Zirconium oxide particles

Abstract

Provided are zirconium oxide particles having a circularity of 0.10-0.50 and a convexity of 0.30-0.90. A dispersion for polishing and a powder for polishing according to the present invention can be used in chemical-mechanical polishing (CMP) of a SiC wafer and the like, and can be used in a semiconductor manufacturing process and the like.

Description

Zirconium oxide particles

[0001] The present invention relates to zirconium oxide particles having a new shape, a group of zirconium oxide particles containing the particles in a predetermined ratio, a polishing dispersion and a polishing powder containing the particles, and a polishing method using them.

[0002] Polishing is widely used in the microelectronics industry. Materials such as silicon carbide (SiC) boast a dielectric breakdown strength 10 times that of silicon and a band gap three times that of silicon. They have also attracted attention in recent years as power semiconductors with excellent high-temperature and energy-saving properties. For similar reasons, gallium nitride (GaN), diamond, and sapphire are also attracting attention and are being actively developed. High-yield production of high-performance devices requires atomic-level flatness and smoothness of substrates. However, these substrates are harder and more brittle than silicon, and are chemically more stable and difficult to process, resulting in low productivity and rising substrate processing costs. Traditionally, after slicing the crystal, multi-stage, long-term polishing is performed using chemical mechanical polishing (CMP) with diamond or colloidal silica particles. However, this process incurs significant costs in terms of consumables and equipment, resulting in costs several times higher than those for silicon substrates. Reducing this processing cost is strongly required for the widespread use of power semiconductors. Several dispersions using zirconium oxide as an abrasive have also been proposed.

[0003] For example, Patent Document 1 discloses a polishing slurry that contains 1 to 20 mass % of monoclinic zirconium oxide having a crystallite size of 10 to 1,000 nm and an average particle size of 30 to 2,000 nm, and further contains a carboxylic acid having three or more carboxy groups in the molecule and a quaternary alkyl ammonium hydroxide, and has a pH of 9 to 12.

[0004] Patent Document 2 discloses a polishing powder containing zirconium oxide particles, characterized in that the zirconium oxide particles have crystallite sizes of 330 Å or more, calculated based on the diffracted X-ray intensities at 2θ of around 28.0° and 31.0° as measured by powder X-ray diffraction, and the zirconium oxide particles have an average primary particle size of 0.2 μm or more.

[0005] Patent Document 3 discloses a slurry for chemical mechanical polishing (CMP) containing an aqueous liquid carrier, a transition metal oxy-compound selected from oxy-nitrates, oxy-chlorides, oxy-sulfates, oxy-carbonates, and C2 to C10 oxy-alkanoates, and a per-based oxidizing agent, and discloses a SiC abrasive slurry using zirconia particles.

[0006] Patent Document 4 discloses a method for producing a polishing composition containing zirconium oxide sol, the method comprising the steps of: calcining a zirconium compound having a d50 (where d50 represents a particle size where the number of particles having this particle size or less accounts for 50% of the total number of particles) of 5 to 25 μm and a d99 (where d99 represents a particle size where the number of particles having this particle size or less accounts for 99% of the total number of particles) of 60 μm or less when a slurry of the zirconium compound is measured by a laser diffraction method, at a temperature range of 400 to 1000° C.; and wet-pulverizing the obtained zirconium oxide powder in an aqueous medium until the d50 of the zirconium oxide particles reaches 80 to 150 nm and the d99 of the zirconium oxide particles reaches 150 to 500 nm when the zirconium oxide slurry is measured by a laser diffraction method.

[0007] JP 2006-324639 A, WO 2012 / 169515, JP 2023-512216 A, WO 2006 / 123562

[0008] However, since SiC and the like are hard and difficult to process, further improvements in production efficiency and the like are required.

[0009] The present invention provides zirconium oxide particles having a new shape, a zirconium oxide particle group containing the particles in a specified ratio, and a polishing dispersion and polishing powder that have an excellent polishing rate and excellent surface smoothness after polishing.

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

[13] . [1] Zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90. [2] A zirconium oxide sol containing the zirconium oxide particles according to item [1]. [3] A group of zirconium oxide particles having the following ratio A of 40% by number or more: Ratio A: the ratio of the particle major axis in a transmission electron microscope (TEM) image to the particle diameter D ５０ [4] A group of zirconium oxide particles in which the following ratio B is 30% by number or more: Ratio B: The ratio of the major axis of a particle in a transmission electron microscope (TEM) image to the particle diameter D ５０[5] A zirconium oxide sol containing the zirconium oxide particle group according to [3] or [4]. [6] A polishing dispersion containing zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid. [7] A polishing method comprising polishing using the polishing dispersion according to [6]. [8] A method for producing a polishing dispersion comprising a step of preparing a dispersion using zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid. [9] A method for improving a polishing rate comprising polishing using zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid.

[10] A method for reducing surface roughness Ra, comprising polishing using zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid.

[11] A polishing powder comprising a zirconium oxide powder containing zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90.

[12] A polishing method, comprising polishing using the polishing powder according to

[11] .

[13] A method for producing zirconium oxide particles by a liquid phase synthesis method, comprising a step of heat-aging zirconium hydroxide in an aqueous solvent under an acidic atmosphere, wherein in the heat-aging step, zirconium oxide seed crystals are allowed to coexist with the zirconium hydroxide, and acid is added in multiple stages, with the amount of acid added in the first stage being [acid] / [ZrO of zirconium hydroxide]. ２ ] is an amount that is 0.01 to 0.15 in moles, and the total amount of acid added in all stages is [acid] / [ZrO of zirconium hydroxide]. ２ ] in an amount of 0.10 to 0.60 in terms of moles.

