Aluminum nitride precision ceramic for semiconductor devices and method for manufacturing the same

Abstract

This invention discloses an aluminum nitride precision ceramic for semiconductor devices and its preparation method, relating to the field of ceramic materials technology for semiconductor devices. The invention utilizes a chemical vapor infiltration process to grow a thick hexagonal boron nitride thin film in situ on the geometrical outer surface and subsurface pore inner walls of a polycrystalline aluminum nitride ceramic substrate. This hexagonal boron nitride thin film alternates with aluminum nitride grains in the polycrystalline aluminum nitride ceramic substrate, forming a boron nitride / aluminum nitride superlattice protective layer on the surface. When high-energy arsenic or phosphorus ions bombard the surface, the hexagonal boron nitride thin film effectively absorbs and dissipates the ion bombardment kinetic energy through an interlayer slip mechanism. Furthermore, the low atomic numbers and light atomic weights of boron and nitrogen significantly reduce the physical sputtering yield of aluminum atoms, achieving comprehensive anti-sputtering protection while ensuring a high-strength bond between the protective layer and the substrate. It also maintains the intrinsic thermal conductivity and insulation properties of AlN ceramics, making it suitable for the operating conditions of high-energy ion implanters.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology for semiconductor devices, specifically to a precision aluminum nitride ceramic for semiconductor devices and its preparation method. Background Technology

[0002] Semiconductor ion implantation is a crucial step in integrated circuit manufacturing. Its working principle involves accelerating high-energy arsenic or phosphorus ions and bombarding the silicon wafer surface to achieve doping modification. The inner wall of the ion implanter chamber is typically made of high-purity aluminum nitride precision ceramic as a protective liner or chamber material. However, under long-term, continuous bombardment by high-energy ion beams, aluminum atoms on the aluminum nitride ceramic surface undergo severe physical sputtering, detaching from the substrate to form metallic particulate contaminants. These contaminants randomly fall onto the processed silicon wafer surface, leading to device short circuits, threshold voltage drift, and a significant decrease in chip yield.

[0003] To address the sputtering contamination problem on the inner wall of aluminum nitride ceramic cavities, existing technologies typically employ surface coating processes such as physical vapor deposition (PVD) or plasma-enhanced chemical vapor deposition (PECVD) to deposit a diamond-like carbon (DLC) or boron nitride (BN) coating as a protective barrier layer. However, the coatings prepared by PVD or PECVD only adhere to the geometrical outer surface of the aluminum nitride ceramic, creating a significant heterogeneous interface with the substrate. Due to the mismatch in thermal expansion coefficients between the coating material and the aluminum nitride ceramic substrate, the coating is highly susceptible to cracking or large-scale peeling under the frequent high and low temperature thermal cycling conditions of the ion implanter. These peeled-off, flaky coating particles become new sources of contamination, exacerbating the risk of silicon wafer particle contamination. Existing coating processes cannot penetrate into the subsurface micropores and grain boundary fissures remaining after aluminum nitride ceramic sintering for effective protection. These unprotected micro-regions will still release aluminum atom contaminants under high-energy ion bombardment.

[0004] Therefore, there is an urgent need to develop a new type of aluminum nitride precision ceramic and its preparation method that can form a dense protective barrier layer on the surface and subsurface of aluminum nitride ceramic to suppress the physical sputtering of aluminum atoms, while ensuring high bonding strength between the protective layer and the aluminum nitride ceramic substrate and eliminating the risk of coating peeling under thermal cycling conditions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an aluminum nitride precision ceramic for semiconductor devices and its preparation method. Through chemical vapor infiltration, a thick hexagonal boron nitride thin film is grown in situ on the geometrical outer surface and subsurface pore inner walls of a polycrystalline aluminum nitride ceramic substrate. This hexagonal boron nitride thin film and the aluminum nitride grains of the polycrystalline aluminum nitride ceramic substrate are arranged alternately, forming a boron nitride / aluminum nitride superlattice protective layer on the surface. When high-energy arsenic ions or high-energy phosphorus ions bombard the surface, the hexagonal boron nitride thin film effectively absorbs and dissipates the ion bombardment kinetic energy through an interlayer slip mechanism. Furthermore, the low atomic numbers and light atomic weights of boron and nitrogen significantly reduce the physical sputtering yield of aluminum atoms, achieving comprehensive anti-sputtering protection while ensuring a high-strength bond between the protective layer and the substrate. It also takes into account the intrinsic thermal conductivity and insulation properties of AlN ceramics, making it suitable for the operating conditions of high-energy ion implanters.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On the one hand, an aluminum nitride precision ceramic for semiconductor devices includes an aluminum nitride ceramic substrate, wherein a hexagonal boron nitride (h-BN) thin film is grown in situ on the surface and subsurface pore inner walls of the aluminum nitride ceramic substrate, and the aluminum nitride ceramic substrate and the in-situ grown hexagonal boron nitride (h-BN) thin film together constitute a BN / AlN superlattice protective layer; The thickness of the hexagonal boron nitride (h-BN) film is 5-20 nm, the porosity of the aluminum nitride ceramic substrate is 0.1-0.5%, and the pore size of the subsurface pores is 0.5-5 μm.

