Universität Stuttgart
Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1
Browse
20 results
Search Results
Item Open Access Mass-producible micro-optical elements by injection compression molding and focused ion beam structured titanium molding tools(2020) Ristok, Simon; Roeder, Marcel; Thiele, Simon; Hentschel, Mario; Guenther, Thomas; Zimmermann, André; Herkommer, Alois; Giessen, HaraldItem Open Access Use of PtC nanotips for low-voltage quantum tunneling applications(2022) Haub, Michael; Guenther, Thomas; Bogner, Martin; Zimmermann, AndréThe use of focused ion and focused electron beam (FIB/FEB) technology permits the fabrication of micro- and nanometer scale geometries. Therefore, FIB/FEB technology is a favorable technique for preparing TEM lamellae, nanocontacts, or nanowires and repairing electronic circuits. This work investigates FIB/FEB technology as a tool for nanotip fabrication and quantum mechanical tunneling applications at a low tunneling voltage. Using a gas injection system (GIS), the Ga-FIB and FEB technology allows both additive and subtractive fabrication of arbitrary structures. Using energy dispersive X-ray spectroscopy (EDX), resistance measurement (RM), and scanning tunneling microscope (STM)/spectroscopy (STS) methods, the tunneling suitability of the utilized metal–organic material–platinum carbon (PtC) is investigated. Thus, to create electrode tips with radii down to 15 nm, a stable and reproducible process has to be developed. The metal–organic microstructure analysis shows suitable FIB parameters for the tunneling effect at high aperture currents (260 pA, 30 kV). These are required to ensure the suitability of the electrodes for the tunneling effect by an increased platinum content (EDX), a low resistivity (RM), and a small band gap (STM). The STM application allows the imaging of highly oriented pyrolytic graphite (HOPG) layers and demonstrates the tunneling suitability of PtC electrodes based on high FIB aperture currents and a low tunneling voltage.Item Open Access Analysis of tempering effects on LDS-MID and PCB substrates for HF applications(2023) Wolf, Marius; Werum, Kai; Guenther, Thomas; Schleeh, Lisa; Eberhardt, Wolfgang; Zimmermann, AndréMechatronic Integrated Devices or Molded Interconnect Devices (MID) are three-dimensional (3D) circuit carriers. They are mainly fabricated by laser direct structuring (LDS) and subsequent electroless copper plating of an injection molded 3D substrate. Such LDS-MID are used in many applications today, especially antennas. However, in high frequency (HF) systems in 5G and radar applications, the demand on 3D circuit carriers and antennas increases. Electroless copper, widely used in MID, has significantly lower electrical conductivity compared to pure copper. Its lower conductivity increases electrical loss, especially at higher frequencies, where signal budget is critical. Heat treatment of electroless copper deposits can improve their conductivity and adhesion to the 3D substrates. This paper investigates the effects induced by tempering processes on the metallization of LDS-MID substrates. As a reference, HF Printed Circuit Boards (PCB) substrates are also considered. Adhesion strength and conductivity measurements, as well as permittivity and loss angle measurements up to 1 GHz, were carried out before and after tempering processes. The main influencing factors on the tempering results were found to be tempering temperature, atmosphere, and time. Process parameters like the heating rate or applied surface finishes had only a minor impact on the results. It was found that tempering LDS-MID substrates can improve the copper adhesion and lower their electrical resistance significantly, especially for plastics with a high melting temperature. Both improvements could improve the reliability of LDS-MID, especially in high frequency applications. Firstly, because increased copper adhesion can prevent delamination and, secondly, because the lowered electrical resistance indicates, in accordance with the available literature, a more ductile copper metallization and thus a lower risk of microcracks.Item Open Access Injection compression molded microlens arrays for hyperspectral imaging(2018) Röder, Marcel; Drexler, Marc; Rothermel, Thilo; Meissner, Thomas; Guenther, Thomas; Zimmermann, AndréItem Open Access Direct processing of PVD hard coatings via focused ion beam milling for microinjection molding(2023) Ruehl, Holger; Guenther, Thomas; Zimmermann, AndréHard coatings can be applied onto microstructured molds to influence wear, form filling and demolding behaviors in microinjection molding. As an alternative to this conventional manufacturing procedure, “direct processing” of physical-vapor-deposited (PVD) hard coatings was investigated in this study, by fabricating submicron features directly into the coatings for a subsequent replication via molding. Different diamondlike carbon (DLC) and chromium nitride (CrN) PVD coatings were investigated regarding their suitability for focused ion beam (FIB) milling and microinjection molding using microscope imaging and areal roughness measurements. Each coating type was deposited onto high-gloss polished mold inserts. A specific test pattern containing different submicron features was then FIB-milled into the coatings using varied FIB parameters. The milling results were found to be influenced by the coating morphology and grain microstructure. Using injection–compression molding, the submicron structures were molded onto polycarbonate (PC) and cyclic olefin polymer (COP). The molding results revealed contrasting molding performances for the studied coatings and polymers. For CrN and PC, a sufficient replication fidelity based on AFM measurements was achieved. In contrast, only an insufficient molding result could be obtained for the DLC. No abrasive wear or coating delamination could be found after molding.Item Open Access Open-eco-innovation