In this paper, a second generation MEMS mass flow controller (MFC) for liquid fuel delivery to a miniaturized homogeneous charge compression ignition (HCCI) engine is presented. In contrast to the first generation MFC [1], it has a highly improved on/off-characteristic and fuel delivery range. This is achieved by a complete redesign of the valve cap and package, minimizing particles in the fuel outlet and package stress. Various fuels (and water) are calibrated, for instance, ethanol and water with maximum mass flow rates of 15 g/min and 20 g/min, respectively (at 100 kPa inlet pressure). The on/off-ratio with water is nearly 3300:1 (at 100 kPa inlet pressure). The maximum power consumption during continuous operation is 50 μW.

Due to the demand of low-cost sensor applications and new technologies for efficient production, the printing of functional inks is one of the most sustainable and fastest-growing markets in the electronic industry. This statement is confirmed by the "Roadmap for Organic and Printed Electronics", which predicts that the global market value of this sector will increase by about 50% to about 43 billion USD by 2020. The reason for this enormous growth is the continuous development of various nanomaterials, with the possibilities to bind smallest particles of a material in a solvent and to apply the resulting inks with different printing techniques on temperature-sensitive large substrates. These comparatively simple additive processes allow for example a combination of conductive polymers and inorganic materials, to manufacture cost-efficient electronic systems. This work presents the development of a 2D-printed photosensor for the detection of ultraviolet radiation in the wavelength range of 310 nm - 390 nm for wearable applications. This interdigitated electrode sensor can be completely realized by applying inkjet printing technology with nanoparticle-based inks. It detects electromagnetic radiation resistively. The semiconductor layer (ZnO-based) reacts on the UV radiation. Figure 1 shows a schematic representation of the sensor structure and figure 2 the printed sensor. Due to the transparency of zinc oxide in the visible range of the electromagnetic spectrum, the printed sensing material is marked with a red square.

In this paper, we present our work developing a family of silicon-on-insulator (SOI)–based high-g micro-electro-mechanical systems (MEMS) piezoresistive sensors for measurement of accelerations up to 60,000 g. This paper presents the design, simulation, and manufacturing stages. The high-acceleration sensor is realized with one double-clamped beam carrying one transversal and one longitudinal piezoresistor on each end of the beam. The four piezoresistors are connected to a Wheatstone bridge. The piezoresistors are defined to 4400 Ω, which results in a width-to-depth geometry of the pn-junction of 14 μm × 1.8 μm. A finite element method (FEM) simulation model is used to determine the beam length, which complies with the resonance frequency and sensitivity. The geometry of the realized high-g sensor element is 3 × 2 × 1 mm3. To demonstrate the performance of the sensor, a shock wave bar is used to test the sensor, and a Polytec vibrometer is used as an acceleration reference. The sensor wave form tracks the laser signal very well up to 60,000 g. The sensor can be utilized in aerospace applications or in the control and detection of impact levels.

In this paper we present a printed, fast, high-sensitive and cheap wireless incontinence sensor [...]

Anodic bonding technology is a well-established industrial technique, which is reported to be the most widely used MEMS packaging method. This Paper studies residual stress issue caused by different coefficients of thermal expansion (CTE) between silicon and glass during the anodic bonding process and its influence on MEMS-based sensors. For this purpose, SW-YY ® Glass from ASAHI is selected. Firstly, the SW-YY ® glass material is characterized in the bonding temperature range from 250°C to 500°C and voltage range from 400V-800V. Secondly, a MEMS based pressure sensor and two type glass substrates (SW-YY ® , Pyrex ® 7740) were fabricated and bonded to evaluate the stress issue. Results show that the offset of the pressure sensor introduced by mismatched CTE was reduced significantly with SW-YY ® glass than standard Pyrex ® ®7740 glass. The proposed method can be used to reduce the influence of the internal stress caused with bonding temperature and the mismatched CTEs for stress sensitive MEMS.

Due to the growing numbers of elderly people in the world, who suffer from incontinence and are in the need of care, technologies are necessary to increase the effectiveness of nursing staff and enhance the hygiene for humans to improve life quality. For this reason a low cost humidity sensor system printed onto the substrate of a diaper with the novel organic conductive ink PEDOT:PSS (Poly (3,4-ethylenedioxythio-phene):Poly(styrene sulfonate)) was developed in previous work [1]. The novel material PEDOT:PSS is still expensive because of rare use in research and market demand. Therefore a way for optimization of the sensor is aimed to print the sensor with less material, but at the same time with no loss of sensitivity. With this purpose, two theoretical models are developed. An analytic model with geometrical based calculations and a Finite Element Analysis (FEA) simulation model, for deeper understanding of electric field effects with focus on the total capacitance of the sensor. To verify these theoretical models a characterization measurement of manufactured samples of previous work [1] is made, to obtain a comparison between every experimental method. For the theoretical models the necessary material parameters are characterized.

