Method for preparing high-performance tantalum sputtering target material through low-temperature asymmetrical rolling

Abstract

The invention discloses a method for preparing a high-performance tantalum sputtering target material through low-temperature asymmetrical rolling, which comprises the following steps: step 1, carrying out vacuum arc melting on a high-purity tantalum block to obtain a high-purity tantalum ingot; 2, the high-purity tantalum ingot is placed in liquid nitrogen to be soaked for the first time, one-pass low-temperature asymmetrical rolling is conducted after soaking is completed, and a first-pass tantalum target blank is obtained; 3, the tantalum target blank is placed in liquid nitrogen for secondary soaking, the soaked tantalum target blank rotates in the normal direction relative to one pass in the step 2, the front face and the back face of the tantalum target blank are turned over, secondary low-temperature asymmetrical rolling is conducted, and a second-pass tantalum target blank is obtained; step 4, repeating the steps 2-3 to obtain a tantalum sputtering target material sample; and 5, carrying out vacuum recrystallization annealing on the tantalum sputtering target material sample, and cooling to obtain the tantalum sputtering target material. According to the method for preparing the high-performance tantalum sputtering target material, the problems that a tantalum target blank prepared in the prior art is large in grain size and the texture gradient of the tantalum target material is large are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of sputtering target material preparation, and in particular relates to a method for preparing a high-performance tantalum sputtering target material by low-temperature asynchronous rolling. Background Art

[0002] With the development of semiconductor technology, the Al / Ti layer of metal interconnects has exposed shortcomings such as high contact resistance and solid-solid diffusion. Tantalum has unique physical and chemical properties, such as high melting point, high density, good ductility and corrosion resistance. Therefore, it is widely used in the electronic industry such as tantalum capacitors and sputtering targets. In semiconductor integrated circuits, tantalum is considered to be a good substitute for Al / Ti. As a barrier layer, it can effectively prevent Cu atoms from diffusing into the circuit substrate Si. The tantalum barrier layer is a thin film deposited by sputtering technology. The microstructure of the high-purity tantalum target used for sputtering determines the performance of the film. During the sputtering process, the grain size and grain orientation of the tantalum target will affect the sputtering rate and the uniformity of the sputtered film. The smaller the grain size, the faster the sputtering rate. From the perspective of the effect of grain orientation on the sputtering rate, {110} is the fastest, {100} is in the middle, and {111} is the slowest. According to the atomic close-packed characteristics of tantalum, the slip system that is easiest to start is {110} <111> , making it easy for tantalum materials to form {111} texture. Too high a {111} texture ratio will lead to a decrease in the sputtering rate of the tantalum target. For large-sized tantalum targets, uneven texture components are often produced due to the uneven mechanical deformation of the target blank inside and outside during processing. In order to obtain uniform structure and texture as well as fine grains, a Chinese invention patent with a publication date of September 9, 2022 and publication number CN115029668A: A method for preparing high-performance tantalum sputtering targets by stacking, a high-purity tantalum sputtering target was prepared by stacking, and the high-purity tantalum target prepared by this method has a fine and uniform microstructure, and the {111} content on the sputtering surface is ≤50%. However, this method has high requirements on equipment and requires special rolling equipment and auxiliary facilities. The Chinese invention patent with publication date of September 2, 2022 and publication number CN114990502A: A method for preparing a high-performance tantalum target blank, comprising: (1) providing a tantalum ingot, upsetting, and cutting to obtain a primary tantalum target blank; (2) forging and drawing, annealing (1050°C) to obtain an intermediate tantalum target blank; (3) first cold rolling (75%), annealing (1000°C), second cold rolling (60%), annealing (1000°C) to obtain a final tantalum target blank. The tantalum target blank prepared by this method has a larger grain size. How to refine the grain size and weaken the texture gradient generated by rolling while increasing the {110} orientation content as much as possible is the focus of the present invention. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling, which solves the problems of large grain size of the tantalum target blank prepared by the prior art and large texture gradient of the tantalum target.

