JP4663456B2 - Positive resist composition and resist pattern forming method - Google Patents

Description

  The present invention relates to a positive resist composition 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, conventionally, ultraviolet rays typified by g-line and i-line were used, but now KrF excimer laser (248 nm) is the center of mass production, and ArF excimer laser (193 nm) is mass-produced. It has begun to be introduced. Research is also being conducted on lithography technology using an F ₂ excimer laser (157 nm), EUV (extreme ultraviolet light), EB (electron beam) or the like as a light source (radiation source).

A resist material used for lithography using such a light source is required to have high sensitivity to the light source. Further improvements are also required for various lithography characteristics (resolution, depth of focus characteristics, resist pattern shape, etc.) other than sensitivity.
As one of resist materials satisfying such requirements, a chemically amplified resist composition containing a base resin and an acid generator that generates an acid upon exposure is known. The chemically amplified resist composition includes a positive type in which the alkali solubility in the exposed area increases and a negative type in which the alkali solubility in the exposed area decreases.
At present, as a base resin of a chemically amplified resist composition, for example, when a KrF excimer laser is used as a light source, a polyhydroxystyrene (PHS) resin is mainly used. When an ArF excimer laser is used as a light source, a resin (acrylic resin) having a structural unit derived from (α-lower alkyl) acrylic acid in the main chain is generally used. .
In the production of a base resin, the so-called temperature rising batch polymerization method, in which a raw material monomer, a polymerization initiator, and if necessary, a chain transfer agent are dissolved in a polymerization solvent and then polymerized by heating, is most commonly used. It has been.

However, the resist material as described above has a problem that defects are likely to occur on the surface of the resist pattern to be formed. Defects are general defects detected when a developed resist pattern is observed from directly above, for example, with a surface defect observation apparatus (trade name “KLA”) manufactured by KLA Tencor. Examples of the defects include scum, bubbles, dust, bridges between resist patterns, uneven color, and precipitates after development.
Improving the defect becomes important as a resist pattern having a high resolution is required. In particular, when an ArF excimer laser is used, that is, when a fine pattern such as a resist pattern of 130 nm or less is formed using ArF excimer laser, F ₂ excimer laser, EUV, EB, etc. as a light source, the problem of defect resolution becomes more severe. ing.

As one of the causes of the defect, there may be a variation in the molecular weight of each molecule constituting the base resin, and a polarity deviation in the molecule.
In other words, the reaction system after the polymerization reaction has a wide range from those having relatively low molecular weights such as unreacted monomers, by-produced oligomers and low molecular weight polymers to polymers having a high degree of polymerization and relatively high molecular weights. There is a molecular weight. Each of these molecules has a different solubility in a solvent or an alkaline developer, and this is considered to be one of the causes of worsening the defect.
Currently, in the production of a base resin, two or more types of monomers are usually used as raw material monomers in order to obtain good lithography characteristics. For example, Patent Document 1 discloses, as a monomer, a (meth) acrylic acid ester having an acid dissociable, dissolution inhibiting group in an ester portion, a (meth) acrylic acid ester having a lactone skeleton such as a γ-butyrolactone skeleton in an ester portion, and an ester portion. Describes a polymer using a (meth) acrylic acid ester having a polycyclic group containing a polar group such as a hydroxyl group. And these monomers differ in the reactivity (polymerization rate) in a polymerization reaction, respectively. For this reason, in the base resin produced by the temperature rising batch polymerization method, the structural units derived from the respective monomers tend to be unevenly distributed, which is considered to be one of the causes of worsening the defect.

  Variation in molecular weight can be reduced by purifying the resin after polymerization. For example, Patent Document 2 describes that the resin is washed with a lower alcohol such as methanol. This removes unreacted monomers, by-produced oligomers, low molecular weight polymers, and the like.

Recently, the monomer and the polymerization initiator are separately dissolved in a solvent, and at least one of the solutions is dropped into the polymerization solvent heated to the polymerization temperature, and the monomer and the polymerization initiator are reacted in the polymerization solvent. It has been proposed to produce a base resin by a method of performing polymerization by so-called dropping polymerization (see, for example, Patent Documents 3 and 4). For example, in Patent Document 4, a monomer, a polymerization initiator and, if necessary, a chain transfer agent are dissolved in the same or different solvent as a polymerization solvent, and the solution is dropped into a polymerization solvent heated to a polymerization temperature for polymerization. A method for producing a resist polymer by performing the above is disclosed. The drop polymerization method has higher reaction efficiency, higher yield, lower cost, etc. than the temperature rising type batch polymerization method in which the temperature is raised to the polymerization temperature in a state where all the raw material monomers and the polymerization initiator are mixed. There are benefits.
JP 2003-167347 A JP 2004-231834 A JP 2003-206315 A JP 2004-269855 A

According to the drop polymerization method, a resin with less variation in molecular weight distribution, distribution of various structural units in the molecule, and the like can be obtained as compared with the temperature rising batch polymerization method. Therefore, it is considered that the resin obtained by the dropping polymerization method has little variation in solubility in, for example, a solvent or an alkaline developer, and therefore, a reduction in defects can be expected.
However, according to the study by the present inventors, when a resin produced by the dropping polymerization method is used as a base resin, the lithography properties such as the depth of focus are poor and there is a problem in practical use.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a positive resist composition and a resist pattern forming method with few defects and excellent lithography characteristics.

As a result of intensive studies, the inventors of the present invention have one of the causes that the lithography properties are poor because the proportion of the molecular weight distribution of the resin produced by the drop polymerization method is relatively small. And it discovered that the said subject was solved by containing the low molecular weight body of molecular weight 100-10000 within a specific range, and completed this invention.
That is, the first aspect of the present invention is a positive resist composition containing a resin component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon irradiation with radiation. Because
The resin component (A) has a structural unit (a1) derived from an (α-lower alkyl) acrylic acid ester having an acid dissociable, dissolution inhibiting group, and a lactone-containing monocyclic or polycyclic group (α- A structural unit (a2) derived from a lower alkyl) acrylate ester, a structural unit (a3) derived from an (α-lower alkyl) acrylate ester containing a polar group-containing aliphatic hydrocarbon group, containing dissociable aliphatic polycyclic group (alpha-lower alkyl) is a copolymer having the structural unit (a4) in the main chain derived from an acrylate ester, after that by the dropping polymerization method polymerizing the obtained polymerization reaction solution, methanol: water = 100: 8-20 is prepared by purifying dropwise to a mixed solvent (mass ratio), weight average molecular weight of 5,000 to 20,000, and Gerupa A positive resist composition characterized in that the ratio of the peak area of the low molecular weight region having a molecular weight of 100 to 10,000 is 55 to 80% of the total peak area in the molecular weight distribution measured by the association chromatography. is there.
According to a second aspect of the present invention, a resist film is formed on a substrate using the positive resist composition of the first aspect, the resist film is exposed, and the resist film is developed to form a resist. It is a resist pattern formation method including the process of forming a pattern.
The third aspect of the present invention is to produce a positive resist composition containing a resin component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon irradiation with radiation. A way to
(Α-lower alkyl) acrylate ester having acid dissociable, dissolution inhibiting group, (α-lower alkyl) acrylate ester having lactone-containing monocyclic or polycyclic group, polar group-containing aliphatic hydrocarbon group (Α-Lower alkyl) acrylic acid ester and (α-lower alkyl) acrylic acid ester containing an acid non-dissociable aliphatic polycyclic group were polymerized by a dropping polymerization method, and the resulting polymerization reaction solution was treated with methanol. : Water = 100: In a molecular weight distribution measured by gel permeation chromatography, the molecular weight is 100 when the weight average molecular weight is 5000 to 20000 by purification by dropping into a mixed solvent of 100: 8 to 20 (mass ratio). Produces a copolymer in which the ratio of the peak area of the low molecular weight region of 10000 is 55 to 80% with respect to the entire peak area , The copolymer is a method for producing a positive resist composition which comprises using as the resin component (A).

In the present invention, the “structural unit” means a monomer unit constituting a polymer (resin component).
“Exposure” is a concept that includes general irradiation of radiation.

  The present invention provides a positive resist composition and a resist pattern forming method with few defects and excellent lithography properties.

≪Positive resist composition≫
The positive resist composition of the present invention comprises a resin component (A) whose alkali solubility is increased by the action of an acid (hereinafter referred to as (A) component), and an acid generator component (B) that generates an acid upon irradiation with radiation. (Hereinafter referred to as component (B)).
In the positive resist composition of the present invention, by containing the component (A) and the component (B), the acid generated from the component (B) by exposure acts on the component (A) due to exposure (A). ) The alkali solubility of the component is increased, and the alkali insoluble is changed to the alkali soluble. Therefore, when a resist film obtained using a positive resist composition is selectively exposed in the formation of a resist pattern, or when post-exposure heating (PEB) is performed in addition to exposure, the exposed portion is alkali-soluble. On the other hand, since the unexposed portion remains insoluble in alkali and does not change, a positive resist pattern can be formed by alkali development.

<(A) component>
The component (A) is a resin having a mass average molecular weight of 5,000 to 20,000 produced by a dropping polymerization method, and a molecular weight distribution measured by gel permeation chromatography (GPC) in a low molecular weight region having a molecular weight of 100 to 10,000. The ratio of the peak area is 55 to 80% with respect to the entire peak area. Thereby, the effect of the present invention is exhibited.

