Aluminum nitride ceramic with high resistivity and preparation method and application thereof

Abstract

The invention provides aluminum nitride ceramic with high resistivity as well as a preparation method and application of the aluminum nitride ceramic. The preparation method comprises the following steps: S1, refining a mixture of aluminum nitride, cubic boron nitride, yttrium oxide and a carbon source to obtain composite powder; s2, the composite powder is subjected to deoxidation treatment in a reducing atmosphere at the temperature lower than 1550 DEG C; s3, performing two-step hot pressed sintering on the deoxidized composite powder; wherein the hot pressing sintering in the first step is carried out at 1550-1700 DEG C, and the hot pressing sintering in the second step is carried out at 1750-1900 DEG C; and after the hot pressing sintering is finished, releasing the pressure to obtain the aluminum nitride ceramic. The aluminum nitride ceramic provided by the invention has high thermal conductivity and high resistivity at high temperature, overcomes the technical bottleneck that the thermal conductivity is greatly reduced when the high-temperature resistivity of the traditional aluminum nitride ceramic is improved, and is beneficial to promoting the application of the high-performance aluminum nitride ceramic in the fields of third-generation semiconductor manufacturing and the like.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials, specifically relating to high-performance ceramic materials, their preparation methods and applications, and particularly to an aluminum nitride ceramic for high-temperature and high-insulation applications, its preparation method and applications. Background Technology

[0002] Aluminum nitride (AlN) ceramics, due to their high thermal conductivity, good insulation properties, and matched coefficient of thermal expansion, have become a key insulating material for electrostatic chucks (ESCs) in semiconductor manufacturing, widely used in second-generation semiconductor equipment to ensure the efficiency and yield of wafer processing. However, with the rise of third-generation semiconductors such as silicon carbide, their fabrication processes involve high-temperature ion implantation, oxidation, and annealing at temperatures above 600°C, placing more stringent requirements on the high-temperature insulation performance of ESC materials at 500-600°C.

[0003] Oxygen impurities in AlN ceramics form oxygen vacancies, which are the primary source of charge carriers. At high temperatures, the thermal excitation of charge carriers intensifies, and their mobility increases, leading to a significant decrease in the high-temperature resistivity of the material. While existing AlN ceramics possess high resistivity (>10⁻⁶) at room temperature... 13 Its resistivity is Ω·cm, but it decreases exponentially with increasing temperature, falling below 1.0×10⁻⁶ at 500℃. 7 Ω·cm (Applied Physics Express, 2022, 15, 95501), high temperature insulation deteriorates significantly, which can easily lead to high voltage breakdown risk and make it difficult to meet the ESC reliability requirements of third-generation semiconductor manufacturing.

[0004] Oxygen impurities in AlN raw materials are generally difficult to completely avoid, and low-oxygen-content powder raw materials are expensive. Therefore, the method of improving the high-temperature resistivity of ceramics simply by reducing the oxygen content of AlN raw materials is limited in practical applications. Oxide doping can effectively constrain the migration of charge carriers in AlN ceramics, thereby improving their high-temperature resistivity. For example, MgO doping can increase the high-temperature resistivity of AlN ceramics at 500℃ by more than three orders of magnitude (>1.0 × 10⁻⁶). 10 However, this method leads to a significant decrease in the thermal conductivity of the material; for example, the thermal conductivity after doping is only about 90 W·cm. -1 ·K -1 (CeramicsInternational, 2022, 48, 26022-26027) This makes it difficult to meet the demands of high thermal conductivity applications. Therefore, how to significantly improve the high-temperature resistivity of AlN ceramics while maintaining their high thermal conductivity has become a key technical challenge that urgently needs to be overcome in this field.

[0005] To solve the above problems, it is necessary to develop a new type of aluminum nitride ceramic and its preparation method. Summary of the Invention

[0006] This application provides the following technical solution:

[0007] A method for preparing aluminum nitride ceramics includes the following steps: S1, a mixture of aluminum nitride, cubic boron nitride, yttrium oxide and carbon source is refined to obtain composite powder; S2, the composite powder is subjected to deoxidation treatment in a reducing atmosphere and at a temperature below 1550°C. S3, the composite powder that has undergone the deoxidation treatment is subjected to two-step hot pressing sintering; wherein, the first step of hot pressing sintering is carried out at 1550-1700℃, and the second step of hot pressing sintering is carried out at 1750-1900℃; after the hot pressing sintering is completed, the pressure is released to obtain the aluminum nitride ceramic.

[0008] This application also provides the following technical solutions: An aluminum nitride ceramic is obtained by the aforementioned preparation method.

[0009] This application also provides the following technical solutions: The aforementioned applications of aluminum nitride ceramics in semiconductor manufacturing.

