Towards new hermeticity test methods for MEMS

Hermeticity is a measure of how well a package can maintain its intended ambient cavity environment over the device lifetime. Since many Micro-Electro-Mechanical Systems (MEMS) sensors, actuators and microelectronic devices require a known cavity environment for optimum operational performance, it is important to know the leak rate of the package for lifetime prediction purposes. In this field, limitations in the traditional leak detection methods and standards used originally for integrated circuits and semiconductors have been blindly and often incorrectly applied to MEMS and microelectronic packages. The aim of this project is to define accurately the limitations of the existing hermeticity test methods and standards when applied to low cavity volume MEMS and microelectronic packages and to demonstrate novel test methods, which are applicable to such packages. For the first time, the use of the Lambert-W function has been demonstrated to provide a closed form expression of the maximum true leak rate achievable for the most commonly used existing hermeticity test method, the helium fine leak test. This expression along with the minimum detectable leak rate expression is shown to provide practical guidelines for the accurate testing of hermeticity for ultra-low volume packages. The three leak types which MEMS and microelectronic packages are subject to: molecular leaks, permeation and outgassing, are explained in detail and it is found that the helium leak test is capable of quantifying only molecular leak in packages with cavity volumes exceeding 2.6 mm3. With many MEMS and microelectronic package containing cavities with lower volumes, new hermeticity test methods are required to fill this gap and to measure the increasingly lower leak rates which adversely affect such packages. Fourier Transform Infra-Red (FTIR) spectroscopy and Raman spectroscopy are investigated as methods of detecting gas pressure within MEMS and microelectronics packages. Measured over time, FTIR can be used to determine the molecular and permeation leak rates of packages containing infra-red transparent cap materials. Future work is required to achieve an adequate signal to noise ratio to enable Raman spectroscopy to be a quantitative method to determine molecular leaks, permeation leaks and potentially outgassing. The design, fabrication and calibration procedure for three in-situ test structures intended to monitor the hermeticity of packages electrically are also presented. The calibration results of a piezoresistive cap deflection test structure show the structure can be used to detect leak ii rates of any type down to 6.94×10-12 atm.cm3.s-1. A portfolio of hermeticity test methods is also presented outlining the limitations and advantages of each method. This portfolio is intended to be a living document and should be updated as new research is undertaken and new test methods developed

DESIGN OF SMART SENSORS FOR DETECTION OF PHYSICAL QUANTITIES

Microsystems and integrated smart sensors represent a flourishing business thanks to the manifold benefits of these devices with respect to their respective macroscopic counterparts. Miniaturization to micrometric scale is a turning point to obtain high sensitive and reliable devices with enhanced spatial and temporal resolution. Power consumption compatible with battery operated systems, and reduced cost per device are also pivotal for their success. All these characteristics make investigation on this filed very active nowadays. This thesis work is focused on two main themes: (i) design and development of a single chip smart flow-meter; (ii) design and development of readout interfaces for capacitive micro-electro-mechanical-systems (MEMS) based on capacitance to pulse width modulation conversion. High sensitivity integrated smart sensors for detecting very small flow rates of both gases and liquids aiming to fulfil emerging demands for this kind of devices in the industrial to environmental and medical applications. On the other hand, the prototyping of such sensor is a multidisciplinary activity involving the study of thermal and fluid dynamic phenomenon that have to be considered to obtain a correct design. Design, assisted by finite elements CAD tools, and fabrication of the sensing structures using features of a standard CMOS process is discussed in the first chapter. The packaging of fluidic sensors issue is also illustrated as it has a great importance on the overall sensor performances. The package is charged to allow optimal interaction between fluids and the sensors and protecting the latter from the external environment. As miniaturized structures allows a great spatial resolution, it is extremely challenging to fabricate low cost packages for multiple flow rate measurements on the same chip. As a final point, a compact anemometer prototype, usable for wireless sensor network nodes, is described. The design of the full custom circuitry for signal extraction and conditioning is coped in the second chapter, where insights into the design methods are given for analog basic building blocks such as amplifiers, transconductors, filters, multipliers, current drivers. A big effort has been put to find reusable design guidelines and trade-offs applicable to different design cases. This kind of rational design enabled the implementation of complex and flexible functionalities making the interface circuits able to interact both with on chip sensors and external sensors. In the third chapter, the chip floor-plan designed in the STMicroelectronics BCD6s process of the entire smart flow sensor formed by the sensing structures and the readout electronics is presented. Some preliminary tests are also covered here. Finally design and implementation of very low power interfaces for typical MEMS capacitive sensors (accelerometers, gyroscopes, pressure sensors, angular displacement and chemical species sensors) is discussed. Very original circuital topologies, based on chopper modulation technique, will be illustrated. A prototype, designed within a joint research activity is presented. Measured performances spurred the investigation of new techniques to enhance precision and accuracy capabilities of the interface. A brief introduction to the design of active pixel sensors interface for hybrid CMOS imagers is sketched in the appendix as a preliminary study done during an internship in the CNM-IMB institute of Barcelona

