A piezoelectric MEMS loudspeaker

Abstract

A piezoelectric MEMS loudspeaker. The application discloses a MEMS structure, comprising: a substrate comprising an inner ring body and an outer ring body connected by a connecting rod, having a first cavity between the inner ring body and the outer ring body, and having a second cavity in the inner ring body; a piezoelectric composite vibration layer formed above the substrate, comprising an edge portion formed above the outer ring body and a center portion formed above the inner ring body, having a partition gap between the edge portion and the center portion. In summary, the piezoelectric MEMS loudspeaker provided by the application comprises an edge portion and a center portion, wherein the edge portion is used to generate a high-frequency sound pressure level, and the center portion is used to generate a low-frequency sound pressure level. The combination of the edge portion and the center portion makes the piezoelectric MEMS loudspeaker have a relatively flat sound pressure level frequency response curve with a wider range, thereby improving the auditory effect in the entire frequency band.

Description

Technical Field

[0001] This application relates to the field of micromechanical technology, and more specifically, to a piezoelectric MEMS (Micro-Electro-Mechanical System) loudspeaker. Background Technology

[0002] A piezoelectric MEMS loudspeaker is a small electroacoustic device that uses piezoelectric materials as sound conversion elements. It works by utilizing the inverse piezoelectric effect: by inputting a voltage signal to a diaphragm containing piezoelectric material, the diaphragm vibrates, causing the diaphragm and surrounding air to vibrate and radiate sound. Compared to traditional moving-coil loudspeakers, piezoelectric MEMS loudspeakers offer advantages such as small size, low power consumption, simple manufacturing process, and low cost, making them widely applicable to various portable electronic devices.

[0003] Currently, most piezoelectric MEMS loudspeakers have poor low-frequency response and uneven sound pressure level frequency response curves, which affects the user's listening experience. Summary of the Invention

[0004] To address the problems in related technologies, this application proposes a piezoelectric MEMS loudspeaker that can achieve a flat sound pressure level frequency response curve.

[0005] The technical solution of this application is implemented as follows:

[0006] According to one aspect of this application, a MEMS structure is provided, comprising:

[0007] A substrate includes an inner ring body and an outer ring body connected by a connecting rod, wherein a first cavity is provided between the inner ring body and the outer ring body, and a second cavity is provided within the inner ring body.

[0008] A piezoelectric composite vibration layer is formed above the substrate, including an edge portion formed above the outer ring and a central portion formed above the inner ring, with a dividing gap between the edge portion and the central portion.

[0009] The connecting rod is located at the bottom or middle of the substrate.

[0010] The dividing gap is connected to the first cavity.

[0011] The fixed end of the edge portion is connected above the outer ring body, and the free end of the edge portion is suspended above the first cavity.

[0012] The outer edge of the central portion is fixed to the upper part of the inner ring.

[0013] The piezoelectric composite vibration layer includes:

[0014] A vibration support layer is formed above the substrate;

[0015] A first electrode layer is formed above the vibration support layer;

[0016] A first piezoelectric layer is formed above the first electrode layer;

[0017] A second electrode layer is formed above the first piezoelectric layer.

[0018] The area of ​​the vibration support layer in the central part is larger than the area of ​​the first electrode layer, and the areas of the first electrode layer, the first piezoelectric layer and the second electrode layer are equal.

[0019] The piezoelectric composite vibration layer further includes:

[0020] A second piezoelectric layer is formed above the second electrode layer;

[0021] The third electrode layer is formed above the second piezoelectric layer.

[0022] The dividing gap is less than or equal to 5 μm.

[0023] In summary, the piezoelectric composite resonant layer of the piezoelectric MEMS loudspeaker provided in this application includes an edge portion and a central portion, wherein the edge portion is used to generate high-frequency sound pressure levels, and the central portion is used to generate low-frequency sound pressure levels. The combination of the edge portion and the central portion enables the piezoelectric MEMS loudspeaker to have a wider and flatter sound pressure level frequency response curve, thereby improving the auditory effect across the entire frequency range. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A perspective view of a piezoelectric MEMS loudspeaker structure provided according to some embodiments is shown;

[0026] Figure 2 A cross-sectional perspective view of a piezoelectric MEMS loudspeaker structure provided according to some embodiments is shown;

[0027] Figure 3 A top view of a piezoelectric MEMS loudspeaker structure provided according to some embodiments is shown;

[0028] Figure 4A top view of a second substrate provided according to some embodiments is shown;

[0029] Figure 5 The sound pressure level frequency response curves for the edge and center portions of a piezoelectric MEMS loudspeaker structure with specific materials and size parameters are shown.

