Fixing-fixing film of micro-electro-mechanical system microphone

Abstract

The present invention relates to a fixation-fixation membrane for a micro-electro-mechanical system (MEMS) microphone. In one embodiment, a MEMS acoustic sensor includes a substrate; a film parallel to the substrate; and at least one vent hole formed in the membrane, where the at least one vent hole is a curved opening in the membrane, and where the at least one vent hole is disposed substantially along a length of the membrane.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The subject application claims priority to U.S. application serial number 17 / 931,783, filed on September 13, 2022, entitled “FIXED-FIXED MEMBRANE FOR MICROELECTROMECHANICAL SYSTEM MICROPHONE,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates generally to micro-electromechanical systems (MEMS) devices and, more particularly, to MEMS microphones. Background Art

[0004] A MEMS condenser microphone typically has a diaphragm that forms a variable capacitor with an underlying backplate. Receiving an audible signal causes the diaphragm to vibrate, thereby generating a variable capacitance signal that represents the audible signal. It is this variable capacitance signal that can be amplified, recorded, or otherwise transmitted to another electronic device.

[0005] The vibrating membrane of a MEMS microphone is usually constructed as a membrane composed of one or more layers. The membrane is usually tensioned and fully clamped, for example, to a back plate. However, the tensioned and fully clamped membrane may exhibit undesirable stiffness, for example, causing the membrane to have low compliance and low average to maximum deflection. This in turn may result in lower sensitivity than expected. Therefore, it is desirable to implement a technique to improve the sensitivity of a MEMS microphone. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Non-limiting embodiments of the present disclosure are described with reference to the following drawings, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified:

[0007] Figure 1A is a top perspective view depicting a packaged microphone having a MEMS microphone die 16 configured in accordance with various embodiments of the present disclosure.

[0008] Figure 1B It is a depiction Figure 1A A bottom perspective view of the packaged microphone is shown.

[0009] Figure 1C is described as Figure 1A Cross-sectional view of a packaged microphone oriented as shown.

[0010] Figure 1D is a cross-sectional diagram depicting a similar packaged microphone with a bottom port.

[0011] Figure 2 is a cross-sectional perspective view depicting an exemplary MEMS microphone according to various embodiments of the present disclosure.

[0012] Figure 3 is a diagram depicting a fixed-fixed membrane for a MEMS microphone according to various embodiments of the present disclosure.

[0013] Figure 4 is a cross-sectional diagram depicting various layers of a MEMS microphone membrane according to various embodiments of the present disclosure.

[0014] Figure 5 It is a depiction Figure 3 A top perspective view of a quarter portion of a membrane layer is shown.

[0015] Figure 6 is an enlarged view depicting an end of a vent hole formed in a MEMS microphone membrane according to various embodiments of the present disclosure.

[0016] 7A to 7C is a diagram depicting various MEMS microphone membrane configurations that may be used in accordance with various embodiments of the present disclosure. DETAILED DESCRIPTION

[0017] One or more aspects of the present disclosure are generally directed to MEMS microphones and corresponding methods of use. For example, the MEMS microphones described herein can utilize a tensioned "fixed-fixed" membrane. As used herein, "fixed-fixed" refers to a membrane that is fixed to a substrate at opposite ends or edges without the use of springs or a fully clamped design. By way of another example, a MEMS microphone as described herein can utilize a curved vent slit that narrows the width of the membrane at its center relative to the fixed ends of the membrane, thereby eliminating and / or reducing wrinkling of the membrane.

[0018] By utilizing the fixed-fixed membranes described herein, various advantages that improve the performance of MEMS microphones can be achieved. These advantages may include, but are not limited to, the following. Compared to a fully clamped design, for example, higher microphone sensitivity can be achieved due to a higher average deflection. Compared to existing membranes, the membranes described herein can be constructed using a wider variety of shapes, aspect ratio die sizes, etc. Compared to spring-based designs, the clamping force can be increased, resulting in higher robustness. The length of the membrane can be defined by the vents rather than by the undercut of oxide and / or other sacrificial materials in the sensing gap between the membrane and the backplate, thereby reducing the impact of process variations. An elliptically curved vent shape can be used with a beam width at the center that is less than the beam width at the edges, thereby reducing and / or eliminating wrinkling of the membrane. Other advantages are also possible.

