Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Investigation and Modeling of Etching Through Silicon Carbide Vias (TSiCV) for SiC Interposer and Deep SiC Etching for Harsh Environment MEMS by DoE
    ( 2022)
    Mackowiak, Piotr
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    Erbacher, Kolja
    ;
    Schiffer, Michael
    ;
    Manier, Charles-Alix
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    Töpper, Michael
    ;
    Ngo, H.-D.
    ;
    Schneider-Ramelow, M.
    ;
    Lang, K.-D.
    This article presents prime results on process development and optimization of dry etching of silicon carbide (SiC) for via formation and deep etching for SiC-based microsystems. The investigations and corresponding results of the process developments enable the first realization of a full SiC-based technological demonstrator composed of a SiC-interposer with a flip chip mounted deep etched micro electromechanical system (MEMS) SiC Device. By optimizing the process, etch depth of 200 μm with an etch rate of up to 2 μm /min can be achieved for via etching. In addition, a design of experiments (DoEs) with a total of 29 experiments with seven factors was done to characterize the deep etching of large areas into the SiC. Hereby, vertical sidewalls with low micromasking, low microtrenching and an etch rate of up to 4 μm /min could be achieved. The findings and optimized processes were implemented to develop on the one hand a 200- μm -thick SiC interposer with copper metallization. On the other hand, a SiC-MEMS Device was manufactured with a deep etched cavity in SiC bulk wafer forming by the end a 50- μm thin membrane. The results demonstrate the ability of etching monocrystalline SiC with a high etch rate, enabling new fundamental topologies/structures and packaging concepts for harsh environments MEMSs and high-power electronics. The developed etching technologies demonstrate and enable various applications for 3-D Integration with wide bandgap substrates taking advantage of the superior electrical and mechanical properties of SiC.
  • Publication
    Development and characterization of a novel low-cost water-level and water quality monitoring sensor by using enhanced screen printing technology with PEDOT:PSS
    ( 2020)
    Wang, B.
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    Baeuscher, M.
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    Hu, X.
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    Woehrmann, M.
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    Becker, K.
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    Juergensen, N.
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    Hubl, M.
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    Mackowiak, P.
    ;
    Schneider-Ramelow, M.
    ;
    Lang, K.-D.
    ;
    Ngo, H.-D.
    A novel capacitive sensor for measuring the water-level and monitoring the water quality has been developed in this work by using an enhanced screen printing technology. A commonly used environment-friendly conductive polymer poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) for conductive sensors has a limited conductivity due to its high sheet resistance. A physical treatment performed during the printing process has reduced the sheet resistance of printed PEDOT:PSS on polyethylenterephthalat (PET) substrate from 264.39 W/sq to 23.44 W/sq. The adhesion bonding force between printed PEDOT:PSS and the substrate PET is increased by using chemical treatment and tested using a newly designed adhesive peeling force test. Using the economical conductive ink PEDOT:PSS with this new physical treatment, our capacitive sensors are cost-efficient and have a sensitivity of up to 1.25 pF/mm.
  • Publication
    Mixed-Port Scattering and Hybrid Parameters for High-Speed Differential Lines
    ( 2019)
    Engin, A.E.
    ;
    Ndip, I.
    ;
    Lang, K.-D.
    ;
    Aguirre, G.
    High-speed transmission lines are commonly routed as differential lines to control sensitivity to noise on the reference planes at higher speeds. Differential lines are typically characterized in terms of mixed-mode scattering parameters, as they provide insight into the behavior of differential and common signals, as well as the mode conversion among them. These mixed-mode scattering parameters can be mathematically obtained from single-ended parameters, which can, for example, be measured with a four-port vector network analyzer. There has been recent efforts to develop extended or modified versions of mixed-mode scattering parameters, especially for tightly-coupled lines. This can be a point of confusion in interpreting the behavior of differential lines. In this paper, we introduce the mixed-port scattering and hybrid parameters, which do not suffer from any such ambiguous definitions. Mixed-port hybrid parameters are the most natural way to represent any four-port differential circuit, as they are based on intuitive differential and common-port excitations of the network. They also enable extraction of the current division factor experimentally, which is a critical parameter for electromagnetic interference analysis of differential lines. Mixed-port scattering parameters are also defined based on common and differential port excitations, allowing a simpler interpretation than their mixed-mode counterparts, without the need for defining even, odd, common, or differential-mode impedances. As such, mixed-port scattering and hybrid parameters can be used to analyze the performance of a general differential network, certainly including coupled or asymmetrical lines, without any ambiguity.
