bluuebunny/crossref_metadata_2025 huggingface dataset:
Complete Genome of
Serratia
sp. Strain FGI 94, a Strain Associated with Leaf-Cutter Ant Fungus Gardens
Authors: Aylward Frank O. , Tremmel Daniel M. , Starrett Gabriel J. , Bruce David C. , Chain Patrick , Chen Amy , Davenport Karen W. , Detter Chris , Han Cliff S. , Han James , Huntemann Marcel , Ivanova Natalia N. , Kyrpides Nikos C. , Markowitz Victor , Mavrommatis Kostas , Nolan Matt , Pagani Ioanna , Pati Amrita , Pitluck Sam , Teshima Hazuki , Deshpande Shweta , Goodwin Lynne , Woyke Tanja , Currie Cameron R.
Published: March 2013

Serratia
sp. strain FGI 94 was isolated from a fungus garden of the leaf-cutter ant
Atta colombica
. Analysis of its 4.86-Mbp chromosome will help advance our knowledge of symbiotic interactions and plant biomass degradation in this ancient ant-fungus mutualism.
Destructive post-traumatic chondrolysis of the subtalar joint: a case report and review of the literature
Authors: Kumar Vishwajeet , Debnath Ujwal K , Karmegam Anand , Hariharan K
Published: March 2013

Injuries to the subtalar joint are often associated with fractures of the talus or calcaneum. These injuries often lead to degenerative changes resulting in pain, restriction of movement and difficulty in weight bearing. This can cause significant deformity and disability for the patient. Occult injury of the subtalar joint has been described as an isolated event or in association with a subluxation/dislocation of this joint. They are difficult to assess with plain radiography therefore, they are generally diagnosed with advanced imaging like CT scan or MRI scan. We present a case of a 66-year-old man who presented with destructive chondrolysis of the subtalar joint 2 years following conservative treatment of a minimally displaced distal fibular fracture. It was treated by subtalar and talonavicular arthrodesis. Overall, the patient made an excellent recovery and was satisfied with the outcome.
Successful management of immunological rejection following allogeneic simple limbal epithelial transplantation (SLET) for bilateral ocular burns
Authors: Bhalekar Swapnil , Basu Sayan , Sangwan Virender S
Published: March 2013

A 41-year-old woman presented with bilateral total limbal stem cell deficiency, one year after chemical injury. She underwent allogeneic simple limbal epithelial transplantation (SLET) from a cadaveric donor in her right eye. One month later her unaided visual acuity (VA) improved to 20/100 from hand-motions. The corneal surface was avascular and epithelialised. Three months later, she presented with acute pain in right eye with peripheral corneal neovascularisation encircling the transplants, engorged and tortuous perilimbal vessels and diffuse epithelial haze. For a diagnosis of allograft rejection, pulse doses of intravenous methyl prednisolone with intensive topical steroids were administered. Her symptoms resolved in a week, confirming the diagnosis. She recovered her pre-rejection VA. She was maintained on systemic immunosuppressive agents. Her ocular surface continues to be stable. This case describes hitherto unknown clinical features of allograft rejection following SLET and emphasises the importance of continued immunosuppression in allogeneic limbal transplantation.
Fatal road traffic injuries in Ibadan, using the mortuary as a data source
Authors: Eze Uwom O , Kipsaina Chebiwot Caroline , Ozanne-Smith Joan
Published: March 2013

Background

Road Traffic Injury (RTI) in Africa represents 14% of global RTI deaths. Lack of timely, reliable data undermines road safety interventions. Available fatality data are aggregated, limited in detail or scarce in surveys. This is the first fatal RTI surveillance study in Nigeria.

Objective

To pilot a systematic mortuary-based data collection in Ibadan, determine the nature and circumstances of fatal RTI and assess data quality against existing data sources.

Methods

Using a draft data collection system developed jointly by WHO and Monash University, the detailed information was prospectively collected on RTI University College Hospital mortuary admissions in Ibadan September 2010 to February 2011. Demographics, road user type, counterpart vehicle, intent, manner and medical cause of death were recorded.

Results

Mortuary admissions included 80 fatal RTI cases: 81.3% males. By road user category, 28 (35.0%) were pedestrians; 28 (35.0%) motorised 2-wheeler users; 18.8% car occupants; and 11.3% bus occupants. In 70% of cases, medical cause of death was head injury, including 25 of 28 motorised 2-wheeler users (89.3%). Estimates from this study indicate apparent increased mortuary capture of fatal RTI compared with police data.

Conclusions

This study demonstrates the feasibility of collecting detailed, timely RTI fatality data through mortuary-based surveillance in Ibadan. While not all RTI deaths are reported to any authority in Ibadan, this large case series complements existing data sources and suggests that pedestrians and motorised 2-wheeler users die most often in road traffic crashes. Frequent head injuries among motorised 2-wheeler users strongly support the need for helmet wearing interventions.
How is nutrition transition affecting dietary adequacy in Eeyouch (Cree) adults of Northern Quebec, Canada?
Authors: Johnson-Down Louise M. , Egeland Grace M.
Published: March 2013

