ZnO thin film transistors and circuits on glass and polyimide by low-temperature PEALD

We report using a novel, weak oxidant, plasma-enhanced atomic layer deposition (PEALD) process to fabricate stable, high mobility ZnO thin film transistors (TFTs) and fast circuits on glass and polyimide substrates at 200 °C. Weak oxidant PEALD provides a simple, fast deposition process that results in uniform, conformal coatings and enhancement-mode MOSFETs from uncompensated films. Our PEALD ZnO TFTs have field-effect mobility of 20-30 cm²/V·s and simple gate-self-aligned saturated-load ring oscillators on glass with 2.5 ¿m gate length had propagation delay <10 ns/stage at V_DD = 18 V. We also report the fastest oxide semiconductor circuits on polyimide substrates with propagation delay of ~60 ns/stage at V_DD = 18 V.