Manufacturing method of high-density and high-purity WSix target material

Abstract

The invention discloses a manufacturing method of a high-density and high-purity WSix target material, relates to the technical field of powder metallurgy, and aims to solve the problems of insufficient purity and non-uniform structure in WSix target material manufacturing in the prior art. The method comprises the following steps; the method comprises the following steps: S1, preparing a high-purity W blocky material greater than or equal to 5N and a Si powdery material according to a weight ratio of 70.79: 29.21, then preparing a copper crucible with a middle channel at the bottom, arranging a high-pressure argon nozzle at the tail part of the middle channel, and then putting the materials into the crucible; and S2, then preparing a full-suspension type vacuum induction melting furnace, vacuumizing the interior of the full-suspension type vacuum induction melting furnace, and then putting the crucible into the full-suspension type vacuum induction melting furnace. The method has the advantage of improving the purity and density of the WSix target material.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, and more specifically, to a method for manufacturing a high-density, high-purity WSix target material. Background Technology

[0002] With its core advantages such as low resistance, high thermal stability, excellent filling capability and reliability, WSix has demonstrated significant application value in the semiconductor chip field, especially suitable for key links such as contact holes, gates and interconnects. At the same time, its role in advanced process nodes, high-power applications, high-performance computing and third-generation semiconductor fields will be further highlighted. In addition, the electromigration (EM) lifetime of tungsten silicon compounds is significantly better than that of pure aluminum or copper, enabling it to meet the requirements of high current density applications (such as power devices).

[0003] Currently, there are two main traditional methods for manufacturing WSix sputtering targets: The first approach involves directly mixing high-purity W powder (99.999%) with high-purity Si powder in the required atomic ratio, then placing the mixture into a graphite mold and sintering it in a high-temperature, high-pressure sintering furnace under vacuum conditions. Finally, the sintered WSix preform is machined into a sputtering target.

[0004] The second approach involves first preparing the WSix compound through vacuum melting. This involves placing 99.999% pure tungsten blocks, silicon blocks, or silicon powder into a graphite crucible, heating it to above 1400℃, and then vacuum melting it into the WSix compound. Next, the material is crushed using a ball mill, and powder meeting the particle size requirements is sieved through a screen. Then, hot isostatic pressing (HIP) is used for shaping and sintering. Under isotropic pressure (3-5 MPa), a cavity temperature of 1300-1400℃, and a holding time of 180 minutes, the WSix powder is sintered into a shape (density ≥ 98% of theoretical density). Finally, according to the dimensions of the sputtering machine's backplate, the high-hardness WSix preform is ground, ultrasonically cleaned, and then bound to the backplate for use in the sputtering machine.

[0005] However, the WSix target material for semiconductor chips has stringent requirements regarding material purity (higher than 5N), density (≥98% of theoretical density), and uniform distribution of W and Si atoms within the target's internal microstructure. Therefore, the two existing solutions have significant drawbacks: The problem with the first option: From the perspective of reaction kinetics, if W powder and Si powder do not react completely during sintering, they are prone to forming WSi2 compounds and excess segregated Si. This microstructure leads to the generation of a large number of particles during sputtering.

[0006] The melting points of W (melting point 3422℃) and Si (melting point 1414℃) are very different. To increase the sintering density, the temperature needs to be increased. However, excessively high temperatures will cause Si to soften and be extruded into the mixture under high pressure, resulting in uneven microstructure of WSix preforms and uneven distribution of W and Si components.

[0007] When hot isostatic pressing (HIP) is used for sintering, the isotropic pressure will cause excessive stress in the WSix preform, making it prone to breakage during processing or sputtering.

[0008] The problem with the second option: The crucible melting and ball milling steps in the powder making process require direct contact with the inner wall of the crucible, the ball mill jar, the metal balls, and the screen, which inevitably introduces impurities such as Fe, Cr, Ni, C, and Al, making it difficult to meet the 5N purity requirements for semiconductor chip production.

[0009] During the high-temperature smelting and powdering process, atmospheric gaseous impurities such as O and N are easily introduced, while semiconductor-grade WSix targets typically require an oxygen content of ≤500ppm, which is difficult to meet with this solution.

[0010] In view of this, we propose a method for manufacturing high-density, high-purity WSix targets. Summary of the Invention

[0011] The purpose of this invention is to provide a method for manufacturing high-density, high-purity WSix targets, which aims to solve the problems of insufficient purity and uneven structure in the manufacturing of WSix targets in the prior art.

