Properties of Pr-based high k dielectric films obtained by Metal-Organic Chemical Vapor Deposition
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Properties of Pr-based high k dielectric films obtained by Metal-Organic Chemical Vapor Deposition Raffaella Lo Nigro,1 Roberta G. Toro,2 Graziella Malandrino,2 Vito Raineri1 and Ignazio L. Fragalà2 1 IMM, sezione di Catania, CNR Stradale Primosole n 50, I-95121 Catania, Italy 2 Dipartimento di Scienze Chimiche, Università di Catania, and INSTM, UdR Catania. Viale Andrea Doria n 5, I-95125 Catania, Italy. ABSTRACT We report the results of a recent study on the deposition of praseodymium oxides thin films on silicon substrates by Metal-Organic Chemical Vapor Deposition (MOCVD). A suited Pr(III) β-diketonate precursor has been used as the metal source and the deposition conditions have been carefully selected because of a large variety of possible PrO2-x (x= 0-0.5) phases. Pr2O3 films have been obtained in a hot-wall MOCVD reactor under non oxidising ambient at 750°C deposition temperature. The structural and morphological characteristics of Pr2O3 films have been carried out by X-ray diffraction (XRD) and high resolution transmission electron microscopy (TEM). Chemical compositional studies have been performed by X- ray photoelectron spectroscopic (XPS) analysis and a fully understanding of the MOCVD process has been achieved. Preliminary electrical measurements point to MOCVD as a reliable growth technique to obtain good quality praseodymium oxide based films.
INTRODUCTION The need for a higher dielectric constant replacement for silicon dioxide in order to sustain Si complementary-metal-oxide-semiconductor (CMOS) scaling is well documented [1]. It is desirable to employ a dielectric which exhibits an enhanced permittivity over that of SiO2, which remains physically and chemically stable during manufacturing processes and avoids the need for a reaction barrier at the interface. Therefore electrical and physical criteria for a material to be considered as a gate dielectric and the design requirements limit the list of potential candidates. The currently studied high k materials consist of oxides and alloys of the transition metals. Representative metal oxides include: column 4B materials such as ZrO2 and HfO2 and rare earth oxides such as Y2O3, La2O3, Gd2O3 and Pr2O3 [2-4]. Among the rare earth oxides, praseodymium oxide, Pr2O3, has not been extensively studied for microelectronic applications so far, despite of its high dielectric constant (ε=26-30) and middle band gap (3.9 eV) [5,6]. Moreover, Pr2O3 films with EOT of 1.4 nm have leakage current densities below 10-8 A/cm2 at Vg = +-1.0 V. This is at least 104 times lower than the best published values for HfO2 or ZrO2 films with the same EOT, and the leakage current of a 3 nm thick SiO2 layer. These data represents the principal advantage of Pr2O3 films over the other rare earth oxides. To date, few reports on MBE growth and pulsed laser deposition of PrO2 and/or Pr2O3 films on silicon substrates have appeared in literature [7-9]. Nevertheless, a large-scale film growth through Metal-Organic Chemical Vapor Deposition (MOCVD) would take advantages of
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