JPH08179509A - Antireflection composition and formation of resist pattern - Google Patents

Abstract

PURPOSE: To obtain a compsn. which is usable as an antireflection film, allows the formation of a coating film with an aq. medium, etc., and has good step coverage even with a small film thickness by incorporating a polyvinyl alcohol(PVA) resin of a specific saponification rate into the above compsn. CONSTITUTION: The antireflection compsn. applied between a substrate and a photoresist film contains the PVA resin having the saponification rate of >=70%. This saponification rate is a value expressing the ratio of the hydroxyl group by mol%. The PVA resins having various properties by these saponification rates are known. The developer resistance at the time of, for example, developing is poor and the mixing with the photoresist film arises if the saponification rate is <=70% and, therefore, such rate is undesirable. The higher saponification rate yields a better result in the developer resistance and the more preferable saponification rate is >=75%. Conversely, the preservable property of the compsn. tends to degrade (leads to the production of insoluble foreign matter) if the hydrolysis rate is too high. The saponification rate is preferably <=99% and further preferably <=98%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for forming an antireflection film and a pattern forming method using the antireflection film in photolithography which can be used for fine processing required for producing a semiconductor device or the like. Regarding

[0002]

2. Description of the Related Art In recent years, microfabrication technology represented by integrated circuit manufacturing and the like has been increasingly improved in machining accuracy. Taking a dynamic random access memory (DRAM) as an example, submicron processing is now performed. Technology is established as mass production level technology. For this submicron processing, g line (436 nm), i line (365 nm),
A photolithography technique using short-wavelength light such as KrF excimer laser light (248 nm) is used. In these photolithography techniques, a photoresist composition is used, and the photoresist composition has also been improved and various high-performance compositions have been studied (see, for example, JP-A-59-45439). Kaisho 62
-136637, JP-A-62-153950, JP-A-4-136860, and JP-A-4-136.
941).

The characteristics required of the photoresist composition are, of course, higher resolution.
It is important that the dimensions of the transferred pattern do not vary depending on the coating thickness of the photoresist composition. However, since photolithography is affected by optical interference, there is a limit to reducing the dimensional variation of the pattern with respect to the variation of the resist film thickness.

That is, the irradiation light is usually monochromatic light, and the light incident on the photoresist film is reflected on the substrate and further on the upper surface of the photoresist film, so that Repeat multiple reflections. As a result, the sensitivity causes a periodic change in sensitivity to changes in the coating film thickness, and the finished dimension of the line width of the transferred pattern also changes periodically in response to changes in the coating film thickness. There was a limit to the dimensional accuracy of the pattern.

Further, when the irradiated light is reflected on the substrate, the light is also irradiated to the resist portion which is not originally irradiated with the light, and as a result, the transfer pattern is deformed. It was In general, the reflectance increases as the wavelength of light becomes shorter, and thus the problem of the reflection of light from the substrate as described above becomes a greater problem due to the shortening of the wavelength of irradiation light in recent years.

It is known to form an antireflection film between a photoresist film and a substrate in order to reduce reflection of light from the substrate (eg, monthly Semicondu).
center World, June 1994, p. 83-). Such an antireflection film is usually formed by coating and baking an antireflection composition having sufficient absorption for an exposure wavelength on a substrate, and after forming a photoresist film thereon, exposing and developing. Pattern transfer by (1) dissolving the antireflection film at the same time as the resist film during development after exposure, or (2) forming the resist pattern by development and then forming the antireflection film by dry etching using oxygen plasma or the like. The antireflection film is removed by a selective etching method.

The performance required for the antireflection film using these methods is as follows. In the above method (2), if the etching takes a long time, the photoresist film is also etched.
In order to shorten the etching time of the antireflection film, the film thickness is preferably thin. Therefore, as the antireflection composition,
It is required to be able to use the thinnest possible film thickness.
The antireflection film needs to have a uniform film thickness over the entire substrate, but since the substrate to be used usually has a step, especially the step portion (edge portion) of the substrate having such a step. Also, it is possible to form an antireflection film with the same thickness as other parts (good step coverage)
Is required. In the above method (2), the photoresist composition is required to have high dry etching resistance, while the antireflective composition has low dry etching resistance (good dry etching property). Desired. When the antireflection film and the photoresist film are mixed, the resolution is lowered and the pattern shape is deteriorated. Therefore, the photoresist composition applied on the antireflection film should not be dissolved and mixed with each other (no mixing).
Is required.

