Implementation of the CMOS MEMS Condenser Microphone with Corrugated Metal Diaphragm and Silicon Back-Plate

This study reports a CMOS-MEMS condenser microphone implemented using the standard thin film stacking of 0.35 μm UMC CMOS 3.3/5.0 V logic process, and followed by post-CMOS micromachining steps without introducing any special materials. The corrugated diaphragm for the microphone is designed and implemented using the metal layer to reduce the influence of thin film residual stresses. Moreover, a silicon substrate is employed to increase the stiffness of the back-plate. Measurements show the sensitivity of microphone is −42 ± 3 dBV/Pa at 1 kHz (the reference sound-level is 94 dB) under 6 V pumping voltage, the frequency response is 100 Hz–10 kHz, and the S/N ratio >55 dB. It also has low power consumption of less than 200 μA, and low distortion of less than 1% (referred to 100 dB)

MINIATURE LOW-COHERENCE FIBER OPTIC ACOUSTIC SENSOR WITH THIN-FILM UV POLYMER DIAPHRAGM

A miniature low-coherence fiber optic acoustic sensor with a thin-film UV polymer diaphragm is developed and studied in this thesis to address the fundamental challenge of miniaturizing acoustic sensors. When miniaturizing an acoustic sensor, there is a critical size limitation at which the transduction mechanism deformation becomes too small for detection. However, a solution to this problem is to utilize a high resolution, low coherence fiber optic interferometric detection system coupled with a soft, thin-film transduction mechanism. A novel fabrication technique was developed to enable the use of elastomers, which inherently exhibit desirably low Young's modulus properties. In addition, the fabrication process enables fabrication of diaphragms at thicknesses on the order of nanometers. The fabrication process also renders highly tunable sensor performance and superior sensing quality at a low cost. The sensor developed exhibits a flat frequency response between 50 Hz and 4 kHz with a useable bandwidth up to 20 kHz, a dynamic range of 117.55 dB SPL, a signal to noise ratio (SNR) of 58 dB, and a sensitivity up to 1200 mV/Pa. In this thesis, it is further demonstrated that by using an array these sensors fabricated from the same batch facilitates accurate directional sound localization by utilizing the interaural phase difference (IPD) exhibited by sensor pairs. Future work is suggested to optimize the sensor performance for a specific application, to carry out studies of more complex array configurations, and to develop algorithms that can help increase the sound localization accuracy

