Characteristics of He/O2 atmospheric pressure glow discharge and its dry etching properties of organic materials

In this study, the characteristics of atmospheric low temperature plasmas generated by capillary electrodes with capillary dielectrics were investigated for the application of microelectronic cleaning processes. The characteristics of the plasmas were studied as a function of capillary aspect ratios, input power, electrode distance, He/O2 gas flow rate, etc., using a high voltage probe, current probe, and optical emission spectroscopy (OES). The voltage between the electrodes increased with the increase of input power, the increase of electrode distance, the decrease of He flow rate, and the increase of O2 flow rate. The increase of the voltage has led to unstable filamentary discharge from the stable capillary discharge. The use of electrodes with capillary dielectrics instead of a conventional dielectric barrier electrode (the electrode covered with non-capillary dielectric) not only decreased the electrode voltage, therefore, increased the stability of the plasma but also increased the discharge current and, therefore, the intensity of the plasma. Increased ionization and dissociation of the plasma species could be observed by OES with the increase of input power in He/O2 mixtures. However, with the increase of O2 flow rate in a constant He flow rate, the emission peaks from He decreased due to the increased electron consumption by oxygen while the emission peaks from O2+ and O increased due to the increased ionization and dissociation rates with the increase of oxygen concentration in the He/O2 gas mixtures. Also, using a He/O2 gas mixture, organic materials such as photoresist could be successfully removed with the average etch rates higher than 200 nm/min.