The impact of uniform strain applied via bonding onto plastic substrate on MOSFET performance

For the first time, this letter presents a novel post-backend strain applying technique and the study of its impact on MOSFET device performance. By bonding the Si wafer after transistor fabrication onto a plastic substrate (a conventional packaging material FR-4), a biaxial-tensile strain (/spl sim/0.026%) was achieved globally and uniformly across the wafer due to the shrinkage of the bonded adhesive. A drain-current improvement (average /spl Delta/I/sub d//I/sub d//spl sim/10%) for n-MOSFETs uniformly across the 8-in wafer is observed, independent of the gate dimensions (L/sub g//spl sim/55 nm -0.530 /spl mu/m/W /spl sim/2-20 /spl mu/m). The p-MOSFETs also exhibited I/sub d/-improvement by /spl sim/7% under the same biaxial-tensile strain. The strain impact on overall device characteristics was also studied, including increased gate-induced drain leakage and short-channel effects.     

Handheld use condition-based bend test development

For handheld electronic applications such as cell phones and personal digital assistants (PDAs), repeated key strokes could result in considerable flexure of the printed circuit board (PCB) mounted inside the housing. In this study, a standardized four-point bend test, including test board design, test setup, and test input level, has been developed. The S-N curve has been obtained by plotting the reliability at all deflection levels as a function of solder joint strain energy density. The effect of test frequency has also been evaluated. The reliability model prediction of three-point bend reliability matches the experimental data extremely well. The transfer function between reliability stressing and field condition is a strain-energy-density-based power law relationship. Finite-element simulation has been conducted for the worst case cell phone subjected to key presses. The use condition data including strain profiles and frequency have been incorporated in the field life prediction. The four-point bend performance can be converted into the component reliability during cell phone field use conditions. This study establishes the correlation between the use conditions and reliability tests. The cyclic four-point bend test will be implemented in the Joint Electron Device Engineering Council (JEDEC) bend test standard for handheld components.     

Simultaneous strain and temperature distribution sensing using two fiber Bragg grating pairs and a genetic algorithm

This study uses two pairs of FBGs to perform simultaneous strain and temperature field measurements. The first pair of FBGs, comprising one uniform FBG and one chirped FBG, measures the strain and temperature fields, while the second pair of FBGs, also comprising one uniform FBG and one chirped FBG, measures the temperature field only. A genetic algorithm is applied to reconstruct the arbitrary strain and temperature distribution profiles simultaneously from the measured reflection intensity spectra of the four FBGs. Various examples of nonmonotonic variations in the strain and temperature fields are considered for illustration purposes. It is found that the proposed scheme successfully reconstructs the applied strain and temperature fields.     

The evolution path of 4G networks: FDD or TDD?

Frequency-division duplexing and time-division duplexing are two common duplexing methods used in various wireless systems. However, there are advantages and technical issues associated with them. In this article we discuss in detail the features, and the design and implementation challenges of FDD and TDD systems for 4G wireless systems. In particular, we present a number of advantages and flexibilities an TDD system can bring to 4G systems that an FDD system cannot offer, and identify the major challenges, including cross-slot interference, in applying TDD in practice. Due to the fact that cross-slot interference is one of the critical challenges to employing TDD in cellular networks, we also provide a quantitative analysis on its impact on co-channel and adjacent channel interfering cells     

Determination of gate-bias dependent source/drain series resistance and effective channel length for advanced MOS devices

In this paper, an improved method for determining the gate-bias dependent source and drain series resistances R_D and effective channel length L_eff = L_M − ΔL (L_M is the mask channel length and ΔL is the channel length reduction) of advanced MOS devices is developed for the purpose of providing a better accuracy for the modeling of the current–voltage characteristics of LDD MOSFETs operating from 25 to 120 °C. Our results show that both ΔL and R_SD decrease with increasing gate-bias, but increase with increasing temperature. In addition, the gate-bias dependence of ΔL and R_SD becomes weaker as the temperature rises. Experimental data obtained from devices fabricated using the 0.14 and 0.09 μm DRAM technologies are included in support of the theoretical work developed.     