Rapid development, including the building of hydroelectric projects and roads in remote areas of Northern Quebec, Canada, has led to concerns about the contamination of traditional foods (TF) and a transition to a diet characterized by increased commercial food intake. A cross-sectional study of 850 Cree adults, aged ≥19 years, from 7 of the 9 Eeyouch communities was conducted during the spring and summer seasons of 2005–2008. Anthropometric measures were collected. TF and dietary intake were assessed using food-frequency questionnaires (FFQs) and 24-h recalls. Obesity was high, with 77% of the women and 64% of the men classified as obese. Past-year TF consumption was 100%, and 41% of participants reported eating TF on the 24-h recall. TF intake as reported on both the FFQs and the 24-h recalls was higher in individuals aged >50 years of age and in men, relative to younger adults and women, respectively. TF consumption increased protein, vitamin D, iron, and magnesium in all individuals, and energy, cholesterol, magnesium, sodium, and zinc in men aged 19–50 years; it decreased vitamin C in men and women aged ≥51 years. Participants reported drinking a mean daily 0.78 ± 1.34 cans of soft drinks or other high-sugar beverages per day or 5.28% ± 8.92% of total energy. It is important to identify behaviours that are contributing to obesity and its health consequences in this population and to find culturally appropriate ways to promote the consumption of TF and to reduce the consumption of energy-dense and nutrient-poor beverages and food items.
Effects of carbohydrate ingestion during exercise on substrate oxidation in physically active women with different body compositions
Authors: Mitchell Nicole M. , Potteiger Jeffery A. , Bernardoni Brittney , Claytor Randal P.
Published: March 2013

We examined the effects of consuming a 6% carbohydrate (CHO) beverage during exercise on substrate oxidation in active, young Caucasian women with higher body fat (HF) (>25%) and lower body fat (LF) (<25%). The HF group (n = 9) had 32.4% ± 5.6% fat and the LF group (n = 8) had 20.0% ± 3.0% fat. Subjects completed 2 sessions of 45 min of treadmill exercise at 55% of maximal oxygen consumption. Immediately prior to and at 15-min intervals during exercise, subjects consumed 25% of a total volume of a CHO beverage (1 g CHO·kg−1) or a placebo (PLC). During exercise and for 2 h after exercise, expired gases were analyzed to determine oxidation rates for CHO (CHO-OX) and fat (FAT-OX). During exercise, significant differences (p < 0.05) in CHO-OX (mg·kg fat-free mass−1·min−1) were found between groups for the CHO trial (LF, 35.4 ± 4.7 vs. HF, 29.8 ± 3.6) and the PLC trial (LF, 33.7 ± 6.4 vs. HF, 26.3 ± 4.3). CHO-OX was significantly higher during the first hour of recovery in both the LF group (CHO, 9.3 ± 2.1 vs. PLC, 5.3 ± 2.4) and the HF group (CHO, 8.7 ± 2.0 vs. PLC, 4.2 ± 1.0), but during the second hour of recovery, only the HF group had a higher CHO-OX (CHO, 5.3 ± 1.8 vs. PLC, 3.9 ± 1.1). FAT-OX was significantly lower during the first hour of recovery in both the LF group (CHO, 0.6 ± 0.4 vs. PLC, 1.0 ± 0.4) and the HF group (CHO, 0.4 ± 0.4 vs. PLC, 1.4 ± 0.4), as well as during the second hour of recovery in both the LF group (CHO, 0.8 ± 0.4 vs. PLC, 1.3 ± 0.5) and the HF group (CHO, 0.9 ± 0.6 vs. PLC, 1.6 ± 0). CHO ingestion promotes CHO-OX and suppresses FAT-OX during and following exercise in physically active women with low and high levels of body fat.
Anthropometric and dietary predictors of insulin sensitivity in 10- to 14-year-old boys and girls
Authors: Forbes Laura E. , Downs Shauna M. , Fraser Shawn N. , Majumdar Sumit R. , Ball Geoff D.C. , Plotnikoff Ronald C. , Wozny Paul D. , Torrance Brian D. , McCargar Linda J. , Lewanczuk Richard Z. , McGavock Jonathan M.
Published: March 2013

The high prevalence of pediatric obesity has made preventing chronic diseases through healthy lifestyle behaviours a priority within pediatrics. Examining the association between diet and insulin sensitivity (IS) in youth may provide important insights for tailoring preventative dietary interventions. The objective of this study was to explore the associations among anthropometry, diet, and IS in 10- to 14-year-olds. In this cross-sectional study, the primary outcome measure was IS, measured noninvasively using a 13C glucose breath test. Exposure variables included body mass index (BMI) z score and several dietary variables, including glycemic index (GI), glycemic load, and fiber, magnesium, vegetable and fruit, and fat intakes, all of which were derived from a validated, Web-based 24-h recall tool. Multiple regression analyses were performed for boys and girls separately. In total, 378 students (227 girls) aged 12.1 ± 1.2 years were studied. In this sample ∼24% of youth were considered overweight or obese (BMI z score = 0.41 ± 0.93). Multiple regression analyses showed that BMI z score was negatively and independently associated with 13C insulin sensitivity score (13CISS) in both boys and girls (boys: β = −0.501; girls: β = −0.446; both p < 0.001). GI was negatively and independently related to 13CISS in boys (β = −0.195, p < 0.05) but not in girls. Other dietary variables were not associated with IS. In addition to BMI z score, a low GI diet predicted 13CISS in boys but not in girls. This finding suggests that interventions that reduce BMI (in both sexes) and include a low GI diet among boys may improve IS.
Hydrogen transfer reactions in viscous media — Potential and free energy surfaces in solvent–solute coordinates and their kinetic implications
Authors: Wiebe Heather , Prachnau Melissa , Weinberg Noham
Published: March 2013

