Preparation method of piezoelectric MEMS smart speaker

Abstract

The present invention specifically relates to a method for preparing a piezoelectric MEMS smart speaker, including: using a theoretical formula for film vibration frequency to preliminarily calculate the film vibration frequency according to a target frequency range; using finite element analysis software to perform simulation and predict the resonance frequency of each vibration membrane to determine the material of each layer; selecting a piezoelectric material; selecting a substrate material; sputtering a first electrode material on the substrate, and etching to form a required electrode pattern; depositing a piezoelectric layer material to ensure uniform thickness; sputtering a second electrode material on the piezoelectric layer, and etching to form a required electrode pattern; testing the actual performance frequency of the speaker; adjusting the thickness or shape of the piezoelectric layer according to the test results; and also including using a dynamic algorithm to adjust the thickness or shape of the piezoelectric layer; re-depositing the piezoelectric layer and adjusting it; until the resonance frequencies of all vibration membranes are within the target range.

Description

Technical Field

[0001] The present invention belongs to the field of smart speakers, and in particular relates to a method for preparing a piezoelectric MEMS smart speaker. Background Art

[0002] With the development of portable electronic devices and IoT technology, the demand for miniaturized, high-performance speakers is growing. Piezoelectric MEMS (micro-electromechanical systems) speakers have attracted considerable attention due to their compact size, low power consumption, and fast response speed. However, the design of piezoelectric MEMS speakers with a dual-ring surround-circular diaphragm structure presents the technical challenge of precisely controlling the resonant frequencies of the different diaphragms (circular and annular) to achieve full audio coverage (20Hz-20kHz). This challenge stems primarily from the need to precisely control the thickness, shape, and material properties of the piezoelectric layer, a high-precision requirement that existing manufacturing technologies and design methods often struggle to achieve.

[0003] The existing piezoelectric MEMS speaker design with a dual-ring surround circular diaphragm structure includes a substrate with a back chamber on the back side. A first electrode, a piezoelectric layer, and a second electrode are deposited in sequence on the front side of the substrate. The diaphragm layer is composed of these three layers and the actuating layer of the back chamber, including a central circular diaphragm, an inner ring diaphragm, and an outer ring diaphragm. These diaphragms are separated by groove gaps and connected by support beams. The different resonant frequencies of the three diaphragms (central circular diaphragm: 10kHz-20kHz; center + inner ring diaphragms: 1kHz-10kHz; all three diaphragms: 20Hz-1kHz) achieve coverage of the full audio range of 20Hz-20kHz.

[0004] With existing technologies, it is difficult to control the resonant frequency: since the resonant frequencies of the three vibrating membranes need to be controlled simultaneously, precise adjustment becomes a problem.

[0005] For existing technologies, material and structure sensitivity: the thickness, shape and material properties of the piezoelectric layer have a direct impact on the resonant frequency of the vibration membrane and require extremely precise control.

[0006] For existing technologies, manufacturing process limitations: Current manufacturing processes make it difficult to achieve the required high-precision control, especially in adjusting the thickness and shape of the piezoelectric layer. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing a piezoelectric MEMS smart speaker to solve the problems raised in the above background technology.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] A method for preparing a piezoelectric MEMS speaker with a double-ring surrounding circular vibration membrane structure comprises:

[0010] Preliminary calculation of the membrane vibration frequency using theoretical formulas based on the target frequency range; simulation using finite element analysis software to predict the resonant frequency of each diaphragm to determine the materials for each layer, or directly determine the materials for each layer based on empirical data; selection of a piezoelectric material; selection of a substrate material; sputtering of a first electrode material onto the substrate and etching to form the desired electrode pattern; and deposition of the piezoelectric layer material to ensure uniform thickness.

[0011] Sputter a second electrode material on the piezoelectric layer and etch to form the desired electrode pattern; etch to form a first trench gap, a second trench gap, and a third trench gap, with the support beams using cross-shaped vertical beams, three cross-shaped beams, or four cross-shaped beams; etch to form a back cavity on the back of the substrate; test the actual performance frequency of the speaker; and adjust the thickness or shape of the piezoelectric layer based on the test results.

[0012] If the test results show that the resonant frequency of the circular diaphragm is too high, the diameter of the circular diaphragm structure is increased;

[0013] If the test results show that the resonant frequency of the circular diaphragm is too low, the diameter of the circular diaphragm structure is reduced;

[0014] If the test results show that the resonance frequency of the first annular diaphragm is too high, the ring width of the first annular diaphragm structure is increased;

[0015] If the test results show that the resonance frequency of the first annular diaphragm is too low, the ring width of the first annular diaphragm structure is reduced;

[0016] If the test results show that the resonance frequency of the second annular diaphragm is too high, the ring width of the second annular diaphragm structure is increased;

[0017] If the test results show that the resonance frequency of the second annular diaphragm is too low, then the ring width of the second annular diaphragm structure is reduced; and the method also includes using a dynamic algorithm to adjust the thickness or shape of the piezoelectric layer;

[0018] The piezoelectric layer is redeposited and adjusted until the resonant frequencies of all diaphragms are within the target range.

