| 摘要 |
The invention relates to the fabrication of a gate stack or other layered structure in a semiconductor device, and more particularly to methods to selectively etch a metal silicide layer, such as tungsten silicide (WSix), without etching excessive amounts of an underlying polysilicon or gate dielectric layer. The methods of the invention employ an etch chemistry that minimizes or eliminates the formation of lateral growth structures on a metal silicide layer during oxidation steps following etch of a gate stack. A preferred etch composition comprises ammonium fluoride and less than 2% by volume hydrogen peroxide in an aqueous solution with a pH control agent to maintain the solution at about pH 7 to 10.
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