Base material for lithography

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention is a novel substrate material for lithography, more specifically, a substrate material for lithography that has conformality, can suppress the influence of diffused reflection and standing waves from a substrate, has an excellent antireflection effect, and can form a good resist pattern. Regarding.

【0002】

[Previous technology]

Conventionally, in the manufacture of semiconductor devices, microfabrication by lithography using a phosphate composition has been performed. In the microfabrication, a thin film of a photoresist composition is formed on a silicon wafer, and an active ray such as an ultraviolet ray is irradiated through a mask pattern on which a pattern of a semiconductor device is drawn to develop the resist. This is a processing method in which a silicon wafer is etched using a pattern as a protective film. However, in recent years, the degree of integration of semiconductor devices has been increasing, and the active light beam used tends to be shortened from the i-line (365 nm) to the ArF excimer laser (248 nm). Along with this, the influence of diffused reflection of active light from the substrate and standing waves becomes a big problem, and as a base material for lithography to solve it, for example, in Japanese Patent Application Laid-Open No. 59-93448, curcumin, picricin, and coumarin are selected. The base material containing the dye and polyamic acid polymer is a base material containing a resin obtained by polymerizing a diphenylamine derivative and a melamine derivative in the presence of an acid catalyst and a highly absorbent substance, etc. Has been proposed. However, the substrate material for lithography has insufficient compatibility between the ultraviolet absorber and the resin component, the amount of the ultraviolet absorber that can be blended is limited, and intermixing is performed between the resist layer and the antireflection layer. The antireflection effect could not be sufficiently enhanced. Therefore, the applicant has published a base material containing a copolymer of glycidyl methacrylate and methyl methacrylate and an ultraviolet absorber as a base material for lithography without the above-mentioned defects in Japanese Patent Application Laid-Open No. 6-35201, and at least two crosslinks are formed. A base material for lithography containing a triazine compound having a functional group, a highly absorbent substance, and an alkali-insoluble acrylic resin was proposed in Japanese Patent Application Laid-Open No. 8-87115. The substrate material for lithography suppresses the reflection of irradiation light from the substrate and enhances the fidelity of the resist pattern to the mask pattern. However, the miniaturization of the semiconductor element is from half micron (0.5 μm) to quarter micron (0). ..

【0003】

[Problems to be Solved by the Invention]

In view of this situation, the present inventors have conducted extensive research, and as a result, it is possible to reduce the difference between the film thickness of the upper part of the step and the film thickness of the lower part of the step substrate of the base material coating film, that is, to improve the so-called conformability. It was found that it is preferable to form a fine resist pattern of quarter micron or less, and in order to enhance this conformability, it was found that the degree of polymerization of the alkali-insoluble acrylic resin should be 500,000 or more, and the present invention has been found. Is completed.

【0004】

That is, an object of the present invention is to provide a base material for lithography which is excellent in conformality and antireflection effect and can form a good resist pattern.

【0005】

[Means for solving problems]

The present invention that achieves the above object is a substrate for lithography containing an alkali-insoluble acrylic resin having a weight average molecular weight of 500,000 to 2,000,000, a highly absorbent substance, and, if necessary, a triazine compound having at least two crosslink-forming functional groups. Related to materials.

【0006】

The alkali-insoluble acrylic resin in the present invention is a (meth) acrylic acid such as glycidyl (meth) acrylate such as glycidyl acrylate and glycidyl methacrylate, methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. A polymer obtained by polymerizing a monomer such as alkyl, which has a weight average molecular weight of 500,000 to 2,000,000, preferably 800,000 to 1,300,000, such as polyglycidyl (meth) acrylate, polymethyl (meth) acrylate, and polyethyl (meth) acrylate. , A copolymer of glycidyl (meth) acrylate and alkyl (meth) acrylate. Among them, the base material containing a copolymer having a weight ratio of glycidyl (meth) acrylate and methyl methacrylate of 2: 8 to 8: 2, preferably 3: 7 to 7: 3, does not have intermixing with the resist layer. Moreover, it indicates the degree of film reduction of the base material with respect to the upper layer resist, and has a high selection ratio, which is suitable. If the weight average molecular weight of the alkali-insoluble acrylic resin is less than 500,000, the conformality is not improved, and if the weight average molecular weight exceeds 2,000,000, the solubility of the base material in the solvent deteriorates, and a uniform coating film is formed. Is difficult, and the antireflection effect is inferior.

