JPS61249049A - Method for developing resist - Google Patents

Abstract

PURPOSE:To obtain a fine pattern high in resolution by using a developing soln. contg. fatty acid esters in the specified b.p. range for developing a positive type radiation resist contg. a copolymer of a specified styrene type monomer and a specified acrylate type monomer. CONSTITUTION:The positive type radiation resist contains a copolymer of repeating units each represented by formula I and those each represented by formula II, and in these formulae, R<1>, R<2>, R<3> are each halogen, lower alkyl, lower haloalkyl, OH, CN NH2 or the like, R<4> is lower alkyl, lower haloalkyl, or CN, and R<5> is lower alkyl, lower haloalkyl, aryl, or aralkyl. This resist is developed with a developing soln. contg. fatty acid ester in the b.p. range of 70-180 deg.C alone or in its mixture at room temp. thus permitting an image high in contrast to be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resist development method when forming a fine pattern using a positive resist material.

[Conventional technology]

In recent years, in the semiconductor industry, there has been a demand for higher integration of LSIs, and as a result, the minimum processing line width of circuits has become increasingly finer, from several microns to microns, and even to the submicron range. It is strongly desired that the However, the current mainstream photoresists that are sensitive to visible light and ultraviolet rays have a practical processing limit of about 1 micron, and are not suitable for ultra-fine processing of shorter wavelengths such as far ultraviolet rays, X@,
It is required to use a resist material that is sensitive to high-energy radiation such as electron beams, gamma rays, and ion beams. In this case, the resist material has characteristics such as high resolution, high dry etching resistance, and high sensitivity! ! required. In particular, resolution is the first factor that determines how precisely a fine circuit pattern can be formed, and the higher it is, the better.

In other words, a resist material with a contrast (γ value) that is a measure of resolution is preferable. Polymethyl methacrylate (P) is currently one of the resist materials with the highest resolution.
MMA) is known, and its resolution is said to be less than 0.1 μm (for example, Masao Kato, Kagaku Shokukan, Len 4.,
P, ] 3 ]-143 (1984)).

PMMAt'i was first reported as an electron beam resist material in 1968, although its dry etching resistance was not good and its sensitivity was not particularly high (I.

Haller et al., IBM Journal
Al, May ] 9681251 (1968)), it is the most commonly used resist material. This is due to its extremely high resolution, and shows how the resolution of the resist material is yjLJM: in submicron microfabrication.

In a previous patent application, the present inventors have developed a copolymer (patent application) that has excellent dry etching resistance, without deteriorating sensitivity and contrast, and in some cases even improving it, compared to PMMA, etc. No. 113494/1982) and compositions (I# Application No. 163686/1983, Patent Application No. 183359/1983), and also PMMA, which has a sensitivity of 10 times or more, contrast, and dry etching resistance. Copolymer with excellent properties (Patent application 1986-163)
No. 617) was disclosed.

[Problem that the invention seeks to solve]

A feature of the resist material disclosed by the present inventors is that the sensitivity and contrast of the resist are strongly influenced by the type of developing solvent used in the developing step.

An object of the present invention is to provide a method for realizing even more excellent high-contrast development without sacrificing the sensitivity and dry etching resistance of the resist material, and without causing any handling problems. .

[Means for solving problems]

According to the research conducted by the present inventors, when the above resist material is developed using a developer containing fatty acid ester solvent gold as the main component, it becomes an indicator of resolution, which is the most important factor during microfabrication. It was discovered that development with extremely high contrast can be achieved, leading to the present invention.

That is, the present invention uses a developer having a boiling point of 70 to 180'C when developing a positive radiation resist material # containing a copolymer A mainly composed of structural units represented by the following general formulas 1 and H. This is a resist developing method characterized by using a resist developer comprising a fatty acid ester within a range.

Copy H3 E' (here, kl, R2, R'' are hydrogen, halogen, lower, where the content of structural unit l in the copolymer AK is 3
~97 mole, preferably 3 to 50 mole. Further, the content of the structural unit n is 97 to 3 molt, preferably 50
~97 mol% d(! I.