The component (A) is a resin obtained by a dropping polymerization method, and the mass average molecular weight (Mw) (polystyrene conversion standard by gel permeation chromatography) needs to be in the range of 5000 to 20000. If it is below the upper limit of this range, there is sufficient solubility in a resist solvent for use as a resist. When it is at least the lower limit of this range, the lithography properties are good, and the dry etching resistance and resist pattern cross-sectional shape are good. As for Mw, 6000-15000 are more preferable, and 7000-12000 are the most preferable.
Further, the dispersity (Mw / Mn) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

In the dropping polymerization method, a monomer and a polymerization initiator are separately dissolved in a solvent, and at least one of the solutions is dropped into a polymerization solvent (polymerization reaction system) heated to a polymerization temperature. In this method, polymerization is performed by reacting a polymerization initiator (and a chain transfer agent if necessary).
A known method can be used as the dropping polymerization method. For example, a method in which a monomer solution and a polymerization initiator solution are dropped separately in a polymerization reaction system, in which one of a monomer and a polymerization initiator is previously dissolved in the polymerization reaction system, and the other solution is dropped therein. Methods and the like.
In the present invention, as the dropping polymerization method, at least one monomer solution containing at least one monomer as a raw material, and a polymerization initiator solution containing a polymerization initiator are held in independent tanks, respectively. A method of radical polymerization by supplying continuously or intermittently into the polymerization system is preferably used.

  The monomer is not particularly limited as long as it has a polymerizability that can be polymerized with each other to form a polymer, and is determined according to the composition of the target resin. For example, a monomer for deriving various structural units such as structural units (a1) to (a4) described later may be used.

The polymerization initiator used for the polymerization reaction is not particularly limited as long as it is generally used as a radical generator. Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), dimethyl 2,2′-azobisisobutyrate, 1,1′- Azo compounds such as azobis (cyclohexane-1-carbonitrile) and 4,4′-azobis (4-cyanovaleric acid); decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, bis (3,5,5-trimethyl) Hexanoyl) peroxide, succinic acid peroxide, tert-butylperoxy-2-ethylhexanoate and other organic peroxides can be used alone or in combination.
The amount of the polymerization initiator used can be selected depending on the monomer used for the polymerization reaction, the type and amount of the chain transfer agent described later, the polymerization temperature, the polymerization conditions such as the polymerization solvent, and the like.

In the polymerization reaction, a chain transfer agent may be used.
The chain transfer agent, typically those used in the polymerization reaction can be used, for example, _{HS-CH 2 -CH 2 -CH 2} -C (CF 3) 2 -OH, dodecanethiol, mercaptoethanol, mercapto propanol, mercapto Any one of these thiol compounds such as acetic acid and mercaptopropionic acid can be used alone or in admixture of two or more.
Among these, when a fluoride such as HS—CH ₂ —CH ₂ —CH ₂ —C (CF ₃ ) ₂ —OH is used, an alkyl group such as —C (CF ₃ ) ₂ —OH group at the molecular end is used. A hydroxyalkyl group in which a part of hydrogen atoms is substituted with fluorine atoms is introduced. As described above, a polymer in which a hydroxyalkyl group in which a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom is introduced has a reduction in development defects and LER (line edge roughness: uneven unevenness of a line side wall). Effective for reduction.
The chain transfer agent may be used by dissolving in a monomer solution together with the monomer, or may be used by dissolving in a polymerization initiator solution together with a polymerization initiator.

In the polymerization reaction, in order to dissolve the monomer to be used, to dissolve the polymerization initiator, or to be inserted into the reaction vessel (that is, to constitute a polymerization reaction system to which the monomer solution and the polymerization initiator solution are supplied). A solvent can be used for this purpose.
As the solvent for dissolving the monomer, the solvent for dissolving the polymerization initiator, and the solvent (polymerization solvent) put into the reaction vessel, those capable of dissolving the monomer, the polymerization initiator, and the polymer produced in the polymerization reaction system, respectively. If it is, it will not be restrict | limited in particular. These solvents may be the same or different.
Specific examples of such solvents include ketones such as acetone, methyl ethyl ketone, methyl amyl ketone and cyclohexanone; ethers such as tetrahydrofuran, dioxane, glyme and propylene glycol monomethyl ether; esters such as ethyl acetate and ethyl lactate; propylene glycol methyl Examples include ether esters such as ether acetate; lactones such as γ-butyrolactone, and any of these may be used alone or in admixture of two or more.

In the monomer solution and polymerization initiator solution supplied into the polymerization system, when the monomer or polymerization initiator to be used is liquid, it can be supplied as it is without being dissolved in the solvent, and it can be diluted by adding a solvent. Can also be used. When the monomer or the polymerization initiator is a viscous liquid, it is preferable to dilute by adding a solvent. Moreover, when a monomer or a polymerization initiator is a solid, it needs to be dissolved in a solvent and used.
The monomer concentration in the monomer solution and the concentration of the polymerization initiator in the initiator solution are preferably higher in terms of productivity. However, if the concentration of the solute (monomer or polymerization initiator) is too high, the solution viscosity becomes high and the operability may deteriorate, or if the solute is a solid, it may precipitate. Therefore, it is preferable to select a concentration in which each monomer and the polymerization initiator are sufficiently dissolved and do not precipitate during the supply in a viscosity range that does not cause a problem in the supply operation. The specific concentration varies depending on the combination of the solute and the solvent in each solution, but it is usually preferable that the concentration of the solute is adjusted to be in the range of 5 to 60% by mass, and 10 to 50% by mass. More preferred.

In the dropping polymerization method, it is preferable to preheat each of the above solutions before feeding them into the polymerization system. Thereby, since the solubility of a monomer or a polymerization initiator improves, a higher concentration solution can be prepared. In particular, regarding the monomer solution, if the temperature at which the monomer solution is supplied into the polymerization system is too low, a region having a low temperature and a high monomer concentration may be locally formed in the heated polymerization system. In such a region, a high molecular weight polymer is likely to be produced, and the defect may be deteriorated. Therefore, it is preferable that the monomer solution is supplied after being preheated by a heat exchanger or the like immediately before being supplied into the storage tank or the polymerization system.
The temperature for preheating the monomer solution is preferably 25 ° C. or higher, more preferably 40 ° C. or higher. In the preheating of the monomer solution, when the monomer solution is preheated in a storage tank, the monomer solution is kept in a heated state for a long time. Therefore, when the temperature is high, a high molecular weight polymer is easily generated. Therefore, when preheating in a storage tank, it is preferable to set it as 50 degrees C or less. On the other hand, in the case of preheating with a heat exchanger or the like immediately before being supplied into the polymerization system, since the holding time in a high temperature state is short, it is possible to heat to a higher temperature, for example, to the polymerization temperature It is also possible.

  The polymerization temperature varies depending on the boiling point of the polymerization solvent to be used, but is preferably selected in the range of 60 to 120 ° C, particularly preferably 70 to 100 ° C.

The monomer solution and the initiator solution may be supplied independently from the storage tank to the polymerization tank, or may be premixed immediately before the polymerization.
The supply rate of the monomer solution and the initiator solution can be set independently so that a resin having a desired molecular weight distribution can be obtained, and the supply rate of any or all of these solutions is changed. Thus, it is possible to obtain a resin having a wide molecular weight distribution from narrow dispersion to polydispersion with good reproducibility.
The feed rates of the monomer solution and the initiator solution can be changed steplessly or stepwise.
When the monomer solution and the initiator solution are supplied as slowly as possible, the monomer composition, temperature, and radical concentration in the polymerization system can be kept constant. Changes in molecular weight can be reduced. However, if the supply rate is too slow, the time required for the supply becomes long and the production efficiency per hour deteriorates. Also, for monomers with low stability, deterioration of the monomer solution may become a problem. The time required for supplying the initiator solution is preferably selected from the range of 0.5 to 20 hours, preferably 1 to 10 hours.

  The order in which the monomer solution and the initiator solution are started is not particularly limited. However, it is preferable to supply the monomer solution and the initiator solution at the same time or the initiator solution first. Generation is suppressed and the effect of reducing defects is enhanced.

  The polymerization reaction is started and continued with the supply of the monomer solution and the initiator solution, but it is preferable that the remaining unreacted monomer is reacted by aging while maintaining the polymerization temperature for a certain time after the supply is completed. The aging time is preferably selected from the range of 6 hours or less, preferably from 1 to 4 hours, from the viewpoint of production efficiency.

In the present invention, after the polymerization by the dropping polymerization method as described above, the obtained resin (crude resin) is purified, and the molecular weight distribution measured by GPC has a peak in a low molecular weight region having a molecular weight of 100 to 10,000. It is necessary to adjust the area ratio within the range of 55 to 80% with respect to the entire peak area.
Here, the ratio of the peak area of the low molecular weight region having a molecular weight of 100 to 10,000 to the entire peak area is the ratio of the molecule (low molecular weight body) having a molecular weight of 100 to 10,000 to all the molecules constituting the component (A) ( %).
For example, after the polymerization reaction is completed, if the proportion of low molecular weight substances having a molecular weight of 100 to 10,000 in the resin is less than 55%, some or all of the molecules having a molecular weight of less than 100 are removed and / or the molecular weight is The proportion of low molecular weight substances having a molecular weight of 100 to 10,000 can be increased by removing a part of the molecules exceeding 10,000.
Further, after the polymerization reaction, when the ratio of the low molecular weight substance having a molecular weight of 100 to 10,000 exceeds 80% in the resin, the proportion of the low molecular weight substance is removed by removing a part of the low molecular weight substance having a molecular weight of 100 to 10,000. Can be lowered.

