Molybdenum-tungsten alloy for ion implanter and preparation method of molybdenum-tungsten alloy

Abstract

The invention provides a molybdenum-tungsten alloy for an ion implanter and a preparation method of the molybdenum-tungsten alloy. The preparation method comprises the following steps: (1) weighing Mo powder, W powder, HfC powder and ZrB2 powder in proportion; (2) mixing and stirring to obtain Mo powder coated with HfC powder and W powder coated with ZrB2 powder, and mixing to obtain mixed powder; (3) performing cold isostatic pressing on the mixed powder to obtain a pressed blank; and (4) the pressed blank is dried and sintered, and the molybdenum-tungsten alloy for the ion implanter is obtained. HfC and ZrB2 which are excellent in ablation resistance are added on the basis of Mo-W alloy, the high melting point of HfO2 is combined with the compact repairing capacity of ZrO2 + B2O3 glass phase in the ablation process, a composite oxide film of a high-melting-point framework and compact filling is formed, and the barrier effect is far better than that of single-phase addition. And a respective coating and mixing process is adopted, so that HfC and ZrB2 in the mixed powder are uniformly distributed on the surfaces of Mo and W particles and particle gaps, and a foundation is laid for the performance uniformity of the alloy after subsequent sintering.

Description

Technical Field

[0001] This invention relates to the field of alloys, and in particular to a molybdenum-tungsten alloy for ion implanters and its preparation method. Background Technology

[0002] Ion implantation is a very important technology in modern integrated circuit manufacturing. It uses an ion implanter to dope semiconductors. Specifically, a tungsten wire is used as a cathode to emit electrons to bombard gas molecules containing specific impurity elements. The resulting ionized impurity atoms are accelerated by an electrostatic field and then implanted into the surface of a silicon single-crystal wafer, changing the conductivity and ultimately forming a transistor structure.

[0003] Because the conversion of the ion source to plasma ions generates operating temperatures exceeding 2000℃, and the ion beam ejection also produces significant ion kinetic energy, most metals would melt quickly. However, tungsten and molybdenum possess excellent high-temperature resistance, maintaining stability under high-temperature environments and resisting thermal deformation or damage. Therefore, using tungsten-molybdenum components ensures reliable operation of the equipment under high-temperature conditions. Simultaneously, tungsten and molybdenum exhibit high chemical stability, resisting reactions or corrosion with other chemicals. In ion implantation equipment, tungsten-molybdenum components maintain stability in strong chemical environments, preventing chemical damage or corrosion, thus extending the equipment's lifespan. Furthermore, components in ion implantation equipment require sufficient mechanical strength and wear resistance to withstand the impact of the ion beam and potential mechanical wear during operation. Tungsten and molybdenum possess high mechanical strength and hardness, enabling them to withstand significant pressure and friction within the ion implantation equipment, ensuring stable operation. Finally, components in ion implantation equipment need good electrical conductivity to ensure accurate ion beam transmission and implantation. Tungsten and molybdenum are excellent conductors, effectively conducting current and ensuring the stability and accuracy of the ion implantation process. Therefore, due to the advantages of tungsten and molybdenum materials such as stable high-temperature chemical properties, small thermal deformation, and long service life, ion source components and consumables of ion implanters in the semiconductor industry are mostly made of tungsten and molybdenum materials. These devices include shielding cylinders for emitting electron cathodes, emission panels, central fixing rods, and wire plates in arc-starting chambers, which we collectively refer to as tungsten parts for ion implantation and molybdenum parts for ion implantation.

[0004] Molybdenum (Mo), as one of the new generation of strategically important rare metals, has a melting point as high as 2625℃ and possesses excellent high-temperature strength, electrical and thermal conductivity, resistance to high-temperature creep, and a low coefficient of thermal expansion. However, due to the low-temperature brittleness, easy oxidation at high temperatures, and relatively low strength of pure molybdenum, its applications are greatly limited. Therefore, its applications in various fields are mostly in the form of molybdenum alloys. Among them, molybdenum-tungsten (Mo-W) alloys, due to their superior high-temperature performance and strength compared to pure molybdenum, can be used as components for ion implanters. Although the high-temperature ablation resistance of Mo-W alloys is currently quite good and can meet the requirements of ordinary plasma implanters, there are still shortcomings when facing higher ablation temperatures. Further improvements are needed to enhance its high-temperature ablation resistance to meet application requirements.

