Applying RF current harmonics for end-point detection during etching multi-layered substrates and cleaning discharge chambers with NF₃ discharge

The present paper reports the results of studying the characteristics of the etching process of multi-layered materials (Si₃N₄/SiO₂/Si and SiO₂/Si) and of cleaning technological chambers covered with silicon nitride films (Si₃N₄) in a NF₃ RF capacitive discharge. The process of chamber cleaning was monitored with a mass spectrometer. The gas pressure, RF voltage amplitude, current-voltage phase shift, ohmic current as well as the second harmonic of the RF current were also recorded. The opportunity of using these parameters for end-point detection of etching and plasma cleaning is discussed. It is found that the second harmonic of the RF current may be successfully used for end-point detection of multi-layered materials etching and to monitor the cleaning process of technological chambers. The cleaning of chambers of complicated design may possess a double-stage pattern.