JPH0455502B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a resist containing a styrenic copolymer having silicon atoms as a component. 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, attempts have been made to use a copolymer of trimethylsilylstyrene and a crosslinkable monomer as a resist material (Japanese Patent Application Laid-Open No. 15419/1983), but since this copolymer is produced by radical polymerization, the molecular weight The distribution becomes wide, and when this copolymer is used as a resist, the resolution is never sufficient. Problems to be Solved by the InventionObject of the Invention The present invention provides a resist having a narrow molecular weight distribution and having excellent oxygen plasma resistance, dry etching resistance, and resolution, which is made of a styrene-based copolymer into which silicon atoms are introduced. The purpose is to provide. Means for Solving the Invention Summary of the Invention The present invention consists of a combination of the following repeating units (A), (B), and (C), and the weight average molecular weight/number average molecular weight =
Resist containing a styrene copolymer with a molecular weight distribution of 1.0 to 2.0

【formula】

【formula】

[Formula] [However, R ¹ , R ² and R ³ are the same or different alkyl groups having 1 to 6 carbon atoms or alkenyl groups having 2 to 6 carbon atoms, and at least R ¹ , R ² and R ³ are One is an alkenyl group. In addition, (A) is 5 to 50 mol%,
(B) 5 to 40 mol%, and (C) 20 to 80 mol%. ] is the gist. Styrenic copolymer The styrenic copolymer, which is a component of the resist of the present invention, is either a combination of the repeating units (A), (B), and (C) mentioned above, or a combination of the repeating units (A) and (B) A random bonding portion with a repeating unit and (C) a repeating unit portion are block-bonded. Desirably, it is a random copolymer of (A), (B), and (C). (A),
The proportions of (B) and (C) are (A) 5 to 50 mol%, (B) 5 to 40 mol%, and (C) 20 to 80 mol%. This styrenic copolymer has a weight average molecular weight of several thousand to several million, and has a weight average molecular weight (
It has a molecular weight distribution of w)/number average molecular weight (n) = 1.0 to 2.0, but especially w = 10,000 to 500,000, w/
A material with n=1.0 to 1.5 is preferable because it has a large effect when used as a resist. Method for producing styrenic copolymer Styrenic copolymer is a random or block copolymer (hereinafter referred to as PMS copolymer) of p-methylstyrene (hereinafter referred to as PMS) and α-methylstyrene (hereinafter referred to as αMS). ) is brought into contact with an organolithium compound to partially lithiate the para-methyl groups in the PMS copolymer, and then the formula (R ¹ )(R ² )(R ³ )SiX [where R ¹ , R ² and R ³ are the same or different alkyl groups having 1 to 6 carbon atoms or alkenyl groups having 2 to 6 carbon atoms, and R ¹ , R ² and
At least one of R ³ is an alkenyl group. or,
X represents a halogen atom. ] It can be produced by reacting with a silicon compound represented by: Each compound used in producing the styrenic copolymer will be explained. PMS copolymer PMS copolymer can be produced by random or block copolymerization of PMS and αMS using normal radical polymerization method or living polymerization method. Especially, when living polymerization method is adopted, narrow molecular weight This is desirable because a copolymer with a well-distributed distribution can be obtained. Further, if the repeating units (B) of the styrene copolymer are uniformly dispersed, the effect is great when used as a resist, so a random copolymerization method is preferable. Living polymerization is carried out in the presence of an initiator that forms a styryl anion, such as an organolithium compound such as n-butyllithium or sec-butyllithium. Moreover, living polymerization can be performed in the presence of a solvent. As a solvent, hexane, heptane, octane, cyclohexane, benzene, toluene,
Examples include hydrocarbons such as xylene, and ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, and dioxane. In living polymerization, PMS and αMS are heated from -80℃ to +50℃.
It is carried out by reacting at a temperature of 0.5 to 50 hours. Random copolymerization is carried out by simultaneously copolymerizing PMS and αMS, and 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
(mole ratio) is 2 to 98/98/2, preferably 25 to
75/75~25. By doing this, several thousand ~
Number average molecular weight of several million, preferably 10,000 to 500,000,
Mw/n is less than 2.0, preferably 1.0 to 1.5,
