Spray Pyrolyzed Amorphous InGaZnO for High Performance, Self-Aligned Coplanar Thin-Film Transistor Backplanes

High-performance, spray-pyrolyzed amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistor (TFT) with self-aligned (SA) coplanar structure is demonstrated. The spray-pyrolyzed a-IGZO film exhibits bubbles-free smooth surface roughness (0.81 nm) and low oxygen-related defects (22.5%). The fluorine-doped a-IGZO film shows a low resistivity of 1.18 x 10(-3) ohm-cm by NF3 plasma treatment. This is sufficient to obtain ohmic contact with the source/drain electrodes and doped IGZO in the offset region of the SA coplanar TFT. The spray-pyrolyzed a-IGZO TFT exhibits the field-effect mobility (mu(FE)) of 18.17 cm(2) V-1 s(-1), the threshold voltage (V-TH) of -1.52 V, the subthreshold swing (SS) of 0.266 V dec(-1), and a high on/off current ratio (I-on/I-off) over 10(8) with a very low gate leakage current (<10(-13) A). The hysteresis-free and highly stable performances are achieved due to the excellent a-IGZO channel and SiO2 gate insulator interface. A twenty-three-stage ring oscillator is demonstrated with SA coplanar TFTs, exhibiting a high oscillation frequency of 2.66 MHz and a low propagation delay of 8.17 ns/stage. Therefore, the spray-pyrolyzed a-IGZO film can be a promising metal oxide semiconductor for high-performance TFTs backplane in large areas and high-resolution display applications.