Cathodic Disbonding in Microelectronics Observed by In Situ Scanning Acoustic Microscopy

Abstract Acoustic microscopy has been used to follow the in situ degradation of the interface of a 2 μm polyimide coating on Al-metallized SiO2, which comprise a model microelectronic device. The polyimide coating contained artificial defects (pinholes). The acoustic microscope distinguishes regions of interfacial degradation at the earliest stages when optical microscopy remains insensitive. Hence, degradation could be followed as a function of time and applied voltage while the sample was immersed in deionized water. Anodic degradation did not initiate at the pinhole but initiates at sites in the coating, whereas cathodic polarization caused rapid loss of adhesion initiating at the pinhole and propagating away from the pinhole.