DROPLET FORMATION DURING LASER SPUTTERING OF SILICON

High purity single-crystal silicon was ablated with nitrogen laser rad iation wavelength 337 nm, pulse length 6 ns, maximal energy density 1. 1 J/cm(2), nonuniform. target energy distribution. Many droplets were observed around the damaged target area, which seem to be ejected out of it and splashed vigorously onto the surrounding target surface. The ir diameters are found to be in the range of a micrometer. The droplet s were most probably produced within a single laser pulse as a result of hydrodynamical instability of the molten surface layer. Intense spl ashing occurs as a consequence of the large plume pressure generated b y the most intense parts of the laser beam. The irregular power distri bution on the target seems to enhance droplet formation significantly, since their abundance is drastically lower or even missing in similar experimental conditions but with uniform power distribution. (C) 1998 Elsevier Science B.V. All rights reserved.