Micro ultrasonic transducer and ultrasonic conversion method
By designing a micro-ultrasonic transducer with the lower electrode layer located within the substrate, and combining DC bias and AC voltage signals, the advantages of CMUT and PMUT are realized, solving the problem of simultaneous optimization of transmission and reception performance, and achieving efficient ultrasonic transmission and high-sensitivity reception.
Patent Information
- Application Number
- CN202511999064.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-02-27
AI Technical Summary
Existing CMUTs and PMUTs are difficult to optimize in terms of both transmission and reception performance at the same time, making it difficult to achieve both strong acoustic output and high-sensitivity reception in ultrasound imaging applications.
Design a micro-ultrasonic transducer in which the lower electrode layer is located within a substrate, and the piezoelectric functional layer and the lower electrode layer form a variable capacitor. By combining the application of DC bias and AC voltage signals, ultrasonic wave reception in pure capacitive mode and ultrasonic wave transmission in pure piezoelectric mode can be achieved.
It achieves high transmission efficiency, high receiving sensitivity, and high signal-to-noise ratio, improving the application flexibility of the device and enabling the selection of voltage modes in different scenarios to optimize the receiving and transmission performance of ultrasonic waves.
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Figure CN121571364A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor devices, and in particular to a micro-ultrasound transducer and an ultrasonic conversion method. BACKGROUND
[0002] Micro-machined ultrasonic transducers are mainly divided into two technical routes: capacitive micromachined ultrasonic transducers (CMUT) and piezoelectric micromachined ultrasonic transducers (PMUT).
[0003] CMUT: works based on electrostatic effect. Its advantages are high receiving sensitivity, wide bandwidth, and easy integration with circuits. However, its main disadvantage is relatively low transmission efficiency, and a high DC bias signal (tens to hundreds of volts) is usually required to obtain sufficient output sound pressure, which increases the complexity and power consumption of the driving circuit.
[0004] PMUT: works based on piezoelectric effect. Its advantage is high transmission efficiency, and it can produce high output sound pressure at a lower driving voltage. However, its main disadvantage is low receiving sensitivity, and compared with CMUT, the bandwidth of PMUT is usually narrower.
[0005] Due to the problems that need to be overcome by existing CMUT and PMUT, CMUT and PMUT need to make compromises in transmission performance or receiving performance. For example, in ultrasonic imaging applications, it is desired that the transducer has strong sound output when transmitting to penetrate tissue, and it is also desired that it can detect extremely weak high-frequency echoes when receiving. However, a single CMUT or PMUT cannot simultaneously optimally meet these two requirements. SUMMARY
[0006] The present application provides a micro-ultrasound transducer and an ultrasonic conversion method to simultaneously optimize the transmission performance and receiving performance of the device to solve the above technical problems.
[0007] According to a first aspect of the present application, a micro-ultrasound transducer is provided, the method comprising: a substrate; a lower plate layer located in the substrate, the top surface of the lower plate layer being flush with the surface of the substrate; a bottom electrode located on the surface of the substrate and in contact with the lower plate layer; a piezoelectric functional layer on the lower electrode plate layer, a cavity between the piezoelectric functional layer and the lower electrode plate layer, the piezoelectric functional layer and the lower electrode plate layer forming a variable capacitor, the piezoelectric functional layer as an upper electrode plate of the variable capacitor, and the lower electrode plate layer as a lower electrode plate of the variable capacitor; a top electrode on a surface of the piezoelectric functional layer.
[0008] Optionally, the piezoelectric functional layer is made of at least one of aluminum nitride, lead zirconate titanate, and lithium bismuth tantalate.
[0009] Optionally, the bottom electrode is made of at least one of heavily doped silicon and metal material.
[0010] Optionally, the top electrode is made of metal film.
