Mechanism of Date Retention Improvement by High Temperature Annealing of Al(2)O(3) Blocking Layer in Flash Memory Device

Abstract

The mechanism underlying improved data retention via high-temperature oxygen annealing of the Al2O3 blocking layer in a charge-trap type flash memory device is investigated in comparison with the case of high-temperature nitrogen annealing. The results show that significant improvement of the retention property can be achieved by oxygen annealing at 1100 degrees C, compared to nitrogen annealing. Experimental evidence indicated that the underlying mechanism does not arise from suppression of the trap-assisted tunneling current through the blocking oxide; instead it is caused by a reduction of the thermionic emission component of the charge loss factor. This is possibly due to changes of the conduction band offset of the crystallized Al2O3. (C) 2011 The Japan Society of Applied Physics