CN105714253B - The preparation method of large scale, fine grain molybdenum tantalum alloy-sputtering targets material - Google Patents

Abstract

A method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target, including the steps of cold isostatic pressing by combining a steel mold and a rubber plate, sintering, leveling and shaping, and hot isostatic pressing , rolling steps, machining steps. The grain size of the produced target is less than 50 microns, and the grain size change is maintained within 20%, and the grains are uniformly distributed in the plane direction and thickness direction of the target; the relative density of the target is more than 97% ; Moreover, large-size sputtering targets with a length of about 2m and a width of about 1.3m can be produced.

Description

Preparation method of large-size, fine-grained molybdenum-tantalum alloy sputtering target

technical field

The invention relates to the technical field of targets, in particular to a method for preparing large-sized, fine-grained molybdenum-tantalum alloy sputtering targets.

Background technique

Sputtering is one of the main techniques for preparing thin film materials. The accelerated ions are used to bombard the solid surface, and the ions and solid surface atoms exchange momentum, so that the atoms on the solid surface leave the solid and deposit on the substrate surface. This process is called sputtering. The solid being bombarded is the source material for sputtering thin films, often called the target.

The film deposited by sputtering with the target has high density and good adhesion to the substrate. Sputtering thin film materials have been widely used in semiconductor integrated circuits, recording media, flat display and surface coating of workpieces. Therefore, the demand for sputtering targets, a functional material with high added value, is increasing year by year. In recent years, my country's electronic information industry has developed rapidly, and a large number of joint ventures or sole proprietorships have emerged in the production lines of integrated circuits, optical discs and displays. my country has gradually become one of the regions with the largest demand for thin film targets in the world. But so far, China still does not have a large professional company specializing in the production of target materials, and a large number of target materials are still imported from abroad. Especially for alloy targets, the alloy has high temperature and low plasticity, so it cannot be produced by rolling. When forming by powder metallurgy, the molybdenum powder is subjected to cold isostatic pressing, then sintered, rolled, machined, and then bound to the back plate. The sputtering target is bombarded during the sputtering coating process. At this time, due to the sudden release of the gas in the internal pores of the target, large-sized target particles or particles are splashed, or the film is bombarded by secondary electrons after film formation, resulting in particle splashing. Due to the lagging development of the domestic target material industry, a large part of the target material market in China is currently occupied by foreign companies. With the rapid development of high-tech industries such as microelectronics, China's target material market will expand day by day, which provides opportunities and challenges for the development of China's target material manufacturing industry.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a sputtering target material of large-sized, fine-grained molybdenum-tantalum alloy with fine grain and relative density >97%.

The technical solution adopted by the present invention to achieve the above object is: a method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target, comprising the following steps:

Step 1. After pretreatment, the molybdenum powder and tantalum powder are sieved respectively. After sieving, the Fischer particle size ratio of tantalum powder and molybdenum powder is 1.6:1. The sieved molybdenum powder and tantalum powder are 90~ 94: The mass ratio of 6~10 is ball milled and mixed for more than 16 hours to prepare molybdenum and tantalum mixed powder for later use;

Step 2. According to the target size of the required compact, weigh the mass or volume of the molybdenum-tantalum mixed powder required to form a compact, and make a cold isostatic pressing mold with the same volume as the molding cavity and the molybdenum-tantalum mixed powder , using a powder feeder to make the molybdenum-tantalum mixed powder freely fall into the forming cavity of the cold isostatic pressing mold. Blank, spare;

Step 3: Demoulding, take out the first sequence of compacts, put the first sequence of compacts in the furnace body, raise the temperature to 2150~2200°C at a heating rate of 30~40°C/min, and keep it at this temperature for 8~9h , naturally cool down to room temperature with the furnace, take out the green body, and set aside;

Step 4. After placing the green body in the leveling die for leveling, place the green body in the shaping die for shaping and set aside;

Step 5. After surface treatment, the green body is subjected to hot isostatic pressing treatment to obtain a second-order green body, which is ready for use; wherein, the hot isostatic pressing process is: pre-burning at 800~1000°C for 30 minutes, and then raising the temperature and pressure to 1450~ 1500℃, 180~200MPa, heat preservation and pressure holding for 1~3h;

Step 6: Rolling along the longitudinal direction of the second-order green body at 1400°C, and rolling along the transverse direction of the second-order green body at 1200°C when the primary deformation of the second-order green body is 20-60% , when the secondary deformation of the second-order green body is 70%, keep the second-order green body at 1250°C for 2 hours, and set aside;

Step 7: Machining the secondary green body to make its shape reach the target shape size, and connecting it with the back plate to make a molybdenum-tantalum alloy target.

