JP6623562B2 - Method for producing lithographic material, method for producing lithographic composition, and method for producing substrate on which pattern is formed - Google Patents

Description

  The present invention relates to a method for manufacturing a lithographic material, a method for manufacturing a lithographic composition, and a method for manufacturing 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, and the like has been rapidly miniaturized due to progress in lithography technology. As a method of miniaturization, there is a method of shortening the wavelength of irradiation light. Specifically, the wavelength of irradiation light has been shortened 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 (wavelength: 13.5 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.
High sensitivity is required for a resist material used for forming a resist film by lithography using the short-wavelength irradiation light or electron beam. In response to such a demand, a chemically amplified resist containing a photoacid generator has been proposed, and improvement and development of the chemically amplified resist are currently underway.

In the lithography process, various films such as an anti-reflection film, a gap fill film, and a top coat film are used in addition to the resist film. In general, a film containing a polymer is used for forming these films, and various characteristic groups are introduced into the polymer in order to exhibit a function according to a use. For example, examples of the chemically amplified resist polymer include those having a polar group, an acid-eliminable group, and the like. Examples of the polymer for an antireflection film include those having a light absorbing group that absorbs exposure light, a reactive functional group that can react with a curing agent, and the like.
As a method for producing a polymer (polymer for lithography) used in these lithography steps, a method in which a monomer is dissolved in a polymerization solvent and polymerized in the presence of a polymerization initiator is generally used. The polymerization reaction solution after the polymerization is subjected to a purification step or the like as necessary, and the obtained lithography polymer or a solution thereof is filled in a container for storage, transportation, and the like.

In recent years, miniaturization of resist patterns has progressed, and in order to obtain an excellent resist pattern profile, it is required to reduce metal impurities in a polymer solution for lithography.
Patent Document 1 discloses that a polymerization raw material is handled in a clean room whose cleanliness level specified in ISO 14644-1 is less than or equal to class 8 and is transferred to a polymerization vessel in-line without being brought into contact with outside air exceeding class 8 to carry out a polymerization reaction. A method is described in which the obtained polymer or polymerization solution is transferred in-line and filled in a container in a clean room of class 8 or less.

JP 2013-103977 A

  According to the method described in Patent Literature 1, it is understood that all the processes from the polymerization raw material to the filling of the target polymer into a container may be performed in a facility including a class 8 or lower clean room and in-line transfer. . However, in some cases, for example, in existing factories, it is difficult to realize this because of the heavy burden of equipment introduction.

The present invention has been made in view of the above circumstances, and in a method of manufacturing a lithography material in which a lithography polymer is contained in a container for storage, transportation, and the like, while suppressing the burden of introducing equipment, the weight of the lithography polymer is reduced. Provided is a method for producing a lithography material, which can highly reduce metal impurities in coalescence.
The present invention also provides a method for producing a lithography composition using the method for producing a lithography material, and a method for producing a substrate on which a pattern is formed, using the method for producing a lithography composition.

The present inventors have conducted a filling step in which a polymer or a polymer solution is filled in a container and hermetically sealed in a protected space in which a specific filter is controlled, so that metal impurities in a polymer for lithography can be effectively used. It has been found that this can be reduced, leading to the present invention.
In addition, the present inventors have found that the metal impurities in the lithography polymer can be more effectively reduced by performing the measuring step of measuring the polymerization raw material and the filling step in a protected space in which a specific filter is controlled. And found the present invention.

The present invention has the following aspects.
[1] A filling step of filling a container with a polymer for lithography or a polymer solution and sealing the container is performed, and the filling step is performed in a protected space, and the gas in the protected space and the polymer for lithography or A method for producing a lithography material in which a polymer solution is contained in a container, wherein a gas that has passed through a filter is supplied to the protection space, and a pressure difference between before and after passing through the filter is 60 to A method for producing a lithography material, which is maintained at 220 Pa.
[2] Maintaining the differential pressure before and after passing through the first filter at Z ± 50 Pa (Z indicates the median of the range of the differential pressure and satisfies 110 Pa ≦ Z ≦ 150 Pa), [1] 3. The method for producing a lithography material according to item 1.

[3] Further, the method includes a measuring step of measuring a polymerization raw material used for the polymerization reaction, and a polymerization step of supplying the measured polymerization raw material to a polymerization vessel to perform a polymerization reaction, wherein the measuring step is performed in a second protected space. Then, the gas that has passed through the second filter is continuously supplied to the second protection space, and the differential pressure before and after passing through the second filter is maintained at 60 to 220 Pa, [1]. Or the method for producing a lithography material according to [2].
[4] The differential pressure before and after the passage through the second filter is maintained at Z ± 50 Pa (Z indicates the median of the range of the differential pressure and 110 Pa ≦ Z ≦ 150 Pa) [3]. 3. The method for producing a lithography material according to item 1.

[5] A step of producing a lithographic material by the production method according to [1] to [4], and mixing a lithographic polymer in the container with a compound that generates an acid upon irradiation with actinic rays or radiation. A method for producing a lithography composition having a step.
[6] a step of producing a resist composition by the method of producing a lithographic composition according to [5], and a step of applying the obtained resist composition on a surface to be processed of a substrate to form a resist film; A method for manufacturing a substrate on which a pattern is formed, comprising a step of exposing the resist film and a step of developing the exposed resist film using a developer.

ADVANTAGE OF THE INVENTION According to the manufacturing method of the material for lithography of this invention, the metal impurity contained in the polymer for lithography can be reduced highly, suppressing the burden of introducing equipment. Therefore, a lithography material in which the container is filled with the lithography polymer having a low content of metal impurities is obtained.
ADVANTAGE OF THE INVENTION According to the manufacturing method of the lithography composition of this invention, the lithography composition in which metal impurities were highly reduced can be manufactured, suppressing the burden of installation of equipment.
According to the method for manufacturing a substrate having a pattern formed thereon according to the present invention, a resist composition in which metal impurities are highly reduced is produced while suppressing the burden of introducing equipment, and a pattern is formed using the resist composition. By manufacturing a substrate, the generation of defects due to the incorporation of metal impurities is highly reduced, and a high-quality substrate can be manufactured stably.
The method for producing a polymer for lithography of the present invention is particularly suitable as a method for producing a polymer for semiconductor lithography used in the production of semiconductors. ADVANTAGE OF THE INVENTION According to this invention, the polymer for semiconductor lithography which can stably form the board | substrate of the semiconductor circuit with few defects when used for a semiconductor lithography composition can be manufactured.

In the present specification and claims, "polymer solution" means a solution in which a polymer is dissolved or a polymer reaction solution.
In the present specification and claims, "polymerization raw material" means a raw material used for a polymerization reaction.
In this specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, and “(meth) acryloyloxy” means acryloyloxy or methacryloyloxy.

<Polymer for lithography>
The polymer for lithography (hereinafter, sometimes simply referred to as a polymer) in the present invention is a polymer used in a lithography step, and has at least a structural unit having a polar group.
A `` polar group '' is a group having a polar functional group or a polar atomic group.Specific examples include a hydroxy group, a cyano group, an alkoxy group, a carboxy group, an amino group, a carbonyl group, and a fluorine atom. Groups, a group containing a sulfur atom, a group containing a lactone skeleton, a group containing an acetal structure, a group containing an ether bond, and the like.
The use of the polymer for lithography is not particularly limited as long as it is used in the lithography process. For example, a polymer for resist used for forming a resist film, an antireflection film (TARC) formed on an upper layer of the resist film, or a reflection polymer used for forming an antireflection film (BARC) formed on a lower layer of the resist film. Examples of the polymer include a polymer for a prevention film, a polymer for a gap fill film used for forming a gap fill film, and a polymer for a top coat film used for forming a top coat film. Preferred embodiments of the polymer for each application will be described later.
The polymer for lithography in the present invention is particularly suitable as a polymer for semiconductor lithography used in a lithography step in a semiconductor manufacturing process.

