A method of machining a titanium-aluminum alloy target

Abstract

The present application relates to brittle alloy Ti-Al intermetallic compound mechanical processing technical field, specifically to a kind of mechanical processing method of titanium-aluminum alloy target material, suitable for the preparation of high-purity sputtering target material with purity 4N5 above for 28nm line thread below specification chip.The method uses constant linear speed numerical control machining+axial vacuum chuck fixed mode to the target blank after casting, and carries out surface processing to titanium-aluminum alloy target blank.The present application optimizes target blank clamping mode and numerical control processing process parameters, avoids the problems such as deformation, collapse angle and uneven surface roughness of brittle titanium-aluminum alloy target blank during processing, so that titanium-aluminum alloy target material obtains good size control and surface integrity, realizes the stable control of size precision and conductivity of brittle titanium-aluminum alloy target material which is easy to deform.

Description

Technical Field

[0001] This invention relates to the field of machining technology for brittle alloy Ti-Al intermetallic compounds, specifically to a machining method for titanium-aluminum alloy sputtering targets, suitable for the preparation of high-purity sputtering targets with a purity of 4N5 or higher for chips with a specification of 28nm or less. Background Technology

[0002] High-purity Ti50Al alloy is one of the core materials for sputtering coating of large-scale integrated circuits with chips below 28nm. The technical requirements for sputtering targets are as follows: 1. Ti:Al = 50%:50% (±1at%), Ti:Al = 64%:36% (±0.8wt%), purity > 4N5; 2. Target size: 3. The machined surface is free from deformation, contamination, and scratches, with a roughness Ra < 0.5 μm.

[0003] High-purity 4N5 large-size titanium-aluminum sputtering targets are particularly difficult to manufacture due to their brittleness, large size, and high purity. Currently, the market is experiencing a shortage of power management chips, display driver chips, and automotive electronic chips, all manufactured using the 28nm process. From a cost perspective, 28nm chips have a more mature process, a more complete IP library, and offer higher cost-effectiveness. Leading domestic semiconductor companies are actively developing high-purity titanium-aluminum sputtering targets for integrated circuits. They are using cold-walled copper crucibles for high-purity melting and casting to prepare TiAl alloy sputtering targets. Test results show that compared to existing powder-metallurgical targets with Al content decreasing from 0.53% to 0.47% during sputtering, the cast targets maintain an optimal Al content of 0.5%, exhibiting excellent service life. However, the processing of large-size target blanks made of brittle titanium-aluminum alloys has consistently affected the product delivery yield, specifically manifested in problems such as target warping, edge chipping, and inconsistent surface roughness leading to significant differences in conductivity. Summary of the Invention

[0004] In view of the difficulties existing in the prior art, the purpose of this invention is to provide a machining method for titanium-aluminum alloy targets. The method can obtain large-size, high-precision Ti50Al alloy targets and solve the quality problems that lead to scrapping during the machining of titanium-aluminum alloy targets.

[0005] The technical solution of this invention is:

[0006] A machining method for titanium-aluminum alloy targets involves first using a radial mechanical clamping method. The target blank is fixed by the radial mechanical pressure jaws of a mechanically preloaded chuck and then machined to thin it. Once the flatness of both surfaces is ≤1mm and the roughness is ≤Ra6.4μm, meeting the basic contour requirements, the target blank is then fixed by an axial vacuum chuck. After thinning to a single-sided allowance of 2.5–3.5mm, the edges of the target blank are rounded. Next, the thickness of the target blank is thinned using a constant linear velocity machining method. By switching the front and rear faces, the target blank is machined to the specified thickness, and the rounded edges are removed accordingly. Finally, the circumferential edges of the target blank are removed by machining to obtain a target material with acceptable dimensions.

[0007] The machining method for the titanium-aluminum alloy target material eliminates the traditional mechanical preload chuck during target blank machining, and replaces the multi-angle radial mechanical pressure chuck with multiple axial vacuum suction cups for fixation.

[0008] The machining method for the titanium-aluminum alloy target material includes 4 to 8 radial mechanical pressure jaws with a preload of 100N to 1000N; and 6 to 20 axial vacuum chucks with a diameter of 20 to 50mm and a suction force of 100N to 500N.

