A low-defect high-purity fine-grain copper or copper alloy target material, a preparation method thereof and applications thereof

Abstract

The application provides a low-defect high-purity fine-grain copper or copper alloy target material and a preparation method and application thereof, and relates to the technical field of sputtering targets. The high-purity fine-grain copper or copper alloy target material has the following characteristics: (a) purity is greater than or equal to 6N; and (b) grain size is less than or equal to 20 mu m. The target material can meet the requirement of a defect rate of a chip process below 3 nm. The preparation method is simple, strict control of the size of internal defects of an ingot or a target blank is introduced in each process step, the size of the defects is gradually reduced, the distribution of the defects is improved, the method is suitable for large-scale production of high-purity copper and copper alloy target materials, and the method has the advantages of high process stability, strong defect control capability and uniform grain structure.

Description

Technical Field

[0001] This invention relates to the field of sputtering target technology, and in particular to a low-defect, high-purity fine-grained copper or copper alloy target, its preparation method, and its application. Background Technology

[0002] As semiconductor chip manufacturing processes enter the sub-3nm node, high-purity copper and copper alloy sputtering targets, as core materials for copper interconnect processes, have seen their defect control standards raised to "the number of defects such as >10μm carbon inclusions and metal oxides approaching zero." Traditional high-purity copper and copper alloy sputtering target preparation processes mainly rely on multi-stage electron beam melting purification and "hot rolling and annealing" to refine grains and eliminate defects, but two major technical bottlenecks exist: Firstly, in order to suppress copper volatilization during the smelting stage, the electron beam power is usually limited to below 300kW, resulting in insufficient molten pool depth (only 1 / 5 to 1 / 4 of the raw material diameter), low thermal gradient, less than 30% breakage rate of carbon and metal oxide inclusion defects at the hundred-micron level, low defect removal efficiency, and a large number of original defects remaining. Secondly, the use of unidirectional forging in the processing stage makes it easy for defects to be elongated along the deformation direction (length-to-diameter ratio > 5), forming long strip-shaped hard inclusions; and the cold rolling deformation is generally less than 70%, which cannot completely break up micron-level defects, resulting in the proportion of defects with a size greater than 50μm in the total number of defects in the target material reaching 5%-8%.

[0003] The above process results in incomplete defect breaking, leading to a large number of large-sized inclusion defects of carbon and metal oxides remaining. These defects can trigger micro-arcs during target sputtering, causing defects such as holes and bumps on the wafer surface, severely reducing wafer yield and causing serious economic losses.

[0004] Therefore, effectively solving the technical problem of incomplete defect fragmentation in high-purity fine-grained copper and copper alloy sputtering targets has become the key to breaking through the bottleneck of advanced chip manufacturing materials. Summary of the Invention

[0005] This invention provides a low-defect, high-purity fine-grained copper or copper alloy target material, its preparation method, and its application, in order to solve the problem of incomplete defect fragmentation in existing high-purity fine-grained copper and copper alloy targets.

[0006] In a first aspect, the present invention provides a low-defect, high-purity fine-grained copper or copper alloy target material, wherein the number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects, and the high-purity fine-grained copper or copper alloy target material further has the following characteristics: (a) Purity ≥ 6N; (b) The grain size is ≤20μm.

[0007] The size of internal defects in the low-defect, high-purity, fine-grained copper or copper alloy target of the present invention can be precisely controlled within a range of less than or equal to 10 μm. The number of defects within this size range is precisely controlled to be more than 99.5% of the total number. In addition, it also has the characteristics of high purity and low target grain size, which improves the stability of the target sputtering process and meets the stringent requirements of sputtering target internal defects for 3nm and below processes.

[0008] A second aspect of the present invention provides a method for preparing a low-defect, high-purity, fine-grained copper or copper alloy target, comprising the following steps: S1. Smelt pure copper or copper alloy, and perform preliminary crushing and directional removal of defects larger than 100μm to obtain a copper or copper alloy initial ingot, so that the size of the defects in the copper or copper alloy initial ingot is within 100μm. S2. Forge the copper or copper alloy initial casting ingot along the X, Y, and Z directions respectively, break the residual defects and eliminate the directionality of the defects to obtain a copper or copper alloy casting ingot, so that the size of the defects in the copper or copper alloy casting ingot is ≤50μm. S3. The copper or copper alloy ingot is subjected to asynchronous cold rolling to obtain a copper or copper alloy rough target billet with a defect size of less than or equal to 10 μm, and then annealed and held to obtain a copper or copper alloy target billet. S4. After each step S1 to S3 is completed, the size and number of defects inside the product obtained in each step are detected. If the size and number of defects do not meet the requirements of each step, the corresponding step is returned for rework.