<Method for producing lithography material>
The first embodiment of the production method of the present invention is a method for producing a lithography material having a filling step of filling a container with a polymer or a polymer solution for lithography and sealing the container. In the present embodiment, the filling step is performed in a protection space (hereinafter, referred to as a first protection space). The obtained lithography material is a container in which the gas in the first protection space and the lithography polymer or polymer solution are contained in a container.
The polymer solution filled in the container in the filling step may be a polymerization reaction solution obtained by solution polymerization or the like in the polymerization step, or a solution obtained by adding a solvent to a polymer recovered from the polymerization reaction solution and dissolving the polymer. May be. The solvent in the polymer solution only needs to dissolve the polymer for lithography, and a known solvent can be used. Preferred are those mentioned as a polymerization solvent described below, those described as a diluting solvent described later, and mixtures of two or more different kinds thereof.
The polymer filled in the container in the filling step is preferably a powder, may be a wet powder, or may be a polymer in a dry powder form. It is preferably a dry powder.
As the container for filling the polymer or the polymer solution, a known container can be used depending on the type and properties of the polymer. It is preferable to use a container made of a material with less elution of metal impurities from the inner surface of the container. For example, a polyethylene container, a glass container, various metal containers made of polyethylene on the inner surface, and the like are preferable.
A known filling method can be used for the filling method of the polymer or the polymer solution.

The second embodiment of the production method of the present invention includes, in addition to the filling step of the first embodiment, a measuring step of measuring a polymerization raw material, and a polymerization in which the measured polymerization raw material is supplied to a polymerization vessel to perform a polymerization reaction. This is a method for producing a semiconductor lithography material having a step. In this embodiment, the measuring step is performed in the second protected space, and the filling step is performed in the first protected space. The first protection space and the second protection space may be the same space.
The polymerization raw material is a raw material used for a polymerization reaction, and is a raw material supplied to a polymerization vessel. As the polymerization raw material, at least a monomer is essential, and a polymerization solvent, a polymerization initiator, and the like are included as necessary. The monomer is selected according to the polymer to be produced. Known monomers can be used.
The polymerization step can be performed using a known method. It is preferable to appropriately use a known method for making it difficult to mix metal impurities.

Other steps may be provided between the polymerization step and the filling step, if necessary. As other steps, known steps can be used.
Other steps are, for example, a reprecipitation step, a drying step, a reslurry step, a re-dissolution step, a concentration step, a purification step and the like. Each step will be described later.
The other steps are preferably performed as appropriate using a known method for making it difficult to mix metal impurities.
Other steps are performed using in-line equipment designed so that the feed supplied to each step and the products generated in each step (intermediate products) do not come into contact with outside air (gas outside the apparatus). Is preferred. Further, it is preferable that the transfer of the substance between the devices is performed in-line by using a transfer means designed so as not to contact the outside air.

In the present invention, not all the steps are necessarily configured in-line, and may have an off-line step. Therefore, the burden of equipment introduction can be reduced.
Off-line process means a process in which a feed supplied to the process and / or a product (intermediate product) generated in the process passes through a space without a filter for obtaining a clean gas. I do.
For example, even if the devices used in each step are continuously provided, there may be an opening through which outside air without a filter flows into the device depending on the pressure difference between the inside of the device and the outside air. In such a case, even if the process is performed by a continuous device, the device has passed through a state where it can be exposed to the outside air (a space without a filter for obtaining a clean gas) and has gone through an offline process. become. Also, when the equipment used in each step is not continuous and the product (intermediate product) is transferred to a transfer container, the inside of the container is required to obtain a clean gas, such as when entering a container without a filter. If the space does not have a filter, it means that an offline process has been performed.

[Protected space]
The term "protected space" in the present invention means a space in which the flow of gas is restricted and the indoor pressure is higher than the external pressure in order to maintain a clean space. Usually, the supply of gas into the space is performed through a filter. The gas is discharged out of the space in a state where the backflow is prevented by a check damper or the like.
The following is a configuration common to the first protection space and the second protection space. The first protection space and the second protection space may be the same space, or may be different spaces that are independently controlled. Hereinafter, when the two are not distinguished, they are referred to as “protected space”.
The gas that has passed through the filter is supplied to the protection space, and is managed and controlled so that the differential pressure before and after the filter (also referred to as the differential pressure before and after the filter) is maintained at 60 to 220 Pa. ing.
The gas passed through the filter is not particularly limited. Usually, air or humidified air obtained by adjusting the humidity of air to a predetermined range is used.
The differential pressure before and after passing through the filter can be measured with a known differential pressure gauge.
The pressure difference before and after passing through the filter can be adjusted by the performance of the filter and the flow rate (air volume) of the gas passing through the filter. The performance of the filter differs depending on the type of the filter, and when the filter is not new, it also changes depending on the used time (use time).

As the filter, a known air filter used for purifying a gas can be used. For example, a pre-filter, a medium-performance filter, a medium-high-performance filter, a high-performance filter, an ultra-high-performance filter (HEPA (High Efficiency Particulate Air) filter), an ultra-high-performance filter (ULPA (Ultra Low Penetration Air) filter), an ultra-ULPA filter, etc. Is preferred.
The HEPA filter is preferable because the differential pressure before and after the passage of the filter can be easily controlled within the above range.
The HEPA filter refers to an air filter having a particle collection rate of 99.97% or more with respect to particles having a particle size of 0.3 μm at a rated air volume and having an initial pressure loss of 245 Pa or less.
The rated airflow of a HEPA filter is generally about 17 cubic meters per minute for a filter having a filtration area of 8 square meters.

The flow rate (gas volume) of the gas passing through the filter is preferably such that at least 5 times or more of the protective space capacity per hour is passed through the filter, more preferably 10 times or more, and even more preferably 15 times or more.
The upper limit of the air volume is not particularly limited, but is preferably 200 times or less, more preferably 100 times or less the capacity of the protected space per hour, from the viewpoint that the flow of the airflow in the protected space does not become too fast.

In the present invention, the “volume of the protection space” is the volume of the space surrounded by the surface that defines the protection space. For example, when the protection space has a rectangular parallelepiped shape, it is calculated by a base area × height.
The volume of the protection space is not particularly limited, but if it is too large, a large amount of gas must be supplied through a filter in order to sufficiently clean the inside of the protection space. If the size is too small, the workability in the protection space deteriorates, so that a range where such inconvenience does not occur is preferable. For example, 1 to 3000 m ³ is preferable, 5 to 2500 m ³ is more preferable, 10 to 2000 m ³ is more preferable, and 15 to 1500 m ³ is particularly preferable.
The filtration area of the filter is preferably 0.02 to 6.4 square meters, more preferably 0.04 to 3.2 square meters, and more preferably 0.08 to 1.6 square meters per cubic meter of the volume of the protected space. Is more preferred.
The filtration area of the filter means the total area through which gas passes.
Two or more filters may be provided for one protection space, and in that case, the total filtration area of each filter is preferably within the above range.
When two or more filters are provided in one protection space, the flow rate (air volume) of the gas passing through the filters is the sum of the air volumes in each filter.

