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High-rate through-mold electrodeposition of thick (<200 μm) NiFe MEMS components with uniform composition

1999; Institute of Electrical and Electronics Engineers; Volume: 8; Issue: 4 Linguagem: Inglês

10.1109/84.809052

1941-0158

Steven D. Leith, Daniel T. Schwartz,

Semiconductor materials and devices

An electrodeposition process for achieving good uniformity, growth rate, and yield in NiFe microgears is described. Microgears are electrodeposited from a mixed nickel sulfanate/iron chloride electrolyte through a 230-/spl mu/m-thick poly methylmethacrylate mold patterned using synchrotron X-ray radiation. Despite the use of a plating cell with nearly ideal wafer-scale electrolyte mixing characteristics [the uniform injection cell (UIC)], a degree of compositional variation in the microgears can arise. The composition variation is shown to be due primarily to nonuniformities in microscopic electrolyte mixing patterns within the mold. To a lesser extent, nonuniformity in the local current distribution also contributes to feature-scale composition variation. Improved composition uniformity is achieved when the plating bath is formulated to reduce the sensitivity to electrolyte agitation. Electrodeposition of MEMS components from a low-flow sensitivity electrolyte using the UIC results in NiFe growth rates greater than 60 /spl mu/m/h, yields in excess of 90% and good compositional uniformity. Analysis of mechanical properties illustrates that NiFe parts made using this technique compare favorably to typical electrodeposited MEMS components made from nickel and copper.