Stress decoupling in MEMS transducers

A MEMS transducer (200) comprises a substrate (101) having a first surface (102) and a membrane (103) formed relative to an aperture in the substrate. The MEMS transducer (200) further comprises one or more bonding structures (107) coupled to the substrate, wherein the one or more bonding structures (107), during use, mechanically couple the MEMS transducer to an associated substrate (111). The MEMS transducer (200) comprises a sealing element (109) for providing a seal, during use, in relation to the substrate (101) and the associated substrate (111). A stress decoupling member (119) is coupled between the substrate (101) and the sealing element (109).

This application relates to methods and apparatus relating to stress decoupling in MEMS transducers and, in particular, to methods and apparatus for providing stress decoupling in connection with a sealing element of a MEMS transducer.

BACKGROUND

Consumer electronics devices are continually getting smaller and, with advances in technology, are gaining ever-increasing performance and functionality. This is clearly evident in the technology used in consumer electronic products and especially, but not exclusively, portable products such as mobile phones, audio players, video players, PDAs, wearable devices, mobile computing platforms such as laptop computers or tablets and/or games devices, or devices operable in an Internet-of-Things (IoT) environment. Requirements of the mobile phone industry for example, are driving the components to become smaller with higher functionality and reduced cost. It is therefore desirable to integrate functions of electronic circuits together and combine them with transducer devices such as microphones and speakers.

Micro-electromechanical-system (MEMS) transducers, such as MEMS microphones are finding application in many of these devices. There is therefore also a continual drive to reduce the size and cost of MEMS devices.

Microphone devices formed using MEMS fabrication processes typically comprise one or more membranes with electrodes for read-out/drive deposited on the membranes and/or a substrate. In the case of MEMS pressure sensors and microphones, the read out is usually accomplished by measuring the capacitance between the electrodes. In the case of output transducers, the membrane is moved by electrostatic forces generated by varying a potential difference applied across the electrodes.

To provide protection the MEMS transducer will typically be contained within, or may itself form a package. The package effectively encloses the MEMS transducer and can provide environmental protection and may also provide shielding for electromagnetic interference (EMI) or the like.

FIG. 1illustrates an example of a MEMS microphone package100, and in particular a chip scale (CS) MEMS transducer package, also known as a wafer level package (WLP). A MEMS transducer103, for example a flexible membrane, is attached to a first surface of a package substrate101. The MEMS transducer103may typically be formed on a semiconductor die by known MEMS fabrication techniques. The package substrate101may be silicon or PCB or any other suitable material. A cover105is mechanically attached to a second surface of the package substrate101(and possibly electrically connected).

The type of packaging arrangement shown inFIG. 1may be referred to as a “bottom port” configuration, wherein the MEMS transducer package100is “flip-chip” bonded to the next level of interconnect, for example to a host substrate111(e.g. PCB) within a product device. In such a mounting arrangement the host substrate111may comprise a sound port113to allow passage of acoustic signals to/from the MEMS transducer103. The sound port113may be arranged to substantially line up with the MEMS transducer103. The sound port113acoustically couples to a first volume on one side of the MEMS transducer103, which may sometimes be referred to as a front volume. It is noted that other bottom-port arrangements may comprise alternative paths for channeling acoustic signals to/from the MEMS transducer103, in place of the sound port113.

The package substrate101comprises a first cavity115, with the cover or cap105of this example also comprising a second cavity117. The first and second cavities115/117form what is referred to as a back volume. The back volume may be filled with air (or some other fluid or gas), and is sized sufficiently so that the MEMS transducer103, e.g. flexible membrane, provides the desired acoustic response.

The back volume115/117is generally required to allow the membrane to move freely in response to incident sound or pressure waves, and this back volume may be substantially sealed (although it will be appreciated by one skilled in the art that for MEMS microphones and the like the first and second volumes may be connected by one or more flow paths, such as small holes in the membrane, that are configured so as present a relatively high acoustic impedance at the desired acoustic frequencies but which allow for low-frequency pressure equalisation between the two volumes to account for pressure differentials, for example due to temperature changes. It is noted that in some applications, such as bidirectional microphones, a sound port104may also be acoustically coupled to the back volume115/117, such that the MEMS transducer103receives acoustic signals via both the front volume and the back volume.