Further, the pretreatment method in the first step is: annealing the molybdenum powder and the tantalum powder under vacuum condition for 2 hours, and the annealing temperature is 1300°C.

In the present invention, the cold isostatic pressing mold in step 2 includes a steel mold, a rubber plate laid on the opening of the steel mold, and a pressing plate laid on the rubber plate, wherein the steel mold, the rubber plate, and the pressing plate are passed through The bolts are connected, and there are sealing gaskets between the steel mold and the bolts, between the steel mold and the rubber plate, and there is a semicircular groove at the joint between the upper end of the steel mold and the rubber plate located inside the bolt, and the groove is embedded A rubber sealing ring is provided, and the pressure plate is provided with an injection hole for injecting a cold isostatic pressure medium between the pressure plate and the rubber plate.

Further, the inner chamfer at the upper end of the steel mold is rounded, the thickness of the rubber plate is 5-10mm, the thickness of the pressure plate is 10-15mm, and the diameter of the injection hole is 10mm.

Further, the surface treatment process of the green body in step five is: ball mill the molybdenum powder and tantalum powder to 100~200nm respectively, after mixing, disperse the mixture into a slurry with water, and spray the slurry onto the green body by thermal spraying The thickness of the coating on the surface of the green body is 100-300 microns. Surface treatment of the green body with nanocrystalline molybdenum powder and tantalum powder eliminates defects such as pores and cracks on the surface of the green body and improves the density of the final product.

Further, the hot isostatic pressing process in Step 5 is as follows: pre-calcine the surface-treated green body at 1000°C for 30 minutes, then raise the temperature and pressure to 1500°C and 200 MPa, and keep the temperature and pressure for 3 hours.

In the present invention, rolling in the cross direction is carried out after hot isostatic pressing, the vertical and horizontal structures are overlapped and staggered, and the grains are arranged more uniformly, which can effectively avoid defects caused by uneven force in each direction, and the cross rolling The direction of the crack is less synchronized with the rolling direction, and the effective length of the propagation path is long, which hinders the further extension of the crack.

Beneficial effects: 1. The present invention utilizes the combination of steel mold and rubber plate for cold isostatic pressing forming, injects cold isostatic pressing medium between the pressing plate and the rubber plate at a constant speed through the injection hole provided on the pressing plate, and the mold solves the sealing problem, It breaks through the boundary between steel mold and cold isostatic pressing, overcomes the defect of poor dimensional accuracy of traditional cold isostatic pressing compacts, not only can meet the requirements of traditional steel mold pressing products, but also can produce large workpieces.

2. After cold isostatic pressing, sintering is carried out, and the temperature is raised to 2150~2200℃ at a heating rate of 30~40℃/min, which can make the fluidity of the crystal grains the best, and it is not easy to form bubbles and segregation defects; the temperature and heating rate The matching of the green body avoids the problem of rolling cracks in the subsequent machining process of the green body; moreover, it can be confirmed through experiments that exceeding this temperature range will easily lead to chapped edges of the green body. Before the green body is sintered, nanocrystalline molybdenum powder and tantalum powder are thermally sprayed onto the surface, and distributed in a dispersed state, which improves the crack resistance of the product; the invention adopts cold isostatic pressing, sintering and hot isostatic pressing to treat phase The molybdenum-tantalum powder is processed in a combined way, so that the dislocation density inside the product is high, and the dislocations intersect each other to form cut steps, which improves the strength and hardness of the product. The grain size of the produced target is less than 50 microns, and the grain size variation is maintained within 20%, and the grains are uniformly distributed in the direction of the plane and thickness of the target; the relative density of the target is more than 97% ; Moreover, large-size sputtering targets with a length of about 2m and a width of about 1.3m can be produced.

