JP4249096B2 - Substrate for pattern forming material, positive resist composition, and resist pattern forming method - Google Patents

Description

  The present invention relates to a substrate for a pattern forming material, a positive resist composition, and a resist pattern forming method.

In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, pattern 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, conventionally, ultraviolet rays typified by g-line and i-line have been used, but at present, mass production of semiconductor elements using a KrF excimer laser or an ArF excimer laser has started. Further, F ₂ excimer laser having a shorter wavelength than these excimer lasers, electron beams, also consider such extreme ultraviolet radiation and X-rays have been made.
Further, as one of pattern forming materials capable of forming a pattern with fine dimensions, a chemically amplified resist containing a base material component having a film forming ability and an acid generator component that generates an acid upon exposure is known. ing. Chemically amplified resists include a negative type in which alkali solubility is reduced by exposure and a positive type in which alkali solubility is increased by exposure.
Conventionally, a polymer having a mass average molecular weight of about 5000 or more is used as a main base material component of a pattern forming material such as a resist.

However, when a pattern is formed using such a pattern forming material, there is a problem that roughness is generated on the upper surface of the pattern and the surface of the side wall.
Such roughness has not been a problem in the past. However, in recent years, with the rapid miniaturization of semiconductor elements and the like, a higher resolution, for example, a resolution with a dimension width of 90 nm or less, has been demanded, and accordingly, roughness has become a serious problem. For example, when forming a line pattern, the line width to be formed varies due to roughness of the pattern side wall surface, that is, LER (line edge roughness), and the management width of the variation in the line width is about 10% of the dimension width. The following is desired, and the smaller the pattern dimension, the greater the influence of LER. For example, when forming a line pattern having a dimension of about 90 nm, it is desired that the management width of the variation in the line width is about 10 nm or less.
However, a polymer generally used as a base material has a large mean square radius per molecule of around several nanometers, and the above management width is only about several polymers. Therefore, as long as a polymer is used as the base material component, it is very difficult to reduce LER.

On the other hand, it has been proposed to use a low-molecular material having an alkali-soluble group such as a hydroxyl group and partially or entirely protected with an acid-dissociable, dissolution-inhibiting group as a substrate (for example, Patent Documents 1 and 2). reference). Such a low molecular weight material is expected to have a small mean square radius because of its low molecular weight, and a small contribution to LER increase.
JP 2002-099088 A JP 2002-099089 A

However, even if these low molecular weight materials are used, it is difficult to sufficiently improve LER, and further reduction of LER is required.
The present invention has been made in view of the above circumstances, and provides a substrate for a pattern forming material, a positive resist composition, and a resist pattern forming method capable of forming a high-resolution pattern with reduced LER. For the purpose.

As a result of intensive studies, the present inventors have determined that a phenolic hydroxyl group has an acid dissociable dissolution with respect to a polyhydric phenol compound having a specific molecular weight and a specific molecular weight dispersibility and capable of forming an amorphous film by spin coating. The present inventors have found that the above problems can be solved by using a low molecular weight compound protected with an inhibitory group, and completed the present invention.
That is, the first aspect of the present invention includes a base material component (A) having an acid dissociable, dissolution inhibiting group and increasing alkali solubility by the action of an acid, and an acid generator component (B) that generates an acid upon exposure. And a positive resist composition not containing a polymer ,
Said base component (A) has two or more phenolic hydroxyl groups, the following (1), (2) and part acid of the phenolic hydroxyl group in (3) satisfy the polyhydric phenol compound (x) low molecular weight compounds that are protected by dissociable (X1) forming material for substrate der consisting is, the protection rate of the phenolic hydroxyl groups of the pattern forming material for the substrate in the 5 to 50 mol% There is a positive resist composition.
(1) Molecular weight is 500-1500
(2) The molecular weight dispersity is 1.5 or less. (3) An amorphous film can be formed by a spin coating method. The second aspect of the present invention is the substrate of the positive resist composition of the first aspect. The resist pattern forming method is characterized in that a resist pattern is formed by applying PEB (post-exposure heating), applying alkali, and developing after pre-baking and selective exposure.

  In the present invention, “exposure” means radiation irradiation, electron beam drawing or irradiation.

  The pattern forming material substrate, the positive resist composition, and the resist pattern forming method of the present invention can form a high-resolution pattern with reduced LER.

Hereinafter, the present invention will be described in more detail.
≪Pattern for pattern forming material≫
The substrate for a pattern forming material of the present invention has two or more phenolic hydroxyl groups, and part or all of the phenolic hydroxyl groups in the polyhydric phenol compound (x) satisfying the conditions (1) to (3) above. Contains a low molecular compound (X1) protected with an acid dissociable, dissolution inhibiting group.