[0004] The technical solution adopted by the present invention is a method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling, comprising the following steps: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; Step 2, placing the high-purity tantalum ingot in liquid nitrogen for a soaking, and after the soaking is completed, placing it between two rollers for a low-temperature asynchronous rolling to obtain a first-pass tantalum target blank; Step 3, placing the tantalum target blank in liquid nitrogen for a second soaking, rotating the soaked tantalum target blank along the normal direction relative to the first pass in step 2, and turning over the front and back sides of the tantalum target blank, performing two passes of low-temperature asynchronous rolling, and obtaining a second pass of tantalum target blank; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; Step 5: Perform vacuum recrystallization annealing on the tantalum sputtering target sample, and then cool it to obtain a tantalum sputtering target.

[0005] The present invention is also characterized in that: The purity of the high-purity tantalum block in step 1 is not less than 99.95%.

[0006] In step 1, the diameter of the high-purity tantalum ingot is 40-50 mm, and the thickness of the high-purity tantalum ingot is 8-10 mm.

[0007] The soaking time in step 2 is 18-20 minutes, and the rolling speed ratio of the two rollers in step 2 is (1-1.2):1.

[0008] The time of the secondary immersion in step 3 is 5-10 minutes, and the angle of rotation in step 3 is 120°-135°.

[0009] The specific process of step 4 is: repeating steps 2 and 3, performing a total of sixteen low-temperature asynchronous rolling passes to obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%.

[0010] The annealing temperature in step 5 is 1100-1200°C.

[0011] The annealing holding time in step 5 is 0.5-1h.

[0012] The beneficial effects of the present invention are: The invention provides a method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling. The prepared high-purity tantalum sputtering target has high microstructure uniformity and fine grains, and can meet the requirements of magnetron sputtering target. The high-purity tantalum target is prepared by the low-temperature asynchronous rolling method. By rotating along the normal direction and flipping the front and back surfaces in each pass, the occurrence of grain orientation is reduced, the texture gradient of the tantalum target is weakened, the {111} orientation of the sputtering surface is reduced to less than 20%, and the {110} orientation is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the operation of the method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to the present invention; Figure 2 It is a schematic diagram of the turning of the tantalum target during rolling of the present invention; Figure 3 is a longitudinal cross-sectional orientation distribution diagram of the tantalum target material after low-temperature asynchronous rolling in Example 3 of the present invention; Figure 4 is a longitudinal cross-sectional orientation distribution diagram of the tantalum target material after low-temperature synchronous rolling in Example 4 of the present invention; Figure 5 is a longitudinal cross-sectional orientation distribution diagram of the tantalum target material after asynchronous rolling at room temperature in Example 5 of the present invention; Figure 6 This is the longitudinal cross-section orientation distribution diagram of the tantalum target material after room temperature synchronous rolling in Example 6 of the present invention. DETAILED DESCRIPTION

[0014] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling proposed by the present invention comprises the following steps: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; The purity of high-purity tantalum block is not less than 99.95%; the diameter of high-purity tantalum ingot is 40-50 mm, and the thickness of high-purity tantalum ingot is 8-10 mm; Step 2: Place the high-purity tantalum ingot in liquid nitrogen for a soak. Figure 1 As shown, after the soaking is completed, the target blank is placed between two rollers for a low-temperature asynchronous rolling to obtain the first tantalum target blank; The soaking time is 18-20 minutes, and the rolling speed ratio of the two rollers is (1-1.2): 1; Step 3: Place the tantalum target blank in liquid nitrogen for secondary immersion, such as Figure 2 As shown, the soaked tantalum target blank is rotated along the normal direction relative to the first pass in step 2, and the front and back sides of the tantalum target blank are turned over, and two passes of low-temperature asynchronous rolling are performed to obtain the second pass tantalum target blank; The secondary immersion time is 5-10 minutes, and the rotation angle is 120°-135°; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; The specific process is: repeat step 2-step 3, perform low-temperature asynchronous rolling for a total of 16 times, and obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%; Step 5, performing vacuum recrystallization annealing on the tantalum sputtering target sample, and then cooling it to obtain a tantalum sputtering target; The annealing temperature is 1100-1200°C; the annealing holding time is 0.5-1h.