3. The present invention uses cold isostatic pressing and sintering before hot isostatic pressing, which helps the diffusion and flow of molybdenum and tantalum powder particles in the sintering process, shortens the sintering cycle, and can effectively inhibit the target The growth of the grain size in the material. The sintered green body is subjected to hot isostatic pressing treatment, and the target is not easy to be reduced because gas such as Ar is used as a pressure medium for pressure sintering at high temperature. The hot isostatic pressing process of the present invention does not need to use a sheath, and a uniform and isotropic microstructure has been obtained after pre-processing. After hot isostatic pressing and rolling, the pores and defects inside the billet are compacted and eliminated. The internal pores are eliminated, and the grains are uniform, the isotropy is good, and the relative density after rolling is close to more than 99% of the theoretical value. At the same time, hot isostatic pressing makes the fibrous structure of the green body formed by cold isostatic pressing break again and recrystallize, avoiding the occurrence of tissue delamination, uneven grain distribution and uneven grain size, and the obtained structure Uniform and fine, the grain size is less than 50 microns.

Description of drawings

Fig. 1 is the cold isostatic pressing die among the present invention.

Reference signs: 1, steel mold, 2, rubber plate, 3, pressing plate, 4, bolt, 5, groove, 6, injection hole.

detailed description

The present invention will be further described below in conjunction with specific examples, so that those skilled in the art can better understand the present invention and implement it, but the given examples are not intended to limit the present invention.

The method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target comprises the following steps: step 1, pretreating molybdenum powder and tantalum powder and then sieving respectively, the Fischer particle size of tantalum powder and molybdenum powder after sieving The ratio is 1.6:1, and the sieved molybdenum powder and tantalum powder are ball milled and mixed according to the mass ratio of 90~94:6~10 for more than 16 hours, and the molybdenum-tantalum mixed powder is prepared for use;

Step 2. According to the target size of the required compact, weigh the mass or volume of the molybdenum-tantalum mixed powder required to form a compact, and make a cold isostatic pressing mold with the same volume as the molding cavity and the molybdenum-tantalum mixed powder , using a powder feeder to make the molybdenum-tantalum mixed powder freely fall into the forming cavity of the cold isostatic pressing mold. Blank, spare;

Step 3: Demoulding, take out the first sequence of compacts, put the first sequence of compacts in the furnace body, raise the temperature to 2150~2200°C at a heating rate of 30~40°C/min, and keep it at this temperature for 8~9h , naturally cool down to room temperature with the furnace, take out the green body, and set aside;

Step 4. After placing the green body in the leveling die for leveling, place the green body in the shaping die for shaping and set aside;

Step 5. After surface treatment, the green body is subjected to hot isostatic pressing treatment to obtain a second-order green body, which is ready for use; wherein, the hot isostatic pressing process is: pre-burning at 800~1000°C for 30 minutes, and then raising the temperature and pressure to 1450~ 1500℃, 180~200MPa, heat preservation and pressure holding for 1~3h;

Step 6: Rolling along the longitudinal direction of the second-order green body at 1400°C, and rolling along the transverse direction of the second-order green body at 1200°C when the primary deformation of the second-order green body is 20-60% , when the secondary deformation of the second-order green body is 70%, keep the second-order green body at 1250°C for 2 hours, and set aside;

Step 7: Machining the secondary green body to make its shape reach the target shape size, and connecting it with the back plate to make a molybdenum-tantalum alloy target.

Wherein, the cold isostatic pressing mold in step 2 is as shown in Figure 1, comprises steel mold 1, the rubber sheet 2 that is laid on the opening of steel mold 1 and the pressing plate 3 that is tiled on rubber sheet 2, wherein, steel mold 1 , the rubber plate 2 and the pressure plate 3 are connected by bolts 4, and there are sealing gaskets between the steel mold 1 and the bolts 4, between the steel mold 1 and the rubber plate 2, and the upper end of the steel mold 1 located inside the bolt 4 The connecting part with the rubber plate 2 is provided with a semicircular groove 5, and the groove 5 is embedded with a rubber sealing ring. Injection hole 6 for pressure medium; the inner knuckle at the upper end of steel mold 1 is rounded, the thickness of rubber plate 2 is 5-10mm, the thickness of pressure plate 3 is 10-15mm, and the diameter of injection hole 6 is 10mm.