[0007] Furthermore, the raw material composition of the aluminum nitride ceramic matrix includes: 92-97 wt% aluminum nitride powder and 3-8 wt% rare earth sintering aids. The total content of heavy metal impurities Fe, Cr, Ni, and Cu in the powder is ≤5 ppm. The rare earth sintering aids are at least one of yttrium oxide, lanthanum oxide, and scandium oxide, and yttrium oxide accounts for ≥70% of the total mass of the sintering aids. The aluminum nitride ceramic matrix has a room temperature thermal conductivity ≥180 W / (m·K) and a volume resistivity ≥1×10⁻⁶. 14 Ω·cm, flexural strength ≥350MPa.

[0008] Furthermore, in the BN / AlN superlattice protective layer, the hexagonal boron nitride h-BN film and the aluminum nitride ceramic matrix are bonded at the interface through B-Al-N chemical bonds, and the interface bonding strength is ≥80MPa; The hexagonal boron nitride (h-BN) thin film is a continuous and dense single-crystal / polycrystalline thin film that completely covers the outer surface and the inner wall of the subsurface pores of the aluminum nitride ceramic substrate, without pinholes or detached areas.

[0009] On the other hand, a method for preparing aluminum nitride precision ceramics for semiconductor devices includes the following steps: S1. Preparation of aluminum nitride ceramic green body: Aluminum nitride powder, rare earth sintering aid, binder, dispersant and solvent are mixed, and then ball-milled, spray-granulated and dry-pressed to obtain aluminum nitride ceramic green body; S2. Sintering of aluminum nitride ceramic matrix: The aluminum nitride ceramic blank is placed in a graphite sintering furnace and sintered at high temperature under a high-purity nitrogen protective atmosphere to obtain an aluminum nitride ceramic matrix. After the high-temperature sintering is completed, the temperature inside the furnace is reduced to the chemical vapor infiltration reaction temperature and kept warm for later use. S3. In-situ chemical vapor infiltration growth of h-BN thin film: A mixed reaction gas of diborane (B2H6) and ammonia (NH3) is continuously introduced into the graphite sintering furnace. Using the micropores remaining in the aluminum nitride ceramic substrate as infiltration channels, a chemical vapor infiltration reaction is carried out on the surface and subsurface pore walls of the substrate to grow an h-BN thin film in situ, forming a BN / AlN superlattice protective layer. S4. Post-processing: After the reaction is completed, the flow of the mixed reaction gas is stopped, and the furnace is cooled to room temperature under the protection of high-purity nitrogen. The workpiece is then removed and subjected to precision machining and ultrasonic cleaning to obtain aluminum nitride precision ceramics for semiconductor equipment.

[0010] Furthermore, in S1, the average particle size of the aluminum nitride powder is 0.5-2μm, the purity is ≥99.99%, the amount of rare earth sintering aid added is 3-8wt% of the total mass of the aluminum nitride powder, the ball-to-material ratio of the ball milling mixture is 5:1-10:1, and the ball milling time is 12-24h.

[0011] Furthermore, in S2, the high-temperature sintering temperature is 1800-1900℃, the holding time is 4-8h, and the nitrogen pressure inside the furnace is 0.1-0.5MPa; After sintering, the furnace temperature is reduced to the chemical vapor infiltration reaction temperature of 1000-1200℃ at a cooling rate of 5-10℃ / min, and high-purity nitrogen is maintained throughout the process.

[0012] Furthermore, in S3, the molar ratio of diborane to ammonia in the mixed reaction gas is 1:3-1:10, the total flow rate of the mixed reaction gas is 50-200 sccm, the furnace pressure is controlled at 1-5 kPa during the reaction, the reaction holding time is 30-120 min, and high-purity nitrogen is used as the carrier gas throughout the process.

[0013] Furthermore, the specific steps for the S3 in-situ chemical vapor infiltration growth of h-BN thin films are as follows: Pretreatment: Maintain the furnace temperature at 1000-1200℃ and the pressure at 1-5kPa. Purge the furnace with high-purity nitrogen for 8-15 minutes to completely remove residual air, water vapor and trace impurities generated during sintering, ensuring that the reaction atmosphere is free of oxidation and impurities. Carrier gas pre-circulation: After purging, keep high-purity nitrogen carrier gas flowing in, with the flow rate controlled at 30-50 sccm, to maintain stable pressure inside the furnace and provide a stable airflow environment for the introduction of mixed reaction gases, avoiding uneven film growth caused by local airflow turbulence. Mixed gas introduction and pre-reaction: Diborane (B2H6) and ammonia (NH3) are mixed evenly at a molar ratio of 1:3-1:10 and slowly introduced into the furnace at 1 / 3 of the total flow rate. The pre-reaction is maintained for 5-8 minutes to allow the mixed gas to diffuse evenly to all areas of the furnace and to initially contact the surface of the aluminum nitride ceramic substrate, activating the active sites on the substrate surface. In-situ infiltration and thin film growth: The flow rate of the mixed reaction gas is increased to 50-200 sccm, and the temperature and pressure inside the furnace are kept stable. The reaction is continued for 30-120 min. The mixed gas permeates into the subsurface pores through the micropores remaining in the aluminum nitride ceramic substrate. Diborane and ammonia undergo decomposition reactions on the substrate surface and the inner wall of the pores. The generated B atoms and N atoms nucleate and grow in-situ at the active sites, forming a hexagonal phase h-BN thin film. At the interface between the substrate and the h-BN thin film, B atoms and N atoms react with Al atoms in the AlN substrate to generate a B-Al-N ternary transition layer, realizing in-situ chemical bonding between the h-BN thin film and the AlN substrate. Reaction termination: After the reaction time is reached, stop the introduction of diborane and ammonia, and continue to purge with high-purity nitrogen for 5-10 minutes to remove any unreacted gases and reaction byproducts remaining in the furnace, and to prevent residual gases from contaminating the grown h-BN film.

