JP3290793B2 - Photosensitive composition and pattern forming method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive composition applicable to a photoresist or the like.

[0002]

2. Description of the Related Art Microfabrication technology by photolithography is employed in the manufacture of semiconductor devices such as LSIs.
This technique is specifically performed according to the following process. That is, first, a photoresist film is formed on a substrate such as a silicon single crystal wafer by, for example, a spin coating method. Next, after exposing the resist film, processing such as development and rinsing is performed to form a resist pattern. Subsequently, by exposing the exposed wafer surface using the resist pattern as an etching resistant mask, fine lines and windows are opened to form a desired pattern.

In an LSI manufacturing process, a processing technology capable of forming a finer pattern is required for a lithography technology in accordance with a high integration of the LSI. In response to such demands, attempts have been made to shorten the wavelength of an exposure light source. As a specific measure, a lithography technique using a deep UV as a light source such as a KrF excimer laser (wavelength: 248 nm) and an ArF excimer laser (wavelength: 193 nm) is being studied.

However, in the conventional resist material,
Because the absorption of deep UV is excessively large, at the time of exposure, a portion separated from the surface of the resist film (for example,
UV light cannot sufficiently reach the interface region of the resist film in contact with the substrate. As a result, in the exposed portion of the resist film, the chemical change due to the exposure does not sufficiently occur over the entire film thickness, and the solubility in the developing solution in the film thickness direction becomes non-uniform. In particular, the solubility at the portion away from the surface of the resist film as described above is not sufficient, and the cross-sectional shape of the developed resist pattern becomes triangular. Therefore, when the obtained resist pattern is used as an etching resistant mask, a target fine pattern cannot be transferred to a substrate or the like, which has been a problem.

As a resist material which solves such a problem, a resist called a chemically amplified type has been proposed. A chemically amplified resist is a photosensitive compound containing a compound that generates a strong acid when irradiated with light, that is, an acid generator and a compound in which a hydrophobic group is decomposed into a hydrophilic substance by the generated acid. A composition. Specifically, H. It
o, C, G, Wilson, J .; M. J. Franch
et. U.S. Pat. No. 4,491,628 (1985).
Discloses a positive resist containing a polymer obtained by blocking a hydroxyl group of poly (p-hydroxystyrene) with a butoxycarbonyl group, and an onium salt as an acid generator. Also, M. J. O'Brien, J, V. Cr
ivello, SPIE Vol, 920, Advan
ces inResist Technology a
nd Processing, p42, (1988), m-cresol novolak resin and naphthalene-2-
A positive resist containing carboxylic acid-tert-butyl ester and a triphenylsulfonium salt as an acid generator is disclosed. Further, H. Ito, SPIE Vo
1,920, Advances in Resist
Technology and Processing,
p33, (1988) includes 2,2-bis (4-ter
A positive resist containing (t-butoxycarbonyloxyphenyl) propane or a polyphthalaldehyde salt and an onium salt as an acid generator is disclosed.

In these chemically amplified resists, the acid generated from the acid generator functions as a catalyst, and causes a chemical change inside the resist efficiently even in a trace amount. As a result, when the resist film is exposed, the reaction sufficiently proceeds even in the film where radiation hardly reaches compared to the film surface, and the cross-sectional shape of the formed resist pattern is being improved. However, in the above-mentioned resist, when the content of the dissolution inhibiting group is increased in order to enhance the resolution, the compatibility with the resin or the resin having the dissolution inhibiting group becomes poor, and phase separation occurs. This phase separation causes irregularities on the surface and side surfaces of the pattern after the development processing, and as a result, a high-resolution pattern cannot be formed.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a high sensitivity and a high resolution to a short wavelength light source. An object is to provide a photosensitive composition that can be obtained stably.

[0008]

In order to solve the above-mentioned problems, the present invention relates to a compound which is decomposed by an acid and becomes soluble in an alkaline solution (a dissolution inhibitor), and a compound which generates an acid upon irradiation with light. (Acid generator), wherein the compound which is decomposed by the acid and becomes soluble in an alkali solution includes: a) a component having a small molecular polarity and a low alkali dissolution rate; A component having a large polarity of the molecule and a high alkali dissolution rate, and a component having a small polarity of the molecule and a low alkali dissolution rate account for 20% of the alkali-soluble group.
The above is a polymer compound protected by an acid-decomposable group and having a weight average molecular weight of 5,000 or more, and the component having a large polarity and a high alkali dissolution rate of the molecule is 2% to 20% of the alkali-soluble group. below is protected by the group decomposable by an acid, Ri compound der weight average molecular weight of less than 10,000, the polarity is small alkali dissolution rate of the molecule slow
When the molecular weight of the component is large,
A photosensitive composition characterized by having a higher dissolution rate than the molecular weight of the component .

