Atomic layer doping of silicon

One of the major requirements for the boosting of Si MOSFET performances in ultra large scale integration is the aggressive scaling of the source and drain extension junctions in silicon-based devices. As the nano-electronic industry is aiming at sub-10 nm junction depths, the achievement of low sheet resistance becomes even more challenging. The degradation of the junction quality when an amorphization process is used to minimize dopant channeling poses serious difficulties to the beamline ion implantation technique. Furthermore, in the case of 3D devices such as multi-gate FETs, the constraint of doping conformality raises additional issues that cannot be solved by the latter method, which suffers from shadowing effects for patterns with high density of devices. Consequently, there is currently a strong need for novel doping strategies in both planar and non-planar device technologies.
On the one hand, potential alternatives such as atomic layer epitaxy and plasma immersion ion implantation have already shown promising results. On the other hand, sub-melt millisecond laser anneal is considered as the method of choice for dopant activation while classical rapid thermal treatments result in excessive dopant diffusion and limited electrical activation. In this talk, a study on the physical properties of ultra shallow junctions obtained by the combination of atomic layer doping and laser anneal will be presented and the challenges related to the fabrication and the metrology of high quality, low-resistance, defect-free junctions with sharp dopant profiles will be discussed.