Although not shown, the package substrate101may comprise integrated electronic circuitry, for example integrated electronic circuitry provided for operation of the transducer, which may for example be a low-noise amplifier for amplifying the signal from a MEMS microphone. Such integrated electronic circuitry is electrically connected to electrodes of the transducer103and is also attached to the first surface of the package substrate101, for example to one or more bonding structures107, which are provided for mechanical and/or electrical connection to another device, e.g. an associated host substrate111of a consumer product in which the MEMS package is being used.

The MEMS package100may further comprise a sealing element109coupled to the first surface of the package substrate101, the sealing element109surrounding the MEMS transducer103. In one example the sealing element109comprises an acoustic sealing element, such as an acoustic sealing ring. Other shaped sealing elements may also be used. The sealing element109is provided for acoustically sealing the MEMS transducer103, for example such that the MEMS transducer103only receives acoustic signals being channeled to/from the MEMS transducer103in a bottom-port configuration via the sound port113.

Thus, the sealing element109, which may be a metalized ring, i.e. a metalized annular bonding structure, is provided to aid in forming an acoustic channel in an assembled host device.

The package substrate101and associated substrate111to which the MEMS transducer package is affixed in an assembled host device may have different thermal expansion characteristics. As a consequence, changes in temperature can lead to the package substrate101expanding at a different rate to the associated substrate111, and since the package substrate101and associated substrate111are mechanically fixed by one or more bonding structures107, this can result in an acoustic seal formed by the sealing element109being broken.

SUMMARY

It is an aim of the present invention to provide a method and apparatus which obviate or reduce at least one or more of the disadvantages mentioned above.

According to a first aspect of the present invention there is provided a MEMS transducer comprising a substrate having a first surface, and a membrane formed relative to a cavity in the substrate. The MEMS transducer comprises one or more bonding structures coupled to the substrate, wherein the one or more bonding structures, during use, mechanically couple the MEMS transducer to an associated substrate. The MEMS transducer comprises a sealing element for providing a seal, during use, in relation to the substrate and the associated substrate. A stress decoupling member is coupled between the substrate and the sealing element, for allowing movement of the sealing element relative to the substrate.

According to another aspect of the present invention there is provided a method of fabricating a MEMS transducer. The method comprises forming a substrate having a first surface, and forming a membrane relative to a cavity in the substrate. The method comprises forming one or more bonding structures on the substrate, wherein the one or more bonding structures, during use, mechanically couple the MEMS transducer to an associated substrate. The method comprises forming a sealing element for providing a seal, during use, in relation to the substrate and the associated substrate. The method comprises forming a stress decoupling member between the substrate and the sealing element.

According to another aspect, there is provided a MEMS transducer comprising a substrate, and a membrane formed relative to a cavity in the substrate. One or more bonding structures are coupled to the substrate, wherein the one or more bonding structures, during use, mechanically couple the MEMS transducer to an associated substrate. A stress decoupling member is coupled between the substrate and at least one bonding structure, for allowing movement of the bonding structure relative to the substrate.

According to another aspect, there is provided a MEMS transducer comprising a substrate, and one or more bonding structures coupled to the substrate, wherein the one or more bonding structures, during use, mechanically couple the MEMS transducer to an associated substrate. A stress decoupling member is coupled between the substrate and at least one bonding structure, for allowing movement of the bonding structure relative to the substrate.

DESCRIPTION

Embodiments of the present invention relate to a MEMS transducer device, for example a microphone. In some examples the MEMS transducer device forms part of a MEMS transducer package, and may relate to a chip scale (CS) MEMS capacitive microphone package that is formed at wafer-level. In some examples the wafer level package (WLP) comprises a substrate, for example a silicon substrate, which incorporates both the MEMS capacitive microphone and its associated integrated electronic circuitry, for example electronic circuitry for providing drive & read-out circuitry; and a package cover or cap, for example a silicon cap, for protecting the silicon substrate and providing a back-volume for the microphone.

