MECHANISM OF PLATINUM-ENHANCED OXIDATION OF SILICON AT LOW-TEMPERATURES

The mechanism of platinum (Pt)-enhanced oxidation of Si below 300 degr ees C has been investigated by means of high-resolution x-ray photoele ctron spectroscopy. When a Pt layer is deposited on the similar to 1-n m-thick silicon oxide-covered Si, low-temperature heat treatment grows the silicon oxide layer between the Pt layer and the Si substrate, wh ile silicon oxide is formed mainly on the Pt layer in cases where Pt i s directly deposited on the Si substrate. Oxidation is enhanced by the application of a positive bias voltage to the Si substrate with respe ct to the Pt layer during the heat treatment of the specimens with [si milar to 4 nm Pt/silicon oxide/Si(100)] structure in oxygen, and in th is case, a similar to 8-nm-thick oxide layer is formed at 300 degrees C for 2 h, It demonstrates that oxygen ions are the moving species in the oxide layer. The plots of oxide thickness with respect to oxidatio n time are linear in the oxide thickness region below 3 similar to 4 n m, indicating that the reaction at the interface is the rate-determini ng step. The activation energy for the interfacial reaction is estimat ed to be similar to 0.55 eV: much lower than that for oxidation throug h reaction with oxygen molecules of similar to 2 eV. The plots for the subsequent oxidation stage are expressed by logarithmic functions, sh owing that the migration of oxygen ions in the oxide layer is the rate -limiting process. (C) 1998 American Institute of Physics.