JP2006003781A - Positive resist composition and method for forming resist pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide techniques capable of obtaining a satisfactory pattern controllability in a thermal flow process. <P>SOLUTION: The positive resist composition contains (A) a base resin component having an acid dissociable solubility suppressing group and having the alkali solubility which increases by the effect of acid; and (B) an acid generating agent component generating an acid by irradiation of radiation. The component (A) contains a resin, having ≤1.0 (1/μm) absorbance at 193 nm wavelength and ≤1.5 dispersion degree (Mw/Mn). The positive resist composition is used for the thermal flow process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to a positive resist composition for a thermal flow process and a resist pattern forming method.

  In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, miniaturization has rapidly progressed due to advances in lithography technology. As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, in the past, ultraviolet rays typified by g-line and i-line were used, but now KrF excimer laser (248 nm) is introduced, and ArF excimer laser (193 nm) has begun to be introduced. Yes.

As one of the resist materials that satisfy the conditions of high resolution capable of reproducing patterns with fine dimensions, a base resin whose alkali solubility is changed by the action of an acid and an acid generator that generates an acid upon exposure are used as an organic solvent. Dissolved chemically amplified resist compositions are known.
A chemically amplified positive resist composition proposed as a resist material suitable for an exposure method using an ArF excimer laser is generally a (meth) acrylic acid resin having an acid dissociable, dissolution inhibiting group as a base resin. Is used (see, for example, Patent Document 1).

On the other hand, in addition to countermeasures for ultra-miniaturization from the resist material side, research and development of techniques that exceed the resolution limit of resist materials are being conducted from the aspect of pattern formation methods.
As one of such miniaturization techniques, recently, a thermal flow process has been proposed in which after a resist pattern is formed by a normal lithography technique, the resist pattern is subjected to heat treatment to reduce the pattern size (for example, (See Patent Documents 2 and 3).
In the thermal flow process, after a resist pattern is once formed by photolithography technology, the resist is heated, softened, and flowed in the pattern gap direction, so that the resist pattern pattern size, that is, the portion where the resist is not formed Is reduced (such as the hole diameter of the hole pattern and the space width of the line and space (L & S) pattern).
JP 2003-164347 A JP 2000-188250 A JP 2000-356850 A

However, the thermal flow process has a problem that it is difficult to control the pattern size during the flow. If the pattern size controllability at the time of flow is inferior, for example, the pattern size largely fluctuates with variation in heating temperature, and the in-plane uniformity of pattern dimensions is low.
The present invention has been made in order to solve the above-described problems, and is a technique with good pattern controllability in a thermal flow process, that is, a small flow rate during thermal flow (a dimensional change amount of a resist pattern with respect to a temperature change). It is an object of the present invention to provide a positive resist composition having the following formula:

In order to achieve the above object, the present invention employs the following configuration.
That is, the positive resist composition of the present invention has (A) a base resin component having an acid dissociable, dissolution inhibiting group and increased in alkali solubility by the action of an acid, and (B) generating an acid upon irradiation with radiation. A positive resist composition containing an acid generator component,
The component (A) includes a resin having an absorbance at 193 nm of 1.0 (1 / μm) or less and a dispersity (Mw / Mn) of 1.5 or less, and the positive resist composition has a thermal It is for a flow process.
In the resist pattern forming method of the present invention, a positive resist composition is applied onto a substrate, pre-baked, selectively exposed, then subjected to PEB (post-exposure heating), alkali development, and resist development. A thermal flow process is performed after the pattern is formed.

  In the present specification, “(α-lower alkyl) acrylic acid ester” means one or both of an α-lower alkyl acrylic acid ester such as methacrylic acid ester and an acrylic acid ester. Here, the “α-lower alkyl acrylate ester” means that a hydrogen atom bonded to the α carbon atom of the acrylate ester is substituted with a lower alkyl group. The “structural unit” means a monomer unit constituting the polymer. Further, the “structural unit derived from (α-lower alkyl) acrylate” means a structural unit formed by cleavage of the ethylenic double bond of (α-lower alkyl) acrylate.

  In the present invention, the controllability of the pattern size during the flow can be improved in the thermal flow process. That is, it is possible to provide a positive resist composition that exhibits a low flow rate.

[Positive resist composition]
(A) Component In the present invention, the component (A) is a resin having an absorbance at 193 nm of 1.0 (1 / μm) or less and a dispersity (Mw / Mn) of 1.5 or less [hereinafter, (A -1) It may be referred to as a component].

First, the absorbance will be described. “The absorbance at 193 nm is 1.0 (1 / μm) or less” is preferably used to achieve the resolution required for a resist composition when an ArF excimer laser is used as a light source. Is a characteristic. The smaller the absorbance, the higher the transparency, and the exposure light reaches the bottom of the substrate in the resist film, which is preferable because of excellent resolution and resist pattern shape. The numerical value is preferably 0.8 (1 / μm) or less, more preferably 0.5 (1 / μm) or less, and still more preferably 0.3 (1 / μm) or less. In addition, what is necessary is just to measure the light absorbency by the well-known absorptiometric method.
Specifically, the component (A-1) is dissolved in a soluble organic solvent such as propylene glycol monomethyl ether acetate to form a uniform solution, which is applied on a glass substrate so as to have a film thickness of 1.0 μm. Measure with light.

Next, the degree of dispersion will be described.
The degree of dispersion is a value represented by mass average molecular weight / number average molecular weight (Mw / Mn). When the degree of dispersion is 1.5 or less, the pattern controllability during flow is improved, and the PEB margin and resist heat resistance are improved. The numerical value of the dispersity is preferably 1.4 or less, more preferably 1.3 or less, and still more preferably 1.2 or less. The lower limit is theoretically 1.0, but the lower the value, the better.

