Acoustic device

Abstract

The application relates to the technical field of acoustic sensors, in particular to an acoustic device. The acoustic device comprises a functional layer, a material layer and a substrate layer which are arranged in a stack; the material layer is located between the functional layer and the substrate layer, and the functional layer comprises a piezoelectric layer and a patterned electrode layer. The patterned electrode layer makes the acoustic device equivalent to a series circuit of multiple RC modules. The thickness of the material layer arranged adjacent to the patterned electrode layer is greater than 220 nm, and the potential of the substrate layer is suspended so that the parasitic capacitance is reduced. In the acoustic device in which the patterned electrode layer is equivalent to a series circuit of multiple RC modules, the thickness of the material layer and the potential suspension structure of the substrate layer effectively suppress the parasitic capacitance effect inside the acoustic device, significantly reduce the interference of the parasitic capacitance on signal transmission, thereby improving the transmission efficiency and signal quality of the acoustic device, and realizing optimization of key performance indicators such as sensitivity and signal-to-noise ratio of the acoustic device.

Description

Technical Field

[0001] This application relates to the field of acoustic sensor technology, and in particular to an acoustic device. Background Technology

[0002] A piezoelectric MEMS microphone is a miniature acoustic sensor based on Micro-Electro-Mechanical Systems (MEMS) and the piezoelectric effect, characterized by its small size, low power consumption, and high reliability. Its core principle is to utilize the charge generated by piezoelectric materials under the influence of sound waves, converting it into an electrical signal. Compared to traditional capacitive MEMS microphones, piezoelectric microphones require no bias voltage, have stronger resistance to electromagnetic interference, and are suitable for high-temperature or harsh environments.

[0003] In existing acoustic devices with series diaphragm structures, the proportion of parasitic capacitance tends to increase. A higher proportion of parasitic capacitance leads to a decrease in the effective output voltage of the acoustic device, resulting in problems such as decreased microphone sensitivity, deterioration of the signal-to-noise ratio, increased noise levels, and nonlinear distortion. Summary of the Invention

[0004] The purpose of this application is to provide an acoustic device that can effectively suppress the parasitic capacitance effect inside the acoustic device, significantly reduce the interference of parasitic capacitance on signal transmission, thereby improving the transmission efficiency and signal quality of the acoustic device, and optimizing key performance indicators such as sensitivity and signal-to-noise ratio of the acoustic device.

[0005] An acoustic device, comprising:

[0006] A stacked functional layer, the functional layer including a piezoelectric layer and a patterned electrode layer;

[0007] A material layer is disposed adjacent to the patterned electrode layer;

[0008] A substrate layer is disposed adjacent to the material layer;

[0009] The patterned electrode layer enables the acoustic device to be equivalent to a series circuit of multiple RC modules;

[0010] The material layer disposed adjacent to the patterned electrode layer has a thickness greater than 220 nm and the substrate layer is suspended at a potential to reduce parasitic capacitance.

[0011] In one embodiment, the functional layer includes: a piezoelectric layer and two electrode layers respectively stacked on top of and below the piezoelectric layer.

[0012] In one embodiment, the functional layer includes: two piezoelectric layers and three electrode layers respectively stacked on top, in the middle and bottom of the piezoelectric layers.

[0013] In one embodiment, the substrate layer comprises a silicon substrate, the substrate layer being actively levitated or passively levitated.

[0014] In one embodiment, the substrate layer includes a silicon substrate and an insulating layer; the silicon substrate is disposed between the material layer and the insulating layer such that the substrate layer is levitated by an active potential, or...

[0015] The substrate layer includes: a silicon substrate; the silicon substrate is connected to an external insulating layer so that the substrate layer is passively levitated.

[0016] In one embodiment, a first cavity is provided in the material layer, and a second cavity is provided in the substrate layer;

[0017] The functional layer, the first cavity, and the second cavity are coaxially arranged, and the bottom of the functional layer is adjacent to the first cavity.

[0018] In one embodiment, the first cavity and the second cavity have the same parameters, or the first cavity and the second cavity have different parameters.

[0019] In one embodiment, the functional layer further includes: a support structure and a plurality of electrical connectors;

[0020] The support structure supports at least two alternately stacked electrode layers and one piezoelectric layer;

[0021] Each of the electrical connectors is distributed on the surface of the support structure.

[0022] In one embodiment, the functional layer includes: one or more cantilever beam structures; and multiple cantilever beam structures are arranged at intervals around the central axis of the functional layer.

[0023] In one embodiment, the acoustic device further includes: a support layer;

[0024] The support layer is a single-layer material or a multi-layer material;

[0025] The support layer is disposed between the functional layer and the material layer.

[0026] This application has at least the following advantages or beneficial effects:

[0027] 1. The acoustic device provided in this application, through a patterned electrode layer, makes the acoustic device equivalent to a series circuit of multiple RC modules. Furthermore, by controlling the thickness of the material layer to be greater than 220 nm and the substrate layer potential to be suspended, parasitic capacitance is reduced. When the substrate layer potential is suspended, it automatically couples to the average potential value of the upper boundary. This minimizes the sum of the potential differences between the electrode surfaces of the upper and lower electrodes of the material layer (which can be a thermo-oxidative layer or a silicon dioxide layer), thus minimizing the parasitic capacitance of the acoustic device.

