JP5696868B2 - A method for producing a copolymer for resist. - Google Patents

Description

  The present invention relates to a method for producing a polymer, a resist composition containing the polymer, and more particularly to a technique related to a resist composition suitable for microfabrication using excimer laser or electron beam lithography.

  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 from conventional ultraviolet rays typified by g-line (wavelength: 438 nm) and i-line (wavelength: 365 nm) to shorter wavelength DUV (Deep Ultra Violet). .

  Furthermore, 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. ing. 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 resist patterns using short-wavelength irradiation light or electron beams, and is currently chemically amplified. Improvements and developments in mold resist compositions are underway.
Accordingly, an acrylic polymer that is transparent to light having a wavelength of 193 nm has attracted attention as a chemically amplified resist polymer used in ArF excimer laser lithography.

  As such an acrylic polymer, for example, a polymer having an acetal skeleton-containing (meth) acrylic monomer as a structural unit is suitable as a resist composition and a polymer having good thermal stability. It is disclosed. Furthermore, as a method for producing such a polymer, it is also disclosed that the monomer having an acetal skeleton and another monomer are produced by radical polymerization (Patent Document 1).

  However, in the conventional production method in which the acetal skeleton-containing monomer and another monomer are simply radically polymerized, a part of the acetal group in the monomer may be converted into another monomer during the polymerization reaction. There is a problem in that a copolymer having a desired composition cannot be obtained by being decomposed by a trace amount of impurities contained in the product to generate a carboxyl group. In addition, since the amount of impurities differs depending on the monomer raw material lot, there is a problem that the decomposition of the acetal group occurs irregularly and stable quality control is difficult. Further, when these are used as a resist copolymer, there is a problem that the resist performance becomes unstable.

On the other hand, the problem of thermal decomposition of the monomer during polymerization occurs when a hemiacetal group-containing monomer is polymerized. For example, polymerization is performed in the presence of an amino group-containing compound in order to prevent the hemiacetal group from being decomposed by heat during polymerization to produce a carboxyl group and to inhibit the produced carboxyl group from being incorporated into the polymer. A method (Patent Document 2) and a method of polymerizing in the presence of a monomer having basic nitrogen (Patent Document 3) have been proposed.
JP 2007-45924 Japanese Patent Laid-Open No. 05-155945 JP 05-222134 A

  However, the polymers described in Patent Documents 2 and 3 are used for coating applications and adhesive applications, and are not suitable for use in resist applications that require fine processing performance and high purity performance. . In addition, Patent Documents 2 and 3 only describe the decomposition of the hemiacetal group by heat at the time of polymerization, and the acetal group due to a trace amount of impurities contained in the monomer constituting the resist polymer. It does not suggest any problems or solutions due to the decomposition of.

  The present invention has been made in view of the above circumstances, and an object thereof is to suppress decomposition of an acetal group due to impurities contained in other monomers during the production of a (meth) acrylic polymer having an acetal group. And It is another object of the present invention to provide a method for producing a copolymer having a stable composition and a performance when used as a resist copolymer, regardless of the production lot of the monomer.

The first gist of the present invention is that a (meth) acrylic monomer having an acetal group and another (meth) acrylic monomer copolymerizable with the monomer are combined with each other. The present invention relates to a method for producing a copolymer for resist that is polymerized in the presence of a basic compound having a boiling point of 0.016 parts by mass or more and 0.1 parts by mass or less with respect to the total amount and does not volatilize during measurement and polymerization .

  Moreover, the 2nd summary of this invention exists in the composition for resists containing the copolymer for resists obtained by the said method.

  The third gist of the present invention includes a step of applying a composition containing the resist composition and a photoacid generator on a substrate to be processed to form a resist film, and a wavelength of 450 nm or less on the resist film. The method includes the step of forming a latent image by irradiating the light and a step of developing the resist film on which the latent image is formed with a developer.

  According to the method for producing a resist polymer, it is possible to prevent a part of the acetal group from being decomposed by a trace amount of impurities contained in another monomer during the polymerization reaction. Regardless of the production lot, a copolymer having a composition with stable performance and quality can be obtained.

  In addition, according to the method for producing a resist polymer, a copolymer having a desired composition can be obtained. Therefore, when used as a resist composition, performance can be stabilized.

  In addition, according to the above manufacturing method, a substrate on which a fine pattern is formed can be stably supplied, thereby improving the productivity and reliability of a semiconductor substrate or the like.

  In this specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, and “(meth) acrylic monomer” means an acrylic monomer or a methacrylic monomer. .

