Robust MEMS microphones

Abstract

A robust MEMS transducer includes a kinetic energy diverter disposed within its front chamber. The rigid kinetic energy diverter attenuates or diverts the kinetic energy of air moving through the front chamber before it reaches the diaphragm of the MEMS transducer. The kinetic energy diverter makes the MEMS transducer more robust and resistant to damage from this moving air.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 958,050 (Attorney Docket No. 4403-10701), filed on January 7, 2020, entitled “Robust MEMS Microphone,” and naming Craig Core, Hamid Basaeri, and Robert Littrell as inventors.

[0003] The disclosures of the aforementioned applications are incorporated herein by reference in their entirety. Technical Field

[0004] The present disclosure relates to acoustic sensors, and more particularly to improving the reliability of acoustic sensors. Background Art

[0005] Microelectromechanical systems (MEMS) acoustic transducers / sensors convert acoustic energy into electrical signals and / or convert electrical signals into acoustic energy. An example of a MEMS acoustic transducer is a MEMS microphone, which converts sound pressure into an electrical voltage. Based on their transduction mechanism, MEMS microphones can be made in various forms, such as capacitive microphones or piezoelectric microphones.

[0006] MEMS condenser microphones and electret condenser microphones (ECMs) currently dominate consumer electronics. However, piezoelectric MEMS microphones are increasingly popular in the consumer market and offer distinct advantages over their capacitive MEMS counterparts. In particular, piezoelectric MEMS microphones require no backplate, eliminating the squeeze-film damping that is an inherent noise source in capacitive MEMS microphones. Furthermore, piezoelectric MEMS microphones are reflow-compatible and can be mounted to printed circuit boards (PCBs) using typical lead-free soldering processes, which can irreparably damage typical ECMs.

[0007] MEMS transducers, such as microphones, can be damaged by high-speed air striking the microphone's diaphragm. For example, some mobile phones include a MEMS microphone positioned in an opening in the phone's surface. If the mobile phone is dropped and lands with the opening touching a flat surface, air can be forced into the opening and strike the diaphragm. In response, the diaphragm can move beyond its physical limits and deform or rupture, or it can strike another structure, such as the backplate in a condenser microphone.

[0008] Conventional condenser microphones have a flexible diaphragm nestled against a backplate. Depending on the position of the diaphragm and backplate, incoming air may reach the diaphragm first and push it into the backplate, potentially damaging it and / or causing it to stick to the backplate. Alternatively, if the air reaches the backplate first, it may pass through and push the diaphragm away from it, potentially damaging it.

[0009] Some mobile phone manufacturers require that a MEMS microphone withstand being dropped from a specified height (such as one meter) onto a flat surface without adverse effects on the MEMS microphone.

[0010] Manufacturers of MEMS microphones have taken various approaches to making their microphones more robust. Some manufacturers have made their diaphragms and their suspension assemblies thicker and / or stiffer, but such diaphragms are less flexible than more flexible diaphragms, and their response to impinging sound energy is undesirably limited. Summary of the Invention

[0011] According to an exemplary embodiment, a transducer system includes: a semiconductor substrate having a top layer and a bottom surface opposite to the top layer; a front cavity extending from the bottom surface into the substrate and forming a hole at the bottom surface; a transducer element having a movable diaphragm, the movable diaphragm being arranged at the top layer of the substrate and exposed to the hole via the front cavity; and a rigid kinetic energy diverter configured to divert kinetic energy of air moving toward the movable diaphragm, the rigid kinetic energy diverter being arranged in the front cavity and extending into the front cavity in a direction away from the movable diaphragm, the kinetic energy diverter having an end exposed to the hole and away from the diaphragm, so that the exposed distal end is closer to the bottom surface than the distance to the diaphragm.

[0012] In some embodiments, the movable diaphragm includes a first diaphragm and a second diaphragm, each of the first diaphragm and the second diaphragm being configured to generate an electrical output (e.g., a first electrical output and a second electrical output, respectively) in response to incoming acoustic energy, and wherein the first diaphragm and the second diaphragm are separated by a bridge; the rigid kinetic energy diverter is suspended from the bridge; and the first diaphragm is electrically coupled to the second diaphragm to add the separate outputs such that the first diaphragm and the second diaphragm form a single capacitor.

[0013] In some embodiments, the movable diaphragm has a geometric center, and the rigid kinetic energy diverter is arranged to be consistent with the geometric center of the movable diaphragm.

[0014] In some embodiments, the exposed end of the rigid kinetic energy diverter is concave.

[0015] In some embodiments, the distance between the top layer and the bottom surface defines a thickness of the substrate, and wherein the rigid kinetic energy diverter extends from the top layer into the antechamber a distance that is at least half the thickness of the substrate.

[0016] In some embodiments, the rigid kinetic energy diverter extends through the front cavity such that the exposed end extends to a plane defined by the bottom surface.

[0017] In some embodiments, the rigid kinetic energy diverter is adjacent to the top layer.

[0018] In some embodiments, the front cavity has a plurality of sections separated by the rigid kinetic energy diverter, each of the plurality of sections exposing an underside of the transducer structure through the front cavity.

[0019] In some embodiments, the front cavity defines a set of side walls, and wherein the rigid kinetic energy diverter is suspended from the set of side walls.

[0020] Some embodiments further include a backplate that forms a variable capacitor with the movable diaphragm, the backplate being disposed between the front cavity and the movable diaphragm, and wherein the rigid kinetic energy shunt is suspended from the backplate.

[0021] Another embodiment is a method of manufacturing a robust MEMS transducer, the method comprising the steps of providing an initial substrate having a top surface and a bottom surface; fabricating a transducer structure in or on the top surface; and fabricating a front cavity, the front cavity forming a hole in the bottom surface of the initial substrate and extending inward from the bottom surface toward and to the transducer structure, the front cavity comprising a shunt structure suspended within the front cavity, the shunt structure having a bottom surface that is closer to the bottom surface of the substrate than to the transducer structure.

