Pressure valve for microelectromechanical system die

Abstract

A pressure valve for a microelectromechanical system die. A microelectromechanical system die includes: a substrate having an opening; a diaphragm attached to the substrate around a periphery of the opening to cover the opening, the diaphragm having a hole; and a back plate spaced apart from the diaphragm and disposed on an opposite side of the diaphragm from the substrate, the back plate including a plug extending toward the hole from an attached end to a free end. In one embodiment, the free end of the plug has a smaller area than the aperture, and the plug is separated from the diaphragm by a gap, where the gap is sized to determine a level of fluid communication across the diaphragm through the aperture.

Description

Technical Field

[0001] The present disclosure relates to a valve for a microelectromechanical system (MEMS) die, and more particularly, to a valve that opens to relieve reverse overpressure that could damage a diaphragm of a MEMS die. Background Art

[0002] It is known that in the manufacture of MEMS devices, multiple devices are typically manufactured in a single batch process, wherein the individual parts of the batch process representing a single MEMS device are referred to as dies. Thus, multiple MEMS dies may be manufactured in a single batch process and then singulated or otherwise separated for further manufacturing steps or for their final use, such as, but not limited to, other parts including use as acoustic transducers or microphones.

[0003] The physical components of a MEMS microphone (e.g., diaphragm or backplate) can experience significant pressure stimuli during random or controlled air-burst events. Examples of random events include accidental device drops, sudden pressure changes due to events such as door closings, or compressed air cleaning during the assembly process. Examples of controlled events include standardized static pressure tests, drop tests, and flip tests.

[0004] Under large pressure stimuli (e.g., pressures exceeding 10 psi), components of the MEMS die may experience large deflections. As a result, stresses caused by large deflections may accumulate at different locations of the MEMS die (e.g., in the diaphragm or backplate). The concentration of stress depends on the geometry and pressure. Beyond certain pressure levels, the fracture limit of the MEMS component is exceeded, which leads to catastrophic failure in terms of fracture or irreversible cracks in the MEMS component, which renders the MEMS die inoperative. Summary of the invention

[0005] A first aspect of the present invention relates to a micro-electromechanical system (MEMS) die, which includes: a substrate having an opening; a diaphragm, which is attached to the substrate around the periphery of the opening to cover the opening, and the diaphragm has a hole; and a back plate, which is separated from the diaphragm and arranged on the side of the diaphragm opposite to the substrate, and the back plate includes a plug extending from an attachment end to a free end toward the hole, wherein the free end of the plug has an area smaller than the hole, and the plug is separated from the diaphragm by a gap, and wherein the size of the gap determines the level of fluid connectivity across the diaphragm through the hole.

[0006] When the diaphragm is in a rest position, the plug extends into the hole.

[0007] The stationary position of the diaphragm relative to the backplate is achieved by applying an electrostatic bias voltage between the backplate and the diaphragm.

[0008] The stationary position of the diaphragm relative to the backplate is achieved by adjusting the residual stress of the diaphragm or the backplate or both during manufacturing.

[0009] The plug is tapered, with the cross-sectional area of ​​the plug increasing as it moves away from the free end.

[0010] As the diaphragm moves toward the backplate, the size of the gap decreases, thereby reducing the level of fluid communication through the diaphragm in response to positive pressure.

[0011] As the diaphragm moves away from the backplate, the size of the gap increases, thereby increasing the level of fluid communication through the diaphragm in response to negative pressure.

[0012] The plug includes a member extending between the back plate and a solid cylindrical end including a circumferential surface oriented perpendicular to the back plate.

[0013] When the diaphragm is in a rest position, the circumferential surface is at least partially arranged within the aperture.

[0014] As the diaphragm moves away from the back plate and beyond the peripheral surface, the gap increases in size, thereby increasing the level of fluid communication through the diaphragm in response to negative pressure.

[0015] As the diaphragm moves toward the backplate and beyond the circumferential surface, the gap increases in size, thereby increasing the level of fluid communication through the diaphragm in response to positive pressure.

[0016] A second aspect of the present invention relates to a micro-electromechanical system MEMS die, which includes: a substrate having an opening; a diaphragm, which is attached to the substrate around the periphery of the opening to cover the opening, and the diaphragm has a hole; and a back plate, which is separated from the diaphragm and arranged on the side of the diaphragm opposite to the substrate, and the back plate includes a plug extending from an attachment end to a free end toward the hole, wherein the free end of the plug has an area larger than the hole.