[0019] Furthermore, finite element analysis software was used to simulate and predict the resonant frequency of each diaphragm to determine the material of each layer, specifically:

[0020] Based on the designed double-ring surrounding circular diaphragm structure, a geometric model was created using CAD software;

[0021] Input the physical and mechanical properties of each layer material, such as elastic modulus, Poisson's ratio, and density;

[0022] Define the fixed endpoints of the support beam as boundary conditions, as well as the pressure conditions for the back chamber;

[0023] For the diaphragm area, a finer mesh is used to improve the simulation accuracy;

[0024] Use a coarser mesh in non-critical areas;

[0025] Applying a voltage between the first electrode and the second electrode to simulate the excitation of the loudspeaker in a working state;

[0026] Perform frequency response analysis, gradually increasing the excitation frequency to find the resonant frequency of each diaphragm;

[0027] Perform modal analysis to extract the first few natural frequencies and corresponding vibration modes;

[0028] Furthermore, a frequency response analysis is performed to confirm the stability of the resonant frequency and its corresponding vibration mode;

[0029] Compare the simulation results with the theoretical calculation results to verify the effectiveness of the model;

[0030] Based on the simulation results, adjust the thickness, shape, or material properties of the piezoelectric layer to achieve the target resonant frequency range.

[0031] Furthermore, the piezoelectric material includes PZT, ZnO, and AlN; the substrate material includes SOI wafer, PDMS, PE, and PI.

[0032] Further, sputtering the first electrode material on the substrate includes:

[0033] Depositing the electrode material on the substrate using a sputtering process in a physical vapor deposition technique;

[0034] Controlling the sputtering time or deposition rate to achieve the desired electrode thickness;

[0035] Monitor the quality of thin films during deposition;

[0036] Measure the thickness of electrode materials;

[0037] Etching to form the desired electrode pattern:

[0038] Evenly coating a layer of photoresist on the surface of the deposited electrode material;

[0039] Spin coater is used for coating to ensure uniform distribution of photoresist;

[0040] exposing the photoresist using a mask to transfer the desired electrode pattern;

[0041] Using a developer to remove the photoresist in the exposed areas, leaving the photoresist in the unexposed areas as a mask for subsequent etching;

[0042] Using dry etching or wet etching to remove the electrode material not masked by the photoresist to form a desired electrode pattern;

[0043] Remove residual photoresist;

[0044] Check the quality of the electrode pattern after cleaning to ensure there is no residual photoresist or other impurities;

[0045] Inspect the integrity, edge quality, and dimensional accuracy of the electrode pattern using an optical microscope or scanning electron microscope;

[0046] Confirm that the electrode pattern is exactly the same as the design file.

[0047] Furthermore, the process of depositing the piezoelectric layer material includes:

[0048] Prepare the deposition chamber:

[0049] Clean the deposition chamber to ensure it is free of impurities;

[0050] Load the base and set the position of the support beams;

[0051] Select ALD or PLD deposition method and set deposition parameters such as temperature and gas flow rate;

[0052] Start deposition and monitor film thickness via an online monitoring system;

[0053] Ensure that the film thickness is uniform and the deviation is within the allowable range;

[0054] The crystalline quality of the films was examined using XRD;

[0055] Use AFM to examine the surface roughness of the film;

[0056] Check the uniformity of film thickness using ellipsometer;

[0057] If the film thickness is uneven or does not meet the design requirements, adjust the deposition parameters or re-deposit.

[0058] Furthermore, the second electrode material is sputtered on the piezoelectric layer, and the required electrode pattern is formed by etching in the same manner as the process of sputtering the first electrode material on the substrate.

[0059] Further, etching is performed to form a first trench gap, a second trench gap, and a third trench gap. Specifically:

[0060] uniformly coating a layer of photoresist on the completed electrode and piezoelectric layer structure;

[0061] Use a spin coater for coating to ensure uniform distribution of photoresist;

[0062] exposing the photoresist using a mask to transfer the desired trench gap pattern;

[0063] Using a developer to remove the photoresist in the exposed areas, leaving the photoresist in the unexposed areas as a mask for subsequent etching;

[0064] Using dry etching to remove material not masked by the photoresist to form the desired trench gap;

[0065] The first groove gap is located between the central circular diaphragm and the inner annular diaphragm;

[0066] The second groove gap is located between the inner annular diaphragm and the outer annular diaphragm;

[0067] The third groove gap is used to separate the outer annular vibration membrane from other structures.

