MEMS loudspeaker, manufacturing method thereof and electronic device

Abstract

The invention discloses an MEMS loudspeaker, a manufacturing method thereof and an electronic device, and the method comprises the steps: providing a semiconductor substrate which comprises a first surface and a second surface which are opposite to each other, and sequentially forming a vibrating diaphragm layer, an insulating layer and a first electrode layer on the first surface of the semiconductor substrate; forming a lithium niobate piezoelectric layer on the first electrode layer; forming a second electrode layer on the lithium niobate piezoelectric layer; patterning the lithium niobate piezoelectric layer, the first electrode layer, the insulating layer and the diaphragm layer to form a vibration structure and a fixed end which are separated by a groove; a flexible covering layer covering the bottom and the side wall of the groove is formed, and the vibration structure is connected with the fixed end through the flexible covering layer; and etching the semiconductor substrate from the second surface of the semiconductor substrate to form a cavity. The sound pressure level of the MEMS loudspeaker can be improved by adopting lithium niobate as the piezoelectric layer, and the amplitude of the vibration structure can be improved by adopting the flexible covering layer to connect the vibration structure and the fixed end.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a MEMS speaker and a manufacturing method thereof, and an electronic device. Background Art

[0002] Speakers are an important type of MEMS devices and play a very important role in the audio field. Compared with traditional dynamic and balanced armature speakers, MEMS speakers have better sound pressure level performance at full frequency (20Hz-20kHz). They mainly include piezoelectric, electrostatic, electromagnetic, and thermoacoustic types. Piezoelectric MEMS speakers are widely used in mobile phones, Bluetooth headsets and other industries because of their small size, fast response speed, and low power consumption of piezoelectric drive.

[0003] At present, the piezoelectric materials used to make speakers are mostly ZnO (zinc oxide), AlN (aluminum nitride) and PZT (lead zirconium titanate). ZnO is the earliest piezoelectric material used in the speaker field, but its power consumption is too high and its chemical stability is poor; AlN has gradually become the mainstream due to its better chemical stability and lower power consumption, but due to its low piezoelectric coefficient, the sound pressure level (SPL) performance at low frequencies is not good enough; PZT can improve the sound pressure level of the speaker at low frequencies to a certain extent due to its extremely high piezoelectric coefficient, but due to process limitations, it cannot be made thicker to reduce the resonant frequency, and the improved sound pressure level is also limited. In addition, PZT piezoelectric materials are incompatible with general production lines because they contain lead elements. Summary of the invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention, which will be further described in detail in the Detailed Description of the Invention. The Summary of the Invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.

[0005] In view of the existing problems, an embodiment of the present invention provides a method for manufacturing a MEMS speaker, comprising:

[0006] Providing a semiconductor substrate, the semiconductor substrate comprising a first surface and a second surface opposite to each other, a diaphragm layer, an insulating layer and a first electrode layer being sequentially formed on the first surface of the semiconductor substrate;

[0007] forming a lithium niobate piezoelectric layer on the first electrode layer;

[0008] forming a second electrode layer on the lithium niobate piezoelectric layer;

[0009] forming a groove penetrating the second electrode layer, the lithium niobate piezoelectric layer, the first electrode layer, the insulating layer and the diaphragm layer to obtain a vibration structure and a fixed end separated by the groove;

[0010] forming a flexible covering layer covering the bottom and side walls of the groove, wherein the vibration structure is connected to the fixed end through the flexible covering layer;

[0011] The semiconductor substrate is etched from the second surface of the semiconductor substrate to form a cavity.

[0012] Exemplarily, forming a lithium niobate piezoelectric layer on the first electrode layer includes:

[0013] Providing a lithium niobate substrate, the lithium niobate substrate comprising a first surface and a second surface opposite to each other;

[0014] forming a bonding layer on the first surface of the lithium niobate substrate;

[0015] bonding the bonding layer to the first electrode layer;

[0016] The lithium niobate substrate is thinned from the second surface of the lithium niobate substrate to obtain a lithium niobate piezoelectric layer with a preset thickness.

