The next generation of satellites will need to tackle tomorrow's challenges for communication, navigation and observation. In order to do so, it is expected that the amount of satellites in orbit will keep increasing, form smart constellations and miniaturize individual satellites to make access to space cost effective. To enable this next generation of activities in space, it is vital to ensure the ability of these satellites to properly navigate themselves. This control starts with attitude measurement by the dedicated sensors on the satellite, commonly performed by sun position sensors. The state-of-the art is confronted by large signal distortions caused by light reflected by the Earth's albedo as well as keeping up with the satellite miniaturization trend. This work aims to address both these issues, by presenting a microfabricated albedo insensitive sun position sensor in silicon carbide with wafer-level integrated optics. The presented 10 mm×10 mm×1 mm system reaches a mean angular accuracy of 5.7° in a ±37° field-of-view and integrates an on-chip temperature sensor with a -3.9 mV K⁻¹ sensitivity in the 20 °C to 200 °C range.

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The wide bandgap of silicon carbide (SiC) has attracted a large interest over the past years in many research fields, such as power electronics, high operation temperature circuits, harsh environmental sensing, and more. To facilitate research on complex integrated SiC circuits, ensure reproducibility, and cut down cost, the availability of a low-voltage SiC technology for integrated circuits is of paramount importance. Here, we report on a scalable and open state-of-the-art SiC CMOS technology that addresses this need. An overview of technology parameters, including MOSFET threshold voltage, subthreshold slope, slope factor, and process transconductance, is reported. Conventional integrated digital and analog circuits, ranging from inverters to a 2-bit analog-to-digital converter, are reported. First yield predictions for both analog and digital circuits show great potential for increasing the amount of integrated devices in future applications.

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This work demonstrates the first on-chip UV optoelectronic integration in 4H-SiC CMOS, which includes an image sensor with 64 active pixels and a total of 1263 transistors on a 100 mm2 chip. The reported image sensor offers serial digital, analog, and 2-bit ADC outputs and operates at 0.39 Hz with a maximum power consumption of 60 μW, which are significant improvements over previous reports. UV optoelectronics have applications in flame detection, satellites, astronomy, UV photography, and healthcare. The complexity of this optoelectronic system paves the way for new applications such harsh environment microcontrollers.@en

In this paper, stability and mechanistic simulations for a four-beam-mass-based MEMS gravimeter were conducted, and guidelines for the gravimeter design were proposed. Based on a prototyped MEMS device, the nonlinear finite element model was validated first against the experimental results. Then, we demonstrated three different scenarios in design that have three distinct modes of deformation: the mode with buckling (case 1), the mode without buckling but with a single zero-stiffness point (case 2), and the mode without both buckling and zero-stiffness point (case 3). Both case 1 and case 2 presented an unstable and sensitive region, in which a tiny perturbation could result in a rapid increase of the resonance frequency. Case 3, on the other hand, could provide a stable and low resonance frequency with a linear relationship between the displacement and gravitational acceleration. An optimized design of a beam/spring-mass-based relative gravimeter could be achieved using the above guidelines.

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Accurately sensing the temperature in silicon carbide (power) devices is of great importance to their reliable operation. Here, temperature sensors by resistive and CMOS structures are fabricated and characterized in an open silicon carbide CMOS technology. Over a range of 25-200°C, doped design layers have negative temperature coefficients of resistance, with a maximum change of 79%. Secondly, CMOS devices are used to implement a CTAT, which achieves a maximum sensitivity of 7.5mV/K in a temperature range of 25-165°C. The integration of readout electronics and sensors that are capable of operation in higher temperature than silicon, opens application in harsher environments.@en

The application of pressure sensors in harsh environments is typically hindered by the stability of the material over long periods of time. This work focuses on the design and fabrication of surface micromachined Pirani gauges which are designed to be compatible with state-of-the-art Silicon Carbide CMOS technology. Such an integrated platform would boost harsh environment compatibility while reducing the required packaging complexity. An analytical model was derived describing the design variables of the Pirani gauges followed by Finite Element Analysis. The Pirani gauges were fabricated in a CMOS compatible cleanroom with a process employing only three masks, thus suitable for mass production. The SiC-based Pirani gauge is far more competitive than the traditional Si-based Pirani gauge in terms of endurance in high-temperature environments. From 25°C to 650°C, the gauge shows a reproducible response to pressure changes and has a maximum sensitivity of $17.63~\Omega $ /Pa at room temperature, and of $1.23~\Omega $ /Pa at 650°C. Additionally, some of the gauges were demonstrated to operate at temperatures up to 750°C.

