The aim of this paper is to give a thorough overview of flash memory cells. Basic operations and charge-injection mechanisms that are most commonly used in actual flash memory cells are reviewed to provide an understanding of the underlying physics and principles in order to appreciate the large number of device structures, processing technologies, and circuit designs presented in the literature. New cell structures and architectural solutions have been surveyed to highlight the evolution of the flash memory technology, oriented to both reducing cell size and upgrading product functions. The subject is of extreme interest: new concepts involving new materials, structures, principles, or applications are being continuously introduced. The worldwide semiconductor memory market seems ready to accept many new applications in fields that are not specific to traditional nonvolatile memories.

Flash memory cells-an overview

New guidelines for exercise in pregnancy and postpartum have been published by the American College of Obstetricians and Gynecologists

In January 2002 the American College of Obstetricians and Gynecologists (ACOG) published new recommendations and guidelines for exercise during pregnancy and the postpartum period.1 Regular exercise is promoted for its overall health benefits. Pregnancy is recognised as a unique time for behaviour modification and is no longer considered a condition for confinement. It is currently recognised that habits adopted during pregnancy could affect a woman's health for the rest of her life. For the first time the recommendation suggests a possible role for exercise in the prevention and management of gestational diabetes.

The recommendations also promote exercise for sedentary women and those with medical or obstetric complications, but only after medical evaluation and clearance.

Box 1 lists the absolute contraindications to aerobic exercise during pregnancy, and box 2 the relative contraindications. As with any form of exercise prescription, these recommendations also include the warning signs to terminate exercise while pregnant (box 3). The recommendations also offer guidelines for sports and recreational activities. It cautions against participation in contact sports and recommends avoidance of scuba diving.

As for postpartum resumption of activities, the recommendations note that rapid resumption has no adverse effects, but gradual return to former activities is advised. This review includes background and comments to the above recommendations.

The health benefits of physical activity are well recognised, and conversely sedentary habits and low levels of cardiorespiratory fitness are leading risk factors for subsequent development of cardiovascular disease.2,3

The Centers for Disease Control and Prevention and the American College of Sports Medicine (CDC-ACSM) have recommended the accumulation of 30 minutes or more of moderate intensity physical activity on most, and preferably all, days of the week.4 Moderate …

https://bjsm.bmj.com/content/bjsports/37/1/6.full.pdf

Guidelines of the American College of Obstetricians and Gynecologists for exercise during pregnancy and the postpartum period

In order to model the RF behavior of a device-under-test (DUT), e.g., active and passive devices, dedicated on-wafer test-structures are required. However, parasitic components in the test-structure stemming from the contact pads, the metal interconnections and the silicon substrate, largely influence the RF behavior of the actual DUT. They need to be subtracted from the measurement results if one wants to model the RF behavior of the actual DUT accurately. This subtraction procedure is referred to as de-embedding. In this paper, we propose an improved three-step de-embedding method to subtract the influence of parasitics. The de-embedding method has been applied not only to S-parameter measurement results on MOSFETs but also, for the first time, to large-signal vectorial RF measurements.

Improved three-step de-embedding method to accurately account for the influence of pad parasitics in silicon on-wafer RF test-structures

Regular physical activity is associated with improved physiological, metabolic and psychological parameters, and with reduced risk of morbidity and mortality. Current recommendations aimed at improving the health and well-being of nonpregnant subjects advise that an accumulation of > or =30 minutes of moderate physical activity should occur on most, if not all, days of the week. Regardless of the specific physiological changes induced by pregnancy, which are primarily developed to meet the increased metabolic demands of mother and fetus, pregnant women benefit from regular physical activity the same way as nonpregnant subjects. Changes in submaximal oxygen uptake (VO(2)) during pregnancy depend on the type of exercise performed. During maternal rest or submaximal weight-bearing exercise (e.g. walking, stepping, treadmill exercise), absolute maternal VO(2) is significantly increased compared with the nonpregnant state. The magnitude of change is approximately proportional to maternal weight gain. When pregnant women perform submaximal weight-supported exercise on land (e.g. level cycling), the findings are contradictory. Some studies reported significantly increased absolute VO(2), while many others reported unchanged or only slightly increased absolute VO(2) compared with the nonpregnant state. The latter findings may be explained by the fact that the metabolic demand of cycle exercise is largely independent of the maternal body mass, resulting in no absolute VO(2) alteration. Few studies that directly measured changes in maternal maximal VO(2) (VO(2max)) showed no difference in the absolute VO(2max) between pregnant and nonpregnant subjects in cycling, swimming or weight-bearing exercise. Efficiency of work during exercise appears to be unchanged during pregnancy in non-weight-bearing exercise. During weight-bearing exercise, the work efficiency was shown to be improved in athletic women who continue exercising and those who stop exercising during pregnancy. When adjusted for weight gain, the increased efficiency is maintained throughout the pregnancy, with the improvement being greater in exercising women. Regular physical activity has been proven to result in marked benefits for mother and fetus. Maternal benefits include improved cardiovascular function, limited pregnancy weight gain, decreased musculoskeletal discomfort, reduced incidence of muscle cramps and lower limb oedema, mood stability, attenuation of gestational diabetes mellitus and gestational hypertension. Fetal benefits include decreased fat mass, improved stress tolerance, and advanced neurobehavioural maturation. In addition, few studies that have directly examined the effects of physical activity on labour and delivery indicate that, for women with normal pregnancies, physical activity is accompanied with shorter labour and decreased incidence of operative delivery. However, a substantial proportion of women stop exercising after they discover they are pregnant, and only few begin participating in exercise activities during pregnancy. The adoption or continuation of a sedentary lifestyle during pregnancy may contribute to the development of certain disorders such as hypertension, maternal and childhood obesity, gestational diabetes, dyspnoea, and pre-eclampsia. In view of the global epidemic of sedentary behaviour and obesity-related pathology, prenatal physical activity was shown to be useful for the prevention and treatment of these conditions. Further studies with larger sample sizes are required to confirm the association between physical activity and outcomes of labour and delivery.

