X-ray and single crystal values of the elastic constants and determination of machining residual stresses in AlN

AlN is of increasing importance as structural material in microelectronics and microsystems in order to replace Al2O3. However, the knowledge of mechanical properties of this material is still restricted, and an enhanced understanding about the material behaviour of AlN requires the knowledge concerning the residual stresses. In order to determine the residual stresses by means of X-ray diffraction, X-ray elastic constants are needed which account for the elastic anisotropy and the coupling conditions of the crystallites in the polycrystalline material. Therefore, the X-ray elastic constants of AlN were determined for selected lattice planes {hkl} by X-ray diffraction. From the single crystal elastic constants calculated on the base of this knowledge, the X-ray elastic constants were derived for all sets of lattice planes {hkl} of interest. Employing these data, X-ray residual stress analyses were performed on differently machined samples of AlN.