Boom microphone

Abstract

The application provides a cantilever microphone, comprising: a substrate; a cantilever, comprising a rotor frame, a cover plate arranged on the rotor frame, and a plurality of rotor comb fingers; the cantilever is provided with a first edge fixed to the substrate and a second edge arranged opposite to the first edge, and the plurality of rotor comb fingers are fixed to the edge of the cover plate close to the second edge; the rotor comb fingers and the rotor frame are arranged at intervals; a stator is fixed to the substrate, the stator comprises a plurality of stator comb fingers, and the plurality of stator comb fingers and the plurality of rotor comb fingers are staggered and spaced; wherein the material of the rotor frame comprises at least one of polysilicon, silicon nitride, silicon oxide or silicon carbide. For the cantilever microphone of the application, high mechanical sensitivity of the cantilever and high electrostatic sensitivity of the comb structure can be realized, so as to improve the performance or signal-to-noise ratio of the cantilever microphone.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microelectronics, and in particular to a cantilever microphone.

BACKGROUND

[0002] With the development of MEMS microfabrication, many MEMS microphone structures have been developed, among which the cantilever beam is one of them. For a cantilever microphone, one edge of the cantilever is anchored to a substrate, while the other edge is not fixed, so when the cantilever microphone is subjected to pressure, the free edge opposite the anchoring edge will move freely up and down. Several cantilever MEMS microphones can be found in the literature, most of which use piezoelectric technology, in which the cantilever structure includes at least one piezoelectric layer that generates an electric charge when the cantilever is driven by sound pressure to produce movement. A new type of cantilever microphone using capacitive sensing technology is proposed in the recent reference US9938133B2 by Infineon, in which the free edge can be used as a sensing area to create a capacitive sensor.

[0003] However, the frame structure of the cantilever is made of single crystal silicon, which has manufacturing advantages but also limitations. Therefore, it is necessary to propose a capacitive cantilever MEMS microphone with other advantages.

SUMMARY

[0004] The technical problem to be solved by the present application is to provide a cantilever microphone with high mechanical sensitivity and electrostatic sensitivity.

[0005] To solve the above technical problems, the present application provides a cantilever microphone, comprising:

[0006] a substrate;

[0007] a cantilever, the cantilever comprising a rotor frame, a cover plate arranged on the rotor frame, and a plurality of rotor comb fingers; the cantilever is provided with a first edge fixed to the substrate and a second edge opposite the first edge, and a plurality of rotor comb fingers are fixed to the edge of the cover plate close to the second edge; the rotor comb fingers and the rotor frame are arranged at a distance from each other; and

[0008] a stator fixed to the substrate, the stator comprising a plurality of stator comb fingers, and the plurality of stator comb fingers and the plurality of rotor comb fingers are interleaved and spaced apart;

[0009] wherein the material of the rotor frame comprises at least one of polysilicon, silicon nitride, silicon oxide or silicon carbide.

[0010] As an improvement, a plurality of rotor comb fingers are arranged on the side of the cover plate facing the rotor frame, and the rotor comb fingers are perpendicular to the edge of the cover plate close to the second edge.

[0011] As an improvement, each of the rotor comb fingers and the stator comb fingers adjacent thereto are spaced apart to form a comb gap, the comb gap ranging from 0.1 um to 5 um.

[0012] As an improvement, each of the rotor comb fingers has a height ranging from 1 um to 50 um; each of the stator comb fingers has a height ranging from 1 um to 50 um.

[0013] As an improvement, the ratio of the height of the rotor comb fingers to the comb gap is 1 to 100; the ratio of the height of the stator comb fingers to the comb gap is 1 to 100.

[0014] As an improvement, the stator further comprises a stator frame fixed to the substrate, and the plurality of stator comb fingers are fixedly connected to the stator frame.

[0015] As an improvement, the stator frame surrounds the plurality of stator comb fingers.

[0016] As an improvement, the cover plate comprises an extension portion extending beyond the rotor frame, the extension portion covering at least a portion of the substrate and / or a portion of the stator.

[0017] As an improvement, the material of the cover plate comprises at least one of silicon nitride, silicon oxide, polymer, silicon carbide, or polysilicon.

[0018] As an improvement, a side of the cover plate facing the rotor frame is provided with a layer of conductive material.

[0019] As an improvement, the portion of the cover plate used to fix the rotor comb fingers is made of conductive material.

[0020] As an improvement, the plurality of rotor comb fingers and the plurality of stator comb fingers are both made of conductive material.

[0021] As an improvement, the plurality of rotor comb fingers are made of insulating material, and the plurality of stator comb fingers are made of conductive material; or, the plurality of rotor comb fingers are made of conductive material, and the plurality of stator comb fingers are made of insulating material.

[0022] As an improvement, the plurality of rotor comb fingers and the plurality of stator comb fingers are both made of single crystal silicon or polysilicon.