[0014] Furthermore, during ultrasonic cleaning in step S4, the workpiece is placed in anhydrous ethanol and ultrasonically cleaned at a frequency of 40-60 kHz for 15-25 minutes to remove residual organic impurities on the surface. Then, it is transferred to ultrapure water and ultrasonically cleaned at a frequency of 40-60 kHz for 15-20 minutes to remove residual ethanol and trace inorganic impurities. After cleaning, the workpiece is placed in a vacuum oven and dried for 1.5-3 hours under conditions of vacuum degree > 0.09 MPa and temperature of 80-120℃ to ensure that the workpiece surface is free of moisture and residual impurities.

[0015] Compared with existing technologies, the aluminum nitride precision ceramic for semiconductor devices and its preparation method have the following advantages: This invention utilizes the micropores remaining after the sintering of AlN ceramic matrix as permeation channels. Through chemical vapor infiltration, an h-BN thin film is grown in situ not only on the outer surface of the ceramic but also on the inner wall of the subsurface pores, achieving full coverage protection of the outer surface and internal pores. This solves the problems of collapse and sputtering contamination caused by high-energy ion bombardment of subsurface pores. The formed BN / AlN superlattice protective layer slows down and blocks high-energy ions. Combined with the low sputtering characteristics of h-BN itself, the physical sputtering yield of the ceramic is reduced.

[0016] This invention allows for the in-situ growth of h-BN thin films within the same furnace after AlN ceramic sintering. Both h-BN and AlN are hexagonal crystal systems with low lattice mismatch. During growth, B-Al-N chemical bonds are formed at the interface, achieving metallurgical-grade bonding with an interfacial bonding strength ≥80MPa. Under conditions of repeated bombardment by high-energy ions and temperature cycling, the protective layer exhibits no cracking, peeling, or detachment, significantly extending the service life of the components.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 A flowchart illustrating the steps of a method for preparing aluminum nitride precision ceramics for semiconductor devices; Figure 2 This is a flowchart illustrating the in-situ chemical vapor infiltration growth of h-BN thin films in this invention. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0021] To overcome the limitations of existing aluminum nitride ceramics for semiconductor devices, such as easy surface sputtering, easy coating peeling, lack of protection against subsurface porosity, poor thermal cycling stability, and high risk of chip contamination, this invention proposes a precision aluminum nitride ceramic for semiconductor devices and its preparation method, such as... Figure 1As shown, the steps of this preparation method are as follows: S1. Preparation of aluminum nitride ceramic green body: Aluminum nitride powder, rare earth sintering aid, binder, dispersant and solvent are mixed, and then ball-milled, spray-granulated and dry-pressed to obtain aluminum nitride ceramic green body; S2. Sintering of aluminum nitride ceramic matrix: The green blank is placed in a graphite sintering furnace and sintered at high temperature under the protection of high-purity nitrogen. After sintering, the temperature is lowered to the chemical vapor infiltration reaction temperature and kept warm for later use. S3. In-situ chemical vapor infiltration growth of h-BN thin film: A mixture of diborane and ammonia reaction gas is introduced into the furnace. Using the residual micropores of the substrate as infiltration channels, h-BN thin film is grown in-situ on the surface and the inner wall of the subsurface pores to form a BN / AlN superlattice protective layer. S4. Post-processing: Stop the flow of reaction gas, cool the furnace under the protection of high-purity nitrogen, and obtain aluminum nitride precision ceramics for semiconductor equipment through precision machining and ultrasonic cleaning.

[0022] This invention achieves a high-strength interfacial bond by in-situ growing a 5-20 nm continuous dense h-BN thin film on the surface and subsurface pore walls of an aluminum nitride ceramic substrate, forming a BN / AlN superlattice protective layer. High-strength interfacial bonding (≥80 MPa) is achieved through B-Al-N chemical bonds. While retaining the intrinsic properties of AlN ceramics—high thermal conductivity, high insulation, and high strength—this invention significantly reduces the aluminum atom sputtering yield under ion bombardment, solving the problems of coating thermal mismatch peeling and subsurface contamination. This results in an aluminum nitride precision ceramic solution that combines all-around sputtering resistance, high interfacial bonding, thermal cycling stability, and compatibility with high-energy ion implantation conditions in semiconductors.

[0023] This invention is primarily applied in the semiconductor equipment field, addressing the sputtering contamination and coating failure issues of ion implanter cavity liners and protective components under high-energy ion bombardment and frequent thermal cycling conditions. Traditional surface coatings only cover the outer surface, resulting in weak interfacial bonding, easy cracking and peeling, and unprotected subsurface pores that still release metallic contaminants, affecting chip yield and device reliability. This invention achieves full-scale protection of both the outer and subsurface pores through in-situ chemical vapor infiltration, superlattice structure design, and interfacial chemical bonding, improving component lifespan and process stability, and meeting the requirements of advanced integrated circuit manufacturing for high-purity, low-contamination, and long-life ceramic components.

