Atmospheric-pressure air plasma jet and its application to photoresist material etching

Summary form only given. We describe the application of an atmospheric-pressure air plasma jet (APAPJ) source to polymer etching. The electrical and optical emission spectrum (OES) characteristics of APAPJ have been studied and analyzed. From OES measurements, it can be found that the emission intensities of metastable and ionized molecular nitrogen N2* and N²⁺ is stronger and the emission intensity of N2* is dominant. With the increase of power voltage, the emission intensity of excited species is increased. Based on this APAPJ source, etching of photoresist (PR) 193 nm material has been examined by using real-time ellipsometry. Etch rates increase with source voltage u and as the distance between sample and needle tip s is decreased. The influence of distance s and voltage u on etch rates is very significant. For distances of 5 mm, 8 mm and 10 mm (Singleelectrode system), the etch rates are 61.29, 20.55 and 5.47 nm/min respectively. When the voltages are increased from 7 kV to 8 kV, the etch rates are increased from 2.84 nm/min to 20.55 nm/min respectively. The etch rates are decreased when the gas flow rates are increased from 5 lpm to 15 lpm, but not significantly. In this paper, single-electrode and two-electrode systems are both adopted to etch PR material. Results show that the single-electrode system can get larger etching rates. Etched samples have been observed by microscope, the significant circular spots can be observed, which is likely to be due to the charging of samples in APAPJ discharge. The density and diameter of spots by two-electrode system is smaller than that by single-electrode system. For two-electrode system, the spots diameters will be decreased with the increase of the distance s.