bluuebunny/crossref_metadata_2025 huggingface dataset:
The Immunopathology of Sepsis: Pathogen Recognition, Systemic Inflammation, the Compensatory Anti‐Inflammatory Response, and Regulatory T Cells
Authors: Lewis D.H. , Chan D.L. , Pinheiro D. , Armitage‐Chan E. , Garden O.A.
Published: March 2012

Sepsis, the systemic inflammatory response to infection, represents the major cause of death in critically ill veterinary patients. Whereas important advances in our understanding of the pathophysiology of this syndrome have been made, much remains to be elucidated. There is general agreement on the key interaction between pathogen‐associated molecular patterns and cells of the innate immune system, and the amplification of the host response generated by pro‐inflammatory cytokines. More recently, the concept of immunoparalysis in sepsis has also been advanced, together with an increasing recognition of the interplay between regulatory T cells and the innate immune response. However, the heterogeneous nature of this syndrome and the difficulty of modeling itin vitroorin vivohas both frustrated the advancement of new therapies and emphasized the continuing importance of patient‐based clinical research in this area of human and veterinary medicine.
Metagenomic Analysis of Streptomyces lividans Reveals Host-Dependent Functional Expression
Authors: McMahon Matthew D. , Guan Changhui , Handelsman Jo , Thomas Michael G.
Published: March 2012

Most functional metagenomic studies have been limited by the poor expression of many genes derived from metagenomic DNA in
Escherichia coli
, which has been the predominant surrogate host to date. To expand the range of expressed genes, we developed tools for construction and functional screening of metagenomic libraries in
Streptomyces lividans
. We expanded on previously published protocols by constructing a system that enables retrieval and characterization of the metagenomic DNA from biologically active clones. To test the functionality of these methods, we constructed and screened two metagenomic libraries in
S. lividans
. One was constructed with pooled DNA from 14 bacterial isolates cultured from Alaskan soil and the second with DNA directly extracted from the same soil. Functional screening of these libraries identified numerous clones with hemolytic activity, one clone that produces melanin by a previously unknown mechanism, and one that induces the overproduction of a secondary metabolite native to
S. lividans
. All bioactive clones were functional in
S. lividans
but not in
E. coli
, demonstrating the advantages of screening metagenomic libraries in more than one host.
Natural Product Biosynthetic Gene Diversity in Geographically Distinct Soil Microbiomes
Authors: Reddy Boojala Vijay B. , Kallifidas Dimitris , Kim Jeffrey H. , Charlop-Powers Zachary , Feng Zhiyang , Brady Sean F.
Published: March 2012

The number of bacterial species estimated to exist on Earth has increased dramatically in recent years. This newly recognized species diversity has raised the possibility that bacterial natural product biosynthetic diversity has also been significantly underestimated by previous culture-based studies. Here, we compare 454-pyrosequenced nonribosomal peptide adenylation domain, type I polyketide ketosynthase domain, and type II polyketide ketosynthase alpha gene fragments amplified from cosmid libraries constructed using DNA isolated from three different arid soils. While 16S rRNA gene sequence analysis indicates these cloned metagenomes contain DNA from similar distributions of major bacterial phyla, we found that they contain almost completely distinct collections of secondary metabolite biosynthetic gene sequences. When grouped at 85% identity, only 1.5% of the adenylation domain, 1.2% of the ketosynthase, and 9.3% of the ketosynthase alpha sequence clusters contained sequences from all three metagenomes. Although there is unlikely to be a simple correlation between biosynthetic gene sequence diversity and the diversity of metabolites encoded by the gene clusters in which these genes reside, our analysis further suggests that sequences in one soil metagenome are so distantly related to sequences in another metagenome that they are, in many cases, likely to arise from functionally distinct gene clusters. The marked differences observed among collections of biosynthetic genes found in even ecologically similar environments suggest that prokaryotic natural product biosynthesis diversity is, like bacterial species diversity, potentially much larger than appreciated from culture-based studies.
Development of an Engineered Bioluminescent Reporter Phage for Detection of Bacterial Blight of Crucifers
Authors: Schofield David A. , Bull Carolee T. , Rubio Isael , Wechter W. Patrick , Westwater Caroline , Molineux Ian J.
Published: March 2012

Bacterial blight, caused by the phytopathogen
Pseudomonas cannabina
pv.
alisalensis
, is an emerging disease afflicting important members of the
Brassicaceae
family. The disease is often misdiagnosed as pepper spot, a much less severe disease caused by the related pathogen
Pseudomonas syringae
pv.
maculicola
. We have developed a phage-based diagnostic that can both identify and detect the causative agent of bacterial blight and differentiate the two pathogens. A recombinant “light”-tagged reporter phage was generated by integrating bacterial
luxAB
genes encoding luciferase into the genome of
P. cannabina
pv.
alisalensis
phage PBSPCA1. The PBSPCA1::
luxAB
reporter phage is viable and stable and retains properties similar to those of the wild-type phage. PBSPCA1::
luxAB
rapidly and sensitively detects
P. cannabina
pv.
alisalensis
by conferring a bioluminescent signal response to cultured cells. Detection is dependent on cell viability. Other bacterial pathogens of
Brassica
species such as
P. syringae
pv.
maculicola
,
Pseudomonas marginalis
,
Pectobacterium carotovorum
,
Xanthomonas campestris
pv.
campestris
, and
X. campestris
pv.
raphani
either do not produce a response or produce significantly attenuated signals with the reporter phage. Importantly, the reporter phage detects
P. cannabina
pv.
alisalensis
on diseased plant specimens, indicating its potential for disease diagnosis.
Cytoplasmic pH Response to Acid Stress in Individual Cells of Escherichia coli and Bacillus subtilis Observed by Fluorescence Ratio Imaging Microscopy
Authors: Martinez Keith A. , Kitko Ryan D. , Mershon J. Patrick , Adcox Haley E. , Malek Kotiba A. , Berkmen Melanie B. , Slonczewski Joan L.
Published: March 2012

