FIB process for selective and clean etching copper in high aspect ratio holes

A new solution for etching copper over low-k dielectrics using FIB for circuit edit purposes is presented and compared to the existing two copper etch solutions. For the comparison, a copper line buried under several microns of dielectric and embedded in a low-k dielectric was exposed through a high aspect ratio hole and then cut using each solution and the results were compared in three categories: the over-etch into low-k at optimal cut conditions, sensitivity of the over-etch to the change of the cut conditions to more aggressive and the clarity of the endpointing of the cut.