Microelectromechanical acoustic sensor with film etch release structure and method of manufacturing same

Abstract

A low cost, robust, and high performance micro-electro-mechanical system (MEMS) acoustic sensor is described. The microelectromechanical system acoustic sensor may include a set of etch release structures in the acoustic sensor membrane that facilitate rapid and / or uniform etch release of the acoustic sensor membrane. Additionally, the MEMS acoustic sensor may include a set of membrane position control structures of the acoustic sensor membrane, which may reduce bending stresses of the acoustic sensor membrane. The microelectromechanical system acoustic sensor may also include a three-layer acoustic sensor film that provides enhanced robustness. Further design flexibility and improvements are described that provide enhanced robustness and / or cost savings, and provide a low cost process for a microelectromechanical system acoustic sensor.

Description

Technical Field

[0001] This patent application claims the priority of a U.S. Provisional Patent Application filed on October 20, 2022, with the title "MICROPHONE PROCESS" and application number 63 / 380,274, and a U.S. Non-Provisional Patent Application filed on October 19, 2023, with the title "MICROELECTROMECHANICAL ACOUSTIC SENSOR WITH MEMBRANE ETCH RELEASE STRUCTURES AND METHOD OF FABRICATION" and application number 18 / 490,312. The entire contents of both applications are incorporated herein by reference. Background Art

[0002] Microelectromechanical systems (MEMS) are a class of structures and / or devices fabricated using semiconductor-like processes. MEMS structures and / or devices exhibit mechanical properties, including the ability to move or deform. Examples of MEMS components include, but are not limited to, gyroscopes, accelerometers, magnetometers, pressure sensors, radio frequency components, etc. A silicon wafer including MEMS structures is referred to as a MEMS wafer. There are unique challenges in providing MEMS devices and / or structures with improved performance and reliability.

[0003] For example, robustness requirements may dictate that fabricated devices such as MEMS acoustic sensors be able to withstand extreme environmental conditions such as drop tests. At the same time, performance requirements (e.g., high sensitivity and high active capacitance) may require high membrane compliance and low parasitic capacitance at MEMS readout nodes, which are further electroacoustic design criteria. Additionally, size and / or cost considerations (e.g., low MEMS process cost) may conflict with these other design considerations.

[0004] Accordingly, there is a desire to provide improved MEMS acoustic sensor designs and processes that address these and other deficiencies. The above deficiencies are only intended to provide an overview of some problems with conventional implementations and are not intended to be exhaustive. Other problems with general implementations and techniques, as well as the corresponding benefits of the various aspects described herein, may become more apparent upon review of the following description. Summary of the Invention

[0005] A simplified overview of the present specification is presented below to provide a basic understanding of some aspects of the present specification. This summary of the invention is not an extensive overview of the specification. It is neither intended to identify the key or essential elements of the specification nor to depict the scope of any embodiment of the specification or the scope of any claims. Its sole purpose is to present some concepts of the present specification in a simplified form as a prelude to the embodiments presented later.

[0006] In non - limiting examples, low - cost, robust, and high - performance microelectromechanical systems (MEMS) acoustic sensors are described. In non - limiting aspects, an exemplary MEMS acoustic sensor can include a set of etch - release structures in an acoustic sensor membrane that facilitate rapid and / or uniform etch - release of the acoustic sensor membrane. In another non - limiting aspect, an exemplary MEMS acoustic sensor can include a set of membrane position - control structures of the acoustic sensor membrane that can reduce the bending stress of the acoustic sensor membrane. In another non - limiting aspect, the MEMS acoustic sensor can include a three - layer acoustic sensor membrane that provides enhanced robustness.

[0007] Additionally, further flexibility and improvements that provide enhanced robustness and / or cost savings are described. Further, a low - cost process for the exemplary MEMS acoustic sensors described above is provided.

[0008] These and other embodiments are described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various non - limiting embodiments are further described with reference to the accompanying drawings, in which:

[0010] Figure 1 A cross - sectional view of an exemplary microelectromechanical system (MEMS) acoustic sensor is provided that depicts various non - limiting aspects of the exemplary MEMS acoustic sensor described herein;

[0011] Figure 2 Another cross - sectional view of the exemplary MEMS acoustic sensor is provided that depicts further non - limiting aspects of the exemplary MEMS acoustic sensor described herein;

[0012] Figure 3 Another cross - sectional view of the exemplary MEMS acoustic sensor is provided that depicts further non - limiting aspects of the exemplary MEMS acoustic sensor described herein;

[0013] Figure 4 Non - limiting aspects of an exemplary acoustic sensor membrane applicable to the exemplary MEMS acoustic sensor described herein are depicted;

[0014] Figure 5Depicts further non - limiting aspects of an exemplary acoustic sensor membrane suitable for the exemplary MEMS acoustic sensors described herein;

[0015] Figure 6 Depicts specific aspects of a non - limiting membrane position control structure suitable for the exemplary MEMS acoustic sensors described herein;

[0016] Figure 7 Illustrates specific aspects of a non - limiting membrane position control structure suitable for the exemplary MEMS acoustic sensors described herein;

[0017] Figure 8-31 Illustrates an exemplary non - limiting cross - sectional view of an exemplary MEMS acoustic sensor undergoing a process according to one or more embodiments described herein; and

[0018] Figure 32 Provides a flowchart of a method associated with the fabrication of exemplary MEMS acoustic sensors according to various non - limiting embodiments described herein. Detailed Description

[0019] Overview

[0020] Although a brief overview is provided, for purposes of illustration and not limitation, certain aspects of the invention disclosed are described or depicted herein. Accordingly, variations of the disclosed embodiments suggested by the disclosed apparatus, systems, and methods are intended to be covered within the scope of the subject matter disclosed herein.

[0021] As noted above, the robustness requirements of MEMS devices may dictate that fabricated devices such as MEMS acoustic sensors be able to withstand extreme environmental conditions such as drop tests (e.g., high - pressure shock tests with pressures between 0.1 megapascals (MPa) and 0.8 MPa). At the same time, the performance requirements of MEMS readout nodes (e.g., high sensitivity and high active capacitance) require high membrane compliance and low parasitic capacitance, which are further electro - acoustic design criteria. Additionally, size and / or cost considerations (e.g., low MEMS process costs roughly determined by the number of photolithography masks) may conflict with these other design considerations. The various embodiments described herein may provide a small, low - cost MEMS acoustic sensor process that results in devices with high robustness, excellent electro - acoustic performance (e.g., high sensitivity and high active capacitance), high membrane compliance, and low parasitic capacitance at the MEMS readout nodes.

[0022] For these and / or related purposes, various aspects of microelectromechanical system (MEMS) acoustic sensors, devices, systems, and methods thereof are described. The various embodiments of the present disclosure are described herein for illustrative purposes and not for purposes of limitation. For example, the embodiments disclosed herein are described in the context of MEMS sensors (e.g., MEMS acoustic sensors). However, it will be understood that the various aspects of the present disclosure are not limited thereto. As will be further detailed below, the various illustrative embodiments may find application in other areas of MEMS sensor design and / or packaging without departing from the subject matter described herein.

[0023] Illustrative embodiments

[0024] One or more embodiments are now described more fully hereinafter with reference to the accompanying drawings that show illustrative embodiments. In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the various embodiments.