for SMEs with pan-European key enabling technology centres(2020) Civelek, Faruk; Kulkarni, Romit; Fritz, Karl-Peter; Meyer, Tanja; Troulos, Costas; Guenther, Thomas; Zimmermann, AndréThe project “key enabling technologies for clean production” (KET4CP), which is supported by the European Commission, has the aim to connect small and medium-sized enterprises (SME) and Technology Centres (TC) for cleaner, greener and more efficient production. Within this context, SMEs and TCs across Europe work together to establish an open-innovation network and to raise awareness in productivity and environmental performance. This article presents how an open European network of TCs opens its innovation process to support SMEs to become cleaner, greener and more efficient. Furthermore, this article shows how the TCs and SMEs become a part of the open-eco-innovation platform in clean production and how successful the open-eco-innovation process of different European countries is. We revealed that a pan-European open innovation process for eco-innovations with TCs for key enabling technologies (KET TCs) and Enterprise Europe Network partners (EEN) is a successful approach for SMEs that want to produce and develop cleaner products. An application example is mentioned, in which TCs from different European countries have contributed to developing a product of a SME for energy harvesting. The SME, together with the TCs, developed a generator that is installed in city-level water supply pipes and so, it is outstanding in its application. This innovative application is also described in this article.Item Open Access FIB-SEM tomography for porosity characterization of inkjet printed nanoparticle gold ink(2024) Ruehl, Holger; Reguigui, Hajer; Guenther, Thomas; Zimmermann, AndréInkjet printing is a versatile technology for the manufacturing of electronic devices to be used in various applications [1,2]. Common inks to create conductive layers are suspensions of a solvent with metal nanoparticles such as gold or silver [3]. After the deposition and solidification of an ink on a substrate, the metal nanoparticles are sintered to realize the conductivity of the printed layer. A porous, solid metal matrix remains, whereby the conductivity of the metal layer tends to be dependent on the porosity. To characterize the porosity of inkjet printed conductive layers, focused ion beam-scanning electron microscope (FIB-SEM) tomography is suggested as a potential characterization method in the presented study. For the experiment, a wafer diced silicon substrate with size of 10 x 10 mm² was used, onto which a 1.2 µm thin layer of commercially available nanoparticle gold ink was inkjet printed and then sintered. Subsequently, a four-step procedure for the FIB-SEM tomography-based porosity characterization was performed: 1) FIB preparation of the volume of interest (VOI), 2) serial sectioning including image acquisition, 3) image processing and 4) 3D-reconstruction and porosity analysis. The steps 1) and 2) were conducted using a FIB-SEM dual beam system ZEISS AURIGA 40 (Carl Zeiss Microscopy Deutschland GmbH, Germany). Prior to serial sectioning, a thin platinum layer was FIB induced deposited on top of the inkjet printed gold layer. A cube-shaped VOI with the size 5000 x 6000 x 5000 nm³ was then prepared by FIB milling. The surface to be sectioned was end face polished and a line trench serving as a reference marker for the image processing was milled along the VOI. The prepared VOI prior to FIB sectioning is shown in Figure 1. a). Next, the serial sectioning was conducted. The ion acceleration voltage was set to 30 kV. The aperture current was set to 50 pA, resulting in an ion beam spot size of 12.5 nm, which corresponds to the section slice thickness. No melting and re-sintering of the solid metal structure could be observed during sectioning. SEM images of the revealing surface areas were acquired with 1024 x 768 pixels image resolution and a pixel size of 5.82 nm. Both a secondary electron (SE) detector as well as a backscattered electron (BSE) detector were used for imaging. In total, a 2D stack of 368 SEM images was recorded. For comparison of individual sections, Figure 1. b) and c) show BSE detector images of the cross-sectioned VOI after slice 70 and slice 140. One can clearly see that the size and distribution of sintered metal particles varies along the VOI, forming a porosity network within the solid gold. Since the images acquired with the BSE detector presented a higher contrast and thus, a better distinction between the pores and the metal structure, these images were used for the image processing and final porosity analysis, for which the software AVIZO (Thermo Fisher Scientific Inc., USA) was used. First, the 2D images were aligned to correct for the shifts which occurred during the serial sectioning. Then, a sub-VOI was cropped out to exclude the reference line. The new 3D VOI was of a size of 3026 x 1164 x 2750 nm³, representing a stack of BSE detector images ranging from slice 30 to 250. Noise interference was minimized by applying a Gaussian filter. Afterwards, thresholding was applied as a segmentation technique to differentiate between pores and the solid gold as well as erosion as morphological operation. As a result, a reconstructed 3D model of the pores located in the solid gold was obtained, as shown in Figure 2. a). Using this 3D pore model, the number of pores and their diameters within the VOI could be determined. For the calculation of the pore diameters, each pore was considered to be of a spherical shape. A total of 1509 pores was counted. The pore diameter distribution is shown in the box plot in Figure 2. b). As it can be obtained from Figure 2. b), a pore size of 23 nm represents the lower quartile, while a pore size of 112 nm represents the upper quartile. The median pore size is 44 nm, while the mean is 63 nm, which indicates a trend towards smaller pores