Some of the embodiments will be described below in the form of a MEMS transducer or wafer level package that is configured as a “bottom port” transducer or package, wherein the transducer or package is “flip-chip” bonded to the next level of interconnect, e.g. bonded to an associated host substrate, for example a PCB within a consumer product. It is noted, however, that the invention may also be used in other packaging arrangements, or in other mounting configurations.

It is noted that any dimensions in the Figures of the embodiments described below are conceptual, and not necessarily to scale.

FIG. 2shows an example of a MEMS transducer200according to an embodiment of the present invention, wherebyFIG. 2relates to a cross-sectional side view of the MEMS transducer (although it is noted that cross-hatching has not been applied to all parts of the transducer in order to assist with the clarity of the drawing).

The MEMS transducer200comprises a substrate101having a first surface102. A membrane103formed relative to a cavity115in the substrate. One or more bonding structures107are coupled to the substrate. The one or more bonding structures107, during use, mechanically couple the MEMS transducer100to an associated substrate111, for example a PCB onto which the MEMS transducer is to be affixed during use, when assembled in a host device. It is noted that the one or more bonding structures107may also act as electrical connections, for example for interfacing electrical signals between the MEMS transducer200and electrical circuitry on the associated substrate111.

The MEMS transducer200comprises a sealing element109, for example an acoustic sealing element, for providing a seal, during use, in relation to the substrate101and the associated substrate111. It is noted that although the embodiments described herein refer to the sealing element being an acoustic sealing element for sealing acoustic signals, it is noted that the sealing element may be provided for other forms of sealing, for example sealing the MEMS transducer from light or other environment factors. It is noted that the sealing element109does not necessarily provide a hermetic seal when acting as an acoustic element, i.e. the sealing element may comprise one or more openings or perforations, provided it still acts as an acoustic seal or barrier for preventing or suppressing the passage of acoustic signals. In a bottom-port arrangement as shown inFIG. 2, the sealing element109can provide an acoustic seal around the membrane103, such that acoustic waves incident on the membrane103are restricted to the acoustic waves that pass through a sound port113in the associated substrate111, i.e. such that no unwanted sound waves are received by the membrane103, e.g. from the side passages between the substrate101and associated substrate111.

A stress decoupling member119is coupled between the substrate101and the sealing element109, for allowing movement of the sealing element109relative to the substrate101.

The stress decoupling member119provides the advantage that, should the substrate101and the associated substrate111(e.g. a PCB to which the MEMS transducer is mechanically attached during use via the one or more bonding structures) thermally expand at different rates, e.g. due to the substrate101and associated substrate111having different thermal expansion coefficients, or move relative to one another, then the stress decoupling member119can allow movement of the acoustic sealing element119relative to the substrate, to maintain the required acoustic seal. This provides a form of stress decoupling within the MEMS transducer200, and in particular to the acoustic sealing element109from movements of the substrate101and associated substrate111which are mechanically fixed.

In one embodiment the stress decoupling member119is configured to allow movement of the sealing element109(e.g. acoustic sealing element) in a lateral direction and/or an orthogonal direction and/or a diagonal direction with respect to the first surface102of the substrate.

FIG. 3ashows an example of one embodiment of a stress decoupling member119. According to this embodiment the stress decoupling member119comprises a cantilever, or leaf spring, type arrangement.

For example, the stress decoupling member119may comprise a first arm119ahaving a first end coupled to the first surface102of the substrate, wherein the first arm119aextends from the first surface102. A second arm119bhas a first end coupled to a second end of the first arm119a, wherein a second end of the second arm119bis free to move. The sealing element109is coupled between the first and second ends of the second arm119b.

