Low frequency MOS-CV technique for selfconsistent determination of dark currents in high resistivity substrates

Abstract

We report a novel self-consistent low frequency MOS-CV characterization method for MOS structures on high resistivity substrates, which are typically used for integrated optical and ionizing radiation sensor applications. High frequency (HF) MOS-CV measurements cannot be applied to MOS samples with a large serial resistance due to the low quality factor of the measured small signal impedance. The low frequency (LF) MOS-CV-technique reported here is based on the measurement of the gate current and the change of the gate charge in response to a step-ramp gate voltage signal. In depletion operation mode the applied gate voltage signal drives the MOS structure in a non-steady non-equilibrium what enables a short measurement time. For extraction of the generation current the doping need not be known. The method proposed does not rely on the assumption of a homogeneously doped silicon substrate. It enables a rapid self-consistent determination of the generation current depth characteristic using commercially available measurement equipment.