<Polyphenol compound (x)>
The polyhydric phenol compound (x) constituting the low molecular compound (X1) has two or more phenolic hydroxyl groups, a molecular weight of 300 to 2500, a molecular weight dispersity of 1.5 or less, a spin Any polyhydric phenol compound capable of forming an amorphous film by a coating method is not particularly limited. For example, many known as sensitizers and heat resistance improvers in non-chemically amplified g-line and i-line resists. A polyhydric phenol compound can be used. Examples of such polyhydric phenol compounds include the following.
Bis (2,3,4-trihydroxyphenyl) methane, 2- (4-hydroxyphenyl) -2- (4′-hydroxyphenyl) propane, 2- (2,3,4-trihydroxyphenyl) -2- (2 ′, 3 ′, 4′-trihydroxyphenyl) propane, bis (4-hydroxy-3,5-dimethylphenyl) -2-hydroxyphenylmethane, bis (4-hydroxy-3,5-dimethylphenyl)- 4-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-methylphenyl) Enyl) -3,4-dihydroxyphenylmethane, bis (4-hydroxy-3-methylphenyl) -2-hydroxyphenylmethane, bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) -2-hydroxyphenylmethane Bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) -4-hydroxyphenylmethane, bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) -3,4-dihydroxyphenylmethane, bis (4 -Hydroxy-3,5-dimethylphenyl) -2-hydroxyphenylmethane, bis (4-hydroxy-2,3,5-trimethylphenyl) -2-hydroxyphenylmethane, bis (4-hydroxy-2,3,5) -Trimethylphenyl) -3-hydroxyphenylmethane, bis ( -Hydroxy-2,3,5-trimethylphenyl) -4-hydroxyphenylmethane, 1- [1- (4-hydroxyphenyl) isopropyl] -4- [1,1-bis (4-hydroxyphenyl) ethyl] benzene , Tetranuclear form of a formalin condensate of phenols such as phenol, m-cresol, p-cresol or xylenol.

  In the present invention, in particular, when it is at least one selected from the group consisting of polyhydric phenol compounds represented by the following general formula (I), (II), or (III), it is amorphous by spin coating. It is preferable because a film can be formed and the effect of the present invention is excellent.

In the general formula (I), R _{11 to} R ₁₇ are each independently a linear, branched or cyclic lower alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, and cyclic 5 to 6 carbon atoms. An alkyl group or an aromatic hydrocarbon group; The alkyl group or aromatic hydrocarbon group may contain a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom in the structure. Examples of the aromatic hydrocarbon group include a phenyl group, a tolyl group, a xylyl group, a mesityl group, a phenethyl group, and a naphthyl group.
g and j are each independently an integer of 1 or more, preferably 1 or 2, k and q are each independently 0 or 1 or more, preferably an integer not exceeding 2, and g + j + k + q is 5 or less.
h is an integer of 1 or more, preferably 1 to 2, l and m are each independently 0 or 1 or more, preferably an integer not exceeding 2, and h + 1 + m is 4 or less.
i is an integer of 1 or more, preferably 1 to 2, n and o are each independently 0 or 1 or more, preferably an integer not exceeding 2, and i + n + o is 4 or less.
p is 0 or 1, preferably 1.
Among these, those in which R ₁₁ is a cycloalkyl group, j is 1, and R ₁₂ is a lower alkyl group, k is 1 and g is 1 are preferable.
Further preferably, R ₁₁ is a cycloalkyl group, the number of j is 1, and R ₁₂ is a lower alkyl group, the number of k is 1, the number of g is 1, and q and l are A compound in which m, n, and o are 0 and h and i are both 1 is preferable because a fine pattern can be formed with high resolution with reduced LER.

  Among the polyhydric phenol compounds represented by the above general formula (I), the most preferred are polyhydric phenol compounds represented by the following formulas (I-1) and (I-2). This is because these polyhydric phenol compounds easily form an amorphous film.

In the general formula (II), R _{21 to} R ₂₆ are each independently a linear, branched or cyclic lower alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, and cyclic 5 to 6 carbon atoms. An alkyl group or an aromatic hydrocarbon group; The alkyl group or aromatic hydrocarbon group may contain a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom in the structure. Examples of the aromatic hydrocarbon group include a phenyl group, a tolyl group, a xylyl group, a mesityl group, a phenethyl group, and a naphthyl group. Among these, R _{21 to} R ₂₆ are all preferably lower alkyl groups.
d and g are each independently an integer of 1 or more, preferably 1 or 2, h is 0 or 1 or more, preferably an integer not exceeding 2, and d + g + h is 5 or less.
e and i are each independently an integer of 1 or more, preferably 1 or 2, j is 0 or 1 or more, preferably an integer not exceeding 2, and e + i + j is 4 or less.
f and k are each independently an integer of 1 or more, preferably 1 or 2, l is 0 or 1 or more, preferably an integer not exceeding 2, and f + k + 1 is 5 or less.
m is an integer of 1 to 20, preferably 2 to 10.