[0011] Optionally, the micro ultrasonic transducer further comprises: a support layer between the lower electrode plate layer and the piezoelectric functional layer, the support layer for supporting the piezoelectric functional layer and forming the cavity between the lower electrode plate layer and the piezoelectric functional layer.
[0012] Optionally, the support layer is made of at least one of silicon nitride and silicon oxide.
[0013] Optionally, the micro ultrasonic transducer further comprises: an insulating layer, part of the insulating layer on part of a surface of the bottom electrode, and the rest of the insulating layer on a surface of the lower electrode plate layer.
[0014] According to a second aspect of the present application, there is provided an ultrasonic conversion method based on the micro ultrasonic transducer according to the first aspect of the present application, the micro ultrasonic transducer having a transmission medium structure formed thereon, the method comprising: applying an alternating voltage signal to be converted to a top electrode and a bottom electrode of the micro ultrasonic transducer, the micro ultrasonic transducer converting the alternating voltage detection signal into a mechanical vibration signal; based on the transmission medium structure, converting the mechanical vibration signal into an ultrasonic wave signal and outputting the ultrasonic wave signal.
[0015] Optionally, the method further comprises: applying a direct current bias signal to the top electrode and the bottom electrode while applying the alternating voltage signal to be converted to the top electrode and the bottom electrode, the piezoelectric functional layer of the micro ultrasonic transducer being deformed under the action of the direct current bias signal to generate an initial deformation alternating voltage signal.
[0016] According to a third aspect of the present application, there is provided an ultrasonic conversion method based on the micro ultrasonic transducer according to the first aspect of the present application, the micro ultrasonic transducer having a transmission medium structure formed thereon, the method comprising: a direct current bias signal is applied to the top electrode and the bottom electrode; Based on the transmission medium structure, the ultrasonic signal to be converted is collected, and the ultrasonic signal is converted into a mechanical vibration signal; Based on the mechanical vibration signal, the instantaneous current generated at the moment of the capacitance change of the variable capacitor is detected to receive the ultrasonic signal.
[0017] Compared with the prior art, the technical scheme of the present application has the following beneficial effects: In the micro-ultrasonic transducer provided by the present application, the lower electrode plate layer is located in the substrate, and the top surface of the lower electrode plate and the surface of the substrate are in the same plane. Since the piezoelectric functional layer is located on the lower electrode plate layer, the piezoelectric functional layer and the lower electrode plate layer form a variable capacitor, and the piezoelectric functional layer serves as the upper electrode plate of the variable capacitor, and the lower electrode plate layer serves as the lower electrode plate of the variable capacitor. At the same time, since a cavity is formed between the piezoelectric functional layer and the substrate, the piezoelectric functional layer can vibrate based on the voltage applied between the top electrode and the bottom electrode by the external environment and the ultrasonic wave input by the external environment.
[0018] When the incident ultrasonic wave is received, the piezoelectric functional layer vibrates, so that the capacitance of the capacitor formed by the piezoelectric functional layer and the lower electrode plate layer changes. At this time, a fixed direct current bias signal is applied between the top electrode and the bottom electrode, and the charge stored on the top electrode and the bottom electrode changes due to the applied direct current bias signal and the capacitance change, thereby generating an instantaneous current to realize ultrasonic wave reception in a pure capacitance mode.
[0019] When transmitting ultrasonic waves, an alternating current voltage signal is applied between the top electrode and the bottom electrode. Based on the inverse piezoelectric effect, the diaphragm vibrates due to the alternating electric field generated by the alternating current voltage signal, and the vibration of the diaphragm squeezes and pushes the surrounding medium, thereby radiating ultrasonic waves outward, realizing ultrasonic wave output in a pure piezoelectric mode.
[0020] In addition, when receiving ultrasonic waves, in addition to the instantaneous current generated due to the change of the stored charge of the capacitor electrode plate, the piezoelectric functional layer also generates an additional piezoelectric current due to the positive piezoelectric effect, so that the instantaneous current and the piezoelectric current can be output in parallel and processed by the subsequent current, thereby improving the signal-to-noise ratio and sensitivity of the receiver.