[0022] In some embodiments of the method, the substrate is or includes a silicon substrate, and the step of manufacturing the front cavity includes etching the front cavity into the bottom surface of the silicon substrate, the front cavity exposing the underside of the transducer structure, the etching leaving a portion of the substrate to form the shunt structure.

[0023] In some embodiments, the front cavity has a plurality of portions separated by the diverter structure, each portion of the plurality of portions exposing the underside of the transducer structure.

[0024] In some embodiments, the distance between the top surface and the bottom surface defines a thickness of the substrate, and wherein the rigid kinetic energy diverter extends a distance from the top layer into the antechamber that is at least half the thickness of the substrate.

[0025] In some embodiments, the distance between the top surface and the bottom surface defines a thickness of the substrate, and wherein the rigid kinetic energy diverter extends from the top layer into the front cavity a distance that is at least three quarters of the thickness of the substrate.

[0026] Another exemplary embodiment includes: a transducer having a transducer element and a front cavity, the transducer element having a movable diaphragm exposed to the front cavity; a transducer system substrate, the system substrate having: an acoustic hole system, the acoustic hole system including a plurality of hole portions; and a rigid septum, the rigid septum being defined by the plurality of hole portions and spanning the acoustic hole system, the rigid septum having an exposed surface away from the movable diaphragm, the rigid septum being configured to divert kinetic energy of air moving toward the diaphragm; the transducer being fixed to the substrate, wherein the front cavity covers the acoustic hole system in a manner that allows an acoustic signal to pass through each of the plurality of hole portions and reach the movable diaphragm.

[0027] In some embodiments, the transducer includes a MEMS transducer, which further has: a rigid kinetic energy diverter, which is configured to divert kinetic energy of air moving toward the movable diaphragm, the rigid kinetic energy diverter is arranged in the front cavity and extends into the front cavity in a direction away from the movable diaphragm, the kinetic energy diverter has an exposed end away from the diaphragm, so that the exposed distal end is closer to the diaphragm than the distance to the diaphragm.

[0028] In some embodiments, wherein the transducer is secured to the top surface of the system substrate by die attach, the die attach having a die attach thickness, the system further comprising a gap between the exposed end of the energy splitter and the spacer, the gap having a thickness equal to the die attach thickness.

[0029] In some embodiments, the system substrate has a top surface, and the energy diverter is aligned with the spacer in such a manner that a line perpendicular to the top surface of the system substrate passes through both the energy diverter and the spacer.

[0030] In some embodiments, the transducer system further comprises a cover secured to the system substrate, the cover and the system substrate defining a packaging volume, wherein the transducer is secured to the system substrate within the packaging volume together with the ASIC, the ASIC being coupled to the transducer to receive an electrical output generated by the transducer in response to an acoustic signal entering the system through the acoustic hole system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Features of the embodiments will be more readily understood by referring to the following detailed description taken with reference to the accompanying drawings, in which:

[0032] Figure 1A and Figure 1B Schematically illustrates a cross section of a prior art microphone system;

[0033] Figure 2A schematically illustrates a cross-section of an embodiment of a robust MEMS transducer;

[0034] Figure 2B schematically illustrates a cross-section of an embodiment of a robust MEMS transducer;

[0035] Figure 2C Schematically illustrates an embodiment of a dual-diaphragm transducer;

[0036] Figure 2D schematically illustrates a cross-section of another embodiment of a robust MEMS transducer;

[0037] Figure 2E schematically illustrates a cross-section of another embodiment of a robust MEMS transducer;

[0038] Figure 3A schematically illustrates a cross-section of an embodiment of a robust MEMS transducer on a substrate;

[0039] Figure 3B schematically illustrates a cross-section of an embodiment of a packaged robust MEMS transducer;

[0040] Figure 4A is a flow chart of a process of an embodiment of fabricating a robust MEMS transducer;

[0041] Figure 4B is a flow chart of a process of an embodiment of fabricating a robust MEMS transducer;

[0042] Figure 5A 、 Figure 5B 、 Figure 5C 、 Figure 5D 、 Figure 5E 、 Figure 5F 、 Figure 5G 、 Figure 5H as well as Figure 5I each schematically illustrates a cross-section of an embodiment of a robust MEMS transducer at various stages of fabrication;

[0043] Figure 6A 、 Figure 6B as well as Figure 6C A cross section of an alternative embodiment of a transducer system is schematically illustrated. DETAILED DESCRIPTION

[0044] Various embodiments disclose a MEMS transducer having enhanced resistance to damage from incoming moving air (eg, as might occur if the transducer or a device incorporating the transducer is dropped).

[0045] definition:

[0046] "ASIC" is an application-specific integrated circuit.

[0047] A "set" includes at least one member. For example, a set of transducer elements may include as few as a single transducer element, or a plurality of two or more transducer elements.

[0048] The term "acoustic signal" refers to energy propagated through a fluid medium via a mechanical wave. An acoustic signal can propagate through a stationary fluid medium, where the fluid medium can experience zero net displacement due to the propagation of the acoustic energy through the medium. A fluid (e.g., air) should not be considered a fluid that moves simply because an acoustic signal is propagating through it.

[0049] A "transducer" is a device that converts a change in a physical quantity, such as an acoustic signal or pressure, into an electrical signal, or vice versa. Examples of transducers include, but are not limited to, microphones, pressure sensors, and speakers. Some embodiments herein are described and illustrated using microphone transducers, but the embodiments are not limited to microphones, and the claims are not limited to microphones unless expressly limited to microphones.

