Performance Improvement by Double-Layer a-IGZO TFTs with a Top Barrier
Journal
IEEE Journal of the Electron Devices Society
Date Issued
2021
Author(s)
Abstract
The double-layer a-IGZO thin film transistors (DL-TFTs) using a quantum well channel and a top barrier can reduce the subthreshold swing and hysteresis by 0.73x and 0.13x, respectively, in the transfer characteristics using the bottom gate sweep as compared to the single-layer TFTs (SL-TFTs). The wide bandgap barrier on top of the narrow bandgap IGZO channel serves as a protection layer between the IGZO channel and the SiO2 top gate insulator to prevent plasma-induced damage on the IGZO channel caused by the S/D metal etching and the top gate insulator deposition. As for the mobility using the bottom gate operation with the top gate grounded, the DL-TFTs show higher mobility (1.06x) at the room temperature due to less Coulomb scattering caused by the plasma-induced damage for percolation conduction, while the SL-TFTs have higher mobility at low temperatures due to the improved hopping efficiency for thermally activated hopping. The hysteresis is temperature independent down to 160 K, indicating the electrons tunneling between the channel and the top gate insulator is dominant. As for the reliability, DL-TFT has a smaller Vth shift than SL-TFT under both positive bias temperature stress (PBTS) due to less subgap defect in the channel. Author
Subjects
Amorphous InGaZnO (a-IGZO)
band alignment
double layers
Etching
Hysteresis
In-Ga-Zn-O
Insulators
Logic gates
Metals
mobility enhancement
Plasma temperature
quantum well
Thin film transistors
thin-film transistor (TFT).
Amorphous films
Energy gap
Gallium compounds
Semiconducting indium compounds
Semiconductor quantum wells
Silica
Solvents
Thin film circuits
Thin films
Wide band gap semiconductors
Zinc compounds
Amorphous InGaZnO
Band alignments
C. thin film transistor (TFT)
Double layers
In-ga-zn-O
Insulator
Mobility enhancement
Quantum-wells
Thin-film transistor .
Type
journal article