Sjoerd Haasl

Arrays of monocrystalline silicon micromirrors fabricated using CMOS compatible transfer bonding

In this paper, we present CMOS compatible fabrication of monocrystalline silicon micromirror arrays using membrane transfer bonding. To fabricate the micromirrors, a thin monocrystalline silicon device layer is transferred from a standard silicon-on-insulator (SOI) wafer to a target wafer (e.g. a CMOS wafer) using low temperature adhesive wafer bonding. In this way, very flat, uniform and low stress micromirror membranes made of monocrystalline silicon can be directly fabricated on top of CMOS circuits. The mirror fabrication does not contain any bond alignment between the wafers; thus, the mirror dimensions and alignment accuracies are only limited by the photolithographic steps. Micromirror arrays with 4/spl times/4 pixels and a pitch size of 16 /spl mu/m /spl times/16 /spl mu/m have been fabricated.

A silicon straight tube fluid density sensor

In this paper, a new and simple silicon straight tube is tested as a fluid density sensor. The tube structure has a hexagonal cross section. The fabrication process consists of anisotropic silicon etching and silicon fusion bonding. A tube structure with a length of 2.65 cm was tested. The sample volume is 9.3 μL. The first three modes of vibrations were investigated with a laser Doppler vibrometer for air and five liquid mixtures. The fluid density sensitivity of each mode was measured and the average was −256 ± 6 ppm (kg m−3)−1 around the density of water. The density of an unknown fluid can be continuously monitored using this sensor by measuring the resonance frequency of one of the vibration modes and extracting the density from the calibration curves.

Hybrid-mounted micromachined aluminum hotwires for wall shear-stress measurements

In this paper, we present a micromachined metal hotwire anemometer sensor for use in wall shear-stress measurements. We describe its design and fabrication. A novel hybrid assembly method has been developed to make it possible to measure close to the surface without contacting leads interfering with the flow. Experimental results illustrate the behavior and characteristics of this sensor.

Out-of-Plane Knife-Gate Microvalves for Controlling Large Gas Flows

This paper considers design issues for microvalves for large gas flow control. It introduces out-of-plane knife-gate microvalves as a novel design concept and a proportional microvalve concept for pressure control applications. The design of three different actuator-gate configurations and first prototypes are presented. The first valve prototypes feature thermal silicon-aluminum bimorph actuators and the pressure-flow performance per chip area of the demonstrator valve presented is greatly increased using out-of-plane actuation and an out-of-plane orifice. The characterization of the actuators and of the pressure-flow performance is presented. The prototype valve allows for a flow change of DeltaQ= 3.4 standard liters per minute (SLPM) at a pressure change of DeltaP= 95 kPa (Pin= 196.3 kPa, Pout= 101.3 kPa) on an active chip area of only 2.3times3.7 mm21515

Polymer Gap Adapter for Contactless, Robust, and Fast Measurements at 220–325 GHz

Radiation leakages are a considerable problem when measuring waveguide structures at high frequencies. In order to maintain good electrical contact, flanges need to be tightly and evenly screwed to the device under test. This can be a time-consuming operation, especially with repeated measurements. We present a metamaterial-based adapter, which prohibits leakage even in the presence of gaps at the interconnects. This so-called gap adapter has been fabricated from a metallized polymer (SU8). The reflection coefficient is below -20 dB throughout the band for a 50-μm gap on both sides of the gap adapter. In comparison, a conventional waveguide with a 50-μm gap on both sides has a reflection coefficient of -10 dB. The gap adapter can be used to perform fast measurements, since the normal flange screws are redundant. We compare the SU8 gap adapter with a Si version and to a smooth metal waveguide reference disc. The SU8 gap adapter performed better than the Si version and much better than the waveguide disc in all test cases. SU8 gap adapters were used to measure on a waveguide component. The SU8 gap adapters with 50-μm gaps performed comparable with the waveguide component with the flange screws carefully tightened. The polymer also makes the gap adapter mechanically robust and easy to mass fabricate.

2.07 – Flow Sensors

Micromachined flow sensors have been evolving for over 40 years. This chapter provides background for the understanding of micromachined flow sensing and reviews the micromachined flow sensors presented in the literature to date. The sensors are classified according to the domain in which they function and their operating principles. Thermal flow sensors account for the largest part. Flow sensors based on mechanical and differential-pressure sensing constitute about half of the remaining sensors, while the other half consists of optical, ultrasonic, Coriolis force, carbon nanotube (CNT)-based and direct electrical flow sensors. The integration of electronics into flow sensors is discussed briefly. At the end of the chapter, wall shear stress-sensing and medical applications are discussed.

Stress-Minimized Packaging of Inertial Sensors by Double-Sided Bond Wire Attachment

This paper presents a novel approach for low-stress packaging of microelectromechanical system (MEMS)-based gyroscopes. The proposed approach makes use of conventional ball-stitch wire bonding. The gyroscope die is attached exclusively by means of bond wire connections between the package frame, and the top and bottom surfaces of the die. The process enables the electrical connection of metal pads on the top and the bottom side of the MEMS die within the same process. No adhesives, glue, or solder is used for the die attach. The stiffness of the proposed die attach is evaluated by scanning laser Doppler vibrometry. White-light interferometry is used to investigate stress in the die that is induced by the die attach. The bond wire attachment is compared with conventional single-sided die attach using two types of commercially available adhesives. It was found that the proposed packaging system exhibits multiple resonance modes and displays a dependence on the amount of bond wires. White-light interferometry reveals a centered bow across the die and shows low-induced stresses compared with conventionally attached dies using epoxy adhesives.

Micromachined contactless pin-flange adapter for robust high-frequency measurements

We present the first micromachined double-sided contactless WR03 pin-flange adapter for 220-325 GHz based on gap waveguide technology. The pin-flange adapter is used to avoid leakage at the interface of two waveguides even when a gap between them is present and can be fitted onto any standard WR03 waveguide flange. Tolerance measurements were performed with gaps ranging from 30-100 mu m. The performance of the micromachined pin flange has been compared to a milled pin flange, a choke flange and to standard waveguide connections. The micromachined pin flange is shown to have better performance than the standard connection and similar performance to the milled pin flange and choke flange. The benefits of micromachining over milling are the possibility to mass produce pin flanges and the better accuracy in the 2D design. Measurements were performed with and without screws fixing the flanges. The flanges have also been applied to measure two devices, a straight rectangular waveguide of 1.01 inch and a ridge gap resonator. In all cases, the micromachined pin flange performed flawlessly while the standard flange experienced significant losses at already small gaps.

Hybrid mounted micromachined aluminium hot-wire for near-wall turbulence measurements

We present the first micromachined metal hot-wire anemometer sensor for use in near-wall turbulence measurements. To measure close to the surface without the circuitry interfering with the flow, a novel hybrid assembly of the sensor has been developed. We present the design, fabrication and characteristics of this sensor.

Small footprint knife gate microvalves for large flow control

This paper introduces the first area-optimized micromachined knife gate microvalve. In comparison to recent microvalves the pressure-flow performance is increased using out-of-plane actuators and an out-of-plane orifice. Three different actuator-gate designs and their fabrication are described. The valve features integrated thermal silicon/aluminum bimorph actuators where the aluminum layer forms the resistive heater as well as the bimorph material. The characterization of the actuators and of the pressure-flow performance are presented. The valve allows a flow change of /spl Delta/Q=3.4 l/min at 100 kPa on an active chip area of only 2.3/spl times/3.7 mm/sup 2/.