4,881 research outputs found
CONDUCTING DIFFUSION BARRIER : FORMATION AND CHARACTERISATION OF WN OBTAINED BY THERMAL ANNEALING UNDER NH3 OF W FILMS DEPOSITED ON Si
No full text- A partir de la RBS et de la diffraction X, nous montrons qu'au dessus d'une épaisseur critique de W (inférieure à 2000 Å), WSi2 couvert par γ WN peut être formé par recuit sous NH3 au dessus de 800° C de films de W déposés sur C-Si. La résistivité du γ WN est ~ 100µΩ-cm.- From Rutherford Backscattenng and X-ray diffraction we show that above a critical W thickness (< 2000 Å), WSi2 covered by γ WN can be formed by annealing under NH3 of W films deposited on C-Si. Its resistivity is ~ 100µΩ-cm
Morphological and Compositional Studies on Al/Ti/TiN/Si, Al/TiN/Si, Al/W/Si, Al/WN/Si Systems to Test the Diffusion Barrier Properties of Nanoscale-Thick Layers between Al and Si
No full textIn this work, an investigation of the properties of nanoscale-thick Ti/TiN, TiN, W, WN layers as diffusion barriers between Si and Al is carried out in view of Si-based electronic applications. Heat treatments were performed on the samples to activate interdiffusion between Si and Al. Changing annealing time and temperature, each sample was morphologically characterized by scanning electron microscopy and atomic force microscopy and compositionally characterized by Rutherford backscattering analysis. The aim is to evaluate the efficiency of the layers as diffusion barriers between Si and Al and, at the same time, to evaluate the surface morphological changes upon annealing processes
STRUCTURAL-PROPERTIES OF TITANIUM-DIOXIDE FILMS GROWN ON P-SI BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION AT LOW-TEMPERATURE
No full textMetal-organic chemical vapor deposition of TiO2 via pyrolysis using Ti (OC3H7)4 and N2O was investigated with the goal of producing TiO2 epitaxial films on p-Si(100) substrates. X-ray diffraction analysis showed that the grown TiO2 layer was a polycrystalline film. Auger depth profiles demonstrated that the TiO2/Si interface was relatively abrupt, and transmission electron microscopy verified the formation of an interfacial layer in the TiO2/Si interface and the formation of a polycrystalline TiO2 thin film. These results indicate that the failure to form the TiO2 epitaxial films originated from the formation of an interfacial amorphous layer at the initial growth stage
Selective Oxidation of Si in the Presence of W and Wn
No full textABSTRACTIn various device fabrication processes, such as in metal gate and low resistance word line fabrication, one needs to be able to oxidize Si without oxidizing metals present. We developed such a process using a combination of H2 and O2 in the H2 rich regime. The process developed is safe and is production worthy with excellent uniformity.When carrying out the selective oxidation using H2/O2, a high Si oxidation rate is preferred which requires a high oxygen concentration. At the same time, the increase in metal sheet resistance, if any, must be small. We found that with an oxygen concentration as high as 20%, the increase in W sheet resistance is small. We present data on the oxidation rate of Si under different conditions as well as the selectivity of the process with respect to W and WN.</jats:p
Ru/WN<sub>x</sub> Bilayers as Diffusion Barriers for Cu Interconnects
No full text
Bilayers of Ru (7 nm)/WN
x
(8 nm) prepared by sputtering were investigated as diffusion barriers between Cu and Si, and their performances were compared as a function of N2 flow rate during the deposition of WN
x
. The Ru/WN
x
bilayer diffusion barriers were stable upon annealing at up to at least 650 °C for 30 min while a Ru single layer (15 nm in thickness) failed after annealing at 450 °C owing to the formation of Cu silicide. Grazing-angle X-ray diffractometry results showed that the crystallinity of the WN
x
film was degraded but that its nanocrystalline state preserved upon annealing at higher temperatures with increasing N2 flow rate during the deposition. These resulted in the better performance against Cu attack of bilayer diffusion barriers with the WN
x
film prepared with a higher N2 flow rate.
