bluuebunny/crossref_metadata_2025 huggingface dataset:
Paleomagnetism of the mid-Cretaceous gem-bearing pegmatite dikes of San Diego County, California, USA
Authors: Symons D. T.A. , Smith T. E. , Kawasaki K. , Walawender M. J.
Published: September 2009

Pegmatite dikes in the Peninsular Ranges batholith of southwestern California have produced spectacular crystals of semiprecious and precious minerals for over a century. Aside from their economic importance, these dikes straddle a major tectonic boundary and were used to test hypotheses related to the timing and development of this composite batholith. Paleomagnetic analysis of 252 specimens from 20 sites (12 and 8 sites in the western and eastern zones of the batholith, respectively, from 11 mines in five dike districts) isolated a stable characteristic remanent magnetization direction at 19 sites. The site mean directions for the western and eastern zones are statistically indistinguishable at 95% confidence, supporting petrologic and geochemical arguments that the dikes of the two zones are coeval and cogenetic. After correction for the Neogene opening of the Gulf of California, the paleopole for all 19 site mean directions is indistinguishable from the 94 Ma reference paleopole for North America and supports hypotheses that (1) the dikes are genetically related to intrusion of the La Posta-type plutons; (2) the batholith was already assembled beside the northwestern coastline of Mexico at 94 Ma; (3) ENE-side-up tilting of fault blocks in the batholith’s western zone ended by ∼94 Ma; and (4) the far-sided and clockwise-rotated discordant paleopoles found commonly in Late Cretaceous and younger sedimentary rocks of the batholith’s region are mostly the result of inclination-flattening of the remanence and (or) remagnetization by fluid flow, creating a secondary remanence, excluding Neogene tectonic rotations.
Prediction of decadal slope changes in Canada by glacial isostatic adjustment modellingThis article is one of a series of papers published in this Special Issue on the theme GEODESY.
Authors: van der Wal Wouter , Braun Alexander , Wu Patrick , Sideris Michael G.
Published: September 2009

In Canada, glacial isostatic adjustment (GIA) is the dominant process to cause vertical motion of the land surface. A GIA model is presented herein that can be used to predict slope changes at given locations in North America where GIA is the primary cause for vertical motion. Uncertainty in Pleistocene ice cover and viscosity in the Earth’s mantle prevent one from picking a single GIA model from the literature to predict uplift rates in the region. Therefore, in this study, a range of mantle viscosity values as well as two different ice-loading histories are used in a forward model of the GIA process. The combination of viscosities and ice model that gives the best fit to recently available continuous and episodic GPS observations is assumed to provide the best prediction of slope changes in North America. This model can be used to quantify GIA-induced vertical deformation in local geomorphologic studies. We show that the predicted differential uplift rate in the Nelson River with respect to Lake Winnipeg reaches 1 mm/year over a 200 km distance using the model that best fits the GPS data whereas the ICE-5Gv1.2/VM2 model gives a slightly larger value. The difference in uplift rate between the northern and southern shore of Lake Michigan amounts up to 3 mm/year (slightly larger than the ICE-5Gv1.2/VM2 model), which could lead to a change in shorelines of tens of metres horizontally over a period of 100 years.
Breeding strategies for Larixoccidentalis: adaptations to the biotic and abiotic environment in relation to improving growth
Authors: Rehfeldt Gerald E.
Published: September 2009

Two disparate studies detected additive genetic variances and covariances for traits reflecting growth, growth rhythm, and disease resistance in Larixoccidentalis Nutt. after 4 and 8 years of field testing. Heritabilities of moderate size combined with large phenotypic variances to presage relatively large responses to direct selection: genetic gains in growth of about 9% seemed readily feasible per unit of selection intensity. Strong genetic correlations (absolute value is greater than 0.6) linked growth traits with several traits that reflect growth rhythm and with defoliation from Meria needle cast (Merialaricis Vuill.). The results suggest that selecting for increased growth also increases resistance to needle cast but disrupts the growth rhythm typical of natural populations. Selecting for the rate of shoot elongation, however, should increase resistance to the needle cast, prevent the deterioration of growth rhythm, and still provide 70% of the gains in growth that would be available from direct univariate selection.
Estimating genetic gains from alternative breeding strategies for clonal forestry
Authors: Mullin T.J. , Park Y.S.
Published: September 2009

Concepts and procedures are presented for the analysis of progeny trials that incorporate clonal replication as a means to resolve variance arising from nonadditive gene effects. Components of variance from the linear model may be expressed in terms of expected covariances among relatives, and these, in turn, may be used to derive approximations of additive, dominance, and epistatic components of genetic variance. In addition to the usual assumptions applied to conventional progeny trials, the use of this expanded genetic model in the analysis of tests with clonal replicates assumes that the greatest portion of the total epistasis is due to interactions involving groups of more than two or three loci. If this assumption is not satisfied, estimates of additive and dominance variance, including those from trials without clonal replicates, will be contaminated by a large fraction of epistasis, and total epistasis will be underestimated by a corresponding amount. Heritability and gain formulae for alternative selection and deployment schemes are developed and illustrate the use of genetic parameters in the comparison of seedling and clonal reforestation strategies.
Patterns of cone distribution in crowns of young Piceamariana. I. Effect of tree age on seed cones
Authors: Caron G.E. , Powell G.R.
Published: September 2009

