Piezoelectric MEMS loudspeaker, manufacturing method thereof and electronic equipment

Abstract

The invention relates to the field of semiconductor devices, and provides a piezoelectric MEMS loudspeaker, a manufacturing method thereof and electronic equipment. The piezoelectric MEMS loudspeaker comprises a substrate and a vibrating diaphragm located on the upper side of the substrate in the thickness direction, the vibrating diaphragm comprises an electrode layer and a piezoelectric layer which are stacked in the thickness direction, and the piezoelectric layer is located on the upper side of the substrate in the thickness direction. The resonant frequency f of the piezoelectric MEMS loudspeaker, the effective area S of the vibrating diaphragm and the total thickness t of the piezoelectric layer meet a predetermined relational expression and predetermined constraint conditions. Therefore, by making the resonant frequency of the loudspeaker, the effective area of the vibrating diaphragm and the total thickness of the piezoelectric layer meet the preset relational expression and constraint conditions, the size, the output sound pressure, the resonant frequency, the energy consumption efficiency and other performance parameters of the loudspeaker can be more balanced, and the high-performance piezoelectric MEMS loudspeaker is obtained.

Description

Technical Field

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

[0002] With the development of semiconductor technology, devices based on micro-electromechanical systems (MEMS) technology are widely used in electronic products such as smart phones due to their small size and good performance. Among them, speakers based on MEMS technology (hereinafter referred to as "MEMS speakers") can be manufactured using semiconductor processes. Compared with traditional speakers, MEMS speakers have the advantages of small size, good performance, low cost, and are easy to mass-produce. They are expected to be widely used in small electronic products such as mobile phones and headphones.

[0003] MEMS speakers can generally be divided into three categories according to their working principles: electromagnetic, electrostatic and piezoelectric. Among them, piezoelectric MEMS speakers have a simple structure, and their processing technology and integration technology are simpler than those of electromagnetic MEMS speakers and electrostatic MEMS speakers. Therefore, they have greater advantages in achieving lightness, miniaturization and high performance.

[0004] However, due to the low electromechanical conversion efficiency of piezoelectric devices, the difficulty in realizing piezoelectric MEMS speakers lies in the excessive driving voltage and insufficient output sound pressure.

[0005] This section is intended to provide a background or context to the embodiments of the present application as recited in the claims. No admission is made that the description herein is prior art by inclusion in this section. Summary of the invention

[0006] When designing a piezoelectric MEMS speaker, the existing solution to the problem of excessive driving voltage and insufficient output sound pressure is to mechanically decouple the entire diaphragm into a multi-petal structure to obtain a higher degree of freedom, or to use cantilever beams on all four sides to drive the central diaphragm to achieve a piston vibration mode.

[0007] The inventors found that these solutions have a good effect in improving the mid- and low-frequency response, but they are essentially at the expense of moving the resonant frequency forward. If the resonant frequency is too forward, the speaker system will enter the inertial control area too early, thereby greatly reducing the high-frequency response of the speaker. Existing solutions all make a trade-off between sensitivity and resonant frequency, often losing one while gaining the other, and it is difficult to maintain a balance between various performances.

[0008] In order to solve at least one of the above problems or other similar problems, the embodiments of the present application provide a piezoelectric MEMS speaker, a manufacturing method thereof, and an electronic device.

[0009] According to a first aspect of an embodiment of the present application, a piezoelectric MEMS speaker is provided. The piezoelectric MEMS speaker includes a substrate and a diaphragm located on the upper side in the thickness direction of the substrate. Among them, the diaphragm includes an electrode layer and a piezoelectric layer stacked in the thickness direction.

[0010] Moreover, the resonant frequency f of the piezoelectric MEMS speaker, the effective area S of the diaphragm, and the total thickness t of the piezoelectric layer satisfy the following relational expression:

[0011]

[0012] And the relational expression satisfies the following constraint conditions:

[0013] y > 1.67e12,

[0014] Among them, keff is the square root of the effective electromechanical coupling coefficient keff^2, ε33 represents the relative dielectric constant of the piezoelectric layer, and ρ represents the density of the piezoelectric layer.

[0015] According to a second aspect of an embodiment of the present application, a manufacturing method of a piezoelectric MEMS speaker is provided. The manufacturing method includes:

[0016] Forming a diaphragm on the upper side in the thickness direction of the substrate. The diaphragm includes an electrode layer and a piezoelectric layer stacked in the thickness direction.