[0009]

[0010]

[0011]

[0012]

The present invention also includes a compound which is decomposed by an acid and becomes soluble in an alkaline solution, and a compound which generates an acid by irradiation with light, and which is decomposed by the acid and becomes soluble in an alkaline solution. The compound comprises a component having a small molecule polarity and a low alkali dissolution rate, and a component having a large molecule polarity and a high alkali dissolution rate. Is a polymer compound having a weight average molecular weight of 5,000 or more, which is protected by an acid-decomposable group, and a component having a large polarity and a high alkali dissolution rate of the molecule is 2% of the alkali-soluble group. or more but less than 20% is protected by a group decomposable by an acid, I compound der weight average molecular weight of less than 10,000, the polarity is small alkali soluble in the molecule
The molecular weight of a component having a slow solution rate has a large polarity of the molecule.
A step of forming a layer of a photosensitive composition having a higher alkali dissolution rate than the molecular weight of the component on a substrate, a step of pattern-exposing the layer of the photosensitive composition to a predetermined shape, and a step of exposing the photosensitive composition to light. The present invention provides a pattern forming method comprising a step of baking a layer of a product and a step of developing the layer of the photosensitive composition after the baking with an alkaline solution.

Hereinafter, the present invention will be described in detail.

[0015] The dissolution inhibiting group for protecting an alkali-soluble group, tert- butyl esters of carboxylic acids as disclosed in JP fairness 2-27660, tert-
Protecting group, cyclohexyl as disclosed in JP-A-63-139 343 Patent, sec- butyl group, secondary protecting group having carbon atoms such as isopropyl group having a tertiary carbon such as butyl carbonate, It is incompatible with acids such as a trialkyl group and a phenylsilyl group as disclosed in JP-A-60-52845, a tetrahydropyranyl group and a methylmethoxy group as disclosed in JP-A-2-19847. And stable protecting groups.

As the alkali-soluble compound, a resin containing an aryl group or a carboxy group into which a hydroxy group has been introduced is desirable. Specifically, any copolymer such as phenol novolak resin, cresol novolak resin, xylenol novolak resin, vinylphenol resin, isopropenylphenol resin, vinylphenol and acrylic acid, methacrylic acid derivative, acrylonitrile, styrene derivative; and isopropenylphenol Copolymers of acrylic acid, methacrylic acid derivatives, acrylonitrile, styrene derivatives, etc .; copolymers of styrene derivatives with acrylic resins, methacrylic resins, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, acrylonitrile, etc .; or these And a compound containing silicon in the polymer. However, from the viewpoint of resistance during dry etching, a resin containing an aromatic ring is preferable, and examples thereof include a phenol novolak resin and a cresol novolak resin.

Further, polyhydric phenol compounds, polyhydric carboxylic acid compounds and the like may be used.

As the compound (acid generator) which generates an acid upon irradiation with light, which corresponds to the photosensitizer in the photosensitive composition of the present invention, various known compounds and mixtures thereof can be used. it can. For example, CF ₃ S
O ₃ ⁻ , p-CH ₃ PhSO ₃ ⁻ , p-NO ₂ PhSO
₃ ^- diazonium salts such as a counter anion, phosphonium salts, sulfonium salts and iodonium salts, organic halogen compounds, such as o-quinonediazide sulfonic acid ester may be used. Further, an organic halogen compound known as a photoinitiator that forms a free radical is also a compound that forms a hydrohalic acid, and can be used as a compound that generates an acid upon irradiation with light in the present invention.

Specific examples of the acid generator include di (p-tert-butylphenyl) iodonium trifluoromethanesulfonate, benzoin tosylate, orthonitrobenzenep-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate, and tri (tert-butylphenyl) sulfonium. Trifluoromethanesulfonate, benzenediazonium paratoluenesulfonate, tris-dibromomethyl-s-triazine, o-naphthoquinonediazide-4-sulfonic acid ester and the like.

