HfSi _xO _y-HfO ₂ gate insulator for thin film transistors

We propose a new technique to grow HfSi _xO _yHfO ₂ film on Si substrate by using a 500°C process, and demonstrate the feasibility of multi-layered high-k oxide film (i.e., HfSi _xO _y-HfO ₂) as alternative gate insulator for thin film transistors (TFTs). Hf metal films were directly deposited on Si wafers at substrate temperatures of 25 - 400°C by using a non-reactive rf-magnetron sputtering system. Oxidation at 500°C in dry O ₂ ambient and subsequent annealing at the same temperature in N ₂ ambient result in electrically stable multi-layered HfSi _xO _y-HfO ₂ gate insulator for TFTs. We also investigate the effects of the substrate temperature on the physical and electrical properties of HfSi _xO _y-HfO ₂ films, and show that substrate temperature must be set at 25°C for the sputtering of Hf metal films to obtain optimum electrical characteristics (e.g., high dielectric constant, no hysteresis phenomenon, and low leakage current).