In the general formula (III), R _{31 to} R ₃₆ are each independently a linear, branched or cyclic lower alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, and cyclic 5 to 6 carbon atoms. An alkyl group or an aromatic hydrocarbon group; The alkyl group or aromatic hydrocarbon group may contain a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom in the structure. Examples of the aromatic hydrocarbon group include a phenyl group, a tolyl group, a xylyl group, a mesityl group, a phenethyl group, and a naphthyl group. Among these, all of R _{31 to} R ₃₆ are preferably lower alkyl groups.
a and e are each independently an integer of 1 or more, preferably 1 or 2, f is 0 or 1 or more, preferably an integer not exceeding 2, and a + e + f is 5 or less.
b and h are each independently an integer of 1 or more, preferably 1 or 2, g is 0 or 1 or more, preferably an integer not exceeding 2, and b + h + g is 5 or less.
c and i are each independently an integer of 1 or more, preferably 1 or 2, j is 0 or 1 or more, preferably an integer not exceeding 2, and c + i + j is 5 or less.
d is an integer of 1 or more, preferably 1 to 2, k and l are each independently 0 or 1 or more, preferably an integer not exceeding 2, and d + k + 1 is 3 or less.

  In the present invention, the polyphenol compound (x) needs to have a molecular weight of 300 to 2500, preferably 450 to 1500, more preferably 500 to 1200. When the molecular weight is not more than the upper limit value, the effect of reducing LER is sufficient. Also, the resolution is improved. Moreover, when it is at least the lower limit value, a resist pattern having a good profile shape can be formed.

In addition, the polyphenol compound (x) needs to have a molecular weight dispersity (Mw / Mn) of 1.5 or less for the effect of the present invention. This is because the polyhydric phenol compound (x) has a narrow molecular weight distribution with a dispersity of 1.5 or less, so that the phenolic hydroxyl group protected by the acid dissociable, dissolution inhibiting group in the polyhydric phenol material. Even if a plurality of low molecular compounds (X1) having different numbers (protection numbers) are included, it is considered that the alkali solubility of each low molecular compound (X1) becomes relatively uniform. The degree of dispersion is preferably as small as possible, more preferably 1.4 or less, and most preferably 1.3 or less.
The dispersity is usually used for polydisperse compounds such as polymers, but even monodisperse compounds, due to the presence of impurities such as by-products during production and residual starting materials, When analyzed by gel permeation chromatography (GPC) or the like, a distribution may appear in the molecular weight apparently. That is, in the case of a monodispersed compound, a degree of dispersion of 1 means that the purity is 100%, and the greater the degree of dispersion, the greater the amount of impurities. In the present invention, the degree of dispersion is a method for measuring a mass average molecular weight (Mw) and a number average molecular weight (Mn) of a polymer that is generally used for a compound showing such an apparent molecular weight distribution, such as GPC. Can be calculated by measuring Mw and Mn and determining the Mw / Mn ratio.
The degree of dispersion is determined by synthesizing the polyphenol compound (x), which is the final target product, and then purifying and removing reaction by-products and impurities, or removing unnecessary molecular weight portions by known methods such as molecular weight fractionation. Can be adjusted.

Further, the polyhydric phenol compound (x) needs to be a material capable of forming an amorphous film by a spin coating method.
Here, the amorphous film means an optically transparent film that does not crystallize.
The spin coating method is one of the commonly used thin film forming methods. Whether a polyphenol compound is a material capable of forming an amorphous film by the spin coating method is determined on an 8-inch silicon wafer. It can be discriminated by whether or not the coating film formed by the spin coating method is entirely transparent. More specifically, for example, the determination can be made as follows.
First, for the polyhydric phenol material, using a solvent generally used as a resist solvent, for example, a mixed solvent of ethyl lactate / propylene glycol monoethyl ether acetate = 40/60 (mass ratio) (hereinafter referred to as EM and (Abbreviated) is dissolved to a concentration of 14% by mass, subjected to ultrasonic treatment (dissolution treatment) using an ultrasonic cleaner, and spin-coated at 1500 rpm on the wafer, Optionally, dry baking (PAB, Post Applied Bake) is performed at 110 ° C. for 90 seconds, and in this state, it is visually confirmed whether an amorphous film is formed depending on whether it is transparent. A cloudy film that is not transparent is not an amorphous film.
In the present invention, the polyphenolic material (x) preferably has good stability of the amorphous film formed as described above. For example, after the PAB, the polyphenolic material (x) is allowed to stand at room temperature for 2 weeks. The amorphous state is preferably maintained.

<Low molecular compound (X1)>
The low molecular compound (X1) is obtained by protecting a part or all of the hydroxyl groups of the phenolic hydroxyl group of the polyhydric phenol compound (x) with an acid dissociable, dissolution inhibiting group.
The acid dissociable, dissolution inhibiting group is not particularly limited, and is appropriately selected from among those proposed for hydroxystyrene resins, (meth) acrylic acid resins and the like used in chemically amplified resist compositions for KrF and ArF. It can be selected and used.
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-ethoxymethyl group, 1-methoxymethylethyl group, 1-methoxymethyl group, 1-isopropoxyethyl group, 1-methoxypropyl group, 1-ethoxypropyl group. 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 an aliphatic polycyclic group such as a chain tertiary alkyl group such as a tert-butyl group and a tert-amyl group, a 2-methyl-adamantyl group, and a 2-ethyladamantyl group. And tertiary alkyl groups containing a group.
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 chain alkoxyalkyl group is preferable because it is excellent in dissociation, can improve the uniformity of the low molecular compound (X1), and can improve LER, and is preferably a 1-ethoxyethyl group or 1-ethoxymethyl group. Groups are more preferred.

