Micro electro mechanical system sound production unit and loudspeaker

Abstract

The utility model discloses a sound production unit and a loudspeaker of a micro electro mechanical system. The micro-electro-mechanical system sound production unit comprises a substrate layer; the base layer is provided with a cavity, and the cavity penetrates through the base layer in the first direction. A diaphragm layer; the vibrating diaphragm layer is arranged on one side, provided with the cavity, of the base layer and is divided into a fixed part and a vibrating part; the fixed part is arranged around the vibrating part, a first slit is arranged between the vibrating part and the fixed part, and the first slit penetrates through the vibrating diaphragm layer along a first direction; a stop block; the stop block is arranged on the side, away from the substrate layer, of the vibrating diaphragm layer, the stop block is arranged on the side, close to the first slit, of the fixing part, and the length of the stop block is larger than or equal to that of the first slit; wherein the first direction is a direction from the substrate layer to the diaphragm layer. According to the utility model, low-frequency sound pressure attenuation is improved.

Description

Technical Field

[0001] This utility model relates to the field of microelectromechanical systems (MEMS) technology, and in particular to a microelectromechanical system (MEMS) sound generating unit and loudspeaker. Background Technology

[0002] Microelectromechanical systems (MEMS) loudspeakers are attracting increasing attention due to their advantages such as small size, low power consumption, mass production capability, and potential on-chip integration with electronic circuits.

[0003] The main component of a microelectromechanical system (MEMS) loudspeaker is a diaphragm with a piezoelectric film. The diaphragm is driven by applying an excitation voltage between the top and bottom electrodes of the piezoelectric layer. The applied electric field creates transverse stress in the active piezoelectric layer, which in turn produces a displacement perpendicular to the diaphragm surface, thereby generating sound waves in the air. For a diaphragm of a given size, to achieve higher vibration displacement and a higher sound pressure level, slots are typically introduced into the diaphragm to reduce the film stiffness. However, with the introduction of slots, when the diaphragm undergoes a large displacement, the device experiences severe acoustic attenuation at low frequencies. Utility Model Content

[0004] This invention provides a microelectromechanical system (MEMS) sound-generating unit and loudspeaker to improve low-frequency sound pressure attenuation.

[0005] According to one aspect of the present invention, a microelectromechanical system (MEMS) sound generating unit is provided, the MEMS sound generating unit comprising:

[0006] basal layer;

[0007] Diaphragm layer; The diaphragm layer is disposed on the side of the base layer where the cavity is provided. The diaphragm layer is divided into a fixed part and a vibrating part; The fixed part is disposed around the vibrating part, and a first slit is provided between the vibrating part and the fixed part, wherein the first slit penetrates the diaphragm layer along a first direction;

[0008] The blocking block is located on the side of the diaphragm layer away from the base layer, and on the side of the fixing part near the first slit. The length of the blocking block is greater than or equal to the length of the first slit. The first direction is the direction from the base layer to the diaphragm layer.

[0009] Furthermore, the diaphragm layer includes a buried oxide layer, an elastic layer, a first electrode layer, a piezoelectric layer, and a second electrode layer stacked sequentially, with the buried oxide layer in contact with the substrate layer.

[0010] Furthermore, the surface of the fixing part near the first slit is flush with the surface of the blocking block near the first slit.

[0011] Furthermore, the microelectromechanical system (MEMS) sound-generating unit also includes:

[0012] Second slit;

[0013] The second slit is positioned between the two first slits, and the second slit penetrates the diaphragm layer in a direction perpendicular to the first slits.

[0014] Furthermore, the second slit is positioned on the line connecting the midpoints of the two first slits.

[0015] Furthermore, the piezoelectric layer includes at least one piezoelectric thin film.

[0016] Furthermore, the thickness of the substrate ranges from 300 μm to 600 μm.

[0017] According to another aspect of the present invention, a microelectromechanical system (MEMS) loudspeaker is provided, the MEMS loudspeaker including at least one MEMS sound-generating unit as described in any of the above embodiments.

