Effects of Nitrogen Addition to Microwave Oxygen Plasma in Surface Wave with Disk-Plate Window and Photoresist Ashing

Abstract

The effects of nitrogen addition to an oxygen plasma in the surface-wave mode with a disk-plate window at a 2.45 GHz microwave in the TM01 mode, and photoresist ashing are investigated in the pressure range from 65.5 Pa to 399 Pa at a microwave power of 1.3 kW. No change in electron density was observed in the experimental range of the amount of nitrogen added (0–50%). On the other hand, atomic oxygen density determined by actinometry reaches the maximum intensity at a nitrogen ratio of 20% and the intensity at 20% is twice as large as that at 0%. Although oxygen plasma generation is different from previous work, similar tendencies of nitrogen addition effects are observed, where the electron density in the surface-wave mode exceed the cutoff density of the microwave. An ashing rate at 20% is twice as large as that at 0%. The Activation energies of the ashing reaction at 0 and 20% accompanied by an aluminum shower head are approximately 0.5 eV, which is equal to the value ashed by atomic oxygen. The nitrogen addition effect on ashing using an oxygen surface-wave mode plasma are clarified.