Exploring New Channel Materials for Nanoscale CMOS
The improved transport properties of new channel materials, such as Ge and III-V semiconductors, along with new device designs, such as dual gate, tri gate or FinFETs, are expected to enhance the performance of nanoscale CMOS devices. Novel process techniques, such as ALD, high-k dielectrics, and metal gates are now being used to experimentally explore such devices. New materials in the channel promise reduced series resistance and higher on-currents. The theoretical assessment of such devices is a challenge because bandstructure, arbitrary wafer orientation, quantum effects and electrostatics must all be treated. In the first part of this work, a general theoretical approach for the quantum mechanical simulation of n-MOSFETs within the Non Equilibrium Green’s Function (NEGF) formalism is introduced, and its application is demonstrated by performing a scaling study for the end of the ITRS Ge device. In the second part of this work, a systematic analysis of the bandstructure effects in deeply scaled n- and p- MOSFETs with Si, Ge, GaAs and InAs channel is performed. Here, a 20 orbital sp3d5s*-SO tight-binding model and a top-of-thebarrier quasi-2D ballistic transport model have revealed important trends in deeply scaled new channel material devices.
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