Piezoelectric MEMS accelerometer and piezoelectric vector hydrophone

Abstract

The utility model provides a piezoelectric MEMS accelerometer and a piezoelectric vector hydrophone, and belongs to the technical field of sound wave sensing. The piezoelectric MEMS accelerometer comprises a base body, wherein the middle part of the base body is provided with a cylindrical through area; the mass block is cylindrical and is arranged in the through area, and an annular area is formed between the mass block and the base body; the multiple cantilever beams are evenly arranged in the annular area in the circumferential direction of the mass block, the two ends of each cantilever beam are connected with the mass block and the base body respectively, each cantilever beam comprises a substrate layer, a lower electrode layer, a piezoelectric layer and an upper electrode layer which are sequentially stacked, a through hole used for exposing the lower electrode layer is formed in the piezoelectric layer, and a through hole used for exposing the upper electrode layer is formed in the upper electrode layer. The upper electrode layer comprises an inner electrode and an outer electrode which are arranged at intervals in the radial direction of the mass block, and the inner electrode and the outer electrode are located in opposite cantilever beam deformation areas. The piezoelectric MEMS accelerometer provided by the utility model is adjustable in sensitivity and flexible to use.

Description

Technical Field

[0001] The present application relates to the field of acoustic wave sensing technology, and in particular to a piezoelectric MEMS accelerometer and a piezoelectric vector hydrophone. Background Art

[0002] A vector hydrophone is an underwater acoustic sensor that can simultaneously detect both sound pressure and particle velocity (vibration speed) in an acoustic field. While traditional scalar hydrophones can only detect sound pressure, vector hydrophones, by combining both pressure and velocity, can provide more information about the acoustic field, including the direction of sound wave propagation. This gives vector hydrophones significant advantages in applications such as target location, sound source identification, environmental noise monitoring, and underwater communications.

[0003] Currently, MEMS vector hydrophones are primarily categorized into three types: capacitive, piezoresistive, and piezoelectric. Capacitive vector hydrophones offer high sensitivity and low noise floor, but their capacitor structure is relatively complex, manufacturing is expensive, and they are sensitive to ambient temperature fluctuations, requiring precise temperature compensation. Piezoresistive vector hydrophones have a mature manufacturing process and are relatively simple to manufacture, but they exhibit low sensitivity and the resistance of the piezoresistive material is susceptible to temperature changes. In contrast, piezoelectric vector hydrophones require no external DC bias and offer advantages such as high sensitivity, low noise, and strong anti-interference capabilities.

[0004] The structure of existing piezoelectric MEMS vector hydrophone chips typically includes a silicon substrate, an insulating layer, a lower electrode layer, a piezoelectric layer, and an upper electrode layer stacked in sequence from bottom to top. The upper and lower electrode layers have pins extending from the outer edges for wiring. Chips with this structure have a relatively simple operating mode. During testing, there is only one test mode in which the upper and lower electrode layers are connected, and the corresponding sensitivity cannot be adjusted. Utility Model Content

[0005] An object of the first aspect of the present utility model is to provide a piezoelectric MEMS accelerometer with adjustable sensitivity.

[0006] Another object of the present invention is to improve the mechanical reliability and durability of the device.

[0007] A further object of the present invention is to provide an accelerometer that is more suitable for low-frequency detection.

[0008] An object of the second aspect of the present invention is to provide a piezoelectric vector hydrophone comprising the above-mentioned piezoelectric MEMS accelerometer.

[0009] An embodiment of the present utility model provides a piezoelectric MEMS accelerometer, comprising:

[0010] a base body, wherein a cylindrical through region is provided in the center thereof;

[0011] a mass block, which is cylindrical and disposed in the through-passing region, with an annular region formed between the mass block and the base;

[0012] A plurality of cantilever beams are uniformly arranged in the annular area along the circumference of the mass block, and both ends of each cantilever beam are respectively connected to the mass block and the substrate, wherein each cantilever beam includes a substrate layer, a lower electrode layer, a piezoelectric layer and an upper electrode layer stacked in sequence, the piezoelectric layer is formed with a through hole for exposing the lower electrode layer, and the upper electrode layer includes an inner electrode and an outer electrode arranged at intervals along the radial direction of the mass block, and the inner electrode and the outer electrode are in areas where the cantilever beam has opposite deformations.

[0013] Furthermore, the material of the piezoelectric layer is aluminum nitride doped with scandium.

