JP2010159393A - Polymer, resist composition, and method for forming patterned substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer capable of forming a high-sensitivity resist film and excellent in solvent solubility when it is formed into a resist composition. <P>SOLUTION: The polymer (P) is obtained by radical polymerization and satisfying the following formula (1) P[α<SB>A</SB>]/P[α<SB>B</SB>]≤0.7 when subjected to gel permeation chromatography (GPC). In formula (1), P[α<SB>A</SB>] is the ratio of the peak area from the peak start molecular weight to the peak top molecular weight to the total polymer peak area when the polymer (P) is subjected to gel permeation chromatography, and P[α<SB>B</SB>] is the ratio of the peak area from the peak top molecular weight to the peak end molecular weight to the total polymer peak area when polymer (P) is subjected to gel permeation chromatography. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polymer, a resist composition, and a method for producing a substrate on which a pattern is formed.

  In recent years, a resist pattern formed in a manufacturing process of a semiconductor element, a liquid crystal element, or the like has been rapidly miniaturized due to progress in lithography technology. As a technique for miniaturization, there is a reduction in wavelength of irradiation light. Specifically, the irradiation light has become shorter in wavelength from ultraviolet rays typified by conventional g-line (wavelength: 438 nm) and i-line (wavelength: 365 nm) to shorter wavelength DUV (Deep Ultra Violet). .

  Recently, KrF excimer laser (wavelength: 248 nm) lithography technology has been introduced, and ArF excimer laser (wavelength: 193 nm) lithography technology and EUV excimer laser (wavelength: 13 nm) lithography technology for further shortening the wavelength have been studied. . Furthermore, these immersion lithography techniques are also being studied. Also, as a different type of lithography technology, electron beam lithography technology has been energetically studied.

A “chemically amplified resist composition” containing a photoacid generator has been proposed as a high-resolution resist composition used for forming a resist pattern using the irradiation light or electron beam of the short wavelength. Improvement and development of the amplified resist composition are underway.
For example, as a chemically amplified resist polymer used in ArF excimer laser lithography, an acrylic polymer that is transparent with respect to light having a wavelength of 193 nm has attracted attention. As the acrylic polymer, for example, a polymer of (meth) acrylic acid ester having an adamantane skeleton in an ester portion and (meth) acrylic acid ester having a lactone skeleton in an ester portion has been proposed (Patent Document 1). 2).

  However, these polymers often have insufficient solubility in a solvent when preparing a composition used in a lithography process for manufacturing a semiconductor device such as a resist composition, and it takes a long time to dissolve or is insoluble. In some cases, the production of the composition may be hindered, for example, the number of manufacturing steps may increase due to the generation of minutes. In addition, during storage of the composition, the polymer contained in the composition aggregates over time, generating an insoluble matter called microgel, and in the case of a resist composition, the resist pattern is missing. As a result, the circuit may be disconnected or defective.

In addition, it has been proposed to improve the solubility in various solvents such as resist solvents and alkaline developers by suppressing the formation of trace amounts of high molecular weight components (high polymers) contained in the polymer (Patent Literature). 3). However, development of a polymer that sufficiently satisfies the required performance such as solubility in a resist solvent has not been achieved yet.
JP 10-319595 A JP-A-10-274852 JP 2004-269855 A

  The present invention has been made in view of the above circumstances. When used as a polymer for DUV excimer laser lithography and electron beam lithography, a highly sensitive resist film can be formed, and a resist composition or the like can be prepared. It aims at providing the polymer excellent in the solubility to a solvent, the resist composition containing this polymer, and the pattern formation method using this resist composition.

The first gist of the present invention is a polymer (P) obtained by radical polymerization, which satisfies the following formula (1) when the polymer is measured by gel permeation chromatography (GPC). Resist polymer.
P [α _A ] / P [α _B ] ≦ 0.7 (1)
(In Formula (1), P [α _A ] represents a peak area ratio from the peak start molecular weight to the peak top molecular weight with respect to the total area of the polymer peak when the polymer (P) is measured by GPC, and P [α _B ] Represents the ratio of the peak area from the peak top molecular weight to the peak end molecular weight with respect to the total area of the polymer peak when the polymer (P) is measured by GPC.)

  Furthermore, the second gist of the present invention resides in a resist composition containing the polymer (P).

  Furthermore, the third aspect of the present invention includes a step of applying the resist composition onto a substrate to be processed to form a resist film, and irradiating the resist film with light having a wavelength of 250 nm or less to form a latent image. There is a method for manufacturing a substrate on which a pattern is formed, which includes a step of forming and a step of developing a resist film on which the latent image is formed with a developer.

  According to the said polymer (P), the solubility etc. to a resist solvent etc. can be improved notably by making the ratio of the high molecular weight component and low molecular weight component in a polymer into a predetermined range.

  According to the resist composition, since the insoluble component can be reduced by using the polymer having excellent solubility in the resist solvent as described above, a resist film having excellent sensitivity is formed. be able to.

  According to the manufacturing method, a highly accurate fine pattern with few defects can be formed on the substrate, so that productivity can be improved.

  In the present specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, and “(meth) acryloyloxy” means acryloyloxy or methacryloyloxy.

In this specification, the peak start molecular weight is the rising point of the detection peak of the polymer after the sample is injected in the gel permeation chromatography (GPC) measurement, that is, the detection peak on the high molecular weight side. And the base line.
In this specification, the peak top molecular weight means the position of a polymer peak having the highest signal intensity detected in gel permeation chromatography (GPC) measurement.
In the present specification, the peak end molecular weight is the point at which the detection peak of the polymer ends during gel permeation chromatography (GPC), that is, the contact point between the detection peak on the low molecular weight side and the baseline. means.

