Sub-Micron Platinum Electrodes by Through-Mask Plating

A through-mask electroplating process is described for forming Pt electrode structures with the vertical sidewalls and sub-micron dimensions desired for dynamic random access memory (DRAM) applications. The plating process used an aqueous KOH-based solution of "Pt A Salt" (Engelhard) and a sputter-deposited Pt plating base. Plating conditions were first optimized for blanket films on 200 mm-diameter wafers by examining the characteristics of the Pt deposits as a function of plating bath temperature and current density. Electrode features were then formed on similar wafers by plating through a patterned SiO2 mask. Integration issues discussed include potential reactions of the dielectric mask with the underlying Pt plating base, surface modification of the exposed Pt plating base prior to plating, and erosion of the dielectric mask by the plating solution.