Location of Oxide Breakdown Events under Off-state TDDB in 28nm N-MOSFETs dedicated to RF applications

A detailed analysis of Off-state gate-oxide breakdown (BD) mode and its location under non-uniform electric field is performed in 28nm FDSOI N-MOSFET devices. We show that hard breakdown (HBD) occurs exclusively from the middle of the channel to the drain overlap extension for Off-state TDDB. HBD is characterized under DC stress with different gate-length L
G
as a function of drain voltage V
DS
and temperature. We check that the leakage current is the better monitor for TDDB dependence precursor to HBD under Off-mode stress by using the proper modeling and discussing the different possible origin of the higher form factor β value under Off mode stressing.