[0019] In one aspect disclosed herein, a MEMS acoustic sensor includes a substrate, a membrane disposed parallel to the substrate, and at least one vent formed in the membrane. The at least one vent may be a curved and substantially linear opening in the membrane, and the at least one vent may be disposed substantially along the length of the membrane.

[0020] In another aspect disclosed herein, another MEMS acoustic sensor may include a substrate and a polygonal shaped membrane attached to the substrate at respective edges of the membrane. The membrane may have at least one vent, which may be a curved and substantially linear opening in the membrane.

[0021] In another aspect disclosed herein, a membrane for a MEMS microphone may include a first membrane portion configured to flex in response to receiving an acoustic signal. The membrane may also include a second membrane portion configured to be attached to a substrate. The membrane may also include a third membrane portion having at least one vent, wherein each of the at least one vent is a curved through hole in the third membrane portion. Each of the at least one vent may have a corresponding substantially elliptical hole located at a corresponding end of each of the at least one vent, and the membrane may have a rectangular shape.

[0022] Other embodiments and various examples, scenarios and implementations are described in more detail below. The following description and accompanying drawings set forth certain illustrative embodiments of the present specification. However, these embodiments are merely indicative of a few of the various ways in which the principles of the present specification may be employed. Other advantages and novel features of the described embodiments will become apparent from the following description when considered in conjunction with the accompanying drawings.

[0023] Referring now to the drawings, various views of an exemplary MEMS microphone assembly are provided. It should be noted that the drawings are not drawn to scale, either within a single drawing or between different drawings.

[0024] Figure 1A Schematically illustrates a top perspective view of a packaged microphone 10 that may be combined with a MEMS microphone die 16 (eg, Figure 1C , 1D and other dies discussed below). In a corresponding manner, Figure 1B A bottom perspective view of the same packaged microphone 10 is schematically shown.

[0025] Figure 1A to Figure 1B The packaged microphone 10 shown has a package base 12 and a corresponding cover 14, forming an inner cavity containing a microphone die 16 and, if desired, a separate microphone circuit chip 18 (dies 16 and 18 are arranged in a Figure 1C and 1D 1 and discussed below). The cover 14 in this embodiment is a cavity-type cover having four walls extending generally orthogonally from the top inner surface to form a cavity. In one embodiment, the cover 14 is formed of metal or other conductive material to shield the microphone die 16 from electromagnetic interference. The cover 14 is secured to the top surface of the substantially planar package base 12 to form an inner cavity.

[0026] The cover 14 also has an audio input port 20 that allows audio signals to enter the cavity. However, in alternative embodiments, the audio port 20 is located in another location, such as through the package base 12, or through one of the side walls of the cover 14. The audio signal entering the internal cavity interacts with the microphone die 16 to generate an electrical signal, which, together with additional (external) components (such as a speaker and accompanying circuitry), generates an output audible signal corresponding to the input audible signal.

[0027] Figure 1B A bottom surface 22 of package base 12 is shown having a plurality of contacts 24 for electrically connecting (and in some embodiments physically connecting) microphone die 16 to a substrate, such as a printed circuit board or other electrical interconnect. Packaged microphone 10 may be used in any of a variety of applications. For example, packaged microphone 10 may be used with mobile phones, land-line telephones, computer equipment, video games, hearing aids, hearing instruments, biometric security systems, two-way radios, public address systems, and other devices that convert signals. In addition, packaged microphone 10 may also be used desirably as a speaker to produce an audible signal from an electronic signal.

[0028] In some embodiments, Figure 1A and Figure 1B The package base 12 shown in the figure can be a printed circuit board material, such as FR-4, or a pre-molded lead frame type package (also referred to as a "pre-molded package"). Other embodiments can use different package types, such as ceramic cavity packages. Therefore, the discussion of a specific type of package is for illustrative purposes only.