[0005] In view of the above, there is an urgent need to provide a molybdenum-tungsten alloy for ion implanters and its preparation method, so that it has excellent resistance to plasma ablation.

[0006] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a molybdenum-tungsten alloy for ion implanters and its preparation method, so as to solve the problem of insufficient high-temperature ablation resistance of molybdenum-tungsten alloys in the prior art.

[0008] To achieve the above and other related objectives, the present invention provides a method for preparing a molybdenum-tungsten alloy for an ion implanter, the method comprising: (1) Weigh 85-90 parts of Mo powder and 10-15 parts of W powder according to the ratio, weigh 0.5%~1% of HfC powder of total mass of Mo powder and W powder, and 2%~3% of ZrB2 powder of total mass of Mo powder and W powder; (2) Mix Mo powder and HfC powder evenly to obtain Mo powder coated with HfC powder. Mix W powder and ZrB2 powder evenly to obtain W powder coated with ZrB2 powder. Mix the Mo powder coated with HfC powder and the W powder coated with ZrB2 powder evenly to obtain mixed powder. (3) The mixed powder from step (2) is cold isostatically pressed to obtain a compact; (4) Sinter the pressed blank obtained in step (3) to obtain a molybdenum-tungsten alloy for ion implantation machine.

[0009] Optionally, the particle size D of the Mo powder and W powder 50 The size is 3-5μm, and the purity is ≥99%.

[0010] Optionally, the particle size D of the HfC powder and ZrB2 powder is... 50 The thickness is 0.5~1μm.

[0011] Optionally, the mixing in step (2) is carried out in a V-type mixer, and the mixing time is 6~8 hours.

[0012] Optionally, the pressure of the cold isostatic pressing in step (3) is 180~220MPa.

[0013] Optionally, in step (4), the sintering equipment is a medium-frequency induction sintering furnace, the sintering atmosphere is a hydrogen atmosphere, the sintering temperature is 2200~2400℃, and the sintering time is 4~6h.

[0014] Optionally, in step (4), the sintering process involves first heating the temperature to 700-800℃ at a heating rate of 5-8℃ / min and holding it for 1-2 hours, then heating the temperature to 1700-1800℃ at a heating rate of 3-4℃ / min and holding it for 6-8 hours, and finally heating the temperature to 2200-2400℃ at a heating rate of 1-2℃ / min and holding it for 4-6 hours.

[0015] The present invention also provides a molybdenum-tungsten alloy for ion implanters, wherein the molybdenum-tungsten alloy for ion implanters is prepared by any one of the above-described methods for preparing molybdenum-tungsten alloys for ion implanters.

[0016] As described above, the molybdenum-tungsten alloy for ion implanters and its preparation method of the present invention have the following beneficial effects: (1) This invention adds HfC and ZrB2 with excellent ablation resistance to the Mo-W alloy. HfO2, generated by the oxidation of HfC, has a melting point as high as 2900℃ and a thermal conductivity of only 1.5W / m·K. Moreover, it has a dense structure and can adhere tightly to the surface of the Mo-W matrix. On the one hand, it blocks the diffusion of corrosive media such as oxygen and high-temperature airflow to the matrix, and avoids the oxidation of Mo and W to generate easily volatile MoO3 and WO3. On the other hand, it reduces the heat conduction of the matrix, lowers the matrix temperature, and delays its softening, melting or evaporation. ZrB2 is oxidized to generate ZrO2 and B2O3. ZrO2 acts as a rigid skeleton to support the oxide film structure, while B2O3 forms a glass phase at high temperature, which can fill the tiny pores in the oxide film and further improve the density of the film. At the same time, B2O3 has fluidity and can repair the tiny cracks generated by thermal shock or airflow impact on the oxide film, and avoid barrier failure. The two phases work synergistically, with the high melting point of HfO2 combined with the dense repair ability of the ZrO2+ B2O3 glass phase, forming a composite oxide film of "high melting point skeleton + dense filling", which has a barrier effect far exceeding that of adding a single phase.