  Also, a plurality of low molecular compounds (X1) having different numbers of phenolic hydroxyl groups protected by acid dissociable, dissolution inhibiting groups (protection number) (hereinafter sometimes referred to as isomers) in the pattern forming material substrate Is included, the closer the number of protected isomers is, the better the effect of the present invention is.

  In the substrate for pattern forming material, the proportion of the low molecular compound (X1) is preferably more than 40% by mass, more preferably more than 50% by mass, still more preferably more than 80% by mass, most preferably 100% by mass.

<Unprotected body (X2)>
In the present invention, in the substrate for pattern forming material, the phenolic hydroxyl group in the polyhydric phenol compound (x) is not protected at all by the acid dissociable, dissolution inhibiting group (hereinafter referred to as unprotected body (X2)). ) Is preferably as small as possible.
In the substrate for pattern forming material of the present invention, the proportion of the unprotected body (X2) is preferably 60% by mass or less. The proportion of the unprotected body (X2) is preferably as small as possible, more preferably 50% by mass or less, still more preferably 10% by mass or less, and most preferably 0% by mass. When the unprotected body (X2) is 60% by mass or less, LER can be further reduced when a pattern is formed. Also, the resolution is excellent.

The pattern forming material substrate is, for example, a method of protecting all or part of the phenolic hydroxyl groups with an acid dissociable, dissolution inhibiting group by a known method for one or more polyphenol compounds (x). Etc. can be manufactured.
Examples of the method for setting the proportion of the unprotected body (X2) to 60% by mass or less include, for example, all or part of the phenolic hydroxyl groups of one or two or more polyphenol compounds (x), a well-known technique. After preparing by a method of protecting with an acid dissociable dissolution inhibiting group, etc., the unprotected body (X2) is separated by gel permeation chromatography (GPC) or protected with the acid dissociable dissolution inhibiting group. It can be adjusted by the method.
In the low molecular compound (X1), the number of protected isomers can be adjusted by a method of protecting with the acid dissociable, dissolution inhibiting group.
The ratio of each of the low molecular compound (X1) and each isomer in the low molecular compound (X1) and the unprotected body (X2) in the substrate for pattern forming material can be measured by means such as reverse phase chromatography. it can.

  Further, the protection rate of the phenolic hydroxyl group in the substrate for the pattern forming material, that is, the acid dissociable dissolution inhibiting group with respect to the total amount of the phenolic hydroxyl group protected with the acid dissociable dissolution inhibiting group and the unprotected phenolic hydroxyl group. The ratio of the phenolic hydroxyl group protected with is preferably 5 to 50 mol%, more preferably 7 to 30 mol% in view of resolution and LER reduction effect.

  The base material for pattern forming materials of this invention is suitable as a base material of the positive resist composition mentioned later.

≪Positive resist composition≫
The positive resist composition of the present invention has a base component (A) (hereinafter sometimes referred to as component (A)) having an acid dissociable, dissolution inhibiting group and increasing alkali solubility by the action of an acid; An acid generator component (B) that generates an acid upon exposure (hereinafter also referred to as component (B)).
In the component (A), when an acid generated from the component (B) acts upon exposure, the acid dissociable, dissolution inhibiting group is dissociated, thereby changing the entire component (A) from alkali-insoluble to alkali-soluble.
Therefore, in the formation of the resist pattern, when the resist film made of the positive resist composition is selectively exposed or heated after exposure in addition to the exposure, the exposed portion turns into alkali-soluble while the unexposed portion becomes alkali-insoluble. Thus, a positive resist pattern can be formed by alkali development.

<(A) component>
(A) A component is the base material for pattern formation materials of the said this invention (henceforth a polyhydric phenol type base material (A1)).
The content of the component (A) in the positive resist composition of the present invention may be adjusted according to the resist film thickness to be formed. Generally, the solid concentration is 3 to 25% by mass, more preferably 10 to 20% by mass.

<(B) component>
In the present invention, 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, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, trifluoromethane sulfonate of diphenylmonomethylsulfonium, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate . Of these, onium salts having a fluorinated alkyl sulfonate ion as an anion are preferable.

  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.

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.

<Organic solvent (C)>
The positive resist composition of the present invention can be produced by dissolving the above-described component (A), component (B), and any of the components described below in an organic solvent (C).
As the organic solvent (C), any solvent can be used as long as it can dissolve each component used to form a uniform solution, and any one of conventionally known solvents for chemically amplified resists can be used. Or it can select and use 2 or more types suitably.
For example, ketones such as γ-butyrolactone, acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol Or polyhydric alcohols such as monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether of dipropylene glycol monoacetate and derivatives thereof, cyclic ethers such as dioxane, methyl lactate, lactic acid Ethyl (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy Methyl propionate, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents (C) may be used alone or as a mixed solvent of two or more.
Further, a mixed solvent in which propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent are mixed is preferable, but the mixing ratio may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent. It is preferable to be within a range of 1: 9 to 9: 1, more preferably 2: 8 to 8: 2.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 2: 8 to 8: 2, more preferably 3: 7 to 7: 3.
In addition, as the organic solvent (C), 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.
The amount of the organic solvent (C) used is not particularly limited, but 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 It is made into the range of -20 mass%, Preferably it is 5-15 mass%.