[0010] The technical solution provided in this application has the following beneficial effects: (1) The aluminum nitride ceramic preparation method provided in this application uses cubic boron nitride as a dopant, and induces its phase transformation under high temperature conditions to form onion-shaped hexagonal boron nitride as a grain boundary phase with excellent high-temperature insulation properties. By controlling the distribution of onion-shaped hexagonal boron nitride at the grain boundaries, a significant grain boundary barrier effect can be generated, which effectively blocks the migration of charge carriers at high temperatures, thereby significantly improving the high-temperature resistivity of the ceramic. At the same time, since onion-shaped hexagonal boron nitride itself has good thermal conductivity, it effectively avoids the problem of significant decrease in thermal conductivity caused by traditional oxide doping methods.

[0011] (2) The preparation method provided in this application can effectively remove oxide impurities in the raw materials, especially boron oxide (B2O3) on the surface of cubic boron nitride, by introducing a specific deoxidation treatment step. The deoxidation treatment can prevent oxide impurities from melting and entering the aluminum nitride lattice during subsequent high-temperature sintering, thus avoiding the deterioration of the material's thermal conductivity. The deoxidation treatment is carried out in a reducing atmosphere (especially a hydrogen atmosphere), which can achieve efficient removal of oxide impurities. The deoxidation treatment is carried out at a temperature lower than the sintering temperature (e.g., not higher than 1550°C, preferably not higher than 1400°C), which can prevent the premature phase transformation of cubic boron nitride and will not significantly affect the morphology and phase structure of aluminum nitride and yttrium oxide.

[0012] (3) The preparation method provided in this application adopts a two-step hot-pressing sintering process. The first step mainly promotes the transformation of cubic boron nitride to onion-shaped hexagonal boron nitride; at the same time, the yttrium oxide additive forms a suitable sintering liquid phase, which acts as a migration carrier under lower pressure conditions, which is conducive to the migration of onion-shaped hexagonal boron nitride to the grain boundaries. The second step achieves powder densification under increased temperature and pressure conditions, thereby obtaining high-density, high-performance aluminum nitride ceramics.

[0013] (4) The preparation method provided in this application may also include a heat treatment step to eliminate residual internal stress generated during hot pressing and sintering, reduce the risk of stress concentration during use, and thus effectively prevent stress cracking of ceramic components during service.

[0014] (5) Through the synergistic effect of cubic boron nitride doping, deoxidation treatment, and two-step hot-pressing sintering, the aluminum nitride ceramic provided in this application can simultaneously achieve significantly improved high-temperature resistivity and high thermal conductivity, overcoming the technical bottleneck of a significant decrease in thermal conductivity when improving the high-temperature resistivity of traditional aluminum nitride ceramics. In particular, the resistivity of the aluminum nitride ceramic provided in this application can reach 1.0 × 10⁻⁶ at 500 °C. 10 It has a thermal conductivity of at least 145 W·m and an Ω·cm or higher. -1 ·K -1 This will help promote the application of high-performance aluminum nitride ceramics in fields such as third-generation semiconductor manufacturing. Attached Figure Description

[0015] Figure 1 The image shows a SEM micrograph of the high-resistivity aluminum nitride ceramic prepared in Example 1.

[0016] Figure 2 The resistivity performance curve of the high-resistivity aluminum nitride ceramic prepared in Example 1 is shown. Invention Details 1. Terminology Explanation All patents and other publications cited herein are incorporated herein in their entirety. In the event of any conflict between any description of terminology herein and any document incorporated herein by reference, this document shall prevail.

[0017] Numerical ranges can be represented by a hyphen "-" or a tilde "~". Unless otherwise stated, the range should be understood to encompass both the endpoint values ​​and any values ​​in between. There are no particular restrictions on the type of numeric values ​​within the range, including but not limited to integers, decimals, fractions, percentages, etc., unless explicitly excluded by the context or a particular numeric type is technically unavailable. The type of numeric values ​​within the range is not limited by the specific representation of the endpoints.

[0018] The terms “including,” “containing,” and similar expressions have a non-restrictive meaning.

[0019] The terms "optional" or "optional" are used to indicate that a certain feature (including but not limited to components, steps, parameters, or structures) may be present in some embodiments but not in others, thereby providing technical flexibility for different implementations without departing from the core concept of the present invention.

[0020] A “combination” of the enumeration items refers to any two or more of the enumeration items that coexist or are used together, including but not limited to any two-item combination, any three-item combination, any more items, and any combination of all the enumeration items, unless the context explicitly excludes it or a particular combination is technically impossible.

[0021] The use of labels such as a), b), i), ii), 1), 2), S1, S2, etc. to number the steps of a method is only for the convenience of description and reading, and does not mean that the corresponding steps must be performed in the order of the numbers, unless the text explicitly states or the information in the text can be clearly inferred that there is a logical or temporal relationship between specific steps.

[0022] When the content of solid components is expressed as a percentage (%), it is given by default as a weight percentage (wt%).

[0023] "Balance" refers to the content that makes the sum of the contents of all components 100%.

