Evidence of coexistence of micro and nanoporosity of organo-silica polymeric films deposited on silicon by plasma deposition Viswas Purohit a, * , Ela Mielczarski a , Jerzy A. Mielczarski a , Laurent Akesso b a Laboratoire Environnment et Mineralurgie, UMR 7569 CNRS, INPL-ENSG, BP.40, 54501 Vandoeuvre-les-Nancy, France b Teer Coatings Ltd., Droitwich, Worcestershire WR9 9AS, UK highlights  Hybrid organo-polymer silicon films deposited by RF plasma on silicon substrates.  FTIR and XPS reveal porosity by interpreting bonding between Si and eO.  Quantification of nano & microporosity are identified with bonding of Si with eO. article info Article history: Received 29 September 2012 Received in revised form 7 April 2013 Accepted 26 April 2013 Keywords: Microporous materials Polymers Plasma deposition FTIR XPS abstract A range of hybrid, SiOCH films were deposited on silicon substrates within a radio frequency plasma reactor using hexamethyldisiloxane (HMDSO) as a precursor. The plasma polymerized films were deposited at various HMDSO/argon/oxygen ratios. The composition and structure, at microscopic and nanoscopic levels, of the deposited films were determined by external reflection and transmission Fourier Transform Infrared (FTIR) spectroscopy as well as by X-Ray Photoelectron Spectroscopy (XPS). The content of carbon and oxygen in films were found to be inversely proportional to each other. XPS results showed that the outermost surface of the deposited films are nanoporous and coexist with microporosity which was revealed by electron microscopy. The structure of deposited coatings is anisotropic as was documented by polarized external reflection FTIR spectroscopy. Several correlations between the film chemical composition, surface structure, and macroscopic properties of the films such as: hydrophobicity and hydrophilicity were established. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Polymeric organiceinorganic materials have emerged in the recent years as very promising candidates for advanced electronic devices [1,2]. The main concern of advanced electronics, namely Ultra Large Scale Integration (ULSI) manufacturing industries is the minimization of the RC-based electrical delay (R, the resis- tance of the metal lines; C, the line capacitance). In order to maintain good interconnect performance, power consumption, the delay time and parasitic crosstalk level need to be decreased as much as possible. This is achieved by using porous films in electronic devices whose porosity is tunable between micro and nano levels. It is of interest that such type of organiceinorganic hybrid materials are also a source for novel applications like antifouling coatings [3]. The incorporation of carbon and hydrogen in the silicon matrix was found to be a crucial element in the decrease of the silicon oxide dielectric constant. The ability of these materials to modify the local structure of silicon oxide gives rise to low density mate- rials, i.e., the replacement of SieO with SieCH 3 , causes porosity due to the formation of voids of nanodimensional sizes within the sil- icon oxide matrix [4]. The attachment of methyl groups to the sil- icon oxide based matrix, induces pores (free volume) through the breaking of the SieO network formation. This in turn decrease the permittivity leading to the creation of ultra low k dielectrics also called as porous carbon doped hydrogenated silicon dioxide (SiOCH). These glassy alloy material containing Si, O, C and H atoms are obtained by Plasma Enhanced Chemical Vapor deposition (PECVD) technique on the desired substrate. The structural properties and porosity of the produced SiOCH materials deposited by PECVD method depends on the type of precursors used [4e7]. The value of the dielectric constant in * Corresponding author. Present address: Symbiosis Institute of Technology, Symbiosis InternationalUniversity, Lavale, Mulshi, Pune 411042, India. Tel.: þ91 20 39116300; fax: þ91 20 39116460. E-mail address: vishwas.purohit@gmail.com (V. Purohit). Contents lists available at SciVerse ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys 0254-0584/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matchemphys.2013.04.040 Materials Chemistry and Physics 141 (2013) 602e612