MEMS device

Abstract

Embodiments of the present invention generally relate to MEMS devices. A microelectromechanical system (MEMS) device includes a flexible membrane disposed over a substrate and a first backplate disposed over the flexible membrane. The first backplate includes a first plurality of protrusions facing the flexible membrane. The MEMS device further includes a plurality of features disposed at the flexible membrane, wherein each feature of the plurality of features is associated with a corresponding one of the first plurality of protrusions.

Description

Technical Field

[0001] The present invention generally relates to electronic devices, and in particular embodiments, to the structure of microelectromechanical systems (MEMS) devices. Background Art

[0002] A sensor is a device that includes a conversion element. The converter is applied within an electronic device to convert a signal from one domain to another. For example, some converters can convert a mechanical signal into an electrical signal. This is the case for an acoustic microphone that includes a conversion element that converts sound waves into an electrical signal. Information from the electrical signal is collected and then transferred to a signal processor that interprets the received signal and provides an output through a readout mechanism within the sensor device.

[0003] MEMS-based sensors include various converters, such as accelerometers, oscillators, resonators, gyroscopes, and microphones. MEMS-based sensors are produced using a series of microfabrication techniques similar to those used in integrated circuit manufacturing.

[0004] Conventional electrostatic MEMS microphones utilize capacitance characteristics to convert physical stimuli (such as speech) into an electrical signal. In such an application, the capacitance change in the sensor is converted into a voltage signal by using an interface circuit. These MEMS devices are composed of a flexible membrane structure arranged parallel to a rigid backplate structure. They work together as two electrode plates within the capacitive MEMS device. When sound waves penetrate the cavity within the device, due to the pressure difference, they cause oscillations between the flexible membranes. This in turn causes a change in the distance of the air gap between the flexible membrane and the backplate. Therefore, the change in the distance of the air gap between the flexible membrane and the backplate is proportional to the capacitance change of the MEMS device.

[0005] Generally, when such a deviation occurs between the flexible membrane and the backplate, electrostatic force accumulation may cause the two surfaces to stick together when they come into contact with each other. To alleviate this situation, anti-sticking protrusions are fabricated within the bottom surface of the backplate, so that they are located between the two electrode surfaces. These anti-sticking protrusions serve to maintain a certain working distance between the flexible membrane and the backplate to reduce the size of the contact area between the two electrode surfaces. Summary of the Invention

[0006] According to an embodiment of the present invention, a microelectromechanical system (MEMS) device includes a flexible membrane disposed over a substrate and a first backplate disposed over the flexible membrane. The first backplate includes a first plurality of protrusions facing the flexible membrane. The MEMS device further includes a plurality of features disposed at the flexible membrane, wherein each feature of the plurality of features is associated with a corresponding one of the first plurality of protrusions.

[0007] According to another embodiment of the present invention, a microelectromechanical system (MEMS) device includes a deflectable layer disposed over a substrate and a first backplate disposed over the deflectable layer. The first backplate includes a first plurality of anti-sticking structures facing the deflectable layer. The MEMS device further includes a plurality of reinforcement regions disposed at the deflectable layer. The plurality of reinforcement regions are configured to reinforce the deflectable layer to prevent stress-induced failures. The plurality of reinforcement regions are associated with a corresponding one of the first plurality of anti-sticking structures.

[0008] According to another embodiment of the present invention, a microelectromechanical system (MEMS) device includes a first backplate including a first plurality of anti-sticking protrusions, and a flexible membrane including a first major surface and an opposite second major surface, a second plurality of anti-sticking protrusions at the first major surface, and a plurality of features at the second major surface. Each of the plurality of features is associated with a corresponding one of the second plurality of anti-sticking protrusions. The MEMS device further includes a second backplate, wherein the flexible membrane is disposed between the first backplate and the second backplate. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To more fully understand the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1A A cross-sectional view of an embodiment of a MEMS microphone is shown, wherein additional material is deposited on top of the flexible membrane at the level of the protrusions, and wherein Figure 1B shows Figure 1A an enlarged view of the dashed region shown;

[0011] Figure 2A A cross-sectional view of an embodiment of a MEMS microphone is shown, wherein an alternative embodiment of the side profile is described, and wherein Figure 2B and Figure 2C shows Figure 2A an enlarged view of the dashed region shown;

[0012] Figure 3 A cross-sectional view of an embodiment of a MEMS microphone is shown, wherein additional material is deposited on top of the flexible membrane at the level of the protrusions and disposed below the flexible membrane;

[0013] Figure 4 A cross-sectional view of an embodiment of a MEMS microphone is shown, wherein the additional material deposited on top of the flexible membrane is composed of the same material;