In this specification, the baseline refers to the time when the rate of change of the signal intensity with respect to the measurement time changes after the sample is injected during the gel permeation chromatography (GPC) measurement (the polymer is detected). It can be set by connecting the signal intensity (immediately before) and the signal intensity when the rate of change of the signal intensity with respect to the measurement time does not change after the peak top position appears (immediately after the detection of the polymer). it can.
In the present specification, P [α _A ] means a peak curve from the peak start molecular weight to the peak top molecular weight, a perpendicular line from the peak top molecular weight to the baseline, and the two lines with respect to the total area of the polymer peak. It means the peak area ratio in the range surrounded by the baseline.
In the present specification, P [α _B ] means the peak curve from the peak top molecular weight to the peak end molecular weight, the perpendicular from the peak top molecular weight to the baseline, and the two lines with respect to the total area of the polymer peak. It means the peak area ratio in the range surrounded by the baseline.
In this specification, the polymer peak is a main peak detected when gel permeation chromatography (GPC) measurement is performed on the polymer (P), and is a residual monomer contained in the polymer. It means that peaks such as are not included.

(Polymer)
The polymer (P) of the present invention is a polymer satisfying the following formula (1).
P [α _A ] / P [α _B ] ≦ 0.7 (1)
The fact that P [α _A ] / P [α _B ] is 0.7 or less means that, in the polymer (P), the polymer peak measured by GPC has a high molecular weight component and a low molecular weight component at the peak top molecular weight. when divided into a peak area of the high molecular weight component side from the peak top (P [α _a]) it is meant that smaller than the peak area of the low molecular weight components side (P [α _B]) from the peak top.

In the polymer satisfying the above formula (1), the ratio of the high molecular weight component to the ratio of the low molecular weight component is not more than a predetermined value, that is, the generation of the high molecular weight component is suppressed, and the formation of the microgel is suppressed Therefore, when used in a resist composition, a resist film having excellent solubility in a resist solvent and excellent sensitivity can be formed.
In addition, since the polymer satisfying the above formula (1) suppresses the generation of a high molecular weight component as described above and can suppress the formation of a microgel and the like, When used, it is possible to form an antireflection film excellent in solubility in a thin film forming solvent and excellent in antireflection effect.
In the polymer (P), P [α _A ] / P [α _B ] is 0.7 or less. Further, P [α _A ] / P [α _B ] is preferably 0.69 or less, and more preferably 0.68 or less, because of excellent solubility in a solvent and short time for complete dissolution in a solvent.

In addition, since the polymer can be produced industrially with good reproducibility, in the polymer (P), P [α _A ] / P [α _B ] is preferably 0.4 or more, more preferably 0.5 or more, 0.6 or more is more preferable.

(Structural unit having acid labile group)
The polymer (P) of the present invention preferably has an acid labile group when used for resist. The “acid labile group” is a group having a bond that is cleaved by an acid, and a part or all of the acid labile group is removed from the main chain of the polymer by cleavage of the bond.
When used as a resist composition, a polymer having a structural unit having an acid labile group is soluble in an alkali by an acid, and has an effect of enabling resist pattern formation.

Examples of the structural unit having an acid labile group include a structural unit derived from a monomer having an acid labile group.
As the monomer having an acid labile group, for example, a (meth) acryl having an alicyclic hydrocarbon group having 6 to 20 carbon atoms and a group capable of being removed by the action of an acid. Acid ester etc. are mentioned. The alicyclic hydrocarbon group may be directly bonded to an oxygen atom constituting an ester bond of (meth) acrylic acid ester, or may be bonded via a linking group such as an alkylene group.

  The (meth) acrylic acid ester has an alicyclic hydrocarbon group having 6 to 20 carbon atoms and a tertiary carbon atom at the bonding site with the oxygen atom constituting the ester bond of the (meth) acrylic acid ester. A (meth) acrylic acid ester having an alicyclic group or an alicyclic hydrocarbon group having 6 to 20 carbon atoms and a -COOR group (R may have a substituent) on the alicyclic hydrocarbon group. (Meth) acrylic acid ester in which a tertiary hydrocarbon group, a tetrahydrofuranyl group, a tetrahydropyranyl group, or an oxepanyl group is bonded directly or via a linking group is included.

Examples of the monomer having an acid labile group include 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, and 1- (1′-adamantyl) -1- Examples include methylethyl (meth) acrylate, 1-methylcyclohexyl (meth) acrylate, 1-ethylcyclohexyl (meth) acrylate, 1-methylcyclopentyl (meth) acrylate, 1-ethylcyclopentyl (meth) acrylate, and the like.
As the monomer having an acid labile group, one type may be used alone, or two or more types may be used in combination as necessary.

  The content of the monomer having an acid labile group is not particularly limited, but is preferably 20 mol% or more and more preferably 25 mol% or more in the total charge amount (100 mol%) of all monomers. . Moreover, as an upper limit of the said content, 60 mol% or less is preferable, 55 mol% or less is more preferable, and 50 mol% or less is further more preferable. If the content is 20 mol% or more, preferably 25 mol% or more, sensitivity and resolution tend to be improved, and the content is 60 mol% or less, preferably 55 mol% or less, If it is preferably 50 mol% or less, the resolution tends to be improved.

(Constitutional unit having a lactone skeleton)
The polymer of the present invention may further have a structural unit having a lactone skeleton.
Examples of the lactone skeleton include a lactone skeleton having about 4 to 20 members. The lactone skeleton may be a monocycle having only a lactone ring, or an aliphatic or aromatic carbocyclic or heterocyclic ring may be condensed with the lactone ring.

Examples of the structural unit having a lactone skeleton include structural units derived from a monomer having a lactone skeleton.
As the monomer having a lactone skeleton, a (meth) acrylic acid ester having a substituted or unsubstituted δ-valerolactone ring, a substituted or unsubstituted γ-butyrolactone ring from the viewpoint of excellent adhesion to a substrate or the like. Preferably, at least one selected from the group consisting of monomers having a non-substituted γ-butyrolactone ring is particularly preferable.