The amount of the acid generator in the photosensitive composition of the present invention is preferably in the range of about 0.01 to about 20% by weight based on the total weight of the solid content of the photosensitive composition. More preferably, it is in the range of 0.1 to 10% by weight.
When the amount is less than 0.01% by weight, the effect of adding the compound is not obtained. On the other hand, when the amount exceeds 10% by weight, there is a possibility that the coating properties may be deteriorated during film formation.

A) used in the photosensitive composition of the present invention;
A component having a low molecular dissolution rate and a low alkali dissolution rate and b) a component having a high molecular polarity and a high alkali dissolution rate are mixed so that either component is present in at least 1% by weight.

In the photosensitive composition of the present invention, if necessary, for example, a surfactant such as a surfactant as a coating film modifier, or a base such as an amine as an acid trapping agent for suppressing acid diffusion. An alkali-soluble compound such as a carboxylic acid or a phenol as a dissolution rate regulator, or a dye as an antireflection film may be blended.

Next, the polarity of the molecule as the component a is small,
The component having a low alkali dissolution rate and the component having a large polarity of the molecule b and having a high alkali dissolution rate will be described in detail.

The polarity of the molecule is related to the degree of protection of the alkali-soluble group by the dissolution inhibiting group. The higher the degree of protection, the lower the polarity. Further, the dissolution rate with respect to the alkali decreases as the molecular weight increases, and increases as the molecular weight decreases. For example, the polarity of a high molecular weight compound in which an alkali-soluble group is protected by a dissolution inhibiting group decreases as the protection rate increases, and increases as the protection rate decreases.

Furthermore, the alkali dissolution rate also depends on the alkali-soluble group to be protected. For example, the dissolution rate of a compound in which a carboxyl group is protected by a dissolution inhibiting group is faster than that of a compound in which a phenol group is protected.

These factors that give a relative difference between the polarity of the molecule and the alkali dissolution rate are arbitrarily selected to obtain a component having a small polarity and a low alkali dissolution rate and a component having a large polarity and a high alkali dissolution rate. . The photosensitive composition of the present invention is prepared using these two types having incompatible properties.

In the first embodiment, as the component a, a compound having a weight average molecular weight of 5,000 or more and protected with an alkali-soluble group of 20 mol% or more is used. Less than 10,000,
A compound having a protection rate of an alkali-soluble group of less than 20 mol% is used.

If the protection ratio of the alkali-soluble group by the dissolution inhibiting group is lower than 20%, the dissolution rate ratio between the exposed and unexposed portions cannot be maintained, resulting in poor resolution. Therefore, the protection rate of the dissolution inhibiting group in the high molecular weight component is desirably 20% or more, and the protection rate in the low molecular weight component is 20% or more.
% Is desirable.

Examples of the compound having a weight average molecular weight of less than 10,000 include polyhydric phenol compounds and polycarboxylic acid compounds among the alkali-soluble compounds described above. 000
The above is a polymer compound.

The protection ratio of the alkali-soluble group by the dissolution inhibiting group in each component can be set to a predetermined value in the production process.

In the second embodiment, a compound having a substituent having a phenol group protected by a dissolution inhibiting group is used as the component a, and a compound having a carboxyl group protected by a dissolution inhibiting group is used as the component b. Use compounds.

As the phenol compound, a resin having a phenol group or a low molecular compound is used. Specifically, phenol novolak resin; cresol novolac resin; xylenol novolak resin, vinyl phenol resin; isopropenylphenol resin, vinyl phenol and acrylonitrile, styrene derivatives, A click Li <br/> Le esters, methacrylic acid esters and Copolymers of isopropenylphenol and acrylonitrile, styrene derivatives, acrylates, methacrylates and the like. As the low-molecular-weight phenol compound, a substituted or unsubstituted phenol or a polyhydric phenol compound is used.
Examples include phenol, t-butylphenol, amylphenol, xylenol, isopropylphenol, bisphenol A, bisphenol S, bisphenol F, triphenol derivatives, and condensates of triphenol derivatives and phenol compounds.