[0017] Exemplarily, thinning the lithium niobate substrate from the second surface of the lithium niobate substrate comprises:

[0018] Before forming a bonding layer on the first surface of the lithium niobate substrate, ion implantation is performed on the first surface of the lithium niobate substrate to divide the lithium niobate substrate into an implantation layer and a non-implantation layer;

[0019] The lithium niobate substrate is heat treated to peel off the non-implanted layer from the lithium niobate substrate.

[0020] Exemplarily, the ions implanted by the ion implantation include helium ions.

[0021] Exemplarily, thinning the lithium niobate substrate from the second surface of the lithium niobate substrate comprises:

[0022] The lithium niobate substrate is thinned by a mechanical grinding process.

[0023] Exemplarily, the method further comprises performing chemical mechanical polishing on the thinned lithium niobate substrate.

[0024] Exemplarily, after forming the flexible cover layer and before forming the cavity, the method further includes:

[0025] forming a first contact hole exposing the first electrode layer and a second contact hole exposing the second electrode layer in the flexible cover layer;

[0026] A first lead-out structure electrically connected to the first electrode layer is formed in the first contact hole, and a second lead-out structure electrically connected to the second electrode layer is formed in the second contact hole.

[0027] Exemplarily, the material of the flexible cover layer includes polyimide.

[0028] A second aspect of an embodiment of the present invention provides a MEMS speaker, wherein the MEMS speaker is manufactured by the method as described above.

[0029] A third aspect of an embodiment of the present invention provides an electronic device, wherein the electronic device includes the MEMS speaker as described above.

[0030] According to the MEMS speaker and the manufacturing method thereof provided by the present invention, a lithium niobate film is used as the piezoelectric layer of the MEMS speaker, which has a high piezoelectric coefficient and can form a thick film, thereby enabling the MEMS to have a higher sound pressure level; and the manufacturing process of the lithium niobate piezoelectric layer is simple and compatible with general process production lines. In addition, the embodiment of the present invention uses a flexible covering layer to connect the vibration structure and the fixed end, which can increase the amplitude of the vibration structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following drawings of the present invention are used to understand the present invention as part of the present invention. The embodiments of the present invention are shown in the drawings and the description thereof is used to explain the principle of the present invention.

[0032] In the attached figure:

[0033] Figure 1 A schematic flow chart showing a method for manufacturing a MEMS speaker according to a specific embodiment of the present invention;

[0034] FIG. 2A to FIG. 2H A cross-sectional schematic diagram of a MEMS speaker obtained by sequentially implementing each step of the manufacturing method of the MEMS speaker according to an embodiment of the present invention is shown;

[0035] FIG. 3A to FIG. 3D A schematic diagram showing the formation of a lithium niobate piezoelectric layer using ion cutting technology according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0036] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0037] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

[0038] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there may be no intervening elements or layers. It should be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0039] Spatially relative terms such as "under," "below," "below," "under," "above," "above," etc., may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0040] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0041] The main problem facing MEMS piezoelectric speakers at present is the insufficient sound pressure level (SPL) output at low frequencies. Although a high SPL of more than 90bB has been achieved in a few piezoelectric MEMS speakers, they were all measured in special environments such as the ear canal. The sound pressure level is still insufficient in the open air and low-frequency range.

[0042] See also Figure 1 , the expression of sound pressure level P(z) is:

[0043]

[0044] Simplified to:

[0045]

[0046] Among them, S is the surface area of ​​the piezoelectric layer, w is the vibration amplitude, ρ is the air density, and f is the vibration frequency.

[0047] It can be seen from the above formula that the sound pressure level is mainly affected by the amplitude, the surface area of ​​the piezoelectric layer and the vibration frequency, so to produce a higher sound pressure output at a low frequency, a larger amplitude and a larger surface area are required.