[0029] Figure 1C Schematically shows the Figure 1A FIG. 1 is a cross-sectional view of packaged microphone 10 along line CC. As shown and described above, cover 14 and base 12 form an inner cavity for accommodating MEMS microphone die 16 and electronic device 18 for controlling and driving microphone die 16. In an exemplary embodiment, the electronic device is implemented as a second independent integrated circuit, such as an application specific integrated circuit (ASIC) 18. However, other embodiments may form the MEMS microstructure and the electronic circuit on a single chip.

[0030] Adhesive or other fastening mechanisms secure the microphone die 16 and the ASIC die 18 to the base 12. Wires electrically connect the microphone die 16 and the ASIC die 18 to contact pads (not shown) inside the package base 12 and to each other.

[0031] Although Figures 1A to 1C A top port packaged microphone design is shown, but some embodiments position the input port elsewhere, such as through the base 12. For example, Figure 1D A cross-sectional view of a similar packaged microphone 10 is schematically shown, wherein the microphone die 16 covers the input port, thereby creating a large back volume. Other embodiments not shown position the microphone die 16 so that it does not cover the input port 20 through the base 12.

[0032] Discussion of specific packaged microphones is for illustrative purposes only. Figures 1A to 1D The discussion of packaged microphone 10 is not intended to limit all embodiments of the present disclosure.

[0033] Next reference Figure 2 , provides a cross-sectional perspective view of an exemplary MEMS microphone 200. Figure 2 As shown, the stationary portion of the microphone 200 has a back plate 32, which together with the membrane 50 forms a variable capacitor. As known to those skilled in the art, the variable capacitor generates an electrical signal representing the input acoustic signal incident on the membrane 50. For ease of operation, the back plate 32 can have a plurality of through holes (also referred to herein as back plate holes or simply holes) that lead to the back cavity. The shape, size and configuration of the holes can optimize performance.

[0034] In one embodiment, Figure 2The membrane 50 shown in FIG. 5 may be deposited on and / or otherwise coupled to other portions of the underlying acoustic sensor, such as the back plate 32, a substrate (e.g., as will be described below with reference to FIG. 5 ), and / or a plurality of other portions of the acoustic sensor. Figure 3 Depending on the embodiment, the substrate can be positioned on either side of the backplate 32 relative to the membrane 50. Thus, for example, the substrate can be located between the backplate 32 and the membrane 50 (forming a membrane-substrate-backplate stack), or the substrate can be placed opposite the membrane 50 (forming a membrane-backplate-substrate stack).

[0035] Figure 2 The back plate 32 shown in FIG. 5 can be composed entirely or partially of polysilicon and / or another conductive material. By using a conductive material in the back plate, the electrode patterning can be performed within the membrane 50 rather than on the back plate 32 and / or other portions of the underlying acoustic sensor (e.g., as described below with reference to FIG. 5 ). Figure 3 As stated above). Figure 2 As further shown, the membrane 50 may be composed of multiple layers, for example, 3 layers consisting of a conductive layer between two non-conductive (eg, silicon nitride) layers, except for the contact area 34 between the conductive portion of the back plate 32 and the membrane 50. Figure 4 The film 50 and its corresponding layers are described in greater detail.

[0036] like Figure 2 As further shown in FIG. 5 , portions of the back plate 32 may have corresponding dimples 36 or other protrusions that extend outwardly in the direction of the membrane 50. In one embodiment, the height of the dimples 36 may be determined to meet the mAOP associated with the microphone 200. Figure 2 As further shown in , portions of the back plate 32 and / or membrane 50 may be attached to a handle (block) 40 for manufacturing the microphone 200 .

