Conventional Technological Boosters for Injection Velocity in Ultrathin-Body MOSFETs

Abstract

To meet ITRS requirements, highly scaled MOSFETs will have to operate close to the quasi-ballistic regime and to exhibit enhanced injection velocity. Good performances may be achieved thanks to high transport materials such as germanium or III-V semiconductors. However their integration is still very challenging. Following a different approach, this paper proposes to examine how to improve the injection in conventional (100) silicon ultrathin-body (UTB) MOSFETs. A systematic investigation of the impact of the different usual technological parameters highlights that SG and DG exhibit comparable performances and that no improvement in the injection velocity is expected with the silicon thickness thinning down to 4 nm. Moreover the degradation of the injection velocity with the integration of high- dielectrics is shown. Finally, a significant improvement of the injection velocity due to a higher confinement in asymmetrical double gate MOSFET has been found. Similarly, it is shown that, single gate UTB MOSFETs with thin buried oxide (BOX) exhibit an enhanced injection velocity. In conclusion, only the reduction of the BOX thickness and the integration of strained channel have been found to be realistic and significant boosters of the injection velocity in silicon (100) MOSFETs. Prediction of the evolution of the injection velocity along the roadmap, using a pragmatic strategy of scaling, confirms that these two parameters will play a significant role in improving highly scaled (100) silicon devices performances.