Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Fan-Out Wafer and Panel Level Packaging - A Platform for 3D Integration
    ( 2021)
    Braun, T.
    ;
    Becker, K.-F.
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    Töpper, M.
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    Aschenbrenner, R.
    ;
    Schneider-Ramelow, M.
    The constant drive to further miniaturization and heterogeneous system integration leads to a need for new packaging technologies that also allow large area processing and 3D integration with strong potential for low cost applications. Here, Fan-Out Wafer Level Packaging [FOWLP] is one of the latest packaging trends in microelectronics. The technology can be also used for multi-chip packages or System in Package (SiP). 3D integration is typically done by package on package (PoP) stacking where the electrical 3D routing is done by through mold (TMV) or through package vias (TPV) and a redistribution layer on both sides of the FOWLP. In summary the paper will give a review of the different technology approaches for through mold vias in a Fan-out Wafer or Panel Level Package.
  • Publication
    Thermo-mechanical-optical coupling within a digital twin development for automotive LiDAR
    ( 2021)
    Tavakolibasti, Majid
    ;
    Meszmer, Peter
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    Böttger, Gunnar
    ;
    Kettelgerdes, Marcel
    ;
    Elger, Gordon
    ;
    Erdogan, Hüseyin
    ;
    Seshaditya, A.
    ;
    Wunderle, Bernhard
    In the current work, the steps of the development of a Reduced Complexity Model (RCM) of a Light Detection and Ranging (LiDAR) system and the requirements for the preparation of a Digital Twin (DT) from such system are discussed. Preliminary thermal and optical simulations are presented, along with different concepts for cooling of the system. Additionally, the current barrier of coupling of the thermo-mechanical simulations produced in Ansys Mechanical and optical simulations done by Zemax OpticStudio is discussed.
  • Publication
    Influence of Ball Size and Geometry on the Reliability and RF Performance of mmWave System-in-Package: A Simulation Approach
    ( 2021)
    Dilek, S.
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    Ndip, I.
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    Rossi, M.
    ;
    Tschoban, C.
    ;
    Kuttler, S.
    ;
    Wittler, O.
    ;
    Lang, K.-D.
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    Goetze, C.
    ;
    Berger, D.
    ;
    Wieland, M.
    ;
    Schneider-Ramelow, M.
    Solder ball reliability is a long-discussed topic in microelectronic packaging. With new package types needed for mmWave applications a trade-off between reliability and RF performance may arise, when the solder ball geometry has to be selected for specific package assemblies. In this work, the lifetime for different solder ball geometries is investigated within a numerical simulation workflow, by means of a sensitivity analysis in which the ball diameter, pad sizes and stand-off distance are varied. Next to lifetime estimations, 3D full-wave simulations have been applied to analyze the RF performance of the structures under investigation at 77-79 GHz (E-band) center frequencies relevant for automotive radar applications. Finally, the trade-off between RF performance and reliability is illustrated and quantified.
  • Publication
    Towards a wireless system that can monitor the encapsulation of mm-sized active implants in vivo for bioelectronic medicine
    ( 2021)
    Rodrigues, G.
    ;
    Neca, M.
    ;
    Silva, J.
    ;
    Brito, D.
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    Rabuske, T.
    ;
    Fernandes, J.
    ;
    Mohrlok, R.
    ;
    Jeschke, C.
    ;
    Meents, J.
    ;
    Nanbakhsh, K.
    ;
    Giagka, V.
