High-purity tungsten silicide target and preparation method thereof

Abstract

The invention discloses a high-purity tungsten silicide target and a preparation method thereof, and belongs to the technical field of sputtering target materials, and the preparation method comprises the following steps: mixing silicon powder and tungsten powder to obtain a first mixture; in a vacuum or inert gas environment, the first mixture is sintered for the first time, a pre-sintered blank is obtained, in the first-time sintering process, silicon and tungsten fully react to generate tungsten disilicide, and the pre-sintered blank contains tungsten disilicide, unreacted excessive silicon and silicon monoxide generated by reaction of oxygen impurities contained in the raw materials; crushing the pre-sintered blank to obtain a tungsten-silicon material; doping amorphous carbon into the tungsten-silicon material to obtain a second mixture; in a vacuum or inert gas environment, the second mixture is subjected to pressure sintering, in the pressure sintering process, amorphous carbon and silicon monoxide react to be reduced into silicon, carbon monoxide gas is generated, impurities are discharged, and therefore the high-purity tungsten silicide target is obtained. Compared with the prior art, oxygen impurities can be removed, the microdefects of the target material are reduced, and the compactness of the target material is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of sputtering target technology, and more specifically, to a high-purity tungsten silicide target and its preparation method. Background Technology

[0002] Tungsten-silicon thin films are a common type of thin film in the semiconductor field, and their mainstream preparation method is magnetron sputtering. This method involves bombarding a tungsten silicide target with particles, causing the target particles to deposit on the wafer surface to form a functional thin film. Tungsten-silicon thin films are commonly used as functional layers for precision components such as gate contact layers, barrier layers, or adhesion layers. In the semiconductor field, the performance stability of precision components largely depends on the resistance uniformity of the functional thin film. Existing technologies involve mixing tungsten powder and excess silicon powder and then directly sintering the mixture to obtain the tungsten silicide target, such as the preparation process disclosed in patent document CN202110295606.2. This preparation method makes it difficult to remove oxygen impurities from the tungsten powder and silicon powder, resulting in numerous micropores and microcracks in the target material and poor density.

[0003] Therefore, how to provide a new method for preparing tungsten silicide targets, remove oxygen impurities from the raw materials, and reduce the oxygen content of the tungsten silicide targets has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a high-purity tungsten silicide target (the core phase of the high-purity tungsten silicide target described in this invention is tungsten disilicide WSi2) and its preparation method, so as to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-purity tungsten silicide target includes the following steps: Silicon powder and tungsten powder are mixed to obtain a first mixture; In a vacuum or inert gas environment, the first mixture is sintered for the first time to obtain a pre-sintered billet. During the first sintering process, silicon and tungsten react fully to generate tungsten disilicide. The pre-sintered billet contains tungsten disilicide, unreacted excess silicon, and silicon monoxide generated by the reaction of oxygen impurities contained in the raw materials. The pre-sintered billet is crushed to obtain tungsten-silicon material; Amorphous carbon is added to the tungsten-silicon material to obtain a second mixture; In a vacuum or inert gas environment, the second mixture is subjected to pressure sintering. During the pressure sintering process, amorphous carbon and silicon monoxide react to reduce it to silicon, and carbon monoxide gas is generated to remove impurities, thereby obtaining a high-purity tungsten silicide target.

[0006] Preferably, the doping of carbon into the tungsten-silicon material specifically includes the following steps: A carbon source material is incorporated into the tungsten-silicon material and subjected to heat treatment to obtain a second mixture. The carbon source material incorporated into the tungsten-silicon material undergoes thermal decomposition into amorphous carbon and byproducts. The amorphous carbon remains in the tungsten-silicon material and is uniformly distributed therein. The byproducts are discharged from the tungsten-silicon material in a gaseous state.

[0007] Preferably, the carbon source is phenolic resin, and the incorporation of carbon into the tungsten-silicon material specifically includes the following steps: Place the tungsten-silicon material in the vacuum environment of the vacuum equipment; Phenolic resin was dissolved in ethanol, and the resulting solution was added to a vacuum device and mixed uniformly with the tungsten-silicon material therein to obtain a tungsten-silicon-carbon mixture. A tungsten-silicon-carbon mixture is heat-treated in a vacuum environment to obtain a second mixture. During the heat treatment, the phenolic resin in the tungsten-silicon-carbon mixture is decomposed into amorphous carbon and by-products. The by-products and ethanol are discharged from the tungsten-silicon-carbon mixture in a gaseous state. The amorphous carbon remains in the tungsten-silicon-carbon mixture and is uniformly distributed therein.

