Filtering method for a liquid containing an abrasive additive, liquid containing an abrasive additive, abrasive composition, method for manufacturing an abrasive composition, and filter

Abstract

Provided: A method for filtering a liquid containing additives, which enables the use of a grinding composition to maintain a practical filter life and exhibit excellent defect reduction capabilities. The method for filtering a liquid containing grinding additives provided by the present invention includes the step of filtering the liquid containing grinding additives using a filter that meets the following conditions (1) and (2): (1) The average pore size P, measured by a pore size distribution meter, is 0.15 μm or less. (2) The average pore size S on the inlet side, measured by SEM observation, is... in Average aperture S on the outlet side out The ratio of the aperture gradient (S) in / S out () is below 3.

Description

Technical Field

[0001] This invention relates to a method for filtering liquids containing additives. More specifically, it relates to a method for filtering liquids containing additives (grinding additives) used in grinding compositions. This application claims priority based on Japanese Patent Application No. 2019-146778, filed August 8, 2019, the entire contents of which are incorporated herein by reference. Background Technology

[0002] For the surface of materials such as metals, semi-metals, non-metals, and their oxides, precision grinding is performed using a grinding composition. Typically, the purpose is to remove or reduce coarse particles and foreign matter that may cause a decrease in surface smoothness. The grinding composition and its components are filtered using various filters before being used for grinding. Patent documents 1 and 2 are cited as prior art documents relating to this technology.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. Hei 11-302633

[0006] Patent Document 2: Japanese Patent Application Publication No. 2017-75316 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In recent years, higher quality surfaces have been required for substrates such as silicon wafers and semiconductor substrates, demanding defect suppression at levels previously not considered problematic. Therefore, there is a need for more precise removal and reduction of coarse particles and foreign matter contained in abrasive compositions. For example, the technology described in Patent Document 2 involves filtering abrasive-containing liquids. However, given the trend towards higher substrate quality as described above, simply filtering abrasive particles or abrasive-containing liquids has become increasingly insufficient.

[0009] Grinding compositions not only contain abrasive grains, but also various additives (grinding additives) to improve various grinding performances. Compared to abrasive grains and coarse particles derived from abrasive grains, coarse particles and foreign matter derived from these various additives tend to have relatively small particle sizes, making them difficult to remove simultaneously with larger abrasive grains. Therefore, filtering the additives or additive-containing liquids is effective in order to remove coarse particles and foreign matter derived from additives with high precision.

[0010] In the filtration of liquids containing additives, the coarse particles originating from the additives are relatively small in size. Therefore, compared to filters used in conventional filtration of grinding compositions, filters with higher precision (i.e., those designed to remove smaller particles) are sometimes required. However, filtration based on high-precision filters is prone to clogging, and the filtration flow rate often decreases relatively early after filtration begins. Therefore, in the filtration of liquids containing additives, it is difficult to simultaneously achieve high precision in removing coarse particles and impurities originating from the additives, as well as long filter life, low pressure loss, and high flow rate.

[0011] This invention was made in view of this fact, and its object is to provide a method for filtering a liquid containing a grinding additive, wherein the grinding composition, in the filtration of the liquid containing the grinding additive, can maintain the life of a practical filter and exhibit excellent defect reduction capabilities. Another related object of this invention is to provide a liquid containing a grinding additive filtered using the above-described filtration method. Furthermore, another related object of this invention is to provide a grinding composition comprising the grinding additive contained in the filtered liquid containing the grinding additive. Another related object of this invention is to provide a method for manufacturing the grinding composition. Moreover, another related object of this invention is to provide a filter for filtering a liquid containing a grinding additive.

[0012] Solution for solving the problem

[0013] This invention provides a method for filtering a liquid containing a grinding additive. The filtration method includes a step of filtering the liquid using a filter having the following characteristics: an average pore size P measured using a perm-porometer is 0.15 μm or less; and an average pore size S on the inlet side measured using SEM. in Average aperture S on the outlet side out The ratio of the aperture gradient (S) in / S out () is below 3.

[0014] According to the filter possessing this characteristic, since the average pore size P measured by the pore size distribution meter is less than 0.15 μm, even relatively small coarse particles originating from grinding additives can be appropriately captured. Furthermore, the pore size gradient (S...) in / S out When the value is below 3, filter clogging is less likely to occur during filtration, and filter life is easily improved. Therefore, according to this filtration method, a practical filter life can be maintained in the filtration of liquids containing additives, and coarse particles and foreign matter originating from grinding additives can be removed and reduced with high precision.

[0015] In a preferred embodiment of the technology disclosed herein, the aforementioned abrasive additive comprises a water-soluble polymer. In liquids containing water-soluble polymers, sometimes a portion of the water-soluble polymer exists in a state of low solubility, associative aggregates, high molecular weight aggregates, etc., and this water-soluble polymer may be a cause of coarse particles. According to the technology described in this specification, filter life can be maintained and coarse particles originating from water-soluble polymers, as described above, can be removed with high precision. Therefore, it is meaningful to apply the technology disclosed herein to additive-containing liquids containing water-soluble polymers.

[0016] In a preferred embodiment of the technology disclosed herein, the aforementioned water-soluble polymer comprises a cellulose derivative. In liquids containing cellulose derivatives, a portion of the cellulose derivative may sometimes exist as a poorly soluble form, an associated form, a high molecular weight form, etc., and this cellulose derivative may contribute to the formation of coarse particles. The technology disclosed herein is applicable to liquids containing abrasive additives and cellulose derivatives, and can more appropriately maintain filter life and remove or reduce coarse particles originating from the additives.

[0017] In a preferred embodiment of the technology disclosed herein, the liquid comprises water. Additionally, at least a portion of the water-soluble polymer is dissolved in the water. The technology of this invention is applicable to liquids containing abrasive additives that comprise water-soluble polymers and water, with at least a portion of the water-soluble polymer dissolved in the water, enabling more suitable maintenance of filter life and removal or reduction of coarse particles originating from the additives.

[0018] In a preferred embodiment of the technology disclosed herein, the liquid substantially does not contain abrasive particles. Abrasive particles, and coarse particles derived from abrasive particles, tend to be larger in size than additives other than abrasive particles, and coarse particles derived from those additives. Therefore, filtration in a substantially abrasive-free manner is effective for high-precision filtration of additives with an average size smaller than that of abrasive particles. The filtration method disclosed herein can be used for additive-containing liquids that substantially do not contain abrasive particles, is capable of suppressing filter clogging, and accurately captures, removes, or reduces relatively small-diameter coarse particles derived from additives in additive-containing liquids.

[0019] In a preferred embodiment of the technology disclosed herein, the liquid is a filtrate that has undergone one or two or more pre-filtrations. According to this filtration method, filtering a liquid containing abrasive additives, which has had coarse particles that could cause filter clogging removed to some extent through pre-filtration, using a specific filter, easily improves filter life.

[0020] According to this specification, a liquid containing abrasive additives, filtered using any of the methods disclosed herein, is provided. This liquid containing abrasive additives readily becomes a liquid from which coarse particles and foreign matter originating from the additives are removed or reduced with high precision. With such a liquid containing abrasive additives, using it by including the abrasive additives contained in the liquid in an abrasive composition tends to improve defect reduction capabilities.

