Patent Description:
Sensors are devices that contain transducing elements. Transducers are employed within electronic devices to convert signals from one domain to another. For example, some transducers can convert mechanical signals into electrical signals. Such is the case with acoustic microphones that contain transducing elements which convert sound waves into electrical signals. The information from the electronic signals is collected and then transferred to a signal processor that interprets the received signals and delivers output through readout mechanisms within the sensing device.

MEMS based sensors include a variety of transducers, such as accelerometers, oscillators, resonators, gyroscopes, and microphones. MEMS based sensors are produced using a range of microfabrication techniques similar to those used in the fabrication of integrated circuits.

Common electrostatic MEMS microphones utilize capacitive behavior to transduce physical stimuli, such as speech, into electrical signals. In such applications, the capacitive change in the sensor is converted to a voltage signal using interface circuits. These MEMS devices are comprised of a flexible membrane structure arranged in parallel to a rigid backplate structure. Together, they serve as the two electrode plates within the capacitive MEMS device. As sound waves penetrate through cavities within the device, they induce oscillations amongst the flexible membrane due to the pressure difference. This in turn causes variance in the distance of the air gap between the flexible membrane and the backplate. Resultantly, the variation in the air gap between the flexible membrane and the back plate is directly proportional to the change in capacitance of the MEMS device.

Often times, when this deflection occurs between the flexible membrane and the backplate, electrostatic forces buildup may cause the two surfaces to stick together when they come into contact with one another. To alleviate this occurrence, anti-sticking bumps are fabricated within the bottom surface of the backplate so they are positioned between the two electrode surfaces. These anti-sticking bumps serve the purpose of maintaining a certain working distance between the flexible membrane and the backplate so as to reduce the amount of contact area between the two electrodes surfaces.

<CIT> relates to Micro-Electro-Mechanical systems (MEMS) device and a method for fabricating the MEMS.

<CIT> relates to a Micro-Electro-Mechanical system (MEMS) device and to a fabrication method thereof.

<CIT> relates to a system and method for a MEMS transducer.

<CIT> relates to a MEMS sound transducer, a MEMS microphone and a method for providing a MEMS sound transducer.

In accordance with an embodiment of the present invention, a micro electrical mechanical systems (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 bumps facing the flexible membrane. The MEMS device further includes a plurality of features disposed at the flexible membrane, where each of the plurality of features being associated with a corresponding one of the first plurality of bumps.

In accordance with another embodiment of the present invention, a micro electrical mechanical systems (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 configured to reinforce the deflectable layer from stress induced failure, the plurality of reinforcement regions being associated with a corresponding one of the first plurality of anti-sticking structures.

In accordance with another embodiment of the present invention, a micro electrical mechanical systems (MEMS) device includes a first backplate including a first plurality of anti-sticking bumps and a flexible membrane including a first major surface and an opposite second major surface, a second plurality of anti-sticking bumps 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 bumps. The MEMS device further includes a second backplate, where the flexible membrane is disposed between the first and the second backplates.

The present invention is directed to a micro electrical mechanical systems (MEMS) device according to claim <NUM> and to a micro electrical mechanical systems (MEMS) device according to claim <NUM>.

Further aspects of the present invention are defined by the dependent claims.

The structure and using of various embodiments of a MEMS microphone are discussed in detail below. However, it should be valued that the various embodiments detailed herein may be applicable in a wide variety of disciplines. The specific embodiments described herein are merely illustrative of specific ways to make and use various embodiments, and should not be construed in a limited scope.

Conventional MEMS devices such as microphones are susceptible to be damaged by dust and particles during operation / assembly. For example, random particles traveling at high enough speeds can damage an electrode. These high speed particles can be generated in a multitude of fashions. For example, a mechanical shock can dislodge a loosely attached, otherwise dormant, particle within a duct between the outside of the device and the port. Similarly, particles suspended in air may be accelerated towards the microphone during the air-gun cleaning process during assembly of the device or after packaging.

