JP2005249807A - Photoresist composition for photomask and method for forming resist pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoresist composition for a photomask with which a pattern shape having a side wall exhibiting high perpendicularity and a cross section being nearly rectangular is obtained in the manufacture of a photomask. <P>SOLUTION: The photoresist composition for a photomask comprises (A) a resin component having a constituting unit derived from an (α-lower alkyl)acrylic acid as a primary component, (B) an acid generator generating an acid by the exposure to a light, and (D) a polymer compound containing a hydroxystyrene constituting unit (d11) and a constituting unit (d12) having a dissolution inhibiting group being dissociated by an acid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photoresist composition for a photomask and a method for forming a resist pattern.

  In photolithography technology, for example, a resist layer made of a resist composition is formed on a substrate, and selectively exposed to radiation such as light and electron beams through a photomask on which a predetermined pattern is formed, and developed. Then, a step of forming a resist pattern having a predetermined shape on the resist layer is performed. A resist composition in which the exposed portion changes to a property that dissolves in the developer is referred to as a positive type, and a resist composition that changes to a property in which the exposed portion does not dissolve in the developer is referred to as a negative type.

By the way, the photomask is also manufactured using a resist composition.
The photomask includes a transparent substrate and a shielding layer formed in a predetermined pattern thereon.
For example, the photomask is conventionally manufactured as follows.
That is, a shielding substrate material provided with a shielding layer mainly composed of a shielding material such as chromium on a transparent substrate such as a glass substrate is prepared, a resist layer is formed thereon, and a photomask for forming a photomask is interposed therebetween. Selective exposure, development, and formation of a resist pattern on the shielding layer.
Next, using the resist pattern as a mask, a portion of the shielding layer where the pattern is not formed is etched to transfer the pattern to the shielding layer, thereby providing a transparent substrate and a shielding layer having a predetermined pattern thereon. A photomask is obtained (for example, see Non-Patent Document 1 below).
Isao Tanabe et al., “The story of photomask technology”, Industrial Research Co., Ltd., first edition, August 20, 1996, p. 10-19

  However, conventionally, when a photomask is manufactured, when a resist layer is formed on the shielding layer of the shielding substrate material and exposed, there is a problem that a favorable pattern shape having a high cross-sectional rectangle with high verticality cannot be obtained. . Specifically, a standing wave is generated on the side wall of the pattern, or the cross-sectional shape of the pattern becomes a T-top shape. In some cases, the pattern collapses, which is a problem. In addition, if the shielding layer is etched using such a defective resist pattern as a mask, the pattern cannot be transferred faithfully, and a precise mask cannot be obtained. This tendency becomes particularly prominent when a resist layer is formed directly on the shielding layer.

Conventionally, in order to improve such a problem of the pattern shape, a technique for devising the shielding substrate material itself has been proposed. For example, it is a multilayer type shielding substrate material in which a chromium oxide interference film is formed on the surface of a chromium film (see Non-Patent Document 1 above). In this shielding substrate material, it is said that the reflectance can be reduced to 20% or less by providing a chromium oxide layer on the chromium layer, thereby improving the problem of the pattern shape.
However, there is a demand for a technique for reducing the problem of the pattern shape by means other than devising the shielding substrate material.

  The present invention has been made in view of the above circumstances, and in manufacturing a photomask, a photoresist composition for a photomask capable of obtaining a pattern shape close to a rectangular cross section with high verticality of the side wall, and the photoresist composition for the photomask are used. It is an object of the present invention to provide a resist pattern forming method.

In order to achieve the above object, a photoresist composition for a photomask according to the present invention comprises (A) a resin component mainly composed of a structural unit derived from (α-lower alkyl) acrylic acid, and (B) exposure. It comprises an acid generator that generates an acid, (D) a hydroxystyrene structural unit (d11), and a polymer compound including a structural unit (d12) having an acid dissociable, dissolution inhibiting group.
In the resist pattern forming method of the present invention, a photoresist composition for a photomask of the present invention is applied on a transparent substrate provided with a shielding layer, pre-baked (PAB), selectively exposed, and then exposed to PEB (exposure). The resist pattern is formed by performing post-heating and alkali development.
In the claims and in this specification, “exposure” includes irradiation with an electron beam or the like.
The “α-lower alkyl acrylic acid” means a hydrogen atom bonded to the α carbon atom of acrylic acid substituted with a lower alkyl group.
“(Α-Lower alkyl) acrylic acid” refers to one or both of α-lower alkylacrylic acid and acrylic acid. “Structural unit” refers to a monomer unit constituting a polymer.
The structural unit derived from (α-lower alkyl) acrylate ester [(α-lower alkyl) acrylate] is a structure formed by cleavage of an ethylenic double bond of (α-lower alkyl) acrylate ester. Unit.

  In the present invention, a photoresist composition for a photomask can be provided in which a pattern shape close to a rectangular cross section with high verticality of side walls can be obtained.