[0014] Furthermore, the cantilever beam is fan-shaped.

[0015] Furthermore, the gap between the inner electrode and the outer electrode is located in the middle of the cantilever beam.

[0016] Furthermore, the cantilever beam further comprises:

[0017] an insulating layer, disposed above the piezoelectric layer and used to isolate the outer electrode, the inner electrode and the lower electrode layer;

[0018] Three electrode leads are separately connected to the outer electrode, the inner electrode and the lower electrode layer.

[0019] Furthermore, the base body has a rectangular shape.

[0020] Furthermore, the substrate layer is an SOI wafer with the bottom silicon layer removed.

[0021] Furthermore, the mass block is arranged symmetrically up and down relative to the cantilever beam.

[0022] In particular, an embodiment of the present invention further provides a piezoelectric vector hydrophone, comprising:

[0023] A packaging shell having a cavity inside;

[0024] A MEMS chip is fixedly mounted in the cavity, wherein the MEMS chip includes a substrate and the piezoelectric MEMS accelerometer described in any one of the above items;

[0025] A charge amplifier is disposed in the cavity, and the charge amplifier is connected to one of the inner electrode and the outer electrode of the piezoelectric MEMS accelerometer, and the lower electrode layer.

[0026] Furthermore, the MEMS chip is detachably connected to the bottom surface of the housing via fasteners.

[0027] According to the first aspect of the present invention, the upper electrode layer of the piezoelectric MEMS accelerometer includes an inner electrode and an outer electrode, and the upper surface of the lower electrode layer is exposed. When the piezoelectric MEMS accelerometer is used to prepare a piezoelectric vector hydrophone for detection, one of the inner and outer electrodes and the lower electrode layer can be selected for connection, such as connection to a charge amplifier, to detect underwater sound waves. The accelerometer of this structure provides two optional upper electrodes (i.e., the inner electrode and the outer electrode), and is therefore more flexible in use. By selecting the inner or outer electrode to connect, the sensitivity of the device can be flexibly adjusted. For different measurement ranges, by selecting the appropriate electrode, the signal-to-noise ratio can be effectively optimized, thereby improving measurement accuracy and reliability. In addition, by rationally configuring the connection method of the inner electrode, the outer electrode, and the lower electrode layer, differential signal output can be achieved, which can effectively suppress common-mode noise and improve detection accuracy and signal stability.

[0028] Furthermore, the circular shape of the device's mass provides a more uniform mass distribution, helping to improve the consistency of the device's response in all directions. The circular mass evenly distributes vibration energy, thus stabilizing the accelerometer's resonant frequency characteristics when detecting vibrations and reducing the impact of parasitic vibration modes on measurement accuracy. Furthermore, the circular structure is less susceptible to stress concentration when subjected to external forces, thereby improving the device's mechanical reliability and durability.

[0029] Furthermore, since the connections between the upper electrode layer and the lower electrode layer are both arranged at the top, the leads can be directly led out from the top of the device. The leads are arranged vertically and will not bend. They are not prone to deformation and breakage during use, which is beneficial to improving the stability of detection.

[0030] According to a second aspect of the present invention, the cantilever beam is arranged in a fan-shaped configuration. The mass distribution of the fan-shaped cantilever beam results in a lower resonant frequency, making it more suitable for detecting low-frequency or small-amplitude vibration signals. When fixed at both ends, the stress distribution of the fan-shaped cantilever beam tends to be greater near the fixed end and less at the wide end. This uneven stress distribution may cause inconsistent sensing signals at different locations, but in specific designs, it may help improve the cantilever's sensitivity to certain directions or frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of a piezoelectric MEMS accelerometer according to one embodiment of the present invention;

[0032] Figure 2 for Figure 1A top view of the piezoelectric MEMS accelerometer in FIG.