The inventors of this application have determined that the flexible membrane is a significantly susceptible portion of the microphone because of stress induced by the particle. In particular, the inventors of this application determined that regions of the flexible membrane designed to be in contact with the anti-sticking bumps are more susceptible due to stress concentration in small regions. Embodiments of the present invention describe MEMS devices that are more immune to failure, e.g., due to particle damage, by the formation of additional features on the flexible membrane and optionally as well as on the plates of the MEMS devices.

A structural design of a MEMS device will first be described using <FIG> and <FIG>. Alternative designs of the MEMS devices will then be described using <FIG>.

<FIG> illustrates a cross sectional view of an embodiment of a MEMS microphone and wherein <FIG> represents a magnified portion of the dashed region illustrated by <FIG>.

Referring to <FIG>, in one or more embodiments, a micro electrical mechanical systems (MEMS) device <NUM> includes a substrate <NUM>, a first clamping layer <NUM> and a second clamping layer <NUM>, a flexible membrane <NUM>, and a first backplate <NUM>. In one embodiment, the MEMS device <NUM> is a microphone.

<FIG> represents a magnified portion of the MEMS device <NUM> indicated by the dashed region within <FIG>. In such embodiments, the flexible membrane <NUM> is a deflectable sensing membrane that forms a parallel plate capacitor with the first backplate <NUM>. Sound pressure waves are incident on the flexible membrane <NUM> from the cavity <NUM>, which is connected to a sound port (not shown) in the MEMS microphone. During operation, sound pressure waves incident from the cavity <NUM> may cause oscillations of the flexible membrane <NUM> towards and away from the first backplate <NUM>, thereby changing the distance between the flexible membrane <NUM> and the first backplate <NUM>, which in turn changes the capacitance between the flexible membrane <NUM> and the first backplate <NUM>. For example, the change in capacitance may be sensed by readout electronics coupled to the flexible membrane <NUM> and the first backplate <NUM> through conductive lines (not shown).

The first backplate <NUM>, which is disposed over the flexible membrane <NUM>, is a rigid layer. In one embodiment, the first backplate <NUM> comprises a first insulating layer <NUM> and a second insulating layer <NUM>, a conductive layer <NUM>, and a first plurality of bumps <NUM>. The first plurality of bumps <NUM> serve as anti-sticking bumps to alleviate sticking due to electro-static forces that may arise when the flexible membrane <NUM> comes into contact with the first backplate <NUM>. Anti-sticking bumps serve to maintain a certain distance between the first backplate <NUM> and the flexible membrane <NUM>, and assist in reducing surface area contact. According to some embodiments, the first backplate <NUM> may include the perforations <NUM> of varying diameter sizes ranging from small to large. The perforations <NUM> may serve as release holes during an etch fabrication step in which portions of the second clamping layer <NUM> are removed. In one or more embodiments, the perforations <NUM> may include numerous small diameter holes arranged closely together and around the perimeter of a deflectable portion of the flexible membrane <NUM>. The spacing and size of the perforations <NUM> may be used to control both the position and smoothness of the second clamping layer <NUM> and the second clamping layer edges <NUM>, respectively.

According to various embodiments, the substrate <NUM> may be comprised of silicon material or any other material that can be utilized to form a supportive substrate structure for the various layers within the MEMS device <NUM>.

A cavity <NUM> is formed within the substrate <NUM>. In various embodiments, the cavity <NUM> may be formed using an etch fabrication technique, such as a Bosch process etch, that produces scalloped edges along the substrate sidewall <NUM>. The flexible membrane <NUM> may include a fixed portion that is supported by the first clamping layer <NUM> and the second clamping layer <NUM>, and an unfixed portion that is disposed over a cavity <NUM>. According to various embodiments, the flexible membrane <NUM> may be comprised of any conductive material, such as doped polysilicon.

The first clamping layer <NUM> is disposed above the substrate <NUM>. In some embodiments, the substrate sidewall <NUM> of the substrate <NUM> may extend past the first clamping layer edge <NUM>. Alternatively, in other embodiments the first clamping layer edge <NUM> may extend past the substrate sidewall <NUM> and into the cavity <NUM>. The first clamping layer <NUM> may be comprised of insulating material, such as tetraethyl orthosilicate (TEOS) oxide in some embodiments. Alternatively, the first clamping layer <NUM> may be formed of any other insulating material, such as another oxide or a dielectric.

