bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytological studies of the nucleolus organizing regions in the Medicago complex: sativa–coerulea–falcata
Authors: Calderini O. , Pupilli F. , Cluster P. D. , Mariani A. , Arcioni S.
Published: May 2008

A cytological examination of the nucleolus organizing regions (NORs) of three species from the Medicago sativa complex was conducted to evaluate the structural and functional evolution of the ribosomal RNA (rRNA) loci that encode the 18S, 5.8S, and 26S rRNAs. Mitotic chromosomes in root-tip preparations from tetraploid M. sativa and diploids Medicago coerulea and Medicago falcata were visualized by four methods that provide new data. Fluorescent in situ hybridization using the M. sativa 18S gene as probe localized the structural rDNA to the constricted regions of the satellited chromosomes only. Chromomycin A3 (CMA3) staining and 4′,6-diamidino-2-phenylindole (DAPI) staining identified these chromosomal segments as the most GC-rich regions in the alfalfa karyotype. Medicago falcata exhibited fewer DAPI bands and chromocenters than did M. sativa and M. coerulea. Positive silver nitrate staining showed that all four rDNA regions in M. sativa (located in two chromosome pairs) and both rDNA sites in both diploid species remain transcriptionally active. Counts of nucleoli confirmed that all rDNA regions are independently capable of nucleolus organization. Thus, the number of active NORs in M. sativa is double the number found in M. coerulea or M. falcata. Consequently, if M. sativa originated from sexual hybridization of 2n gametes involving one or both diploid species, no major reorganization or loss of structural or functional rDNA loci has occurred. Key words : alfalfa evolution, CMA3 banding, DAPI banding, fluorescent in situ hybridization, silver nitrate staining.
Genetic resolution and verification of quantitative trait loci for flowering and plant height with recombinant inbred lines of maize
Authors: Austin David F. , Lee Michael
Published: May 2008

Recombinant inbred (RI) lines offer several advantages for detecting quantitative trait loci (QTLs), including increased precision of trait measurements, power for detection of additive effects, and resolution of linked QTLs. This study was conducted to detect and characterize QTLs in maize for flowering and plant height and to compare QTL detection in an early (F2:3) generation of the same population. One hundred and eighty-six RIs from a cross between inbred lines Mo17 and H99 were evaluated in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms. QTLs were identified by single-factor analysis of variance. A total of 59 QTLs were detected for plant height, ear height, top height, anthesis, silk emergence, and anthesis to silk interval. Individual QTLs explained 2.2–15.4% of trait variation, and multiple models including all QTLs detected for a trait explained up to 52.5% of the phenotypic variation. Comparison of QTLs detected with 150 F2:3lines from the same population indicated that 16 (70%) of the 23 F2:3QTLs were also observed in the F6:7generation. Parental effects were consistent across generations. At 14 of the 16 QTLs detected in both generations, genetic effects were smaller in the F6:7. Also, some QTLs detected in the F2:3were resolved into multiple linked QTLs in the F6:7, indicating the additional power of RI populations for mapping, with important implications for marker-assisted selection as well as map-based cloning of QTLs. Key words : Zea mays, RFLP, plant breeding, genetics, recombination.
Cytological expression of early response to infection by Heterodera glycines Ichinohe in resistant PI 437654 soybean
Authors: Mahalingam R. , Skorupska H. T.
Published: May 2008

The soybean PI 437654 is resistant to all known races of the soybean cyst nematode (SCN) in the U.S.A. and became a new source of resistance genes in cultivar development. Race 3, a wide-ranging nematode pathotype, was used to examine root cells of PI 437654 and susceptible 'Essex', 2, 3, and 5 days after inoculation (DAI). In initial response to SCN, both genotypes formed syncytia by cell wall dissolutions. Hypertrophy of syncytium component cells and hyperplasia of cells near syncytia were observed. At 2 DAI, incompatible response of PI 437654 to SCN was exhibited: limited cell hypertrophy, inhibition of syncytium growth, initiation of necrosis, and wall appositions. At 3 DAI, cellular events appeared to be a sum of the operative mechanisms for SCN resistance: irregular wall thickening, pronounced wall appositions, necrosis, and nuclear breakdown followed by cytoplasmic collapse. The cells surrounding the syncytia showed necrosis, wall apposition, and accumulation of electron-dense bodies. By 5 DAI, syncytia and neighboring cells were totally devoid of ground plasma and the degeneration process was completed. The normal route for early syncytium development in 'Essex' (increased number of organelles, intense vacuolization, accumulation of dense deposits in vacuoles, and wall ingrowths) suggests the involvement of portions of the developmental pathway of differentiating tissues in organogenesis. Early onset of SCN resistance 2 DAI in PI 437654 suggests rapid activation of genes in a cascade reaction leading to cell death. Key words : soybean, nematode, syncytium, cell death.
Analysis of a hotspot for deletion formation within the intron of the chloroplast trnI gene
Authors: Johnson Douglas A. , Hattori Jiro
Published: May 2008

