JP2008159874A - Method for forming resist pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new resist pattern forming method capable of forming a resist pattern having excellent pattern transfer reproducibility and a high resolution. <P>SOLUTION: In the resist pattern forming method for forming a resist film on a support body and selectively exposing the resist film a plurality of times through a photomask, the width of an exposure portion of the resist film in each selective exposure is larger than the width of a light transmitting portion of the photomask. <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.
Resist compositions include a chemically amplified type that utilizes a phenomenon in which acid is generated by radiation from a mixed acid generator, and a non-chemically amplified type that utilizes a direct radiation chemical reaction to a substrate component. 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. For this reason, immersion exposure is expected to be able to form resist patterns with low cost, high resolution, and excellent depth of focus. 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, improvement of various lithographic characteristics is required. For example, as the pattern is miniaturized, the line width of a line pattern that should be uniform when transferred with good reproducibility is obtained. The phenomenon of non-uniformity becomes a problem.
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 excellent pattern transfer reproducibility and high resolution.

In order to achieve the above object, the present invention employs the following configuration.
That is, the present invention is a resist pattern forming method in which a resist film is formed on a support and selective exposure is performed a plurality of times through a photomask on the resist film. In the resist pattern forming method, the exposed portion width is larger than the light transmitting portion width of the photomask.

In the present specification and claims, the “translucent portion width of the photomask” means the width of the translucent portion itself of the phototransparent portion and the light-shielding portion of the photomask in the same magnification exposure. In the reduced projection exposure, the width of the theoretical reduction magnification of the light transmitting portion of the light transmitting portion and the light shielding portion of the photomask is referred to.
The “exposed portion width of the resist film” refers to the width of the exposed portion of the latent image formed on the resist film when selective exposure is performed through the photomask, corresponding to the light transmitting portion of the photomask. .
“Exposure” is a concept including general irradiation of radiation.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a novel resist pattern forming method capable of forming a resist pattern having excellent pattern transfer reproducibility and high resolution.

≪Resist pattern formation method≫
The resist pattern forming method of the present invention is a method in which a resist film is formed on a support and selective exposure is performed a plurality of times on the resist film through a photomask. Here, the resist film on the support can be formed by applying a resist composition on the support.

[Resist composition (pattern forming material)]
The resist composition for forming a resist film on the support is not particularly limited, and can be selected from a large number of resist compositions such as chemically amplified and non-chemically amplified resist compositions proposed so far. The exposure light source to be used, the lithography characteristics, etc. can be appropriately selected and used.
The resist composition may be a negative resist composition or a positive resist composition, preferably a positive resist composition.
The resist composition may be a non-chemically amplified resist composition or a chemically amplified resist composition. A chemically amplified resist composition is preferred.

  Examples of the non-chemically amplified resist composition include a main chain decomposition type positive resist composition in which the main chain in the base material component is decomposed by exposure to increase the solubility in a developer, and the base material component is exposed by exposure. Examples thereof include a positive resist composition that changes to alkali solubility and a negative resist composition in which the base component changes to hardly soluble upon exposure.

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.
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 them, a carboxy group, an alcoholic hydroxyl group, and a phenolic hydroxyl group are preferable because they can form a resist pattern having a small line edge roughness (unevenness on the pattern side wall) at the nano level.

  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 a tert-butyloxycarbonyl group or a tert-pentyloxycarbonyl group; a tert-butyloxycarbonylmethyl group or a tert-butyloxycarbonylethyl group. Tertiary alkyloxycarbonylalkyl groups such as these; tertiary alkyl groups such as tert-butyl and tert-pentyl 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.

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-pentyl 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-pentyl 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 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 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 5-position or 6-position of the norbornyl 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.

<(B) component>
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 component>
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 isopentyl ketone, and 2-heptanone; ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene Polyhydric alcohols such as glycol 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), acetic acid Can chill, 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>
The resist pattern forming method of the present invention is a resist pattern forming method (hereinafter referred to as “double exposure method”) in which a resist film is formed on a support and selective exposure is performed multiple times on the resist film through a photomask. The exposed portion width of the resist film for each selective exposure is larger than the light transmitting portion width of the photomask.

