TSV fabrication technology using direct electroplating of Cu on the electroless plated barrier metal

We propose a new TSV fabrication process using electroless plating of a barrier metal layer in TSV, and succeeding direct electroplating of Cu on the barrier without Cu seed layer. The conformal and thick ( > 50 nm) CoWB barrier layer deposition inside a high aspect ratio TSV enables direct electro-plating of Cu from top to bottom of TSV entirely. Uniformity of CoWB thickness is within 10 % in 8-inch wafer. Furthermore, we successfully fabricated a daisy chain of TSVs of 1200 steps and evaluated electrical properties. Excellent endurance property of the TSV daisy chain was obtained without any change of the resistance. This technology is promising for the 3D LSIs that uses high aspect ratio TSVs.