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M Guglielmi - One of the best experts on this subject based on the ideXlab platform.
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multimode equivalent network for boxed multilayer arbitrary planar circuits
IEEE Transactions on Microwave Theory and Techniques, 2020Co-Authors: Celia Gomez Molina, Fernando Daniel Quesada Pereira, Alejandro Alvarez Melcon, Vicente E Boria, Stephan Marini, Miguel A Sanchezsoriano, M GuglielmiAbstract:The multimode equivalent network (MEN) formulation has been originally developed for the efficient and accurate analysis of waveguide devices. In this article, we extend the use of the MEN to the analysis of zero-thickness, planar printed circuits in a metallic enclosure. The formulation is developed for metallic areas of arbitrary shape and includes both internal and external ports in the transverse plane to model connections to external components, and coaxial input/output ports. The boundary integral resonant mode expansion (BI-RME) method is used for the analysis of the arbitrary shape Metallizations. On this basis, shielded multilayered microstrip circuits of complex geometry are analyzed in the common frame of the MEN technique. To validate the theoretical formulation, several boxed microstrip structures are analyzed, including multilayered configurations with several metallization interfaces, showing good agreement with respect to both other commercial tools, and measurements.
I Adesida - One of the best experts on this subject based on the ideXlab platform.
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differences in the reaction kinetics and contact formation mechanisms of annealed ti al mo au ohmic contacts on n gan and algan gan epilayers
Journal of Applied Physics, 2007Co-Authors: Liang Wang, Fitih M Mohammed, I AdesidaAbstract:Ti∕Al-based multilayer Metallizations are usually used interchangeably for n-GaN and AlGaN∕GaN epilayers. Our investigations show that, although excellent Ohmic performances were obtained on both cases, the reaction pathways/kinetics and Ohmic contact formation mechanisms of Ti∕Al∕Mo∕Au metallization on n-GaN and AlGaN∕GaN are different. In the case of n-GaN, the reaction proceeds by the formation of continuous TiN layer at the metal/GaN interface. Low-barrier Schottky contact or tunneling contact is the possible contact formation mechanisms. On AlGaN∕GaN heterostructures, the existence of the AlGaN layer significantly modifies the reaction pathway, where discrete TiN protrusions form nonuniformly along threading dislocations. The TiN protrusions penetrate through the AlGaN layer and form direct electrical link between the two-dimensional electron gas and the metal contacts which would otherwise be separated by the AlGaN barrier layer. A contact formation mechanism, similar to the “spike mechanism,” which...
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ohmic contact formation mechanism of ta al mo au and ti al mo au Metallizations on algan gan hemts
Journal of Vacuum Science & Technology B, 2005Co-Authors: Fitih M Mohammed, Liang Wang, D Selvanathan, I AdesidaAbstract:A comparative study of Ta∕Al∕Mo∕Au and Ti∕Al∕Mo∕Au Metallizations for AlGaN∕GaN high electron mobility transistors is presented. By the optimization of surface treatment schemes and annealing temperature, contact resistances of 0.172 and 0.228Ωmm, and specific contact resistivities of 2.96×10−7 and 1.09×10−6Ωcm2 were obtained for Ti∕Al∕Mo∕Au and Ta∕Al∕Mo∕Au, respectively. Auger electron spectroscopy (AES), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were utilized to study microstructural changes occurring in the metallization layers as a result of heat treatment. Results indicate dynamic systems of severe intermixing between atoms from the metallization layers and epilayers resulting in changes in surface morphology, as determined by atomic force microscopy (AFM). The formation of intermetallics and interfacial compounds was observed. The combined effect of surface treatment and annealing-induced reaction is proposed as the mechanisms for low-resistance Ohmic contact formation.
Sabeur Msolli - One of the best experts on this subject based on the ideXlab platform.