[0009] The preferred method for machining the titanium-aluminum alloy target material involves 10 to 15 axial vacuum chucks with a diameter of 25 to 40 mm and a suction force of 200 to 350 N.

[0010] In the machining method for the titanium-aluminum alloy target material, during the machining of the large-size surface of the target blank, the machining parameters are changed from constant angular velocity input to constant linear velocity input control.

[0011] In the machining method of the titanium-aluminum alloy target, during the lathe machining process, the constant angular velocity range parameter of 1~10r / s is changed to a constant linear velocity range of 1400~14000mm / s.

[0012] The preferred method for machining the titanium-aluminum alloy target material is to change the constant angular velocity range parameter of 3-8 r / s to a constant linear velocity range of 4200-11200 mm / s.

[0013] The machining method for the titanium-aluminum alloy target material involves pre-machining the fillets at the circumferential edge of the target blank before performing a constant linear speed thickness reduction process.

[0014] The machining method for the titanium-aluminum alloy target material involves pre-machining the fillet radius R of the target blank's circumferential edge, which ranges from 6 to 10 mm.

[0015] In the preferred method for machining the titanium-aluminum alloy target material, the radius R of the pre-machined circumferential edge of the target blank is in the range of 7.5 to 9.0 mm.

[0016] The design concept of this invention is:

[0017] This invention replaces traditional mechanical clamps with a rotatable axial vacuum chuck, avoiding target warping and deformation caused by radial clamping force on large-diameter, thin-thickness target blanks, thus preventing the target flatness from exceeding tolerance.

[0018] In this invention, the target material processing adopts the constant linear velocity parameter input of CNC lathe to replace the angular velocity parameter, so as to obtain a good and consistent surface roughness of the target material (the roughness is closely related to the tool travel speed) and ensure the stable conductivity of the inner and outer surfaces of the target material.

[0019] To address the issue of chipped outer edges of the target material, this invention employs a pre-formed rounded corner design. This design ensures that the cutting tool does not impact the target material substrate during edge processing. After the target thickness is reached, the rounded corner is also removed layer by layer, guaranteeing that the target material's profile meets the drawing requirements.

[0020] The advantages and beneficial effects of this invention are:

[0021] 1. For example Figures 1-3 As shown, this invention optimizes the processing method for thin-film brittle materials by changing the radial clamping of the titanium-aluminum alloy target blank to axial suction fixation. This avoids warping deformation of large-diameter, thin-thick titanium-aluminum alloy target blanks caused by the application and release of clamping force, ensuring the production of high-precision target materials. This processing method, by optimizing the vacuum suction position and suction force of the target blank, achieves the technical requirement of a flatness of less than 0.02mm through three face-changing processes. Furthermore, without interference from radial chucks, it ensures the accessibility of the tool to the circumferential edges of the target blank, avoiding the destructive effects of traditional mechanical clamping on brittle edges, and guaranteeing a good and stable dimensional profile for the target material. Figure 3 ).

[0022] 2. This invention optimizes the processing sequence of brittle, disc-shaped targets. The traditional method first processes the circumferential dimension to 454±0.2mm, then processes the thickness to 11.8±0.02mm. This creates right angles at the disc-shaped edge, and each thickness reduction pass causes tool breakage impact at this point. For brittle titanium-aluminum materials, this often leads to corner chipping, rendering the target unusable. See [link to relevant documentation]. Figure 4(a) and (c). This invention involves pre-processing the circumferential corners with a radius (R) calculated during machining. Subsequently, during thickness reduction, the tool gradually conforms to the target substrate, preventing significant impact. Furthermore, the rounded corner structure ensures no corner chipping occurs. Once the ideal thickness is achieved in the thickness direction, the rounded corner radius decreases synchronously (≤0.1mm), meeting the target contour requirements. This optimized machining method for brittle materials significantly improves the success rate of target machining. See [link to relevant documentation]. Figure 4 (b) and (d).

