MEMS loudspeaker structure and electrical product

Abstract

The embodiment of the invention provides an MEMS loudspeaker structure and an electrical product, and relates to the technical field of semiconductors. According to the MEMS loudspeaker structure, at least one supporting layer is added among a plurality of voltage layers, and the appropriate thickness of the piezoelectric layer and the appropriate thickness of the supporting layer are selected according to the relation between the thickness of the piezoelectric layer and the thickness of the supporting layer, so that the output sound pressure level and the power sensitivity of the MEMS loudspeaker can be improved under the condition that the bandwidth is not lost, and the sound pressure output efficiency of the MEMS loudspeaker is improved; the performance and the resonance frequency of the MEMS loudspeaker are ensured at the same time; and the rigidity of the device is increased, and the reliability and the manufacturing consistency of the device are improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a MEMS speaker structure and electrical products. Background Art

[0002] At present, piezoelectric MEMS (Micro-Electro-Mechanical System) speakers are easy to manufacture in large quantities and have advantages that traditional speakers cannot have, such as compatibility with CMOS. However, the problem encountered in its current development is that it is difficult to obtain high sound efficiency. Therefore, the goal that piezoelectric MEMS speakers need to achieve is to obtain a higher output sound pressure level with a smaller driving voltage, and to obtain a higher output sound pressure level with a smaller driving power.

[0003] In recent years, with the development of piezoelectric MEMS speaker technology, some solutions to this problem have emerged, such as mechanically decoupling the complete diaphragm into a multi-petal structure to obtain a higher degree of freedom, or using cantilever beams on all sides to drive the central diaphragm to achieve a piston vibration mode.

[0004] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art just because they are described in the background technology section of this document. Summary of the invention

[0005] The inventors found that the essence of the above existing solutions is to shift the resonant frequency forward as a price. If the resonant frequency is too far forward, the speaker system will enter the inertial control area too early, which will greatly reduce the high-frequency response of the speaker and reduce the bandwidth. However, since the existing solutions cannot simultaneously meet the trade-off between power sensitivity and resonant frequency (bandwidth), and there is no unified evaluation standard, power sensitivity and resonant frequency cannot be guaranteed at the same time. In addition, the diaphragm of the MEMS speaker is thin and has a low equivalent mechanical stiffness. Therefore, it is easy to break during use, especially when impacted, and the device reliability is low.

[0006] In order to solve at least one of the above problems existing in the prior art, embodiments of the present application provide a MEMS speaker structure and an electrical product.

[0007] According to a first aspect of an embodiment of the present application, a MEMS speaker structure is provided, comprising: a plurality of piezoelectric layers; and at least one supporting layer formed between the plurality of voltage layers in a thickness direction of the MEMS speaker structure, wherein the thickness of the supporting layer is related to the thickness of the piezoelectric layer.

[0008] According to a second aspect of the embodiment of the present application, the performance index of the MEMS speaker structure is determined according to the thickness of the piezoelectric layer and the thickness of the supporting layer.

[0009] According to a third aspect of the embodiment of the present application, the material of the piezoelectric layer is single crystal PZT or polycrystalline PZT or doped PZT, and the material of the support layer is silicon.

[0010] According to a fourth aspect of the embodiment of the present application, the performance indicator is a figure of merit FOM, log(FOM) represents the sound pressure level at a preset resonant frequency, and the log(FOM) is greater than 112.

[0011] According to a fifth aspect of an embodiment of the present application, the log(FOM) is greater than 118.

[0012] According to a sixth aspect of the embodiment of the present application, the total thickness of the plurality of piezoelectric layers is less than or equal to 1 micron, and the thickness of the piezoelectric layer is less than or equal to 0.5 micron.

[0013] According to a seventh aspect of the embodiment of the present application, the total thickness of the plurality of piezoelectric layers is less than or equal to 0.5 micrometers, and the thickness of the piezoelectric layer is less than or equal to 0.25 micrometers.

[0014] According to an eighth aspect of the embodiment of the present application, the thickness of the support layer is greater than or equal to 0.1 times the thickness of the piezoelectric layer, and less than or equal to 1.5 times the thickness of the piezoelectric layer.

[0015] According to a ninth aspect of the embodiment of the present application, the thickness of the support layer is greater than or equal to 0.25 times the thickness of the piezoelectric layer, and less than or equal to 0.75 times the thickness of the piezoelectric layer.

[0016] According to a tenth aspect of the embodiment of the present application, the thickness of the support layer is greater than or equal to 0.01 micrometers and less than or equal to 0.15 micrometers.

[0017] According to an eleventh aspect of the embodiment of the present application, the thickness of the support layer is greater than or equal to 0.025 micrometers and less than or equal to 0.075 micrometers.

[0018] According to a twelfth aspect of the embodiment of the present application, the material of the piezoelectric layer is single crystal AlN or polycrystalline AlN or doped AlN, and the supporting layer is an electrode layer or the material of the supporting layer is silicon.

[0019] According to the thirteenth aspect of the embodiment of the present application, the performance indicator is a figure of merit FOM, log(FOM) represents the sound pressure level at a preset resonant frequency, and the log(FOM) is greater than 86.3.

[0020] According to the fourteenth aspect of the embodiment of the present application, the log(FOM) is greater than 88.4.

[0021] According to the fifteenth aspect of the embodiment of the present application, the total thickness of the plurality of piezoelectric layers is less than or equal to 0.4 micrometers, and the thickness of the piezoelectric layer is less than or equal to 0.2 micrometers.

[0022] According to the sixteenth aspect of the embodiment of the present application, the total thickness of the plurality of piezoelectric layers is less than or equal to 0.2 micrometers, and the thickness of the piezoelectric layer is less than or equal to 0.1 micrometers.

[0023] According to a seventeenth aspect of the embodiment of the present application, the thickness of the support layer is greater than or equal to 0.02 micrometers and less than or equal to 0.25 micrometers.

[0024] According to an eighteenth aspect of the embodiment of the present application, the thickness of the support layer is greater than or equal to 0.05 micrometers and less than or equal to 0.2 micrometers.