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Study of the Fracture Mechanisms of Electroplated Metallization Systems Using In Situ Microtension Test
Electronic Materials Letters, 2018Co-Authors: Sabeur Msolli, Heung Soo KimAbstract:This framework assesses the mechanical behavior of some potential thin/thick metallization systems in use as either ohmic contacts for diamond semi-conductors or for metallization on copper double bounded ceramic substrates present in the next-generation power electronics packaging. The interesting and unique characteristic of this packaging is the use of diamond as a semi-conductor material instead of silicon to increase the lifetime of embedded power converters for use in aeronautical applications. Theoretically, such packaging is able to withstand temperatures of up to 300 °C without breaking the semi-conductor, provided that the constitutive materials of the packaging are compatible. Metallization is very important to protect the chips and substrates. Therefore, we address this issue in the present work. The tested metallization systems are Ni/Au, Ni/Cr/Au and Ni/Cr. These specific systems were studied since they can be used in conjunction with existing bonding technologies, including AuGe soldering, Ag–In Transient liquid Phase Bonding and silver nanoparticle sintering. The metallization is achieved via electrodeposition, and a mechanical test, consisting of a microtension technique, is carried out at room temperature inside a scanning electron microscopy chamber. The technique permits observations the cracks initiation and growth in the metallization to locate the deformation zones and identify the fracture mechanisms. Different failure mechanisms were shown to occur depending on the metallic layers deposited on top of the copper substrate. The density of these cracks depends on the imposed load and the involved metallization. These observations will help choose the metallization that is compatible with the particular bonding material, and manage mechanical stress due to thermal cycling so that they can be used as a constitutive component for high-temperature power electronics packaging.Graphical Abstract
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Assessment of candidate metallization systems deposited on diamond using nano-indentation and nano-scratching tests
Thin Solid Films, 2016Co-Authors: Sabeur Msolli, Joël Alexis, Olivier Dalverny, Moussa KaramaAbstract:Mechanical suitability of ohmic contacts among the select metallization systems, deposited on a p-type heavily boron-doped homoepitaxial diamond layer, was evaluated via mechanical tests on the nanoscale. Two candidate metallization systems were considered: Si/Al and Ti/Pt/Au. Metallizations were performed using two different techniques: plasma-enhanced chemical vapour deposition and “lift-off”. Effectiveness of the techniques was assessed via mechanical tests on the microscale and the nanoscale. Nano-indentation experiments were performed to determine the mechanical properties of the layers. Nano-scratching experiments were used to evaluate the mechanical adhesion on the diamond substrate. Scanning electron microscopy was applied for observation of the morphology of the surface and the indent and for detecting defects.
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An assessment of contact metallization for high power and high temperature diamond Schottky devices
Diamond and Related Materials, 2012Co-Authors: Sodjan Koné, Sabeur Msolli, Henri Schneider, Karine Isoird, Fabien Thion, Jocelyn Achard, Riadh Issaoui, Joël AlexisAbstract:Different metals W, Al, Ni and Cr were evaluated as Schottky contacts on the same p-type lightly boron doped homoepitaxial diamond layer. The current-voltage (I-V) characteristics, the series resistance and the thermal stability are discussed in the range of RT to 625 K for all Schottky devices. High current densities close to 3.2 kA/cm2 are displayed and as the series resistance decreases with increasing temperature, proving the potential of diamond for high power and high temperature devices. The thermal stability of metal/diamond interface investigated with regards to the Schottky barrier height (SBH) and ideality factor n fluctuations indicated that Ni and W are thermally stable in the range of RT to 625 K. Current-voltage measurements at reverse bias indicated a maximum breakdown voltage of 70 V corresponding to an electric field of 3.75 MV/cm. Finally, these electrical measurements have been completed with mechanical adhesion tests of contact Metallizations on diamond by nano-scratching technique. These studies clearly reveal Ni as a promising contact metallization for high power, high temperature and good mechanical strength diamond Schottky barrier diode applications.
Celia Gomez Molina - One of the best experts on this subject based on the ideXlab platform.
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multimode equivalent network for boxed multilayer arbitrary planar circuits
IEEE Transactions on Microwave Theory and Techniques, 2020Co-Authors: Celia Gomez Molina, Fernando Daniel Quesada Pereira, Alejandro Alvarez Melcon, Vicente E Boria, Stephan Marini, Miguel A Sanchezsoriano, M GuglielmiAbstract:The multimode equivalent network (MEN) formulation has been originally developed for the efficient and accurate analysis of waveguide devices. In this article, we extend the use of the MEN to the analysis of zero-thickness, planar printed circuits in a metallic enclosure. The formulation is developed for metallic areas of arbitrary shape and includes both internal and external ports in the transverse plane to model connections to external components, and coaxial input/output ports. The boundary integral resonant mode expansion (BI-RME) method is used for the analysis of the arbitrary shape Metallizations. On this basis, shielded multilayered microstrip circuits of complex geometry are analyzed in the common frame of the MEN technique. To validate the theoretical formulation, several boxed microstrip structures are analyzed, including multilayered configurations with several metallization interfaces, showing good agreement with respect to both other commercial tools, and measurements.
