Photo-resist ashing by atmospheric pressure glow discharge

Homogeneous glow plasma at atmospheric pressure without streamers and arcing was generated by making use of a radio-frequency (RF, 13.56 MHz) power supply. Oxygen gas was added to Ar/He gas as reactive agents for photo-resist (PR) ashing. The input power, flow rate, oxygen concentration, treatment time, substrate temperature are controlled for high ashing rate and uniform ashing. Thickness of PR film was measured by NANOSPEC (AFT200) and α-Step (P-10). An unstable discharge occurs destroying the uniformity, when the input power exceeds a threshold value determined from the distance between the substrate and plasma source. An increase of oxygen quantity or temperature increase makes high ashing rate, but the ashing surface is rugged. The PR ashing rate was related to oxygen atom in plasma. The number of treatment may not be important in PR ashing at the atmospheric pressure.