JP2008098231A - Resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel resist pattern forming method capable of forming a resist pattern in a good shape with high resolution. <P>SOLUTION: The resist pattern forming method includes steps of applying a chemically amplified resist composition on a base 1 to form a resist film 2 and selectively exposing the resist film 2 through a photo mask 5 a plurality of times, wherein a total of transmissivity of a light-shielding part of the photo mask 5 used for each of selective exposures is 0 to less than 12%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a resist pattern forming method.

A technology (pattern formation technology) that forms a fine pattern on a substrate and processes the lower layer of the pattern by etching using this as a mask has been widely adopted for IC creation in the semiconductor industry, and has received great attention. ing.
The fine pattern is usually made of an organic material, and is formed by a technique such as a lithography method or a nanoimprint method. For example, in the lithography method, a resist film made of a resist composition containing a base material component such as a resin is formed on a support such as a substrate, and a photomask in which a predetermined pattern is formed on the resist film ( A step of forming a resist pattern having a predetermined shape on the resist film is performed by performing selective exposure with radiation such as light and electron beam through a mask pattern) and performing development processing. 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.
And a semiconductor element etc. are manufactured through the process of processing a board | substrate by an etching using the said resist pattern as a mask.

In recent years, the miniaturization of patterns has been rapidly progressed by the advancement of lithography technology.
As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, conventionally, ultraviolet rays typified by g-line and i-line have been used, but now mass production of semiconductor elements using KrF excimer laser and ArF excimer laser has been started. Lithography using an ArF excimer laser enables pattern formation with a resolution of 45 nm. In addition, in order to further improve the resolution, studies have been made on F ₂ excimer lasers, electron beams, EUV (extreme ultraviolet rays), X-rays, and the like having shorter wavelengths than these excimer lasers.
The resist composition is required to have lithography characteristics such as sensitivity to these exposure light sources and resolution capable of reproducing a pattern with fine dimensions. As a resist composition satisfying such requirements, a chemically amplified resist composition containing a base material component whose alkali solubility is changed by the action of an acid and an acid generator that generates an acid upon exposure is used. (For example, refer to Patent Document 1). For example, a positive chemically amplified resist usually contains a resin whose alkali solubility is increased by the action of an acid as a base component, and when acid is generated from an acid generator by exposure during resist pattern formation, The exposed part becomes alkali-soluble.

As one of the methods for further improving the resolution, exposure (immersion exposure) is performed by interposing a liquid (immersion medium) having a higher refractive index than air between the objective lens of the exposure machine and the sample. A so-called immersion lithography (hereinafter referred to as “immersion exposure”) is known (for example, see Non-Patent Document 1).
According to immersion exposure, even when a light source having the same exposure wavelength is used, the same high resolution as when using a light source with a shorter wavelength or using a high NA lens can be achieved, and the depth of focus can be reduced. It is said that there is no decline. In addition, immersion exposure can be performed by applying an existing exposure apparatus. Therefore, immersion exposure is expected to be able to form a resist pattern with low cost, high resolution, and excellent depth of focus, and in the manufacture of semiconductor devices that require a large capital investment. In particular, in terms of lithography characteristics such as resolution, the semiconductor industry is attracting a great deal of attention.
Immersion exposure is effective in forming all pattern shapes, and can be combined with super-resolution techniques such as the phase shift method and the modified illumination method that are currently being studied. Currently, as an immersion exposure technique, a technique mainly using an ArF excimer laser as a light source is being actively researched. Currently, water is mainly studied as an immersion medium.

Recently, as one of newly proposed lithography techniques, there is a double patterning method in which a resist pattern is formed by performing patterning twice or more (see, for example, Non-Patent Documents 2 to 3).
According to this double patterning method, a pattern finer than a resist pattern formed by one patterning can be formed.
Also, according to the double patterning method, it is possible to form a resist pattern with higher resolution even when using a light source having the same exposure wavelength or using the same resist composition. The double patterning method can be performed using an existing exposure apparatus.
JP 2003-241385 A Proceedings of SPIE, 5754, 119-128 (2005). Proceedings of SPIE, 5256, 985-994 (2003). Proceedings of SPIE, 6153, 615301-1-19 (2006).

However, in the conventional double patterning method, in order to form a pattern on a substrate or the like, the resist film must be patterned at least twice and the substrate or the like must be etched at least twice, which increases the number of processes. As a result, there is a problem such as a decrease in throughput.
Therefore, there is a demand for a resist pattern forming method that can form a fine pattern with a small number of steps.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel resist pattern forming method capable of forming a resist pattern having a good shape and high resolution.

In order to achieve the above object, the present invention employs the following configuration.
That is, an aspect of the present invention is a resist pattern in which a chemically amplified resist composition is applied onto a support to form a resist film, and the resist film is selectively exposed multiple times through a photomask. In this method, the total sum of the transmittances of the light-shielding portions of the photomask used for each selective exposure is set to 0 to less than 12%.

  In the present specification and claims, “exposure” is a concept including general irradiation of radiation.

  According to the present invention, a novel resist pattern forming method capable of forming a resist pattern having a good shape and high resolution can be provided.

≪Resist pattern formation method≫
The resist pattern forming method of the present invention is a method in which a chemically amplified resist composition is applied onto a support to form a resist film, and the resist film is selectively exposed multiple times through a photomask. It is.

<Chemically amplified resist composition>
The chemically amplified resist composition is not particularly limited, and can be selected from among many chemically amplified resist compositions that have been proposed as chemically amplified resist compositions according to the exposure light source used, lithography characteristics, and the like. It can be appropriately selected and used.
The chemically amplified resist composition may be a negative resist composition or a positive resist composition, preferably a positive resist composition.

The chemically amplified resist composition includes a base material component (A) whose alkali solubility is changed by the action of an acid (hereinafter referred to as “component (A)”) and an acid generator component (B) (which generates an acid upon exposure) ( Hereinafter, the component (B) is generally dissolved in the organic solvent (S) (hereinafter referred to as the component (S)).
Here, the “base material component” is an organic compound having a film forming ability, and an organic compound having a molecular weight of 500 or more is preferably used. When the molecular weight of the organic compound is 500 or more, the film-forming ability is improved and a nano-level resist pattern is easily formed.
The organic compound having a molecular weight of 500 or more is roughly classified into a low molecular weight organic compound having a molecular weight of 500 or more and 2000 or less (hereinafter referred to as a low molecular compound) and a high molecular weight resin having a molecular weight of 2000 or more (polymer). Is done. As the low molecular weight compound, a non-polymer is usually used. In the case of a resin (polymer), a polystyrene-reduced weight average molecular weight by GPC (gel permeation chromatography) is used as the “molecular weight”. Hereinafter, the term “resin” simply means a resin having a molecular weight of more than 2000.
The component (A) may be a low molecular compound whose alkali solubility is changed by the action of an acid, a resin whose alkali solubility is changed by the action of an acid, or a mixture thereof. Good.

As the component (A), organic compounds that are usually used as base components for chemically amplified resists can be used alone or in combination of two or more.
The component (A) of the chemically amplified resist composition used in the present invention preferably has a hydrophilic group. By having a hydrophilic group, when a resist pattern is formed using the chemically amplified resist composition, for example, a coating film having good adhesion can be formed uniformly on the resist pattern. it can. That is, when the component (A) has a hydrophilic group, the hydrophilic group exists on the resist pattern surface. The hydrophilic group functions as, for example, a functional group (reactive group) that is firmly bonded to a metal oxide film formed on the resist pattern, whereby a uniformly high-density coating film is formed on the resist pattern. Can be formed.
The hydrophilic group in the component (A) includes a hydroxyl group, a carboxy group, a carbonyl group (—C (O) —), an ester group (ester bond; —C (O) —O—), an amino group, and an amide group. One or more selected from the group consisting of Among these, a hydroxyl group (particularly an alcoholic hydroxyl group or a phenolic hydroxyl group), a carboxy group, and an ester group are more preferable.
Among these, a carboxy group, an alcoholic hydroxyl group, and a phenolic hydroxyl group are particularly preferable because they easily form a coating film on the resist pattern surface, for example. In addition, a resist pattern having a small line edge roughness (unevenness on the pattern side wall) at the nano level can be formed, which is preferable.

