Polishing slurry and polishing method

Abstract

This invention provides a polishing slurry that enables wet polishing of objects containing aluminum nitride while controlling the generation of ammonia gas during the polishing process. [Solution] A polishing slurry used for polishing materials containing aluminum nitride, characterized in that it contains polishing particles and zeolite in at least an aqueous medium and has a pH of 2 to 6.

Description

Technical Field

[0001] The present invention relates to a polishing slurry and a polishing method using the polishing slurry, and is related to a polishing slurry that can be used for polishing the surface of a material containing aluminum nitride for forming, for example, a semiconductor device substrate mounted on an optical component, an electronic component, a semiconductor sensor component, etc.

Background Art

[0002] Aluminum nitride has high thermal conductivity and excellent characteristics such as heat radiation, thermal shock resistance, and electrical insulation, and is being widely used in semiconductor devices, light-emitting devices, etc. Polishing for smoothing the surface of aluminum nitride is generally carried out by wet polishing using a dispersion of polishing particles. For example, Japanese Unexamined Patent Application Publication No. 2018-159033 (Patent Document 1) discloses a polishing agent composition for an aluminum nitride substrate that contains alumina particles, a dispersant, an acid, a hydrogen ion supply agent, and water, and has a pH value (25°C) of 0.1 or more and less than 5.0. Also, Japanese Unexamined Patent Application Publication No. 2021-104547 (Patent Document 2) discloses a polishing slurry used for polishing an aluminum nitride polycrystalline substrate that contains alumina abrasive grains and an anionic surfactant and has a pH of 10 or more.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in wet polishing of aluminum nitride, the sludge generated during polishing undergoes a hydrolysis reaction with water, producing ammonia gas. In particular, in the primary polishing of substrates containing aluminum nitride, high polishing speeds and polishing volumes are required, resulting in the generation of large amounts of ammonia gas, which poses environmental and operational problems.

[0005] In view of the above issues, one embodiment of the present invention aims to provide a polishing slurry that enables wet polishing of an object containing aluminum nitride while controlling the generation of ammonia gas during the polishing process. Another embodiment of the present invention aims to provide a polishing method using such a polishing slurry. [Means for solving the problem]

[0006] The inventors diligently studied to achieve the above objectives and focused on the ion exchange capacity of zeolites, which can selectively adsorb and remove ammonia. The inventors discovered that by using a polishing slurry containing zeolite with a pH of 2 to 6, wet polishing can be performed on objects containing aluminum nitride while controlling the generation of ammonia gas during polishing, thus completing the present invention. Embodiments of the present invention can be found in the following [1] to [6].

[0007] [1] A polishing slurry used for polishing materials containing aluminum nitride, characterized in that it contains polishing particles and zeolite in at least an aqueous medium and has a pH of 2 to 6. [2] The polishing slurry according to [1], characterized in that the aforementioned material is a substrate material. [3] The polishing slurry according to [1] or [2], characterized in that the zeolite is mordenite with a molar ratio of SiO2 / Al2O3 of 30 or less, and the cations in the zeolite are hydrogen ions. [4] The polishing slurry according to any one of [1] to [3], characterized in that the particle size (D50) at 50% of the volume integrated value in the particle size distribution determined by laser diffraction scattering of the polishing particles is 1 to 10 μm, the particle size (D50) at 50% of the volume integrated value in the particle size distribution determined by laser diffraction scattering of the zeolite is 0.1 μm or more and less than 1 μm, and the particle size (D90) at 90% of the volume integrated value in the particle size distribution determined by laser diffraction scattering of the zeolite is smaller than the particle size (D10) at 10% of the volume integrated value in the particle size distribution determined by laser diffraction scattering of the polishing particles. [5] The polishing slurry according to any one of [1] to [4], characterized in that the content of the abrasive particles is 1 to 10% by mass, the content of the zeolite is 0.5 to 10% by mass, and the ratio of the content of the zeolite to the content of the abrasive particles (zeolite content / abrasive particle content) is 1 or less. [6] A polishing method characterized by comprising the step of supplying a polishing slurry described in any of [1] to [5] to the surface of a material containing aluminum nitride, and polishing the surface of the material containing aluminum nitride. [Effects of the Invention]

