Front- and Back-Interface Trap Densities and Subthreshold Swings of Fully Depleted Mode Metal-Oxide-Semiconductor Transistors Fabricated on Separation-by-Implanted-Oxygen Substrates

By measuring the charge pumping current ( I CP ) and the subthreshold swing, we examined the front- and back-interface trap densities ( D fit and D bit ) of long channel N-type metal-oxide-semiconductor transistors fabricated on separation-by-implanted-oxygen (SIMOX) substrates, as a function of the total oxygen implantation dose. The front-channel subthreshold swing ( S f ) measured in the coupled condition was larger than that calculated with D fit and D bit obtained from I CP . However, dose dependences of the D fit and D bit obtained from I CP were consistent with those of the front- and back-channel peak mobilities, while those obtained from the subthreshold swings were not. These seemingly contradictory results can be satisfactorily explained by the existence of lateral nonuniformities (LNU) in the front- and the back-channel local threshold voltages. We propose that the experimentally determined S f can be used as an index of LNU in the SIMOX and other silicon-on-insulator substrates, just by comparing it with the theoretical value of S f .