JPH07333855A - Antireflection coating composition and pattern forming method - Google Patents

Abstract

PURPOSE:To provide an antireflection coating compsn. having a higher antireflection effect than a conventional one and to provide a pattern forming method using this antireflection coating compsn. CONSTITUTION:This antireflection coating compsn. is applied to form an antireflection film 21 on a photoresist film 22 to be used to transfer a pattern. This antireflection coating compsn. contains such an absorbent of light that absorbs light of the same wavelength as the wavelength of light 20 with which the photoresist film 22 and the antireflection film 21 are irradiated when a pattern is transferred. The pattern forming method is carried out using this compsn. By using the absorbent for light, the light quantity of the second reflected light 27 is made the same as that of the third reflected light 28.

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. A photoresist composition is used in these photolithography techniques, and various photoresist compositions having high performance have been proposed by improving the photoresist composition.

The properties required for this photoresist composition are, of course, higher resolution, but the dimensions of the transferred pattern do not vary depending on the coating thickness of the photoresist composition. is important. 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 irradiated light is usually monochromatic light, and the light incident on the photoresist film repeats intra-film multiple reflection at the upper and lower boundary surfaces of the photoresist film. as a result,
Due to the interference effect, the effective light amount changes depending on the coating film thickness, so that the sensitivity periodically changes with respect to the coating film thickness. Further, even when the exposure amount is the same, the finished size of the transferred pattern periodically changes in accordance with the variation of the coating film thickness, which limits the dimensional accuracy of the pattern.

As a method for solving this problem, a method has been proposed in which an antireflection film is formed on a photoresist film to reduce the influence of the multiple reflection in the film and improve the dimensional controllability (special feature. JP-A-62-62520, JP-A-62-62521, JP-A-5-188598). The antireflection film is a transparent film having a refractive index different from that of the photoresist film, and by appropriately selecting the film thickness and the refractive index, effective optical interference is caused, and the effect of intra-film multiple reflection is exerted. Is to reduce. FIG. 1 is a schematic sectional view showing the principle of reducing intra-film multiple reflection by an antireflection film. A photoresist film 22 is formed on a substrate 23 to be processed, and an antireflection film 21 is further formed on the photoresist film 22. The irradiation light 20 is
The light passes through the antireflection film 21 and the photoresist film 22, reaches the substrate 23, and is reflected by the substrate 23. The reflected first reflected light 24 reaches the boundary surface 26 between the antireflection film 21 and the photoresist film 22, a part of which is reflected (second reflected light 27) and the rest is transmitted. Part of the transmitted light is further reflected by the boundary surface 25 between the antireflection film 21 and the outside thereof (third reflected light 28). By causing the second reflected light 27 and the third reflected light 28 to interfere with each other, the intensity thereof can be reduced.

Generally, the amplitude of a composite wave of two sine waves having a phase difference δ changes depending on the phase difference δ, and when δ = π, the minimum value |
A−B | is taken (A and B represent the amplitudes of the respective sine waves), but by making A and B approximately equal, the amplitude of the composite wave becomes approximately 0, that is, more complete antireflection is performed. It can be carried out. Antireflection by the antireflection film is based on such a principle, but with the conventional antireflection coating composition, more complete antireflection was very difficult.

It is very difficult to achieve more complete antireflection in the conventional antireflection coating composition for the following reason. In the antireflection method shown in FIG. 1, the antireflection film 2
An antireflection coating composition for forming an antireflection film 21 as well as setting the film thickness of 1 to an odd multiple of (λ / 4n) (λ represents the wavelength of irradiation light and n represents the refractive index of the antireflection film) It is said that it is preferable to set the refractive index of the above as the square root of the refractive index of the photoresist film. Generally, since the refractive index of the photoresist film is about 1.6 to 1.7, the preferable refractive index of the antireflection coating composition is about 1.27 to 1.3. A fluorine compound is a candidate for such a compound having a low refractive index.

On the other hand, the antireflection coating composition is also required to be water-soluble. That is, when the method as described above is applied industrially, it is necessary not to change the process of photoresist coating-exposure-development, which is required in the conventional photolithography technique, and therefore, it is generally used. This is because it is extremely preferable that the antireflection film can be dissolved and removed by the developing solution of the aqueous medium. The antireflection coating composition is required to have an appropriate refractive index as described above and to be water-soluble, but it is presently known because there are few water-soluble fluorine compounds. The refractive index of the water-soluble antireflection coating composition is about 1.4, which is not the optimum value. That is, at the present stage, although the method of forming a pattern using an antireflection film and the principle of antireflection are known, the means for embodying them are insufficient, and in order to further enhance the antireflection effect. It was the current situation that the means of (1) was hardly found.

