Direct measurement of stress-induced void growth by thermal wave modulated optical reflectance image

Thermal wave modulated optical reflectance imaging, for imaging stress-induced voids in metallization, is described. This method nondestructively detects, with submicron resolution, voids within metallization without removal of the stress-originating passivation layers. The width, area, location, and a thickness parameter for each void are measured after heat treatment at 673 K for various times. All voids in a selected field of view are automatically labeled and measured at each time step. This removes the tedium of manually measuring individual voids and greatly increases void growth statistics. These statistics are then compared with a stress-driven diffusive model of void growth. This nondestructive technique has allowed observation of two new stress-void phenomena: a growth process akin to Ostwald ripening and the physical movement and agglomeration of voids.<>