Aluminum target material and processing method thereof, and aluminum thin film for integrated circuit

Abstract

The application provides an aluminum target material and a processing method thereof, and an aluminum film for integrated circuits, and relates to the technical field of metal materials. The processing method of the aluminum target material comprises the following steps: cutting a purity >=5N aluminum ingot to obtain a cast aluminum plate; using a stirring head to perform friction stir processing on the cast aluminum plate to obtain an aluminum target material; the stirring head comprises a stirring needle and a shaft shoulder which are coaxially arranged, the shaft shoulder has a working end face facing the cast aluminum plate, a first end portion of the stirring needle is connected with the working end face, and a second end portion of the stirring needle protrudes from the working end face in the axial direction; the stirring head is rotated at a rotating speed A r / min and is pressed into the cast aluminum plate along the thickness direction of the cast aluminum plate, and then is moved at a moving speed B mm / min to obtain the aluminum target material; A / B is 0.25-0.5. The application can solve the problem that the purity >=5N aluminum target material is prone to grain coarsening in the conventional processing method, thereby affecting the sputtering efficiency of the target material and the performance of the formed aluminum film.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, specifically to an aluminum target material and its processing method, and an aluminum thin film for integrated circuits. Background Technology

[0002] Aluminum sputtering targets are commonly used sputtering source materials in magnetron sputtering processes, and can be used to deposit aluminum thin films for integrated circuits on substrate surfaces. The purity, grain size, grain uniformity, and internal defects of the aluminum target affect the stability of the sputtering process and the uniformity of the deposited film. Generally, the smaller the grain size and the more uniform the microstructure of the target, the better it is to reduce the sputtering rate differences caused by different grain orientations, and improve the thickness uniformity and surface quality of the aluminum film.

[0003] High-purity aluminum with a purity ≥5N has low levels of impurity elements and second-phase components, resulting in fewer particles providing heterogeneous nucleation sites during casting and solidification, thus easily leading to the formation of coarse as-cast grains. Simultaneously, high-purity aluminum possesses high stacking fault energy, facilitating dynamic recovery during plastic deformation, and lacks internal second-phase particles and solute atoms to hinder grain boundary migration. Therefore, the fine grains formed after deformation in high-purity aluminum tend to grow during subsequent hot working or heat treatment, increasing the difficulty of preparing and stabilizing the fine-grained structure.

[0004] Existing high-purity aluminum sputtering targets typically employ a process route of "casting-forging or rolling-heat treatment-machining". Forging and rolling are used to break up the coarse-grained structure of the cast state, accumulate plastic deformation, and process the ingot into a sheet, which is then further heat-treated to form a recrystallized structure. This process involves multiple plastic deformations and heat treatments, resulting in a long process flow. Furthermore, the repeated transfers, heating, and equipment contact increase the risk of high-purity aluminum being contaminated by impurities.

[0005] Friction stir machining (FSM) applies intense shear deformation to metallic materials through the rotation and movement of the stirring head, causing plastic flow and dynamic recrystallization within the processing area, thus enabling grain refinement. Existing technologies have proposed FSM for aluminum alloy sheets or sputtering targets, but some methods still use rolled sheets as the processing target, or only process localized areas, surface layers, or back-side reinforced regions of the target. Furthermore, when using higher rotational speeds or lower travel speeds, the frictional action per unit area is prolonged, easily resulting in high heat input. For ≥5N high-purity aluminum lacking second-phase pinning, high heat input may cause recrystallized grains to regrow during or after processing, making it difficult to simultaneously achieve sufficient refinement of the as-cast coarse grains and stable control of the refined microstructure. Summary of the Invention

[0006] In view of the technical problems existing in the background art, the present invention provides an aluminum sputtering target and its processing method, and an aluminum thin film for integrated circuits, to solve the technical problem that the existing pure ≥5N is prone to grain coarsening in conventional processing methods, which in turn affects the sputtering efficiency of the target and the surface quality and conductivity of the formed aluminum thin film.

[0007] To solve the above problems, according to a first aspect of the present invention, a method for processing an aluminum target is provided, comprising the following steps: S1, cutting an aluminum ingot with a purity ≥ 5N to obtain a cast aluminum plate; S2, performing friction stirring on the cast aluminum plate using a stirring head to obtain an aluminum target; the stirring head includes a stirring pin and a shoulder coaxially arranged, the shoulder having a working end face facing the cast aluminum plate, the stirring pin having a first end and a second end, the first end being connected to the working end face, and the second end protruding axially from the working end face; during the friction stirring process, the stirring head is rotated at a rotational speed A r / min and pressed down into the cast aluminum plate along the thickness direction, and then the stirring head is kept in a rotating and pressing state and moved at a travel speed B mm / min; wherein, A and B satisfy: A / B is 0.25~0.5.

[0008] Furthermore, in step S2, the rotation speed of the stirring head is 200 r / min to 600 r / min, and the travel speed of the stirring head is 600 mm / min to 800 mm / min.

[0009] Furthermore, the thickness of the cast aluminum plate is H mm; during the friction stir machining process, the second end of the stirring pin presses down by an amount L mm along the thickness direction of the cast aluminum plate, and the working end face of the shoulder presses down by an amount D mm along the thickness direction of the cast aluminum plate, satisfying L+D=H.

[0010] Furthermore, the thickness of the cast aluminum plate is 8mm~12mm; the dimension of the second end of the stirring needle pressing down along the thickness direction of the cast aluminum plate is 7.8mm~11.9mm; and the dimension D of the working end face of the shoulder pressing down along the thickness direction of the cast aluminum plate is 0.1mm~0.3mm.

[0011] Furthermore, the aluminum target material has two opposing plates along its thickness direction, wherein the surface roughness Ra of either plate is ≤1μm.

[0012] Furthermore, the diameter of the first end of the stirring needle is 4mm~9mm; the tilt angle of the stirring head is 1°~3°.

[0013] Furthermore, the diameter of the shoulder is 10mm~30mm.

[0014] Furthermore, the cast aluminum plate is divided into N strip-shaped processing areas along its length or width, with an overlapping area between adjacent strip-shaped processing areas; the overlap width of the overlapping area is 1 / 3 to 1 / 2 of the shoulder diameter, and the N strip-shaped processing areas together cover the processing area of ​​the cast aluminum plate, where N is an integer greater than or equal to 2; during the friction stir processing, the stirring head performs friction stir processing in each strip-shaped processing area in sequence, and after completing the friction stir processing of each strip-shaped processing area, the stirring head moves to the next strip-shaped processing area, and the single friction stir processing time of the stirring head in each strip-shaped processing area is 5s to 30s.

[0015] Furthermore, after completing the friction stir processing in each strip-shaped processing zone, the stirring head stops working and the cast aluminum plate is cooled to below 25°C before proceeding to the next strip-shaped processing zone.

[0016] Furthermore, the average grain size of the aluminum target is ≤20μm.

[0017] According to a second aspect of the present invention, an aluminum target material is provided, which is prepared by the above-described processing method for aluminum target materials.

[0018] According to a third aspect of the present invention, a method for preparing an aluminum thin film for integrated circuits is provided, comprising using an aluminum target having two plates disposed opposite to each other along its thickness direction; using either plate of the aluminum target as a sputtering surface facing a substrate, performing magnetron sputtering to sputter aluminum atoms from the sputtering surface and deposit them on the substrate surface to form an aluminum thin film for integrated circuits; wherein the aluminum target includes an aluminum target prepared by the above-described aluminum target processing method, or the above-described aluminum target.

[0019] By applying the technical solution of this invention, high-purity aluminum ingots with a purity ≥5N are used as raw materials. These ingots are directly cut into as-cast aluminum plates, and friction stirring is performed without forging, rolling, or recrystallization annealing. By coaxially positioning the stirring pin with the shoulder, and with the second end of the stirring pin protruding axially from the working end face of the shoulder, the frictional heat generated between the stirring head and the as-cast aluminum plate during rotation, pressing, and movement of the stirring head causes the high-purity aluminum to heat up and plasticize in a solid state. The stirring pin further shears, compresses, and stirs the plasticized material, causing coarse as-cast grains to undergo severe plastic deformation and transform into fine equiaxed grains through dynamic recrystallization. Therefore, high-purity aluminum plates that retain their as-cast structure after cutting can be directly subjected to grain refinement and microstructure homogenization, eliminating the need for traditional forging, rolling, and recrystallization annealing processes, shortening the processing flow, and reducing the introduction of impurities that may be introduced from different processing stages and equipment. Meanwhile, by controlling the ratio of the stirring head's rotational speed A to its travel speed B to 0.25~0.5, it is possible to ensure sufficient plasticization and dynamic recrystallization of the cast high-purity aluminum while reducing heat input and heat accumulation per unit processing length. This lowers the risk of grain re-growth due to the lack of grain boundary pinning effect in high-purity aluminum. Therefore, this invention can obtain high-purity aluminum targets with high purity, fine grains, and uniform structure, which helps to improve the sputtering rate and sputtering stability of the target, and improve the surface quality, thickness uniformity, and conductivity of the formed aluminum thin films for integrated circuits. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the friction stir processing method of the present invention;

[0021] Figure 2 Metallographic microstructure of the aluminum target material prepared in Example 1 of this invention;

[0022] Figure 3 EBSD test image of the aluminum target microstructure obtained in Example 1 of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] As described in the background section of this invention, in the prior art, aluminum sputtering targets with a purity ≥5N are prone to grain coarsening during conventional processing methods, which affects the sputtering efficiency of the target and the surface quality and conductivity of the formed aluminum film. To solve this problem, in a typical embodiment of this invention, a processing method for aluminum sputtering targets is provided, comprising the following steps: S1, cutting an aluminum ingot with a purity ≥5N to obtain a cast aluminum plate; S2, using a stirring head to perform friction stirring processing on the cast aluminum plate to obtain an aluminum sputtering target; the stirring head includes a stirring pin and a shoulder coaxially arranged, the shoulder having a working end face facing the cast aluminum plate, the stirring pin having a first end and a second end, the first end being connected to the working end face, and the second end protruding axially from the working end face; during the friction stirring process, the stirring head is rotated at a speed of A r / min and pressed down into the cast aluminum plate along its thickness direction, then the rotating and pressing state of the stirring head is maintained, and it moves at a travel speed of B mm / min; wherein A and B satisfy: A / B is 0.25~0.5.

