Zirconium oxide sol

Abstract

This polishing dispersion and this polishing powder can be used in chemical-mechanical polishing (CMP) of a SiC wafer etc., and can be employed in a semiconductor production process etc. Provided is a zirconium oxide sol containing a zirconium oxide particle group exhibiting a layered structure in a scanning electron microscope image.

Description

Zirconium oxide sol

[0001] The present invention relates to a zirconium oxide sol containing a group of zirconium oxide particles with a novel structure, a polishing dispersion and a polishing powder containing the particle group, and a polishing method using these.

[0002] Polishing is widely used in the microelectronics industry. Silicon carbide (SiC) and other materials have attracted attention in recent years as power semiconductors due to their superior dielectric breakdown strength (10 times that of Si) and band gap (3 times that of Si), as well as their high-temperature and energy-saving properties. For similar reasons, gallium nitride (GaN), diamond, and sapphire are also attracting attention and undergoing active development. To manufacture high-performance devices with good yield, atomic-level flattening and smoothing of the substrate is necessary. However, these substrates are harder and more brittle than Si, and their chemical stability makes them difficult to process, resulting in low productivity and contributing to increased substrate processing costs. Conventionally, after slicing the crystal, multi-stage, long-duration polishing is performed using CMP (Chemical Mechanical Polishing) with diamond particles or colloidal silica particles. However, this incurs significant costs in terms of consumables and equipment, resulting in costs several times higher than those of Si substrates. Reducing these processing costs is strongly desired for the widespread adoption of power semiconductors. Several dispersions using zirconium oxide as abrasive particles have also been proposed.

[0003] For example, Patent Document 1 discloses a polishing slurry characterized by containing 1 to 20% by mass of monoclinic zirconium oxide with a crystallite size of 10 to 1,000 nm and an average particle diameter of 30 to 2,000 nm, and further containing a carboxylic acid having three or more carboxyl groups in its molecule and a quaternary alkylammonium hydroxide, and having a pH of 9 to 12.

[0004] Patent Document 2 discloses an abrasive powder containing zirconium oxide particles, characterized in that the crystallite size of the zirconium oxide particles, calculated based on the diffracted X-ray intensity at approximately 28.0° and 31.0° of 2θ as measured by powder X-ray diffraction, is 330 Å or larger, and the average primary particle diameter of the zirconium oxide particles is 0.2 μm or larger.

[0005] Patent Document 3 discloses a slurry for chemical mechanical polishing (CMP) comprising an aqueous liquid carrier, an oxynitrate, an oxychloride, an oxysulfate, an oxycarbonate, a transition metal oxy compound selected from C2 to C10 oxyalkanoates, and a Per-type oxidizing agent, and also discloses a SiC polishing slurry using zirconia particles.

[0006] Patent Document 4 discloses a method for producing an abrasive composition containing zirconium oxide sol, wherein the zirconium compound has a d50 (wherein d50 represents the particle size meaning that the number of particles smaller than or equal to this particle size accounts for 50% of the total number of particles) of 5 to 25 μm when the slurry of the zirconium compound is measured by laser diffraction, and the d99 (wherein d99 represents the particle size meaning that the number of particles smaller than or equal to this particle size accounts for 99% of the total number of particles) of the zirconium compound particles is 60 μm or less, and the zirconium compound is calcined at a temperature range of 400 to 1000°C; and the obtained zirconium oxide powder is wet-milled in an aqueous medium until the d50 of the zirconium oxide particles, when the slurry of the zirconium oxide is measured by laser diffraction, is 80 to 150 nm, and the d99 of the zirconium oxide particles is 150 to 500 nm.

[0007] Japanese Patent Publication No. 2006-324639 WO2012 / 169515, Japanese Patent Publication No. 2023-512216 WO2006 / 123562

[0008] However, because materials like SiC are hard and difficult to process, further improvements in production efficiency and other aspects are required.

[0009] This invention provides a zirconium oxide sol containing a group of zirconium oxide particles with a novel structure, as well as a polishing dispersion and polishing powder that exhibit excellent polishing rates and superior surface smoothness after polishing.

[0010] The present invention relates to the following [1] to

[19] . [1] A zirconium oxide sol comprising a group of zirconium oxide particles showing a layered structure in a scanning electron microscope image. [2] The zirconium oxide sol according to [1], wherein the layered structure comprises a structure in which the layers are stacked in an X-shape and / or T-shape. [3] The zirconium oxide sol according to [1] or [2], wherein the ratio of the short side to the long side of the particles (short side / long side), calculated from the scanning electron microscope image using particle analysis software, is 0.50 to 0.95, and the ratio of the height to the long side of the particles (height / long side), calculated from the atomic force microscope image, is 0.20 to 1.00. [4] The zirconium oxide sol according to any one of [1] to [3], wherein the Heywood diameter calculated from the scanning electron microscope image using particle analysis software is 1 to 150 nm and the circularity is 0.1 to 0.8. [5] A polishing dispersion comprising a group of zirconium oxide particles showing a layered structure in scanning electron microscope images, and a polishing aid. [6] The polishing dispersion according to [5], wherein the polishing aid comprises one or more selected from the group consisting of peroxides, nitrate compounds, persulfate compounds, chlorine compounds, bromine compounds, iodine compounds, hypochlorite compounds, iron acids, permanganates, chromic acids, vanadic acids, ruthenic acids, molybdic acids, rhenic acids, and tungstic acids. [7] SiC wafer, polycrystalline SiC, GaN, GaAs, Ga ２ O ３[5] or [6] A polishing dispersion for use in polishing GaP or diamond substrates. [8] A polishing method using the polishing dispersion described in any of [5] to [7]. [9] A method for producing a polishing dispersion, comprising the step of preparing a dispersion using a group of zirconium oxide particles showing a layered structure in a scanning electron microscope image and a polishing aid.