[0017] The diaphragm is in contact with the free end in a rest position.

[0018] In response to negative pressure, the diaphragm moves away from the free end, thereby allowing fluid communication across the diaphragm through the hole.

[0019] The stationary position of the diaphragm relative to the backplate is achieved by applying an electrostatic bias voltage between the backplate and the diaphragm.

[0020] The stationary position of the diaphragm relative to the backplate is achieved by adjusting the residual stress of the diaphragm or the backplate or both during manufacturing.

[0021] A third aspect of the present invention relates to a micro-electromechanical system MEMS die, which comprises: a substrate having an opening; a diaphragm, which is attached to the substrate around the periphery of the opening to cover the opening, and the diaphragm has a hole; and a back plate, which is separated from the diaphragm and arranged on the side of the diaphragm opposite to the substrate, and the back plate comprises a plug extending from an attachment end to a free end toward the hole, wherein the free end of the plug has an area larger than the hole, and wherein the free end of the plug has a through hole, which allows fluid communication through the back plate and the hole.

[0022] The diaphragm is in contact with the free end in the rest position.

[0023] In response to negative pressure, the diaphragm moves away from the free end, thereby allowing additional fluid communication across the diaphragm through the hole.

[0024] The stationary position of the diaphragm relative to the backplate is achieved by applying an electrostatic bias between the backplate and the diaphragm or by adjusting the residual stress of the diaphragm or the backplate or both during manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The foregoing and other features of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings. These drawings depict only several embodiments according to the present disclosure and therefore should not be considered to limit the scope thereof.

[0026] Figure 1 is a schematic cross-sectional view of an exemplary MEMS die illustrating a positive pressure applied to the MEMS die in accordance with an embodiment.

[0027] Figure 2 is a schematic cross-sectional view of an exemplary MEMS die illustrating negative pressure applied to the MEMS die in accordance with an embodiment.

[0028] Figure 3 is a schematic cross-sectional view of an exemplary MEMS die in a rest position according to an embodiment.

[0029] Figure 4 Positive pressure is applied Figure 3 Schematic cross-sectional view of a MEMS die.

[0030] Figure 5 Negative pressure is applied Figure 3 Schematic cross-sectional view of a MEMS die.

[0031] Figure 6 Exemplary numbers and configurations of holes disposed through the diaphragm are shown according to various embodiments.

[0032] Figure 7 Exemplary shapes of holes disposed through a diaphragm are shown according to various embodiments.

[0033] Figure 8 is a schematic cross-sectional view of an exemplary MEMS die in a rest position according to another embodiment.

[0034] Fig. 9 Positive pressure is applied Figure 8 Schematic cross-sectional view of a MEMS die.

[0035] Fig.10 Negative pressure is applied Figure 8 Schematic cross-sectional view of a MEMS die.

[0036] Fig.11 is a schematic cross-sectional view of an exemplary MEMS die in a rest position according to another embodiment.

[0037] Fig.12 Negative pressure is applied Fig.11 Schematic cross-sectional view of a MEMS die.

[0038] Fig.13 is a schematic cross-sectional view of an exemplary MEMS die in a rest position according to yet another embodiment.

[0039] Fig.14 Negative pressure is applied Fig.13 Schematic cross-sectional view of a MEMS die.

[0040] Fig.15 is a schematic cross-sectional view of a microphone assembly according to an embodiment. DETAILED DESCRIPTION

[0041] According to one embodiment, a MEMS die includes: a substrate having an opening; a diaphragm attached to the substrate at the periphery of the opening to cover the opening, the diaphragm having a hole; and a back plate separated from the diaphragm and disposed on the side of the diaphragm opposite to the substrate, the back plate including a plug extending from an attachment end to a free end toward the hole. In one embodiment, the free end of the plug has an area smaller than the hole, and the plug is separated from the diaphragm by a gap, wherein the size of the gap determines the level of fluid communication through the diaphragm through the hole. In one embodiment, when the diaphragm is in a static position, the plug extends into the hole. In one embodiment, the static position of the diaphragm relative to the back plate is achieved by applying an electrostatic bias voltage between the back plate and the diaphragm. In one embodiment, the static position of the diaphragm relative to the back plate is achieved by adjusting the residual stress of the diaphragm or the back plate or both during manufacturing.

