Segregation and activation of Ga in high Ge content SiGe by UV melt laser anneal

The feasibility of dopant activation surpassing the equilibrium solid solubility limit by using an out of equilibrium melt laser annealing (MLA) process was investigated. To that end, we used an UV excimer nanosecond laser annealing and studied the segregation and activation of dopants in a Ga-implanted SiGe 50% epilayer. Dopant segregation is of great interest for future nodes to further improve contact resistivity in transistors. However, there is a lack of in-depth study about their activation. In this paper, we first reported very high Ga activation well above the equilibrium solid solubility limit when the partial Si0.5Ge0.5:Ga melt regime was assessed. The dopant segregation phenomenon, together with the surface morphology change of the Si0.5Ge0.5:Ga epilayer, was then induced by MLA. A very clear honeycomblike surface pattern was observed in the full Si0.5Ge0.5:Ga melt regime, while it was less pronounced in the partial melt regime. This honeycomblike pattern would be the result of dopant precipitation at the liquid–solid interface during solidification. Our simulation results highlighted that solidification velocity could play a key role in the substitutional incorporation of Ga atoms in a SiGe lattice.