High-rate through-mold electrodeposition of thick (> 200 mu m) NiFe MEMS components with uniform composition

An electrodeposition process for achieving good uniformity, growth rate, an d yield in NiFe microgears is described. Microgears are electrodeposited fr om a mixed nickel sulfamate/iron chloride electrolyte through a 230-mu m-th ick polymethylmethacrylate mold patterned using synchrotron X-ray radiation . Despite the use of a plating cell with nearly ideal wafer-scale electroly te mixing characteristics [the uniform injection cell (UIC)], a degree of c ompositional variation in the microgears can arise. The composition variati on is shown to be due primarily to nonuniformities in microscopic electroly te mixing patterns within the mold. To a lesser extent, nonuniformity in th e local current distribution also contributes to feature-scale composition variation. Improved composition uniformity is achieved when the plating bat h is formulated to reduce the sensitivity to electrolyte agitation. Electro deposition of MEMS components from a low-flow sensitivity electrolyte using the UIC results in NiFe growth rates greater than 60 mu m/h, yields in exc ess of 90% and good compositional uniformity. Analysis of mechanical proper ties illustrates that NiFe parts made using this technique compare favorabl y to typical electrodeposited MEMS components made from nickel and copper. [386].