Two-dimensional potential energy and free energy surfaces are obtained using quantum mechanical and molecular dynamics calculations for four hydrogen transfer reactions in n-hexane solvent: the methyl–methane, n-propyl–n-propane, n-pentyl–n-pentane, and t-butyl–isobutane systems. The resultant surfaces have similar landscapes despite the fact the equilibrated solvent cavities for these systems are notably different in size and shape. The kinetic implications of these landscapes are discussed. The Arrhenius and tunneling kinetics of hydrogen transfer in nonpolar hydrocarbon solute–solvent systems are not expected to show any significant viscosity dependence.
Alterations in litter decomposition patterns in tropical montane forests of Colombia: a comparison of oak forests and coniferous plantations
Authors: Loaiza-Usuga Juan Carlos , León-Peláez Juan D. , González-Hernández María I. , Gallardo-Lancho Juan Fernando , Osorio-Vega Walter , Correa-Londoño Guillermo
Published: March 2013

Understanding the alterations in litter decay patterns that follow changes in land use in tropical montane forests is essential for comprehending carbon, energy, and nutrient dynamics in this understudied ecosystem. The main objective of this study was to determine the changes in organic matter, carbon return, and nutrient cycling when oak forests are replaced by coniferous plantations in tropical montane forests. Five litter decay models (single, double, and triple pool exponential, gamma pk, log-uniform pk) were used to fit litter mass loss data over time. Although all models properly fitted the data, the triple pool exponential model was chosen because all parameters (coefficient of determination (R2), mean square of error (MSE), and Akaike information criterion (AIC)) were statistically the most adequate. Results indicated that litter of coniferous species decomposes more slowly than oak litter material, thus slowing the nutrient cycling. In this study, lignin content, C:N ratio, and N:P ratio were poor predictors of litter decomposition.
SHIFT OF BAND GAP FROM DIRECT TO INDIRECT AND OPTICAL RESPONSE OF LiF UNDER PRESSURE
Authors: SAJID A. , MURTAZA G. , RESHAK A. H.
Published: March 2013

We hereby are reporting the transition pressure at which lithium fluoride ( LiF ) compound transforms from direct band gap to indirect band gap insulator on the basis of FP-LAPW calculations. The fundamental band gap of LiF compound suffers direct to indirect transition at a pressure of 70 GPa. The study of the pressure effect on the optical properties e.g. dielectric function, reflectivity, refractive index and optical conductivity of LiF in the pressure between 0–100 GPa, shows that this pressure range is very critical for LiF compound as there are significant changes in the optical properties of this compound.
Photophysical and ligand binding studies of metalloporphyrins bearing hydrophilic distal superstructure
Authors: Chatterjee Sudipta , Sengupta Kushal , Bhattacharyya Sohini , Nandi Amrit , Samanta Subhra , Mittra Kaustuv , Dey Abhishek
Published: March 2013

UV-vis absorption and emission studies on zinc and iron porphyrin complexes bearing H-bonding distal superstructures have been performed in two different organic solvents- tetrahydrofuran (THF) (coordinating) and dichloromethane (DCM) (non-coordinating). Quantum yields and lifetimes have been measured for these complexes which are in good agreement with the other reported metalloporphyrins. Binding affinities with anionic ligands such as N3-, CN-, S-2, F-were monitored for these two complexes in aqueous media and the respective binding constant values were calculated. The Zn complex shows more selectivity towards cyanide while the Fe complex shows more selectivity towards azide.
Molecular structure and tautomers of [30]trithia-2,3,5,10,12,13,15,20,22,23,25,30-dodecaazahexaphyrin
Authors: Zhabanov Yuriy A. , Zakharov Alexander V. , Shlykov Sergei A. , Trukhina Olga N. , Danilova Elena A. , Koifman Oscar I. , Islyaikin Mikhail K.
Published: March 2013

The gas-phase molecular structure of the unsubstituted [30]trithia-2,3,5,10,12,13,15,20,22,23,25,30-dodecaazahexaphyrin (C30H15N15S3) has been studied by a synchronous gas electron diffraction and mass spectrometric experiment and density functional theory calculations using the B3LYP hybrid method and cc-pVTZ basis sets. The molecule has an equilibrium structure of D 3h symmetry with a planar macrocycle and the thiadiazole rings oriented in such a way that the sulfur atoms point outwards from the inner cavity. Tautomers of this compound have been studied by DFT computations.
Probing Molecular Solids with Low-Energy Ions
Authors: Bag Soumabha , Bhuin Radha Gobinda , Natarajan Ganapati , Pradeep T.
Published: March 2013

Ion/surface collisions in the ultralow- to low-energy (1–100-eV) window represent an excellent technique for investigation of the properties of condensed molecular solids at low temperatures. For example, this technique has revealed the unique physical and chemical processes that occur on the surface of ice, versus the liquid and vapor phases of water. Such instrument-dependent research, which is usually performed with spectroscopy and mass spectrometry, has led to new directions in studies of molecular materials. In this review, we discuss some interesting results and highlight recent developments in the area. We hope that access to the study of molecular solids with extreme surface specificity, as described here, will encourage investigators to explore new areas of research, some of which are outlined in this review.
New Mechanistic and Functional Insights into DNA Topoisomerases
Authors: Chen Stefanie Hartman , Chan Nei-Li , Hsieh Tao-shih
Published: March 2013