[0023] 3. For example Figure 5 As shown, this invention combines the influence of the surface roughness of titanium-aluminum alloy target material on contact conductivity, breaking through the traditional concept of constant angular velocity machining parameter input in the machining industry. By creatively writing a constant linear velocity program on a CNC lathe (the rotational speed increases from the outside to the inside while the tool linear velocity remains constant), a uniform roughness is formed on the surface of the target material, thus achieving stable control of the surface conductivity of the titanium-aluminum target material. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the machining process for a radial mechanical clamping device for a target blank. (a) is a side view, and (b) is a front view.

[0025] Figure 2 This is a schematic diagram of the machining process for an axial vacuum chuck fixing device. (a) is a front view, and (b) is a side view.

[0026] Figure 3 This image shows the effect of processing the Ti50Al alloy target material without warping under the suction cup bracket fixing condition of the present invention.

[0027] Figure 4 These are schematic diagrams showing the before and after rounding treatment of the target blank's circumferential edge to prevent chipping, as well as the processing effect. (a) Before rounding treatment, (b) After rounding treatment, (c) Before rounding treatment, and (d) After rounding treatment.

[0028] Figure 5 This study demonstrates the effect of optimizing the input constant angular velocity to a constant linear velocity during lathe machining to improve the uniformity of the target surface roughness and the stability of its conductivity. (a) shows the surface roughness at 10 points (0.733 μm) in Figure (c) under constant angular velocity conditions; (b) shows the surface roughness at 10 points (0.497 μm) in Figure (c) under constant linear velocity conditions; and (c) shows the distribution of measurement points for roughness and conductivity.

[0029] The attached figures are labeled as follows: 1 target blank, 2 radial mechanical pressure jaw, 3 axial vacuum chuck, 4 chuck bracket, 5 vacuum suction tube. Detailed Implementation

[0030] In specific implementation, the titanium-aluminum alloy target material of this invention has a purity greater than 99.995 wt%, and by atomic percentage, Ti:Al = 50%:50% (±1 at%), with gas content of less than 500 ppm oxygen, less than 50 ppm nitrogen, and less than 20 ppm hydrogen. The dimensions of the titanium-aluminum target material are... The target blank used for machining titanium-aluminum target materials is made of sponge titanium with a purity of 99.9wt% and Al bean with a purity of 99.9999%. After being uniformly mixed and pressed according to the required percentage of components, the ingot is obtained by vacuum arc self-consumable melting (VAR) + vacuum induction melting casting.

[0031] like Figure 1 As shown in (a)-(b), during the processing of the target blank 1, when a conventional radial mechanical clamping device for the target blank is used, the radial mechanical pressure claws 2 of the mechanical preload chuck are evenly distributed radially around the target blank 1.

[0032] like Figure 2 As shown in (a)-(b), during the processing of the target blank 1, the axial vacuum chuck 3 of the axial vacuum chuck fixing device is installed on one side of the chuck bracket 4. The axial vacuum chuck 3 are evenly distributed and correspond to the back side of the target blank 1. The other side of the chuck bracket 4 is connected to the vacuum pump through the vacuum suction pipe 5. The vacuum pump is connected to the channels of the chuck bracket 4 and the axial vacuum chuck 3 in sequence through the vacuum suction pipe 5.

[0033] like Figure 3 As shown, under the suction cup bracket fixing conditions of the present invention, the Ti50Al alloy target material does not warp or deform after processing.

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] In this embodiment, high-purity Ti50Al (Ti:Al = 50%:50% (±1 at%)) raw materials are uniformly mixed according to the required composition and then pressed. TiAl alloy is obtained through a combination of primary vacuum arc remelting (VAR) and secondary vacuum arc remelting (VAR). The secondary-melted ingot is then sawn into four 50kg portions and placed in an induction water-cooled copper crucible (ISM) for melting and casting TiAl alloy target billet material. The diameter of this casting target billet is... Thickness H30mm, with fine and uniform structure.

