Influence of dry etching using argon on structural and electrical properties of crystalline and non-crystalline SrBi2Ta2O9 thin films

After patterning the Platinum / crystalline SrBi2Ta2O9 bilayer by Argon bas ed Reactive Ion Etching (RIE), a degradation of the remanent polarization a nd leakage current of the capacitors for smaller feature sizes is observed. To simulate the study of the side wall of the capacitors, etching of blank et SBT is used as a model experiment. It is shown that etching of crystalli ne SBT is damaging the SBT material, resulting in the formation of small cr ystallites (SEM), the appearance of an unknown peak (XRD) and reduction of the Bismuth content on the SBT surface (AES). Using non-crystalline SBT, ne ither a degradation of electrical properties for smaller feature sizes nor a structural damage of blanket SBT is found after etching and recrystalliza tion annealing although after etching of non-crystalline SBT also a loss of Bi is seen as indicated by AES. Therefore the following model is proposed: Patterning the Pt / crystalline SBT capacitor leads to a Bi deficient edge of the dielectric. Due to the crystalline SBT, this damaged zone can not b e recovered by the final recovery anneal. For the non-crystalline SBT howev er, the Bi deficient regions at the edge are recovered during final anneal by the crystallizing SBT material itself.