Stress analysis of silicon membranes with electroplated permalloy films using Raman scattering

We have measured the stress profile on a silicon membrane electroplated wit h a permalloy film using Raman scattering. The effect of silicon membrane t hickness and permaIloy film thickness on stress distribution was studied. D epending upon the nature of stress, the optic phonon in silicon at 520 cm(- 1) either shifts upward (compressive) or downward (tensile). The phonon fre quency shift is proportional to the magnitude of stress. A microscope X-Y s tage was used to map the stress distribution over the silicon membrane that was covered and uncovered by the permaIloy film. Silicon membranes in the thickness range, 9 mum < t(m) < 12 mum, and permalloy films in the thicknes s range, 6 mum < t(p) < 13 mum showed evidence of compressive stress. Based on the present results, membrane type microvalve design is optimized to pr event leakage, originating from stressed membranes. Such a nondestructive a nd noncontact microscopic stress analysis technique can be applied for desi gn optimization in various magnetic MEMS devices.