<(D) component>
In the positive resist composition of the present invention, a nitrogen-containing organic compound (D) (hereinafter referred to as “component (D)”) is further added as an optional component in order to improve the resist pattern shape, stability over time and the like. Can be blended.
Since a wide variety of components (D) have already been proposed, any known one may be used, but amines, particularly secondary aliphatic amines and tertiary aliphatic amines are preferred.
Here, the aliphatic amine refers to an alkyl or alkyl alcohol amine having 15 or less carbon atoms, and examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, -N-propylamine, tripentylamine, tri-n-octylamine, diethanolamine, triethanolamine, etc., but especially tertiary alkanolamines such as triethanolamine and tri-n-octylamine Tertiary amines are preferred.
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.

<(E) component>
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 an oxo acid of phosphorus or a derivative thereof (optional) 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 used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

<Other optional components>
The positive resist composition of the present invention further contains miscible additives as desired, for example, additional resins for improving the performance of the resist film, surfactants for improving coating properties, dissolution inhibitors, A plasticizer, a stabilizer, a colorant, an antihalation agent, and the like can be appropriately added and contained.
Examples of the additional resin include those proposed as base resins such as conventional chemically amplified KrF positive resist compositions and ArF positive resist compositions. It can be suitably selected according to the type of light source. The ratio of the additional resin is within a range that does not impair the effects of the present invention, and is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total solid content of the positive resist composition.

≪Resist pattern formation method≫
Using the positive resist composition of the present invention, a resist pattern can be formed by, for example, the following resist pattern forming method.
That is, first, the positive resist composition is applied onto a substrate such as a silicon wafer with a spinner, and prebaking (PAB) is performed at a temperature of 80 to 150 ° C. for 40 to 120 seconds, preferably 60 to 90 seconds. Then, this is selectively exposed to an electron beam, extreme ultraviolet rays, or the like, for example, by an electron beam drawing apparatus. That is, after exposing through a mask pattern or drawing by directly irradiating an electron beam without passing through a mask pattern, PEB (post-exposure heating) is performed at a temperature of 70 to 150 ° C. for 40 to 500 seconds, preferably Apply for 60-300 seconds. Next, this is developed using an alkali developer, for example, an aqueous solution of 0.1 to 10% by mass of tetramethylammonium hydroxide. In this way, a resist pattern faithful to the mask pattern can be obtained.
An organic or inorganic antireflection film can be provided between the substrate and the coating layer of the resist composition.
The wavelength used for the exposure is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. Can be done using radiation. In particular, the positive resist composition according to the present invention is effective for EB and EUV, particularly EB.

As described above, the positive resist composition containing the pattern forming material substrate of the present invention and the polyphenol-based substrate (A1) as a base component enables high resolution and fine resolution with reduced LER. A pattern can be formed.
The reason why LER is reduced is not clear, but the following reasons are conceivable. That is, the roughness (LER) on the resist film surface when the resist pattern is formed is, for example, the following 1. 2. As described above, one of the causes can be found in the variation in solubility in the alkaline developer for each matrix molecule constituting the substrate component of the resist film.
1. The number of acid dissociable, dissolution-inhibiting groups of each matrix molecule and the number of unprotected alkali-soluble groups in a substrate containing matrix molecules having alkali-soluble groups partially or wholly protected with acid-dissociable, dissolution-inhibiting groups 1. Variation in alkali solubility of the substrate itself caused by the broad molecular weight distribution (polydispersion) of each matrix molecule Variation in deprotection reaction of acid-dissociable protecting group added to chemically amplified alkali-soluble matrix during exposure

Based on such an idea, in the case of a polymer conventionally used as a base material component of a resist, at least one of the above factors. Is difficult to control. That is, the polymer can be obtained by a technique such as polymerization, but it is very difficult to make the molecular weight of the obtained polymer uniform. For example, there is living polymerization as a process for obtaining a polymer with a relatively uniform molecular weight distribution. However, there are many restrictions on the monomer skeleton and polymerization solvent that can be used to apply living polymerization. It is difficult to obtain a polymer having a high molecular weight. Furthermore, as a polymer that is usually used as a pattern forming material, a copolymer using two or more types of monomers having different functions such as structure and alkali solubility is used, but monomers having different side chain structures are used. Introduce uniformly into each copolymer, that is, make the monomer composition of the resulting copolymer perfectly match for each copolymer, and make the distribution of each monomer in each copolymer uniform. It is extremely difficult.
Thus, it is considered that many problems occur in the lithography process because a polymer having a non-uniform molecular weight distribution and monomer composition ratio as a substrate for a pattern forming material is used from a microscopic viewpoint. For example, in a spin coating process for forming a resist film, highly hydrophilic polymers and highly hydrophobic polymers each form a domain, thereby causing variations in the distribution of acid generators and the like. As a result, the degree of progress when the dissociation (deprotection reaction) of the acid dissociable, dissolution inhibiting group by the generated acid proceeds at the interface between the exposed part and the unexposed part is not uniform. The alkali solubility varies, and the dissolution rate of the resist film also varies.
And a slight difference in the solubility of each polymer in such a resist will increase LER. Therefore, in order to reduce LER, it is necessary to control the alkali dissolution behavior of each polymer. However, as described above, it is difficult to make the alkali solubility of the polymer itself uniform, and it is difficult to reduce LER.