[0025] According to the nineteenth aspect of the embodiment of the present application, the MEMS speaker structure includes two piezoelectric layers and a supporting layer located between the two piezoelectric layers.

[0026] According to the twentieth aspect of the embodiment of the present application, the thicknesses of the multiple piezoelectric layers are different, or the thicknesses of some of the multiple piezoelectric layers are different.

[0027] According to the twenty-first aspect of the embodiment of the present application, the MEMS speaker structure further includes a plurality of electrode layers, which are alternately arranged with the piezoelectric layer and the support layer in a thickness direction of the MEMS speaker structure.

[0028] According to the twenty-second aspect of the embodiment of the present application, the multiple electrode layers include a lower electrode, an intermediate electrode and an upper electrode, and the intermediate electrode serves as the supporting layer.

[0029] According to a twenty-third aspect of the embodiments of the present application, an electrical product is provided, comprising at least one MEMS speaker structure according to any one of the first to twenty-second aspects of the embodiments of the present application.

[0030] One of the beneficial effects of the embodiments of the present application is that at least one supporting layer is added between multiple voltage layers, and through the relationship between the thickness of the piezoelectric layer and the thickness of the supporting layer, a suitable thickness of the piezoelectric layer and the supporting layer is selected, which can improve the output sound pressure level and power sensitivity of the MEMS speaker without losing bandwidth, and improve its output sound pressure efficiency, that is, simultaneously ensure the performance and resonant frequency of the MEMS speaker; and increase the stiffness of the device, thereby improving the reliability and manufacturing consistency of the device.

[0031] Furthermore, the performance indicators of the MEMS speaker structure are determined according to the thickness of the piezoelectric layer and the thickness of the supporting layer, which can effectively improve the quasi-steady-state response sound pressure level of the speaker without changing the resonant frequency. At the same time, it also has a better high-frequency response than many existing solutions, that is, a better full-bandwidth response.

[0032] Furthermore, the total thickness of the multiple piezoelectric layers is less than or equal to 1 micron, and the thickness of the piezoelectric layer is less than or equal to 0.5 micron, which can improve the performance of the MEMS speaker.

[0033] Furthermore, the thickness of the support layer is greater than or equal to 0.1 times the thickness of the piezoelectric layer and less than or equal to 1.5 times the thickness of the piezoelectric layer, which can improve the performance and reliability of the MEMS speaker.

[0034] Furthermore, the thickness of the support layer is greater than or equal to 0.25 times the thickness of the piezoelectric layer and less than or equal to 0.75 times the thickness of the piezoelectric layer, which can further improve the performance and reliability of the MEMS speaker.

[0035] Furthermore, the thickness of the support layer is greater than or equal to 0.01 micrometers and less than or equal to 0.15 micrometers, thereby improving the performance of the MEMS speaker, reducing the difficulty of manufacturing, and improving the reliability of the MEMS speaker.

[0036] Furthermore, the thickness of the support layer is greater than or equal to 0.025 micrometers and less than or equal to 0.075 micrometers, thereby further improving the performance of the MEMS speaker, reducing the difficulty of manufacturing, and improving the reliability of the MEMS speaker.

[0037] Furthermore, the total thickness of the multiple piezoelectric layers is less than or equal to 0.2 micrometers, and the thickness of the piezoelectric layer is less than or equal to 0.1 micrometers, which can improve the performance of the MEMS speaker.

[0038] Furthermore, the thickness of the support layer is greater than or equal to 0.02 micrometers and less than or equal to 0.25 micrometers, thereby improving the performance of the MEMS speaker, reducing the difficulty of manufacturing, and improving the reliability of the MEMS speaker.

[0039] Furthermore, the thickness of the support layer is greater than or equal to 0.05 micrometers and less than or equal to 0.2 micrometers, thereby further improving the performance of the MEMS speaker, reducing the difficulty of manufacturing, and improving the reliability of the MEMS speaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Many aspects of the present application may be better understood with reference to the following drawings. The components in the drawings are not drawn to scale, but are only for the purpose of illustrating the principles of the present application. For the convenience of illustrating and describing some parts of the present application, corresponding parts in the drawings may be enlarged or reduced. The elements and feature information described in one drawing or one embodiment of the present application may be combined with the elements and feature information shown in one or more other drawings or embodiments. In addition, in the drawings, similar reference numerals represent corresponding components in several drawings and may be used to indicate corresponding components used in more than one embodiment.

[0041] In the attached picture:

[0042] Figure 1 is a cross-sectional view of an implementation of the MEMS speaker structure of Example 1 of the present application;

[0043] Figure 2 Yes Figure 1 A simplified cross-sectional view of the MEMS speaker structure shown;

[0044] Figure 3 is a cross-sectional view of another implementation of the MEMS speaker structure of Example 1 of the present application;

[0045] Figure 4 is a figure of merit distribution diagram of the MEMS speaker structure at different thicknesses according to Example 1 of the present application;

[0046] Figure 5 is a curve diagram showing the relationship between FOM and thickness value in the MEMS speaker structure of Example 1 of the present application;

[0047] Figure 6 is a curve diagram of FOM and equivalent rigidity in the MEMS speaker structure of Example 1 of the present application;

[0048] Figure 7 is a curve diagram showing the relationship between piezoelectric layers and support layers of different thicknesses and FOM in the MEMS speaker structure of Example 1 of the present application;

[0049] Figure 8 is a cross-sectional view of an implementation of the MEMS speaker structure of Example 2 of the present application;

[0050] Fig. 9 is a cross-sectional view of another implementation of the MEMS speaker structure of Example 2 of the present application;

[0051] Fig.10 is the figure of merit distribution of the MEMS speaker structure at different thicknesses of Example 2 of the present application;

[0052] Fig.11 is a curve diagram showing the relationship between FOM and thickness value in the MEMS speaker structure of Example 2 of the present application;

[0053] Fig.12 is a curve diagram of FOM and equivalent rigidity in the MEMS speaker structure of Example 2 of the present application;

[0054] Fig.13 It is a curve diagram of the relationship between piezoelectric layers of different thicknesses, intermediate electrodes and FOM in the MEMS speaker structure of Example 2 of the present application. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the embodiments of the present application more clear, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings. Here, 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.

