JP2001133984A - Antireflection film material and pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-soluble antireflection film material containing an alkylamine or an alkanolamine in which part or all of the hydrogen atoms of the hydrocarbon group have been substituted by fluorine. SOLUTION: The antireflection film material forms a minute resist pattern with high dimensional accuracy, high accuracy of alignment and good reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-reflection coating material that enables high-precision microfabrication even on a substrate having irregularities, particularly in photolithography using a photoresist, and a resist pattern using the same. It relates to a method of forming.

[0002]

2. Description of the Related Art In recent years,
As the integration and speed of LSIs increase, the pattern rule is required to be finer. With the light exposure currently used as a general-purpose technology, the essential resolution limit derived from the wavelength of the light source is approaching. It is getting.

As exposure light used in forming a resist pattern, light exposure using a g-line (436 nm) or i-line (365 nm) of a mercury lamp as a light source is widely used as a means for further miniaturization. A method of shortening the wavelength of exposure light has been effective. For this reason, in a mass production process of a 64 Mbit (dynamic random access memory) DRAM having a processing size of 0.25 μm or less, a short wavelength KrF excimer laser (248 nm) is used as an exposure light source instead of i-line (365 nm). Has come to be used. However, in order to manufacture a DRAM having an integration degree of 256 M and 1 G or more, which requires a finer processing technique (processing dimension of 0.2 μm or less), a light source having a shorter wavelength is required. In particular, an ArF excimer laser (193n) is required.
Photolithography using m) has been studied.

[0004] In the early stage of KrF lithography, a stepper combining an achromatic lens or a reflection optical system with broadband light was developed.
However, since the accuracy of the achromatic lens or the aspherical reflecting optical system was not sufficient, the combination of the monochromatic light and the refractive optical system lens became mainstream. Here, in half-wavelength exposure, it is a well-known phenomenon that the incident light interferes with the reflected light from the substrate to generate a standing wave. The standing wave caused a dimensional change such as a line width of the pattern, a shape collapse, and the like.

On the other hand, the use of coherent monochromatic light further amplifies the standing wave and the halation as the wavelength becomes shorter.

Conventionally, as a method of suppressing the standing wave, a method of adding a light absorbing agent to a resist material, a method of forming an upper surface of a resist layer (ARC
OR method, JP-A-62-62520, JP-A-62-62
No. 521, JP-A-60-38821) and a method of laying an anti-reflection film on a substrate surface (BARC method, JP-A-62-15)
No. 9143). The ARCOR method is a method including a step of forming a transparent anti-reflection film on a resist layer and peeling off after exposure, and is a method of forming a fine pattern with high precision and high alignment precision by a simple method. When a perfluoroalkyl compound (perfluoroalkylpolyether, perfluoroalkylamine) of a low refractive index material is used as the antireflection film, the reflected light at the resist-antireflection film interface is greatly reduced, and the dimensional accuracy is improved.

However, since the above-mentioned perfluoroalkyl compounds have low compatibility with organic substances, fluorocarbons or the like are used as a diluent for controlling the coating film thickness.
As is well known, the use of CFCs is a problem at present from the viewpoint of environmental protection. Further, the above compound has a problem in uniform film forming property, and cannot be said to be sufficient as an antireflection film. In addition, before the development of the photoresist layer, the antireflection film had to be peeled off with Freon. for that reason,
A conventional system had to be provided with an additional system for peeling off the antireflection film, and the cost of the fluorocarbon solvent was considerably increased.

When the antireflection film is to be peeled off without adding to the conventional apparatus, it is most preferable to peel it off using a developing unit. Since the solutions used in the photoresist developing unit are an aqueous alkali solution as a developing solution and pure water as a rinsing solution, it can be said that an antireflection film material that can be easily peeled off with these solutions is desirable. Therefore, many water-soluble antireflective coating materials and a pattern forming method using the same have been proposed. For example, JP-A-6-27392
6, 6-289620, 7-160002, 7-181
684, 7-234514, 7-295210, 7-3
33855, 8-44066, 8-95253, 8-1
79509, 8-292562, 8-320569, 9
-50129, 9-90615, 9-236915, 9
-258452, 9-258453, 9-29122
8, 9-325500, 10-3001, 10-176
No. 23, 10-69091, 11-124531,
Patent Nos. 2643056, 2878150, 280354
No. 9 is exemplified.

