Thickness and temperature dependence of stress relaxation in nanoscale aluminum films

We have found that stress relaxation of nanoscale Al thin films is strongly dependent on both film thickness and temperature. Films 33, 107, and 205 nm thick prepared by evaporation onto a silicon nitride membrane substrate were studied using membrane resonance. A single thermal cycle to 300 degreesC was used to establish a stress, after which the time dependence of the stress was measured for the three film thicknesses at 50, 75, and 100 degreesC. The relaxation rate is highest for the highest temperature and the thinnest film. A dislocation locking mechanism is suggested as a possible explanation for the observed thickness dependence. (C) 2003 American Institute of Physics.