Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

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Diamond-like amorphous carbon

Rapid progress in the synthesis and processing of materials with structure on nanometer length scales has created a demand for greater scientific understanding of thermal transport in nanoscale devices, individual nanostructures, and nanostructured materials. This review emphasizes developments in experiment, theory, and computation that have occurred in the past ten years and summarizes the present status of the field. Interfaces between materials become increasingly important on small length scales. The thermal conductance of many solid–solid interfaces have been studied experimentally but the range of observed interface properties is much smaller than predicted by simple theory. Classical molecular dynamics simulations are emerging as a powerful tool for calculations of thermal conductance and phonon scattering, and may provide for a lively interplay of experiment and theory in the near term. Fundamental issues remain concerning the correct definitions of temperature in nonequilibrium nanoscale systems. Modern Si microelectronics are now firmly in the nanoscale regime—experiments have demonstrated that the close proximity of interfaces and the extremely small volume of heat dissipation strongly modifies thermal transport, thereby aggravating problems of thermal management. Microelectronic devices are too large to yield to atomic-level simulation in the foreseeable future and, therefore, calculations of thermal transport must rely on solutions of the Boltzmann transport equation; microscopic phonon scattering rates needed for predictive models are, even for Si, poorly known. Low-dimensional nanostructures, such as carbon nanotubes, are predicted to have novel transport properties; the first quantitative experiments of the thermal conductivity of nanotubes have recently been achieved using microfabricated measurement systems. Nanoscale porosity decreases the permittivity of amorphous dielectrics but porosity also strongly decreases the thermal conductivity. The promise of improved thermoelectric materials and problems of thermal management of optoelectronic devices have stimulated extensive studies of semiconductor superlattices; agreement between experiment and theory is generally poor. Advances in measurement methods, e.g., the 3ω method, time-domain thermoreflectance, sources of coherent phonons, microfabricated test structures, and the scanning thermal microscope, are enabling new capabilities for nanoscale thermal metrology.

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Nanoscale thermal transport

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 character...

Low dielectric constant materials for microelectronics

Probing surface and interface morphology with Grazing Incidence Small Angle X-Ray Scattering

Modern computer microprocessor chips are marvels of engineering complexity. For the current 45 nm technology node, there may be nearly a billion transistors on a chip barely 1 cm2 and more than 10 000 m of wiring connecting and powering these devices distributed over 9-10 wiring levels. This represents quite an advance from the first INTEL 4004B microprocessor chip introduced in 1971 with 10 μm minimum dimensions and 2 300 transistors on the chip! It has been disclosed that advanced microprocessor chips at the 32 nm node will have more than 2 billion transistors.1 For instance, Figure 1 shows a sectional 3D image of a 90 nm IBM microprocessor, containing several hundred million integrated devices and 10 levels of interconnect wiring, designated as the back-end-of-the-line (BEOL). Since the invention of microprocessors, the number of active devices on a chip has been exponentially increasing, approximately doubling every two years. This trend was first described in 1965 by Gordon Moore,2 although the original discussion suggested doubling the number of devices every year, and the phenomenon became popularly known as Moore’s Law. This progress has proven remarkably resilient and has persisted for more than 50 years. The enabler that has permitted these advances is known as scaling, that is, the reduction of minimum device dimensions by lithographic advances (photoresists, tooling, and process integration optimization) by ∼30% for each device generation.3 It allowed more active devices to be incorporated in a given area and improved the operating characteristics of the individual transistors. It should be emphasized that the earlier improvements in chip performance were achieved with very few changes in the materials used in the construction of the chips themselves. The increase of performance with scaling * Corresponding author. E-mail: gdubois@us.ibm.com. † IBM Almaden Research Center. ‡ Stanford University. Willi Volksen received his B.S. in Chemistry (magna cum laude) from New Mexico Institute of Mining and Technology in 1972 and his Ph.D. in Chemistry/Polymer Science from the University of Massachusetts, Lowell, in 1975. He then joined the research group of Prof. Harry Gray/Dr. Alan Rembaum at the California Institute of Technology as a postdoctoral fellow and upon completion of the one-year appointment joined Dr. Rembaum at the Jet Propulsion Laboratory as a Senior Chemist in 1976. In 1977 Dr. Volksen joined the IBM Research Division at the IBM Almaden Research Center in San Jose, CA, where he is an active research staff member in the Advanced Materials Group of the Science and Technology function.

