Piezoelectric micromechanical ultrasonic transducer and ultrasonic detection system

Abstract

The present invention discloses a piezoelectric micromechanical ultrasonic transducer and an ultrasonic detection system, wherein the piezoelectric micromechanical ultrasonic transducer comprises a PMUT unit and a baffle, wherein the PMUT unit comprises a PMUT array element formed on a substrate at least for transmitting and receiving ultrasonic waves, and the baffle covers the emission direction of one side of the part of the PMUT array element emitting ultrasonic waves. The piezoelectric micromechanical ultrasonic transducer is provided with a baffle in the emission direction of one side of the part of the PMUT array element emitting ultrasonic waves, so that the part of the PMUT array element with the baffle can only transmit or receive ultrasonic waves in the emission direction of the side without the baffle, and the PMUT array element without the baffle can simultaneously transmit or receive ultrasonic waves in the emission directions of both sides thereof. The present invention adopts such a combination of single-side detection and double-side detection, while increasing the detection range of the PMUT device, by comparing the echo signal of the single-side detection with the echo signal of the double-side detection, the position of the target object can be accurately determined, thereby improving the detection accuracy and detection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic detection, and in particular to a piezoelectric micromechanical ultrasonic transducer and an ultrasonic detection system. Background Art

[0002] Ultrasonic sensing technology has outstanding application value in the field of intelligent sensing due to its many advantages such as high sensitivity, low power consumption, low cost, no influence of the color or transparency of the object being measured, and can be used in dark environments. Compared with traditional bulk piezoelectric ceramic ultrasonic transducers, piezoelectric micromechanical ultrasonic transducers (PMUTs) have benefited from the rapid development of micromachining technology. They are small in size, and the preparation process is compatible with the process of complementary metal oxide semiconductors, and are easy to miniaturize ultrasonic sensing systems. They are widely used. At present, detection based on PMUT is mostly one-way detection using array beamforming technology, or using multiple array elements at the cost of space occupation and using motors to control the movement and rotation of PMUT to increase the detection range. Therefore, without increasing the size of PMUT devices, improving the detection range of PMUT devices in the air is an urgent problem to be solved.

[0003] In the prior art, Przybyla RJ et al. proposed an on-chip three-dimensional ultrasonic rangefinder, which uses the back cavity surface of the ultrasonic 3D rangefinder to transmit ultrasonic waves, and can locate a target 1 meter away within the ±45° field of view through the receiving beam synthesis technology. Shao et al. proposed a 4×4 PMUT array based on an ultrasonic beam forming scheme to realize the deflection emission and reception of a one-dimensional deflected sound beam, and realized the detection of three-dimensional objects 1 meter away within the ±67.5° field of view. Wang et al. proposed a five PMUT array elements distributed in space based on the arrival time difference positioning, realizing an ultra-low power consumption centimeter-level three-dimensional ultrasonic indoor positioning system. Liu et al. proposed a detection system that uses an electric turntable to drive PMUT for cylindrical scanning.

[0004] However, the above-mentioned prior art has defects such as a small detection range of the PMUT array for unidirectional detection through beam synthesis technology, or multi-directional detection of multiple PMUT array elements, or using an electric turntable to drive PMUT scanning detection, which greatly increases the size and mechanical power consumption of the sensor.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a piezoelectric micromechanical ultrasonic transducer and an ultrasonic detection system, which are used to solve the technical problem of how to increase the detection range of a PMUT device in the air without increasing the volume of the PMUT device.

[0007] To achieve the above-mentioned purpose, an embodiment of the present invention provides a piezoelectric micromechanical ultrasonic transducer, which includes: a PMUT unit, the PMUT unit includes a PMUT array element formed on a substrate at least for transmitting and receiving ultrasonic waves; and a baffle, the baffle covers a side emission direction of a portion of the PMUT array element that transmits ultrasonic waves.

