Logarithmic behavior of degradation dynamics in metal--oxide semiconductor devices

In this paper the authors describe a theoretical simple statistical modelling of relaxation process in metal-oxide semiconductor devices that governs its degradation. Basically, starting from an initial state where a given number of traps are occupied, the dynamics of the relaxation process is measured calculating the density of occupied traps and its fluctuations (second moment) as function of time. Our theoretical results show a universal logarithmic law for the density of occupied traps $\bar{} \sim \phi (T,E_{F}) (A+B \ln t)$, i.e., the degradation is logarithmic and its amplitude depends on the temperature and Fermi Level of device. Our approach reduces the work to the averages determined by simple binomial sums that are corroborated by our Monte Carlo simulations and by experimental results from literature, which bear in mind enlightening elucidations about the physics of degradation of semiconductor devices of our modern life

Técnicas probabilísticas para análise de yield em nível elétrico usando propagação de erros e derivadas numéricas

Em tecnologias nanométricas, variações nos parâmetros CMOS são um desafio para o projeto de circuitos com yield apropriado. Neste trabalho nós propomos uma metodologia eficiente e precisa para a modelagem estatística de circuitos. Propagação de erros e técnicas numéricas são aplicadas para a modelagem em nível elétrico de variações aleatórias e sistemáticas durante o processo de fabricação. O modelo considera covariâncias entre os parâmetros e correlação espacial, e tem como saída os estimadores estatísticos que podem ser usados em ferramentas de mais alto nível, tais como ferramentas de análise estatística de atraso (SSTA). Além disso, desenvolvemos uma metodologia para a análise quantitativa da contribuição de cada parâmetro para a variância da resposta do circuito. Como estudos de caso, modelamos o yield de uma memória SRAM e uma porta NOR dinâmica de pré-carga. No primeiro, consideramos o impacto do comprimento do canal e da tensão de limiar no tempo de acesso da célula de memória SRAM. Nós desenvolvemos um modelo probabilístico para o atraso de uma NOR dinâmica com keeperb estático, considerando variações na largura do canal e na tensão de limiar. Comparamos os resultados calculados pela metodologia proposta com dados estatístico obtidos a partir de simulações Monte Carlo. Reportamos ganho de desempenho de 70×, com um erro menor que 1%

Low Frequency Noise Considerations for CMOS Analog Circuit Design

Abstract: This paper gives an overview on 1/f-noise issues relevant for today's CMOS analog circuit design. The device-to-circuit relation of noise and the relevant operating conditions are reviewed. Modeling of the biasing dependence of 1/f-noise amplitude including large signal and statistical effects are discussed. The noise corner frequency 1 is shown to increase with CMOS technology scaling, and statistical effects are shown to even scale worse compared to the 1/fnoise. Moreover circuit design measures against noise are investigated. Finally, reliability issues concerning 1/f-noise in analog circuits are reviewed

Sub-Saharan Africa's Mothers, Newborns, and Children: Where and Why Do They Die?

In the first article in a series on maternal, newborn, and child health in sub-Saharan Africa, Joy Lawn and colleagues outline where and why deaths among mothers and children occur and what known interventions can be employed to prevent these deaths

Addressing disparities in maternal health care in Pakistan: gender, class and exclusion

Background: After more than two decades of the Safe Motherhood Initiative and Millennium Development Goals aimed at reducing maternal mortality, women continue to die in childbirth at unacceptably high rates in Pakistan. While an extensive literature describes various programmatic strategies, it neglects the rigorous analysis of the reasons these strategies have been unsuccessful, especially for women living at the economic and social margins of society. A critical gap in current knowledge is a detailed understanding of the root causes of disparities in maternal health care, and in particular, how gender and class influence policy formulation and the design and delivery of maternal health care services. Taking Pakistan as a case study, this research builds upon two distinct yet interlinked conceptual approaches to understanding the phenomenon of inequity in access to maternal health care: social exclusion and health systems as social institutions. Methods/Design: This four year project consists of two interrelated modules that focus on two distinct groups of participants: (1) poor, disadvantaged women and men and (2) policy makers, program managers and health service providers. Module one will employ critical ethnography to understand the key axes of social exclusion as related to gender, class and zaat and how they affect women’s experiences of using maternal health care. Through health care setting observations, interviews and document review, Module two will assess policy design and delivery of maternal health services. Discussion: This research will provide theoretical advances to enhance understanding of the power dynamics of gender and class that may underlie poor women’s marginalization from health care systems in Pakistan. It will also provide empirical evidence to support formulation of maternal health care policies and health care system practices aimed at reducing disparities in maternal health care in Pakistan. Lastly, it will enhance inter-disciplinary research capacity in the emerging field of social exclusion and maternal health and help reduce social inequities and achieve the Millennium Development Goal No. 5