JP2010189563A - Method for removing metal ion impurity in polymer compound for photolithography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently removing metal ion impurities or gel particles without causing changes in the chemical structures of a polymer compound suitably in use for compositions for photoresists or anti-reflection films due to the reaction with strongly acidic ion exchange groups. <P>SOLUTION: The invention relates to a method for removing metal ion impurities in a solution containing a polymer compound with a crosslinking agent attached to its side chains. The method includes passing the solution through not less than one filter which does not contain strong acid ion exchange groups in the filter medium and contain charge controllers generating zeta potential. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a polymer compound suitable for use as a composition for photolithography, for example, a photoresist or an antireflection film composition.

  Conventionally, fine processing by photolithography has been used in a semiconductor device manufacturing process. For example, a thin film of a photolithography composition such as a photoresist or an antireflection film is formed on a semiconductor substrate such as a silicon wafer, and then a semiconductor. By irradiating actinic rays such as ultraviolet rays through a mask pattern on which a device pattern is drawn and developing the photoresist pattern as a protective film, the substrate is etched to correspond to the pattern on the substrate surface. Fine irregularities are formed.

  Metal ion contamination is a major factor in the production of high density integrated circuits, computer chips and computer hard drives, often resulting in increased defects and yield loss, resulting in reduced performance. For example, in a plasma process, if metal ions such as sodium and iron are present in a photolithography composition, contamination may occur during plasma stripping. However, these problems can be mitigated to a substantial extent in the manufacturing process by utilizing contaminant HCl gettering during the high temperature anneal cycle.

  On the other hand, when producing a polymer compound such as a photoresist and an antireflection film as a lithography composition, free acid or gel particles may remain or be generated in the polymer compound and / or polymer compound solution. is there. These factors can cause defects in photoresists, antireflective coatings, and other electronic materials such as hard mask coatings, interlayer coatings, and fill layer coatings.

  With the development of microfabrication techniques such as photolithography, electronic devices have become more sophisticated, and it is difficult to completely solve these problems. It has often been observed that the presence of very low levels of metal ion impurities reduces the performance and stability of semiconductor devices, and these main factors are particularly the sodium and iron ions contained in the photolithography composition. It has been confirmed that.

  Furthermore, it has also been found that metal ion impurity concentrations of less than 100 ppb in photolithography compositions adversely affect the performance and stability of such electronic devices. Conventionally, the metal ion impurity concentration in the photolithography composition is selected by selecting a material that satisfies the strict impurity concentration standard, and the thorough process management is performed so that the metal ion impurity is not mixed at the adjustment stage of the photolithography composition. It is managed by that.

  Patent Documents 1 and 2 disclose a method of removing ionic impurities and metal ion impurities from a photoresist composition using a filter containing an ion exchange resin. Furthermore, Patent Literature 3 and Patent Literature 4 disclose a metal removal method by potential adsorption.

US Pat. No. 6,103,122 JP 2007-291387 A JP-A-8-165313 Japanese Patent Laid-Open No. 10-237125

  However, along with the recent miniaturization of semiconductor integrated circuits, high reproducibility of lithographic characteristics is required not only in the process of removing impurities such as metal ions but also in the physical properties of the composition for photolithography. High reproducibility is required for the physical properties of the polymer compound in the photoresist composition or antireflective coating composition, which is a composition contained in the composition, such as molecular weight, dispersion degree, and optical constant.

  In other words, it is necessary to control the reduction of metal ion impurities contained in the composition for photolithography and the high reproducibility of the polymer compound used therein in a very precise region, and the refractive index and extinction that are optical constants. Since the coefficient is greatly influenced by the polymer compound, it is required to remove metal ion impurities without changing the chemical structure of the polymer compound. On the other hand, in Patent Documents 1 to 4, the filtration process is performed using a filter containing a strongly acidic ion exchange resin, and the conventional techniques used to remove such metal ion impurities are used. Problems such as elimination of protective groups in the photoresist composition by chemical reaction with these ion-exchange groups or progress of the crosslinking reaction of the antireflection film composition containing a polymer compound having a crosslinking agent added to the polymer side chain was there.