Here, the refractive index of the upper antireflection film for reducing the standing wave to zero is ideally the square root of the refractive index of the resist layer. Since the refractive index of the polyhydroxystyrene-based resist layer used in KrF is 1.8, the ideal value is 1.34. Since the alicyclic resist layer used for ArF has no aromatic ring, the refractive index is generally lower than that of the aromatic polymer. For example, polyacrylate is 1.6, and the ideal value is reduced to 1.27. Materials having such a low refractive index are limited to Teflon-based materials, but since the upper antireflection film is more process-friendly if it can be peeled off during alkali development, as described above, the water-soluble material It is necessary to be.
However, when a hydrophilic substituent is introduced to make a very hydrophobic perfluoro-based material water-soluble, the refractive index increases. In the conventional case, KrF is around 1.42 and A
The limit of rF was around 1.5. Therefore, in KrF lithography, in the patterning of 0.20 μm or less, it is becoming impossible to control the size by suppressing the influence of the standing wave only by the combination of the light absorbing agent and the upper antireflection film. In the ArF lithography, the effect of the upper antireflection film can hardly be expected for the above-mentioned reason at present, and even in the case of KrF, if the line width is strictly controlled due to the further reduction of the line width, the refractive index will be further increased. It is considered necessary to reduce the volume.

An anti-reflection film provided in a lower layer with respect to an anti-reflection film in an upper layer of a resist can obtain a high anti-reflection effect. The underlying anti-reflection film is p-Si or Al
In the case of a high-reflection substrate such as, the optimal refractive index (n value),
By setting the material of the extinction coefficient (k value) to an appropriate film thickness, reflection from the substrate can be reduced to 1% or less, and an extremely large effect can be exhibited. For example, assuming that the refractive index of the resist layer is 1.8, the exposure wavelength is 248 nm, n
When the thickness is set to 1.5, k0.55, and the film thickness is set to 55 nm, the reflectance can be reduced to 0.5% or less. However, when there is a step on the base, the thickness of the antireflection film greatly fluctuates on the step. The anti-reflection effect of the base uses not only light absorption but also an interference effect.
Although the first base of nm has a higher antireflection effect, the reflectance greatly varies depending on the film thickness. A material has been proposed in which the molecular weight of the base polymer used for the antireflection film material is increased to improve the conformal property in which the film thickness variation on the step is suppressed (Japanese Patent Laid-Open No. 10-69072). When the height is high, there is a problem that pinholes are easily generated after spin coating and a problem such that filtration cannot be performed.In addition, conformability can be exhibited only in a step having a relatively low height. Yes, not all-purpose.

Therefore, the thickness of the antireflection film is increased so that the change in reflectance due to the change in film thickness is relatively small (80 nm).
The above method is generally adopted. In addition, when the underlayer of the antireflection film is a transparent film such as a silicon oxide film or a nitride film, and there is a step under the transparent film, even if the surface of the transparent film is flattened by CMP or the like, the reflection does not occur. Higher parts appear. Also in this case, in order to stabilize the reflectance, the thickness of the antireflection film needs to be 80 nm or more as described above. However, when the underlying anti-reflection film is set to 80 nm or more, the reflectance increases, and reflection of up to 4% occurs. In dimensional control of ultrafine processing of 0.20 μm or less, the reflectance must be at least 2% or less, and there is a limit to the use of the underlying antireflection film alone. However, it is thought that it can be further reduced by the combined use with the upper antireflection film, and further lowering of the refractive index of the upper antireflection film is required.

Further, the upper anti-reflection film not only functions as an original anti-reflection film, but also functions as an environmental barrier film after exposure, or prevents development defects by increasing affinity with a developing solution. It also has functions and is expected to become an increasingly important material in the future.

