Combine fluorescence with infrared microscopy to learn the chemical makeup of particles. By Thomas J. Tague, Jr., CooperSurgical, Shelton, CT The semiconductor industry has been waiting for an inspection technique that will let users see particle contaminants on integrated wafers and help determine the contaminants' chemical make-up. Fluorescence illumination makes viewing and identifying contaminants easier and more accurate. Fluorescent compounds absorb light and immediately emit it at longer wavelengths than those absorbed.
Primary fluorescence occurs in minerals and many chemicals due to the structure of the compounds.
When your sample doesn't exhibit primary fluorescence, you can use a fluorescent dye, or fluorochrome, that binds to samples. The attached fluorochrome reveals the presence of the sample by secondary fluorescence, which has made fluorescence microscopy a common analytical tool. Fortunately for analysis purposes, most contaminants of interest to semiconductor manufacturers exhibit natural fluorescence. By combining darkfield fluorescence illumination with IR spectroscopy, inspectors can quickly locate contaminants and identify their composition. That information helps locate and eliminate the source of contamination on a production line.