Delamination analysis of Cu/low-k technology subjected to chemical-mechanical polishing process conditions

The mechanical response at the interface between the silicon, low-k and copper layer of the wafer is simulated herein under the loading of the chemical-mechanical polishing (CMP). To identify the possible generation/propagation of the initial crack, the warpage induced by the thin-film fabrication process are considered, and applying pressure, status of slurry and the copper thickness are treated as the parameter in the simulation. Both the simulation and experimental results indicate that the large blanket wafer within high applying pressure would exhibit high stresses possible to delaminate the interface at the periphery of the wafer, and reducing the copper thickness can diminish the possibility of the delamination/failure of the low-k material.     

Carrier transport in HfO/sub 2//metal gate MOSFETs: physical insight into critical parameters

Electron and hole mobility in HfO/sub 2//metal gate MOSFETs is deeply studied through low-temperature measurements down to 4.2 K. Original technological splits allow the decorrelation of the different scattering mechanisms. It is found that even when charge trapping is negligible, strong remote coulomb scattering (RCS) due to fixed charges or dipoles causes most of the mobility degradation. The effective charges are found to be located in the HfO/sub 2/ near the SiO/sub 2/ interface within 2 nm. Experimental results are well reproduced by RCS calculation using 7/spl times/10/sup 13/ cm/sup -2/ fixed charges at the HfO/sub 2//SiO/sub 2/ interface. We also discuss the role of remote phonon scattering in such gate stacks. Interactions with surface soft-optical phonon of HfO/sub 2/ are clearly evidenced for a metal gate but remain of second order. All these remote interactions are significant for an interfacial oxide thickness up to 2 nm, over which, these are negligible. Finally, the metal gate (TiN) itself induces a modified surface-roughness term that impacts the low to high effective field mobility even for the SiO/sub 2/ gate dielectric references.     

Autometallographic demonstration of zinc ions in rat sperm cells

An in-vitro technique for autometallographic (AMG) demonstration of chelatable zinc in electroejaculated sperm cells and spermatozoa from the epididymis is presented and the localization of zinc ions in rat spermatozoa is described. Sperm cells from caput epididymis showed zinc staining in all parts of the tail and a sparse, dispersed staining in the acrosome. Spermatozoa from cauda epididymis showed heavy staining in the acrosome but no staining in the tail, or post-acrosomal part of the sperm head. This distinct acrosomal AMG staining was also found in ejaculated spermatozoa, but additionally a segmentation of the tail was seen based on differences in staining intensity. The membrane penetrating chelator diethyldithiocarbamate (DEDTC) was found to block the AMG staining whereas calcium-EDTA, known not to pass through cell membranes, did not influence the staining, proving that the detected zinc ions are intracellularly located. Two different approaches for demonstrating the presence of a chelatable zinc pool at electron microscope levels are presented, and the ultrastructural presence of AMG grains located in the acrosome and in the mitochondria of the midpiece is demonstrated. It is postulated that an exchange of zinc ions takes place between the epididymal epithelium and the sperm cells as they pass along the epididymal duct.     

Optimized High-Order Derivative and Dissipation Operators Satisfying Summation by Parts,and Applications in Three-dimensional Multi-block Evolutions

We construct optimized high-order finite differencing operators which satisfy summation by parts. Since these operators are not uniquely defined, we consider several optimization criteria: minimizing the bandwidth, the truncation error on the boundary points, the spectral radius, or a combination of these. We examine in detail a set of operators that are up to tenth order accurate in the interior, and we surprisingly find that a combination of these optimizations can improve the operators’ spectral radius and accuracy by orders of magnitude in certain cases. We also construct high-order dissipation operators that are compatible with these new finite difference operators and which are semi-definite with respect to the appropriate summation by parts scalar product. We test the stability and accuracy of these new difference and dissipation operators by evolving a three-dimensional scalar wave equation on a spherical domain consisting of seven blocks, each discretized with a structured grid, and connected through penalty boundary conditions. In particular, we find that the constructed dissipation operators are effective in suppressing instabilities that are sometimes otherwise present in the restricted full norm case.     

Prediction and verification of process induced warpage of electronic packages

During the manufacturing, testing and service, thermally induced deformations and stresses will occur in IC devices and packages, which may cause various kinds of product failures. FEM techniques are widely used to predict the thermal deformations and stresses and their evolutions. However, due to the complexity of the real engineering problems, various assumptions and simplifications have to be made in conducting FEM modelling. Therefore, the applicability of the predicted results depend strongly on the reliability and accuracy of the developed FEM-based prediction models which should be verified before applications.In this paper, FEM models are developed to predict the thermal deformations of certain electronic packages and naked die samples under packaging and testing loading. For all the package constituents, appropriate material properties and models are used, including temperature-dependent visco-elasticity, anisotropy, and temperature-dependent elasticity and plasticity. To verify the developed FE models, a series of optical metrology tests are performed. A compact 3D interferometry testing system that can measure simultaneously out-of plane and in-plane deformations has been developed. Thermal deformation measurements are performed on samples of both real electronic packages and naked dies attached on a leadframe. Identical deformation patterns were found for the measured fringe patterns in the U-, V-, and W-fields and the simulated ones. Also, quantitatively, the maximum deformation mismatch between the predicted and tested results is within 15%. It is concluded that the thermally induced deformations predicted by the non-linear FEM models match well with measured deformations for both the naked die and the real packages.     

Note on a simple algorithm for a computer-produced reading ease score.

Describes 3 relatively simple computer algorithms for estimating the average number of syllables/word in text from letter counts. The syllable counts were used to determine Flesch Reading Ease Scores for text by computer. Vowel counts worked well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)