[0037] Next reference Figure 3 , a schematic diagram 300 is provided, depicting a fixed-fixed membrane 50 for a MEMS acoustic sensor (e.g., a MEMS microphone), also referred to herein as a membrane. For the sake of brevity, repeated descriptions of similar elements used in other embodiments described herein are omitted. Figure 3 and the following figures, it should be noted that the term "membrane" is used to describe a structural element equivalent to the vibrating membrane 30 described above. It should also be noted that when used to describe the corresponding structure, the terms "membrane" and "vibrating membrane" can be based on the operating state of the structure. For example, the term "membrane" can be used to indicate that the corresponding structure is under tension, while the term "vibrating membrane" can be used to indicate that the same structure is at rest (i.e., not under tension). However, it should also be noted that in some cases, the terms "membrane" and "vibrating membrane" can be used interchangeably in this article.

[0038] As shown in schematic diagram 300, film 50 is attached to an underlying substrate 60 and / or another suitable device surface. Techniques by which film 50 may be attached to substrate 60 are described in more detail below. Although film 50 shown in diagram 300 is shown attached to substrate 60, it should be noted that in some embodiments, film 50 may not be directly attached to substrate 60. For example, film 50 may be attached to a backplane (e.g., as described above with respect to Figure 2 The back plate 32 is described above, with a layer of optional spacing material placed between the membrane 50 and the back plate. The back plate can then be attached to the substrate 60, with another layer of optional spacing material placed between the back plate and the substrate 60. Other implementations may also be used.

[0039] As further shown in Figure 300, the film 50 can have a substantially rectangular shape, that is, so that the perimeter of the film 50 has two longer sides and two shorter sides. The film 50 can also take other shapes, which will be referred to below. 7A to 7C Some examples of these are described in more detail. The film 50 may be composed of one or more layers, for example, as will be described below with reference to Figures 4 to 5 As described above, each layer may be solid and / or have corresponding holes or other openings (e.g., as described above with reference to Figure 2 The holes 38 may be provided to adjust a low frequency corner of an associated acoustic sensor, to improve airflow through the membrane 50, and / or for other purposes.

[0040] The membrane 50 shown in Figure 300 can be conceptually divided into three membrane parts. The first part 302 of the membrane 50, also referred to herein as the sensing area or electrode, can be configured to sense the deflection of the membrane 50 in response to receiving an acoustic signal, for example, as described above with respect to Figures 1A to 1D As further shown in diagram 300, the perimeter of electrode 25 is defined by electrode grooves 52 embedded in membrane 50. Electrode grooves 52 may also terminate at electrical contacts 54, which may be embedded and / or otherwise attached to substrate 60, backplane, and / or other suitable surface, as will be described in further detail below.

[0041] In one embodiment, the electrode 302 may be positioned as shown in FIG300, i.e., substantially at the center of the membrane 50. This may be done, for example, to maximize the distance between the electrode 302 and the edge of the membrane 50, which in turn may improve acoustic sensitivity due to a higher capacitance change associated with a displacement of the membrane 50 at the region of the electrode 302. As further shown in FIG300, the electrode 302 may exhibit curvature on one or more sides relative to the edge of the membrane 50, for example, to follow the displacement profile of the membrane 50 caused by a vent 70 formed in the membrane, as described below. With respect to the example shown in FIG300, it should be noted that the electrode 302 shown in FIG300 is for illustrative purposes only, and other electrode shapes and / or sizes may also be implemented.

[0042] As further shown in diagram 300, the second portion 304 of the membrane 50 can be configured to attach the membrane 50 to the substrate 60. In one embodiment, the second portion 304 of the membrane 50 can include an anchor, an adhesive, and / or any other suitable means for permanently attaching the membrane 50 to the substrate 60. In another embodiment, the size and / or shape of the membrane 50 can be such that the second portion 304 of the membrane 50 attaches the edge of the membrane 50 to the substrate 60 while leaving a gap, such as an air gap, between the membrane 50 and the substrate 60 at the active area of ​​the membrane 50 to facilitate full displacement of the membrane 50 in response to the acoustic signal.

