Three dimensional characterization of silicon wafer Vias from combined on-top microscopic and bottom-through laser fringes measurement

摘要

A collimated laser beam is directed towards the wafer bottom such that the impinging light is partially forward deflected along the vias' bottom edges. Concentric laser interference fringes occur on the wafer top from constructive and destructive interference between the forward deflected and directly through propagating laser. A top down optical image from a number of vias' top openings and a top down fringe image from the same vias' concentric fringe sets are processed to three dimensionally characterize the vias.