A Two-Mask Process for Fabrication of Bottom-Gate IGZO-Based TFTs

Abstract

A simple process is presented with which a bottom-gate-type oxide thin-film transistor (TFT) can be fabricated by using two photomasks. The active channel, the source-drain electrode, and the pixel electrode layers were simultaneously formed via a single photolithography using a gray-tone mask (GTM). In particular, the gray-tone profiles of the photoresist were carefully observed to ensure process feasibility with the GTM. From the transparent-oxide TFTs fabricated in this letter, functional indices, such as threshold voltage V-T = 4.13 V (at V-DS = 10 V), subthreshold swing S = 0.59 V/dec, field-effect mobility mu(FE) = 12.41 cm(2)/V.s, ON-OFF current ratio lesser than 8 x 10(6), and transmittance higher than 85%, were obtained.