[0050] The term "diaphragm" refers to the portion of a transducer that moves in response to an impinging physical signal (e.g., an acoustic signal) to generate or play a role in generating an electrical signal in response to the physical signal (e.g., in a microphone), or generates a physical signal (e.g., an acoustic signal) in response to an applied electrical signal (e.g., as a speaker). For example, in some transducers, the diaphragm is a membrane that moves relative to a backplate, e.g., because the diaphragm is flexible and / or because the diaphragm is suspended from a substrate by flexure. As another example, in some transducers, the diaphragm includes a set of cantilevered plates that independently flex in response to an impinging acoustic signal and generate an electrical signal due to the piezoelectric effect.

[0051] Figure 1A and Figure 1B A prior art microphone system 100 is schematically illustrated. System 100 includes a microphone (e.g., a MEMS microphone) 110 mounted on a system substrate (which may be a printed circuit board) 120 and an application specific integrated circuit ("ASIC") 130. In this illustration, microphone 110 defines a front cavity 111 having a width (960 μm in this embodiment).

[0052] A cover 140 mounted on the printed circuit board 120 covers the microphone 110 and an application specific integrated circuit (“ASIC”) 130 that is coupled to the microphone 110 and configured to receive electrical signals from the microphone 110 .

[0053] The printed circuit board 120 includes an acoustic hole 121 that is arranged to be aligned with the microphone 110, and in particular aligned with the front cavity 111, so that acoustic energy (e.g., acoustic signals) from outside the system 100 can impinge on the microphone 110. The acoustic hole has a width (750 μm in this embodiment). Figure 1A and Figure 1B As shown, the acoustic port 121 and the front cavity 111 combine to form an uninterrupted passage from the space external to the system 100 to the transducer 112 of the microphone 110 .

[0054] Figure 2A An embodiment of a robust MEMS transducer system 200 is schematically illustrated.

[0055] The MEMS transducer system 200 has a top side 213 and a substrate 210 having a top surface 211 and a bottom surface 212, and a thickness defined as the distance between the top side 213 and the bottom surface 212. In the exemplary embodiment, the substrate 210 is silicon, but in other embodiments it can be other semiconductors or other materials. In some embodiments, the top side 213 of the MEMS transducer 200 is also the top surface 211 of the substrate 210. Figure 2A In the exemplary embodiment of , thickness 215 (defined as the distance between the top surface 211 of the substrate and the bottom surface 212 of the substrate) is 400 μm.

[0056] The MEMS transducer 200 also has a transducer element 230 disposed in or at the top surface 211 of the substrate 210. The transducer element 230 may be described as being in or at the top layer of the substrate 210. The transducer element 230 may be any of a variety of transducers known in the art, including but not limited to a capacitive transducer having a backplate 291 and a flexible diaphragm 290, or a piezoelectric transducer, to name a few examples.

[0057] Although the transducer element 230 is a single transducer, in some embodiments, the sub-element includes two transducer elements, such as a first transducer sub-element 231 and a second transducer sub-element 232, as shown in FIG. Figure 2C Schematically illustrated, the transducer element subelements 231, 232 form a single transducer element 230. For example, in some embodiments having two transducer subelements 231, 232, the transducer subelements 231, 232 are electrically coupled to act as a single transducer in response to an incoming acoustic signal. To this end, in some embodiments, the two transducer subelements 231, 232 can be electrically coupled to one another via a conductive coupler 233. In some embodiments, the transducer subelements 231, 232 are coupled to one another so that the separate signals generated by the transducer subelements 231, 232 are summed. For example, in an exemplary embodiment, the transducer subelements 231, 232 are configured or coupled electrically in parallel to form a single capacitor.

[0058] In some embodiments, the transducer sub-elements 231 , 232 are disposed on either side of the bridge 235 , such that the bridge 235 extends between the first transducer sub-element 231 and the second transducer sub-element 232 . Figure 2C One such embodiment is schematically illustrated.

[0059] The MEMS transducer 200 also has a front cavity 220. The front cavity 220 extends from the bottom surface 212 into the substrate 210 and exposes the transducer 230 through the substrate 210. The exemplary embodiment of the front cavity 220 has two parts (221, 222) as described below. In the exemplary embodiment, the front cavity 220 forms a hole in the bottom surface 212 of the substrate 210.

[0060] The MEMS transducer 200 also has an energy diverter 240 disposed within the front cavity 220. The energy diverter 240 may also be referred to as an "energy attenuator." When a fluid (e.g., air) moves into the front cavity 220 toward the transducer 230, the energy diverter 240 diverts kinetic energy in the fluid. Therefore, the energy diverter 240 may be referred to as a "kinetic" energy diverter 240, where the adjective "kinetic" refers to the energy being diverted. In an exemplary embodiment, the energy diverter 240 is a static structure.

[0061] In exemplary embodiments, the energy diverter 240 is adjacent to the top layer and extends from the top layer of the transducer substrate 210 into the front cavity 220. In some exemplary embodiments that include a bridge 235, the energy diverter 240 is adjacent to the bridge 235 and extends from the bridge 235 into the front cavity 220. In other words, in some embodiments, the energy diverter 240 is suspended from the bridge 235 into the front cavity 220. For example, see Figure 2A In some embodiments, the diverter 240 is suspended from the side wall 226 of the front chamber 220 in addition to being suspended from the bridge 235. In other embodiments (such as Figure 2D In the embodiment schematically illustrated, the shunt 240 is suspended from the side wall 226 of the front cavity 220, rather than from the bridge 235. In an embodiment (such as the embodiment of ... Figure 2E In the exemplary embodiment, the diverter 240 can be suspended from the back plate 291. In the exemplary embodiment, the diverter 240 is arranged to coincide with the geometric center 234 of the movable diaphragm of the transducer 230, for example, Figure 2A In an exemplary embodiment (e.g., as shown in FIG. 2 ) the transducer 230 includes a back plate 291. Figure 2E In the diagram (illustrated schematically and only as an example), the energy diverter 240 is arranged in such a way that kinetic energy entering the front cavity 220 from outside the transducer 200 reaches the energy diverter 240 before it reaches the back plate 291.