[0008] According to one embodiment of the present invention, a polishing slurry is provided that enables wet polishing of an object containing aluminum nitride while controlling the generation of ammonia gas during the polishing process. According to another embodiment of the present invention, a polishing method using such a polishing slurry is provided. [Brief explanation of the drawing]

[0009] [Figure 1] The evaluation results for Experimental Example 2 are shown below. [Figure 2] The evaluation results for Experimental Example 3 are shown below. [Figure 3] The evaluation results for Experimental Example 4 are shown below. [Modes for carrying out the invention]

[0010] The polishing slurry and polishing method according to the present invention will be described in detail below.

[0011] (Polishing slurry) An abrasive slurry according to one embodiment of the present invention contains abrasive particles and zeolite in at least an aqueous medium. The aqueous medium is not particularly limited as long as it is an aqueous medium capable of dispersing the abrasive particles and zeolite, but it is preferably water that does not contain impurities, and for example, pure water, ultrapure water, distilled water, etc. are suitably used.

[0012] The amount of aqueous medium contained in the polishing slurry is preferably 80.0% by mass or more, and more preferably 90.0% by mass or more. Furthermore, the amount of aqueous medium contained in the polishing slurry is preferably 99.5% by mass or less, and more preferably 99.0% by mass or less.

[0013] In one embodiment of the present invention, abrasive particles are dispersed in an aqueous medium. The abrasive particles can be selected from at least one of the following or any combination thereof: cerium oxide, zirconium oxide, ferric oxide, silicon oxide, chromium oxide, aluminum oxide, zirconium silicate, diamond, silicon carbide, and boron carbide. In particular, for primary polishing of substrate materials containing aluminum nitride, zirconium silicate and aluminum oxide are preferred, and aluminum oxide is preferred for obtaining a polished surface with high polishing speed and good surface properties. This makes it possible to efficiently obtain a polished surface with good surface properties at a high polishing speed while controlling the generation of ammonia gas during polishing of the workpiece containing aluminum nitride.

[0014] The particle size (D50) at 50% volume integration in the particle size distribution determined by laser diffraction scattering of polished particles is preferably 1 to 10 μm, more preferably 3 to 10 μm, and even more preferably 5 to 8 μm. Details of the particle size distribution measurement method will be explained in the examples.

[0015] Also, the content of the abrasive particles in the entire polishing slurry is preferably 1 to 10% by mass, more preferably 1 to 8% by mass, and still more preferably 1 to 5% by mass.

[0016] In one embodiment of the present invention, the zeolite is dispersed in an aqueous medium. By using zeolite in the polishing slurry, the generation of ammonia gas during the polishing process for the polishing object containing aluminum nitride can be controlled. On the other hand, since the polishing power of zeolite is lower than that of the abrasive particles, it tends to reduce the polishing power of the polishing slurry (in other words, inhibit the polishing power of the abrasive particles). Therefore, in order to fully exert the polishing power of the abrasive particles, the particle diameter of the abrasive particles is preferably larger than the particle diameter of the zeolite (in other words, the particle diameter of the zeolite is preferably smaller than the particle diameter of the abrasive particles), and the content of the abrasive particles in the entire polishing slurry is preferably equal to or more than the content of the zeolite.