In the present invention, the ratio of the peak area of the low molecular weight region having a molecular weight of 100 to 10,000 (hereinafter sometimes simply referred to as the ratio of the peak area of the low molecular weight region) is 55 to 80% with respect to the entire peak area. As a result, the lithography properties are improved. This is because a low molecular weight substance having a molecular weight of 100 to 10000 is important for lithography properties, and by containing the low molecular weight substance in a ratio of 55% to 80%, sensitivity, line edge roughness (LER), Lithographic properties such as exposure margin, depth of focus (DOF), proximity effect, etc. are improved and development defects are reduced.
The ratio of the peak area of the low molecular weight region having a molecular weight of 100 to 10,000 is more preferably 60 to 75%, and further preferably 65 to 75%.

The molecular weight distribution can be measured by GPC, for example, using a refractive index detector (RI) as a detector and based on a calibration curve created from a commercially available polystyrene standard sample.
The ratio of the peak area of the low molecular weight region having a molecular weight of 100 to 10,000 (hereinafter sometimes simply referred to as the ratio of the peak area of the low molecular weight region) is a low molecular weight of 100 to 10,000 from the molecular weight distribution measured as described above. The peak area A _L of the molecular weight region and the entire peak area A _A can be obtained and calculated by applying the calculation formula below.
Formula: Ratio of peak area in low molecular weight region (%) = (A _L / A _A ) × 100

Below, a preferable example of the measurement conditions of molecular weight distribution by GPC is shown.
[GPC measurement conditions]
・ Device: “HLC-8220 GPC” manufactured by TOSOH
Guard column: “TSK Super HH” manufactured by TOSOH
-Column: "TSK Gel Super HM-N" x 3 manufactured by TOSOH-Detector: Differential refractive index (RI) detector-Eluent: Tetrahydrofuran (THF) (dibutylhydroxytoluene (BHT) concentration: 0 ppm)
・ Flow rate: 0.6 mL / min ・ Injection volume: 40 μL
・ Measurement temperature: 40 ℃
Measurement time: 20 minutes Sample: THF solution in which resin is dissolved so that the solid content concentration is about 0.2% by mass

The purification of the crude resin can be carried out, for example, by dropping the polymerization reaction solution after the completion of the polymerization reaction into a washing solvent and depositing it.
In this case, the ratio of the peak area of the low molecular weight region can be adjusted by adjusting the solubility of the washing solvent used for the purification in the resin produced by the dropping polymerization.
That is, the weaker the solubility of the washing solvent in the resin, the smaller the molecular weight of the molecule that can be dissolved by the washing solvent (that is, that can be removed by the washing solvent), while the stronger the washing solvent, the more Since the molecular weight of molecules that can be dissolved (that is, removed by a washing solvent) tends to increase, the molecular weight range of molecules to be removed can be adjusted by adjusting the solubility.
A suitable soluble cleaning solvent is a solvent in which the molecular weight in which range is removed by GPC after purification with a solvent, and the ratio of the peak area in the low molecular weight region is within the above range. It can be determined by conducting a test to find out.
In addition, when the above test is performed for several solvents and a poor solvent and a good solvent for the resin are obtained, a poor solvent or a mixed solvent of a poor solvent and a good solvent may be used as a cleaning solvent. it can.

  In particular, when a copolymer having a structural unit (a1), the structural unit (a2), the structural unit (a3), and the structural unit (a4) described later is used as the component (A), washing is performed. As the solvent, a mixed solvent of methanol and water is preferably used. When using such a copolymer, methanol is a good solvent and water is a poor solvent. Therefore, by using such a mixed solvent, it is possible to remove unnecessary substances such as unreacted monomer, polymerization initiator and reaction residue thereof without removing or hardly removing molecules having a molecular weight of 100 or more. The mixing ratio of methanol and water is preferably in the range of methanol: water = 100: 8 to 20 (mass ratio), more preferably 100: 12 to 16.

The amount of the washing solvent is preferably 2 times by mass or more, more preferably 4 to 5 times by mass with respect to the polymerization solvent, from the viewpoint of removing impurities such as unreacted monomers.
After the washing solvent is added, the crude resin becomes a solid when it is stirred, shaken, etc. at 10 to 40 ° C., preferably 20 to 30 ° C. for 10 to 60 minutes, preferably 25 to 35 minutes. Come. The resin is obtained by filtering the precipitated solid.
Washing with a washing solvent can be repeated as necessary. That is, the resin obtained after the above-described washing can be dissolved again in a polymerization solvent such as tetrahydrofuran, purified by dripping in the washing solvent, and the precipitated resin can be repeatedly filtered.

  The constitution of the component (A) is not particularly limited as long as it satisfies the above-mentioned ratio of Mw and the peak area of the low molecular region, and heretofore has been proposed as a base resin for a chemically amplified positive resist It may be the composition of. Specifically, the base resin is an alkali-insoluble one having a so-called acid dissociable dissolution inhibiting group, and when acid is generated from the component (B) by exposure, the acid dissociates the acid dissociable dissolution inhibiting group. By making it, (A) component becomes alkali-soluble. Therefore, in the formation of the resist pattern, when the resist composition applied on the substrate is selectively exposed, the alkali solubility of the exposed portion increases and alkali development can be performed.

  Since the component (A) is highly transparent to an exposure light source such as an ArF excimer laser and has excellent lithography properties such as resolution, a structural unit derived from an (α-lower alkyl) acrylate ester is used as the main chain. It is preferable to have.

Here, in the present invention, “(α-lower alkyl) acrylic acid ester” means one or both of α-lower alkyl acrylic acid ester such as methacrylic acid ester and acrylic acid ester.
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 derived from (α-lower alkyl) acrylate ester” means a structural unit having a structure in which the ethylenic double bond of (α-lower alkyl) acrylate ester is cleaved.
“Having a structural unit derived from (α-lower alkyl) acrylate ester in the main chain” is derived from an ethylenic double bond of a structural unit derived from (α-lower alkyl) acrylate ester. It means that two carbon atoms constitute the main chain of the polymer.
The “alkyl group” includes linear, branched and cyclic monovalent saturated hydrocarbon groups unless otherwise specified.

(Α-Lower alkyl) A hydrogen atom or a lower alkyl group is bonded to the α-position of the acrylate ester. (Α-Lower alkyl) A lower alkyl group as a substituent at the α-position of an acrylate ester is an alkyl group having 1 to 5 carbon atoms, and specifically includes a methyl group, an ethyl group, a propyl group, and isopropyl. And a lower linear or branched alkyl group such as a group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group and neopentyl group. A hydrogen atom or a methyl group is preferably bonded to the α-position in terms of industrial availability.
Examples of the structural unit derived from the (α-lower alkyl) acrylate ester include the structural unit (a1) to the structural unit (a4) described later.
In the present invention, the component (A) preferably contains 20 mol% or more, more preferably 50 mol% or more of a structural unit derived from an (α-lower alkyl) acrylic acid ester. It is desirable because it is obtained.

・ Structural unit (a1)
The component (A) preferably has a structural unit (a1) derived from an (α-lower alkyl) acrylate ester having an acid dissociable, dissolution inhibiting group.
The lower alkyl group as the substituent at the α-position of the (α-lower alkyl) acrylate ester is the same as the lower alkyl group as the substituent at the α-position of the (α-lower alkyl) acrylate ester. Is mentioned.

  The acid dissociable, dissolution inhibiting group in the structural unit (a1) has an alkali dissolution inhibiting property that makes the entire component (A) insoluble in alkali before dissociation, and changes the entire component (A) to alkali soluble after dissociation. If it is so far, what has been proposed as an acid dissociable, dissolution inhibiting group of a base resin for a chemically amplified resist can be used. Generally, a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group of (meth) acrylic acid, or a group that forms a cyclic or chain alkoxyalkyl ester is widely known. . “(Meth) acrylic acid ester” means one or both of acrylic acid ester and methacrylic acid ester.

Here, the tertiary alkyl ester is an ester formed by substituting a hydrogen atom of a carboxy group with an alkyl group or a cycloalkyl group, and a carbonyloxy group (—C (O) —O—). ), The tertiary carbon atom of the alkyl group or cycloalkyl group is bonded to the terminal oxygen atom. In this tertiary alkyl ester, when an acid acts, a bond is cut between an oxygen atom and a tertiary carbon atom.
The alkyl group or cycloalkyl group may have a substituent.
Hereinafter, a group that is acid dissociable by constituting a carboxy group and a tertiary alkyl ester is referred to as a “tertiary alkyl ester type acid dissociable, dissolution inhibiting group” for convenience.
In addition, the cyclic or chain alkoxyalkyl ester forms an ester by replacing the hydrogen atom of the carboxy group with an alkoxyalkyl group, and the carbonyloxy group (—C (O) —O—) A structure in which the alkoxyalkyl group is bonded to a terminal oxygen atom is shown. In this alkoxyalkyl ester, when an acid acts, a bond is cut between an oxygen atom and an alkoxyalkyl group.

  As the structural unit (a1), one type selected from the group consisting of structural units represented by general formula (a1-0-1) shown below and structural units represented by general formula (a1-0-2) shown below. It is preferable to use the above.

（式中、Ｒは水素原子または低級アルキル基を示し；Ｘ^１は酸解離性溶解抑制基を示す。）

(In the formula, R represents a hydrogen atom or a lower alkyl group; X ¹ represents an acid dissociable, dissolution inhibiting group.)

（式中、Ｒは水素原子または低級アルキル基を示し；Ｘ^２は酸解離性溶解抑制基を示し；Ｙ^２は脂肪族環式基を示す。）

(In the formula, R represents a hydrogen atom or a lower alkyl group; X ² represents an acid dissociable, dissolution inhibiting group; Y ² represents an aliphatic cyclic group.)