This arrangement has the advantage of allowing the sealing element109to move, for example in response to respective movement of an associated substrate to which the sealing element109is affixed during use, in relation to the substrate101to which the sealing element109is also coupled (via the stress decoupling member119).

In this example the first arm119aextends at an angle from the first surface102of the substrate101. It is noted, however, that the first arm could extend substantially orthogonal to the first surface102.

In this example the second arm119bextends, for example during non-stressed conditions, from the second end of the first arm119ain a plane that is substantially parallel to the plane of the first surface102.

In some examples the first and second arms119a,119bare integrally formed as part of the first surface102of the substrate101, or part of another layer formed on the first surface102. For example, in one embodiment the first and second arms119a,119bare integrally formed as part of a membrane layer forming at least part of the first surface102of the substrate101. In other words, when forming another layer or structure on another part of the substrate101, such as forming a membrane103, the stress decoupling member119may be formed as part of such a process. In such an example the stress decoupling member119may be formed from the same material as the membrane.

It is noted that the stress decoupling member119ofFIG. 3amay comprise other shapes, for example a continuous curved structure comprising the first and second arms, e.g. an “S-shaped” structure. The stress decoupling member119ofFIG. 3amay also comprise further arms or curves. It is noted that various parameters may be controlled to change the stress decoupling characteristics of the stress decoupling member119, for example any one or more of the size, width, height, thickness, or material of the stress decoupling member119itself.

FIG. 3bshows an example of a portion of a MEMS transducer package, comprising a MEMS transducer and cover, wherein stress decoupling members119are provided between a substrate of the MEMS transducer and acoustic sealing elements109, the stress decoupling members119being of the type shown in the embodiment ofFIG. 3a.

FIG. 4ashows an example according to another embodiment of a stress decoupling member119. The stress decoupling member119comprises a raised section extending from the first surface102of the substrate101.

In one example the raised section comprises a sidewall section119cextending from the first surface of the substrate101. A support section119dreceives the sealing element119, e.g. acoustic sealing element. A resilient section119eis coupled between the sidewall section119cand the support section119d, wherein the resilient section119eis configured to allow movement of the support section119drelative to the sidewall section119c.

In one example, the resilient section119eis configured to allow movement of the support section119din a lateral direction and/or an orthogonal direction and/or a diagonal direction with respect to the first surface102of the substrate101. In some examples, it is noted that the sidewall119cmay also contribute to any movement in the lateral direction and/or an orthogonal direction and/or a diagonal direction with respect to the first surface102of the substrate101.

The resilient section119emay comprise a corrugated or spring type arrangement.

In the example ofFIG. 4athe support section119dlies, for example during non-stressed conditions, in a plane substantially parallel to a plane of the first surface102of the substrate101. The sidewall section119cextends at an angle from the first surface102of the substrate101, although it is noted that the sidewall section119cmay also extend substantially orthogonal to the first surface102.

In some examples the sidewall section119c, support section119dand resilient section119eare integrally formed as part of the first surface102of the substrate101, or another layer formed on the first surface102.

For example, the sidewall section119c, support section119dand resilient section119emay be integrally formed as part of a membrane layer forming at least part of the first surface102of the substrate101. In other words, when forming another layer of the package substrate, the stress decoupling member can be formed during the same etching process, and from the same material as that other layer.

The sealing element119may comprise an acoustic sealing element that is configured such that it completely surrounds a membrane. For example the acoustic sealing element119may comprise an annular or cylindrical structure, or ring, for surrounding a membrane. The acoustic sealing element119may be formed, for example, from a metalized or silicon layer. As mentioned earlier, the acoustic element need not necessarily provide a hermetic seal, provided it provides an acoustic barrier. As such, one or more openings may be provided in the annular structure. In each of the embodiments described herein, it is noted that a sealing element109may itself comprise multiple components or materials, for example formed from one or more of a plurality of different materials (e.g. silicon, semiconductor, PCB, ceramic, laminate, plastic, metal, nickel, gold, silver), and may include a solder section for affixing the sealing element109to another substrate.