[0037] like Figures 1-2 As shown, the target blank was first fixed using a radial mechanical clamping method, followed by machining to thin it. Once the flatness (≤1mm) and roughness (≤Ra6.4μm) of both surfaces met the basic contour requirements, it was then fixed using an axial vacuum chuck. After thinning to H17.8mm (with a 3mm allowance on one side), the edges of the target blank were rounded (R8.94mm). See [details omitted]. Figure 4 (b); The target blank is then thinned by constant linear speed machining at a speed of 5200 mm / s, and the blank is machined to the specified thickness (H11.8) through three conversions between the front and back faces in the thickness direction. -0.05 The rounded corners are then removed; finally, the circumferential edges of the target blank are removed to obtain the diameter (mm). For target materials that meet the required dimensions, the axial vacuum chuck fixing device is used to inspect the Ti50Al target blank. The flatness is 0.02mm, and the roughness of the edge and center is Ra0.2~0.4μm.

[0038] like Figure 3 , Figure 4 (d) Figure 5 As shown, the titanium-aluminum alloy target blank prepared by this processing method in this embodiment has no warping deformation or chipping defects. Its dimensional accuracy and surface roughness meet the technical requirements. The conductivity of the target material at 10 points is measured to be in the range of 3 to 3.5 MS / m, which meets the target material delivery standard.

[0039] Example 2

[0040] In this embodiment, the high-purity Ti50Al raw material is uniformly mixed according to the required composition and then pressed. The TiAl alloy is obtained by a combined vacuum arc remelting (VAR) and secondary VAR remelting process. The secondary-melted ingot is then sawn into four 40kg portions and placed in a vacuum induction water-cooled copper crucible (ISM) for melting and casting the TiAl alloy target billet. The diameter of this cast target billet is... It has a thickness of H24mm and a fine, uniform structure.

[0041] like Figures 1-2 As shown, the target blank was first fixed using a radial mechanical clamping method, followed by machining to thin it. Once the flatness (≤0.8mm) and roughness (≤Ra3.2μm) of both surfaces met the basic requirements, it was then fixed using an axial vacuum chuck. After thinning to H15.8mm (with a 2mm allowance on one side), the edges of the target blank were rounded (R7.9mm). See [details omitted]. Figure 4(b); The target blank is then thinned by constant linear speed machining at 8400 mm / s, and the blank is machined to the specified thickness (H11.8) through four conversions between the front and back faces. +0.03 The rounded corners are then removed; finally, the circumferential edges of the target blank are removed to obtain the diameter (mm). For a target material with acceptable dimensions, the axial vacuum chuck fixing device is used to inspect the Ti50Al target blank. The flatness is 0.015mm, and the roughness of the edge and center is Ra0.2~0.3μm.

[0042] like Figure 3 , Figure 4 (d) Figure 5 As shown, the titanium-aluminum alloy target blank prepared by this processing method did not exhibit springback deformation or chipping defects. Its dimensional accuracy and surface roughness met the technical requirements. The conductivity of the target material at 10 points was measured to be in the range of 3 to 3.5 MS / m, which meets the target material delivery standards.

[0043] Example 3

[0044] In this embodiment, the high-purity Ti50Al raw material is uniformly mixed according to the required composition and then pressed. After obtaining the TiAl alloy using a three-stage vacuum arc remelting (VAR) combined melting method, the ingot from the three melting processes is sawn into six 60kg portions. Each portion is placed in a vacuum induction water-cooled copper crucible (ISM) for melting and casting the TiAl alloy target billet material. The diameter of this cast target billet is... Thickness H35mm, with fine and uniform structure.

[0045] like Figures 1-2 As shown, the target blank was first fixed using a radial mechanical clamping method, followed by machining to thin it. Once the flatness (≤0.6mm) and roughness (≤Ra4.8μm) of both surfaces met the basic requirements, it was then fixed using an axial vacuum chuck. After thinning to H16.8mm (with a single-sided allowance of 2.5mm), the edges of the target blank were rounded (R8.4mm). See [details omitted]. Figure 4 (b); The target blank is then thinned using a constant linear speed machining method at a linear speed of 12000 mm / s, and the blank is machined to the specified thickness (H11.8) through 6 transformations of the front and back faces in the thickness direction. -0.02 The rounded corners are then removed; finally, the circumferential edges of the target blank are removed to obtain the diameter (mm). The Ti50Al target blank is inspected by releasing the axial vacuum chuck fixing device after the target material is qualified in size. The flatness is 0.012mm and the roughness of the edge and center is Ra0.15~0.3μm.

