High Performance Dual Gate Blue Laser Annealed Poly-Si Thin-Film Transistor for High-Resolution Displays

• Published in: IEEE transactions on electron devices Vol. 68; no. 8; pp. 3863 - 3869
• Main Authors: Jeong, Duk Young, Billah, Mohammad Masum, Siddik, Abu Bakar, Han, Byungju, Chang, Yeoungjin, Jang, Jin
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Annealing; Blue laser annealing (BLA); CAD; Carrier density; Computer aided design; coplanar thin-film transistor (TFT); Crystallization; Electrodes; Grain boundaries; Iron; Logic gates; low temperature polysilicon (LTPS); Performance evaluation; Photomicrographs; Polysilicon; Semiconductor devices; Shift registers; technology computer-aided design (TCAD); Thin film transistors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2021.3091965

We report a dual gate (DG), low-temperature polysilicon (LTPS) thin-film transistor (TFT) using blue laser annealing (BLA) of amorphous silicon. The DG TFTs with variable bottom gate lengths (L BG ) from 2 to 8 <inline-formula> <tex-math notation="LaTeX">\mu \text {m} </tex-math></inline-formula> and a fixed top gate length (L TG ) of 6 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> are investigated. The drain currents of the DG LTPS TFT with L BG > L TG by 2 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> under DG sweep (DS) are ~4.3 times those of the single gate TFT. The high carrier concentrations (~10 19 cm −3 ) at both interfaces (top gate insulator (GI)/poly-Si and poly-Si/bottom GI) under DS is confirmed by technology computer-aided design (TCAD) simulation, which might lead to high drain currents. The poly-Si layer exhibits no grain boundary protrusion from the transmission electron microscopy (TEM) cross-sectional micrograph and thus induces a strong bulk accumulation effect under DS. The fabricated DG TFT-based ring oscillator (RO) and shift register (SR) exhibit an excellent oscillation frequency of 15.8 MHz, fast-rising and falling time of 370 and 366 ns at a driving voltage of −10 V, respectively.