LASER-INDUCED NICKEL SILICIDE FORMATION

Nickel silicide compounds were formed via excimer laser irradiation (193 nm) of a (111) silicon substrate coated with 85 nm thick nickel films. Irradiation was carried out in a laser energy range from 2 J cm-2 to 0.2 J cm-2 at a repetition rate of 2 Hz and scanning speed of 0.2 mm s-1. Two distinct processes of silicide formation were observed. At laser energies in the range 1.28-0.5 J cm-2 the silicides were formed via melting and recrystallization of the nickel coating and part of the silicon substrate. The main phase observed was NiSi2. At laser energies below 0.5 j cm-2 the nickel coating was unaffected and only the inner part was consumed. The main phases observed were Ni5Si2 and Ni3Si2. The microstructure and composition of the silicide formed were analysed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Auger spectroscopy.