[0008] In one or more embodiments of the present invention, the PMUT array element includes a cavity formed on the substrate and a diaphragm covering the cavity, and the diaphragm includes a supporting layer, a lower electrode, a piezoelectric layer and an upper electrode stacked in sequence.

[0009] In one or more embodiments of the present invention, the material of the lower electrode is one of molybdenum, gold, platinum, aluminum or tin.

[0010] In one or more embodiments of the present invention, the material of the upper electrode is one of gold, molybdenum, platinum, aluminum or tin.

[0011] In one or more embodiments of the present invention, the material of the piezoelectric layer is scandium-doped aluminum nitride, aluminum nitride, zinc oxide or lead zirconate titanate piezoelectric ceramic.

[0012] In one or more embodiments of the present invention, the support layer includes a first support layer and a second support layer which are stacked, the material of the first support layer is silicon oxide, and the material of the second support layer is silicon.

[0013] In one or more embodiments of the present invention, the substrate is made of silicon, and the baffle is made of silicon, steel or aluminum.

[0014] In one or more embodiments of the present invention, the shape of the PMUT array element is circular, rectangular, square or polygonal.

[0015] In one or more embodiments of the present invention, the baffle and the PMUT array element are bonded by wafer bonding, 3D printing, or gluing.

[0016] In another aspect of the present invention, there is also provided an ultrasonic detection system, comprising:

[0017] The piezoelectric micromechanical ultrasonic transducer as described above is used at least to transmit and receive ultrasonic waves;

[0018] An ultrasonic wave transmitting driving unit, electrically connected to the piezoelectric micromechanical ultrasonic transducer, and used for driving the piezoelectric micromechanical ultrasonic transducer to transmit ultrasonic waves;

[0019] an ultrasonic processing unit, electrically connected to the piezoelectric micromechanical ultrasonic transducer, and configured to process an echo signal received by the piezoelectric micromechanical ultrasonic transducer;

[0020] a control unit, connected to the ultrasonic emission drive unit and the ultrasonic processing unit, respectively, and used to control the ultrasonic emission drive unit and the ultrasonic processing unit to work based on a driving signal; and

[0021] The storage unit is connected to the control unit and the ultrasonic processing unit respectively, and is used to store the driving signal and the echo signal fed back by the ultrasonic processing unit.

[0022] Compared with the prior art, the piezoelectric micromechanical ultrasonic transducer according to the embodiment of the present invention sets a baffle in the emission direction of one side of some PMUT array elements that emit ultrasonic waves, so that when the PMUT array elements emit or receive ultrasonic waves, some PMUT array elements with baffles can only emit ultrasonic waves in the emission direction of the side without baffles when their membranes vibrate, or receive echo signals for single-sided target detection; while the remaining PMUT array elements without baffles can bidirectionally emit ultrasonic waves in the emission directions on both sides of the membrane when their membranes vibrate, or receive echo signals for double-sided target detection.

[0023] The present invention adopts this method of combining single-side detection and double-side detection. While increasing the detection range of the PMUT device in the air, by comparing the echo signal of single-side detection with the echo signal of double-side detection, the direction of the target object can be accurately determined, thereby improving the detection accuracy and detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a piezoelectric micromechanical ultrasonic transducer in which a baffle covers a portion of the PMUT array element back cavity according to an embodiment of the present invention;

[0025] Figure 2 It is a schematic structural diagram of a piezoelectric micromechanical ultrasonic transducer in which a baffle covers a surface of a side of a part of PMUT array elements opposite to a back cavity according to an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of a PMUT array element in a piezoelectric micromechanical ultrasonic transducer generating bidirectional ultrasonic waves according to an embodiment of the present invention;

[0027] Figure 4It is a schematic diagram of using beam synthesis technology in a piezoelectric micromechanical ultrasonic transducer according to an embodiment of the present invention to enable a PMUT array element to emit deflected and focused ultrasonic waves.

[0028] Figure 5 Schematic diagram of the structure of an ultrasonic detection system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0030] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0031] like Figure 1 As shown, an embodiment of the piezoelectric micromechanical ultrasonic transducer of the present invention is introduced. In this embodiment, the piezoelectric micromechanical ultrasonic transducer includes a PMUT unit and a baffle 13.

[0032] The PMUT unit includes a PMUT array element 12 formed on a substrate 11 and at least used for transmitting and receiving ultrasonic waves. Specifically, the PMUT array element 12 includes a cavity 121 formed on the substrate 11 and a diaphragm covering the cavity 121, and the diaphragm includes a support layer, a lower electrode 124, a piezoelectric layer 125 and an upper electrode 126 stacked in sequence, wherein the support layer includes a first support layer 122 and a second support layer 123 stacked in sequence.

[0033] In some embodiments, the substrate 11 and the second support layer 123 can be made of silicon, and the first support layer 122 can be made of silicon oxide; the lower electrode 124 can be made of one of molybdenum, gold, platinum, aluminum or tin, and the upper electrode 126 can be made of one of gold, molybdenum, platinum, aluminum or tin; the piezoelectric layer 125 can be made of scandium-doped aluminum nitride, aluminum nitride, zinc oxide or lead zirconate titanate piezoelectric ceramics. The baffle 13 can be made of silicon, steel or aluminum, or other materials that can effectively block the propagation of sound waves.

[0034] It should be noted here that the material of each structural layer of the PMUT array element 12 can be changed according to actual needs, and the thickness and size of each structural layer can also be changed.

[0035] On the other hand, in some embodiments, the shape of the PMUT array element 12 may be circular, rectangular, square or polygonal, etc. The array arrangement of the PMUT array element 12 may be rectangular array arrangement, circular array arrangement or other shape arrangement, and the number of the PMUT array elements 12 may be set according to actual needs.

[0036] like Figure 3 As shown, in this embodiment, each PMUT array element 12 has the same structure and is a thin film structure, wherein the upper electrode 126 and the lower electrode 124 serve as an electrode connection circuit, which can both emit pulse waves to stimulate the array element film vibration and convert the array element film vibration into an echo voltage signal.

[0037] like Figure 4 As shown, each PMUT array element 12 can be driven individually. Through the beam synthesis technology, the PMUT array element 12 is driven with a delay to form a deflectable and focused beam, so that the PMUT array element 12 transmits or receives ultrasonic waves in a specific direction to detect the target object.

[0038] In some implementations, the baffle 13 and the PMUT array element 12 may be combined by wafer bonding, or combined by 3D printing technology, or by adhesive bonding.

[0039] In this embodiment, the baffle 13 can cover the emission direction of one side of some PMUT array elements emitting ultrasonic waves, so that when the PMUT array elements 12 emit or receive ultrasonic waves, some PMUT array elements 12 with baffles can only emit ultrasonic waves in the emission direction of the side without baffles when their membranes vibrate, and receive single-side echo information of the membrane; while the remaining PMUT array elements 12 without baffles can simultaneously emit ultrasonic waves in both directions on both sides of the membrane when their membranes vibrate, and receive echo information on both sides of the membrane.

[0040] For example, Figure 1 As shown, the baffle 13 can cover the back cavity of part of the PMUT array elements 12, that is, the emission direction of the ultrasonic wave emitted from one side of the cavity 121 of the PMUT array element 12. It is assumed that the part of the PMUT array elements 12 covered with the baffle 13 is the PMUT array elements of group A, and the remaining PMUT array elements 12 not covered by the baffle 13 are the PMUT array elements of group B. At this time, when the PMUT array elements 12 emit and receive ultrasonic waves, the PMUT array elements of group A can only emit ultrasonic signals or receive echo signals in the emission direction of one side of the film relative to the back cavity for single-sided target detection, and the PMUT array elements of group B can simultaneously emit ultrasonic waves or receive echo signals on both sides of the film for double-sided target detection.

