Effect of post deposition annealing on residual stress stability of gold films

Gold films with the thickness of 360 nm were deposited by electron beam evaporation. Post deposition annealing under 100-400 °C in ambient atmosphere was performed to the films to study the effect of annealing on the microstructure and residual stress stability of the films. After annealing, a combined process consisting of natural placement and thermal holding under 80 °C was conducted. Evolution of residual stress in this process was investigated. Results show that stability of the residual stress of gold films increased after annealing, the stress level also increased. SEM and STEM observation revealed that for annealing temperature of 175 °C and below, microstructure change of the films was mainly manifested by the voids elimination. For annealing temperature higher than 175 °C, besides of the void elimination, grain coalescence occurred and cross grain twins formed. Mechanism of the residual stress evolution was discussed based on the driving force analysis.