[0048] Therefore, one way to increase the sound pressure level is to increase the piezoelectric coefficient, so that a larger vibration amplitude can be generated under the same driving voltage. Another way is to increase the diaphragm surface area, but at the same time, in order to ensure the fidelity of the speaker, the resonant frequency usually needs to be designed to be 2kHz-3kHz, and the expression of the resonant frequency is:

[0049]

[0050] Among them, t is the thickness of the diaphragm and a is the radius of the diaphragm.

[0051] That is to say, in order to maintain the resonant frequency, the diaphragm thickness needs to be increased while increasing the surface area of ​​the piezoelectric layer. However, the commonly used PZT (lead zirconium titanate) piezoelectric layer cannot be made thicker due to process limitations.

[0052] In view of the existence of the above technical problems, the embodiment of the present invention provides a MEMS speaker and a manufacturing method thereof, such as Figure 1 As shown, the manufacturing method of the MEMS speaker of the embodiment of the present invention includes the following steps:

[0053] In step S101, a semiconductor substrate is provided, wherein the semiconductor substrate comprises a first surface and a second surface opposite to each other, and a diaphragm layer, an insulating layer and a first electrode layer are sequentially formed on the first surface of the semiconductor substrate;

[0054] In step S102, a lithium niobate piezoelectric layer is formed on the first electrode layer;

[0055] In step S103, forming a second electrode layer on the lithium niobate piezoelectric layer;

[0056] In step S104, a groove is formed that penetrates the second electrode layer, the lithium niobate piezoelectric layer, the first electrode layer, the insulating layer, and the diaphragm layer to obtain a vibration structure and a fixed end separated by the groove;

[0057] In step S105, a flexible covering layer is formed to cover the bottom and side walls of the groove, and the vibration structure is connected to the fixed end through the flexible covering layer;

[0058] In step S106, the semiconductor substrate is etched from the second surface of the semiconductor substrate to form a cavity.

[0059] The MEMS speaker and its manufacturing method of the embodiment of the present invention use lithium niobate film as the piezoelectric layer of the MEMS speaker, which has a high piezoelectric coefficient and can form a thick film, so that the MEMS has a higher sound pressure level; and the manufacturing process of the lithium niobate piezoelectric layer is simple and compatible with general process production lines. The use of a flexible covering layer to connect the vibration structure and the fixed end can increase the amplitude of the vibration structure.

[0060] Below, reference FIG. 2A to FIG. 2H The manufacturing method of the MEMS speaker of the embodiment of the present invention is described in detail, wherein: FIG. 2A to FIG. 2H The cross-sectional schematic diagram of a MEMS speaker obtained by sequentially implementing each step of the manufacturing method of the MEMS speaker according to an embodiment of the present invention is shown.

[0061] First, if Figure 2A As shown, a semiconductor substrate 200 is provided, and the semiconductor substrate 200 includes a first surface and a second surface opposite to each other. Figure 2A In the embodiment, the upper surface of the semiconductor substrate 200 is the first surface, and the lower surface of the semiconductor substrate 200 is the second surface.

[0062] Exemplarily, the material of the semiconductor substrate 200 may include at least one of the following: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, or the semiconductor substrate 200 may also include silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) or germanium on insulator (GeOI), etc. Although several examples of materials that can form the semiconductor substrate 200 are described herein, any material that can be used as the semiconductor substrate 200 falls within the spirit and scope of the present invention. In a specific example, the semiconductor substrate 200 is a silicon on insulator substrate.

[0063] Exemplarily, a sacrificial layer 201 is formed on the first surface of the semiconductor substrate 200. The material of the sacrificial layer 302 may include at least one of the following materials: silicon oxide, phosphosilicate glass, borosilicate glass, borophosphosilicate glass-like materials. The sacrificial layer 201 may be formed by thermal oxidation, chemical vapor deposition (CVD), physical vapor deposition, etc.