[0025] The aluminum target material prepared by this invention can be used to prepare aluminum thin films for integrated circuits via magnetron sputtering. During magnetron sputtering, one surface of the aluminum target is used as the sputtering surface, allowing aluminum atoms to be sputtered from the sputtering surface and deposited on the substrate surface, thereby forming an aluminum thin film for integrated circuits. Aluminum thin films have high requirements for purity, surface flatness, thickness uniformity, and conductivity. The purity, grain size, and microstructure uniformity of high-purity aluminum targets affect the sputtering rate and sputtering stability. When the grains of the aluminum target are coarse or the grain size distribution is uneven, the sputtering rate between different grain orientations is prone to differ, leading to uneven etching of the target surface and affecting the surface roughness, thickness uniformity, and resistivity of the formed aluminum thin film. Therefore, it is necessary to refine and homogenize the grain structure while maintaining the purity of the aluminum target.

[0026] This invention uses high-purity aluminum ingots with a purity ≥ 5N as raw material. Here, ≥ 5N purity means that the mass percentage of aluminum element is ≥ 99.999%, and the total content of unavoidable impurity elements is ≤ 0.001%. Because the content of impurity elements, solute atoms, and second-phase particles in this high-purity aluminum is extremely low, its as-cast microstructure typically exhibits coarse grains. Furthermore, during subsequent processing and heating, the grain boundary migration lacks the pinning effect of solute atoms and second-phase particles, making the refined grains prone to regrowth. Therefore, existing high-purity aluminum sputtering tools typically require forging, rolling, and recrystallization annealing after ingot cutting to refine and homogenize the coarse as-cast microstructure through plastic deformation and recrystallization. However, this process is lengthy and increases the risk of introducing impurities during processing. Specifically, the purity of the high-purity aluminum ingot can be 5N, 5N5, 6N, or 6N5.

[0027] Unlike the aforementioned processing methods, this invention, after cutting high-purity aluminum ingots into as-cast aluminum plates, no longer involves forging, rolling, or recrystallization annealing of the as-cast aluminum plates. Instead, it directly performs friction stir processing. The cutting process primarily alters the shape and size of the high-purity aluminum ingot, while essentially preserving its main as-cast microstructure. Consequently, the resulting as-cast aluminum plates retain coarse as-cast grains. Subsequent friction stir processing directly refines the as-cast microstructure, replacing the microstructure refinement and homogenization processes performed by forging, rolling, and recrystallization annealing. This shortens the processing flow of high-purity aluminum targets and reduces the introduction of impurities that may occur during intermediate processing steps.

[0028] Specifically, this invention employs a stirring head with a stirring pin and a shoulder. The stirring pin and shoulder are coaxially arranged, and the shoulder has a working end face facing the cast aluminum plate. The first end of the stirring pin is connected to the shoulder, and the second end protrudes axially from the working end face of the shoulder. The working end face facing the cast aluminum plate means that the working end face is located on the side of the shoulder closest to the cast aluminum plate and can act on the cast aluminum plate during the downward pressing of the stirring head; it does not mean that the working end face is parallel to the surface of the cast aluminum plate. When the stirring head has an angle, the working end face can form a corresponding angle with the stirring head as a whole relative to the surface of the cast aluminum plate. Thus, the end of the stirring pin protruding from the working end face can face the cast aluminum plate, and the shoulder drives the stirring pin to rotate stably and synchronously. When the stirring head rotates and presses down along the thickness direction of the cast aluminum plate, the portion of the stirring pin protruding from the working end face gradually enters the interior of the cast aluminum plate, thereby rubbing, shearing, squeezing, and stirring the material inside the cast aluminum plate.

[0029] The friction between the stirring pin and the cast aluminum plate, along with the plastic deformation of the material within the plate, generates heat. This causes the high-purity aluminum in the processing area to heat up, reduce its deformation resistance, and plasticize without melting. Subsequently, the stirring head is kept rotating and pressed down, moving along the surface of the cast aluminum plate, allowing the area of ​​action of the stirring pin to continuously extend with its movement. The rotating stirring pin continuously shears, compresses, and stirs the plasticized high-purity aluminum, causing intense plastic deformation in the processing area. This leads to the breakup of coarse cast grains and the formation of fine equiaxed grains through dynamic recrystallization. Therefore, the cut cast aluminum plate can achieve refined and homogenized microstructure without prior forging, rolling, and recrystallization annealing.

[0030] Furthermore, this invention controls the ratio of the stirring head's rotational speed A to its travel speed B to be 0.25–0.5, equivalent to the stirring head traveling 2 mm–4 mm forward per revolution. This ratio coordinates the frictional heat generation and plastic deformation during the friction stirring process: on the one hand, it generates sufficient heat in the processing area to reduce the deformation resistance of high-purity aluminum, and through the shearing, squeezing, and stirring action of the stirring head, it causes coarse cast grains to undergo severe plastic deformation and dynamic recrystallization; on the other hand, it reduces the number of revolutions of the stirring head per unit travel distance, shortening the time the same area is continuously subjected to friction and stirring, thereby reducing heat input and heat accumulation per unit processing length. Since there are fewer solute atoms and second-phase particles in ≥5N high-purity aluminum that can hinder grain boundary migration, the above-mentioned combination of rotational speed and travel speed can reduce the risk of grains growing again due to heat accumulation after dynamic recrystallization, thereby improving the stability and uniformity of the refined structure while ensuring sufficient plasticization and dynamic recrystallization of the cast high-purity aluminum.

[0031] Therefore, this invention uses high-purity aluminum ingots with a purity ≥5N as raw material, directly cuts the ingots into as-cast aluminum plates, and performs friction stir processing without forging, rolling, or recrystallization annealing. By setting the stirring pin coaxially with the shoulder and making the second end of the stirring pin axially protrude from the working end face of the shoulder, the frictional heat generated between the stirring head and the as-cast aluminum plate during the rotation, pressing, and movement of the stirring head causes the high-purity aluminum to heat up and plasticize in the solid state. The stirring pin further shears, extrudes, and stirs the plasticized material, causing the coarse as-cast grains to undergo severe plastic deformation and transform into fine equiaxed grains through dynamic recrystallization. Thus, the grain refinement and microstructure homogenization of high-purity aluminum plates that still retain the as-cast structure after cutting can be directly achieved, omitting the traditional forging, rolling, and recrystallization annealing processes, shortening the processing flow, and reducing the introduction of impurities that may be caused by different processing steps and equipment. Meanwhile, by controlling the ratio of the stirring head's rotational speed A to its travel speed B to 0.25~0.5, it is possible to ensure sufficient plasticization and dynamic recrystallization of the cast high-purity aluminum while reducing heat input and heat accumulation per unit processing length. This lowers the risk of grain re-growth due to the lack of grain boundary pinning effect in high-purity aluminum. Therefore, this invention can obtain high-purity aluminum targets with high purity, fine grains, and uniform structure, which helps to improve the sputtering rate and sputtering stability of the target, and improve the surface quality, thickness uniformity, and conductivity of the formed aluminum thin films for integrated circuits.

[0032] Specifically, A / B can be a range of 0.25r / mm, 0.3r / mm, 0.4r / mm, 0.45r / mm, 0.5r / mm, or any two of these ranges.

[0033] In some embodiments of the present invention, before step S1, an aluminum ingot is prepared. The aluminum ingot is obtained by semi-continuous casting or vacuum casting. Specifically, high-purity aluminum raw material is melted to form an aluminum melt, and the aluminum melt is gradually cooled and solidified in a crystallizer using a semi-continuous casting method, or the high-purity aluminum raw material is melted and cast under vacuum conditions, and after cooling and solidification, a high-purity aluminum ingot with a purity ≥5N is obtained. Among them, semi-continuous casting helps to obtain high-purity aluminum ingots with relatively stable dimensions and composition, while vacuum casting helps to reduce the introduction of gases, oxides and foreign impurities during melting and solidification, thereby maintaining the purity of the high-purity aluminum ingot. After the high-purity aluminum ingot is obtained, it is cut to obtain a cast aluminum plate with a thickness ≥8mm, and the cast aluminum plate is not forged, rolled and recrystallized annealed before friction stir processing. By making the cast aluminum plate ≥8mm, sufficient thickness can be reserved for friction stir processing and subsequent surface processing, reducing the risk of significant deformation of the cast aluminum plate due to insufficient thickness or contact between the stirring pin and the bottom pad.

