Growth of Pr 2 O 3 layers by pulsed injection MOCVD
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Growth of Pr2O3 layers by pulsed injection MOCVD A. Abrutis1, A. Bartasyte1, A. Teiserskis1, Z.Saltyte1, P.K. Baumann2, M. Schumacher2, J. Lindner2, T. McEntee2 1 Vilnius University, Dep. of General and Inorganic Chemistry, 24 Naugarduko, LT-2006 Vilnius, Lithuania 2 AIXTRON AG, Kackertstr 15-17, 52072 Aachen, Germany ABSTRACT Praseodymium oxide Pr2O3 (and Pr6O11) layers were deposited by innovative pulsed injection MOCVD technique on Si(100) in the temperature range 400-750°C. Praseodymium 2,2,6,6-tetramethyl-3,5-heptanedionate dissolved in monoglyme (1,2-dimethoxyethane) or toluene was used as precursor material. The influence of deposition conditions on film composition, growth rate, crystallization and surface roughness has been investigated. The main parameters influencing film composition and properties were substrate temperature and partial oxygen pressure during deposition. The presence of molecular oxygen in the reactor leads to the growth of Pr6O11 as the most stable phase or its mixture with PrO2, while deposition in inert atmosphere (Ar, 2 torr) allows to obtain Pr2O3 films which were amorphous or crystalline depending on the deposition temperature. Crystallized (polycrystalline) Pr2O3 films can be obtained at the growth temperatures 650°C and higher, while crystalline Pr6O11 films grow starting 400°C. Ex-situ annealing (750°C, vacuum, 2 hours) of the amorphous Pr2O3 films leads to film crystallization. Step coverage study has been performed for amorphous and crystallized Pr2O3 films. Electrical properties of thin (~10 nm) Pr2O3 films were investigated and encouraging EOT (equivalent oxide thickness), leakage current data have been obtained.
INTRODUCTION The continuous scaling down of CMOS technology forces to look for new high k-dielectrics to replace the SiO2 gate [1]. Replacing gate insulator should satisfy requirements such as high k value, low leakage current, high breakdown strength, high thermal stability on silicon, etc. Currently various metal oxides are investigated as alternative dielectrics. However, it is difficult to find an oxide satisfying all requirements. For example, HfO2, ZrO2, Ta2O5 have rather high k values but react with silicon [2]. On the contrary, Al2O3 is thermally stable on Si but has small dielectric constant compared to other high-k oxides. Recently, Pr2O3 has attracted attention due to their good dielectric properties and compatibility with conventional CMOS process [3-6]. Up to now, mainly physical deposition techniques such as molecular beam epitaxy and pulsed laser deposition have been used for the deposition of Pr oxide films. [7-10]. A shortcoming of these techniques is reduced step coverage, which is necessary in CMOS technology adopting three-dimensional high-k structures. More suitable for these purposes is chemical vapor deposition technique. To date, only very little has been reported on the use of MOCVD technique for the growth of Pr2O3 films on silicon [11,12]. In these reports low leakage current (~10-7 A/cm2 at 1 V) has been obtained in 44 nm thick fi
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