A semiconductor device fabrication method includes forming a barrier layer upon a dielectric layer, forming a pillar interconnect structure upon the barrier layer, forming solder upon the pillar interconnect structure, reflowing the solder to release solder voids, forming a perimeter material around at least a portion of an exposed sidewall of the pillar, and removing the barrier layer exterior to the pillar interconnect structure. Another fabrication method includes forming the barrier layer, forming the pillar interconnect structure, forming the solder upon the pillar interconnect structure, forming a perimeter material on exposed surfaces of the pillar interconnect structure, and removing the barrier layer on the surface of the dielectric layer exterior to the pillar interconnect structure. Another fabrication method includes forming the barrier layer, forming the pillar interconnect structure, forming a wettable material on sidewalls of the pillar, and removing the barrier layer exterior to the pillar interconnect structure.