Development of Low Temperature Al₂O₃ MOCVD for Ferroelectric Film Passivation on 8″ Wafers

A long-term consideration in the application of ferroelectrics in device production is hydrogen-induced failures. Subsequent to ferroelectric formation, post-capacitor processes of inter-level dielectric layers contain hydrogen and are performed at elevated temperatures. Free hydrogen may react with the ferroelectric oxides, reducing portions of the dielectric layer and creating leakage paths. For optimum ferroelectric film performance, protection against hydrogen infusion is needed. In part, a design solution to this problem is to employ an Al₂O₃ hydrogen diffusion barrier in the device structure. We have focused on MOCVD of the barrier layer using an array of precursors--including trimethylaluminum (TMAl) and aluminum iso-propoxide (Al i-Pr) among others. We have successfully lowered the Al₂O₃ deposition temperature from 600°C to 350°C without sacrificing film quality or deposition rate. We have produced Al₂O₃ MOCVD films in a SpinCVD™ cluster tool rotating disk low-pressure reactor. The Al₂O₃ films are uniform and reproducible. The MOCVD process provides uniform precursor and temperature distributions necessary for coverage over topology in stacked architectures. This paper describes the MOCVD process and resultant film properties.