Influence of Dry Etching using Argon on Structural and Electrical Properties of Crystalline and Non-Crystalline SrBi_2Ta_2O_9 Thin Films

摘要

After patterning the Platinum/crystalline SrBi_2Ta_2O_9 bilayer by Argon based Reactive Ion Etching (RIE), a degradation of the remanent polarization and leakage current of the capacitors for smaller feature sizes is observed. To simulate the study of the side wall of the capacitors, etching of blanket SBT is used as a model experiment. It is shown that etching of crystalline SBT is damaging the SBT material, resulting in the formation of small crystallites (SEM), the appearance of an unknown peak (XRD) and reduction of the Bismuth content on the SBT surface (AES). Using non-crystalline SBT, neither a degradation of electrical properties for smaller feature sizes nor a structural damage of blanket SBT is found after etching and recrystallization 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 be recovered by the final recovery anneal. For the non-crystalline SBT however, the Bi deficient regions at the edge are recovered during final anneal by the crystallizing SBT material itself.