Thermally Stable InGaSnO Thin-Film Transistors Using Crystalline Oxide Semiconductor

In this work, we developed a high-performance, coplanar crystalline InGaSnO (C-IGTO) thin-film transistor (TFT). An amorphous indium gallium tin oxide (IGTO) film was deposited with reactive sputtering with H2 introduction, followed by an O2 post-deposition crystallization at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$500~^{\circ }$ </tex-math></inline-formula>C, resulting in a highly oriented crystal with smooth surface. The transfer characteristics of the C-IGTO TFT exhibit negligible temperature dependency up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$150~^{\circ }$ </tex-math></inline-formula>C and endure up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400~^{\circ }$ </tex-math></inline-formula>C post-fabrication annealing in air. The gate shift register (GSR) and ring oscillator (RO) circuits made of C-IGTO TFTs exhibit outstanding performance. A 24-stage, GSR operates effectively with the TFTs of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.3~\mu $ </tex-math></inline-formula>m channel length. These circuits maintain excellent operational stability without degradation at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~^{\circ }$ </tex-math></inline-formula>C. In addition, The RO exhibits a low propagation delay of 2.14 ns. To evaluate the applicability for high-density memory devices, we fabricated a capacitorless, two-transistor (2T0C) dynamic random access memory (DRAM) cell. This shows a long retention time over 2000 s with extremely low <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.5\times 10^{-{20}}$ </tex-math></inline-formula> A/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m). The successful demonstrations of DRAM cell and integrated circuits using the C-IGTO TFTs highlight the potential for integration of memory and TFT circuits for next-generation memory and IT applications.