An ultrasonic transduction assembly and an ultrasonic transduction array
By using PMUT units of different sizes and shapes in the ultrasonic transducer for sensitivity curve compensation, the problem of limited PMUT bandwidth was solved, and high resolution and depth detection of high-frequency ultrasonic imaging were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUAWEI TECH CO LTD
- Filing Date
- 2022-08-30
- Publication Date
- 2026-07-10
AI Technical Summary
Existing piezoelectric micromechanical ultrasonic transducers (PMUTs) have limited operating bandwidth, making it difficult to achieve large bandwidth at high frequencies, which limits their effectiveness in ultrasonic imaging applications.
By employing first and second PMUT units of different sizes and shapes, modal coupling is achieved through mutual compensation of sensitivity curves, thereby improving the operating bandwidth of the ultrasonic transducer.
The increased bandwidth of the ultrasonic transducer improves imaging resolution and detection depth, meeting the requirements of high-frequency ultrasonic imaging.
Smart Images
Figure CN117654862B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of ultrasonic applications, and more particularly to an ultrasonic transducer component and an ultrasonic transducer array. Background Technology
[0002] An ultrasonic transducer can function as both an actuator (emitting sound waves) and a sensor (receiving sound waves). When a voltage is applied to an ultrasonic transducer, it responds to the time-varying driving voltage by generating mechanical vibrations, emitting high-frequency pressure waves into the surrounding medium (such as air, water, glass, or body tissue), thus completing the sound wave emission. When an external pressure wave is applied to the ultrasonic transducer from the surrounding medium, the transducer converts the received pressure wave into an electrical signal, enabling the detection of the external pressure wave. In ultrasonic imaging applications, the bandwidth and sensitivity of the ultrasonic transducer determine the imaging resolution and detection depth of the imaging system. A larger bandwidth results in higher imaging resolution.
[0003] Piezoelectric micromachined ultrasonic transducers (PMUTs) utilize the direct and inverse piezoelectric effects of piezoelectric thin film materials to transmit and receive ultrasonic waves. They eliminate the need for high DC bias and extremely small gaps, resulting in simple circuitry and fabrication, and offer advantages such as high linearity. Therefore, PMUTs are increasingly being studied in ultrasonic imaging applications. However, current PMUT technologies have limited operating bandwidth, making it difficult to achieve large bandwidths at high frequencies (e.g., above 7.5 MHz), thus limiting their application in ultrasonic imaging. Summary of the Invention
[0004] This application provides an ultrasonic transducer component and an ultrasonic transducer array, which can improve the operating bandwidth of the ultrasonic transducer component.
[0005] In a first aspect, embodiments of this application provide an ultrasonic transducer assembly. The ultrasonic transducer assembly includes: a substrate, at least one first PMUT unit, and at least one second PMUT unit, the first and second PMUT units being located on the substrate. The cross-sectional shape of the first PMUT unit has a major axis and a minor axis, and the cross-sectional shape of the second PMUT unit also has a major axis and a minor axis, with the cross-section parallel to the substrate. The dimensions of the first PMUT unit and the second PMUT unit are different. The difference between the frequency corresponding to the peak position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the trough position on the sensitivity curve of the second PMUT unit is less than a preset value, and / or, the difference between the frequency corresponding to the trough position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the peak position on the sensitivity curve of the second PMUT unit is less than a preset value.
[0006] In this embodiment, the sensitivity curves of the first PMUT unit and the second PMUT unit can compensate for each other. The difference between the peaks and troughs of the sensitivity between different modes on the compensated sensitivity curve is smaller, which facilitates modal coupling within a certain bandwidth range and thus improves the working bandwidth of the ultrasonic transducer.
[0007] In some possible implementations, the difference in size between the first PMUT unit and the second PMUT unit is reflected in the difference in cross-sectional area between the first PMUT unit and the second PMUT unit, which ensures the practical effect of this solution.
[0008] In some possible implementations, the difference in size between the first PMUT unit and the second PMUT unit is reflected in the difference in thickness between the first PMUT unit and the second PMUT unit, which improves the flexibility of this solution.
[0009] In some possible implementations, the size of the first PMUT unit is larger than that of the second PMUT unit, and the number of first PMUT units is less than the number of second PMUT units. It should be understood that the operating vibration area of a single first PMUT unit is larger than that of a single second PMUT unit, and the sensitivity of a single second PMUT unit is lower than that of a single first PMUT unit. Therefore, a greater number of second PMUT units than first PMUT units is needed to achieve a better compensation effect.
