Production worthy method to structure platinum electrodes for ferroelectric devices elisabeth

Abstract

Platinum (Pt) is a viable electrode material for use with ferroelectric films to form FeRAM cells. Due to the chemical stability of Pt etching at low-temperature, drawbacks like tapered Pt profiles with poor CD control and low mean time between cleans are resulting.

In this work plasma etching of sub-micron Pt electrodes with vertical and veil-free profiles was successfully demonstrated. This was obtained by maintaining substrate temperatures >250°C, assisting etch by-product volatility and promotion of necessary chemical reactions.

The production worthiness of high-temperature Pt etching was evaluated by a marathon run on simulated product material while monitoring the process parameter stability. Production was successfully simulated by 950 product like substrates for more than 34 plasma hours. Stable wafer-to-wafer performance in all monitored parameters demonstrated the production worthiness of this platinum electrode structuring method for applications in FeRAM manufacturing.     

Impact of platinum contamination on ferroelectric memories

Abstract

The impact of platinum contamination on the breakdown properties of gate oxide is reported. Wafers were intentionally contaminated with 1×10¹³ to 4×10¹⁴ at/cm² Pt after a 7.5 nm gate oxide growth, 300 nm poly-silicon deposition and subsequent phosphorus doping. Breakdown characteristics were evaluated using a voltage ramp method. The current-voltage curves of MOS capacitors show very few low field breakdown events, and the main field breakdown occurs at 12 MV/cm. If compared to clean wafers, platinum does not increase the defect density seriously. It is found from the E-Ramp results that platinum contamination up to 4×10¹⁴ at/cm² does not have a pronounced effect on the gate oxide integrity if the contamination occurs after front-end-of-line processing of device fabrication.     

Giant Magnetoelectric Effect in Thin‐Film Composites

Highly sensitive AC magnetic field sensors are presented using magnetoelectric composites consisting of magnetostrictive and piezoelectric phases. They are offering passive nature, high sensitivity, large effect enhancement at mechanical resonance, and large linear dynamic range. Thin‐film magnetoelectric 2‐2 composites benefit from perfect coupling between the piezoelectric and magnetostrictive phases and from the reduction in size which is essential for high spatial resolution. Their design uses AlN and a plate capacitor or PZT with interdigital electrodes and magnetostrictive amorphous FeCoSiB single layers or exchanged biased multilayers. At mechanical resonance and depending on the geometry, extremely high ME coefficients of up to 9.7 kV/cm Oe in air and up to 19 kV/cm Oe under vacuum were obtained. To avoid external DC magnetic bias fields, composites consisting of exchanged biased multilayers serving as the magnetostrictive component with a maximum magnetoelectric coefficient at zero magnetic bias field are employed. Furthermore, the anisotropic response of these exchanged biased composites can be utilized for three‐dimensional vector field sensing. Sensitivity and noise of the sensors revealed limits of detection as good as to 2.3 pT/Hz^1/2 at mechanical resonance. Sensitivity between 0.1 and 1000 Hz outside resonance can be enhanced through frequency conversion using AC magnetic bias fields.     

New Methods for Preparing Submicrometer Powders of The Tungstate‐Ion Conductor Sc2(WO4)3 and its Al and In Analogs

Two new methods for preparing submicrometer powders of M₂(WO₄)₃, M = Sc, In, and Al via combustion synthesis are reported. Stoichiometric combinations of trivalent metal nitrates, ammonium metatungstate, and either urea or carbohydrazide as the fuel were reacted at 550°C, producing amorphous or poorly crystallized powders with an average particle size ranging from 164 to 350 nm. Calcining the powders at 800°C for 1 h produced well‐crystallized, phase‐pure powders with an average particle size ranging from 210 to 711 nm. Powders sintered at 1000°C for 14 h resulted in pellets that were 87%–95% of the theoretical density, which is notably higher than typically obtained from powders prepared by solid‐state reaction. Whereas there was little difference in the microstructure of Al₂(WO₄)₃ pellets prepared with the two different powders, the carbohydrazide‐derived powders resulted in In₂(WO₄)₃ and Sc₂(WO₄)₃ pellets with a larger grain size than those prepared with urea‐derived powders. The electrical conductivity of the sintered pellets, while comparable to that reported for polycrystalline M₂(WO₄)₃ prepared by solid‐state reaction, was strongly influenced by grain‐boundary effects.     

Heat and mass transfer in air-fed pressurised suits

Air-fed pressurised suits are used to protect workers against contamination and hazardous environments. The specific application here is the necessity for regular clean-up maintenance within the torus chamber of fusion reactors. The current design of suiting has been developed empirically. It is, therefore, very desirable to formulate a thermo-fluids model, which will be able to define optimum designs and operating parameters. Two factors indicate that the modelling should be as comprehensive as possible. Firstly, the overall thermo-fluids problem is three-dimensional and includes mass as well as heat transfer. The fluid field is complex, bounded on one side by the human body and on the other by what may be distensible, porous and multi-layer clothing.In this paper, we report firstly the modelling necessary for the additional mass and heat transport processes. This involves the use of Fick’s and Fourier’s laws and conjugate heat transfer. The results of an initial validation study are presented. Temperatures at the outlet of the suits were obtained experimentally and compared with those predicted by the overall CFD model. Realistic three-dimensional geometries were used for the suit and human body. Calculations were for turbulent flow with single- and two-component (species) models.     

