In this work, the size effect of the aluminum nitride's Young's modulus is demonstrated. It manifests in a decreasing Young's modulus with decreasing layer thickness. The observed thickness dependence is significant for thickness below 300 nm. The results were demonstrated on AlN grown by metal organic chemical vapor deposition using microelectromechanical structures. Measuring and analyzing the resonator length dependence of the resonance frequency using a modified Euler-Bernoulli description allowed to extract the thickness dependence of the Young's modulus. The cantilever curvatures were determined using a newly developed model. It is also demonstrated that the current existing models do not reflect the observed thickness dependence of the Young′s modulus in a satisfactory way. A model is derived to describe the deviation in the thin film limit.
This work was funded by the Thuringian Ministry of Education, Science and Culture (TMBWK), (UseNEMS: B714-0965) and by European Regional Development Funds (ERDF/EFRE). The authors thank S. Michael for providing the ability of resonance frequency measurements at IMMS gGmbH and M. Stubenrauch for carrying out the etching of the MEMS structures as well as K. Tonisch for the growth of AlN.
I. INTRODUCTION II. SAMPLE GROWTH III. RESULTS AND DISCUSSIONS IV. CONCLUSIONS