MEMS ultrasonic transducers for the testing of solids

“…This process can be used to make cMUTs for experimentation [22–25]. Because of the specific thicknesses of the structure layers (Poly0, 1, 2) and the sacrificial layers (Oxide 1, 2), the only standard configurations in MUMPs cMUTs can be one of the four designs found in Table 1.…”

Section: Fabrication Technologymentioning

confidence: 99%

“…The cost for a full wafer costs a total of $4000, but the process allows for building up to 25 shared designs on a single wafer so that 15 2mm × 2mm devices can be obtained for $160 to $180 (<12 per chip). Recently, it has been used to fabricate single and multiple-element cMUT transducers [22–25]. These papers do not, however, report the capability and limitations of this process compared to customized processes in terms of electrical and acoustical performances.…”

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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“…Capacitive-and resonant-type MEMS AE sensors have been actively researched in the academic field [6][7][8][9][10]. Capacitive MEMS sensors have moving electrodes parallel to the fixed ones manufactured by surface micromachining processes.…”

Section: Introductionmentioning

confidence: 99%

Elastic Wave Measurement Using a MEMS AE Sensor

et al. 2017

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Abstract:In recent years, with the continuing progress of aging social infrastructures such as bridges and tunnels, there has been high demand for the assessment of deterioration of their performance and conditions. Since current inspection methods for those structures have mainly relied on human resources, it is important to reduce their increasing maintenance cost. One of the key methods for achieving effective maintenance without expensive human costs is to use sensors to discriminate between healthy and unhealthy conditions. In this paper, a MEMS (micro electro mechanical systems) wideband frequency sensor, which is referred to as a super acoustic (SA) sensor, is evaluated through the pencil lead break (PLB) test. Due to its wideband frequency characteristics, the SA sensor is expected to be a promising alternative to the existing vibration sensors, including acoustic emission (AE) sensors. Several PLB signals were generated on an aluminum plate (5 mm thick), and propagating Lamb waves were detected by both AE and SA sensors. SA sensors were able to identify the location of PLB sources on the plate by measuring time differences between each sensor. By comparing the wave spectrums of both the AE and SA sensors analyzed by wavelet transform, the applicability of SA sensor for AE measurement is verified.

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MEMS ultrasonic transducers for the testing of solids

Cited by 20 publications

References 10 publications

Micro-electro-mechanical-systems (MEMS) for assessing and monitoring civil infrastructures

Micro-electro-mechanical-systems (MEMS) for assessing and monitoring civil infrastructures

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

Elastic Wave Measurement Using a MEMS AE Sensor

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