Active Matrix OTFT Display With Anodized Gate Dielectric

A complete process for an active-matrix (AM) organic thin-film transistor (OTFT) polymer dispersed liquid crystal (PDLC) display is presented. Evaporated pentacene is used as semiconductor. The display comprises 64 times 64 pixel, each with a pixel pitch of (312.5 times 312.5) mum². The AM display is fabricated with standard photolithographic processes. Since all process temperatures are below 180degC the processes for the AM backplane can be easily transferred to plastic substrates like PEN or PET. Due to the thin anodically oxidized Al₂O₃ gate dielectric with a thickness of 60 nm and epsiv_r = 9, driving voltages between 10 and 12 V are sufficient. To protect the pentacene against the PDLC, it is encapsulated with sputtered Ta₂O₅ layer. After the passivation a field effect mobility of 0.2 cm²/V ldr s is obtained for the OTFTs.