[0028] 2. The acoustic device provided in this application generates an equivalent circuit model corresponding to the acoustic device through a preset substrate layer connection method. Based on the initial device parameters of other layers in the acoustic device except the target layer and the equivalent circuit model, the output capacitance change curve of the acoustic device is generated, and the intrinsic capacitance value of the diaphragm in a functional region is determined. Thus, the thickness of the target layer of the acoustic device can be determined based on the intrinsic capacitance value and the output capacitance change curve. The thickness of the target layer in the acoustic device can be accurately determined, improving the device performance of the acoustic device. At the same time, it can also perform rapid prototype iteration and shorten the research and development cycle. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 A cross-sectional schematic diagram of the acoustic device provided in this application;

[0031] Figure 2 A side view schematic diagram of the acoustic device provided in this application;

[0032] Figure 3 A perspective schematic diagram of the acoustic device provided in this application;

[0033] Figure 4a A planar schematic diagram of a diaphragm in the acoustic device provided in this application;

[0034] Figure 4b A planar schematic diagram of another type of diaphragm in the acoustic device provided in this application;

[0035] Figure 4c This is a planar schematic diagram of yet another type of diaphragm in the acoustic device provided in this application;

[0036] Figure 4d This is a planar schematic diagram of another type of diaphragm in the acoustic device provided in this application;

[0037] Figure 5 A circuit diagram that represents an ideal circuit model of an acoustic device provided in the prior art;

[0038] Figure 6 The equivalent circuit provided in the prior art for the complete eight-lobed diaphragm case;

[0039] Figure 7 The equivalent circuit provided in the prior art when there is only one diaphragm lobe;

[0040] Figure 8 A simulated electric field distribution diagram under a side view of an acoustic device provided in the prior art;

[0041] Figure 9 A simulated electric field distribution diagram under a top view of an acoustic device provided in the prior art;

[0042] Figure 10 A flowchart illustrating the process of determining the thickness range in the acoustic device provided in this application;

[0043] Figure 11 A schematic diagram of the equivalent circuit of the acoustic device provided in this application under the substrate grounding connection method;

[0044] Figure 12 A schematic diagram of the equivalent circuit of the acoustic device provided in this application under the substrate layer levitation connection method;

[0045] Figure 13 This is a schematic diagram of the capacitive output of an acoustic device under different connection methods.

[0046] Figure 14 A flowchart illustrating the process of determining the substrate connection method in the acoustic device provided in this application;

[0047] Figure 15 A scatter plot of the output capacitance of an acoustic device provided in this application;

[0048] Figure 16 Another cross-sectional schematic diagram of the acoustic device provided in this application;

[0049] Figure 17 Another side view schematic diagram of the acoustic device provided in this application;

[0050] Figure 18 Another side view schematic diagram of the acoustic device provided in this application;

[0051] Figure 19 Another side view schematic diagram of the acoustic device provided in this application;

[0052] Figure 20Another planar schematic diagram of the diaphragm in the acoustic device provided in this application;

[0053] Figure 21 Another cross-sectional schematic diagram of the acoustic device provided in this application.

[0054] Figure label:

[0055] Functional layer - 100; Material layer - 200; Substrate layer - 300; Silicon substrate layer - 302; Insulating layer - 303; First cavity - 201; Second cavity - 301; Diaphragm - 101; Diaphragm support structure - 102; Electrical connector - 103; Electrode layer - 1011; Piezoelectric layer - 1012; Slit - 1013; Functional area - 1014; Support layer - 400. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0057] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0058] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0059] In the description of this application, it should be noted that the terms "center," "upper," "lower," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. In addition, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0060] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0061] In the description of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0062] In existing acoustic devices with series diaphragm structures, the proportion of parasitic capacitance tends to increase. A higher proportion of parasitic capacitance leads to a decrease in the effective output voltage of the acoustic device, resulting in problems such as decreased microphone sensitivity, deterioration of the signal-to-noise ratio, increased noise levels, and nonlinear distortion.

[0063] Based on the aforementioned problems, this application proposes an acoustic device. By positioning the parasitic capacitance generation locations in the functional layer, material layer, and substrate layer of the stacked acoustic device, and setting the thickness of the material layer within a preset thickness range (which can be set to a thickness greater than 220 nm for a material layer of 200 nm), and setting the substrate layer to be electrically suspended, the parasitic capacitance generated by the material layer and substrate layer is reduced, thereby lowering the total parasitic capacitance of the acoustic device. This ensures the transmission efficiency and quality of the acoustic device during signal transmission, improves the sensitivity and other key capabilities of the acoustic device, and enhances the signal-to-noise ratio of the acoustic device.

[0064] It is understood that the acoustic device provided in this application can be applied to any scenario where sound waves need to be converted into electrical signals, such as as a microphone device, a speaker device, or other device in an acoustic sensor.

[0065] The acoustic device provided in this application will be described in detail below. Figure 1 This is a cross-sectional schematic diagram of the acoustic device provided in this application. Figure 2 This is a side view schematic diagram of the acoustic device provided in this application. Figure 3 A perspective schematic diagram of the acoustic device provided in this application, with reference to... Figure 1 , Figure 2 as well as Figure 3 As shown, the acoustic device provided in this application includes: a functional layer 100, a material layer 200, and a substrate layer 300 stacked together. Among them, Figure 3 A perspective view of the three-dimensional structure of an acoustic device. Figure 3The acoustic device shown includes two piezoelectric layers 1012 spaced apart and three electrode layers (the electrode layers are too thin to be shown in the three-dimensional diagram at this angle). For a detailed view of the functional layer comprising the two piezoelectric layers 1012 and the three spaced electrode layers 1011, please refer to [reference needed]. Figure 17 ).