[0008]

SUMMARY OF THE INVENTION In view of the above background, an object of the present invention is to provide an antireflection coating composition having a greater antireflection effect than ever before, and to use such an antireflection coating composition. To provide a conventional pattern forming method.

[0009]

As a result of various studies conducted by the present inventors in order to solve such problems, in order to equalize the light amounts of the second and third reflected lights in FIG. The present invention has been completed by finding that the above object can be achieved by incorporating a light absorber in the antireflection coating composition. That is, the gist of the present invention is an antireflection coating composition for forming an antireflection film by coating on a photoresist film used for pattern transfer, wherein the photoresist film and the antireflection film are irradiated during pattern transfer. The antireflection coating composition is characterized by containing a light absorber that absorbs light having a wavelength equal to the wavelength of light.

Another aspect of the present invention is to apply a photoresist composition onto a substrate to form a photoresist film, and apply an antireflection coating composition onto the photoresist film to form an antireflection film. In a pattern forming method, including a step of forming, a step of exposing the photoresist film and the antireflection film to transfer a predetermined pattern to the photoresist film, and a step of developing the photoresist film with an alkaline aqueous solution, The pattern forming method is characterized in that the antireflection coating composition contains a light absorbing agent that absorbs light having a wavelength equal to the wavelength of light used for exposure.

The present invention will be described in detail below. First, the basic principle of the present invention will be described with reference to FIG. The essence of the present invention is to equalize the light amounts of the second reflected light 27 and the third reflected light 28 shown in FIG. As described above, the refractive index of the antireflection film is the square root of the refractive index of the photoresist film, and its thickness is (λ /
4n), which is preferably an odd multiple (λ represents the wavelength of irradiation light, and n represents the refractive index of the antireflection film), but the conventional antireflection coating composition has a desired refractive index. In addition, since no water-soluble substance was found, the antireflection effect was never sufficient. That is, the intensity of the second reflected light 27 is weaker than the intensity of the third reflected light 28, and the respective light amounts are different from each other. In the present invention, this difference in the amount of light is reduced by using a light absorber. That is, in a preferred embodiment of the present invention, the refractive index of the antireflection film is close to the square root of the refractive index of the photoresist film.
And making the light quantities of the third reflected light close, and making a slight difference in light quantity equal by the light absorber.

In the present invention, the light absorber used is
There is no particular limitation as long as it absorbs light having a wavelength of light irradiated at the time of pattern transfer, but from the industrial point of view described above, those having water solubility are preferable. Specifically, those containing a water-soluble group such as a carboxyl group, a sulfonic acid group, a phenolic hydroxyl group and an ammonium base in the molecule are preferable. Examples of such a suitable light absorbing agent include cresol red, methyl red, neutral red, phenol red, bromophenol red, methyl orange, methyl yellow, thymol blue, bromothymol blue, and orange II, depending on the wavelength of light to be irradiated. , Alizarin Yellow R, Bromocresol Green, Bromophenol Blue, Tetrabromophenol Blue,
Tropeoline OO, methyl violet 6B, CI-direct yellow 8, CI-direct yellow 24,
CI-Direct Yellow 26, CI-Direct Yellow 28, CI-Direct Yellow 50, CI-Direct Yellow 86, CI-Direct Yellow 87,
CI-Acid Yellow 25, CI-Acid Yellow 38, CI-Acid Yellow 61, CI-Acid Yellow 131, CI-Acid Yellow 135, CI-
Basic Yellow 13, CI-Basic Yellow 2
1, CI-Basic Yellow 28, CI-Basic Yellow 51, CI-Basic Yellow 67 and the like. Two or more kinds of light absorbers may be mixed and used.

Since the light absorbing agent also absorbs the primary light before reaching the substrate, it is preferable that the amount used is as small as possible within the range where the antireflection effect is exerted, but if it is appropriately selected depending on the refractive index of the antireflection film. Good. Generally, when the film thickness of the antireflection film is (λ / 4n) (λ represents the wavelength of the irradiation light and n represents the refractive index of the antireflection film), the light transmittance of the irradiation light is 50.
% Or more, especially 60% or more, and 99.9% or less, especially 99%
It is preferable to add a light absorber so as to be as follows. If the transmittance is too high, the difference in intensity between the second reflected light and the third reflected light will not be so small that the effect of the present invention may not be sufficiently obtained. Further, if the transmittance is too low, the intensity of the irradiated primary light itself becomes small, and as a result, the sensitivity of the photoresist may decrease.