((Meth) acrylic monomer having acetal group)
The (meth) acrylic monomer having an acetal group is not particularly limited as long as it has at least one acetal group in one molecule. For example, the one represented by the following formula Is mentioned.

  The content of the (meth) acrylic monomer having an acetal group is not particularly limited, but is 1 with respect to the total charged amount (100 mol%) of all monomers that are constituent units of the copolymer. It is preferably used in the range of ˜30 mol%, more preferably in the range of 5 to 15 mol%. If the content of the (meth) acrylic monomer having an acetal group is 1 mol% or more, preferably 5 mol% or more, the line edge roughness tends to be small and defects tend to be reduced. When the amount is 30 mol% or less, preferably 15 mol% or less, there is a tendency that the number of defects is small and the solubility in an organic solvent is good.

(Other acrylic monomers that can be copolymerized)
As the other (meth) acrylic monomer copolymerizable with the (meth) acrylic monomer having an acetal group, particularly if it is a (meth) acrylic monomer having no acetal group Although not limited, a (meth) acrylic monomer having a lactone skeleton from the viewpoint of imparting substrate adhesion, a (meth) acrylic monomer having an acid labile group from the viewpoint of resist pattern formation, and the resist (Meth) acrylic monomers having a hydrophilic group are exemplified from the viewpoint of improving solubility in a solvent and imparting etching resistance, and one or more of these can be arbitrarily combined.

((Meth) acrylic monomer having 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 carbon ring or a heterocyclic ring may be condensed with the lactone ring.
The (meth) acrylic monomer having a lactone skeleton is a (meth) acrylic acid ester having a substituted or unsubstituted δ-valerolactone ring, substituted or unsubstituted, because it has excellent adhesion to a substrate or the like. At least one selected from the group consisting of (meth) acrylic monomers having a γ-butyrolactone ring is preferred, and (meth) acrylic monomers having an unsubstituted γ-butyrolactone ring are particularly preferred.

Examples of the (meth) acrylic monomer having the lactone skeleton include β-methacryloyloxy-β-methyl-δ-valerolactone, 4,4-dimethyl-2-methylene-γ-butyrolactone, and β-methacryloyloxy. -Γ-butyrolactone, β-methacryloyloxy-β-methyl-γ-butyrolactone, α-methacryloyloxy-γ-butyrolactone, 2- (1-methacryloyloxy) ethyl-4-butanolide, pantoyllactone methacrylate, etc. . Examples of the monomer having a similar structure include methacryloyloxysuccinic anhydride.
The (meth) acrylic monomer having the lactone skeleton may be used alone or in combination of two or more as necessary.

The content of the (meth) acrylic monomer having the lactone skeleton is not particularly limited, but is 20 mol% in the total charged amount (100 mol%) of all monomers that are constituent units of the copolymer. The above is preferable, and 30 mol% or more is more preferable. 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%. Hereinafter, if it is preferably 55 mol% or less, more preferably 50 mol% or less, the sensitivity and resolution tend to be improved and defects tend to be reduced.

((Meth) acrylic monomer having acid labile group)
The acid labile group is a group having a structure that is eliminated by the action of an acid, and the structural unit containing the acid labile group is decomposed by an acid to become an alkali-soluble group and a residue derived from the acid labile group. . Such an acid labile group becomes soluble in an alkali by an acid when the polymer is used as a resist polymer, and has an effect of enabling formation of a resist pattern.

  The (meth) acrylic monomer having an acid labile group is not particularly limited, but a group having an alicyclic hydrocarbon group having 6 to 20 carbon atoms and detachable by the action of an acid. Examples include (meth) acrylic acid esters. A monomer having such an alicyclic hydrocarbon group is preferable because it tends to be excellent in dry etching resistance. 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.

Examples of the (meth) acrylic monomer having an acid labile group include 2-methyl-2-adamantyl methacrylate and 2-ethyl-2-adamantyl methacrylate.
Moreover, the (meth) acrylic-type monomer which has the said acid labile 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 (meth) acrylic monomer having an acid labile group is not particularly limited, but it is 20 in the total charged amount (100 mol%) of all monomers that are constituent units of the copolymer. The mol% or more is preferable, and 25 mol% or more is more preferable. 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.

