Inventors:
Hoiman (Raymond) Hung - San Jose CA
Joseph P. Caulfield - Sunnyvale CA
Hongchin Shan - San Jose CA
Kenneth S. Collins - San Jose CA
Chunshi Cui - Santa Clara CA
Michael Rice - Pleasanton CA
Assignee:
Applied Materials Inc. - Santa Clara CA
International Classification:
H01L 213065
US Classification:
216 67, 216 72, 216 79, 438723, 438738, 438743
Abstract:
A plasma etching process, particularly useful for selectively etching oxide over a feature having a non-oxide composition, such as silicon nitride and especially when that feature has a corner that is prone to faceting during the oxide etch. A primary fluorine-containing gas, preferably hexafluorobutadiene (C F ), is combined with a significantly larger amount of the diluent gas xenon (Xe) to enhance nitride selectivity without the occurrence of etch stop. The chemistry is also useful for etching oxides in a time oxide etch in which holes and corners have already been formed, for example counterbore vias in a dual damascene structure. In this case, the relative amount of xenon need not be so high, but xenon still reduces faceting of the oxide corners. The invention may be used with related heavy fluorocarbons and other fluorine-based etching gases. The plasma etching preferably includes striking the plasma with argon, switching to xenon and the fluorine-based gas but at reduced bias power to stabilize the plasma, and then increasing the bias to a full etching level.