Formation of aluminum oxynitride diffusion barriers for Ag metallization

Aluminum oxynitride (AlxOyNz) diffusion barriers have been formed in the te mperature range of 400-725 degrees C by annealing Ag/Al bilayers on oxidize d Si substrates in an ammonia (NH3) ambient. Rutherford backscattering spec trometry showed that the out-diffused Al reacted with ammonia and oxygen in the ambient and encapsulated the Ag films. The resulting Ag resistivity va lues are 1.75+/-0.35 mu Omega cm. Higher processing temperatures and thinne r original Al layers showed to improve the resistivity of the encapsulated Ag layers. The thermal stability of these diffusion barriers was evaluated by depositing 50 nm of Cu films onto the encapsulated samples, and then ann ealing in either vacuum or flowing He-0.5% H-2. Results showed that these b arriers sustained interdiffusion between Cu and Ag up to 620 degrees C at l east for 30 min in either ambient. This temperature is a 200 degrees C impr ovement over previously reported values for the self-encapsulated Cu and Ag films. (C) 1999 American Institute of Physics. [S0003-6951(99)04801-9].