[0011] According to the present invention, it is possible to provide zirconium oxide particles having a new shape, a zirconium oxide particle group containing the particles in a specified ratio, and a polishing dispersion and a polishing powder that have an excellent polishing rate and excellent surface smoothness after polishing.

[0012] 1 shows an image of the particle contour and its interior (white area) after image processing in Example 2. FIG. 2 is an enlarged view of the particle (No. 17) in FIG.

[0013] It has been known that the polishing rate of an abrasive powder is generally proportional to the average particle size of the abrasive powder. Meanwhile, it is generally believed that the smallest possible average particle size of the abrasive is desirable to obtain a polished surface with low surface roughness and minimal surface defects. In response to this, the inventors have newly discovered that using zirconium oxide particles with specific circularity and convexity for polishing results in both excellent polishing rates and excellent surface smoothness after polishing. While the mechanism is unclear, the higher the circularity and convexity values, the easier the abrasive particle's shape is to rotate, reducing the frictional force with the workpiece and resulting in poor polishing performance. Meanwhile, low values ​​of these indicate a thin structure with narrow protrusions, which are prone to breaking and fracture due to insufficient strength, resulting in the inability to perform polishing. Furthermore, particle fracture leads to polydispersity of particle sizes, reducing the contact points between the workpiece and the particles, which is thought to increase the contact pressure and cause scratches. In other words, the shape of the present invention, in which the circularity and convexity are within a specific range, is presumed to be suitable for achieving a polishing rate and surface smoothness while ensuring the frictional force with the surface to be polished and particle strength.

[0014] (Zirconium oxide particles) From the viewpoint of polishing rate and smoothness, the circularity of the zirconium oxide particles according to the present invention is 0.10 to 0.50, preferably 0.13 to 0.47, more preferably 0.15 to 0.45, even more preferably 0.15 to 0.40, still more preferably 0.15 to 0.35, even more preferably 0.15 to 0.30, and still more preferably 0.15 to 0.25.

[0015] From the viewpoints of polishing rate and smoothness, the convexity of the zirconium oxide particles according to the present invention is 0.30 to 0.90, preferably 0.35 to 0.85, more preferably 0.40 to 0.80, even more preferably 0.45 to 0.75, still more preferably 0.50 to 0.75, and still more preferably 0.55 to 0.75.

[0016] The circularity relative to convexity (circularity / convexity) of the zirconium oxide particles according to the present invention is preferably 0.20 to 0.70, more preferably 0.23 to 0.65, even more preferably 0.25 to 0.60, even more preferably 0.27 to 0.55, even more preferably 0.29 to 0.50, and still more preferably 0.30 to 0.50, from the viewpoints of polishing rate and smoothness.

[0017] Examples of particle shapes that satisfy the above circularity and convexity include cross, arrow, crescent, etc. On the other hand, semicircular, bow, elliptical, parallelogram, triangular, etc. do not satisfy the above circularity and / or convexity.

[0018] The zirconium oxide particles according to the present invention preferably have 3 to 20 closed regions enclosed by the particle outline and the convex hull outline of the particle, more preferably 4 to 18, even more preferably 5 to 16, and even more preferably 6 to 14. For example, in Figure 2, there are 1 to 10 closed regions enclosed by the particle outline and the convex hull outline of the particle (broken line), and in this case the number of closed regions is 10.

[0019] The circularity, convexity, and convex hull contour are determined by analyzing images of zirconium oxide particles obtained by a transmission electron microscope (TEM), as will be described in detail later.

