Fast Flexible Plastic Substrate ZnO Circuits

We report thin-film transistors (TFTs) and circuits fabricated on flexible plastic substrates using ZnO thin films deposited by plasma-enhanced atomic layer deposition at 200°C. Crossover test structures fabricated on flexible substrates have a good yield, and ZnO TFTs have a field-effect mobility of 20 cm
²
/V · s. The 15-stage ring oscillators are operated at > 2 MHz with a supply voltage of V
_DD
= 18 V, corresponding to a propagation delay of < 20 ns/stage. To the best of our knowledge, these are the fastest oxide-semiconductor circuits on flexible substrates reported to date.