Diffusion phenomena in a Pt/IrO2/Ir/TiN/W multilayer structure during annealing in oxygen

The process generating hillock structures at the surface of a Pt/IrO2/Ir/TiN/W multilayer stack has been studied at a temperature of 700 degreesC. This phenomenon has been related to a structural modification of the barrier that involves iridium and platinum layers, and consists of platinum atoms diffusing downwards while iridium atoms move upwards. Once in the surface proximity, iridium has been oxidized forming large grains, the hillocks, that have grown and protruded up to the sample surface. Nevertheless, oxygen was not able to deeply penetrate the barrier stack, and therefore, the inner TiN and W layers have been preserved from oxidation.