JPH0635201A - Ground surface material for lithography and formation of pattern by using the same - Google Patents

Abstract

PURPOSE:To easily obtain resist patterns which are rectangular in section and have a high resolution and high selection ratio by a simplified process. CONSTITUTION:This ground surface material for lithography is constituted by consisting the material of a copolymer of glycidyl methacrylate and methyl methacrylate or incorporating a UV absorbent therein. This method forms patterns by successively executing (A) a stage for forming a first layer consisting of the ground surface material on a substrate, (B) a stage for providing a second layer consisting of a positive type resist on this first layer, then patterning the layer by exposing, then development processing, (C) a stage for sylilating the patterned resist layer by silicon-contg. vapor and (D) a stage for patterning the first layer consisting of the ground surface material by a dry etching method using gaseous oxygen with the resist patterns subjected to the sylilation treatment as a mask.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel base material for lithography and a pattern forming method using the same. More specifically, the present invention relates to a base material for lithography which has a rectangular cross section and can obtain a resist pattern of high resolution and high selection ratio, and a simplified pattern forming method using the same.

[0002]

2. Description of the Related Art In recent years, in semiconductor devices, circuits are becoming highly integrated and miniaturized, and circuit patterns are also becoming multilayered. Then, as the number of layers increases, it is necessary to stack circuit patterns.
Flattening technology is important.

As such a technique, for example, (1) a thermosoftening resin made of polymethylmethacrylate is formed on a substrate, the surface is heated and flattened, and a novolac-based resist is formed thereon, followed by exposure and development treatments. Then, the upper novolak-based resist is silylated, and the lower layer thermosoftening resin is patterned by reactive ion etching using oxygen gas with this silylated resist pattern as a mask (Japanese Patent Laid-Open Publication No. HEI-3). -1800
33), (2) a wet developable lower resist layer and an upper resist layer having different sensitivities to actinic rays are provided on a substrate, and the upper resist layer is first exposed and developed, and then silylated, and then the lower resist. A method of forming a pattern by irradiating the layer with deep ultraviolet rays through a resist pattern of an upper layer and then developing the layer (JP-A-62-258).
No. 449) has been proposed.

However, in the method (1), since polymethylmethacrylate is used as the base material, the resist in the upper layer and the base material are likely to cause intermixing, and it is difficult to obtain a pattern with good resolution. In addition, since the silylation is performed by plasma surface treatment using a gas plasma containing silicon such as SiF ₄ and SiCl ₄ , there is a drawback that the process is complicated.

On the other hand, in the method (2), the lower resist layer has sensitivity in the far ultraviolet region using a methacrylic terpolymer composed of methyl methacrylate, methacrylic acid and methacrylic anhydride as a resin component. However, there is a drawback in that a deep ultraviolet ray irradiating step for the lower resist layer is required, the pattern forming step becomes complicated, and a resist pattern having a high selection ratio is difficult to obtain.

Here, the selection ratio means b / when the amount of film loss when the silylated upper layer resist is dry-etched is a and the amount of film loss when the underlayer material is dry-etched is b / The value represented by a.
A high selection ratio is required in the pattern formation method, because in dry etching, an excellent pattern is formed as the film thickness of the upper layer resist decreases and the film thickness of the base material increases.

On the other hand, there is known a color filter having a color layer containing an organic dye on a substrate and an organic material layer made of polyglycidyl methacrylate containing a benzophenone-based ultraviolet absorber on the color layer. (Tokuhei 3
No. 81122), the organic material in this case is for a color filter and is not a base material for lithography, and when such a polyglycidyl methacrylate is used as the base material, a resist having a high selection ratio is obtained. I can't get the pattern.

[0008]

Under the above circumstances, the present invention provides a resist pattern having a rectangular cross section and high resolution and high selectivity without causing intermixing between the upper layer resist and the base material. The object of the present invention is to provide a base material for lithography obtained and a method for forming a resist pattern having the above-mentioned preferable properties by a simple process using the base material.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have found that a copolymer of glycidyl methacrylate and methyl methacrylate or, if desired, an ultraviolet absorber is contained therein. The underlying material does not cause an intermixing phenomenon with the positive type resist, and the film reduction ratio upon dry etching is different, and the first layer made of the underlying material and the positive type on the substrate. A second layer made of a resist is provided, and the second layer is exposed and developed to be patterned, and then silylated by a specific method, and then dry etching is performed using this as a mask. It was found that by patterning the layer, a rectangular resist pattern with high resolution and high selectivity can be easily formed. Which resulted in the completion of the Akira.

