Characterization of the progressive growth of columns by excimer laser irradiation of silicon

The growth mechanism of columns produced by excimer laser irradiation of a silicon target is investigated. The micrometric columns are formed by a cumulative process with well-defined steps. The first steps lead to silicon hillocks, which evolve to columns through a little-understood mechanism. To investigate it, we irradiated a Si(100) single crystal in air with the necessary pulses of an excimer laser beam to obtain two samples, one with a partially and one with a fully developed column structure. Then we alternated scanning electron microscopy observations with irradiation pulses on the same target area. The progressive evolution of the laser-generated structures is presented. Columns grow at notably high rates, from around 0.5 mu m/pulse during the early stages to 0.2 mu m/pulse on average for 10-20 mu m tall columns. The experimental results lead us to suggest a hydrodynamic growth mechanism. (C) 1999 American Institute of Physics. [S0003-6951(99)02447-X].