[0017] Zeolite is a microporous three-dimensional crystalline solid of aluminosilicate. The crystal skeleton of zeolite composed of Si, Al, and O has an anionic skeleton structure with regular tubular pores and cavities, and maintains electrical neutrality by containing cations existing outside the crystal skeleton in the pores. The characteristic of zeolite is the fine pore structure derived from the skeleton structure. In addition to the molecular sieve effect by the pore structure, since the cations existing outside the crystal skeleton can be arbitrarily ion-exchanged, ammonia gas can be chemically adsorbed. At the same time, there is also an adsorption effect derived from the pore structure, and molecules smaller than the pore diameter can be physically adsorbed. The adsorption characteristics of zeolite depend on the crystal form, the size of the pore diameter, the SiO2 / Al2O3 ratio (molar ratio) of the crystal skeleton, and the type of cations outside the crystal skeleton. In one embodiment of the present invention, zeolite is required to rapidly adsorb ammonia gas generated during the polishing process of a material containing aluminum nitride.

[0018] There are many types of zeolites, and in terms of adsorbing ammonia gas, it is preferable to select at least one from the group including beta, ferrielite, mordenite, ZSM-5, L-type, Y-type, etc., or any combination thereof. Among these, mordenite is particularly preferred. Mordenite has high ammonia gas adsorption persistence and is suitable for polishing materials containing aluminum nitride, where the polishing slurry is circulated and supplied to the polishing machine for polishing.

[0019] In one embodiment of the present invention, the zeolite preferably has a molar ratio of SiO2 / Al2O3 of 30 or less, and more preferably 20 or less, from the viewpoint of rapidly adsorbing ammonia gas generated during the polishing process of a material containing aluminum nitride. Furthermore, the zeolite preferably has a molar ratio of SiO2 / Al2O3 of 2 or more, and more preferably 5 or more. The SiO2 / Al2O3 molar ratio of the zeolite can be determined, for example, by dissolving zeolite powder in an alkaline aqueous solution and analyzing the solution obtained by dissolving a specified weight of the powder sample using plasma emission spectroscopy (ICP emission spectrometer).

[0020] As mentioned above, zeolites typically contain cations within their pores. Here, hydrogen ions are preferred as the cations. In particular, when the molar ratio of SiO2 / Al2O3 is 30 or less and the cations are hydrogen ions, ammonia gas generated during polishing can be adsorbed relatively quickly. The pore diameter of the zeolite is preferably 3 to 10 Å, and more preferably 6 to 8 Å. The pore diameter of the zeolite can be determined, for example, by measuring the pore distribution using the mercury intrusion method. The mercury intrusion method is a method that utilizes the high surface tension of mercury to apply pressure to infiltrate mercury into the pores of a powder, and then determines the pore distribution (average pore diameter) from the pressure and the amount of mercury injected.

[0021] In one embodiment of the present invention, the zeolite is preferably mordenite with a molar ratio of SiO2 / Al2O3 of 30 or less, and the cations in the zeolite are preferably hydrogen ions.

[0022] The pH of the polishing slurry according to one embodiment of the present invention mainly depends on the type and content of zeolite. In one embodiment of the present invention, the pH of the polishing slurry is preferably 2 to 6, and more preferably 3 to 6. When the pH of the polishing slurry according to one embodiment of the present invention is within the range of 2 to 6, the ammonia deodorizing effect is high. Here, the pH of the polishing slurry is measured at a temperature of 25°C.

[0023] The particle size (D50) at 50% of the integrated volume in the particle size distribution determined by laser diffraction scattering of zeolite is preferably 0.1 μm or more and less than 1 μm, more preferably 0.1 to 0.8 μm, and even more preferably 0.1 to 0.6 μm. As described above, zeolite has lower abrasive power than abrasive particles and therefore tends to reduce the abrasive power of the abrasive slurry (in other words, inhibits the abrasive power of the abrasive particles). For this reason, it is preferable that the particle size of the zeolite is smaller than that of the abrasive particles. Specifically, it is preferable that the particle size (D90) at 90% of the integrated volume in the particle size distribution determined by laser diffraction scattering of zeolite is smaller than the particle size (D10) at 10% of the integrated volume in the particle size distribution determined by laser diffraction scattering of abrasive particles. Details of the particle size distribution measurement method will be explained in the examples.