[0021] In summary, the micro ultrasonic transducer provided by the application can perform ultrasonic wave receiving in a pure capacitive mode and ultrasonic wave output in a pure piezoelectric mode, so that the receiving performance of ultrasonic waves can be optimized, the transmitting performance of ultrasonic waves can be optimized, and high transmitting efficiency, high receiving sensitivity and high signal-to-noise ratio of ultrasonic waves are realized. In addition, the micro ultrasonic transducer provided by the application can also apply different voltages based on application scenarios to realize ultrasonic wave receiving and transmitting in different modes, so that the application flexibility of the device is improved.
[0022] Further, when transmitting ultrasonic waves, an alternating current is applied, and a direct current bias signal is additionally applied between the top electrode and the bottom electrode. The electrostatic force generated by the direct current bias signal can make the piezoelectric functional layer in the best working state of pre-stress, and cooperate with the inverse piezoelectric effect to greatly improve the transmitting sound pressure and transmitting efficiency. BRIEF DESCRIPTION OF DRAWINGS
[0023] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.
[0024] Figure 1 A cross-sectional structure schematic diagram of the micro ultrasonic transducer provided by the first embodiment of the application.
[0025] 10 - substrate; 20 - lower plate layer; 30 - bottom electrode; 40 - insulating layer; 50 - piezoelectric functional layer; 60 - support layer; 70 - top electrode. DETAILED DESCRIPTION
[0026] As described in the background, since the existing CMUT has problems of transmitting efficiency, and the existing PMUT has problems of receiving sensitivity, the CMUT and PMUT based on the problems to be overcome of the existing CMUT and PMUT need to make compromises in transmitting performance or receiving performance, so that it is difficult to simultaneously optimally meet the requirements of transmitting and receiving.
[0027] Therefore, the micro ultrasonic transducer provided by the present application can realize the advantages of CMUT in ultrasonic wave receiving and the advantages of PMUT in ultrasonic wave transmitting, and further realize the simultaneous optimization of the device in ultrasonic wave transmitting and receiving.
[0028] Therefore, the micro ultrasonic transducer provided by the present application can realize the advantages of CMUT in ultrasonic wave receiving and the advantages of PMUT in ultrasonic wave transmitting, and further realize the simultaneous optimization of the device in ultrasonic wave transmitting and receiving.
[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.
[0030] The terms "first", "second", "third", "fourth" and the like (if any) in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to the process, method, product or device.
[0031] The technical solutions of the present application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and some embodiments may not be described again for the same or similar concepts or processes.
[0032]
First embodiment
[0033] The micro ultrasonic transducer provided by the embodiment can include a substrate 10, a lower electrode plate layer 20, a bottom electrode 30, an insulating layer 40, a piezoelectric functional layer 50, a support layer 60, and a top electrode 70.
[0034] The substrate 10 is a silicon substrate. Of course, the substrate 10 can also be an SOI substrate, which is not limited herein.
[0035] In the embodiment, the lower electrode plate layer 20 is located in the substrate 10, and the top surface of the lower electrode plate layer 20 and the surface of the substrate 10 are in the same plane, that is, the top surface of the lower electrode plate layer 20 and the surface of the substrate 10 are flush.
[0036] Specifically, the lower electrode plate layer 20 is a doped layer in the substrate 10, which is formed by implanting ions in a set region of the substrate 10 to make the substrate 10 in the set region have a conductive ability.
[0037] In the embodiment, the piezoelectric functional layer 50 is located on the lower electrode plate layer 20, and a cavity is formed between the piezoelectric functional layer 50 and the lower electrode plate layer 20. The piezoelectric functional layer 50 and the lower electrode plate layer 20 constitute a variable capacitor, and the piezoelectric functional layer 50 serves as an upper electrode plate of the variable capacitor, and the lower electrode plate layer 20 serves as a lower electrode plate of the variable capacitor. Specifically, the lower electrode plate layer 20 serves as a fixed lower electrode plate of the variable capacitor.
