Etching by atomic hydrogen of Ge overlayers on Si(100)

Abstract

X-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectrometry (LEISS) have been employed to study the kinetics of etching by atomic hydrogen of Ge overlayers on Si(100). The coverage of Ge as deduced by both XPS and LEISS decreases dramatically after exposure to atomic hydrogen, and the decrease is exponential with exposure time. The etch rate of Ge derived from these experiments is found to be a linear function of the flux of atomic hydrogen at sufficiently low temperatures (<180 °C). The rate of etching also depends upon the substrate temperature and a maximum in the etch rate is observed at about 180 °C. A kinetic model is proposed to describe the experimental data quantitatively. The model successfully describes the variation in the rate of etching as functions of the flux of atomic hydrogen and substrate temperature. In particular, the peak observed in the etch rate as a function of substrate temperature is interpreted as due to a similar variation in the coverage of an important reaction intermediate, namely a GeH2(a) surface species.