Recovery of time-dependent dielectric breakdown lifetime of thin oxide films by thermal annealing

Electrical properties of thin silicon dioxide films have been investigated for samples that suffered from the Fowler-Nordheim (F-N) stress and subsequent annealing. The time-dependent dielectric breakdown (TDDB) lifetime for samples after annealing > 400 degrees C was found to be longer than that without anneal; about 60% of the amount of damage responsible for the lifetime was annealed out at a temperature of typically 800 degrees C for 30 min. On the other hand, capacitance-voltage (C-V) measurements indicated that trapped charges were almost annealed out even at a temperature of 300 degrees C for 30 min. Moreover, the reinjection of F-N current showed that the trapping sites of holes and electrons which are electrically neutral remained after the annealing of trapped charges at temperatures > 300 degrees C. It follows that the recovery of TDDB lifetime presently observed through annealing at temperatures >400 degrees C was caused by the anneal of neutral trapping sites created by F-N stresses. (C) 1997 American Institute of Physics.