Thermal stability and bonding configuration of fluorine-modified low-k SiOC:H composite films Shiu-Ko JangJian a,b , Chuan-Pu Liu a , Ying-Lang Wang b, * , Weng-Sing Hwang a , Wei-Tsu Tseng a,1 a Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan b Taiwan Semiconductor Manufacturing Company Ltd., Tainan, Taiwan Available online 11 September 2004 Abstract Fluorine-modified organosilicate glass (F-SiOC:H) and unmodified organosilicate glass (OSG) films were deposited for comparison at various temperatures (200–400 8C) by plasma enhanced chemical vapor deposition (PECVD) method using mixed precursors of tetrafluorosilane, trimethelysilane and oxygen. Subsequently, the films were investigated by examining bonding configuration, index of refraction, surface composition, hardness, leakage current density and breakdown field strength with various annealing cycles, where each cycle represents annealing at 400 8C for 30 min followed by cooling to room temperature. The absorption spectra of Fourier transform infrared (FTIR) spectroscopy show that the frequency of Si–O stretching vibration mode in the as-deposited F-SiOC:H films shifted to higher wave number (blueshift) with fluorine incorporation compared with the OSG films, while that shifted to lower wave number (redshift) upon annealing. The FTIR results also show the reduction of fluorine and methyl group upon annealing, which coincided with X-ray photoelectron spectroscopy (XPS) analysis. The dielectric constant of the annealed F-SiOC:H films is higher than that of the as-deposited films. However, this is still lower than the annealed OSG films. The higher hardness and breakdown voltage strength were achieved in the F-SiOC:H films due to fluorine introduction and more perfect network structures. Comparing these results to those obtained OSG films shows that the mechanical and electrical strength of the F-SiOC:H films was improved by introducing of fluorine incorporation and annealing treatment, while maintaining or lowering a dielectric constant. D 2004 Elsevier B.V. All rights reserved. Keywords: Thermal stability; Bonding configuration; F-SiOC:H 1. Introduction Copper and low dielectric constant (low-k ) materials in replace of conventional aluminum and SiO 2 , respectively, as new interconnect and inter-metal-dielectric (IMD) layers have been widely employed in order to reduce resistance– capacitance (RC) time delay as the feature size in ultra-large scale integrated circuits (ULSI) is shrunk into submicron. Although the International Technology Roadmap for Semi- conductors (ITRS) has suggested that IMD dielectric materials should reach a dielectric constant of 1.6–2.2 by 2005 to fulfill the specific performance targeted by Moore’s Law since 1999 [1], the progress has been much less successful [2,3] despite the prevalence of copper intercon- nects in today’s advanced semiconductor devices. Among all the developing lower-k materials, carbon-doped oxides or organosilicate glass (OSG, SiCO:H) have become the major candidates for the potential applications beyond 130- nm device node. It has been shown that organic functional groups can dramatically decrease dielectric constant by increasing the free volume of films. [4–6] However, from process integration point of view, this new group of low-k materials, which usually is of low density and high porosity, has yet to demonstrate improved mechanical properties, such as higher hardness and higher elastic modulus in the 0040-6090/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2004.06.192 * Corresponding author. Tel.: +886 6 5051400x3031; fax: +886 6 5051273. E-mail address: ylwang@tsmc.com (Y.-L. Wang). 1 Now with IBM Semiconductor R&D Center, Hopewell Jct., NY 12533, USA. Thin Solid Films 469–470 (2004) 460 – 465 www.elsevier.com/locate/tsf