High frequency C-V investigation of metal-oxide-semiconductor capacitors prepared by low temperature subatmospheric pressure chemical vapour deposition of SiO 2 films on silicon substrates

Abstract

SiO 2 films were prepared by three different methods of low temperature chemical vapour deposition (CVD): plasma-enhanced CVD (PECVD) (tetraethylorthosilicate (TEOS)-O 2 chemistry), low pressure CVD (SiH 4O 2 chemistry) and medium pressure CVD (TEOS-O 3 chemistry). The variation in electrical characteristics of Al-CVD SiO 2Si metal-oxide-semiconductor (MOS) capacitors (determined from high frequency capacitance-voltage C-V curves) with respect to wafer cleaning procedure, deposition method and subsequent thermal annealing at temperatures less than or equal to 500 °C was investigated. The modification of the electrical propeties of CVD SiO 2 films with processing parameters was interpreted in terms of physiochemical changes involved in the different processes of MOS capacitor fabrication: (i) the variation in bulk CVD SiO 2 properties (relative dielectric constant and resistivity) was interpreted in terms of the evolution of water content in the films vs. the preparation conditions; (ii) the behaviour of a parameter which characterizes the SiSiO 2 interface (positive fixed charge) was interpreted in terms of changes which occur at this interface as a result of native oxide growth and as a result of ion implantation at low energy during argon plasma etching of silicon wafers, or by ion implantation of oxygen, carbon and hydrogen atoms during the initial stage of the PECVD process.