专利汇可以提供Capacitive Micromachined Ultrasound Transducers with Pressurized Cavities专利检索,专利查询,专利分析的服务。并且A capacitive micromachined ultrasonic transducer (CMUT) is provided that includes a substrate, a bottom conductive layer disposed on a bottom surface of the substrate, a cavity disposed into a top surface of the substrate, a nonconductive layer disposed on the substrate top surface and on the cavity, a CMUT plate disposed on the nonconductive layer and across the cavity, a top conductive layer disposed on a top surface of the CMUT plate, a pressure control via that spans from the cavity to an ambient environment, and an active pressure controller connected to the pressure control via, wherein the active pressure controller is capable of actively varying a pressure differential across the CMUT plate.,下面是Capacitive Micromachined Ultrasound Transducers with Pressurized Cavities专利的具体信息内容。
What is claimed:
This application claims priority from U.S. Provisional Patent Application 61/768,050 filed Feb. 22, 2013, which is incorporated herein by reference.
The present invention relates generally to Capacitive Micromachined Ultrasound Transducers (CMUTs). More particularly, the invention relates to CMUTs with pressurized cavities for operating in environments with extreme pressure variations.
Capacitive Micromachined Ultrasound Transducers (CMUTs) are increasingly being considered as a better alternative to traditional piezoelectric ultrasound transducers. In airborne applications, CMUTs offer the advantage of better impedance matching to the medium than piezoelectric transducers. One such application for CMUTs is in transit-time ultrasound flowmeters used for flare gas metering. Flare gas metering presents unique challenges due to the large variation in the flow velocities, gas pressures and gas composition. Ultrasound flowmeters are ideal for use in this application. However conventional CMUTs with vacuum backed plates cannot be used under widely varying ambient pressures. The pressure differential across the plate changes the static deflection of the plate, and as a result, the electric field through the gap. In a varying ambient pressure, the transmit and receive sensitivities and the operating frequency would vary considerably. Beyond a certain pressure, the CMUT plates would collapse onto the substrate and would drastically change their operating frequency.
In one attempt to address this problem, one group proposed operating CMUTs in a permanent contact mode even under 1 atm pressure. This would enable a more stable operating point over a wider operating pressure range. However, even such a CMUT would still be limited by the mechanical strength of the structure. Beyond a certain pressure, such a CMUT would fail mechanically.
What is needed is a CMUT that is capable of operating in environments ranging from relatively low pressure to several atmospheres of pressure.
To address the needs in the art, a capacitive micromachined ultrasonic transducer (CMUT) is provided that includes a substrate, a bottom conductive layer disposed on a bottom surface of the substrate, a cavity disposed into a top surface of the substrate, a nonconductive layer disposed on the substrate top surface and on the cavity, a CMUT plate disposed on the nonconductive layer and across the cavity, a top conductive layer disposed on a top surface of the CMUT plate, a pressure control via that spans from the cavity to an ambient environment, and an active pressure controller connected to the pressure control via, wherein the active pressure controller is capable of actively varying a pressure differential across the CMUT plate.
In one aspect of the invention, the CMUT plate is capable of operating at multiple resonance modes, where the resonance modes are a result of the interaction between the resonant mode of the plate and the acoustic resonance in the medium of the cavity and vias.
In a further aspect of the invention, the pressure control via spans from the cavity through the bottom conductive layer, or from the cavity through the CMUT plate.
According to another aspect of the invention, the active pressure controller is capable of controlling the signal gain of the CMUT, the signal bandwidth of the CMUT, or the signal gain and the signal bandwidth of the CMUT.
In another aspect of the invention, the signal gain and signal bandwidth of the CMUT are determined by parameters that include the size of the CMUT, the shape of the CMUT, the location of the pressure control vias and the number of the pressure control vias.
The current invention includes venting the cavities of CMUTs for environments with extreme pressure variations. In one embodiment, the CMUT has zero differential pressure across the plate at any ambient pressure, thus ensuring a stable operating point and preventing mechanical failure. The venting vias are etched through the substrate or throughout the CMUT plate (see
Helmholtz resonance dominated mode maintains its frequency and bandwidth under varying ambient pressure.
A CMUT cavity vented to the ambient environment ensures a zero differential pressure across the plate, and provides a stable operating point for the CMUT under varying ambient pressure. Also, with no pressure across the plate, such a CMUT is able to operate under any pressure condition with no risk of mechanical damage or failure.
According to embodiments of the current invention, the CMUT cavity is vented by etching via holes through the CMUT plate or through the substrate. According to one embodiment, the fabrication process for the CMUT 100 starts with a low resistivity silicon wafer 102 (see
The signal gain and signal bandwidth of the CMUT are determined by parameters that include the size of the CMUT, the shape of the CMUT, the location of the pressure control vias and the number of the pressure control vias.