That is, the present invention provides a lithographic undercoating material comprising a copolymer of glycidyl methacrylate and methyl methacrylate, or an ultraviolet absorber contained in the copolymer, and (A) a substrate, A step of forming a flattened first layer made of the base material for lithography, (B) on the first layer made of the base material,
A step of forming a second layer made of a positive type resist, imagewise exposing and then developing and patterning;
(C) contacting the patterned resist layer with a vapor containing silicon to perform a silylation treatment, and (D)
A pattern forming method characterized in that the step of patterning the first layer made of the base material is sequentially performed by dry etching using an oxygen-based gas using the silylated resist pattern as a mask. Is.

The base material of the present invention is a copolymer of glycidyl methacrylate and methyl methacrylate or an ultraviolet absorber contained therein, and the copolymer includes glycidyl methacrylate units and methyl methacrylate units. Is a weight ratio of 2: 8 to 8: 2, preferably 3: 7 to 7: 3, and has an average molecular weight of 10,000 to 200,000, preferably 20,000 to 100,000. Is. If the composition ratio or average molecular weight deviates from the above range, intermixing with a positive resist is likely to occur, flattenability is poor, and a resist pattern excellent in high selection ratio, high resolution and profile shape is difficult to obtain. .

There is no particular limitation on the ultraviolet absorber blended in the copolymer as desired, and examples thereof include salicylate-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based, azo-based, polyene-based and anthraquinone-based. Although any of the above can be used, benzophenone-based compounds are preferable in the present invention.

As the benzophenone type ultraviolet absorber,
For example, 2,4-dihydroxybenzophenone, 2,
2 ', 4,4'-tetrahydroxybenzophenone, 2
-Hydroxy-4-methoxybenzophenone, 2,2 '
-Dihydroxy-4-methoxybenzophenone, 2,
2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2-hydroxy-4- (2-hydroxy-3-methacryloxy) propoxybenzophenone, N, N'-tetramethyl-4,4'-diaminobenzophenone, 2-hydroxybenzophenone, 4- Hydroxybenzophenone, 4,4'-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,4,5-trihydroxybenzophenone, 2,
4,6-trihydroxybenzophenone, 2,4,4 '
-Trihydroxybenzophenone, 2,2 ', 3,4-
Tetrahydroxybenzophenone, 2,3,4,4'-
Tetrahydroxybenzophenone, 2,2'3,4
4'-pentahydroxybenzophenone, 2,3,3 '
4,4 ', 5'-hexahydroxybenzophenone and the like can be mentioned.

Examples of salicylate type ultraviolet absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate and the like.

Examples of the benzotriazole type ultraviolet absorber include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole and 2- (2'-hydroxy-
5'-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-ter
t-Butylphenyl) benzotriazole, 2- (2 '
-Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-
(2'-Hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2-
Examples thereof include (2'-hydroxy-3 ', 5'-di-tert-aminophenyl) benzotriazole.

Examples of the cyanoacrylate type ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3-
Diphenyl acrylate, ethyl-2-cyano-3,3
-Diphenyl acrylate and the like. Examples of the azo ultraviolet absorber include 4-dimethylamino-4 '
-Hydroxyazobenzene, 1-ethoxy-4- (4 '
-N, N-diethylaminophenylazo) -benzene and the like. Examples of the polyene-based ultraviolet absorber include 4-dimethylamino-4'-hydroxy-3'-nitrostilbene and 4-diethylamino-4'-hydroxy-3'-nitrostilbene. Examples of the anthraquinone-based ultraviolet absorber include 1, 2, 5,
8-tetrahydroxyanthraquinone, 1,4,9,1
Examples thereof include 0-tetrahydroxyanthracene and 1,5-diaminoanthraquinone. These ultraviolet absorbers may be used alone or in combination of two or more.

The amount of the ultraviolet absorber used is not particularly limited and may be appropriately selected depending on the light reflectance of the substrate used, but is usually 10 to 40% by weight based on the copolymer.
It is preferably used in a proportion of 20 to 30% by weight. By including this ultraviolet absorber, a resist pattern having a rectangular cross section and high resolution can be obtained even when a high reflectance substrate such as aluminum is used.

Next, the pattern forming method of the present invention will be described. First, in the step (A), the above-mentioned copolymer of glycidyl methacrylate and methyl methacrylate is formed on a suitable substrate, or this copolymer is used. Forming a flattened first layer of base material containing the UV absorber. The substrate used at this time is not particularly limited, and those conventionally used for pattern formation by lithography, such as silicon wafers and metal substrates such as aluminum and tantalum, are used.

In order to provide the first layer consisting of a base material on the substrate, a copolymer of glycidyl methacrylate and methyl methacrylate and an optional UV absorber are dissolved and applied in a suitable solvent. Prepare the liquid,
This solution may be applied onto the substrate using a spinner or the like and dried.