[10] A method for improving the polishing rate, comprising polishing using a group of zirconium oxide particles showing a layered structure in a scanning electron microscope image and a polishing aid.

[11] A method for reducing surface roughness Sa, comprising polishing using a group of zirconium oxide particles showing a layered structure in a scanning electron microscope image and a polishing aid.

[12] A polishing powder containing zirconium oxide powder containing a group of zirconium oxide particles showing a layered structure in a scanning electron microscope image.

[13] The polishing powder according to

[12] , wherein the average secondary particle size of the zirconium oxide powder is 0.002 to 5 μm.

[14] The polishing powder according to

[12] or

[13] , wherein the average secondary particle size of the zirconium oxide powder is 0.1 μm or less.

[15] The polishing powder according to any one of

[12] to

[14] , wherein the purity of the zirconium oxide powder is 97% by mass or more.

[16] The polishing powder according to any one of

[12] to

[15] , wherein the zirconium oxide powder is produced by a liquid-phase synthesis method.

[17] The specific surface area of ​​the zirconium oxide powder is 20 m². ２

[12] to

[16] or greater, polishing powder according to any of

[12] to

[16] .

[18] A polishing method comprising polishing using the polishing powder according to any of

[12] to

[17] .

[19] A method for producing zirconium oxide sol by liquid-phase synthesis, comprising the step of heating and aging zirconium hydroxide in an acidic atmosphere in an aqueous solvent, wherein in the heating and aging step, a seed crystal of zirconium oxide is made to coexist with the zirconium hydroxide, and acid is added in multiple stages, with a linear carboxylate added in at least one of these stages, for a method of producing zirconium oxide sol.

[0011] According to the present invention, it is possible to provide a zirconium oxide sol containing a group of zirconium oxide particles with a novel structure, as well as a polishing dispersion and polishing powder that have excellent polishing rates and excellent surface smoothness after polishing.

[0012] Scanning electron microscope images of the zirconium oxide particle groups of Example 1 and their image diagrams, scanning electron microscope images of the zirconium oxide particle groups of Example 2 and their image diagrams, scanning electron microscope images of the zirconium oxide particle groups of Example 3 and their image diagrams

[0013] When the present inventors studied the above problems, they newly found that by using a zirconium oxide particle group showing a layered structure in a scanning electron microscope image (SEM image) for polishing, the polishing rate is excellent and the surface smoothness after polishing is excellent. Although this mechanism is not clear, in the X-shaped and T-shaped particles composed of a layered structure, the protruding parts bite into the pad surface, and the holding force on the pad surface is improved, so that the rolling of the particles due to the rotation of the surface plate hardly occurs, and fine polishing (grinding) can proceed stably and smoothly for a long time (long distance). It is also presumed that the particle edges act as effective cutting edges, realizing the expression of a sharp abrasive grain function and obtaining both a high polishing rate and an excellent smooth surface. Generally, when particles are broken, the particles become polydispersed and the contact points between the polished object and the particles decrease, so it is presumed that the pressure at the contact points increases, causing scratches and surface roughness. The shape of the present invention, which is X-shaped and T-shaped particles composed of a layered structure, is estimated to be suitable for the polishing rate and the surface smoothness because it can increase the gripping force of the particles on the pad and provide effective cutting edges.

[0014] The zirconium oxide sol of the present invention contains a zirconium oxide particle group showing a layered structure in a scanning electron microscope image. The layered structure confirmed in the above scanning electron microscope image refers to a structure in which rod-shaped, needle-shaped, or plate-shaped structural units are laminated as shown in FIGS. 1 to 3. The layered structure in the zirconium oxide particle group of the present invention may be a structure in which the structural units are laminated in the same direction (FIG. 1), or may be a structure laminated in an X-shape or a T-shape and intersecting (FIGS. 2 and 3). From the viewpoint of the polishing rate and the surface smoothness after polishing, it is preferable to include a structure laminated in an X-shape and / or a T-shape and intersecting in the laminated structure.

