Blog posts

M.A. Hussein and Jun He (Intel Corporation)

IEEE Transactions on Semiconductor Manufacturing, vol. 18, No. 1, p.69-85, 2005

In this work, we explain how the manufacturing technology and reliability for advanced interconnects is impacted by the choice of metallization and interlayer dielectric (ILD) materials. The replacement of aluminum alloys by copper, as the metal of choice at the 130nm technology node, mandated notable changes in integration, metallization, and patterning technologies. Those changes directly impacted the reliability performance of the interconnect system. Although further improvement in interconnect performance is being pursued through utilizing progressively lower dielectric constant (low-k) ILD materials from one technology node to another, the inherent weak mechanical strength of low-k ILDs and the potential for degradation in the dielectric constant during processing, pose serious challenges to the implementation of such materials in high volume manufacturing. We will consider the cases of two ILD materials; carbon-doped silicon dioxide (CDO) and low-k spin-on-polymer to illustrate the impact of ILD choice on the process technology and reliability of copper interconnects. preprint pdf 2.49 MB

Flip-chip plastic ball grid array (FC-PBGA) packages are widely used in high performance components. However, its die back is normally under tensile stress at low temperatures. This paper presents a probabilistic mechanics approach to predict the die failure rate in the FC-PBGA qualification process. The methodology consists of three parts:

Ting Y. Tsui, Andrew J. McKerrow, and Joost J. Vlassak

Published in the Journal of The Mechanics and Physics of Solids, 54 (5), 887-903 (2006)

Abstract – Organosilicate glass (OSG) is a material that is used as a dielectric in advanced integrated circuits. It has a network structure similar to that of amorphous silica where a fraction of the Si-O bonds has been replaced by organic groups. It is well known from prior work that OSG is sensitive to subcritical crack growth as water molecules in the environment are transported to the crack tip and assist in rupturing Si-O bonds at the crack tip. In this study, we demonstrate that exposure of an OSG containing film stack to water prior to fracture results in degradation of the adhesion of the film stack. This degradation is the result of the diffusion of water into the film stack. We propose a quantitative model to predict adhesion degradation as a function of exposure time by coupling the results of independent subcritical crack growth measurements with diffusion concentration profiles. The model agrees well with experimental data and provides a novel method for measuring the water diffusion coefficient in film stacks that contain OSG. This study has important implications for the reliability of advanced integrated circuits.

Computational models of the cell nucleus, along with experimental observations, can help in understanding the biomechanics of force-induced nuclear deformation and mechanisms of stress transition throughout the nucleus. Here, we develop a computational model for an isolated nucleus undergoing indentation, which includes separate components representing the nucleoplasm and the nuclear envelope. The nuclear envelope itself is composed of three separate layers: two thin elastic layers representing the inner and outer nuclear membranes and one thicker layer representing the nuclear lamina. The proposed model is capable of separating the structural role of major nuclear components in the force-induced biological response of the nucleus (and ultimately the cell). A systematic analysis is carried out to explore the role of major individual nuclear elements, namely inner and outer membranes, nuclear lamina, and nucleoplasm, as well as the loading and experimental factors such as indentation rate and probe angle, on the biomechanical response of an isolated nucleus in atomic force microscopy indentation experiment.

Microcantilevers have taken much attention as devices for label-free detection of molecules and/or their conformations in solutions and air. Recently, microcantilevers have allowed the nanomechanical mass detection of thin film [1-3], small molecules [4, 5], and biological components such as viruses [6] and vesicles [7] in the order of a pico-gram to a zepto-gram. The great potential of microcantilevers is the sensitive, reliable, fast label-free detection of proteins and/or protein conformations. Specifically, microcantilevers are capable of label-free detection of marker proteins related to diseases, even at a low concentration in solution [8-17]. Microcantilevers, operated in a viscous fluid, have also enabled the real-time monitoring of protein-protein interactions [8, 12-15]. Furthermore, microcantilevers are able to recognize the specific protein conformations [18] and/or reversible conformation changes of proteins/polymers [19, 20].

The Department of Mechanical Engineering at the University of Wyoming invites applications for a tenure-track faculty position. Applicants are sought at the Associate or Assistant Professor level with expertise in experimental mechanics and particularly in emerging areas of science and technology. Such areas include but are not limited to the study of biomaterials, tissue engineering, nanomechanics of engineering materials, as well as thin films and multilayers, fracture, fatigue and damage.

The successful applicant will be expected to establish a strong, funded research program, as well as teach at the graduate and undergraduate levels. She/He will be expected to participate in interdisciplinary research efforts both within and outside the College of Engineering. Minimum qualifications include an earned doctorate in mechanical engineering, materials science/engineering, or a closely related field.