The content ratio of the hydrophilic group in the component (A) affects the amount per unit area of the hydrophilic group present on the resist pattern surface. Therefore, for example, the adhesion and density of the coating film formed on the resist pattern can be affected.
When the component (A) is a low molecular compound, the component (A) preferably has 1 to 20 equivalents of hydrophilic groups per molecule, more preferably 2 to 10 equivalents.
Here, “having 1 to 20 equivalents of hydrophilic group per molecule” means that 1 to 20 hydrophilic groups are present in one molecule.
When the component (A) is a resin, the component (A) preferably has a hydrophilic group of 0.2 equivalent or more, more preferably 0.5 to 0.8 equivalent, and still more preferably 0.6 to 0. A range of .75 equivalents. If the resin is composed of a structural unit having a hydrophilic group and other structural units, the former structural unit is 20 mol% or more, more preferably 50 to 80 mol%, and even more preferably 60 mol% to It means 75 mol%.
In the present specification, “structural unit” and “unit” mean a monomer unit constituting a resin (polymer).

When the chemically amplified resist composition is a negative resist composition, as the component (A), a base material component whose alkali solubility is reduced by the action of an acid is used, and a crosslinking agent is further blended.
In such a negative resist composition, when an acid is generated from the component (B) by exposure, crosslinking occurs between the component (A) and the crosslinking agent by the action of the acid, and the component (A) is alkali-soluble to alkali. It turns into insoluble. Therefore, in the formation of a resist pattern, when selective exposure is performed on a resist film obtained by applying the negative resist composition on a substrate, the exposed portion turns into alkali-insoluble while the unexposed portion becomes alkaline. Since it remains soluble, it can be developed with an alkali.
As the component (A) of the negative resist composition, an alkali-soluble resin is usually used. As the alkali-soluble resin, α- (hydroxyalkyl) acrylic acid or lower alkyl of α- (hydroxyalkyl) acrylic acid is used. A resin having a unit derived from at least one selected from esters is preferable because a good resist pattern with less swelling can be formed. In addition, α- (hydroxyalkyl) acrylic acid includes acrylic acid in which a hydrogen atom is bonded to the α-position carbon atom to which the carboxy group is bonded, and a hydroxyalkyl group (preferably having a carbon number) in the α-position carbon atom. One or both of α-hydroxyalkylacrylic acid to which 1-5 hydroxyalkyl groups) are bonded.
As the crosslinking agent, for example, it is usually preferable to use an amino crosslinking agent such as glycoluril having a methylol group or an alkoxymethyl group because a good resist pattern with less swelling can be formed. It is preferable that the compounding quantity of a crosslinking agent is 1-50 mass parts with respect to 100 mass parts of alkali-soluble resin.

When the chemically amplified resist composition is a positive resist composition, as the component (A), a base component having an acid dissociable, dissolution inhibiting group and increasing alkali solubility by the action of an acid is used.
Such a positive resist composition is insoluble in alkali before exposure. When an acid is generated from the component (B) by exposure during resist pattern formation, the acid dissociable, dissolution inhibiting group is dissociated by the action of the acid, and (A ) The component changes to alkali-soluble. Therefore, in the formation of a resist pattern, when selective exposure is performed on a resist film obtained by applying the positive resist composition on a substrate, the exposed portion turns alkali-soluble, while the unexposed portion becomes alkaline. Since it remains insoluble and does not change, alkali development can be performed.

As the (A) component of the positive resist composition, those having a hydrophilic group and an acid dissociable, dissolution inhibiting group are preferred, and the following (A-1) component and / or (A-2) component are more preferred.
The hydrophilic group may also serve as an acid dissociable, dissolution inhibiting group.
Component (A-1): a resin having a hydrophilic group and an acid dissociable, dissolution inhibiting group.
Component (A-2): a low molecular compound having a hydrophilic group and an acid dissociable, dissolution inhibiting group.
Hereinafter, preferred embodiments of the component (A-1) and the component (A-2) will be described more specifically.

[(A-1) component]
As the component (A-1), a resin having a structural unit having a hydrophilic group and a structural unit having an acid dissociable, dissolution inhibiting group is preferable.
The proportion of the structural unit having the hydrophilic group in the resin is preferably 20 to 80 mol%, more preferably 20 to 70 mol%, based on the total amount of all the structural units constituting the resin. 20 to 60 mol% is more preferable.
The proportion of the structural unit having the acid dissociable, dissolution inhibiting group in the resin is preferably 20 to 80 mol% with respect to the total amount of all structural units constituting the resin. Is more preferable, and 30 to 60 mol% is more preferable.
Preferably, the structural unit having a hydrophilic group is a structural unit having a carboxy group, an alcoholic hydroxyl group or a phenolic hydroxyl group, more preferably an acrylic acid, methacrylic acid or an alcoholic hydroxyl group (α-lower alkyl). A unit derived from an acrylate ester and hydroxystyrene.

More specifically, the component (A-1) is derived from a novolak resin having a hydrophilic group and an acid dissociable, dissolution inhibiting group, a hydroxystyrene resin, an (α-lower alkyl) acrylate resin, and hydroxystyrene. And a copolymer resin containing a structural unit derived from an (α-lower alkyl) acrylate ester are preferably used.
In this specification, “(α-lower alkyl) acrylic acid” refers to one or both of acrylic acid (CH ₂ ═CH—COOH) and α-lower alkylacrylic acid.
α-Lower alkyl acrylic acid refers to one in which a hydrogen atom bonded to a carbon atom to which a carbonyl group in acrylic acid is bonded is substituted with a lower alkyl group.
“(Α-Lower alkyl) acrylic acid ester” is an ester derivative of “(α-lower alkyl) acrylic acid” and represents one or both of acrylic acid ester and α-lower alkyl acrylic acid ester.
The “structural unit derived from (α-lower alkyl) acrylic acid ester” is a structural unit formed by cleavage of an ethylenic double bond of (α-lower alkyl) acrylic acid ester. -Lower alkyl) acrylate structural unit.
“(Α-lower alkyl) acrylate” refers to one or both of acrylate and α-lower alkyl acrylate.
The “structural unit derived from hydroxystyrene” is a structural unit formed by cleaving an ethylenic double bond of hydroxystyrene or α-lower alkylhydroxystyrene, and may hereinafter be referred to as a hydroxystyrene unit.
“Α-lower alkylhydroxystyrene” indicates that the lower alkyl group is bonded to the carbon atom to which the phenyl group is bonded.
In the “structural unit derived from an α-lower alkyl acrylate ester” and the “structural unit derived from an α-lower alkylhydroxystyrene”, the lower alkyl group bonded to the α-position has 1 to 5 carbon atoms. An alkyl group, preferably a linear or branched alkyl group, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group Etc. Industrially, a methyl group is preferable.

The resin component suitable as the component (A-1) is not particularly limited. For example, a unit having a phenolic hydroxyl group such as the following structural unit (a1), the following structural unit (a2) and the following structural unit Resin component having a structural unit having at least one acid dissociable, dissolution inhibiting group selected from the group consisting of units (a3), and an alkali-insoluble unit such as structural unit (a4) used as necessary Hereinafter, it may be referred to as (A-11) component).
In the component (A-11), cleavage occurs in the structural unit (a2) and / or the structural unit (a3) by the action of the acid generated from the acid generator upon exposure. In the resin which is insoluble to the resin, the alkali solubility is increased. As a result, a chemically amplified positive resist pattern can be formed by exposure and development.

..Structural unit (a1)
The structural unit (a1) is a unit having a phenolic hydroxyl group, and is preferably a unit derived from hydroxystyrene represented by the following general formula (I).

（式中、Ｒは水素原子または低級アルキル基を示す。）

(In the formula, R represents a hydrogen atom or a lower alkyl group.)

