Al-doped In-Sn-Zn-O thin-film transistor with enhanced electrical properties via application of trench structure

Abstract

This work is for enhancing the properties of oxide thin-film-transistor by application of newly introduced ‘Trench structure’, and for finding out the principles of the ‘Trench TFT’. As displays are developing toward high-resolution, requirements for TFTs with high mobility and also small size have been largely growing. However, they are hardly compatible because decrease in size usually results in deterioration of electrical properties. This issue is not a problem anymore for the Trench TFT. For 15μm channel length, the Trench TFT showed mobility of 189.73cm$^2$/Vs, which is about 5 times higher than that of an usual ITZO-active TFT, and about 60 times higher on-current than the conventional planar structured TFT which had the same footprint. Furthermore, even for 5μm’s short channel, it had 68.79cm$^2$/Vs mobility and about 20 times higher on-current than the conventional one. That is, the Trench TFT can meet the demands for keeping high mobility even when the size decreases. In this paper, the principles of this ‘on-current boosting’ effect of the Trench TFT were researched on by proving a theory: the horizontal part of the Trench TFT acted as a current path, while the vertical part acted as the effective channel. Through quantitative analyzes and splitting fabrication conditions for Trench TFTs, the theory has been verified one by one.Keywords Trench structure, Trench TFT, On-current boosting, High mobility, Oxide thin-film-transistor, Current path