Dynamic growth mechanism and interface structure of crystalline zirconia on silicon
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Dynamic growth mechanism and interface structure of crystalline zirconia on silicon S J Wang1, A C H Huan1 and C K Ong2 1. Institute of Materials Research & Engineering, 3 Research Link, Singapore 117602 2. Department of Physics, National University of Singapore, Low Kent Ridge Road, Singapore 119260
ABSTRACT In present report, we have studied the initial stage of the growth of crystalline yttriastabilized zirconia (YSZ) films on the natively oxidized Si (100) wafer by pulsed-laser deposition. X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) show that, for the first few monolayers of crystalline YSZ deposited on Si (100), the dynamic processes appear to be the decomposition of SiO2 to SiO, the formation of ZrO2, and the desorption of SiO. The native amorphous silicon oxide layer is removed completely with the continued deposition of YSZ and the oxygen in this layer is used as oxygen source for forming stable crystalline oxide film. XPS depth profile and HRTEM investigation showed that the interface of crystalline YSZ film in contact with silicon was found to be atomically sharp and commensurately crystallized without an amorphous layer. The interface structure is suggested to have a sequence of -Si-O-Zr-O-. For the film with electrical equivalent oxide thickness 1.46 nm, the leakage current is about 1.1×10-3 A/cm2 at 1 V bias voltage. The hysteresis and interface state density in this film are measured to be less than 10 mV and 2.0×1011eV-1cm-2.
INTRODUCTION Developments in the semiconductor industry over the past twenty years have dramatically reduced the feature size of metal-oxide-semiconductor (MOS) transistors, and the gate oxide SiO2 thickness has been scaled down to around 2 nm [1, 2]. To further the ambition of minimizing feature sizes, alternative gate dielectrics with much higher dielectric constant (ε) are needed to replace the conventional SiO2 (εsilica~4) [3-4] dielectrics. Crystalline oxides on silicon as alternative gate dielectrics [5-10], maintaining one-to-one atomic correspondence at the oxide/silicon interface without the formation of an underlying SiO2 layer, are expected to have excellent physical properties and chemical stability. However, the issue concerning the dynamic growth process of crystalline oxide on silicon and the interface structure is a very crucial step and should be solved first for the implementation of this new structure. In this study we present experimental results that reveal the dynamic growth mechanism of crystalline zirconia on natively oxidized silicon wafer and discuss its interface structure contacting with silicon.
EXPERIMENTAL The YSZ thin films were grown on native silicon wafer with the laser MBE technique. The chamber was equipped with reflective high-energy electron diffraction (RHEED) to in situ real monitor the surface smoothness and crystallinity of the silicon substrate and deposited films. All the Si substrates were cut from one piece of as-purchased Si wafer used in chip manufacturing. T
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