to item. (3) a. It is shown by the following formula (1),

[Chemical 13]

[Chemical 14] (Here, R ⁶ = CH ₃ , C ₂ H ₅ , and C ₃ H ₇ are represented)

[Chemical 15] (Where R ⁵ = H, Cl, OCOCH ₃ , OH, ClC
H ₂ represents chemical formula 14. Chemical formula 15 represents a monocyclic or polycyclic aromatic ring. Also, p represents the sequence length and represents 1 to 10).

[Chemical 16] b. 30 to 50 mol% of the structural unit represented by Chemical formula 16 and 5
A positive resist composition containing 0 to 70 mol% of a vinyl compound (excluding nucleus-substituted trialkylsilylstyrene) as a structural unit and a binary copolymer having a weight average molecular weight of 1,000 to 1,000,000 as an active ingredient.

The present invention will be described in detail below. The binary copolymer of the present invention is a linear polymer compound represented by the formula (1).

[0006]

[Chemical 17]

[Chemical 18] (Here, R ⁶ = CH ₃ , C ₂ H ₅ , and C ₃ H ₇ are represented)

[Chemical 19]

(Where R ⁵ = H, Cl, OCOCH ₃ ,
OH, ClCH ₂ , and Chemical formula 19 represents a monocyclic or polycyclic aromatic ring. P is the sequence length, 1
10 is shown). The structural unit shown in formula (1) has 1
-Vinylnaphthalene, 2-vinylnaphthalene, chlorostyrene, acetoxystyrene, hydroxystyrene and the like are included.

[0008]

[Chemical 20]

The binary copolymer of the present invention (hereinafter sometimes referred to as the copolymer of the present invention) is prepared from a known radical polymerization method or a redox system by using sulfur dioxide and one of the above-mentioned nucleus-substituted aromatic vinyl compounds as a raw material. It can be synthesized by a polymerization method.

The composition of the copolymer of the present invention depends on the selection, blending and polymerization temperature of sulfur dioxide and the vinyl compound.
The molecular weight can be controlled by properly selecting the type and amount of the polymerization initiator and the polymerization temperature. As the polymerization initiator, any known initiator for free radical polymerization can be used. Preferred examples include azobisisobutyronitrile, t-butyl hydroperoxide or di-t-butyl peroxide.
The copolymer of the present invention can also be obtained by irradiation with light. In any of the above cases, it is possible to obtain the target molecular weight of the copolymer by increasing or decreasing the amount of the polymerization initiator used. The practical use amount is, but not limited to, 1 to 100 mmol / liter.

The polymerization temperature is -100 to 10 depending on the desired molecular weight and the desired composition ratio shown in the above formula (1).
A predetermined temperature can be selected within the range of 0 ° C. Here, in the chemical formula (1), the composition ratio of the (styrene derivative) p-sulfone portion depends on the polymerization temperature, and the value of p becomes smaller as the polymerization temperature is lowered. That is, the ratio approaches 1: 1.
On the other hand, when the copolymer of the present invention is used as an electron beam or X-ray resist, the decomposition sensitivity by the electron beam or X-ray irradiation is improved as the value of p approaches 1. Therefore, particularly when the binary copolymer of the present invention is used as a resist, the polymerization temperature is preferably +30 to -100 ° C.

The copolymerization reaction relating to the method of the present invention can be carried out by a bulk polymerization method or a solution polymerization method. The solvent used in the solution polymerization method is not limited, but for example, chlorobenzene, 0-dichlorobenzene or dichloromethane is preferable. The time required for the copolymerization reaction varies depending on other copolymerization conditions, but it is 1 to 120 hours, preferably 4 to 4 hours.
8 hours. After a predetermined copolymerization time has passed, unreacted monomers, solvents and the like are separated by a known method to obtain a solid or solution (if necessary) copolymer. By properly selecting the type, amount and polymerization temperature of the polymerization initiator and the polymerization solvent as described above, the weight average molecular weight is 1,000 to 1,000,
It is 000, and a copolymer having a predetermined structural unit composition ratio can be obtained.

When the copolymer of the present invention is used as a resist material, its weight average molecular weight affects the performance of the material and is not decisive in terms of its performance, but the range of the molecular weight is the weight average molecular weight. 50.000 to 1,000,000 is preferable.
The binary copolymer of the present invention is a solution of a general-purpose organic solvent,
It can be uniformly applied to the substrate by spraying or spin coating. The solution usually has a concentration of the copolymer of about 3 to 2
It is used as a 0% by weight, preferably about 4 to 10% by weight solution. As the preferred solvent, those having a boiling point not higher than the thermal decomposition temperature of the copolymer are used, for example, dioxane,
Chlorobenzene, methyl cellosolve acetate (MC
A) and the like are preferable.