[0024] "Carbon source" refers to a carbon-containing substance that can effectively provide carbon elements and participate in carbothermic reduction reactions under high-temperature conditions. It can be used to synergistically promote the removal of oxide impurities in a system with reducing gases. Exemplary carbon sources include, but are not limited to, the following categories: carbon black, such as thermal black, acetylene black, channel black, furnace black, lamp black, etc.; graphite, such as flake graphite, graphite powder, etc.; porous carbon materials, such as activated carbon, biochar, petroleum coke, etc.; organic carbon precursors and their pyrolysis products, such as sucrose, glucose, polyvinyl alcohol, cellulose, gum, resin, etc.

[0025] "Refinement processing" refers to processing methods that reduce the average particle size of solid materials by applying external forces. Refinement processing can also improve the particle size distribution, specific surface area, and surface reactivity of powders. Refinement processing includes, but is not limited to, mechanical grinding and powder classification, such as reducing particle size through shearing, impact, and friction. Mechanical grinding includes, but is not limited to, ball milling, roller milling, hammer milling, sand milling, vibratory milling, and other conventional mechanical grinding methods. Refinement processing can be carried out under dry (without additional liquid media) or wet conditions. Wet refinement processing can be carried out in liquid media such as water, organic solvents, and grinding aids / dispersants, and may include, as needed, a step of removing the liquid media to obtain dry powder (e.g., filtration, centrifugation, drying, or spray drying). Powder classification includes, but is not limited to, sieving, air classifying, centrifugal classification, and other conventional powder classification methods. Appropriate equipment and process parameters can be selected for refinement processing based on the type of powder, target particle size, and other requirements.

[0026] "Average particle size" refers to the statistical average of a set of particle sizes, applicable to solid materials with different particle size ranges, including but not limited to nanoscale (1-100 nm), submicron (100-1000 nm), or micron (1-1000 μm) powders. The average particle size can be obtained using particle size measurement methods commonly used in the art. For submicron or nanoscale particles, particle size measurement methods include, but are not limited to, dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). For particles at the micron and larger scales, their average particle size can be measured using methods such as laser diffraction or sieving. The statistical average can be calculated based on different weighting methods, such as particle number, volume, or scattering intensity. Unless otherwise specified, the average particle size provided in this application is a statistical average based on the number of particles.

[0027] A "reducing atmosphere" refers to a gaseous atmosphere applied to a reaction system that provides a reducing chemical environment. It primarily comprises one or more reducing gases (e.g., hydrogen, carbon monoxide) and optionally one or more inert gases (e.g., nitrogen, argon). Under high-temperature conditions, the reducing gas can react with the oxides, converting them into gaseous products or other easily removable substances, thereby effectively reducing the oxygen content of the system.

[0028] "Deoxygenation treatment" refers to the process of partially or completely removing or transforming oxygen-containing impurities in a system through reduction reactions, thermal decomposition, or other processes, thereby reducing the total oxygen content of the system.

[0029] Heat treatment of ceramic materials refers to the process of subjecting them to high-temperature holding. Heat treatment can release or eliminate residual stress within the material, improve the uniformity of the microstructure, and enhance the structural stability of the material. Unless otherwise specified, heat treatment of ceramic materials also includes a cooling step after the holding period.

[0030] Cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) are two crystalline allotropes of boron nitride. c-BN has a three-dimensional cubic symmetrical atomic arrangement. h-BN typically has a graphite-like lamellar structure, with layers stacked by relatively weak van der Waals forces. At the nanoscale, h-BN can also form a special onion-like structure with multiple shells through bending, folding, and even closing of the lamellars. During the hot-pressing sintering process for ceramic preparation, c-BN can transform into h-BN with an onion-like structure. The transformation of c-BN to h-BN begins at approximately 1550 °C; the transformation ratio gradually increases with increasing temperature, and it can completely transform into onion-like h-BN at approximately 1850 °C (Ceramics International, 2024, 50, 1419-1427).

[0031] "Semiconductor manufacturing" refers to a series of processes, equipment, materials, and operations performed to prepare, process, package, and test wafers, chips, and their components for microelectronic, optoelectronic, or integrated circuit devices. It encompasses the entire process from raw material and wafer preparation, wafer-level front-end processes (e.g., photolithography, thin-film deposition CVD / PVD / ALD, ion implantation, dry / wet etching, thermal treatment, chemical mechanical polishing, cleaning, etc.) to back-end packaging and testing (e.g., dicing, interconnection, packaging, aging, and final testing); it also includes equipment and components used in the above processes (e.g., Electrostatic chucks, wafer carriers, heating plates, bases, focusing rings / edge rings / gas distribution rings, plasma processing chamber components, seals and process accessories), their operating environment and process conditions (e.g., vacuum or inert / active atmosphere, high temperature of several hundred degrees Celsius, radio frequency or microwave field, electromagnetic and chemical media, high purification and cleanliness requirements) and the performance requirements of related materials (including but not limited to, high volume resistivity, low leakage current and electric field resistance, excellent thermal conductivity and thermal cycling stability, resistance to plasma and chemical corrosion, low degassing and dimensional / mechanical stability, etc.).

