Initial Stages of Growth of Heteroepitaxial Yttria-Stabilized Zirconia Films on Silicon Substrates

Abstract

The growth of heteroepitaxial yttria-stabilized zirconia (YSZ) has attracted considerable attention over the past 15 years due to its usefulness as a heteroepitaxial buffer layer. A specific example of its utility is in the growth of yttrium barium copper oxide (YBCO) on Si substrates. 1 Direct contact between the Si substrate and the YBCO film results in interdiffusion of components, which will spoil the superconducting properties of the YBCO film. The YSZ material forms an effective chemical buffer layer separating the Si substrate and the oxide superconducting film, while still permitting the transfer of the crystalline template structure to the superconducting film. The YSZ material film has also been used in superconductor material combinations that utilize substrate materials other than Si; e.g., rolling assisted biaxially textured Ni substrates. Another application for epitaxial YSZ material is in the formation of silicon-on-insulator (SOI). 3,4 The YSZ material is an effective electrical insulator with a relative dielectric constant of 27 at a frequency of 10 GHz. In theory, a top Si epitaxial layer can be regrown on the YSZ film to form the SOI structure. This could be performed on blanket wafers or accomplished later in the fabrication process to form isolated islands on the chip surface. Another application involving the dielectric properties of YSZ is in the formation of advanced dielectrics for dynamic random access memory devices. 5 The diffusivity of O 2 in YSZ is very high, and it is possible to grow a thermal oxide on the Si surface, subsequent to the growth of a YSZ film. The YSZ/SiO 2 sandwich structure combines the high electrical permittivity of the YSZ layer with the effective passivation of a thermal SiO 2 layer.To date, single-crystal YSZ films have been deposited on Si substrates by a variety of techniques including ion beam sputtering, 6 electron beam evaporation, 7-9 pulsed laser deposition, 10-12 reactive sputtering, 13 and metallorganic chemical vapor deposition. 14 An important component of these investigations has involved the development of a model which describes the growth of the YSZ material film at its initial stages on the Si substrate. Previous discussions were often concerned with the presence or absence of a silicon oxide film on the Si surface prior to film growth. In this investigation, the oxide layer has been shown to be essential for the heteroepitaxial growth process. Further, once epitaxial growth is established in a thin seed layer, subsequent epitaxial material can be deposited at temperatures as low as 200ЊC. ExperimentalThe YSZ thin-film samples were deposited by a reactive sputter process in an electron cyclotron resonance (ECR) reactor. Briefly, an Ar plasma stream generated in a broad beam ECR reactor was directed at the Si substrate located in the downstream position. The YSZ material was sputtered from a radio frequency (rf) coupled magnetron sputter gun located above the substrate. This apparatus was used previously to perform a similar investigation on the...

Nanostructured Dense ZrO2 Thin Films from Nanoparticles Obtained by Emulsion Precipitation

“…Thin homogeneous nanocrystalline zirconia films with grain sizes Ͻ20 nm have been prepared by reactive sputter deposition [1][2][3] and sol-gel methods. 4 Dense layers made by deposition of nonagglomerated nanoparticle dispersions may lead to systems with substantially reduced sintering temperature and minimal grain growth.…”

Growth mechanism of epitaxial YSZ on Si by Pulsed Laser Deposition

“…Very smooth surfaces can be obtained by a variety of Physical Vapor Deposition techniques, e.g. Pulsed Laser Deposition (PLD) 7 – 9 , radio-frequency magnetron sputtering 10 and electron-beam evaporation 6 , 11 . The highest quality films have a full width at half maximum (FWHM) of the X-ray Diffraction (002) rocking curve of around 0.7°.…”

“…Epitaxial YSZ films on Si have been made with PLD since the 90 s. Initially, YSZ films were grown on Si with the native oxide removed in advance 7 . Growth on silicon with native oxide was introduced short time later 17 , and appeared to deliver films with higher crystalline qualities 6 , 10 , 18 . Typically, a two step growth process is used 8 , 13 .…”

Influence of Electrostatic Forces on the Growth of One‐Dimensional Nanostructures

“…The nanorods have previously been found to be single crystal by X-ray diffraction analysis but randomly oriented relative to one another as displayed by the SEM pattern shown in Figure 1. The main difference in the growth process used by our group, and that used in other papers involving a sputter process, is that our process utilized a high plasma density (10 10 cm −3 versus 10 8 cm −3 ) [13,[15][16][17] and a lower mole fraction of oxygen in the reactor ambient gas mixture (5% versus 50%) [12].…”