Embodiments in which the copolymer of the present invention is used as a resist material are as follows. A solvent solution of the above-mentioned copolymer, that is, a resist solution is spin-coated on a substrate, and then the solvent in the coated material is completely removed by heating and evaporation to form a uniform resist film. The film thickness of the film is preferably 0.4 to 1 μm. The film thus obtained is irradiated with an adjusted electron beam or X-ray to cause decomposition in the irradiated portion. Then, the irradiated portion is dissolved by using a developing solution (described later) to develop. As a suitable developing solution, for example, a good solvent such as amyl acetate, methyl cellosolve acetate, chlorobenzene, cyclopentanone, dioxane or tetrahydrofuran and a poor solvent such as 2-methoxyethanol or isopropanol in a suitable ratio, for example, a good solvent. 10:
A mixed solvent obtained by mixing poor solvent 1 to good solvent 1: poor solvent 10 (both in volume ratio) can be mentioned.

The copolymer containing a compound having a silyl group and / or an aromatic ring in the copolymer of the present invention, when used as a resist film, exhibits a role as a mask when processing a substrate. That is, a resist film having a silyl group and / or an aromatic ring is decomposed by plasma etching, and at the same time, cross-linking between aromatic rings occurs,
Shape the barrier layer. In addition, the silyl group is oxidized by oxygen plasma, a SiOx layer is formed on the surface of the resist layer, and it becomes a barrier layer, which exhibits more excellent plasma resistance. As shown in the test examples, like the copolymer of the present invention, styrene, chlorostyrene, chloromethylstyrene, acetoxystyrene, hydroxystyrene, trimethylsilylstyrene,
Those containing silyl groups and / or aromatic rings such as trimethylvinylsilane and trimethylallylsilane have excellent plasma resistance.

The present invention will be described below with reference to examples. Example 1 Freshly distilled p- in a 100 ml pressure-resistant glass polymerization tube.
Add 20 g of acetoxystyrene and 22 mg of azobisisobutyronitrile. Then, oxygen in the polymerization tube was removed by repeating vacuum deaeration while cooling the contents in the polymerization tube, and then liquid SO ₂ dehydrated and dried with P ₂ O ₅ (at -10 ° C).
Add 5.4 ml, seal the tube and mix well. This polymerization tube is placed in a constant temperature water bath at 60 ° C. and polymerized for 100 minutes. Then, the polymerization tube is rapidly cooled to −70 ° C. or lower to stop the polymerization reaction, and after unsealing, unreacted SO ₂ is expelled. A small amount of THF is added to the remaining polymerization liquid to make a uniform solution, and the solution is poured into a large amount of methanol with stirring, whereby a white polymer is precipitated. This polymer is purified by repeating dissolution-precipitation and then vacuum dried at 30 ° C. for 24 hours. The yield is 3.8 g. The IR spectrum of this polymer is shown in FIG. I
Than R spectrum and elemental analysis the polymer is p- acetoxystyrene - in binary copolymer of sulfone, the composition of p- acetoxystyrene unit 67 mol%, SO ₂ units was 33 mol%. In addition, this binary copolymer is GPC
Analysis revealed that the polystyrene equivalent weight average molecular weight was 390,00
0, the dispersity was 1.8.

Example 2 60 ml of dioxane was placed in a 200 ml Erlenmeyer flask, 2 g of the p-acetoxystyrene-sulfone copolymer obtained in Example 1 was added thereto, and the mixture was stirred for a long time to form a uniform solution. . 4 ml of 1N hydrochloric acid aqueous solution is added to this flask, and it is hydrolyzed by stirring at room temperature for 24 hours. Then 40 ml of dichloromethane are added to this solution and the polymer is transferred to the solvent layer. Then, the solvent layer is transferred to a separating filter, and the produced acetic acid and residual hydrochloric acid are washed with a sufficient amount of water until neutral.
The polymer layer is precipitated by pouring the neutralized solvent layer into a large amount of hexane. When IR spectroscopy of the polymer thus obtained was found, most of the acetoxy groups had disappeared, and the polymer was a p-hydroxystyrene-sulfone binary copolymer. The p-hydroxystyrene-sulfone copolymer can also be obtained by the method shown in Example 1, that is, the polymerization reaction of p-hydroxystyrene and SO _{2 in} the presence of a polymerization initiator.

Example 3 A 100 ml pressure-resistant glass-made polymerization tube was subjected to fresh distillation of p-
Add 38 ml of chlorostyrene and 40 mg of azobisisobutyronitrile. Then, as in Example 1, oxygen in the polymerization tube was removed, 9 ml of SO ₂ (at −10 ° C.) was added, and they were mixed well. The polymerization tube was immersed in a constant temperature water bath at 30 ° C for 19
React for hours. Then, the polymerization tube is rapidly cooled to −70 ° C. or lower to stop the polymerization reaction. Post-treatment was carried out in the same manner as in Example 1 to obtain 5.0 g of a polymer. IR of this polymer
The spectrum is shown in FIG. According to the IR spectrum and the elemental analysis value, this polymer was a p-chlorostyrene-sulfone copolymer, and its composition was 60 mol% p-chlorostyrene units and 40 mol% SO ₂ units. The weight average molecular weight of this copolymer was 463,000 and the dispersity was 2.2.

