The Effect of a Passivation Layer on the Anelastic Response of Gold Thin Films

The anelastic response in 500nm Au films has been studied through stress relaxation measurements using gas pressure bulge testing under iso-strain conditions. Samples were subjected to various processing techniques before testing to determine if these parameters affected steady state behavior of films. Stress relaxation experiments consisted of a rapid pressure ramp from zero strain to an applied strain of 0.1% and held for 3 hours. A series of such tests were conducted on each sample, one per day, to allow for any viscoelastic stress recovery. Stress relaxation consisted of two components: a fully recoverable viscoelastic component and a non-recoverable plastic (creep) component. The non-recoverable component decreased to zero after a series of three hour iso-strain tests, until a steady state was reached with purely a viscoelastic component remaining. By varying surface conditions on the film (passivation layer presence, titanium adhesive layers, SiNx substrate layers), it was concluded that at these temperatures and testing conditions result in a dislocation based mechanism for deformation rather than a surface and grain boundary diffusion based mechanism seen in other work. Dislocation double-kink nucleation is proposed as a possible mechanism for relaxation.