The distribution of seed cones on shoots, on branches, and within the crown was determined for young Piceamariana (Mill.) B.S.P. (black spruce) trees aged 6–18 years. The seed-cone zone was restricted to distal 1-year-old shoots until ages 7 and 8. It expanded with increasing tree age, and in association with increases in cone numbers, to include older branches and a great variety of smaller shoots on those branches. By age 18, about 25, 55, and 20% of the cone crop was borne by 1-, 2-, and 3-year-old branches, respectively; hence, a concentration of cones, typical of the species, was maintained near the tree apex. Order 1 shoots bore all cones up to tree ages 7 and 8, but proportions on such shoots decreased with increasing tree age. By tree age 18, order 1, 2, and 3 shoots bore 27, 72, and 1% of the crop, respectively. Seed cones occurred progressively from proximal to distal and finally terminal positions on shoots of different categories following three patterns of decreasing shoot vigour (length). Medial and distal cones were most common. Terminal cones were located only on the weakest shoots within the seed-cone zone.
Long-term partitioning of biomass and nitrogen following application of nitrogen fertilizer to Corsican pine
Authors: Proe M.F. , Dutch J. , Miller H.G. , Sutherland J.
Published: September 2009

The effects of N fertilizer on Corsican pine (Pinusnigra var. maritima (Ait.) Melv.) were studied for 22 years. Basal area increment significantly (p < 0.05) increased in response to N fertilizer for 3, 6, 11, and 13 years after applications ceased, in treatments that received 252, 504, 1008, and 1512 kg N•ha−1, respectively. Volume increment changed from a quadratic to a linear response to N level during the study period. Overall, the highest rate of N fertilizer increased the aboveground standing biomass by 42%, four-fifths of which occurred in stems. The response of crown components was variable, but there was evidence of a prolonged increase in foliage biomass due to N fertilizer. Initial retention of N within stands was sustained in the longer term, although N distribution altered. These results supported earlier predictions that the growth response to N fertilizer could be sustained through internal cycling, without increasing demands for N uptake from the soil. Increase of N within stands (over and above fertilizer inputs) was similar to estimated rates of atmospheric input, with indirect evidence of a positive feedback between increased foliage biomass and increased levels of N interception by crowns.
Effects of intra- and inter-specific competition on root and shoot biomass of young Douglas-fir and red alder
Authors: Shainsky L.J. , Newton M. , Radosevich S.R.
Published: September 2009

The effects of intra- and inter-specific competition on root and shoot biomass of 5-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and red alder (Alnusrubra Bong.) were studied in experimentally manipulated stands. The density of each species was varied systematically in a two-way density matrix composed of five monoculture densities and 25 mixtures of all possible pairwise combinations of monoculture densities. Roots and shoots were harvested after the fourth growing season. Response surfaces for root, shoot, and total biomass per tree were generated within the matrix. Regression analysis quantified the effect of each species' density on biomass components. Alder overtopped the Douglas-fir in all mixed stands. Alder density influenced the root and shoot biomass of both species more than Douglas-fir density. Douglas-fir density interacted with red alder density to influence all biomass components. While increasing the density of each species reduced root and shoot biomass per tree, allocation of biomass to roots and shoot was not affected by competition, nor were the allometric equations relating biomass to stem diameter and stem volume index.
Genetically stable, individual-specific differences in hypervariable DNA in Norway spruce, detected by hybridization to a phage M13 probe
Authors: Kvarnheden Anders , Engström Peter
Published: September 2009

DNA fingerprinting techniques have significantly improved the resolution of the analysis of genetic polymorphisms in major eukaryotic taxa. The techniques are based on the use of specific DNA probes, which hybridize to families of related minisatellite loci that are dispersed in the genomes of a range of eukaryotes. These sequences are highly variable as a result of a variation in the numbers of a core repeat sequence at each locus. We wanted to establish whether one such probe, the DNA of the bacteriophage M13, could be used to detect hypervariable loci in the conifer Norway spruce, Piceaabies (L.) Karst., and to examine if the method could detect genetic differences at the level of populations and (or) individual trees. The results show that hypervariable minisatellite sequences that hybridize to the M13 probe are present in Norway spruce. The minisatellite sequences are stably inherited, and the variability within the species is sufficiently high to allow the distinction of different individuals. The differences between populations are of the same order of magnitude as those between trees within populations. The method is potentially useful in population genetics research on conifers, as well as in breeding programs.
Global marketing strategies for forest product industries
Authors: Cohen David H. , Smith Paul M.
Published: September 2009

The rapid globalization of markets in the 1980s combined with increasing disposable incomes in Japan and western Europe has mandated global thinking by both forest products companies and producing regions. Moreover, competitive threats of both domestic and foreign origin must be addressed in strategic planning and operations for firms to compete effectively. The two end points for the continuum of strategic options for the export of wood products are international and global marketing. International marketing targets specific customer segments with distinctive product lines developed for each segment. Global marketing exports a single standardized product line to all customer segments regardless of geographical location. To successfully compete in the increasingly competitive world marketplace, companies and (or) industries in producing countries must understand the requirements, benefits, and disadvantages of these two dissimilar export approaches.
Dormancy release and growth responses of 3+0 bare-root white spruce (Piceaglauca) seedlings subjected to moisture stress before freezer storage
Authors: Rose Robin , Omi Steven K. , Court Barry , Yakimchuk Kathy
Published: September 2009

