Low‐Temperature Polysilicon Oxide Thin‐Film Transistors with Coplanar Structure Using Six Photomask Steps Demonstrating High Inverter Gain of 264 V V−1

The low‐temperature polysilicon oxide (LTPO) complementary metal‐oxide‐semiconductor (CMOS) thin‐film transistors (TFTs) is fabricated by p‐type low‐temperature polysilicon (LTPS) TFT and n‐type amorphous indium‐gallium‐zinc oxide (a‐IGZO) TFT using coplanar structure. A double‐stack SiO 2 layer deposited by high temperature first and then low‐temperature process is used as a gate insulator for LTPS TFT, leading to reduce the number of photomask steps. The p‐channel LTPS TFT of the fabricated LTPO circuits exhibits the field‐effect mobility ( μ FE ) and threshold voltage ( V TH ) of 89.9 cm 2 (V s) −1 and −5.5 V, respectively. However, the a‐IGZO TFT exhibits the μ FE of 22.5 cm 2 (V s) −1 and V TH of −1.3 V. Both the LTPS TFT and a‐IGZO TFT show excellent bias stability (Δ V TH of <0.1 V) and zero hysteresis voltage, which reveals the excellent interface between gate insulator and semiconductor. The LTPO CMOS inverter exhibits a gain of 264.5 V V −1 and a high noise margin of 4.29 V, and a low noise margin of 3.69 V at V DD of 8 V. Therefore, the LTPO TFT technology developed in this work can be a promising candidate for low cost, large‐area manufacturing of display, and TFT electronics.