The chloroplast genomes of higher plants encode several tRNA genes that contain highly conserved type II introns. Using primers specific to conserved 5′ and 3′ regions within the introns of the genes trnA (tRNA-ala) and trnI (tRNA-ile) we have PCR amplified parts of these introns from 36 plant species representing a wide range of plant families. Deletions were found in the introns of both tRNA genes. Fourteen species had detectable deletions within the intron of trnI and four species within the intron of trnA. The occurrence of these deletions among the various plant families suggests that the events leading to the formation of these deletions occurred independently many times during the evolution of higher plants. Analysis of the amplified PCR products from the trnI intron suggests that these independent deletions may not be random but appear to fall into two size classes. Several members of each class were cloned and sequenced and the end points of the deletions were mapped. The 3′ ends of all deletions studied terminate within the same short region. The 5′ ends of the deletions map to two different regions, giving rise to the two size classes. These two 5′ deletion endpoint regions show some sequence similarity. Only two of the identified deletions contain directly repeated sequences at the deletion endpoints, a feature associated with homologous recombination. Our results suggest that within the trnI intron, there are preferred sites or "hotspots" for deletion formation involving a novel imprecise recombination mechanism. The significance of these sequences and possible mechanisms for deletion formation are discussed. Key words : chloroplast, intron, deletion, sequence.
Detection of a variable number of ribosomal DNA loci by fluorescent in situ hybridization inPopulusspecies
Authors: Prado E. A. , Faivre-Rampant P. , Schneider C. , Darmency M. A.
Published: May 2008

Fluorescent in situ hybridization (FISH) was applied to related Populus species (2n = 19) in order to detect rDNA loci. An interspecific variability in the number of hybridization sites was revealed using as probe an homologous 25S clone from Populus deltoides. The application of image analysis methods to measure fluorescence intensity of the hybridization signals has enabled us to characterize major and minor loci in the 18S–5.8S–25S rDNA. We identified one pair of such rDNA clusters in Populus alba; two pairs, one major and one minor, in both Populus nigra and P. deltoides; and three pairs in Populus balsamifera, (two major and one minor) and Populus euroamericana (one major and two minor). FISH results are in agreement with those based on RFLP analysis. The pBG13 probe containing 5S sequence from flax detected two separate clusters corresponding to the two size classes of units that coexist within 5S rDNA of most Populus species. Key words : Populus spp., fluorescent in situ hybridization, FISH, rDNA variability, image analysis.
Generation of a YAC contig encompassing the extra glume gene,eg, in rice
Authors: Houten Wim Van , Kurata Nori , Umehara Yosuke , Sasaki Takuji , Minobe Yuzo
Published: May 2008

We have used DNA markers from a high density molecular map of rice (Oryza sativa) to tag a single gene expressed as a flower morphogenesis mutation, extra glume (eg). Using an F2population segregating for eg, obtained from a cross between IR24 and F136 (eg/eg), we constructed a partial molecular map and located eg relative to restriction fragment length polymorphism markers. The region between two markers appears to span the eg locus on rice chromosome 1 and extends to a genetic length of 3.8 cM. The yeast artificial chromosome (YAC) library obtained from rice variety 'Nipponbare', which carries the wild-type allele of eg, was screened to completely cover the locus by overlapping YAC clones. The eg allele should be contained in two overlapping YACs. YAC size determination by pulsed-field gel electrophoresis indicated that this region has a physical length of approximately 400 kb. We anticipate that the tagging of eg in a relatively short stretch of DNA will allow a molecular characterization of this gene through map-based cloning. Key words : rice, gene tagging, YAC contig, flower morphogenesis, extra glume.
Genetic determinism of δ3-carene in maritime pine using RAPD markers
Authors: Plomion Christophe , Yani Abdelhamid , Marpeau Anne
Published: May 2008

An F2progeny of maritime pine (Pinus pinaster Aïton) was used to investigate the mode of inheritance of δ3-carene using a quantitative and a qualitative approach. A previously reported genetic map constructed with random amplified polymorphic DNA (RAPD) markers made it possible to locate one major quantitative trait locus (QTL) accounting for most of the phenotypic variation of this trait on linkage group 5. In the qualitative approach, the "C" locus that controls the relative quantity of δ3-carene (C+ for the richness allele and C− for the poorness allele) was found to be strongly associated with RAPD markers in the same genomic region of linkage group 5. The colocation between the QTL and the "C" locus suggests that a major gene or closely linked loci affect the variation in δ3-carene expression. Key words : Pinus pinaster, terpenes, QTL, RAPD, linkage analysis.
A preliminary germplasm evaluation of onion landraces from West Africa
Authors: Rouamba A. , Robert T. , Sarr A. , Ricroch A.
Published: May 2008

Genetic erosion is observed in traditional populations of onion in West Africa. The present study aimed to assess the agronomical potential for six important traits of 14 landraces collected in West Africa. A multivariate procedure was used to establish a classification within this germplasm on the basis of these traits. The phenotypic variability both within and between landraces is considerable but could be due to traditional agricultural practices still occurring in this area. Three statistically coherent clusters have been identified despite the great phenotypic variation between landraces and could be a basis for building a core collection of West African onion germplasm. This first analysis of traditional onion landraces provides convincing information regarding their agronomic potential. Key words : Allium cepa L., onion, genetic resources, diversity.
Cloning and characterization of a highly repeated DNA sequence in Hordeum vulgare L.
Authors: Liu Kebin , Somerville Shauna
Published: May 2008