[0034] In some embodiments of the present invention, a ceramic or graphite pad and a clamp are used to fix the cast aluminum plate before friction stir processing. Specifically, the ceramic or graphite pad is placed on the worktable of the friction stir processing equipment, and the cast aluminum plate is then placed flat on the pad. The clamp is positioned in the edge area of ​​the cast aluminum plate or in a non-processing area that does not affect the movement of the stirring head, and a clamping force is applied to the cast aluminum plate towards the pad through the clamp, so that the cast aluminum plate is attached to and fixed on the pad. The pad can provide support for the cast aluminum plate during the downward pressing of the stirring head, and the clamp can restrict the movement of the cast aluminum plate along the plate surface direction, rotation around a direction perpendicular to the plate surface, or warping along the thickness direction, thereby reducing vibration, offset, and warping generated during friction stir processing, and helping to maintain the processing trajectory and downward pressing dimension stability of the stirring head. At the same time, the ceramic and graphite pads have good heat resistance and are not prone to introducing metal impurities such as iron and copper into the high-purity aluminum, which can reduce the contamination caused by direct contact between the cast aluminum plate and the metal worktable, and is beneficial to maintaining the purity of the high-purity aluminum target material.

[0035] In some embodiments of the present invention, the stirring head is made of high-temperature hard alloy or cubic boron nitride ceramic. The high-temperature hard alloy can be a tungsten-rhenium alloy. By using high-temperature hard alloy or cubic boron nitride ceramic to prepare the stirring head, the high hardness, heat resistance, and wear resistance of these materials can be utilized to maintain good structural and dimensional stability of the stirring pin and shoulder during rotation, compression, and movement, reducing the risk of wear or deformation of the stirring head under high temperature and continuous friction. Furthermore, compared to using a steel stirring head, using a tungsten-rhenium alloy or cubic boron nitride ceramic stirring head can reduce the risk of introducing metallic impurities such as iron and chromium into the high-purity aluminum during processing, which is beneficial for maintaining the purity of the high-purity aluminum target material.

[0036] In some embodiments of the present invention, the process after friction stir processing further includes machining the cast aluminum plate after friction stir processing. Specifically, the periphery of the cast aluminum plate can be machined to remove burrs, uneven areas on the surface, and pre-reserved machining allowances generated during friction stir processing. The cast aluminum plate is then machined to the required dimensions, thickness, and surface roughness for the high-purity aluminum target, resulting in the high-purity aluminum target. Machining improves the dimensional accuracy and surface flatness of the high-purity aluminum target, reduces protrusions, scratches, and local defects on the surface, and enables the high-purity aluminum target to be stably mounted in the magnetron sputtering equipment. Simultaneously, it helps reduce localized abnormal discharges and uneven erosion during sputtering, improves sputtering stability, and enhances the surface quality and thickness uniformity of the formed aluminum film.

[0037] In some embodiments, in step S2, the rotational speed of the stirring head is 200 r / min to 600 r / min, and the travel speed of the stirring head is 600 mm / min to 800 mm / min. By controlling the stirring head to use a lower rotational speed and a higher travel speed for processing, while generating sufficient frictional heat and plastic deformation to plasticize and dynamically recrystallize cast high-purity aluminum, the time during which the same area is continuously subjected to friction and stirring can be shortened, reducing the heat input per unit processing length, thereby reducing the risk of grain re-growth and improving the efficiency of friction stir processing. Specifically, the rotational speed of the stirring head can be within the range of 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, or any combination thereof; the travel speed of the stirring head can be within the range of 600 mm / min, 650 mm / min, 700 mm / min, 750 mm / min, 800 mm / min, or any combination thereof.

[0038] In some embodiments, the thickness of the cast aluminum plate is H mm; during the friction stir machining process, the second end of the stirring pin presses down along the thickness direction of the cast aluminum plate by an amount of L mm, and the working end face of the shoulder presses down along the thickness direction of the cast aluminum plate by an amount of D mm, satisfying L+D=H. Here, the pressing down of the second end of the stirring pin along the thickness direction of the cast aluminum plate refers to the effective dimension of the second end of the stirring pin acting inside the cast aluminum plate along the thickness direction when the stirring head is in the friction stir machining state. It should be noted that when the stirring head has an angle, L represents the effective pressing down dimension of the stirring pin along the thickness direction of the cast aluminum plate, not the actual length of the stirring pin along its own axial direction. The pressing down dimension D of the working end face of the shoulder refers to the depth to which the working end face of the shoulder is pressed into the cast aluminum plate relative to the plate surface before pressing down. Therefore, L+D represents the total effective machining depth from the plate surface before pressing down to the deepest point of action of the stirring pin in the thickness direction. By making L+D=H, the total effective processing depth of the stirring head can be matched with the thickness of the cast aluminum plate. This allows the stirring pin's action range to reach the bottom of the cast aluminum plate along the thickness direction, reducing the amount of unprocessed cast structure remaining at the bottom. This achieves grain refinement and microstructure homogenization of the high-purity aluminum target material along the thickness direction. Simultaneously, after the working end face of the shaft shoulder is pressed into the cast aluminum plate, it applies friction, constraint, and forging action to the plasticized material near the plate surface, promoting the flow and dense bonding of the plasticized material and reducing the risk of defects such as holes and grooves in the processed area.

[0039] In some embodiments, the thickness of the cast aluminum plate is 8mm to 12mm; the second end of the stirring pin presses down along the thickness direction of the cast aluminum plate by an amount of 7.8mm to 11.9mm; and the working end face of the shoulder presses down along the thickness direction of the cast aluminum plate by an amount D of 0.1mm to 0.3mm. By controlling the above-mentioned size range, the working depth of the stirring pin can be adapted to the thickness of the cast aluminum plate, and the shoulder can apply appropriate friction and forging action to the material near the plate surface, thereby taking into account both the microstructure refinement effect in the thickness direction and the plate surface forming quality. This avoids insufficient material backfilling and dense bonding due to insufficient shoulder pressing, and also reduces excessive heat input, excessive material extrusion, increased flash, and plate surface depression caused by excessive shoulder pressing.

[0040] Specifically, the thickness of the cast aluminum plate can be 8mm, 9mm, 10mm, 11mm, 12mm or any combination thereof; the dimension of the second end of the stirring pin pressing down along the thickness direction of the cast aluminum plate can be 7.8mm, 8mm, 9mm, 10mm, 11.9mm or any combination thereof; the dimension D of the working end face of the shoulder pressing down along the thickness direction of the cast aluminum plate can be 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm or any combination thereof.

[0041] In some embodiments, the aluminum target material has two opposing plates along its thickness direction, wherein the surface roughness Ra of either plate is ≤1 μm. By surface-processing both plates and controlling their surface roughness, protrusions, scratches, and local defects on both plates can be reduced, allowing the high-purity aluminum target material to select either plate as the sputtering surface according to the installation direction. When one plate is used as the sputtering surface, it helps to improve the stability of the electric field distribution and sputtering state on the target surface, reduce local abnormal discharge, particle shedding, and uneven erosion, thereby reducing the surface roughness of the formed aluminum film and improving the surface flatness and thickness uniformity of the aluminum film.

[0042] In some embodiments, the diameter of the first end of the stirring pin is 4mm to 9mm; the tilt angle of the stirring head is 1° to 3°. By controlling the diameter of the stirring pin, the shear range, degree of plastic deformation, and material conveying capacity of the stirring pin for high-purity aluminum can be adjusted. This ensures sufficient deformation and dynamic recrystallization of the cast high-purity aluminum while avoiding insufficient processing range due to an excessively small stirring pin diameter, or excessive processing resistance and heat input due to an excessively large stirring pin diameter. Furthermore, by controlling the stirring head to have an appropriate tilt angle, a downward extrusion force can be applied to the plasticized material behind the stirring pin, promoting the backfilling and dense bonding of the plasticized material, reducing processing defects such as holes, tunnels, and surface grooves, while avoiding excessive extrusion of the sheet material due to an excessively large tilt angle.

[0043] Specifically, the diameter of the first end of the stirring needle can be 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or any combination thereof; the tilt angle of the stirring head can be 1°, 1.5°, 2°, 2.5°, 3° or any combination thereof.

[0044] In some embodiments, the diameter of the shoulder is 10mm to 30mm. By controlling the diameter of the shoulder, the range of action of the shoulder on the material near the plate surface and the degree of frictional heat generation can be adjusted. This ensures that the material is fully plasticized and forms a suitable processing width, while reducing excessive heat input, plate deformation, and increased flash caused by an excessively large shoulder diameter, thus balancing the efficiency of friction stir processing and the quality of plate forming. Specifically, the diameter of the shoulder can be 10mm, 15mm, 20mm, 25mm, 30mm, or any combination thereof.

