Inspection and Defect Detection Using Digital Holography for Advanced Packaging

Abstract

Advanced packaging processes such as hybrid bonding require defect-free surfaces with nanometre-level cleanliness. Conventional bright-field and dark-field inspection struggle on patterned substrates: bright-field contrast is dominated by the nominal pattern, while dark-field is overwhelmed by diffracted orders from periodic structures. We apply digital holography to this problem, using differential-phase processing to suppress the nominal substrate geometry and isolate defect-induced optical path differences with sub-diffraction-limit sensitivity. We present detection results, demonstrating that weak (transparent or sub-resolution) defects invisible in intensity imaging are revealed in the phase channel.