  The first gist of the present invention is a solution containing a polymer compound in which a cross-linking agent is added to a side chain, and one or more containing a charge control agent that does not contain a strong acidic ion exchange group in the filter medium and generates a zeta potential. In this method, the metal ion impurities in the solution are removed by passing the filter.

  The second gist of the present invention resides in a solution containing a polymer compound in which each metal ion impurity concentration is less than 100 ppb and obtained by the above method and having a crosslinking agent added to the side chain.

  According to the above method, it is possible to remove metal ion impurities contained in a polymer compound suitable for use in a lithography process or a solution containing the polymer compound to a very low concentration.

  Further, by using the method for removing metal ion impurities of the present invention, a polymer compound suitable for use in a photoresist composition or an antireflection film composition is reacted with a strongly acidic ion-exchange group. Metal ion impurities or gel particles can be efficiently removed without causing a change in chemical structure or the like.

It is a GPC chart (acid side) by a pH dependence test. It is a GPC chart (basic side) by a pH dependence test.

  In the present specification, “(meth) acrylate” means acrylate or methacrylate, and “(meth) acrylic polymer compound” means an acrylic polymer compound or a methacrylic polymer compound.

<Polymer compound with a crosslinking agent added to the side chain>
In the present invention, the polymer compound in which a crosslinking agent is added to the side chain may be one in which a crosslinking agent is added to the side chain of the polymer compound having a site that absorbs actinic rays used in the lithography process. That's fine.

  The polymer compound includes, for example, an aromatic ring and / or isocyanuric acid, and is typically a (meth) acrylate monomer, or at least two kinds including a carboxylic acid and a hydroxyl group as functional groups. Examples thereof include (meth) acrylic polymer compounds produced by polymerizing monomers, polyester polymer compounds, polyether polymer compounds, and polyamide polymer compounds. Although not particularly limited, a (meth) acrylic polymer compound or a polyester polymer compound is preferable from the viewpoint of antireflection film performance.

Examples of the crosslinking agent added to the side chain in the polymer compound include glycoluril, methylated glycoluril, butylated glycoluril, tetramethoxyglycoluril, methylated melamine resin, N-methoxymethyl-melamine, and urethane. Selected from the group comprising urea, amino groups or vinyl ethers.
In particular, glycoluril is preferable from the viewpoint of excellent antireflection film performance. Furthermore, the etching rate can be improved by combining non-aromatic characteristics.

  The polyester-based polymer compound can be obtained by, for example, a polycondensation reaction by dissolving at least two monomers containing a carboxylic acid and a hydroxyl group as functional groups in a polymerization solvent and heating to a temperature suitable for the polymerization reaction. . Although not particularly limited, the condensation polymerization reaction is preferably performed at 100 to 150 ° C, more preferably 120 to 145 ° C. From the viewpoint of shortening the reaction time until the target molecular weight is reached and precise control of the molecular weight, a condensation polymerization reaction within the above range is preferred.

  Next, an acid catalyst (for example, p-toluenesulfonic acid), a cross-linking agent (for example, glycoluril or the like) is added to the reaction solution containing the polyester polymer compound obtained by the condensation polymerization reaction of the functional group carboxylic acid and hydroxyl group. By adding and reacting melamine), a crosslinking agent can be added to the functional group contained in the polyester polymer compound, and a polymer compound in which a crosslinking agent is added to the side chain of the polymer compound is synthesized. be able to. This crosslinking agent addition reaction is desirably 50 ° C. or less, preferably 15 to 30 ° C., and more preferably 18 to 22 ° C. From the viewpoint of both efficient progress of the crosslinking agent addition reaction and precise control of the molecular weight, it is preferable to carry out the crosslinking agent addition reaction within the above range.

