Pulsed laser melting of implant amorphized Si1-xGex thin films

Abstract

Nanosecond pulsed laser annealing using a frequency doubled Nd:YAG laser (λ = 532 nm) was performed on undoped implant amorphized Si and 40 nm Si1-xGex epitaxial thin films ranging from x = 0.1 to 0.5. Ge+ implants were used to create ~ 15 nm thick surface amorphous layers. The microstructural evolution of the layers was investigated for laser powers that ranged from the sub-melt, partial amorphous layer melt, full amorphous layer melt, to full epi-layer melt regimes. Time resolved reflectometry and transmission electron microscopy was used to couple the impact of melt dynamics with resulting microstructures and to determine processing benchmarks as a function of Ge concentration. It was shown that for the right combination of power and amorphous layer thickness, defect free regrowth is possible. At melt depths ≥ 22 nm for the Si0.7Ge0.3 films, it was found that progressive liquid/solid interface roughening during solidification led to lateral germanium segregation coupled with the formation of dislocation half loops and dislocation loop clusters at the surface. These results are important for the exploration of pulsed laser melting of Si1-xGex for CMOS source/drain contact and channel strain engineering applications.