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This paper presents a continuous-time integrated readout interface for inertial sensors with high energy efficiency and high resolution. A dual digital-to-analog conversion (dual DAC) scheme is proposed which reduces the large DC baseline capacitance while preserving a high gain in the capacitance-to-voltage converter (CVC). A continuous-time delta-sigma modulator (CTΔΣM) is used to digitize the output signal of the CVC without kT/C noise. This results in a precision capacitive readout IC with a 5.5aF resolution in 0.5ms conversion time. It consumes 1.8mW. An inertial sensing system, consisting of the readout IC and a MEMS inertial sensor, achieves a resolution of 17.02ng/√Hz.@en

Exhaust gas measurement in the harsh environment of the tailpipe of a combustion engine by optical techniques is a highly robust technique, provided that optical access is maintained in the presence of particulate matter (PM). The considerations are presented for the systematic design of membranes with integrated heaters in SiC-on-Si technology for generating a well-defined lateral temperature profile with peak temperatures above 600 °C. Periodically raising the temperature of the membranes to such a level is demonstrated to keep the surface transparent by oxidation of soot deposits. This paper is about continuous heating of the membrane to a temperature slightly higher than that of the exhaust gas. At such temperatures thermophoretic repulsion of PM allows allows long-term optical measurement in the exhaust without the thermo-mechanical loading by repetitive thermal cycling.@en

The resistive particulate matter sensor is a simple device that transduces the presence of soot through impedance change across inter-digital electrodes (IDEs). We investigate the information provided by impedance spectroscopy over the frequency range from 100 Hz to 10 kHz for two purposes. The first is to investigate the opportunities for an improved sensor response to particulate matter (PM), based on the additional information provided by the measurement of both the in-phase (resistive) and out-of-phase (capacitive) components of the change in impedance over this frequency range as compared to DC resistance measurement only. Secondly, the origin of the capacitive response of the device is investigated from the perspective that soot on the device is in the form of bendable dendrites that grow in three dimensions. An IDE structure with the housing acting as an additional suspended electrode for introducing a controllable vertical electric field component has been used for this purpose. The formation of dipoles, due to bending of the charged dendrites, is found to be the source of the capacitive response. Simulation of electrostatic soot deposition reinforces dendritic self-assembly mechanisms, driven by charged particle trajectories along electric field lines. Optical microscopy confirms that dendrites growing out of the substrate plane are sensitive to electric and flow forces, bending when force balances are appropriate. We also apply impedance spectroscopy under varying electric field strengths, showing that capacitive response is only observed when conditions are conducive to dendrite bending in response to the applied AC electric fields.

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Traditional lighting is focused on the prevention of hardware failures. With the trend towards controlled and connected systems, other components will start playing an equal role in the reliability of it. Here reliability needs to be replaced by availability and other modeling approaches are to be considered. System prognostics and health management is the next step to service the connected complex systems in the most effective way possible. In this chapter, we will highlight the next frontiers that will need to be taken in order to move the traditional lighting catastrophic failure thinking into a thinking more towards new ways how system (degraded) functions can fail or be compromised. Results in the failure mode of lumen maintenance and its uncertainty are presented. An industrial use case is presented demonstrating how smart lighting will eventually be able to forecast maintenance schedules more efficiently.@en