[0016] The prepared high-purity tantalum sputtering target has high microstructure uniformity and fine grains, which can meet the requirements of magnetron sputtering target materials. The high-purity tantalum target is prepared by low-temperature asynchronous rolling method. The occurrence of grain orientation is reduced and the texture gradient of the tantalum target is weakened by rotating along the normal direction and flipping the front and back surfaces in each pass. The {111} orientation of the sputtering surface reaches less than 20%, and the {110} orientation increases.

[0017] Example 1 The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling proposed in this embodiment comprises the following steps: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; Step 2: Place the high-purity tantalum ingot in liquid nitrogen for a soak. Figure 1 As shown, after the soaking is completed, the target blank is placed between two rollers for a low-temperature asynchronous rolling to obtain the first tantalum target blank; Step 3: Place the tantalum target blank in liquid nitrogen for secondary immersion, such as Figure 2 As shown, the soaked tantalum target blank is rotated along the normal direction relative to the first pass in step 2, and the front and back sides of the tantalum target blank are turned over, and two passes of low-temperature asynchronous rolling are performed to obtain the second pass tantalum target blank; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; Step 5: Perform vacuum recrystallization annealing on the tantalum sputtering target sample, and then cool it to obtain a tantalum sputtering target.

[0018] Example 2 The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling proposed in this embodiment comprises the following steps: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; The purity of high-purity tantalum blocks is not less than 99.95%; The diameter of the high purity tantalum ingot is 40-50 mm, and the thickness of the high purity tantalum ingot is 8-10 mm; Step 2: Place the high-purity tantalum ingot in liquid nitrogen for a soak. Figure 1 As shown, after the soaking is completed, the target blank is placed between two rollers for a low-temperature asynchronous rolling to obtain the first tantalum target blank; The soaking time is 18-20 minutes, and the rolling speed ratio of the two rollers is (1-1.2): 1; Step 3: Place the tantalum target blank in liquid nitrogen for secondary immersion, such as Figure 2 As shown, the soaked tantalum target blank is rotated along the normal direction relative to the first pass in step 2, and the front and back sides of the tantalum target blank are turned over, and two passes of low-temperature asynchronous rolling are performed to obtain the second pass tantalum target blank; The secondary immersion time is 5-10 minutes, and the rotation angle is 120°-135°; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; The specific process is: repeat step 2-step 3, perform low-temperature asynchronous rolling for a total of 16 times, and obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%; Step 5, performing vacuum recrystallization annealing on the tantalum sputtering target sample, and then cooling it to obtain a tantalum sputtering target; The annealing temperature is 1100-1200°C; The annealing holding time is 0.5-1h.

[0019] Example 3 The method for preparing high-performance tantalum sputtering target by low-temperature asynchronous rolling proposed in this embodiment is as follows: Figure 1 As shown, the following steps are included: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; The purity of high-purity tantalum blocks is not less than 99.95%; The diameter of the high-purity tantalum ingot is 40 mm, and the thickness of the high-purity tantalum ingot is 8 mm; Step 2: Place the high-purity tantalum ingot in liquid nitrogen for a soak. Figure 1 As shown, after the soaking is completed, the target blank is placed between two rollers for a low-temperature asynchronous rolling to obtain the first tantalum target blank; The soaking time is 20 minutes, and the rolling speed ratio of the two rollers is 1.2:1; Step 3: Place the tantalum target blank in liquid nitrogen for secondary immersion, such as Figure 2 As shown, the soaked tantalum target blank is rotated along the normal direction relative to the first pass in step 2, and the front and back sides of the tantalum target blank are turned over, and two passes of low-temperature asynchronous rolling are performed to obtain the second pass tantalum target blank; The secondary immersion time was 5 min, and the rotation angle was 135°; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; The specific process is: repeat step 2-step 3, perform low-temperature asynchronous rolling for a total of 16 times, and obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%; Step 5: vacuum recrystallization annealing is performed on the tantalum sputtering target sample, followed by cooling to obtain a tantalum sputtering target, such as Figure 3 As shown; The annealing temperature is 1200°C; The annealing holding time is 1h; The results are shown in Table 1. It can be seen that the grain size is significantly refined, with an average grain size of 65.01 μm, a {111} content of 6.45% on the sputtered surface, and a {110} content of 27.7%.

