micro-electromechanical systems

Abstract

A micro-electromechanical system (MEMS) includes a backplate and a diaphragm. The backplate includes a plurality of stator elements spaced apart with gaps therebetween, the stator elements including a first conductive element; the diaphragm includes a plurality of folds corresponding to the gaps, each fold including a groove formed on a surface away from the backplate, and the folds including a second conductive element. The diaphragm moves relative to the backplate in response to applied pressure, causing the folds to move into or out of the corresponding gaps, thereby changing the capacitance formed between the first conductive element and the second conductive element. The folds are defined by the grooves formed on the surface away from the backplate, which helps control the compliance of the diaphragm and reduce the stiffness of the diaphragm. The folds can be formed with a low aspect ratio, which allows them to be formed using a standard front-facing process.

Description

Technical Field

[0001] The present invention relates to the field of electroacoustic conversion devices, and in particular to a microelectromechanical system (MEMS) used in electroacoustic conversion devices. Background Art

[0002] Microelectromechanical systems (MEMS) are widely used in electroacoustic transducers. A typical MEMS consists of a backplate, a diaphragm facing the backplate, fixed comb teeth attached to the backplate, and dynamic comb teeth attached to the diaphragm. The dynamic and fixed comb teeth include electrode fingers that typically have a high aspect ratio and a mechanical stiffness that is orders of magnitude higher than that of the diaphragm. Displacement of the diaphragm causes the dynamic and fixed comb teeth to shift relative to each other. This displacement causes the output voltage to vary proportionally with the displacement of the dynamic and fixed comb teeth. A particular advantage of MEMS is that the dynamic and fixed comb teeth can be configured to provide sliding motion relative to each other, rather than the squeezing motion that occurs in most parallel plate microphones.

[0003] However, the high stiffness of the moving and fixed comb electrode fingers relative to the diaphragm places a premium on diaphragm compliance, making it difficult to achieve reasonable sensitivity in low-gain implementations using application-specific integrated circuits (ASICs). High stiffness also drives a high aspect ratio to produce sufficiently high operating capacitance. Furthermore, specialized processes, such as expensive silicon-on-insulator (SOI) wafers, are required to fabricate fingers with high aspect ratios.

[0004] Therefore, people hope to provide an improved micro-electromechanical system that can overcome at least one of the above problems. Summary of the Invention

[0005] In view of this, an embodiment of the present invention provides a micro-electromechanical system comprising: a backplate including a plurality of stator elements spaced apart with gaps therebetween, the stator elements including a first conductive element; and a diaphragm including a plurality of folds corresponding to the gaps, each fold including a groove formed on a surface distal from the backplate, the folds including a second conductive element. The diaphragm moves relative to the backplate in response to pressure applied thereto, causing the folds to move into or out of the corresponding gaps, thereby changing the capacitance formed between the first conductive element and the second conductive element.

[0006] Preferably, the corrugation includes an insulating corrugated portion, and the second conductive element is corrugated and embedded in the insulating corrugated portion.

[0007] Preferably, the corrugation further comprises an insulating connection portion connecting two adjacent insulating corrugated portions and a conductor embedded in the insulating connection portion, and two adjacent second conductive elements are connected to each other via the conductor embedded in the insulating connection portion.

[0008] Preferably, two adjacent second conductive elements are disconnected from each other, so that a differential signal can be output through the two adjacent second conductive elements.

[0009] Preferably, the folds further include an insulating connection portion, and the insulating connection portion is formed integrally with the insulating fold portion.

[0010] Preferably, the corrugation further includes an insulating connection portion, the second conductive element is exposed outside the diaphragm, and two adjacent second conductive elements are disconnected from each other and connected to the insulating connection portion.

[0011] Preferably, each pleat extends along a first direction, and a plurality of the pleats are arranged in a row along a second direction that is angled relative to the first direction.

[0012] Preferably, in a cross section perpendicular to the first direction, the folds are U-shaped or V-shaped.

[0013] Preferably, the center line of the fold and the center line of the corresponding gap are arranged opposite each other and parallel to the moving direction of the fold.

[0014] Preferably, the micro-electromechanical system further includes an insulator arranged between the diaphragm and the back plate.