Physical activity and pregnancy: cardiovascular adaptations, recommendations and pregnancy outcomes.

In an EL display device in which color purity of each of red, blue and green is different, the EL display device displaying an image of a desired balance of red, blue and green is provided. A video signal supplied to each EL element is gamma (γ)-corrected by a correction circuit, the color purity of each of blue luminescence, green luminescence, and red luminescence is suitably controlled in accordance with the voltage and current of the corrected video signal.

EL display device and electronic device

When applying a high voltage to the floating gate of a split-gate transistor, enhanced hot-electron injection is observed that can be used for 5-V compatible EPROM or flash EEPROM device operation. The current collected on the gate is equal to the total electron injection current. Charge-pumping measurements and device simulations are used to analyze the electron injection and to determine its exact position in the transistor channel. Gate currents only show a weak dependence on both transistor channel lengths. The width of the spacer between both transistor gate has, however, been determined to be an important injection parameter. >

Analysis of the enhanced hot-electron injection in split-gate transistors useful for EEPROM applications

A flash E/sup 2/PROM device which is programmed with a highly efficient hot-electron injection mechanism is described. This high-injection MOS (HIMOS) device combines a very high programming speed at 5-V-only operation with a low development entry cost, which renders it highly attractive for embedded memory applications. The HIMOS concept exhibits complete soft-write immunity and the possibility of overerasure without causing any problem in a memory architecture. It is shown that this device can also operate with a 3.3-V voltage supply, which is of a major importance for the next generation of submicron flash E/sup 2/PROM technologies. >

HIM0S-a high efficiency flash E/sup 2/PROM cell for embedded memory applications

In this paper, the forward current‐voltage (I‐V) characteristics of Si p‐n junction diodes, fabricated in different state‐of‐the‐art complementary‐metal‐oxide‐semiconductor (CMOS) technologies, are investigated at liquid helium temperatures. As will be shown, three different I‐V regimes can exist: a forward breakdown/hysteresis regime at a turn‐on voltage which may be larger than the built‐in potential of the junction; a thermionic emission regime, corresponding to a I=A exp(qV/kT) relation and a high‐injection space‐charge‐limited regime, giving rise to a current which is proportional to Vn. The anomalous turn‐on behavior can be explained by considering the small barrier for carrier injection, which exists at the ‘‘ohmic’’ contact. It will be demonstrated that the presence of this forward breakdown is strongly determined by the fabrication technology used. In extreme cases (large‐area well diodes) multiple breakdown is observed, indicating an inhomogeneous, filamentary current flow. As will be shown, sim...

The behavior of silicon p‐n junction‐based devices at liquid helium temperatures

To optimize the electrical characteristics of polysilicon emitter bipolar transistors, the poly emitter interface needs careful engineering. In this paper, bipolar transistors of a 0.5 /spl mu/m BiCMOS process have been fabricated with intentionally grown oxides in an LPCVD cluster for precise control over the interfacial oxide thickness and uniformity. The trade off between current gain enhancement and increased 1/f noise will be discussed for various interfacial oxide thicknesses and emitter annealing conditions. It will be demonstrated that for sufficiently large base currents, both for large (20 /spl mu/m/spl times/20 /spl mu/m) and small (0.5 /spl mu/m/spl times/5 /spl mu/m) emitter areas the interfacial oxide dominates the 1/f noise spectrum of the base current. Hence, the polysilicon emitter interface engineering will not only set the current gain at a predefined value, but at the same time the associated oxide-tunnelling noise is fixed, within the constraint that the emitter-base junction depth is constant. Finally, it will be shown that the current gain enhancement and increased 1/f noise have compensating effects on the output noise of practical circuits.

Impact of polysilicon emitter interfacial layer engineering on the 1/f noise of bipolar transistors

A new quantitative model is developed that allows an excellent prediction of the disturb behavior of tunnel oxide flash E/sup 2/PROM devices after write/erase cycling and provides a well-understood and consistent cell optimization procedure. This model requires as only input a measurement of the oxide quality on capacitors and transistors, and some basic cell characteristics.

Ludo Deferm

Papers

Analysis of the enhanced hot-electron injection in split-gate transistors useful for EEPROM applications

HIM0S-a high efficiency flash E/sup 2/PROM cell for embedded memory applications

The behavior of silicon p‐n junction‐based devices at liquid helium temperatures

Impact of polysilicon emitter interfacial layer engineering on the 1/f noise of bipolar transistors

A new quantitative model to predict SILC-related disturb characteristics in Flash E2PROM devices