[0064] Next, a diaphragm layer 202 is formed on the sacrificial layer. The material of the diaphragm layer 202 may be various conductive materials, for example, a single metal such as Al, W or Cu, or an alloy formed by at least two metals, or doped polycrystalline silicon, or doped amorphous silicon. The diaphragm layer 202 may be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or atomic layer deposition (ALD), or may be formed by one of low pressure chemical vapor deposition (LPCVD), laser ablation deposition (LAD) and selective epitaxial growth (SEG). An insulating layer 203 is formed on the diaphragm layer 202 to isolate the diaphragm layer 202 from the first electrode layer 204. The insulating layer 203 may be made of insulating materials well known in the art such as silicon nitride and silicon oxide.

[0065] Next, a first electrode layer 204 is formed on the insulating layer 203. The first electrode layer 204 can be made of a conductive material such as titanium (Ti) or aluminum (Al), and can be formed by a deposition process or sputtering.

[0066] Next, a lithium niobate piezoelectric layer 205 is formed on the first electrode layer 204. Lithium niobate (LN) has excellent piezoelectric properties, and its piezoelectric coefficient is three times that of AlN (aluminum nitride). It can form a thick film, and the manufacturing process is simpler than PZT (lead zirconium titanate). In addition, it does not contain lead elements and is compatible with general process production lines.

[0067] Due to the high brittleness of lithium niobate materials, it is usually difficult to form them into the piezoelectric layer thickness required for MEMS speakers. FIG. 3A to FIG. 3D The method shown forms the lithium niobate piezoelectric layer 205 .

[0068] like Figure 3A As shown, a lithium niobate substrate 300 is first provided, and the lithium niobate substrate 300 includes a first surface and a second surface opposite to each other. In the example of FIG. 3 , the upper surface of the lithium niobate substrate 300 is the first surface, and the lower surface is the second surface.

[0069] Then, if Figure 3B As shown, a bonding layer 301 is formed on the first surface of the lithium niobate substrate 300. The bonding layer 301 may be formed by sputtering or deposition. The bonding layer 301 may be made of a metal material. Exemplarily, the material of the bonding layer 301 is the same as that of the first electrode layer 204, for example, may include titanium, aluminum, etc., but is not limited thereto; the material of the bonding layer 301 may also be different from the material of the first electrode layer 204.

[0070] Then, if Figure 3C As shown, the bonding layer 301 is bonded to the first electrode layer 204. Exemplarily, the bonding layer 301 can be bonded to the first electrode layer 204 using a eutectic bonding process. Eutectic bonding is a bonding process that converts two or more metal layers from solid to liquid through high temperature treatment, and forms a eutectic phase on the bonding surface through metal recrystallization. The bonding process may also include hot pressing bonding, reaction bonding, etc.

[0071] Then, if Figure 3D As shown, the lithium niobate substrate is thinned from the second surface of the lithium niobate substrate 300 to obtain a lithium niobate piezoelectric layer of a preset thickness. The method of bonding first and then thinning can solve the problem that the lithium niobate piezoelectric layer of a preset thickness cannot be directly formed due to the high brittleness of the lithium niobate material.

[0072] In one embodiment, the lithium niobate substrate is thinned from the second surface of the lithium niobate substrate, including: thinning the lithium niobate substrate by a mechanical grinding process. The mechanical grinding process removes a large amount of material and can quickly thin the lithium niobate substrate, but in order to make the final lithium niobate piezoelectric layer have a high flatness and accurately control its thickness, after performing the mechanical grinding process, the lithium niobate piezoelectric layer is flattened by a chemical mechanical polishing (CMP) process.

[0073] In another practical example, the lithium niobate substrate 300 may be thinned by using an ion cutting process. Figure 3AAs shown, before forming a bonding layer on the first surface of the lithium niobate substrate 300, ion implantation is performed on the first surface of the lithium niobate substrate 300 to divide the lithium niobate substrate 300 into an implantation layer and a non-implantation layer. It can be understood that the portion implanted with doped ions is the implantation layer, and the portion not containing doped ions is the non-implantation layer. Exemplarily, the doped ions implanted into the lithium niobate substrate 300 are helium (He) ions. After the helium ions are implanted, the lithium niobate substrate is bonded to the first electrode layer.

