Mechanical Properties of Aluminum Nitride Substrates
Jay S. Wallace, Lin-Sien H. Lum
Aluminum nitride (AlN),because of its high thermal conductivity, is seeing increased use for heat management applications of semiconductor devices. With the likelihood of large mechanical stresses, both during fabrication as well as in service, mechanical properties become an important aspect of overall device reliability. The mechanical properties of three AlN compositions were characterized: one (high-fired) commercial grade material, one high-fired prototype material, and one prototype low-fired material. Mechanical property characterization included strength, Weibull parameters, toughness, and crack growth susceptibility. Properties of the commercial material were very consistent with a characteristic strength of 404 MPa, a Weibull modulus of 14, a fracture toughness of 3.6 Mpa m, and a crack growth susceptibility parameter of 125. In contrast, properties of the prototype materials were generally not as good and showed more variability. Phase analysis and microstructural characterization complemented the mechanical property measurements. The property variability appeared to be associated with second phase composition, surface contamination and inhomogeneities in the microstructure.