A novel repetitive DNA sequence, R10hvcop, has been identified in the barley (Hordeum vulgare L.) genome. This 830 base pair (bp) DNA sequence has a 606-bp open reading frame and is present as approximately 1.96 × 105 copies per haploid barley genome. Southern blot analysis revealed that repetitive DNA elements containing R10hvcop and related sequences were dispersed within the barley chromosomes. Sequences similar to R10hvcop were also found in wheat (Triticum aestivum L.), rye (Secale cereale L.), and oat (Avena sativa L.) with copy numbers of 8 × 104, 1.39 × 105, and 7.9 × 104 per haploid genome, respectively. Sequences similar to R10hvcop were also present in the corn (Zea mays L. ssp. mays) genome, but they were not highly repeated. Barley, wheat, rye, oat, and corn showed species-specific restriction fragment length polymorphisms of R10hvcop and related sequences. Computer-based similarity searches revealed that R10hvcop is closely related to reverse transcriptase genes in retrotransposons and retrotransposon-like elements of several plant species and of Drosophila. The highly repetitive nature, interspersed distribution, and high degree of similarity to reverse transcriptase genes suggests that R10hvcop contains the sequence of a diverged reverse transcriptase gene. Key words : repetitive DNA, barley, reverse transcriptase gene, sequence divergence.
Chromosome pairing affinity and quadrivalent formation in polyploids: do segmental allopolyploids exist?
Authors: Sybenga J.
Published: May 2008

When polyploid hybrids with closely related genomes are propagated by selfing or sib-breeding, the meiotic behaviour will turn into essentially autopolyploid behaviour as soon as the affinity between the genomes is sufficient to permit occasional homoeologous pairing. An allopolyploid will only be formed when the initial differentiation is sufficient to completely prevent homoeologous pairing (in some cases enhanced by specific genes), or when segregational dysgenesis prevents transmission of recombined chromosomes. A new polyploid hybrid may be considered a segmental allopolyploid and may show reduced multivalent formation as a result of preferential pairing between the least differentiated genomes. An established polyploid is either an autopolyploid or an allopolyploid. In exceptional cases it is thinkable that a stable segmental allopolyploid arises, in which some sets of chromosomes are well differentiated and behave as in an allopolyploid, whereas other sets are not well differentiated and behave as in an autopolyploid. No clear cases have been found in the literature so far. Key words : chromosome, pairing affinity, quadrivalent frequency, segmental allopolyploidy.
A codominant DNA marker closely linked to the rice nuclear restorer gene, Rf-1, identified with inter-SSR fingerprinting
Authors: Akagi Hiromori , Yokozeki Yumi , Inagaki Akiko , Nakamura Atsushi , Fujimura Tatsuhito
Published: May 2008

A new molecular marker (OSRRf) closely linked to the nuclear restorer gene (Rf-1) for fertility in rice has been found. The Rf-1 gene is essential for hybrid rice seed production. A PCR-fingerprinting technique using simple sequence repeats (SSRs) was applied to compare two near-isogenic lines with (MTC-10R) or without (MTC-10A) the Rf-1 gene. Of 76 inter-SSR primers tested, only one primer, (AG)8YC, generated polymorphisms. The tetranucleotide repeats generating polymorphisms were found within each amplicon. The genetic distance between OSRRf and Rf-1 was 3.7 ± 1.1 cM. As in the case of a codominant marker, this marker will be applied not only to breeding both restorer lines and maintainer lines, but also to the purity management of hybrid rice seeds. Key words : Oryza sativa L., restorer gene Rf-1, microsatellite, inter-repeat fingerprinting.
Differential sensitivity of some human alphoid and classical satellite DNA regions from lymphocyte chromosomes to in situ exonuclease III digestion
Authors: Fernández José Luis , López-Fernández Carmen , Gosálvez Jaime , Goyanes Vicente
Published: May 2008

Fluorescent in situ hybridization of alphoid and classical satellite III DNA sequences was performed on fixed chromosomes from human lymphocytes that were previously digested in situ with exonuclease III to produce single-stranded DNA motifs. Digital image analysis showed that while labeled alphoid satellite DNAs produced signals of similar strength to thermally denatured chromosomes, those of classical satellite III DNAs of chromosomes 9 and Yq were around 50% weaker. This result shows a differential sensitivity of these satellite DNA regions to in situ exonuclease III digestion and suggests structural differences in the higher-order organization of both subchromosomal constitutive heterochromatic regions. Key words : alphoid sequences, classical satellite, exonuclease III, FISH, human cytogenetics, satellite DNA.
Chromosomal location of three wheat sequences with homology to pollen allergen encoding, DNA replication regulating, and DNA (cytosine-5)-methyltransferase genes in wheat and rye
Authors: Korzun V. , Balzer H.-J. , Balzer A. , Bäumlein H. , Börner A.
Published: May 2008

Three wheat sequences, shown to be homologous to pollen allergen encoding, DNA replication regulating, and DNA (cytosine-5)-methyltransferase genes were localized on chromosomes using nullisomic–tetrasomic wheat ('Chinese Spring') and wheat–rye ('Chinese Spring'/'Imperial') addition lines. Whereas the loci for the pollen allergen encoding sequence (Tri a III) were shown to be located on homoeologous group 4, the DNA replication regulating (Rep) and DNA (cytosine-5)-methyltransferase (Mtase) genes were located to homoeologous groups 1 and 7, respectively, of Triticeae. Chromosomal rearrangements in wheat and rye relative to each other are discussed. Key words : chromosomal location, known function probes, RFLP, rye, wheat.
Basal-area projection equations for thinned natural even-aged forest stands
Authors: Murphy Paul A. , Farrar Jr. Robert M.
Published: May 2008

Several existing basal-area projection equations, including one with a thinning term, were compared by using data from a long-term thinning study in natural even-aged stands of loblolly (Pinustaeda L.) and shortleaf pine (Pinusechinata Mill.) in the West Gulf Coastal Plain. The model with the thinning term was no better than existing models with no thinning variable. These results prompted a search to improve the projection models that include thinning. A general technique for introducing a thinning variable into basal-area projection models was developed. This study found that the efficacy of adding a thinning term depends upon the accuracy requirements of the user.
Plantlet production from anthers of Eastern cottonwood (Populusdeltoïdes)
Authors: Uddin M. Rafique , Meyer Jr. Martin M. , Jokela J. J.
Published: May 2008

