Silicon photonics is the study and application of integrated optical systems which use silicon as an optical medium, usually by confining light in optical waveguides etched into the surface of silicon-on-insulator (SOI) wafers. The term microelectromechanical systems (MEMS) refers to the technology of mechanics on the microscale actuated by electrostatic actuators. Due to the low power requirements of electrostatic actuation, MEMS components are very power efficient, making them well suited for dense integration and mobile operation. MEMS components are conventionally also implemented in silicon, and MEMS sensors such as accelerometers, gyros, and microphones are now standard in every smartphone. By combining these two successful technologies, new active photonic components with extremely low power consumption can be made. We discuss our recent experimental work on tunable filters, tunable fiber-to-chip couplers, and dynamic waveguide dispersion tuning, enabled by the marriage of silicon MEMS and silicon photonics.

In this paper we report of a novel and very simple fabrication method for realizing amperometric gas sensors using conventional wire bonding technology. Working and counter electrodes are made of 360 vertically standing bond wires, entirely manufactured by a fully automated, standard wire bonding tool. Our process enables standing bond wires with a length of 1.24 mm, resulting in an extremely high aspect-ratio of 50, thus effectively increasing the surface area of the working electrode. All gas sensor electrodes are embedded in a polymer-based, solid electrolyte. Therefore, laborious handling of liquid electrolytes can be avoided. Here, we report of a nitric oxide (NO) gas sensor that is capable of detecting NO gas concentrations down to the single-digit ppm range. The proposed approach demonstrates the feasibility towards a scalable and entire back-end fabrication concept for low-cost NO gas sensors.

Non-dispersive infrared (NDIR) gas spectroscopy is a highly accurate optical gas sensing technology, which has been implemented in various industrial applications. However NDIR systems remain too expensive for many consumer and automotive apphcations. The cost of the infrared (IR) emitter component is a substantial part of the total system cost. In this paper we report of a single filament IR emitter that is fabricated using wire bonding technology. Our fabrication approach offers the prospect of a fully automated assembly by means of utihzing a wire bonding tool to integrate the single filament to the MEMS structured silicon substrate. An apphcation-specific wire bond trajectory enables the mechanical attachment of the filament to form the meander-shaped emitter with a total area of 1 mm². The fabricated IR emitter utilizes a Kanthal (FeCrAl) filament with very high thermal stability and excellent emitting properties under atmospheric conditions. The packaged IR emitter has been characterized using Fourier transform infrared (FTIR) spectroscopy to study the emitted IR spectrum with respect to the requirements of NDIR systems.

Nanogap electrodes consist of pairs of electrically conducting tips that exhibit nanoscale gaps. They are building blocks for a variety of applications in quantum electronics, nanophotonics, plasmonics, nanopore sequencing, molecular electronics, and molecular sensing. Crack-junctions (CJs) constitute a new class of nanogap electrodes that are formed by controlled fracture of suspended bridge structures fabricated in an electrically conducting thin film under residual tensile stress. Key advantages of the CJ methodology over alternative technologies are that CJs can be fabricated with wafer-scale processes, and that the width of each individual nanogap can be precisely controlled in a range from <2 to >100 nm. While the realization of CJs has been demonstrated in initial experiments, the impact of the different design parameters on the resulting CJs has not yet been studied. Here we investigate the influence of design parameters such as the dimensions and shape of the notches, the length of the electrode-bridge and the design of the anchors, on the formation and propagation of cracks and on the resulting features of the CJs. We verify that the design criteria yields accurate prediction of crack formation in electrode-bridges featuring a beam width of 280 nm and beam lengths ranging from 1 to 1.8 mu m. We further present design as well as experimental guidelines for the fabrication of CJs and propose an approach to initiate crack formation after release etching of the suspended electrode-bridge, thereby enabling the realization of CJs with pristine electrode surfaces.

