Conformal barrier/seed layers deposition for voids free copper electroplating in high aspect ratio TSV

In this paper, conventional PVD method with fine-tuned process parameters is used to deposit barrier/seed layers in our 10×100μm TSV interposer process. High power and low power RF bias are alternately applied to the substrate in order to get more conformal barrier/seed layers on the recessed features of TSVs. The high power RF bias has been found to offer many benefits such as enhancing nucleation density and adhesion, increasing the metal coverage on the lower parts of TSVs and redistributing the metal already deposited. Low power RF bias can ensure good metal coverage on top and middle parts of the TSV sidewall as well as the bottom corner. Finally, with the optimized PVD process, voids free Cu electroplating in the 10×100μm TSVs across a 300mm wafer is successfully achieved, which is confirmed by X-Ray and cross section measurements.