Experimental Study of Impact Ionization Phenomena in Sub- 0.1 µm Si Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs)

Abstract

Impact ionization phenomenon in sub-0.1 µm Si metal-oxide-semiconductor field effect transistors (MOSFETs) has been examined in detail. N-MOSFETs with gate oxide of 4, 6 and 8 nm thickness were fabricated using pocket implantation technology. The test devices have n+ polysilicon gate electrodes and shallow extension formed by arsenic implantation at the acceleration voltage of 15 keV. Sub-band-gap impact ionization can be observed for the 0.08 µm N-MOSFET. It is clearly observed that thin gate oxide suppresses impact ionization. Simulation results reveal that the lateral electric field near the drain is decreased by thinner gate oxide of 4 nm thickness. In addition, the dependence of the impact ionization rate on the gate oxide thickness decreases with decreasing gate length.