Low dielectric constant materials (k < 3.0) have the advantage that higher performance IC devices may be manufactured with minimal increases in chip size. The reduced capacitance given by these materials permits shrinking spacing between metal lines to below 0.25 μm and the ability to decrease the number of levels of metal in a device. The technologies being considered for low k applications are CVD or spin-on of inorganic or organic polymeric materials. Traditional spin-on silicates or siloxanes have been used as planarizing dielectrics during the last 15 years and usually have k > 3.0.

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Germyl silyl complexes Cp2W(SiMe3)(GeR3) have been synthesized by the reaction of the tungsten silene complex Cp2W(η2-Me2SiCH2) with germanes HGeR3 (GeR3 = GeMe3 (2), GeMe2H (3a), Ge t Bu2H (3b), GePh2H (3c)). Chlorogermyl derivatives are synthesized by the reaction of 3a-c with CCl4 to yield Cp2W(SiMe3)(GeMe2Cl) (4a), Cp2W(SiMe3)(Ge t Bu2Cl) (4b), and Cp2W(SiMe3)(GePh2Cl) (4c). Complex 4a has been structurally characterized by a single-crystal X-ray diffraction study. The corresponding triflate derivative, Cp2W(SiMe3)(GeMe2OTf) (5a), has been prepared by the reaction of 4a and trimethylsilyl triflate. Substitution of triflate for chloride in Cp2W(SiMe3)(Ge t Bu2Cl) (4b) requires mild heating (80 °C) and is accompanied by concurrent redistribution of groups between silyl and germyl centers to yield the silyl triflate Cp2W(SiMe2OTf)(Ge t Bu2Me) (6b). Under thermolytic conditions, germyl silyl complexes undergo intra- and intermolecular redistribution of substituents between the germyl and silyl ligands. This process is proposed to occur via a cationic germylene complex formed by triflate or chloride dissociation.

New dielectric ®lms are prepared by both pyrolytic and photolytic conversion of b-chloroethyl-silsesquioxane (BCESSQ). Film thickness, refractive index, composition, density and morphology are characterized using a palette of techniques including ellipsometry, Rutherford backscattering and forward recoil spectrometry, X-ray re¯ectivity, and atomic force and electron microscopies. After annealing at 3508C, BCESSQ ®lms, initially 200 nm thick reach about 55% of their original thickness after 20 min. For ®lms heated in air for 4 h, the atom fractions of carbon and hydrogen monotonically decrease to 10 and 30%, respectively, as annealing temperature increases from 225 to 4508C. The BCESSQ reactivity is re¯ected in the loss of chlorine at 4008C. At 4508C, the ®lm density is 1.88 g/cm 3 , or 84% of thermally-grown silicon oxide. Upon exposure to ultraviolet ozone radiation, ®lms ranging from ca. 200 to 700 nm are found to convert to ormosil ®lms within 30 min. Surprisingly, the chlorine concentration is found to decrease more quickly than the hydrogen and carbon concentrations, suggesting that the ormosil ®lm evolves HCl leaving a vinyl group of SiZCHvCH 2 . This reaction pathway differs from the thermal case. For ®lms prepared by pyrolytic and photolytic methods, atomic force and electron microscopy studies show that the surface is smooth and featureless, the bulk is void free when view at a magni®cation of 50 000 £ , and the ormosil/substrate interface is continuous.

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