Here, the “transparent part width of the photomask” means the width of the translucent part of the photomask among the translucent part and the light-shielding part of the photomask in the same magnification exposure. In other words, it refers to the width of the theoretical reduction magnification of the light transmitting portion and the light shielding portion of the photomask. More specifically, when the photomask pattern is a line pattern such as a line-and-space pattern or an isolated line pattern, the width of the line or space corresponding to the translucent portion is used. In the case of a hole pattern, it refers to the width of the hole corresponding to the translucent portion.
The “light-shielding portion width of the photomask” refers to a portion where light is not transmitted in the binary mask, and a halftone portion (portion where light is transmitted at a constant rate) in the halftone mask.
The “exposed portion width of the resist film” refers to the width of the exposed portion of the latent image formed on the resist film when selective exposure is performed through the photomask, corresponding to the light transmitting portion of the photomask. . Specifically, the exposed portion width of the resist film can be evaluated by the pattern width of the resist pattern obtained by development.
As the “double exposure method”, for example, a resist pattern forming method (a) shown below is preferable.

Resist pattern forming method (a):
A step of coating the resist composition on the support to form a resist film (hereinafter referred to as “film forming step (0)”), and exposing the resist film to the resist film through a photomask. Under the condition that the part width is larger than the light-transmitting part width of the photomask, selective exposure is continuously performed a plurality of times, followed by development to form a resist pattern (hereinafter referred to as “patterning step (0)”). And a resist pattern forming method.

Hereinafter, a preferred embodiment of the resist pattern forming method (a) of the present invention will be described with reference to FIG. This embodiment is an example of a case where, for example, a chemically amplified positive resist composition is used as the resist composition, and selective exposure through a photomask is continuously performed twice.
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, with respect to the resist film 2, under the condition that the exposed portion width of the resist film 2 is larger than the translucent portion width of the photomask 5 through the photomask 5. Selective exposure is performed.
Subsequently, as shown in FIG. 1C, the photomask 5 is moved a predetermined distance in a predetermined direction, and the exposed portion width of the resist film is again passed through the photomask 5 through the photomask 5. Selective exposure is performed under conditions that are greater than the optical part width.
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 (quartz glass, etc.) 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. Further, an inorganic and / or organic antireflection film may be provided on the substrate.

There is no restriction | limiting in particular as a resist composition, It can select and use suitably from many resist compositions, such as the above-mentioned chemically amplified type and non-chemically amplified type.
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 resist composition on the support 1. Application of the resist composition can be performed 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, the width of the exposed portion of the resist film 2 is larger than the width of the light transmitting portion of the photomask 5 through the photomask 5 on which a predetermined pattern is formed. Selective exposure (hereinafter sometimes referred to as “first exposure”) is performed under the following exposure amount condition. Subsequently, the photomask 5 is moved by a predetermined distance in a predetermined direction, and the width of the exposed portion of the resist film 2 is changed to the light transmittance of the photomask 5 through the photomask 5 again. Selective exposure (hereinafter sometimes referred to as “second exposure”) is performed under an exposure amount condition that is larger than the part width.
In the present invention, in the patterning step (0), it is essential that the width of the exposed portion of the resist film for each selective exposure is larger than the width of the light transmitting portion of the photomask. The ratio of the light transmitting portion width of the photomask to the exposed portion width of the resist film is preferably 60 to 99%, more preferably 70 to 95%, and most preferably 80 to 90%. . By setting this range, a resist pattern having a more uniform line shape and a better shape can be formed.

  As the photomask 5, the same photomask may be used for each selective exposure, or different photomasks may be used. In the present invention, if the width of the exposed portion of the resist film is larger than the width of the light-transmitting portion of the photomask, the ratio of the width of the light-transmitting portion of the photomask to the width of the exposed portion of the resist film is selective. The same conditions may be used for each exposure, or different conditions may be used.

  In the present invention, as a photomask, for example, a binary mask (Binary-Mask) with a light-shielding part having a transmittance of 0% or a halftone phase shift mask (HT-Mask) with a light-shielding part having a transmittance of 6%. Can be used.