The ability of
Escherichia coli
and
Bacillus subtilis
to regulate their cytoplasmic pH is well studied in cell suspensions but is poorly understood in individual adherent cells and biofilms. We observed the cytoplasmic pH of individual cells using ratiometric pHluorin. A standard curve equating the fluorescence ratio with pH was obtained by perfusion at a range of external pH 5.0 to 9.0, with uncouplers that collapse the transmembrane pH difference. Adherent cells were acid stressed by switching the perfusion medium from pH 7.5 to pH 5.5. The
E. coli
cytoplasmic pH fell to a value that varied among individual cells (range of pH 6.2 to 6.8), but a majority of cells recovered (to pH 7.0 to 7.5) within 2 min. In an
E. coli
biofilm, cells shifted from pH 7.5 to pH 5.5 failed to recover cytoplasmic pH. Following a smaller shift (from pH 7.5 to pH 6.0), most biofilm cells recovered fully, although the pH decreased further than that of isolated adherent cells, and recovery took longer (7 min or longer). Some biofilm cells began to recover pH and then failed, a response not seen in isolated cells.
B. subtilis
cells were acid shifted from pH 7.5 to pH 6.0. In
B. subtilis
, unlike the case with
E. coli
, cytoplasmic pH showed no “overshoot” but fell to a level that was maintained. This level of cytoplasmic pH post-acid shift varied among individual
B. subtilis
cells (range of pH, 7.0 to 7.7). Overall, the cytoplasmic pHs of individual bacteria show important variation in the acid stress response, including novel responses in biofilms.
Quantitative Fluorescence
In Situ
Hybridization Analysis of Microbial Consortia from a Biogenic Gas Field in Alaska's Cook Inlet Basin
Authors: Dawson Katherine S. , Strąpoć Dariusz , Huizinga Brad , Lidstrom Ulrika , Ashby Matt , Macalady Jennifer L.
Published: March 2012

Filter-collected production water samples from a methane-rich gas field in the Cook Inlet basin of Alaska were investigated using whole-cell rRNA-targeted fluorescence
in situ
hybridization (FISH) and 16S rRNA tag pyrosequencing. Both techniques were consistent in determining the microbial community composition, including the archaeal or bacterial dominance of samples. The archaeal community is dominated by the obligate methylotrophic methanogen genus
Methanolobus
as well as the nutritional generalist methanogen genus
Methanosarcina
, which is capable of utilizing acetate, CO
2
, and methyl-bearing compounds. The most-abundant bacterial groups are
Firmicutes
, notably of the
Acetobacterium
genus, and
Cytophaga-Flexibacter-Bacteroides
species (CFBs) affiliated with the order
Bacteroidales
. We observed spatial variation among samples in both the percentage of members of
Archaea
compared to that of members of
Bacteria
and the dominant members of the bacterial community, differences which could not be explained with the available geochemical data. Based upon the microbial community composition and the isotopic signature of methane associated with the Cook Inlet basin site, we propose a simplified reaction network beginning with the breakdown of coal macromolecules, followed by fermentation and methylotrophic and acetoclastic methane production.
Markerless Gene Deletion System for Sphingomonads
Authors: Kaczmarczyk Andreas , Vorholt Julia A. , Francez-Charlot Anne
Published: March 2012

Here, we suggest that natural streptomycin resistance of many sphingomonads resides within
rpsL
. We constructed a dominant, streptomycin-sensitive
rpsL
allele and demonstrated its use as a counterselection marker in several sphingomonads. An
rpsL
-based markerless gene deletion system was developed and validated by deleting four genes in
Sphingomonas
sp. strain Fr1.
Genomic Sequence of Bacteriophage ATCC 8074-B1 and Activity of Its Endolysin and Engineered Variants against Clostridium sporogenes
Authors: Mayer Melinda J. , Gasson Michael J. , Narbad Arjan
Published: March 2012

Lytic bacteriophage ATCC 8074-B1 produces large plaques on its host
Clostridium sporogenes
. Sequencing of the 47,595-bp genome allowed the identification of 82 putative open reading frames, including those encoding proteins for head and tail morphogenesis and lysis. However, sequences commonly associated with lysogeny were absent. ORF 22 encodes an endolysin, CS74L, that shows homology to
N
-acetylmuramoyl-
l
-alanine amidases, and when expressed in
Escherichia coli
, the protein causes effective lysis of
C. sporogenes
cells when added externally. CS74L was also active on
Clostridium tyrobutyricum
and
Clostridium acetobutylicum
. The catalytic domain expressed alone (CS74L
1–177
) exhibited a similar activity and the same host range as the full-length endolysin. A chimeric endolysin consisting of the CS74L catalytic domain fused to the C-terminal domain of endolysin CD27L, derived from
Clostridium difficile
bacteriophage ΦCD27, was produced. This chimera (CSCD) lysed
C. sporogenes
cells with an activity equivalent to that of the catalytic domain alone. In contrast, the CD27L C-terminal domain reduced the efficacy of the CS74L catalytic domain when tested against
C. tyrobutyricum
. The addition of the CD27L C-terminal domain did not enable the lysin to target
C. difficile
or other CD27L-sensitive bacteria.
The β-Arrestin-Like Protein Rim8 Is Hyperphosphorylated and Complexes with Rim21 and Rim101 To Promote Adaptation to Neutral-Alkaline pH
Authors: Gomez-Raja Jonathan , Davis Dana A.
Published: March 2012

