200 mm wafer-scale integration of bilayer wurtzite ferroelectric AlScN exhibiting effective d33,f > 26.8 pm/V and e31,f > 4.6 C/m2

Abstract

We report the successful integration of a bilayer ferroelectric aluminum–scandium–nitride (Al0.64Sc0.36N) thin film on an industrial-scale 200 mm silicon (100) wafer. Microstructural analysis revealed that both the bottom and top Al0.64Sc0.36N layers exhibit comparable characteristics. Wafer-scale ferroelectric and piezoelectric characterization of the individual layers showed similar average values for permittivity (ɛ), loss tangent (tan δ), and piezoelectric coefficients (d33,f and e31,f). Findings suggest that the bottom Al0.64Sc0.36N layer has a lower leakage current than the top layer in the bilayer configuration. We present a strategy for efficiently actuating both the top and bottom layers to generate a high equivalent longitudinal strain and transverse stress without requiring any complex or additional electrical circuitry. Upon excitation, the bilayer structure yields equivalent d33,f and e31,f values of >26.8 pm/V and >4.6 C/m2, respectively, among the highest ever reported within bilayers of complementary metal–oxide–semiconductor (CMOS) compatible ferroelectric nitride thin films. Such high piezoelectric coefficients enable the broader adoption of lead-free ferroelectric materials for actuator applications.