JPH08305031A - Protective film material for chemical amplification type resist - Google Patents

Abstract

PURPOSE: To stably perform high precision microfabrication at the time of forming a pattern by photolithography when a semiconductor integrated circuit is produced. CONSTITUTION: This protective film material is based on a polymer having a sulfonic acid group in each molecule but having no arom. group and soluble in water or an alkaline aq. soln., e.g. sulfonic acid modified polyvinyl alcohol. This protective film material has function as an upper protective film of a chemical amplification type resist material, has satisfactory film forming property and makes it possible to easily form a resist pattern with high productivity and satisfactory reproducibility.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention has a high sensitivity to high-energy rays such as deep ultraviolet rays, electron beams, and X-rays, and is suitable for a fine processing technique capable of forming a pattern by developing with an alkaline aqueous solution. The present invention relates to a protective film material effective as an upper protective film for a chemically amplified resist layer.

[0002]

2. Description of the Related Art LSI to be Solved
With the higher integration and higher speed, deep-ultraviolet lithography is considered promising as a next-generation microfabrication technology. The deep-UV lithography can also process 0.3 to 0.4 μm, and when a resist material having low light absorption is used, it becomes possible to form a pattern having a side wall that is almost vertical to the substrate. In recent years, a technique using a high-intensity KrF excimer laser as a light source for far-ultraviolet rays has attracted attention, and a resist material having low light absorption and high sensitivity is required for its use as a mass production technique.

From this point of view, a chemically amplified positive resist material using an acid catalyst which has been developed in recent years (Japanese Patent Publication No. 2-27).
660, JP-A-63-27829, US Pat. No. 4,491,628, US Pat. No. 5,310,619.
No.) is a resist material which is particularly promising for deep-UV lithography because of its excellent characteristics such as high sensitivity, resolution and dry etching resistance.

However, the conventional chemically-amplified positive resist material is exposed to PEB (Post Exposur) when exposed to deep ultraviolet rays, electron beams, and X-ray lithography.
If the standing time until eBake) becomes long, the line pattern becomes T-top shape when the pattern is formed, that is, the upper part of the pattern becomes thick [PED (Pos
t Exposure Delay)],
It is considered that this is because the solubility of the surface of the resist layer is lowered, which is a major drawback in practical use. Therefore, it is difficult to control the dimensions in the lithography process, and the dimension controllability is impaired even when the substrate is processed using dry etching [Reference: W. Hinsberg, e
t al. , J. et al. Photopolym. Sci. Te
chnol. , 6 (4), 535-546 (199
3). , T. Kumada, et al. , J. et al. Photo
opolym. Sci. Technol. , 6
(4), 571-574 (1993),]. There is no chemically amplified positive resist material that solves this problem and is satisfactory.

PE in chemically amplified positive resist materials
The cause of the problem of D is considered to be that the basic compounds in the air are largely involved. The acid on the resist layer surface generated by exposure reacts with and deactivates the basic compound in the air,
The longer the standing time to PEB is, the more the amount of deactivated acid increases, so that the acid labile group is less likely to be decomposed. Therefore, a poorly soluble layer is formed on the surface, and the pattern becomes a T-top shape.

However, by adding a small amount of a basic compound to the chemically amplified positive resist material, the acid concentration distribution at the mask edge portion can be made sharp even if the optical contrast of the mask pattern is lowered near the resolution limit. It is known that the problem of resist scum is solved because the acid generated by the light interference in the mask light-shielding portion is completely neutralized by the basic compound in order to improve the dimensional controllability (Japanese Patent Laid-Open No. Hei 5) -127369).

Further, it is known that the addition of a basic compound can suppress the influence of the basic compound in the air, so that it is also effective for PED (Japanese Patent Application Laid-Open No. 232706/1993). (Kaihei 5-249683), the basic compound used here is not incorporated into the resist film due to volatilization, or has poor compatibility with each component of the resist, resulting in uneven dispersion in the resist film. However, there was a problem in the reproducibility of the effect, and the resolution was lowered.

