Abrasive slurry

Abstract

This abrasive slurry comprises ceria-based abrasive grains, magnesium hydroxide-based abrasive grains, a dispersant, and a solvent, wherein the average grain diameter of the ceria-based abrasive grains and the magnesium hydroxide-based abrasive grains is 0.01-0.5 [mu] m (inclusive).

Description

Technical Field

[0001] The present invention relates to abrasive material slurries. Background Art

[0002] As semiconductor devices become increasingly dense and precise, CMP (Chemical Mechanical Polishing) has been developed as a technique for planarizing the surface of a thin film after it is formed by methods such as CVD (Chemical Vapor Deposition) in the manufacturing process of semiconductor wafers.

[0003] The performance of the CMP method is greatly affected by the selection of the abrasive slurry, the selection of the polishing pad, etc. In particular, the selection of the abrasive slurry is the main reason that has a great influence on the performance of the CMP method. The abrasive slurry used in the CMP method contains abrasive particles such as silicon dioxide (SiO2) and cerium (IV) oxide (CeO2). For example, Patent Document 1 discloses an abrasive composition containing cerium oxide microparticles as abrasive particles. Among them, the abrasive composition disclosed in Patent Document 1 contains cerium oxide microparticles with a purity of 99% by mass or more (whose average particle size (D50) is 0.01μm to 1.0μm), a chelating agent, a dispersant having a polyacrylic acid group or a polymethacrylic acid group, and elements such as Mg, Al, K, and C (whose content is 30ppm or less).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2001 / 080296 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, the abrasive composition disclosed in Patent Document 1 has a disadvantage in that the polishing rate decreases over time due to the fine cerium oxide particles contained as abrasive grains. In addition, the management cost of the abrasive increases in order to maintain the polishing rate during the polishing process.

[0009] In view of the above problems, the present invention provides an abrasive slurry capable of suppressing a decrease in polishing rate due to time-dependent changes even when the particle size of abrasive grains is fine.

[0010] Means for solving problems

[0011] The polishing material slurry of the present invention, which has been developed to solve the above problems, comprises cerium oxide abrasive grains, magnesium hydroxide abrasive grains, a dispersant, and a solvent, wherein the average abrasive grain size of the cerium oxide abrasive grains and the magnesium hydroxide abrasive grains is 0.01 μm or more and 0.5 μm or less.

[0012] The polishing material slurry of the present invention comprises cerium oxide abrasive, magnesium hydroxide abrasive, a dispersant and a solvent, and thus can suppress the reduction in polishing rate caused by time-dependent changes even if the average particle size of the cerium oxide abrasive and the magnesium hydroxide abrasive is as fine as 0.01 μm or more and 0.5 μm or less.

[0013] As cerium oxide abrasive grains, cerium oxide abrasive grains are preferred. Specifically, cerium (IV) oxide and cerium (III) oxide can be listed. From the perspective of material stability, cerium (IV) oxide is preferred. In addition, the cerium oxide abrasive grains can be a single type of cerium oxide-based particles or a mixture of two or more types of cerium oxide-based particles. It should be noted that the cerium oxide abrasive grains may also contain other elements such as F (fluorine), Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. In particular, other elements such as F (fluorine), La, Pr, and Nd may also be contained.

[0014] The grinding material slurry of the present invention has magnesium hydroxide abrasive grains in addition to the above-mentioned cerium oxide abrasive grains. It is speculated that magnesium hydroxide abrasive grains will adsorb the grinding chips (fine powder after grinding) of the object to be ground and suppress the reduction of grinding performance compared to cerium oxide abrasive grains, and therefore function as an additive. As magnesium hydroxide abrasive grains, for example, magnesium hydroxide abrasive grains are preferred. In addition, magnesium hydroxide abrasive grains can be one kind of magnesium hydroxide particles or a mixture of two or more kinds of magnesium hydroxide particles. It should be noted that magnesium hydroxide abrasive grains can also contain other elements such as Ca, Si, Fe, Al, S, and B. In particular, other elements such as Ca and Si can also be contained.

[0015] The polishing material slurry of the present invention contains the cerium oxide abrasive and magnesium hydroxide abrasive as described above, as well as a solvent and a dispersant. If the cerium oxide abrasive is fine, it is easy to aggregate. Therefore, the dispersant improves the dispersibility in the solvent.

[0016] In the polishing material slurry of the present invention, from the viewpoint of suppressing a decrease in the polishing rate and reducing the surface roughness Ra of the polished surface, the average abrasive particle size of the cerium oxide abrasive and the magnesium hydroxide abrasive is preferably 0.01 μm or more and 0.5 μm or less. In addition, the average abrasive particle size of the cerium oxide abrasive and the magnesium hydroxide abrasive is more preferably 0.05 μm or more and 0.2 μm or less.

[0017] The average abrasive particle size of the cerium oxide-based abrasive and the magnesium hydroxide-based abrasive is a particle size (D50) measured by a particle size distribution measurement method using a dynamic light scattering method, and can be measured as follows.

[0018] Dynamic light scattering refers to a method in which the light scattering intensity from a group of particles undergoing Brownian motion is measured by irradiating a solution such as a suspension solution with light such as a laser, and the particle size and distribution are determined based on the time variation of the intensity. Specifically, the particle size distribution is evaluated using a Zeta potential particle size molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000ZS) in accordance with JIS Z8828:2019 "Particle size analysis-dynamic light scattering method". The abrasive slurry of the present invention is diluted with pure water in a manner such that the solid content concentration is 0.005% by mass to 0.1% by mass, and the solid content concentration can be calculated as follows. First, 5 g of the abrasive slurry of the present invention is collected, heated at 180 ° C for 60 minutes under an atmospheric atmosphere, and the mass (Xg) of the obtained solid content is measured. Then, the solid content concentration can be calculated by calculating Xg (solid content mass) ÷ 5g (collected abrasive slurry mass of the present invention) × 100. Immediately before measurement, the sample was filtered through a filter with a particle capture capacity of 11 μm or greater and ultrasonically treated for 3 minutes using an ultrasonic cleaner (AS ONE: VS-100III). Furthermore, the sample liquid temperature was adjusted to 25°C. The particle size (D50) refers to the median diameter (D50), which represents the 50% cumulative value of the cumulative distribution curve.

