Comparative Study of the Low-Frequency-Noise Behaviors in a-IGZO Thin-Film Transistors With and 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 Al₂O₃ and Al₂O₃/SiN_x gate dielectrics. The LFN is proportional to 1/f^gamma, with gamma ~ 1 for both devices, but the normalized noise for the Al₂O₃/SiN_x device is two to three orders of magnitude lower than that for the Al₂O₃ 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 Al₂O₃/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 Al₂O₃ dielectric. Hooge's parameter is extracted to ~6.0 times 10^-3 in Al₂O₃/SiN_x devices.