Hot Carrier Effect in UltraThin Gate Oxide Metal Oxide Semiconductor Field Effect Transistor

Abstract

We have analyzed the degradation introduced by the hot-carrier effect in an ultrathin gate oxide n-channel metal oxide semiconductor field effect transistor (MOSFET). To investigate the hot-carrier effect, stress bias dependence on degradation was measured. From the stress gate bias and stress drain bias dependences, we found that the drain avalanche effect dominated the degradation. The gate length dependence was evaluated with MOSFET of various gate lengths. With decreasing gate length, degradation became remarkable, particularly at less than 100 nm. In a MOSFET with a smaller gate length, we speculated that the damaged region is expanded from the drain region to the source region. By device simulation, we found that a potential hole was observed in the source region that corresponded to a “pocket” profile, and that lines of force terminate there. By emission microscope, we found that hot carriers are generated. This phenomenon supports the results of a stress test and device simulation. We proposed a new model that explains experimental and theoretical results consistently.