Background Reduction Methods and Vacuum Technology at the KATRIN Spectrometers

The goal of KATRIN is to measure the absolute mass of the electron-antineutrino with a sensitivity of 200 meV by analyzing the shape of the tritium-beta-decay energy spectrum. To minimize the background due to residual gas ionization, a pressure in the lower 10E-11 mbar region is required. This work focuses on the applied vacuum technology. In addition a system of LN2 cooled baffles was designed that eliminates radon-induced background, which is essential for a neutrino mass measurement

Microscale Radiometer Based on the Knudsen Thermal Force

Radiometric phenomena arise in non-isothermal rarefied gas flows for which the molecular mean-free path is approximately equal to the characteristic scale of the temperature gradient. The non-equilibrium nature of these flows results in thermal stresses which are capable of exerting forces and moments on immersed structures. When the stresses are established between unequally heated bodies the forces are referred to as Knudsen thermal forces. This work presents the design, fabrication, and characterization of a novel in-plane microscale radiometer capable of both producing and resolving Knudsen forces in low pressures. The current work differs from previous implementations in that both capacitance and temperature measurements are acquired simultaneously, extending permissible measurement range by up to 3 pressure decades. Sensitivity to ambient pressure, temperature gradient, as well as gas composition is demonstrated, illustrating the mechanism\u27s versatility in measuring various macroscopic fluid properties. For constant input power force output is shown to vary non-monotonically with ambient pressure, having peak magnitude at a Knudsen number of approximately unity. Using thermal microscopy, results are presented in terms of a non-dimensional force coefficient, showing output enhancement of over 7 times at peak magnitude compared to existing out-of-plane cantilevered configurations

Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids

Boosting the sensitivity of continuous gravitational waves all-sky searches using advanced filtering techniques

The work presented in this PhD thesis has been done in the context of gravitational-waves searches. Since the first detection on the 14th September 2015 by the LIGO-Virgo collaboration, a growing number of gravitational-wave events has been detected, all emitted by the coalescence of binary systems involving black holes and/or neutron stars. My work is focused on the search for continuous gravitational waves, which still miss the first detection. These signals are expected to be emitted, for instance, by spinning neutron stars with an asymmetric shape with respect to the rotation axis, and are at least five orders of magnitude weaker than the typical amplitude of detected binary coalescences. In this PhD thesis I report on the work done in four different projects, with the common purpose of increasing the sensitivity of continuous-wave searches, involving both data analysis and instrumental aspects. The first project is a contribution to the commissioning of the Virgo interferometer in view of the next observing run, O4, which will start in May 2023. My contribution has been mainly devoted to the noise hunting activity, focused on the identification and mitigation of instrumental-noise sources that can degrade the sensitivity of continuous-wave searches. The other three projects are related to data analysis. I have focused, in particular, on all-sky searches for sources without electromagnetic counterpart and long-lasting signals from rapidly evolving newly-born neutron stars. I have studied in great detail the robustness of an all-sky data analysis method in the case of overlapping signals. This is relevant for some exotic classes of continuous wave sources and, more generally, in view of third generation detectors, like Einstein Telescope. I have developed a two-dimensional filter, called triangular filter, to be applied to the search for long-lasting gravitational waves from unstable neutron stars, showing that thanks to this method an increase of the search sensitivity of about $20\%$ is achievable. Finally, I describe the first steps of a wide work to develop a new procedure for all-sky continuous-wave searches, exploiting a statistics based on the sidereal modulation, that affects astrophysical signals, due to the Earth rotation

