Photoemission Optogalvanic Spectroscopy: An in situ Plasma-Surface Diagnostic

Abstract

AbstractAn obstacle to better design and control of plasma processes is our limited ability to monitor surface properties in situ. We describe a new plasma diagnostic technique, photoemission optogalvanic spectroscopy, which can be used to monitor surface contamination, etching rates, and end points. The experiment consists of irradiating a surface with a pulsed excimer or dye laser whose photon energy is above the substrate work function. Photoemission of electrons from the surface is detected by monitoring changes in the discharge current (optogalvanic effect). The technique is characterized by measuring signal strengths as a function of laser intensity, laser wavelength, and bias voltage in vacuum and in an Ar plasma. The technique is used to monitor contamination and etching end points in F-containing plasmas.