[0032] 2. Implementation Plan One embodiment of this application is as follows: A method for preparing aluminum nitride ceramics includes the following steps: S1, a mixture of aluminum nitride, cubic boron nitride, yttrium oxide and carbon source is refined to obtain composite powder; S2, the composite powder is subjected to deoxidation treatment in a reducing atmosphere and at a temperature below 1550°C. S3, the composite powder that has undergone the deoxidation treatment is subjected to two-step hot pressing sintering; wherein, the first step of hot pressing sintering is carried out at 1550-1700℃, and the second step of hot pressing sintering is carried out at 1750-1900℃; after the hot pressing sintering is completed, the pressure is released to obtain the aluminum nitride ceramic.

[0033] In some specific implementations, the refining process includes mechanical grinding under wet conditions, and optionally also includes powder classification.

[0034] In some specific implementations, the liquid medium used in the wet process is anhydrous ethanol.

[0035] In some specific implementations, the liquid medium is removed after grinding.

[0036] In some specific implementations, the liquid medium is removed by drying; the drying is preferably carried out at 70-90°C; and the drying time is preferably 6-12 hours.

[0037] In some specific embodiments, the amount of the liquid medium is 100-200% of the total weight of aluminum nitride, cubic boron nitride and yttrium oxide, preferably 150%; In some specific implementations, the mechanical grinding is selected from any one of ball mills, roller mills, hammer mills, sand mills, vibratory mills, and combinations thereof.

[0038] In some specific implementations, the powder grading is performed by sieving.

[0039] In some specific implementations, the sieving process uses a 100-400 mesh sieve, preferably a 200 mesh sieve.

[0040] In some specific implementation schemes, the amounts of cubic boron nitride, yttrium oxide, and aluminum nitride, based on a total of 100 wt%, are as follows: Cubic boron nitride: 0.2-5 wt%, preferably 1-4 wt%; Yttrium oxide: 2-4 wt%, preferably 3 wt%; Aluminum nitride: Balance.

[0041] In some specific embodiments, the aluminum nitride is a submicron or micron-sized powder, with an average particle size preferably of 0.5-2 μm, more preferably of 0.8-1.2 μm.

[0042] In some specific embodiments, the cubic boron nitride is a nano or submicron-sized powder with an average particle size preferably of 300-800 nm, more preferably of 400-600 nm.

[0043] In some specific embodiments, the yttrium oxide is a nano or submicron-sized powder, with an average particle size preferably of 200-600 nm, more preferably 300-500 nm.

[0044] In some specific implementation schemes, the carbon source is selected from any one of carbon black, graphite, porous carbon materials, organic carbon precursors and their pyrolysis products, preferably carbon black.

[0045] In some specific implementations, the amount of carbon source used is 10-20 wt% of cubic boron nitride.

[0046] In some specific implementations, the reducing atmosphere is a hydrogen atmosphere.

[0047] In some specific implementations, the deoxygenation treatment is carried out at 1100-1400°C, preferably at 1300-1400°C.

[0048] In some specific implementations, the deoxygenation treatment lasts for 1-12 hours, preferably 2-6 hours.

[0049] In some specific implementation schemes, the first step of hot pressing sintering is carried out at 1650-1700℃.

[0050] In some specific implementation schemes, the second step of hot pressing sintering is carried out at 1750-1850℃.

[0051] In some specific implementation schemes, the first step of hot pressing sintering takes 1-5 hours, preferably 2-3 hours.

[0052] In some specific implementation schemes, the first-step hot pressing sintering pressure is increased to 2-3 MPa within 10-20 minutes and maintained.

[0053] In some specific implementation schemes, the second step of hot pressing and sintering takes 2-10 hours, preferably 3-6 hours.

[0054] In some specific implementations, the second-step hot-pressing sintering pressure is increased to 20-30 MPa within 10-20 minutes and maintained.

[0055] In some specific implementations, the depressurization is carried out when the temperature drops to 1000-1200°C.

[0056] In some specific implementations, the preparation method further includes heat treatment of the aluminum nitride ceramic obtained in step S3.

[0057] In some specific embodiments, the heat treatment is carried out under an inert atmosphere, preferably under a nitrogen or argon atmosphere.

[0058] In some specific implementations, the heat treatment is carried out at 1400-1700°C, preferably at 1450-1550°C.

[0059] In some specific implementations, the heat treatment duration is 1-48 hours, preferably 12-24 hours.

[0060] Another implementation of this application is as follows: An aluminum nitride ceramic, obtained by any of the aforementioned preparation methods.

[0061] In some specific implementations, the aluminum nitride ceramic contains 0.2-5 wt% hexagonal boron nitride.

[0062] In some specific implementations, the hexagonal boron nitride in the aluminum nitride ceramic has an onion-like structure.

[0063] In some specific implementations, the hexagonal boron nitride in the aluminum nitride ceramic is a combination of a lamellar structure and an onion-like structure.

[0064] In some specific embodiments, the aluminum nitride ceramic contains 3 wt% yttrium oxide.