[0024] Furthermore, the zeolite content relative to the entire polishing slurry is preferably 0.5 to 10% by mass, more preferably 0.5 to 8% by mass, and even more preferably 1 to 5% by mass.

[0025] Furthermore, the ratio of zeolite content to abrasive particle content (zeolite content / abrasive particle content) is preferably 1 or less, and more preferably 0.5 or less. Also, the ratio of zeolite content to abrasive particle content is preferably 0.1 or more, and more preferably 0.2 or more. Here, zeolite content refers to the zeolite content relative to the entire abrasive slurry, and abrasive particle content refers to the abrasive particle content relative to the entire abrasive slurry.

[0026] The total content of abrasive particles and zeolite relative to the entire abrasive slurry is preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass.

[0027] The polishing slurry according to one embodiment of the present invention may contain additives such as dispersants and thickeners as needed. When polishing materials containing aluminum nitride, it is necessary to select the appropriate additives with care, as the generated ammonia gas may dissolve into the aqueous medium and react with the additives to produce reactive substances that exhibit heat generation and toxicity.

[0028] Known dispersants can be used, such as those that utilize the steric hindrance of molecular chains in surfactants, or those that improve dispersion through electrical repulsion of particle surface potentials. For example, ionic polymer surfactants such as polyacrylates and polystyrene sulfons, or acids such as acetic acid, nitric acid, propionic acid, and succinic acid can be used. The content of the dispersant is not particularly limited, but for example, it can be 0.0001 to 1% by mass relative to the entire polishing slurry, preferably 0.001 to 0.1% by mass, and more preferably 0.002 to 0.05% by mass.

[0029] In a preferred embodiment, since there is a difference in particle size between the abrasive particles and the zeolite, a thickening agent can be added to improve the uniformity and stability of the dispersion state of the two types of particles with different particle sizes. Examples of thickening agents include surfactants and water-soluble polymers. Water-soluble polymers, in particular, can be suitably used to prevent the precipitation of larger abrasive particles and to improve dispersion stability.

[0030] As water-soluble polymers, anionic (anionic) polymers such as polycarboxylic acid-based water-soluble polymers can be used, such as polyacrylic acid-based water-soluble polymers such as polyacrylic acid or its salts, acrylic acid-(meth)acrylic acid ester copolymers or their salts, alginates, and cellulose derivatives such as carboxymethylcellulose. Nonionic (nonionic) polymers include cellulose derivatives such as hydroxyethylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and polyacrylamide. As cationic (cationic) water-soluble polymers, polyethyleneimine can be used. Nonionic (nonionic) water-soluble polymers are particularly suitable because they help to suppress polishing inhibition, such as a decrease in polishing speed on the workpiece due to an excessive increase in viscosity. The content of the water-soluble polymer is, for example, 0.01 to 1% by mass, preferably 0.1 to 1% by mass, relative to the total polishing slurry.

[0031] A polishing slurry according to one embodiment of the present invention is a polishing slurry used for polishing a material containing aluminum nitride, and preferably a polishing slurry used for primary polishing (especially rough grinding) of a material containing aluminum nitride. The material is preferably a substrate material containing aluminum nitride. Examples of substrates containing aluminum nitride include semiconductor device substrates mounted on optical components, electronic components, semiconductor sensor components, etc.

[0032] (Method for manufacturing polishing slurry) A method for producing a polishing slurry according to one embodiment of the present invention can be used, for example, by dispersing, stirring, and mixing polishing particles, zeolite, and optionally additives in an aqueous solvent, and then diluting the mixture. For example, a polishing slurry can be produced by adding polishing particles and optionally additives such as dispersants to an aqueous medium and dispersing them using a bead mill or the like so that the particle size (D50) of the polishing particles is preferably 1 to 10 μm. Similarly, a zeolite can be added to an aqueous medium and dispersing it using a bead mill or the like so that the particle size (D50) of the zeolite is preferably 0.1 μm or more and less than 1 μm. By stirring and mixing these two dispersions so that the ratio of zeolite content to polishing particle content is preferably 1 or less, and then diluting the mixture, a polishing slurry suitable for polishing materials containing aluminum nitride can be produced.