[0020] The method for producing zirconium oxide particles according to the present invention is not particularly limited, and they can be produced by a liquid phase synthesis method. For example, a method for producing zirconium oxide particles by a liquid phase synthesis method includes a step of heat-aging zirconium hydroxide in an aqueous solvent under an acidic atmosphere, in which zirconium oxide seed crystals are allowed to coexist with zirconium hydroxide in the heat-aging step, and acid is added in multiple stages, with the amount of acid added in the first stage being [acid] / [ZrO of zirconium hydroxide]. ２ ] is an amount that is 0.01 to 0.15 in moles, and the total amount of acid added in all stages is [acid] / [ZrO of zirconium hydroxide]. ２A suitable example of a method for producing zirconium oxide particles is a method for directly synthesizing zirconium oxide from an amorphous precursor by heating in a liquid phase, primarily in the aqueous phase of an aqueous solvent, without using high-temperature heating such as calcination or electrofusion. Specifically, in the step of thermally aging zirconium hydroxide in an aqueous solvent under an acidic atmosphere, zirconium oxide seed crystals are allowed to coexist with zirconium hydroxide, and acid addition and temperature elevation are carried out in multiple stages, thereby achieving the characteristic shape of the zirconium oxide particles of the present invention. The zirconium hydroxide is not particularly limited, and one obtained by neutralizing an aqueous zirconium salt solution with a base can be used. The type of acid used in thermal aging is not particularly limited, and hydrochloric acid, nitric acid, etc. can be used. The aqueous solvent refers to an aqueous medium such as water, ion-exchanged water, or pure water. The acidic atmosphere preferably has a pH of 0 to 3.0, more preferably 0.5 to 2.0. In order to obtain the shape of zirconium oxide of the present invention, it is necessary to control nucleation and grain growth. By using seed crystals, grain growth can be promoted from the initial stage of the heat aging, without waiting for homogeneous nucleation. Furthermore, although the mechanism is not clear, seed crystals can easily form the shape of zirconium oxide of the present invention through grain growth, whereas this is difficult with nuclei generated by homogeneous nucleation. The zirconium oxide seed crystals have a specific particle diameter D ５０ It is preferable to use a seed crystal having a particle diameter D ５０ is preferably 1 to 100 nm, more preferably 3 to 50 nm, and even more preferably 5 to 20 nm. ５０ In order to satisfy the above condition, the seed crystals are preferably in the form of a zirconium oxide sol. In the embodiment in which the seed crystals are zirconium oxide sol, the dispersoid zirconia (ZrO ２ ) contains alkali metal oxides (M ２ O, M: Li, Na, K, Rb, Cs). The type of crystalline phase and crystallite size of the seed crystals are not particularly limited. Zirconium oxide that can be used as the seed crystals can be obtained by known methods. Specific examples include the method disclosed in Example 1 of JP-A-2008-31023. The amount of seed crystals to be added is determined by the ratio of ZrO ２] / [zirconium hydroxide ZrO ２ In terms of moles, the acid addition and temperature increase is preferably 0.005 to 0.20, more preferably 0.008 to 0.15, and even more preferably 0.01 to 0.10. The number of stages of acid addition and temperature increase carried out in multiple stages is at least two, preferably 2 to 5, and more preferably 2 to 3. The total amount of acid added in the second and subsequent stages is preferably greater than the amount of acid added in the first stage. The amount of acid added in the first stage is determined by the ratio of [acid] / [ZrO of zirconium hydroxide]. ２ The total amount of acid added in all stages is preferably 0.01 to 0.15, more preferably 0.05 to 0.10, in terms of moles of [acid] / [ZrO of zirconium hydroxide]. ２ ] in mole terms, is preferably 0.10 to 0.60, more preferably 0.20 to 0.50. The amount of acid added is a value obtained by dividing by the valence of the acid used. The aging temperature of the acid is preferably increased with each stage. The aging temperature in the first stage is preferably 40 to 60°C, more preferably 45 to 55°C. The aging temperature in the final stage is preferably 90 to 110°C, more preferably 95 to 105°C. Although the mechanism is unclear, it is believed that the shape of the present invention can be achieved by controlling the grain growth rate of the seed crystals through the stepwise addition of acid and temperature increase as described above. The production method of this embodiment can produce a group of zirconium oxide particles (hereinafter, sometimes simply referred to as "zirconium oxide") containing zirconium oxide particles of the present invention having a predetermined circularity and convexity. The proportion of the zirconium oxide particles of the present invention in the obtained zirconium oxide is not particularly limited, but it is preferable that the following ratio A and / or ratio B be equal to or greater than a predetermined value. Since it is believed that larger particles have a greater impact on polishing performance, it is preferable that the particle major axis is greater than the particle diameter D ５０ It is considered that when the ratio of particles having a predetermined circularity and convexity is high among particles having a value larger than the value of (a), the polishing performance is excellent. The form of the particle group is not particularly limited, but examples thereof include a dispersion form such as sol, slurry, suspension, and aerosol in which the particle group is a dispersoid, and a dispersion form using a liquid dispersion medium such as sol and slurry is preferred. Ratio A: The particle major axis in a transmission electron microscope (TEM) image is the particle diameter D ５０Ratio B: The ratio of particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90 to all particles larger than the value of ５０ The ratio of particles having a circularity of 0.10 to 0.50, a convexity of 0.30 to 0.90, and a circularity / convexity ratio of 0.20 to 0.70, among all particles larger than the value of

[0021] From the viewpoint of polishing performance, the ratio A is preferably 40% by number or more, more preferably 50% by number or more, even more preferably 60% by number or more, even more preferably 70% by number or more, and even more preferably 80% by number or more. The upper limit of the ratio A is 100% by number, and the closer to 100% by number the better, but in practice it may be, for example, 95% by number or less, 90% by number or less, 80% by number or less, 70% by number or less, 60% by number or less, etc. The ratio A is calculated by the method described in the examples below. That is, the image analysis is carried out by the method described in the examples below, ５０ For example, in Table 2, when the particle major diameter is larger than the value of D in Example 2 described later, the particle major diameter is obtained by the proportion of particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90. ５０ There are 11 particles (Nos. 8 to 18) in the TEM image that are larger than the particle diameter (50.0 nm). In this case, 11 particles are used as the denominator (100% by number), and the percentage by number of particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90 is calculated. In the example of Table 2, all 11 particles satisfy the predetermined circularity and convexity, so both ratio A and ratio B are 100% by number. Note that the particle major axis is the particle diameter D ５０ If the number of particles larger than the value is less than 10, add fields of view to adjust the denominator to a value of 10 or more.

[0022] From the viewpoint of polishing performance, ratio B is preferably 30% by number or more, more preferably 40% by number or more, even more preferably 50% by number or more, even more preferably 60% by number or more, even more preferably 70% by number or more, and even more preferably 80% by number or more. The upper limit of ratio B is 100% by number, and the closer to 100% by number is the more preferable, but in practice it may be, for example, 95% by number or less, 90% by number or less, 80% by number or less, 70% by number or less, 60% by number or less, 50% by number or less, etc. Ratio B is calculated in the same manner as ratio A and is calculated by the method described in the examples below.

