A Subthreshold Analysis of Triple-Material Cylindrical Gate-All-Around (TM-CGAA) MOSFETs

Abstract

With the technological leap to another milestone in sub 20nm regime, the conventional FETs seems to be of little use in continuing scaling with the least short channel effects (SCEs). Hence, non-conventional devices had to intervene in the rescue of the ITRS. Where the devices with the silicon-on-insulator substrates, strain, double gate, finned gate, omega and pi gates upheld the Moore’s law, the Gate-All-Around (GAA) emerged to be the ultimate solution. To further improve the sub threshold electrical parameters, a multi material gate may be inserted as the gate material. Thus, extending the idea of a triple material gate in the cylindrical GAA (CGAA) MOSFET, a TM-CGAA is obtained with better SCE characteristics. In this work, an accurate analytical sub threshold models has been developed for an undoped tri-material cylindrical gate-all-around (TM-CGAA) MOSFET considering parabolic approximation of the channel. The centre (axial) as well as the surface potential model is obtained by solving the 2-D Poisson’s equation in the cylindrical co-ordinates. The work refutes the estimation of the characteristic length using surface potential as in the previous work and proposes the use of centre potential based characteristic length formulation for an accurate analysis.