The antireflection film for ArF has a problem of transmittance as well as the problem of refractive index described above. As a result of various studies by the present inventors, it was found that most of the antireflection films developed for KrF have strong absorption for ArF light.

If there is strong absorption in the upper antireflection film, light does not reach the lower resist, which causes a problem that sensitivity is reduced. It is known that aromatics such as phenyl groups and unsaturated hydrocarbon groups such as vinyl groups have strong absorption for ArF light, but carboxylic acid amides also have strong absorption. For this reason, amine salts of carboxylic acids, fluorinated surfactants or fluorinated polymers containing carboxylic amides are added as hydrophilic substituents to reduce the refractive index, or polyvinylpyrrolidone is used as a binder polymer. It was found that those cannot be used for ArF.

It is also conceivable to use ethylene oxide, propylene oxide, alcohol, amine, or the like as a hydrophilic group. However, amine is neutralized with an acid generated from a resist to form a T-top profile, and other amines are used. The thing mixed with the resist and caused mixing.

The present invention has been made in view of the above circumstances,
Provide an anti-reflection coating material for forming a resist pattern that is fine, has high dimensional accuracy and high alignment accuracy, is simple, has no environmental problems, has high productivity, and has good reproducibility, and a method of forming a resist pattern using the same. The purpose is to do.

[0017]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, have found that fluorinated alkylamines or alkanolamines, especially fluorinated alkylamines or alkanolamines The use of an anti-reflective coating containing a perfluoro compound containing as a counter cation reduces reflected light at the resist layer surface without loss of incident light, and pattern dimensional accuracy due to multiple light reflection interference at the resist layer Was found to be able to be prevented, and the peeling could be easily carried out with water or an alkali developing solution. That is,
According to the study of the present inventors, further reduction in the refractive index and A
It has been found that it is effective to add perfluoroamine as a counter cation of the hydrophilic substituent for improving the transparency in the rF excimer laser. As described above, carboxylic acid amide and amine salt of carboxylic acid are 193
Although it has a strong absorption at nm, it has been found that a perfluoroamine salt of a carboxylic acid has a small absorption and that the refractive index is lowered by an increase in the fluorine content, and the present invention has been accomplished.

Accordingly, the present invention provides a water-soluble polyperfluoroalkyl material having a sulfonyl group in a side chain, which is suitable as a base resin for an antireflection film material used in microfabrication in a manufacturing process of a semiconductor device or the like. Anti-reflective coating material, far ultraviolet rays, KrF excimer laser light (2
48 nm), ArF excimer laser light (193 nm)
And (2) a method for forming a pattern suitable for using a high energy ray such as a light source as an exposure light source, wherein (1) an alkylamine or an alkanolamine in which some or all of the hydrogen atoms of a hydrocarbon group are substituted with fluorine. (2) a water-soluble anti-reflective coating material comprising, as a main component, a perfluoro compound containing the fluorine-substituted alkylamine or alkanolamine as a counter cation; Forming an anti-reflection layer made of the anti-reflection film material as an upper layer of a photoresist layer; removing the anti-reflection layer after exposing the resist layer through the anti-reflection layer; A method for forming a pattern is provided.

Hereinafter, the present invention will be described in more detail.
The water-soluble antireflective coating material of the present invention contains an alkylamine or an alkanolamine in which part or all of the hydrogen atoms of the hydrocarbon group is fluorine-substituted. It is preferable to use a perfluoro compound containing a counter cation as a main component.

The above-mentioned alkylamine and alkanolamine are preferably monovalent hydrocarbon groups, particularly those having 1 to 20 carbon atoms, especially 1 to 10 carbon atoms as alkyl groups. Any of them may be used. Specific examples of the fluorine-substituted alkylamine and alkanolamine include perfluorotriethylamine, perfluorotriethanolamine, perfluorotripropylamine, perfluorotributylamine, perfluoropentylamine, trifluoroethylamine, trifluoropropylamine, 4,4,4-trifluoro-
DL-valine, 5,5,5-trifluoro-DL-leucine and the like.