[0010] In some possible implementations, the major axis of the cross-sectional shape of the first PMUT unit is larger than the major axis of the cross-sectional shape of the second PMUT unit, and the minor axis of the cross-sectional shape of the first PMUT unit is larger than the minor axis of the cross-sectional shape of the second PMUT unit. This implementation provides a specific way to achieve different cross-sectional areas for the first and second PMUT units, improving the practicality of this solution.
[0011] In some possible implementations, the first PMUT unit is located between two second PMUT units, which can reduce acoustic coupling crosstalk caused by the two first PMUT units being adjacent.
[0012] In some possible implementations, the ratio of the major axis to the minor axis of the cross-sectional shape of the first PMUT unit is denoted as k, and the ratio of the major axis to the minor axis of the cross-sectional shape of the second PMUT unit is also denoted as k. When k is sufficiently large, a single first PMUT unit or a single second PMUT unit can achieve multi-mode fusion, thereby obtaining a large bandwidth effect. When k is too small, the frequencies of each mode of a single first PMUT unit or a single second PMUT unit differ significantly, resulting in a large difference between the peaks and troughs on the sensitivity curve, making it difficult to achieve modal coupling within a certain orientation. When k is too large, although multi-mode coupling can be achieved, the overall bandwidth decreases because the resonant frequencies of higher-order modes drop too much. In summary, the preferred value range for k is 4-7.
[0013] In some possible implementations, the first PMUT unit and the second PMUT unit are arranged in the same direction, and the major axis of the cross-sectional shape of the first PMUT unit is parallel to or coincides with the major axis of the cross-sectional shape of the second PMUT unit. This implementation provides a specific arrangement of the first PMUT unit and the second PMUT unit, which is more regular and has better practical effect.
[0014] In some possible implementations, the cross-sectional shapes of both the first and second PMUT elements are elliptical. Alternatively, the cross-sectional shapes of both the first and second PMUT elements are polygons, with the polygons having more than four upper sides. It should be understood that the closer the cross-sectional shapes of the first and second PMUT elements are to ellipses, the better the performance.
[0015] In some possible implementations, the substrate includes multiple cavities, with the first PMUT unit and the second PMUT unit suspended on their respective cavities to ensure that both the first PMUT unit and the second PMUT unit have sufficient vibration space.
[0016] Secondly, embodiments of this application provide an ultrasonic transducer array. The ultrasonic transducer array includes a plurality of ultrasonic transducer components as described in any embodiment of the first aspect. The plurality of ultrasonic transducer components are distributed in at least one column, each column including at least one ultrasonic transducer component, and the first PMUT unit and the second PMUT unit in each ultrasonic transducer component are arranged sequentially in the column direction.
[0017] In some possible implementations, the number of first PMUT units in each ultrasonic transducer assembly is the same, the number of second PMUT units in each ultrasonic transducer assembly is the same, and the first PMUT units and second PMUT units in each ultrasonic transducer assembly are arranged in the same order.
[0018] In some possible implementations, the ultrasonic transducer components in each adjacent pair of columns of the ultrasonic transducer array are arranged in an alternating pattern. It should be understood that, compared to a side-by-side arrangement, the alternating arrangement of the ultrasonic transducer components can increase the spacing between PMUT units, thereby reducing acoustic coupling crosstalk between PMUT units of the same size in adjacent pairs of columns, achieving both high sensitivity and a large bandwidth.
[0019] In some possible implementations, the first ultrasonic transducer and the second ultrasonic transducer are distributed in two adjacent columns, the first ultrasonic transducer and the second ultrasonic transducer are arranged in the same order in their respective columns, two first PMUT units arranged in the same order in the first ultrasonic transducer and the second ultrasonic transducer are offset in the column direction, and two second PMUT units arranged in the same order in the first ultrasonic transducer and the second ultrasonic transducer are offset in the column direction.
[0020] In some possible implementations, the major axis of the cross-sectional shape of the first PMUT unit in each ultrasonic transducer assembly is greater than the major axis of the cross-sectional shape of the second PMUT unit. The positional offset in the column direction of two first PMUT units arranged in the same order in the first and second ultrasonic transducers assembly is less than the length of the major axis of the cross-sectional shape of the first PMUT unit. The positional offset in the column direction of two second PMUT units arranged in the same order in the first and second ultrasonic transducers assembly is less than the length of the major axis of the cross-sectional shape of the first PMUT unit.
[0021] In some possible implementations, the minor axis of the cross-sectional shape of the first PMUT unit in each ultrasonic transducer is greater than the minor axis of the cross-sectional shape of the second PMUT unit, and the spacing between the ultrasonic transducer units in each adjacent column of the ultrasonic transducer array in the direction perpendicular to the column is less than or equal to the length of the minor axis of the cross-sectional shape of the first PMUT unit.