[0014] Figure 5 A cross-sectional view of an embodiment of a MEMS microphone is shown, wherein the additional material disposed below the flexible membrane is composed of the same material;

[0015] Figure 6AA cross-sectional view of an embodiment of a MEMS microphone is shown, where a portion of the flexible membrane is replaced by an alternative material, and where Figure 6B is shown Figure 6A an enlarged portion of the dashed region shown;

[0016] Figure 7 A cross-sectional view of an embodiment of a dual-plate MEMS microphone is shown, where the flexible membrane includes additional material deposited above the flexible membrane, and anti-sticking protrusions added below the flexible membrane, where the additional material is deposited on top of the anti-sticking protrusions of the membrane. DETAILED DESCRIPTION

[0017] The structures and uses of various embodiments of the MEMS microphone will be discussed in detail below. However, it should be understood that the various embodiments described in detail herein can be widely applied to various subjects. The specific embodiments described herein only illustrate the specific ways of implementing and using the various embodiments, and should not be construed as limiting the scope.

[0018] Conventional MEMS devices (such as microphones) are prone to damage by dust and particles during operation / assembly. For example, random particles moving at a fast enough speed can damage the electrodes. These high-speed particles can be generated in various ways. For example, mechanical shock can release loose or stationary particles in the conduit between the outside of the device and the port. Similarly, during device assembly or during air gun cleaning after encapsulation, particles suspended in the air can be accelerated towards the microphone.

[0019] The inventors of the present application have determined that due to the stress caused by particles, the flexible membrane is a significantly sensitive part of the microphone. In particular, due to the stress concentrated in a small area, the inventors of the present application have determined that the area of the flexible membrane designed to contact the anti-sticking protrusions is more sensitive. Embodiments of the present invention describe MEMS devices that are more resistant to failure, such as failure due to particles formed by additional features on the flexible membrane and selectively on the plates of the MEMS device.

[0020] First, use Figures 1A to 1B and Figures 2A to 2B to describe the structural design of the MEMS device. Then, use Figures 3 to 7 to describe an alternative design of the MEMS device.

[0021] Figure 1A A cross-sectional view of an embodiment of a MEMS microphone is shown and where Figure 1B is shown Figure 1A an enlarged portion of the dashed region shown.

[0022] Refer to Figure 1A, in one or more embodiments, a microelectromechanical system (MEMS) device 100 includes a substrate 101, a first clamping layer 102 and a second clamping layer 104, a flexible membrane 103, and a first backplate 105. In one embodiment, the MEMS device 100 is a microphone.

[0023] Figure 1B shows Figure 1A an enlarged portion of the MEMS device 100 shown within the dashed area. In such an embodiment, the flexible membrane 103 is a deflectable sensing membrane that forms a parallel plate capacitor with the first backplate 105. Sound pressure waves are incident on the flexible membrane 103 from the cavity 112, which is connected to a sound port (not shown) of the MEMS microphone. During operation, the sound pressure waves incident from the cavity 112 may cause the flexible membrane 103 to oscillate towards and away from the first backplate 105, thereby changing the distance between the flexible membrane 103 and the first backplate 105, and thus changing the capacitance between the flexible membrane 103 and the first backplate 105. For example, the change in capacitance can be sensed by readout electronics coupled to the flexible membrane 103 and the first backplate 105 through conductive lines (not shown).

[0024] The first backplate 105 disposed above the flexible membrane 103 is a rigid layer. In one embodiment, the first backplate 105 includes a first insulating layer 108 and a second insulating layer 110, a conductive layer 109, and a first plurality of protrusions 107. The first plurality of protrusions 107 serve as anti-sticking protrusions to relieve adhesion caused by electrostatic forces that may occur when the flexible membrane 103 contacts the first backplate 105. The anti-sticking protrusions are used to maintain a certain distance between the first backplate 105 and the flexible membrane 103 and help reduce the contact surface area. According to some embodiments, the first backplate 105 may include perforations 106 of different diameter sizes from small to large. The perforations 106 can be used as release holes during an etching manufacturing step in which a portion of the second clamping layer 104 is removed. In one or more embodiments, the perforations 106 may include many small diameter holes closely arranged together and around the perimeter of the deflectable portion of the flexible membrane 103. The spacing and size of the perforations 106 can be used to control the position and smoothness of the second clamping layer 104 and the second clamping layer edge 113, respectively.

[0025] According to various embodiments, the substrate 101 may be composed of a silicon material or any other material that can be used to form a support substrate structure for the various layers within the MEMS device 100.

