Optical emission investigation of the plasma enhanced chemical vapor deposition of silicon oxide films

During plasma enhanced chemical vapor deposition of silicon oxide films, plasma diagnostics is important for process control and reproducibility of film quality. In this study the film growth rate has been investigated with special emphasis on plasma properties to seek a better understanding of the deposition process. Light emissions from the plasma were monitored using an optical multichannel analyzer for various deposition conditions. The electron temperature and density were determined from the spectral data. With increasing silane concentration, the number density of the electrons, the concentrations of active species and the deposition rate increased. The growth rate also increased with nitrous oxide concentration. However, the emission intensities did not show a concomitant increase because of the radiation quenching effect. Analysis of the results emphasizes the crucial importance of electron density to generate sufficient concentration of active species responsible for determining the film growth rate. Among the peaks monitored, the intensity of a hydrogen peak correlated well with the deposition rate. The hydrogen peak intensity can be used for reliable, on-line, non-contact, instantaneous monitoring of the film growth rate.