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The implementation of a novel, cost-effective PVDF piezo-film sensor array for unsteady wall-pressure measurements in supersonic flows is introduced. With this type of technique, multiple local pointwise measurements can be taken simultaneously from a single thin foil without disturbing the flow field. The paper presents a detailed explanation of the design of the sensor array and of its signal conditioning system. The sensor array is tested in a turbulent incident shockwave/boundary layer interaction (SBLI) at Mach 2 and validated through favorable comparison with a classical Kulite piezoresistive transducer. The results of unsteady wall-pressure measurements also show good agreement with other SBLI studies already presented in the literature.

This paper 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 MEMS SiC Device. By optimizing the process, etch depth of 200μm with an etch rate of up to 2μm/min can be achieved for via etching. In addition, a Design Of Experiments (DOE) with a total of 29 experiments with seven factors was done to characterize the deep etching of large areas into the silicon carbide. Hereby, vertical sidewalls with low micro masking, low micro trenching 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 micro electromechanical systems (MEMS) and high-power electronics. The developed etching technologies demonstrate and enable various applications for 3D Integration with wide bandgap substrates taking advantage of the superior electrical and mechanical properties of SiC.

Safety is a crucial issue in hydrogen energy applications due to the unique properties of hydrogen. Accordingly, a suitable hydrogen sensor for leakage detection must have at least high sensitivity and selectivity, rapid response/recovery, low power consumption and stable functionality, which requires further improvements on the available hydrogen sensors. In recent years, the mature development of nanomaterials engineering technologies, which facilitate the synthesis and modification of various materials, has opened up many possibilities for improving hydrogen sensing performance. Current research of hydrogen detection sensors based on both conservational and innovative materials are introduced in this review. This work mainly focuses on three material categories, i.e., transition metals, metal oxide semiconductors, and graphene and its derivatives. Different hydrogen sensing mechanisms, such as resistive, capacitive, optical and surface acoustic wave-based sensors, are also presented, and their sensing performances and influence based on different nanostructures and material combinations are compared and discussed, respectively. This review is concluded with a brief outlook and future development trends.

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 µm to a depth of 300 µm with a maximum etching rate of 4 µm/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.

From electronic devices to large-area electronics, from individual cells to skin substitutes, printing techniques are providing compelling applications in wide-ranging fields. Research has thus fueled the vision of a hybrid, printing platform to fabricate sensors/electronics and living engineered tissues simultaneously. Following this interest, we have fabricated interdigitated-electrode sensors (IDEs) by inkjet printing to monitor epithelial cell cultures. We have fabricated IDEs using flexible substrates with silver nanoparticles as a conductive element and SU-8 as the passivation layer. Our sensors are cytocompatible, have a topography that simulates microgrooves of 300 &micro, m width and ~4 &micro, m depth, and can be reused for cellular studies without detrimental in the electrical performance. To test the inkjet-printed sensors and demonstrate their potential use for monitoring laboratory-growth skin tissues, we have developed a real-time system and monitored label-free proliferation, migration, and detachment of keratinocytes by impedance spectroscopy. We have found that variations in the impedance correlate linearly to cell densities initially seeded and that the main component influencing the total impedance is the isolated effect of the cell membranes. Results obtained show that impedance can track cellular migration over the surface of the sensors, exhibiting a linear relationship with the standard method of image processing. Our results provide a useful approach for non-destructive in-situ monitoring of processes related to both in vitro epidermal models and wound healing with low-cost ink-jetted sensors. This type of flexible sensor as well as the impedance method are promising for the envisioned hybrid technology of 3D-bioprinted smart skin substitutes with built-in electronics.

This paper describes the research on the process development and process optimization of via etching of silicon carbide using reactive ion etching. The experiments were performed using a design of experiments (DOE) with a total 26 experiments and D-efficiency of over 85.4 finding the most significant process parameters impacting the etch result. Optimizing the process we could achieve etch depth of 200µm with an etch rate of up to 2µm/min. The ability of etching SiC with a high etch rate enables new application for harsh environments micro electromechanical systems (MEMS) and high power electronics.