[0025] Figure 1 A cross-sectional view of an illustrative MEMS acoustic sensor 100 is provided, depicting various non-limiting aspects of the illustrative MEMS acoustic sensor 100 described herein. The illustrative MEMS acoustic sensor 100 may include a device substrate 102 (e.g., a wafer substrate). In non-limiting aspects, the device substrate 102 may include, for example, a silicon wafer. Additionally, the illustrative MEMS acoustic sensor 100 may include an acoustic sensor membrane 104. For example, the acoustic sensor membrane 104 may be suspended above the device substrate 102 and mechanically coupled to the device substrate 102 at the periphery of the acoustic sensor membrane 104, wherein, according to non-limiting aspects, the acoustic sensor membrane 104 is configured to deform in response to acoustic pressure (e.g., acoustic pressure applied via a device package port). As used herein, the term "periphery" is used to refer to the outer edge of a shape, regardless of the shape employed. For example, the various non-limiting embodiments described herein may employ any configuration of the imaginable shapes of the suitable acoustic sensor membrane 104, as further described herein with respect to Figures 4 to 5 as further described.

[0026] In additional non-limiting embodiments, the illustrative MEMS acoustic sensor 100 may further include an acoustic sensor backplate or top plate 106. In non-limiting aspects, the illustrative acoustic sensor backplate or top plate 106 may be mechanically coupled to the acoustic sensor membrane 104. In additional non-limiting aspects, the illustrative acoustic sensor backplate or top plate 106 may include an opening 108 that allows acoustic pressure to pass through.

[0027] In additional non-limiting embodiments, the exemplary MEMS acoustic sensor 100 may further include a set of membrane position control structures 110 for the acoustic sensor membrane 104. As a non-limiting example, an exemplary set of membrane position control structures 110 may be disposed on the acoustic sensor membrane 104 and near the periphery of the acoustic sensor membrane 102. In additional non-limiting aspects, an exemplary set of membrane position control structures 110 may extend perpendicular to the surface of the acoustic sensor membrane 104 that faces the acoustic sensor backplate or top plate 106. It will be appreciated that the exemplary membrane position control structures 110 are shown in cross-section, which limits the description of the features of the exemplary membrane position control structures 110. As further described herein, the number, position (e.g., spacing and distance), configuration (shape and / or construction), and arrangement (relative to other components) of the exemplary membrane position control structures 110 may vary, but are not limited thereto.

[0028] In still other non-limiting embodiments, the exemplary MEMS acoustic sensor 100 may further include a set of etch release structures 112 located within the acoustic sensor membrane 104. In non-limiting aspects, an exemplary set of etch release structures 112 may be located between the periphery of the acoustic sensor membrane 104 and the exemplary set of membrane position control structures 110. In a further non-limiting aspect of the exemplary MEMS acoustic sensor 100, the set of etch release structures 112 may be configured to enable uniform wet etching in the regions of the acoustic sensor membrane 104, the lateral etch stop structures 114, and the set of membrane position control structures 110 during the acoustic sensor membrane 104 etch release process. As a non-limiting example, the set of etch release structures 112 within the acoustic sensor membrane 104 may include a set of passages through the acoustic sensor membrane 104 that are configured to allow wet etching to enter the region. In a further non-limiting aspect of the exemplary MEMS acoustic sensor 100, the set of passages through the acoustic sensor membrane 104 may be configured to reduce the etch time required to equalize the etching in the region. In still other non-limiting aspects of the exemplary MEMS acoustic sensor 100, the number, position, and arrangement of the set of passages of the set of etch release structures 112 within the acoustic sensor membrane 104 may vary, but are not limited thereto, as further described herein.

[0029] In still other non-limiting embodiments, the exemplary microelectromechanical system acoustic sensor 100 may further include a lateral etch stop structure 114 disposed on the acoustic sensor membrane 104. In a non-limiting aspect, the exemplary lateral etch stop structure 114 may be located at the periphery of the acoustic sensor membrane 104, where the acoustic sensor membrane 104 is mechanically coupled to the device substrate 102. As with the description of the exemplary membrane position control structure 110, it can be understood that the exemplary lateral etch stop structure 114 is shown in cross-section, which limits the description of the features of the exemplary lateral etch stop structure 114. Thus, it is contemplated that the exemplary lateral etch stop structure 114 conforms to the selected shape of the exemplary acoustic sensor membrane 104.

[0030] In a further non-limiting aspect of the exemplary microelectromechanical system acoustic sensor 100, the set of membrane position control structures 110 may be configured to restrict movement of the acoustic sensor membrane 104 in a direction away from the acoustic sensor backplate or top plate 106. In another non-limiting aspect of the exemplary microelectromechanical system acoustic sensor 100, the set of membrane position control structures 110 may be configured to reduce the bending stress on the acoustic sensor membrane 104 at the junction of the acoustic sensor membrane 104 and the lateral etch stop structure 114, e.g., as further described herein with respect to Figures 6 to 7 As a non-limiting example, a set of membrane position control structures 110 of the exemplary microelectromechanical system acoustic sensor 100 may include a plurality of individual membrane position control structures 110, each membrane position control structure 110 being perpendicular to the surface of the acoustic sensor membrane 104, opposite the acoustic sensor backplate or top plate 106, and protruding toward the device substrate 102, as Figures 1 to 2 shown and further described below with respect to Figure 3 and 5 through 7. As a further non-limiting example, a set of exemplary membrane position control structures 110 of the exemplary microelectromechanical system acoustic sensor 100 may be arranged as a single sequence of membrane position control structures near the periphery of the acoustic sensor membrane 104, multiple sequences of membrane position control structures near the periphery of the acoustic sensor membrane 104, and / or other arrangements, configurations, and / or numbers that may be configured to restrict movement of the acoustic sensor membrane 104 in a direction away from the acoustic sensor backplate or top plate 106 or reduce the bending stress on the acoustic sensor membrane 104 at the junction of the acoustic sensor membrane 104 and the lateral etch stop structure 114, as further described below with respect to Figure 3 and 5 through 7.

[0031] Throughout the disclosure, the following abbreviations are used to describe various semiconductor processes and materials used in the exemplary MEMS processes. It is understood that suitable alternatives or substitute materials and / or processes may exist to implement the described technologies, devices, processes, etc. Thus, the description herein of the various semiconductor processes and materials used in the exemplary MEMS processes is intended to provide an understanding of the appended claims rather than a limitation. For example, as used herein, PECVD TEOS 116 refers to an exemplary MEMS process that includes one or more plasma-enhanced chemical vapor deposition (PECVD) processes using tetraethylorthosilicate (TEOS) and the resulting layers / structures derived from such processes including any photolithographic patterning and / or etching processes, as further described herein with respect to Figures 8 to 31 as further described.

[0032] LPCVD TEOS 118 refers to an exemplary MEMS process that includes one or more low pressure chemical vapor deposition (LPCVD) processes using tetraethylorthosilicate (TEOS) and the resulting layers / structures derived from such processes including any photolithographic patterning and / or etching processes. Additionally, LPCVD LSN 120 refers to an exemplary MEMS process that includes one or more LPCVD low stress silicon nitride (LSN) deposition processes and the resulting layers / structures derived from such processes including any photolithographic patterning and / or etching processes.

