Zr-silicide formation during the epitaxial growth of Y-stabilized zirconia films on Si(100) and its avoidance by ion beam assisted deposition at a reduced temperature

Yttrium-stabilized zirconia (YSZ) buffer layers were deposited onto Si(100) substrates by ion beam sputtering under different conditions. Deposition at a temperature of 750 degrees C and oxygen partial pressures p(O2) <2 X 10(-6) mbar lead to epitaxially grown films containing a significant amount of Si as detected by in situ Auger electron spectroscopy (AES). By means of X-ray diffractometry (XRD), this Si content could be attributed to a simultaneous formation of the silicide ZrSi2, which is found to grow also epitaxially under the above conditions. Its orientation, however, relative to the substrate is ZrSi2[101]//Si[100], in contrast to the [100]//Si[100] orientation observed for YSZ. For p(O2) > 2 X 10(-6) mbar, the as-prepared YSZ film exhibits no Si within the resolution of the Auger technique. AES depth profile analysis, however, shows a Zr-rich layer at the YSZ/Si interface. Applying the same technique, it turns out, that the formation of this interlayer can be avoided by reducing the substrate temperature to 580 degrees C, The observed loss in epitaxial quality of the buffer layer due to this reduced preparation temperature could be totally compensated by an ion beam assisted deposition (IBAD) bombarding the growing film with 180 eV Ar+ ions at an ion-to-atom ratio of 2.0.