[0015] Preferably, the distance between the center lines of two adjacent wrinkles is in the range of 3um to 20um.

[0016] Preferably, the distance between the center lines of two adjacent folds is between 6um and 10um.

[0017] Preferably, the distance between two adjacent stator elements is in the range of 0.5um to 6um.

[0018] Preferably, the distance between two adjacent stator elements is in the range of 1 um to 3 um.

[0019] Preferably, the diaphragm includes a main body for suspending the corrugations, and the distance between the main body and the stator element in the moving direction of the corrugations is between 1.5 um and 12 um.

[0020] Preferably, the back plate further comprises an anchor point mounted on a base plate and a plurality of spokes extending from a center of the back plate to the anchor point, the anchor point and the stator element are arranged on concentric rings, and the stator element is suspended by the spokes.

[0021] Preferably, the diaphragm has a circular structure, and the folds are arranged in concentric rings; each of the rings includes a plurality of spaced-apart fold portions, and cutouts are formed between adjacent fold portions to allow the corresponding spokes to pass through.

[0022] Preferably, the pleated portion includes a pair of opposite arc ends, and each of the arc ends extends toward the corresponding incision.

[0023] Preferably, the stator element protrudes from the surface of the spoke facing the diaphragm; or the stator element is formed between adjacent spokes, and the stator element and the surfaces of the spoke facing the diaphragm are coplanar.

[0024] In an embodiment of the present invention, the corrugations are defined by grooves formed on its surface away from the back plate, which help control the compliance of the diaphragm. Unlike conventional comb-tooth electrode fingers that may increase the stiffness of the diaphragm, the grooves of the corrugations effectively reduce the stiffness of the diaphragm. When the corrugations are close to the stator element, lower noise conduction can be obtained, avoiding the squeeze film damping and rotational resistance common in parallel plate microphones. When the corrugations are arranged axially on the diaphragm, a lower aspect ratio can be formed than conventional comb-tooth electrode fingers, which makes it possible to form using standard front-side processes and avoid the cost of expensive silicon-on-insulator (SOI) type processes.

[0025] Using insulating high-yield material to form the main body of the diaphragm and / or the insulating corrugated portion of the corrugation improves the mechanical reliability of devices using microelectromechanical systems. The second conductive element of the corrugation can be separate or continuous, allowing the components to be electrically arranged in a differential format and capable of driving higher turn-on voltages. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly explain the technical solutions of the embodiments of the present disclosure, the following briefly describes the drawings used to illustrate the embodiments. Obviously, the drawings described below only relate to some embodiments of the present disclosure. If a skilled person has not invented an invention, other drawings can be obtained based on the drawings of the skilled person.

[0027] Figure 1 A top view of a micro-electromechanical system according to an embodiment of the present invention;

[0028] Figure 2 for Figure 1 A partially enlarged schematic diagram of a micro-electromechanical system is shown;

[0029] Figure 3 for Figure 1 A partially enlarged cross-sectional view of the micro-electromechanical system shown;

[0030] Figure 4 for Figure 1 A top view of the backplane of the MEMS is shown;

[0031] Figure 5 for Figure 1 A top view of the diaphragm of the MEMS is shown;

[0032] Figure 6 for Figure 1 A partial perspective view of the back plate and diaphragm of the MEMS shown;

[0033] Figure 6A for Figure 6 A partial enlarged view of

[0034] Figures 7 to 9 The figure shows the folds of a modified embodiment of the present invention;

[0035] Figure 10 The present invention provides an electroacoustic converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described with reference to the accompanying drawings. It should be noted that elements with similar structures or functions are represented by similar numbers in the figures. These embodiments are not intended to be exhaustive or descriptive of various embodiments, nor to serve as limitations on the scope of the claims or other aspects that one skilled in the art can achieve based on the embodiments described herein. Furthermore, the illustrated embodiments do not necessarily provide all aspects or advantages that may be achieved.

