bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Sintering of Waste Forms in an Underground Disposal Environment
Authors: Ojovan Michael I. , Gibb Fergus G. F. , Lee William E. 
Published: April 2011

ABSTRACTA waste management scheme is described, which aims to utilise the ambient pressure of a disposal environment, its radiation shielding and extended time of storage to ensure reliable immobilisation of radioactive waste in a glass composite or polycrystalline matrix form. The conditions required for natural sintering of the waste form in the repository are assessed for viscous flow and grain boundary diffusion mechanisms. In situ sintering of materials in the repository creates geochemically stable materials in equilibrium with the disposal environment ensuring a higher degree of safety compared to existing approaches.
Leaching Behavior of Unirradiated High Temperature Reactor (HTR) UO2-ThO2 Mixed Oxides Fuel Particles
Authors: Landesman Catherine , Delaunay Sandra , Grambow Bernd 
Published: April 2011

ABSTRACTThe dissolution rate of small UO2, ThO2 and mixed UO2–ThO2 particles, representative of unirradiated HTR fuel, are investigated in the pH range 1.7 to 5.5 under oxic conditions. For UO2 particles, the dissolution is kinetically control while for ThO2 particles, a solubility control mechanism seems to prevail for pH > 2. In the mixed oxides UO2–ThO2 particles, a selective release of uranium is observed, which could be either the result of a dissolution/precipitation mechanism in which thorium reprecipitate as oxide or hydroxide phase, or a result of a higher accessible surface area. Under oxic conditions, uranium may be considered as a tracer for the other soluble elements. So, assuming constant conditions with time, one can estimate from these preliminary results that unirradiated thorium based fuel kernels seem to present intrinsic confinement properties for 15000 years relative to soluble elements.
Evaluation of an alternative technique for the fabrication of direct detector X-ray imagers: spray pyrolysis of lead iodide and mercury iodide
Authors: Condeles J. F. , Ugucioni J. C. , Mulato M. 
Published: April 2011

ABSTRACTThis work discusses the new use of an old deposition technique: spray pyrolysis. The objective is the deposition of thin films of lead iodide and mercury iodide and their future use as photoconductors in medical X-ray digital imagers. We discuss the main advantages and limitations of the deposition process comparing both materials. The final thin films are structurally investigated using X-ray diffraction and microscopy. The deposition technique seems to be very promising for the future development of large area radiation detectors.
A Phase Diagram for Morphology and Properties of Low Temperature Deposited Polycrystalline Silicon Grown by Hot-wire Chemical Vapor Deposition
Authors: Richardson Christine E. , Mason Maribeth S. , Atwater Harry A. 
Published: April 2011

ABSTRACTThe fabrication of low temperature polycrystalline silicon with lifetimes close to single crystalline silicon, but with internal surface passivation similar to that observed in deposited microcrystalline silicon, is a promising direction for thin film polycrystalline silicon photovoltaics. To achieve this, large grains with passivated grain boundaries and intragranular defects are required. We investigate the low-temperature (250-550°C) epitaxial growth of thin silicon films by hot-wire chemical vapor deposition (HWCVD) on Si(100) substrates and large-grained polycrystalline silicon template layers formed by selective nucleation and solid phase epitaxy (SNSPE). Using reflection high energy electron diffraction (RHEED) and transmission electron microscopy (TEM), we have observed epitaxial, twinned epitaxial, mixed epitaxial/polycrystalline and polycrystalline phases in the 50 nm–15 μm thickness regime. HWCVD growth on Si(100) was performed using a mixture of diluted silane (4% in He) and hydrogen at a H2/SiH4 ratio of 50:1 at substrate temperatures from 300–475°C. We will discuss the relationship between the microstructure and photoconductive decay lifetimes of these undoped layers on Si(100) and SNSPE templates as well as their suitability for use in thin-film photovoltaic applications.
Effects of Facet Growth and Nucleation on Microcrystalline Silicon by Numerical Model
Authors: Kobayashi Yasuyuki , Satake Koji 
Published: April 2011

ABSTRACTWe have presented a model of microcrystalline silicon (μc-Si) growth based on the Van der Drift model. The model needs growth velocities of the facets (100) and (111), an amorphous silicon growth velocity and a grain nucleation rate. The growth velocity ratio of the facets, (100) and (111), determines the preferred orientation and the morphology of the μc-Si film, especially oriented to (110). As the grain nucleation rate increases, the ratio of the living grain number to the total grain number decreases and the crystallinity increases, so the grain nucleation rate governs the trade-off relation of the μc-Si cells between decreasing the open circuit voltage and increasing the short circuit current as the crystallinity increases.
Evaluation of Ar-Diluted Silane PECVD for Thin Film Si:H Based Solar Cells
Authors: Selvan J. A. Anna , Li Yuan-Min , Li Liwei , Delahoy Alan E. 
Published: April 2011

