The Effect of Al/Pt Interface Reaction on Lead-zirconate-titanate Capacitor and the Optimization of Via Contact for Double Metal Ferroelectric RAM

The effect of the platinum and aluminum interface reaction on the capacitor properties were investigated in 64 k ferroelectric random access memory (RAM). Aluminum diffused into platinum and reacted to form an intermetallic compound during the post-anneal when aluminum had direct contact with the top platinum layer of the ferroelectric capacitor. The Al/Pt/PZT contact was changed into an Al–Pt and lead-zirconate-titanate contact by the reaction. As a result, ferroelectric properties degraded and the leakage current of the top electrode and lead-zirconate-tianate contact started to increase after annealing at 300°C. The capacitor structure was destroyed by the volume expansion due to the Al/Pt reaction at 400°C. To prevent this reaction, a TiN layer was introduced as the barrier layer. This contact scheme showed no breakdown of the ferroelectric capacitor up to 400°C, which indicated that TiN acts as a good diffusion barrier for the double-metal process.