[0041] like Figure 2As shown in the figure, when the baffle 13 covers the surface of one side of the PMUT array element 12 relative to its back cavity, that is, in the emission direction of the ultrasonic wave emitted from the upper electrode 126 side of the PMUT array element 12, the part of the PMUT array element 12 covered with the baffle 13 is also set as the PMUT array element of group A, and the remaining PMUT array element 12 not covered by the baffle 13 is the PMUT array element of group B. At this time, when the PMUT array element 12 emits and receives ultrasonic waves, the PMUT array element of group A can only emit ultrasonic signals or receive echo signals on one side of the back cavity of its film to detect single-side targets, and the PMUT array element of group B can simultaneously emit ultrasonic waves or receive echo signals on both sides of its film to detect double-side targets.

[0042] In this way, by combining single-sided detection and double-sided detection, the detection range of the PMUT array element 12 in the air is increased. By comparing the echo signal of single-sided detection with the echo signal of double-sided detection, the position of the target object can be accurately determined, thereby improving the detection accuracy and efficiency.

[0043] It should be noted that, in this embodiment, the location of the baffle 13 can be changed according to actual needs.

[0044] Ginseng Figure 5 , introduces an embodiment of the ultrasonic detection system of the present invention. In this embodiment, the ultrasonic detection system includes a piezoelectric micromechanical ultrasonic transducer 1, an ultrasonic emission drive unit 2, an ultrasonic processing unit 3, a control unit 4 and a storage unit 5.

[0045] The piezoelectric micromechanical ultrasonic transducer 1 in this embodiment includes a PMUT unit and a baffle 13, wherein the PMUT unit includes a PMUT array element 12 formed on a substrate 11 and at least used for transmitting and receiving ultrasonic waves, and the baffle 13 can cover the transmitting direction of one side of the PMUT array element 12 transmitting ultrasonic waves. The specific principle has been described in detail above and will not be repeated here.

[0046] The ultrasonic transmission driving unit 2 is electrically connected to the piezoelectric micromechanical ultrasonic transducer 1 and is used to drive the piezoelectric micromechanical ultrasonic transducer 1 to transmit ultrasonic signals.

[0047] In this embodiment, the ultrasonic transmitting drive unit 2 mainly includes a voltage driving circuit. After the control unit 4 reads the driving signal of specific frequency, pulse width and delay stored in the storage unit 5, the voltage driving circuit generates a transmitting pulse waveform of a certain amplitude, and applies the waveform to the piezoelectric micromechanical ultrasonic transducer 1, thereby driving the piezoelectric micromechanical ultrasonic transducer 1 to send an ultrasonic signal.

[0048] The ultrasonic processing unit 3 is electrically connected to the piezoelectric micromechanical ultrasonic transducer 1 and is used for processing the echo signal received by the piezoelectric micromechanical ultrasonic transducer 1 .

[0049] In this embodiment, the ultrasonic processing unit 3 mainly integrates filtering, amplification, beam synthesis and other circuits, which are used to process the echo signal of the PMUT array element 12, and feed the processed echo signal back to the control unit 4 and the storage unit 5. The control unit 4 can determine whether there is a target object and the approximate location of the target object based on the echo signal.

[0050] The control unit 4 is connected to the ultrasonic emission driving unit 2 and the ultrasonic processing unit 3 respectively, and is used to control the ultrasonic emission driving unit 2 and the ultrasonic processing unit 3 to work based on the driving signal.

[0051] In this embodiment, the control unit 4 mainly includes a microcontroller (MCU) or an FPGA, which can determine whether there is a target object in the detection field according to the echo signal. When it is determined that there is a target object, the size, speed, shape and distance between the target object and the target object can be determined by the echo intensity, Doppler shift, spectrum characteristics and time delay information. At the same time, the control unit 4 combines the echo signal detected by the single side of the PMUT array element 12 and the echo signal detected by the double sides, so as to more quickly and accurately determine the approximate direction of the target object.