[0024] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. In all embodiments and comparative examples, the raw materials used are commercially available qualified products, wherein the aluminum nitride powder has a purity ≥99.99%, the yttrium oxide content in the rare earth sintering aid is ≥70%, and the diborane and ammonia are of electronic grade purity, and the high-purity nitrogen has a purity ≥99.999%. Example 1

[0025] This embodiment prepares an aluminum nitride precision ceramic for semiconductor equipment. The target h-BN film thickness is 5 nm. Yttrium oxide is selected as a rare earth sintering aid (accounting for 100% of the total mass of sintering aid). The thickness of its h-BN film, the porosity of the substrate, and its mechanical and physicochemical properties all meet the requirements for use in semiconductor high-energy ion implanters. It can effectively reduce the high-energy ion sputtering yield and avoid silicon wafer contamination.

[0026] The specific preparation method of the aluminum nitride precision ceramic for semiconductor devices prepared in this embodiment is as follows: S1. Preparation of Aluminum Nitride Ceramic Green Body: Aluminum nitride powder with an average particle size of 0.5 μm and a purity of 99.99% (total content of heavy metal impurities of Fe, Cr, Ni, and Cu ≤ 3 ppm) was selected. According to the raw material composition ratio (97 wt% aluminum nitride powder, 3 wt% rare earth sintering aid), 3 wt% yttrium oxide (rare earth sintering aid, yttrium oxide percentage 100%) was added as a sintering aid. Anhydrous ethanol was added as a solvent, polyvinyl alcohol as a binder, and ammonium polyacrylate as a dispersant. The binder was added at 2 wt% of the total mass of the aluminum nitride powder, and the dispersant was added at 2 wt% of the total mass of the aluminum nitride powder. The amount was 0.5 wt%; using silicon nitride balls as the grinding medium, the mixture was ball-milled at a ball-to-material ratio of 5:1 for 12 hours. The rotation speed was controlled at 300 r / min during the ball milling process to ensure uniform mixing and no agglomeration of the materials. The slurry after ball milling was spray-granulated (inlet air temperature 180℃, outlet air temperature 80℃) to obtain granulated powder with excellent flowability and a particle size distribution of 100-200 μm. The granulated powder was dry-pressed at 100 MPa with uniform pressing pressure and a holding time of 5 min to obtain aluminum nitride ceramic green bodies with dimensions of 100 mm × 100 mm × 10 mm. The green body surface was free of cracks and missing corners and had uniform density.

[0027] S2. Sintering of aluminum nitride ceramic matrix: The above-mentioned aluminum nitride ceramic blank is placed in a graphite sintering furnace. After closing the furnace door, high-purity nitrogen is first introduced into the furnace to purge the air for 5 minutes to remove the air inside the furnace. Then, a high-purity nitrogen protective atmosphere is maintained, and the nitrogen pressure inside the furnace is controlled at 0.1 MPa. The temperature is raised to 1800℃ at a heating rate of 10℃ / min. After reaching the set temperature, it is held at the temperature for sintering for 8 hours. During this period, high-purity nitrogen is continuously introduced to ensure that there is no oxidation or impurity contamination during the sintering process. After the high-temperature sintering is completed, the temperature inside the furnace is lowered to 1000℃ at a cooling rate of 5℃ / min and held at the temperature for later use. High-purity nitrogen protection is maintained throughout the process to avoid oxidation of the matrix or introduction of impurities.

[0028] S3. In-situ chemical vapor infiltration growth of h-BN thin films: Completed within the same graphite sintering furnace, eliminating the need to transfer the workpiece, such as... Figure 2 As shown, the specific steps are as follows: Pretreatment: Maintain the furnace temperature at 1000℃ and the pressure at 1kPa. Purge the furnace with high-purity nitrogen for 8 minutes to completely remove residual air, water vapor and trace impurity gases generated during sintering, ensuring that the reaction atmosphere is free of oxidation and impurities. Carrier gas pre-flow: After purging, keep high-purity nitrogen carrier gas continuously flowing in at a flow rate of 30 sccm and maintain the furnace pressure at 1 kPa to provide a stable gas flow environment for the mixed reaction gas and avoid uneven film growth caused by local gas flow disturbance. Mixed gas introduction and pre-reaction: Electronic grade diborane (B2H6) and electronic grade ammonia (NH3) are mixed evenly at a molar ratio of 1:3. The mixture is then slowly introduced into the furnace at 17 sccm and maintained for 5 min for pre-reaction. This allows the mixed gas to diffuse evenly into all areas of the furnace and initially contact the surface of the aluminum nitride ceramic substrate, activating the active sites on the substrate surface and laying the foundation for subsequent in-situ film growth. In-situ infiltration and thin film growth: The flow rate of the mixed reaction gas was increased to 50 sccm, and the furnace temperature was kept stable at 1000℃ and the pressure at 1 kPa for 30 min. During this period, the mixed gas gradually infiltrated into the subsurface pores through the micropores remaining in the aluminum nitride ceramic substrate. Diborane and ammonia decomposed on the substrate surface and the inner wall of the pores, and the generated B and N atoms nucleated and grew in situ at the active sites to form a hexagonal h-BN thin film. At the same time, at the interface between the substrate and the h-BN thin film, B and N atoms reacted with Al atoms in the AlN substrate to generate a B-Al-N ternary transition layer, realizing in-situ chemical bonding between the h-BN thin film and the AlN substrate. Reaction termination: After a reaction time of 30 min, stop the introduction of diborane and ammonia, and continue to purge with high-purity nitrogen for 5 min to remove any unreacted gases and reaction byproducts remaining in the furnace, thus preventing residual gases from contaminating the grown h-BN film.