[0017] (2) The present invention adopts the process of "separate coating + mixing". HfC is preferentially and tightly attached to the surface of Mo powder, and ZrB2 is preferentially coated on the surface of W powder. The ceramic phase is fixed by the surface adsorption force of the base metal powder. When the two coated powders are mixed in the future, the ceramic phase has been "anchored" by the metal powder and will not aggregate due to density difference or stirring. Finally, HfC and ZrB2 are evenly distributed on the surface of Mo and W particles and in the gaps between particles in the mixed powder, which lays the foundation for the uniformity of the alloy performance after subsequent sintering. Detailed Implementation

[0018] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0022] To achieve the above and other related objectives, the present invention provides a method for preparing a molybdenum-tungsten alloy for an ion implanter, the method comprising: (1) Weigh 85-90 parts of Mo powder and 10-15 parts of W powder according to the ratio, weigh 0.5%~1% of HfC powder of total mass of Mo powder and W powder, and 2%~3% of ZrB2 powder of total mass of Mo powder and W powder; (2) Mix Mo powder and HfC powder evenly to obtain Mo powder coated with HfC powder. Mix W powder and ZrB2 powder evenly to obtain W powder coated with ZrB2 powder. Mix the Mo powder coated with HfC powder and the W powder coated with ZrB2 powder evenly to obtain mixed powder. (3) The mixed powder from step (2) is cold isostatically pressed to obtain a compact; (4) Sinter the pressed blank obtained in step (3) to obtain a molybdenum-tungsten alloy for ion implantation machine.

[0023] Optionally, the particle size D of the Mo powder and W powder 50 The size is 3-5μm, and the purity is ≥99%.

[0024] Optionally, the particle size D of the HfC powder and ZrB2 powder is... 50 The thickness is 0.5~1μm.

[0025] Optionally, the mixing in step (2) is carried out in a V-type mixer, and the mixing time is 6~8 hours.

[0026] Optionally, the pressure of the cold isostatic pressing in step (3) is 180~220MPa.

[0027] Optionally, in step (4), the sintering equipment is a medium-frequency induction sintering furnace, the sintering atmosphere is a hydrogen atmosphere, the sintering temperature is 2200~2400℃, and the sintering time is 4~6h.

[0028] Optionally, in step (4), the sintering process involves first heating the temperature to 700-800℃ at a heating rate of 5-8℃ / min and holding it for 1-2 hours, then heating the temperature to 1700-1800℃ at a heating rate of 3-4℃ / min and holding it for 6-8 hours, and finally heating the temperature to 2200-2400℃ at a heating rate of 1-2℃ / min and holding it for 4-6 hours.

[0029] The present invention also provides a molybdenum-tungsten alloy for ion implanters, wherein the molybdenum-tungsten alloy for ion implanters is prepared by any one of the above-described methods for preparing molybdenum-tungsten alloys for ion implanters.

[0030] This invention adds HfC and ZrB2, which have excellent ablation resistance, to a Mo-W alloy. HfC oxidizes to form HfO2, and ZrB2 oxidizes to form ZrO2 and B2O3. ZrO2 acts as a rigid framework to support the oxide film structure, while B2O3 forms a glassy phase at high temperatures. The two phases work synergistically; the high melting point of HfO2 combined with the dense repair ability of the ZrO2 + B2O3 glassy phase forms a composite oxide film of "high melting point framework + dense filling," with a barrier effect far exceeding that of adding a single phase. The "separate coating + mixing" process ensures that HfC and ZrB2 are uniformly distributed on the surface and between Mo and W particles in the mixed powder, laying the foundation for the uniformity of the alloy's properties after sintering.