In addition, in the case of the low molecular weight materials proposed in the above-mentioned Patent Documents 1 and 2, etc., it is considered that LER is difficult to increase because the root mean square radius is smaller than that of the polymer. The difference in solubility is not taken into consideration at all, and whether the material itself is a material capable of forming an amorphous film is not taken into consideration at all, so that LER can be sufficiently reduced. Probably not.
That is, as a cause of the deterioration of LER, there may be a problem of foreign matter aging in which a foreign substance is generated in the resist composition during storage and a development defect (defect) seen on the pattern surface during pattern formation. According to the study by the inventors, these problems are not certain, but the low molecular weight compound is a highly crystalline material, so that it is partly because an amorphous film cannot be formed by itself. Guessed. That is, in order to reduce LER, it is considered that the matrix itself must be able to form an amorphous and stable film.
In the conventional resist composition, even if the matrix itself is a material having high crystallinity, generally, the crystallinity of the substance is lowered by mixing a substance having a different structure, that is, a so-called impurity. Therefore, as a whole resist composition obtained by adding a plurality of components such as an acid generator, a quencher, and a solvent to an alkali-soluble matrix provided with an acid-dissociable protecting group, the resist composition is amorphous. It is considered that the material can provide a film.

On the other hand, the substrate for a pattern forming material of the present invention has a specific molecular weight, a polydispersity of molecular weight, and a polyhydric phenol compound (x) capable of forming an amorphous film, particularly a specific structure (I) to By containing the low molecular weight compound (X1) in which the phenolic hydroxyl group (alkali-soluble group) of the polyhydric phenol compound having (III) is protected with an acid dissociable, dissolution inhibiting group, the alkali solubility of the entire material is relatively uniform. Thus, LER is considered to be improved.
In addition, because of the low molecular weight within a specific range, even if the number of protected alkali-soluble groups in one molecule is small, the number of protections is sufficient for the whole substrate, so that the dissolution contrast after exposure is sufficiently high. Can be obtained, and the resolution is also improved.
Furthermore, in the present invention, defects (development defects), which is one of the problems that are a problem in the current lithography process, are also improved. In other words, the defect appears in various forms due to various factors, but it is recognized as one of the main causes of the polymer having extremely different dissolution behavior in the resist composition, more specifically in the base material. ing. Speaking of the current polymer system, a polymer in which a monomer having a non-acid dissociable, dissolution inhibiting group that does not have alkali solubility is introduced at a high ratio has an extremely low degree of polarity change due to acid in the exposed area, It is observed as a development scrap, or the surrounding polymer dissolves, but even if it dissolves once during the development process, it re-deposits and adheres to the resist thin film surface during the transition to the rinse process with pure water. That is expected. However, in the present invention, as described above, since the alkali solubility of each molecule in the material is relatively uniform, it is considered that the defect is also improved.

Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples.
Reference example 1
A polyhydric phenol compound represented by the following formula: About 01-19, the solubility and amorphous property were evaluated in the following procedure.

[Solubility]
Each compound No. For 01 to 19, a mixed solvent of ethyl lactate / propylene glycol monoethyl ether acetate = 40/60 (mass ratio) (hereinafter abbreviated as EM) was added in an amount of 14% by mass, and ultrasonic cleaning was performed. The sample was subjected to ultrasonic treatment (dissolution treatment) using a vessel. After sonication, each sample was allowed to stand at room temperature all day and night, and its dissolved state was visually confirmed.
Subsequently, in the evaluation of the solubility in EM, those that were not completely dissolved were subjected to the same evaluation using tetrahydrofuran (THF) and methyl ethyl ketone (MEK) instead of EM.
The results are shown in Table 1. In Table 1, ◯ indicates that it was completely dissolved, △ indicates that it was not completely dissolved and insoluble matter was observed, and X was dissolved after sonication but recrystallized after standing. Or it was not dissolved immediately after sonication.