[0018] The microelectromechanical system (MEMS) sound-generating unit designed in this embodiment of the invention can block most of the acoustic leakage path by setting a blocking block on the side of the diaphragm layer away from the substrate layer and setting the blocking block on the side of the fixing part close to the first slit, and setting the length of the blocking block to be greater than or equal to the length of the first slit. This makes the acoustic leakage path become the width of the first slit when the diaphragm layer is not deformed, thereby improving the low-frequency sound pressure attenuation.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a simulation diagram of a microelectromechanical system speaker without added blocking blocks in the prior art when it generates the maximum displacement.

[0022] Figure 2 This is a schematic diagram of the structure of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention;

[0023] Figure 3 yes Figure 2 A schematic diagram of the cross-sectional structure along the A-A' direction;

[0024] Figure 4According to an embodiment of the present invention, a frequency-sound pressure level relationship curve is provided for a microelectromechanical system (MEMS) sound-generating unit with added blocking blocks of different heights;

[0025] Figure 5 This is a schematic diagram of another microelectromechanical system sound-generating unit provided according to an embodiment of the present invention;

[0026] Figure 6 This is a flowchart of a method for manufacturing a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram illustrating the manufacturing process of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention.

[0028] Figure 8 This is a schematic diagram illustrating the manufacturing process of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention.

[0029] Figure 9 This is a schematic diagram illustrating the manufacturing process of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention.

[0030] Figure 10 This is a schematic diagram illustrating the manufacturing process of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention.

[0031] Figure 11 This is a schematic diagram illustrating the manufacturing process of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention.

[0032] Figure 12 This is a schematic diagram of the manufacturing process of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0034] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0035] This utility model embodiment provides a microelectromechanical system (MEMS) sound generating unit. Figure 1 This is a simulation diagram of a microelectromechanical system (MEMS) speaker without added blocking blocks generating maximum displacement in the prior art. Figure 2 This is a schematic diagram of the structure of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention. Figure 3 yes Figure 2 A schematic diagram of the cross-sectional structure along the A-A' direction. Figure 4 According to an embodiment of this utility model, a frequency-sound pressure level relationship curve is provided for a microelectromechanical system (MEMS) sound-generating unit with added blocking blocks of different heights. (Refer to...) Figures 1-4 The microelectromechanical system (MEMS) sound-generating unit includes:

[0036] The base layer 10 has a cavity 11, and the cavity 11 penetrates the base layer 10 along the first direction X.

[0037] Diaphragm layer 20; Diaphragm layer 20 is disposed on the side of the base layer 10 where the cavity 11 is provided. Diaphragm layer 20 is divided into a fixed part 21 and a vibrating part 22. The fixed part 21 is disposed around the vibrating part 22. A first slit 90 is provided between the vibrating part 22 and the fixed part 21. The first slit 90 penetrates the diaphragm layer 20 along the first direction X.

[0038] Blocking block 30; Blocking block 30 is disposed on the side of diaphragm layer 20 away from base layer 10, and blocking block 30 is disposed on the side of fixing part 21 near first slit 90, and the length of blocking block 30 is greater than or equal to the length of first slit 90; wherein, the first direction X is the direction from base layer 10 to diaphragm layer 20.

[0039] Specifically, when a voltage signal is applied to the diaphragm layer 20, the vibrating part 22 of the diaphragm layer 20 will move up and down according to the applied voltage signal, thereby pushing air molecules to generate sound pressure, thus achieving the effect of sound amplification. At this time, as... Figure 3As shown, the acoustic leakage path at the first slit position 90° causes attenuation of the sound pressure level in the microelectromechanical system (MEMS) speaker unit at low frequencies. The larger the acoustic leakage path, the more severe the low-frequency sound pressure level attenuation. High-fidelity MEMS speakers typically require attenuation of no more than 3dB at 40Hz. Figure 4 As shown, when the microelectromechanical system (MEMS) sound unit does not have the blocking block 30, a large displacement of the vibrating part 22 of the diaphragm layer 20 will cause the first slit 90 to enlarge, resulting in a larger acoustic leakage path and thus severe low-frequency sound pressure level attenuation. However, adding blocking blocks 30 of different heights will change the low-frequency sound pressure level to varying degrees. As the height of the blocking block 30 increases, the low-frequency sound pressure level gradually increases, and the effect of blocking the low-frequency acoustic leakage path becomes more significant. For example, if the vibrating part 22 of the diaphragm layer 20 does not displace, the width of the first slit 90 is 1 μm, while at the maximum displacement, the maximum width of the first slit 90 is 9.03 μm. When the height of the blocking block 30 is 9 μm, the sound pressure level at 40 Hz is 2.1 dB lower than the sound pressure level at 1 kHz, meeting the requirements of a high-fidelity MEMS sound unit. However, without the addition of the blocking block 30, the sound pressure level at 40Hz is 14.5dB lower than that at 1kHz, which does not meet the requirements of a high-fidelity microelectromechanical system (MEMS) sound unit.