[0043] In the embodiment shown in FIG. 300 , the second portion 304 of the film 50 may extend along the entire perimeter of the film 50, including all sides of the film 50. In alternative embodiments, the second portion 304 of the film 50 may attach the film 50 to the substrate 60 at less than all sides (e.g., longer sides, shorter sides, etc.) of the film 50. In another alternative embodiment, the second portion 304 of the film 50 may be discontinuous along the perimeter of the film 50, for example, such that the film 50 is attached to the substrate 60 at discrete points along the perimeter of the film 50. Other embodiments are also possible.

[0044] As further shown in Figure 300, the third portion 306 of the membrane 50 includes at least one vent 70, which is an opening formed in the first portion 306 of the membrane 50 and is disposed substantially along the length of the membrane 50. In the example shown in Figure 300, the membrane 50 has two vents 70, each of which is located along a respective one of the longer sides of the membrane 50. It should be noted that the vents 70 may be located in other ways relative to the membrane 50, for example, along the shorter sides of the membrane, along all sides of the membrane, etc. 7A to 7C Alternative techniques for positioning vents 70 within rectangular membranes and positioning vents 70 within non-rectangular membranes are described in greater detail.

[0045] In the embodiment shown in Figure 300, the vents 70 are curved openings in the membrane 50. In the example shown in Figure 300, the vents 70 are semi-elliptical openings, i.e., openings that present a curved shape that forms a portion of an ellipse. These openings are also positioned so that the major axis of the ellipse corresponding to the shape of the vents 70 is positioned along the edge of the membrane 50.

[0046] Due to the vent 70 shown in FIG. 300, the active area of ​​the membrane 50 (e.g., the first portion 302 of the membrane 50) is a non-rectangular area whose width at the center of the first portion 302 is less than the width of the short edge of the membrane 50 to which the first portion 302 is attached. When tension is applied to the short edge of the membrane 50, this causes the first portion 302 of the membrane 50 to assume a shape similar to a hammock, e.g., the ends of the first portion 302 are pulled apart and the center of the first portion 301 is suspended. In addition, due to the curvature of the vent 70 shown in FIG. 300, wrinkling of the membrane 50 under tension can be reduced compared to an embodiment using a straight (non-curved) vent.

[0047] By using a membrane 50 with vents 70 as shown in Figure 300, the compliance of the membrane 50 can be increased, which in turn can increase the sensitivity of the underlying acoustic sensor. In addition, the vents 70 can allow air to flow from the front to the back of the underlying acoustic sensor, which can be used to make the membrane 50 act as a microphone and set its corresponding low frequency corner.

[0048] Reference now Figure 4 , provides a diagram depicting a MEMS microphone membrane 50 (eg Figure 2 For the sake of brevity, repeated descriptions of similar elements used in other embodiments described herein are omitted. Figure 4 As shown, film 50 may generally be composed of three layers, including a conductive layer 410 positioned between two non-conductive layers 420. In one embodiment, conductive layer 410 may be composed of polysilicon and non-conductive layer 420 may be composed of silicon nitride. Other compositions are also possible.

[0049] Figure 4 The illustrated membrane 50 may include one or more electrode trenches 52 in which the conductive (polysilicon) layer 410 is removed, leaving only the non-conductive (silicon nitride) layer 420 in the location of the trenches 52. This may be done, for example, by electrically isolating a sensing region of the membrane 50 from a non-sensing region of the membrane 50.

[0050] like Figure 4 As further shown in FIG. 5 , the vent 70 formed in the membrane 50 may be a complete opening through the membrane 50, for example, such that all layers of the membrane 50 are removed at the location of the vent 70. As described above, for example, with reference to Figure 3Completely removing membrane material at the location of the vent 70 can increase the compliance of the membrane 50, thereby increasing the acoustic sensitivity by increasing the deflection of the sensing area of ​​the membrane 50.