((Meth) acrylic monomer having hydrophilic group)
The “hydrophilic group” is not particularly limited, and examples thereof 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.
The (meth) acrylic monomer having a hydrophilic group is, for example, a (meth) acrylic acid ester having a terminal hydroxy group, substitution of an alkyl group, a hydroxy group, a carboxy group or the like on the hydrophilic group of the monomer. Group-containing derivative, cyclic hydrocarbon group-containing monomer (cyclohexyl (meth) acrylate, 1-isobornyl (meth) acrylate, adamantyl (meth) acrylate), tricyclodecanyl (meth) acrylate, ( (Meth) acrylic acid dicyclopentyl, (meth) acrylic acid 2-methyl-2-adamantyl, (meth) acrylic acid 2-ethyl-2-adamantyl, etc.) as a substituent with a hydrophilic group such as a hydroxy group or a carboxy group. The monomer which has. A monomer having a cyclic hydrocarbon group is preferable because it tends to be excellent in dry etching resistance.

Examples of the (meth) acrylic monomer having a hydrophilic group include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and (meth) acrylic acid. Examples include 2-hydroxy-n-propyl, 4-hydroxybutyl (meth) acrylate, 3-hydroxyadamantyl methacrylate, and the like, and 1-methacryloyloxy-3-hydroxyadamantane is preferable from the viewpoint of adhesion to a substrate and the like. .
The (meth) acrylic monomer having a hydrophilic group may be used alone or in combination of two or more as necessary.

  The content of the (meth) acrylic monomer having a hydrophilic group is, in terms of the resist pattern rectangularity, in the total charged amount (100 mol%) of all monomers that are constituent units of the copolymer. 5-30 mol% is preferable, and 10-25 mol% is more preferable. If the content is 5 mol% or more, preferably 10 mol% or more, the resist pattern tends to be good, and if the content is 20 mol% or less, preferably 25 mol% or more, the microgel There is a tendency to have few defects.

(Basic compound)
The polymerization of the monomer is performed in the presence of a basic compound.
In the present specification, “in the presence of the basic compound” means that the basic compound is present in the polymerization reaction system. For example, the basic compound is added together with the monomer and the polymerization initiator. Alternatively, a basic compound may be added separately from the monomer and the polymerization initiator.
Each of the above monomers contains a small amount of impurities such as an acid and an acid generator, and the acid derived from the impurities can cause decomposition of the monomer having an acetal group during polymerization. However, the presence of a predetermined amount of the basic compound in the polymerization reaction system neutralizes the acid derived from the trace amount of impurities, so that a single amount having an acetal group due to the acid derived from the impurities during polymerization. Degradation of the body can be suppressed.

  As an example of the mechanism by which the acetal group is decomposed by a trace amount of impurities contained in the monomer, an acid is generated by a bromo compound contained in α-methacryloyloxy-γ-butyrolactone (α-GBLMA) or the like. As a result, there may be a case where the acetal is decomposed, a case where the acetal is further decomposed by an acid generated by the decomposition of the acetal, but the invention is not limited to these theories.

Examples of the basic compound include diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, n-butylamine, di-n-butylamine, isobutylamine, sec-butylamine, cyclohexyl. Amine, ethylenediamine, tetramethylenediamine, hexamethylenediamine or the like can be used.
Of these, triethylamine is preferably used from the viewpoint of having a boiling point that does not volatilize during metering and polymerization and that can be removed during purification.

  The amount of the basic compound is 0.016 parts by mass or more with respect to 100 parts by mass of the total amount of monomers constituting the copolymer. If the said amount is 0.016 mass part or more, the trace amount impurity contained in a monomer etc. will be neutralized and decomposition | disassembly of an acetal group by this impurity can be suppressed. The upper limit of the amount is 2 parts by mass or less, preferably 0.5 parts by mass or less, and more preferably 0.1 parts by mass or less from the viewpoint of lithography performance and the like.

(Polymerization method)
Examples of the polymerization method include known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these, the solution polymerization method is preferred because it is necessary to remove the monomer remaining after the completion of the polymerization reaction and the molecular weight of the polymer needs to be relatively low in order not to reduce the light transmittance. .

  In the solution polymerization method, the monomer and the polymerization initiator may be supplied to the polymerization vessel continuously or intermittently. As a solution polymerization method, a monomer and a polymerization initiator are dropped into a polymerization vessel from the viewpoint that a variation in average molecular weight and molecular weight distribution due to differences in production lots is small and a reproducible polymer can be easily obtained. The dropping polymerization method is preferred.

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.
The monomer may be dropped only with the monomer, or may be dropped as a monomer solution in which the monomer is dissolved in a solvent (hereinafter also referred to as “dropping solvent”).

