JPH0453420B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a photosensitive resin composition formed by blending polysilsesquioxane with a styrene polymer having silicon atoms. Conventional Technology In recent years, in the manufacture of semiconductors, etc., as patterns have become finer, dry etching using gas plasma, etc. has been used instead of conventional wet etching in order to accurately transfer resist patterns onto substrates. It became. In general, styrene polymers have relatively good resistance to dry etching by gas plasma and the like, and are often used as resist materials. In recent years, multilayer resists using oxygen plasma have attracted attention, and a resist material having oxygen plasma resistance is desired as an upper layer thereof. Resist materials containing silicon atoms have excellent oxygen plasma resistance, and several of these resist materials are known. A typical example is siloxane-based polymers, but these polymers generally have a low thermal transition temperature and are viscous liquids or gums at room temperature, so they tend to attract dust and are difficult to adjust the film thickness. It has drawbacks such as difficulty. Recently, as a resist material having oxygen plasma resistance, for example, a styrene-based polymer having a silicon atom obtained by copolymerizing trimethylsilylstin and a crosslinking monomer (Japanese Patent Application Laid-Open No. 15419/1983) is known.
Oxygen plasma resistance is not necessarily sufficient. Problems to be Solved by the Invention An object of the present invention is to provide a photosensitive resin composition that has a high silicon content and can provide a resist pattern with excellent oxygen plasma resistance, dry etching resistance, and resolution. . Means for Solving the Problems The present invention is based on the general formula [In the formula, R ¹ , R ² and R ³ are the same or different C ₁ to C ₆ alkyl groups or C ₂ to _{C 6} alkenyl groups,
At least one of R ¹ , R ² and R ³ is an alkenyl group] A styrenic polymer containing a repeating unit of the general formula [In the formula, R and R' are the same or different alkyl groups,
aryl group or alkenyl group], and at least one of the repeating units has at least one alkenyl group. shall be. Method for producing styrenic polymer The styrenic polymer used in the present invention contains a unit represented by the above general formula (), and the polymer is p-methylstyrene (hereinafter referred to as PMS
A polymer or a random or block copolymer of PMS and α-methylstyrene (αMS) (hereinafter referred to as PMS copolymer) is contacted with an organolithium compound to form a lithiated PMS polymer or a lithiated PMS copolymer. The polymer is then reacted with a silicon compound represented by the formula (R ¹ ) (R ² ) (R ³ ) six [wherein R ¹ , R ² and R ³ have the same meanings as above, and x represents a halogen atom]. It can be manufactured by Each compound used in producing the styrenic polymer will be explained. PMS Polymer and PMS Copolymer The PMS polymer used in the present invention is a polymer having a repeating unit of a PMS skeleton, and is typically polyPMS. PolyPMS is produced by solution polymerization of PMS or a methylstyrene mixture with a PMS content of 95% or more, preferably 97% or more, in an inert hydrocarbon solvent such as benzene or toluene, or precipitation of calcium phosphate, polyvinyl alcohol, hydroxyethyl cellulose, etc. It can be obtained by polymerization such as suspension polymerization in a solution containing an inhibitor or emulsion polymerization in an aqueous medium containing an appropriate surfactant. The polymerization may be carried out in the presence of a free radical type, anionic type or cationic type polymerization catalyst, or may be carried out by thermal polymerization. In the present invention, those having a weight average molecular weight of several thousand to several million can be used. PMS copolymers can be produced by random or block copolymerization of PMS and αMS using normal radical polymerization or living polymerization. In particular, when living polymerization is adopted, copolymers with a narrow molecular weight distribution are produced. This is desirable because a polymer can be obtained. Furthermore, if PMS is uniformly dispersed in the repeating units of the styrene copolymer, it will be more effective when used as a resist, so a random copolymerization method is preferable. Living polymerization is performed using an initiator that forms a styryl anion, e.g. n-butyllithium, sec.
