Method and design for sputter target attachment to a backing plate

Abstract

A method of assembling the components of a sputter cathode assembly via thermal expansion of projections provided on one assembly member to provide thermal contact to the other assembly member, and the sputter cathode formed thereby are described. The method forms a temporary mechanical attachment of component members that ends when the components are cooled below the predetermined contact temperature. The method optionally includes mechanically interlocking the assembly components together.

Description

[0001] This application claims priority under 35 U.S.C. .sctn.119(e) of prior U.S. Provisional Patent Application No. 60 / 480,196 filed Jun. 20, 2003, which is incorporated in its entirety by reference herein.[0002] The present invention relates to sputtering components. More particularly, the present invention relates to a mechanical method of joining the components of a sputter cathode assembly.[0003] In the sputter application field, sputtering is widely used for depositing a film or thin layer of material from a sputter target onto a desired substrate. A sputter cathode assembly including the sputter target and an electrode can be placed together with an anode in a sputtering device or chamber filled with an inert gas. The desired substrate is positioned in the chamber near the anode with a receiving surface of the substrate oriented normally to a path between the sputter cathode assembly and the anode. A high voltage electric field is applied across the sputter cathode assembly ...

AI Technical Summary

Benefits of technology

[0011] It is therefore a feature of the present invention to provide a sputter cathode assembly for which the debonding issue is avoided by providing a fail-safe bond between the assembly components.

[0012] Another feature of the present invention is to provide a sputter cathode assembly in which the assembly components can be separated from each other by nondestructive means and the recovered usable components can be reused and / or recycled.

[0013] A further feature of the present invention is to provide a sputter cathode assembly, especially a large-area sputter cathode assembly, that avoids the undesirable arcing and contamination issues that are present in conventional soldered sputter cathode assemblies of multi-target construction.

[0014] Yet another feature of the present invention is to provide a sputter cathode assembly in which the sputter target component can be readily removed and replaced without the need to also remove the electrode from the sputtering chamber.

Problems solved by technology

The differential thermal expansion between the target material and the backing plate material which occurs when bonding is accomplished at elevated temperatures by diffusion bonding, friction welding, explosion bonding and the like, can generate very high levels of mechanical stress in the metal bodies.

The mechanical stress often causes deflection of the sputter target and can cause the bond to fail so that the sputter target separates from the backing plate during the elevated temperatures attained during the sputtering process.

Thus, controlling strain, .epsilon., presents a particular challenge for large area sputter cathode assemblies that are needed to coat a relatively large-area substrate, such as for a flat glass panel to be used in a flat panel display of a computer monitor or a television screen.

Another disadvantage to permanently attaching the sputter cathode assembly members by a metallurgical bond is that separating the assembly members is typically achieved in a destructive manner, such as machining or chemical etching.

The backing plate flange assembly typically contains features, e.g., bolt holes, alignment marks, and / or an o-ring groove, that are difficult and expensive to machine.

Although solder or low temperature brazing techniques reduce net strain via a comparatively low bonding temperature, T, the bond strength achieved can be insufficient for large sputter targets.

However, the solder can intrude the joints between the multi-piece target segments of the assembly and thus becomes a source of arcing and particle emission (i.e., contamination) during sputtering.

Also, the sputtering behavior of the edges of the individual target tiles may differ from that of the bulk of the target array, resulting in a deposited film having diminished thickness uniformity.

This makes change-out of a sputter target a costly and time-consuming process.

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