The second clamping layer <NUM> is disposed above the flexible membrane <NUM>, effectively lending itself as a support structure by "clamping" the fixed portion of the flexible membrane <NUM>. In various embodiments of MEMS device <NUM>, the first and the second clamping layers <NUM> and <NUM> may be rearranged such that the first clamping layer <NUM> extends beyond the substrate sidewall <NUM> and into the cavity <NUM>, where the second clamping layer <NUM> does not extend beyond the substrate sidewall <NUM>. In some embodiments, the second clamping layer <NUM> may be thicker than the first clamping layer <NUM>, and vice versa. Similarly to the first clamping layer <NUM>, the second clamping layer <NUM> may be comprised of insulating material, such as tetraethyl orthosilicate (TEOS) oxide or any another oxide or dielectric.

The first backplate <NUM> is formed on top of the second clamping layer <NUM> and, as stated, includes the first insulating layer <NUM>, the conductive layer <NUM>, and the second insulating layer <NUM>. In one embodiment, the first and the second insulating layers <NUM> and <NUM> are formed as silicon nitride layers. However, the conductive layer <NUM> is formed as a doped polysilicon layer. In general, the first backplate <NUM> can be fabricated from any combination of insulating or conductive materials known in the art. The air gap that exists between the first backplate <NUM> and the flexible membrane <NUM> may have a distance typically ranging from <NUM> to <NUM>. As stated earlier, the first backplate <NUM> also includes a first plurality of bumps <NUM> that serve as anti-sticking bumps to alleviate sticking due to electro-static forces that may arise when the flexible membrane <NUM> comes into contact with the first backplate <NUM>. This first plurality of bumps <NUM> is comprised of layers from the second insulating layer <NUM> and the conductive layer <NUM> of the first backplate <NUM>. Therefore, in one embodiment of MEMS device <NUM>, the first plurality of bumps <NUM> may be comprised of a layer of silicon nitride and a layer of doped polysilicon. In other embodiments, the first plurality of bumps <NUM> may be fabricated from any other combination of insulating or conductive materials known to the art. The first plurality of bumps <NUM> may have a size of <NUM> to <NUM> in height, and may have a variably sharp tip with a radius of curvature ranging from <NUM> to <NUM>. Likewise, the first plurality of bumps <NUM> may have a flatter tip around the size of <NUM> to <NUM>.

As illustrated in <FIG>, a first plurality of features 111a is disposed on the flexible membrane <NUM>. The first plurality of features 111a comprise protrusions extending from the flexible membrane <NUM> in a direction towards the first plurality of bumps <NUM>. Each of the first plurality of features 111a is associated with a corresponding one of the first plurality of bumps <NUM>. The first plurality of features 111a comprise protrusions extending from the flexible membrane <NUM> in a direction towards the first plurality of bumps <NUM>. According to some embodiments, the first plurality of features 111a may comprise a different material than the flexible membrane <NUM> (as shown in <FIG>).

Each of the first plurality of features 111a comprises sidewalls orthogonal to a major outer surface of the flexible membrane <NUM>. According to some embodiments, the first plurality of features 111a may be composed of a different material than that of the flexible membrane <NUM> (as shown in <FIG>).

In various embodiments, the first plurality of features 111a comprises a material that is more immune to cracking than the flexible membrane <NUM>, and in particular, has a higher fracture toughness than the flexible membrane <NUM>. For example, the flexible membrane if made of polysilicon has a fracture toughness Kc of about <NUM> MPa. However, in one or more embodiments, materials with similar or even lower fracture toughness (e.g., silicon oxide) may be used since the thickness increase provided by the first plurality of features 111a helps to dissipate the stress energy within the first plurality of features 111a and thereby avoiding it from reaching the flexible membrane <NUM>. This is because cracks formed on the first plurality of features 111a do not have a functional impact on the operation of the MEMS device unlike cracks on the flexible membrane <NUM>.

