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The Integration of Low-k Dielectric Material Hydrogen Silsesquioxane (HSQ) with Nitride Thin Films as Barriers Yuxiao Zeng1, Linghui Chen, and T. L. Alford Department of Chemical, Bio and Materials Engineering, NSF Center for Low Power Electronics, Arizona State University, Tempe, Arizona 85287-6006, USA 1 Current address: Epitronics Corporation, an ATMI company, Mesa, AZ 85210,USA ABSTRACT HSQ (hydrogen silsesquioxane) is one of the promising low-k materials used in VLSI technology as an intra-metal dielectric to reduce capacitance-related issues. Like any other dielectrics, the integration of HSQ in multilevel interconnect schemes has been of considerable importance. In this study, the compatibility of HSQ with different nitride barrier layers, such as PVD and CVD TiN, PVD TaN, and CVD W2N, has been investigated by using a variety of techniques. The refractory metal barriers, Ti and Ta, are also included for a comparison. The degradation of HSQ films indicates a strong underlying barrier layer dependence. With CVD nitrides or refractory metals as barrier, HSQ exhibits a better structural and property stability than that with PVD nitrides. The possible mechanisms have been discussed to account for these observations. INTRODUCTION HSQ (hydrogen silsesquioxane), an inorganic spin-on material, is receiving attention as one of the promising low-k dielectrics due to its low dielectric constant, excellent gapfill and planarization performance, and capability of using standard spin-on production technique [1-3]. HSQ has a general formula (HSiO1.5)2n, where n = 3 to 8. It has a cagelike structure with each silicon atom connected to one hydrogen atom and 1.5 oxygen atoms. In real device structures, the potential interaction between HSQ and metal via is a reliability issue deleterious to device properties. A common failure mode is via poisoning [4-5] Furthermore, for the HSQ films, it is preferred to avoid any undesired interaction in order to maintain the dielectric properties of HSQ. The alleviation of these problems requires a proper diffusion barrier to be used. Due to their high melting points and high thermal stability, refractory metals and their nitrides, such as Ti, Ta, TiN, TaN, and W2N, have been intensely investigated as diffusion barriers in interconnect schemes [6-8] Specifically, Ti and TiN are mainly aimed at Al metallizations, and the other three are primarily intended for Cu metallizations. In this paper, we choose these barriers to study their potential interactions with the HSQ and evaluate their effectiveness as the barrier between the HSQ and the metal via. The conventionally used intermetal dielectric PETEOS - silicon dioxide deposited from tetraethylorthosilicate (TEOS) by plasma-enhanced chemical vapor deposition process is also selected for the purpose of comparison.

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EXPERIMENTAL HSQ films (350 nm thick) were deposited on (100) Si wafers by spin-on technique, followed by sequential bakes at different temperatures (100-300 °C) and a final cure process (400 °C). PETEOS films with a thickness