DNA topoisomerases are nature's tools for resolving the unique problems of DNA entanglement that occur owing to unwinding and rewinding of the DNA helix during replication, transcription, recombination, repair, and chromatin remodeling. These enzymes perform topological transformations by providing a transient DNA break, formed by a covalent adduct with the enzyme, through which strand passage can occur. The active site tyrosine is responsible for initiating two transesterifications to cleave and then religate the DNA backbone. The cleavage reaction intermediate is exploited by cytotoxic agents, which have important applications as antibiotics and anticancer drugs. The reactions mediated by these enzymes can also be regulated by their binding partners; one example is a DNA helicase capable of modulating the directionality of strand passage, enabling important functions like reannealing denatured DNA and resolving recombination intermediates. In this review, we cover recent advances in mechanistic insights into topoisomerases and their various cellular functions.
(Invited) Technologies and Challenges of Fine Pitch Backside Via-Last TSV Process Integration for 3DIC Applications
Authors: Ku Tzukun , Lin C. H. , Tzeng P. J. , Chen E. H. , Hsu T. C. , Chen S. C. , Wang C. C. , Chen J. C. , Chen C. C. , Hsin Y. C. , Liao S. C. , Chang P. C. , Lin Y. M. , Chang Y. H.
Published: March 2013

TSV based 3D stacking IC technology has been aggressively studied recently because of strong benefits in terms of significantly form factor shrinkage, superior system performance (bandwidth & speed), great power reduction, and heterogeneous integration capability. According to different applications, there are different integration options for TSV processing. For high performance 3D system applications which required fine TSV pitch and massive IO connections, how to establish a proper TSV integration scheme became a key importance of enabling 3D IC commercialization. In additional to common foundry used via-middle (VM) process, two another via last approaches, either forming TSV form front-side or backside were also been considered as major TSV process schemes. Although front-side via last (FVL) TSV is widely adopted by OSATs, this scheme is inherently not suitable for fine pitch and high density TSV applications because of significant area penalty and wire routing constraint comparing to VM TSV process. Another backside via last (BVL) TSV process, however, showed many advantages over common VM TSV process while achieving same TSV scalability/density and routing flexibility. For examples: (1) Cu TSVs of BVL were formed after completely CMOS FEOL+BEOL processes, thus it is naturally much less or no Cu pumping out induced yield loss issues comparing to VM process; (2) BVL TSV etching can be stopped on front-side metal 1 layer instead of time etching in blind TSV of VM scheme; (3) No complicated and yield sensitive backside Cu reveal issue were involved; (4) TSV & RDL can be formed together via dual-damascene like processing to simplify process flow and reduce cost of ownership; (5) BVL process can be adopted by either foundry or OSAT manufacturers resulting in most flexible business model in 3DIC supply chain. Despite of the vantage of backside via-last scheme, many process challenges still need to be solved. In this paper, key issues of via middle integration were briefly reviewed. A capable of high aspect ratio and fine pitch TSV (CD … 5um) manufacture scheme was proposed via backside via last integration scheme. Key process technologies and challenges of this BVL scheme, such as temporary bonding, glue material selection, wafer thinning, backside TSV formation, CMP planarization as well as cost reduced TSV/RDL dual damascene flow are investigated.
HKMG All Last to Meet 20nm Logic Device Challenge
Authors: Xie Xinyun , Ju Jianhua , Yu Shaofeng , Fu Fenghua , Zhao Jie , Chen Yong , Liu Huanxin , Zhang Ziying , Han Qiuhua , Bu Weihai , Liao Miao , Li Yong , Tao Jiajia , Yan Jiang , Yang Hong
Published: March 2013

In this paper, we studied High-K & Metal Gate (HKMG) all last process for sub-28nm logic device, including gate insulator Tinv, gate leakage, hysteresis, device mobility, Gate Oxide Integrity (GOI) etc. We also evaluated the different interface layer of chemical oxide and conventional thermal oxide. Compared to the high-K first approach, the high-K last process can significantly improve gate insulator performance to meet the 20nm logic device requirements.
Diamond-Shaped e-SiGe Optimization by TCAD Simulation to Improve P-type MOSFET Performance for 28nm Logic Technology and Beyond
Authors: Wu Hong , Pan ZiCheng , Shi XueJie , Lee Byunghak , Ding Yu , He FengYing , Ye Bin , Yu TzuChiang , He YongGen , Zhang HaiYang , Yu Shaofeng
Published: March 2013

The embedded-SiGe (e-SiGe) stressor has been an indispensable p-channel MOSFET (pFET) performance booster in the advanced logic technology nodes. In this work, we did extensive study by TCAD simulation on the optimization of the tip location, the Ge concentration profile, the in-situ doped B concentration profile of the diamond-shaped e-SiGe stressor. We observed that a shallower and closer-to-channel e-SiGe tip, higher overall Ge concentration, and faster Ge concentration ramp-up rate starting from the Si/e-SiGe interface could increase compressive stress and therefore improved the device Ion/Ioff by hole mobility enhancement. The in-situ doped B concentration profile needs to be optimized to avoid short channel effect (SCE) degradation while reducing Rext. A relatively low in-situ B concentration at Si/e-SiGe interface and a high in-situ B concentration in the “bulk” SiGe are desired. On the other hand, the e-SiGe overfill height and the e-SiGe profile at the diffision/STI boundry also play an important role in the pFET performance. The above findings serve as useful references for the e-SiGe stressor optimization for the 28nm logic technology node and beyond.
(Invited) Negative-Bias Temperature Instability – Insight from Recent Dynamic Stress Experiments
Authors: Ang Diing Shenp , Boo A. A. , Gao Y.
Published: March 2013