Next, in the step (B), a second layer made of a positive type resist is provided on the first layer made of the base material thus formed, and then imagewise exposing and then developing. Process and pattern. As the positive resist used in the step (B), a combination of an alkali-soluble resin as a film-forming substance and a quinonediazide group-containing compound as a photosensitive component is usually used. Examples of the alkali-soluble resin include novolac resins, acrylic resins, copolymers of styrene and acrylic acid, polymers of hydroxystyrene, polyvinylphenol, poly-α-methylvinylphenol, and the like. Is preferred.

The alkali-soluble novolac resin is not particularly limited, and those conventionally used as film-forming substances in positive photoresists, such as aromatic hydroxy compounds such as phenol, cresol and xylenol, and aldehydes such as formaldehyde. And the like are used in the presence of an acidic catalyst.
The alkali-soluble novolac resin has a weight average molecular weight of 2000 to 2000 with the low molecular weight region cut.
The range of 0, preferably 5000 to 15000 is preferable.

On the other hand, examples of the quinonediazide group-containing compound include partial or complete esterification of sulfonic acids of quinonediazides such as orthobenzoquinonediazide, orthonaphthoquinonediazide, orthoanthraquinonediazide and compounds having a phenolic hydroxyl group or an amino group. Alternatively, a partially or completely amidated product may be used. Examples of the compound having a phenolic hydroxyl group or an amino group include 2,3,4-trihydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone and 2,3,4,4'-tetrahydroxybenzophenone. Polyhydroxybenzophenone, alkyl gallate, aryl gallate, phenol, phenolic resin, p-methoxyphenol, dimethylphenol, hydroquinone, polyhydroxydiphenylalkane, polyhydroxydiphenylalkene, bisphenol A, α, α ′, α ″ -tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, 1- [1- (4-hydroxyphenyl) isopropyl] -4- [1,1-bis (4-hydroxyphenyl)
Ethyl] benzene, tris (hydroxyphenyl) methane or a methyl-substituted product thereof, naphthol, pyrocatechol, pyrogallol, pyrogallol monomethyl ether,
Pyrogallol-1,3-dimethyl ether, gallic acid,
Examples include gallic acid, aniline, p-aminodiphenylamine and the like, which are esterified or etherified with some hydroxyl groups remaining. Particularly preferred quinonediazide group-containing compounds are polyhydroxybenzophenone and naphthoquinone-
1,2-diazide-5-sulfonic acid or naphthoquinone-
It is a complete esterified product or a partial esterified product with 1,2-diazide-4-sulfonic acid, and particularly, one having an average degree of esterification of 70% or more is preferable. The photosensitive component comprising the quinonediazide group-containing compound may be used alone, or 2
You may use it in combination of 2 or more types.

This quinonediazide group-containing compound can be obtained, for example, by using the above polyhydroxybenzophenone and naphthoquinone-1,2-diazide-5-sulfonyl chloride or naphthoquinone-1,2-diazide-4-sulfonyl chloride in a suitable solvent such as dioxane. It can be produced by condensing in the presence of an alkali such as triethanolamine, an alkali carbonate or an alkali hydrogencarbonate to complete esterification or partial esterification.

In the present invention, the positive resist is
It is preferable to dissolve the alkali-soluble resin and the quinonediazide group-containing compound in a suitable solvent and use them in the form of a solution.

Examples of such a solvent include acetone,
Ketones such as methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 1,1,1-trimethylacetone, and ethylene glycol, ethylene glycol monoacetate, diethylene glycol or diethylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or Polyhydric alcohols such as monophenyl ether and its derivatives, cyclic ethers such as dioxane, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate,
Mention may be made of esters such as methyl pyruvate, ethyl pyruvate and 3-ethoxyethyl propionate. These may be used alone or in combination of two or more.

If desired, the resist may further contain compatible additives such as additional resins, plasticizers, stabilizers or developed images for improving the performance of the resist film. A colorant for making it visible and a commonly used one such as a sensitizer for further improving the sensitizing effect can be added and contained.

In the step (B) in the method of the present invention, the positive resist thus prepared is placed on the first layer composed of the base material formed in the step (A).
A second layer composed of a positive resist is applied by coating with a spinner or the like and dried, and then a light source that emits ultraviolet rays, for example, a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, an arc lamp,
Is exposure through a required mask pattern using a xenon lamp or the like? Alternatively, irradiation is performed while scanning the electron beam. Next, when this is dipped in a developing solution, for example, a weak alkaline aqueous solution such as a 1-10 wt% tetramethylammonium hydroxide aqueous solution, the portion solubilized by exposure is selectively dissolved and removed, and a pattern faithful to the mask pattern is obtained. Is formed.