[Photoresist composition for photomask]
The photoresist composition for a photomask of the present invention comprises (A) a resin component mainly composed of a structural unit derived from (α-lower alkyl) acrylic acid, and (B) an acid generator that generates an acid upon exposure, (D) It includes a polymer compound containing a hydroxystyrene structural unit (d11) and a structural unit (d12) having an acid dissociable, dissolution inhibiting group.
By containing the component (A) and the component (D), the pattern shape is improved, and a pattern shape close to a rectangular cross section is obtained.

-(A) Resin Component The resist composition of the present invention can be one or two or more alkali-soluble resins or alkali-soluble resins that are usually used as the base resin for chemically amplified resists as the component (A). Resin can be used. In the former case, a so-called negative type resist composition is used, and in the latter case, a so-called positive type resist composition. The resist composition of the present invention is preferably a positive type.
In the case of the negative type, a crosslinking agent is blended in the resist composition together with the component (B). When an acid is generated from the component (B) by exposure at the time of resist pattern formation, the acid acts to cause crosslinking between the component (A) and the cross-linking agent, resulting in alkali insolubility. As the crosslinking agent, for example, an amino crosslinking agent such as melamine, urea or glycoluril having a methylol group or alkoxymethyl group is usually used.
In the case of the positive type, the component (A) is an alkali-insoluble one having a so-called acid dissociable dissolution inhibiting group. When an acid is generated from the component (B) by exposure, the acid dissociates the acid dissociable dissolution inhibiting group. By dissociating, the component (A) becomes alkali-soluble.

The component (A) is less likely to absorb light with a wavelength of 193 nm from the viewpoint of improving resolution when an ArF excimer laser (wavelength: 193 nm) is used as an exposure light source in both positive and negative types. It is preferable that the structural unit is a main component. This is because the photoresist composition for a photomask of the present invention is useful for a process using an ArF excimer laser (wavelength: 193 nm) as an exposure light source as described later.
Therefore, the component (A) preferably contains a structural unit derived from an (α-lower alkyl) acrylate ester.
In the present invention, a preferable resist composition can be obtained when the constituent unit derived from (α-lower alkyl) acrylic acid is preferably 20 mol% or more, more preferably 50 mol% or more in the component (A). So desirable.
More preferably, the component (A) is a resin component whose main component is a structural unit derived from (α-lower alkyl) acrylic acid. Here, the main component is preferably such that the proportion of structural units derived from (α-lower alkyl) acrylic acid in all structural units constituting the component (A) is 60 mol% or more, preferably 70 mol%. More preferably, it is 80 mol% or more (most preferably 100 mol%).
The structural unit derived from (α-lower alkyl) acrylic acid has an aromatic ring (for example, a benzene ring, a naphthalene ring, etc.) having the ability to absorb light having a wavelength of 193 nm from the viewpoint of improving the resolution. The anthracene ring and the like are preferably composed of structural units that are not contained in the resin skeleton.
In the preferred embodiment, the component (A) may contain a structural unit other than the structural unit derived from (α-lower alkyl) acrylic acid, but from the viewpoint of improving the resolution, the wavelength is 193 nm. It is preferably composed of a structural unit that does not contain an aromatic ring (for example, a benzene ring, a naphthalene ring, an anthracene ring, etc.) in the resin skeleton, such as a hydroxystyrene structural unit or a styrene structural unit, that has the ability to absorb the light. .

  The component (A) includes a structural unit (a1) derived from an (α-lower alkyl) acrylate ester containing a monocyclic or polycyclic group-containing acid dissociable, dissolution inhibiting group, a lactone-containing monocyclic or polycyclic group. Structural unit (a2) derived from (α-lower alkyl) acrylate ester containing cyclic group, Structural unit (a3) derived from (α-lower alkyl) acrylate ester containing hydroxyl group-containing polycyclic group It is preferable to contain. In this case, the component (A) may be a copolymer containing the structural unit or a mixed resin, but is preferably a copolymer.

(A1) to (a4)
・ Structural unit (a1)
The structural unit (a1) is a unit derived from an (α-lower alkyl) acrylate ester containing a monocyclic or polycyclic group-containing acid dissociable, dissolution inhibiting group.
Examples of the monocyclic group include a group obtained by removing one hydrogen atom from a cycloalkane, for example, an aliphatic monocyclic group such as a cyclohexyl group. As the polycyclic group, bicycloalkane, tricycloalkane, tetracycloalkane, etc., a group in which one hydrogen atom is removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, An aliphatic polycyclic group is mentioned. Here, many of these monocyclic groups or polycyclic groups have been proposed in ArF resists, and in the present invention, these monocyclic groups or polycyclic groups can be arbitrarily selected and used. However, it is preferable to use an aliphatic polycyclic group such as an adamantyl group, a norbornyl group, or a tetracyclododecanyl group from the viewpoint of industrial availability.