[0066] Classified by function, functional layer 100 includes a diaphragm 101 for receiving sound wave pressure and generating vibration, thereby inducing a piezoelectric effect and generating an electrical signal. Diaphragm 101 may include a complete diaphragm composed of eight valves, four valves, or other numbers of valves. Classified by structure, functional layer 100 includes a piezoelectric layer (…). Figure 17 The piezoelectric layer 1012 and the patterned electrode layer (in the middle) Figure 17 The functional layer 100 may include one piezoelectric layer 1012 and two patterned electrode layers 1011, or two piezoelectric layers 1012 and three patterned electrode layers 1011, or three piezoelectric layers 1012 and four patterned electrode layers 1011, or other numbers of piezoelectric layers 1012 and other numbers of patterned electrode layers 1011. The patterned electrode layers 1011 enable the acoustic device to be equivalent to a series circuit of multiple RC modules. The series circuit of multiple RC modules can be understood as a series circuit of multiple parallel RC modules.

[0067] Material layer 200 is located between functional layer 100 and substrate layer 300. The thickness of material layer 200 is greater than 220 nm and substrate layer 300 is suspended at a potential, so as to reduce parasitic capacitance.

[0068] The acoustic device in this embodiment has a patterned electrode layer that makes the acoustic device equivalent to a series circuit of multiple RC modules. Furthermore, by controlling the thickness of the material layer 200 to be greater than 220 nm and the potential of the substrate layer 300 to be suspended, the parasitic capacitance is reduced.

[0069] Specifically, in this embodiment, the patterned electrode layer 1011 enables the acoustic device to be equivalent to a series circuit of multiple RC modules. When the substrate layer 300 is suspended at a potential, it will automatically couple to the average potential value of the upper boundary. In this way, the sum of the potential difference between the electrode surfaces of the upper and lower electrodes of the material layer (which can be set as a thermo-oxidative layer or a silicon dioxide layer) 200 is minimized, and the parasitic capacitance of the acoustic device is minimized.

[0070] In this embodiment, the patterned electrode layer allows the acoustic device to be equivalent to a series circuit of multiple RC modules. The thickness of the material layer 200 adjacent to the patterned electrode layer is greater than 220 nm, and the substrate layer 300 is levitated to reduce parasitic capacitance. In the acoustic device where the patterned electrode layer is equivalent to a series circuit of multiple RC modules, the thickness design of the material layer 200 and the levitated structure of the substrate layer 300 effectively suppress the parasitic capacitance effect inside the acoustic device, significantly reducing the interference of parasitic capacitance on signal transmission, thereby improving the transmission efficiency and signal quality of the acoustic device and optimizing key performance indicators such as sensitivity and signal-to-noise ratio of the acoustic device.

[0071] In one embodiment, the acoustic device involved in this application includes a series circuit of n RC modules, and the output capacitance of the acoustic device is... , Due to parasitic capacitance It acts directly on the output capacitor. Therefore, for the acoustic device with a series circuit containing multiple RC modules involved in this application, its parasitic capacitance... The effect will be more significant (i.e.) occupy (The ratio is relatively large). Where n is a positive integer greater than or equal to 2.

[0072] The functional layer 100 includes a diaphragm 101, a first cavity 201 is disposed in the material layer 200, and a second cavity 301 is disposed in the substrate layer 300; the substrate layer 300 is electrically levitated, and the electrical levitation includes: active electrical levitation and passive electrical levitation.

[0073] It is worth noting that substrate 300 potential levitation refers to a state in which substrate 300 satisfies charge isolation and levitation stability. Specifically, potential levitation includes active potential levitation and passive potential levitation.

[0074] Active potential levitation can be understood as the connection between acoustic devices and external circuits via an insulating medium. Active potential levitation, while ensuring the necessary physical connection, blocks charge flow through the high impedance characteristics of the insulating medium.

[0075] In this context, passive potential levitation can be understood as the inclusion of an insulating medium in the substrate layer 300 of the acoustic device, so as to achieve charge isolation and levitation stability through the insulating medium.

[0076] The diaphragm 101, the first cavity 201 and the second cavity 301 are coaxially arranged, and the bottom of the diaphragm 101 is adjacent to the first cavity 201.

[0077] Optionally, a diaphragm 101 is disposed along the center of the functional layer 100. Figure 4a , Figure 4b , Figure 4c , Figure 4d Here are four planar schematic diagrams of the diaphragm in the acoustic device provided in this application, with reference to Figure 4a , Figure 4b , Figure 4c , Figure 4d As shown, in the plane where the diaphragm 101 is located, the shape of the diaphragm 101 can be a rectangle, a circle or any polygon, etc., where the geometric shape can be a whole composed of a complete geometric shape, or it can be a collection of multiple sub-geometric shapes obtained by dividing a certain geometric shape.

