Influence of Ar gas flow rate in organosilicon plasma for the fabrication of SiO:CH thin films by PECVD method Yongsup Yun a, ⁎, Takanori Yoshida b , Norifumi Shimazu b , Naoki Nanba b , Yasushi Inoue a , Nagahiro Saito b , Osamu Takai a a EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan b Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan ABSTRACT ARTICLE INFO Available online 6 June 2008 Keywords: Binder film of nano-cluster XPS FT-IR OES Water contact angle SiO:CH films were prepared by capacitively coupled RF PECVD to investigate the dependence on Ar gas flow ratio based on plasma reactions and film properties. The introduced Ar gas flow rate increases an the amorphous carbon network, and dangling bonds or –OH terminations due to Ar ion bombardment. Moreover, Ar gas flow rate alters the dissociation reactions and leads to change the chemical bonding states and the water contact angle. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Plasma-enhanced chemical vapor deposition (PECVD) using organo- silicon reactants has been studied for the last few decades as a low- temperature deposition process of silicon oxide (SiO x ) films [1–3], and novel functional films have been proposed by PECVD, such as SiOF films for its dielectric properties, SiON for its mechanical properties, and SiO:CH films for its ultra-water repellent as well as dielectric properties [4–9]. As applications of these SiO:CH films, Takai laboratory has been succeeded in fabricating ultra-ultra water-repellent (UWR) films, with a water contact angle greater than 150°, at room temperature by PECVD [8–9], and S. Nunomura et al. proposed nano-cluster composite porous films having a dielectric constant of 1.7 - –3.5 [11]. According to these reports, these films are deposited with agglomerates of nano-clusters which formed in Ar- organosilicon plasma, and these agglomerates are bound by SiO:CH films [12]. Moreover, it is important to investigate the formation process of the SiO:CH thin films on substrates in order to fabricate those high performance films. In this study, we investigated the SiO:CH films as a binder material of agglomerates. Except the bonding process of agglomerates and SiO:CH films, formation mechanism of SiO:CH films with varying Ar gas flow rate was considered. On the basis of the deposition rate, chemical composition, chemical bonding state and optical emission spectroscopy, we discussed the influence of Ar gas flow rate in the Ar-trimethylmethoxysilane (TMMOS) plasma. 2. Experimental This work was carried out with a capacitively coupled RF PECVD system. As shown in Fig. 1 , the PECVD system consists of a deposition chamber with a height and diameter of 200 and 300 mm, respectively, a power supply system, a vacuum system, and gas supply lines. A 13.56 MHz generator (Astec Co. Ltd., R-300) supplied the RF power into the lower electrode through a matching network in order to activate the discharge. N-type Si (100) substrates were located on the upper electrode in order to avoid ion impact by negative self-self bias voltage and attachment of dusty particles produced in the chamber. The Surface & Coatings Technology 202 (2008) 5259–5261 ⁎ Corresponding author. Tel.: +81 52 789 2796; fax: +81 52 789 5941. E-mail address: ysyun@nagoya-u.jp (Y. Yun). Fig. 1. The schematic diagram of the capacitively coupled RF PECVD system. 0257-8972/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2008.06.004 Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat