Advances in FIB-SEM Analysis of TSV and Solder Bumps—Approaching Higher Precision, Throughput, and Comprehensiveness

Abstract

Cross sections of large Through Silicon Vias (TSV) and solder bumps are often prepared using the Focused Ion Beam (FIB). The high current Xe plasma ion source allows fast and precise target preparation of TSV with small diameter. Solder bumps can be accessed due to the high milling rate too. However, the high current milling by plasma FIB causes the worsening of the milled surface quality. An optimized FIB scanning strategy accompanied with the novel rocking stage for the sample tilting during the milling has been developed for the plasma FIB. Whole milling process is observed by the Scanning Electron Microscopy (SEM). Time to prepare a cross section is accelerated and the excellent quality is suitable for subsequent failure analysis. Also important is proper sample cleaving before FIB milling. Using an accurate method to cleave the sample prior to FIB preparation further reduces the overall sample preparation time. The high quality cross sections prepared using this new method are ready not only for SEM but also for EDX and EBSD analysis, either 2D or 3D, when combined with FIB slicing. Broadening the analysis to these techniques increases the obtainable information, allowing the arrangement of materials and their crystalline structure to be studied in a detail.