[0068] Further, etching the back side of the substrate to form a back cavity includes:

[0069] Evenly coating a layer of photoresist on the back side of the substrate;

[0070] Spin coater is used for coating to ensure uniform distribution of photoresist;

[0071] exposing the photoresist using a mask to transfer the pattern of the back cavity;

[0072] A developer is used to remove the photoresist in the exposed areas, leaving the photoresist in the unexposed areas as a mask for subsequent etching.

[0073] Furthermore, the actual performance frequency of the test speaker is specifically:

[0074] Set up the test bench and microphone positions, ensuring the distance between the speaker and microphone meets the test requirements;

[0075] Connect to the acoustic test system and configure the corresponding hardware and software settings;

[0076] Set the test signal parameters, including sweep frequency range and signal amplitude;

[0077] Start the test signal and begin the frequency response test;

[0078] Record the output signal of the loudspeaker at different frequencies;

[0079] Process the recorded data using the acoustic test system's software to generate a frequency response curve;

[0080] Analyze the frequency response curve to determine the actual resonant frequency of each diaphragm;

[0081] Compare the actual resonant frequency with the design target to assess whether the expected frequency range is achieved;

[0082] Evaluate whether the actual performance frequency of the speaker meets the design requirements based on the test results.

[0083] Furthermore, the modification process data of the vibration membrane structure is obtained, and the modification amount of the vibration membrane structure is adjusted using a particle swarm optimization algorithm, including:

[0084] Based on the preliminary tests, the actual resonance frequency data of each diaphragm was sorted out;

[0085] Determine the parameters that need to be optimized, including the thickness of the piezoelectric layer and the diameter of the vibration membrane;

[0086] Particle swarm initialization:

[0087] Set the size of the particle swarm;

[0088] Randomly initialize the position and velocity of each particle to ensure that the particles are distributed in the parameter space;

[0089] The fitness function is defined as the inverse of the sum of squares of deviations from the target frequency range, that is, the closer to the target frequency range, the higher the fitness;

[0090] Use the standard PSO update rule, considering the particle's current position, personal optimal position, and global optimal position;

[0091] When updating particle speed and position, ensure that the parameter values ​​remain within a reasonable range;

[0092] Iterative optimization process:

[0093] In each iteration, the fitness value of each particle is evaluated;

[0094] Update the particle's position and velocity;

[0095] Repeat the iteration until the preset maximum number of iterations is reached or the fitness value converges;

[0096] According to the optimal parameter values ​​obtained through optimization, the structure of the vibration membrane is adjusted.

[0097] Compared with the prior art, the present invention has the following advantages:

[0098] Finite element analysis software is used for simulation to predict the resonant frequency of each vibration membrane, ensuring the accuracy of the design.

[0099] Fine etching and photolithography processes have been implemented to form high-precision electrode patterns, groove gaps and support beam structures, enhancing the structural stability and acoustic performance of the speaker. By precisely controlling the thickness, shape and material properties of the piezoelectric layer and dynamically adjusting the design parameters, effective coverage of the full audio range of 20Hz-20kHz is achieved.

[0100] By precisely controlling the resonance frequencies of different vibration membranes (circular and annular), the speaker is ensured to have a smooth frequency response curve within the full audio range, thereby improving the sound quality.

[0101] The particle swarm optimization algorithm (PSO) is used to automatically adjust the parameters of the vibration membrane structure, such as the thickness of the piezoelectric layer and the diameter of the vibration membrane, which improves the accuracy and efficiency of the design.

[0102] Through the iterative optimization process, the best parameter combination can be found quickly, reducing the time and effort required for manual adjustments and accelerating the product development cycle.

[0103] Materials with suitable piezoelectric properties (such as PZT, ZnO, AlN) and substrate materials with good mechanical strength and chemical stability (such as SOI wafer, PDMS, PE or PI) are selected.

[0104] The sputtering process and deposition parameters were optimized to ensure high-quality preparation of electrodes and piezoelectric layers, improving the performance and reliability of the loudspeaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] Figure 1 This is a flow chart of the method of this application. DETAILED DESCRIPTION

[0106] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0107] The preparation method of the piezoelectric MEMS speaker with a double-ring surrounding circular vibration membrane structure is as follows: Figure 1 As shown,

[0108] Including steps:

[0109] The film vibration frequency is preliminarily calculated using the theoretical formula of the film vibration frequency according to the target frequency range.

[0110] The theoretical formula of film vibration frequency is used to preliminarily calculate the film vibration frequency f:

[0111] ,

[0112] Where T is the tension on the film, ρ is the surface density of the film, and A is the effective vibration area of ​​the film;

[0113] Use finite element analysis software to simulate and predict the resonance frequency of each vibration membrane to determine the material of each layer, or directly determine the material of each layer based on empirical data. Specifically:

[0114] 1. Prepare the model

[0115] Establish a geometric model: Based on the designed double-ring surround circular vibration membrane structure, use CAD software to create a three-dimensional model.