Plantlets were obtained by organogenesis from cultured anthers of Populusdeltoides (Bartr.). Anthers formed callus in the dark on modified Murashige and Skoog medium supplemented with 9.0 μM 2,4-dichlorophenoxyacetic acid and 4.7 μM kinetin. Anther calli were differentiated into shoots by sequential transfer in the light onto Murashige and Skoog medium containing 4.4 μM benzylamino purine and 1.1 μM naphthaleneacetic acid for 4 weeks, followed by several transfers to woody plant medium with 2.2 μM benzylamino purine and 1.1 μM naphthaleneacetic acid. The shoots that formed were rooted by excising and transferring to woody plant medium supplemented with 1.0 μM indole-3-butyric acid. A few of these plants were found to be haploid. Two plants developed male terminal inflorescences, but died shortly thereafter.
The influence of metal halide and high-pressure sodium lamps during photoperiod extension on the allocation of carbon between lignin and cellulose in black spruce seedlings
Authors: Margolis Hank A. , Bégin Jacques , Beeson Richard , Bellefleur Pierre
Published: May 2008

Containerized black spruce seedlings (Piceamariana (Mill.) B.S.P.) were grown at the greenhouse at CIP Inc., Harrington, Québec, from February until May, 1987. We wished to test whether differences in the quantity and quality of light received from two commercially available lamps during photoperiod extension would alter the allocation of carbon between lignin and cellulose in shoots and roots. Photoperiods were extended from 17:00 to 01:00 using either metal halide and high-pressure sodium lamps together or high-pressure sodium lamps alone. At night, the treatment using both types of lamp together increased the photon flux density of blue light (400–500 nm) at seedling height 10-fold, from 0.32 to 3.2 μE m−2 s−1. Photosynthetically active radiation was increased 4-fold, from 4.5 to 17.9 μE m−2 s−1. Total seedling biomass did not differ statistically between light treatments at any given time. However, seedling biomass averaged over all times was statistically higher (p ≤ 0.03) for seedlings in the treatment using both types of lamp together. Percent lignin, percent cellulose, and lignin to cellulose ratios were not significantly affected by the light source used during photoperiod extension. As expected, percent lignin and percent cellulose in shoots and roots increased significantly with time. The percentage of seedlings judged unacceptable because of spiralized stems was not affected by light source and averaged 21.9%.
Propagation of interior spruce by somatic embryogenesis
Authors: Webster F. B. , Roberts D. R. , McInnis S. M. , Sutton B. C. S.
Published: May 2008

To apply somatic embryogenesis to clonal propagation of forest species, the technique must be applicable to a broad range of genotypes and allow efficient regeneration of phenotypically normal plants. Seventy-one lines (genotypes) of embryogenic cultures from six open-pollinated families were obtained by culturing immature embryos of interior spruce. Interior spruce represents a mixture of two closely related species, Piceaglauca (Moench) Voss and Piceaengelmannii Parry, from the interior of British Columbia where they hydridize with one another. The abscisic acid dependent developmental profile (the proportion of rooty embryos, shooty embryos, precociously germinating embryos, and mature embryos over a range of abscisic acid concentrations) differed among genotypes, but in general, production of mature somatic embryos was highest at 40 and 60 μM abscisic acid. Treatment of mature embryos with a high relative humidity treatment resulted in partial drying of the embryos and upon rehydration, markedly enhanced germination of the eight genotypes tested. Within 1 week of being placed under germination conditions, somatic embryos treated with the high relative humidity treatment showed 80–100% germination for 12 of the genotypes, and most genotypes had germination rates of greater than 40%. Survival of "emblings" (germinants from somatic embryos) following transfer to soil, acclimatization, and first season's growth in the nursery was 80% or greater for most genotypes. Over 1200 emblings were tested for nursery performance, representing the first large-scale evaluation of conifer somatic embryos under exvitro conditions. Growth rates, final height, shoot and root morphology, and frost hardiness were similar for emblings and seedlings following the first growing season. These results indicate that somatic embryogenesis can be used for the production of planting stock for a range of interior spruce genotypes.
Effectiveness of paclobutrazol in retarding height growth of Eucalyptusglobulus seedlings
Authors: Hetherington S. , Jones K. M.
Published: May 2008

Foliar applications of paclobutrazol significantly reduced height growth and internode length in Eucalyptusglobulus Labill. seedlings. Monthly applications of 125 or 500 mg/L had a more pronounced effect than one single application of 125, 500, or 2000 mg/L. The greatest reduction in plant height was achieved by applying 500 mg/L at monthly intervals over 5 months. Two months after this treatment was ceased the growth retardant effects persisted.
Building Dielectric Materials from the Bottom Up: Nano-Structured Materials
Authors: Grebel Haim
Published: May 2008

The concept of composite dielectric materials is extended to structured films at the nano-scale. We demonstrate it by several leading examples.
Scanning Probe Microscopy for Dielectric and Metal Characterization
Authors: Kopanski Joseph J. , Walker Thomas R.
Published: May 2008