[0008] Preferably, the carbon source is sucrose, and the incorporation of carbon into the tungsten-silicon material specifically includes the following steps: Place the tungsten-silicon material in the vacuum environment of the vacuum equipment; A sucrose aqueous solution is added to a vacuum device and mixed uniformly with the tungsten-silicon material therein to obtain a tungsten-silicon-carbon mixture; A tungsten-silicon-carbon mixture is heat-treated in a vacuum environment to obtain a second mixture. During the heat treatment, the sucrose in the tungsten-silicon-carbon mixture is decomposed into amorphous carbon and byproducts. The byproducts and water are discharged from the tungsten-silicon-carbon mixture in a gaseous state, while the amorphous carbon remains in the tungsten-silicon-carbon mixture and is uniformly distributed therein.

[0009] Preferably, mixing silicon powder and tungsten powder to obtain the first mixture specifically includes the following steps: In an inert gas environment, tungsten powder and silicon powder are ball-milled and wet-mixed. The liquid medium for ball milling and wet mixing is ethanol, and the grinding contact layer of the grinding head is made of tungsten.

[0010] Preferably, a graphite hot zone vacuum furnace is used to sinter the first mixture in a vacuum environment to obtain a pre-sintered billet.

[0011] Preferably, the pre-fired billet is ground and crushed in an inert gas environment to obtain tungsten-silicon material, and the grinding contact layer of the grinding head is made of tungsten.

[0012] Preferably, the pressure sintering of the second mixture is carried out using a hot isostatic pressing (HIP) process.

[0013] Preferably, the hot isostatic pressing sintering process for the second mixture is as follows: Sinter at 1000-1200℃ and 110-130MPa for 2-4 hours; Sinter at 1300-1400℃ and 150-180MPa for 4-8 hours.

[0014] According to another aspect of the present invention, a high-purity tungsten silicide target is provided, which is obtained by the aforementioned preparation method.

[0015] Tungsten powder and silicon powder inevitably contain oxygen impurities. This invention involves a first sintering of a mixture of silicon powder and tungsten powder. Tungsten and excess silicon react fully at high temperature to form tungsten disilicide, while oxygen impurities in the powder react with excess silicon at high temperature to form silicon monoxide impurities. Therefore, the pre-sintered blank obtained from the first sintering contains a large amount of tungsten disilicide, excess silicon, and silicon monoxide impurities. This is essentially similar to existing technologies. However, this application adds steps such as crushing, carbon doping, and a second sintering. The uniformly distributed amorphous carbon is used to reduce silicon monoxide to silicon, and carbon monoxide gas is generated to expel the oxygen impurities introduced from the raw materials and the added carbon impurities, resulting in a tungsten disilicide target with lower oxygen content and higher purity.

[0016] The matrix phase of the tungsten silicide target consists of tungsten disilicide grains, forming the framework and main body of the material. Excess silicon forms a second phase, filling the boundaries between multiple tungsten disilicide grains, i.e., grain boundaries, especially triple grain boundaries, as an intergranular phase. At the high temperature of sintering, the excess silicon forms a liquid phase, which, under the action of capillary forces, penetrates into the gaps and grain boundaries between the tungsten disilicide grains, and the continuous phase locally encapsulates the grains. The excess elemental silicon is covalently bonded to each other, and has highly active dangling bonds at its phase interface with the matrix phase.

[0017] In existing technologies, oxygen has strong electronegativity and a strong affinity for silicon, while also exhibiting a weak interaction with tungsten in tungsten disilicide. It segregates at the aforementioned phase interface and bonds with dangling bonds to form Si-O bonds, becoming a pre-existing crack and porosity source. Silicon monoxide is a brittle phase with a significantly different coefficient of thermal expansion compared to tungsten disilicide, easily generating stress during the cooling process of sintering, leading to microcracks and porosity. Furthermore, grain boundaries are weak points in the mechanical strength of materials, and their location at the aforementioned phase interface, precisely at the grain boundary where stress is most easily concentrated, promotes crack growth and exacerbates micro-defects. However, this application reduces silicon monoxide to silicon using carbon. The generated carbon monoxide is discharged in the gaseous phase before the cooling step of hot pressing sintering. During cooling, the aforementioned grain interface is composed of silicon, not silicon monoxide, reducing the difference in thermal expansion coefficients between silicon and tungsten disilicide. This reduces the stress caused by cooling, effectively inhibiting crack growth, reducing the number of pores, minimizing micro-defects in the target material, and improving the density of the target material. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a metallographic image of Embodiment 1 of this application; Figure 2 This is a schematic diagram of the negative pressure liquid extraction device provided in this application.