[0116] Material property definition: Input the physical and mechanical properties of each layer material (substrate, electrode, piezoelectric layer), such as elastic modulus, Poisson's ratio, and density.

[0117] Boundary condition settings: Define the fixed end points of the support beam as boundary conditions, and the pressure conditions of the back chamber.

[0118] 2. Model meshing

[0119] Fine Mesh: For the diaphragm area, a finer mesh is used to improve simulation accuracy.

[0120] Coarser mesh: Use a coarser mesh in non-critical areas to reduce computing time and resource consumption.

[0121] 3. Provide incentives

[0122] Apply voltage: Apply voltage between the first electrode and the second electrode to simulate the excitation of the speaker in working state.

[0123] Frequency sweep: Performs a frequency response analysis by gradually increasing the excitation frequency to find the resonant frequency of each diaphragm.

[0124] 4. Perform modal analysis

[0125] Modal Extraction: Perform modal analysis to extract the first few natural frequencies and corresponding mode shapes.

[0126] Frequency response analysis: Further frequency response analysis is performed to confirm the stability of the resonant frequency and its corresponding vibration mode.

[0127] 5. Analyze the results

[0128] Comparison with theoretical calculations: Compare the simulation results with the results of theoretical calculations to verify the effectiveness of the model.

[0129] Optimize design parameters: Adjust the thickness, shape, or material properties of the piezoelectric layer based on simulation results to achieve the target resonant frequency range.

[0130] 6. Repeat

[0131] Optimize the design: If the resonant frequency of some diaphragms is found to deviate from the target range, adjust the relevant design parameters and repeat the simulation until the resonant frequency of all diaphragms meets the design requirements;

[0132] Select a suitable piezoelectric material (e.g. PZT, ZnO, AlN).

[0133] Select the substrate material (e.g. SOI wafer, PDMS, PE, or PI).

[0134] PZT (lead zirconate titanate): has a high piezoelectric coefficient and good temperature stability, suitable for high-frequency applications.

[0135] ZnO (zinc oxide): has good chemical stability and a high piezoelectric coefficient, suitable for high-frequency and low-frequency applications.

[0136] AlN (aluminum nitride): has good thermal stability and dielectric properties, is suitable for high-frequency applications, and can still maintain good performance at high temperatures.

[0137] Selection Criteria

[0138] Piezoelectric coefficient: A higher piezoelectric coefficient can improve conversion efficiency.

[0139] Mechanical quality factor: A higher mechanical quality factor helps to improve the clarity of the resonance peak.

[0140] Temperature stability: Good temperature stability can ensure the consistency of performance at different temperatures.

[0141] Chemical stability: Good chemical stability can extend the service life of the device;

[0142] SOI (Silicon on Insulator): has good mechanical strength and chemical stability, and is suitable for the manufacture of MEMS devices.

[0143] PDMS (polydimethylsiloxane): It is a soft polymer with good flexibility and biocompatibility, suitable for structures that require flexibility or deformability.

[0144] PE (polyethylene): has good mechanical strength and chemical stability and low cost.

[0145] PI (polyimide): has excellent thermal and chemical stability and is suitable for high temperature environments.

[0146] Selection Criteria

[0147] Mechanical strength: Sufficient mechanical strength to withstand the stress during processing.

[0148] Chemical stability: Good chemical stability can prevent the material from degrading during use.

[0149] Thermal stability: Good thermal stability can maintain performance in high temperature environments.

[0150] Compatibility with piezoelectric materials: The substrate material should have good adhesion and matching with the piezoelectric material.

[0151] Sputtering the first electrode material (e.g. Pt, Au, Cr, Al) on the substrate:

[0152] Select the appropriate electrode material based on the piezoelectric layer material and design requirements. For example, Pt (platinum), Au (gold), Cr (chromium), or Al (aluminum) metal can be used as the electrode material.

[0153] Pt and Au have good electrical conductivity and chemical stability and are suitable for use as electrode materials.

[0154] Cr and Al are low cost and have good conductivity, but may require additional protective layers to prevent oxidation or corrosion.

[0155] Sputtering process:

[0156] The electrode material is deposited on the substrate using a sputtering process in physical vapor deposition (PVD) technology.

[0157] Ensure that the sputtering conditions (such as working gas pressure, sputtering power, and target-substrate distance) are appropriate to obtain uniform and well-adhered films.

[0158] The sputtering time or deposition rate is controlled to achieve the desired electrode thickness, typically tens to hundreds of nanometers.

[0159] Quality Control:

[0160] Monitor the quality of thin films during deposition to ensure there are no defects such as pinholes or non-uniformities.

[0161] Measure the thickness of the electrode material to ensure it is within the design range.

