JPH0627673A - Formation of pattern - Google Patents

Abstract

PURPOSE:To improve definition by decreasing defects of shapes, such as skirting and galling, of resist patterns. CONSTITUTION:A protective layer 12 which can suppress the diffusion of the contaminants from a substrate 11 is formed on this substrate and a resist layer 13 consisting of a chemical amplification type resist is formed on this protective layer 12. In succession, prescribed regions 14 of the resist layer 13 are selectively exposed and are further baked at a prescribed temp., by which a latent image 16 is formed. The resist layer 13 after the baking is subjected to development processing to selectively remove the exposed regions 14, by which the resist patterns 17 are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method.

[0002]

2. Description of the Related Art Various electronic parts such as semiconductor integrated circuits such as LSIs require ultrafine processing, and resists are widely used in the processing technology. In particular, ultrafine resist patterns are required in order to achieve high-density integration along with high-density electronic components.

Examples of resists used for such ultrafine processing include resists (chemically amplified resists) disclosed in, for example, JP-A-63-27829.
This resist is generally an alkali-soluble resin,
A composition containing a dissolution inhibitor and an acid generator. In such a composition, although the dissolution inhibitor suppresses the solubility of the alkali-soluble resin in the unexposed state, light (radiation),
The acid generator generates an acid by exposure to X-rays or high-energy electron beams, and the acid decomposes the dissolution inhibitor by baking. That is, this composition corresponds to a positive resist in which the exposed portion exhibits alkali solubility and dissolves in the developer.

Conventionally, the formation of a pattern by the above-mentioned positive resist has been performed according to the following process. That is, first, a resist is applied on a substrate, and the resist layer is subjected to pattern exposure, that is, a predetermined region of the resist layer is selectively exposed. Then, after the exposed resist layer is baked, it is treated with an alkali developing solution to dissolve and remove only the exposed region of the resist layer to form a desired pattern.

However, in the positive resist and the pattern forming process using the same as described above,
Depending on the type of substrate, the pattern formed has a hem, and its resolution is limited. Therefore, using this pattern as a mask, it is impossible to further process an ultrafine pattern. In particular, when processing a fine groove or a fine contact hole, the desired shape cannot be obtained due to the hem of the resist pattern.

FIG. 3 shows a cross-sectional shape of a pattern formed by a positive resist according to a conventional process. In the drawing, the resist pattern 32 formed on the substrate 31 has a skirt, and lines and spaces having a desired width are not clearly resolved.

Further, as a resist used for ultrafine processing, there is a composition containing an acid generator, a compound having a substituent crosslinkable by an acid, and an alkali-soluble resin if necessary. In this composition, an acid generator is generated by exposure to light (radiation), X-rays or high-energy electron beams, and the acid promotes crosslinking by baking. That is, this composition corresponds to a negative resist in which the alkali solubility of the exposed part is lowered and the part remains in the development process.

The pattern formation with such a negative type resist is also performed according to the same process as in the case of the positive type resist as described above, and finally only the exposed region of the resist layer is left with an alkaline developing solution, Form the desired pattern.

However, in this case, depending on the type of the substrate, the bottom of the pattern formed opposite to that of the positive resist is bitten, and the resolution is insufficient, resulting in an ultrafine pattern. Can not be processed.

FIG. 4 shows a sectional shape of a pattern formed by a negative resist according to a conventional process. In the figure, the bottom of the resist pattern 42 formed on the substrate 41 is bitten, and lines and spaces having a desired width are not clearly resolved.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and improves the shape of a resist pattern in ultra-fine processing of electronic parts, and in particular, reduces the bottoming and erosion of the pattern. However, the purpose is to further improve the resolution.

[0012]

Means and Actions for Solving the Problems The present inventors have
As a result of earnest efforts to achieve the above object, the main cause of deterioration of the shape of the resist pattern is that contaminants diffusing from the substrate side deactivate the acid in the resist, which decomposes the dissolution inhibitor, for example. In order to improve the shape of the resist pattern to be formed, it is very effective to prevent the diffusion of contaminants by blocking or significantly limiting the interaction between the substrate and the resist layer. I found that.

That is, the object of the present invention is to provide a step of forming a protective film on a substrate capable of suppressing diffusion of contaminants from the substrate, and having a substituent group which is decomposed or cross-linked by an acid on the protective film. A step of forming a resin layer containing a photosensitive composition containing a compound and a compound that generates an acid upon exposure as a main component; a step of pattern-exposing the resin layer; and a step of exposing the resin layer after exposure at a predetermined temperature. This is achieved by a pattern forming method including a step of baking, and a step of developing the resin layer after baking to selectively remove or leave the exposed region of the resin layer.

The method of the present invention is most characteristic in that a protective film is first formed on a substrate, and a resin layer containing a photosensitive composition as a main component is formed on the protective film to form a pattern. is there. Specifically, when a photosensitive composition containing a compound having a substituent that is decomposed by an acid (dissolution inhibitor) is used, in the exposure step, in the exposed area of the resin layer containing the photosensitive composition as a main component. Acid is generated, and in the baking step, the acid decomposes the dissolution inhibitor in the exposed area, so that the area exhibits alkali solubility and is dissolved in the developing solution to be selectively removed to form a pattern. At this time, since the protective film suppresses diffusion of contaminants from the substrate to the resin layer, deactivation of acid generated in the exposed region of the resin layer is reduced, and the dissolution inhibitor is decomposed efficiently. Therefore, the alkali solubility, that is, the solubility with respect to the developing solution is uniformly increased over the entire exposed region, the bottoming of the finally formed resist pattern is prevented, and the shape thereof is improved.

On the other hand, when a photosensitive composition containing a compound having a substituent crosslinkable with an acid is used, an acid is generated in the exposed area of the resin layer containing the photosensitive composition as a main component in the exposure step. In the baking process,
Since the acid crosslinks the compound in the exposed area, the area is not dissolved in the developing solution and selectively remains, so that a pattern is formed. At this time, since the protective film suppresses diffusion of contaminants from the substrate to the resin layer, deactivation of the acid generated in the exposed region of the resin layer is reduced, and the above compounds are efficiently crosslinked. Therefore, the alkali solubility, that is, the solubility in the developing solution is uniformly suppressed over the entire exposed region, and the shape of the resist pattern finally formed is improved.

An example of the pattern forming method of the present invention will be described in detail below with reference to FIG. Here, the case of using a photosensitive composition (positive resist) containing a compound having a substituent that is decomposed by an acid will be described.

First, as a first step, as shown in FIG. 1A, a protective film 12 capable of suppressing diffusion of contaminants from the substrate surface is formed on a substrate 11.

The substrate used here is not particularly limited, but examples thereof include a chromium vapor deposition mask, an aluminum vapor deposition mask, a BPSG coated substrate, a PSG coated substrate, an SOG coated substrate and the like.

On the other hand, the protective film formed on the substrate is required to have the following characteristics. The first characteristic is that when a resist is applied onto this protective film in the subsequent steps, it does not cause mixing of the protective film and the resist layer, so that physical and chemical reactions such as mixing with the resist-containing component do not occur. At the same time, it is not attacked by the resist solvent typified by 1-acetoxy-2-ethoxyethane (ethyl cellosolve acetate). The second characteristic is
It is possible to form a thin film having a film thickness of about 0.003 μm to 0.3 μm on the substrate in order to suppress the diffusion of contaminants from the substrate side and not to adversely affect the resolution of the resist. Furthermore, the third characteristic is that since it is necessary to finally transfer the resist pattern of the upper layer onto the substrate, it can be removed by a wet method using an acid or alkali aqueous solution or reactive ion etching (RIE). is there.

As the protective film satisfying the above conditions, for example, various inorganic films such as carbon, silicon and their compounds, and an organic high film made of a thermosetting resin or a resin capable of forming a three-dimensional network structure are used. Examples thereof include an organic film such as a molecular film.

The method of forming such a protective film can be appropriately selected depending on the material of the film. For example, in the case of an inorganic film, a vapor deposition method or a CVD method is used, and in the case of an organic film, a spin coating method using a solution of an organic material is used.