[0009] In the preparation process of the target material of the present invention, pure copper or copper alloy is first melted, which can improve the purity of copper and copper alloy, realize the initial crushing and directional removal of large-sized defects, and reduce the size of the crushed defects to within 100μm, thereby improving production efficiency and the qualification rate of the finished target material and reducing scrap costs. Then, the internal defects of the copper or copper alloy ingot are further crushed by three-dimensional forging to suppress the formation of long strip-shaped hard inclusions, refine the size of the defects to 0~50μm, and further reduce the grain size of the target material and improve the grain uniformity. Then, asynchronous cold rolling is used to break the internal defects of copper or copper alloy ingots to a size of less than or equal to 10μm through strong shearing. Annealing and heat preservation are then carried out to make the grains uniform and refined. At the same time, the size and quantity distribution of internal defects in the products obtained in each step are accurately detected. Unqualified target billets are further reworked to further ensure the precise control of defect size.

[0010] In the above technical solution, the control standard for the internal defect size of the product obtained in steps S1 to S3 was obtained through multiple creative experiments. Research showed that when the defect size in steps S1 and S2 is precisely controlled within 100 μm and 50 μm respectively, it facilitates subsequent further crushing and allows for precise control of defect size and quantity. Controlling the defect size in step S1 to within 200 μm increases the difficulty of subsequent crushing to within 50 μm; similarly, controlling the defect size in step S2 to within 80 μm increases the difficulty of subsequent crushing to within 10 μm. This makes it impossible to effectively crush defects and precisely control their size and quantity during the preparation process, increasing processing difficulty and rework frequency, significantly reducing preparation efficiency and the performance of the copper or copper alloy target.

[0011] In some optional embodiments of the present invention, the number of defects with internal dimensions greater than 100 μm in the initial copper or copper alloy ingot obtained after step S1 is less than 0.5% of the total number of defects; the number of defects with internal dimensions between 0 and 50 μm in the initial copper or copper alloy ingot obtained after step S2 is more than 99% of the total number of defects; and the number of defects with internal dimensions less than or equal to 10 μm in the target blank obtained after step S3 is more than 99.5% of the total number of defects. Theoretically, the more defects there are, the lower the wafer yield will be. The fewer defects greater than or equal to 10 μm, the better, but the processing cost will increase exponentially. Considering both cost and performance, and based on experimental data, the standard for the number of defects with internal dimensions less than or equal to 10 μm in the target blank to account for more than 99.5% of the total number of defects is set.

[0012] The above-described scheme innovatively introduces strict control over the internal defect size of the ingot or target blank at each process step, achieving a gradual reduction in defect size and improved defect distribution. This has led to the development of a high-purity copper and copper alloy target preparation technology with end-to-end process defect control. Through this synergistic control, the number of defects with internal dimensions less than or equal to 10 μm accounts for more than 99.5% of the total defects in the prepared target, with a purity ≥6N and a grain size ≤20 μm. This solves the problem of large-sized defects (hundreds of micrometers) remaining in traditional processes, improves the stability of the target sputtering process, and meets the stringent requirements for internal defects in sputtering targets for 3nm and below processes.

[0013] Furthermore, the defects include carbon inclusion defects and metal oxide inclusion defects.

[0014] Further, step S4 includes: If the number of defects with an internal size greater than 100μm in the initial copper or copper alloy casting ingot accounts for more than 0.5% of the total number of defects, then the initial copper or copper alloy casting ingot is returned to step S1, and the melting parameters are adjusted for rework. If the number of defects with internal dimensions greater than 50 μm and less than or equal to 100 μm in the copper or copper alloy ingot accounts for more than 0.5% of the total number of defects, then the copper or copper alloy ingot is returned to step S2, and the forging parameters are adjusted for rework. If the number of defects with internal dimensions greater than 10 μm and less than or equal to 50 μm in the copper or copper alloy target billet accounts for more than 0.5% of the total number of defects, then the copper or copper alloy target billet is returned to step S3, and the parameters of the asynchronous cold rolling are adjusted for rework.

[0015] This invention precisely returns target blanks that do not meet the condition that "the number of defects less than or equal to 10 μm accounts for more than 99.5% of the total number of defects" to specific processes for further processing. This achieves full-process control of defect size, which helps to accurately control the size and number of internal defects in the prepared target material within the range of "the number of defects less than or equal to 10 μm accounts for more than 99.5% of the total number of defects". This improves process stability, avoids batch quality fluctuations, enhances the stability of the target sputtering process, and is suitable for large-scale industrial production.

[0016] Preferably, before the target blank is inspected, its surface needs to be precision machined and cleaned; precision machining can improve the detection resolution and accuracy of defect scanning.

[0017] Preferably, the detection method includes ultrasound detection and CT detection.