[0020] Example 4 The method for preparing high-performance tantalum sputtering target by low-temperature asynchronous rolling proposed in this embodiment is as follows: Figure 1 As shown, the following steps are included: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; The purity of high-purity tantalum blocks is not less than 99.95%; The diameter of the high-purity tantalum ingot is 45 mm, and the thickness of the high-purity tantalum ingot is 9 mm; Step 2: Place the high-purity tantalum ingot in liquid nitrogen for a soak. Figure 1 As shown, after the soaking is completed, the target blank is placed between two rollers for a low-temperature synchronous rolling to obtain the first tantalum target blank; The soaking time is 20 min, and the rolling speed ratio of the two rollers is 1:1; Step 3: Place the tantalum target blank in liquid nitrogen for secondary immersion, such as Figure 2 As shown, the soaked tantalum target blank is rotated along the normal direction relative to the first pass in step 2, and the front and back sides of the tantalum target blank are turned over, and two passes of low-temperature synchronous rolling are performed to obtain the second pass tantalum target blank; The secondary immersion time was 5 min, and the rotation angle was 135°; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; The specific process is: repeat step 2-step 3, perform 16 passes of low-temperature synchronous rolling in total, and obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%; Step 5: vacuum recrystallization annealing is performed on the tantalum sputtering target sample, followed by cooling to obtain a tantalum sputtering target, such as Figure 4 As shown; The annealing temperature is 1200°C; The annealing holding time is 1h; The results are shown in Table 1. It can be seen that the grain size is refined, the average grain size is 74.83 μm, the {111} content of the sputtered surface is 43.6%, and the {110} content is 6.17%.

[0021] Example 5 The method for preparing high-performance tantalum sputtering target by low-temperature asynchronous rolling proposed in this embodiment is as follows: Figure 1 As shown, the following steps are included: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; The purity of high-purity tantalum blocks is not less than 99.95%; The diameter of the high-purity tantalum ingot is 50 mm, and the thickness of the high-purity tantalum ingot is 10 mm; Step 2: Figure 1 As shown, a high-purity tantalum ingot is placed between two rollers and subjected to asynchronous rolling at room temperature to obtain a first-pass tantalum target blank; The rolling speed ratio of the two rollers is 1.2:1; Step 3: Figure 2 As shown, the first pass tantalum target blank is rotated along the normal direction relative to the first pass in step 2, and the front and back sides of the tantalum target blank are turned over, and two passes of room temperature asynchronous rolling are performed to obtain the second pass tantalum target blank; The rotation angle is 135°; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; The specific process is: repeat step 2-step 3, perform asynchronous rolling at room temperature for a total of 16 times, and obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%; Step 5: vacuum recrystallization annealing is performed on the tantalum sputtering target sample, followed by cooling to obtain a tantalum sputtering target, such as Figure 5 As shown; The annealing temperature is 1200°C; The annealing holding time is 1h; The results are shown in Table 1 , where it can be seen that the average grain size is 75.74 μm, the {111} content of the sputtered surface is 10.2%, and the {110} content is 36.5%.