Greenhouse and field experiments were conducted with white spruce (Piceaglauca (Moench) Voss) seedlings from three seed sources to determine how plant moisture stress before storage and length of freezer storage (8–209 days) affect dormancy release and growth responses of outplanted seedlings. During storage, plant water potential remained lower (more negative) in seedlings subjected to high prestorage plant moisture stress than in those subjected to low prestorage plant moisture stress. However, as duration of storage increased, overall plant moisture stress declined. High prestorage plant moisture stress had little influence on dormancy except to delay terminal bud break in seedlings from the southernmost seed source by 10% and, after an 8-day storage period, to delay bud break of seedlings by 15% compared with the low moisture stress treatment. Seed source and storage period were associated with the greatest variation in growth. The central seed source produced more growth in height and biomass than the other seed sources. Better height growth of seedlings subjected to high moisture stress was attained after all but the 8-day storage period. Seedling responses were complex and not clearly related to their performance in nursery and field outplantings.
EQUILIBRIUM CONFIGURATIONS OF TWO-DIMENSIONAL STRESSED DOMAINS ON THE SURFACE OF ISOTROPIC AND CUBIC CRYSTALS
Authors: PRÉVOT GEOFFROY , CROSET BERNARD
Published: September 2009

In this paper, we derive analytical formulations of the elastic energy of a stressed domain on a crystalline substrate. Taking care of the singularity of the elastic Green function at r = 0, we obtain a universal expression for the isotropic case. By using the analogy between electric dipolar and elastic interactions, we developed similar analytical calculations for the (001) surface of a cubic crystal.

We showed that the anisotropy of the boundary energy and the anisotropy of the substrate govern the shape of the domains, favoring either compact shapes or stripe configurations. The analytical approach adopted in this paper also allows us to discuss the role of elastic anisotropy for the existence of attractive interactions between domains.
PREPARATION OF Co–W–P MAGNETIC THIN FILMS BY ELECTROLESS DEPOSITION
Authors: YU YUNDAN , WEI GUOYING , GE HONGLIANG , GAO YING , ZHAO ZHEN , JIANG LAN
Published: September 2009

An alkaline bath was developed for electroless deposition of Co – W – P thin films on a copper substrate. Effects of pH values, various concentrations of reducing agent, and different powers of ultrasonic on composition, microstructure, and magnetic properties of the films were investigated. It was found out that higher pH could improve cobalt atomic percentage and reduce amounts of phosphorus and tungsten in the film while larger amounts of NaH 2 PO 2 would decrease the cobalt content but increase the tungsten and phosphors content. The ultrasonic was introduced during the electroless deposition. Few effects of ultrasonic on the cobalt content were observed. X-ray diffraction showed that almost all of the deposited films were crystalline and contained hexagonal cobalt with a preferred crystallographic orientation (002). However, a typical amorphous Co – W – P film, which has smooth surface, and no crystallite with definite grains could be obtained when the concentration of NaH 2 PO 2 in the bath was over 1.2 mol/L. The films with rougher and agglomerate nodular structures would be formed in the bath with a higher pH value. Certain power (60 W, 40 kHz) of ultrasonic could smash the grains and led to the formation of a denser and smoother surface. Cracks appeared at the surface of the film when the ultrasonic power was 150 W. Vibration sample magnetometer results showed that the film with maximum magnetization (600 emu/g) and coercivity (1000 Oe) could be achieved when introducing ultrasonic (60 W, 40 kHz) during the deposition.
STRUCTURAL AND MORPHOLOGY OF NANOPOWDERS COPPER-STABILIZED ZIRCONIA
Authors: VAHIDSHAD Y. , ABDIZADEH H. , BAHARVANDI H. R. , BASERI M. AKBARI
Published: September 2009

The structural and morphology of copper-stabilized zirconia samples prepared by sol–gel techniques in different calcination time and temperature are reported. This research work has been proposed and verified that the calcination temperature and time strongly influenced the morphology as well as interaction between the active species and the support. The results obtained from the laboratory test indicate that cubic ZrO 2 and copper oxide are present in the structure if the calcination temperature is under 400°C. Cubic ZrO 2, tetragonal ZrO 2 with small amount of monoclinic ZrO 2, and CuO are formed after calcination at 500°C. Heating under 500°C will result in amorphous compounds being formed, suggesting that 500°C could be a phase transition point. The effect of calcination time is investigated by morphology and structural changes of CuO – ZrO 2 at 600°C during 2, 3.5, 5.5, 7.5, and 10 h. Incorporation of copper in ZrO 2 lattice results in a loss of order in the ZrO 2 structure when it is calcined. A further increase in the temperature of calcination leads to the phase changes in ZrO 2 structure.
A SILVER-COATED SINUSOIDAL SUB-WAVELENGTH STRUCTURE WITH POLARIZATION FEATURE FOR LIGHT EMITTING DIODE
Authors: KO CHENG-HAO , LIN JIAN-SHIAN , CHEN CHANG-TAI , CHEN NIEN-PO
Published: September 2009

