JP2002278076A - Chemical amplification type resist pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical amplification type resist pattern forming method by which the deterioration of the sensitivity and resolution of a chemical amplification type resist film formed on a substrate with age is suppressed and a resist pattern having a rectangular section shape and excellent in dimensional faithfulness is formed. SOLUTION: In the method for forming a chemical amplification type resist pattern by photolithography, a chemical amplification type resist film is formed on a substrate, a coating comprising amorphous polyolefins and having a smaller thickness than the resist film is formed on the resist film and the formation of a latent image pattern, the removal of the coating and development are successively carried out to form the objective chemical amplification type resist pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a chemically amplified resist pattern. More specifically, the present invention relates to a method for forming a resist pattern suitably applied to the production of a photomask used particularly in the manufacture of a semiconductor device or the like, the method comprising storing a chemically amplified resist film formed on a substrate. The present invention relates to a method for efficiently forming a chemically amplified resist pattern having a rectangular cross-section and excellent dimensional fidelity while suppressing deterioration of sensitivity and resolution over time during and during transportation.

[0002]

2. Description of the Related Art In recent years, miniaturization of processing by photolithography has been used as a means for improving the degree of integration of semiconductor devices. The miniaturization by the photolithography is performed by, for example, using g-line to i-line, i-line to KrF excimer laser light, or KrF excimer laser light to ArF
Excimer laser light has been achieved by shortening the wavelength of the exposure light source. With the improvement of such fine processing by photolithography, fine workability is also required for a photomask used therein. As a resist for processing this photomask, P
BS resist [Chisso Corp., trade name], CMS resist [Tosoh Corp., trade name], electron beam resist ZEP series [Nihon Zeon Corp., trade name], etc. are used. With respect to the above, a chemically amplified resist having higher sensitivity and higher resolution is required. By the way, a large and square substrate is used for manufacturing a photomask. Unlike resist coating on circular substrates used to manufacture general semiconductor devices, coating resist on large, square substrates requires uniformity of film thickness up to the corners, Advanced technology is needed. Due to such a request, in manufacturing a photomask, a resist film forming process on a substrate and a pattern forming process may be performed by another company. In this case,
The resist flows in a state of a resist film applied to the substrate. However, the chemically amplified resist, which is being considered for application to next-generation masks, uses an acid-catalyzed reaction that occurs in the presence of a trace amount of acid.
It is known that the sensitivity and the resolution are significantly deteriorated with the passage of time due to environmental contaminants during storage and transportation of a resist film formed on a substrate.
That is, it is difficult to maintain a stable resist film until the pattern forming step.

[0003]

SUMMARY OF THE INVENTION Under such circumstances, the present invention is intended to reduce the sensitivity and resolution of a chemically amplified resist film formed on a substrate over time during storage and transportation. It is an object of the present invention to provide a method for efficiently forming a chemically amplified resist pattern having a rectangular cross section and excellent in dimensional fidelity.

[0004]