In general formula (a1-0-1), R is the same as the lower alkyl group as a substituent at the α-position of the above (α-lower alkyl) acrylate ester.
X ¹ is not particularly limited as long as it is an acid dissociable, dissolution inhibiting group, and examples thereof include an alkoxyalkyl group, a tertiary alkyl ester type acid dissociable, dissolution inhibiting group, and the like. Acid dissociable, dissolution inhibiting groups are preferred. Examples of the tertiary alkyl ester type acid dissociable, dissolution inhibiting group include an aliphatic branched acid dissociable, dissolution inhibiting group and an acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group.
Here, “aliphatic” in the claims and the specification is a relative concept with respect to aromatics, and is defined to mean a group, a compound, or the like that does not have aromaticity. The “aliphatic cyclic group” means a monocyclic group or polycyclic group having no aromaticity.
The “aliphatic cyclic group” in the structural unit (a1) may or may not have a substituent. Examples of the substituent include a lower alkyl group having 1 to 5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, an oxygen atom (= O), and the like.
The basic ring structure excluding the substituent of the “aliphatic cyclic group” is not limited to a group consisting of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. The “hydrocarbon group” may be either saturated or unsaturated, but is usually preferably saturated. A polycyclic group is preferred.
Specific examples of such aliphatic cyclic groups include, for example, monocycloalkanes, bicycloalkanes, trialkyls which may or may not be substituted with a lower alkyl group, a fluorine atom or a fluorinated alkyl group. Examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as cycloalkane or tetracycloalkane. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Specific examples of the aliphatic branched acid dissociable, dissolution inhibiting group include a tert-butyl group and a tert-amyl group.
Examples of the acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group include a group having a tertiary carbon atom on the ring skeleton of a cycloalkyl group. Specifically, 2-methyl- Examples thereof include an adamantyl group and a 2-ethyladamantyl group. Alternatively, as a structural unit represented by the following general formula, a group having an aliphatic cyclic group such as an adamantyl group and a branched alkylene group having a tertiary carbon atom bonded thereto can be used.

［式中、Ｒは上記と同じであり、Ｒ^１５、Ｒ^１６はアルキル基（直鎖、分岐鎖状のいずれでもよく、好ましくは炭素数１〜５である）を示す。］

[Wherein, R is the same as described above, and R ¹⁵ and R ¹⁶ represent an alkyl group (which may be linear or branched, and preferably has 1 to 5 carbon atoms). ]

  Further, the alkoxyalkyl group is preferably a group represented by the following general formula.

（式中、Ｒ^２１、Ｒ^２２はそれぞれ独立してアルキル基または水素原子であり、Ｒ^２３はアルキル基又はシクロアルキル基である。または、Ｒ^２１とＲ^２３の末端が結合して環を形成していてもよい。）

(In the formula, R ²¹ and R ²² are each independently an alkyl group or a hydrogen atom, and R ²³ is an alkyl group or a cycloalkyl group. Alternatively, the ends of R ²¹ and R ²³ are combined to form a ring. You may do it.)

In R ²¹ and R ²² , the alkyl group preferably has 1 to 15 carbon atoms, may be linear or branched, and is preferably an ethyl group or a methyl group, and most preferably a methyl group. In particular, it is preferable that one of R ²¹ and R ²² is a hydrogen atom and the other is a methyl group.
R ²³ is an alkyl group or a cycloalkyl group, preferably having 1 to 15 carbon atoms, and may be linear, branched or cyclic. When R ²³ is linear or branched, it preferably has 1 to 5 carbon atoms, more preferably an ethyl group or a methyl group, and most preferably an ethyl group.
When R ²³ is cyclic, it preferably has 4 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbon atoms. Specifically, one or more polycycloalkanes such as monocycloalkane, bicycloalkane, tricycloalkane, and tetracycloalkane, which may or may not be substituted with a fluorine atom or a fluorinated alkyl group, are included. Examples include a group excluding a hydrogen atom. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Among them, a group obtained by removing one or more hydrogen atoms from adamantane is preferable.
In the above formula, R ²¹ and R ²³ are each independently an alkylene group having 1 to 5 carbon atoms, and the end of R ^{23 and} the end of R ²¹ may be bonded.
In this case, a cyclic group is formed by R ²¹ , R ²³ , the oxygen atom to which R ²³ is bonded, and the carbon atom to which the oxygen atom and R ²¹ are bonded. The cyclic group is preferably a 4- to 7-membered ring, and more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

In general formula (a1-0-2), R is the same as described above. X ² is the same as X ¹ in formula (a1-0-1).
Y ² is a divalent aliphatic cyclic group.
Since Y ² is a divalent aliphatic cyclic group, it is the same as the description of the “aliphatic cyclic group” in the structural unit (a1) except that a group in which two or more hydrogen atoms are removed is used. Can be used.

  More specifically, examples of the structural unit (a1) include structural units represented by the following general formulas (a1-1) to (a1-4).

［上記式中、Ｘ’は第３級アルキルエステル型酸解離性溶解抑制基を表し、Ｙは炭素数１〜５の低級アルキル基、または脂肪族環式基を表し；ｎは０または１〜３の整数を表し；ｍは０または１を表し；Ｒは前記と同じであり、Ｒ^１’、Ｒ^２’はそれぞれ独立して水素原子または炭素数１〜５の低級アルキル基を表す。］

[In the above formula, X ′ represents a tertiary alkyl ester type acid dissociable, dissolution inhibiting group, Y represents a lower alkyl group having 1 to 5 carbon atoms, or an aliphatic cyclic group; 3 represents an integer of 3; m represents 0 or 1; R is the same as defined above; R ¹ ′ and R ² ′ each independently represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms. ]

At least one of R ¹ ′ and R ² ′ is preferably a hydrogen atom, more preferably a hydrogen atom. n is preferably 0 or 1.

X ′ is the same as the tertiary alkyl ester type acid dissociable, dissolution inhibiting group exemplified in X ¹ above.
Examples of the aliphatic cyclic group for Y include the same groups as those exemplified in the description of the “aliphatic cyclic group” in the structural unit (a1).

  Specific examples of the structural units represented by the general formulas (a1-1) to (a1-4) are shown below.

As the structural unit (a1), one type may be used alone, or two or more types may be used in combination. Among these, the structural unit represented by the general formula (a1-1) is preferable, and specifically, (a1-1-1) to (a1-1-6) or (a1-1-35) to (a1- It is more preferable to use at least one selected from structural units represented by 1-41).
Furthermore, as the structural unit (a1), in particular, those represented by the following general formula (a1-1-01) including the structural units of the formulas (a1-1-1) to (a1-1-4) And the following general formula (a1-1-02) including the structural units of the formulas (a1-1-36), (a1-1-38), (a1-1-39) and (a1-1-41) preferable.

（式中、Ｒは水素原子または低級アルキル基を示し、Ｒ^１１は低級アルキル基を示す。）

(In the formula, R represents a hydrogen atom or a lower alkyl group, and R ¹¹ represents a lower alkyl group.)

（式中、Ｒは水素原子または低級アルキル基を示し、Ｒ^１２は低級アルキル基を示す。ｈは１〜３の整数を表す）

(Wherein R represents a hydrogen atom or a lower alkyl group, R ¹² represents a lower alkyl group, h represents an integer of 1 to 3)

In general formula (a1-1-01), R is the same as defined above. The lower alkyl group for R ^{11 is the same as} the lower alkyl group for R, and is preferably a methyl group or an ethyl group.

In general formula (a1-1-02), R is the same as defined above. The lower alkyl group for R ^{12 is the same as} the lower alkyl group for R, preferably a methyl group or an ethyl group, and most preferably an ethyl group. h is preferably 1 or 2, and most preferably 2.

  In the component (A), the proportion of the structural unit (a1) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, more preferably 25 to 50 mol%, based on all structural units constituting the component (A). Is more preferable. By setting it to the lower limit value or more, a pattern can be obtained when the resist composition is used, and by setting it to the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a2)
In addition to the structural unit (a1), the component (A) preferably has a structural unit (a2) derived from an (α-lower alkyl) acrylate ester having a lactone-containing monocyclic or polycyclic group. . When the lactone-containing monocyclic or polycyclic group of the structural unit (a2) is used for forming the resist film, the (A) component is used to increase the adhesion of the resist film to the substrate or to be hydrophilic with the developer. It is effective in raising
Here, the lactone-containing monocyclic or polycyclic group refers to a cyclic group containing one ring (lactone ring) containing an —O—C (O) — structure. The lactone ring is counted as the first ring, and when it is only the lactone ring, it is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure.

As the structural unit (a2), any structural unit can be used without particular limitation as long as it has both such a lactone structure (—O—C (O) —) and a cyclic group.
Specifically, examples of the lactone-containing monocyclic group include groups in which one hydrogen atom has been removed from γ-butyrolactone. Examples of the lactone-containing polycyclic group include groups in which one hydrogen atom has been removed from a bicycloalkane, tricycloalkane, or tetracycloalkane having a lactone ring. In particular, a group obtained by removing one hydrogen atom from a lactone-containing tricycloalkane having the following structural formula is advantageous in that it is easily available industrially.

  More specifically, examples of the structural unit (a2) include structural units represented by general formulas (a2-1) to (a2-5) shown below.

［式中、Ｒは水素原子または低級アルキル基であり、Ｒ’は水素原子、低級アルキル基、または炭素数１〜５のアルコキシ基であり、ｍは０または１の整数である。］

[Wherein, R is a hydrogen atom or a lower alkyl group, R ′ is a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms, and m is an integer of 0 or 1. ]

In general formulas (a2-1) to (a2-5), the lower alkyl group for R and R ′ is the same as the lower alkyl group for R in the structural unit (a1).
In general formulas (a2-1) to (a2-5), R ′ is preferably a hydrogen atom in view of industrial availability.