The purpose of this paper is to summarize key experimental evidences on the important role of hole trapping on negative-bias temperature instability (NBTI). For a long time, the focus of this research topic had been on interface degradation driven by hydrogen transport and hole trapping was regarded as a side effect arising out of fast measurement techniques proposed to mitigate the effect of recovery on measurement data. In recent studies, we showed that the threshold voltage (V
t) fluctuations one typically observed under dynamic NBTI were mainly the result of hole trapping and not hydrogen-transport driven interface-state generation/passivation proposed earlier. In particular, the cyclical V
t shifts and constant V
t recovery are inconsistent with the basic principle of the hydrogen transport model. Such behaviors are better described in terms of hole trapping/detrapping at pre-existing oxide defects. We have also shown that interface degradation during NBTI stressing has no apparent impact on bulk (oxide) trap generation, i.e. interface trap generation does not lead to bulk trap generation. This result raises further questions on the validity of the hydrogen transport mechanism and the long standing hypothesis on hydrogen-induced bulk trap generation and gate oxide breakdown. Finally, it is shown that the transient hole trapping responsible for the V
t shift fluctuations could be transformed into more permanent trapped holes under NBTI stressing. The extent of transformation is accelerated by a high oxide field and temperature. An excellent correlation with stress induced leakage current indicates that such transformation underlie the generation of bulk traps reported by earlier studies.
(Invited) Comparative Study for SRAM Cells in Near and Sub-Threshold Region
Authors: Yang Young Hwi , Park Ju Hyun , Song Seung Chul , Yang Frank Bin , Wang Joseph , Yeap Geoffrey , Jung Seong Ook
Published: March 2013

Low power circuit is an important concern for portable and battery operated applications. An attractive method to achieve low power consumption is supply voltage scaling. However, lowering the supply voltage causes a problem of stability in circuit, especially a static random access memory (SRAM). Since the SRAM occupies a large portion of the system-on-a-chip (SoC), the SRAM cell is typically designed using very small transistors for high integration, which causes the large mismatch between transistors in the SRAM cell. Thus, as supply voltage scales down, the static noise margin (SNM) of the 6T SRAM can limit the supply voltage scaling. The stability of read operation is especially sensitive to voltage scaling. To deal with these problems, recently proposed SRAM cells decouple the storage node from the bitline. In this paper, we analyze recently proposed SRAM cells for low voltage operation using 22 nm FinFET model.
Electrical Properties and Interfacial Structures of High-k/Metal Gate MOSCAP Using Ti/TiN Scavenging Stack between High-κ Dielectric and Metal Gate
Authors: Ma Xueli , Wang Xiaolei , Han Kai , Wang Wenwu , Yang Hong , Zhao Chao , Chen Dapeng , Ye Tianchun
Published: March 2013

High permittivity materials have been required to replace traditional SiO2 to be gate dielectric to extend Moore’s law. However, growth of a thin SiO2-like interfacial layer (IL) is almost unavoidable during the deposition or subsequent high temperature anneal. This limits the scaling benefits of incorporating high-k dielectrics into transistors. A promising approach, in which O-scavenging metal layer and a barrier layer preventing scavenging metal diffusing into high-k gate dielectric are used to engineer the thickness of the IL, is reported in this paper. Using a Ti scavenging layer and TiN barrier layer on HfO2 dielectric, the equivalent oxide thickness (EOT) decreased due to the effect of O-scavenging indicated by the C-V measurement results. From high resolution transmission electron microscopy (HRTEM) pictures and X-ray photoelectron spectroscopy (XPS), the removal of interfacial layer (IL) has been seen clearly.
A Study on the AA/STI Corner Shape Impact on Narrow Width MOSFET Idsat/Ioff Performance for 28nm Technology Node
Authors: Pu YueJiao , Shi XueJie , Kim JeongGi , Yu ShaoFeng
Published: March 2013

In this work, shallow trench isolation (STI) divot depth and active area (AA) cornerrounding effects on narrow width MOSFET performance were investigated through3-dimensional (3D) TCAD simulation. More poly-silicon wrap down on thetransistor channel by deeper divot enlarges the effective channel width andimproves the gate electrostatic control over the channel. However, it is found thatthe Idsat/Ioff improvement from deep divot is only half of the effective widthincrement. By comparing the trends of extrapolated Vt at maximum Gm (Vtgm)and constant current defined Vt at sub-threshold regime (Vtsat), it is explained thatearly turn-on of the corner transistor is the main reason of the performancedescrepancy. It is demonstrated that large corner rounding can reduce the effect andhence improve Idsat/Ioff. Moreover, conformal source/drain (s/d) extension dopingshould be obtained to remove the underlap at AA side-wall.
(Invited) Patterning Process Model Challenges for 14 Nm
Authors: Sturtevant John Lynch
Published: March 2013

The taxonomy of semiconductor technology nodes has long since decoupled from the minimum critical dimension (CD) associated with the designs, but each new node nonetheless features a variety of difficult challenges. CD control and placement budgets continue to tighten with each node as new and more complex RET strategies such as multi-layer patterning, model-based assist feature, pixelated illumination sources, and negative tone develop processes are deployed. Optical Proximity Correction (OPC) is of course a vital enabler for advanced manufacturing, and OPC models describe the entire patterning process, including photomask, optics, resist, and etch as a set of separate modules. There are many factors which impact the accuracy and predictive power of these semi-empirical photomask, optical, and resist models, and care must be taken to ensure appropriate representation of all physical system parameters. These include mask critical dimension (XY) and optical (Z) properties, since 3DEMF effects are important at 14 nm node dimensions. In addition to single plane CD prediction, models must be aware of various three dimensional patterning failure modes such as SRAF printing, resist toploss, and resist pattern collapse. This paper will review the critical challenges for patterning process models for the 14 nm node.
(Invited) Efficient Mask Synthesis with Augmented Lagrangian Methods in Computational Lithography
Authors: Li Jia , Lam Edmund Y
Published: March 2013

