Electromigration drift and threshold in Cu thin-film interconnects

The electromigration-induced ionic drift velocity and critical length-current density product, (jl_c) of Cu thin film conductors, were measured using the Blech-Kinsbron edge-displacement technique. Unencapsulated Cu edge-displacement segments on TiN conductors were stressed in vacuum at a modest current density of 6×10⁵ A/cm² in the temperature range of 175-275°C. Drift velocity was observed to be between 1-1/2 to 3 orders-of-magnitude lower than that previously measured for unencapsulated Al in this temperature range. We measured an activation energy for EM-induced drift of 1.25±0.08 eV which corresponds to grain boundary diffusion in Cu. Critical lengths were measured and the jl_c threshold was estimated to range between 900-1600 A/cm. We calculated a Cu grain boundary Z* value of -0.7, to our knowledge, this study is the first to measure Z* for electromigration in Cu thin film conductors     

Operation of a quantum-dot cellular automata (QCA) shift register and analysis of errors

Quantum-dot cellular automata (QCA) is a digital logic architecture that uses single electrons in arrays of quantum dots to perform binary operations. A QCA latch is an elementary building block which can be used to build shift registers and logic devices for clocked QCA architectures. We discuss the operation of a QCA latch and a shift register and present an analysis of the types and properties of errors encountered in their operation.     

A 100-MHz macropipelined VAX microprocessor

A macropipelined CISC microprocessor was implemented in a 0.75-μm CMOS 3.3-V technology. The 1.3-million-transistor custom chip measures 1.62×1.46 cm² and dissipates 16.3 W. The 100-MHz parts were benchmarked at 50 SPEC marks. The on-chip clocking system and several high-performance logic and circuit techniques are described. Macroinstruction handling, micropipeline management, and control store structures highlight the design architecture. The hierarchical array organization and fast tag comparison technique of the primary cache are discussed. Power estimation procedures are outlined, and the results are compared to measurements. Physical design and verification methods, and CAD tools are also described. After extensive functional verification efforts are described, chip and system test results are presented     

Detailed study and projection of hard breakdown evolution in ultra-thin gate oxides

The mechanism responsible for post-soft breakdown leakage current increase in ultra-thin oxides depends on the nature of the conducting filament formed at the instant of dielectric breakdown. The conductance of the filament formed during soft breakdown has been observed to be either stable until hard breakdown occurs or to increase continually with time. The acceleration factors for predicting hard breakdown are different in each case. Recent experimental results suggest that the “hardness” of the first breakdown influences the type of conducting filament formed during the soft breakdown event the time in which hard breakdown subsequently occurs. Electron current-induced defect formation appears to be the driving force for the eventual hard breakdown event.     

Assessment of acceleration models used for BGA solder joint reliability studies

Solder joint reliability was one of the top priorities when evaluating the reliability of electronic packages. In general, an acceleration model would be used to predict solder joint fatigue life in the use conditions. However, the accuracy of the model was difficult to validate. As a result, the fatigue life of the solder joints could be over-designed with added cost or time, or under-estimated with a compromised reliability performance. It was an important goal for engineers to use valid and accurate life models to predict the field life of the solder joints and reduce development cost and time.Many empirical models including Norris-Landzberg model and its modifications usually considered the effects of temperature range, the cycle frequency, and the maximum temperature. No matter what the package structures were or the materials were used, engineers had been using the same model parameters for many years. Moreover, little was done to validate the models for modern packages structures and materials.In this article, a variety of package was studied and the failure data was analyzed through a reliability engineering approach. The results showed that the available model parameters were not suitable to predict the solder joint life of test samples exclusively. A new set of model parameters might be required for certain cases. Also, the acceleration factor models would depend on the solder joint materials and microstructures. The solder joint fatigue life performance was too complicated to be assumed as a fixed empirical model. One of the reasons was there were too many factors affecting the strain which the solder joints would endure.In the future study, critical factors such as materials or structures could be integrated into the current model format. Additionally, the ramp rate could be a concern especially when dealing with cases under thermal shock conditions. The methodology to develop an acceleration factor model and the demonstration of their weakness would help achieve reliable solder connections in the future.     

The politics of conservative elites and the 'liberal media' argument

Recent evidence suggests that conservative elites' claims of a liberal media are having an impact upon public perceptions of news coverage. With this in mind, we examined two related questions in the context of the 1988, 1992, and 1996 presidential elections. First, what factors may be prompting conservative elites to make allegations of liberal media bias? Second, what factors may influence when news media report these criticisms during presidential campaigns? Findings suggest that these criticisms of news media are at least partly strategic and reflect a dynamic relationship between political elites and journalists during a presidential campaign.     

Encapsulation process development for flexible-circuit based chip scale packages

The ultimate driving forces for the development of small form-factor chip scale packages (CSPs) are the market demands for small, light and high performance products. The flex-based /spl mu/BGA technology has been a very successful package format, and tremendous efforts have been implemented in the process development for the technology. In this article, three flex-based chip scale packages (based on patented /spl mu/BGA technology) will be discussed. The focus will be on the encapsulation process development. Because of the unique package structures and material sets used in the flex-based CSPs, various encapsulation challenges were raised. The encapsulation solutions are compared and discussed for each type of flex-based /spl mu/BGA technologies, including the dispensing pump technologies, material characterization, process characterization and optimization. Based on the evaluation results, type C /spl mu/BGA technology is recommended for its simple assemble process flow, balanced protection on beam leads and solder ball joints and shorter manufacturing cycle time as well.     

Estimation of human dose of staphylococcal enterotoxin A from a large outbreak of staphylococcal food poisoning involving chocolate milk

An outbreak of gastroenteritis in a school district in the United States was determined to be staphylococcal food poisoning due to 2% chocolate milk containing staphylococcal enterotoxin A (SEA). Twelve one-half pint (approx 0.28 l) cartons of the 2% chocolate milk from this outbreak were analyzed for the quantity of SEA present in the milk. The amount of SEA in the cartons varied from 94 to 184 ng with the average being 144 ng (mean = 139 +/- 45). The attack rate for vomiting among those who consumed more than one carton was greater (38.3%) than among those who consumed only one carton (31.5%) with the highest attack rate among those who consumed three or more cartons (44.4%).     

The dependence of HNO2 mutagenesis in phage T4 on ligase and the lack of dependence of 2AP mutagenesis on repair functions

A temperature sensitive ligase allele of phage T4 reduced or eliminated HNO2 induced reversion of am mutants. Since at the temperatures used, the ligase mutant is defective in the repair of some types of lethal lesions (i.e., UV, MMS and EMS induced lesions) these results indicate that HNO2 mutagenesis may occur through a ligase dependent repair pathway. In contrast, 2AP induced mutation was not inhibited by mutants defective in the gene 30 ligase or in genes 32, 39, 41, 42, 44, 45, 46, 47, 49, 52, 56, 58-61 and v. This indicates that 2AP mutagenesis probably does not depend on a repair pathway in phage T4.