MEASUREMENTS OF THE CATHODE SHEATH IN A MAGNETRON SPUTTERING DISCHARGE USING LASER-INDUCED FLUORESCENCE

Magnetron discharges are widely used as sputtering sources for thin fi lm deposition. Despite the importance of the sheath region where the e lectric field can be very high, there have been few experimental inves tigations of this region in magnetron plasmas. We report values of the sheath thickness deduced from measurements of the electric field dist ribution using laser spectroscopy. With this technique, a transition w hich is normally forbidden becomes in the presence of an electric fiel d partially allowed so that laser induced fluorescence on this transit ion can be used as a measure of the electric field. It was found that the sheath thickness was approximately equal to the maximum displaceme nt, in the absence of collisions, of a secondary electron from the cat hode surface.