[0162] Etching to form the desired electrode pattern:

[0163] Photoresist coating:

[0164] A layer of photoresist is evenly coated on the surface of the deposited electrode material.

[0165] Use a spin coater for coating to ensure uniform distribution of the photoresist.

[0166] Exposure and development:

[0167] The photoresist is exposed using a mask to transfer the desired electrode pattern.

[0168] A developer is used to remove the photoresist in the exposed areas, leaving the photoresist in the unexposed areas as a mask for subsequent etching.

[0169] Dry or wet etching:

[0170] Dry etching (such as reactive ion etching (RIE)) or wet etching (such as chemical etching) is used to remove the electrode material not masked by the photoresist to form the desired electrode pattern.

[0171] Cleaning and degumming:

[0172] Remove residual photoresist, usually using ion cleaning or chemical solvent cleaning.

[0173] Check the quality of the electrode pattern after cleaning to ensure there is no residual photoresist or other impurities.

[0174] Quality Check:

[0175] Use an optical microscope or a scanning electron microscope (SEM) to check the integrity, edge quality, and dimensional accuracy of the electrode pattern.

[0176] Confirm that the electrode pattern is exactly the same as the design file.

[0177] Deposit the piezoelectric layer material, ensuring uniform thickness.

[0178] Deposition process of piezoelectric layer material:

[0179] Prepare the deposition chamber:

[0180] Clean the deposition chamber to ensure it is free of impurities.

[0181] Load the base and set the position of the support beams.

[0182] Deposition of the piezoelectric layer:

[0183] Choose between ALD or PLD deposition methods.

[0184] Set deposition parameters such as temperature and gas flow rate.

[0185] Deposition was started and the film thickness was monitored by an online monitoring system.

[0186] Ensure that the film thickness is uniform and the deviation is within the allowable range.

[0187] Quality Check:

[0188] The crystalline quality of the films was examined using XRD.

[0189] The surface roughness of the films was examined using AFM.

[0190] Ellipsometer was used to check the uniformity of film thickness.

[0191] Adjustments and optimizations:

[0192] If the film thickness is uneven or does not meet the design requirements, adjust the deposition parameters or re-deposit.

[0193] Preparation of the second electrode:

[0194] sputtering a second electrode material on the piezoelectric layer,

[0195] Etching to form the required electrode pattern. Sputtering the second electrode material on the piezoelectric layer and etching to form the required electrode pattern is consistent with the process of sputtering the first electrode material on the substrate.

[0196] Forming the groove gap:

[0197] Etching is performed to form a first trench gap, a second trench gap, and a third trench gap. Specifically:

[0198] Photoresist coating:

[0199] A layer of photoresist is evenly coated on the completed electrode and piezoelectric layer structure.

[0200] Use a spin coater for coating to ensure uniform distribution of the photoresist.

[0201] Exposure and development:

[0202] The photoresist is exposed using a mask to transfer the desired trench gap pattern.

[0203] A developer is used to remove the photoresist in the exposed areas, leaving the photoresist in the unexposed areas as a mask for subsequent etching.

[0204] Dry etching:

[0205] Use dry etching (such as reactive ion etching RIE) to remove the material not masked by the photoresist to form the required trench gap.

[0206] The first groove gap is located between the central circular diaphragm and the inner annular diaphragm.

[0207] The second groove gap is located between the inner annular diaphragm and the outer annular diaphragm.

[0208] The third groove gap is used to separate the outer annular vibration membrane from other structures.

[0209] Quality Check:

[0210] Use an optical microscope or scanning electron microscope (SEM) to inspect the integrity of the trench gap, edge quality, and dimensional accuracy.

[0211] Confirm that the groove gap is exactly the same as the design document to ensure isolation between the diaphragms.

[0212] Etching forms a supporting beam structure to enhance structural stability.

[0213] The supporting beams are cross-shaped vertical beams, three-cross beams or four-cross beams.

[0214] A back cavity is formed by etching the back side of the substrate.

[0215] Etching a back cavity on the back side of the substrate includes:

[0216] A layer of photoresist is evenly coated on the back of the substrate.

[0217] Use a spin coater for coating to ensure uniform distribution of the photoresist.

[0218] Exposure and development:

[0219] The photoresist is exposed using a mask to transfer the pattern of the back cavity.

[0220] A developer is used to remove the photoresist in the exposed areas, leaving the photoresist in the unexposed areas as a mask for subsequent etching.

[0221] Test the actual performance frequency of the speaker.

[0222] The actual performance frequency of the test speaker is specific:

[0223] Use a professional acoustic test system, such as a B&K (Brüel & Kjær) or other brand acoustic analyzer.

[0224] Ensure that the test system has a broadband response, covering the frequency range of 20Hz to 20kHz.