In addition, (A) component should just contain resin [(A-1) component] which has a light absorbency and dispersion degree as mentioned above.
In other words, the component (A) may contain the above component (A-1) and other resins, but is particularly composed of one or more of the above components (A-1). Preferably there is.
That is, in particular, with regard to the degree of dispersion, for example, by mixing two or more resins having a degree of dispersion of 1.5 or less, the component (A) (mixture) may have a degree of dispersion exceeding 1.5. Absent. In short, it is sufficient that at least one kind of dispersion of each resin at the time of mixing is 1.5 or less, and it is particularly preferable that all of the resins to be mixed have a dispersion of 1.5 or less.
In addition, when (A) component contains resin with a dispersion degree exceeding 1.5, it is set as the range by which the objective of this invention is achieved.
Regarding the absorbance, the component (A) only needs to contain at least one component (A-1), but the component (A) as a whole satisfies the above value of 1.0 (1 / μm) or less. It is preferable.

In addition, the mass average molecular weight (Mw; polystyrene conversion standard by gel permeation chromatography) of the component (A) of the present invention is about 2000 to 50000, preferably about 3000 to 30000, more preferably about 5000 to 15000. It is preferable because it has moderate alkali solubility, can form a good resist pattern, and has a good flow rate.
Moreover, the preferable range of (A-1) component is also the same.

The component (A-1) preferably has the following glass transition point (Tg), and this can be realized with a small degree of dispersion.
In other words, conventional ArF resist resins include those containing a structural unit derived from an (α-lower alkyl) acrylate ester (hereinafter sometimes abbreviated as the structural unit (a)). In the structural unit (a), the lower alkyl group bonded to the α carbon atom of the α-lower alkyl acrylic acid may be linear or branched, preferably an alkyl group having 1 to 5 carbon atoms, Preferred is a methyl group having 1 carbon atom.

More specifically, examples of the resin including the structural unit (a) include the following three types (a) to (c).
(A) a polymer of a full acrylate unit consisting only of a structural unit derived from an acrylate ester (hereinafter sometimes abbreviated as a structural unit (aa)),
(B) a polymer of a full α-lower alkyl acrylate ester unit consisting only of a structural unit derived from an α-lower alkyl acrylate ester (hereinafter sometimes abbreviated as a structural unit (ma)),
(C) A copolymer of an acrylate ester / α-lower alkyl acrylate ester unit comprising the structural unit (aa) and the structural unit (ma).

The Tg of the polymer (a) is about 110 to 140 ° C., the Tg of the polymer (b) is about 140 to 180 ° C., and the Tg of the copolymer (c) is a numerical value therebetween. It becomes.
In the present invention, the component (A) preferably contains the structural unit (a).
In the present invention, the resin (A-1) having a dispersity of 1.5 or less used for the component (A) is a conventional resin having a dispersity exceeding 1.5 as described above and having the same Mw. It has been confirmed that Tg is increased by about 10 to 30 ° C. compared to the resin used. It has also been confirmed that the effect of increasing the Tg is the same in the above (a), (b) and (c).
Therefore, the component (A-1) can be characterized by having a Tg of preferably 120 ° C. or higher, more preferably 135 ° C. or higher. More preferably, the Tg of the entire component (A) is 120 ° C. or higher.
The upper limit of Tg is not particularly limited as long as it is below the decomposition point of the resin, but is preferably about 200 ° C or lower, preferably 180 ° C or lower, more preferably 160 ° C or lower. By having such Tg, PEB margin and resist heat resistance are improved.
In particular, from the viewpoint of improving controllability in the thermal flow process, in the present invention, it is preferable to use the resin (a) and the resin (c) in the component (A) [preferably the component (A-1)]. In particular, the resin (c) is preferable.
In addition, in the component (A) [preferably the component (A-1)], the structural unit (ma) preferably has 20 mol% or more.
In addition, in the component (A) [preferably the component (A-1)], the structural unit (aa) is preferably 40 mol% or more.
In the case of the resin (c), in the component (A) [preferably the component (A-1)], the proportion of the structural unit (aa) is particularly 40 to 80 mol%, particularly 50 to 70 mol. %, The proportion of the structural unit (ma) is preferably 60 to 20 mol%, particularly 30 to 50 mol%.

The acid dissociable, dissolution inhibiting group in component (A) has an alkali dissolution inhibiting property that renders the entire component (A) insoluble to alkali before exposure, and simultaneously dissociates after exposure by the action of an acid generated from component (B). As long as it changes the whole component (A) to be alkali-soluble, it is not particularly limited, and known materials can be used so far.
As such an acid dissociable, dissolution inhibiting group, for example, one or more of those conventionally used for (meth) acrylic acid-based resins used in resist compositions for ArF excimer lasers are used. Can be used in any combination, and specific examples include a chain alkoxyalkyl group, a tertiary alkyloxycarbonyl group, a tertiary alkyl group, a tertiary alkoxycarbonylalkyl group, and a cyclic ether group. .

