Horizontally Redundant, Split-Gate a-Si:H Thin Film Transistors

A new type of tri-layer amorphous silicon (a-Si:H) thin film transistor (TFT) is presented. This transistor has 1) a split-gate that supplies the redundant-channel structure, and 2) a long channel width that gives a high on current. It also has a self-aligned source/drain-to-gate configuration and uniformly narrow source/drain vias. The finished transistor shows an on/off current ratio greater than 10(sup7) and the on current in proportional to the channel to width-to-length ratio. Compared with a conventional single-channel TFT that occupies the same area, this new TFT has a higher channel width-to-length ratio and a higher on current. The physical limitations of the new TFT, based on the current large area lithography tool, are also discussed. This TFT can be applied to displays and imagers that require a high on current and a low area occupancy.