Formation of Ultra-Shallow Junctions in Silicon- Germanium by Pulsed Laser Annealing

Abstract

This work reports an alternative scheme, in which the melt and junction depth are independent of the laser fluence used by using the fact that the melting point of the SiGe alloy is lower than that of c-Si. This gives us a process window within which the melt depth is controlled by the thickness of the SiGe layer instead of the laser fluence. The sheet resistances of single pulse excimer laser annealed samples, were consistently lower than the flash annealed sample. The Hall mobilities showed the correct conductivity type p-type), indicating that there were unlikely to be any EOR defects in these laser annealed samples. The absence of defects at the SiGe/Si interface was confirmed by HRTEM examinations. The junction depth was estimated to be about 30 nm, which was the thickness of the SiGe layer demonstrating that there is a sufficient process window to allow us to anneal and activate the dopants, while maintaining a good control of the junction depth, producing defect-free, highly activated and ultra-shallow boron junctions achieved by single-pulse laser annealing.