A combi-beam microphone

Abstract

The application provides a combined beam microphone, belonging to the field of piezoelectric microphones, which comprises a substrate, a circular recess is formed on the upper surface of the substrate, a cavity is formed in the recess, and the cavity is located directly below the recess; a center diaphragm is arranged in the recess and located at the center of the recess; transition beams are arranged at intervals around the center diaphragm and connected to the center diaphragm, and first gaps are formed between adjacent transition beams; fixed beams are arranged at intervals around the center diaphragm, and the two ends of the fixed beams along the radial direction of the recess are connected to the inner wall of the recess and the transition beams respectively; cantilever beams are arranged between adjacent fixed beams and connected to the transition beams, and second gaps are formed between the cantilever beams, the inner wall of the recess and the fixed beams. By changing the structure of the beams in the microphone, increasing the number of fixed beams and the combination form between the beams, increasing the area of the high stress concentration region, and combining the reasonable layout of the center diaphragm, the transition beams, the fixed beams and the cantilever beams, the stress distribution is more uniform, and the effective utilization rate of the diaphragm area is improved.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric microphone technology, and more particularly to a composite beam microphone. Background Technology

[0002] A microphone is a device that converts sound signals into electrical signals, widely used in microphones, mobile phones, PCs, and automotive voice recognition devices. After long-term development, current microphone performance indicators focus more on intelligence, digitalization, and miniaturization. MEMS piezoelectric microphone technology is increasingly integrated with aerospace, biomedicine, consumer electronics, information and communication, and military industries, placing higher demands on microphone reliability and sensitivity. Currently, condenser microphones hold the majority market share, but piezoelectric microphones, due to their durability, high sensitivity, low noise, and lack of external power supply, will have wide applications in the future of aeroacoustics.

[0003] Traditional beam-type piezoelectric microphones have fixed ends on the beams located at the periphery or center of the vibration zone. For example, the piezoelectric MEMS microphone disclosed in Chinese patent CN115278490A has two cantilever beams intersecting to form a fixed boundary. This results in only one high-stress concentration area on each beam, located near the fixed boundary, leading to a small effective area for the piezoelectric film and consequently, a lower microphone output. Therefore, it is necessary to improve the cantilever beam structure to increase the effective area of ​​the film and improve microphone performance. Summary of the Invention

[0004] In view of this, the present invention proposes a composite beam microphone to solve the problem that current piezoelectric microphones typically have only one high stress concentration area on a single beam, resulting in a small effective area for the piezoelectric film and consequently a smaller microphone output.

[0005] The technical solution of this invention is implemented as follows: This invention provides a composite beam microphone, including a substrate with a circular groove on its upper surface and a cavity inside, the cavity being located directly below the groove; a central diaphragm, disposed within the groove and located at the center of the groove; a plurality of transition beams, spaced around the central diaphragm and connected to the central diaphragm, with a first gap between adjacent transition beams; a plurality of fixed support beams, spaced around the central diaphragm, with both ends of the fixed support beams connected to the inner wall of the groove and the transition beams respectively along the radial direction of the groove; and a cantilever beam, disposed between adjacent fixed support beams and connected to the transition beams, with a second gap between the cantilever beam and the inner wall of the groove and the fixed support beams.

[0006] Based on the above technical solutions, preferably, the central diaphragm, transition beam, fixed support beam and cantilever beam are all made of piezoelectric thin film material and form a piezoelectric layer. The upper and lower surfaces of the piezoelectric layer are respectively covered with a top electrode and a bottom electrode to form a piezoelectric stacked structure. The substrate includes a device layer and a release layer. The piezoelectric stacked structure is provided on the device layer, and the release layer is provided below the device layer and surrounds the cavity.

[0007] More preferably, the surface of the piezoelectric layer is provided with electrode areas for laying electrodes, and the electrode areas located on the central diaphragm, transition beam, fixed support beam and cantilever beam are isolated.

[0008] In an even more preferred design, the composite beam microphone has an axisymmetric structure with the center diaphragm as its center, and the overall structure is divided into four quadrants, with each quadrant having a consistent structure.