Examples of the chain alkoxyalkyl group include 1-ethoxyethyl group, 1-methoxymethylethyl group, 1-isopropoxyethyl group, 1-methoxypropyl group, 1-n-butoxyethyl group and the like.
Examples of the tertiary alkyloxycarbonyl group include a tert-butyloxycarbonyl group and a tert-amyloxycarbonyl group.
The tertiary alkyl group includes a branched tertiary alkyl group such as a tert-butyl group and a tert-amyl group, an aliphatic polycyclic group such as a 2-methyl-adamantyl group and a 2-ethyladamantyl group. Examples include tertiary alkyl groups, 1-methylcyclopentyl groups, 1-ethylcyclopentyl groups, 1-methylcyclohexyl groups, aliphatic monocyclic group-containing tertiary alkyl groups such as 1-ethylcyclohexyl groups, and the like.
Examples of the tertiary alkoxycarbonylalkyl group include a tert-butyloxycarbonylmethyl group and a tert-amyloxycarbonylmethyl group.
Examples of the cyclic ether group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

  Among these, a tertiary alkyl group is preferable, and an aliphatic monocyclic or polycyclic group-containing tertiary alkyl group is more preferable.

  Here, the aliphatic monocyclic group and the aliphatic polycyclic group represent a monocyclic group or a polycyclic group having no aromaticity. Particularly preferred are lipoaliphatic polycyclic groups. The aliphatic monocyclic group or aliphatic polycyclic group is not limited to a group consisting of carbon and hydrogen, and may have a substituent, but is preferably a hydrocarbon group. The hydrocarbon group may be either saturated or unsaturated, but is usually preferably saturated.

As an aliphatic polycyclic group, it can be arbitrarily selected from those proposed in the ArF resist. Specifically, examples of the bicycloalkane, tricycloalkane, tetracycloalkane, etc. include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, etc. It is done. Of these, an adamantyl group, norbornyl group, and tetracyclodecanyl group are preferred industrially.
Furthermore, as the aliphatic polycyclic group-containing tertiary alkyl group, an aliphatic polycyclic group in which the carbon atom bonded to the ester portion of (α-lower alkyl) acrylate ester forms a tertiary alkyl group Containing tertiary alkyl groups are preferred.

  Such an acid dissociable, dissolution inhibiting group is usually bonded to a side chain of the resin, and specifically, preferably bonded to an ester portion of a structural unit derived from a carboxylic acid ester. Especially, it is preferable to couple | bond with the ester part of the structural unit induced | guided | derived from ((alpha) -lower alkyl) acrylate ester, and (A) component becomes resin containing the structural unit (a) in this case.

-Structural unit (a-1)
Component (A) (preferably Component (A-1)) is a structural unit (a-1) derived from an acid dissociable, dissolution inhibiting group-containing (α-lower alkyl) acrylate ester as the structural unit (a). It is preferable to contain.
The structural unit (a-1) is selected from the group consisting of structural units having an aliphatic polycyclic group-containing tertiary alkyl group represented by the following general formulas (I), (II) and (III) Those containing at least one selected from the above are excellent in dry etching resistance and excellent in high resolution.

In the above formulas (I) to (III), R is a hydrogen atom or a lower alkyl group, R ¹ is a lower alkyl group, R ² and R ³ are each independently a lower alkyl group, and R ⁴ is a tertiary alkyl group. is there.
The lower alkyl group for R may be linear or branched, and is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group having 1 carbon atom.
The lower alkyl group for R ¹ , R ² and R ³ may be linear or branched, preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group or ethyl having 1 to 2 carbon atoms. Groups.
Examples of the tertiary alkyl group for R ⁴ include branched tertiary alkyl groups such as a tert-butyl group and a tert-amyl group.

  Among these, from the structural unit represented by the general formula (I), and among them (α-lower alkyl) acrylic acid ester having a 2-lower alkyladamantyl group such as 2-methyladamantyl group and 2-ethyladamantyl group. It is preferable to have a derived structural unit because an excellent resist pattern can be obtained.

・ Structural unit (a-2)
In addition to the structural unit (a-1), the component (A) [preferably the component (A-1)] further contains a lactone-containing aliphatic monocyclic or polycyclic group ( When the structural unit (a-2) derived from (α-lower alkyl) acrylate ester is included, the adhesion between the resist film and the substrate can be increased, and the hydrophilicity with the developer can be increased. In this case, the film does not peel off, which is preferable.
Here, the aliphatic monocyclic group and the aliphatic polycyclic group represent a ring structure having no aromaticity as described above.
The lactone-containing aliphatic monocyclic or polycyclic group is a monocyclic group consisting of a lactone ring or a polycyclic group having a lactone ring. In this case, the lactone ring indicates one ring containing a —CO—O— structure, and this is counted as the first ring. Therefore, here, in the case of only a lactone ring, it is called a lactone-containing monocyclic group, and when it has another ring structure, it is called a lactone-containing polycyclic group regardless of the structure.

    Examples of the lactone-containing aliphatic monocyclic group in the structural unit (a-2) include a group in which one hydrogen atom has been removed from γ-butyrolactone. The aliphatic polycyclic group in the structural unit (a-2) can be appropriately selected from a large number of polycyclic groups similar to those exemplified in the structural unit (a-1). Preferable examples include groups in which one hydrogen atom is removed from a lactone-containing polycycloalkane having the following structural formula.

    As the structural unit (a-2), the following general formula (IV) or (V) derived from an (α-lower alkyl) acrylate ester containing a lactone-containing aliphatic monocyclic group or aliphatic polycyclic group: ), (VI), (VII) and structural units represented by (VIII) are preferred.

（式中、Ｒは前記に同じであり、Ｒ^５は、水素原子又は低級アルキル基であり、ｋは１乃至４の整数である。）
Ｒ^５としては、直鎖状でも分岐状でもよく、好ましくは炭素原子数１〜５、より好ましくは１〜３のアルキル基が挙げられる。

(In the formula, R is the same as above, R ⁵ is a hydrogen atom or a lower alkyl group, and k is an integer of 1 to 4.)
R ⁵ may be linear or branched, and is preferably an alkyl group having 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms.

