High purity aluminum target blank and method of making same
By upsetting, drawing, forging, cross rolling, and stacking rolling processes on high-purity aluminum ingots, the grain and orientation problems of high-purity aluminum sputtering targets were solved, and the high-efficiency sputtering performance of high-purity aluminum sputtering targets was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PIONEER FILM MATERIALS (ANHUI) CO LTD
- Filing Date
- 2023-10-13
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies make it difficult to prepare high-purity aluminum targets, especially those with a purity of 5N5 or higher. It is also difficult to achieve a target structure with fine grains, uniform structure, and (100) plane orientation, which affects sputtering efficiency and stability.
High-purity aluminum ingots are forged using upsetting and drawing methods, followed by two rolling processes, including cross rolling and stacked rolling, combined with a heat treatment and a crystallization heat treatment to control grain size and orientation distribution.
A high-purity aluminum target blank with a grain size of <200μm and an (100) plane orientation content of >70% was prepared, which improved sputtering efficiency and sputtering stability and is suitable for the actual production of high-purity aluminum targets.
Smart Images
Figure CN117512530B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials processing technology, and particularly relates to a high-purity aluminum target blank and its preparation method. Background Technology
[0002] Physical vapor deposition (PVD) is the most critical technology in semiconductor chip manufacturing. PVD sputtering metal targets are one of the most important raw materials in semiconductor chip manufacturing and processing, with high-purity aluminum targets being the most widely used. According to the sputtering process principle, the finer the grains, the more uniform the composition and microstructure, the more concentrated the orientation, and the lower the surface roughness of the target, the better the quality of the thin film deposited on the substrate by the PVD method. Meanwhile, in recent years, the purity requirements for aluminum targets used in TFT displays for sputtering coating have reached 5N and above. This high purity leads to a high grain boundary migration rate during aluminum plate processing and annealing, making it difficult to obtain aluminum targets with fine grains and uniform microstructure.
[0003] To obtain fine and uniform grains in target materials, various studies have been conducted in the existing technology. Currently, the main method used both domestically and internationally is the low-temperature large plastic deformation method, which includes forging, rolling, and other channel extrusion as well as cumulative stacking rolling. Some processes, such as the equal channel extrusion method, are inherently difficult to produce large-size high-purity aluminum target materials due to their characteristics. Among them, CN109174996A uses hot rolling technology and obtains a high-purity aluminum plate with an average grain size of <200μm by changing the amount of pressing and stretching; CN107119244 obtains a fine-grained target material with (200) plane orientation by changing the cooling method between rolling passes through a single rolling method.
[0004] However, the existing technologies described above only target aluminum targets with a purity of 5N, without further research on aluminum targets with higher purity. Furthermore, those skilled in the art know that the target material requires a fine-grained structure, with an average grain size of less than 200 μm and predominantly (100) plane orientation; however, the existing technologies do not explore how to achieve a predominantly (100) plane orientation. Therefore, there is an urgent need to find a method that can specifically improve the purity of high-purity aluminum ingots above 5N5, has a high-efficiency preparation process, and can also improve target uniformity and increase the proportion of (100) direction grain orientation, thereby optimizing the internal structure of the target material and improving sputtering efficiency during the sputtering process. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-purity aluminum target blank with a simple process, small grain size and (100) plane orientation, and a method for preparing the same.
[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a high-purity aluminum target blank, the method comprising the following steps:
[0007] (1) Forging high-purity aluminum ingots: first, draw the high-purity aluminum ingots to 140-160% of their original height, and then uplift them to 45-55% of their original height.
[0008] (2) After forging, perform a heat treatment and then cool.
[0009] (3) The cooled workpiece is cross-rolled to a height of 14-40mm, followed by a water cooling;
[0010] (4) Stack the workpieces after the first water cooling and roll them together, followed by a second water cooling;
[0011] (5) After secondary water cooling, the workpiece is separated and subjected to crystallization heat treatment and cooling to obtain a high-purity aluminum target billet.