[0026] The cavity 112 is formed within the substrate 101. In various embodiments, the cavity 112 can be formed using an etching fabrication technique such as Bosch process etching, generating a scalloped edge along the substrate sidewall 115. The flexible membrane 103 can include a fixed portion supported by the first clamping layer 102 and the second clamping layer 104, and a non-fixed portion disposed above the cavity 112. According to various embodiments, the flexible membrane 103 can be composed of any conductive material, such as doped polysilicon.

[0027] The first clamping layer 102 is disposed above the substrate 101. In some embodiments, the substrate sidewall 115 of the substrate 101 can extend to the first clamping layer edge 114. Alternatively, in other embodiments the first clamping layer edge 114 can extend to the substrate sidewall 115 and into the cavity 112. In some embodiments the first clamping layer 102 can be composed of an insulating material, such as tetraethyl orthosilicate (TEOS) oxide. Alternatively, the first clamping layer 102 can be formed of any other insulating material, such as additional oxides or dielectrics.

[0028] The second clamping layer 104 is disposed above the flexible membrane 103, effectively making the second clamping layer 104 a support structure by "clamping" the fixed portion of the flexible membrane 103. In various embodiments of the MEMS device 100, the first and second clamping layers 102 and 104 can be rearranged such that the first clamping layer 102 extends beyond the substrate sidewall 115 and into the cavity 112, where the second clamping layer 104 does not extend beyond the substrate sidewall 115. In some embodiments, the second clamping layer 104 can be thicker than the first clamping layer 102, and vice versa. Similar to the first clamping layer 102, the second clamping layer 104 can be composed of an insulating material, such as tetraethyl orthosilicate (TEOS) oxide or any other oxide or dielectric.

[0029] The first backplane 105 is formed on top of the second clamping layer 104 and, as described above, includes a first insulating layer 108, a conductive layer 109, and a second insulating layer 110. In one embodiment, the first and second insulating layers 108 and 110 are formed as silicon nitride layers. However, the conductive layer 109 is formed as a doped polysilicon layer. Generally, the backplane 105 can be fabricated from any combination of insulating or conductive materials known in the art. The air gap present between the first backplane 105 and the flexible membrane 103 can have a distance typically in the range of 500 nm to 5 μm. As described above, the first backplane 105 further includes a first plurality of protrusions 107 that serve as anti-sticking protrusions to relieve adhesion caused by electrostatic forces that may occur when the flexible membrane 103 contacts the first backplane 105. The first plurality of protrusions 107 is composed of the second insulating layer 110 and the conductive layer 109 of the first backplane 105. Thus, in one embodiment of the MEMS device 100, the first plurality of protrusions 107 can be composed of a silicon nitride layer and a doped polysilicon layer. In other embodiments, the first plurality of protrusions 107 can be fabricated from any other combination of insulating or conductive materials known in the art. The first plurality of protrusions 107 can have a size in height of 100 nm to 2000 nm and can have a tip with a radius of curvature ranging from 10 nm to 1000 nm. Similarly, the first plurality of protrusions 107 can have a flatter tip with a size of approximately 50 nm to 500 nm.

[0030] As Figure 1A and Figure 1B shown, a first plurality of features 111a are arranged on the flexible membrane 103. The first plurality of features 111a includes protrusions extending from the flexible membrane 103 in a direction towards the first plurality of protrusions 107. Each feature in the first plurality of features 111a is associated with a corresponding one of the first plurality of protrusions 107. The first plurality of features 111a includes protrusions extending from the flexible membrane 103 in a direction towards the first plurality of protrusions 107. According to some embodiments, the first plurality of features 111a can include a material different from that of the flexible membrane 103 (as Figure 1A and 1B shown).

[0031] Each feature in the first plurality of features 111a includes a sidewall orthogonal to the main outer surface of the flexible membrane 103. According to some embodiments, the first plurality of features 111a can be composed of a material different from that of the flexible membrane 103 (as Figure 1A and 1B shown).

[0032] In various embodiments, the first plurality of features 11a includes a material that is less prone to cracking than the flexible membrane 103, and in particular, has a higher fracture toughness than the flexible membrane 103. For example, a flexible membrane made of polysilicon has a fracture toughness Kc greater than 1 MPa.sqrt(m). However, in one or more embodiments, materials with similar or lower fracture toughness (such as silicon oxide) may be used because the increased thickness provided by the first plurality of features 111a helps to dissipate the stress energy within the first plurality of features 111a, thereby preventing the stress energy from reaching the flexible membrane 103. This is because, unlike cracks on the flexible membrane 103, cracks formed on the first plurality of features 111a do not have a functional impact on the operation of the MEMS device.

