Thomas Kwok

Electromigration in metals

This paper provides an overview on the current understanding of electromigration in metals. The discussion is first focused on studies in bulk metals and alloys. This part includes a thermodynamic formulation of electromigration, a kinetic analysis of the atomic processes and a review of the theory. In addition, experimental results in interstitial and substitutional systems are summarised. The second part of the paper reviews the studies in metallic thin films. This emerged as an important area of electromigration studies since the late 1960s when electromigration damage was found to cause failure of conductor lines in integrated circuits. The discussion will review first the basic nature of electromigration in thin films with emphasis on the role of grain boundaries in mass transport and damage formation. Then the materials issues of electromigration will be explored according to the scaling trends in VLSI technology. Finally, the recent results of electromigration in fine lines and device contacts of dimensions in the micrometre range are discussed.

A Software as a Service with Multi-tenancy Support for an Electronic Contract Management Application

In most commercial electronic contract management applications available today, different customized code base has to be developed, deployed and operated to support each tenant. Few advanced commercial electronic contract management applications use a single code base with configuration options to support multi-tenants. However, a separate instance of the code base still has to be deployed and operated for each tenant even in these applications. The business model of having to support a single application instance for each tenant makes an electronic contract management application and other critical business applications out of reach for most small and medium businesses (SMBs), in particular, the very small businesses (SVBs) because of its high development and maintenance cost. Recently, a new business model of a single application instance supporting multi-tenancy based on software as a service (SaaS) has emerged making expensive business applications more affordable for SMBs and SVBs for multi-tenancy [1]. In this paper, we present the first of a kind multi-tenancy SaaS electronic contract management application. We also describe several novel methods used in the metadata, security and shared services, as well as customization and tenant extensions modules to support multi-tenancy SaaS in this application. This multi-tenancy SaaS application has shown to benefit both the application service providers as well as their tenants. This new multi-tenancy SaaS model can reduce the application hosting cost and make the application more affordable to the tenants because of its capabilities in customization and scalability while continuing to support an increasing number of tenants. It furthers benefits tenants by saving their money and time with immediate access to the latest IT innovations and infrastructure improvements on a single application code base. Most end users of tenants have found their productivities increased, the contract transaction time accelerated, contractual errors reduced in using this multi-tenancy SaaS electronic contract management application as demonstrated in several ongoing IBM pilot programs serving more than ten tenants with over 3000 end users.

Resource Calculations with Constraints, and Placement of Tenants and Instances for Multi-tenant SaaS Applications

Cost of customization, deployment and operation of a software application supporting multiple tenants can be lowered through multi-tenancy in a new application business model called Software as a Service (SaaS). However, there are a number of technical challenges that need to be tackled before these benefits can be realized. These challenges include calculations of resource requirements for multi-tenants with applied constraints in a shared application instance, the optimal placement of tenants and instances with maximum cost savings but without violating any requirements of service level agreements for all tenants in a set of servers. Moreover, previously reported capacity planning and resource allocation methods and tools are not tenant aware. This paper will address and provide novel solutions to these challenges. We also describe the first of a kind, a multi-tenant placement tool for application deployment in a distributed computing environment.

Autonomic Ranking and Selection of Web Services by Using Single Value Decomposition Technique

With the proliferation of Web services as a business solution to enterprise application integration, ranking and selecting the best Web services among the providers become an important factor in the success of the business solution. Quality of service (QoS) determines the quality and usability of a service including its price, performance, reliability, integrity, accessibility, availability, interoperability, and security. Given a set of QoS attributes from a variety of sources, it is a challenge to sort through all of them and be able to get the best services that meet QoS requirement. In this paper, we describe a novel method by which Web services can be ranked and selected automatically based on a number of observed QoS parameters and feedback responses learned from prior knowledge. This new approach treats the observed Web services QoS attributes and target Web services relationship, represented by a matrix, as a statistical problem. Using singular value decomposition (SVD) technique, and an user assisted weighting system, implicit higher order correlations among Web services and their associated QoS attributes are extracted and used to estimate the selection of recommended Web services.

Current Density and Temperature Distributions in Multilevel Interconnection with Studs and Vwas

Studs and vias are two basic structures in multilevel interconnection. For higher device density and better speed performance inl VLSI technology, the stud or via aspect ratio has to be increased from the present value of 0.5 to about 2.0. The high aspect ratio would raise a reliability concern of current crowding and local heating. In this study, finite element method has been used to calculate the distributions of current density and temperature in multilevel interconnection with studs and vias. The results show that current density peaks in the stud increase with decreasing stud width and thus with increasing aspect ratio. The rate of increase is faster for submicron lines than for wider lines. Current crowding in the via is found to increase with increasing step angle due to the thining down of the step cross-section. The results also indicate that current crowding in the 60° via step region gives rise to a hot spot due to Joule heating. Results of these calculations provide a general approach to optimize the aspect ratio and geometries of stud and via structures for minimal current crowding and local heating in multilevel interconnection.

