Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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Laboratory X-ray Microscopy of 3D Nanostructures in the Hard X-ray Regime Enabled by a Combination of Multilayer X-ray Optics

2024 , Lechowski, Bartlomiej , Kutukova, Kristina , Grenzer, Jörg , Panchenko, Juliana , Krüger, Peter , Clausner, André , Zschech, Ehrenfried

High-resolution imaging of buried metal interconnect structures in advanced microelectronic products with full-field X-ray microscopy is demonstrated in the hard X-ray regime, i.e., at photon energies > 10 keV. The combination of two multilayer optics—a side-by-side Montel (or nested Kirkpatrick–Baez) condenser optic and a high aspect-ratio multilayer Laue lens—results in an asymmetric optical path in the transmission X-ray microscope. This optics arrangement allows the imaging of 3D nanostructures in opaque objects at a photon energy of 24.2 keV (In-Kα X-ray line). Using a Siemens star test pattern with a minimal feature size of 150 nm, it was proven that features < 150 nm can be resolved. In-Kα radiation is generated from a Ga-In alloy target using a laboratory X-ray source that employs the liquid-metal-jet technology. Since the penetration depth of X-rays into the samples is significantly larger compared to 8 keV photons used in state-of-the-art laboratory X-ray microscopes (Cu-Kα radiation), 3D-nanopattered materials and structures can be imaged nondestructively in mm to cm thick samples. This means that destructive de-processing, thinning or cross-sectioning of the samples are not needed for the visualization of interconnect structures in microelectronic products manufactured using advanced packaging technologies. The application of laboratory transmission X-ray microscopy in the hard X-ray regime is demonstrated for Cu/Cu6Sn5/Cu microbump interconnects fabricated using solid–liquid interdiffusion (SLID) bonding.

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Use of Rotary Ultrasonic Plastic Welding as a Continuous Interconnection Technology for Large-Area e-Textiles

2023-01-28 , Dils, Christian , Hohner, Sebastian , Schneider-Ramelow, Martin

For textile-based electronic systems with multiple contacts distributed over a large area, it is very complex to create reliable electrical and mechanical interconnections. In this work, we report for the first time on the use of rotating ultrasonic polymer welding for the continuous integration and interconnection of highly conductive ribbons with textile-integrated conductive tracks. For this purpose, the conductive ribbons are prelaminated on the bottom side with a thermoplastic film, which serves as an adhesion agent to the textile carrier, and another thermoplastic film is laminated on the top side, which serves as an electrical insulation layer. Experimental tests are used to investigate the optimum welding process parameters for each material combination. The interconnects are initially electrically measured and then tested by thermal cycling, moisture aging, buckling and washing tests, followed by electrical and optical analyses. The interconnects obtained are very low ohmic across the materials tested, with resulting contact resistances between 1 and 5 mOhm. Material-dependent results were observed in the reliability tests, with climatic and mechanical tests performing better than the wash tests for all materials. In addition, the development of a heated functional prototype demonstrates a first industrial application.

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Intermetallic growth and thermal impedance at the In32.5Bi16.5Sn/Cu interface

2023 , Chen, Chun-Hao , Yang, Chunglin , Chuang, Tung Han

Present developing trends in the miniaturization and power escalation on electronic components have driven research interest in thermal interface materials (TIMs) to solve the fundamental issue of heat dissipation. Among the various TIMs, the In32.5Bi16.5Sn low melting alloy (LMA) has drawn much attention owing to its low melting point and great bondability, which could mitigate the warpage issue and provide very low thermal interface resistance. In this study, the Cu/In32.5Bi16.5Sn/Cu structure was used to simulate the practical conditions of the application of TIM in joining the substrate and heat sink. The thermal properties before and after an aging test at 80 °C were measured with a thermal tester, and the growth kinetics of the intermetallic compound (IMC) at the In32.5Bi16.5Sn/Cu interface were investigated. Without fast dissolution of Cu into the In32.5Bi16.5Sn alloy, the growth kinetics of the IMC at the interface were found to be diffusion-controlled at the temperature studied. It was found that the main change in the Cu/In32.5Bi16.5Sn/Cu system after the aging test was the thickening of the IMC, and the interface was free of cracks. As the aging time increased, the thermal impedance increased to twice that of the initial value, showing parabolic degradation, which is relevant to the growth kinetics of the IMC at the interface. Implications for the degradation of the thermal performance and further research are also discussed.

