阅读说明：本技术 基于Helmholtz共振腔的可调频声波接收装置 (Frequency-adjustable sound wave receiving device based on Helmholtz resonant cavity ) 是由 孙成亮 王磊 吴志鹏 朱伟 胡博豪 林炳辉 周禹 于 2019-08-15 设计创作，主要内容包括：本发明涉及一种基于Helmholtz共振腔的可调频声波接收装置,包括Helmholtz共振腔和声学传感器,所述Helmholtz共振腔包括腔体以及与所述腔体连通的通孔,所述Helmholtz共振腔设置在所述声学传感器上且所述腔体与所述声学传感器的表面接触连接。本发明将MEMS声学传感器和Helmholtz共振腔相结合,灵敏度高,能够提高超声换能器的电声能量转换效率。(The invention relates to a frequency-adjustable sound wave receiving device based on a Helmholtz resonant cavity, which comprises the Helmholtz resonant cavity and an acoustic sensor, wherein the Helmholtz resonant cavity comprises a cavity body and a through hole communicated with the cavity body, the Helmholtz resonant cavity is arranged on the acoustic sensor, and the cavity body is in contact connection with the surface of the acoustic sensor. The invention combines the MEMS acoustic sensor with the Helmholtz resonant cavity, has high sensitivity and can improve the electro-acoustic energy conversion efficiency of the ultrasonic transducer.)

1. The utility model provides an adjustable frequency sound wave receiving arrangement based on Helmholtz resonant cavity which characterized in that, includes Helmholtz resonant cavity and acoustic sensor, the Helmholtz resonant cavity include the cavity and with the through-hole of cavity intercommunication, the Helmholtz resonant cavity sets up on the acoustic sensor and the cavity with acoustic sensor's surface contact is connected.

2. The Helmholtz-resonator-based tunable acoustic wave receiving device according to claim 1, wherein said cavity is formed by a hollow silicon structure provided on the surface of said acoustic sensor and enclosing the surface of said acoustic sensor, said through hole being provided on said silicon structure.

3. the tunable acoustic wave receiving device based on a Helmholtz resonant cavity of claim 1, wherein the size, number, shape and location of said through holes are determined by the resonant frequency of said Helmholtz resonant cavity.

4. The Helmholtz-resonant-cavity-based adjustable-frequency acoustic wave receiving device of claim 1, wherein said acoustic sensor is a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer.

5. the Helmholtz resonant cavity-based tunable acoustic wave receiving device as claimed in claim 4, wherein said piezoelectric ultrasonic transducer is of a sandwich structure or a bimorph structure.

6. the tunable acoustic wave receiving device according to claim 5, wherein the piezoelectric ultrasonic transducer in a sandwich structure comprises a substrate, a bottom electrode, a piezoelectric layer, a top electrode, an insulating layer, and a first electrode and a second electrode led out from the top electrode, the bottom electrode, the piezoelectric layer, the top electrode, the insulating layer, and the Helmholtz resonant cavity being disposed on the insulating layer.

Technical Field

the invention relates to the technical field of sensors, in particular to a frequency-adjustable sound wave receiving device based on a Helmholtz resonant cavity.

Background

an ultrasonic transducer is a transducing element that can be used to both transmit and receive ultrasonic waves, which is the core of an acoustic sensor. When the transducer works in a transmitting mode, electric energy is converted into vibration of the transducer through electrostatic force or inverse piezoelectric effect so as to radiate sound waves outwards; when the transducer works in a receiving mode, sound pressure acts on the surface of the transducer to enable the transducer to vibrate, and the transducer converts the vibration into an electric signal. At present, the most widely used ultrasonic sensor is mainly based on a piezoelectric transducer, the piezoelectric transducer mainly utilizes a thickness vibration mode of piezoelectric ceramics to generate ultrasonic waves, and because the resonant frequency of the thickness mode is only related to the thickness of the transducer, the ultrasonic transducers with different resonant frequencies are difficult to manufacture on the same plane. When the high-frequency-resistant high-frequency. The ultrasonic transducer (MEMS ultrasonic transducer) manufactured by the micromachining technology vibrates in a bending mode, has a vibrating membrane with lower rigidity, has lower acoustic impedance, and can be better coupled with gas and liquid. And the resonant frequency is controlled by the in-plane dimension, so that the requirement on the machining precision is low. With the gradual maturity of the MEMS ultrasonic transducer technology, the technology of the ultrasonic sensor tends to turn to the MEMS ultrasonic transducer because of its advantages of high performance, low cost and easy realization of mass production. The MEMS ultrasonic transducer mainly comprises two capacitance type (cMUT) and piezoelectric type (pMUT), the sensitivity of the pMUT is slightly lower than that of the cMUT, but the cMUT needs to provide bias voltage and a tiny air gap is arranged between capacitance polar plates, adhesion is easily formed, and the pMUT has the advantages of simple structure and high transduction efficiency of transduction materials, but the manufacture of the pMUT is more complex.