[0033] (polishing method) The polishing slurry according to one embodiment of the present invention can be used for wet polishing of materials containing aluminum nitride, particularly substrate materials containing aluminum nitride, and is particularly suitable for primary polishing (rough grinding) of substrate materials containing aluminum nitride. For this reason, the polishing method according to one embodiment of the present invention is a polishing method using the above-described polishing slurry, and preferably includes the step of supplying the above-described polishing slurry to the surface of a material containing aluminum nitride and polishing the surface of the material containing aluminum nitride.

[0034] The polishing apparatus is not particularly limited, and various general polishing apparatuses can be used, and it may be a single-sided polishing apparatus or a double-sided polishing apparatus. For example, when using a single-sided polishing apparatus, the substrate material containing aluminum nitride is held by a holder such as a carrier, and a polishing slurry according to one embodiment of the present invention is supplied to the surface of the substrate material containing aluminum nitride. Then, if necessary, a platen with a predetermined polishing pad attached is pressed against the object to be polished and the platen is rotated to roughly grind the surface of the substrate material containing aluminum nitride, thereby reducing its thickness and correcting any undulations, irregularities, or warping in the material.

[0035] According to a polishing method of one embodiment of the present invention, wet polishing can be performed on an object containing aluminum nitride while controlling the generation of ammonia gas during the polishing process. Preferably, even for materials with relatively high mechanical strength, such as substrate materials containing aluminum nitride, a polished surface with good surface properties can be obtained at a high polishing speed. This enables efficient polishing while controlling the generation of ammonia gas.

[0036] Furthermore, according to the polishing method of one embodiment of the present invention, the polishing speed of the substrate material containing aluminum nitride can be 10 μm / h or more, more preferably 20 μm / h or more, and even more preferably 25 μm / h or more. There is no particular upper limit for the recommended polishing speed, but if it is too fast, it may become difficult to adjust the desired amount of material removed and control the ammonia gas, so it is typically preferable to set it to 250 μm / h or less, and more preferably 150 μm / h or less. The polishing load on the substrate material containing aluminum nitride is, for example, 10 to 500 g / cm², although this is not limited to the above. 2 It can be made to a comfortable 100-200 g / cm³ 2 It can be done this way.

[0037] According to a polishing method of one embodiment of the present invention, a polished surface with good surface properties can be obtained. Specifically, on the surface of a substrate material containing aluminum nitride, a primary (roughly polished) surface with good surface properties can be obtained, having a surface roughness (arithmetic mean height Sa) according to ISO 25178 preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.65 μm or less. [Examples]

[0038] The following are experimental examples relating to the present invention. These examples are provided to help you better understand the present invention and its advantages, and are not intended to limit the invention.

[0039] (Experimental Example 1) Eleven types of zeolites (No. 1 to No. 11, all manufactured by Tosoh Corporation) with different crystal forms, cations, and SiO2 / Al2O3 ratios (molar ratios) were prepared, and the ammonia deodorizing effect of each zeolite was evaluated. To confirm the deodorizing effect, 5g of a 0.01% by mass ammonia aqueous solution and 5g of a 1% by mass zeolite aqueous dispersion were mixed in a 100mL flask, and the ammonia concentration in the flask was measured using an ammonia detection tube. The evaluation results are shown in Table 1. In Table 1, "Blank" represents an experimental example using a 0.01% by mass ammonia aqueous solution without zeolite, and the ammonia concentration in the flask without zeolite was measured. The product number is the product number of the zeolite manufactured by Tosoh Corporation, the pH is the value of the 1% by mass zeolite aqueous dispersion at 25°C, and the NH3 concentration is the ammonia gas concentration (volume ppm) measured with an ammonia detection tube. All of these zeolites were found to have a deodorizing effect on ammonia gas.

