Whereabouts of missing atoms in a laser-injected Si: Part 1

In a stealth dicing of Si wafers, voids are formed in laser-induced modified volumes (LIMVs). Most of the voids are free from apparent defects such as dislocations and cracks. Needless to say, in what will become a void (pre-void) upon laser injection, Si atoms are present prior to the laser injection. The critical issue is where these missing atoms are after the laser injection. Two obvious possibilities are that (1) they remain inside the Si wafer as interstitials (I’s) or (2) these I’s reach the surface of the wafer to disappear. If (1) is the case, I’s are to coagulate to form dislocation loops of I-type upon post laser-injection annealing. However, it has been shown that this is not the case. In order to see whether (2) is the case, surfaces of a laser-injected Si wafer were studied by a scanning electron microscope in detail. No evidence of I’s having reached the surfaces was obtained.