The acid dissociable, dissolution inhibiting group has an alkali dissolution inhibiting property that makes the entire component (A) insoluble in alkali before exposure, and is dissociated by the action of an acid generated from the component (B) described later after exposure. A) The whole component is changed to alkali-soluble.
As such an acid dissociable, dissolution inhibiting group, for example, those that form a cyclic or chain tertiary alkyl ester with a carboxyl group of (α-lower alkyl) acrylic acid are widely known.
As the structural unit (a1), any unit can be used without particular limitation as long as it has the functions described above. Specifically, at least one structural unit selected from the following general formula (1), (2), or (3) is preferable in that it has excellent resolution and dry etching resistance.

（式中、Ｒは水素原子または低級アルキル基、Ｒ^１は低級アルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group, and R ¹ is a lower alkyl group)

（式中、Ｒは水素原子または低級アルキル基、Ｒ^２およびＲ^３はそれぞれ独立して低級ア
ルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group, and R ² and R ³ are each independently a lower alkyl group)

（式中、Ｒは水素原子または低級アルキル基、Ｒ^４は第３級アルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group, and R ⁴ is a tertiary alkyl group)

In the structural unit represented by the general formula (1), the carbon atom adjacent to the oxygen atom (—O—) of the ester part of (α-lower alkyl) acrylic acid is a third unit on a ring skeleton such as an adamantyl group. This is the case when it becomes a secondary alkyl group.
R is a hydrogen atom or a methyl group, and further a lower alkyl group of about C2 to C5, specifically an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, Examples include lower linear or branched alkyl groups such as an isopentyl group and neopentyl group, and a hydrogen atom or a methyl group is preferable.
R ¹ is a lower linear or branched group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, or a neopentyl group. Of the alkyl group. Here, if R ¹ is an alkyl group having 2 or more carbon atoms, the acid dissociation tends to be higher than that of a methyl group, which is preferable. However, industrially, a methyl group or an ethyl group is most preferable.

In the structural unit represented by the general formula (2), the carbon atom adjacent to the oxygen atom (—O—) of the ester portion of (α-lower alkyl) acrylic acid is a tertiary alkyl group, Further, a ring skeleton such as an adamantyl group is present. In the structural unit represented by the general formula (2), R has the same definition as in the general formula (1), and R ² and R ³ are independent lower alkyl groups, that is, about the above-described C1 to C5. These are linear or branched alkyl groups. Such groups tend to be more acid dissociable than 2-methyl-2-adamantyl groups. In addition, it is industrially preferable that R ² and R ³ are both methyl groups.

The structural unit represented by the general formula (3) is not a (α-lower alkyl) acrylic ester part, but a carbon atom adjacent to an oxygen atom (—O—) of another ester part is a tertiary alkyl group. Yes, this is the case where the ester moiety and the (α-lower alkyl) acrylic acid ester moiety are linked by a ring skeleton such as a tetracyclododecanyl group. In the unit represented by the general formula (3), R has the same definition as in the general formula (1), and R ⁴ is a tertiary alkyl group such as a tert-butyl group or a tert-amyl group. . As for ^{R 4} is, to an tert- butyl group is preferred industrially.
Among the structural units represented by the general formulas (1) to (3), particularly, the structural unit represented by the general formula (1), and R ¹ is a methyl group or an ethyl group However, it is preferable in terms of excellent resolution.

・ Structural unit (a2)
The structural unit (a2) is a structural unit derived from an (α-lower alkyl) acrylate ester containing a lactone-containing monocyclic or polycyclic group. The lactone functional group is effective in increasing the adhesion of the resist film formed from the composition of the present invention to the shielding substrate material or increasing the hydrophilicity with the developer.
As the structural unit (a2), any unit can be used without particular limitation as long as it has both such a lactone functional group and a cyclic group.
Specifically, examples of the lactone-containing monocyclic group include groups obtained by removing one hydrogen atom from γ-butyrolactone, and examples of the lactone-containing polycyclic group include bicycloalkanes having a lactone group, tricyclo groups. Examples include groups in which one hydrogen atom has been removed from an alkane or tetracycloalkane. In particular, a group obtained by removing one hydrogen atom from a lactone-containing tricycloalkane having the following structural formula (6) or structural formula (7) is advantageous in that it is easily available in the industry.

  Specific examples of the structural unit (a2) include structural units derived from (α-lower alkyl) acrylate esters containing a lactone-containing monocycloalkyl group or tricycloalkyl group, and more specifically. And structural units represented by the following general formulas (8) to (10).

（式中、Ｒは水素原子または低級アルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group)

結合位置が５位又は６位の異性体の混合物として存在する。
（式中、Ｒは水素原子または低級アルキル基である）

It exists as a mixture of isomers at the 5-position or 6-position.
(Wherein R is a hydrogen atom or a lower alkyl group)

（式中、Ｒは水素原子または低級アルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group)

In addition, among the structural units represented by the general formulas (8) to (10), the general formula having an ester bond on the α carbon (for example, the effect of suppressing and reducing the proximity effect is excellent) The structural unit derived from γ-butyrolactone ester of (α-lower alkyl) acrylic acid represented by 10), that is, (α-lower alkyl) acrylate ester of γ-butyrolactone is preferred.
In addition, a structural unit derived from a norbornane lactone ester of (α-lower alkyl) acrylic acid represented by the general formulas (8) and (9), that is, a (α-lower alkyl) acrylate ester of norbornane lactone is obtained. This is preferable because the shape of the resist pattern to be formed, for example, rectangularity is even better. In particular, the structural unit represented by the general formula (9) is preferable because of its extremely high effect.

