Low temperature process and thin SBT films for ferroelectric memory devices

At crystallization temperatures of about 800 degreesC bismuth layered oxide SrBi2Ta2O9 (SBT) deposited by MOD develops good ferroelectric properties f or use in FeRAM devices. But scaling down the film thickness of SET below 1 50 nm only shorts are measured at this crystallization temperature after to p electrode deposition. Working Pt/SBT/Pt-capacitors are achieved by reduci ng the crystallization temperature. Also temperatures of 800 degreesC are t oo high for. integration of the SET module in a stacked capacitor architect ure for high density memory devices. Therefore. a process is needed to redu ce the crystallization temperature of SET, called "Low Temperature Process" . In this work the electric properties of spin-on processed SET crystallized in a temperature window from 650 degreesC up to 800 degreesC are investigat ed. As shown by XRD: transition of the nonferroelectric Fluorite phase to t he Aurivillius phase rakes place at approximately 625 degreesC. Increasing the crystallization temperature gives better crystallized SET films with bi gger SET grains. However, film porosity is also increasing with temperature . Electrical results of stoichiometric variations of SET are presented. SEM pictures show that cluster formation is correlated with less film porosity at lower temperatures.