Counter electrode structure and double-diaphragm MEMS microphone

Abstract

The invention provides a counter electrode structure and a double-diaphragm MEMS microphone. The double-diaphragm MEMS microphone comprises a base body and a capacitance system, the capacitance system comprises a first electrode diaphragm and a second electrode diaphragm which are arranged at an interval to form a containing cavity, the cross sections of the two electrode diaphragms in the radial direction are both corrugated, and the wave crest of one electrode diaphragm and the wave trough of the other electrode diaphragm are connected to form a supporting body. The capacitance system further comprises a counter electrode structure suspended in the containing cavity, the counter electrode structure comprises a plurality of circumferential beams arranged at intervals from inside to outside and a plurality of radial beams connected to the circumferential beams and extending from inside to outside, and a via hole extending around the center of the counter electrode structure is formed between every two adjacent circumferential beams inside and outside. The support body passes through the via hole and is spaced from the edge of the via hole. And the arrangement of the electrode structure enables the two electrode diaphragms to realize a double-corrugated diaphragm structure, so that the sound pressure is more sensitive, and the sensitivity performance can be remarkably improved.

Description

[Technical field]

[0001] The invention belongs to the technical field of acoustic-electric conversion, and in particular relates to an electrode structure and a double-diaphragm MEMS microphone. [Background technology]

[0002] MEMS sensors are the result of the development of MEMS (micro-electromechanical systems) technology and have a wide range of applications, such as MEMS microphones. Compared with other types of sensor devices, MEMS sensors have the advantages of small size and good frequency response characteristics.

[0003] The dual-diaphragm microphone is well known. It includes two electrode diaphragms spaced apart to form a capacitor, with a cavity between the two electrode diaphragms. When working, the spacing between the two electrode diaphragms changes, causing the capacitance to change, thereby converting the sound wave signal into an electrical signal. In the related art, the electrode diaphragms in the dual-diaphragm microphone are all planar, and a pair of electrodes are set in the space between the two electrode diaphragms to improve the signal-to-noise ratio. However, the structure in the related art is not sensitive enough to sound pressure and has low sensitivity. [Summary of the invention]

[0004] The object of the present invention is to provide an electrode structure and a dual-diaphragm MEMS microphone, which can be adapted to a dual-diaphragm MEMS microphone with a corrugated diaphragm to obtain a structure that is more sensitive to sound pressure.

[0005] The technical solution of the present invention is as follows: a counter electrode structure is provided, which is applied to a dual-diaphragm MEMS microphone, wherein the counter electrode structure includes a plurality of circumferential beams arranged at intervals from the inside to the outside and a plurality of radial beams connected to the circumferential beams and extending from the inside to the outside, wherein the circumferential beams extend around the center of the counter electrode structure, and each of the radial beams is arranged at intervals around the center of the counter electrode structure, and a via hole extending around the center of the counter electrode structure is formed between two adjacent circumferential beams inside and outside.

[0006] Furthermore, the radial beams extend from the edges of the electrode structures to the central region.

[0007] Further, the radial beam includes a first sub-beam whose inner end extends to be connected to the innermost circumferential beam and whose outermost end extends to the outer side of the outermost circumferential beam.

[0008] Furthermore, the radial beam also includes a second sub-beam whose inner end is connected to the circumferential beam between the innermost circle and the outermost circle and whose outermost end extends to the outside of the circumferential beam of the outermost circle.

[0009] Furthermore, the circumferential beam is in the shape of a complete ring or an open ring.

[0010] Furthermore, the contour shape of the circumferential beam is a circle or a regular polygon.

[0011] Furthermore, the widths of the circumferential beams are equal, and the spacings between adjacent circumferential beams are equal;

[0012] Alternatively, the width of at least some of the circumferential beams is not equal to the width of the remaining circumferential beams, and the intervals between adjacent circumferential beams are not equal.

[0013] Furthermore, the radial beams are arranged at equal angles around the center of the electrode structure.

[0014] Further, the width of the radial beam is equal at all locations along its extension direction;

[0015] Alternatively, the width of the radial beam gradually increases from the inside to the outside.

[0016] Furthermore, the circumferential beam and the radial beam are both provided with through holes penetrating in the thickness direction.

