Remco J. Wiegerink

A capacitive RF power sensor based on MEMS technology

An environment decontaminating system has an air cleaning and deodorizing function. It includes a housing having an inlet and an outlet for passage of air. A DC high voltage dust collector and a dust catching filter are provided adjacent the inlet. An ozone generator is positioned adjacent the filter. An odor/ozone turbulent mixing plate is positioned adjacent the ozone generator. A deodorizing catalyst is positioned adjacent the mixing plate. An acid gas absorbent, a suction scavaging fan, and an ozone concentration sensor are positioned adjacent an outlet of the housing.

Modeling, design, fabrication and characterization of a micro Coriolis mass flow sensor

This paper discusses the modeling, design and realization of micromachined Coriolis mass flow sensors. A lumped element model is used to analyze and predict the sensor performance. The model is used to design a sensor for a flow range of 0–1.2 g h−1 with a maximum pressure ndrop of 1 bar. The sensor was realized using semi-circular channels just beneath the surface of a silicon wafer. The channels have thin silicon nitride walls to minimize the channel mass with respect to the mass of the moving fluid. Special comb-shaped electrodes are integrated on the nchannels for capacitive readout of the extremely small Coriolis displacements. The comb-shaped electrode design eliminates the need for multiple metal layers and sacrificial layer etching methods. Furthermore, it prevents squeezed film damping due to a thin layer of air between the capacitor electrodes. As a result, the sensor operates at atmospheric pressure with a quality factor in the order of 40 and does not require vacuum packaging like other micro nCoriolis flow sensors. Measurement results using water, ethanol, white gas and argon are presented, showing that the sensor measures true mass flow. The measurement error is ncurrently in the order of 1% of the full scale of 1.2 g h−1.

Low-drift flow sensor with zero-offset thermopile-based power feedback

A thermal flow sensor has been realised consisting of freely-suspended silicon-rich silicon-nitride microchannels with an integrated Al/poly-Si++ thermopile in combination with up- and downstream Al heater resistors. The inherently zero offset of the thermopile is exploited in a feedback loop controlling the dissipated power in the heater resistors, eliminating inevitable influences of resistance drift and mismatch of the thin-film metal resistors. The control system cancels the flow-induced temperature difference across the thermopile by controlling a power difference between both heater resistors, thereby giving a measure for the flow rate. The flow sensor was characterised for power difference versus water flow rates up to 1.5 mul-min-1, being in good agreement with a thermal model of the sensor, and the correct low-drift operation of the temperature-balancing control system has been verified.

An HTS quasi-one junction SQUID-based periodic threshold comparator for a 4-bit superconductive flash A/D converter

An all high-T/sub c/ periodic threshold comparator for application in a 4-bit superconductive A/D converter has been realized and tested. The theoretical threshold curve of the comparator is calculated and compared to the measured results. Furthermore, the thermal noise immunity and the influence of flux-flow are considered, resulting in practical design constraints for the comparator circuit.<<ETX>>

A high-T/sub c/ 4-bit periodic threshold analog-to-digital converter

Using ramp-type Josephson junctions a 4-bit periodic threshold ADC has been designed, fabricated and tested. Practical design constraints will be discussed in terms of noise immunity, flux flow, available technology, switching speed etc. In a period of four years we fabricated about 100 chips in order to bring the technology to an acceptable level and to test various designs and circuit layouts. This resulted in a basic comparator that is rather insensitive to the stray field generated by the analog input signal or variations in mask alignment during fabrication. The input signal is fed into the comparators using a resistive divider network. Full functionality at low frequencies has been demonstrated.

Low-drift U-shaped thermopile flow sensor

A thermal flow sensor has been realised consisting of a freely-suspended U-shaped microchannel. The structure is symmetrically heated by a heater at the top of the U-shape. The thermal imbalance caused by liquid flow is sensed by an integrated Al/poly-Si++ thermopile. The U-shape microchannel facilitates the integration of a large number of thermocouple junctions, resulting in a highly-sensitive calorimetric flow sensor (40 mV/mulldrmin-1 at 2 mW heating power). The heating power is controlled accurately by forcing a current, while measuring the voltage over the heater resistor. Influences of thermal gradients across the chip are minimised by the freely-suspended microchannel ends being fixed to the substrate over a small distance. The inherently zero-offset of the thermopile can furthermore be exploited in a control system cancelling temperature imbalance by liquid flow using additional heaters. This makes the flow sensor independent of heater resistor values and thermopile output characteristics. Accurate measurements up to 400 nlldrmin-1 water flow have been obtained applying a temperature-balancing control system.

Measurement setup for detecting the Casimir force between parallel plates separated at a sub-micron distance

In microelectromechanical systems (MEMS), parallel plate structures with sub-micron separation have been of much use in various types of sensors and actuators. As the separation distance in these devices reaches down to hundreds of nm, it gets difficult to control the gap due to parasitic charging and the Casimir force. The Casimir force and its dependence on the boundary conditions of electromagnetic fields is a phenomenon that is mostly avoided rather than explored. In this paper, we present a methodology involving a micromachined parallel-plate geometry to measure the Casimir force at sub-micron separation. The new feature in this setup is the micromechanical means of parallelism control to measure the force at extremely small separation distances. A fabrication process for the micromachined parallel-plate structure is also given.

Fully integrated micro coriolis mass flow sensor operating at atmospheric pressure

This paper discusses the design and realization of a micromachined micro Coriolis flow sensor with integrated electrodes for both electrostatic actuation and capacitive readout. The sensor was realized using semicircular channels just beneath the surface of the silicon wafer. The channels have thin silicon nitride walls to minimize the channel mass with respect to the mass of the moving fluid. A comb-shaped electrode design is used to prevent squeezed film damping so that the sensor can operate at atmospheric pressure, thus eliminating the need for vacuum packaging. The new sensor chip no longer requires large external magnets and the size of the chip itself has been reduced to 7.5×7.5 mm2.

Fabrication of thick silicon nitride blocks embedded in low-resistivity silicon substrates for radio frequency applications

Thick silicon nitride blocks embedded in silicon wafers were recently proposed as a substrate for RF devices. In this paper we show that deep trenches filled with silicon nitride—having thin slices of monocrystalline silicon in between—already result in a significantly improved RF behavior. Measurement results are presented on RF coplanar waveguides using solid silicon nitride blocks and silicon nitride filled trenches with various dimensions and orientations with respect to the transmission line. A clear difference exists between trenches parallel and perpendicular to the transmission line due to the different associated loss mechanisms. S-parameter measurements on the coplanar waveguides show an improvement of the transmission losses at 4 GHz from 3.5 dB mm-1 on a standard silicon substrate to 0.7 dB mm-1 on silicon nitride filled trenches and 0.2 dB mm-1 on a solid silicon nitride block. In this way, an RF performance very close to dedicated glass substrates such as AF45 is obtained (with transmission losses of 0.1 dB mm-1 at 4 GHz).