[0019] Reference numerals: 100, tank; 200, liquid storage tank; 300, buffer tank; 400, vacuum pump. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Regarding the attached image... Figure 2 In the middle, the buffer tank 300 is equipped with a settling component, which uses gravity and a flow-blocking structure to settle and suck up any powder that is not trapped, thus protecting the vacuum pump 400. The vacuum pump 400 is a 1.5kW water ring vacuum pump.

[0022] This invention provides a method for preparing a high-purity tungsten silicide target, comprising the following steps: Silicon powder and tungsten powder are mixed in a set ratio to obtain a first mixture; In a vacuum or inert gas environment, the first mixture is sintered for the first time to obtain a pre-sintered billet. During the first sintering process, silicon and tungsten react fully to generate tungsten disilicide. The pre-sintered billet contains tungsten disilicide, unreacted excess silicon, and silicon monoxide generated by the reaction of oxygen impurities contained in the raw materials. Crushing pre-sintered billets yields tungsten-silicon materials; Amorphous carbon was added to tungsten-silicon material to obtain a second mixture; In a vacuum or inert gas environment, the second mixture is sintered a second time using a pressure sintering process. During the pressure sintering process, amorphous carbon and silicon monoxide react to reduce it to silicon, and carbon monoxide gas is generated to remove impurities, thereby obtaining a high-purity tungsten silicide target (the main component is tungsten disilicide, containing some silicon and a small amount of other impurities).

[0023] Tungsten powder and silicon powder inevitably contain oxygen impurities. This invention involves a first sintering of a mixture of silicon powder and tungsten powder. Tungsten and excess silicon react fully at high temperature to form tungsten disilicide, while oxygen impurities in the powder react with excess silicon at high temperature to form silicon monoxide impurities. Therefore, the pre-sintered blank obtained from the first sintering contains a large amount of tungsten disilicide, excess silicon, and silicon monoxide impurities. This is essentially similar to existing technologies. However, this application adds steps such as crushing, carbon doping, and a second sintering. The uniformly distributed amorphous carbon is used to reduce silicon monoxide to silicon, and carbon monoxide gas is generated to expel the oxygen impurities introduced from the raw materials and the added carbon impurities, resulting in a tungsten disilicide target with lower oxygen content and higher purity.

[0024] The matrix phase of the tungsten silicide target consists of tungsten disilicide grains, forming the framework and main body of the material. Excess silicon forms a second phase, filling the boundaries between multiple tungsten disilicide grains, i.e., grain boundaries, especially triple grain boundaries, as an intergranular phase. At the high temperature of sintering, the excess silicon forms a liquid phase, which, under the action of capillary forces, penetrates into the gaps and grain boundaries between the tungsten disilicide grains, and the continuous phase locally encapsulates the grains. The excess elemental silicon is covalently bonded to each other, and has highly active dangling bonds at its phase interface with the matrix phase.

[0025] In existing technologies, oxygen has strong electronegativity and a strong affinity for silicon, while also exhibiting a weak interaction with tungsten in tungsten disilicide. It segregates at the aforementioned phase interface and bonds with dangling bonds to form Si-O bonds, becoming a pre-existing crack and porosity source. Silicon monoxide is a brittle phase with a significantly different coefficient of thermal expansion compared to tungsten disilicide, easily generating stress during the cooling process of sintering, leading to microcracks and porosity. Furthermore, grain boundaries are weak points in the mechanical strength of materials, and their location at the aforementioned phase interface, precisely at the grain boundary where stress is most easily concentrated, promotes crack growth and exacerbates micro-defects. However, this application reduces silicon monoxide to silicon using carbon. The generated carbon monoxide is discharged in the gaseous phase before the cooling step of hot pressing sintering. During cooling, the aforementioned grain interface is composed of silicon, not silicon monoxide, reducing the difference in thermal expansion coefficients between silicon and tungsten disilicide. This reduces the stress caused by cooling, effectively inhibiting crack growth, reducing the number of pores, minimizing micro-defects in the target material, and improving the density of the target material.

[0026] It should be noted that in the fields of materials science and chemical engineering for target preparation, doping refers to the process of adding one component to another host material in a certain proportion and manner, striving to achieve uniform distribution. Amorphous carbon is an amorphous, solid carbon material, referring to the doped carbon element, whose carbon atoms do not possess a long-range periodic crystal structure and whose carbon atoms are mainly in sp... 2 Hybridization (with a small amount of SP) 3 The atoms are bonded in a hybrid form, with ordered domains (such as twisted aromatic rings or chain structures) in the short-range scale (<2 nm), but the atoms are arranged randomly in the long-range range.

[0027] Amorphous carbon has a highly disordered atomic arrangement, with numerous lattice defects, edge sites, and unsaturated chemical bonds (dangling bonds). These sites possess extremely high surface energy, making them active sites for chemical reactions. Compared to well-structured and stable crystalline carbon materials such as graphite, the carbon atoms in amorphous carbon are in a metastable state, significantly reducing the activation energy required for its reduction reaction with oxygen-containing compounds such as silicon monoxide (SiO + C → Si + CO↑). This allows the reduction reaction to proceed at relatively lower temperatures and at a faster rate, reducing the risk of silicon and tungsten volatilization caused by high-temperature deoxidation. During the holding stage of the second sintering (hot pressing sintering) (1000-1200℃), amorphous carbon can rapidly and thoroughly react with silicon monoxide impurities, achieving deep deoxidation and reducing the oxygen content to extremely low levels.

[0028] In this application, the final carbon content depends on the oxygen content in the tungsten-silicon material (due to raw materials and upstream processes). The amount of carbon incorporated can be determined based on the known oxygen content of the tungsten powder and silicon powder. The upstream process (the process before carbon doping in the preparation method) should minimize the risk of oxygen impurities introduced by oxidation, and the process influence should be ignored. Preferably, the upstream process is carried out in a vacuum or inert gas environment. Alternatively, the oxygen content in the tungsten powder and silicon powder can be measured using measuring instruments, or the oxygen content in the tungsten-silicon material can be measured before carbon doping. This application does not specifically limit the measuring instruments and methods, as long as the principle of accurate measurement is followed. For example, sampling can be performed using the pulse heating inert gas melting-infrared absorption method, and the operation can be carried out according to industry standard measurement methods. The amount of carbon incorporated is determined based on the oxygen content. Preferably, the amount of carbon incorporated (atomic number) is consistent with the amount of oxygen in the tungsten-silicon material, and the ratio (stoichiometric ratio, molar ratio, atomic number ratio) of carbon incorporated to oxygen in the tungsten-silicon material is 1:0.9-1.1, preferably 1:0.9 or 1:1. The amounts of carbon and oxygen are equal or slightly excessive to adequately remove oxygen and reduce the carbon content of the target material.

[0029] In one possible implementation, mixing silicon powder and tungsten powder in a predetermined ratio to obtain a first mixture specifically includes the following steps: In an inert gas environment (e.g., argon), tungsten powder and silicon powder are ball-milled and wet-mixed. The liquid medium for ball milling and wet mixing is a volatile ethanol solution / ethanol-water solution that does not react with the material being milled and leaves no residue. The grinding contact layer of the grinding head is made of tungsten material (≥5N). Preferably, the grinding head is a tungsten grinding head, and the entire head is made of tungsten material. Preferably, the atomic ratio of tungsten to silicon is 1:2-3.5, more preferably 1:2.5-2.8, and more preferably 1:2.6.

[0030] The fine-particle tungsten and silicon powders used in this application are preferably tungsten powder with a particle size of 0.8-2.0 μm and a purity of ≥99.999% and silicon powder with a particle size of 0.8-6.0 μm and a purity of ≥99.999%, so that the two can be fully mixed to ensure that the tungsten and silicon react fully in the subsequent process and that the finished target material has a uniform structure.

[0031] This application uses inert gas to prevent oxidation caused by prolonged contact between powder and air during ball milling; it uses wet mixing instead of dry mixing, utilizing the liquid medium to effectively inhibit the agglomeration of fine powder during ball milling, resulting in more uniform mixing; and it uses tungsten balls instead of silicon balls in the grinding head, which reduces the risk of introducing impurities due to non-tungsten-silicon grinding heads. Furthermore, tungsten balls are hard and less likely to wear down and mix into the material being ground during mixing, thereby changing the ratio of tungsten-silicon powder. This also allows the powder to be finer, promoting uniform mixing of the two.

[0032] The first mixture is obtained through the aforementioned ball milling and wet mixing process. After drying, the first mixture is placed in a tungsten crucible and then subjected to a first sintering in a vacuum furnace, as described above, to form a pre-sintered billet. The purpose of the first sintering is pre-sintering, which is to allow the tungsten powder and silicon powder to react fully to generate tungsten disilicide (WSi2). A graphite hot zone vacuum furnace is preferred, but a refractory metal hot zone vacuum furnace can also be used.