[0018] Preferably, when adjusting the melting parameters, the electron beam power of the melting is increased by 30~50kW, more preferably by 50kW, and the adjusted electron beam power is controlled at 300~500kW.

[0019] Preferably, when adjusting the forging parameters, the number of forging passes in each of the X, Y, and Z directions is increased by 1, and the number of passes in each direction after adjustment is controlled to be between 3 and 5.

[0020] Preferably, when adjusting the parameters of the asynchronous cold rolling, the single-pass deformation amount of the asynchronous cold rolling is increased by 3%-5%, more preferably by 5%, and the adjusted single-pass deformation amount is controlled at 25-35%.

[0021] Furthermore, in step S1, the melting is electron beam melting, and its parameters include: vacuum degree ≤ 4 × 10⁻⁶. -2Pa, accelerating voltage of 40~50kV, molten pool temperature gradient ≥200K / cm, electron beam power of 300~500kW, and molten pool depth of 1 / 3-1 / 2 of the raw material diameter.

[0022] Preferably, after the smelting process, the copper volatilization rate is <0.5wt%.

[0023] In some optional embodiments of the present invention, the melting time is 6-8 hours.

[0024] Controlling the smelting parameters within the above range helps to control the smelting process, break up inclusion defects through ionization, excitation and oscillation, and break up defects by utilizing stress concentration caused by thermal expansion differences, the synergistic effect of thermocapillary flow and buoyancy flow and the strengthening effect of forced convection, thereby improving defect removal efficiency and reducing the residue of large-size defects.

[0025] Furthermore, in step S2, the forging parameters include: forging 3 to 5 times in each of the X, Y, and Z directions, with a single-pass deformation of 45 to 50%, an initial forging temperature of 600 to 950°C, and a final forging temperature of 200 to 500°C.

[0026] By controlling the final forging temperature, forging passes, single deformation amount, and cumulative deformation amount within the above range, better crushing effect and efficiency of defects can be achieved, defect directionality can be eliminated, and the residue of large-size defects can be further reduced.

[0027] Furthermore, in step S3, the parameters of asynchronous cold rolling include: a roll speed ratio of 1.1 to 1.5:1, a single-pass deformation of 25% to 35%, and a cumulative deformation of 90% to 95%.

[0028] By controlling the deformation amount and number of deformation passes of asynchronous cold rolling within the above range, better crushing effect and crushing efficiency can be achieved through strong shearing action, so that the internal defects of the target material are crushed to a size of less than 10μm, in order to meet the stringent requirements of sputtering target internal defects for 3nm and below processes.

[0029] Furthermore, the parameters for the annealing and heat preservation include: vacuum annealing at 300~400℃, with a heat preservation time of 40min~60min.

[0030] Furthermore, the grain size of the copper or copper alloy target blank is ≤20μm.

[0031] Furthermore, the purity of the pure copper is 6N or higher; or, the copper content in the copper alloy is ≥99 wt%.

[0032] Preferably, the copper alloy comprises copper-aluminum and / or copper-manganese alloys.

[0033] Furthermore, after step S3 is completed, the copper or copper alloy target blank that meets the set target conditions is machined to obtain a low-defect high-purity copper or copper alloy target material. The set target conditions are: the number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects.

[0034] A third aspect of the present invention provides the application of the low-defect high-purity fine-grained copper or copper alloy target prepared by the above-described method for preparing the low-defect high-purity fine-grained copper or copper alloy target in sputtering coating of integrated circuit interconnects.

[0035] The beneficial effects of the low-defect, high-purity fine-grained copper or copper alloy target material, its preparation method, and its application provided by this invention are as follows: In the target material of this invention, the number of defects with a size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects, the purity is ≥6N, and the grain size is ≤20 μm, which can meet the defect rate requirements of chip manufacturing processes below 3nm; its preparation method is simple, and each process step introduces strict control over the internal defect size of the ingot or target blank, so as to gradually reduce the defect size and improve the defect distribution. It is suitable for the large-scale production of low-defect, high-purity copper and copper alloy target materials, and has the advantages of high process stability, strong defect control capability, and uniform grain structure. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a process flow diagram of the present invention for preparing low-defect, high-purity fine-grained copper or copper alloy targets.

[0038] Figure 2 This is a 40X SEM image of the low-defect, high-purity, fine-grained copper target material prepared in Example 1, showing a defect size of 3.5 μm.

[0039] Figure 3 This is a 50X microstructure image of the low-defect, high-purity, fine-grained copper target material prepared in Example 1.

[0040] Figure 4 This is a 200X SEM image of a 50μm defect in a low-defect, high-purity, fine-grained copper target prepared in Comparative Example 1.

