Chemical Identification of sub 10-µm defects and contamination in packaging

Contamination and defects in microelectronic packages can have deleterious effects to device reliability and usability. With increasingly smaller feature sizes, pitch and sophisticated advanced packaging and components, such as interposers, FOWLP and FOPLP, even miniscule defects and contaminations are increasingly effective in disabling devices. With feature sizes of dark-colored contamination and defects in the order of submicron to 10 micrometers, conventional Fourier-transform infrared (FT-IR) and Raman microscopes would not provide sufficient spatial resolution and sensitivity for meaningful root-cause analyses in the past few decades. In recent years, a new pump-probe excitation-detection chemical analysis concept offering sub-micron spatial resolution in Optical PhotoThermal InfraRed microscopic instrumentation (O-PTIR) has been developed to address the needs for high spatial resolution and ultra-high sensitivity analyses in a non- contact reflection-based operation manner. To further speed up analysis of chemically complex specimen, co-located auto- fluorescence imaging of specimen can be further exploited to qualitatively assess its spatio-chemical distribution before conducting sub-micron infrared analysis on the same sample stage of the instrument. Best of all, auto-fluorescence poses no ill-effects to the quality of O-PTIR spectra. In this contribution, we will detail the enabling concept and relevant case studies, covering examples including underfill cross-sections and contamination on metal pads.