The antireflection coating composition used in the present invention is not particularly limited as long as it has a suitable low refractive index such as a refractive index of about 1.27 to 1.3, but it is coated with an aqueous medium. -It is preferably composed of a water-soluble material that can be removed. An example of such a material is a water-soluble polymer as a base compounded with a water-soluble fluorine compound.
As the water-soluble polymer, polyacrylic acid, polyacrylic acid-based polymers such as polyacrylamide, polyvinyl alcohol-based polymers such as polyvinyl alcohol, polyvinylpyrrolidone-based polymers such as polyvinylpyrrolidone,
Polyether glycols such as polyethylene glycol and polypropylene glycol, polymer amines such as polyvinylamine and polyethyleneimine, and the like. Also, natural products such as alginic acid, salts of alginic acid, soluble starch, amylose, and pullulan are used. Is also good.
Two or more kinds of water-soluble polymers may be mixed and used. Water-soluble polymers are generally low in the desired low refractive index, so it is preferable that the amount used is small from the viewpoint of the refractive index, but if it is too small, coatability may deteriorate, so it is usually a total solid. It is used in a proportion of 5 to 60%, preferably 10 to 50%, based on the weight of the component.

As the water-soluble fluorine compound, perfluoroalkylcarboxylic acid such as perfluorooctanoic acid,
And ammonium salts or tetraalkylammonium salts thereof, perfluoroalkylsulfonic acids such as perfluorooctanesulfonic acid, ammonium salts or tetraalkylammonium salts thereof, and fluorine-substituted polyethers such as polyethylene glycol perfluoroalkyl ethers. Two or more kinds of water-soluble fluorine compounds may be mixed and used. Since the water-soluble fluorine compound generally has a low refractive index, it is preferable that the amount used is large in terms of the refractive index.
If the amount is too large, the coatability may be deteriorated. Therefore, it is used in a proportion of 40 to 95%, preferably 50 to 90%, based on the total solid content weight.

The antireflection coating composition of the present invention is preferably prepared by dissolving the above-mentioned light absorber, water-soluble polymer and water-soluble fluorine compound in a solvent. In this case, an aqueous medium is usually used as the solvent. Further, an organic solvent which can be mixed with water may be contained in the aqueous medium. Examples of the organic solvent include methanol, ethanol, propanol,
Besides alcohols which may be fluorine-substituted, such as butanol, tetrafluoropropanol, octafluoropentanol, and the like, acetone, acetic acid, dimethoxymethane, and the like having a boiling point of 50 to 300 ° C. at 1 atmospheric pressure can be mentioned.

When the amount of these organic solvents used is too large, they may dissolve the photoresist film formed under the antireflection film, and therefore, they are usually 50% or less based on the total solid content weight. , Preferably 30% or less. The proportion of solids such as a water-soluble polymer varies depending on the film thickness of the antireflection film to be applied, but it is usually 1% in an aqueous medium.
Used by dissolving about 10%. Further, a surfactant or the like may be added to the composition of the present invention in order to further improve the coating property and the like.

In the pattern forming method of the present invention, as a target photoresist composition, in principle, all photoresist compositions using monochromatic light can be used. That is, conventional g-line, i-line, excimer laser light (248n
m, 193 nm) and a positive type or negative type material can be used.

Specific photoresist compositions include:
Polyvinylcinnamate-based and polyisoprene cyclized rubber-based photocrosslinking photoresist compositions (Journal of Organic Chemistry, Vol. 42, No. 11, 979 etc.), 1,2-naphthoquinonediazide-based photosensitizer And an alkali-soluble resin dissolved in an organic solvent (Journal of Synthetic Organic Chemistry, Vol. 42, No. 11, p. 979, JP-A-62-13663).
No. 7, JP-A-62-153950, etc.), a so-called chemically amplified photoresist which exhibits the performance of a photoresist by being polymerized or depolymerized by an acid or a base generated by light irradiation (JP-A-59-45439). No. 4, JP-A-4-1368
No. 60, JP-A-4-136941, etc.) and the like.