  • Publication
    Process optimization and implementation of online monitoring process in the transfer molding for electronic packaging
    ( 2019)
    Kaya, B.
    ;
    Kaiser, J.-M.
    ;
    Becker, K.-F.
    ;
    Braun, T.
    ;
    Lang, K.-D.
    The quality of molded packages heavily depends on the process parameters of the molding process and on the material characteristics of epoxy molding compounds (EMCs). When defects are introduced into the electronic packages in one of the last steps in the manufacturing process, namely, during encapsulation, it may cause high failure costs. To decrease the number of defects due to the molding process, a comprehensive understanding of the impact of process parameters and variations in the characteristics of the EMC on package quality is necessary. This study aimed at supporting a deeper understanding of the influence of process parameters and variations in the material characteristics of the EMC on package quality. A systematic approach was introduced to generate a process model describing the correlation between process parameters and package quality to obtain optimum process parameters for the transfer molding process. The influence of the alterations in material characteristics of the EMC due to prolonged storage duration and humidity on void formation and wire sweep was investigated. An online monitoring method, dielectric analysis (DEA), was implemented into the transfer molding process to monitor the variations in the cure behavior of the EMC. A second molding compound was used to analyze the similarities in the alteration behavior of the molding compounds when subjected to the same preconditioning and to generalize the characteristic information obtained from DEA.
  • Publication
    Closed-form multipole debye model for time-domain modeling of lossy dielectrics
    ( 2019)
    Engin, A.E.
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    Ndip, I.
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    Lang, K.-D.
    ;
    Aguirre, J.
    Lossy dielectrics in printed circuit boards and integrated circuit packages can be represented by using a Debye model. This allows accurate signal and power integrity analysis, which depends on the accuracy of material properties of the board or package. Such a Debye model needs multiple poles for accurate representation of the loss tangent over a broad frequency range. Electromagnetic and circuit simulations can then include the impact of frequency-dependent dielectric constant and loss. In this letter, we present an efficient and closed-form multipole Debye model, automating the modeling of lossy dielectrics for inclusion in time-domain electromagnetic or circuit simulators.
  • Publication
    A numerical study on mitigation of flying dies in compression molding of microelectronic packages
    ( 2019)
    Dreissigacker, M.
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    Hoelck, O.
    ;
    Bauer, J.
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    Braun, T.
    ;
    Becker, K.-F.
    ;
    Schneider-Ramelow, M.
    ;
    Lang, K.-D.
    Compression molding with liquid encapsulants is a crucial process in microelectronic packaging. Material properties of highly filled systems of reactive epoxy molding compounds depend on process conditions in a complex manner, such as shear-thinning behavior, which is superimposed by a time- and temperature-dependent conversion rate, both strongly affecting viscosity. The focus is set on forces exerted on individual dice during encapsulation in fan-out wafer-level packaging (FOWLP). The presented framework consists of an analytical approach to calculate the melt front velocity and simulations carried out to capture the nonlinear kinematics, chemorheology, and to extract forces exerted on individual dice. It offers separate evaluation of pressure and shear contributions for two cases, 0° and 45° between the dice' frontal area and the melt front. Process parameters, such as compression speed, thus cycle time, and process temperature, are determined to keep the forces on the dice below the critical level, where drag forces exceed adhesive forces. As a result, process parameters are determined to minimize flying dice and thereby maximize yield. The approach is easily transferable to arbitrary geometries and is therefore well suited to face the challenges that come with the current efforts toward the transition from FOWLP to larger substrates.
  • Publication
    Development and Validation of a Chip Integration Concept for Multi-Die GaAs Front Ends for Phased Arrays up to 60 GHz
    ( 2018)
    Curran, B.
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    Reyes, J.
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    Tschoban, C.
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    Höfer, J.
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    Grams, A.
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    Wüst, F.
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    Hutter, M.
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    Leiß, J.
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    Martínez-Vázquez, M.
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    Baggen, R.
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    Ndip, I.
    ;
    Lang, K.-D.