[0037] See also Figure 1-Figure 4 The micro-electromechanical system 10 includes a back plate 20, a diaphragm 40 that moves relative to the back plate 20 based on pressure applied thereto, and an insulator 60 disposed around the periphery of the diaphragm 40 and the periphery of the back plate 20. In some embodiments, the micro-electromechanical system 10 further includes a substrate 80. The back plate 20 is mounted on the substrate 80.

[0038] The backplate 20 includes an anchor point 22 mounted on the base plate 80, a plurality of spokes 23 extending from the center of the backplate 20 to the anchor point 22, and a plurality of stator elements 24 suspended by the spokes 23. In some embodiments, the anchor point 22 and the stator elements 24 are arranged in concentric rings. The spokes 23 extend radially. The stator elements 24 may protrude from the surface of the spokes 23 and face the diaphragm 40. Alternatively, the stator elements 24 may be formed between adjacent spokes 23, with the surfaces of the stator elements 24 and the spokes 23 facing the diaphragm 40 being coplanar. The stator elements 24 are attached to or integrally formed with the spokes 23. The spokes 23 may be made of a conductive or insulating material. Preferably, the spokes 23 are made of a material with a density low enough to merely suspend the stator elements 24 in place. The stator elements 24 are spaced apart from each other, forming gaps 26 therebetween. The stator elements 24 include a first conductive element 242. In some embodiments, the stator element 24 is made of a conductive material as the first conductive element 242. In some other embodiments, the stator element 24 further includes an insulating element 244, and the first conductive element 242 is embedded in the insulating element 244 or coated on the surface of the insulating element 244. A plurality of voids 26 extend through the back plate 20. The voids 26 can be through-holes, gaps, openings, etc.

[0039] The diaphragm 40 includes a plurality of folds 42 facing the plurality of gaps 26 in the axial direction. Each fold 42 includes a groove 421 formed on a surface away from the back plate 20. The fold 42 includes a second conductive element 424 (such as Figure 7-9 As shown in FIG. 4 , when the diaphragm 40 moves up and down relative to the backplate 20, the wrinkles 42 reciprocate in and out of the gap 26. The capacitance between the diaphragm 40 and the backplate 20 is primarily determined by the overlap between the first conductive element 242 and the second conductive element 424. That is, the further the wrinkles 42 extend into the gap 26, thereby increasing the overlap between the first conductive element 242 and the second conductive element 424, and thus the greater the capacitance. Similarly, the less the wrinkles 42 extend into the gap 26, the less overlap between the first conductive element 242 and the second conductive element 424 is reduced, and the smaller the capacitance. Based on the change in capacitance, an electrical signal is generated and output.

[0040] Each pleat 42 extends along a first, longitudinal, circumferential direction. Pleats 42 are evenly spaced and arranged in rows along a second, transverse, radial direction. In a cross-section perpendicular to the first, longitudinal, circumferential direction, pleats 42 may be U-shaped or V-shaped. Preferably, the centerline of a pleat 42 is aligned with the centerline of the corresponding gap 26 and parallel to the direction of movement of the pleat 42. In some embodiments, the direction of movement of the pleats is parallel to the axial direction of the diaphragm 40 and perpendicular to the first and second directions.

[0041] like Figure 5-Figure 6As shown in Figure A, in some embodiments, the diaphragm 40 has a circular structure with pleats 42 arranged in concentric rings. The surfaces of the stator element 24 and spokes 23 facing the diaphragm 40 are coplanar, or the height of the stator element 24 extending beyond the surface of the spokes 23 facing the diaphragm 40 is less than the height of the pleats 42. The portions of the pleats 42 aligned with the spokes 23 have cutouts 43 to prevent interference between the pleats 42 and the spokes 23 when the pleats 42 move relative to the stator element 24. In this embodiment, the surface of the diaphragm 40 facing the spokes 23 of the backplate 20 defines a plurality of radially extending slots. The portions of the slots between adjacent pleats 42 form cutouts 43 to allow the corresponding spokes 23 to pass through. That is, each ring of pleats 42 includes multiple pleat portions 422, with cutouts 43 formed between adjacent pleat portions 422. The arcuate end 425 of each pleat portion 422 extends into the corresponding cutout 43. Preferably, the arc ends 425 of the corrugated portions 422 extending toward the corresponding cutouts 43 are circular. Alternatively, the diaphragm 40 has other configurations, such as a rectangular configuration.