R is a hydrogen atom or a lower alkyl group. The lower alkyl group is as described above, and a hydrogen atom or a methyl group is particularly preferable. The description of R is the same below.
The bonding position of —OH to the benzene ring is not particularly limited, but the position 4 (para position) described in the formula is preferred.
The structural unit (a1) is preferably contained in an amount of 40 to 80 mol%, preferably 50 to 75 mol% in the component (A-11) from the viewpoint of forming a resist pattern. By setting it to 40 mol% or more, solubility in an alkali developer can be improved, and an effect of improving the resist pattern shape can be obtained. The balance with other structural units can be taken by setting it as 80 mol% or less.

..Structural unit (a2)
The structural unit (a2) is a structural unit having an acid dissociable, dissolution inhibiting group, and is represented by the following general formula (II).

（式中、Ｒは上記と同じであり、Ｘは酸解離性溶解抑制基を示す。）

(In the formula, R is the same as above, and X represents an acid dissociable, dissolution inhibiting group.)

The acid dissociable, dissolution inhibiting group X is an alkyl group having a tertiary carbon atom, and the tertiary carbon atom of the tertiary alkyl group is bonded to the ester group [—C (O) O—]. Examples thereof include acid-dissolving dissolution inhibiting groups, tetrahydropyranyl groups, and cyclic acetal groups such as tetrahydrofuranyl groups.
As such an acid dissociable, dissolution inhibiting group X, for example, those other than those described above can be arbitrarily used from among those used in a chemically amplified positive resist composition.

  As the structural unit (a2), for example, those represented by general formula (III) shown below are preferred.

In the formula, R is the same as described above, and R ¹¹ , R ¹² , and R ¹³ may each independently be a lower alkyl group (either a straight chain or a branched chain. Preferably, it has 1 to 5 carbon atoms. ). Or, among R ¹¹ , R ¹² and R ¹³ , R ¹¹ may be a lower alkyl group, and R ¹² and R ¹³ may be bonded to form a monocyclic or polycyclic aliphatic cyclic group. . The aliphatic cyclic group preferably has 5 to 12 carbon atoms.
Here, “aliphatic” means that the group or compound does not have aromaticity, and “aliphatic cyclic group” means a monocyclic group or polycyclic group having no aromaticity. Means group.
When R ¹¹ , R ¹² and R ¹³ do not have an aliphatic cyclic group, for example, it is preferable that R ¹¹ , R ¹² and R ¹³ are all methyl groups.
In the case where any of R ¹¹ , R ¹² and R ¹³ has an aliphatic cyclic group, when the aliphatic cyclic group is a monocyclic aliphatic cyclic group, as the structural unit (a2), for example, cyclopentyl And those having a cyclohexyl group are preferred.
When the aliphatic cyclic group is a polycyclic alicyclic group, preferred examples of the structural unit (a2) include those represented by the following general formula (IV).

［式中、Ｒは上記と同じであり、Ｒ^１４は低級アルキル基（直鎖、分岐鎖のいずれでもよい。好ましくは、炭素数は１〜５である。）］

[Wherein, R is the same as above, and R ¹⁴ is a lower alkyl group (which may be linear or branched. Preferably, it has 1 to 5 carbon atoms)]

  Moreover, what is represented by the following general formula (V) is preferable as what has an acid dissociable dissolution inhibiting group containing a polycyclic aliphatic cyclic group.

［式中、Ｒは上記と同じであり、Ｒ^１５、Ｒ^１６は、それぞれ独立に低級アルキル基（直鎖、分岐鎖のいずれでもよい。好ましくは、炭素数は１〜５である。）である。］

[Wherein, R is the same as above, and R ¹⁵ and R ¹⁶ each independently represent a lower alkyl group (which may be either a straight chain or a branched chain, preferably has 1 to 5 carbon atoms). is there. ]

  The structural unit (a2) is preferably present in the component (A-11) in an amount of 5 to 50 mol%, preferably 10 to 40 mol%, more preferably 10 to 35 mol%.

..Structural unit (a3)
The structural unit (a3) is a structural unit having an acid dissociable, dissolution inhibiting group, and is represented by the following general formula (VI).

（式中、Ｒは上記と同じであり、Ｘ’は酸解離性溶解抑制基を示す。）

(In the formula, R is the same as above, and X ′ represents an acid dissociable, dissolution inhibiting group.)

The acid dissociable, dissolution inhibiting group X ′ is a tertiary alkyloxycarbonyl group such as tert-butyloxycarbonyl group or tert-amyloxycarbonyl group; tert-butyloxycarbonylmethyl group or tert-butyloxycarbonylethyl group. Tertiary alkyloxycarbonylalkyl groups such as these; tertiary alkyl groups such as tert-butyl and tert-amyl groups; cyclic acetal groups such as tetrahydropyranyl and tetrahydrofuranyl groups; ethoxyethyl groups and methoxypropyl groups And the like.
Among these, a tert-butyloxycarbonyl group, a tert-butyloxycarbonylmethyl group, a tert-butyl group, a tetrahydropyranyl group, and an ethoxyethyl group are preferable.
As the acid dissociable, dissolution inhibiting group X ′, those other than those described above can be arbitrarily used from among those used in, for example, a chemically amplified positive resist composition.
In the general formula (VI), the bonding position of the group (—OX ′) bonded to the benzene ring is not particularly limited, but the position 4 (para position) shown in the formula is preferable.

  The structural unit (a3) is in the range of 5 to 50 mol%, preferably 10 to 40 mol%, more preferably 10 to 35 mol% in the component (A-11).

..Structural unit (a4)
The structural unit (a4) is an alkali-insoluble unit and is represented by the following general formula (VII).

（式中、Ｒは上記と同じであり、Ｒ^４’は低級アルキル基を示し、ｎ’は０または１〜３の整数を示す。）

(In the formula, R is the same as above, R ^{4 ′} represents a lower alkyl group, and n ′ represents 0 or an integer of 1 to 3).

The lower alkyl group for R ^{4 ′} may be either a straight chain or a branched chain, and the carbon number is preferably 1 to 5.
n ′ represents 0 or an integer of 1 to 3, and is preferably 0.

  The structural unit (a4) is 1 to 40 mol%, preferably 5 to 25 mol%, in the component (A-11). By setting it to 1 mol% or more, the effect of improving the shape (particularly, improving film loss) is enhanced, and by setting it to 40 mol% or less, it is possible to balance with other structural units.

In the component (A-11), the structural unit (a1) and at least one selected from the group consisting of the structural unit (a2) and the structural unit (a3) are used as essential structural units, and any structural unit ( a4) may be included. In addition, a copolymer having all these units may be used, or a mixture of polymers having one or more of these units may be used. Or you may combine these.
Further, the component (A-11) can optionally contain components other than the structural units (a1), (a2), (a3), and (a4), but the proportion of these structural units is 80 mol%. Above, preferably 90 mol% or more (100 mol% is most preferable).

In particular, “any one of the copolymers having the structural units (a1) and (a3), or a mixture of two or more of the copolymers”, or “the structural units (a1), (a2) and An embodiment in which any one of the copolymers having (a4) or a mixture of two or more of the copolymers is used or mixed is most preferable because an effect can be easily obtained. Moreover, it is preferable also from the point of heat resistance improvement.
In particular, a mixture of polyhydroxystyrene protected with a tertiary alkyloxycarbonyl group and polyhydroxystyrene protected with a 1-alkoxyalkyl group is preferred. When such mixing is performed, the mixing ratio (mass ratio) of each polymer (polyhydroxystyrene protected with a tertiary alkyloxycarbonyl group / 1-polyhydroxystyrene protected with 1-alkoxyalkyl group) is, for example, 1/9 to The ratio is 9/1, preferably 2/8 to 8/2, and more preferably 2/8 to 5/5.

