ELS EVI E R Thin Solid Films 380 (2000) 201-203 www.elsevier.com/locate/tsf Growth of patterned thin epitaxial CoSi,-films by a titanium oxide mediated epitaxy process P. Hutha>*, C. Detavernierb, Q.-T. Zhao”, J. Xu”, H.-P. Bochem”, St. Lenk”, S. Mantl” aInstitutfiir Schicht- und Ionentechnik (ISI-IT), Forschungszentrum Julich, 0-52425 Julich, Gemany bVakgroep Vaste Stof Wetenschappen,Laboratonum voor fistallograjie en Studie van de Vaste Stof; Universiteit Gent, Knjgslaan 281 / S1, B-9000 Gent, Belgium Abstract A new method for fabricating thin patterned CoSi, layers has been studied. The silicide layers were generated by a solid phase epitaxy process, in which Co and Ti were deposited on a thin chemical oxide on Si(100) substrates. Rapid thermal annealing (RTA) of this structure leads to the formation of epitaxial CoSi, with a capping layer on top. Two-step annealing in a forming ambient gas produces high quality epitaxial layers with a capping layer which can be easily removed by wet chemicals. A layer structure consisting of 30 nm SiO, and 300 nm Si,N,, which is patterned using conventional optical lithography and dry etching, induces a stress field into the underlying layers near the patterning edges. This leads to a formation of separated CoSi, layers during the silicide formation caused by the anisotropic diffusion of the atoms in the stress field. Such layers show nearly uniform gaps of approximately 100 nm in width. 0 2000 Elsevier Science B.V. All rights reserved. Keywords: Patterning; Silicide; Solid phase epitaxy; CoSi, 1. Introduction Due to its low resitivity, high scalability and good epitaxial alignment, CoSi, is well established as a con- tact and interconnect material in silicon technology. Epitaxial CoSi, , with its high thermal stability and sharp interface to the silicon substrate, provides better control of processing and improved electrical proper- ties than the widely used polycrystalline material. How- ever, epitaxial CoSi, cannot be formed by simple depo- sition and annealing on most silicon surfaces [l]. To overcome this problem, different methods for the for- mation of epitaxial CoSi, on silicon surfaces have been developed. Oxide-mediated epitaxy (OME) [2], titanium-interlayer-mediated epitaxy (TIME) [3], and * Corresponding author. Tel.: + 49-2461-61-4505; fax: + 49-2461- E-mail address: p.kluth@fz-juelich.de (P. Kluth). 61-4673. molecular beam allotaxy (MBA) [4,5] are some exam- ples. As the minimum feature sizes decrease to sub 100 nm dimensions, conventional optical lithography reaches its limits, and, therefore, alternative methods have to be applied. E-beam and ion-beam projection lithography seem to be the most promising candidates for replacing the current methods, though they have not yet proven their cost effectiveness and production maturity. Furthermore, no suitable gases for reactive ion etching (RIE) of CoSi, exist. However, the wide range of applications of nanopatterned silicides in mi- croelectronics require new and reasonably priced pat- terning methods. Recently we published a new self assembling pattern- ing method based on the local oxidation of silicide layers (LOCOSI) and application of local stress 161. There we used 20 nm epitaxial CoSi,-layers grown by molecular beam allotaxy (MBA) which were patterned into nanostructures with dimensions down to 50 nm. 0040-6090/00/$ - see front matter 0 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 0 - 6 0 9 0 ( 0 0 ) 0 15 0 4 - 2