（Ｒは前記に同じである。）

(R is the same as above.)

（Ｒは前記に同じである。）

(R is the same as above.)

（Ｒは前記に同じであり、oは０又は１である。）

(R is the same as above, and o is 0 or 1.)

（Ｒは前記に同じである。）

(R is the same as above.)

Among these, the structural unit represented by general formula (IV), (V), and (VI), especially the structural unit represented by general formula (IV) were obtained (A-1). It is most preferable because it is suitable for monodispersing components and has excellent flow controllability, resolution, and PEB margin.
More preferable examples of the general formula (IV) include the following general formula (IX).

（Ｒは前記に同じである。）

(R is the same as above.)

・ Structural unit (a-3)
In addition, the component (A) [preferably the component (A-1)] is the structural unit (a), in addition to the structural unit (a-1), or the structural unit (a-1) unit and the structural unit. In addition to (a-2), when having a structural unit (a-3) derived from an (α-lower alkyl) acrylate ester containing a polar group-containing aliphatic hydrocarbon group, development of the entire component (A) Hydrophilicity with the liquid is increased, and alkali solubility is improved in the exposed area. Therefore, it contributes to the improvement of resolution.
Examples of the polar group include a hydroxyl group and a cyano group, and a hydroxyl group is preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group (alkylene group) having 1 to 10 carbon atoms and an aliphatic polycyclic group. Here, “aliphatic” refers to those having no aromaticity as in the case described above. The aliphatic polycyclic group in the structural unit (a-3) can be appropriately selected from a number of polycyclic groups similar to those exemplified in the structural unit (a-1).

  As the structural unit (a-3), when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a chain hydrocarbon group having 1 to 10 carbon atoms, hydroxyethyl of (α-lower alkyl) acrylic acid When a structural unit derived from an ester or the hydrocarbon group is an aliphatic polycyclic group, a structural unit represented by the following general formula (X) is preferred.

（式中、Ｒは前記に同じであり、ｎは１乃至３の整数である）

(Wherein R is the same as above, and n is an integer of 1 to 3)

  Among these, those in which the number of n is 1 and the hydroxyl group is bonded to the 3-position of the adamantyl group are preferable.

  The proportion of each structural unit is preferably excellent in resolution when the structural unit (a-1) is in the range of 30 to 60 mol%, preferably 30 to 50 mol%. When the structural unit (a-2) is in the range of 20 to 60 mol%, preferably 20 to 50 mol%, the resolution is excellent. When the structural unit (a-3) is in the range of 0 to 50 mol%, preferably in the range of 10 to 40 mol%, the resist pattern shape is excellent.

・ Structural unit (a-4)
In addition, the component (A) [preferably the component (A-1)] is the structural unit (a-4) other than the structural units (a-1), (a-2), and (a-3). A structural unit derived from an (α-lower alkyl) acrylate ester containing an aliphatic polycyclic group may be included.
Here, the terms other than the structural units (a-1), (a-2), and (a-3) mean that they do not overlap with each other, and the aliphatic polycyclic group is as described above (a-1 ), (A-2), and a number of aliphatic polycyclic groups similar to those in (a-3). Many structural units (a-4) have been known as ArF positive resist materials, and in particular, tricyclodecanyl (meth) acrylate, adamantyl (meth) acrylate, tetracyclodeca A unit derived from at least one selected from nyl (meth) acrylate is preferable in terms of industrial availability.
These structural units are shown below as structural formulas.

（Ｒは前記に同じである。）

(R is the same as above.)

（Ｒは前記に同じである。）

(R is the same as above.)

（Ｒは前記に同じである。）

(R is the same as above.)

  The proportion of each unit in the case of a quaternary system is 25 to 50 mol%, preferably 30 to 40 mol% in the structural unit (a-1), and 25 in the structural unit (a-2). -50 mol%, preferably in the range of 30-40 mol%, the structural unit (a-3) is in the range of 10-30 mol%, preferably 10-20 mol%, and the structural unit (a-4) Is in the range of 5 to 25 mol%, preferably 10 to 20 mol%, since the depth of focus of the isolated pattern can be improved and the proximity effect can be reduced. In addition, when deviating from this range, there is a problem that the resolution is lowered, which is not preferable.

-About the synthesis | combining method of (A-1) component In this invention, it is preferable that (A-1) component is resin synthesize | combined by the living radical polymerization method.
The conventional best known conventional synthesis method is free radical polymerization. However, in free radical polymerization, for example, as disclosed in JP-A-2001-48931, even if narrow (mono) dispersion can be achieved, it is about 1.8, and monodispersion beyond that is difficult.
A method called living anion polymerization is also known. However, in living anion polymerization, for example, a catalyst such as butyllithium is used. However, for certain monomers, there is a problem that the catalyst is lost and the chain reaction does not proceed (monomer selectivity). More specifically, when a monomer containing a γ-butyrolactone residue contained in the structural unit (a-2) or a monomer containing a hydroxyl group contained in the structural unit (a-3) is used, the catalyst is Since the carbonyl group and the hydroxyl group are attacked preferentially over the ethylenic double bond, the polymerization reaction does not proceed.
On the other hand, in living radical polymerization, there is no problem of monomer selectivity seen in living / anionic polymerization, and a wide range of monomers can be selected. In addition, it can be monodispersed significantly compared to free radical polymerization.
Therefore, in the present invention, as each structural unit of the component (A-1), a γ-butyrolactone residue or a structural unit contained in the structural unit (a-2), which is difficult to use in the living anion polymerization described above, is used. When the hydroxyl group contained in (a-3) is included, the advantage in living radical polymerization is exhibited.