[0225] The tests were conducted in an anechoic chamber to eliminate external noise interference.

[0226] Keep the temperature and humidity of the test environment stable to ensure the accuracy of the test results.

[0227] The test was performed using a swept frequency signal, gradually increasing from the lowest frequency (20 Hz) to the highest frequency (20 kHz).

[0228] The signal can be generated by the speaker driving circuit to ensure the purity and stability of the signal.

[0229] Place the speaker on the test bench, ensuring it is a fixed distance from the microphone.

[0230] The sound from the loudspeaker is captured using a microphone and the sound signal is recorded using an acoustic test system.

[0231] Use the acoustic test system's software to analyze the frequency response curve of the speaker output.

[0232] The curves are analyzed to determine the actual resonant frequency of each diaphragm.

[0233] Compare with the design target to evaluate whether the predetermined frequency range is achieved.

[0234] Specific test steps:

[0235] Prepare the test environment:

[0236] Make sure the temperature and humidity in the anechoic chamber are at stable levels.

[0237] Set up the test bench and microphone positions, ensuring the distance between the speaker and microphone meets the test requirements.

[0238] Set up the test system:

[0239] Connect the acoustic test system and configure the appropriate hardware and software settings.

[0240] Set the test signal parameters, such as sweep frequency range and signal amplitude.

[0241] To test:

[0242] Start the test signal and begin the frequency response test.

[0243] Record the loudspeaker's output signal at different frequencies.

[0244] Data Analysis:

[0245] The recorded data was processed using the acoustic test system's software to generate a frequency response curve.

[0246] Analyze the frequency response curve to determine the actual resonant frequency of each diaphragm.

[0247] Compare the actual resonant frequency with the design target to assess whether the expected frequency range is achieved.

[0248] Result evaluation:

[0249] Evaluate whether the actual performance frequency of the speaker meets the design requirements based on the test results.

[0250] Adjust the thickness or shape of the piezoelectric layer based on the test results:

[0251] If the test results show that the resonant frequency of the circular diaphragm is too high, the diameter of the circular diaphragm structure is increased;

[0252] If the test results show that the resonant frequency of the circular diaphragm is too low, the diameter of the circular diaphragm structure is reduced;

[0253] If the test results show that the resonance frequency of the first annular diaphragm is too high, the ring width of the first annular diaphragm structure is increased;

[0254] If the test results show that the resonance frequency of the first annular diaphragm is too low, the ring width of the first annular diaphragm structure is reduced;

[0255] If the test results show that the resonance frequency of the second annular diaphragm is too high, the ring width of the second annular diaphragm structure is increased;

[0256] If the test results show that the resonance frequency of the second annular diaphragm is too low, the ring width of the second annular diaphragm structure is reduced;

[0257] Preferably, adjusting the thickness or shape of the piezoelectric layer according to the test results further includes obtaining modification process data of the vibration membrane structure and adjusting the modification amount of the vibration membrane structure using a particle swarm optimization algorithm; including:

[0258] After each test, record the actual performance frequency data of the loudspeaker, especially the resonance frequency of each diaphragm;

[0259] Collect and test other parameters, including piezoelectric layer thickness and vibration membrane diameter;

[0260] Organize test data into tables or databases to facilitate subsequent analysis and optimization;

[0261] The particle swarm optimization algorithm is used to adjust the modification amount of the vibration membrane structure:

[0262] Set the size of the particle swarm, where each particle represents a set of possible parameter values ​​(including piezoelectric layer thickness and diaphragm diameter);

[0263] Initialize the position and velocity of each particle. The position represents a specific set of parameter values, and the velocity represents the trend of parameter change.

[0264] Evaluate particle fitness:

[0265] Conduct simulation or experimental tests on the parameter combination represented by each particle to obtain the corresponding fitness value;

[0266] The fitness function can be defined based on the closeness to the target frequency range, for example, minimizing the sum of squared deviations from the target frequency range;

[0267] Update particle position and velocity:

[0268] According to the rules of the particle swarm optimization algorithm, the position and velocity of each particle are updated;

[0269] The update rule considers the influence of the global optimal solution and the personal optimal solution to guide the particles to move towards a better solution;

[0270] Iterative optimization:

[0271] Repeat the evaluation and update steps until the termination condition is met (such as reaching the maximum number of iterations or the fitness value converges);

[0272] Select the best particle position as the optimized parameter value;

[0273] The structural parameters of the vibration membrane, such as the thickness of the piezoelectric layer and the diameter of the vibration membrane, are adjusted according to the optimization results.