[0023] As an improvement, the distance between the cover plate and the stator comb fingers adjacent to an end of the cover plate is controlled to reduce electrostatic nonlinearity and distortion.

[0024] It should be understood that the foregoing general description and the following detailed description are merely exemplary of the application, and are not restrictive of the scope of the application disclosed. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments description. Obviously, the drawings in the following description only represent some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0026] Figure 1 Fig. 1 is a structural schematic diagram of a cantilever microphone according to an embodiment of the present application;

[0027] Figure 2 Fig. 2 is an enlarged view of part A shown in Fig. 1; Figure 1

[0028] Figure 3 Fig. 3 is a partial perspective view of a cantilever microphone according to another embodiment of the present application;

[0029] Figure 4 Fig. 4 is a perspective view of a cantilever microphone according to another embodiment of the present application;

[0030] Figure 5 Fig. 5 is a perspective view of a cantilever microphone according to another embodiment of the present application;

[0031] Figure 6 Fig. 6 is a partial perspective view of a cantilever microphone according to another embodiment of the present application.

DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without any creative effort should fall within the scope of the present application.

[0033] The terms used in the embodiments disclosed in the present application are only used to describe the specific embodiments, and are not intended to limit the present application. Unless otherwise specified in the text, the singular form expressions used in the embodiments and the additional claims are also intended to represent the plural form expressions.

[0034] It should be noted that the terms "upper", "lower", "left", "right", and the like mentioned in the embodiments of the present application are described with reference to the placement state in the drawings, and should not be interpreted as the limiting embodiments of the present application. In addition, it should also be understood that in the text, when referring to an element "above" or "below" another element, it is possible that the element is directly "above" or "below" another element, or the element is "above" or "below" another element through an intermediate element.​

[0035] Please refer to Figure 1 , Figure 1 is a structural schematic diagram of a cantilever microphone according to the present application. The present application provides a cantilever microphone 100, which comprises a substrate 1, a cantilever 2 and a stator 4.

[0036] The cantilever 2 comprises a first edge fixed to the substrate 1 and a second edge 2a opposite to the first edge, which serves as a free end of the cantilever 2. Specifically, the cantilever 2 comprises a rotor frame 7, a cover plate 8 covering the rotor frame 7 and a plurality of rotor comb fingers 3. The plurality of rotor comb fingers 3 are fixedly arranged at an edge of the cover plate 8 close to the second edge 2a.

[0037] The stator 4 is fixed to the substrate 1, and of course, the stator 4 can also be connected to a substructure of the substrate 1 to allow displacement from the substrate 1.

[0038] The stator comprises a plurality of stator comb fingers 5, and the plurality of stator comb fingers 5 and the plurality of rotor comb fingers 3 are interlaced and spaced.

[0039] Each of the rotor comb fingers 3 and the stator comb fingers 5 adjacent thereto are spaced to form a comb gap, so that the rotor comb fingers 3 and the stator comb fingers 5 in the present embodiment are used as electrodes of a capacitor to form a capacitive sensor.

[0040] In the process of the related technical solution, the frame structure and the comb finger structure are simultaneously manufactured by etching the same single crystal silicon layer, and the comb finger structure is formed by extension of the frame structure, so they are naturally the same material.

[0041] For the above technical solution of the present application, the rotor frame 7 is made of silicon nitride. The rotor comb fingers 3 are arranged on the cover plate 8 of the cantilever 2. Since the rotor frame 7 is made of silicon nitride, the rotor comb fingers 3 cannot be formed by extension of the rotor frame 7, and single crystal silicon and silicon nitride cannot be attached by the side. Therefore, the only method is to attach the rotor comb fingers 3 to the bottom of the cover plate 8. Another advantage of the area of the cover plate 8 covering the rotor comb fingers 3 is that the acoustic resistance of the comb gap can be increased, thereby effectively improving the signal-to-noise ratio of the cantilever microphone 100 of the present application.

[0042] Therefore, in the present embodiment, the plurality of rotor comb fingers 3 are arranged on the side of the cover plate 8 facing the rotor frame 7.

[0043] In the present embodiment, the material for manufacturing the rotor frame 7 comprises at least one of polysilicon, silicon nitride, silicon oxide or silicon carbide.

[0044] In this embodiment, the material of the cover plate 8 comprises at least one of silicon nitride, silicon oxide, polymer, silicon carbide or polysilicon. In a preferred embodiment, the side of the cover plate 8 facing the rotor frame 7 is provided with a layer of electrically conductive material. By providing the layer of electrically conductive material at the bottom of the rotor frame 7, the performance of the cantilever microphone 100 of the present application can be significantly improved, in particular the electrostatic sensitivity.