surrounded by larger pores. Based on the obtained results, FIB-SEM tomography with subsequent image processing is assessed by the authors to be a proper method to characterize the porosity of inkjet printed conductive layers, which was tested by means of a nanoparticle gold ink.Item Open Access Development and proof of concept of a miniaturized MEMS quantum tunneling accelerometer cased on PtC tips by focused ion beam 3D nano-patterning(2021) Haub, Michael; Bogner, Martin; Guenther, Thomas; Zimmermann, André; Sandmaier, HermannMost accelerometers today are based on the capacitive principle. However, further miniaturization for micro integration of those sensors leads to a poorer signal-to-noise ratio due to a small total area of the capacitor plates. Thus, other transducer principles should be taken into account to develop smaller sensors. This paper presents the development and realization of a miniaturized accelerometer based on the tunneling effect, whereas its highly sensitive effect regarding the tunneling distance is used to detect small deflections in the range of sub-nm. The spring-mass-system is manufactured by a surface micro-machining foundry process. The area of the shown polysilicon (PolySi) sensor structures has a size smaller than 100 µm × 50 µm (L × W). The tunneling electrodes are placed and patterned by a focused ion beam (FIB) and gas injection system (GIS) with MeCpPtMe3 as a precursor. A dual-beam system enables maximum flexibility for post-processing of the spring-mass-system and patterning of sharp tips with radii in the range of a few nm and initial distances between the electrodes of about 30-300 nm. The use of metal–organic precursor material platinum carbon (PtC) limits the tunneling currents to about 150 pA due to the high inherent resistance. The measuring range is set to 20 g. The sensitivity of the sensor signal, which depends exponentially on the electrode distance due to the tunneling effect, ranges from 0.4 pA/g at 0 g in the sensor operational point up to 20.9 pA/g at 20 g. The acceleration-equivalent thermal noise amplitude is calculated to be 2.4-3.4 mg/√Hz. Electrostatic actuators are used to lead the electrodes in distances where direct quantum tunneling occurs.Item Open Access Investigation of focused ion and electron beam platinum carbon nano-tips with transmission electron microscopy for quantum tunneling vacuum gap applications(2021) Haub, Michael; Guenther, Thomas; Bogner, Martin; Zimmermann, AndréTo realize quantum tunneling applications with movable electrodes, sharp tips with radii down to several tens of nanometers are necessary. The use of a focused ion beam (FIB) and focused electron beam (FEB) with a gas injection system (GIS) allows the integration of geometries in the nanoscale directly into micro and nano systems. However, the implementation of the tunneling effect clearly depends on the material. In this work, a metal-organic precursor is used. The investigation of the prepared tunneling electrodes enables an insight into FIB/FEB parameters for the realization of quantum tunneling applications. For this purpose, a high-resolution transmission electron microscopy (HRTEM) analysis is performed. The results show a dependence of the material nanostructure regarding platinum (Pt) grain size and distribution in an amorphous carbon matrix from the used beam and the FIB currents. The integration of the tips into a polysilicon (PolySi) beam and measuring the current signal by approaching the tips show significant differences in the results. Moreover, the approach of FEB tips shows a non-contact behavior even when the tips are squeezed together. The contact behavior depends on the grain size, proportion of platinum, and the amount of amorphous carbon in the microstructure, especially at the edge area of the tips. This study shows significant differences in the nanostructure between FIB and FEB tips, particularly for the FIB tips: The higher the ion current, the greater the platinum content, the finer the grain size, and the higher the probability of a tunneling current by approaching the tips.Item Open Access Characterization and benchmark of a novel capacitive and fluidic inclination sensor(2021) Schwenck, Adrian; Guenther, Thomas; Zimmermann, AndréIn this paper, a fluidic capacitive inclination sensor is presented and compared to three types of silicon-based microelectromechanical system (MEMS) accelerometers. MEMS accelerometers are commonly used for tilt measurement. They can only be manufactured by large companies with clean-room technology due to the high requirements during assembly. In contrast, the fluidic sensor can be produced by small- and medium-sized enterprises (SMEs) as well, since only surface mount technologies (SMT) are required. Three different variants of the fluidic sensor were investigated. Two variants using stacked printed circuit boards (PCBs) and one variant with 3D-molded interconnect devices (MIDs) to form the sensor element are presented. Allan deviation, non-repeatability, hysteresis, and offset temperature stability were measured to compare the sensors. Within the fluidic sensors, the PCB variant with two sensor cavities performed best regarding all the measurement results except non-repeatability. Regarding bias stability, white noise, which was determined from the Allan deviation, and hysteresis, the fluidic sensors outperformed the MEMS-based sensors. The accelerometer Analog Devices ADXL355 offers slightly better results regarding offset temperature stability and non-repeatability. The MEMS sensors Bosch BMA280 and TDK InvenSense MPU6500 do not match the performance of fluidic sensors in any category. Their advantages are the favorable price and the smaller package. From the investigations, it can be concluded that the fluidic sensor is competitive in the targeted price range, especially for applications with extended requirements regarding bias stability, noise, and hysteresis.