Growth and characterisation of thin MgO layers on Si(100) surfaces

Abstract

In this study, the growth, stochiometry and electrical characteristics of MgO thin films, deposited by electron beam evaporation on Si(100) surfaces, have been investigated. Films of different thicknesses were deposited on HF last and chemical oxide Si(100) surfaces in order to determine the effect of factors such as film thickness, surface preparation and substrate temperature on film growth. Using atomic force microscopy (AFM), the predominant film growth mechanism was found to be Volmer Weber, with factors such as film thickness determining the height at which 3 dimensional islands coalesce to form a continuous film. Chemical analysis using X-ray photoelectron spectroscopy (XPS) showed that MgO deposition on hydrogen terminated silicon surfaces produced films of more uniform thickness than those deposited on surfaces with a native chemical oxide. XPS spectra of the O1s core level exhibits two oxygen peaks, a lower binding energy peak (LBE) which can be attributed to the lattice oxygen in the MgO, along with a higher binding energy (HBE) oxygen peak associated with the formation of magnesium hydroxide at the surface of the MgO film upon air exposure. Increasing the substrate temperature during deposition was shown to improve the stochiometry of the films. Based on electrical characterisation of Pd/MgO/Si(100) capacitor structures, the dielectric constant of the MgO layer is calculated as 8.1.