As the carboxylic acid compound, a resin having a carboxyl group or a low molecular weight compound is used. Specifically, a resin composed of acrylic acid or a derivative thereof; a resin composed of methacrylic acid or a derivative thereof; acrylic acid and acrylonitrile, a styrene derivative,
Copolymers of vinyl or substituted vinyl group-containing monomers such as acrylates and methacrylates; copolymers of methacrylic acid with vinyl- or substituted vinyl-group-containing monomers such as acrylonitrile, styrene derivatives, acrylates and methacrylates Copolymer; maleic acid polymer; a copolymer of maleic acid with a monomer containing a vinyl group or a substituted vinyl group such as a styrene derivative, methyl vinyl ether or acrylonitrile. Examples of the low molecular weight compound include a phenyl group-containing compound such as substituted or unsubstituted benzoic acid, and a carboxylic acid composed of an alkyl derivative such as malic acid or hexane.

In the following third and fourth embodiments, the photosensitive composition of the present invention is produced using a compound prepared by combining factors that determine the polarity of the molecule and the alkali dissolution rate.

In the third embodiment, the polyhydric phenol compound shown in Chemical formula 1 is used as the component b having a large polarity, and an alkali-soluble polymer is used as the component a. The alkali-soluble polymer may be used as a polymer dissolution inhibitor in which the alkali-soluble group is protected by a dissolution inhibiting group.

In the polyhydric phenol compound, the protection ratio of the alkali-soluble group in the first embodiment is less than 20%,
It corresponds to a compound having a weight average molecular weight of less than 10,000. The triphenol compound represented by the following general formula (II) is methylolated with formalin in an alkaline solution, and further represented by the following general formula (III). Can be easily synthesized by condensing with a phenol compound.

[0037]

Embedded image Examples of the phenol compound represented by the general formula (III) include, for example, phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol , M-propylphenol, p-propylphenol, o-iso-propylphenol, m-is
o-propylphenol, p-iso-propylphenol, on-butylphenol, mn-butylphenol, pn-butylphenol, o-iso-butylphenol, m-iso-butylphenol, pi
so-butylphenol, ot-butylphenol,
mt-butylphenol, pt-butylphenol, o-amylphenol, m-amylphenol, p
-Amylphenol, o-iso-amylphenol,
m-iso-amylphenol, p-iso-amylphenol, o-cyclohexylphenol, m-cyclohexylphenol, p-cyclohexylphenol,
2,3-xylenol, 2,4-xylenol, 2,5
-Xylenol, 2,6-xylenol, 2,3-di-
Isopropylphenol, 2,4-di-isopropylphenol, 2,5-di-isopropylphenol, 2,
6-di-isopropylphenol, 2,3-di-t-butylphenol, 2,4-di-t-butylphenol,
2,5-di-t-butylphenol, 2,6-di-t-
Butylphenol and the like can be mentioned.

Examples of the dissolution inhibiting group that can be used include, for example,
t-butoxycarbonyl group, tetrahydropyranyl group,
and a t-butoxycarbonylmethyl group.

Examples of the alkali-soluble polymer include poly (p-hydroxystyrene), a copolymer of m-isopropenylphenol and acrylonitrile,
A copolymer of isopropenylphenol and methyl methacrylate, a copolymer of p-hydroxystyrene and styrene, a copolymer of p-isopropenylphenol and styrene, and a copolymer of m-isopropenylphenol and styrene And a copolymer of m-hydroxystyrene and styrene, a copolymer of t-butyl methacrylate and methyl methacrylate, and the like. These polymers are
They may be used alone or in the form of a mixture.

The degree of protection of the dissolution inhibiting group in the polymer dissolution inhibitor is from 5 to 100%, preferably from 10 to 50%.
Range. If the protection ratio is less than 5%, a sufficient alkali dissolution inhibiting effect cannot be given to the alkali-soluble polymer. Incidentally, depending on the type of the dissolution inhibiting group, development with an aqueous alkaline solution may not be possible at a high protection rate.

In the fourth embodiment, as the component a having a small polarity, a compound obtained by protecting the hydroxyl group in the phenol skeleton of the polyhydric phenol represented by the general formula (I) shown in Chemical Formula 1 with a dissolution inhibiting group. And a photosensitive composition is prepared using an alkali-soluble polymer as the component b.