[0029] S4. Post-processing: After the reaction is terminated, maintain high-purity nitrogen protection and cool the furnace to room temperature at a cooling rate of 3℃ / min. After cooling to below 200℃, open the furnace door, remove the workpiece, and perform precision machining on the workpiece, controlling the dimensional tolerance ≤ ±0.005mm and the surface roughness Ra ≤ 0.2μm. Then, perform ultrasonic cleaning by placing the workpiece in electronic-grade anhydrous ethanol and ultrasonically cleaning it at a frequency of 40kHz for 15min to remove residual organic impurities on the surface. Subsequently, transfer it to ultrapure water and ultrasonically clean it at a frequency of 40kHz for 15min to remove residual ethanol and inorganic trace impurities. After cleaning, place the workpiece in a vacuum oven and dry it for 1.5h under a vacuum of 0.1MPa and a temperature of 80℃ to ensure that the workpiece surface is free of moisture and residual impurities. After drying, remove the workpiece to obtain the aluminum nitride precision ceramic for semiconductor equipment in this embodiment.

[0030] The aluminum nitride ceramic matrix prepared in this embodiment has a porosity of 0.1%, a subsurface pore size of 0.5-2 μm, an h-BN film thickness of 5.1 nm, an interfacial bonding strength of 82 MPa, a room temperature thermal conductivity of 195 W / (m·K), and a volume resistivity of 2.5 × 10⁻⁶. 14 Ω·cm, flexural strength of 380MPa, total heavy metal impurity content ≤3ppm, yttrium oxide content in rare earth sintering aid is 100%, targeting 80-200keVAs + The sputtering yield of ions is 0.11 atoms / ion, and the sputtering yield reduction rate is 85.5%. The h-BN film of this product is continuous and dense, without pinholes or shedding, and completely covers the surface of the substrate and the inner wall of the subsurface pores. It meets the high cleanliness and usage requirements of semiconductor ion implanters. The preparation process is stable, repeatable, and free from secondary pollution. Example 2

[0031] This embodiment prepares an aluminum nitride precision ceramic for semiconductor devices, with a target h-BN film thickness of 12 nm. A yttrium oxide and lanthanum oxide composite rare earth sintering aid (yttrium oxide accounts for 70%) is selected. The relevant parameters of sintering and CVI reaction are adjusted to take into account excellent anti-sputtering performance, thermal conductivity and insulation performance and interfacial bonding strength, and to adapt to the working conditions of semiconductor high-energy ion implanters.

[0032] S1. Preparation of aluminum nitride ceramic green body: Aluminum nitride powder with an average particle size of 1.2μm and a purity of 99.99% was selected. The total content of heavy metal impurities Fe, Cr, Ni, and Cu was ≤4ppm. The raw material composition ratio was 95wt% aluminum nitride powder and 5wt% rare earth sintering aid. Rare earth sintering aids of 5wt% of the total mass of aluminum nitride powder were added: 70% yttrium oxide and 30% lanthanum oxide. Anhydrous ethanol solvent, 3wt% polyvinyl alcohol binder, and 0.8wt% ammonium polyacrylate dispersant were added. The mixture was ball-milled with silicon nitride balls as the grinding medium at a ball-to-material ratio of 8:1 for 18 hours at a speed of 350 r / min. The slurry was spray-granulated at an inlet air temperature of 190℃ and an outlet air temperature of 85℃ to obtain granulated powder. The granulated powder was dry-pressed at 120MPa for 6 minutes to obtain aluminum nitride ceramic green body with dimensions of 100mm×100mm×10mm.

[0033] S2. Sintering of aluminum nitride ceramic matrix: The green blank is placed in a graphite sintering furnace, purged with high-purity nitrogen for 8 minutes, and the nitrogen pressure in the furnace is maintained at 0.3 MPa. The temperature is increased to 1850℃ at 10℃ / min and held for sintering for 6 hours. After sintering, the temperature is decreased to 1100℃ at 8℃ / min and held for use. High-purity nitrogen protection is used throughout the process.

[0034] S3, In-situ chemical vapor infiltration growth of h-BN thin films: Pretreatment: Furnace temperature 1100℃, pressure 3kPa, purged with high-purity nitrogen for 12min; Carrier gas pre-flow: High-purity nitrogen flow rate 40 sccm, maintaining stable pressure; Pre-reaction of mixed gas: The molar ratio of diborane to ammonia is 1:6. First, it is introduced at 40 sccm and maintained for 7 min. In-situ permeation growth: The mixed gas flow rate was increased to 120 sccm, the temperature was 1100℃, the pressure was 3 kPa, and the reaction was continued for 75 min to generate h-BN film and B-Al-N transition layer. Reaction termination: Stop the flow of reaction gas and purge with high-purity nitrogen for 8 minutes.