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.
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 resist pattern forming method of the present invention, it is preferable to use a halftone phase shift mask (HT-Mask) because it is excellent due to the effects of the present invention.

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 a line-and-space resist pattern is formed, selective exposure is performed using a line-and-space photomask 5 in which a plurality of lines are arranged at a constant pitch in the first exposure, and then the photomask 5 Is selectively moved so that a line pattern is formed by the second exposure at an intermediate position between the line pattern and the line pattern selectively exposed by the first exposure. By performing the exposure, the line-and-space resist pattern 3 is formed at a pitch of about ½ of the line-and-space pitch that is selectively exposed in the first exposure.

For example, in the first exposure, a resist using a line-and-space photomask (transmission part width of the photomask = 80 nm) in which line patterns with a line width of 320 nm are arranged at equal intervals (space width 80 nm, pitch 400 nm) After performing selective exposure under the condition that the exposed portion width of the film is 100 nm, the photomask is translated by 200 nm in a direction perpendicular to the direction of the line, and the second exposure is performed under the same conditions and developed. Thus, a line and space pattern with a line width of 100 nm and a line width: space width = 1: 1 can be formed. For example, by exposing with an exposure amount larger than the optimum exposure amount (Eop) at which the exposed portion width of the resist film and the light transmitting portion width of the photomask are equal, the exposed portion width of the resist film is reduced to the light transmitting amount of the photomask. It can be larger than the part width.
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.).

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, oxygen plasma etching or etching using CF ₄ gas or CHF ₃ gas is preferable from the viewpoint of high resistance 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.

The organic film-forming material further contains miscible additives as desired, for example, additional resins for improving the performance of organic films, surfactants for improving coating properties, dissolution inhibitors, plasticizers, Stabilizers, colorants, antihalation agents and the like can be appropriately contained.
The organic film forming material can be manufactured by dissolving the above-described materials such as the resin component in an organic solvent. As an organic solvent, the thing similar to what was illustrated as (S) component of the chemically amplified resist composition mentioned above can be used.

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 uniform line width and a 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. For this reason, the contrast between the exposed portion and the unexposed portion is reduced. For example, in the case of a positive resist composition, when a part of the unexposed portion is dissolved, the resist pattern shape is deteriorated. Conceivable.
In the present invention, the contrast between the exposed portion and the unexposed portion is improved by controlling the exposed portion width of the resist film for each selective exposure to a condition larger than the light transmitting portion width of the photomask. It is estimated that the occurrence of is suppressed. Therefore, according to the present invention, it is considered that a resist pattern having excellent pattern transfer reproducibility, that is, a line pattern having a uniform line width 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” (manufactured by Brewer Science Co., Ltd.) was applied on an 8-inch silicon wafer subjected to hexamethyldisilazane (HMDS) treatment (110 ° C., 60 s) using a spinner, An organic antireflection film having a thickness of 89 nm was formed by baking on a plate at 205 ° C. for 60 seconds and drying.
On the organic antireflection film, a chemically amplified positive resist composition “TArF-P6239 ME” (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied using a spinner. A resist film having a thickness of 125 nm was formed by performing a pre-baking (PAB) treatment at 60 ° C. for 60 seconds and drying.

  Next, a protective film-forming coating solution “TSRC-002” (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied onto the resist film using a spinner and heated at 90 ° C. for 60 seconds. A top coat having a thickness of 28 nm was formed.

Next, line and space using an immersion ArF exposure apparatus NSR-S609B (manufactured by Nikon; NA (numerical aperture) = 1.07, σ = Di-pole, reduction ratio 1/4 times, immersion medium: water) Through a pattern halftone mask (Dai Nippon Printing Co., Ltd .; light shielding part (halftone part) width 333 nm, transmittance 6%, light transmitting part width 67 nm, pitch 400 nm), “line width 300 nm, space width 100 nm, ArF excimer laser (193 nm) is selectively irradiated to the resist film on which the top coat is formed under the condition (exposure amount: 40 mJ / cm ² ) that targets “line width: space width = 3: 1”. (Exposed portion width of resist film 100 nm).
Subsequently, the halftone 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 (exposure amount 40 mJ / cm ² ).