[0031] Example 1 This embodiment provides a method for preparing a molybdenum-tungsten alloy for an ion implanter, the method comprising: (1) Weigh D according to the proportion. 50 85 parts of 3μm Mo powder, D 50 15 portions of W powder with a particle size of 3μm were weighed, and 1% of the total mass of Mo powder and W powder was added to D powder. 50 The total mass of HfC powder (0.5μm), Mo powder, and W powder is 3% D. 50 ZrB2 powder with a particle size of 1 μm; (2) Mix Mo powder and HfC powder in a V-type mixer for 6 hours until they are evenly mixed to obtain Mo powder coated with HfC powder. Mix W powder and ZrB2 powder in a V-type mixer for 6 hours until they are evenly mixed to obtain W powder coated with ZrB2 powder. Add the Mo powder coated with HfC powder and the W powder coated with ZrB2 powder to the V-type mixer and mix for 8 hours until they are evenly mixed to obtain mixed powder. (3) The mixed powder in step (2) is cold isostatically pressed under a pressure of 200 MPa to obtain a compact; (4) The pressed billet obtained in step (3) is placed in a medium-frequency induction sintering furnace and sintered in a hydrogen atmosphere. First, the temperature is raised to 700°C at a heating rate of 6°C / min and held for 2 hours. Then, the temperature is raised to 1800°C at a heating rate of 4°C / min and held for 6 hours. Finally, the temperature is raised to 2300°C at a heating rate of 2°C / min and held for 6 hours. The billet is then cooled in the furnace to obtain a molybdenum-tungsten alloy for ion implanters.

[0032] Example 2 This embodiment provides a method for preparing a molybdenum-tungsten alloy for an ion implanter, the method comprising: (1) Weigh D according to the proportion. 50 90 parts of 3μm Mo powder, D 50 Ten portions of W powder with a particle size of 3μm were weighed, and 1% of the total mass of Mo powder and W powder was added to the D powder. 50 The total mass of HfC powder (0.5μm), Mo powder, and W powder is 3% D. 50 ZrB2 powder with a particle size of 1 μm; (2) Mix Mo powder and HfC powder in a V-type mixer for 6 hours until they are evenly mixed to obtain Mo powder coated with HfC powder. Mix W powder and ZrB2 powder in a V-type mixer for 6 hours until they are evenly mixed to obtain W powder coated with ZrB2 powder. Add the Mo powder coated with HfC powder and the W powder coated with ZrB2 powder to the V-type mixer and mix for 8 hours until they are evenly mixed to obtain mixed powder. (3) The mixed powder in step (2) is cold isostatically pressed under a pressure of 200 MPa to obtain a compact; (4) The pressed billet obtained in step (3) is placed in a medium-frequency induction sintering furnace and sintered in a hydrogen atmosphere. First, the temperature is raised to 700°C at a heating rate of 6°C / min and held for 2 hours. Then, the temperature is raised to 1800°C at a heating rate of 4°C / min and held for 6 hours. Finally, the temperature is raised to 2300°C at a heating rate of 2°C / min and held for 6 hours. The billet is then cooled in the furnace to obtain a molybdenum-tungsten alloy for ion implanters.

[0033] Comparative Example 1 This comparative example provides a method for preparing a molybdenum-tungsten alloy for an ion implanter, the method comprising: (1) Weigh D according to the proportion. 50 90 parts of 3μm Mo powder, D 50 Ten portions of W powder with a particle size of 3μm were weighed, and 1% of the total mass of Mo powder and W powder was added to the D powder. 50 The total mass of HfC powder (0.5μm), Mo powder, and W powder is 3% D. 50 ZrB2 powder with a particle size of 1 μm; (2) Add Mo powder, HfC powder, W powder and ZrB2 powder together into a V-type mixer and mix for 6 hours until the mixture is uniform to obtain a mixed powder; (3) The mixed powder in step (2) is cold isostatically pressed under a pressure of 200 MPa to obtain a compact; (4) The pressed billet obtained in step (3) is placed in a medium-frequency induction sintering furnace and sintered in a hydrogen atmosphere. First, the temperature is raised to 700°C at a heating rate of 6°C / min and held for 2 hours. Then, the temperature is raised to 1800°C at a heating rate of 4°C / min and held for 6 hours. Finally, the temperature is raised to 2300°C at a heating rate of 2°C / min and held for 6 hours. The billet is then cooled in the furnace to obtain a molybdenum-tungsten alloy for ion implanters.