In order to obtain particularly good step coverage, the coating film thickness may be increased. On the other hand, there is also a demand for thinning the coating film. Therefore, the antireflection composition having good step coverage even when thinly coated. Was required. Even in the past, an attempt was made to use an antireflection film by adding a light-absorbing material to an existing quinonediazide-based photoresist composition or a polyimide-based polymer to form an antireflection composition, and heat-curing the coating to insolubilize it. However, it has been difficult to solve all of the above problems even with such an antireflection composition.

Further, in a quinonediazide type photoresist composition and a polyimide type antireflection composition, a large amount of an organic medium is used as a medium, and it cannot be said that there is no problem in terms of environment. It is also desired to form an antireflection film. In order to solve this problem, an antireflection method using a water-soluble organic compound has been studied (JP-A-1-147535, etc.). However, when these methods are applied to the above method, although the antireflection film does not cause mixing with the photoresist composition,
Since the antireflection film is easily dissolved in the developing solution during development of the photoresist film after exposure, even the antireflection film under the photoresist film is dissolved and removed in the developing solution, and the fine pattern peels away. There was a problem and it was difficult to use. Therefore, it can be applied with an aqueous medium, and
There is a demand for an antireflection film that is insoluble in a developing solution and has no problems during development.

[0010]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and an object thereof is to be used as an antireflection film for preventing reflection of light from a substrate, and for use in an aqueous medium or the like. Coating film can be formed by using this method, the mixing with the photoresist is suppressed, the step coverage is good even with a thin film thickness, the antireflection film does not dissolve during the development of the photoresist film, and the dry etching is performed. An object is to provide an antireflection composition having good properties. Another object of the present invention is to provide a pattern forming method in which the deterioration of resolution and the deformation of resist pattern are small and the change in sensitivity due to the change in coating film thickness is suppressed.

[0011]

As a result of various studies conducted by the present inventors to achieve the above object, an antireflection composition having excellent performance can be obtained by containing a polyvinyl alcohol resin having a specific saponification degree. The present invention has been accomplished, and it was found that a good pattern can be formed by forming an antireflection film by using this antireflection composition, and arrived at the present invention. That is, the gist of the present invention relates to an antireflection composition applied between a substrate and a photoresist film, which comprises a polyvinyl alcohol resin having a saponification degree of 70% or more. Exist.

Another aspect of the present invention is a step of applying an antireflection composition on a substrate to form an antireflection film, and applying a photoresist composition on the antireflection film to form a photoresist film. In the pattern forming method, which comprises a step of forming, a step of exposing the photoresist film to transfer a predetermined pattern to the photoresist film, and a step of developing the photoresist film with a developing solution, the antireflection composition. As a product, there is provided a pattern forming method characterized by using an antireflection composition containing a polyvinyl alcohol resin having a saponification degree of 70% or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In the antireflection composition of the present invention, the saponification degree is 70
It is essential to contain a polyvinyl alcohol resin in an amount of at least%. Usually, a polyvinyl alcohol resin is produced by hydrolyzing polyvinyl acetate to convert acetyl groups in polyvinyl acetate molecules into hydroxyl groups. A value in which the ratio of the hydroxyl groups is expressed in mol% is called a saponification degree, and polyvinyl alcohol resins are known to have various properties depending on the saponification degree. For example, polyvinyl alcohol resins are generally known to be water-soluble, whereas vinyl acetate is not water-soluble, and if the saponification degree is 60% or less, the solubility in water is poor and the saponification degree is 30%. If it is less than%, practically no dissolution occurs. On the other hand, if the degree of saponification is too high, the solubility is low, and 85 to 90% has the highest solubility. In the present invention, it is essential to include a polyvinyl alcohol resin having a saponification degree of 70% or more among these polyvinyl alcohol resins. When the saponification degree is 70% or less, for example, the resistance to a developing solution at the time of development is deteriorated, and mixing with the photoresist film occurs, which is not preferable. Further, a higher saponification degree gives better results in developer resistance, preferably a saponification degree of 75
% Or more. On the other hand, if it is too high, the storage stability of the composition tends to be poor (generation of insoluble foreign matter) tends to occur.
% Or less, more preferably 98% or less.

