IC Surface Corrosion Inspection by C-Mode Scanning Acoustic Microscopy

摘要

Cmode scanning acoustical microscopy,CSAM, is widely used in plastic package evaluations and for failure analysis. It permits to detect subsurface delaminations, cracks and pores (air bubbles) for different microelectronics packages. In this study, abnormality was observed in CSAM daily test, the images showed no delaminations but inhomogeneities on the IC surface.Corrosion was found by optical microscope and scanning electron microscope after decapsulation. It can be revealed as the acoustic impedance is different between corrosion and normal area. The presence of inhomogeneities and discontinuities along ultrasonic waves' propagation paths inside the matter causes modifications in the amplitude and polarity of ultrasonic waves. However, CSAM's capability in detecting IC surface corrosion has not been presented. The capability will be illustrated and the inspection mechanism will be discussed in this paper.