[0017] Moreover, the resonant frequency f of the piezoelectric MEMS speaker, the effective area S of the diaphragm, and the total thickness t of the piezoelectric layer satisfy the following relational expression:

[0018]

[0019] And the relational expression satisfies the following constraint conditions:

[0020] y > 1.67e12,

[0021] Among them, keff is the square root of the effective electromechanical coupling coefficient keff^2, ε33 represents the relative dielectric constant of the piezoelectric layer, and ρ represents the density of the piezoelectric layer.

[0022] According to a third aspect of an embodiment of the present application, an electronic device is provided. The electronic device includes the piezoelectric MEMS speaker described in the embodiment of the first aspect.

[0023] One of the beneficial effects of the embodiment of the present application is that by making the resonant frequency of the speaker, the effective area of the diaphragm, and the total thickness of the piezoelectric layer satisfy the predetermined relational expression and constraint conditions, the performance parameters such as the size, output sound pressure, resonant frequency, and energy consumption efficiency of the speaker can be made more balanced, and a high-performance piezoelectric MEMS speaker can be obtained. Brief Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic diagram of a piezoelectric MEMS speaker according to an embodiment of the present application.

[0026] Figure 2 It is a schematic diagram of an embodiment of the diaphragm according to an embodiment of the present application.

[0027] Figure 3 It is a graph of resonant frequency - total thickness of the piezoelectric layer - diaphragm area of an embodiment of the piezoelectric MEMS speaker according to an embodiment of the present application when y > 1.67e12.

[0028] Figure 4 It is a graph of resonant frequency - total thickness of the piezoelectric layer - diaphragm area of an embodiment of the piezoelectric MEMS speaker according to an embodiment of the present application when y > 1e13.

[0029] Figure 5 It is a graph of resonant frequency - total thickness of the piezoelectric layer - diaphragm area of another embodiment of the piezoelectric MEMS speaker according to an embodiment of the present application when y > 1.67e12.

[0030] Figure 6 It is a graph of resonant frequency - total thickness of the piezoelectric layer - diaphragm area of another embodiment of the piezoelectric MEMS speaker according to an embodiment of the present application when y > 1e13.

[0031] Figure 7 It is a graph of sound pressure level - frequency of the piezoelectric MEMS speaker according to an embodiment of the present application at the same resonant frequency (f = 5000 Hz) and the same diaphragm area (S = 3e - 6 m 2 ).

[0032] Figure 8 It is a graph of diaphragm area - relationship formula of the piezoelectric MEMS speaker according to an embodiment of the present application at the same output sound pressure level (SPL = 93 dB) and the same resonant frequency (f = 4000 Hz).

[0033] Figure 9 It is a graph of sound pressure level - frequency of the piezoelectric MEMS speaker according to an embodiment of the present application at the same output sound pressure level and the same diaphragm area (S = 3e - 6 m 2 ).

[0034] Figure 10 It is a schematic diagram of a manufacturing method of a MEMS speaker according to an embodiment of the present application. Detailed implementation manners

[0035] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer and more understandable, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings. Herein, the illustrative embodiments of the present application and their descriptions are used to explain the present application, but are not intended to limit the present application.

[0036] In the embodiments of the present application, terms such as "first", "second", "upper", "lower", etc. are used to distinguish different elements in terms of appellation, but do not represent the spatial arrangement or time sequence of these elements, and these elements should not be limited by these terms. The term "and / or" includes any one and all combinations of one or more of the associated listed terms. Terms such as "comprising", "including", "having", etc. mean the presence of the stated features, elements, components or assemblies, but do not exclude the presence or addition of one or more other features, elements, components or assemblies.

[0037] In the embodiments of the present application, the singular forms "a", "the", etc. include the plural forms and should be broadly understood as "a kind" or "a class" rather than being limited to the meaning of "one"; in addition, the term "the" should be understood to include both the singular form and the plural form unless the context clearly indicates otherwise. In addition, the term "according to" should be understood as "at least partially according to...", and the term "based on" should be understood as "at least partially based on...", unless the context clearly indicates otherwise.

[0038] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0039] The embodiments of the present application provide a piezoelectric MEMS speaker. Figure 1 It is a schematic diagram of a piezoelectric MEMS speaker according to an embodiment of the present application, Figure 2 It is a schematic diagram of an embodiment of a diaphragm according to an embodiment of the present application.