As the resin component other than the component (A-11) suitable as the component (A-1), an (α-lower alkyl) acrylate resin is particularly preferable in that a pattern having lower etching resistance can be formed. A resin component ((α-lower alkyl) acrylate resin) is preferable, and a resin component made of (α-lower alkyl) acrylate resin is more preferable.
In the (α-lower alkyl) acrylate resin, a resin component (hereinafter referred to as (A-12) having a structural unit (a5) derived from an (α-lower alkyl) acrylate ester containing an acid dissociable, dissolution inhibiting group. ) Component))). The α-lower alkyl group is the same as described above.
The acid dissociable, dissolution inhibiting group of the structural unit (a5) has an alkali dissolution inhibiting property that makes the entire component (A-12) before exposure insoluble in alkali, and at the same time, an action of an acid generated from the component (B) after exposure. Is a group that dissociates and changes the entire component (A-12) to alkali-soluble.
In the (α-lower alkyl) acrylic ester resin component, when the acid dissociable, dissolution inhibiting group in the structural unit (a5) is dissociated by the acid generated from the component (B), a carboxylic acid is generated. Due to the presence of the generated carboxylic acid, for example, adhesion with a coating film formed on the resist pattern is improved.

As the acid dissociable, dissolution inhibiting group, for example, a resin for resist compositions of ArF excimer laser can be appropriately selected and used from among many proposed ones. In general, a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group of (α-lower alkyl) acrylic acid, or a cyclic or chain alkoxyalkyl group is widely known.
Here, the “group that forms a tertiary alkyl ester” is a group that forms an ester by substituting the hydrogen atom of the carboxy group of acrylic acid. That is, it shows a structure in which the tertiary carbon atom of a chain-like or cyclic tertiary alkyl group is bonded to the terminal oxygen atom of the carbonyloxy group [—C (O) —O—] of the acrylate ester. . In this tertiary alkyl ester, when an acid acts, a bond is cut between an oxygen atom and a tertiary carbon atom.
The tertiary alkyl group is an alkyl group having a tertiary carbon atom.
Examples of the group that forms a chain-like tertiary alkyl ester include a tert-butyl group and a tert-amyl group.
Examples of the group that forms a cyclic tertiary alkyl ester include those exemplified in the “acid dissociable, dissolution inhibiting group containing an alicyclic group” described later.

The “cyclic or chain alkoxyalkyl group” forms an ester by substituting a hydrogen atom of a carboxy group. That is, a structure is formed in which the alkoxyalkyl group is bonded to the terminal oxygen atom of the carbonyloxy group [—C (O) —O—] of the acrylate ester. In such a structure, the bond between the oxygen atom and the alkoxyalkyl group is broken by the action of the acid.
Examples of such cyclic or chain alkoxyalkyl groups include 1-methoxymethyl group, 1-ethoxyethyl group, 1-isopropoxyethyl, 1-cyclohexyloxyethyl group, 2-adamantoxymethyl group, 1-methyladamant Examples thereof include a xymethyl group, a 4-oxo-2-adamantoxymethyl group, a 1-adamantoxyethyl group, and a 2-adamantoxyethyl group.

As the structural unit (a5), a structural unit containing an acid dissociable, dissolution inhibiting group containing a cyclic group, particularly an aliphatic cyclic group, is preferred.
Here, “aliphatic” and “aliphatic cyclic group” are as defined above.
The aliphatic cyclic group may be monocyclic or polycyclic, and can be appropriately selected and used from among many proposed, for example, ArF resists. From the viewpoint of etching resistance, a polycyclic alicyclic group is preferred. The alicyclic group is preferably a hydrocarbon group, and particularly preferably a saturated hydrocarbon group (alicyclic group).
Examples of the monocyclic alicyclic group include groups in which one hydrogen atom has been removed from a cycloalkane. Examples of the polycyclic alicyclic group include groups in which one hydrogen atom has been removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like.
Specifically, examples of the monocyclic alicyclic group include a cyclopentyl group and a cyclohexyl group. Examples of the polycyclic alicyclic group include groups in which one hydrogen atom has been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Among these, an adamantyl group obtained by removing one hydrogen atom from adamantane, a norbornyl group obtained by removing one hydrogen atom from norbornane, a tricyclodecanyl group obtained by removing one hydrogen atom from tricyclodecane, tetra A tetracyclododecanyl group obtained by removing one hydrogen atom from cyclododecane is industrially preferred.

More specifically, the structural unit (a5) is preferably at least one selected from the following general formulas (I ′) to (III ′).
In addition, a unit derived from an (α-lower alkyl) acrylic acid ester having a cyclic alkoxyalkyl group as described above, specifically a 2-adamantoxymethyl group, 1-methyladamant Aliphatic polycyclic alkyloxy lower alkyl (α which may have a substituent such as xymethyl group, 4-oxo-2-adamantoxymethyl group, 1-adamantoxyethyl group, 2-adamantoxyethyl group, etc. -Lower alkyl) It is preferably at least one selected from units derived from acrylic acid esters.

［式（Ｉ’）中、Ｒは上記と同じであり、Ｒ^１は低級アルキル基である。］

[In the formula (I ′), R is the same as above, and R ¹ is a lower alkyl group. ]

［式（ＩＩ’）中、Ｒは上記と同じであり、Ｒ^２及びＲ^３はそれぞれ独立に低級アルキル基である。］

[In formula (II ′), R is as defined above, and R ² and R ³ each independently represents a lower alkyl group. ]

［式（ＩＩＩ’）中、Ｒは上記と同じであり、Ｒ^４は第３級アルキル基である。］

[In the formula (III ′), R is the same as above, and R ⁴ is a tertiary alkyl group. ]

In formulas (I ′) to (III ′), the hydrogen atom or lower alkyl group of R is the same as described above for the hydrogen atom or lower alkyl group bonded to the α-position of the acrylate ester.
The lower alkyl group for R ¹ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specifically includes a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. , A pentyl group, an isopentyl group, a neopentyl group, and the like. Among these, a methyl group and an ethyl group are preferable because they are easily available industrially.
The lower alkyl group for R ² and R ³ is preferably each independently a linear or branched alkyl group having 1 to 5 carbon atoms. Of these, the case where R ² and R ³ are both methyl groups is industrially preferred. Specific examples include structural units derived from 2- (1-adamantyl) -2-propyl acrylate.

R ⁴ is a chain-like tertiary alkyl group or a cyclic tertiary alkyl group. Examples of the chain-like tertiary alkyl group include a tert-butyl group and a tert-amyl group, and the tert-butyl group is industrially preferable.
The cyclic tertiary alkyl group is the same as that exemplified in the aforementioned “acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group”, and includes a 2-methyl-2-adamantyl group, 2-ethyl- A 2-adamantyl group, 2- (1-adamantyl) -2-propyl group, 1-ethylcyclohexyl group, 1-ethylcyclopentyl group, 1-methylcyclohexyl group, 1-methylcyclopentyl group and the like can be mentioned.
The group —COOR ⁴ may be bonded to the 3 or 4 position of the tetracyclododecanyl group shown in the formula, but the bonding position cannot be specified. Similarly, the carboxy group residue of the acrylate structural unit may be bonded to the position 8 or 9 shown in the formula.

The structural unit (a5) can be used alone or in combination of two or more.
In the (α-lower alkyl) acrylate resin component, the proportion of the structural unit (a5) is 20 to 60 mol% with respect to the total of all the structural units constituting the (α-lower alkyl) acrylate resin component. Is preferable, 30 to 50 mol% is more preferable, and 35 to 45 mol% is most preferable. A resist pattern can be obtained by setting it to the lower limit value or more, and a balance with other structural units can be achieved by setting the upper limit value or less.

In addition to the structural unit (a5), the (α-lower alkyl) acrylic acid ester resin preferably further has a structural unit (a6) derived from an acrylate ester having a lactone ring. The structural unit (a6) is effective in increasing the adhesion of the resist film to the substrate and increasing the hydrophilicity with the developer. In addition, a coating film having high adhesion to the resist pattern can be formed.
In the structural unit (a6), a lower alkyl group or a hydrogen atom is bonded to the α-position carbon atom. The lower alkyl group bonded to the α-position carbon atom is the same as described for the structural unit (a5), and is preferably a methyl group.
As the structural unit (a6), a structural unit in which a monocyclic group consisting of a lactone ring or a polycyclic cyclic group having a lactone ring is bonded to the ester side chain portion of the acrylate ester can be mentioned.
At this time, the lactone ring refers to one ring containing an —O—C (O) — structure, and this is counted as one ring. Therefore, here, when only the lactone ring is present, it is referred to as a monocyclic group, and when it has another ring structure, it is referred to as a polycyclic group regardless of the structure.
Examples of the structural unit (a6) include a monocyclic group obtained by removing one hydrogen atom from γ-butyrolactone, and a polycyclic group obtained by removing one hydrogen atom from a lactone ring-containing bicycloalkane. It is done.
More specifically, the structural unit (a6) is preferably at least one selected from, for example, the following general formulas (IV ′) to (VII ′).