Habitat diversity and fish assemblage structure in local river widenings: A case study on a swiss river

We investigated habitat availability and fish assemblage structure in three local river widenings, completed 3–14 years ago, and five adjacent canalized reaches on the river Thur, a seventh‐order river in Switzerland. To account for seasonal variability, surveys were repeated in winter and summer 2005. Results were compared with historical pre‐disturbance data to evaluate whether the current abiotic and biotic conditions in the study reaches have attained historic near‐natural levels. Hydro‐physical habitat diversity (depth, flow velocity, cover availability) was considerably greater in the two longer widenings (>900 m length) than in the canalized reaches and in the shortest widening (300 m length), with higher proportions of shallow or deep areas of different flow velocities. However, the comparison of current and historical near‐natural shoreline lengths indicated that the current geomorphological complexity is still considerably impaired in all reaches. No overall significant relationship was found between the reach type (canalized or rehabilitated) and the number of species or the total fish abundance which were strongly correlated with the availability of suitable cover and moderate flow velocity. However, highest winter abundances were observed in deep, well‐structured backwaters of the rehabilitated reaches, documenting their significance as wintering habitats. Assemblage structure and composition were similar in canalized and rehabilitated reaches. Compared to the historical data, however, fewer and different dominant species were found, and guild composition changed towards a higher representation of generalists and tolerant species. Copyright © 2008 John Wiley & Sons, Ltd.     

Size-dependent joule heating of gold nanoparticles using capacitively coupled radiofrequency fields

Capacitively coupled shortwave radiofrequency fields (13.56 MHz) resistively heat low concentrations (∼1 ppm) of gold nanoparticles with a thermal power dissipation of ∼380 kW/g of gold. Smaller diameter gold nanoparticles (< 50 nm) heat at nearly twice the rate of larger diameter gold nanoparticles (≥50 nm), which is attributed to the higher resistivity of smaller gold nanostructures. A Joule heating model has been developed to explain this phenomenon and provides critical insights into the rational design and engineering of nanoscale materials for noninvasive thermal therapy of cancer. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. These two authors made an equal contribution to the work.     

A longitudinal study of rumination and distraction in formerly depressed inpatients and community controls.

The response styles theory (S. Nolen-Hoeksema, B. E. Wisco, & S. Lyubomirsky, 2008) supposes that ruminative coping is a cognitive risk factor for the course of depression, whereas distractive coping has protective effects. The authors present a longitudinal study on reciprocal relations between coping styles and depressive symptoms. They investigated 82 formerly depressed inpatients 4 weeks, 6 months, and 3.5 years after hospital discharge together with 76 age- and gender-matched community controls. Depressive symptoms predicted future symptom-focused rumination over the initial short-term interval in both samples. In former inpatients, this predictive effect was also significant over the subsequent long-term interval. Symptom-focused rumination and distraction were significant predictors of future depressive symptoms across both intervals, with sample-specific effects. In the community sample, symptom-focused rumination predicted more depressive symptoms, whereas in former inpatients, distractive coping predicted fewer depressive symptoms over time. The authors conclude that interventions aimed at reducing rumination should preferably be applied in preventive and early intervention settings, although in individuals with a history of more severe and long-standing depression rumination might gradually lose its capacity to predict the further illness course. In these persons, interventions should particularly strengthen distractive coping. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy performance of wood-burning cookstoves in Michoacan, Mexico

There have been few detailed assessments of the actual impacts of improved stove interventions in rural communities, although many improved stove projects have reported overall efficiencies from tests in simulated kitchens using water-boiling tests (WBTs). This paper presents an integrated energy evaluation of the Patsari cookstove, an efficient wood-burning cookstove developed in Mexico that has recently obtained international recognition, in comparison to traditional cookstoves in rural communities of Michoacan, Mexico. The evaluation uses three standard protocols: the WBT, which quantifies thermal efficiency and firepower; the controlled cooking test (CCT), which measures specific energy consumption associated with local cooking tasks, and the kitchen performance test (KPT), which evaluates the behavior of the stoves in-field conditions and estimates fuel savings. The results showed that the WBT gave little indication of the overall performance of the stove in rural communities. Field testing in rural communities is of critical importance, therefore, in estimating the benefits of improved stoves. In the CCT for tortilla making, the main cooking task in Mexican rural households, Patsari stoves showed fuelwood savings ranging from 44% to 65% in relation to traditional open fires (n=6; P<0.05). These savings were similar in magnitude to the average energy savings from KPT before and after Patsari adoption of 67% (n=23; P<0.05) in rural households exclusively using fuelwood. Similar energy savings of 66% for fuelwood and 64% for LPG, respectively, were also observed in households using mixed fuels. With sound technical design, critical input from local users and proper dissemination strategies, therefore, improved stoves can significantly contribute to improvements in the quality of life of rural people with potential benefits to the surrounding environment.