Piezoresistive mechanical sensors play a very important role in modern industries. MEMS pressure sensor market is one of the biggest markets among all MEMS components [1]. Global pressure sensor market is growing from $6.4 billion in 2012 to $8.8 billion in 2018. The main applications are automotive, medical, consumer electronics, industry and aerospace/defense. Today, there is a growing demand for cost effective high-temperature and harsh-environment semiconductor devices, capable of operating at temperatures in the 500°C range. Developments in aircraft and space applications, automotive electronics, the oil and gas industry, the plastic and chemical industry, and the military sector are among the main drivers for research on high-temperature sensors and electronics. Existing semiconductor devices based on silicon are limited to operating temperatures below 150°C, as thermal generation of charge carriers severely degrades device operation at higher temperatures. The development of SOI (silicon on insulator) technology helped to extend device operating temperatures to approximately 400°C. However, at temperatures over 400°C, the material silicon reaches its physical limits as plastic deformation starts to occur when mechanical stress is applied. Silicon carbide is considered to be the most promising semiconductor for future high-temperature and harsh-environment applications as it features a unique combination of favorable physical, electrical, mechanical, and chemical properties. It is an extremely hard and robust material with a high thermal stability, and is chemically inert up to temperatures of several hundred degrees. Moreover, it has a higher thermal conductivity than copper, and its wide energy bandgap allows operation at high temperatures and in high radiation environments without suffering from intrinsic conduction effects. Performance and reliability of metal-semiconductor contacts, conducting paths and the capability of etching 3D mechanical structures in SiC (such membrane or bridge) remain limiting factors for high-temperature operation of SiC electronic mechanical sensors today.

Together with the Kirchhoff-Institute for Physics the Fraunhofer IZM has developed a full wafer redistribution and embedding technology as base for a large-scale neuromorphic hardware system. The paper will give an overview of the neuromorphic computing platform at the Kirchhoff-Institute for Physics and the associated hardware requirements which drove the described technological developments. In the first phase of the project standard redistribution technologies from wafer level packaging were adapted to enable a high density reticle-to-reticle routing on 200 mm CMOS wafers. Neighboring reticles were interconnected across the scribe lines with an 8 μm pitch routing based on semi-additive copper metallization which was photo defined by full field mask aligning equipment. Passivation by photo sensitive benzocyclobutene (BCB) was used to enable a second intra-reticle routing layer. Final IO pads of nickel with flash gold were generated on top of each reticle. For final electrical connection the wafers were placed into mechanical fixtures and the IOs of all reticles were touched by elastomeric connectors. With that concept neuromorphic systems based on full wafers could be assembled and tested. The fabricated high density inter-reticle routing revealed a very high yield of larger than 99.9 %. In order to allow an upscaling of the system size to a large number of wafers with feasible effort a full wafer embedding concept for printed circuit boards was developed and proven in the second phase of the project. The wafers were thinned to 250 μm and laminated with additional prepreg layers and copper foils into a core material. A 200 mm circular cut was done into the core material and the inner prepreg layers to create the required clearance for the wafer. After lamination of the PCB panel the reticle IOs of the embedded wafer were accessed by micro via drilling, copper electroplating, lithography and subtractive etching of the PCB wiring structure. The created wiring with 50 μm line width enabled an access of the reticle IOs on the embedded wafer as well as a board level routing. The panels with the embedded wafers were subsequently stressed with up to 1000 thermal cycles between 0 °C and 100 °C and have shown no severe failure formation over the cycle time.

In the present work, an intermediate sodium-rich glass layer was deposited on silicon wafer by a PVD (Physical Vapor Deposition) process for further silicon to silicon anodic bonding. The anodic bonding process was carried out at low direct-current voltage of about 40 V-100 V and temperature from 320°C to 400°C. The concentration of alkali ion (sodium) in the deposited thin glass layer, the surface roughness of the thin film, and the bonding properties of the thin glass layer were studied in detail and later on this technology was used to fabricate a MEMS based pressure sensor (bonding voltage 40 V and bonding temperature 360°C). The infrared microscopy (IR) was used as the visual method to detect the bonding defects. The offset value was measured with varied temperature to check the stress issues. The purpose of the proposed method is to reduce the offset value for MEMS based pressure sensor by using the thin glass bonding layer. This novel method can be applied to the other type of MEMS sensors, which requires anodic bonding process to improve the performance.

In this paper we present the first time our development work of a family of silicon on insulator (SOI)-based piezoresistive MEMS very high G sensors for measurement of accelerations up to 60.000 g. Two sensors have been realized, one for 20.000g and one for 60.000g.

In this paper, we present and discuss our new WSi–WSiN–Pt metallization scheme for SiC-based microsystems for applications in harsh environments. Stoichiometric material WSi was selected as contact material for SiC. The diffusion barrier material WSiN was deposited from the same target as the contact material in order to limit the number of different chemical elements in the scheme. Our scheme was kept as simple as possible regarding the number of layers and chemical elements. Our scheme shows very good long-term stability and suitability for SiC-based microsystems. The experimental evaluation concept used here includes a combination of physical, electrical, and mechanical analysis techniques. This combined advance is necessary since modern physical analysis techniques still offer only limited sensitivity for detecting minimal changes in the metallization scheme.