  Specific structural units of the general formulas (a2-1) to (a2-5) are exemplified.

In general formulas (a2-1) to (a2-5), R ′ is preferably a hydrogen atom in view of industrial availability.
Among these, it is preferable to use at least one selected from general formulas (a2-1) to (a2-5), and at least one selected from general formulas (a2-1) to (a2-3). It is preferable to use more than one species. Specifically, chemical formulas (a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2), (a2-3-1), (a2-3) -2), at least one selected from (a2-3-9) and (a2-3-10) is preferably used.

In the component (A), as the structural unit (a2), one type may be used alone, or two or more types may be used in combination.
The proportion of the structural unit (a2) in the component (A) is preferably 5 to 60 mol%, more preferably 10 to 50 mol%, based on the total of all structural units constituting the component (A). 50 mol% is more preferable. By setting it to the lower limit value or more, the effect of containing the structural unit (a2) is sufficiently obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a3)
The component (A) is an (α-lower alkyl) acrylic group containing a polar group-containing aliphatic hydrocarbon group in addition to the structural unit (a1) or in addition to the structural units (a1) and (a2). It is preferable to have a structural unit (a3) derived from an acid ester. By having the structural unit (a3), the hydrophilicity of the component (A) is increased, the affinity with the developer is increased, the alkali solubility in the exposed area is improved, and the resolution is improved.
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and a hydroxyalkyl group in which a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom. A hydroxyl group is particularly preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group having 1 to 10 carbon atoms (preferably an alkylene group) and a polycyclic aliphatic hydrocarbon group (polycyclic group). . As the polycyclic group, for example, a resin for a resist composition for ArF excimer laser can be appropriately selected from among many proposed ones.
Among them, an aliphatic polycyclic group containing a hydroxyalkyl group in which a part of hydrogen atoms of a hydroxyl group, a cyano group, a carboxy group, or an alkyl group is substituted with a fluorine atom, and (α-lower alkyl) acrylic A structural unit derived from an acid ester is more preferred. Examples of the polycyclic group include groups in which one or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane or the like. Specific examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Such a polycyclic group can be appropriately selected and used from among many proposed polymers (resin components) for resist compositions for ArF excimer lasers. Among these polycyclic groups, there are groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane. Industrially preferable.

  As the structural unit (a3), when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms, (α-lower alkyl) acrylic acid A structural unit derived from hydroxyethyl ester is preferred, and when the hydrocarbon group is a polycyclic group, a structural unit represented by the following formula (a3-1), a structural unit represented by (a3-2) The structural unit represented by (a3-3) is preferable.

（式中、Ｒは前記に同じであり、ｊは１〜３の整数であり、ｋは１〜３の整数であり、ｔ’は１〜３の整数であり、ｌは１〜５の整数であり、ｓは１〜３の整数である。）

(In the formula, R is the same as above, j is an integer of 1 to 3, k is an integer of 1 to 3, t 'is an integer of 1 to 3, and l is an integer of 1 to 5) And s is an integer of 1 to 3.)

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When j is 2, it is preferable that the hydroxyl group is bonded to the 3rd and 5th positions of the adamantyl group. When j is 1, it is preferable that the hydroxyl group is bonded to the 3-position of the adamantyl group.
j is preferably 1, and a hydroxyl group bonded to the 3-position of the adamantyl group is particularly preferred.

  In formula (a3-2), k is preferably 1. The cyano group is preferably bonded to the 5th or 6th position of the norbornyl group.

  In formula (a3-3), t ′ is preferably 1. l is preferably 1. s is preferably 1. In these, a 2-norbornyl group or a 3-norbornyl group is preferably bonded to the terminal of the carboxy group of (α-lower alkyl) acrylic acid. The fluorinated alkyl alcohol is preferably bonded to the 5th or 6th position of the norbornyl group.

As the structural unit (a3), one type may be used alone, or two or more types may be used in combination.
In the component (A), the proportion of the structural unit (a3) is preferably 5 to 50 mol%, more preferably 15 to 45 mol%, most preferably with respect to all the structural units constituting the component (A). Preferably 15 to 35 mol% is more preferable.

・ Structural unit (a4)
In addition to the structural unit (a1), the component (A), in addition to the structural units (a1) and (a2), or in addition to the structural units (a1), (a2) and (a3) It is preferable to have a structural unit (a4) derived from an (α-lower alkyl) acrylic acid ester containing a non-acid-dissociable aliphatic polycyclic group.
Examples of the aliphatic polycyclic group include those similar to those exemplified in the case of the structural unit (a1), and for ArF excimer laser and KrF excimer laser (preferably ArF excimer laser). A large number of hitherto known materials can be used as the resin component of the resist composition.
In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, an isobornyl group, and a norbornyl group is preferable in terms of industrial availability. These polycyclic groups may be substituted with a linear or branched alkyl group having 1 to 5 carbon atoms.
Specific examples of the structural unit (a4) include those represented by the following general formulas (a4-1) to (a4-5).

（式中、Ｒは前記と同じである。）

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

  The structural unit (a4) is not an essential component of the component (A). However, when the structural unit (a4) is contained in the component (A), the proportion of the structural unit (a4) is the total composition of the component (A). It is preferable that it is 1-30 mol% with respect to a unit, and 10-20 mol% is more preferable.

-Other structural unit (A) The component may contain other structural units other than the said structural unit (a1)-(a4) in the range which does not impair the effect of this invention.
Such a structural unit is not particularly limited as long as it is another structural unit that is not classified into the structural units (a1) to (a4) described above. For ArF excimer laser, for KrF excimer laser (preferably for ArF excimer laser) A number of hitherto known materials can be used for resist resins such as

  In the present invention, the component (A) is a copolymer having the structural unit (a1), the structural unit (a2), the structural unit (a3), and the structural unit (a4). The quaternary copolymer composed of the structural units (a1) to (a4) is particularly preferable because of excellent effects of the present invention. By using such a copolymer as the component (A), the lithography properties are particularly good.

<(B) component>
The component (B) is not particularly limited, and those that have been proposed as acid generators for chemically amplified resists can be used. Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, and the like. There are various known diazomethane acid generators, nitrobenzyl sulfonate acid generators, imino sulfonate acid generators, disulfone acid generators, and the like.

  Examples of the onium salt acid generator include compounds represented by the following general formula (b-1) or (b-2).

［式中、Ｒ^１”〜Ｒ^３”，Ｒ^５”〜Ｒ^６”は、それぞれ独立に、アリール基またはアルキル基を表し；Ｒ^４”は、直鎖、分岐または環状のアルキル基またはフッ素化アルキル基を表し；Ｒ^１”〜Ｒ^３”のうち少なくとも１つはアリール基を表し、Ｒ^５”〜Ｒ^６”のうち少なくとも１つはアリール基を表す。］

[Wherein, R ¹ ″ to R ³ ″ and R ⁵ ″ to R ⁶ ″ each independently represents an aryl group or an alkyl group; R ⁴ ″ represents a linear, branched or cyclic alkyl group or fluorinated group. Represents an alkyl group; at least one of R ¹ ″ to R ³ ″ represents an aryl group, and at least one of R ⁵ ″ to R ⁶ ″ represents an aryl group.]

In formula (b-1), R ¹ ″ to R ³ ″ each independently represents an aryl group or an alkyl group. At least one of R ¹ ″ to R ³ ″ represents an aryl group. Of R ¹ ″ to R ³ ″, two or more are preferably aryl groups, and most preferably all of R ¹ ″ to R ³ ″ are aryl groups.
The aryl group for R ¹ ″ to R ³ ″ is not particularly limited, and is, for example, an aryl group having 6 to 20 carbon atoms, in which part or all of the hydrogen atoms are alkyl groups, alkoxy groups It may or may not be substituted with a group, a halogen atom or the like. The aryl group is preferably an aryl group having 6 to 10 carbon atoms because it can be synthesized at a low cost. Specific examples include a phenyl group and a naphthyl group.
The alkyl group that may be substituted for the hydrogen atom of the aryl group is preferably an alkyl group having 1 to 5 carbon atoms, and is a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group. Is most preferred.
The alkoxy group that may be substituted with a hydrogen atom of the aryl group is preferably an alkoxy group having 1 to 5 carbon atoms, and most preferably a methoxy group or an ethoxy group.
The halogen atom that may be substituted for the hydrogen atom of the aryl group is preferably a fluorine atom.
The alkyl group for R 1 ^{"~R 3",} is not particularly limited, for example, a straight, include alkyl groups such as branched or cyclic. It is preferable that it is C1-C5 from the point which is excellent in resolution. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, and a decanyl group. A methyl group is preferable because it is excellent in resolution and can be synthesized at low cost.
Among these, it is most preferable that all of R ¹ ″ to R ³ ″ are phenyl groups.

R ⁴ ″ represents a linear, branched or cyclic alkyl group or a fluorinated alkyl group.
The linear alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.
The cyclic alkyl group is a cyclic group as indicated by R ¹ ″ and preferably has 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms, and more preferably 6 carbon atoms. Most preferably, it is -10.
The fluorinated alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms. Also. The fluorination rate of the fluorinated alkyl group (ratio of fluorine atoms in the alkyl group) is preferably 10 to 100%, more preferably 50 to 100%, and particularly those in which all hydrogen atoms are substituted with fluorine atoms. Since the strength of the acid is increased, it is preferable.
R ⁴ ″ is most preferably a linear or cyclic alkyl group or a fluorinated alkyl group.