[0030] Figure 6 The sound pressure level frequency response curves of the piezoelectric MEMS loudspeaker structure are shown under specific material and size parameters. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0032] See Figure 1 , Figure 2 and Figure 3 According to embodiments of this application, a piezoelectric MEMS loudspeaker is provided, which can improve low-frequency sound pressure levels and has a wider and flatter sound pressure level frequency response curve. This piezoelectric MEMS loudspeaker can, but is not limited to, other sensors or actuators, such as microphones or ultrasonic sensors. The piezoelectric MEMS loudspeaker includes a substrate 10, a piezoelectric composite resonant layer, and a connecting rod 30. Details will be described in detail below.

[0033] The substrate 10 includes an inner ring body 12 and an outer ring body 11 connected by a connecting rod 30. A first cavity 13 is provided between the inner ring body 12 and the outer ring body 11, and a second cavity 14 is provided within the inner ring body 12. The connecting rod 30 is located at the bottom or middle of the substrate 10 and is used to support and connect the inner ring body 12 and the outer ring body 11. Figure 2 Only one embodiment is shown with the link 30 located at the bottom of the substrate 10. The substrate 10 comprises silicon or any suitable silicon-based compound or derivative (e.g., silicon wafer, SOI, polycrystalline silicon on SiO2 / Si).

[0034] A piezoelectric composite resonant layer is formed above the substrate 10. The piezoelectric composite resonant layer includes an edge portion 20 formed above the outer ring body 11 and a central portion 21 formed above the inner ring body 12, with a dividing gap 22 between the edge portion 20 and the central portion 21. The dividing gap 22 communicates with the first cavity 13. Preferably, to prevent sound leakage caused by an excessively large dividing gap 22, the dividing gap 22 is less than or equal to 5 μm.

[0035] The edge portion 20 is used to generate high-frequency sound pressure levels. The fixed end of the edge portion 20 is connected above the outer ring body 11, and the free end of the edge portion 20 is suspended above the first cavity 13. The center portion 21 is used to increase the low-frequency sound pressure level and widen the flat range of the sound pressure level frequency response curve. The outer edge of the center portion 21 is connected and fixed above the inner ring body 12. The area of ​​the vibration support layer 23 of the center portion 21 is larger than the area of ​​the first electrode layer 24, and the areas of the first electrode layer 24, the first piezoelectric layer 25, and the second electrode layer 26 are equal, thereby generating a larger diaphragm amplitude and sound pressure level.

[0036] In addition, Figure 1 , Figure 2 and Figure 3 The illustration shows an embodiment where the substrate 10 and the piezoelectric composite resonant layer are circular. In other embodiments, the substrate 10 and the piezoelectric composite resonant layer may be triangular, square, hexagonal, or other suitable shapes.

[0037] The structure of the piezoelectric composite vibration layer will be explained in detail below.

[0038] In an embodiment where the piezoelectric composite vibration layer is a single wafer, the piezoelectric composite vibration layer includes a vibration support layer 23 formed above the substrate 10, a first electrode layer 24 formed above the vibration support layer 23, a first piezoelectric layer 25 formed above the first electrode layer 24, and a second electrode layer 26 formed above the first piezoelectric layer 25. The first piezoelectric layer 25 can convert electrical energy into acoustic energy, and the first electrode layer 24 and the second electrode layer 26 can provide voltage to the first piezoelectric layer 25.

[0039] In an embodiment where the piezoelectric composite vibration layer is a bicrystalline wafer, the piezoelectric composite vibration layer may further include a second piezoelectric layer (not shown in the figure) formed above the second electrode layer 26 and a third electrode layer (not shown in the figure) formed above the second piezoelectric layer.

[0040] In some embodiments, the vibration support layer 23 includes a single-layer or multi-layer composite film structure made of silicon nitride (Si3N4), silicon oxide, monocrystalline silicon, polycrystalline silicon, or other suitable support material.

[0041] In some embodiments, the materials of the first piezoelectric layer 25 and the second piezoelectric layer include zinc oxide, aluminum nitride, organic piezoelectric film, lead zirconate titanate (PZT), perovskite piezoelectric film, or other suitable materials. The first electrode layer 24, the second electrode layer 26, and the third electrode layer include aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films thereof, or other suitable materials.

[0042] It is worth noting that a MEMS structure without the connecting rod 30 and without the segmentation gap 22 at the vibration support layer 23 can be formed using existing processes. In other words, this MEMS structure is similar to... Figure 2 The only difference in the piezoelectric MEMS loudspeaker shown is that the MEMS structure lacks the connecting rod 30, and the vibration support layer 23 of the MEMS structure lacks the segmented gap 22. Then, as... Figure 4 As shown, a second substrate with a connecting rod 30 can be formed through photolithography and etching processes. This second substrate includes an inner ring 32 and an outer ring 31 connected by the connecting rod 30. The second substrate is then bonded to the substrate 10 of the aforementioned MEMS structure. Finally, a vibration support layer 23 with a segmented gap 22 is formed by etching to release the central portion 21 and the edge portion 20. This ultimately yields... Figure 1 and Figure 2 The piezoelectric MEMS loudspeaker shown.

