Simulation of Copper Electrodeposition in Through-Hole Vias
Trevor M. Braun, Daniel Josell, Thomas P. Moffat, Jimmy John
Copper electrodeposition processes for filling metallized through-hole (TH) and through-silicon vias (TSV) depend on selective breakdown of a co-adsorbed polyether-chloride adlayer within the recessed surface features. In this work, a co-adsorption-dependent suppression model that has previously captured experimental observations of Cu deposition in TSV is used to explore filling of TH features. Simulation of potentiodynamic and galvanostatic TH filling are presented. An appropriate applied potential or current localizes deposition to the middle of the TH. Subsequent deposition proceeds most rapidly in the radial direction leading to sidewall impingement at the via center creating two blind vias. The growth front then evolves primarily in the z-direction to completely fill the TH in a manner analogous to TSV filling. Applied potentials, or currents, that are overly reducing result in metal ion depletion within the via and void formation. Simulations in larger TH features (i.e., diameter = 85 μm instead of 10 μm) indicate that lateral diffusional gradients within the via can lead to fluctuations between active and passive deposition along the metal/electrolyte interface.