[0033] ISDP 122 refers to an exemplary MEMS process that includes one or more in-situ phosphorous doped (ISDP) polysilicon deposition processes and the resulting layers / structures derived from such processes including any photolithographic patterning and / or etching processes. PECVD LSN 124 refers to an exemplary MEMS process that includes one or more PECVD low stress silicon nitride (LSN) deposition processes and the resulting layers / structures derived from such processes including any photolithographic patterning and / or etching processes, as further described herein with respect to Figures 8 to 32 as further described. Metal (CrAu) 126 refers to an exemplary MEMS process that includes one or more metal deposition processes using a gold metal alloy and the resulting layers / structures derived from such processes including any photolithographic patterning and / or etching processes.

[0034] Figure 2 Another cross-sectional view of an exemplary microelectromechanical system (MEMS) acoustic sensor is provided, which depicts a further non-limiting aspect of the exemplary MEMS acoustic sensor described herein. As Figure 2 shown, a further non-limiting embodiment of the exemplary MEMS acoustic sensor 100 may include an exemplary acoustic sensor membrane 104, which includes a stacked arrangement of a first silicon nitride (SiN) acoustic sensor membrane 104 layer 202, a polysilicon (poly-Si) acoustic sensor membrane 104 electrode layer 204, and a second silicon nitride acoustic sensor membrane 104 layer 206. Another non-limiting embodiment of the exemplary MEMS acoustic sensor 100 may include a polysilicon contact 208 coupled to the polysilicon acoustic sensor membrane 104 electrode layer 204.

[0035] In addition, a further non-limiting embodiment of the exemplary MEMS acoustic sensor 100 may include an exemplary acoustic sensor backplate or top plate 106, which includes a polysilicon backplate or top plate 106 electrode layer 210 adjacent to a second silicon nitride backplate or top plate 106 layer 212, and a first silicon nitride backplate or top plate 106 layer 214 adjacent to the polysilicon backplate or top plate 106 electrode layer 210 and opposite to the second silicon nitride backplate or top plate 106 layer 212. In another non-limiting embodiment, the exemplary MEMS acoustic sensor 100 may further include a metal contact 216 coupled to the polysilicon backplate or top plate 106 electrode layer 210. In yet another non-limiting embodiment, the exemplary acoustic sensor backplate or top plate 106 may be configured with one or more backplate or top plate 106 stoppers 218. Since Figure 2 is an enlarged cross-sectional view of the exemplary MEMS acoustic sensor 100, thus Figure 2 only one of the one or more exemplary backplate or top plate 106 stoppers 218 is depicted in Figure 1 while Figure 1 depicts multiple such exemplary structures. In a further non-limiting aspect, the exemplary one or more backplate or top plate 106 stoppers 218 may be composed of the first silicon nitride backplate or top plate 106 layer 214. In another non-limiting aspect, the exemplary one or more backplate or top plate 106 stoppers 218 may be adapted to limit the contact between the acoustic sensor membrane 104 and the acoustic sensor backplate or top plate 106.

[0036] In other non-limiting embodiments of the exemplary MEMS acoustic sensor 100, the exemplary acoustic sensor membrane 104 may further include one or more vent holes 220 formed in the acoustic sensor membrane 104, e.g., as described herein with respect to Figure 4Further described. In non-limiting aspects, a portion of one or more exemplary ventilation holes 220 may include a curved opening in the acoustic sensor membrane 104. In another non-limiting aspect, one or more exemplary ventilation holes 220 may be disposed substantially along one side of the acoustic sensor membrane 104, e.g., as described herein with respect to Figure 4 Further described. Since Figure 2 is an enlarged cross-sectional view of the exemplary microelectromechanical system acoustic sensor 100, thus Figure 2 only one of the one or more exemplary ventilation holes 220 is depicted therein, while Figure 1 depicts many such exemplary structures, e.g., as described with respect to Figure 4 Further described.

[0037] In still other non-limiting embodiments, the exemplary microelectromechanical system acoustic sensor 100 may further include an acoustic port 222 formed in the device substrate 102, which is configured to direct acoustic pressure to the acoustic sensor membrane 104 to deflect the acoustic sensor membrane 104 towards the acoustic sensor backplate or top plate 106. In other non-limiting embodiments, the exemplary microelectromechanical system acoustic sensor 100 may further include a front cavity 224, which is formed in the port 222, close to the acoustic sensor membrane 104, and is configured to prevent the acoustic sensor membrane 104 from contacting the device substrate 102. In non-limiting aspects, based on the use of the number or array (e.g., multiple sequences) of the membrane position control structures 110, the exemplary front cavity 224 in the acoustic port 222 may be omitted from the process and the resulting device, e.g., as described herein with respect to Figure 3 Further described.

[0038] For example, Figure 3 Another cross-sectional view 300 of the exemplary microelectromechanical system acoustic sensor 100 is provided, which depicts further non-limiting aspects of the exemplary microelectromechanical system acoustic sensor described herein. Thus, as described above, in non-limiting aspects, based on the use of the number or array (e.g., multiple sequences) of the membrane position control structures 110, the exemplary front cavity 224 in the acoustic port 222 may be omitted from the process and the resulting device. That is, by omitting the exemplary front cavity 224 in the acoustic port 222 from the process and the resulting device, e.g., as described herein with respect to Figure 3Further described. In still other non-limiting embodiments, the exemplary MEMS acoustic sensor 100 may further include an exemplary backplate or top plate 106 lateral etch stop structure 226. In a non-limiting aspect, the exemplary backplate or top plate 106 lateral etch stop structure 226 may define the physical extent of the exemplary backplate or top plate 106. In other non-limiting aspects, the exemplary backplate or top plate 106 lateral etch stop structure 226 may be disposed on the acoustic sensor backplate (e.g., the exemplary backplate or top plate 106), and may be located at the position where the acoustic sensor backplate (e.g., the exemplary backplate or top plate 106) is mechanically coupled to the acoustic sensor membrane (e.g., the exemplary acoustic sensor membrane 104).

[0039] Figure 4 Depicts non-limiting aspects of an exemplary acoustic sensor membrane 104 suitable for use in the exemplary MEMS acoustic sensor 100 described herein. Figure 4 Depicts an exemplary fixed-fixed acoustic sensor membrane 104 that may be employed in the exemplary MEMS acoustic sensor 100. As Figure 4 shown, the acoustic sensor membrane 104 may be mechanically coupled to the underlying device substrate 102 and / or another suitable device surface. Techniques for coupling the acoustic sensor membrane 104 to the device substrate 102 are described in more detail below.

[0040] As Figure 4 further shown, the acoustic sensor membrane 104 may have a substantially rectangular shape, i.e., such that the perimeter of the acoustic sensor membrane 104 has two longer sides and two shorter sides. As described above, the term "periphery" is used to refer to the outer edge of a shape, regardless of the shape employed. Thus, for Figure 4 the rectangular shape of the acoustic sensor membrane 104, the periphery may be generally rectangular. In other non-limiting embodiments, the acoustic sensor membrane 104 may assume any configuration of conceivable shapes of a suitable acoustic sensor membrane 104, as described herein with respect to Figure 5 further described, where the resulting periphery conforms to the selected shape.