The structural unit (a3) is a structural unit derived from an (α-lower alkyl) acrylate ester containing a hydroxyl group-containing polycyclic group, and has a hydroxyl group that is a polar group, thereby developing the entire component (A). This improves the hydrophilicity with the liquid and improves the alkali solubility of the exposed portion, thereby contributing to the improvement of the resolution. Here, as the polycyclic group, the same polycyclic group as in the structural unit (a1) can be used.
Such a structural unit (a3) is not particularly limited as long as it is a hydroxyl group-containing polycyclic group, and any unit can be used. Specifically, a hydroxyl group-containing adamantyl group, particularly a structural unit represented by the following general formula (4) is preferable in that it has an effect of increasing dry etching resistance and an effect of making the pattern cross section rectangular.

（式中、Ｒは水素原子または低級アルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group)

The component (A) preferably further has the following structural unit (a4).
・ Structural unit (a4)
The structural unit (a4) is a structural unit derived from an (α-lower alkyl) acrylate ester containing a polycyclic group-containing non-acid dissociable, dissolution inhibiting group other than the structural units (a2) and (a3). .
A structural unit derived from an (α-lower alkyl) acrylate ester containing a polycyclic group-containing non-acid dissociable, dissolution inhibiting group means that the hydrophobicity of the entire component (A) before and after exposure is increased and alkali solubility is increased. It is a structural unit having a function to suppress. That is, the alkali solubility of the entire component (A) before exposure is reduced, and the acid dissociable dissolution of the structural unit (a1) is suppressed without being dissociated by the action of an acid generated from the component (B) after exposure. It is a structural unit containing a group having a dissolution inhibitory property that reduces the alkali solubility of the entire component (A) when the entire component (A) is changed to alkali-soluble due to the dissociation of the group within a range that does not become insoluble in alkali.
The structural unit (a4) does not overlap with the structural unit (a1), the structural unit (a2), or the structural unit (a3). That is, none of the groups such as the acid dissociable, dissolution inhibiting group in the structural unit (a1), the lactone group in the structural unit (a2), and the hydroxyl group in the structural unit (a3) are retained.
As the polycyclic group for the structural unit (a4), the same polycyclic groups as those for the structural unit (a1) can be used.
As such a structural unit (a4), many conventionally known ArF positive resist materials can be used. Particularly, tricyclodecanyl (α-lower alkyl) acrylate, adamantyl (α- A structural unit derived from at least one selected from lower alkyl) acrylate and tetracyclododecanyl (α-lower alkyl) acrylate is preferable in terms of industrial availability. These exemplified structural units are shown below as general formulas (11) to (13). Among these, the structural unit represented by the general formula (11) is preferable because the shape of the obtained resist pattern, for example, rectangularity is particularly good.

結合位置が５位又は６位の異性体の混合物として存在する。
（式中、Ｒは水素原子または低級アルキル基である）

It exists as a mixture of isomers at the 5-position or 6-position.
(Wherein R is a hydrogen atom or a lower alkyl group)

（式中、Ｒは水素原子または低級アルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group)

（式中、Ｒは水素原子または低級アルキル基である）

(Wherein R is a hydrogen atom or a lower alkyl group)

As the component (A), at least one structural unit selected from the general formulas (1) to (3) and at least one structural unit selected from the general formulas (8) to (10) Those having a structural unit represented by the general formula (4) are preferred.
In particular, the structural unit (a1) includes the structural unit represented by the general formula (1), the structural unit (a2) includes the structural unit represented by the general formula (10), and the structural unit (a3 ) Is preferably a copolymer containing at least three structural units including the structural unit represented by the general formula (4).

(A) About the ratio of each structural unit (a1)-(a3) in a component, structural unit (a1) is 25-50 mol%, Preferably it is the range of 30-40 mol%, and structural unit (a2) Is in the range of 25 to 50 mol%, preferably 30 to 40 mol%, and the structural unit (a3) is in the range of 10 to 30 mol%, preferably 10 to 20 mol%.
When the structural unit (a4) is included, the structural unit (a4) is preferably in the range of 3 to 25 mol%, preferably 5 to 20 mol%.
With such a range, the depth of focus of the isolated pattern formed from the resist composition obtained can be greatly improved, and the proximity effect can be sufficiently suppressed to greatly reduce this. In addition, if it deviates greatly from the said range, there exists a possibility that the malfunction that resolution may fall may arise.

  The resin component exemplified above can be obtained by polymerizing a monomer for deriving each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN). .

  The weight average molecular weight (Mw: polystyrene conversion standard by gel permeation chromatography) of the component (A) is 3000 to 30000, preferably 5000 to 20000.