Means for Solving the Problems The present inventors have studied the formation of a film on a chemically amplified resist film in order to suppress the deterioration of sensitivity, resolution and the like with time of the resist film. In addition, it has been found that it is effective to provide a film made of amorphous polyolefins (JP-A-6-9553).
No. 97). In this publication, an amorphous polyolefin film is formed in order to solve the problem that the surface of the resist film is easily insolubilized due to contact of impurities such as amines in the atmosphere with the resist film and the surface of the resist film easily becomes overhanging. It has been proposed to provide a resist film. According to the pattern forming method described in the example of the publication, a film thicker than the resist film is provided. However, the present inventors, in such a thick film, when using a particle beam such as an electron beam, which is an energy source widely used in photomask production for pattern formation, due to particle scattering when passing through the film, It was confirmed that a good pattern shape could not be obtained and the resolution was low. Accordingly, the present inventors have further studied a film that effectively suppresses the deterioration of sensitivity and resolution over time of a chemically amplified resist film and gives a good resist pattern, and as a result, the thickness of the film is reduced. It has been found that by setting the thickness to not more than the thickness of the resist film, a good pattern can be obtained, and the deterioration of sensitivity and resolution when the resist film is left is suppressed. The present invention has been completed based on such findings. That is, the present invention comprises (1) (A) a step of forming a chemically amplified resist film on a substrate, and (B) an amorphous polyolefin which may be substituted with fluorine on the chemically amplified resist film. Forming a film, (C) irradiating ionizing radiation to a chemically amplified resist film having the surface provided with the film to perform selective exposure to form a latent image pattern,
(D) a step of removing the film made of the amorphous polyolefins which may be substituted with fluorine, and (E) developing a chemically amplified resist film having a latent image pattern,
A method of forming a resist pattern including a step of visualizing the latent image pattern, wherein a film made of an amorphous polyolefin that may be substituted with fluorine, which is formed on the resist film in the step (B), is formed. 2. The chemical amplification type resist pattern forming method according to claim 1, wherein the thickness is not more than the thickness of the resist film, and (2) the ion amplification radiation used in the step (C) is a particle beam. (3) a method for producing a photomask, comprising: a step of applying the method for forming a resist pattern according to (1) or (2); an etching step; and a resist pattern removing step. A) a chemically amplified resist film and an amorphous polyolefin which may be substituted by fluorine and has a thickness equal to or less than the thickness of the resist film provided thereon. Semiconductor device manufacturing substrate characterized by having a film, there is provided a.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for forming a chemically amplified resist pattern according to the present invention includes steps (A) to (E), and each step will be described below. Step (A) in the method of the present invention is a step of forming a chemically amplified resist film on a substrate. In the step (A), as the chemically amplified resist composition used for forming the resist film, either a positive type or a negative type can be used. There is no particular limitation on the chemically amplified positive resist composition, and conventionally known compositions such as a resin whose solubility in alkali changes by the action of an acid and a compound which generates an acid by irradiation with ionizing radiation are essential components. As a resist composition. Further, the chemically amplified negative resist composition is not particularly limited, and conventionally known ones, for example, an alkali-soluble resin, an acid-crosslinkable substance,
A resist composition containing, as an essential component, a compound capable of generating an acid upon irradiation with ionizing radiation can be used. In the chemically amplified positive resist composition, the resin whose solubility in alkali is changed by the action of an acid has at least a part of a group imparting alkali solubility such as a phenolic hydroxyl group or a carboxyl group in the alkali-soluble resin. It is protected by an acid-dissociable substituent and has become hardly soluble in alkali. Examples of the alkali-soluble resin include novolak resins obtained by condensing phenols such as phenol, m-cresol, p-cresol, xylenol, and trimethylphenol with aldehydes such as formaldehyde in the presence of an acidic catalyst, and hydroxystyrene. Polyhydroxystyrene resins such as homopolymers of styrene or copolymers of hydroxystyrene with other styrene monomers, copolymers of hydroxystyrene with acrylic acid or methacrylic acid or derivatives thereof, acrylic acid or methacrylic acid And an alkali-soluble resin such as an acrylic acid or methacrylic acid-based resin which is a copolymer of and a derivative thereof.