    Active neural interfaces for bioelectronic medicine are envisioned to be mm-sized. Such miniaturization is at the moment hampered by the available wireless power techniques as well as the large volume the conventional hermetic packaging adds to the implant. Alternatively, conformal coatings are being explored for the protection of the implant electronics. Such approach has the potential to allow for the use of RF (radio-frequency) energy for powering, and miniaturization to the extreme of having a single IC (integrated circuit) as the whole implant (single chip implants). The longevity of conformal encapsulation can be assessed using accelerated soak tests in a dedicated apparatus in vitro, but these are usually not sufficient, as they fail to reveal additional failure modes that manifest themselves in vivo. Therefore, to investigate the performance of conformal coatings in vivo a compact, mm-sized wireless monitoring system is required. The development of such a system exhibits several challenges, mostly concerned with how to receive enough energy in such a small implant to power the monitoring sensor and transmit information regarding the integrity of the coating. In this paper we propose a system architecture for such a mm-sized wireless system, suitable for medium-to-Iong term monitoring of implants, by designing the whole system as a single monolithic IC. It is shown, by experiments, simulation or analytically that the identified challenges are possible to overcome, allowing to proceed towards the practical prototype.
  • Publication
    RF Modeling and Measurement of a Novel Aperture-Coupled Hybrid Glass-Silicon 5G Antenna Array
    ( 2021)
    Le, T.H.
    ;
    Rossi, M.
    ;
    Ndip, Ivan
    ;
    Kaiser, Michael
    ;
    Manier, Charles-Alix
    ;
    Gernhardt, Robert
    ;
    Oppermann, Hermann
    ;
    Lang, Klaus-Dieter
    ;
    Reichl, Herbert
    In this work, the electromagnetic modelling and measurement of a novel aperture-coupled hybrid glass-silicon 1x2 antenna array is presented. The patch elements are located under a glass substrate, which is placed on a silicon layer. The antenna array is fed using aperture coupling. A cavity is etched in the silicon layer to reduce the impact of silicon, and thus ensures significant improvement of the antenna efficiency and gain. The proposed antenna was fabricated and measured. Very good correlation is obtained between simulation and measurement.
  • Publication
    Self-oscillating very high frequency inverter for gate driver power supply
    ( 2021)
    Kieninger, A.
    ;
    Hoene, E.
    High side gate drivers are today supplied either by a bootstrap circuit or transformers with potential separation. With switching speed generated by WBG semiconductors both come to a limit, the boots trap diode due to its revers recovery and capacitance, the transformer due to its coupling capacitance between primary and secondary. This paper introduces an alternative way of supplying gate drivers with the potential to miniaturize them further than possible today. It is based on a VHF self resonating circuit (76 MHz) and a potential separation via a 1 pF high voltage capacitor. This low capacitance value is sufficient to supply the driver with up to 35 mW.
  • Publication
    Investigation of Wafer Dicing and Cleaning Processes for Die-to-die Oxide direct Bonding Technology
    ( 2021)
    Khurana, G.
    ;
    Hanisch, A.
    ;
    Rudolph, C.
    ;
    Meyer, J.
    ;
    Wieland, M.
    ;
    Panchenko, I.
    A feasibility study of die-to-die (D2D) direct bonding with oxide surface is conducted using regular industrial cleanroom tools for wafer processing. The study highlights the influence of different wafer dicing, die handling and cleaning methods on the die surface quality and the quality of D2D bonding. The presented work features particle control as the biggest challenge and current bottleneck in D2D direct oxide bonding. The successful bonding of the known good dies (KGD's) with minimum defects on the bonding surface, sufficiently clean die surface, suitable roughness and sufficiently high hydrophilicity is achieved. Techniques such as stealth dicing for wafer singulation, modified RCA-SC1 (Radio Corporation of America - Standard Clean 1) recipe for cleaning and tuned plasma activation resulted in the successful D2D direct bonding. Thus, the presented work enables various applications to benefit from higher degree of design flexibility provided by D2D direct bonding approach.
  • Publication
    Dorsal root ganglion (DRG) versatile stimulator prototype developed for use in locomotion recovery early clinical trials
    ( 2021)
    Kolovou-Kouri, K.
    ;
    Soloukey, S.
    ;
    Huygen, F.J.P.M.
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    Harhangi, B.S.
    ;
    Serdijn, W.A.
    ;
    Giagka, V.
