A Vertical Thin Film Transistor Based on Low Temperature Technology (T<600oC)

Abstract

A new concept of vertical Thin Film Transistor (TFT) family called Thin Film Transistor Comb (TFTC) using only low temperature process (less than 600{degree sign}C) based on polycrystalline silicon (polysilicon) has been fabricated. This structure, compatible with glass substrate, can have up to 5 teeth and allows increasing channel width simultaneously to a better control and reduction of channel length, leading to an increase of the average current and device densities. In contrast to other vertical TFTs, the channel of TFTCs is made of non-intentionally doped silicon between two layers in-situ doped polysilicon, all deposited by low pressure chemical vapor deposition. Analyses of characteristics of main studied pattern, a comb with 3 teeth, show a high on-current, a threshold voltage of 1.6V, a transconductance of 97µS, a very low gate leakage current, but in the first layout a high off-current due to the large area of the drain and source overlapping.