[0065] In some specific implementations, the resistivity of the aluminum nitride ceramic at 500°C is not less than 1.0 × 10⁻⁶. 10 Ω·cm.

[0066] In some specific embodiments, the aluminum nitride ceramic has a thermal conductivity of not less than 145 W·m at room temperature. -1 ·K -1 .

[0067] Another implementation of this application is as follows: Application of any of the aforementioned aluminum nitride ceramics in semiconductor manufacturing.

[0068] In some specific implementations, the aluminum nitride ceramic is used in front-end process equipment for wafer manufacturing.

[0069] In some specific implementations, the wafer manufacturing front-end process equipment is selected from any one of etching equipment, thin film deposition equipment, ion implantation equipment, photolithography equipment, or thermal processing equipment.

[0070] In some specific embodiments, the aluminum nitride ceramic is used for at least one of the following: (i) The dielectric material or dielectric layer of the electrostatic chuck; (ii) As a wafer carrier device; (iii) As a heating plate or base; (iv) As a ceramic component in a cavity of an etching apparatus, thin film deposition apparatus, ion implantation apparatus, photolithography apparatus or heat treatment apparatus; (v) As a high-frequency transmission window; (vi) As an isolation component, support component, or seal within a plasma processing chamber; (vii) As a repair or recoating material for ceramic dielectric layers in semiconductor manufacturing equipment. Detailed Implementation The raw materials used in this application can be purchased or synthesized in-house. The following specific embodiments are used to further describe the implementation of the present invention and do not limit the scope of the invention.

[0071] Example 1 95 g of aluminum nitride powder, 2 g of cubic boron nitride powder, 3 g of yttrium oxide powder, 0.3 g of carbon black, and 150 g of anhydrous ethanol were mixed and ball-milled in a nylon ball mill jar for 5 hours. After ball milling, the mixture was transferred to a drying oven and dried at 80°C for 8 hours. After drying, the powder was passed through a 200-mesh sieve to obtain a uniform composite powder. The composite powder was then placed in a reduction furnace and reduced at 1350°C for 3 hours under a hydrogen atmosphere. After the reduction, the powder was cooled with the furnace to obtain a deoxidized composite powder. The deoxidized composite powder was loaded into a graphite mold and placed in a hot press furnace. Under a nitrogen atmosphere, the temperature was raised to 1650°C, and the pressure was increased to 2.5 MPa within 20 minutes, and the temperature was held for 3 hours. Subsequently, the temperature was raised to 1850°C, and the sintering pressure was increased to 30 MPa within 10 minutes, and the temperature was held for 3 hours. After the heat treatment is completed, the furnace is cooled to 1200℃ and the pressure is released to obtain aluminum nitride ceramic. The aluminum nitride ceramic is placed in a heat treatment furnace and held at 1500℃ for 18 hours under a nitrogen atmosphere, and then cooled with the furnace to obtain high-resistivity aluminum nitride ceramic.

[0072] SEM characterization results ( Figure 1 The data shows that onion-shaped hexagonal boron nitride is basically uniformly distributed around the aluminum nitride grain boundaries, with no obvious agglomeration. Meanwhile, the sintering aid (yttrium oxide) is distributed in the form of dots at the triangular grain boundaries.

[0073] The test methods for high-temperature resistivity and thermal conductivity are as follows: Resistivity: Prepare an aluminum nitride ceramic sheet with a diameter of 12 mm × 1 mm, coat its surface with silver paste and dry it. The test is carried out in air at room temperature to 500℃. A resistance test system (RMS-1650) is used to apply a voltage of 200 V / mm and the resistivity at each temperature is calculated according to formula (1).

[0074]

[0075] In the formula, ρ RR is the resistivity. V To measure the resistance, S is the sample area and d is the sample thickness.

[0076] Thermal conductivity: The room temperature thermal diffusivity of aluminum nitride ceramics was measured using a laser thermal conductivity meter (LFA 457, German), and the thermal conductivity λ was calculated using formula (2). Ten measurements were taken, and the average value was used.

[0077]

[0078] In the formula, α Thermal diffusivity; ρ The density of aluminum nitride ceramics was determined by the water displacement method. C p The specific heat capacity of aluminum nitride ceramics was determined by differential scanning calorimetry (DSC).

[0079] The aforementioned testing methods were also used in subsequent embodiments and comparative examples.

[0080] The high-resistivity aluminum nitride ceramic prepared in this embodiment has a high-temperature resistivity of 5.3 × 10⁻⁶ at 500°C, as tested. 10 Ω·cm, thermal conductivity at room temperature is 151 W·m -1 ·K -1 Its resistivity performance curve is as follows Figure 2 As shown.

