A Method for Microvia-Fill Process Modeling in a Cu Plating System with Additives

Abstract

A microvia-fill model is formulated for control-design purposes of the via-fill process in 100μmscale. The formulas required to model aCu–Cu-electrode electroplating system with generic additive-type chemicals in both single-directional and bidirectional processes are given in detail. The model relies on principles familiar from a submicrometer-scale via-filling model known as the curvature-enhanced accelerator accumulation model. Additive coverage is modeled based on a simplified method based on local surface-area computation and an analytical formula for surfactant coverage is given. A galvanostatic control law that does not require computing cell voltage is derived. The model also considers theCu(II)-ion activity vsCu(II)-ion concentration. A finite element method-based implementation, applying the arbitrary Lagrange–Eulerian method to compute geometry changes, is tested and compared to via-fill experiment results.