Then, in the step (C), the patterned resist layer is exposed to vapor containing silicon for silylation treatment. This silylation treatment is performed on vapors containing silicon such as hexamethyldisilazane, hexamethylcyclotrisilazane, and other polyfunctional silazanes, preferably 1 to 6 at a temperature in the range of 30 to 100 ° C.
It is performed by exposing the patterned resist layer for about 0 minutes.

Next, in the step (D), the resist pattern silylated as described above is used as a mask.
The first layer made of the base material is patterned by a dry etching method using an oxygen-based gas. As the dry etching method, a conventionally known method such as a plasma etching method is advantageous. In this way, a resist pattern having a rectangular cross section and high resolution and high selectivity can be easily obtained.

[0030]

When the base material for lithography of the present invention is used in combination with a positive resist, a resist pattern having a rectangular cross section and a high resolution and a high selection ratio can be provided. Further, by using this base material, the resist pattern having the above-mentioned preferable properties can be easily obtained by a simplified process.

[0031]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example 1 (1) Preparation of base material 100 g of glycidyl methacrylate and 100 g of methyl methacrylate were mixed, 2 g of N, N'-azobisisobutyronitrile was added, and the mixture was stirred at 60 ° C. in a nitrogen gas atmosphere. The reaction was carried out for about 7 hours. 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 polymer yield was 150 g and the weight average molecular weight (Mw) was 1
It was 0,000 and the dispersity was 1.7.

10 g of the copolymer of glycidyl methacrylate and methyl methacrylate obtained by the above operation and 3 g of 2,2 ', 4,4'-tetrahydroxybenzophenone were dissolved in 100 g of ethylene glycol monoethyl ether acetate, and the mixture was filtered with a membrane filter. A base material solution was obtained by filtering and removing impurities.

(2) Formation of resist pattern A solution of the base material obtained in (1) above is applied onto a silicon wafer on which aluminum is vapor-deposited by spinner coating,
It was baked at 180 ° C. for 5 minutes to form a flat lower layer having a thickness of about 0.5 μm. Next, positive photoresist THMRip
2800 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied onto the flattening layer by spinner and baked at 90 ° C. for 90 seconds to form a layer having a thickness of about 1.26 μm. This resist layer is N
SR-150517A (manufactured by Nikon Corporation) was used for exposure through a mask, followed by development with a 2.38 wt% tetramethylammonium hydroxide aqueous solution for patterning.

The patterned wafer was then placed in a desiccator flooded with hexamethyldisilazane by the method described above, and
It vapor-processed at 0 degreeC for 15 minutes. OAP (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used as hexamethyldisilazane.
Next, using a plasma etching apparatus TCA-2400 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), the volume ratio of CHF ₃ and O ₂ is 2: 3.
Dry etching was performed under the conditions of 0.80 Torr, output of 300 W, stage temperature of 60 ° C., and etching time of 30 seconds, using the mixed gas of 2) as a reaction gas. The selection ratio obtained from the residual film at that time was 6.0. In addition, the pattern of the formed upper layer resist had a good rectangular cross section.

Furthermore, the state of intermixing of the formed base material and the upper layer resist, the state of notching (deformation of the resist pattern due to the reflection of irradiation light from the substrate),
As a result of observing the flatness and the flattening property, good results were obtained in all of them. The results are shown in Table 1.

Comparative Example 1 and Comparative Example 2 In Comparative Example 1, the same operation as in Example 1 was carried out except that the base material was polymethyl methacrylate and in Comparative Example 2 the base material was polyglycidyl methacrylate. A resist pattern was formed and the selection ratio was determined.
Furthermore, the state of intermixing, the state of notching,
The flatness and profile shape were observed. The results are shown in Table 1.

Comparative Example 3 A resist pattern was formed in the same manner as in Example 1 except that the silylation treatment was not performed, and the selection ratio was determined. Furthermore, the state of intermixing, the state of notching, the flatness, and the profile shape were observed. The results are shown in Table 1.

Comparative Example 4 and Comparative Example 5 In Comparative Example 4, the same operation as in Comparative Example 3 was carried out except that the base material was polymethyl methacrylate and in Comparative Example 5 the base material was polyglycidyl methacrylate. A resist pattern was formed and the selection ratio was determined.
Furthermore, the state of intermixing, the state of notching,
The flatness and profile shape were observed. The results are shown in Table 1.