[0034] Comparative Example 2 This comparative example provides a method for preparing a molybdenum-tungsten alloy for an ion implanter, the method comprising: (1) Weigh D according to the proportion. 50 90 parts of 3μm Mo powder, D 50 10 parts of W powder with a particle size of 3μm; (2) Add Mo powder and W powder together into a V-type mixer and mix for 6 hours until the mixture is uniform to obtain a mixed powder; (3) The mixed powder in step (2) is cold isostatically pressed under a pressure of 200 MPa to obtain a compact; (4) The pressed billet obtained in step (3) is placed in a medium-frequency induction sintering furnace and sintered in a hydrogen atmosphere. First, the temperature is raised to 700°C at a heating rate of 6°C / min and held for 2 hours. Then, the temperature is raised to 1800°C at a heating rate of 4°C / min and held for 6 hours. Finally, the temperature is raised to 2300°C at a heating rate of 2°C / min and held for 6 hours. The billet is then cooled in the furnace to obtain a molybdenum-tungsten alloy for ion implanters.

[0035] The molybdenum-tungsten alloys prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to ablation performance tests. Plasma ablation experiments were selected to examine the ablation resistance of the materials. The ablation test method followed the requirements of GJB323A-96 standard. The working parameters were optimized through experiments to obtain a stable plasma flow. An infrared thermometer was used to capture the temperature of the test sample surface, and the ablation temperature was indirectly controlled by adjusting the distance. The ablation parameters were: ablation temperature of 2000℃, ablation angle perpendicular to the sample surface, ablation distance of 50mm, and ablation time of 60s. The mass loss of the material before and after ablation was measured to calculate the mass ablation rate of the sample. Detailed test results are shown in Table 1.

[0036] Table 1 Ablation rate of different samples ; As can be seen from Examples 1, 2, and Comparative Example 2, the present invention can significantly improve the ablation resistance of molybdenum-tungsten alloys by adding HfC powder and ZrB2 powder. As can be seen from Examples 2 and Comparative Example 1, the "separate coating + mixing" process of the present invention can better utilize the ablation resistance of HfC powder and ZrB2 powder.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a molybdenum-tungsten alloy for an ion implanter, characterized in that: The preparation method includes: (1) Weigh 85-90 parts of Mo powder and 10-15 parts of W powder according to the ratio, weigh 0.5%~1% of HfC powder of total mass of Mo powder and W powder, and 2%~3% of ZrB2 powder of total mass of Mo powder and W powder; (2) Mix Mo powder and HfC powder evenly to obtain Mo powder coated with HfC powder. Mix W powder and ZrB2 powder evenly to obtain W powder coated with ZrB2 powder. Mix the Mo powder coated with HfC powder and the W powder coated with ZrB2 powder evenly to obtain mixed powder. (3) The mixed powder from step (2) is cold isostatically pressed to obtain a compact; (4) The pressed blank obtained in step (3) is dried and sintered to obtain a molybdenum-tungsten alloy for ion implantation machine.

2. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 1, characterized in that: The particle size D of the Mo powder and W powder 50 It is 3-5μm.

3. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 1, characterized in that: The purity of the Mo powder and W powder is ≥99%.

4. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 1, characterized in that: The particle size D of the HfC powder and ZrB2 powder 50 The thickness is 0.5~1μm.

5. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 1, characterized in that: The mixing in step (2) is carried out in a V-type mixer, and the mixing time is 6-8 hours.

6. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 1, characterized in that: The pressure of the cold isostatic pressing in step (3) is 180~220MPa.

7. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 1, characterized in that: In step (4), the sintering equipment is a medium-frequency induction sintering furnace, and the sintering atmosphere is a hydrogen atmosphere.

8. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 1, characterized in that: In step (4), the sintering temperature is 2200~2400℃ and the sintering time is 4~6h.

9. The method for preparing a molybdenum-tungsten alloy for an ion implanter according to claim 8, characterized in that: In step (4), the sintering process involves first heating the temperature to 700-800℃ at a heating rate of 5-8℃ / min and holding it for 1-2 hours, then heating the temperature to 1700-1800℃ at a heating rate of 3-4℃ / min and holding it for 6-8 hours, and finally heating the temperature to 2200-2400℃ at a heating rate of 1-2℃ / min and holding it for 4-6 hours.

10. The molybdenum-tungsten alloy for ion implanters prepared by the method for preparing a molybdenum-tungsten alloy for ion implanters according to any one of claims 1 to 9.