- carried out in the presence of an organolithium compound such as butyllithium. Moreover, living polymerization can be performed in the presence of a solvent. As a solvent,
Hydrocarbons such as hexane, heptane, octane, cyclohexane, penzene, toluene, xylene, etc., which are inert to the initiator and generated anions;
Examples include ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, and dioxane. In living polymerization, PMS and αMS are heated from -80℃ to +
It is carried out by reacting for 0.5 to 50 hours at a temperature of 50°C. Random copolymerization is achieved by copolymerizing using PMS and αMS simultaneously.
Further, block copolymerization is carried out by first homopolymerizing one of PMS or αMS and then copolymerizing the other. The usage ratio of PMS and αMS is usually PMS/
αMS (molar ratio) is 2-98/98-2, preferably
25-75/75-25. By doing so,
Number average molecular weight of several thousand to several million, preferably 10,000 to 500,000, w/n less than 2.0, preferably 1.0
~1.5, and the PMS part/αMS part has the above molar ratio.
A PMS copolymer is obtained. Organolithium Compound The organolithium compound used in lithiation of the PMS polymer or PMS copolymer is represented by the general formula RLi. Specifically, compounds in which R is an alkyl group having 1 to 12 carbon atoms are mentioned, and typical compounds include methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, Examples include n-pentyl lithium, tert-pentyl lithium, hexyl lithium, octyl lithium, dodecyl lithium, etc., but butyl lithium is particularly preferred. Silicon compound The silicon compound is represented by the above formula,
When R ¹ , R ² , R ³ are alkyl groups in the formula,
Preferably methyl, ethyl, n-propyl, n
-butyl group, particularly methyl and ethyl groups. When R ¹ , R ² , and R ³ are alkenyl groups, vinyl, allyl, pyropenyl, isopropenyl, and butenyl groups are preferable, and vinyl and allyl groups are particularly preferable. X is preferably a chlorine atom. Reaction between PMS polymer or PMS copolymer and organolithium compound The reaction between the PMS polymer or PMS copolymer and organolithium compound can be carried out in a solvent that is inert to the organolithium compound. Examples of solvents that can be used include hydrocarbons such as hexane, heptane, octane, cyclohexane, benzene, toluene, and xylene, and ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, and dioxane. The reaction is carried out in these solvents.
The PMS polymer or PMS copolymer is dissolved or swollen with a solvent, and an organic lithium compound is applied. At this time, components that increase the reactivity of the organolithium compound, such as amines, can be used. Amines that can be used include N, N, N',
N'-tetramethylethylenediamine is preferred. The reaction temperature can be freely set from -70°C to the boiling point temperature of each solvent, but in order to efficiently achieve a high lithiation rate, a temperature of room temperature or higher is desirable. Further, the amount of the organolithium compound to be used can be arbitrarily set with respect to the para-methylstyrene skeleton units present, and the lithiation rate can be adjusted as desired. The amines may be used in an equivalent amount to the organolithium compound, but may be used in an excess amount. The reaction time is
Although it varies depending on the reaction temperature, it is usually 0.1 to 100 hours, and the lithiation rate can be increased by increasing the reaction time. The lithiated PMS polymer or PMS copolymer prepared in this way has high reactivity and reacts with moisture in the air.
It is desirable to use it in subsequent reactions. Reaction between the lithiated PMS polymer or PMS copolymer and a silicon compound The reaction between the lithiated PMS polymer or PMS copolymer and a silicon compound is carried out in the first stage in which the lithiated PMS polymer or PMS copolymer is present. This is achieved by directly adding and contacting a silicon compound to the reaction system. The silicon compound is usually used in a molar amount of 1 to 100 times, preferably 1 to 10 times, the amount of the organic lithium compound used in the first stage. The reaction is from -50°C to +150°C, preferably from 0 to 50°C, and from 0.1 to
It is carried out for 100 hours, preferably 0.5 to 20 hours. The produced polymer is preferably washed with water, dilute hydrochloric acid, etc., and is preferably purified by reprecipitation or the like. The styrenic polymer obtained as described above has the following formula:

