Anisotropic and Selective Etching of Tungsten Silicide-Tungsten- Tungsten Silicide Composite Stack
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
This article discusses an etch chemistry that improves etch selectivity and eliminates preferential attacks of a tungsten silicide-tungsten- tungsten silicide stack during a reactive ion etch (RIE). The figure shows a composite film structure of tungsten silicide (WSix), tungsten (W) and tungsten silicide with a mask on top and a narrow-dimensioned topographical feature on the substrate below. Highly anisotropic and selective etching of CVD (chemical vapor deposited) W/WSix films can be achieved using admixtures of SiF4 and O2 as etch gasses. It is generally accepted that W and Si etching occurs in plasma systems by a combination of the etched materials with atomic fluorine. Volatile fluoride products form and are pumped away, e.g., WF6 or SiF4 . Thus, the RIE species is fluorine.