[0040] In particular, it was found that using zeolites with a molar ratio of SiO2 / Al2O3 of 30 or less and hydrogen ions as cations resulted in a high deodorizing effect on ammonia gas.

[0041] [Table 1]

[0042] (Experimental Example 2) In Experimental Example 1, zeolites No. 2, No. 4-6, and No. 9 showed high deodorizing effects against ammonia. The repeated deodorizing effect against ammonia was evaluated under the assumption that polishing slurry was circulated and supplied to a polishing machine during the polishing process. To confirm the deodorizing effect, 5g of a 0.01% by mass ammonia aqueous solution and 5g of a 1% by mass zeolite aqueous dispersion were mixed in a 100mL flask. The ammonia concentration in the flask was measured using an ammonia detection tube (first measurement). For subsequent measurements, 0.5g of a 0.1% by mass ammonia aqueous solution was added to the flask each time, and the ammonia concentration was measured again. The evaluation results are shown in Table 2 and Figure 1.

[0043] No. 5, with a molar ratio of SiO2 / Al2O3 of 240, showed lower repeated deodorizing effect against ammonia compared to No. 2, No. 4, No. 6, and No. 9, which had a molar ratio of SiO2 / Al2O3 of 30 or less. Furthermore, when comparing No. 2, No. 4, No. 6, and No. 9, which have different crystal forms but also a molar ratio of SiO2 / Al2O3 of 30 or less, mordenite (No. 4) showed the highest repeated deodorizing effect against ammonia.

[0044] [Table 2]

[0045] From the above, it was found that zeolites with a molar ratio of SiO2 / Al2O3 of 30 or less, hydrogen ions as cations, and mordenite crystal form rapidly deodorize ammonia gas and have high deodorizing power.

[0046] (Experimental Example 3) Polishing slurries were prepared using zeolites No. 2 and No. 4, which showed high deodorizing effects against ammonia in Experimental Examples 1 and 2, and the repeated deodorizing effect against ammonia was evaluated in the same manner as in Experimental Example 2.

[0047] Alumina particles (WA#2500, manufactured by Fujimi Incorporated Co., Ltd.) were used as abrasive particles. An abrasive particle / water mixture containing 40% by mass of abrasive particles was dispersed in a bead mill, and then diluted with water to prepare an aqueous dispersion of abrasive particles with a content (abrasive particle concentration) of 3% by mass. Similarly, using zeolites No. 2 and No. 4, a zeolite / water mixture containing 40% by mass of zeolite was dispersed in a bead mill, and then diluted with water to prepare an aqueous dispersion of zeolite with a content (zeolite concentration) of 3% by mass. The prepared aqueous dispersions of abrasive particles and zeolites were mixed and stirred to prepare polishing slurries containing abrasive particles and zeolites in an aqueous medium at the content shown in conditions 2 to 6 in Table 3. Note that for condition 1, the aqueous dispersion of abrasive particles without zeolite was used as is. Zeolite No. 4 was used for conditions 2 to 4, and zeolite No. 2 was used for conditions 5 and 6. In conditions 1-6, the total content of abrasive particles and zeolite relative to the entire abrasive slurry was adjusted to 3.0% by mass. The pH of the abrasive slurry in conditions 1-6 was measured at 25°C.

[0048] The deodorizing effect of ammonia was confirmed for polishing slurries under conditions 1 to 6 shown in Table 3. To confirm the deodorizing effect, 5 g of a 0.01% by mass ammonia aqueous solution and 5 g of polishing slurry with a total content of polishing particles and zeolite of 3% by mass were mixed in a 100 mL flask. The ammonia concentration in the flask was measured using an ammonia detection tube (first measurement), and then 0.5 g of a 0.1% by mass ammonia aqueous solution was added to the flask in subsequent measurements. The evaluation results are shown in Table 3 and Figure 2.