[0078] Optionally, when the shape of the diaphragm 101 is obtained by a set of multiple sub-geometry patterns, the gaps between the multiple sub-geometry patterns, i.e. slits, penetrate the functional layer 100 in the direction perpendicular to the functional layer 100.

[0079] For example, consider a diaphragm 101 as a polygon divided along its sides. The functional layer 100 of the polygon includes multiple sets of corresponding sub-electrodes. These multiple sets of corresponding sub-electrodes make the acoustic device equivalent to a series circuit of multiple RC modules. The sub-electrodes may include: upper and lower sub-electrodes, upper, middle and lower sub-electrodes, or other layers of sub-electrodes.

[0080] For example, Figure 3 The example shown uses a diaphragm 101 as a regular octagon divided along its sides. The functional layer 100 of the regular octagon includes at least eight sets of corresponding upper and lower sub-electrodes. These at least eight sets of corresponding upper and lower sub-electrodes make the acoustic device equivalent to a series circuit of eight RC modules. In other embodiments, the regular octagonal structure includes at least eight sets of corresponding upper, middle, and lower sub-electrodes. These at least eight sets of corresponding upper, middle, and lower sub-electrodes make the acoustic device equivalent to a series circuit of eight RC modules.

[0081] Optionally, the material layer 200 includes a first cavity 201 and a material support structure, wherein the material support structure is the other part of the material layer 200 besides the first cavity 201, and is used for support.

[0082] For example, the material support structure can also be used to enhance mechanical properties, for example, it can be made of silicon oxide, silicon nitride or silicon carbide, which can improve the stiffness of the substrate.

[0083] Optionally, the substrate layer 300 includes a second cavity 301 and a substrate support structure, wherein the substrate support structure is the other part of the substrate layer 300 besides the second cavity 301, and is used to fix and support the overall structure of the acoustic device provided in this application.

[0084] The first cavity 201 and the second cavity 301 are connected. Both the first cavity 201 and the second cavity 301 are used to provide vibration space. The diaphragm 101 is used to receive sound wave pressure and generate vibration, thereby triggering the piezoelectric effect and generating an electrical signal.

[0085] Optionally, the parameters of the first cavity 201, the second cavity 301, and the diaphragm 101 can be the same or different, and can be adjusted according to the actual situation. These parameters may include size, shape, circumference, and radius, etc.

[0086] It is understood that the functional layer 100 may have at least one piezoelectric layer and multiple electrode layers arranged alternately according to the hierarchical structure. When the sound wave acts on the diaphragm 101 in the form of air pressure change, the diaphragm 101 vibrates up and down. When the diaphragm 101 vibrates, the piezoelectric layer in the diaphragm 101 deforms. Due to the existence of the positive piezoelectric effect, the piezoelectric layer generates charge during the deformation process. The charge generated by the piezoelectric layer is collected by the electrode layers above and below the piezoelectric layer, so that the deformation generated by the vibration can be converted into electrical energy for output.

[0087] Alternatively, when an alternating voltage is applied to the electrode layer of the functional layer 100, an electric field is formed. The piezoelectric layer in the functional layer 100 is polarized under the action of the electric field, and the internal lattice structure undergoes directional deformation. As a result of the existence of the inverse piezoelectric effect, the diaphragm 101 is driven to vibrate periodically up and down. With the vibration of the diaphragm 101, the surrounding air is further pushed, generating sound waves.

[0088] Meanwhile, by adjusting the material layer 200 and the substrate layer 300, the material layer can suppress parasitic capacitance in the acoustic device. This adjustment includes modifying the thickness and connection method of the material layer 200 and the substrate layer 300.

[0089] For example, the functional layer may include a piezoelectric layer and two electrode layers.

[0090] For example, the functional layer may include two piezoelectric layers and three electrode layers. The upper and lower electrodes are of equal potential (e.g., the upper and lower electrodes are positive, and the middle electrode is negative). Based on the deformation that occurs during vibration, the acoustic device involved in this embodiment can integrate the potentials of the two piezoelectric layers. The potential of the acoustic device with two piezoelectric layers is twice that of the single-layer piezoelectric layer; the capacitance of the acoustic device with two piezoelectric layers is twice that of the single-layer piezoelectric layer.

[0091] In this embodiment, through multi-layer structure optimization design, a functional layer, a material layer, and a substrate layer are sequentially stacked in the acoustic device. The location of parasitic capacitance generation is precisely located in the material layer, and the size of the parasitic capacitance is determined to decrease as the thickness of the material layer increases. This allows for effective suppression of the parasitic capacitance effect inside the acoustic device by adjusting the thickness of the material layer to a preset range and designing the substrate layer as a potential-floating structure. This reduces the parasitic capacitance in the acoustic device, thereby significantly reducing the interference of parasitic capacitance on signal transmission, improving the transmission efficiency and signal quality of the acoustic device, and optimizing key performance indicators such as sensitivity and signal-to-noise ratio of the acoustic device.

[0092] The following explains the sources of the two parasitic capacitances found by the inventors in the prior art.

[0093] On the one hand, in existing technologies, such as Figures 1-3 The acoustic device shown is equivalent to, for example, Figure 5 The ideal circuit model is shown. The ideal circuit model is constructed by connecting one or more parallel resistors R0 and capacitors C0 in series to form the equivalent circuit of the functional area, and introducing an equivalent total resistance R1 into the main circuit at the output or input terminals to form the ideal device equivalent circuit. Thus, the inventors, combining data measured in actual experiments, obtained the initial parameters of each device and the first output capacitance value through simulation. However, all acoustic devices in reality have parasitic capacitance, so the magnitude of the parasitic capacitance contained in the aforementioned first output capacitance value can be verified experimentally. The inventors removed multiple series-parallel R0 and C0 connections, retaining only one parallel R0 and C0 connection for testing, obtaining the third output capacitance value. By comparing the data of the first capacitance value and the third capacitance value, the inventors made a preliminary estimate of the parasitic capacitance (e.g., ...). Figure 6 and Figure 7 The size of Cp in the above. Figure 5 , Figure 6 and Figure 7 In the circuit diagram, green represents electronic components, and red represents the connecting lines between electronic components.

[0094] Furthermore, the inventors determined the location of the parasitic capacitance Cp. The location of Cp was obtained through processing the electric field lines during simulation. Figure 8 and Figure 9 As shown, the inventors discovered that the electric field lines are generally distributed between the diaphragm functional area and the Si substrate. Figure 8 The distribution of electric field lines is shown in the side view. Figure 8The direction of the black arrows represents the direction of the electric field, and the length of the black arrows represents the electric field strength. During the simulation, on the one hand, due to the uneven potential of the diaphragm, the electric field lines will bend at the edges of the diaphragm, the steps of the substrate, or the abrupt changes in structure, thus forming a reverse component locally; on the other hand, because there are areas with large and small potential differences, when viewed laterally from a cross section, there will be more and denser arrows in areas with larger potential differences, and relatively fewer arrows in areas with relatively smaller potential differences. Figure 8 In areas where the electric field points upwards, there exists a right angle on the model at the interface between the diaphragm (functional layer) and the insulating layer of the acoustic device. Therefore, the electric field lines in this part... Figure 8 The orientation displayed in the image will be distorted. Figure 8 The main focus is on the direction of most electric field lines. Because image processing magnifies the electric field lines, some otherwise subtle distorted electric field lines are amplified, making them appear more prominent. Figure 8 It will be observed / recorded (e.g.) Figure 8 (The shorter black arrows in the middle) In fact, these electric field lines are ignored as outliers when conducting the conclusion analysis. Figure 9 The distribution of electric field lines is shown in the top view. Figure 9 Regions 1 and 2 in the image have been enlarged. Figure 9 The leftmost rectangle encloses areas 1 and 2. (Example) Figure 9 As shown by the yellow dashed line, in the horizontal plane, electric field lines are only distributed at the edge of the diaphragm electrode and in the area where the surface electrode and the Si substrate projection coincide. Inside the diaphragm electrode and on the Si substrate, except near the metal electrodes, there are almost no electric field lines.

[0095] Through the Figure 8 and Figure 9 Based on observation of the contents, it was determined that the parasitic capacitance Cp is mainly composed of the Si substrate and the diaphragm, i.e., the metal electrode at the edge of the diaphragm. Therefore, the specific structure of the parasitic capacitance Cp is as follows: the diaphragm and its edge can be abstracted as one of the plates of the parasitic capacitance Cp, and the Si substrate is the other plate of Cp, with the silicon oxide in it serving as the dielectric. Thus, the inventors have confirmed that the material layer is an important source of parasitic capacitance.

[0096] On the other hand, in existing technologies, to avoid storing large charges during device testing, which could lead to test abnormalities or electrostatic breakdown causing device failure, the test platform's stage is grounded during experiments. However, the inventors of this application discovered a significant difference in the output capacitance values ​​obtained when performing normal grounding tests and substrate potential floating tests on the test device during actual testing. The output capacitance value when the substrate potential is floating is less than the output capacitance value when the substrate is grounded. Therefore, the inventors concluded that grounding the device substrate introduces additional parasitic capacitance.

[0097] The following describes the specific process of determining the preset thickness range.

[0098] As one possible implementation, the inventors suspend the substrate potential and, under the premise of suspending the substrate potential, further determine the preset thickness range of the material layer 200 (the thickness of the material layer is greater than 220nm). Figure 10 This is a flowchart illustrating the process of determining the thickness range in the acoustic device provided in this application, with reference to... Figure 10 As shown, the process of determining the thickness range specifically includes:

[0099] S501. Obtain the initial device parameters of the acoustic device.

[0100] It is understandable that the initial device parameters of the acoustic device can be obtained, and the device parameters corresponding to the material layer in the initial device parameters can be adjusted based on the initial device parameters to achieve the effect of suppressing parasitic capacitance.

[0101] Optionally, the initial device parameters of the acoustic device can be obtained from the user's pre-configured or set parameters.

[0102] Optionally, an equivalent circuit model of the acoustic device can be obtained. Taking a diaphragm as a regular octagon divided along each side as an example, the equivalent circuit model can be a circuit with eight pairs of parallel resistors and capacitors connected in series. Under high-frequency AC excitation, the theoretical first output capacitance value can be obtained, and the second output capacitance value of the acoustic device can be obtained through simulation testing. The first capacitance value of a capacitor in the equivalent circuit model can be calculated through the second output capacitance value.

[0103] Optionally, the seven pairs of parallel capacitors and resistors in the equivalent circuit model can be removed, and the third output capacitor value can be obtained through simulation testing. The third output capacitor value is then compared with the first capacitor value. If the deviation between the third output capacitor value and the first capacitor value is greater than a preset threshold, it can be determined that the acoustic device has parasitic capacitance under the initial device parameters.