[0038] In the embodiment, the piezoelectric functional layer 50 can include a material with high piezoelectric ability, such as aluminum nitride, lead zirconate titanate, or lithium tantalate, which is not limited herein.
[0039] In the above embodiment, the piezoelectric functional layer 50 is a key structure of the micro ultrasonic transducer, which not only deforms based on the inverse piezoelectric effect under the action of an electric field to emit ultrasonic waves outward, but also generates electric charges based on the positive piezoelectric effect when subjected to force, and simultaneously serves as an upper electrode plate of a variable capacitor to change the capacitance value of the capacitor through its own vibration, so that the micro ultrasonic transducer can not only realize ultrasonic wave reception in a pure capacitance mode, but also realize ultrasonic wave emission in a pure piezoelectric mode. Because ultrasonic wave reception in a pure capacitance mode has the advantages of high sensitivity and wide bandwidth, and ultrasonic wave emission in a pure piezoelectric mode has the advantages of high emission efficiency and high output sound pressure, the micro ultrasonic transducer provided by the embodiment realizes optimization of both the receiving performance and the emitting performance of ultrasonic waves based on the working principle of the piezoelectric functional layer 50 itself and the variable capacitor formed by the piezoelectric functional layer 50 and the lower electrode plate layer 20.
[0040] In the embodiment, the bottom electrode 30 is located on the surface of the substrate 10, and the bottom electrode 30 is in contact with the lower electrode plate layer 20.
[0041] In the embodiment, the bottom electrode 30 is located on the interface surface between the substrate 10 and the lower plate layer 20.
[0042] In the embodiment, the material of the bottom electrode 30 can be heavily doped silicon. Of course, the material of the bottom electrode 30 can also be metal, which is not limited herein. If the material of the bottom electrode 30 is metal, the material of the bottom electrode 30 can be molybdenum.
[0043] Since the bottom electrode 30 is in contact with the lower plate layer 20, the bottom electrode 30 serves as the lower lead of the variable capacitor and the lower electrode of the piezoelectric effect.
[0044] In the embodiment, the top electrode 70 is located on the surface of the piezoelectric functional layer 50.
[0045] Specifically, the material of the top electrode 70 can be metal, such as aluminum or titanium nitride, which is not limited herein.
[0046] Since the top electrode 70 is in contact with the piezoelectric functional layer 50, the bottom electrode 30 serves as the upper lead of the variable capacitor and the upper electrode of the piezoelectric effect.
[0047] In the embodiment, part of the insulating layer 40 is located on part of the surface of the bottom electrode 30, and the remaining insulating layer 40 is located on the surface of the lower plate layer 20.
[0048] Specifically, the insulating layer 40 is L-shaped, the horizontal structure of the insulating layer 40 is located on and in contact with part of the surface of the bottom electrode 30, and the vertical structure of the insulating layer 40 covers the sidewall of the bottom electrode 30 close to the top electrode 70 and is located on the surface of the lower plate layer 20 adjacent to the bottom electrode 30.
[0049] In the embodiment, the insulating layer 40 serves as an electrical isolation for the bottom electrode 30 to prevent short circuit failure of the bottom electrode 30, the piezoelectric functional layer 50 located above the bottom electrode 30, and the top electrode 70.
[0050] Further, the material of the insulating layer 40 is a material with insulating properties, such as silicon dioxide or silicon nitride, which is not limited herein.
[0051] In the embodiment, the support layer 60 is located between the lower plate layer 20 and the piezoelectric functional layer 50 to support the piezoelectric functional layer 50 and form the cavity between the lower plate layer 20 and the piezoelectric functional layer 50.
[0052] Specifically, the material of the support layer 60 at least includes silicon nitride or silicon oxide or other dielectric materials with high mechanical strength, which is not limited herein.