[0009] More preferably, each quadrant includes a transition beam, two fixed beams and a cantilever beam; the two fixed beams are symmetrically arranged on both sides of the cantilever beam; a first gap is left between adjacent fixed beams in adjacent quadrants.

[0010] Even more preferably, the transition beam, fixed support beam, and cantilever beam are all fan-shaped.

[0011] More preferably, the radius of the piezoelectric layer is r1, the sum of the radii of the central diaphragm and the transition beam is r2, and the radius of the central diaphragm is r3, satisfying r2=r1×k1 and r3=r2×k2, where k1 and k2 are proportionality coefficients and their values ​​range from 0 to 1.

[0012] More preferably, the output of the electrode region of the piezoelectric layer increases with increasing k1 and decreases with increasing k2; the characteristic frequency of the composite beam microphone increases with increasing k1 and increases with increasing k2.

[0013] More preferably, a third gap is provided on the device layer, and the third gap connects the second gap and the cavity.

[0014] More preferably, the substrate is an SOI wafer substrate or a thermo-oxidized sheet, and the piezoelectric thin film material is one of aluminum nitride, scandium-doped aluminum nitride, PZT, PVDF, LiNbO3, LiTaO3, and PMN-PT.

[0015] The combined beam microphone of the present invention has the following advantages over the prior art:

[0016] (1) This invention improves the effective utilization rate of the diaphragm area and increases the sensitivity of the microphone by changing the structural form of the inner beam of the microphone, increasing the number of fixed beams and the combination form between beams, thereby increasing the area of ​​high stress concentration area; at the same time, combined with the reasonable layout of the central diaphragm, transition beam, fixed beam and cantilever beam, the stress distribution is more uniform, and the microphone can maintain high structural stability and reliability.

[0017] (2) By adjusting two proportional coefficients, the characteristic frequency of the microphone can be flexibly adjusted to adapt to different sound acquisition needs. As k1 increases, the characteristic frequency of the device increases, which is suitable for high-frequency sound acquisition; while as k2 increases, the frequency response is further adjusted to meet the usage needs in different scenarios. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a top view of a quarter-section structure of the composite beam microphone of the present invention;

[0020] Figure 2 This is a top view of a quarter structure of another embodiment of the combined beam microphone of the present invention;

[0021] Figure 3 This is a quarter-section view of the composite beam microphone of the present invention;

[0022] Figure 4 This is a perspective view of a quarter-section structure of another embodiment of the combined beam microphone of the present invention;

[0023] Figure 5 The diagram shows the simulation relationship between the proportional coefficients k1 and k2 of this invention and the characteristic frequency and output voltage of the device.

[0024] Figure 6 The simulation stress diagrams are shown for comparison between the structure and the structure of the present invention, where a is the comparison structure and b is the structure of the present invention.

[0025] In the figure: 1. Substrate; 11. Device layer; 12. Release layer; 101. Groove; 102. Cavity; 103. Third gap; 2. Central diaphragm; 3. Transition beam; 301. First gap; 4. Fixed beam; 5. Cantilever beam; 501. Second gap; 6. Piezoelectric layer; 61. Top electrode; 62. Bottom electrode. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, combined with Figure 4 The present invention provides a composite beam microphone, comprising a substrate 1, a central diaphragm 2, a transition beam 3, a fixed support beam 4, and a cantilever beam 5.

[0028] The substrate 1 has a circular groove 101 on its upper surface and a cavity 102 inside it, located directly below the groove 101. The substrate 1 serves as the basic support structure for the entire microphone, supporting and isolating the various components. The cavity 102 reduces external noise interference with the microphone's performance, ensuring more accurate audio signal acquisition. The position and structure of the cavity 102 effectively enhance the microphone's frequency response range and sensitivity.

[0029] The central diaphragm 2 is positioned within the groove 101 and at its center. The central diaphragm 2 is the core component of the microphone; it directly responds to sound fluctuations and converts them into electrical signals. The design of the central diaphragm 2 optimizes its frequency response characteristics through parameters such as material, thickness, and shape, and further enhances signal acquisition by connecting it to the transition beam 3.