[0062] The flow divider 240 defines two portions 221, 222 of the front cavity 220, each portion 221, 222 being associated with and providing an acoustic path to the transducer 230. For example, see Figure 2A For example, in an embodiment having two transducer elements 231, 232, each such portion 221, 222 of the front cavity 220 can be associated with a corresponding one of the transducer elements 231, 232 and provide an acoustic path to the corresponding transducer element. Such an embodiment can be described as having a front cavity 220 having a plurality of portions 221, 222 separated by a rigid kinetic energy diverter 240, with each portion of the plurality of portions 221, 222 being exposed to the underside of the transducer structure 230 via the front cavity 220.

[0063] The flow divider 240, in conjunction with the sidewall 226, defines the width of such portions 221, 222. For example, Figure 2ASchematically illustrated, the width of each portion 221, 222 extends 660 μm from the side wall 226 of the front chamber 220 to the facing side wall 246 of the diverter 240. In this embodiment, the width of the diverter 240 is 160 μm.

[0064] In an exemplary embodiment, the various portions 221, 222 of the front cavity 220 have the same physical length, such that such portions 221, 222 do not change the relative phases of the portions of the acoustic signal as the acoustic signal propagates through the front cavity 220 to the transducer 230. In such an embodiment, the portions 221, 222 may be described as having the same acoustic length.

[0065] In operation, when moving air with kinetic energy moves in the direction of the transducer 230 and into and through the front cavity 220, the air first encounters the end (or bottom surface) 241 of the energy diverter 240. In some embodiments, the bottom surface 241 of the diverter 240 is flat. In some embodiments, the bottom surface 241 of the diverter 240 is concave, and in some embodiments, the bottom surface 241 of the diverter 240 is convex.

[0066] Some of this kinetic energy is reflected by the end 241 of the energy splitter, and / or some of this kinetic energy may be absorbed by the end 241 of the energy splitter 240 and / or by one or more side surfaces 246 of the energy splitter 240. Some of this energy is shunted or redirected, for example, into the sidewalls 226 or other air atoms so that it does not directly strike the diaphragm 290. Thus, the kinetic energy of the air is attenuated, wherein at least some of the kinetic energy of the air is prevented from reaching, or at least prevented from directly striking, the transducer 230.

[0067] To this end, the bottom surface 241 of the diverter 240 is suspended in the front cavity 220 at a certain position so that the air entering and moving through the front cavity 220 will hit the bottom surface 241 of the diverter 240 at a certain position so that the diverter 240 can sufficiently redirect, divert, or attenuate the kinetic energy to protect the transducer 230, as described above. If the bottom surface 241 of the diverter 240 is too close to the transducer 230, the diverter may not be able to adequately redirect, divert, or attenuate the kinetic energy. Therefore, in the exemplary embodiment, the diverter 240 is positioned in the front cavity so that the kinetic energy reaches the bottom surface 241 before reaching the transducer 230.

[0068] In the exemplary embodiment, the bottom surface 241 of the shunt 240 is disposed at least midway between the transducer 230 (or bridge 235) and the bottom surface 212 of the substrate 220. In some embodiments, such as Figure 2A, the energy diverter 240 extends through the antechamber 220 such that the bottom surface 241 of the diverter 240 is parallel to the bottom surface 212 of the substrate 210. In other words, in some embodiments, the energy diverter 240 extends through the antechamber 220 such that the bottom surface 241 of the diverter 240 extends to the plane defined by the bottom surface 212.

[0069] In some embodiments, the distance between the top surface of the substrate and the bottom surface of the substrate defines the thickness of the substrate. In some embodiments, the rigid kinetic energy diverter 240 extends from the top layer of the substrate or the top surface of the substrate into the antechamber a distance that is at least half the thickness of the substrate. In some embodiments, the rigid kinetic energy diverter 240 extends from the top layer of the substrate or the top surface of the substrate into the antechamber a distance that is at least three-quarters the thickness of the substrate. In some embodiments, the rigid kinetic energy diverter 240 extends from the top layer of the substrate or the top surface of the substrate into the antechamber and all the way to the bottom surface of the substrate.

[0070] The energy diverter 240 has a height 245 measured along a direction extending from the bottom surface 212 of the substrate 210 toward the top surface 211 of the substrate 210. In some embodiments, the height 245 of the energy diverter 240 is equal to the thickness 215 of the substrate 210. In other embodiments, the height 245 of the energy diverter 240 is less than half the thickness 215 of the substrate 210. For example, in exemplary embodiments, the height 245 of the energy diverter 240 can be 0.45 times the thickness 215 of the substrate 210, or 0.40 times the thickness 215 of the substrate 210, or 0.35 times the thickness 215 of the substrate 210, or 0.30 times the thickness 215 of the substrate 210, or 0.25 times the thickness 215 of the substrate 210, to name a few examples. In other embodiments, the height 245 of the energy diverter 240 is at least half the thickness 215 of the substrate 210. For example, in an exemplary embodiment, the height 245 of the energy diverter 240 can be half the thickness 215 of the substrate 210; three-quarters the thickness 215 of the substrate 210; 0.6 times the thickness 215 of the substrate 210, 0.7 times the thickness 215 of the substrate 210, 0.8 times the thickness 215 of the substrate 210, or 0.9 times the thickness 215 of the substrate 210, to name a few examples.

[0071] Energy splitter 240 also has a width 244, which is measured in a direction perpendicular to height 245, e.g. Figure 2BSchematically illustrated. In some embodiments, the width 244 is defined along a direction parallel to the top surface 211 of the substrate 210. The energy diverter 240 has an aspect ratio along a cross-section, which is defined as the ratio of the height 245 of the energy diverter to its width 244. In an exemplary embodiment, the height 245 of the energy diverter 240 is greater than the width 244 of the energy diverter 240, so that the aspect ratio of the energy diverter is greater than 1, but the aspect ratio is less than 100. For example, in some embodiments, the aspect ratio is greater than 2; in some embodiments, the aspect ratio is greater than 3; in some embodiments, the aspect ratio is greater than 4; and in some embodiments, the aspect ratio is greater than 5.