The solvent may be charged in the polymerization vessel in advance, or the solvent may not be charged in 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, or may be dissolved in the monomer solution, or may be dissolved only in the dropping solvent.

  In addition, the monomer and the polymerization initiator may be dropped into the polymerization vessel after mixing in the same storage tank, or may be dropped into the polymerization container from an independent storage tank, or They may be mixed immediately before being supplied from an independent storage tank to the polymerization vessel and dropped into the polymerization vessel.

  In addition, the monomer and the polymerization initiator may be dropped one after the other, and then the other may be dropped with a delay, or both may be dropped 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 monomer and the polymerization initiator may be added dropwise continuously or intermittently.

  The composition and molecular weight of the copolymer can be controlled by appropriately selecting various polymerization conditions and methods as described above. For example, a copolymer having a desired molecular weight or a copolymer having a uniform composition can be obtained.

  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 solvent include the following.
Ethers: chain ethers (propylene glycol monomethyl ether, etc.), cyclic ethers (tetrahydrofuran (hereinafter referred to as “THF”), etc.) and the like.
Esters: ethyl lactate, propylene glycol monomethyl ether acetate (hereinafter referred to as “PGMEA”), γ-butyrolactone, and the like.
Ketones: methyl ethyl ketone and the like.
Alicyclic hydrocarbons: cyclohexane and the like.
The said solvent may be used individually by 1 type, and may use 2 or more types together as needed.

  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 resist composition of the present invention is obtained by dissolving the above copolymer 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.

  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.

  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.

  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.

  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.

  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.

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. Then, the substrate to be processed coated with the resist composition is dried by baking (PAB) or the like, thereby forming a resist film on the substrate.

Next, the resist film is irradiated with light having a wavelength of 450 nm or less, preferably 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 exposure, heat treatment (PEB) is performed as appropriate, 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 (PEB) 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.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these. Further, “part” in each example and comparative example means “part by mass” unless otherwise specified.
Further, the composition and physical properties of the copolymer were measured using the following methods.
Furthermore, the amount of methacrylic acid (BDADMA / methacrylic acid ratio), which is a decomposition product of BDADMA, was also measured.

-Each monomer composition (mol%) in copolymerization, BDADMA / methacrylic acid ratio It calculated | required by the measurement of following < ¹ > H-NMR.
Using a GSX-400 type FT-NMR manufactured by JEOL Ltd., a 5% by mass solution of each copolymer (deuterated dimethyl sulfoxide solution) is put in a test tube having a diameter of 5 mmφ, an observation frequency of 400 MHz, single In the pulse mode, the measurement was performed 64 times. The measurement temperature was 60 ° C. when deuterated dimethyl sulfoxide was used as a solvent.

Measurement of Eth, Measurement of γ Value (1) Preparation of Lithographic Composition The following materials were mixed and prepared so as to have the following composition.
Copolymer: 10 parts Photoacid generator (TPS-105): 0.2 parts Leveling agent (L-7001): 0.2 parts Solvent: PGMEA 90 parts

(2) Dry Lithography A lithographic 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-790, manufactured by RISOTEC Japan), development is performed for 65 seconds with a 2.38% tetramethylammonium hydroxide aqueous solution at 23.5 ° C. The change with time of the resist film thickness during development at each exposure amount was measured.

(3) Analysis Based on the obtained data, the logarithm of the exposure amount (mJ / cm ² ) and the remaining film thickness ratio (hereinafter referred to as the remaining film ratio) when developed for 60 seconds with respect to the initial film thickness (%) Curve (hereinafter referred to as exposure amount-residual film rate curve), and Eth (required exposure amount for setting the residual film rate to 0%, which represents sensitivity) and γ value (exposure amount-residual amount). It is the slope of the tangent to the film rate curve and represents the development contrast).
Eth: exposure amount (mJ / cm ² ) at which the exposure amount-residual film rate curve intersects with a residual film rate of 0%
γ value: E50 (mJ / cm ² ) of exposure amount at 50% of the remaining film rate of the exposure amount-residual film rate curve, and a tangent line at E50 of the exposure amount-residual film rate curve of 100% and the remaining film rate The exposure amount intersecting with the line with a film rate of 0% was determined as E100 and E0, respectively, and the following calculation formula was used.
γ = 1 / {log (E0 / E100)}
The higher the γ value, the higher the resolution and the better the resolution performance of the fine pattern.

