The influence of discharge current on the intrinsic stress in Mo films deposited using cylindrical and planar magnetron sputtering sources

Abstract

Previous work has shown that the transition pressure, pt, below which large compressive stresses are found in magnetron sputtered metal films deposited at low T/Tm, increases with the discharge current, at least for the case of cylindrical-post magnetrons with magnetic field configurations generated by magnets mounted within the cathode barrels. This paper reports measurements of the internal stress as a function of discharge current for Mo films deposited using a planar magnetron and also a cylindrical-post magnetron having an externally generated magnetic field which permitted the discharge voltage to be varied independent of the current. At each current, coatings were deposited over a sufficient pressure range to identify pt. Transition pressures, determined by stress, resistivity, and optical reflectance measurements, for both the planar and cylindrical magnetrons, exhibited an increase with discharge current, consistent with the previous work. Reducing the cylindrical magnetron magnetic field to increase the discharge voltage at a fixed current consistently yielded higher pt. Strong correlations were seen between pt and the discharge voltage for both the cylindrical and planar magnetrons. It is concluded that the increase in pt with discharge current is significantly influenced by the accompanying increase in discharge voltage and not associated with the concurrent increase in deposition rate per se.