Modeling Extreme Bottom-Up Filling of Through Silicon Vias
Daniel Josell, Daniel Wheeler, Thomas P. Moffat
Extreme bottom-up superfilling of through silicon vias (TSV) was recently described wherein deposition occurs on the bottom surface of the vias with negligible deposition on their sidewalls or the field around them. The process uses a deposition suppressing additive whose deposition-blocking adsorbate is subject to breakdown through the metal deposition reaction. Positive feedback associated with this suppressor disruption coupled with resistive electrolyte losses decouples the interface potential from the applied potential and underlies the bottom-up feature filling dynamic. A simple pseudo steady state model that links suppressor disruption with voltage drop between the reference and working electrodes in resistive electrolytes is shown to capture essential aspects of the bottom-up filling process. Understanding the coupling of potential and additive concentration gradients provides a rational design strategy for bottom-up filling of recessed surface features that offers to minimize unneeded deposition on the substrate surface thereby permitting substantially decreased fill times and more efficient materials utilization.