【0007】

The alkali-insoluble acrylic resin is produced, for example, by the following method. That is, organic solvents such as methyl ethyl ketone and acetone, aromatic hydrocarbons such as benzene, toluene and ethyl benzene, chloroform, carbon tetrachloride and the like, which are 1 to 5 times by weight of the total weight of the above-exemplified monomers. Dissolve in halogenated hydrocarbons, etc., and add polymerization initiators such as azobisisobutyronitrile, azobisvaleronitrile, benzoylperoxide, and laurylperoxide at a ratio of 0.01 to 0.5% by weight based on the total weight of the monomers. A method in which the polymer is added and reacted at a reaction temperature of 50 to 80 ° C for 3 to 12 hours in a nitrogen atmosphere, the obtained polymer is added to alcohol such as methanol and ethanol to precipitate, and the polymer is dried under reduced pressure. And so on.

【0008】

The highly absorbent substance, which is a component of the base material of the present invention, has a high absorption ability for light in the photosensitive characteristic wavelength range of the photosensitive component in the resist layer formed on the base material, and is reflected from the substrate. Any substance can be used as long as it can prevent diffused reflection due to standing waves and steps on the surface of the substrate, and a known absorbent substance can be used as a component of the base material or the antireflection film. Specifically, salichet-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based, azo-based, polyene-based, anthraquinone-based or generalized formula 1 [0009]

[Chemical 1]

<img file="JPH1069072A_D0001.tif" />(In the formula, X is -CO-, -SO- or -SO₂-, R₁, R₂Are hydrogen atoms, halogen atoms, lower alkyl groups or lower alkoxy groups, respectively, which may be the same or different from each other, where k, m, p and q are integers 1 to 3 respectively. Satisfy the relationship of k + m = 5 and p + q = 5. R₁If there is more than one, each R₁May be the same or different, and R₂If there is more than one, each R₂May be the same or different. ), And the like. Specific examples of the compound represented by the general formula 1 in which X is -CO- include 2,2'-dihydroxybenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, and 2-hydroxy-4-methoxy. Examples include hydroxybenzophenones such as benzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and X is -SO.₂-Specific examples include bis (2,4-dihydroxyphenyl) sulfone, bis (3,4-dihydroxyphenyl) sulfone, bis (3,5-dihydroxyphenyl) sulfone, bis (3,6-dihydroxyphenyl) sulfone. , Bis (4-hydroxyphenyl) sulfone, Bis (3-hydroxyphenyl) sulfone, Bis (2-hydroxyphenyl) sulfone, Bis (hydroxyphenyl) sulfone such as Bis (3,5-dimethyl-4-hydroxyphenyl) sulfone Specific examples of X being -SO- include bis (2,3-dihydroxyphenyl) sulfoxide, bis (2,4-dihydroxyphenyl) sulfoxide, bis (2,5-dihydroxyphenyl) sulfoxide, and bis. (3,4-dihydroxyphenyl) sulfoxide, bis (3,5-dihydroxyphenyl) sulfoxide, bis (5-chloro-2,3-dihydroxyphenyl) sulfoxide, bis (5-chloro-2,4-dihydroxyphenyl) sulfoxide , Bis (5-chloro-2,3,4-trihydroxyphenyl) sulfoxide, bis (5-chloro-2,4,6-trihydroxyphenyl) sulfoxide, bis (2,4-dihydroxy-6-methylphenyl) Examples thereof include bis (hydroxyphenyl) sulfoxides such as sulfoxide, bis (2,3,4-trihydroxy-6-methylphenyl) sulfoxide, and bis (2,4,6-trihydroxy-6-methylphenyl) sulfoxide. In particular, hydroxybenzophenones, especially 2,2', 4,4'-tetrahydroxybenzophenone, bis (hydroxyphenyl) sulfones, especially bis (4-hydroxyphenyl) sulfones, bis (hydroxyphenyl) sulfoxides, especially bis ( Base materials containing 2,4-dihydroxyphenyl) sulfoxide have low transmission to i-line (365 nm) or deep UV, especially KrF excima laser with a wavelength of 248 μm, can increase thermal cross-linking reactivity, and do not cause intermixing. Is suitable.

