Full Paper Deposition of Thin Films of SiO x C y H in a Surfatron Microwave Plasma Reactor with Hexamethyldisiloxane as Precursor** By Agnieszka Walkiewicz-Pietrzykowska, JosØ Cotrino, and Agustin R. Gonzµlez-Elipe* Thin films of SiO x C y H have been prepared by plasma enhanced (PE)CVD in a surface-wave, microwave reactor. The films were deposited in direct mode by using hexamethyldisiloxane (HMDSO) as the precursor, and mixtures of oxygen/argon as the plasma gas. Analysis of the plasma by optical emission spectroscopy (OES) showed that, under reaction conditions, the molecules of the precursor are not greatly fragmented in the plasma. This suggests that polymerization occurs after adsorption oftheprecursorspeciesonthesurfaceofthegrowingfilms.Thechemicalstructureandcompositionofthefilmswereexamined byFourier-transforminfrared(FTIR)spectroscopyandX-rayphotoelectronspectroscopy(XPS).Astrongcorrelationisfound between the composition and bonding structure of the thin films and the oxygen:HMDSO ratio in the plasma gas. Raising the oxygen concentration leads to an increase in the growth rate and to the removal of the organic groups from the films that, forO 2 :HMDSOratiosgreaterthan0.8,reachacompositionclosetosilicondioxide.IthasbeenshownthattheAugerparameter of silicon determined by XPS depends on the composition of the films (e.g., 1714.5 for O 2 :HMDSO = 0, and 1712.3 for O 2 :HMDSO = 0.75). It is shown that this parameter can be taken as a measurement of the polarizability of the films. It is concluded that surfatron launchers are a versatile set-up for an efficient control of the composition and properties of thin films of SiO x C y H prepared by PECVD. Keywords: Auger parameter, HMDSO, SiO x C y H thin films, Surfatron PECVD, XPS 1. Introduction Thin films of SiO 2 and silicon oxycarbide (SiO x C y H) have found many applications in microelectronics, [1,2] op- tics, [3] as protection layers, [4±6] gas filtering membranes, [7] or as biocompatible materials. [8] Over recent years, PECVD has become one of most important techniques for the production of silicon dioxide and silicon oxycarbide thin films. [9] Among the variety of existing PECVD methods, direct plasma [10] is a versatile procedure that offers both relatively high growth rates and the ability to deposit films on different substrates at low temperature. Hazardous mixtures of silane (SiH 4 ) with an oxidizer (O 2 ,O 3 , or N 2 O), and hydrocarbons (CH 4 ,C 2 H 4 , C 2 H 2 ) have been extensively applied for the preparation of SiO 2 and SiO x C y H films under direct plasma condi- tions. [3,11] A safer and simpler alternative is the use of organosilicon precursors. In their structure these chemicals bear O±Si±C bonds which, in this way, can be readily incor- porated into the film. Perhaps the most common and widely utilized organosilicon single-source precursor is hexamethyldisiloxane (HMDSO, O-(Si(CH 3 ) 3 ) 2 ), [3±7,12±14] a product that is non-explosive, non-flammable, non-toxic, and relatively cheap. In the present work we describe the use of a microwave (MW) surfatron device as a launcher to induce a surface wave plasma CVD process to obtain SiO x C y H films with controlled composition. Surface wave discharges can be achieved in the tubes of various configurations and shapes, and this technology has been used for the deposition of thin films of materials such as amorphous silicon, diamond, or polymers. [15] On the other hand, surfatrons are well-known surface wave devices that provide a high plasma density at relatively low microwave power. [16] Here we report the preparation of thin films of SiO x C y H by PECVD using this launcher and HMDSO as the precursor. The structure and chemical composition of the SiO x C y H films have been investigated by FTIR and XPS. OES has been used for plasma diagnostics. The main aim of this work is to check the viability of a surfatron system for deposition of this type of thin film. The analysis of the deposition conditions and the characterization of this process is also addressed in this study. The second objective is to prepare thin films of SiO x C y H with controlled compositions and structures using a HMDSO precursor. Chem. Vap.Deposition 2005, 11, 317±323 DOI: 10.1002/cvde.200506374  2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 317 ± [*] Prof. A. R. Gonzµlez-Elipe, Dr. A. Walkiewicz-Pietrzykowska, J. Cotrino InstitutodeCienciadeMaterialesdeSevilla(CSIC-Univ.deSevilla)and Dpts. Química Inorgµnica and Física Atómica, Molecular y Nuclear Avda. AmØrico Vespucio s/n, E-41092 Sevilla (Spain) E-mail: arge@icmse.csic.es Dr. A. Walkiewicz-Pietrzykowska Centre of Molecular and Macromolecular Studies Polish Academy of Sciences Sienkiewicza 112, PL-90-363 Lodz (Poland) [**] We thank the Spanish Ministerium of Science and Education (SMSE) (MAT2004-01558) for financial support. AWP acknowledges a post- doctoral grant of SMSE for one year stay in the ICMSE.