[0074] Exemplarily, after the ion implantation is performed, the lithium niobate substrate 300 is also subjected to heat treatment at a temperature of about 220°C. During the heat treatment, the helium ions will be heated and foamed to destroy the chemical bonds of the lithium niobate crystals near the implanted layer, so that the non-implanted layer can be peeled off from the lithium niobate substrate 300. Exemplarily, after the thinning is completed, annealing can be performed at about 450°C for a certain period of time to repair the chemical bonds of the lithium niobate that were damaged during the helium ion implantation process. Finally, the surface of the lithium niobate substrate 300 can also be processed by a chemical mechanical polishing (CMP) process to obtain a high-quality lithium niobate piezoelectric layer 205.

[0075] Then, if Figure 2C As shown, a second electrode layer 206 is formed on the lithium niobate piezoelectric layer 205. The second electrode layer 206 can be made of a conductive material such as titanium (Ti) or aluminum (Al), and can be formed by a deposition process or sputtering molding. The second electrode layer 206 and the first electrode layer 204 may be made of the same or different materials.

[0076] Next, a groove is formed penetrating the second electrode layer 206, the lithium niobate piezoelectric layer 205, the first electrode layer 304, the insulating layer 203 and the diaphragm layer 202 to obtain a vibration structure and a fixed end separated by the groove.

[0077] For example, first Figure 2C As shown, the second electrode layer 206 and the lithium niobate piezoelectric layer 205 are patterned to obtain a first opening, and the first opening has a first width. The patterning process includes a dry etching process, and illustratively, a photoresist layer is first formed on the second electrode layer 206, and the photoresist layer is exposed, developed, and other processes are performed to pattern it, and finally the second electrode layer 206 and the lithium niobate piezoelectric layer 205 are etched using the patterned photoresist layer as a mask to form the first opening.

[0078] Then, if Figure 2DAs shown, the first electrode layer 204 and the insulating layer 203 are patterned to form a second opening at the bottom of the first opening that penetrates the first electrode layer 204 and the insulating layer 203, and the second opening has a second width that is smaller than the first width. Specifically, the first electrode layer 204 and the insulating layer 203 are etched using a dry etching process to obtain the second opening.

[0079] Then, if Figure 2E As shown, the diaphragm layer 202 is patterned to form a third opening penetrating the diaphragm layer 202 at the bottom of the second opening, and the third opening has a third width, which is smaller than the second width. Specifically, the diaphragm layer 202 is etched using a dry etching process to obtain the third opening. The groove is composed of the first opening, the second opening and the third opening, that is, the groove has a stepped sidewall, and its width decreases stepwise from top to bottom.

[0080] Then, if Figure 2F As shown, a flexible covering layer 207 is formed to cover the bottom and side walls of the groove. Exemplarily, the flexible covering layer 207 is also formed on the upper surface of the vibration structure. In one embodiment, the material of the flexible covering layer 207 is polyimide (PI), which has good fluidity and can fully cover the bottom and side walls of the groove. In other examples, the flexible covering layer 207 can also be made of other polyurethanes or other flexible organic films. The flexible covering layer 207 can seal the openings on both sides of the vibration structure, thereby improving the performance of the MEMS speaker. In addition, compared with silicon-based materials, the elastic modulus of flexible organic materials is smaller. Therefore, when the flexible covering layer 207 is used as the connecting portion between the vibration structure and the fixed end, it is beneficial to increase the amplitude of the vibration structure and improve the sound pressure level of the speaker at low frequencies.

[0081] Next, a first contact hole exposing the first electrode layer 204 and a second contact hole exposing the second electrode layer 206 are formed in the flexible cover layer 207. For example, a photoresist layer may be formed on the flexible cover layer 207, and the photoresist layer may be exposed and developed to form windows corresponding to the first contact hole and the second contact hole, and finally the flexible cover layer 207 may be etched to form the first contact hole and the second contact hole. For example, after the first contact hole and the second contact hole are formed, the flexible cover layer 207 may be cured.