[0033] Figure 3 for Figure 2 Sectional view along section line AA;

[0034] Figure 4 is a cross-sectional view of a piezoelectric MEMS accelerometer according to another embodiment of the present invention;

[0035] Figure 5 Schematic diagram of the structure of a piezoelectric vector hydrophone according to one embodiment of the present invention;

[0036] Figure 6 : is an equivalent sound pressure sensitivity frequency response characteristic curve of a piezoelectric vector hydrophone according to one embodiment of the present utility model;

[0037] Reference numerals:

[0038] 100-piezoelectric MEMS accelerometer, 10-substrate, 20-mass block, 30-cantilever beam, 301-annular area, 31-substrate layer, 32-lower electrode layer, 33-piezoelectric layer, 34-upper electrode layer, 331-through hole, 341-inner electrode, 342-outer electrode, 331-top silicon layer, 312-buried oxide layer, 313-bottom silicon layer, 35-insulating layer, 36-electrode lead, 210-package shell, 220-MEMS chip, 200-substrate, 230-charge amplifier. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. It will be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some, rather than all, structures related to the present application are shown in the accompanying drawings. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0040] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0041] In addition, numerous specific details are provided in the following detailed description to better illustrate the present invention. Those skilled in the art will appreciate that the present invention can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art are not described in detail in order to highlight the main points of the present disclosure.

[0042] It should be understood that the term "and / or" as used herein simply describes an association between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " as used herein indicates that the related objects are in an "or" relationship.

[0043] In the embodiments of the present invention, the term "multiple" refers to two or more. The terms "first," "second," and so on, appearing in the embodiments of the present invention are for illustrative purposes only and are intended to distinguish the objects being described. They are not in any particular order and do not represent a specific limit on the number of objects in the embodiments of the present invention. They do not constitute any limitation on the embodiments of the present invention.

[0044] Figure 1 FIG. 1 is a structural diagram of a piezoelectric MEMS accelerometer 100 according to the first embodiment of the present invention. Figure 2 for Figure 1 FIG. 1 is a top view of the piezoelectric MEMS accelerometer 100 . Figure 3 for Figure 2 The sectional view along the AA section line. Figure 1 As shown, in one embodiment, a piezoelectric MEMS accelerometer 100 includes a substrate 10, a mass block 20, and multiple cantilever beams 30. A cylindrical through-region is provided in the middle of the substrate 10. The cylindrical mass block 20 is disposed within the through-region, and an annular region 301 is formed between the mass block 20 and the substrate 10. Multiple cantilever beams 30 are evenly arranged within the annular region 301 along the circumference of the mass block 20. The two ends of each cantilever beam 30 are connected to the mass block 20 and the substrate 10, respectively. Each cantilever beam 30 includes a substrate layer 31, a lower electrode layer 32, a piezoelectric layer 33, and an upper electrode layer 34, which are stacked in sequence. The piezoelectric layer 33 is formed with a through hole 331 for exposing the lower electrode layer 32. The upper electrode layer 34 includes an inner electrode 341 and an outer electrode 342 spaced apart along the radial direction of the mass 20. The inner electrode 341 and the outer electrode 342 are located in opposite deformation regions of the cantilever beam 30. For example, during detection, the inner electrode 341 is located in the region where the cantilever beam 30 bends upward, while the outer electrode 342 is located in the region where the cantilever beam 30 bends downward. Therefore, due to the piezoelectric effect, the charge polarity generated by the inner electrode 341 and the outer electrode 342 is opposite. In one embodiment, the gap between the inner electrode 341 and the outer electrode 342 is located in the middle of the cantilever beam 30. The middle here does not specifically refer to the midpoint, but includes the middle region of the midpoint.

[0045] The substrate layer 31 in this embodiment can be an SOI wafer with the bottom silicon layer 313 removed. The SOI wafer includes a bottom silicon layer 313, an intermediate buried oxide layer 312, and a top silicon layer 311 stacked in sequence. The material of the upper electrode layer 34 and the lower electrode layer 32 can include one or more of aluminum, molybdenum, gold, chromium, platinum, and titanium. The material of the piezoelectric layer 33 can be a zinc oxide piezoelectric film, an aluminum nitride piezoelectric film, a lead zirconate titanate piezoelectric film, a PMN-PT piezoelectric film, a perovskite piezoelectric film, an organic piezoelectric film, or a doped film formed by at least one of these piezoelectric films and a doping element. For example, the material of the piezoelectric layer 33 is aluminum nitride doped with scandium (Sc). 0.2 Al 0.8 N. The mass block 20 is made of the same material as the base 10 . The only difference between the mass block 20 and the cantilever beam 30 is that the mass block 20 does not include the upper electrode layer 34 .