[0045] In some embodiments, the cast aluminum plate is divided into N strip-shaped processing areas along its length or width, and there is an overlapping area between two adjacent strip-shaped processing areas; the overlap width of the overlapping area is 1 / 3 to 1 / 2 of the shoulder diameter, and the N strip-shaped processing areas together cover the processing area of ​​the cast aluminum plate, where N is an integer greater than or equal to 2; during the friction stir processing, the stirring head performs friction stir processing in each strip-shaped processing area in sequence, and after completing the friction stir processing of each strip-shaped processing area, the stirring head moves to the next strip-shaped processing area, and the single friction stir processing time of the stirring head in each strip-shaped processing area is 5s to 30s.

[0046] Specifically, when processing along the length of the cast aluminum plate, the stirring head moves from one end of the area to be processed along the length to the other, forming a strip-shaped processing zone along the length. After completing this strip-shaped processing zone, the stirring head moves along the width of the cast aluminum plate to an adjacent position, and then moves again along the length to form the next strip-shaped processing zone along the length. There is an overlapping area between two adjacent strip-shaped processing zones. In this case, the width of the overlapping area refers to the dimension of the overlapping area along the width of the cast aluminum plate, and the width of the overlapping area is 1 / 3 to 1 / 2 of the shoulder diameter. Each strip-shaped processing zone covers the dimension of the area to be processed along the length direction, and multiple strip-shaped processing zones are arranged sequentially along the width direction and together cover the dimension of the area to be processed along the width direction, thereby covering the entire area to be processed.

[0047] When processing along the width of the cast aluminum plate, the stirring head moves from one end of the area to be processed along the width to the other, forming a strip-shaped processing zone along the width. After completing this strip-shaped processing zone, the stirring head moves along the length of the cast aluminum plate to an adjacent position, and then moves again along the width to form the next strip-shaped processing zone along the width. There is an overlapping area between two adjacent strip-shaped processing zones. In this case, the width of the overlapping area refers to the dimension of the overlapping area along the length of the cast aluminum plate, and the width of the overlapping area is 1 / 3 to 1 / 2 of the shoulder diameter. Each strip-shaped processing zone covers the dimension of the area to be processed along the width. Multiple strip-shaped processing zones are arranged sequentially along the length and together cover the dimension of the area to be processed along the length, thus covering the entire area to be processed.

[0048] By partially overlapping two adjacent strip-shaped processing zones, the risk of insufficiently processed areas remaining between adjacent zones can be reduced, ensuring that all areas to be processed undergo plastic deformation and dynamic recrystallization. Controlling the width of the overlapping area to 1 / 3 to 1 / 2 of the shoulder diameter ensures complete coverage of the area to be processed while preventing excessively large overlapping areas from causing repeated heating of localized materials and the re-growth of refined grains, thereby improving the microstructure uniformity of the high-purity aluminum sputtering material in the plate direction.

[0049] By controlling the single-cycle stirring and friction processing time of the stirring head in each strip processing zone, the stirring head can complete the processing of the current strip processing zone at a predetermined travel speed, ensuring that the high-purity aluminum in each strip processing zone receives relatively uniform friction, shearing, extrusion, and stirring effects. If the travel time is too short, the stirring head may not have completed the processing of the entire strip processing zone, easily resulting in areas that are not sufficiently plasticized or refined; if the travel time is too long, the time that the same area is subjected to friction and stirring increases, easily leading to excessive heat input and heat accumulation, causing the grains after dynamic recrystallization to grow again. Therefore, by controlling the travel time, the complete processing of the strip processing zone, the degree of grain refinement, and the heat input can be balanced, and different strip processing zones can obtain a relatively uniform grain structure, thereby improving the microstructure uniformity of the high-purity aluminum target material in the plate direction.

[0050] Specifically, the single stirring friction processing time of the stirring head in each strip-shaped processing zone can be a range of 5s, 10s, 15s, 20s, 30s, or any combination thereof.

[0051] In some embodiments, after each strip-shaped processing zone completes friction stir processing, the stirring head stops working, and the cast aluminum plate is cooled to below 25°C before proceeding to the next strip-shaped processing zone. Stopping the stirring head means that it stops rotating, stops moving, and exits the surface of the cast aluminum plate before cooling. By controlling the cooling temperature between adjacent processing passes, the impact of residual heat from the previous pass on the subsequent pass can be reduced, avoiding continuous heat accumulation between different passes. Simultaneously, processing in each strip-shaped processing zone at a relatively consistent initial temperature helps stabilize the plasticization degree and dynamic recrystallization process of high-purity aluminum, suppresses grain growth in overlapping areas and subsequent processing areas, thereby improving the microstructure uniformity and process repeatability between different processing zones.

[0052] In some embodiments, the average grain size of the aluminum target is ≤20 μm. By controlling the average grain size within this range, the local sputtering rate differences caused by coarse grains and different grain orientations can be reduced, resulting in more uniform sputtering erosion of the target surface, thereby improving the sputtering rate, sputtering stability, and utilization of the target. Simultaneously, a fine and uniform grain structure helps reduce abnormal particles generated during sputtering, allowing aluminum atoms to be deposited more uniformly on the substrate surface, thereby reducing the surface roughness and resistivity of the aluminum film and improving the thickness uniformity, surface quality, and conductivity of the aluminum film.

[0053] In some embodiments of the present invention, the grain size fluctuation value of the aluminum target along the thickness direction is ≤5μm. Specifically, multiple locations along the thickness direction of the aluminum target are selected for grain size detection, and the difference between the average grain size at each location and the average grain size of the aluminum target is used as the grain size fluctuation value. By controlling the grain size fluctuation value, the occurrence of locally coarse grains or insufficiently refined regions along the thickness direction of the aluminum target can be reduced, ensuring uniform grain structure throughout the entire thickness range. Therefore, both surfaces of the aluminum target can serve as sputtering surfaces, and as the target is gradually consumed during sputtering, a relatively consistent sputtering state can still be maintained at different thickness locations.

[0054] In a second aspect, the present invention provides an aluminum target material prepared by the above-described aluminum target material processing method.

[0055] The above-mentioned preparation method results in aluminum sputtering targets with high purity, fine and uniform grain structure, and good thickness-direction consistency. It also reduces microstructural and surface defects such as coarse grains, grooves, and localized unevenness in the cast state. Furthermore, the machined aluminum sputtering targets exhibit high dimensional accuracy and surface flatness, with both surfaces meeting the required surface roughness, which helps improve the uniformity of the microstructure, structural integrity, surface quality, and performance consistency of the aluminum sputtering targets.

[0056] A third aspect of the present invention provides a method for preparing an aluminum thin film for integrated circuits, using an aluminum target having two plates disposed opposite to each other along its thickness direction; magnetron sputtering is performed on either plate of the aluminum target as a sputtering surface facing a substrate, so that aluminum atoms are sputtered from the sputtering surface and deposited on the substrate surface to form an aluminum thin film for integrated circuits; wherein the aluminum target includes an aluminum target prepared by the above-described high-purity aluminum target processing method, or the above-described aluminum target.

[0057] Because the aluminum target is used for magnetron sputtering, it has high purity, fine and uniform grain structure and relatively flat sputtering surface. Therefore, it is not easy for local areas to be eroded too fast or too slow during magnetron sputtering. This allows aluminum atoms to be deposited on the substrate surface at a relatively stable and uniform rate, thereby improving the sputtering rate and sputtering stability of the aluminum target, reducing the surface roughness and resistivity of the formed aluminum film, and improving the surface flatness, thickness uniformity and conductivity of the aluminum film.

[0058] In some embodiments of the present invention, magnetron sputtering includes: installing an aluminum target in a target position of a magnetron sputtering cavity; selecting either of the two surfaces of the aluminum target as a sputtering surface, such that the sputtering surface faces the substrate and is spaced apart from the substrate; evacuating the magnetron sputtering cavity to achieve a predetermined base vacuum level; introducing argon gas into the magnetron sputtering cavity and applying sputtering power to the aluminum target to ionize the argon gas and form plasma; and bombarding the sputtering surface of the aluminum target under the action of an electric field, causing aluminum atoms to be sputtered from the sputtering surface and move toward the substrate, thereby depositing on the substrate surface to form an aluminum thin film for integrated circuits.

[0059] The vacuum level of the magnetron sputtering cavity is 1×10⁻⁶. -6 Torr~1×10 -5 The sputtering parameters are: Torr (sputtering power 200W~400W), argon flow rate 40sccm~80sccm, target-substrate spacing 60mm~100mm, and sputtering time 5min~20min. The target-substrate spacing refers to the distance between the sputtering surface of the aluminum target and the substrate surface facing the sputtering surface. By controlling these magnetron sputtering conditions, a relatively stable plasma can be formed within the magnetron sputtering cavity, allowing argon ions to continuously bombard the sputtering surface of the aluminum target and ensuring that the sputtered aluminum atoms are deposited more uniformly on the substrate surface, thereby improving the deposition uniformity and surface quality of the aluminum thin film.