[0019] Furthermore, from the viewpoint of achieving the subject of the present application, the average abrasive grain size of the cerium oxide-based abrasive is preferably 0.01 μm or more and 0.5 μm or less, and may be 0.05 μm or more and 0.2 μm or less.

[0020] From the viewpoint of achieving the object of the present application, the average abrasive grain size of the magnesium hydroxide-based abrasive grains is preferably 0.01 μm or more and 0.5 μm or less, and may be 0.05 μm or more and 0.2 μm or less.

[0021] Furthermore, the abrasive slurry of the present invention contains ZrO₂ and Al₂O₃, which are shavings from the media used in the paint shaker and bead mill, because a paint shaker and bead mill are used in the step of grinding the cerium oxide-based abrasive grains and the magnesium hydroxide-based abrasive grains in the abrasive slurry manufacturing method of the present invention described below. It should be noted that the content of ZrO₂ and Al₂O₃ in the abrasive slurry of the present invention does not affect the polishing performance of the abrasive slurry of the present invention.

[0022] Furthermore, the polishing material slurry of the present invention is characterized by comprising a solvent, and the solvent contains water.

[0023] The grinding material slurry of the present invention has a high dispersibility to water, so pure water can be used as a solvent. In addition, as a solvent, pure water, and water-soluble organic solvents such as alcohols and ketones or mixtures thereof are preferably used from the perspective of fully improving the grinding rate, and water is more preferably used. When the grinding material slurry of the present invention is set to 100% by mass, the content of the solvent is preferably 60% by mass or more and 99.9% by mass or less, more preferably 80% by mass or more and 90% by mass or less. Typically, when the grinding material slurry of the present invention is set to 100% by mass, the content of the solvent can be 98% by mass or less, can also be 97% by mass or less, and can also be 95% by mass or less.

[0024] Furthermore, the polishing material slurry of the present invention is characterized by comprising a dispersant containing one or more selected from the group consisting of organic acid and alkali metal salts, phosphoric acids, and polymer dispersants.

[0025] The abrasive slurry of the present invention contains a dispersant containing one or more selected from organic acid and alkali metal salts, phosphoric acids, and polymer dispersants, thereby being able to suppress aggregation of cerium oxide-based abrasive grains.

[0026] The organic acid alkali metal salt preferably comprises one or more selected from sodium citrate, sodium gluconate, and sodium tartrate. Furthermore, as sodium citrate, monosodium citrate, disodium citrate, and trisodium citrate can be listed. In addition, as sodium tartrate, monosodium tartrate and disodium tartrate can be listed. As sodium tartrate, it can be L-isomer, D-isomer, meso-isomer, and mixtures thereof. As the organic acid alkali metal salt, it can be a hydrate.

[0027] And then, the mensuration of organic acid alkali metal salt contained in the grinding-material slurry of the present invention is preferably high performance liquid chromatography.Use high performance liquid chromatography, can measure the kind and weight thereof of organic acid alkali metal salt by known method.In addition, also can measure after the organic acid alkali metal salt contained in the grinding-material slurry of the present invention is separated.

[0028] Examples of the phosphoric acid include phosphoric acid, condensed phosphoric acid, and alkali metal salts thereof, wherein the alkali metal salt includes one or more phosphoric acids selected from the group consisting of sodium phosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium tetrapolyphosphate, and sodium superpolyphosphate.

[0029] Furthermore, the determination of the phosphoric acid contained in the abrasive slurry of the present invention is preferably performed by high performance liquid chromatography. In high performance liquid chromatography, the type and weight of the phosphoric acid can be determined by a known method by using a non-inhibitor anion analysis column. For example, a Shodex inhibitor-free anion analysis column IC1-524A (manufactured by Shoko Scientific Co., Ltd.) can be used as a non-inhibitor anion analysis column. By using this non-inhibitor anion analysis column, the phosphoric acid contained in the abrasive slurry of the present invention can be separated and determined.

[0030] Examples of the polymer dispersant include one or more water-soluble organic polymers selected from polyacrylic acid, polycarboxylic acid, polycarboxylate, and copolymers thereof. The polymer dispersant is particularly preferably a polyacrylate, and more preferably an ammonium polyacrylate.

[0031] In addition, the grinding material slurry of the present invention is characterized in that, when the grinding material slurry is set to 100 mass%, the content of the cerium oxide-based abrasive is greater than or equal to 0.5 mass% and less than or equal to 40 mass%, and the content of the magnesium hydroxide-based abrasive is greater than or equal to 0.005 mass% and less than or equal to 20 mass%.

[0032] From the viewpoint of being able to achieve a good polishing rate, the content of cerium oxide abrasive particles in the grinding material slurry of the present invention is preferably 0.5 mass % or more and 40 mass % or less. In addition, the content of cerium oxide abrasive particles is more preferably 3.0 mass % or more and 35.0 mass % or less, further preferably 4.0 mass % or more and 30.0 mass % or less, particularly preferably 5.0 mass % or more and 25.0 mass % or less, and most preferably 15.0 mass % or more and 25.0 mass % or less. Typically, the content of cerium oxide abrasive particles in the grinding material slurry of the present invention can be 40 mass % or less, or 38 mass % or less, or 36 mass % or less. It should be noted that the content of cerium oxide abrasive particles in the grinding material slurry of the present invention is taken as the total content of total rare earth oxide (TREO) rare earth oxide and F (fluorine) in the grinding material slurry of the present invention.