The degree of polymerization of the polyvinyl alcohol resin is usually represented by the viscosity of a 4% aqueous solution (20 ° C.),
Usually, a material having a thickness of about 1 to 80 cps (mPa · s) is general. Among them, the polyvinyl alcohol resin used in the present invention is usually 5 cps or more, and 70 cp.
s or less, preferably 10 cps or more, and 65 cps
It is the following.

In the present invention, other water-soluble resins may coexist as long as they do not adversely affect the present invention. Examples of these resins include polyacrylic acid, polyvinylpyrrolidone and water-soluble cellulose derivatives. To be If the amount of these coexisting resins is too large, the effect of the present invention may be impaired. Therefore, the content of the resin in the antireflective composition is usually 30% by weight or less, preferably 10% by weight.
The following is good.

The composition of the present invention usually comprises the above resin and water. If necessary, other organic solvents may be mixed and used, and examples of the solvent include alcohols such as isopropyl alcohol, butanol, methoxyethanol, ethoxyethanol, methoxypropanol, diacetone alcohol; ethylene glycol, propylene glycol, etc. Glycols; dialkyl ethers of glycols such as dipropylene glycol dimethyl ether; hydroxy or oxyalkylcarboxylic acid alkyl esters such as ethyl lactate and ethyl pyruvate; amides such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc. Is mentioned. It is preferable that the amount of these organic solvents is small, and in the mixture with water, usually 5
It is 0% by weight or less, preferably 30% by weight or less. The ratio of the resin to the solvent is appropriately selected in consideration of the coating property and the coating film thickness, etc., but the resin is usually added to the solvent at a ratio of 0.
It is contained in a proportion of about 1% by weight or more and about 50% by weight or less. Among them, it is particularly preferable that the content is 1% by weight or more and 30% by weight or less.

The antireflection composition of the present invention usually contains an absorbing material which absorbs the light to be irradiated. Specific examples of these materials include 4,4′-diethylaminobenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,2′-dihydroxy-4, 4'-dimethoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone-5-sulfonic acid, (4-benzoylbenzyl) trimethylammonium chloride , 4-hydroxyazobenzene, 4-aminoazobenzene, 4-chloro-4'-dimethylaminoazobenzene, 4-hydroxy-4'-dimethylaminoazobenzene, 4- (2'-hydroxynaphthylazo)
Azobenzene, 4- (3'-methyl-4'-hydroxyphenylazo) azobenzene, 2-methyl-4- (4 '
-Hydroxyphenylazo) -5-methoxyazobenzene, cresol red, methyl red, neutral red, bromophenol red, methyl orange, methyl yellow, thymol blue, sudan III, sudan red B, sudan orange G, CI-direct yellow 2
8, CI-Direct Yellow 50, CI-Direct Yellow 86, Acid Yellow 25, Acid Yellow 38, Acid Yellow 76, Alizarin Yellow G
G, Moderne Yellow 7, Moderne Yellow 10,
For example, Mordanto Yellow 12 and the like.

The proportion of such an absorbing material is appropriately selected depending on the extinction coefficient of the absorbing material and the film thickness of the antireflection film, but is usually 50 per 100 parts by weight of the total weight (solid content) excluding the solvent in the composition. The amount is not more than 40 parts by weight, preferably not more than 40 parts by weight, more preferably not more than 30 parts by weight, and usually not less than 1 part by weight, preferably not less than 3 parts by weight, more preferably not less than 5 parts by weight.

The antireflection composition of the present invention may further contain a surfactant in order to improve coatability. The addition amount of such an additive is appropriately selected according to the desired required performance. The antireflection composition of the present invention is applied between the substrate and the photoresist film and acts as an antireflection film. After the antireflection composition and the photoresist composition are sequentially applied, a predetermined pattern is transferred to the photoresist film by exposure and developed with a developing solution.