[0046] The upper electrode layer 34 of the piezoelectric MEMS accelerometer 100 includes an inner electrode 341 and an outer electrode 342. The upper surface of the lower electrode layer 32 is exposed. When the piezoelectric MEMS accelerometer 100 is used to fabricate a piezoelectric vector hydrophone for detection, one of the inner and outer electrodes 341, 342, and the lower electrode layer 32 can be connected, for example, to the charge amplifier 230, thereby detecting underwater sound waves. This structure provides two optional upper electrodes (i.e., the inner electrode 341 and the outer electrode 342), thus providing greater flexibility in use. By selecting either the inner electrode 341 or the outer electrode 342, the sensitivity of the device can be flexibly adjusted. By selecting the appropriate electrode for different measurement ranges, the signal-to-noise ratio can be effectively optimized, improving measurement accuracy and reliability. Furthermore, by properly configuring the connection between the inner electrode 341, the outer electrode 342, and the lower electrode layer 32, a differential signal output can be achieved, effectively suppressing common-mode noise and improving detection accuracy and signal stability.

[0047] Furthermore, the circular shape of mass block 20 provides a more uniform mass distribution, which helps improve the consistency of the device's response in all directions. The circular mass block 20 also evenly distributes vibration energy, making the accelerometer's resonant frequency characteristics more stable when detecting vibrations and reducing the impact of parasitic vibration modes on measurement accuracy. Furthermore, the circular structure is less likely to cause stress concentration when subjected to external forces, thereby improving the device's mechanical reliability and durability.

[0048] Furthermore, since the connections between the upper electrode layer 34 and the lower electrode layer 32 are both arranged at the top, the leads can be directly led out from the top of the device. The leads are arranged vertically and will not bend. They are not prone to deformation and breakage during use, which is beneficial to improving the stability of detection.

[0049] Furthermore, when the piezoelectric layer 33 uses aluminum nitride doped with scandium, the introduction of this doping element can significantly improve the piezoelectric response capability of the material, and can generate a stronger electrical signal under the same external force or acceleration, thereby improving the sensitivity of the sensor. And due to the increase in the piezoelectric coefficient, the scandium-doped aluminum nitride material can produce a larger electric displacement under a smaller external force. In this way, in piezoelectric drive or sensing applications, a lower drive voltage can be used to achieve the same effect, thereby reducing power consumption. In addition, scandium-doped aluminum nitride maintains physical and chemical properties similar to traditional aluminum nitride, so it is compatible with existing MEMS manufacturing processes and does not require large-scale process adjustments, which reduces production difficulty while maintaining the economy of the manufacturing process.

[0050] In one embodiment, the base 10 is rectangular in shape, and the cantilever beam 30 is fan-shaped. The rectangular base 10 is relatively simple to process. Compared with a regular rectangular cantilever beam 30, the mass distribution of the fan-shaped cantilever beam 30 results in a lower resonance frequency, making it more suitable for detecting low-frequency or small-amplitude vibration signals. Under the condition of double-end fixation, the stress distribution of the fan-shaped cantilever beam 30 tends to be larger near the fixed end and smaller at the wide end. This uneven stress distribution may cause the sensing signal to show inconsistency at different positions, but in specific designs it may help to improve the sensitivity of the cantilever to certain specific directions or frequencies.

[0051] Figure 4 FIG is a cross-sectional view of a piezoelectric MEMS accelerometer 100 according to another embodiment of the present invention. Figure 4 The direction of the cutting line is Figure 2 Same. Figure 4 As shown, in another embodiment, the cantilever beam 30 further includes an insulating layer 35 and three electrode leads 36. The insulating layer 35 is disposed above the piezoelectric layer 33 to isolate the outer electrode 342, the inner electrode 341, and the lower electrode layer 34. The insulating layer 35 can be made of at least one of silicon dioxide, silicon nitride, polysilicon, and phosphosilicate glass. The three electrode leads 36 are individually connected to the outer electrode 342, the inner electrode 341, and the lower electrode layer. The electrode leads 36 can be made of commonly used conductive materials, such as aluminum, molybdenum, gold, chromium, platinum, or titanium.

[0052] Example 1

[0053] The piezoelectric MEMS accelerometer 100 of this embodiment is prepared according to the following steps:

[0054] An 8-inch SOI wafer is used as the silicon substrate. The top silicon layer has a thickness of 4 μm after polishing, the buried oxide layer 312SiO2 has a thickness of 1 μm, and the bottom Si substrate has a thickness of 400 μm.