The dissolution rate of the polyphenol compound represented by the general formula (I) is lower than the dissolution rate of the alkali-soluble polymer.

As the dissolution inhibiting group that can be used here, the same dissolution inhibiting groups that protect the alkali-soluble group of the alkali-soluble compounds described above can be used. The average protection ratio of these dissolution inhibiting groups to the polyhydric phenol compound is 5 to 100%, preferably 10 to 100%. If the introduction ratio is less than 5%, a sufficient alkali dissolution inhibiting effect cannot be given to the polyhydric phenol compound.

As the alkali-soluble polymer, those described above can be used.

In addition, together with these alkali-soluble polymers, a polymer dissolution inhibitor in which an alkali-soluble group is protected by a dissolution inhibiting group may be used in combination. Examples of dissolution inhibitors that can be used include the compounds described above.

The photosensitive composition of the present invention can be suitably used particularly as a positive photoresist due to the function of the acid generator. That is, in the photosensitive composition of the present invention, the acid-labile dissolution inhibiting group acts as a hydrophobic protective group in an unexposed state as described above, so that the solubility in alkali is suppressed. On the other hand, at the time of exposure, an acid is generated from the acid generator by the light irradiation in the exposed portion, and this acid decomposes the dissolution inhibiting group that has blocked the alkali-soluble group of the alkali-soluble compound. The dissolution inhibiting group changes from a hydrophobic protecting group to a hydrophilic group such as a hydroxyl group or a carboxylic acid group. As a result, in the exposed region of the photosensitive composition, the solubility of the compound whose alkali solubility has been suppressed in an alkali developer increases. Thereafter, the photosensitive composition is subjected to development processing with an alkaline developer having an appropriate concentration, whereby only the exposed area of the photosensitive composition can be dissolved and removed, and a positive resist pattern is formed. Is done.

In the photosensitive composition of the present invention,
When an appropriate organic developer is used in the development step after exposure, the hydrophobic unexposed area dissolves, so that a negative pattern can be formed.

Next, a more specific pattern forming process when the photosensitive composition of the present invention is used as a photoresist will be described.

First, the photosensitive composition of the present invention is dissolved in an organic solvent, and this solution is applied on a substrate by spin coating or dipping, and then heated and dried at 60 ° C. to 140 ° C. to form a resist film. I do. If the temperature is lower than 60 ° C., drying of the resist film becomes insufficient. On the other hand, if the temperature exceeds 140 ° C., the performance of the resist may be deteriorated due to denaturation of each component in the composition.

As the substrate, for example, a silicon wafer, a silicon wafer having steps on the surface on which various insulating films, electrodes, wirings, etc. are formed, a blank mask, or the like can be used. Examples of the organic solvent for dissolving the photosensitive composition include ketone solvents such as cyclohexanone, acetone, methyl ethyl ketone and methyl isobutyl ketone, and cellosolve solvents such as methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate and butyl cellosolve acetate. , Ethyl acetate, butyl acetate, isoamyl acetate and the like. These organic solvents can be used alone or in the form of a mixture.

Next, pattern exposure is performed on the resist film. At this time, acid is generated in the exposed portion of the resist film. The light source for the exposure here is, for example, i of a mercury lamp.
For example, ultraviolet rays, X-rays, electron beams, or ion beams such as a line, an h-line, a g-line, a xenon lamp, a KrF excimer laser, and an ArF excimer laser can be used. As a specific method of pattern exposure, when using ultraviolet rays and X-rays,
The resist film is selectively exposed through a predetermined pattern mask. On the other hand, when an electron beam, an ion beam, or the like is used, pattern exposure can be performed directly on the resist film by scanning these radiations without using a mask.

Subsequently, the resist film after pattern exposure is heat-treated (baked). The treatment conditions vary depending on the type of the acid generator, but may be, for example, 30 seconds to 600 seconds within a range of 40 ° C. or more and 140 ° C. or less.
By such baking, in the exposed part of the resist film,
The acid diffuses and reacts with compounds having substituents that are labile to the acid. In this compound, the substituent is decomposed to change to an alkali-soluble compound. When the baking temperature is 4
When the temperature is lower than 0 ° C., the decomposition reaction of the dissolution inhibiting group by the generated acid does not sufficiently proceed in the exposed portion of the resist film. On the other hand, when the temperature exceeds 140 ° C., thermal decomposition proceeds in unexposed portions of the resist film, and the contrast of the finally formed resist pattern may be reduced.