In various embodiments, the material of the first plurality of features 111a is more rigid than the flexible membrane <NUM> helping to minimize deformation of the underlying flexible membrane <NUM>. Because of the higher rigidity of the first plurality of features 111a, it is less susceptible to stress induced failure. Thus excessive stress applied by the first plurality of bumps, which otherwise may have caused cracking of the flexible membrane, is absorbed by the first plurality of features 111a minimizing damage to the flexible membrane <NUM>.

Accordingly, the first plurality of features 111a may be composed of silicon nitride layers (SiN), silicon oxide layers (SiO2), silicon carbide layers (SiC), or any other combination of insulating material known to the art.

In various embodiments, the first plurality of features 111a may be constructed through conventional microfabrication schemes. For example, an insulating material, like those mentioned above, can be deposited on the top surface of the flexible membrane <NUM>. Through various photolithographic and etching steps, coupled along with additional microfabrication processing schemes known to a person skilled in the art, such as cleaning and planarization, the first plurality of features 111a may be formed.

<FIG>, illustrates a cross sectional view of an embodiment of a MEMS device <NUM> in which alternative embodiments for the side profile of the first plurality of features 111a are depicted. <FIG> represent a magnified portion of the dashed regions illustrated by <FIG>.

As detailed above, the edges of the first plurality of features 111a can be etched in a manner that achieves a vertical sidewall profile (as illustrated in <FIG>). In other embodiments of the MEMS device <NUM>, the sidewalls 111c of the first plurality of features 111a can be etched in a manner that achieves more of an angled sidewall profile (as illustrated in <FIG>). The rationale behind it being, a more angled sidewall profile for the first plurality of features 111a reduces the concentration of stress endured at the interface (indicated by the arrows in <FIG>) where the edges of the first plurality of features 111a meets the top surface of the flexible membrane <NUM>. The first plurality of features 111a range in size from <NUM> to <NUM> in thickness and have a lateral dimension around <NUM> to <NUM> larger than that of the contact area of the first plurality of bumps <NUM>.

<FIG> illustrates a cross sectional view of an alternative embodiment of a MEMS device <NUM>. In this particular embodiment of a MEMS microphone, material is not only deposited on top of the flexible membrane in the form of the first plurality of features 111a (as detailed above), but the same, or similar, insulating material is additionally disposed below the flexible membrane <NUM>, in the form of a second plurality of features 111b.

The second plurality of features 111b disposed below the flexible membrane <NUM> provides additional reinforcement to the otherwise fragile flexible membrane <NUM>. Moreover, the second plurality of features 111b balances the stress induced by the additional material on the flexible membrane <NUM>.

<FIG> illustrates a cross sectional view of an embodiment of a MEMS device <NUM>.

In this embodiment, a third plurality of features 111d is deposited on top of the flexible membrane <NUM> may be comprised of the same material as the flexible membrane <NUM>. in other words, in this embodiment, portions of the flexible membrane <NUM> that are likely to be more susceptible to stress induced failure are made thicker.

Accordingly, the additional material added to the flexible membrane <NUM> can be thought of as a local thickening of the membrane material. The third plurality of features 111d can be fabricated using similar fabrication techniques adopted for the construction of the first plurality of features 111a. Alternately, in some embodiments, the third plurality of features 111d may be formed along with the flexible membrane <NUM>, where regions without the third plurality of features 111d are recessed.

In this embodiment, additional material is disposed on the bottom of the flexible membrane <NUM> as fourth plurality of features 111e, which may also be comprised of the same material as the flexible membrane <NUM>. Advantageously, this embodiment reinforces the flexible membrane <NUM> without any change in capacitance between the flexible membrane <NUM> and the first backplate <NUM>.

As previously discussed, the fourth plurality of features 111e can be fabricated using similar fabrication techniques adopted for the construction of the first plurality of features 111a. Alternatively, the fourth plurality of features 111e may be formed along with the flexible membrane <NUM>, where regions without the fourth plurality of features 111e are recessed.