In the present invention, the gas is continuously supplied to the protection space through a filter, and the pressure difference between before and after passing through the filter is maintained at 60 to 220 Pa, so that the filling step or the measurement in the protection space is performed. Incorporation of metal impurities during the process can be reduced to a high degree. If the differential pressure is too high or too low, metal impurities are likely to be mixed.
Further, the differential pressure before and after passing through the filter satisfies the above range, and the fluctuation range thereof is preferably 50 Pa or less (within ± 50), preferably 10 Pa or less (within ± 10). More preferably, there is.
For example, when the fluctuation of the differential pressure before and after the passage of the filter is maintained within a predetermined range, if the median of the range of the differential pressure is represented by Z, it is maintained at Z ± 50 Pa (Z = 110 to 170 Pa). Preferably. The value of Z is more preferably 110 to 150 Pa.
More preferably, the differential pressure before and after the passage through the filter is maintained at Z ± 10 Pa (Z = 110 to 170 Pa), and the value of Z is more preferably 110 to 150 Pa.

A preferred embodiment of the protection space has, for example, an exhaust structure in which the volume is 1 to 3000 m ³ , the filtration area of the filter is 0.02 to 6.4 square meters per cubic meter of the volume of the protection space, and the backflow is prevented. It is a closed space.
The protection space includes a measuring means (differential pressure gauge) for measuring a pressure difference before and after the filter passes, a means for monitoring the pressure difference over time, and a method for measuring the pressure difference within a predetermined range. It is preferable to provide a control means for adjusting the flow rate (air volume) of the air supplied to the filter so that the air pressure is maintained at a value.

[Polymerization step]
The polymerization step can be suitably performed by, for example, a solution polymerization method in which a monomer is radically polymerized using a polymerization initiator in the presence of a polymerization solvent.

<Polymerization solvent>
Examples of the polymerization solvent used in the solution polymerization method include the following.
Ethers: chain ethers (diethyl ether, propylene glycol monomethyl ether (hereinafter, referred to as “PGME”) and the like), cyclic ethers (tetrahydrofuran (hereinafter, referred to as “THF”), 1,4-dioxane, and the like. )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 hydrocarbon: benzene, toluene, xylene and the like.
Aliphatic hydrocarbons: hexane and the like.
Alicyclic hydrocarbon: cyclohexane and the like.
One type of organic solvent may be used alone, or two or more types may be used in combination.

<Polymerization initiator>
As the polymerization initiator, those which efficiently generate radicals by heat are preferable. For example, azo compounds (2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] And organic peroxides (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, di (4-tert-butylcyclohexyl) peroxydicarbonate, etc.).
The suitable use temperature of these polymerization initiators according to the decomposition temperature is in the range of 50 to 150 ° C.

In the polymerization step of the solution polymerization method, a polymerization solvent, a polymerization initiator, and a monomer are supplied into a polymerization vessel, and a radical polymerization reaction is performed while maintaining a predetermined polymerization temperature.
The supply of the monomer and the polymerization initiator to the polymerization vessel may be continuous supply or drop supply. A drop polymerization method in which a monomer and a polymerization initiator are dropped into a polymerization vessel is preferred from the viewpoint that a variation in the average molecular weight, the molecular weight distribution, and the like due to the difference in the production lot is small and a reproducible polymer is easily obtained.

In the drop polymerization method, after the temperature inside the polymerization vessel is adjusted to a predetermined polymerization temperature, the monomer and the polymerization initiator are 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 polymerization solvent.
The polymerization solvent and / or monomer may be charged in the polymerization vessel in advance.
The polymerization initiator may be directly dissolved in the monomer, may be dissolved in the monomer solution, or may be dissolved only in the polymerization solvent.
The monomer and the polymerization initiator may be dropped into the polymerization vessel after being mixed in the same storage tank; and may be dropped into the polymerization vessel from each independent storage tank; from the independent storage tank to the polymerization vessel. The mixture may be mixed immediately before the supply and dropped into the polymerization vessel.
One of the monomer and the polymerization initiator may be dropped first, and then the other may be dropped later, or both may be dropped at the same timing.
The dropping rate may be constant until the end of the dropping, or may be changed in multiple stages according to the consumption rate of the monomer or the polymerization initiator.
Dropping may be performed continuously or intermittently.
The polymerization temperature is preferably set within a range of a suitable use temperature of the polymerization initiator. For example, 50 to 150 ° C. is preferable.

In the solution polymerization method, the viscosity of a reaction solution in which a polymerization reaction is performed increases as the polymerization reaction of a monomer proceeds. If the viscosity of the reaction solution is too high, the polymerization reaction may proceed rapidly, that is, a so-called runaway reaction may occur.
In the present specification, a reaction solution in which a monomer is subjected to a polymerization reaction using a polymerization initiator in the presence of a polymerization solvent is referred to as a polymerization reaction solution. The polymerization reaction solution contains a polymer formed by the polymerization reaction.
The viscosity of the polymerization reaction solution decreases as the amount of the polymerization solvent used in the polymerization reaction increases, and increases as the amount of the polymerization solvent used decreases. The amount of the polymerization solvent used in the polymerization reaction may be set so that the viscosity of the reaction solution is low enough not to cause the runaway reaction described above. The larger the amount of the polymerization solvent used, the lower the production efficiency.
The viscosity of the polymerization reaction solution can be adjusted to an arbitrary viscosity by diluting with a solvent. Specific examples of the diluting solvent include 1,4-dioxane, acetone, THF, MEK, cyclopentanone, cyclohexanone, MIBK, γ-butyrolactone, PGMEA, PGME, ethyl lactate, methyl 2-hydroxyisobutyrate, methanol, ethanol, and isopropyl Examples thereof include alcohol, water, hexane, heptane, diisopropyl ether, and a mixed solvent thereof.
The viscosity of the polymerization reaction solution at 25 ° C. is preferably 25 mPa · s or more, more preferably 50 mPa · s or more, more preferably 100 mPa · s or more, and particularly preferably 150 mPa · s or more from the viewpoint of production efficiency. The upper limit of the viscosity of the polymerization reaction solution may be any range as long as the runaway reaction does not occur. For example, the viscosity is preferably 10,000 mPa · s or less, and more preferably 9,000 mPa · s or less.
The dilution with the solvent can be performed during the polymerization step, and can also be performed during the stop step described below.

(Stop process)
In the polymerization step, after a radical polymerization reaction is performed while maintaining the polymerization temperature at a predetermined polymerization time for a preset polymerization time, the polymerization reaction of the obtained polymerization reaction solution is stopped.
In a radical polymerization reaction, polymerization proceeds by a chain mechanism consisting of four elementary reactions of a start reaction, a growth reaction, a termination reaction, and a chain transfer reaction, and the molecular weight of the produced polymer is determined by the speed and mechanism of each elementary reaction. The growth reaction rate is proportional to the product of the monomer concentration and the radical concentration, and the termination reaction is proportional to the square of the radical concentration.
In the present invention, "stopping the polymerization reaction" means that the amount of radicals generated by the decomposition of the polymerization initiator is set to a state where the initiation reaction and the growth reaction do not occur sufficiently.
As a method of stopping the polymerization reaction, a step of cooling the reaction solution is generally used, but the reaction can be stopped by adding a radical scavenger such as a polymerization inhibitor or oxygen.