[0030] Several transition beams 3 are spaced around and connected to the central diaphragm 2, with a first gap 301 between adjacent transition beams 3. The function of the transition beams is to effectively transmit the sound waves captured by the diaphragm to the fixed beams 4 and the cantilever beams 5, and to control the movement of the diaphragm. The first gap 301 between the transition beams and adjacent beams is ingeniously designed to ensure the stability and accuracy of signal transmission.

[0031] Several fixed support beams 4 are spaced around the central diaphragm 2. The two ends of the fixed support beams 4 along the radial direction of the groove 101 are connected to the inner wall of the groove 101 and the transition beam 3, respectively. The fixed support beams 4 are located on the periphery of the transition beam 3, and their presence provides necessary support for the central diaphragm 2, preventing excessive deformation of the central diaphragm 2 and ensuring accurate transmission of audio signals. The layout and design of the fixed support beams 4 directly affect the microphone's frequency response, sensitivity, and other performance characteristics.

[0032] A cantilever beam 5 is positioned between adjacent fixed beams 4 and connected to the transition beam 3. A second gap 501 is left between the cantilever beam 5 and the inner wall of the groove 101 and the fixed beams 4. The cantilever beam 5 further enhances audio signal transmission and vibration modulation. The design of the second gap 501 between the cantilever beam 5 and the fixed beams 4 can effectively suppress unnecessary resonance and optimize signal transmission.

[0033] This embodiment can perform different electrode configurations on the device according to different requirements, such as Figure 1 The electrode area is divided by dashed lines into fixed beam 4, cantilever beam 5, transition beam 3, and central diaphragm 2, with different electrical connection methods, such as full series, full parallel, or a combination of series and parallel connections. The electrodes cover the entire sector beam, resulting in a large capacitance and significant introduced capacitive noise. The electrode coverage area can be optimized to cover only high-stress areas to achieve a larger output response and introduce less noise, thus improving the device's signal-to-noise ratio.

[0034] exist Figure 3 In a preferred embodiment shown, the central diaphragm 2, transition beam 3, fixed support beam 4, and cantilever beam 5 are all made of piezoelectric thin film material and form a piezoelectric layer 6. A top electrode 61 and a bottom electrode 62 are respectively deposited on the upper and lower surfaces of the piezoelectric layer 6, forming a single-crystal piezoelectric stack structure. Alternatively, the piezoelectric stack structure can also be configured as a bottom electrode 62, a piezoelectric layer 6, a middle electrode, another piezoelectric layer 6, and a top electrode 61, forming a dual-crystal piezoelectric stack structure. The piezoelectric stack structure can be configured with different polarization methods. Lead-out electrodes for extracting electrical signals are respectively provided on the outer side of the substrate 1. An insulating layer is provided between the lead-out electrodes of different electrode layers. The bottom electrode 62, the middle electrode, and the top electrode 61 can be electrically connected in a fully series, fully parallel, or a combination of series and parallel connections.

[0035] Substrate 1 includes a device layer 11 and a release layer 12. A piezoelectric stack structure is disposed on device layer 11, and release layer 12 is disposed below device layer 11 and surrounds cavity 102. During the microphone's MEMS manufacturing process, release layer 12 acts as a temporary support layer, helping to maintain the position and shape of other structures (such as diaphragms, beams, etc.) and preventing deformation or instability in subsequent processing steps. Especially in microfabrication or thin-film deposition techniques, release layer 12 is typically temporary, intended to be removed (i.e., "released") after other device processes are completed. Removing release layer 12 allows structures such as diaphragms and beams to move or vibrate freely, thereby enabling the microphone's sensing function.

[0036] exist Figure 1In a preferred embodiment shown, the surface of the piezoelectric layer 6 is provided with electrode areas for laying electrodes, and the electrode areas located on the central diaphragm 2, transition beam 3, fixed support beam 4, and cantilever beam 5 are isolated. This electrode distribution design not only ensures signal transmission efficiency but also avoids signal interference and current noise.

