Design of a poly silicon MEMS microphone for high signal-to-noise ratio
01 Sep 2013-pp 292-295
TL;DR: This paper reports on the state of the art silicon micromachined microphone utilizing a dual poly silicon membrane system, where the perfect fit of simulation versus measurements enables deeper analysis and balancing of noise contributors.
Abstract: This paper reports on the state of the art silicon micromachined microphone utilizing a dual poly silicon membrane system. MEMS chips from 1.4mm down to 1.0mm side length are applied for mobile communication. Design aspects related with key performance parameters such as sensitivity, signal to noise ration and distortion are discussed. Sensitivity of − 38BV/Pa is achieved for different microphone membrane diameters. A maximum signal to noise ration of 66dB(A) for the largest system could be achieved. The perfect fit of simulation versus measurements enables deeper analysis and balancing of noise contributors. Environmental noise suppression of 5dB by acoustical high pass design is demonstrated. ()
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TL;DR: This review is to identify the issues in MEMS microphone designs and thoroughly discuss the state-of-the-art solutions that have been presented by the researchers to improve performance and serve as a starting guide for new researchers in the field of capacitive MEMS microphones.
Abstract: This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of this review is to identify the issues in MEMS microphone designs and thoroughly discuss the state-of-the-art solutions that have been presented by the researchers to improve performance. Considerable research work has been carried out in capacitive MEMS microphones, and this field has attracted the research community because these designs have high sensitivity, flat frequency response, and low noise level. A detailed overview of the omnidirectional microphones used in the applications of an audio frequency range has been presented. Since the microphone membrane is made of a thin film, it has residual stress that degrades the microphone performance. An in-depth detailed review of research articles containing solutions to relieve these stresses has been presented. The comparative analysis of fabrication processes of single- and dual-chip omnidirectional microphones, in which the membranes are made up of single-crystal silicon, polysilicon, and silicon nitride, has been done, and articles containing the improved performance in these two fabrication processes have been explained. This review will serve as a starting guide for new researchers in the field of capacitive MEMS microphones.
23 citations
Cites methods or result from "Design of a poly silicon MEMS micro..."
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TL;DR: The test results show that the structure of the square diaphragm with partially-etched piezoelectric layer can significantly improve the transducer sensitivity.
Abstract: A square piezoelectric composite diaphragm was analyzed by the finite element method to enhance the sensitivity of a piezoelectric micromachined ultrasound transducer (pMUT). The structures of electrode and piezoelectric film were optimized and a centric electrode was designed to avoid the counteraction of stress in the centre and edges. In order to further improve the sensitivity; a pMUT with partially-etched piezoelectric film was adopted. The receive and transmit sensitivities of the pMUT were analyzed in details. The receive sensitivity of pMUT with partially-etched ZnO film is 3.3 dB or 6.8 dB higher than those with a centric and whole electrode, respectively; and the amplitude of a partially-etched ZnO film pMUT under a certain voltage is 5.5 dB and 30 dB higher than those with centric and whole electrode separately. Two pMUT-based ZnO films were fabricated by micromachining technology and their receive and transmit sensitivities were tested. The ZnO films deposited by direct current (DC) magnetron sputtering exhibit a densely packed structure with columnar crystallites. The test results show that the structure of the square diaphragm with partially-etched piezoelectric layer can significantly improve the transducer sensitivity. The receive sensitivity and transmit sensitivity are −238.35 dB (ref. 1 V/μPa) and 150.42 dB (ref. 1 μPa/V); respectively.
16 citations
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TL;DR: Graphene is a promising candidate for future electronic devices because of its outstanding electronic and mechanical properties as discussed by the authors, and the high charge carrier mobility in graphene, particularly in substrategies, has been demonstrated.
Abstract: Graphene is a promising candidate for future electronic devices because of its outstanding electronic and mechanical properties. The high charge carrier mobility in graphene, particularly in substr...
16 citations
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TL;DR: In this paper, a programmable MEMS microphone with variable bias voltage and variable gain was developed and fabricated and the sensitivity of this microphone can be adjusted within a range of 11dB.
Abstract: This paper presents a method for calibrating MEMS microphones after the fabrication process. This allows compensating process tolerances and packaging stress of the capacitive membrane-backplate system. A programmable MEMS microphone with variable bias voltage and variable gain was developed and fabricated. The sensitivity of this microphone can be adjusted within a range of 11 dB. The adjustability was used to trim the sensitivity towards a specified value and to reduce the variation of the sensitivity. In mass production a tight sensitivity of ±1 dB could be reached, for a specified sensitivity of −38 dBV/Pa @ 1 kHz. In addition the microphone signal to noise ratio was increased to values above 66 dB(A) by choosing high bias voltages and matching gain calibration. The relationship between bias supply voltage and the non-linear dynamics of a double backplate sensor is explained. The influence of programming on the sensitivity, noise, SNR, THD and frequency response was investigated.
15 citations
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TL;DR: In this article, the series resistance limit of the vertically stacked cantilever (VSC) nanowire has been investigated and the feasibility of improving current level within the same footprint and without degrading sub-threshold performance is demonstrated.
Abstract: We had successfully suspended the vertically stacked cantilever (VSC) nanowire by two approaches: 1) inserting a SiN layer as reinforcement to sustain the gate-stack thermal budget and 2) adopting high- ${k}$ metal gate low-temperature process and realizing gate-all-around structure, which shows better subthreshold characteristics. Feasibility of improving current level within the same footprint and without degrading subthreshold performance is demonstrated. Series resistance limit is pointed out as a bottle neck for current increment with respect to layers of channels. Further investigation of reducing the series resistance of VSC nanowire is needed for any future circuit integration.
13 citations
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References
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TL;DR: In this article, an algebraic expression for the mechanical compliance of corrugated membranes and membranes supported at spring elements has been derived for both types of membranes with the help of an enhanced theory of circular membranes.
Abstract: In this paper, advanced membrane designs are simulated in order to improve the sensitivity of micromachined silicon condenser microphones. Analytical analyzes and finite element simulations have been carried out to derive algebraic expressions for the mechanical compliance of corrugated membranes and membranes supported at spring elements. It is shown that the compliance of both types of membranes can be modeled with the help of an enhanced theory of circular membranes. For spring membranes, a numerically derived and design dependent constant takes into account the reduced suspension. The mechanical stress in corrugated membranes is calculated using a geometrical model and is confirmed by finite element simulations. A very good agreement between theory and experimental results is demonstrated for spring membranes of different shape and for membranes with varying number of corrugations. In a silicon microphone application, a high electro-acoustical sensitivity up to 8.2 mV/Pa/V is achieved with a membrane diameter of only 1 mm.
52 citations
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TL;DR: In this paper, a single-chip capacitive microphone has been developed at Siemens, utilizing a modified standard CMOS process with adjacent bulk micromachining, enabling low output impedance of the signal.
Abstract: Applications ranging from hearing aids over communication to noise cancellation open up a high volume market for low‐cost, batch producible and reliable microphones. To obey these conditions, a single‐chip capacitive microphone has been developed at Siemens, utilizing a modified standard CMOS process with adjacent bulk micromachining. In a first step, the microphone is integrated with a source follower, enabling low output impedance of the signal. The technology allows for the future integration of advanced circuitry. The microphone consists of an acoustically sensitive polycrystalline silicon membrane and a highly perforated back‐plate as the counter electrode. To achieve highly sensitive devices, special emphasis was given to the stress of the polycrystalline silicon membrane, which should be slightly tensile. Another key issue during the fabrication and in operation is to prevent stiction of the sensitive membrane. Since the overall chip size is below 3‐mm side length, surface mounting in low‐cost SMD packages is possible.
25 citations
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01 Jan 2007
TL;DR: In this paper, an typischen Demonstratoren werden Wege aufgezeigt, wie die Komplexitat der Modelle, angepasst an die jeweilige Problemstellung, so reduziert kann, da diese gekoppelten Effekte moglichst genau und physikalisch basiert, but dennoch mit angemessenem Rechenaufwand in die Simulationen einbezogen wennt konnen.
Abstract: Im Rahmen der vorliegenden Arbeit werden Ansatze und Methoden zur Modellierung von gekoppelten Effekten in Mikrosystemen auf Bauelemente- und Systemebene entwickelt. Im Mittelpunkt der Untersuchungen stehen hierbei die elektromechanische Kopplung und die Fluid-Struktur-Wechselwirkung mit einem Schwerpunkt auf der viskosen Dampfung bei dynamisch betriebenen Mikrobauelementen. An typischen Demonstratoren werden Wege aufgezeigt, wie die Komplexitat der Modelle, angepasst an die jeweilige Problemstellung, so reduziert werden kann, da diese gekoppelten Effekte moglichst genau und physikalisch basiert, aber dennoch mit angemessenem Rechenaufwand in die Simulationen einbezogen werden konnen.
11 citations
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