Intrinsic stress evolution in aluminum nitride thin films and the influence of multistep processing

Curvature measurements were used to investigate intrinsic stresses in AlN thin films grown by molecular beam epitaxy. In situ stress evolution experiments show that tensile stress is generated at the time where individual islands coalesce into a continuous film, and for some time after coalescence. Compressive stress is also generated both before and after coalescence. Introducing an intermediate annealing stage appears to reduce tensile stress evolution after coalescence, ultimately increasing the final intrinsic compressive stress. The maximum reduction in the tensile intrinsic stress is obtained when the sample is annealed at roughly the time where the islands coalesce into a continuous film.