Thermal Stability Concern of Metal-Insulator-Semiconductor Contact: A Case Study of Ti/TiO₂/n-Si Contact

Abstract

This work discusses the thermal stability of metal-insulator-semiconductor (MIS) contacts. A case study is performed on a typical low-Schottky barrier height (qφb) MIS contact: Ti/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /n-Si. By incorporating different levels of donor concentration in n-Si, we perform a systematic Ti/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /n-Si thermal stability study under different electron conduction mechanisms. We find that both qφ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> and contact resistivity (ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of the Ti/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /n-Si MIS contacts vary dramatically after mere 300°C-500°C 1-min rapid thermal treatments. The variations in qφ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> and ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> are related to the thermally driven TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> decomposition. This thermal stability study of Ti/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /n-Si reveals a general concern for the MIS contact application: since the MIS contacts on n-type semiconductor generally utilize a reactive lowwork function metal and an ultrathin insulator, it is difficult to maintain their interface quality considering the thermal budget in standard manufacturing of integrated circuits. Possible solutions to this MIS thermal stability issue are discussed.