[0021] According to the specification, a grinding composition is provided, comprising a grinding additive, the grinding additive being contained in a liquid containing the grinding additive, the liquid containing the grinding additive being filtered by a filter having the following characteristics: an average pore size P measured by a pore size distribution meter is less than 0.15 μm; and an average pore size S on the inlet side measured by SEM observation. in Average aperture S on the outlet side out The ratio of the aperture gradient (S) in / S out The value is 3 or less. In the above-mentioned liquid containing abrasive additives, coarse particles and foreign matter derived from the abrasive additives can be removed or reduced with high precision. Abrasive compositions containing such abrasive additives with removed or reduced coarse particles tend to have superior defect reduction capabilities.

[0022] According to this specification, a method for manufacturing a grinding composition is provided. The method is characterized in that the grinding composition comprises a grinding additive, the grinding additive being contained in a liquid containing the grinding additive, the liquid containing the grinding additive being filtered using a filter having the following characteristics: an average pore size P measured by a pore size distribution meter is 0.15 μm or less; and an average pore size S on the inlet side measured by SEM observation. in Average aperture S on the outlet side out The ratio of the aperture gradient (S) in / S out The concentration of the abrasive additive is 3 or less. By filtering the liquid containing the abrasive additive using a filter with the above-described properties, coarse particles and foreign matter originating from the additive that may deteriorate the defect reduction ability of the abrasive composition can be removed or reduced with high precision. Therefore, by the above method, it is possible to manufacture an abrasive composition with excellent defect reduction ability.

[0023] According to this specification, a filter for use in filtering liquids containing abrasive additives is provided. The filter has the following characteristics: an average pore size P, as measured by a pore size distribution analyzer, is less than 0.15 μm; and an average pore size S on the inlet side, as measured by SEM observation. in Average aperture S on the outlet side out The ratio of the aperture gradient (S) in / Sout The concentration is 3 or less. This filter can be used for filtering liquids containing abrasive additives, maintaining a practical filter life, and precisely removing or reducing coarse particles and foreign matter contained in the liquid containing abrasive additives. Furthermore, this filter can provide abrasive compositions with excellent defect reduction properties. Detailed Implementation

[0024] The following describes suitable embodiments of the present invention. It should be noted that, for matters not specifically described in this specification but necessary for the implementation of the present invention, those skilled in the art should understand them based on existing technology and conventional technical means. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the field.

[0025] <Filtering Methods>

[0026] (Filtering target liquid)

[0027] The filtration method disclosed herein filters a liquid containing abrasive additives (hereinafter also referred to as "additive-containing liquid"). Here, in this specification, abrasive additives (hereinafter also referred to as "additives") refer to all components used in the abrasive composition other than the abrasive grains. However, the fact that the abrasive additive is a component other than the abrasive grains does not preclude the possibility that the additive itself has the function of mechanically abrading the object being abraded.

[0028] In addition, in this specification, for the convenience of distinguishing it from the filtrate containing a grinding additive (hereinafter also referred to as "filtrate containing additive"), the filtrate containing a grinding additive that is the object of filtration is also referred to as "the filtrate to be filtered".

[0029] There are no particular limitations on the additives mentioned above; they can be selected and used from a variety of additives commonly used in the field of grinding compositions. Examples of the additives mentioned above include water-soluble polymers, surfactants, basic compounds, water, chelating agents, organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, fungicides, oxidants, etc. These additives can be used alone or in combination of two or more.

[0030] (Water-soluble polymer)

[0031] The technology disclosed herein is preferably applicable to filter media containing water-soluble polymers as abrasive additives. In filter media containing water-soluble polymers, some of the water-soluble polymers sometimes exist in the form of low-solubility forms, associative forms, high-molecular-weight forms, etc. These low-solubility forms of water-soluble polymers easily become coarse particles. According to the technology disclosed herein, a practical filter lifespan can be maintained, and coarse particles originating from water-soluble polymers, as described above, can be removed with high precision. Therefore, it is meaningful to apply the technology disclosed herein to filter media containing water-soluble polymers.

[0032] There are no particular restrictions on the types of water-soluble polymers; those having at least one functional group selected from cationic, anionic, and nonionic groups can be used. Water-soluble polymers can have hydroxyl, carboxyl, acyl, acyloxy, sulfonyl, amide, quaternary ammonium, heterocyclic, vinyl, and polyoxyalkylene structures, etc.

[0033] Examples of water-soluble polymers include cellulose derivatives; starch derivatives; polymers containing oxyalkylene units, such as copolymers of ethylene oxide (EO) and propylene oxide (PO); vinyl alcohol polymers such as polyvinyl alcohol (PVA); polymers containing N-vinyl monomer units, imine derivatives, polymers containing N-(meth)acryloyl monomer units, and other nitrogen-containing polymers. Among these, vinyl alcohol polymers, cellulose derivatives, and polymers containing N-(meth)acryloyl monomer units are preferred from the viewpoint that they readily produce coarse particles, thus making them suitable for the present invention, and from the viewpoint that they can be used in grinding compositions to improve grinding performance. Cellulose derivatives are preferred, and cellulose derivatives are more preferred. These water-soluble polymers can be used alone or in combination of two or more.

[0034] Cellulose derivatives are polymers containing β-glucose units as the main repeating units. Specific examples of cellulose derivatives include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, etc. Among these, HEC is preferred.

[0035] As a water-soluble polymer, there are no particular limitations; both natural and synthetic polymers can be used. However, natural polymers have limitations in purity and foreign matter control, thus making it easier to achieve the effects of the filtration method disclosed herein.

[0036] There is no particular limitation on the weight-average molecular weight (Mw) of water-soluble polymers (e.g., cellulose derivatives). From the viewpoint of protecting the surface being ground and improving grinding performance, the Mw of water-soluble polymers is typically 0.4 × 10⁻⁶. 4 The above is appropriate, and preferably 1×104 The above, more preferably 10×10 4 The above. In a further preferred embodiment, Mw is, for example, 15 × 10. 4 The above can then be converted to 20×10 4 The above can also be 25×10 4 That's all. From the perspective of improving filter life in the filtration of the target liquid, the Mw of the water-soluble polymer can be set to approximately 300 × 10⁻⁶. 4 Below, 150×10 4 The following is appropriate. The aforementioned Mw could, for example, be 100×10. 4 The following can be 50×10 4 The following can also be 40×10 4 the following.

[0037] It should be noted that, in this specification, Mw, as a water-soluble polymer, can be a value based on gel permeation chromatography (GPC) (conversion between aqueous and polyethylene oxide systems). The GPC measuring device can be the HLC-8320GPC manufactured by Tosoh Corporation. The measurement conditions can be set as follows. The examples described later also use the same method.

[0038] [GPC Measurement Conditions]

[0039] Sample concentration: 0.1% by weight

[0040] Column: TSKgel GMPW XL

[0041] Detector: Differential refractometer

[0042] Eluent: 0.1 mol / L NaNO3 aqueous solution

[0043] Flow rate: 1.0 mL / min

[0044] Measurement temperature: 40℃

[0045] Sample injection volume: 200 μL

[0046] There is no particular limitation on the content of water-soluble polymers in the filtered liquid (when the filtered liquid contains two or more water-soluble polymers, it is their total content). For example, the content of water-soluble polymers in the filtered liquid can be set to 0.001% by weight or more, or 0.01% by weight or more. From the viewpoint of filtration efficiency, the content of water-soluble polymers in the filtered liquid is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and even more preferably 0.8% by weight or more (e.g., 1.0% by weight or more). From the viewpoint of maintaining filter life, it is appropriate for the content of water-soluble polymers in the filtered liquid to be 30% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less (e.g., 1.5% by weight or less).