[0033] In various embodiments, the material of the first plurality of features 111a is more rigid than the flexible membrane 103, which helps to reduce the deformation of the underlying flexible membrane 103. Due to the higher rigidity of the first plurality of features 111a, it is not easily susceptible to stress-induced failures. Therefore, excessive stress applied by the first plurality of protrusions is absorbed by the first plurality of features 111a to reduce damage to the flexible membrane 103, which might otherwise cause rupture of the flexible membrane.

[0034] Therefore, the first plurality of features 111a may be composed of a silicon nitride layer (SiN), a silicon oxide layer (SiO2), a silicon carbide layer (SiC), or any other combination of insulating materials known in the art.

[0035] In various embodiments, the first plurality of features 111a can be constructed through conventional microfabrication schemes. For example, as described above, an insulating material can be deposited on the top surface of the flexible membrane 103. Through various lithography and etching steps, as well as additional microfabrication processing schemes known to those skilled in the art, such as cleaning and planarization, the first plurality of features 111a can be formed.

[0036] Figure 2A A cross-sectional view of an embodiment of the MEMS device 100 is shown, where an alternative embodiment of the side profile of the first plurality of features 111a is described. Figure 2B and Figure 2C shows Figure 2A an enlarged portion of the dashed region shown.

[0037] As described above, the edges of the first plurality of features 111a can be etched in a manner that achieves a vertical sidewall profile (as shown in Figure 2B ). In other embodiments of the MEMS device 100, the sidewalls 111c of the first plurality of features 111a can be etched in a manner that achieves a more angled sidewall profile (as shown in Figure 2Cas shown). The principle behind this is that the more angled sidewall profile of the first plurality of features 111a reduces the stress concentration borne at the interface (as shown by the arrows in Figure 2B ), where the edges of the first plurality of features 111a intersect the top surface of the flexible membrane 103.

[0038] The thickness dimension of the first plurality of features 111a can range between 10 nm and 1 μm, and the lateral dimension can range between approximately 500 nm and 5 μm, which is larger than the contact area of the first plurality of protrusions 107.

[0039] Figure 3 A cross-sectional view of an alternative embodiment of the MEMS device 200 is shown. In a particular embodiment of the MEMS microphone, the material is deposited not only on top of the flexible membrane in the form of the first plurality of features 111a (as described above), and simultaneously, an insulating material is additionally arranged below the flexible membrane 103 in the form of a second plurality of features 111b.

[0040] The second plurality of features 111b arranged below the flexible membrane 103 provide additional reinforcement for the fragile flexible membrane 103. In addition, the second plurality of features 111b balance the stress caused by the additional material on the flexible membrane 103.

[0041] Figure 4 A cross-sectional view of an embodiment of the MEMS device 400 is shown.

[0042] In this embodiment, a third plurality of features 111d are deposited on top of the flexible membrane 103 and can be composed of the same material as the flexible membrane 103. In other words, in this embodiment, the part of the flexible membrane 103 that is more vulnerable to stress-induced failures is thickened.

[0043] Therefore, the additional material added to the flexible membrane 103 can be considered as a locally thickened membrane material. The third plurality of features 111d can be fabricated using manufacturing techniques similar to those employed for the construction of the first plurality of features 111a. Alternatively, in some embodiments, the third plurality of features 111d can be formed along the flexible membrane 103, where the regions without the third plurality of features 111d are recessed.

[0044] Figure 5 A cross-sectional view of an embodiment of the MEMS device 500 is shown.

[0045] In this embodiment, an additional material is deposited as a fourth plurality of features 111e on the bottom of the flexible membrane 103 and can be composed of the same material as the flexible membrane 103. Advantageously, this embodiment strengthens the flexible membrane 103 without changing the capacitance between the flexible membrane 103 and the first backplate 105.

[0046] As described above, the fourth plurality of features 111e can be fabricated using manufacturing techniques similar to those employed in the construction of the first plurality of features 111a. Alternatively, the fourth plurality of features 111e can be formed along the flexible membrane 103, where the regions without the fourth plurality of features 111e are recessed.