β-Arrestin proteins are critical for G-protein-coupled receptor desensitization and turnover. However, β-arrestins have recently been shown to play direct roles in nonheterotrimeric G-protein signal transduction. The
Candida albicans
β-arrestin-like protein Rim8 is required for activation of the Rim101 pH-sensing pathway and for pathogenesis. We have found that
C. albicans
Rim8 is posttranslationally modified by phosphorylation and specific phosphorylation states are associated with activation of the pH-sensing pathway. Rim8 associated with both the receptor Rim21 and the transcription factor Rim101, suggesting that Rim8 bridges the signaling and activation steps of the pathway. Finally, upon activation of the Rim101 transcription factor,
C. albicans
Rim8 was transcriptionally repressed and Rim8 protein levels were rapidly reduced. Our studies suggest that Rim8 is taken up into multivesicular bodies and degraded within the vacuole. In total, our results reveal a novel mechanism for tightly regulating the activity of a signal transduction pathway. Although the role of β-arrestin proteins in mammalian signal transduction pathways has been demonstrated, relatively little is known about how β-arrestins contribute to signal transduction. Our analyses provide some insights into potential roles.
Efficient Decoding of the UAG Triplet as a Full-Fledged Sense Codon Enhances the Growth of a
prfA
-Deficient Strain of Escherichia coli
Authors: Ohtake Kazumasa , Sato Aya , Mukai Takahito , Hino Nobumasa , Yokoyama Shigeyuki , Sakamoto Kensaku
Published: March 2012

We previously reassigned the amber UAG stop triplet as a sense codon in
Escherichia coli
by expressing a UAG-decoding tRNA and knocking out the
prfA
gene, encoding release factor 1. UAG triplets were left at the ends of about 300 genes in the genome. In the present study, we showed that the detrimental effect of UAG reassignment could be alleviated by increasing the efficiency of UAG translation instead of reducing the number of UAGs in the genome. We isolated an amber suppressor tRNA
Gln
variant displaying enhanced suppression activity, and we introduced it into the
prfA
knockout strain, RFzero-q, in place of the original suppressor tRNA
Gln
. The resulting strain, RFzero-q3, translated UAG to glutamine almost as efficiently as the glutamine codons, and it proliferated faster than the parent RFzero-q strain. We identified two major factors in this growth enhancement. First, the
sucB
gene, which is involved in energy regeneration and has two successive UAG triplets at the end, was expressed at a higher level in RFzero-q3 than RFzero-q. Second, the ribosome stalling that occurred at UAG in RFzero-q was resolved in RFzero-q3. The results revealed the importance of “backup” stop triplets, UAA or UGA downstream of UAG, to avoid the deleterious impact of UAG reassignment on the proteome.
Usefulness of nefopam in treating pain of severe uncomplicated renal colics in adults admitted to emergency units: a randomised double-blind controlled trial. The ‘INCoNU’ study
Authors: Moustafa Farès , Liotier Jérôme , Mathevon Thierry , Pic Daniel , Perrier Christophe , Schmidt Jeannot
Published: March 2012

Background

Renal colic pain is a frequent cause of emergency department admissions (1–2% of admissions). It is extremely painful, often requiring intravenous morphine titration. The aim of this study was to estimate the effect of adding nefopam to ketoprofen upon subsequent morphine consumption and the time needed to achieve adequate analgesia in renal colic.

Methods

The authors undertook a prospective, monocentric, randomised, double-blind, placebo-controlled, parallel-group study, using an intent-to-treat analysis. Patients admitted to the emergency department for suspected hyperalgesic (evaluated with a visual analogue scale (VAS)) renal colic were enrolled in the study. They were administered an initial treatment of ketoprofen before being randomly assigned to either the placebo or nefopam group.

Results

Thirty patients admitted to the emergency department were enrolled in the study. Morphine analgesia was necessary for 10 patients (66.6%) (95% CI 40% to 90%) in the nefopam group and 8 (53.3%) (95% CI 30% to 80%) in the placebo group, with no statistically significant difference found (difference 13.3%, 95% CI −51% to 24%). The time needed to achieve adequate analgesia in the case of morphine titration was 8.3 min (95% CI 4.2 to 12.5) in the nefopam group and 9 min (95% CI 2.7 to 15.3) in the placebo group, with no statistically significant difference (difference 0.7, 95% CI 7.25 to 8.58).

Conclusion

This study did not reveal any significant difference between nefopam and placebo. This may be due to lack of statistical power or lack of effectiveness.

Clinical trial registration number

http://ClinicalTrials.govID numberNCT00639574.
Modified early warning score with rapid lactate level in critically ill medical patients: the ViEWS-L score
Authors: Jo Sion , Lee Jae Baek , Jin Young Ho , Jeong Tae Oh , Yoon Jae Chol , Jun Yong Kyu , Park Bo Young
Published: March 2012

Objectives

To examine whether the predictive value of the early warning score (EWS) could be improved by including rapid lactate levels, and to compare the modified EWS with the pre-existing risk scoring systems.

Design

Retrospective observational study in South Korea.

