Evaluation of Film Property and Strength in Hexagonal AlN Thin Film
Yoshiaki AKINIWA and Takuya WATANABE
Abstract:AlN thin films were deposited on the polyimide films by reactive RF magnetron sputtering in Ar and N2 gas environment. Most of the films possess <10¥0> or <00¥1> fiber texture. The properties such as the fiber texture, residual stress and tensile strength of the film were estimated by using X-ray method. The fiber texture of the film was strongly influenced by the N2 gas flow ratio and changed from <10¥0> to <00¥1> with increasing gas flow ratio. The intensities of AlN 11¥0 and AlN10¥3 diffraction were also changed. Residual stress of the films was affected by the deposition conditions. The compressive residual stress increased with increasing N2 gas flow ratio or decreasing process pressure. The surface of the film was observed by using SEM. For the films with strong <00¥1> fiber texture, the grain structure observed with scanning electron microscope was equiaxial. On the other hand, elongated grains were observed for the films with weak <00¥1> fiber texture. For the films sputtered at lower temperature, many voids were observed between grains. In-situ tensile tests were carried out for each specimen in order to estimate the strength of the films. The maximum stress measured by X-ray method during tensile loading increased with decreasing intensity ratio of 00¥2 diffraction. When compared at the same intensity ratio, the strength of the films sputtered at higher temperature was higher than that sputtered at lower temperature. Key Words:AlN thin film, Sputtering, X-ray, Fiber texture, Residual stress, Tensile strength