[0042] According to one embodiment, the plug is tapered, the plug having an increasing cross-sectional area as it moves away from the free end, wherein the size of the gap decreases as the diaphragm moves toward the back plate, thereby reducing the level of fluid communication through the diaphragm in response to positive pressure, and wherein the size of the gap increases as the diaphragm moves away from the back plate, thereby increasing the level of fluid communication through the diaphragm in response to negative pressure. In one embodiment, the plug includes a member extending between the back plate and a solid cylindrical end, the solid cylindrical end including a circumferential surface oriented perpendicular to the back plate, wherein the circumferential surface is at least partially arranged within the hole when the diaphragm is in a resting position. In one embodiment, the size of the gap increases as the diaphragm moves away from the back plate and beyond the circumferential surface, thereby increasing the level of fluid communication through the diaphragm in response to negative pressure, and the size of the gap increases as the diaphragm moves toward the back plate and beyond the circumferential surface, thereby increasing the level of fluid communication through the diaphragm in response to positive pressure.

[0043] In one embodiment, a MEMS die comprises: a substrate having an opening; a diaphragm attached to the substrate around the periphery of the opening to cover the opening, the diaphragm having a hole; and a back plate spaced apart from the diaphragm and disposed on a side of the diaphragm opposite the substrate, the back plate comprising a plug extending from an attachment end to a free end toward the hole. In one embodiment, the free end of the plug has a larger area than the hole. In one embodiment, the diaphragm in a rest position contacts the free end, and in response to negative pressure, the diaphragm moves away from the free end, thereby allowing fluid communication across the diaphragm through the hole.

[0044] In one embodiment, a MEMS die comprises: a substrate having an opening; a diaphragm attached to the substrate around the periphery of the opening to cover the opening, the diaphragm having a hole; and a backplate spaced apart from the diaphragm and disposed on a side of the diaphragm opposite the substrate, the backplate comprising a plug extending from an attachment end to a free end toward the hole. In one embodiment, the free end of the plug has an area larger than the hole, wherein the free end of the plug has a perforation that allows fluid communication through the backplate and the hole. In one embodiment, the diaphragm in a rest position contacts the free end, and in response to negative pressure, the diaphragm moves away from the free end, thereby allowing additional fluid communication across the diaphragm through the hole.

[0045] refer to Figure 1 and Figure 2 , a schematic cross-sectional view of a portion of an exemplary MEMS die 100 is shown. The MEMS die 100 or any of the MEMS dies 100, 200, 300, 400 described herein may be used, for example but not limited to, as part of a microphone, a motion sensor, or other device. In one embodiment, the MEMS die 100 includes a substrate 110 having an opening 120 and a diaphragm 130 attached to the substrate 110 around the periphery of the opening 120 to cover the opening 120. The back plate 135 is separated from the diaphragm 130 and disposed on a side of the diaphragm 130 opposite to the substrate 110. Referring to Figure 1 , the positive pressure 140 as shown by the box arrow pushes the diaphragm 130 toward the back plate 135. Figure 2 , the negative pressure 150 as indicated by the box arrow pushes the diaphragm 130 away from the back plate 135 .

[0046] It has been observed through extensive empirical studies across multiple platforms that MEMS microphone diaphragms (e.g., diaphragm 130) suffer failure at lower magnitudes of negative pressure 150 than positive pressure 140. This is because in the case of positive pressure 140, backplate 135 provides structural support for diaphragm 130. In the case of negative pressure 150, diaphragm 130 cannot rely on backplate 135 for support.

[0047] The valve, described more fully below, is implemented in several embodiments. The valve opens to reduce the negative pressure 150, which reduces the maximum stress in the diaphragm 130 to a level below a predetermined stress limit that would otherwise damage the diaphragm 130. By reducing the negative pressure 150, the durability of the diaphragm 130 can be improved. In one embodiment, the valve is implemented using features constructed with the back plate 135, which would otherwise already exist, representing a novel approach to valve implementation previously constructed on the diaphragm 130.