[0022] In this embodiment, a first PMUT unit and a second PMUT unit of different sizes are disposed on the substrate of the ultrasonic transducer. The difference between the frequency corresponding to the peak position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the trough position on the sensitivity curve of the second PMUT unit is less than a preset value, and / or the difference between the frequency corresponding to the trough position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the peak position on the sensitivity curve of the second PMUT unit is less than a preset value. In other words, the sensitivity curves of the first PMUT unit and the second PMUT unit can compensate for each other. The difference between the peaks and troughs of the sensitivity between different modes on the compensated sensitivity curve is smaller, which facilitates modal coupling within a certain bandwidth range, thereby improving the operating bandwidth of the ultrasonic transducer. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of an ultrasonic probe imaging system.
[0024] Figure 2 This is a three-dimensional structural schematic diagram of an ultrasonic transducer component according to an embodiment of this application;
[0025] Figure 3(a) is a planar top view of an ultrasonic transducer assembly in an embodiment of this application;
[0026] Figure 3(b) is a top view of another planar structure of the ultrasonic transducer assembly in an embodiment of this application;
[0027] Figure 4(a) shows the sensitivity curves of the first PMUT unit and the second PMUT unit respectively;
[0028] Figure 4(b) is a schematic diagram of the sensitivity curves after the sensitivity curves of the first PMUT unit and the second PMUT unit have been mutually compensated.
[0029] Figure 5 A schematic diagram comparing the sensitivity curves of a single-size PMUT unit and multiple-size PMUT units;
[0030] Figure 6 This is a top view of another planar structure of the ultrasonic transducer assembly in the embodiments of this application;
[0031] Figure 7 This is a schematic diagram of the sensitivity curves of the PMUT unit under different k values.
[0032] Figure 8(a) is an exploded three-dimensional view of an ultrasonic transducer component in an embodiment of this application;
[0033] Figure 8(b) is a side view of a planar structure of the ultrasonic transducer assembly in an embodiment of this application;
[0034] Figure 9 This is a top view of a planar structure of the ultrasonic transducer array in an embodiment of this application;
[0035] Figure 10 These are schematic diagrams of several three-dimensional structures of the ultrasonic transducer array in the embodiments of this application;
[0036] Figure 11 This is a schematic diagram of the sensitivity curves of several ultrasonic transducer arrays with different distributions. Detailed Implementation
[0037] This application provides an ultrasonic transducer assembly and an ultrasonic transducer array, which can improve the operating bandwidth of the ultrasonic transducer assembly. It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of units is not necessarily limited to those units, but may include other units not explicitly listed or inherent to these processes, methods, products, or apparatuses.
[0038] It should be noted that ultrasonic transducers, with their high operating frequency, strong penetration, and immunity to ambient light, are widely used in medical ultrasound imaging, medical diagnostics, industrial electronics (non-destructive testing, flow rate / volume detection, etc.), automotive electronics (ultrasonic ranging, gesture interaction, etc.), consumer electronics (ultrasonic fingerprint recognition, touch feedback and interaction, etc.), and smart homes (distance sensing, robotic vacuum cleaners, etc.). In ultrasonic imaging applications, the bandwidth and sensitivity of the ultrasonic transducer determine the imaging resolution and detection depth of the imaging system. A larger bandwidth results in higher imaging resolution. Bandwidth (BW) is a function of the actual sound pressure generated by the excitation voltage. A large bandwidth allows for a shorter ringing time and a shorter sound pressure pulse length, thereby achieving high axial resolution (axial resolution: resolution parallel to the direction of the ultrasonic beam) and a short blind zone (blind zone: the area between the transducer surface and the nearest clearly imaged area).
[0039] The ultrasonic transducer component provided in this application includes multiple PMUT units of different sizes. This ultrasonic transducer component can be applied to scenarios requiring the measurement of ultrasonic pulse transmission time, such as ultrasonic imaging (medical, fingerprint, etc.), ultrasonic flow rate / volume detection, and ultrasonic ranging. Using a wideband ultrasonic transducer component can improve the accuracy and resolution of transmission time measurement. One product form of the ultrasonic transducer component provided in this application is integration into a medical ultrasound probe. Furthermore, the ultrasonic transducer component provided in this application can also be used in modules such as fingerprint recognition, flow detection, and distance sensing, or it can be integrated with a flexible substrate to create wearable devices for human health monitoring.
[0040] The following uses medical ultrasound imaging as an example to introduce a possible application scenario of ultrasound transducers. In this scenario, ultrasound transducers emit ultrasound waves into the human body. During the propagation of ultrasound waves in human organs and tissues, various information is generated due to reflection, refraction, and diffraction. This information is then received, amplified, and processed by the ultrasound transducers to form waveforms, curves, images, or spectra. Finally, the information is transmitted to a display screen via cable or wirelessly for display.