[0055] The magnetron sputtering method is used to deposit 0.2 μm Mo (i.e., the lower electrode layer 32), 0.8 μm Sc and 1.5 μm Cr on the surface of the SOI wafer. 0.2 Al 0.8 N piezoelectric layer 33 and 0.2 μm Mo (i.e., upper electrode layer 34);

[0056] The upper electrode layer 34 is patterned using reactive ion etching (RIE);

[0057] Plasma enhanced chemical vapor deposition (PECVD) technology is used to deposit SiO2 to form an insulating layer 35;

[0058] The SiO2 layer was etched using reactive ion etching (RIE) and then etched using Sc 0.2 Al 0.8 The piezoelectric layer 33 is etched by N-anisotropic etching to produce a through hole 331 from the top surface to the lower electrode layer 32;

[0059] Depositing 1 μm thick Al, etching and patterning it to form three electrode leads 36;

[0060] Etch excess SiO2, Sc 0.2 Al 0.8 N, Mo and the top silicon layer 311 of the SOI wafer form the upper hollow areas between each cantilever beam 30;

[0061] Deep reactive ion etching (DRIE) is performed to etch the bottom silicon layer 313 from the back of the SOI wafer to form the bottom area of the cantilever beam 30. Then, the buried oxide layer 312 is etched by wet etching (Buffered Oxide Etchant, BOE) to form a hollow area running through the cantilever beams 30, thereby finally releasing the cantilever beams 30.

[0062] The base in this embodiment has a square shape and includes four fan-shaped cantilever beams 30 , with a central angle of 45° for each cantilever beam 30 .

[0063] The parameters of the device of this embodiment are shown in Table 1 below:

[0064] Table 1

[0065] parameter describe Value (μm) <![CDATA[L1]]> Matrix 10 side length 2200 <![CDATA[L2]]> Mass 20 diameter 425 <![CDATA[L3]]> Cantilever beam 30 length 630 <![CDATA[L4]]> Width of outer electrode 342 220 <![CDATA[L5]]> Inner electrode 341 width 185 <![CDATA[t so ]]> Buried oxide layer 312 thickness 1 <![CDATA[t s ]]> Thickness of top silicon layer 311 4 <![CDATA[t p ]]> Thickness of piezoelectric layer 33 0.8 <![CDATA[t e ]]> Thickness of upper electrode layer 34 / lower electrode layer 32 0.2 <![CDATA[t m ]]> Bottom silicon layer 313 400

[0066] In a further embodiment, the mass block 20 is arranged symmetrically with respect to the cantilever beam 30. The symmetrical arrangement of the mass block 20 can ensure that the torque generated when subjected to external force is relatively small, which helps to maintain the stability and sensitivity of the device.

[0067] The present application also provides a piezoelectric vector hydrophone, comprising a packaging shell 210, a MEMS chip 220 and a charge amplifier 230. A cavity is provided inside the packaging shell 210, and the MEMS chip 220 is fixed in the cavity. The MEMS chip 220 comprises a substrate 200 and the piezoelectric MEMS accelerometer 100 in any of the above-mentioned embodiments. The charge amplifier 230 is disposed in the cavity, and the charge amplifier 230 is connected to one of the inner electrode 341 and the outer electrode 342 of the piezoelectric MEMS accelerometer 100 and the lower electrode layer. The packaging shell 210 here may include a cylindrical portion with an opening and an upper cover, and the upper cover is provided with a hollow columnar portion for passing the lead wire through, and the output lead wire of the charge amplifier 230 is led out through the hollow columnar portion. The MEMS chip 220 is detachably connected to the bottom surface of the shell by fasteners (such as screws).

[0068] When sound waves propagate in water, they cause particles in the water to vibrate. The isotropic vector hydrophone in a free state will vibrate along with the particles. These vibrations are related to the sound pressure. Therefore, by measuring the vibration velocity and amplitude direction of the vector hydrophone with a built-in accelerometer, the sound wave information in the sound field can be calculated. In a plane wave sound field, the relationship between the water particle vibration velocity and sound pressure is:

[0069]

[0070] Where p0 is the sound pressure, ρ0 is the density of water, c is the speed of sound in water, and v0 is the vibration velocity of the medium at a certain point in the sound field. For a freely moving rigid cylinder, if its size is much smaller than the wavelength, the relationship between its vibration velocity and the vibration velocity of the water particle is:

[0071]

[0072] Where V s is the velocity amplitude of the vector hydrophone, V0 is the velocity amplitude of the sound particle at that position when there is no vector hydrophone, ρ s is the average density of the vector hydrophone, k is the acoustic wave number, and a is the radius of the water volume hydrophone. s =ρ0, then the vibration speed V s =V0, and the phase It approaches 0, that is, the vector hydrophone can accurately obtain the amplitude and phase of the sound wave velocity in the medium.