Next, as a second step, as shown in FIG. 1 (B), a resist solution is applied onto the protective film 12 and preferably prebaked at a predetermined temperature to form a resin layer, that is, the resist layer 13. To form.

The resist is preferably a chemically amplified resist, for example, an alkali-soluble resin, a compound having a substituent decomposable by an acid (dissolution inhibitor), and a compound generating an acid by exposure (acid generator). A photosensitive composition containing (positive resist) can be used. Here, the alkali-soluble resin and the dissolution inhibitor may be the same. Specific examples of these resists are disclosed in Japanese Patent Laid-Open No.
0-263143, JP-A-63-250642, JP-A-59-45439 and the like are acid catalyst type resists.

Next, as a third step, as shown in FIG. 1C, the resist layer 13 is pattern-exposed, that is, a predetermined region 14 of the resist layer 13 is selectively exposed (arrow 15). Draw a pattern. This exposure is performed by irradiating, for example, X-rays, high-energy electron beams, synchrotron radiation, characteristic lines of a high-pressure mercury lamp, excimer laser light, and the like. Further, as a fourth step, as shown in FIG.
As shown in (D), a latent image 16 is formed on the exposed area 14 of the resist by performing post-exposure baking.

Subsequently, as a fifth step, as shown in FIG. 1 (E), the resist layer 13 is developed with a predetermined developing solution, so that the resist layer 13 in FIG. 1 (D) is developed.
The exposed area 14 (latent image 16) is removed by selectively dissolving it, and a resist pattern 17 is formed. The developing solution used here may be appropriately selected depending on the resist material, and examples thereof include an alkaline developing solution such as a tetramethylammonium hydroxide solution.

After completion of the above steps, the substrate on which the pattern is formed is treated with an oxygen asher in order to remove bridges and scum in the resist pattern, if necessary. Further, as shown in FIG. 1F, the protective film 12 is selectively stripped by the developing solution used in the developing step or another developing solution by RIE or the above-mentioned oxygen asher using the resist pattern 17 as a mask.

Subsequently, the underlying substrate is selectively etched using the formed resist pattern and protective film pattern as an etching resistant mask to perform ultrafine processing.

In the pattern forming method of the present invention, as the resist, for example, a composition containing a compound having a substituent crosslinkable by an acid (negative resist) can be used. In this case, the development treatment is carried out. Thus, the exposed area of the resist layer selectively remains. When this mechanism is made to correspond to the process of FIG. 1 described above, in the developing process shown in FIG. 1E, the exposed region 14 is not dissolved in the developing solution and selectively remains, and a resist pattern opposite to that in FIG. 1 is formed. To be done.

In the first step of the pattern forming method of the present invention, as the protective film formed on the substrate, among the above-mentioned ones, the organic film is taken into consideration in that it is easy to remove after forming the resist pattern. Is preferred. As a material for forming such an organic film, for example, a polyamide resin, a polyimide resin, a polyamide imide resin, a polyamino bismaleimide resin, a polyether imide, a phenol resin,
Diallyl phthalate resin, urea resin (urea resin), alkyd resin, urethane resin, unsaturated polyester resin,
Silicone resin, fluororesin, ebonite (hard rubber), polyacetal resin, polysulfone, polyether sulfone, polyparaxylylene, melamine resin,
Examples include but are not limited to Bakelite, epoxy resins and their derivatives. These resins are applied onto the substrate in the form of, for example, varnish, and are applied as they are, or after application, they are cured by heat treatment or ultraviolet rays to form a film. In addition, a thermosetting agent may be added to the above resin, JP-A-56-1933, JP-A-60-14235,
JP-A-61-240237, JP-A-63-170639
It is also possible to mix and cure a photosensitive curing agent or a heat-sensitive curing agent such as a bisazide or diazo compound disclosed in US Pat.

In particular, in the present invention, the protective film formed on the substrate is a polyimide (resin) represented by the following general formula (1), in which a part or all of the imide ring of the polyimide is imide. A polymer film made of a resin containing an unmodified precursor (polyamic acid) or a polymer film made of only the polyimide precursor is suitable.

[0031]

[Chemical 1] In the formula, R ₁ is a tetravalent organic group, R ₂ is a divalent organic group,
n represents the degree of polymerization, respectively.

Examples of the tetravalent organic group R ₁ in this polyimide (1) include the following groups.

[0033]

[Chemical 2] The following groups can be given as examples of the divalent organic group R ₂ in the polyimide (1).

[0034]

[Chemical 3] In the above-mentioned tetravalent and divalent organic groups, some or all of the hydrogen atoms are monovalent organic groups such as an alkyl group, a halogen atom, a nitro group, a hydroxyl group, a carboxyl group, and an esterified carboxyl group. It may be substituted. Further, some or all of the aromatic rings contained in these organic groups may be heterocyclic rings in which some of the carbon atoms are substituted with nitrogen atoms, oxygen atoms, sulfur atoms and the like.

In the present invention, a polymer film made of epoxy resin is also suitable as the protective film formed on the substrate. This epoxy resin is, for example, one obtained by ring-opening polymerization of a compound containing two or more functional groups such as epoxy group, oxirane group or ethoxyline group in one molecule with a polyfunctional or catalytic curing agent. Used. Specific examples of the compound having the functional group include a phenol-based glycidyl ether type, an alcohol-based glycidyl ether type, a glycidyl ester type, a glycidyl amine type, an alicyclic type, and a mixed type of the above epoxy resins.
In the above epoxy resin, some or all of the hydrogen atoms may be substituted with a monovalent organic group such as an alkyl group, a halogen atom, a nitro group, a hydroxyl group, a carboxyl group, and an esterified carboxyl group. Further, some or all of the aromatic rings and aliphatic rings contained in these epoxy resins may be heterocyclic rings in which some of the carbon atoms are substituted with nitrogen atoms, oxygen atoms, sulfur atoms or the like. . On the other hand, as the curing agent, a catalytic curing agent (curing accelerator) such as aliphatic polyamine, amidoamine, polyamide, aromatic polyamine, acid anhydride, polyphenol, boron oxyfluoride-amine vinegar, or phenol resin can be used. Examples thereof include co-reactive resin (crosslinking agent).

In addition to the above, in the first step of the pattern forming method of the present invention, as the protective film formed on the substrate, a polyacrylate resin represented by the following formula (2), a part or all of the polyacrylate is A resin containing a compound in which the α-position is substituted with a halogen atom, or a polymer film made of α-chloropolyacrylate is also suitable.

[Chemical 4] In the formula, R ₃ and R ₄ may be the same or different, and each is hydrogen, a halogen atom, an alkyl group such as methyl or ethyl, or an alkyl in which a part or all of hydrogen is substituted with a halogen atom. Represents a group.

Particularly, the film made of the acrylate polymer represented by the formula (2) has a remarkably high dry etching rate as compared with the resist film, so that it is easy to remove after forming the resist pattern. It can be quickly removed by treatment with an asher. Further, since the acrylate-based polymer film is decomposed by high energy, it is applied to the lower protective film of a positive resist, and after pattern formation,
It can be easily dissolved and removed by a solvent having a particularly small polarity such as toluene which is a poor solvent for the resist.

In the pattern forming method of the present invention, the second
As the material of the resin layer formed on the protective film in the step, that is, the resist layer, a positive or negative chemically amplified resist is used as described above, but more specifically,
(RA), (RB), or (R) as described below
The photosensitive composition (acid-catalyzed resist) having the composition of C) is suitable. By applying these photosensitive compositions,
It becomes possible to obtain a pattern having a rectangular cross section with higher resolution.

The photosensitive composition (RA) has an alkali-soluble resin, a compound having a substituent that is decomposed by an acid and generating an alkali-soluble group after decomposition (dissolution inhibitor), or a substituent that is crosslinked by an acid. It contains a compound and a compound (acid generator) represented by the following general formula (3) that generates an acid upon exposure.