[0047] The target filtration liquid disclosed herein preferably includes a surfactant. The surfactant can help improve the dispersion stability of the grinding slurry or its concentrate. There are no particular limitations on the surfactant; any of amphoteric, cationic, anionic, and nonionic surfactants can be used. Furthermore, an organic compound with a Mw of less than 4000 can be used, for example. From the viewpoint of the filterability of the target filtration liquid and the cleaning properties of the object being ground, the Mw of the surfactant is preferably 3500 or less. In another preferred embodiment of the technology disclosed herein, the Mw of the surfactant is 100 or more, more preferably 200 or more, further preferably 250 or more, and particularly preferably 300 or more. By using a surfactant having the above-mentioned Mw in the grinding composition, an improved grinding speed can be easily obtained.

[0048] The molecular weight (Mw) of a surfactant can be determined using GPC (conversion between aqueous and polyethylene glycol systems). The GPC measurement conditions can be set to the same conditions as those for measuring the Mw of water-soluble polymers. If the above conditions cannot be used to determine Mw, the value calculated from the chemical formula can be used. Examples of situations where Mw cannot be determined include cases where the surfactant's Mw is low.

[0049] Examples of surfactants include nonionic surfactants such as alkylene oxide polymers like polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glycerol ether fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene polyoxypropylene glycol and other polyoxyalkylene oxide adducts; and copolymers of various alkylene oxides (diblock, triblock, random, alternating types). Surfactants containing polyoxyalkylene structures are preferred among these surfactants. These surfactants can be used alone or in combination of two or more.

[0050] Specific examples of nonionic surfactants containing polyoxyalkylene structures include block copolymers of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymers, PEO-PPO-PEO triblock copolymers, PPO-PEO-PPO triblock copolymers, etc.), random copolymers of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecanyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene hexadecyl ether, polyoxyethylene stearyl ether, etc. Ethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene styrene phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, etc.

[0051] There is no particular limitation on the content of surfactants in the target liquid (or their total content when the target liquid contains two or more surfactants). For example, the content of surfactants in the target liquid can be set to 0.0005% by weight or more, or 0.001% by weight or more. Preferably, the content of surfactants in the target liquid is 0.01% by weight or more, more preferably 0.05% by weight or more, and even more preferably 0.08% by weight or more (e.g., 0.1% by weight or more). It is appropriate for the content of surfactants in the target liquid to be 3% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less, and even more preferably 0.3% by weight or less (e.g., 0.2% by weight or less).

[0052] (water)

[0053] The filtration liquid disclosed herein preferably contains water. The water contained in the filtration liquid can preferably be ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. For the water used, in order to minimize the obstruction of the effect of other components contained in the filtration liquid or the grinding composition, the total content of transition metal ions is preferably 100 ppb or less. For example, the purity of the water can be improved by removing impurity ions based on ion exchange resins, removing foreign matter based on filters, distillation, etc.

[0054] The filtration liquid disclosed herein, in a preferred embodiment, comprises a water-soluble polymer and water, with at least a portion of the water-soluble polymer dissolved in the water. Applying the technique disclosed herein to this filtration liquid enables the maintenance of a practical filter life and the precise removal and reduction of coarse particles originating from additives.

[0055] (Alkaline compound)

[0056] The filtration liquid disclosed herein preferably contains an alkaline compound. In this specification, an alkaline compound is defined as a compound that, when dissolved in water, raises the pH of the aqueous solution. Using an alkaline compound increases the solubility of water-soluble polymers in the filtration liquid. Examples of alkaline compounds include nitrogen-containing organic or inorganic alkaline compounds, alkali metal hydroxides, alkaline earth metal hydroxides, quaternary phosphorus compounds, various carbonates, bicarbonates, etc. Examples of nitrogen-containing alkaline compounds include quaternary ammonium compounds, ammonia, and amines (preferably water-soluble amines). Such alkaline compounds can be used alone or in combination of two or more.

[0057] Among these basic compounds, at least one basic compound selected from alkali metal hydroxides, quaternary ammonium hydroxides, and ammonia may be preferred. Potassium hydroxide, tetraalkylammonium hydroxide (e.g., tetramethylammonium hydroxide), and ammonia are more preferred, with ammonia being particularly preferred.

[0058] (Other ingredients)

[0059] Furthermore, to the extent that it does not significantly impair the effects of the present invention, the filtration liquid disclosed herein may, as needed, contain chelating agents, organic acids, organic acid salts, inorganic acids, inorganic acid salts, oxidizing agents, preservatives, fungicides, and other known additives that can be used in polishing compositions (typically polishing compositions used in the polishing process of silicon wafers).

[0060] The target filtration solution disclosed herein preferably does not contain abrasive particles. Abrasive particles, and coarse particles derived from abrasive particles, tend to have a particle size larger than that of additives other than abrasive particles, and coarse particles derived from such additives. Therefore, when the target filtration solution contains abrasive particles, the filter is prone to clogging and its lifespan is reduced. Here, "the target filtration solution does not contain abrasive particles" means that abrasive particles are not intentionally mixed in, specifically meaning that the content of abrasive particles in the target filtration solution is 0.001% by weight or less (preferably 0.0001% by weight or less, more preferably 0.00001% by weight or less). In a preferred embodiment, the content of abrasive particles in the target filtration solution is 0% by weight.

[0061] <ph>

[0062] The pH of the filtration solution disclosed herein is not particularly limited. From the viewpoint of improving the solubility of water-soluble polymers, a pH of 7.0 or higher for the filtration solution is appropriate, preferably 8.0 or higher, more preferably 8.5 or higher, and may also be 9.0 or higher. Furthermore, from the viewpoint of improving the dispersion stability of water-soluble polymers, a pH of 12.0 or lower for the filtration solution is preferably 12.0 or lower, more preferably 11.0 or lower, and even more preferably 10.5 or lower, for example, may be 10.0 or lower.

[0063] The pH of the filtered liquid can be determined as follows: Using a pH meter (e.g., a glass electrode hydrogen ion concentration indicator (model F-23) manufactured by Horiba Corporation), after three-point calibration using standard buffer solutions (phthalate pH buffer pH: 4.01 (25°C), neutral phosphate pH buffer pH: 6.86 (25°C), and carbonate pH buffer pH: 10.01 (25°C)), the glass electrode is placed in the composition of the test object, and the value is measured after more than 2 minutes and after stabilization.

[0064] (Filter)

[0065] In the filtration method disclosed herein, the target liquid is filtered using a filter. The filter satisfies the following conditions (1) and (2).

[0066] (1) The average pore size P measured by the pore size distribution measuring instrument is less than 0.15 μm.

[0067] (2) The average aperture S on the inlet side was measured by SEM. in Average aperture S on the outlet side out The ratio of the aperture gradient (S) in / S out () is below 3.

[0068] Here, the average pore size P of the filter in this specification is taken as the value of pore size D50, which corresponds to 50% of the cumulative pore size distribution in the fine pore size distribution obtained based on the semi-dry method according to ASTM E1294-89. For example, it can be measured using a pore size distribution measuring instrument (CFP-1200AXL) manufactured by PMI. The above measurement method is also used in the embodiments described later.