    High-gain steerable antenna arrays in the K-, Ka-, and V-frequency bands have the potential to facilitate high-bandwidth satellite communication for a variety of applications. Copper-core printed circuit boards (PCBs) can offer a cost-effective integration platform for such systems by simultaneously addressing both the high frequency and thermal challenges. Integrating GaAs dies into test vehicles has shown that copper-core PCBs can be automatically assembled and provide high-frequency systems that show adequate reliability during thermal cycling. A single 60-GHz transmitter front end, designed to drive a single element of a phased array, with a 2-GHz bandwidth signal, composed of four GaAs dies, including a phase shifter, integrated onto a copper-core PCB produces an output power of -4 dBm and maintains an on-chip temperature under 51 °C.
  • Publication
    Corrosion behaviour of sintered silver under maritime environmental conditions
    ( 2018)
    Kolbinger, E.
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    Wagner, S.
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    Gollhardt, A.
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    Rämer, O.
    ;
    Lang, K.-D.
    One of the most critical influences of long-term reliability of electronic applications is corrosion. However, corrosion is not considered in accelerated testing, mostly. In particular power electronics applications, for example offshore wind power systems, are exposed to the harshest of environmental conditions. For these applications, highly reliable die attach technology is absolutely essential. One of the most promising technologies is the sinter silver technology. This paper gives an overview of corrosion behaviour of sintered silver under harsh environmental conditions. Investigations are performed on the influence of different pressures of the sinter atmosphere on the corrosion behaviour. To characterize corrosion issues of sintered silver, various electrochemical and analytical methods are used.
  • Publication
    Nonoverlapping Power/Ground Planes for Suppression of Power Plane Noise
    ( 2018)
    Engin, A.E.
    ;
    Ndip, I.
    ;
    Lang, K.-D.
    ;
    Aguirre, G.
    Providing low IR-drop and inductance are two major roles of power and ground (PG) planes in chip packages and boards. However, planes can also cause switching noise coupling, especially when they resonate. This is a concern for mixed-signal boards, high-speed I/Os, and electromagnetic compatibility. Discrete decoupling capacitors are ineffective to control switching noise at gigahertz frequency regime due to their inductance. To filter such high-frequency noise, a possible approach is modifying the shape of the PG planes, such as in power islands or electromagnetic bandgap structures. In this paper, we introduce the nonoverlapping PG planes design methodology for filtering of gigahertz power plane noise. Unlike existing approaches, our approach is simple and has wide bandwidth, while avoiding narrow inductive bridges that increase IR-drop.
  • Publication
    On the Radiation Characteristics of Full-Loop, Half-Loop and Quasi Half-Loop Bond Wire Antennas
    ( 2018)
    Ndip, I.
    ;
    Lang, K.-D.
    ;
    Reichl, H.
    ;
    Henke, H.
    The theory, modeling, measurement and analysis of the radiation characteristics of bond wire antennas (BWAs) is presented in this work. We commence with rigorous formulations, and derivations of analytical models for calculating the vector potential, radiated electromagnetic fields and directivity of full-loop BWAs (FL-BWAs), considering non-constant current distribution along the BWAs. Based on the image theory, we derive an analytical model for calculating the directivity of half-loop BWAs (HL-BWAs) from that of FL-BWAs. Very good correlation is obtained between the directivities calculated analytically using the derived models, and numerically using commercial full-wave solvers, thus validating our analytical approach. We apply the verified models to thoroughly analyze the radiation characteristics of FL-BWAs and HL-BWAs. The radiation characteristics of a HL-BWA is based on the assumption that its reference plane is infinitely large and perfectly conducting. However , for the development of wireless systems, reference planes of finite sizes are required. Therefore, we investigate the impact of realistic dimensions of reference planes. Our results reveal that the radiation characteristics of BWAs referred to as ""HL-BWAs"" in published literature differ significantly from those of true HL-BWAs. Hence, we introduce the term ""quasi half-loop BWA (QHL-BWA)"" to describe BWAs with small reference planes. Finally, we analyze the radiation characteristics of QHL-BWAs, and compare their radiation patterns to that of HL-BWAs. For experimental verification, QHL-BWAs were fabricated and measured in the 60 GHz band. Very good correlation was obtained between measurement and simulation results.