[0040]

[Chemical 5] In the formula, R ₃₁ represents a monovalent organic group or a monovalent organic group into which at least one selected from the group consisting of a halogen atom, a nitro group and a cyano group is introduced, and R ₃₂ , R ₃₃ and R ₃₄ has each independently introduced at least one selected from the group consisting of a hydrogen atom, a halogen atom, a nitro group, a cyano group, a monovalent organic group, or a halogen atom, a nitro group and a cyano group. Represents a monovalent organic group.

The photosensitive composition (RB) has an alkali-soluble resin, a compound having a substituent capable of decomposing by an acid and producing an alkali-soluble group after decomposition (dissolution inhibitor), or a substituent crosslinkable by an acid. It contains a compound and a compound (acid generator) represented by the following general formula (4) which generates an acid upon exposure.

[0042]

[Chemical 6] In the formula, R ₄₁ and R ₄₃ are each independently a monovalent organic group,
Alternatively, it represents a monovalent organic group into which at least one selected from the group consisting of a halogen atom, a nitro group, and a cyano group is introduced, and R ₄₂ represents a sulfonyl group or a carbonyl group.

The photosensitive composition (RC) has an alkali-soluble resin, a compound having a substituent capable of decomposing by an acid and producing an alkali-soluble group after decomposition (dissolution inhibitor), or a substituent cross-linking by an acid. It contains a compound and a compound (acid generator) which generates an acid upon exposure, which is represented by the following general formula (5).

[0044]

[Chemical 7] In the formula, R ₅₁ , R ₅₂ and R ₅₅ each independently have a monovalent organic group or at least one selected from the group consisting of a halogen atom, a nitro group and a cyano group.
Represents a valent organic group, R ₅₃ represents a hydrogen atom, a monovalent organic group,
Or a monovalent organic group into which at least one selected from the group consisting of a halogen atom, a nitro group, and a cyano group is introduced, R ₅₄ is a sulfonyl group, a sulfinyl group,
Represents a sulfur atom or a carbonyl group.

These photosensitive compositions (RA), (RB),
And (RC) have varying alkali solubilities, ie
It is a chemically amplified resist whose dissolution rate in an alkaline solution varies.

First, in the case where the photosensitive composition contains a compound having a substituent capable of decomposing by an acid (dissolution inhibitor), in the unexposed state, the action of the dissolution inhibitor on the alkali-soluble resin causes Insoluble in the solution. However, when exposure and baking are performed, an acid is generated from the acid generator, and the acid decomposes the dissolution inhibitor to generate an alkali-soluble group.
As a result, the exposed area of the photosensitive composition becomes soluble in the alkaline solution. That is, in this case, in the method of the present invention, the photosensitive composition functions as a positive resist material in which only the exposed region is dissolved in the alkali developing solution and selectively remains.

On the other hand, when the photosensitive composition contains a compound having a substituent crosslinkable by an acid, it is soluble in an alkali solution in the unexposed state due to the characteristics of the alkali-soluble resin. . However, when exposure and baking are performed, an acid is generated from the acid generator, and the compound having a substituent crosslinkable by the acid acts to crosslink the alkali-soluble resin. As a result, the exposed area of the photosensitive composition becomes insoluble in the alkaline solution. That is, in this case, the photosensitive composition is
In the method of the present invention, only the exposed region is dissolved in the alkali developing solution and functions as a negative resist material that selectively remains.

In the above-mentioned photosensitive compositions (RA), (RB) and (RC), the acid generator among the above components means an acid upon exposure, that is, irradiation with short wavelength ultraviolet rays, electron beams, X-rays and the like. Is a compound capable of generating. These photosensitive compositions each contain the above-mentioned general formulas (3) to (5) as an acid generator.
Is characterized in that it contains a compound having a sulfonyl group represented by any of the above.

Particularly in the method of the present invention, the general formula (3)
Exposure from the compound represented by any one of (5) to (5)
The acid generated by the process) is rarely deactivated during the period after the exposure until baking (fourth process). Therefore, in the method of the present invention, the photosensitive composition (R
A), (RB), and (RC) are very stable throughout the process, have excellent performances such as excellent sensitivity and resolution, and their use can form a pattern with high resolution.

Further, in the method of the present invention, when the photosensitive compositions (RA), (RB) and (RC) function as a positive resist, any one of the above general formulas (3) to (5) is used. The compound represented by suppresses unnecessary cross-linking reaction during baking after exposure. For this reason, the alkali solubility in the exposed area is further increased, sensitivity deterioration is prevented, and a pattern can be formed with higher resolution.

In the photosensitive composition (RA), the compound (3) used as an acid generator is an organic compound having one sulfonyl group.

This compound (3) has R ₃₁ , R ₃₂ , R ₃₃ ,
And specific examples of the monovalent organic group introduced as R ₃₄ include allyl, anisyl, anthraquinolyl, acetonaphthyl, anthryl, azulenyl, benzofuranyl, benzoquinolyl, benzoxazinyl, benzoxazolyl,
Benzyl, biphenylenyl, bornyl, butenyl, butyl, cinnamyl, crezotoyl, cumenyl, cyclobutanedienyl, cyclobutenyl, cyclobutyl, cyclopentadienyl, cyclopentatrienyl, cycloheptyl, cyclohexenyl, cyclopentyl, cyclopropyl, cyclopropenyl, decyl, Dimethoxyphenethyl, diphenylmethyl, docosyl, dodecyl, eicosyl, ethyl, fluorenyl, furfuryl, geranyl, heptyl, hexadecyl, hexyl, hydroxymethyl,
Indanyl, isobutyl, isopropyl, isopropylbenzyl, isoxazolyl, menthyl, mesityl, methoxybenzyl, methoxyphenyl, methyl, methylbenzyl, naphthyl, naphthylmethyl, nonyl, norbornyl, octacodyl, octyl, oxazinyl, oxazolidinyl, oxazolinyl, oxazolyl, pentyl,
Phenacyl, phenanthryl, phenethyl, phenyl,
Phthalidyl, propynyl, propyl, pyranyl, pyridyl, quinazonyl, quinolyl, salicyl, terephthalyl,
Tetrazolyl, thiazolyl, thiaftenyl, thienyl,
Examples include tolyl, trityl, trimethylsilylmethyl, trimethylsilyloxymethyl, undecyl, valeryl, veratyl, xylyl and the like. Further, as the monovalent organic group into which at least one selected from the group consisting of a halogen atom, a nitro group and a cyano group is introduced, those obtained by substituting the hydrogen atoms of the groups listed above can be mentioned. .

Specific examples of the compound (3) include phenylmethyl sulfone, ethylphenyl sulfone, phenylpropyl sulfone, methylbenzyl sulfone, benzyl sulfone (dibenzyl sulfone), methyl sulfone,
Ethyl sulfone, butyl sulfone, methyl ethyl sulfone, methylsulfonyl acetonitrile, phenylsulfonyl acetonitrile, toluenesulfonyl acetonitrile, benzylphenyl sulfone, nitrophenylsulfonyl acetonitrile, fluorophenylsulfonyl acetonitrile, chlorophenylsulfonyl acetonitrile,
Methoxyphenylsulfonylacetonitrile, α-methylphenylsulfonylacetonitrile, ethylsulfonylacetonitrile, methylthiomethyl p-toluylsulfone, phenylsulfonylacetophenone, phenylsulfonylpropionitrile, phenylsulfonylpropionic acid and its ester compounds, bromomethyl-2- (phenylsulfonylmethyl) Examples thereof include benzene, naphthylmethyl sulfone, 1-methyl-2-((phenylsulfonyl) methyl) benzene, trimethyl-3- (phenylsulfonyl) orthopropionate and the like.

In the photosensitive composition applied to the method of the present invention, R ₃₂ , R ₃₃ and R 3 are used as the compound (3).
Among ₃₄ , at least one is preferably an electron-withdrawing group, and particularly, a cyano group is preferable in that the acid generation efficiency during exposure is high and the sensitivity of the photosensitive composition (resist) is improved. Further, a compound in which at least one of R ₃₂ , R ₃₃ and R ₃₄ is a hydrogen atom has a high alkali solubility and reduces the generation of scum when a developing treatment using an alkaline solution is applied to the resist. It is preferable in terms.