[0104] The initial device parameters include: functional layer parameters, material layer parameters, substrate layer parameters, and the equivalent resistance and equivalent capacitance values ​​of the acoustic devices. Specifically, the functional layer parameters may include the material and thickness of each piezoelectric layer and electrode layer within the functional layer; the material layer parameters may include the material and thickness of the material layers; and the substrate layer parameters may include the material and thickness of the substrate layer.

[0105] S502. Generate the equivalent circuit model corresponding to the acoustic device according to the preset substrate connection method.

[0106] Optionally, the preset substrate connection method can be a substrate floating connection or a substrate ground connection. Optionally, Figure 11 The equivalent circuit diagram of the acoustic device provided in this application under the substrate grounding connection method is shown in the figure below. Figure 11 As shown, taking the substrate layer connection method as the substrate layer ground connection method as an example, the equivalent circuit model corresponding to the acoustic device can be obtained as follows: Figure 11 As shown.

[0107] Optionally, Figure 12 The equivalent circuit diagram of the acoustic device provided in this application under the substrate layer levitation connection method is shown in the figure below. Figure 12 As shown, taking the substrate layer connection method as a floating connection method as an example, the equivalent circuit model corresponding to the acoustic device can be obtained as follows: Figure 12 As shown above. Figure 11 and Figure 12 In the circuit diagram, green represents electronic components, and red represents the connecting lines between electronic components.

[0108] The equivalent circuit model can be a circuit consisting of eight pairs of parallel resistors R0 and capacitors C0 connected in series. The circuit also includes an equivalent substrate capacitance CpSiO and a parasitic capacitance CpGND.

[0109] S503. Based on the initial device parameters of the other layers in the acoustic device (excluding the material layer) and the equivalent circuit model, generate the output capacitance variation curve of the acoustic device.

[0110] Optionally, after obtaining the equivalent circuit model, simulation can be performed based on the initial device parameters of the other layers in the acoustic device besides the material layer and the equivalent circuit model to generate the output capacitance variation curve of the acoustic device.

[0111] For example, taking the substrate layer connection method as a floating connection method, simulation can be performed based on the initial device parameters of the other layers in the acoustic device besides the material layer and the equivalent circuit model under the substrate layer floating connection method to generate the first output capacitance change curve of the acoustic device.

[0112] For example, taking the substrate layer connection method as the ground connection method, the second output capacitance change curve of the acoustic device can be generated by simulation based on the initial device parameters of the other layers in the acoustic device except for the material layer and the equivalent circuit model under the substrate layer ground connection method.

[0113] For example, Figure 13 This is a schematic diagram of the capacitive output of acoustic devices under different connection methods, refer to... Figure 13 As shown, taking the material layer as an example, the capacitance output under different material layer thicknesses can be simulated based on the functional layer parameters and substrate layer parameters in the initial device parameters, and the output capacitance variation curve of the acoustic device under different connection methods of the substrate layer can be obtained.

[0114] S504. Determine the intrinsic capacitance value of the diaphragm in a functional region.

[0115] Optionally, the sub-diaphragm of the diaphragm in a functional region can be simulated to obtain the capacitance value of a single-lobe diaphragm under ideal conditions, and the intrinsic capacitance value of the diaphragm in a functional region can be calculated.

[0116] For example, taking a diaphragm as a regular octagon divided along each side, the capacitance value of a single-lobe diaphragm under ideal conditions, C0 = 31.107 pF, can be obtained through simulation, and the intrinsic capacitance value of the diaphragm in one functional region, Cout = 3.888 pF, can be calculated.

[0117] S505. Determine the thickness range of the material layer of the acoustic device based on the intrinsic capacitance value and the output capacitance change curve.

[0118] Optionally, the intrinsic capacitance value can be calculated by combining a preset error range to obtain the target capacitance value, and the thickness of the target layer of the acoustic device can be found from the output capacitance change curve of the corresponding acoustic device by combining the current substrate layer connection method.

[0119] For example, with a preset error range of 15%, the target capacitance value of the acoustic device can be obtained as <4.47pF. Taking the substrate layer 300 as a floating connection method, it can be found from the first output capacitance change curve that the thickness of the material layer 200 needs to be greater than 220nm.

[0120] For example, the material layer 200 includes silicon oxide material, and the thickness of the material layer 200 is greater than 1100 nm.

[0121] For example, the material layer 200 includes silicon oxide material, the thickness of the material layer 200 is greater than 1500 nm, and the output capacitance of the acoustic device is less than 4.1 pF.

[0122] By using a preset substrate layer connection method, an equivalent circuit model corresponding to the acoustic device is generated. Based on the initial device parameters of the other layers in the acoustic device (excluding the target layer) and the equivalent circuit model, the output capacitance variation curve of the acoustic device is generated, and the intrinsic capacitance value of the diaphragm in a functional region is determined. Thus, the thickness of the target layer of the acoustic device can be determined based on the intrinsic capacitance value and the output capacitance variation curve. This allows for accurate determination of the thickness of the target layer in the acoustic device, improving the device performance. At the same time, it also enables rapid prototype iteration and shortens the R&D cycle.