Example 1

The preparation method of large-size, fine-grained molybdenum-tantalum alloy sputtering target material comprises the following steps: step 1, pretreating molybdenum powder and tantalum powder and then sieving respectively, the Fischer particle size of tantalum powder after sieving is 9.6 microns , the Fischer particle size of the molybdenum powder is 6 microns, and the molybdenum powder and tantalum powder after sieving are ball-milled and mixed according to a mass ratio of 94:6 for 16 hours to obtain a molybdenum-tantalum mixed powder for subsequent use; wherein, the pretreatment method is: Molybdenum powder and tantalum powder were annealed under vacuum condition for 2h, and the annealing temperature was 1300°C.

Step 2. According to the target size of the required compact, weigh the mass or volume of the molybdenum-tantalum mixed powder required to form a compact, and make a cold isostatic pressing mold with the same volume as the molding cavity and the molybdenum-tantalum mixed powder , using a powder feeder to make the molybdenum-tantalum mixed powder freely fall into the forming cavity of the cold isostatic pressing mold. The cold isostatic pressing process conditions are: hold the pressure at 200MPa for 5 minutes; obtain a first-order compact after processing, and set aside;

Step 3: Demoulding, take out the first sequence of compacts, put the first sequence of compacts in the furnace body, raise the temperature to 2165°C at a heating rate of 40°C/min, and keep it at this temperature for 8.5h, then cool naturally with the furnace to room temperature, take out the green body, and set aside;

Step 4. After placing the green body in the leveling die for leveling, place the green body in the shaping die for shaping and set aside;

Step 5. After surface treatment, the green body is subjected to hot isostatic pressing treatment to obtain a second-order green body for future use; wherein, the hot isostatic pressing process is: pre-burning at 1000°C for 30 minutes, and then raising the temperature and pressure to 1450°C and 190MPa , heat preservation and pressure holding for 3 hours; among them, the surface treatment process of the green body is as follows: ball mill the molybdenum powder and tantalum powder to 100nm respectively, after mixing, disperse the mixture into a slurry with water, and spray the slurry on the surface of the green body by thermal spraying , the thickness of the coating on the surface of the green body is 100 microns.

Step 6. Rolling along the longitudinal direction of the second-order green body at 1400°C, when the primary deformation of the second-order green body is 60%, rolling along the transverse direction of the second-order green body at 1200°C, when When the secondary deformation of the second-order green body is 70%, keep the second-order green body at 1250°C for 2 hours, and set aside;

Step 7: Machining the secondary green body to make its shape reach the target shape size, and connecting it with the back plate to make a molybdenum-tantalum alloy target.

Example 2

The preparation method of large-size, fine-grained molybdenum-tantalum alloy sputtering target material comprises the following steps: step 1, pretreating molybdenum powder and tantalum powder and then sieving respectively, the Fischer particle size of tantalum powder after sieving is 16 microns , the Fischer particle size of the molybdenum powder is 10 microns, and the molybdenum powder and tantalum powder after sieving are ball-milled and mixed according to the mass ratio of 90:10 for 20 hours, and the molybdenum-tantalum mixed powder is prepared for subsequent use; the pretreatment method is: Molybdenum powder and tantalum powder were annealed under vacuum condition for 2h, and the annealing temperature was 1300°C.

