Large deformation and geometric instability of substrates with thin-film deposits

Experimental and theoretical results are presented on the evolution of large elastic deformation, non-uniform curvature, shape changes and geometric instability in substrates of Si wafers with metal films. The critical diameter and thickness of the Si wafer, for which large deformation and shape instability occur, are identified, as functions of the line tension in the film (which is the product of the biaxial stress in the film and the film thickness). Observations of the curvature and shape variations along the wafer diameter and geometry-dependence of the shape instability compare favorably with those predicted by detailed finite element analyses. (C) 1997 American Institute of Physics.