[0069] In addition, the aperture gradient (S in / S out The determination method is as follows. First, the filter surface on the inlet side (primary side) of the filtered liquid is observed using a scanning electron microscope (SEM). Image analysis software is used to analyze the obtained top view, thereby determining the average pore size S on the inlet side of the filter. in Similarly, the filter surface on the liquid outflow side (secondary side) was observed using SEM, and the obtained top view was analyzed using image analysis software to determine the average pore size S on the filter outlet side. out The pore size gradient of the filter (S) in / S out ) with the average aperture S on the inlet side in Relative to the average aperture S on the outlet side out The ratio is calculated. For SEM, Hitachi High-Technologies Corporation's SU8000 series or equivalents can be used. For image analysis software, MOUNTECH Co., Ltd.'s Mac-View or equivalents can be used. The above-described measurement method is also used in the examples described later.

[0070] Filters with an average pore size P as small as 0.15 μm, as measured by a pore size distribution analyzer, can accurately capture and remove even coarse particles from the target liquid, including those derived from additives, which are smaller in size than other particles such as abrasive particles. Furthermore, the pore size gradient (S) can also be used to... in / S out Filters with a diameter of 3 or less are less prone to clogging during filtration, resulting in a longer filter lifespan. Therefore, when using this filter to filter the target liquid, it can maintain a practical filter lifespan and easily and accurately remove or reduce coarse particles and foreign matter from additives.

[0071] As a result of making the filter's pore size gradient (S in / S out The reason for achieving a good filter life with a pore size gradient (S) of 3 or less is not to be interpreted in a limiting way, but can be considered, for example, as follows: That is, compared with the pore size gradient (S) in / S out Compared to filters with relatively large pore size gradients (S), in / S out Relatively small filters have more fine pores that are effective at capturing coarse particles originating from additives. Therefore, the pore size gradient (S) in / S out Filters as small as 3 mm can capture more coarse particles until the filter becomes clogged. As a result, the filter can be used to filter the target liquid and achieve a good filter life.

[0072] In the technology disclosed herein, by selecting a filter with an average pore size P measured by a pore size distribution meter of 0.15 μm or less, the removal of foreign matter from the target liquid can be achieved with good efficiency. From the perspective of achieving particularly good efficiency in removing foreign matter from the target liquid, in a preferred embodiment, the average pore size P of the filter can be 0.14 μm or less, more preferably 0.13 μm or less, and even more preferably 0.12 μm or less. Furthermore, by further selecting a pore size gradient (S) from the filter having the aforementioned average pore size P... in / S out For applications with a pore size of 3 or less, high-precision filtration of coarse particles is achieved, along with long lifespan, low pressure loss, and high flow rate. Particularly considering the long lifespan, a pore size gradient (S) filter is preferred. in / S out For those with a value of 2.5 or less, it is more preferable to have a value of 2 or less.

[0073] The structure of the filter is not particularly limited as long as the filter meets the conditions (1) and (2) above. In a preferred embodiment of the technology disclosed herein, the filter is a membrane filter comprising a layer of porous membrane. In another preferred embodiment, the filter has a filter fiber layer made of filter fibers. As an example of a filter having a filter fiber layer, a fabric filter (screen filter) can be cited.

[0074] There are no particular limitations on the material of the membrane filter. Examples of materials for membrane filters include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene (PE) and polypropylene (PP), polyamides such as nylon, fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), cellulose polymers such as cellulose, cellulose acetate, and cellulose mixed esters, polyimide, polysulfone (PSF), and polyethersulfone (PES). From the viewpoint of easily satisfying the conditions (1) and (2) related to the average pore size P and pore size gradient mentioned above, polyethersulfone, polysulfone, and nylon are preferred, and polyethersulfone and polysulfone are more preferred.

[0075] The filter may or may not contain a support. Filters without a support tend to have superior filtration performance. The support may also be the filter fiber layer described above.

[0076] When the above-mentioned filter has a filter fiber layer, the material of the filter fiber is not particularly limited. Inorganic fibers such as glass fiber (GF) and carbon fiber, and organic fibers such as polymer fibers can be used. Inorganic fibers impregnated with resin (preferably GF) can also be used. As polymer fibers, for example, fibers formed from one or more of the following can be used: polyolefins such as polyethylene (PE) and polypropylene (PP), polyamides such as nylon, polyesters such as polyethylene terephthalate, fluoropolymers such as polytetrafluoroethylene (PTFE), polycarbonate, polyethersulfone, acrylic resins, polystyrene, polyurethane, cellulose, and cellulose acetate. For example, considering resistance to strong acids and alkalis, filter fibers can be made of polyolefin fibers, polyamide fibers, polyester fibers, fluoropolymer fibers, or polypropylene fibers. In addition, one or more of inorganic fibers such as GF can be combined with one or more of organic fibers such as polyolefin fibers, polyamide fibers, and polyester fibers.

[0077] Furthermore, the filter fibers (and thus the filter fiber layer, the filter) disclosed herein can also undergo cationization treatment. Through this cationization treatment, the filter fibers (and thus the filter fiber layer, the filter) can possess a positive zeta potential. The method of cationization treatment is not particularly limited; examples include adding (e.g., impregnating) amines (primary, secondary, or tertiary amines) or cationic substances (cationic polyamides) having cationic groups such as quaternary ammonium groups into the filter fibers. The filter fibers that have undergone the above-described cationization treatment can retain the aforementioned cationic substances.

[0078] The shape of the filter medium disclosed herein is not particularly limited, and filters with various structures, shapes, and functions can be appropriately used. Specific examples include depth filters, surface filters, depth-pleated filters that make the depth filter pleated, and pleated filters that make the surface filter pleated. From the viewpoint of improving the filterability of the target liquid, pleated filters are preferred.

[0079] The overall structure of the filter element incorporating the filter disclosed herein is not particularly limited. The filter element may, for example, be substantially cylindrical. The filter element may be a cartridge type capable of periodic replacement. In addition to the filter material, the filter element may also include other components such as a core, but these are not features of the invention and therefore are not specifically described herein.

[0080] (filter)

[0081] The target liquid (containing additives) disclosed herein is filtered using the filter disclosed herein. Typically, the technique disclosed herein involves filtering the target liquid using a filter. Regarding the filtration conditions (e.g., filtration differential pressure, filtration rate, filtration volume), appropriate settings can be made based on common knowledge in the art and considering target quality, production efficiency, etc. The filtration disclosed herein is preferably implemented, for example, under conditions where the filtration differential pressure is 0.8 MPa or less (e.g., 0.5 MPa or less, typically 0.3 MPa or less). The filtration method is not particularly limited; for example, in addition to natural filtration at atmospheric pressure, known filtration methods such as suction filtration, pressure filtration, and centrifugal filtration can be appropriately employed.

[0082] In the filtration based on the filters disclosed herein, the filtration speed (flow rate) is not particularly limited. For example, when using a disc filter with a diameter of 47 mm, a flow rate of 1.0 g / min or more is appropriate, and from the viewpoint of production efficiency, it is preferable to be 1.2 g / min or more, more preferably 1.5 g / min or more, and even more preferably 2.0 g / min or more.

[0083] Furthermore, there is no particular limitation on the filtration volume of the filters disclosed herein. For example, when using a disc filter with a diameter of 47 mm, a filtration volume of 25 g or more is appropriate, and from the viewpoint of production efficiency, it is preferable to have a filtration volume of 50 g or more, more preferably 100 g or more, and even more preferably 120 g or more.