Examples of the monomer having a lactone skeleton include β-methacryloyloxy-β-methyl-δ-valerolactone, 4,4-dimethyl-2-methylene-γ-butyrolactone, β-methacryloyloxy-γ-butyrolactone, β-methacryloyloxy-β-methyl-γ-butyrolactone, α-methacryloyloxy-γ-butyrolactone, 2- (1-methacryloyloxy) ethyl-4-butanolide, pantoyllactone methacrylate, 5- (meth) acryloyloxy- 2,6-norbornanecarbolactone, 8-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one, 9-methacryloxy-4-oxatricyclo [5.2.1 .0 ^2,6 ] decan-3-one and the like. Examples of the monomer having a similar structure include methacryloyloxysuccinic anhydride.
The monomers having the lactone skeleton may be used alone or in combination of two or more as necessary.

  The content of the monomer having a lactone skeleton is not particularly limited, but is preferably 20 mol% or more, and more preferably 35 mol% or more in the total charged amount (100 mol%) of all monomers. Moreover, as an upper limit of the said content, 60 mol% or less is preferable, 55 mol% or less is more preferable, and 50 mol% or less is further more preferable. If the content of the monomer having a lactone skeleton is 20 mol% or more, preferably 30 mol% or more, the adhesion to a substrate or the like tends to be good, and the content is 60 mol%. If the amount is 55 mol% or less, more preferably 50 mol% or less, the sensitivity and resolution are improved and defects tend to be reduced.

(Structural unit having a hydrophilic group)
The polymer of the present invention may further have a structural unit having a hydrophilic group. Examples of the “hydrophilic group” include at least one of —C (CF ₃ ) ₂ —OH, a hydroxy group, a cyano group, a methoxy group, a carboxy group, and an amino group.

Examples of the structural unit having a hydrophilic group include a structural unit derived from a monomer having a hydrophilic group.
Examples of the monomer having a hydrophilic group include (meth) acrylic acid ester having a terminal hydroxy group, and a derivative having a substituent such as an alkyl group, a hydroxy group, or a carboxy group on the hydrophilic group of the monomer. , Monomer having a cyclic hydrocarbon group (cyclohexyl (meth) acrylate, 1-isobornyl (meth) acrylate, adamantyl (meth) acrylate), tricyclodecanyl (meth) acrylate, (meth) acrylic acid Dicyclopentyl, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, etc.) have a hydrophilic group such as a hydroxy group, a carboxy group, or a cyano group as a substituent. Monomer. A monomer having a cyclic hydrocarbon group is preferable because it tends to be excellent in dry etching resistance.

Examples of the monomer having a hydrophilic group include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxy- (meth) acrylate. -Propyl, 4-hydroxybutyl (meth) acrylate, 3-hydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl-2-adamantyl (meth) acrylate, etc. From the viewpoint of adhesion to a substrate or the like, 1-methacryloyloxy-3-hydroxyadamantane, 2- or 3-cyano-5-norbornyl (meth) acrylate and the like are preferable.
The said monomer which has a hydrophilic group may be used individually by 1 type, and may be used in combination of 2 or more type as needed.

  The content of the monomer having a hydrophilic group is preferably from 5 to 30 mol%, more preferably from 10 to 25 mol%, in the total charged amount (100 mol%) of all monomers. If the content is 5 mol% or more, preferably 10 mol% or more, the resist pattern rectangularity tends to be good, and if the content is 20 mol% or less, preferably 25 mol% or more, There is a tendency for microgels and defects to be small.

(Method for producing polymer)
The polymer (P) of the present invention can be obtained by a radical polymerization method. In order not to lower the light transmittance, it is necessary to remove the monomer remaining after the completion of the polymerization reaction, and the molecular weight of the polymer is determined. The solution radical polymerization method is preferable because it needs to be relatively low, and the drop polymerization method is easy because a reproducible polymer can be easily obtained with small variations in average molecular weight and molecular weight distribution due to differences in production lots. Is more preferable.

  In the dropping polymerization method, after the inside of the polymerization vessel is heated to a predetermined polymerization temperature, the monomer and the polymerization initiator can be dropped into the polymerization vessel independently or in any combination. A monomer may be dripped only with a monomer, or may be dripped as a monomer solution in which a monomer is dissolved in a solvent. The solvent may be charged into the polymerization vessel in advance, or the solvent may not be charged into the polymerization vessel in advance. When the solvent is not charged in the polymerization vessel in advance, the monomer or the polymerization initiator is dropped into the polymerization vessel in the absence of the solvent.

The polymerization initiator may be dissolved directly in the monomer, dissolved in the monomer solution, or dissolved only in the solvent. The monomer and the polymerization initiator may be mixed in the same storage tank and then dropped into the polymerization container, or may be dropped into the polymerization container from each independent storage tank, or polymerized from each independent storage tank. They may be mixed immediately before being supplied to the container and dropped into the polymerization container. The monomer and the polymerization initiator may be added dropwise one after the other, or the other may be added with a delay, or both may be added at the same timing.
The dropping speed may be constant until the dropping is completed, or may be changed in multiple stages according to the consumption speed of the monomer or the polymerization initiator. The dripping may be performed continuously or intermittently.

  As a method for obtaining the polymer (P) of the present invention, when the dropping polymerization method based on the solution radical polymerization is used, there is a method of increasing the supply rate of the polymerization initiator at the initial stage of polymerization to suppress the formation of a high molecular weight product. Can be mentioned.

  As a method for increasing the supply amount of the polymerization initiator at the initial stage of the polymerization, for example, about 20% by mass to 80% by mass, more preferably about 25% by mass to 75% by mass, and particularly preferably about 30% by mass of the total amount of the polymerization initiator used. A method of supplying mass% to 70% mass into the polymerization system at the initial stage of polymerization (for example, within 1 hour to the start of polymerization) can be mentioned.

