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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We demonstrate an improvement by more than 1 order of magnitude of the figure of merit (FoM) of plasmonic nanoparticle sensors by means of the diffractive coupling of localized surface plasmon resonances. The coupling in arrays of nanoparticles leads to Fano resonances with narrow line widths known as surface lattice resonances, which are very suitable for the sensitive detection of small changes in the refractive index of the surroundings. We focus on the sensitivity to the bulk refractive index and find that the sensor FoM scales solely with the frequency difference between the surface lattice resonance and the diffracted order grazing to the surface of the array. This result, which can be extended to other systems with coupled resonances, enables the design of plasmonic sensors with a high FoM over broad spectral ranges with unprecedented accuracy.

Palladium nanowires were fabricated on silicon substrates using conventional microfabrication techniques. Sensors based on such nanowires show a reversible response to hydrogen concentrations as low as 27 ppm with response times varying from 5 s (H2 concentrations >20%) to 30 s (H2 concentrations <100 ppm) at room temperature. The response times can be reduced by increasing the applied bias due to resistive heating. The noise spectrum of the nanowires shows a 1/f behavior, sufficiently low to enables the detection of hydrogen with an ultralow-power consumption. The influence of oxygen on the nanowire response was also investigated.

As the dimensions of conductors shrink into the nanoscale, their electrical conductivity becomes dependent on their size even at room temperature. Although the behavior varies dramatically as temperatures increase from nanokelvins to hundreds of kelvins, the effect is generally to increase the resistivity above that of bulk material. As such, the underlying size-dependent phenomena have become increasingly important as advanced technologies have shifted their focus first from macro- to microscale and more recently from micro- to nanoscale dimensions. Indeed, the size-dependent increase of electrical resistivity that results from electron scattering on external and internal surfaces of copper conductors has already become technology limiting in modern microelectronics. This article summarizes the phenomena that underlie size effects, focusing on conduction in copper lines in particular. Attention is given to describing key innovations in both theoretical and experimental assessments that have significantly modified, facilitated, or advanced understanding.

We examine the influence of surface and grain-boundary scattering on the total electrical resistivity of copper as dimensions are reduced close to the bulk electron mean free path (39 nm). Through resistivity and grain size characterization on copper wires with sizes down to 95×130 nm2 in a temperature range of 4.2 to 293 K, it was found that the influence of surface scattering is less than previously speculated, while grain-boundary scattering is dominant. A reduction of the background scattering length due to small grains accounts for the observed behavior. The reflection coefficient varies as expected from impurity enrichment in the grain boundaries.

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