[0084] Furthermore, in the technology disclosed herein, additional filtration processes can be performed before or after the aforementioned filtration, depending on the purpose of removing coarse particles or achieving high-precision filtration. For example, the additional filtration processes can be performed before the filtration disclosed herein, and can be performed using a filter with the same level of filtration precision as the filter used in the filtration, or a filter with a higher filtration precision than the filter used in the filtration. Alternatively, the additional filtration processes can also be performed after the filtration disclosed herein, and can be performed using a filter with the same level of filtration precision as the filter used in the filtration, or a filter with a lower filtration precision than the filter used in the filtration. In a preferred embodiment, one or more pre-filtration processes can be performed before the filtration disclosed herein for the purpose of removing foreign matter such as coarse particles. In this case, the filtration disclosed herein can be one step in a multi-stage filtration process.

[0085] Pre-filtration can be performed for example using a filter with a filtration accuracy of 0.05 μm or more and less than 1 μm (preferably 0.1 μm or more and less than 0.5 μm, more preferably 0.15 μm or more and less than 0.25 μm) for the first stage of filtration, and a filter with a filtration accuracy of 0.01 μm or more and less than 0.5 μm (preferably 0.03 μm or more and less than 0.1 μm, more preferably greater than 0.04 μm and less than 0.06 μm) for the second stage of filtration. Alternatively, pre-filtration may include either the first stage filtration or the second stage filtration described above, as well as other pre-filtration methods. The filtration accuracy described above can be the manufacturer's rated value. The same applies to the embodiments described later.

[0086] The filtration in the disclosed technology is preferably performed just before the additive is mixed with the abrasive-containing liquid. That is, the filtration in the disclosed technology is preferably performed as a final stage in the filtration of the additive-containing liquid. The filtered filtrate is kept in a container until it is mixed with the abrasive-containing liquid. The filtrate may be part B of the multi-component grinding composition described later.

[0087] (mix)

[0088] According to this specification, a method for manufacturing a grinding composition using an additive-containing liquid (a filtrate containing additives) is provided, wherein the additive-containing liquid (a filtrate containing additives) has been filtered using any of the filtration methods disclosed herein. The method for manufacturing the grinding composition may, for example, include a step of mixing the components contained in the grinding composition. Typically, the grinding composition can be manufactured by mixing the components contained in the grinding composition using known mixing apparatus such as a blade mixer, an ultrasonic disperser, or a homogenizer. There are no particular limitations on the manner in which these components are mixed; for example, all components may be mixed at once, or they may be mixed in a suitably predetermined order.

[0089] <Grinding Composition>

[0090] According to the technology disclosed herein, a grinding composition is provided, comprising an additive contained in a filtrate containing the additive obtained by filtration using any of the filtration methods disclosed herein. The grinding compositions disclosed herein are not particularly limited except for containing the aforementioned additive. The grinding compositions may also contain other components (e.g., abrasive particles) not present in the aforementioned additive-containing filtrate.

[0091] (Abrasive grains)

[0092] The abrasive composition disclosed herein preferably includes abrasive grains. The abrasive grains function to mechanically abrade the surface of the object being abraded. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected based on the intended use and method of application of the abrasive composition. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and iron oxide red particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles (here, (meth)acrylic acid refers to the meaning including acrylic acid and methacrylic acid), and polyacrylonitrile particles. Such abrasive grains can be used alone or in combination of two or more.

[0093] As the aforementioned abrasive grains, inorganic particles are preferred, particularly particles formed from oxides of metals or semi-metals, and especially silicon dioxide particles. The use of silicon dioxide particles as abrasive grains is particularly meaningful for abrasive compositions that can be used in abrasive objects having surfaces composed of silicon, such as silicon wafers, as described later. In the technology disclosed herein, it is preferable, for example, to implement the aforementioned abrasive grains substantially composed of silicon dioxide particles. Here, "substantially" means that 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and can be 100% by weight) of the particles constituting the abrasive grains are silicon dioxide particles.

[0094] Specific examples of silica particles include colloidal silica, fumed silica, and precipitated silica. Silica particles can be used alone or in combination of two or more types. Colloidal silica is particularly preferred from the perspective of easily obtaining a polished surface with excellent quality after grinding. As colloidal silica, colloidal silica produced by ion exchange using water glass (sodium silicate) as a raw material, or alkoxide-based colloidal silica (colloidal silica produced by the hydrolysis and condensation reaction of alkoxysilanes) is preferred. Colloidal silica can be used alone or in combination of two or more types.

[0095] The BET diameter of the abrasive grains (typically silica particles) is not particularly limited, but from the viewpoint of grinding efficiency, it is preferably 5 nm or more, more preferably 10 nm or more. From the viewpoint of obtaining higher grinding effects (e.g., reduction of haze, removal of defects, etc.), the aforementioned BET diameter is preferably 15 nm or more, more preferably 20 nm or more (e.g., greater than 20 nm). In addition, from the viewpoint of preventing scratches, the BET diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less. The technology disclosed herein is preferably suitable for grinding where a high-quality surface is required after grinding because it easily produces a high-quality surface (e.g., a surface with a low LPD number). As the abrasive grains used in this grinding composition, abrasive grains with a BET diameter of 35 nm or less (typically less than 35 nm, more preferably 32 nm or less, for example less than 30 nm) are preferred.

[0096] It should be noted that in this specification, BET diameter refers to the specific surface area (BET value) determined using the BET method, calculated as BET diameter (nm) = 6000 / (true density (g / cm³)). 3 )×BET value (m 2 The particle size can be calculated using the formula ( / g). For example, for silica particles, the particle size can be calculated using BET diameter (nm) = 2727 / BET value (m). 2 / g) Calculate the BET diameter. Specific surface area can be determined, for example, using a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0097] (Water-soluble polymer)

[0098] The grinding composition disclosed herein preferably includes a water-soluble polymer. When the additive-containing filtrate used in manufacturing the above-described grinding composition contains a water-soluble polymer, the grinding composition may contain only the water-soluble polymer contained in the additive-containing filtrate, or it may contain other water-soluble polymers in addition to the water-soluble polymer contained in the additive-containing filtrate. Suitable water-soluble polymers used in the grinding composition disclosed herein may be one of the substances listed as water-soluble polymers used in the above-described filtration liquid, or two or more may be used in combination. Specific details regarding the water-soluble polymers used in the grinding composition are omitted due to repetition.

[0099] (surfactant)

[0100] In a preferred embodiment of the grinding composition disclosed herein, a surfactant is included. When the additive-containing filtrate used in manufacturing the above-described grinding composition contains a surfactant, the grinding composition may contain only the surfactant contained in the additive-containing filtrate, or it may contain other surfactants besides the surfactant contained in the additive-containing filtrate. Suitable surfactants used in the grinding compositions disclosed herein may be one or more substances listed as surfactants used in the target filtrate, used alone or in combination. Specific details regarding the surfactants used in the grinding compositions are omitted for repetition.

[0101] (water)

[0102] The grinding composition disclosed herein preferably includes water. The same water listed herein as that used as the filtration liquid can be suitably used as the grinding composition disclosed herein.