[0060] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0061] Example 1

[0062] This embodiment provides a method for processing aluminum sputtering targets, including the following steps:

[0063] S1, place high-purity aluminum raw material in a vacuum melting furnace at a vacuum degree of 10. -3 The high-purity aluminum raw material was heated to 750℃ under Pa conditions to melt it and form an aluminum melt. The aluminum melt was held at 750℃ for 30 minutes, and then cast using vacuum casting at a temperature of 690℃. The cooling water flow rate during solidification was 30 L / min. After cooling and solidification, a high-purity aluminum ingot with a purity of 5N5 was obtained. The high-purity aluminum ingot was cut using a saw to obtain a cast aluminum plate with a length of 200 mm, a width of 200 mm, and a thickness H of 8 mm.

[0064] S2. A graphite pad is placed on the worktable of the friction stir processing equipment. The cast aluminum plate is placed flat on the graphite pad, and the edge area of ​​the cast aluminum plate is clamped and fixed using a clamp. A stirring head with a stirring pin and a shoulder is used to perform friction stir processing on the cast aluminum plate. The stirring head is made of tungsten-rhenium alloy, the shoulder diameter is 25mm, the diameter of the first end of the stirring pin is 5mm, and the stirring pin and the shoulder are coaxially arranged. The shoulder has a working end face facing the cast aluminum plate. The first end of the stirring pin is connected to the shoulder, and the second end protrudes axially from the working end face of the shoulder. The tilt angle of the stirring head is 2°.

[0065] The stirring head is rotated at a speed of A (200 r / min) and pressed down along the thickness direction of the cast aluminum plate. Under friction stir machining conditions, the pressing dimension L of the second end of the stirring pin along the thickness direction of the cast aluminum plate is 7.9 mm, and the pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0.1 mm, L + D = 8 mm. Maintaining the rotation and pressing state of the stirring head, the stirring head is subjected to friction stir machining along the length direction of the cast aluminum plate at a travel speed B (800 mm / min). The ratio of the rotational speed A to the travel speed B, A / B, is 0.25 r / mm.

[0066] The stirring head moves from one end of the cast aluminum plate along its length to the other, forming a strip-shaped processing zone. The processing trajectory length within each strip-shaped processing zone is 200 mm, and the moving time of the stirring head within each strip-shaped processing zone is 15 seconds. After completing one strip-shaped processing zone, the stirring head stops working, and the cast aluminum plate is cooled to below 25°C. Subsequently, the stirring head moves along the width direction of the cast aluminum plate to an adjacent position, and then processes the next strip-shaped processing zone along its length.

[0067] There is an overlapping area between two adjacent strip-shaped processing areas. The width of the overlapping area along the width direction of the cast aluminum plate is 1 / 3 of the shoulder diameter, which is 8.3 mm. The above processing and cooling process is repeated until multiple strip-shaped processing areas are arranged sequentially along the width direction of the cast aluminum plate and together cover the entire area to be processed of the cast aluminum plate, thus obtaining the processed aluminum plate.

[0068] S3 uses a CNC machine tool to cut the aluminum plate, removing keyholes, burrs, uneven areas, and materials outside the target area of ​​the aluminum target formed at the start and end positions of the friction stir machining. The two sides and perimeter of the aluminum plate are then finished to obtain a disc-shaped high-purity aluminum target with a diameter of 6 inches and a thickness of 5 mm.

[0069] Example 2

[0070] The difference between this embodiment and Embodiment 1 is that:

[0071] In S1, a high-purity aluminum ingot with a purity of 5N is used. The high-purity aluminum ingot is cut using a saw to obtain a cast aluminum plate with a length of 150mm, a width of 150mm, and a thickness H of 8mm.

[0072] In S2, the stirring head is made of tungsten-rhenium alloy, the shoulder diameter is 20mm, and the tilt angle of the stirring head is 1°. Under friction stir processing, the downward pressing dimension L of the second end of the stirring pin along the thickness direction of the cast aluminum plate is 7.9mm, the downward pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0.1mm, and L+D=8mm.

[0073] The stirring head has a rotational speed A of 300 r / min and a travel speed B of 800 mm / min, with an A / B ratio of 0.375 r / mm. The processing trajectory length within each strip-shaped processing zone is 150 mm, and the moving time of the stirring head within each zone is 11.25 s. The overlap between two adjacent strip-shaped processing zones, along the width direction of the cast aluminum plate, is half the shoulder diameter, i.e., 10 mm.

[0074] In S3, a CNC machine tool is used to cut the aluminum plate to remove keyholes, burrs, uneven areas on the surface, and materials other than the target area of ​​the high-purity aluminum target. The two sides and the perimeter of the aluminum plate are then finished to obtain a disc-shaped high-purity aluminum target with a diameter of 4 inches and a thickness of 5 mm.

[0075] Except for the differences mentioned above, all other steps and parameters in this embodiment are the same as in Embodiment 1.

[0076] Example 3

[0077] The difference between this embodiment and Embodiment 1 is that:

[0078] In S1, a high-purity aluminum ingot with a purity of 5N5 is used. The high-purity aluminum ingot is cut using a saw to obtain a cast aluminum plate with a length of 300mm, a width of 300mm, and a thickness H of 12mm.

[0079] In S2, the stirring head is made of cubic boron nitride ceramic, the shoulder diameter is 30mm, and the tilt angle of the stirring head is 2°. Under friction stir processing, the downward pressing dimension L of the second end of the stirring pin along the thickness direction of the cast aluminum plate is 11.7mm, the downward pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0.3mm, and L+D=12mm.

[0080] The stirring head rotates at a speed A of 200 r / min and travels at a speed B of 600 mm / min, with a ratio of A / B of approximately 0.33 r / mm. The processing trajectory length within each strip-shaped processing zone is 300 mm, and the moving time of the stirring head within each zone is 30 s. The overlap between two adjacent strip-shaped processing zones, along the width direction of the cast aluminum plate, is half the shoulder diameter, i.e., 15 mm.

[0081] In S3, a CNC machine tool is used to cut the aluminum plate to remove keyholes, burrs, uneven areas on the surface, and materials other than the target area of ​​the high-purity aluminum target. The two sides and the perimeter of the aluminum plate are then finished to obtain a disc-shaped high-purity aluminum target with a diameter of 8 inches and a thickness of 6.35 mm.

[0082] Except for the differences mentioned above, all other steps and parameters in this embodiment are the same as in Embodiment 1.

[0083] Example 4

[0084] The difference between this embodiment and Embodiment 1 is that:

[0085] In S1, a high-purity aluminum ingot with a purity of 6N is used, and after being cut by a saw, a cast aluminum plate with a length of 210mm, a width of 180mm, and a thickness of H of 9mm is obtained.

[0086] In S2, a ceramic pad and clamps are used to fix the cast aluminum plate. The stirring head is made of tungsten-rhenium alloy, with a shoulder diameter of 24mm and an inclination angle of 1.5°. The downward pressing dimension L of the second end of the stirring pin along the thickness direction of the cast aluminum plate is 8.8mm, and the downward pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0.2mm, so L+D=9mm.

[0087] The stirring head rotates at a speed A of 280 r / min, travels at a speed B of 700 mm / min, and has a ratio of A / B of 0.4 r / mm. The processing trajectory length within each strip-shaped processing zone is 210 mm, and the moving time of the stirring head within each zone is 18 s. The overlap between two adjacent strip-shaped processing zones is 1 / 3 of the shoulder diameter, or 8 mm, along the width direction of the cast aluminum plate. After completing each strip-shaped processing zone, the cast aluminum plate is cooled to 20°C before processing the next strip-shaped processing zone.

[0088] In S3, a CNC machine tool is used to cut the aluminum plate to obtain a disc-shaped high-purity aluminum target with a diameter of 6 inches and a thickness of 5.5 mm.

[0089] Example 5

[0090] The difference between this embodiment and Embodiment 1 is that:

[0091] In S1, a high-purity aluminum ingot with a purity of 6N5 is used, which is cut by a saw to obtain a cast aluminum plate with a length of 240mm, a width of 240mm, and a thickness H of 10mm.

[0092] In S2, the stirring head is made of cubic boron nitride ceramic, the shoulder diameter is 20mm, and the tilt angle of the stirring head is 3°. The downward pressing dimension L of the second end of the stirring pin along the thickness direction of the cast aluminum plate is 9.8mm, the downward pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0.2mm, and L+D=10mm.

[0093] The stirring head rotates at a speed A of 320 r / min, travels at a speed B of 800 mm / min, and has a ratio of A / B of 0.4 r / mm. The processing trajectory length within each strip-shaped processing zone is 240 mm, and the moving time of the stirring head within each zone is 18 s. The overlap between two adjacent strip-shaped processing zones is half the shoulder diameter, or 10 mm, along the width direction of the cast aluminum plate. After completing each strip-shaped processing zone, the cast aluminum plate is cooled to 25°C before processing the next strip-shaped processing zone.

[0094] In S3, a CNC machine tool is used to cut the aluminum plate to obtain a disc-shaped high-purity aluminum target with a diameter of 8 inches and a thickness of 6 mm.

[0095] Example 6

[0096] The difference between this embodiment and Embodiment 1 is that:

[0097] In S1, a high-purity aluminum ingot with a purity of 5N is used, and after being cut by a saw, a cast aluminum plate with a length of 180mm, a width of 180mm, and a thickness of H of 11mm is obtained.