[0040] The microelectromechanical system (MEMS) sound-generating unit designed in this embodiment of the invention provides a blocking block 30 on the side of the diaphragm layer 20 away from the base layer 10, and sets the blocking block 30 on the side of the fixing part 21 close to the first slit 90. The length of the blocking block 30 is greater than or equal to the length of the first slit 90, which can block most of the acoustic leakage path, making the acoustic leakage path the width of the first slit 90 when the diaphragm layer 20 is not deformed, thereby improving the low-frequency sound pressure attenuation.

[0041] Further reference Figure 2 and Figure 3 The diaphragm layer 20 includes a buried oxide layer 40, an elastic layer 50, a first electrode layer 60, a piezoelectric layer 70, and a second electrode layer 80 stacked in sequence, with the buried oxide layer 40 in contact with the substrate layer 10.

[0042] The diaphragm layer 40 includes an oxygen-embedded vibrating part and an oxygen-embedded fixing part, with a thickness ranging from 0.1 μm to 3 μm; the elastic layer 50 includes an elastic vibrating part and an elastic fixing part, with a thickness ranging from 2 μm to 20 μm; the first electrode layer 60 includes a first electrode vibrating part and a first electrode fixing part, with a thickness ranging from 80 nm to 300 nm; the piezoelectric layer 70 includes a piezoelectric vibrating part and a piezoelectric fixing part, with a thickness ranging from 0.5 μm to 3 μm; the second electrode layer 80 includes a second electrode vibrating part and a second electrode fixing part, with a thickness ranging from 80 nm to 300 nm; the oxygen-embedded vibrating part, the elastic vibrating part, the first electrode vibrating part, the piezoelectric vibrating part, and the second electrode vibrating part constitute the vibrating part 22 of the diaphragm layer 20, and the oxygen-embedded fixing part, the elastic fixing part, the first electrode fixing part, the piezoelectric fixing part, and the second electrode fixing part constitute the fixing part 21 of the diaphragm layer 20.

[0043] Specifically, after a voltage signal is applied to the first electrode layer 60 and the second electrode layer 80, the buried oxygen vibration part, the elastic vibration part, the first electrode vibration part, the piezoelectric vibration part and the second electrode vibration part will move up and down according to the applied voltage signal, thereby pushing air molecules to generate sound pressure, and thus achieving the effect of amplification.

[0044] Further reference Figure 2 and Figure 3 The surface of the fixing part 21 near the first slit 90 is flush with the surface of the blocking block 30 near the first slit 90.

[0045] Specifically, by aligning the surface of the fixing part 21 near the first slit 90 with the surface of the blocking block 30 near the first slit 90, the width of the acoustic leakage path is further reduced, thereby further improving the sound pressure level at low frequencies.

[0046] Furthermore, Figure 5 This is a schematic diagram of another microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention, with reference to... Figure 5 The microelectromechanical system (MEMS) sound-generating unit also includes a second slit 91; the second slit 91 is disposed between the two first slits 90, and the second slit 91 penetrates the diaphragm layer 20 in a direction perpendicular to the first slits 90.

