US 4,392,938 AGranted

Radio frequency etch table with biased extension member

AssigneeVarian Associates, Inc.

InventorsDavid J. Harra, Frederick T. Turner

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Abstract

An RF etch table has a biased extension member positioned adjacent its periphery. The extension member is electrically conductive, but is insulated from other conductive members in the system. The extension member is positioned with respect to the periphery of the table in a manner such that the boundary of the plasma induced above the etch table is continued beyond the periphery of the etch table, thereby eliminating the focusing of ions onto the edges of an item being etched on the table. The potential impressed upon the extension member produces a dark space above its surface having a sufficient height so that the horizontal configuration of the sheath above the etch table is continued beyond its edges. More uniform etching is accomplished.

Claims11

Dependent claims

An RF etch table for uniformly etching a semiconductor wafer by sputtering, comprising,

a table structure adapted to receive and hold a generally circular semiconductor wafer to be subjected to sputter etching;
an RF power supply electrically connected to said table structure;
an extension member positioned adjacent the periphery of said table, said extension member being electrically conductive and being insulated from other conductive members;
a bias power supply means for applying an electrical potential to said extension member whereby the plasma generated above said table structure extends horizontally beyond the periphery of said etch table and above at least a portion of said extension member;
and
a shielding member placed over said extension member, but not in electrical communication with said extension member, whereby said biased extension member is protected from unwanted sputtering to thereby avoid metallic contamination of said semiconductor wafer.

3 more elements

Dependencies are inferred from the claim text.