Theoretical analysis of current distributions in electrochemical systems.

摘要

The role of current distribution is considered for a variety of length scales. Often, the current distribution on a large length scale is governed primarily by the electrical potential field, while on a smaller length scale it is governed primarily by the mass transfer of reacting species. The most important electrochemical design objective is frequently the attainment of a uniform current distribution. An experimental approach to achieving such a goal may be limited due to practical constraints. Thus a numerical analysis may be required to more systematically investigate the role of a potentially large set of design parameters on the current distribution.; Pulse and pulse-reverse plating of copper into high aspect ratio vias with a height ranging from 10 mum to 1000 mum under controlled hydrodynamic conditions were investigated by a numerical analysis. The behavior of time-averaged current distributions inside the vias was simulated for a range of bath compositions, boundary layer thicknesses, feature sizes, and the amount of convection within the feature. Simulation results for different conditions are compared with one another to predict optimal pulse plating and pulse-reverse plating waveform parameters. This simulation can be used to guide process development.; The employment of an insulating shield for spatial redistribution of the plating rate on a three-inch silicon wafer that has been previously metallized with a seed layer was considered. Numerical analysis was used to evaluate the influence of shield shape and position on the deposition uniformity. Experimental data were shown to be in good agreement with simulations describing the effect of insulating shields on current distribution.; Cell designs employing an insulating shield or employing a ring-disk anode for minimizing resistive substrate effects on 300-mm wafer metallization were explored by numerical simulation. Both designs were intended to modify the potential field in the electrolyte to compensate for significant potential variations in a resistive substrate.; Galvanic corrosion of a Zn/Fe interface beneath a thin layer electrolyte was examined by a numerical analysis. The cathodic protection of Fe was analyzed for various electrolyte thicknesses and conductivities and for the impact of the defect size, where the zinc coating has been removed.