Self-Aligned Staggered Amorphous-Indium-Gallium-Zinc-Oxide Thin-Film Transistors With Ultra-Low Contact Resistance for High-Speed Circuits Application

A self-aligned (SA) staggered structure for amorphous-In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) is proposed. The bottom contact between n+-IGZO and source/drain (S/D) enables larger contact area and shorter current-transmission distance, thus reducing the contact resistance. The non-overlap structure helps to eliminate the overlap-induced parasitic capacitance, thereby improving the device operating speed. The fabricated SA staggered a-IGZO TFTs exhibit good performance, including channel-width-normalized contact resistance (RCW) as low as 1.53 $\Omega \cdot \mathrm{~cm}$ and transit frequency (fT) as high as 1.4 GHz, which are quite competitive in the field of high-speed a-IGZO TFTs.