Focused Ion Beam Assisted Etching of Aluminum.

Focused ion beam (FIB) milling is widely used for circuit repair, mask repair, and SEM sample prepair for cross-section observation. In the circuit repair application, it is important to achive a higher material selectivity of Al/SiO2, and a higher milling rate. In order to realize both of these, focused ion beam assisted etching (FIBAE), where a chlorine containing gas is injected towards the milling site, was performed. Using Cl2 gas only caused a significant side etch, though the etching rate of aluminum was quite high. When etching Al-Cu-Si alloy with a chlorine containing gas, a residue of Cu-Cl compound was formed. This can be decreased by heating the sample as high as 200°C. An etching selectivity (Al/SiO2) of 100 was achived, without side-etching, by a gas mixture of SiCl4 (95%) and Cl2 (5%).