MOLYBDENUM SPUTTERING TARGET ASSEMBLY AND METHOD OF MAKING

Abstract

A molybdenum sputtering target assembly includes molybdenum sputtering target diffusion bonded directly to a molybdenum backing plate. The molybdenum sputtering target consists of molybdenum and the molybdenum backing plate consists of molybdenum or a molybdenum alloy.

Claims

1. A molybdenum sputtering target assembly comprising: a molybdenum sputtering target consisting of molybdenum; and a molybdenum backing plate consisting of molybdenum or a molybdenum alloy and diffusion bonded directly to the molybdenum sputtering target.

2. The molybdenum sputtering target assembly of 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 of claim 1, wherein the molybdenum backing plate consists of molybdenum having a lower purity than the molybdenum of the molybdenum sputtering target.

4. The molybdenum sputtering target assembly of claim 1, wherein the molybdenum sputtering target has an average grain size of less than about 100 m.

5. The molybdenum sputtering target assembly of claim 4, wherein the grain size differs by +/5 m through the thickness of the molybdenum sputtering target.

6. The molybdenum sputtering target assembly of claim 1, wherein the molybdenum sputtering target has an average grain size of less than about 50 m.

7. The molybdenum sputtering target assembly of claim 1, wherein the molybdenum sputtering target is between about 0.2 inches and about 0.6 inches in thickness.

8. A method for forming a sputtering target assembly, the method comprising: diffusion bonding a molybdenum sputtering target directly to a molybdenum backing plate by hot isostatic pressing at a pressure equal to or greater than 15 ksi and a temperature of from about 700 C. and about 1500 C., wherein the molybdenum sputtering target consists of molybdenum and the molybdenum backing plate consists of molybdenum or a molybdenum alloy.

9. The method of 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 backing plate consists of molybdenum having a lower purity than the molybdenum 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 m.

12. The method of claim 8, wherein after the hot isostatic pressing, the grain size differs by +/5 m through the thickness of the molybdenum sputtering target.

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 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic illustration of a sputtering apparatus.

[0021] FIG. 2 is a schematic illustration of an exemplary molybdenum sputtering target assembly.

DETAILED DESCRIPTION

[0022] Disclosed herein is an improved molybdenum sputtering target assembly and a method of making the same. FIG. 2 is a schematic cross-sectional view of molybdenum sputtering target assembly 100 which includes molybdenum backing plate 102 and molybdenum sputtering target 104. Molybdenum backing plate 102 and molybdenum sputtering target are joined directly to one another by a diffusion bond.

[0023] Molybdenum sputtering target 104 is formed from 100% molybdenum and inevitable impurities. For example, molybdenum sputtering target 104 consists of or consists essentially of molybdenum. Sputtering target 104 has a sufficient average grain for interconnect material. For example, molybdenum sputtering target 104 has an average grain size less than about 100 m. In some examples, molybdenum sputtering target 104 has an average grain size less than about 50 m. In still further examples, molybdenum sputtering target 104 has an average grain size of about 20 m to about 50 m or about 30 m.

[0024] Molybdenum sputtering target 104 may have uniform grain size through the thickness. Grain size uniformity can be determined by measuring the grain size at various locations across the thickness of the sputtering target. For example, the grain size can be measured at near the surface of the sputtering target and at the thickness center of the sputtering target. In some examples, the grain size differs by +/5 m through the thickness of the sputtering target.

[0025] Molybdenum sputtering target 104 has a thickness of from about 0.2 inches to about 0.6 inches. In comparison, a monolithic sputtering target typically has a thickness of about 0.9 inches to about 1.3 inches. A monolithic sputtering target also typically has a much bigger grain size, and the grain size is typically non-uniformly distributed through the thickness of the sputtering target.

[0026] In some embodiments, molybdenum backing plate 102 can be formed from 100% molybdenum and inevitable impurities or from a molybdenum alloy. For example, molybdenum backing plate 102 can consists of or consist essentially of molybdenum. In some embodiments, molybdenum backing plate 102 can be formed from a lower purity molybdenum than molybdenum sputtering target 104. In other embodiments, molybdenum backing plate 102 can be formed from a molybdenum alloy. Exemplary molybdenum alloys include TZM (titanium-zirconium-molybdenum Alloy), MoW (molybdenum tungsten alloy) (i.e., 30-50 wt. % W, such as Mo30W containing 30 wt. % W), MoCu (molybdenum copper alloy) (i.e., Mo15Cu containing 15 wt. % Cu), MHC (molybdenum hafnium carbon alloy) (i.e., 1.2 wt. % Hf, 0.5-0.12 wt. % C).

[0027] In some embodiments, molybdenum sputtering target 104 can be formed from 100% molybdenum having a CTE of 5 m/(m.Math.K) and molybdenum backing plate 102 can be formed from 100% molybdenum having a CTE of 5 m/(m.Math.K) TZM alloy having a CTE from 4.9-5.3 m/(m.Math.K), Mo15Cu alloy having a CTE of 6.75 m/(m.Math.K), or M30W alloy having a CTE of 4.85 m/(m.Math.K). In this way, the CTEs of molybdenum sputtering target 104 and molybdenum backing plate 102 are the same or are substantially the same, which reduces the likelihood that molybdenum sputtering target 104 will crack during use and bonding.

[0028] Molybdenum sputtering target 104 and molybdenum backing plate 102 are diffusion bonded to one another. In some embodiments, molybdenum sputtering target 104 and molybdenum backing plate 102 are bonded by hot isostatic pressing (HIP) or vacuum hot press. In some embodiments, molybdenum sputtering target 104 and molybdenum backing plate 102 are bonded by HIP at a pressure greater than or equal to 15 kilopound force per square inch (ksi) (103,421 kilopascals) and a temperature from about 700 C. and about 1500 C. In other embodiments, molybdenum sputtering target 104 and molybdenum backing plate 102 are bonded by HIP at a pressure greater than or equal to 15 ksi (103,421 kilopascals) and a temperature from about 700 C. and about 1300 C.

[0029] In some embodiments, molybdenum sputtering target 104 and molybdenum backing plate 102 are bonded directly to one another. For example, in some embodiments there is no joining material, such as a joining powder, between molybdenum sputtering target 104 and molybdenum backing plate 102. Directly joining molybdenum sputtering target 104 to molybdenum backing plate 102 reduces the likelihood that molybdenum sputtering target 104 will crack during use because of a difference in CTEs.

[0030] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above-described features.