[0041] Figure 1 This is a schematic diagram of an ultrasonic probe imaging system. Figure 1 As shown, the surface of the ultrasonic transducer is covered with an acoustic lens, which serves to protect the transducer and focus the sound beam. When excited by an external pulse, the ultrasonic transducer emits ultrasonic waves towards the human body. These waves are emitted within the body tissue and return to the transducer. The transducer receives these waves and converts them into electrical signals, which are then output to the backend for processing and imaging. The backend of the ultrasonic transducer is connected to an analog front-end circuit. Specifically, the analog front-end circuit is divided into a transmit excitation channel and an echo receiving channel via a switch. The transmit excitation channel mainly consists of a pulse transmitter, responsible for generating pulse excitation waveforms of a certain frequency and amplitude. The echo receiving channel mainly includes a time gain compensation circuit, a low-noise amplifier circuit, a filter circuit, and an analog-to-digital converter circuit. The backend of the analog front-end circuit is connected to a Field Programmable Gate Array (FPGA), which is responsible for signal control, processing, and algorithms. The FPGA transmits I / O data to the platform for IQ data processing.
[0042] The ultrasonic transducer assembly provided in the embodiments of this application will be described in detail below.
[0043] Figure 2 This is a three-dimensional structural diagram of an ultrasonic transducer component according to an embodiment of this application. Figure 2 As shown, the ultrasonic transducer assembly includes a substrate 10, a first PMUT unit 20, and a second PMUT unit 30. The first PMUT unit 20 and the second PMUT unit 30 are located on the substrate 10. It should be understood that the first PMUT unit 20 and the second PMUT unit 30 have different sizes, and this application does not limit the specific number of the first PMUT unit 20 and the second PMUT unit 30. Typically, [the following is a list of components]... Figure 2 For example, if the size of the first PMUT unit 20 is larger than the size of the second PMUT unit 30, then the number of the first PMUT units 20 is less than the number of the second PMUT units 30.
[0044] In one possible implementation, the difference in size between the first PMUT unit 20 and the second PMUT unit 30 is reflected in the difference in their cross-sectional areas, where a cross-section refers to a section parallel to the upper surface of the substrate. In another possible implementation, the difference in size between the first PMUT unit 20 and the second PMUT unit 30 is reflected in the difference in their thicknesses. In yet another possible implementation, the first PMUT unit 20 and the second PMUT unit 30 have different cross-sectional areas, and also different thicknesses.
[0045] For ease of explanation, the following embodiments and figures are illustrated using the example of different cross-sectional areas of the first PMUT unit 20 and the second PMUT unit 30.
[0046] Figure 3(a) is a planar top view of an ultrasonic transducer assembly in an embodiment of this application. As shown in Figure 3(a), the cross-sectional shapes of the first PMUT unit 20 and the second PMUT unit 30 both have a major axis and a minor axis, with the length of the major axis being greater than the length of the minor axis. Taking Figure 3(a) as an example, the cross-sectional shapes of the first PMUT unit 20 and the second PMUT unit 30 are both elliptical. It should be noted that the cross-sectional shapes of the first PMUT unit 20 and the second PMUT unit 30 are not limited to elliptical shapes; any shape having a major axis and a minor axis is within the scope of protection of this application. Specifically, the major axis is the line connecting the two points furthest apart on the outline of the cross-sectional shape, and the minor axis is also the line connecting two points on the outline of the cross-sectional shape, with the perpendicular bisectors of the minor axis and the major axis coinciding.
[0047] Figure 3(b) is a top view of another planar structure of the ultrasonic transducer assembly in this embodiment. As shown in Figure 3(b), the cross-sectional shape of the first PMUT unit 20 and the second PMUT unit 30 is a polygon, and the cross-sectional shape of the first PMUT unit 20 and the second PMUT unit 30 also has a major axis and a minor axis. It should be understood that if the number of sides of the above polygon is equal to 4, that is, the polygon is rectangular, since the peak-valley sensitivity difference of a single rectangular PMUT unit is greater than that of a single elliptical PMUT unit under high-frequency operation, it is difficult to achieve modal coupling within a certain range, which is not conducive to achieving a large bandwidth. Therefore, preferably, the number of sides of the above polygon is usually greater than 4, and the more sides there are, the closer it is to an ellipse, and the better the effect.