</jats:p
Throughput Scaling of Covert Communication Over Wireless Adhoc Networks
No full textWe consider the problem of covert communication over wireless adhoc networks in which (roughly) n legitimate nodes (LNs) and nκ for κ>0 non-communicating warden nodes (WNs) are randomly distributed in a square of unit area. Each legitimate source wants to communicate with its intended destination node while ensuring that every WN is unable to detect the presence of the communication. In this scenario, we study the throughput scaling law. Due to the covert communication constraint, the transmit powers are necessarily limited. Under this condition, we introduce a preservation region around each WN. This region serves to prevent transmission from the LNs and to increase the transmit power of the LNs outside the preservation regions. For the achievability results, multi-hop (MH), hierarchical cooperation (HC), and hybrid HC-MH schemes are utilized with some appropriate modifications. In the proposed MH and hybrid schemes, because the preservation regions may impede communication along direct data paths, the data paths are suitably modified by taking a detour around each preservation region. To avoid the concentration of detours resulting extra relaying burdens, we distribute the detours evenly over a wide region. In the proposed HC scheme, we control the symbol power and the scheduling of distributed multiple-input multiple-output transmission. We also present upper bounds on the throughput scaling under the assumption that every active LN consumes the same average transmit power over the time period in which the WNs observe the channel outputs. For 0<κ<1 , these upper bounds match with the achievable throughput scalings.
Synthesis of high temperature wear resistant WC and WN coatings
No full textCataloged from PDF version of article.Includes bibliographical references leaves 57-66.In this study, WC and WN thin films were synthesized using reactive magnetron
sputter deposition in order to develop promising alternatives to the well known wearresistant
coatings such as CrN, TiN, TiAlN and TiB2 etc. For this purpose, WC and WN
coatings were deposited on Si(100) and steel (100Cr6) substrates by a Direct Current
(DC) reactive magnetron sputtering system. X-ray Diffraction (XRD) and X-ray
Photoelectron Spectroscopy (XPS) were used to uncover the atomic structure of the
films and the change in the chemical bonding states of the atoms. Also, the hardness
measurements were performed using a nano-indentation tester on as-deposited films and
after the films were subjected to 500°C for two hours. A pin-on-disc tribometer was used
to investigate the wear-rates of these coatings at room temperature (RT) and 500°C
under ambient atmosphere conditions using 6 mm in diameter Al2O3 balls. Scanning
electron microscopy (SEM) was used to investigate the microstructure and measure the
thickness of the coatings. Also, for chemical analysis energy dispersive spectroscopy
(EDS) was used.
Two sets of experiments were designed and performed for the preparation of WN
coatings. In the first set, effect of N2 flow rates during deposition was investigated on the structure and properties of coatings deposited. The N2 flow rates were varied between
17% - 66% of the total flow (Ar+N2). The results of these experiments exhibited a
significant drop for the hardness and wear rates of WN coatings deposited with
increasing N2 flow rates when tested after 500°C treatment. On the contrary, RT wear
test results indicated an improvement in the wear rates with increasing N2 flow rates.
XRD data for the samples subjected to 500°C. XRD analysis indicated the presence of a
soft tet-WO3 layer over the coatings treated at 500°C which is found to be the main
culprit for the degradation of the tribological properties. In order to prevent the
formation of this soft oxide layer on WN coatings, W/WN multilayer coatings were
synthesized in the second set of experiments where the W layers were used as diffusion
barriers for oxygen. After the optimization of deposition parameters for synthesizing
W/WN multilayer coatings, subsequent tribological examinations indicated the
multilayer coatings to be comparably wear resistant at both RT and 500°C. Furthermore,
hardness of the multilayer coatings with optimized parameters were found to be around
20-25 GPa at RT and 15-20 GPa at 500°C and their corresponding wear resistances were
measured to be ~2.0x10-6 mm3
/Nm at RT and ~4.0x10-6 mm3
/Nm at 500oC.
