Micromechanical ultrasonic transducer based on piezoelectric effect and medical imaging device

Abstract

The present disclosure provides a micro-mechanical ultrasonic transducer based on piezoelectric effect and a medical imaging device, the micro-mechanical ultrasonic transducer comprising a substrate, an array element formed on the substrate, the array element comprising a plurality of cavities formed on the substrate at intervals; a plurality of coupling cavities respectively formed on the substrate and in communication with the plurality of cavities; a response component arranged on the substrate; and an electrode component arranged on the response component, the response component being adapted to receive and respond to an alternating excitation signal applied through the electrode component, vibrate within the array element and radiate sound waves externally; or, the response component being adapted to receive sound wave signals from the outside, vibrate within the array element, generate voltage signals and output through the electrode component; wherein the cavities of different sizes are arranged so that the corresponding response components have different intrinsic resonant frequencies, and the plurality of coupling cavities are arranged so that the response components are shifted to different degrees near the intrinsic resonant frequencies to generate resonant frequencies different from the intrinsic resonant frequencies.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of micro-mechanical ultrasonic transducers, and particularly relates to a micro-mechanical ultrasonic transducer based on piezoelectric effect and a medical imaging device. BACKGROUND

[0002] Compared with traditional ultrasonic transducers, micro-mechanical ultrasonic transducers (MUT) combined with micro-electro-mechanical system (MEMs) technology have the advantages of micro size, low power consumption, and integration, and have broad application scenarios in the field of interventional cardiovascular intraluminal ultrasound imaging.

[0003] MUTs are generally divided into two categories: one is a micro-mechanical ultrasonic transducer based on capacitance (CMUT), and the other is a micro-mechanical ultrasonic transducer based on piezoelectric effect (PMUT). The advantage of PMUT over CMUT is that it does not require a large bias voltage and has a simple process, but the biggest disadvantage of PMUT is narrow bandwidth.

[0004] A common method for PMUT to achieve multi-frequency and wide bandwidth is to change at least one of the horizontal and vertical dimensions of the micro-mechanical ultrasonic transducer (i.e., to place micro-mechanical ultrasonic transducers with different horizontal and vertical dimensions on the same substrate). Due to the sensitivity of the resonant frequency of PMUT to the horizontal and vertical dimensions of the micro-mechanical ultrasonic transducer, the interval between the two different resonant frequencies obtained by changing at least one of the horizontal and vertical dimensions is large, making it difficult to achieve "fine tuning" of the frequency, and it is also difficult to achieve wide bandwidth through the coupling of resonant frequencies between adjacent working frequency bands. SUMMARY

[0005] To solve at least one of the technical problems in the prior art, the present disclosure provides a micro-mechanical ultrasonic transducer based on piezoelectric effect, which can couple the resonant frequencies between adjacent working frequency bands to achieve wide bandwidth.

[0006] In one aspect of the embodiments of the present disclosure, a micro-mechanical ultrasonic transducer based on piezoelectric effect is provided, which includes a substrate, a response component and an electrode component. The substrate is formed with an array element, which includes a plurality of cavities and a plurality of coupling cavities. The plurality of cavities are spaced apart on the substrate; the plurality of coupling cavities are formed on the substrate and communicate with the plurality of cavities, respectively; the response component is disposed on the substrate. The electrode component is disposed on the response component, and the response component is adapted to receive and respond to an alternating excitation signal applied through the electrode component to vibrate within the array element and radiate sound waves outward; or, the response component is adapted to receive a sound wave signal from outside to vibrate within the array element to generate a voltage signal and output through the electrode component; wherein the plurality of coupling cavities are arranged such that the response component is offset to different degrees near a corresponding natural resonant frequency of each of the cavities to generate a resonant frequency different from the natural resonant frequency, thereby widening the bandwidth of the micro-mechanical ultrasonic transducer.

[0007] According to the embodiments of the present disclosure, the response component includes an elastic layer and a piezoelectric layer. The elastic layer is disposed on the substrate, and the piezoelectric layer is disposed on the elastic layer and is adapted to generate internal stress under the excitation of the excitation signal to drive the elastic layer to produce bending vibration and radiate sound waves outward; or, receive the sound wave signal from outside to vibrate and generate the voltage signal.

[0008] According to the embodiments of the present disclosure, the electrode component includes a first electrode and a second electrode. The first electrode is disposed on the response component, and the second electrode is disposed on the response component in a spaced-apart manner with the first electrode, and the second electrode is matched with the first electrode to be located above each of the cavities to receive the excitation signal from outside or the voltage signal from the response component to form an electric field between the first electrode and the second electrode.