La technologie CMOS-MEMS pour des applications acoustiques

ISBN : 978-2-11-129183-6Recently, several teams have demonstrated a MEMS fabrication process based on a CMOS technology combined with a surface micromachining not requiring an etching mask. Unlike an earlier CMOS-based approach, where the release of MEMS structures is made by the silicon etching, the proposed technology etches oxide sacrificial layers to release the MEMS structures made of metallic layers of the CMOS process. In this project, we propose to fabricate MEMS-based acoustic devices with the AMS 0.35 μm standard CMOS process. The work is divided in two parts. In the first part, we have developed a complete etching process (etching type, etching time). After considering different aspects of the CMOS-MEMS technology available in the literature, the CMOS-MEMS process has been defined. This process consists of silicon dioxide sacrificial layers etching to release MEMS structures made by metallic layers of the AMS 0.35 μm CMOS process. Microstructures, like cantilever beams or fixed-fixed beams, have been used to develop and validate this process. The second part of the work was focused on the validation of the CMOS-MEMS process based on the AMS 0.35 μm CMOS technology for the fabrication of a capacitive MEMS microphone. A lumped parameters equivalent circuit, based on the electro-acoustic and electro-mechanical analogies, has been realized and used for the simulation of the capacitive MEMS microphone. The model takes into account various aspects of the industrial AMS 0.35 μm CMOS process (materials, dimensions, design rules,...). Each parameter of the equivalent circuit is determined with a help of analytical relations and simulation software based on the finite element method (ANSYS, CoventorWare). After the modeling, the layout of several MEMS microphones structures has been finalized in Cadence Virtuoso software and sent to AMS foundry. After the completion of the CMOS process, the etching process, studied previously, was applied in order to release the MEMS microphones and other test structures. Finally, electrical and mechanical measurements have been performed, firstly, on the MEMS microphones to determine its characteristics (resonant frequency, sensitivity,...) and secondly, on the test microstructures, to estimate the mechanical properties (Young's modulus and residual stress) of the metallic layers used to form the microphones structures. Thus, the equivalent circuit was improved according to obtained results and validated.Récemment, des travaux montrant la faisabilité des MEMS à base de la technologie CMOS complétée par un micro-usinage en surface sans masque ont été publiés. A la différence de l'approche plus ancienne où la libération des composants MEMS a été faite par une gravure du silicium, la technologie proposée consiste en la gravure des couches d'oxyde afin de libérer les couches métalliques issues de la technologie CMOS. Ce sujet de thèse propose donc de fabriquer des microsystèmes à vocation acoustique à partir d'une technologie CMOS standard : AMS 0.35 μm. Il sera, pour cela, composé de deux parties. Dans la première partie, il s'agit de développer un procédé technologique (déterminer le type de gravure, les temps de gravure, ainsi que les dimensions extrêmes réalisables pour les structures simples en technologie CMOS). En effet, après avoir étudié les différentes possibilités de la technologie CMOS-MEMS proposées dans la littérature, un procédé CMOSMEMS a été mis au point. Ce procédé consiste à graver une couche sacrificielle d'oxyde afin de libérer des microstructures constituées des couches métalliques issues de la technologie CMOS 0.35 μm d'AMS. Le procédé est premièrement testé sur des échantillons contenant des microstructures telles que des ponts et des poutres. La seconde partie du travail est consacrée à la validation du procédé CMOS-MEMS par un développement de structures MEMS acoustiques représentées par un microphone MEMS capacitif. Dans un premier temps, un microphone MEMS capacitif a été réalisé à partir de la technologie CMOS 0.35 μm d'AMS. Après avoir pris connaissance des différents aspects de la technologie CMOS 0.35 μm d'AMS (matériaux, dimensions, règles de dessin,...), une modélisation de microphone MEMS capacitifs est proposée grâce à la réalisation d'un schéma électrique équivalent basé sur les analogies entre les domaines électrique, mécanique et acoustique. Chaque paramètre de ce circuit est déterminé par l'intermédiaire de relations connues et par des logiciels de simulation utilisant la méthode des éléments finis (ANSYS, CoventorWare). Une fois les performances des microphones estimés à partir de ce circuit équivalent, un layout, représentant les différents microphones conçus, a été créé sous Cadence afin d'être envoyé au fondeur AMS. Dès la réception des échantillons, le procédé CMOSMEMS mise en oeuvre précédemment a été appliqué afin de libérer les structures des différents dispositifs. Ensuite, une série de caractérisations a pu être réalisée sur les premiers échantillons. Ces caractérisations visent à déterminer les performances des différents dispositifs fabriqués, mais aussi à estimer les propriétés mécaniques des différentes couches utilisées pour former la structure des microphones. De cette façon, le circuit équivalent pourra être validé ou être amélioré selon les résultats obtenus

Stacked Disks Resonators and Micromachined Microphones: Design and Modeling

In this thesis, the design and modeling of two micromachined systems are presented. The two devices are a novel stacked disks resonator designed for radio frequency systems and a set of microphones with released membrane designs for photoacoustic gas sensing for CO2 monitoring in demand controlled ventilation systems. For the novel stacked disk resonator design, an analytical model for the frequency separation is derived and verified using finite element analysis. The model provides useful insight into the coupling mechanisms of two or more vertically stacked disks connected via a central stem. One unsuccessful and one incomplete fabrication trial is presented and analyzed. In addition, an analytical model for support losses adapted from a simple model for soil-structure interaction is investigated and found useful for estimating the support losses. The novelty of stacked disk resonator is vertical integration of devices previously only demonstrated integrated in-plane. Vertical integration allows smaller footprint. Although fabrication has yet proved unsuccessful, useful models have been developed and insight into the coupling mechanisms gained. Two different designs of the miniaturized microphones have been designed, fabricated and characterized. Both designs feature released membranes, but of different thickness. They are designed for high sensitivity at low frequencies. Compared to a similar microphone published in the literature, the microphones presented here feature a doubling and thirty fold improvement in sensitivity for the frequency range of interest for the two designs

Design et développement d'un capteur acoustique imprimé.