[0098] In S2, a ceramic pad and clamps are used to fix the cast aluminum plate. The stirring head is made of tungsten-rhenium alloy, with a shoulder diameter of 28mm and an inclination angle of 2°. The downward pressing dimension L of the second end of the stirring pin along the thickness direction of the cast aluminum plate is 10.7mm, and the downward pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0.3mm, so L+D=11mm.

[0099] The stirring head rotates at a speed A of 300 r / min, travels at a speed B of 600 mm / min, and the ratio of A to B is 0.5 r / mm. The processing trajectory length within each strip-shaped processing zone is 180 mm, and the movement time of the stirring head within each zone is 18 s. The overlap between two adjacent strip-shaped processing zones is 2 / 5 of the shoulder diameter, or 11.2 mm, along the width direction of the cast aluminum plate. After completing each strip-shaped processing zone, the cast aluminum plate is cooled to 20°C before processing the next strip-shaped processing zone.

[0100] In S3, a CNC machine tool is used to cut the aluminum plate to obtain a disc-shaped high-purity aluminum target with a diameter of 6 inches and a thickness of 6.35 mm.

[0101] Example 7

[0102] The difference between this embodiment and Embodiment 1 is that:

[0103] In S2, the stirring head rotates at a speed A of 500 r / min, travels at a speed B of 1000 mm / min, and the ratio of A to B is 0.5 r / mm. The processing trajectory length within each strip-shaped processing zone is 200 mm, and the moving time of the stirring head within each strip-shaped processing zone is 12 s.

[0104] Example 8

[0105] The difference between this embodiment and Embodiment 1 is that:

[0106] In S2, the thickness H of the cast aluminum plate is 8mm, the downward pressing dimension L of the second end of the stirring needle along the thickness direction of the cast aluminum plate is 6mm, the downward pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0.1mm, and L+D is 6.1mm, which is less than the thickness H of the cast aluminum plate.

[0107] In S3, a high-purity aluminum target with a thickness of 7mm is obtained after machining.

[0108] Example 9

[0109] The difference between this embodiment and Embodiment 1 is that:

[0110] In S2, the width of the overlapping area between two adjacent strip-shaped processing areas along the width direction of the cast aluminum plate is 1 / 5 of the shoulder diameter, i.e., 5mm.

[0111] Example 10

[0112] The difference between this embodiment and Embodiment 1 is that:

[0113] In S2, after each strip-shaped processing area is completed, the cast aluminum plate is cooled to 50°C before processing the next strip-shaped processing area.

[0114] Example 11

[0115] The difference between this embodiment and Embodiment 1 is that:

[0116] In S2, the working end face of the shoulder contacts the surface of the cast aluminum plate but does not press into it. The downward pressing dimension D of the working end face of the shoulder along the thickness direction of the cast aluminum plate is 0 mm. The downward pressing dimension L of the second end of the stirring pin along the thickness direction of the cast aluminum plate is 6 mm. The thickness H of the cast aluminum plate is 8 mm, and L + D = 6 mm, which is less than the thickness H of the cast aluminum plate. Therefore, the processing area formed by the stirring head does not penetrate the cast aluminum plate along the thickness direction.

[0117] Except for the differences mentioned above, all other steps and parameters of this non-preferred embodiment are the same as those of Embodiment 1.

[0118] Comparative Example 1

[0119] The difference between this comparative example and Example 1 is as follows:

[0120] In S1, aluminum ingots with a purity of 4N are used, where 4N indicates that the mass percentage of aluminum element is 99.99%. The aluminum ingots are cut into cast aluminum plates with a length of 200mm, a width of 200mm, and a thickness of 8mm using a saw.

[0121] The remaining processing steps and parameters are the same as in Example 1, resulting in a disc-shaped aluminum target with a diameter of 6 inches and a thickness of 5 mm.

[0122] Comparative Example 2

[0123] The difference between this comparative example and Example 1 is as follows:

[0124] In S2, the stirring head rotates at a speed A of 800 r / min, travels at a speed B of 400 mm / min, and the ratio of A to B is 2 r / mm. The processing trajectory length within each strip-shaped processing zone is 200 mm, and the moving time of the stirring head within each strip-shaped processing zone is 30 s.

[0125] The remaining processing steps and parameters are the same as in Example 1.

[0126] Comparative Example 3

[0127] The difference between this comparative example and Example 1 is as follows:

[0128] In S2, the stirring head rotates at a speed A of 100 r / min, travels at a speed B of 800 mm / min, and the ratio of A to B is 0.125 r / mm. The processing trajectory length within each strip-shaped processing zone is 200 mm, and the moving time of the stirring head within each strip-shaped processing zone is 15 s.

[0129] The remaining processing steps and parameters are the same as in Example 1.

[0130] Comparative Example 4

[0131] This comparative example uses high-purity aluminum ingots with a purity of 5N5, and follows the traditional high-purity aluminum target processing technology, sequentially performing forging, rolling, and recrystallization annealing. Specifically, the high-purity aluminum ingot is forged at 300℃ with a forging deformation of 75%; subsequently, it undergoes multiple rolling passes with a total rolling deformation of 80%, yielding a high-purity aluminum plate with a thickness of 8mm; the high-purity aluminum plate is then recrystallized and annealed at 250℃ for 4 hours. After annealing, it is machined using a CNC machine tool to obtain a disc-shaped high-purity aluminum target with a diameter of 6 inches and a thickness of 5mm.

[0132] Test methods

[0133] 1. Preparation of aluminum thin film

[0134] After fixing the cast aluminum plate to the pad, the surface of the plate facing away from the pad is designated as the first surface, and the surface facing the pad is designated as the second surface. For the embodiments and comparative examples that undergo friction stir processing, the first surface is the surface facing the stirring head; for the comparative examples that do not undergo friction stir processing, the cast aluminum plate is placed on the pad in the same direction, and the first and second surfaces are marked accordingly.

[0135] The target materials prepared in Examples 1-11 and Comparative Examples 1-4 were respectively processed into magnetron sputtering test targets with a diameter of 2 inches. The test targets were installed in the target positions of the magnetron sputtering cavity, with the first plate facing the silicon wafer, and the target-substrate spacing was controlled to be 80 mm. The magnetron sputtering cavity was evacuated to a vacuum level of 5 × 10⁻⁶. -6 Torr; then, argon gas was introduced into the magnetron sputtering chamber at a flow rate of 60 sccm, and a sputtering power of 300 W was applied to the test target. Magnetron sputtering was continued for 10 minutes, causing aluminum atoms to be sputtered from the first plate surface and deposited on the silicon wafer surface to form an aluminum thin film.

[0136] 2. Surface roughness of aluminum target material

[0137] Before magnetron sputtering, a contact surface roughness tester was used to detect the surface roughness of the first and second surfaces of the target. A test point was selected at the center and four perimeter positions of both surfaces, for a total of five test points. The surface roughness Ra of each test point was recorded, and the arithmetic mean of the five test results was taken as the surface roughness of either the first or second surface of the target. The surface roughness of the first surface was denoted as Ra1, and the surface roughness of the second surface was denoted as Ra2.

[0138] 3. Average grain size of aluminum sputtering target

[0139] Metallographic samples were cut from the central region of the test target along the thickness direction, and then ground, polished, and etched. Five detection areas were selected at equal intervals along the thickness direction of the test target, and no fewer than three metallographic images were acquired in each detection area. Grain boundaries and grain areas were identified using image analysis software.

[0140] Grain size is measured using the section method: d = L / (N × M);

[0141] Where d is the average intercept (mm, often directly used as the average grain size), L is the total length of all test segments on the metallographic photograph (mm), N is the total number of intersections between all test segments and grain boundaries, and M is the magnification of the metallographic microscope. The number of grains counted for each test target is no less than 200.

[0142] 4. Grain size fluctuation value of aluminum sputtering target along the thickness direction

[0143] Based on the above grain size test results, the average grain size of the five selected test areas along the thickness direction was calculated. The difference between the average grain size of each test area and the overall average grain size of the five test areas was calculated, and the absolute value of the difference was taken. The maximum value among the differences for the five test areas was taken as the grain size fluctuation value of the test target along the thickness direction.

[0144]

[0145] Where W is the grain size fluctuation value, and d1~d5 are the average grain sizes of the five detection zones, respectively.

[0146] 5. Surface roughness of aluminum film

[0147] The surface roughness of the aluminum thin film was detected using atomic force microscopy. A detection area was selected at the center and four periphery positions of the prepared aluminum thin film, with a scanning range of 5 μm × 5 μm for each area. The surface roughness Ra of each detection area was recorded, and the arithmetic mean of the test results from the five detection areas was taken as the surface roughness of the aluminum thin film.

[0148] 6. Resistivity of aluminum thin film

[0149] The thickness of the aluminum film was measured using a thickness gauge, and the resistivity of the aluminum film was measured using a four-probe resistivity meter.

[0150] 7. Sputtering rate of aluminum target

[0151] With all process parameters such as vacuum, power, gas pressure, and target-substrate distance fixed, sputter continuously for a specified time, measure the thickness of the aluminum film on the substrate, and calculate the deposition rate.

[0152] The sputtering rate of aluminum target material is calculated according to the following formula: R=H / t;

[0153] In the formula, R: thin film deposition rate, H: aluminum thin film thickness, and t: sputtering time. The test results are shown in Table 1.