[0009] According to the embodiments of the present disclosure, the first electrode includes a first interdigital portion and a first connecting portion. The first interdigital portion is disposed on the piezoelectric layer, and the first connecting portion is electrically connected with the first interdigital portion. The second electrode includes a second interdigital portion and a second connecting portion. The second interdigital portion is disposed on the piezoelectric layer in a spaced-apart manner with the first interdigital portion and is disposed above the array element in correspondence with the first interdigital portion, and the second connecting portion is electrically connected with the second interdigital portion and is adapted to cooperate with the first connecting portion to receive the excitation signal or output the voltage signal.

[0010] According to an embodiment of the present disclosure, the first electrode is disposed on the piezoelectric layer, and the second electrode is disposed between the elastic layer and the piezoelectric layer, wherein the first electrode comprises a plurality of body portions and a third connecting portion. The plurality of body portions are respectively disposed above the plurality of cavities; and the third connecting portion connects the plurality of body portions and is adapted to cooperate with the second electrode to receive the excitation signal or output the voltage signal.

[0011] According to an embodiment of the present disclosure, each of the first electrodes covers an area of 70% of a corresponding cavity.

[0012] According to an embodiment of the present disclosure, an intrinsic cavity is formed on the substrate and spaced from the array elements, and the intrinsic cavity is adapted to cooperate with the response assembly to provide a reference resonant frequency.

[0013] According to an embodiment of the present disclosure, a distance between two adjacent cavities in the array element is half of a corresponding acoustic wavelength, so as to reduce the grating lobe effect.

[0014] According to an embodiment of the present disclosure, sizes of the plurality of cavities in the array element are configured to be different, so that the corresponding response assembly has different intrinsic resonant frequencies.

[0015] As another aspect of the embodiments of the present disclosure, a medical imaging device is provided, comprising: a transducer array comprising a plurality of the above-described micro-mechanical ultrasonic transducers.

[0016] According to the micro-mechanical ultrasonic transducer based on the piezoelectric effect of the embodiments of the present disclosure, by disposing a plurality of coupling cavities, the response assembly can be shifted to different degrees near the intrinsic resonant frequency, so as to generate resonant frequencies different from the intrinsic resonant frequencies corresponding to the cavities, and widen the bandwidth of the micro-mechanical ultrasonic transducer. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 An exploded view of a micro-mechanical ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure is schematically shown;

[0018] Figure 2 An exploded view of a micro-mechanical ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure is schematically shown; Figure 1 A top view of a substrate of a micro-mechanical ultrasonic transducer based on the piezoelectric effect is shown;

[0019] Figures 3a-3d Top views of substrates of micro-mechanical ultrasonic transducers based on the piezoelectric effect according to four embodiments of the present disclosure are schematically shown;

[0020] Figure 4 A partial top view of a micro-mechanical ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure is schematically shown.

[0021] Figure 5 schematically illustrates Figure 4 A cross-sectional view along the line A-A of the micro-machined ultrasonic transducer based on the piezoelectric effect shown;

[0022] Figure 6 schematically illustrates an exploded view of a micro-machined ultrasonic transducer based on the piezoelectric effect according to another embodiment of the present disclosure;

[0023] Figure 7 schematically illustrates a partial cross-sectional view of a micro-machined ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure;

[0024] Figure 8 schematically illustrates a partial top view of a micro-machined ultrasonic transducer based on the piezoelectric effect according to yet another embodiment of the present disclosure;

[0025] Figure 9 schematically illustrates Figure 8 A cross-sectional view along the line A-A of the micro-machined ultrasonic transducer based on the piezoelectric effect shown;

[0026] Figure 10 schematically illustrates a comparison between the two cases of the presence of a coupling cavity and the absence of a coupling cavity;

[0027] Figures 11a-11c schematically illustrates a flow chart of the preparation of a micro-machined ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure;

[0028] Figure 12 schematically illustrates simulation results of a micro-machined ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure; and

[0029] Figure 13 schematically illustrates calculation results of a micro-machined ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure in the air domain for acoustic field simulation.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS:

[0031] 1 - substrate;

[0032] 11 - cavity; 12 - coupling cavity; 13 - intrinsic cavity;

[0033] 2 - response component;

[0034] 21 - elastic layer; 22 - piezoelectric layer;

[0035] 3 - electrode component;

[0036] 31 - first electrode;

[0037] 311 - first interdigital portion; 312 - first connecting portion; 313 - main body portion;

[0038] 32 - second electrode;

[0039] 321 - second interdigital portion; 312 - second connecting portion;

[0040] 4 - etching hole. DETAILED DESCRIPTION

[0041] For the purposes of the present disclosure, the technical solutions and advantages will be more clearly apparent, the following will be combined with specific embodiments, and referring to the drawings, the present disclosure is further described in detail. However, the present disclosure can be implemented in different forms, and should not be interpreted as being limited to the embodiments presented here. On the contrary, the presentation of these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. In the drawings, in order to be clear, the size and relative size of the layers and regions can be exaggerated, and the same reference signs represent the same elements throughout.