[0015] The zirconium oxide particle group of the present invention has a ratio of the short side to the long side (short side / long side) of the particles calculated using particle analysis software from the above scanning electron microscope image, which is preferably 0.50 to 0.95, more preferably 0.50 to 0.80, and still more preferably 0.60 to 0.75 from the viewpoint of the polishing rate. As the particle analysis software, Mac-view (manufactured by MOUNTECH), ImageJ (freeware, https: / / imagej.net / ij / , as of September 25, 2024), etc. can be used.

[0016] The zirconium oxide particle group of the present invention has a ratio of the height to the long side (height / long side) of the particles calculated from the atomic force microscope image (AFM image), which is preferably 0.20 to 1.00, more preferably 0.20 to 0.80, and still more preferably 0.25 to 0.60 from the viewpoint of the polishing rate.

[0017] The zirconium oxide particle group of the present invention has a Heywood diameter calculated using particle analysis software from the above scanning electron microscope image, which is preferably 1 to 150 nm, more preferably 5 to 120 nm, and still more preferably 20 to 100 nm from the viewpoint of the smoothness of the surface after polishing.

[0018] The zirconium oxide particle group of the present invention has a circularity calculated using particle analysis software from the above scanning electron microscope image, which is preferably 0.1 to 0.8, more preferably 0.15 to 0.7, and still more preferably 0.2 to 0.5 from the viewpoint of the polishing rate.

[0019] The method for producing zirconium oxide sol according to the present invention is not particularly limited, but it can be produced by a liquid-phase synthesis method. For example, a preferred example is a method for producing zirconium oxide sol by a liquid-phase synthesis method, which includes a step of heating and aging zirconium hydroxide in an acidic atmosphere in an aqueous solvent, wherein in the heating and aging step, a seed crystal of zirconium oxide is made to coexist with the zirconium hydroxide, and acid is added in multiple stages, with a linear carboxylate salt being added in at least one of these stages. The liquid-phase synthesis method in this embodiment is a method for directly synthesizing zirconium oxide from an amorphous precursor by heating in a liquid phase, mainly in an aqueous phase of an aqueous solvent, without going through high-temperature heating such as calcination or electrofusion. Specifically, in the process of heating and aging zirconium hydroxide in an aqueous solvent under an acidic atmosphere, a seed crystal of zirconium oxide is made to coexist with the zirconium hydroxide, and the acid addition and heating are performed in multiple stages, with a linear carboxylate added in at least one of these stages, thereby obtaining the characteristic layered structure of the zirconium oxide particle group of the present invention. The zirconium hydroxide is not particularly limited, and one obtained by neutralizing an aqueous solution of zirconium salt with a base can be used. The type of acid used in heating and aging is not particularly limited, and hydrochloric acid and nitric acid can be used. The type of linear carboxylate used in heating and aging is not particularly limited, and sodium acetate, sodium propionate, etc. can be used. The aqueous solvent refers to an aqueous medium such as water, deionized water, or pure water. The acidic atmosphere is preferably pH 0 to 3.0, more preferably 0.5 to 2.0. The seed crystal of zirconium oxide has a specific particle size D. ５０ It is preferable to use the seed crystal with particle size D ５０ The wavelength is preferably 1 to 100 nm, more preferably 3 to 50 nm, and even more preferably 5 to 20 nm. (See above D) ５０ To satisfy this condition, the seed crystal is preferably in the form of a zirconium oxide sol. In the form of a zirconium oxide sol seed crystal, the dispersed phase is zirconia (ZrO ２ ) contains alkali metal oxides (M ２O, M: (Li, Na, K, Rb, Cs) may be included. The type and crystallite size of the crystal phase in the seed crystal are not particularly limited. Zirconium oxide that can be used as the above seed crystal can be obtained by known methods. Specifically, the method disclosed in Example 1 of JP-A-2008-31023 can be mentioned. The addition amount of the seed crystal is preferably 0.005 to 0.20, more preferably 0.008 to 0.15, and still more preferably 0.01 to 0.10 in terms of molar conversion of [ZrO of the seed crystal] / [ZrO of zirconium hydroxide]. The number of steps of acid addition and temperature increase performed in multiple steps is at least two steps or more, preferably 2 to 5 steps, and more preferably 2 to 3 steps. It is preferable that the total sum of the acid addition amounts in the second and subsequent steps is larger than the acid addition amount in the first step. The addition amount of the acid in the first step is preferably 0.01 to 0.15, more preferably 0.05 to 0.10 in terms of molar conversion of [acid] / [ZrO of zirconium hydroxide]. The total amount of the acid addition amount in all steps is preferably 0.10 to 0.60, more preferably 0.20 to 0.50 in terms of molar conversion of [acid] / [ZrO of zirconium hydroxide]. The value obtained by dividing the above acid addition amount by the valence of the acid used is used. It is preferable to increase the temperature for the aging temperature of the above acid for each additional step. The linear carboxylate is added in at least one of the steps of acid addition performed in multiple steps. The total addition amount of the linear carboxylate is preferably 0.01 to 0.50, more preferably 0.05 to 0.40 in terms of molar conversion of [linear carboxylate] / [ZrO]. The aging temperature in the first step is preferably 40 to 60°C, more preferably 45 to 55°C. The aging temperature in the final step is preferably 90 to 110°C, more preferably 95 to 105°C. By the production method of this aspect, a zirconium oxide sol (hereinafter, may sometimes be simply referred to as "zirconium oxide") containing a group of zirconium oxide particles showing a layered structure in a scanning electron microscope image (SEM image) can be obtained.