[0048] In one possible implementation, the major axis of the cross-sectional shape of the first PMUT unit 20 is larger than the major axis of the cross-sectional shape of the second PMUT unit 30, and the minor axis of the cross-sectional shape of the first PMUT unit 20 is larger than the minor axis of the cross-sectional shape of the second PMUT unit 30. Preferably, the major axis of the cross-sectional shape of the second PMUT unit 30 is n times the major axis of the cross-sectional shape of the first PMUT unit 20, and the minor axis of the cross-sectional shape of the second PMUT unit 30 is n times the minor axis of the cross-sectional shape of the first PMUT unit 20, where 0.6 < n < 1.
[0049] In one possible implementation, the first PMUT unit 20 and the second PMUT unit 30 are arranged in the same direction, and the major axis of the cross-sectional shape of the first PMUT unit 20 and the major axis of the cross-sectional shape of the second PMUT unit 30 are parallel or coincident. Arranging the first PMUT unit 20 and the second PMUT unit 30 in this way results in a more regular arrangement and better practical application performance.
[0050] It should be noted that the sensitivity curves of the first PMUT unit 20 and the second PMUT unit 30 in the ultrasonic transducer assembly can compensate for each other, thereby improving the operating bandwidth of the ultrasonic transducer assembly. Specifically, the difference between the frequency corresponding to the peak position on the sensitivity curve of the first PMUT unit 20 and the frequency corresponding to the trough position on the sensitivity curve of the second PMUT unit 30 is less than a preset value, and / or, the difference between the frequency corresponding to the trough position on the sensitivity curve of the first PMUT unit 20 and the frequency corresponding to the peak position on the sensitivity curve of the second PMUT unit 30 is less than a preset value. Further explanation is provided below with reference to simulation diagrams.
[0051] Figure 4(a) shows the sensitivity curves of the first PMUT unit and the second PMUT unit respectively. Figure 4(b) shows the sensitivity curves of the first PMUT unit and the second PMUT unit after mutual compensation. As shown in Figure 4(a), the dashed line represents the sensitivity curve of the first PMUT unit 20, and the solid line represents the sensitivity curve of the second PMUT unit 30. There are instances where the peak position of the sensitivity curve of the first PMUT unit 20 coincides with the trough position of the sensitivity curve of the second PMUT unit 30, and vice versa. The sensitivity curves of the first PMUT unit and the second PMUT unit mutually compensate each other. The overall sensitivity curve of the ultrasonic transducer assembly after compensation is shown in Figure 4(b). In Figure 4(b), the dashed line represents the -6dB bandwidth cutoff position. It can be seen that the compensated sensitivity curve has a larger portion above the dashed line. Therefore, the ultrasonic transducer assembly formed by the combination of the first PMUT unit 20 and the second PMUT unit 30 has a larger operating bandwidth than an independent PMUT unit.
[0052] It should be understood that if the size of the first PMUT unit is larger than the size of the second PMUT unit, the operating vibration area of a single first PMUT unit is larger than that of a single second PMUT unit, and the sensitivity of a single second PMUT unit is lower than that of a single first PMUT unit. Therefore, the number of second PMUT units needs to be greater than the number of first PMUT units to achieve a better compensation effect. Furthermore, the first PMUT unit is usually located between two second PMUT units to reduce acoustic coupling crosstalk caused by the proximity of two first PMUT units. Figure 2 Taking Figures 3(a) and 3(b) as examples, the ultrasonic transducer assembly includes one first PMUT unit 20 and two second PMUT units 30.
[0053] Figure 5 This is a schematic diagram comparing the sensitivity curves of a single-size PMUT cell with those of multiple sizes. Figure 5 As shown, the solid line represents the sensitivity curve of the ultrasonic transducer component provided in this application, and the dashed line represents the sensitivity curve of a combination of multiple single-sized PMUT units. The comparison demonstrates that the ultrasonic transducer component provided in this application can achieve a significant bandwidth expansion effect.
[0054] As another example, Figure 6 This is a top view of another planar structure of the ultrasonic transducer assembly in an embodiment of this application. (See attached image.) Figure 6As shown, the ultrasonic transducer assembly includes two first PMUT units 20 and three second PMUT units 30. In practical applications, the ultrasonic transducer assembly may also include three or more PMUT units of different sizes to achieve mutual compensation of sensitivity curves, thereby obtaining a larger operating bandwidth. No further illustrations are provided here.
[0055] In one possible implementation, the cross-sectional shape of the first PMUT unit 20 and the second PMUT unit 30 is elliptical, as an example. The ratio of the major axis to the minor axis of the cross-sectional shape of the first PMUT unit 20 is denoted as k, and the ratio of the major axis to the minor axis of the cross-sectional shape of the second PMUT unit 30 is also denoted as k. When the ultrasonic transducer operates in a high-damping environment (such as water, oil, etc.), when k is sufficiently large, a single first PMUT unit 20 or a single second PMUT unit 30 can achieve multi-mode fusion, thereby obtaining a large bandwidth effect. When k is too small, the frequencies of each mode of a single first PMUT unit 20 or a single second PMUT unit 30 differ significantly, resulting in a large difference between the peaks and troughs on the sensitivity curve, making it difficult to achieve modal coupling within a certain orientation. When k is too large, although multi-mode coupling can be achieved, the overall bandwidth decreases because the resonant frequency of the higher-order modes drops too much. In summary, the preferred value range for k is 4-7.