The objective of this work was to design and fabricate a low cost resonant capacitive acoustic sensor using printing techniques. It falls within the frame of a collaborative research project named “Spinnaker”, set up by TAGSYS RFID, a French company, which has planned to integrate this sensor to improve the geolocalization of their RFID tags. This work started with the design and optimization of the sensor using finite element modeling (COMSOL) and design of experiments (DOE). This first step has enabled the identification of the optimum set of parameters and demonstrated that the output responses were in accordance with the specifications. Then, we have developed the different technological building blocks required for the fabrication of the prototypes using jointly the 2D inkjet printing technique and 3D printing method. The functionality of the sensors has been characterized using both capacitive and acoustic measurements using laser Doppler vibrometer. Experimental results showed that sensitivity and selectivity were within the specifications and in good agreement with the modeling results. Finally, we investigated the piezoelectric approach which could be an interesting option to the capacitive one. Since no inkjet printable piezoelectric ink is commercially available, stable inkjet printable polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) ink has been developed. PVDF-TrFE layers were then successfully printed and characterized. The results were quite promising, however further improvements of the ink and printing process are required before stepping towards piezoelectric based device fabrication.L’objectif de ce travail était de concevoir et réaliser par impression un capteur acoustique capacitif résonant bas coût. Il s’inscrit dans le cadre d’un projet collaboratif de recherche intitulé « Spinnaker », défini par la société Tagsys RFID qui souhaite intégrer ce capteur afin d’améliorer la géolocalisation des étiquettes RFID. Ce travail a débuté par la conception et l’optimisation du design en utilisant la simulation par éléments finis (COMSOL) ainsi que des plans d’expériences (DOE : Design of Experiment). Cette première étape a permis de déterminer les paramètres optimaux et démontrer que les performances obtenues étaient conformes aux spécifications. Nous avons ensuite développé les différentes briques technologiques nécessaires à la réalisation des prototypes en utilisant conjointement l’impression 2D par inkjet et l’impression 3D. Nous avons vérifié la fonctionnalité de ces capteurs à l’aide de mesures électriques capacitives et acoustiques par vibrométrie laser. Nous avons démontré la sélectivité en fréquence des capteurs réalisés et comparé les résultats expérimentaux à ceux obtenus par simulation. Enfin, nous avons enfin exploré la « voie piezoélectrique » qui nous semble être une alternative intéressante au principe capacitif. En l’absence d’encre piézoélectrique commerciale imprimable par jet de matière, nous avons formulé une encre imprimable à base du co-polymère PVDF-TrFE et démontré le caractère piézoélectrique des couches imprimées. Les résultats sont prometteurs mais des améliorations doivent encore être apportées à cette encre et au procédé d’impression avant de pouvoir fabriquer des premiers prototypes