[0041] Figure 5 This is a 20X microstructure image of the low-defect, high-purity, fine-grained copper target material prepared in Comparative Example 1. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0043] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0044] In this invention, defects include carbon inclusion defects and metal oxide inclusion defects, and their size refers to the maximum cross-sectional diameter of the defect's front view.

[0045] The detection methods for each performance and indicator in this invention are as follows: Methods for detecting the size and number of defects: Characterization is performed using SEM sections, ultrasound, or CT scans, specifically as follows: SEM section inspection follows the "General Rules for Measurement Methods of Scanning Electron Microscopes with Lengths in the Micrometer Scale" GB / T 16594-2008; ultrasonic inspection follows the "Ultrasonic Wave Testing Method for Metal Sheets" GB / T 8651-2015; CT inspection follows the "General Requirements for Non-Destructive Testing - Industrial Computed Tomography (CT) Inspection" GB / T 29070-2012. The method for determining grain size is: GB / T 6394-2017, "Method for Determination of Average Grain Size of Metals". Purity: Refer to GDMS data; The wafer sputtering yield is determined by the following criteria, as specified in GB / T 16525-2018, "General Rules for Packaging and Testing of Semiconductor Integrated Circuits": film thickness, sheet resistance, uniformity, and defects.

[0046] The following are the raw material information used in the examples and comparative examples: Electrolytic copper plate: purity 99.97%, the number of defects with an initial size greater than 100μm accounts for 12% of the total number of defects.

[0047] Example 1 This embodiment provides a method for preparing a low-defect, high-purity, fine-grained copper target, the flowchart of which is shown below. Figure 1 As shown, Figure 1 The semi-finished products mentioned refer to the high-purity copper primary ingot, high-purity copper ingot, and high-purity copper ingot target blank obtained after processing S1, S2, and S3, respectively. The preparation method includes the following steps: S1. High-energy electron beam melting: Electrolytic copper plates are melted using an electron beam. The parameters for electron beam melting are: vacuum degree 4×10⁻⁶. -2 Pa, accelerating voltage of 45kV, electron beam power of 450kW, molten pool temperature gradient of 220K / cm, smelting time of 8h, molten pool depth of 1 / 3 of raw material diameter, to obtain crack-free high-purity copper initial casting ingot. Electron beam melting was used to initially break down and directionally eliminate defects larger than 100 μm, ensuring that the size of defects in the high-purity copper ingot was within 100 μm. After testing, the copper volatilization rate after melting was 0.45 wt%. At the same time, the number and distribution of internal defects were tested, and the number of defects larger than 100 μm in the high-purity copper ingot accounted for 0.3% of the total number of defects, so no rework was required. S2. Large Deformation Triaxial Forging: The high-purity copper ingot is forged four times in each of the X, Y, and Z directions, with a single-pass deformation of 50%. The initial forging temperature is 600℃, and the final forging temperature is 350℃. Residual defects are broken up and their directionality is eliminated. The defects are then broken up again to a size ≤50μm to obtain a high-purity copper ingot. The number and distribution of internal defects are detected. The test shows that the number of internal defects with a size of 0~50μm in the high-purity copper ingot obtained in this step accounts for more than 99.5% of the total number of defects. The defects are non-directional and do not require rework. S3. Asynchronous cold rolling with large deformation: The high-purity copper ingot is subjected to asynchronous cold rolling. The parameters of asynchronous cold rolling are: roll speed ratio of 1.3:1, single-pass deformation of 35%, cumulative deformation of 6 passes of 92.5%, and the defects are broken down into smaller than or equal to 10 μm in three stages to obtain a high-purity copper rough target billet; then, it is vacuum annealed at 350℃ for 40 min to obtain a high-purity copper target billet. S4. Internal Defect Data Detection: The number and distribution of internal defects were detected. The high-purity copper target blank obtained in step S3 showed that defects with an internal size of 10 μm or less accounted for 99.7% of the total defects, with a grain size of 19 μm. The SEM images of these defects are shown below. Figure 2 As shown, its microstructure diagram is as follows: Figure 3 As shown, no rework is required; S5. Precision Machining: The high-purity copper target blank obtained in step S3 meets the requirement that "the number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects." After each process is completed, it passes inspection and does not need to be returned to steps S1, S2, and S3 for further processing. It can be directly subjected to subsequent machining to obtain a low-defect, high-purity, fine-grained copper target material. Target material performance: The number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects; purity ≥6N; wafer sputtering yield 99.9%; grain size 19 μm.