Since the comonomer (A) is composed of the above structural units I and (2), it does not pose any problems as a positive radiation resist material in itself, and has extremely excellent properties, especially in terms of contrast and dry etching resistance. However, if it is desired to further improve the sensitivity, adhesion to the substrate, film-forming properties, etc., a small amount of any other structural unit may be introduced according to a conventional method. For example, a small amount of a third structural unit can be added to the above polymer to further improve sensitivity. That is, if the present 1-layer method disclosed in the present invention is applied when using a joint N base body having the following structures I, II, and m as a positive radiation resist material, contrast and durability can be improved. Highly sensitive development is possible without sacrificing dry etching properties.

H3 (Here, R', R2, R'' are the same 0 as above) COO
R5< is 97 to 50 molty (here, R4 and R5 are the same as above). Here, the structure of It can also be introduced by forming a corresponding copolymer from monomers such as methacrylamide, and converting some or all of the methacrylamide units into methylol by a conventional method.

(Here, R6 and R7 are the same as above.) In this case, the structural units of the general formulas (1) and (2) coexist, but this does not cause any deterioration in the performance of the resist. In some cases, resist properties may be improved if the number of structural units (■') is larger than that of (III).

In order to improve the dry etching resistance, a polymer (B) having the structural unit 1t as a main component may be blended with the above-mentioned comonomer (A). At that time, the blend ratio of polymer (B) to co-monomer A is 3! It is preferably in the range of from 1 to 50% by weight, particularly from 0 to 50Ji:it%. If the polymer (B) is blended in an amount exceeding 501 ir%, although the dry etching resistance is improved, other properties such as sensitivity may be lowered.

Examples of structural unit I include the following.

゛Hs Also, the preferred structures of (1) are shown in monomer units: methyl methacrylate, butyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, t-butyl methacrylate, octyl methacrylate. methacrylic acid lower alkyl esters such as
Aryl methacrylates such as phenyl methacrylate, aralkyl methacrylates such as benzyl methacrylate and dimethylbenzyl methacrylate, trifluoroethyl methacrylate, trifluoroisopropyl methacrylate, tetrafluoropropyl methacrylate, pentamethacrylate Fluoroalkyl methacrylates such as fluoropropyl, hexafluorobutyl methacrylate, heftafluoropter, nonafluorohexyl methacrylate, chloroalkyl methacrylates such as dichloroethyl methacrylate, trichloroethyl methacrylate, α-Cyanacrylic acid alkyl esters such as α-methyl cyanacrylate, α-methyl cyanacrylate, α-cyanoacrylate, α-cyanoacrylic acid trifluoroether, α
-α- Methyl chloroacrylate, α-ethyl dichloroacrylate, α-trifluoroethyl chloroacrylate, etc.
Examples thereof include chloroacrylic acid alkyl esters and α-halofurkylacrylic acid esters such as methyl α-trifluoromethylacrylate.

Examples of the structural unit (■) include the following.

N (-CH2-C+ CONHCIhOH In the present invention, the copolymer may contain not only one type but also two or more types of structural units represented by the general formulas 1.ff and m.

The polymer (fl) and copolymer (A) used in the present invention can be easily developed by known methods. For example, polyα-methylstyrene can be synthesized by cationic polymerization or anionic polymerization, and a polyα-methylstyrene-methacrylic acid me,te,ru-N-methylolmethacrylamide terpolymer can be synthesized by emulsion copolymerization.

In addition, the molecular weight is 1.0, which is the same as normal resist.
If the molecular weight is too small in the range of 00 to 1,000,000, not only will film forming properties be poor, but also sufficient sensitivity may not be obtained. Furthermore, if the molecular weight is too high, not only will synthesis be a national problem, but film-forming properties may also be deteriorated. The preferred molecular weight is 10,000-i, o o o, o o o
It is.

The radiation used in the present invention includes electron beam,
Examples include @, ion beam, gamma rays, and far ultraviolet rays. The method of drawing patterns using these rays is as follows:
Either a direct pattern writing method in which a beam is scanned or an indirect pattern writing method in which a mask having a desired pattern is interposed can be employed. Note that positive type means that the portions irradiated with these radiations decompose.