The properties of both insulators and metals can be characterized capacitively with scanning probe microscopy, though the techniques employed are different. Intermittent contact scanning capacitance microscopy (IC-SCM) is a useful technique for characterizing the dielectric constant of insulators. Scanning Kelvin force microscopy (SKFM) can image potential distributions and work functions within conductors. Both techniques depend on the capacitance between the tip and sample, which has an inverse square dependence on tip-sample separation, limiting spatial resolution. A differential data acquisition technique to improve spatial resolution is described.
Electrical and Reliability Characteristics in Strained-Si MOSFETs
Authors: Yang Chia-Cheng , Pan Tung-Ming , Chen Kai-Ming , Liu Chuan-Hsi
Published: May 2008

In this study, surface-channel MOSFETs processed on strained-Si on relaxed Si1-xGex virtual substrates feature significantly enhanced carrier mobility (64% for electrons and 45% for holes) than that of the bulk-Si control devices. The drain current of the strained-Si nMOSFET increases by 45% compared to 4.5% in strained-Si pMOSFET. The strained-Si pMOSFETs surface roughness scattering begins to dominate at a relatively low effective field (~0.2 MV/cm) that accordingly limits the drive current enhancement of strained-Si pMOSFETs. Furthermore, experimental data indicates that hot carrier and negative bias temperature instability are a potential reliability concern for strained-Si nMOSFETs and pMOSFETs, respectively.
Enhancement in Thermal Stability of Metal-Insulator-Metal Capacitors for Deep Trench DRAM Application
Authors: Hsieh Chun-I , Pan Tung-Ming , Huang Tsai-Yu , Liang Wen-Ping , Lin Jian-Chyi , Wu Chang-Rong , Shih Steven
Published: May 2008

The high-temperature thermal stability of a metal-insulator-metal (MIM) capacitor has been disclosed and improved by embedding a WN barrier layer between bottom electrodes and high-k dielectrics. The interfacial reaction between high-k dielectrics and bottom electrode during high temperature annealing was suppressed. Therefore, both equivalent oxide thickness (EOT) and leakage current were well controlled to meet the criterion of deep trench DRAM technology beyond 50nm.
Novel Non-Oxidative Aqueous Cleaning Solutions for Tungsten Layers
Authors: Park Jung Dae , Kim Se-Yeon , Lee Da-Hee , Jun Pil K. , Yi Hun-Jung , Chae Seung-Ki
Published: May 2008

As memory devices shrink, the introductions of new processes and materials have been prerequisite for high speed and reliability of semiconductors. Particularly, enlargement of processes using metal layers in fabricating devices led to many cleaning problems like metal corrosion, particle adsorption, and polymer remnants after stripping process. On account of the absence of an effective cleaning solution for metal layers, major semiconductor manufacturing companies have been experienced yield drops and endurance fails. In this study, we will report the development of novel cleaning solution for tungsten layers and its application of mass production line. New cleaning chemical is composed of tetramethylammonium hydroxide (TMAH), hydrofluoric acid (HF), and two additives. It could remove polymers formed by RIE (reactive ion etching) without corrosion of metal layers and prevent the adsorption of particles and metal ions accumulated from consecutive cleaning processes. Compared with APM (ammonia peroxide mixture) used as the standard cleaning, this cleaning solution showed the same particle removal efficiency but didn't absorb metal ions on the silicon wafer surface. Furthermore, sidewall and bottoms polymers could be removed effectively in cleaning process of tungsten bit line and various contact holes. In addition, we could obtain the lower resistance of line and contact patterns, and enhancement of yield in memory production line, applying this novel solution to the corresponding cleaning processes instead of amine-based organic stripper.
Metal-Ferroelectric-Insulator-Semiconductor (MFIS) Devices Based on DyScO3 Buffer Layer and Ferroelectric Bi3.25Nd0.75Ti3O12 Thin Film
Authors: Thomas Reji , Pradhan Dillip K. , Melgarejo Ricardo E. , Saavedra-Arias Jose.J. , Karan Naba.K. , Palai Ratnakar , Murari Nishit M. , Katiyar Ram S
Published: May 2008

DyScO3 linear dielectric films based metal-insulator-silicon (MIS); Bi3.25Nd0.75Ti3O12 non-linear dielectric films based metal-ferroelectric-metal (MFM); and DyScO3 insulator as a buffer layer for the metal-ferroelectric-insulator-silicon (MFIS) structures with Bi3.25Nd0.75Ti3O12 ferroelectric films are considered. DyScO3 films on Si substrates were amorphous and dense with smooth surface morphology, and showed negligible CV hysteresis and low leakage current. Remnant polarization ~ 20µC/cm2, zero field dielectric constant ~ 400 and loss tangent ~ 0.04 were obtained for the ferroelectric Bi3.25Nd0.75Ti3O12 film on Pt/TiO2/SiO2/Si substrates. The MFIS capacitors showed a memory window of 0.7 V, which may be sufficient for the practical applications in nonvolatile RAM.
Defect Engineering for Ultrashallow Junctions using Surfaces
Authors: Seebauer Edmund , Kwok Charlotte , Vaidyanathan Ramakrishnan , Kondratenko Yevgeniy , Yeong S. H. , Srinivasan M. P. , Colombeau Benjamin , Chan Lap
Published: May 2008

The behavior of point defects within silicon can be changed significantly by controlling the chemical state at the surface. In ultrashallow junction applications for integrated circuits, such effects can be exploited to reduce transient enhanced diffusion and increase dopant activation. The present work demonstrates such effects experimentally for arsenic and boron.
Implementation of High-k / Metal Gate in High-Volume Manufacturing
Authors: Arghavani Reza , Agustine Melody , Ahmed Khaled , Cheng Chern-Ping , Gandikota Srinivas , Hung Steven , Schreutelkamp Robert , Yoshida Naomi , Yu May
Published: May 2008