[0082] Then, if Figure 2GAs shown, a first lead-out structure 208 electrically connected to the first electrode layer 204 is formed in the first contact hole, and a second lead-out structure 209 electrically connected to the second electrode layer 206 is formed in the second contact hole. The first lead-out structure 208 and the second lead-out structure 209 are made of metal materials. Exemplarily, the first lead-out structure 208 and the second lead-out structure 209 can be formed by a lift-off process, that is, firstly, a photoresist layer is formed on the flexible cover layer 207, the photoresist layer includes windows exposing the first electrode layer 204 and the second electrode layer 206, that is, the photoresist layer for forming the first contact hole and the second contact hole is retained, and the metal material is covered on the photoresist layer, and finally, the photoresist layer is removed and the metal layer above it is lifted off together, and only the metal layer located inside the window is retained as the first lead-out structure 208 and the second lead-out structure 209.

[0083] Then, if Figure 2H As shown, the semiconductor substrate 200 is etched from the second surface of the semiconductor substrate 200 to form a cavity. Exemplarily, the second surface of the semiconductor substrate 200 can be etched using a deep silicon etching process to form a cavity. The deep silicon etching process is also called deep reactive ion etching (DRIE), which can form a groove structure with a high aspect ratio, i.e., a cavity, in the semiconductor substrate 200. In some embodiments, the semiconductor substrate 200 can be first thinned from the second surface of the semiconductor substrate 200 (for example, thinned to less than 400um), and then etched to form a cavity.

[0084] Finally, the sacrificial layer 201 is released by a wet etching process. Specifically, after etching the semiconductor substrate 200 to form a cavity, the sacrificial layer exposed at the bottom of the cavity can be removed by a wet etching process, and at this time, both sides of the vibration structure are connected to the fixed end through the flexible cover layer 207, so that the vibration structure can vibrate in a direction perpendicular to the surface of the semiconductor substrate.

[0085] At this point, the process steps implemented in the method for manufacturing the MEMS speaker according to the first aspect of the embodiment of the present invention are completed. It can be understood that the method for manufacturing the MEMS speaker of this embodiment not only includes the above steps, but may also include other necessary steps before, during or after the above steps, which are all included in the scope of the manufacturing method of this embodiment.

[0086] The manufacturing method of the MEMS speaker provided in the embodiment of the present invention uses a lithium niobate film as the piezoelectric layer of the MEMS speaker. The piezoelectric coefficient is high and a thick film can be formed, so that the MEMS has a higher sound pressure level. The manufacturing process of the lithium niobate piezoelectric layer is simple and compatible with general process production lines. In addition, the embodiment of the present invention uses a flexible covering layer to connect the vibration structure and the fixed end, which can increase the amplitude of the vibration structure.

[0087] The second aspect of the present invention further provides a MEMS speaker, which can be prepared by the method in the first embodiment.

[0088] Below, reference Figure 2H The MEMS speaker of the present invention is introduced and described in detail. It is worth mentioning that in order to avoid repetition, only a brief description is given for the same components and structures as in the aforementioned embodiment 1. For specific explanations and descriptions, reference can be made to the description in embodiment 1.

[0089] Specifically, Figure 2H As shown, the MEMS speaker of the embodiment of the present invention comprises: a semiconductor substrate 200, the semiconductor substrate 200 comprises a first surface and a second surface opposite to each other, a vibration structure and a fixed end separated by a groove are formed on the first surface of the semiconductor substrate 200, the vibration structure and the fixed end respectively comprise a diaphragm layer 202, an insulating layer 203, a first electrode layer 204, a lithium niobate piezoelectric layer 205 and a second electrode layer 206 from bottom to top, a flexible covering layer 207 is formed on the bottom and sidewall of the groove, that is, the vibration structure and the fixed end are connected through the flexible covering layer 207. A cavity is formed on the second surface of the semiconductor substrate 200, and the cavity exposes the lower surfaces of the diaphragm layer 202 and the flexible covering layer 207.