In formula (b-2), R ⁵ ″ to R ⁶ ″ each independently represents an aryl group or an alkyl group. At least one of R ⁵ ″ to R ⁶ ″ represents an aryl group. Of R ⁵ ″ to R ⁶ ″, two or more are preferably aryl groups, and all of R ⁵ ″ to R ⁶ ″ are most preferably aryl groups.
As the aryl group for R ⁵ ″ to R ⁶ ″, the same as the aryl groups for R ¹ ″ to R ³ ″ can be used.
Examples of the alkyl group for R ⁵ ″ to R ⁶ ″ include the same as the alkyl group for R ¹ ″ to R ³ ″.
Among these, it is most preferable that all of R ⁵ ″ to R ⁶ ″ are phenyl groups.
"As ^{R 4} in the formula (b-1)" ^{R 4} in the In the formula (b-2) include the same as.

  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 E) phenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate, diphenyl (1- (4-methoxy) naphthyl) sulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate Is mentioned. In addition, onium salts in which the anion portion of these onium salts is replaced with methanesulfonate, n-propanesulfonate, n-butanesulfonate, or n-octanesulfonate can also be used.

  Moreover, what replaced the anion part with the anion part represented by the following general formula (b-3) or (b-4) in the said general formula (b-1) or (b-2) can also be used. (The cation moiety is the same as (b-1) or (b-2)).

［式中、Ｘ”は、少なくとも１つの水素原子がフッ素原子で置換された炭素数２〜６のアルキレン基を表し；Ｙ”、Ｚ”は、それぞれ独立に、少なくとも１つの水素原子がフッ素原子で置換された炭素数１〜１０のアルキル基を表す。］

[Wherein X ″ represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom; Y ″ and Z ″ each independently represent at least one hydrogen atom as a fluorine atom; Represents an alkyl group having 1 to 10 carbon atoms and substituted with

X ″ is a linear or branched alkylene group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms, Preferably it is C3.
Y ″ and Z ″ are each independently a linear or branched alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably It is C1-C7, More preferably, it is C1-C3.
The carbon number of the alkylene group of X ″ or the carbon number of the alkyl group of Y ″ and Z ″ is preferably as small as possible because the solubility in the resist solvent is good within the above carbon number range.
In addition, in the alkylene group of X ″ or the alkyl group of Y ″ and Z ″, as the number of hydrogen atoms substituted with fluorine atoms increases, the strength of the acid increases, and high-energy light or electron beam of 200 nm or less The ratio of fluorine atoms in the alkylene group or alkyl group, that is, the fluorination rate is preferably 70 to 100%, more preferably 90 to 100%, and most preferably all. Are a perfluoroalkylene group or a perfluoroalkyl group in which a hydrogen atom is substituted with a fluorine atom.

  In the present invention, the oxime sulfonate acid generator is a compound having at least one group represented by the following general formula (B-1), and has a property of generating an acid upon irradiation with radiation. . Such oxime sulfonate-based acid generators are frequently used for chemically amplified resist compositions, and can be arbitrarily selected and used.

（式（Ｂ−１）中、Ｒ^２１、Ｒ^２２はそれぞれ独立に有機基を表す。）

(In formula (B-1), R ²¹ and R ²² each independently represents an organic group.)

In the present invention, the organic group is a group containing a carbon atom, and has an atom other than a carbon atom (for example, a hydrogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom (fluorine atom, chlorine atom, etc.)). It may be.
The organic group for R ²¹ is preferably a linear, branched or cyclic alkyl group or aryl group. These alkyl groups and aryl groups may have a substituent. There is no restriction | limiting in particular as this substituent, For example, a fluorine atom, a C1-C6 linear, branched or cyclic alkyl group etc. are mentioned. Here, “having a substituent” means that part or all of the hydrogen atoms of the alkyl group or aryl group are substituted with a substituent.
As an alkyl group, C1-C20 is preferable, C1-C10 is more preferable, C1-C8 is more preferable, C1-C6 is especially preferable, and C1-C4 is the most preferable. As the alkyl group, a partially or completely halogenated alkyl group (hereinafter sometimes referred to as a halogenated alkyl group) is particularly preferable. The partially halogenated alkyl group means an alkyl group in which a part of hydrogen atoms is substituted with a halogen atom, and the fully halogenated alkyl group means that all of the hydrogen atoms are halogen atoms. Means an alkyl group substituted with Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable. That is, the halogenated alkyl group is preferably a fluorinated alkyl group.
The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the aryl group, a partially or completely halogenated aryl group is particularly preferable. The partially halogenated aryl group means an aryl group in which a part of hydrogen atoms is substituted with a halogen atom, and the fully halogenated aryl group means that all of the hydrogen atoms are halogen atoms. Means an aryl group substituted with.
R ²¹ is particularly preferably an alkyl group having 1 to 4 carbon atoms having no substituent or a fluorinated alkyl group having 1 to 4 carbon atoms.

As the organic group for R ²² , a linear, branched, or cyclic alkyl group, aryl group, or cyano group is preferable. As the alkyl group and aryl group for R ^22, the same alkyl groups and aryl groups as those described above for R ²¹ can be used.
R ²² is particularly preferably a cyano group, an alkyl group having 1 to 8 carbon atoms having no substituent, or a fluorinated alkyl group having 1 to 8 carbon atoms.

  More preferable examples of the oxime sulfonate-based acid generator include compounds represented by the following general formula (B-2) or (B-3).

［式（Ｂ−２）中、Ｒ^３１は、シアノ基、置換基を有さないアルキル基またはハロゲン化アルキル基である。Ｒ^３２はアリール基である。Ｒ^３３は置換基を有さないアルキル基またはハロゲン化アルキル基である。］

[In Formula (B-2), R ³¹ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³² is an aryl group. R ³³ is an alkyl group having no substituent or a halogenated alkyl group. ]

［式（Ｂ−３）中、Ｒ^３４はシアノ基、置換基を有さないアルキル基またはハロゲン化アルキル基である。Ｒ^３５は２または３価の芳香族炭化水素基である。Ｒ^３６は置換基を有さないアルキル基またはハロゲン化アルキル基である。ｐは２または３である。］

[In the formula (B-3), R ³⁴ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³⁵ is a divalent or trivalent aromatic hydrocarbon group. R ³⁶ is an alkyl group having no substituent or a halogenated alkyl group. p is 2 or 3. ]

In the general formula (B-2), the alkyl group or halogenated alkyl group having no substituent for R ³¹ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and more preferably carbon atoms. Numbers 1 to 6 are most preferable.
R ³¹ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group.
The fluorinated alkyl group for R ³¹ is preferably fluorinated by 50% or more of the hydrogen atom of the alkyl group, more preferably 70% or more, and even more preferably 90% or more.

As an aryl group of R ³² , one hydrogen atom is removed from an aromatic hydrocarbon ring such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, an anthracyl group, or a phenanthryl group. And a heteroaryl group in which a part of carbon atoms constituting the ring of these groups is substituted with a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom. Among these, a fluorenyl group is preferable.
The aryl group represented by R ³² may have a substituent such as an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. The alkyl group or halogenated alkyl group in the substituent preferably has 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. The halogenated alkyl group is preferably a fluorinated alkyl group.

The alkyl group or halogenated alkyl group having no substituent for R ³³ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms.
R ³³ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group, and most preferably a partially fluorinated alkyl group.
The fluorinated alkyl group in R ³³ preferably has 50% or more of the hydrogen atom of the alkyl group, more preferably 70% or more, and even more preferably 90% or more. This is preferable because the strength of the acid is increased. Most preferably, it is a fully fluorinated alkyl group in which a hydrogen atom is 100% fluorine-substituted.

In the general formula (B-3), the alkyl group or halogenated alkyl group having no substituent for R ³⁴ is the same as the alkyl group or halogenated alkyl group having no substituent for R ^31. Is mentioned.
Examples of the divalent or trivalent aromatic hydrocarbon group for R ³⁵ include groups obtained by further removing one or two hydrogen atoms from the aryl group for R ³² .
Examples of the alkyl group or halogenated alkyl group having no substituent for R ³⁶ include the same alkyl groups or halogenated alkyl groups as those having no substituent for R ³³ .
p is preferably 2.

Specific examples of oxime sulfonate acid generators include α- (p-toluenesulfonyloxyimino) -benzyl cyanide, α- (p-chlorobenzenesulfonyloxyimino) -benzyl cyanide, α- (4-nitrobenzenesulfonyloxy). Imino) -benzylcyanide, α- (4-nitro-2-trifluoromethylbenzenesulfonyloxyimino) -benzylcyanide, α- (benzenesulfonyloxyimino) -4-chlorobenzylcyanide, α- (benzenesulfonyl) Oxyimino) -2,4-dichlorobenzylcyanide, α- (benzenesulfonyloxyimino) -2,6-dichlorobenzylcyanide, α- (benzenesulfonyloxyimino) -4-methoxybenzylcyanide, α- ( 2-Chlorobenzenesulfonyloxyimino) 4-methoxybenzylcyanide, α- (benzenesulfonyloxyimino) -thien-2-ylacetonitrile, α- (4-dodecylbenzenesulfonyloxyimino) -benzylcyanide, α-[(p-toluenesulfonyloxyimino) -4-methoxyphenyl] acetonitrile, α-[(dodecylbenzenesulfonyloxyimino) -4-methoxyphenyl] acetonitrile, α- (tosyloxyimino) -4-thienyl cyanide, α- (methylsulfonyloxyimino) -1-cyclo Pentenylacetonitrile, α- (methylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (methylsulfonyloxyimino) -1-cycloheptenylacetonitrile, α- (methylsulfonyloxyimino) -1-cyclooctene Acetonitrile, α- (trifluoromethylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -cyclohexylacetonitrile, α- (ethylsulfonyloxyimino) -ethylacetonitrile, α- (propyl Sulfonyloxyimino) -propylacetonitrile, α- (cyclohexylsulfonyloxyimino) -cyclopentylacetonitrile, α- (cyclohexylsulfonyloxyimino) -cyclohexylacetonitrile, α- (cyclohexylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- ( Ethylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (isopropylsulfonyloxyimino) -1-cyclope Nthenyl acetonitrile, α- (n-butylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (ethylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (isopropylsulfonyloxyimino) -1-cyclohexenylacetonitrile , Α- (n-butylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoro Methylsulfonyloxyimino) -phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p- Butoxy phenylacetonitrile, alpha-(propylsulfonyl oxyimino)-p-methylphenyl acetonitrile, alpha-like (methylsulfonyloxyimino)-p-bromophenyl acetonitrile.
Moreover, the compound represented by the following chemical formula is mentioned.