A fast approach based on augmented Lagrangian methods (ALMs) is proposed to solve the inverse imaging problem in optical lithography, known as inverse lithography technology. We develop a constrained optimization framework where the objective function includes a data- fidelity term and a binary equality constraint. We show how optimal solutions are reached with less execution time by applying the quasi-Newton method to the sub-problem. The proposed scheme also includes a tentative penalty parameter schedule for adjustment and control. Simulation results are compared with existing source-mask optimization (SMO) to illustrate the performance improvement in terms of pattern fidelity, convergence rate and process window size.
Improvement of Contact OPC Model Accuracy by Using Corner Chopping
Authors: Huang Yibin , Zhang Wanjuan , Liu Qingwei , Shi Xuelong , Gu Yiming , Shao Feng , Zhang Liguo , Zhu Yu , Du Chunshan
Published: March 2013

An accurate OPC model with good extrapolating capability plays an important role in achieving the accurate OPC. OPC model usually consists of physical part and empirical part which correspond to optical and resist models respectively. The optical physics has a solid theoretical foundation to follow, this part is very critical to the model accuracy and extrapolation capability. The closer the parameters (illumination, geometrical shape on real masks, etc) to real conditions are fed into optical part, the more accurate the model will be. For contact layer, the corner rounding of patterns on the real mask leads to significant deviations from original post OPC patterns. This deviation can no longer be ignored in both OPC model set up and OPC run at 32nm node and beyond. In this paper we employed a corner chopping technique to emulate the real mask shape and used it to calibrate the contact OPC model. We compared the model fitting error and extrapolate capability. The results showed the improvements in both OPC model accuracy and its extrapolation capability are significant.
Study Of Gate Critical Dimension Uniformity (CDU) Budget and Improvement at 28nm Node
Authors: Shu Qiang , Wu Qiang , Zu Yanlei , Wang Tiezhu , Zhang Shijian , Li Tianhui , Lin Yishih , Gu Yiming
Published: March 2013

Achieving good gate’s critical dimension uniformity (CDU) is very challenging since the CDU has shown not only high sensitivities to the variations in resist track recipe, scanner hardware and control, and etcher condition, but also have high correlation to the feature shape and pattern environment. For process generations at 28 nm half pitch, more aggressive CDU requirement will result in a push of OPC, reticle making and litho process to their limits. To more systematically analyze the linewidth variation and to find a viable solution to achieve required linewidth uniformity, we constructed linewidth variation budget, which includes variations in lithographic process, mask linewidth, optical proximity correction (OPC) error, and scanner control. Through analyzing the CDU requirement from process integration needs and referencing the ITRS roadmap’s recommendation, we have identified key budget contributors, which are OPC and mask making. In this paper, we will demonstrate our achievement in linewidth uniformity improvement.
Accurate Matching for CDSEM on ADI Wafers
Authors: Li Wen-Hui , Lin Yi-Shih , Yang Siyuan Frank , Cai Bo-Xiu , Huang Yi
Published: March 2013

There exist great difficulties and challenges in CD-SEM matching because of the destructive interaction between e-beam and resist. This paper presents a new cross sampling method which uses two separate locations of resist line and performs cross measurements by two separate tools in a special sequence. This sampling method together with a special designed calculation can eliminate the impact from both resist line shrinkage and measurement locations difference. It removes the error component with magnitude of second shrinkage in the conventional approach of matching, however a difference of second shrinkages from two tools is introduced although it is smaller than the second shrinkage itself. After introduce an exponential decay model of the resist shrinkages in multiple subsequent measurements to the sampling method, we could estimate first and second shrinkages for both CD-SEM tools with the measurement results from one of the above cross sampling plan, we are able to determine the real difference of measured CDs after the first measurement from these two CD-SEM tools, which cannot be obtained by direct measurements because of the memory of any previous measurement.
(Invited) Negative Tone Development Process and Resist Materials with ArF Immersion Exposure Process
Authors: Tarutani Shinji
Published: March 2013

Negative tone development (NTD) process was proposed as a good candidate to obtain good quality in resist pattern for trench and contact hole (C/H) pattern with ArF immersion resist process. Advantages of NTD compared to positive tone development (PTD) process are discussed in detail. High volume manufacturing capabilities, mainly in the performances of CD uniformity and defectivity, are discussed. The challenges in resist material are addressed, and the material design strategies and new resist materials are introduced.
New Approach for Reducing the Out of Band effect and Outgassing by Applying Top Coat Materials
Authors: Sakamoto Rikimaru , Onishi Ryuji , Fujitani Noriaki , Ho Bang-ching
Published: March 2013