ABSTRACTDilution by Ar of silane plasma has been reported to increase the stability of a-Si:H films. A critical question is whether Ar diluted i-layers offer higher stabilized solar cell efficiencies than the conventional hydrogen dilution method. We have fabricated a-Si:H p-i-n solar cells with RF-PECVD i-layers by Ar dilution of silane. Ar dilution ratio (ADR, Ar/SiH4), RF power,pressure, and i-layer thickness were varied. At low ADR < 20, such solar cells show comparable initial efficiencies and stability as those devices having H2-diluted i-layers of similar thickness. For cells made with ADR > 20, the initial efficiency decreases dramatically with further increase in Ar dilution, and light soaking causes only mild changes in efficiencies. The stabilized efficiencies of cells made with high ADR are inferior to the cells produced with low ADR or cells prepared by H2 dilution. Further, Voc of solar cells made with high ADR (> 50) decreases substantially in ambient, indicating a porous microstructure susceptible to oxidation. While thermal annealing improves the Voc, a full recovery of Voc is made by accelerated light soaking.The combination of high power and high ADR can lead to nanocrystalline silicon (nc-Si:H) growth, although nucleation is much more difficult to attain by the Ar dilution method compared to hydrogen dilution. We have succeeded in fabricating p-i-n solar cells with nc-Si:H i-layers prepared by the Ar dilution approach. The double dilution by Ar and hydrogen of silane (Ar+H2+SiH4) can result in nc-Si:H i-layers with enhanced long wavelength spectral response compared to devices incorporating nc-Si:H i-layers grown by H2 dilution only. The nc-Si:H solar cells with Ar+H2 diluted i-layers exhibit no light-induced degradation.Using energetic Ar-rich plasma, in a process much simpler than the traditional nc-Si:H technique, doped a-Si:H thin layers can be prepared to form excellent tunnel junctions for multi-junction solar cells. We demonstrate such a novel, non-contaminating tunnel junction in tandem a-Si/a-Si and a-Si/nc-Si solar cells entirely fabricated in a single-chamber RF-PECVD system.
Atomistic Modeling of Ion Beam Induced Defects in Si: From Point Defects to Continuous Amorphous Layers.
Authors: Pelaz Lourdes , Marqués Luis A. , López Pedro , Santos Iván , Aboy María 
Published: April 2011

ABSTRACTWe present an atomistic model that describes the evolution of ion induced damage ranging from individual defects to continuous amorphous layers. The elementary units used to reproduce the defective zones are Si interstitials, vacancies and the IV pair, which is a local distortion of the Si lattice without any excess or deficit of atoms. More complex defect structures can be formed as these elementary units cluster. The amorphous pockets are treated as agglomerates of IV pairs, whose recrystallization rate depends on the local density of these defects. The local excess or deficit of atoms in the amorphous regions experiences some rearrangement as recrystallization takes place. In sub-amorphizing implants amorphous pockets are disconnected and when they recombine, they leave behind the local excess of Si interstitials and vacancies. When a continuous amorphous layer initially extends to the surface, the excess or deficit atoms within the amorphous layer are swept towards the surface where they are annihilated and only the defects beyond the amorphous-crystalline interface remain.
Measurements of Ultra-Shallow Junction (USJ) Sheet Resistance with a Non-Penetrating Four Point Probe
Authors: Hillard Robert J. , Mazur Robert G. , Alexander William J. , Ye C. Win , Benjamin Mark C. , Borland John O. 
Published: April 2011

ABSTRACTAn accurate method to measure the four point probe (4PP) sheet resistance (Rs) of USJ Source-Drain structures is described. The new method utilizes Elastic Material probes (EM- probe) to form non-penetrating contacts to the silicon surface. The probe design is kinematic and the force is controlled to ensure elastic deformation of the probe material. The probe material is selected so that large direct tunneling currents can flow through the native oxide thereby forming a low impedance contact. Sheet resistance measurements on USJ implanted P+/N structures with SIMS junction depths as shallow as 15 nm have been measured. The sheet resistance values obtained with the new EM-probe 4PP method were found to be consistent with expectations. In this paper, the method will be demonstrated on a variety of implanted USJ structures.
Erbium-Silicided Source/Drain Junction Formation by Rapid Thermal Annealing Technique for Decananometer-Scale Schottky Barrier Metal-Oxide-Semiconductor Field- Effect Transistors
Authors: Jang Moongyu , Kim Yarkyeon , Shin Jaeheon , Park Kyoungwan , Lee Seongjae 
Published: April 2011