  In general, in the case of the dropping polymerization method, when the monomer and the polymerization initiator are dropped at the same dropping time and at a uniform rate, a high molecular weight product tends to be formed at the initial stage of polymerization. According to the above method, the initiator is decomposed at the initial stage of polymerization, and the generation and deactivation of radicals are steadily generated. Since generation | occurrence | production of a molecular weight body can be suppressed, it is preferable.

  As a specific method, there may be mentioned a method of preparing two or more dropping liquids and changing the supply speed of each dropping liquid in multiple stages. For example, a mixture A comprising a polymerization initiator and a solvent, etc. and a mixture B comprising a monomer and a solvent are prepared separately, and the mixture A is prepared for a short time such as from the start of polymerization to within 1 hour. The method of dripping this mixture B over 1 to several hours or more simultaneously with supplying with time is mentioned.

  Further, a mixture A ′ comprising a part of a polymerization initiator and a solvent, etc., and a mixture B ′ comprising a monomer, the remainder of the polymerization initiator, a solvent and the like are prepared separately, and the mixture A method of dropping A ′ over 1 to several hours at the same time as supplying A ′ in a short time such as from the start of polymerization to within 1 hour may be mentioned.

  Moreover, as another polymerization method of the polymer (P) of this invention, well-known polymerization methods, such as a block polymerization method, a suspension polymerization method, and an emulsion polymerization method, can be used.

  The polymerization temperature is not particularly limited, but usually it is preferably performed in the range of 50 to 150 ° C. The polymerization reaction is preferably performed in an inert gas atmosphere such as nitrogen or argon.

Examples of the monomer or initiator solvent include the following.
Ethers: chain ether (diethyl ether, propylene glycol monomethyl ether (hereinafter referred to as “PGME”), etc.), cyclic ether (tetrahydrofuran (hereinafter referred to as “THF”), 1,4-dioxane, etc. )etc.
Esters: methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, propylene glycol monomethyl ether acetate (hereinafter referred to as “PGMEA”), γ-butyrolactone, and the like.
Ketones: acetone, methyl ethyl ketone (hereinafter referred to as “MEK”), methyl isobutyl ketone (hereinafter referred to as “MIBK”), cyclohexanone, and the like.
Amides: N, N-dimethylacetamide, N, N-dimethylformamide and the like.
Sulfoxides: dimethyl sulfoxide and the like.
Aromatic hydrocarbons: benzene, toluene, xylene and the like.
Aliphatic hydrocarbon: hexane and the like.
Alicyclic hydrocarbons: cyclohexane and the like.
A solvent may be used individually by 1 type and may use 2 or more types together.

  As said polymerization initiator, what generate | occur | produces a radical efficiently with a heat | fever is preferable. Examples of the polymerization initiator include azo compounds (2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis [2- (2-imidazoline). -2-yl) propane], etc.), organic peroxides (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, di (4-tert-butylcyclohexyl) peroxydicarbonate, etc. Etc.).

  The polymer solution obtained by the solution radical polymerization method is diluted to a suitable solution viscosity with a good solvent such as 1,4-dioxane, acetone, THF, MEK, MIBK, γ-butyrolactone, PGMEA, and PGME, if necessary. Then, it may be dropped into a large amount of poor solvent such as methanol, water, hexane or heptane to precipitate the polymer. This process is called reprecipitation and is very effective for removing unreacted monomers, polymerization initiators and the like remaining in the polymer solution. If these unreacted substances remain as they are, there is a possibility that the performance of the resist film may be adversely affected. The reprecipitation process may be unnecessary depending on circumstances.

Thereafter, the precipitate is filtered off and sufficiently dried to obtain the polymer (P). Moreover, after filtering off, you may use it as a wet powder, without drying.
The polymer solution may be used as it is as a resist composition, or the polymer solution may be diluted with an appropriate solvent and used as a resist composition, or the polymer solution may be concentrated and used as a resist composition. Good. At that time, additives such as a storage stabilizer may be appropriately added.

  Even if the polymer does not satisfy the above formula (1), it is dissolved in a good solvent that can be used for the polymerization reaction, and a high-molecular weight material is precipitated by adding a poor solvent that can be used in the reprecipitation step. The polymer (P) satisfying the formula (1) can be obtained by filtering the high molecular weight product.

<Resist composition>
The resist composition of the present invention is obtained by dissolving the polymer (P) of the present invention in a solvent. When the resist composition of the present invention is used as a chemically amplified resist composition, a photoacid generator is further dissolved.

(solvent)
As a solvent, the thing similar to the solvent used for manufacture of the said polymer is mentioned. A solvent may be used individually by 1 type and may use 2 or more types together as needed.

(Photoacid generator)
The photoacid generator can be arbitrarily selected from those that can be used as the photoacid generator of the chemically amplified resist composition. A photo-acid generator may be used individually by 1 type, and may use 2 or more types together as needed.

Examples of the photoacid generator include onium salt compounds, sulfonimide compounds, sulfone compounds, sulfonic acid ester compounds, quinone diazide compounds, diazomethane compounds, and the like.
0.1-20 mass parts is preferable with respect to 100 mass parts of polymers, and, as for the quantity of a photo-acid generator, 0.5-10 mass parts is more preferable.

(Nitrogen-containing compounds)
The chemically amplified resist composition may contain a nitrogen-containing compound. By including the nitrogen-containing compound, the resist pattern shape, the stability over time, and the like are further improved. That is, the cross-sectional shape of the resist pattern becomes closer to a rectangle, and the resist film is irradiated with light, then baked (PEB), and then left for several hours before the next development process. Although it is a line, the occurrence of deterioration of the cross-sectional shape of the resist pattern is further suppressed when left as such (timed).