【0010】

In addition, the triazine compound having at least two crosslink-forming functional groups, which is a component of the base material of the present invention and is added as needed, includes either or both of the components that are self-sufficient or used in combination by heating. Generalization with at least two functional groups capable of forming crosslinks between them 2 [0011]

[Chemical 2]

<img file="JPH1069072A_D0002.tif" />(In the formula, R is a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or -NR.₃R₄Is the basis and R₃, R₄The groups may be the same or different from each other, representing a hydrogen atom, a methylol group, an alkoxymethyl group, respectively, and 4 to 6 Rs in the molecule.₃, R₄At least two of them are methylol groups or alkoxymethyl groups. ) Can be mentioned as a substituted melamine or a substituted guanamine. Examples of the functional group include a methylol group and an alkoxymethyl group, and the methylol group or the alkoxymethyl group per triazine ring is contained in the range of 3 or more and less than 6 on average. The triazine compound may be a dimer or a trimer, and can be produced by reacting melamine or guanamine with formalin in boiling water to form methylol, or further reacting this with a lower alcohol to form an alkoxyl. Among these compounds, melamine having an average of 3.7 methoxymethyl groups substituted and melamine having an average of 5.8 methoxymethyl groups substituted are commercially available products M._X-750 and M_WAvailable as -30 (manufactured by Sanwa Chemical Co., Ltd.).

【0012】

The blending ratio of each component in the present invention is 10 to 40 parts by weight, preferably 20 to 30 parts by weight of the highly absorbent substance with respect to 100 parts by weight of the alkali-insoluble acrylic resin, and if it is less than the above range, the antireflection effect is obtained. It is not preferable because it becomes insufficient, and if it exceeds it, intermixing occurs and a uniform solution cannot be obtained.

【0013】

If necessary, when a triazine compound having at least two crosslink-forming functional groups is blended, 1 to 100 parts by weight of an alkali-insoluble acrylic resin is added to 100 parts by weight of the total amount of the triazine compound and the highly absorbent substance. , Preferably 5 to 20 parts by weight. If the blending amount exceeds the above range, a uniform solution cannot be obtained and the antireflection effect becomes insufficient, which is not preferable.

【0014】

When using the base material of the present invention, it is preferable to dissolve it in a solvent, and the solvent specifically includes acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl amyl ketone, methyl isoamyl ketone, 1,1,1. -Ketones such as trimethylacetone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate or their monomethyl ethers, monoethyl ethers, monopropyl ethers, monobutyl ethers, monophenyl ethers, etc. Polyhydric alcohols and derivatives thereof, cyclic ethers such as dioxane, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate. Esters such as. The solvent may be used alone or in combination of two or more.

【0015】

In addition to the above components, a compatible additive can be added to the substrate material for lithography of the present invention, if necessary. For example, acetic acid, oxalic acid, maleic acid, o-hydroxybenzoic acid, 3,5-dinitrobenzoic acid, 2,6-dihydroxybenzoic acid, SAX (manufactured by Mitsui Toatsu Chemical Co., Ltd.), which are triazine compound cross-linking reaction accelerators, etc. Organic acid can be added in the range of less than 5% by weight based on the solid content of the base material. In addition, surfactants for improving coatability and preventing striations, specifically Surfron SC-103, SR-100 (manufactured by Asahi Glass Co., Ltd.) EF-351 (manufactured by Tohoku Fertilizer Co., Ltd.), Florard Fc-431, Florard Fluorescent surfactants such as Fc-135, Florard Fc-98, Florard Fc-430, and Florard Fc-176 (manufactured by Sumitomo 3M) can be mentioned. The amount of the additive added is preferably less than 2000 ppm with respect to the solid content of the base material.

【0016】

The substrate material for lithography of the present invention can be used in any resist regardless of whether it is a negative type or a positive type. Such resists include (i) positive resists containing a naphthoquinone diazide compound and a novolak resin, (ii) compounds that generate an acid upon exposure, and compounds that have a group that decomposes with an acid and increases solubility in an alkaline aqueous solution. And positive resists containing alkali-soluble resins, (iii) compounds that generate acids upon exposure, positive resists containing alkali-soluble resins that have groups that decompose with acids and increase solubility in alkaline aqueous solutions, (iv). Examples thereof include, but are not limited to, a compound that generates an acid upon exposure, a cross-linking agent, and a negative resist containing an alkali-soluble resin.

