Molybdenum sputter target assembly and method of manufacture
By using diffusion bonding between the molybdenum sputtering target and the molybdenum or molybdenum alloy backing plate, and hot isostatic pressing, the bonding interface stress problem of the molybdenum sputtering target assembly during high-power sputtering is solved, achieving lower cost and more uniform grain size, which is suitable for semiconductor manufacturing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOZOTEX PERFORMANCE MATERIALS AMERICA INC
- Filing Date
- 2024-12-13
- Publication Date
- 2026-07-14
AI Technical Summary
Existing molybdenum sputtering target assemblies suffer from high stress at the bonding interface due to the mismatch in thermal expansion coefficients during high-power sputtering, leading to target peeling or cracking. Furthermore, thick single-layer molybdenum sputtering targets are costly and difficult to meet grain size requirements.
A molybdenum sputtering target is used to bond with a molybdenum or molybdenum alloy backing plate through diffusion. Hot isostatic pressing is then used to directly bond the target under high pressure and high temperature, ensuring uniform grain size and CTE matching, and reducing the risk of breakage.
This technology achieves efficient bonding of molybdenum sputtering targets, reduces the risk of breakage, decreases thickness requirements, lowers costs, and ensures uniform grain size, making it suitable for semiconductor manufacturing.
Smart Images
Figure CN122396813A_ABST
Abstract
Description
[0001] Cross-references to related applications
[0002] This application claims priority to U.S. Provisional Application No. 63 / 610,598, filed December 15, 2023, and U.S. Patent Application No. 18 / 975,119, filed December 10, 2024, the entire contents of which are incorporated herein by reference. Technical Field
[0003] This disclosure relates to a sputtering target assembly including a molybdenum sputtering target and a molybdenum-containing backplate. Background Technology
[0004] Physical vapor deposition (PVD) is widely used to form thin films of materials on a variety of substrates. One important application of this deposition technology is semiconductor manufacturing. Figure 1 The diagram illustrates a portion of an exemplary physical vapor deposition (“PVD”) apparatus 8. In one configuration, the sputtering target assembly 10 includes a backplate 12 to which a target 14 is coupled. A substrate 18 (such as a semiconductive material wafer) is located within the PVD apparatus 8 and is positioned spaced apart from the target 14. The surface 16 of the target 14 is the sputtering surface. As shown, the target 14 is disposed above the substrate 18 and positioned such that the sputtering surface 16 faces the substrate 18. In operation, sputtering material 22 is displaced from the sputtering surface 16 of the target 14 and used to form a coating (or thin film) 20 on the substrate 18.
[0005] Copper, copper alloys, and aluminum alloys are currently used as interconnect materials in semiconductor manufacturing. Over time, new interconnect materials will be needed to support the demand for faster, smaller, and more energy-efficient microelectronic devices. Two key material parameters for these new interconnects are low film resistivity, often expressed as a quality factor (volume resistivity × mean free path) and electromigration resistance. Molybdenum has a lower quality factor than copper and alternatives such as tungsten, making it a promising candidate for next-generation interconnect materials. Molybdenum also has a higher melting point than copper and aluminum alloys, resulting in improved electromigration properties.
[0006] High power is typically required for sputtering molybdenum sputtering targets. Therefore, diffusion-bonded targets may be necessary. Existing sputtering target assemblies include molybdenum sputtering targets diffusion-bonded to a copper-zinc backing plate. During sputtering, the temperatures of the sputtering target and backing plate fluctuate during the duty cycle. Large thermal stresses are generated at the bonding interface between the molybdenum sputtering target and the copper alloy backing plate, at least in part due to the mismatch in the coefficients of thermal expansion (CTE) between the target and backing plate during thermal cycling. This stress can lead to delamination or cracking of the sputtering target.
[0007] Alternatively, monolithic molybdenum sputtering targets have been used to avoid these problems. Monolithic molybdenum targets are formed from a single molybdenum sheet. The molybdenum sheet must be relatively thick, typically about 0.9 inches to 1.3 inches, because a separate backing plate is not used with a monolithic assembly. This thickness requirement increases cost and makes it difficult to meet grain size requirements due to thermomechanical processing challenges, such as insufficient total rolling reduction. For sheets of typical thickness, significant effort is required to achieve an average grain size of less than 100 μm. Furthermore, achieving a uniform grain size is more difficult in these thicker sheets. An improved molybdenum sputtering target assembly is needed. Summary of the Invention
[0008] Implementation scheme 1 is a molybdenum sputtering target assembly, which includes a molybdenum sputtering target composed of molybdenum and a molybdenum backplate composed of molybdenum or a molybdenum alloy and directly diffused and bonded to the molybdenum sputtering target.
[0009] Implementation scheme 2 is the sputtering target assembly according to implementation scheme 1, wherein the molybdenum alloy is selected from the group consisting of titanium-zirconium-molybdenum alloy, molybdenum-tungsten alloy, molybdenum-copper alloy and molybdenum-hafnium carbon alloy.