[0042] In the following, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, many specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it is obvious that one or more embodiments can be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concept of the present disclosure.

[0043] In the field of medical ultrasound imaging, the working bandwidth of the micro-mechanical ultrasonic transducer has an important influence on the resolution of the ultrasound image, the larger the working bandwidth, the higher the resolution of the image. In the field of medical ultrasound imaging, the resonant frequency of the micro-mechanical ultrasonic transducer also has an influence on the image resolution, the higher the resonant frequency, the higher the resolution of the image, but the ultrasonic wave attenuates faster and the transmission distance is shorter. In practical applications, the selection of the working frequency needs to be compromised between the imaging distance and the resolution, so the micro-mechanical ultrasonic transducer with multi-frequency working and wide bandwidth has broad application prospects.

[0044] It should be noted that the thickness (height) direction of the micro-mechanical ultrasonic transducer based on the piezoelectric effect refers to the growth direction of the device in the first plane, i.e. the direction perpendicular to the first plane (such as the direction indicated by the Z axis shown in Figure 1 The lateral direction is the direction indicated by the X axis shown in the first plane Figure 1 The longitudinal direction is the direction indicated by the Y axis shown in the first plane Figure 1 The longitudinal direction is the direction indicated by the Y axis shown in the first plane

[0045] Figure 1A diagram illustrating a piezoelectric effect-based micromechanical ultrasonic transducer according to an embodiment of the present disclosure is shown, Figure 2 A diagram illustrating a piezoelectric effect-based micromechanical ultrasonic transducer according to an embodiment of the present disclosure is shown, Figure 1 A diagram illustrating a piezoelectric effect-based micromechanical ultrasonic transducer according to an embodiment of the present disclosure is shown.

[0046] As an aspect of an embodiment of the present disclosure, a piezoelectric effect-based micromechanical ultrasonic transducer is provided, which includes a substrate, a response component, and an electrode component. Figure 1 As shown, the piezoelectric effect-based micromechanical ultrasonic transducer includes a substrate 1, a response component 2, and an electrode component 3. As shown, Figure 1 As shown, the piezoelectric effect-based micromechanical ultrasonic transducer includes a substrate 1, a response component 2, and an electrode component 3. As shown, Figure 2 As shown, the substrate 1 is formed with an array element, which includes a plurality of cavities 11 and a plurality of coupling cavities 12. The plurality of cavities 11 are spaced apart on the substrate 1, and the plurality of coupling cavities 12 are formed on the substrate 1 and respectively communicate with the plurality of cavities 11. The response component 2 is disposed on the substrate 1, and the electrode component 3 is disposed on the response component 2. The response component 2 is adapted to receive and respond to an alternating excitation signal applied by the electrode component 3, vibrate within the array element, and radiate sound waves to the outside; or, the response component 2 is adapted to receive sound wave signals from the outside, vibrate within the array element, generate voltage signals, and output the voltage signals through the electrode component 3. The plurality of coupling cavities 12 are arranged such that the response component 2 is shifted to different degrees around the natural resonant frequency corresponding to each cavity, to generate resonant frequencies different from the natural resonant frequencies, and to widen the bandwidth of the micromechanical ultrasonic transducer.

[0047] According to the piezoelectric effect-based micromechanical ultrasonic transducer of an embodiment of the present disclosure, the plurality of coupling cavities are arranged such that the response component is shifted to different degrees around the natural resonant frequency corresponding to each cavity, to generate resonant frequencies different from the natural resonant frequencies, and to widen the bandwidth of the micromechanical ultrasonic transducer.

[0048] As understood by those skilled in the art, for different micromechanical ultrasonic transducers, the stiffness of the response component can be changed by adjusting the size of the coupling cavities, so as to control the resonant frequency of the response component in the array element.

[0049] According to an embodiment of the present disclosure, the natural resonant frequency is the vibration frequency generated at each cavity 11 when the response component 2 responds to an alternating excitation signal applied by the electrode component 3, which is positive and negative in phase, from the outside, or receives sound wave signals from the outside, without the coupling cavities 12 being arranged.

[0050] In an illustrative embodiment, the plurality of cavities are configured to have at least partially different sizes, and the response component corresponding to the cavities of different sizes has different natural resonant frequencies. The plurality of coupling cavities are arranged such that the response component is shifted to different degrees around the different natural resonant frequencies, to generate a plurality of resonant frequencies different from the natural resonant frequencies, and to widen the bandwidth of the micromechanical ultrasonic transducer.

[0051] According to an embodiment of the present disclosure, the shape of the coupling cavity can include any one of a rectangle, an arc, an S shape, etc. Figures 3a-3d One plan view of a substrate of a piezoelectric effect-based micro-machined ultrasonic transducer according to four embodiments of the present disclosure is schematically shown.