[0274] Specific implementation steps

[0275] Data preparation:

[0276] Based on the preliminary tests, the actual resonance frequency data of each diaphragm was sorted out;

[0277] Determine the parameters that need to be optimized, such as the thickness of the piezoelectric layer and the diameter of the diaphragm;

[0278] Particle swarm initialization:

[0279] Set the size of the particle swarm, for example 50 particles;

[0280] Randomly initialize the position and velocity of each particle to ensure that the particles are distributed in the parameter space;

[0281] Fitness function definition:

[0282] The fitness function is defined as the inverse of the sum of squares of deviations from the target frequency range, that is, the closer to the target frequency range, the higher the fitness;

[0283] Particle update rules:

[0284] Use the standard PSO update rule, considering the particle's current position, personal optimal position, and global optimal position;

[0285] When updating particle speed and position, ensure that the parameter values ​​remain within a reasonable range;

[0286] Iterative optimization process:

[0287] In each iteration, the fitness value of each particle is evaluated;

[0288] Update the particle's position and velocity;

[0289] Repeat the iteration until the preset maximum number of iterations is reached or the fitness value converges;

[0290] Optimization results application:

[0291] Adjust the structure of the vibration membrane according to the optimal parameter values ​​obtained through optimization;

[0292] In this way, the particle swarm optimization algorithm can be effectively used to automatically adjust the parameters of the diaphragm structure, improving the accuracy and efficiency of the design. This method is particularly suitable for complex design processes that require multiple rounds of iteration and optimization.

[0293] The piezoelectric layer is redeposited and adjusted.

[0294] Re-deposit the piezoelectric layer and ensure uniform thickness.

[0295] Repeat the previous etching steps to form the desired electrode pattern, trench gap and support beam structure.

[0296] Retest the actual performance frequency of the speaker to verify the effect of the adjustment.

[0297] Until the resonant frequencies of all diaphragms are within the target range.

[0298] The present invention proposes a method for preparing a piezoelectric MEMS loudspeaker with a double-annular surround circular vibration membrane structure, uses finite element analysis software for simulation and prediction of the resonant frequency of each vibration membrane, and ensures the accuracy of the design.

[0299] Fine etching and photolithography processes have been implemented to form high-precision electrode patterns, groove gaps and support beam structures, enhancing the structural stability and acoustic performance of the speaker. By precisely controlling the thickness, shape and material properties of the piezoelectric layer and dynamically adjusting the design parameters, effective coverage of the full audio range of 20Hz-20kHz is achieved.

[0300] By precisely controlling the resonance frequencies of different vibration membranes (circular and annular), the speaker is ensured to have a smooth frequency response curve within the full audio range, thereby improving the sound quality.

[0301] The particle swarm optimization algorithm (PSO) is used to automatically adjust the parameters of the vibration membrane structure, such as the thickness of the piezoelectric layer and the diameter of the vibration membrane, which improves the accuracy and efficiency of the design.

[0302] Through the iterative optimization process, the best parameter combination can be found quickly, reducing the time and effort required for manual adjustments and accelerating the product development cycle.

[0303] Materials with suitable piezoelectric properties (such as PZT, ZnO, AlN) and substrate materials with good mechanical strength and chemical stability (such as SOI wafer, PDMS, PE or PI) are selected.

[0304] The sputtering process and deposition parameters were optimized to ensure high-quality preparation of electrodes and piezoelectric layers, improving the performance and reliability of the loudspeaker.

