EFFECT OF ALUMINUM ON OXIDE GROWTH AND OXIDE CHARGES IN SILICON WAFERS

摘要

Effect of aluminum (Al) on oxide growth rates and oxide charges in n-type (001) silicon (Si) wafers were studied by using ac surface photovoltage (SPV) and X-ray photoelectron spectroscopy (XPS). For wafers intentionally contaminated with Al, the Al enhanced the oxide growth rate in comparison with cleaned wafers until the thickness was slightly less than 25nm at the oxidation of 850℃ in a dry oxygen (O) ambient, whereas Al suppressed the rate by about 10% when thickness grew to about 60nm. If trivalent Al~(3+) ions are replaced by quadrivalent Si~(4+) ions, (AlOSi)~- networks are formed, thus generating Al-induced negative charge in the native oxide. This negative charge is retained in thermal oxide films, but decreases with increasing oxidation time. XPS analysis clarified that Al sub-oxide in SiO_2 decreased as oxidation proceeded, and coincided with a decrease in negative charge. Based on our results for oxidized Al-contaminated wafers, (AlOSi)~- networks that cause a negative charge are related to the Al sub-oxide in SiO_2.