[0072] The inventors have discovered that acoustic energy (e.g., energy in the acoustic signal) propagating into the front cavity 220 is not significantly damped by the energy diverter 240. All or substantially all of the acoustic energy enters and passes through the front cavity, arriving at and impinging on the transducer 230 (e.g., transducer elements 232, 232). This is in contrast to the kinetic energy of the moving air, which is damped or diverted by the energy diverter 240.

[0073] Therefore, it can be Figure 2A 、 Figure 2B 、 Figure 2C 、 Figure 2D as well as Figure 2E The MEMS transducer 200 is described as being more robust than the prior art microphone 110 because the MEMS transducer 200 can withstand drops (e.g., as described above) without incurring the aforementioned damage (or at least being less susceptible to the aforementioned damage) while maintaining its characteristics as a transducer (e.g., a speaker or microphone).

[0074] In practice, the MEMS transducer 200 is most likely manufactured as part of a wafer having a plurality of such MEMS transducers 200. After the wafer is manufactured, the wafer is diced (as is known in the art) to isolate the plurality of such MEMS transducers 200 into separate individual devices, each having a transducer 230 and a front cavity 220, as described above in conjunction with FIG. Figure 2A 、 Figure 2B 、 Figure 2C 、 Figure 2D as well as Figure 2E described.

[0075] Figure 3A The MEMS transducer 200 according to the above embodiment is schematically illustrated, and the MEMS transducer is coupled to the system substrate 120. Figure 3A The center is represented by a printed circuit board having a thickness 122 (in this embodiment, a thickness of 200 μm) and having an acoustic hole 121.

[0076] The MEMS transducer 200 is coupled to the system substrate 120 via the die attach 125 .

[0077] Figure 3B Schematically illustrated is a cover 140 coupled to the system substrate 120 and enclosing the MEMS transducer 200 within an interior volume (or "packaging volume") 310. This embodiment also includes an ASIC 130 enclosed within the interior volume 310. The ASIC is in electrical communication with the transducer 200 and is configured to receive and process signals output from the transducer 200.

[0078] manufacture

[0079] Figure 4A The flowchart of FIG. 4 illustrates a method of manufacturing a robust MEMS transducer according to the aforementioned embodiments, and the method includes the steps of providing a substrate (step 401), manufacturing the transducer 230 on or in the substrate (step 402), and manufacturing the front cavity 220 including the shunt structure 240 (step 403). The shunt structure can be any of the energy shunts 240 described herein. Some embodiments also include step 404, which includes cutting the wafer to singulate the transducer 200 from the wafer (for embodiments in which the transducer 200 is manufactured as part of the wafer), and may also include securing the transducer 200 to the system substrate 120 over the acoustic port and capping the transducer 200 by securing a cover (or cap) 140 over the transducer 200.

[0080] Figure 4B is a flow chart illustrating a method 410 of fabricating a robust MEMS transducer 200 . Figure 5A 、 Figure 5B 、 Figure 5C 、 Figure 5D 、 Figure 5E 、 Figure 5F 、 Figure 5G 、 Figure 5H as well as Figure 5I Each schematically illustrates a cross-section of an embodiment of a robust MEMS transducer 200 at various stages of fabrication. For purposes of illustration, Figure 5A 、 Figure 5B 、 Figure 5C 、 Figure 5D 、 Figure 5E 、 Figure 5F 、 Figure 5G 、 Figure 5H as well as Figure 5I The schematically illustrated transducer 200 is a piezoelectric microphone, but the type of transducer 200 does not limit the manufacture of the shunt 240 .

[0081] Step 415 includes setting up an initial wafer. Figure 5A An embodiment of a starting wafer 500 is schematically illustrated. In this embodiment, the starting wafer 500 includes a semiconductor (e.g., silicon) substrate 210 having a top surface 213 and a bottom surface 212. In this embodiment, the starting wafer 500 includes a silicon oxide (SiO2) layer 505 disposed on and covering the upper surface 213 of the starting wafer, and a metal layer ("Metal 1") 506 disposed on the silicon oxide layer 505. For example, the first metal layer 506 (as well as the second metal layer 515 and the third metal layer 545, as described herein) can be or include molybdenum.

[0082] Step 420 includes patterning the first metal layer 506 to form a patterned first metal layer, such as Figure 5B Schematically illustrated.

[0083] Step 425 includes adding a first piezoelectric material layer (e.g., aluminum scandium nitride (AlScN)) 510 over the patterned first metal layer 506, followed by adding a second metal layer ("Metal 2") 515 over the first piezoelectric material layer 510, as shown in FIG. Figure 5C Schematically illustrated.

[0084] Step 430 is to pattern the second metal layer 515 to form a patterned second metal layer 515, such as Figure 5D Schematically illustrated.

[0085] Step 435 includes adding a second piezoelectric material layer 530 covering the patterned second metal layer 515, such as Figure 5E Schematically illustrated.

[0086] Step 440 includes patterning the second piezoelectric material layer 530 to expose a portion of the patterned second metal layer 515 in the first cavity 532; and patterning the piezoelectric material 510 to expose a portion of the patterned first metal layer 506 in the first cavity 531, as shown in FIG. Figure 5F Schematically illustrated.

[0087] Step 445 includes depositing a third metal layer 545 and then depositing a passivation layer 546 (eg, AlN) over the third metal layer 545. Figure 5G Step 445 further includes: patterning the passivation layer 546 and the third metal layer 545 to expose the cavities 531 and 532, and then depositing metal in the cavities 531 and 532 to form through holes 541 and 542, as shown in FIG. Figure 5GIn an exemplary embodiment, the vias 541 , 542 may be or include a conductive alloy of aluminum and copper (eg, AlCu).