[0046] like Figure 3 , Figure 4 (d) Figure 5 As shown, the titanium-aluminum alloy target blank prepared by this processing method has no warping deformation or chipping defects. Its dimensional accuracy and surface roughness meet the technical requirements. The conductivity of the target material at 10 points is measured to be in the range of 3 to 3.5 MS / m, which meets the target material delivery standard.

[0047] Table 1 Comparison of the effects of two Ti50Al alloy sputtering methods

[0048]

[0049] As can be seen from Table 1, this invention addresses the shortcomings of Ti50Al target billet machining by proposing an optimized approach for machining brittle Ti50Al target billets. Through three targeted measures, Ti50Al alloy target billets achieve good machining results, significantly improving the machinability of the target billets and exhibiting good dimensional accuracy and stable conductivity.

[0050] The results show that the machining method for the titanium-aluminum alloy target material of this invention includes: machining the cast target blank using a constant linear speed CNC lathe and fixing it with an axial vacuum chuck to perform surface machining on the Ti50Al alloy target blank. This invention, by optimizing the target blank clamping method and CNC machining process parameters, avoids the problems of deformation, chipping, and uneven surface roughness during the machining of brittle Ti50Al alloy target blanks, enabling the Ti50Al alloy target material to achieve good dimensional control and surface integrity, and realizing stable control of the dimensional accuracy and conductivity of the brittle and easily deformable Ti50Al alloy target material.

Claims

1. A method of machining a titanium-aluminum alloy target material, characterized by, The first radial mechanical clamping method is used to fix the target blank by the radial mechanical pressure clamp of the mechanical pre-tightening chuck, and then the target blank is thinned by turning. After the flatness of both sides is less than or equal to 1mm and the roughness is less than or equal to Ra6.4μm, the target blank is fixed by the axial vacuum chuck, and the thickness is thinned to a single side allowance of 2.5~3.5mm. Then, the edge of the target blank is rounded. The thickness of the target blank is thinned by the constant linear speed processing method. The thickness of the target blank is processed to the specified thickness size by converting the front and back, and the edge roundness is removed. Finally, the circular arc of the circumferential edge of the target blank is removed to obtain the target material with qualified size.

2. The method of machining a titanium aluminum alloy target according to claim 1, wherein, During the processing of the target blank, the traditional mechanical pre-tightening chuck is cancelled, and the multi-angle radial mechanical pressure clamp is replaced by a plurality of axial vacuum chucks.

3. The method of machining a titanium-aluminum alloy target according to claim 2, wherein The number of the plurality of radial mechanical pressure clamps is 4~8, and the pre-tightening force is 100N~1000N. The number of the plurality of axial vacuum chucks is 6~20, the diameter is 20~50mm, and the suction force is 100N~500N.

4. The method of machining a titanium-aluminum alloy target according to claim 3, wherein The number of the plurality of axial vacuum chucks is 10~15, the diameter is 25~40mm, and the suction force is 200~350N.

5. The method of machining a titanium-aluminum alloy target according to claim 1, wherein During the processing of the large size surface of the target blank, the turning processing parameter is changed from constant angular velocity input to constant linear velocity input control.

6. The method of machining a titanium-aluminum alloy target according to claim 5, wherein During the lathe processing, the constant angular velocity range parameter is changed from 1~10r / s to constant linear velocity range 1400~14000mm / s.

7. The method of machining a titanium-aluminum alloy target according to claim 6, wherein The constant angular velocity range parameter is changed from 3~8r / s to constant linear velocity range 4200~11200mm / s.

8. The method of machining a titanium-aluminum alloy target according to claim 1, wherein During the processing of the circumferential edge of the target blank, the roundness is pre-turned and then the thickness is thinned by constant linear speed.

9. The method of machining a titanium-aluminum alloy target according to claim 8, wherein The radius R of the pre-turned roundness of the circumferential edge of the target blank ranges from 6 to 10mm.

10. The method of machining a titanium-aluminum alloy target according to claim 9, wherein The radius R of the pre-turned roundness of the circumferential edge of the target blank ranges from 7.5 to 9.0mm.

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