Examples of the perfluoro compound include compounds represented by the following general formulas (1) to (16).

[0022]

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[0023]

Embedded image (Where a and b are integers from 0 to 20, c, d, e, f,
g, h, i, j, k, l, m, and n are integers from 0 to 15,
o and t are 0 to 100, p and u are 1 to 100, q, r, s
Represents an integer of 0 to 15, and M represents an alkylamine or alkanolamine in which part or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are substituted with fluorine. )

Here, M represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, particularly an alkylamine or alkanolamine in which some or all of the hydrogen atoms of the alkyl group have been substituted with fluorine. Is done.

Further, the equations (1), (2), (9), (1)
A) and b are integers of 0 to 20, especially 3 to 15. In formulas (3) and (11), c, d, and e are 0 to 1.
5, particularly an integer of 0 to 10, wherein c + d + e is 1 to 1
It is preferably 0, especially 1 to 8. Equations (4), (1
In 2), f and g are integers of 0 to 15, especially 0 to 10, and f + g is preferably 1 to 10, particularly 1 to 8. In Equations (5) and (13), h, i, j are 0
To 15, particularly 0 to 10, and h + i + j is 1 to
10, preferably 1 to 8. Equation (6),
In (14), k, l (ell), m and n are 0 to 1
5, especially an integer of 0 to 10, and k + 1 + m + n is 1 to
10, preferably 1 to 8.

Equations (7), (15) and (8), (16)
O is 0 to 5 when p = 1
0, particularly an integer of 0 to 30, and q, r, and s are 0 to 1
5, particularly an integer of 0 to 10, and q + r + s is 1 to 2
It is preferably 0, particularly preferably 1 to 10. When u is 1, t is 0 to 100, preferably 0 to 50, and more preferably 0 to 30.

The fluorinated alkylamine or alkanolamine of M is used in an amount of 0.01 to 10 mol per mol of the carboxyl group or sulfonic acid group of the perfluoro compound represented by the general formulas (1) to (16). It is desirable to add it in molar.

The anti-reflective coating material of the present invention may contain various water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethylene oxide, amylose, dextran, cellulose, etc. It is optional to add 0 to 300 parts by weight of pullulan or the like based on 100 parts by weight of the perfluoro compound.

The antireflective coating material of the present invention may contain a surfactant which is commonly used to improve coating properties. In addition, the addition amount can be made a normal amount within a range not to impair the effects of the present invention.

Here, examples of the surfactant include perfluoroalkyl polyoxyethylene ethanol, fluorinated alkyl ester, perfluoroalkylamine oxide, and fluorine-containing organosiloxane compound. For example, Florad “FC-430”, “FC-43”
1 "(all manufactured by Sumitomo 3M Limited), Surflon" S-141 "," S-145 "," S-381 ",
"S-383" (all manufactured by Asahi Glass Co., Ltd.), Unidyne "DS-401", "DS-403", "DS-45"
1 "(all manufactured by Daikin Industries, Ltd.), MegaFac" F-8151 "," F-171 "," F-172 ",
"F-173", "F-177" (all manufactured by Dainippon Ink Industries, Ltd.), "X-70-092", "X-70"
-093 "(all manufactured by Shin-Etsu Chemical Co., Ltd.) and the like. Preferably, Florad “FC-43
0 "(manufactured by Sumitomo 3M Limited)," X-70-09 "
3 "(manufactured by Shin-Etsu Chemical Co., Ltd.).

The water-soluble antireflection coating material is liable to generate bubbles, and it is said that microbubbles in the order of microns called microbubbles generate pattern defects. In order to reduce microbubbles, a method of adding an antifoaming agent is generally used. As antifoaming agents for aqueous solutions, natural oils and fats such as soybean oil, corn oil, olive oil, linseed oil, castor oil, lard oil, long-chain alcohols such as amyl alcohol and octyl alcohol, and silicone resins are common. These are materials which have low or no hydration properties. Although the above-mentioned material has excellent defoaming properties, when it is added to a water-soluble material to form a film by spin coating, coating unevenness occurs and a uniform film cannot be formed. In order to form a uniform film by spin coating, an antifoaming agent having high hydration property is required. In the present invention, methanol,
Alcohols such as ethanol, isopropyl alcohol, n-butyl alcohol, n-hexyl alcohol and ethylene glycol, or the following general formulas (17) and (1)
The acetylene-based antifoaming agent represented by 8) can be used in an effective amount.

