Effect of sputtering on depositing platinum by focused ion beam

The focused ion beam (FIB) is a tempting maskless technique for modifying and debugging microcircuits. In this paper, the process of FIB induced platinum deposition was examined, employing atomic force microscopy working in the tapping mode. The geometry of FIB patterned Pt depends on the interaction between ion beam and materials, including metal organic gas, substrate and deposited Pt. According to the competition between depositions and sputtering, the Pt can be formed well only when selecting a certain range of ion flux. Ga⁺ ion interaction with SiO₂ substrate leads to sputtering, and the SiO₂ substrate surface that neighbors the deposited Pt is concave compared with the unsoiled substrate when the ion dose is larger than 200 PC/μm². Under different ion current, the patterned Pt central maximum height deviation at a certain ion dose can be explained by different ion sputtering rate for SiO₂ and Pt. The effects of patterned Pt width extension and its saturation were investigated; due to the back scattering Ga⁺ ions shoot around and cause Pt redeposition. These results will help us to fabricate nanoscale structures using FIB under more accurate control.