Quantitative Estimation of Aluminum-Induced Negative Charge Region Top Area of SiO2 Based on Frequency-Dependent AC Surface Photovoltage

Abstract

Most aluminum (Al) in Al-contaminated and thermally oxidized n-type silicon (Si) dioxide (SiO2) is clarified to be segregated at the very top area of SiO2, causing a negative charge, as has been suggested by the formation of an (AlOSi)- network and/or AlO2- based on AC surface photovoltage (SPV). For a strongly inverted state at an oxidation temperature of 800 °C for 1 h, the thickness of the Al-induced negative charge region is quantitatively determined to be 2.4 nm on the basis of AC SPV after successive step etching and chemical analysis. As oxidation duration increased at 800 °C for 3 h, the strongly inverted state changed into a weakly inverted state, where the thickness of the Al-rich region is reduced (0.8 nm), proving that more than half of the (AlOSi)- network collapse and/or Al diffuses inside SiO2 during a longer oxidation duration.