In the compound (3), R ₃₁ , R ₃₂ and R
₃₃ or R ₃₄ is bonded to each other, or R ₃₂ ,
R ₃₃ and R ₃₄ may combine with each other to form a ring. In this case, the derived cyclic compounds include phenylsulfonyltetrahydropyran, phenylsulfonylcyclohexane, 3-phenyl 2H-thiopyran 1,1-dioxide and 6-methyl 3-phenyl 2H-thiopyran 1,1-dioxide. Thiopyrandioxide compounds, trimethylene sulfone, tetramethylene sulfone, 4-methyl-2,6,
Examples thereof include biscyclic trisulfone compounds such as 7-trithiabicyclo [2,2,2] -octane-2,2,6,6,7,7-hexaoxide and the following compounds.

[0056]

[Chemical 8] In the photosensitive composition (RB), the compound (4) used as the acid generator has two sulfonyl groups or one sulfonyl group and one carbonyl group bonded to a specific carbon atom. It is an organic compound. Examples of the monovalent organic group introduced as R ₄₁ and R ₄₃ into this compound (4) include the same groups as those exemplified as the monovalent organic group introduced into the above compound (3). . The hydrogen atom of these organic groups may be substituted with at least one selected from the group consisting of a halogen atom, a nitro group, and a cyano group.

Specific examples of the compound (4) include bis (phenylsulfonyl) methane, bis (methylsulfonyl) methane, bis (ethylsulfonyl) methane, (methylsulfonyl) (phenylsulfonyl) methane, phenylsulfonylacetophenone and methyl. Examples thereof include sulfonylacetophenone.

Also in the above compound (4), R ₄₁ and R ₄₃
And may combine with each other to form a ring. in this case,
Examples of the derived cyclic compound include the following cyclic sulfone compounds.

[0059]

[Chemical 9] The compound (4) is a more preferable acid generator because it has high alkali solubility and high acid generation efficiency during exposure, and improves the sensitivity of the photosensitive composition (RB) in the method of the present invention.

In the photosensitive composition (RC), the compound (5) used as an acid generator has a linking group having at least two sulfonyl groups at a specific carbon atom, and a sulfur-containing linking group or one. An organic compound having a carbonyl group bonded. The monovalent organic groups introduced as R ₅₁ , R ₅₂ , R ₅₃ and R ₅₅ into this compound (5) include the groups exemplified as the monovalent organic groups introduced into the above compound (5). The same thing is mentioned. Further, the hydrogen atom of those organic groups is at least one selected from the group consisting of a halogen atom, a nitro group, and a cyano group, a hydroxyl group,
It may be substituted with a carboxyl group or an esterified carboxyl group. On the other hand, R ₅₄ is preferably a sulfonyl group, a sulfinyl group, or a sulfur atom.

Specific examples of the compound (5) include tris (phenylsulfonyl) methane, phenylthio-bis (phenylsulfonyl) -methane and phenylmercapto.
-Bis (methylsulfonyl) -methane, tris (methylsulfonyl) methane, tris (ethylsulfonyl) methane, bis (phenylsulfonyl) -methylsulfonyl-
Methane, bis (methylsulfonyl) -phenylsulfonyl-methane, phenylsulfonyl-ethylsulfonyl-
Methylsulfonyl-methane, tris (4-nitrophenylsulfonyl) methane, tris (2,4-nitrophenylsulfonyl) methane, bis (phenylsulfonyl)-(4-nitrophenylsulfonyl) -methane, bis (phenylsulfonyl)-( 3-nitrophenylsulfonyl) -methane, bis (phenylsulfonyl)-(2-nitrophenylsulfonyl) -methane, bis (phenylsulfonyl)-(p-tolylsulfonyl) -methane, bis (methylsulfonyl)-(4-nitro Phenylsulfonyl) -methane, bis (methylsulfonyl)-(4-chlorophenylsulfonyl) -methane, bis (phenylsulfonyl)-(4-fluorophenylsulfonyl) -methane, 1,1,1-tris (phenylsulfonyl) ethane, etc. Is mentioned.

In the method of the present invention, the compound (3), (4) or (5) as described above, for example, R ₃₁ ,
The pattern finally obtained when at least one of R ₄₁ and R ₄₃ , or at least one of R ₅₁ , R ₅₂ and R ₅₅ is an aromatic group, especially when exposure by a KrF excimer laser is applied. It is preferable in terms of improving dry etching resistance and heat resistance. In addition, an acid generator having a melting point of 50 ° C. or higher and high solubility in an organic solvent is also preferable.

On the other hand, when the compounds (3), (4) and (5) are sulfonyl compounds having a basic substituent such as sulfamide, the acid generated by exposure may be deactivated. Further, in the case of a sulfonyl compound having an acidic group having high alkali solubility such as sulfonic acid, the alkali solubility in the unexposed portion of the photosensitive composition may be excessively increased. Therefore, the use of these sulfonyl compounds as an acid generator in the photosensitive composition employed in the method of the present invention may be severely limited.

The compounding amount of the acid generator in each of the photosensitive compositions (RA), (RB) and (RC), that is,
The compounding amount of the compound (3) in the composition (RA), the compounding amount of the compound (4) in the composition (RB), or the compounding amount of the compound (5) in the composition (RC) is preferably an alkali-soluble resin. It is at least about 0.1 part by weight or more and less than about 40 parts by weight with respect to 100 parts by weight. The reason for this is that if the amount is less than 0.1 parts by weight, the sensitivity of the photosensitive composition tends to decrease, and conversely, if it is 40 parts by weight or more, the photosensitive composition on the protective film is increased. This is because the coating film properties of the product and the dissolution rate in the developer tend to be significantly reduced. Particularly preferably, the compounding amount of the acid generator is usually 2 to 10 parts by weight with respect to 100 parts by weight of the alkali-soluble resin.

On the other hand, the photosensitive compositions (RA) and (R
As the alkali-soluble resin corresponding to the resin components of B) and (RC), the same resin can be used in any composition.

As the alkali-soluble resin, a polymer having a phenol skeleton can be generally used.
For example, phenol novolac resin, cresol novolac resin, xylenol novolac resin, vinyl phenol resin, isopropenyl phenol resin; copolymer of vinyl phenol and acrylic acid, methacrylic acid derivative, acrylonitrile, or styrene derivative; isopropenyl phenol and , Acrylic acid, methacrylic acid derivatives, acrylonitrile, styrene derivatives and the like. More specifically, poly (p-vinylphenol), a copolymer of p-isopropenylphenol and acrylonitrile, a copolymer of p-isopropenylphenol and styrene, a copolymer of p-vinylphenol and methylmethacrylate. Examples thereof include polymers and copolymers of p-vinylphenol and styrene. It is also possible to use a silicon-containing alkali-soluble polymer such as a polysiloxane having phenol as a side chain, the same polysilane, or a novolac resin synthesized from a phenol having silicon as a side chain.

In particular, as the alkali-soluble resin, an alkali-soluble resin having a softening point of about 150 ° C. or more for forming a fine pattern and having an average molecular weight of about 3,000 to 8,000 particularly when an electron beam is used as an exposure source. Resins are preferred. This is for the following reason. That is, when the softening point of the resin component of the photosensitive composition used for the resist material is low, the acid generated from the acid generator upon exposure is excessively diffused by the baking treatment after exposure. Due to the diffusion of the acid, the latent image in the exposed portion is blurred, and the resolution of the finally formed resist pattern may be lowered, which may cause a problem. Further, when a photosensitive composition containing a compound having a substituent decomposable by an acid and a resin component having a distribution in a high molecular weight region is exposed to ionizing radiation, the exposure and the exposure are performed. The subsequent baking treatment may accelerate the crosslinking reaction, which may deteriorate the image quality and sensitivity of the positive resist pattern. Therefore,
It is preferable to apply an alkali-soluble resin that satisfies the conditions such as the softening point and the molecular weight described above.