[Reprecipitation step]
In the method for producing a polymer of the present invention, the polymerization reaction solution obtained through the preservation step is mixed with a poor solvent (preferably, dropped into the poor solvent) to precipitate the polymer in the polymerization reaction solution. Good. This step is called reprecipitation and is very effective for removing impurities such as unreacted monomers and polymerization initiator remaining in the polymer solution. If unreacted monomer remains as it is, the sensitivity will decrease when used as a resist composition, it is preferable to remove as much as possible.
The amount of the poor solvent when the solution after the dilution is dropped into the poor solvent is not particularly limited, but is preferably equal to or more than the same volume as the solution after the dilution from the viewpoint that the unreacted monomer can be more easily reduced. It is preferably at least 4 times, more preferably at least 4 times, even more preferably at least 5 times, particularly preferably at least 6 times. The upper limit is preferably 15 times or less on a volume basis from the viewpoint that the amount of the poor solvent used is not too large and the productivity is not reduced.
Then, the target polymer is obtained in the form of a wet powder by filtering off the precipitate in the poor solvent.

[Drying process]
In the reprecipitation step, the target polymer is obtained in a dry powder state by drying the wet powder obtained by filtering out the precipitate in the poor solvent.
[Resurrection process]
Alternatively, the wet powder filtered in the reprecipitation step may be dispersed again in a poor solvent to form a polymer dispersion, and then the filtration operation may be repeated. This step is called a re-slurry step, and is effective for further reducing impurities such as unreacted monomers and polymerization initiator remaining in the polymer wet powder.
From the viewpoint that the polymer can be obtained while maintaining high productivity, it is preferable to perform purification only by the reprecipitation step without performing the reslurry step.

[Re-dissolution step]
The wet powder filtered off in the reprecipitation step or the reslurry step may be dissolved in an appropriate solvent as it is without drying to obtain a polymer solution.
[Concentration step]
The wet powder filtered off in the reprecipitation step or the reslurry step may be dissolved in a suitable solvent as it is without drying, and may be further concentrated to remove a low-boiling compound before forming a polymer solution.
Alternatively, the wet powder may be dried, dissolved in an appropriate solvent, and further concentrated to remove low-boiling compounds, and then used as a polymer solution.

[Purification step]
A solution containing a polymer (hereinafter, also referred to as a “purified solution”) can be passed through a filtration filter under specific conditions to be filtered.
The step of purifying the polymer solution for lithography is applied where the target polymer is in a solution state during the production process of the polymer. The polymer production step is a period from the polymerization step to the time of use as a composition for lithography, and includes the step of storing the polymer solution in a container.
Specifically, the solution to be purified is a polymerization reaction solution obtained by performing a polymerization reaction in solution polymerization, a solution obtained by re-dissolving the wet powder obtained in the reprecipitation step or the reslurry step, obtained in the reprecipitation step or the reslurry step. The solution in which the wet powder was re-dissolved was concentrated to remove the low-boiling compounds, the solution in which the wet powder was dried and then dissolved in an appropriate solvent, and the solution in which the wet powder was dried and then dried. It is preferably at least one selected from the group consisting of a solution obtained by concentrating a dissolved solution to remove low-boiling compounds and a polymer solution contained in a container.
In the point that by-produced by the polymerization reaction, it is possible to efficiently remove a polymer having a higher molecular weight than the intended weight average molecular weight or a polymer having a poor copolymerization and poor solubility in the copolymer composition, such as drying and concentration. It is preferable to carry out the purification step using the solution obtained in the step having the thermal history as the solution to be purified.

Filtration of the solution to be purified is preferably performed with a filtration filter having a rated filtration accuracy of 0.1 μm or less, and the solution is preferably passed while maintaining the differential pressure before and after filtration at 250 kPa or less. The rated filtration accuracy is a particle diameter at which the filtration efficiency becomes 99.9% or more, and the filtration efficiency is a value obtained by the following equation (1).
(Number of particles before filtration−number of particles after filtration) / number of particles before filtration × 100 (1)
The smaller the rated filtration accuracy, the finer the filtration filter.
The differential pressure before and after filtration is the value obtained by subtracting the value of the pressure applied to the polymer solution after passing from the pressure applied to the polymer solution before passing through the filtration filter of the solution to be purified passing through the filtration filter. That is. Usually, there is a passage resistance of the filtration membrane and the pressure before the passage of the liquid increases, so that the differential pressure before and after the filtration is a positive value.

By subjecting the solution to be purified to filtration with a filtration filter having a rated filtration accuracy of 0.1 μm or less, a polymer having a higher molecular weight than the target weight average molecular weight and a disproportionate solubility of the copolymer composition produced as a by-product in the polymerization reaction. Poor polymer can be removed.
Such a high molecular weight polymer or a polymer having an uneven copolymer composition is often a gel substance in a solution to be purified, and deforms without keeping its shape constant under the influence of heat or stress. . Therefore, in order to perform purification while maintaining stable filtration efficiency, it is preferable to perform filtration while maintaining the pressure difference before and after filtration at 250 kPa or less. Filtration while maintaining the pressure at 250 kPa or less means that 90% by mass of the solution to be filtered (the solution to be purified passing through the filtration filter) is passed from the start of filtration (the time when the solution is passed through the filtration filter). Means that the differential pressure before and after filtration does not exceed 250 kPa until the end of the process.
The lower limit of the differential pressure before and after the filtration is not particularly limited, but is preferably maintained at 10 kPa or more, more preferably at 20 kPa or more, from the viewpoint that the filtration rate is reduced and the productivity is reduced.
In order to maintain the filtration efficiency in a high state, the differential pressure before and after filtration at the start of filtration is more preferably controlled to 190 kPa or less, still more preferably to 140 kPa or less, and most preferably to 90 kPa or less. .
In addition, before and after filtration, from the start of filtration (the time when the liquid is passed through the filtration filter) to the time when the 90% by mass of the solution to be filtered (the solution to be purified passed through the filter) is completed. It is preferable to perform filtration while always keeping the pressure difference within ± 50 kPa of the pressure difference before and after filtration at the start of filtration.
Specifically, a method of maintaining the pressure difference before and after filtration within a predetermined range is to pressurize the solution to be purified to a constant pressure, and if the pressure difference fluctuates after the start of filtration, apply the pressure so that the pressure difference becomes constant. Control the pressure applied to the purification solution. Examples of the method of pressurizing the solution to be purified include a method of sending the solution using a pump, a method of applying pressure using a compressed gas, and the like.

The mass of the solution to be filtered (the solution to be purified passing through the filtration filter) is the mass of the solution to be purified when the solution is passed through the filtration filter once. For example, in the case where filtration is performed twice by circulating filtration described below, twice the mass of the solution to be purified is the mass of the solution to be filtered (the solution to be purified passing through the filtration filter).
By maintaining the differential pressure during filtration within ± 50 kPa at the start of filtration, it is possible to perform filtration while maintaining the filtration accuracy during filtration constant, and to provide a lithographic polymer solution for semiconductors that exhibits stable solubility. Obtainable. The pressure difference is preferably maintained within ± 40 kPa, more preferably ± 30 kPa.

When using a filtration filter having a rated filtration accuracy of more than 0.1 μm when purifying the solution to be purified, it is possible to efficiently remove a polymer having a high molecular weight or a polymer having an uneven copolymer composition that is desired to be removed. There is a risk of disappearing.
The rated filtration accuracy of the filtration filter used for the purification is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably 0.04 μm or less, still more preferably 0.02 μm or less, and particularly preferably 0.01 μm or less. , 0.005 μm or less.
Examples of the material of the filtration filter (filtration membrane) include a fluorine polymer such as PTFE (polytetrafluoroethylene); a polyolefin polymer such as polyethylene and polypropylene; and a polyamide polymer such as nylon 6, nylon 66, and nylon 46. A filtration membrane composed of the coalesced composition is preferred. It is more preferable to include a polymer having a polar group.
A polyamide polymer having an amide bond as a polar group is capable of efficiently removing a polymer having a higher molecular weight than the target weight average molecular weight or a polymer having a biased copolymer composition by-produced in the polymerization reaction. It is preferable to use a filtration filter having a filtration membrane containing coalescence.