[0017] Furthermore, the perforations are arranged along the extension direction of the circumferential beam, and each of the perforations is distributed near the inner edge and the outer edge of the circumferential beam.

[0018] Furthermore, grooves are provided on the surfaces of the circumferential beam and the radial beam, and the through holes are located outside the grooves.

[0019] Furthermore, the circumferential beam and the radial beam are both electrically conductive.

[0020] Furthermore, the circumferential beam and the radial beam each include at least two stacked layers, and at least one layer is insulated.

[0021] Furthermore, a dual-diaphragm MEMS microphone is provided, comprising a substrate having a back cavity and a capacitor system connected to the substrate and covering the back cavity, the capacitor system comprising a first electrode diaphragm and a second electrode diaphragm arranged at an interval, a receiving cavity being formed between the first electrode diaphragm and the second electrode diaphragm, the cross-sectional shapes of the first electrode diaphragm and the second electrode diaphragm in the radial direction are both corrugated, the crests of the first electrode diaphragm and the troughs of the second electrode diaphragm are connected to form a supporting body, the capacitor system also comprises an electrode structure as described in any one of the above items connected to the substrate and suspended in the receiving cavity, the supporting body passes through the via hole and is spaced apart from the edge of the via hole.

[0022] Furthermore, the ambient pressure around the electrode structure is less than 0.5 ambient atmospheric pressure.

[0023] Furthermore, the ambient pressure around the electrode structure is less than 0.1 ambient atmospheric pressure.

[0024] The beneficial effect of the present invention is that: in this solution, the electrode structure can be used in a dual-diaphragm MEMS microphone and suspended between two electrode diaphragms, wherein a via hole is arranged to extend around the center of the electrode structure, and the support body between the two electrode diaphragms can pass through the via hole without contacting the electrode structure. In this way, the two electrode diaphragms can realize a dual corrugated diaphragm structure, which is more sensitive to sound pressure and can significantly improve the sensitivity performance.

Brief Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the overall structure of the dual-diaphragm MEMS microphone of the present invention;

[0026] Figure 2 It is a schematic diagram of the top view of the double-diaphragm MEMS microphone of the present invention;

[0027] Figure 3 It is a schematic diagram of the cross-sectional structure layout of the dual-diaphragm MEMS microphone of the present invention;

[0028] Figure 4 It is a schematic diagram of the top view of the electrode structure of the present invention. [Specific implementation method]

[0029] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0030] Combination Figure 1-4 , a dual-diaphragm MEMS microphone is provided, comprising a substrate 100 having a back cavity 101 and a capacitor system 200 connected to the substrate 100 and covering the back cavity 101, the capacitor system 200 comprising a first electrode diaphragm 1 and a second electrode diaphragm 2 arranged at intervals, a receiving cavity being formed between the first electrode diaphragm 1 and the second electrode diaphragm 2, the cross-sectional shapes of the first electrode diaphragm 1 and the second electrode diaphragm 2 in the radial direction are both corrugated, the crests of the first electrode diaphragm 1 and the troughs of the second electrode diaphragm 2 are connected to form a support body 3, the capacitor system 200 also comprises a counter electrode structure 4 connected to the substrate 100 and suspended in the receiving cavity.

[0031] Among them, the electrode structure 4 includes a plurality of circumferential beams 41 arranged at intervals from the inside to the outside and a plurality of radial beams 42 connected to the circumferential beams 41 and extending from the inside to the outside. The circumferential beams 41 extend around the center of the electrode structure 4, and each radial beam 42 is arranged at intervals around the center of the electrode structure 4. A via 4201 extending around the center of the electrode structure 4 is formed between the two adjacent circumferential beams 41 inside and outside. The support body 3 passes through the via 4201 and is spaced from the edge of the via 4201.

[0032] In this solution, the electrode structure 4 can be used in a dual-diaphragm MEMS microphone and suspended between two electrode diaphragms, wherein a via 4201 is arranged to extend around the center of the electrode structure 4, and the support body 3 between the two electrode diaphragms can pass through the via 4201 without contacting the electrode structure 4. In this way, the two electrode diaphragms can realize a dual corrugated diaphragm structure, which is more sensitive to sound pressure and can significantly improve the sensitivity performance.