[0033] If the temperature is too high, the silicon powder melts, and silicon segregation is likely to occur in the final pre-sintered billet; if the temperature is too low or the holding time is too short, the diffusion time between tungsten and silicon is insufficient, resulting in incomplete reaction; if the holding time is too long, the tungsten-silicon powder is prone to partial sintering, increasing the difficulty of subsequent crushing. The first sintering can be a hot isostatic pressing (HIP) process. This application provides the following HIP process for the first sintering: holding the sinter at 40-50 MPa (preferably 45 MPa) and 900-1400℃ (preferably 1000℃ or 1200℃) for 4-12 hours, preferably 7 hours. This application does not specify the methods for heating, pressurizing, cooling, and depressurizing. For details, please refer to the second sintering (the pressure inside the furnace is preset to 10 MPa. A tungsten crucible containing the first mixture is placed in the furnace. The temperature is increased at a rate of 3-5°C / min, preferably 4°C / min, until the temperature reaches the target temperature (900-1400°C), and the pressure naturally expands to the target pressure value (40-50 MPa, preferably 45 MPa) (overpressure venting, specifically, refers to venting gas through a pressure relief valve to maintain pressure stability when the pressure exceeds the set value).

[0034] The pre-fired billet is placed in a ball mill filled with inert gas. During the crushing process, the pre-fired billet is always under the protection of inert gas. First, the pre-fired billet is manually crushed into small pieces. Then, tungsten balls are used as grinding heads to pulverize the pre-fired billet into powder without adding alcohol. The resulting powder is tungsten-silicon material.

[0035] Carbon is incorporated into tungsten-silicon materials. The specific steps include: A carbon source material is added to tungsten silicon material and then heat-treated to obtain a second mixture. The carbon source material added to the tungsten silicon material is thermally decomposed into amorphous carbon and by-products. The amorphous carbon remains in the tungsten silicon material and is evenly distributed therein, while the by-products are discharged from the tungsten silicon material in a gaseous state.

[0036] In one possible implementation, the carbon source material is incorporated into powdered tungsten-silicon material by solution impregnation.

[0037] For example, if the carbon source is phenolic resin, the specific steps for incorporating carbon into tungsten-silicon materials include: Place the tungsten-silicon material in the vacuum environment of the vacuum equipment; Phenolic resin was dissolved in ethanol, and the resulting solution was added to a vacuum device and mixed uniformly with the tungsten-silicon material therein to obtain a tungsten-silicon-carbon mixture. A second mixture is obtained by heat treatment of a tungsten-silicon-carbon mixture in a vacuum environment. During the heat treatment, the phenolic resin in the tungsten-silicon-carbon mixture is decomposed into amorphous carbon and by-products. The by-products and ethanol are discharged from the tungsten-silicon-carbon mixture in gaseous state, while the amorphous carbon remains in the tungsten-silicon-carbon mixture and is uniformly distributed therein.

[0038] The specific operation is as follows: Remove the tungsten-silicon material from the ball mill and place it in… Figure 2 In the container 100 shown, phenolic resin is melted by heating at 50-80°C and thoroughly mixed with ethanol (volume ratio) at a ratio of 1:(1.5-3), preferably phenolic resin:ethanol (volume ratio) at a ratio of 1:2. The container 100 is evacuated to a vacuum degree >0.1 MPa, and the resulting solution is placed in... Figure 2 The liquid is drawn into the storage tank 200 as shown. The liquid is then pumped into the tank 100 using a negative pressure pumping method. The stirring component inside the tank 100 is activated, and the liquid is pumped under negative pressure while being stirred and mixed to obtain a tungsten-silicon-carbon mixture.

[0039] Using the heating equipment of tank 100, the temperature inside the tank is raised to 80-120°C, preferably 100°C. The tungsten-silicon-carbon mixture is mixed and heat-treated under vacuum conditions. The byproducts are discharged from the tank in gaseous form, while carbon atoms remain in the tungsten-silicon-carbon mixture in the form of amorphous carbon. The resulting tungsten-silicon-carbon mixture is the second mixture obtained.

[0040] For example, if the carbon source is sucrose, the specific steps for incorporating carbon into tungsten-silicon materials include: Place the tungsten-silicon material in the vacuum environment of the vacuum equipment; A sucrose aqueous solution is added to a vacuum device and mixed uniformly with the tungsten-silicon material therein to obtain a tungsten-silicon-carbon mixture; Tungsten-silicon-carbon is mixed in a vacuum environment to obtain a second mixture. During the mixing process, the sucrose in the tungsten-silicon-carbon mixture is decomposed into amorphous carbon and by-products by heating. The by-products and water are discharged from the tungsten-silicon-carbon mixture in gaseous state, while the amorphous carbon remains in the tungsten-silicon-carbon mixture and is uniformly distributed therein.

