Effect of AlN seed layer on crystallographic characterization of piezoelectric AlN

Ultrathin aluminum nitride (AlN) films are of great interest for integration into nanoelectromechanical systems for actuation and sensing. Given the direct relationship between crystallographic texture and piezoelectric (PZE) response, x-ray diffraction has become an important metrology step. However, signals from layers deposited below the PZE AlN thin film may skew the crystallographic analysis and give misleading results. In this work, the authors compare the use of a Ti or AlN seed layer on the crystallographic quality of PZE AlN. The authors also analyze the influence of several AlN seed layer thicknesses on the rocking curve FWHM of PZE AlN and demonstrate a larger effect of the AlN seed layer on the θ-2θ AlN <0002> crystallographic peak for increasing AlN seed layer thickness.