The use of TSV (Through Silicon Via) technology has widely spread in the past decade. Its advantages in complexity reduction of the RDL (Redistribution Layer) and shortening the total routing length and also the reduction of total resistance of the RDL plus the possibility of higher integration lead to the successfully implementation. All these advantages are attractive for new application, which has been assembled and designed with planar technologies and wire bonding technologies before. Our target application are avalanche photo diodes, which are powered with high voltage. Standard TSV Process is designed with thin inorganic passivation liner deposition like silicon dioxide using PECVD which cannot withstand very high voltages because of breakthrough of the oxide [1]. Optical arrays with a higher pixel count cannot be unbundled in a conventional RDL anymore. The limit will be in the range of an 8x8 diode array. Making use of interposer technology this limitation can be overcome. In the presented work we used Backside Via Last TSV approach and used dry film BCB as passivation layer in the Via which has been opened using a 248 nm excimer laser. We measured the leakage current of the powered devices and observed a very low leakage currents as low as 15 pA at 160 V and a breakthrough of above 250 V

Graphene Nanoribbons (GNRs) are an emerging candidate to challenge the place of current semiconductor-based technology. In this work, we extend a model for Armchair Graphene Nanoribbons Field-Effect Transistor (AGNRFET) to the high-k dielectrics realm and examine the influences of quantum capacitance on its transient phenomena. The model is coded with Verilog-A and evaluated through SPICE simulations. We have considered a comparison between the extended model with and without the influence of the quantum capacitance. Simulation results show a realistic scenario where influence of the quantum capacitance significantly impacts the transient behaviour in circuit design. This proves the proposed model to be a valuable aid for the circuit design of future graphene-based applications.

This work is about the design, manufacturing process and characterization of an interdigital capacitor (IDC) sensor for graphene based biosensing applications. Certain layouts with different active sensor area and linespace ratios are investigated with analytic models and simulation models. Furthermore chips are manufactured and characterized on wafer level among the electrical parameters resistance and capacitance. The sensors have been used, for the detection of biomarkers through a functional layer reduced graphene oxide, immobilized with biomolecules, and characterized with low frequency electrochemical impedance spectroscopy (EIS). The aim is to identify the sensor layout with the best sensitivity at low frequency.

Three-dimensional printing and rapid prototyping are becoming more and more important in the field of research and low volume production. There are many systems that can print a wide variety of materials. In the field of thin-film technology, as required for MEMS applications, only a few approaches are available. One of the promising technologies in this field is sputtering at atmospheric pressure with miniaturized plasma sources. This paper introduces a new anode nozzle geometry that increases the productivity of this novel technology substantial. It shows that three-dimensional thin-film metal structures can be printed more economically.

In this paper, a second generation MEMS mass flow controller (MFC) for liquid fuel delivery to a miniaturized homogeneous charge compression ignition (HCCI) engine is presented. In contrast to the first generation MFC [1], it has a highly improved on/off-characteristic and fuel delivery range. This is achieved by a complete redesign of the valve cap and package, minimizing particles in the fuel outlet and package stress. Various fuels (and water) are calibrated, for instance, ethanol and water with maximum mass flow rates of 15 g/min and 20 g/min, respectively (at 100 kPa inlet pressure). The on/off-ratio with water is nearly 3300:1 (at 100 kPa inlet pressure). The maximum power consumption during continuous operation is 50 µW.

The paper describes the fabrication of high-density flex circuits based on wafer level redistribution technology. The systems are build up by sequential processing of polyimide layers and semi-additive structured metal layers on a temporary carrier wafer. With the final removal of the carrier only 20-50 µm thick flexible circuit layers are generated. The technology allows multi-layer routing with up to three levels having line pitches of 30 µm and 35 µm vias in staggered configuration using the standard process by photo structuring of the polymer. With an advanced process, line pitches of 14 µm with vias of 10 µm diameter in stacked configuration are possible using laser structuring of the polymer. As additional features, thin active ICs can be embedded into the flex layers and with a special release sequence a partial rigidness of the flex can be obtained. A 24 GHz radar module was fabricated as first demonstrator of the described flex technology featuring two embedded only 20 µm thin transceiver ICs per module. Due to a partial carrier release a rigid-flex configuration was obtained, which allows the antenna arrays of the module to be tilted relative to the center part of the module where the transceiver ICs and IOs are located. A vibration and stress sensor module was fabricated as second demonstrator with two only 20 µm thin stress and acceleration sensor chips integrated into a flex circuit. The flex with the acceleration sensor overhangs the rigid part of the module, which allows the detection of oscillations with high sensitivity.

Micro-Electro-Mechanical Systems (MEMS) devices are widely used for motion, pressure, light, and ultrasound sensing applications [...]

