Impact of Pore Size and Morphology of Porous Organosilicate Glasses on Integrated Circuit Manufacturing
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0914-F01-02
Impact of Pore Size and Morphology of Porous Organosilicate Glasses on Integrated Circuit Manufacturing Mark L O'Neill1, Mary K Haas1, Brian K Peterson2, Raymond N Vrtis1, Scott J Weigel1, Dingjun Wu1, Mark D Bitner1, and Eugene J Karwacki1 1 Electronics Technology, Air Products & Chemicals, Inc, 7201 Hamilton Blvd., Allentown, PA, 18195 2 Computational Modeling Center, Air Products & Chemicals, Inc, 7201 Hamilton Blvd., Allentown, PA, 18195 ABSTRACT Porous organosilicate materials produced by plasma enhanced chemical vapor deposition are the leading candidates for back-end-of-line dielectric insulators for IC manufacturing at 45nm design features and beyond. The properties of porous organosilicate glass films of dielectric constant k=2.50 ± 0.05 formed using diethoxymethylsilane and five different porogen precursors with an ultraviolet post treatment are reported. By varying the porogen precursor type pore sizes of 1-2 nm (equivalent spherical diameter) and porosities in the range of 24-31% were measured. While there were no observable trends in pore size with the molecular volume or plasma reactivity of the porogen precursor, modulus values ranged from 6.6 to 10.8 GPa. Porous films with the highest mechanical properties were found to have the highest matrix dielectric constant, highest network connectivity (lowest methyl content), and highest density. Within this process space, maximizing the network connectivity of the film was found to be more important to mechanical properties than lowering the total porosity. In effect, the choice of porogen precursor dictates the film morphology through its impact on the organosilicate glass matrix and pore size. INTRODUCTION Materials with increasingly lower dielectric constant values are needed for future generation integrated circuits (ICs) in order to continue to enhance signal propagation. Current state of the art IC production uses organosilicate glasses (OSGs) with dielectric constant (k) values on the order of 3.0. Dense OSG materials, however, are inherently limited to k values ≥ 2.7 [1-3]. To achieve k values of < 2.5 alternative materials, processing, or a combination of both must be used. The introduction of porosity is one commonly used technique to reduce dielectric constant, where the degree of reduction depends largely upon the film porosity. While porous materials inherently suffer from inferior mechanical properties relative to their non-porous predecessors, post-treatment processes such as UV and e-beam can dramatically improve the integratibility of these materials. It is known that a variety of organosilane / organosiloxane precursors can be used to produce OSG films by chemical vapor deposition (CVD) with acceptable mechanical properties [1, 2, 4-7]. It has been shown in previous studies [1, 8] the benefits of diethoxymethylsilane (DEMS™ ILD precursor) as a precursor for interlayer/intermetal dielectric films in providing an excellent balance of electrical and mechanical properties for a methyldoped silicate glass. Porous OSG materials produ
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