[0033] Further, the ambient pressure around the electrode structure 4 is less than 0.5 ambient atmospheric pressure. Preferably, the ambient pressure around the electrode structure 4 is less than 0.1 ambient atmospheric pressure. It should be understood that the receiving chamber is sealed, and taking the standard atmospheric pressure as an example, the air pressure in the receiving chamber is less than 0.1 atm, so that the noise impact of the dual-diaphragm MEMS microphone can be effectively reduced and the signal-to-noise ratio can be improved.

[0034] Furthermore, the radial beam 42 extends from the edge of the electrode structure 4 to the central area, thereby supporting each circumferential beam 41 and improving the structural stability of the electrode structure 4. Specifically, the radial beam 42 includes a first sub-beam 421 whose inner end extends to the circumferential beam 41 connected to the innermost circle and whose outermost end extends to the outer side of the circumferential beam 41 of the outermost circle, and a second sub-beam 422 whose inner end is connected to the circumferential beam 41 between the innermost circle circumferential beam 41 and the outermost circle circumferential beam 41 and whose outermost end extends to the outer side of the circumferential beam 41 of the outermost circle, wherein the outermost ends of the first sub-beam 421 and the second sub-beam 422 are both connected to the substrate 100, specifically, they are clamped and fixed between the first electrode diaphragm 1 and the second electrode diaphragm 2 and then connected to the substrate 100 through the corresponding diaphragms, so that the radial beam 42 can stably and reliably suspend the middle area of ​​the electrode structure 4 in the receiving cavity, and the force is evenly applied.

[0035] In this embodiment, the innermost end of each first sub-beam 421 is connected to the innermost circumferential beam 41, and the innermost end of each second sub-beam 422 is connected to the second circumferential beam 41 from the outside to the inside, wherein a second sub-beam 422 is provided between each two adjacent first sub-beams 421. In some embodiments, the innermost end of each second sub-beam 422 can be connected to the third, fourth, fifth or sixth circumferential beam 41 from the outside to the inside, and all the circumferential beams 41 on the extension path thereof are connected, and the specific connection position can be adaptively adjusted according to actual conditions, and the via hole 4201 is formed by the adjacent radial beams 42 and the adjacent circumferential beams 41. In this way, the via hole 4201 near the central area and the via hole 4201 near the peripheral area can reach a suitable size, and can pass through the support body 3 with sufficient strength to ensure the structural stability between the first electrode film and the second electrode film. In addition, it can ensure the structural stability of the internal circumferential beam 41 in the electrode structure 4 and the structural stability of the external circumferential beam 41. In some embodiments, two, three, or more second sub-beams 422 may be disposed between adjacent first sub-beams 421. In some embodiments, the cross-sectional shape of the support body 3 in a direction perpendicular to the counter electrode structure 4 may be rectangular, trapezoidal, triangular, or the like, and the angle between the support body 3 and the counter electrode structure 4 may be greater than 0° and less than or equal to 90°, such as 45°, 60°, or the like.

[0036] Further, the circumferential beam 41 is a complete ring or an open ring; the contour shape of the circumferential beam 41 is a circle or a regular polygon. The width of each circumferential beam 41 is equal, and the spacing between adjacent circumferential beams 41 is equal; or, the width of at least some circumferential beams 41 is not equal to the width of the remaining circumferential beams 41, and the spacing between adjacent circumferential beams 41 is not equal.

[0037] In this embodiment, the circumferential beam 41 is a complete annular shape, the center of the circumferential beam 41 is located at the center of the electrode structure 4, and each radial beam 42 is arranged at equal angles around the center of the electrode structure 4, and the intersection of each radial beam 42 is located at the center of the electrode structure 4, so that the entire electrode structure 4 is similar to a spider web, forming a spider web structure, which is more sensitive to sound pressure, which is conducive to realizing a low-noise microphone, while optimizing sensitivity and preventing sensitivity changes under different pressures. Moreover, the formed via 4201 is also an arc shape, wherein the support body 3 formed between the first electrode diaphragm 1 and the second electrode diaphragm 2 is adapted to the via 4201, that is, the support body 3 is an arc shape, therefore, the support bodies 3 of the same circle with the same radius can jointly form a larger cylindrical shape, thereby achieving good support for the first electrode diaphragm 1 and the second electrode diaphragm 2, preventing the electrode diaphragm from bending and deforming, and significantly improving the stability and reliability of the microphone, so that there can be a larger distance between adjacent vias 4201, and there is no need to set a large number of vias 4201.