Studies of glycolysis of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. I. Influences of glycolysis conditions

The glycolysis of recycled poly(ethylene terephthalate) flakes by ethylene glycol (EG) is investigated. Bis‐2‐hydroxyethyl terephthalate (BHET) and oligomers are predominately glycolysis products. The influences of glycolysis temperature, glycolysis time, and the amount of catalyst (cobalt acetate) are illustrated. The BHET, dimer, and oligomers are predominately glycolysis products. The optimum glycolysis temperature is found to be 190°C. If a 190°C glycolysis temperature, 1.5‐h glycolysis time, and 0.002 mol glycolysis catalyst (cobalt acetate) are used, the glycolysis conversion is almost 100%. The glycolysis conversion rate increases significantly with the glycolysis temperature, glycolysis time, and the amount of cobalt acetate. Thermal analyses of glycolysis products are examined by differential scanning calorimetry. In addition, the chemical structures of glycolysis products are also determined by a Fourier transform IR spectrophotometer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 943–948, 2001     

Lincomycin solar photodegradation, algal toxicity and removal from wastewaters by means of ozonation

Antibiotic molecules have been reported among the xenobiotics present at trace levels in sewage treatment plant (STP) effluents and aquatic environment. Lincomycin, one of the most used in clinical practices whose presence in the STP effluents has been often documented, is submitted to an extensive investigation to assess its persistence in the environment and toxicity towards different algal strains. The possibility to remove the lincomycin from water by means of ozonation is demonstrated and a reduction of toxicity of ozonated solutions on S. leopoliensis, with respect to untreated solutions containing this compound, is obtained even just for 1h of treatment. Kinetic constants for the attack to lincomycin of ozone (from 1.53 x 10(5) M(-1)s(-1) at pH = 3.0 and 4.93 x 10(5) M(-1)s(-1) at pH = 6.7) and OH radicals (4.37 x 10(9) M(-1)s(-1) at pH = 5.5 and 4.59 x 10(9) M(-1)s(-1) at pH = 7.5) are also evaluated.     

Hardness and carbonate effects on the reactivity of zero-valent iron for Cr(VI) removal

Zero-valent iron (Fe0) was used to remove hexavalent chromium, Cr(VI), in groundwater via a coupled reduction-oxidation reaction. Nine columns were set up under various groundwater geochemistry to investigate the effects of hardness and carbonate on Cr(VI) removal. The Cr(VI) removal capacity of Fe0 was found to be about 4 mgCr/g Fe0 in the control column (i.e., column 1). A slight decrease in the Cr(VI) removal capacity was found in the presence of calcium hardness. However, there was a 17% drop in the Cr(VI) removal capacity when magnesium hardness was present at low to moderately hard level. Results also revealed that carbonate changed the morphology of the Fe0 by formation of pale green precipitates on the iron filings. Furthermore, there was a 33% decrease in the Cr(VI) removal capacity of Fe0 when both carbonate and hardness ions were present. In general, the presence of hardness ions and carbonate in groundwater have great impact on the Fe0 by formation of passivated precipitates, such as CaCO3, on the Fe0 surface resulting in a diminished lifespan of the Fe0 by blocking electron transfer.     

Mass spectrometric and toxicological assays of Athabasca oil sands naphthenic acids

This work concerns the analysis of model naphthenic acids and authentic naphthenic acids from the tailings ponds of the Athabasca tar sands. A first objective was to compare atmospheric pressure chemical ionization mass spectrometry (APCI-MS) with the previously studied electrospray mass spectrometry (ESI-MS) in this analysis. APCI-MS had a wider range of quantitation than ESI-MS, but its detection limit was poorer and model compounds showed greater variation in calibration sensitivity. A second objective was fractionation of naphthenic acids from tailings pond water and analysis by the Microtox toxicity assay. Fractionation on the basis of solubility gave fractions that did not differ significantly either in their congener distribution by ESI-MS or in their response to the Microtox assay. When partial separation was achieved by anion exchange chromatography, fractions with a higher proportion of multi-ring structures exhibited lower toxic potency. This finding is consistent with field observations that indicate that the toxic potency of tailings ponds water declines as the samples age-multi-ring structures are more highly branched and therefore more resistant to microbial degradation.