Interface state-induced shift of the oxide and semiconductor core levels for metal-oxide-semiconductor devices

Measurements of x-ray photoelectron spectra are performed for ∼3-nm-thick Pt/∼3.6-nm-thick silicon oxide/n-Si(100) devices under biases between the Pt layer and the Si substrate. It is observed that the oxide Si 2p peak as well as the substrate peaks is shifted upon applying biases. These shifts are caused by a bias-induced change of the potential drop across the oxide layer due to the change in the amount of the interface state charge. The amount of the shift of the oxide Si 2p peak is well correlated to that of the substrate Si 2p_3/2 peak. The energy distribution of the interface states is obtained by analyzing the amount of the shift of the substrate Si 2p_3/2 peak measured as a function of the bias voltage. The interface state spectrum has one peak near the midgap, and the peak is attributed to isolated Si dangling bond states.