[0053] The following describes the ultrasonic conversion method and working principle of the micro ultrasonic transducer in detail.
[0054] The embodiment also provides an ultrasonic conversion method based on the micro ultrasonic transducer provided by the embodiment, wherein a transmission medium structure is formed on the micro ultrasonic transducer, and the transmission medium structure comprises water or biological tissue. The ultrasonic conversion method can comprise the following steps: When emitting ultrasonic waves, an alternating voltage signal to be converted is applied to the top electrode and the bottom electrode of the micro ultrasonic transducer, and the micro ultrasonic transducer converts the alternating voltage detection signal into a mechanical vibration signal. Then, based on the transmission medium structure, the mechanical vibration signal is converted into an ultrasonic wave signal and output. The specific principle is as follows: Based on the substrate 10 providing mechanical support, the bottom electrode 30 and the top electrode 70 above the substrate 10 form a voltage application circuit, and the support layer 60 forms a cavity between the lower electrode plate layer 20 and the piezoelectric functional layer 50, thereby reserving necessary space for the vibration of the piezoelectric functional layer 50.
[0055] When emitting ultrasonic waves, an alternating voltage signal is applied between the bottom electrode 30 and the top electrode 70, which excites an electric field with alternating directions inside the piezoelectric functional layer 50. The electric field forces the material lattice of the piezoelectric functional layer 50 to periodically deform through the inverse piezoelectric effect. When the direction of the electric field changes, the piezoelectric functional layer 50 alternately performs lateral stretching and compression, thereby performing bending vibration of sequentially protruding upwards and sinking downwards. The periodic vibration of the piezoelectric functional layer 50 squeezes and pushes the transmission medium structure, such as water or biological tissue, above the piezoelectric functional layer 50, so as to convert the mechanical vibration into ultrasonic waves and radiate outward, thereby realizing the conversion from the alternating voltage signal to the mechanical vibration of the piezoelectric functional layer 50 and then to the ultrasonic waves.
[0056] The micro ultrasonic transducer provided by the embodiment can realize efficient emission of ultrasonic waves by only using an alternating voltage signal, and the driving circuit is simplified, and therefore the micro ultrasonic transducer is particularly suitable for scenarios requiring high sound pressure, such as medical imaging.
[0057] When receiving ultrasonic waves, based on the transmission medium structure, the ultrasonic wave signal to be converted is collected, and the ultrasonic wave signal is converted into a mechanical vibration signal. Then, based on the mechanical vibration signal, the instantaneous current generated at the moment of the capacitance change of the variable capacitor is detected, so as to receive the ultrasonic wave signal. The specific principle is as follows: Based on the substrate 10 providing mechanical support, the bottom electrode 30 and the top electrode 70 above the substrate 10 form a voltage application circuit, and the support layer 60 forms a cavity between the lower electrode plate layer 20 and the piezoelectric functional layer 50, thereby reserving necessary space for the vibration of the piezoelectric functional layer 50. Meanwhile, the lower electrode plate layer 20 and the piezoelectric functional layer 50 form a variable capacitor, so as to realize the change of the capacitance value of the capacitor through the vibration of the piezoelectric functional layer 50.
[0058] When receiving the ultrasonic wave, the ultrasonic wave is received by the transmission medium structure and acts on the piezoelectric functional layer 50 to exert an alternating pressure on the piezoelectric functional layer 50, which drives the piezoelectric functional layer 50 to produce mechanical vibration, thereby causing the spacing between the lower plate layer 20 and the piezoelectric functional layer 50 to fluctuate up and down with the initial spacing as the base point.
