Fluorescence Microscopy Methodology for Visualizing Microscale Interfacial Defects In Packaging Materials

Polydimethylsiloxane (PDMS) is widely used in the packaging industry in conjunction with passivated silicon dioxide, SiO
2
, to protect semiconducting devices. However, defects on the SiO
2
film have been shown to affect adhesion between the PDMS and the SiO
2
film. In this study, x-ray reflectivity and x-ray diffraction are used to confirm metrology fidelity. In addition, confocal fluorescence microscopy is used to visualize defects quickly and non-invasively. We show that imaging surface defects as small as 1 μm is possible on SiO
2
films. Single molecule fluorescent tracking is conducted to examine the diffusion coefficient of PDMS. The diffusion of the polymer chain into the substrate microcavities can be used determine possibilities of improving adhesion between the two interfaces. Adhesion is estimated by area measurements of residue after peeling PDMS from the SiO
2
surface as well as changes to surface roughness. To validate our methodology, various sized defects on substrates such as filter paper and microporous aluminum foil are visualized.