Significant breakthroughs emerged in the field of the IC technology in the past decade. The backend of the line saw a transition to copper and ultra low-k interlayer dielectric for RC delay improvement with unique integration approaches such as dual damascene. Advanced Patterning Films have enabled the introduction of Double Patterning and Dual Exposure Lithography allowing line printing at sub-45nm node. Introduction of uniaxial strain at 90nm logic node and a combination of mobility enhancing stressors boosted logic cell performance to meet 45nm node logic requirements. Reliable gate oxynitride of only a few atomic monolayers is now routinely used in high performance devices. Nonetheless, Intel co-founder Gordon Moore stated that introducing high-k and metal gates to transistors is the biggest change in transistor technology in nearly 40 years, firmly pushing Moore's Law scaling back on track. Indeed, high-k and metal gate implementation has been one of the industry's grand challenges. Today this process is in high-volume manufacturing and this paper discusses key challenges associated with transition from oxynitride to high-k and metal gates.
Sc Addition In HfO2 Thin Films Prepared By Liquid-injection MOCVD
Authors: Brize Virginie , Terrenoir Frédéric , Matko Igor , Rochat Nevine , Holländer Bernhard , Feist B. , Blasco Nicolas , Dubourdieu Catherine
Published: May 2008

Hf-Sc-O thin films were deposited at 500{degree sign}C on p-type Si(100)/SiO2 substrates by metal organic chemical vapour deposition. Hf(OtBu)2(mmp)2 and Sc(3mod)3 were used as precursors. The mixture of the precursors in a same solution leads to a rather low Sc incorporation. From XRD and ATR, it is found that the addition of a few percent of Sc (1 to 2 %) leads to the stabilization of the cubic phase. From plane-views TEM, the films are nanocrystallised, with an average grain size of 10 nm. The C(V) measurements on MOS structures show that the relative permittivity is maximum at ~ 1 to 2 % at. Sc in the films (epsilon ~ 25).
Oxidation of Suspended Stacked Silicon Nanowire for Sub-10nm Cross-Section Shape Optimization
Authors: Hubert Alexandre , Colonna Jean-Philippe , Bécu Stéphane , Dupré Cécilia , Maffini-Alvaro Virginie , Hartmann Jean-Michel , Pauliac Sébastien , Vizioz Christian , Aussenac François , Carabasse Catherine , Delaye Vincent , Ernst Thomas , Deleonibus Simon
Published: May 2008

Suspended, stacked and rounded nanowires with diameters as small as 5nm have been obtained thanks to thermal oxidation. Those structures can be used for novel 3D Gate-All-Around Field Effect Transistor (GAAFET) architectures. As the oxidation rate is strongly affected by the nature of the oxidant, the temperature and the wire curvature, both wet and dry oxidations (at 950{degree sign}C and at 1100{degree sign}C, respectively) have been investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the shape and the oxidation kinetic of the oxidized Si nanowires compared to planar references.
Material Aspects and Challenges for SOI FinFET Integration
Authors: Van Dal Mark J. , Vellianitis Georgios , Duffy Ray , Doornbos Gerben , Pawlak Bartek , Duriez Blandine , Lai Lhi-Shue , Hikavyy Andriy Y. , Vandeweyer Tom , Demand Marc , Altamirano Efrain , Rooyackers Rita , Witters Liesbeth , Collaert Nadine , Jurczak Malgorzata , Kaiser Monja , Weemaes Robbert G. , Lander Rob
Published: May 2008

FinFET is a promising device concept towards the 32 nm CMOS technology node and beyond as it combines the benefits of multi-gated architecture, intrinsically having superior scaling behavior, with a highly manufacturable process. The present paper will deal with material aspects of the SOI FinFET integration. We investigate scalability, performance and variability of high aspect ratio trigate FinFETs fabricated with 193nm immersion lithography and conventional dry etch. The effect of gate stack conformality on device performance is studied. The use of ion implantation for extension and the selective epitaxial growth of Si to achieve larger contact area on the source/drain areas are discussed from a materials perspective.
The Electrical Properties of Low Temperature Polycrystalline Si Thin Film Transistor Prepared by Nickel-ALD Process
Authors: Lee Seung Min , Lee Choong Hee , Jeong Tae Hoon , Kim Hyun Jae
Published: May 2008

We have fabricated low temperature polycrystalline Si thin film transistors (LTPS TFTs) for flat panel displays. In this work, metal induced crystallization (MIC) using atomic layer deposition (ALD) was employed to obtain poly-Si as an active layer in LTPS TFTs. The small amounts of nickel atoms by ALD were deposited on amorphous Si to minimize the metal contaminations. The poly-Si thin films have large and uniform grains with average size of 27 um by self-limited reaction process of ALD. The n-type LTPS TFT exhibits a high field effect mobility of about 76 cm^2/Vs, a sub-threshold slope of 0.09 V, a threshold voltage of 4.79 V, and an on-off ratio of 4.9 x 10^6
Multi-Wavelength Raman and HRTEM Study of Ni/Si Interface after NiSi Formation at Low Temperatures using Various Heating Methods
Authors: Sasaki Takashi , Minami Hiroaki , Harima Hiroshi , Isshiki Toshiyuki , Yoshimoto Masahiro , Yoo Woo Sik
Published: May 2008