[0041] Other shapes may also be used for the acoustic sensor membrane 104, some examples of which are described in more detail below with reference to Figure 5 Further. The exemplary acoustic sensor membrane 104 may be composed of one or more layers, e.g., as described herein, each layer may be solid and / or have corresponding holes or other openings (e.g., one or more exemplary vent holes 220, a set of etch release structures 112) to improve air flow through the acoustic sensor membrane 104, thereby providing uniform and / or rapid etching, and / or for other purposes. Figure 4The illustrated acoustic sensor membrane 104 can be conceptually divided into three membrane portions. A first portion of the acoustic sensor membrane 104, also referred to herein as the sensing region of the acoustic sensor membrane 104 electrode layer 204 or electrode 402, can be configured to sense deflection of the acoustic sensor membrane 104 in response to deflection under an applied acoustic pressure.

[0042] As Figure 4 Further shown, the perimeter of the sensing region or electrode 402 is defined by electrode trenches 404 embedded in the acoustic sensor membrane 104. The electrode trenches 404 can also terminate at electrical contacts 406 coupled to polysilicon contacts 208. In one embodiment, the electrode 402 can be placed as Figure 4 shown, i.e., substantially at the center of the acoustic sensor membrane 104. This can be done, for example, to maximize the distance between the electrode 402 and the edge of the acoustic sensor membrane 104, and this in turn can result in improved acoustic sensitivity due to the higher capacitance change associated with the displacement of the acoustic sensor membrane 104 in the region of the electrode 402. As Figure 4 Further shown, the electrode 402 can exhibit curvature on one or more sides relative to the edge of the acoustic sensor membrane 104, e.g., following the displacement profile of the acoustic sensor membrane 104 created by one or more vent holes 220 formed in the membrane, as will be described below. Regarding the example shown in FIG. 400, it should be noted that Figure 4 the illustrated electrode 402 is for illustrative purposes only, and other electrode shapes and / or sizes can also be implemented.

[0043] As Figure 4 Further shown, a second portion of the acoustic sensor membrane 104 can also include a lateral etch stop structure 114 disposed on the acoustic sensor membrane 104 and between the acoustic sensor membrane 104 and the device substrate 102, as further described herein. In an embodiment, the second portion of the acoustic sensor membrane 104 can serve as an anchor or mechanical coupling of the acoustic sensor membrane 104 to the device substrate 102 by virtue of the integrated fabrication of the acoustic sensor membrane 104 on the device substrate 102 and subsequent membrane etch release, as further described herein.

[0044] In non-limiting aspects, a second portion of the acoustic sensor membrane 104 including the exemplary lateral etch stop structure 114 can extend along the entire perimeter of the acoustic sensor membrane 104, including all sides of the acoustic sensor membrane 104. In an alternative embodiment, the second portion of the acoustic sensor membrane 104 including the exemplary lateral etch stop structure 114 can attach the acoustic sensor membrane 104 to the device substrate 102 on not all sides of the acoustic sensor membrane 104 (e.g., only on the longer sides, shorter sides, etc.). In another alternative embodiment, the second portion of the acoustic sensor membrane 104 including the exemplary lateral etch stop structure 114 can be discontinuous along the perimeter of the acoustic sensor membrane 104, such that the acoustic sensor membrane 104 is connected to the device substrate 102 at discrete points along the perimeter of the acoustic sensor membrane 104.

[0045] As Figure 4 Further shown, a third portion 408 of the acoustic sensor membrane 104 can include one or more vent holes 220, which are openings formed in the third portion of the acoustic sensor membrane 104 and are set substantially along the length of the acoustic sensor membrane 104. In Figure 4 the example shown, the acoustic sensor membrane 104 has two vent holes 220, each vent hole being disposed along a respective long side of the acoustic sensor membrane 104. Note that the one or more vent holes 220 can be arranged relative to the acoustic sensor membrane 104 in other ways, such as along the shorter sides of the membrane, along all sides of the membrane, etc. Alternative techniques for setting the one or more vent holes 220 within a rectangular membrane and techniques for setting the one or more vent holes 220 within a non-rectangular membrane will be described in further detail below with reference to Figure 5 Further described in detail.

[0046] In Figure 4 the embodiment shown, the one or more vent holes 220 are curved openings in the acoustic sensor membrane 104. In Figure 4 the example shown, the one or more vent holes 220 are semi-elliptical openings, i.e., openings presenting a curved shape that forms a part of an ellipse. These openings are also arranged such that the major axis of the ellipse corresponding to the shape of the one or more vent holes 220 is disposed along the side of the acoustic sensor membrane 104.

[0047] Since Figure 4One or more vent holes 220 as shown, the active region of the acoustic sensor membrane 104 (e.g., the first part of the acoustic sensor membrane 104, also referred to herein as the sensing region or electrode 402 of the acoustic sensor membrane 104) is a non-rectangular region, the width of which is located at the center of the first part of the acoustic sensor membrane 104, and this width is less than the width of the short edge of the acoustic sensor membrane 104 to which the first part of the acoustic sensor membrane 104 (e.g., the sensing region or electrode 402) is attached. When tension is applied to the short edge of the acoustic sensor membrane 104, this causes the first part of the acoustic sensor membrane 104 (also referred to herein as the sensing region or electrode 402) to assume a shape similar to a hammock, e.g., the ends of the first part of the acoustic sensor membrane 104 (also referred to herein as the sensing region or electrode 402) are pulled apart, and the center of the first part of the acoustic sensor membrane 104 (also referred to herein as the sensing region) serves as the suspended sensing region or electrode 402. Additionally, due to Figure 4 the curvature of one or more vent holes 220 as shown, compared to an embodiment using straight (non-curved) vent holes, for example, wrinkling of the acoustic sensor membrane 104 when under tension can be reduced.

[0048] By using an acoustic sensor membrane 104 having one or more vent holes 220 as Figure 4 shown, the compliance of the acoustic sensor membrane 104 can be improved, which in non-limiting aspects can in turn increase the sensitivity of the underlying acoustic sensor. Additionally, one or more vent holes 220 can allow air to flow from the front to the back of the underlying acoustic sensor, which in further non-limiting aspects can be used to enable the acoustic sensor membrane 104 to function as a microphone and set its corresponding low-frequency corner.

[0049] As Figure 4 further shown in the inset, the acoustic sensor membrane 104 and the second part of the acoustic sensor membrane 104 include exemplary lateral etch stop structures 114, and various exemplary embodiments can include one or more of a set of membrane position control structures 110 (e.g., in a single sequence 410 or in an array or multiple sequences 412, each sequence extending around the periphery of the acoustic sensor membrane 104 according to shape, a feature set of the membrane including one or more vent holes, etc.) or a set of etch release structures 112, as further described herein with respect to Figures 1 to 3 this.

[0050] Figure 5 Further non-limiting aspects of an exemplary acoustic sensor membrane 500 applicable to the exemplary microelectromechanical system acoustic sensor 100 described herein are depicted. In Figure 5Therein, illustrative acoustic sensor membranes 502, 506, 508 depicting the corresponding membrane configurations of the microelectromechanical system acoustic sensor 100 are provided. Although the various examples above relate to specific examples of rectangular membranes, the membranes described herein can have any suitable polygonal shape, e.g., quadrilaterals (e.g., squares, rectangles, etc.), hexagons, octagons, etc. For example, in Figure 5 In the example shown by the illustrative acoustic sensor membrane 502 in, a square acoustic sensor membrane 502 can be used, wherein one or more corresponding curved vent holes 220 can be disposed along opposite sides of the square acoustic sensor membrane 502, e.g., as described above for the case of the rectangular membrane. As further shown in the illustrative acoustic sensor membrane 502, one or more straight vent openings 504 can be disposed along the side edges of the square acoustic sensor membrane 502 that are not associated with the one or more curved vent holes 220.