【formula】

【formula】

[Formula] A polymer consisting of (A) and (B) or a copolymer consisting of (A), (B) and (C). The polymer consisting of repeating units of the above formulas (A) and (B) has a weight average molecular weight of several thousand to several million, weight average molecular weight (w) / number average molecular weight (n) = 1.0 to 1.2
The molecular weight distribution is extremely narrow, and the content of silicon-containing substituents (-SiR ¹ R ² R ³ ) is usually 5 to 80 unit mol %, particularly 5 to 50 unit mol %. In addition, PMS copolymers are composed of randomly bonded repeating units of (A), (B), and (C), or randomly bonded portions of (A) repeating units and (B) repeating units, and (C). ) repeating unit parts are block-coupled. Desirably, it is a random copolymer of (A), (B), and (C). The proportions of (A), (B) and (C) are (A) 1 to 70 mol%, (B) 1 to 97 mol%, and (C) 2 to 98 mol%,
Especially (A) 5-50 mol%, (B) 5-40 mol%, (C) 20-80
% by mole is preferable when used as a resist. This PMS copolymer has a weight average molecular weight of several thousand to several million, and has a weight average molecular weight (w) /
It has a molecular weight distribution of number average molecular weight (n) = 2.0 or less, especially w = 10,000 to 500,000, w/n = 1.0
~1.5 is desirable because it has a large effect when used as a resist. R ¹ , R ² , and R ³ of the repeating unit (A) of the styrenic polymer obtained as described above are the same as in the case of the silicon compound. That is, at least one of R ¹ to R ³ is an alkenyl group. R ¹ , R ² or R ³
When is an alkyl group, a C ₁ -C ₄ alkyl group is preferable, and a methyl and ethyl group are particularly preferable. or,
In the case of the alkenyl group, a _C2 - _C4 alkenyl group is preferable, and vinyl and allyl groups are particularly preferable. The polysilsesquioxane used in the present invention has the general formula is expressed as a repeating unit. Here R and
R' is the same or different alkyl group such as methyl group, ethyl group or propyl group, aryl group such as phenyl group or tolyl group, or alkenyl group such as vinyl group or allyl group. Among these, at least one alkenyl group must be included in at least one of the repeating units. The alkenyl group preferably contains 5 to 30 unit mol% of the total polysilsesquioxane. Among the above R and R', those with methyl group, phenyl group and vinyl group are preferred from the viewpoint of heat resistance. Note that hydrogen and a hydroxyl group are usually bonded to the terminal of the general formula []. The polysilsesquioxane used in the present invention has a weight average molecular weight of several thousand to several hundred thousand. Next, the method for producing polysilsesquioxane is as follows:
For example, it is specifically disclosed in Japanese Patent Application Laid-Open No. 58-59222. According to this, polysilsesquioxanes include lower alkyltrihalogenosilanes such as methyltrichlorosilane and ethyltrichlorosilane, alkenyltrihalogenosilanes such as vinyltrichlorosilane and allyltrichlorosilane, and optionally aryl trihalogenosilanes such as phenyltrichlorosilane. Trihalogenosilane is hydrolyzed in a solvent such as methyl isobutyl ketone or dioxane in the coexistence of an amine such as triethylamine at a temperature of 10 to 50°C. ~
It can be produced by condensation at 110°C for 1 to 6 hours. The proportion of polysilsesquioxane in the composition of the present invention is preferably 10 to 50 parts by weight based on 100 parts by weight of the styrene polymer. If the amount of polysilsesquioxane blended is large, such as exceeding 50 parts by weight, the resolution tends to decrease when used as a resist material. The composition of the present invention can be prepared by dissolving the styrenic polymer and polysilsesquioxane in a solvent and then removing the solvent, or by directly using the dissolved solution. The solvent used to dissolve both is not particularly limited, but
For example, aromatic hydrocarbons such as benzene, toluene, and xylene, and halogenated aromatic hydrocarbons such as monochlorobenzene, dichlorobenzene, and monochlorotoluene can be used. When the photosensitive resin composition thus obtained is used as a resist in the production of semiconductor devices, a commonly used spinner coating method can be used. By dissolving the composition in the above-mentioned solvent and applying the solution to a desired concentration onto a commonly used substrate using a spinner, a uniform resist layer can be formed on the substrate. The resist layer is usually
It is 0.2 to 1.0 μm. This resist layer is usually prebaked, and the conditions are generally 90 to 130°C.
It is 0.1 to 1 hour. Of course, the reaction may also be carried out under reduced pressure and at a lower temperature. Next, the pattern is printed by irradiation with electron beams, X-rays, hyperopic external rays, etc., and after post-paking if necessary, it is developed with a developer of the above-mentioned solvent.
A sharp negative pattern can be obtained. Examples Hereinafter, the present invention will be explained in detail by examples.
The product was identified using the following equipment. ^1H NMR: The sample is a 20 wt% solution of _CDCl3 ,
Measured with Varian EM360A (60MHz). Measurement conditions: 20°C Resist evaluation was performed using the following equipment and conditions. Spinner: Mikasa Co., Ltd., Spinner 1H-D2 type electron beam lithography equipment: Elionix ELS-5000 Irradiation conditions: Irradiation current 7×10 ^-12 A, beam diameter
0.01 μm, accelerating voltage 20 kV Film thickness measurement: Talystep, manufactured by Rank Taylor Hobson Co., Ltd. Example 1 Synthesis of PMS copolymer 100 ml of tetrahydrofuran purified by distillation and 0.54 mmol of n-butyl lithium were placed in a flask purged with nitrogen gas, and dried. It was cooled in an ice-methanol bath and stirred to form a solution. In a separate container, 5.5 ml of PMS and 5.5 ml of αMS under nitrogen gas atmosphere.
and mixed both. Add this mixture to the n-
The mixture was added to the butyllithium solution, and the polymerization reaction was started while stirring. After 2 hours, 2 ml of methanol was added to stop the polymerization reaction. Next, the reaction solution was poured into methanol to precipitate 10.3 g of PMS copolymer. The obtained PMS copolymer was dissolved in tetrahydrofuran and measured by GPC.
Mw=39400, w/n=1.38. or,
As a result of H ¹ NMR analysis, the PMS portion was 50 mol%.
The αMS portion was 50 mol%. The above obtained product was added to a flask purged with nitrogen gas.
2.0 g of PMS copolymer and 40 ml of cyclohexane were added and stirred to form a solution. To this, a solution of 17.4 mmol of n-butyllithium in n-hexane and N,N,
17.4 mmol of N',N'-tetramethylethylenediamine (TMEDA) was added and reacted at 50°C for 2 hours to obtain a lithiated PMS copolymer. The reaction system was then cooled to 20°C, 40 mmol (5.4 g) of allyldimethylchlorosilane was added, and the reaction was continued for 2 hours. After washing the reaction solution with water, it was dropped into methanol to precipitate the polymer, resulting in a white polymer.
2.25g was obtained. When measured by GPC, w
= 44700, w/n = 1.42. The ^1H NMR chemical shift value of this polymer is
It was as follows. ^1H NMR [δ (ppm)]: 7.12-6.14 (benzene ring),
5.74 ( -CH =CH ₂ ), 4.87, 4.82 (-CH= CH
₂ ), 2.24(

