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M. Gillinger, M. Schneider, A. Bittner, P. Nicolay, U. Schmid:
"High temperature performance of sputter-deposited piezoelectric aluminum nitride thin films";
Talk: Smart Sensors, Actuators and MEMS VII - 2015, Barcelona, Spain; 05-04-2015 - 05-06-2015; in: "Proc. of SPIE Vol. 9517-9520", SPIE, 9517 (2015), ISSN: 0277-786x; Paper ID 951707, 8 pages.

Aluminum nitride (AlN) is a promising material for sensor applications in harsh environments such as turbine exhausts
or thermal power plants due to its piezoelectric properties, good thermal match to silicon and high temperature stability.
Typically, the usage of piezoelectric materials in high temperature is limited by the Curie-temperature, the increase of the
leakage current as well as by enhanced diffusion effects in the materials. In order to exploit the high temperature
potential of AlN thin films, post deposition annealing experiments up to 1000°C in both oxygen and nitrogen gas
atmospheres for 2 h were performed. X-ray diffraction measurements indicate that the thin films are chemically stable in
a pure oxygen atmosphere for 2 h at annealing temperatures of up to 900°C. After a 2 h annealing step at 1000°C in pure
oxygen. However, a 100 nm thin AlN film is completely oxidized. In contrast, the layer is stable up to 1000°C in pure
nitrogen atmosphere. The surface topology changes significantly at annealing temperatures above 800°C independent of
annealing atmosphere. The surface roughness is increased by about one order of magnitude compared to the "as
deposited" state. This is predominantly attributed to recrystallization processes occurring during high temperature
loading. Up to an annealing temperature of 700°C, a Poole-Frenkel conduction mechanism dominates the leakage current
characteristics. Above, a mixture of different leakage current mechanisms is observed.

Aluminum nitride (AlN) is a promising material for sensor applications in harsh environments such as turbine exhausts
or thermal power plants due to its piezoelectric properties, good thermal match to silicon and high temperature stability.
Typically, the usage of piezoelectric materials in high temperature is limited by the Curie-temperature, the increase of the
leakage current as well as by enhanced diffusion effects in the materials. In order to exploit the high temperature
potential of AlN thin films, post deposition annealing experiments up to 1000°C in both oxygen and nitrogen gas
atmospheres for 2 h were performed. X-ray diffraction measurements indicate that the thin films are chemically stable in
a pure oxygen atmosphere for 2 h at annealing temperatures of up to 900°C. After a 2 h annealing step at 1000°C in pure
oxygen. However, a 100 nm thin AlN film is completely oxidized. In contrast, the layer is stable up to 1000°C in pure
nitrogen atmosphere. The surface topology changes significantly at annealing temperatures above 800°C independent of
annealing atmosphere. The surface roughness is increased by about one order of magnitude compared to the "as
deposited" state. This is predominantly attributed to recrystallization processes occurring during high temperature
loading. Up to an annealing temperature of 700°C, a Poole-Frenkel conduction mechanism dominates the leakage current
characteristics. Above, a mixture of different leakage current mechanisms is observed.

aluminum nitride, magnetron, sputtered, harsh environment, XRD, leakage current

http://dx.doi.org/10.1117/12.2179442