Examples of the resin used in the photoresist composition include a polyvinyl cinnamate resin produced from polyvinyl alcohol and cinnamic acid chloride, and a cyclized rubber resin containing 1,4-cis polyisoprene as a main component. To be
In addition, if necessary, 4,4′-diazidochalcone,
A photo-crosslinking agent such as 2,6-di- (4′-azidobenzylidene) cyclohexanone may be added.

1, 2 used in the photoresist composition
-As the naphthoquinonediazide-based photosensitizer, 1,2-benzoquinonediazide-4-sulfonic acid ester derivatives, 1,2-naphthoquinonediazide-4-sulfonic acid ester derivatives of compounds having a phenolic hydroxyl group, 1,
2-naphthoquinone diazide-5-sulfonic acid ester derivative etc. are mentioned. Here, the compound having a phenolic hydroxyl group is produced from polyhydroxybenzophenones such as 2,3,4-trihydroxybenzophenone, polyhydroxybenzoate esters such as ethyl gallate, phenols and aldehydes. Examples thereof include polyphenols and novolac resins.

Examples of the alkali-soluble resin used in the photoresist composition include novolak resins obtained by polycondensing a phenol derivative and an aldehyde derivative, acrylic acid derivatives, cinnamic acid derivatives, styrene derivatives, maleic acid derivatives and the like as monomers. Examples thereof include polymers obtained by polymerizing these.

Examples of the photoresist composition include a resin having an acid-labile group such as poly (p-tert-butoxycarbonyloxy) styrene and an acid by irradiation with light such as triphenylsulfonium hexafluoroarsenate. And a photo-irradiating portion which is solubilized or insolubilized in a developing solution. Further, it is composed of a novolak resin obtained by polycondensing a phenol derivative and an aldehyde derivative, and a compound that generates an acid by light irradiation such as alkoxymethyl urea or halogenated methyl triazine, and the light irradiation portion becomes insoluble in the developing solution. A photoresist composition and the like are also included.

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 di-ethylene glycol; mono- or di-, such as propylene glycol monomethyl ether
Propylene glycol mono- or di-alkyl ethers; Propylene glycol monomethyl ether acetate and other alkyl cellosolve acetates; Esters such as ethylene carbonate and γ-butyrolactone; Methyl ethyl ketone, 2-heptanone, cyclopentanone and other ketones; Lactic acid And hydroxy, alkoxy or oxyalkyl carboxylic acid alkyl esters such as ethyl, 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 and the stability of the photoresist composition. Further, these photoresist compositions, if necessary,
It may contain a surfactant for improving coatability, a sensitizer for improving sensitivity, and the like.

The substrate used in the pattern forming method of the present invention is not particularly limited, but a substrate for IC production such as a silicon substrate or a gallium arsenide substrate is generally used. The method of applying the photoresist composition on the substrate and the method of applying the antireflection coating composition on the photoresist film are not particularly limited, and a spin coater or the like is used according to a conventional method. The film thickness of the obtained photoresist composition is usually about 0.3 to 5.0 μm.

After coating the photoresist composition on the substrate, heat-drying treatment may be carried out, usually using a hot plate or the like at 70 to 100 ° C. for 30 to 120 seconds. The film thickness of the antireflection film may be appropriately optimized according to the exposure wavelength and the like according to the above-described antireflection principle. When a water-soluble composition is used as the composition for forming the antireflection film, the formed antireflection film can be easily removed after exposure, during development with an alkaline aqueous solution, or by simply washing with water.

The exposure wavelength used for transferring an image to a photoresist film formed on a substrate is usually g-line (436 nm), i-line (365 nm), XeCl excimer laser light (308 nm), KrF excimer laser. Light (248 nm), ArF excimer laser light (193n
m) etc. are effective. After exposing the photoresist film and the antireflection film, if necessary, post-exposure heating (PEB) may be performed. As a PEB condition, a hot plate or the like is used, and a condition of about 90 to 120 ° C. for about 60 to 120 seconds is 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 the alkaline aqueous solution for developing the photoresist after the exposure, inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, aqueous ammonia, sodium silicate and sodium metasilicate, ethylamine and n-propylamine are used. Primary amines such as
Aqueous solutions of secondary amines such as diethylamine and di-n-propylamine, tertiary amines such as triethylamine and methyldiethylamine, and quaternary ammonium salts such as tetramethylammonium hydroxide and trimethylhydroxyethylammonium hydroxide. Alternatively, a product obtained by adding alcohol or the like to this can be used. Further, a surfactant or the like can be added for use as necessary. The developing time is preferably about 30 to 180 seconds and the developing temperature is preferably about 15 to 30 ° C. The photoresist developing solution is used after being filtered to remove insoluble matters.