Such an alkali-soluble resin has an aromatic ring in the resin skeleton and is used as a resist for UV exposure of a short wavelength or a resist exhibiting dry etching resistance (usually, 2.
Those having a dissolution rate of about 0.1 to 500 nm / sec and a softening point of about 150 ° C. or higher with respect to a 38 wt% tetramethylammonium hydroxide aqueous solution are preferable.

Examples of the alkali-soluble resin satisfying the conditions such as the softening point and the average molecular weight as described above include those similar to the above-mentioned alkali-soluble resin. As a specific example, a novolak resin obtained by polycondensing a phenol derivative with formaldehyde under acidic conditions, and a polymer containing xylenol, ethylphenol, butylphenol, halogenated phenol, naphthol and the like in its skeleton can be mentioned.

Besides, vinylphenol resin, melamine
-Formaldehyde resin, poly 4-hydroxymaleimide, poly α-methylstyrene, 4-hydroxymaleimide, α-methylstyrene, copolymer of vinylphenol and acrylic acid or methacrylic acid, vinyl compound containing aromatic ring and poly Examples thereof include copolymers with acrylic acid and polymethacrylic acid, and polyimide precursors (polyamic acids). These resins may be used alone or in the form of a mixture of two or more kinds.

Of the above resins, the novolak resin having xylenol in the copolymer composition has sufficient solubility and heat resistance to impart high resolution to the resist, and is an alkali-soluble resin satisfying the above conditions. Particularly preferred. As such a novolac resin, specifically, a novolac resin containing at least two selected from the group consisting of 2,5-xylenol, 3,5-xylenol, m-cresol, p-cresol, and o-cresol Examples of the resin include a resin having a polymerization composition and containing at least 20 to 60 parts by weight of xylenol in the copolymer composition. In particular, novolak resins containing 2,5-xylenol have excellent solubility and heat resistance,
Further, since the novolac resin containing 3,5-xylenol has an excellent interaction with a compound having a substituent decomposable by an acid, it is preferable to use a mixture of these two kinds.

More specifically, the novolak resin having the above-mentioned copolymer composition preferably has a limited composition in order to satisfy the conditions such as the softening point, the average degree of polymerization and the dissolution rate. For example, in the copolymer composition 2,
If 5-xylenol is included, the amount of xylenol is 20-
It is preferable that the composition range is 60 parts by weight, m-cresol is 30 to 80 parts by weight, and p-cresol and o-cresol are 0 to 50 parts by weight. When the copolymer composition contains 3,5-xylenol, the amount of xylenol is 20 to 50.
It is preferable that the composition range is 30 to 80 parts by weight for m-cresol, and 0 to 50 parts by weight for p-cresol and o-cresol.

The novolak resin having the above-mentioned copolymer composition may have a broad molecular weight distribution. However, in order to increase the softening point of the resin, it is preferable that the residual monomer component and the 1-2 nucleus polymer component content in the resin are as low as possible. This is achieved by increasing the degree of vacuum during removal of residual monomers during synthesis of the novolac resin, increasing temperature, or fractional precipitation after polymerization. In the above molecular weight distribution, the high molecular weight component is mainly the increase in softening point,
Since the low molecular weight component contributes to the improvement of resolution, the molecular weight component in the intermediate region may be treated by fractional precipitation to process the entire molecular weight distribution, depending on the properties required for the polymer.

In addition, the novolak resin having the above-mentioned copolymer composition is improved in transparency to far ultraviolet rays by substituting a part or all of the vinylphenol resin, that is, by mixing the vinylphenol resin. You can As the vinylphenol resin, ordinary polyvinylphenol, a polymer whose transparency is improved by hydrogenating part or all of polyvinylphenol, that is, a polymer having improved light transmittance, and a part of hydroxyl groups of polyvinylphenol are dissolved at a rate thereof. In order to suppress the formation of polyvinylphenol derivative protected with methyl group, acetyl group, butyloxycarbonyl group, pyranyl group, etc., styrenated polyvinylphenol with styrene etc. added with platinum catalyst, or copolymer of vinylphenol and styrene. Etc. In this case, the amount of the vinylphenol resin added to the novolac resin is preferably at least 5% by weight or more, and particularly preferably 20 to 100% by weight.

In any of the above-mentioned photosensitive compositions (RA), (RB) and (RC), a compound having a substituent decomposable by an acid, which corresponds to a dissolution inhibitor, is the same compound in any composition. Can be used.

As such a dissolution inhibitor, it preferably has a dissolution inhibiting function for the alkali-soluble resin in the unexposed state as described above, while it has a substituent capable of decomposing in the presence of an acid and decomposes. It is possible to use compounds in which the latter product yields —COO ⁻ or —SO ₃ ^— by the action of an alkaline solution. As a result, the photosensitive composition exhibits strong alkali solubility after a series of steps such as exposure, baking, and development.

Examples of the dissolution inhibitor described above include compounds represented by the following general formula (6).

[0078]

[Chemical 10] However, R ₆₁ and R ₆₂ in the formula, which may be the same or different, each represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, a silyl group, or a monovalent organic group. Incidentally, R ₆₁ and R ₆₂ may be bonded to each other to form a ring. X is,> C = O or -SO ₂ - shows a. Y represents a divalent organic group. It should be noted that any one or more of R ₆₁ , R _{62 and} Y has a substituent that is decomposed by an acid.

Examples of the monovalent organic group introduced as R ₆₁ or R _{62 in} the general formula (6) include, for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,
a substituted or unsubstituted alkyl group such as t-butyl, a substituted or unsubstituted aromatic group such as phenyl, tolylnaphthyl, anthranyl, pyridyl, cyclohexyl, piperidyl,
Examples thereof include a substituted or unsubstituted alicyclic or heterocyclic group such as pyranyl.

Examples of the divalent organic group Y introduced in the general formula (6) include substituted or unsubstituted aliphatic groups such as ethylene, propylene and butylene, benzene, naphthalene, anthracene, phenanthrene, pyridine, A group derived from a substituted or unsubstituted aromatic ring such as piperazine,
Examples thereof include groups derived from a substituted or unsubstituted aliphatic ring or hetero ring such as cyclohexane, pyrazine, pyran and morpholane.

Examples of the group decomposable by an acid introduced into any one or more of R ₆₁ , R ₆₂ or Y in the general formula (6) include, for example, t-butyl ester, isopropyl ester,
Esters such as ethyl ester, methyl ester, benzyl ester, ethers such as tetrahydropyranyl ether, alkoxycarbonyls such as t-butoxycarbonyl (t-butyl carbonate), methoxycarbonyl (methyl carbonate), ethoxycarbonyl (ethyl carbonate) And silyl ethers such as trimethylsilyl ether, triethylsilyl ether and triphenylsilyl ether.

As the compound represented by the general formula (6), compounds having the structures of the following general formulas (7) to (9) are more preferable.

[0083]

[Chemical 11] However, in the general formulas (7) to (9), R ₇₁ , R ₇₂ , R
₇₃ may be the same or different and represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, a silyl group, or the above-mentioned monovalent organic group. X is,> C = O or -SO ₂ - shows a. Y represents the above-mentioned divalent organic group. k is 1 to 5
, M is an integer of 1 to 4, and n is an integer of 1 to 7.
Incidentally, any one or more of R ₇₁ , R ₇₂ , R _{73 and} Y has a substituent decomposable by the above-mentioned acid.