The shape of the filtration filter may be a known one. For example, a filter in which a filtration membrane is housed in a container such as a disk type or a cartridge type may be used. The filtration filter may have a plurality of filtration membranes of the same or different materials.
The surface area of the filtration filter, the temperature of the polymer solution, and the flow rate at the time of passing the solution are preferably adjusted as appropriate according to the amount, viscosity, and the like of the solution to be filtered (the solution to be purified passing through the filtration filter).
It is preferable that the temperature of the solution to be purified passed through the filtration filter be kept substantially constant from the start to the end of the flow. For example, the temperature is preferably maintained within the range of x ± 3 ° C. (x is 0 to 35 ° C.). If the temperature of the solution to be purified is higher than the upper limit of the above range, purification may not be performed while maintaining stable filtration efficiency, and if the temperature is lower than the lower limit, the solution viscosity increases and the filtration speed is reduced. It is not preferable because productivity is lowered.

In the production method of the present invention, filtration with a filtration filter having a rated filtration accuracy of 0.1 μm or less can be performed in two or more stages. Alternatively, the solution to be purified once filtered may be repeatedly passed through the same filtration filter again for filtration.
When the filtration is performed in two or more stages, the filtration at the first stage and the filtration at the second stage or more can use any combination of the rated filtration accuracy and the material of the filtration filter. In order to prevent a decrease in filterability due to clogging of the filter, the filter with the highest rated filtration accuracy is used as the first-stage filtration filter. Preferably, it is smaller.
When performing filtration by dividing the filtration filter with a rated filtration accuracy of 0.1 μm or less into two or more stages, the pressure applied to the polymer solution before passing through the filtration filter with the initial filtration accuracy of 0.1 μm or less, and the final It is sufficient that the difference from the pressure applied to the polymer solution after passing through a filtration filter having a rated filtration accuracy of 0.1 μm or less is 250 kPa or less.
In the case of performing circulating filtration in which the polymer solution for semiconductor lithography once filtered is repeatedly passed through the same filtration filter again, the number of times of circulating filtration is preferably 3 or more times, and more preferably 4 times or more in terms of increasing the filtration efficiency. More preferably, it is more preferably performed 5 times or more.

<Polymer for lithography>
Hereinafter, as a specific example of the polymer for lithography, a polymer for an antireflection film, a polymer for a gap fill film, a polymer for a top coat film, and a polymer for a resist will be described.
[Polymer for anti-reflective coating]
Examples of the polymer for an anti-reflection film include a structural unit having a light-absorbing group, and an amino group, an amide group, a hydroxy group, and an epoxy group that can be cured by reacting with a curing agent to avoid mixing with a resist film. And a structural unit having a reactive functional group. The light-absorbing group is a group having high absorption performance for light in a wavelength region where the photosensitive component in the resist composition has sensitivity, and specific examples thereof include an anthracene ring, a naphthalene ring, a benzene ring, and a quinoline ring. And a group having a ring structure (which may have an arbitrary substituent) such as a quinoxaline ring and a thiazole ring. In particular, when KrF laser light is used as the irradiation light, an anthracene ring or an anthracene ring having an optional substituent is preferable, and when ArF laser light is used, benzene ring or benzene having an optional substituent is used. Rings are preferred.

  Examples of the optional substituent include a phenolic hydroxyl group, an alcoholic hydroxyl group, a carboxy group, a carbonyl group, an ester group, an amino group, and an amide group. Among these, those having a protected or unprotected phenolic hydroxyl group as the light-absorbing group are preferred from the viewpoint of good developability and high resolution. Examples of the structural unit / monomer having a light absorbing group include benzyl (meth) acrylate, p-hydroxyphenyl (meth) acrylate, and the like.

[Polymer for gap fill film]
Examples of polymers for gap fill films include reactive polymers that have an appropriate viscosity to flow into narrow gaps, and can be cured by reacting with a curing agent to avoid mixing with resist films and anti-reflective films. A copolymer containing a structural unit having a group, specifically, a copolymer of a monomer such as styrene, an alkyl (meth) acrylate, or a hydroxyalkyl (meth) acrylate with hydroxystyrene can be given.
[Polymer for top coat film]
Examples of the polymer for a top coat film used for immersion lithography include a copolymer containing a constitutional unit having a carboxyl group, a copolymer containing a constitutional unit having a fluorine-containing group substituted by a hydroxyl group, and the like.

[Polymer for resist]
Examples of the resist polymer include a copolymer containing at least one structural unit having an acid leaving group and at least one structural unit having a polar group.
Among these, the resist polymer applied to the pattern forming method of exposing with light having a wavelength of 250 nm or less preferably has a lactone skeleton as a polar group-containing structural unit, and further has a hydrophilic unit described below. It is preferable to have a structural unit having a functional group.

(Structural unit / monomer having lactone skeleton)
Examples of the lactone skeleton include a lactone skeleton having about 4 to 20 membered rings. The lactone skeleton may be a single ring having only a lactone ring, or an aliphatic or aromatic carbon ring or heterocyclic ring may be condensed to the lactone ring.
When the polymer contains a structural unit having a lactone skeleton, the content is preferably 20 mol% or more, more preferably 25 mol% or more, of all the structural units (100 mol%) from the viewpoint of adhesion to a substrate or the like. Is more preferred. Further, from the viewpoint of sensitivity and resolution, it is preferably at most 60 mol%, more preferably at most 55 mol%, even more preferably at most 50 mol%.

  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 is preferred in terms of excellent adhesion to a substrate or the like. At least one member selected from the group consisting of monomers having a substituent is preferable, and a monomer having an unsubstituted γ-butyrolactone ring is particularly preferable.

Specific examples of the monomer having a lactone skeleton include β- (meth) acryloyloxy-β-methyl-δ-valerolactone, 4,4-dimethyl-2-methylene-γ-butyrolactone, β- (meth) acryloyl Oxy-γ-butyrolactone, β- (meth) acryloyloxy-β-methyl-γ-butyrolactone, α- (meth) acryloyloxy-γ-butyrolactone, 2- (1- (meth) acryloyloxy) ethyl-4-butanolide , Pantoyl lactone (meth) acrylate, 5- (meth) acryloyloxy-2,6-norbornanecarboractone, 8-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decane-3 - one, 9-methacryloxy-4-oxatricyclo [5.2.1.0 ^{2, 6]} cited decan-3-one and the like . Examples of the monomer having a similar structure include methacryloyloxysuccinic anhydride.
As the monomer having a lactone skeleton, one type may be used alone, or two or more types may be used in combination.

(Structural unit / monomer having hydrophilic group)
The “hydrophilic group” in the present specification is 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.
Among these, the resist polymer applied to the pattern forming method for exposing with light having a wavelength of 250 nm or less preferably has a hydroxy group or a cyano group as a hydrophilic group.
The content of the structural unit having a hydrophilic group in the resist polymer is preferably 5 to 30 mol%, and more preferably 10 to 25 mol%, of all the structural units (100 mol%) from the viewpoint of the rectangularity of the resist pattern. More preferred.