  Although it does not restrict | limit especially as a polymerization solvent used for superposition | polymerization of the said polyester-type high molecular compound, The solvent which can melt | dissolve any of a monomer, an acid catalyst, and a polymer is preferable. Examples of such an organic solvent include anisole, 1,4-dioxane, isopropyl alcohol, acetone, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, γ-butyrolactone, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and the like.

  In the above polycondensation reaction, it is preferable to control the dehydration and dealcoholization reaction using a monomer in which a carboxylic acid as a functional group is protected with an alkyl group. Since gelation etc. can be suppressed by this, it is possible to obtain the polyester-type high molecular compound suitable for using for the composition for lithography, especially the high molecular compound for anti-reflective films.

  The (meth) acrylic polymer compound can be obtained using a technique known in the prior art. For example, it is synthesized by a free radical polymerization technique using 2′-azobisisobutyronitrile (AIBN), dimethyl 2,2′-azobis (2-methylpropionate) (V-601) or the like as a polymerization initiator. be able to.

  For example, the (meth) acrylic polymer compound can be obtained by solution polymerization. The polymerization method for the solution polymerization is not particularly limited, and may be batch polymerization or solution dropping polymerization. In particular, from the viewpoint of easily obtaining a polymer having a narrow composition distribution and / or molecular weight distribution, a polymerization method called dropping polymerization in which a monomer is dropped into a polymerization vessel is preferable. The monomer to be dropped may be only the monomer, or may be a solution in which the monomer is dissolved in an organic solvent.

  In the dropping polymerization method, for example, an organic solvent is previously charged in a polymerization vessel (this organic solvent is also referred to as “charging solvent”), heated to a predetermined polymerization temperature, and then a monomer and a polymerization initiator are independently or arbitrarily selected. In this combination, a solution dissolved in an organic solvent (this organic solvent is also referred to as “dropping solvent”) is dropped into the charged solvent. The monomer may be dropped without dissolving in the dropping solvent. In that case, the polymerization initiator may be dissolved in the monomer, or a solution in which only the polymerization initiator is dissolved in the organic solvent is dropped into the organic solvent. May be. Further, the monomer or the polymerization initiator may be dropped into the polymerization vessel in a state where the charged solvent is not present in the polymerization vessel.

  The polymerization solvent used for the polymerization of the polymer compound is not particularly limited, but a solvent that can dissolve any of the monomer, the polymerization initiator, and the polymer is preferable. Examples of such an organic solvent include 1,4-dioxane, isopropyl alcohol, acetone, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, γ-butyrolactone, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and the like.

  The monomer and the polymerization initiator may be directly dropped from an independent storage tank to a charged solvent heated to a predetermined polymerization temperature, or immediately before being dropped from an independent storage tank to a charged solvent heated to a predetermined polymerization temperature. And may be added dropwise to the charged solvent.

  Furthermore, the timing at which the monomer or the polymerization initiator is dropped into the charged solvent may be dropped after the monomer has been dropped first, or the monomer and the polymerization initiator may be dropped at the same timing. Good. These dropping speeds 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, or intermittently dropping. May be stopped or started.

  Although the polymerization temperature in the dropping polymerization method is not particularly limited, it is usually preferably in the range of 50 to 150 ° C.

  The amount of the polymerization solvent used is not particularly limited, and an optimal one can be selected as appropriate. Usually, it is desirable to use within the range of 30-70 mass parts with respect to 100 mass parts of monomer whole quantity used for copolymerization.

  The amount of the charged solvent is not particularly limited, and an optimal one can be selected as appropriate. Usually, it is desirable to use within the range of 30-70 mass parts with respect to 100 mass parts of monomer whole quantity used for copolymerization.

  The amount of the polymerization initiator used is not particularly limited, and from the viewpoint of increasing the yield of the copolymer, it is preferably 0.3 mol% or more with respect to 100 mol% of the total amount of monomers used in the copolymer, and preferably 1 mol%. The above is preferable, and from the viewpoint of narrowing the molecular weight distribution of the copolymer, 30 mol% or less is desirable with respect to 100 mol% of the total amount of monomers used for copolymerization.