patent CN109196671A discloses a piezoelectric micromachined ultrasonic transducer (pMUT) that reduces acoustic diffraction by adding a high acoustic velocity material to the transducer to generate high frequencies. The PMUT has a low quality factor, providing shorter start-up and shut-down times, to enable better suppression of spurious reflections through time-gating. Patent CN107394036A discloses an electrode configuration of pMUT and pMUT transducer arrays, which makes the transducer have different modes of action by using a dual electrode or multiple electrodes in the upper electrode, by applying the same or different electrical signals to the different electrodes. Patent CN106660074A discloses a piezoelectric ultrasonic transducer and a process, which uses an anchoring structure and a mechanical layer to form a cavity, adjusts the position of the central axis of the stacked layers through the mechanical layer, thereby allowing the stacked layers to vibrate in bending, and adjusts the parameters of resonance frequency, quality factor Q, etc. through the use of a concave portion. Overall, the current pMUT improvements are mainly directed to the electrode shape thereof, the addition of materials to the outside, and the like, but have a limited effect on improving the pMUT energy conversion efficiency. In summary, the current ultrasonic transducer has low sensitivity and small transmission sound pressure, which limits its application to a great extent.

Disclosure of Invention

the invention aims to provide a frequency-adjustable sound wave receiving device based on a Helmholtz resonant cavity, which has high sensitivity and can improve the electro-acoustic energy conversion efficiency of an ultrasonic transducer.

The scheme adopted by the invention for solving the technical problems is as follows:

the utility model provides an adjustable frequency sound wave receiving arrangement based on Helmholtz resonant cavity, includes Helmholtz resonant cavity and acoustic sensor, Helmholtz resonant cavity include the cavity and with the through-hole of cavity intercommunication, Helmholtz resonant cavity sets up on the acoustic sensor just the cavity with acoustic sensor's surface contact is connected.

Further, the cavity is formed by enclosing a hollow silicon structure arranged on the surface of the acoustic sensor and the surface of the acoustic sensor, and the through hole is arranged on the silicon structure.

further, the size, number, shape and position of the through holes are determined by the resonance frequency of the Helmholtz resonator.

Further, the acoustic sensor is a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer.

further, the piezoelectric ultrasonic transducer is of a sandwich structure or a bimorph structure.

Furthermore, the piezoelectric ultrasonic transducer with the sandwich structure comprises a substrate, a bottom electrode, a piezoelectric layer, a top electrode, an insulating layer, a first electrode and a second electrode, wherein the bottom electrode, the piezoelectric layer, the top electrode and the insulating layer are sequentially deposited on the substrate, the first electrode and the second electrode are led out from the top electrode, and the Helmholtz resonant cavity is arranged on the insulating layer.

compared with the prior art, the invention has at least the following beneficial effects:

1) The MEMS acoustic sensor is combined with the Helmholtz resonant cavity; when the MEMS acoustic sensor receives sound waves, when the frequency of the sound waves is consistent with the resonant frequency of the Helmholtz resonant cavity, the sound waves are transmitted to the hole opening to cause medium in the cavity to resonate and consume the sound wave energy of the resonant frequency so as to cause the sound pressure in the cavity to increase, and the sound pressure acts on the surface of the sensor to vibrate; the resonant frequency of the Helmholtz resonant cavity and the resonant frequency of the MEMS acoustic sensor can be the same or different; when the MEMS acoustic sensor adopts an MEMS piezoelectric or capacitive ultrasonic transducer, when the resonant frequency of the MEMS ultrasonic transducer is consistent with the resonant frequency of the Helmholtz resonant cavity, the vibration amplitude of the transducer can be increased, so that the electroacoustic energy conversion efficiency of the ultrasonic transducer is improved; when the resonance frequencies of the MEMS acoustic sensor and the Helmholtz resonant cavity are different, the sound pressure acted on the MEMS acoustic sensor is very large due to the amplification of the Helmholtz resonant cavity to the sound pressure, and larger amplitude can still be generated; overall, the generated signal of the MEMS acoustic sensor can be increased;

2) The size, shape and position of the opening of the silicon structure can realize the adjustment of the resonance frequency of the Helmholtz resonant cavity, thereby adjusting the working frequency of the sound wave receiving device.

Drawings

FIG. 1 is a cross-sectional view of an acoustic wave receiving device according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of an acoustic wave receiving device employing a piezoelectric transducer in a sandwich configuration in accordance with another embodiment of the present invention;

FIG. 3 is a cross-sectional view of an acoustic wave receiving device employing a piezoelectric transducer of bimorph configuration according to another embodiment of the present invention;

FIG. 4 is a cross-sectional view and a top view of another embodiment of the present invention employing a capacitive ultrasound transducer;

FIG. 5 is a block diagram of a bottom electrode deposited on a CSOI wafer as processed by an embodiment of the present invention using a sandwich structure in a piezoelectric transducer;

FIG. 6 is a block diagram of a deposition stack on a CSOI wafer when processing with a sandwich structure in a piezoelectric transducer according to an embodiment of the present invention;

FIG. 7 is a structural diagram of the forming of the processing step S3 when an embodiment of the invention employs a sandwich structure in a piezoelectric transducer;

FIG. 8 is a block diagram of a processing step S4 when an embodiment of the invention employs a sandwich structure in a piezoelectric transducer;

Fig. 9 is a schematic structural diagram of an acoustic wave receiving device completed by the processing step S6 when a sandwich structure in a piezoelectric transducer is adopted in the embodiment of the present invention.

