Residual stress measurements and mechanical properties of AlN thin films as ultra-sensitive materials for nanoelectromechanical systems

Abstract

Knowledge of the mechanical properties of new materials is essential for their usability and functionality when used in micro- and nanoelectromechanical systems (MEMS/NEMS). Recently, Group III nitrides have gained interest for MEMS and NEMS application. In order to test these materials, three different types of microstructures were fabricated by etching processes: rhombus-shaped structures and doubly-clamped beams for the determination of tensile and compressive stress as well as cantilever structures for the determination of stress gradients in the surface. Furthermore, three different methods were applied for determining the residual stress of AlN thin films: wafer bending measurements, Fourier transform infrared spectroscopic ellipsometry before the etching processes and laser Doppler vibrometer measurements after the etching processes using the doubly-clamped beams. All three methods showed a good correlation of the residual stress in the AlN thin films.

Keywords:

• residual stress
• Group III nitride
• thin film
• FTIR ellipsometry
• laser Doppler vibrometer
• AlN
• MEMS
• NEMS

Acknowledgements

This work was funded by the Thuringian Minister of Education, Science and Culture (TMBWK), (UseNEMS: B714-0965) and the European Regional Development Fund (EFRE).