[0103] (Alkaline compound)

[0104] The grinding composition disclosed herein preferably includes an alkaline compound. When the additive-containing filtrate used in manufacturing the above-described grinding composition contains an alkaline compound, the grinding composition may contain only the alkaline compound contained in the additive-containing filtrate, or it may contain other alkaline compounds besides the alkaline compound contained in the additive-containing filtrate. As suitable alkaline compounds for use in the grinding composition disclosed herein, one or more of the substances listed as alkaline compounds used in the target filtrate may be used alone, or two or more may be used in combination. Specific details regarding the alkaline compounds used in the grinding composition are omitted for repetition.

[0105] <Other Ingredients>

[0106] Furthermore, to the extent that it does not significantly impair the effects of the present invention, the polishing compositions disclosed herein may, as needed, contain chelating agents, organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, fungicides, and other known additives that can be used in polishing slurries (typically, polishing slurries used in the polishing process of silicon wafers).

[0107] The polishing composition disclosed herein preferably does not contain an oxidizing agent. This is because when an oxidizing agent is included in the polishing composition, the surface of the substrate (e.g., a silicon substrate) is oxidized by supplying the composition, forming an oxide film, which may reduce the polishing rate. Here, "practically free of oxidizing agents" means that oxidizing agents are not intentionally mixed in, and it is acceptable that trace amounts of oxidizing agents derived from raw materials, manufacturing processes, etc., are unavoidably included. These trace amounts refer to a molar concentration of the oxidizing agent in the polishing composition of 0.0005 mol / L or less (preferably 0.0001 mol / L or less, more preferably 0.00001 mol / L or less, and particularly preferably 0.000001 mol / L or less). A preferred polishing composition does not contain an oxidizing agent. The polishing composition disclosed herein is preferably implemented in a manner that does not contain hydrogen peroxide, sodium persulfate, ammonium persulfate, or sodium dichloroisocyanurate.

[0108] <ph>

[0109] The pH of the grinding composition disclosed herein is typically 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, and even more preferably 9.3 or higher, for example 9.5 or higher. The grinding efficiency tends to increase as the pH of the grinding composition increases. On the other hand, from the viewpoint of preventing the dissolution of abrasive particles (e.g., silica particles) and suppressing the reduction of mechanical grinding effect, a pH of 12.0 or lower is suitable, preferably 11.0 or lower, more preferably 10.8 or lower, and even more preferably 10.5 or lower. The pH can be measured using the same method as the pH measurement method for the target filtration liquid described above.

[0110] <Application>

[0111] The abrasive composition disclosed herein is applicable to abrasive objects of various materials and shapes. The abrasive object can be, for example, metals or semi-metals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, and stainless steel, or their alloys; glassy materials such as quartz glass, aluminosilicate glass, and glassy carbon; ceramic materials such as alumina, silicon dioxide, sapphire, silicon nitride, tantalum nitride, and titanium carbide; compound semiconductor substrate materials such as silicon carbide, gallium nitride, and gallium arsenide; resin materials such as polyimide resin; etc. It can also be an abrasive object composed of multiple of these materials.

[0112] The polishing compositions disclosed herein are particularly preferred for polishing surfaces formed of silicon (typically silicon wafers). A typical example of a silicon wafer referred to herein is a monocrystalline silicon wafer, such as a monocrystalline silicon wafer obtained by slicing a monocrystalline silicon ingot.

[0113] The polishing composition disclosed herein is preferably applicable to polishing processes of objects to be polished (e.g., silicon wafers). For objects to be polished, conventional treatments suitable for the objects to be polished can also be performed in upstream processes such as grinding or etching, prior to the polishing process based on the polishing composition disclosed herein.

[0114] The polishing composition disclosed herein is preferably used, for example, in the polishing of a workpiece (e.g., a silicon wafer) whose surface roughness has been adjusted to 0.1 nm to 100 nm through an upstream process. The surface roughness Ra of the workpiece can be measured, for example, using a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement Systems Inc. Use in final polishing (fine polishing) or polishing just before final polishing is effective, and use in final polishing is particularly preferred. Here, final polishing refers to the final polishing step in the manufacturing process of the workpiece (i.e., a step after which no further polishing is performed).

[0115] The grinding compositions disclosed herein are typically supplied to a grinding object as a grinding slurry for grinding the object. The grinding slurry can be prepared, for example, by diluting any of the grinding compositions disclosed herein (typically, with water). Alternatively, the grinding composition can be used directly as a grinding slurry. That is, the concept of a grinding composition in the art disclosed herein includes both a grinding slurry (working slurry) supplied to a grinding object for grinding the object, and a concentrated solution diluted for use as a grinding slurry (i.e., the stock solution of the grinding slurry). Other examples of grinding slurries containing the grinding compositions disclosed herein include grinding slurries prepared by adjusting the pH of the composition.

[0116] (Grinding slurry)

[0117] The content of abrasive particles in the grinding fluid is not particularly limited, but is typically 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.10% by weight or more, and for example, 0.15% by weight or more. Higher grinding speeds can be achieved by increasing the content of abrasive particles. From the viewpoint of particle dispersion stability in the grinding composition, the above-mentioned content is suitable to be 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, further preferably 2% by weight or less, for example, 1% by weight or less, and can be 0.7% by weight or less. In a preferred embodiment, the above-mentioned content can be 0.5% by weight or less, or 0.2% by weight or less.

[0118] The concentration (total concentration) of the water-soluble polymer in the grinding slurry is not particularly limited, and can be set to 0.0001% by weight or more, for example. From the viewpoint of reducing haze, a concentration of 0.0005% by weight or more is preferred, more preferably 0.001% by weight or more, for example 0.003% by weight or more, or 0.005% by weight or more. Furthermore, from the viewpoint of grinding speed, the concentration of the water-soluble polymer is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, or 0.05% by weight or less (e.g., 0.01% by weight or less).

[0119] There is no particular limitation on the concentration of alkaline compounds in the polishing slurry. From the viewpoint of increasing polishing speed, it is preferable to set the concentration to 0.001% by weight or more of the polishing slurry, more preferably 0.003% by weight or more (e.g., 0.004% by weight or more). Furthermore, from the viewpoint of reducing haze, it is appropriate to set the concentration to less than 0.3% by weight, preferably less than 0.1% by weight, more preferably less than 0.05% by weight, and even more preferably less than 0.03% by weight (e.g., less than 0.01% by weight).

[0120] (Concentrated solution)

[0121] The grinding composition disclosed herein can be in a concentrated form (i.e., a concentrated grinding slurry, or it can be used as a concentrate of the grinding slurry) before being supplied to the object being ground. This concentrated form of the grinding composition is advantageous from the viewpoints of convenience in manufacturing, distribution, and storage, as well as cost reduction. The concentration ratio is not particularly limited; for example, it can be set to approximately 2 to 100 times the volume, and typically 5 to 50 times (e.g., approximately 10 to 40 times) is appropriate.

[0122] Such a concentrate can be diluted at a desired time to prepare a grinding slurry (working slurry), and then used by supplying the grinding slurry to the workpiece being ground. This dilution can be, for example, by adding water to the concentrate and mixing.

[0123] The content of abrasive particles in the above-mentioned concentrate can be set to, for example, 50% by weight or less. From the viewpoint of the processability of the above-mentioned concentrate (e.g., the dispersion stability and filterability of abrasive particles), the content of abrasive particles in the above-mentioned concentrate is preferably 45% by weight or less, more preferably 40% by weight or less. In addition, from the viewpoint of convenience in manufacturing, distribution, and storage, and cost reduction, the content of abrasive particles can be set to, for example, 0.5% by weight or more, preferably 1% by weight or more, more preferably 3% by weight or more.