Step 2. According to the target size of the required compact, weigh the mass or volume of the molybdenum-tantalum mixed powder required to form a compact, and make a cold isostatic pressing mold with the same volume as the molding cavity and the molybdenum-tantalum mixed powder , use the powder feeder to make the molybdenum-tantalum mixed powder freely fall into the forming cavity of the cold isostatic pressing mold, apply glycerin or alcohol on the outer wall of the forming cavity, and the cold isostatic pressing process conditions are: hold the pressure at 170MPa for 8 minutes; Processed to obtain a sequence of green compacts, ready for use;

Step 3: Demoulding, take out the first sequence of compacts, place the first sequence of compacts in the furnace body, raise the temperature to 2150°C at a heating rate of 36°C/min, and keep it at this temperature for 9 hours, then cool naturally with the furnace to room temperature, take out the green body, set aside;

Step 4. After placing the green body in the leveling die for leveling, place the green body in the shaping die for shaping and set aside;

Step 5. Put the green body after surface treatment at 1000°C for 30 minutes, then raise the temperature and pressure to 1500°C and 200MPa, keep the temperature and pressure for 3 hours, and obtain the second-order green body for use; the surface treatment process of the green body The method is: ball mill molybdenum powder and tantalum powder to 200nm respectively, after mixing, disperse the mixture into a slurry with water, spray the slurry on the surface of the green body by thermal spraying, and the coating thickness on the surface of the green body is 200 microns.

Step 6. Rolling along the longitudinal direction of the second-order green body at 1400°C, when the primary deformation of the second-order green body is 20%, rolling along the transverse direction of the second-order green body at 1200°C, when When the secondary deformation of the second-order green body is 70%, keep the second-order green body at 1250°C for 2 hours, and set aside;

Step 7: Machining the secondary green body to make its shape reach the target shape size, and connecting it with the back plate to make a molybdenum-tantalum alloy target.

Example 3

The preparation method of large-size, fine-grained molybdenum-tantalum alloy sputtering target material comprises the following steps: step 1, pretreating molybdenum powder and tantalum powder and then sieving respectively, the Fischer grain size of tantalum powder after sieving is 24 microns , the Fisherman's particle size of the molybdenum powder is 15 microns, the molybdenum powder and the tantalum powder after the sieving are ball milled and mixed according to the mass ratio of 92:8 for 25 hours, and the molybdenum-tantalum mixed powder is prepared for subsequent use; wherein the pretreatment method is: Molybdenum powder and tantalum powder were annealed under vacuum condition for 2h, and the annealing temperature was 1300°C.

Step 2. According to the target size of the required compact, weigh the mass or volume of the molybdenum-tantalum mixed powder required to form a compact, and make a cold isostatic pressing mold with the same volume as the molding cavity and the molybdenum-tantalum mixed powder , using a powder feeder to make the molybdenum-tantalum mixed powder freely fall into the forming cavity of the cold isostatic pressing mold. The cold isostatic pressing process conditions are: keep the pressure at 150MPa for 10 minutes; after processing, obtain a sequence of green compacts for use;

Step 3: Demoulding, take out the first sequence of compacts, put the first sequence of compacts in the furnace body, raise the temperature to 2200°C at a heating rate of 30°C/min, and keep it at this temperature for 8 hours, then cool naturally with the furnace to room temperature, take out the green body, set aside;

Step 4. After placing the green body in the leveling die for leveling, place the green body in the shaping die for shaping and set aside;

Step 5. After surface treatment, the green body is subjected to hot isostatic pressing treatment to obtain a second-order green body for future use; wherein, the hot isostatic pressing process is: pre-burning at 800°C for 30 minutes, and then raising the temperature and pressure to 1470°C and 180MPa , heat preservation and pressure holding for 1h; the surface treatment process of the green body is as follows: ball mill the molybdenum powder and tantalum powder to 160nm respectively, after mixing, disperse the mixture into a slurry with water, and spray the slurry on the surface of the green body by thermal spraying , the thickness of the coating on the surface of the green body is 300 microns.

Step 6: Rolling along the longitudinal direction of the second-order green body at 1400°C, when the primary deformation of the second-order green body is 45%, rolling along the transverse direction of the second-order green body at 1200°C, when When the secondary deformation of the second-order green body is 70%, keep the second-order green body at 1250°C for 2 hours, and set aside;

Step 7: Machining the secondary green body to make its shape reach the target shape size, and connecting it with the back plate to make a molybdenum-tantalum alloy target.

The relative density of the sputtering target prepared by the present invention is relatively high. In the process of use, the target surface of the target is not easy to generate nodules during the sputtering process, and the arcing phenomenon is effectively suppressed, and the occurrence of impurity defects in the formed film is reduced. probability. Moreover, there will not be a large number of voids in the target of the high-density target material, thereby ensuring the purity and composition uniformity of the film during the sputtering process.