[0041] The specific operation is as follows: Remove the tungsten-silicon material from the ball mill and place it in… Figure 2 The container 100 is shown. A vacuum is drawn until the vacuum level in container 100 is >0.1 MPa. Sucrose is dissolved in water, and the resulting sucrose solution is placed in… Figure 2 The liquid is drawn into the storage tank 200 as shown. The liquid is then pumped into the tank 100 using a negative pressure pumping method. The stirring component inside the tank 100 is activated, and the liquid is pumped under negative pressure while being stirred and mixed to obtain a tungsten-silicon-carbon mixture.

[0042] Using the heating equipment of the tank 100, the temperature inside the tank is raised to 80-120°C, preferably 100°C, and the tungsten-silicon-carbon mixture is heat-treated under vacuum conditions. The by-products are discharged out of the tank in gaseous form, and the carbon atoms remain in the tungsten-silicon-carbon mixture in the form of amorphous carbon. The resulting tungsten-silicon-carbon mixture is the second mixture obtained.

[0043] In another possible implementation, the carbon source material is in a gaseous state. This gaseous carbon source material is continuously introduced into a sealed container, thereby incorporating it into powdered tungsten-silicon material. Simultaneously, the sealed container is heated to heat-treat its contents. The carbon source material incorporated into the tungsten-silicon material decomposes into amorphous carbon and byproducts upon heating. The byproducts are discharged from the sealed container as a gas, while the amorphous carbon remains in the tungsten-silicon material, forming a second mixture.

[0044] For example, the carbon source material is a gas such as methane, which is deposited and grown in situ on the surface of the solid powder when passing through tungsten-silicon powder. The nucleation and growth of carbon in the gas phase, leading to deposition as amorphous carbon particles, can be suppressed by controlling the heat treatment temperature and duration, while promoting the nucleation and growth of carbon on the solid surface of the powder, resulting in deposition as amorphous carbon particles. Preferably, the carbon source material is methane, the heat treatment temperature is 700-1200℃, preferably 1000℃, and the heat treatment duration is 1-2 hours, preferably 1.5 hours. Different carbon source materials have different thermal decomposition processes, and the heat treatment temperature and duration can be adjusted according to the specific properties of the carbon source material. For example, after adding the carbon source material, the carbon content in the second mixture is 300-700 ppm.

[0045] In one possible implementation, the second sintering of the second mixture in a vacuum or inert gas environment is preferably hot isostatic pressing (HIP). The specific process for HIP of the second mixture is as follows: The pressure inside the equipment is preset to 40-60 MPa, preferably 50 MPa. The second mixture is placed in the hot isostatic pressing furnace. The temperature is increased at a rate of 3-5 °C / min, preferably 4 °C / min, until the temperature reaches the first preset temperature, and the pressure naturally expands to the first preset pressure (overpressure venting). The material is sintered at a first preset temperature and a first preset pressure for 2-4 hours, preferably 3 hours. The first preset temperature is 1000-1200℃, preferably 1200℃, and the first preset pressure is 110-130MPa, preferably 120MPa. Carbon reacts fully with silicon monoxide to produce carbon monoxide, which is then discharged, without reacting with tungsten to form tungsten carbide. The temperature is increased at a rate of 1-3℃ / min, preferably 2℃ / min, until the temperature rises to the second preset temperature, and the pressure naturally expands to the second preset pressure (overpressure venting). The target material is sintered at a second preset temperature and a second preset pressure for 4-8 hours, preferably 6 hours. The second preset temperature is 1300-1400℃, preferably 1400℃, and the second preset pressure is 150-180MPa to achieve densification. The furnace is cooled at a rate of 1-5℃ / min, preferably 3℃ / min. The pressure decreases naturally with the temperature drop, and the furnace gas is recovered naturally due to the pressure difference between the inside and outside of the furnace (pressure difference between the inside and outside of the furnace, recovering the inert gas inside the furnace). When the furnace pressure reaches 30MPa, the remaining inert gas is recovered with the assistance of a compressor. When the temperature approaches room temperature (25℃) and the pressure drops to 5MPa, the remaining gas is vented, and the second mixture (density > 7.6g / cm³) after hot isostatic pressing sintering is taken out. 3 ( ) is the high-purity tungsten silicide target prepared.

