Impact of "Terminal Effect" on Cu Plating: Theory and Experimental Evidence

When plating onto resistive substrates, the potential drop across the wafer surface can cause non-uniformities in the current density distribution. This so-called "terminal effect" leads to a naturally higher deposition rate at the wafer edge compared to the center. While it is not difficult to find in literature theory and models describing terminal effect and current density distribution associated with resistive substrates, full wafer plating experimental results are scarce. In this work, an analytical solution for the barrier/seed resistance-controlled plating current distribution is obtained and validated through full wafer plating experiments.