[0023] The zirconium oxide obtained by the above-mentioned production method generally refers to one containing a few percent of hafnium oxide as an unavoidable impurity, generally 1.0 to 3.0%, but may also be one that has been purified to remove hafnium oxide. The zirconium oxide may also be stabilized zirconium oxide, in which case calcium, magnesium, yttrium, cerium, and other rare earth elements may be solid-solved. Other elements that can be solid-solved in zirconium oxide may also be included. Zirconium oxide and particles of other oxides may be combined 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.

[0024] Known crystalline phases of zirconium oxide include monoclinic, tetragonal, and cubic phases, but the present invention is not particularly limited to the crystalline phase.

[0025] (Polishing dispersion) The polishing dispersion of the present invention contains the zirconium oxide particles of the present invention and a polishing aid. As a means for incorporating the zirconium oxide particles of the present invention, an embodiment using zirconium oxide obtained by the above-mentioned manufacturing method can be mentioned, and preferably an embodiment using zirconium oxide in which the ratio A and the ratio B are equal to or greater than a predetermined value, but the present invention is not limited thereto. Below, an embodiment using zirconium oxide obtained by the above-mentioned manufacturing method will be described.

[0026] The median particle diameter (particle diameter D５０ From the viewpoint of polishing rate and smoothness, the median diameter (particle diameter D ５０ ) is measured by the method described in the Examples below. As described above, it is believed that the function of the present invention is exhibited mainly by the inclusion of the zirconium oxide particles of the present invention, and therefore the agglomerated particle size is not particularly limited.

[0027] The content of zirconium oxide 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. Furthermore, abrasive particles other than zirconium oxide may coexist as long as the polishing performance of the present invention is not impaired. 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 the like.

[0028] The concentration of the abrasive grains other than zirconium oxide is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total abrasive grain concentration, and the lower limit can be 0% by mass, 1% by mass or more, 2% by mass or more, or 3% by mass or more.

[0029] The grinding aid of the present invention is a component that enhances the effect of polishing, and is preferably water-soluble.As the grinding aid, peroxides such as hydrogen peroxide; nitrate compounds such as iron nitrate, silver nitrate, aluminum nitrate, and its complex cerium ammonium nitrate; persulfates such as potassium peroxomonosulfate, peroxodisulfate, and its salts, persulfate compounds such as ammonium persulfate, potassium persulfate; chlorine compounds such as chloric acid, its salts, perchloric acid, and its salts, potassium perchlorate; bromine compounds such as bromic acid, its salts, potassium bromate; iodic acid, its salts, ammonium iodate; periodic acid, its salts, sodium periodate, potassium periodate, and other iodine compounds; iron acids such as ferric acid, its salts, potassium ferrate; permanganic acids such as permanganic acid, its salts, sodium permanganate, potassium permanganate; chromic acids such as chromic acid, its salts, potassium chromate, potassium dichromate; Examples of suitable oxidizing agents include vanadic acids such as vanadic acid and its salts, ammonium vanadate, sodium vanadate, sodium metavanadate, and potassium vanadate; ruthenic acids such as perruthenic acid and its salts; molybdic acids such as molybdic acid and its salts, ammonium molybdate and disodium molybdate; rhenic acids such as perrhenium and its salts; and tungstic acids such as tungstic acid and its salts, disodium tungstate; and these oxidizing agents can be used alone or in combination of two or more. Among these, from the viewpoint of polishing efficiency, oxidizing agents are preferred, and potassium permanganate, sodium permanganate, periodic acid, potassium persulfate, and aqueous hydrogen peroxide are particularly preferred.

[0030] 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 mass %, preferably 1.0 to 10.0 mass %.

[0031] The dispersion medium of the polishing dispersion of the present invention is not limited as long as it can ensure polishing performance, but is usually water, and ion-exchanged water, pure water, ultrapure water, distilled water, etc. can also be used. If necessary, it may further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water. The content of water 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.

[0032] The pH of the polishing dispersion of the present invention is not limited and can be adjusted as needed to adjust the potential between the abrasive grains and the surface to be polished. For example, the pH can be 0.5 to 13.5, 1.0 to 12.0, 1.3 to 8.5, or 1.5 to 5.0. The pH can be adjusted 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.

[0033] The polishing dispersion of the present invention may optionally contain various additives other than those described above. Examples of known additives include chelating agents, thickeners, dispersants, surface protective agents, wetting agents, pH adjusters, surfactants, organic acids, organic acid salts, inorganic acids, inorganic acid salts, rust inhibitors, preservatives, and antifungal agents. The type and concentration of these optional additives are not limited as long as they ensure the polishing performance of the present invention.

[0034] The polishing dispersion of the present invention may contain impurities such as inorganic ions such as nitrate ions, chloride ions, and sulfate ions, metal ions such as sodium, potassium, iron, and titanium, and organic ions such as acetate ions and tetramethylammonium ions, but this is not a particular problem as long as the polishing performance of the present invention is ensured.