ABSTRACTThe stable growth conditions of erbium-silicide on silicon-on-insulator (SOI) are investigated considering annealing temperature, SOI and sputtered erbium thickness. From the sheet resistance measurement, X-ray diffraction and Auger electron spectroscopy analysis, the optimum annealing temperature is determined as 500°C. Also, for the stable growth of erbium- silicide on SOI, the sputtered erbium thickness should be less than 1.5 times of SOI thickness. As the SOI thickness decreases below this critical thickness, erbium-rich region is formed at the erbium-silicide and buried-oxide interface. By applying the optimized erbium-silicide growth conditions, 50-nm-gate-length n-type SB-MOSFET is manufactured, which shows the possible usage of erbium-silicide as the source and drain material in the n-type Schottky barrier MOSFETs for decananometer regime applications.
Simultaneous Phosphorus and Si Self-Diffusion in Extrinsic, Isotopically Controlled Silicon Heterostructures
Authors: Silvestri Hughes H. , Bracht Hartmut A. , Sharp Ian D. , Hansen John , Nylandsted-Larsen Arne , Haller Eugene E. 
Published: April 2011

ABSTRACTWe present experimental results of impurity and self-diffusion in an isotopically controlled silicon heterostructure extrinsically doped with phosphorus. As a consequence of extrinsic doping, the concentration of singly negatively charged native defects is enhanced and the role of these native defect charge states in the simultaneous phosphorus and Si self-diffusion can be determined. Multilayers of isotopically controlled 28Si and natural silicon enable simultaneous analysis of 30Si self-diffusion into the 28Si enriched layers and phosphorus diffusion throughout the multilayer structure. An amorphous 260 nm thick Si cap layer was deposited on top of the Si isotope heterostructure. The phosphorus ions were implanted to a depth such that all the radiation damage resided inside this amorphous cap layer, preventing the generation of excess native defects and enabling the determination of the Si self-diffusion coefficient and the phosphorus diffusivity under equilibrium conditions. These samples were annealed at temperatures between 950 and 1100°C to study the diffusion. Detailed analysis of the diffusion process was performed on the basis of a P diffusion model which involves neutral and positively charged mobile P species and neutral and singly negatively charged self-interstitial.
Current Understanding and Modeling of B Diffusion and Activation Anomalies in Preamorphized Ultra-Shallow Junctions
Authors: Colombeau B. , Smith A.J. , Cowern N.E.B. , Pawlak B.J. , Cristiano F. , Duffy R. , Claverie A. , Ortiz C.J. , Pichler P. , Lampin E. , Zechner C. 
Published: April 2011

ABSTRACTThe formation of ultra-shallow junctions (USJs) for future integrated circuit technologies requires preamorphization and high dose boron doping to achieve high activation levels and abrupt profiles. To achieve the challenging targets set out in the semiconductor roadmap, it is crucial to reach a much better understanding of the basic physical processes taking place during USJ processing. In this paper we review current understanding of dopant-defect interactions during thermal processing of device structures – interactions which are at the heart of the dopant diffusion and activation anomalies seen in USJs. First, we recall the formation and thermal evolution of End of Range (EOR) defects upon annealing of preamorphized implants (PAI). It is shown that various types of extended defect can be formed: clusters, {113} defects and dislocation loops. During annealing, these defects exchange Si interstitial atoms and evolve following an Ostwald ripening mechanism. We review progress in developing models based on these concepts, which can accurately predict EOR defect evolution and interstitial transport between the defect layer and the surface. Based on this physically based defect modelling approach, combined with fully coupled multi-stream modelling of dopant diffusion, one can perform highly predictive simulations of boron diffusion and de/re-activation in Ge-PAI boron USJs. Agreement between simulations and experimental data is found over a wide range of experimental conditions, clearly indicating that the driving mechanism that degrades boron junction depth and activation is the dissolution of the interstitial defect band. Finally, we briefly outline some promising methods, such as co-implants and/or vacancy engineering, for further down-scaling of source-drain resistance and junction depth.
Activation, Diffusion and Defect Analysis of a Spike Anneal Thermal Cycle
Authors: Paul Silke , Lerch Wilfried , Hebras Xavier , Cherkashin Nikolay , Cristiano Fuccio 
Published: April 2011