[0038] In some embodiments, the circumferential beam 41 may be a complete regular polygon, such as a square, a regular pentagon, a regular hexagon, etc., and the first sub-beam 421 is preferably connected to the corner position of the polygonal circumferential beam 41. In some embodiments, the circumferential beam 41 may be an open ring, such as a semicircular ring, a quarter of a circular ring, etc., or a square, a regular pentagon, a half, a third, a quarter, etc. of a regular hexagon, and two adjacent circumferential beams 41 in the circumferential direction are arranged to be staggered in the radial direction. In some embodiments, the arrangement of each radial beam 42 around the center of the electrode structure 4 may also be at different angles.

[0039] Furthermore, the width of the radial beam 42 is equal at all places in its extension direction, which is equivalent to a rectangle; or, the width of the radial beam 42 gradually increases from the inside to the outside. In this embodiment, the width of the radial beam 42 gradually increases from the inside to the outside, similar to a cone, and the widths and spacings of the circumferential beams 41 are equal. The area of ​​the circumferential beam 41 of the inner ring is also smaller. Therefore, the smaller width of the radial beam 42 connected thereto can also ensure the structural stability of the circumferential beam 41.

[0040] Furthermore, the circumferential beam 41 and the radial beam 42 are both provided with a perforation 4202 that penetrates in the thickness direction. The setting of the perforation 4202 can connect the spaces on both sides of the electrode structure 4. When the microphone is working, the pressure between the spaces on both sides can be balanced, and the noise reduction effect is better. Moreover, the sensitivity can be optimized and the sensitivity can be prevented from changing with the atmospheric pressure. Among them, the shape of the perforation 4202 is preferably a circular hole. In some implementations, the perforation 4202 can be a regular non-circular hole, such as a regular polygon hole, a rectangular hole, a parallelogram hole, etc. Of course, the shape of the perforation 4202 can also be an irregular special-shaped perforation 4202. In addition, a hole ring can be embedded in the perforation 4202 to strengthen the structural strength of the perforation 4202.

[0041] Preferably, the perforations 4202 are arranged along the extension direction of the circumferential beam 41, and each perforation 4202 is distributed near the inner edge and near the outer edge of the circumferential beam 41. Specifically, each circumferential beam 41 is provided with a circle of perforations 4202 near the inner edge and near the outer edge, respectively, and the perforations 4202 in the same circle are arranged at intervals. This increases the flexibility of the electrode structure 4, while reducing the inter-plate capacitance between the first electrode membrane 1 and the second electrode membrane 2, so as to improve the sensitivity of the MEMS device.

[0042] Furthermore, one of the first electrode membrane 1 and the second electrode membrane 2 is provided with a release hole, and a portion of the through hole 4202 on the electrode structure 4 is directly opposite to the release hole.

[0043] In some embodiments, grooves may be provided on the surface of the circumferential beam 41 and the radial beam 42, and the through-holes 4202 are located outside the grooves. The provision of the grooves is equivalent to providing a reinforcing rib structure for the corresponding beams, which can improve the strength of the electrode structure 4.

[0044] Furthermore, the circumferential beam 41 and the radial beam 42 are both conductive, so that they can form two capacitors with the first electrode membrane 1 and the second electrode membrane 2. When the first electrode membrane 1 and the second electrode membrane 2 vibrate, the sizes of the two capacitors can be changed respectively, thereby outputting corresponding electrical signals.

[0045] In one embodiment, the circumferential beam 41 and the radial beam 42 may be completely composed of a conductive layer formed by doping conductive ions in a semiconductor material.

[0046] In some embodiments, the circumferential beam 41 and the radial beam 42 each include at least two stacked layers, and at least one layer is insulating. Preferably, the outermost layers are all insulating materials, and at least one inner layer is conductive, so that even if the first electrode membrane 1 or the second electrode membrane 2 touches the electrode structure 4, insulation can be ensured, and reliability is higher.

