Surface Morphology and Microstructure of Pulsed DC Magnetron Sputtered Piezoelectric AlN and AlScN Thin Films

Reactive pulsed DC magnetron co-sputtering is used to grow piezoelectric aluminum nitride (AlN) and aluminum scandium nitride (AlScN) thin films on Si(001) substrates. By using grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and piezoresponse force microscopy (PFM), we investigate how the microstructure and the presence of misoriented grains affect the piezoelectric properties of the material. N-2 concentration and target-to-substrate distance are finely tuned to achieve thin films without misoriented grains, resulting in Al0.87Sc0.13N thin films with low roughness, high degree of c-axis orientation, homogenous polarity, and piezoelectric coefficient d(33)=-12.3pC/N.