As the alkali-soluble resin having a hydroxyl group protected by an acid-dissociable substituent, a hydroxy group in which a part of a hydroxyl group of an acidic group such as a hydroxyl group or a carboxyl group in the resin is protected by an acid-dissociable substituent. Styrene homopolymer or copolymer of the hydroxystyrene and other styrene monomers, copolymer of the hydroxystyrene and acrylic acid or methacrylic acid or a derivative thereof, or a part of the hydroxyl group in the carboxyl group And acrylic acid or methacrylic acid in which is protected by an acid-dissociable substituent and a derivative thereof, and a copolymer of hydroxystyrene or hydroxystyrene in which a part of a hydroxyl group is protected by an acid-dissociable substituent. On the other hand, as the acid dissociable substituent,
For example, alkoxycarbonyl groups such as tert-butoxycarbonyl group and tert-amyloxycarbonyl group, tertiary alkyl groups such as tert-butyl group, alkoxyalkyl groups such as ethoxyethyl group and methoxypropyl group, tetrahydropyranyl group, tetrahydrofuran An acetal group such as a benzyl group, a benzyl group, a trimethylsilyl group, a 2-propenyl group having two or more substituents,
A cycloalkyl group having a substituent at the 1-position such as -ethylcyclohexyl group. The protection ratio of hydroxyl groups by these acid-dissociable substituents is usually in the range of 1 to 60 mol%, preferably 5 to 50 mol% of the hydroxyl groups in the resin. On the other hand, the compound that generates an acid upon irradiation with ionizing radiation (hereinafter, referred to as an acid generator) is not particularly limited, and any compound can be selected from conventionally known compounds used as an acid generator of a chemically amplified resist. Can be used. Examples of such acid generators include bissulfonyldiazomethanes such as bis (p-toluenesulfonyl) diazomethane, p-toluenesulfonic acid 2
Nitrobenzyl derivatives such as -nitrobenzyl, sulfonic acid esters such as pyrogallol trimesylate,
Onium salts such as diphenyliodonium hexafluorophosphate, benzoin tosylate such as benzoin tosylate, 2- (4-methoxyphenyl)-
Examples thereof include halogen-containing triazine compounds such as 4,6- (bistrichloromethyl) -1,3,5-triazine, and cyano group-containing oxime sulfonate compounds such as α- (methylsulfonyloxyimino) -phenylacetonitrile.

One of these acid generators may be used alone, or two or more thereof may be used in combination.
The amount is 0.5 to 30 parts by weight based on 100 parts by weight of the resin whose solubility in alkali changes due to the action of the acid.
Parts by weight, preferably 1 to 10 parts by weight. When the amount is less than this range, image formation cannot be performed. When the amount is too large, a uniform solution is not obtained, and storage stability is reduced. Further, in the chemically amplified negative resist composition, as the alkali-soluble resin, for example, a phenol novolak type resin, a cresol novolak type resin, or a copolymer of polyhydroxystyrene and hydroxystyrene with a monomer copolymerizable therewith. Hydroxystyrene resins such as polymers can be mentioned. Examples of the hydroxystyrene resin include hydroxystyrene homopolymer, hydroxystyrene and acrylic acid derivative, acrylonitrile, methacrylic acid derivative, methacrylonitrile, styrene, α
-Methylstyrene, p-methylstyrene, o-methylstyrene, p-methoxystyrene, copolymers with styrene derivatives such as p-chlorostyrene, hydrogenated resins of hydroxystyrene homopolymer, and hydroxystyrene and the above acrylic acid derivatives , A methacrylic acid derivative, a hydrogenated resin of a copolymer with a styrene derivative, and the like. In addition, those obtained by protecting a part of hydroxyl groups of acidic groups such as hydroxyl group and carboxyl group in these resins with an acid dissociable substituent can also be suitably used. On the other hand, as the acid-crosslinkable substance, conventionally, as a crosslinking agent for a chemically amplified negative resist, an N-methylolated or alkoxymethylated melamine resin, an epoxy compound, a urea resin, or the like, which is commonly used, is used alone. , Or a mixture of two or more.