  Moreover, the example of a preferable compound is shown below among the compounds represented by the said general formula (B-2) or (B-3).

  Among the above exemplified compounds, the following three compounds are preferable.

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 (when A = 3) and 1,4-bis (phenylsulfonyldiazo) having the following structure. Methylsulfonyl) butane (when A = 4), 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane (when A = 6), 1,10-bis (phenylsulfonyldiazomethylsulfonyl) decane (A = 10) 1), 1,2-bis (cyclohexylsulfonyldiazomethylsulfonyl) ethane (when B = 2), 1,3-bis (cyclohexylsulfonyldiazomethylsulfonyl) propane (when B = 3), 1,6- Bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane (when B = 6) (For B = 10) 1,10-bis (cyclohexyl diazomethylsulfonyl) decane and the like.

(B) As a component, these acid generators may be used individually by 1 type, and may be used in combination of 2 or more type. In the present invention, an onium salt having a fluorinated alkyl sulfonate ion as an anion is particularly preferable.
Content of (B) component in the positive resist composition of this invention is 0.5-30 mass parts with respect to 100 mass parts of (A) component, Preferably it is 1-10 mass parts. By setting it within the above range, pattern formation is sufficiently performed. Moreover, since a uniform solution is obtained and storage stability becomes favorable, it is preferable.

<Optional 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 been proposed, any known one may be used, but aliphatic amines, particularly secondary aliphatic amines and tertiary aliphatic amines are preferred. .
Examples of the aliphatic amine include amines (alkyl amines or alkyl alcohol amines) in which at least one hydrogen atom of ammonia NH ₃ is substituted with an alkyl group or hydroxyalkyl group having 12 or less carbon atoms. Specific examples thereof include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine; diethylamine, di-n-propylamine, di-n-heptylamine, Dialkylamines such as di-n-octylamine and dicyclohexylamine; trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine, tri-n-heptyl Trialkylamines such as amine, tri-n-octylamine, tri-n-nonylamine, tri-n-decanylamine, tri-n-dodecylamine; diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, di-n -Ok Noruamin, alkyl alcohol amines such as tri -n- octanol amine. Among these, alkyl alcohol amines and trialkyl amines are preferable, and alkyl alcohol amines are most preferable. Of the alkyl alcohol amines, triethanolamine and triisopropanolamine are most 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.

In addition, the positive resist composition of the present invention includes an organic carboxylic acid as an optional component for the purpose of preventing sensitivity deterioration due to the blending of the component (D), and improving the resist pattern shape, retention stability, and the like. Acid or phosphorus oxo acid or its derivative (E) (hereinafter referred to as component (E)) can be contained. In addition, (D) component and (E) component can also be used together, and any 1 type can also be used.
As the organic carboxylic acid, for example, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Phosphorus oxoacids or derivatives thereof include phosphoric acid, phosphoric acid di-n-butyl ester, phosphoric acid diphenyl ester and other phosphoric acid or derivatives thereof such as phosphonic acid, phosphonic acid dimethyl ester, phosphonic acid- Like phosphonic acids such as di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, phosphonic acid dibenzyl ester and derivatives thereof, phosphinic acids such as phosphinic acid, phenylphosphinic acid and their esters Among these, phosphonic acid is particularly preferable.
(E) A component is used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

  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, Plasticizers, stabilizers, colorants, antihalation agents, dyes, and the like can be added and contained as appropriate.

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, lactones such as γ-butyrolactone, ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate Polyhydric alcohols such as dipropylene glycol or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and derivatives thereof, cyclic ethers such as dioxane, Methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, pyruvate Le, methyl methoxypropionate, 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 blending ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. 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 1: 9 to 9: 1, more preferably 2: 8 to 8: 2.
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.

<Resist pattern formation method>
The resist pattern forming method of the present invention can be performed, for example, as follows.
That is, first, the positive resist composition is applied onto a substrate such as a silicon wafer with a spinner and prebaked for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C. After selectively exposing ArF excimer laser light through a desired mask pattern using, for example, an ArF exposure apparatus or the like, PEB (post-exposure heating) is performed for 40 to 120 seconds at a temperature of 80 to 150 ° C., preferably Apply for 60-90 seconds. Subsequently, 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 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 photoresist composition according to the present invention is effective for an ArF excimer laser.

As described above, according to the positive resist composition and the resist pattern forming method of the present invention, there are few defects and lithography characteristics such as sensitivity, line edge roughness (LER), exposure margin, and depth of focus (DOF). In addition, an excellent resist pattern can be formed.
Further, the positive resist composition of the present invention has a good proximity effect. The proximity effect is a phenomenon in which the size and shape of a resist pattern to be formed are affected by the pattern in the vicinity thereof. When the proximity effect is increased, when the pattern dimensions in the mask are the same, there is a difference in the size of the pattern formed between the dense part (line and space part) and the other part (isolated pattern part). The proximity effect is preferably as small as possible because it increases.
Furthermore, the positive resist composition of the present invention is excellent in quality stability, for example, the number of defects hardly increases even after being stored at a high temperature of 40 ° C., for example.

Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples.
In the following synthesis examples 1 to 4, the molecular weight distribution is measured by GPC under the following conditions to determine the peak area A _L and the total peak area A _A of a low molecular region having a molecular weight of 100 to 10,000, and _A to A A The ratio (%) of _L was calculated.
[GPC measurement conditions]
・ Device: “HLC-8220 GPC” manufactured by TOSOH
Guard column: “TSK Super HH” manufactured by TOSOH
-Column: "TSK Gel Super HM-N" x 3 manufactured by TOSOH-Detector: Differential refractive index (RI) detector-Eluent: Tetrahydrofuran (THF) (dibutylhydroxytoluene (BHT) concentration: 0 ppm)
・ Flow rate: 0.6 mL / min ・ Injection volume: 40 μL
・ Measurement temperature: 40 ℃
Measurement time: 20 minutes Sample: THF solution in which resin is dissolved so that the solid content concentration is about 0.2% by mass

Synthesis Example 1 (Drip polymerization method)
MEK 8000 g was charged into a container kept in a nitrogen atmosphere, and 2590 g of 2-methyl-2-adamantyl methacrylate, 1880 g of α-methacryloyloxy-γ-butyrolactone, 1120 g of 3-hydroxy-1-adamantyl methacrylate, and 1040 g of tricyclodecanyl methacrylate. A monomer solution was prepared by dissolution. Further, 180 g of polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 1000 g of MEK in another container kept in a nitrogen atmosphere to prepare an initiator solution. In a reaction vessel maintained in a nitrogen atmosphere, 5000 g of MEK was added and the temperature was raised to 80 ° C. while stirring. It was fed into the kept reaction vessel. After the completion of the supply, the polymerization temperature was kept at 80 ° C. for 2 hours, and the mixture was cooled to room temperature and the polymerization solution was taken out.
The obtained polymerization solution is poured into a well-stirred water-methanol mixed solution (water: 16% by mass), and the precipitated solid is separated by filtration and dried to give a resin represented by the following formula (I) (A) -1 was obtained.
As a result of GPC measurement, in the molecular weight distribution of Resin (A) -1, the ratio of the peak area in the low molecular weight region having a molecular weight of 100 to 10,000 was 73%. Resin (A) -1 has Mw = 10000 and Mw / Mn = 2.2. As a result of measurement of carbon 13 ( ¹³ C) nuclear magnetic resonance spectrum, the composition of each structural unit in formula (I) The ratio was p / q / r / s = 35/35/15/15 (molar ratio).

Synthesis Example 2 (Drip polymerization method)
MEK 8000 g was charged into a container kept in a nitrogen atmosphere, and 2590 g of 2-methyl-2-adamantyl methacrylate, 1880 g of α-methacryloyloxy-γ-butyrolactone, 1120 g of 3-hydroxy-1-adamantyl methacrylate, and 1040 g of tricyclodecanyl methacrylate. A monomer solution was prepared by dissolution. Further, 120 g of polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 1000 g of MEK in another container kept in a nitrogen atmosphere to prepare an initiator solution. In a reaction vessel maintained in a nitrogen atmosphere, 5000 g of MEK was added and the temperature was raised to 80 ° C. while stirring. It was fed into the kept reaction vessel. After the completion of the supply, the polymerization temperature was kept at 80 ° C. for 2 hours, and the mixture was cooled to room temperature and the polymerization solution was taken out.
The obtained polymerization solution is poured into a well-stirred water-methanol mixed solution (water: 16% by mass), and the precipitated solid is separated by filtration and dried to obtain a resin represented by the formula (I). (A) -2 was obtained.
As a result of GPC measurement, in the molecular weight distribution of Resin (A) -2, the ratio of the peak area in the low molecular weight region having a molecular weight of 100 to 10,000 was 50%. Resin (A) -2 has Mw = 15000 and Mw / Mn = 2.1. As a result of measurement of carbon 13 ( ¹³ C) nuclear magnetic resonance spectrum, each of the structural units in the formula (I) The composition ratio was p / q / r / s = 35/35/15/15 (molar ratio).