Example 1
Under a nitrogen atmosphere, 72.3 parts of PGMEA was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 25.4 parts α-methacryloyloxy-γ-butyrolactone (α-GBLMA) (31.8 mol% based on the total charge of all monomers), 2-methacryloyloxy-2-methyladamantane (MAdMA) 35. 0 parts (31.8 mol% with respect to the total charge of all monomers), 26.3 parts of 2-cyano-5-norbornene methacrylate (CNNNMA) (27.27 with respect to the total charge of all monomers). 3 mol%), 2-propenoic acid-2-methyl-1,4-butanediylbis (oxyethylidene) ester (BDDADMA) 13.4 parts (9.1 mol% with respect to the total charge of all monomers), 129.9 parts of PGMEA, 24.5 parts of dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, Ltd., V-601 (trade name)) and 0.023 part of triethylamine were mixed. Monomer solution over 4 hours at a constant rate, was dropped into the flask, followed by maintaining the temperature of 80 ° C. 3 hours. Subsequently, the obtained reaction solution was dropped into about 7 times amount of methanol with stirring to obtain a white precipitate. The resulting precipitate was filtered off and poured again into about 7 times the amount of methanol. This was separated by filtration, collected, and dried under reduced pressure at 60 ° C. for about 40 hours to obtain a copolymer A powder.

(Example 2)
Using a raw material of a different production lot (changing the production lot of GBLMA and using the raw material of the same production lot as that of Example 1 for the other raw materials), the same experiment as in Example 1 was conducted, and copolymer B Got.

(Example 3)
The experiment similar to (Example 1) was performed by changing the amount of triethylamine to 0.032 parts, and a copolymer C was obtained (the production lot of CNNMA was changed, and other raw materials were produced in the same manner as in Example 1). Use lot raw materials).

(Comparative Example 1)
An experiment similar to (Example 1) was carried out by changing the raw material production lot without adding triethylamine, to obtain a copolymer D (using raw materials of the same production lot as in Example 3 for all raw materials).

(Comparative Example 2)
The same experiment as in (Example 1) was performed by changing the triethylamine amount to 0.015 part, and a copolymer E was obtained (using raw materials of the same production lot as in Example 3 for all raw materials).

  About the said copolymers A-E, the obtained composition and the measurement result of the physical property were put together in the following tables. In addition, BDADMA / methacrylic acid shows the mol% of methacrylic acid with respect to that when the amount of BDADMA in the polymer is 100.

When 0.016 parts by mass or more of the basic compound (triethylamine) is added (Examples 1 to 3), the decomposition amount of the acrylic monomer having an acetal group is only 0.6 to 0.7 mol%. It was confirmed that the amount of methacrylic acid that was suppressed and the decomposition product (5.65 to 7.69 mol% with respect to BDADMA100) was also small.
Moreover, in the case of the said Examples 1-3, there was no dispersion | variation in a numerical value also in dry lithography evaluation results, such as a sensitivity and development contrast, and it was confirmed that the physical property as a resist copolymer is stable.
On the other hand, even when polymerized using the same raw material material as in Example 3, the basic compound was added (Comparative Example 1), or the basic compound (triethylamine) addition amount was 0.016. When the amount is less than parts by mass (Comparative Example 2), the amount of decomposition of the acrylic monomer having an acetal group (Comparative Example 2) compared to the case where the basic compound addition amount is 0.016 mass or more (Example 3) ( It was confirmed that the amount of methacrylic acid as a decomposition product (30.51 to 57.41 mol% with respect to BDADMA100) also increased as the amount increased (1.9 to 2.3 mol%).
Moreover, in the case of the said Comparative Examples 1-2, the numerical value of dry lithography evaluation results, such as a sensitivity and development contrast, also has dispersion | variation, and it was confirmed that the physical property is not stable as a resist copolymer.

Claims (4)

The (meth) acrylic monomer having an acetal group and another (meth) acrylic monomer copolymerizable with the monomer are 0% relative to 100 parts by mass of the total amount of the monomers. A method for producing a copolymer for resist, which is polymerized in the presence of a basic compound having a boiling point that does not volatilize during measurement and polymerization, in a range of .016 parts by mass to 0.1 parts by mass.   The production method according to claim 1, wherein the basic compound is triethylamine.   A resist composition comprising a resist copolymer obtained by the method according to claim 1. Applying a composition comprising the resist composition according to claim 3 and a photoacid generator on a substrate to be processed to form a resist film;
Irradiating the resist film with light having a wavelength of 450 nm or less to form a latent image;
And a step of developing the resist film on which the latent image is formed with a developer.