Microanalysis of Impurity Contamination in Masklessly Etched Area Using Focused Ion Beam

Localized contamination during 30keV Ga + focused ion beam (FIB) processing with and without iodine gas has been investigated using micro-Rutherford backscattering spectrometry (RBS) and RBS mapping images by a microprobe with 300 keV Be 2+ with a beam spot size of 80 nm. Etching rates with and without iodine gas were compared with those by simulation. Residual Ga atoms of an order of 10 16 ions/cm 2 were found to be distributed at and nearby the bottom of the etched area due to implantation and redeposition from the Ga FIB. It was also confirmed that the gas assisted etching technique was more effective to reduce the contamination of etched areas.