As the photoresist composition coated on the upper layer of the antireflection film, various conventionally known radiation-sensitive compositions can be used. For example, conventional g-line, i-line,
A photoresist composition for excimer laser light (248 nm, 193 nm) can be used, and the material can be either positive type or negative type. As a specific photoresist composition, a polyvinyl cinnamate-based and polyisoprene cyclized rubber-based photocrosslinking type photoresist composition (for example, Journal of Organic Synthetic Chemistry, Vol. 42, No. 11).
No. 979), 1,2-quinonediazide compound and an alkali-soluble resin dissolved in an organic solvent (for example, Journal of Organic Synthetic Chemistry, Vol. 42, No. 11, 979).
Page, JP-A-62-1336637, JP-A-62-1
53950 gazette, etc.), a so-called chemically amplified photoresist composition that exhibits radiation-sensitive performance by polymerizing or depolymerizing with an acid or a base generated by light irradiation (for example,
JP-A-59-45439 and JP-A-4-13686
No. 0, JP-A-4-136941) and the like.

Resins used in the photoresist composition include polyvinyl cinnamate resins produced from polyvinyl alcohol and cinnamic acid chloride, and cyclized rubber resins mainly containing 1,4-cis polyisoprene. Can be mentioned. A photo-crosslinking agent such as 4,4′-diazidochalcone or 2,6-di- (4′-azidobenzylidene) cyclohexanone may be added to these resins, if necessary.

1, 2 used in the photoresist composition
The quinonediazide compound is 1,2-benzoquinonediazide-4 which is a compound having a phenolic hydroxyl group.
-Sulfonic acid ester derivative, 1,2-naphthoquinonediazide-4-sulfonic acid ester derivative, 1,2-
Examples thereof include naphthoquinonediazide-5-sulfonic acid ester derivative. Here, the compound having a phenolic hydroxyl group is produced from polyhydroxybenzophenones such as 2,3,4-trihydroxybenzophenone, polyhydroxybenzoic acid esters such as ethyl gallate, phenols and carbonyl compounds. Examples thereof include polyphenols such as bisphenol A and novolac resins. As the alkali-soluble resin used in the photoresist composition, novolak resins obtained by polycondensing a phenol derivative and an aldehyde derivative,
Examples thereof include polymers obtained by polymerizing acrylic acid derivatives, cinnamic acid derivatives, styrene derivatives, maleic acid derivatives and the like as monomers.

The photoresist composition (1) may be a resin having an acid-labile group such as poly (p-tert-butoxycarbonyloxy) styrene, and a photo-irradiation such as triphenylsulfonium hexafluoroarsenate. Examples thereof include a photoresist composition which comprises a compound that generates an acid and whose light-irradiated portion is solubilized or insoluble in a developing solution (for example, JP-A-59-45439). Further, a novolak resin obtained by polycondensing a phenol derivative and an aldehyde derivative, a cross-linking agent such as alkoxymethylated melamine and alkoxymethylated urea, a compound that generates an acid by light irradiation such as halogenated methyltriazine, A photoresist composition in which the light-irradiated portion is insoluble in the developer is also included. (For example, JP-A-4
No. 136860, Japanese Patent Laid-Open No. 4-136941).

The photoresist composition usually contains an organic solvent, and examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene; acetic acid esters such as ethyl acetate; and mono or organic solvents such as ethyl cellosolve. Mono- or di-alkyl ethers of diethylene glycol; mono- or di-alkyl ethers of mono- or di-propylene glycol such as propylene glycol monomethyl ether; alkyl cellosolve acetates such as propylene glycol monomethyl ether acetate; esters such as ethylene carbonate and γ-butyrolactone; Methyl ethyl ketone, 2
-Ketones such as heptanone and cyclopentanone; alkoxy or oxyalkylcarboxylate alkyls such as ethyl lactate, methyl 3-methoxypropionate and ethyl pyruvate; and the like. These solvents are appropriately selected in consideration of the solubility of the resin and the photosensitizer, the stability of the photoresist composition, and the like.

Further, these photoresist compositions are
If necessary, a surfactant for improving coatability and a sensitizer for improving sensitivity can be contained. The substrate used for pattern formation is not particularly limited, but a substrate for IC production such as a silicon substrate or a gallium arsenide substrate is generally used, and a substrate having a highly reflective layer such as aluminum is formed on the surface. Can be mentioned.