-(B) Acid generator (B) A component is not specifically limited, The well-known acid generator currently used in the chemically amplified photoresist composition can be used.
Various acid generators have been known such as onium salts such as iodonium salts and sulfonium salts, oxime sulfonates, bisalkyl or bisarylsulfonyldiazomethanes, nitrobenzyl sulfonates, iminosulfonates, and disulfones. Therefore, these known acid generators can be used without particular limitation.
Of these, onium salts containing fluorinated alkyl sulfonate ions as anions (hereinafter referred to as onium salt acid generators) are particularly preferred because the strength of the acid generated is strong.
Examples of the cation of the onium salt acid generator include a lower alkyl group such as a methyl group, an ethyl group, a propyl group, an n-butyl group and a tert-butyl group; a lower alkoxy group such as a methoxy group and an ethoxy group. Preferred are mono- or diphenyliodonium, mono-, di-, or triphenylsulfonium; dimethyl (4-hydroxynaphthyl) sulfonium and the like.

  The anion of the onium salt acid generator is a fluorine atom in which part or all of the hydrogen atoms of a linear alkyl group having 1 to 7 carbon atoms, more preferably 1 to 3 carbon atoms are substituted with fluorine atoms. Alkyl sulfonate ions are preferred because of their high safety. When the number of carbon atoms is 7 or less, the strength as a sulfonic acid is increased. Further, the fluorination rate of the fluorinated alkyl sulfonate ion (ratio of fluorine atoms in the alkyl group) is preferably 10 to 100%, more preferably 50 to 100%. Particularly, all the hydrogen atoms are fluorine atoms. The substituted one is preferable because the strength of the acid is increased. Specific examples thereof include trifluoromethane sulfonate, heptafluoropropane sulfonate, and nonafluorobutane sulfonate.

Specific examples of such onium salt acid generators include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, triphenylsulfonium. Trifluoromethanesulfonate, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, tri (4-methylphenyl) sulfonium trifluoromethanesulfonate, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, dimethyl (4-hydroxynaphthyl) sulfonium Trifluoromethanesulfonate, its heptafluoropropanesulfonate Or its nonafluorobutane sulfonate, monophenyldimethylsulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, diphenyl monomethylsulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, etc. Is mentioned.
(B) A component can be used individually by 1 type or in mixture of 2 or more types.

  The content of the component (B) is preferably 0.5 to 30 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the component (A). By setting the amount to 0.5 parts by mass or more, the acid dissociable, dissolution inhibiting group (A) component (in the case of positive type) or (A) component and a crosslinking agent (in the case of negative type) are provided with the necessary acid component. And can be resolved. By setting it as 30 mass parts or less, a uniform solution can be obtained and the storage stability of a resist composition becomes favorable.

-(C) Organic solvent The resist composition of the present invention can be produced by dissolving or dispersing the material in the component (C).
As the component (C), any component can be used as long as it can dissolve each component to be used to form a uniform solution, and any one of conventionally known solvents for chemically amplified resists can be used. Two or more types can be appropriately selected and used.
For example, ketones such as γ-butyrolactone, acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol Or polyhydric alcohols such as monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether of dipropylene glycol monoacetate and derivatives thereof, cyclic ethers such as dioxane, methyl lactate, lactic acid Ethyl (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy Methyl propionate, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.

Among these, a mixed solvent of propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable. The mass ratio between PGMEA and the polar solvent may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, but is preferably 1: 9 to 8: 2, more preferably 2: 8 to 5: 5. It is preferable to be within the range.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 2: 8 to 5: 5, more preferably 3: 7 to 4: 6. In addition, as the organic solvent, a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone is also preferable. In this case, the mixing ratio of the former and the latter is preferably 70:30 to 95: 5.

  (C) Although the usage-amount of a component is not specifically limited, Although it is a density | concentration which can be apply | coated to a board | substrate etc. and is suitably set according to a coating film thickness, generally the solid content density | concentration 2-2 of a resist composition. It is within the range of 20% by mass, preferably 5-15% by mass.

In the photoresist composition of the present invention, a polymer compound containing a hydroxystyrene structural unit (d11) and a structural unit (d12) having an acid dissociable, dissolution inhibiting group is used as the component (D). When a resist pattern is formed using a photoresist composition containing such a polymer compound (D), the contrast is particularly excellent. Moreover, it can contribute to the absorptivity in wavelength 193nm by having an aromatic ring.
The hydroxystyrene structural unit (d11) (hereinafter sometimes referred to as “hydroxystyrene unit”) is a structural unit represented by the following general formula.

（式中、Ｒは水素原子または低級アルキル基を表し、ｍは１〜３の整数である。）

(In the formula, R represents a hydrogen atom or a lower alkyl group, and m is an integer of 1 to 3.)

  R represents a hydrogen atom or a linear or branched lower alkyl group having 1 to 5 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group) Group, isopentyl group, neopentyl group), preferably a hydrogen atom. Moreover, it is preferable that m = 1. When m = 1 in the above formula (14), the position of the hydroxyl group may be any of the o-position, m-position, and p-position, but the p-position is easily available and inexpensive. preferable.