[0042] The width of gap 26 in the second / lateral / radial direction is greater than the width of pleats 42, allowing pleats 42 to be inserted into gap 26 without interference. The distance W1 between the centerlines of adjacent pleats 42 and the width W2 of gap 26 are selected to minimize noise in the MEMS while ensuring sufficient operating capacitance. Preferably, the width W2 of gap 26 is in the range of 0.5 μm to 6 μm, more preferably 1 μm to 3 μm. The width W2 between the centerlines of adjacent pleats 42 is in the range of 3 μm to 20 μm, more preferably 6 to 10 μm.

[0043] The diaphragm 40 also includes a main body 44 for suspending the folds 42 spaced apart from the back plate 20. The folds 42 extend from the main body 44 toward the back plate 20. Preferably, the main body 44 is made of an insulating material having a high yield force, including but not limited to silicon nitride, silicon carbide or some other oxide. The periphery of the main body 44 is fixed to the periphery of the back plate 20 by an insulator 60. The periphery of the back plate 20 can be anchored to the substrate 80 of the micro-electromechanical system. The gap G3 between the stator element 24 of the back plate 20 and the main body 44 of the diaphragm 40 in the moving direction of the folds 42 is in the range of 1.5um-12um. Preferably, the gap G3 is in the range of 3um-6um.

[0044] like Figure 7As shown, in some embodiments, the corrugations 42 include a plurality of insulating corrugated portions 426, an insulating connecting portion 428 connecting two adjacent insulating corrugated portions 426, and a conductor 427 embedded in the insulating connecting portion 428. The second conductive element 424 is corrugated and embedded in the insulating corrugated portion 426. Two adjacent second conductive elements 424 are connected to each other by a conductor 427, which is embedded in the insulating connecting portion 428 connecting the adjacent insulating corrugated portions 426. Preferably, the second conductive element 424 is made of a continuous film, thereby forming a continuous second conductive element 424.

[0045] like Figure 8 As shown, in some embodiments, two adjacent second conductive elements 424 are disconnected from each other, so that differential signals can be output through the two adjacent second conductive elements 424 .

[0046] like Figure 9 As shown, in some embodiments, the entire corrugation 42 is made of a conductive material and has no insulating portion, that is, the second conductive element 424 is exposed outside the diaphragm 40 . Two adjacent second conductive elements 424 are disconnected from each other and connected to the insulating connecting portion 428 .

[0047] The second conductive element 424 of the corrugation 42 may be made of a conductive barrier material including but not limited to polysilicon and metal elements or titanium nitride.

[0048] Figure 10 Disclosed is an electroacoustic converter 100 using the micro-electromechanical system 10. The electroacoustic converter 100 further includes an application-specific integrated circuit ASIC electrically connected to the micro-electromechanical system 10. The electroacoustic converter 100 may be a micro-electromechanical microphone.

[0049] In an embodiment of the present application, the corrugations 42 are defined by grooves 421 formed on their surface facing away from the backplate 20. These grooves 421 help control the compliance of the diaphragm 40. Unlike conventional comb-tooth electrode fingers, which may increase the stiffness of the diaphragm 40, the grooves 421 of the corrugations 42 effectively reduce the stiffness of the diaphragm 40. When the corrugations 42 are positioned close to the stator element 24, lower noise conduction is achieved, avoiding the squeeze film damping and rotational resistance common in parallel plate microphones. When the corrugations 42 are axially aligned on the diaphragm 40, a lower aspect ratio can be achieved compared to conventional comb-tooth electrode fingers. This allows for standard front-end processing and avoids the cost of expensive silicon-based processing. Using an insulating high-yield material to form the main body 44 of the diaphragm 40 and / or the insulating corrugated portions 426 of the corrugations 42 improves the mechanical reliability of devices employing microelectromechanical systems. The second conductive element 424 of the corrugations 42 can be split or continuous, allowing for the electrical arrangement of components in a differential format and enabling the use of higher turn-on voltages.