Low dielectric constant materials.

▪ Abstract As integrated circuit (IC) dimensions continue to decrease, RC delay, crosstalk noise, and power dissipation of the interconnect structure become limiting factors for ultra-large-scale integration of integrated circuits. Materials with low dielectric constant are being developed to replace silicon dioxide as interlevel dielectrics. In this review, the general requirements for process integration and material properties of low-k dielectrics are first discussed. The discussion is focused on the challenge in developing materials with low dielectric constant but strong thermomechanical properties. This is followed by a description of the material characterization techniques, including several recently developed for porous materials. Finally, the material characteristics of candidate low-k dielectrics will be discussed to illustrate their structure-property relations.

Low Dielectric Constant Materials for ULSI Interconnects

Purpose
To demonstrate drug/polymer nanoparticles can increase the rate and extent of oral absorption of a low-solubility, high-permeability drug.

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Polymeric Nanoparticles for Increased Oral Bioavailability and Rapid Absorption Using Celecoxib as a Model of a Low-Solubility, High-Permeability Drug

Improving the oral absorption of compounds with low aqueous solubility is a common challenge that often requires an enabling technology. Frequently, oral absorption can be improved by formulating the compound as an amorphous solid dispersion (ASD). Upon dissolution, an ASD can reach a higher concentration of unbound drug than the crystalline form, and often generates a large number of sub-micrometer, rapidly dissolving drug-rich colloids. These drug-rich colloids have the potential to decrease the diffusional resistance across the unstirred water layer of the intestinal tract (UWL) by acting as rapidly diffusing shuttles for unbound drug. In a prior study utilizing a membrane flux assay, we demonstrated that, for itraconazole, increasing the concentration of drug-rich colloids increased membrane flux in vitro. In this study, we evaluate spray-dried amorphous solid dispersions (SDDs) of itraconazole with hydroxypropyl methylcellulose acetate succinate (HPMCAS) to study the impact of varying concentrations ...

http://pubs.acs.org/doi/pdf/10.1021/acs.molpharmaceut.7b00338

Impact of Drug-Rich Colloids of Itraconazole and HPMCAS on Membrane Flux in Vitro and Oral Bioavailability in Rats

Femtosecond Raman-induced polarization spectroscopy studies of rotational coherence in O2, N2 and CO2

An experimental method based on the 3ω technique has been developed to measure thermal conductivity of porous Xerogel films as a function of porosity. The results show that the thermal conductivity of these porous dielectric films can be an order of magnitude smaller than that of SiO2. To account for the porosity dependence of thermal conductivity, two porosity weighted semiempirical models are introduced. These models suggest the scaling rule expressing the thermal conductivity as a function of porosity. The decrease observed in thermal conductivity of porous films suggests that the tradeoff between thermal and electrical performance is an important consideration when implementing porous dielectric materials as interlevel dielectrics for on-chip interconnects.

Michael M. Morgen

Papers

Low Dielectric Constant Materials for ULSI Interconnects

Polymeric Nanoparticles for Increased Oral Bioavailability and Rapid Absorption Using Celecoxib as a Model of a Low-Solubility, High-Permeability Drug

Impact of Drug-Rich Colloids of Itraconazole and HPMCAS on Membrane Flux in Vitro and Oral Bioavailability in Rats

Femtosecond Raman-induced polarization spectroscopy studies of rotational coherence in O2, N2 and CO2

Thermal conductivity study of porous low-k dielectric materials