FIG. 4bshows an example of part of a MEMS transducer package, comprising a MEMS transducer and cover, wherein stress decoupling members119are provided between a substrate of the MEMS transducer and acoustic sealing elements109, the stress decoupling members119being the type shown in the embodiment ofFIG. 4a.

Although not shown in the examples ofFIGS. 2 to 4, it is noted that the substrate101may comprise integrated electronic circuitry. For example, the integrated electronic circuitry may comprise analogue circuitry and/or digital circuitry.

It is also noted that, although the embodiments described above shows one membrane formed in relation to one cavity or aperture in the MEMS transducer, the MEMS transducer may comprise multiple individual membranes formed relative to one or more openings in the substrate. At least one of said multiple individual membranes may be a different type of transducer to at least one other of said multiple individual membranes, for example where different individual membranes are designed to have different characteristics for a particular application.

The MEMS transducers described herein may comprises a cover, wherein the MEMS transducer and cover form a MEMS transducer package.

In the embodiments described above the MEMS transducer may comprise a MEMS microphone.

As mentioned above, although the embodiments described herein refer to the sealing element being an acoustic sealing element for sealing acoustic signals, it is noted that the sealing element may be provided for other forms of sealing, for example sealing the MEMS transducer from light or other environment factors.

According to another embodiment, there is provided an electronic device comprising a MEMS transducer as described herein. The electronic apparatus may comprise, for example, a portable device; a wearable device, a battery power device; a computing device; a communications device; a device adapted for use in an Internet-of-Things (IoT) system, a gaming device; a mobile telephone; a personal media player; a laptop, tablet or notebook computing device.

According to another aspect of the invention, there is provided a method of fabricating a MEMS transducer200.

In one embodiment the method comprises: forming a substrate101having a first surface102; forming a membrane103relative to an aperture in the substrate; forming one or more bonding structures107on the substrate, wherein the one or more bonding structures107, during use, mechanically couple the MEMS transducer100to an associated substrate111; forming a sealing element109for providing a seal, during use, in relation to the substrate101and the associated substrate111; and forming a stress decoupling member119between the substrate101and the sealing element109, for allowing movement of the sealing element109relative to the substrate101.

The method may comprise the steps of forming the stress decoupling member119such that it allows movement of the sealing element119in a lateral direction and/or an orthogonal direction and/or diagonal direction with respect to the first surface102of the substrate101.

The step of forming the stress decoupling member119comprises forming a cantilever, or leaf spring, type arrangement.

In some embodiments the step of forming the stress decoupling member119comprises the steps of: depositing a sacrificial layer such that the sacrificial layer comprises the desired shape of the stress decoupling member; forming the stress decoupling member over the sacrificial layer; and removing the sacrificial layer to allow movement of the stress decoupling member119.

FIGS. 5ato 5eillustrate such a method for forming a stress decoupling member according to the embodiment ofFIG. 3a.

FIG. 5ashows the step of depositing a sacrificial layer50such that the sacrificial layer comprises the desired shape of the stress decoupling member. The sacrificial layer may be deposited on a first surface102of a substrate101(or to another layer, not shown, formed on the surface of the substrate101).

FIG. 5bshows the step of forming the stress decoupling member over the sacrificial layer50. In this particular example, this results in the method forming a stress decoupling member by forming a first arm119ahaving a first end coupled to a first surface102of the substrate101(or to another layer, not shown, formed on the surface of the substrate101) wherein the first arm119aextends from the first surface102. The method comprises forming a second arm119bhaving a first end coupled to a second end of the first arm119a, wherein a second end of the second arm119bis free to move (as described below, after removal of the sacrificial layer50).

FIG. 5cshows the step of forming the acoustic sealing element109between the first and second ends of the second arm119b. The sealing element109may be formed from one or more materials, including for example one or more of silicon, semiconductor, PCB, ceramic, laminate, plastic, nickel, gold, silver, solder.

FIG. 5dshows the step of removing the sacrificial layer to allow movement of the stress decoupling member119.

