High Speed Cu Plating Technology for Wafer Level Packaging

According to Moore's Law, the wafer level packaging and fan-out packaging market is expected to witness a compound annual growth rate (CAGR) of 18% during the forecasted period (2021 – 2026). And there are also some challenges for the high speed plating technology in the production of wafer level advanced packaging. Recently after a long time development, ACM announces high-speed copper (Cu) plating technology, which is now available for its ECP ap system. The tool supports Cu pillar bumping for copper(Cu), nickel (Ni) and tin-silver (SnAg) plating. The unique paddle design enables the new high-speed electroplating technology to support the copper electroplating chamber with a stronger mass transfer capacity during the electroplating process. Also, the channel of diffusion layer becomes shorter and the diffusion efficiency of cation is improved. The second anode well control the electric field the distribution of cations on the wafer surface, and with the paddle stirring action, the cathode polarization phenomenon is reduced, which improved the electroplating efficiency and effectively reduced the boundary layer thickness to ensure the electroplating quality. Not only does it perform well in electroplated copper pillars, it can still maintain good uniformity and coplanarity in the electroplating of oversized bumps with higher aspect ratios and more stringent requirements for electroplating speed. The test results of ACM Ultra ECP ap series equipment meet the requirements of high speed volume production and the uniformity is also at leading edge level.