[0035] The polishing dispersion of the present invention and the polishing powder of the present invention described below have excellent polishing rates and excellent surface smoothness after polishing, and therefore can be suitably used for polishing substrates such as Si, SiC, GaN, and sapphire, oxide films, and metal films such as W and Cu, and can be particularly suitably used for polishing SiC wafers. Therefore, the present invention also provides a polishing method, a method for improving the polishing rate, and a method for reducing the surface roughness Ra, which use the polishing dispersion or polishing powder of the present invention for polishing. Here, polishing using zirconium oxide and a polishing aid includes not only an embodiment in which a polishing dispersion in which zirconium oxide and a polishing aid are mixed in advance is used, but also an embodiment in which these are used separately for polishing.

[0036] Regarding the polishing performance of the polishing dispersion of the present invention, for example, the polishing rate under the conditions of the examples described later (Si surface polishing of SiC wafer) is preferably 0.5 μm / h or more, more preferably 0.6 μm / h or more, and even more preferably 0.7 μm / h or more. As long as the surface roughness does not exceed a certain level, the higher the polishing rate, the better, but it can be, for example, 5 μm / h or less, 3 μm / h or less, etc.

[0037] The smoothness after polishing using the polishing dispersion of the present invention, for example, under the conditions of the examples described later (polishing the Si face of a SiC wafer), is preferably 1.0 Å or less, more preferably 0.9 Å or less, and even more preferably 0.8 Å or less. The smaller the surface roughness Ra of the polished surface, the better, but it can be, for example, 0.1 Å or more, 0.2 Å or more, etc.

[0038] The method for producing the polishing dispersion of the present invention is not particularly limited, but an example is a production method including a step of preparing a dispersion using the zirconium oxide particles and polishing aid of the present invention. For example, the polishing dispersion of the present invention can be produced by mixing a predetermined zirconium oxide containing the zirconium oxide particles of the present invention, a polishing aid, a dispersion medium, and any additives. The method and order of mixing these 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 below. In the first step, a predetermined zirconium oxide is dispersed as a dispersoid in a dispersion medium. If necessary, a pulverization process using a bead mill or the like may be performed. In this case, 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, an acid, a base, a dispersant, etc. can be added to aid in the dispersion of zirconium oxide. In measuring the particle size distribution of the dispersion obtained in the first step by dynamic light scattering, D ５０ The first step can be considered complete when the value of is 2.0 to 5000.0 nm. Next, in the second step, an oxidizing agent (polishing aid) such as potassium permanganate or hydrogen peroxide, and, if necessary, abrasive grains other than zirconium oxide, a common acid (hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, etc.) primarily intended for pH adjustment, a common base (sodium hydroxide, ammonia, amine, etc.), a dispersant, and other chemicals of interest, etc., can be added to the dispersion obtained in the first step to produce a polishing dispersion.

[0039] (Polishing Powder) The polishing powder of the present invention contains a predetermined zirconium oxide powder containing the zirconium oxide particles of the present invention described above. As a means for incorporating the zirconium oxide particles of the present invention, an embodiment using zirconium oxide powder obtained by the above-mentioned manufacturing method can be mentioned, and an embodiment using zirconium oxide powder in which the above ratio A and ratio B are equal to or greater than a predetermined numerical value can be mentioned, but the present invention is not limited thereto.

[0040] The zirconium oxide powder according to the polishing powder of the present invention can be produced by a liquid phase synthesis method, and has a purity of preferably 97 to 100 mass %, more preferably 98 to 100 mass %, and even more preferably 99 to 100 mass %.

[0041] The average secondary particle size of the zirconium oxide powder according to the polishing powder of 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 viewpoints of polishing rate and smoothness. The average secondary particle size is measured by a general dynamic light scattering method.

[0042] The specific surface area of ​​the zirconium oxide powder according to the polishing powder of the present invention is preferably 20 to 200 m from the viewpoint of polishing rate and smoothness. ２ / g, more preferably 30 to 180 m ２ / g, more preferably 40 to 170 m ２ / g, more preferably 50 to 160 m ２ / g, more preferably 100 to 160 m ２ The specific surface area is measured by a general BET method using nitrogen adsorption.

[0043] The content of zirconium oxide powder in the polishing powder of the present invention is preferably 97.0 to 99.9 mass %, more preferably 98.0 to 99.5 mass %, and even more preferably 98.5 to 99.0 mass %.

[0044] The polishing powder of the present invention may optionally contain abrasive grains other than the zirconium oxide, a surface modifier, and the like.

[0045] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0046] [Particle diameter D ５０ Measurement] The polishing dispersion obtained in each Example and Comparative Example was ２ The solution was diluted to 1.0 mass % in terms of the total mass of the solution, and then placed in a dynamic light scattering particle size distribution analyzer ("Zetasizer Nano ZS" manufactured by Malvern Panalytical) to measure the particle diameter D ５０(volume frequency distribution standard) was measured. <Measurement conditions> Measurement temperature: 25°C Scattering angle: 173° Dispersoid: ZrO ２ Dispersion medium: Water Cell: Genuine disposable cell Number of repetitions: 3 (D ５０ is the average of three measurements)