A two-dimensional sub-wavelength grating (SWG) is fabricated on light-emitting diodes (LEDs). The SWG is simulated by finite-difference time-domain (FDTD) method. The SWG surface has silver-coated dielectric materials with sinusoidal structures, 175 nm period and 125 m depth of groove. When the incident wave is in the red light region of 600–700nm, the transmission efficiency of TM propagated light will reach 0.82. If this SWG structure is applied in LCD direct backlight module, the lower polarization piece can be replaced and fluorescence efficiency of LED can be improved.
STUDY OF ELECTRICAL CONDUCTIVITY FOR COPPER NANOPARTICLES WITH VAPOR-DEPOSITED SAMs
Authors: LEE GYE-YOUNG , SEONG MI-RYN , KWON JINHYEONG , KIM DONG-KWON , LEE CAROLINE SUNYONG , YI GI-RA , KIM YOUNG-SEOK
Published: September 2009

A self-assembled monolayer (SAM) of octanethiol was vapor-deposited onto the surface of copper ( Cu ) nanoparticles as a means of preventing oxidation. The presence of octanethiol on the surface of Cu nanoparticles was verified using Fourier transform infrared spectroscopy and transmission electron microscopy. The electrical resistance of copper nanoparticles with deposition of a 12-nm thickness of octanethiol on the surface was found to be 100 times greater than that of uncoated powders, indicating uniform SAM coating of the particles.
BIFURCATION OF A MUTUALISTIC SYSTEM WITH VARIABLE COEFFICIENTS AND IMPULSIVE EFFECTS
Authors: PEI YONGZHEN , YANG YONG , LI CHANGGUO
Published: September 2009

In this paper, we introduce and study an impulsive mutualistic model with variable coefficients. By using Floquent theorem, the invasion threshold and the stability of the boundary periodic solution are obtained. Furthermore, by using standard techniques of bifurcation theory, the existent condition of the positive periodic solution is obtained. Finally, numerical simulations are carried out to confirm the main theorems.
A SEMI-STOCHASTIC MODEL FOR HIV POPULATION DYNAMICS
Authors: XIAO YANNI
Published: September 2009

A semi-stochastic model is developed and investigated for human immunodeficiency virus type-1 (HIV-1) population dynamics. The model includes both stochastic parts (changes of CD4+ T cells) and deterministic parts (changes of free virions). Using the best currently available parameter values, we estimate the distributions of the time of occurrence and the magnitude of the early peak in virions. We investigated the effects of varying parameter values on mean solutions in order to assess the stochastic effects of between-patient variability. Numerical simulation shows that the lower the infection rate, the higher the death rate of the infected cells, more rapid clearance of virions and lower rate of virion emission by the infected cells result in lower speed of infection progression and magnitude but a greater variability in response. We also examine the probability that a small viral inoculum fails to establish an infection. Further, we theoretically quantify the expected variability around the infected equilibrium for each population by using diffusion approximation.
PERMANENCE FOR A DELAYED DISCRETE PREDATOR–PREY MODEL WITH PREY DISPERSAL
Authors: WU CHUNQING , CUI JING-AN
Published: September 2009

First, we obtain a new result for the permanence of a well known delayed discrete-time model of single species. Second, based on this new condition, we discuss the permanence of a delayed discrete-time predator–prey model in which the prey disperses in two patches with biased dispersion. The biological implications of the results are briefly discussed.
MACRO- AND MICROSCOPIC SELF-SIMILARITY IN NEURO- AND PSYCHO-DYNAMICS
Authors: IVANCEVIC VLADIMIR G. , IVANCEVIC TIJANA T.
Published: September 2009

The unique Hamiltonian description of neuro- and psycho-dynamics at the macroscopic, classical, inter-neuronal level of brain's neural networks, and microscopic, quantum, intra-neuronal level of brain's microtubules, is presented in the form of an open Liouville equation. This implies the arrow of time in both neuro- and psycho-dynamic processes and proves the existence of the formal neuro-biological space-time self-similarity. This proof implies the existence of a unique neurodynamical law, which acts on different scales of brain's functioning.
MODELING THE CUMULATIVE EFFECT OF ECOLOGICAL FACTORS IN THE HABITAT ON THE SPREAD OF TUBERCULOSIS
Authors: NARESH RAM , PANDEY SURABHI , SHUKLA J. B.
Published: September 2009

In this paper, the cumulative effect of ecological factors in the habitat on the spread of tuberculosis (TB) in human population is modeled and analyzed. The total human population is divided into two classes, susceptibles and infectives. It is assumed that TB is not only spread by direct contacts with infectives in the population but also indirectly by bacteria which are emitted by infectives in the habitat. It is assumed further that bacteria survive due to conducive ecological factors such as flower pots, plants, grasses, human clothes, etc. in the habitat. The cumulative density of ecological factors in the habitat is assumed to be governed by a population density dependent logistic model. The analysis of the model shows that as parameters governing the conducive ecological factors in the habitat increase, the spread of TB increases. The same result is also found with the increase in the parameter governing the survival and accumulation of bacteria in the habitat. It is further found that due to immigration of the population TB becomes more endemic. A numerical study of the model is also carried out to support the analytical results.
Cleaning and Strip Requirement for Metal Gate Based CMOS Integration
Authors: Schram Tom , Farid Sebai , Cleas Martine , Vos Rita , Wada Masayuki , Albert Johan , Rohr Erika , Kubicek Stefan
Published: September 2009

This paper describes the basic process steps involved in the dual metal gate CMOS integration. It focuses on the differences between a dual metal dual dielectric and single metal dual dielectric integration. The focus is on basic process steps involved in both process flows, but device data are also presented to illustrate the processes.
Interplay between Dry Etch and Wet Clean in Patterning La2O3/HfO2 Containing High-k/metal Gate Stacks
Authors: Vos Ingrid , Hellin David , Vrancken Christa , Geypen Jef , Bender Hugo , Vecchio Guglielma , Paraschiv Vasile , Vertommen Johan , Boullart Werner
Published: September 2009