[0033] In addition, from the viewpoint of being able to suppress the reduction of the grinding rate, it is preferred that the content of the magnesium hydroxide-based abrasive in the grinding material slurry of the present invention is 0.005 mass % or more and 20 mass % or less. In addition, the content of the magnesium hydroxide-based abrasive is more preferably 0.05 mass % or more and 5 mass % or less, further preferably 0.1 mass % or more and 5 mass % or less, and particularly preferably 0.5 mass % or more and 3 mass % or less. Typically, the content of the magnesium hydroxide-based abrasive in the grinding material slurry of the present invention can be 20 mass % or less, or 18 mass % or less, or 16 mass % or less. It should be noted that the content of the magnesium hydroxide-based abrasive in the grinding material slurry of the present invention is used as the Mg content in the grinding material slurry of the present invention.

[0034] The total rare earth oxide (TREO) and rare earth oxide content was measured using an ICP-OES (inductively coupled plasma optical emission spectrometry) device or an ICP-MS (inductively coupled plasma mass spectrometry) device, and the F (fluorine) content was measured using a fluoride ion electrode method. Furthermore, the Mg content contained in the magnesium hydroxide-based abrasive was measured using an ICP-OES device or an ICP-MS device.

[0035] Specifically, 100 ml of the abrasive slurry of the present invention is placed in a glass beaker and heated and dried at 120° C. for 24 hours to obtain a dried abrasive of the present invention. The dried abrasive of the present invention is used to measure the content of each component. The total rare earth oxide (TREO) content is measured by the oxalate precipitation-calcination-weight method (unit: solid: mass %, liquid: g / L). As a pretreatment, the dried abrasive of the present invention is dissolved using nitric acid, perchloric acid, and hydrogen peroxide, and boiled to prepare a measurement sample. In addition, if the object of measurement is a liquid, it does not need to be dissolved using nitric acid or the like and can be directly boiled.

[0036] Regarding the F (fluorine) content, the solid material (ground material) to be measured is dissolved by alkali melting and hot water extraction, and the F concentration in the solution is measured by the fluoride ion electrode method, thereby calculating the F content (mass %) in the solid material.

[0037] Furthermore, the Mg content can be determined as follows. Nitric acid, perchloric acid, and hydrogen peroxide are added to the dried abrasive of the present invention, and the solution is decomposed by heating. The Mg concentration can be measured using an ICP-OES apparatus. The added magnesium hydroxide content can be estimated by multiplying this by the hydroxide coefficient. The hydroxide coefficient is Mg(OH)2 / Mg = {24.3 + (16.0 + 1.01) × 2} / 24.3 ≈ 2.40.

[0038] And then, from the viewpoint that dispersibility improves, the content of the dispersant in the preferred grinding material slurry of the present invention is 0.001 mass % or more and 15 mass % or less. In addition, the content of the dispersant is more preferably 0.001 mass % or more and 10 mass % or less, further preferably 0.005 mass % or more and 5 mass % or less, particularly preferably 0.5 mass % or more and 3 mass % or less. Typically, the content of the dispersant in the grinding material slurry of the present invention can be 15 mass % or less, can also be 13 mass % or less, can also be 11 mass % or less.

[0039] The content of the dispersant in the polishing material slurry of the present invention is measured by gel permeation chromatography (GPC), liquid chromatography (LC), or liquid chromatography-mass spectrometry (LC-MS).

[0040] In this specification, unless otherwise specified, the contents of the cerium oxide abrasive, magnesium hydroxide abrasive, and dispersant in the polishing slurry of the present invention are the contents in the polishing slurry before polishing.

[0041] Furthermore, the abrasive slurry of the present invention is characterized in that the weight ratio of the magnesium hydroxide-based abrasive grains to the cerium oxide-based abrasive grains is 1.25×10 -4 Above and below 40.

[0042] From the viewpoint of suppressing a decrease in the polishing rate, the weight ratio of the magnesium hydroxide-based abrasive grains to the cerium oxide-based abrasive grains contained in the polishing material slurry of the present invention is preferably 1.25×10 -4 Above and below 40.

[0043] Furthermore, the weight ratio of the magnesium hydroxide-based abrasive to the cerium oxide-based abrasive is more preferably 0.001 to 1, and even more preferably 0.01 to 0.1.

[0044] As described above, the weight of the cerium oxide abrasive in the grinding material slurry of the present invention is the total content of total rare earth oxide (TREO) and rare earth oxides and F (fluorine). In addition, the weight of the magnesium hydroxide abrasive in the grinding material slurry of the present invention is the magnesium hydroxide content as described above. Thus, the weight ratio of the weight of the magnesium hydroxide abrasive to the weight of the cerium oxide abrasive is calculated. It should be noted that, by SEM-EDX analysis of the cerium oxide abrasive, when the cerium oxide abrasive contains Mg, the average value of the weight ratio of Mg to Ce in 20 particles of the cerium oxide abrasive is calculated based on the results of semi-quantitative analysis. The weight of the magnesium hydroxide abrasive can be calculated by removing the weight of Mg contained in the cerium oxide abrasive from the Mg content contained in the entire grinding material slurry of the present invention.

