SELECTIVE REMOVAL OF A SI0.7GE0.3 LAYER FROM SI(100)

The selective removal of epitaxial Si0.7Ge0.3 from {100} silicon using an aqueous based etch is reported. An etch consisting of HNO3:H2O:HF (0.5%), 40:20:5 at 22-degrees-C, removes Si0.7Ge0.3 at a rate of 207 angstrom/min, and removes {100} Si at a rate of 16 angstrom/min. This corresponds to a selectivity of 13 +/- 1 where the selectivity is defined as the ratio of the Si0.7Ge0.3 to {100} Si etch rates. This etch leaves the surface smooth and free from pitting or trenching as observed by optical microscopy. The results obtained are consistent with a germanium enhanced oxidation mechanism of the Si0.7Ge0.3 alloy during semiconductor removal.