Silicate interface formation during the deposition of Y 2 O 3 on Si
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E6.15.1
Silicate interface formation during the deposition of Y2O3 on Si C. Durand1, C. Vallée1, C. Dubourdieu2, M. Bonvalot1, E. Gautier3, O. Joubert1 Laboratoire des Technologies de la Microélectronique (LTM/CNRS), 17 avenue des Martyrs (CEA-LETI), 38054 Grenoble Cedex 9, France. 2 Laboratoire des Matériaux et du Génie Physique, UMR-CNRS 5628, ENSPG, BP 46, 38402 Saint Martin d'Hères cedex, France. 3 Institut des Matériaux de Nantes (IMN), 2 rue de la Houssinière, BP 32229, 44322 Nantes cedex 3, France 1
ABSTRACT The interface behaviour during PE-MOCVD deposition of Y2O3 thin films on Si/SiO2 (8 Å) substrates has been investigated by XPS, TEM and OES analysis. The deposition process involves the sequential injection of MO precursors into the CVD chamber and is assisted by an O2 plasma. The injection frequency greatly influences the interface behaviour in terms of thickness and composition. The O2 plasma and the solvent also greatly affect substrate oxidation, and subsequently interface formation during deposition. Several mechanisms are discussed to account for substrate oxidation in view of a careful control of interface formation. INTRODUCTION The control of the interface during the deposition process of a high k material is a crucial point for any potential high k device applications. The key challenge is not only to limit the interface formation but to understand its formation in order to be able to control its thickness and chemical phase separation [1-3]. Silicates of high k materials have been shown to be more stable with the substrate than high k materials themselves. Thus, zirconium and hafnium silicates are potential high k gate dielectric candidates with an amorphous microstructure after annealing. However, a limitation for the integration of transition metal silicate alloys such as (HfO2)x(SiO2)1-x as gate dielectrics is chemical phase separation into SiO2 and transition metal oxides. Yttrium silicate also shows desirable properties, which can be obtained from the oxidation of yttrium on silicon in dry air at 500-700° C [4]. Thick Y2.45Si0.55O5 films (26 nm) have been prepared using this process. The annealing of an yttrium layer deposited on top of a SiO2 layer at 900-940°C also leads to a selective thermal decomposition of SiO2 into a silicate/Si interface [5,6]. The present study is focused on yttrium silicate formation during the deposition of Y2O3 on Si/SiO2 substrates. Y2O3 films are obtained by a PE-MOCVD (Plasma-Enhanced, Metal-Organic Chemical-Vapor-Deposition) process, which combines plasma assistance and a liquid precursor supply set-up. The liquid supply system used is based on the sequential injection of micro-amounts of precursors inside a heated evaporator. Yttrium silicate has been investigated at several precursor injection frequencies. Results are discussed based on X-ray photoelectron spectroscopy (XPS) data as well as Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS) analysis. Mechanisms involved in the silicate formation are discussed. O2 plasma
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