A method for ensuring the uniformity of target thickness and its application

Abstract

This invention provides a method for ensuring the uniformity of target thickness and its application. The method includes the following steps: (1) welding the target blank and the back plate, and then shaping them to obtain the target material; (2) placing a pad on the side of the target material away from the back plate, and using a pressing method to remove residual welding stress inside the target material, so that the uniformity of the target material thickness is controlled within 0.3 mm. This invention uses a pressing method to relieve stress, causing the residual welding stress inside the target material to yield and relax, thereby removing welding stress to the greatest extent. This greatly improves the dynamic deformation phenomenon of the target material during processing and ensures that the uniformity of the target material thickness is controlled within 0.3 mm.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor sputtering targets, specifically relating to a method for ensuring the uniformity of target thickness and its application. Background Technology

[0002] For diffusion-welded sputtering targets, the significant difference in thermal expansion coefficients between the tungsten target blank and the copper backing plate after welding results in residual welding stress within the target, specifically at the weld joint. This residual stress remains even after conventional cold working processes such as shaping. During dimensional machining, factors such as thinning of the backing plate and target blank, and clamping disrupt this stress balance, leading to dynamic deformation of the target and ultimately resulting in uneven target thickness. Therefore, ensuring uniform target thickness hinges on removing stress from the weld surface before dimensional machining.

[0003] Generally, materials with large differences in thermal expansion coefficients will exhibit residual welding stress after diffusion welding. Current research on stress relief for welded materials has been reported. Patent CN202011561458.6 discloses a stress-relieving device and its usage method for titanium alloy welding. It designs a device including a plasma torch, a support arm, and an ultrasonic generator. This patent utilizes the principle of ultrasonic stress relief to achieve stress relief for Ti welded samples. However, ultrasonic stress relief results in significant noise pollution and poor stress relief effect for large-sized dissimilar material welded samples. Patent CN202023109224.6 discloses a stress-relieving fixture for turbine diaphragm welding. By designing a special fixture jig tailored to the product size, the fixture, along with the turbine diaphragm, is placed in a heat treatment furnace. It utilizes the principle of stress relief through heat treatment annealing, combined with a jig that restricts material thermal expansion to offset welding stress. However, this method is energy-intensive, and stress-relieving annealing is not significantly effective in removing stress caused by large-area welding of dissimilar materials.

[0004] In summary, methods for removing welding stress mainly include ultrasonic vibration and using fixtures to limit thermal expansion and deformation. However, these methods are not suitable for stress removal of large-size, large-area weldable materials such as target materials, as they are inefficient and ineffective.

[0005] Furthermore, based on the structural characteristics of the target material, the welding surface is a large flat surface with a regular shape (mainly circular and rectangular). Common backing materials (Al alloys and copper alloys) generally have good ductility. Therefore, common target blank materials (such as Al and Ti) retain good overall ductility after welding with the backing plate. Thus, internal stress can be removed by repeatedly shaping the upper and lower surfaces. However, for brittle metals such as tungsten, the shaping process is very sensitive to pressure and prone to over-shaping and cracking. Therefore, repeatedly shaping the upper and lower surfaces is not suitable for removing stress on the welding surface. Patent CN202211294592.3 provides a stress-relief shaping method for brittle metal targets. This method designs a gradient shaping approach, which can shape the welded tungsten target to a flatness within 0.1mm. However, during subsequent dimensional processing, the target material will continuously deform, resulting in a final target thickness uniformity >0.7mm. Low target thickness uniformity may affect the voltage stability of the target material during use.

[0006] Therefore, how to effectively remove welding stress from the target material to the greatest extent, ensure that the target material does not undergo dynamic deformation during subsequent dimensional processing, and at the same time ensure that the thickness uniformity of the target material is controlled within 0.3 mm, is a key area that urgently needs to be studied. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method and its application for ensuring the uniformity of target material thickness. The present invention utilizes a flat-pressing stress-relief method to cause the residual welding stress inside the target material to yield, thereby relaxing the residual welding stress and maximizing the removal of welding stress. This significantly improves the dynamic deformation phenomenon of the target material during processing, ensuring that the target material thickness uniformity is controlled within 0.3 mm.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for ensuring the uniformity of target material thickness, the method comprising the following steps:

[0010] (1) Weld the target blank and the back plate together and shape them to obtain the target material;

[0011] (2) A pad is placed on the side of the target material away from the back plate. When the pad is pressed flat, the residual welding stress inside the target material is removed, so that the thickness uniformity of the target material is controlled within 0.3mm.

[0012] This invention uses a flat-pressure stress relief method to cause the residual welding stress inside the target material to yield and relax, thereby maximizing the removal of welding stress. This greatly improves the dynamic deformation phenomenon of the target material during processing and ensures that the thickness uniformity of the target material is controlled within 0.3mm.

[0013] In this invention, the uniformity of the target material thickness is controlled within 0.3 mm, for example, it can be 0.3 mm, 0.28 mm, 0.26 mm, 0.24 mm, 0.22 mm, 0.2 mm, 0.18 mm, 0.16 mm, 0.14 mm, 0.12 mm or 0.1 mm, etc.

[0014] In this invention, if the uniformity of the target material thickness is too low, i.e., the uniformity of the thickness is greater than 0.3 mm, there will be too much residual internal stress in the material, which will further aggravate the deformation during the finished product processing, ultimately leading to uneven thickness of the finished target blank, which will cause problems such as target deformation and cracking during sputtering. As a preferred technical solution of this invention, the target blank in step (1) is made of tungsten.

[0015] Preferably, the material of the backplate in step (1) includes copper alloy or Al alloy.

[0016] As a preferred technical solution of the present invention, the flatness of the target material in step (1) is <0.1mm, for example, it can be 0.08mm, 0.07mm, 0.06mm, 0.05mm, 0.04mm, 0.03mm, 0.02mm or 0.01mm, etc. However, it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] As a preferred technical solution of the present invention, the material of the pad in step (2) includes any one of Al, aluminum alloy or stainless steel.

[0018] This invention does not limit the specific type of aluminum alloy. For example, it can be a 2-series aluminum alloy or a 6-series aluminum alloy.

[0019] In this invention, the purpose of setting a pad on the side of the target material away from the back plate is because the pressure loading is mainly applied by a hydraulic press. The hydraulic press head is generally of a fixed size. Therefore, pads need to be added to target materials of different sizes to adjust the contact surface so that the entire surface of the target blank is uniformly pressed.

[0020] Preferably, the diameter of the pad in step (2) is greater than the diameter of the target material.

[0021] In this invention, if the diameter of the pad is less than or equal to the diameter of the target material, the force will be uneven at the non-contact areas of the pad, leading to problems such as material cracking.

[0022] The present invention does not specifically limit the diameter of the target material; for example, it can be 450 mm.

[0023] Preferably, the thickness of the pad in step (2) is >30mm, for example, it can be 35mm, 38mm, 40mm, 43mm, 45mm, 48mm or 50mm, etc. However, it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] It should be noted that the thickness of the pad block only needs to ensure that the material does not deform within the pressure range.

[0025] As a preferred technical solution of the present invention, the pressure applied during the pressing of the block in step (2) is 4-5 MPa, for example, it can be 4 MPa, 4.1 MPa, 4.2 MPa, 4.3 MPa, 4.4 MPa, 4.5 MPa, 4.6 MPa, 4.7 MPa, 4.8 MPa, 4.9 MPa, or 5 MPa, etc. However, it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0026] In this invention, if the pressure applied by the pressing block is too small, it will not achieve the effect of flattening, and the internal stress of the material will still exist; if the pressure applied by the pressing block is too large, it will easily lead to problems such as cracking and deformation of the material.

[0027] As a preferred technical solution of the present invention, the holding time for pressing the block in step (2) is 12-30 minutes, for example, it can be 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes or 30 minutes, etc. However, it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] In this invention, if the holding time during the flat pressing of the pressing block is too short, the effect of removing internal stress is not obvious; if the holding time during the flat pressing of the pressing block is too long, the effect of improving uniformity becomes less and less obvious, and the work efficiency is reduced and the work cost is increased.

[0029] As a preferred technical solution of the present invention, the method includes the following steps:

[0030] (1) Weld the tungsten target blank and the back plate together and shape them to obtain a tungsten target with a flatness of <0.1mm;

[0031] (2) An Al pad with a thickness of >30mm is provided on the surface of the tungsten target away from the back plate. When the pressure block is used to flatten the target, the welding stress inside the target assembly is removed, so that the thickness uniformity of the target is controlled within 0.3mm.

[0032] Among them, the diameter of the pad is greater than the diameter of the target material, the pressure of the pad during flat pressing is 4-5 MPa, and the holding time of the pad during flat pressing is 12-30 min.

