No abstract

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.

Commercially available gravimeters and seismometers can be used for measuring Earth's acceleration at resolution levels in the order of ng= ffiffiffiffiffiffi Hz p (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= ffiffiffiffiffiffi Hz p 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= ffiffiffiffiffiffi Hz p. 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.

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 hightemperature environments. From 25°C to 650°C, the gauge shows a reproducible response to pressure changes and has a maximum sensitivity of 17.63 Ω/Pa at room temperature, and of 1.23 Ω/Pa at 650°C. Additionally, some of the gauges were demonstrated to operate at temperatures up to 750°C.

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 μm device exhibits a logarithmic impedance behavior yielding a response of 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.

Since it is obvious that Moore's Law in its classical way of scaling, which proved to be powerful over the last decades, is coming to an end, alternative routes towards technological progress are investigated [1]. One of the main fundamental reasons for this is that the smallest features size in newest technology nodes is approaching the level of only a few atom layers. As a result, the development and implementation of technology nodes based on a scaled-down version of the previous one, gets increasingly more expensive. An alternative approach to ensure technological progress of the microelectronics world and the semiconductor industry is described by a trend called "More than Moore" (MtM) [2], based on diversification and integration. In terms of diversification, materials beyond silicon can be considered for the development of sensors and electronics, while the integration aspects come to expression by combining different parts of a system in a smart and optimal way. Wide bandgap (WBG) materials, such as gallium nitride (GaN) or silicon carbide (SiC) are mature for power applications, but for other applications such as lowvoltage (Bi)CMOS and/or VLSI they are still in the research phase. By integrating electronics monolithically on a sensor chip, improved system performance can be obtained by having signal amplifications close to the physical transducer. The integration aspects are strongly related to the packaging of microelectronic and

No abstract

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.