Experimental results on silicon annealing by a long-pulse, high-power XeCl laser system

The XeCl laser facility Hercules, delivering a maximum energy of 8 J in 160 ns FWHM, has been used to irradiate amorphous silicon (a-Si) films on glass substrate. We designed an optical homogeneizer to reshape the large cross-section of the laser beam(10 x 5) cm(2), in order to reach a fluence up to 0.5 J/cm(2) over a (13 x 1) cm(2) area. The beam resulted spatially homogenous within 10% (referred to peak-to-peak fluctuations). We obtained poly-silicon films with grain size ranging from 0.1 to 2 mu m, depending on the laser energy density. These preliminary results show that the grain size is critically fluence-dependent when the so-called super-lateral-growth regime is approached (approximately at 0.42 J/cm(2) for a 50 nm-thick a-Si film), with a maximum slope of the grain size vs, energy density greater than 0.5 mu m/(mJ/cm(2)).