Communications Polymeric Sacrificial Layers for the Control of Microstructure and Porosity of Oxide Thin Films Deposited by Plasma-Enhanced Chemical Vapor Deposition A. Barranco,* ,† J. Cotrino, †,‡ F. Yubero, † and A. R. Gonza ´ lez-Elipe † Instituto de Ciencia de Materiales de Sevilla and Departamento Quimica Inorga ´ nica, CSIC-Universidad de Sevilla, c/Ame ´ rico Vespucio s/n, 41092 Sevilla, Spain, and Departamento de Fı ´sica Ato ´ mica, Molecular y Nuclear, Facultad de Fı ´sica, Universidad de Sevilla, Avda. Reina Mercedes s/n, Sevilla, Spain Received January 23, 2003 Revised Manuscript Received June 29, 2003 Plasma-enhanced chemical vapor deposition (PECVD) is a well-known technique developed during the past decades for the deposition of thin films of oxides, polymers, metals, and so forth, and the treatment of surfaces. These films and plasma-based treatments have been successfully applied in fields such as microelec- tronics, the packaging industry, optical films, and biomaterials. 1-4 A new method for the control of the porosity and microstructure of oxide thin films deposited at room temperature by remote PECVD has been developed in our laboratory. The method is based in the removal of a sacrificial polymeric layer, which is deposited in the same reactor used for the deposition of the oxide film. This novel procedure is independent of the particular organometallic precursor employed for the deposition and, therefore, of the type of oxide. A critical requisite for this polymeric layer is that it is plasma-etched with a sufficiently high rate during the deposition of the oxide. This requires that the polymeric layer is easily and fully oxidized into volatile species. In this communication, we present some basic char- acteristics of these polymeric films and show several experimental results that illustrate the possibilities of their use for the preparation of porous oxide films. The reactor employed for the PECVD synthesis of both the polymeric and oxide materials is a remote microwave reactor that has been described in previous papers. 5-7 The polymeric films have been deposited using a plasma of toluene (5 sccm) and oxygen (20 sccm), controlling the pumping capacity of the chamber to achieve a final pressure of ∼1 Torr. The C 1s core level spectrum measured by X-ray photoelectron spectroscopy (XPS) of a polymeric film is shown in Figure 1a). The figure includes the fitting of the C 1s core level with different components that account for the different carbon functionalities of the film. 8 From the XPS analysis, the O/C ratio of the polymer thin film is 0.78 with 70% of carbon atoms in * To whom correspondence should be addressed. E-mail: angelbar@ cica.es. Tel: +34-954489528. Fax: +34-954460665. † Instituto de Ciencia de Materiales de Sevilla and Departamento de Quı ´mica Inorga ´ nica. ‡ Departamento de Fı ´sica Ato ´mica, Molecular y Nuclear. (1) Grill, A. Cold Plasma in Materials Fabrication; IEEE Press: Piscataway, NJ, 1994. (2) Yasuda, H. Plasma Polymerization; Academic Press: New York, 1985. (3) d’Agostino, R.; Favia, P.; Fracassi, F., Eds. Plasma Processing of Polymers; Kluwer Academic: Dordrecht, The Netherlands, 1996. (4) Gro ¨ning, P. Cold Plasma Processes in Surface Science and Technology. In Handbook of Thin Film Materials; Nalwa, H. S., Ed.; Academic Press: New York, 2001; Vol. 1, p 219. (5) Barranco, A.; Cotrino, J.; Yubero, F.; Espino ´ s, J. P.; Benı ´tez, J.; Clerc, C.; Gonza ´ lez-Elipe, A. R. Thin Solid Films 2001, 401, 150. (6) Cotrino, J.; Palmero, A.; Rico, V.; Barranco, A.; Espino ´s, J. P.; Gonza ´ lez-Elipe, A. R. J. Vac. Sci. Technol. B 2001, 19, 210. (7) Martin, A.; Espinos, J. R.; Justo, A.; Holgado, J. R.; Yubero, F.; Gonza ´ lez-Elipe, A. R. Surf. Coat. Technol. 2002, 151-152, 298. VOLUME 15, NUMBER 16 AUGUST 12, 2003 © Copyright 2003 by the American Chemical Society 10.1021/cm034023z CCC: $25.00 © 2003 American Chemical Society Published on Web 07/22/2003