[0056] Figure 7 This is a schematic diagram showing the sensitivity curves of the PMUT unit under different k values. Figure 7 As shown, the dashed lines in examples (a), (b), (c), and (d) indicate the -6dB bandwidth cutoff. By comparison... Figure 7 As the examples show, as the value of k increases, the portion of the sensitivity curve above the dashed line increases, which helps to achieve the fusion of multiple modes and thus obtain a large bandwidth effect. However, if the value of k is greater than 7, the resonant frequency of the first-order mode remains basically unchanged, while the resonant frequencies of higher-order modes decrease significantly, and the overall bandwidth actually decreases. Therefore, a value of k in the range of 4-7 is more conducive to obtaining a large bandwidth effect.
[0057] Figure 8(a) is an exploded three-dimensional view of an ultrasonic transducer assembly according to an embodiment of this application. Figure 8(b) is a side view of a planar structure of an ultrasonic transducer assembly according to an embodiment of this application. As shown in Figures 8(a) and 8(b), the ultrasonic transducer assembly consists of three layers in the thickness direction: an anchoring layer, a mechanical support layer, and a piezoelectric stacking layer. The mechanical support layer can also be referred to as an elastic layer. Specifically, the anchoring layer includes a substrate 10 and an insulating layer 40, with the insulating layer 40 located on the substrate. The substrate 10 also has multiple cavities 50 cut out. The mechanical support layer includes anchor points 60 and multiple support structures 70, wherein each support structure 70 corresponds one-to-one with a cavity 50, and each support structure 70 is located above the corresponding cavity 50. The anchor points 60 are the areas on the mechanical support layer other than the multiple support structures 70. The piezoelectric stacked layer includes an upper electrode layer 80, a piezoelectric layer 90, and a lower electrode layer 100. The piezoelectric layer 90 is located between the upper electrode layer 80 and the lower electrode layer 100, and the piezoelectric layer 90 may include one or more layers of piezoelectric material. Optionally, the three-layer structure can be arranged in the following order from bottom to top: anchor layer, mechanical support layer, and piezoelectric stacked layer, or anchor layer, piezoelectric stacked layer, and mechanical support layer. Optionally, the anchor layer may only include the substrate 10. Optionally, the lower electrode layer 100 may also directly serve as the mechanical support layer.
[0058] It should be understood that the structure above each cavity 50 can be considered an independent PMUT unit. The cavity 50 allows the PMUT diaphragm to flex, bend, or vibrate under external excitation, defining the effective vibration region of the PMUT diaphragm. The diaphragm structural characteristics are determined by the cavity 50, which allows at least a portion of the mechanical support layer and piezoelectric stack to be suspended, thus generating mechanical vibration. It should be noted that when an electrical signal is applied between the upper and lower electrodes, the piezoelectric layer is excited by the signal and deforms according to the inverse piezoelectric effect, generating a sound signal. When external sound pressure is applied to the piezoelectric layer, charges are generated on the upper and lower surfaces of the piezoelectric layer according to the direct piezoelectric effect, and the electrical signal is read out through the upper and lower electrodes.
[0059] Based on the above description of the ultrasonic transducer, it can be seen that the substrate of the ultrasonic transducer has a first PMUT unit and a second PMUT unit of different sizes. Specifically, the difference between the frequency corresponding to the peak position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the trough position on the sensitivity curve of the second PMUT unit is less than a preset value, and / or, the difference between the frequency corresponding to the trough position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the peak position on the sensitivity curve of the second PMUT unit is less than a preset value. In other words, the sensitivity curves of the first PMUT unit and the second PMUT unit can compensate for each other. The difference between the peaks and troughs of the sensitivity between different modes on the compensated sensitivity curve is smaller, which facilitates modal coupling within a certain bandwidth range, thereby improving the operating bandwidth of the ultrasonic transducer.
[0060] Based on the aforementioned ultrasonic transducer components, this application also provides an ultrasonic transducer array. The ultrasonic transducer array includes multiple ultrasonic transducer components as described in the above embodiments, and the ultrasonic transducer array will be described in detail below.
