Apparatus for DC reactive plasma vapor deposition of an electrically insulating material using a shielded secondary anode

Abstract

In a plasma vapor deposition reactor for depositing an electrically insulating material using a DC sputtering process the plasma is stabilized, maintaining its sputtering efficiency, by provision of a secondary anode, preferably held at a positive bias with respect to the primary anode. The secondary anode is shielded from exposure to the stream of sputtered material, yet situated close enough to the plasma discharge to attract electrons from the plasma to maintain its charge balance. In reactive sputtering, the sputtering chamber contains both a sputtering gas, for example argon, and a reactive gas, for example oxygen. Positive ions of the sputtering gas bombard a target of the material to be sputtered. Atoms of the target material, the sputtered atoms, are emitted from the target in all directions into the chamber, some of them falling on the substrate surface to be sputter coated. At the surface or in the chamber they chemically combine with the reactive gas. In the instance to which this invention applies, the chemical combination forms an electrically insulating coating on the substrate. The same electrically insulating material coats all other surfaces expose to the flux of sputtered atoms. In an embodiment of the invention the positively biased secondary anode, being shielded from the sputtered atoms is not coated by the electrically insulating material, thus maintaining its ability to draw electrons from the plasma.

Dependencies are inferred from the claim text.