    This paper presents the development of a Dorsal Root Ganglion (DRG) stimulator system intended for use in early clinical trials for motor recovery after Spinal Cord Injury (SCI). It allows for independent control of multisite/multilevel bilateral (on both sides of the spinal cord) stimulation, it can supply a high output current of 25.4mA, and has the ability to program pulse sequences similar to actual locomotion patterns. These characteristics ultimately provide the required versatility for examining the effects of DRG stimulation on locomotion recovery, which is lacking in currently available commercial systems. The device is created using commercially available components to make the design reproducible by other research labs and to facilitate the critical approval procedure for use in a clinical research environment. Throughout the design phase, essential considerations regarding the safety of the participating patient, as well as of the medical personnel involved, were taken into account and these are analyzed and demonstrated in this paper. Such considerations are very rarely discussed in scientific literature and the authors consider that, apart from the design of the system itself, this discussion is a critical contribution of this paper.
  • Publication
    Study on FO-WLP Warpage Behavior - Influence of Process Temperature and Geometry
    ( 2021)
    Dijk, M. van
    ;
    Huber, S.
    ;
    Stegmaier, A.
    ;
    Walter, H.
    ;
    Wittler, O.
    ;
    Schneider-Ramelow, M.
    Controlling warpage effects in fan-out wafer level packaging (FO-WLP) is of key importance for realizing reliable and cost-efficient system in packages (SiPs). During the manufacturing process however, warpage effects occur caused by a combination of mismatch in thermal expansion coefficient of different materials and cure-shrinkage effects of polymeric materials. An approach of controlling the warpage could be realized by assessing a numerical simulation workflow of the FO-WLP process chain in which the relevant material properties and geometry are needed as input. Since there are many different steps included in the FO-WLP process, accompanied by complex material behavior (e.g. curing of polymers), this workflow is not straight forward. In this study the first couple of FO-WLP processing steps are investigated in detail by performing extensive thermomechanical material characterization, temperature dependent warpage measurements and numerical simulations. The warpage measurements indicate an irreversible effect after exceeding certain processing temperatures, which are significant for the final warpage at room temperature. A new approach for measuring the coefficient of thermal expansion is discussed, where a temperature profile is used based on occurring temperatures in the process instead of the typical three identical temperature ramps according to the standards. A positive side effect of this approach is that it allows to determine possible shrinkage effects. Within the simulation model, the shrinkage values are used, as well as different CTE values in order to represent the hysteresis effect observed in the experiments. Very good agreement between experiment and simulation is achieved which is shown for three demonstrators having different epoxy mold compound thicknesses.
  • Publication
    Investigation of Deep Dry Etching of 4H SIC Material for MEMS Applications Using DOE Modelling
    ( 2021)
    Erbacher, K.
    ;
    Mackowiak, P.
    ;
    Schiffer, M.
    ;
    Lang, K.-D.
    ;
    Schneider-Ramelow, M.
    ;
    Ngo, H.-D.
    In this paper the reactive ion etching (RIE) of 4H silicon carbide (SiC) with an SF 6 /O 2 /He gas mixture is investigated in an inductively coupled plasma etcher (ICP). Objective is the analysis of the manufacturing process of a SiC diaphragm for a bulk micromechanical pressure sensor, by etching a cavity into silicon carbide wafer. In addition, the selectivity of etching masks made from Nickel and Copper against SiC are examined. By means of Design of Experiments (DOE) in the software JMP, a test series with 29 recipes is set up. The process is varied over the parameters chamber pressure, source power, platen power, SF 6 flow rate, O 2 flow rate, clamp cooling and mask material. To evaluate the etched samples quantitatively, cross sections of 29 specimens are made. The results are used to create a mathematically model for the prediction of etching rate, profile angle and occurring micro masking. The model is evaluated by etching samples. Etching a cavity with an opening width of 800 mm to a depth of 300 mm with a maximum etching rate of 4 mm/min, vertical profile walls and a smooth and even etched base is demonstrated. The selectivity of the modelled process is 115 compared to Cu, the observed selectivity of Cu is higher compared to Ni.