[0046] This application does not specifically limit whether post-processing is required after hot-pressing sintering. The second mixture after hot-pressing sintering can be collected directly as the high-purity tungsten silicide target, or the second mixture after hot-pressing sintering can be subjected to necessary post-processing to obtain a high-purity tungsten silicide target. For example, the second mixture after hot-pressing sintering can be taken out and subjected to post-processing such as machining (removing the skin) and finishing to obtain a high-purity tungsten silicide target.

[0047] According to another aspect of the present invention, a high-purity tungsten silicide target is provided, which is obtained by the aforementioned preparation method.

[0048] In addition, this application also provides Example 1: Powder preparation: Use tungsten powder with a particle size of 1μm and a purity of ≥99.999% and silicon powder with a particle size of 5μm and a purity of ≥99.999%. The purpose of using fine-particle tungsten and silicon is to ensure that they are fully mixed to ensure that the tungsten and silicon react fully in the subsequent process and that the finished target material has a uniform structure.

[0049] Mixed powder: Tungsten powder and silicon powder are mixed, and the atomic ratio of tungsten to silicon (preset ratio) is 1:2.4.

[0050] In this embodiment, a ball milling wet mixing process is used to mix tungsten powder and silicon powder. Argon gas is filled into the ball milling equipment, ethanol is added as a liquid medium, and tungsten balls are used as grinding balls.

[0051] First sintering: After drying the mixed powder, place it in a tungsten crucible and then in a graphite thermal vacuum furnace. Sinter at 1000℃ and a pressure of 45 MPa for 8 hours. Crushing and secondary mixing: The pre-fired billet is placed in a ball mill filled with inert gas, first manually crushed into small pieces, and then dry-milled without adding alcohol to obtain tungsten silicon material.

[0052] Carbon doping treatment: The tungsten-silicon material is removed from the ball mill and placed in... Figure 2 In the container 100 shown, phenolic resin is melted by heating at 60°C and thoroughly mixed with ethanol (volume ratio) at a ratio of 1:2. A vacuum is then created in container 100 until the vacuum level is >0.1 MPa. The resulting solution is then placed in... Figure 2 The liquid is drawn into the storage tank 200 as shown. Liquid is pumped into the tank 100 using negative pressure until the final carbon content reaches 600 ppm and the ratio of carbon to oxygen atoms is 1:0.9. The stirring component inside the tank 100 is then activated, simultaneously pumping liquid under negative pressure and stirring to obtain a tungsten-silicon-carbon mixture.

[0053] Using the heating equipment of tank 100, the temperature inside the tank is raised to 100°C, and the tungsten-silicon-carbon mixture is heat-treated under vacuum conditions. The by-products are discharged from the tank in gaseous form, while carbon atoms remain in the tungsten-silicon-carbon mixture in the form of amorphous carbon. The heat-treated tungsten-silicon-carbon mixture is the second mixture obtained.

[0054] Hot isostatic pressing (HIP) sintering: The second mixture was placed in a graphite hot press mold and heated to 1100℃ at a rate of 3℃ / min, with a pressure of 120MPa. Sintering was then carried out at 120MPa and 1100℃ for 3 hours. The temperature was then increased to 1400℃ at a rate of 2℃ / min, with a pressure of 160MPa, and sintered at 1400℃ and 160MPa for 6 hours. Cooling was then carried out with the furnace at a rate of 3℃ / min, recovering inert gases from the furnace using natural pressure difference (pressure difference between inside and outside the furnace, recovering inert gases). When the furnace pressure reached 30MPa, the remaining inert gases were recovered using a compressor. When the temperature approached room temperature (25℃) and the pressure dropped to 5MPa, the remaining gases were vented, and the second mixture after HIP sintering was removed. Samples were taken for microscopic examination; the SEM image of the microstructure is shown below. Figure 1 As shown; the sampling measurement performance shows a density of 8.2 g / cm³. 3Carbon content ≤100ppm, oxygen content 280ppm, <400ppm, metallographic diagram as follows Figure 1 As shown, the target material exhibits a uniform microstructure, with tungsten disilicide and silicon evenly distributed, and small, uniformly distributed pore sizes. No obvious large-pore, low-density micro-defects were found.