<FIG> illustrates a cross sectional view of an embodiment of a MEMS device <NUM> while <FIG> represents a magnified portion of the dashed region illustrated by <FIG>. In this embodiment, sections of the flexible membrane <NUM>, at the level of the first plurality of bumps <NUM>, are replaced by an alternate reinforcement material, in the form of the fifth plurality of features 111f. The fifth plurality of features 111f may be composed of a different material than the flexible membrane <NUM>. In various embodiments, the fifth plurality of features 111f comprises a material that is more immune to cracking than the flexible membrane <NUM>, and in particular, may have a higher fracture toughness than the flexible membrane <NUM>. The fifth plurality of features 111f may comprise materials that are more rigid than the flexible membrane <NUM>. For example, the fifth plurality of features 111f may be composed of silicon nitride layers (SiN), silicon oxide layers (SiO2), silicon carbide layers (SiC), TiN, TaN, and others.

Each of the fifth plurality of features 111f comprises sidewalls that can be orthogonal or have a slope to a major outer surface of the flexible membrane <NUM>. The fifth plurality of features 111f comprises a first portion filled within through holes in the flexible membrane <NUM>. A second annular region extends over a portion of the top surface of the flexible membrane <NUM>. The second annular region may comprise protrusions extending from the flexible membrane <NUM> in a direction towards the first plurality of bumps <NUM>.

The fifth plurality of features 111f may be constructed through conventional microfabrication schemes, many of which have been mentioned herein in various embodiments.

<FIG> illustrates a cross sectional view of an embodiment of a MEMS device which is a dual backplate MEMS microphone.

The dual backplate MEMS microphone design provides a differential MEMS sensor. Accordingly, the dual backplate MEMS microphone outputs two symmetrical <NUM> degree phase shifted signals due to the motion of the flexible membrane.

Unlike the prior embodiments, because of the additional backplate, this embodiment includes a different design for the anti-sticking bumps and the protrusions. In one or more embodiments, the anti-sticking bumps and the protrusions on the flexible membrane <NUM> may be directly aligned in a vertical direction.

Similar to prior embodiments, the MEMS device <NUM> includes a substrate <NUM>, a first, a second, and a third clamping layers <NUM>, <NUM>, and <NUM>, a bottom backplate <NUM>, a flexible membrane <NUM>, and a top backplate <NUM>. According to various embodiments, the flexible membrane <NUM> is positioned between the bottom backplate <NUM> and the top backplate <NUM>. The first clamping layer <NUM> is disposed between the substrate <NUM> and the bottom backplate <NUM>. The second clamping layer <NUM> is disposed between the bottom backplate <NUM> and the flexible membrane <NUM>. The third clamping layer <NUM> is disposed between the flexible membrane <NUM> and the top backplate <NUM>. According to an embodiment of the MEMS device <NUM>, the flexible membrane <NUM> separates the bottom cavity 215a from the top cavity 215b.

Similar to prior embodiments, some of the clamping layers may be retracted further inwards than substrate edge <NUM> and/or other clamping layers within the device. For example, in one embodiment, the second clamping layer <NUM> extends further into the bottom cavity 215a than its other counterparts, namely the first clamping layer <NUM> and the third clamping layer <NUM>. In various embodiments, extension of the first, the second, and the third clamping layers <NUM>, <NUM>, and <NUM>, may be determined by the size and position of the perforations <NUM>, fabricated within the bottom and the top backplates <NUM> and <NUM>.

Details about the functionality and characteristics of the perforations <NUM> can be referenced above to the perforations <NUM> detailed in discussions about the single backplate MEMS device in <FIG>. In some embodiments, some clamping layers may be thicker than other clamping layers. For example, in one embodiment, the first clamping layer <NUM> may be much thinner than the second clamping layer <NUM> or the third clamping layer <NUM>.

