Effect of excimer laser annealing on the structural properties of silicon germanium films

We investigated the use of a pulsed excimer laser having a wavelength of 248 nm, a pulse duration of 38 ns, and an average fluence between 120 and 780 mJ/cm² to locally tailor the physical properties of Si_1−xGe_x (18% < x < 90%) films deposited by low-pressure chemical vapor deposition at temperatures between 400 and 450 °C. Amorphous as-deposited films showed, after laser annealing, strong {111} texture, a columnar grain microstructure, and an average resistivity of 0.7 mΩ cm. Atomic force microscopy indicated that the first few laser pulses resulted in a noticeable reduction in surface roughness, proportional to the pulse energy. However, a large number of successive pulses dramatically increased the surface roughness. The maximum thermal penetration depth of the laser pulse is demonstrated to depend on the fluence and the film structure being either polycrystalline or amorphous. Finally, a comparison between excimer laser annealing and metal-induced crystallization and rapid thermal annealing is presented.