[0061] Figure 9 This is a top view of a planar structure of an ultrasonic transducer array according to an embodiment of this application. Figure 9 As shown, in an ultrasonic transducer array, ultrasonic transducer components are distributed in at least one column, and each column includes at least one ultrasonic transducer component. The first PMUT unit and the second PMUT unit in each ultrasonic transducer component are arranged sequentially in the column direction. It should be understood that all ultrasonic transducer components in the ultrasonic transducer array can share the same substrate; that is, the first PMUT unit and the second PMUT unit in all ultrasonic transducer components are located on the same substrate. In one possible implementation, the structure of all ultrasonic transducer components in the ultrasonic transducer array is identical. Specifically, the number of first PMUT units in each ultrasonic transducer component is the same, the number of second PMUT units in each ultrasonic transducer component is the same, and the first PMUT units and the second PMUT units in each ultrasonic transducer component are arranged in the same order.
[0062] It should be noted that, Figure 9 The illustration shows ultrasonic transducers distributed in multiple columns with each adjacent column arranged in an alternating pattern. In practical applications, ultrasonic transducers can also be distributed in a single column, or they can be distributed in multiple columns arranged side by side.
[0063] Figure 10 These are schematic diagrams of several three-dimensional structures of the ultrasonic transducer array in the embodiments of this application. Figure 10 Example a in the text illustrates an embodiment in which the ultrasonic transducer components are distributed in a row in an ultrasonic transducer array. Figure 10Example b in the text illustrates an embodiment in which ultrasonic transducer components are arranged side-by-side in multiple columns in an ultrasonic transducer array. Figure 10 Example c in the diagram illustrates an embodiment where ultrasonic transducer components are staggered across multiple columns in an ultrasonic transducer array. It should be noted that, compared to side-by-side arrangement, staggered arrangement of ultrasonic transducer components increases the spacing between PMUT units, thereby reducing acoustic coupling crosstalk between adjacent columns of PMUT units of the same size, achieving both high sensitivity and large bandwidth.
[0064] Figure 11 This is a schematic diagram showing the sensitivity curves of ultrasonic transducer arrays with several different distribution configurations. For example... Figure 11 As shown, the 1×6 array corresponds to the above. Figure 10 Example 'a' in the text, a 2×6 side-by-side arrangement corresponds to the above. Figure 10 Example b in the text, a 2×6 staggered arrangement corresponds to the above. Figure 10 Example c in the text. The comparison shows that staggered ultrasonic transducer arrays achieve a larger bandwidth compared to side-by-side ultrasonic transducer arrays. Multi-column ultrasonic transducer arrays achieve higher sensitivity compared to single-column arrays due to the increased working area.
[0065] like Figure 9 As shown, in the embodiment where the ultrasonic transducer array is arranged in a staggered manner, each pair of adjacent columns is staggered. For example, the first and second columns are offset in the column direction, the second and third columns are offset in the column direction, the third and fourth columns are offset in the column direction, and the first and third columns are not offset in the column direction, the second and fourth columns are not offset in the column direction, and so on. It should be understood that in practical applications, besides Figure 9 In addition to the vertical arrangement of the ultrasonic transducers shown, the ultrasonic transducers can also be arranged in an inclined direction, as detailed in the attached diagrams.
[0066] In one possible implementation, to Figure 9 For example, the major axis of the cross-sectional shape of the first PMUT unit is larger than the major axis of the cross-sectional shape of the second PMUT unit, and the position offset Y between any two adjacent columns in the column direction is less than the length a of the major axis of the cross-sectional shape of the first PMUT unit. Preferably, the position offset Y is 0.25-0.75 times the length a of the major axis.
[0067] In one possible implementation, to Figure 9 For example, the minor axis of the cross-sectional shape of the first PMUT unit is greater than the minor axis of the cross-sectional shape of the second PMUT unit, and the spacing X between any two adjacent columns in the direction perpendicular to the column is less than or equal to the length b of the minor axis of the cross-sectional shape of the first PMUT unit. Preferably, the smaller the spacing X, the higher the area utilization and the higher the sensitivity.
[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. An ultrasonic transducer assembly, characterized in that, include: The device comprises a substrate, at least one first piezoelectric micromechanical ultrasonic transducer (PMUT) unit, and at least one second PMUT unit, the first and second PMUT units being located on the substrate, the first PMUT unit having a cross-sectional shape with a major axis and a minor axis, the second PMUT unit having a cross-sectional shape with a major axis and a minor axis, the cross-sections being parallel to the substrate, and the dimensions of the first PMUT unit and the second PMUT unit being different. The difference between the frequency corresponding to the peak position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the trough position on the sensitivity curve of the second PMUT unit is less than a preset value, and / or the difference between the frequency corresponding to the trough position on the sensitivity curve of the first PMUT unit and the frequency corresponding to the peak position on the sensitivity curve of the second PMUT unit is less than the preset value.