[0088] At step 450, the method 410 includes etching a cavity (or "diaphragm cavity") 551 through the passivation layer 546, the third metal layer 545, the second piezoelectric material layer 530, the second metal layer 515, the first piezoelectric material layer 510, and the first metal layer 506. Figure 5H Schematically illustrated.

[0089] The method 410 further includes etching the front cavity 220 (eg, portions 221 and 222) at step 455, such as Figure 5I Schematically illustrated. Note that step 455 includes forming the energy diverter 240 by selective etching, which is formed by leaving a portion of the substrate 210. In other words, the etching leaves a portion of the substrate to form the diverter structure. Figure 5I In the embodiment, the front cavity 220 merges with the diaphragm cavity 551 to form the diaphragm hole 561.

[0090] Step 460 includes oxide etching and release to fabricate the MEMS transducer 200, for example, to produce a movable diaphragm. In some embodiments, step 460 also includes dicing the wafer to separate the transducer 200 from the wafer. In some embodiments, step 460 may also include securing the transducer 200 to the system substrate 120 over the acoustic port and capping the transducer 200 by securing a cover (or cap) 140 over the transducer 200.

[0091] Figure 6A 、 Figure 6B as well as Figure 6C An alternative embodiment of a transducer system 600 comprising a transducer 600 (which may be, for example, a microphone) and a packaging substrate 120 is schematically illustrated.

[0092] Transducer 610 may be transducer 200 as shown and described above, but is not required to be such a transducer.

[0093] The transducer 620 has a front cavity 611 , and a transducer element 630 having a movable diaphragm 613 exposed to the front cavity 611 .

[0094] The system substrate 120 has an acoustic hole system 620 having a plurality of hole portions 621 , 622 .

[0095] The acoustic aperture system 620 also includes a rigid septum 623 extending across the acoustic aperture system 620. In the exemplary embodiment, the rigid septum 623 is defined by a plurality of aperture portions 621, 622. The rigid septum 623 is configured to attenuate and / or redirect (e.g., reflect) the kinetic energy of air moving toward the diaphragm. To this end, the rigid septum 623 has an exposed surface 624 facing away from the movable diaphragm 613.

[0096] The two hole portions 621, 622 each pass an incoming acoustic signal from outside the system 600 into the front cavity 611 of the MEMS transducer 610. The two hole portions 621, 622 and the diaphragm 623 have no adverse effect on the propagation of acoustic energy into the front cavity 611.

[0097] The transducer 610 is fixed to the system substrate 120, wherein the front cavity 611 covers the acoustic hole system 620, so that the acoustic signal can pass through each of the plurality of hole portions 621, 622 and reach the movable diaphragm 613. In the exemplary embodiment, the transducer 610 is connected to the top surface 122 of the system substrate 120 by the chip mount 125. In some embodiments, the energy splitter 240 is aligned with the septum 623 so that a straight line perpendicular to the top surface 122 of the system substrate 120 passes through both the energy splitter 240 and the septum 623. For example, see Figure 6C The positions of the energy splitter 240 and the spacer 623 are schematically illustrated.

[0098] In some embodiments, such as Figure 6C In the exemplary embodiment, the transducer 600 is as follows Figure 2A Schematically illustrated is a transducer 200. To this end, the transducer has a rigid kinetic energy diverter 240 that is configured to redirect and / or attenuate kinetic energy of air moving toward the movable diaphragm. As described above, the rigid kinetic energy diverter 240 is disposed within the front cavity and extends into the front cavity in a direction away from the movable diaphragm. The exposed end 241 of the kinetic energy diverter 240 is distal to the transducer 230 such that the exposed distal end 241 is closer to the septum 623 than to the transducer 230. Some embodiments include a gap 625 between the end 241 of the energy diverter 240 and the septum 623, the gap 625 having a thickness equal to the thickness of the chip mount 125 securing the transducer 610 to the system substrate 120.

[0099] Some embodiments further include a cover 140 secured to the system substrate 120, the cover and the system substrate defining a packaging volume 310, wherein the transducer 200 is secured to the system substrate 120 within the packaging volume 130 along with an ASIC 130 electrically coupled to the transducer 200 to receive an electrical output generated by the transducer 200 in response to an acoustic signal entering the system 600 through the acoustic port system 620.

[0100] A list of certain reference numbers is provided below.

[0101] 100: microphone system of prior art;

[0102] 110: MEMS microphone of prior art;

[0103] 111: the front cavity of a microphone in the prior art;

[0104] 112: Transducer of a microphone in the prior art;

[0105] 120: a package substrate (e.g., a printed circuit board (“PCB”));

[0106] 121: Acoustic holes in printed circuit boards;

[0107] 122: Thickness of the package substrate (or "system" substrate);

[0108] 124: top surface of the system substrate;

[0109] 125: Chip mounting;

[0110] 130: ASIC;

[0111] 140: lid;

[0112] 200:MEMS transducer;

[0113] 210: substrate;

[0114] 211: top surface of the transducer substrate;

[0115] 212: bottom surface of the transducer substrate;

[0116] 213: top surface of the transducer;

[0117] 215: thickness of the transducer substrate;

[0118] 220: anterior cavity;

[0119] 221: first part of the anterior cavity;

[0120] 221: the second part of the anterior cavity;

[0121] 226: lateral wall of the anterior cavity;

[0122] 230: transducer element (or "transducer" element);

[0123] 231: first transducer subelement;

[0124] 232: second transducer subelement;

[0125] 233: conductive connector;

[0126] 234: Geometric center of the transducer;

[0127] 235: Bridge;

[0128] 240: Energy diverter;

[0129] 241: End of the energy splitter;

[0130] 244: Width of the energy splitter;

[0131] 245: Height of the energy diverter;

[0132] 246: Side view of the energy splitter;

[0133] 290: diaphragm;

[0134] 291: back panel;

[0135] 310: Package volume;