[0040] As Figure 1 shown, the piezoelectric MEMS speaker 1 includes a substrate 30 and a diaphragm 10. The diaphragm 10 is located on the upper side in the thickness direction z of the substrate 30. The diaphragm 10 includes an electrode layer 12 and a piezoelectric layer 11 stacked in the thickness direction z. The number of the piezoelectric layer 11 and the electrode layer 12 is arbitrary. For example, as Figure 1 and Figure 2As shown, the diaphragm 10 may include three electrode layers 12 and two piezoelectric layers 11 stacked alternately. In addition, the diaphragm 10 may also include a structural layer. For example, the diaphragm 10 may include a structural layer, an electrode layer, a piezoelectric layer, and an electrode layer stacked in sequence from bottom to top, and the number of the structural layer, the electrode layer, and the piezoelectric layer is arbitrary. In addition, as Figure 2 shown, the diaphragm 10 may also include a slit 110, and the slit 110 may be located in the central region of the diaphragm 10. The embodiments of the present application do not limit whether the diaphragm includes a slit and the structure of the slit. In addition, the diaphragm only needs to include an electrode layer and a piezoelectric layer, and the embodiments of the present application do not limit the specific structure of the diaphragm, and corresponding design can be carried out according to needs.

[0041] In some embodiments, the substrate 30 may be formed of a semiconductor material, or may also be formed by compounding multiple materials. The embodiments of the present application do not limit this. For example, the substrate 30 may be formed of single-crystalline silicon, for example, formed of a high-resistance silicon material, and the resistivity of the silicon material is, for example, greater than 1000 Ω·cm, for example, the resistivity > 5000 Ω·cm. The embodiments of the present application do not limit this. For example, the substrate 30 may also be formed of materials such as lithium niobate, lithium tantalate, silicon carbide (SiC), sapphire, and quartz. In addition, the substrate 30 may also be formed of semiconductor materials such as silicon dioxide, silicon nitride, polysilicon, and amorphous silicon. The embodiments of the present application do not limit this.

[0042] In some embodiments, the piezoelectric layer 11 may be formed of piezoelectric materials such as aluminum nitride (AlN), doped aluminum nitride, doped zinc oxide (ZnO), lead zirconate titanate (PZT), or doped lead zirconate titanate. The corresponding piezoelectric material can be selected according to actual needs or performance requirements. The embodiments of the present application do not limit the specific material.

[0043] In some embodiments, the effective electromechanical coupling coefficient keff^2 of aluminum nitride or doped aluminum nitride may be 0.3% - 10%, the relative dielectric constant ε33 may be 9 - 15, and the density ρ may be 3000 - 4000 kg / m^3.

[0044] In some embodiments, the effective electromechanical coupling coefficient keff^2 of lead zirconate titanate or doped lead zirconate titanate may be 4% - 30%, the relative dielectric constant ε33 may be 450 - 1200, and the density ρ may be 7000 - 8000 kg / m^3.

[0045] In addition, the material for forming the electrode layer 12 can be a metal, for example, elemental metals such as molybdenum (Mo), aluminum (Al), copper (Cu), platinum (Pt), tantalum (Ta), tungsten (W), palladium (Pd), ruthenium (Ru), gold (Au), titanium (Ti), chromium (Cr), etc., or their alloys or their composite laminates; the material of the electrode layer 12 can also be doped polysilicon, and the doping elements can be boron (B), phosphorus (P), arsenic (As), etc., and the doping concentration is, for example, 10 19 cm -3 Above, within a certain range, the higher the doping concentration, the lower the sheet resistance of the electrode made of polysilicon, and the lower the electrical loss. The embodiments of the present application do not limit this.

[0046] In addition, the material for forming the structural layer can be silicon, silicon dioxide, fluorine-doped silicon dioxide, silicon nitride, silicon oxynitride, aluminum nitride, aluminum oxide, titanium oxide, tantalum pentoxide, etc., and can be a single layer or a combination of multiple different dielectric materials. The embodiments of the present application do not limit this.

[0047] As Figure 1 shown, a cavity 20 is formed between the upper part of the thickness direction z of the diaphragm 10 and the substrate 30, and the effective area S of the diaphragm 10 is the area of the region where the diaphragm 10 and the cavity 20 overlap in the thickness direction z. That is to say, in the thickness direction z, the projection of the diaphragm 10 overlaps with the projection of the cavity 20, and the overlapping area of the diaphragm 10 and the cavity 20 is called the "effective area S of the diaphragm 10". The larger the projection area of the cavity 20, the larger the effective area of the diaphragm 10, and the larger the sound pressure level (SPL) of the piezoelectric MEMS speaker 1. In addition, at least a part of the cavity 20 in the thickness direction z can be formed as the sound cavity of the piezoelectric MEMS speaker 1. For example, the cavity 20 can be Figure 1 the through hole shown, so as to constitute the sound cavity and sound hole of the piezoelectric MEMS speaker 1. However, the embodiments of the present application do not limit this, and how to form the sound cavity and sound hole specifically can refer to related technologies.