[0049] [Table 3]

[0050] The results showed that a zeolite content of 0.5% by mass or more relative to the total polishing slurry resulted in a high ammonia deodorizing effect, and a zeolite content of 1% by mass or more resulted in a high repeated deodorizing effect of ammonia. Furthermore, zeolite No. 4 showed a higher deodorizing effect than zeolite No. 2.

[0051] (Experimental Example 4) Polishing slurries were prepared using zeolites No. 2 and No. 4, which showed high ammonia deodorizing effects in Experimental Examples 1 and 2. The polishing speed, surface roughness, and ammonia deodorizing effect on aluminum nitride substrates were then evaluated.

[0052] Alumina particles (WA#2500, manufactured by Fujimi Incorporated) were used as abrasive particles, and an aqueous dispersion of abrasive particles was prepared by dispersing an abrasive particle / water mixture containing 40% by mass of abrasive particles in a bead mill. Similarly, zeolite aqueous dispersions were prepared by dispersing a zeolite / water mixture containing 40% by mass of zeolite in a bead mill using zeolite No. 2 and No. 4 zeolites. The prepared aqueous dispersions of abrasive particles and zeolite were mixed and stirred, and diluted with water to prepare abrasive slurries containing abrasive particles and zeolite in an aqueous medium at the concentrations shown in Table 4 for conditions 7, 8, 10, and 11. Note that the abrasive slurry for condition 1 was prepared by diluting an aqueous dispersion of abrasive particles without zeolite to the abrasive particle concentrations shown in Table 4. Zeolite No. 4 was used for conditions 7 and 8, and zeolite No. 2 was used for conditions 10 and 11. Separately, using zeolite No. 4, a zeolite aqueous dispersion was prepared by stirring and mixing it in an impeller-type stirrer so that the zeolite content in the aqueous medium was 3% by mass. This dispersion was then mixed and stirred with an aqueous dispersion of abrasive particles containing 3% by mass, prepared in the same manner as in Experimental Example 3, to prepare a polishing slurry containing abrasive particles and zeolite in the aqueous medium at the content shown in Condition 9 of Table 4. The prepared polishing slurry was evaluated as follows.

[0053] <Measurement of particle size> Particle size was measured using a laser diffraction / scattering particle size distribution analyzer (Horiba LA-960) with aqueous dispersions of polished particles and zeolite. Specifically, several drops of either the aqueous dispersion or the polished particle dispersion were added to water circulated by a fan, and the particle size was measured. The particle size values ​​were evaluated as the particle diameter at 10% volume integration (D10), 50% volume integration (D50), and 90% volume integration (D90) in the particle size distribution determined by the laser diffraction scattering method. The results are shown in Table 4.

[0054] <Polishing Test> The polishing was performed using an Engis EJ-300IN polishing device under the following conditions. Objects to be polished: Aluminum nitride substrates (30mm x 30mm x 3 pieces) Polishing surface plate, cast iron surface plate, XY grid / 20mm pitch Polishing pressure: 150 g / cm² 2 Rotation speed: 36 rpm / 50 rpm Slurry flow rate: 50 ml / min Polishing time 20min

[0055] <Measurement of polishing speed> The polishing rate was measured by measuring the weight change of the object to be polished (aluminum nitride substrate) before and after polishing using a precision balance. The polishing rate was then calculated by converting the density of the object to be polished and the polishing area into the amount of film thickness reduction per unit polishing time. The results are shown in Table 4. Note that the polishing rate values ​​in Table 4 are the average values ​​of the polishing rates calculated from each of the three aluminum nitride substrates.

[0056] <Measurement of surface roughness> Surface roughness was measured on the polished objects (aluminum nitride substrates) using a shape analysis laser microscope (VK-X1100) manufactured by Keyence Corporation. The surface roughness value was calculated using the arithmetic mean height (Sa) as defined in ISO 25178. The results are shown in Table 4. Note that the surface roughness values ​​in Table 4 are the average values ​​of the surface roughness calculated from each of the three aluminum nitride substrates.

