0167-9317/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2007.04.126 www.elsevier.com/locate/mee Microelectronic Engineering 84 (2007) 2263–2266 Effects of thermal treatments on chemical composition and electrical properties of ultra-thin Lu oxide layers on Si A. Zenkevich a,* , Yu. Lebedinskii a , S. Spiga b , C. Wiemer b , G. Scarel b , M. Fanciulli b a Moscow Engineering Physics Institute (state university), 115409 Moscow, Russia b National Laboratory MDM-CNR/INFM, Via C. Olivetti 2, 20041 Agrate Brianza (MI), Italy Abstract The correlation between chemical composition, layered structure evolution, and electrical properties of ultra-thin (2-5 nm) Lu oxide layers grown on chemically oxidized Si(100) and exposed to different thermal treatments was monitored by x-ray photoelectron spectroscopy, x-ray reflectivity and C-V, G-V measurements, respectively. These ultra-thin Lu 2 O 3 films in contact with Si are not stable against silicate formation upon both ultra high vacuum (UHV) annealing and rapid thermal processing (RTP) in N 2 atmosphere. A procedure to convert the Lu-silicate layer back to continuous Lu 2 O 3 oxide on Si using high-temperature UHV annealing was identified. Keywords: high- dielectrics; rare earth oxide; silicates; thermal stability 1. Introduction Among rare earth oxides, Lu 2 O 3 was proposed as a candidate to substitute SiO 2 in CMOS devices, since it has several advantages, in particular: i) wide band gap was measured on single crystals [1]; ii) a large conduction band offset (CBO) at the oxide/silicon interface [2]; iii) besides, Lu 2 O 3 has an unique oxidation state (equal to 3), which avoids mixed metal oxide stoichiometries with different Corresponding author. Tel.: +7 4953248419; fax: +7 4953242111 E-mail address: a.zenkevich@mephi.ru (A. Zenkevich) electronic structures; iv) for Lu the intrinsic high energy of the 5d shell and its low occupancy (only one electron) should, in principle, limit the density of interfacial traps in Lu 2 O 3 [3]. However, despite several advantageous properties [3,4], ultra-thin Lu 2 O 3 layers grown on Si(100) were predicted [5] and experimentally observed [6] to be thermodynamically unstable with respect to silicate formation. In this work, we investigate the effects of post deposition annealing on chemical composition and electrical properties of ultra-thin (2-5 nm) Lu oxide layers. Various thermal treatments in nitrogen and in ultra high vacuum (UHV), in the 300-950 °C