[0032]

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Here, R ¹ , R ² , R ³ , R ⁴ , R ⁷ , and R ⁸ are the same or different hydrogen atoms or C 1 -C 2, respectively.
An alkyl group of 0, R ⁵ , R ⁶ , and R ¹⁰ are an alkylene group having 1 to ¹⁰ carbon atoms, and x, y, and z are integers of 0 to 20.

In order to form a resist pattern using the anti-reflection coating material of the present invention, a known method can be employed, for example, by a lithography process shown in FIG. First, a photoresist layer 2 is formed on the upper layer of the substrate 1 by a method such as spin coating (A), and in some cases, prebaking is performed, and the anti-reflection coating material of the present invention is spin-coated on the photoresist layer 2. The anti-reflection layer 3 is formed by applying such a method as described above and, if necessary, further performing prebaking (B). The light reflection preventing layer 3 has a wavelength of 180
Exposure of ultraviolet rays 4 of up to 500 nm in a pattern shape by a reduced projection exposure method, that is, exposure of the portion A in FIG. 1C, removal of the antireflection layer 3 and development of the resist using a developing solution. A pattern 5 can be formed (D). After exposure, post-exposure bake (PEB) may be performed in some cases, but if the resist layer is a chemically amplified resist layer, a PEB step is essential. In this case, after removing the light reflection preventing layer, PEB
After PEB, the anti-reflection layer may be removed.

Note that pure water can be used as a diluent for the anti-reflection coating material. Further, the removal of the anti-reflection layer can be carried out by using a normal photoresist developing unit, which can be rinsed with pure water, and can be peeled off simultaneously with development if it is peeled off after PEB.

Here, the light reducing effect of the anti-reflection film of the present invention will be described with reference to FIGS. 2 and 3. As shown in FIG. I ₀ is the air - resist interface at occur considerable reflection Ir _1, with the amount of incident light is lost, light resist layer containing the resist layer 2 - reflected Ir ₂ on the base surface, the reflected light Ir ₂ resist layer - for repeated that again reflected Ir ₃ at the air interface, the light multiple reflection interference occurs in the resist layer.

On the other hand, as shown in FIG. 3, by forming the anti-reflection film 3 of the present invention on the resist layer 2, the reflection I of the incident light I _{0 at} the air-light anti-reflection film interface is improved.
r ₄ , the reflection Ir ₅ at the interface between the antireflection film and the resist layer can be reduced, so that the loss of the incident light amount is reduced, and Ir ₆ and I
Since the film thickness of the anti-reflection coating layer 3 is set so that r ₇ has the opposite phase of light, they are weakened to each other, and optical multiplex interference in the resist layer 2 is suppressed.

From the principle of anti-reflection, assuming that the refractive index of the resist to the exposure light is n and the wavelength of the exposure light is λ, the refractive index n ′ of the anti-reflection film is Δn, and the film thickness is λ / 4n ′. As the number approaches an odd number, the reflectance decreases, and the effect of the standing wave can be reduced.

[0039]

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

Examples and Comparative Examples F1 to F shown below
6, F9-F14 fluorine compound 1 g, molecular weight 80,0
0.7 g of polyvinyl alcohol having a saponification degree of 60% was sufficiently dissolved in 40 g of pure water, and filtered with a filter having a size of 0.1 μm to prepare an antireflection film solution. The following F
1 g of a fluoropolymer compound of 7, F8, F15, F16, and F17 was sufficiently dissolved in 40 g of pure water, and filtered with a filter having a size of 0.1 μm to prepare an antireflection coating solution. As a comparative example, 1 g of a fluorine compound of F18 to F23 shown below, 0.7 g of polyvinyl alcohol having a molecular weight of 80,000 and a saponification degree of 60% were sufficiently dissolved in 40 g of pure water,
The solution was filtered through a filter having a size of μm to prepare an antireflection film solution. Further, 1 g of a fluoropolymer compound represented by the following F24 and F25 was sufficiently dissolved in 40 g of pure water, and 0.1 μm
The solution was filtered through a filter having a size to prepare an antireflection coating solution.

