Crystallographic Texture of Submicron Thin Aluminum Nitride Films on Molybdenum Electrode for Suspended Micro and Nanosystems

Abstract

The structural properties of piezoelectric AlN/Mo/AlN stacks have been investigated for obtaining an improved c-axis oriented, piezoelectric AlN thin film on Mo electrodes to be employed in suspended nano- and micromechanical devices. With increasing thickness of the AlN interlayer up to 80 nm, the texture of the overgrown Mo layer improves significantly, marked by a significant reduction in full-width-at-half-maximum of the rocking curve obtained around 220 Bragg reflections. The improved orientation of Mo crystallites promotes the growth of preferentially c-axis oriented columns in the overgrown AlN film as evidenced by analyzes of crystal orientation determined by scanning nano-beam transmission electron diffraction. Atomic-Force Microscopy revealed only a slight deterioration of the surface roughness of AlN films upon introduction of the interlayer. The whole film stack has a total thickness of less than 1 μm and is, thus, promising for suspended piezoelectric active RF devices.