M. A. Korhonen - One of the best experts on this subject based on the ideXlab platform.
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under bump Metallizations for lead free solders
Electronic Components and Technology Conference, 2000Co-Authors: T. M. Korhonen, S. J. Hong, M. A. KorhonenAbstract:Several under bump metallization (UBM) schemes using CuNi alloys as the solderable layer were investigated. The nickel slows down the dissolution of the UBM into the solder and the formation of intermetallics during reflow. Ni containing UBMs were fabricated and reflowed with eutectic SnAg solder balls. The solder/UBM interfaces were analysed with SEM to find out how the Ni concentration affects the reaction, and how much Ni is needed to obtain a sufficiently slow reaction rate. Reflows were also made on top of bulk substrates to study the reaction when there is an unlimited amount of CuNi available. To determine the rate of dissolution of the substrate material into solder, CuNi foils of different concentrations were immersed in pure Sn and eutectic PbSn solder baths for soldering times ranging from 30 seconds to 30 minutes. Since nickel Metallizations often have high stresses, stress in the UBMs was measured by the wafer curvature method. Stress vs. Ni content plots show that while stresses increase somewhat with the Ni content, the adhesion layer under the CuNi layer has a much larger effect on the stress.
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Development of under bump Metallizations for flip chip bonding to organic substrates
Journal of Electronic Materials, 1999Co-Authors: T. M. Korhonen, S. J. Hong, M. A. KorhonenAbstract:Several under bump metallization (UBM) schemes using CuNi alloys as the solderable layer were investigated. Nickel slows down dissolution of the UBM into the solder and formation of intermetallics during reflow. To study the intermetallic reaction, CuNi foils of different concentrations were immersed in a eutectic PbSn solder bath for reaction times ranging from 30 seconds to 30 minutes. It was observed that when 10% and 20% Ni is added into copper, the intermetallic forms a continuous layer, instead of the discrete scallops seen in pure Cu/solder interfaces. However, the thickness of the intermetallic remained about the same. For 30% and 45% Ni alloys a definite decrease in the intermetallic thickness was observed compared to the lower Ni alloys. Actual under bump Metallizations were also made on Si wafers to study the reactions when there is a limited supply of CuNi available. Cr or Ti was used as the adhesion layer, and the solderable layer was a copper-nickel alloy, instead of pure copper used in the conventional UBM scheme. The metal layers were deposited on a wafer by evaporation and patterned into contact pads. Eutectic PbSn solder balls were reflowed on top of the pads. SEM micrographs of the intermetallic that forms at the UBM/solder interface show the refining effect of Ni in the interfacial microstructure. Since nickel Metallizations often have high stresses, stress in the UBMs was measured by the wafer curvature method. Stress vs Ni content plots show that while stresses increase somewhat with the Ni content, the adhesion layer under the CuNi layer has a much larger effect on the stress. UBMs with Cr/CrCu adhesion layer had stresses ranging from about 300 to 600 MPa, while the stresses in UBMs with Ti/TiNi layers were between 70 and 350 MPa.
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stress induced nucleation of voids in narrow aluminum based Metallizations on silicon substrates
Journal of Applied Physics, 1991Co-Authors: M. A. Korhonen, W R LafontaineAbstract:This work investigates thermal stress‐induced voiding, and void nucleation in particular, in narrow, passivated aluminum‐based Metallizations on silicon substrates. After excursions to a higher temperature, the thermal stress is tensile, and increases during cooldown to room temperature, after which it relaxes with time. Experiments conducted on two aluminum alloy Metallizations suggest that stress‐induced void nucleation is a one shot phenomenon during cooldown from the heat treatment temperature. Further, the high thermal stresses present, and the strong constraints against deformation provided by the substrate and passivation layer, make void nucleation unique in narrow passivated Metallizations. Finally, voids always appear to be connected to grain boundaries. The above experimental evidence and theoretical considerations together suggest that grain boundary sliding is the main mechanism facilitating void nucleation in passivated aluminum alloy Metallizations.
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mechanisms of thermal stress relaxation and stress induced voiding in narrow aluminum based Metallizations
Journal of Applied Physics, 1991Co-Authors: M. A. Korhonen, C A PaszkietAbstract:Thermal stress‐induced voiding in narrow aluminum‐based Metallizations used as interconnects in microelectronic circuits has recently become a serious reliability concern. Room‐temperature stress relaxation and associated physical phenomena in passivated and unpassivated aluminum‐based Metallizations, subsequent to exposure to high temperatures, are analyzed based both on theoretically estimated and experimentally determined thermal stresses. It is shown that stress relaxation at longer times involves mainly dislocation climb, while short‐term relaxation during cool down from higher temperatures, and immediately thereafter, involves significant dislocation glide. Void growth, frequently observed in passivated Metallizations, provides a new source of atoms to feed stress relaxation by the same processes as in the absence of voiding.