Examples of the acid generator include the same compounds as the compounds exemplified in the aforementioned chemically amplified positive resist composition. About the compounding ratio of each component, with respect to 100 parts by weight of the alkali-soluble resin, usually,
It is selected in the range of 3 to 70 parts by weight of the acid crosslinking substance and 0.5 to 20 parts by weight of the acid generator. When the amount of the acid crosslinkable substance is less than 3 parts by weight, a resist pattern is hardly formed, and when the amount exceeds 70 parts by weight, the developability is reduced. If the amount of the acid generator is less than 0.5 part by weight, the sensitivity is lowered,
If the amount exceeds 0 parts by weight, it is difficult to obtain a uniform resist, and the developability also decreases. These resist compositions are usually used in the form of a solution obtained by dissolving the above components in a solvent. Examples of the solvent include ketones such as acetone, methyl ethyl ketone, cyclohexanenone, methyl isoamyl ketone, and 2-heptanone; ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, and dipropylene. Glycol or dipropylene glycol monoacetate, or polyhydric alcohols such as monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and derivatives thereof; cyclic ethers such as dioxane; and methyl lactate , Ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxyprop Methyl phosphate, esters such as ethyl ethoxypropionate, N, N-dimethylformamide, N,
Amide-based solvents such as N-dimethylacetamide and N-methyl-2-pyrrolidone can be exemplified. These may be used alone or as a mixture of two or more.

The solution of the resist composition thus prepared may further contain, if desired, a miscible additive,
For example, additional resins, organic amines, organic carboxylic acids, and the like to improve the performance, sensitivity, and resolution of the resist film,
Further, commonly used substances such as a plasticizer, a stabilizer, a surfactant and an antioxidant can be contained. The substrate used in the step (A) is not particularly limited, and various substrates are used depending on the application. For example, a silicon wafer for a semiconductor device, a blank for a photomask, and the like can be given. The shape is not particularly limited, and may be any of a circular shape (for example, a silicon wafer) and a square shape (for example, a photomask blank). A solution of the above-described chemically amplified resist composition is applied to these substrates, and a heat treatment is performed to form a chemically amplified resist film. As a coating method, spin coating is generally preferably used. The heat treatment is performed to dry and remove the solvent. The heating temperature is usually about 60 to 160 ° C., and the heating time is about 1 to 30 minutes. The thickness of the resist film thus formed varies depending on the application, but is usually selected in the range of 10 to 1000 nm. In the case of manufacturing a photomask, the thickness is generally about 100 to 400 nm. The step (B) in the method of the present invention comprises, on the chemically amplified resist film thus formed on the substrate,
This is a step of forming a film made of an amorphous polyolefin that may be substituted by fluorine (hereinafter, may be simply referred to as an amorphous polyolefin).

The film is provided to block the atmosphere from the chemically amplified resist film and the atmosphere. (1) The film has high transparency with respect to the exposure wavelength and transmits a particle beam such as an electron beam. It has properties such as being excellent in film forming ability, (3) not transmitting impurities contained in the atmosphere, and (4) being chemically stable. Examples of the amorphous polyolefins include alkenes, cycloalkanes,
Alkadienes, olefins such as cycloalkadienes, and perfluoroalkenes, perfluorocycloalkenes, perfluoroalkadienes, homo- or copolymers of fluorinated olefins such as perfluorocycloalkadienes and These hydrogenated products: hydrogenated products of ring-opened polymers of cycloalkenes: addition polymers of cycloalkenes and alkenes: addition polymers of cycloalkenes and α-olefins: There is no particular limitation as long as it is a good polyolefin and is an amorphous substance. One of these amorphous polyolefins may be used alone, or two or more thereof may be used in combination. Coatings made of these amorphous polyolefins have excellent coatability and a water absorption of 0.01.
% By weight or less, and can be removed with a general-purpose solvent. The amorphous polyolefin is dissolved in an appropriate solvent to prepare a coating solution, and applied on a chemically amplified resist film by a spin coating method or the like, and then coated at 60 to 1
By heating and drying at a temperature of about 30 ° C., a desired film is formed. As the solvent, a solvent that does not dissolve or hardly dissolves the resist film is selected. For example, unsaturated hydrocarbons such as aliphatic hydrocarbons such as n-hexane, cyclohexane, n-heptane, methylcyclohexane, t-butylcyclohexane, n-octane, isooctane, n-decane, decalin and ligroin; α-pinene and limonene Examples include hydrogens, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, isopropylbenzene, and diethylbenzene, and halogenated aliphatic hydrocarbons such as carbon tetrachloride, chloroform, trichloroethane, perfluoropentane, and perfluorohexane. Can be Among them, in order to obtain good coating properties, the boiling point is 80 to 200 ° C, preferably 100 to 15 ° C.
It is desirable to select one at 0 ° C. These solvents are 1
The seeds may be used alone, or two or more kinds may be used in combination. Of course, ethers and esters can also be added to these solvents.

