Characterisation of electroplated NiFe films using test structures and wafer mapped measurements

Nickel-iron alloys have useful magnetic properties that are of interest to the MEMS industry, but the high stress levels that can develop during the fabrication process pose a real challenge. This paper addresses the characterisation of NiFe films using suspended rotating structures, electrical test structures and X-ray fluorescence measurements. An automated measurement system has been developed, which facilitates rapid wafer mapping to spatially compare stress levels at different stages of the fabrication process. This has been used, together with other wafer mapped parameters such as alloy composition, sheet resistance and layer thickness, to identify correlations and provide an increased understanding of the relationships between the different process control factors.