Comparison of FIB-induced physical and chemical etching

The localized impurity incorporation during 30 keV Ga/sup +/ FIB processing such as physical etching and gas assisted etching with iodine gas has been investigated using the RBS mapping images by a 300 keV Be/sup 2+/ microprobe with a beam spot size of 80 nm. Sputtering process simulation using the TRIDYN code was performed to compare the etching rate and residual Ga atoms with those by experiment. Residual Ga atoms were found to distribute at and nearby the bottom of the etched area due to implantation and redeposition from the Ga FIB. The residual Ga concentration increased with the increase in ion dose up to 4/spl times/10/sup 16/ Ga/sup +//cm/sup 2/ due to the implantation, while above 1/spl times/10/sup 17/ Ga/sup +//cm/sup 2/ the Ga concentration gradually saturated due to the beginning of sputtering.