[0056] In the embodiments of the present application, the terms "first", "second", "upper", "lower", etc. are used to distinguish different elements in terms of title, but do not indicate the spatial arrangement or time order of these elements, etc., 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. The terms "comprising", "including", "having", etc. refer to the presence of the stated features, elements, components or components, but do not exclude the presence or addition of one or more other features, elements, components or components.

[0057] In the embodiments of the present application, the singular forms "a", "the", etc. include plural forms and should be broadly understood as "a kind" or "a type" rather than being limited to the meaning of "one"; in addition, the term "said" should be understood to include both singular and plural forms, unless the context clearly indicates otherwise. In addition, the term "according to" should be understood as "at least in part according to...", and the term "based on" should be understood as "at least in part based on...", unless the context clearly indicates otherwise.

[0058] The preferred embodiments of the present application will be described below with reference to the accompanying drawings.

[0059] Example 1

[0060] Embodiment 1 of the present application provides a MEMS speaker structure.

[0061] In the embodiment of the present application, the MEMS speaker structure is also referred to as a piezoelectric MEMS speaker structure, that is, a MEMS speaker structure including a piezoelectric layer.

[0062] In an embodiment of the present application, the MEMS speaker structure includes: multiple piezoelectric layers; and at least one supporting layer, which is formed between the multiple voltage layers in the thickness direction of the MEMS speaker structure, and the thickness of the supporting layer is related to the thickness of the piezoelectric layer.

[0063] In the embodiments of the present application, the stacking direction of each layer (i.e., the thickness direction of each layer) is referred to as the vertical direction or the up-down direction or the vertical direction, and the direction extending along the length direction of each layer is referred to as the horizontal direction or the left-right direction or the lateral direction.

[0064] In the MEMS speaker structure, the number of piezoelectric layers can be two or more, and the number of supporting layers can be one or more. The specific number of piezoelectric layers and supporting layers can be determined according to actual conditions, and the embodiments of the present application do not limit this.

[0065] In addition, the thicknesses of the plurality of piezoelectric layers may be the same or different.

[0066] In the embodiment of the present application, the MEMS speaker structure may further include a plurality of electrode layers, which are arranged alternately with the piezoelectric layer and the support layer in the thickness direction of the MEMS speaker structure.

[0067] Different implementations of Example 1 of the present application are described below based on different numbers of piezoelectric layers and support layers.

[0068] First, the structure of the MEMS speaker including two piezoelectric layers and a supporting layer is described.

[0069] Figure 1 It is a cross-sectional view of an implementation of the MEMS speaker structure of Example 1 of the present application.

[0070] like Figure 1 As shown, the MEMS speaker structure includes: a piezoelectric layer 101 and a piezoelectric layer 103, a support layer 102, and a plurality of electrode layers 104, 105, 106, 107. The plurality of electrode layers 104, 105, 106, 107 are arranged alternately with the piezoelectric layer 101, the piezoelectric layer 103 and the support layer 102 in the thickness direction.

[0071] In order to more clearly illustrate the MEMS speaker structure 100 , the thicknesses of the plurality of electrode layers 104 , 105 , 106 , and 107 are neglected, thereby obtaining a simplified structure of the MEMS speaker structure 100 . Figure 2 Yes Figure 1 The MEMS speaker structure shown is a simplified cross-sectional view.

[0072] like Figure 2 As shown, the simplified MEMS speaker structure 100 only includes a piezoelectric layer 101 , a piezoelectric layer 103 and a supporting layer 102 located between the two piezoelectric layers 101 , 103 .

[0073] The piezoelectric layer 101 is arranged on one side of the support layer 102 in the thickness direction, and the piezoelectric layer 103 is arranged on the other side of the support layer 102 in the thickness direction. A MEMS speaker structure having a support layer 102 is formed between the two piezoelectric layers. Figure 1 and Figure 2 In the embodiment, the thickness of the piezoelectric layer 101 and the piezoelectric layer 103 are the same, and the thickness of the support layer 102 is related to the thickness of the piezoelectric layer 101 or the piezoelectric layer 103 .

[0074] Figure 3 FIG. 1 is a cross-sectional view of another embodiment of the MEMS speaker structure of Example 1 of the present application. Figure 3 As shown, the MEMS speaker structure 100' includes a piezoelectric layer 101 and a piezoelectric layer 103 of different thicknesses, and a support layer 102 is formed between the piezoelectric layer 101 and the piezoelectric layer 103, and the thickness of the support layer 102 is related to the thickness of the piezoelectric layer 101 and the piezoelectric layer 103. In addition, Figure 3 The structure shown also ignores the electrode layers.

[0075] In this way, at least one supporting layer 102 is formed between the voltage layer 101 and the piezoelectric layer 103 in the thickness direction of the MEMS speaker structure. By selecting appropriate thicknesses of the piezoelectric layer 101 and the piezoelectric layer 103 and the thickness of the supporting layer 102, the output sound pressure level and power sensitivity of the MEMS speaker can be improved without losing bandwidth, and the efficiency of its output sound pressure can be improved, that is, the performance and resonant frequency of the MEMS speaker are guaranteed at the same time; and the rigidity of the device is increased, and the reliability and manufacturing consistency of the device are improved.

[0076] As described above, the thickness of the support layer 102 is related to the thickness of the piezoelectric layer 101 and the piezoelectric layer 103, so that the appropriate thickness can be determined. Figure 1 The thickness correlation of the piezoelectric layer 101, the piezoelectric layer 103 and the support layer 102 in the MEMS speaker structure shown in the figure is described. However, the determination of the thickness correlation in the embodiment of the present application is not limited to the following method.

[0077] In some embodiments, the performance index of the MEMS speaker structure is determined according to the thickness of the piezoelectric layer 101 and the piezoelectric layer 103 and the thickness of the support layer 102 .