Anodic bonding technology is a well-established industrial technique, which is reported to be the most widely used MEMS packaging method. This Paper studies residual stress issue caused by different coefficients of thermal expansion (CTE) between silicon and glass during the anodic bonding process and its influence on MEMS-based sensors. For this purpose, SW-YY® Glass from ASAHI is selected. Firstly, the SW-YY® glass material is characterized in the bonding temperature range from 250°C to 500°C and voltage range from 400V-800V. Secondly, a MEMS based pressure sensor and two type glass substrates (SW-YY®, Pyrex®7740) were fabricated and bonded to evaluate the stress issue. Results show that the offset of the pressure sensor introduced by mismatched CTE was reduced significantly with SW-YY® glass than standard Pyrex® ®7740 glass. The proposed method can be used to reduce the influence of the internal stress caused with bonding temperature and the mismatched CTEs for stress sensitive MEMS.

In this paper we present a printed, fast, high-sensitive and cheap wireless incontinence sensor system, which could be integrated in a common diaper for urinary detection. The system consists of a flexible screen-printed IDEs (Inter Digital Electrodes) sensor with bio compatible conducting PEDOT:PSS material, a battery, a readout electronics for sensor signal and a wireless module.

Due to the growing numbers of elderly people in the world, who suffer from incontinence and are in the need of care, technologies are necessary to increase the effectiveness of nursing staff and enhance the hygiene for humans to improve life quality. For this reason a low cost humidity sensor system printed onto the substrate of a diaper with the novel organic conductive ink PEDOT:PSS (Poly (3,4-ethylenedioxythio-phene):Poly(styrene sulfonate)) was developed in previous work [1]. The novel material PEDOT:PSS is still expensive because of rare use in research and market demand. Therefore a way for optimization of the sensor is aimed to print the sensor with less material, but at the same time with no loss of sensitivity. With this purpose, two theoretical models are developed. An analytic model with geometrical based calculations and a Finite Element Analysis (FEA) simulation model, for deeper understanding of electric field effects with focus on the total capacitance of the sensor. To verify these theoretical models a characterization measurement of manufactured samples of previous work [1] is made, to obtain a comparison between every experimental method. For the theoretical models the necessary material parameters are characterized.

Piezoresistive mechanical sensors play a very important role in modern industries. MEMS pressure sensor market is one of the biggest markets among all MEMS components [1]. Global pressure sensor market is growing from $6.4 billion in 2012 to $8.8 billion in 2018. The main applications are automotive, medical, consumer electronics, industry and aerospace/defense. Today, there is a growing demand for cost effective high-temperature and harsh- environment semiconductor devices, capable of operating at temperatures in the 500 °C range. Developments in energy, aircraft and space applications, automotive electronics, the oil and gas industry, the plastic and chemical industry, and the military sector are among the main drivers for research on high-temperature sensors and electronics. Existing semiconductor devices based on silicon are limited to operating temperatures below 150 °C, as thermal generation of charge carriers severely degrades device operation at higher temperatures. The development of SOI (silicon on insulator) technology helped to extend device’s operating temperatures to approximately 400 °C. However, at temperatures over 400 °C, the material silicon reaches its physical limits as plastic deformation starts to occur when mechanical stress is applied. Silicon carbide is considered to be the most promising semiconductor for future high-temperature and harsh-environment applications as it features a unique combination of favorable physical, electrical, mechanical, and chemical properties. It is an extremely hard and robust material with a high thermal stability, and is chemically inert up to temperatures of several hundred degrees. Moreover, it has a higher thermal conductivity than copper, and its wide energy bandgap allows operation at high temperatures and in high radiation environments without suffering from intrinsic conduction effects. Performance and reliability of metal-semiconductor contacts, conducting paths and the capability of etching 3D mechanical structures in SiC (such membrane or bridge) remain limiting factors for high-temperature operation of SiC electronic mechanical sensors today. In this chapter we discuss and review materials (Silicon, pSOI, SOI, 3C-SiC and 4H/6H-SiC) and technologies, which are applicable to realize MEMS piezoresistive mechanical sensor elements for applications at elevated temperatures.

In this paper, we present our work developing a family of silicon-on-insulator (SOI)–based high-g micro-electro-mechanical systems (MEMS) piezoresistive sensors for measurement of accelerations up to 60,000 g. This paper presents the design, simulation, and manufacturing stages. The high-acceleration sensor is realized with one double-clamped beam carrying one transversal and one longitudinal piezoresistor on each end of the beam. The four piezoresistors are connected to a Wheatstone bridge. The piezoresistors are defined to 4400 Ω, which results in a width-to-depth geometry of the pn-junction of 14 μm × 1.8 μm. A finite element method (FEM) simulation model is used to determine the beam length, which complies with the resonance frequency and sensitivity. The geometry of the realized high-g sensor element is 3 × 2 × 1 mm3. To demonstrate the performance of the sensor, a shock wave bar is used to test the sensor, and a Polytec vibrometer is used as an acceleration reference. The sensor wave form tracks the laser signal very well up to 60,000 g. The sensor can be utilized in aerospace applications or in the control and detection of impact levels.

