EFFECT OF CHEMICAL OXIDE LAYERS ON PLATINUM-ENHANCED OXIDATION OF SILICON

Si oxidation promoted by a platinum (Pt) overlayer has been investigat ed using x-ray photoelectron spectroscopy and synchrotron radiation ul traviolet photoelectron spectroscopy. Heat treatments of the specimens with (similar to 5-nm-Pt/0.5-1-nm-chemical oxide/Si(100)) structure a t 300-400 degrees C increase the oxide thickness to 4-5 nm. The amount s of the suboxide species, a(Si+), a(Si2+), and a(Si3+), in the chemic al oxide layers formed in hydrochloric acid (HCl) plus hydrogen peroxi de (H2O2) are in the order of a(Si+)>a(Si2+)>a(Si3+), while those for the oxide layers formed in nitric acid (HNO3) have an order of a(Si3+) >a(Si2+)approximate to a(Si+). The amounts of the suboxide species in the former oxide layers are much higher than those in the latter oxide layers. These results indicate that the HNO3 oxide layers are more hi ghly oxidized, probably resulting in a higher atomic density and a low er defect density. Although the initial chemical oxide layers formed i n HCl+H2O2 are thinner than those grown in HNO3, the former oxide laye rs become thicker than the latter after the Pt deposition and the heat treatments below 200 degrees C. This result is attributed to the lowe r atomic density and the higher defect density of the chemical oxide l ayers produced in HCl+H2O2, which enhance the diffusion of oxidizing s pecies. It is suggested that the variation in the atomic density of th e chemical oxide layers cause the different energy distribution of int erface states in the Si band gap. (C) 1997 American Institute of Physi cs.