Setting

An urban, academic, tertiary hospital.

Participants

Consecutive adult patients who were admitted to the medical intensive care unit via the emergency department (ED).

Outcome measures

A newly developed EWS—the VitalPAC EWS (ViEWS), was used in the present study. Lactate level, ViEWS and HOTEL score were obtained from patients at presentation to the ED, and APACHE II, SAPS II and SAPS III scores were obtained after admission. The area under curve of each risk scoring system for in-hospital, 1-week, 2-week and 4-week mortality was compared.

Results

151 patients were enrolled and the mortality was 42.4%. The ViEWS-L score was calculated as follows: ViEWS-L score=ViEWS+lactate (mmol/l) according to the regression coefficient. The mean ViEWS-L score was 11.6±7.3. The ViEWS-L score had a better predictive value than the ViEWS score for hospital mortality (0.802 vs 0.742, p=0.009), 1-week mortality (0.842 vs 0.707, p<0.001), 2-week mortality (0.827 vs 0.729, p<0.001) and 4-week mortality (0.803 vs 0.732, p=0.003). The ViEWS-L score also had a better predictive value than the HOTEL and APACHE II scores. The predictive value of ViEWS-L was comparable with SAPS II and SAPS III.

Conclusions

The ViEWS-L score performed as well as or better than the pre-existing risk scoring systems in predicting mortality in critically ill medical patients who were admitted to the medical intensive care unit via the ED.
Two-Dimensional Self-Limiting Oxidation for Non-Planar Silicon Nano-Devices from Top-Down Approach: Experiments and Modeling
Authors: Fan Jiewen , Xu Qiumin , Jiang Zizhen , Ai Yujie , Wang Runsheng , Huang Ru
Published: March 2012

A CMOS compatible method to fabricate non-planar silicon nanowires is realized on bulk silicon substrate using self-limiting oxidation with high control-capability of the nanowire size and shape. A predictive model of 2-D self-limiting oxidation for non-planar silicon nanodevices is also proposed and shows its good agreement with the experimental data in a wide range of oxidation temperatures, process time, and variety initial silicon core sizes. The shape evolution of silicon core during oxidation is successfully modeled and is verified by high-resolution SEM. Unlike traditional planar oxidation model which is limited in planar oxidation without any stress, the proposed predictive model is based on cylindrical Deal-Grove (D-G) equation including stress effect, and takes into account of the orientation dependence and the flow of SiO2 as viscous fluid, which can be successfully applied to process engineering of non-planar Si nanowire transistors.
Prospects for Nanoelectronics CMOS Scaling and Functional Diversification
Authors: Deleonibus Simon
Published: March 2012

Nanoelectronics will have to face major challenges in the next decades in order to proceed with increasing progress and reduced variability. New progress laws combined to the scaling down of CMOS based technology will emerge to enable new paths to Functional Diversification. New materials and disruptive architectures, Heterogeneous Integration, introducing 3D schemes at the Front End and Back End levels, will be introduced to make it possible.
Analytical-Numerical Model for the Total Mobility of AlGaN/GaN High Electron Mobility Transistors
Authors: Yahyazadeh Rajab , Hashempour Zahra
Published: March 2012

An analytical- numerical model for the total mobility of AlGaN/GaN based high electron mobility transistors has been developed that is capable to predict accurately the effects of depletion layer thickness on the total mobility in different temperature , gate source biases. In addition taking into account the combined contributions from each of the individual electron scattering mechanisms. Salient features of the model are incorporated of fully and partially occupied sub-bands in the interface quantum well. Close agreement with the experimental data confirms the validity of the present model.
Effects of Annealing Treatment on Optical and Electronic Properties of GaN Based LEDs with ITO Films
Authors: Wang Wanjing , Li Xifeng , Zhang Jinsong , Zhang Jianhua
Published: March 2012

Indium-Tin-Oxide (ITO) film prepared by DC magnetron sputtering was used as a current spread layer for LEDs. After the annealing treatment, the physical prosperities of p-GaN based LED have been investigated. The N2 annealing improved the surface roughness of ITO film to reach the smallest value (8 nm RMS) and exhibited an ohmic contact for ITO/p-GaN interface with the forward voltage decreasing. In comparison with electron beam evaporation, the ITO film prepared by DC magnetron sputtering had better optical and electronic prosperities after the annealing treatment.
Resistance Switching Characteristics of Sputtered Titanium Oxide on a Flexible Substrate
Authors: Wu Changqiang , Zhang Kailiang , Wang Fang , Wei Xiaoying , Zhao Jinshi
Published: March 2012

Flexible resistance random access memory (RRAM) consisting of titanium oxide was investigated in this study. The TiO2 thin film was sputtered on a flexible substrate at room temperature. The fabricated (Cu/TiO2/Cu) device on polyethersulfone (PES) showed stable unipolar resistive switching behaviors with an on/off ratio of ~100 at 0.2V. Because of the good ductility of electrode, the performance of resistive switching was not degraded by different substrate bending, and the resistive switching characteristic was still remained after being physically flexed more than 100 times, even when the substrate is bent up to 10 mm radius. The good performance of the device indicates that TiO2 thin film has high potential for flexible RRAM applications.
Optimization of nLDMOS Ruggedness under Unclamped Inductive Switching (UIS) Stress Conditions by Poly-Gate Extension
Authors: Agarwal Neelam , Sharma Karuna N. , Tsai Jung-Ruey , Sheu Gene , Yang Shao-Ming
Published: March 2012

