Published online by Cambridge University Press: 28 February 2011
Etching of silicon by molecular fluorine is accelerated when trace quantities of copper are present on the surface. Copper is a residue formed when sputter-deposited aluminum (containing 0.5 % copper) is selectively removed by HF from the silicon surface. The temperature dependence of the etching rate was studied in the range 60–290°C. At temperatures higher than 80°C copper causes a ˜100-fold increase in the rate of etching of the underlying silicon (100), compared to unmetallized samples. Above 180°C, F2 exhibits a higher absolute etch rate than equivalent concentrations of fluorine atoms. Preliminary results for other metal contaminants and etchant gases indicate that silver also accelerates F2 etching, and copper enhances etching by NF3. The results are interpreted in terms of a catalytic mechanism.