[0123] As one possible implementation method, Figure 14 This is a flowchart illustrating the process of determining the substrate connection method in the acoustic device provided in this application, with reference to... Figure 14 As shown, the process of determining the substrate layer interconnection method includes:

[0124] S901. Obtain the first electrical connection method and the second electrical connection method of the substrate layer.

[0125] Optionally, the first electrical connection method can be the aforementioned floating connection method, and the second electrical connection method can be the aforementioned grounding connection method.

[0126] S902. Determine multiple first output capacitance values ​​of the material layer at each test thickness according to the first electrical connection method.

[0127] Optionally, under the first electrical connection method, multiple first output capacitance values ​​of the material layer at each test thickness can be tested.

[0128] For example, Figure 15 A scatter plot of the output capacitance of an acoustic device provided in this application is shown below. Figure 15 As shown, devices with different silicon oxide thicknesses can be tested in a floating connection mode to obtain multiple first output capacitance values, such as... Figure 15 As shown, that is Figure 15 The image shows multiple scatter points corresponding to the potential suspension of the Si substrate.

[0129] S903. Determine multiple second output capacitance values ​​of the material layer at each test thickness according to the second electrical connection method.

[0130] Optionally, under the second electrical connection method, multiple second output capacitance values ​​of the material layer at each test thickness can be tested.

[0131] For example, continue to refer to Figure 15 As shown, devices with different silicon oxide thicknesses can be tested under grounding connection to obtain multiple second output capacitance values, such as... Figure 15 As shown, that is Figure 15 The image shows multiple scattered points corresponding to the grounding of the Si substrate.

[0132] S904. Determine the substrate connection method based on the values ​​of each first output capacitor and each second output capacitor.

[0133] Optionally, the substrate connection method can be determined by comparing the values ​​of each first output capacitor and each second output capacitor.

[0134] For example, continue to refer to Figure 15 As shown, it can be seen that, under the same silicon oxide thickness, the output capacitance when the Si substrate is suspended is less than the output capacitance when the Si substrate is grounded. Therefore, it can be determined that the better way to connect the substrate layers is the suspension connection method.

[0135] As one possible implementation method, Figure 16 Another cross-sectional schematic diagram of the acoustic device provided in this application is shown below. Figure 16 As shown, in the first example, the substrate 300 includes a silicon substrate 302 and an insulating layer 303. The silicon substrate 302 is disposed between the material layer 200 and the insulating layer 303, so that the substrate 300 is levitated by an active potential.

[0136] Alternatively, in the second example, substrate 300 includes: a silicon substrate layer; the silicon substrate layer is used to connect an external insulating layer so that the substrate layer is passively levitated.

[0137] As one possible implementation, the material layer 200 is also provided with silicon oxide material, and the substrate layer 300 is also provided with a silicon substrate.

[0138] Optionally, the material support structure is made of silicon oxide.

[0139] Alternatively, the substrate support structure is made of a silicon substrate, which can provide a stable support platform for acoustic devices.

[0140] As one possible implementation, the thickness of silicon oxide is greater than 220 nm.

[0141] That is, the preset thickness range is greater than 220nm.

[0142] In the acoustic device provided in this application, when the thickness of silicon oxide is greater than 220 nm, the greater the thickness of silicon oxide, the smaller the parasitic capacitance of the acoustic device provided in this application. Thus, by changing the thickness of silicon oxide, the parasitic capacitance in the acoustic device is reduced, thereby improving the key capabilities of the acoustic device such as sensitivity and improving the signal-to-noise ratio of the acoustic device.

[0143] As one possible implementation, the first cavity 201 and the second cavity 301 have the same radius, or the first cavity 201 and the second cavity 301 have different radii.

[0144] In the first example, continue to refer to Figure 1 As shown, the first cavity 201 and the second cavity 301 have the same parameters.

[0145] In the second example, the first cavity 201 and the second cavity 301 have different parameters.

[0146] The parameters can include size, shape, perimeter, and radius.

[0147] For example, the first cavity 201 and the second cavity 301 have the same lateral dimension.

[0148] As one possible implementation method, Figure 17 This is another side view schematic diagram of the acoustic device provided in this application. Figure 18 This is another side view schematic diagram of the acoustic device provided in this application. Figure 19 Another side view schematic diagram of the acoustic device provided in this application.

[0149] Reference Figure 17 , Figure 18 as well as Figure 19 As shown, the functional layer 100 also includes: a diaphragm support structure 102 and a plurality of electrical connectors 103.

[0150] The diaphragm support structure 102 supports the diaphragm 101; both the diaphragm 101 and the diaphragm support structure 102 include: at least two alternately stacked electrode layers 1011 and one piezoelectric layer 1012.

[0151] Specifically, the piezoelectric layer can use materials such as aluminum nitride (AlN) and scandium-doped aluminum nitride (ScAlN).

[0152] For example, Figure 17 Taking an example where both the diaphragm 101 and the diaphragm support structure 102 include three alternately stacked electrode layers 1011 and two piezoelectric layers 1012, the number of electrode layers and piezoelectric layers can be flexibly adjusted according to actual conditions. For example, different arrangements of the electrode layers can be made depending on different situations. The electrode layers 1011 can be fully covered (e.g., ...). Figure 17 As shown), it is also possible to not fully cover the floor (as shown). Figure 18 (As shown). Figure 18 There is a layer only at the diaphragm 101, while no electrode layer 1011 is provided at the diaphragm support structure 102.