The developer used in the present invention has a boiling point of 70-[
It is mainly composed of fatty acid esters at a temperature of 80°C, particularly 70 to 150°C. If the boiling point is below 70°C, stable development may not be possible because of the tendency to evaporate.If the boiling point is above 180°C, residual developer may become a problem after development. Solvents that meet the above conditions include ethyl acetate (boiling point 76.8°C), methyl propionate (boiling point 76.8°C),
7℃), propyl formate (81.2℃), isopropyl acetate (89.4℃), isopnal formate (97.7℃), tert-butyl acetate (97.8℃), ethyl propionate (99.1' C) % propyl acetate (101,6°C),
Methyl butyrate (102,3°C), inglovir propionate (106°C), butyl formate (106,8°C), acetic acid 5
ec-butyl (112,2°C), isobutyl acetate (11
6℃), ether butyrate (121.3℃), propyl propionate (122℃), inamyl formate (123.6℃)
, butyl acetate (126,3°C), methyl valerate (127
°C), amyl formate (] 330 °C, isobutyl propionate (138 °C), inamyl acetate (142 °C), propyl butyrate (144 °C), ethyl valerate (145.5 °C),
Butyl propionate (146.8℃), amyl acetate (1
48.9℃), methyl caproate (150℃), isobutyl butyrate (157℃), butyl butyrate (164.8℃),
Ethyl turnipate (167.7℃), hexyl acetate (1
71.5°C), methyl enanthate (173°C), and in7mil butyrate (179°C), but acetic acid esters are preferred, and isoamyl acetate is particularly preferred. On the other hand, non-applicable fatty acid esters include methyl formate (boiling point 31.5°C), ethyl formate (54.1°C), methyl acetate (56.3°C), propyl caproate (185°C),
Enanthate ether (187℃), methyl caprylate (1
93°C), phenyl acetate (195.7°C), and benzyl acetate (214.9°C).

Regarding the components of the developer, in order to achieve high-contrast development, it is practically preferable to use a single solvent or a mixture of two or more solvents that meet the above conditions. - Other solvents may be mixed and used within the following ranges.

Fine pattern formation by the resist development method of the present invention is as follows:
This method can be carried out in exactly the same manner as the conventional fine pattern forming method using a positive resist material. In other words, it is as follows. A solution in which the resist material used in the present invention is dissolved in a suitable solvent is formed into a thin film on a substrate by a commonly used spin code method, and this is irradiated with radiation to draw a fine pattern. Next, this substrate is immersed in the developer disclosed in the present invention at a predetermined temperature for a predetermined time to remove the irradiated area, and dry etched to etch the substrate with high density to form a fine pattern. form.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

Resist Synthesis Synthesis Example 1 Methylene chloride 5201117. α-methylstyrene (M
The system consisting of 8f was maintained at -78° C. under dry nitrogen, and 0.68% of boron trifluoride ethyl ether complex was added thereto and reacted for 3 hours. The reaction mixture was precipitated into methanol to obtain a homopolymer of α-methylstyrene with a yield of 95m. The weight average molecular weight (Mw) of the polymer measured by gel permeation chromatography (abbreviated as GPC) using polystyrene as a standard was 360,000, and the Mw/Mn (number average molecular weight) was 2.5. .

Synthesis Example 2 Water 6011/, MS77F, methyl methacrylate (MM
A system consisting of 135f (abbreviated as A) and 1.1f of sodium dodecylbenzenesulfonate is heated to 80°C under nitrogen, and 0.
85F was added and reacted for 4 hours with stirring. After the completion of the reaction, the resulting product was salted out with 9m sodium chloride and washed with water and methanol to obtain a white polymer with a yield of 80%.

The white polymer was then dissolved in tetrahydro7ran, and fractionated by adding hexane for fractional precipitation. The molecular weight of the polymer by GPC is 6 with a Mw of 350.000.
J), MW/Mn was 2.1T6. The copolymer composition ratio (molar ratio) calculated from the elemental analysis value and the HNMR spectrum was MS/MMA=30/70.

Synthesis Example 3 600 d of water, MSI 1 B? , MMA] QQf, N-
A system consisting of 6.9f of methylolmethacrylamide (sometimes abbreviated as MMAM) and 2.22f of sodium dodecylbenzenesulfonate was heated to 80'G K under nitrogen, and 0.44F of potassium beluochinisulfate was added and stirred. The reaction was continued for 200 hours. After the reaction was completed, the resulting product was salted out with sodium chloride and washed with water and methanol to obtain a white polymer with a yield of p70'lA. The white polymer was then dissolved in tetrahydrofuran and separated by fractional precipitation by adding hexane.