[0073] The sensitive element of the piezoelectric vector hydrophone is a piezoelectric MEMS accelerometer 100. The sensitivity M of the piezoelectric vector hydrophone and the voltage sensitivity M of the piezoelectric MEMS accelerometer 100 are a The relationship between them is:

[0074]

[0075] Where ρ0c is the acoustic impedance in water and ω is the vibration angular frequency.

[0076] In one embodiment, the packaging shell of the piezoelectric vector hydrophone is an aluminum shell cylindrical structure with a diameter of 26 mm, a height of 34 mm, a total mass of 18.26 g, and an average density of 1.04 kg / cm 3 This embodiment adopts the piezoelectric MEMS accelerometer 100 in the first embodiment, whose voltage sensitivity M a is 500mV / g. According to formula (3), the equivalent sound pressure sensitivity of the vector hydrophone is:

[0077] RVS=201g(M)-120 (4)

[0078] The unit of equivalent sound pressure sensitivity RVS is dB, and the reference value is 0dB = 1V / μPa. From formula (4), we can know that the equivalent sound pressure sensitivity frequency response characteristic curve of the piezoelectric vector hydrophone is as follows: Figure 6 As shown in the figure, in the range of 5-2kHz, the equivalent sound pressure sensitivity of the piezoelectric vector hydrophone increases with frequency.

[0079] The sound pressure sensitivity increases linearly with the increase of the frequency, increasing by 6dB per octave. The sound pressure sensitivity reaches -176dB, and the difference in sensitivity between the Z and X axes exceeds 20dB, showing good vector performance.

[0080] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present utility model patent shall be determined by the appended claims.

Claims

1. A piezoelectric MEMS accelerometer, characterized in that: include: a base body, wherein a cylindrical through region is provided in the center thereof; a mass block, which is cylindrical and disposed in the through-region, with an annular region formed between the mass block and the base; A plurality of cantilever beams are uniformly arranged in the annular area along the circumference of the mass block, and both ends of each cantilever beam are respectively connected to the mass block and the substrate, wherein each cantilever beam includes a substrate layer, a lower electrode layer, a piezoelectric layer and an upper electrode layer stacked in sequence, the piezoelectric layer is formed with a through hole for exposing the lower electrode layer, and the upper electrode layer includes an inner electrode and an outer electrode arranged at intervals along the radial direction of the mass block, and the inner electrode and the outer electrode are in areas where the cantilever beam has opposite deformations.

2. The piezoelectric MEMS accelerometer according to claim 1, wherein: The material of the piezoelectric layer is aluminum nitride doped with scandium.

3. The piezoelectric MEMS accelerometer according to claim 1, wherein: The cantilever beam is fan-shaped.

4. The piezoelectric MEMS accelerometer according to claim 1, wherein: The gap between the inner electrode and the outer electrode is located in the middle of the cantilever beam.

5. The piezoelectric MEMS accelerometer according to any one of claims 1 to 4, characterized in that: The cantilever beam further comprises: an insulating layer, disposed above the piezoelectric layer and used to isolate the outer electrode, the inner electrode and the lower electrode layer; Three electrode leads are separately connected to the outer electrode, the inner electrode and the lower electrode layer.

6. The piezoelectric MEMS accelerometer according to claim 1, wherein: The outer shape of the base is rectangular.

7. The piezoelectric MEMS accelerometer according to claim 1, wherein: The substrate layer is an SOI wafer with the bottom silicon layer removed.

8. The piezoelectric MEMS accelerometer according to claim 1, wherein: The mass block is arranged symmetrically with respect to the cantilever beam.

9. A piezoelectric vector hydrophone, characterized in that: include: A packaging shell having a cavity inside; A MEMS chip is fixedly disposed in the cavity, wherein the MEMS chip comprises a substrate and the piezoelectric MEMS accelerometer according to any one of claims 1 to 8; A charge amplifier is disposed in the cavity, and the charge amplifier is connected to one of the inner electrode and the outer electrode of the piezoelectric MEMS accelerometer, and the lower electrode layer.

10. The piezoelectric vector hydrophone according to claim 9, characterized in that: The MEMS chip is detachably connected to the bottom surface of the housing through fasteners.

Images