[0048] Reference Figures 3 to 5In an embodiment of the MEMS die 100, the diaphragm 130 includes one or more holes 160. In an embodiment, the one or more holes 160 may be located anywhere on the diaphragm 130 relative to the center or outer edge of the diaphragm 130. Figure 6 , showing several exemplary configurations for one or more holes 160 disposed through the diaphragm 130, which are Figure 6 The left side is shown as a circle, Figure 6 The right side is shown as a square. Figure 6 A non-limiting example of the actual number and configuration of one or more holes 160 is provided in FIG; however, all possibilities are too numerous to be included in the drawings herein. Similarly, the shape of the diaphragm 130 as viewed in plan view can be circular or square as shown, or any desired shape, but all possibilities for the shape of the diaphragm 130 are too numerous to be included in the drawings herein.

[0049] Brief reference Figure 7 Each hole 160 may also have any desired cross-sectional shape. For example, but not limited to, the shape of the hole 160 may be a circle 161, an ellipse 162, a hexagon 163, an octagon 164, a square 165, a square with rounded corners 166, or any other regular or irregular polygonal shape desired. Figure 7 Non-limiting examples of shapes for one or more apertures 160 are provided in , but all possibilities are too numerous to include in the figures herein.

[0050] Reference again Figures 3 to 5 In one embodiment, the back plate 135 includes one or more holes 170. In one embodiment, the back plate 135 includes one or more plugs 180, each plug extending from an attachment end 182 to a free end 184 toward one of the one or more holes 160. In one embodiment, the free end 184 of each plug 180 has a cross-sectional area A that is smaller than the cross-sectional area B of the hole 160 toward which the free end of the plug extends. In one embodiment, each plug 180 is separated from the diaphragm 130 by a gap 190, wherein each gap 190 has a size determined by the position of each plug 180 relative to the diaphragm 130. In one embodiment, the size of each gap 190 determines the level of fluid communication across the diaphragm 130 through each hole 160.

[0051] exist Figure 3In the illustrated embodiment, the diaphragm 130 is shown in an exemplary resting position. In one embodiment, when the diaphragm 130 is in the resting position, each plug 180 extends into the hole 160, and the plug extends toward the hole 160. In one embodiment, the resting position of the diaphragm 130 is achieved by applying an electrostatic bias voltage between the back plate 135 and the diaphragm 130. In one embodiment, the resting position of the diaphragm 130 relative to the back plate 135 can be adjusted by changing the level of the applied electrostatic bias voltage. In one embodiment, the resting position of the diaphragm 130 relative to the back plate 135 is achieved by adjusting the residual stress of the diaphragm 130 or the back plate 135 or both during manufacturing.

[0052] Reference Figures 3 to 5 In one embodiment, each plug 180 is tapered, with its cross-sectional area increasing as it moves away from the free end 184. In one embodiment, positive pressure applied to the diaphragm 130 causes the diaphragm 130 to move toward the back plate 135. Thus, Figure 4 As shown, when the diaphragm 130 moves toward the back plate 135, in response to the positive pressure, the size of each gap 190 decreases, thereby reducing the level of fluid communication through the diaphragm 130. In one embodiment, the negative pressure applied to the diaphragm 130 moves the diaphragm 130 away from the back plate 135. Figure 5 As shown, when the diaphragm 130 moves away from the back plate 135 , in response to the negative pressure, the size of each gap 190 increases, thereby increasing the level of fluid communication through the diaphragm 130 .

[0053] Thus, each plug 180 and the hole 160 to which it extends together act as a valve having a gap 190 representing the opening of the valve. In response to negative pressure on the diaphragm 130, the increase in the size of the gap 190 between each plug 180 and the associated hole 160 represents the opening of the valve. Opening the valve increases the level of fluid communication through the diaphragm 130, thereby reducing the impact of the applied negative pressure and the stress generated in the diaphragm 130. In one embodiment, each valve opens to reduce the maximum stress in the diaphragm 130 to a level below a predetermined stress limit that would otherwise damage the diaphragm 130, thereby improving the durability of the diaphragm 130.

[0054] refer to Figures 8 to 10 , a schematic cross-sectional view of an exemplary MEMS die 200 is shown. In one embodiment, the MEMS die 200 includes a substrate 210 having an opening 220 and a diaphragm 230 attached to the substrate 210 around the periphery of the opening 220 to cover the opening 220. The back plate 235 is separated from the diaphragm 230 and arranged on the side of the diaphragm 230 opposite to the substrate 210. In one embodiment, the diaphragm 230 includes one or more holes 260. Figure 6 and Figure 7The one or more holes 160 discussed are similar to the diaphragm 130. In one embodiment, the one or more holes 260 may be located anywhere on the diaphragm 230 relative to the center or outer edge of the diaphragm 230. In one embodiment, the back plate 235 includes one or more holes 270.

