Preparation of α-FeSi 2 by laser annealing Jinmin Zhang, Quan Xie ⁎, Ping Yu, Qingquan Xiao, Yong Zhang, Ziyi Yang, Yan Liang College of Electronic Science and Information Technology, Guizhou University Guiyang, 550025, Guizhou, PR China ABSTRACT ARTICLE INFO Article history: Received 20 January 2007 Received in revised form 21 May 2008 Accepted 16 June 2008 Available online 21 June 2008 Keywords: Magnetron sputtering Laser annealing X-ray diffraction Scanning electron microscopy Fe films were deposited on both heated and not-heated Si (100) substrates using direct current magnetron sputtering, and were subsequently annealed by pulsed laser with various laser energy densities. Direct formation of single-phase α-FeSi 2 was confirmed using X-ray diffraction and the surface morphology of films was characterized by scanning electron microscopy. The results show that the crystallinity of the films deposited at room temperature is improved with increasing laser energy densities, while the crystallinity of the films deposited on heated substrates is improved with increasing substrate temperatures. For the samples deposited at the room temperature, the optimal laser energy density for the formation of α-FeSi 2 is 0.95 J cm - 2 . © 2008 Elsevier B.V. All rights reserved. 1. Introduction The iron silicides have been the interest of research in the recent years for their potential applications in the silicon-based integrated circuits and photo-electronic devices [1–5], as well as the abundance of their raw materials in natural resources and their non-toxicity [6]. Fe– Si system has many specific phases according to its phase diagram [7,8]. There are at least two distinguished phases in the region of the disilicide composition: high temperature α-FeSi 2 with tetragonal structure and low temperature β-FeSi 2 with orthorhombic structure. Most iron silicides are metallic except β-FeSi 2 and monosilicide FeSi which are semiconducting [9–12]. Though most of researchers are interested in semiconducting β-FeSi 2 , one should be noticed that metallic α-FeSi 2 may have practical applications in the circuits or devices based on β-FeSi 2 . Since the bulk α-FeSi 2 has electric resistivity as low as 2.5×10 - 4 Ω cm, it can be used as an electrode or interconnection [13] of a β-FeSi 2 based device, and then the process of electrode or interconnection formation can be greatly simplified. The transition temperature from β to α-phase is 1210 K, however, some researchers reported that they got α-phase in the low temperature by epitaxial growth [14,15]. As an alternative to conventional furnace thermal processing, laser annealing (LA) [16] was recently demonstrated to be suitable for forming various kinds of films. Datta et al. [17] and Wagner et al. [18] prepared β-FeSi 2 using LA from Fe/Si structures deposited by electron beam evaporation or pulse laser deposition. Otogawa et al. [13] used α-FeSi 2 layer prepared by LA from β-FeSi 2 as an electrode and con- firmed that α-FeSi 2 had good ohmic contact with β-FeSi 2 . Motivated by these results, we demonstrates the possibility to anneal the Fe film deposited by magnetron sputtering on both heated and not-heated silicon (100) substrate to form high temperature phase α-FeSi 2 directly. The formation of α-FeSi 2 was confirmed by X-ray diffraction (XRD) and the surface morphology was characterized by scanning electron microscope (SEM). 2. Experimental details Two groups of Fe films (about 50 nm thick) were deposited on Si (100) substrates (p-type, 7–13 Ω cm) by direct current magnetron sputtering at room temperature or the temperatures range from 673 to 773 K. The base pressure was 2.0 × 10 - 5 Pa. In all case, the sputtering was performed in a 2.0 Pa argon gas ambient with about 100 W source powers on a pure iron (99.95%) target for 10 min, respectively. Under the preparation conditions, the rate of Fe film deposited on Si (100) was 5 nm/min for all samples. After deposition, samples were subsequently annealed in air using a diode-pumping laser YAG (λ =1.06 μm and 140 ns pulse duration). The laser energy density was tuned from0.11 to 2.25 J cm - 2 and the nearest scanning distance was 10 μm. The first group of samples was deposited at room temperature with the same preparation conditions and was followed by LA with laser energy densities: 0.11, 0.27, 0.30, 0.95 and 1.60 J cm - 2 , respectively. The second group of samples was deposited on heated substrates at temperatures of 673, 728, 753 and 773 K and was followed by LA with the same laser energy density 2.25 J cm - 2 . As a comparison, the third group of samples was deposited at room temperature but annealed for 1 h at temperature of 1223,1273, 1323 and 1373 K in the diffusion furnace with Ar ambient. The crystallinity Thin Solid Films 516 (2008) 8625–8628 ⁎ Corresponding author. Tel./fax: +86 851 3623248. E-mail address: quanxiegz@gzu.edu.cn (Q. Xie). 0040-6090/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2008.06.048 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf