Quartz resonator techniques for simultaneous measurement of areal mass density, lateral stress, and temperature in thin films

Abstract

A technique has been developed which allows real time monitoring of mass change, lateral stress change and temperature during processes to thin films. The technique uses AT-, BT- and SC-cut quartz resonators to separate the three effects. The AT-cut and BT-cut resonators have a stress vs frequency coefficient which is approximately equal in magnitude but opposite in sign. The choice of a stress compensated (SC cut) resonator for the third resonator and the development of an algorithm to solve the system of equations representing the temperature characteristics of the three resonators are presented. Calculations are done in real time by a personal computer which also controls the data acquisition process. The results presented show, in addition to the mass change and lateral stress build-up which occur when sputtering a gold film with an argon ion beam, the radiation-induced temperature rise and the radiation-induced stress caused by temperature gradients.