[0037] exist Figure 2 In one preferred embodiment shown, the composite beam microphone has an axisymmetric structure with respect to the center diaphragm 2, and the overall structure is divided into four quadrants, each with a consistent structure. Ideally, more quadrants could be used, but four quadrants are preferred.

[0038] exist Figure 2 In a preferred embodiment shown, each quadrant includes a transition beam 3, two fixed beams 4, and a cantilever beam 5; the two fixed beams 4 are symmetrically arranged on both sides of the cantilever beam 5; a first gap 301 is left between adjacent fixed beams 4 in adjacent quadrants. Based on the design of this embodiment, see [reference needed]. Figure 6 It provides a contrast structure, for example Figure 6 As shown in (a). Compared to this embodiment ( Figure 6 Compared to the structure shown in (b), although the comparative structure also has a fixed beam 4 and a cantilever beam 5, both are directly connected to the central diaphragm 2 without passing through the transition beam 3. The structure in this embodiment adds a transition beam 3 compared to the comparative structure, resulting in a further increase in the effective utilization area of ​​the membrane. The stress was obtained after simulating the above two structures. Figure 6 The simulated stress diagram shown reveals that the high stress concentration area of ​​the structure in this embodiment is uniform and larger in area, and for the dual-chip structure, the characteristic frequency does not drop to the audible range.

[0039] exist Figure 2 In a preferred embodiment shown, the transition beam 3, the fixed support beam 4, and the cantilever beam 5 are all fan-shaped with arc-shaped boundaries; the three together form the entire fan-shaped beam structure, and the electrodes can cover the entire fan-shaped beam.

[0040] exist Figure 5 In a preferred embodiment shown, the radius of the piezoelectric layer 6 is r1, the sum of the radii of the central diaphragm 2 and the transition beam 3 is r2, and the radius of the central diaphragm 2 is r3. The radius is obtained by parametric scanning using the multiphysics numerical analysis software Comsol Multiphysics. Figure 5 The proportionality coefficients shown are related to the device characteristic frequency and output voltage, satisfying r2 = r1 × k1 and r3 = r2 × k2, where k1 and k2 are proportionality coefficients and their values ​​range from 0 to 1.

[0041] exist Figure 5In a preferred embodiment shown, with fixed device size and electrical connections, the output of the electrode region of the piezoelectric layer 6 increases with increasing k1 and decreases with increasing k2; the characteristic frequency of the composite beam microphone increases with increasing k1 and increases with increasing k2. Based on these principles, different scaling factors can be selected according to different requirements, such as high frequency or low frequency.

[0042] exist Figure 4 In a preferred embodiment shown, a third gap 103 is provided on the device layer 11, which connects the second gap 501 and the cavity 102. The third gap 103 effectively improves the dynamic response and stability of the microphone, while helping to avoid interference from air fluctuations.

