Band-edge high-performance high-κ /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-κ/Metal nMOSFETs stable to 1000°C, that exhibit the highest mobility (203 cm 2/Vs @ 1MV/cm) at the thinnest Tinv (1.4 nm) reported to date. These stacks are formed by capping HfO2 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 [1, 2], in a conventional gate-first flow. Increasing the cap thickness tunes the Vt/V fb, from a midgap position to BE while maintaining high mobility & good PBTI. The addition of La can enhance the effective κ 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 Vt shift are discussed. © 2006 IEEE.