[0047] Figure 6A A cross-sectional view of an embodiment of the MEMS device 600 is shown, while Figure 6B is shown Figure 6A an enlarged view of the dashed region shown. In this embodiment, the portion of the flexible membrane 103 at the level of the first plurality of protrusions is replaced by an alternative reinforcing material in the form of a fifth plurality of features 111f. The fifth plurality of features 111f can be composed of a material different from that of the flexible membrane 103. In various embodiments, the fifth plurality of features 111f includes a material that is less prone to cracking than the flexible membrane 103, and in particular, has a higher fracture toughness than the flexible membrane 103. The fifth plurality of features 111f can include a material that is more rigid than the flexible membrane 103. For example, the fifth plurality of features 111f can be composed of a silicon nitride layer (SiN), a silicon oxide layer (SiO2), a silicon carbide layer (SiC), TiN, TaN, etc.

[0048] Each feature of the fifth plurality of features 111f includes sidewalls that are orthogonal or inclined with respect to the main outer surface of the flexible membrane 103. The fifth plurality of features 111f includes a first portion filled within a through-hole of the flexible membrane 103. A second annular region extends over a portion of the top surface of the flexible membrane 103. The second annular region can include protrusions extending from the flexible membrane 103 in a direction towards the first plurality of protrusions 107.

[0049] The fifth plurality of features 111f can be constructed by conventional microfabrication schemes, many of which have been mentioned in various embodiments herein.

[0050] Figure 7 A cross-sectional view of an embodiment of the MEMS device of a dual-backplate MEMS microphone is shown.

[0051] The dual-backplate MEMS microphone design provides a differential MEMS sensor. Thus, due to the movement of the flexible membrane, the dual-backplate MEMS microphone outputs two symmetric 180-degree phase-shifted signals.

[0052] Different from the previous embodiment, due to the additional backplate, this embodiment includes a different design for the anti-sticking protrusions and protrusions. In one or more embodiments, the anti-sticking protrusions and protrusions on the flexible membrane 205 can be directly aligned in the vertical direction.

[0053] Similar to the previous embodiments, the MEMS device 700 includes a substrate 201, a first clamping layer 202, a second clamping layer 204, and a third clamping layer 206, a bottom backplane 203, a flexible membrane 205, and a top backplane 207. According to various embodiments, the flexible membrane 205 is located between the bottom backplane 203 and the top backplane 207. The first clamping layer 202 is disposed between the substrate 201 and the bottom backplane 203. The second clamping layer 204 is disposed between the bottom backplane 203 and the flexible membrane 205. The third clamping layer 206 is disposed between the flexible membrane 205 and the top backplane 207. According to an embodiment of the MEMS device 200, the flexible membrane 205 separates the bottom cavity 215a from the top cavity 215b.

[0054] Similar to the previous embodiments, some clamping layers may be retracted further than the edge 216 of the substrate and / or other clamping layers within the device. For example, in one embodiment, the second clamping layer 204 extends deeper into the bottom cavity 215a than other portions (i.e., the first clamping layer 202 and the third clamping layer 206). In various embodiments, the extension of the first clamping layer 202, the second clamping layer 204, and the third clamping layer 206 may be determined by the size and location of the perforations 208 fabricated within the bottom backplane 203 and the top backplane 207.

[0055] Details regarding the function and characteristics of the perforations 208 may refer to the perforations 106 described in detail in the discussion of the single-backplane MEMS device above. Figure 1A In some embodiments, some clamping layers may be thicker than other clamping layers. For example, in one embodiment, the first clamping layer 202 may be much thinner than the second clamping layer 204 or the third clamping layer 206.

[0056] According to various embodiments, the substrate 201 may be composed of a silicon material or any other material that can be used to form a support substrate structure for the various layers within the MEMS device 200. The bottom cavity 215a is formed within the substrate 201 as described above. The previously discussed first clamping layer 202, second clamping layer 204, and third clamping layer 206 serve as support structures for the various layers within the MEMS device 200. More specifically, the first clamping layer 202, the second clamping layer 204, and the third clamping layer 206 help support the bottom backplane 203, the top backplane 207, and the flexible membrane 205. In some embodiments, the first clamping layer 202, the second clamping layer 204, and the third clamping layer 206 are composed of an insulating material, such as tetraethyl orthosilicate (TEOS) oxide. Alternatively, the first clamping layer 202, the second clamping layer 204, and the third clamping layer 206 may be formed of any other insulating material, such as other oxides or dielectrics.

[0057] The bottom backplane 203 located between the first clamping layer 202 and the second clamping layer 204 is a rigid structure composed of a first insulating layer 210, a second insulating layer 212, and a conductive layer 211. According to some embodiments, the bottom backplane 203 further includes perforations 208 of different diameter sizes from small to large having connecting members 231. As described above, the perforations 208 can be used as release holes during the etching manufacturing step. In various embodiments, the perforations 208 can include a plurality of small-diameter perforations arranged closely together and around the perimeter of the deflectable portion of the flexible membrane 205. The spacing and size of the perforations 208 can be used to control the position and smoothness of the edges of any adjacent clamping layers.

