Influence of metal electrodes on c-axis orientation of AlN thin films deposited by DC magnetron sputtering

Nanocrystalline aluminum nitride (AlN) thin films were deposited on two types of metallic seed layers on silicon substrates, (111) textured Pt and (110) Mo, by reactive DC magnetron sputtering at low temperature (200 degrees C). Both textured films of Pt and Mo promote nucleation, thereby improving the crystallinity and epitaxial growth condition for AlN thin films. The deposited films were examined by X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques. The results indicated that the preferred orientation of crystallites greatly depends upon the kinetic energy of the sputtered species (target power) and seed layers used. Furthermore, AlN thin films with c-axis perpendicular to the substrate grew on both types of metal electrodes at all power levels larger than 100W. By comparing the structural properties and compressive stresses at perfect c-axis orientation conditions, it is evident that AlN films deposited on (110) oriented Mo substrates exhibited superior properties as compared with Pt/Ti seed layers. Furthermore, less values of compressive stresses (-3GPa) as compared with Pt/Ti substrates (-7.08GPa) make Mo preferentially better candidate to be employed in the field of suspended Micro/Nano - electromechanical systems (MEMS/NEMS) for piezoelectric devices. Copyright (c) 2017 John Wiley & Sons, Ltd.