[0035] S4. Post-processing: Under high-purity nitrogen protection, the furnace is cooled to room temperature at 4℃ / min; precision machining is performed to a dimensional tolerance of ±0.005mm and Ra≤0.2μm; ultrasonic cleaning is performed using anhydrous ethanol at 50kHz for 20min, followed by ultrapure water at 50kHz for 18min; and vacuum drying is performed at 0.1MPa, 100℃, and 2h to obtain the final product.

[0036] The aluminum nitride precision ceramic prepared in this embodiment has a matrix porosity of 0.25%, subsurface pore size of 1-3 μm, h-BN film thickness of 11.7 nm, interfacial bonding strength of 90 MPa, matrix room temperature thermal conductivity of 188 W / (m·K), and volume resistivity of 3.2 × 10⁻⁶. 14 Ω·cm, flexural strength 365MPa, total heavy metal impurity content ≤4ppm, yttrium oxide content in rare earth sintering aids 70%, targeting 80-200keVAs + The sputtering yield of ions is 0.08 atoms / ion, and the sputtering yield reduction rate is 89.5%. During the preparation process, the product h-BN film is continuous and dense, with a conformal coverage of ≥99%, no pinholes or shedding, and excellent resistance to high-energy ion sputtering, which can meet the long-term service requirements of semiconductor ion implanters. Example 3

[0037] This embodiment prepares an aluminum nitride precision ceramic for semiconductor devices. The target h-BN film thickness is 20 nm. A yttrium oxide and scandium oxide composite rare earth sintering aid is selected, with yttrium oxide accounting for 80%. The ball milling time, sintering temperature, and CVI reaction time parameters are adjusted.

[0038] S1. Preparation of aluminum nitride ceramic green body: Aluminum nitride powder with an average particle size of 2μm and a purity of 99.99% was selected. The total content of heavy metal impurities Fe, Cr, Ni, and Cu was ≤5ppm. 92wt% aluminum nitride powder and 8wt% rare earth sintering aid were added. 8wt% of the total mass of aluminum nitride powder was added as rare earth sintering aid. Yttrium oxide accounted for 80% and scandium oxide accounted for 20%. Anhydrous ethanol solvent, polyvinyl alcohol binder 4wt%, and ammonium polyacrylate dispersant 1wt% were added. Silicon nitride balls were used as the grinding medium and ball milling was carried out at a ball-to-powder ratio of 10:1 for 24 hours at a speed of 400r / min. The slurry was spray-granulated at an inlet air temperature of 200℃ and an outlet air temperature of 90℃ to obtain granulated powder. The granulated powder was dry-pressed at 150MPa and held for 8 minutes to obtain an aluminum nitride ceramic green body with dimensions of 100mm×100mm×10mm.

[0039] S2. Sintering of aluminum nitride ceramic matrix: The green blank is placed in a graphite sintering furnace, purged with high-purity nitrogen for 10 minutes, and the nitrogen pressure in the furnace is maintained at 0.5 MPa. The temperature is increased to 1900℃ at 10℃ / min and held for sintering for 4 hours. After sintering, the temperature is decreased to 1200℃ at 10℃ / min and held for use. High-purity nitrogen protection is used throughout the process.

[0040] S3, In-situ chemical vapor infiltration growth of h-BN thin films: Pretreatment: Furnace temperature 1200℃, pressure 5kPa, purged with high-purity nitrogen for 15min; Carrier gas pre-flow: High-purity nitrogen flow rate 50 sccm, maintaining stable pressure; Pre-reaction of mixed gas: Diborane and ammonia in a molar ratio of 1:10 were first introduced at 67 sccm and maintained for 8 min; In-situ permeation growth: The mixed gas flow rate was increased to 200 sccm, the temperature was 1200℃, the pressure was 5 kPa, and the reaction was continued for 120 min to generate h-BN film and B-Al-N transition layer. Reaction termination: Stop the flow of reaction gas and purge with high-purity nitrogen for 10 minutes.

[0041] S4. Post-processing: Under high-purity nitrogen protection, cool to room temperature in the furnace at 5℃ / min; precision machine to dimensional tolerance ±0.005mm, Ra≤0.2μm; ultrasonic cleaning: anhydrous ethanol (60kHz, 25min), ultrapure water (60kHz, 20min); vacuum oven drying (vacuum degree 0.12MPa, 120℃, 3h) to obtain the final product.

[0042] The aluminum nitride precision ceramic prepared in this embodiment has a matrix porosity of 0.5%, subsurface pore size of 3-5 μm, h-BN film thickness of 19.5 nm, interfacial bonding strength of 86 MPa, matrix room temperature thermal conductivity of 182 W / (m·K), and volume resistivity of 2.7 × 10⁻⁶. 14 Ω·cm, flexural strength 355MPa, total heavy metal impurity content ≤5ppm, yttrium oxide content in rare earth sintering aids 80%, targeting 80-200keVAs + The sputtering yield is 0.09 atoms / ion, with a sputtering yield reduction rate of 88.2%. The product h-BN film is continuous, dense, pinhole-free, and does not detach, completely covering the substrate surface and the inner wall of subsurface pores. It has excellent long-term resistance to high-energy ion bombardment, with no detachment or crystal form degradation, making it suitable for use in semiconductor ion implanters. Comparative Example 1

[0043] This comparative example uses pure aluminum nitride ceramic without in-situ growth of h-BN thin film. The raw material composition and preparation process are the same as in Example 1. It is used to compare the performance with the product of the present invention to verify the sputtering resistance advantage and various performance improvement effects of the BN / AlN superlattice protective layer of the present invention.