  Examples of the monomer having a hydrophilic group include (meth) acrylic acid esters having a terminal hydroxy group; derivatives having a substituent such as an alkyl group, a hydroxy group, or a carboxy group on the hydrophilic group of the monomer; Monomers having a cyclic hydrocarbon group (for example, 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) having a hydrophilic group such as a hydroxy group or a carboxy group as a substituent; No.

Specific examples of the monomer having a hydrophilic group include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxy-n- (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 and the like Is mentioned. From the viewpoint of adhesion to a substrate or the like, 3-hydroxyadamantyl (meth) acrylate, 3,5-dihydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl- 2-adamantyl (meth) acrylate and the like are preferred.
As the monomer having a hydrophilic group, one type may be used alone, or two or more types may be used in combination.

[Structural unit having an acid leaving group]
The resist polymer preferably has a structural unit having an acid-eliminable group in addition to the structural unit having a polar group described above for use in resist applications. You may have.
The “acid-eliminable group” is a group having a bond that is cleaved by an acid, and a group in which part or all of the acid-eliminable group is eliminated from the main chain of the polymer by the cleavage of the bond.
In the resist composition, a polymer having a structural unit having an acid-eliminable group reacts with an acid component and becomes soluble in an alkaline solution, and has an effect of enabling formation of a resist pattern.
From the viewpoint of sensitivity and resolution, the proportion of the constituent unit having an acid-eliminable group is preferably at least 20 mol%, more preferably at least 25 mol%, of all the constituent units (100 mol%) constituting the polymer. . In addition, from the viewpoint of adhesion to a substrate or the like, the content is preferably 60 mol% or less, more preferably 55 mol% or less, and still more preferably 50 mol% or less.

The monomer having an acid leaving group may be a compound having an acid leaving group and a polymerizable multiple bond, and a known compound can be used. The polymerizable multiple bond is a multiple bond that is cleaved during a polymerization reaction to form a copolymer chain, and an ethylenic double bond is preferable.
Specific examples of the monomer having an acid leaving group include (meth) acrylates having an alicyclic hydrocarbon group having 6 to 20 carbon atoms and having an acid leaving group. Can be The alicyclic hydrocarbon group may be directly bonded to an oxygen atom constituting an ester bond of the (meth) acrylate, or may be bonded via a linking group such as an alkylene group.
The (meth) acrylate has an alicyclic hydrocarbon group having 6 to 20 carbon atoms, and a tertiary carbon atom is bonded to an oxygen atom constituting an ester bond of the (meth) acrylate. (Meth) acrylic acid ester having an alicyclic hydrocarbon group having 6 to 20 carbon atoms, and the alicyclic hydrocarbon group has a -COOR group (R may have a substituent. (Representing a tertiary hydrocarbon group, a tetrahydrofuranyl group, a tetrahydropyranyl group, or an oxepanyl group)) directly or via a linking group.

In particular, in the case of producing a resist composition applied to a pattern forming method of exposing with light having a wavelength of 250 nm or less, as a preferred example of a monomer having an acid-labile group, for example, 2-methyl-2- Adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, 1- (1′-adamantyl) -1-methylethyl (meth) acrylate, 1-methylcyclohexyl (meth) acrylate, 1-ethylcyclohexyl ( (Meth) acrylate, 1-methylcyclopentyl (meth) acrylate, 1-ethylcyclopentyl (meth) acrylate, isopropyl adamantyl (meth) acrylate, 1-ethylcyclooctyl (meth) acrylate, and the like.
As the monomer having an acid leaving group, one kind may be used alone, or two or more kinds may be used in combination.

<Method for producing resist composition>
According to the production method of the present invention, a lithography material in which a polymer or a polymer solution is contained in a container is obtained. A resist composition can be produced by mixing a polymer or a polymer solution in a container, a compound that generates an acid upon irradiation with actinic rays or radiation, and a resist solvent if necessary. Preferably, the polymer and a compound capable of generating an acid upon irradiation with actinic rays or radiation are dissolved in a resist solvent.

[Resist solvent]
As the resist solvent, the solvents mentioned above as the polymerization solvent can be used.
[Compound that generates an acid upon irradiation with actinic rays or radiation]
The compound that generates an acid upon irradiation with actinic rays or radiation can be arbitrarily selected from those that can be used as a photoacid generator in a chemically amplified resist composition. One photoacid generator may be used alone, or two or more photoacid generators may be used in combination.
Examples of the photoacid generator include an onium salt compound, a sulfonimide compound, a sulfone compound, a sulfonate compound, a quinonediazide compound, and a diazomethane compound.
The use amount of the photoacid generator is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the polymer.

[Nitrogen-containing compound]
The chemically amplified resist composition may contain a nitrogen-containing compound. By including the nitrogen-containing compound, the resist pattern shape, the stability with time of storage, and the like are further improved. In other words, the mass production of a semiconductor device is such that 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 until the next development processing. Although it is a line, the occurrence of deterioration of the cross-sectional shape of the resist pattern when left unattended (aged) is further suppressed.
As the nitrogen-containing compound, an amine is preferable, and a secondary lower aliphatic amine and a tertiary lower aliphatic amine are more preferable.
The amount of the nitrogen-containing compound is preferably from 0.01 to 2 parts by mass based on 100 parts by mass of the polymer.

[Organic carboxylic acid, phosphorus oxo acid or derivative thereof]
The chemically amplified resist composition may contain an organic carboxylic acid, an oxo acid of phosphorus or a derivative thereof (hereinafter, these are collectively referred to as an acid compound). By containing an acid compound, sensitivity deterioration due to the compounding of the nitrogen-containing compound can be suppressed, and the resist pattern shape, the stability over time, and the like are further improved.
Examples of the organic carboxylic acid include malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.
Examples of the oxo acid of phosphorus or a derivative thereof include phosphoric acid or a derivative thereof, phosphonic acid or a derivative thereof, and phosphinic acid or a derivative thereof.
The amount of the acid compound is preferably 0.01 to 5 parts by mass based on 100 parts by mass of the polymer.

[Additive]
The resist composition may contain various additives such as a surfactant, other quencher, a sensitizer, an antihalation agent, a storage stabilizer, and an antifoaming agent, if necessary. Any of the additives can be used as long as they are known in the art. Further, the amounts of these additives are not particularly limited, and may be determined as appropriate.

<Manufacturing method of substrate on which fine pattern is formed>
An example of the method for manufacturing a substrate on which a fine pattern is formed according to the present invention will be described.
First, a resist composition obtained by the manufacturing method of the present invention is applied by spin coating or the like on a surface (work surface) of a work substrate such as a silicon wafer on which a desired fine pattern is to be formed. Then, the substrate to which the resist composition is applied is dried by baking (pre-baking) or the like to form a resist film on the substrate.

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). The irradiation light, KrF excimer laser, ArF excimer laser, _{F 2} excimer laser, the EUV excimer laser Preferably, ArF excimer laser is particularly preferable. Further, an electron beam may be irradiated.
Liquid immersion for irradiating light 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, an appropriate heat treatment (post-exposure bake, PEB) is performed, an alkali developer is brought into contact with the resist film, and the exposed portion is dissolved in the developer and removed (development). As the alkali developer, a known one can be used.
After the development, the substrate is appropriately rinsed with pure water or the like. Thus, 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 portions where there is no resist.
After the etching, the resist is removed with a stripping agent to obtain a substrate on which a fine pattern is formed.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. In addition, “parts” in each of Examples and Comparative Examples indicates “parts by mass” unless otherwise specified. The following methods were used for measurement and evaluation.

