Piezoelectric properties of polycrystalline AlN thin films for MEMS application

The piezoelectric coefficient d33eff of aluminium nitride thin films was measured using both, the piezoresponse force microscopy and an interferometric technique. Wurtzite AlN thin films were prepared on Si (1 1 1) substrates by reactive dc-sputtering and by metal organic chemical vapor deposition (MOCVD). Direct measurements of the inverse piezoelectric effect in the picometer range showed that the acceptable tolerance in the crystal orientation is much larger for MEMS applications than expected previously. The value of the effective piezoelectric coefficient d33 for the prepared AlN thin films remained as high as 5.1 pm/V even for lower degrees of texture.