A method of applying an antireflection composition on a substrate,
And, the method of applying the photoresist composition on the antireflection film is not particularly limited, using a spin coater or the like,
It is performed according to the usual method. The applied antireflection composition,
Usually, the solvent is removed by heat treatment using a hot plate or the like, but if the temperature is too low, the water resistance of the formed antireflection film is not improved and the antireflection film is also dissolved during development, which is not preferable. On the other hand, if the temperature is too high, the polyvinyl alcohol is decomposed and particles are generated, which is not preferable. The heat treatment temperature for obtaining good water resistance of the antireflection film is preferably 110 ° C. or higher and 260 ° C. or lower, and is preferably 115.
The temperature is not less than 0 ° C and not more than 240 ° C. Further, the heat treatment temperature has a more suitable range depending on the type of polyvinyl alcohol used, and when the optimum saponification degree of the polyvinyl alcohol is included, the saponification degree of the polyvinyl alcohol and the heat treatment temperature are represented in a two-dimensional graph. In the range
Point A (saponification degree 70%, heat treatment temperature 160 ° C), point B
(Saponification degree 70%, heat treatment temperature 240 ° C), point C (saponification degree 100%, heat treatment temperature 260 ° C), point D (saponification degree 100%, heat treatment temperature 110 ° C) Is preferred. Further, more preferably, point E (saponification degree 75%, heat treatment temperature 170 ° C.), point F (saponification degree 7)
5%, heat treatment temperature 230 ° C., point G (saponification degree 99%,
The conditions in the range surrounded by the points of heat treatment temperature 240 ° C.) and point H (saponification degree 99%, heat treatment temperature 115 ° C.) are preferable, and most preferable are point E (saponification degree 75%, heat treatment temperature 170 ° C.). ), Point I (saponification degree 75%, heat treatment temperature 20)
0 ° C), point J (saponification degree 98%, heat treatment temperature 200)
C.) and point K (saponification degree 98%, heat treatment temperature 120.degree. C.). The heat treatment time is usually 30 seconds or longer and 600 seconds or shorter, preferably 60 seconds or longer and 300 seconds or shorter.

Since the composition of the present invention has a higher shrinkage ratio during heat treatment than that of the conventional one, it can be applied with a relatively thick film so as to have good step coverage during application, while the film can be applied by subsequent heat treatment. Can be finally contracted to obtain a thin antireflection film. As a result, by using the antireflection composition of the present invention, it is possible to form an antireflection film having good step coverage and a thin film thickness. In order to obtain good water resistance of the antireflection film, the heat treatment temperature of 200 ° C. or lower is sufficient, but in order to obtain the antireflection film having a thin film thickness by being greatly contracted, a higher temperature, for example, It is also possible to perform heat treatment at a high temperature of 200 to 220 ° C, further 220 to 260 ° C. However, if the heat treatment is carried out at a too high temperature for a long time, the polyvinyl alcohol is decomposed and the film is deteriorated, which is not preferable.

Even when the composition of the present invention is subjected to the above heat treatment, the dry etching property is better than that of, for example, novolac resin or polyimide resin. (Dry etching resistance is low.) The thickness of the antireflection film thus obtained varies depending on the concentration of the light absorber in the antireflection film, the requirements from the photolithography process, and the like, but is about 0.05 to 2 μm. Usually, it is about 0.1 to 1 μm.

Various conventionally known methods can be adopted as a coating method, an exposing method, a developing method and the like of the photoresist composition after forming the antireflection film. The film thickness of the applied photoresist composition is usually about 0.3 to 5 μm. Further, after applying the photoresist composition, a heat drying treatment may be carried out, and it is usually carried out at 70 to 130 ° C. for 30 to 120 seconds using a hot plate or the like.

The exposure wavelength used to transfer an image to the formed photoresist film is usually g-line (436n).
m), i-line (365 nm), XeCl excimer laser light (308 nm), KrF excimer laser light (248
nm), ArF excimer laser light (193 nm), etc. are effective. After exposure of the photoresist film, post-exposure heating (PEB) may be performed if necessary. As the PEB condition, a hot plate or the like is used and the temperature is 70 to 130 ° C.
Conditions of about 0 to 120 seconds are preferably used. A convection oven may be used instead of the hot plate, but this usually requires a longer time than when using a hot plate.