[0048] In some embodiments, the piezoelectric MEMS speaker 1 can include a single diaphragm, or can include an array composed of multiple array elements. That is to say, the diaphragm 10 can be the structure of the entire thin film, or can be an array structure composed of multiple array elements. For example, a single array element includes a thin film and a corresponding cavity, or a single diaphragm corresponds to multiple sub-cavities, or multiple sub-diaphragms correspond to one cavity. The embodiments of the present application do not limit this.

[0049] For example, the diaphragm 10 can include multiple sub-diaphragms, and the effective area S of the diaphragm 10 is the sum of the areas of the regions where the multiple sub-diaphragms and the cavity 20 overlap in the thickness direction z.

[0050] For another example, the cavity 20 may include a plurality of sub-cavities, and the effective area S of the diaphragm 10 is the area of the region where the diaphragm 10 overlaps with the plurality of sub-cavities in the thickness direction z.

[0051] For another example, the diaphragm 10 may include a plurality of sub-diaphragms, the cavity 20 may include a plurality of sub-cavities, the plurality of sub-cavities correspond to the plurality of sub-diaphragms respectively, and the effective area S of the diaphragm 10 is the sum of the areas of the regions where the plurality of sub-diaphragms overlap with the corresponding sub-cavities in the thickness direction z.

[0052] In the embodiments of the present application, for the convenience of description, the thickness direction of the substrate 30 is denoted as the "z direction", the width direction of the substrate 30 is denoted as the "x direction", the length direction of the substrate 30 is denoted as the "y direction", the x direction, the y direction and the z direction are perpendicular to each other. In addition, without causing ambiguity, sometimes the "z direction" is also referred to as the "vertical direction", and the x direction and the y direction are referred to as the "horizontal direction". In addition, for the convenience of description, for the thickness direction, the direction from the substrate 30 to the diaphragm 10 is called "up", and the direction from the diaphragm 10 to the substrate 30 is called "down", unless otherwise specified. In addition, those skilled in the art should understand that the "up" and "down" described in the embodiments of the present application are only used to distinguish different elements in terms of name, but do not represent the spatial arrangement of these elements.

[0053] In addition, in the embodiments of the present application, unless otherwise specified, for the formulas involved in the embodiments of the present application, the units of all variables use the MKS international unit system, that is, the unit of the frequency f is Hz (Hertz), the unit of the density ρ is kg / m^3 (kilogram per cubic meter), the unit of the thickness t is m (meter), the unit of the area S is m^2 (square meter). In addition, the relative dielectric constant ε33 and the effective electromechanical coupling coefficient keff are dimensionless numbers.

[0054] In some embodiments, the resonance frequency f of the piezoelectric MEMS speaker, the effective area S of the diaphragm, and the total thickness t of the piezoelectric layer satisfy the following relational formula:

[0055]

[0056] And, this relational formula satisfies the following constraint conditions:

[0057] y>1.67e12,

[0058] where keff is the square root of the effective electromechanical coupling coefficient keff^2, ε33 represents the relative dielectric constant of the piezoelectric layer, and ρ represents the density of the piezoelectric layer.

[0059] Thus, by making the resonance frequency of the speaker, the effective area of the diaphragm, and the total thickness of the piezoelectric layer satisfy a predetermined relationship y and a predetermined constraint condition y > 1.67e12, it is possible to make the performance parameters such as the size, output sound pressure, resonance frequency, and energy consumption efficiency of the speaker more balanced, and a high-performance piezoelectric MEMS speaker can be obtained.

[0060] In the embodiments of the present application, sometimes scientific notation such as "aeb" or "aEb" or "a*10^b" is used to represent numbers, and these forms can be converted to each other, which will not be elaborated one by one below.

[0061] In some embodiments, the above relationship may further satisfy the following constraint condition: y > 1e13. Thus, the performance parameters such as the size, output sound pressure, resonance frequency, and energy consumption efficiency of the speaker are further balanced, and a piezoelectric MEMS speaker with higher performance can be obtained.