The structural unit (d12) having an acid dissociable, dissolution inhibiting group (hereinafter sometimes referred to as “unit having an acid dissociable, dissolution inhibiting group”) may be a unit derived from the above hydroxystyrene unit. The unit may be derived from other structural units.
Examples of the unit derived from a hydroxystyrene unit and having an acid dissociable, dissolution inhibiting group include those in which the hydrogen atom of the hydroxyl group of the hydroxystyrene unit is substituted with an acid dissociable, dissolution inhibiting group.
The other unit derived from a structural unit and having an acid dissociable, dissolution inhibiting group is a unit derived from (α-lower alkyl) acrylic acid, and is a hydrogen atom of the carboxyl group of (α-lower alkyl) acrylic acid. Are units substituted with an acid dissociable, dissolution inhibiting group. Specific examples of such a structural unit include the structural unit (a1) described in the component (A).

  The acid dissociable, dissolution inhibiting group can be arbitrarily selected from the groups used for protecting the hydroxyl group of the film-forming component resin in the conventional chemically amplified positive resist. In view of acid dissociability, heat resistance, pattern shape and the like, a tertiary alkoxycarbonyl group, a tertiary alkyl group, an alkoxyalkyl group and a cyclic ether group are preferred. Examples of the tertiary alkoxycarbonyl group include a tert-butyloxycarbonyl group and tert-amyloxycarbonyl group. Examples of the tertiary alkyl group include a tert-butyl group and tert-amyl group. . Examples of the cyclic ether group include a tetrahydropyranyl group and a tetrahydrofuranyl group. Examples of the alkoxyalkyl group include lower alkoxyalkyl groups such as a 1-ethoxyethyl group and a 1-methoxypropyl group.

The content of the hydroxystyrene unit (d11) is 60 to 90 mol%, preferably 70 to 85 mol%, relative to 100 mol% of the component (D). This is because it is advantageous in increasing the contrast. The content of the unit (d12) having an acid dissociable, dissolution inhibiting group is 5 to 40 mol%, preferably 10 to 30 mol%, relative to 100 mol% of the component (D). This is because it is advantageous in increasing dry etching resistance.
Moreover, it is preferable that the mass mean molecular weight (Mw: polystyrene conversion reference | standard by gel permeation chromatography) of this high molecular compound (D) is 3000-50000, Preferably it is 5000-20000.

  The polymer compound may contain other structural units in addition to the structural units (d11) and (d12). As another structural unit, a styrene-type unit (d13) etc. are mentioned, for example. The styrenic unit is a structural unit represented by the following general formula (15).

（式中、Ｒは水素原子または低級アルキル基を表し、Ｒ^５は低級アルキル基を示し、ｎは０または１〜３の整数である。）

(In the formula, R represents a hydrogen atom or a lower alkyl group, R ⁵ represents a lower alkyl group, and n is 0 or an integer of 1 to 3).

R represents a hydrogen atom or a straight or branched lower alkyl group having 1 to 5 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group). Group, isopentyl group, neopentyl group), preferably a hydrogen atom. R ⁵ is a linear or branched lower alkyl group having 1 to 5 carbon atoms, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl Group, isopentyl group, neopentyl group and the like. R ⁵ is preferably a methyl group or an ethyl group industrially.
The n is 0 or an integer of 1 to 3. Of these, n is preferably 0 or 1, and is particularly preferably 0 industrially.
When n is 1 to 3, the substitution position of R ⁵ may be any of the o-position, m-position, and p-position, and when n is 2 or 3, any substitution is possible. The positions can be combined.

Since the styrenic unit contains an aromatic ring, it can contribute to the absorption ability of the component (D) at a wavelength of 193 nm.
When using a styrene-type unit, 5-30 mol% is preferable with respect to 100 mol% of (D) component, and its 7-20 mol% is more preferable.

  Among the polymer compounds (D), a copolymer containing a structural unit represented by the following general formula (16) is preferably used.

  (D) Although the compounding quantity of a component is suitably adjusted with the light absorptivity of the wavelength of 193 nm, it is 3-15 mass parts with respect to 100 mass parts of (A) component, Preferably it is 5-10 mass parts. By setting it as the above range, the resist pattern can be formed into a rectangular shape.