[0029]

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.

(Preparation Example 1 of coating composition for antireflection film) 1.8 g of perfluoroalkyl alcohol / polyethylene oxide adduct (manufactured by Neos; Futgent 250), ammonium perfluoroalkylcarboxylate (manufactured by Daikin Industries, Ltd .; DS- 101) 4.2 g and 0.18 g of CI-Direct Yellow 86 as a light absorber
Was dissolved in 100 g of water and filtered through a 0.2 μm filter to prepare antireflection coating composition A. The refractive index of the antireflection coating composition A was 1.37. (Preparation Example 2 of coating composition for antireflection film) In the same manner as Preparation Example 1 of antireflection coating composition except that no light absorber was added,
An antireflection coating composition B was prepared. The refractive index of the antireflection coating composition B was 1.37.

(Example 1 and Comparative Examples 1 and 2) Quinonediazide positive photoresist (manufactured by Mitsubishi Kasei Co., Ltd .: M)
CPR-i6600) is spin-coated on multiple 5-inch silicon wafers, and is hot-plate coated at 80 ° C for 9
The coated film is dried by heating and baking for 0 seconds.
A plurality of photoresist coating films having a film thickness of 500Å were obtained. Further, each of the antireflection coating compositions A and B was spin-coated on this photoresist film, and the coating was applied on a hot plate to form a film.
The coating film was dried by heating at 0 ° C. for 90 seconds to obtain a photoresist-coated film wafer with an antireflection film (film thickness 650Å). The light transmittance of the antireflection film was 70%.

Further, in the same manner, a wafer having a photoresist coating film not coated with the antireflection coating composition was obtained. These wafers were exposed with an i-line stepper (manufactured by Nikon Corporation: NSR1755i7A) through a mask with a test pattern, and then exposed on a hot plate at 110 ° C. for 9 minutes.
After post-exposure baking for 0 seconds, paddle development was performed for 60 seconds with a 2.38 wt% tetramethylammonium hydroxide aqueous solution. Minimum exposure required to develop and remove the photoresist coating film to the substrate (Eth:
The same applies hereinafter). The results are shown in Figure 2. Table 1 shows the change in sensitivity with respect to the film thickness of the photoresist.
As is clear from Table-1, the change in sensitivity is smaller than in the case where the antireflection coating composition is not used, and further in the case where the light absorber is not contained in the antireflection coating composition. It can be seen that the change in sensitivity is small.

[0033]

[Table 1] * 1: (Eth at film thickness 11300Å) / (film thickness 1080
Eth at 0Å) * 2: (Eth at film thickness 10700Å) / (film thickness 1010
Eth at 0Å)

[0034]

INDUSTRIAL APPLICABILITY According to the present invention, an antireflection coating composition suitable as an antireflection coating can be provided, and by using such an antireflection coating composition, the antireflection coating composition can be used much more than conventional pattern formation. Further, it is possible to provide a pattern forming method having a large antireflection effect.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the principle of reducing intra-film multiple reflection by an antireflection film.

FIG. 2 is a graph showing changes in the minimum exposure amount required for developing and removing the photoresist coating film up to the substrate with respect to the photoresist film thickness in Example 1 and Comparative Examples 1 and 2.

[Explanation of symbols]

 20 Irradiation Light 21 Antireflection Film 22 Photoresist Film 23 Substrate 24 First Reflected Light 25 Boundary between Antireflection Film and Its Outside 26 Boundary between Antireflection Film and Photoresist Film 27 Second Reflected Light 28 3 reflected light

Claims (2)

[Claims] 1. An antireflection coating composition for forming an antireflection film by coating on a photoresist film used for pattern transfer, wherein the wavelength of light applied to the photoresist film and the antireflection film during pattern transfer. An antireflection coating composition comprising a light absorber that absorbs light having a wavelength equal to 2. A step of applying a photoresist composition on a substrate to form a photoresist film, a step of applying an antireflection coating composition on a photoresist film to form an antireflection film, the photoresist film And a step of exposing the antireflection film to transfer a predetermined pattern to the photoresist film,
And a step of developing the photoresist film with an alkaline aqueous solution, wherein the antireflection coating composition contains a light absorber which absorbs light having a wavelength equal to that of light used for exposure. A pattern forming method characterized by the above.