【0017】

An example of a preferable method of using the base material for lithography of the present invention will be described. First, for example, a base material solution prepared by dissolving the base material of the present invention in the above-mentioned organic solvent is rotationally coated on a substrate by a spinner or the like. After that, it is baked at a temperature of 100 to 300 ° C to form a base material layer having a film thickness of 0.05 to 0.5 μm. At the above temperature, the base material of the present invention undergoes a cross-linking reaction and becomes insoluble in an alkaline solution, making it difficult to form an intermixing layer with the upper resist layer. After forming the base material layer, a resist layer is rotationally applied onto the resist layer with a spinner or the like, and dried to provide a resist layer. Then, a light source that emits ultraviolet rays, such as a low-pressure mercury lamp, a high-pressure mercury lamp, an arc lamp, a xenon lamp, or an excimer laser stepper, is used for exposure through a mask pattern, or irradiation is performed while manipulating an electron beam. Then, when immersed in a developing solution, for example, an alkaline aqueous solution such as 1 to 10% by weight of tetramethylammonium hydroxide aqueous solution, the exposed portion is selectively dissolved and removed if it is a positive type, and the unexposed portion is selectively removed if it is a negative type. A resist pattern that is faithful to the mask pattern is formed.

【0018】

The base layer is patterned by a dry etching method using chlorine gas or the like using a resist pattern as a mask. In the above treatment, the upper resist layer may be silylated in order to increase the selectivity. As an example of the silylation treatment, after patterning the upper resist, the vapor of a silylating agent such as hexamethyldisilazane, hexamethylcyclotrisilazane, and other polyfunctional silazanes is added to the vapor in the range of 30 to 100 ° C. This can be done by exposing the patterned resist layer at temperature for 1-60 minutes, but is not limited to these.

【0019】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention will be described in more detail based on Examples, but the present invention is not limited to these examples.

【0020】

Production Example 1 (Production of acrylic resin with a weight average molecular weight of 1.3 million) 100 g of glycidyl methacrylate and 100 g of methyl methacrylate were dissolved in 200 g of methyl ethyl ketone, 0.02 g of N, N'-azobisisobutyronitrile was added, and the mixture was reacted at 60 ° C for about 7 hours while stirring in a nitrogen gas atmosphere. .. After completion of the reaction, the reaction product was poured into 1 liter of methanol to precipitate a polymer, and the obtained polymer was dried under reduced pressure at room temperature. The yield of the polymer was 100 g, and the weight average molecular weight was 1.3 million.

【0021】

Production Example 2 (Production of acrylic resin with a weight average molecular weight of 570,000) In Production Example 1, a polymer was obtained in the same manner as in Production Example 1 except that 0.04 g of N, N'-azobisisobutyronitrile was used. The yield of the polymer was 100 g, and the weight average molecular weight was 570,000.

【0022】

Production Example 3 (Production of acrylic resin with a weight average molecular weight of 170,000) In Production Example 1, a polymer was obtained in the same manner as in Production Example 1 except that 0.08 g of N, N'-azobisisobutyronitrile was used. The yield of the polymer was 100 g, and the weight average molecular weight was 170,000.

【0023】

Production Example 4 (Production of acrylic resin with a weight average molecular weight of 80,000) In Production Example 1, a polymer was obtained in the same manner as in Production Example 1 except that 0.2 g of N, N'-azobisisobutyronitrile was used. The yield of the polymer was 100 g, and the weight average molecular weight was 80,000.

【0024】

Manufacturing example 5 10 g of the polymer obtained in Production Example 1 and M in which 3.7 methoxymethylol groups are substituted on average per melamine ring._X-750 (manufactured by Sanwa Chemical Co., Ltd.) 50 g, bis (4-hydroxyphenyl) sulfone 50 g and fluorine-based surfactant F_C-430 (manufactured by Sumitomo 3M Ltd.) 500 ppm was dissolved in 1000 g of propylene glycol monomethyl ether acetate and filtered using a membrane filter having a pore size of 0.2 μm to obtain a solution of the base material.

【0025】

Manufacturing example 6 In Production Example 5, a solution of the base material was obtained in the same manner as in Production Example 5, except that the polymer was replaced with that obtained in Production Example 2.

【0026】

Manufacturing example 7 In Production Example 5, a solution of the base material was obtained in the same manner as in Production Example 5, except that the polymer was replaced with that obtained in Production Example 3.

