Smooth mesoporous silica films (see Figure) can now be obtained with very low dielectric constants by spin coating, whereby the thickness and hydrophobicity of the films can also be controlled. This is thanks to a functionalized precursor as is unveiled in this communication. These films are sure to be on the wanted list for semiconductor applications as they combine dielectric stability with a low processing temperature, an excellent thermal stability, and reliable mechanical properties.

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The fabrication of high aspect ratio macropore arrays on p-type silicon under optimum anodization conditions is demonstrated. The depth of the macropore can reach 400 µm with an aspect ratio of 100. The thickness of the pore wall is 1-2 µm. Presence of cationic surfactant in the electrolyte protects the pore walls and promotes the growth of the unidirectional macropores. The shape of preetched pits is critical for the formation of high aspect ratio macropores on p-type silicon. A self-supported silicon membrane of straight-through macroporous channels has also been obtained.

Microstructural and mechanical properties of organic surfactant templated nanoporous thin silica films have been studied by X-ray diffraction, Fourier transform infrared spectroscopy, and nanoindentation. Compared with many other porous low-k dielectrics, the self-assembled molecularly templated nanoporous silica films demonstrate better mechanical properties. This is ascribed to the presence of a well-ordered pore channel structure in the nanoporous silica thin films. Hardness and elastic modulus are strongly dependent on film preparation and modification methods. Trimethylsilylation by hexamethylsilazane vapor treatment effectively enhances the mechanical strength of the nanoporous silica films. When the sol precursor solution is mixed with trimethylchlorosilane ͑TMCS͒, the resulting nanoporous films have a weaker mechanical strength. The pore channel structure of the nanoporous silica film becomes less ordered for the TMCS derivatized nanoporous films. In addition, the chemical structure in the silica solid matrix of the TMCS derivatized films is more disordered than those without TMCS modification. The nanoindentation measurement results are discussed in terms of the pore microstructure of the nanoporous silica network and the springback effect due to the presence of trimethylsilyl groups in the nanopores.