[0078] For example, the performance index of the MEMS speaker structure is the figure of merit FOM. The larger the figure of merit FOM, the better the sound effect of the MEMS speaker. The quasi-steady-state response sensitivity P (the output sound pressure of the low and medium frequencies) and the resonant frequency f jointly affect the response of the entire working bandwidth of the MEMS speaker, and the product of the two can be used to evaluate the overall performance of a speaker. Therefore, for a single piezoelectric MEMS diaphragm, the product of the sound pressure level output per unit area under unit voltage excitation (a certain low frequency, such as 100Hz) and the first-order resonant frequency of the speaker diaphragm is defined as the figure of merit FOM of the speaker.

[0079] In the embodiment of the present application, the figure of merit FOM is mainly related to the thickness of the piezoelectric layer and the thickness of the support layer, for example, it can be obtained according to the following formula (1):

[0080]

[0081] Where γ represents the specific heat ratio of air; P0 represents the atmospheric pressure; S represents the diaphragm area; E P represents the Young's modulus of the piezoelectric layer material; d 31 represents the piezoelectric coefficient of the piezoelectric layer material; U represents the driving voltage; V 711 represents the volume of the artificial ear; ρ P represents the density of the piezoelectric layer material; ρ n represents the density of the support layer; t p represents the thickness of the piezoelectric layer; t n Indicates the thickness of the support layer.

[0082] It can be seen from formula (1) that the figure of merit FOM is related to the material of the piezoelectric layer and the material of the supporting layer.

[0083] The following is a specific description based on some examples of materials for making the piezoelectric layer and the support layer. However, the embodiments of the present application do not limit the materials of the piezoelectric layer and the support layer.

[0084] In some embodiments, the material of the piezoelectric layer 101 and the piezoelectric layer 103 is single crystal lead zirconate titanate (Pb(Zr1-xTiO3), PZT) or polycrystalline lead zirconate titanate (PZT) or doped lead zirconate titanate (PZT), and the material of the support layer 102 is silicon Si.

[0085] For example, a support layer 102 made of silicon is added between the piezoelectric layers 101 and 103. The preferred thickness of the silicon layer as the support layer 102 can be determined by the merit FOM formula, wherein the PZT merit FOM can be obtained by substituting the specific heat ratio of air, atmospheric pressure, Young's modulus of the piezoelectric layer 101 material, piezoelectric coefficient of the piezoelectric layer 101 material, driving voltage, simulated ear volume, density of the piezoelectric layer 101 material and density of the support layer 102 into the merit FOM formula (1) to obtain the following PZT merit FOM formula (2):

[0086]

[0087] Where S represents the diaphragm area; t p represents the thickness of the piezoelectric layer; t n Indicates the thickness of the support layer.

[0088] For ease of understanding, the PZT figure of merit FOM can be logarithmically expressed according to the following formula (3) to express the sound pressure level at a certain resonant frequency:

[0089] log(FOM)=20*log 10 (P*f) (3)

[0090] By changing the thickness of the piezoelectric layer 101, the piezoelectric layer 103 and the silicon material support layer 102, different PZT merit FOMs can be obtained, thereby optimizing the thickness of multiple piezoelectric layers 101, 103 and the support layer 102 to obtain a high PZT merit FOM and improve device performance.

[0091] In this way, the performance indicators of the MEMS speaker structure are determined according to the thickness of the piezoelectric layers 101 and 103 and the thickness of the supporting layer 102. It can effectively improve the quasi-steady-state response sound pressure level of the speaker without changing the resonant frequency. At the same time, it also has a better high-frequency response than many existing solutions, that is, a better full-bandwidth response.

[0092] Figure 4 This is a figure of merit distribution diagram of the MEMS speaker structure at different thicknesses according to Example 1 of the present application.

[0093] For example, Figure 4 As shown, according to the above formula (3), in order to make the figure of merit (FOM) exceed a certain value, a certain thickness range (such as Figure 4 Therefore, preferably, log(FOM) is greater than 112; further, preferably, log(FOM) is greater than 118.

[0094] like Figure 2 and Figure 4As shown, the piezoelectric layer 101 and the piezoelectric layer 103 have the same thickness. Taking this structure as an example, the piezoelectric layer 101 is described.

[0095] The FOM value when the thickness of the piezoelectric layer 101 (single-layer PZT piezoelectric layer) is less than or equal to 0.5 microns is greater than the FOM value when the thickness of the piezoelectric layer 101 is greater than 0.5 microns. That is to say, for example, when the thickness of the piezoelectric layer 101 is less than or equal to 0.5 microns, the FOM value increases; on the other hand, when the thickness of the piezoelectric layer 101 is less than or equal to 0.5 microns, a reasonable choice of the thickness of the supporting layer 102 can improve the FOM value to a certain extent, while when the thickness of the piezoelectric layer 101 is greater than 0.5 microns, the change in the thickness of the supporting layer 102 has little effect on the FOM value.

[0096] Therefore, in this embodiment, preferably, the thickness of the piezoelectric layer 101 is less than or equal to 0.5 micrometers, and the sum of the thicknesses of the piezoelectric layer 101 and the piezoelectric layer 103 is less than or equal to 1 micrometer.

[0097] In some embodiments, Figure 4 As shown, the FOM value when the thickness of the piezoelectric layer 101 is less than or equal to 0.25 microns is greater than the FOM value when the thickness of the piezoelectric layer 101 is greater than 0.25 microns; on the other hand, when the thickness of the piezoelectric layer 101 is less than or equal to 0.25 microns, the reasonable selection of the thickness of the supporting layer 102 has a greater impact on improving the FOM value than when the thickness of the piezoelectric layer 101 is greater than 0.25 microns. Therefore, in this embodiment, it is preferred that when the thickness of the piezoelectric layer 101 is less than or equal to 0.25 microns, the sum of the thicknesses of the multiple piezoelectric layers 101 and 103 is less than or equal to 0.5 microns.