[0022] Example 6 The method for preparing high-performance tantalum sputtering target by low-temperature asynchronous rolling proposed in this embodiment is as follows: Figure 1 As shown, the following steps are included: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; The purity of high-purity tantalum blocks is not less than 99.95%; The diameter of the high-purity tantalum ingot is 50 mm, and the thickness of the high-purity tantalum ingot is 10 mm; Step 2: Figure 1 As shown, a high-purity tantalum ingot is placed between two rollers and synchronously rolled at room temperature to obtain a first-pass tantalum target blank; The rolling speed ratio of the two rollers is 1:1; Step 3: Figure 2 As shown, the tantalum target blank is rotated along the normal direction relative to the first pass in step 2, and the front and back sides of the tantalum target blank are turned over, and two passes of room temperature synchronous rolling are performed to obtain a second pass of tantalum target blank; The rotation angle is 135°; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; The specific process is: repeat step 2-step 3, perform synchronous rolling at room temperature for a total of 16 times, and obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%; Step 5: vacuum recrystallization annealing is performed on the tantalum sputtering target sample, followed by cooling to obtain a tantalum sputtering target, such as Figure 6 As shown; The annealing temperature is 1200°C; The annealing holding time is 1h; The results are shown in Table 1 , where it can be seen that the average grain size is 108.34 μm, the {111} content of the sputtered surface is 42.3%, and the {110} content is 12.5%.

[0023] Comparing the results of Example 3 with Examples 4-6, it can be seen that the grain size in Example 3 is finer, the {111} content of the sputtered surface is less and the {110} content is improved. Figure 3 This is the longitudinal section microstructure of Example 3. It can be seen that the overall structure of the target blank is evenly distributed. Figure 4 This is the longitudinal cross-section microstructure of Example 4. It can be seen that the overall structure of the target blank is unevenly distributed compared with Example 3, and there is a {111} texture. Figure 5 This is the microstructure of the longitudinal section of Example 5. It can be seen that the uniformity of the overall structure of the target blank is lower than that of Example 3, {111} and {110} textures exist, and the grain size is increased. Figure 6 This is the microstructure of the longitudinal section of Example 6. It can be seen that the overall structure of the target blank is extremely unevenly distributed compared with Example 3, with a strong {111} texture and coarse grain size.

[0024] In summary, it can be seen that the tantalum target prepared by the low-temperature asynchronous rolling method has a uniform overall microstructure distribution, a smaller grain size, and a correspondingly better sputtering performance, which can meet the use requirements of magnetron sputtering targets.

[0025] Table 1 Comparison of target material preparation results of Example 3 and Examples 4-6 of the present invention

Claims

1. A method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling, characterized in that: The following steps are involved: Step 1, vacuum arc melting a high-purity tantalum block to obtain a high-purity tantalum ingot; Step 2, placing the high-purity tantalum ingot in liquid nitrogen for a soaking, and after the soaking is completed, placing it between two rollers for a low-temperature asynchronous rolling to obtain a first-pass tantalum target blank; Step 3, placing the tantalum target blank in liquid nitrogen for a second soaking, rotating the soaked tantalum target blank along the normal direction relative to the first pass in step 2, and turning over the front and back sides of the tantalum target blank, performing two passes of low-temperature asynchronous rolling, and obtaining a second pass of tantalum target blank; Step 4, repeating steps 2-3 to obtain a tantalum sputtering target sample; Step 5: Perform vacuum recrystallization annealing on the tantalum sputtering target sample, and then cool it to obtain a tantalum sputtering target.

2. The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to claim 1, characterized in that: The purity of the high-purity tantalum block in step 1 is not less than 99.95%.

3. The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to claim 1, characterized in that: The diameter of the high-purity tantalum ingot in step 1 is 40-50 mm, and the thickness of the high-purity tantalum ingot is 8-10 mm.

4. The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to claim 1, characterized in that: The soaking time in step 2 is 18-20 minutes, and the rolling speed ratio of the two rollers in step 2 is (1-1.2):

1.

5. The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to claim 1, characterized in that: The time of the secondary immersion in step 3 is 5-10 minutes, and the angle of rotation in step 3 is 120°-135°.

6. The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to claim 1, characterized in that: The specific process of step 4 is: repeating steps 2 and 3, performing a total of sixteen low-temperature asynchronous rolling passes to obtain a tantalum sputtering target sample, and the total deformation of the tantalum sputtering target sample is 80%.

7. The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to claim 1, characterized in that: The annealing temperature in step 5 is 1100-1200°C.

8. The method for preparing a high-performance tantalum sputtering target by low-temperature asynchronous rolling according to claim 1, characterized in that: The annealing holding time in step 5 is 0.5-1h.

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