Etching behaviors of SrBi2Ta2O9 thin films in Cl2/Ar inductively coupled plasma

In this study, SrBi2Ta2O9 (SBT) thin films were etched ill different Cl-2/Ar gas mixing ratio. The maximum etch rate of SBT was 883 Angstrom /min in Cl-2(20 %)/Ar(80 %). X-ray photoelectron spectroscopy (XPS) was carried out to investigate the chemical reactions on the near surface. The results of XPS analysis showed the decrease of Bi content and nonvolatile etch products such its Sr-Cl and Ta-Cl. The secondary ion mass spectrometry (SIMS) confirmed the chemical reactions between Cl radical and metal element (Sr and Ta). Atomic force microscopy (AFM) and x-ray diffraction (XRD) were used in order to evaluate the changes of surface morphology and crystallinity on the near surface of etched SBT thin films. The rms values of etched samples in Ar only or (% only plasma were higher than those of as-deposited and Cl-2/Ar plasma. The crystallinity of the etched samples decreased in Ar only or Cl-2 only plasma, but maintained constant in Cl-2/Ar plasma. This can be illustrated by a decrease of Bi content or nonvolatile etching products (Sr-Cl and resulting in the changes of stoichiometry on the etched surface of the SBT thin films.