As a developing solution for developing the photoresist after exposure, an alkaline aqueous solution is usually used, and examples thereof include inorganic materials such as sodium hydroxide, potassium hydroxide, sodium carbonate, aqueous ammonia, sodium silicate and sodium metasilicate. Alkali, primary amines such as ethylamine and n-propylamine, diethylamine, di-
Aqueous solutions of secondary amines such as n-propylamine, tertiary amines such as triethylamine and methyldiethylamine, quaternary ammonium salts such as tetramethylammonium hydroxide and trimethylhydroxyethylammonium hydroxide, or the like. The thing which added alcohol etc. is mentioned. Further, a surfactant or the like can be added for use as necessary. Development time is 30
Desirably, the developing temperature is about 180 seconds and the developing temperature is about 15 to 30 ° C. In addition, the developer is usually used after being filtered to remove insoluble matter at the time of use.

[0032]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist. The photoresist compositions of the following examples were all handled in a class 100 clean room using a fluorescent lamp that shielded light of 500 nm or less (so-called yellow room) unless otherwise specified.

(Example 1) Polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., GH-20, saponification degree; 86.
5.1 g of 5- (89.0%) and 1.4 g of tetramethylammonium salt of 5- (3'-nitrophenylazo) salicylic acid (Alizarin Yellow GG) were dissolved in 93 g of water. This was filtered with a membrane filter having a pore size of 0.2 μm to prepare antireflection composition A.

On the other hand, m-cresol, p-cresol and 2,5-xylenol (molar ratio = 5: 4: 1), formaldehyde and acetaldehyde (molar ratio =)
8: 2), 14.0 g of a cresol-based novolak resin (average molecular weight 3,500), a novolak resin (average molecular weight 1,000) synthesized from m-cresol and acetaldehyde, and 1,2-naphthoquinonediazide-
7.3 g of a photosensitizer synthesized from 5-sulfonic acid chloride (average esterification rate: 40%) was dissolved in 56 g of methyl 3-methoxypropionate. This is the hole diameter 0.2μ
m through a membrane filter to prepare a photoresist composition A.

This antireflection composition A was applied on a silicon wafer on which aluminum was sputtered to a thickness of 0.2 μm by a spin coater and then baked on a hot plate at 180 ° C. for 60 seconds to give a 0.2 μm thick reflection film. A protective film was formed. A photoresist composition A was further applied onto this antireflection film by a spin coater in the same manner, and then baked on a hot plate at 80 ° C. for 90 seconds to form a 1.07 μm thick photoresist film.

The results of examining the state of mixing of the obtained antireflection film and photoresist film are shown in Table 1. This wafer is an i-line stepper (manufactured by Nikon Corporation NA =
0.5) and exposed to PEB (110
C., 90 seconds) and development (using a 2.38 wt% aqueous solution of tetramethylammonium hydroxide) at 23.degree. C., 60
Second).

The cross-sectional shape of the transferred pattern with an exposure amount that makes 0.5 μm lines and spaces 1: 1
The results of observation with an electron microscope are shown in Table-1. At this time, the antireflection film was not removed by dissolution during development and remained. On the other hand, the antireflection composition A was applied on a silicon wafer having a pattern having a step of 1 μm by a spin coater to form an antireflection film having a thickness of 0.20 μm.

This antireflection film is further treated at 200 ° C. for 60 minutes.
Bake on a hot plate for 0 seconds. The film thickness of the obtained film was measured to examine the decrease in film thickness due to the heat treatment, and the state of step coverage of the step portion at this time was examined. The results are shown in Table 1. Furthermore, a heat-treated antireflection-coated wafer having a film thickness of 0.5 μm obtained by the same method as described above, and a photoresist composition A as described above.
After applying to a silicon wafer with a spin coater,
Wafers with a photoresist film obtained by baking on a hot plate for 90 seconds at 0 ° C. were prepared, and these coating films were subjected to dry etching by oxygen plasma (pressure 15 Pa, RF power 300 W, etching gas oxygen). The speed was measured, and the etching rate ratio between the antireflection film and the photoresist film (etching rate of antireflection film / etching rate of photoresist film) was determined. The results are shown in Table 1.