[0136] 500: initial wafer;

[0137] 505: silicon oxide layer;

[0138] 506: first metal layer;

[0139] 510: First piezoelectric material layer

[0140] 515: second metal layer;

[0141] 530: Second piezoelectric material layer

[0142] 531: First cavity;

[0143] 532: Second cavity;

[0144] 541: first through hole;

[0145] 542: second through hole;

[0146] 545: third metal layer;

[0147] 546: passivation layer;

[0148] 551: first diaphragm cavity;

[0149] 552: second diaphragm cavity;

[0150] 561: first diaphragm hole;

[0151] 600: transducer system;

[0152] 610: transducer;

[0153] 611: anterior cavity;

[0154] 621: first part of the sound hole;

[0155] 622: The second part of the sound hole;

[0156] 623: spacer (or "span");

[0157] 624: Surface of the septum

[0158] Various embodiments may be characterized by potential claims listed in the paragraphs following this paragraph (and before the actual claims provided at the end of this application). These potential claims form part of the written description of this application. Therefore, the subject matter of the following potential claims may be presented as actual claims in subsequent proceedings involving this application or any application claiming priority based on this application. The inclusion of such potential claims should not be interpreted as meaning that the actual claims do not cover the subject matter of the potential claims. Therefore, a decision not to raise these potential claims in subsequent proceedings should not be interpreted as a gift of that subject matter to the public.

[0159] Without limitation, potential subject matter that may be claimed (prefaced with the letter "P" to avoid confusion with the actual claims being issued) includes:

[0160] P1. A MEMS transducer, comprising: a substrate having a top layer and a bottom surface opposite to the top layer; a front cavity extending from the bottom surface into the substrate; a transducer having a movable diaphragm, the movable diaphragm being arranged at the top layer of the substrate and exposed to the front cavity; and a rigid kinetic energy diverter configured to divert kinetic energy of air moving toward the movable diaphragm, the rigid kinetic energy diverter being arranged in the front cavity and extending into the front cavity in a direction away from the movable diaphragm, the kinetic energy diverter having an exposed end away from the diaphragm, so that the exposed distal end is closer to the bottom surface than the distance to the diaphragm.

[0161] P2. A MEMS transducer according to P1, wherein the movable diaphragm includes a first diaphragm and a second diaphragm, and wherein the first diaphragm and the second diaphragm are separated by a bridge; the rigid kinetic energy shunt is suspended from the bridge; and the first diaphragm is electrically connected to the second diaphragm to add the separate outputs so that the first diaphragm and the second diaphragm form a single capacitor.

[0162] P3. A MEMS transducer according to any one of P1 to P2, wherein the movable diaphragm has a geometric center, and the rigid kinetic energy shunt is arranged to coincide with the geometric center of the movable diaphragm.

[0163] P4. A MEMS transducer according to any one of P1 to P3, wherein the exposed end of the rigid kinetic energy shunt is concave.

[0164] P5. A MEMS transducer according to any one of P1 to P4, wherein the top layer and the bottom surface define the thickness of the substrate, and wherein the distance that the rigid kinetic energy shunt extends from the top layer into the front cavity is at least half the thickness of the substrate.

[0165] P6. A MEMS transducer according to any one of P1 to P5, wherein the rigid kinetic energy shunt extends through the front cavity so that the exposed end extends to a plane defined by the bottom surface.

[0166] P7. A MEMS transducer according to any one of P1 to P6, wherein the rigid kinetic energy shunt is adjacent to the top layer.

[0167] P8. A MEMS transducer according to any one of P1 to P7, wherein the front cavity has a plurality of parts separated by the rigid kinetic energy shunt, each of the plurality of parts exposing the underside of the transducer structure.

[0168] P9. A MEMS transducer according to any one of P1 to P8, wherein the front cavity defines a set of side walls, and wherein the rigid kinetic energy shunt is suspended from the set of side walls.

[0169] P10. The MEMS transducer according to P1 to P9 further comprises a backplate, wherein the backplate and the movable diaphragm form a variable capacitor, the backplate being arranged between the front cavity and the movable diaphragm, and wherein the rigid kinetic energy shunt is suspended from the backplate.

[0170] P11. A MEMS transducer according to P1 to P10, wherein the substrate comprises a semiconductor material.

[0171] P12. A MEMS transducer according to P1 to P11, wherein the substrate comprises silicon.

[0172] P13. A method for manufacturing a robust MEMS transducer, the method comprising the following steps: providing an initial substrate having a top surface and a bottom surface; manufacturing a transducer structure in or on the top surface; and manufacturing a front cavity extending inward from the bottom surface toward and to the transducer structure, the front cavity including a shunt structure suspended within the front cavity, the shunt structure having a bottom surface that is closer to the bottom surface of the substrate than to the transducer structure.

[0173] P14. A method for manufacturing a robust MEMS transducer according to P13, wherein the substrate comprises a silicon substrate, and the step of manufacturing the front cavity comprises: etching the front cavity into the bottom surface of the silicon substrate, the front cavity exposing the underside of the transducer structure.

[0174] P15. A method of manufacturing a robust MEMS transducer according to any one of P13 to P14, wherein the front cavity has a plurality of portions separated by the shunt structure, each portion of the plurality of portions exposing the underside of the transducer structure.

[0175] P16. A transducer system, comprising: a transducer having a transducer element and a front cavity, the transducer having a movable diaphragm exposed to the front cavity; a substrate having: an acoustic hole system, the acoustic hole system comprising a plurality of hole portions; and a rigid diaphragm defined by the plurality of hole portions and spanning the acoustic hole system, the rigid diaphragm having an exposed surface away from the movable diaphragm, the rigid diaphragm being configured to divert kinetic energy of air moving toward the diaphragm; the transducer being fixed to the substrate, wherein the front cavity covers the acoustic hole system in a manner such that an acoustic signal can pass through each of the plurality of hole portions and reach the movable diaphragm.

