Method of producing a tubular target

Abstract

A method for producing a tubular target formed of molybdenum or a molybdenum alloy which has an oxygen content of less than 50 μg / g, a density of greater than 99% of the theoretical density and an average grain size of less than 100 μm and which is connected to a supporting tube. The molybdenum or molybdenum alloy tube is produced by extrusion.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This is a continuing application, under 35 U.S.C. §120, of copending international application No. PCT / AT2006 / 000406, filed Oct. 5, 2006, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of Austrian patent application No. GM 699 / 2005, filed Oct. 14, 2005; the prior applications are herewith incorporated by reference in their entirety.BACKGROUND OF THE INVENTION Field of the Invention [0002] The invention relates to a method for producing a tubular target, which comprises a tube of molybdenum or a molybdenum alloy with an oxygen content of less than 50 μg / g, a density of greater than 99% of the theoretical density, and an average grain size transversely to the axial direction of less than 100 μm as well as a supporting tube of a non-magnetic material. [0003] A target is understood as meaning the material to be sputtered of a cathode atomization system. Rotating tubular targets are known ...

AI Technical Summary

Benefits of technology

[0011] It is accordingly an object of the invention to provide a method of producing a sputtering target which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which on the one hand is inexpensive and on the other hand produces a product which is uniformly eroded in the sputtering process, does not tend to give a locally increased sputtering rate and does not lead to any contamination of the substrate or the deposited layer.

[0026] In order to reduce the discharge loss of molybdenum during the extrusion, it is advantageous to mechanically fasten a steel end piece to one end of the molybdenum tube blank. This mechanical fastening may be performed for example by means of a screwed or bolted connection. The outer diameter and the inner diameter of the steel end piece of the tube blank in this case correspond to the outer diameter and the inner diameter of the molybdenum tube blank.

[0030] Suitable as connecting methods are both those methods which lead to a material bond and those which lead to a form-fitting connection. One condition, however, is that the contact area between the molybdenum tube and the supporting tube be at least 30% of the theoretically possible area. If the area is smaller, the heat removal is hindered too much. Also the low coefficient of thermal expansion of molybdenum has to be considered. Therefore, the joining temperature must be chosen to be as low as possible. If, for example, the connection between the molybdenum tube and the supporting tube is performed by a forging process, in that the supporting tube is positioned in the molybdenum tube and forged over a mandrel, lowest possible forming temperatures of about 500° C. to 800° C. must be chosen. Furthermore, it is advantageous if the material of the supporting tube has a low yield strength, in order that stresses occurring due to plastic flow can be reduced.

[0035] Use of a gap with a steel powder fill lying in between has the effect of improving the bond between the supporting tube and the molybdenum tube during the co-extrusion. A gap width of from 3 mm to 20 mm proves to be advantageous.

[0037] After the extrusion / co-extrusion process, it may be advantageous for the extruded tube to be straightened. This can be performed by a forging process over a mandrel.

Problems solved by technology

Below 1600° C., adequate densification is not achieved.