[0010] Implementation scheme 3 is a sputtering target assembly according to implementation scheme 1, wherein the molybdenum backplate is composed of molybdenum with a purity lower than that of the molybdenum sputtering target.
[0011] Implementation scheme 4 is a sputtering target assembly according to implementation scheme 1, wherein the molybdenum sputtering target has an average grain size of less than about 100 μm.
[0012] Implementation scheme 5 is a sputtering target assembly according to implementation scheme 4, wherein the grain size of the molybdenum sputtering target varies by + / - 5 μm over its entire thickness.
[0013] Implementation scheme 6 is a sputtering target assembly according to implementation scheme 1, wherein the molybdenum sputtering target has an average grain size of less than about 50 μm.
[0014] Implementation scheme 7 is a sputtering target assembly according to implementation scheme 1, wherein the thickness of the molybdenum sputtering target is between about 0.2 inches and about 0.6 inches.
[0015] Implementation scheme 8 is a method for forming a sputtering target assembly, the method comprising directly diffusion bonding a molybdenum sputtering target to a molybdenum backing plate by hot isostatic pressing at a pressure equal to or greater than 15 ksi and a temperature of about 700°C to about 1500°C. The molybdenum sputtering target is composed of molybdenum, and the molybdenum backing plate is composed of molybdenum or a molybdenum alloy.
[0016] Implementation scheme 9 is the method according to implementation scheme 8, wherein the molybdenum alloy is selected from the group consisting of titanium-zirconium-molybdenum alloy, molybdenum-tungsten alloy, molybdenum-copper alloy and molybdenum-hafnium carbon alloy.
[0017] Implementation scheme 10 is the method according to implementation scheme 8, wherein the molybdenum backplate is composed of molybdenum with a purity lower than that of the molybdenum sputtering target.
[0018] Implementation scheme 11 is the method according to implementation scheme 8, wherein after the hot isostatic pressing, the molybdenum sputtering target has an average grain size of less than about 100 μm.
[0019] Implementation scheme 12 is the method according to implementation scheme 8, wherein after the hot isostatic pressing, the grain size difference across the entire thickness of the molybdenum sputtering target is + / - 5 μm.
[0020] Implementation scheme 13 is the method according to implementation scheme 8, wherein after the hot isostatic pressing, the molybdenum sputtering target has an average grain size of less than about 50 μm.
[0021] While several embodiments have been disclosed, other embodiments of the invention will become apparent to those skilled in the art from the following detailed description illustrating and describing exemplary embodiments of the invention. Therefore, the drawings and detailed description should be considered illustrative rather than restrictive in nature. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of a sputtering device.
[0023] Figure 2 This is a schematic diagram of an exemplary molybdenum sputtering target assembly. Detailed Implementation
[0024] This paper discloses an improved molybdenum sputtering target assembly and its manufacturing method. Figure 2 This is a schematic cross-sectional view of a molybdenum sputtering target assembly 100, including a molybdenum backplate 102 and a molybdenum sputtering target 104. The molybdenum backplate 102 and the molybdenum sputtering target are directly bonded to each other via diffusion bonding.
[0025] The molybdenum sputtering target 104 is formed from 100% molybdenum and unavoidable impurities. For example, the molybdenum sputtering target 104 is composed of molybdenum or is substantially composed of molybdenum. The sputtering target 104 has a sufficient average grain size for interconnect materials. For example, the molybdenum sputtering target 104 has an average grain size of less than about 100 μm. In some examples, the molybdenum sputtering target 104 has an average grain size of less than about 50 μm. In other examples, the molybdenum sputtering target 104 has an average grain size of about 20 μm to about 50 μm or about 30 μm.
[0026] A uniform grain size can be achieved across the entire thickness of the molybdenum sputtering target 104. Grain size uniformity can be determined by measuring the grain size at different locations along the thickness of the sputtering target. For example, the grain size can be measured near the surface of the sputtering target and at the center of the thickness of the sputtering target. In some examples, the grain size varies by + / - 5 μm across the entire thickness of the sputtering target.
[0027] The molybdenum sputtering target 104 has a thickness of approximately 0.2 inches to approximately 0.6 inches. In contrast, a monolithic sputtering target typically has a thickness of approximately 0.9 inches to approximately 1.3 inches. Monolithic sputtering targets also typically have much larger grain sizes, and the grain size is generally not uniformly distributed across the entire thickness of the sputtering target.
[0028] In some embodiments, the molybdenum backing plate 102 may be formed of 100% molybdenum and unavoidable impurities or of a molybdenum alloy. For example, the molybdenum backing plate 102 may consist of molybdenum or be substantially composed of molybdenum. In some embodiments, the molybdenum backing plate 102 may be formed of molybdenum with a lower purity than that of the molybdenum sputtering target 104. In other embodiments, the molybdenum backing plate 102 may be formed of a molybdenum alloy. Exemplary molybdenum alloys include TZM (titanium-zirconium-molybdenum alloy), MoW (molybdenum-tungsten alloy) (i.e., 30 wt% to 50 wt% W, such as Mo30W containing 30 wt% W), MoCu (molybdenum-copper alloy) (i.e., Mo15Cu containing 15 wt% Cu), and MHC (molybdenum-hafnium carbon alloy) (i.e., 1.2 wt% Hf and 0.5 wt% to 0.12 wt% C).