[0154] 8. Surface roughness verification

[0155] Taking Example 1 as an example, two parallel test targets prepared in Example 1 were used. One test target used the first plate surface as the sputtering surface, and was designated Example 1-A; the other test target used the second plate surface as the sputtering surface, and was designated Example 1-B. Both Example 1-A and Example 1-B prepared aluminum films according to the above-described aluminum film preparation method, under the same vacuum degree, argon flow rate, sputtering power, target-substrate spacing, and sputtering time.

[0156] The sputtering surface roughness, sputtering rate, and surface roughness and resistivity of the formed aluminum thin film were tested for Examples 1-A and 1-B, respectively. Specific test results are shown in Table 2. By comparing the test results of Examples 1-A and 1-B, the suitability of both surfaces of the aluminum target material prepared in Example 1 as sputtering surfaces was evaluated. Test results are shown in Table 2.

[0157] Table 1

[0158]

[0159] Table 2

[0160]

[0161] Figure 1 This is a schematic diagram of the friction stir processing process of the present invention; as shown. Figure 1 As shown, during the friction stir processing, a cast aluminum plate is fixed on a pad, and a stirring head presses down along the thickness direction of the cast aluminum plate while maintaining rotation and moving along the surface of the plate. The frictional heat generated between the stirring head and the cast aluminum plate causes the aluminum in the processing area to plasticize in the solid state. The rotating stirring needle further shears, compresses, and stirs the plasticized aluminum, causing the coarse cast grains to undergo severe plastic deformation and form fine equiaxed grains through dynamic recrystallization.

[0162] like Figure 2 As shown, after friction stir processing, the coarse cast grains in the aluminum target were significantly refined, forming a finer and more uniform grain structure. The size of each grain in different directions was approximately the same, and the overall grains were approximately circular or polygonal, without exhibiting obvious elongated fiber or lamellar morphology. This indicates that friction stir processing promoted the formation of fine equiaxed grains, further demonstrating that friction stir processing can refine and homogenize the grain structure of cast aluminum.

[0163] like Figure 3As shown, different colored areas in the EBSD test image represent grains with different crystallographic orientations, and the color changes between adjacent grains indicate that adjacent grains have certain orientation differences. Combined with the grain morphology, it can be seen that the grains formed after friction stirring are relatively close in size in different directions. Simultaneously, relatively fine equiaxed grains are formed in the aluminum target material, and the grain distribution is relatively uniform, further demonstrating that the processing method of the present invention can improve the grain structure of the aluminum target material.

[0164] As shown in Table 1, compared with Comparative Examples 1-4, Examples 1-11 used high-purity aluminum ingots with a purity ≥5N. The high-purity aluminum ingots were directly cut into as-cast aluminum plates and then subjected to friction stir processing. At the same time, the ratio A / B of the stirring head rotation speed A to the travel speed B was controlled to be 0.25-0.5, so that the effective processing depth of the stirring head matched the thickness of the as-cast aluminum plate. Through the overlap of adjacent strip processing zones and the cooling treatment between processing zones, on the one hand, the coarse as-cast grains can undergo sufficient plastic deformation and dynamic recrystallization, and on the other hand, the heat accumulation during the friction stir processing can be reduced and the grains can be refined and regrown, and the microstructure uniformity of the aluminum target material along the plate surface direction and thickness direction can be improved. Therefore, the average grain size of the aluminum target materials obtained in Examples 1 to 11 is 15 μm to 38 μm, the grain size fluctuation along the thickness direction is ≤12 μm, the sputtering rate of the aluminum target material is 9 μm / h to 20 μm / h, the surface roughness Ra of the obtained aluminum film is 1.8 nm to 4.5 nm, and the resistivity is 2.6 μΩ·cm to 3.1 μΩ·cm. Overall, it exhibits good grain refinement effect, uniform structure, sputtering performance and film formation performance.

[0165] Comparative Example 1 used only aluminum ingots with a purity of 4N, and all other friction stir processing conditions were the same as in Example 1. Due to the low purity of the aluminum raw material and the relatively high content of impurity elements, although the impurity elements and the second phase could suppress grain boundary migration to some extent, resulting in an aluminum target with a relatively small average grain size of 13μm and a thickness-direction grain size fluctuation of ≤3μm, the high impurity content affected the sputtering behavior of the target and entered the resulting aluminum film during the sputtering process, which was detrimental to obtaining a high-purity aluminum film with low resistivity. Therefore, the sputtering rate of the aluminum target in Comparative Example 1 was only 12μm / h, and the resistivity of the resulting aluminum film increased to 3.0μΩ·cm. This demonstrates that the present invention, using high-purity aluminum with a purity ≥5N as the target raw material, can achieve grain refinement while further ensuring the purity and electrical properties of the target and the resulting aluminum film.

[0166] In Comparative Example 2, the stirring head rotation speed A was increased to 800 r / min, and the travel speed B was decreased to 400 mm / min, increasing the A / B ratio to 2 r / mm. The higher rotation speed and lower travel speed significantly increased the number of rotations of the stirring head per unit travel distance, increasing the time the same area was subjected to friction and stirring, resulting in excessive heat input and accumulation during processing. For high-purity aluminum lacking solute atoms and second-phase particle pinning, excessive heat input easily causes the fine grains formed by dynamic recrystallization to grow again, resulting in uneven grain structure at different thicknesses. Therefore, the average grain size of the aluminum target obtained in Comparative Example 2 increased to 55 μm, the grain size fluctuation in the thickness direction increased to ≤18 μm, the sputtering rate of the aluminum target was only 8 μm / h, the surface roughness Ra of the obtained aluminum film increased to 5.2 nm, and the resistivity increased to 3.4 μΩ·cm.

[0167] In Comparative Example 3, the rotational speed A of the stirring head was reduced to 100 r / min, while the travel speed B was maintained at 800 mm / min, reducing the A / B ratio to 0.125 r / mm. Because the number of rotations of the stirring head per unit travel distance was too small, the frictional heating, shearing, extrusion, and stirring effects applied by the stirring pin to the cast high-purity aluminum were insufficient. This made it difficult for the coarse cast grains to undergo sufficient plastic deformation and dynamic recrystallization, thus reducing the grain refinement and microstructure uniformity. Therefore, the average grain size of the aluminum target obtained in Comparative Example 3 was 28 μm, the grain size fluctuation in the thickness direction was ≤9 μm, the sputtering rate of the aluminum target was only 10 μm / h, the surface roughness Ra of the obtained aluminum film was 3.5 nm, and the resistivity was 2.9 μΩ·cm. This further illustrates that controlling the A / B ratio between 0.25 and 0.5 helps to balance the sufficient plasticization and dynamic recrystallization of the cast high-purity aluminum with heat input control during processing.

[0168] Comparative Example 4 employed traditional high-purity aluminum sputtering techniques, sequentially forging, rolling, and recrystallizing annealing a 5N5 high-purity aluminum ingot, instead of using the friction stir processing method of this invention to directly process the cast high-purity aluminum plate. In traditional processing, although forging and rolling can induce plastic deformation in the cast structure, the continuous heat from subsequent recrystallization annealing easily leads to grain growth after recrystallization of the high-purity aluminum, and it is difficult to obtain the same strong local shearing and dynamic recrystallization effects as the friction stir processing of this invention. Therefore, the aluminum sputtering material obtained in Comparative Example 4 achieved an average grain size of 95 μm, a grain size fluctuation value in the thickness direction of ≤14 μm, a sputtering rate of only 9 μm / h, a surface roughness Ra of 4.2 nm, and a resistivity of 3.2 μΩ·cm. This demonstrates that by directly performing friction stirring on cast high-purity aluminum plates, the present invention can not only shorten the traditional forging, rolling, and recrystallization annealing process, but also obtain a finer and more uniform grain structure, and further improve the sputtering performance of the target material as well as the surface quality and conductivity of the resulting aluminum film.

[0169] Furthermore, compared to Example 7, Examples 1-6 further control the travel speed B of the stirring head to 600-800 mm / min. In Example 7, the travel speed B was increased to 1000 mm / min. Although A / B remained at 0.5 r / mm, the higher travel speed shortened the action time of the stirring head within the unit processing area. The friction, shearing, extrusion, and stirring effects of the stirring head on the cast high-purity aluminum were relatively weakened, which was not conducive to the full plastic deformation and dynamic recrystallization of the coarse cast grains. Therefore, the average grain size of the aluminum target material obtained in Example 7 increased to 23 μm, the grain size fluctuation value in the thickness direction increased to ≤6 μm, the surface roughness Ra of the obtained aluminum film increased to 3.0, and the resistivity increased to 2.9 μΩ·cm. Furthermore, Examples 1-6 further control the travel speed of the stirring head, which helps to maintain an appropriate working time within the unit processing area, allowing the cast high-purity aluminum to undergo sufficient plastic deformation and dynamic recrystallization, and improving the grain refinement and microstructure uniformity in different processing areas, thereby further improving the surface quality and conductivity of the obtained aluminum film.