[0047] Furthermore, if Figure 3 , the first electrode membrane 1 and the second electrode membrane 2 are both provided with ventilation holes 201. Optionally, the ventilation holes 201 pass through the first electrode membrane 1 and the second electrode membrane 2, which is equivalent to forming a ventilation hole that penetrates the first electrode membrane 1 and the second electrode membrane 2, thereby significantly increasing the compliance of the membrane in the area where the ventilation holes 201 are located. The ventilation holes 201 on the first electrode membrane 1 and the second electrode membrane 2 can have the same size and shape, or different, which is not limited here.

[0048] The above description is only an implementation mode of the present invention. It should be pointed out that, for ordinary technicians in this field, improvements can be made without departing from the creative concept of the present invention, but these all belong to the protection scope of the present invention.

Claims

1. A pair of electrode structures, applied to a dual-diaphragm MEMS microphone, characterized in that: The electrode structure includes a plurality of circumferential beams spaced apart from the inside to the outside and a plurality of radial beams connected to the circumferential beams and extending from the inside to the outside. The circumferential beams extend around the center of the electrode structure, and each of the radial beams is spaced apart and arranged around the center of the electrode structure. A via hole extending around the center of the electrode structure is formed between two adjacent circumferential beams.

2. The electrode structure according to claim 1, characterized in that: The radial beams extend from the edge of the counter electrode structure to the central region.

3. The counter electrode structure according to claim 1, characterized in that: The radial beam includes a first sub-beam whose inner end extends to be connected to the innermost circumferential beam and whose outermost end extends to the outer side of the outermost circumferential beam.

4. The counter electrode structure according to claim 3, characterized in that: The radial beam further includes a second sub-beam whose inner end is connected to the circumferential beam between the innermost circle and the outermost circle and whose outermost end extends to the outer side of the circumferential beam of the outermost circle.

5. The counter electrode structure according to claim 1, characterized in that: The circumferential beam is in the shape of a complete ring or an open ring.

6. The counter electrode structure according to claim 5, characterized in that: The contour shape of the circumferential beam is a circle or a regular polygon.

7. The counter electrode structure according to claim 1, characterized in that: The widths of the circumferential beams are equal, and the spacings between adjacent circumferential beams are equal; Alternatively, the width of at least some of the circumferential beams is not equal to the width of the remaining circumferential beams, and the intervals between adjacent circumferential beams are not equal.

8. The counter electrode structure according to claim 1, characterized in that: The radial beams are arranged at equal angles around the center of the electrode structure.

9. The electrode structure and dual-diaphragm MEMS microphone according to claim 1, characterized in that: The width of the radial beam is equal at all points along its extension direction; Alternatively, the width of the radial beam gradually increases from the inside to the outside.

10. The counter electrode structure according to claim 1, characterized in that: The circumferential beam and the radial beam are both provided with through holes penetrating in the thickness direction.

11. The counter electrode structure according to claim 10, characterized in that: The through holes are arranged along the extension direction of the circumferential beam, and each of the through holes is distributed near the inner edge and the outer edge of the circumferential beam.

12. The counter electrode structure according to claim 10, characterized in that: Grooves are provided on the surfaces of the circumferential beam and the radial beam, and the through holes are located outside the grooves.

13. The counter electrode structure according to claim 1, characterized in that: The circumferential beams and the radial beams are both electrically conductive.

14. The counter electrode structure according to claim 13, characterized in that: The circumferential beam and the radial beam each include at least two stacked layers, and at least one layer is insulated.

15. A dual-diaphragm MEMS microphone, comprising a substrate having a back cavity and a capacitor system connected to the substrate and covering the back cavity, the capacitor system comprising a first electrode diaphragm and a second electrode diaphragm arranged at intervals, a receiving cavity being formed between the first electrode diaphragm and the second electrode diaphragm, characterized in that: The cross-sectional shapes of the first electrode membrane and the second electrode membrane in the radial direction are both corrugated, and the crests of the first electrode membrane and the troughs of the second electrode membrane are connected to form a support body. The capacitor system also includes an electrode structure as described in any one of claims 1 to 14 connected to the substrate and suspended in the receiving cavity, and the support body passes through the via hole and is spaced apart from the edge of the via hole.

16. The dual-diaphragm MEMS microphone according to claim 15, characterized in that: The ambient pressure around the counter electrode structure is less than 0.5 ambient atmospheres.

17. The dual-diaphragm MEMS microphone according to claim 16, characterized in that: The ambient pressure around the electrode structure is less than 0.1 ambient atmosphere.

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