[0059] Since the lower plate layer 20 and the piezoelectric functional layer 50 form a flat plate capacitor, according to the formula of the parallel plate capacitor C = ε0εᵣA / d, it can be known that the capacitance value and the spacing of the plate are inversely proportional, so a small change in the spacing between the lower plate layer 20 and the piezoelectric functional layer 50 will cause a significant change in the capacitance value. Wherein, C is the capacitance value of the capacitor, A is the plate area, d is the spacing between the lower plate layer 20 and the piezoelectric functional layer 50, εᵣ is the vacuum dielectric constant, and ε0 is the relative dielectric constant.
[0060] At this time, a fixed DC bias signal is applied between the bottom electrode 30 and the top electrode 70, and according to the formula of the stored charge on the capacitor plate Q = C・V_DC, it can be known that the change in the capacitance value will directly cause the corresponding change in the stored charge on the lower plate layer 20 and the piezoelectric functional layer 50. Wherein, Q is the amount of charge stored on the lower plate layer 20 and the piezoelectric functional layer 50, C is the capacitance value of the capacitor formed by the lower plate layer 20 and the piezoelectric functional layer 50, and V_DC is the DC bias signal applied between the top electrode 70 and the bottom electrode 30.
[0061] According to the formula of the instantaneous current i (t) = dQ / dt, it can be known that the change of the charge with time will form an instantaneous current, and this weak instantaneous current will flow through the readout resistance outside the device. Finally, the instantaneous current is converted into a voltage signal on the readout resistance, which can be detected and processed by the subsequent amplifier, and the voltage signal can accurately reflect the strength and waveform of the incident ultrasonic wave, thereby completing the reception process of the ultrasonic wave.
[0062] The micro ultrasonic transducer provided by the embodiment utilizes the characteristic that a small change in the spacing between the lower plate layer 20 and the piezoelectric functional layer 50 can cause an observable change in the capacitance, generates an instantaneous current for ultrasonic wave detection, and adapts to the detection of weak echo signals, thereby realizing high reception sensitivity of the ultrasonic wave.
[0063] In addition, when receiving the ultrasonic wave, in addition to the instantaneous current generated due to the change in the stored charge of the capacitor plate, the piezoelectric functional layer 50 will also generate an additional piezoelectric current due to the positive piezoelectric effect, so the instantaneous current and the piezoelectric current can be output in parallel and processed by the subsequent current, thereby improving the signal-to-noise ratio and sensitivity of the reception.
[0064] Therefore, the micro ultrasonic transducer can be applied with different voltages based on actual application scenarios to realize ultrasonic wave receiving and emitting in different modes, thereby improving application flexibility of the device.
[0065] In conclusion, the micro ultrasonic transducer can realize ultrasonic wave receiving in a pure capacitive mode and ultrasonic wave output in a pure piezoelectric mode, thereby realizing optimization of receiving performance and emitting performance of ultrasonic waves, and further realizing high emitting efficiency, high receiving sensitivity and high signal-to-noise ratio of ultrasonic waves.
[0066] In addition, the micro ultrasonic transducer can be applied with different voltages based on application scenarios to realize ultrasonic wave receiving and emitting in different modes, thereby improving application flexibility of the device.
[0067]
Second Embodiment
[0068] When receiving ultrasonic waves, a piezoelectric current generated by the piezoelectric functional layer 50 is collected while the instantaneous current is detected, and the piezoelectric current and the instantaneous current are fused.
[0069] The micro ultrasonic transducer of the second embodiment has the same structure as the above embodiment, and thus will not be described here.
[0070] The improvement points and improvement principles of the second embodiment are described in detail as follows.
[0071] When emitting ultrasonic waves, a direct current bias signal and an alternating voltage signal are simultaneously applied between the bottom electrode 30 and the top electrode 70.
[0072] The direct current bias signal forms a strong electrostatic field between the bottom plate layer 20 and the piezoelectric functional layer 50 and generates a continuous electrostatic attraction force to pull down the piezoelectric functional layer 50, so that the piezoelectric functional layer 50 generates static bending deformation, i.e., moves from an initial position to a pre-stressed state close to the bottom electrode.
