Conducting barrier electrodes for direct contact of PZT thin films on tungsten

Two W protection schemes for direct-contact bottom electrodes for PZT thin films, namely RuO2/Cr and RuO2/Ru, were compared with respect to protective performance and contact resistance up to 800 degrees C annealing temperature in oxygen. Cr clearly offers better protection for W than Ru-based schemes by forming a passivating Cr2O3 layer. No Cr is detected on the RuO2 surface, even after annealing at 800 degrees C, due to its entrapment by RuO2 by oxidoreduction. However, the formation of a continuous Cr2O3 film at the RuO2/Cr interface gives rise to an increased contact resistance above 650 degrees C. RuO2/Ru does not show any measurable contact resistance on W, but fails above 600 degrees C.