Fracture Toughness of AlTiN Coatings Investigated by Nanoindentation and Microcantilever Bending

Metal nitride coatings are increasingly used in MEMS applications. The brittle nature of these coatings makes fracture one of the main failure mechanisms during operation. Therefore, quantifying the fracture toughness of nitride coatings in a reliable fashion is important to understand the failure behavior and to optimize device performance and reliability. This study investigated the fracture toughness of AlTiN coatings produced by cathodic arc evaporation, a widely used technique in the industry. Nanoindentation and microcantilever bending-based measurements indicated a fracture toughness of 6.6 and 4.8 MPa & sdot;m1/2, respectively. The lower toughness results of microcantilever bending were attributed to the columnar growth of the coating, which promoted crack propagation perpendicular to the film surface. The results provide useful data toward a better understanding of the fracture of hard coatings and give insight into the advantages and disadvantages of different measurement methods.