Future of nano CMOS technology

Although Si MOS devices have dominated the integrated circuit applications over the four decades, it has been anticipated that the development of CMOS would reach its limits after the next decade because of the difficulties in the technologies for further downscaling and also because of some fundamental limits of MOSFETs. However, there have been no promising candidates yet, which can replace Si MOSFETs with better performance with low cost. Thus, for the moment, it seems that we have to stick to the Si MOSFET devices until their end. The downsizing is limited by the increase of off-leakage current between source and drain. In order to suppress the off-leakage current, multi-gate structures (FinFET, Tri-gate, and Si-nanowire MOSFETs) are replacing conventional planar MOSFETs, and continuous innovation of high-k/metal gate technologies has enabled EOT scaling down to 0.9 nm in production. However, it was found that the multi-gate structures have a future big problem of significant conduction reduction with decrease in fin width. Also it is not easy to further decrease EOT because of the mobility and reliability degradation. Furthermore, the development of EUV (Extremely Ultra-Violet) lithography, which is supposed to be essential for sub-10 nm lithography, delays significantly because of insufficient illumination intensity for production. Thus, it is now expected that the reduction rate of the gate length, which has a strong influence on the off-leakage current, will become slower in near future.