Optimization of High-Speed Electrolytic Plating of Copper Pillar to Achieve a Flat Top Morphology and Height Uniformity

Abstract

Cu plating bath for high-speed electrodeposition of Cu pillar was designed in consideration of a flat top morphology of pillar and a pillar height uniformity. An ideal polarization curve was assumed for the flat top morphology. To obtain the ideal polarization curve, an effect of organic additive concentration and solution agitation on the polarization curve were investigated. The basic bath components were optimized considering a Wagner number to improve the pillar height uniformity. To confirm the pillar top morphology and the pillar height uniformity, a 300-mm diameter wafer was plated with Cu at 20 A/dm2. As a result, improved pillar top morphology and pillar height uniformity were obtained. The optimized plating bath was applied to the plating of a large-size panel of 415 × 510 mm.