[0048] Example 2 This embodiment provides a method for preparing a low-defect, high-purity, fine-grained copper target, comprising the following steps: S1. High-energy electron beam melting: Electrolytic copper plates are melted using an electron beam. The parameters for electron beam melting are: vacuum degree 4×10⁻⁶. -2 Pa, accelerating voltage of 50kV, electron beam power of 500kW, molten pool temperature gradient of 245K / cm, smelting time of 6h, molten pool depth of 1 / 2 of raw material diameter, to obtain crack-free high-purity copper initial casting ingot. Electron beam melting was used to initially break down and directionally eliminate defects larger than 100 μm, ensuring that the size of defects in the high-purity copper ingot was within 100 μm. After testing, the copper volatilization rate after melting was 0.49 wt%. At the same time, the number and distribution of internal defects were tested, and the number of defects larger than 100 μm in the high-purity copper ingot accounted for 0.5% of the total number of defects, so no rework was required. S2. Large Deformation Triaxial Forging: The high-purity copper initial casting is forged four times in each of the X, Y, and Z directions, with a single-pass deformation of 45%. The initial forging temperature is 600℃, and the final forging temperature is 350℃. Residual defects are broken up and their directionality is eliminated. The defects are then broken up again to a size of 0~50μm to obtain a high-purity copper casting. The number and distribution of internal defects are detected. The test shows that the number of internal defects with a size between 0~50μm accounts for more than 99.2% of the total number of defects in the high-purity copper casting obtained in this step. The defects are non-directional and do not require rework. S3. Asynchronous cold rolling with large deformation: The high-purity copper ingot is subjected to asynchronous cold rolling. The parameters of asynchronous cold rolling are: roll speed ratio of 1.1:1, single-pass deformation of 25%, cumulative deformation of 8 passes of 90%, and the defects are broken down into smaller than or equal to 10μm in three stages to obtain a high-purity copper rough target billet; then, it is vacuum annealed at 350℃ for 40min to obtain a high-purity copper target billet. S4. Detect internal defect data: Detect the number and distribution of internal defects. After detection, the number of internal defects with an internal size of less than or equal to 10μm in the high-purity copper target blank obtained in step S3 accounts for 99.5% of the total number of defects, and the grain size is 19μm. No rework is required. S5. Precision Machining: The high-purity copper target blank obtained in step S3 meets the requirement that "the number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects." After each process is completed, it passes inspection and does not need to be returned to steps S1, S2, and S3 for further processing. It can be directly subjected to subsequent machining to obtain a low-defect, high-purity, fine-grained copper target material. Target material performance: The number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects; purity ≥6N; wafer sputtering yield 99.8%; grain size 19 μm.

[0049] Example 3 This embodiment provides a method for preparing a low-defect, high-purity, fine-grained copper alloy target, comprising the following steps: S1. High-energy electron beam melting: Electrolytic copper plates and high-purity aluminum (6N purity) are fed into the furnace at a weight ratio of 499:1 for electron beam melting. The parameters for electron beam melting are: vacuum degree 4×10 -2 Pa, accelerating voltage of 50kV, electron beam power of 500kW, molten pool temperature gradient of 245K / cm, melting time of 6h, molten pool depth of 1 / 2 of raw material diameter, to obtain crack-free high-purity copper-aluminum alloy initial casting ingot. Electron beam melting was used to initially break down and directionally eliminate defects larger than 100 μm, ensuring that the size of defects in the high-purity copper-aluminum alloy ingot obtained after melting was within 100 μm. After testing, the copper volatilization rate after melting was 0.49 wt%. At the same time, the number and distribution of internal defects were tested, and the number of defects larger than 100 μm in the high-purity copper-aluminum alloy ingot accounted for 0.3% of the total number of defects, which did not require rework. S2. Large Deformation Triaxial Forging: The high-purity copper-aluminum alloy initial ingot is forged four times in each of the X, Y, and Z directions, with a single-pass deformation of 45%. The initial forging temperature is 600℃, and the final forging temperature is 350℃. Residual defects are broken up and their directionality is eliminated. The defects are then broken up again to a size of 0~50μm to obtain a high-purity copper-aluminum alloy ingot. The number and distribution of internal defects are detected. The test shows that the number of internal defects with a size between 0~50μm accounts for more than 99% of the total number of defects in the high-purity copper-aluminum alloy ingot obtained in this step. The defects are non-directional and do not require rework. S3. Asynchronous cold rolling with large deformation: The high-purity copper-aluminum alloy ingot is subjected to asynchronous cold rolling. The parameters of asynchronous cold rolling are: roll speed ratio of 1.3:1, single-pass deformation of 31%, cumulative deformation of 8 passes of 95%, and the defects are broken down into smaller than or equal to 10μm in three stages to obtain a high-purity copper-aluminum rough target billet; then, it is vacuum annealed at 350℃ for 40min to obtain a high-purity copper-aluminum target billet. S4. Detect internal defect data: Detect the number and distribution of internal defects. After detection, the number of internal defects with an internal size of less than or equal to 10μm in the high-purity copper-aluminum target blank obtained in step S3 accounts for 99.5% of the total number of defects, and the grain size is 17μm. No rework is required. S5. Precision Machining: The high-purity copper-aluminum target blank obtained in step S3 meets the requirement that "the number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects." After each process is completed, it passes inspection and does not need to be returned to steps S1, S2, and S3 for further processing. It can be directly subjected to subsequent machining to obtain a low-defect, high-purity, fine-grained copper alloy target material. Target material performance: The number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects; purity ≥6N; wafer sputtering yield 99.82%; grain size 17 μm.

