Electrical Properties of Ion Beam Sputtering Grown Epitaxial Ytiria Stabilized Zirconia Films on Silicon
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ELECI7RICAL PROPERTIES OF ION BEAM SPUTTERING GROWN EPITAXIAL YTIRIA STABILIZED ZIRCONIA FILMS ON SILICON P.HESTO*, C.PELLET*, C.SCHWEBEL*, E.DUPONT-NIVET **, A.LE NOXAIC* Institut d'Electronique Fondamentale, CNRS URA D-022, Universit6 Paris-Sud, 91405 Orsay, France ** Service Electronique, CEA/DAM, BP12, 91680 Bruy~res-le-Chfitel, France. ABSTRACT Yttria stabilized zirconia (YSZ) films have been characterized. The refractive index measured by ellipsometry is about 2.1. The breakdown electric field is greater than 4MV/cm for small area capacitors with a decrease for large area capacitors. This dielectric strength is weakly dependent on the film thickness within the range 0.2-1.ltm. The analysis of the 1MHz C(V) curves by the Terman method leads to a density of interface states of the order of 1012cm'2eV"1 in the middle of the bandgap with an increase near the conduction and the valence bands. The sensitivity of zirconia to the irradiations has been characterized by analysing 1MHz C(V). With or without electric field applied during the irradiations, the Flat-Band voltage shifts are lower for YSZ films than for thermal silicon dioxide films (2 times smaller). INTRODUCTION SOI is a very promising technology for VLSI high speed and radiation-hard applications. The advantages of SOI technologies compared to bulk technologies result from the complete dielectric insulation between devices. So the junction capacitors are reduced and the speed is increased. Moreover the dielectric layer beetween the devices and the substrate reduces the volume collection during irradiations mainly for transient doses and heavy ions (SEU immunity). Two methods [1] are used to obtain a monocrystalline layer of silicon onto an insulator layer: -The growth of a monocrystalline layer of silicon onto a monocrystalline layer of insulator. -The SIMOX (Separation by IMplanted OXygen) and the ZMR (Zone Melted Recrystallisation) techniques. For the first method, an epitaxial yttria stabilized zirconia film (YSZ) deposited onto a monocrystalline silicon substrate is an interesting material. The physical and electrical qualities of these films have been demonstrated [2] and it is possible to deposit thin epitaxial layers of silicon onto crystalline YSZ films. Moreover for cumulative dose irradiations, the greater the back insulator capacitor, the smaller the voltage shift of the back parasitic transistor. Thus because the permittivity is high, YSZ is a suitable material for SOI applications. To achieve high speed and radiation hard integrated circuits, the breakdown voltages and the qualities of the interfaces between the buried insulator and the channel and the substrate are of main importance. So we have studied some electrical properties of Metal-YSZ-Si capacitors *such as the breakdown voltages, the density of interface states and the sensitivity to the irradiations. PREPARATION AND PHYSICAL PROPERTIES OF THE YSZ FILMS Thin films of yttria-stabilized zirconia (YSZ) have been grown on Si substrates by ion beam sputtering deposition using an ultra-hi
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