[Amorphous]
A sample (14% by mass EM solution) for which the solubility evaluation was not x was filtered through a 0.45 micron pore size disk filter, and then spin-coated at 1500 rpm on a silicon wafer at 2 mL to form a 450 nm film. Was provided. In this state, it was visually confirmed whether an amorphous film (an optically transparent film) was formed.
After the spin coating, the wafer on which the amorphous film was formed was subjected to dry baking (PAB, Post Applied Bake) at 110 ° C. for 90 seconds. In this state, it was visually confirmed whether or not an amorphous film was formed.
After the spin coating, the wafer on which the amorphous film was formed was left in a wafer cassette case for 2 weeks in a room temperature environment. In this state, it was visually confirmed whether or not an amorphous film was formed.
The results are shown in Table 1. In Table 1, ◯ indicates that an amorphous film is formed, and Cryst indicates that a crystallized portion is formed on the wafer partially or entirely. “After coating” means after spin coating and before PAB processing, and “after PAB” means from the start of PAB until the wafer returns to room temperature after PAB processing.
In Table 1, * 1 means insoluble in ethyl lactate, toluene, butyl acetate, and 2-heptanone.

  From the results in Table 1, No. The compounds of 03-09, 12-14, and 17-19 had good solubility in EM. Also, an amorphous film could be formed both after Coat and after PAB. Furthermore, the stability of the film was good and the amorphous state was maintained even after 2 weeks.

[Production Example 1]
No. in Reference Example 1 above. 18 polyphenol compounds (molecular weight 981: hereafter, abbreviated as MBSA), 10 g was dissolved in 33 g of tetrahydrofuran, and 1.8 g of ethyl vinyl ether was added thereto and reacted at room temperature for 12 hours with stirring. After completion of the reaction, extraction and purification were performed in a water / ethyl acetate system. This obtained 10.1 g of base materials for pattern forming materials (a1).

About the obtained base material for pattern formation materials (a1), it was protected by the number of phenolic hydroxyl groups and 1-ethoxyethyl group in the base material for pattern formation materials (a1) by 400 MHz proton NMR made by JEOL. When the number of phenolic hydroxyl groups was measured and the protection rate (mol%) of the polyhydric phenol material (a1) was determined by the following formula, the protection rate was 19.9 mol%.
{Number of phenolic hydroxyl groups protected with 1-ethoxyethyl group / (number of phenolic hydroxyl groups + 1) (number of phenolic hydroxyl groups protected with 1-ethoxyethyl group)} × 100

[Production Example 2]
No. in Reference Example 1 above. 19 g of polyhydric phenol compound (molecular weight 708: hereinafter abbreviated as MBSA-2) was dissolved in 33 g of tetrahydrofuran, and 4.9 g of ethyl vinyl ether was added thereto and reacted at room temperature for 12 hours with stirring. After completion of the reaction, extraction and purification were performed in a water / ethyl acetate system. This obtained the base material (a2) for pattern formation materials.

  About the obtained base material for pattern formation materials (a2), it was protected by the number of phenolic hydroxyl groups and 1-ethoxyethyl group in the base material for pattern formation materials (a2) by proton NMR of 400 MHz made by JEOL. When the number of phenolic hydroxyl groups was measured and the protection rate (mol%) of the polyhydric phenol material (a2) was determined by the following formula, the protection rate was 50.1 mol%.

[Example 1]
10% by mass of triphenylsulfonium nonafluorobutanesulfonate and 1% by mass of tri-n-octylamine based on the substrate for pattern forming material (a1) obtained in Production Example 1 and the total solid content thereof Dissolved in ethyl lactate / propylene glycol monomethyl ether acetate = 40/60 (mass ratio) to obtain a positive resist composition solution having a solid content concentration of 6 mass%.

[ Reference Example 2]
A positive resist composition solution was obtained in the same manner as in Example 1 except that the polyhydric phenol material (a1) used in Example 1 was changed to the polyhydric phenol material (a2).

[Comparative Example 1]
In the polyhydric phenol material (a1) used in Example 1, the phenolic hydroxyl group of the polyhydroxystyrene resin (polystyrene equivalent Mw by GPC is 8000, the dispersity is 2.65) was protected by 1-ethoxyethyl group. A positive resist composition solution was obtained in the same manner as in Example 1 except that the resin (protection rate: 30.7 mol%) was changed.

[Evaluation test]
The following evaluation was performed using the positive resist compositions obtained in Example 1, Reference Example 2 and Comparative Example 1.
"resolution"
A positive resist composition solution is uniformly applied on an 8-inch silicon substrate subjected to hexamethyldisilazane treatment using a spinner and baked (PAB) at 110 ° C. for 90 seconds to form a resist film (film thickness) 150 nm) was formed. The resist film is drawn by an electron beam drawing machine (Hitachi HL-800D, 70 kV acceleration voltage) and subjected to 90 seconds baking treatment (PEB) at 110 ° C. and tetramethylammonium hydroxide (TMAH) 2. A line and space (L / S) pattern was formed by developing for 60 seconds with a 38 mass% aqueous solution and rinsing with pure water for 30 seconds.
The obtained resist pattern was observed with a length measurement SEM, and the resolution was determined.
In Reference Example 2, PAB was changed to 80 ° C. for 90 seconds and PEB was changed to 70 ° C. for 300 seconds.
As a result, Example 1 formed 50 nm line and space, Reference Example 2 formed 80 nm line and space, and Comparative Example 1 formed 70 nm line and space.

