Structural and piezoelectric properties of AlN thin films grown by pressure gradient sputtering

Aluminum nitride (AlN) thin films were grown by pressure gradient sputtering (PGS) and conventional sputtering methods. A pressure gradient with low pressure at a substrate position was measured only in the PGS method. AlN films highly oriented along the c -axis were grown by both methods, but there were remarkable differences in the surface roughness and the piezoelectric properties. The average surface roughness (Ra) obtained by atomic force microscopy images was much smaller in the AlN grown by the PGS method. The piezoelectric constant ( d 33 ) of the AlN grown by the PGS method was higher than that of the conventional method. These results revealed that the PGS technique has an advantage in the growth of AlN films that are highly c -axis oriented with a single dielectric domain.