A dry-wet patterning process for La2O3/HfO2-containing high-κ/ metal gate stacks was successfully developed. The process meets the stringent requirements of complete removal of the high-κ layers and metal-containing sidewall residues without inducing silicon recess or undercut. The interaction between the dry etch and wet clean steps was studied. Use of a BCl3-based plasma process facilitated the cleaning process as it damages and modifies the high-κ layers in the active area. When the dry etch process ends with a BCl3-step, La-containing residues were formed inhomogeneously over the wafer within the time scale of hours. These residues could no longer be removed with a wet clean, but were not observed when the dry etch and wet clean processes were integrated. This demonstrates that an integrated etch-clean process enlarges the process window.
Structural Changes of La2O3-doped Hf-based High-k Dielectrics during Aqueous HF Treatment
Authors: Sugita Yoshihiro , Hayashi Manabu , Aoyama Takayuki , Ikeda Kazuto
Published: September 2009

The wet removal of La2O3-doped Hf-based dielectrics is examined for future high-k metal-insulator-semiconductor field-effect-transistor (MIS-FET) processing. XPS observations reveal that aqueous HF treatment removes Hf and Si components from La2O3-doped HfSiON, and LaFx residue remains on the processed wafer surface. It is shown that the sequential treatment of strong acid and HF is effective to reduce unfavorable LaFx adhesion. It is pointed out that HF-treatment fluorinates La in HfO2 film with no-film-dissolution and reactive-ion-etching (RIE) must be selected to remove La2O3-doped HfO2 film. To clarify the effect of removal processing on actual MIS-FET structure, SEM and high resolution STEM observations are carried out. The observations suggest that both the side etching of HfSiON dielectrics during HF-treatment and the substrate recess during HfO2 film removal with RIE are serious issues for the manufacturing of La2O3-doped high-k MIS-FETs.
Surfactants as an Additive to Wet Cleaning Solutions for Plasma Etch Residue Removal: Compatibility to a Porous CVD-SiCOH Ultra Low-k Dielectric Material
Authors: Ahner Nicole , Schulz Stefan E. , Zacher Manuela
Published: September 2009

With decreasing feature sizes and integration of porous low-k dielectrics within the interconnect system of integrated circuits, plasma etch residue removal becomes challenging. Plasma cleaning processes are known to degrade low-k material's properties and wet cleaning becomes a promising alternative. Using water based cleaning solutions turns out to be critical as they may not be able to wet low-energy residue surfaces or to penetrate into small features. Lowering the surface tension of the solutions will be essential and the application of surfactants is a promising approach. We investigated the static and dynamic surface tension of different surfactant solutions in DIW and their compatibility to a porous CVD-SiCOH low-k dielectric. The choice of the rinsing solution applied after surfactant treatment turned out to be essential for removing residual surfactant species. Optical, electrical and structural analysis showed that in contrast to DIW an IPA-rinse is able to remove remaining surfactant species.
Cleaning of Silicon Wafer Surfaces with Reactive Gases
Authors: Vierhaus Joerg , Haase Cornelia , Briesemeister Jens , Burte Edmund
Published: September 2009

The Reactive Gas / Wet Cleaning uses reactive gases together with deionized water instead of wet chemistry to produce the corresponding cleaning chemicals for RCA cleaning processes directly on the surface of silicon wafers in the cleaning tool. The fast and strong reactions of the hydrophilic reactants with water and the diffusion through the thin liquid layer covering the wafer surfaces on top and bottom of the wafer lead to process times of 10 seconds, comparable to the wetting of wafer surfaces with diluted liquid chemicals in standard cleaning processes. To reveal the potential of this cleaning approach intentionally with cations contaminated wafers were subjected to the cleaning with NH3(gas)/O3(gas)/H2O (SC1) and HCl(gas)/O3(gas)/H2O (SC2). Vapor phase decomposition atomic absorption spectroscopy showed that the surface contami¬nation of all used elements on the wafer surfaces could be reduced below the detection limits of about 1E+10to 1E+9 cm-2.
Characterization of the HCl Absorption & Outgassing Mechanisms by FOUPs' Polymers
Authors: Fontaine Hervé , Borde Yannick , Brych Christophe , Danel Adrien
Published: September 2009

The HCl absorption and release by FOUP polymers was characterized through the determination of its solubility and diffusion coefficients in PC and PEEK in clean room conditions (21{degree sign}C and 40% humidity). For the first time, HCl diffusion coefficients were determined (D = 2.9 +/- 1.7 x 10-9 cm².s-1 in PC and D = 1.4 +/- 0.8 x 10-9 cm².s-1 in PEEK). These experimental data were then applied. First, the HCl concentration profiles in a FOUP's PC wall depending on the contamination time were calculated showing that HCl migrates until 0.5 mm thickness in less than 16h, but also that the full crossing is likely unreachable in an industrial context. Second, the efficiency of usual cleanings were evaluated depending on the temperature or time. For FOUP materials saturated in HCl, relatively low HCl rate (<35%) were determined even for high process temperature.
Solar Cell Texturing: A Simplified Recipe
Authors: Vukosav Tom , Herrera Pete , Reinhardt Karen
Published: September 2009