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

Piezoresistive Microphone with Arc-shaped Springs

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2021. 2. 조동일.미세전자기계시스템 (microelectromechanical system; MEMS) 센서는 사물인터넷 (internet of things; IoT)의 급성장을 중심으로 다품종, 고성능 제품에 대한 수요가 크게 증가하여 새로운 호황을 맞이하고 있다. 특히, MEMS 마이크로폰의 경우 스마트폰 출시와 더불어 최근 스마트모빌리티, AI 기술 기반 음성인식으로의 적용으로 급격한 시장 성장세를 보인다. MEMS 마이크로폰은 감지방식에 따라 정전용량형, 압전형, 압저항형 3가지로 구분된다. 정전용량형 마이크로폰의 경우 면적이 크고 공정의 복잡성이 높은 단점이 있다. 압전형의 마이크로폰의 경우 압전층을 구성하는 물질 중 박막형태로 가공가능한 종류가 제한적이며 저주파의 신호 측정에는 특성이 불안정하다는 단점이 있다. 압저항 감지방식은 위 두가지 방식의 단점을 해결할 수 있으나 도핑 방법으로는 압저항 효과를 증가시키는데 한계가 있으며, 이로 인해 센서의 민감도 향상에 제한적이다. 본 논문에서는 이러한 문제를 해결하기 위해 수행한 스마트센서용 초소형 NEMS 공정플랫폼 개발 과제의 일한으로 관련 공정설계를 하였으며 최종적으로 마이크로폰을 제작하여 성능의 측정을 진행하였다. 과제에서 제안된 마이크로폰은, 멤브레인의 가장자리에 위치한 스프링 구조물을 호형태로 구부려 멤브레인을 둘러싸는 구조로 설계하여 면적을 최소화할 수 있으며, 우수한 압저항 특성을 가진 실리콘 나노와이어를 호형태 스프링 구조물의 최대응력이 발생하는 위치에 배치해 높은 민감도를 확보할 수 있도록 하였다. 공정은 본 연구진 고유의 실리콘 나노와이어 제조 공정 기술을 응용하여 2~300 nm 급 크기를 가지며 Si3N4 기반 스프링 구조물 및 멤브레인과 함께 부유된 실리콘 나노와이어 기반 MEMS 마이크로폰의 공정설계를 하고 제작하였다. 최종적으로, 제작한 마이크로폰에 대해 성능평가를 진행해 민감도 52.94 mV/Pa 및 SNR 52.89 를 확보하였고, 이는 타연구진의 실리콘 나노와이어 기반 MEMS 마이크로폰 연구결과보다 우수하며, 상용 마이크로폰에 준하는 특성을 보인다.Microelectromechanical system (MEMS) sensors are receiving increased attention due to the rapid growth of the Internet of things (IoT), as the demand for multi-species and high-performance products has increased significantly. In particular, MEMS microphones are showing a rapid market growth with the launch of smartphones and the application of smart mobility and AI technology-based voice recognition. Depending on the sensing method MEMS microphones are classified into three types: capacitive, piezoelectric, and piezoresistive. The capacitive microphones require a large area for a large capacitance and also require high process complexity. In the case of the piezoelectric microphones, among the materials constituting the piezoelectric layer, there are limited types of materials that can be processed into a thin film form and the characteristic is unsuitable in measuring low-frequency signals. The piezoresistive microphones can solve the drawbacks of the above two methods, but there is a limit to increasing the piezoresistive effect with the doping method, which limits the improvement of the sensitivity of the sensor. To solve this problem a microphone was designed and fabricated to measure its performance in this paper ,which is a part of a research project named Development of bulk-Si SOLID NEMS fabrication platform for smart sensors performed in our laboratory. The microphone proposed in the project is possible to minimize the area by designing a structure surrounding the membrane by bending the spring structure located at the edge of the membrane in an arc shape. Silicon nanowires with excellent piezoresistance characteristics are designed to secure high sensitivity by placing them in the location where the maximum stress occurs in the arc-shaped spring structure. The process was designed and fabricated for a silicon nanowire-based MEMS microphone with a Si3N4 based spring structure and membrane with a size of 200-300 nm by applying the unique silicon nanowire fabricating process technology of our laboratory. Finally, performance evaluation of the manufactured microphone was conducted to obtain a sensitivity of 52.94 mV/Pa and SNR 52.89, which is superior to the results of research on silicon nanowire-based MEMS microphones by other researchers, and shows characteristics comparable to those of commercial microphones.제 1 장 서 론 1 제 1 절 연구의 배경 1 제 2 절 연구의 내용 5 제 2 장 본 론 7 제 1 절 실리콘 나노와이어 7 제 1 항 실리콘 나노와이어의 압저항 효과 8 제 2 항 실리콘 나노오이어의 공정 기술 8 제 3 항 본 연구진이 보유한 실리콘 나노와이어 공정 기술 10 제 2 절 마이크로폰 설계 12 제 1 항 마이크로폰의 스프링 및 멤브레인 12 제 2 항 마이크로폰의 실리콘 나노와이어 15 제 3 항 호형태 스프링 설계 17 제 3 절 마이크로폰 공법 20 제 1 항 실리콘 나노와이어를 포함하는 마이크로폰 공법 20 제 2 항 마이크로폰 제작결과 24 제 4 절 마이크로폰 측정 및 분석 38 제 1 항 마이크로폰 소자 및 실험환경 구성 38 제 2 항 마이크로폰 특성 평가 방법 43 제 3 항 마이크로폰 특성 평가 결과 및 분석 44 제 2 장 결 론 52 제 1 절 결론 52 제 2 절 향후 계획 53 참고문헌 54 Abstract 60Maste

Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

Fabrication of suspended plate MEMS resonator by micro-masonry

L'impression par transfert, une technique utilisée pour transférer divers matériaux tels que des molécules d'ADN, de la résine photosensible ou des nanofils semi-conducteurs, s'est dernièrement révélée utile pour la réalisation de structures de silicium statiques sous le nom de micro-maçonnerie. L'étude présentée ici explore le potentiel de la technique de micro-maçonnerie pour la fabrication de résonateurs MEMS. Dans ce but, des microplaques de silicium ont été transférées sur des couches d'oxyde avec cavités intégrées à l'aide de timbres de polymère afin de créer des structures de type plaques suspendues. Le comportement dynamique de ces structures passives a été étudié sous pression atmosphérique et sous vide en utilisant une excitation externe par pastille piézo-électrique mais aussi le bruit thermomécanique. Par la suite, des résonateurs MEMS actifs, à actionnement électrostatique et détection capacitive intégrés, ont été fabriqués en utilisant des étapes supplémentaires de fabrication après impression. Ces dispositifs ont été caractérisés sous pression atmosphérique. Les facteurs de qualité intrinsèques des dispositifs fabriqués ont été évalués à 3000, ce qui est suffisant pour les applications de mesure à pression atmosphérique et en milieu liquide. Nous avons démontré que, puisque l'adhérence entre la plaque et l'oxyde est suffisamment forte pour empêcher une diaphonie mécanique entre les différentes cavités d'une même base, plusieurs résonateurs peuvent être facilement réalisés en une seule étape d'impression. Ce travail de thèse montre que la micro-maçonnerie est une technique simple et efficace pour la réalisation de résonateurs MEMS actifs de type plaque à cavité scellée.Lately, transfer printing, a technique that is used to transfer diverse materials such as DNA molecules, photoresist, or semiconductor nanowires, has been proven useful for the fabrication of various static silicon structures under the name micro-masonry. The present study explores the suitability of the micro-masonry technique to fabricate MEMS resonators. To this aim, silicon microplates were transfer-printed by microtip polymer stamps onto dedicated oxide bases with integrated cavities in order to create suspended plate structures. The dynamic behavior of fabricated passive structures was studied under atmospheric pressure and vacuum using both external piezo-actuation and thermomechanical noise. Then, active MEMS resonators with integrated electrostatic actuation and capacitive sensing were fabricated using additional post-processing steps. These devices were fully characterized under atmospheric pressure. The intrinsic Q factor of fabricated devices is in the range of 3000, which is sufficient for practical sensing applications in atmospheric pressure and liquid. We have demonstrated that since the bonding between the plate and the device is rigid enough to prevent mechanical crosstalk between different cavities in the same base, multiple resonators can be conveniently realized in a single printing step. This thesis work shows that micro-masonry is a powerful technique for the simple fabrication of sealed MEMS plate resonators

Development of dynamic pressure sensor for high temperature applications

Pressure measurement under high temperature environments is required in many engineering applications and it poses many practical problems. Pressure patterns are highly desirable for health monitoring for improved performance and accurate prediction of remaining life of systems used in various applications. Data acquisition in harsh environments has always been a major challenge to the available technology. Sensing becomes more intricate in case if it has to operate under extreme conditions of temperature. Propulsion system applications represent one such area that requires a sensor that is absolutely accurate and has utmost sensitivity coupled with the ability to withstand high temperature. The need for such sensors is driven by the dependence of the performance of propulsion system on pressure pattern encountered along the gas path. Associated with that, high resolution, small size, low time dependent drift and stable range of measurement will complete the performance of such Microsystems Sensors using the current technology are capable of reliable measurement for a limited time at an extremely high cost and are bulky thereby preventing online monitoring. Improvement in the durability of the sensors requires new technology and will definitely open new areas of research. A number of technologies have been lately investigated, these technologies targeting specific applications and they are limited by the maximum operating temperature. The objective of this research is to develop a dynamic pressure measurement system that would be capable of operating at high temperatures with the technology of the device based on Silicon Carbon Nitride (SiCN). The principle of operation is based on the drag effect. Silicon carbon-nitride (SiCN) is a material that has been little explored. The service temperature of SiCN is in the range of 1400°C. The structure is produced from a liquid polymer precursor that could be originally formed into any shape. The proposed micro sensor can measure dynamic pressure and detects flow which is very important to know as the flow continuity is critical in many applications. Furthermore pressure measurement can be used as a base for many aspects. For example the proposed micro sensor could be designed and packaged to be fitted in the gas turbine engine. The correlation of the acquired data from the sensors may provide valuable timely information on imminent instability in the gas flow, detect leakage, improve efficiency et