Spectroscopy Diagnostics Of CF₂Number Density In CHF₃/Ar Dielectric Barrier Discharge Plasma

In this work, the density of CF2in CHF3/Ar dielectric barrier discharge (DBD) plasma was measured by using the optical emission and absorption spectroscopy, respectively. The dependences of the CF2density on the discharge power, gas pressure, electrode distance, and the concentration of CHF3have been investigated with the above two techniques. Furthermore, by comparing the results of the actinometry and the absorption spectroscopy, the applicability and accuracy of using the actinometry for measurring the CF2density in this plasma were discussed. Basically we have the following conclusions:In the range of260-380Pa, CF2number density increases with the increasing of gas pressure at various concentration of CHF3; Within the discharge power which is5-18W, CF2number density increases with the increasing of power; When the CHF3concentration varies from10%to75%, CF2density increases with the increasing of CHF3concentration.When the electrode distance varies in the range of4-8mm, the absolute density of CF2, which was measured by using the broadband absorption spectroscopy (BBAS), decreases with the increasing of the electrode distance. In contrast, it increases with the increasing of electrode distance by the actinometry.By comparing the measurement results of BBAS and actinometry, we found that the ratio of CF2densities measured by two methods was almost linear with the same electrode distance. Therefore, it can be deduced that the electron energy distribution function (EEDF) has probably changed little, and the actinometry method is suitable under these conditions. While the variation of CF2densities ratio with the increase of electrode distance is not exactly linear, which is mainly due to the change of the EEDF. It also suggests that the actinometry could not be used to measure the CF2density with the change of electrode distance.