Influence of sputtering atmosphere on polarity distribution of piezoelectric aluminum nitride thin films

Pulsed-DC reactive sputtering was employed to make fully (0002)-textured aluminum nitride (AlN) thin films on molybdenum (Mo) electrodes for piezoelectric applications. The tilt of the lattice planes in the (0002)-oriented columnar grains was measured by the full widths at half maximum (FWHM) of (0002) rocking curve and the polarity distribution with respect to each fine grain constituting the AlN films by piezoresponse force microscopy (PFM). As the sputtering atmosphere changes from 40 to 100% N2, no significant effect on polarity distribution was found except a minor increase and group-up of the N-polarity region at 100% N2. On the other hand, oxygen contamination effectively increased and grouped up the Al-polarity region. The variation of polarity distribution was also shown to be independent of the FWHM of (0002) rocking curve.