Catalyzed gaseous etching of silicon

Abstract
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 etching rate of an underlying (100) silicon, compared to unmetallized samples, at temperatures above 80 °C. Above 180 °C, F2 exhibits a higher absolute etch rate than equivalent concentrations of fluorine atoms. The temperature dependence of the reaction is interpreted in terms of a Cu-CuF(x=1,2) catalytic cycle in which CuF(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 F2/Si reaction are discussed.

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