Thin Solid Films 460 (2004) 291–294 0040-6090/04/$ - see front matter  2004 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2004.01.050 Room temperature indium tin oxide by XeCl excimer laser annealing for flexible display Wonsuk Chung *, Michael O. Thompson , Paul Wickboldt , Daniel Toet , Paul G. Carey a, a b b b Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14850, USA a FlexICs, Inc., 165 Topaz Street, Milpitas, CA 95035, USA b Received 10 June 2003; received in revised form 24 November 2003; accepted 7 January 2004 Abstract A XeCl excimer laser (ls308 nm) has been used to anneal Indium Tin Oxide (ITO) films deposited at 25 8C using DC magnetron sputtering. With increasing laser fluence, the film crystallinity was improved while retaining the as-deposited N111M texture. As a result of laser irradiation, the sheet resistance of 100 nm ITO films decreased from 191 Vyh (1.91=10 V cm) y3 to 25 Vyh (2.5=10 V cm), while the optical transmittance in the visible range increased from 70% to more than 85%. y4 Surface roughness and etching properties were also significantly improved following laser annealing.  2004 Elsevier B.V. All rights reserved. Keywords: Indium tin oxide; Excimer laser; Annealing 1. Introduction Indium tin oxide (ITO) is widely used as a transparent conducting electrode in display and sensor applications w1x. There has been considerable effort expended to optimize deposition conditions to achieve low resistivity while maintaining high optical transmittance. With new applications in flexible circuits, it is now necessary also to maintain a low thermal budget to ensure compatibility with polymeric substrates. Materials such as polyethyl- ene terephthalate (PET) or poly-ethersulfone (PES) are being considered for both LCD and OLED based dis- plays w2–5x. Plastic substrates pose two distinct chal- lenges. First, ITO is often annealed to achieve both low resistivity and transparency, but plastics limit static annealing to temperatures between 100 and 150 8C. Second, the properties of ITO are found to be influenced by the substrate materials, with substantially poorer properties on polymeric films w6x. Thus it is necessary to develop a low thermal budget annealing procedure for ITO compatible with polymeric substrates. Excimer laser annealing has been previously used to fabricate thin-film-transistors on plastic substrates. By *Corresponding author. Tel.: q1-408-7124750; fax: q1-408- 2623880. E-mail address: wc58@cornell.edu (W. Chung). using a suitable barrier layer, such as a thick SiO film, 2 the silicon layer can be annealed to temperatures exceed- ing the melting point of Si (1683 K) without damaging the polymer substrate w7x. Motivated by this result, we have investigated 308 nm excimer laser annealing of ITO as a potential means of annealing room temperature deposited ITO films on polymer substrates. This work focuses on the ITOylaser interaction and is initially based on films deposited on glass substrates. Electrical, optical and chemical etching characteristics of excimer laser annealed ITO films are reported here. 2. Experimental details ITO films (100 nm thick) were deposited at 25 8C on 100 mm Corning 1737 glass substrates by DC magnetron sputtering. Sputtering was performed in a 5=10 Torr argon only gas ambient with 50 W source y3 power on a In O :SnO (90:10 wt.%) ceramic target. 2 3 2 These deposition conditions were optimized for mini- mum sheet resistivity and maximum optical transparency following laser irradiation. In general, lower pressures and powers yielded better films, consistent with lower deposition rates. Samples were subsequently annealed in air using a 10=10 or 4=4 mm spatially homoge- 2 nized XeCl excimer laser (ls308 nm, 35 ns pulse