An automatic electronic contract document signing system in a secure environment

Superimposing electronic signing data on a signed electronic contract usually involves a large number of complex manual steps. These manual steps are tedious and may cause security faults. In this paper, we present an automatic electronic contract document signing system in a secure environment. The system comprises a document and signature profile module, a signing text template module and a signing information superimposed module. The document and signature profile module parses the contract document and signature information. Based on this information, the signing text template module creates a signing text template with empty text fields. The signing information superimposed module carry out a novel electronic document signing method. This novel method consists of four processing steps: inserting signing text data into empty text fields, converting the text template into an image template, adding signing image data onto the image template, and superimposing the signing image template on the contract document to produce a signed electronic contract document. This automation system has found to improve substantially the efficiency, and at the same time eliminate the potential for human errors and security breaches in signing electronic contract documents.

Ink Retrieval from Handwritten Documents

This paper compares several information retrieval (IR) methods applied to the problem of retrieving specific words from a handwritten document. The methods compared include variants of the Okapi formula and Latent Semantic Indexing (LSI); recognition-based retrieval; and keyword search. One novel aspect of the work presented is that it uses the output stack of a Hidden Markov Model (HMM) handwriting recognizer with a 30,000-word lexicon to convert each handwritten word into a document which is then used for document retrieval. Preliminary experiments on a database of 1158 words from 75 writers indicate that the keyword search has superior precision and recall for text queries, and that ink queries result in minor performance reductions.

An Enterprise Electronic Contract Management System Based on Service-Oriented Architecture

Electronic contract systems deal with the lifecycle automation and management of contract documents from their establishment to expiry. Many existing contract systems are built as monolithic, vertical stand-alone applications that are inflexible and difficult to scale and interoperate with other enterprise systems. This paper proposes a service-oriented electronic contract system that leverages a number of common middleware services to provide an open, extensible and interoperable solution. The basic common services include the content repository services, the workflow and document routing services, the security services, and the notification services. A standard data model is defined to specify the metadata properties for managing, tracking and storage of contract documents in a central repository. Integration services are also introduced to enable the system to collaborate and share contract data with external applications such as contract authoring and fulfillment tracking tools. The implementation of an enterprise multi-party electronic contract system using standard commercial middleware components will be presented to illustrate the simplicity, reusability, interoperability and flexibility of this service- based approach.

Electromigration and reliability in submicron metallization and multilevel interconnection

Abstract There are increasing reliability concerns of electromigration-induced and thermal stress-induced failures in submicron interconnects and in multilevel interconnection with W studs. The electromigration characteristics of Al and Al-Cu submicron lines, two-level Al-Cu lines with W studs, Al fine lines under pulsed current stressing at high frequencies, and Al and Al-Cu fine lines under temperature cycling have been systematically studied. Lifetime is affected by grain size, grain morphology and bend structure in submicron metal lines. The lifetime of W stud chains is less than a half of that of Al-Cu flat lines. The discontinuity of the supply of Cu at Al-Cu/ W interfaces accounts for most of the reduction in the electromigration resistance of W stud chains. Under pulsed current stressing at frequencies 50–200 MHz, our data indicate no drastic change in lifetime within this frequency range. However, lifetime increases with duty cycle as t50αr−2.7, which is a remarkable improvement over an average current density model. Lifetime also depends explicitly on both current-on time and current-off period. The extra thermal stress induced by temperature cycling shortens the lifetime of both Al and Al-Cu fine lines by more than an order of magnitude. Our results also show that the addition of Cu in Al fine lines improves the resistance to thermal stress-induced failures, probably by the suppression of grain boundary sliding and migration.

Effect of metal line geometry on electromigration lifetime in Al-Cu submicron interconnects

The dependence of electromigration lifetime on the metal line geometry in Al-Cu submicron lines was investigated. Results indicated that as the linewidth decreases, the lifetime initially decreases and then increases below a crucial width. The lifetime also decreases with increasing film thickness. Those Al-Cu submicron lines with line width comparable to or smaller than film thickness have longer electromigration lifetime than other Al-Cu fine lines. The effect of line length on electromigration lifetime was found to be small. >