Zeolite Low-k Film Properties Dependence on Nanocrystal Size
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0914-F03-08
Zeolite Low-k Film Properties Dependence on Nanocrystal Size Salvador Eslava-Fernandez1,2, M.R. Baklanov1, F. Iacopi1, Brongersma S.H. 1, C.E.A. Kirschhock3, and K. Maex2 1 IMEC, Kapeldreef 75, Leuven, B3001, Belgium 2 ESAT, K.U.Leuven, Leuven, B3001, Belgium 3 COK, K.U.Leuven, Leuven, B3001, Belgium ABSTRACT Spin-on pure-silica-zeolite MFI films consist of zeolite nanocrystals embedded in a compacted silica matrix of zeolite primary nanoparticles. They appear to be promising as a low-k material due to their good mechanical properties and high microporosity, parallel to their intrinsic low k-value. Results are promising but the implementation of this material is still far away. To contribute to the implementation we present a study on the final film properties depending on the zeolite MFI nanocrystal size. Different techniques are used for the characterization: Dynamic Light Scattering, X-ray diffraction, Scanning Electron Microscopy, Nitrogen adsorption, EllipsoPorosimetry using toluene and NanoIndentation. The results show a clear dependence of the film properties on the nanocrystal size. Clearly, smaller nanocrystals provide better homogeneity, smaller pore size and higher mechanical properties. However, due to the hydrophilicity of the silica matrix lower k-values are only obtained for larger zeolite nanocrystals which provide with higher crystallinity in the films. INTRODUCTION Zeolite low-k films can be obtained spinning a pure-silica zeolite suspension obtained from a hydrothermal treatment of a precursor sol [1]. This zeolite suspension consists of a nanoparticle suspension of silica-zeolite nanocrystals and primary silica nanoparticles that are already present in the original precursor sol. The silica-zeolite nanocrystals have the desired properties of bulk zeolites such as crystallinity and microporosity. However, the nature of the primary silica nanoparticles is not totally understood [2]. The final properties obtained for silicalite-1 films (pure-silica-zeolite MFI) deposited by spinning a zeolite nanoparticle suspension are reported by Whang et al. [1]. The dielectric constant is 2.3 with an elastic modulus of 16-18 GPa but films are hydrophilic. The high elastic modulus make them promising but implementation requires a depth understanding of the final properties. To contribute to the implementation we present a study on the film properties depending on the zeolite MFI nanocrystal size used. EXPERIMENTAL DETAILS Zeolite films were prepared following the recipe described by Wang et al. [1]. First, a clear solution was prepared by mixing tetraethyl-orthosilicate (TEOS), aqueous tetrapropylammonium hydroxide (TPAOH), and ethanol (EtOH) in a molar ratio of 2.8TEOS/40Water/11.2EtOH/1TPAOH in an autoclavable polypropylene bottle. The clear solution was kept under stirring for 3 days and then slowly heated up to 80 ºC in an oil bath.
During the hydrothermal treatment of the clear solution, samples were withdrawn at different times to obtain suspensions of differently sized nanocrystals. Every na
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