[0045] The abrasive slurry of the present invention is characterized in that, when the cerium oxide abrasive grains are 100 mass %, the Ce content of the cerium oxide abrasive grains is 100 mass % or less in terms of CeO2, the La content is 40 mass % or less in terms of La2O3, the F content is 10 mass % or less in terms of F, and the Pr content is 10 mass % or less in terms of Pr6O3. 11 The Nd content is 10% by mass or less when converted to Nd2O3.

[0046] Cerium oxide-based abrasive grains are preferred because higher purity of cerium oxide leads to higher polishing rates. On the other hand, if the cerium oxide particles contain impurities, the proportion of rare earth elements other than cerium as impurities is preferably as low as possible to improve the polishing rate. Low proportions of rare earth elements other than cerium, particularly lanthanum (La) and praseodymium (Pr), further improve the polishing rate.

[0047] From the viewpoint of achieving a good polishing rate, the Ce content in the cerium oxide-based abrasive of the present invention is preferably 100% by mass or less, calculated as CeO2. Furthermore, the Ce content is more preferably 50% by mass or more and 100% by mass or less, further preferably 60% by mass or more and 100% by mass or less, particularly preferably 70% by mass or more and 100% by mass or less, particularly preferably 80% by mass or more and 100% by mass or less, and particularly preferably 90% by mass or more and 100% by mass or less. Typically, the Ce content may be 100% by mass or less, 98% by mass or less, or 96% by mass or less.

[0048] The La content in the cerium oxide-based abrasive of the present invention may be 40% by mass or less, calculated as La2O3. Furthermore, the La content may be 0% by mass or more and 40% by mass or less, 0.1% by mass or more and 40% by mass or less, or 20% by mass or more and 40% by mass or less. Typically, the La content may be 40% by mass or less, 38% by mass or less, or 36% by mass or less.

[0049] The F content in the cerium oxide-based abrasive of the present invention may be 10% by mass or less in terms of F. Furthermore, the F content may be 0% by mass or more and 10% by mass or less, or 2% by mass or more and 8% by mass or less. Typically, the F content may be 10% by mass or less, 8% by mass or less, or 6% by mass or less.

[0050] The Pr content in the cerium oxide abrasive of the present invention is expressed as Pr6O 11The Pr content can be 10% by mass or less. In addition, the Pr content can be 0% by mass or more and 10% by mass or less, or 0.1% by mass or more and 10% by mass or less, or 2% by mass or more and 8% by mass or less. Typically, the Pr content can be 10% by mass or less, or 8% by mass or less, or 6% by mass or less.

[0051] The Nd content in the cerium oxide-based abrasive of the present invention may be 10% by mass or less, calculated as Nd2O3. Furthermore, the Nd content may be 0% by mass or more and 10% by mass or less, 0.1% by mass or more and 10% by mass or less, or 0.1% by mass or more and 5% by mass or less. Typically, the Nd content may be 10% by mass or less, 8% by mass or less, or 6% by mass or less.

[0052] The contents of each component in the cerium oxide abrasive of the present invention can be determined as follows. Specifically, the measurement sample obtained by the above-mentioned total rare earth oxide (TREO) measurement can be dissolved in perchloric acid and hydrogen peroxide, and measured by ICP-OES to calculate CeO2 / TREO. In addition, for La2O3 / TREO and Pr6O 11 / TREO and Nd2O3 / TREO can also be calculated in the same way.

[0053] Furthermore, the grinding material slurry of the present invention may contain any additive other than the above-mentioned cerium oxide abrasive, magnesium hydroxide abrasive, dispersant and solvent. Wherein, the arbitrary additive is a dispersant, a pH regulator, a viscosity regulator, a chelating agent, an oxidizing agent, a surfactant and a rust inhibitor, etc. When the grinding material slurry of the present invention is set to 100% by mass, the content of the arbitrary additive is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. Typically, the content of the arbitrary additive can be 10% by mass or less, or 8% by mass or less, or 6% by mass or less.

[0054] A polishing method for polishing an object to be polished using the polishing material slurry of the present invention will be described below.

[0055] The following polishing methods can be listed: the polishing material slurry of the present invention is supplied to a polishing pad, the polished surface of the object to be polished is brought into contact with the polishing pad, and polishing is performed by relative motion between the two. Among them, it can also be a method of pouring the polishing material slurry of the present invention, or a method of circulating the polishing material slurry of the present invention by repeatedly performing the following operation: the polishing material slurry of the present invention supplied to the polishing pad for polishing is recovered and the recovered polishing material slurry of the present invention is supplied to the polishing pad again. The polishing material slurry of the present invention can be circulated and repeatedly polish the object to be polished, so the usage amount can be suppressed. Among them, the polishing pad can use, for example, the non-woven fabric used in the past, a pad impregnated with a resin such as polyurethane or epoxy resin, and a suede material. Considering the aspects of the polishing force and the ease of operation of the polishing fixture, it is preferred that the polishing pressure is 5 kPa or more and 1.0×10 2 kPa or less, particularly 5 kPa or more and 5.0×10 kPa or less. The supply rate of the polishing material slurry is preferably 10 mL / min or more and 2000 mL / min or less, more preferably 50 mL / min or more and 800 mL / min or less.