[0057] <Confirmation test of ammonia deodorizing effect> The deodorizing effect of ammonia was confirmed for polishing slurries under conditions 1 and 7-11. To confirm the deodorizing effect, 5g of a 0.01% by mass aqueous ammonia solution and 5g of polishing slurry were mixed in a 100mL flask, and the ammonia concentration in the flask was measured using an ammonia detection tube. The results are shown in Table 4. The presence and degree of ammonia odor during the polishing test were also confirmed.

[0058] <Experimental Results> The evaluation results are shown in Table 4 and Figure 3.

[0059] [Table 4]

[0060] The polishing slurry under Condition 1, which did not contain zeolite, showed good polishing characteristics with a polishing speed of 25 μm / h or more and a surface roughness of 0.65 μm or less, but a faint ammonia odor was detected during polishing. The polishing slurries under Conditions 7 and 10 showed polishing characteristics equivalent to Condition 1 at a polishing speed of 25 μm / h or more, and there was almost no ammonia odor detected during polishing. The particle size (D90) of the zeolite contained in the polishing slurry under Conditions 7 and 10 at 90% of its volume integrated value was smaller than the particle size (D10) of the polishing particles at 10% of their volume integrated value, and the ratio of zeolite content to polishing particle content was 1 or less, so there was no effect on the polishing characteristics due to the inclusion of zeolite in the polishing slurry. The polishing slurries under Conditions 8 and 11 had a lower polishing speed than the polishing slurries under Conditions 7 and 10 due to the lower polishing particle content, but still showed good polishing characteristics with a polishing speed of 20 μm / h or more and a surface roughness of 0.65 μm or less. Furthermore, no ammonia odor was detected during the polishing process.

[0061] On the other hand, the polishing slurry under condition 9, which contained zeolite with a larger particle size, did not emit an ammonia odor during polishing, but the polishing speed was significantly lower compared to other polishing slurries. It was found that even with a large particle size, zeolite has lower polishing power than polishing particles and inhibits the polishing power of the polishing particles. It is preferable that the particle size of the zeolite is smaller than that of the polishing particles, and that the particle size at 90% of the volume integrated value in the particle size distribution determined by laser diffraction scattering of the zeolite (D90) is smaller than the particle size at 10% of the volume integrated value in the particle size distribution determined by laser diffraction scattering of the polishing particles (D10). Furthermore, it was confirmed that the ratio of zeolite content to polishing particle content should be 1 or less.

Claims

1. A polishing slurry used for polishing materials containing aluminum nitride, characterized in that it contains polishing particles and zeolite in at least an aqueous medium, and has a pH of 2 to 6.

2. The polishing slurry according to claim 1, characterized in that the aforementioned material is a substrate material.

3. The zeolite is SiO 2 / Al 2 O 3 The polishing slurry according to claim 1, characterized in that the molar ratio of mordenite is 30 or less, and the cations in the zeolite are hydrogen ions.

4. The polishing slurry according to claim 1, characterized in that the particle size (D50) at 50% of the integrated volume in the particle size distribution determined by laser diffraction scattering of the polishing particles is 1 to 10 μm, the particle size (D50) at 50% of the integrated volume in the particle size distribution determined by laser diffraction scattering of the zeolite is 0.1 μm or more and less than 1 μm, and the particle size (D90) at 90% of the integrated volume in the particle size distribution determined by laser diffraction scattering of the zeolite is smaller than the particle size (D10) at 10% of the integrated volume in the particle size distribution determined by laser diffraction scattering of the polishing particles.

5. The polishing slurry according to claim 1, characterized in that the content of the abrasive particles is 1 to 10% by mass, the content of the zeolite is 0.5 to 10% by mass, and the ratio of the content of the zeolite to the content of the abrasive particles (zeolite content / abrasive particle content) is 1 or less.

6. A polishing method characterized by comprising the step of supplying a polishing slurry according to any one of claims 1 to 5 to the surface of a material containing aluminum nitride, and polishing the surface of the material containing aluminum nitride.

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