[0050] Example 4 This embodiment provides a method for preparing a low-defect, high-purity, fine-grained copper target, the process of which includes the following steps: S1. High-energy electron beam melting: Electrolytic copper plates are melted using an electron beam. The parameters for electron beam melting are: vacuum degree 4×10⁻⁶. -2 Pa, accelerating voltage of 38kV, electron beam power of 380kW, molten pool temperature gradient of 180K / cm, smelting time of 8h, molten pool depth of 1 / 5 of raw material diameter, to obtain crack-free high-purity copper initial casting ingot. Testing revealed that the copper volatilization rate after smelting was 0.40 wt%. Simultaneously, the number and distribution of internal defects were examined. Defects larger than 100 μm accounted for 1% of the total defects in the high-purity copper ingot, necessitating rework and remelting. During remelting, the power was increased by 50 kV while other parameters remained unchanged. Larger defects were further crushed and eliminated. The resulting high-purity copper ingot was crack-free. Testing showed that defects larger than 100 μm accounted for 0.4% of the total defects, requiring no rework. S2. Large Deformation Three-Dimensional Forging: The high-purity copper ingot is forged four times in each of the X, Y, and Z directions, with a single-pass deformation of 50%. The initial forging temperature is 600℃, and the final forging temperature is 350℃. Residual defects are broken up and their directionality is eliminated. The defects are then broken up again to a size ≤50μm to obtain a high-purity copper ingot. The number and distribution of internal defects are detected. The test shows that the high-purity copper ingot obtained in this step has more than 99.6% of the internal defects with a size of 0~50μm. The defects are non-directional and do not require rework. S3. Asynchronous cold rolling with large deformation: The high-purity copper ingot is subjected to asynchronous cold rolling. The parameters of asynchronous cold rolling are: roll speed ratio of 1.3:1, single-pass deformation of 35%, cumulative deformation of 6 passes of 92.5%, and the defects are broken down into smaller than or equal to 10 μm in three stages to obtain a high-purity copper rough target billet; then, it is vacuum annealed at 350℃ for 40 min to obtain a high-purity copper target billet. S4. Detect internal defect data: Detect the number and distribution of internal defects. After detection, the number of internal defects with an internal size of less than or equal to 10μm in the high-purity copper target blank obtained in step S3 accounts for 99.65% of the total number of defects, and the grain size is 20μm. No rework is required. S5. Precision Machining: The high-purity copper target blank obtained in step S3 meets the requirement that "the number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects". It can be directly subjected to subsequent machining to obtain a low-defect, high-purity, fine-grained copper target material.

[0051] Finished sputtering target performance: the number of defects with internal dimensions less than or equal to 10μm accounts for more than 99.5% of the total number of defects, the purity is ≥6N, and the wafer sputtering yield is 99.75%.

[0052] Comparative Example 1 This comparative example is basically the same as Example 1, except that: S2 adopts unidirectional forging: the high-purity copper ingot is unidirectionally forged 4 times, the deformation amount per pass is 50%, the final forging temperature is 600℃, and the actual measured final forging temperature is 280℃; after testing, the defects of the high-purity copper ingot obtained in this step are elongated along the flow direction (length-to-diameter ratio > 5), and the number of defects with a size ≥ 100μm still accounts for 0.3% of the total number of defects, and the number of defects with a size ≥ 50μm accounts for more than 10% of the total number of defects; The high-purity copper ingot obtained by unidirectional forging was then processed using the same large deformation asynchronous cold rolling process parameters as in Example 1 to obtain a high-purity copper target billet. Testing revealed that defects with internal dimensions greater than 25 μm accounted for 6.2% of the total defects in the high-purity copper target billet, failing to meet the requirement that "defects with dimensions less than or equal to 10 μm account for more than 99.5% of the total defects," and the grain size was 40 μm. The SEM images of these defects are shown below. Figure 4 As shown, its microstructure diagram is as follows: Figure 5 As shown; The same machining method as in Example 1 was used to obtain the finished sputtering target. The performance of the finished sputtering target was as follows: it did not meet the requirement that "the number of defects with a size less than or equal to 10 μm accounted for more than 99.5% of the total number of defects," the purity was 6N, the wafer yield was 95.5%, and the grain size was 40 μm.