[0098] Therefore, in some embodiments, the total thickness of the piezoelectric layer 101 and the piezoelectric layer 103 is less than or equal to 1 micron, and the thickness of the piezoelectric layer 101 and the piezoelectric layer 103 is less than or equal to 0.5 micron. More preferably, the total thickness of the piezoelectric layer 101 and the piezoelectric layer 103 is less than or equal to 0.5 micron, and the thickness of the piezoelectric layer 101 and the piezoelectric layer 103 is also less than or equal to 0.25 micron. Based on the distribution of the figure of merit FOM under different piezoelectric layer and support layer thicknesses, the preferred scheme of the thickness of the piezoelectric layer 101, the piezoelectric layer 103 and the support layer 102 is obtained.

[0099] In this way, the total thickness of the multiple piezoelectric layers is less than or equal to 1 micron, and the thickness of the piezoelectric layer is less than or equal to 0.5 micron, which can improve the performance of the MEMS speaker.

[0100] Figure 5 It is a curve diagram of the relationship between FOM and thickness value in the MEMS speaker structure of Example 1 of the present application.

[0101] like Figure 5As shown, the thickness of the support layer 102 is preferably equal to about half of the thickness of the piezoelectric layer 101. For example, when the thickness of the piezoelectric layer 101 is 0.3 microns, the thickness of the support layer 102 is 0.15 microns. Preferably, the thickness of the support layer 102 is greater than 0.1 times the thickness of the piezoelectric layer 101 and less than 1.5 times the thickness of the piezoelectric layer 101.

[0102] In some embodiments, the thickness of the support layer 102 is greater than or equal to 0.25 times the thickness of the piezoelectric layer 101 , and less than or equal to 0.75 times the thickness of the piezoelectric layer 101 .

[0103] Preferably, the thickness of the support layer 102 is greater than or equal to 0.25 times the thickness of the piezoelectric layer 101 , and less than or equal to 0.75 times the thickness of the piezoelectric layer 101 .

[0104] like Figure 5 As shown, when the thickness of the piezoelectric layer 101 is 0.1 microns, it can be seen that as the thickness of the supporting layer 102 increases from 0.075 microns to 0.45 microns, the value of the increased figure of merit Δlog (FOM) gradually increases. That is to say, the smaller the thickness of the piezoelectric layer 101, the larger the Δlog (FOM) corresponding to the increased thickness of the supporting layer 102.

[0105] Therefore, in some embodiments, the thickness of the support layer 102 is greater than or equal to 0.1 times the thickness of the piezoelectric layer 101, and less than or equal to 1.5 times the thickness of the piezoelectric layer 101. Thus, the specific thicknesses of the piezoelectric layer and the support layer can be determined based on the thickness relationship between the piezoelectric layer and the support layer to obtain a high merit, which can improve the performance and reliability of the MEMS speaker.

[0106] Furthermore, in some embodiments, the thickness of the support layer 102 is greater than or equal to 0.25 times the thickness of the piezoelectric layer 101, and less than or equal to 0.75 times the thickness of the piezoelectric layer 101. Thus, by obtaining a more accurate relationship between the thickness of the support layer and the piezoelectric layer, the performance and reliability of the MEMS speaker can be further improved.

[0107] Figure 6 It is a curve diagram of FOM and equivalent rigidity in the MEMS speaker structure of Example 1 of the present application.

[0108] like Figure 6 As shown, when the thickness of the piezoelectric layer 101 is 0.1 micron, the thickness of the support layer 102 is changed, and the FOM and equivalent stiffness are calculated. Figure 6 It can be seen that when the thickness of the support layer 102 is selected to be in the range of 0.01 micrometers to 0.15 micrometers, the equivalent rigidity value increases from 1 to 6 and then gradually decreases, and the FOM value gradually increases.

[0109] More specifically, when the thickness of the support layer 102 is 0.025 micrometers, the equivalent stiffness is 3, and then continues to increase. When the thickness of the support layer 102 increases to 0.075 micrometers, the equivalent stiffness reaches a peak value of 6, and the equivalent stiffness value begins to drop as the thickness of the support layer 102 continues to increase. Therefore, when the thickness of the support layer 102 ranges from 0.025 micrometers to 0.075 micrometers, the equivalent stiffness value is a preferred value.

[0110] Thus, in some embodiments, the thickness of the support layer 102 is greater than or equal to 0.01 micrometers and less than or equal to 0.15 micrometers, thereby improving the performance of the MEMS speaker, reducing the manufacturing difficulty, and improving the reliability of the MEMS speaker.

[0111] In some embodiments, the thickness of the support layer 102 is greater than or equal to 0.025 micrometers and less than or equal to 0.075 micrometers, thereby further improving the performance of the MEMS speaker, reducing the manufacturing difficulty, and improving the reliability of the MEMS speaker.

[0112] As described above, the thickness of the piezoelectric layers may be the same or different. In some embodiments, for the case where the piezoelectric layers have different thicknesses, for example, the thicknesses of the multiple piezoelectric layers are different, or the thicknesses of some of the multiple piezoelectric layers are different.

[0113] Figure 7 It is a relationship curve diagram between piezoelectric layers and support layers of different thicknesses and FOM in the MEMS speaker structure of Example 1 of the present application.

[0114] like Figure 3 and Figure 7 As shown, the thickness of the piezoelectric layer 101 and the piezoelectric layer 103 are different, and adding the support layer 102 can still achieve the same effect as the above embodiment with the same piezoelectric layer thickness.

[0115] For example, a support layer 102 made of silicon is formed between a piezoelectric layer 101 and a piezoelectric layer 103 of different thicknesses, and the thicknesses of the piezoelectric layer 101 and the piezoelectric layer 103 can be adjusted to, respectively, when the thickness of the piezoelectric layer 101 is 0.5 microns and the thickness of the piezoelectric layer 103 is 0.5 microns; when the thickness of the piezoelectric layer 101 is 0.4 microns and the thickness of the piezoelectric layer 103 is 0.6 microns; when the thickness of the piezoelectric layer 101 is 0.3 microns and the thickness of the piezoelectric layer 103 is 0.7 microns; the relationship curve graphs of the piezoelectric layers 101, 103 and the support layer 102 of different thicknesses and the FOM have the same growth trend of the FOM values ​​as the relationship curve graphs of the piezoelectric layers 101, 103 and the support layer 102 of the same thicknesses and the FOM. That is to say, the thickness of the support layer 102 maintains a certain correlation with the total thickness of the piezoelectric layer 101 and the piezoelectric layer 103, which can ensure a high FOM value, and at this time the total thickness of the piezoelectric layer 101 and the piezoelectric layer 103 is less than or equal to 1 micron.