[0055] Machining: The high-carbon outer layer of the material taken out in the previous step is removed by machining to obtain a high-density, low-oxygen tungsten-silicon target. Finally, after surface finishing, a high-purity tungsten silicide target is obtained.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-purity tungsten silicide target, characterized in that, Includes the following steps: Silicon powder and tungsten powder are mixed to obtain a first mixture; In a vacuum or inert gas environment, the first mixture is sintered for the first time to obtain a pre-sintered billet. During the first sintering process, silicon and tungsten react fully to generate tungsten disilicide. The pre-sintered billet contains tungsten disilicide, unreacted excess silicon, and silicon monoxide generated by the reaction of oxygen impurities contained in the raw materials. The pre-sintered billet is crushed to obtain tungsten-silicon material; Amorphous carbon is added to the tungsten-silicon material to obtain a second mixture; In a vacuum or inert gas environment, the second mixture is subjected to pressure sintering. During the pressure sintering process, amorphous carbon and silicon monoxide react to reduce it to silicon, and carbon monoxide gas is generated to remove impurities, thereby obtaining a high-purity tungsten silicide target.

2. The method for preparing a high-purity tungsten silicide target according to claim 1, characterized in that, The process of doping carbon into the tungsten-silicon material specifically includes the following steps: A carbon source material is incorporated into the tungsten-silicon material and subjected to heat treatment to obtain a second mixture. The carbon source material incorporated into the tungsten-silicon material undergoes thermal decomposition into amorphous carbon and byproducts. The amorphous carbon remains in the tungsten-silicon material and is uniformly distributed therein. The byproducts are discharged from the tungsten-silicon material in a gaseous state.

3. The method for preparing a high-purity tungsten silicide target according to claim 2, characterized in that, The carbon source material is phenolic resin, and the incorporation of carbon into the tungsten-silicon material specifically includes the following steps: Place the tungsten-silicon material in the vacuum environment of the vacuum equipment; Phenolic resin was dissolved in ethanol, and the resulting solution was added to a vacuum device and mixed uniformly with the tungsten-silicon material therein to obtain a tungsten-silicon-carbon mixture. A tungsten-silicon-carbon mixture is heat-treated in a vacuum environment to obtain a second mixture. During the heat treatment, the phenolic resin in the tungsten-silicon-carbon mixture is decomposed into amorphous carbon and by-products. The by-products and ethanol are discharged from the tungsten-silicon-carbon mixture in a gaseous state. The amorphous carbon remains in the tungsten-silicon-carbon mixture and is uniformly distributed therein.

4. The method for preparing a high-purity tungsten silicide target according to claim 2, characterized in that, The carbon source is sucrose, and the incorporation of carbon into the tungsten-silicon material specifically includes the following steps: Place the tungsten-silicon material in the vacuum environment of the vacuum equipment; A sucrose aqueous solution is added to a vacuum device and mixed uniformly with the tungsten-silicon material therein to obtain a tungsten-silicon-carbon mixture; A tungsten-silicon-carbon mixture is heat-treated in a vacuum environment to obtain a second mixture. During the heat treatment, the sucrose in the tungsten-silicon-carbon mixture is decomposed into amorphous carbon and byproducts. The byproducts and water are discharged from the tungsten-silicon-carbon mixture in a gaseous state, while the amorphous carbon remains in the tungsten-silicon-carbon mixture and is uniformly distributed therein.

5. The method for preparing a high-purity tungsten silicide target according to claim 1, characterized in that, The process of mixing silicon powder and tungsten powder to obtain a first mixture specifically includes the following steps: In an inert gas environment, tungsten powder and silicon powder are ball-milled and wet-mixed. The liquid medium for ball milling and wet mixing is ethanol, and the grinding contact layer of the grinding head is made of tungsten.

6. The method for preparing a high-purity tungsten silicide target according to claim 1, characterized in that, The first mixture was sintered for the first time in a vacuum environment using a graphite hot zone vacuum furnace to obtain a pre-sintered billet.

7. The method for preparing a high-purity tungsten silicide target according to claim 1, characterized in that, In an inert gas environment, the pre-sintered billet is ground and crushed to obtain tungsten-silicon material, and the grinding contact layer of the grinding head is made of tungsten.

8. The method for preparing a high-purity tungsten silicide target according to claim 1, characterized in that, The pressure sintering of the second mixture is carried out using a hot isostatic pressing (HIP) process.

9. The method for preparing a high-purity tungsten silicide target according to claim 8, characterized in that, The hot isostatic pressing (HIP) sintering process for the second mixture is as follows: Sinter at 1000-1200℃ and 110-130MPa for 2-4 hours; Sinter at 1300-1400℃ and 150-180MPa for 4-8 hours.

10. A high-purity tungsten silicide target, characterized in that, The high-purity tungsten silicide target is obtained by any one of the preparation methods described in claims 1-9.

Images