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A. Ababneh, U. Schmid, J. Hernando-Garcia, J.L. Sànchez-Rojas, H. Seidel:
"The influence of sputter deposition parameters on piezoelectric and mechanical properties of AlN thin films";
Materials Science and Engineering B, 172 (2010), 3; 253 - 258.

Aluminium nitride (AlN) reactively sputter-deposited from an aluminium target is an interesting piezoelectric
thin film material with high CMOS compatibility. A good c-axis orientation is essential for
obtaining high piezoelectric coefficients. Therefore, the influence of different sputtering conditions on the
microstructure of AlN thin films with a typical thickness of about 500nm was investigated. In this study
it is demonstrated that highly c-axis oriented AlN thin films can be deposited on nominally unheated
(1 0 0) silicon substrates, most preferentially when using a pure nitrogen atmosphere. The degree of
c-axis orientation increases with higher nitrogen concentration and with decreasing the sputtering pressure,
whereas the influence of plasma power on the microstructure was found to be negligible. A low
sputtering pressure is also useful for minimizing the amount of oxygen contaminations in the deposition
chamber and hence for reducing the incorporation of impurities into the AlN films. Intrinsic stress values
of AlN thin films were determined by wafer bow measurements and were found to be between −3.5 and
750MPa depending on choice of deposition parameters. Finally, the piezoelectric coefficients d33 and d31
were determined experimentally by laser scanning vibrometry in conjunction with a theoretical model.
Effective values in c-axis oriented 500nm films with FWHM of 0.33◦ are 3.0 and −1.0 pm/V. For a film of
2.4µm thickness, values of 5.0 and −1.8 pm/V were measured, which are near the bulk values.

Aluminium nitride Sputter deposition technique XRD pattern c-Axis orientation Biaxial film stress Piezoelectric coefficients Interferometric measurements

http://dx.doi.org/10.1016/j.mseb.2010.05.026