[0176] P17. A transducer system according to P16, wherein the transducer includes a MEMS microphone, and the MEMS transducer further includes: a rigid kinetic energy diverter, wherein the rigid kinetic energy diverter is configured to divert kinetic energy of air moving toward the movable diaphragm, the rigid kinetic energy diverter is arranged in the front cavity and extends into the front cavity in a direction away from the movable diaphragm, the kinetic energy diverter has an exposed end away from the diaphragm, so that the exposed distal end is closer to the diaphragm than the distance to the diaphragm.

[0177] The embodiments of the invention described above are intended to be exemplary only; many variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to fall within the scope of the invention as defined in any accompanying innovations and / or any accompanying claims.

Claims

1. A MEMS transducer, comprising: a semiconductor substrate having a top surface and a bottom surface opposite the top surface; a front cavity extending from the bottom surface into the substrate and forming a hole at the bottom surface; a transducer element having a movable diaphragm disposed at the top layer of the substrate and exposed to the hole via the front cavity; a rigid kinetic energy diverter configured to divert kinetic energy of air moving toward the movable diaphragm, the rigid kinetic energy diverter being disposed in the front cavity and extending into the front cavity in a direction away from the movable diaphragm, the rigid kinetic energy diverter having an end exposed to the hole and away from the diaphragm, such that the exposed distal end is closer to the bottom surface than to the diaphragm; as well as A back plate forms a variable capacitor with the movable diaphragm, the back plate being disposed between the front cavity and the movable diaphragm, and wherein the rigid kinetic energy shunt is suspended from the back plate.

2. The MEMS transducer according to claim 1, wherein: The movable diaphragm has a geometric center, and the rigid kinetic energy diverter is arranged to coincide with the geometric center of the movable diaphragm.

3. The MEMS transducer according to claim 1, wherein: The exposed end of the rigid kinetic energy diverter is concave.

4. The MEMS transducer according to claim 1, wherein: The distance between the top layer and the bottom surface defines a thickness of the substrate, and wherein the rigid kinetic energy diverter extends from the top layer into the front cavity a distance that is at least half the thickness of the substrate.

5. The MEMS transducer according to claim 1, wherein: The rigid kinetic energy diverter extends through the front cavity such that an exposed end extends to a plane defined by the bottom surface.

6. The MEMS transducer according to claim 1, wherein: The front cavity has a plurality of sections separated by the rigid kinetic energy diverter, each of the plurality of sections exposing an underside of the transducer structure through the front cavity.

7. The MEMS transducer according to claim 1, wherein: The front cavity defines a set of side walls, and wherein the rigid kinetic energy diverter is suspended from the set of side walls.

8. A method of manufacturing a robust MEMS transducer, the method comprising the steps of: providing an initial substrate having a top surface and a bottom surface; fabricating a transducer structure in or on said top surface; fabricating a front cavity, the front cavity forming a hole in the bottom surface of the initial substrate and extending inwardly from the bottom surface toward and to the transducer structure, the front cavity including a diverter structure suspended within the front cavity, the diverter structure having a bottom surface closer to the bottom surface of the substrate than to the transducer structure; and A back plate is provided, the back plate forming a variable capacitor with the movable diaphragm of the transducer structure, the back plate being disposed between the front cavity and the movable diaphragm, and wherein the shunt structure is suspended from the back plate.

9. The method of manufacturing a robust MEMS transducer according to claim 8, wherein: The substrate comprises a silicon substrate, and the step of fabricating the front cavity comprises etching the front cavity into the bottom surface of the silicon substrate, the front cavity exposing an underside of the transducer structure, the etching leaving a portion of the substrate to form the shunt structure.

10. The method of manufacturing a robust MEMS transducer according to claim 8, wherein: The front cavity has a plurality of portions separated by the diverter structure, each of the plurality of portions exposing an underside of the transducer structure.

11. The method of manufacturing a robust MEMS transducer according to claim 8, wherein: A distance between the top surface and the bottom surface defines a thickness of the substrate, and wherein the diverter structure extends from the top surface into the front cavity a distance that is at least half the thickness of the substrate.

12. The method of manufacturing a robust MEMS transducer according to claim 8, wherein: The distance between the top surface and the bottom surface defines a thickness of the substrate, and wherein the diverter structure extends from the top surface into the front cavity a distance that is at least three quarters of the thickness of the substrate.

13. A transducer system, comprising: The MEMS transducer according to any one of claims 1 to 7; A transducer system substrate, the system substrate comprising: an acoustic pore system, the acoustic pore system comprising a plurality of pore portions; as well as a rigid diaphragm defined in part by the plurality of apertures and spanning the acoustic aperture system, the rigid diaphragm having an exposed surface facing away from the movable diaphragm, the rigid diaphragm being configured to divert kinetic energy of air moving toward the diaphragm; The transducer is fixed on the substrate, wherein the front cavity covers the acoustic hole system in a manner that enables an acoustic signal to pass through each of the plurality of hole portions and reach the movable diaphragm.

14. The transducer system of claim 13, wherein: The transducer is secured to the top surface of the system substrate by die attach, the die attach having a die attach thickness, and the system further includes a gap between the exposed end of the rigid kinetic energy diverter and the rigid spacer, the gap having a thickness equal to the die attach thickness.

15. The transducer system of claim 13, the system substrate having a top surface, and wherein: The rigid kinetic energy diverter is aligned with the rigid spacer in such a manner that a straight line perpendicular to the top surface of the system substrate passes through both the rigid kinetic energy diverter and the rigid spacer.

16. The transducer system of claim 13, further comprising a cover secured to the system substrate, the cover and the system substrate defining a packaging volume, wherein: The transducer is secured to the system substrate within the packaging volume along with an ASIC coupled to the transducer to receive an electrical output generated by the transducer in response to an acoustic signal entering the system through the acoustic port system.

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