【0027】

Manufacturing example 8 In Production Example 5, a solution of the base material was obtained in the same manner as in Production Example 5, except that the polymer was replaced with that obtained in Production Example 4.

【0028】

Manufacturing example 9 10 g of the polymer obtained in Production Example 1, 3 g of 2,2', 4,4'-tetrahydroxybenzophenone, and F, which is a fluorine-based surfactant._C-430 (manufactured by Sumitomo 3M Ltd.) 500 ppm was dissolved in 100 g of propylene glycol monomethyl ether acetate and filtered using a membrane filter having a pore size of 0.2 μm to obtain a solution of the base material.

【0029】

Manufacturing example 10 In Production Example 9, a solution of the base material was obtained in the same manner as in Production Example 9, except that the polymer was replaced with that obtained in Production Example 2.

【0030】

Production example 11 In Production Example 9, a solution of the base material was obtained in the same manner as in Production Example 9, except that the polymer was replaced with that obtained in Production Example 3.

【0031】

Manufacturing example 12 In Production Example 9, a solution of the base material was obtained in the same manner as in Production Example 9, except that the polymer was replaced with that obtained in Production Example 4.

【0032】

[Example]

Examples 1 and 2 and Comparative Examples 1 and 2 The solution of each base material obtained in Production Examples 5 to 8 was applied on a silicon wafer having a step of 0.2 μm with a spinner to form a base material layer having a film thickness of 0.2 μm. Then, it was dried at 90 ° C for 90 seconds and heated at 180 ° C for 90 seconds to form a base material coating. The difference between the upper step film thickness and the lower step film thickness of the base material coating was measured to examine the conformality, and the results are shown in Table 1.

【0033】

Subsequently, TDUR-P007 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a chemically amplified positive resist composed of an acid generator and a hydroxystyrene resin, is applied onto the base material film with a spinner and dried at 90 ° C for 90 seconds. Then, a resist layer having a film thickness of 0.7 μm was formed. The resist layer was exposed to NSR-2005EX8A (manufactured by Nikon Corporation) through a mask pattern, and then heat treatment (PEB) was performed at 110 ° C. for 90 seconds after exposure to obtain a 2.38 wt% tetramethylammonium hydroxide aqueous solution. To form a resist pattern. Next, using a plasma etching apparatus TUE-1102 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), dry etching was performed using chlorine gas as an etchant at 30 mTorr, an output of 150 W, and a temperature of 20 ° C. Table 1 shows the results of examining the shape of the obtained resist pattern.

【0034】

In the table, A means a sharp pattern on a rectangle, and B means a pattern with a rounded top.

【0035】

[table 1]

<img file="JPH1069072A_D0003.tif" />【0036】

Examples 3 and 4 and Comparative Examples 3 and 4 The solution of each base material obtained in Production Examples 9 to 12 was applied on a silicon wafer having a step of 0.2 μm with a spinner to form a base material layer having a film thickness of 0.2 μm. Then, it was dried at 90 ° C for 90 seconds and heated at 180 ° C for 90 seconds to form a base material coating. The difference between the upper step film thickness and the lower step film thickness of the base material coating was measured to examine the conformality, and the results are shown in Table 1.

【0037】

Subsequently, THMR-iN200 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a chemically amplified negative resist composed of an acid generator, an alkali-soluble resin, and a cross-linking agent, is applied onto the base material coating with a spinner, and 90 at 110 ° C. It was dried for seconds to form a resist layer having a thickness of 0.7 μm. The resist layer was exposed to NSR-2005i10D (manufactured by Nikon Corporation) through a mask pattern, and then heat treatment (PEB) after exposure was performed at 100 ° C. for 90 seconds to obtain a 2.38 wt% tetramethylammonium hydroxide aqueous solution. To form a resist pattern. Next, using a plasma etching apparatus TUE-1102 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), dry etching was performed using chlorine gas as an etchant at 30 mTorr, an output of 150 W, and a temperature of 20 ° C. Table 1 shows the results of examining the shape of the obtained resist pattern.

【0038】

In the table, A means a sharp pattern on a rectangle, and B means a pattern with a rounded top.

【0039】

[Table 2]

<img file="JPH1069072A_D0004.tif" />【0040】

[Effect of the invention]

The base material for lithography of the present invention has high conformality and an excellent antireflection effect, and can satisfactorily form a resist pattern, particularly a resist pattern of 0.25 μm or less, and is suitable as a base material for microfabrication.