According to various embodiments, the substrate <NUM> may be comprised of silicon material or any other material that can be utilized to form a supportive substrate structure for the various layers within the MEMS device <NUM>. A bottom cavity 215a is formed within the substrate <NUM> as described previously. The first, the second, and the third clamping layers <NUM>, <NUM>, and <NUM>, which have been discussed in earlier mentions, are used as support structures for various layers within the MEMS device <NUM>. More specifically, the first, the second, and the third clamping layers <NUM>, <NUM>, and <NUM> help lend support to the bottom and the top backplates <NUM> and <NUM>, as well as the flexible membrane <NUM>. The first, the second, and the third clamping layers <NUM>, <NUM>, and <NUM> may be comprised of insulating material such as tetraethyl orthosilicate (TEOS) oxide in some embodiments. Alternatively, the first, the second, and the third clamping layers <NUM>, <NUM>, and <NUM> may be formed of any other insulating material, such as another oxide or a dielectric.

The bottom backplate <NUM>, which is positioned between the first clamping layer <NUM> and the second clamping layer <NUM> is a rigid structure comprised of the first and the second insulating layers <NUM> and <NUM>, and a conductive layer <NUM>. According to some embodiments, the bottom backplate <NUM> may also include perforations <NUM> of various sized diameters, ranging from small to large, with connecting members <NUM>. As discussed earlier, the perforations <NUM> may serve as release holes for an etch fabrication step. In various embodiments, the perforations <NUM> may include numerous small diameter perforations arranged closely together and around the perimeter of a deflectable portion of the flexible membrane <NUM>. The spacing and size of the perforations <NUM> may be used to control both the position and smoothness of any adjacent clamping layer edges.

The top backplate <NUM>, which is disposed above the third clamping layer <NUM>, may also be a rigid structure comprised of the first and the second insulating layers <NUM> and <NUM>, and a conductive layer <NUM>.

Similar to prior embodiments, the top backplate <NUM> may comprise a first plurality of anti-sticking bumps <NUM> that minimize sticking with the flexible membrane <NUM>. The first plurality of anti-sticking bumps <NUM> is comprised of layers from the second insulating layer <NUM> and the conductive layer <NUM> of the top backplate <NUM>. Therefore, in an embodiment, the first plurality of anti-sticking bumps <NUM> may be comprised of a layer of silicon nitride and a layer of doped polysilicon. In other embodiments, the first plurality of anti-sticking bumps <NUM> may be fabricated from any other combination of insulating or conductive materials known to the art. Much like the bottom backplate <NUM>, the top backplate <NUM> may also contain perforations <NUM> of various diameters.

Although the first plurality of anti-sticking bumps <NUM> are shown aligned with the plurality of features <NUM>, in various embodiments, they may be located in other regions of the top backplate <NUM>. In contrast, in various embodiments, the second plurality of anti-sticking bumps <NUM> are aligned with connecting members <NUM> and not the perforations <NUM> on the bottom backplate <NUM>.

Embodiments of the MEMS device <NUM> include a flexible membrane <NUM> positioned between the bottom backplate <NUM> and the top backplate <NUM>; more specifically, between the second and the third clamping layers <NUM> and <NUM>. The flexible membrane <NUM> comprises a first major surface <NUM> and an opposite second major surface <NUM>.

A second plurality of anti-sticking bumps <NUM> is disposed at the first major surface <NUM>. The second plurality of anti-sticking bumps <NUM> mitigate the sticking of the flexible membrane <NUM> with the bottom backplate <NUM>. The inventors of this application have identified that a portion of the second major surface <NUM> that overlays the second plurality of anti-sticking bumps <NUM> are the points with high stress intensity after a particle impact. Therefore, a sixth plurality of features <NUM> is disposed on the flexible membrane <NUM> so as to vertically overlap with the second plurality of anti-sticking bumps <NUM>.

As in prior embodiments, the sixth plurality of features <NUM> comprise protrusions extending from the second major surface <NUM> of the flexible membrane <NUM> in a direction towards the first plurality of anti-sticking bumps <NUM>. Each of the sixth plurality of features <NUM> is associated with a corresponding one of the second plurality of anti-sticking bumps <NUM>. However, since the sixth plurality of features <NUM> vertically overlap with the second plurality of anti-sticking bumps <NUM>, they may not be overlap with the first plurality of anti-sticking bumps <NUM> but are rather staggered relative to the first plurality of anti-sticking bumps <NUM>.

