A practical, low-cost research system for the fluorescent optical imaging of BCB (DVS-bisBCB) thin films has been used for the first time to evaluate coating quality on spin coated silicon wafers. In general, DVS-bisBCB thin films are easily produced defect free with a high degree of planarization. Various features of the coating are enhanced visually by the fluorescence making detection, digital storage, and quantification easier. Examples of features found in defective coatings made intentionally by a process to generate several common thin film defects are variations in film thickness, foreign particles, pinholes, and residual polymer in vias. The fluorescent bands of the normally transparent resin are easily excited in the near UV with a mercury lamp, causing a semi-opaque visible emission which could be observed by conventional imaging hardware. The BCB fluorescent quantum yield, or efficiency, is similar to fluorescent dyes so that only a small amount of BCB need be present in a substrate to allow optical inspection.
This strong fluorescent property of DVS-bisBCB polymer, not possessed by many polyimide resins, could reduce labor costs of manual inspections and improve multichip module (MCM) processing yields. This digital imaging technique has potential for further development as a cost-effective automated optical inspection (AOI) method.