An electroplating apparatus prevents anode-mediated degradation of electrolyte
additives by creating a mechanism for maintaining separate anolyte and catholyte
and preventing mixing thereof within a plating chamber. The separation is accomplished
by interposing a porous chemical transport barrier between the anode and cathode.
The transport barrier limits the chemical transport (via diffusion and/or convection)
of all species but allows migration of ionic species (and hence passage of current)
during application of sufficiently large electric fields within electrolyte.
