Study on Complementary Auxiliary Cathode Method for Improving the Microstructure Uniformity of Electroplated Thick Metal Film

The uniformity of electroplating thick metal film in microstructure devices is an important factor affecting the surface quality, dimensional accuracy, performance and yield of devices. There are few studies on the traditional electroplating assisted cathode to improve the thickness uniformity of metal coating, and most of them use a single surrounding structure, which is difficult to adapt to the thickness uniformity improving of thick metal coating in complex microstructure devices. This paper presents a method for improving the uniformity of coating thickness by using complementary auxiliary cathode structure. A cross-shaped on-chip auxiliary cathode structure complementary to the mask pattern is designed to disperse the local over-concentrated current density. At the same time, the annular off-chip auxiliary cathode is combined to improve the uniformity of the same batch and single module at the wafer level and module level. A FEM model is established to optimize the structure, size and position distribution of the auxiliary cathode. The simulation results show that compared with the structure without auxiliary cathode, the uniformity between the components and inside the components of film thickness are improved by 90.1% and 55.9% respectively. This is of great significance to ensure the processing consistency and performance stability of thick metal film microstructure devices.