TEMPERATURE DEPENDENCE OF STRESSES IN Ti, Cr, AND Cu THIN FILMS.

Abstract

Stresses in thin films of Ti, Cu, and Cr deposited onto fused quartz substrates are measured as a function of temperature and film thickness using a cantilevered bending beam technique. The stresses in as-deposited films are strongly dependent on the film thickness up to 1000 angstrom. Upon heating, the stress in Cu films becomes compressive from tensile and exhibits relaxation above about 150 degree C. Upon cooling, the stress in Cu returns to its tensile character; a 1. 6- mu m film has a higher value of 2 multiplied by 10**9 dynes/cm**2 , for example. The relaxation of thermally induced compressive stress is accompanied by hillock growth (plastic flow). The hillocks were examined by a scanning electron microscope. In the case of Ti or Cr films, as the annealing temperature was increased, the stresses markedly deviated from the thermally induced stress due to an increase in the intrinsic stress. However, stresses in Ti or Cr can be predicted directly by thermal mismatch between the films and substrate during either cooling or heating provided the metal films were preannealed at a higher temperature than at which measurements were made.