Stress-induced current in nitride and oxidized nitride thin films

We have studied the stress-induced current in nitride and oxidized nitride DRAM films using MOS capacitors and p-channel MOSFET transistors. When the gate current is measured as a function of electric field in MOS capacitors, gate current on oxidized nitride film is considerably lower than in nitride film. After subjecting both films to a constant current stress, however, measured gate current in oxidized nitride film becomes much greater than in nitride film. Using PMOSFET transistor, it is observed that holes dominate the current conduction both for nitride and oxidized nitride films. When the films are subjected to a constant current stress, both the hole and electron currents increased compared to those before stress. After the constant current stress. The electron current is increased more in the nitride film, while in oxidized nitride film, hole current increase is dominant. Hence it can be said that the current increase in nitride films is due to the stress-generated trap of electrons, while in oxidized nitride film, it is due to stress-generated hole traps in the top oxide.>