[0170] Furthermore, compared to Example 8, Examples 1-6 further matched the effective processing depth of the stirring head along the thickness direction of the cast aluminum plate with the thickness of the cast aluminum plate. In Example 8, L+D was only 6.1 mm, which is less than the thickness of the cast aluminum plate H=8 mm, and the final thickness of the high-purity aluminum target was 7 mm, resulting in areas of the target material that were not sufficiently processed by friction stirring along the thickness direction. The coarse cast structure in this area could not undergo sufficient plastic deformation and dynamic recrystallization, leading to an increase in the average grain size of the obtained aluminum target to 32 μm, an increase in the grain size fluctuation value in the thickness direction to ≤10 μm, a decrease in the sputtering rate to 11 μm / h, an increase in the surface roughness Ra of the obtained aluminum film to 3.6 nm, and an increase in resistivity to 2.9 μΩ·cm. In contrast, Examples 1-6, by matching the effective processing depth with the thickness of the cast aluminum plate, helped to improve the grain refinement and microstructure uniformity of the aluminum target material along the thickness direction.

[0171] Furthermore, compared to Example 9, Examples 1-6 further control the overlap width between two adjacent strip-shaped processing areas to 1 / 3 to 1 / 2 of the shoulder diameter. In Example 9, the overlap width is only 1 / 5 of the shoulder diameter. This excessively small overlap width reduces the degree of stirring friction at the interface between adjacent strip-shaped processing areas, increasing the risk of insufficient processing in localized areas and uneven microstructure at different plate surfaces. Although the average grain size in Example 9 still reaches 16 μm, and the grain size fluctuation in the thickness direction remains ≤5 μm, the sputtering rate of the aluminum target is reduced to 13 μm / h, the surface roughness Ra of the resulting aluminum film increases to 2.9 nm, and the resistivity is 2.8 μΩ·cm. This indicates that further controlling the overlap width to 1 / 3 to 1 / 2 of the shoulder diameter helps to subject the entire processing area to more sufficient and continuous stirring friction, improving the microstructure consistency of the aluminum target in the plate surface direction, and further improving sputtering performance and film quality.

[0172] Furthermore, compared to Example 10, Examples 1-6 further cool the cast aluminum plate to below 25°C after completing the friction stir processing of one strip-shaped processing zone before performing the friction stir processing of the next strip-shaped processing zone. Example 10 only cools the plate to 50°C before continuing processing the next strip-shaped processing zone, making it easier for the residual heat generated in the previous processing zone to superimpose with the frictional heat of the subsequent processing zone. This is especially true in the overlapping areas of adjacent processing zones, where higher local heat input is easily generated, thereby promoting the re-growth of fine grains after dynamic recrystallization. As a result, the average grain size of the aluminum target material obtained in Example 10 increases to 22 μm, the grain size fluctuation value in the thickness direction increases to ≤6 μm, and the surface roughness Ra of the obtained aluminum film is 2.7 nm, with a resistivity of 2.8 μΩ·cm. In contrast, Examples 1-6, by controlling the cooling temperature between adjacent processing zones to below 25°C, help reduce heat accumulation between different processing zones, allowing each processing zone to perform friction stir processing at a more consistent initial temperature, thereby further improving grain refinement and microstructure uniformity.

[0173] Furthermore, compared to Example 11, Examples 1-6 further involve pressing the working end face of the shoulder into the cast aluminum plate, and matching the effective processing depth of the stirring head along the thickness direction with the thickness of the cast aluminum plate. In Example 11, the downward pressing dimension D of the shoulder is 0 mm, and the shoulder only contacts the surface of the cast aluminum plate without pressing it in. At the same time, the downward pressing dimension L of the stirring needle along the thickness direction is only 6 mm, making L+D significantly less than the 8 mm thickness of the cast aluminum plate. The processing area formed by the stirring head does not cover the cast aluminum plate along the thickness direction. As a result, on the one hand, the forging, constraint, and backfilling effect of the shoulder on the plasticized material near the plate surface is weakened; on the other hand, there is an area in the thickness direction of the cast aluminum plate that is not sufficiently subjected to stirring friction, leading to a significant decrease in grain refinement and thickness direction microstructure uniformity. Therefore, the average grain size of the aluminum target material obtained in Example 11 reached 38 μm, the grain size fluctuation value in the thickness direction reached ≤12 μm, the sputtering rate was only 9 μm / h, the surface roughness Ra of the obtained aluminum film increased to 4.5 nm, and the resistivity increased to 3.1 μΩ·cm. This further illustrates that properly pressing the shoulder into the cast aluminum plate and fully extending the friction stir processing area along the thickness direction plays an important role in obtaining a fine and uniform grain structure throughout the entire thickness.

[0174] Furthermore, as shown in Table 2, when the first plate surface of the high-purity aluminum target material prepared in Example 1 is used as the sputtering surface, the sputtering surface roughness Ra is 0.8 μm, the sputtering rate is 15 μm / h, and the resulting aluminum film has a surface roughness Ra of 1.8 nm and a resistivity of 2.6 μΩ·cm. When the second plate surface is used as the sputtering surface, the sputtering surface roughness is also 0.8 μm, the sputtering rate is also 15 μm / h, and the resulting aluminum film has a surface roughness Ra of 1.9 nm and a resistivity of 2.7 μΩ·cm. The properties are basically consistent under both sputtering directions, indicating that the processing method of the present invention can enable the aluminum target material to form a relatively uniform grain structure and properties along the thickness direction, allowing both plates of the aluminum target material to be used as sputtering surfaces.

[0175] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for processing aluminum sputtering targets, characterized in that, Includes the following steps: S1, cut aluminum ingots with a purity ≥5N to obtain cast aluminum plates; S2, The cast aluminum plate is subjected to stirring friction processing using a stirring head to obtain the aluminum target material; The stirring head includes a stirring pin and a shoulder arranged coaxially. The shoulder has a working end face facing the cast aluminum plate. The stirring pin has a first end and a second end. The first end is connected to the working end face, and the second end protrudes axially from the working end face. During the friction stir processing, the stirring head is rotated at a speed of A r / min and pressed down into the cast aluminum plate along the thickness direction. Then, the stirring head is kept in a rotating and pressing state and moves at a travel speed of B mm / min. A and B satisfy: A / B is 0.25~0.

5.

2. The processing method for the aluminum target material according to claim 1, characterized in that, In step S2, the rotational speed of the stirring head is 200 r / min to 600 r / min, and the travel speed of the stirring head is 600 mm / min to 800 mm / min.

3. The processing method for the aluminum target material according to claim 1, characterized in that, The thickness of the cast aluminum plate is H mm; during the friction stir processing, the second end of the stirring pin presses down by an amount of L mm along the thickness direction of the cast aluminum plate, and the working end face of the shoulder presses down by an amount of D mm along the thickness direction of the cast aluminum plate, satisfying L+D=H.

4. The processing method for the aluminum target material according to claim 3, characterized in that, The thickness of the cast aluminum plate is 8mm~12mm; during the friction stir processing, the second end of the stirring pin is pressed down by 7.8mm~11.9mm along the thickness direction of the cast aluminum plate; the working end face of the shoulder is pressed down by 0.1mm~0.3mm along the thickness direction of the cast aluminum plate. And / or, the aluminum target has two opposing plates along its thickness direction, wherein the surface roughness Ra of either plate is ≤1μm.

5. The method for processing the aluminum target material according to any one of claims 1 to 4, characterized in that, The diameter of the first end of the stirring needle is 4mm to 9mm; the tilt angle of the stirring head is 1° to 3°. And / or, the diameter of the shoulder is 10mm~30mm.

6. The processing method for the aluminum target material according to claim 5, characterized in that, The cast aluminum plate is divided into N strip-shaped processing areas along its length or width, and there is an overlapping area between two adjacent strip-shaped processing areas; the overlap width of the overlapping area is 1 / 3 to 1 / 2 of the diameter of the shoulder, and the N strip-shaped processing areas together cover the area to be processed of the cast aluminum plate, where N is an integer greater than or equal to 2; During the friction stirring process, the stirring head sequentially performs friction stirring in each of the strip-shaped processing zones. After completing the friction stirring in one strip-shaped processing zone, the stirring head moves to the next strip-shaped processing zone. The single friction stirring process time of the stirring head in each strip-shaped processing zone is 5s to 30s.

7. The processing method for the aluminum target material according to claim 6, characterized in that, After each strip-shaped processing zone is completed, the stirring head stops working and the cast aluminum plate is cooled to below 25°C before the next strip-shaped processing zone is processed.

8. The processing method for the aluminum sputtering target according to claim 6, characterized in that, The average grain size of the aluminum target is ≤20μm.

9. An aluminum target material, characterized in that, It is prepared by the processing method of any one of claims 1 to 8.

10. A method for preparing an aluminum thin film for integrated circuits, characterized in that, An aluminum target material is used, the aluminum target material having two plates arranged opposite each other along its thickness direction; either plate of the aluminum target material is used as a sputtering surface facing the substrate, and magnetron sputtering is performed, so that aluminum atoms are sputtered from the sputtering surface and deposited on the surface of the substrate to form the aluminum thin film for integrated circuits; wherein, the aluminum target material includes the aluminum target material prepared by the processing method of any one of claims 1 to 8, or the aluminum target material as described in claim 9.

Images