[0033] In a second aspect, the present invention provides an application of the method described in the first aspect, the method being used to remove residual welding stress inside a target material.

[0034] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention uses a flat-pressure stress relief method to cause the residual welding stress inside the target material to yield and relax, thereby maximizing the removal of welding stress. This greatly improves the dynamic deformation phenomenon of the target material during processing and ensures that the thickness uniformity of the target material is controlled within 0.3mm. Attached Figure Description

[0037] Figure 1 This is a simplified structural diagram of the method for removing welding stress in Embodiment 1 of the present invention.

[0038] Figure 2 A schematic diagram of the thickness detection points is shown during thickness uniformity detection.

[0039] Among them, 1-copper alloy backplate; 2-tungsten target blank; 3-tungsten target material; 4-Al pad. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0041] Example 1

[0042] This embodiment provides a method for ensuring the uniformity of target material thickness, the method comprising the following steps:

[0043] (1) Weld the tungsten target blank 2 and the copper alloy back plate 1 together and perform shaping treatment to obtain a tungsten target material 3 with a flatness of <0.1mm;

[0044] (2) An Al pad 4 with a thickness of 35mm is provided on the surface of the tungsten target 3 away from the back plate. When the pressure block is used to flatten the target, the welding stress inside the target assembly is removed, so that the thickness uniformity of the target is controlled within 0.3mm.

[0045] Among them, the diameter of Al pad 4 is greater than the diameter of tungsten target 3, the pressure during the pressing of the pad is 4 MPa, and the holding time for the pressing of the pad is 15 min.

[0046] Figure 1 A simplified structural diagram of the method for removing welding stress in this embodiment is shown.

[0047] Example 2

[0048] This embodiment provides a method for ensuring the uniformity of target material thickness, the method comprising the following steps:

[0049] (1) Weld the tungsten target blank and the copper alloy backing plate together and shape them to obtain a tungsten target with a flatness of <0.1mm;

[0050] (2) A 40mm thick Al pad is provided on the surface of the tungsten target away from the back plate. When the pressure block is used to flatten the target, the welding stress inside the target assembly is removed, so that the thickness uniformity of the target is controlled within 0.3mm.

[0051] Among them, the diameter of the pad is greater than the diameter of the target material, the pressure of the pressure block during flat pressing is 4MPa, and the pressure holding time of the pressure block during flat pressing is 30min.

[0052] Example 3

[0053] This embodiment provides a method for ensuring the uniformity of target material thickness, the method comprising the following steps:

[0054] (1) Weld the tungsten target blank and the copper alloy backing plate together and shape them to obtain a tungsten target with a flatness of <0.1mm;

[0055] (2) A 50mm thick Al pad is provided on the surface of the tungsten target away from the back plate. When the pressure block is used to flatten the target, the welding stress inside the target assembly is removed, so that the thickness uniformity of the target is controlled within 0.3mm.

[0056] Among them, the diameter of the pad is greater than the diameter of the target material, the pressure of the pad during flat pressing is 5MPa, and the holding time of the pad during flat pressing is 30min.

[0057] Example 4

[0058] The difference between this embodiment and embodiment 2 is that the pressure of the pressure block during flattening in step (2) is 1 MPa.

[0059] The remaining preparation methods and parameters are consistent with those in Example 1.

[0060] Example 5

[0061] The difference between this embodiment and embodiment 2 is that the pressure of the pressure block during flat pressing in step (2) is 2 MPa.

[0062] The remaining preparation methods and parameters are consistent with those in Example 1.

[0063] Example 6

[0064] The difference between this embodiment and embodiment 2 is that the pressure of the pressure block during flat pressing in step (2) is 3MPa.

[0065] The remaining preparation methods and parameters are consistent with those in Example 1.

[0066] Example 7

[0067] The difference between this embodiment and embodiment 2 is that the pressure of the pressure block during flattening in step (2) is 6 MPa.

[0068] The remaining preparation methods and parameters are consistent with those in Example 1.

[0069] Example 8

[0070] The difference between this embodiment and embodiment 1 is that the pressure holding time for the pressure block in step (2) is 1 minute.

[0071] The remaining preparation methods and parameters are consistent with those in Example 1.

[0072] Example 9

[0073] The difference between this embodiment and embodiment 1 is that the pressure holding time for the pressure block in step (2) is 5 minutes.

[0074] The remaining preparation methods and parameters are consistent with those in Example 1.