[0012] In the preparation method of a high-purity aluminum target blank provided by the present invention, the high-purity aluminum ingot is first forged by upsetting and drawing, and then rolled twice. First, the single workpiece is cross-rolled to a specific height, then the cross-rolled workpieces are stacked, and the stacked workpieces are stacked and rolled. Finally, separation and crystallization heat treatment are performed. In this way, a high-purity aluminum target blank with a grain size of <200μm and (100) plane orientation content of >70% can be obtained. That is, the high-purity aluminum target blank has a small grain distribution and high uniformity of orientation distribution, which can ensure that the prepared high-purity aluminum target blank has high sputtering efficiency and good sputtering stability.
[0013] In a preferred embodiment of the preparation method described in this invention, the purity of the high-purity aluminum ingot is >99.9995%.
[0014] The inventors have discovered that the method provided by this invention is applicable to high-purity aluminum, i.e., high-purity aluminum ingots with a purity of 5N or higher, and is also applicable to high-purity aluminum ingots with a purity of 5N5 or higher. This solves the technical problem in the prior art that the ingots used in the preparation of high-purity aluminum target billets cannot achieve a purity of 5N5 or higher.
[0015] In a preferred embodiment of the preparation method of the present invention, in step (1), the drawing temperature is 20-30℃, and the drawing passes are cooled with ice water.
[0016] As a preferred embodiment of the preparation method of the present invention, in step (1), the material is kept at 180-200℃ for 15-20 minutes before roughing.
[0017] Preheating before upsetting can remove stress from the elongation process, and the upsetting process can also be repeated after reheating.
[0018] Preferably, an ice-water cooling step is performed after forging.
[0019] The inventors discovered that by first upsetting and drawing high-purity aluminum ingots within a specific range, the forged workpieces can be made to have better processing plasticity, thus avoiding different structural orientations during subsequent rolling processes, which would affect the uniformity of the product's orientation distribution.
[0020] In a preferred embodiment of the preparation method of the present invention, in step (2), the temperature of the first heat treatment is 110-120℃ and the time is 50-70min.
[0021] The inventors discovered that introducing a heat treatment after forging, and limiting the temperature and time of the heat treatment to the above range, can ensure that the workpiece obtains better processing plasticity. If the temperature is too low, the plasticity is difficult to guarantee, which will affect the uniformity of deformation. If the temperature is too high, the energy accumulated by deformation will be released, making it difficult to achieve subsequent steps.
[0022] In a preferred embodiment of the preparation method of the present invention, in step (4), the number of workpieces stacked is 2-3.
[0023] Preferably, in step (4), the number of workpieces stacked is 2.
[0024] The inventors discovered that by introducing two rolling processes, with the first rolling being a single workpiece and the second rolling being a stacked rolling of 2-3 workpieces, the problem of high grain boundary mobility that occurs when rolling a single workpiece can be avoided, thereby achieving a product with good orientation distribution uniformity. In particular, by further selecting to stack and roll 2 workpieces, a good balance between equipment matching the production line and orientation distribution uniformity can be achieved.
[0025] In a preferred embodiment of the preparation method of the present invention, in step (4), the workpiece is rolled to a diameter of 350-400 mm and a height of 7-20 mm.
[0026] Preferably, the rolling process involves 4-8 passes, with a single pass having a pressing depth of 8-12 mm.
[0027] Preferably, the number of passes in the rolling process is 2-4, and the pressing amount per pass is 1-10 mm.
[0028] Preferably, the total rolling deformation rate of the stacked rolling is 50-80%.
[0029] The inventors discovered that further controlling the size of the workpiece after rolling and stacking, the number of passes and the single-pass pressing amount during rolling and stacking, as well as the total rolling deformation rate during stacking, can result in a higher uniformity of orientation distribution and smaller grain size in the high-purity aluminum target billet.