Pixelated LEDs are a new, high efficient light source which allows to control the beam pattern and which are therefore suitable for adaptive front light systems. We will present a concept for hybrid 3D flip chip stacking of pixelated LED chips onto an active matrix driver IC using a new interconnect structure to address thermal management and bonding robustness challenges. Two types of interconnect materials have been investigated: electroplated AuSn solder and nanoporous gold (NPG). We will present the deposition methods and the bonding approach for chip-to-chip and chip-to-wafer bonding and the characteristic results of the bonded interconnects achieved.

For a large number of industrial, technical processes and in aerospace science, the monitoring and control of water content of solid, liquid, or gaseous materials is a central and quality determining task [1]. In this paper we present our work on development of a humidity sensor array for detecting of absolute trace humidity using Pt-P2O5 electrolytic cells. Many sensor solutions on the market are using this material system for detecting of humidity. Disadvantages of these systems are their non-ability to monitor the absolute amount of water in air and their limited robustness and redundancy. One of important focuses in this work is the development of a robust and stable package for the developed sensor system. The package has to protect the sensors from surrounding, but has to provide the interface between the sensor surface and the atmosphere and a sensor electrical interface for electronics. For a reliable detection of humidity in air, a constant and laminar flow over the sensor surface is needed. The system is containing 4 sensors (cells) in a row, which allows detection of total water in the air. Our realized sensor system shows a high reliable and accurate behavior and is suitable for use in aerospace and industry [2].

In this paper we present high reliable and accurate silicon-based trace humidity sensors for use in aerospace and process industry. The sensors have been realized by using simple MEMS technology in this work. One is a single sensor (sensor cell) for monitoring of humidity, and sensor array is able to measure the total trace humidity in the atmosphere. It’s very suitable for aerospace and process industry such pharmacy applications.

This work helps to clarify the effects on bondable Low Temperature Cofiered Cofired Ceramic(LTCC) material from Fraunhofer IKTS under different bonding conditions as changes in temperature, voltage and time. The Paper investigates silicon bonded to LTCC and silicon with a thin aluminum layer bonded to LTCC and compares both with anodic bonding of standard Borofloat 33® from Schott GmbH to silicon. The result of this work provides a comprehensive overview of bonding parameters for the materials Borofloat 33® and LTCC. An inspection of the bonding quality is carried out, which includes the optical inspection of the bonded area and interface observation via a scanning electron microscope (SEM). The bonding quality is also shown with the charge transfer during the bonding process. This paper can be used to achieve a higher degree of freedom in the design of hermetic wafer level packaging for various Micro-Electro-Mechanical System(MEMS) devices made of glass and ceramic materials.

In this paper we present and discuss two innovative liquid-free SOI sensors for pressure measurements in harsh environments. The sensors are capable of measuring pressures at high temperatures. In both concepts media separation is realized using a steel membrane. The two concepts represent two different strategies for packaging of devices for use in harsh environments and at high temperatures. The first one is a "one-sensor-one-packaging_technology" concept. The second one uses a standard flip-chip bonding technique. The first sensor is a "floating-concept", capable of measuring pressures at temperatures up to 400 °C (constant load) with an accuracy of 0.25% Full Scale Output (FSO). A push rod (mounted onto the steel membrane) transfers the applied pressure directly to the center-boss membrane of the SOI-chip, which is placed on a ceramic carrier. The chip membrane is realized by Deep Reactive Ion Etching (DRIE or Bosch Process). A novel propertied chip housing employing a sliding sensor chip that is fixed during packaging by mechanical preloading via the push rod is used, thereby avoiding chip movement, and ensuring optimal push rod load transmission. The second sensor can be used up to 350 °C. The SOI chips consists of a beam with an integrated centre-boss with was realized using KOH structuring and DRIE. The SOI chip is not "floating" but bonded by using flip-chip technology. The fabricated SOI sensor chip has a bridge resistance of 3250 Ω. The realized sensor chip has a sensitivity of 18 mV/µm measured using a bridge current of 1 mA.

This system consists of a pressure silicon sensor, calibration module and wireless module. The pressure sensor used in this work is a piezoresistive silicon sensor that developed by Technical University Berlin. After calibration of the sensors output signals, the XBee-chip was used for wireless transmission. The three components with peripheral circuits and batteries were integrated in a 50mm × 50mm PCB. The system was then tested in a climate chamber at different temperatures and pressures. Programs for signal receiving and processing were developed in Matlab-environment. The experimental results show that this system works well for the short range (15m indoor).

The piezoresistive silicon pressure sensor used in this work is developed by Technical University Berlin. It is mainly composed of a silicon-membrane and four implanted piezoresistors connected in form of a Wheatstone bridge. After wire bonding, the sensor was evaluated in a climate cabinet at different temperatures and pressures. The characteristic curve of the sensor shows its good linearity and strong dependence on the temperature. The sensor ́s temperature coefficient of sensitivity and zero shift were compensated using ASIC MLX90308. The experimental results show that this method of compensation accurately solved the sensors temperature dependence problems.