Self-aligned ZnO thin-film transistors with 860 MHz fT and 2 GHz fmax for large-area applications

摘要

High-frequency thin film transistors (TFTs) enable many important thin film circuits used in flexible large-area systems such as large bandwidth instrumentation amplifiers (related to f) and high-frequency oscillators (related to f) [1,2]. In [3] f=10GHz and f=2.9GHz were reported but using Si substrates and pulsed laser deposition for ZnO growth, which are incompatible with low-cost large-area processing on a meter scale. More modest reports of f=1GHz with sputtered IGZO on glass have relied on a very sensitive alignment process, impractical for fabrication over large substrates [4]. In this work we present a ZnO-channel TFT process fully compatible with flexible large-area substrates. We achieve an f=2GHz and f=860MHz by reducing source/drain (S/D) to gate overlaps (X) and scaling channel lengths down to 500nm via a self-aligned process.