[0116] It can be seen from the above embodiments that at least one supporting layer 102 is formed between the voltage layer 101 and the piezoelectric layer 103 in the thickness direction of the MEMS speaker structure. By selecting appropriate piezoelectric layer and supporting layer thicknesses based on the relationship between the thicknesses of the piezoelectric layer 101 and the piezoelectric layer 103 and the thickness of the supporting layer 102, the output sound pressure level and power sensitivity of the MEMS speaker can be improved without losing bandwidth, thereby improving the efficiency of its output sound pressure, that is, ensuring the performance and resonant frequency of the MEMS speaker at the same time; and increasing the stiffness of the device, thereby improving the reliability and manufacturing consistency of the device.

[0117] Example 2

[0118] Embodiment 2 of the present application also provides a MEMS speaker structure. Different from Embodiment 1, the material of the piezoelectric layer is aluminum nitride AlN (Aluminum Nitride), and the supporting layer is an electrode layer or the material of the supporting layer is silicon, that is, the supporting layer is the same material as the electrode layer or the material of the supporting layer is silicon. For the same structure as Embodiment 1, please refer to the description in Embodiment 1, and no further description will be given here.

[0119] Figure 8 FIG. 2 is a cross-sectional view of an implementation of the MEMS speaker structure of Example 2 of the present application. Figure 8 The MEMS speaker structure 200 shown includes: a plurality of electrodes, a lower electrode 202 , a middle electrode 204 , an upper electrode 206 , and piezoelectric layers 203 , 205 .

[0120] In some embodiments, when the thickness of the piezoelectric layers 203 and 205 is relatively large, the smaller the thickness of the middle electrode 204 located in the middle, the better the performance of the device. Increasing the thickness of the middle electrode 204 will reduce the performance of the device. Conversely, when the thickness of the piezoelectric layers 203 and 205 is relatively small, appropriately increasing the thickness of the middle electrode 204 can improve the performance of the speaker.

[0121] Fig. 9 is a cross-sectional view of another embodiment of the MEMS speaker structure of Example 2 of the present application. Figure 8 The MEMS speaker structure shown, Fig. 9 The MEMS speaker structure shown is more specific.

[0122] like Fig. 9 As shown, the MEMS speaker structure 200 ′ includes: a passivation layer 201 , a lower electrode 202 , a piezoelectric layer 203 , a middle electrode 204 as a support layer, a piezoelectric layer 205 , and an upper electrode 206 .

[0123] In some embodiments, the passivation layer 201 may also be replaced by a seed layer.

[0124] The material of the piezoelectric layer 203 and the piezoelectric layer 205 is AlN, for example, the material of the piezoelectric layer 203 and the piezoelectric layer 205 is single crystal AlN or polycrystalline AlN or doped AlN, and the material of the intermediate electrode 204 as a support layer is the same as that of other electrode layers.

[0125] Taking the material of the piezoelectric layer 203 and the piezoelectric layer 205 as single crystal AlN as an example, the specific heat ratio of air, atmospheric pressure, Young's modulus of the piezoelectric layer 203 material, piezoelectric coefficient of the piezoelectric layer 203 material, driving voltage, simulated ear volume, density of the piezoelectric layer 203 material and density of the intermediate electrode 204 are substituted into the figure of merit FOM formula (1), so that the AlN figure of merit FOM formula can be obtained as follows:

[0126]

[0127] Where S represents the diaphragm area; t p represents the thickness of the piezoelectric layer; t n Indicates the thickness of the support layer.

[0128] For ease of understanding, the AlN figure of merit FOM can be logarithmically expressed according to the following formula (5) to express the sound pressure level at a certain resonant frequency:

[0129] log(FOM)=20*log 10 (P*f) (5)

[0130] In this way, by changing the thickness of the piezoelectric layer 203, the piezoelectric layer 205 and the intermediate electrode 204, different AlN figure of merit FOMs can be obtained, so that the thickness of multiple piezoelectric layers 203, 205 and the intermediate electrode 204 can be optimized to obtain a high AlN figure of merit FOM and improve device performance.

[0131] Fig.10 This is the figure of merit distribution of the MEMS speaker structure of Example 2 of the present application at different thicknesses.

[0132] For example, Fig.10 According to the above formula (5), in order to make the figure of merit (FOM) exceed a certain value, a certain thickness range (such as Fig.10 Therefore, preferably, log(FOM) is greater than 86.3; further, preferably, log(FOM) is greater than 88.4.

[0133] like Fig. 9 and Fig.10 As shown, the piezoelectric layer 203 and the piezoelectric layer 205 have the same thickness. Taking this structure as an example, the piezoelectric layer 203 is now described.

[0134] In some embodiments, the FOM value when the thickness of the piezoelectric layer 203 is less than or equal to 0.2 microns is greater than the FOM value when the thickness of the piezoelectric layer 203 is greater than 0.2 microns; on the other hand, when the thickness of the piezoelectric layer 203 is less than or equal to 0.2 microns, the FOM value of the thickness of the intermediate electrode 204 is improved by the local preferred value, and when the thickness of the piezoelectric layer 203 is greater than 0.2 microns, the smaller the thickness of the intermediate electrode 204, the better, and there is no local preferred value, and the smaller the thickness of the intermediate electrode 204, the worse the reliability.

[0135] Therefore, in this embodiment, preferably, the thickness of the piezoelectric layer 203 is less than or equal to 0.2 micrometers, and the total thickness of the piezoelectric layer 203 and the piezoelectric layer 205 is less than or equal to 0.4 micrometers.