[0055] In one embodiment, the back plate 235 includes one or more plugs 280, each plug 280 extending toward one of the one or more holes 260. Figure 8 , an embodiment of the plug 280 shown enlarged includes a member 282 extending between a back plate 235 and a solid cylindrical end 284, the solid cylindrical end 284 including a circumferential surface 286 oriented perpendicular to the back plate 235. In one embodiment, each plug 280 is separated from the diaphragm 230 by a gap 290, wherein each gap 290 has a size determined by the position of each solid cylindrical end 284 relative to the diaphragm 230. In one embodiment, the size of each gap 290 determines the level of fluid communication across the diaphragm 230 through each hole 260.

[0056] Still reference Figure 8 , showing the diaphragm 230 in an exemplary resting position. In one embodiment, when the diaphragm 230 is in the resting position, the circumferential surface 286 of each plug 280 is at least partially disposed within the hole 260 toward which the plug 280 extends. In one embodiment, the resting position of the diaphragm 230 is achieved by applying an electrostatic bias voltage between the back plate 235 and the diaphragm 230. In one embodiment, the resting position of the diaphragm 230 relative to the back plate 235 can be adjusted by changing the level of the applied electrostatic bias voltage. In one embodiment, the resting position of the diaphragm 230 relative to the back plate 235 is achieved by adjusting the residual stress of the diaphragm 230 or the back plate 235 or both during manufacturing.

[0057] In one embodiment, a positive pressure applied to the diaphragm 230 causes the diaphragm 230 to move toward the back plate 235. In one embodiment, as Fig. 9 As shown, when the diaphragm 230 moves toward the back plate 235 and beyond the circumferential surface 286, the size of the gap 290 increases, thereby increasing the level of fluid communication through the diaphragm 230 in response to the positive pressure. In one embodiment, the negative pressure applied to the diaphragm 230 moves the diaphragm 230 away from the back plate 235. In one embodiment, as shown in FIG. Fig.10 As shown, as the diaphragm 230 moves away from the back plate 235 and beyond the circumferential surface 286, the size of the gap 290 increases, thereby increasing the level of fluid communication through the diaphragm 230 in response to the negative pressure.

[0058] Thus, each plug 280 and the hole 260 to which it extends together act as a valve having a gap 290 representing the opening of the valve. In response to negative or positive pressure on the diaphragm 230, the increase in the size of the gap 290 between each plug 280 and the associated hole 260 indicates the opening of the valve. Opening the valve increases the level of fluid communication through the diaphragm 230, thereby reducing the effects of the applied negative or positive pressure and the stress generated in the diaphragm 230. In one embodiment, each valve opens to reduce the maximum stress in the diaphragm 230 to a level below a predetermined stress limit that would otherwise damage the diaphragm 230, thereby improving the durability of the diaphragm 230.

[0059] In the above-described embodiments of the MEMS die 100, 200, the diaphragm 130, 230 is maintained in close proximity to one or more plugs 180, 280 during normal operating conditions. In these embodiments, the gap 190, 290 is small enough to inhibit contamination via particles or water from entering through the gap 190, 290 under normal operating conditions.

[0060] refer to Fig.11 and Fig.12 , shows a schematic cross-sectional view of an exemplary MEMS die 300. In one embodiment, the MEMS die 300 includes a plurality of Figures 1 to 5 The MEMS die 300 has the same structural components as the MEMS die 100 shown in FIG. For example, the MEMS die 300 includes a substrate 110 having an opening 120 and a diaphragm 130 attached to the substrate 110 around the periphery of the opening 120 to cover the opening 120. The back plate 135 is separated from the diaphragm 130 and arranged on the side of the diaphragm 130 opposite to the substrate 110. In one embodiment, the diaphragm 130 includes one or more holes 160. As described above with respect to Figure 6 and Figure 7 As discussed, in one embodiment, one or more holes 160 may be located anywhere on the diaphragm 130 relative to the center or outer edge of the diaphragm 130. In one embodiment, the back plate 135 includes one or more holes 170.

