Catalyzed gaseous etching of silicon.

Traces of copper and silver are shown to accelerate the etching of silicon by molecular fluorine. Copper residue formed by aqueous HF etching of sputter-deposited aluminum (0.5% Cu) produces a 100-fold increase in the rate of etching the underlying (100) silicon, compared to unmetallized samples at temperatures above 80C. Above 180C, F sub 2 exhibits a higher absolute etch rate than equivalent concentrations of fluorine atoms. These temperature dependence of the reaction is interpreted in terms of a Cu-CuF sub (x = 1,2) catalytic cycle in which CuF sub (x = 1, 2) is the active intermediate. Preliminary results for other gases and metals are presented, and the origin of discrepancies in published rate data for the F sub 2/Si reaction are discussed.