Texas Instruments Corporation

Donald E Brown

Alan Dee Rose

Roger A Robbins

David W Buck

A method and apparatus is provided for reducing wall erosion in a plasma containment tube (20), such as, for example, a quartz plasma tube (20) used in a microwave-induced plasma reaction process for etching semiconductor wafers. A pure benign or non-corrosive gas (Ar) is introduced into the 'upstream' section (22a) of the tube (22), where the microwave energy is imparted to create a plasma. The activated benign gas flows 'downstream' through a flange (28), preferably made of quartz, which is seated on o-rings (50) inside a water-cooled metal flange (48). These sealing o-rings (50) are thus cooled and removed from the ultraviolet light created by the plasma. The corrosive etchant gas (SF.sub.6) is introduced into the 'downstream' section (22b) of the tube (22) beyond the flange (28), where it is activated by the benign gas (Ar). The benign gas (Ar) flows principally along the inner sidewalls of the tube (22), and the etchant gas (SF.sub.6) is thus principally contained by the benign gas (Ar) in the center of this section (22b) of the tube. This 'downstream' section (22b) of the tube (22) is surrounded by a water jacket (24), which channels coolant around the outer surface of the tube (22b). Consequently, etching erosion of the inner surface of the tube (22) is minimized in the 'upstream' or microwave section (22a) where the plasma is hottest, and also in the 'downstream' section (22b) where the corrosive etchant gas (SF.sub.6) is activated.

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Bedford, TX, United States of America

Donald E Brown