Surface stress induced in Cu foils during and after low energy ion bombardment

We present measurements of the stress induced by low energy Ar ion bombardment on Cu foils using a wafer curvature technique. The observed stress is found to be on the order of a few GPa, assuming a range for the Ar in Cu of several nanometers. At room temperature, a compressive stress is observed to build up on the surface during sputtering. The stress relaxes after the beam is turned off, leaving a residual tensile stress in the foil. To determine the mechanisms controlling the stress evolution, we have measured the temperature and flux dependence of the induced stress. At elevated temperature (similar to 100-200 degrees C), both the compressive and tensile stresses are reduced. The observed temperature and flux dependence is discussed in terms of the different kinetics processes (ion incorporation, defect generation, stress relaxation, etc.) occurring in the film. (c) 2007 Elsevier B.V. All rights reserved.