A PMS copolymer having the above molar ratio of PMS portion/αMS portion is obtained. Organolithium Compound The organolithium compound used in lithiation of the 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-pentyllithium, tert-pentyllithium, hexylylithium, octyllithium, and todecyllithium, but butyllithium is particularly preferred. Silicon compound The silicon compound is represented by the above formula, and when R ¹ , R ² , and R ³ in the formula are alkyl groups, it is preferably a methyl, ethyl, n-propyl, or n-butyl group, particularly methyl, Ethyl group is preferred.
When R ¹ , R ² , and R ³ are alkenyl groups, vinyl, allyl, propenyl, isopropenyl, and butenyl groups are preferable, and vinyl and allyl groups are particularly preferable. X is preferably a chlorine atom. Reaction between PMS copolymer and organolithium compound The reaction between PMS copolymer and organolithium compound is as follows.
This 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. In the reaction, the PMS copolymer is dissolved or swollen in these solvents, and then an organic lithium compound is allowed to act on the PMS copolymer. 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. Furthermore, the amount of the organolithium compound to be used can be arbitrarily set with respect to the existing paramethylstyrene bone core units, 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 copolymer thus prepared has high reactivity and reacts with moisture in the air, so it is desirable to use it in the subsequent reaction without separating it. Reaction between lithiated PMS copolymer and silicon compound The reaction between lithiated PMS copolymer and silicon compound is carried out by directly adding the silicon compound to the first reaction system in which the lithiated PMS copolymer is present. This is achieved by The silicon compound usually has a ratio of 1 to 1 to the organolithium compound used in the previous step.
It is used in an amount of 100 times the mole, preferably 1 to 10 times the mole.
The reaction is carried out at 50°C to +150°C, preferably 0 to 50°C with a temperature of 0.1
~100 hours, preferably 0.5 to 20 hours.
The produced polymer is preferably washed with water, diluted hydrochloric acid, etc., and is preferably purified by reprecipitation or the like. R ¹ , R ² , and R ³ of the repeating unit (A) of the styrenic copolymer 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
When R ³ is an alkyl group, a C ₁ -C ₄ alkyl group is preferable, and a methyl and ethyl group are particularly preferable.
Further, in the case of an alkenyl group, a C ₂ -C ₄ alkenyl group is preferable, and vinyl and allyl groups are particularly preferable. When the styrene copolymer thus obtained is used as a resist in the production of semiconductor devices, a commonly used spinner coating method can be used. The solvent and developer used to dissolve the copolymer are not particularly limited, but include aromatic hydrocarbons such as benzene, toluene, and xylene, and halogenated aromatic hydrocarbons such as monochlorobenzene, dichlorobenzene, and monochlorotoluene. etc. can be used. The copolymer was dissolved in the above-mentioned solvent and the solution was prepared to a desired concentration, and then applied onto a commonly used substrate.
Spinner coating forms a uniform resist layer on the substrate. The resist layer is usually
It is 0.2-1.0 μm. This resist layer is usually prebaked, and its conditions are generally 90~130°C with a temperature of 0.1
~1 hour. Of course, the reaction may also be carried out under reduced pressure and at a lower temperature. Next, the pattern is baked by irradiation with electron beams, X-rays, deep ultraviolet rays, etc., post-baked if necessary, and then developed with the developer described above to obtain a sharp negative pattern. Effects of the Invention The styrene copolymer according to the present invention has a very narrow molecular weight distribution, so it has excellent resolution, and since it contains silicon atoms, it can be used as a resist with excellent oxygen plasma resistance. It combines the advantages of combination, such as ease of handling and excellent dry etching resistance.
Furthermore, the pattern can be printed with a very small amount of radiation and has high sensitivity. In addition, since the copolymer has excellent heat resistance, it does not swell during development.
Therefore, it has excellent resolution. 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 2.0 to 6.0×10 ^-11 A, beam diameter
0.01 μm, accelerating voltage 20 kV Film thickness measurement: manufactured by Lacterra Hopson, Takstep 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%. Furthermore, this
The glass transition temperature (Tg) of PMS copolymer is 132.2
It was warm at ℃. Synthesis of styrenic copolymer The above-obtained
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. Also, Tg is
It was 98.3℃. 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 ),

