Abstract
The stress evolution in nanoporous gold (np-Au) films and the influence of annealing temperature and duration was studied. Pore morphology was controlled by simply annealing the np-Au films. To study the relationship between porosity and stress evolution, np-Au films were fabricated on silicon wafers and the porosity was varied by thermal annealing at temperatures 200, 300, and 400{degree sign}C with durations of 2.5, 10, and 20 minutes. Analysis of porosity (via digital image processing of scanning electron microscope images) revealed that the average pore radii of samples increased non-monotonically with the annealing temperature and reached a steady-state value with time. Wafer curvature tests showed that the tensile residual stress in films increased with temperature, and leveled off with time (except for 400{degree sign}C, where it increased). While thicknesses of the np-Au films remained relatively unchanged for 200 and 300{degree sign}C cases, it decreased for 400{degree sign}C.