[Formula]), 2.08 to 1.14 (− CH ₂

[Formula] Main chain), 0.48-0.00 (

[Formula]), −0.07(

[Formula]) From the integral ratio of the above NMR analysis, the introduction rate of allyldimethylsilyl group is 32.0 unit mol%,
The PMS portion is 18.0 unit mol% and the αMS portion is 50.0 unit mol%. Therefore, this styrenic copolymer is a random copolymer consisting of the following repeating units (A), (B), and (C). found.

【formula】

【formula】

[Formula] Synthesis of polysilsesquioxane In a nitrogen-substituted flask, add 80 ml of methyl isobutyl ketone, 7 ml of triethylamine, 8 ml of trichloromethylsilane, and 2 ml of trichlorophenylsilane.
and 2.5 ml of trichlorovinylsilane were added thereto, and 25 ml of the solution was slowly added over 30 minutes while stirring in an ice-water solution. After the addition was complete, the mixture was heated and stirred at 100° C. for 4 hours. The reaction mixture was washed with water until the washing water was neutral, and the solvent was removed to remove the solids.
9.0g was obtained. When the obtained solid content was made into a CDCl ₃ solution and ¹ H NMR was measured, it was found that δ7.00-7.90 (phenyl group),
Absorption was observed at δ6.10 (vinyl group) and δ0.10 (methyl group). By integrating these absorptions, we get
When the ratio of substituents on the side chains of organopolysilsesquioxane was determined, it was phenyl group: vinyl group:
The ratio of methyl groups was 25:18:57. Resist evaluation 0.3 g of the styrene copolymer containing silicon atoms obtained above and 0.1 g of polysilsesquioxane
was dissolved in 3.6 g of xylene to prepare a xylene solution.
This solution was spin-coated onto a silicon wafer to a thickness of 0.4 μm, pre-baked at 70°C for 30 minutes, irradiated with an electron beam at an irradiation current of 7×10 ^-12 A, developed with a cyclohexanone-isopropanol mixture, and After post-baking for 20 minutes at °C,
A fine pattern of 0.5 μm was resolved. The sensitivity curve showing the relationship between the irradiation dose and the normalized residual film rate is D ^0.5 _g = 2.5 × 10 ^-6 c/cm ² and γ≒2, as shown in curve 1 in the drawing, and when polysilsesquioxane is blended. No decrease in γ value due to this was observed. Oxygen plasma resistance evaluation The above composition was subjected to electron beam irradiation, development and post-bake in the same way as resist evaluation.
A square pattern of m×100 μm was obtained. On the obtained pattern, reactive ion etching of oxygen was performed using a parallel plate reactive ion etching device manufactured by ULVAC under the following conditions: RF output of 100 W, degree of vacuum of 0.05 Torr, and oxygen flow rate of 22 sccm. For comparison, a novolak positive type photoresist ONPR800 (trade name) manufactured by Tokyo Ohka Co., Ltd. was applied to a thickness of 2.0 μm on a silicon wafer.
After baking at ℃ for 30 minutes, reactive ion etching of oxygen was performed in the same manner. The results obtained by etching for 5 minutes were 800 Å for the composition of the present invention and 6000 Å for ONPR800.
The results showed that the composition of the present invention had excellent oxygen plasma resistance. Example 2 Synthesis of PMS Polymer 100 ml of tetrahydrofuran purified by distillation and 0.39 mmol of n-butyllithium were placed in a flask purged with nitrogen gas, cooled in a dry ice-methanol bath, and stirred. refined here
10 g of PMS was added and polymerization was started while stirring. After 2 hours, 2 ml of methanol was added to stop the polymerization reaction. Next, the reaction solution was poured into methanol to obtain 10 g of polymer. When measured by GPC as a tetrahydrofuran solution, w = 34900,
Mw/n=1.16. 2.0 g of the polymer obtained above and 40 ml of cyclohexane were placed in a flask purged with nitrogen gas and stirred to form a solution. To this, a solution of 17.4 mmol of n-butyllithium in n-hexane and N,N,N',N'-
Tetramethylethylenediamine (TMEDA) 17.4
mmol was added and reacted at 50°C for 2 hours to obtain a lithiated PMS polymer. This reaction system was then heated to 20°C.
40 mmol of allyldimethylchlorosilane was added and reacted for 2 hours. After washing the reaction solution with water, it was dropped into methanol to precipitate a polymer, yielding 2.55 g of a white polymer. As a result of GPC measurement, w=45200 and w/n=1.17. According to ¹ H NMR analysis, the introduction rate of allyldimethylsilyl groups was 40.6 unit mol%. ^1H NMR [δ (ppm)]: 7.02-6.10 (aromatic ring), 5.78
( -CH = _CH2 ), 4.94, 4.72( _-CH = CH2 ),
2.25 (