The molecular weight of the polymer determined by GPC is Mw of 360,000.
The MW/Mn was 2.31. The copolymer composition ratio (molar ratio) calculated from the elemental analysis value is MS/MMA/
MMAM=35.0/64.0/1.0 〇Example Specified resist polymer was mixed with 3s toluene or 1.4
- Prepare a dioxane solution, form this into a film with a thickness of about 400 OA on a glass substrate using a spin code, and then heat it to a temperature of 180°C.
After prebaking at ~190° C. for 20 minutes, it was irradiated with an electron beam (acceleration, voltage 4 KV, irradiation current density 8.9×10 −′ C/d ). Thereafter, development was performed at 25° C. for a predetermined time using a predetermined developer.Sensitivity Table 1 shows the results for the copolymer system. When the development method of the present invention is used, compared to the case where methyl isobutyl ketone (sometimes abbreviated as MIBK) or the like is used for a copolymer of the same composition, there is almost no decrease in sensitivity and high contrast development can be achieved. It turns out that it can be done.

Table 2 shows the experimental results for the blend system. Polymer B here is polyα-methylstyrene synthesized in Synthesis Example]. In this case as well, when the developing method of the present invention is used, the contrast is increased while maintaining almost the same sensitivity as when developing using MI BK.

Table 3 shows the resist properties of a polymer obtained by copolymerizing a methacrylic acid ester other than t1MMA with MS in the same manner as in Synthesis Examples 2 and 3 using isoamyl acetate as a developer. It can be seen that in these cases as well, the contrast is increased while maintaining almost the same sensitivity as in the case of MIBK development.

In addition, copolymers with compositions not described in the previous synthesis examples were synthesized according to the previous synthesis examples.
The following margins [Effects of the Invention] By using the resist developing method of the present invention, development with extremely high contrast has become possible without causing any operational problems. In particular, for example, MS-MMA-MMA
When a highly sensitive resist material such as M ternary copolymer is used, it satisfies all of the strong requirements for a resist material for ultrafine processing: high sensitivity, high contrast, and high dry etching resistance. A patterning method is provided.

Claims (5)

[Claims] (1) When developing a positive radiation resist material containing a copolymer (A) mainly composed of structural units represented by the following general formulas I and II, the developer has a boiling point of 7.
A resist developing method characterized by using a resist developer comprising fatty acid esters having a temperature in the range of 0 to 180°C. I ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (Here, R^1, R^2, R^3 are hydrogen, halogen, lower alkyl group, lower haloalkyl group, lower alkoxy group, lower acyl group, hydroxy group, cyano group, amino group,
The same or different substituents are selected from lower alkylamino groups. ) II▲Mathematical formulas, chemical formulas, tables, etc.▼ (Here, R^4 is a lower alkyl group, a lower haloalkyl group,
halogen or cyano group, and R^5 is a lower alkyl group, lower haloalkyl group, aryl group, or aralkyl group). (2) A copolymer containing 3 to 50 mol% of structural units represented by the following general formula I and 50 to 97 mol% of structural units represented by the following general formula II as the copolymer (A). The developing method according to claim 1, which uses the following. I ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (Here, R^1, R^2, R^3 are the same as above) II▲There are mathematical formulas, chemical formulas, tables, etc.▼ (Here, R^4, R^3 5 is the same as above) (3) The developing method according to claim 1, wherein a copolymer having the structural units and compositions represented by the following general formulas I, II and III is used as the copolymer (A). I ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ 3 to 97 mol% (Here, R^1, R^2, R^3 are the same as above.) II ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ 97 to 3 Mol% (Here, R^4 and R^5 are the same as above.) III▲There are mathematical formulas, chemical formulas, tables, etc.▼0.01 to 20
Mol% (where R^6 is a lower alkyl group, halogen or cyano group, and R^7 is hydrogen or a lower alkyl group.) (4) The developing method according to claim 3, wherein a copolymer having a structural unit and composition represented by the following general formulas I, II, and III is used as the copolymer (A). I ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ 3 to 50 mol% (Here, R^1, R^2, R^3 are the same as above.) II ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ 97 to 50 Mol% (Here, R^4 and R^5 are the same as above.) III▲There are mathematical formulas, chemical formulas, tables, etc.▼0.01 to 0 mole% (Here, R^6 and R^7 are the same as above. .) (5) Claim 2, characterized in that the resist material is a composition in which not more than 50% by weight of a polymer (B) containing structural units of general formula I below is mixed. Developing method according to item 3 or 4. I ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (Here, R^1, R^2, and R^3 are the same as above.)