[0124] (Preparation of the composition for grinding)

[0125] The grinding compositions used in the technology disclosed herein are preferably multi-component compositions, primarily two-component compositions. For example, they can also be configured as follows: a grinding slurry is prepared by mixing a portion A, which contains at least abrasive particles, with a portion B, which contains at least a portion of the remaining components, and then mixing and diluting them as needed at appropriate times. Portion B can be the aforementioned additive-containing filtrate. Portion A can be filtered once or twice or more.

[0126] There are no particular limitations on the preparation method of the grinding composition. For example, known mixing devices such as blade mixers, ultrasonic dispersers, and homogenizers can be used to mix the components constituting the grinding composition. There are no particular limitations on the way these components are mixed; for example, all components can be mixed at once, or they can be mixed in a suitably set order. In addition, after mixing, filtration can be performed once or twice or more, or filtration can be omitted.

[0127] <Grinding>

[0128] The polishing composition disclosed herein can be used for polishing an object, for example, by including the following operations. A suitable method for polishing an object (e.g., a silicon wafer) using the polishing composition disclosed herein will be described below.

[0129] That is, a grinding slurry comprising any of the grinding compositions disclosed herein is prepared. Preparing the grinding slurry may include adjusting the concentration (e.g., dilution), pH, etc., of the grinding composition. Alternatively, the grinding composition may be used directly as the grinding slurry.

[0130] Then, the polishing slurry is supplied to the object to be polished, and polishing is performed using conventional methods. For example, in the fine polishing of a silicon wafer, typically, the silicon wafer that has undergone a polishing process is placed in a conventional polishing apparatus, and polishing slurry is supplied to the surface of the silicon wafer to be polished through the polishing pad of the polishing apparatus. Typically, while the polishing slurry is continuously supplied, the polishing pad is pressed against the surface of the silicon wafer to be polished, and the two are moved relative to each other (e.g., rotated). After this polishing process, the polishing of the object to be polished is completed.

[0131] There are no particular limitations on the abrasive pads used in the above-described polishing process. For example, abrasive pads made of foamed polyurethane, non-woven fabric, or suede type can be used. Each abrasive pad may or may not contain abrasive particles. Generally, abrasive pads without abrasive particles are preferred.

[0132] For objects to be ground using the grinding composition disclosed herein, cleaning is typically performed. Cleaning can be performed using a suitable cleaning solution. The cleaning solution used is not particularly limited; for example, commonly used solutions in the semiconductor field, such as SC-1 (a mixture of ammonium hydroxide (NH4OH), hydrogen peroxide (H2O2), and water (H2O)) or SC-2 (a mixture of HCl, H2O2, and H2O), can be used. The temperature of the cleaning solution can be set, for example, in the range of room temperature (typically about 15°C to 25°C) to about 90°C. From the viewpoint of improving the cleaning effect, a cleaning solution with a temperature of about 50°C to 85°C is preferred.

[0133] Example

[0134] The following describes some embodiments related to the present invention, but it is not intended to limit the present invention to the content shown in the embodiments. It should be noted that, unless otherwise specified, "%" in the following description refers to weight.

[0135] <Experimental Example 1; Filtration Test>

[0136] [Preparation of the target liquid for filtration]

[0137] By using Mw28×10 4 A water-soluble polymeric liquid containing 1.012% HEC and a pH of approximately 9 was prepared by mixing HEC, water, and ammonia. The prepared water-soluble polymeric liquid was pre-filtered using a pre-filter with a filtration precision of 0.05 μm, and the filtrate was used as the target filtration liquid.

[0138] [Filtration Test]

[0139] Prepare pores with the average pore size P and pore size gradient (S) shown in Table 1. in / S out Filters FL1 (filter material: PSF membrane, average pore size: 0.118 μm, pore size gradient: 1.99, filter diameter: 47 mm), FL2 (filter material: PES membrane, average pore size: 0.145 μm, pore size gradient: 1.74, filter diameter: 47 mm), FL3 (filter material: PES membrane, average pore size: 0.144 μm, pore size gradient: 4.25, filter diameter: 47 mm), and FL4 (filter material: nylon membrane, average pore size: 0.418 μm, pore size gradient: 1.11, filter diameter: 47 mm) were used. Filtration tests were conducted using filters FL1 through FL4 to filter the prepared target liquid. In these filtration tests, a delivery pump was used, and pressure filtration was performed under conditions of a filtration pressure difference of less than 0.2 MPa. In the above filtration test, 120g of the target liquid was filtered and the filtration flow rate at the end was recorded. Based on the magnitude of this filtration flow rate, the filter life of filters FL1 to FL4 was evaluated according to the following two levels. The evaluation results of the obtained filter life are shown in Table 1.

[0140] When the filtration flow rate is 2.1 g / min or higher: Good (G)

[0141] When the filtration flow rate is less than 2.1 g / min, or when the filtration test cannot continue due to filter blockage before filtration of 120 g of target liquid is completed: Poor (P)

[0142] [Table 1]

[0143] Table 1

[0144]

[0145] It should be noted that the same filtration test was performed on the additive-containing liquid containing polyoxyethylene polyoxypropylene glycol (Mw3100, average molar addition of oxyethylene 160) in addition to HEC, and the results or trends were confirmed to be the same until the filter life.

[0146] <Experimental Example 2; Grinding Test>

[0147] <Preparation of Grinding Compositions>

[0148] (Example 1)

[0149] HEC, polyoxyethylene polyoxypropylene glycol, water, and ammonia were mixed to prepare an additive-containing liquid with a concentration of 1.012% HEC, 0.149% polyoxyethylene polyoxypropylene glycol, and a pH of approximately 9. The Mw of HEC was 28 × 10⁻⁶. 4 The Mw of the polyoxyethylene polyoxypropylene glycol is 3100, and the average molar addition of oxyethylene is 160. The above-mentioned additive-containing liquid was pre-filtered using a pre-filter with a rated filtration accuracy of 0.05 μm, and then filtered using filter FL1. The filtrate thus obtained was used as the additive-containing filtrate for the preparation of the grinding composition of Example 1.

[0150] In addition, an abrasive-containing liquid containing abrasive particles, water, and ammonia was prepared. This abrasive-containing liquid was mixed with the additive-containing filtrate prepared above, thereby preparing a composition containing 3.5% abrasive particles, 0.10% ammonia, 0.17% HEC, and 0.025% polyoxyethylene polyoxypropylene glycol. This composition was used as the grinding composition for Example 1. Colloidal silica with a BET diameter of 25 nm was used as the abrasive particles. The BET diameter was measured using a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0151] (Example 2~Example 4)

[0152] The additive-containing liquid was filtered using the filter shown in Table 2 instead of filter FL1, and the grinding composition of this example was prepared in the same manner as in Example 1. It should be noted that in Example 3, where filter FL3 was used, the specified amount of additive-containing liquid could not be filtered due to clogging of filter FL3, and therefore the grinding composition could not be prepared.

[0153] Grinding of silicon wafers

[0154] The contents of the pre-grinding process applicable to each example are shown.

[0155] (Pre-grinding process)

[0156] A front-end grinding composition comprising 19% abrasive particles, 1.3% alkaline compound, and the balance being water was prepared. Colloidal silica with a BET diameter of 35 nm was used as the abrasive particles. Potassium hydroxide (KOH) was used as the alkaline compound.