The compounds having the structures of the above general formulas (7) to (9) are specifically derivatives of compounds having the following hydroxyl groups, which are blocked by the above-mentioned acid-decomposable groups. What is present can be used. Examples of the compound containing a hydroxyl group include 3-hydroxy-3
-Methylphthalide, ascorbic acid, bromocresol green, bromocresol purple, bromocresol blue, bromoxylenol blue, α-chloro-α
-Hydroxy-o-toluenesulfonic acid-γ-sultone, chlorophenol red, cresolphthalein,
Eosin B, Eosin Y, fluorescein, fluorescein isocyanate, phenolphthalein, phenol red, tetrabromophenol blue, 3 ', 3 ",
5 ', 5 "-Tetrabromophenolphthalein, 4,5,6,7
-Tetrachlorofluorescein, 3 ', 3 ", 5', 5" -Tetraiodophenolphthalein, 3 ', 3 ", 5', 5"-
Examples thereof include tetraiodophenolsulfonephthalein, thymolphthalein, naphtholphthalein, thymolblue and the like. These compounds are, for example, two or more bound via a divalent or higher valent group as shown below, and dimerized,
It may be a trimerized compound.

[0085]

[Chemical 12] The content of the dissolution inhibitor as described above in each of the photosensitive compositions (RA), (RB) and (RC) is
Preferably, it is about 3 to 40 parts by weight based on 100 parts by weight of the alkali-soluble resin. The reason for this is that if the amount of the compound added is less than 3 parts by weight, the solubility of the unexposed area increases, and the resolution tends to decrease. On the contrary, if it exceeds 40 parts by weight, resist residues tend to occur. Because there is.

The photosensitive compositions (RA) and (RB)
In each of (RC) and (RC), when an alkali-soluble resin having a softening point of 150 ° C. or higher and an average molecular weight of about 3,000 to 8,000 is used as the resin component, these resin components are chemically sensitized type. The dissolution inhibitors are not limited to the compounds as described above as they are suitable for use. That is, in the case of a compound that suppresses the alkali solubility of the resin component at the time of non-exposure and has a substituent that is decomposed by an acid and produces an alkali-soluble group after decomposition, at least one substituent that is decomposed by an acid is a, and the product after decomposition -COO ^- or -SO ₃
There is no particular limitation on the compound that produces ⁻ , for example, the compound of the general formula (6).

Examples of the compound having a substituent decomposable by such an acid include, for example, US Pat. No. 4,491,628.
No. 4,603,101, JP-A-63-2782.
No. 9 or the like, or a compound having a carboxylic acid group or a phenolic hydroxyl group in its skeleton, in which a part or all of the hydroxy terminal thereof is substituted with an acid-decomposable protecting group, or the like is used. obtain. Examples of this protecting group include t-butyl ester, t-butoxycarbonyl (t-butyl carbonate), tetrahydropyranyl,
Examples include silyl and the like. Specific examples of such compounds are listed below. In these chemical formulas, m and n represent the degree of polymerization or the composition (weight ratio) of the copolymer.

[0088]

[Chemical 13]

[Chemical 14]

[Chemical 15]

[Chemical 16]

[Chemical 17]

[Chemical 18]

[Chemical 19]

[Chemical 20]

[Chemical 21]

[Chemical formula 22]

[Chemical formula 23]

[Chemical formula 24]

[Chemical 25] When these dissolution inhibitors are used in each of the photosensitive compositions (RA), (RB) and (RC), the compounding amount thereof is preferably the alkali-soluble resin 10 described above.
It is at least 3 parts by weight and less than 40 parts by weight with respect to 0 parts by weight. The reason is that the amount of the dissolution inhibitor blended is 3
If it is less than parts by weight, the resolution of the photosensitive composition tends to be lowered, and conversely if it is 40 parts by weight or more, the coating property of the photosensitive composition on the protective film and the developing solution are This is because the dissolution rate tends to decrease significantly. Particularly preferably, the content of the dissolution inhibitor is usually 10 to 30 parts by weight based on 100 parts by weight of the alkali-soluble resin. Incidentally, when the dissolution inhibitor is an alkali-soluble polymer compound, a resin component in the photosensitive composition,
That is, it can also be used as an alkali-soluble resin.
In this case, the compounding amount of the compound may be preferably set to 10 to 98 parts by weight of the total amount of the solid content, because the resin equivalent amount is added.

However, the photosensitive composition (R
In each of A), (RB) and (RC), the softening point is 150 ° C. or higher and the average molecular weight is 3000 to 8
When an alkali-soluble resin of 000 is used,
By using a specific compound such as the compound of the general formula (6) as a dissolution inhibitor, the change in solubility in an alkaline solution after exposure can be made remarkable. Therefore, the combination of such an alkali-soluble resin and a dissolution inhibitor (a compound having a substituent capable of decomposing by an acid) is particularly preferable in the method of the present invention for enhancing the resolution of the photosensitive composition.

As the compound having a substituent crosslinkable by an acid contained in each of the photosensitive compositions (RA), (RB) and (RC), the same compound can be used in any composition.

As the compound having a substituent capable of being crosslinked by such an acid, an aminoplast resin can be usually used. Examples of the aminoplast resin include melamine-formaldehyde resin, urea-formaldehyde resin, glycol-formaldehyde resin, benzoguanamine-formaldehyde resin and the like. They are,
They may be used alone or as a mixture of two or more. Available aminoplast resins include, for example, Cymel,
Beetle series (manufactured by American Cynamide) and the like are known.

In each of the above-mentioned photosensitive compositions (RA), (RB) and (RC), when a compound having a substituent crosslinkable with these acids is used, its compounding amount is preferably alkali-soluble. It is 3 to 20 parts by weight with respect to 100 parts by weight of the resin. The reason is that if the compounding amount of the compound is less than 3 parts by weight, the sensitivity is lowered, and conversely, if it exceeds 20 parts by weight, a resist residue is likely to be generated.

The photosensitive compositions (RA), (RB) and (RC) are each the above-mentioned alkali-soluble resin, a compound having a substituent decomposable or cross-linkable by an acid, and the above-mentioned acid. Generating agent, that is, the general formula (3),
It is prepared by dissolving the compound represented by (4) or (5) in an organic solvent and filtering. Examples of the organic solvent include ketone solvents such as cyclohexanone, acetone, methyl ethyl ketone, and methyl isobutyl ketone, methyl cellosolve, methyl cellosolve acetate,
Cellosolve solvents such as ethyl cellosolve acetate, butyl cellosolve acetate, ethyl acetate, butyl acetate,
Ester solvents such as isoamyl acetate, γ-butyl lactone, dimethyl sulfoxide, dimethylformamide N-
Methylpyrrolidone and the like can be mentioned. These organic solvents may be used alone or in the form of a mixture. In addition, these may contain an appropriate amount of an aliphatic alcohol such as xylene, toluene or isopropylyl alcohol.

Further, the photosensitive compositions (RA) and (R
In B) and (RC), in addition to the above-mentioned three components, if necessary, a surfactant as a coating modifier, or another polymer such as epoxy resin, polymethylmethacrylate, polymethylacrylate, A propylene oxide-ethylene oxide copolymer, polystyrene, or a dye as an antireflection agent may be added.

In the pattern forming method of the present invention, the second
After the process, a coating layer having a specific function is formed on the resin layer (resist layer), and subsequently, the exposure, baking, and development processes in and after the third process are performed, whereby the sectional shape of the finally obtained pattern is obtained. Can be improved. Hereinafter, formation of such a coating layer will be described in detail.

Since the chemically amplified resist that can be used in the method of the present invention has extremely high sensitivity, it is easily affected by oxygen, moisture, and other trace components in the process atmosphere. For example, S. A. MacDonald, et al. , S
PIE vol. 1466, Advance in R
eist Technology and Proce
In Ssinging, P2, (1991), a trace amount of dimethylaniline contained in the atmosphere deactivates the acid generated near the surface of the resist layer by light irradiation. It has been reported that a layer having a remarkably low dissolution rate with respect to a liquid is generated, and this poorly soluble layer remains as an eaves-like pattern on the surface of the resist pattern after exposure and development treatment. This insoluble layer deteriorates the resolution performance of the resist, and the eaves generated in the resist pattern due to this may adversely affect the etching accuracy of the semiconductor substrate region.