[0051] As Figure 5 Another illustration shown, the hexagonal acoustic sensor membrane 506 can have three curved vent holes 220 disposed along alternating sides of the hexagonal acoustic sensor membrane 506. Similarly, as Figure 5 shown, the octagonal acoustic sensor membrane 508 can have four curved vent holes 220, which are similarly disposed along alternating sides of the octagonal acoustic sensor membrane 508. Generally speaking, for a polygonal membrane having an even number n of side edges, n / 2 vent holes 220 can be formed in the membrane and disposed at alternating side edges of the membrane, i.e., one vent hole 220 is disposed for every two sides of the membrane, which can be extended to other shapes, such as circular, oval, etc., where the number of one or more vent holes 220 employed can vary, but can be determined for the rectangular or polygonal shapes as described above.

[0052] Figure 5 The first part of the acoustic sensor membrane 104, which is also referred to herein as the sensing region or electrode 402, is not shown in. The second part of the acoustic sensor membrane 104 includes the illustrative lateral etch stop structure 114 and the set of etch release structures 112.

[0053] Figure 6 A perspective view 600 is provided, which depicts specific aspects of the non-limiting membrane position control structure 110, referred to as a membrane stopper in Figure 6 , which is suitable for use in the illustrative microelectromechanical system acoustic sensors described herein. Figure 7 A functional block diagram 700 is provided, which shows specific aspects of the non-limiting membrane position control structure 110 suitable for use in the illustrative microelectromechanical system acoustic sensor 100 described herein. Figures 6 to 7One or more vent holes 220 and a set of etch release structures 112 are not shown. As further described herein, the number, position (e.g., spacing and distance), configuration (shape and / or construction), and arrangement (relative to other components such as the suspension, one or more vent holes 220, a set of etch release structures 112) of the exemplary membrane position control structures 110 can vary, but are not limited thereto. As Figure 7 shown, the positive pressure impulse 702 of the applied acoustic pressure can cause the acoustic sensor membrane 104 to deflect in the direction towards the acoustic sensor backplate or top plate 106, which can be limited by one or more backplate or top plate 106 stoppers 218 (not shown). However, in the case of the negative pressure impulse 704 of the applied acoustic pressure, the acoustic sensor membrane 104 can be deflected in the direction towards the device substrate, which can be partially accommodated by the exemplary membrane position control structures 110 and / or the front cavity 224. However, the bending stress on the acoustic sensor membrane 104 will occur at the junction between the lateral etch stop structure 114 provided on the acoustic sensor membrane 104 and the backplate or top plate 106 lateral etch stop structure 226. Therefore, in various non-limiting embodiments, position control of the acoustic sensor membrane 104 can be achieved via an exemplary set of membrane position control structures 110 of the exemplary microelectromechanical system acoustic sensor 100. As described, the exemplary set of membrane position control structures 110 of the exemplary microelectromechanical system acoustic sensor 100 can be arranged as a single sequence of membrane position control structures near the periphery of the acoustic sensor membrane 104, multiple sequences of membrane position control structures near the periphery of the acoustic sensor membrane 104, and / or other arrangements, configurations, and / or quantities, which can be configured to limit the movement of the acoustic sensor membrane 104 in the direction away from the acoustic sensor backplate or top plate 106 or reduce the bending stress on the acoustic sensor membrane 104 at the junction of the acoustic sensor membrane 104 and the lateral etch stop structure 114, thereby reducing the bending stress on the acoustic sensor membrane 104 at the junction of the acoustic sensor membrane 104 and the lateral etch stop structure 114.

[0054] Therefore, in various non-limiting embodiments, the disclosed subject matter provides a robust microelectromechanical system acoustic sensor 100. As further provided herein, it has been demonstrated that such a robust microelectromechanical system acoustic sensor 100 can be fabricated based on a low-cost process. It can be understood that the production cost of a microelectromechanical system device generally depends on the number of photolithography steps (and thus the number of photolithography masks used) for patterning the various layers of the microelectromechanical system device. Therefore, Figure 8-31 An exemplary non-limiting cross-sectional view of an exemplary microelectromechanical system acoustic sensor 100 undergoing a process according to one or more embodiments described herein is shown, wherein,Figure 8 Depicts the starting device substrate 102 applicable to the exemplary microelectromechanical system acoustic sensor 100 described herein. For the sake of brevity, the repeated description of similar elements employed in other embodiments described herein is omitted. Note that, for purposes of illustration and not limitation, the process diagrams are annotated with non-limiting process step numbers. Additionally, the individual figures are labeled M1, M2, etc. to reflect the number and specificity of the photolithography masks used in the process or for a particular step, as an illustration of the economic benefits of the low mask count microelectromechanical system acoustic sensor 100 process. It should be understood that such specific process details do not limit the scope of the appended claims.

[0055] Therefore, Figure 8 Depicts the starting device substrate 102 applicable to the exemplary microelectromechanical system acoustic sensor 100 described herein, where the device substrate 102 is marked, cleaned and the front cavity 224 is lithographically defined (e.g., via mask Ml) and etched into the device substrate 102. Subsequently, the front cavity 802 is filled with an oxide (e.g., PECVD TEOS 116), as further described herein. As further described herein, for example, with respect to Figure 3 , the lithography step (and thus mask M1 and associated etching and deposition steps) can be eliminated by eliminating the exemplary front cavity 224 from the process and resulting device through the use of multiple or arrays (e.g., multiple sequences) of membrane position control structures 110, e.g., as further described herein with respect to Figure 3 , thereby providing further economic advantages for the exemplary microelectromechanical system acoustic sensor 100.

[0056] Figure 9 Shows the result 900 of a chemical / mechanical polishing (CMP) step that retains the front cavity 224 of the device substrate 102, which is filled with an oxide, e.g., PECVD TEOS 116. Figure 10 Depicts the result 1000 of a bulk oxide deposition (e.g., PECVD TEOS 116). Figure 11 Depicts an exemplary process result 1100, where an exemplary membrane position control structure 110 (e.g., a single sequence of membrane position control structures 110) is lithographically defined (e.g., via mask M2) and etched into the bulk oxide deposition (e.g., PECVD TEOS 116) deposited on the device substrate 102, as Figure 10 shown. As described above, for example, as further described herein with respect to Figure 3 , the elimination of the exemplary front cavity 224 from the process and resulting device can be facilitated through the use of multiple or arrays (e.g., multiple sequences) of membrane position control structures 110, which would result in a change to result 1100.

[0057] Figure 12 Depicts the result 1200 of oxide deposition, where the oxide is, for example, LPCVD TEOS 118 and is used as a spacer 1202 on a bulk oxide deposition (e.g., PECVD TEOS 116). Figure 13 Depicts an exemplary process result 1300, where an exemplary lateral etch stop structure 114 is lithographically defined (e.g., via mask M3) and etched through the spacer 1202 oxide (e.g., LPCVD TEOS 118) and the bulk oxide deposition (e.g., PECVD TEOS 116) deposited on the device substrate 102.