Therefore, a method using polyacrylic acid, polyvinyl alcohol, polyvinyl butyral, or polystyrene sulfonic acid as a protective film for a chemically amplified resist film (Japanese Patent Laid-Open No. 5-507154) has been proposed. Butyral and polystyrene sulfonic acid are insoluble or sparingly soluble in water, so it is necessary to add a peeling device, which is not preferable in the process. Further, polystyrene sulfonic acid is not preferable because it absorbs ultraviolet rays having a wavelength of around 250 nm, which reduces the amount of light incident on the resist film.

Further, a resist material using an onium salt as a photoacid generator (US Pat. No. 4,491,628, US Pat. No. 5,310,619, Japanese Patent Application No. 6-95560).
When using polyacrylic acid as a protective film,
Trifluoromethylsulfonyloxybicyclo [2.2.1] disclosed in JP-A-5-507154.
-Hept-5-ene-2,3-dicarboximide (M
Unlike a resist material in which DT) is used as a photo-acid generator, polyacrylic acid inhibits the reaction during photolysis of the onium salt, and thus it has been found that a surface-insoluble layer that causes the T-top shape is formed. It was When polyvinyl alcohol is used as the protective film, PEB (Po
It was found that when st Exposure Bake) is performed, intermixing may occur depending on the type of resist solvent, and particles are increased due to generation of microgels, resulting in poor storage stability in an aqueous solution.

The present invention has been made in view of the above circumstances, and provides a chemically amplified resist layer suitable for a microfabrication technique for solving the problem of the surface-insoluble layer which is the cause of the T-top shape, that is, the problem of PED. It is intended to provide a novel protective film material.

[0011]

Means for Solving the Problems The present inventor has made earnest studies to achieve the above object, and as a result, high energy rays such as deep ultraviolet rays, electron beams, and X-rays, particularly deep ultraviolet rays (wavelength 245 to 245). 255 nm), high sensitivity to
As an upper protective film material for the chemically amplified positive resist layer or negative resist layer, it can be used in water or alkaline aqueous solution that has a sulfonic acid group in the molecule such as polyvinyl alcohol modified with sulfonic acid and does not have an aromatic group. By using a soluble polymer as the main component of the protective film material, T-
The problem of the surface poorly soluble layer that causes the top shape, that is, PED
It has been found that it can be a new protective film material for a chemically amplified resist layer suitable for a microfabrication technique that solves the above problem.

That is, batch development is possible by using a polymer having a sulfonic acid group in the molecule of the present invention and having no aromatic group and soluble in water or an alkaline aqueous solution as the main component of the protective film material. Therefore, it is not necessary to add a peeling device, so the process is simple, and since it does not absorb ultraviolet rays near the wavelength of 250 nm, it does not reduce the amount of light incident on the resist film, and it also generates onium salts and other photoacids. When the polymer of the present invention is used as a protective film in the chemically amplified resist material used as an agent, the sulfonic acid of the polymer, which is the main component of the protective film material of the present invention, is an onium salt or a sulfonic acid ester-based acid generator. , Does not cause reaction inhibition during photolysis of diazomethane-based acid generators, does not form a surface-insoluble layer that is the cause of the T-top shape, and further ammonia or amination from the environment Was found that a high barrier property against alkaline substance things like.

Further, the protective film material of polyvinyl alcohol is used together with the resist layer in PEB (Post Exposur).
e Bake) may cause intermixing depending on the type of the resist solvent, and the number of particles increases due to the generation of microgels, resulting in poor storage stability in an aqueous solution. Due to the effect of sulfonic acid in the main component polymer, hydrophilicity is increased, intermixing with lipophilic resist layer is difficult, and solubility in water is also increased to suppress the generation of microgels and to stabilize storage of particles. It was also found that the properties are good, and the present invention has been completed.

Therefore, according to the present invention, a chemical amplification type resist is characterized in that a polymer having a sulfonic acid group in the molecule and having no aromatic group and soluble in water or an alkaline aqueous solution is a main component. Provide a protective film material for use.

The present invention will be described in more detail below. As described above, the chemically amplified resist protective film material of the present invention is a water-soluble compound having a sulfonic acid group in the molecule but no aromatic group. The main component is a polymer that is soluble or soluble in an alkaline aqueous solution.