ABSTRACTIn this paper, the evolution of sheet resistance, junction depth and defects during the whole thermal cycle of a typical spike anneal with a peak temperature of 1050°C was investigated in detail. To this purpose, spike anneals were performed at peak temperatures ranging from 800°C up to 1050°C in temperature steps of 50°C. These experiments were done both on B+ (500 eV, 1.1015 cm−2) and BF2+ (2.2 keV, 1.1015 cm−2) implanted wafers. It is found that for temperatures below 850°C BF2+ implanted wafers exhibit a much better electrical activation, resulting in a lower sheet resistance, than B+ implanted ones, due to the amorphisation process occurring during the BF2+ implant and the subsequent solid phase epitaxial growth. In this low temperature regime, boron clustering takes place very rapidly in B+ implanted wafers, as confirmed by both SIMS and TEM analysis. In particular, “large” clusters, i.e. with diameter above the TEM detection limit (∼2 nm), undergo a classical Ostwald ripening process (increase in size, decrease in density). SRP measurements indicate that boron activation in this low temperature regime is not related to cluster dissolution. On the other hand, after the initial solid phase epitaxial regrowth, BF2+ implanted wafers exhibit a slight increase in sheet resistance, due to boron clustering induced by the dissolution of end of range defects. Finally, it is found that at higher spike anneal temperatures (above 850°C), both B+ and BF2+ implanted wafers exhibit a similar behaviour, with a progressive decrease in sheet resistance due to boron cluster dissolution and dopant diffusion.
The Effect of Photoresist Outgassing on Boron Clustering and Diffusion in Low Energy BF2+ Ion Implantation
Authors: Kopalidis Peter , Kondratenko Serguei 
Published: April 2011

ABSTRACTDuring high current ion implantation into photoresist-covered substrates, evolution of gaseous by-products of photoresist breakdown occurs that can affect the dose control of the process as well as diffusion and activation of the implanted dopants in silicon. The dosimetry effects are well understood and accounted for in modern ion implanter design. In this work, we report on the effect of photoresist outgassing on the distribution of boron concentration in silicon during the subsequent annealing process, boron electrical activation and sheet resistance measurements. Experiments were performed on mono- crystalline and pre-amorphized silicon and oxide covered wafers that help elucidate the mechanism of boron accumulation and diffusion. Higher carbon concentration on the wafer surface due to photoresist outgassing results in boron clustering and reduction of transient enhanced diffusion, leading to higher sheet resistance at low anneal temperature. Implantation through a thin oxide layer can be used to reduce carbon surface contamination and minimize the effects on the boron profiles and sheet resistance.
Repair of Porous Methylsilsesquioxane Films using Supercritical Carbon Dioxide
Authors: Xie Bo , Muscat Anthony J. 
Published: April 2011

AbstractPorous methylsilsesquioxane (p-MSQ) films (JSR LKD 5109) were treated with alkyldimethylmonochlorosilanes having chain lengths of one, four, and eight carbon atoms dissolved in supercritical carbon dioxide at 150-300 atm and 50-60°C to repair oxygen ashing damage. Fourier transform infrared (FTIR) spectroscopy showed that trimethylchlorosilane (TMCS), butyldimethylchlorosilane (BDMCS), and octyldimethylchlorosilane (ODMCS) reacted with silanol groups on the surfaces of the pores producing covalent Si-O-Si bonds. Selfcondensation between alkylsilanols produced a residue on the surface, which was partially removed using a pure scCO2 rinse. The hydrophobicity of the blanket p-MSQ surface was recovered after silylation treatment as shown by contact angles >85°. The initial dielectric constant of 2.4 ± 0.1 increased to 3.5 ± 0.1 after oxygen plasma ashing and was reduced to 2.6 ± 0.1 by TMCS, 2.8 ± 0.1 by BDMCS, and 3.2 by ODMCS.
Ruthenium Sputter Deposition on Organosilicate Glass and on Paralyne: an XPS Study of Interfacial Chemistry, Nucleation and Growth
Authors: Zhao X. , Magtoto N.P. , Kelber J. A. 
Published: April 2011