<Measurement of weight average molecular weight>
The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer were determined in terms of polystyrene by gel permeation chromatography under the following conditions (GPC conditions).
[GPC conditions]
Apparatus: Tosoh high-speed GPC apparatus HLC-8220GPC (trade name) manufactured by Tosoh Corporation.
Separation column: a column in which three Shodex GPC K-805L (trade name) manufactured by Showa Denko KK are connected in series.
Measurement temperature: 40 ° C.
Eluent: tetrahydrofuran (THF).
Sample: A solution obtained by dissolving about 20 mg of the polymer in 5 mL of THF and filtering through a 0.5 μm membrane filter.
Flow rate: 1 mL / min.
Injection volume: 0.1 mL.
Detector: Differential refractometer.

Calibration curve I: A solution obtained by dissolving about 20 mg of standard polystyrene in 5 mL of THF and injecting it into a separation column under the above conditions using a solution filtered with a 0.5 μm membrane filter was used to determine the relationship between elution time and molecular weight. As the standard polystyrene, the following standard polystyrene (all trade names) manufactured by Tosoh Corporation was 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 (Mw = 682, 578, 474, 370, 260 mixture).

Measurement time 0 to 3 minutes: solution A / solution B = 90% by volume / 10% by volume.
Measurement time 3 to 24 minutes: From solution A / solution B = 90% by volume / 10% by volume to 50% by volume / 50% by volume.
Measurement time 24 to 36.5 minutes: From solution A / solution B = 50% by volume / 50% by volume to 0% by volume / 100% by volume.
Measurement time 36.5 to 44 minutes: solution A / solution B = 0 vol% / 100 vol%.

<Number of particles (number of particles) in space>
The number of particles having a particle diameter of 0.5 μm or more in one cubic foot was measured using a particle counter (Met One / Royco Particle Counter Model 227B, manufactured by Hack).
<Metal analysis>
Na, K, Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Pb, n, by a high frequency inductively coupled plasma mass spectrometer (ICP-MS-Inductively Coupled Plasma Mass Spectrometer: 7500 cs manufactured by Agilent Technologies). , Co, Li, Ti, Ag, W, V, Ba, Au, As, and Cd were determined by metal analysis.
The obtained metal concentration was divided by the polymer concentration to calculate a metal concentration (metal impurity content) in terms of polymer solid content.

<Example 1>
In this example, the step of measuring the monomer, the polymerization solvent and the polymerization initiator (the measurement step) and the step of filling the container with the produced polymer solution for semiconductor lithography and sealing the container are performed in the same protective space. went. That is, in this example, the first protection space and the second protection space are the same space.
Of the other steps, the step was performed offline between the re-slurry step described below and the purification step after re-dissolution. Other steps were performed in-line.
The protection space is provided with one gas inlet and four gas outlets. A filter is provided at the gas inlet, and gas that has passed through the filter at a predetermined flow rate (air volume) is continuously supplied into the protection space. The gas discharge port is provided with a check damper, and is configured to prevent gas outside the protection space from entering the inside through the gas discharge port. The gas passed through the filter is air.
In this example, the filter has a rated air flow of 17 cubic meters per minute, a particle collection rate of 99.97% or more for particles having a particle diameter of 0.3 μm or more, and an initial pressure loss of 245 Pa or less. A new air filter (HEPA filter) was used. The volume of the protected space is 51 m ³ and the filtration area of the filter is about 8 square meters. Further, a differential pressure gauge for measuring a differential pressure before and after passing through the filter, a device for monitoring the differential pressure with time, and an air supply to the filter so that the differential pressure is maintained within a predetermined range. A control device for adjusting the flow rate (air volume) is provided.
The flow rate (air volume) of the gas supplied to the filter is initially set to 20 times the volume of the protective space per hour, and while controlling the air volume so that the differential pressure in the filter is maintained within the range of 110 ± 10 Pa, A polymer was produced continuously for 35 hours. The air volume at the end of the production of the polymer was 20 times the protected space volume per hour.
Table 1 shows the measurement results of the number of particles having a particle diameter of 0.5 μm or more (unit: particles / cubic foot) in the protected space (the same applies hereinafter).

Under a nitrogen atmosphere, 67.8 parts of pre-measured ethyl lactate were placed in a flask (reactor) equipped with a nitrogen inlet, a stirrer, a condenser, a dropping funnel, and a thermometer. The flask was placed in a water bath, and the temperature of the solution in the flask was raised to 80 ° C. while stirring the inside of the flask.
Separately from this, a dropping solution containing the following monomers, a solvent, and a polymerization initiator measured in advance was prepared.
The obtained dropping solution was dropped from the funnel into the flask at a constant dropping rate over a period of 4 hours, and the temperature at 80 ° C. was maintained for 3 hours.
Seven hours after the start of the dropping of the dropping solution, the reaction was stopped by cooling to 25 ° C to obtain a polymerization reaction solution.
28.56 parts (40 mol%) of monomer m-1,
32.93 parts (40 mol%) of monomer m-2,
19.82 parts (20 mol%) of monomer m-3,
122.0 parts of ethyl lactate,
2.415 parts of dimethyl-2,2'-azobisisobutyrate (2.5 mol% based on the total amount of the monomers supplied).

The resulting polymerization reaction solution was added dropwise to a 10-fold amount (by volume, hereinafter the same) of a poor solvent while stirring the poor solvent to precipitate a polymer (white precipitate) (reprecipitation). Process). As a poor solvent, a mixed solvent of methanol and water (methanol / water = 80/20 volume ratio) was used.
The precipitate was separated by filtration to obtain a wet polymer powder. Again, the same amount of methanol and water as above was added to a mixed solvent (methanol / water = 85/15 by volume), and the precipitate was washed with stirring. Then, the precipitate after the washing was separated by filtration to obtain 160 parts of a polymer wet powder [releasing step].

160 parts of the obtained polymer wet powder is withdrawn through a filter into a container having no outside air intake, and is transferred to a dissolving tank via an open air space with the container opening closed to dissolve the polymer wet powder. It was put into the tank. The wet powder in the dissolution tank was mixed and dissolved with 600 parts of PGMEA, and while controlling the temperature of the obtained solution at 20 ° C., the pressure difference before and after filtration was 70 kPa with a nylon filter cartridge having a rated filtration accuracy of 0.04 μm. The polymer solution was filtered under pressure so that the pressure difference before and after the filtration became 70 ± 10 kPa until the 90% by mass of the polymer solution passed, while controlling the discharge pressure of the liquid sending pump. [Purification step after redissolution].
The obtained filtrate (the polymer solution after filtration) was concentrated under the conditions of a pressure of 10 kPa and a temperature of 40 ° C. When the distillate was no longer produced, the conditions were changed to a pressure of 5 kPa and a temperature of 55 ° C. Concentration was performed until the concentration reached 20% by mass [concentration step].
While controlling the temperature of the obtained polymer solution after concentration at 20 ° C., pressure was applied by a nylon filter cartridge (filtration filter) having a rated filtration accuracy of 0.04 μm so that the differential pressure before and after filtration was 100 kPa. Until 90% by mass of the polymer solution passes through, the mixture is filtered under pressure while controlling the discharge pressure of the liquid sending pump so that the differential pressure before and after filtration becomes 100 ± 10 kPa. A polymer solution for semiconductor lithography (P1) was obtained by mass% (purification step after concentration).
At the end of the filtration, the polymer solution was not filled in the filtration filter, and the differential pressure before and after the filtration was 0 kPa.
The obtained polymer solution for semiconductor lithography (P1) was filled in a container, and the remaining part of the container was hermetically sealed with the gas in the protective space contained therein [filling step].
The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer solution for semiconductor lithography (P1) obtained 35 hours after the start of the production were measured. Table 2 shows the results.
Further, the metal content (metal concentration in terms of polymer solid content) was measured. Table 2 shows the measurement results (unit: ppb).

