Selective wet-etch processing of optically transparent flexible InGaZnO thin-film transistors

Abstract

Flexible InGaZnO (IGZO) thin-film transistors (TFTs) having more than 85% optical transparency in the visible regime were fabricated on polyethylene naphthalate substrates using a selective wet etching process at a maximum temperature of 150 °C. An etch selectivity of >15 was used to pattern Al-doped ZnO S/D contacts on IGZO channel layers in a back-channel etch process. Flexible IGZO TFTs exhibited a field-effect mobility of ∼9.5 cm2/V s, threshold voltage of ∼4 V, subthreshold swing of 0.5 V/decade, and an Ion/Ioff ratio of ∼107. Similar I-V characteristics were measured for flexible TFTs under flat, tensile and compressive strain while a 3.8 V threshold voltage shift was observed after application of a dc gate-bias for 3600 s with the TFTs operating in the linear regime.