  After cooling the solution containing the polymer compound obtained by the above method, an acid catalyst such as p-toluenesulfonic acid and a cross-linking agent such as tetramethoxyglycoluril or melamine are added and reacted ( A crosslinking agent can be added to a crosslinking site such as a hydroxyl group contained in the (meth) acrylic resin. This crosslinking agent addition reaction is desirably 50 ° C. or less, preferably 15 to 30 ° C., and more preferably 18 to 22 ° C. From the viewpoint of both efficient progress of the crosslinking agent addition reaction and precise control of the molecular weight, it is preferable to carry out the crosslinking agent addition reaction within the above range.

<Filter>
The solution containing the polymer compound obtained as described above often contains impurities such as metal ions from the raw materials or in the manufacturing process, and it is also clear that these impurities such as metal ions adversely affect the performance and stability of the electronic device. Therefore, it is necessary to remove impurities such as the above metal ions to a low concentration by filtration or the like.

  In the present invention, in order to remove impurities such as metal ions in the solution to a low concentration, the solution does not contain a strongly acidic ion exchange group in the filter medium and contains one or more charge control agents that generate a zeta potential. Processed through a filter.

  By using the above filter, it is possible to efficiently remove metal ion impurities and gel particles contained in the solution without causing a change in chemical structure or the like due to the reaction of the polymer compound with the strongly acidic ion-exchange group. Can do.

  Examples of the strongly acidic ion exchange group include a sulfonic acid group. For example, when a polymer compound has a structure capable of causing a chemical reaction with an acid (for example, a cross-linking agent, etc.), if a filter containing such a strong acidic ion-exchange group is used for filtration, the cross-linking reaction proceeds, resulting Changes in the chemical structure and molecular weight of molecular compounds can occur. By performing filtration using such a filter that does not contain a strongly acidic ion exchange group, the progress of the crosslinking reaction as described above can be suppressed.

  In the above filter, the charge control agent that generates a zeta potential is described in, for example, a polyamide-amine epichlorohydrin cation resin described in JP-B 63-17486, and JP-B 36-20045. Resin reacted with N, N′-diethanolpiperazine, melamine, formalin and glycerin phthalate, such as melamine-formaldehyde cation resin as described in US Pat. No. 4,0071,13, described in US Pat. No. 2,802,820 A dicyandiamide, a reaction product of monoethanolamine and formaldehyde, and an aminotriazine resin as described in US Pat. No. 2,839,506 are generally used. Among these, polyamide-amine epichlorohydrin cationic resin is particularly preferably used because it gives a stable cationic charge to the filter.

  Although the said filter is not specifically limited, Preferably it is a sheet form. When used as a filter sheet, the pore size and number of filter sheets can be appropriately selected in the production process.

  Although it does not specifically limit, As a uniform state of the said filter (sheet | seat), you may be a filter sheet which has an average hole diameter of about 0.5-10 micrometers.

  In the filter (sheet), the particulate filter aid is preferably uniformly distributed, and the metal ion impurity can be removed from the solution by causing the particulate filter aid to adsorb the metal ion impurity to the potential. .

  The filter (sheet) includes a self-supporting fiber matrix, and the fiber matrix can include a particulate filter aid, optionally a binder resin, immobilized therein. Furthermore, it is preferable that the particulate filter aid and optionally contained binder resin are uniformly distributed in the matrix cross section.

  There are various kinds of particulate filter aids contained in the filter (sheet), and are produced, for example, by diatomaceous earth, magnesia, perlite, talc, colloidal silica, polymeric particulates, such as emulsion polymerization or suspension polymerization. For example, polystyrene, polyacrylate, polyvinyl acetate, polyethylene, activated carbon, clay and the like.

  Suitable self-supporting fibrous matrices for using the filter (sheet) include, for example, polyacrylonitrile fiber, nylon fiber, rayon fiber, polyvinyl chloride fiber, cellulose fiber, such as wood pulp and cotton, and cellulose acetate. For example, fiber. Preferably, the self-supporting matrix is a matrix composed of cellulose fibers. The cellulose fibers are preferably unbeaten cellulose pulp having a Canadian standard freeness of about +400 to about +800 ml and a Canadian standard form of about +100 to about −600 ml, as disclosed in US Pat. No. 4,606,824. Derived from a cellulose pulp mixture containing highly beaten cellulose pulp having a freeness.

