Measurement of High Voltage Stress Induced Traps Inside Thin Silicon Oxide Films

Abstract

ABSTRACTAfter thin silicon oxide films were stressed at high voltages, two changes occurred in the current-voltage and transient current characteristics of the films. The low-level, pre-tunneling current rose and the transient decay of the current after removal of a voltage pulse changed from an exponential RC time constant decay to a very long decay that was characterized by a 1/t time dependence. Using an extension of the tunneling front discharge model, previously developed to describe the transient changes in the threshold voltages of transistors after avalanche injection or irradiation, the 1/t time dependence was derived. This 1/t transient discharge current was used to determine the density and distribution of the traps inside of the oxide after the high voltage stress. The technique and model used for determining the trap densities and distributions from the transient currents will be described. The model was used to describe the charging of traps in the oxide.