[0056] The object to be ground utilizing the grinding material slurry of the present invention to grind, for example, can be enumerated as glass, quartz, silicon oxide, silicon (silicon wafer, etc.), high hardness materials with a Mohs hardness of 8 or more. And then, the grinding material slurry of the present invention can also be expected to carry out chemical mechanical polishing (CMP, Chemical Mechanical Polishing) by the chemical reaction to the object to be ground caused by cerium oxide. In addition, by adding an oxidizing agent, such as an oxidizing agent such as potassium permanganate or hydrogen peroxide, to the grinding material slurry of the present invention, it is also possible to carry out a CMP process that accelerates the chemical reaction more effectively. The object to be ground in the CMP process is, for example, a high hardness material with a Mohs hardness of 8 or more. Wherein, Mohs hardness refers to the hardness obtained by digitizing the hardness based on the mode of applying scratches to a standard substance, and can be measured using a Mohs hardness meter with a conventional method. The Mohs hardness scale assigns standard materials a hardness rating of 1 to 10, starting with the softest material. Specifically, the Mohs hardness of standard materials is: 1 for talc, 2 for gypsum, 3 for calcite, 4 for fluorite, 5 for apatite, 6 for orthoclase, 7 for quartz, 8 for topaz, 9 for corundum, and 10 for diamond. Examples of high-hardness materials with a Mohs hardness rating of 8 or higher include silicon carbide (Mohs hardness of approximately 9), gallium nitride (Mohs hardness of approximately 9), and diamond.

[0057] In addition, the object to be ground using the grinding material slurry of the present invention is preferably a silicon wafer having a silicon oxide layer on the surface, or a multilayer structure, or a composite material formed by compounding multiple materials. In particular, in the case of silicon, the grinding material slurry of the present invention can be used when forming an STI (Shallow Trench Isolation) structure in the manufacturing process of a semiconductor element with a substrate (wafer), flattening a pre-metal insulating material or an interlayer insulating material, forming a plug or buried metal wiring, etc.

[0058] Next, the method for producing the abrasive slurry of the present invention will be described below. Examples of the method for producing the abrasive slurry of the present invention include a method based on wet pulverization and a method based on dry pulverization.

[0059] In the wet pulverization method or dry pulverization method described later, the raw material particle size of cerium oxide (abrasive, CeO2) or magnesium hydroxide (additive, abrasive, Mg(OH)2) used as the raw material is the particle size at a volume-based cumulative fraction of 50% (D50), as measured by laser diffraction / scattering particle size distribution measurement. Specifically, the raw material is diluted with water to a concentration of approximately 0.01%, thereby preparing a measurement sample. The particle size at a volume-based cumulative fraction of 50% (D50) is then measured using a laser diffraction / scattering particle size distribution analyzer (MicrotracBEL Co., Ltd., MT3300EXII).

[0060] First, the method for producing the abrasive slurry of the present invention by wet grinding will be described below.

[0061] Pure water, cerium oxide (abrasive, CeO2), magnesium hydroxide (additive, abrasive, Mg(OH)2), and a dispersant (e.g., trisodium citrate) are placed in a container. The container is then placed in a paint shaker (60 Hz) and rotated at high speed to form a slurry. Note that a bead mill may be used instead of a paint shaker.

[0062] Beads (made of zirconia, φ0.1 mm) were placed in the container, and the slurried mixture was wet-pulverized to pulverize the cerium oxide in the mixture.

[0063] The mixture containing the mixed and pulverized cerium oxide in the container was filtered using a filter to separate the beads, and the slurry was collected.

[0064] The solid content concentration of the collected supernatant, that is, the cerium oxide abrasive concentration, is measured using a heated moisture meter, and pure water is added and mixed to obtain the abrasive slurry of the present invention.

[0065] Next, the method for producing the abrasive slurry of the present invention by dry grinding will be described below.

[0066] Cerium oxide (abrasive grains, CeO 2 ) and beads (0.4 mm in diameter, made of zirconia) were placed in a container, and the container was placed in a paint shaker (60 Hz). The container was rotated at high speed to dry-grind the cerium oxide.

[0067] The mixture containing the dry-pulverized cerium oxide in the container was separated from the beads using a filter, and the mixture containing the dry-pulverized cerium oxide was collected.

[0068] Then, pure water, dry-ground cerium oxide (abrasive, CeO2), magnesium hydroxide (additive, abrasive, Mg(OH)2) and a dispersant (e.g., trisodium citrate) are further added to the container, and the container is placed in a paint shaker (60 Hz) and rotated at high speed to slurry the mixture.

[0069] Then, the collected slurry is filtered using a filter having particle capture performance (for example, particle capture performance of 2 μm or more), and the solid content concentration in the supernatant, that is, the cerium oxide abrasive concentration, is measured using a heated moisture meter. Pure water is added to achieve a specified concentration and mixed to obtain the grinding material slurry of the present invention.

[0070] It should be noted that, in this specification, when expressed as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", and also includes the meaning of "preferably greater than X" or "preferably less than Y". In addition, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it also includes the intention of "preferably greater than X" or "preferably less than Y".

[0071] Effects of the Invention

[0072] The polishing slurry of the present invention can suppress a decrease in polishing rate due to a change over time even when the particle size of the abrasive grains is fine. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 This is a table showing the physical property values and measurement results of the polishing material slurries of Examples 1 to 9 and Comparative Examples 1 to 5. DETAILED DESCRIPTION

[0074] Hereinafter, the polishing material slurry according to the embodiment of the present invention will be further described by the following examples. However, the following examples do not limit the present invention.

[0075] (Example 1)

[0076] First, pure water, cerium oxide (CeO2, raw material particle size 22.2 μm) as cerium oxide-based abrasive, magnesium hydroxide (Mg(OH)2, raw material particle size 3.5 μm) as an additive and magnesium hydroxide-based abrasive, and trisodium citrate as a dispersant were added to a container and mixed to form a mixture slurry containing cerium oxide. The amount of magnesium hydroxide added was 0.78% by mass, based on 100% by mass of the abrasive slurry of Example 1. Furthermore, the amount of trisodium citrate added was 0.6% by mass, based on 100% by mass of the abrasive slurry of Example 1.

