Wafer mapping of the transverse piezoelectric coefficient, e31,f, using the wafer flexure technique with sputter deposited Pt strain gauges

Measurement of the transverse piezoelectric coefficient (e31,f) in thin films is crucial for the development of microfabricated sensors, actuators, and transducers. Here, a method is described such that lithographically defined strain gauges enable non-destructive, position-dependent characterization of e31,f in conjunction with the wafer flexure technique. Measurements of 100 nm thick Pt gauges deposited on 1 μm thick PbZr0.52Ti0.48O3 thin films yield gauge factors of 6.24, with a gauge-to-gauge variation that is 5% of this value. The system allows for simultaneous measurement of the charge and strain, improving the overall accuracy of measurement. The small footprint of the combined strain gauge array/electrode pattern used for determining e31,f, allows for a non-destructive mapping of the transverse piezoelectric coefficient across large-area wafers. Due to the clamping configuration used in wafer flexure experiments, e31,f values can accurately be obtained within the central ∼2/3 of a full wafer. Measurements performed on a 1.3 μm thick randomly oriented polycrystalline PbZr0.52Ti0.48O3 film made deposited on a 4 in. platinized silicon wafer by the sol–gel process show a high degree of uniformity, with e31,f of −6.37 ± 0.60 C/m2 for points measured within r = 3 cm.

► Developed lithographically defined strain gauge patterns.
► Sputter deposited platinum strain gauges for in-plane strain measurements on piezoelectric thin films.
► Determined gauge factor values for Pt gauges, which allows for accurate measurement of e31,f coefficient in piezoelectric thin films through simultaneous measurements of charge and strain using the wafer flexure technique.
► Conducted wafer mapping of e31,f for a PZT 52/48 film demonstrating efficacy of using sputter deposited strain gauges in conjunction with wafer flexure technique.