  Binder resins that can optionally be included in the filter include melamine formaldehyde colloids disclosed in US Pat. Nos. 4,0071, and 4,007114, and polyamide-polyamines, disclosed in US Pat. No. 4,859,340. Examples thereof include epichlorohydrin resins and polyalkylene oxides disclosed in US Pat. No. 4,596,660.

  After washing the solution containing the polymer compound with ultrapure water, passing the filter through a suitable organic solvent or a solvent in which the polymer compound is dissolved, the metal ion impurities into the particulate filter aid contained in the filter As a result of the potential adsorption, metal ion impurities can be removed to a very low concentration.

The filter having the above-mentioned properties is preferably a CUNO ^™ Zeta Plus ^™ filter cartridge EC commercially available from Sumitomo 3M, and can be obtained as a GN grade.

  Considering the progress of the crosslinking reaction by the catalytic action of the acid and the decomposition of the ester bond by the base, the optimum pH range for carrying out the present invention is preferably 3.5 to 11.0. Furthermore, it is preferable to implement in the temperature range of 0-40 degreeC. More preferably, it is carried out in a temperature range of 10 to 30 ° C. In order to suppress the progress of the cross-linking reaction due to the catalytic operation of the acid and the decomposition of the ester bond and the like by the base, and maintain the optimum viscosity for filtration, it is preferably carried out in the above range.

  In one embodiment of the present invention, the polymer compounds suitable for use as a lithographic composition are each less than 100 ppb, preferably less than 50 ppb, more preferably less than 25 ppb each, particularly preferably less than 10 ppb each. Has metal ion impurities. Moreover, the gel particles can be removed simultaneously by using the filter.

  The solution in which the metal ion impurities contained in the solution obtained by the polymerization are removed by passing through the filter, anisole, 1,4-dioxane, acetone, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, After dilution to a suitable concentration with a good solvent such as γ-butyrolactone, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, etc., it consists of methanol, isopropyl alcohol, diisopropyl ether, water, hexane, heptane, etc., or a mixed solvent thereof. The polymer may be precipitated by dropping it into a large amount of poor solvent.

  This process is generally called reprecipitation, and is effective for removing unreacted monomers, polymerization initiators, acid catalysts and the like remaining in the polymer solution. If these unreacted substances remain as they are, there is a high possibility that they will adversely affect the performance of the resist and the antireflection film, and it is preferable to remove them as much as possible. The reprecipitation step can be omitted in some cases. Thereafter, the precipitate is filtered off and sufficiently dried to obtain a film-forming resin suitable for use in a photolithography composition. Moreover, after filtering off, it is also possible to use it as a moist powder without including a drying step.

  The characteristic of the above method is that the metal ion impurities are removed by potential adsorption to the particulate filter aid contained in the filter without contacting the strongly acidic ion-exchange group. Even when a sensitive group is contained, metal ion impurities and gel particles can be easily and efficiently removed without being affected by the removal of the protecting group.

  Furthermore, in the case of a polymer compound used for an antireflection film, a crosslinking agent that undergoes a crosslinking reaction by an acid catalyst may be contained in the polymer compound skeleton or a solution in which it is dissolved. Therefore, by using the method for removing metal ion impurities according to the present invention, metal ion impurities and gel particles can be easily and efficiently removed without being affected by the progress of a crosslinking reaction by using an acid catalyst before and after passing through a filter. can do.

  By treating a solution containing a polymer compound suitable for use as a photolithography composition in the method described herein, a metal ion impurity derived from a raw material and / or a manufacturing process is reduced to a very low concentration. Can be removed. At the same time, the gel particles contained in the solution can also be efficiently removed.