[0043] Figure 5 and Figure 6 represent Figure 1 The sound pressure level frequency response curves (SPR) of the low-frequency and high-frequency components of the piezoelectric MEMS loudspeaker, as well as the overall SPR of the structure, are presented under specific material and dimensional parameters. Specifically, the outer ring 11 has a radius of 0.5 cm, the inner ring 12 has a radius of 0.4 cm, the difference between the outer and inner diameters of the edge portion 20 is 0.1 cm, the width of the dividing gap 22 is 5 μm, the thickness of the vibration support layer 23 is 7 μm, the thickness of the first piezoelectric layer 25 is 2 μm, and the thicknesses of the first electrode layer 24 and the second electrode layer 26 are 0.1 μm. The radius of the first electrode layer 24, the first piezoelectric layer 25, and the second electrode layer 26 in the central portion 21 is 0.27 cm. The radius of the vibration support layer 23 in the central portion 21 is 0.4 cm. The vibration support layer 23 is made of silicon (Si), the first piezoelectric layer 25 is made of piezoelectric ceramic (PZT), and the first electrode layer 24 and the second electrode layer 26 are made of aluminum (Al). A voltage of 2V is applied, and the sound pressure level is measured at a distance of 5cm from the top surface of the center part of the piezoelectric MEMS speaker.

[0044] from Figure 5 The sound pressure level frequency response curves show that the edge portion 20 has a higher sound pressure level in the high-frequency range, but experiences significant attenuation in the low-frequency range. Conversely, the central portion 21 has a higher sound pressure level in the low-frequency range. Therefore, the two portions can work together, with the central portion 21 operating at frequencies from 0Hz to 3900Hz, and the edge portion 20 operating at frequencies from 3900Hz to 20000Hz. Figure 6 The corresponding frequency response curve of the overall sound pressure level shows that the overall sound pressure level in the low-frequency range has increased by more than 20dB, and the output sound pressure level in the 1000Hz-20000Hz range has reached more than 80dB, which has improved the auditory effect of the entire frequency range.

[0045] The above only presents the sound pressure level frequency response curve for a structure with specific dimensions and material parameters. It is intended to illustrate the working principle and does not represent the optimal result. Those skilled in the art can adjust the structural dimensions and material parameters as needed to obtain higher sound pressure level outputs and frequency response curves with wider frequency ranges and flatter sound pressure levels.

[0046] In summary, the piezoelectric composite resonant layer of the piezoelectric MEMS loudspeaker provided in this application includes an edge portion 20 and a central portion 21, wherein the edge portion 20 is used to generate high-frequency sound pressure levels, and the central portion 21 is used to generate low-frequency sound pressure levels. The combination of the edge portion 20 and the central portion 21 enables the piezoelectric MEMS loudspeaker to have a wider and flatter sound pressure level frequency response curve, thereby improving the auditory effect across the entire frequency range.

[0047] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A piezoelectric MEMS loudspeaker, characterized in that, include: A substrate includes an inner ring body and an outer ring body connected by a connecting rod, wherein a first cavity is provided between the inner ring body and the outer ring body, and a second cavity is provided within the inner ring body. A piezoelectric composite vibration layer is formed above the substrate, including an edge portion formed above the outer ring and a central portion formed above the inner ring, with a dividing gap between the edge portion and the central portion; The fixed end of the edge portion is connected to the upper part of the outer ring body, and the free end of the edge portion is suspended above the first cavity; the outer edge of the central portion is connected and fixed to the upper part of the inner ring body. The piezoelectric composite vibration layer includes: a vibration support layer formed above the substrate; a first electrode layer formed above the vibration support layer; a first piezoelectric layer formed above the first electrode layer; and a second electrode layer formed above the first piezoelectric layer; wherein the area of ​​the vibration support layer in the central portion is larger than the area of ​​the first electrode layer, and the areas of the first electrode layer, the first piezoelectric layer, and the second electrode layer are equal.

2. The piezoelectric MEMS loudspeaker according to claim 1, characterized in that, The connecting rod is located at the bottom or middle of the substrate.

3. The piezoelectric MEMS loudspeaker according to claim 1, characterized in that, The dividing gap is connected to the first cavity.

4. The piezoelectric MEMS loudspeaker according to claim 1, characterized in that, The piezoelectric composite vibration layer also includes: A second piezoelectric layer is formed above the second electrode layer; The third electrode layer is formed above the second piezoelectric layer.

5. The piezoelectric MEMS loudspeaker according to claim 1, characterized in that, The dividing gap is less than or equal to 5 μm.

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