Photoresist etching using Ar/O2 and He/O2 atmospheric pressure plasma

Abstract

This study compared the effects of Ar/O2 and He/O2 plasma on the photoresist (PR) removal of a silicon wafer under a pressure of one atmosphere. In the atmospheric pressure plasma, the Ar-plasma-treated surface had a higher surface energy and was more hydrophilic than the He-plasma-treated surface. The density of the active species in the Ar/O2 plasma was much larger than that in the He/O2 plasma. Therefore, an Ar/O2 plasma discharge is much more efficient in etching a PR than a He/O2 plasma. The PR etch rate was measured as a function of the nozzle to sample distance and the feed flow rate, as well as the radio frequency (RF) power and additive gas(O2) flow rate. In these experiments, a maximum etch rate was about to 190 nm/min at an RF power of 120 W, Ar/O2 flow rates of 8 slm/70 sccm, and a treatment time of 3 min. The surface of the etched PR was characterized using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM showed that the etch reaction of the Ar/O2 plasma occurs via sputter etching and that of the He/O2 plasma occurs via chemical reaction. From the XPS results, it is concluded that the Ar/O2 plasma effectively removes the carbon component from the PR coated surface.