In this paper, the effect of poly-gate extension on improved ruggedness of n-type LDMOS is evaluated by two-dimensional (2D) device and circuit simulation. Multi-finger dimension of n-type LDMOS is subjected to Unclamped Inductive Switching (UIS) stress test to determine its ruggedness. It is shown that the poly-gate extended device yields approximately 15% higher avalanche energy handling capability (Emax) as compared to that without extended poly-gate region. This work suggests that the improvement in ruggedness of the optimized design is attributed to the suppression and shift of the electric field peaks away from the critical regions. The results from simulation are found to be in good correlation with experimental UIS test results in terms of avalanche energy range, identification of the mechanism of device-failure and hot-spot location. It is believed from the results obtained that this approach will have remarkable impact in the ruggedness if implemented for large-array devices (LAD).
EPI Surface Particle Reduction on NROM Word Line Application
Authors: Yang He , Tang Ji Y. , Wang Chenyu , Li David , Hu Bruce , Li Peng
Published: March 2012

Epitaxy (Epi) technology is widely used for Logic, DRAM and Flash memory process in semiconductor manufacturing industry. Reduced pressure Epi chamber of Applied Materials applied for NROM Flash memory application is introduced, and particle issue occurred during Word Line poly-silicon deposition process is solved.
Improved Characteristics of HKMG MOS Capacitor with Different Ultrathin Interface Layers
Authors: Xiong WenJuan , Xiang Jinjuan , Ou Wen
Published: March 2012

In order to improve the HKMG interface states density and electrical characteristics, four different interface layers have been studied in this paper. They are 7Aå thickness of SiO2 produced by rapid thermal annealing process at 1000°C, 4Aå thickness of SiO2 produced by rapid thermal annealing process at 700°C, 10Aå thickness of silicon nitride produced by LPCVD process at 620°C, and 20Aå thickness of SiO2 produced by traditional horizontal furnace process at 830°C. It was found that there were two samples, the interface layers of 7Aå SiO2 and 10Aå silicon nitride, having excellent interface state density (1.5~1.7×1011cm-2ev-1) and gate leakage (3.1~3.5×10-7A). Considering the thinner equivalent oxide thickness (Eot), we choose 10Aå silicon nitride as the best one
Effect of AlGaN Barrier Thickness on the Cut Off Frequency of AlGaN/GaN High Electron Mobility Transistors
Authors: Yahyazadeh Rajab , Hashempour Zahra
Published: March 2012

An analytical- numerical model for the drain source and gate source currents of AlGaN/GaN based HEMTs has been developed that is capable to predict accurately the effects of AlGaN barrier thickness on the cut off frequency in different gate source and drain source biases. Salient features of the model are incorporated of fully and partially occupied sub-bands in the interface quantum well, combined with a self-consistent solution of the Schrödinger and Poisson equations. In addition current in the barrier of AlGaN, traps density in AlGaN are also take in to account. The calculated model results are in very good agreement with existing experimental data for HEMTs device.
Extended Use of Immersion Tool for the 2x nm HP and Beyond
Authors: Imai Motokatsu , Suzuki Hiroyuki
Published: March 2012

The recent technology roadmap suggests a continuous trend of miniaturizing the pattern size in the upcoming generation. Double patterning technology is already in practical use for 32 nm HP patterning for memory device production. EUVL may be in need for 2x nm HP and beyond. However, it is facing challenges such as insufficient source power, mask defects and resist. EUVL development is supposed to delay due to those remaining technical obstacles. In that case, double patterning technology will be most likely the solution to accommodate 2x nm HP and beyond.
DFM Study in Low k1 Lithography Process
Authors: Wang Lei , Guo Xiaobo , Li Weifeng , Tong Yufeng , Chen Fucheng , Meng Honglin , Su Bo , Xiao Sheng'An
Published: March 2012

For low k1 lithography process, some minor facotrs' impacts are strongly enhanced such as MEEF, lens distortion, wafer topography, pattern density and so on. How to minimize those impacts becomes more and more important. Unfortunately those impacts are not controlled by lithography process itself and caused by other modules such as layout design, integration schemes, mask making, film deposition, CMP and so on. A method to reduce those impacts is quietly needed. DFM (Design for Manufacturability) is a popular and effective approach to get more robust process by reducing pattern loading effect. In this paper, we will show our study on wafer local topography in low k1 lithography process. Products with sub-90nm design rules and different device structures are processed by pure KrF process. The maximum 0.82NA KrF scanner tools are used. The k1 factor is low enough to enhance the impacts. By using DFM solutions, we had resolved these issues and the process window are obviously improved.
A Multi-Objective Layout Decomposition Framework for Self-Aligned Double Patterning Lithography
Authors: Luo Kaisheng , Shi Zheng , Lin Bin , Qi Jing
Published: March 2012

Due to the limitation of current lithography technology, double patterning lithography (DPL) has become the leading candidate for lithography process in sub-30nm integrated circuit (IC) manufacturing. Among all DPL technologies, self-aligned double patterning (SADP) lithography presents greatest potential to real implementation in recent studies. An optimal decomposition strategy is always necessary to implement SADP in 2D design. An efficient SADP decomposition algorithm based on satisfactory (SAT) problem for 2D design has been proposed in recent studies. In this paper, we present a multi-objective layout decomposition framework for SADP based on graph partitioning algorithm and previously proposed SAT problem. Experimental results show that with less runtime our framework can get more balanced density of core mask, more simplified core mask and trim mask and less overlay impact compared to previous work.
Substrate Effect on CD Control for Ion Implantation Layer Lithography Beyond 45nm Node
Authors: Hu HuaYong , Wu Qiang , Lin Yishih , Gu Yiming
Published: March 2012