[0012] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for manufacturing a high-density, high-purity WSix target material, the method comprising the following steps; S1. Prepare ≥5N high-purity W block material and Si powder material in a weight ratio of 70.79:29.21. Then prepare a copper crucible with a middle channel at the bottom and set a high-pressure argon nozzle at the end of the middle channel. Then put the material into the crucible. S2. Next, prepare a fully suspended vacuum induction melting furnace and evacuate the inside of the furnace to a vacuum. Then, place the crucible into the furnace and start it. The furnace heats and melts W block material and Si powder material through induction coils to make W+Si melt. The electromagnetic forces acting on the W+Si melt and the crucible by the induction coils are like-pairs and repel each other, causing the W+Si melt to suspend. The eddy currents generated by the induction coils will make the W+Si melt fully mixed. S3. Adjust the power value of the induction coil of the fully suspended vacuum induction melting furnace so that the electromagnetic force generated is less than the gravity of the W+Si melt. This allows the W+Si melt to pass through the middle channel at a uniform speed under the action of gravity. The high-pressure argon nozzle is opened in advance so that when the W+Si melt flows to the end of the channel, it is atomized into W+Si droplets by the high-pressure argon and rapidly cooled to form high-purity, uniformly sized non-equilibrium WSi powder, which is then collected through a vacuum collection tank. S4. WSix sputtering targets are formed using WSi powder.

[0013] Preferably, step S1 above also includes designing a water-cooling channel for the crucible to prevent the copper crucible from overheating and softening.

[0014] Preferably, in step S4 above, the specific steps for processing and forming the WSix sputtering target include filling WSi powder into a graphite mold, then placing it in a vacuum hot pressing sintering furnace, evacuating the vacuum hot pressing sintering furnace to a vacuum, and then sintering it through the vacuum hot pressing sintering furnace. After sintering is completed, the WSix target blank is cooled to obtain the WSix target blank, and then the WSix sputtering target is processed and formed by a mechanical grinding machine.

[0015] Preferably, in step S2 above, when evacuating the interior of the fully suspended vacuum induction melting furnace to a vacuum level, the interior of the fully suspended vacuum induction melting furnace is evacuated to an internal vacuum degree ≤10. -3 Pa, and when the fully suspended vacuum induction melting furnace melts W block materials and Si powder materials, its induction power is 280KW, the induction frequency is 8KHz, and the melting time is 20 minutes.

[0016] Preferably, the vacuum hot pressing sintering furnace heats the temperature to 1400°C at an average rate of 15°C / min and applies 450 tons of hydraulic pressure to maintain the temperature for 180 minutes.

[0017] Preferably, when evacuating the vacuum hot pressing sintering furnace to a vacuum level, the internal vacuum degree is ≤10. -3 Pa.

[0018] Preferably, when applying 450 tons of hydraulic pressure to the vacuum hot-press sintering furnace, a stepped pressurization method is used: 50 tons / min for 0-100 tons, 40 tons / min for 100-300 tons, and 25 tons / min for 300-450 tons.

[0019] Preferably, in step S3 above, the injection angle of the high-pressure argon nozzle when injecting high-pressure argon is 45°, and the distance between the high-pressure argon nozzle and the tail of the middle channel is 8-12mm.

[0020] Compared with the prior art, the beneficial effects of the present invention are: This invention uses high-purity W and Si raw materials with ≥5N purity and combines them with fully suspended vacuum induction melting technology to avoid direct contact contamination between the material and the crucible. At the same time, it uses electromagnetic force to achieve molten suspension and eddy current mixing, which solves the problem of insufficient purity caused by contact with the container in traditional manufacturing processes. Furthermore, the powder formed by atomization and cooling after the molten liquid is fully mixed has a uniform particle size, ensuring the uniformity and density of the target material structure from the source.

[0021] This invention utilizes non-equilibrium WSi powder for vacuum hot pressing sintering. Under high temperature and high pressure, the powder particles are tightly bonded, reducing internal porosity. Compared with ordinary sintering processes, this significantly improves the density of WSix target materials, meeting the requirements for high-density target materials.

