A Self-Aligned, Trilayer, A-Si:H Thin Film Transistor Prepared from Two Photomasks

A new self-aligned TFT structure that requires two photomasks is described in this paper. Three process steps, i.e., the backlight lithography, the top dielectric etch, and the n+ etch, have been studied in detail. The finished TFT has transfer characteristics and Jd – Vd curves similar to those of a TFT prepared from a more complicated conventional process. TFT structure parameters, such as the channel length, the a-Si thickness, the source/drain via size, and the contact resistance, affect the field effect mobility and the Ion /Ioff ratio. These relations were examined. Including a Ta2O5 thin layer in the gate dielectric structure changes the device characteristics. The relation between the Ta2O5 process and the device has been studied. © 1991, The Electrochemical Society, Inc. All rights reserved.