Living radical polymerization is performed by using S = CZ-SR ′ [as a medium for controlling the active / inactive cycle, as described in documents such as Macromolecular Symposia 1999, 143, 291 and Macromolecules 2000, 34, 402. In the formula, Z represents an aryl group, and R ′ represents an alkyl group.] This can be performed by reversible addition fragmentation chain transfer polymerization (RAFT), which is a polymerization method using a dithio compound represented by the formula:
Specifically, in the free radical polymerization, polymerization may be performed using the dithio compound. More specifically, each monomer, a polymerization initiator, and the dithio compound are dissolved in an organic solvent and reacted by heating, stirring, or the like. Just do it. The temperature and time for the polymerization may be substantially the same as those for free radical polymerization, and may be appropriately adjusted depending on the polymer having the target constitutional unit and its mass average molecular weight.
The Mw and dispersity (Mw / Mn) of the component (A-1) thus obtained can be determined by gel permeation chromatography based on polystyrene.
Moreover, it is preferable that all of 1 type or 2 types or more of resin which comprises (A) component is resin synthesize | combined by living radical polymerization.

Component (B) The component (B) can be used without particular limitation from known acid generators used in conventional chemically amplified resist compositions.
Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, There are various known diazomethane acid generators such as diazomethane nitrobenzyl sulfonates, imino sulfonate acid generators and disulfone acid generators.
Specific examples of the onium salt-based acid generator include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, and triphenylsulfonium trifluoromethane. Sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-methylphenyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethane Sulfonate, its heptafluoropropane sulphonate or its Nafluorobutane sulfonate, trifluoromethane sulfonate of monophenyldimethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, trifluoromethane sulfonate of diphenyl monomethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, (4- Trifluoromethanesulfonate of methylphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of (4-methoxyphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, tri (4 -Tert-bu Le) trifluoromethanesulfonate triphenylsulfonium, its like heptafluoropropane sulfonate or nonafluorobutane sulfonates.

  Specific examples of the oxime sulfonate acid generator include α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoromethylsulfonyloxyimino)- Phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (propylsulfonyloxyimino) -p-methylphenylacetonitrile, α- (methylsulfonyloxyimino) -p-bromophenylacetonitrile and the like can be mentioned. Of these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile is preferred.

Among diazomethane acid generators, specific examples of bisalkyl or bisarylsulfonyldiazomethanes include bis (isopropylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, Examples include bis (cyclohexylsulfonyl) diazomethane, bis (2,4-dimethylphenylsulfonyl) diazomethane, and the like.
Examples of poly (bissulfonyl) diazomethanes include 1,3-bis (phenylsulfonyldiazomethylsulfonyl) propane (Compound A, decomposition point 135 ° C.), 1,4-bis (phenyl) having the following structure. Sulfonyldiazomethylsulfonyl) butane (compound B, decomposition point 147 ° C.), 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane (compound C, melting point 132 ° C., decomposition point 145 ° C.), 1,10-bis (phenyl) Sulfonyldiazomethylsulfonyl) decane (compound D, decomposition point 147 ° C.), 1,2-bis (cyclohexylsulfonyldiazomethylsulfonyl) ethane (compound E, decomposition point 149 ° C.), 1,3-bis (cyclohexylsulfonyldiazomethylsulfonyl) ) Propane (Compound F, decomposition point 153 ° C.), , 6-bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane (Compound G, melting point 109 ° C., decomposition point 122 ° C.), 1,10-bis (cyclohexylsulfonyldiazomethylsulfonyl) decane (Compound H, decomposition point 116 ° C.), etc. Can be mentioned.

  In the present invention, it is particularly preferable to use an onium salt having a fluorinated alkyl sulfonate ion as an anion as the component (B).

As the component (B), one type of acid generator may be used alone, or two or more types may be used in combination.
(B) Content of a component is 0.5-30 mass parts with respect to 100 mass parts of (A) component, Preferably it is 1-10 mass parts. If the amount is less than the above range, pattern formation may not be sufficiently performed, and if the amount exceeds the above range, a uniform solution is difficult to obtain, which may cause a decrease in storage stability.

(D) Nitrogen-containing organic compound In the positive resist composition of the present invention, a nitrogen-containing organic compound (D) (hereinafter, (Referred to as component (D)).
Since a wide variety of components (D) have already been proposed, any known one may be used, but amines, particularly secondary lower aliphatic amines and tertiary lower aliphatic amines are preferred. .
Here, the lower aliphatic amine refers to an alkyl or alkyl alcohol amine having 5 or less carbon atoms, and examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, Tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, triisopropanolamine and the like can be mentioned, and tertiary alkanolamines such as triethanolamine are particularly preferable.
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.