The top coat was removed using a protective film removing solution “TS-Remover-S” (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.), followed by PEB treatment at 110 ° C. for 60 seconds, and further at 23 ° C. Development was carried out with a 38 mass% tetramethylammonium hydroxide (TMAH) aqueous solution for 60 seconds, followed by water rinsing with pure water for 20 seconds, followed by shake-off drying.
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.

(Examples 2-4, Reference Example 1, Comparative Examples 1-2)
Using the half-tone mask (pitch 400 nm) with the translucent width described in Examples 2 to 4, Reference Example 1 and Comparative Examples 1 and 2 in Table 1, “line width 300 nm, space width 100 nm, line width: space A line-and-space (1) in which line patterns with a line width of 100 nm are arranged at equal intervals (a pitch of 200 nm) are the same as in Example 1 except that the exposure amount is adjusted with a target of “width = 3: 1”. : 1) resist pattern (LS pattern (1)) was formed.

(Example 5)
Using a line-and-space pattern halftone mask (Dai Nippon Printing Co., Ltd .; light-shielding part (halftone part) width 300 nm, light-transmitting part width 60 nm, pitch 360 nm), “line width 270 nm, space width 90 nm, line width : Space width = 3: 1 ”, except that the target condition (exposure amount 44 mJ / cm ² ) was adjusted, and line patterns with a line width of 90 nm were arranged at equal intervals (pitch 180 nm) in the same manner as in Example 1. A line-and-space (1: 1) resist pattern (LS pattern (2)) was formed (second exposure amount 44 mJ / cm ² ).

(Examples 6-8, Reference Example 2, Comparative Examples 3-4)
Using the half-tone masks having the translucent width described in Examples 6 to 8, Table 2 and Comparative Examples 3 to 4 in Table 2 (all pitch 360 nm), “line width 270 nm, space width 90 nm, line width : Space width = 3: 1 ”, except that the amount of exposure was adjusted, and line and space in which line patterns with a line width of 90 nm were arranged at equal intervals (pitch 180 nm) in the same manner as in Example 5. A (1: 1) resist pattern (LS pattern (2)) was formed.

[Evaluation of resist pattern shape]
About each LS pattern formed above, each upper surface shape is observed with a scanning electron microscope (made by Hitachi, Ltd., brand name: S-9380), and a cross-sectional shape is a scanning electron microscope (made by Hitachi, Ltd., brand name). : S-4700), and the resist pattern shape was evaluated.

<Evaluation of line width roughness (LWR)>
In addition, the line width of these LS patterns was measured at five locations in the longitudinal direction of the line with the scanning electron microscope (measurement voltage 300 V), and from the result, a value that is three times the standard deviation (s) as a measure of LWR. (3 s; unit nm) was calculated. The results are shown in Tables 1 and 2.
The smaller the value of 3s, the smaller the roughness of the line width, which means that a resist pattern with a more uniform width was obtained.

As a result, the exposure amount for each selective exposure is made larger than the normal optimum exposure amount so that the width of the exposed portion of the resist film is larger than the width of the light-transmitting portion of the photomask. It was confirmed that the LS patterns formed in Examples 1 to 8 had a good shape with a low LWR, a uniform line width, and a high rectangularity.
On the other hand, by reducing the exposure amount for each selective exposure, the exposed portion width of the resist film is smaller than the translucent portion width of the photomask. The LS pattern had a large LWR, a non-uniform line width, and a very bad resist pattern shape.

  From the above results, according to the resist pattern forming method according to the present invention, the resist pattern transfer reproducibility is excellent, the LWR is small, the line width of the line pattern is uniform, the shape is good, and the resolution is high. It was confirmed that a pattern could be formed.

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 (2)

A resist pattern forming method in which a resist film is formed on a support, and the resist film is selectively exposed multiple times through a photomask,
The resist pattern forming method, wherein an exposed portion width of the resist film for each selective exposure is larger than a light transmitting portion width of the photomask.   The resist pattern forming method according to claim 1, wherein a ratio of a light transmitting portion width of the photomask to an exposed portion width of the resist film is 60 to 99%.

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