[0157] Dilute the pre-grinding composition 20 times with water, and use the resulting liquid as the grinding slurry (working slurry). Grind the silicon wafer to be ground under the following pre-grinding conditions. The silicon wafer used is a commercially available 300mm diameter single-crystal silicon wafer (conductivity: P-type, crystal orientation: ...) that has undergone grinding and etching. <100> Resistivity: ≥1Ω·cm and <100Ω·cm, no COP).

[0158] [Pre-grinding conditions]

[0159] Grinding device: Single-blade grinding machine, model "PNX-332B", manufactured by Okamoto Machinery Manufacturing Co., Ltd.

[0160] Grinding load: 20 kPa

[0161] Plate rotation speed: 20 rpm

[0162] Carrier rotation speed: 20 rpm

[0163] Grinding pad: Grinding pad manufactured by Fujibo Holdings, Inc., product name "FP400"

[0164] Slurry supply rate: 1 liter / minute

[0165] The temperature of the grinding slurry: 20℃

[0166] The temperature of the cooling water for the flat plate is 20℃.

[0167] Grinding time: 2.1 minutes

[0168] (Fine grinding process)

[0169] Dilute the polishing composition of each example 20 times with water, use the resulting liquid as polishing fluid (working slurry), and polish the silicon wafer that has completed the above-mentioned pre-polishing process under the fine polishing conditions described below.

[0170] [Fine grinding conditions]

[0171] Grinding device: Single-blade grinding machine, model "PNX-332B", manufactured by Okamoto Machinery Manufacturing Co., Ltd.

[0172] Grinding load: 15 kPa

[0173] Plate rotation speed: 30 rpm

[0174] Carrier rotation speed: 30 rpm

[0175] Polishing pad: Polishing pad manufactured by Fujibo Holdings, Inc., trade name "POLYPAS27NX"

[0176] Slurry supply rate: 2 liters / minute

[0177] The temperature of the grinding slurry: 20℃

[0178] The temperature of the cooling water for the flat plate is 20℃.

[0179] Grinding time: 2.1 minutes

[0180] The polished silicon wafers were removed from the polishing apparatus and cleaned using a cleaning solution with a volume ratio of NH4OH (29%):H2O2 (31%):deionized water (DIW) of 2:5.4:20 (SC-1 cleaning). More specifically, a cleaning tank equipped with an ultrasonic oscillator at a frequency of 720 kHz was prepared. The cleaning solution was placed in the cleaning tank and maintained at 60°C. The polished silicon wafers were immersed in the cleaning tank for 6 minutes, followed by cleaning with ultrapure water. This process was repeated twice, and then the silicon wafers were dried.

[0181] [Defect Measurement (LPD-N)]

[0182] Using a wafer inspection device manufactured by KLA-Tencor, trade name "SURFSCAN SP2" XP The number of LPD-N particles present on the surface (polished surface) of a silicon wafer was measured using the DCO mode of the device. The measured number of LPD-N particles is shown in Table 2.

[0183] [Defect Measurement (MAGICS)]

[0184] The number of defects on the surface (polished surface) of a silicon wafer was measured using a Lasertec wafer inspection device, trade name "MAGICS M5350". The measured defect counts (MAGICS) are shown in Table 2.

[0185] [Table 2]

[0186] Table 2

[0187]

[0188] As shown in Table 1, the aperture gradient (S) in / S out Filters with a pore size of 3 or less, such as FL1, FL2, and FL4, exhibit good filter life in the filtration of liquids containing HEC. On the other hand, using a pore size gradient (S... in / S out When the filter FL3 is greater than 3, it is known that the filter life will deteriorate when filtering liquids containing HEC.

[0189] Furthermore, according to the results shown in Table 2, compared with the grinding composition of Example 4 prepared using FL4 with an average pore size P greater than 0.15 μm, the composition prepared using FL4 with an average pore size P of 0.15 μm or less, as measured by a pore size distribution meter, showed a better result. in / S out The grinding compositions of Examples 1 and 2, prepared using filters FL1 and FL2 with a pore size of 3 or less, showed a significant reduction in the defect number of both LPD-N and MAGICS. Based on these results, it can be concluded that by using filters with an average pore size P of 0.15 μm or less and a pore size gradient (S... in / S out The filters FL1 and FL2, which are 3 or less, can maintain a practical filter life and properly remove coarse particles and foreign matter from grinding additives, thereby exhibiting excellent defect reduction capabilities.

[0190] The specific examples of the present invention have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes solutions obtained by various modifications and alterations to the specific examples described above.< / ph> < / ph>

Claims

1. A method for filtering a liquid containing an additive for silicon wafer polishing, comprising the step of filtering the liquid using a filter. The additive for silicon wafer grinding contains a water-soluble polymer. The liquid does not contain abrasive particles. The filter has the following characteristics: The average pore size P, as measured by a pore size distribution analyzer, is below 0.15 μm; and The average aperture S on the inlet side was measured using SEM. in Average aperture S on the outlet side out The ratio of the aperture gradient S in / S out Values ​​between 1.11 and 2.5 The liquid is a filtrate that has undergone one or more pre-filtrations. The filtration accuracy of the first stage of the pre-filtration is above 0.05 μm and below 0.25 μm. The weight-average molecular weight of the water-soluble polymer is 0.4 × 10⁻⁶. 4 above.

2. The method according to claim 1, wherein, The water-soluble polymer includes cellulose derivatives.

3. The method according to claim 1 or 2, wherein, The liquid contains water. At least a portion of the water-soluble polymer is dissolved in the water.

4. A silicon-containing wafer polishing additive liquid, which has been filtered by the method according to any one of claims 1 to 3.

5. A composition for polishing silicon wafers, comprising a silicon wafer polishing additive, said silicon wafer polishing additive being contained in a silicon-containing wafer polishing additive liquid, said silicon-containing wafer polishing additive liquid being filtered using a filter. The additive for silicon wafer grinding contains a water-soluble polymer. The liquid does not contain abrasive particles. The filter has the following characteristics: The average pore size P, as measured by a pore size distribution analyzer, is below 0.15 μm; and The average aperture S on the inlet side was measured using SEM. in Average aperture S on the outlet side out The ratio of the aperture gradient S in / S out Values ​​between 1.11 and 2.5 The liquid is a filtrate that has undergone one or more pre-filtrations. The filtration accuracy of the first stage of the pre-filtration is above 0.05 μm and below 0.25 μm. The weight-average molecular weight of the water-soluble polymer is 0.4 × 10⁻⁶. 4 above.

6. A method for manufacturing a composition for grinding silicon wafers, characterized in that, The composition for silicon wafer polishing includes a silicon wafer polishing additive, which is contained in a liquid containing a silicon wafer polishing additive, and the liquid containing the silicon wafer polishing additive is filtered using a filter. The additive for silicon wafer grinding contains a water-soluble polymer. The liquid does not contain abrasive particles. The filter has the following characteristics: The average pore size P, as measured by a pore size distribution analyzer, is below 0.15 μm; and The average aperture S on the inlet side was measured using SEM. in Average aperture S on the outlet side out The ratio of the aperture gradient S in / S out Values ​​between 1.11 and 2.5 The liquid is a filtrate that has undergone one or more pre-filtrations. The filtration accuracy of the first stage of the pre-filtration is above 0.05 μm and below 0.25 μm. The weight-average molecular weight of the water-soluble polymer is 0.4 × 10⁻⁶. 4 above.

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