In the method of the present invention, in order to reduce the generation of eaves due to the insolubilized layer near the surface of the resist layer and obtain a fine pattern having a rectangular cross section, after the completion of the second step, the photosensitive composition is prepared. It is preferable that a coating layer having a specific function is further formed on the resin layer made of, that is, a resist layer, and in this state, the third and subsequent steps, that is, the steps after the exposure are performed.

As the coating layer, an acidic coating layer can be preferably formed. The acidic coating layer may be an acidic layer which does not substantially absorb the exposure rays used in the present invention, and its constituent components include, for example, (C
A) acidic water-soluble polymer, (CB) organic acid and water-soluble polymer, (CC) organic acid and acidic water-soluble polymer are preferred.

As a specific process for forming the acidic coating layer, first, an acidic water-soluble polymer, an organic acid and a water-soluble polymer, or a combination of an organic acid and an acidic water-soluble polymer is used. A polymer aqueous solution obtained by dissolving in pure water is applied on the resin layer (resist layer) by a spin coating method or a dipping method. Then, about 15
By drying at 0 ° C. or lower, preferably 120 ° C. or lower, an acidic coating layer having the above-mentioned constitution (CA), (CB) or (CC) is formed. In this case, the surface of the resin layer containing an organic substance as a main component such as a chemically amplified resist does not dissolve or swell due to the layer formation using the aqueous solution. .

The acidic water-soluble polymer which forms the coating layer having the above-mentioned constitution (CA) or (CC) is a polymer having a carboxy group or a sulfonyl group as a substituent, and a carboxy group or a sulfonyl group as a substituent. A copolymer containing the monomer unit having is preferable. As a specific example,
Polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polymaleic acid, polyitaconic acid, itaconic acid
-Acrylic acid copolymer, itaconic acid-methacrylic acid copolymer, ethylene-maleic anhydride copolymer, ethylene-
Methacrylic acid polymer, methyl vinyl ether-maleic anhydride copolymer, styrene-maleic anhydride copolymer,
Examples thereof include an isobutylene-maleic anhydride copolymer and a copolymer in which the above-mentioned copolymer containing maleic anhydride as a constituent unit is partially esterified by reacting with alcohol. Examples of the alcohol used for partial esterification include methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol. These acidic water-soluble polymers may be used alone or in the form of a mixture of two or more kinds.
Incidentally, among the acidic water-soluble polymers exemplified, the copolymer containing maleic anhydride is a carboxylic acid which is cleaved when the anhydrous bond in maleic anhydride is cleaved when dissolved in pure water in the process of forming the coating layer. And becomes acidic.

As the organic acid forming the coating layer having the above-mentioned structure (CB) or (CC), a compound having a carboxy group, a sulfonyl group or a hydroxyl group as a substituent is preferable. Specific examples include acetic acid, propionic acid, butyric acid, methacrylic acid, sorbic acid, oxalic acid, succinic acid, maleic acid, 2-hydroxybutyric acid, malic acid, sulfoacetic acid, isethionic acid, cyclohexanedicarboxylic acid, hexahydrocarboxylic acid, Phenol, resirudin, pyrogallol,
Phthalic acid, pyromellitic acid, salicylic acid, resorcylic acid, sulfobenzoic acid, 5-sulfosalicylic acid, benzenesulfonic acid, toluenesulfonic acid, benzenedisulfonic acid, phenol-2,4-disulfonic acid, naphthalenesulfonic acid, etc. it can. These organic acids may be used alone or in the form of a mixture of two or more kinds.

Specific examples of the water-soluble polymer which forms the coating layer having the above-mentioned constitution (CB) include polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyethylene oxide, pullulan, dextran, methyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, poly Partially saponified vinyl acetate, a copolymer of vinylpyrrolidone and vinyl alcohol, a copolymer of styrene and ethylene oxide, a copolymer of ethylene and vinyl alcohol, polyvinyl methyl ether, carboxyvinyl polymer and the like can be mentioned. These water-soluble polymers may be used alone or in the form of a mixture of two or more kinds.

If necessary, the acidic coating layer may contain a surfactant as a coating film modifier. A nonionic surfactant is suitable for such a surfactant. Specific examples thereof include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene / polyoxypropylene block polymer, sorbitan fatty acid ester, and fatty acid alkylol. Examples thereof include amide, polyoxyethylene lanolin alcohol ether, polyoxyethylene lanolin fatty acid ester and the like. The coating layer containing these interface modifiers is preferable in that precipitation of the polymer in the subsequent step can be prevented.

The thickness of the acidic coating layer is preferably
About 10 to 1000 nm, more preferably 50 to 500 n
The range is m. When the thickness of the coating layer is less than 10 nm, it may be difficult to sufficiently achieve the effect of preventing the formation of the hardly soluble layer near the surface of the resin layer (resist layer). On the other hand, if the thickness of the coating layer exceeds 1000 nm, the resolution of the formed pattern may be reduced. The thickness of the acidic coating layer does not depend on the thickness of the resin layer which is the lower layer, and can be appropriately determined by assuming the thickness of the hardly soluble layer formed on the surface of the resin layer.

Incidentally, such an acidic coating layer can be completely dissolved and removed from the resin layer regardless of the exposed region and the unexposed region in the developing process step, especially by the developing process using an alkali developing solution.

Further, after the exposure and baking, prior to the developing treatment step, the acidic coating layer is removed by treating with pure water, and the exposed resin layer is treated with a developing solution such as an alkaline aqueous solution. Good. Thus, by removing the acidic coating layer prior to treatment with the developer,
It is possible to prevent the alkali concentration of the alkaline aqueous solution, which is the developing solution, from changing due to the influence of the acidic component constituting the coating layer, for example, the influence of the acidic water-soluble polymer and / or organic acid. As a result, it becomes possible to stably form a pattern with high resolution.

In the method of the present invention, by forming an acidic coating layer on the resin layer, the resin layer (resist layer) is contained in the photosensitive composition as its main component through the steps of exposure and baking. It is possible to completely shield from harmful components in the process atmosphere that hinder the reaction between the components, especially components that can deactivate the acid. As a result, the formation of the hardly soluble layer on the surface of the resin layer is prevented, and a fine pattern having a rectangular cross section can be formed by the subsequent development processing.

In the acidic coating layer, the acid component can neutralize basic compounds such as amines, which are considered to be the cause of the formation of the poorly soluble layer on the surface of the resin layer. In this way, it becomes possible to form a fine pattern having a rectangular cross section without eaves on the surface.

Further, when the acidic coating layer contains both the acidic water-soluble polymer and the organic acid, harmful components in the atmosphere can be blocked for a long time, so that the formation of the poorly soluble layer is more effective. Can be suppressed.

In addition to the above, in the method of the present invention, as the coating layer, the polymer is dissolved in an organic solvent which does not substantially dissolve the photosensitive composition constituting the resin layer, and the obtained polymer solution is It is also possible to form a neutral coating layer by coating on the resin layer and drying.

Examples of the polymer used here include butyl rubber, isoprene rubber, nitrile rubber, chloroprene rubber, ethylene-propylene rubber, poly-4-methylpentene-1, polystyrene, polyvinyl butyral, and one of these polymers. Examples thereof include rubber-based compounds such as an alkyl modified product or a copolymer in which a part is substituted with an alkyl group. These polymers, even when used alone,
You may use it in the form of a mixture of 2 or more types.

The organic solvent that dissolves the polymer is preferably selected from aromatic hydrocarbons, chlorine-containing hydrocarbons and aliphatic hydrocarbons that do not substantially dissolve the resin layer containing the photosensitive composition as a main component. It Examples of the aromatic hydrocarbon include toluene, xylene, ethylbenzene, and chlorobenzene. Examples of the chlorine-containing hydrocarbon include methylene chloride, propylene chloride, ethylene chloride and the like. Examples of the aliphatic hydrocarbons include hexane and cyclohexane. These organic solvents may be used alone or in a mixture of two or more. The neutral coating layer, using these organic solvents,
After pattern exposure and baking, it can be easily dissolved and removed before the development process.