Detailed Description

The following examples are provided to further illustrate the present invention for better understanding, but the present invention is not limited to the following examples.

The invention provides a frequency-adjustable sound wave receiving device based on a Helmholtz resonant cavity, which comprises a Helmholtz resonant cavity 2 and a MEMS acoustic sensor 1. The Helmholtz resonator 2 is arranged on the MEMS acoustic sensor 1. The Helmholtz resonator 2 comprises a hollow silicon structure 20 arranged on the surface of the MEMS acoustic sensor 1, a cavity 21 formed by the hollow silicon structure 20 and the surface of the MEMS acoustic sensor 2, and a through hole 22 arranged on the silicon structure 20 and communicating with the cavity 21. The through hole 22 communicates the external atmosphere with the cavity 21, thereby facilitating the propagation and resonance of the acoustic wave. In addition, the cavity 21 is in contact connection with the surface of the MEMS acoustic sensor 1, so that the sound pressure amplified by the Helmholtz resonant cavity 2 can directly act on the MEMS acoustic sensor 1, which is beneficial to improving the acoustoelectric energy conversion efficiency of the acoustic sensor.

in the sound wave receiving device, the MEMS acoustic sensor 1 is used for receiving sound waves in the cavity 21 when the Helmholtz resonant cavity 2 resonates, and the resonant frequency of the MEMS acoustic sensor 1 and the resonant frequency of the Helmholtz resonant cavity 2 may be set to be the same, so that the vibration amplitude of the MEMS acoustic sensor 1 may be increased, and the electroacoustic energy conversion efficiency of the MEMS acoustic sensor 1 may be improved. Of course, the resonance frequency of the MEMS acoustic sensor 1 and the resonance frequency of the Helmholtz resonator 2 may also differ. When the resonant frequencies of the MEMS acoustic sensor 1 and the Helmholtz resonant cavity 2 are different, the sound pressure of the MEMS acoustic sensor 1 directly acted on by the Helmholtz resonant cavity 2 is still large due to the amplification of the sound pressure by the Helmholtz resonant cavity 2, and still generates a large amplitude. Overall, this structure may increase the generated signal of the MEMS acoustic sensor 1.

According to the formula of the resonance frequency of the Helmholtz resonant cavity:

In the formula, c is the sound velocity in the medium, S is the area of the through hole, t is the height of the through hole, d is the diameter of the through hole, and V is the volume of the cavity. Based on the above formula, we can adjust the operating frequency of the acoustic wave receiving device by adjusting the size, number, shape and arrangement position of the through holes 22 to realize the adjustment of the resonant frequency of the Helmholtz resonant cavity 2. That is, in actual use, the size, number, shape, and arrangement position of the through-holes 22 are determined according to the required resonance frequency of the Helmholtz resonant cavity 2.

In addition, the MEMS acoustic sensor 1 in the present invention can be in various forms, as shown in fig. 2, fig. 3 and fig. 4, the MEMS acoustic sensor 1 can be either a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer, or any other form of ultrasonic transducer. When the MEMS acoustic sensor 2 is a piezoelectric ultrasonic transducer, it may adopt a conventional sandwich structure or a bimorph structure. Of course, the shape of the MEMS acoustic sensor 1 may also be in various forms, such as a circle, square, rectangle, hexagon or other polygon.

To further illustrate the sound wave receiving device of the present invention, as shown in fig. 5-9, the present invention provides a process for preparing a sound wave receiving device when the MEMS acoustic sensor is a piezoelectric transducer with a sandwich structure, which comprises the following steps:

s1: performing CMP on a CSOI wafer 10, and polishing the silicon layer on the CSOI wafer 10 to a designed size;

S2: sequentially depositing a bottom electrode 11, a piezoelectric layer 12 and a top electrode 13 on the polished CSOI wafer 10 to form a laminated structure on the CSOI wafer 10;

s3: depositing a SiO2 insulating layer 14 on the CSOI wafer 10 with the laminated structure deposited thereon for bonding with the silicon structure 20 and leading out the electrode;

S4: a first gold electrode 15 and a second gold electrode 16 are respectively led out from two sides of the top electrode 13;

S5: bonding the stacked structure and the hollow silicon structure 20;

S6: a via 22 is etched in the hollow silicon structure 20, releasing the structure to form a Helmholtz resonator 2 in the MEMS acoustic sensor 1.

While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.