[Evaluation of resist composition]
500 parts of a polymer solution for semiconductor lithography (P1) filled in a container, 2 parts of triphenylsulfonium triflate as a photoacid generator, and PGMEA as a solvent were mixed at a polymer concentration of 12.5 mass. % To form a uniform solution, and filtered while applying a pressure such that the filtration pressure difference becomes 200 kPa with a polyethylene cartridge filter having a pore size of 0.02 μm while controlling the temperature at 20 ° C. to obtain a resist composition. Got. The sensitivity (Eth sensitivity, unit: mJ / cm ² ) of the obtained resist composition was measured. Table 2 shows the results.

<Example 2>
In Example 1, the protection space was changed as shown in Table 1. That is, the initial flow rate (air volume) of the gas supplied into the protection space was set to 40 times the volume of the protection space per hour, and the differential pressure in the filter was controlled to be maintained within a range of 150 ± 10 Pa. . As the filter, the same new HEPA filter as in Example 1 was used. Materials such as monomers used in the same lot as in Example 1 were used. The air volume at the end of the production of the polymer was 40 times the protected space volume per hour.
Otherwise, a polymer solution for semiconductor lithography was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 2 (the same applies hereinafter).

<Example 3>
In Example 1, the protection space was changed as shown in Table 1. That is, the initial flow rate (air volume) of the gas supplied into the protection space was set to 16 times the volume of the protection space per hour, and the pressure difference in the filter was controlled to be maintained within the range of 140 ± 10 Pa. . The filter was changed to a HEPA filter after being used for 700 hours. Materials such as monomers used in the same lot as in Example 1 were used. The air volume at the end of the production of the polymer was 16 times the protected space volume per hour.
Otherwise, a polymer solution for semiconductor lithography was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

<Example 4>
The steps from the measurement step and the polymerization step to the concentration step were performed under the same conditions as in Example 1. In the purification step after concentration, the pore size of the filtration filter was changed to 0.05 μm. That is, Protego Plus LT (trade name, manufactured by Nippon Integris Co., Ltd.) was used as a filtration filter.
Otherwise, a polymer solution for semiconductor lithography was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

<Comparative Example 1>
In Example 1, the HEPA filter was changed to a new medium-performance filter. The filter used has a rated air volume of 56 cubic meters per minute, an average particle repair rate of 60% or more (JIS B 9908 type 2 colorimetric method), and an initial pressure loss of 110 Pa or less. .
The protection space was changed as shown in Table 1. That is, the initial flow rate (air volume) of the gas supplied into the protection space is set to 20 times the volume of the protection space per hour, which is the same as that of the first embodiment, and the differential pressure in the filter is maintained within the range of 50 ± 5 Pa. Managed. Materials such as monomers used in the same lot as in Example 1 were used. The air volume at the end of the production of the polymer was 20 times the protected space volume per hour.
Otherwise, a polymer solution for semiconductor lithography was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

<Comparative Example 2>
In Example 1, the protection space was changed as shown in Table 1. That is, the initial flow rate (air volume) of the gas supplied into the protection space was set to four times the volume of the protection space per hour, and the differential pressure in the filter was controlled to be maintained within the range of 40 ± 5 Pa. . As the filter, the same new HEPA filter as in Example 1 was used. Materials such as monomers used in the same lot as in Example 1 were used. The air volume at the end of the production of the polymer was four times the volume of the protected space per hour.
Otherwise, a polymer solution for semiconductor lithography was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

<Comparative Example 3>
In Example 1, the HEPA filter was changed to a HEPA filter after being used for 5000 hours. The protection space was changed as shown in Table 1. That is, the initial flow rate (air volume) of the gas supplied into the protection space was set to 9 times the volume of the protection space per hour, and the pressure difference in the filter was controlled to be maintained within the range of 260 ± 30 Pa. Materials such as monomers used in the same lot as in Example 1 were used. The air volume at the end of the production of the polymer was 9 times the protected space volume per hour.
Otherwise, a polymer solution for semiconductor lithography was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

As shown in the results of Tables 1 and 2, the measuring step and the filling step were performed in the protected space, and gas was continuously supplied into the protected space via a filter. In Examples 1 to 4 controlled to be maintained at 220 Pa, the metal ion impurities in the polymer solution for semiconductor lithography were reduced even though the process between the reslurry process and the purification process after re-dissolution was performed offline. Highly eliminated.
On the other hand, in Comparative Examples 1 and 2 in which the differential pressure of the filter is too low than the above range, or in Comparative Example 3 in which the metal ion impurities in the polymer solution for semiconductor lithography are significantly higher than those in Examples 1 to 4. Was.
The weight average molecular weight, molecular weight distribution, and sensitivity of the polymer did not differ between Examples 1 to 4 and Comparative Examples 1 to 3.

Claims (6)

A filling step of filling the container with a polymer or a polymer solution for lithography and sealing the container,
Performing the filling step in a protected space,
A gas in the protected space;
A method for producing a lithography material, wherein the lithography polymer or polymer solution is contained in a container,
In the protection space,
The gas passing through a filter having a particle collection rate of 99.97% or more with respect to particles having a particle diameter of 0.3 μm at a rated air flow rate and having an initial pressure loss of 245 Pa or less is collected per hour. Gas of 10 times or more and 200 times or less of the protection space capacity is continuously supplied at the air volume passing through the filter ,
Maintaining the differential pressure before and after the filter at 60-220 Pa,
A method for producing a lithography material.   2. The lithographic material according to claim 1, wherein a differential pressure before and after the passage of the filter is maintained at Z ± 50 Pa (Z indicates a median of a range of the differential pressure and 110 Pa ≦ Z ≦ 150 Pa). Manufacturing method. Further, a measuring step of measuring a polymerization raw material used for the polymerization reaction,
A polymerization step of performing a polymerization reaction by supplying the measured polymerization raw materials to a polymerization vessel,
Performing the weighing step in a second protected space;
In the second protected space,
The gas passing through the second filter having a particle collection rate of 99.97% or more for particles having a particle diameter of 0.3 μm at a rated air flow and having an initial pressure loss of 245 Pa or less is 1 The gas of 10 times or more and 200 times or less of the protection space capacity per hour is continuously supplied at the air volume passing through the filter ,
Maintaining the differential pressure before and after passing through the second filter at 60 to 220 Pa,
A method for producing a lithography material according to claim 1.   4. The pressure difference according to claim 3, wherein the pressure difference before and after the passage through the second filter is maintained at Z ± 50 Pa (Z indicates a median of a range of the pressure difference and 110 Pa ≦ Z ≦ 150 Pa). 5. A method for producing a lithography material. A step of producing a lithography material by the production method according to any one of claims 1 to 4,
A method for producing a lithography composition, comprising a step of mixing a polymer for lithography in the container with a compound capable of generating an acid upon irradiation with actinic rays or radiation.   A step of producing a resist composition by the method for producing a lithographic composition according to claim 5, a step of applying the obtained resist composition on a surface to be processed of a substrate to form a resist film, and the resist film A method of manufacturing a substrate on which a pattern is formed, comprising: a step of exposing a substrate to light and a step of developing the exposed resist film using a developer.