[0062] Figure 3 is a resonance frequency - total thickness of piezoelectric layer - diaphragm area diagram of an embodiment of the piezoelectric MEMS speaker in the present application embodiment when y > 1.67e12 is satisfied, Figure 4 is a resonance frequency - total thickness of piezoelectric layer - diaphragm area diagram of an embodiment of the piezoelectric MEMS speaker in the present application embodiment when y > 1e13 is satisfied. In Figure 3 and Figure 4 example, Figure 1 the material of the piezoelectric layer shown is aluminum nitride (AlN) or doped aluminum nitride, and the material of the electrode layer is molybdenum (Mo). Figure 3 the area below the curved surface shown is the area that satisfies y > 1.67e12, Figure 4 the area below the curved surface shown is the area that satisfies y > 1e13.

[0063] Figure 5 is a resonance frequency - total thickness of piezoelectric layer - diaphragm area diagram of another embodiment of the piezoelectric MEMS speaker in the present application embodiment when y > 1.67e12 is satisfied, Figure 6 is a resonance frequency - total thickness of piezoelectric layer - diaphragm area diagram of another embodiment of the piezoelectric MEMS speaker in the present application embodiment when y > 1e13 is satisfied. In Figure 5 and Figure 6 example, Figure 1 the material of the piezoelectric layer shown is lead zirconate titanate (PZT) or doped lead zirconate titanate, and the material of the electrode layer is platinum / gold (Pt / Au). Figure 5 the area below the curved surface shown is the area that satisfies y > 1.67e12, Figure 6 the area below the curved surface shown is the area that satisfies y > 1e13.

[0064] Figure 7is the sound pressure level - frequency graph of the piezoelectric MEMS speaker according to the embodiments of the present application at the same resonance frequency (f = 5000 Hz) and the same diaphragm area (S = 3e - 6 m 2 ). Figure 8 is the diaphragm area - relationship graph of the piezoelectric MEMS speaker according to the embodiments of the present application at the same output sound pressure level (SPL = 93 dB) and the same resonance frequency (f = 4000 Hz). Figure 9 is the sound pressure level - frequency graph of the piezoelectric MEMS speaker according to the embodiments of the present application at the same output sound pressure level and the same diaphragm area (S = 3e - 6 m 2 ).

[0065] It can be seen from Figure 7 that under the conditions of the same resonance frequency and the same diaphragm area, the sound pressure level of the speaker satisfying y > 1.67e12 is higher.

[0066] It can be seen from Figure 8 that under the conditions of the same output sound pressure level and the same resonance frequency, a piezoelectric MEMS speaker with a smaller diaphragm area can be obtained.

[0067] It can be seen from Figure 9 that under the conditions of the same sound pressure level and the same diaphragm area, a piezoelectric MEMS speaker with a higher resonance frequency can be obtained.

[0068] In some embodiments, the resonance frequency f is the frequency corresponding to the first maximum sound pressure measured in a free - field environment. The effective electromechanical coupling coefficient keff^2 is defined as: keff^2 = (fp^2 - fs^2) / fp^2, where fs represents the frequency corresponding to the minimum value of the electrical impedance of the speaker closest to the resonance frequency, and fp represents the frequency corresponding to the maximum value of the electrical impedance of the speaker closest to the resonance frequency. For some typical materials, keff^2 can take empirical values. For example, for aluminum nitride (AlN) or doped aluminum nitride, keff^2 can take 0.3% - 10%, and for lead zirconate titanate (PZT) or doped lead zirconate titanate, keff^2 can take 4% - 30%.

[0069] In the embodiments of the present application, compared with other speakers, the piezoelectric MEMS speaker satisfying y > 1.67e12 has better performance, specifically manifested as:

[0070] (1) Under the conditions of the same diaphragm area and resonance frequency, a larger output sound pressure level and power sensitivity can be obtained;

[0071] (2) Under the conditions of the same output sound pressure level and resonance frequency, a smaller diaphragm area can be obtained;

[0072] (3) Under the condition that the diaphragm area and the output sound pressure level are the same, a higher resonant frequency can be obtained.

[0073] In some embodiments, the ratio of the single-layer thickness of the electrode layer to the total thickness of the piezoelectric layer is 0.5 or less. For example, as Figure 1 shown, the thicknesses of the three electrode layers 12 are d1, d2, and d3 respectively, the total thickness t of the piezoelectric layer is the sum of the thicknesses t1 and t2 of the two piezoelectric layers 11, and d1 / t, d2 / t, and d3 / t are all 0.5 or less.