[0075] Example 10

[0076] The difference between this embodiment and embodiment 1 is that the pressure holding time for the pressure block in step (2) is 10 minutes.

[0077] The remaining preparation methods and parameters are consistent with those in Example 1.

[0078] Example 11

[0079] The difference between this embodiment and embodiment 1 is that the pressure holding time for the pressure block in step (2) is 45 minutes.

[0080] The remaining preparation methods and parameters are consistent with those in Example 1.

[0081] Comparative Example 1

[0082] The difference between this comparative example and Example 1 is that the method of pressing the block described in step (2) is not performed.

[0083] The remaining preparation methods and parameters are consistent with those in Example 1.

[0084] Performance testing

[0085] Thickness uniformity was tested on the targets obtained in Examples 1-11 and Comparative Example 1.

[0086] Testing Procedure: Thickness measurement is performed using an ultrasonic thickness gauge. 25 points are used in a star-shaped pattern for testing. Target thickness uniformity is calculated by subtracting the minimum thickness from the maximum thickness measured. A schematic diagram of the thickness testing points is shown below. Figure 2 As shown.

[0087] The test results are shown in Table 1.

[0088] Table 1

[0089]

[0090] analyze:

[0091] As shown in the table above, the present invention uses the flat pressure method to relieve stress, causing the residual welding stress inside the target material to yield and relax, thereby removing the welding stress to the greatest extent. This greatly improves the dynamic deformation phenomenon of the target material during the processing and ensures that the thickness uniformity of the target material is controlled within 0.3mm.

[0092] The data results from Examples 2 and 4-7 show that if the pressure during the flat pressing of the block is too small, it will not improve the thickness uniformity, resulting in uneven thickness of the target material with a thickness uniformity greater than 0.3 mm. If the thickness uniformity of the target material is too large, the effect will be insignificant, and in severe cases, it will increase the material extrusion and increase the risk of cracking.

[0093] The data results from Examples 1 and 8-11 show that if the holding time during the flat pressing of the pressure block is too short, it will not improve the thickness uniformity, resulting in uneven thickness of the target material with a thickness uniformity greater than 0.3 mm. If the holding time during the flat pressing of the pressure block is too long, although the thickness uniformity of the target material can be controlled within the range of 0.3 mm, the effect is not obvious, and extending the holding time will reduce work efficiency and increase costs.

[0094] As can be seen from the data results of Example 1 and Comparative Example 1, if the residual welding stress is not removed by the flat pressing method, the residual stress inside the target material is difficult to remove efficiently, resulting in uneven thickness of the target material, with the thickness uniformity being greater than 0.3 mm.

[0095] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for removing residual welding stress inside a target material to ensure uniform target thickness, characterized in that, The method includes the following steps: (1) Weld the target blank and the back plate together and shape them to obtain the target material; The flatness of the target material in step (1) is <0.1mm; (2) A pad is placed on the side of the target material away from the back plate. When the pad is pressed flat, the residual welding stress inside the target material is removed, so that the thickness uniformity of the target material is controlled within 0.3 mm. In step (2), the diameter of the pad is greater than the diameter of the target material; The pressure holding time for the pressing block in step (2) is 12-30 minutes; The pressure during the flat pressing of the block in step (2) is 4-5 MPa.

2. The method according to claim 1, characterized in that, The target blank in step (1) is made of tungsten.

3. The method according to claim 1, characterized in that, The material of the backplate in step (1) includes copper alloy or Al alloy.

4. The method according to claim 1, characterized in that, The material of the pad in step (2) includes any one of elemental Al, aluminum alloy or stainless steel.

5. The method according to claim 1, characterized in that, The thickness of the pad in step (2) is >30mm.

6. The method according to claim 1, characterized in that, The method includes the following steps: (1) Weld the tungsten target blank and the back plate together and shape them to obtain a tungsten target with a flatness of <0.1mm; (2) An Al pad with a thickness of >30mm is provided on the surface of the tungsten target away from the back plate. When the pressure block is used to flatten the target, the welding stress inside the target assembly is removed, so that the thickness uniformity of the target is controlled within 0.3mm. Among them, the diameter of the pad is greater than the diameter of the target material, the pressure of the pad during flat pressing is 4-5 MPa, and the holding time of the pad during flat pressing is 12-30 min.

7. An application of the method as described in any one of claims 1-6, characterized in that, The method is used to remove residual welding stress inside the target material.

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