The ever increasing requirements for electrical performance of on-chip wiring has driven three major technological advances in recent years. First, copper has replaced Aluminum as the new interconnect metal of choice, forcing also the introduction of damascene processing. Second, alternatives for SiO2 with a lower dielectric constant are being developed and introduced in main stream processing. The many new resulting materials needs to be classified in terms of their materials characteristics, evaluated in terms of their properties, and tested for process compatibility. Third, in an attempt to lower the dielectric constant even more, porosity is being introduced into these new materials. The study of processes such as plasma interactions and swelling in liquid media now becomes critical. Furthermore, pore sealing and the deposition of a thin continuous copper diffusion barrier on a porous dielectric are of prime importance. This review is an attempt to give an overview of the classification, the characteristics and properties of low-k dielectrics. In addition it addresses some of the needs for improved metrology for determining pore sizes, size distributions, structure, and mechanical properties.

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Four types of Si rich SiO2 layers on the Si substrates have been prepared by Si ion implantation or by magnetron co‐sputtering of the Si and SiO2 targets. The types differed from each other in the contents of excess Si, which were about 5 at%, 15 at%, 25 at% and 35 at%. High temperature (up to 1100 °C) anneals of the samples were performed in neutral ambient under normal or elevated (up to 1.5 GPa) hydrostatic pressures. Photoluminescence spectroscopy, Raman scattering and electron diffraction were used for the characterizations. For the lowest concentration of the excess Si the high‐pressure annealing prevents the formation of the light‐emitting Si nanocrystals, but stimulates an appearance of the centers luminescing in the visible range. These centers are believed to be numerous Si nanoclusters, segregated from the oxide network. Increase in Si content provides during the high‐pressure anneals the formation of the quantum‐size Si nanocrystals able to emit strong PL near the wavelength of 800 nm. The effect of the high‐pressure annealing is ascribed to the enhanced energetically favorable segregation of Si from the oxide network. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)