[0074] When designing a piezoelectric MEMS speaker, for example, the constraint conditions of the resonant frequency f and the effective area S of the diaphragm can be determined according to the above-mentioned predetermined relationship y and the predetermined constraint condition y > 1.67e12, as well as the selected material and thickness requirements of the piezoelectric layer, so as to achieve the effects of the above (1) to (3). For example:

[0075] In some embodiments, the material of the piezoelectric layer can be aluminum nitride (AlN) or doped aluminum nitride. When the total thickness t of the piezoelectric layer < 1 μm, the resonant frequency f and the effective area S of the diaphragm of the piezoelectric MEMS speaker satisfy the following constraint conditions:

[0076] 1.0258*f^2 - 3.3670*10^11*S > 0.

[0077] In some embodiments, the material of the piezoelectric layer can be aluminum nitride (AlN) or doped aluminum nitride. When the total thickness t of the piezoelectric layer < 0.2 μm, the resonant frequency f and the effective area S of the diaphragm of the piezoelectric MEMS speaker satisfy the following constraint conditions:

[0078] 9.1291*f^2 - 1.6835*10^12*S > 0.

[0079] In some embodiments, the material of the piezoelectric layer can be lead zirconate titanate (PZT) or doped lead zirconate titanate. When the total thickness t of the piezoelectric layer < 1 μm, the resonant frequency f and the effective area S of the diaphragm of the piezoelectric MEMS speaker satisfy the following constraint conditions:

[0080] 6.6480*f^2 - 1.4815*10^10*S > 0.

[0081] In some embodiments, the material of the piezoelectric layer is lead zirconate titanate (PZT) or doped lead zirconate titanate. When the total thickness t of the piezoelectric layer < 0.6 μm, the resonant frequency f and the effective area S of the diaphragm of the piezoelectric MEMS speaker satisfy the following constraint conditions:

[0082] 1.1102*f^2 - 2.4741*10^9*S > 0.

[0083] As can be seen from the above embodiments, by making the resonance frequency of the speaker, the effective area of the diaphragm, and the total thickness of the piezoelectric layer satisfy a predetermined relational expression and predetermined constraint conditions, it is possible to make the performance parameters such as the size, output sound pressure, resonance frequency, and energy consumption efficiency of the speaker more balanced, and a high-performance piezoelectric MEMS speaker can be obtained.

[0084] An embodiment of the present application further provides a manufacturing method for a piezoelectric MEMS speaker. Figure 10 It is a schematic diagram of the manufacturing method of the MEMS speaker according to the embodiment of the present application.

[0085] As Figure 10 shown, the manufacturing method includes:

[0086] 1001: Form a diaphragm on the upper side in the thickness direction of the substrate, and the diaphragm includes an electrode layer and a piezoelectric layer stacked in the thickness direction,

[0087] wherein, the resonance frequency f of the piezoelectric MEMS speaker, the effective area S of the diaphragm, and the total thickness t of the piezoelectric layer satisfy the following relational expression:

[0088]

[0089] And, the relational expression satisfies the following constraint conditions:

[0090] y>1.67e12,

[0091] wherein, keff is the square root of the effective electromechanical coupling coefficient keff^2, ε33 represents the relative dielectric constant of the piezoelectric layer, and ρ represents the density of the piezoelectric layer.

[0092] In some embodiments, the relational expression satisfies the following constraint condition: y>1e13.

[0093] In some embodiments, the ratio of the single-layer thickness of the electrode layer to the total thickness of the piezoelectric layer is 0.5 or less.

[0094] In some embodiments, the material of the piezoelectric layer is aluminum nitride or doped aluminum nitride.

[0095] In some embodiments, the effective electromechanical coupling coefficient keff^2 of the piezoelectric layer is 0.3%-10%.

[0096] In some embodiments, the relative dielectric constant ε33 of the piezoelectric layer is 9-15, and the density ρ is 3000-4000 kg / m^3.

[0097] In some embodiments, when the total thickness t of the piezoelectric layer is less than 1 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint:

[0098] 1.0258*f^2 - 3.3670*10^11*S > 0.

[0099] In some embodiments, when the total thickness t of the piezoelectric layer is less than 0.2 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint:

[0100] 9.1291*f^2 - 1.6835*10^12*S > 0.

[0101] In some embodiments, the material of the piezoelectric layer is lead zirconate titanate or doped lead zirconate titanate.