If necessary, the neutral coating layer may contain the same surfactant as that used for the acidic coating layer as a coating film modifier.

The thickness of the neutral coating layer is preferably about 10 to 100 for the same reason as that of the acidic coating layer.
It may be set in the range of 0 nm, more preferably 50 to 500 nm.

In the method of the present invention, when a neutral coating layer is formed on the resin layer, a slightly soluble layer is formed on the surface of the resin layer, but after pattern exposure and baking,
The sparingly soluble layer can be simultaneously removed by dissolving and removing the coating layer with a predetermined organic solvent. As a result, it is possible to prevent the formation of eaves due to the poorly soluble layer in the pattern formed after the development process.

In the method of the present invention, the resin layer (resist layer)
By using the protective film as the lower layer and the coating layer as the upper layer in combination, a pattern having extremely high resolution and steep lines and spaces can be formed.

[0117]

EXAMPLES The present invention will be described in more detail below with reference to examples. Incidentally, these examples are described for the purpose of facilitating the understanding of the present invention, and do not particularly limit the present invention.

Example 1 Polyamide acid (manufactured by Toshiba Chemical Co .:
Chemitite CT4002T) was spin-coated and then heated at 250 ° C. for 5 minutes to imidize the polyamic acid to form a protective film made of a polyimide resin. The thickness of this protective film is about 0.05 to 0.1 μm.
Met.

Next, a chemically amplified resist solution was applied on the protective film to form a resist layer. This resist was used as a dissolution inhibitor in 100 parts by weight of polyvinylphenol in which a part of the side chain was tert-butoxymethylated.
17 parts by weight of tert-butoxylated cresolphthalein and 7 bis (phenylsulfonyl) methane as an acid generator
It is a photosensitive composition containing parts by weight. That is, radiation,
It is a positive resist in which an acid is generated from an acid generator upon irradiation with X-rays or high-energy electron beams, and the acid decomposes the dissolution inhibitor.

Then, in order to prevent a deactivating substance from the air on this resist layer, a copolymer containing methyl vinyl ester and maleic anhydride as a main component and having a thickness of 0.1 to
A 0.2 μm coating layer was formed. Subsequently, a pattern was drawn by scanning the resist layer with a high-energy electron beam having a beam diameter of 0.5 μm through the coating layer under the condition of 5 μC / cm ² .

Next, the exposed resist layer is set to 100
After baking at 2 ° C. for 2 minutes, an aqueous solution of tetramethylammonium hydroxide (TMAH) (concentration: 1.
90% or 1.67%), and a resist pattern was formed by removing only the exposed region of the resist layer by dissolving it in a developing solution.

With respect to the resist pattern thus formed, the sectional shapes of the lines and spaces are schematically shown in FIG. In the figure, a substrate (chrome mask) 21
Resist pattern 2 formed on top of which a protective film 22 is provided
In the cross section of No. 3, as compared with the pattern formed by the conventional method shown in FIG. In addition, the rectangularity of the pattern for processing the contact hole was significantly improved.

Example 2 On a chromium mask, a bisphenol F type epoxy resin (Okaka Shell Epoxy Co., Ltd .: Epicoat 807) and a phenol type curing agent (Dainippon Ink and Co .: VH-417) were used.
0) and triphenylphosphine as a curing catalyst are spin-coated, and then 1
It was cured by heating at 75 ° C. for 30 seconds to form a protective film made of an epoxy resin. The thickness of this protective film was about 0.05 to 0.1 μm.

Next, the same chemically amplified resist as in Example 1 was applied on this protective film to form a resist layer, and in order to prevent the deactivating substance from the air on the resist layer, A similar coating layer was formed. Subsequently, a pattern was drawn by scanning the resist layer with a high-energy electron beam having a beam diameter of 0.5 μm through the coating layer under the condition of 5 μC / cm ² .

Next, with respect to the resist layer after exposure, 110
After baking at 0 ° C. for 1 minute, a developing treatment is performed using a TMAH aqueous solution (concentration: 1.90%), and only the exposed region of the resist layer is dissolved and removed in the developing solution to form a resist. A pattern was formed.

In the resist pattern thus formed, the skirting was remarkably reduced, and fine lines and spaces were accurately resolved.

Example 3 A solution of poly (trifluoroethyl-α-chloroacrylate) (trade name EBR-9: manufactured by Toray Industries, Inc.) was spin-coated on a chromium mask. This was heated at 90 ° C. for 5 minutes and then at 180 ° C. for 30 minutes to cure by complete removal of the solvent to give poly (trifluoroethyl).
A protective film made of -α-chloroacrylate) was formed. The thickness of this protective film was about 0.05 to 0.2 μm. The solvent of this EBR-9 is the same as the solvent used for the resist below (ethyl cellosolve acetate), but mixing can be prevented by the heat treatment at the above-mentioned high temperature.

Next, the same chemically amplified resist as in Example 1 was applied onto this protective film to form a resist layer, and in order to prevent the deactivating substance from the air on the resist layer, A similar coating layer was formed. Subsequently, a pattern was drawn by scanning the resist layer with a high-energy electron beam having a beam diameter of 0.5 μm through the coating layer under the condition of 5 μC / cm ² .

Next, with respect to the resist layer after exposure, 110
After baking at 0 ° C. for 1 minute, a developing treatment is performed using an aqueous TMAH solution (concentration 1.90% or 1.67%) to dissolve only the exposed region of the resist layer in the developing solution. After removal, a resist pattern was formed.

In the resist pattern thus formed, the bottoming was remarkably reduced, and fine lines and spaces were accurately resolved.

Subsequently, the chromium mask substrate on which the resist pattern is formed is exposed to an oxygen asher for 80 seconds so that the lower poly (trifluoroethyl-α-chloroacrylate) corresponding to the space portion of the pattern is formed.
The protective film consisting of was easily removed. Then, by using this resist pattern as an etching mask, the chromium layer of the substrate was subjected to etching treatment, whereby a fine pattern could be transferred with high dimensional accuracy.

[0132]

As described in detail above, according to the present invention,
The shape of the formed resist pattern is improved, and in particular, when the chemically amplified resist is used, the tailing and erosion of the formed pattern are reduced, and the resolution is significantly improved. Therefore, the present invention is effective for ultra-fine processing of electronic parts, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a pattern forming method according to the present invention along each step.

FIG. 2 is a cross-sectional view showing the shape of a resist pattern formed by the method of the present invention.

FIG. 3 is a cross-sectional view showing a shape of a pattern formed using a positive resist by a conventional method.

FIG. 4 is a cross-sectional view showing the shape of a pattern formed using a negative resist by a conventional method.

[Explanation of symbols]

11, 21, 31, 41 ... Substrate, 12, 22 ... Protective film,
13 ... Resist layer, 14 ... Exposure region, 15 ... Exposure, 16
... latent image, 17, 23, 32, 42 ... resist pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Jōnai, 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Corporation Tamagawa factory (72) Inventor Toru Gokawachi Komukai-Toshiba, Kawasaki-shi, Kanagawa Town No. 1 Incorporated company Toshiba Research & Development Center (72) Inventor Satoshi Saito No. 1 Komukai Toshiba Town, Kouki-ku, Kawasaki City, Kanagawa Prefecture Incorporated Toshiba Research & Development Center (72) Inventor Hirokazu Niki Kawasaki City, Kanagawa Prefecture Komukai-Toshiba-cho, No. 1 Inside the Toshiba Research and Development Center, Ltd. (72) Inventor Sai Tada Komukai-Toshi-cho, No. 1 Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Research and Development Center

Claims (1)

[Claims] 1. A step of forming a protective film on a substrate capable of suppressing diffusion of contaminants from the substrate, a compound having a substituent decomposable or crosslinked by an acid on the protective film, and an acid generated by exposure. Forming a resin layer containing a photosensitive composition containing a compound as a main component, pattern exposing the resin layer, baking the resin layer after the exposure at a predetermined temperature, and after baking Developing the resin layer, and selectively removing or leaving the exposed region of the resin layer.