The nitrogen-containing compound is preferably an amine, more preferably a secondary lower aliphatic amine or a tertiary lower aliphatic amine.
As for content of the said nitrogen-containing compound, 0.01-2 mass parts is preferable with respect to 100 mass parts of polymers.

(Organic carboxylic acid, phosphorus oxo acid or its derivative)
The chemically amplified resist composition may contain an organic carboxylic acid, an oxo acid of phosphorus, or a derivative thereof (hereinafter collectively referred to as an acid compound). By including an acid compound, it is possible to suppress deterioration in sensitivity due to the blending of the nitrogen-containing compound, and further improve the resist pattern shape, stability with time of leaving, and the like.

Examples of the organic carboxylic acid include malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.
Examples of the phosphorus oxo acid or derivatives thereof include phosphoric acid or derivatives thereof, phosphonic acid or derivatives thereof, phosphinic acid or derivatives thereof, and the like.
As for content of the said acid compound, 0.01-5 mass parts is preferable with respect to 100 mass parts of polymers.

(Other)
The resist composition of the present invention may contain various additives such as surfactants, other quenchers, sensitizers, antihalation agents, storage stabilizers, and antifoaming agents as necessary. Any additive can be used as long as it is known in the art. The amount of these additives is not particularly limited and can be determined as appropriate.

<Manufacturing method of substrate on which pattern is formed>
Next, an example of a method for manufacturing a substrate on which a pattern according to the present invention is formed will be described.
First, the resist composition of the present invention is applied to the surface of a substrate to be processed such as a silicon wafer on which a desired fine pattern is to be formed by spin coating or the like. And the resist film is formed on a board | substrate by drying the to-be-processed board | substrate with which this resist composition was apply | coated by baking process (prebaking) etc.

Next, the resist film is irradiated with light having a wavelength of 250 nm or less through a photomask to form a latent image (exposure). As irradiation light, a KrF excimer laser, an ArF excimer laser, an F ₂ excimer laser, and an EUV excimer laser are preferable, and an ArF excimer laser is particularly preferable. Moreover, you may irradiate an electron beam.

  In addition, immersion in which light is irradiated with a high refractive index liquid such as pure water, perfluoro-2-butyltetrahydrofuran, or perfluorotrialkylamine interposed between the resist film and the final lens of the exposure apparatus. Exposure may be performed.

After the exposure, heat treatment is appropriately performed (post-exposure baking, PEB), an alkali developer is brought into contact with the resist film, and the exposed portion is dissolved in the developer and removed (development). Examples of the alkaline developer include known ones.
After development, the substrate is appropriately rinsed with pure water or the like. In this way, a resist pattern is formed on the substrate to be processed.

The substrate on which the resist pattern is formed is appropriately heat-treated (post-baked) to strengthen the resist and selectively etch the portion without the resist.
After the etching, the resist is removed with a release agent to obtain a substrate on which a fine pattern is formed.

Since the polymer (P) of the present invention described above has a molecular weight distribution represented by the formula (1), it has excellent solubility in a solvent when preparing a resist composition.
Moreover, the resist composition using the polymer of the present invention can form a highly sensitive resist film and has a small amount of insolubles in the composition.
Further, by using the resist composition of the present invention, a highly accurate fine resist pattern with few defects can be stably formed.
Therefore, the polymer and resist composition of the present invention can be suitably used for DUV excimer laser lithography or electron beam lithography, particularly lithography using ArF excimer laser (193 nm).

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In addition, “part” in each example and comparative example means “part by mass” unless otherwise specified.
Moreover, the polymer and the resist composition were evaluated as follows.

(Weight average molecular weight measurement)
The weight average molecular weight (Mw) of the polymer was determined in terms of polystyrene by gel permeation chromatography under the following conditions (GPC conditions).
<GPC conditions>
Equipment: Tosoh Corporation, Tosoh High Speed GPC Equipment HLC-8220GPC (trade name),
Separation column: manufactured by Showa Denko, Shodex GPC K-805L (trade name) connected in series,
Measurement temperature: 40 ° C.
Eluent: THF,
Sample: A solution in which about 20 mg of a polymer is dissolved in 5 mL of THF and filtered through a 0.5 μm membrane filter.
Flow rate: 1 mL / min,
Injection volume: 0.1 mL,
Detector: differential refractometer.

Calibration curve: About 20 mg of standard polystyrene was dissolved in 5 mL of THF and injected into a separation column under the above conditions using a solution filtered through a 0.5 μm membrane filter, and the relationship between elution time and molecular weight was determined. As the standard polystyrene, the following standard polystyrene manufactured by Tosoh Corporation (both trade names) were used.
F-80 (Mw = 706,000),
F-20 (Mw = 190,000),
F-4 (Mw = 37,900),
F-1 (Mw = 10,200),
A-2500 (Mw = 2,630),
A-500 (mixture of Mw = 682, 578, 474, 370, 260).
Further, by using the calculation program of the GPC apparatus, the base line and peak top lines are drawn for the obtained polymer peaks, and the peak area ratio (P [α _a]) and the low molecular weight side peak area ratio from the peak top to the polymer peak total area (P [α _B]) was determined.

(Solubility)
20 parts of the polymer and 80 parts of PGMEA were mixed, stirred while being kept at 25 ° C., and the time until complete dissolution determined by visual observation was measured.

(sensitivity)
<Preparation of resist composition>
It prepared so that it might become the following compositions.
Polymer: 100 parts by mass (solid content conversion)
Photoacid generator: 2 parts by mass of triphenylsulfonium triflate Solvent: PGMEA (amount at which the concentration of the polymer is 12.5% by mass)

<Sensitivity measurement>
The resist composition was spin-coated on a 6-inch silicon wafer and pre-baked (PAB) at 120 ° C. for 60 seconds on a hot plate to form a thin film having a thickness of 300 nm. Using an ArF excimer laser exposure apparatus (VUVES-4500 manufactured by RISOTEC Japan), 18 shots of 10 mm × 10 mm ² were exposed while changing the exposure amount. Next, after post-baking (PEB) at 110 ° C. for 60 seconds, using a resist development analyzer (RDA-800 manufactured by RISOTEC Japan), development is performed with an aqueous 2.38 mass% tetramethylammonium hydroxide solution at 23 ° C. for 65 seconds. The change with time of the resist film thickness during development at each exposure amount was measured.