-(E) Nitrogen-containing organic compound In the photoresist composition of the present invention, a nitrogen-containing organic compound (E) ((E) is further added as an optional component in order to improve the resist pattern shape, the stability over time and the like. Component) can be blended.
Since a wide variety of components (E) have already been proposed, any known one may be used, but amines, particularly secondary lower aliphatic amines and tertiary lower aliphatic amines are preferred. .
Here, the lower aliphatic amine refers to an alkyl or alkyl alcohol amine having 5 or less carbon atoms, and examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, Tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, triisopropanolamine and the like can be mentioned, and tertiary alkanolamines such as triethanolamine are particularly preferable.
(E) A component may be used independently and may be used in combination of 2 or more type.
(E) A component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

-(F) component Moreover, the organic carboxylic acid or phosphorus oxo acid is further included as an optional component for the purpose of preventing sensitivity deterioration due to the blending of the (E) component and improving the resist pattern shape, retention stability, etc. Or its derivative (F) (henceforth (F) component) can be contained. As the organic carboxylic acid, for example, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Phosphorus oxoacids or derivatives thereof include phosphoric acid, phosphoric acid di-n-butyl ester, phosphoric acid diphenyl ester and other phosphoric acid or derivatives thereof such as phosphonic acid, phosphonic acid dimethyl ester, phosphonic acid- Like phosphonic acids such as di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, phosphonic acid dibenzyl ester and derivatives thereof, phosphinic acids such as phosphinic acid, phenylphosphinic acid and their esters Among these, phosphonic acid is particularly preferable.
Component (F) is used in a proportion of 0.01 to 5.0 parts by mass per 100 parts by mass of component (A).

Other optional components The photoresist composition for photomasks of the present invention may further contain miscible additives as desired, for example, additional resins for improving the performance of resist films, and surfactants for improving coating properties. Further, a dissolution inhibitor, a plasticizer, a stabilizer, a colorant, an antihalation agent, and the like can be appropriately added and contained.

[Photomask manufacturing method]
Hereinafter, the photomask material, manufacturing process, and the like that are preferable when the photomask photoresist composition of the present invention is applied will be described.

-Shielding substrate material A shielding substrate material has a transparent substrate and the shielding layer (before pattern formation) provided on it.
.. Transparent substrate As the transparent substrate, a film made of a synthetic resin such as polyester or a glass substrate can be used, but a glass substrate is preferable in terms of processing accuracy, heat resistance, mechanical strength, and the like. Examples of the glass substrate include substrates made of soda lime glass, low expansion glass, quartz glass, and the like, and any of them can be used and is appropriately selected depending on the use and the like. The shape, size, thickness, and the like of the substrate can be appropriately selected depending on the application.

.. Shielding layer A metal thin film is generally used as the light shielding material for forming the shielding layer.
As a material for the metal thin film, chromium is mainly used, but other examples include silicon, iron oxide, molybdenum silicon side, and the like.
Conventional methods can be applied to the method of forming the shielding layer on the transparent substrate. The thickness and the like of the shielding layer can be appropriately selected depending on the application.

-Procedure of manufacturing method Hereinafter, the case where the shielding board | substrate material provided with the shielding layer which consists of metal thin films, such as chromium, on a glass substrate is demonstrated as an example.
First, the photoresist composition for a photomask of the present invention is applied on the shielding layer of the shielding substrate material with a spinner or the like. Then, pre-baking is performed for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C., and ArF excimer laser light is selectively exposed through a desired mask, for example, using an ArF exposure apparatus or the like. After that, PEB (post-exposure heating) is applied for 40 to 120 seconds, preferably 60 to 90 seconds, at a temperature of 80 to 150 ° C. Next, this is developed using an alkali developer, for example, an aqueous solution of 0.1 to 10% by mass of tetramethylammonium hydroxide (TMAH). In this way, a resist pattern faithful to the mask pattern can be obtained.

The type (form) of the pattern is not particularly limited and can be appropriately selected depending on the application, etc., but for the line shape that easily causes the above pattern shape problem, such as an L & S (line and space) pattern, an isolated line pattern, etc. The photoresist composition for a photomask of the present invention is particularly effective.
The wavelength used for exposure is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray It can be performed using radiation. In particular, the photoresist composition for a photomask of the present invention is effective for an ArF excimer laser that is advantageous in terms of fine processing and throughput.

  Next, using the resist pattern as a mask, the underlying shielding layer is etched, and the pattern is transferred to the shielding layer. Finally, the photomask is obtained by removing the resist pattern.

  An organic or inorganic antireflection film may be provided between the shielding substrate material and the coating layer of the resist composition. However, when the photoresist composition for a photomask of the present invention is used, the pattern shape can be improved without providing an antireflection film. This is because it is necessary to further remove the antireflection film. Moreover, it is very difficult to selectively remove only the antireflection film having a film thickness of about 50 to 80 nm, for example, by dry etching, and as a result, the underlying shielding layer may be eroded. It is.

  As described above, by using the photoresist composition for a photomask of the present invention, a resist pattern formed at the time of manufacturing the photomask can have a pattern shape with a high verticality of the side wall and close to a rectangular cross section. Specifically, it is possible to improve the problem that a standing wave is generated on the side wall of the pattern or the cross-sectional shape of the pattern becomes a T-top shape. This problem can also be improved when a resist layer is formed directly on the shielding layer.

Hereinafter, the present invention will be described in more detail with reference to examples.
-Production of photoresist composition "Example 1"
The following components were mixed to produce a positive photoresist composition.