［式（ＩＶ’）中、Ｒは上記と同じであり、Ｒ^５、Ｒ^６は、それぞれ独立に、水素原子または低級アルキル基である。］

[In formula (IV ′), R is the same as defined above, and R ⁵ and R ⁶ each independently represent a hydrogen atom or a lower alkyl group. ]

［式（Ｖ’）中、Ｒは上記と同じであり、ｍは０または１である。］

[In the formula (V ′), R is the same as described above, and m is 0 or 1. ]

［式（ＶＩ’）中、Ｒは上記と同じである。］

[In formula (VI ′), R is the same as defined above. ]

［式（ＶＩＩ’）中、Ｒは上記と同じである。］

[In formula (VII ′), R is the same as defined above. ]

In formula (IV ′), R ⁵ and R ⁶ each independently represent a hydrogen atom or a lower alkyl group, preferably a hydrogen atom. In R ⁵ and R ⁶ , the lower alkyl group is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. Tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.

Among the structural units represented by the general formulas (IV ′) to (VII ′), the structural unit represented by (IV ′) is inexpensive and industrially preferable, and among the structural units represented by (IV ′). , R is a methyl group, R ⁵ and R ⁶ are hydrogen atoms, and the position of the ester bond between the methacrylic acid ester and γ-butyrolactone is α-position on the lactone ring is α-methacryloyloxy-γ-butyrolactone Most preferably it is.
The structural unit (a6) can be used alone or in combination of two or more.
In the (α-lower alkyl) acrylate resin component, the proportion of the structural unit (a6) is 20 to 60 mol% with respect to the total of all the structural units constituting the (α-lower alkyl) acrylate resin component. Is preferable, 20-50 mol% is more preferable, and 30-45 mol% is the most preferable. Lithographic characteristics are improved by setting the value to the lower limit value or more, and balance with other structural units can be achieved by setting the upper limit value or less.

In addition to the structural unit (a5) or in addition to the structural units (a5) and (a6), the (α-lower alkyl) acrylic ester resin component further includes acrylic acid containing a polar group-containing polycyclic group. It is preferable to have a structural unit (a7) derived from an ester.
The structural unit (a7) increases the hydrophilicity of the entire (α-lower alkyl) acrylate resin component, increases the affinity with the developer, improves the alkali solubility in the exposed area, and improves the resolution. Contributes to improvement. In addition, a coating film having high adhesion to the resist pattern can be formed.
In the structural unit (a7), a lower alkyl group or a hydrogen atom is bonded to the α-position carbon atom. The lower alkyl group bonded to the α-position carbon atom is the same as described for the structural unit (a5), and is preferably a methyl group.
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and an amino group, and a hydroxyl group is particularly preferable.
As the polycyclic group, among the aliphatic cyclic groups exemplified in the “acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group” which is the structural unit (a5), a polycyclic group is appropriately selected. It can be selected and used.
The structural unit (a7) is preferably at least one selected from the following general formulas (VIII ′) to (IX ′).

［式（ＶＩＩＩ’）中、Ｒは上記と同じであり、ｎは１〜３の整数である。］

[In formula (VIII ′), R is the same as above, and n is an integer of 1 to 3. ]

R in the formula (VIII ′) is the same as R in the above formulas (I ′) to (III ′).
Among these, those in which n is 1 and the hydroxyl group is bonded to the 3-position of the adamantyl group are preferable.

［式（ＩＸ’）中、Ｒは上記と同じであり、ｋは１〜３の整数である。］

[In formula (IX ′), R is the same as described above, and k is an integer of 1 to 3. ]

  Among these, those in which k is 1 are preferable. Moreover, it is preferable that the cyano group has couple | bonded with 5th-position or 6th-position of norbornanyl group.

The structural unit (a7) can be used alone or in combination of two or more.
In the (α-lower alkyl) acrylate resin component, the proportion of the structural unit (a7) is 10 to 50 mol% with respect to the total of all the structural units constituting the (α-lower alkyl) acrylate resin component. Is preferable, 15-40 mol% is more preferable, and 20-35 mol% is further more preferable. Lithographic characteristics are improved by setting the value to the lower limit value or more, and balance with other structural units can be achieved by setting the upper limit value or less.

  In the (α-lower alkyl) acrylate resin component, the total of these structural units (a5) to (a7) is preferably 70 to 100 mol% with respect to the total of all the structural units, 80 to More preferably, it is 100 mol%.

The (α-lower alkyl) acrylic acid ester resin component may contain a structural unit (a8) other than the structural units (a5) to (a7).
The structural unit (a8) is not particularly limited as long as it is another structural unit that is not classified into the structural units (a5) to (a7).
For example, a structural unit containing a polycyclic aliphatic hydrocarbon group and derived from an (α-lower alkyl) acrylate is preferable. The polycyclic aliphatic hydrocarbon group is appropriately selected from, for example, polycyclic ones among the aliphatic cyclic groups exemplified in the aforementioned “acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group”. Can be used. In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, a norbornyl group, and an isobornyl group is preferable in terms of industrial availability. The structural unit (a8) is most preferably an acid non-dissociable group.
Specific examples of the structural unit (a8) include the following structures (X) to (XII).

（式中、Ｒは上記と同じである。）

(In the formula, R is the same as above.)

（式中、Ｒは上記と同じである。）

(In the formula, R is the same as above.)

（式中、Ｒは上記と同じである。）

(In the formula, R is the same as above.)

  When the structural unit (a8) is included, the proportion of the structural unit (a8) in the (α-lower alkyl) acrylate resin component is the sum of all the structural units constituting the (α-lower alkyl) acrylate resin component. 1 to 25 mol% is preferable, and 5 to 20 mol% is more preferable.

  The (α-lower alkyl) acrylate resin component is preferably a copolymer having at least the structural units (a5), (a6) and (a7). Examples of such a copolymer include a copolymer composed of the structural units (a5), (a6) and (a7), and a copolymer composed of the structural units (a5), (a6), (a7) and (a8). A polymer etc. can be illustrated.

  The component (A-1) can be obtained by polymerizing the monomer related to the structural unit by a known method. For example, the monomer related to each structural unit can be obtained by polymerizing by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN).

The component (A-1) is preferably 30000 or less, more preferably 20000 or less, and further preferably 12000 or less, in terms of mass average molecular weight (polystyrene-converted mass average molecular weight by gel permeation chromatography, hereinafter the same). preferable. The lower limit may be more than 2000, and is preferably 4000 or more, and more preferably 5000 or more, from the viewpoint of suppressing pattern collapse and improving resolution.
Further, the dispersity (Mw / Mn) is not particularly limited, but is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5. . In addition, Mn shows a number average molecular weight.

[(A-2) component]
The component (A-2) has a molecular weight of 500 or more and 2000 or less, has a hydrophilic group, and has an acid dissociable, dissolution inhibiting group X or X as exemplified in the description of the component (A-1). Low molecular weight compounds having 'are preferred.
Specific examples include those in which a part of the hydrogen atoms of the hydroxyl group of the compound having a plurality of phenol skeletons is substituted with the acid dissociable, dissolution inhibiting group X or X ′.
The component (A-2) contains, for example, a part of the hydrogen atom of the hydroxyl group of a low molecular weight phenol compound known as a sensitizer or heat resistance improver for non-chemically amplified g-line or i-line resists. Those substituted with a dissociable, dissolution inhibiting group are preferred and can be arbitrarily used.

