Advances in Trace Metal Contaminant Analysis by Laser-SNMS

The detection and control of metallic contaminants on silicon surfaces is essential for development of silicon circuit technologies. The current methods for detection and quantification of surface and near surface impurities include total reflection x-ray fluorescence (TXRF), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and vapor phase decomposition (VPD) coupled with different types of mass spectroscopy. Each of these techniques comes with its unique analytical limitations for characterizing surface metal contaminants. These techniques all have a nominal detection sensitivity of 5x109 atoms/cm2. This research project, laser-secondary neutral mass spectrometry (laser-SNMS), focuses specifically on the development of an analytical technique for trace metal contaminants on Si. Surface metal impurities are desorbed/ablated with a pulsed UV laser, the desorbed neutrals are then intercepted and post-ionized by a second laser and mas analysis of these ions is performed with a time-of-flight mass spectromete