[0090] The MEMS speaker of the embodiment of the present invention uses a lithium niobate film as the piezoelectric layer of the MEMS speaker, which has a high piezoelectric coefficient and can form a thick film, thereby improving the sound pressure level of the MEMS speaker.

[0091] The third aspect of the present invention further provides an electronic device in an embodiment, comprising the aforementioned MEMS speaker, wherein the MEMS speaker is manufactured according to the aforementioned method.

[0092] The electronic device of this embodiment can be any electronic product or device such as a mobile phone, a tablet computer, a laptop computer, a netbook, a game console, a television, a VCD, a DVD, a navigator, a digital photo frame, a camera, a video camera, a voice recorder, an MP3, an MP4, a PSP, etc., or any intermediate product including a circuit. The electronic device of the embodiment of the present invention has better performance due to the use of the above-mentioned MEMS speaker.

[0093] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for manufacturing a MEMS speaker, characterized in that: The method comprises: Providing a semiconductor substrate, the semiconductor substrate comprising a first surface and a second surface opposite to each other, a diaphragm layer, an insulating layer and a first electrode layer being sequentially formed on the first surface of the semiconductor substrate; forming a lithium niobate piezoelectric layer on the first electrode layer; forming a second electrode layer on the lithium niobate piezoelectric layer; forming a groove penetrating the second electrode layer, the lithium niobate piezoelectric layer, the first electrode layer, the insulating layer and the diaphragm layer to obtain a vibration structure and a fixed end separated by the groove; forming a flexible covering layer covering the bottom and side walls of the groove, wherein the vibration structure is connected to the fixed end through the flexible covering layer; The semiconductor substrate is etched from the second surface of the semiconductor substrate to form a cavity.

2. The manufacturing method according to claim 1, characterized in that The step of forming a lithium niobate piezoelectric layer on the first electrode layer comprises: Providing a lithium niobate substrate, the lithium niobate substrate comprising a first surface and a second surface opposite to each other; forming a bonding layer on the first surface of the lithium niobate substrate; bonding the bonding layer to the first electrode layer; The lithium niobate substrate is thinned from the second surface of the lithium niobate substrate to obtain a lithium niobate piezoelectric layer with a preset thickness.

3. The manufacturing method according to claim 2, characterized in that: The step of thinning the lithium niobate substrate from the second surface of the lithium niobate substrate comprises: Before forming a bonding layer on the first surface of the lithium niobate substrate, ion implantation is performed on the first surface of the lithium niobate substrate to divide the lithium niobate substrate into an implantation layer and a non-implantation layer; The lithium niobate substrate is heat treated to peel off the non-implanted layer from the lithium niobate substrate.

4. The manufacturing method according to claim 3, characterized in that: The ions implanted by the ion implantation include helium ions.

5. The manufacturing method according to claim 2, characterized in that: The step of thinning the lithium niobate substrate from the second surface of the lithium niobate substrate comprises: The lithium niobate substrate is thinned by a mechanical grinding process.

6. The manufacturing method according to any one of claims 2 to 5, characterized in that: The method also includes chemical mechanical grinding of the thinned lithium niobate substrate.

7. The manufacturing method according to claim 1, characterized in that: After forming the flexible covering layer and before forming the cavity, the method further includes: forming a first contact hole exposing the first electrode layer and a second contact hole exposing the second electrode layer in the flexible cover layer; A first lead-out structure electrically connected to the first electrode layer is formed in the first contact hole, and a second lead-out structure electrically connected to the second electrode layer is formed in the second contact hole.

8. The manufacturing method according to claim 1, characterized in that: The material of the flexible cover layer includes polyimide.

9. A MEMS speaker, characterized in that: The MEMS speaker is manufactured by the method described in any one of claims 1-8.

10. An electronic device, characterized in that: The electronic device comprises the MEMS speaker as claimed in claim 9.

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