[0051] Figure 5 500 in FIG. 500 shows a top perspective view of an example membrane having layers similar to those shown in FIG. 400 (i.e., conductive layer 410 and non-conductive layer 420), wherein the top non-conductive layer 420 has been removed for illustrative purposes. It is noteworthy that, in order to simplify the illustration, FIG. 500 only shows a portion of the complete membrane, such as a quarter of the membrane. As shown in FIG. 500, the area of ​​the membrane that is not associated with the vent 70 or the electrode groove 52 has the conductive layer 410 below the top non-conductive layer 420. FIG. 500 further shows that all layers of the membrane are removed in the area of ​​the vent 70, and no material corresponding to the conductive layer 410 is deposited in the area corresponding to the electrode groove 52, i.e., the groove 52 is completely composed of the non-conductive layer 420.

[0052] Next go to Figure 6 , a diagram 600 is provided showing an enlarged view of the end 610 of the vent hole 70 formed in the MEMS microphone membrane 50. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted. More specifically, the diagram 600 shows the Figure 3 300 of . As shown in FIG. 600 , the vent 70 terminates in a generally elliptical (circular, elliptical, near-elliptical, etc.) hole or opening 610. As further shown in FIG. 600 , the diameter (e.g., major diameter, minor diameter, etc.) of the opening 610 can be greater than the width of the corresponding vent 70, for example, such that the opening 610 at the end of the vent 70 is wider than the vent 70 itself. As shown in FIG. 600 , by terminating the vent 70 with a larger opening 610, the mechanical stress applied to the end of the vent 70 can be dispersed to a larger area (e.g., the area of ​​the opening 610), thereby increasing the stress tolerance of the membrane 50.

[0053] Although FIG. 600 shows only a single opening 610 of a single vent 70, it should be noted that the opening 610 shown in FIG. 600 may be placed at respective ends of individual vents 70 formed in a given membrane 50. Thus, for example, the vent 70 shown in FIG. 300 may each terminate at both ends of the vent 70 with an opening 610 as shown in FIG. 600.

[0054] Next reference 7A to 7C, provides diagrams 700, 702, 704 depicting various MEMS microphone membrane configurations. Although the various examples above relate to specific examples of rectangular membranes, the membranes described herein may be any suitable polygon, such as a quadrilateral (e.g., square, rectangular, etc.), a hexagon, an octagon, etc. For example, in Fig. 7A In the example shown in Figure 700 in FIG, a square membrane 710 can be used, wherein corresponding curved vents 70 can be provided along opposite sides of the membrane 710, for example, as in the case of a rectangular membrane as described above. As further shown in Figure 700, additional straight vents 720 can be provided along sides of the membrane 710 that are not associated with the curved vents 70.

[0055] like Figure 7B As another example shown in FIG. 702 of FIG. 704 , a hexagonal membrane 712 may have three curved vents 70 positioned along alternating sides of the membrane 712. Similarly, Figure 7C The octagonal membrane 714 shown in Figure 704 can have four curved vents 70 that are similarly positioned along alternating sides of the membrane 714. In general, for a polygonal membrane having an even number n of sides, n / 2 vents 70 can be formed in the membrane and located on alternating sides of the membrane, i.e., every other side of the membrane.

[0056] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic associated with the embodiment is included in at least one embodiment. Therefore, the phrases "in one embodiment" or "in one implementation" appearing in various places in this specification do not necessarily all refer to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0057] Additionally, in this specification, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless specified otherwise or clear from the context, "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" holds true in any of the above cases. Additionally, the articles "a" and "an" used in this specification and the drawings should generally be interpreted as "one or more" unless specified otherwise or the context clearly dictates a singular form.

[0058] In addition, the terms "example" and "for example" are used herein to mean serving as an example or illustration. Any embodiment or design described herein as an "example" or associated with an "for example" clause is not necessarily to be construed as being superior to other embodiments or designs. On the contrary, the use of the word "example" or "for example" is intended to present the concept in a concrete way. Unless the context clearly indicates otherwise, the terms "first", "second", "third", etc. used in the claims and the specification are for clarity only and do not necessarily indicate or imply any temporal order.

