Thin Solid Films 425 (2003) 68–71 0040-6090/03/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII:S0040-6090 Ž 02 . 01306-8 Hafnium silicate formation by ultra-violet y ozone oxidation of hafnium silicide P. Punchaipetch, G. Pant, M. Quevedo-Lopez, H. Zhang, M. El-Bouanani, M.J. Kim, R.M. Wallace, B.E. Gnade* Department of Materials Science, University of North Texas, Denton, TX 76203, USA Received 9 July 2002; received in revised form 11 October 2002; accepted 10 December 2002 Abstract We report the room temperature growth of hafnium silicate by ultra-violetyozone oxidation of hafnium silicide. Hafnium silicide was deposited by magnetron sputtering on hydrogen terminated (100) Si. The film was then exposed to UV radiation while in an O ambient. Hafnium silicate films are obtained with no detectable SiO interfacial layer as characterized by X-ray 2 x photoelectron spectroscopy and high-resolution transmission electron microscopy.  2002 Elsevier Science B.V. All rights reserved. Keywords: Dielectrics; Hafnium; Oxidation; X-ray photoelectron spectroscopy (XPS) 1. Introduction The continuous reduction in metal oxide semi- conductor field effect transistor dimensions results in the need for an alternate gate dielectric to SiO w1x. The 2 requirements for higher permittivity (k), minimal low-k interfacial layer, low leakage current and high thermal stability in direct contact with silicon have made hafni- um silicate a promising replacement for SiO w2–4x. 2 Hafnium silicate (;6 nm) deposited by reactive sputtering of a hafnium silicide target at room tempera- ture, using Ar and O as the sputter gases (ratio 1:2) 2 results in a distinct SiO layer formation at the interface. x The formation of interfacial low-k layers on silicon during reactive sputtering and chemical vapor deposition has been reported w5,6x. The kinetics of formation of these layers has also been studied w7x. The relatively low permittivity material at the interface dominates the overall capacitance of the dielectric film and limits the minimum achievable equivalent oxide thickness (t ) eq w8x. Extensive studies have been carried out on the ultra violet (UV) yozone (O ) oxidation of silicon w9x. 3 *Corresponding author. Tel.: q1-940-565-3333; fax: q1-940-565- 4824. E-mail address: gnade@unt.edu (B.E. Gnade). Recently, studies on high quality zirconia formation by UVyO oxidation of zirconium have been reported by 3 Ramanathan et al. w10–12x. Thermal oxidation of metals sputtered directly on silicon to form high-k oxides has shown silicide formation at the interfaces w6,12x. Cham- bers and Parsons have reported that stable metal silicides also have a high affinity for oxygen w13x. In this letter, we report the growth of hafnium silicate films by UVy O oxidation of hafnium silicide to minimize the for- 3 mation of a distinct low-k interfacial layer. 2. Experimental details For all depositions, n-type (100) Si wafers (resistiv- ity between 0.01 and 0.02 V cm) were cleaned using a modified RCA cleanup followed by a 1% HF last to provide a clean hydrogen terminated surface w14x. The wafers were introduced in a high vacuum chamber at a base pressure of 1=10 mbar. Hafnium silicide was y8 deposited with the substrate at room temperature by magnetron sputtering of a hafnium silicide target using an Ar carrier gas (50 W power, 17 mbar Ar gas pressure) at a rate of 1 nmymin. This hafnium silicide film was transferred in vacuo to an adjacent high vacuum chamber, which was then backfilled with O to a partial pressure of 533 mbar. 2