Next, the resist film after baking is developed using an alkaline solution to selectively dissolve and remove exposed portions of the resist having a bad shape, thereby obtaining a desired pattern. Here, as the alkaline solution used as the developing solution, any alkaline solution may be used as long as the exposed portion of the resist film is rapidly dissolved and the dissolution rate with respect to other exposed portions is extremely low. Specific examples include a tetramethylammonium-based aqueous solution such as a tetramethylammonium hydroxide aqueous solution, and an inorganic alkali aqueous solution such as potassium hydroxide and sodium hydroxide. These alkaline aqueous solutions are usually used at a concentration of 15% by weight or less. As the developing means, for example, an immersion method, a spray method, or the like can be used.

The substrate and the resist film (resist pattern) after the development process are subjected to a rinsing process using water or the like, and further dried.

Using the resist pattern formed as described above as a mask, the substrate (wafer) is etched by a wet etching method, a dry etching method, or the like. When a fine pattern of 3 μm or less is formed, a dry etching method is preferable.

The wet etching agent can be appropriately selected according to the etching target. For example, when the etching target is a silicon oxide film, a phosphoric acid aqueous solution, an acetic acid aqueous solution, a nitric acid aqueous solution, or the like can be used. , An aqueous cerium ammonium nitrate solution can be used.

Examples of the dry etching gas include CF ₄ , C ₂ F ₆ , CCl ₄ , BCl ₃ , Cl ₂ , and the like.
HCl and the like, and these gases may be used in combination as needed.

The etching conditions are based on the combination of the type of the substrate on which the fine pattern is to be formed and the photosensitive composition, the concentration of the wet etching agent in the reaction tank, the concentration of the gas for dry etching, and the reaction temperature. , Reaction time and the like can be set, but the method is not particularly limited.

Further, after the etching, the resist pattern of the photosensitive composition remaining on the substrate, and the remaining flattening layer when the multilayer resist technique is adopted, are removed with, for example, a release agent (J-100). : Nagase Kasei Co., Ltd.), oxygen gas plasma or the like.

In addition to the above steps, other steps can be adopted as needed. For example, the adhesiveness between the resist film formed by the photosensitive composition of the present invention and the substrate, and the adhesiveness between the resist film and the planarizing layer when the multilayer resist technology is adopted, between the planarizing layer and the substrate, etc. Pretreatment is performed on each layer for the purpose of enhancement. In addition, baking may be performed before and after the development processing, and ultraviolet irradiation may be performed before dry etching.

[0061]

The photosensitive composition of the present invention comprises a compound which is decomposed by an acid and becomes soluble in an alkali solution, and a compound which generates an acid by irradiation with light. And two components: a component having a small molecular polarity and a low alkali dissolution rate; and a component having a large molecular polarity and a high alkali dissolution rate.

The present inventors have applied a solution containing a photosensitive composition on a substrate and dried the resist film. In the resist film, small-polarity components are concentrated near the surface of the resist layer, and the polarity is near the substrate. It has been found that there is a distribution in which large components are concentrated.

It was also found that the dissolution rate in the thickness direction of the photosensitive composition was made slower in the upper layer near the surface and faster in the lower layer, whereby the cross-sectional shape became vertical.

The polarity of the molecule is determined by the degree of protection of the alkali-soluble group with the dissolution inhibiting group, and the alkali dissolution rate is determined by the molecular weight. The type of the alkali-soluble group to be protected is also a factor that determines the rate of alkali dissolution.

Therefore, by combining these factors, the alkali dissolution rate of the low-polarity component existing on the surface is reduced, and the alkali dissolution rate of the high-polarity component existing in the lower layer is increased. That is, the dissolution rate of the resist film coated with the photosensitive composition of the present invention is relatively slow in the vicinity of the surface exposed to the alkaline solution for the longest time and relatively in the vicinity of the substrate exposed to the alkaline solution for the shortest time. Be faster. Therefore, when the photosensitive composition of the present invention is used, a fine pattern having a rectangular cross-sectional shape can be formed.

Next, the above mechanism will be described with reference to the drawings.