Continuous technology-driven scaling has brought ion implantation (IMP) layers to a point, where the achievement of necessary resolution and line width start to meet significant process and material challenges, such as the non-negligible substrate effect. Underlying topography and film stack variation have created severe substrate reflectivity variation that affects critical dimension (CD), CD uniformity, resist profiles, and possibly defectivity, especially, the CD may vary according to different substrate film stacks, such as, trench isolation oxide (blank), and silicon. To minimize such CD offset on topography and blank area, photoresist (PR) thickness optimization in needed in addition to mask size adjustment which may meet some design rule constraints. Besides, in this paper we found that IMP process especially pre-amorphous implantation (PAI) for lightly doped drain (LDD) or source-drain (SD), may introduce one intermediate layer with different n,k that render extra effect on substrate reflectivity which will bring more complexity to photo CD control.
The Impact of the Use of Strongly Absorbing Etch Hard Masks and Shallow Topography to Alignment Signal Strength in 28 nm Technology Nodes and Beyond
Authors: Wu Qiang , Hao JingAn , Shi Xuelong , Gu Yiming
Published: March 2012

As the design rule of the semiconductor fabrication continue to shrink in the lateral dimensions, the vertical dimension becomes thinner and the requirement on the planarization becomes higher. In the front end of the line (FEOL), the shallower topography after STI CMP has become significantly thinner than 20 nm, adding the use of strongly absorbing hard mask, such as, amorphous carbon, the signal for alignment detection at the poly layer becomes significantly less than 1% in ASML's wafer quality metric. To get better signal, one will be forced to use an extra mask step to clear out some of the oxide in the STI trenches in the alignment and overlay marks to create necessary topography. In the back end of the line (BEOL), the use of strongly absorbing hard masks, such as, amorphous carbon or titanium containing compound, can also adversely affect alignment signals. At the contact layer, the alignment signal strength can be reduced to around the detection limit, ~1%. At the via layers, due to the use of titanium containing hard mask, the alignment signal to can also be significantly reduced by 1 order of magnitude. In this paper, we will use alignment mark signal simulation to analyze the impact of the shallow topography and the use of typical hard mask to the alignment signal.
The Effects of Nominal Process Focus Definition on the OPC Model
Authors: Wang Kobe , Qi Vanessa , Cheng Johnny , Liu Winnie , Liu Qingwei , Shi Xuelong , Gu Yiming , Zhang Recco , Zhu Yu
Published: March 2012

Both nominal and process window (PW) OPC models were calibrated against wafer data from single and multiple process conditions, respectively. Based on different definition for nominal process focus condition, different OPC models were obtained. The effects of nominal process focus definition on the model performance were explored by analyzing the focus parameters calibrated and the data fitting accuracy and prediction capabilities of the models for different process conditions. For both nominal and PW OPC models, the nominal process focus setting has no obvious influence on fitting accuracy for particular process, however, proper nominal process focus selection results in better PW OPC model for nominal process defined.
DOF and Coherence Optimization in Sub-32 nm Contact Lithography
Authors: Xu Yao , Wu Qiang , Shi Xuelong , Gu Yiming
Published: March 2012

As lithography process steps into deep low k1 factor (~0.3 or smaller) generation, imaging quality and lithography process window (PW) are highly sensitive to the illumination pupil. Maintaining the depth of focus (DOF) becomes more challenging for sub-32 nm tech node micro-lithographic process especially for contact patterns, and carefully selection of accurate illumination setting is significant during the course of process development. Although Source Mask Optimization (SMO) has become one of the most important techniques available for extending ArF immersion lithography, for logic and foundry patterns, source optimization only is still an effective method to extend lithographic capability and maximize depth of focus. In this paper, we present our study on the determination of the optimized illumination mode for 28 nm contact lithography through both photolithographic simulation and experiments with different imaging coherence settings. This simulation and experimental study show that even a previously believed "tiny" sigma change, such as, 0.01 can lead to a significant effect on depth of focus, which can be as much as 30%. This indicates that photolithographic process optimization and development have entered an era where intensive simulation and parameter mapping becomes inevitable in order to achieve success. Also, the heavy dependence of an acceptable process on the illumination has put a more stringent requirement on the scanner's control on the illumination pupil's accuracy and stability.
LRC Based OPC Recipe Qualification
Authors: Zhu Liang , Lugg Robert
Published: March 2012

Typical IC layouts are simple shapes such as rectangles and 45 degree triangles. However, the high-spatial-frequency components of the mask spectrum cut off by the low-pass pupil will result in the rounded images and pattern distortions. Although optical proximity correction (OPC) has been proposed to address this issue as a standard industry practice, there are no theoretically perfect corrections due to some physical or chemical limitations. Therefore, how to qualify the correction results has become a problem. In this paper, the lithography rule check (LRC) based OPC recipe qualification is proposed. By extracting and grouping the LRC databases, the point-to-point post-OPC comparison matrix is shown. Finally, this new methodology can be integrated into the regression flow. When changing to a new software version or different OPC flow, this new validation methodology can not only tell the differences, but also report if there are any OPC quality degradations.
SRAF Optimization for sub-40nm Technology Node Contact Patterning
Authors: Wang Benny , Zhang Jasmine , Zhu Yu , Huang Vincent , Cheng Johnny , Liu Qingwei , Shi Xuelong , Gu Yiming , Zhang Recco
Published: March 2012

