Comparative Study of the Low-Frequency-Noise Behaviors in a-IGZO Thin-Film Transistors With $\hbox{Al}_{2}\hbox{O}_{3}$ and $\hbox{Al}_{2}\hbox{O}_{3}/\hbox{SiN}_{x}$ Gate Dielectrics

A comparative study is made of the low-frequency noise (LFN) in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Al
₂
O
₃
and Al
₂
O
₃
/SiN
_x
gate dielectrics. The LFN is proportional to 1/f
^gamma
, with gamma ~ 1 for both devices, but the normalized noise for the Al
₂
O
₃
/SiN
_x
device is two to three orders of magnitude lower than that for the Al
₂
O
₃
device. The mobility fluctuation is the dominant LFN mechanism in both devices, but the noise from the source/drain contacts becomes comparable to the intrinsic channel noise as the gate overdrive voltage increases in Al
₂
O
₃
/SiN
_x
devices. The SiN
_x
interfacial layer is considered to be very effective in reducing LFN by suppressing the remote phonon scattering from the Al
₂
O
₃
dielectric. Hooge's parameter is extracted to ~6.0 times 10
^-3
in Al
₂
O
₃
/SiN
_x
devices.