Degradations of Threshold Voltage, Mobility, and Drain Current and the Dependence on Transistor Geometry For Stressing at 77 K and 300 K

Based on test results and a procedure that can isolate threshold voltage degradation and mobility degradation from drain current degradation, we found that the log-log curves of mobility degradation show saturation with a change of slope from about 0.4 to smaller values at room temperature. Although both the mobility and threshold voltage degradations are more severe at 77 K than at 300 K for the same stress time, the temperature effect on the mobility degradation is larger than that on the threshold voltage degradation. In addition, the degradations of transistors with three different widths are compared after the stress tests at room and cryogenic temperatures, leading to the observation of degradation dependence on the transistor width. It is observed that the width dependence is more evident at 300 K, and the temperature plays a more significant role on the degradation for larger width transistors.