Synthesis Example 3 (Drip polymerization method)
MEK 8000 g was charged into a container kept in a nitrogen atmosphere, and 2590 g of 2-methyl-2-adamantyl methacrylate, 1880 g of α-methacryloyloxy-γ-butyrolactone, 1120 g of 3-hydroxy-1-adamantyl methacrylate, and 1040 g of tricyclodecanyl methacrylate. A monomer solution was prepared by dissolution. Moreover, 260 g of polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 1000 g of MEK in another container kept in a nitrogen atmosphere to prepare an initiator solution. In a reaction vessel maintained in a nitrogen atmosphere, 5000 g of MEK was added and the temperature was raised to 80 ° C. while stirring. It was fed into the kept reaction vessel. After the completion of the supply, the polymerization temperature was kept at 80 ° C. for 2 hours, and the mixture was cooled to room temperature and the polymerization solution was taken out.
The obtained polymerization solution is poured into a well-stirred water-methanol mixed solution (water: 16% by mass), and the precipitated solid is separated by filtration and dried to obtain a resin represented by the formula (I). (A) -3 was obtained.
As a result of GPC measurement, in the molecular weight distribution of Resin (A) -3, the ratio of the peak area in the low molecular weight region having a molecular weight of 100 to 10,000 was 83%. Resin (A) -3 has Mw = 7700 and Mw / Mn = 1.87. As a result of measurement of carbon 13 ( ¹³ C) nuclear magnetic resonance spectrum, each structural unit in the formula (I) The composition ratio was p / q / r / s = 35/35/15/15 (molar ratio).

Synthesis example 4 (temperature raising type batch polymerization method)
In Example 1, a mixed solution in which the monomer solution and the initiator solution were mixed in one container was supplied to the reaction container, and the reaction was performed using the same method except that the polymerization reaction was performed while heating to 80 ° C. went.
The obtained reaction liquid was poured into well-stirred methanol, and the precipitated solid was separated by filtration and dried to obtain a resin (A ′)-1 represented by the above formula (I).
As a result of GPC measurement, in the molecular weight distribution of the resin (A ′)-1, the ratio of the peak area in the low molecular weight region having a molecular weight of 100 to 10,000 was 71%. Resin (A ′)-1 has Mw = 10000 and Mw / Mn = 2.7. As a result of measurement of carbon 13 ( ¹³ C) nuclear magnetic resonance spectrum, each structural unit in formula (I) The composition ratio was p / q / r / s = 35/35/15/15 (molar ratio).

Examples 1-3, Comparative Examples 1-3
Using the compounds (A) -1 to (A) -3 and (A ′)-1 obtained in Synthesis Examples 1 to 4, the components shown in Table 1 below were mixed and dissolved to prepare a positive resist composition solution. Obtained.

In Table 1, the numerical values in [] indicate the blending amount (parts by mass). Moreover, the symbol in Table 1 has the following meaning.
(B) -1: triphenylsulfonium nonafluoro-n-butanesulfonate (B) -2: compound represented by the following formula (B) -2 (B) -3: represented by the following formula (B) -3 Compound (D) -1: Triethanolamine (S) -1: PGMEA
(S) -2: PGMEA / ethyl lactate = 8/2 (mass ratio) mixed solvent

Subsequently, the following evaluation was performed using the obtained positive resist composition solution.
<Lithography characteristics>
Evaluation of resolution Organic antireflection film composition “AR19” (trade name, manufactured by Rohm and Haas) was applied onto an 8-inch silicon wafer using a spinner, and baked on a hot plate at 215 ° C. for 90 seconds. Then, an organic antireflection film having a film thickness of 82 nm was formed by drying. By applying a positive resist composition solution having the composition shown in Table 1 on the antireflection film using a spinner, prebaking (PAB) at 120 ° C. for 90 seconds on a hot plate, and drying, A resist film having a thickness of 350 nm was formed.
Next, an ArF excimer laser (193 nm) was applied to the resist film with an ArF exposure apparatus S-302 (Nikon Corp .; NA (numerical aperture) = 0.60, σ = 2/3 annular illumination), and a mask pattern. Selectively irradiated via (6% halftone).
Next, PEB treatment was performed at 120 ° C. for 90 seconds, followed by development with a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. for 60 seconds, followed by water rinsing with pure water for 30 seconds and shaking off. Drying was performed. Furthermore, it was dried by heating (post-baking) at 100 ° C. for 60 seconds. As a result, a 130 nm line and space pattern (130LS) of line width: space width = 1: 1 was formed regardless of which positive resist composition solution was used.

LER Evaluation For 130LS obtained with the optimum exposure amount Eop (mJ / cm ² ) at which the 130LS is formed, 3σ, which is a measure indicating LER, was obtained. 3σ is a side length SEM (manufactured by Hitachi, Ltd., product name “S-9220”). The width of the resist pattern of the sample was measured at 32 locations, and the standard deviation (σ) calculated from the result was 3 times the value (3σ ). This 3σ means that the smaller the value, the smaller the roughness and the uniform width resist pattern was obtained. The measurement voltage is 300V.

-Exposure amount margin evaluation The obtained resist pattern (130LS) is observed with a side length SEM (manufactured by Hitachi, Ltd., product name "S-9220"), and each pattern is formed with a size within the range of the target size ± 10%. The exposure amount that can be obtained is within what percentage of the Eop determined above (exposure amount margin). The larger the exposure amount margin, the smaller the change amount of the pattern size with the variation of the exposure amount.

-Depth of focus width (DOF) evaluation In the above Eop, the focus is appropriately shifted up and down, and the depth of focus (DOF) at which the resist pattern (130LS) can be formed within the range of the dimensional change rate of the target size ± 10% ( nm). DOF is a range in which a good resolution can be obtained even if the exposure focus is deviated, and it is preferably as large as possible. The results are shown in Table 2.

<Defect evaluation>
About the resist pattern formed above, the number of defects (pieces / cm ² ) in the wafer was measured using a surface defect observation apparatus KLA2351 (product name) manufactured by KLA Tencor. The results are shown in Table 2.

As shown in the above results, among the lithography properties, for DOF, Examples 1 to 3 were as good as or better than Comparative Examples 1 to 3. The resolution, exposure amount margin, and LER were the same.
Regarding defects, Examples 1 to 3 had a small number of defects. From this, it can be seen that Examples 1 to 3 are excellent in quality stability. On the other hand, in Comparative Examples 1-2, the number of defects exceeded twice that of Examples 1-3. In Comparative Example 3, the number of defects was too large to be measured.

Claims (5)

A positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid, and an acid generator component (B) which generates an acid upon irradiation with radiation,
The resin component (A) has a structural unit (a1) derived from an (α-lower alkyl) acrylic acid ester having an acid dissociable, dissolution inhibiting group, and a lactone-containing monocyclic or polycyclic group (α- A structural unit (a2) derived from a lower alkyl) acrylate ester, a structural unit (a3) derived from an (α-lower alkyl) acrylate ester containing a polar group-containing aliphatic hydrocarbon group, containing dissociable aliphatic polycyclic group (alpha-lower alkyl) is a copolymer having the structural unit (a4) in the main chain derived from an acrylate ester, after that by the dropping polymerization method polymerizing the obtained polymerization reaction solution, methanol: water = 100: 8-20 is prepared by purifying dropwise to a mixed solvent (mass ratio), weight average molecular weight of 5,000 to 20,000, and Gerupa In the molecular weight distribution measured by instantiation chromatography, the ratio of the peak area of the low molecular weight region of molecular weight 100 to 10000 A positive resist composition, characterized in that 55 to 80% relative to the total peak area.   The positive resist composition according to claim 1, wherein the structural unit (a4) is selected from structural units represented by the following general formulas (a4-1) to (a4-5).

(In the formula, R represents a hydrogen atom or a lower alkyl group.) Furthermore, the positive resist composition according to claim 1 or 2 comprising a nitrogen-containing organic compound (D). Forming a resist film on a substrate using a positive resist composition according to any one of claim 1 to 3 conducting exposure of the resist film, and a resist pattern by developing the resist film A resist pattern forming method including a forming step.   A method for producing a positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid, and an acid generator component (B) which generates an acid upon irradiation with radiation,
  (Α-lower alkyl) acrylate ester having an acid dissociable, dissolution inhibiting group, (α-lower alkyl) acrylate ester having a lactone-containing monocyclic or polycyclic group, and a polar group-containing aliphatic hydrocarbon group (Α-Lower alkyl) acrylic acid ester and (α-lower alkyl) acrylic acid ester containing an acid non-dissociable aliphatic polycyclic group were polymerized by a dropping polymerization method, and the resulting polymerization reaction solution was treated with methanol. : Water = 100: In a molecular weight distribution measured by gel permeation chromatography, the molecular weight is 100 when the weight average molecular weight is 5000 to 20000 by purification by dropping into a mixed solvent of 100: 8 to 20 (mass ratio). Produces a copolymer in which the ratio of the peak area of the low molecular weight region of 10000 is 55 to 80% with respect to the entire peak area The method of manufacturing a positive resist composition which comprises using the copolymer as the resin component (A).