[0045] In this embodiment, the rotor comb fingers 3 and the stator comb fingers 5 are made of an electrically conductive material. For example, each of the rotor comb fingers 3 and the stator comb fingers 5 is made of a metallic material. In a preferred embodiment, the rotor comb fingers 3 and the stator comb fingers 5 are made of single crystal silicon or polysilicon.

[0046] Figure 2 is Figure 1 an enlarged view of part a shown in Fig. 1. As Figures 1-2 shown in Fig. 2, the rotor comb fingers 3 can be provided at and extend from the edge of the cover plate 8 adjacent to the end of the second edge 2a.

[0047] Figure 3 is a perspective view of a cantilever microphone according to another embodiment of the present application. The rotor comb fingers 3 can be provided on the surface of the side of the cover plate 8 facing the rotor frame 7, and the rotor comb fingers 3 are provided perpendicular to the end of the cover plate 8 adjacent to the second edge 2a. Figure 3 shown in Fig. 3, the rotor comb fingers 3 are provided within the comb region 2b of the cover plate 8. The part of the cover plate 8 used to fix the rotor comb fingers 3 is the comb region 2b.

[0048] In this embodiment, the comb region 2b is made of an electrically conductive material. By using the electrically conductive material for the comb region of the cover plate 8 covering the rotor comb fingers 3, the performance of the cantilever microphone 100 can be significantly improved. In particular, by controlling the distance between the cover plate 8 and the stator comb fingers 5 adjacent to the end of the cover plate 8, i.e. the distance between the electrically conductive material part of the cover plate 8 and the top of the stator comb fingers 5, the electrostatic non-linearity can be greatly reduced, and finally the distortion can be reduced.

[0049] Figure 4 is a perspective view of a cantilever microphone according to another embodiment of the present application. As Figure 4 shown in Fig. 4, a gap 6 is provided between the rotor comb fingers 3 and the rotor frame 7. The rotor comb fingers 3 and the rotor frame 7 are spaced apart from each other to form the gap 6.

[0050] As Figure 5 shown in Fig. 5, the gap 6 is provided between the rotor comb fingers 3 and the rotor frame 7. Figure 5This is a perspective view of a cantilever microphone according to another embodiment of the present invention. The stator 4 may further include a stator frame 9 fixed to the substrate 1, and a plurality of stator comb fingers 5 are fixedly connected to the stator frame 9. In this embodiment, the stator frame 9 is arranged around the plurality of stator comb fingers 5. The stator frame 9 may be disposed below the cover plate 8 of the cantilever 2. In this embodiment, the stator frame 9 may also be disposed at the gap 6 between the rotor comb fingers 3 and the rotor frame 7.

[0051] The above technical solution can improve the robustness of the stator 4 and the anti-sticking properties between the stator comb fingers 5 and the rotor comb 3 while providing the stator frame 9.

[0052] like Figure 6 As shown, Figure 6 This is a partial perspective view of a cantilever microphone according to another embodiment of the present invention. The cover plate 8 includes an extension 2c extending beyond the rotor frame 9 to cover at least a portion of the substrate 1 and / or the stator 4, i.e., the extension 2c covers at least a portion of the substrate 1 and / or a portion of the stator. The extension 2c is spaced apart from the substrate 1 and / or the stator 4.

[0053] Although an extension 2c of the cover plate 8 is provided, the acoustic resistance of the vent is increased, thereby enabling control over the microphone's attenuation under different wind conditions. In conventional microphones, the vent is simply a deliberately made small opening. Here, a disadvantage of the cantilever microphone 100 is that, since the edges are free, this vent must surround the cantilever 2. Large or long vents are detrimental to the signal-to-noise ratio. The distance between the frame of the cantilever 2 and the edge of the substrate 1 / substrate is preferably 0.1µm to 5µm, and the smaller the better. Since the movement of the cantilever 2 cannot make this size too small, one way to overcome low acoustic resistance is through an extended plate structure to cover this distance gap, preferentially covering all edges of the cantilever 2. By doing so, the acoustic resistance is not driven by the gap edge of the cantilever frame / substrate 1, but by the gap between the cover plate 8 and the substrate 1. Therefore, this edge gap can be increased (and thus easier to manufacture), while the attenuation is controlled by the gap between the cover plate 8 and the substrate 1.

[0054] In this embodiment, the rotor tines 3 are made of an insulating material and the stator tines 5 are made of a conductive material, or vice versa (the rotor tines 3 are made of a conductive material and the stator tines 5 are made of an insulating material). Here, instead of creating a capacitance between two adjacent tines, a capacitance is created between two tines from the same component (rotor tines 3 or stator tines 5), and an insulating tine from the other component is placed between the two tines creating the capacitance, which changes the capacitance size between the two conductive tines creating the capacitance. This concept is derived from the C = ε.A / d relationship, where ε is the dielectric constant of the material between the two electrodes, A is the adjacent area between the two electrodes, and d is the gap between the two electrodes: when the rotor tines 3 are driven by the acoustic pressure, instead of modifying the adjacent area (A) of its adjacent tine, the dielectric constant ε between its adjacent tines is modified, since the insulating tine modifies the dielectric constant at the place where the electric field propagates (in this case, the gap d is the gap between the two electrodes of the same component: either two adjacent stator tines 5 or two adjacent rotor tines 3, unlike the previous case, in which the gap between the two adjacent electrodes after interleaving the stator tines 5 and the rotor tines 3 is also the comb gap, since each adjacent tine is the opposite electrode).