We present graphene-based CO2 sensing and analyze its cross-sensitivity with humidity. In order to assess the selectivity of graphene-based gas sensing to various gases, measurements are performed in argon (Ar), nitrogen (N2), oxygen (O2), carbon dioxide (CO2), and air by selectively venting the desired gas from compressed gas bottles into an evacuated vacuum chamber. The sensors provide a direct electrical readout in response to changes in high concentrations, from these bottles, of CO2, O2, nitrogen and argon, as well as changes in humidity from venting atmospheric air. From the signal response to each gas species, the relative graphene sensitivity to each gas is extracted as a relationship between the percentage-change in graphene's resistance response to changes in vacuum chamber pressure. Although there is virtually no response from O2, N2 and Ar, there is a sizeable cross-sensitivity between CO2 and humidity occurring at high CO2 concentrations. However, under atmospheric concentrations of CO2, this cross-sensitivity effect is negligible – allowing for the use of graphene-based humidity sensing in atmospheric environments. Finally, charge density difference calculations, computed using density functional theory (DFT) are presented in order to illustrate the bonding of CO2 and water molecules on graphene and the alterations of the graphene electronic structure due to the interactions with the substrate and the molecules.

Interposers with through-silicon vias (TSVs) play a key role in the three-dimensional integration and packaging of integrated circuits and microelectromechanical systems. In the current practice of fabricating interposers, solder balls are placed next to the vias; however, this approach requires a large foot print for the input/output (I/O) connections. Therefore, in this study, we investigate the possibility of placing the solder balls directly on top of the vias, thereby enabling a smaller pitch between the solder balls and an increased density of the I/O connections. To reach this goal, inkjet printing (that is, piezo and super inkjet) was used to successfully fill and planarize hollow metal TSVs with a dielectric polymer. The under bump metallization (UBM) pads were also successfully printed with inkjet technology on top of the polymer-filled vias, using either Ag or Au inks. The reliability of the TSV interposers was investigated by a temperature cycling stress test (-40 °C to +125 °C). The stress test showed no impact on DC resistance of the TSVs; however, shrinkage and delamination of the polymer was observed, along with some micro-cracks in the UBM pads. For proof of concept, SnAgCu-based solder balls were jetted on the UBM pads.

This paper reports a narrow footprint sealing ring design for low-temperature, hermetic, and mechanically stable wafer-level packaging. Copper (Cu) sealing rings that are as narrow as 8 μm successfully seal the enclosed cavities on the wafers after bonding at a temperature of 250 °C. Different sealing structure designs are evaluated and demonstrate excellent hermeticity after 3 months of storage in ambient atmosphere. A leak rate of better than 3.6×10'16 mbarL/s is deduced based on results from residual gas analysis measurements. The sealing yield after wafer bonding is found to be not limited by the Cu sealing ring width but by a maximum acceptable wafer-to-wafer misalignment.

High-temperature-resistant inertial sensors are increasingly requested in a variety of fields such as aerospace, automotive and energy. Capacitive detection is especially suitable for sensing at high temperatures due to its low intrinsic temperature dependence. In this paper, we present high-temperature measurements utilizing a capacitive accelerometer, thereby proving the feasibility of capacitive detection at temperatures of up to 400 degrees C. We describe the observed characteristics as the temperature is increased and propose an explanation of the physical mechanisms causing the temperature dependence of the sensor, which mainly involve the temperature dependence of the Young's modulus and of the viscosity and the pressure of the gas inside the sensor cavity. Therefore a static electromechanical model and a dynamic model that takes into account squeeze film damping were developed.

Achieving near-atomic-scale electronic nanogaps in a reliable and scalable manner will facilitate fundamental advances in molecular detection, plasmonics, and nanoelectronics. Here, a method is shown for realizing crack-defined nanogaps separating TiN electrodes, allowing parallel and scalable fabrication of arrays of sub-10 nm electronic nanogaps featuring individually defined gap widths.

We report on dye-based photonic sensing systems which are fabricated and packaged at wafer scale. For the first time luminescent organic nanocomposite thin-films deposited by plasma technology are integrated in photonic sensing systems as active sensing elements. The realized dye-based photonic sensors include an environmental NO2 sensor and a sunlight ultraviolet light (UV) A+B sensor. The luminescent signal from the nanocomposite thin-films responds to changes in the environment and is selectively filtered by a photonic structure consisting of a Fabry-Perot cavity. The sensors are fabricated and packaged at wafer-scale, which makes the technology viable for volume manufacturing. Prototype photonic sensor systems have been tested in real-world scenarios. (C) 2016 Elsevier B.V. All rights reserved.