Similar to prior embodiments, each of the sixth plurality of features <NUM> may comprise sidewalls orthogonal to a major outer surface of the flexible membrane <NUM> (as previously discussed, e.g., in <FIG>). While in other embodiments, each of the sixth plurality of features <NUM> may comprise angled sidewalls (as depicted in <FIG>) to alleviate the buildup of stress concentrated at the major outer surface of the flexible membrane <NUM>.

According to some embodiments, the sixth plurality of features <NUM> may be composed of a different material than that of the flexible membrane <NUM>. As in prior embodiments, the sixth plurality of features <NUM> may be composed of silicon nitride layers (SiN), silicon oxide layers (SiO2), silicon carbide layers (SiC), or other insulating material.

In various embodiments, the sixth plurality of features <NUM> may be constructed through conventional microfabrication processes. For example, an insulating material, like those mentioned above, can be deposited on the top surface of the flexible membrane <NUM>. Through various photolithographic and etching steps, coupled along with additional microfabrication processing schemes known to the art, such as cleaning and planarization, the formation of the sixth plurality of features <NUM> is revealed. As noted earlier, the edges of the sixth plurality of features <NUM> can be etched in a manner that achieves a vertical sidewall profile (as illustrated in <FIG>). In other embodiments, the edges of the sixth plurality of features <NUM> can be etched in a manner that achieves more of an angled sidewall profile (as illustrated in <FIG>). The sixth plurality of features <NUM> range in size from <NUM> to <NUM> in thickness and have a lateral dimension around <NUM> to <NUM> larger than that of the contact area of the first plurality of anti-sticking bumps <NUM>.

The second plurality of anti-sticking bumps <NUM> can be fabricated using similar fabrication techniques detailed herein; and furthermore may comprise the same material utilized for the flexible membrane <NUM>.

Advantages of various embodiments described herein may include devices exhibiting improved robustness for shock and loud sound pressure waves. Furthermore, improvements may be seen in regards to the membrane which becomes particularly sensitive when a particle hits at the vicinity of an anti-stinking bump, causing highly destructive stress during deflection of the flexible membrane. The various embodiments described herein avoid destructive damage to the layers of the MEMS microphone, by reinforcing the flexible membrane so it is more robust, particularly in areas near the vicinity of any anti-sticking bumps.

Although embodiments of the present application have been described in a specific context using namely MEMS microphones, various embodiments include other MEMS devices and structure that includes MEMS capacitive acoustic transducer systems, MEMS microphone systems, silicon microphone systems, single and double backplate microphone systems, and mechanical support MEMS microphone systems.

Claim 1:
A micro electrical mechanical systems (MEMS) device (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) comprising:
a flexible membrane (<NUM>; <NUM>) disposed over a substrate (<NUM>; <NUM>);
a first backplate (<NUM>; <NUM>) disposed over the flexible membrane (<NUM>; <NUM>), the first backplate (<NUM>; <NUM>) comprising a first plurality of bumps (<NUM>; <NUM>) facing the flexible membrane (<NUM>; <NUM>); and
a plurality of features (<NUM> a, 111b, 111d, 111e, 111f; <NUM>) disposed at the flexible membrane (<NUM>; <NUM>), each of the plurality of features (111a, 111b, 111d, 111e, 111f; <NUM>) being associated with a corresponding one of the first plurality of bumps (<NUM>; <NUM>) and being configured to reinforce the flexible membrane (<NUM>; <NUM>) from stress induced failure;
wherein the plurality of features (111a, 111b, 111d, 111e, 111f) comprises locally thicker regions of the flexible membrane (<NUM>), and wherein the plurality of features (<NUM> a, 111b, 111d, 111e, 111f; <NUM>) ranges in size from <NUM> to <NUM> in thickness and has a lateral dimension around <NUM> to <NUM>.