[0153] Optionally, each electrical connector 103 is distributed on the surface of the diaphragm support structure 102 so that the acoustic device provided in this application can be connected to an external circuit. Optionally, each electrical connector 103 includes at least a positive electrode connector Vcc and a negative electrode connector GND.

[0154] Optionally, each electrical connector 103 may also include: multiple electrical connection structures VIA.

[0155] The functional areas 1012 are connected through various electrical connection structures.

[0156] As one possible implementation, the diaphragm includes: one or more cantilever beam structures, with multiple cantilever beam structures arranged at intervals around the central axis of the diaphragm.

[0157] As one possible implementation method, Figure 20 Here is another planar schematic diagram of the diaphragm in the acoustic device provided in this application, with reference to... Figure 20 As shown, in the first example, the diaphragm 101 has multiple slits 1013, one end of each slit 1013 is connected to the geometric center of the diaphragm 101, and the other end extends radially, with the slits 1013 arranged at intervals.

[0158] Each slit 1013 penetrates the diaphragm 101 in the direction perpendicular to the diaphragm 101; the connecting edge of the diaphragm 101 and the diaphragm support structure 102 and two adjacent slits 1013 constitute an acoustic functional area 1014, and the diaphragm 101 includes multiple functional areas 1014.

[0159] Optionally, multiple acoustic functional zones 1014 can vibrate independently.

[0160] For example, combined Figure 19 as well as Figure 20 As shown, the diaphragm 101 is a regular octagon divided along each side as an example.

[0161] Alternatively, in the second example, diaphragm 101 is a monolithic diaphragm.

[0162] Optionally, when the diaphragm 101 is an integral diaphragm, it can be understood that the diaphragm 101 is a standard piezoelectric film structure, that is, a continuous thin film without slits.

[0163] As one possible implementation method, Figure 21 Another cross-sectional schematic diagram of the acoustic device provided in this application is shown below. Figure 21 As shown, in Figure 1 In addition to the above, the acoustic device also includes: support layer 400.

[0164] The support layer 400 can be a single-layer or multi-layer material.

[0165] The support layer 400 is disposed between the functional layer 100 and the material layer 200.

[0166] Among them, the single film material can be a thin film layer composed of a single functional material, such as silicon nitride (SIN), single crystal silicon (c-Si), and polycrystalline silicon (Poly-Si).

[0167] Among them, the multi-layer material can be a thin film layer composed of the above-mentioned materials stacked together.

[0168] For example, continue to refer to Figure 21 As shown, the support layer 400 may not include a cavity, and the support layer 400 is tightly bonded between the functional layer 100 and the material layer 200.

[0169] For example, the support layer 400 may also include a third cavity. The parameters of the third cavity may be the same as or different from the parameters of the first cavity, the diaphragm, and the second cavity, and can be adjusted according to the actual application.

[0170] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An acoustic device, comprising: A stacked functional layer, the functional layer including a piezoelectric layer and a patterned electrode layer; A material layer is disposed adjacent to the patterned electrode layer; A substrate layer is disposed adjacent to the material layer; The feature is that the patterned electrode layer enables the acoustic device to be equivalent to a series circuit of multiple RC modules; The material layer disposed adjacent to the patterned electrode layer has a thickness greater than 220 nm and the substrate layer is suspended at a potential to reduce parasitic capacitance.

2. The acoustic device according to claim 1, characterized in that, The functional layer includes: a piezoelectric layer and two electrode layers respectively stacked on top of and below the piezoelectric layer.

3. The acoustic device according to claim 1, characterized in that, The functional layer includes: two piezoelectric layers and three electrode layers respectively stacked on top, in the middle and bottom of the piezoelectric layers.

4. The acoustic device according to claim 1, characterized in that, The substrate layer includes a silicon substrate, and the substrate layer is either actively levitated or passively levitated.

5. The acoustic device according to claim 1, characterized in that, The substrate layer includes a silicon substrate and an insulating layer; the silicon substrate is disposed between the material layer and the insulating layer, such that the substrate layer is levitated by an active potential, or... The substrate layer includes: a silicon substrate; the silicon substrate is connected to an external insulating layer so that the substrate layer is passively levitated.

6. The acoustic device according to claim 1, characterized in that, The material layer has a first cavity, and the substrate layer has a second cavity; The functional layer, the first cavity, and the second cavity are coaxially arranged, and the bottom of the functional layer is adjacent to the first cavity.

7. The acoustic device according to claim 6, characterized in that, The first cavity and the second cavity have the same parameters, or the first cavity and the second cavity have different parameters.

8. The acoustic device according to any one of claims 1-7, characterized in that, The functional layer also includes: a support structure and multiple electrical connectors; The support structure supports at least two alternately stacked electrode layers and one piezoelectric layer; Each of the electrical connectors is distributed on the surface of the support structure.

9. The acoustic device according to any one of claims 1-7, characterized in that, The functional layer includes: one or more cantilever beam structures; and multiple cantilever beam structures are arranged at intervals around the central axis of the functional layer.

10. The acoustic device according to any one of claims 1-7, characterized in that, The acoustic device further includes: a support layer; The support layer is a single-layer material or a multi-layer material; The support layer is disposed between the functional layer and the material layer.

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