EUV lithography is one of the next generation lithography candidates for hp22nm and beyond. However the light source, tools, masks and resists are still the key issues for the EUV lithography. For the development of the EUV light source, the low power is one of the critical issues that will make the low throughput. Another one is the Out of Band (OoB) light existing in the EUV source. OoB is concerned to be the cause of deterioration of the lithography performance. The outgassing from resist is another big issue for the EUV lithography, and how to prevent and keep the cleanness of exposure tool is very important topic. The OoB effect and outgassing from resist issues must be resolved toward the high volume manufacturing. In order to resolve these critical issues, applying top coat material can be the promising candidate process. The key characteristics for top coat material are reducing the OoB effect, preventing the outgassing form resist as barrier layer, and controlling the resist profile and process window. The material is called OBPL (Outgass and OoB Protection Layer). This paper describes the material design having the high absorption in OoB range and high transmittance for 13.5nm wavelength, and having the outgassing barrier performance to reduce the outgassing from resist. Finally we will study the lithography performance with top coat material.
All-In-One Etch Scheme to the Fabrication of Metal Hard-Mask Based Cu/Ultra Low-K Interconnects
Authors: Hu Min-Da , Zhou Jun-Qing , Wang Dong-Jiang , Zhang Cheng-Long , Huang Jack , Wang Xin-Peng , Zhang Hai-Yang , Mo Zhou , Shindo Toshihiko , Chen Li-Hung
Published: March 2013

Due to the inherent limitation from overlay shift control, the punch-through scheme coupled with via CD shrink and the definition optimization of metal hard-mask open was proven to be the current-best choice and only feasible way for the enhancement of TDDB performance and gap-fill window of metal hard-mask based ultra low-k dielectric interconnects. The disadvantages of metal hard-mask based all-in-one etch include the potential defect from TixFy and the early copper exposure before liner removal step. The copper exposure time during all-in-one etch needs well controlled to avoid the via/trench bottom roughness and the inter-layer VBD. Stress migration (SM) also attracts special attention in metal hard-mask based process and its performance can be improved from the point of view of WET clean and post etch treatment (PET). RC (resistance/capacitance) curve can be also improved to target by means of PET.
CD Bias Loading Control in Metal Hard Mask Open Process
Authors: Wang Dongjiang , Hu Minda , Zhou Junqing , Zhang Chenglong , Wang Xinpeng , Zhang Haiyang
Published: March 2013

In this work, CD (critical dimension) etching bias loading performance between dense and isolated (ISO) line was systematically investigated on Metal Hard Mask (M-HM) etch process in the scope of chemical gas, source power, pressure, bias power, and ESC temperature. Particularly, a CH4 based plasma curing upon photo resist mask was found with special capability to control the dense & ISO CD loading while keeping an on-target dense CD if it was properly applied. Furthermore, the remarkable impact of etch chemical gas on CD loading was also noticed between Cl2-based and HBr-based BARC open step. Besides, the stress and post-etch profile of M-HM were also found impacting CD loading performance. Based on these findings, a solution was successfully demonstrated on a case of electrical interconnection improvement between tungsten contact and copper trench.
Dry Etching Solutions to Contact Etch for Advanced Logic Technologies
Authors: Wang Xin-Peng , Huang Jing-Yong , Huang Yi , Han Qiu-Hua , Zhang Hai-Yang
Published: March 2013

Dry Etching Solutions to Contact Etch for Advanced Logic Technologies Heavy polymer and byproducts from CD shrinkage will easily cause contact hole open, especially for the tapered hole profile. The sufficient over-etch without any silicon loss and too much silicide loss is also required to maintain enough process window for less junction leakage. Meanwhile, the circularity of contact hole needs to be well controlled to avoid the potential contact to poly gate bridge issue. In this work, we investigated the impact of dry etching process on contact hole profile and circularity, balanced contact hole CD shrink and contact open issue. Results demonstrate the overall contact hole profile needs to be rigorously controlled by optimizing the etch selectivity of silicon oxide over silicon nitride, the etch treatment is imperative to reduce the contact open issue. The circularity of contact hole can be well improved by tuning the etching chemistry at bottom anti-reflective coating open step and optimizing patterning film stack.
Review of Plasma-Based Etch Treatment in Dielectric Etch Processes
Authors: Han Qiuhua , Wang Xinpeng , Zhou Junqing , Hu Minda , Zhang Haiyang
Published: March 2013

This work mainly focuses on the post-etch treatment (PET) in dielectric etch processes from contact etch, trench etch to all-in-one etch. PET step is optimized not only to efficiently remove the byproducts formed on the sidewall/bottom of contact/via hole during etch proceses but also to eliminate the surface corrosion of the etched metal comprising feature. Besides, we also leveraged PET to repair low-k damage and prevent the formation of mositure on film surface by modifing film from hydrophilic to hydrophobic, especially for low-k/ultra low-k dielectric processes. Results show the actual effect of PET in terms of reliability performance highly relies on the specific etch recipe, wet clean condition and substrate material in back end of line (BEOL). We also addressed the pre-etch treatment to effectively reduce the impact of photo-resist scumming in contact etch. In brief, plasma-based etch treatment is imperative to extend the tightened process window margin.
Etched Profile Control of the Multi-Layer Oxide/Poly-Si Stack Using Pulsed Plasma for 3D VG NAND Application
Authors: Hsu Fang Hao , Yang Zusing , Lee Hong Ji , Lian Nan Tzu , Yang Tahone , Chen Kuang Chao , Lu Chih Yuan
Published: March 2013

This paper reported a simple and systematic etching process for fabricating smooth vertical edge profile in multiple layers, which consists of multiple alternative silicon oxide (OX) and poly-Si (PL) layers in a three-dimensional vertical gate (3D VG) NAND. It is found that by applying appropriated bias power pulsing conditions (such as frequency and duty cycle) can reach an excellent etch loading and profile control in the multi-layer OX/PL stack architecture. An etch loading (open-to-dense depth ratio) evolution from 1.82 to 1.14 is achieved successfully as the bias power pulsing within 1kHz with 20% of duty cycle at 875W. The pulsed plasma etching technique shows its potential in better profile control/etch loading effect and less cost in α-C hard mask.
Early Observations between Magnet and Film Properties for AlN Deposition by Reactive Magnetron Sputtering
Authors: Zhao Sha , Yang Yi , Cox Michael , Deyo Dan , Rosa Mike
Published: March 2013

