INFLUENCE OF STRESS IN THIN-FILM MODULUS MEASUREMENTS BY THE VIBRATING REED TECHNIQUE

One method to measure thin film elastic properties is use of the vibra ting reed technique to compare stiffness of uncoated and coated cantil ever beams. Since the change of frequency is used to calculate the mod ulus, the change of frequency caused by curvature due to film stress h as to be investigated. We present simultaneous measurement of resonant frequencies and curvature to show that curvature can cause large effe cts, depending on the geometry. An approximate calculation indicates i n which cases stress may be neglected. A method to determine stress fr om combination of torsional and flexural vibrating frequency measureme nts is proposed. (C) 1998 Elsevier Science S.A. All rights reserved.