Comparative study on sample preparation techniques for Cu-Al interfacial analysis

Traditional mechanical sample preparation via grinding and polishing not only can cause surface deformation that obscures the original property of the material, but it also can induce secondary contamination that affects the analysis accuracy. In this paper, a comparative study is carried out on conventional, semi-dry, and dry methods used in the sample preparation for the analysis of the Cu-Al interface in Cu-wired semiconductor packages. We show that "semi-dry" method using Ar ion flat milling and "full-dry" technique using Ga ion milling can avoid processing artifact as ell as secondary contamination and thus render more reliable physical and chemical analysis results.