Component (E) In addition, for the purpose of preventing sensitivity deterioration due to the blending with the component (D) and improving the resist pattern shape, retention stability, etc., an organic carboxylic acid or phosphorus oxoacid is further included as an optional component. Or its derivative (E) (henceforth (E) component) 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 used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

Cross-linking agent (F)
When the positive resist composition of the present invention is used in a thermal flow process including thermal flow treatment, the positive resist composition of the present invention further contains a crosslinking agent (F) (hereinafter referred to as (F) component). May be.
As the component (F), what is known as a crosslinking agent component in a chemically amplified resist composition suitable for thermal flow treatment can be appropriately used.
Specifically, as the component (F), a compound having at least two crosslinkable vinyl ether groups can be used, such as polyoxyalkylene glycol such as alkylene glycol, dialkylene glycol, trialkylene glycol, or trimethylolpropane. Further, a compound in which at least two hydroxyl groups of a polyhydric alcohol such as pentaerythritol and pentaglycol are substituted with a vinyl ether group can be used. Specific examples of the preferred component (E) include cyclohexyldimethanol divinyl ether.
(F) A component may be used independently and may be used in combination of 2 or more type.
When (F) component is used, (F) component is 0.1-25 mass% normally with respect to (A) component, Preferably it is used in 1-15 mass%.

Organic solvent The positive resist composition of the present invention can be produced by dissolving the material in an organic solvent.
Any organic solvent may be used as long as it can dissolve each component to be used to form a uniform solution, and one or two kinds of conventionally known solvents for chemically amplified resists can be used. These can be appropriately selected and used.

For example, ketones such as γ-butyrolactone, acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol Or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and other polyhydric alcohols and derivatives thereof, cyclic ethers such as dioxane, methyl lactate, lactic acid Ethyl (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy Methyl propionate, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.

A mixed solvent obtained by mixing propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable. The mixing ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, but is preferably 1: 9 to 9: 1, more preferably 2: 8 to 6: 4. It is preferable to be within the range.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 8: 2 to 2: 8, more preferably 7: 3 to 3: 7.
In addition, as the organic solvent, a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone is also preferable. In this case, the mixing ratio of the former and the latter is preferably 70:30 to 95: 5.
Although the amount of the organic solvent used is not particularly limited, it is a concentration that can be applied to a substrate and the like, and is appropriately set according to the coating film thickness. In general, the solid content concentration of the resist composition is 2 to 20 mass. %, Preferably 5-15% by mass.

Other optional components In the positive resist composition of the present invention, there are further miscible additives as desired, for example, additional resins for improving the performance of the resist film, surfactants for improving the coating properties, A dissolution inhibitor, a plasticizer, a stabilizer, a colorant, an antihalation agent and the like can be appropriately added and contained.

  The positive resist composition of the present invention, when used in a thermal flow process, has good controllability of pattern size at the time of flow while maintaining good sensitivity, resolution, and resist pattern characteristics, and has a low flow rate. Has characteristics. Therefore, it is suitable as a positive resist composition for a thermal flow process.

[Method of forming resist pattern]
In the pattern forming method having thermal flow treatment according to the present invention, a positive resist composition is applied on a substrate, pre-baked, selectively exposed, then subjected to PEB (post-exposure heating), and alkali development. Then, after forming a resist pattern, thermal flow treatment is performed. In this specification, the process of heating and narrowing the pattern after pattern formation is called thermal flow treatment.
Details will be described below.

First, the positive resist composition of the present invention is applied onto a substrate such as a silicon wafer with a spinner or the like, and then pre-baked.
Next, using an exposure apparatus or the like, the coating film of the positive resist composition is selectively exposed through a desired mask pattern, and then subjected to PEB (post-exposure heating). Subsequently, after developing with an alkali developer, rinsing is performed, and the developer on the substrate and the resist composition dissolved by the developer are washed away and dried.
The steps so far can be performed using a known method. The operating conditions and the like are preferably set as appropriate according to the composition and characteristics of the positive resist composition to be used.
The exposure is preferably performed using an ArF excimer laser, but is also useful for KrF excimer laser resist, electron beam resist, X-ray resist, EUV (extreme ultraviolet light), and the like.
An organic or inorganic antireflection film can be provided between the substrate and the coating film of the resist composition.

Next, the resist pattern thus formed is subjected to thermal flow processing to narrow the resist pattern.
The thermal flow process is performed by heating the resist pattern at least once. Increasing the number of times of heating is preferable because the amount of change in resist pattern size per unit temperature (hereinafter sometimes referred to as a flow rate) is small, but the number of steps increases, and the time required for processing increases. There is also an aspect that the throughput deteriorates.
Here, when the flow rate in the thermal flow process is small, the in-plane uniformity of the pattern dimension on the wafer in the narrowed resist pattern is high, and the cross-sectional shape of the resist pattern is also excellent. If the resist film thickness is 1000 nm or less, the film thickness has little influence on the flow rate.

The heating temperature in the thermal flow treatment is selected from the range of 100 to 200 ° C., preferably 110 to 180 ° C., according to the composition of the resist pattern. When heating is performed twice or more, the second and subsequent heating is performed at the same temperature as or higher than the first heating.
The heating time is not particularly limited as long as the desired resist pattern size can be obtained without hindering the throughput, but it is usually preferable that each heating be within a range of 30 to 270 seconds. Preferably, it is within the range of 60 to 120 seconds.

  A resist pattern forming method having a thermal flow process is suitably used for forming a fine resist hole pattern, which is difficult to form by a normal method.

In the present invention, in the thermal flow process, the controllability of the pattern size during the flow can be improved while the sensitivity, resolution, and resist pattern are also good.
Therefore, for example, it is possible to solve problems such as a large variation in pattern size accompanying a variation in heating temperature and a low in-plane uniformity of pattern dimensions.

Example 1
The following materials were mixed to produce a positive resist composition having a solid content concentration of 10% by mass.