[0047] [Measurement of Circularity, Convexity, and Circularity / Convexity] TEM images of the zirconium oxide produced in each Example and Comparative Example were obtained. Image analysis of the TEM images was performed using ImageJ (freeware, https: / / imagej.net / ij / , as of March 2, 2024). ImageJ operations were performed according to the following steps (1) to (9). Through these operations, the circularity, convexity, and circularity / convexity of particles having a specific size in the TEM image (see section (9) below) were determined, and the ratio of particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90 (ratio A) was calculated. Furthermore, the ratio of particles having a circularity of 0.10 to 0.50, a convexity of 0.30 to 0.90, and a circularity / convexity of 0.20 to 0.70 (ratio B) of particles having a specific size in the TEM image was calculated. (1) Open the TEM image file and use the graphics drawing function (Straight) to draw a straight line the same length as the scale bar on the TEM image. (2) Select Analyze > Set Scale. The Set Scale window will appear. <Settings> Distance in pixels: Check that the number of pixels of the straight line drawn in (1) is displayed. If not, manually enter the number of pixels. Known distance: Enter the length displayed on the TEM image of the scale bar. Pixel Aspect ratio: 1.0 Unit of length: Enter the unit of length displayed on the TEM image of the scale bar. (3) Select Image > Type > 8 bit. (4) Select Image > Adjust > Threshold. (5) The Threshold window will appear. In addition, the original TEM image is converted into a binary image in which the particle outline and interior are white and the rest is black. Normally, the automatically set values ​​are used for the Lower and Upper Threshold Level values. If there is a clear error in the particle outline recognized by the software, adjust them manually as appropriate. (6) Press the Apply button in the Threshold window. (7) Select Analyze > Set Measurements.<Option settings> Area: ON Fit lipse: ON Shape descriptors: ON Limit to threshold: ON Display label: ON (8) Analyze > Analyze Particles and press the OK button. The Results window will appear, showing the Circularity and Solidity in the order of particle numbers recognized by the software. <Option settings> Size (pixel^2): 0-Infinity Circularity: 0.00-1.00 Show: Overlay Marks Display results: ON Exclude on edges: ON Include holes: ON (9) The value displayed in the Major column of the Results window is the particle diameter D. ５０ The Circularity (Circularity) and Solidity (Convexity) of particles larger than the value of 1000 are defined as the circularity and convexity of the zirconium oxide particles, respectively. The circularity / convexity is calculated from the circularity and convexity. Images of the particle contour and its interior (white area) after image processing in the measurement of circularity and convexity performed in Example 2 are shown in Figure 1. The major diameter (Major), circularity (Circularity), convexity (Solidity), and circularity / convexity of isolated particles obtained from the images are also shown in Table 2. The numbers in Figure 1 correspond to particle No. 17 in Table 2.

[0048] [Polishing Performance Evaluation] SiC wafers were polished using the polishing dispersions of Examples and Comparative Examples, and the polishing rate and surface roughness Ra of the polished surface were measured. The polishing rate was measured by measuring the weight of the substrate before and after polishing and calculating the difference. The surface roughness Ra of the polished surface of the object to be polished after polishing was measured under conditions where the viewing angle was 5.0 μm × 5.0 μm. The surface roughness Ra was measured using an atomic force microscope (AFM) (Dimension Edge, manufactured by Bruker) in accordance with JIS B 0601-2001. The polishing conditions were as follows: Substrate (object to be polished): 4H-SiC wafer, 4 inches, Si surface, off-axis angle 4 degrees, non-doped (surface roughness Ra approx. 1 Å) Polishing device: Single-sided polishing device (ENGIS EJ-380N) Polishing pad: SUBA600 (Nitta DuPont) Polishing load: 280 g / cm ２ Rotation speed of the surface plate: 80 rpm (linear velocity: 9.5 m / min) Polishing time: 2 hours Supply rate of the polishing composition: 10 mL / min Measurement area of ​​the object to be polished: 5.0 μm×5.0 μm (surface roughness)

[0049] [Evaluation of surface defects] After polishing the object to be polished, surface defects were measured at five random points within a 1.0 x 1.0 mm field of view using a digital microscope (Keyence, VHX-7100), and the average value was used to evaluate the surface defects according to the following evaluation criteria: (Evaluation criteria) ◎: Not detected ○: More than 0 and 1 or less △: More than 1 and 2 or less ×: More than 2

[0050] (Example of Seed Crystal Production) A zirconium oxide sol (zirconia sol) was produced according to Example 1 of JP 2008-31023 A. That is, an aqueous zirconium oxychloride solution was added to an aqueous sodium hydroxide solution heated to 90°C, followed by cooling, filtration, and washing to produce zirconium hydroxide. The resulting zirconium hydroxide was dispersed in water, and then an acid was added, followed by heating and aging to produce a zirconium oxide sol (zirconia sol). The ZrO ２ The converted concentration is 29.8% by mass, and the particle diameter D ５０ was 12 nm.