[0047] Specifically, by setting a second slit 91 in the diaphragm layer 20, not only can most of the acoustic leakage path be blocked by the shielding block 30, making the acoustic leakage path the width of the first slit 90 when the diaphragm layer 20 is not deformed, thereby improving the low-frequency sound pressure attenuation, but also can increase the vibration displacement of the diaphragm layer 20, thereby improving the sound-generating effect of the microelectromechanical system sound-generating unit.

[0048] Further reference Figure 5The second slit 91 is located on the line connecting the midpoints of the two first slits 90.

[0049] Specifically, by setting the second slit 91 on the line connecting the midpoints of the two first slits 90, the vibration displacement of the diaphragm layers on both sides of the second slit 91 can be the same and the resonant frequency can be consistent during operation, thereby improving the sound-emitting effect of the microelectromechanical system (MEMS) sound-emitting unit. At the same time, it can also reduce the acoustic leakage path during operation, further reduce the low-frequency sound pressure attenuation, and improve the sound-emitting effect of the MEMS sound-emitting unit.

[0050] Furthermore, the piezoelectric layer includes at least one piezoelectric thin film.

[0051] Specifically, "at least one layer" can be understood as one or more layers. By setting multiple piezoelectric thin films in the piezoelectric layer, the thickness of the piezoelectric layer can be increased, which in turn can increase the vibration displacement of the diaphragm layer and improve the sound-generating effect of the microelectromechanical system (MEMS) sound-generating unit.

[0052] Further reference Figure 2 and Figure 3 The thickness of the substrate 10 ranges from 300μm to 600μm.

[0053] This utility model provides a microelectromechanical system (MEMS) loudspeaker, including at least one MEMS sound-generating unit as described in any of the above embodiments. "At least one" can be understood as one or more units. The MEMS loudspeaker provided by this utility model includes the MEMS sound-generating unit as described in any of the above technical solutions, and therefore possesses the beneficial effects of the aforementioned MEMS sound-generating units, which will not be elaborated further here.

[0054] This utility model embodiment provides a method for manufacturing a sound generating unit for a microelectromechanical system. Figure 6 This is a flowchart illustrating a method for manufacturing a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of the present invention. Figures 7-12 This is a schematic diagram illustrating the manufacturing process of a microelectromechanical system (MEMS) sound-generating unit according to an embodiment of this utility model. (Refer to...) Figure 3 , Figures 7-12 The production method includes:

[0055] S110. A diaphragm layer is provided in the base layer; the diaphragm layer includes a vibrating part and a fixing part; the fixing part is arranged around the vibrating part, and a first slit is provided between the vibrating part and the fixing part, wherein the first slit penetrates the diaphragm layer along a first direction.

[0056] Specifically, firstly, two silicon wafers are bonded together using thermal-oxygen bonding technology, forming a buried oxide layer 40 of silicon dioxide in the middle. One side of the buried oxide layer 40 serves as the substrate layer 10, and the silicon wafer on the side of the buried oxide layer 40 away from the substrate layer 10 is thinned to a predetermined thickness to form an elastic layer 50, thereby forming a structure such as... Figure 7 The structure shown, exemplarily, allows for the oxidation treatment of the surface of the elastic layer 50 away from the substrate layer 10. Subsequently, a first electrode layer 60 is deposited on the side of the elastic layer 50 away from the substrate layer 10 using reactive magnetron sputtering. A piezoelectric layer 70 is then deposited on the same side of the first electrode layer 60 away from the substrate layer 10 using sputtering, sol-gel, or molecular beam epitaxy. A second electrode layer 80 is then deposited on the same side of the piezoelectric layer 70 away from the substrate layer 10 using reactive magnetron sputtering, thus forming a structure as shown... Figure 8 The structure is shown. Then, a first etching process is performed on the first electrode layer 60, the piezoelectric layer 70, and the second electrode layer 80 to form a slit 93, thereby forming the structure shown. Figure 9 The structure shown is exemplary. The first etching process can be either dry etching or wet etching; this embodiment of the invention is not limited in this regard. Subsequently, a second etching process is performed on the elastic layer 50 and the buried oxide layer 40 to form the first slit 90, thereby forming the structure as described above. Figure 10 The structure shown is exemplary, and the second etching process can be dry etching, but this embodiment of the present invention does not limit this.