2. The ultrasonic transducer assembly according to claim 1, characterized in that, The cross-sectional area of the first PMUT unit is different from that of the second PMUT unit.
3. The ultrasonic transducer assembly according to claim 1 or 2, characterized in that, The thickness of the first PMUT unit is different from the thickness of the second PMUT unit.
4. The ultrasonic transducer assembly according to claim 1 or 2, characterized in that, The size of the first PMUT unit is larger than the size of the second PMUT unit, and the number of the first PMUT units is less than the number of the second PMUT units.
5. The ultrasonic transducer assembly according to claim 4, characterized in that, The major axis of the cross-sectional shape of the first PMUT unit is greater than the major axis of the cross-sectional shape of the second PMUT unit, and the minor axis of the cross-sectional shape of the first PMUT unit is greater than the minor axis of the cross-sectional shape of the second PMUT unit.
6. The ultrasonic transducer assembly according to claim 4, characterized in that, The first PMUT unit is located between the two second PMUT units.
7. The ultrasonic transducer assembly according to claim 1 or 2, characterized in that, The ratio of the major axis to the minor axis of the cross-sectional shape of the first PMUT unit is greater than or equal to 4 and less than or equal to 7, and the ratio of the major axis to the minor axis of the cross-sectional shape of the second PMUT unit is greater than or equal to 4 and less than or equal to 7.
8. The ultrasonic transducer assembly according to claim 1 or 2, characterized in that, The first PMUT unit and the second PMUT unit are arranged in the same direction, and the major axis of the cross-sectional shape of the first PMUT unit is parallel to or coincides with the major axis of the cross-sectional shape of the second PMUT unit.
9. The ultrasonic transducer assembly according to claim 1 or 2, characterized in that, The cross-sectional shape of the first PMUT unit and the cross-sectional shape of the second PMUT unit are both elliptical, or the cross-sectional shape of the first PMUT unit and the cross-sectional shape of the second PMUT unit are both polygonal, and the number of sides of the polygon is greater than 4.
10. The ultrasonic transducer assembly according to claim 1 or 2, characterized in that, The substrate includes multiple cavities, and the first PMUT unit and the second PMUT unit are respectively suspended on their respective cavities.
11. An ultrasonic transducer array, characterized in that, The device includes a plurality of ultrasonic transducers as described in any one of claims 1 to 10, the plurality of ultrasonic transducers being distributed in at least one column, each column including at least one of the ultrasonic transducers, and the first PMUT unit and the second PMUT unit in each of the ultrasonic transducers being arranged sequentially in the column direction.
12. The ultrasonic transducer array according to claim 11, characterized in that, The number of first PMUT units in each of the ultrasonic transducer components is the same, the number of second PMUT units in each of the ultrasonic transducer components is the same, and the first PMUT units and second PMUT units in each of the ultrasonic transducer components are arranged in the same order.
13. The ultrasonic transducer array according to claim 12, characterized in that, The ultrasonic transducer components in each adjacent pair of columns of the ultrasonic transducer array are arranged in an alternating pattern.
14. The ultrasonic transducer array according to claim 13, characterized in that, The first ultrasonic transducer and the second ultrasonic transducer are located in two adjacent columns. The first ultrasonic transducer and the second ultrasonic transducer are arranged in the same order in their respective columns. The two first PMUT units in the first ultrasonic transducer and the second ultrasonic transducer that are arranged in the same order are offset in the column direction. The two second PMUT units in the first ultrasonic transducer and the second ultrasonic transducer that are arranged in the same order are offset in the column direction.
15. The ultrasonic transducer array according to claim 14, characterized in that, In each of the ultrasonic transducers, the major axis of the cross-sectional shape of the first PMUT unit is greater than the major axis of the cross-sectional shape of the second PMUT unit. The positional offset in the column direction of two first PMUT units arranged in the same order in the first and second ultrasonic transducers is less than the length of the major axis of the cross-sectional shape of the first PMUT unit. The positional offset in the column direction of two second PMUT units arranged in the same order in the first and second ultrasonic transducers is less than the length of the major axis of the cross-sectional shape of the first PMUT unit.
16. The ultrasonic transducer array according to any one of claims 11 to 15, characterized in that, In each of the ultrasonic transducer components, the minor axis of the cross-sectional shape of the first PMUT unit is greater than the minor axis of the cross-sectional shape of the second PMUT unit, and the spacing between the ultrasonic transducer components of every two adjacent columns in the ultrasonic transducer array in the direction perpendicular to the column is less than or equal to the length of the minor axis of the cross-sectional shape of the first PMUT unit.