AbstractThe interactions of sputter-deposited ruthenium with organosilicate glass (OSG) at 300 K have been studied by x-ray photoelectron spectroscopy (XPS) for Ru coverages from ∼ 0.1 monolayer to several monolayers, using in-situ sample transfer between the deposition and analysis chambers. The results indicate Stranski-Krastanov (SK) type growth, with the completion of the first layer of Ru at an average thickness corresponding to 1 monolayer average coverage. Ru(0) is the only electronic state present. XPS core level spectra indicate weak chemical interactions between Ru and the substrate. A less pronounced tendency towards SK growth was observed for Ru deposition on parylene. Deposition of Ru on OSG followed by electroless deposition of Cu resulted in the formation of a shiny copper film that failed the Scotch Tape test. Results indicate failure mainly at the Ru/OSG interface.
Nucleation and Growth Dependence of ALD WNC on Substrate Surface Condition
Authors: Abell Thomas , Schuhmacher Jörg , Travaly Youssef , Maex Karen 
Published: April 2011

AbstractALD WNC nucleation and growth was observed strongly affected by different substrate materials and surface chemistries. Nucleation was inhibited on most pristine low k surfaces, which is attributed to low concentrations of chemisorption sites (Si-OH). Plasma treatments were used to alter the surface chemistry to improve nucleation. Surface closure and surface roughness of the WNC layer were found to strongly correlate with starting surface condition. Resistivities of the resulting films were also found dependent on starting surface treatment. But the relationship between W content of the films, surface treatment and resistivity was not fully comprehended.
Preparation and Characterization of Copper Film on Plastic Substrate by ECR-MOCVD Coupled with a DC Bias
Authors: Jeon Bup Ju , Lee Joong Kee 
Published: April 2011

AbstractCopper films were prepared at room temperature under a Cu(hfac)2-Ar-H2 atmosphere in order toobtain metallized plastics by using ECR-MOCVD (Electron Cyclotron Resonance Metal OrganicChemical Vapor Deposition) coupled with a DC bias system. Structural analysis of the films byECR showed that fine copper grains were embedded in an amorphous plastic matrix with goodadherence. Considering the AES result of the film prepared by ECR-CVD, we construe that thecopper film is chemically bonded with a plastic substrate. The delamination force determined bythe nano-scratch tester® showed in the range from 10 to 20mN.
Cross-Section Nano-Indentation for Rapid Adhesion Evaluation
Authors: Brongersma S. H. , Degryse Dominiek , Souiller Jerome , Vandevelde Bart , Maex K. 
Published: April 2011

AbstractCross-section nano-indentation is a technique that consists of cleaving a wafer, indenting behind the stack on the side surface causing delamination, and measuring the delaminated area in an optical microscope. It is shown to be a reliable rapid technique for adhesion evaluation and process optimization of the SiO2/barrier/copper stack.
Fatal Void Size Comparisons in Via-Below and Via-Above Cu Dual-Damascene Interconnects
Authors: Choi Z. -S. , Gan C. L. , Wei F. , Thompson C. V. , Lee J. H. , Pey K. L. , Choi W. K. 
Published: April 2011

AbstractThe median-times-to-failure (t50's) for straight dual-damascene via-terminated copper interconnect structures, tested under the same conditions, depend on whether the vias connect down to underlaying leads (metal 2, M2, or via-below structures) or connect up to overlaying leads (metal 1, M1, or via-above structures). Experimental results for a variety of line lengths, widths, and numbers of vias show higher t50's for M2 structures than for analogous M1 structures. It has been shown that despite this asymmetry in lifetimes, the electromigration drift velocity is the same for these two types of structures, suggesting that fatal void volumes are different in these two cases. A numerical simulation tool based on the Korhonen model has been developed and used to simulate the conditions for void growth and correlate fatal void sizes with lifetimes. These simulations suggest that the average fatal void size for M2 structures is more than twice the size of that of M1 structures. This result supports an earlier suggestion that preferential nucleation at the Cu/Si3N4 interface in both M1 and M2 structures leads to different fatal void sizes, because larger voids are required to span the line thickness in M2 structures while smaller voids below the base of vias can cause failures in M1 structures. However, it is also found that the fatal void sizes corresponding to the shortest-times-to-failure (STTF's) are similar for M1 and M2, suggesting that the voids that lead to the shortest lifetimes occur at or in the vias in both cases, where a void need only span the via to cause failure. Correlation of lifetimes and critical void volumes provides a useful tool for distinguishing failure mechanisms.