Example 4 45.8 ml of freshly distilled chloromethylstyrene (mixture of o- and p-forms) in a 100 ml pressure-resistant glass polymerization tube.
And 91 mg of azobisisobutyronitrile. Then, the oxygen in the polymerization tube was removed in the same manner as in Example 1, and S
Add 9 ml of O ₂ (at -10 ° C) and mix well. This polymerization tube is immersed in a constant temperature water bath at 30 ° C. and reacted for 25 hours. Then, the polymerization tube is rapidly cooled to −70 ° C. or lower to stop the polymerization reaction. Post-treatment was carried out in the same manner as in Example 1 to obtain 6.3 g of a polymer. The IR spectrum of this polymer is shown in FIG. From the IR spectrum and the elemental analysis value, this polymer is a chloromethylstyrene-sulfone copolymer, and its composition is 67 mol% of chloromethylstyrene unit and SO.
₂ units were 33 mol%. The weight average molecular weight of this copolymer was 320,000 and the dispersity was 2.0.

Test Example 1 The binary copolymer obtained in Example 4 was dissolved in methyl cellosolve acetate (MCA) to prepare a 5.0% by weight solution, which was filtered through a 0.2 μm filter. This solution was spun on a silicon wafer using a spinner at 200 rpm.
The coating was performed at 0 rpm for 60 seconds, and the coated object was prebaked in a clean oven at 120 ° C. for 1 hour. The coating film thickness at this time was 0.48 μm. An electron beam writer was used for this thing, and the irradiation amount was changed and electron beam irradiation was performed. Then, this substrate was immersed in a mixed solvent of dioxane-isopropanol (volume ratio 1: 8) for 1 minute at room temperature, and then rinsed with isopropanol for 30 seconds for development.
Then, post baking was performed in an oven at 120 ° C. for 30 minutes. The coating film thickness at this time was 0.40 μm. An electron beam writer was used for this thing, and the irradiation amount was changed and electron beam irradiation was performed. Next, this substrate was immersed in a mixed solvent of dioxane 9: isopropanol: 5 (both in volume ratio) for 1 minute at room temperature, and then rinsed with isopropanol for 30 seconds for development. Then, post baking was performed at 120 ° C. for 30 minutes. In the case of this test example, the non-irradiated part was completely dissolved, and the irradiated part was crosslinked and cured,
The residual film was measured with a stylus profilometer, and the irradiation dose (sensitivity) of the cured portion of 0.3 μm was determined to be 1 × 10 ⁻⁶ C / c
It was m ² . In addition, the etching resistance of this resist was measured by CF ₄ + 5% O ₂ gas with a parallel plate type etching device.
Flow rate 200 ml / min. RF power density 0.24w /
cm ² and pressure 10 Pa, 550 / m
in. Met. The etching rate of the novolac resin (trade name AZ-1350J) used for comparison was 530.
/ Min. Met.

Test Examples 2 and 3 The etching resistance of the p-chlorostyrene-sulfone binary copolymer obtained in Example 3 was measured in the same manner as in Test Example 1. Further, as Test Example 3, the etching resistance of the styrene-sulfone copolymer (composition 60 mol% -40 mol%) was measured. The result was used as a comparison AZ-1350J
The results are shown in Table 1 together with the etching rates.

[0022]

[Table 1]

[Brief description of drawings]

1 to 3 show infrared absorption spectra of the copolymer of the present invention.

FIG. 1 is the copolymer obtained in Example 1.

FIG. 2 is the copolymer obtained in Example 3.

3 is the copolymer obtained in Example 4. FIG.

Claims (3)

[Claims] 1. A. It is represented by the following formula (1): [Chemical 2] (Here, R ⁶ = CH ₃ , C ₂ H ₅ , and C ₃ H ₇ are represented.) (Where R ⁵ = H, Cl, OCOCH ₃ , OH, ClC
H ₂ represents chemical formula ₂ . Chemical formula 3 represents a monocyclic or polycyclic aromatic ring. Further, p represents a sequence length and represents 1 to 10). b. 30 to 50 mol% of the structural unit represented by Chemical formula 4 and 50
A binary copolymer having a structural unit of from about 70 mol% of a vinyl compound (excluding nucleus-substituted trialkylsilylstyrene) and having a weight average molecular weight of 1,000 to 1,000,000. 2. The binary copolymer according to claim 1, wherein the vinyl compound is any compound selected from chlorostyrene, chloromethylstyrene, acetoxystyrene and hydroxystyrene. 3. a. It is represented by the following formula (1): [Chemical 6] (Here, R ⁶ = CH ₃ , C ₂ H ₅ , and C ₃ H ₇ are represented.) (Where R ⁵ = H, Cl, OCOCH ₃ , OH, ClC
H ₂ represents Chemical formula 6. Chemical formula 7 represents a monocyclic or polycyclic aromatic ring. Further, p represents a sequence length and represents 1 to 10). b. 30 to 50 mol% of the structural unit represented by Chemical formula 8 and 50
A positive resist composition containing as an active ingredient a binary copolymer having a weight-average molecular weight of 1,000 to 1,000,000 as a structural unit and a vinyl compound (excluding nuclear-substituted trialkylsilylstyrene) of ˜70 mol%.