Positive bias stress instability of In-Ga-Zn-O thin-film transistors with Al2O3/TEOS oxide gate dielectrics

The Vth shift (ΔV
_th
) of a-IGZO devices with gate dielectrics of Al
₂
O
₃
and TEOS oxide after at a gate bias of + 20 V for 3600 s are +3.66V and -2.18V, respectively. Moreover, the V
_th
shift of two stacked dielectrics Al
₂
O
₃
/TEOS oxide by using the equivalent capacitance with 100-nm-thick TEOS oxide. Two stacked dielectrics with a 10-nm-thick Al
₂
O
₃
and a 96-nm-thick TEOS oxide, ΔVth decreases to -0.42V after a gate bias of +20 V for 6400 s.