[0077] Next, the container was placed in a paint shaker (60 Hz), and the container was rotated at high speed to perform wet grinding so that the final average particle size of the abrasive grains of cerium oxide (CeO 2 ) and magnesium hydroxide (Mg(OH) 2 ) became 0.1 μm.

[0078] The mixture slurry containing the wet-pulverized cerium oxide in the container was filtered using a filter to separate the beads, and the mixture slurry was collected.

[0079] The collected mixture slurry was added with pure water using a heating moisture meter so that the solid content concentration in the supernatant, i.e., the cerium oxide abrasive concentration, would be 10% by mass when the abrasive slurry of Example 1 was 100% by mass, thereby obtaining the abrasive slurry of Example 1.

[0080] (Example 2)

[0081] In Example 2, the same manufacturing method as in Example 1 was carried out except that the raw material particle size of magnesium hydroxide (Mg(OH) 2 ) was set to 6 μm, thereby obtaining the abrasive slurry of Example 2.

[0082] (Example 3)

[0083] In Example 3, the same manufacturing method as in Example 1 was carried out except that the raw material particle size of magnesium hydroxide (Mg(OH) 2 ) was set to 0.15 μm, thereby obtaining the abrasive slurry of Example 3.

[0084] (Example 4)

[0085] In Example 4, the same manufacturing method as in Example 1 was carried out except that the addition amount of magnesium hydroxide (Mg(OH) 2 ) was set to 0.1 mass %, thereby obtaining the abrasive slurry of Example 4.

[0086] (Example 5)

[0087] In Example 5, the same production method as in Example 1 was carried out except that the dispersant was changed from trisodium citrate to trisodium gluconate to obtain the abrasive slurry of Example 5.

[0088] (Example 6)

[0089] In Example 6, the same production method as in Example 1 was carried out except that the dispersant was changed from trisodium citrate to disodium (L)-tartrate dihydrate, thereby obtaining the abrasive slurry of Example 6.

[0090] (Example 7)

[0091] In Example 7, the same manufacturing method as in Example 1 was carried out except that the addition amount of magnesium hydroxide (Mg(OH) 2 ) was set to 0.01 mass %, thereby obtaining the abrasive slurry of Example 7.

[0092] (Example 8)

[0093] In Example 8, the same manufacturing method as in Example 1 was carried out except that the addition amount of magnesium hydroxide (Mg(OH) 2 ) was set to 10% by mass, thereby obtaining the abrasive slurry of Example 8.

[0094] (Example 9)

[0095] In Example 9, cerium oxide (CeO2) as cerium oxide abrasive and magnesium hydroxide (Mg(OH)2) as magnesium hydroxide abrasive are wet-milled so that the final average particle size of the abrasive becomes 0.3 μm. Except for this, the same manufacturing method as in Example 1 is implemented to obtain the grinding material slurry of Example 9.

[0096] (Comparative Example 1)

[0097] In Comparative Example 1, the additive was changed from magnesium hydroxide (Mg(OH)2, raw material particle size 3.5μm) to calcium hydroxide (Ca(OH)2, raw material particle size 26.9μm). Except for this, the same manufacturing method as Example 1 was implemented to obtain the grinding material slurry of Comparative Example 1.

[0098] (Comparative Example 2)

[0099] In Comparative Example 2, the additive was changed from magnesium hydroxide (Mg(OH)2, raw material particle size 3.5μm) to aluminum hydroxide (Al(OH)3, raw material particle size 70.1μm). Except for this, the same manufacturing method as Example 1 was implemented to obtain the grinding material slurry of Comparative Example 2.

[0100] (Comparative Example 3)

[0101] In Comparative Example 3, the same production method as in Example 1 was carried out except that no additive was added, thereby obtaining an abrasive slurry of Comparative Example 3.

[0102] (Comparative Example 4)

[0103] In Comparative Example 4, the average particle size of cerium oxide (CeO2) as a cerium oxide abrasive and magnesium hydroxide (Mg(OH)2) as a magnesium hydroxide abrasive is set to 0.7 μm. Except for this, the same manufacturing method as Example 1 is implemented to obtain the grinding material slurry of Comparative Example 4.

[0104] (Comparative Example 5)

[0105] In Comparative Example 5, the same manufacturing method as in Example 1 was carried out except that no additive was added and the average particle size of the cerium oxide (CeO 2 ) abrasive grains as the cerium oxide-based abrasive grains was set to 0.7 μm, thereby obtaining an abrasive slurry of Comparative Example 5.

[0106] Then, the following physical properties were measured for the polishing material slurries of Examples 1 to 9 and Comparative Examples 1 to 5. The measured physical properties and their measuring methods are shown below, and the measurement results are shown in FIG. Figure 1 .