[Formula]), 2.08~1.05 (

[Formula] Main chain) −0.05 (

[Formula]) Resist evaluation 0.3g of silicon-containing PMS polymer obtained above
and polysilsesquioxane synthesized in Example 1
0.1 g was dissolved in 3.6 g of xylene to form a solution. It was coated on a silicon wafer to a thickness of 0.4 μm, prebaked at 70°C for 30 minutes, irradiated with an electron beam at 7×10 ^-12 A, developed with a cyclohexanone-isopropanol mixture, and post-baked at 90°C for 20 minutes, resulting in a thickness of 0.6 μm.
The fine patterns were resolved. The sensitivity curve is like curve 2 in the drawing, D ^0.5 _g = 4.0×10 ^-6 c/cm ² , γ≒
2, and no decrease in γ value was observed due to polysilsesquioxane. Oxygen Plasma Resistance The above composition was subjected to reactive ion etching using oxygen in the same manner as in Example 1. By etching for 5 minutes
ONPR800 was etched to 6000 Å, while the above composition was etched to only 900 Å. Effects of the invention The composition according to the invention has silicon atoms,
Styrenic polymers with extremely narrow molecular weight distribution,
By blending polysilsesquioxane having a silicon atom and a crosslinkable group, a resist pattern with a high silicon content can be obtained. This resist with a high silicon content has excellent oxygen plasma resistance and can be used as an upper layer of a multilayer resist to transfer a pattern to a lower layer using oxygen plasma. Furthermore, the pattern can be printed with a small amount of irradiation, resulting in high sensitivity.

[Brief explanation of drawings]

The drawing is a graph showing the electron beam irradiation sensitivity curve of a resist using the photosensitive resin composition of the present invention. Curve 1 shows the resist of Example 1, and curve 2 shows the resist of Example 2.

Claims (1)

[Claims] 1. General formula [In the formula, R ¹ , R ² and R ³ are the same or different C ₁ to C ₆ alkyl groups or C ₁ to C ₆ alkenyl groups,
At least one of R ¹ , R ² and R ³ is an alkenyl group] A styrenic polymer containing a repeating unit of the general formula [In the formula, R and R' are the same or different alkyl groups,
1. A photosensitive resin composition comprising a polysilsesquioxane having repeating units of [aryl group or alkenyl group], and at least one of the repeating units having at least one alkenyl group.