The improved performance of the semiconductor microprocessors was achieved for several decades by continuous scaling of the device dimensions while using the same materials for all device generations. At the 0.25 μm technology node, the interconnect of the integrated circuit (IC) became the bottleneck to the improvement of IC performance. One solution was introduction of new materials to reduce the interconnect resistance-capacitance. After the replacement of Al with Cu in 1997, the inter- and intralevel dielectric insulator of the interconnect (ILD), SiO2, was replaced about 7 years later with the low dielectric constant (low-k) SiCOH at the 90 nm node. The subsequent scaling of the devices required the development of ultralow-k porous pSiCOH to maintain the capacitance of the interconnect as low as possible. The composition and porosity of pSiCOH dielectrics affected, among others, the resistance of the dielectrics to damage during integration processing and reduced their mechanical strength, thereby affecting the reliability of the VLSI microprocessor. New ILDs had to be developed to overcome such problems and enable the fabrication of reliable high performance devices. The capacitance of the interconnect is also affected by the dielectric caps separating the Cu conductor from the ILD. This effect has increasing impact as interconnect dimensions shrink further with each technology node. New caps with lower k values and smaller thickness have been developed to reduce the impact of the caps to the capacitance of the interconnect and enable fabrication of devices of high reliability. This paper reviews the development of advanced ultralow-k (ULK) ILD dielectrics and caps with reduced capacitance contributions and presents the state of the art of these interconnect dielectrics.

A high throughput methodology for the study of surface segregation in alloys has been developed and applied to the Cu x Pd 1Àx system. A novel offsetfilament deposition tool was used to prepare Cu x Pd 1Àx composition spread alloy films (CSAFs), high throughput sample libraries with continuous lateral composition variation spanning the range x = 0.05À0.95. Spatially resolved low energy ion scattering spectroscopy (LEISS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the films' top-surface and near-surface compositions, respectively, as functions of alloy composition, x, and temperature. Electron backscatter diffraction (EBSD) was used to identify the bulk phases in the CSAF as a function of alloy composition, x. Films equilibrated by annealing at temperatures g 700 K displayed preferential segregation of Cu to their top-surfaces at all bulk compositions; segregation patterns did not, however, depend on local structure. The LangmuirÀMcLean thermodynamic model was applied to segregation measurements made in the temperature range 700À900 K in order to estimate the enthalpy (ΔH seg ) and entropy (ΔS seg ) of segregation as a function of bulk Cu x Pd 1Àx composition. Segregation measurements at x = 0.30 on the CSAF compare well with results previously reported for a bulk, polycrystalline Cu 0.30 Pd 0.70 alloy, demonstrating the utility of the CSAF as a high throughput library for study of segregation.

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Composition spread alloy films (CSAFs) are combinatorial materials libraries that contain broad, continuous composition ranges of binary or higher-order alloys on a single, compact substrate. When characterized for composition and functional properties using spatially resolved methods, CSAF libraries enable rapid determination of composition-property relationships across broad continuous regions of alloy composition space. In this report, we describe the design and operation of a novel offset filament deposition tool for preparation of CSAFs. The spatial distribution of individual alloy component fluxes to the substrate surface, and thus the film composition across the substrate, is controlled by the location and temperature of chemically distinct evaporative line sources. The tool can be used for quantitative deposition of thin (100 nm) CSAFs with up to four components. The authors demonstrate the performance of the tool by applying it to preparation of 100 nm thick Pd-Cu CSAFs, with lateral composition gradients that span the range Cu 0.05 Pd 0.95 to Cu 0.95 Pd 0.05 , on a 12 mm diameter Mo(110) substrate. V