Examples of such low molecular weight phenol compounds include the following.
Bis (4-hydroxyphenyl) methane, bis (2,3,4-trihydroxyphenyl) methane, 2- (4-hydroxyphenyl) -2- (4′-hydroxyphenyl) propane, 2- (2,3,3) 4-trihydroxyphenyl) -2- (2 ′, 3 ′, 4′-trihydroxyphenyl) propane, tris (4-hydroxyphenyl) methane, bis (4-hydroxy-3,5-dimethylphenyl) -2- Hydroxyphenylmethane, bis (4-hydroxy-2,5-dimethylphenyl) -2-hydroxyphenylmethane, bis (4-hydroxy-3,5-dimethylphenyl) -3,4-dihydroxyphenylmethane, bis (4- Hydroxy-2,5-dimethylphenyl) -3,4-dihydroxyphenylmethane, bis (4-hydroxy-3-methylphenol) Nyl) -3,4-dihydroxyphenylmethane, bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) -4-hydroxyphenylmethane, bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) -3 , 4-dihydroxyphenylmethane, 1- [1- (4-hydroxyphenyl) isopropyl] -4- [1,1-bis (4-hydroxyphenyl) ethyl] benzene, phenol, m-cresol, p-cresol or xylenol And 2,3,4 nuclei of formalin condensates of phenols and the like. Of course, it is not limited to these.
The acid dissociable, dissolution inhibiting group is not particularly limited, and examples thereof include those described above.

[Component (B)]
As the component (B), any conventionally known acid generator for chemically amplified resists can be appropriately selected and used. Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, and poly (bissulfonyl) diazomethanes. There are various known diazomethane acid generators, nitrobenzyl sulfonate acid generators, imino sulfonate acid generators, disulfone acid generators, and the like.

  Specific examples of the onium salt acid generator include diphenyliodonium trifluoromethanesulfonate, (4-methoxyphenyl) phenyliodonium trifluoromethanesulfonate, bis (p-tert-butylphenyl) iodonium trifluoromethanesulfonate, and triphenylsulfonium trifluoromethanesulfonate. (4-methoxyphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-methylphenyl) diphenylsulfonium nonafluorobutanesulfonate, (p-tert-butylphenyl) diphenylsulfonium trifluoromethanesulfonate, diphenyliodonium nonafluorobutanesulfonate, bis (p -Tert-Butylphenyl) iodonium nonafluorobutans Honeto include triphenylsulfonium nonafluorobutanesulfonate. Among these, an onium salt having a fluorinated alkyl sulfonate ion as an anion is preferable.

  Examples of oxime sulfonate compounds include α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -phenyl. Acetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (propylsulfonyloxyimino) -p-methylphenylacetonitrile, α -(Methylsulfonyloxyimino) -p-bromophenylacetonitrile and the like. Among these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile is preferable.

  Specific examples of the diazomethane acid generator include bis (isopropylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, bis (cyclohexylsulfonyl) diazomethane, bis (2, 4-dimethylphenylsulfonyl) diazomethane and the like.

As the component (B), one type of acid generator may be used alone, or two or more types may be used in combination.
(B) The usage-amount of a component shall be 1-20 mass parts with respect to 100 mass parts of (A) component, Preferably it is 2-10 mass parts. By setting it to be equal to or higher than the lower limit value of the above range, sufficient pattern formation is performed.

[Optional ingredients]
The chemical amplification resist composition is further mixed with a nitrogen-containing organic compound (D) (hereinafter referred to as the component (D)) as an optional component in order to improve the pattern shape, the stability over time and the like. Can do.
Since a wide variety of component (D) has already been proposed, any known component 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. Examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, and di-n-propylamine. , Tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, triisopropanolamine and the like, and tertiary alkanolamines such as triethanolamine and triisopropanolamine are particularly preferable.
These may be used alone or in combination of two or more.
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

In addition, the chemically amplified resist composition may contain an organic carboxylic acid as an optional component for the purpose of preventing deterioration of sensitivity due to the blending with the component (D) and improving the pattern shape, stability of placement, etc. Alternatively, phosphorus oxo acid or its derivative (E) (hereinafter referred to as component (E)) can be contained. In addition, (D) component and (E) component can also be used together, and any 1 type can also be used.
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.
(E) A component is normally used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

  If desired, the chemically amplified resist composition may further contain miscible additives such as an additional resin for improving the performance of the coating film of the resist composition, a surfactant for improving the coating property, A dissolution inhibitor, a plasticizer, a stabilizer, a colorant, an antihalation agent and the like can be appropriately contained.

The chemically amplified resist composition can be produced by dissolving the material in an organic solvent (S) (hereinafter referred to as “component (S)”).
As the component (S), any component can be used as long as it can dissolve each component to be used to obtain a uniform solution. Conventionally, any one or two of known solvents for resist compositions can be used. More than one species can be appropriately selected and used.
Specific examples include lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone; ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol Polyhydric alcohols such as monoacetate, propylene glycol monomethyl ether acetate (PGMEA), dipropylene glycol, or 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, ethyl lactate (EL), Le, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and the like esters such as ethyl ethoxypropionate. Among these, PGMEA, EL, and propylene glycol monomethyl ether (PGME) are preferable.
These (S) components may be used independently and may be used as 2 or more types of mixed solvents.
Although the usage-amount of (S) component is not specifically limited, The quantity used as a liquid of the density | concentration with which a chemically amplified resist composition can be apply | coated on a support body is used.

<Resist pattern formation method>
In the resist pattern forming method of the present invention, a resist film is formed by applying a chemically amplified resist composition on a support, and the resist film is selectively exposed multiple times through a photomask. A pattern forming method (hereinafter, sometimes referred to as “double exposure method”), wherein the sum of the transmittances of the light-shielding portions of the photomask used for each selective exposure is 0 to less than 12%. Features.
As the “double exposure method”, for example, a resist pattern forming method (a) shown below is preferable.

Resist pattern forming method (a):
A process of forming a resist film by applying a chemically amplified resist composition on a support (hereinafter referred to as “film forming process (0)”) and selective exposure through a photomask multiple times. And then developing the resist pattern to form a resist pattern (hereinafter referred to as “patterning step (0)”).

Hereinafter, a preferred embodiment of the resist pattern forming method (a) of the present invention will be described with reference to FIG. In this embodiment, a positive resist composition is used as a chemically amplified resist composition, and selective exposure through a photomask is performed twice in succession.
In this embodiment, first, as shown in FIG. 1A, a chemically amplified resist composition (positive resist composition) is applied on a support 1 to form a resist film 2 (film formation). Step (0)).
Next, as shown in FIG. 1B, selective exposure is performed on the resist film 2 through a photomask 5.
Subsequently, as shown in FIG. 1C, the photomask 5 is moved by a predetermined distance in a predetermined direction, and selective exposure is performed again through the photomask 5.
Thereafter, by developing, as shown in FIG. 1 (d), the exposed portions 3 a and 3 b of the two selective exposures in the resist film 2 are removed. As a result, a plurality of resist patterns 3 are formed on the support 1. It is formed (patterning step (0)).
Thus, according to the resist pattern forming method (a), it is possible to form a resist pattern with a narrower pitch than in the case of the resist pattern forming method in which selective exposure is performed once, for example.
Hereinafter, each step will be described in more detail.

[Film Formation Step (0)]
The support 1 is not particularly limited, and a conventionally known one can be used. For example, a substrate for electronic components, a substrate on which a predetermined wiring pattern is formed, and the like can be exemplified. More specifically, a silicon substrate, a metal substrate such as copper, chromium, iron, and aluminum, a glass substrate, and the like can be given. As a material for the wiring pattern, for example, copper, aluminum, nickel, gold or the like can be used.
An organic antireflection film may be provided on the support 1.

There is no restriction | limiting in particular as a chemically amplified resist composition, It can select suitably from many chemically amplified resist compositions proposed as a chemically amplified resist composition as mentioned above.
The chemically amplified resist composition may be a positive resist composition or a negative resist composition, and it is preferable to use a positive resist composition.

