Ž . Applied Surface Science 154–155 2000 382–386 www.elsevier.nlrlocaterapsusc Deposition and annealing of tantalum pentoxide films using 172 nm excimer lamp Jun-Ying Zhang ) , Boon Lim, Ian W. Boyd Electronic and Electrical Engineering, UniÕersity College London, Torrington Place, London WC1E 7JE, UK Received 1 June 1999; accepted 14 July 1999 Abstract Ž . We report the growth of thin tantalum pentoxide films on Si 100 by photo-assisted chemical vapor deposition Ž . Ž U . photo-CVD from a tantalum ethoxide source using an excimer lamp Xe , 172 nm . The effects of substrate temperature 2 Ž . and ultraviolet UV annealing on the film formed have been studied using ellipsometry and Fourier transform infrared Ž . spectroscopy FTIR measurements. The FTIR spectra reveal suboxide formation in the as-deposited films that disappeared Ž . after subsequent UV annealing. The electrical properties of the films were determined by capacitance–voltage C– V and Ž . current–voltage I – V techniques on AlrTa O rSi metal oxide semiconductor structures. The I – V characteristics of both 2 5 as-deposited and annealed films can be described by the Fowler–Nordheim tunneling mechanism. Dielectric constant values of about 24 were readily achievable in the as-deposited films that are comparable to those obtained by other techniques. q 2000 Published by Elsevier Science B.V. All rights reserved. PACS: 42 P 72 P qh; 61.80.Ba; 81.60.Cp; 85.50.Na Keywords: Photo-CVD; Excimer lamp; UV annealing; Thin Ta O film; Dielectric constant 2 5 1. Introduction Ž . As dynamic random access memories DRAMs are scaled down, the thickness of their gate oxides must be correspondingly reduced and thickness con- trol becomes a critical issue. For 0.1-mm technology and beyond, the necessity for a high gate dielectric constant k, to avoid excessive direct tunneling of the current through the SiO as the thickness is scaled 2 ) Ž. Corresponding author. Tel.: q 44- 0 171-419-3196; fax: q 44- Ž. 0 171-387-4350. Ž . E-mail address: jzhang@ee.ucl.ac.uk J.-Y. Zhang . below 2.0 nm has been identified. Recently, high dielectric constant materials such as PbZr Ti O x 1yx 3 Ž . Ž . PZT , Ta O , Ba Sr TiO BST , and TiO have 2 5 x 1yx 3 2 been extensively investigated. Among these di- Ž . electrics, tantalum pentoxide Ta O appears to be 2 5 one of the best candidates for replacing SiO be- 2 cause of its compatibility with ultra-large-scale-in- Ž . w x tegrated ULSI processing 1–4 . A variety of tech- w niques have been used to deposit Ta O films 2,4– 2 5 x 7 . To date, however, the large leakage current in as-deposited films remains a problem to be over- come. Various post-deposited annealing techniques w x have been proposed to reduce this 5,6,8,9 and it has Ž . been recognized that ultraviolet UV annealing is 0169-4332r00r$ - see front matter q 2000 Published by Elsevier Science B.V. All rights reserved. Ž . PII: S0169-4332 99 00387-6