Here, as such a polymer, one obtained by modifying a part of hydroxyl groups of polyvinyl alcohol with a sulfonic acid group is preferable. The sulfonic acid-modified polyvinyl alcohol is, for example, sodium alkyl sulfonate modified by Nippon Synthetic Chemical Industry Co., Ltd .: Gocelan L-3266, L-0302, Kuraray Co., Ltd .: Kuraray SK Polymer SK-5102, S-2217, etc. It is possible to use polyvinyl alcohol obtained by substituting hydrogen atoms for sodium. The hydrogen atom substitution can be carried out by passing a solution of polyvinyl alcohol modified with sodium alkylsulfonate such as Gohcelan in water in an ion exchange resin. The average saponification degree of the polyvinyl alcohol is preferably 50 mol% or more, and particularly preferably 75 mol% or more.

Further, as the above-mentioned polymer, 2-acrylamido-2-methyl-1-propanesulfonic acid / vinyl acetate copolymer, 2-acrylamido-2-methyl-
1-propanesulfonic acid / vinyl alcohol copolymer,
2-acrylamido-2-methyl-1-propanesulfonic acid / acrylic acid copolymer, 2-acrylamido-2-
Methyl-1-propanesulfonic acid / methyl acrylate copolymer, 2-acrylamido-2-methyl-1-propanesulfonic acid / methacrylic acid copolymer, 2-acrylamido-2-methyl-1-propanesulfonic acid / methacryl Acid methyl copolymer, 2-acrylamido-2-methyl-1-propanesulfonic acid / maleic anhydride copolymer,
2-acrylamido-2-methyl-1-propanesulfonic acid / itaconic anhydride copolymer, vinylsulfonic acid / vinyl acetate copolymer, vinylsulfonic acid / vinyl alcohol copolymer, vinylsulfonic acid / acrylic acid copolymer ,
Vinyl sulfonic acid / methyl acrylate copolymer, vinyl sulfonic acid / methacrylic acid copolymer, vinyl sulfonic acid / methyl methacrylate copolymer, vinyl sulfonic acid / maleic anhydride copolymer, vinyl sulfonic acid / itaconic anhydride Examples thereof include copolymers. These water-soluble polymers may be used alone or in combination of two or more. Moreover, you may use it, mixing with another water-soluble polymer.

The weight average molecular weight of the polymer of the protective film material is 5,000 to 50,000, and particularly 5,000 to 1.
It is preferably 10,000. If the thickness is less than 5,000, the film thickness may not reach 300 Å or more.
If it exceeds 50,000, the viscosity becomes too high and it becomes difficult to apply, which is not preferable in some cases.

The degree of sulfonic acid modification of the polymer of the protective film material is preferably 0.1 to 20 mol%, particularly 0.2 to 5 mol%. If it is less than 0.1 mol%, the acidity becomes low, the solubility in water becomes small, the storage stability may deteriorate, and the barrier property against alkaline substances from the environment may weaken. If it exceeds, the acidity becomes high and the resist layer is dissolved, which is not preferable in some cases.

The protective film material of the present invention can be prepared as an aqueous solution in which the above polymer is dissolved in water and which can be injected by rotation. In this case, the concentration of the polymer in the aqueous solution is set to 300 for the thickness of the protective layer.
To set to ~ 3,000Å (0.03-0.3μm), 1-30% by weight, especially 2-15% by weight is desirable, and if less than 1% by weight, the film thickness becomes less than 300Å for protection. The effect, that is, the barrier property against an alkaline substance from the environment may be weakened, and if it exceeds 30% by weight, the film thickness becomes more than 3,000Å and the burden in the peeling process becomes large, which is not preferable in some cases.

In order to form a resist pattern using the protective film material of the present invention, a known method of a chemically amplified resist material can be adopted, and for example, it can be carried out by a lithography step of a positive resist material. First, a resist layer is formed on a substrate such as a silicon wafer by a method such as spin coating, and the protective film material of the present invention is applied on the resist layer by a method such as spin coating to form a protective layer, and protection is performed. The layer is exposed to ultraviolet rays having a wavelength of 190 to 500 nm or an excimer laser in a desired pattern shape by a reduction projection method, and PEB (Post Exposure Bake) is exposed.
Then, the protective layer is removed with water, and the resist pattern can be formed by a method of developing with a developing solution. It is also possible to remove the protective layer and develop at the same time by using an alkaline developer during development.

In this case, the resist material is not limited to the positive type as described above, and the chemically amplified type resist material may be a positive type or a negative type as long as it shows a contrast threshold of a predetermined level with respect to light of a predetermined wavelength. Any of them can be used, but in particular, the protective film material of the present invention has a wavelength of 245-2.
It is most suitable for fine patterning by deep ultraviolet ray of 55 nm and KrF excimer laser of wavelength 248 nm.

[0023]

INDUSTRIAL APPLICABILITY The protective film material of the present invention has a function as an upper protective film for a chemically amplified resist material, has good film-forming properties, is simple and has high productivity, and is capable of forming a resist pattern with good reproducibility. It can be possible. Therefore, by using the material of the present invention, it is possible to stably perform highly precise microfabrication when forming a pattern for photolithography when manufacturing a semiconductor integrated circuit.

[0024]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 As the positive type chemically amplified resist material, the following composition was used. Polyhydroxystyrene in which hydroxyl groups are partially protected with tert-butoxycarbonyl group 75 parts by weight Trifluoromethanesulfonic acid (tert-butoxyphenyl) diphenylsulfone 5 parts by weight 2,2′-bis (4-tert-butoxycarbonyloxyphenyl) ) Propane 20 parts by weight Ethyl lactate / butyl acetate (85% by weight / 15% by weight) 500 parts by weight As the protective film material, the following composition was used. L-3266 (Nippon Gosei Kagaku Kogyo: average saponification degree about 88%: weight average molecular weight about 16,000: sulfonic acid modification degree about 0.4 mol%) 6.5 parts by weight Ultrapure water 93.5 parts by weight In this case, use the above aqueous solution as an ion exchange resin EG-290H.
It was passed through a column filled with G (manufactured by Organo) for demetalization, and sodium sulfonate-modified polyvinyl alcohol in which sodium atoms were replaced by hydrogen atoms was used.

Using the above materials, a resist pattern was formed according to a usual lithography process.

First, the positive chemically amplified resist material was spin-coated on a substrate and prebaked at 100 ° C. for 90 seconds to form a resist layer having a thickness of 0.75 μm.

Next, the protective layer material was spin-coated on the resist layer to form a protective layer of 1.0 μm.

Then, the film was exposed by using an excimer laser stepper (NSR-2005EX8A, NA = 0.5, manufactured by Nikon Corporation), the protective layer was peeled off with ultrapure water, and PEB was applied at 90 ° C. for 60 seconds to give 2.38. % Tetramethylammonium hydroxide aqueous solution, a positive 0.26 μm line-and-space resist pattern was obtained in a rectangular shape without forming a surface-insoluble layer. In addition, even when the standing time from the exposure to the PEB was set to 2 hours, the resolution could be similarly obtained.

When the protective layer is not stripped with ultrapure water before PEB and after PEB, the protective layer is not stripped with ultrapure water before and after PEB.
Similar results could be obtained when the water-soluble layer was peeled off and developed simultaneously with a 38% aqueous solution of tetramethylammonium hydroxide.

The storage stability of this protective film material was 3 to 6 months at room temperature (using a submerged particle counter manufactured by Rion, particles having a particle size of 0.3 μm or more
It was stable when the number was 00 / ml or less).

[Example 2] As the protective film material, the following composition was used. SK-5102 (manufactured by Kuraray: average saponification degree about 97%: weight average molecular weight about 22,000: sulfonic acid modification degree about 3 mol%) 6.5 parts by weight ultrapure water 93.5 parts by weight In this case, the above aqueous solution Ion exchange resin EG-290H
It was passed through a column filled with G (manufactured by Organo) for demetalization, and sodium sulfonate-modified polyvinyl alcohol in which sodium atoms were replaced by hydrogen atoms was used.

A resist pattern was formed in the same manner as in Example 1. As a result, a positive 0.28 μm line-and-space resist pattern could be obtained in a rectangular shape without forming a surface insoluble layer. From exposure to P
Even when the standing time until EB was set to 2 hours, it was possible to similarly resolve.

When the protective layer is not stripped with ultrapure water before PEB and after PEB, the protective layer is not stripped with ultrapure water before and after PEB.
Similar results could be obtained when the water-soluble layer was peeled off and developed simultaneously with a 38% aqueous solution of tetramethylammonium hydroxide. The storage stability of this protective film material was 3 to 6 months at room temperature.