Example 2 Polyvinyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd., polymerization degree of about 2000, weight average molecular weight of 8)
8,000 g, saponification degree 78-82%) 4.8 g and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (trihydrate) (manufactured by Cypro Kasei Co., SEESORB)
101S) 1.2 g was dissolved in water 94 g. This was filtered through a membrane filter having a pore size of 0.2 μm to prepare antireflection composition B.

On the other hand, the part t- of polyvinylphenol (manufactured by Maruzen Petrochemical Co., Ltd., weight average molecular weight: 5,200).
20 g of butoxycarbonyl compound and 2,6-bis (2-
8.6 g of t-butoxycarbonyl compound of hydroxy-5-methylbenzyl) -4-methylphenol and triphenylsulfonium triflate (Midori Kagaku Co., Ltd.)
1.4 g) was dissolved in 78 g of diethylene glycol dimethyl ether.

This was filtered through a membrane filter having a pore size of 0.2 μm to prepare a photoresist composition B.
The antireflection composition B was applied to a silicon wafer by a spin coater and then baked on a hot plate at 200 ° C. for 300 seconds to form an antireflection film having a thickness of 0.2 μm. The photoresist composition B was applied onto the antireflection film by a spin coater in the same manner, and then 1
Bake on a hot plate for 90 seconds at 20 ° C,
A wafer with a photoresist film was obtained. At this time, a plurality of wafers are prepared, and 0.9 to 1.
The film thickness was adjusted to 05 μm.

Table 1 shows the results of examining the state of mixing of the obtained antireflection film and photoresist film. The obtained wafer was exposed (KrF excimer laser) by an ordinary method using an excimer laser stepper (manufactured by Nikon Corporation, NA = 0.42), and PEB (80 ° C., 90 ° C.).
Second) and development (using a 2.38 wt% aqueous solution of tetramethylammonium hydroxide, 23 ° C., 60 seconds).

The minimum exposure amount (Eth) required for developing and removing the photoresist film having a 2 mm square blank pattern up to the substrate was measured. As described above, this sensitivity changes periodically with changes in the photoresist film thickness. In this case, the photoresist film thicknesses of 0.93 μm and 1.00.
Sensitivity ratio in μm (corresponding to peaks and valleys of the above cycle) [Eth at film thickness 0.93 μm / Et at film thickness 1.00 μm
h] was measured. The results are shown in Table 1. In addition, Example 1
Similarly to the above, the decrease of the film thickness of the 0.2 μm thick antireflection film due to the heat treatment was examined, and the state of the step coverage of the step portion at this time was examined. The results are shown in Table 1.

Example 3 The polyvinyl alcohol was changed from that manufactured by Wako Pure Chemical Industries, Ltd. to that manufactured by Denki Kagaku Kogyo (H-20, saponification degree 95.0-96.0%). The antireflective composition C was prepared in the same manner as in Example 2 except that the photoresist film thickness of 0.
The sensitivity ratio at 93 μm and 1.00 μm was measured. The results are shown in Table 1.

(Comparative Example 1) A transfer pattern of 0.5 μm line and space was transferred at an exposure dose of 1: 1 in the same manner as in Example 1 except that the antireflection composition was not applied. The cross-sectional shape was observed. The results are shown in Table 1. (Comparative Example 2) The photoresist film thickness was 0.93 in the same manner as in Example 2 except that the antireflection composition was not applied.
The sensitivity ratio at μm and 1.00 μm was measured. The results are shown in Table 1.

(Comparative Example 3) A cresol-based novolak resin (average molecular weight: 1) synthesized from m-cresol and p-cresol (molar ratio = 6: 4) and formaldehyde.
2,000) 7.6 g, a novolak resin (average molecular weight 1,300) synthesized from pyrogallol and acetone, and 1,
Photosensitizer synthesized from 2-naphthoquinonediazide-5-sulfonic acid chloride (average esterification rate 50%) 0.1
3 g and 4- (3'-methyl-4'-hydroxyphenylazo) azobenzene (manufactured by Mitsubishi Chemical Corporation) 2.5
g was dissolved in 90 g of methyl 3-methoxypropionate. This was filtered through a membrane filter having a pore size of 0.2 μm to prepare antireflection composition D.