<Analysis>
A curve plotting the logarithm of the exposure amount (mJ / cm ² ) and the residual film thickness ratio (hereinafter referred to as the residual film ratio) (%) when developed for 60 seconds with respect to the initial film thickness, based on the obtained data (Hereinafter, exposure amount-residual film rate curve) was prepared, and Eth (required exposure amount for setting the residual film rate to 0% and representing sensitivity) was determined as follows.
Eth: exposure amount (mJ / cm ² ) at which the exposure amount-residual film rate curve intersects with a residual film rate of 0%

[Example 1]
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer, 243.6 parts of ethyl lactate was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 1 was dropped into the flask from the dropping funnel over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours. Simultaneously with the start of dropping of the mixture 1, the following mixture 2 was dropped into the flask from another dropping funnel over 0.1 hour.

(Mixture 1)
95.20 parts of a monomer of the following formula (m1),
131.04 parts of a monomer of the following formula (m2),
66.08 parts of a monomer of the following formula (m3),
430.5 parts ethyl lactate,
2.14 parts of dimethyl-2,2'-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).
(Mixture 2)
8.0 parts ethyl lactate,
4.30 parts of dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was added dropwise to a mixed solvent of about 10 times the amount of methanol and water (methanol / water = 80/20 volume ratio) with stirring to obtain a white precipitate (polymer P1). The precipitate was separated by filtration and again poured into a mixed solvent of methanol and water in the same amount as above (methanol / water = 90/10 volume ratio), and the precipitate was washed with stirring. And the precipitate after washing | cleaning was separated by filtration, and 10 g of polymer wet powder was dried at 40 degreeC under pressure reduction for about 40 hours. The resulting polymer P1 has a weight average molecular weight (Mw) of 9,300, a molecular weight distribution (Mw / Mn) of 1.63, P [α _A ] of 40.10, P [α _B ] of 59.90, P [α _A ] / P [α _B ] was 0.669.

The remaining polymer wet powder was poured into 88,000 parts of PGMEA, completely dissolved, and then passed through a nylon filter having a pore diameter of 0.04 μm (P-NYLON N66FILTER 0.04M (trade name) manufactured by Nippon Pole Co., Ltd.). The polymer solution was filtered.
The polymer solution was heated under reduced pressure to distill off methanol and water, and further PGMEA was distilled off to obtain a polymer P1 solution having a polymer concentration of 25% by mass. At this time, the maximum ultimate vacuum was 0.7 kPa, the maximum solution temperature was 65 ° C., and the distillation time was 8 hours.

  400 parts of a polymer solution, 2 parts of triphenylsulfonium triflate as a photoacid generator, and PGMEA as a solvent are mixed so that the polymer concentration becomes 12.5% by mass to obtain a uniform solution. And filtered through a membrane filter having a pore size of 0.1 μm to obtain a resist composition. The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

[Example 2]
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer, 250.1 parts of ethyl lactate was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Then, the following mixture 3 was dropped into the flask over 4 hours from the dropping funnel, and the temperature of 80 ° C. was further maintained for 3 hours. Simultaneously with the start of dropping of the mixture 3, the following mixture 4 was dropped into the flask from another dropping funnel over 0.1 hour.

(Mixture 3)
95.20 parts of a monomer of the following formula (m1),
109.76 parts of a monomer of the following formula (m4),
66.08 parts of a monomer of the following formula (m3),
442.2 parts ethyl lactate,
2.14 parts of dimethyl-2,2'-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).
(Mixture 4)
8.0 parts ethyl lactate,
4.30 parts of dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).
The charge ratio (mol%) of each monomer is shown in Table 1.

About the obtained reaction solution, operation similar to Example 1 was performed and the polymer P2 was obtained.
The resulting polymer P2 has a weight average molecular weight (Mw) of 9,300, a molecular weight distribution (Mw / Mn) of 1.62, P [α _A ] of 40.48, and P [α _B ] of 59.52. P [α _A ] / P [α _B ] was 0.680.
Moreover, operation similar to Example 1 was performed using the polymer P2, and the polymer P2 solution was obtained.
Moreover, operation similar to Example 1 was performed using the polymer P2 solution, and the resist composition was obtained. The resulting resist composition was evaluated for solubility and sensitivity. The results are shown in Table 2.

Example 3
Under a nitrogen atmosphere, 133.9 parts of ethyl lactate and 133.9 parts of γ-butyrolactone were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 5 was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours. Simultaneously with the start of dropping of the mixture 5, the following mixture 6 was dropped into the flask from another dropping funnel over 0.1 hour.

(Mixture 5)
124.32 parts of a monomer of the following formula (m5),
131.04 parts of a monomer of the following formula (m2),
66.08 parts of a monomer of the following formula (m3),
235.1 parts ethyl lactate,
γ-butyrolactone 235.1 parts Dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, Ltd., V601 (trade name)) 3.22 parts.

(Mixture 6)
6.0 parts ethyl lactate,
γ-butyrolactone 6.0 parts Dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, Ltd., V601 (trade name)) 6.44 parts. The charge ratio (mol%) of each monomer is shown in Table 1.