[0050] Although the present invention has been described with reference to one or more embodiments, the above description of the embodiments is intended only to enable those skilled in the art to practice or use the present invention. It should be noted that a person skilled in the art may make a number of variations and improvements without departing from the scope of the present invention, and these variations and improvements are within the scope of the present invention. The above embodiments should not be construed as limiting the present invention, and the scope of the present invention should be determined with reference to the claims.

Claims

1. A micro-electromechanical system, characterized in that: The micro-electromechanical system comprises: a back plate comprising an anchor point mounted on a base plate, a plurality of spokes extending from a center of the back plate to the anchor point, and a plurality of stator elements spaced apart with gaps therebetween, the anchor point and the stator elements being arranged on concentric rings, the stator elements being suspended by the spokes, the stator elements comprising a first conductive element; and a diaphragm comprising a plurality of corrugations respectively corresponding to the plurality of gaps, each corrugation comprising a groove formed on a surface away from the back plate, and the corrugations comprising a second conductive element; The diaphragm moves relative to the back plate in response to the pressure applied thereon, causing the wrinkles to move into or out of the corresponding gaps, thereby changing the capacitance formed between the first conductive element and the second conductive element.

2. The micro-electromechanical system according to claim 1, wherein: The corrugation includes an insulating corrugated portion, and the second conductive element is corrugated and embedded in the insulating corrugated portion.

3. The micro-electromechanical system according to claim 2, wherein: The corrugation further includes an insulating connection portion connecting two adjacent insulating corrugated portions and a conductor embedded in the insulating connection portion. Two adjacent second conductive elements are connected to each other via the conductor embedded in the insulating connection portion.

4. The micro-electromechanical system according to claim 2, wherein: Two adjacent second conductive elements are disconnected from each other, so that differential signals can be output through the two adjacent second conductive elements.

5. The micro-electromechanical system according to claim 2, wherein: The corrugation further includes an insulating connection portion, which is integrally formed with the insulating corrugation portion.

6. The micro-electromechanical system according to claim 1, wherein: The corrugation further includes an insulating connection portion, the second conductive element is exposed outside the diaphragm, and two adjacent second conductive elements are disconnected from each other and connected to the insulating connection portion.

7. The micro-electromechanical system according to claim 1, wherein: Each pleat extends along a first direction, and a plurality of the pleats are arranged in a row along a second direction that is angled relative to the first direction.

8. The micro-electromechanical system according to claim 7, wherein: In a cross section perpendicular to the first direction, the corrugations are U-shaped or V-shaped.

9. The micro-electromechanical system according to claim 1, wherein: The center line of the fold and the center line of the corresponding gap are arranged opposite to each other and are parallel to the moving direction of the fold.

10. The micro-electromechanical system according to claim 1, wherein: The micro-electromechanical system further includes an insulator disposed between the diaphragm and the back plate.

11. The micro-electromechanical system according to claim 1, wherein: The distance between the center lines of two adjacent wrinkles is in the range of 3um to 20um.

12. The micro-electromechanical system according to claim 11, wherein: The distance between the center lines of two adjacent wrinkles is between 6um and 10um.

13. The micro-electromechanical system according to claim 1, wherein: The distance between two adjacent stator elements is in the range of 0.5um to 6um.

14. The micro-electromechanical system according to claim 13, wherein: The distance between two adjacent stator elements is in the range of 1um to 3um.

15. The micro-electromechanical system according to claim 1, wherein: The diaphragm includes a main body for suspending the corrugations, and a distance between the main body and the stator element in the moving direction of the corrugations is between 1.5um and 12um.

16. The micro-electromechanical system according to claim 1, wherein: The diaphragm has a circular structure, and the folds are arranged in concentric rings; Each of the rings includes a plurality of spaced-apart folds, with cutouts formed between adjacent folds to allow the corresponding spokes to pass through.

17. The micro-electromechanical system according to claim 16, wherein: The folded portion includes a pair of opposite arc ends, and each of the arc ends extends toward the corresponding cutout.

18. The micro-electromechanical system according to claim 1, wherein: The stator element protrudes beyond the surface of the spoke facing the diaphragm; or The stator element is formed between adjacent ones of the spokes, and surfaces of the stator element and the spokes facing the diaphragm are coplanar.

Images