[0081] Example 2 96 g of aluminum nitride powder, 1 g of cubic boron nitride powder, 3 g of yttrium oxide powder, 0.2 g of carbon black, and 150 g of anhydrous ethanol were mixed and ball-milled in a nylon ball mill jar for 5 hours. After ball milling, the mixture was transferred to a drying oven and dried at 80°C for 6 hours. After drying, the powder was passed through a 200-mesh sieve to obtain a uniform composite powder. The composite powder was then placed in a reduction furnace and reduced at 1300°C for 6 hours under a hydrogen atmosphere. After the reduction, the powder was cooled with the furnace to obtain a deoxidized composite powder. The deoxidized composite powder was loaded into a graphite mold and placed in a hot press furnace. Under a nitrogen atmosphere, the temperature was raised to 1700°C, and the pressure was increased to 2.5 MPa within 20 minutes, and the temperature was held for 2 hours. Subsequently, the temperature was raised to 1800°C, and the sintering pressure was increased to 30 MPa within 10 minutes, and the temperature was held for 4 hours. After the heat treatment is completed, the furnace is cooled to 1200℃ and the pressure is released to obtain aluminum nitride ceramic. The aluminum nitride ceramic is placed in a heat treatment furnace and held at 1550℃ for 12 hours under a nitrogen atmosphere, and then cooled with the furnace to obtain high-resistivity aluminum nitride ceramic.

[0082] The high-resistivity aluminum nitride ceramic prepared in this embodiment has a high-temperature resistivity of 4.1 × 10⁻⁶ at 500°C, as tested. 10 Ω·cm, thermal conductivity at room temperature is 155 W·m-1 ·K -1 .

[0083] Example 3 93 g of aluminum nitride powder, 4 g of cubic boron nitride powder, 3 g of yttrium oxide powder, 0.5 g of carbon black, and 150 g of anhydrous ethanol were mixed and ball-milled in a nylon ball mill jar for 6 hours. After ball milling, the mixture was transferred to a drying oven and dried at 80°C for 8 hours. After drying, the powder was passed through a 200-mesh sieve to obtain a uniform composite powder. The composite powder was then placed in a reduction furnace and reduced at 1400°C for 2 hours under a hydrogen atmosphere. After the reduction, the powder was cooled with the furnace to obtain a deoxidized composite powder. The deoxidized composite powder was loaded into a graphite mold and placed in a hot press furnace. Under a nitrogen atmosphere, the temperature was raised to 1650°C, and the pressure was increased to 2.5 MPa within 20 minutes, and the temperature was held for 3 hours. Subsequently, the temperature was raised to 1850°C, and the sintering pressure was increased to 30 MPa within 10 minutes, and the temperature was held for 5 hours. After the heat treatment is completed, the furnace is cooled to 1200℃ and the pressure is released to obtain aluminum nitride ceramic. The aluminum nitride ceramic is placed in a heat treatment furnace and held at 1450℃ for 24 hours under a nitrogen atmosphere to obtain high-resistivity aluminum nitride ceramic.

[0084] The high-resistivity aluminum nitride ceramic prepared in this embodiment has a high-temperature resistivity of 6.5 × 10⁻⁶ at 500°C, as tested. 10 Ω·cm, room temperature thermal conductivity is 145 W·m -1 ·K -1 .

[0085] Comparative Example 1 This comparative example uses a one-step hot pressing sintering method to prepare aluminum nitride ceramics.

[0086] 95 g of aluminum nitride powder, 2 g of cubic boron nitride powder, 3 g of yttrium oxide powder, 0.3 g of carbon black, and 150 g of anhydrous ethanol were mixed and ball-milled in a nylon ball mill jar for 5 hours. After ball milling, the mixture was transferred to a drying oven and dried at 80°C for 8 hours. After drying, the powder was passed through a 200-mesh sieve to obtain a uniform composite powder. The composite powder was then placed in a reduction furnace and reduced at 1350°C for 3 hours under a hydrogen atmosphere. After the reduction, the powder was cooled with the furnace to obtain a deoxidized composite powder. The deoxidized composite powder was placed in a graphite mold and placed in a hot press furnace. Under a nitrogen atmosphere, the temperature was raised to 1850°C, and the sintering pressure was increased to 30 MPa within 10 minutes, and the temperature was held for 3 hours. After the reduction, the temperature was lowered with the furnace to 1200°C and the pressure was released to obtain aluminum nitride ceramic. The aluminum nitride ceramic was placed in a heat treatment furnace and held at 1500℃ for 18 hours under a nitrogen atmosphere, and then cooled with the furnace.

[0087] The aluminum nitride ceramic prepared in this comparative example has a room temperature thermal conductivity of 149 W·m. -1 ·K -1 However, its high-temperature resistivity at 500℃ is only 4.1×10⁻⁶. 9 The result of Ω·cm indicates that the one-step hot-pressing sintering method failed to achieve a high high-temperature resistivity. The main reason is likely that most of the onion-shaped hexagonal boron nitride is still distributed inside the aluminum nitride matrix and has not migrated sufficiently to the grain boundaries, resulting in the incomplete utilization of its grain boundary barrier effect.

[0088] Comparative Example 2 This comparative example does not employ deoxygenation treatment.