About the obtained reaction solution, operation similar to Example 1 was performed and the polymer P3 was obtained.
The resulting polymer P3 has a weight average molecular weight (Mw) of 9,400, a molecular weight distribution (Mw / Mn) of 1.76, P [α _A ] of 40.62, P [α _B ] of 59.38, And P [α _A ] / P [α _B ] was 0.684.
Moreover, operation similar to Example 1 was performed using the polymer P3, and the polymer P3 solution was obtained.
Moreover, operation similar to Example 1 was performed using the polymer P3 solution, and the resist composition was obtained. The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

Example 4
A flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer was charged with 104.5 parts of ethyl lactate and 69.7 parts of PGMEA under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 7 was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours. Simultaneously with the start of dropping of the mixture 7, the following mixture 8 was dropped from another dropping funnel into the flask over 0.1 hour.

(Mixture 7)
94.40 parts of a monomer of the following formula (m6),
91.00 parts of a monomer of the following formula (m7),
23.60 parts of a monomer of the following formula (m3),
146.7 parts ethyl lactate,
PGMEA 125.4 parts Dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)) 4.600 parts.

(Mixture 8)
41.4 parts ethyl lactate,
4.600 parts of dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was subjected to the same operation as in Example 1 to obtain a polymer P4.
The resulting polymer P4 has a weight average molecular weight (Mw) of 9,600, a molecular weight distribution (Mw / Mn) of 1.65, P [α _A ] of 40.96, P [α _B ] of 59.04, And P [α _A ] / P [α _B ] was 0.694.
Moreover, operation similar to Example 1 was performed using the polymer P4, and the polymer P4 solution was obtained.
Moreover, operation similar to Example 1 was performed using the polymer P4 solution, and the resist composition was obtained. The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

Example 5
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer, 164.2 parts of PGMEA was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Then, the following mixture 9 was dropped into the flask over 4 hours from the dropping funnel, and the temperature of 80 ° C. was further maintained for 3 hours. Simultaneously with the start of dropping of the mixture 9, the following mixture 10 was dropped into the flask from another dropping funnel over 0.3 hours.

(Mixture 9)
62.40 parts of a monomer of the following formula (m8),
93.60 parts of a monomer of the following formula (m2),
41.00 parts of a monomer of the following formula (m9),
PGMEA 289.1 parts,
Dimethyl-2,2'-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)) 8.050 parts.

(Mixture 10)
32.2 parts of PGMEA,
Dimethyl-2,2'-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)) 8.050 parts.
The charge ratio (mol%) of each monomer is shown in Table 1.

About the obtained reaction solution, operation similar to Example 1 was performed and the polymer P5 was obtained.
The resulting polymer P5 has a weight average molecular weight (Mw) of 9,200, a molecular weight distribution (Mw / Mn) of 1.73, P [α _A ] of 40.38, P [α _B ] of 59.62, And P [α _A ] / P [α _B ] was 0.677.
Moreover, operation similar to Example 1 was performed using the polymer P5, and the polymer P5 solution was obtained.
Moreover, operation similar to Example 1 was performed using the polymer P5 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

Example 6
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer, 175.7 parts of PGMEA was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Then, the following mixture 11 was dropped into the flask over 4 hours from the dropping funnel, and the temperature of 80 ° C. was further maintained for 3 hours. Simultaneously with the start of dropping of the mixture 11, the following mixture 12 was dropped into the flask from another dropping funnel over 0.2 hours.

(Mixture 11)
85.00 parts of a monomer of the following formula (m1),
78.60 parts of a monomer of the following formula (m10),
47.20 parts of a monomer of the following formula (m3),
PGMEA 309.2 parts,
8.740 parts of dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).

(Mixture 12)
35.0 parts of PGMEA,
8.740 parts of dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).
The charge ratio (mol%) of each monomer is shown in Table 1.

About the obtained reaction solution, operation similar to Example 1 was performed and the polymer P6 was obtained.
The resulting polymer P6 has a weight average molecular weight (Mw) of 8,800, a molecular weight distribution (Mw / Mn) of 1.55, P [α _A ] of 41.11, P [α _B ] of 58.89, And P [α _A ] / P [α _B ] was 0.698.
Moreover, operation similar to Example 1 was performed using the polymer P6, and the polymer P6 solution was obtained.
Moreover, operation similar to Example 1 was performed using the polymer P6 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

[Comparative Example 1]
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, a dropping funnel, and a thermometer, 243.6 parts of ethyl lactate was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 1 ′ was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours.
(Mixture 1 ')
95.20 parts of a monomer of the following formula (m1),
131.04 parts of a monomer of the following formula (m2),
66.08 parts of a monomer of the following formula (m3),
438.5 parts ethyl lactate,
8.69 parts of dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, Ltd., V601 (trade name)).
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was subjected to the same operation as in Example 1 to obtain a polymer P′1.
The weight average molecular weight (Mw) of the obtained polymer P1 ′ was 9,900, the molecular weight distribution (Mw / Mn) was 1.67, P [α _A ] was 41.87, and P [α _B ] was 58.13. , And P [α _A ] / P [α _B ] were 0.720.
Moreover, operation similar to Example 1 was performed using polymer P'1, and polymer P'1 solution was obtained.
Moreover, operation similar to Example 1 was performed using polymer P'1 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

[Comparative Example 2]
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, one dropping funnel, and a thermometer, 250.1 parts of ethyl lactate was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 3 ′ was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours.
(Mixture 3 ')
95.20 parts of a monomer of the following formula (m1),
109.76 parts of a monomer of the following formula (m4),
66.08 parts of a monomer of the following formula (m3),
450.2 parts ethyl lactate,
8.69 parts of dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, Ltd., V601 (trade name)).
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was subjected to the same operation as in Example 1 to obtain a polymer P′2.
The weight average molecular weight (Mw) of the obtained polymer P2 ′ was 9,700, the molecular weight distribution (Mw / Mn) was 1.64, P [α _A ] was 42.18, and P [α _B ] was 57.82. , And P [α _A ] / P [α _B ] were 0.730.
Moreover, operation similar to Example 1 was performed using polymer P'2, and polymer P'2 solution was obtained.
Moreover, operation similar to Example 1 was performed using polymer P'2 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

