Effect of pre-existing defects on reliability assessment of high-K gate dielectrics

Response of the high-k gate dielectrics to low voltage stresses was studied by probing high-k transistors with various voltage/time measurements at different temperatures. The observed dependence of the transistor threshold voltage on stress time was attributed to electron trapping at pre-existing defects in the high-k dielectric rather than stress-induced trap generation. The dominance of the contribution from the reversible electron trapping on the pre-existing defects in the low voltage stress response raises the question on the applicability of the conventional reliability assessment methodology to the high-k dielectrics.