A method for cost reduction and green processing of silicon-based solar cells by replacing cleaning baths with simplified rinsing processes is presented. Reduction of the amount of chemical and water used is demonstrated. The rinsing processes can be used for acidic texturing using HF/HNO3 or alkaline-based texturing using KOH. Rinses with low-concentration of chemicals have been show to be just as effective as concentrated chemicals. Results show that the initial texturing topology and reflectivity is not affected by the subsequent rinses and the doping uniformity is also the same as with the standard chemicals.
Removal of Photoresist and BARC in Cu BEOL using an All-wet Process
Authors: Le Quoc Toan , Klipp Andreas , Lux Marcel , Li Yunlong , Zhao Larry , Vereecke Guy
Published: September 2009

Wet removal of post-etch photoresist (PR) and bottom anti-reflective coating (BARC) was studied using "multi functional" cleaning solutions based on BASFs tool box. For blanket wafer, Fourier-transform infrared (FTIR) data showed that both PR and BARC layers were completely removed at a megasonic power of 10 W for 2 min. For patterned structure, the plasma used for opening of the BARC layer and metal hard mask resulted in the formation of fluorine- and titanium-containing species in the PR crust. Cross-sectional secondary electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS) data indicated that complete removal of post-etch PR can be achieved under experimental conditions typical for single wafer processing. Subsequent patterning of porous low-k layer showed good low-k profile. Wet processes using solvent-based chemistry followed by a bake at 350 {degree sign}C for 1 min at low pressure was found to have no detrimental impact on k-value degradation.
Removal of Post-dry Etch Residue uing Ultra Low Environmental Load Technique
Authors: Hayashida Atsushi , Seki Akiko , Mashiko Takashi , Sanada Toshiyuki , Watanabe Masao
Published: September 2009

A novel ultra low environmental load removal technique of post-dry etch residue is developed, by applying physical force cleaning technique using high-speed steam-water mixture spray. It is found that the removal rate of the proposed technique depends on the dry-etch processes, and that the steam-water mixture spray almost completely removes the post-dry etch residue from some kinds of dry etched wafers without help of any chemicals. It is also found that the proposed technique requires very dilute concentration of inorganic solution, if necessary, to remove post-dry etch residue completely from other kinds of wafers and that removal process using amine compound with isopropyl alcohol is unnecessary. By contrast, air-water mixture spray could not remove the dry-etch residue at all even with some chemicals. Therefore it is understood that steam atmosphere significantly contributes the proposed technique. The characteristic feature and efficiency of the proposed technique are discussed.
Reevaluation of Hydrogen Gas Dissolved Cleaning Solutions in Single Wafer Megasonic Cleaning
Authors: Kang Bong-Kyun , Lee Seung-Ho , Kim In-Jung , Choi Eun-Suck , Kim Bong-Woo , Busnaina Ahmed A. , Hattori Takeshi , Park Jin-Goo
Published: September 2009

In this study, the capability of hydrogenated DI water was reevaluated to apply instead of conventional cleaning process to the semiconductor and FPD (flat panel display) industries. Its characteristics such as half life time, ORP (oxidation reduction potential), DO (dissolved oxygen) concentration, pH, and surface tension were measured as a function of hydrogen gas concentration. Also, hydrogenated DI water cleaning efficiency with addition of NH4OH by combining with MS (megasonic) was compared with cleaning efficiency of SC-1 and DI water. It was found that H2-DIW would be a valuable cleaning solution to avoid higher chemical consumption with better PRE than conventional cleaning solution.
Damage-free Design of Megasonic Waveguide for Single Wafer Process
Authors: Ahn Youngki , Yu Donghyun , Yang Jichul , Kulkarni Atul , Kim Jeongin , Lee Heemyung , Kim Taesung
Published: September 2009

Megasonic cleaning process is routinely used in the semiconductor industry for removal of contaminant particles from wafer surfaces. Effective cleaning is achieved through proper choice of chemical solutions, transducer power density and frequency of the acoustic field. Two principal mechanisms, namely acoustic streaming and acoustic cavitation, are considered to be responsible for the removal of particles from a contaminated surface. In this study, we designed two megasonic waveguides, indirect type and direct type, for a comparative study of cleaning wafers with 70 nm poly-Si pattern. We observed that the indirect type waveguide has more uniform megasonic energy which is transferred to the wafer. Also bubble size was smaller than conventional direct type. The conventional direct type waveguide has better in energy transfer, but can cause structural damages on the wafer.
Influence of Subharmonics on Megasonic Cleaning
Authors: Higuchi Ayumi
Published: September 2009

In this paper, the correlation between 'subharmonic' and cleaning performance, including particle removal efficiency (PRE) and poly line damage in the megasonic cleaning, will be reported. It was found that pattern damage could occur by unexpected cavitation from subharmonics in the cleaning bath. It was possible to reduce the subharmonics and damage by appropriate chemical addition to the bath.
Gold Wet Etch Optimization on 200mm Substrates for MEMS Applications
Authors: Gabette Laurence , Segaud Roselyne , Fadloun Sabrina , Avale Xavier , Besson P.
Published: September 2009

