Uniformity control of Ni thin film microstructures deposited by through-mask plating

The thickness uniformity within a specimen and the cross-sectional profiles of electroplated individual Ni microstructures have been investigated as a function of the electroplating conditions. It was found that the uniformity and profiles of microstructures could be controlled by varying the process conditions. A uniform thickness distribution and microstructures with flat profiles could be obtained at optimal plating conditions of 8 mA/cm2 and 60°C. Above this optimal plating current density, the microstructure has a rabbit-ears profile, and the thickness of a narrow microstructure is thicker than that of wide ones. Below this current density, the microstructure has a cap-like cross-sectional profile, and a narrow structure is thinner than wide ones. Increasing the plating temperature enhances the nonuniformity, whereas other process parameters have insignificant effects on it. The current crowding observed in patterned specimens is responsible for the rabbit-ears profile of individual microstructures, while a combination of the fluidic friction on the sidewall of the photoresist and the electrophoresis of the ions in the solution are believed to be responsible for the abnormal cap-like profile of individual microstructures and the thinning effect on narrow microstructures.

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