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A forecast on future raw material demand and recycling potential of lithium-ion batteries in electric vehicles

2023 , Maisel, Franziska , Neef, Christoph , Marscheider-Weidemann, Frank , Nissen, Nils F.

The market for electromobility has grown constantly in the last years. To ensure a future supply of raw materials for the production of new batteries for electric vehicles, it is essential to estimate the future demand for battery metals. This study focuses on the future demand for electric vehicle battery cathode raw materials lithium, cobalt, nickel, and manganese by considering different technology and growth scenarios. The results show that in 2040 the future material demand for lithium, cobalt, and nickel for Lithium-Ion Batteries in electric vehicles exceeds current raw material production. Depending on the growth and technology scenario, the future demand for lithium and cobalt exceeds today's production by up to 8 times in 2040. Nickel exceeds today's production in one scenario. For manganese, future demand in 2040 remains far below today's production. The recycling potential for lithium and nickel is more than half the raw material demand for Lithium-Ion Batteries in 2040. For cobalt, the recycling potential even exceeds the raw material demand in 2040. In conclusion, it remains a challenge for the industry to massively scale up resource production and focus on the recycling of battery metals in the future to meet the increasing consumption of electromobility.

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Forced Motion Activated Self-Alignment of Micro-CPV Solar Cells

2024 , Kaiser, Elisa , Wiesenfarth, Maike , Vareilles, Victor , Schneider-Ramelow, Martin , Glunz, Stefan , Helmers, Henning

In micro-concentrating photovoltaics (micro-CPV), the size of solar cells is reduced (<1x1 mm 2 ) compared to conventional CPV. However, the quantity and requirement for placement accuracy of solar cells is increased. To be economically competitive, a promising possibility for the die assembly is a high throughput and relatively unprecise pick and place process combined with surface tension-driven self-alignment of the liquid solder. In this article, this approach is experimentally investigated, with a focus on the influences of solder volume, receiving pad layouts, and initial displacements of the cells on the self-alignment accuracy. Here, we show that an induced motion due to the initial displacement of the cells or due to solder flow along tracks leads to a more robust and accurate process. We found that less solder and rather smaller pads than cells (here by 92 μm or 10.4% of the cell length) are beneficial for self-alignment accuracy. However, for micro-CPV, conductor tracks connected to the pad are required for electrical interconnection and heat dissipation. Here, all cells are self-aligned and reach an accuracy between -15 and +15 μm, which is mainly due to the cell-to-pad size difference. Optical simulations show that this displacement would lead to an optical loss of 0.1% abs instead of 12.1% abs when displacing the cell by 150 μm. Thus, the self-alignment using the surface tension of the liquid solder leads to sufficient accuracy.

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Investigation of failure mechanism of aluminum-scandium wire bond contact under active power cycle test

2023 , Yamaguchi, Tadashi , Suto, Yuya , Araki, Noritoshi , Eto, Motoki , Fischer, Felix , Groth, Anne

The failure mechanism of aluminum-scandium (Al-Sc) wire bond in comparison with pure Al wire bond under active power cycle (APC) test was investigated. To monitor the degradation of the bond quality, bond shear forces (shear force) were measured over the testing cycles at different level of temperature swing (ΔT). The results show that the Al-Sc wire bond was much more robust than the pure Al wire bond when the ΔT (Tmax) was mild. On the other hand, as the ΔT was increased, the shear force reduction in the Al-Sc wire bond became more and more remarkable. In the cross-sectional analysis of bond contact after the APC tests, a significant crack propagation was observed even for low ΔT conditions for the pure Al wire, and the crack progressed primarily on the wire side of the bond area. As for the Al-Sc wire, while the bond crack was efficiently suppressed for low ΔT conditions, a significant progress of crack was observed at high ΔT conditions, and the crack grew mainly through the Al pad side of the bond area. A detailed analysis at the bond interface after the APC test at high ΔT condition revealed three phenomena at the Al pad side of the bond area: grain coarsening, precipitation of Cu particles, and large void formation. As the material strength is compromised by these effects, the crack grew more easily through the Al pad side of the contact area, resulting in a rapid reduction of shear force at high ΔT. The bond failure mechanism obtained in this study will provide a valuable insight for the future development of high reliability power semiconductor device.