(A) component: 100 mass parts of following polymers (A1)

Polymer (A1): a polymer obtained by polymerizing monomers represented by the following chemical formulas (1), (2), and (3) by living radical polymerization at a ratio of 40 mol%: 40 mol%: 20 mol% The dispersity is 1.38, the weight average molecular weight is 9200, and the Tg is 145 ° C. Moreover, the light absorbency in 193 nm is 0.32 (1 / micrometer).

(B) Component: Triphenylsulfonium nonafluorobutanesulfonate (A) 3.5 parts by mass with respect to 100 parts by mass of component

(D) Component: Triethanolamine (A) 0.1 part by mass with respect to 100 parts by mass of component

Organic solvent: PGMEA / EL = 6/4 (mass ratio) (A) 930 parts by mass with respect to 100 parts by mass of the component.

(Example 2)
A positive resist composition was produced in the same manner as in Example 1 except that the component (A) was changed to the following.

(A) Component: A mixture of the following polymer (A2) and the following polymer (A3) in a mass ratio of 1: 1 (mass average molecular weight: 10300, dispersity: 2.1, Tg 140 ° C.) 100 parts by mass Absorbance at 193 nm is 0.31 (1 / μm).

Polymer (A2): a polymer obtained by polymerizing the monomers represented by the chemical formulas (1), (2), and (3) by living radical polymerization at a ratio of 40 mol%: 40 mol%: 20 mol% And having a dispersity of 1.32, a weight average molecular weight of 5600, and a Tg of 137 ° C. Moreover, the light absorbency in 193 nm is 0.32 (1 / micrometer).

Polymer (A3): a polymer obtained by polymerizing the monomers represented by the chemical formulas (1), (2), and (3) by living radical polymerization at a ratio of 40 mol%: 40 mol%: 20 mol% And having a dispersity of 1.41, a weight average molecular weight of 15000, and a Tg of 141 ° C. Moreover, the light absorbency in 193 nm is 0.29 (1 / micrometer).

Example 3
A positive resist composition was produced in the same manner as in Example 1 except that the component (A) was changed to the following.

Polymer (A4): monomers represented by the following chemical formulas (1 ′), (2 ′) and (3 ′) are polymerized by living radical polymerization at a ratio of 40 mol%: 40 mol%: 20 mol%. A polymer having a dispersity of 1.46, a weight average molecular weight of 10900, and a Tg of 127 ° C. Moreover, the light absorbency in 193 nm is 0.28 (1 / micrometer).

(Comparative Example 1)
A positive resist composition was produced in the same manner as in Example 1 except that the component (A) was changed to the following.

(A) Component: the following polymer (A5) 100 parts by mass polymer (A5): the monomers represented by the chemical formulas (1), (2) and (3), 40 mol%: 40 mol%: 20 mol %, A polymer polymerized by free radical polymerization, having a dispersity of 2.24, a weight average molecular weight of 11200, and a Tg of 123 ° C. Moreover, the light absorbency in 193 nm is 0.27 (1 / micrometer).

(Comparative Example 2)
A positive resist composition was produced in the same manner as in Example 3 except that the component (A) was changed to the following.

(A) Component: the following polymer (A6) 100 parts by mass polymer (A6): 40 mol%: 40 mol% of monomers represented by the chemical formulas (1 ′), (2 ′), (3 ′) : A polymer polymerized by free radical polymerization at a ratio of 20 mol%, having a dispersity of 2.25, a weight average molecular weight of 10100, and a Tg of 94 ° C. Moreover, the light absorbency in 193 nm is 0.32 (1 / micrometer).

[Evaluation]
(Evaluation by dense hole pattern)
The positive resist compositions of Examples 1 and 2 and Comparative Example 1 were evaluated as follows.
An organic antireflection film (product name: ARC29, manufactured by Brewer Science) was applied on an 8-inch silicon wafer and heated at 205 ° C. for 60 seconds to prepare a substrate having a thickness of 77 nm. .
Next, a positive resist composition was applied onto the substrate using a spinner, prebaked on a hot plate at 105 ° C. for 90 seconds, and dried to form a resist layer having a thickness of 340 nm.

Next, an ArF excimer laser exposure apparatus Nikon S-302 (product name, manufactured by Nikon, NA (numerical aperture) = 0.6, σ = 0.75) was used to form an ArF excimer laser (193 nm) with a dense hole pattern (multiple holes). These holes were selectively irradiated through a binary reticle on which a pattern of holes arranged at predetermined intervals was drawn.
Then, PEB treatment was performed at 90 ° C. for 90 seconds, and further paddle development was performed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. for 60 seconds, followed by water rinsing with pure water for 15 seconds. Shake off and dry. Thereafter, the resist pattern was formed by heating at 100 ° C. for 60 seconds and drying.
As a result, a pattern in which a plurality of hole patterns having a diameter of 140 nm were arranged at intervals of 160 nm was obtained.

The thus obtained resist pattern was subjected to thermal flow treatment under the following five temperature conditions, and the change in the diameter of the hole pattern was examined.
1) 140 ° C, 90 seconds 2) 150 ° C, 90 seconds 3) 155 ° C, 90 seconds 4) 160 ° C, 90 seconds 5) 165 ° C, 90 seconds

  The results for Example 1, Example 2 and Comparative Example 1 are shown graphically in FIG. The horizontal axis represents the temperature of the thermal flow treatment, and the vertical axis represents the diameter of the hole after the thermal flow treatment. From these results, the flow rates of Example 1, Example 2, and Comparative Example 1 were 1.3 nm / ° C., 1.5 nm / ° C., and 3.8 nm / ° C., respectively.

