Impact of crystallinity of High-k oxides on Vt instabilities of NMOS devices assessed by physical and electrical measurements

This paper investigates the impact of crystallinity of HfO
₂
oxides on V
_T
instabilities. Wet etch rate measurements enhances a critical thickness t
_HK

^C
for HfO
₂
which marks the transition between a monoclinic crystalline phase to a near amorphous state, both clearly identified by ATR FTIR. Using electrical measurements and modeling, it is demonstrated that this transition from the crystalline phase to an amorphous state is accompanied by a strong reduction of the density of bulk HfO
₂
defects responsible for electron trapping, Prevents the crystallization of an high-k layer is therefore fundamental to improve its BTI reliability.