Interpretation of capacitance-voltage characteristics of polycrystalline silicon thin-film transistors

Measurements of the gate-to-channel capacitance in thin-film transistors are potentially useful for rapid evaluation of insulator and interface quality. In this paper, we develop a transmission line model of the gate-to-channel capacitance. We then compare the model with measurements made on unpassivated polycrystalline silicon thin-film transistors. An excellent fit to the measurements is obtained. Finally, we discuss the influence of semiconductor traps and insulator charge on the measured capacitance.