[0030] In a preferred embodiment of the preparation method of the present invention, in step (5), the temperature of the crystallization heat treatment is 280-300℃ and the time is 30-40min.
[0031] Preferably, the cooling is performed using a cooling medium, which may be ice water or liquid nitrogen.
[0032] In a second aspect, the present invention provides a high-purity aluminum target blank, which is prepared by the preparation method described in the present invention.
[0033] As a preferred embodiment of the high-purity aluminum target blank of the present invention, the high-purity aluminum target blank has a grain size of <200μm and an (100) plane orientation content of >70%.
[0034] The high-purity aluminum target blank provided by this invention has excellent orientation distribution uniformity and small grain size, thus it can be effectively used in subsequent target sputtering, and has high sputtering efficiency and good sputtering stability when applied.
[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0036] The method for preparing high-purity aluminum target blanks provided by this invention involves first forging high-purity aluminum ingots using upsetting and drawing, followed by two rolling processes: first, cross-rolling individual workpieces to a specific height, then stacking the cross-rolled workpieces, and finally performing stack rolling on the stacked workpieces, followed by separation and crystallization heat treatment. This yields high-purity aluminum target blanks with a grain size <200μm and (100) plane orientation content >70%. The resulting high-purity aluminum target blanks have a small grain distribution and high orientation uniformity, ensuring high sputtering efficiency and good sputtering stability. Furthermore, the preparation method provided by this invention is applicable to high-purity aluminum ingots with a purity of 5N5 or higher, and can also produce products with high dimensional uniformity. Simultaneously, the preparation method provided by this invention has a simple process flow, short preparation time, and can reduce preparation costs, making it applicable to actual production. Attached Figure Description
[0037] Figure 1 Metallographic microscope image of the high-purity aluminum target blank prepared in Example 1;
[0038] Figure 2 Metallographic microscope image of the high-purity aluminum target blank prepared in Example 2;
[0039] Figure 3 This is a metallographic microscope image of the high-purity aluminum target blank prepared in Comparative Example 3. Detailed Implementation
[0040] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.
[0041] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in the field.
[0042] Example 1
[0043] This invention provides a high-purity aluminum target blank, the preparation method of which includes the following steps:
[0044] (1) Take a high-purity aluminum ingot with a purity of 6N, a diameter of 120-160mm, and a height of 90-340mm for forging. First, draw the high-purity aluminum ingot to 160% of its original height at room temperature (25℃). Cool it with ice water between drawing passes. After drawing, place the workpiece at 200℃ for 20 minutes and then perform upsetting to 55% of its original height. After upsetting, cool it with ice water.
[0045] (2) Place the workpiece treated in step (1) at 120℃ for 50 minutes and cool it with ice water after the heat preservation is completed;
[0046] (3) The workpiece after step (2) is cross-rolled to a height of 40mm. The rolling passes are cooled with ice water. The single pass pressure is 10mm. A total of 6 passes are rolled. The pressure is released in the last pass to adjust the edge. After rolling, the workpiece is cooled with ice water.
[0047] (4) Stack and fix the two workpieces after step (3), and then perform stack rolling until the diameter of a single workpiece is 400mm and the height is 20mm. Cool with ice water between stack rolling passes. The pressure of a single pass is 10mm. Perform a total of 3 rolling passes. Release the control pressure in the last pass to adjust the edge. Cool with ice water after rolling is completed.
[0048] (5) Separate the stacked workpieces after step (4) by machining;
[0049] (6) Place the workpiece processed in step (5) at 300°C for 30 minutes, and then cool it with ice water to obtain a high-purity aluminum target blank.
[0050] Example 2
[0051] This invention provides a high-purity aluminum target blank, the preparation method of which includes the following steps:
[0052] (1) Take a high-purity aluminum ingot with a purity of 6N, a diameter of 120-160mm, and a height of 90-340mm for forging. First, draw the high-purity aluminum ingot at room temperature (25℃) to 140% of its original height. Cool it with ice water between drawing passes. After drawing, place the workpiece at 180℃ for 15 minutes and then perform upsetting to 45% of its original height. After upsetting, cool it with ice water.
