Yield enhancement effect of low‐energy O2+ ion bombardment in Ga focused ion beam SIMS

Abstract

AbstractThe effect of low‐energy oxygen ion irradiation during Ga focused ion beam (FIB) SIMS analyses has been investigated. The positive secondary ion yield in Ga FIB‐SIMS analysis was increased dramatically due to the bombardment of O2+ ions. The degree of yield enhancement increased with increased oxygen doses until it became constant above 1.5 × 1016 atoms cm−2, indicating saturation of the oxygen concentration at the analysis depth. Secondary ion images of a line‐and‐space pattern of boron in the silicon matrix have been obtained with 3 keV and 0.7 keV O2+ ions. It was revealed that the enhancement effect of irradiation with 0.7 keV O2+ ions is of the same degree as that with the 3 keV O2+ ions. From the perspective of sensitivity, however, a lower energy beam is more effective because the sputtering of the sample surface by the O2+ irradiation is reduced, resulting in a greater volume for analysis by the Ga+ beam. A secondary ion image of 0.6 at.% boron from the 0.5 µm line width with an analysis depth of 6 nm has been obtained readily by irradiation of the 0.7 keV O2+ beam. Copyright © 2001 John Wiley & Sons, Ltd.