This paper reports the findings taken from early experimentation towards the development of high quality AlN layers deposited using physical vapor deposition (PVD)-production tool. In these experiments, the magnetron was equipped with a rotating magnet to enable full-face target erosion. Four magnet designs were tested with various nitrogen (N2) ratios in the gas mixture with argon (Ar). These results show the thickness non-uniformity for AlN film trending across a range of N2 ratios differs with magnet design. Similarly, it has been verified that the N2 ratio is an effective knob for stress control of an AlN film and that the measured in-film stress trends linearly with N2 ratio for all four magnet designs. Using an optimized magnet design and finely tuned process conditions, these early experiments have shown highly uniform AlN films on 200 mm Si wafer with a strong c-axis orientation and tunable stress, which help the learning and development of AlN film for applications in MEMS and BAW devices.
(Invited) Extraction of Oxide Traps in III-V MOSFETs Using RF Transconductance Measurements
Authors: Lind Erik , Johansson Sofia
Published: March 2013

We here present simulations of the effect of border traps on the behavior of a III-V FET's transconductance with respect to frequency. We also compare simulations with a recently developed analytical model for extracting the border trap distribution through measurements of the transconductance, find good agreement between the extracted and simulated transconductance.
Characterization and Simulation of Pattern-Dependency in ECP Topography
Authors: Bai Yingying , Fang Jingxun , Zhang Shoulong , Wei ZhengYing , Wei Fang , Kan Huan , Chen Y. W.
Published: March 2013

Electronic Copper Plating (ECP) topography is known affected by layout design and dummy inserting. With different electroplate liquid, copper can be filled in the trench by the forms of conformal-fill, bottom-up or supper-fill. Such post ECP topography not only depends on process conditions, but also exhibits strong pattern-related dependency. Here, pattern-related effects of ECP topography were characterized with a pre-designed test chip that contains test-keys of line/space arrays of varying line and space widths, and varying pattern-density (PD). It was shown that: 1) Fixed PD at 50%, the characteristics of test features array height (AH) and Step-height (SH) are strongly associated with line-width (LW). 2) Fixed LW, different trends were observed for narrow lines and wide lines, in both AH and SH vs. varying PD. A semi-empirical model was built to simulate post-ECP topography. It captured all key pattern-dependency in post-ECP AH and SH with acceptable fitting GOF (R2>90%).
Bump Shape Prediction of Cu Pillar via an Electrochemical Method
Authors: Chen Wei-Chih , Huang Tzu-Tsang , Lai Chien-Hsun , Chou Shih-Wei , Shih Chien-Hsueh
Published: March 2013

A galvanostatic measurement is developed to study the correlation of organic additives vs. pillar shape formation. According to the electrochemical characteristics of organic additives measured using a galvanostat method, a protrusion agent (denoted as “protrutor”) and a recess agent (denoted as “recessor”) are defined. A protrutor in the bath causes a positive slope in electrochemical response curve and produces a pillar with domed shape. On the contrary, a recessor shows a negative slope and forms a concave shaped pillar. A flat surface pillar can be produced by controlling or balancing the interaction between protrutor and recessor. Using this approach, additives can be quickly screened and bump profile can be predicted before conducting a plating experiment on test wafers.
Resistive Switching Characteristics Based on Cu/VOx/Al Structure
Authors: Kuo Sun , Kailiang Zhang , Fang Wang , Yinping Miao , Kai Liu , Tao Lu , Wenxiang Sun
Published: March 2013

In this work, device cell with the Cu/VOx/Al structure was fabricated. The resistance switching performance was tested by Semiconductor Device Analyzer (Agilent B1500). This structure performs bipolar behavior. Controllable Set process and gradual Reset process, and various RLRS and RHRS could be obtained by controlling its current compliance (Icc) and reset stop voltage (Vstop), respectively. The Reset current could decrease to sub-10μA when Icc dropped to 40μA. The RHRS could be greater than 1E8 ohm with 1.5 V amplitude of applied reset voltage. This structure also has a good endurance (>1000 cycles) and reliable read disturbance times (>1000s) with 80oC ambient temperature. Local filament was observed in LRS by conducting atomic force microscope (CAFM), and Schottky barrier height modulation was obtained by I-V fitting in Reset process.
(Invited) Surface Adsorption of CMP Slurry Additives on Abrasive Particles
Authors: Moinpour Mansour , Wayman Ashley , Rawat Ashwani , Carver Colin T , Remsen Edward E
Published: March 2013

Fluorescence correlation spectroscopy (FCS) is used to study additive-abrasive particle interactions in chemical-mechanical planarization (CMP) slurries. FCS provides quantitative determinations of the binding between additives and abrasive particles by characterizing the competitive adsorption of the additive and a fluorescent probe molecule, Alexa fluor 546 (A546) at the surface of a silica abrasive particle. Analysis of the adsorption of benzotriazole (BTA) on colloidal silica confirms the displacement of A546 by added BTA. However, glycine enhances the adsorption of A546 by colloidal silica. FCS is also shown to be a sensitive technique for detecting differences in the surface chemistry between different types of colloidal silica abrasive particles used in CMP processes.