Interfacial structure and crystallinity of YSZ thin films grown by ion beam sputtering for MFIS-FRAM

Yttria stabilized zirconia (YSZ) thin films, having cube-on-cube epitaxial relationship with Si, have been often fabricated by using ion beam sputtering for various buffer layer applications. Since the charging of Ar⁺ ion on targets is detrimental to the sputtering, an appropriate neutralizer eliminating the charging of YSZ target should be used in the sputtering. In order to identify optimum neutralizer for the YSZ film growth, various neutralizers, such as tungsten (W) and zirconium (Zr) have been tried for the ion beam sputtering of YSZ film at 800degC. For the evaluation of the crystallinity and texture of YSZ films, X-ray diffraction (XRD) analysis and high resolution electron microscopy (HREM) were performed. The YSZ films grown with W neutralizer exhibited a texture with (111) preferred orientation. In addition, W particles of a 2~3 nm in diameter were often observed at the interface between the YSZ and Si substrate. Evaporated W during the deposition process was suggested to prevent the formation of (002) textured grain. The YSZ films with Zr neutralizer, however, revealed (002) preferred orientation without any precipitations present at the interface. Oxygen pressure with Zr neutralizer could increase effectively the (002) texture. Present results suggest that a Zr neutralizer is the best neutralizer for the growth of (002) textured YSZ thin film.