IN-SITU FILM THICKNESS MEASUREMENT AND GASEOUS SPECIES DETECTION IN DIAMOND CVD PROCESSES USING FTIR EMISSION-SPECTROSCOPY

The development of an in situ diagnostic technique is highly desirable for diamond CVD processes to ensure reproducible results and to assist with process development. We have successfully applied Fourier transform IR (FTIR) emission spectroscopy to monitor film thickness and gaseous species in real time during diamond film growth. The experimental apparatus consists of an ASTeX diamond deposition system with a heating stage, associated optics, and an FTIR spectrometer. Owing to reflection at the surface, the IR radiation from the heated substrate forms two coherent beams on passing through the growing diamond film. The film thickness is obtained by determining the path length difference for the two beams directly from the interferogram. When the heated substrate is used as a radiation source, gas phase absorption by CH4, C2H2, and CO is readily detected.