Highly Scaled BEOL-Compatible Thin Film Transistors With Ultrathin Atomic Layer Deposited Indium-Tin-Zinc-Oxide Channel

In this article, we have demonstrated the utilization of innovative atomic-layer-deposited (ALD) ultrathin (similar to 1.8 nm) amorphous InSnZnO (alpha-ITZO) channel material in the development of a back-end-of-line (BEOL) compatible thin film transistor (TFT). Through the optimization of the indium/tin/zinc (In/Sn/Zn) ratio, the bottom gate (BG) TFT with In0.83Sn0.11Zn0.06O channel and the channel length (L-ch) of 40 nm demonstrates remarkable performances, including positive threshold voltage (Vth) of 0.38 V, excellent subthreshold swing (SS) value of 66.4 mV/dec, high field-effect mobility (mu(FE)) of 48 cm(2)/V-s, maximum ON-state current density (I-ON) of 686 mu A/mu m at V-DS = 2 V (@ V-G = 4 V), and extremely low drain-induced barrier lowering (DIBL) performance of 22 mV/V. Furthermore, the excellent stabilities of the alpha -ITZO TFT were shown by negative bias stress (NBS) and positive bias stress (PBS) under V-G of (V-th +/- 3 V), and V-th shift (Delta V-th) of - 40 and 60 mV (L-ch = 700 nm) after 3600 s was exhibited. We also simulated the current gain cutoff frequency (fT) by technology computer-aided design (TCAD) simulation to further investigate the potential of radio frequency (RF) applications. These results establish a competitive standard for TFTs based on quaternary ultrathin (T-ch < 5 nm) amorphous oxide semiconductors (AOSs).