[0102] In some embodiments, the effective electromechanical coupling coefficient keff^2 of the piezoelectric layer is 4% - 30%.

[0103] In some embodiments, the relative permittivity ε33 of the piezoelectric layer is 450 - 1200, and the density ρ is 7000 - 8000 kg / m^3.

[0104] In some embodiments, when the total thickness t of the piezoelectric layer is less than 1 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint:

[0105] 6.6480*f^2 - 1.4815*10^10*S > 0.

[0106] In some embodiments, when the total thickness t of the piezoelectric layer is less than 0.6 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint:

[0107] 1.1102*f^2 - 2.4741*10^9*S > 0.

[0108] In some embodiments, the diaphragm includes electrode layers, piezoelectric layers, electrode layers, piezoelectric layers, and electrode layers stacked in sequence from top to bottom in the thickness direction.

[0109] In some embodiments, the diaphragm further includes a structural layer, and the diaphragm includes a structural layer, an electrode layer, a piezoelectric layer, and an electrode layer stacked in sequence from top to bottom in the thickness direction.

[0110] In some embodiments, a cavity is formed between the diaphragm and the upper part in the thickness direction of the substrate.

[0111] The effective area S of the diaphragm is the area of the region where the diaphragm and the cavity overlap in the thickness direction.

[0112] In some embodiments, slits are formed in the region of the diaphragm corresponding to the cavity.

[0113] In some embodiments, at least a part of the cavity in the thickness direction forms the sound cavity of the piezoelectric MEMS speaker.

[0114] In some embodiments, the diaphragm includes a plurality of sub - diaphragms, and the effective area S of the diaphragm is the sum of the areas of the regions where the plurality of sub - diaphragms and the cavity overlap in the thickness direction.

[0115] In some embodiments, the cavity includes a plurality of sub - cavities, and the effective area S of the diaphragm is the area of the region where the diaphragm and the plurality of sub - cavities overlap in the thickness direction.

[0116] In some embodiments, the diaphragm includes a plurality of sub - diaphragms, the cavity includes a plurality of sub - cavities, and the plurality of sub - cavities correspond to the plurality of sub - diaphragms respectively.

[0117] The effective area S of the diaphragm is the sum of the areas of the regions where the plurality of sub - diaphragms and the corresponding sub - cavities overlap in the thickness direction.

[0118] In the embodiments of the present application, the processes for forming the diaphragm and the cavity may refer to the related technologies, and the embodiments of the present application do not limit this.

[0119] The embodiments of the present application further provide an electronic device, which includes the piezoelectric MEMS speaker described in the foregoing embodiments. Since the structure and characteristics of the piezoelectric MEMS speaker have been described in detail in the above - mentioned embodiments, the content is incorporated herein and the description is omitted here.

[0120] The electronic device in the embodiments of the present application is, for example, a headphone or a speaker of a smart phone, etc., and the embodiments of the present application do not limit this.

[0121] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present application. It should be understood that the above - mentioned are only the specific embodiments of the present application and are not used to limit the protection scope of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A piezoelectric MEMS speaker, the piezoelectric MEMS speaker comprising a substrate and a diaphragm located on the upper side in the thickness direction of the substrate, characterized in that, the diaphragm comprises an electrode layer and a piezoelectric layer stacked in the thickness direction, and, the resonance frequency f of the piezoelectric MEMS speaker, the effective area S of the diaphragm, and the total thickness t of the piezoelectric layer satisfy the following relational expression: And, the relational expression satisfies the following constraint conditions: y > 1.67e12, where keff is the square root of the effective electromechanical coupling coefficient keff^2, ε33 represents the relative dielectric constant of the piezoelectric layer, and ρ represents the density of the piezoelectric layer.

2. The piezoelectric MEMS speaker according to claim 1, characterized in that, the relational expression satisfies the following constraint condition: y > 1e13.

3. The piezoelectric MEMS speaker according to claim 1, characterized in that, the ratio of the single-layer thickness of the electrode layer to the total thickness of the piezoelectric layer is 0.5 or less.

4. The piezoelectric MEMS speaker according to claim 1, characterized in that, the material of the piezoelectric layer is aluminum nitride or doped aluminum nitride.

5. The piezoelectric MEMS speaker according to claim 4, characterized in that, the effective electromechanical coupling coefficient keff^2 is 0.3% - 10%.

6. The piezoelectric MEMS speaker according to claim 4, characterized in that, the relative dielectric constant ε33 of the piezoelectric layer is 9 - 15, and the density ρ is 3000 - 4000 kg / m^3.