If desired, the step of removing the sacrificial layer to allow movement of the stress decoupling member119may comprise retaining at least a portion50aof the sacrificial layer, for example to control the stress decoupling characteristics of the stress decoupling member119. It is noted that other parameters may be controlled to change the stress decoupling characteristics of the stress decoupling member119, for example any one or more of the size, width, height, thickness, or material of the stress decoupling member119itself.

From the above, it can be seen that in this example the method comprises forming the first arm119ato extend at an angle from the first surface102of the substrate101. The method may comprise forming the second arm119bto extend from the second end of the first arm119ain a plane substantially parallel to the plane of the first surface102of the substrate101.

The method steps may be performed as method steps when forming some other part of the MEMS transducer, for example involving integrally forming the first and second arms119a,119bas part of the first surface102of the substrate101, or another layer formed on the first surface. For example, the method may comprise integrally forming the first and second arms as part of the steps of forming a membrane layer in at least part of the first surface102of the substrate101.

FIGS. 6ato 6eillustrate an example of a method for forming a stress decoupling member according to the embodiment ofFIG. 4a. In this example the method therefore comprises the step of forming the stress decoupling member119as a raised section extending from a first surface102of a substrate101.

FIG. 6ashows the step of depositing a sacrificial layer60such that the sacrificial layer60comprises the desired shape of the stress decoupling member.

FIG. 6bshows the step of forming the stress decoupling member over the sacrificial layer60. In this particular example, this results in the method forming a stress decoupling member by forming a sidewall section119cthat extends from the first surface of the substrate (not shown), forming a support section119dfor receiving the sealing element119, and forming a resilient section119ebetween the sidewall section119cand the support section119d, wherein the resilient section is formed to allow movement of the support section119drelative to the sidewall section119c(as described below, after removal of the sacrificial layer60).

The method may comprise forming the resilient section119eto allow movement of the support section119din a lateral direction and/or an orthogonal direction and/or diagonal direction with respect to the first surface102of the substrate101.

The step of forming the resilient section119emay comprises the step of forming a corrugated, or spring, type arrangement.

FIG. 6cshows the step of forming the acoustic sealing element109on the support section119d.

FIG. 6dshows the step of removing the sacrificial layer60to allow movement of the stress decoupling member119.

If desired, the step of removing the sacrificial layer to allow movement of the stress decoupling member119may comprise retaining at least a portion, e.g.60a/60bof the sacrificial layer, for example to control the stress decoupling characteristics of the stress decoupling member119. It is noted that other parameters may be controlled to change the stress decoupling characteristics of the stress decoupling member119, for example any one or more of the size, width, height, thickness, or material of the stress decoupling member119itself.

From the above, it can be seen that in this example the method comprises forming the support section119dto lie in a plane substantially parallel to a plane of the first surface102of the substrate101. In this example the method also comprises forming the sidewall section119cto extend at an angle from the first surface102of the substrate101.

The method steps may be performed as method steps when forming some other part of the MEMS transducer, for example involving integrally forming the sidewall section119c, resilient section119eand support section119das part of the first surface102of the substrate101, or part of another layer formed on the substrate101. For example, the method may comprise integrally forming the first and second arms as part of the steps of forming a membrane layer in at least part of the first surface102of the substrate101.

In some examples the method may comprise forming the sealing element, in the form of an acoustic sealing element that surrounds a membrane. Forming the acoustic sealing element may comprise forming an annular or cylindrical structure or ring around the membrane. The step of forming the acoustic sealing element, in some examples, comprises depositing a metal or silicon sealing element. As mentioned above, the sealing element need not necessarily provide a hermetic seal, provided it provides an acoustic barrier.

According to another embodiment there is provided a MEMS transducer200comprising a substrate101and a membrane103formed relative to a cavity115in the substrate. The MEMS transducer comprises a sealing element109, and a stress decoupling member119coupling the sealing element109to the substrate101, wherein the stress decoupling member119is configured to allow movement of the sealing element109relative to the substrate101.