[0055] According to such an embodiment, the structure should be built by paying attention to more complex electrical circuits on the single component where the conductive tines are located, also paying attention to parasitic capacitances (since the biasing electrodes and the sensing electrodes are very close to each other in several areas).

[0056] This embodiment makes the electrical wiring on one component more complex, unless any electrical part on the other component is removed.

[0057] Dimensions: the following dimensions apply to the embodiments of the present application.

[0058] The comb gap ranges between 0.1 um and 5 um.

[0059] The height of the rotor tines 3 ranges between 1 um and 50 um; the height of the stator tines 5 ranges between 1 um and 50 um. The height of the rotor tines 3 and the height of the stator tines 5 are not necessarily equal: for example, the height of the stator tines 5 can be 10 um and the height of the rotor tines 3 can be any height between 10 um and 1 um.

[0060] Independently from the above dimensions, the ratio between the comb height and the comb gap should be comprised between 1 and 100, i.e. the ratio between the height of the rotor tines 3 and the comb gap is comprised between 1 and 100; the ratio between the height of the stator tines 5 and the comb gap is comprised between 1 and 100.

[0061] The above-mentioned embodiments are only preferred embodiments of the present application, but not limit the present application. Any modification, equivalent replacement and improvement within the scope of the present application shall fall into the protection scope of the present application.

Claims

1. A boom microphone, characterized by The application relates to a cantilever microphone, comprising: a substrate; a cantilever, which comprises a rotor frame, a cover plate arranged on the rotor frame, and a plurality of rotor comb fingers; the cantilever is provided with a first edge fixed to the substrate and a second edge arranged opposite to the first edge, and the plurality of rotor comb fingers are fixed to an edge of the cover plate close to the second edge; the rotor comb fingers and the rotor frame are arranged in mutual spacing; and a stator fixed to the substrate, which comprises a plurality of stator comb fingers, and the plurality of stator comb fingers and the plurality of rotor comb fingers are interlaced and spaced. The material of the rotor frame comprises at least one of polysilicon, silicon nitride, silicon oxide or silicon carbide. The plurality of rotor comb fingers are arranged on the side of the cover plate facing the rotor frame, and the rotor comb fingers are perpendicular to the edge of the cover plate close to the second edge. Each rotor comb finger and the adjacent stator comb finger are spaced to form a comb gap, and the range of the comb gap is 0.1-5um. The distance between the cover plate and the stator comb finger adjacent to the end of the cover plate is controlled to reduce electrostatic nonlinearity and distortion.

2. The boom microphone of claim 1, wherein The height of each rotor comb finger is 1-50um, and the height of each stator comb finger is 1-50um.

3. The cantilever microphone according to claim 2, wherein the ratio of the height of the rotor comb finger to the comb gap is 1-100, and the ratio of the height of the stator comb finger to the comb gap is 1-100.

4. The boom microphone of claim 1, wherein, The stator further comprises a stator frame fixed to the substrate, and the plurality of stator comb fingers are fixedly connected to the stator frame.

5. The boom microphone of claim 4, wherein The stator frame surrounds the plurality of stator comb fingers.

6. The boom microphone of claim 1, wherein, The cover plate comprises an extension part extending out of the rotor frame, which covers at least a part of the substrate and / or a part of the stator.

7. The boom microphone of claim 1, wherein The material of the cover plate comprises at least one of silicon nitride, silicon oxide, polymer, silicon carbide or polysilicon.

8. The boom microphone of claim 7, wherein, The side of the cover plate facing the rotor frame is provided with a layer of conductive material.

9. The boom microphone of claim 7, wherein, The part of the cover plate for fixing the rotor comb fingers is made of conductive material.

10. The boom microphone of claim 1, wherein, The plurality of rotor comb fingers and the plurality of stator comb fingers are made of conductive material.

11. The boom microphone of claim 1, wherein, The plurality of rotor comb fingers are made of insulating material, and the plurality of stator comb fingers are made of conductive material; or the plurality of rotor comb fingers are made of conductive material, and the plurality of stator comb fingers are made of insulating material.

12. The boom microphone of claim 1, wherein, The plurality of rotor comb fingers and the plurality of stator comb fingers are made of single crystal silicon or polysilicon.

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