“Gated diode” characterization of hot carrier induced interface state and oxide charge lateral profiles in SOI MOSFET´s

The quality and the degradation (induced by hot carriers, irradiation, etc.) of the Si-SiO₂ interfaces remains an important issue in the development of SOI CMOS technologies, and continues to be difficult to measure and characterize. We previously described (Zhao and Ioannou, 1999) a “gated-diode” (Speckbacher et al, 1995; Okhonin et al, 1996) based approach to measure the interface state densities of both front and back interfaces in n- and p-channel SOI MOSFETs. To measure a particular interface, the forward drain-to-body diode current is measured while scanning the corresponding gate voltage from accumulation, through depletion, to inversion. Complicated, but information-rich current curves result that contain a narrow peak, from which the interface state density can be obtained. The purpose of this paper is to incorporate opposite channel based charge injection (Ioannou et al, 1998) in the experiment, and present a more complete and more thorough extended analysis, not limited to a narrow segment around the peak, but covering the whole voltage range of the current curves. From this, a method is developed and used to obtain not only the “averaged-out” density of interface states, but also their lateral profile as well as the lateral profile of the oxide charge along the channel length