Low-temperature formation processes of Ni silicide were studied by Raman scattering and cross-sectional transmission electron microscopy (TEM) using Si wafer samples deposited with thin Ni layers. Comparisons were made between two annealing methods; lamp based rapid thermal process (lamp RTP) and a hot wall chamber RTP system. The TEM and Raman observations showed good agreement on the Ni silicidation scheme at the Ni/Si interface. It is shown that Raman scattering spectroscopy is a convenient, non-contact and non-destructive characterization tool to probe and investigate the Ni-silicide formation process in the top nm-order surface of metal/Si contact.
Memory Technologies for Sub-40nm: Materials, Processes, and Structures
Authors: Ha Daewon , Kim Kinam
Published: May 2008

This paper reviews key memory technologies for sub-40 nm node. Physical challenges to shrink the technology are addressed for DRAM, NAND Flash, and PRAM, and potential solutions are discussed in terms of materials, processes and device structures. It is believed that DRAM can scale down to at least 30 nm node with the aid of novel capacitor materials and 3-dimentional cell transistors, and NAND Flash can scale down to at least 30 nm node with the help of high-k dielectrics and novel cell structures. PRAM will create a new market with its new functionality in near future.
Novel Batch Titanium Nitride CVD Process for Advanced Metal Electrodes
Authors: Zagwijn Peter M. , Verweij Wilco , Pierreux Dieter , Adjeroud Noureddine , Bankras Radko , Oosterlaken Ed , Snijders Gert Jan , Van den Hout Michiel , Fischer Pamela , Wilhelm Rudi , Knapp Martin
Published: May 2008

This article describes a novel CVD process for TiN films developed in a 300 mm Vertical Furnace. We have solved Chlorine incorporation at low temperature inside the TiN layer while at the same time the batch process yields a 3 times higher throughput per dual reactor system compared to a single wafer system with 3 chambers.We show process results for load sizes ranging from 5 to as much as 100 wafers that prove filler wafers are only required to a minimum. Applications of the developed TiN process in Metal-Insulator-Metal memory devices such as Deep Trench DRAM, Stack DRAM, as well as Control Electrodes in Charge trapping Flash memory
Chemical Mechanical Planarization Historical Review and Future Direction
Authors: Banerjee Gautam , Rhoades Robert L.
Published: May 2008

The advances in interconnection technology have played a key role in allowing continued improvements in manufacturing of an ever expanding list of semiconductor devices. Chemical Mechanical Planarization (CMP) is a key enabling technology to generate extremely flat and smooth surface at several critical steps in this manufacturing process flow. From the time CMP was first introduced two decades ago to flatten/planarize oxide inter-level dielectric layers, it has come a long way and is now used for tungsten for contacts or vias, for shallow trench isolation and for copper interconnects in dual damascene architecture. Along the way, many integration schemes now require the use of other low-k dielectric films, all of which are planarized using CMP process. In this review paper, various factors influencing CMP will be discussed. The discussion will focus on material challenges to develop consumables such as pad, slurry, post CMP cleaning solution etc. and the challenges for integrating different material stack including the cost of ownership issue. The authors will also provide some direction related to new applications under development and future potential direction.
Effect of Wettability of Silicon and Poly Silicon on Polishing Performance
Authors: Kang Young-Jae , Kang Bong-Kyun , Park Jin-Goo , Hong Yi-Koan , Han Sang-Yeob , Yun Seong-Kyu , Yoon Bo-Un , Hong Chang-Ki
Published: May 2008

Heavily doped poly silicon films have been widely used as gate electrodes and interconnection in MOS circuits. The shrinkage of devices below 100 nm requires more stringent and new CMP processes including poly silicon CMP. Poly silicon can be polished easily with similar pads and slurries as they are used for the planarization of silicon oxide. In this study, single crystal and poly silicon wafers were polished as a function of pH in fumed silica based slurry to understand and compare the polishing mechanism of silicon. The static and dynamic etch rates and polishing temperature were measured as a function of slurry pH (11 ~ 13) with friction forces. The single crystal silicon (bare silicon) showed higher removal rate than poly silicon. However, higher friction force was measured on poly silicon wafer than on bare wafer. The initial wettability of poly silicon with HF and without HF was treatment.
Practical Gate-First Metal Gate/Dual High-k CMOS Integration with Low Threshold Voltages
Authors: Nara Yasuo , Mise Nobuyuki , Kadoshima Masaru , Morooka Tetsu , Kamiyama Satoshi , Matsuki Takeo , Sato Motoyuki , Ono Tetsuo , Aoyama Takayuki , Eimori Takahisa , Ohji Yuzuru
Published: May 2008

We will give practical and manufacturable solutions for metal gate/dual high-k CMOS fabrication processes with low threshold voltages which are suitable for scaled CMOS device manufacturing.
Anomalous Field Transistor BTI Failure Mechanism in an 80V Technology
Authors: Williams Brett N. , Bauwens Filip , Haskett Thomas , Vandeweghe Steven , Corsetti Todd A. , Lappan Raymond E.
Published: May 2008

During the transfer of an 80V 0.35µm based technology (I3T80U) developed at AMI Semiconductor from the mother fab to a second fab, field transistor biased-temperature instability (BTI) failures were encountered. The polarity of the degradation in the field transistor threshold voltage does not indicate a mobile ion problem. Also, the behavior does not follow a typical signature of traps at the silicon-oxide interface. The degradation model will be shown. The proposed mechanism is the presence of a residual film. Simulation results of the proposed mechanism, as well as a manufacturing solution for these failures is explained in this paper.
Tumor necrosis factor inhibits ligand-stimulated EGF receptor activation through a TNF receptor 1-dependent mechanism
Authors: McElroy Steven J. , Frey Mark R. , Yan Fang , Edelblum Karen L. , Goettel Jeremy A. , John Sutha , Polk D. Brent
Published: May 2008