[0136] In some embodiments, Fig. 9 and Fig.10 As shown, the FOM value when the thickness of the piezoelectric layer 203 is less than or equal to 0.1 micron is greater than the FOM value when the thickness of the piezoelectric layer 205 is greater than 0.1 micron; on the other hand, when the thickness of the piezoelectric layer is less than or equal to 0.1 micron, the reasonable selection of the thickness of the intermediate electrode 204 has a greater influence on improving the FOM value than the influence of the change in the thickness of the intermediate electrode 204 when the thickness of the piezoelectric layer 203 is greater than 0.1 micron. Therefore, in this embodiment, it is preferred that the thickness of the piezoelectric layer 203 is less than or equal to 0.1 micron, and the total thickness of the piezoelectric layer 203 and the piezoelectric layer 205 is less than or equal to 0.2 micron.

[0137] In some embodiments, the thickness of the upper electrode 206 and the lower electrode 202 is 0.01 microns, and the thickness of the middle electrode 204 is scanned. When the thickness of the piezoelectric layer 203 exceeds 0.15 microns, the thickness of the middle electrode 204 is preferably negative twelve times the thickness of the middle electrode 204. The preferred thickness of the middle electrode 204 is related to the thickness of the upper electrode 206 and the thickness of the seed layer 201. The thickness of the seed layer 201 is adjusted, and the thickness of the piezoelectric layer 203 and the piezoelectric layer 205 are both less than or equal to 0.2 microns, which is the preferred solution and is still valid.

[0138] Thus, in some embodiments, the total thickness of the piezoelectric layer 203 and the piezoelectric layer 205 is less than or equal to 0.4 microns, and the thickness of the piezoelectric layer 203 and the piezoelectric layer 205 is less than or equal to 0.2 microns. More preferably, the total thickness of the piezoelectric layer 203 and the piezoelectric layer 205 is less than or equal to 0.2 microns, and the thickness of the piezoelectric layer 203 and the piezoelectric layer 205 is less than or equal to 0.1 microns. Based on the distribution of the figure of merit FOM under different film thicknesses, the preferred scheme of the thickness of the piezoelectric layer 203, the piezoelectric layer 205 and the intermediate electrode 204 is obtained.

[0139] In this way, the total thickness of the multiple piezoelectric layers is less than or equal to 0.2 micrometers, and the thickness of the piezoelectric layer is less than or equal to 0.1 micrometers, which can improve the performance of the MEMS speaker.

[0140] Fig.11 is a curve diagram showing the relationship between FOM and thickness value in the MEMS speaker structure of Example 2 of the present application; Fig.12 It is a curve diagram of FOM and equivalent rigidity in the MEMS speaker structure of Example 2 of the present application.

[0141] Fig.11 As shown in the figure, the smaller the thickness of the piezoelectric layer 203 is, the greater the increase Δlog(FOM) value of the device figure of merit (FOM) corresponding to the increase in the thickness of the intermediate electrode 204 is; when the thickness of the piezoelectric layer 203 is 0.05 microns, the thickness of the intermediate electrode 204 is preferably 0.14 microns. As the thickness of the piezoelectric layer 203 increases, the preferred value of the thickness of the intermediate electrode 204 decreases. It can be seen that when the thickness of the piezoelectric layer 203 is between 0.05 microns and 0.2 microns, the preferred thickness of the intermediate electrode 204 is in the range of 0.14 microns to 0.02 microns, and when the thickness of the piezoelectric layer exceeds 0.2 microns, the preferred value of the thickness of the intermediate electrode 204 is close to zero, and the reliability is reduced.

[0142] like Fig.12 As shown, when the thickness of the piezoelectric layer 203 is 0.1 micron, the thickness of the middle electrode 204 is changed, and the FOM and equivalent stiffness are calculated. It can be seen that when the thickness of the middle electrode 204 increases from 0 micron to 0.1 micron, the equivalent stiffness value increases from 1 to 7, and the FOM value is gradually increasing. As the thickness of the middle electrode 204 increases, the equivalent stiffness value gradually decreases.

[0143] Thus, when the thickness of the middle electrode 204 is selected to be between 0.02 micrometers and 0.25 micrometers, a good equivalent rigidity value and FOM value can be obtained. More preferably, when the thickness of the middle electrode 204 is between 0.05 micrometers and 0.2 micrometers, a higher equivalent rigidity value and FOM value can be obtained.

[0144] Thus, in some embodiments, the thickness of the middle electrode 204 is greater than or equal to 0.02 micrometers and less than or equal to 0.25 micrometers, thereby improving the performance of the MEMS speaker, reducing the manufacturing difficulty, and improving the reliability of the MEMS speaker.

[0145] In some embodiments, the thickness of the middle electrode 204 is greater than or equal to 0.05 micrometers and less than or equal to 0.2 micrometers, thereby further improving the performance of the MEMS speaker, reducing the manufacturing difficulty, and improving the reliability of the MEMS speaker.

[0146] Fig.13 It is a curve diagram of the relationship between piezoelectric layers of different thicknesses, intermediate electrodes and FOM in the MEMS speaker structure of Example 2 of the present application.

[0147] In some embodiments, the thicknesses of the piezoelectric layer 203 and the piezoelectric layer 205 are different, and increasing the thickness of the intermediate electrode 204 as a support layer can still achieve the same effect as the above embodiment.

[0148] An intermediate electrode 204 is formed as a supporting layer between the piezoelectric layers 203 and 205 of different thicknesses. The thicknesses of the piezoelectric layers 101 and 103 are, respectively, when the thickness of the piezoelectric layer 203 is 0.1 micron and the thickness of the piezoelectric layer 205 is 0.1 micron; when the thickness of the piezoelectric layer 203 is 0.08 micron and the thickness of the piezoelectric layer 205 is 0.12 micron; when the thickness of the piezoelectric layer 203 is 0.06 micron and the thickness of the piezoelectric layer 205 is 0.14 micron; the thickness of the intermediate electrode 204 maintains a certain correlation with the total thickness of the piezoelectric layer 203 and the piezoelectric layer 205, ensuring a high FOM value.