[0058] Figure 14 Depicts the result 1400 of the deposition of the first silicon nitride acoustic sensor membrane 104 layer 202 (e.g., LPCVD LSN 120). Figure 15 Depicts the result 1500 of the deposition of the polysilicon acoustic sensor membrane 104 electrode layer 204 (e.g., ISDP 122). Figure 16 Depicts the result 1600 of the deposition of the second silicon nitride acoustic sensor membrane 104 layer 206 (e.g., LPCVD LSN 120).

[0059] Figure 17 Depicts an exemplary process result 1700, where the range and critical dimensions of the features (e.g., one or more vent holes 220, a set of etch release structures 112, etc.) of the exemplary acoustic sensor membrane 104 are lithographically defined (e.g., via mask M4) and etched through the exemplary acoustic sensor membrane 104, which includes a stacked arrangement of the first silicon nitride (SiN) acoustic sensor membrane 104 layer 202, the polysilicon (poly-Si) acoustic sensor membrane 104 electrode layer 204, and the second silicon nitride acoustic sensor membrane 104 layer 206.

[0060] Figure 18 Depicts the result 1800 of the deposition of an oxide layer, which may also be referred to as the first air gap oxide 1802, e.g., PECVD TEOS 116, a portion of which will be etched in subsequent steps to release the acoustic sensor membrane 104 from the exemplary acoustic sensor backplate or top plate 106, as further described herein.

[0061] Figure 19Illustrative process result 1900 is depicted, where the scope and critical dimensions of features of the illustrative backplane or top plate 106 (e.g., one or more backplane or top plate 106 stoppers 218, illustrative backplane or top plate 106 lateral etch stop structures 226, etc.) are lithographically defined (e.g., via mask M5) and etched through the first air gap oxide 1802 (e.g., PECVD TEOS 116). Additionally, structures 1902 associated with polysilicon contacts 208 coupled to the polysilicon acoustic sensor membrane 104 electrode layer 204 can be defined and etched.

[0062] Figure 20 Illustrative process result 2000 of oxide layer deposition is depicted, and this oxide layer can also be referred to as the second air gap oxide 2002, e.g., PECVD TEOS 116, a portion of which will be etched in subsequent steps to release the acoustic sensor membrane 104 from the illustrative acoustic sensor backplane or top plate 106, as further described herein.

[0063] Figure 21 Illustrative process result 2100 is depicted, where the scope and critical dimensions of features of the illustrative backplane or top plate 106 (e.g., illustrative backplane or top plate 106 lateral etch stop structures 226, etc.) are lithographically defined (e.g., via mask M6) and etched through the second air gap oxide 2002 (e.g., air gap oxide), e.g., PECVD TEOS 116. Additionally, structures 1902 associated with polysilicon contacts 208 coupled to the polysilicon acoustic sensor membrane 104 electrode layer 204 can be defined and etched. The etching of the etched area can terminate at the second silicon nitride acoustic sensor 104 layer 206, e.g., LPCVD LSN120, as Figure 16 shown.

[0064] Figure 22 Illustrative process result 2200 is depicted, where the first silicon nitride backplane or top plate 106 layer 214 is deposited, e.g., LPCVD LSN 120. Additionally, Figure 22 Illustrative process result 2200 is depicted, where the scope and critical dimensions of features (e.g., structures 1902 associated with polysilicon contacts 208 coupled to the polysilicon acoustic sensor membrane 104 electrode layer 204, etc.) are lithographically defined (e.g., via mask M7) and etched through the deposited first silicon nitride backplane or top plate 106 deposition layer 214, e.g., LPCVD LSN 120.

[0065] Figure 23Illustrative process result 2300 depicting the deposition of a polysilicon layer (e.g., ISDP 122) to form an exemplary polysilicon contact 208 in the electrode layer 204 of the polysilicon acoustic sensor membrane 104 and in the polysilicon backplane or top plate 106 electrode layer 210 adjacent to the first silicon nitride backplane or top plate 106 layer 214, the deposition being accompanied by an annealing step as may be appropriate.

[0066] Figure 24 Illustrative process result 2400 is depicted where the scope and critical dimensions of features (e.g., polysilicon contacts 208 in the electrode layer 204 of the polysilicon acoustic sensor membrane 104 and in the polysilicon backplane or top plate 106 electrode layer 210 adjacent to the first silicon nitride backplane or top plate 106 layer 214, etc.) are lithographically defined (e.g., via mask M8) and etched.

[0067] Figure 25 Illustrative process result 2500 depicting the deposition of the second silicon nitride backplane or top plate 106 layer 212 (e.g., PECVD LSN 124), the deposition being accompanied by an annealing step as may be appropriate depending on subsequent wet etch rate adjustment as further described herein.

[0068] Figure 26 Illustrative process result 2600 is depicted where the scope and critical dimensions of features (e.g., metal contacts of polysilicon contact 208 coupled to the electrode layer 204 of the polysilicon acoustic sensor membrane 104 and metal contacts 216 coupled to the polysilicon backplane or top plate 106 electrode layer 210, etc.) are lithographically defined (e.g., via mask M9) and etched. The etching of the etched regions may terminate at the polysilicon contacts 208 coupled to the electrode layer 204 of the polysilicon acoustic sensor membrane 104 and the polysilicon backplane or top plate 106 electrode layer 210, respectively.

[0069] Figure 27 Illustrative process result 2700 is depicted where the scope and critical dimensions of features (e.g., metal contacts 2702 of polysilicon contact 208 coupled to the electrode layer 204 of the polysilicon acoustic sensor membrane 104 and metal contacts 216 coupled to the polysilicon backplane or top plate 106 electrode layer 210, etc.) are lithographically defined (e.g., via mask M10), and then metal, such as metal (CrAu) 126, is deposited and etched.

[0070] Figure 28Illustrative process result 2800 is depicted, where the scope and critical dimensions of features (e.g., openings 108 in the backplane or top plate 106, etc.) are lithographically defined (e.g., via mask M11) and etched. Where applicable, the etching is through the second silicon nitride backplane or top plate 106 layer 212 (e.g., PECVD LSN 124), the polysilicon backplane or top plate 106 electrode layer 210 (e.g., ISDP 122 (if applicable)), and the first silicon nitride backplane or top plate 106 layer 214 (e.g., LPCVD LSN 120) to form the backplane or top plate 106 openings 108.

[0071] Figure 29 Illustrative process result 2900 is depicted, where prior to grinding the device substrate 102 to an appropriate thickness (e.g., approximately 300 micrometers (μm)), plasma enhanced oxide deposition can be utilized to protect the device substrate 102 and the device.

[0072] Figure 30 Illustrative process result 3000 is depicted, where the scope and critical dimensions of features (e.g., cavity 222) are lithographically defined (e.g., via mask M12) and etched. The etching is through the device substrate 102 (e.g., 300 μm device substrate thickness), where the etching terminates at the body oxide deposition (e.g., PECVD TEOS 116), as deposited as described above with respect to Figure 10 that which was deposited.

