Asymmetric Low Metal Contamination Ni-Induced Lateral Crystallization Polycrystalline-Silicon Thin-Film Transistors With Low OFF-State Currents for Back-End of Line (BEOL) Compatible Devices Applications

In this work, polycrystalline-silicon thin-film transistors (poly-Si TFTs) with asymmetric low metal contamination Ni-induced lateral crystallization (LC-NILC) poly-Si channel and high- $\kappa $ HfO2 gate insulator (GI) have been successfully fabricated and demonstrated for the first time. The amounts of Ni diffused into the poly-Si film can be effectively reduced by Ni removal processes prior to NILC. The asymmetric LC-NILC poly-Si TFTs exhibit higher field-effect mobility ( $\mu _{\mathrm{ FE}}$ ), steeper ideal subthreshold swing (S.S.), larger ON/OFF currents ratio ( $\text{I}_{\mathrm{ ON}}/\text{I}_{\mathrm{ OFF}}$ ), better uniformity, and improved C-V curves compared to traditional NILC (T-NILC) poly-Si TFTs owing to better crystallization quality and less low metal contamination. These remarkable device characteristics and the matched complementary TFTs (C-TFTs) electrical characteristics with low $\text{I}_{\mathrm{ OFF}}$ and low operation voltages make the asymmetric LC-NILC poly-Si TFTs promising for the future back-end of line (BEOL) compatible devices applications in monolithic three-dimension integrated circuits (3D-ICs).