[0051] (Example 1) An aqueous solution of zirconium oxychloride (ZrO ２ Neutralization was carried out in two stages by dropwise addition of ammonia water to 8,000 g of ammonia water (10% by mass equivalent). In the first stage, 1,104 g of ammonia water (10% by mass) adjusted to 25°C was added dropwise over 10 minutes. The number of liquid delivery tubes and the drop rate were adjusted so that the volume of the ammonia water droplets was in the range of 0.1 to 0.5 ml. Stirring was then continued for 60 minutes. In the second stage, 9,936 g of ammonia water (10% by mass) adjusted to 25°C was added dropwise over 30 minutes, and stirring was continued for 10 minutes to obtain a zirconium hydroxide precipitate. The temperature of the aqueous zirconium oxychloride solution was adjusted to be maintained within ±5°C of the initial temperature during the dropwise addition of ammonia water and during stirring after the dropwise addition. The zirconium hydroxide was filtered off and dispersed again in ion-exchanged water, and a washing procedure was repeated. This procedure was continued until the Cl concentration was 0.01% or less. The concentration of zirconium hydroxide after washing was ZrO ２ The resulting zirconium hydroxide (3,328 g) was mixed with 4,448 g of ion-exchanged water, 20.4 g of nitric acid (60% by mass), and the zirconia sol (ZrO ２ The resulting slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 204 g of nitric acid (60% by mass) was added to the slurry, mixed, and the mixture was refluxed at 100°C for 120 hours. The resulting zirconium oxide precursor was purified using ultrafiltration, yielding a zirconium oxide sol according to Example 1. The ZrO of the sol was ２ The concentration is 20%, pH 3.0 and D ５０ The specific surface area of ​​the powder obtained by drying the sol was 147 m ２ / g. Next, 952 g of ion-exchanged water and 48 g of potassium permanganate were added to 3,000 g of this zirconium oxide sol and stirred for 30 minutes to obtain a polishing dispersion. The conditions for the heat-aging step are shown in Table 1. The ratios A and B of the zirconium oxide sol and the polishing performance evaluation of the polishing dispersion are shown in Table 3.

[0052] (Example 2) 3,328 g of zirconium hydroxide, 4,448 g of ion-exchanged water, 47.6 g of nitric acid (60 mass%), and the zirconia sol (ZrO ２ The resulting slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 177 g of nitric acid (60% by mass) was added to the resulting slurry, and the mixture was mixed and held at 100°C under reflux for 120 hours. A zirconium oxide sol was obtained in the same manner as in Example 1. The ZrO ２ The concentration is 20%, pH 3.1 and D ５０ The specific surface area of ​​the powder obtained by drying the sol was 155 m ２ / g.

[0053] (Example 3) 3,328 g of zirconium hydroxide, 4,448 g of ion-exchanged water, 81.7 g of nitric acid (60% by mass), and the zirconia sol (ZrO ２ The resulting slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 143 g of nitric acid (60% by mass) was added to the resulting slurry, and the mixture was mixed and held at 100°C under reflux for 120 hours. A zirconium oxide sol was obtained in the same manner as in Example 1. The ZrO ２ The concentration is 20%, pH 3.1 and D ５０ The specific surface area of ​​the powder obtained by drying the sol was 162 m ２ / g.

[0054] (Example 4) 3,328 g of zirconium hydroxide, 4,448 g of ion-exchanged water, 102 g of nitric acid (60% by mass), and the zirconia sol (ZrO ２ The resulting slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 306 g of nitric acid (60% by mass) was added to the resulting slurry, and the mixture was mixed and held at 100°C under reflux for 120 hours. A zirconium oxide sol was obtained in the same manner as in Example 1. The ZrO ２ The concentration is 20%, pH 3.1 and D ５０The specific surface area of ​​the powder obtained by drying the sol was 170 m ２ / g.

[0055] Comparative Example 1 A zirconium oxide sol was obtained in the same manner as in Example 2, except that the zirconia sol (29.8% by mass in terms of ZrO2) produced in the above Production Example was not mixed. ２ The concentration is 22%, pH 3.0 and D ５０ The specific surface area of ​​the powder obtained by drying the sol was 159 m ２ / g.

[0056] Comparative Example 2: 3,328 g of zirconium hydroxide, 4,448 g of ion-exchanged water, and the zirconia sol (ZrO ２ The resulting slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 224 g of nitric acid (60% by mass) was added to the resulting slurry, and the mixture was stirred and stirred. A zirconium oxide sol was obtained in the same manner as in Example 1, except that the mixture was then heated to 100°C under reflux for 120 hours. The ZrO ２ The concentration is 20%, pH 3.0 and D ５０ The specific surface area of ​​the powder obtained by drying the sol was 152 m ２ / g.

[0057] (Comparative Example 3) 3,328 g of zirconium hydroxide, 4,448 g of ion-exchanged water, 136 g of nitric acid (60 mass%), and the zirconia sol (ZrO ２ The resulting slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 88.5 g of nitric acid (60% by mass) was added to the resulting slurry, and the mixture was mixed and held at 100°C under reflux for 120 hours. A zirconium oxide sol was obtained in the same manner as in Example 1. The ZrO ２ The concentration is 20%, pH 3.1 and D ５０ The specific surface area of ​​the powder obtained by drying the sol was 157 m ２ / g.

[0058] Comparative Example 4: 3,328 g of zirconium hydroxide, 4,448 g of ion-exchanged water, 20.4 g of nitric acid (60% by mass), and the zirconia sol (ZrO ２ The slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 40.8 g of nitric acid (60% by mass) was added to the slurry, mixed, and the mixture was kept at 100°C under reflux for 120 hours, in the same manner as in Example 1. Unreacted precipitate remained, making it impossible to evaluate.

[0059] Comparative Example 5: 3,328 g of zirconium hydroxide, 4,448 g of ion-exchanged water, 47.6 g of nitric acid (60% by mass), and the zirconia sol (ZrO ２ The resulting slurry was placed in a separable flask and stirred at 50°C for 6 hours. Next, 429 g of nitric acid (60% by mass) was added to the resulting slurry, and the mixture was mixed and held at 100°C under reflux for 120 hours. A zirconium oxide sol was obtained in the same manner as in Example 1. The ZrO ２ The concentration is 20%, pH 3.0 and D ５０ The specific surface area of ​​the powder obtained by drying the sol was 175 m ２ / g.