The thickness of the film thus formed is
In the present invention, it is necessary that the thickness be equal to or less than the thickness of the chemically amplified resist film on which this film is provided. When the thickness of this film exceeds the thickness of the resist film and is exposed by irradiating with a particle beam such as an electron beam, due to particle scattering at the time of passing through the film, a good pattern shape cannot be obtained and the resolution is also low. . The thickness of this film is preferably 90% or less of the resist film, particularly preferably 80% or less. On the other hand, if the thickness is too small, the effect of providing the coating may not be sufficiently exerted. Therefore, the thickness of this coating is preferably 0.05% or more of the thickness of the resist film, more preferably 0.5%.
It is at least 1%, particularly preferably at least 0.5%. The step (C) in the method of the present invention is a step of irradiating the chemically amplified resist film having the coating on the surface with ionizing radiation to perform selective exposure or drawing to form a latent image pattern.

The ionizing radiation used in this step includes, for example, ultraviolet rays, g-rays, i-rays, KrF excimer laser light, ArF excimer laser light, and particle beams such as electron beams. The method of the present invention shows a remarkable effect particularly when using a particle beam among these ionizing radiations. There is no particular limitation on the method of performing selective exposure by irradiating with ionizing radiation, and a conventionally known method can be used. For example, by a reduction projection exposure device, etc.
UV light, g-ray, i-ray, KrF excimer laser light, Ar
A method of irradiating an F excimer laser beam or the like through a desired mask pattern, a method of drawing with a particle beam such as an electron beam, or the like can be used. Thus, a latent image pattern is formed on the resist film. In the present invention, the step (C) may be performed immediately after the step (B) is performed, or may be performed after being left for an appropriate period as needed, for example, for about several months. . Step (D) in the method of the present invention is a step of removing the film made of amorphous polyolefins on the resist film on which the latent image pattern has been formed in this way. As a method for removing the film, a spin peeling method using a solvent can be used. At this time, as the solvent, the aforementioned (B)
In the description of preparing the coating liquid of the amorphous polyolefin in the process, the same solvents as those exemplified as the solvent can be exemplified. One kind of the peeling solvent may be used alone, or two or more kinds may be used in combination.

After removing the film in this manner, the resist film is usually cured at a temperature of about 60 to 130 ° C. for 1 to 30 minutes.
An operation of heating for about a minute is performed. The step (E) in the method of the present invention includes the step of developing the chemically amplified resist film having the latent image pattern after the step (D),
This is a step of visualizing the latent image pattern. The development processing method in this step is not particularly limited, and a conventionally known method can be used. For example, development processing is performed using an alkaline aqueous solution such as a 1 to 10% by weight aqueous solution of tetramethylammonium hydroxide. After the development processing, a rinsing processing using usually pure water or the like is performed.
In this manner, a resist pattern having a rectangular cross section and excellent dimensional fidelity can be obtained. In the present invention, the base film is further subjected to dry etching using a fluorine-based gas such as CF ₄ or a chlorine-based gas such as Cl ₂ / O ₂ or an aqueous solution of serine ammonium nitrate using the obtained resist pattern as a mask. After performing the used wet etching, a photomask is manufactured by removing the resist pattern using a resist remover. During the process, pellicle coating may be performed to prevent scratches on the photomask surface.