[Formula] 2.08~1.14 (

[Formula] main chain),

【formula】

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

【formula】

【formula】

[Formula] Resist evaluation Xylene of the styrenic copolymer obtained above
A 10% by weight solution was prepared. This solution was spin-coated onto a silicon wafer to a thickness of 0.5 μm and heated at 70°C for 30 min.
Prebaked for a minute. Next, it was irradiated with an electron beam under the above conditions, developed with a mixture of cyclohexanone and isopropanol, and post-baked at 120°C for 20 minutes. was gotten. When a fine pattern of 0.3 μm was resolved after post-baking, it was found that the resulting pattern had good rectangularity and little swelling during development. Furthermore, when this resist pattern was heated in an oven at 120°C for 20 minutes, it did not deform. Example 2 In the same manner as in Example 1, PMS8.4ml and αMS2.8
ml was copolymerized to obtain 10.9 g of PMS copolymer.
The w of this PMS copolymer is 37600, and the w/n is
1.41, and Tg was 120.6°C. Further, the PMS portion was 75.0 mol% and the αMS portion was 25.0 mol%. 2.0 g of this copolymer was lithiated in the same manner as in Example 1, and then reacted with allyldimethylchlorosilane to obtain 2.2 g of a white polymer. The w of this styrene copolymer is 47500, w/
n was 1.57 and Tg was 96.0°C. Also, it consists of the same repeating units (A), (B), and (C) as in Example 1, and (A) _37.9
It was a random copolymer of (B) _37.1 (C) _25.0 . When this styrene copolymer was subjected to resist evaluation in the same manner as in Example 1, a sensitivity curve as shown by the broken line in the drawing was obtained. A fine pattern of 0.3 μm was resolved, and the rectangularity and heat resistance were both as good as in Example 1. Example 3 In the same manner as in Example 1, PMS2.8ml and αMS8.3
ml was copolymerized to obtain 10.4 g of PMS copolymer.
The w of this PMS copolymer is 25800, and the w/n is
1.25, and Tg was 156.7°C. Further, the PMS portion was 25.0 mol% and the αMS portion was 75.0 mol%. 2.0 g of this copolymer was lithiated in the same manner as in Example 1, and then reacted with allyldimethylchlorosila to obtain 2.4 g of a white polymer. The w of this styrene copolymer is 30800, and the w/n is
1.34, Tg was 134.4°C. Also, it consists of the same repeating units (A), (B), and (C) as in Example 1, and (A) _15.5 (B) _9
.
It was a random copolymer of ₅ (C) _75.0 . The resist was evaluated in the same manner as in Example 1, and a sensitivity curve as shown by the dotted line in the drawing was obtained. When a 0.3 μm fine pattern was resolved, it had good rectangularity and heat resistance, and did not deform even when heated to 140°C.

[Brief explanation of drawings]

The drawing is a graph showing the electron beam irradiation sensitivity curve of the resist of the present invention.

Claims (1)

[Claims] 1 Consisting of the following repeating units (A), (B) and (C), weight average molecular weight/number average molecular weight = 1.0 to 2.0
A resist whose component is a styrene copolymer with a molecular weight distribution of . [Formula] [Formula] [Formula] [However, R ¹ , R ² and R ³ are the same or different alkyl groups having 1 to 6 carbon atoms or alkenyl groups having 2 to 6 ^carbon atoms; At least one of ² and R ³ is an alkenyl group. In addition, (A) is 5 to 50 mol%,
(B) 5 to 40 mol%, and (C) 20 to 80 mol%. ]