As the second challenge, WC thin films were synthesized within the framework
of this study. The first set of synthesis experiments was done using acetylene (C2H2) as
the carbon source. It was found that increasing relative amount of C2H2 flow during
sputter deposition resulted in the degradation of tribological properties of coatings due to
amorphous carbon build-up in the films. To overcome this degradation of properties,
alternative solid sputter targets such as B4C (as an alternative C source for 2nd set),
W/B4C (composite targets) and W2C targets (for co-sputtering experiments of 3rd set)
were used for the deposition of WC films. The results of the structural and chemical
analysis indicated the presence of well-crystallized WC phases (WC and W2C) in the
coatings sputter deposited from B4C targets. Comparatively, coatings deposited using
solid WC and W2C targets resulted in coatings with the same phases. Tribological
testing of these coatings indicated that WC films synthesized using B4C targets to have
better mechanical performance after 500oC treatment while coatings co-sputtering from
compound targets worked better at RT.Alagöz, Hüseyi
Toward monitoring and estimating the size of the HFO-contaminated seabed around a shipwreck using MBES backscatter data
No full textFunding Information: The authors are grateful to three anonymous reviewers for their constructive criticism and valuable comments. The authors express their gratitude to the Maritime Institute in Gdansk for making the final version of the report (Maritime Institute in Gdansk, 2016) available. The second author appreciates the support of the Gdynia Maritime University in funding this research through internal grant WN/PZ/2021/02. Funding Information: The second author appreciates the support of the Gdynia Maritime University in funding this research through internal grant WN/PZ/2021/02 . Publisher Copyright: © 2021Despite a progressive reduction of oil spills caused by the activity of maritime transportation, the latent sources of pollution still exist. Although the harmful impact of heavy fuel oil (HFO) on the marine environment is widely known, many shipwrecks cause contamination of the surrounding areas. In this paper, an approach to monitor the area of the HFO spill around a shipwreck is made using a bottom backscattering strength (BBS) obtained by a multibeam echosounder (MBES). As a case study, the s/s Stuttgart wreck located in the Gulf of Gdansk (Poland) is verified. Two different measurement campaigns have been carried out in shallow waters using low (190 kHz) and high (420 kHz) MBES frequency. The results indicate that the polluted area around s/s Stuttgart was estimated at 49.1 ha, which is around 18.3% more in comparison to the geological surveys made four years earlier.Peer reviewe
Reliability of Cu/WN thin Films Deposited on Low Dielectric Constant SiOF ILD
No full textABSTRACTThe effect of the post plasma treatment on the dielectric properties and reliability of fluorine doped silicon oxide (SiOF) films was studied. Also, the thermal stability of a Cu/WN interconnect system with SiOF intermetal dielectrics was examined by RTA. The surface roughness of SiOF films increased with the increasing plasma treatment power due to ion bombardment effect during the plasma treatment. As the plasma treatment power increased, the dielectric constant increased from 3.16 to 3.43, while the change in the relative dielectric constant of the plasma treated films by the boiling treatment was decreased in magnitude. Furthermore, the chemical properties of the plasma treated SiOF films near the top layer tend to resemble those of thermal oxides by the plasma treatment of sufficient power because of the reduction in the Si-F bonding in the films. In the case of Cu/WN/SiOF/Si multilayer structure, surface oxidation and densification due to the plasma treatment seemed to play an important role in protecting the interdiffusion between SiOF and metal interconnects.</jats:p
The Weight and Hopcount of the Shortest Path in the Complete Graph with Exponential Weights
No full textBoth the hopcount HN (the number of links) and the weight WN (the sum of the weights on links) of the shortest path between two arbitrary nodes in the complete graph KN with i.i.d. exponential link weights is computed. We consider the joint distribution of the pair (HN,WN) and derive, after proper scaling, the joint limiting distribution. One of the results is that HN and WN, properly scaled, are asymptotically independent.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc
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