Ensuring optical transparency over a wide spectral range of a window with a view into the tailpipe of the combustion engine, while it is exposed to the harsh environment of sootcontaining exhaust gas, is an essential pre-requisite for introducing optical techniques for long-term monitoring of automotive emissions. Therefore, a regenerable window composed of an optically transparent polysilicon-carbide membrane with a diameter ranging from 100 µm up to 2000 µm has been fabricated in microelectromechanical systems (MEMS) technology. In the first operating mode, window transparency is periodically restored by pulsed heating of the membrane using an integrated resistor for heating to temperatures that result in oxidation of deposited soot (600–700 °C). In the second mode, the membrane is kept transparent by repelling soot particles using thermophoresis. The same integrated resistor is used to yield a temperature gradient by continuous moderate-temperature heating. Realized devices have been subjected to laboratory soot exposure experiments. Membrane temperatures exceeding 500 °C have been achieved without damage to the membrane. Moreover, heating of membranes to ΔT = 40 °C above gas temperature provides sufficient thermophoretic repulsion to prevent particle deposition and maintain transparency at high soot exposure, while non-heated identical membranes on the same die and at the same exposure are heavily contaminated.

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In the coming decade, the development in the area of More than Moore will certainly take over from Moore’s Law. Sensor development and sensor integration will prevail above lower node development. New packaging solutions will be developed which will fuel the integration of sensors. These developments can still be silicon based but where harsh environments are involved wide-bandgap (WBG) materials, such as gallium nitride (GaN) or silicon carbide (SiC), will take over the development efforts spend. In this chapter, the use of WBG SiC material is discussed and reviewed towards possible applications for sensing under harsh environment exposure.@en

A micro-scale pressure sensor based on suspended AlGaN/GaN heterostructure is reported with non-linear sensitivity. By sealing the cavity, vacuum sensing at various temperatures was demonstrated. To validate the proposed concept of the AlGaN/GaN vacuum sensor, a 700 µm diameter circular membrane was electrically characterized under applied static and dynamic pressures at various temperatures ranging from 25 °C to 100 °C. The current change of the AlGaN/GaN heterostructure increased as the vacuum and temperature increases due to the increase of 2DEG density by tensile strain. The dynamic current change from 96 kPa down to 10 Pa of AlGaN/GaN heterostructure pressure sensor was 18.75 % at 100 °C. The maximum sensitivity reached 22.8 %/kPa with a power consumption of 1.8 µW. These results suggest that suspended AlGaN/GaN heterostructures are promising for high vacuum and high-temperature sensing applications.@en

Decision-making on the optimum transition pathway to an energy economy that meets agreed carbon reduction goals in the European Union (EU) by 2050 is challenging, because of the size of the infrastructural legacy, technological uncertainties, affordability and assumptions on future energy demand. This task is even more complicated in transportation because of additional issues, such as minimum travel range at acceptable impact on payload and ensuring hazzle-free long-distance driving in case of regionally varying fuel economies. Biofuels were the first viable option for a large-scale partly renewable fuel economy. E10 and B7 fuels have been successfully and remarkably smoothly introduced, owing to the fact that these are liquid and can be used in conventional combustion engines with little impact on full-tank travel range. In contrast, the decision-making process on biofuels in the EU has been particularly turbulent, with an initially favourable assessment changing into controversial. Here the compatibility between the fuel economies of member states and avoidance of disruptive social effects are considered as essential pre-requisite of a viable transition pathway. Rebalancing three different aspects of the social dimension of sustainability is used to demonstrate that a succession of infrastructures based on liquid fuels, with biofuels as an interlock towards an economy that includes methanol-based eFuel, has the potential to bring continuity, reduce dependence on anticipated technological advances and improve cost management. Awareness of this underexposed prospect of biofuel may positively affect the assessment on its role in a low-carbon fuel economy, potentially influencing the current decision-making process on biofuels.

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Exhaust gas measurement in the harsh environment of the tailpipe by optical techniques is a highly robust technique, provided that optical access is maintained in the presence of soot. The design, fabrication, and testing of membranes in SiC-on-Si with integrated heaters to serve as a regenerable MEMS optical window into the tailpipe are presented. Membranes at slightly elevated temperatures are demonstrated to keep the surface transparent by thermophoresis, while surface regeneration is achieved at pulsed high temperatures, which allows long-term optical measurement in the exhaust.