[0059] The foregoing includes examples of one or more embodiments of the present disclosure. Of course, for the purposes of describing these examples, it is not possible to describe every possible combination of components or methods, and it will be appreciated that many other combinations and permutations of the present embodiments are possible. Therefore, the embodiments disclosed and / or claimed herein are intended to include all such changes, modifications, and variations that fall within the spirit and scope of the detailed description and the appended claims. In addition, if the word "including" is used in the detailed description or the claims, the word is intended to be inclusive in a manner similar to "comprising" in that "including" is interpreted as "comprising" when used as a transitional word in a claim.

Claims

1. A micro-electromechanical system (MEMS) acoustic sensor, comprising: substrate; a membrane, parallel to the substrate; as well as At least one vent is formed in the membrane, wherein a portion of the at least one vent is a curved opening in the membrane, and wherein the at least one vent is disposed substantially along one side of the membrane.

2. The MEMS acoustic sensor according to claim 1, wherein: The membrane has a rectangular shape.

3. The MEMS acoustic sensor according to claim 2, wherein: The at least one vent hole comprises two vent holes, wherein the two vent holes are arranged substantially along respective sides of the two longer sides of the membrane.

4. The MEMS acoustic sensor according to claim 2, wherein: Each side of the film is attached to the substrate.

5. The MEMS acoustic sensor according to claim 1, wherein: Each of the at least one vent is semi-elliptical.

6. The MEMS acoustic sensor according to claim 5, wherein: The major axis of a respective one of the at least one vent is along a respective edge of the membrane.

7. The MEMS acoustic sensor according to claim 1, wherein: Each of the at least one vent has a first end and a second end opposite the first end, and wherein each of the at least one vent includes respective substantially elliptical holes at the first end and the second end.

8. The MEMS acoustic sensor according to claim 7, wherein: The diameter of each of the substantially elliptical holes is greater than the width of each of the at least one vent hole.

9. The MEMS acoustic sensor according to claim 1, further comprising: A back plate is parallel to the membrane and covers at least a portion of the membrane.

10. The MEMS acoustic sensor according to claim 9, wherein: The substrate is located between the backing plate and the membrane.

11. The MEMS acoustic sensor according to claim 9, wherein: The back plate is located between the substrate and the membrane.

12. The MEMS acoustic sensor according to claim 1, wherein: The membrane includes a sensing region comprising a polysilicon layer between two silicon nitride layers.

13. The MEMS acoustic sensor according to claim 12, wherein: The membrane further includes a non-sensing region, wherein the sensing region and the non-sensing region are isolated by at least one of the two silicon nitride layers.

14. The MEMS acoustic sensor according to claim 12, wherein: At least a portion of a perimeter of the sensing area has a curved shape.

15. A micro-electromechanical system (MEMS) acoustic sensor, comprising: substrate; as well as A membrane having a polygonal shape is attached to the substrate at respective edges of the membrane, wherein the membrane has at least one vent hole, the at least one vent hole being a curved opening in the membrane.

16. The MEMS acoustic sensor according to claim 15, wherein: The polygonal shape of the film is selected from the group consisting of quadrilateral, hexagonal and octagonal shapes.

17. The MEMS acoustic sensor according to claim 16, wherein: The vents are located along alternating ones of the sides of the membrane.

18. The MEMS acoustic sensor according to claim 15, wherein: Each of the at least one vent has a first end and a second end opposite the first end, and wherein each of the at least one vent includes respective substantially elliptical holes at the first end and the second end.

19. The MEMS acoustic sensor according to claim 18, wherein: The diameter of each of the substantially elliptical holes is greater than the width of each of the at least one vent hole.

20. A membrane for a micro-electromechanical system (MEMS) microphone, comprising: a first membrane portion configured to flex in response to receiving an acoustic signal; a second film portion configured to be attached to a substrate; A third membrane portion having at least one vent hole, wherein each of the at least one vent hole is a curved through hole in the third membrane portion, wherein each of the at least one vent hole has a corresponding substantially elliptical hole located at a corresponding end of each of the at least one vent hole.

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