OXIDATION OF SILICON BY LOW-ENERGY OXYGEN IONS

This paper gives an overview of recent studies of the oxidation of sil icon during oxygen bombardment, In secondary ion mass spectrometry mea surements, oxygen builds up to stoichiometric SiO2 under appropriate c onditions. When this occurs, some elements are segregated at the Si-Si O2 interface during subsequent sputtering. Temperature-dependent studi es have shown that there is a strong chemical driving force to form Si O2 layers even under liquid nitrogen temperature bombardment. Oxygen i s not mobile in Si during bombardment but is highly mobile in SiO2. Fa st diffusing metals such as Cu, Au and Pd appear to be mobile in an am orphous-Si layer beyond the beam-induced SiO2 layer if the bombardment temperature is sufficiently high. These metals also exhibit low solub ility in SiO2 but high solubility in amorphous or disordered Si. Thus, there is a driving force for segregation at a moving Si-SiO2 interfac e.