Substrate angle-induced fully c-axis orientation of AlN films deposited by off-normal DC sputtering method

A highly c -axis-oriented aluminum nitride (AlN) thin film with smooth and crack-free surface was fabricated by an off-normal direct current (DC) sputtering method in a pure nitrogen atmosphere, in which the rotatable substrate holder positioned in the middle of four side targets was a key approach to guarantee the grain growth with no tilt. The detailed effects of substrate angle on the c -axis orientation of AlN films were investigated by varying the substrate angle from 0° to 90°. Moreover, theoretical analysis and Monte Carlo (MC) simulation reveal that the oblique or even vertical angle could improve the lateral kinetic energy of sputtered atoms deposited on the growing film. A variety of examining techniques including X-ray diffraction (XRD), (002) peak rocking curve, scanning electron microscopy (SEM) were conducted to evaluate the angle dependence on the crystallographic orientation. These test results indicate that larger substrate angle is beneficial to the (002) growth of AlN thin film, and a fully c -axis textured AlN thin film is obtained at 90° with small surface roughness ( R a ) of 3.32 nm. Graphical abstract