Thanks to relaxed pattern dimensions and friendly wet process cost, MEMS technology uses a great number of wet etch process steps during process flow. Nevertheless, as dimensions are downscaling, for the very used gold wet etch process, a limited under etch of the gold layer under photo resist mask is required. This paper makes a comparison between a gold wet etch process in immersion mode and a gold wet etch process with a single wafer spray tool.
Metrology for Implanted Si Substrate and Dopant Loss Studies
Authors: Radisic Dunja , Shamiryan Denis , Mannaert Geert , Boullart Werner , Rosseel Erik , Bogdanowicz Janusz , Goosens Jozefien , Marrant Koen , Bender Hugo , Sonnemans Roger , Berry Ivan
Published: September 2009

Spectroscopic ellipsometry (SE) model was developed to study substrate loss of shallow implanted silicon substrate following photoresist strip. Model is based on different optical properties of silicon oxide (SiO2) and implanted silicon (i-Si) layers and silicon substrate, and is used to characterize relevant layers, i-Si and SiO2, before and after plasma treatment. The increase in SiO2 and decrease in i-Si layer was observed after plasma exposure. Changes in i-Si layer are the result of two phenomena, oxidation and heating induced re-growth of i-Si layer, while changes in SiO2 thickness represent direct measure of substrate loss due to oxidation. Good agreement between TEM and SE measurements confirms that SE model can distinguish between crystalline (c-Si) substrate and i-Si, regardless if i-Si is only damaged, d-Si (crystalline) or amorphized, a-Si after implantation. We have also found consistency in SIMS dopant profiles and substrate losses extracted from SE measurements for plasma processes studied.
Electrochemical and Analytical Study of the Si Etching Mechanism in HF
Authors: Valckx Nick , Vos Rita , Rip Jens , Doumen Geert , Mertens Paul , Bearda Twan , Heyns Marc M. , De Gendt Stefan
Published: September 2009

In this work a methodology and metrology for the Si substrate loss characterization during cleaning and etching of Si semiconductor substrate has been developed. Using this methodology, the substrate loss in different HF based cleaning solutions can be investigated, both in situ and ex situ. The etching mechanism in different HF mixtures is studied, where the effect of dissolved O2, illumination, free F-ions and additives can be explored. Etch rates are determined ex situ by measuring the Si concentration as function of time with Inductively Coupled Plasma - Mass Spectrometry (ICP-MS). By combining both electrochemical and ICP-MS data, the number of electrons n involved in the electron transfer reaction are determined both in darkness and illumination. Results confirm the existing Si etching mechanism under illumination, with n=2. It is shown that in darkness a low etch rate is observed, and even under deoxygenated HF conditions pointing to some chemical etching mechanism.
Technology Evolution of Silicon Nano-Electronics
Authors: Zaima Shigeaki
Published: September 2009

Silicon ultralarge-scale integrated circuits (ULSIs) are now being faced to various physical and technological limits on the scaling. In order to realize future nano-scaled complementary metal-oxidesemiconductor (CMOS) devices, the development of new materials and new functions to integrate on Si platforms and the control of variability and fluctuations of device characteristics is important.
Optical and Electrical Characterizations of Defects in SiGe-on-insulator
Authors: Nakashima Hiroshi , Wang Dong , Yang Haigui
Published: September 2009

In this work, we characterized defects in SiGe-On-Insulator (SGOI) and Ge-On-Insulator (GOI) by optical and electrical methods. All the SGOI and GOI substrates in this work were fabricated using Ge condensation by dry oxidation method. Defect generation and transformation during the temperature ramp-up process of Ge condensation were clarified by photoluminescence. The location of main defect levels were determined to be above mid-gap by back-gate metal-oxide-semiconductor field-effect-transistor (MOSFET) current deep-level-transient-spectroscopy and dual-metal-oxide-semiconductor thermally stimulated capacitance. The defects in fabricated SGOI and GOI were directly observed by transmission-electron-microscopy. These defects unintentionally induced high hole concentration in SGOI and GOI. The dependence of energy level position on Ge fraction was investigated in detail for the defect-related acceptor levels by Hall effect and back-gate MOSFET drain current vs. gate bias voltage. The suppressions of defects by post-Al-deposition-annealing and forming gas annealing were also discussed.
Atomically Controlled CVD Processing for Doping of Si-Based Group IV Semiconductors
Authors: Murota Junichi , Sakuraba Masao , Tillack Bernd
Published: September 2009

The concept of atomically controlled processing for group IV semiconductors is shown based on atomic-order surface reaction control in Si-based CVD epitaxial growth. Si or Si1-xGex epitaxial growth on N, P or C atomic layer formed on Si(100) or Si1-xGex (100) surface, is achieved at temperatures below 500 oC. In the Si0.5Ge0.5 epitaxial layer, a N doping dose of 6x1014 cm-2 is confined within an about 1.5 nm thick region and the confined N atoms in Si1-xGex preferentially form Si-N bonds. In Si cap layer growth on the P atomic layer formed on Si1-xGex(100) with the P atom amount below about 4x1014 cm-2 using Si2H6 instead of SiH4, the incorporated P atoms are almost confined within the 1 nm region around the heterointerface. Heavy C atomic-layer doping suppresses strain relaxation as well as intermixing between Si and Ge at the nm-order thick Si1-xGex/Si heterointerface.
Integration Challenges in Standard CMOS with Multiple Gate Oxide Thicknesses
Authors: Naughton John J. , Towner Janet
Published: September 2009