[0073] Figure 31 Illustrative process result 3100 is depicted, where during the etch release process, the acoustic sensor membrane 104 is released from the acoustic sensor backplane or top plate 106. In a non - limiting aspect, an illustrative etch release process can include a buffered oxide etch (BOE), the rate and / or uniformity of which can be enhanced through the implementation of the disclosed set of etch release structures 112. Thus, Figure 31 is the process result 3100 for the etch release of the defined structures (e.g., structures fabricated with respect to Figure 8-31 ). The term "release" means that all sacrificial materials should be removed (e.g., the body oxide deposition (e.g., PECVD TEOS 116) deposited as described above with respect to Figure 10 , the spacer 1202 oxide (e.g., LPCVD TEOS 118) deposited as described above with respect to Figure 10 , the first air gap oxide 1802 (e.g., PECVD TEOS 116) deposited as described above with respect to Figure 18 , and as described above with respect to Figure 20The deposited second air gap oxide 2002 (e.g., PECVD TEOS 116)) can have its speed and / or uniformity enhanced by implementing the disclosed set of etch release structures 112.

[0074] Accordingly, a low-cost, robust, and high-performance microelectromechanical system (MEMS) acoustic sensor 100 is described herein. In non-limiting aspects, an exemplary MEMS acoustic sensor can include a set of etch release structures 112 in an acoustic sensor membrane 104 that facilitate rapid and / or uniform etch release of the acoustic sensor membrane 104. In another non-limiting aspect, an exemplary MEMS acoustic sensor 100 can include a set of membrane position control structures 114 for the acoustic sensor membrane 104 that can reduce the bending stress of the acoustic sensor membrane. In another non-limiting aspect, the MEMS acoustic sensor 100 can include a three-layer acoustic sensor membrane 104 that provides, for example, increased robustness (e.g., higher yield strength), as further described herein. In another non-limiting aspect, the MEMS acoustic sensor 100 can include a multi-layer acoustic sensor backplate or top plate 106 that increases robustness to backplate pressure by including a first silicon nitride backplate or top plate layer 214 adjacent to a polysilicon backplate or top plate 106 electrode layer 210, which can be selectively defined to allow for high sensitivity, high active capacitance, and low parasitic capacitance of the MEMS acoustic sensor 100.

[0075] In other non-limiting aspects, the MEMS acoustic sensor 100 can include a front cavity 224 that helps prevent the acoustic sensor membrane 104 from contacting the device substrate 102 under a reverse acoustic pressure pulse. Additionally, a fixed-fixed beam design including the acoustic sensor membrane 104 can provide high acoustic compliance / sensitivity.

[0076] In view of the subject matter described above, reference Figure 32 to the flowchart will better understand the method that can be implemented according to the disclosure of the present invention. Although, for the purpose of simplicity of explanation, the method is shown and described as a series of blocks, it should be understood and appreciated that such a diagram or corresponding description is not limited by the order of the blocks, as some blocks can occur in a different order and / or simultaneously with other blocks depicted and described herein. Any non-sequential or branched flow shown via the flowchart should be understood to indicate the order of various other branches, flow paths, and blocks that can achieve the same or similar results. Additionally, not all of the blocks shown are required to implement the method described below.

[0077] Exemplary method

[0078] Figure 32 A non - limiting flowchart of an exemplary method 3200 in accordance with various non - limiting aspects described herein is provided. For example, at step 3202, an exemplary method 3200 of fabricating a MEMS acoustic sensor 100 may include forming an acoustic sensor membrane 104 (e.g., forming an acoustic sensor membrane 104 having a stacked arrangement including a first silicon nitride acoustic sensor membrane 104 layer 202, a polysilicon acoustic sensor membrane 104 electrode layer 204, and a second silicon nitride acoustic sensor membrane 104 layer 206), as described herein, for example, with respect to Figures 8 to 31 that is further described.

[0079] The exemplary method 3200 may further include, at step 3204, forming a set of membrane position control structures 114 on the acoustic sensor membrane 104. In a further non - limiting aspect, the exemplary method 3200 may further include, at step 3204, forming a set of etch release structures 112 in the acoustic sensor membrane 104.

[0080] In additional non - limiting embodiments, the exemplary method 3200 may include, at step 3206, forming an acoustic sensor backplate or top plate 106 mechanically coupled to the acoustic sensor membrane 104. In a non - limiting aspect, the exemplary acoustic sensor backplate or top plate 106 may include a polysilicon backplate or top plate 106 electrode layer 210 adjacent to a second silicon nitride backplate or top plate 106 layer 212, and a first silicon nitride backplate or top plate 106 layer 214 adjacent to the polysilicon backplate or top plate 106 electrode layer 210 and the second silicon nitride backplate or top plate 106 layer 212.

[0081] In still further non - limiting embodiments, the exemplary method 3200 may include, at step 3208, forming a polysilicon contact 208 of the MEMS acoustic sensor 100 coupled to the polysilicon acoustic sensor membrane 104 electrode layer 204.

[0082] In other non - limiting embodiments, the exemplary method 3200 may include, at step 3210, cavity etching a cavity 222 into the device substrate 102, the device substrate 102 being mechanically coupled to the acoustic sensor membrane 104 located above the device substrate 102, to expose a sacrificial oxide layer adjacent to the acoustic sensor membrane 104 (e.g., as described above with respect to Figure 10The deposited bulk oxide deposition (e.g., PECVD TEOS 116)). For example, the exemplary method 3200 may include, at step 3210, etching a cavity 222 into the device substrate 102, the device substrate 102 being mechanically coupled to the exemplary acoustic sensor membrane 104, the exemplary acoustic sensor membrane 104 being fixed to the device substrate 102 at the periphery of the acoustic sensor membrane 104, wherein the acoustic sensor membrane 104 includes a set of membrane position control structures 114 that are near the periphery and project towards the device substrate 102.

[0083] Additionally, the exemplary method 3200 may include, at step 3212, membrane release etching of a sacrificial oxide layer adjacent to the acoustic sensor membrane 104 (e.g., as described above with respect to Figure 10 the deposited bulk oxide deposition (e.g., PECVD TEOS 116)). Thus, the exemplary method 3200 may include, at step 3212, membrane release etching (e.g., etching the first air gap oxide 1802 as described above with respect to Figure 18 the deposited first air gap oxide 1802 (e.g., PECVD TEOS 116) and the second air gap oxide 2002 as described above with respect to Figure 20 the deposited second air gap oxide 2002 (e.g., PECVD TEOS 116)) in the cavity between the acoustic sensor membrane 104 and the acoustic sensor backplate or top plate 106, the acoustic sensor backplate or top plate 106 being located opposite the device substrate 102 cavity 222 via one or more ventilation holes 220 in the acoustic sensor membrane 104, and etching the region of the acoustic sensor membrane 104 and the set of membrane position control structures 114 via a set of etch release structures 112 in the acoustic sensor membrane 104 that are located between the periphery and the set of membrane position control structures 114.

[0084] The foregoing description includes examples of embodiments disclosed in the present invention. Of course, for the purpose of describing the claimed subject matter, it is not possible to describe every conceivable combination of configurations, components, and / or methods, but it should be understood that many further combinations and permutations of the various embodiments are possible. Accordingly, the claimed subject matter is intended to cover all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims. Although specific embodiments and illustrations have been described for illustrative purposes, various modifications contemplated within the scope of these embodiments and illustrations are possible, as would be recognized by one of ordinary skill in the art. For example, although the embodiments disclosed in the present invention are described herein in the context of microelectromechanical system sensors (e.g., microelectromechanical system acoustic sensors, etc.), it should be understood that the present disclosure is not limited thereto. For example, various illustrative embodiments may find application in other fields of microelectromechanical system sensors, devices, and methods without departing from the subject matter described herein.

