A method for shortening effective channel length in oxide TFT by partial formation of conductive region

In this paper, a method for shortening effective channel lengths in etch-stop type In-Ga-Sn-O (IGTO) thin-film transistors that works by inducing the partial formation of a conductive region in the IGTO is proposed. We found that the resistance of an IGTO film with a SiNX/SiOX passivation layer could be reduced significantly by thermal annealing due to hydrogen diffusion from the SiNX passivation layer into the IGTO film through the SiOX layer. In this process, a conductive region is formed selectively in the channel by suppressing hydrogen diffusion in a self-aligned manner using source/drain (S/D) electrodes between the IGTO and the SiNX passivation layer as a physical barrier. Using this method, we demonstrate that the drain current can be increased by shortening the effective channel length and that the effective channel length can be controlled by varying the length of the region where the S/D electrodes and the IGTO overlap. (C) 2019 The Japan Society of Applied Physics