[0107] Component Analysis

[0108] The total rare earth oxide (TREO) content of each content in the cerium oxide abrasive used in the abrasive slurries of Examples 1 to 9 and Comparative Examples 1 to 5 was measured using the oxalate precipitation-calcination-gravimetric method (units: solid: mass %, liquid: g / L). As a pretreatment for this measurement, if the measurement object was a solid (abrasive raw material or abrasive), it was dissolved using nitric acid, perchloric acid, and hydrogen peroxide, and then boiled. If the measurement object was a liquid, it was directly boiled. Specifically, 100 ml of the abrasive slurry of Examples 1 to 9 and Comparative Examples 1 to 5 was placed in a glass beaker and heated and dried at 120°C for 24 hours to prepare a dry powder. Then, 5 mL of 60% nitric acid, 5 mL of 60% perchloric acid, and 1 mL of 35% hydrogen peroxide solution were added to dissolve the powder and boiled to prepare the measurement samples of Examples 1 to 9 and Comparative Examples 1 to 5. The total rare earth oxide (TREO) content of the samples of Examples 1 to 9 and Comparative Examples 1 to 5 was then measured by the oxalate precipitation-calcination-gravimetric method. The sample obtained by the above-mentioned total rare earth oxide (TREO) measurement was dissolved by adding 5 mL of 60% nitric acid, 5 mL of 60% perchloric acid, and 1 mL of 35% hydrogen peroxide solution, and the CeO2 / TREO ratio was calculated by ICP-OES. 11 / TREO and Nd2O3 / TREO were calculated in the same manner. Furthermore, regarding the fluorine (F) content, the measurement sample was dissolved by alkali fusion and then extracted with warm water. The F concentration in the solution was measured using the fluoride ion electrode method, and the F content (mass %) in the measurement sample was calculated.

[0109] The magnesium hydroxide abrasive content used in the abrasive slurries of Examples 1-9 and Comparative Examples 1-5 was determined by adding 5 mL of 60% nitric acid, 5 mL of 60% perchloric acid, and 1 mL of 35% hydrogen peroxide to the solid sample (abrasive raw material or abrasive). The solution was then heated and decomposed, and the Mg concentration was measured using an ICP-OES apparatus. The added magnesium hydroxide content was estimated by multiplying the solution by the hydroxide coefficient. As mentioned above, the hydroxide coefficient was 2.40.

[0110] <Particle size evaluation>

[0111] The average abrasive particle size of cerium oxide (CeO2), magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), and aluminum hydroxide (Al(OH)3) in the abrasive slurries of Examples 1 to 9 and Comparative Examples 1 to 5 is a particle size (D50) measured by a particle size distribution measurement method using a dynamic light scattering method. The particle size distribution is evaluated using a Zeta potential particle size molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000ZS) in accordance with JIS Z8828:2019 "Particle size analysis-dynamic light scattering method" to measure the particle size (D50) at a cumulative fraction of 50% based on volume. In addition, the abrasive slurries of Examples 1 to 9 and Comparative Examples 1 to 5 are diluted with pure water as needed so that the solid content concentration in each abrasive slurry becomes 0.005% by mass to 0.1% by mass, and used as a measurement sample. Immediately before measurement, the sample was filtered through an 11 μm pore size filter and ultrasonically treated for 3 minutes using an ultrasonic cleaner (AS ONE: VS-100III). Furthermore, the sample liquid temperature was adjusted to 25°C. The particle size (D50) refers to the median diameter (D50), which represents the 50% cumulative value of the cumulative distribution curve.

[0112] Polishing rate measurement test

[0113] The polishing rates of the abrasive slurries of Examples 1 to 9 and Comparative Examples 1 to 5 were evaluated by the following steps. Soda lime glass with a diameter of 60 mm was used as the polishing object. A single-sided polishing machine manufactured by MAT was used as the polishing device. A polyurethane polishing pad was used as the polishing pad mounted on the base. Furthermore, the abrasive slurry used in the measurement was prepared by adjusting the abrasive concentration of the abrasive slurries of Examples 1 to 9 and Comparative Examples 1 to 5 to 100 g / L. In addition, the supply rate of the abrasive slurry was set to 600 mL / min, and the pressure on the polishing surface was set to 9.8 kPa (100 g / cm 2 ), the rotation speed of the grinder was set to 60 rpm. Then, a grinding process was performed, and the mass of the soda-lime glass to be ground before and after the grinding process was measured. The amount of mass reduction of the soda-lime glass caused by the grinding process was thus determined, and the grinding rate was calculated based on the value. The grinding rate after 20 minutes of grinding was taken as the initial rate, and the grinding rate after 6 hours of grinding was taken as the time-dependent rate. If the initial rate was 0.45 μm / min or more, it was evaluated as "○○ (excellent)", if the initial rate was 0.40 μm / min or more and less than 0.45 μm / min, it was evaluated as "○ (good)", and if the initial rate was less than 0.40 μm / min, it was evaluated as "× (poor)". If the time-dependent rate was 80% or more of the initial rate, it was evaluated as "○○ (excellent)", if it was 60% or more and less than 80% of the initial rate, it was evaluated as "○ (good)", and if it was less than 60% of the initial rate, it was evaluated as "× (poor)". The rate over time is preferably 0.2 μm / min or higher, more preferably 0.32 μm / min or higher, and particularly preferably 0.36 μm / min or higher.

[0114] <Grinding accuracy evaluation>

[0115] The polished surface of the soda lime glass that has been subjected to 6 hours of grinding process in the above-mentioned grinding rate determination test is cleaned with pure water, and after being dried in a dust-free state, the evaluation of grinding accuracy is carried out. The evaluation of grinding accuracy is as follows: for the polished surface after grinding process, within the measurement range of 10 μm × 10 μm, an atomic force microscope (Atomic Force Microscope (AFM); Hitachi High-Tech Science Co., Ltd. AFM5400L) is used to measure, and the surface roughness Ra of the polished surface is calculated, thus evaluating. If surface roughness Ra is less than 0.24nm, it is evaluated as "00 (excellent)", if surface roughness Ra is more than 0.25nm and less than 0.30, it is evaluated as "0 (good)", if surface roughness Ra is more than 0.30nm, it is evaluated as "× (poor)".

