Mechanical Modeling and Sensitivity Evaluation of an Electrodynamic MEMS Microsensor (original) (raw)

Electroacoustic Analysis of a Controlled Damping Planar CMOS-MEMS Electrodynamic Microphone

Archives of Acoustics, 2015

This paper gives a detailed electroacoustic study of a new generation of monolithic CMOS micromachined electrodynamic microphone, made with standard CMOS technology. The monolithic integration of the mechanical sensor with the electronics using a standard CMOS process is respected in the design, which presents the advantage of being inexpensive while having satisfactory performance. The MEMS microphone structure consists mainly of two planar inductors which occupy separate regions on substrate. One inductor is fixed; the other can exercise out-off plane movement. Firstly, we detail the process flow, which is used to fabricate our monolithic microphone. Subsequently, using the analogy between the three different physical domains, a detailed electro-mechanical-acoustic analogical analysis has been performed in order to model both frequency response and sensitivity of the microphone. Finally, we show that the theoretical microphone sensitivity is maximal for a constant vertical positio...

Highly flexible membrane systems for micromachined microphones-modeling and simulation

This paper presents a mechanical modeling of membrane systems applicable to micromachined microphones requiring a low stiffness constant. We have recently developed a single-chip electrodynamic microphone in a CMOS MEMS technology. The microphone consists of a suspended square membrane of 1.4mm side, 3µm thick and 10µg, and two concentric inductors. This suspended moving membrane is fixed to the substrate with 4 attachments arms. In order to achieve a desired flat frequency response characteristic, covering the entire acoustic band, several attachment designs are presented, studied and compared. These designs include crab-leg, meander, U-spring and serpentine forms. We have found that for comparable dimensions, the U-spring form presents the highest compliance and the meander type is the stiffest.

Electromagnetic modeling of an integrated micromachined inductive microphone

This paper presents a detailed electromagnetic modeling for a new structure of a monolithic CMOS micromachined inductive microphone. This study is of capital importance for the optimization of this new microphone structure based on the variation of mutual inductance between an external fixed inductor and an internal suspended inductor. A prototype fabrication of this microphone has been done in a CMOS compatible process using a 0.6 /lm technology. The modeling results show that the use of an AC current in the primary fixed inductor gives a much larger induced voltage in the secondary inductor comparing to the case when a DC current is used. The induced voltage evaluated, in the /l V range using a DC current solution, is multiplied by a factor of 3 to 6 when using the AC alternative current. We find a value of I nA for the current induced in the secondary inductor, which indicates that the Laplace force generated will have a negligible effect on the membrane displacement. We have proposed the use of the symmetric dual-layer spiral inductor structure that can increase the induced emfvalue by a factor of 4.

An analytical-numerical method for determining the mechanical response of a condenser microphone

The Journal of the Acoustical Society of America, 2011

The paper is based on determining the reaction pressure on the diaphragm of a condenser microphone by integrating numerically the frequency domain Stokes system describing the velocity and the pressure in the air domain beneath the diaphragm. Afterwards, the membrane displacement can be obtained analytically or numerically. The method is general and can be applied to any geometry of the backplate holes, slits, and backchamber. As examples, the method is applied to the Bruel & Kjaer (B&K) 4134 1/2-inch microphone determining the mechanical sensitivity and the mechano-thermal noise for a domain of frequencies and also the displacement field of the membrane for two specified frequencies. These elements compare well with the measured values published in the literature. Also a new design, completely micromachined (including the backvolume) of the B&K micro-electro-mechanical systems (MEM) 1/4-inch measurement microphone is proposed. It is shown that its mechanical performances are very similar to those of the B&K MEMS measurement microphone.

A Novel Method for Reducing the Sensitivity Deviation of MEMS Microphones by Programming

Procedia Engineering, 2015

This paper describes a novel method for trimming a low noise, differential micro-electromechanical system (MEMS) microphone with a state of the art signal to noise ratio (SNR) of 66 dB(A) and a sensitivity of-38 dBV/Pa 1kHz after completing the fabrication process. The method allows compensating the electroacoustic variations caused by process tolerances and reducing specification limits of the microphone sensitivity from ±3 dB to ±0.5 dB. Trimming is done by programming the bias supply voltage of the capacitive membrane-backplate-system and the gain factor of the output pre-amplifier. Microphone sensitivity can be modified within a range of 11.2 dB. Thus the standard deviation of the sensitivity of a production batch could be reduced from 0.97 dB to 0.11 dB. Furthermore the SNR could be increased to 66.5 dB(A).

Design Of Spring-Supported Diaphragm Capacitive MEMS Microphone

2016

In this research project, the design and performance optimization techniques of a microelectromechanical (MEMS) condenser microphone will be studied and described using several established plate theories and numerical analysis. MEMS microphone is shown to have been increasingly popular to be used in various consumer electronic products especially in the mobile phone industry and hearing aid devices. Thus, it is important for the microphone designers to be able to design and improve a microphone’s performance given sets of design constraints in the shortest time possible while reducing the overall overhead cost associated with the mass production exercise. The proposed new spring-supported diaphragm MEMS microphone has a higher open-circuit sensitivity, sufficiently high pull-in voltage, adequate frequency response in the audio range bandwidth, and uses fewer fabrication masks to reduce the overall production cost and possibly reduce the production rejection rate. The mathematical mo...

Design Approaches of MEMS Microphones for Enhanced Performance

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.

A Review of MEMS Capacitive Microphones

Micromachines

This review collates around 100 papers that developed micro-electro-mechanical system (MEMS) capacitive microphones. As far as we know, this is the first comprehensive archive from academia on this versatile device from 1989 to 2019. These works are tabulated in term of intended application, fabrication method, material, dimension, and performances. This is followed by discussions on diaphragm, backplate and chamber, and performance parameters. This review is beneficial for those who are interested with the evolutions of this acoustic sensor.

Design and implementation of an acoustic-vibration capacitive MEMS microphone

AIP Advances

A novel acoustic-vibration capacitive microelectromechanical system microphone is designed, fabricated, and implemented in this paper. The new microphone consists of a rigid diaphragm and mass blocks sensitive to low-frequency vibratory and sound signals. This sensor takes advantage of the semiconductor technology to design the capacitance sensor structure by surface micromachining technology, and the inertial mass blocks are shaped using the bulk silicon micromachining technology. The structure of the anti-stiction-dimple array is designed and deployed at the bottom of the diaphragm and the backplate to avoid the risk of sensor failure by vibration stiction. The bottom and top of the backplate are designed with an anti-humidity hydrophobic insulation protective layer, which avoids adsorption of moisture and attachment of foreign particles. The thickness of the mass blocks can be controlled by the combination of the dry and the wet micromachining method, which is sensitive to differ...

Performance of Piezoelectric MEMS Microphones

2019

This semester project deals with the study of at fully clamped plates with various geome- tries (circular and square), piezoelectric properties and uniformly distributed load (normal to the surface). The stress distribution is analyzed in order to obtain an electrical displacement. The objective is to distinguish positive and negative stresses areas in our plate in order to dene an area for current measurements for microphone applications. For the circular plate, a straightforward analytical resolution of the problem is presented. For the square plate, the method of study is carried out mainly using the Galerkin method combined with the help of the symbolic algebraic software, Mathematica. The de ection of the plates is expressed in a series of polynomials which satisfy the homogeneous boundary conditions. Mathematica is used to solve for the coecients and generating the trial functions. The stress of the plate is then determined. Then the results obtained are compared with the exac...