Component (A): A copolymer composed of structural units represented by the following general formula [n: m: l = 40: 40: 20 (mol%) Mw = 10000] 100 parts by mass

(B) component: triphenylsulfonium nonafluorobutane sulfonate, (A) 2.5 mass parts with respect to 100 mass parts of component

Component (C): Mixed solvent of PGMEA and EL in a mass ratio of 6: 4 Prepared so that the solid content concentration of the resist composition is 9% by mass. Component (D): Copolymer composed of structural units represented by the following general formula Polymer [p: q: r = 65: 10: 25 (mol%), Mw = 12000, Mw / Mn = 2.0], (A) 10 parts by mass with respect to 100 parts by mass of component

(E) component: triethanolamine, (A) 0.25 mass part with respect to 100 mass parts of component

"Comparative Example 1"
A photoresist composition was produced in the same manner as in Example 1 except that the component (D) was not used.

-Formation of resist pattern After a HMDS (hexamethyldisilazane) treatment is applied to a shielding substrate material in which a shielding layer made of chromium is laminated on a glass substrate, a positive photoresist composition is uniformly formed at a film thickness of 300 nm. The film was applied and subjected to a pre-baking process (PAB) at 135 ° C. for 90 seconds.
Next, selective exposure was performed through a binary mask with NSR S-302B (NA = 0.60, 2/3 annu) manufactured by Nikon Corporation, baking at 135 ° C. for 90 seconds (PEB), 2.38% by mass of TMAH. After developing for 60 seconds with a concentrated aqueous solution, rinsing with pure water for 30 seconds, shaking off and drying, baking was performed at 100 ° C. for 60 seconds.
The above operations were performed for three types of resist patterns of L & S patterns having a width of 150 nm, 200 nm, and 300 nm, and the cross-sectional shapes of the obtained patterns were observed and evaluated.

-Results Example 1: A good pattern having a rectangular cross section was obtained at any pattern size.
Comparative Example 1 (Example in which component (D) is not used): The cross-sectional shape was T-top in any pattern size. In particular, pattern collapse was observed at a pattern width of 150 nm.
From these results, it was confirmed that the pattern shape can be improved in the example according to the present invention.
Therefore, in the laminate of the shielding substrate material and the resist pattern obtained in Example 1, it was found that a photomask having a shielding pattern faithful to the resist pattern can be obtained by etching the shielding layer and removing the resist pattern. .

Claims (9)

(A) a resin component whose main component is a structural unit derived from (α-lower alkyl) acrylic acid, (B) an acid generator that generates acid upon exposure, and (D) a hydroxystyrene structural unit (d11). And a high molecular compound containing the structural unit (d12) having an acid dissociable, dissolution inhibiting group. A photoresist composition for a photomask, comprising:   The photoresist composition for a photomask according to claim 1, wherein the component (D) further contains a styrene-based unit (d13). 3. The photomask resist composition according to claim 1, wherein the component (D) is a copolymer containing a structural unit represented by the following general formula.

  Component (A) is a structural unit (a1) derived from an (α-lower alkyl) acrylate ester containing a monocyclic or polycyclic group-containing acid dissociable, dissolution inhibiting group, a lactone-containing monocycle or polycycle A structural unit (a2) derived from an (α-lower alkyl) acrylate ester containing a formula group, and a structural unit (a3) derived from an (α-lower alkyl) acrylate ester containing a hydroxyl group-containing polycyclic group. The photoresist composition for a photomask according to any one of claims 1 to 3. The structural unit (a1) is represented by the following general formula:

(Wherein R is a hydrogen atom or a lower alkyl group, and R ¹ is a lower alkyl group)

(Wherein R is a hydrogen atom or a lower alkyl group, and R ² and R ³ are each independently a lower alkyl group)

(Wherein R is a hydrogen atom or a lower alkyl group, and R ⁴ is a tertiary alkyl group)
At least one kind of structural unit selected from the structural units represented by:
The structural unit (a2) is represented by the following general formula:

(Wherein R is a hydrogen atom or a lower alkyl group)

(Wherein R is a hydrogen atom or a lower alkyl group)

(Wherein R is a hydrogen atom or a lower alkyl group)
At least one structural unit selected from structural units represented by:
And said structural unit (a3) is the following general formula

(Wherein R is a hydrogen atom or a lower alkyl group)
The photoresist composition for a photomask according to claim 4, wherein the photoresist composition is represented by the formula: 6. The photoresist composition for a photomask according to claim 5, wherein the component (A) is a copolymer containing structural units represented by the following general formula.

  7. The photoresist composition for a photomask according to claim 1, wherein the component (B) is an onium salt containing a fluorinated alkyl sulfonate ion as an anion.   The photoresist composition for a photomask according to any one of claims 1 to 7, further comprising (E) a nitrogen-containing organic compound. A photoresist composition for a photomask according to any one of claims 1 to 8 is applied on a transparent substrate provided with a shielding layer, pre-baked (PAB), selectively exposed, and then exposed to PEB (exposure). A resist pattern forming method comprising: performing post-heating) and performing alkali development to form a resist pattern.