[0149] For example, Fig.13As shown in , when the thickness of the piezoelectric layer 203 is 0.06 microns and the thickness of the piezoelectric layer 205 is 0.14 microns, the total thickness of the piezoelectric layer 203 and the piezoelectric layer 205 is 0.2 microns, and at this time, when the thickness of the intermediate electrode 204 is greater than or equal to 0.05 microns and less than or equal to 0.2 microns, the relationship curve of the piezoelectric layers 203, 205, the intermediate electrode 204 and the FOM with different thicknesses is consistent with the FOM value growth trend of the relationship curve of the piezoelectric layers 203, 205, the intermediate electrode 204 and the FOM with the same thickness. The thickness of the intermediate electrode 204 maintains a certain correlation with the total thickness of the piezoelectric layer 203 and the piezoelectric layer 205, ensuring a high FOM value.

[0150] It can be seen from the above embodiments that an intermediate electrode 204 is formed between the voltage layers 203 and 205 in the thickness direction of the MEMS speaker structure. By selecting appropriate thicknesses of the piezoelectric layers 203 and 205 and the intermediate electrode 204, the output sound pressure level and power sensitivity of the MEMS speaker can be improved without losing bandwidth, thereby improving the efficiency of its output sound pressure, that is, ensuring the performance and resonant frequency of the MEMS speaker at the same time; and increasing the stiffness of the device, thereby improving the reliability and manufacturing consistency of the device.

[0151] Example 3

[0152] Embodiment 3 of the present application further provides an electrical product, which comprises at least one MEMS speaker structure described in Embodiment 1 or Embodiment 2.

[0153] In some embodiments, the electrical product may be various devices to which the MEMS speaker structure can be applied, such as wireless stereo (TWS) headphones, mobile phones, hearing aids, VR glasses, speaker glasses, smart watches, tablets, computers, or vehicles.

[0154] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A MEMS speaker structure, characterized in that: The MEMS speaker structure comprises: multiple piezoelectric layers; at least one supporting layer formed between the plurality of voltage layers in a thickness direction of the MEMS speaker structure, The thickness of the support layer is related to the thickness of the piezoelectric layer.

2. The MEMS speaker structure according to claim 1, characterized in that: The performance index of the MEMS speaker structure is determined according to the thickness of the piezoelectric layer and the thickness of the supporting layer.

3. The MEMS speaker structure according to claim 2, characterized in that: The material of the piezoelectric layer is single crystal PZT or polycrystalline PZT or doped PZT. The material of the support layer is silicon.

4. The MEMS speaker structure according to claim 3, characterized in that: The performance index is the figure of merit FOM, log(FOM) represents the sound pressure level at a preset resonant frequency, The log(FOM) is greater than 112.

5. The MEMS speaker structure according to claim 4, characterized in that: The log(FOM) is greater than 118.

6. The MEMS speaker structure according to claim 3, characterized in that: The total thickness of the plurality of piezoelectric layers is less than or equal to 1 micron, The thickness of the piezoelectric layer is less than or equal to 0.5 micrometers.

7. The MEMS speaker structure according to claim 6, characterized in that: The total thickness of the plurality of piezoelectric layers is less than or equal to 0.5 micrometers, The thickness of the piezoelectric layer is less than or equal to 0.25 micrometers.

8. The MEMS speaker structure according to claim 3, characterized in that: The thickness of the support layer is greater than or equal to 0.1 times the thickness of the piezoelectric layer and less than or equal to 1.5 times the thickness of the piezoelectric layer.

9. The MEMS speaker structure according to claim 8, characterized in that: The thickness of the support layer is greater than or equal to 0.25 times the thickness of the piezoelectric layer and less than or equal to 0.75 times the thickness of the piezoelectric layer.

10. The MEMS speaker structure according to claim 3, characterized in that: The thickness of the support layer is greater than or equal to 0.01 micrometers and less than or equal to 0.15 micrometers.

11. The MEMS speaker structure according to claim 10, characterized in that: The thickness of the support layer is greater than or equal to 0.025 micrometers and less than or equal to 0.075 micrometers.

12. The MEMS speaker structure according to claim 2, characterized in that: The material of the piezoelectric layer is single crystal AlN or polycrystalline AlN or doped AlN. The support layer is an electrode layer or the material of the support layer is silicon.

13. The MEMS speaker structure according to claim 12, characterized in that: The performance index is the figure of merit FOM, log(FOM) represents the sound pressure level at a preset resonant frequency, The log(FOM) is greater than 86.

3.

14. The MEMS speaker structure according to claim 13, characterized in that: The log(FOM) is greater than 88.

4.

15. The MEMS speaker structure according to claim 12, characterized in that: The total thickness of the plurality of piezoelectric layers is less than or equal to 0.4 micrometers, The thickness of the piezoelectric layer is less than or equal to 0.2 micrometers.

16. The MEMS speaker structure according to claim 15, characterized in that: The total thickness of the plurality of piezoelectric layers is less than or equal to 0.2 micrometers, The thickness of the piezoelectric layer is less than or equal to 0.1 micrometer.

17. The MEMS speaker structure according to claim 12, characterized in that: The thickness of the support layer is greater than or equal to 0.02 micrometers and less than or equal to 0.25 micrometers.

18. The MEMS speaker structure according to claim 17, characterized in that: The thickness of the support layer is greater than or equal to 0.05 micrometers and less than or equal to 0.2 micrometers.

19. The MEMS speaker structure according to any one of claims 1 to 18, characterized in that: The MEMS speaker structure includes two piezoelectric layers and a supporting layer located between the two piezoelectric layers.

20. The MEMS speaker structure according to any one of claims 1 to 18, characterized in that: The thicknesses of the plurality of piezoelectric layers are different from each other, or the thicknesses of some of the plurality of piezoelectric layers are different from each other.

21. The MEMS speaker structure according to any one of claims 1 to 18, characterized in that: The MEMS speaker structure further includes: A plurality of electrode layers are arranged alternately with the piezoelectric layer and the support layer in the thickness direction of the MEMS speaker structure.

22. The MEMS speaker structure according to claim 21, characterized in that: The plurality of electrode layers include a lower electrode, an intermediate electrode and an upper electrode, Wherein, the intermediate electrode serves as the supporting layer.

23. An electrical product, characterized in that: The electrical product comprises the MEMS speaker structure according to any one of claims 1 to 22.

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