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Lovewear: Haptic Clothing that Allows Intimate Exploration for Movement-Impaired People

2023 , Corti, Emanuela , Parati, Ivan , Dils, Christian

People with disabilities often face physical, political, and societal barriers in expressing their sexuality. The lack of inclusivity in the sex toy market does not support an autonomous experience for impaired individuals who cannot operate toys without external assistance. Lovewear is a collaborative art-science project that combines user-centered design principles with soft robotics integrated into textiles. The aim is to offer an autonomous experience through haptic feedback, allowing self-exploration of intimate sensations and sexual pleasure to females with motor impairments. A pillow interface activates an underwear garment: While caressing and touching the pillow, the wearer triggers the underwear’s inflatable i actuators. This transdisciplinary project used a mixed-methods research design; the objective is to promote the embedment of technology into everyday garments, to improve the wearer’s quality of life.

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Sensor Systems for Extremely Harsh Environments

2023-10-31 , Kappert, Holger , Schopferer, Sebastian , Saeidi, Nooshin , Döring, Ralf , Ziesche, Steffen , Olowinsky, Alexander , Naumann, Falk , Jägle, Martin , Spanier, Malte , Grabmaier, Anton

Sensors are key elements for capturing environmental properties and are today indispensable in the industry for monitoring and control of industrial processes. Many applications are demanding for highly integrated intelligent sensors to meet the requirements on safety, clean and energy efficient operation or to gain process information in the context of industry 4.0. While in many everyday objects highly integrated sensor systems are already state of the art, the situation in an industrial environment is clearly different. Frequently the use of sensor systems is impossible, due to the fact that the extreme ambient conditions of industrial processes like high operating temperatures or strong mechanical loads do not allow a reliable operation of sensitive electronic components. Eight Fraunhofer Institutes have bundled their competencies and have run the Fraunhofer Lighthouse Project ‘eHarsh’ to overcome this situation. The project goal was to realize sensor systems for extremely harsh environments, whereby sensor systems are not only pure sensor elements, rather containing one or multiple sensor elements and integrated readout electronics. Various technologies which are necessary for the realization of such sensor systems have been identified, developed and finally bundled in a technology platform. These technologies are e. g. MEMS and ceramic based sensors, SOI-CMOS based integrated electronics, board assembly and laser based joining technologies. All these developments have been accompanied by comprehensive tests, material characterization and reliability simulations. Based on the platform a pressure sensor for turbine applications has been realized to prove the performance of the eHarsh technology platform.

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6 Core fiber and VCSEL based interferometer sensor for motion or vibration monitoring

2023 , Chorchos, Łukasz , Szostkiewicz, Łukasz , Ledentsov, Nikolay N. , Böttger, Gunnar , Turkiewicz, Jarosław P.

We demonstrate a XYZ motion / vibration sensor based on a 6-core fiber interferometer and a VCSEL lasers array. The sensor can detect changes in movement as low as 500 um and frequencies ranging from 1 Hz to 100 kHz with potential to extend this range further.

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Cu-Cu Thermocompression Bonding with a Self-Assembled Monolayer as Oxidation Protection for 3D/2.5D System Integration

2023 , Lykova, Maria , Panchenko, Juliana , Schneider-Ramelow, Martin , Suga, T. , Mu, F. , Buschbeck, R.

Cu-Cu direct interconnects are highly desirable for the microelectronic industry as they allow for significant reductions in the size and spacing of microcontacts. The main challenge associated with using Cu is its tendency to rapidly oxidize in air. This research paper describes a method of Cu passivation using a self-assembled monolayer (SAM) to protect the surface against oxidation. However, this approach faces two main challenges: the degradation of the SAM at room temperature in the ambient atmosphere and the monolayer desorption technique prior to Cu-Cu bonding. In this paper, the systematic investigation of these challenges and their possible solutions are presented. The methods used in this study include thermocompression (TC) bonding, X-ray photoelectron spectroscopy (XPS), shear strength testing, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results indicate nearly no Cu oxidation (4 at.%) for samples with SAM passivation in contrast to the bare Cu surface (27 at.%) after the storage at −18 °C in a conventional freezer for three weeks. Significant improvement was observed in the TC bonding with SAM after storage. The mean shear strength of the passivated samples reached 65.5 MPa without storage. The average shear strength values before and after the storage tests were 43% greater for samples with SAM than for the bare Cu surface. In conclusion, this study shows that Cu-Cu bonding technology can be improved by using SAM as an oxidation inhibitor, leading to a higher interconnect quality.

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