[0061] However, Fig.11 and Fig.12 The embodiment of the MEMS die 300 shown differs from the previously described embodiments in the following respects. In one embodiment, the back plate 135 of the MEMS die 300 further includes one or more plugs 380, 381, each of which extends from a connection end 382 to a free end 384 toward one of the one or more holes 160. In one embodiment, each plug 381 has a constant or uniform cross-sectional area from the connection end 382 to the free end 384, such as Fig.11 and Fig.12In another embodiment, each plug 380 is tapered so that the cross-sectional area of ​​the plug 380 increases as it moves away from the free end 384, as shown in FIG. Fig.11 and Fig.12 As shown in the plug 380 on the right side of the figure.

[0062] In one embodiment, the free end 384 of each plug 380, 381 has a cross-sectional area C that is larger than the cross-sectional area D of the hole 160 into which it extends. Fig.11 In the illustrated embodiment, the diaphragm 130 is shown in an exemplary resting position, wherein the diaphragm 130 is in contact with the free end (or multiple free ends) 384 of one or more plugs 380, 381. As described above, in one embodiment, the resting position of the diaphragm 130 is achieved by applying an electrostatic bias voltage between the back plate 135 and the diaphragm 130. In one embodiment, the resting position of the diaphragm 130 relative to the back plate 135 can be adjusted by changing the level of the applied electrostatic bias voltage. In one embodiment, the resting position of the diaphragm 130 relative to the back plate 135 is achieved by adjusting the residual stress of the diaphragm 130 or the back plate 135 or both during manufacturing.

[0063] In this embodiment, because the diaphragm 130 in the rest position is in contact with the free end (or multiple free ends) 384 of one or more plugs 380, 381, positive pressure applied to the diaphragm 130 causes the non-contacting portion of the diaphragm 130 to deflect toward the back plate 135, but the contacting portion of the diaphragm 130 remains in contact. In one embodiment, negative pressure applied to the diaphragm 130 causes the diaphragm 130 to move away from the back plate 135. Therefore, as Fig.12 As shown, in response to negative pressure, the diaphragm 130 moves away from the free end (or multiple free ends) 384 of one or more plugs 380, 381, thereby allowing fluid communication across the diaphragm 130 through one or more holes 160. Therefore, each plug 380, 381 and the hole 160 to which it extends act together as a valve, wherein the movement of the diaphragm 130 away from the back plate 135 in response to negative pressure on the diaphragm 130 represents the opening of the valve. Opening the valve allows fluid communication through the diaphragm 130, thereby reducing the impact of the applied negative pressure and the stress generated in the diaphragm 130. In one embodiment, each valve opens to reduce the maximum stress in the diaphragm 130 to a level below a predetermined stress limit that would otherwise damage the diaphragm 130, thereby improving the durability of the diaphragm 130.

[0064] refer to Fig.13 and Fig.14 , a cross-sectional schematic diagram of an exemplary MEMS die 400 is shown. Fig.13 and Fig.14 The MEMS die 400 shown is substantially similar to that described with reference to Fig.11 and Fig.12 The MEMS die 300 is the same, but differs in that it also includes a through hole 401 disposed through the free end (or multiple free ends) 384 of one or more plugs 380, 381. The through hole 401 disposed through the one or more plugs 380, 381 allows fluid communication through the back plate 135 and the hole 160 to which the one or more plugs 380, 381 extend. In this embodiment, in response to negative pressure, the diaphragm 130 moves away from the free end (or multiple free ends) 384 of the one or more plugs 380, 381, thereby allowing additional fluid communication across the diaphragm 130 through the hole 160.

[0065] Thus, each plug 380, 381 together with the hole 160 to which it extends acts as a valve having a through hole 401 for opening. Movement of the diaphragm 130 away from the back plate 135 in response to negative pressure on the diaphragm 130 represents further opening of the valve, which allows additional fluid communication through the diaphragm 130, thereby reducing the effects of the applied negative pressure and the resulting stress in the diaphragm 130. In one embodiment, each valve additionally opens an opening beyond the through hole 401 to reduce the maximum stress in the diaphragm 130 to a level below a predetermined stress limit that would otherwise damage the diaphragm 130, thereby improving the durability of the diaphragm 130.