[0020] ​​​​​​​​​​The zirconium oxide obtained by the above manufacturing method usually contains several percent of hafnium oxide as an unavoidable impurity, generally referring to a content of 1.0 to 3.0%, but it may also be purified to remove hafnium oxide. Furthermore, the zirconium oxide may be stabilized zirconium oxide, in which case calcium, magnesium, yttrium, cerium, and other rare earth elements may be in solid solution. In addition, other elements that can be solid-solved in zirconium oxide may be included. Furthermore, particles of zirconium oxide and other oxides may be compounded to form a single particle. Zirconium oxide functions as an abrasive, and by including the zirconium oxide particles of the present invention, a high polishing rate and low surface roughness can be achieved.

[0021] While monoclinic, tetragonal, and cubic phases are known as crystalline phases of zirconium oxide, the present invention is not particularly limited to any specific crystalline phase.

[0022] (Polishing Dispersion) The polishing dispersion according to the present invention contains the zirconium oxide particle group of the present invention and a polishing aid. One means of incorporating the zirconium oxide particle group of the present invention is to use zirconium oxide obtained by the above manufacturing method, but the present invention is not limited thereto. The following describes an embodiment using zirconium oxide obtained by the above manufacturing method.

[0023] The median diameter (particle size D) of zirconium oxide in the polishing dispersion of the present invention. ５０ The particle size (D) is preferably 2.0 to 5000.0 nm, more preferably 3.0 to 1000.0 nm, even more preferably 4.0 to 500.0 nm, and even more preferably 5.0 to 100.0 nm, from the viewpoint of polishing rate and smoothness. ５０ ) is measured by the method described in the examples below.

[0024] The zirconium oxide content in the polishing dispersion of the present invention can be appropriately selected depending on the object to be polished and the polishing conditions, but is usually 0.1 to 20% by mass, preferably 1 to 15% by mass. In addition, abrasive particles other than zirconium oxide may be present in the present invention. Examples of abrasive particles other than zirconium oxide include known inorganic particles, organic particles, and organic-inorganic composite particles, such as oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles, green silicon carbide (GC) particles, and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; and so on.

[0025] The concentration of abrasive grains other than zirconium oxide is preferably 30% by mass or less, more preferably 15% by mass or less, relative to the total abrasive grain concentration. The lower limit can be 0% by mass, 1% by mass or more, 2% by mass or more, or 3% by mass or more.

[0026] The polishing aid according to the present invention is a component that enhances the effect of polishing, and a water-soluble one is preferably used. Abrasives include peroxides such as hydrogen peroxide; nitrate compounds such as iron nitrate, silver nitrate, aluminum nitrate, and their complex cerium ammonium nitrate; persulfates such as potassium peroxomonosulfate and peroxodisulfate, and their salts ammonium persulfate and potassium persulfate; chlorine compounds such as chloric acid and its salts, perchloric acid and its salt potassium perchlorate; bromine compounds such as bromate and its salt potassium bromate; iodine compounds such as iodic acid and its salt ammonium iodate, periodic acid and its salt sodium periodate and potassium periodate; hypochlorous acid and its salt sodium hypochlorite; iron acids such as iron acid and its salt potassium ironate; permanganates such as permanganates and its salts sodium permanganate and potassium permanganate; chromates such as chromate and its salt potassium chromate and potassium dichromate; Examples include vanadic acid, its salts such as ammonium vanadate, sodium vanadate, sodium metavanadate, and potassium vanadate; ruthenic acids such as perruthenic acid or its salts; molybdic acid, its salts such as ammonium molybdate and disodium molybdate; rhenic acids such as perrhenium or its salts; and tungstic acid, its salt such as disodium tungstate. These can be used individually or in combination of two or more. Among these, oxidizing agents are preferred from the viewpoint of polishing efficiency, and potassium permanganate, sodium permanganate, periodic acid, potassium persulfate, and hydrogen peroxide are particularly preferred.

[0027] The content of the polishing aid in the polishing dispersion of the present invention can be appropriately selected depending on the object to be polished and the polishing conditions, but is usually 0.1 to 20.0% by mass, preferably 0.5 to 10.0% by mass.

[0028] The dispersion medium for the polishing dispersion of the present invention is not limited as long as it ensures polishing performance, but is usually water, and ion-exchanged water, pure water, ultrapure water, distilled water, etc. can be used. In addition, an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water may be further contained as needed. The water content in the dispersion medium is preferably 90% by volume or more, more preferably 95% by volume or more, and even more preferably 100% by volume.