[0058] The top backplane 207 disposed above the third clamping layer 206 can also be a rigid structure composed of a first insulating layer 210, a second insulating layer 212, and a conductive layer 211.

[0059] Similar to the previous embodiments, the top backplane 207 can include a first plurality of anti-sticking protrusions 209 that reduce adhesion to the flexible membrane 205. The first plurality of anti-sticking protrusions are composed of the second insulating layer 212 and the conductive layer 211 of the top backplane 207. Thus, in one embodiment, the first plurality of anti-sticking protrusions 209 can be composed of a silicon nitride layer and a doped polysilicon layer. In other embodiments, the first plurality of anti-sticking protrusions 209 can be fabricated from any other combination of insulating or conductive materials known in the art. Very similar to the bottom backplane 203, the top backplane 207 can also contain perforations 208 of various diameters.

[0060] Although in various embodiments, the first plurality of anti-sticking protrusions 209 are shown aligned with a plurality of features 213, they can be located in other regions of the top backplane 207. Instead, in various embodiments, a second plurality of anti-sticking protrusions 214 are aligned with the connecting members 231 and not with the perforations 208 on the bottom backplane 203.

[0061] An embodiment of the MEMS device 700 includes a flexible membrane 205 located between the bottom backplane 203 and the top backplane 207; more specifically, between the second clamping layer 204 and the third clamping layer 206. The flexible membrane 205 includes a first major surface 214s and an opposite second major surface 213s.

[0062] A second plurality of anti-sticking protrusions 214 are disposed at the first major surface 214s. The second plurality of anti-sticking protrusions 214 reduce the adhesion of the flexible membrane 205 to the bottom backplane 203. The inventors of the present application have determined that a portion of the second major surface 213s covering the second plurality of anti-sticking protrusions 214 is a point with high stress intensity after particle impact. Thus, a sixth plurality of features 213 are disposed on the flexible membrane 205 to vertically overlap the second plurality of anti-sticking protrusions 214.

[0063] As described in the previous embodiments, the sixth plurality of features 213 includes protrusions extending from the second major surface 213s of the flexible membrane 205 in a direction towards the first plurality of anti-stick protrusions 209. Each feature of the sixth plurality of features 213 is associated with a corresponding one of the second plurality of anti-stick protrusions 214. However, since the sixth plurality of features 213 vertically overlaps the second plurality of anti-stick protrusions 214, they do not overlap the first plurality of anti-stick protrusions 209 but are staggered relative to the first plurality of anti-stick protrusions 209.

[0064] Similar to the previous embodiments, each feature of the sixth plurality of features 213 may include sidewalls orthogonal to the major outer surface of the flexible membrane 205 (as described above, for example, Figure 2B ). However, in other embodiments, each feature of the sixth plurality of features 213 may include angled sidewalls (as Figure 2C shown) to relieve the accumulation of stress concentrated at the major outer surface of the flexible membrane 205.

[0065] According to some embodiments, the sixth plurality of features 213 may be composed of a material different from that of the flexible membrane 205. As described in the previous embodiments, the sixth plurality of features 213 may be composed of a silicon nitride layer (SiN), a silicon oxide layer (SiO2), a silicon carbide layer (SiC), or other insulating materials.

[0066] In various embodiments, the sixth plurality of features 213 may be constructed by conventional microfabrication processes. For example, an insulating material as described above may be deposited on the top surface of the flexible membrane 205. Through various lithography and etching steps, as well as additional microfabrication processing schemes known in the art, such as cleaning and planarization, the formation of the sixth plurality of features 213 is revealed. As described above, the edges of the sixth plurality of features 213 may be etched in a manner to achieve a vertical sidewall profile (as Figure 2B shown). In other embodiments, the edges of the sixth plurality of features 213 may be etched in a manner to achieve a more angled sidewall profile (as Figure 2C shown). The thickness dimension of the sixth plurality of features 213 may be between 10 nm and 1 μm, and the lateral dimension may be between approximately 500 nm and 5 μm, which is larger than the contact area of the first plurality of anti-stick protrusions 209.

[0067] The second plurality of anti-stick protrusions 214 may be fabricated using similar manufacturing techniques described in detail herein; and may further include the same material as that used for the flexible membrane 205.

