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

Abstract 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 × 10⁻³ Ω‐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 (µ_FE) of 18.17 cm² 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 10⁸ 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.