Thermal stability studies for advanced Hafnium and Zirconium ALD precursors Simon Rushworth ⁎ , Kathleen Coward, Hywel Davies, Peter Heys, Thomas Leese, Louis Kempster, Rajesh Odedra, Fuquan Song, Paul Williams Epichem Limited, Power Road, Bromborough, Wirral, CH62 3QF, UK Available online 25 April 2007 Abstract The development of novel precursors for advanced semiconductor applications requires molecular engineering and chemical tailoring to obtain specific physical properties and performance capabilities. Having identified promising avenues in ligand design, the first priority when isolating a new compound is to ensure that when used it is safe and will not cause detrimental effects in deposition equipment due to thermal decomposition. We have employed different techniques to study the physical properties and stabilities of highly promising Hafnium and Zirconium compounds particularly suited to the Atomic Layer Deposition technique for fabrication of state-of-the-art metal oxide layers for both logic and memory semiconductor devices to ensure that they may be employed safely. In particular mixed alkyl/alkoxide and alkylcyclopentadienyl substituted compounds [(MeCp) 2 M(OMe) x Me 2 − x M = Hf and Zr x = 0 or 1] were compared to conventional alkylamine sources (M(NEtMe) 4 M = Hf and Zr). The use of thermogravimetric analysis (TGA) to determine evaporation rates under a variety of conditions is employed to determine initial temperature regimes where decomposition may occur. More detailed studies using Nuclear Magnetic Resonance (NMR) are then conducted at fixed temperatures over a prolonged time period with regular monitoring to establish degradation effects more accurately. Our studies show similar trends between both Hf and Zr materials with the Zr derivatives less stable in all cases. Operation temperatures required to achieve suitable vapour transport in the case of MeCp 2 ZrMe 2 have been found to lead to catastrophic decomposition after a relatively short time thus negating the usefulness of this precursor in a production environment. All other sources were deemed safe to employ under standard process conditions. © 2007 Elsevier B.V. All rights reserved. PACS codes: 61.18.Fs; 81.70.Pg; 82.33.Ya Keywords: ALD; High-K; Precursors; Stability; TGA; NMR 1. Introduction In the search for high permittivity layers to replace SiO 2 as the gate dielectric material in 45 nm complementary metal oxide semiconductor technology (CMOS) thin films of Zirconium dioxide (ZrO 2 ) and Hafnium dioxide (HfO 2 ) have been identified as promising candidates [1,2]. Atomic Layer Deposition (ALD) is an attractive technique for the deposition of these materials in a controlled fashion to yield good composition control and film uniformity, and excellent conformal step coverage on nonplanar device geometries [3]. Conventional alkylamide precursors used in this technology [4] present performance limitations due to insufficient thermal stability and subsequent low growth Surface & Coatings Technology 201 (2007) 9060 – 9065 www.elsevier.com/locate/surfcoat ⁎ Corresponding author. Tel: +44 151 334 2774; fax: +44 151 334 6422. E-mail address: RushworthS@epichem.co.uk (S. Rushworth). Fig. 1. TGA measurements for a) MeCp 2 Hf(OMe)Me (HfD-04) b) MeCp 2- HfMe 2 (HfD-02) c) Hf(NEtMe) 4 (HfEMA) d) MeCp 2 Zr(OMe)Me (ZrD-04) b) MeCp 2 ZrMe 2 (ZrD-02) c) Zr(NEtMe) 4 (ZrEMA). 0257-8972/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2007.04.050