[0014]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 As a chemically amplified positive resist, 100 parts by weight of polyhydroxystyrene having a weight average molecular weight of 5,400 in which 25 mol% of hydroxyl groups were protected by a tert-butoxycarbonyl group, 5 parts by weight of triphenylsulfonium triflate, tributylamine A composition comprising 0.09 parts by weight and 1000 parts by weight of propylene glycol monomethyl ether acetate was used. The above chemically amplified positive resist was spin-coated on a disk-shaped silicon substrate having a diameter of 10 cm, and then heat-treated at 95 ° C. for 110 seconds to form a resist film having a thickness of 500 nm. Next, an amorphous polyolefin resin “ZEON” is formed on the resist film.
A 3 wt% xylene solution of "EX480" (trade name, manufactured by Zeon Corporation) was spin-coated, and then heated at 60 ° C. for 80 seconds to form a 400-nm thick film. One minute after the formation of the film, an L / S of 0.5 μm was applied thereto at a dose of 2.2 μC / cm ² using an electron beam lithography system [ELIONICS, trade name “ELS-3300”].
After drawing the pattern, spin peeling treatment was performed with xylene for 15 seconds to remove the polyolefin resin film, and further heat treatment was performed on a hot plate at 90 ° C. for 110 seconds.
Next, after developing with a 2.38% by weight aqueous solution of tetramethylammonium hydroxide for 90 seconds, rinsing with pure water for 10 seconds was performed.

When the cross-sectional shape of the thus obtained resist pattern was observed with a scanning electron microscope (SEM), it was found to be rectangular. Examples 2 to 5 Examples 1 to 5 were carried out in the same manner as in Example 1 except that the thickness of the film of the polyolefin resin and the standing time after the film formation were as shown in Table 1. The results are shown in Table 1.
When the film thickness ratio was 1 or less, it was confirmed that the cross-sectional shape of the resist pattern was kept rectangular. Comparative Example 1 The procedure of Example 1 was repeated, except that the thickness ratio of the film was changed to 1.6. The results are shown in Table 1.
When the film thickness ratio was set to 1.6, the effect (deterioration of shape) due to the scattering of electron beams in the film was observed.

[0016]

[Table 1]

[Note] 1) Film pressure ratio: (film thickness / resist film thickness) × 100 2) Leaving time: time from film formation to exposure.

[0018]

According to the method of the present invention, the deterioration of sensitivity, resolution and the like due to aging during storage and transportation of a chemically amplified resist film formed on a substrate is suppressed, and the cross-sectional shape is rectangular. In addition, a chemically amplified resist pattern having excellent dimensional fidelity can be efficiently formed. The method of the present invention is particularly suitably applied to the manufacture of a photomask used for manufacturing a semiconductor device or the like.

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Claims (4)

[Claims] (A) a step of forming a chemically amplified resist film on a substrate; and (B) a film made of an amorphous polyolefin which may be substituted with fluorine on the chemically amplified resist film. (C) a step of irradiating ionizing radiation to a chemically amplified resist film having a surface provided with the film to perform selective exposure to form a latent image pattern, and (D) a step of forming the latent image pattern which may be substituted with fluorine. A step of removing a film made of crystalline polyolefins, and (E) a step of developing a chemically amplified resist film having a latent image pattern to visualize the latent image pattern. The thickness of the film made of an amorphous polyolefin which may be substituted with fluorine, which is formed on the resist film in the step (B), is not more than the thickness of the resist film. Chemically amplified resist pattern formation method that. 2. The method for forming a chemically amplified resist pattern according to claim 1, wherein the ionizing radiation used in the step (C) is a particle beam. 3. A method of manufacturing a photomask, comprising: a step of performing the method of forming a resist pattern according to claim 1; an etching step; and a resist pattern stripping step. 4. A resist composition comprising a chemically amplified resist film and a film made of an amorphous polyolefin which may be substituted by fluorine and has a thickness equal to or less than the thickness of the resist film provided thereon. Substrate for manufacturing a semiconductor device.