[0022] The WSi powder formed by atomization in this invention has a uniform particle size, which reduces component segregation during subsequent sintering. Furthermore, it can be directly processed into shape by a mechanical grinding machine, which simplifies the target material manufacturing process, shortens the production cycle, and ensures the dimensional accuracy and surface quality of the finished target material. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] Example 1 like Figure 1 As shown, a method for manufacturing a high-density, high-purity WSix target material includes the following steps; S1. Prepare high-purity W block material (≥5N) and Si powder material in a weight ratio of 70.79:29.21. Then prepare a copper crucible with a central channel at the bottom and a high-pressure argon nozzle at the end of the central channel. Place the material into the crucible to ensure that the target material has extremely low impurity content with high-purity raw materials. The precise weight ratio ensures that W and Si form the target melt. The copper crucible, together with the central channel and argon nozzle, provides the structural basis for subsequent melting and atomization, ensuring the continuity of the process. S2. Next, prepare a fully suspended vacuum induction melting furnace and evacuate the inside of the furnace to a vacuum. Then, place the crucible into the furnace and start it. The furnace heats and melts W block material and Si powder material through induction coils to form W+Si melt. The electromagnetic forces acting on the W+Si melt and the crucible by the induction coils repel each other, causing the W+Si melt to suspend. The eddy currents generated by the induction coils will fully mix the W+Si melt, thus avoiding oxidation and gas contamination of the melt in a vacuum environment. Electromagnetic levitation causes the melt to detach from the crucible wall, preventing the crucible material from mixing in and causing a decrease in purity. Eddy current mixing ensures that the W and Si components are uniform, avoiding local component deviations that may affect the target material performance. S3. Adjust the power value of the induction coil of the fully suspended vacuum induction melting furnace so that the electromagnetic force generated is less than the gravity of the W+Si melt. This allows the W+Si melt to pass through the middle channel at a uniform speed under the action of gravity. The high-pressure argon nozzle is opened in advance so that when the W+Si melt flows to the end of the channel, it is atomized into W+Si droplets by the high-pressure argon and rapidly cooled to form high-purity, uniformly sized non-equilibrium WSi powder. The powder is then collected through a vacuum collection tank to ensure atomization stability by ensuring the melt flows at a uniform speed. The high-pressure argon breaks the melt into fine droplets, and the rapid cooling inhibits grain coarsening, forming fine-grained, uniformly composed powder. Vacuum collection avoids powder contamination. The non-equilibrium structure lays the foundation for subsequent high-density sintering. S4. WSix sputtering targets are formed by processing WSi powder to transform powder into dense targets through powder processing technology, which meets the requirements of sputtering coating for target density, purity and structural uniformity, and ensures stable coating quality.

[0026] Preferably, step S1 above also includes designing a water-cooling channel for the crucible to prevent the copper crucible from overheating and softening. This allows the water-cooling channel to remove heat from the crucible in a timely manner, preventing the copper crucible from softening and deforming during high-temperature smelting, ensuring the stability of the crucible structure, extending the service life of the equipment, and preventing the crucible from failing and contaminating the molten liquid.

[0027] Preferably, in step S4 above, the specific steps for processing and forming the WSix sputtering target include filling WSi powder into a graphite mold, placing it in a vacuum hot-pressing sintering furnace, evacuating the vacuum hot-pressing sintering furnace to a vacuum, and then sintering it through the vacuum hot-pressing sintering furnace. After sintering, the WSix target blank is cooled to obtain the WSix target blank, and then the WSix sputtering target is machined and formed by a mechanical grinding machine. This achieves the following: the graphite mold is resistant to high temperatures and does not react with the powder; vacuum hot-pressing sintering can eliminate powder porosity and improve the density of the target; and mechanical processing ensures the final dimensional accuracy and surface finish of the target, meeting the assembly and use requirements of the sputtering equipment.

[0028] Preferably, in step S2 above, when evacuating the interior of the fully suspended vacuum induction melting furnace to a vacuum level, the interior of the fully suspended vacuum induction melting furnace is evacuated to an internal vacuum degree ≤10. -3 Pa, and when the fully suspended vacuum induction melting furnace melts W block materials and Si powder materials, its induction power is 280KW, the induction frequency is 8KHz, and the melting time is 20 minutes, so as to minimize the contamination of the melt by gas impurities with high vacuum. The 280KW power and 8KHz frequency are adapted to the melting requirements of W and Si, ensuring that the materials are completely melted. The 20-minute melting time ensures that W and Si react fully and mix evenly, improving the consistency of powder composition.

[0029] Preferably, during sintering in the vacuum hot pressing sintering furnace, the temperature is increased to 1400°C at an average rate of 15°C / min, and hydraulic pressure of 450 tons is applied and maintained for 180 minutes. This slow heating reduces internal thermal stress in the powder and prevents cracking. The sintering temperature of 1400°C and the high pressure of 450 tons promote the diffusion and bonding of powder particles, eliminate porosity, and significantly improve the density of the target material. Maintaining the pressure for 180 minutes ensures sufficient sintering and makes the target material structure uniform and stable.

[0030] Preferably, when evacuating the vacuum hot pressing sintering furnace to a vacuum level, the internal vacuum degree is ≤10. -3 Pa is used to prevent powder oxidation during sintering in a high vacuum environment, while also avoiding the formation of pores inside the target material by gas, ensuring the purity and density of the target material, and ensuring that the quality is not affected by gas release during sputtering.