[0060]

[0061]

[0062]

[0063] 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 utilized in semiconductor manufacturing processes and the like.

Claims

1. Zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.

90.

2. Zirconium oxide particles according to claim 1, wherein the ratio of circularity to convexity (circularity / convexity) is 0.20 to 0.

70.

3. A zirconium oxide sol containing the zirconium oxide particles according to claim 1 or 2.

4. Zirconium oxide particles in which the following ratio A is 40% by number or more. Ratio A: The particle major axis in a transmission electron microscope (TEM) image is the particle diameter D ５０ The ratio of particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90 to all particles larger than the value of 5. Zirconium oxide particles in which the following ratio B is 30% by number or more. Ratio B: The particle major axis in a transmission electron microscope (TEM) image is the particle diameter D ５０ The ratio of particles having a circularity of 0.10 to 0.50, a convexity of 0.30 to 0.90, and a circularity / convexity ratio of 0.20 to 0.70, among all particles larger than the value of 6. A zirconium oxide sol containing the zirconium oxide particles according to claim 4 or 5.

7. A polishing dispersion comprising zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid.

8. The polishing dispersion according to claim 7, wherein the zirconium oxide particles have a circularity to convexity ratio (circularity / convexity) of 0.20 to 0.

70.

9. The polishing dispersion according to claim 7, wherein the zirconium oxide particle group has the following ratio A of 40% by number or more: Ratio A: The particle diameter D in a transmission electron microscope (TEM) image is ５０ The ratio of particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90 to all particles larger than the value of 10. The polishing dispersion according to claim 8, wherein the zirconium oxide particle group has a ratio B of 30% by number or more. Ratio B: The ratio B is the particle diameter D of the particle in a transmission electron microscope (TEM) image. ５０ The ratio of particles having a circularity of 0.10 to 0.50, a convexity of 0.30 to 0.90, and a circularity / convexity ratio of 0.20 to 0.70, among all particles larger than the value of 11. The polishing dispersion according to claim 7, wherein the polishing aid comprises one or more selected from the group consisting of peroxides, nitric acid compounds, persulfuric acid compounds, chlorine compounds, bromine compounds, iodine compounds, ferric acids, permanganic acids, chromic acids, vanadic acids, ruthenic acids, molybdic acids, rhenic acids, and tungstic acids.

12. The polishing dispersion according to claim 7, for use in polishing SiC wafers.

13. A polishing method comprising polishing using the polishing dispersion according to any one of claims 7 to 12.

14. A method for producing a dispersion for polishing, comprising the step of preparing a dispersion using zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid.

15. A method for improving a polishing rate, comprising polishing using zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid.

16. A method for reducing surface roughness Ra, comprising polishing using zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90, and a polishing aid.

17. A polishing powder comprising zirconium oxide powder containing zirconium oxide particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.

90.

18. The polishing powder according to claim 17, wherein the zirconium oxide particles have a circularity to convexity ratio (circularity / convexity) of 0.20 to 0.

70.

19. The polishing powder according to claim 17, which contains a powder of zirconium oxide particle groups in which the following ratio A is 40% by number or more: Ratio A: The ratio A is the particle diameter D in a transmission electron microscope (TEM) image. ５０ The ratio of particles having a circularity of 0.10 to 0.50 and a convexity of 0.30 to 0.90 to all particles larger than the value of 20. The polishing powder according to claim 18, which contains a powder of zirconium oxide particle groups in which the following ratio B is 30% by number or more: Ratio B: The ratio B is the particle diameter D in a transmission electron microscope (TEM) image. ５０ The ratio of particles having a circularity of 0.10 to 0.50, a convexity of 0.30 to 0.90, and a circularity / convexity ratio of 0.20 to 0.70, among all particles larger than the value of 21. The polishing powder according to claim 17, wherein the zirconium oxide powder has an average secondary particle size of 0.002 to 5 μm.

22. The polishing powder according to claim 17, wherein the zirconium oxide powder has an average secondary particle size of 0.1 μm or less.

23. The polishing powder according to claim 17, wherein the purity of the zirconium oxide powder is 97% by mass or more.

24. The polishing powder according to claim 17, wherein the zirconium oxide powder is produced by a liquid phase synthesis method.

25. The specific surface area of ​​the zirconium oxide powder is 20 m ２ 18. The polishing powder according to claim 17, wherein the abrasive powder has a surface roughness of 1 / g or more.

26. A polishing method using the polishing powder according to any one of claims 17 to 25.

27. A method for producing zirconium oxide particles by a liquid phase synthesis method, comprising a step of heat-aging zirconium hydroxide in an aqueous solvent under an acidic atmosphere, wherein in the heat-aging step, zirconium oxide seed crystals are allowed to coexist with the zirconium hydroxide, and acid is added in multiple stages, with the amount of acid added in the first stage being [acid] / [ZrO of zirconium hydroxide]. ２ ] is an amount that is 0.01 to 0.15 in moles, and the total amount of acid added in all stages is [acid] / [ZrO of zirconium hydroxide]. ２ ] in an amount of 0.10 to 0.60 in terms of moles.

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