[0066] In one embodiment, the material used for the substrate 110, 210 may include, for example, but not limited to, silicon, glass, gallium arsenide (GaAs), and polysilicon. In one embodiment, the material used for the diaphragm 130, 230 and the back plate 135, 235 may include, for example, but not limited to, silicon, polysilicon, gallium arsenide (GaAs), silicon dioxide (SiO2), tetraethyl orthosilicate (TEOS), silicon nitride (SiN), silicon oxynitride (SiON), and metal or other metal compounds. In each of the described embodiments, the diaphragm 130, 230 is connected to the back plate 135 by an insulator 111 (e.g., see Figure 1 ) is separated from the back plate 135, 235 and from the substrate 110, 210, wherein the spacer 111 can be made of a sacrificial material, such as but not limited to TEOS oxide or other sacrificial materials.

[0067] During operation of any embodiment of the MEMS die 100, 200, 300, 400, for example but not limited to as an acoustic transducer, an electric charge is applied to the backplate 135, 235 and the diaphragm 130, 230, thereby inducing an electric field between them. The movement of the air (e.g., caused by sound waves) pushes the surface of the diaphragm 130, 230 facing the opening 120, 220, causing the diaphragm 130, 230 to deflect (enter a deflected state) and deform. This deformation causes a change in capacitance between the backplate 135, 235 and the diaphragm 130, 230, which can be detected and interpreted as sound.

[0068] refer to Fig.15 In an exemplary embodiment, the MEMS die 100, 200, 300, 400 used as an acoustic transducer, for example but not limited to, is configured to be assembled within a microphone assembly generally designated 500. In one embodiment, the assembly 500 includes a housing including a base 502 having a first surface 505 and an opposite second surface 507. In one embodiment, the housing also includes a cover 504 (e.g., a housing cover) and an acoustic port 506. In one embodiment, the acoustic port 506 extends between the first surface 505 and the second surface 507. In one exemplary implementation, the base 502 is a printed circuit board. In one embodiment, the cover 504 is coupled to the base 502 (e.g., the cover 504 can be mounted to the peripheral edge of the base 502). In one embodiment, the cover 504 and the base 502 together form an enclosed volume 508 of the assembly 500.

[0069] like Fig.15 As shown, in one embodiment, an acoustic port 506 is disposed on the base 502 and is configured to transmit sound waves to the MEMS die 100, 200, 300, 400 used as an acoustic transducer located within the enclosed volume 508. In other implementations, the acoustic port 506 is disposed on the cover 504 and / or the sidewall of the cover 504. In some embodiments, the assembly 500 forms part of a compact computing device (e.g., a portable communication device, a smart phone, a smart speaker, an Internet of Things (IoT) device, etc.), in which one, two, three or more components can be integrated for picking up and processing various types of acoustic signals, such as speech and music.

[0070] In one embodiment, assembly 500 includes circuitry disposed within enclosed volume 508. In one embodiment, the circuitry includes an integrated circuit (IC) 510. In one embodiment, IC 510 is disposed on a first surface 505 of base 502. IC 510 may be an application specific integrated circuit (ASIC). Alternatively, IC 510 may include a semiconductor die integrating various analog, analog-digital, and / or digital circuits. In one embodiment, cover 504 is disposed on first surface 505 of base 502, covering MEMS die 100, 200, 300, 400 and IC 510.

[0071] exist Fig.15In the assembly 500 of FIG. 5 , the MEMS die 100, 200, 300, 400 is shown disposed on a first surface 505 of a base 502. When used as a MEMS acoustic transducer, the MEMS die 100, 200, 300, 400 converts acoustic waves received through an acoustic port 506 into corresponding electrical microphone signals and generates an electrical signal (e.g., a voltage) at the transducer output in response to acoustic activity incident on the acoustic port 506. Fig.15 As shown, the transducer output includes pads or terminals of the transducer that are electrically connected to a circuit via one or more bond wires 512 . Fig.15 The assembly 500 also includes one or more electrical contacts (schematically shown as contacts 514), generally disposed on the bottom surface of the base 502. The contacts 514 are electrically coupled to the circuit. The contacts 514 are configured to electrically connect the assembly 500 to one of a variety of host devices.

[0072] The steps in the manufacturing process for manufacturing any of the MEMS dies 100, 200, 300, 400 described above include deposition, etching, masking, patterning and / or cutting. All steps are not described in detail here. The above description of the illustrative embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or limit the precise form disclosed, and modifications and changes may be made according to the above teachings, or modifications and changes may be obtained from the practice of the disclosed embodiments. The scope of the present invention is intended to be limited by the appended claims and their equivalents.

