Multipath-induced c-axis orientation of aluminum nitride films deposited using direct-current magnetron sputtering

Abstract

This study successfully fabricated high-quality c-axis oriented aluminum nitride (AlN) thin films using direct-current reactive magnetron sputtering on a Mo/Si (111) substrate, where the Mo layer has a thickness of 350 nm. The Mo metal layer not only serves as an effective seed layer for AlN growth but also, due to its excellent conductivity and low thermal expansion mismatch, functions as an electrode material for AlN-based micro-electro-mechanical system (MEMS) devices. Few studies explored the fabrication of AlN films on Mo/Si substrates. By adjusting the sputtering power, we successfully achieved a transition in the crystal orientation of AlN from (100) to (002), and the surface morphology changed from spiral-like to regular pebble-like. Further optimization of the growth temperature to 550 °C led to the realization of fully c-axis-oriented AlN films, with the full width at half maximum of the AlN (002) diffraction peak being 0.173°, indicating superior crystal quality. Photoluminescence analysis revealed significant blue and green emission peaks, and with increasing growth temperature, a reduction in oxygen impurities and defects resulted in improved crystallinity and optical properties. This study provides valuable technical insights and theoretical guidance for the preparation of high-performance AlN thin films, particularly in the application of MEMS devices where AlN can effectively function as an electrode material.