[0053] (2) Place the workpiece treated in step (1) at 110℃ for 70 minutes and cool it with ice water after the heat preservation is completed;
[0054] (3) The workpiece after step (2) is cross-rolled to a height of 14mm. The rolling passes are cooled with ice water. The single pass pressure is 10mm. A total of 7 passes are rolled. The pressure is released in the last pass to adjust the edge. After rolling, the workpiece is cooled with ice water.
[0055] (4) Stack and fix the two workpieces after step (3), and then perform stack rolling until the diameter of a single workpiece is 350mm and the height is 7mm. Cool with ice water between stack rolling passes. The pressure of a single pass is 1mm. A total of 4 rolling passes are performed. Release the control pressure in the last pass to adjust the edge. Cool with ice water after rolling is completed.
[0056] (5) Separate the stacked workpieces after step (4) by machining;
[0057] (6) Place the workpiece processed in step (5) at 280°C for 40 minutes and then cool it with ice water to obtain a high-purity aluminum target blank.
[0058] Example 3
[0059] This invention provides a high-purity aluminum target blank. The only difference between the preparation method of the high-purity aluminum target blank and that of Example 1 is that the purity of the high-purity aluminum ingot used in step (1) is 5N5.
[0060] Example 4
[0061] This invention provides a high-purity aluminum target blank. The only difference between the preparation method of the high-purity aluminum target blank and that of Example 1 is that in step (4), three workpieces are stacked and fixed.
[0062] Comparative Example 1
[0063] The present invention provides a high-purity aluminum target blank in a comparative example. The only difference between the preparation method of the high-purity aluminum target blank and that of Example 1 is that step (1) is omitted.
[0064] Comparative Example 2
[0065] The present invention provides a high-purity aluminum target blank in a comparative example. The only difference between the preparation method of the high-purity aluminum target blank and that of Example 1 is the absence of step (2).
[0066] Comparative Example 3
[0067] The present invention provides a high-purity aluminum target billet in a comparative example. The only difference between the preparation method of the high-purity aluminum target billet and that of Example 1 is that steps (4) and (5) are omitted. Step (3) is as follows: the workpiece after step (2) is cross-rolled to a diameter of 400 mm and a height of 20 mm. The workpiece is cooled with ice water between rolling passes. The single pass pressure is 10 mm. A total of 11 rolling passes are performed. The pressure is released in the last pass to adjust the edge. After rolling, the workpiece is cooled with ice water.
[0068] Comparative Example 4
[0069] The present invention provides a high-purity aluminum target blank in a comparative example. The only difference between the preparation method of the high-purity aluminum target blank and that of Example 1 is that the blank is drawn to 170% of its original height in step (1).
[0070] Comparative Example 5
[0071] The present invention provides a high-purity aluminum target blank in comparative example. The only difference between the preparation method of the high-purity aluminum target blank and Example 1 is that the height is uptaken to 40% of the original height in step (1).
[0072] Comparative Example 6
[0073] The present invention provides a high-purity aluminum target blank in a comparative example. The only difference between the preparation method of the high-purity aluminum target blank and that of Example 1 is that in step (3), it is cross-rolled to a height of 55 mm.
[0074] Comparative Example 7
[0075] The present invention provides a high-purity aluminum target blank in a comparative example. The only difference between the preparation method of the high-purity aluminum target blank and that of Example 1 is that in step (3), it is cross-rolled to a height of 8 mm.
[0076] Example of effect
[0077] The effects of this invention are used to verify the performance of the high-purity aluminum target blanks prepared in Examples 1-4 and Comparative Examples 1-7. The average grain size of the obtained samples was measured using a metallographic microscope (ASTM-112), and the grain orientation in the (100) direction was measured using a scanning electron microscope (EBSD). The results are shown in Table 1. Additionally, metallographic microscope images of the products obtained in Examples 1, 2, and 3 are shown in Table 1. Figure 1-3 As shown, from Figure 1-3It can also be seen that the grain size of the product prepared by the method of the present invention is smaller, while the grain size of the product prepared in Comparative Example 3 is larger.
