Spectroscopic Study of Radiofrequency Oxygen Plasma Stripping of Negative Photoresists. I. Ultraviolet Spectrum

Abstract

The stripping of photoresists from a silicon wafer using an rf oxygen plasma has been monitored using the optical emission from electronically excited OH and CO species in the ultraviolet region of the spectrum. The band systems at 283.0 nm (CO*, OH*), 297.7 nm (CO*), and 308.9 nm (OH*) are intense and spectrally isolated from other systems and arise from plasma-induced oxidation of the polymeric photoresist material. The endpoint of plasma stripping and the amount of stripped material is easily determined quantitatively. In addition, variations in stripping rate of photoresist as a function of wafer position in the reaction chamber can be detected.