The following specific examples are examples of a method for producing a polymer compound using the present invention. However, these examples are not intended to limit or reduce the scope of the invention in any way, but teach conditions, parameters or values that must be used exclusively to practice the invention. It should not be construed to do. Also, unless otherwise specified, all parts and percentages are values based on weight.
The weight average molecular weights of the polymer compounds obtained in Synthesis Examples 1 to 4 below were determined in terms of polystyrene by GPC (Gel Permeation Chromatography: Tosoh HLC8220GP) (measurement conditions: dry powder 50 mg / eluent 5 mL, elution Solution: 1.7 mM phosphoric acid / THF).

Synthesis example 1
1,3,5-tris (2-hydroxyethyl) isocyanurate (33.56 g, 0.129 mol), dimethyl decahydro-2,6-naphthalenedicarboxylate (32.68 g, 0.129 mol), p-toluenesulfonic acid -A hydrate (pTSA) (1.303 g, 6.85 mmol) and anisole (39.80 g) were charged into a three-necked flask and subjected to dehydration and demethanol reaction at 130 ° C using a Dean-Stark trap. Polymerized for hours. Thereafter, it was diluted with tetrahydrofuran (THF), tetramethoxyglycoluril (TMGU) (12.81 g, 0.805 mol) was added, and the mixture was reacted at 20 ° C. for 5.5 hours to obtain triethylamine (0.6932 g, 6.85 mmol). To stop the reaction. This reaction solution is diluted with THF and IPA (2-propanol), reprecipitated into a mixture of hexane and IPA, TMGU is added to the hydroxyl group of THEIC in the polymer compound, and the polyester polymer represented by the following formula A compound (weight average molecular weight: 9,142, yield: about 40%) was obtained.

Synthesis example 2
1,3,5-tris (2-hydroxyethyl) isocyanurate (33.56 g, 0.129 mol), dimethyl 2,6-naphthalenedicarboxylate (34.10 g, 0.129 mol), p-toluenesulfonic acid-hydrated (PTSA) (1.303 g, 6.85 mmol) and anisole (39.80 g) were charged into a three-necked flask and polymerized at 130 ° C. for 10 hours while performing dehydration and demethanol reaction using a Dean-Stark trap. . Thereafter, it was diluted with tetrahydrofuran (THF), tetramethoxyglycoluril (TMGU) (12.81 g, 0.805 mol) was added, and the mixture was reacted at 20 ° C. for 5.5 hours to obtain triethylamine (0.6932 g, 6.85 mmol). To stop the reaction. This reaction solution is diluted with THF and IPA (2-propanol), reprecipitated into a mixture of hexane and IPA, TMGU is added to the hydroxyl group of THEIC in the polymer compound, and the polyester polymer represented by the following formula A compound (weight average molecular weight: 10,378, yield: about 45%) was obtained.

Synthesis example 3
1,3,5-tris (2-hydroxyethyl) isocyanurate (33.56 g, 0.129 mol), 1,3-dimethylcyclohexanedicarboxylate (25.83 g, 0.129 mol), p-toluenesulfonic acid- Hydrate (pTSA) (1.303 g, 6.85 mmol) and anisole (39.80 g) are charged into a three-necked flask and subjected to dehydration and demethanol reaction using a Dean-Stark trap for 10 hours at 130 ° C. Polymerized. Thereafter, it was diluted with tetrahydrofuran (THF), tetramethoxyglycoluril (TMGU) (12.81 g, 0.805 mol) was added, and the mixture was reacted at 20 ° C. for 5.5 hours to obtain triethylamine (0.6932 g, 6.85 mmol). To stop the reaction. The reaction solution is diluted with THF and IPA (2-propanol), reprecipitated into a mixture of hexane and IPA, TMGU is added to the hydroxyl group of THEIC of the polymer compound, and a polyester polymer compound represented by the following formula ( Weight average molecular weight: 7,572, yield: about 40%).

