INSITU FOURIER-TRANSFORM IR EMISSION-SPECTROSCOPY OF DIAMOND CHEMICAL-VAPOR-DEPOSITION

Characterization of diamond film during chemical vapor deposition provides new understanding of the deposition process. The mid-IR spectral region contains detailed information on molecular vibrations and hence the chemical structures present in the polycrystalline film. Using Fourier transform IR spectroscopy to study the radiation emitted by externally heated diamond films, we detect both the two-phonon transitions around 2200 cm-1 and the presence of sp3 C-H vibrations near 2800 cm-1. Measurements are conducted with samples of different qualities and the signals from both the two-phonon transition and the C-H emission are correlated with the diamond thermal conductivity. These two signals are then measured in situ during deposition in a d.c. plasma jet reactor. Their evolution is monitored as a function of film growth and process parameters, again correlating with film quality. The technique is then evaluated as an on-line quality-monitoring tool.