[Comparative Example 3]
Under a nitrogen atmosphere, 133.9 parts of ethyl lactate and 133.9 parts of γ-butyrolactone were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, one dropping funnel, and a thermometer. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 5 ′ was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours.
(Mixture 5 ')
124.32 parts of a monomer of the following formula (m5),
131.04 parts of a monomer of the following formula (m2),
66.08 parts of a monomer of the following formula (m3),
241.1 parts ethyl lactate,
γ-butyrolactone 241.1 parts Dimethyl-2,2'-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)) 14.81 parts.
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was subjected to the same operation as in Example 1 to obtain a polymer P′3. The resulting polymer P′3 had a weight average molecular weight (Mw) of 9,500, a molecular weight distribution (Mw / Mn) of 1.73, P [α _A ] of 43.27, and P [α _B ] of 56. 73 and P [α _A ] / P [α _B ] were 0.763.
Moreover, operation similar to Example 1 was performed using polymer P'3, and polymer P'3 solution was obtained.
Moreover, operation similar to Example 1 was performed using the polymer P'3 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

[Comparative Example 4]
Under a nitrogen atmosphere, 104.5 parts of ethyl lactate and 69.7 parts of PGMEA were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, one dropping funnel, and a thermometer. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 7 ′ was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours.
(Mixture 7 ')
94.40 parts of a monomer of the following formula (m6),
91.00 parts of a monomer of the following formula (m7),
23.60 parts of a monomer of the following formula (m3),
188.1 parts ethyl lactate,
PGMEA 125.4 parts Dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)) 9.200 parts.
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was subjected to the same operation as in Example 1 to obtain a polymer P′4.
The resulting polymer P′4 has a weight average molecular weight (Mw) of 10,100, a molecular weight distribution (Mw / Mn) of 1.67, P [αA] of 42.08, P [αB] of 57.92, And P [αA] / P [αB] was 0.727.
Moreover, operation similar to Example 1 was performed using polymer P'4, and polymer P'4 solution was obtained.
Moreover, operation similar to Example 1 was performed using polymer P'4 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

[Comparative Example 5]
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, a dropping funnel, and a thermometer, 164.2 parts of PGMEA was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 9 ′ was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours.
(Mixture 9 ')
62.40 parts of a monomer of the following formula (m8),
93.60 parts of a monomer of the following formula (m2),
41.00 parts of a monomer of the following formula (m9),
295.5 parts of PGMEA,
Dimethyl-2,2'-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)) 20.470 parts.
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was subjected to the same operation as in Example 1 to obtain a polymer P′5.
The resulting polymer P′5 has a weight average molecular weight (Mw) of 9,600, a molecular weight distribution (Mw / Mn) of 1.83, P [α _A ] of 43.83, and P [α _B ] of 56. 17 and P [α _A ] / P [α _B ] were 0.780.
Moreover, operation similar to Example 1 was performed using polymer P'5, and polymer P'5 solution was obtained.
Moreover, operation similar to Example 1 was performed using polymer P'5 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

[Comparative Example 6]
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, one dropping funnel, and a thermometer, 175.7 parts of PGMEA was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the inside of the flask.
Thereafter, the following mixture 11 ′ was dropped from the dropping funnel into the flask over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours.
(Mixture 11 ')
85.00 parts of a monomer of the following formula (m1),
78.60 parts of a monomer of the following formula (m10),
47.20 parts of a monomer of the following formula (m3),
PGMEA 316.2 parts Dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, Ltd., V601 (trade name)) 22.770 parts.
The charge ratio (mol%) of each monomer is shown in Table 1.

The obtained reaction solution was subjected to the same operation as in Example 1 to obtain a polymer P′6.
The resulting polymer P′6 has a weight average molecular weight (Mw) of 9,400, a molecular weight distribution (Mw / Mn) of 1.68, P [α _A ] of 47.76, and P [α _B ] of 52. 24 and P [α _A ] / P [α _B ] were 0.914.
Moreover, operation similar to Example 1 was performed using polymer P'6, and polymer P'6 solution was obtained.
Moreover, operation similar to Example 1 was performed using the polymer P'6 solution, and the resist composition was obtained.
The resulting resist composition was evaluated for solubility and sensitivity. The evaluation results are shown in Table 2.

(Evaluation results)
When a polymer (Examples 1 to 6) having P [α _A ] / P [α _B ] of 0.7 or less is used, a highly sensitive resist composition having excellent solubility in a solvent can be obtained. It was confirmed. On the other hand, even when polymerized using materials having the same monomer composition as in Examples 1 to 6 above (Comparative Examples 1 to 6), P [α _A ] / P [ When [alpha] _B ] exceeds 0.7, it took about twice or more to complete dissolution in the solvent, and it was confirmed that the solubility in the solvent was lowered. Furthermore, it was confirmed that the sensitivity of the resist composition containing these polymers also decreased.

Claims (3)

A polymer (P) obtained by radical polymerization, which satisfies the following formula (1) when the polymer is measured by gel permeation chromatography (GPC).
P [α _A ] / P [α _B ] ≦ 0.7 (1)
(In the formula (1), P [α _A ] represents the ratio of the peak area from the peak start molecular weight to the peak top molecular weight with respect to the total area of the polymer peak when the polymer (P) is measured by gel permeation chromatography. , P [α _B ] represents a peak area ratio from the peak top molecular weight to the peak end molecular weight with respect to the total area of the polymer peak when the polymer (P) is measured by gel permeation chromatography.   A resist composition comprising the polymer (P) according to claim 1. Applying the resist composition according to claim 2 on a substrate to be processed to form a resist film;
Irradiating the resist film with light having a wavelength of 250 nm or less to form a latent image;
And developing the resist film on which the latent image is formed with a developer.