[0029] The pH of the polishing dispersion of the present invention is not limited and can be arbitrarily adjusted as appropriate to adjust the potential between the abrasive grains and the surface to be polished. For example, it can be pH 0.5 to 13.5, pH 1.0 to 12.0, pH 1.3 to 8.5, pH 1.5 to 5.0, etc. pH adjustment can be done by adding a common acid (hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, etc.) or a common base (sodium hydroxide, ammonia, amine, etc.) to the polishing dispersion.

[0030] The polishing dispersion of the present invention may optionally contain various additives other than those listed above. Examples of known additives include chelating agents, thickeners, dispersants, surface protectants, wetting agents, pH adjusters, surfactants, organic acids, organic acid salts, inorganic acids, inorganic acid salts, rust inhibitors, preservatives, and fungicides. The type and concentration of these additives are not limited in any way, as long as they ensure the polishing performance of the present invention.

[0031] The polishing dispersion of the present invention may contain impurities such as inorganic ions including nitrate ions, chloride ions, and sulfate ions, metal ions including sodium, potassium, iron, and titanium, and organic ions such as acetate ions and tetramethylammonium ions. However, this is not a particular problem as long as the polishing performance of the present invention is ensured.

[0032] The polishing dispersion and the polishing powder of the present invention, described later, exhibit excellent polishing rates and smooth surfaces after polishing, and therefore contain Si, SiC, GaN, GaAs, and Ga ２ O ３It can be suitably used for polishing substrates such as GaP, sapphire, and diamond, oxide films, metal films such as W and Cu, and is particularly suitable for polishing SiC wafers, polycrystalline SiC, GaN, GaAs, GaP, and diamond substrates. Accordingly, the present invention also provides a polishing method, a method for improving the polishing rate, and a method for reducing surface roughness Sa, using the polishing dispersion or polishing powder of the present invention. Here, polishing using zirconium oxide and a polishing aid includes not only a method in which a polishing dispersion in which zirconium oxide and a polishing aid are pre-mixed is used, but also a method in which these are used separately for polishing.

[0033] Regarding the polishing performance of the polishing dispersion of the present invention, for example, under the conditions of the example described later (silicon surface polishing of a SiC wafer), the polishing rate is preferably 0.3 μm / h or higher, more preferably 0.5 μm / h or higher, and even more preferably 1.0 μm / h or higher. A higher polishing rate is better as long as the surface roughness does not exceed a certain level, but it can be, for example, 5 μm / h or less, 3 μm / h or less, etc.

[0034] The smoothness after polishing using the polishing dispersion of the present invention is such that, for example, under the conditions of the example described later (silicon surface polishing of a SiC wafer), the surface roughness Sa (5 μm × 5 μm area) is preferably 1.0 Å or less, more preferably 0.9 Å or less, and even more preferably 0.8 Å or less. A smaller surface roughness Sa of the polished surface is preferable, but it can be, for example, 0.1 Å or more, 0.2 Å or more, etc.

[0035] The method for producing the polishing dispersion of the present invention is not particularly limited, but a method including the step of preparing a dispersion using the zirconium oxide particle group and polishing aid of the present invention is exemplified. For example, the polishing dispersion of the present invention can be produced by mixing the zirconium oxide obtained by the above production method, the polishing aid, the dispersion medium, and any additives. The method and order of mixing are not particularly limited as long as the physical properties of the polishing dispersion are achieved. An example of a mixing procedure for producing a polishing dispersion is shown. As a first step, a predetermined amount of zirconium oxide is dispersed as the dispersion phase in the dispersion medium. If necessary, grinding treatment such as a bead mill may be performed. At this time, the concentration of zirconium oxide can be appropriately selected depending on the object to be polished and the polishing conditions. In addition, in the first step, it is also possible to add an acid, a base, and a dispersant to assist in the dispersion of zirconium oxide. In the particle size distribution measurement of the dispersion obtained in the first step by dynamic light scattering, D ５０ If the value is between 0.002 and 5 μm, the first step can be considered complete. Next, as the second step, an oxidizing agent (abrasive aid) such as potassium permanganate and hydrogen peroxide, abrasive grains other than zirconium oxide as needed, a general acid (hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, etc.) mainly for pH adjustment, a general base (sodium hydroxide, ammonia, amine, etc.), a dispersant, and other desired chemicals can be added to the dispersion obtained in the first step to produce an abrasive dispersion.

[0036] (Polishing Powder) The polishing powder of the present invention contains a predetermined zirconium oxide powder containing the group of zirconium oxide particles of the present invention described above. As a means of incorporating the zirconium oxide particles of the present invention, one example is to use the zirconium oxide powder obtained by the above manufacturing method, but the present invention is not limited thereto.

[0037] The zirconium oxide powder for polishing according to the present invention can be produced by a liquid-phase synthesis method, and its purity is preferably 97 to 100% by mass, more preferably 98 to 100% by mass, and even more preferably 99 to 100% by mass.

[0038] The average secondary particle size of the zirconium oxide powder for polishing according to the present invention is preferably 0.002 to 5 μm, more preferably 0.003 to 1 μm, even more preferably 0.004 to 0.5 μm, and even more preferably 0.005 to 0.1 μm, from the viewpoint of polishing rate and smoothness. The average secondary particle size is measured by a general dynamic light scattering method.