This antireflection composition D was used as antireflection composition A
In the same manner as in Example 1 except that the heat treatment condition after coating the antireflection composition D was changed to 250 ° C. for 600 seconds. The state of mixing with the product A) and the cross-sectional shape of the transferred pattern at an exposure amount with which a line and space of 0.5 μm were finished 1: 1 were examined. The results are shown in Table 1. At this time, the antireflection film was not removed by dissolution during development and remained.

Further, as in Examples 1 and 2, the reduction of the film thickness due to the heat treatment was examined, and the state of the step coverage of the step portion at this time was examined. The results are shown in Table 1. Furthermore, the initial thickness of the antireflection film is 0.20 μm.
In the same manner, except that the thickness was changed from m to 0.13 μm, the reduction of the film thickness by heat treatment and the state of step coverage at the step portion were examined. The results are shown in Table 1. Furthermore, the etching rate ratio between the antireflection film and the photoresist film was obtained in the same manner as in Example 1 except that the antireflection film A was replaced with the antireflection film D. The results are shown in Table 1.

(Comparative Example 4) Exposure and development were carried out in the same manner as in Example 1 except that pullulan (manufactured by Hayashibara Co., Ltd.) was used instead of polyvinyl alcohol. When the transferred pattern was observed with an optical microscope after development, most of the patterns of 1.0 μm or less were peeled off and disappeared. (Comparative Example 5) Exposure and development were performed in the same manner as in Example 1 except that the antireflection composition A was replaced with the antireflection composition D. When the transferred pattern was observed with an optical microscope after development, mixing was observed between the antireflection film and the photoresist film, and the resolution, pattern shape, etc. were much higher than in Comparative Example 1 in which the antireflection composition A was not used. Was inferior to

[0050]

[Table 1]

In Table 1, the presence or absence of undercut means that in the resist pattern obtained after development,
Indicates the presence or absence of bite (undercut) near the board. This state is shown in FIG. 1A and 1B are schematic cross-sectional views showing a resist pattern. FIG. 1A shows a good state without undercut, and FIG. 1B shows a state with undercut. In FIG. 1A, the photoresist 1
1 keeps a rectangular shape on the substrate or the antireflection film 12, whereas in FIG. 1B, a hard depression of the photoresist 11 is seen near the substrate or the antireflection film 12.

FIG. 2 is a schematic sectional view showing the quality of step coverage. In FIG. 2, (a) shows a state where the step coverage is good, and (b) shows a bad state. In FIG. 2A, the antireflection film 20 formed on the substrate 21 having a step is formed with a uniform film thickness even in the step. On the other hand, FIG. 2 (b)
In the above, the antireflection film 20 formed on the same substrate 21 does not have a uniform film thickness at the step portion, and the edge is not sufficiently covered.

[0053]

According to the present invention, an antireflection film can be satisfactorily formed even with a small amount of an organic medium, which is an environmental problem, and an antireflection film for preventing reflection of light from a substrate. It can be used as a film, mixing with photoresist is suppressed, and step coverage is good even with a thin film thickness.
Further, it is possible to provide an antireflection composition having good dry etching property. Further, it is possible to provide a pattern forming method in which the resolution is not lowered and the resist pattern is less deformed, and the change in the sensitivity due to the change in the coating film thickness is suppressed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a resist pattern.

FIG. 2 is a schematic cross-sectional view showing the quality of step coverage.

[Explanation of symbols]

 11 Photoresist 20 Antireflection Film 21 Substrate

Claims (3)

[Claims] 1. An antireflection composition applied between a substrate and a photoresist film, which contains a polyvinyl alcohol resin having a saponification degree of 70% or more. 2. A step of applying an antireflection composition on a substrate to form an antireflection film, a step of applying a photoresist composition on the antireflection film to form a photoresist film, the photoresist film 2. A pattern forming method comprising the steps of exposing a photoresist to transfer a predetermined pattern onto a photoresist film, and developing the photoresist film with a developer, wherein the antireflection composition is used as the antireflection composition. A method for forming a pattern, which comprises using an antireflection composition. 3. The pattern forming method according to claim 2, wherein a heat treatment is applied at a temperature of 110 ° C. or higher after applying the antireflection composition.