Synthesis example 4
Using ethyl lactate as a polymerization solvent, γ-butyrolactone-2-yl methacrylate (75.1 g, 0.31 mol), 6-hydroxynaphthalen-2-2-2ylmethyl methacrylate (53.6 g, 0.31 mol), 2 ′ -A high molecular compound was obtained by the dropping solution polymerization method of azobisisobutyronitrile (AIBN) (0.328 g, 2.0 mmol). Thereafter, at 20 ° C., p-toluenesulfonic acid and tetramethoxyglycoluril were added and reacted for 7 hours, and the reaction was stopped by adding triethylamine (0.6932 g, 6.85 mmol). This reaction solution was diluted 1.5 times with ethyl lactate, reprecipitated into IPE (diisopropyl ether), TMGU was added to the hydroxyl group in the polymer compound, and a methacrylic polymer compound represented by Formula 4 (weight average molecular weight) : 21,204, yield: about 85%).

Example 1
Metal ion impurities were removed by a filter sheet (CUNO ^™ Zeta Plus ^™ filter cartridge EC GN grade) obtained by washing the solution containing the polymer compound obtained in Synthesis Example 1 with 5000 mL of ultrapure water and 1000 mL of THF. The solution passed through the filter sheet was reprecipitated in a poor solvent of a mixture of hexane and 2-propanol (hexane / 2-propanol = 1/9) to obtain a polyester polymer compound. The obtained compound was dried under reduced pressure at 40 ° C. for 60 hours, and the weight average molecular weight (Mw) and Z average molecular weight (Mz) were calculated in terms of polystyrene using GPC (Gel Permeation Chromatography: HLC8220GP) manufactured by Tosoh Corporation. (Separation column: Showa Denko, Shodex GPC K-805L (trade name), measurement conditions: dry powder 50 mg / eluent 5 mL, eluent: 1.7 mM phosphoric acid / THF, measurement temperature: 40 ° C., detector: Differential refractive index detector). The solution containing the polymer compound obtained through the filter was subjected to metal analysis using a high frequency inductively coupled plasma mass spectrometer (ICP-MS-Inductively Coupled Plasma Mass Spectrometer: 7500cs manufactured by Agilent Technologies) (measurement sample: polymer compound) Sample obtained by diluting 1.5 g of dry powder of 100 times with N-methyl-2-pyrrolidone purified by distillation), measurement method: standard addition method

Example 2
After removing metal ion impurities with a filter sheet (CUNO ^TM Zeta Plus ^TM filter cartridge EC GN grade) washed with 5000 mL of ultrapure water and 1000 mL of THF, the solution containing the polymer compound obtained in Synthesis Example 2 After the treatment in the same manner as in Synthesis Example 1, the molecular weight and metal ion impurity concentration were analyzed.

Example 3
After removing the metal ion impurities with a filter sheet (CUNO ^TM Zeta Plus ^TM filter cartridge EC GN grade) washed with 5000 mL of ultrapure water and 1000 mL of THF, the solution containing the polymer compound obtained in Synthesis Example 3 After the treatment in the same manner as in Synthesis Example 1, the molecular weight and metal ion impurity concentration were analyzed.

Example 4
After removing metal ion impurities with a filter sheet (CUNO ^TM Zeta Plus ^TM filter cartridge EC GN grade) washed with 5000 mL of ultrapure water and 1000 mL of THF, the solution containing the polymer compound obtained in Synthesis Example 4 After the treatment in the same manner as in Synthesis Example 1, the molecular weight and metal ion impurity concentration were analyzed.

Comparative Example 1
The solution containing the polymer compound obtained in Synthesis Example 1 was washed with 5000 mL of ultrapure water and 1000 mL of THF, and a filter sheet containing a sulfonic acid group as a strongly acidic ion-exchange group (CUNO ^TM Zeta Plus ^TM filter cartridge EC SH Grade)) to remove metal ion impurities. Then, after processing by the method similar to the synthesis example 1, the molecular weight and the metal ion impurity concentration were analyzed.