[0053] Comparative Example 2 This comparative example is basically the same as Example 2, except that the vacuum degree is 4×10 during electron beam melting. -2 Pa, accelerating voltage of 60kV, electron beam power of 600kW, molten pool temperature gradient of 330K / cm, melting time of 6h, molten pool depth of 3 / 5 of raw material diameter, to obtain high-purity copper primary ingot; Testing revealed that the copper volatilization rate after smelting was 1.1 wt%. Due to the excessively high temperature gradient, cracks appeared at the edges of the high-purity copper ingot. Excessive internal flow of the melt caused particles to be trapped in the mold, resulting in the number of defects with a size greater than 100 μm in the high-purity copper ingot accounting for more than 2% of the total number of defects. The high-purity copper ingot was then processed sequentially using the same large deformation three-dimensional forging and large deformation asynchronous cold rolling process parameters as in Example 2 to obtain a high-purity copper target billet. Testing revealed that the high-purity copper target billet obtained in this comparative example had 90% of its internal defects being less than or equal to 10 μm, failing to meet the requirement that "the number of defects less than or equal to 10 μm accounts for more than 99.5% of the total defects," and the grain size was 25 μm.

[0054] The same machining method as in Example 2 was used to obtain the finished sputtering target. The performance of the finished sputtering target was as follows: it did not meet the requirement that "the number of defects with a size less than or equal to 10 μm accounted for more than 99.5% of the total number of defects," its purity was 5N5, and its wafer yield was only 95%.

[0055] Comparative Example 3 This comparative example is basically the same as Example 2, except that: synchronous cold rolling is used with the following parameters: roll speed ratio of 1:1, single-pass deformation amount of 25%, and cumulative deformation amount of 8 passes of 90% to obtain a high-purity copper rough target billet. Then, the high-purity copper rough target billet is vacuum annealed at 350°C for 40 minutes to obtain a high-purity copper target billet. Upon inspection, the high-purity copper target blank obtained in step S3 had 97% of its internal defects with an internal size of less than or equal to 10 μm. Due to insufficient shear force, the number of large-sized defects with a size of more than 50 μm accounted for more than 0.5% of the total number of defects, and the grain size was 30 μm. The sputtering target was machined using the same method as in Example 2 to obtain the finished sputtering target. The finished sputtering target exhibits the following properties: purity of 6N and wafer yield of 94.3%.

[0056] Comparative Example 4 This comparative example is basically the same as Example 4, except that: The specific operating steps for not reworking and remelting high-purity copper initial castings are as follows: S1. High-energy electron beam melting: Electrolytic copper plates are melted using an electron beam. The parameters for electron beam melting are: vacuum degree 4×10⁻⁶. -2 Pa, accelerating voltage of 38kV, electron beam power of 380kW, molten pool temperature gradient of 180K / cm, smelting time of 8h, molten pool depth of 1 / 5 of raw material diameter, to obtain crack-free high-purity copper initial casting ingot. Testing revealed that the copper volatilization rate after smelting was 0.40 wt%, and the number of defects larger than 100 μm in the initial high-purity copper ingot accounted for 1% of the total number of defects. S2. Large Deformation Triaxial Forging: The high-purity copper ingot obtained from the smelting process is forged four times in each of the X, Y, and Z directions, with a single-pass deformation of 50%. The initial forging temperature is 600℃, and the final forging temperature is 350℃. This process breaks up residual defects and eliminates defect directionality, ensuring that the size of defects in the forged copper ingot is ≤50μm, thus obtaining a high-purity copper ingot. Upon testing, the high-purity copper ingot obtained in this step shows that the number of defects with an internal size of 0~50μm accounts for 99% of the total number of defects, and the defects are non-directional. S3. Asynchronous cold rolling with large deformation: The high-purity copper ingot is subjected to asynchronous cold rolling. The parameters of asynchronous cold rolling are: roll speed ratio of 1.3:1, single-pass deformation of 35%, and cumulative deformation of 6 passes of 92.5%, to obtain a high-purity copper rough target billet with a defect size of less than or equal to 10μm; then, it is vacuum annealed at 350℃ for 40min to obtain a high-purity copper target billet. S4. Internal defect detection data: After detection, the number of internal defects with an internal size of less than or equal to 10μm in the high-purity copper target blank obtained in step S3 accounts for 99.3% of the total number of defects, and the grain size is 20μm. S5. The same method as in Example 4 was used for precision processing to obtain the finished target material; the performance of the finished target material was then tested, and the final purity was ≥6N, but the wafer sputtering yield was only 97%.