Claims

1. A micro-electromechanical system (MEMS) die, the MEMS die comprising: a substrate having an opening; a diaphragm attached to the substrate around a periphery of the opening to cover the opening, the diaphragm having a hole; as well as a back plate spaced apart from the diaphragm and disposed on a side of the diaphragm opposite to the substrate, the back plate comprising a plug extending from an attachment end to a free end toward the hole, wherein the free end of the plug has a smaller area than the hole, and the plug is separated from the diaphragm by a gap, and Wherein the size of the gap determines the level of fluid connectivity across the diaphragm through the hole.

2. The MEMS die of claim 1, wherein: When the diaphragm is in a rest position, the plug extends into the hole.

3. The MEMS die of claim 2, wherein: The stationary position of the diaphragm relative to the back plate is achieved by applying an electrostatic bias voltage between the back plate and the diaphragm.

4. The MEMS die of claim 2, wherein: The stationary position of the diaphragm relative to the backplate is achieved by adjusting the residual stress of the diaphragm or the backplate or both during manufacturing.

5. The MEMS die of claim 1, wherein: The plug is tapered, with the cross-sectional area of ​​the plug increasing as it moves away from the free end.

6. The MEMS die of claim 5, wherein: As the diaphragm moves toward the backplate, the size of the gap decreases, thereby reducing the level of fluid communication through the diaphragm in response to positive pressure.

7. The MEMS die of claim 5, wherein: As the diaphragm moves away from the backplate, the size of the gap increases, thereby increasing the level of fluid communication through the diaphragm in response to negative pressure.

8. The MEMS die of claim 1, wherein: The plug includes a member extending between the back plate and a solid cylindrical end including a circumferential surface oriented perpendicular to the back plate.

9. The MEMS die of claim 8, wherein: When the diaphragm is in a rest position, the circumferential surface is at least partially arranged within the aperture.

10. The MEMS die of claim 9, wherein: As the diaphragm moves away from the back plate and beyond the peripheral surface, the gap increases in size, thereby increasing the level of fluid communication through the diaphragm in response to negative pressure.

11. The MEMS die of claim 9, wherein: As the diaphragm moves toward the backplate and beyond the peripheral surface, the gap increases in size, thereby increasing the level of fluid communication through the diaphragm in response to positive pressure.

12. A micro-electromechanical system (MEMS) die, the MEMS die comprising: a substrate having an opening; a diaphragm attached to the substrate around a periphery of the opening to cover the opening, the diaphragm having a hole; as well as a back plate spaced apart from the diaphragm and disposed on a side of the diaphragm opposite to the substrate, the back plate comprising a plug extending from an attachment end to a free end toward the hole, Wherein, the free end of the plug has a larger area than the hole.

13. The MEMS die of claim 12, wherein: The diaphragm is in contact with the free end in a rest position.

14. The MEMS die of claim 13, wherein: In response to negative pressure, the diaphragm moves away from the free end, thereby allowing fluid communication across the diaphragm through the hole.

15. The MEMS die of claim 13, wherein: The stationary position of the diaphragm relative to the back plate is achieved by applying an electrostatic bias voltage between the back plate and the diaphragm.

16. The MEMS die of claim 13, wherein: The stationary position of the diaphragm relative to the backplate is achieved by adjusting the residual stress of the diaphragm or the backplate or both during manufacturing.

17. A micro-electromechanical system (MEMS) die, the MEMS die comprising: a substrate having an opening; a diaphragm attached to the substrate around a periphery of the opening to cover the opening, the diaphragm having a hole; as well as a back plate spaced apart from the diaphragm and disposed on a side of the diaphragm opposite to the substrate, the back plate comprising a plug extending from an attachment end to a free end toward the hole, wherein the free end of the plug has a larger area than the hole, and Wherein the free end of the plug has a through hole, the through hole allowing fluid communication through the back plate and the hole.

18. The MEMS die of claim 17, wherein: The diaphragm is in contact with the free end in a rest position.

19. The MEMS die of claim 18, wherein: In response to negative pressure, the diaphragm moves away from the free end, thereby allowing additional fluid communication across the diaphragm through the hole.

20. The MEMS die of claim 17, wherein: The stationary position of the diaphragm relative to the backplate is achieved by applying an electrostatic bias between the backplate and the diaphragm or by adjusting the residual stress of the diaphragm or the backplate or both during manufacturing.

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