Following the prototype release of an automotive, dual gate oxide, and high voltage process, yield problems were observed on an intermittent basis. An investigation was made into a temperature sense circuit and a differential input of a unity gain operational amplifier used for I/O circuitry. The problem was isolated to a bimodal distribution of threshold voltage values for standard gate oxide thickness transistor test structures. When all such structures on the wafer were electrically probed, their distribution of failures was found to be mostly random. Curiously, this mismatch was consistent with a small increase in gate oxide thickness but not observed in the single gate technology. Microscope inspection following etchback of oxide from standard gate regions provided evidence of water spotting and damage to active areas. Process changes were implemented to minimize this damage. Subsequent lots yielded well and matching problems were eliminated.
The Effect of Material and Process Interactions on BEOL Integration
Authors: Spooner Terry A. , Arnold John C. , Canaperi Donald , Chen James , Chen Shyng-Tsong , Gates Stephen M. , Isobayashi Atsunobu , Leung Pak , Papa Rao Satyavolu S. , Sankarapandian Muthumanickam , Shobha Hosadurga , Van der Straten O.
Published: September 2009

In agreement with the ITRS roadmap, there have been several publications supporting the reduction in critical dimensions and the introduction of new materials to semiconductor processing (1,2,3). This paper highlights the observations and solutions to some of the critical material and process interactions encountered during the integration of the back end of line interconnect.
Comprehensive Study of the Fabrication of SGOI Substrates by the Ge Condensation Technique: Oxidation Kinetics and Relaxation Mechanism
Authors: Souriau Laurent , Wang Gang , Loo Roger , Caymax Matty , Meuris Marc , Heyns Marc M. , Vandervorst Wilfried
Published: September 2009

We report on the fabrication and characterization of thin SiGe on insulator (SGOI) with high Ge content by the condensation technique. While one of the objectives of this report is to describe the process and give a complete characterization of the obtained substrates, the main intention is to focus on the fundamental understanding of key phenomena involved in the Ge condensation method. In particular, we will describe the oxidation kinetic using the conventional Deal and Grove model and show that for such process, since the thickness of oxide grown is large and since the oxide formed is pure SiO2, the oxidation kinetic can be modeled with the same parameters as those used for pure Si. Next, we will discuss the relaxation of the formed SGOI layer using linear elastic theory framework and evidence that even though the condensation method makes use of long high temperature treatments, the obtained layer are not in their equilibrium state and their relaxation is frustrated. However, we will show that it is still possible to predict their relaxation rate and that it is observed to increase with increasing Ge content. This poses some limitations in terms of defectivity of such substrates as they are inevitably partially relaxed. Expanding the analysis of relaxation and defect nucleation, we will finally discuss an approach to decrease the defect density and consider its drawbacks.
Computation from Devices to System Level Thermodynamics
Authors: Shankar Sadasivan , Zhirnov Victor , Cavin Ralph
Published: September 2009

Energy or Power minimization is a universal macro-constraint for on-chip architectures. The computer industry is actively dealing with trade-offs between performance and energy efficiency. The intent of this work is to develop theoretical concepts for bridging architectures with energy efficient computing. We evaluate the efficiency of an ideal computing architecture at the limits of scaling. We achieve this by using concepts from thermodynamics and quantum mechanics and using a simplified layout to represent the computing system. Although efforts have been undertaken on scalability of single devices, we believe that this is the first attempt of energy estimation both in large computing systems and in a single switch using the same physical principles. Similar to design of heat engines, we hope that these concepts will help in evaluating different chip architectures and compare them to an ideal computing engine that is developed in this work.
Charge Storage Characteristics of Hybrid Nanodots Floating Gate
Authors: Miyazaki Seiichi , Makihara Katsunori , Ikeda Mitsuhisa
Published: September 2009

The hybrid nanodots structure in which NiSi nanodots were stacked on Si-QDs with a very thin interlayer oxide was fabricated successfully and implemented to a MOS capacitor as a floating gate. The multiple charge storage in a deep potential well of NiSi nanodots and stepwise progression of charging and discharging in the hybrid nanodots FG have been demonstrated. The discrete energy states of the Si-QDs may play a role on the multistep electron injection to and emission from the NiSi nanodots.
Annealing Reaction for Ni Silicidation of Si Nanowire
Authors: Arai Hideaki , Kamimura Hideyuki , Sato Soshi , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Sugii Nobuyuki , Natori Kenji , Hattori Takeo , Iwai Hiroshi
Published: September 2009

Silicidation of Si Nanowires (Si NWs) has been investigated in terms of the encroachment length of Ni silicide from the edge of exposed Si NWs. Ni silicides were formed by the reaction of Si NW and Ni layer by low temperature RTA processes.We also investigate Ni silicidation of Si NW using 2step annealing process. The encroachment length of Ni silicide is dramatically suppressed for the 2 step annealing process.
Defect Analysis in Solar Cell Silicon by Photoluminescence Spectroscopy and Topography
Authors: Tajima Michio , Sugimoto Hiroki
Published: September 2009

We review the characterization of electrically active intra-grain defects in multicrystalline silicon for solar cells. Origin of the defects was identified to be dislocation clusters forming subgrain boundaries by photoluminescence (PL) spectroscopy and topography combined with electron backscatter diffraction pattern measurement and etching/optical microscopy. PL imaging during HF etching has the advantage of very rapid detection of defects, which allows us to obtain numerous successive PL images of wafers positioned from the bottom to top of the mc-Si ingots, as well as to synthesize the three-dimensional distribution of the defects from the images. We showed the multiplication of dislocation clusters and their interaction with grain boundaries.