[0039] The specific surface area of ​​the zirconium oxide powder related to the polishing powder of the present invention is preferably 20 to 200 m² from the viewpoint of polishing rate and smoothness. ２ / g, more preferably 30 to 180m ２ / g, more preferably 40 to 170m ２ / g, more preferably 50 to 160m ２ / g, more preferably 100 to 160m ２ The value is / g. The specific surface area is measured by the BET method using general nitrogen adsorption.

[0040] The zirconium oxide powder content in the polishing powder of the present invention is preferably 97.0 to 99.9% by mass, more preferably 98.0 to 99.5% by mass, and even more preferably 98.5 to 99.0% by mass.

[0041] The polishing powder of the present invention may optionally contain abrasive particles other than the zirconium oxide mentioned above, surface modifiers, and the like.

[0042] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0043] [Particle size D ５０ [Measurement] The polishing dispersion obtained in each example and comparative example was measured using ZrO ２ Diluted to 1.0 mass%, it was placed in the apparatus (dynamic light scattering particle size distribution analyzer ("Zetasizer Nano ZS", manufactured by Malvern Panalogical)) and measured for particle size D ５０ (Volume frequency distribution criterion) was measured. <Measurement conditions> Measurement temperature: 25°C Scattering angle: 173° Dispersed phase: ZrO ２ Dispersion medium: Water Cell: Genuine disposable cell Number of repetitions: 3 (D ５０ (This is the average of three measurements.)

[0044] [Measurement of particle ratio of short side to long side (short side / long side), circularity, and Heywood diameter] Using a scanning electron microscope (SEM) (Carl Zeiss, Gemini 560), SEM images of zirconium oxide produced in each example and comparative example were obtained. The SEM images were analyzed using Mac-view. (1) Open the SEM image file with Mac-view data acquisition software, draw a straight line the same length as the scale bar in the SEM image, and input and register the scale indicated in the SEM image as the scale length. (2) Use the Mac-view pen function to draw the particle contour. (3) Clicking the confirm button on the screen displays the sample ID input screen. After entering the sample information, click the confirm button.

[0045] [Measurement of the ratio of height to long side of a particle (height / long side)] An atomic force microscope (AFM) (Bruker, Dimension ICON) was used to obtain AFM images of the zirconium oxide produced in each example and comparative example. <Measurement conditions> Cantilever: SAA-HPI-SS (probe diameter: 1 nm) Scan size: 0.3 μm × 0.3 μm Number of data points: 512 × 512 The height profile was calculated by tracing the long side of the particle in the AFM image. The highest point from the height profile was taken as the height.

[0046] [Polishing performance evaluation] ZrO of the example and comparative example ２Using a sol, an aqueous solution with a 6% by mass abrasive particle concentration was prepared with pure water. Potassium permanganate was added as an oxidizing agent to a concentration of 1.2% by mass, and the mixture was stirred for 30 minutes to obtain a polishing solution dispersion, which was then used for polishing tests. Using these dispersions, five 4-inch SiC wafers (Si side) were polished for 120 minutes using a single-sided polishing machine (as shown below), and the polishing speed and the surface roughness Sa of the polished surface were measured. The polishing speed was measured by measuring the weight of the substrate before and after polishing and calculating the difference. The surface roughness Sa of the polished surface of the object after polishing was measured under conditions where the field of view was 5.0 μm × 5.0 μm. The surface roughness Sa was measured using an atomic force microscope (AFM) (Bruker, Dimension Edge) in accordance with JIS B 0601-2001. The polishing conditions were as follows. Substrate (object to be polished): 4H-SiC wafer, 4-inch, Si side, Off-4 degree, undoped (surface roughness Sa approx. 1 Å) Polishing equipment: Single-sided polishing machine (Fujikoshi Machinery Industries, Ltd., SPM-14A) Polishing pad: SUBA600 (Nitta DuPont) Polishing load: 285 g / cm ２ Plate rotation speed: 25 rpm; Polishing time: 2 hours; Polishing composition supply rate: 20 mL / min; Measurement area of ​​object to be polished: 5.0 μm × 5.0 μm (surface roughness)

[0047] [Surface Defect Evaluation] Surface defects after polishing of the polished object were evaluated using the following evaluation criteria, based on the average value of 5 randomly selected points within a 1.0 × 1.0 mm field of view using a digital microscope (Keyence, VHX-7100). (Evaluation Criteria) ◎: Not detected ○: Greater than 0 and less than or equal to 1 △: Greater than 1 and less than or equal to 2 ×: Greater than 2

[0048] (Example of seed crystal production) Zirconium oxide sol (zirconia sol) was produced according to Example 1 of Japanese Patent Publication No. 2008-31023. Specifically, an aqueous solution of zirconium oxychloride was added to an aqueous solution of sodium hydroxide heated to 90°C, cooled, filtered, and washed to produce zirconium hydroxide, the obtained zirconium hydroxide was dispersed in water, and then an acid was added, followed by heating and aging to produce zirconium oxide sol (zirconia sol). The ZrO of the sol ２ The converted concentration is 29.8% by mass, particle size D５０ It was 12 nm.