FIG. 1 is a process chart showing a method for forming a pattern using the photosensitive composition of the present invention.

FIG. 1A shows a state immediately after a resist film 6 containing a component 2 having a small polarity, a component 4 having a large polarity, a photosensitive agent 5 and a solvent 3 is applied onto the substrate 1. As shown in FIG. 1A, in a resist film immediately after application, a component 2 having a small polarity and a component 4 having a large polarity exist at random.

FIG. 1B shows a state in which the solvent 3 present in the resist film 6 is volatilized and the resist film is dried. At this time, a component 2 having a small polarity and a component 4 having a large polarity are shown. And a distribution occurs between That is, the component 2 having a small polarity is concentrated near the surface of the resist film, while the component 4 having a large polarity is concentrated near the substrate.

Next, as shown in FIG. 1C, the resist film 6 is irradiated with exposure light 8 through a mask 7 having a desired pattern, and then heat treatment is performed. By these treatments, an acid is generated in the exposed portion, and the acid decomposes the dissolution inhibiting group.

Finally, the resist film is developed with an alkaline aqueous solution to dissolve the exposed portions. As described above, in the photosensitive composition of the present invention, the dissolution rate of the upper layer of the resist film is low, and the dissolution rate of the lower layer is low. Therefore, the resist pattern 9 having a vertical shape can be formed with high resolution.

[0072]

The present invention will be described below in more detail with reference to examples. (Example 1) The hydroxyl group of polyparavinylphenol (weight average molecular weight: 35,000) was converted to tert-bromoacetic acid.
By reacting with butyl, a polymer in which 25% of the hydroxyl groups were t-butyl acetic acid was obtained, and was referred to as Compound A-1. Further, a polymer having a t-butoxycarbonylmethyl group introduced into 5 mol% of hydroxyl groups of polyparavinylphenol (weight average molecular weight: 7,000) was obtained.
6.

Compound A-1 and compound A-6 are a compound having a small polarity and a small dissolution rate and a compound having a large polarity and a large dissolution rate, respectively. In the present Example, the dissolution inhibitors I and II were used. Used.

23 g of the compound A-1 and compound A-6
2 g, 250 mg of acid generator triphenylsulfonium trifluoromethanesulfonate (B-2) and 100 mg of tri-n-butylamine (C-1) as an additive were dissolved in 75 g of methyl methoxypropionate (S-1). Was filtered using a 0.2 μm fluororesin membrane filter to prepare a solution containing the photosensitive composition of the present invention.

Next, the above solution was applied on a silicon wafer and dried at 100 ° C. for 1 minute on a hot plate.
A resist film having a thickness of 1.0 μm was formed. Subsequently, Kr is applied to the resist film through a mask having a predetermined pattern.
Exposure (50 mJ / cm ² ) was performed using a reduction projection exposure machine using F excimer laser light (248 nm). Further, the exposed resist film is placed on a hot plate at 90 ° C.
After baking for 3 minutes, it was immersed in a 2.38% aqueous solution of tetramethylammonium hydroxide for 1 minute,
It was developed and washed with water to obtain a resist pattern. Observation of the cross section of this pattern with a scanning electron microscope revealed that the line width was 0.25 μm and the resist side angle was 89.5 °.
A high-precision pattern having a rectangular cross section was formed. (Examples 3 to 6) A resist solution was prepared in accordance with the composition shown in Table 1 below, applied to a silicon wafer in the same manner as in Example 1, patterned, and then the cross section of the obtained pattern was observed. As shown in the table, a high-precision resist pattern having a rectangular cross section was formed.

[0076]

[Table 1]

[0077]

[0078]

The compounds used are shown below in Chemical Formulas 3 to 11.

[0080]

[0081]

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[0082]

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[0083]

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[0084]

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[0085]

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[0086]

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[0087]

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[0088]

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[0089]

Embedded image (Comparative Examples 1 and 2) As a dissolution inhibitor I and a dissolution inhibitor II, a compound having a small polarity and a high dissolution rate upon exposure and a compound having a large polarity and a low dissolution rate were used. The resist solution of Comparative Example 1 and the resist solution of Comparative Example 2 which contained a single dissolution inhibitor and no two dissolution inhibitors were prepared in accordance with the compositions shown in Table 3 below. The obtained resist solution was applied and patterned by the same method as in Example 1. As a result, only a pattern having poor resolution and a side angle was obtained.