[0052] In one illustrative embodiment, as shown in Figure 3a a matrix is formed on the substrate 1, the matrix including two rectangular cavities 11 of different sizes, each cavity corresponding to a different eigen-resonant frequency, and a coupling cavity 12 connecting the two cavities, wherein the coupling cavity 12 is configured in a rectangular shape and connected to the middle of the two cavities 11, so that the response assembly is shifted around each different eigen-resonant frequency to produce different resonant frequencies. It can be understood that the coupling cavity 12 can also be connected to the ends of the two rectangular cavities.

[0053] In another illustrative embodiment, as shown in Figure 3b a matrix is formed on the substrate 1, the matrix including two rectangular cavities 11 of the same size, each cavity corresponding to the same eigen-resonant frequency, and a coupling cavity 12 connecting the two cavities, wherein the coupling cavity 12 can be configured in an arc shape. It can be understood that the number of coupling cavities between the two cavities 11 can also be more than one.

[0054] In yet another illustrative embodiment, as shown in Figure 3c a matrix is formed on the substrate 1, the matrix including one cavity 11, and a coupling cavity 12 is provided to shift the response assembly 2 around the eigen-resonant frequency of the cavity 11 to produce a resonant frequency different from the eigen-resonant frequency.

[0055] In still another illustrative embodiment, as shown in Figure 3d a matrix is formed on the substrate, the matrix including three rectangular cavities of the same size, wherein a first coupling cavity is connected between the first cavity and the second cavity, and two second coupling cavities are connected between the second cavity and the third cavity, and the sizes of the three coupling cavities can be set to be the same. It can be understood that in other embodiments, the sizes and shapes of the three coupling cavities can also be set to be partially different or completely different.

[0056] In one illustrative embodiment, a plurality of coupling cavities can be connected between two adjacent cavities.

[0057] In another illustrative embodiment, at least one coupling cavity can be connected to one cavity.

[0058] In yet another illustrative embodiment, a plurality of coupling cavities can connect a plurality of cavities two by two. In still another illustrative embodiment, a plurality of coupling cavities can connect a plurality of cavities two by two.

[0059] In an alternative embodiment, the plurality of cavities are configured to have the same size, and the cavities 11 of the same size correspond to the same eigen-resonant frequency.

[0060] In an illustrative embodiment, referring to Figure 1 and Figure 2 , among the plurality of cavities 11, the distance between two adjacent cavities 11 in the longitudinal direction is equal, and the two adjacent cavities 11 can be connected by a plurality of coupling cavities 12 of different sizes. The coupling cavities 12 of different sizes reduce the stiffness of the response assembly 2, so that the response assembly 2 has different resonant frequencies at the plurality of cavities 11.

[0061] Figure 4 Fig. 1 schematically shows a top view of a partial piezoelectric effect-based micromechanical ultrasonic transducer according to an embodiment of the present disclosure, Figure 5 Fig. 2 schematically shows Figure 4 Fig. 3 shows a cross-sectional view of the piezoelectric effect-based micromechanical ultrasonic transducer along the A-A line.

[0062] According to an embodiment of the present disclosure, as shown in Figure 4 and Figure 5 , the eigen-frequency is related to the transverse and longitudinal dimensions of the cavity 11. In the case of the same transverse dimension, the larger the longitudinal dimension of the cavity 11, the lower the corresponding eigen-frequency. In the case of the same longitudinal dimension, the larger the transverse dimension of the cavity 11, the lower the corresponding eigen-frequency.

[0063] According to an embodiment of the present disclosure, the shape of the plurality of cavities 11 includes, but is not limited to, one of a rectangle, a circle, a hexagon, etc. Changing at least one of the transverse and longitudinal dimensions of the cavity 11 can be achieved by changing the aspect ratio, the radius of the circle, etc.

[0064] In an illustrative embodiment, as shown in Figure 4 and Figure 5 , the shape of the plurality of cavities 11 of the array element is square, and changing the transverse and longitudinal dimensions of the cavity 11, i.e., changing the side length w of the square, can adjust the eigen-frequency corresponding to the cavity 11.

[0065] According to an embodiment of the present disclosure, as shown in Figures 1 to 5 , the response assembly 2 includes an elastic layer 21 and a piezoelectric layer 11. The elastic layer 21 is disposed on the substrate 1, and the piezoelectric layer 22 is disposed on the elastic layer 21. The piezoelectric layer 22 is adapted to generate internal stress under the excitation of the excitation signal, drive the elastic layer 21 to produce bending vibration and radiate sound waves outward; or, receive sound wave signals from the outside, vibrate and generate a voltage signal.

[0066] According to embodiments of the present disclosure, the material of the elastic layer 21 includes, but is not limited to, any one of silicon dioxide (SiO2), silicon nitride (Si3N4), silicon (Si), etc.

