FTIR (Fourier Transform Infrared) is the most important technology for measuring epitaxial film (Epi) thickness, measuring impurities in Silicon and monitoring dielectrcis, like Borophosphosilicate glass (BPSG), FSG, PSG, etc in semiconductor industry. FTIR is evolving from a primarily quality control (wafer supply chain) technology to a tool/process/chamber (test wafers) monitoring technology and more importantly, a device (product wafers) monitoring tool.