Report on how EIONET and EEA can contribute to the urban in situ requirements of a future Copernicus anthropogenic CO2 observing system

This report provides a technical review of CO2 and CH4 emissions monitoring methods based on surface mixing ratio measurements, total column mixing ratio measurements and flux measurements. The review demonstrated that all these measurements would fulfil respective in situ requirements of the Copernicus CO2 MVS capacity, contributing to the validation of space observations in and around cities and/or the system’s city-scale emissions estimates. The review furthermore elaborated on the benefits to climate change mitigation monitoring in the respective cities and how these methods could be implemented to monitor local emissions.Negotiated procedure No EEA/IDM/R0/17/008. Services supporting the European Environment Agency’s (EEA) crosscutting coordination of the Copernicus In Situ Componen

NASA Tech Briefs, May 1989

This issue contains a special feature on the flight station of the future, discussing future enhancements to Aircraft cockpits. Topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, and Mathematics and Information Sciences

High precision measurement of a atmospheric trace gases using fourier transform infrared spectroscopy

Studies in recent years have revealed that the global atmosphere is undergoing rapid change due to anthropogenic activities, potentially leading to climate change through greenhouse warming, and to harmful stratospheric ozone dq)letion. There is a need for more and better measurements of the atmospheric trace gases implicated in these processes, so that the global anthrqpograic impact can be quantified and, if possible, minimised. The three main anthropogenic greenhouse gases are carbon dioxide, methane and nitrous oxide. Nitrous oxide is also implicated in stratospheric ozone depletion. Carbon monoxide, while not directly a greenhouse gas, is intimately connected with the oxidative state of the atmosphere. Measurements of the background atmosphere mixing ratios and of biosphere-atmosphere fluxes of trace gases typically employ seme ensemble of Gas-Chromatogr^hy (GC), Non-Dispersive Infrared (NDIR) spectroscopy and Tunable Diode Laser (TDL) spectroscopy instrumentation. If, in addition, stable isotope ratio data are to be retrieved, Isotope-Ratio-Mass-Spectrometry (IRMS) instrumentation is required. These iostruments all provide high-predsiou measurements. However, their usual singlespecies focus, their variety of deteaor response functions, calibration requirements, varying degree of mobility, as well as their complexity and expense, seriously constrains the accumulation of data in both laboratory and field investigations. This thesis reports the development of a mediod of trace gas and isotope ratio analysis based on Icm ^ resolution FITR spectroscopy, deployable in both laboratory and field implications. The species CO2, CH4, CO and N2O may be analysed simultaneously in a single air sample using this method. Its mixing ratio analytical precision is in all cases superior to or competitive with that of the more usual methods mentioned above. In addition, the FTIR instrument may be used to measure the stable isotope ratio of CO2 in ambient air to a gepphysically useful degree of precision; still exceeded, however, by that attainable using IRMS. The novel FTIR method relies on calibration using synthetically calculated absorbance spectra and a chem(Hnetric multivariate calibration algorithm. Classical Least Squares (CLS). Careful experimental design and control of the instrument environment also contributes to the high degree of precision achieved