In some exemplary embodiments, a variety of CMUTs were fabricated using this process by varying the plate thickness, plate radius and gap height. The dimensions of the vias were kept the same for ease of fabrication however the number of vias and the arrangement of these vias were varied as shown in
The fabricated CMUTs 100 were singulated by dicing, mounted on chip carriers and wirebonded (see
In an exemplary embodiment, the CMUTs were initially characterized under 1 atm pressure. The CMUTs were biased with a DC voltage and excited with an AC voltage while sweeping the frequency. The displacement amplitude was measured under a laser Doppler vibrometer (LDV; OFV-511, Polytec GmbH, Waldbronn, Germany). As expected, the CMUTs exhibit two resonant modes (see
Keeping all other parameters the same, as the plate radius is increased, the Helmholtz dominated mode becomes stronger than the plate dominated mode (see
The frequency of the Helmholtz dominated mode decreases as the plate radius is increased. This trend conforms to the theoretical frequency [6] for a pure Helmholtz resonator of similar dimensions (see
In another exemplary embodiment, a pair of identical devices was arranged in a pitch-catch setup in a pressure chamber at a distance of 7 cm from each other. Since these CMUTs have a relatively large bandwidth, the short circuit resonance frequency of the transmitting CMUT and the open circuit resonance frequency of the receiving CMUT need not be matched perfectly by adjusting the bias voltage.
Ideally both the CMUTs can be biased closer to their collapse voltage to optimize the transmitting and receiving sensitivity. For this example, both the transmitting and receiving CMUT were biased at 300 V (˜65% of collapse). The bias voltage was limited to protect the devices against any dielectric breakdown. The wider bandwidth of these CMUTs allows for a shorter transmit burst signal. In this case, the transmitting CMUT was excited by a 3 cycle AC burst and the signal from the receiving CMUT was recorded (see
The pressure in the chamber was varied from 1.01 bar (1 atm) up to 20 bar and the frequency spectrum of the pitch-catch signal was studied. At lower pressure the devices show a stronger signal at the plate dominated mode (at ˜130 kHz for this design). However as the pressure is increased, the plate dominated mode loses strength. Also its frequency and bandwidth decrease. On the contrary the Helmholtz resonance dominated mode (at ˜35 kHz for this design) becomes stronger with increasing pressure. Also, it maintains its frequency and bandwidth over the varying pressure.
Exemplary fabricated CMUTs are presented with cavities vented to the ambient atmosphere. Such CMUTs exhibit two peaks in their harmonic response, owing to the resonance of the plate and the acoustic Helmholtz resonance of the gas/fluid in the cavity and the venting via holes. The strength of the Helmholtz resonance peak strongly depends on the number of vias venting the CMUT cavity. The relative strength of the two modes also depends on the ambient pressure. With an increase in ambient pressure, the Helmholtz resonance mode becomes stronger while the plate resonance dominated mode weakens. Although its strength varies with the ambient pressure, the Helmholtz resonance mode maintains its frequency and bandwidth under varying pressure. This makes it quite attractive for use in transit-time flowmeters under varying pressure.
The present invention has now been described in accordance with several exemplary embodiments, which are intended to be illustrative in all aspects, rather than restrictive. Thus, the present invention is capable of many variations in detailed implementation, which may be derived from the description contained herein by a person of ordinary skill in the art. All such variations are considered to be within the scope and spirit of the present invention as defined by the following claims and their legal equivalents.
标题 | 发布/更新时间 | 阅读量 |
---|---|---|
声波探针用组合物、声波探针用硅酮树脂、声波探针及超声波探针以及相关装置 | 2020-05-08 | 415 |
微图案化碳-碳纳米管复合材料电极微加工工艺及应用 | 2020-05-17 | 98 |
直肠检查装置的探头及直肠检查装置 | 2020-05-12 | 284 |
Ultrasonic Sensor Microarray and Method of Manufacturing Same | 2020-05-21 | 67 |
Capacitive Micromachined Ultrasound Transducers with Pressurized Cavities | 2020-05-24 | 229 |
Method of varying the flow rate of fluid from a medical pump and hybrid sensor system performing the same | 2020-05-23 | 846 |
ULTRASONIC TRANSDUCER DEVICE WITH THROUGH-SUBSTRATE VIA | 2020-05-15 | 504 |
MULTI-MODE CAPACITIVE MICROMACHINED ULTRASOUND TRANSDUCER AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS | 2020-05-16 | 839 |
ULTRASONIC SENSOR MICROARRAY AND METHOD OF MANUFACTURING SAME | 2020-05-25 | 833 |
ULTRASONIC SENSOR MICROARRAY AND ITS METHOD OF MANUFACTURE | 2020-05-21 | 528 |
高效检索全球专利专利汇是专利免费检索,专利查询,专利分析-国家发明专利查询检索分析平台,是提供专利分析,专利查询,专利检索等数据服务功能的知识产权数据服务商。
我们的产品包含105个国家的1.26亿组数据,免费查、免费专利分析。
专利汇分析报告产品可以对行业情报数据进行梳理分析,涉及维度包括行业专利基本状况分析、地域分析、技术分析、发明人分析、申请人分析、专利权人分析、失效分析、核心专利分析、法律分析、研发重点分析、企业专利处境分析、技术处境分析、专利寿命分析、企业定位分析、引证分析等超过60个分析角度,系统通过AI智能系统对图表进行解读,只需1分钟,一键生成行业专利分析报告。