[0089] 95 g of aluminum nitride powder, 2 g of cubic boron nitride powder, 3 g of yttrium oxide powder, 0.3 g of carbon black, and 150 g of anhydrous ethanol were mixed and ball-milled in a nylon ball mill jar for 5 hours. After ball milling, the mixture was transferred to a drying oven and dried at 80°C for 8 hours. After drying, the powder was passed through a 200-mesh sieve to obtain a uniform composite powder. The obtained powder was placed in a graphite mold and placed in a hot press furnace. Under a nitrogen atmosphere, the temperature was raised to 1650°C, and the pressure was increased to 2.5 MPa within 20 minutes, and held for 3 hours. Subsequently, the temperature was raised to 1850°C, and the sintering pressure was increased to 30 MPa within 10 minutes, and held for 3 hours. After holding, the furnace was cooled to 1200°C and the pressure was released to obtain aluminum nitride ceramic. The aluminum nitride ceramic was placed in a heat treatment furnace and held at 1500°C for 18 hours under a nitrogen atmosphere, and then cooled with the furnace.

[0090] The aluminum nitride ceramic prepared in this comparative example exhibits a high-temperature resistivity of 4.2 × 10⁻⁶ at 500℃. 10 Its thermal conductivity is Ω·cm, but its room temperature thermal conductivity is only 113 W·m. -1 ·K -1 This indicates that omitting the deoxidation process makes it difficult to achieve a significant improvement in the thermal conductivity of aluminum nitride ceramics. The main reason is likely that a large amount of boron oxide impurities on the surface of cubic boron nitride powder were not effectively removed. These impurities entered the aluminum nitride lattice during subsequent hot pressing and sintering, leading to increased phonon scattering and thus reducing thermal conductivity.

[0091] Comparative Example 3 This comparative example uses argon gas for deoxygenation treatment.

[0092] 95 g of aluminum nitride powder, 2 g of cubic boron nitride powder, 3 g of yttrium oxide powder, 0.3 g of carbon black, and 150 g of anhydrous ethanol were mixed and ball-milled in a nylon ball mill jar for 5 hours. After ball milling, the mixture was transferred to a drying oven and dried at 80°C for 8 hours. After drying, the powder was passed through a 200-mesh sieve to obtain a uniform composite powder. The composite powder was then placed in a reduction furnace and reduced at 1350°C for 3 hours under an argon atmosphere. After the reduction, the powder was cooled with the furnace to obtain the composite powder. The composite powder was placed in a graphite mold and placed in a hot press furnace. Under a nitrogen atmosphere, the temperature was raised to 1650°C, and the pressure was increased to 2.5 MPa within 20 minutes, and the temperature was held for 3 hours. Subsequently, the temperature was raised to 1850°C, and the sintering pressure was increased to 30 MPa within 10 minutes, and the temperature was held for 3 hours. After the reduction, the temperature was lowered with the furnace to 1200°C and the pressure was released to obtain aluminum nitride ceramic. Aluminum nitride ceramics were placed in a heat treatment furnace and held at 1500℃ for 18 hours under a nitrogen atmosphere, and then cooled with the furnace to obtain high-resistivity aluminum nitride ceramics.

[0093] The aluminum nitride ceramic prepared in this comparative example exhibits a high-temperature resistivity of 4.3 × 10⁻⁶ at 500℃. 10 Its thermal conductivity is Ω·cm, but its room temperature thermal conductivity is only 116 W·m. -1 ·K -1 The results show that using an argon atmosphere instead of a hydrogen atmosphere for deoxidation is insufficient to significantly improve the thermal conductivity of aluminum nitride ceramics. The main reason is that the deoxidation temperature is relatively low, and the driving force of the carbothermic reduction reaction involving only a carbon source is insufficient to effectively remove the large amount of impurities such as boron oxide and aluminum oxide present on the surface of the raw material powder. The residual oxygen elements enter the aluminum nitride lattice during subsequent hot-pressing sintering, exacerbating phonon scattering and thus leading to a decrease in thermal conductivity.

[0094] Any equivalent structural or procedural transformations made using the content of this application specification, whether directly or indirectly applied to the same or related technical fields as this application, are included within the scope of patent protection of this application.

[0095] For those skilled in the art, the present invention can be practiced in a wide range with equivalent parameters, formulations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments are given in this application, it should be understood that the conditions of the various embodiments can be combined in any suitable manner where technically feasible. To avoid unnecessary repetition, the various possible combinations are not described further in this application. In summary, any modifications, improvements, and other uses made using conventional techniques known in the art based on the principles of the present invention are considered to be disclosed in this application.

Claims

1. A method for preparing aluminum nitride ceramics, characterized in that, Includes the following steps: S1, a mixture of aluminum nitride, cubic boron nitride, yttrium oxide and carbon source is refined to obtain composite powder; S2, the composite powder is subjected to deoxidation treatment in a reducing atmosphere and at a temperature below 1550°C. S3, the composite powder that has undergone the deoxidation treatment is subjected to two-step hot pressing sintering; wherein, the first step of hot pressing sintering is carried out at 1550-1700℃, and the second step of hot pressing sintering is carried out at 1750-1900℃; after the hot pressing sintering is completed, the pressure is released to obtain the aluminum nitride ceramic.

