Band-Edge High-Performance High-k/Metal Gate n-MOSFETs Using Cap Layers Containing Group IIA and IIIB Elements with Gate-First Processing for 45 nm and Beyond

Abstract

We have fabricated electrically reliable band-edge (BE) high-k/metal nMOSFETs stable to 1000degC, that exhibit the highest mobility (203 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs @ 1MV/cm) at the thinnest T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inv</sub> (1.4 nm) reported to date. These stacks are formed by capping HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with ultra-thin layers containing strongly electropositive gp. IIA and IIIB elements (e.g. Mg and La), prior to deposition of the TiN/Poly-Si electrode stack, in a conventional gate-first flow. Increasing the cap thickness tunes the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> /V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fb</sub> from a midgap position to BE while maintaining high mobility and good PBTI. The addition of La can enhance the effective k value of the dielectric stack, resulting in EOTs < 1nm. Short channel devices with band edge characteristics are demonstrated down to 60 nm. Finally, possible mechanisms to explain the nFET V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> shift are discussed