[0052] The storage unit 5 is connected to the control unit 4 and the ultrasonic processing unit 3 respectively, and is used to store the driving signal and the echo signal fed back by the ultrasonic processing unit 3 .

[0053] The circuit system of the ultrasonic detection system in this embodiment may adopt a board-level circuit, or a dedicated integrated circuit, etc.

[0054] In practical applications, the ultrasonic detection system can be loaded on an external mobile device (such as a remote control car, a remote control drone, etc.). The external mobile device can be controlled by a remote control device. The control unit 4 of the ultrasonic detection system communicates with the remote control device, and the remote control device can also include a display unit for displaying the detection scene of the ultrasonic detection system in real time.

[0055] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A piezoelectric micromechanical ultrasonic transducer, It is characterized in that include: A PMUT unit, wherein the PMUT unit includes a PMUT array element formed on a substrate and at least used for transmitting and receiving ultrasonic waves, wherein the PMUT array element includes a cavity formed on the substrate and a diaphragm covering the cavity; and A baffle, the baffle covering a portion of the PMUT array elements in a transmission direction on one side of the array element transmitting ultrasonic waves; When the PMUT array element transmits or receives ultrasonic waves, the PMUT array element with a baffle only transmits ultrasonic waves in the transmission direction of the side of the diaphragm without a baffle or receives single-sided echo information to detect single-sided targets, and the PMUT array element without a baffle simultaneously transmits ultrasonic waves in both directions on both sides of the diaphragm or receives double-sided echo information to detect double-sided targets.

2. The piezoelectric micromechanical ultrasonic transducer according to claim 1, It is characterized in that The diaphragm comprises a supporting layer, a lower electrode, a piezoelectric layer and an upper electrode which are stacked in sequence.

3. The piezoelectric micromechanical ultrasonic transducer according to claim 2, It is characterized in that The material of the lower electrode is one of molybdenum, gold, platinum, aluminum or tin.

4. The piezoelectric micromechanical ultrasonic transducer according to claim 2, It is characterized in that The material of the upper electrode is one of gold, molybdenum, platinum, aluminum or tin.

5. The piezoelectric micromechanical ultrasonic transducer according to claim 2, It is characterized in that The material of the piezoelectric layer is scandium-doped aluminum nitride, aluminum nitride, zinc oxide or lead zirconate titanate piezoelectric ceramics.

6. The piezoelectric micromechanical ultrasonic transducer according to claim 2, It is characterized in that The support layer includes a first support layer and a second support layer which are stacked. The material of the first support layer is silicon oxide, and the material of the second support layer is silicon.

7. The piezoelectric micromechanical ultrasonic transducer according to claim 1, It is characterized in that The material of the substrate is silicon, and the material of the baffle is silicon, steel or aluminum.

8. The piezoelectric micromechanical ultrasonic transducer according to claim 1, It is characterized in that The shape of the PMUT array element is circular or polygonal.

9. The piezoelectric micromechanical ultrasonic transducer according to claim 1, It is characterized in that The baffle and the PMUT array element are bonded by wafer bonding, 3D printing or gluing.

10. An ultrasonic detection system, It is characterized in that include: The piezoelectric micromechanical ultrasonic transducer according to any one of claims 1 to 9, at least for transmitting and receiving ultrasonic waves; An ultrasonic wave transmitting driving unit, electrically connected to the piezoelectric micromechanical ultrasonic transducer, and used for driving the piezoelectric micromechanical ultrasonic transducer to transmit ultrasonic waves; an ultrasonic processing unit, electrically connected to the piezoelectric micromechanical ultrasonic transducer, and configured to process an echo signal received by the piezoelectric micromechanical ultrasonic transducer; A control unit, connected to the ultrasonic emission drive unit and the ultrasonic processing unit, respectively, and used to control the ultrasonic emission drive unit and the ultrasonic processing unit to work based on a driving signal; as well as The storage unit is connected to the control unit and the ultrasonic processing unit respectively, and is used to store the driving signal and the echo signal fed back by the ultrasonic processing unit.

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