2. The method for preparing aluminum nitride ceramic according to claim 1, characterized in that, The refining process includes mechanical grinding under wet conditions, and optionally also includes powder classification; The preferred liquid medium used in the wet process is anhydrous ethanol; The liquid medium is removed after grinding; The amount of the liquid medium is 100-200% of the total weight of aluminum nitride, cubic boron nitride and yttrium oxide, preferably 150%; The mechanical grinding is preferably any one of ball milling, roller milling, hammer milling, sand milling, vibratory milling, and combinations thereof; The preferred method for powder classification is sieving. The sieving process preferably uses a 100-400 mesh sieve, and more preferably a 200 mesh sieve.

3. The method for preparing aluminum nitride ceramics according to claim 1, characterized in that, The amounts of cubic boron nitride, yttrium oxide, and aluminum nitride, based on a total of 100 wt%, are as follows: Cubic boron nitride: 0.2-5 wt%, preferably 1-4 wt%; Yttrium oxide: 2-4 wt%, preferably 3 wt%; Aluminum nitride: Balance.

4. The method for preparing aluminum nitride ceramic according to claim 1, characterized in that, The aluminum nitride is a submicron or micron-sized powder, with an average particle size preferably of 0.5-2 μm, more preferably 0.8-1.2 μm; The cubic boron nitride is a nano or submicron-sized powder, with an average particle size preferably of 300-800 nm, more preferably of 400-600 nm. The yttrium oxide is a nano or submicron-sized powder, with an average particle size preferably of 200-600 nm, more preferably 300-500 nm.

5. The method for preparing aluminum nitride ceramic according to claim 1, characterized in that, The carbon source is selected from any one of carbon black, graphite, porous carbon materials, organic carbon precursors and their pyrolysis products, preferably carbon black; The amount of carbon source used is 10-20 wt% of cubic boron nitride.

6. The method for preparing aluminum nitride ceramic according to claim 1, characterized in that, The reducing atmosphere is a hydrogen atmosphere; The deoxygenation treatment is preferably carried out at 1100-1400℃, and more preferably at 1300-1400℃; The duration of the deoxygenation treatment is preferably 1-12 hours, more preferably 2-6 hours.

7. The method for preparing aluminum nitride ceramic according to claim 1, characterized in that, The first step of hot pressing sintering is carried out at 1650-1700℃, and the second step of hot pressing sintering is carried out at 1750-1850℃. Preferably, the hot pressing and sintering time of the first step is 1-5 hours, more preferably 2-3 hours; Preferably, the hot pressing sintering pressure in the first step is increased to 2-3 MPa within 10-20 minutes and maintained. Preferably, the second step of hot pressing and sintering takes 2-10 hours, more preferably 3-6 hours; Preferably, the second-step hot-pressing sintering pressure is increased to 20-30 MPa within 10-20 minutes and maintained; Preferably, the depressurization is performed when the temperature drops to 1000-1200°C.

8. The method for preparing aluminum nitride ceramic according to claim 1, characterized in that, It also includes heat treatment of the aluminum nitride ceramic obtained in step S3; The heat treatment is carried out under an inert atmosphere, preferably under a nitrogen or argon atmosphere; The heat treatment is carried out at 1400-1700℃, preferably at 1450-1550℃; The heat treatment duration is 1-48 hours, preferably 12-24 hours.

9. An aluminum nitride ceramic, characterized in that, Obtained by the preparation method described in claim 1; Preferably, the aluminum nitride ceramic contains 0.2-5 wt% hexagonal boron nitride; the hexagonal boron nitride has an onion-like structure, or a combination of a lamellar structure and an onion-like structure; Preferably, the aluminum nitride ceramic contains 3 wt% yttrium oxide; Preferably, the resistivity of the aluminum nitride ceramic at 500°C is not less than 1.0 × 10⁻⁶. 10 Ω·cm; Preferably, the aluminum nitride ceramic has a thermal conductivity of not less than 145 W·m at room temperature. -1 ·K -1 .

10. The application of the aluminum nitride ceramic of claim 9 in semiconductor manufacturing; Preferably, the aluminum nitride ceramic is used in front-end process equipment for wafer manufacturing; Preferably, the wafer manufacturing front-end process equipment is selected from any one of etching equipment, thin film deposition equipment, ion implantation equipment, photolithography equipment, or thermal processing equipment; More preferably, the aluminum nitride ceramic is used in at least one of the following: (i) The dielectric material or dielectric layer of the electrostatic chuck; (ii) As a wafer carrier device; (iii) As a heating plate or base; (iv) As a ceramic component in a cavity of an etching apparatus, thin film deposition apparatus, ion implantation apparatus, photolithography apparatus or heat treatment apparatus; (v) as a high-frequency transmission window; (vi) As an isolation component, support component, or seal within a plasma processing chamber; (vii) As a repair or recoating material for ceramic dielectric layers in semiconductor manufacturing equipment.

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