As 193nm immersion lithography is extended to sub-40nm technology node, how to define a single-pass contact hole patterning process with enough common lithography process window is a very challenging task. Sub-resolution assist features (SRAF) optimization is one crucial step besides illumination optimization and mask bias optimization. This paper presents a comprehensive SRAF optimization flow that achieves a set of SRAF solutions that balances SRAF benefits and mask manufacturing feasibility. As the criterion of patterning performance, the through pitch process window is investigated for different SRAF placement options based on simulated PV-band of a given process variation (focus & dose). Full chip optimization with representative layouts is also studied. Silicon level performance verification is done with final SRAF solution for through pitch pattern and typical layouts. Finally, we conclude the paper by demonstrating the overall benefit of SRAF on CD uniformity, from process capability as well as mask complexity perspectives.
The Defectivity Reduction on Hole Layers beyond 45nm Node
Authors: Li Gaorong , Hu HuaYong , Wu Qiang , Lin Yishih , Gu Yiming
Published: March 2012

As the advanced semiconductor manufacturing technology moves in 4X node and beyond, defectivity reduction becomes a more and more challenging in photolithographic process, especially with the use of immersion scanners. In this study, we will focus on the defectivity related to hole layers. The hole layers include contact and Vias, which are always critical layers as they all need immersion exposure for resolution requirement. Defectivity such as blocked holes, undersized holes, and missing holes are often found. We have analyzed several defect types and we conclude from our data that the sources are mainly from un-optimized filtration, developing process, and inadequate imaging contrast. In order to reduce hole missing defect, we have studied the 2 photoresists and the use of different filters, as well as develop process and illumination mode optimization. We conclude that to effectively reduce hole defectivity, there is a need to combine the contribution from resist filtration and image contrast improvement In this paper, we will present our findings.
Subtractive Etching of Cu at Low Temperature in Hydrogen-Based Plasmas
Authors: Wu Fangyu , Levitin Galit , Choi Tae-Seop , Hess Dennis W.
Published: March 2012

Thin film patterning in integrated circuit processing has traditionally been performed by subtractive processes. However, over the past 25 years, the inability to plasma etch copper (Cu) interconnect patterns has led to patterning of Cu by an additive process: the damascene approach. In the current work, a simple subtractive, low temperature hydrogen (H2) plasma etch process is described that permits an alternative method to damascene technology. Cu thin films were etched in an H2 plasma using inductively coupled plasma (ICP) reactors at temperatures between -150 oC and +100 oC. This process achieves anisotropic Cu features (~82o) with a pure H2 etch rate of ~13 nm/min. Both physical (ion bombardment) and chemical contributions (neutral species) are critical to the Cu etch process.
CMP-less ILD0 Planarization Technology for Gate-Last Process
Authors: Meng Lingkuan , Yin Huaxiang
Published: March 2012

As CMOS technology scales to 32nm node and beyond, ILD0 planarization is one of critical technologies in high-K metal gate-last process integration. In this paper, a novel sub-micron gate-last process featuring with CMP-less spin-on glass/silicon oxide (SOG/SiO2) etch-back method was demonstrated for low cost logic platform. The innovative approach of SOG two steps plasma etch-back with O2 treatment can be successfully used for ILD0 planarization of gate-last process. SEM results indicated that there was fairly little "dish effect" and step height close to zero on the 0.4µm gate-stack array and finally achieved a good planarization on the whole substrate.
Dry Etching Solutions to Contact Hole Profile Optimization for Advanced Logic Technologies
Authors: Wang Xin-Peng , Huang Yi , Han Qiu-Hua , Zhang Hai-Yang , Lee Kwok-Fung
Published: March 2012

As CMOS technology has been continuously scaling down and the dual-stress liner scheme is introduced for simultaneous stress enhancement of both n-MOS and p-MOS, contact etch has started to act as a critical role for the robust performance of integrated circuit. In this work, we investigated the impact of dry etching process on contact hole profile. Results demonstrate the overall contact hole profile can be rigorously controlled if the radio frequency (rf) powers and etching chemistries in inter layer dielectric (ILD) etch step are well balanced. Free local pull-back at contact hole sidewall has to leverage the optimization of etch selectivity of silicon nitride over silicon oxide in liner removal step. Besides, the post etch treatment (PET) is also proven to be imperative for the process window enhancement for such pull-back reduction.
Study of Post Plasma Doping Photoresist Strip
Authors: Luo Shijian , Torregrosa Frank , DeLuca James , Hou Jianan , Berry Ivan , Roh Dwight
Published: March 2012

This paper reports on the study and development of post plasma doping photoresist (PR) strip processes which meet the requirements of good dopant retention and cleaning capability for this application. SIMS analysis of plasma implanted silicon wafers processed with these plasma strip approaches have shown improved dopant retention and profile in both n-type and p-type junctions. Stripping of implanted patterned PR wafers with these processes has revealed excellent cleaning and residue removal capability. This work demonstrates that these post plasma doped PR strip processes are viable candidates to meet the demanding clean requirements for USJ fabrication by plasma doping technology.
TiN Metal Hardmask Etch Residues Removal for Cu Dual Damascene Devices with TiN Mask Corner Rounding Scheme
Authors: Cui Hua
Published: March 2012

