Comparison of different techniques for passivation of small-grain polycrystalline-Si MOSFET´s

Different hydrogen passivation techniques have been investigated and correlated with the device characteristics of accumulation mode p-channel MOSFET´s fabricated in small-grain polycrystalline Si (poly-Si). The dependence of characteristics on a) annealing time and temperature, b) different poly-Si deposition conditions, and c) different encapsulation layers has been studied. Using hydrogenation by ion implantation with a subsequent anneal of 10 min at 400°C or an anneal of 25s at 450°C in the presence of a top encapsulating LPCVD Si3N4layer, MOSFET´s with ON/OFF current ratio of 4 × 10⁷have been obtained with drain-to-source voltage of -5 V.