Interface oxidation of epitaxial silicon deposits on (100) yttria stabilized cubic zirconia

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Abstract
(100) single crystal silicon films have been deposited on (100) oriented yttria stabilized zirconia (YSZ) single crystal substrates. Taking advantage of the high-temperature oxygen ion and electronic transport properties of YSZ material, we have subsequently grown buried SiO2 layers (with thicknesses in the 1000-Å range) at the Si/YSZ interface, the result being a Si(100)/a-SiO2/YSZ (100) structure. Since, similarly to silicon films on sapphire, the planar defect density in as-deposited material is highest at the Si/substrate interface, the oxidation process results in an overall increase of the crystalline quality of the epi-Si deposits. We present here our first results of thermal and anodic oxidation of the interface. The buried SiO2 layers have been characterized by Rutherford backscattering spectroscopy and scanning electron microscopy on chemically delineated cross sections. Thermal oxidation has been performed at typically 1150 °C with oxygen pressures ranging from 10−1 to 2 atm. In our operating conditions, the thickness of the buried SiO2 layers has been found to increase linearly as a function of both time and oxygen pressure. Anodic oxidations have also been carried out using either a molten salt (KNO3) solution at 500 °C as electrolyte or an oxygen plasma, the substrates being held at 550 °C. Typically, 1800-Å-thick interfacial SiO2 layers have been grown in 10 min with a current density of 1.5 mA/cm2.