Metal-induced charge and growth rate of ultrathin thermal oxide films grown on Al or Fe contaminated Si (100) surfaces

This paper first describes how growth rate of ultra-thin thermal oxide and oxide charges are influenced by an incorporation of Al and/or Fe into SiO2. Al and Fe in SiO2 enhanced the oxide growth rate at an early stage of thermal oxidation, while they reduced it around 10 percent in several hundreds minutes at 1123 K. In thermally oxidized Al- or Fe-contaminated p-type Si, observed ac surface photovoltages (SPVs) showed that the positive fixed oxide charge (Qf) was compensated by the induction of a negative charge which was already proposed by the conceptual model positing that (AlOSi)- and (FeOSi)- networks are formed in SiO2. During thermal oxidation, the Al and Fe existing in the native oxide were left behind at the very top of the SiO2 causing a metal-induced negative charge. In the course of thermal oxidation of Al- contaminated Si wafers, the net oxide charge has diminished in n-type Si, while it has increased in p-type Si. This is possibly because the Al suboxides, for example, in the thinnest oxides changed into Al2O3 in thicker oxide, resulting in losing the negative charge. The Al-induced negative charge in SiO2 might enhance oxide growth at an early stage of oxidation by compensating the positive Qf. Furthermore, in oxidized n-type Si, a new idea is proposed that most part of positive Qf originating in Si dangling bond may be effectively neutralized by abundant electrons in n-type Si.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.