Interfacial negative charges in PECVD-SiO2/Si films: Correlating Si 2p XPS with electrical properties to construct a physically consistent model

Abstract

The correlation between electrical properties and atomic features was investigated in tetraethyl orthosilicate (TEOS)-based plasma-enhanced chemical vapor deposition SiO2 films on Si(001) using capacitance–voltage analysis and x-ray photoelectron spectroscopy within a data-driven physics framework. The study aimed to clarify the microscopic origins of the electrical property variations. The Si 2p binding energy in the XPS spectra exhibits thickness-dependent behavior distinct from that of thermally grown SiO2 and shows a clear correlation with both the interface trap density (Dit) and the effective positive charge (Qeff). Electrostatic analysis of the Si 2p energy shifts suggests negative charge accumulation near the interface in the thickness range of 4 to over 8 nm, with a positively charged layer formed on top. The amount of this negative charge can reach 1−2×1012cm−2, comparable to the positive Qeff of the order of 2×1012cm−2. These results demonstrate the presence of charge polarity switching in TEOS-based PECVD-SiO2, which can be interpreted as arising from a double-layer structure consisting of a plasma-oxidation-dominant layer and a CVD-dominant layer, with the negative charges attributed to excess oxygen introduced during plasma oxidation. The thickness of the plasma-oxidized layer appears to be governed by the CVD growth rate, whereas the variations in Dit are linked to plasma oxidation conditions, such as the flux of oxygen species arriving at the interface.