Tumor necrosis factor (TNF) and epidermal growth factor (EGF) are key regulators in the intricate balance maintaining intestinal homeostasis. Previous work from our laboratory shows that TNF attenuates ligand-driven EGF receptor (EGFR) phosphorylation in intestinal epithelial cells. To identify the mechanisms underlying this effect, we examined EGFR phosphorylation in cells lacking individual TNF receptors. TNF attenuated EGF-stimulated EGFR phosphorylation in wild-type and TNFR2−/−, but not TNFR1−/−, mouse colon epithelial (MCE) cells. Reexpression of wild-type TNFR1 in TNFR1−/−MCE cells rescued TNF-induced EGFR inhibition, but expression of TNFR1 deletion mutant constructs lacking the death domain (DD) of TNFR1 did not, implicating this domain in EGFR downregulation. Blockade of p38 MAPK, but not MEK, activation of ERK rescued EGF-stimulated phosphorylation in the presence of TNF, consistent with the ability of TNFR1 to stimulate p38 phosphorylation. TNF promoted p38-dependent EGFR internalization in MCE cells, suggesting that desensitization is achieved by reducing receptor accessible to ligand. Taken together, these data indicate that TNF activates TNFR1 by DD- and p38-dependent mechanisms to promote EGFR internalization, with potential impact on EGF-induced proliferation and migration key processes that promote healing in inflammatory intestinal diseases.
Acute ethanol exposure disrupts VEGF receptor cell signaling in endothelial cells
Authors: Radek Katherine A. , Kovacs Elizabeth J. , Gallo Richard L. , DiPietro Luisa A.
Published: May 2008

Physiological angiogenesis is regulated by various factors, including signaling through vascular endothelial growth factor (VEGF) receptors. We previously reported that a single dose of ethanol (1.4 g/kg), yielding a blood alcohol concentration of 100 mg/dl, significantly impairs angiogenesis in murine wounds, despite adequate levels of VEGF, suggesting direct effects of ethanol on endothelial cell signaling (40). To examine the mechanism by which ethanol influences angiogenesis in wounds, we employed two different in vitro angiogenesis assays to determine whether acute ethanol exposure (100 mg/dl) would have long-lasting effects on VEGF-induced capillary network formation. Ethanol exposure resulted in reduced VEGF-induced cord formation on collagen and reduced capillary network structure on Matrigel in vitro. In addition, ethanol exposure decreased expression of endothelial VEGF receptor-2, as well as VEGF receptor-2 phosphorylation in vitro. Inhibition of ethanol metabolism by 4-methylpyrazole partially abrogated the effect of ethanol on endothelial cell cord formation. However, mice treated with t-butanol, an alcohol not metabolized by alcohol dehydrogenase, exhibited no change in wound vascularity. These results suggest that products of ethanol metabolism are important factors in the development of ethanol-induced changes in endothelial cell responsiveness to VEGF. In vivo, ethanol exposure caused both decreased angiogenesis and increased hypoxia in wounds. Moreover, in vitro experiments demonstrated a direct effect of ethanol on the response to hypoxia in endothelial cells, as ethanol diminished nuclear hypoxia-inducible factor-1α protein levels. Together, the data establish that acute ethanol exposure significantly impairs angiogenesis and suggest that this effect is mediated by changes in endothelial cell responsiveness to both VEGF and hypoxia.
Involvement of RhoA/Rho kinase signaling in protection against monocrotaline-induced pulmonary hypertension in pneumonectomized rats by dehydroepiandrosterone
Authors: Homma Noriyuki , Nagaoka Tetsutaro , Karoor Vijaya , Imamura Masatoshi , Taraseviciene-Stewart Laimute , Walker Lori A. , Fagan Karen A. , McMurtry Ivan F. , Oka Masahiko
Published: May 2008

RhoA/Rho kinase (ROCK) signaling plays a key role in the pathogenesis of experimental pulmonary hypertension (PH). Dehydroepiandrosterone (DHEA), a naturally occurring steroid hormone, effectively inhibits chronic hypoxic PH, but the responsible mechanisms are unclear. This study tested whether DHEA was also effective in treating monocrotaline (MCT)-induced PH in left pneumonectomized rats and whether inhibition of RhoA/ROCK signaling was involved in the protective effect of DHEA. Three weeks after MCT injection, pneumonectomized rats developed PH with severe vascular remodeling, including occlusive neointimal lesions in pulmonary arterioles. In lungs from these animals, we detected cleaved (constitutively active) ROCK I as well as increases in activities of RhoA and ROCK and increases in ROCK II protein expression. Chronic DHEA treatment (1%, by food for 3 wk) markedly inhibited the MCT-induced PH (mean pulmonary artery pressures after treatment with 0% and 1% DHEA were 33 ± 5 and 16 ± 1 mmHg, respectively) and severe pulmonary vascular remodeling in pneumonectomized rats. The MCT-induced changes in RhoA/ROCK-related protein expression were nearly normalized by DHEA. A 3-wk DHEA treatment (1%) started 3 wk after MCT injection completely inhibited the progression of PH (mean pulmonary artery pressures after treatment with 0% and 1% DHEA were 47 ± 3 and 30 ± 3 mmHg, respectively), and this treatment also resulted in 100% survival in contrast to 30% in DHEA-untreated rats. These results suggest that inhibition of RhoA/ROCK signaling, including the cleavage and constitutive activation of ROCK I, is an important component of the impressive protection of DHEA against MCT-induced PH in pneumonectomized rats.