7. The piezoelectric MEMS speaker according to claim 4, characterized in that, when the total thickness t of the piezoelectric layer < 1 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint conditions: 1.0258 * f^2 - 3.3670 * 10^11 * S > 0.

8. The piezoelectric MEMS speaker according to claim 4, characterized in that, when the total thickness t of the piezoelectric layer < 0.2 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint conditions: 9.1291 * f^2 - 1.6835 * 10^12 * S > 0.

9. The piezoelectric MEMS speaker according to claim 1, characterized in that, the material of the piezoelectric layer is lead zirconate titanate or doped lead zirconate titanate.

10. The piezoelectric MEMS speaker according to claim 9, characterized in that, the effective electromechanical coupling coefficient keff^2 is 4% - 30%.

11. The piezoelectric MEMS speaker according to claim 9, characterized in that, the relative dielectric constant ε33 of the piezoelectric layer is 450 - 1200, and the density ρ is 7000 - 8000 kg / m^3.

12. The piezoelectric MEMS speaker according to claim 9, characterized in that, when the total thickness t of the piezoelectric layer < 1 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint conditions: 6.6480*f^2 - 1.4815*10^10*S > 0。 13. According to the piezoelectric MEMS speaker as claimed in claim 9, wherein when the total thickness t of the piezoelectric layer is less than 0.6 μm, the resonance frequency f of the piezoelectric MEMS speaker and the effective area S of the diaphragm satisfy the following constraint conditions: 1.1102*f^2 - 2.4741*10^9*S > 0。 14. According to the piezoelectric MEMS speaker as claimed in claim 1, wherein the diaphragm includes electrode layers, piezoelectric layers, electrode layers, piezoelectric layers, and electrode layers stacked in sequence from top to bottom in the thickness direction.

15. According to the piezoelectric MEMS speaker as claimed in claim 1, wherein the diaphragm further includes a structural layer, and the diaphragm includes a structural layer, an electrode layer, a piezoelectric layer, and an electrode layer stacked in sequence from top to bottom in the thickness direction.

16. According to the piezoelectric MEMS speaker as claimed in any one of claims 1 to 15, wherein a cavity is formed between the upper part of the diaphragm and the substrate in the thickness direction, the effective area S of the diaphragm is the area of the region where the diaphragm and the cavity overlap in the thickness direction.

17. According to the piezoelectric MEMS speaker as claimed in claim 16, wherein slits are formed in the region of the diaphragm corresponding to the cavity.

18. According to the piezoelectric MEMS speaker as claimed in claim 16, wherein at least a part of the cavity in the thickness direction is formed as the sound cavity of the piezoelectric MEMS speaker.

19. According to the piezoelectric MEMS speaker as claimed in claim 16, wherein the diaphragm includes a plurality of sub - diaphragms, and the effective area S of the diaphragm is the sum of the areas of the regions where the plurality of sub - diaphragms and the cavity overlap in the thickness direction.

20. According to the piezoelectric MEMS speaker as claimed in claim 16, wherein the cavity includes a plurality of sub - cavities, and the effective area S of the diaphragm is the area of the region where the diaphragm and the plurality of sub - cavities overlap in the thickness direction.

21. According to the piezoelectric MEMS speaker as claimed in claim 16, wherein the diaphragm includes a plurality of sub - diaphragms, the cavity includes a plurality of sub - cavities, the plurality of sub - cavities correspond to the plurality of sub - diaphragms respectively, the effective area S of the diaphragm is the sum of the areas of the regions where the plurality of sub - diaphragms and the corresponding sub - cavities overlap in the thickness direction.

22. A manufacturing method of a piezoelectric MEMS speaker, characterized in that, The manufacturing method includes: forming a diaphragm on the upper side of the substrate in the thickness direction, the diaphragm including an electrode layer and a piezoelectric layer stacked in the thickness direction, wherein, the resonance frequency f of the piezoelectric MEMS speaker, the effective area S of the diaphragm, and the total thickness t of the piezoelectric layer satisfy the following relational formula: And, the relational formula satisfies the following constraint conditions: y > 1.67e12, wherein, keff is the square root of the effective electromechanical coupling coefficient keff^2, ε33 represents the relative dielectric constant of the piezoelectric layer, and ρ represents the density of the piezoelectric layer.

23. An electronic device, characterized in that, The electronic device includes the piezoelectric MEMS speaker according to any one of claims 1 to 21.

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