[0043] exist Figure 1 In a preferred embodiment shown, a piezoelectric microphone is a sensor that operates based on the piezoelectric effect, converting sound wave signals into electrical signals. Therefore, selecting a suitable substrate and piezoelectric material is crucial when designing and manufacturing a piezoelectric microphone. In this embodiment, substrate 1 is an SOI wafer substrate or a thermally oxidized silicon wafer. SOI wafers have good mechanical properties and electrical insulation, making them suitable for microelectromechanical systems (MEMS) applications. They can also effectively isolate electrical signals, reduce noise interference, and improve the microphone's sensitivity and signal-to-noise ratio. Thermally oxidized silicon wafers are commonly used to manufacture high-quality piezoelectric thin films, providing excellent interface quality. Their good thermal stability and mechanical strength make them an ideal choice for piezoelectric devices. The piezoelectric thin film material is one of aluminum nitride, scandium-doped aluminum nitride, PZT, PVDF, LiNbO3, LiTaO3, and PMN-PT. Aluminum nitride is a wide bandgap semiconductor material with good piezoelectric properties and thermal stability. Scandium-doped aluminum nitride is a derivative of aluminum nitride, where scandium is incorporated to enhance its piezoelectric properties, resulting in a higher piezoelectric constant. Lead zirconate titanate (PZT) is one of the most commonly used piezoelectric materials, possessing a high piezoelectric constant and good mechanical strength, making it suitable for low- and high-frequency acoustic applications. However, it is highly sensitive to temperature and humidity. Polyvinylidene fluoride (PVDF) is a polymer material with good flexibility and a high piezoelectric constant. Lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) are both materials with excellent piezoelectric and photoelectric properties, suitable for high-frequency and optoelectronic integration applications. Due to their excellent temperature stability, they are often used in high-precision sensors. PMN-PT (lead magnesium titanate) is a novel piezoelectric material with extremely high piezoelectric performance and sensitivity, suitable for high-precision and high-sensitivity sensors, but its manufacturing cost is relatively high. The piezoelectric microphone in this embodiment is fabricated using MEMS technology.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite beam microphone, characterized in that, include: A substrate (1) has a circular groove (101) on its upper surface and a cavity (102) inside it, the cavity (102) being located directly below the groove (101); The central diaphragm (2) is disposed within the groove (101) and located at the center of the groove (101); Several transition beams (3) are arranged at intervals around the central diaphragm (2) and connected to the central diaphragm (2), with a first gap (301) between adjacent transition beams (3). Several fixed support beams (4) are arranged at intervals around the central diaphragm (2). The two ends of the fixed support beams (4) along the radial direction of the groove (101) are respectively connected to the inner wall of the groove (101) and the transition beam (3). A cantilever beam (5) is set between adjacent fixed support beams (4) and connected to a transition beam (3). A second gap (501) is left between the cantilever beam (5) and the inner wall of the groove (101) and the fixed support beam (4). The central diaphragm (2), transition beam (3), fixed support beam (4) and cantilever beam (5) are all made of piezoelectric thin film material and form a piezoelectric layer (6). The upper and lower surfaces of the piezoelectric layer (6) are respectively covered with a top electrode (61) and a bottom electrode (62) to form a piezoelectric stack structure. The substrate (1) includes a device layer (11) and a release layer (12). A piezoelectric stack structure is disposed on the device layer (11), and the release layer (12) is disposed below the device layer (11) and surrounds the cavity (102). The transition beam (3), the fixed beam (4), and the cantilever beam (5) are all fan-shaped. The radius of the piezoelectric layer (6) is r1. The sum of the radii of the central diaphragm (2) and the transition beam (3) is r2. The radius of the central diaphragm (2) is r3, satisfying r2=r1×k1 and r3=r2×k2, where k1 and k2 are proportionality coefficients and their values ​​range from 0 to 1. The output of the electrode region of the piezoelectric layer (6) increases with the increase of k1 and decreases with the increase of k2. The device characteristic frequency of the combined beam microphone increases with the increase of k1 and increases with the increase of k2.

2. A composite beam microphone according to claim 1, characterized in that: The surface of the piezoelectric layer (6) is provided with an electrode area for laying electrodes, and the electrode areas located on the central diaphragm (2), transition beam (3), fixed support beam (4) and cantilever beam (5) are isolated.

3. A composite beam microphone according to claim 1, characterized in that: The composite beam microphone has an axisymmetric structure with the center diaphragm (2) as its center. The overall structure is divided into four quadrants, and the structure of each quadrant is consistent.

4. A composite beam microphone according to claim 3, characterized in that: Each quadrant includes a transition beam (3), two fixed beams (4) and a cantilever beam (5); the two fixed beams (4) are symmetrically arranged on both sides of the cantilever beam (5); a first gap (301) is left between adjacent fixed beams (4) in adjacent quadrants.

5. A composite beam microphone according to claim 1, characterized in that: A third gap (103) is provided on the device layer (11), and the third gap (103) connects the second gap (501) and the cavity (102).

6. A composite beam microphone according to claim 1, characterized in that: The substrate (1) is an SOI wafer substrate or a thermo-oxidized sheet, and the piezoelectric thin film material is one of aluminum nitride, scandium-doped aluminum nitride, PZT, PVDF, LiNbO3, LiTaO3 and PMN-PT.

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