Effect of ion energy on photoresist etching in an inductively coupled, traveling wave driven, large area plasma source

We report on the effect of ion energy on photoresist etching in an inductiv ely coupled large area plasma source driven by a 13.56 MHz traveling wave w ith oxygen gas. To control the ion energy at the substrate surface, the ele ctrode on which the substrate is placed is independently driven by a capaci tively coupled 1 MHz power source. The etch rate increases with increasing ion energy for gas pressure ranging from 1 to 100 mTorr. Ion-induced desorp tion rate constants (etch yields) are shown to be proportional to the squar e root of the ion energy. An increase in the ion energy leads to etch-unifo rmity improvement over the processing area of 40 cmx50 cm, particularly at a low gas pressure of 5 mTorr. A modified photoresist etch kinetics model c ombined with a spatially-varying oxygen discharge model is used to explain these experimental results. (C) 2001 American Institute of Physics.