The resist film 2 can be formed by applying a chemically amplified resist composition on the support 1. The chemically amplified resist composition can be applied by a conventionally known method using a spinner or the like.
Specifically, for example, a chemically amplified resist composition is applied onto the support 1 with a spinner or the like, and baked (pre-baked) at a temperature of 80 to 150 ° C. for 40 to 120 seconds, preferably 60 to 90 seconds. Then, the resist film 2 can be formed by volatilizing the organic solvent.
The thickness of the resist film 2 is preferably 50 to 500 nm, more preferably 50 to 450 nm. By setting it within this range, there are effects that a resist pattern can be formed with high resolution and sufficient resistance to etching can be obtained.

[Patterning process (0)]
In the patterning step (0), for example, selective exposure (hereinafter sometimes referred to as “first exposure”) is performed on the resist film 2 through the photomask 5 on which a predetermined pattern is formed. Subsequently, the photomask 5 is moved by a predetermined distance in a predetermined direction, and the resist film 2 is again selectively exposed through the photomask 5 (hereinafter referred to as “second exposure”). .)I do.
In the present invention, in the patterning step (0), it is essential that the total transmittance of the light shielding portions of the photomask 5 used for each selective exposure is less than 0 to less than 12%. The total transmittance is 0 to less than 12%, preferably 0 to 8%, and most preferably 0 to 6%. By setting it within this range, a resist pattern having a good shape and high resolution can be formed.
Here, “the transmittance of the light shielding portion of the photomask 5” means the transmittance of radiation of a specific wavelength irradiated for each selective exposure in the light shielding portion.
The “total transmittance of the light shielding portion of the photomask 5” means a value obtained by adding the transmittances of the light shielding portions of the photomask 5 used for each selective exposure. For example, as shown in Table 1 below, a value obtained by adding together the transmittance value of the light shielding portion of the photomask used for the first exposure and the transmittance value of the light shielding portion of the photomask used for the second exposure. Means.

As the photomask 5, the same photomask may be used for each selective exposure, or different photomasks may be used. Moreover, the thing with the same transmittance | permeability of the light-shielding part of a photomask may be used, and a different thing may be used. In the present invention, any one can be used as long as the total transmittance of the light shielding portions of the photomask used for each selective exposure is 0 to less than 12%.
For example, as shown in Example 1 in Table 1, only a photomask having a light shielding portion with a transmittance of 0% may be used. Further, as in Example 2 and Example 3 of Table 1, for example, a photomask having a light shielding portion with a transmittance of 0% and a photomask having a light shielding portion with a transmittance of 6% may be combined. Further, as shown in Example 4 in Table 1, a photomask having a light shielding portion with a transmittance other than 0%, for example, a photomask having a light shielding portion with a transmittance of 3% may be combined.
As described above, the total transmittance of the light shielding portions of the photomask can be adjusted to be 0 to less than 12%.

In the present invention, it is preferable to use at least a photomask having a light shielding portion with a transmittance of 0%. This makes it easy to adjust the total transmittance of the light shielding portions of the photomask to less than 0 to 12%, making it easier to obtain a resist pattern with a good shape and high resolution.
An example of a photomask having a 0% transmittance of the light shielding portion of the photomask is a binary mask.
The binary mask is generally formed by forming a chromium film, a chromium oxide film or the like as a light shielding portion on a quartz glass substrate.
Examples of the photomask having a transmittance of 6% for the light shielding portion of the photomask include a halftone phase shift mask (HT-Mask).
As the halftone phase shift mask, generally, a quartz glass substrate on which a MoSi (molybdenum silicide) film, a chromium film, a chromium oxide film, a silicon oxynitride film, or the like is formed as a light shielding portion is used. .

In the patterning step (0), a position different from the first exposure of the resist film 2 is exposed for the second time and developed. Thereby, for example, when a positive resist composition is used as the chemically amplified resist composition, the exposed portion 3a of the first exposure and the exposed portion 3b of the second exposure are dissolved in the developer, and are thus formed on the support 1. A resist pattern 3 is formed.
Here, in the present invention, all are “positions different from the first exposure” except when they completely coincide with the exposure unit 3a of the first exposure, and when they do not overlap at all, and partially overlap. Including cases where
In the present invention, it is preferable that the exposure part 3a for the first exposure and the position (exposure part 3b) for selective exposure in the second exposure do not overlap at all. Thereby, it is possible to form a resist pattern with a narrow pitch in which the interval (pitch) between patterns is narrower than the resist pattern formed only by the first exposure.

The selective exposure at a position different from the exposure unit 3a for the first exposure can be performed, for example, by moving the photomask 5 used in the first exposure in the horizontal direction.
Such movement of the photomask 5 can be carried out by adjusting the program of the exposure apparatus to be used.
The photomask 5 may be translated in one direction or rotated.
For example, when forming a resist pattern, after performing selective exposure using a line-and-space photomask 5 in which a plurality of lines are arranged at a constant pitch in the first exposure, the photomask 5 is Selective exposure is performed so as to form a line pattern in the second exposure at a middle position between the line pattern and the line pattern that has been subjected to the selective exposure in the first exposure by translating in the direction perpendicular to the direction. As a result, the line-and-space resist pattern 3 is formed at a pitch that is approximately ½ of the line-and-space pitch that is selectively exposed in the first exposure.
For example, in the first exposure, after performing selective exposure using a line-and-space photomask in which line patterns with a line width of 300 nm are arranged at equal intervals (line width: space width = 3: 1; pitch 400 nm). The photomask is translated by 200 nm in a direction perpendicular to the direction of the line, the second exposure is performed, and development is performed, so that a line and space pattern having a line width of 100 nm and a line width: space width = 1: 1 is obtained. Can be formed.
Various resist patterns can be formed by rotating and moving the photomask 5 used in the first exposure or using a photomask different from the photomask 5 used in the first exposure.
As a method other than the method of moving the photomask 5, a method of moving a stage (a table on which a substrate is placed) in the exposure machine can also be used.

Subsequently, baking treatment (PEB (post-exposure heating)) is performed for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C., for example, tetramethylammonium hydroxy having a concentration of 0.1 to 10% by mass. When alkali development is performed with an aqueous solution of TMAH, the exposed portions 3a and 3b are removed if the resist composition used is a positive type (unexposed portions are removed if it is a negative type) to form a resist pattern 3. Is done.
The wavelength used for the exposure is not particularly limited, and includes KrF excimer laser, ArF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. Can be done using radiation.

At this time, the selective exposure of the resist film 2 may be normal exposure (dry exposure) performed in an inert gas such as air or nitrogen, or may be performed by immersion exposure.
In immersion exposure, as described above, the portion between the lens, which has been filled with an inert gas such as air or nitrogen, and the resist film on the wafer at the time of exposure is refracted larger than the refractive index of air. Exposure is performed in a state filled with a solvent (immersion medium) having a high rate.
More specifically, the immersion exposure is a solvent (immersion medium) having a refractive index larger than the refractive index of air between the resist film obtained as described above and the lowermost lens of the exposure apparatus. In that state, exposure (immersion exposure) is performed through a desired photomask.
As the immersion medium, a solvent having a refractive index larger than the refractive index of air and smaller than the refractive index of the resist film 2 formed using the chemically amplified resist composition is preferable. The refractive index of such a solvent is not particularly limited as long as it is within the above range.
Examples of the solvent having a refractive index larger than the refractive index of air and smaller than the refractive index of the resist film 2 include water, a fluorine-based inert liquid, a silicon-based solvent, and a hydrocarbon-based solvent.
Specific examples of the fluorine-based inert liquid include a fluorine-based compound such as C ₃ HCl ₂ F ₅ , C ₄ F ₉ OCH ₃ , C ₄ F ₉ OC ₂ H ₅ , and C ₅ H ₃ F ₇ as a main component. Examples thereof include liquids, and those having a boiling point of 70 to 180 ° C are preferable, and those having a boiling point of 80 to 160 ° C are more preferable. It is preferable that the fluorine-based inert liquid has a boiling point in the above range since the medium used for immersion can be removed by a simple method after the exposure is completed.
As the fluorine-based inert liquid, a perfluoroalkyl compound in which all hydrogen atoms of the alkyl group are substituted with fluorine atoms is particularly preferable. Specific examples of the perfluoroalkyl compound include a perfluoroalkyl ether compound and a perfluoroalkylamine compound.
More specifically, examples of the perfluoroalkyl ether compound include perfluoro (2-butyl-tetrahydrofuran) (boiling point: 102 ° C.). Examples of the perfluoroalkylamine compound include perfluorotributylamine ( Boiling point of 174 ° C.).