Claims

1. A method for preparing a piezoelectric MEMS smart speaker, characterized in that: include: The film vibration frequency is preliminarily calculated using the theoretical formula of the film vibration frequency according to the target frequency range; Use finite element analysis software to perform simulations and predict the resonant frequency of each diaphragm to determine the material of each layer; Select piezoelectric material; Select the base material; sputtering a first electrode material on the substrate and etching to form a desired electrode pattern; Deposit the piezoelectric layer material to ensure uniform thickness; Sputtering a second electrode material on the piezoelectric layer and etching to form a desired electrode pattern; etching to form a first trench gap, a second trench gap, and a third trench gap, with the support beams using a cross-shaped vertical beam, a three-cross beam, or a four-cross beam; and etching to form a back cavity on the back of the substrate; Test the actual performance frequency of the speaker; Adjust the thickness or shape of the piezoelectric layer according to the test results; Using dynamic algorithms to adjust the thickness or shape of the piezoelectric layer; Re-deposit the piezoelectric layer and adjust it until the resonant frequency of all diaphragms is within the target range; The simulation is performed using finite element analysis software to predict the resonant frequency of each diaphragm to determine the material of each layer, specifically including: Based on the designed double-ring surrounding circular diaphragm structure, a geometric model was created using CAD software; Input the physical and mechanical properties of each layer material; Define the fixed endpoints of the support beam as boundary conditions, as well as the pressure conditions for the back cavity; For the diaphragm area, a finer mesh is used to improve simulation accuracy, and a coarser mesh is used in non-critical areas; Applying a voltage between the first electrode and the second electrode to simulate the excitation of the loudspeaker in a working state; Perform frequency response analysis, gradually increasing the excitation frequency to find the resonant frequency of each diaphragm; Perform modal analysis to extract the first few natural frequencies and corresponding vibration modes; Further frequency response analysis is performed to confirm the stability of the resonant frequency and its corresponding vibration mode; Compare the simulation results with the theoretical calculation results to verify the effectiveness of the geometric model; Adjust the thickness, shape, or material properties of the piezoelectric layer based on simulation results to achieve the target resonant frequency range; Adjusting the thickness or shape of the piezoelectric layer according to the test results includes: If the test results show that the resonant frequency of the circular diaphragm is too high, the diameter of the circular diaphragm structure is increased; If the test results show that the resonant frequency of the circular diaphragm is too low, the diameter of the circular diaphragm structure is reduced; If the test results show that the resonance frequency of the first annular diaphragm is too high, the ring width of the first annular diaphragm structure is increased; If the test results show that the resonance frequency of the first annular diaphragm is too low, the ring width of the first annular diaphragm structure is reduced; If the test results show that the resonance frequency of the second annular diaphragm is too high, the ring width of the second annular diaphragm structure is increased; If the test results show that the resonance frequency of the second annular diaphragm is too low, the ring width of the second annular diaphragm structure is reduced; The adjusting the thickness or shape of the piezoelectric layer according to the test results further includes obtaining modification process data of the vibration membrane structure and adjusting the modification amount of the vibration membrane structure using a particle swarm optimization algorithm. The obtaining modification process data of the vibration membrane structure and adjusting the modification amount of the vibration membrane structure using a particle swarm optimization algorithm specifically includes: Based on the preliminary tests, the actual resonance frequency data of each diaphragm was sorted out; Identify parameters that need to be optimized, including piezoelectric layer thickness and diaphragm diameter; Set the size of the particle swarm; Randomly initialize the position and velocity of each particle to ensure that the particles are distributed in the parameter space; The fitness function is defined as the inverse of the sum of squares of deviations from the target frequency range, that is, the closer to the target frequency range, the higher the fitness; Use the standard PSO update rule, considering the particle's current position, personal optimal position, and global optimal position; When updating particle speed and position, ensure that the parameter values ​​remain within a reasonable range; In each iteration, the fitness value of each particle is evaluated; Update the particle's position and velocity; Repeat the iteration until the preset maximum number of iterations is reached or the fitness value converges; According to the optimal parameter values ​​obtained through optimization, the structure of the vibration membrane is adjusted.

2. The method for preparing a piezoelectric MEMS smart speaker according to claim 1, wherein: Piezoelectric materials include PZT, ZnO, and AlN; substrate materials include SOI wafers, PDMS, PE, and PI.

3. The method for preparing a piezoelectric MEMS smart speaker according to claim 1, wherein: The process of depositing the piezoelectric layer material includes: Clean the deposition chamber to ensure it is free of impurities; Load the base and set the position of the support beams; Select ALD or PLD deposition method and set deposition parameters; Start deposition and monitor film thickness via an online monitoring system; Ensure that the film thickness is uniform and the deviation is within the allowable range; The crystalline quality of the films was examined using XRD; Use AFM to examine the surface roughness of the film; Check the uniformity of film thickness using ellipsometer; If the film thickness is uneven or does not meet the design requirements, adjust the deposition parameters or re-deposit.

4. The method for preparing a piezoelectric MEMS smart speaker according to claim 1, wherein: The steps of sputtering the second electrode material on the piezoelectric layer and etching to form the required electrode pattern are the same as those of sputtering the first electrode material on the substrate.

5. The method for preparing a piezoelectric MEMS smart speaker according to claim 1, wherein: Etching a back cavity on the back side of the substrate includes: Evenly coating a layer of photoresist on the back side of the substrate; Spin coater is used for coating to ensure uniform distribution of photoresist; exposing the photoresist using a mask to transfer the pattern of the back cavity; A developer is used to remove the photoresist in the exposed areas, leaving the photoresist in the unexposed areas as a mask for subsequent etching.

6. The method for preparing a piezoelectric MEMS smart speaker according to claim 1, wherein: The actual performance frequencies of the tested speakers include: Set up the test bench and microphone positions, ensuring the distance between the speaker and microphone meets the test requirements; Connect to the acoustic test system and configure the corresponding hardware and software settings; Set the test signal parameters, including sweep frequency range and signal amplitude; Start the test signal and begin the frequency response test; Record the output signal of the loudspeaker at different frequencies; Process the recorded data using the acoustic test system's software to generate a frequency response curve; Analyze the frequency response curve to determine the actual resonant frequency of each diaphragm; Compare the actual resonant frequency with the design target to assess whether the expected frequency range is achieved; Evaluate whether the actual performance frequency of the speaker meets the design requirements based on the test results.

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