Threshold voltage shift of amorphous oxide TFT with various channel length

Abstract

We have fabricated amorphous oxide-based TFTs (thin-film transistors) which have various channel length of 7.5-34 pm and channel width of 40 pm and investigated electric characteristics such as threshold voltage (Vth) shift with various drain voltage (VDS). In case the length is less than 14 pm, Vth decreases with increasing VDS and Vth shift rapidly increases as the channel length becomes shorter. It is explained that short channel effect such as DIBL (Drain Induced Barrier Lowering) broke out until 14 pm in oxide TFTs. We also confirmed that Vth decreases with channel length shortened in oxide TFTs. These phenomena of occurrence of short channel effect for rather long channel in oxide TFTs comparing Si-Based TFTs and Vth variation could be explained with DIBL of back channel and band diagram of oxide TFTs, respectively.