A novel wet cleaning non-fluoride formulation approach was developed with a TiN etch rate of more than 100 Aå/min at 55 ºC. The chemicals are compatible with Cu and low-k materials, and are suitable for Cu dual damascene interconnect 20 nm and smaller technology node applications. The chemicals offer a route to in situ controlled TiN pullback or even complete removal of the TiN mask during the cleaning process in single wafer tool applications. Additionally, development progress for recent formulations with greater than 250 Aå/min at 50 ºC TiN etch rates is reported.
Thin Film Challenges in 28nm Technology Node
Authors: Zhang Beichao , Zhang Bin , Xiao Haibo , Deng Hao , Tong Hao , Tan Jingjing , Zhou Ming , Li Nicola , Guo Shibi , Ren Wanchun , Wang Xiaona , Jing Xuezheng , Xiang Yang Hui , Ping Yanlei , Bao Yu , Zhang Ziying , Wang Zengtao , Lu Wei , Wu Jinggang
Published: March 2012

During 28nm technology node process development, a couple of dozens new thin films and advanced thin film processes have been introduced to meet needs of the CMOS circuit performance. These new films and processes are used for micro-patterning, gap-fill, high-k metal gate (HKMG) work function metals and electrodes, electrical and reliability performance, etc. This article shall report the latest progress in thin film developments at the leading Chinese semiconductor company, SMIC. Some key challenges in the areas mentioned above will be elaborated and various new thin film requirements will be discussed. Examples of some thin film process developments, especially in the micro-patterning, Metal Gate and STI and ILD gap-fill, and HKMG work function tuning, will be provided, and the preliminary results will be presented.
Investigation of Thermal Stability of RFPVD TiAl Metal Alloy
Authors: Zhang Ziying , Ping Yanlei , Wang Xiaona , Xiao Haibo , Chen Yong , Jing Xuezheng , Zhang Beichao
Published: March 2012

In this paper, thermal stability, composition ratio and crystallinity of radio frequency PVD (RFPVD) TiAl metal alloy are investigated, and their effects on work function are studied. An experimental method, to measure TiAl sheet resistance variation before and after annealing, was used to evaluate the interface diffusion of TiAl in the metal stack under varied barrier films. The barrier layer materials included ALD TiN, PVD TiN and ALD TaN.
A High-Quality Spacer Oxide Formation for 28nm Technology Node and Beyond
Authors: Zhang Bin , Xiang Yang Hui , Deng Hao , Guo Shibi , Zhang Beichao
Published: March 2012

In this paper we present a new approach to fabricate spacer oxide for 28nm and beyond CMOS technology. The main advantage of this approach is that it allows a further downscaling of transistor's gate length while maintaining high qualities, such as low thermal budget, excellent conformality, and small pattern loading effect (referring to equal thickness deposition in open and dense areas within an array structure), etc.
Characterization of Metal Schottky Junction for In0.53Ga0.47As Substrates
Authors: Hosoi Ryuji , Suzuki Yuya , Zadeh Darius , Kakushima Kuniyuki , Ahmet Parhat , Kataoka Yoshinori , Nishiyama Akira , Sugii Nobuyuki , Tsutsui Kazuo , Natori Kenji , Hattori Takeo , Iwai Hiroshi
Published: March 2012

The metal/InGaAs Schottky devices with Ni, TiN and stacked Ni/Si were fabricated. J-V and C-V characteristics were measured and Schottky barrier height was calculated.
A Study of SiCN Cap Process Resultant Plasma Induced Damage in 40nm Technology Node
Authors: Zhou Ming , Xiang Yang Hui , Guo Shi Bi , Deng Hao , Zhang Bing , Zhang Beichao
Published: March 2012

Plasma processes are widely used in the manufacturing of very large scale integration (VLSl) devices for dry etching and dielectric film deposition. Damage due to plasma becomes inevitable and can potentially break the gate dielectric bonds to increase gate dielectric leakage current, which would give rise to transistor threshold voltage shift and device failure. In our 40nm device data, there was a gate oxide leakage failure dominantly in wafer center. It was found that this failure is related to SiCN Cu interconnect cap film deposition. The purpose of this work was to investigate its failure mechanism. In the current study, SiCN films were deposited with two different types of commercial tools. The SiCN film surface charge results showed that the charge value in wafer center was obviously higher than that in wafer edge. The plasma density measurement result also showed that plasma density in the chamber center is higher than that of wafer edge. Plasma induced damage (PID) test data showed that the deposition initial step, or the NH3 pretreatment stage, was not the key factor for the device damage, but the main step of SiCN film deposition played the important role in the device damage. By adjusting the main deposition step, the film surface charge value and the charge uniformity were much improved, which led to a solution to the wafer central PID issue at 40nm device.
Influence of Electrode Materials on CeOx Based Resistive Switching
Authors: Kano Shin-ichi , Dou Chunmeng , Hadi Mokhammad S. , Kakushima Kuniyuki , Ahmet Parhat , Nishiyama Akira , Sugii Nobuyuki , Tsutsui Kazuo , Kataoka Yoshinori , Natori Kenji , Miranda Enrique A. , Hattori Takeo , Iwai Hiroshi
Published: March 2012

Resistance changing of ion binding insulator hardly obtain large on and off resistance ratio. Resistance switching properties using Ni, W and Ti as a bottom electrode ware caused of changing resistance of Ce oxide. The influence of metal electrode on resistive switching behavior of CeOx film has been investigated. Resistance switching characteristics using NiSi2 electrode shows a large on and off window as large as 105. The main differences of the switching properties among the electrode materials are thought to be the reaction between the Ce oxide layer and electrodes. The set voltage dependence on the thickness of Ce oxide layers has indicated that the switching behavior is based on electric field.