15.2: Invited Paper: Atomic Layer Deposited Oxide Semiconductor Enabling High Mobility and Low Driving Voltage in TFTs

Abstract

The amorphous indium‐gallium‐zinc oxide (a‐IGZO) thin‐film transistors (TFTs) have become the standard backplane technology for large‐area active‐matrix organic light‐emitting diode (AMOLED) TV. The high‐end mobile OLED demands the high mobility of ∼100 cm2/Vs. So far, the various approaches to improve the mobility of electron carriers in IGZO TFTs have been researched, including the optimization of cation composition, stacked channel structure, and the lattice ordering‐induced crystallization. In this paper, we presented our recent efforts toward the high‐performance and good reliability for IGZO TFTs, which is based on the atomic layer deposition process. First, the merits of the ALD‐derived IGZO compared to sputtered IGZO in terms of the electrical performance of IGZO TFT were investigated. Second, the quantum confinement effect in the IGZO heterojunction channel stacks was exploited, leading to 2DEG‐like high mobility. Finally, the IGZO TFTs with the high‐mobility and low‐driving‐voltage was realized through the bilayer IGZO channel and HfO2‐based gate dielectric stack.

Innovations in thin‐film electronics for the new generation of displays

“…As shown, the median field‐effect mobility is approximately 62 cm 2 /Vs, which is close to values reported for low‐end, rapid laser‐annealed LTPS 39 . We note that this high mobility is achieved using a single IGZO layer, deposited via sputtering, which is more suited for mass production than atomic layer deposition methods used to obtain semiconductor heterojunctions 40 . Moreover, high mobility is achieved using a single‐gate electrode, which uses fewer photolithography steps compared to double‐gate TFTs 41 …”

“…39 We note that this high mobility is achieved using a single IGZO layer, deposited via sputtering, which is more suited for mass production than atomic layer deposition methods used to obtain semiconductor heterojunctions. 40 Moreover, high mobility is achieved using a single-gate electrode, which uses fewer photolithography steps compared to double-gate TFTs. 41 A representative device was selected, exhibiting a peak field-effect mobility of 65 cm 2 /Vs, as shown in Figure 11.…”