[0049] (Example 1) Zirconium oxychloride aqueous solution (ZrO) adjusted to 60°C with a mantle heater ２ Neutralization of 8000 g of 10% by mass (converted to 10%) was carried out in two stages by dropwise addition of ammonia water. In the first stage, 1104 g of 10% by mass ammonia water adjusted to 25°C was added dropwise over 10 minutes. At this time, the number of delivery tubes and the dropping rate were adjusted so that the volume of the ammonia water droplets was in the range of 0.1 to 0.5 ml. After that, stirring was continued for 60 minutes. Then, in the second stage, 9936 g of 10% by mass ammonia water adjusted to 25°C was added dropwise over 30 minutes, and stirring was continued for 10 minutes to obtain a precipitate of zirconium hydroxide. During the addition of ammonia water and the stirring afterward, the zirconium oxychloride aqueous solution was adjusted to maintain within ±5°C of the initial temperature. The zirconium hydroxide was filtered off and the washing operation was repeated by dispersing it again with deionized water. This operation was carried out until the Cl concentration was 0.01% or less. The concentration of zirconium hydroxide after washing was ZrO ２ The converted amount was 24.0% by mass. To the obtained zirconium hydroxide 3328 g, 4448 g of deionized water, 20.4 g of nitric acid (60% by mass), 106 g of sodium acetate, and zirconia sol (ZrO) produced in the above production example were added. ２ 53.6 g of (equivalent to 29.8% by mass) was mixed, and the prepared slurry was placed in a separable flask and stirred while being held at 50°C for 6 hours. Next, 204 g of nitric acid (60% by mass) was added to the slurry and mixed, and held under reflux at 100°C for 120 hours. The resulting zirconium oxide precursor was purified by ultrafiltration to obtain the zirconium oxide sol according to Example 1. ２ The concentration is 20%, pH 2.9, and D ５０ The wavelength was 64 nm. Furthermore, the specific surface area of ​​the powder obtained by drying the sol was 153 m². ２The value was / g. The zirconium oxide sol according to Example 1 had a ratio of the short side to the long side of the particles (short side / long side) of 0.70 calculated using particle analysis software from SEM images, a ratio of the height to the long side of the particles (height / long side) of 0.35 calculated from AFM images, a Haywood diameter of 54 nm, and a circularity of 0.36. Next, 2752 g of deionized water and 48 g of potassium permanganate were added to 1200 g of this zirconium oxide sol and stirred for 30 minutes to obtain a polishing dispersion. The conditions for the heating and aging process are shown in Table 1. The polishing performance evaluation of the polishing dispersion is shown in Table 2.

[0050] (Example 2) The procedure was carried out in the same manner as in Example 1, except that 53 g of sodium acetate was added. ZrO ２ The concentration is 20%, pH 2.9, and D ５０ The specific surface area was 69 nm. The specific surface area of ​​the powder obtained by drying the sol was 146 m². ２ It was / g.

[0051] (Example 3) The procedure was carried out in the same manner as in Example 1, except that 160 g of sodium acetate was added, to obtain a zirconia sol. ZrO ２ The concentration is 20%, pH 2.9, and D ５０ The specific surface area was 58 nm. The specific surface area of ​​the powder obtained by drying the sol was 158 m². ２ It was / g.

[0052] (Example 4) The procedure was carried out in the same manner as in Example 1, except that 124 g of sodium propionate was added instead of sodium acetate, to obtain a zirconia sol. ZrO of the zirconium oxide sol according to Example 4 ２ The concentration is 20%, pH 2.9, and D ５０ The specific surface area was 52 nm. The specific surface area of ​​the powder obtained by drying the sol was 155 m². ２ It was / g.

[0053] (Example 5) A zirconium oxide sol was obtained in the same manner as in Example 1, except that the amount of nitric acid added was as shown in Table 1. The ZrO2 concentration of the sol was 20%, pH 3.1, and D ５０ The wavelength was 57 nm. Furthermore, the specific surface area of ​​the powder obtained by drying the sol was 154 m².２ It was / g.

[0054] (Example 6) Zirconium oxide sol was obtained in the same manner as in Example 1, except that sodium acetate was added simultaneously with the second step of nitric acid. The ZrO2 concentration of the sol was 20%, pH 3.0, and D ５０ The specific surface area was 61 nm. The specific surface area of ​​the powder obtained by drying the sol was 151 m². ２ It was / g.

[0055] (Comparative Example 1) 3395 g of zirconium hydroxide was mixed with 4381 g of deionized water, and the prepared slurry was placed in a separable flask and stirred while being held at 50°C for 6 hours. Next, 243 g of nitric acid (60% by mass) was added to the slurry and mixed, and the slurry was held under reflux at 100°C for 120 hours. The same procedure as in Example 1 was followed to obtain a zirconium oxide sol. The ZrO of the sol ２ The concentration is 20%, pH 2.9, and D ５０ The specific surface area was 45 nm. The specific surface area of ​​the powder obtained by drying the sol was 166 m². ２ It was / g.

