Topographical and chemical surface modification of porous MSQ using silylating agents with different numbers of methoxy groups Casey Smith 1 , Dennis Mueller 2 , Phil Matz 3 , and Rick Reidy 1 1 Materials Science, University of North Texas, 3940 N. Elm St., Denton, TX, 76207 2 Physics, University of North Texas, Denton, 76207 3 Silicon Technology Development, Texas Instruments, Dallas, 75234 ABSTRACT Plasma ash processes that cause surface damage in porous interlayer dielectric materials (ILDs) result in increased water absorption, permittivity, and metal intrusion. In this study, we employ alkoxide silylation agents containing one to three methoxy groups dissolved in supercritical CO 2 to repair O 2 ash damaged low-k methylsilsesquioxane (MSQ) films. Fourier transform infrared spectroscopy (FTIR) was performed using normal incidence transmission and grazing angle attenuated total reflection (GATR) techniques to highlight differences in silylation efficiency based on agent functionality. Contact angle measurements reveal a significant change in hydrophobicity after functionalization of the O 2 ashed samples with multifunctional agents. Atomic force microscopy (AFM) was utilized to determine changes in surface topography after ashing and subsequent repair. These data provide insight into the chemical and topographical changes resulting from ashing and silylation of porous MSQ, and suggest implications for the adhesion, uniformity, and reliability of subsequent metal or barrier layers. INTRODUCTION Continued scaling of critical dimensions in semiconductor devices as outlined in the ITRS roadmap requires maturation of interlayer dielectric (ILD) materials with low (k< 2.4 by 2007) dielectric constants to limit RC delay and crosstalk [1]. Many recent efforts have focused on the use of porous silica-based films such as MSQ, a methyl- functionalized siloxane-based spin-on dielectric, to meet these demands. MSQ films with 3-5nm pores and 40% porosity typically exhibit relative permittivity values less than 2.3 and are inherently hydrophobic. [2]. Unfortunately, exposure to oxidizing (O 2 ) or reducing (H 2 ) environments during plasma ash processes can result in depletion of carbon species to depths up to 30nm and the subsequent formation of hydrophilic Si-OH groups [3]. The presence of silanol moieties dramatically increases water adsorption and surface group polarizability, consequently, increasing the film dielectric constant. Silylation reactions carried out in supercritical carbon dioxide (SCCO 2 ) have proven an effective means of replacing ash- stripped methyl groups and removing adsorbed water, thus, restoring film hydrophobicity, lowering dielectric constant, and preventing metal and organometallic precursor intrusion [4-5]. The zero surface tension environment, tailorable solvating properties, low cost, and non-hazardous nature make SCCO 2 -based systems an excellent medium for processing porous low-k dielectrics [6]. Plasma chemistry and exposure time determine the resultant silanol species (i.e., vicinal and isolated) in a damaged layer of a low-k film. Recent studies have indicated that the extent of repair after SCCO 2 -based silylation is dictated by the number, type, and Mater. Res. Soc. Symp. Proc. Vol. 914 © 2006 Materials Research Society 0914-F04-04