[0073] The alternating voltage signal excites an alternating electric field in the piezoelectric functional layer 50 to cause the piezoelectric functional layer 50 to emit periodic expansion and contraction deformation through the inverse piezoelectric effect. Since the piezoelectric functional layer 50 is already in a static bending state, i.e., in a "tension" state, the expansion and contraction deformation of the piezoelectric functional layer 50 can be efficiently converted into a large-amplitude bending vibration of the piezoelectric functional layer 50 with the effect of "a small boat moving a large boat", and far exceeds the vibration of the piezoelectric functional layer 50 in the pure piezoelectric mode, thereby significantly enhancing the ultrasonic waves radiated to the outside.
[0074] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A micro-ultrasonic transducer, characterized in that, include: Substrate; A lower electrode layer is located within the substrate, and the top surface of the lower electrode layer is flush with the surface of the substrate. The bottom electrode is located on the surface of the substrate and is in contact with the lower electrode layer; A piezoelectric functional layer is located on the lower electrode layer, and a cavity is formed between the piezoelectric functional layer and the lower electrode layer. The piezoelectric functional layer and the lower electrode layer constitute a variable capacitor, and the piezoelectric functional layer serves as the upper electrode of the variable capacitor, while the lower electrode layer serves as the lower electrode of the variable capacitor. The top electrode is located on the surface of the piezoelectric functional layer.
2. The micro-ultrasonic transducer according to claim 1, characterized in that, The piezoelectric functional layer is made of at least aluminum nitride, lead zirconate titanate, or lithium bismuth tantalate.
3. The micro-ultrasonic transducer according to claim 1, characterized in that, The bottom electrode is made of at least heavily doped silicon or a metallic material.
4. The micro-ultrasonic transducer according to claim 1, characterized in that, The top electrode is made of a thin metal film.
5. The micro-ultrasonic transducer according to claim 1, characterized in that, Also includes: A support layer is located between the lower electrode layer and the piezoelectric functional layer. The support layer supports the piezoelectric functional layer and allows the lower electrode layer and the piezoelectric functional layer to form the cavity.
6. The micro-ultrasonic transducer according to claim 5, characterized in that, The material of the support layer includes at least silicon nitride or silicon oxide.
7. The micro-ultrasonic transducer according to claim 1, characterized in that, Also includes: An insulating layer, a portion of which is located on a portion of the surface of the bottom electrode, and the remainder of which is located on the surface of the lower electrode layer.
8. An ultrasonic conversion method based on the micro-ultrasonic transducer according to any one of claims 1 to 7, characterized in that, The micro-ultrasonic transducer has a transmission medium structure formed on it, and the method includes: An AC voltage signal to be converted is applied to the top and bottom electrodes of the micro-ultrasonic transducer, and the micro-ultrasonic transducer converts the AC voltage detection signal into a mechanical vibration signal. Based on the aforementioned transmission medium structure, the mechanical vibration signal is converted into an ultrasonic signal and output.
9. The ultrasonic conversion method according to claim 8, characterized in that, The method further includes: While applying the AC voltage signal to be converted to the top electrode and the bottom electrode, a DC bias signal is also applied to the top electrode and the bottom electrode. Under the action of the DC bias signal, the piezoelectric functional layer of the micro-ultrasonic transducer undergoes initial deformation AC voltage signal.
10. An ultrasonic conversion method based on the micro-ultrasonic transducer according to any one of claims 1 to 7, characterized in that, The micro-ultrasonic transducer has a transmission medium structure formed on it, and the method includes: A DC bias signal is applied to the top electrode and the bottom electrode; Based on the aforementioned transmission medium structure, the ultrasonic signal to be converted is acquired and then converted into a mechanical vibration signal. Based on the mechanical vibration signal, the instantaneous current generated by the instantaneous change in capacitance of the variable capacitor is detected in order to receive the ultrasonic signal.