Comparative Example 1 As the protective film material, the following composition was used. PA-03 (Shin-Etsu Chemical Co., Ltd. polyvinyl alcohol: average saponification degree about 88%: weight average molecular weight about 20,000) 6.5 parts by weight ultrapure water 93.5 parts by weight In this case, the above aqueous solution is used as an ion exchange resin EG. -290H
Demetalization was performed by passing through a column packed with G (manufactured by Organo) to remove sodium acetate existing as an impurity.

A resist pattern was formed according to the same lithography process as above.

First, the positive chemically amplified resist material was spin-coated on a substrate and prebaked at 100 ° C. for 90 seconds to form a resist layer having a thickness of 0.75 μm.

Next, the protective layer material was spin-coated on the resist layer to form a 2.0 μm protective layer.

Then, the film was exposed by using an excimer laser stepper (Nikon Corporation, NSR-2005EX8A, NA = 0.5), the protective layer was peeled off with ultrapure water, and then PEB was applied at 90 ° C. for 60 seconds to carry out 2.38. % Tetramethylammonium hydroxide aqueous solution, a positive 0.28 μm line-and-space resist pattern could be obtained in a rectangular shape without forming a surface insoluble layer. In addition, even when the standing time from the exposure to the PEB was set to 2 hours, the resolution could be similarly obtained.

However, if the protective layer is not stripped with ultrapure water before PEB, but stripped after PEB, P
If the protective layer was not stripped with ultrapure water before EB and after PEB, and the water-soluble layer was stripped and developed together with a 2.38% tetramethylammonium hydroxide aqueous solution, intermixing was performed. The resolution was lowered, and the resolution was only up to 0.30 μm. Further, in this protective film material, generation of microgel occurred due to removal of ionic sodium acetate, and the storage stability was 2 weeks at room temperature.

Comparative Example 2 As the protective film material, the following composition was used. AC-10P (Nippon Pure Chemical Industries, Ltd. polyacrylic acid: weight average molecular weight of about 7,000) 6.0 parts by weight Ultrapure water 94.0 parts by weight In this case, the above aqueous solution is used as an ion exchange resin EG-290H.
Demetallation was carried out by passing through a column packed with G (manufactured by Organo), and sodium in the portion of the sodium carboxylate that was not completely hydrogenated was replaced almost completely with hydrogen.

A resist pattern was formed according to the same lithography process as above.

First, the positive chemically amplified resist material was spin-coated on a substrate and prebaked at 100 ° C. for 90 seconds to form a resist layer having a thickness of 0.75 μm.

Next, the protective layer material was spin-coated on the resist layer to form a 1.0 μm protective layer.

Then, the film was exposed to light using an excimer laser stepper (NSR-2005EX8A, NA = 0.5, manufactured by Nikon Corporation), the protective layer was peeled off with ultrapure water, and PEB was applied at 90 ° C. for 60 seconds for 2.38. % Tetramethylammonium hydroxide aqueous solution, a positive type 0.30 μm line-and-space resist pattern could be obtained, but a surface-insoluble layer was formed and T-
It had a top shape. A resist pattern could not be obtained when the standing time from exposure to PEB was 1 hour.

When the protective layer is not stripped with ultrapure water before PEB and is stripped after PEB, the protective layer is not stripped with ultrapure water before and after PEB.
When the water-soluble layer was peeled off and developed at the same time with an aqueous solution of 38% tetramethylammonium hydroxide, the resolution was lowered due to the carboxylic acid and 0.40 μm.
Only resolved until. The storage stability of this protective film material was 3 to 6 months at room temperature.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshinori Ishihara 28-1 Nishifukushima, Kubiki Village, Nakakubiki District, Niigata Prefecture Shin-Etsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. A protective film material for a chemically amplified resist, which comprises, as a main component, a polymer having a sulfonic acid group in the molecule and having no aromatic group and soluble in water or an alkaline aqueous solution. . 2. The polymer has a weight average molecular weight of 5,000.
The material according to claim 1, which is 0 to 50,000. 3. The material according to claim 1, wherein the polymer is sulfonic acid-modified polyvinyl alcohol. 4. The average saponification degree of polyvinyl alcohol is 5
The material according to claim 3, which is 0 mol% or more.