[0085] In addition, the terms "example" or "exemplary" are used herein to mean an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, the use of the term "exemplary" is intended to present concepts in a concrete fashion. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified, or clear from the context, "X employs A or B" is intended to mean any natural inclusive arrangement. In other words, 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 foregoing instances. Additionally, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless otherwise specified or clear from the context to be directed to the singular form.

[0086] Furthermore, although an aspect may have been disclosed with respect to only one of several embodiments, such aspect may be combined with one or more other features of the other embodiments as desired and advantageous for any given or particular application. Moreover, where the terms "comprise," "include," "have," "contain," their variants, and other similar words are used in a detailed description or claims, these terms are intended to be inclusive in a manner similar to the term "include" as an open transitional term and do not exclude any additional or other elements.

Claims

1. A microelectromechanical system (MEMS) acoustic sensor, comprising: an acoustic sensor membrane suspended above and mechanically coupled to a substrate disposed around the periphery of the acoustic sensor membrane, wherein the acoustic sensor membrane is configured to deform in response to sound pressure; an acoustic sensor backplate mechanically coupled to the acoustic sensor membrane and including an opening that permits the sound pressure to pass therethrough; a plurality of membrane position control structures proximate the periphery of the acoustic sensor membrane, the plurality of membrane position control structures extending perpendicular to a surface of the acoustic sensor membrane opposite the acoustic sensor backplate; and a plurality of etch release structures in the acoustic sensor membrane between the periphery and the plurality of membrane position control structures.

2. The MEMS acoustic sensor according to claim 1, further comprising: a lateral etch stop structure disposed on the acoustic sensor membrane at the periphery and at a location where the acoustic sensor membrane is mechanically coupled to the substrate.

3. The MEMS acoustic sensor according to claim 2, wherein the plurality of etch release structures are configured to enable uniform wet etching in regions of the acoustic sensor membrane, the lateral etch stop structure, and the plurality of membrane position control structures during a membrane etch release process.

4. The MEMS acoustic sensor according to claim 3, wherein the plurality of etch release structures in the acoustic sensor membrane include a set of channels through the acoustic sensor membrane, the set of channels being configured to permit the wet etching to enter the region.

5. The MEMS acoustic sensor according to claim 2, wherein the set of channels through the acoustic sensor membrane is configured to reduce an etch time required to equalize etching in the region.

6. The MEMS acoustic sensor according to claim 2, wherein the plurality of membrane position control structures are configured to restrict movement of the acoustic sensor membrane in a direction away from the acoustic sensor backplate or to reduce bending stress on the acoustic sensor membrane at a junction of the acoustic sensor membrane and the lateral etch stop structure.

7. The MEMS acoustic sensor according to claim 1, wherein the plurality of membrane position control structures include a plurality of individual membrane position control structures, each of the membrane position control structures being perpendicular to the surface of the acoustic sensor membrane, opposite the acoustic sensor backplate, and protruding toward the substrate.

8. The MEMS acoustic sensor according to claim 1, wherein the acoustic sensor membrane includes a stacked arrangement of a first silicon nitride membrane layer, a polysilicon membrane electrode layer, and a second silicon nitride membrane layer.

9. The MEMS acoustic sensor according to claim 8, further comprising: a polysilicon contact coupled to the polysilicon membrane electrode layer.

10. The MEMS acoustic sensor according to claim 8, wherein the acoustic sensor backplate includes a polysilicon backplate electrode layer and a second silicon nitride backplate layer, the polysilicon backplate electrode layer being adjacent to a first silicon nitride backplate layer, the second silicon nitride backplate layer being adjacent to the polysilicon backplate electrode layer and opposite the first silicon nitride backplate layer.

11. The MEMS acoustic sensor according to claim 10, further comprising: a metal contact coupled to the polysilicon backplate electrode layer.

12. The microelectromechanical system acoustic sensor according to claim 10, wherein, the backplate of the acoustic sensor is configured with at least one backplate stopper, and the at least one backplate stopper is at least composed of the first silicon nitride backplate layer and is adapted to limit the contact between the acoustic sensor membrane and the acoustic sensor backplate.

13. The microelectromechanical system acoustic sensor according to claim 10, further comprising: a second lateral etch stop structure disposed on the backplate of the acoustic sensor at a position where the backplate of the acoustic sensor is mechanically coupled to the acoustic sensor membrane.

14. The microelectromechanical system acoustic sensor according to claim 1, further comprising: an acoustic port formed in the substrate and configured to direct the sound pressure to the acoustic sensor membrane to deflect the acoustic sensor membrane toward the acoustic sensor backplate; and a front cavity formed in the port, adjacent to the acoustic sensor membrane, and configured to prevent the acoustic sensor membrane from contacting the substrate.

15. The microelectromechanical system acoustic sensor according to claim 1, wherein, the acoustic sensor membrane further includes at least one vent hole formed into the acoustic sensor membrane, wherein a part of the at least one vent hole is a curved opening in the acoustic sensor membrane, and wherein the at least one vent hole is disposed substantially along one side of the acoustic sensor membrane.

16. The microelectromechanical system acoustic sensor according to claim 1, wherein, the plurality of membrane position control structures are arranged as at least one of a single sequence of membrane position control structures near the periphery of the acoustic sensor membrane or a plurality of sequences of membrane position control structures near the periphery of the acoustic sensor membrane.

17. A method of manufacturing a microelectromechanical system acoustic sensor, comprising: etching a substrate cavity into the substrate, the substrate being mechanically coupled to an acoustic sensor membrane located above the substrate, to expose a sacrificial oxide layer adjacent to the acoustic sensor membrane, wherein the acoustic sensor membrane is fixed to the substrate at the periphery of the acoustic sensor membrane, and wherein the acoustic sensor membrane includes a plurality of membrane position control structures near the periphery and protruding toward the substrate; and performing a membrane release etch on the sacrificial oxide layer adjacent to the acoustic sensor membrane, including etching a cavity between the acoustic sensor membrane and an acoustic sensor backplate via at least one vent hole in the acoustic sensor membrane, the acoustic sensor backplate being located at a position opposite to the substrate cavity, and etching an area of the acoustic sensor membrane and the plurality of membrane position control structures via a plurality of etch release structures in the acoustic sensor membrane between the periphery and the plurality of membrane position control structures.

18. The method according to claim 17, further comprising: forming the acoustic sensor membrane, the acoustic sensor membrane including a stacked arrangement of a first silicon nitride membrane layer, a polysilicon membrane electrode layer, and a second silicon nitride membrane layer.

19. The method according to claim 18, wherein, forming the acoustic sensor membrane includes forming the plurality of membrane position control structures on the acoustic sensor membrane and forming the plurality of etch release structures.

20. The method according to claim 18, further comprising: Form an acoustic sensor backplane mechanically coupled to the acoustic sensor membrane, the acoustic sensor backplane including a polysilicon backplane electrode layer and a second silicon nitride backplane layer, the polysilicon backplane electrode layer being adjacent to a first silicon nitride backplane layer, the second silicon nitride backplane layer being adjacent to the polysilicon backplane electrode layer and opposite the first silicon nitride backplane layer.

21. The method according to claim 18, further comprising: forming a polysilicon contact of the MEMS acoustic sensor coupled to the polysilicon membrane electrode layer.

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