Study of nitrogen-rich silicon oxynitride films obtained by PECVD D. Criado * , I. Pereyra, M.I. Alayo LME, EPUSP, University of Sa ˜o Paulo, CEP 5424-970, CP61548 Sa ˜o Paulo, SP, Brazil Received 15 January 2003; accepted 30 March 2003 Abstract The results of the fabrication and characterization of silicon oxynitride films deposited by the plasma-enhanced chemical vapor deposition (PECVD) technique at low temperature and from N 2 ,N 2 O and SiH 4 gaseous mixtures are reported herein. It is shown that high nitrogen concentration films with characteristics close to stoichiometric silicon nitride (Si 3 N 4 ) can be obtained. In previous experiments utilizing N 2 O and SiH 4 as precursor gases, it was demonstrated that precise control of the refractive index for silicon dioxide-like oxynitride SiO x N y (x + y = 2) material in the 1.46 (SiO 2 ) to 1.57 range can be attained. In this study, nitrogen gas (N 2 ) was added to the previously studied gaseous mixture. In this way, it was possible to control the refractive index from 1.46 (SiO 2 ) to f 2 (Si 3 N 4 ) through the appropriate choice of the deposition parameters. The films were characterized by profilometry, ellipsometry, Rutherford backscattering spectroscopy (RBS) and Fourier transform infrared spectroscopy (FTIR). D 2003 Elsevier Inc. All rights reserved. Keywords: Silicon oxynitride; Silicon nitride; Plasma-enhanced chemical vapor deposition 1. Introduction Within the last decade, chemical vapor deposition (CVD)-grown silicon oxynitride thin films have be- come increasingly important for application in low- cost, compact, integrated optical devices. The major advantage of SiO x N y is given by the tunability of its refractive index over a wide range (n = 1.45–2), resulting in a large degree of freedom for integrated optics design [1,2]. The plasma-enhanced chemical vapor deposition (PECVD) technique is attractive because of the possibility of working with relative high deposition rate and low deposition temperature (300 – 400 jC), so that it is compatible with the well-estab- lished microelectronic processing [3]. Furthermore, this technique permits the control of the structural, mechanical and optical properties of the deposited films by adjusting the deposition parameters. Silicon oxynitride films (SiO x N y ) grown using the PECVD technique have been studied for many appli- cations in the microelectronics and optoelectronics industry, i.e. as passivating coatings, thin gate dielec- trics, as well as membranes and optical waveguides for micromechanical systems (MEMS) [4]. Control- ling the flows among the gases permits SiO x N y films with different silicon, oxygen and nitrogen concen- trations to be obtained [5], and thus properties as refractive index [3] and mechanical stress [6], dielec- tric constant and optical gap can be controlled. 1044-5803/$ - see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S1044-5803(03)00075-5 * Corresponding author. Tel.: +55-11-3091-5256; fax: +55-11- 3091-5585. E-mail address: dcriado@lme.usp.br (D. Criado). Materials Characterization 50 (2003) 167 – 171