Fabrication and characterization of a new capacitive micromachined ultrasonic transducer (cMUT) using polysilicon as membrane and sacrificial layer material

Buhrdorf, A.; Lohfink, A.; Junge, S.; Eccardt, P.-C.; Benecke, W.

doi:10.1109/ultsym.2003.1293299

Cited by 7 publications

(7 citation statements)

References 3 publications

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“…The CMUT fabrication based on surface micromachining method has been extensively studied since its inception in 1994 [1,[41][42][43][44][45][46][47][48][49][50][51][52][53][54]. A general surface micromachining process is illustrated in Figure 2.…”

Section: Surface Micromachiningmentioning

confidence: 99%

Fabrication of capacitive micromachined ultrasonic transducers based on adhesive wafer bonding technique

Wong

Chen

et al. 2016

J. Micromech. Microeng.

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To my supervisor, Prof. Yeow. Thank you for giving me the opportunity to work in AMNDL. Thank you for supporting all the equipment/materials, and facility accesses. I know how expensive they are and without you, I would not have been able to execute my ideas and finish the projects. To my committees, Prof. Huissoon, Prof. Nieva and Prof. Stashuk, Thank you for all the comments and suggestions on my project. Additionally, I would say thank you to Prof. Huissoon. You gave me the to come to study in Waterloo and I will never forget the time I received your email where you asked me to come to Canada. To Prof. Cretu, thank you for agreeing to be the external committee and travelling to Waterloo for my defence. The CMUTs in this thesis were fabricated in G2N and TNFC. I would say thank Richard,

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Section: Surface Micromachiningmentioning

confidence: 99%

Fabrication of capacitive micromachined ultrasonic transducers based on adhesive wafer bonding technique

Wong

Chen

et al. 2016

J. Micromech. Microeng.

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“…Because the membrane mode excitation amplitudes determined from (10) are proportional to the voltage v, (10) and (11) together determine the CMUT admittance.…”

Section: Description Of the Cmutmentioning

confidence: 99%

“…Noting that t (me) zz,l (x, y) equals t zz , we are able to calculate the impedance matrix for the different membrane modes. Combining this with (10) and (11), we get the harmonic admittance Y c (K x , K y , ω)…”

Section: Cmut Water Interfacementioning

confidence: 99%

“…here the excitation amplitudes are obtained from (10). To find the transduction losses from an array of amplifiers feeding the array of CMUTs to the power in radiated output waves is then trivial if it is noted that with equal CMUTs and amplifiers, and spatially harmonic voltages from the amplifiers, the voltage on the CMUTs also will be harmonic both in time and space.…”

Section: Cmut Water Interfacementioning

confidence: 99%

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CMUT array modeling through free acoustic CMUT modes and analysis of the fluid CMUT interface through Fourier transform methods

Ronnekleiv

2005

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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A method for analyzing capacitive micromachined ultrasonic transducer (CMUT) arrays and arrays of elements composed of several CMUTs is proposed. It is based on a combination of a free acoustic mode description of an isolated CMUT, and the coupling of these modes to the fluid in which waves should be excited or detected through an impedance matrix that will depend on frequency. The parameters of the model describing the isolated CMUT is independent of frequency and excitation of neighbor CMUTs, whereas the acoustic impedance matrix describing the coupling to the fluid will depend on both the excitation of neighbor CMUTs and frequency. Hence, this splitting of the calculations has a potential for saving computer time. The analysis gives transfer functions from excitations that vary harmonically with time and space along the array surface to CMUT parameters as current, mode excitations, or output acoustic pressure. Based on this, the response of essentially arbitrary excitations of the CMUTs may be obtained.The method is used to analyze an infinitely large array of circular CMUTs on a rectangular grid. The CMUTs are assumed to be operating in collapsed mode. Sharp resonances are shown to occur that could be significantly damped by adding series resistors to the CMUTs or increasing the water viscosity.

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“…Eccardt, Niederer and colleagues showed a standard BiCMOS process with additional modifications [10–12]. They also published another customized process using polysilicon as both membrane and sacrificial layer material [13]. Knight and Degertekin reported a low-stress plasma enhanced chemical vapor deposition (PECVD) for cMUTs fabrication, which is suitable for CMOS electronics integration on a single chip providing test arrays with significantly reduced parasitic capacitance [14,15].…”

Section: Introductionmentioning

confidence: 99%

Capacitive micromachined ultrasonic transducers using commercial multi-user MUMPs process: Capability and limitations

2009

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The objective of this work is to construct capacitive micromachined ultrasouind transducers (cMUTs) using multi-user MEMS (MicroElectroMechanical Systems) process (MUMPs) and to analyze the capability of this process relative to the customized processes commonly in use. The MUMPs process has the advantages of low cost and accessibility to general users since it is not necessary to have access to customized fabrication capability such as wafer-bonding and sacrificial release processes. While other researchers have reported fabricating cMUTs using the MUMPs process none has reported the limitations in the process that arise due to the use of standard design rules that place limitations on the material thicknesses, gap thicknesses, and materials that may be used. In this paper we explain these limitations, and analyze the capabilities using 1D modeling, Finite Element Analysis, and experimental devices. We show that one of the limitations is that collapse voltage and center frequency can not be controlled independently. However, center frequencies up to 9 MHz can be achieved with collapse voltages of less than 200 volts making such devices suitable for medical and non-destructive evaluation imaging applications. Since the membrane and base electrodes are made of polysilicon, there is a larger series resistance than that resulting from processes that use metal electrodes. We show that the series resistance is not a significant problem. The conductive polysilicon can also destroy the cMUT if the top membrane is pulled in the bottom. As a solution we propose the application of an additional dielectric layer. Finally we demonstrate a device built with a novel beam construction that produces transmitted pressure pulse into air with 6% bandwidth and agrees reasonably well with the 1D model. We conclude that cMUTS made with MUMPS process have some limitations that are not present in customized processes. However these limitations may be overcome with the proper design considerations that we have presented putting a low cost, highly accessible means of making cMUT devices into the hands of academic and industrial researchers. Keywordscapacitive micromachined ultrasonic transducer; MUMPS; finite element analysis

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Fabrication and characterization of a new capacitive micromachined ultrasonic transducer (cMUT) using polysilicon as membrane and sacrificial layer material

Cited by 7 publications

References 3 publications

Fabrication of capacitive micromachined ultrasonic transducers based on adhesive wafer bonding technique

Fabrication of capacitive micromachined ultrasonic transducers based on adhesive wafer bonding technique

CMUT array modeling through free acoustic CMUT modes and analysis of the fluid CMUT interface through Fourier transform methods

Capacitive micromachined ultrasonic transducers using commercial multi-user MUMPs process: Capability and limitations

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