Examples 2 to 4 Lithographic undercoat materials were obtained in the same manner as in Example 1 except that the weight ratio of the undercoat material, the average molecular weight, the kind and addition amount of the ultraviolet absorber were changed. Then, using the obtained base material, a resist pattern was formed by the same operation as in Example 1, and the selection ratio was obtained. Furthermore, the state of intermixing, the state of notching, the flatness, and the profile shape were observed. The results are shown in Table 1.

Comparative Example 6 and Comparative Example 7 In Comparative Example 6, the average molecular weight of the base material was 300,000, and in Comparative Example 7, the average molecular weight of the base material was 5.
A base material for lithography was obtained in the same manner as in Example 1 except that the thickness was changed to 1,000. Then, using the obtained base material, a resist pattern was formed by the same operation as in Example 1, and the selection ratio was obtained. Furthermore, the state of intermixing, the state of notching, the flatness, and the profile shape were observed. The results are shown in Table 1.

Example 5 A base material for lithography was obtained in the same manner as in Example 1 except that the ultraviolet absorber was not added. Further, a resist pattern was formed by the same operation as in Example 1 except that the obtained base material was used and a silicon wafer substrate on which aluminum was not deposited was used.
The selection ratio was calculated. Furthermore, the state of intermixing, the state of notching, the flatness, and the profile shape were observed. The results are shown in Table 1.

Example 6 A base material for lithography was obtained in the same manner as in Example 1 except that the amount of the ultraviolet absorber added was 5% by weight.
Using the obtained base material, a resist pattern was formed in the same manner as in Example 1 except that a silicon wafer substrate on which aluminum was not vapor-deposited was used as in Example 5, and the selectivity was determined. . Furthermore, the state of intermixing, the state of notching, the flatness, and the profile shape were observed. The results are shown in Table 1. In addition, each physical property in Table 1 was evaluated by the following methods.

(1) Selectivity: After coating a substrate for lithography on a substrate and drying it, an etching rate x when dry etching this and a positive resist is coated on the substrate and dried, A pattern was formed, and a ratio x / y to the etching rate y when this was dry-etched was obtained and used as a selection ratio.

(2) Intermixing: The cross section of the sample is observed with a scanning electron microscope, and the case where the intermixing layer is not formed at the boundary between the upper resist and the base material is ◯, and the intermixing layer is formed. The case was marked as x.

(3) Notching: Several linear resist patterns formed parallel to each other on the plane of the sample were observed. When no deformation was observed, it was marked with ◯, and when each straight line was distorted, it was marked with x. .

(4) Flattening property: The cross section of the sample is observed by a scanning electron microscope, and when the upper surface of the base material layer is linear, ○,
The wavy case was marked with x.

(5) Profile shape: The cross section of a sample having a rectangular cross section was observed with an optical microscope. When the edge was sharp, it was marked with ◯, and when it was round, it was marked with x.

The abbreviations in Table 1 mean the following compounds. MMA: Methyl Methacrylate GMA: Glycidyl Methacrylate PMMA: Polymethyl Methacrylate PGMA: Polyglycidyl Methacrylate TEB: 2,2'4,4'-Tetrahydroxybenzophenone TRB: 2,4,5-Trihydroxybenzophenone

[0050]

[Table 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisasamu Nakayama 150 Nakamaruko, Nakahara-ku, Kawasaki-shi, Kanagawa Tokyo Ohka Kogyo Co., Ltd. (72) Nobuo Tokutake 150 Nakamaruko, Nakahara-ku, Kawasaki, Kanagawa Prefecture Tokyo Ohka Kogyo Co., Ltd. (72) Inventor Shinto Saito 150 Nakamaruko Nakahara-ku, Kawasaki-shi, Kanagawa Tokyo Ohka Kogyo Co., Ltd.

Claims (5)

[Claims] 1. A lithographic base material comprising a copolymer of glycidyl methacrylate and methyl methacrylate. 2. A base material for lithography which comprises a copolymer of glycidyl methacrylate and methyl methacrylate containing an ultraviolet absorber. 3. The base material for lithography according to claim 2, wherein the ultraviolet absorber is a benzophenone compound. 4. The benzophenone-based compound is 2,2 ′,
The base material for lithography according to claim 3, which is 4,4'-tetrahydroxybenzophenone. 5. A step of (A) forming a flattened first layer made of the base material for lithography according to claim 1 or 2 on a substrate, (B) a first layer made of the base material, Providing a second layer of a positive resist, exposing it to image formation, and then developing and patterning it; (C) silylating the patterned resist layer by contacting it with vapor containing silicon. And (D) dry etching using an oxygen-based gas using the silylated resist pattern as a mask to pattern the first layer made of the base material. Pattern formation method.