[0057] S120. A blocking block is provided on the side of the diaphragm layer away from the base layer; the blocking block is provided on the side of the fixing part close to the first slit, and the length of the blocking block is greater than or equal to the length of the first slit; wherein, the first direction is the direction from the base layer to the diaphragm layer.

[0058] Specifically, a barrier layer 301 can be formed on the side of the second electrode layer 80 away from the substrate layer 10 by spin coating and chemical vapor deposition, thereby forming a barrier layer 301. Figure 11 The structure shown can also be formed by covering the second electrode layer 80 with a dry film on the side away from the substrate layer 10, followed by etching. Figure 11 The structure shown is then etched onto the barrier layer 301 to form the structure shown. Figure 12 The structure shown can be etched using either dry etching or wet etching. The barrier layer 301 can be made of spin-coated SU-8 photoresist, polyimide (PI), polydimethylsiloxane (PDMS), or epoxy resin.

[0059] S130. A cavity is provided in the base layer, and the cavity penetrates the base layer along the first direction.

[0060] Specifically, the substrate 10 can be etched first using deep reactive ion etching (DRIE) to form a layer such as... Figure 3 The structure shown.

[0061] The method for manufacturing a microelectromechanical system (MEMS) sound unit provided in this embodiment of the invention involves setting a diaphragm layer on a base layer, the diaphragm layer including a vibrating part and a fixing part, a first slit between the vibrating part and the fixing part, then setting a blocking block on the side of the diaphragm layer away from the base layer, the blocking block being located on the side of the fixing part near the first slit, and the length of the blocking block being greater than or equal to the length of the first slit, and finally setting a cavity in the base layer, the cavity penetrating the base layer along a first direction, which can block most of the acoustic leakage path, making the acoustic leakage path become the width of the first slit when the diaphragm layer is not deformed, thereby improving the low-frequency sound pressure attenuation.

[0062] It should be understood that the various forms of the process shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this utility model can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this utility model can be achieved, and this is not limited herein.

[0063] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A microelectromechanical system (MEMS) sound-generating unit, characterized in that, include: A base layer; the base layer is provided with a cavity, and the cavity penetrates the base layer along a first direction; A diaphragm layer; the diaphragm layer is disposed on one side of the base layer where the cavity is disposed, the diaphragm layer is divided into a fixed part and a vibrating part; the fixed part is disposed around the vibrating part, and a first slit is disposed between the vibrating part and the fixed part, wherein the first slit penetrates the diaphragm layer along the first direction; A blocking block; the blocking block is disposed on the side of the diaphragm layer away from the base layer, the blocking block is disposed on the side of the fixing part near the first slit, and the length of the blocking block is greater than or equal to the length of the first slit; wherein, the first direction is the direction from the base layer to the diaphragm layer.

2. The microelectromechanical system (MEMS) sound-generating unit according to claim 1, characterized in that, The diaphragm layer includes a buried oxide layer, an elastic layer, a first electrode layer, a piezoelectric layer, and a second electrode layer stacked sequentially, and the buried oxide layer is in contact with the substrate layer.

3. The microelectromechanical system (MEMS) sound-generating unit according to claim 1, characterized in that, The surface of the fixing part near the first slit is flush with the surface of the blocking block near the first slit.

4. The microelectromechanical system (MEMS) sound-generating unit according to claim 1, characterized in that, Also includes: Second slit; The second slit is disposed between the two first slits, and the second slit penetrates the diaphragm layer in a direction perpendicular to the first slits.

5. The microelectromechanical system sound-generating unit according to claim 4, characterized in that, The second slit is located on the line connecting the midpoints of the two first slits.

6. The microelectromechanical system sound-generating unit according to claim 2, characterized in that, The piezoelectric layer includes at least one piezoelectric thin film.

7. The microelectromechanical system (MEMS) sound-generating unit according to claim 1, characterized in that, The thickness of the substrate layer ranges from 300μm to 600μm.

8. A microelectromechanical system loudspeaker, characterized in that, It includes at least one microelectromechanical system (MEMS) sound-generating unit as described in any one of claims 1-7.

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