[0090]

[Table 3]

[0091]

The compounds used were represented by the following chemical formulas (12) to (16).
Shown in

[0093]

[0094]

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[0095]

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[0096]

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[0097]

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[0098]

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[0099]

[0100]

Comparative Example 3 A resist solution having the same composition as described above was prepared except that the polyhydric phenol compound was not added. The resist solution was applied to a silicon wafer and patterned by the same method as described above . A cross section was observed. At the upper part of the pattern, the hardly-solubilized layer remained in the shape of an eave, and the cross section having a line width of 0.325 μm became a T-shaped resist pattern.

[0102]

The compounds used were represented by the following formulas (17) to (20).
Shown in

[0104]

[0105]

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[0106]

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[0107]

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[0108]

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[0109]

[0110]

[0111]

[0112]

As described in detail above, according to the present invention,
In particular, there is provided a photosensitive composition which has high sensitivity and high resolution with respect to a light source having a short wavelength and is capable of forming a fine resist pattern having a rectangular cross section. Such a photosensitive composition, and the formation of a pattern using the same, have a remarkable effect in the photolithography technology of a semiconductor device manufacturing process, and their industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for forming a pattern using the photosensitive composition of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... low-polarity component, 3 ... solvent, 4 ... high-polarity component 5 ... photosensitive agent, 6 ... resist film, 7 ... mask, 8 ... exposure light, 9 ... pattern.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Rio Hayashi 1 Toshiba-cho, Komukai, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center Co., Ltd. (72) Rumiko Hayase Tokorocho, Komukai-Toshiba-cho, Kawasaki-shi, Kanagawa No. 1 Toshiba Research and Development Center Co., Ltd. (72) Inventor Hirokazu Niki 1 Tokoba Toshiba Research and Development Center, Komukai Toshiba-cho, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-5-232704 (JP, A) JP-A-4-88348 (JP, A) JP-A-6-266108 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F ^7/ 00-7/42

Claims (2)

(57) [Claims] 1. A photosensitive composition comprising a compound which is decomposed by an acid and becomes soluble in an alkaline solution, and a compound which generates an acid by irradiation with light, wherein the photosensitive composition is decomposed by the acid to form an alkaline solution. The compound to be soluble includes a component having a low alkali dissolution rate with a small polarity of the molecule and a component having a high alkali dissolution rate with a large polarity of the molecule, and a component having a low alkali dissolution rate with a small polarity of the molecule. At least 20% of the alkali-soluble group is a polymer compound protected by an acid-decomposable group and has a weight average molecular weight of 5,000 or more. 20% or more and less than 2% is protected by a group decomposable by acid, weight average molecular weight 10,
Compound der less than 000 is, the polarity of the molecule is small A
The molecular weight of the component that has a slow rate of dissolving lukari depends on the polarity of the molecule.
Larger than the molecular weight of components with large alkali dissolution rate
The photosensitive composition characterized by decoction. 2. A compound that is decomposed by an acid and becomes soluble in an alkaline solution and a compound that generates an acid by irradiation with light, and the compound that is decomposed by the acid and becomes soluble in an alkaline solution is: A component having a small molecule polarity and a low alkali dissolution rate, and a component having a large molecule polarity and a high alkali dissolution rate. The component having a small molecule polarity and a low alkali dissolution rate is at least 20% of the alkali-soluble group. Is protected by an acid-decomposable group and has a weight average molecular weight of 5,
The high molecular weight compound having a molecular polarity of at least 2,000 and a high alkali dissolution rate is protected by a group in which 2 % to less than 20% of the alkali-soluble group is decomposed by an acid, and has a weight average molecular weight of 10,000. Tsu der compound of less than
Therefore, the molecular polarity is small and the alkali dissolution rate is low.
The molecular weight of the molecule is large because the polarity of the molecule is large and the alkali dissolution rate is high.
Forming a layer of a photosensitive composition larger than the molecular weight of the fast component on a substrate, pattern-exposing the layer of the photosensitive composition to a predetermined shape, and forming the layer of the photosensitive composition after the exposure. A pattern forming method, comprising: a step of baking a layer; and a step of developing the layer of the photosensitive composition after the baking with an alkaline solution.