Effects of inversion layer quantization on channel profile engineering for nMOSFETs with 0.1 μm channel lengths

Abstract

This paper presents a systematic theoretical investigation of the effects of inversion layer quantization on the performance of nMOSFET devices fabricated with different shapes of channel doping profiles. The bulk nMOSFET simulation structures of effective channel length near 0.1 μm were generated with gate oxide thickness of 3 nm. Abrupt- and graded-retrograde profiles with low surface and high substrate concentrations, and conventional step profiles with high surface and low substrate concentrations were used for channel doping. A hydrodynamic model for semiconductors was used to simulate various device characteristics with and without the quantum mechanical effects in the inversion layer of the devices. The simulation results indicate that the increase in the threshold voltage due to quantum mechanical effects in the inversion layer of the devices and the resulting degradation in the current drivability, drain-induced barrier lowering, and subthreshold slope depend on the shape of the channel doping profiles. The devices with retrograde channel doping profiles provide a superior control of the device performance and the shift in the device performance due to quantum mechanical effects than the devices with step channel doping profiles. It is shown that for nano-MOSFET devices, the impact of quantum mechanical effects and the variation in the device performance due to dopant fluctuations can be optimized by channel profile engineering. The paper, also, demonstrates the importance of QM effects for predictive device simulation.