In the present work we investigate the quality of low temperature Plasma Enhanced Chemical Vapor Deposition (PECVD) and plasma treated Tetraethyl orthosilicate (TEOS)-based TSV-liner films. Different designs of Trough Silicon Via (TSV) Test structures with 10μm and 20μm width and a depth of 100μm have been fabricated. Two differently doped silicon substrates have been used – highly p-doped and moderately doped. The results for break-through, resistivity and capacitance for the 20μm structures show a better performance compared to the 10μm structures. This is mainly due to increased liner thickness in the reduced aspect ratio case. Lower interface traps and oxide charge densities have been observed in the C-V measurements results for the 10μm structures.

In the present work, an intermediate sodium-rich glass layer was deposited on silicon wafer by a PVD (Physical Vapor Deposition) process for further silicon to silicon anodic bonding. The anodic bonding process was carried out at low direct-current voltage of about 40 V–100 V and temperature from 320°C to 400°C. The concentration of alkali ion (sodium) in the deposited thin glass layer, the surface roughness of the thin film, and the bonding properties of the thin glass layer were studied in detail and later on this technology was used to fabricate a MEMS based pressure sensor (bonding voltage 40 V and bonding temperature 360°C). The infrared microscopy (IR) was used as the visual method to detect the bonding defects. The offset value was measured with varied temperature to check the stress issues. The purpose of the proposed method is to reduce the offset value for MEMS based pressure sensor by using the thin glass bonding layer. This novel method can be applied to the other type of MEMS sensors, which requires anodic bonding process to improve the performance.

This system consists of a pressure silicon sensor, calibration module and wireless module. The pressure sensor used in this work is a piezoresistive silicon sensor that developed by Technical University Berlin. After calibration of the sensors output signals, the XBee-chip was used for wireless transmission. The three components with peripheral circuits and batteries were integrated in a 50mm × 50mm PCB. The system was then tested in a climate chamber at different temperatures and pressures. Programs for signal receiving and processing were developed in Matlab-environment. The experimental results show that this system works well for the short range (15m indoor).

The piezoresistive silicon pressure sensor used in this work is developed by Technical University Berlin. It is mainly composed of a silicon-membrane and four implanted piezoresistors connected in form of a Wheatstone bridge. After wire bonding, the sensor was evaluated in a climate cabinet at different temperatures and pressures. The characteristic curve of the sensor shows its good linearity and strong dependence on the temperature. The sensor ́s temperature coefficient of sensitivity and zero shift were compensated using ASIC MLX90308. The experimental results show that this method of compensation accurately solved the sensors temperature dependence problems.

In this paper we present a high reliable, accurate and safe, solid state pressure sensor for high temperature applications. The sensor is based on an unique fluid-free technology using a piezoresistive SOI-based chip enclosed in a sealed metal housing. The proprietary housing concept allows a complete separation of the SOI-chip from the measured media. A thick steel membrane and an elongated member (push-rod) transfer the outside pressure into a small deflection of a silicon membrane on the SOI-chip. The thin silicon membrane is engraved by DRIE (Deep Reactive Ion Etching). The sensor is capable to measure pressures up to 1000 bar at temperature up to 400 °C with an accuracy of ±0,50%FSO. A digital correction enables a compensation of Offset and Sensitivity thermal drifts. The sensor can undergo long-term extreme working conditions without losing its performances.

The number of elderly and care dependent persons is continuously increasing. The percentage of people over 60 years rises worldwide from 10% in 2000 to 21 % of the world's population in 2050. [1] The usage of wearable sensors in combination with telemedicine have a big potential to ensure a continuous healthcare and nursing of chronically ill and old patients and to enable them an independent life into old age. [2] The development and assembly of a modular low-power multi-sensor platform with wireless data transmission allows to set up a specific sensor network depending on location and application on the body. The wearable electronics consisting of a gyroscope, temperature and pressure sensors and low-power microcontroller with Bluetooth transmitter are integrated into a shoe insole and encapsulated in silicone as a first prototype. This smart sensor insole measures the vital and body data to monitor the patient's physical activity. Advanced sensor analysis enables to detect a fall of the wearer, which can be triggered to call for help from nurses or relatives. In a further development an energy harvesting version including a rechargeable microbattery and battery management system leads the way to an energy-autarkic operation and maintenance-free telemedical patients monitoring for homecare and ambient assisted living of our aging and digitalized society.