[0116] pH measurement

[0117] The pH of the polishing material slurries of Examples 1 to 9 and Comparative Examples 1 to 5 was measured after the pH meter (HORIBA: Glass Electrode Hydrogen Ion Concentration Indicator D-53) electrode (HORIBA: Standard ToupH Electrode 9615S-10D) was used to check the liquid temperature at 25°C. The pH was measured after 20 minutes of polishing as the initial pH, and the pH after 6 hours of polishing as the time-dependent pH.

[0118] like Figure 1 As shown, the polishing slurries of Examples 1 to 9, by containing magnesium hydroxide-based abrasive grains as an additive, can suppress deterioration due to time change even when the average abrasive grain diameter of the cerium oxide-based abrasive grains and the magnesium hydroxide-based abrasive grains is 0.01 μm to 0.5 μm.

[0119] The abrasive slurries of Examples 1 to 9 contained one or more selected from sodium citrate, sodium gluconate, and sodium tartrate as a dispersant, thereby suppressing deterioration due to time-dependent changes.

[0120] The abrasive slurries of Examples 1 to 9 suppressed the degradation of polishing rates due to aging and also exhibited excellent surface roughness Ra. On the other hand, the abrasive slurries of Comparative Examples 1 and 2 experienced excessive aggregation during polishing due to aging, resulting in either inability to polish or interrupted polishing. Furthermore, the abrasive slurries of Comparative Examples 4 and 5 exhibited surface roughness Ra of 0.30 nm or greater due to the large average particle size of the cerium oxide-based abrasive or the magnesium hydroxide-based abrasive.

[0121] The pH of the polishing material slurries of Examples 1 to 9 also suppressed fluctuations due to time changes.

[0122] When the polishing material slurry of Examples 1 to 9 is set to 100 mass%, if the content of cerium oxide abrasive is greater than or equal to 0.5 mass% and less than or equal to 40 mass% and the content of magnesium hydroxide abrasive is greater than or equal to 0.005 mass% and less than or equal to 20 mass%, a good polishing rate can be achieved.

[0123] Regarding the polishing material slurries of Examples 1 to 9, if the weight ratio of the weight of the magnesium hydroxide-based abrasive grains to the weight of the cerium oxide-based abrasive grains is 1.25×10 -4 If the value is greater than or equal to 40 and less than or equal to 40, a decrease in the polishing rate can be suppressed.

[0124] Regarding the polishing material slurries of Examples 1 to 9, when the cerium oxide abrasive grains are set to 100 mass %, if the Ce content of the cerium oxide abrasive grains is 100 mass % or less in terms of CeO2, the La content is 40 mass % or less in terms of La2O3, the F content is 10 mass % or less in terms of F, and the Pr content is Pr6O 11When the Nd content is 10% by mass or less and the Nd content is 10% by mass or less as converted to Nd2O3, a good polishing rate can be achieved.

[0125] In addition to the configurations of each invention and embodiment, the invention disclosed in this specification also includes configurations determined by changing their local configurations to other configurations disclosed in this specification within the scope of applicability, or configurations determined by adding other configurations disclosed in this specification to these configurations, or configurations determined by conceptualizing these local configurations to a higher level by deleting them within the limit of being able to obtain local effects.

[0126] Industrial applicability

[0127] The grinding material slurry of the present invention is not easy to cause the grinding rate to decrease due to time change, and the change of pH is suppressed, and is suitable as the grinding material used in the CMP method. In addition, the grinding material slurry of the present invention is not easy to cause the grinding rate to decrease due to time change, and the change of pH is suppressed, so compared with the past, the grinding material slurry can be used for a long time. Therefore, it is possible to reduce the amount of the manufactured object itself and the waste associated therewith, and it is also possible to cut the energy cost during manufacturing and in the disposal process of the waste. Due to these aspects, it is possible to achieve sustainable management of natural resources and efficient advantages and decarbonization (carbon neutralization).

Claims

1. A grinding material slurry, characterized in that: The invention comprises cerium oxide abrasive grains, magnesium hydroxide abrasive grains, a dispersant and a solvent, wherein the average abrasive grain diameter of the cerium oxide abrasive grains and the magnesium hydroxide abrasive grains is 0.01 μm or more and 0.5 μm or less.

2. The abrasive slurry according to claim 1, wherein The solvent comprises water.

3. The abrasive slurry according to claim 1, wherein The dispersant includes at least one selected from organic acid and alkali metal salts, phosphoric acids, and polymer dispersants.

4. The abrasive slurry according to claim 1, wherein The organic acid alkali metal salt comprises one or more selected from sodium citrate, sodium gluconate, and sodium tartrate.

5. The abrasive slurry according to claim 1, wherein The cerium oxide-based abrasive grains are cerium oxide abrasive grains.

6. The abrasive slurry according to any one of claims 1 to 5, characterized in that When the polishing material slurry is set to 100 mass%, the content of the cerium oxide-based abrasive is 0.5 mass% to 40 mass%, and the content of the magnesium hydroxide-based abrasive is 0.005 mass% to 20 mass%.

7. The abrasive slurry according to any one of claims 1 to 5, characterized in that The weight ratio of the magnesium hydroxide-based abrasive to the cerium oxide-based abrasive is 1.25×10 -4 Above and below 40.

8. The abrasive slurry according to any one of claims 1 to 5, characterized in that When the cerium oxide abrasive is set to 100 mass%, the Ce content of the cerium oxide abrasive is 100 mass% or less in terms of CeO2, the La content is 40 mass% or less in terms of La2O3, the F content is 10 mass% or less in terms of F, and the Pr content is 10 mass% or less in terms of Pr6O3. 11 The Nd content is 10% by mass or less when converted to Nd2O3.

9. A grinding method, characterized in that: An object to be polished is polished using the polishing material slurry according to any one of claims 1 to 5.

Images