[0056] (Comparative Example 2) 3395 g of zirconium hydroxide was mixed with 4381 g of deionized water, and the prepared slurry was placed in a separable flask and stirred while being held at 50°C for 6 hours. Next, 208 g of nitric acid (60% by mass) was added to the slurry and mixed, and the slurry was held under reflux at 100°C for 120 hours. The same procedure as in Example 1 was followed to obtain a zirconium oxide sol. The ZrO of the sol ２ The concentration is 20%, pH 3.1, and D ５０ The specific surface area was 58 nm. The specific surface area of ​​the powder obtained by drying the sol was 162 m². ２ It was / g.

[0057] (Comparative Example 3) 3395 g of zirconium hydroxide was mixed with 4381 g of deionized water, and the prepared slurry was placed in a separable flask and stirred while being held at 50°C for 6 hours. Next, 173 g of nitric acid (60% by mass) was added to the slurry and mixed, and the slurry was held under reflux at 100°C for 120 hours. The same procedure as in Example 1 was followed to obtain a zirconium oxide sol. The ZrO of the sol ２ The concentration is 20%, pH 3.2, and D ５０The specific surface area was 69 nm. The specific surface area of ​​the powder obtained by drying the sol was 145 m². ２ It was / g.

[0058]

[0059]

[0060] As shown in Table 2, Examples 1 to 6, which have a layered structure, exhibited excellent polishing rates and satisfactory surface roughness and surface defect control.

[0061] The polishing dispersion and polishing powder of the present invention can be used for chemical mechanical polishing (CMP) of SiC wafers and the like, and can be used in semiconductor manufacturing processes and the like.

Claims

1. A zirconium oxide sol containing a group of zirconium oxide particles that exhibit a layered structure in scanning electron microscope images.

2. The zirconium oxide sol according to claim 1, wherein the layered structure includes a structure in which layers are stacked in an X-shape and / or T-shape.

3. The zirconium oxide sol according to claim 1, wherein the ratio of the short side to the long side of the particle (short side / long side), calculated from the scanning electron microscope image using particle analysis software, is 0.50 to 0.95, and the ratio of the height to the long side of the particle (height / long side), calculated from the atomic force microscope image, is 0.20 to 1.

00.

4. The zirconium oxide sol according to claim 1, wherein the Haywood diameter calculated from the scanning electron microscope image using particle analysis software is 1 to 150 nm and the circularity is 0.1 to 0.

8.

5. A polishing dispersion containing a group of zirconium oxide particles that exhibit a layered structure in scanning electron microscope images, and a polishing aid.

6. The polishing dispersion according to claim 5, wherein the polishing aid comprises one or more selected from the group consisting of peroxides, nitrate compounds, persulfate compounds, chlorine compounds, bromine compounds, iodine compounds, hypochlorite compounds, iron acids, permanganates, chromic acids, vanadic acids, ruthenic acids, molybdic acids, rhenic acids, and tungstic acids.

7. SiC wafers, polycrystalline SiC, GaN, GaAs, Ga ２ O ３ The polishing dispersion according to claim 5, for use in polishing GaP or diamond substrates.

8. A polishing method comprising polishing using the polishing dispersion described in any one of claims 5 to 7.

9. A method for producing a polishing dispersion, comprising the step of preparing a dispersion using a group of zirconium oxide particles that exhibit a layered structure in scanning electron microscope images, and a polishing aid.

10. A method for improving the polishing rate, comprising polishing with a group of zirconium oxide particles that exhibit a layered structure in scanning electron microscope images, and a polishing aid.

11. A method for reducing surface roughness Sa by polishing with a group of zirconium oxide particles that show a layered structure in scanning electron microscope images and a polishing aid.

12. Polishing powder containing zirconium oxide powder, which contains a group of zirconium oxide particles that exhibit a layered structure in scanning electron microscope images.

13. The polishing powder according to claim 12, wherein the average secondary particle size of the zirconium oxide powder is 0.002 to 5 μm.

14. The polishing powder according to claim 12, wherein the average secondary particle size of the zirconium oxide powder is 0.1 μm or less.

15. The polishing powder according to claim 12, wherein the purity of the zirconium oxide powder is 97% by mass or more.

16. The polishing powder according to claim 12, wherein the zirconium oxide powder is produced by a liquid-phase synthesis method.

17. The specific surface area of ​​the zirconium oxide powder is 20 m². ２ The polishing powder according to claim 12, wherein the amount is 1 / g or more.

18. A polishing method comprising polishing using the polishing powder described in any one of claims 12 to 17.

19. A method for producing zirconium oxide sol by liquid-phase synthesis, comprising the step of heating and aging zirconium hydroxide in an acidic atmosphere in an aqueous solvent, wherein in the heating and aging step, a seed crystal of zirconium oxide is present with the zirconium hydroxide, and acid is added in multiple stages, with a linear carboxylate salt being added in at least one of these stages.

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