Uniform copper electroplating on resistive substrates

Abstract

As critical feature size shrinks and seed layer thickness continue to get thinner, it is becoming more challenging to achieve good wafer scale uniformity due to the high substrate resistance associated with thin seeds or even seedless substrates. We have developed an unique electroplating equipment that improves the wafer scale uniformity of copper plating on 5-60nm copper seeded 200 mm or 300 mm wafers. The electroplating cell contains a highly resistive porous element that introduces a physical resistance in the electrolyte. The resistive element is capable of successfully addressing the "terminal effect" during copper electroplating by compensating the high sheet resistance of the substrate. As a result, very uniform electroplated deposits can be achieved. Efforts have been taken to refine and optimize the process and system. Void free feature filling down to nanometer size features has been demonstrated. Planar topography that eliminates mounding over dense patterns is confirmed.