[0029] In some implementations, the molybdenum sputtering target 104 may be composed of a CTE of 5 μm / (m The molybdenum backing plate 102 is formed from 100% molybdenum (K), and the molybdenum backing plate 102 can be made of CTE with a thickness of 5 μm / (m). 100% molybdenum (K) has a CTE of 4.9–5.3 µm / (m The TZM alloy (K) has a CTE of 6.75 µm / (m Mo15Cu alloy with K), or CTE of 4.85µm / (m The molybdenum sputtering target 104 and the molybdenum backing plate 102 are formed from an M30W alloy (K). In this way, the CTE of the molybdenum sputtering target 104 and the molybdenum backing plate 102 are the same or substantially the same, which reduces the possibility of the molybdenum sputtering target 104 breaking during use and bonding.
[0030] The molybdenum sputtering target 104 and the molybdenum backing plate 102 are diffusion bonded together. In some embodiments, the molybdenum sputtering target 104 and the molybdenum backing plate 102 are bonded by hot isostatic pressing (HIP) or vacuum hot pressing. In some embodiments, the molybdenum sputtering target 104 and the molybdenum backing plate 102 are bonded by HIP at a pressure greater than or equal to 15 kpsi (103421 kPa) and a temperature of about 700°C to about 1500°C. In other embodiments, the molybdenum sputtering target 104 and the molybdenum backing plate 102 are bonded by HIP at a pressure greater than or equal to 15 kpsi (103421 kPa) and a temperature of about 700°C to about 1300°C.
[0031] In some embodiments, the molybdenum sputtering target 104 and the molybdenum backing plate 102 are directly bonded to each other. For example, in some embodiments, there is no bonding material such as bonding powder between the molybdenum sputtering target 104 and the molybdenum backing plate 102. Directly bonding the molybdenum sputtering target 104 to the molybdenum backing plate 102 reduces the likelihood of the molybdenum sputtering target 104 breaking during use due to CTE differences.
[0032] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the invention. For example, while the above embodiments relate to specific features, the scope of the invention also includes embodiments with different combinations of features and embodiments that do not include all of the above features.
Claims
1. A molybdenum sputtering target assembly, the molybdenum sputtering target assembly comprising: Molybdenum sputtering target composed of molybdenum; as well as A molybdenum backplate, which is composed of molybdenum or a molybdenum alloy and is directly diffused and bonded to the molybdenum sputtering target.
2. The molybdenum sputtering target assembly according to claim 1, wherein the molybdenum alloy is selected from the group consisting of titanium-zirconium-molybdenum alloy, molybdenum-tungsten alloy, molybdenum-copper alloy and molybdenum-hafnium carbon alloy.
3. The molybdenum sputtering target assembly according to claim 1, wherein the molybdenum backplate is composed of molybdenum with a purity lower than that of the molybdenum sputtering target.
4. The molybdenum sputtering target assembly according to claim 1, wherein the molybdenum sputtering target has an average grain size of less than about 100 μm.
5. The molybdenum sputtering target assembly according to claim 4, wherein the grain size varies by + / - 5 μm over the entire thickness of the molybdenum sputtering target.
6. The molybdenum sputtering target assembly according to claim 1, wherein the molybdenum sputtering target has an average grain size of less than about 50 μm.
7. The molybdenum sputtering target assembly of claim 1, wherein the thickness of the molybdenum sputtering target is between about 0.2 inches and about 0.6 inches.
8. A method for forming a sputtering target assembly, the method comprising: A molybdenum sputtering target is directly diffused and bonded to a molybdenum backing plate by hot isostatic pressing at a pressure equal to or greater than 15 ksi and a temperature of about 700°C to about 1500°C, wherein the molybdenum sputtering target is composed of molybdenum and the molybdenum backing plate is composed of molybdenum or a molybdenum alloy.
9. The method according to claim 8, wherein the molybdenum alloy is selected from the group consisting of titanium-zirconium-molybdenum alloy, molybdenum-tungsten alloy, molybdenum-copper alloy and molybdenum-hafnium carbon alloy.
10. The method of claim 8, wherein the molybdenum backsheet is composed of molybdenum with a purity lower than that of the molybdenum sputtering target.
11. The method of claim 8, wherein after the hot isostatic pressing, the molybdenum sputtering target has an average grain size of less than about 100 μm.
12. The method of claim 8, wherein after the hot isostatic pressing, the grain size across the entire thickness of the molybdenum sputtering target differs by + / - 5 μm.
13. The method of claim 8, wherein after the hot isostatic pressing, the molybdenum sputtering target has an average grain size of less than about 50 μm.