[0067] According to embodiments of the present disclosure, the elastic layer 21, together with the piezoelectric layer 22, forms a diaphragm of a micro-mechanical ultrasonic transducer, and the elastic layer 21 can serve as a stop layer for etching the back of the substrate 1.

[0068] According to embodiments of the present disclosure, the elastic layer 21 can be grown on the substrate 1 by thin film growth, or when etching the substrate 1, a portion of the substrate close to the piezoelectric layer 22 is reserved as the elastic layer 21.

[0069] In some embodiments, the array elements can be configured to connect the plurality of cavities 11 two by two to form a ring structure by the plurality of coupling cavities 12.

[0070] In other embodiments, the plurality of cavities 11 can be arranged in an array on the substrate 1, and two adjacent cavities 11 are connected by the plurality of coupling cavities 12.

[0071] According to embodiments of the present disclosure, the material of the substrate can include silicon (Si), which provides support for the micro-mechanical ultrasonic transducer. The plurality of cavities 11 can be formed by etching on the substrate 1 to release the diaphragm structure, and each cavity 11 forms a vibration unit with the diaphragm at the corresponding cavity 11.

[0072] According to embodiments of the present disclosure, a plurality of array elements can be formed on the substrate 1 of the micro-mechanical ultrasonic transducer based on the piezoelectric effect. For example, the cavities in each array element correspond to different intrinsic resonant frequencies, and by respectively arranging the coupling cavities 12 in each array element to connect the adjacent cavities 11 two by two in each array element, the bandwidth near the corresponding intrinsic resonant frequency of each array element is respectively widened, achieving at least one of multi-frequency and wide bandwidth.

[0073] According to embodiments of the present disclosure, the number of array elements that can be formed on the substrate of the micro-mechanical ultrasonic transducer based on the piezoelectric effect can include, but is not limited to, any one of 1, 2, 3, 5, or 10, etc.

[0074] In an illustrative embodiment, four array elements of the micro-mechanical ultrasonic transducer based on the piezoelectric effect can be formed on the substrate 1, and four different sizes (at least one of the lateral size and the longitudinal size is different) of the plurality of cavities 11 are integrated on the same substrate 1, so that the corresponding operating frequency ranges of each array element are coupled to achieve a large bandwidth.

[0075] In an exemplary embodiment, two different sizes of the elements can be formed on the substrate 1 of the micro-mechanical ultrasonic transducer based on the piezoelectric effect, that is, the sizes of the cavities 11 of the two elements are different, so that each element corresponds to a different frequency range, and two working modes corresponding to a first frequency range (for example, 1-2 MHz) and a second frequency range (for example, 10-15 MHz) higher than the first frequency range.

[0076] According to an embodiment of the present disclosure, when the back of the substrate 11 is etched to release the diaphragm structure, the coupling cavities 12 are formed by etching between two adjacent cavities 11 of the same element, and the coupling cavities 12 reduce the stiffness of the diaphragm and further reduce the resonant frequency of the vibration unit. Compared with changing at least one of the lateral size and the longitudinal size of the cavity 11, the influence of the coupling cavity 12 on the resonant frequency of the device belongs to "fine adjustment". Increasing the width of the coupling cavity 12 further reduces the stiffness of the diaphragm and reduces the resonant frequency corresponding to the two cavities 11 connected to the coupling cavity 12, respectively.

[0077] According to an embodiment of the present disclosure, as shown in Figure 1 and Figure 2 , the resonant frequency corresponding to each cavity 11 in the element can be fine-adjusted by setting multiple coupling cavities 12 with different widths (lateral sizes).

[0078] According to an embodiment of the present disclosure, as shown in Figure 1 , Figure 4 and Figure 5 , the electrode assembly 3 includes a first electrode 31 and a second electrode 32. The first electrode 31 is arranged on the response assembly 2, and the second electrode 32 is arranged on the response assembly 2 spaced apart from the first electrode 31, and the second electrode 32 matches the first electrode 31 to be located above each cavity 11 to receive an excitation signal from the outside or a voltage signal from the response assembly, so that an electric field is formed between the first electrode 31 and the second electrode 32.

[0079] According to an embodiment of the present disclosure, as shown in Figure 1As shown, the first electrode 31 includes a first interdigital portion 311 and a first connecting portion 312. The first interdigital portion 311 is disposed on the piezoelectric layer 22, and the first connecting portion 312 is electrically connected with the first interdigital portion 311. The second electrode 32 includes a second interdigital portion 321 and a second connecting portion 322. The second interdigital portion 321 is disposed on the piezoelectric layer 22 in a manner spaced apart from the first interdigital portion 311, and is disposed above the array element together with the first interdigital portion 311, that is, the first interdigital portion 311 and the second interdigital portion 321 are disposed above each cavity 11 in a matching manner. The second connecting portion 322 is electrically connected with the second interdigital portion 321, and is adapted to cooperate with the first connecting portion 312 to receive an excitation signal or output a voltage signal, so as to form a transverse electric field between the first electrode 31 and the second electrode 32, specifically, form a transverse electric field between the first interdigital portion and the second interdigital portion, so that the piezoelectric layer 22 generates a transverse internal stress under the action of the transverse electric field, and drives the diaphragm to produce bending vibration and radiate sound waves outward, or receive a sound wave signal and generate an electrical response. It can be understood that the first connecting portion 312 and the second connecting portion 322 can also be disposed on the piezoelectric layer 22.

[0080] In such embodiments, the material of the piezoelectric layer 22 includes, but is not limited to, any one of lithium niobate, lithium tantalate, a special cut aluminum nitride material, etc.

[0081] According to embodiments of the present disclosure, the material of the electrode assembly 3 is a conductive material, which can include, but is not limited to, any one or more of aluminum (Al), platinum (Pt), gold (Au), etc.

[0082] In an illustrative embodiment, a plurality of array elements are formed on the substrate 1 of the micro-mechanical ultrasonic transducer based on the piezoelectric effect, and the electrode assembly 3 is correspondingly disposed on each array element. The first connecting portions 312 of the plurality of electrode assemblies 3 are electrically connected, and the plurality of second connecting portions 322 are electrically connected, so that the same external electric field can be used to apply an excitation signal to the plurality of vibration units, so that the plurality of vibration units simultaneously radiate sound wave signals of different frequency bands outward.

[0083] In an illustrative embodiment, a plurality of array elements are formed on the substrate 1 of the micro-mechanical ultrasonic transducer based on the piezoelectric effect, and the electrode assembly 3 is correspondingly disposed on each array element. Any one or more groups of electrodes can be selected to apply an excitation signal as needed.

[0084] Figure 6 An exploded view of a micro-mechanical ultrasonic transducer based on the piezoelectric effect according to another embodiment of the present disclosure is schematically shown, Figure 7 A partial cross-sectional view of a micro-mechanical ultrasonic transducer based on the piezoelectric effect according to an embodiment of the present disclosure is schematically shown.

[0085] According to other embodiments of the present disclosure, as Figure 6 With Figure 7As shown, the first electrode 31 is disposed on the piezoelectric layer 22, and the second electrode 32 is disposed on the elastic layer 21, and the first electrode 31 and the second electrode 32 form an electric field in the height direction. The first electrode 31 includes a plurality of body parts 313 and a third connecting part. The plurality of body parts 313 are respectively disposed above each cavity 11, and the third connecting part electrically connects the plurality of body parts 313. The first electrode 31 is adapted to cooperate with the second electrode 32 to receive an excitation signal or output a voltage signal, so that an electric field in the height direction is formed between the first electrode 31 and the second electrode 32, and specifically, an electric field in the height direction is formed between each body part 313 and the second electrode 32, so that the piezoelectric layer 22 generates internal stress under the action of the electric field in the height direction, drives the diaphragm to produce bending vibration and radiate sound waves outward, or receives sound wave signals and generates an electrical response.

[0086] In such embodiments, the material of the piezoelectric layer includes, but is not limited to, any one of aluminum nitride, scandium-doped aluminum nitride, lead zirconate titanate, zinc oxide, etc.

[0087] According to embodiments of the present disclosure, the area of each first electrode is generally set to 70% of the area of the corresponding cavity.

[0088] According to embodiments of the present disclosure, the distance between two adjacent cavities in an array element is generally set to half of the corresponding sound wavelength, so as to reduce the grating lobe effect.

[0089] According to embodiments of the present disclosure, the distance between two adjacent cavities is set to half of the corresponding sound wavelength at the resonant frequency, if less than half of the corresponding sound wavelength at the resonant frequency, the sound fields generated by the plurality of vibration units will superimpose on each other, resulting in grating lobes; if the distance is greater than half of the corresponding sound wavelength at the resonant frequency, the directivity of the array sound field is poor and not concentrated enough.

[0090] In such embodiments, the second electrode can be a hierarchical structure disposed between the piezoelectric layer 22 and the elastic layer 21. The third connecting part can be realized by etching the piezoelectric layer 22.

[0091] According to embodiments of the present disclosure, an intrinsic cavity 13 can also be formed on the substrate 1 and spaced apart from the array element. The intrinsic resonant frequency corresponding to the intrinsic cavity 13 serves as a reference resonant frequency of the resonant frequency of the array element of the response assembly 2. By setting a plurality of coupling cavities, the response assembly can be offset to different degrees near the reference resonant frequency.

[0092] Figure 8 schematically shows a top view of a partial micro-mechanical ultrasonic transducer based on the piezoelectric effect according to a further embodiment of the present disclosure, Figure 9 schematically shows Figure 8 schematically shows a cross-sectional view of the micro-mechanical ultrasonic transducer based on the piezoelectric effect along the A-A line

[0093] According to an embodiment of the present disclosure, as Figure 8 and Figure 9 shown, etching holes 4 are formed on the response component 2 from the piezoelectric layer in the height direction downward, and the cavity can be formed by etching the substrate 1 through the etching holes 4 to release the diaphragm structure.

[0094] According to an embodiment of the present disclosure, the etching holes 4 are spaced apart from the first electrode 31.

[0095] Figure 10 The contrast between the two cases of coupled cavities and uncoupled cavities is schematically shown.

[0096] In an illustrative embodiment, as Figure 10 shown, in the case without coupling cavities 12, the cavity is an intrinsic cavity. Different sizes of intrinsic cavities correspond to different intrinsic resonance frequencies, and the first intrinsic cavity corresponds to a first intrinsic resonance frequency f1, and the second intrinsic cavity corresponds to a second intrinsic resonance frequency f2. As Figure 1 shown, the micromechanical ultrasonic transducer includes two array elements and two intrinsic cavities. By setting the coupling cavity, the bandwidth of the first array element and the second array element near the respective intrinsic resonance frequencies is increased. In the case where the first intrinsic resonance frequency f1 and the second intrinsic resonance frequency f2 differ greatly, by setting the coupling cavity 12, the micromechanical ultrasonic transducer can realize dual-frequency and wide bandwidth; in the case where the first intrinsic resonance frequency f1 and the second intrinsic resonance frequency f2 differ slightly, by setting the coupling cavity 12, the two frequency bands are coupled, and the micromechanical ultrasonic transducer can realize large bandwidth.

[0097] As another aspect of an embodiment of the present disclosure, a medical imaging device is provided, including a transducer array, the transducer array including any one of the micromechanical ultrasonic transducers described above.

[0098] According to an embodiment of the present disclosure, by respectively applying excitation signals with a certain time delay to each array element of the transducer array, dynamic focusing and scanning of the array sound field are realized in combination with phased array technology.

[0099] Figures 11a-11c A preparation flowchart of the micromechanical ultrasonic transducer based on the piezoelectric effect according to the disclosed embodiment is schematically shown.

[0100] As still another aspect of an embodiment of the present disclosure, a preparation method for manufacturing any one of the micromechanical ultrasonic transducers based on the piezoelectric effect described above is provided, as Figures 11a-11c shown, including:

[0101] Growth of an elastic layer, a piezoelectric layer, and an electrode assembly on a substrate.

[0102] Growth and patterning of an electrode assembly on the top of the piezoelectric layer.

[0103] The back of substrate 1 is etched to form array elements to release the diaphragm structure.

[0104] In another illustrative embodiment, a method for fabricating any of the above-mentioned piezoelectric effect-based micromechanical ultrasonic transducers includes:

[0105] A second electrode is grown on substrate 1.

[0106] A piezoelectric layer is grown on the second electrode.

[0107] The first electrode is grown and patterned on the piezoelectric layer.

[0108] The back of substrate 1 is etched to form array elements, and a portion of the substrate is reserved on the side adjacent to the second electrode as an elastic layer.

[0109] Figure 12 The simulation results of a piezoelectric-based micromechanical ultrasonic transducer according to an embodiment of the present disclosure are illustrated schematically.

[0110] like Figure 12 As shown in Figure 11, the horizontal axis represents frequency (MHz), and the vertical axis represents displacement magnitude (nm). The piezoelectric-based micromechanical ultrasonic transducer includes an array element comprising three square cavities 11, each with a side length of 50 μm. The three cavities 11 are connected by two coupling cavities 12 of different widths. The first coupling cavity has a width of 5 μm, and the second coupling cavity has a width of 15 μm. The length of each coupling cavity (the distance between two adjacent cavities) is 20 μm. As shown in Figure 11, after the square cavities with a side length of 50 μm are connected through coupling cavities of different widths, the corresponding resonant frequency shifts, with an adjustment range of 10-10.5 MHz, achieving fine-tuning of the micromechanical ultrasonic transducer.

[0111] Figure 13 The illustration schematically shows the calculation results of an acoustic field simulation in the air domain for a piezoelectric-based micromechanical ultrasonic transducer according to an embodiment of the present disclosure.

[0112] like Figure 13 As shown, the horizontal axis represents frequency (MHz), and the vertical axis represents the sound pressure level (dB) at a distance of 1 mm from the center of the micromechanical ultrasonic transducer. When the three cavities with coupling chambers emit sound waves in the air domain, three similar resonant peaks appear, enabling fine-tuning of the micromechanical ultrasonic transducer. In practical applications, especially in aquatic environments, the load effect of water is greater than that of air, and the similar peaks couple to form a flatter frequency curve, achieving a larger bandwidth.

[0113] The micro-mechanical ultrasonic transducer based on the piezoelectric effect provided by the present disclosure can realize multi-frequency operation by arranging a plurality of array elements with different intrinsic resonant frequencies, and can switch the operation mode according to actual needs, apply excitation signals to different array elements, and is simple and convenient.

[0114] Compared with the traditional PMUT wide bandwidth implementation scheme (i.e., simply integrating cavities with small differences in transverse and longitudinal dimensions on the same substrate), the present disclosure optimizes the bandwidth of each working frequency band by coupling cavities, and can realize a larger bandwidth after integration between array elements of different sizes. In addition, PMUT is sensitive to changes in transverse and longitudinal dimensions, and cavities with at least one different transverse and longitudinal dimension have a large difference in corresponding resonant frequencies, and it is not easy to couple to realize a large bandwidth. The present disclosure fine-tunes through coupling cavities to make it easier for devices of different frequencies to be coupled.

[0115] The micro-mechanical ultrasonic transducer based on the piezoelectric effect provided by the present disclosure has at least one of the characteristics of multi-frequency and wide bandwidth, and has the advantages of micro-size, low power consumption, etc., and can be used in the field of interventional medical ultrasonic imaging.

[0116] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present disclosure, and it should be understood that the above only describes preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A micromechanical ultrasonic transducer based on the piezoelectric effect, characterized in that, The micro-mechanical ultrasonic transducer comprises: a substrate on which an array element is formed, the array element comprising: a plurality of cavities formed on the substrate and spaced apart; and a plurality of coupling cavities respectively formed on the substrate and in communication with the plurality of cavities; a response component disposed on the substrate; and an electrode component disposed on the response component, the response component being adapted to receive and respond to an excitation signal applied through the electrode component in an alternating current, vibrate within the array element and radiate sound waves externally; or, the response component being adapted to receive a sound wave signal from the outside, vibrate within the array element, generate a voltage signal and output through the electrode component; wherein the plurality of coupling cavities are arranged to change the stiffness of the response component, so that the response component is offset to different degrees near the corresponding intrinsic resonant frequency of each cavity, to generate a resonant frequency different from the intrinsic resonant frequency, and to widen the bandwidth of the micro-mechanical ultrasonic transducer.

2. The micromechanical ultrasonic transducer according to claim 1, characterized in that The response component comprises: an elastic layer disposed on the substrate, a piezoelectric layer disposed on the elastic layer, and adapted to generate internal stress under the excitation of the excitation signal, drive the elastic layer to produce bending vibration and radiate sound waves externally; or, receive the sound wave signal from the outside, vibrate and generate the voltage signal.

3. The micromechanical ultrasonic transducer of claim 2, characterized in that, The electrode component comprises: a first electrode disposed on the response component; a second electrode disposed on the response component in spaced apart from the first electrode, and the second electrode and the first electrode are matched to be located above each cavity, to receive the excitation signal from the outside or the voltage signal from the response component, so that an electric field is formed between the first electrode and the second electrode.

4. The micro-mechanical ultrasonic transducer according to claim 3, wherein The first electrode comprises: a first interdigital portion disposed on the piezoelectric layer; and a first connecting portion electrically connected with the first interdigital portion; The second electrode comprises: a second interdigital portion disposed on the piezoelectric layer in spaced apart from the first interdigital portion, and disposed above the array element corresponding to the first interdigital portion; and a second connecting portion electrically connected with the second interdigital portion, and adapted to cooperate with the first connecting portion to receive the excitation signal or output the voltage signal.

5. The micromechanical ultrasonic transducer of claim 3, characterized in that, The first electrode is disposed on the piezoelectric layer, and the second electrode is disposed between the elastic layer and the piezoelectric layer, wherein The first electrode comprises: a plurality of body portions respectively disposed above a plurality of cavities; and a third connecting portion connecting the plurality of body portions, and adapted to cooperate with the second electrode to receive the excitation signal or output the voltage signal.

6. The micromechanical ultrasonic transducer of claim 5, characterized in that, The coverage area of the first electrode is set to be 70% of the area of the corresponding cavity.

7. The micromachined ultrasonic transducer of claim 1, wherein, An intrinsic cavity is formed on the substrate in spaced apart from the array element, and the intrinsic cavity is adapted to cooperate with the response component to provide a reference resonant frequency.

8. The micromechanical ultrasonic transducer according to any one of claims 1-7, characterized in that, The distance between two adjacent cavities in the array element is half of the corresponding sound wave wavelength, to reduce the grating lobe effect.

9. The micromachined ultrasonic transducer of claim 1, wherein, The sizes of the plurality of cavities in the array element are configured to be different, so that the corresponding response components have different intrinsic resonant frequencies.

10. A medical imaging apparatus, characterized by comprising: a transducer array comprising a plurality of micromechanical ultrasonic transducers according to any of claims 1-9.

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