A Simulation Study Of Schottky Barrier Source/Drain Si MOSFET

A simulation study of metal-oxide-semiconductor field-effect transistor with Silicon-based Schottky Barrier contacts for source and drain (SBSD-MOSFET) is presented in this paper. Instead of using pn junction, the source and drain regions are completely replaced by metal-semiconductor contacts. The device size can be greatly shrunk with effectively suppressing short channel effect and parasitic bipolar effect in conventional MOSFET. Also it has fabrication advantages avoiding the steps of ion implantation and annealing at high temperature.Firstly, the transport mechanism of SBSD-MOSFET is analyzed. The transistor can be regarded as two back-to-back Schottky barrier diodes. The characteristics at the metal/Si interface are similar to that of Schottky barrier diode. Thermionic emission and quantum tunneling are the main current conduction mechanism.Secondly, the operational mechanism of bulk Si SBSD-MOSFET device is simulated and its characteristics are presented in this paper with device simulation program DESSIS. The silulation result shows that there is great leakage current while its gate is in reverse bias in bulk Si SBSD-MOSFET. The leakage current consists of two parts: the thermionic emission from the source and the tunneling current from the drain.Finally, our simulation result shows that conventional SOI SBSD-MOSFET can effectively suppress thermionic emission leakage current, but it still can not suppress tunneling leakage current. Therefor an asymmetric sidewall structure is presented in this paper, in which a thick sidewall at drain side provides low tunneling leakage current, and a thin sidewall at source side insures large drive current. Additionally, the effects of different gate length and doping concentration on the device performance is very small. These advantage hints that asymmetric sidewall structure SOI SBSD-MOSFET can have a high yield in manufacture.