Sputtering-Deposited Hafnium Oxide Dielectric for High-Performance InGaZnO Thin Film Transistors

We fabricate InGaZnO thin film transistors (IGZO TFTs) on glass substrates, where sputtering-deposited hafnium oxide (HfO
₂
) films are utilized as the gate dielectric. The influences of Ar/O
₂
flux ratio (75/25, 80/20, 85/15, and 90/10) of the HfO
₂
films on properties of the IGZO TFTs are investigated. The 85/15 IGZO TFTs show the best performance among all the devices, which manifests as a field-effect mobility of 4.79 cm
²
V
^-1
s
^-1
, a saturation mobility of 6.81 cm
²
V
^-1
s
^-1
, an on-to-off current ratio over 10
⁶
, and a sub-threshold swing of 156.15 mV/decade. By exploring material components, we found that the 85/15 HfO
₂
film has the least oxygen defects, thus resulting in more ideal stoichiometry and device performance. This work confirms the huge potential of sputtering-deposited HfO
₂
films to be the high-κ dielectric of the IGZO TFTs.