  For Example 3 and Comparative Example 2, the graph is not shown, but the pre-baking is 100 ° C. for 90 seconds, PEB is changed to 85 ° C. for 90 seconds, and thermal flow treatment is performed at 120 ° C. to 140 ° C. for 90 seconds each. The flow rate was changed to 5 ° C. and the same flow rate was determined. The results were 2.1 nm / ° C. and 3.2 nm / ° C.

(Evaluation using isolated hole pattern)
An evaluation was performed in the same manner as the dense hole pattern except that an isolated hole pattern (a pattern in which one hole was formed) having a diameter of 140 nm was formed, and thermal flow treatment was performed on this.
The results for Example 1, Example 2 and Comparative Example 1 are shown graphically in FIG. The horizontal axis represents the temperature of the thermal flow treatment, and the vertical axis represents the diameter of the hole after the thermal flow treatment. From these results, the flow rates of Example 1, Example 2, and Comparative Example 1 were 1.0 nm / ° C., 0.9 nm / ° C., and 1.5 nm / ° C., respectively.
For Example 3 and Comparative Example 2, the graph is not shown, but the pre-baking is 100 ° C. for 90 seconds, PEB is changed to 85 ° C. for 90 seconds, and thermal flow treatment is performed at 120 ° C. to 140 ° C. for 90 seconds each. When the temperature was changed in 5 ° C increments and the same flow rate was determined, it was 1.6 nm / ° C and 4.1 nm / ° C.

  As can be seen from the graphs and flow rate values shown in FIGS. 1 and 2, in Examples 1, 2, and 3 according to the present invention, the temperature dependence of the hole size after thermal flow treatment is small, and the flow controllability is good. It was confirmed that.

It is the graph which showed the result of the Example. It is the graph which showed the result of the Example.

Claims (18)

(A) A positive resist composition containing a base resin component having an acid dissociable, dissolution inhibiting group and increasing alkali solubility by the action of an acid, and (B) an acid generator component that generates an acid upon irradiation with radiation. Because
The component (A) includes a resin having an absorbance at 193 nm of 1.0 (1 / μm) or less and a dispersity (Mw / Mn) of 1.5 or less, and the positive resist composition has a thermal A positive resist composition for use in a flow process.    2. The glass transition point (Tg) of a resin having an absorbance at 193 nm of 1.0 (1 / μm) or less and a dispersity (Mw / Mn) of 1.5 or less is 120 ° C. or more. Positive resist composition.    The positive resist composition according to claim 1, wherein the acid dissociable, dissolution inhibiting group is a tertiary alkyl group.   The positive resist composition according to claim 3, wherein the tertiary alkyl group is an aliphatic polycyclic group-containing tertiary alkyl group.     The positive resist composition according to claim 1, wherein the component (A) has a structural unit (a) derived from an (α-lower alkyl) acrylate ester.     The component (A) has, as the structural unit (a), a structural unit (a-1) derived from an (α-lower alkyl) acrylate ester containing an acid dissociable, dissolution inhibiting group. The positive resist composition as described.   The component (A) has, as the structural unit (a), a structural unit (a-2) derived from an (α-lower alkyl) acrylate ester further containing a lactone-containing monocyclic or polycyclic group. The positive resist composition according to claim 6.   The component (A) has, as the structural unit (a), a structural unit (a-3) derived from an (α-lower alkyl) acrylate ester further containing a polar group-containing aliphatic hydrocarbon group. Item 8. The positive resist composition according to Item 6 or 7. The structural unit (a-1) is represented by the following general formulas (I), (II) and (III):

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

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

(Wherein R is a hydrogen atom or a lower alkyl group, and R ⁴ is a tertiary alkyl group)
The positive resist composition according to claim 6, which is at least one selected from the group consisting of structural units represented by: The structural unit (a-2) is represented by the following general formulas (IV), (V) and (VI):

(Wherein R is a hydrogen atom or a lower alkyl group, R ⁵ is a hydrogen atom or a lower alkyl group, and k is an integer of 1 to 4)

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

(In the formula, R is a hydrogen atom or a lower alkyl group.)
The positive resist composition according to claim 7, which is at least one selected from the group consisting of structural units represented by: The structural unit (a-3) is represented by the following general formula (VIII):

11. In the formula, R is a hydrogen atom or a lower alkyl group, and n is an integer of 1 to 3, which is at least one selected from the group consisting of structural units. 2. The positive resist composition according to item 1.   The positive resist composition according to claim 5, wherein the component (A) includes a resin having a structural unit (ma) derived from an α-lower alkyl acrylate ester.     The positive resist composition according to claim 12, wherein a ratio of the structural unit (ma) to a total of all the structural units of the component (A) is 20 mol% or more.     The positive resist composition according to any one of claims 5 to 13, wherein the component (A) contains a resin having a structural unit (aa) derived from an acrylate ester.   The positive resist composition according to claim 14, wherein the ratio of the structural unit (aa) to the total of all the structural units of the component (A) is 40 mol% or more.   The resin having an absorbance at 193 nm of 1.0 (1 / μm) or less and a dispersity (Mw / Mn) of 1.5 or less is a resin obtained by a living radical polymerization method. The positive resist composition as described in any one of the above.   Furthermore, the positive resist composition as described in any one of Claims 1 thru | or 16 which contains 0.01-5 mass parts of nitrogen-containing organic compounds with respect to 100 mass parts of said (A) component. The positive resist composition according to any one of claims 1 to 17 is applied on a substrate, pre-baked, selectively exposed, subjected to PEB (post-exposure heating), and alkali-developed. Then, after forming the resist pattern, a thermal flow process is performed.

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