[0068] Advantages of the various embodiments described herein include devices that exhibit improved robustness to shock and large sound pressure waves. Additionally, improvements can be seen in the membrane, which becomes particularly sensitive when particles hit near the anti-stick protrusions, causing highly destructive stresses during the deflection of the flexible membrane. The various embodiments described herein reinforce the flexible membrane to make it more robust, particularly in regions near any anti-stick protrusions, avoiding destructive damage to the layers of the MEMS microphone.

[0069] Example embodiments of the present invention are summarized herein. Other embodiments can also be understood from the overall disclosure of this specification and the claims presented herein.

[0070] Example 1. A microelectromechanical system (MEMS) device, comprising a flexible membrane disposed over a substrate; a first backplate disposed over the flexible membrane, wherein the first backplate includes a first plurality of protrusions facing the flexible membrane; and a plurality of features disposed at the flexible membrane, wherein each feature of the plurality of features is associated with a corresponding one of the first plurality of protrusions.

[0071] Example 2. The MEMS device of Example 1, wherein the plurality of features are aligned with a corresponding one of the first plurality of protrusions.

[0072] Example 3. The MEMS device of Example 1 or 2, wherein the plurality of features include locally thicker regions of the flexible membrane.

[0073] Example 4. The MEMS device of one of Examples 1 to 3, wherein the plurality of features include protrusions extending from the flexible membrane in a direction toward the first plurality of protrusions.

[0074] Example 5. The MEMS device of one of Examples 1 to 4, wherein the plurality of features include protrusions extending from the flexible membrane in a direction away from the first plurality of protrusions.

[0075] Example 6. The MEMS device of one of Examples 1, 2, 4, 5, wherein the plurality of features include a material different from the flexible membrane.

[0076] Example 7. The MEMS device of one of Examples 1 to 6, wherein the plurality of features are disposed over the flexible membrane and are disposed between the flexible membrane and the first plurality of protrusions.

[0077] Example 8. A MEMS device as described in one of Examples 1 to 7, wherein the plurality of features include: a first set of regions disposed above the flexible membrane and between the flexible membrane and the first plurality of protrusions; and a second set of regions disposed below the flexible membrane, and wherein the flexible membrane is disposed between the second set of regions and the first plurality of protrusions.

[0078] Example 9. A MEMS device as described in one of Examples 1, 2, 4, 6, 7, wherein the plurality of features are disposed within the flexible membrane.

[0079] Example 10. A MEMS device as described in one of Examples 1 to 9, further comprising: a second backplate disposed between the flexible membrane and the substrate; and a second plurality of protrusions disposed on the flexible membrane, wherein the plurality of features are aligned with a corresponding one of the second plurality of protrusions.

[0080] Example 11. A MEMS device as described in one of Examples 1 to 10, wherein each of the first plurality of features includes sidewalls that are inclined with respect to a major outer surface of the flexible membrane.

[0081] Example 12. A MEMS device as described in one of Examples 1 to 11, wherein each of the first plurality of features includes sidewalls that are orthogonal to a major outer surface of the flexible membrane.

[0082] Example 13. A microelectromechanical system (MEMS) device, comprising a deflectable layer disposed above a substrate; a first backplate disposed above the deflectable layer, the first backplate including a first plurality of anti-sticking structures facing the deflectable layer; and a plurality of reinforcement regions disposed at the deflectable layer, the plurality of reinforcement regions being configured to reinforce the deflectable layer to prevent stress-induced failures, the plurality of reinforcement regions being associated with a corresponding one of the first plurality of anti-sticking structures.

[0083] Example 14. The MEMS device of Example 13, wherein the plurality of reinforcement regions include locally thicker regions of the deflectable layer.

[0084] Example 15. The MEMS device of Example 13, wherein the plurality of reinforcement regions include a material different from the deflectable layer.

[0085] Example 16. The MEMS device of Examples 13 to 15, wherein the plurality of reinforcement regions are disposed within the deflectable layer.

[0086] Example 17. A microelectromechanical system (MEMS) device includes a first backplate including a first plurality of anti-sticking protrusions; a flexible membrane including a first major surface and an opposing second major surface, a second plurality of anti-sticking protrusions at the first major surface, and a plurality of features at the second major surface, each feature of the plurality of features being associated with a corresponding one of the second plurality of anti-sticking protrusions; and a second backplate, the flexible membrane being disposed between the first backplate and the second backplate.

[0087] Example 18. The MEMS device of Example 17, wherein one of the first plurality of anti-sticking protrusions is disposed between adjacent features of the plurality of features.

[0088] Example 19. The MEMS device of Example 17 or 18, wherein the second backplate includes a plurality of openings and connection members, and wherein the second plurality of anti-sticking protrusions are aligned with the connection members in a direction orthogonal to the major surface of the second backplate.