[0044] S1. Preparation of aluminum nitride ceramic green body: The preparation method is completely consistent with Example 1. The same aluminum nitride powder and yttrium oxide sintering aid are used, and the same ball milling, spray granulation and dry pressing parameters are used to obtain aluminum nitride ceramic green bodies of the same size.

[0045] S2. Sintering of aluminum nitride ceramic matrix: Completely consistent with Example 1, with the same sintering temperature, holding time, nitrogen pressure and cooling rate, to obtain aluminum nitride ceramic matrix without h-BN film.

[0046] S3. Omit the in-situ chemical vapor infiltration growth of h-BN thin film: After sintering, the film is directly cooled to room temperature in the furnace at 3℃ / min under the protection of high-purity nitrogen, without the need for CVI reaction and related purging steps.

[0047] S4. Post-processing: The same precision machining, ultrasonic cleaning and drying parameters as in Example 1 were used to obtain a pure aluminum nitride ceramic control sample.

[0048] The pure aluminum nitride ceramic prepared in this comparative example has a matrix porosity of 0.12% and subsurface pore sizes of 0.6-2.2 μm. However, no h-BN film was grown, and the h-BN film thickness was 0. The BN / AlN superlattice protective layer of this invention was not formed, therefore no interfacial bonding strength data are available. Its room temperature thermal conductivity is 193 W / (m·K), and its volume resistivity is 1.7 × 10⁻⁶. 14Ω·cm, flexural strength 370MPa, total heavy metal impurity content ≤3ppm, for 80-200keVAs + The sputtering yield of ions was 0.76 atoms / ion, with no sputtering yield reduction rate due to the absence of h-BN films.

[0049] Performance tests were conducted on the samples from Examples 1 to 3 and Comparative Example 1. The test results are shown in the table below (all test data are the average values ​​of 3 parallel samples):

[0050] Based on the performance test results of Examples 1 to 3 and Comparative Example 1, the aluminum nitride ceramic substrates of Examples 1 to 3 have a porosity of 0.1-0.5%, a subsurface pore size of 0.5-5 μm, an h-BN film thickness of 5.1-19.5 nm, an interfacial bonding strength of 82-90 MPa, and the h-BN film is continuous, dense, and free of pinholes, achieving complete coverage of the substrate surface and pore walls. The substrate has a room temperature thermal conductivity of 182-195 W / (m·K) and a volume resistivity of 2.5 × 10⁻⁶. 14 -3.2×10 14 Ω·cm, flexural strength 355-380MPa, total heavy metal impurity content ≤3-5ppm, and sputtering resistance, As in Examples 1 to 3 + Ion sputtering yield is only 0.08-0.11 atoms / ion, with a sputtering yield reduction rate of 85.5-89.5%, while Comparative Example 1, which does not have an h-BN film, has a sputtering yield as high as 0.76 atoms / ion, and has no sputtering resistance advantage.

[0051] In summary, this invention forms a boron nitride / aluminum nitride superlattice protective layer on the surface by alternating hexagonal boron nitride thin films and aluminum nitride grains in a polycrystalline aluminum nitride ceramic substrate. When high-energy arsenic or phosphorus ions bombard the surface, the hexagonal boron nitride thin film effectively absorbs and dissipates the kinetic energy of the ion bombardment through an interlayer slip mechanism, achieving all-round anti-sputtering protection while ensuring a high-strength bond between the protective layer and the substrate. It also takes into account the intrinsic thermal conductivity and insulation properties of AlN ceramics, making it suitable for the operating conditions of high-energy ion implanters.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A precision aluminum nitride ceramic for semiconductor devices, characterized in that, The material includes an aluminum nitride ceramic substrate, on which a hexagonal boron nitride (h-BN) thin film is grown in situ on the surface and the inner wall of the subsurface pores of the aluminum nitride ceramic substrate. The aluminum nitride ceramic substrate and the in-situ grown hexagonal boron nitride (h-BN) thin film together constitute a BN / AlN superlattice protective layer. The thickness of the hexagonal boron nitride (h-BN) thin film is 5-20 nm, the porosity of the aluminum nitride ceramic substrate is 0.1-0.5%, and the pore size of the subsurface pores is 0.5-5 μm. In the BN / AlN superlattice protective layer, the hexagonal boron nitride h-BN film and the aluminum nitride ceramic matrix are bonded at the interface through B-Al-N chemical bonds, and the interface bonding strength is ≥80MPa.

2. The aluminum nitride precision ceramic for semiconductor devices according to claim 1, characterized in that, The raw material composition of the aluminum nitride ceramic matrix includes: 92-97 wt% aluminum nitride powder and 3-8 wt% rare earth sintering aids. The total content of heavy metal impurities Fe, Cr, Ni, and Cu in the powder is ≤5 ppm. The rare earth sintering aids are at least one of yttrium oxide, lanthanum oxide, and scandium oxide, and yttrium oxide accounts for ≥70% of the total mass of the sintering aids. The aluminum nitride ceramic matrix has a room temperature thermal conductivity ≥180 W / (m·K) and a volume resistivity ≥1×10⁻⁶. 14 Ω·cm, flexural strength ≥350MPa.

