Excimer laser-assisted etching of silicon in chlorine: adsorption and desorption

The present paper is devoted to experimental identification of the excimer laser-induced etching mechanism of silicon under “high” chlorine pressures (30–160 Torr). Experimental results on pulsed KrF excimer laser etching of silicon in chlorine atmosphere by a sequence of single and double pulses are presented. The etch rate dependencies on time delay between pulses in the “double” are discussed. Two mechanisms of etching are considered. The first is laser-stimulated thermal desorption of chemisorbed layer, formed between laser pulses. The second one is direct chemical reaction of chlorine molecules with a silicon surface thermally activated by laser heating. On the basis of the analysis of experimental results it is concluded that direct pyrolytic chemical reaction of chlorine with a hot silicon surface heated by excimer laser pulse radiation (pulse duration 17.5 ns) gives a negligible contribution to the total etch rate