Claims (6)

1. The preparation method of large-scale, fine-grained molybdenum-tantalum alloy sputtering target, is characterized in that, comprises the following steps: Step 1. After pretreatment, the molybdenum powder and tantalum powder are sieved respectively. After sieving, the Fischer particle size ratio of tantalum powder and molybdenum powder is 1.6:1. The sieved molybdenum powder and tantalum powder are 90~ 94: The mass ratio of 6~10 is ball milled and mixed for more than 16 hours to prepare molybdenum and tantalum mixed powder for later use; Step 2. According to the target size of the required compact, weigh the mass or volume of the molybdenum-tantalum mixed powder required to form a compact, and make a cold isostatic pressing mold with the same volume as the molding cavity and the molybdenum-tantalum mixed powder , using a powder feeder to make the molybdenum-tantalum mixed powder freely fall into the forming cavity of the cold isostatic pressing mold. Blank, spare; Step 3: Demoulding, take out the first sequence of compacts, put the first sequence of compacts in the furnace body, raise the temperature to 2150~2200°C at a heating rate of 30~40°C/min, and keep it at this temperature for 8~9h , naturally cool down to room temperature with the furnace, take out the green body, and set aside; Step 4. After placing the green body in the leveling die for leveling, place the green body in the shaping die for shaping and set aside; Step 5. After surface treatment, the green body is subjected to hot isostatic pressing treatment to obtain a second-order green body, which is ready for use; wherein, the hot isostatic pressing process is: pre-burning at 800~1000°C for 30 minutes, and then raising the temperature and pressure to 1450~ 1500℃, 180~200MPa, heat preservation and pressure holding for 1~3h; Step 6: Rolling along the longitudinal direction of the second-order green body at 1400°C, and rolling along the transverse direction of the second-order green body at 1200°C when the primary deformation of the second-order green body is 20-60% , when the secondary deformation of the second-order green body is 70%, keep the second-order green body at 1250°C for 2 hours, and set aside; Step 7: Machining the secondary green body to make its shape reach the target shape size, and connecting it with the back plate to make a molybdenum-tantalum alloy target. 2. The method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target according to claim 1, characterized in that: the pretreatment method in step 1 is: annealing molybdenum powder and tantalum powder under vacuum conditions Treat for 2 hours, and the annealing temperature is 1300°C. 3. The method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target according to claim 1, characterized in that: the cold isostatic pressing mold in step 2 includes a steel mold (1), laid on the steel mold ( 1) The rubber plate (2) at the opening and the pressure plate (3) laid flat on the rubber plate (2), wherein the steel mold (1), the rubber plate (2) and the pressure plate (3) are connected by bolts (4) connection, and there are sealing gaskets between the steel mold (1) and the bolt (4), between the steel mold (1) and the rubber plate (2), and the steel mold (1) located inside the bolt (4) A semicircular groove (5) is provided at the connection part between the upper end and the rubber plate (2), and a rubber sealing ring is embedded in the groove (5). ) and the rubber plate (2) into the injection hole (6) for injecting the cold isostatic medium. 4. The method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target according to claim 3, characterized in that: the inner chamfer at the upper end of the steel mold (1) is rounded, and the thickness of the rubber plate (2) is 5-10mm, the thickness of the pressure plate (3) is 10-15mm, and the aperture of the injection hole (6) is 10mm. 5. The method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target according to claim 1, characterized in that: the process of surface treatment of the green body in step 5 is as follows: respectively ball milling molybdenum powder and tantalum powder to 100~200nm. After mixing, the mixture is dispersed with water to form a slurry, and the slurry is sprayed onto the surface of the body by thermal spraying. The thickness of the coating on the surface of the body is 100~300 microns. 6. The method for preparing a large-size, fine-grained molybdenum-tantalum alloy sputtering target according to claim 1, characterized in that: the hot isostatic pressing process in step 5 is: placing the surface-treated green body at 1000 Pre-fire at ℃ for 30min, then raise the temperature and pressure to 1500℃ and 200MPa, keep the temperature and hold the pressure for 3h.