In such an embodiment the stress decoupling member119may be configured according to any of the embodiments described above.

According to another embodiment, in an example where a package cover105comprises an aperture or sound port, for example a sound port104as shown inFIG. 2, and for example whereby such a MEMS transducer package is bonded to a next level interconnect, via bonding structures coupled to the package cover105, the stress decoupling members119of the present invention may also be used to decouple stress in any sealing element109provided around such an aperture104. According to such an embodiment there is therefore provided a MEMS transducer200comprising: a substrate105comprising an aperture104; a sealing element109surrounding the aperture (104); and a stress decoupling member119coupling the sealing element109to the substrate105, wherein the stress decoupling member119is configured to allow movement of the sealing element109relative to the substrate105.

In such an embodiment the stress decoupling member119may be configured according to any of the embodiments described above.

The embodiments described above provide the advantage of having stress decoupling between a sealing element and a MEMS transducer, such that a seal can be maintained despite movements in various parts of the MEMS transducer.

In the examples described herein, it is noted that the membrane103is not necessarily circular. For example, the membrane103may comprise any other shape, including for example a polygon shape or cow-hide shaped device, or a membrane mounted on stress reduction areas.

It is noted that, in the embodiments described herein, although the bonding structures107are shown as being configured or arranged in various corners of a MEMS transducer, the bonding structures may instead be configured in a particular region, for example to one side of a membrane. Such an arrangement can provide yet further stress decoupling.

According to another aspect of the invention, stress decoupling members119as described above may be used to provide stress decoupling between the substrate of a MEMS transducer and one or more of the bonding structures.

FIG. 7shows such an example, whereby a stress decoupling member, e.g. similar to that ofFIG. 3a(but with a first arm orthogonal to the substrate, rather than a slanted first arm) is coupled between the bonding structure on the left of the Figure and the substrate to which it is coupled. It is noted that any shaped stress decoupling member as described herein may be used with a bonding structure.

Thus, according to one embodiment, there is provided a MEMS transducer, for example as described in any of the embodiments above, which further comprises a stress decoupling member coupled between at least one bonding structure and the substrate, wherein the stress decoupling member is configured to allow movement of the bonding structure relative to the substrate.

In other embodiments, stress decoupling members may be used with bonding structures, regardless of whether any stress decoupling members are provided on a sealing element.

In one example there is provided a MEMS transducer comprising a substrate, and a membrane formed relative to a cavity in the substrate. The MEMS transducer comprises one or more bonding structures coupled to the substrate, wherein the one or more bonding structures, during use, mechanically couple the MEMS transducer to an associated substrate. A stress decoupling member is coupled between the substrate and at least one bonding structure, for allowing movement of the bonding structure relative to the substrate.

In another example, there is provided a MEMS transducer comprising a substrate, and one or more bonding structures coupled to the substrate, wherein the one or more bonding structures, during use, mechanically couple the MEMS transducer to an associated substrate. A stress decoupling member is coupled between the substrate and at least one bonding structure, for allowing movement of the bonding structure relative to the substrate.

In the embodiments and examples described above, it is noted that the MEMS transducer and stress decoupling members may be formed by any suitable processing techniques, for instance by using CMOS compatible MEMS fabrication techniques.

It is noted that, as used in this specification, it should be understood that the terms upper and lower should not be in any way construed as limiting to any particular orientation of the transducer during any fabrication step and/or orientation in any package, or indeed the orientation of the package in any apparatus. The relative terms lower, above, below, underside, underneath etc. shall be construed accordingly.

Embodiments may be implemented in a host device, especially a portable and/or battery powered host device such as a mobile telephone, and audio player, a video player, a PDA, a mobile computing platform such as a laptop computer or tablet and/or a games device for example or in an accessory device, such a headset, earbud (possibly noise-cancelling), or microphone assembly, designed for wired, or wireless connection with such host devices, possibly via multi-wire cables, multi-pole jacks, or optical fibres and connectors.