Fast PEALD ZnO Thin-Film Transistor Circuits

We report stable high-mobility ZnO thin-film transistors (TFTs) and fast circuits fabricated using a novel weak reactant plasma-enhanced atomic layer deposition (PEALD) process. This PEALD process is a highly scalable manufacturable process and is a faster and simpler alternative to conventional atomic layer deposition. Using PEALD, we have deposited highly crystalline (002) textured ZnO thin films at a low temperature (200°C). Using PEALD ZnO films, we have fabricated high-mobility TFTs (20-30 cm
²
/V ·s), which have < 100-mV threshold voltage shifts after bias stress at 80°C for 20 000 s. Using these high-performance TFTs, we have also fabricated simple 15-stage ring oscillator circuits with a propagation delay of 22 ns/stage for a supply voltage of 16 V, which, to the best of our knowledge, are the fastest ZnO TFT circuits reported to date.