[0057] Based on the results of the above embodiments and comparative examples, it can be seen that when preparing high-purity fine-grained copper or copper alloy targets by the method of the present invention, internal defects of the target can be effectively broken, and the size and quantity distribution of defects can be precisely controlled. The proportion of defects with an internal size of less than or equal to 10 μm in the total number of defects can be controlled to be above 99.5%. At the same time, the purity of the target can reach above 6N and the grain size can be ≤20 μm, which significantly improves the wafer yield when it is applied.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a low-defect, high-purity, fine-grained copper target, wherein the copper target is made of pure copper or a copper alloy, characterized in that... Includes the following steps: S1. Melt pure copper or copper alloy to obtain a pure copper or copper alloy ingot, so that the size of the defect in the pure copper or copper alloy ingot is within 100μm. S2. The pure copper or copper alloy initial casting ingot is forged along the X, Y and Z directions respectively to obtain pure copper or copper alloy casting ingot, so that the size of the defect in the pure copper or copper alloy casting ingot is ≤50μm. S3. The pure copper or copper alloy ingot is subjected to asynchronous cold rolling to obtain a pure copper or copper alloy rough target billet with a defect size of less than or equal to 10 μm, and then annealed and held to obtain a pure copper or copper alloy target billet. S4. After each step S1 to S3 is completed, the size and number of defects inside the product obtained in each step are detected. If the size and number of defects do not meet the requirements of each step, the corresponding step is returned for rework. If the number of defects with an internal size greater than 100 μm in the initial pure copper or copper alloy ingot exceeds 0.5% of the total number of defects, the initial pure copper or copper alloy ingot is returned to step S1, and the smelting parameters are adjusted for rework. If the number of defects with an internal size greater than 50 μm and less than or equal to 100 μm in the initial pure copper or copper alloy ingot exceeds 0.5% of the total number of defects, the initial pure copper or copper alloy ingot is returned to step S2, and the forging parameters are adjusted for rework. If the number of defects with an internal size greater than 10 μm and less than or equal to 50 μm in the initial pure copper or copper alloy target billet exceeds 0.5% of the total number of defects, the initial pure copper or copper alloy target billet is returned to step S3, and the asynchronous cold rolling parameters are adjusted for rework. The high-purity fine-grained copper target material has defects with internal dimensions of 10 μm or less accounting for more than 99.5% of the total number of defects, and it also has the following characteristics: (a) Purity ≥ 6N; (b) Grain size ≤20μm; Step S4 includes: When adjusting the melting parameters, increase the electron beam power of the melting process by 30~50kW; When adjusting the forging parameters, the number of forging passes is increased by 1; When adjusting the parameters of the asynchronous cold rolling, the single-pass deformation amount of the asynchronous cold rolling is increased by 3-5%.

2. The method for preparing low-defect, high-purity, fine-grained copper target material according to claim 1, characterized in that, In step S1, the melting is electron beam melting, and its parameters include: vacuum degree ≤ 4 × 10⁻⁶. -2 Pa, accelerating voltage of 40~50kV, molten pool temperature gradient ≥200K / cm, electron beam power of 300~500kW, and molten pool depth of 1 / 3-1 / 2 of the raw material diameter; And / or, after the smelting process, the copper volatilization rate is <0.5wt%.

3. The method for preparing low-defect, high-purity, fine-grained copper target material according to claim 1, characterized in that, In step S2, the forging parameters include: forging 3 to 5 times in each of the X, Y, and Z directions, with a single-pass deformation of 45 to 50%, an initial forging temperature of 600 to 950°C, and a final forging temperature of 200 to 500°C.

4. The method for preparing low-defect, high-purity, fine-grained copper target material according to claim 1, characterized in that, In step S3, the parameters of asynchronous cold rolling include: a roll speed ratio of 1.1 to 1.5:1, a single-pass deformation of 25% to 35%, and a cumulative deformation of 90% to 95%.

5. The method for preparing low-defect, high-purity, fine-grained copper target material according to any one of claims 1 to 4, characterized in that, The annealing and heat preservation parameters include: vacuum annealing at 300~400℃, with a heat preservation time of 40min~60min; And / or, the grain size of the pure copper or copper alloy target blank is ≤20μm.

6. The method for preparing low-defect, high-purity, fine-grained copper target material according to any one of claims 1 to 4, characterized in that, The purity of the pure copper is 6N or higher, and the copper alloy is a copper-aluminum or copper-manganese alloy.

7. The method for preparing low-defect, high-purity, fine-grained copper target material according to any one of claims 1 to 4, characterized in that, After step S3 is completed, the pure copper or copper alloy target blank that meets the set target conditions is machined to obtain high-purity copper or copper alloy target material. The set target conditions are: the number of defects with an internal size of less than or equal to 10 μm accounts for more than 99.5% of the total number of defects.

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