"Surface roughness"
A positive resist solution is uniformly applied on an 8-inch silicon substrate subjected to hexamethyldisilazane treatment using a spinner and baked at 110 ° C. for 90 seconds to form a resist film (film thickness 160 nm). did.
The resist film is exposed with an electron beam drawing machine (Hitachi HL-800D, 70 kV acceleration voltage) at an exposure amount of 10 μC / cm ² and baked at 110 ° C. for 90 seconds, tetramethylammonium hydroxide ( After development with a 2.38 mass% aqueous solution of TMAH for a development time in which the film thickness after development is about 90% of the initial film thickness (Example 1 and Reference 2 are developed for 60 seconds, Comparative Example 1 is 15 seconds) Development) and rinsed with pure water for 30 seconds.
After rinsing, the surface of the resist film was observed with an AFM (atomic force microscope: di NanoScope IV / D5000 manufactured by Veeco Instrument Inc.), and the root mean square roughness (Rms) per 1 μm square was determined.

As a result, Example 1 was 1.98 nm, Reference Example 2 was 0.90 nm, and Comparative Example 1 was 5.36 nm.

As described above, the positive resist composition of Example 1 had high resolution and low surface roughness. On the other hand, Comparative Example 1 using a polyhydroxystyrene resin having an Mw of 8000 and a dispersity of 2.65 had a very large surface roughness as compared with Example 1 and Reference Example 2, although the resolution was high.
A positive correlation between surface roughness and pattern LER was pointed out by Yamaguchi et al. (T. Yamaguchi et al., J. Photopolymer. Sci. Technol., 10 (1997) 635, etc.). From the above results, it can be seen that the LER of the patterns obtained using the positive resist compositions of Example 1 and Reference Example 2 is good. In addition, it is fully expected that defects will be improved by improving the roughness of the resist film surface after rinsing.

Claims (5)

A positive type containing an acid dissociable, dissolution inhibiting group, a base component (A) whose alkali solubility is increased by the action of an acid, and an acid generator component (B) which generates an acid upon exposure and no polymer A resist composition comprising:
Said base component (A) has two or more phenolic hydroxyl groups, the following (1), (2) and part acid of the phenolic hydroxyl group in (3) satisfy the polyhydric phenol compound (x) low molecular weight compounds that are protected by dissociable (X1) forming material for substrate der consisting is, the protection rate of the phenolic hydroxyl groups of the pattern forming material for the substrate in the 5 to 50 mol% the positive resist composition characterized in that there is.
(1) Molecular weight is 500-1500
(2) Molecular weight dispersity is 1.5 or less (3) Amorphous film can be formed by spin coating The positive electrode according to claim 1, wherein the polyhydric phenol compound (x) is at least one selected from the group consisting of polyhydric phenol compounds represented by the following general formula (I), (II) or (III). Type resist composition.

[In the formula (I), R _{11 to} R ₁₇ are each independently an alkyl group having 1 to 10 carbon atoms or an aromatic hydrocarbon group, and may contain a hetero atom in the structure thereof; Are independently an integer of 1 or more, k and q are 0 or an integer of 1 or more, and g + j + k + q is 5 or less; h is an integer of 1 or more, and l and m are each independently 0 or 1 or more And h + 1 + m is 4 or less; i is an integer of 1 or more, n and o are each independently 0 or an integer of 1 or more, and i + n + o is 4 or less; p is 0 or 1]

[In the formula (II), R _{21 to} R ₂₆ are each independently an alkyl group having 1 to 10 carbon atoms or an aromatic hydrocarbon group, and the structure thereof may contain a hetero atom; Is independently an integer of 1 or more, h is 0 or an integer of 1 or more, and d + g + h is 5 or less; e is an integer of 1 or more, and i and j are each independently an integer of 0 or 1 or more And e + i + j is 4 or less; f and k are each independently an integer of 1 or more, l is 0 or an integer of 1 or more, and f + k + l is 5 or less; m is 2 to 20 Is an integer]

[In the formula (III), R _{31 to} R ₃₈ are each independently an alkyl group having 1 to 10 carbon atoms or an aromatic hydrocarbon group, and may contain a hetero atom in the structure thereof; Independently an integer of 1 or more, f is 0 or an integer of 1 or more, and a + e + f is 5 or less; b and h are each independently an integer of 1 or more, and g is an integer of 0 or 1 or more And b + h + g is 5 or less; c and i are each independently an integer of 1 or more, j is 0 or an integer of 1 or more, and c + i + j is 5 or less; d is an integer of 1 or more And k and l are each independently 0 or an integer of 1 or more, and d + k + 1 is 3 or less.] Said acid dissociable, dissolution inhibiting groups, chain-like alkoxyalkyl groups, tertiary alkyloxycarbonyl group, tertiary alkyl group, claims are selected from tertiary alkoxycarbonylalkyl group and a group consisting of a cyclic ether group 1 Or the positive resist composition of 2. Furthermore, the positive resist composition as described in any one of Claims 1-3 containing a nitrogen-containing organic compound (D). The positive resist composition according to any one of claims 1 to 4 is applied on a substrate, pre-baked, selectively exposed, subjected to PEB (post-exposure heating), and alkali-developed. And forming a resist pattern.