  In the resist pattern forming method (a), a coating step of forming a coating film made of a metal oxide film may be further provided on the surface of the formed resist pattern 3 after the patterning step (0). . Thereby, the surfaces of the formed resist patterns 3 and 3 are covered with the coating film made of the metal oxide film, and the etching resistance and the like are improved.

In the resist pattern forming method (a), after the patterning step (0), a series of operations of the covering step, the film forming step (0), and the patterning step (0) are repeated a plurality of times. Also good.
That is, a coating film made of a metal oxide film is formed on the surface of the formed resist pattern 3 to form a coating pattern, and the chemically amplified resist composition is formed on the support 1 on which the coating pattern is formed. An operation of forming a resist film by coating, selectively exposing the resist film, and developing to form a resist pattern may be performed a plurality of times. Thereby, it is possible to form a pattern with a narrower pitch or to form a pattern with a complicated shape.

Furthermore, in the resist pattern forming method (a), after the patterning step (0), the support 1 may be etched using the formed resist pattern 3 as a mask.
Thus, a semiconductor device etc. can be manufactured by etching support bodies, such as a board | substrate.

As the etching method, a known method can be used. For example, dry etching is preferable for etching the organic film. In particular, for example, oxygen plasma etching or etching using CF ₄ gas or CHF ₃ gas is preferable from the viewpoint of high resistance of the coating film to etching and production efficiency, and oxygen plasma etching is particularly preferable.
Etching using a halogen gas is preferable for etching the substrate, etching using a fluorocarbon-based gas is preferable, and etching using CF ₄ gas or CHF ₃ gas is particularly preferable.

[Organic film forming material]
In the support 1 used in the film formation step (0) described above, for example, an organic film forming material for forming an organic film which may be formed on a substrate is an electron beam such as a resist film, It does not necessarily require sensitivity to light. Commonly used resists and resins can be used in the manufacture of semiconductor elements and liquid crystal display elements.
In addition, the organic film forming material is an organic film that can be etched, particularly dry-etched, so that the organic film pattern can be formed by etching the organic film using the resist pattern. A material that can be formed is preferred.
Among these, a material capable of forming an organic film capable of etching such as oxygen plasma etching is preferable.
Such an organic film forming material may be a material conventionally used for forming an organic film such as an organic BARC. Examples include the ARC series manufactured by Brewer Science, the AR series manufactured by Rohm and Haas, and the SWK series manufactured by Tokyo Ohka Kogyo.

As described above, according to the present invention, it is possible to provide a novel resist pattern forming method capable of forming a resist pattern having a good shape and high resolution. The reason is not clear, but the resist pattern forming method (double exposure method) in which selective exposure is performed a plurality of times through a photomask is inherently more effective than the conventional resist pattern forming method in which selective exposure is performed once. It is estimated that light is easily irradiated to the position of the unexposed portion. Therefore, for example, in the case of a positive resist composition, it is considered that a defect such as deterioration of the resist pattern shape occurs due to dissolution of a part of the unexposed portion.
In the present invention, by controlling the transmittance of the light-shielding part of the photomask, the irradiation of light to the position of the unexposed part is suppressed, so that it is estimated that the occurrence of the problem is suppressed. Therefore, according to the present invention, it is considered that a resist pattern having a good shape and high resolution can be formed.

Further, according to the resist pattern forming method of the present invention, a fine resist pattern can be formed even by using an existing exposure apparatus or an existing chemical amplification resist composition.
Further, the resist pattern forming method of the present invention, that is, the double exposure method, can form a fine resist pattern by performing, for example, one patterning and one etching of a substrate or the like. Further, according to the double exposure method, the number of steps can be reduced as compared with the double patterning method in which the patterning needs to be performed at least twice and the etching of the substrate or the like needs to be performed at least twice.

  Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples.

(Example 1)
In the following procedure, a resist pattern was formed by the same process as that shown in FIG.
That is, an organic antireflection film composition “ARC29A” (trade name, manufactured by Brewer Science Co., Ltd.) is applied onto an 8-inch silicon wafer using a spinner, and baked on a hot plate at 205 ° C. for 60 seconds to be dried. Thereby, an organic antireflection film having a thickness of 77 nm was formed.
On the organic antireflection film, a chemically amplified positive resist composition “TARF-P6239” (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied using a spinner, and is heated on a hot plate at 110 ° C. for 60 seconds. The resist film having a thickness of 120 nm was formed by performing pre-baking (PAB) treatment and drying.
Next, an ArF excimer laser (193 nm) was applied to the resist film as a photomask using an ArF exposure apparatus NSR-S306C (Nikon Corporation; NA (numerical aperture) = 0.78, σ = Di-pole). Irradiation was selectively performed through a binary mask (manufactured by Dai Nippon Printing Co., Ltd .; transmittance 0%) targeting a line width of 300 nm and a space width of 100 nm (line width: space width = 3: 1).
Subsequently, the binary mask was translated by 200 nm in a direction perpendicular to the line direction, and the resist film was selectively irradiated in the same manner as described above.
Thereafter, PEB treatment is performed at 110 ° C. for 60 seconds, followed by development with an aqueous 2.38 mass% tetramethylammonium hydroxide (TMAH) solution at 23 ° C. for 60 seconds, and then water rinsing with pure water for 20 seconds. Then, it was shaken and dried.
Thereafter, the film is heated at 100 ° C. for 60 seconds (post-bake treatment), dried, and the resist film has a line-and-space (1: 1) pattern in which line patterns with a line width of 100 nm are arranged at equal intervals (pitch 200 nm). A resist pattern (hereinafter referred to as LS pattern (1)) was formed.

(Comparative Example 1)
In Example 1, except that a halftone mask (Dai Nippon Printing Co., Ltd .; transmittance 6%) was used instead of a binary mask (Dai Nippon Printing Co., Ltd .; transmittance 0%) as a photomask. In the same manner as in Example 1, a line-and-space (1: 1) resist pattern (hereinafter referred to as LS pattern (2)) in which line patterns with a line width of 100 nm are arranged at equal intervals (pitch: 200 nm) was formed.

[Evaluation of resist pattern shape]
With respect to the LS patterns (1) to (2) formed above, the top surface shape and cross-sectional shape of each are observed with a length measurement SEM (trade name: S-9220, manufactured by Hitachi, Ltd.), and the resist pattern shape is evaluated. Went.
As a result, it can be confirmed that the LS pattern (1) formed in Example 1 according to the present invention, in which the total transmittance of the light shielding portions of the photomask is 0%, has a good shape with high rectangularity. It was.
On the other hand, the LS pattern (2) formed in Comparative Example 1 different from the present invention, in which the total transmittance of the light-shielding portions of the photomask is 12%, has a remarkably bad resist pattern shape such as pattern film reduction. I was able to confirm.

  From the above results, it was confirmed that the resist pattern forming method of Example 1 according to the present invention can form a resist pattern with a good shape and high resolution.

It is a schematic process drawing explaining the resist pattern formation method (a) of the preferable embodiment of the resist pattern formation method of this invention.

Explanation of symbols

1 ... support,
2 ... resist film,
3 ... resist pattern,
3a: exposure part,
3b ... exposure part,
5 ... Photomask.

Claims (3)

A resist pattern forming method in which a chemically amplified resist composition is applied onto a support to form a resist film, and the resist film is selectively exposed multiple times through a photomask,
A resist pattern forming method, wherein a total sum of transmittances of light shielding portions of a photomask used for each selective exposure is set to less than 0 to less than 12%.   The resist pattern forming method according to claim 1, wherein the total transmittance is 0 to 6%.   The resist pattern forming method according to claim 1, wherein at least a photomask having a light-shielding portion having a transmittance of 0% is used.

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