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This work focusses on the design and fabrication of surface micromachined pressure sensors, designed in a modular way for the integration with analog front-end read-out electronics. Polycrystalline 3C silicon carbide (SiC) was used to fabricate free-standing high topography cavities exploiting surface micromaching. The poly-SiC was in-situ doped and the membrane itself is used as piezoresistive element, thereby forming a so-called self-sensing membrane, easing fabrication. After sacrificial release, the cavity is sealed by conformal deposition of poly-SiC whereby the reference pressure of the absolute pressure sensor is determined. Aluminum and titanium metallizations were used and ohmic contacts were confirmed by wafer-scale measurements. Measurements were carried out on different devices ranging from 100 kPa down to 10 Pa at room temperature. The Wheatstone bridge yields a logarithmic response of 1.1 mVbar-1 V-1. A square 300 μ m device exhibits a logarithmic impedance behavior yielding a response of Δ R/R of 1.6× 10-3 bar-1. The realized pressure devices are a first step toward a SiC ASIC + MEMS platform for intended operation in harsh environments, such as industrial process monitoring, combustion control or structural health monitoring. The future outlook of the integration concept implies extended functionality by front-end transducer read-out, signal amplification and communication.

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Impedance spectroscopy in the frequency range 100 Hz to 10 kHz has been applied to the Inter-Digitated Electrode (IDE) structure that is conventionally operated as a resistive sensor for the measurement of Particulate Matter (PM). The measurement of both the in-phase (resistive) and out-of-phase (capacitive) components of the impedance over this frequency range provides more data on PM as compared to DC resistance measurement only. Experimental validation confirms a more gradual change in capacitance with soot buildup as compared to the sudden reduction of resistance with dendrite formation. The effect of an additional vertical electric field for an increased capacitive sensitivity due to stimulated soot buildup has been experimentally investigated using the electrically conductive flow housing of the IDE structure as an additional suspended electrode.@en

Commercially available gravimeters and seismometers can be used for measuring Earth’s acceleration at resolution levels in the order of ng∕Hz (where g represents earth’s gravity) but they are typically high-cost and bulky. In this work the design of a bulk micromachined MEMS device exploiting non-linear buckling behaviour is described, aiming for ng∕Hz resolution by maximising mechanical and capacitive sensitivity. High mechanical sensitivity is obtained through low structural stiffness. Near-zero stiffness is achieved through geometric design and large deformation into a region where the mechanism is statically balanced or neutrally stable. Moreover, the device has an integrated capacitive comb transducer and makes use of a high-resolution impedance readout ASIC. The sensitivity from displacement to a change in capacitance was maximised within the design and process boundaries given, by making use of a trench isolation technique and exploiting the large-displacement behaviour of the device. The measurement results demonstrate that the resonance frequency can be tuned from 8.7 Hz–18.7 Hz, depending on the process parameters and the tilt of the device. In this system, which combines an integrated capacitive transducer with a sensitivity of 2.55 aF/nm and an impedance readout chip, the theoretically achievable system resolution equals 17.02 ng∕Hz. The small size of the device and the use of integrated readout electronics allow for a wide range of practical applications for data collection aimed at the internet of things.@en

The mechanical part of inertial sensors can be designed to have a large mechanical sensitivity, but also requires the transduction mechanism which translates this displacement. The overall system resolution in mechanical inertial sensors is dictated by the noise contribution of each stage and the magnitude of each sensitivity, see also Figure 1. Maximizing the capacitive sensitivity, results in suppression of noise in the electronics domain. This work focuses on the design and realization of a mechanical to electrical transduction using a capacitive readout scheme. Design considerations and measures are taken to maximize the latter are considered and illustrated using FEM simulations. A capacitive transducer showing a sensitivity of 100 [aF/nm] was designed and realized, by exploiting the large displacement behavior of the inertial sensor which was considered.

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