Next, Sample 1 was dispensed on an 8-inch wafer, and a silicon wafer or a synthetic quartz wafer was rotated at 300 rpm for 3 seconds and then at 4,000 rpm for 20 seconds to form an antireflection film having a thickness of 46 nm. The film thickness and the refractive index were measured by spectroscopic ellipsometry, and the transmittance was measured by a spectrophotometer. The results are shown in Tables 1 and 2.
From these results, it was confirmed that the antireflection coating material of the present invention has a high transmittance and a low refractive index not only in KrF but also in ArF.

[0042]

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[0043]

Embedded image

[0044]

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[0045]

[Table 1]

[0046]

[Table 2]

Then, a photoresist SEPR401 for KrF lithography (Shin-Etsu Chemical Co., Ltd., film transmittance 30% / μm) was spin-coated on an 8-inch Si substrate while changing the rotation speed, and the temperature was 100 ° C. Prebaking was performed under the condition of a time of 90 seconds. An anti-reflective coating solution using F16 was dispensed thereon, and the wafer was first rotated at 300 rpm for 3 seconds and then at 4,000 rpm for 20 seconds to form an anti-reflective coating.

A pattern having a line and space width of 0.20 μm each was exposed with a KrF excimer laser stepper, and then post-exposure baked at a temperature of 110 ° C. for a time of 90 seconds to obtain a tetramethylammonium hydroxide 2.38. 23% by weight in developer
Static paddle development was performed at 60 ° C. for 60 seconds, and pure water rinsing was performed. FIG. 4 shows the results. From the results of FIG. 4, it was confirmed that the use of the antireflection coating material of the present invention can suppress the amplitude of the line width due to the standing wave.

[0049]

The anti-reflection coating material of the present invention is fine, has high dimensional accuracy and alignment accuracy, and can form a resist pattern with good reproducibility.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a lithography process using an anti-reflection film.

FIG. 2 is an explanatory diagram of a reflection state of incident light when a light reflection preventing film is not used.

FIG. 3 is an explanatory diagram of a reflection state of incident light when an anti-reflection film is used.

FIG. 4 is a graph showing a relationship between a resist layer thickness and a resist line width when an anti-reflection film is used and when it is not used.

[Explanation of symbols]

 Reference Signs List 1 base 2 photoresist layer 3 antireflection layer 4 ultraviolet ray 5 resist pattern

Claims (4)

[Claims] 1. A water-soluble anti-reflective coating material characterized in that a part or all of the hydrogen atoms of the hydrocarbon group contain an alkylamine or an alkanolamine substituted with fluorine. 2. A water-soluble anti-reflective coating material comprising, as a main component, a perfluoro compound containing the fluorine-substituted alkylamine or alkanolamine according to claim 1 as a counter cation. 3. The perfluoro compound represented by the following general formula (1)
3. The water-soluble anti-reflective coating material according to claim 2, wherein the material is selected from the following. Embedded image Embedded image (Where a and b are integers from 0 to 20, c, d, e, f,
g, h, i, j, k, l, m, and n are integers from 0 to 15,
o and t are 0 to 100, p and u are 1 to 100, q, r, s
Represents an integer of 0 to 15, and M represents an alkylamine or alkanolamine in which part or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are substituted with fluorine. ) 4. An anti-reflection layer comprising the anti-reflection film material according to claim 1, as an upper layer of the photoresist layer, and after exposing the resist layer via the anti-reflection layer. A method of forming a pattern, comprising removing the anti-reflection layer.