[0078] Table 1
[0079]
[0080] As can be seen from Table 1, when the technical solution of the present invention is adopted, the grain size of the obtained product is small, below 180μm, and the grain orientation is mainly (100) orientation, with the (100) plane orientation accounting for more than 71.9%.
[0081] As can be seen from Example 1 and Comparative Example 1, when there is no forging process, the average grain size of the obtained product increases significantly, and the proportion of grain orientation in the (100) direction decreases significantly, by 52.07% compared with Example 1; As can be seen from Example 1 and Comparative Examples 4-5, when the proportion of elongation or upsetting in Comparative Examples 4-5 is not within the scope of the present invention, the average grain size of the obtained product increases significantly, and the proportion of grain orientation in the (100) direction decreases significantly, by 56.34-67.63% compared with Example 1;
[0082] As can be seen from Example 1 and Comparative Example 2, when no heat treatment is performed after forging, the orientation of the obtained product also deteriorates, with the (100) direction grain orientation accounting for only 36.3%, which is 50% lower than that of Example 1.
[0083] As can be seen from Example 1 and Comparative Example 3, when the stacking rolling step is not used, even if the rolled dimensions are kept consistent, the resulting product is significantly worse than that of Example 1. Compared with Example 1, the grain size increased by 70.59% and the (100) plane orientation ratio decreased by 55.37%.
[0084] As can be seen from Examples 1 and Comparative Examples 6-7, the size after the first cross-rolling also affects the performance of the product. When the size after the first rolling in Comparative Example 6 is not within the scope of the present invention, i.e., too wide, the grain size increases by 105.88% and the (100) plane orientation ratio decreases by 63.64% compared with Example 1. When the size after the first rolling in Comparative Example 7 is not within the scope of the present invention, i.e. too narrow, the grain size increases by 88.23% and the (100) plane orientation ratio decreases by 70.39% compared with Example 1.
[0085] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing a high-purity aluminum target blank, characterized in that, The preparation method includes the following steps: (1) Forging high-purity aluminum ingots involves first drawing the high-purity aluminum ingots to 140-160% of their original height, and then upsetting them to 45-55% of their original height; (2) After forging, a heat treatment is performed, followed by water cooling; the temperature of the heat treatment is 110-120℃. (3) After cooling, the workpiece is cross-rolled to a height of 14-40 mm, and then water-cooled once; (4) Stack and roll the workpieces after the first water cooling, and then water cool them a second time; (5) Separate the workpiece after secondary water cooling and perform crystallization heat treatment and cooling to obtain high-purity aluminum target billet; In step (4), the number of workpieces stacked is 2-3 pieces; In step (4), the stacking is performed until the diameter of a single workpiece is 350-400mm and the height is 7-20mm.
2. The preparation method according to claim 1, characterized in that, The purity of the high-purity aluminum ingot is >99.9995%.
3. The preparation method according to claim 1, characterized in that, In step (1), the drawing temperature is 20-30℃, and ice water is used for cooling between drawing passes.
4. The preparation method according to claim 1, characterized in that, In step (1), the material is kept at 180-200℃ for 15-20 minutes before the roughing process.
5. The preparation method according to claim 1, characterized in that, In step (2), the heat treatment time is 50-70 minutes.
6. The preparation method according to claim 1, characterized in that, In step (5), the temperature of the crystallization heat treatment is 280-300℃ and the time is 30-40min.
7. A high-purity aluminum target blank, characterized in that, The high-purity aluminum target blank is prepared by the preparation method described in any one of claims 1-6.
8. The high-purity aluminum target blank according to claim 7, characterized in that, The high-purity aluminum target blank has a grain size of <200μm and an (100) plane orientation content of >70%.