3. A method for preparing aluminum nitride precision ceramic for semiconductor devices, applicable to the aluminum nitride precision ceramic for semiconductor devices as described in any one of claims 1-2, characterized in that, The preparation method involves the following steps: S1. Preparation of aluminum nitride ceramic green body: Aluminum nitride powder, rare earth sintering aid, binder, dispersant and solvent are mixed, and then ball-milled, spray-granulated and dry-pressed to obtain aluminum nitride ceramic green body; S2. Sintering of aluminum nitride ceramic matrix: The aluminum nitride ceramic blank is placed in a graphite sintering furnace and sintered at high temperature under a high-purity nitrogen protective atmosphere to obtain an aluminum nitride ceramic matrix. After the high-temperature sintering is completed, the temperature inside the furnace is reduced to the chemical vapor infiltration reaction temperature and kept warm for later use. S3. In-situ chemical vapor infiltration growth of h-BN thin film: A mixed reaction gas of diborane (B2H6) and ammonia (NH3) is continuously introduced into the graphite sintering furnace. Using the micropores remaining in the aluminum nitride ceramic substrate as infiltration channels, a chemical vapor infiltration reaction is carried out on the surface and subsurface pore walls of the substrate to grow an h-BN thin film in situ, forming a BN / AlN superlattice protective layer. S4. Post-processing: After the reaction is completed, the flow of the mixed reaction gas is stopped, and the furnace is cooled to room temperature under the protection of high-purity nitrogen. The workpiece is then removed and subjected to precision machining and ultrasonic cleaning to obtain aluminum nitride precision ceramics for semiconductor equipment.

4. The method for preparing aluminum nitride precision ceramics for semiconductor devices according to claim 3, characterized in that, In S1, the aluminum nitride powder has an average particle size of 0.5-2μm and a purity of ≥99.99%. The amount of rare earth sintering aid added is 3-8wt% of the total mass of the aluminum nitride powder. The ball-to-material ratio of the ball milling mixture is 5:1-10:1, and the ball milling time is 12-24h.

5. The method for preparing aluminum nitride precision ceramic for semiconductor devices according to claim 3, characterized in that, In S2, the high-temperature sintering temperature is 1800-1900℃, the holding time is 4-8h, and the nitrogen pressure inside the furnace is 0.1-0.5MPa; After sintering, the furnace temperature is reduced to the chemical vapor infiltration reaction temperature of 1000-1200℃ at a cooling rate of 5-10℃ / min, and high-purity nitrogen is maintained throughout the process.

6. The method for preparing aluminum nitride precision ceramic for semiconductor devices according to claim 3, characterized in that, In step S3, the molar ratio of diborane to ammonia in the mixed reaction gas is 1:3-1:10, the total flow rate of the mixed reaction gas is 50-200 sccm, the furnace pressure is controlled at 1-5 kPa during the reaction, the reaction holding time is 30-120 min, and high-purity nitrogen is used as the carrier gas throughout the process.

7. The method for preparing aluminum nitride precision ceramic for semiconductor devices according to claim 3, characterized in that, The specific steps for the in-situ chemical vapor infiltration growth of h-BN thin films using S3 are as follows: Pretreatment: Maintain the furnace temperature at 1000–1200℃ and the pressure at 1–5 kPa, and purge the furnace with high-purity nitrogen for 8–15 minutes; Carrier gas pre-circulation: After purging, maintain the flow of high-purity nitrogen carrier gas, with the flow rate controlled at 30-50 sccm; Mixed gas introduction and pre-reaction: Diborane (B2H6) and ammonia (NH3) are mixed evenly at a molar ratio of 1:3-1:10 and introduced into the furnace at 1 / 3 of the total flow rate. The pre-reaction is maintained for 5-8 minutes to allow the mixed gas to diffuse evenly to all areas of the furnace and to initially contact the surface of the aluminum nitride ceramic substrate, thereby activating the active sites on the substrate surface. In-situ infiltration and thin film growth: The flow rate of the mixed reaction gas is increased to 50-200 sccm and the reaction is continued for 30-120 min. The mixed gas permeates into the subsurface pores through the micropores remaining in the aluminum nitride ceramic substrate. Diborane and ammonia undergo decomposition reactions on the substrate surface and pore walls. The generated B and N atoms nucleate and grow in-situ at active sites, forming a hexagonal h-BN thin film. At the interface between the substrate and the h-BN thin film, B and N atoms react with Al atoms in the AlN substrate to generate a B-Al-N ternary transition layer, realizing in-situ chemical bonding between the h-BN thin film and the AlN substrate. Reaction termination: After the reaction time is reached, stop the flow of diborane and ammonia, and continue to purge with high-purity nitrogen for 5–10 minutes to remove any remaining unreacted gases and reaction byproducts in the furnace.

8. The method for preparing aluminum nitride precision ceramic for semiconductor devices according to claim 3, characterized in that, In step S4, during ultrasonic cleaning, the workpiece is placed in anhydrous ethanol and ultrasonically cleaned at a frequency of 40-60 kHz for 15-25 minutes to remove residual organic impurities on the surface. Then, it is transferred to ultrapure water and ultrasonically cleaned at a frequency of 40-60 kHz for 15-20 minutes to remove residual ethanol and trace inorganic impurities. After cleaning, the workpiece is placed in a vacuum oven and dried for 1.5-3 hours under conditions of vacuum degree > 0.09 MPa and temperature 80-120℃.

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