Th. Wang et al., A comprehensive study of hot carrier stress-induced drain leakage current degradation in thin-oxide n-MOSFET's, IEEE DEVICE, 46(9), 1999, pp. 1877-1882
The mechanisms and characteristics of hot carrier stress-induced drain leak
age current degradation in thin-oxide n-MOSFET's are investigated. Both int
erface trap and oxide charge effects are analyzed. Various drain leakage cu
rrent components at zero V-gs such as drain-to-source subthreshold leakage,
band-to-band tunneling current, and interface trap-induced leakage are tak
en into account, The trap-assisted drain leakage mechanisms include charge
sequential tunneling current, thermionic-field emission current,:and Shockl
ey-Read-Hall generation current. The dependence of drain leakage current on
supply voltage, temperature, and oxide thickness is characterized. Our res
ult shows that the trap-assisted leakage may become a dominant drain leakag
e mechanism as supply voltage is reduced. In addition, a strong oxide thick
ness dependence of drain leakage degradation is observed. In ultra-thin gat
e oxide (30 Angstrom) n-MOSFET's, drain leakage current degradation is attr
ibuted mostly to interface trap creation, while in thicker oxide (53 Angstr
om) devices, the drain leakage current exhibits two-stage degradation, a po
wer law degradation rate in the initial stage due to interface trap generat
ion, followed by an accelerated degradation rate in the second stage caused
by oxide charge creation.