Comparative Example 2
The solution containing the polymer compound obtained in Synthesis Example 2 was washed with 5000 mL of ultrapure water and 1000 mL of THF. A filter sheet containing a sulfonic acid group as a strongly acidic ion-exchange group (CUNO ^TM Zeta Plus ^TM filter cartridge EC SH Grade)) to remove metal ion impurities. Then, after processing by the method similar to the synthesis example 1, the molecular weight and the metal ion impurity concentration were analyzed.

Comparative Example 3
The solution containing the polymer compound obtained in Synthesis Example 3 was washed with 5000 mL of ultrapure water and 1000 mL of THF. A filter sheet containing a sulfonic acid group as a strongly acidic ion-exchange group (CUNO ^TM Zeta Plus ^TM filter cartridge ECSH grade ) To remove metal ion impurities. Then, after processing by the method similar to the synthesis example 1, the molecular weight and the metal ion impurity concentration were analyzed.

Comparative Example 4
The solution containing the polymer compound obtained in Synthesis Example 4 was washed with 5000 mL of ultrapure water and 1000 mL of THF, and a filter sheet containing a sulfonic acid group as a strongly acidic ion-exchange group (CUNO ^TM Zeta Plus ^TM filter cartridge ECSH grade ) To remove metal ion impurities. Then, after processing by the method similar to the synthesis example 1, the molecular weight and the metal ion impurity concentration were analyzed.

  From the above examples and comparative examples, the results of chemical structure change by filter species and metal ion impurity removal are shown below.

  From the above comparison table, in the case of Comparative Examples 1 to 4, since the area percentage (%) of the high molecular weight component is increased, the strongly acidic ion-exchange group contained in the filter causes the polymer compound side. It can be judged that the crosslinking agent added to the chain has reacted and the crosslinking reaction has proceeded. On the other hand, it can be determined at the same time that metal ion impurities can be reduced to a level at which sufficient performance as a composition for photolithography can be exhibited even by potential adsorption that does not contain a strongly acidic ion exchange group. According to the present invention, metal ion impurities can be efficiently removed under conditions in which the chemical structure of the polymer compound is precisely controlled. Furthermore, it can be easily estimated that the control of the refractive index and the extinction coefficient affecting the lithography performance is also realized.

pH dependence test The polymer compound obtained in Example 3 was adjusted to a solid content concentration of 20% in THF, and the change in molecular weight distribution was confirmed by GPC (measurement conditions: dry powder 50 mg / eluent 5 mL, eluent: 1 .7 mM phosphoric acid / THF). 1 and 2 show GPC charts on the acidic side (pH 6.0 to pH 2.0) and the basic side (pH 6.0 to pH 13.0), respectively. In addition, Table 5 shows the molecular weight change results at each pH. A polymer compound solution obtained by adding sulfuric acid, acetic acid, triethylamine, or an aqueous sodium hydroxide solution to a target pH to a polymer compound solution in which the polymer compound was dissolved in THF so as to be 20% by mass was used. The pH was confirmed using a pH test paper. From the above test results, at pH 3.0 or less, it can be judged that the component in the high molecular weight region (Mw> 10,000) has increased and the crosslinking reaction has proceeded. Moreover, at pH 11.5 or more, the component (Mw <1000) in the low molecular weight region is increased, and it can be determined that the decomposition reaction of the ester bond is proceeding.

Claims (6)

By passing the solution containing the polymer compound having a crosslinking agent added to the side chain through one or more filters containing a charge control agent that does not contain a strong acidic ion exchange group in the filter medium and generates a zeta potential, A method for removing metal ion impurities in a solution.   The method according to claim 1, wherein the polymer compound is a polyester polymer compound.   The method according to claim 1, wherein the polymer compound is a (meth) acrylic polymer compound. The method according to any one of claims 1 to 3, wherein a skeleton of the crosslinking agent is glycoluril.   The method according to any one of claims 1 to 4, wherein the pH of the filter is in the range of 3.5 to 11.0.   The solution containing the high molecular compound by which the crosslinking agent was added to the side chain obtained by the method as described in any one of Claims 1 thru | or 5 whose concentration of each metal ion impurity is less than 100 ppb.

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