[0089] Example 20. The MEMS device of Examples 17 to 19, wherein each feature of the plurality of features is aligned with a corresponding one of the second plurality of anti-sticking protrusions in a direction orthogonal to the major surface of the second backplate.

[0090] Although embodiments of the present application have been described in the context of using MEMS microphones, various embodiments include other MEMS devices and structures, including MEMS capacitive acoustic transducer systems, MEMS microphone systems, silicon microphone systems, single-backplate and double-backplate microphone systems, and mechanically supported MEMS microphone systems.

[0091] Although the invention has been described with reference to the embodiments shown, the present specification is not intended to be construed in a limiting sense. Various modifications and combinations of the embodiments shown and other embodiments of the invention will be apparent to those skilled in the art upon reference to this specification. Accordingly, it is intended that the appended claims include any such modifications or embodiments.

Claims

1. A microelectromechanical system (MEMS) device, comprising: A flexible membrane disposed above a substrate; A first backplate disposed above the flexible membrane, the first backplate including a first plurality of protrusions facing the flexible membrane; And A plurality of features disposed at the flexible membrane, each feature of the plurality of features being associated with a corresponding one of the first plurality of protrusions, Wherein the plurality of features are disposed within the flexible membrane.

2. The MEMS device according to claim 1, wherein the plurality of features are aligned with a corresponding one of the first plurality of protrusions.

3. The MEMS device according to claim 1, wherein the plurality of features include locally thicker regions of the flexible membrane.

4. The MEMS device according to claim 3, wherein the plurality of features include protrusions extending from the flexible membrane in a direction towards the first plurality of protrusions.

5. The MEMS device according to claim 3, wherein the plurality of features include protrusions extending from the flexible membrane in a direction away from the first plurality of protrusions.

6. The MEMS device according to claim 1, wherein the plurality of features include a material different from the flexible membrane.

7. The MEMS device according to claim 6, wherein the plurality of features are disposed above the flexible membrane and between the flexible membrane and the first plurality of protrusions.

8. The MEMS device according to claim 6, wherein the plurality of features include: A first set of regions disposed above the flexible membrane and located between the flexible membrane and the first plurality of protrusions; And A second set of regions disposed below the flexible membrane, and wherein the flexible membrane is disposed between the second set of regions and the first plurality of protrusions.

9. The MEMS device according to claim 1, further comprising: A second backplate disposed between the flexible membrane and the substrate; And A second plurality of protrusions disposed on the flexible membrane, wherein the plurality of features are aligned with a corresponding one of the second plurality of protrusions.

10. The MEMS device according to claim 1, wherein each feature of the first plurality of features includes a sidewall inclined with respect to a main outer surface of the flexible membrane.

11. The MEMS device according to claim 1, wherein each feature of the first plurality of features includes a sidewall orthogonal to a main outer surface of the flexible membrane.

12. A microelectromechanical system (MEMS) device, comprising: A deflectable layer disposed above a substrate; A first backplate disposed above the deflectable layer, the first backplate including a first plurality of anti-sticking structures facing the deflectable layer; And A plurality of reinforcement regions disposed at the deflectable layer, the plurality of reinforcement regions being configured to reinforce the deflectable layer to prevent stress-induced failures, the plurality of reinforcement regions being associated with a corresponding one of the first plurality of anti-sticking structures, Wherein the plurality of reinforcement regions are disposed within the deflectable layer.

13. The MEMS device according to claim 12, wherein the plurality of reinforcement regions include locally thicker regions of the deflectable layer.

14. The MEMS device according to claim 12, wherein the plurality of reinforcement regions include a material different from the deflectable layer.

15. A microelectromechanical system (MEMS) device, comprising: a first backplate including a first plurality of anti-sticking protrusions; a flexible membrane including a first major surface and an opposite second major surface, a second plurality of anti-sticking protrusions at the first major surface, and a plurality of features at the second major surface, each of the plurality of features being associated with a corresponding one of the second plurality of anti-sticking protrusions; and a second backplate, the flexible membrane being disposed between the first backplate and the second backplate, wherein one of the first plurality of anti-sticking protrusions is disposed between adjacent ones of the plurality of features.

16. The MEMS device according to claim 15, wherein the second backplate includes a plurality of openings and connection members, and wherein the second plurality of anti-sticking protrusions are aligned with the connection members in a direction orthogonal to the major surface of the second backplate.

17. The MEMS device according to claim 15, wherein each of the plurality of features is aligned with a corresponding one of the second plurality of anti-sticking protrusions in a direction orthogonal to the major surface of the second backplate.

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