[0031] Preferably, when applying 450 tons of hydraulic pressure in the vacuum hot pressing sintering furnace, a stepped pressurization method is used: 50 tons / min for 0-100 tons, 40 tons / min for 100-300 tons, and 25 tons / min for 300-450 tons. This stepped pressurization method avoids cracking of the powder blank due to sudden pressure rise. The initial rapid pressurization initially compacts the powder, while the subsequent slow pressurization promotes tight particle bonding, ultimately achieving a high-density and uniform structure of the target material.

[0032] Preferably, in step S3 above, the high-pressure argon nozzle sprays high-pressure argon at an angle of 45°, and the distance between the high-pressure argon nozzle and the tail of the middle channel is 8-12mm. This allows the argon to act uniformly on the molten flow at a 45° spray angle, improving atomization efficiency and droplet uniformity. The 8-12mm distance ensures that the argon breaks the molten flow under optimal kinetic energy, avoiding uneven impact due to too close a distance or decreased atomization effect due to too far a distance, thus ensuring consistent powder particle size.

[0033] The embodiments disclosed in this invention are preferred embodiments, but are not limited thereto. Those skilled in the art can easily understand the spirit of this invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. A method for manufacturing a high-density, high-purity WSix target material, the method comprising: providing a tungsten target material; and forming a silicon layer on the tungsten target material. The method Comprise the following steps; S1, prepare ≥5N high-purity W block material and Si powder material in a weight ratio of 70.79:29.21, then prepare a copper crucible provided with an intermediate channel at the bottom, and a high-pressure argon gas nozzle at the tail of the intermediate channel, and then put the materials into the crucible; S2, then prepare a full-suspension vacuum induction melting furnace, and vacuumize the inside of the full-suspension vacuum induction melting furnace, then put the crucible into the full-suspension vacuum induction melting furnace, and then start the full-suspension vacuum induction melting furnace, which heats and melts the W block material and the Si powder material into W+Si molten liquid through an induction coil, and the electromagnetic force of the induction coil acting on the W+Si molten liquid and the crucible repels similarly, so that the W+Si molten liquid is suspended, and the eddy current generated by the induction coil causes the W+Si molten liquid to mix thoroughly; S3, adjust the power value of the induction coil of the full-suspension vacuum induction melting furnace so that the electromagnetic force generated is less than the gravity of the W+Si molten liquid, so that the W+Si molten liquid passes through the intermediate channel at a constant speed under the action of gravity, and the high-pressure argon gas nozzle is opened in advance, so that when the W+Si molten liquid flows to the tail of the channel, it is atomized into W+Si droplets by high-pressure argon gas and rapidly cooled to form high-purity, uniform-particle-size non-equilibrium WSi powder, which is then collected by a vacuum material collecting tank; S4, process the WSi powder into a WSix sputtering target.

2. The method of claim 1, wherein the method is characterized by: In the above step S1, a water cooling channel is designed for the crucible to prevent the copper crucible from overheating and softening.

3. The method of claim 1, wherein the method further comprises: In the above step S4, the specific steps of processing the WSix sputtering target include filling the WSi powder into a graphite mold, then placing it into a vacuum hot pressing sintering furnace, vacuumizing the vacuum hot pressing sintering furnace, then sintering it by the vacuum hot pressing sintering furnace, cooling to obtain a WSix target blank after sintering, and then processing it into a shaped WSix sputtering target by a mechanical grinding machine. ​ 4. The method of claim 1, wherein the method further comprises: In the step S2, the inside of the full-suspension vacuum induction melting furnace is pumped to an internal vacuum degree ≤ 10 -3 Pa, and the induction power is 280 KW, the induction frequency is 8 KHz, and the melting time is 20 minutes when the full-suspension vacuum induction melting furnace melts the W bulk material and the Si powdered material. ​ 5. The method of claim 3, wherein the method further comprises the step of: The vacuum hot pressing sintering furnace is heated at an average rate of 15℃ / min to 1400℃, and a hydraulic pressure of 450 tons is applied for 180 minutes. ​ 6. The method of producing a high-density, high-purity WSix target according to claim 3, wherein When the vacuum hot-press sintering furnace is evacuated, it is evacuated to an internal vacuum degree of ≤ 10 -3 Pa.

7. The method of producing a high-density, high-purity WSix target according to claim 5, wherein When the vacuum hot pressing sintering furnace applies a hydraulic pressure of 450 tons, a stepwise pressure is used, 0-100 tons are loaded at a rate of 50 tons / min, 100-300 tons are loaded at a rate of 40 tons / min, and 300-450 tons are loaded at a rate of 25 tons / min.

8. The method of producing a high-density, high-purity WSix target according to claim 1, wherein In the above step S3, the angle of the high-pressure argon gas nozzle when spraying high-pressure argon gas is 45°, and the distance between the high-pressure argon gas nozzle and the tail of the intermediate channel is 8-12mm.

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