Investigation of intrinsic dielectric breakdown mechanism in Cu/low-/spl kappa/ interconnect system

Using a specifically designed test structure applying human body model electrostatic discharge (ESD) stress, the origin of dielectric breakdown in Cu/low-/spl kappa/ interconnect systems was found to be in interfacial delamination. The interfacial delamination between a SiC capping layer and a SiOC interdielectric layer is responsible for the increase of intermetal dielectric leakage current, causing high current Joule heating as well as catastrophic thermal breakdown. Also, the defect density increased as the delamination becomes wider while the number of ESD zaps increases.     

Multi-phased VSG CDMA with level clipping for high-rate transmission systems

In this letter, a multi-phased CDMA system employing a variable spreading gain (VSG) approach is proposed for high-rate applications, based on four algorithms for selecting a multi-code set. From simulation results, in addition to simple receiver structure thanks to level clipping, the multi-phased VSG CDMA system provides an high bit rate transmission, while maintaining an acceptable performance degradation.     

Profiles of random trees: Plane‐oriented recursive trees

We derive several limit results for the profile of random plane‐oriented recursive trees. These include the limit distribution of the normalized profile, asymptotic bimodality of the variance, asymptotic approximation to the expected width, and the correlation coefficients of two level sizes. Most of our proofs are based on a method of moments. We also discover an unexpected connection between the profile of plane‐oriented recursive trees (with logarithmic height) and that of random binary trees (with height proportional to the square root of tree size). © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2007     

A time-domain method with isotropic dispersion and increased stability on an overlapped lattice

A time-domain method on an overlapped lattice is presented for the accurate and efficient simulation of electromagnetic wave propagation through inhomogeneous media. The method comprises a superposition of complementary approximations to electromagnetic theory on a lattice. The discrete space-time (DST) method, is set on a pair of dual lattices whose field components are collocated on their respective lattice sites. The other, the time-domain element (TDE) method, is set on overlapping dual lattices whose field components are noncollocated. The TDE method is shown to be a generalization and reinterpretation of the Yee algorithm. The benefits of the combined algorithm over comparable methods include: (1) increased accuracy over larger bandwidths; (2) increased stability allowing larger time steps; (3) local stencil-satisfying boundary conditions on interfaces; (4) self-contained mathematical framework; (5) it is physically intuitive.     

μSR studies of borocarbides

The muon‐spin‐relaxation technique has been utilized to characterize the magnetic properties of the borocarbide compounds RNi₂B₂C ( R=\,Tm, Er, Ho and Dy), which exhibit coexistence of superconductivity and magnetism. Some general features of their magnetic ground‐state and unusual results obtained in the Ho, Tm and Dy systems are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Establishing norms for age-related changes in proton T1 of human brain tissue in vivo

The goal of this study was to determine the expected normal range of variation in spin-lattice relaxation time (T₁) of brain tissue in vivo, as a function of age. A previously validated precise and accurate inversion recovery method was used to map T₁ transversely, at the level of the basal ganglia, in a study population of 115 healthy subjects (ages 4 to 72; 57 male and 58 female). Least-squares regression analysis shows that T₁ varied as a function of age in pulvinar nucleus (R² = 56%), anterior thalamus (R² = 51%), caudate (R² = 50%), frontal white matter (R² = 47%), optic radiation (R² = 39%), putamen (R² = 36%), genu (R² = 22%), occipital white matter (R² = 20%) (all p < 0.0001), and cortical gray matter (R² = 53%) (p < 0.001). There were no significant differences in T₁ between men and women. T₁ declines throughout adolescence and early adulthood, to achieve a minimum value in the fourth to sixth decade of life, then T₁ begins to increase. Quantitative magnetic resonance imaging provides evidence that brain tissue continues to change throughout the lifespan among healthy subjects with no neurologic deficits. Age-related changes follow a strikingly different schedule in different brain tissues; white matter tracts tend to reach a minimum T₁ value, and to increase again, sooner than do gray matter tracts. Such normative data may prove useful for the early detection of brain pathology in patients.     

Fabrication and characteristics of all YBCO sandwich-type junctions using highly crystalline DC sputtered superconducting a-axis oriented Y1Ba2Cu3O7-x films

We report on the fabrication and characteristics of sandwich-type tunnel junctions with highly crystalline sputtered a-axis oriented thin film of Y₁Ba₂Cu₃O_7-x (YBC) as the base and the counter electrode. The junctions have been fabricated on SrTiO₃ (100) and MgO (100) substrates. A non-superconducting phase of YBC corresponding to a lattice constant of 4.08 Å is used as the barrier layer making this an all YBC sandwich junction. For all temperatures below T_ce (R=0) of the device, a zero voltage current was observed. The critical current density (J_c) of the device was found to be dependent on the thickness of the barrier layer and the crystallinity of the a-axis oriented YBC electrodes. At 40 K, such a junction fabricated on a SrTiO₃ (100) substrate was found to have a J_c of 1.8 X 10⁴ A/cm² and an I_cR_n product of 0.2 mV.     

Low-complexity architecture of rake receiver for multi-code CDMAsystem

A new low-complexity architecture CDMA rake receiver for multi-code CDMA systems is proposed. It contains shared hardware blocks to reduce hardware complexity. The hardware complexity of the proposed architecture is compared with that of a conventional CDMA rake receiver in terms of the number of Walsh code channels. The result shows that our proposed architecture has a 12 and 18.6% reduction in gate count when the number of Walsh code channels is 4 and 7, respectively     

Photoemission study of CaF2 on Si(001)-2×1 during annealing

We have employed synchrotron radiation photoemission to investigate calcium fluoride deposited on Si(001)-2×1 annealed at 700 °C. The valence band spectra reveal that the initial molecules are dissociated to single Ca atoms resting on the surface. Si 2p core-level spectra manifest a negatively shifted Ca-induced line at 0.35 eV. The dissociated Ca atoms occupy only half of the surface, on top of which the CaF₂ molecules commence growth. This is in contrast to the Si(111)-7×7 counterpart, which exhibits a CaF layer in the interface. Strong elastic scattering due to the absorbed Ca atoms is evident in the photoemission spectra, thus averaging out the angle-dependent features.     

A UNIFIED ENERGY APPROACH TO A CLASS OF MICROMECHANICS MODELS FOR MICROCRACKED SOLIDS

Micromechanics models have been developed for the determination ofthe elastic moduli of microcracked solids based on different approaches andinterpretations,including the dilute or non-interacting solution,the Mori-Tanakamethod,the self-consistent method,and the generalized self-consistent method.It isshown in the present study that all these micromechanics models can be unified withinan energy-equivalence framework,and that they differ only in the way in which themicrocrack opening and sliding displacements are evaluated.Relevance to thedifferential methods and the verification of these models are discussed.