Patent Description:
Document <CIT> discloses a sensor structure, comprising:
a first diaphragm structure; an electrode element; a second diaphragm structure arranged on an opposite side of the electrode element from the first diaphragm structure; and a circuit configured to process at least one signal generated by a deflection of the first diaphragm structure and a deflection of the second diaphragm structure; wherein the first diaphragm structure and the second diaphragm structure form a chamber where the pressure in the chamber is lower than the pressure outside of the chamber.

Document <CIT> discloses a micro-electromechanical system microphone comprising: a first diaphragm element; a second diaphragm element spaced apart from the first diaphragm element; a low pressure region between the first diaphragm element and the second diaphragm element, the low pressure region having a pressure less than an ambient pressure; a first counter electrode element disposed within the low pressure region; and a ventilation hole which extends from the first diaphragm element to the second diaphragm element and is sealed off against the low pressure region.

Document <CIT> discloses a microelectromechanical system wherein at least one self-supporting structural element having at least one electrode is embodied in a layered structure.

Document <CIT> discloses a MEMS transducer package comprising a first integrated circuit die, the first integrated circuit die comprising: an integrated MEMS transducer; and integrated electronic circuitry for operation of the MEMS transducer; wherein the footprint of the MEMS transducer package is substantially the same size as the footprint of the integrated circuit die.

A Microelectromechanical System (MEMS) microphone system is disclosed according to claim <NUM>.

These and other features, aspects, and advantages of this disclosure will become better understood when the following detailed description of certain exemplary embodiments is read with reference to the accompanying drawings in which like characters represent like arts throughout the drawings, wherein:.

The disclosure is a microphone system for a client machine. Within the client machine are several other electronic components, such as sensor devices, speakers, graphical processor units, computer processor units, host systems, MEMS microphones, and any suitable computer implemented devices either directly or indirectly coupled to the microphone system. The client machine may be a personal computer or desktop computer, a laptop, a cellular or smart phone, a tablet, a personal digital assistant (PDA), a gaming console, an audio device, a video device, an entertainment device such as a television, a vehicle infotainment, a wearable device, an entertainment or infotainment remote control, a thin client system, a thick client system, or the like. Other suitable client machines regardless of size, mobility, or configuration may be suggested to include any number of microphone system.

The microphone system includes a package housing or an enclosure for housing any number of sensor devices/dies, internal components, or combination thereof. The sensor devices/dies may be such as MEMS transducers, speakers, receivers, microphones, pressure sensors, thermal sensors, optical sensors, imaging sensors, chemical sensors, gyroscopes, inertial sensors, humidity sensors, accelerometers, gas sensors, environmental sensors, motion sensors, navigation sensors, vital sensors, tunnel magnetoresistive (TMR) sensors, proximity sensors, bolometers, or combination thereof. The microphones may be electret microphones, capacitive microphones, graphene microphones, piezoelectric microphones, silicon microphones, optical microphones, or any suitable acoustic microphones.

<FIG> is a perspective view of a microphone system <NUM> according to an embodiment of the disclosure. The MEMS microphone system <NUM> includes a package housing <NUM> having a lid <NUM>, a spacer <NUM>, and a substrate <NUM> attached to the spacer <NUM> by any suitable methods of attachment. More than one sensor device/die may be mounted within the microphone system <NUM>. The sensor devices/dies may be MEMS transducers, speakers, receivers, microphones, pressure sensors, thermal sensors, optical sensors, imaging sensors, chemical sensors, gyroscopes, humidity sensors, inertial sensors, vital sensors, TMR sensors, accelerometers, gas sensors, environmental sensors, motion sensors, navigation sensors, proximity sensors, bolometers, or combination thereof. Optional components such as ASICs, integrated circuits, processors, controllers, energy storage devices, actuators, sensor circuits or any suitable circuitry may be mounted within the microphone system <NUM>. Depending on the application, any number of opening <NUM> such as a port or a passageway for receiving attributes from an environment may be formed on any location of the package housing <NUM> by etching, piercing, drilling, punching, or any suitable methods. For example, the opening <NUM> may be formed on the lid <NUM>, the substrate <NUM>, or the spacer <NUM>. In some embodiments, the opening <NUM> may be formed on multiple locations of the package housing <NUM>. The attributes may be acoustic signal, pressure signal, optical signal, gas signal, and any suitable signal. An optional barrier may be formed within the opening <NUM>. The barrier is configured and functioned as a filter to remove debris, contamination, particles, vapor, fluid, or the like. In some embodiments, the barrier may formed on the outer surface of the housing <NUM> to cover the opening <NUM> so that debris, contamination, particles, or the like cannot penetrate into the housing. In yet another embodiments, the barrier may be formed below the opening <NUM> in which a portion of the barrier is attached to the inner surface of the housing <NUM> for filtering or removing debris, contamination, particles, or the like. In yet embodiments, the barrier may be fabricated directly onto the movable member such as a diaphragm. In yet another embodiment, the barrier is formed as a layered film or a layered material and may either integrated into the housing <NUM> during fabrication, or disposed on the outer or inner surface of the housing <NUM>. Although one barrier is described, multiple layers of barrier or any suitable number of barrier may be implemented on the MEMS package, depending on the application. The barrier not only functions as the particle removal while exposed to the environment via the opening <NUM>, the barrier can also serve other purposes such as a shock absorber, or a vibration damper, or combination thereof. Although the microphone system <NUM> as depicted comprises a multi-structure package housing <NUM>, various aspects and configurations either in a single structure package housing, a two piece structure package housing, or multi-structure package housing may be used to encapsulate at least one internal component. As an example, the lid <NUM> and the spacer <NUM> may be formed as a single structure, defines a cover or a cap. One or more bonding pads <NUM> may be formed on the substrate <NUM>, the lid <NUM>, the spacer <NUM>, or multiple locations of the package housing <NUM> by any suitable method. Once bonding pads <NUM> are introduced, the microphone system <NUM> can be easily mounted to an external printed circuit board or another support member of the client machine. In some embodiments, the package housing further includes an interposer coupled the cover <NUM> to either the spacer <NUM> or the substrate <NUM>.

<FIG> illustrate cross-sectional view of the microphone systems <NUM> of <FIG> having various opening configuration formed on different location of the packaging housing <NUM> in accordance with a described embodiment of the disclosure. Although one opening <NUM> is illustrated in each figures, any suitable number of opening <NUM> in various sizes and geometry may be formed by any methods on the packaging housing <NUM>. The microphone system <NUM> includes a sensor device/die <NUM> and a component <NUM> mounted within any location of the package housing <NUM>. The opening <NUM> formed on at least one location of the package housing <NUM> that is adjacent to at least one of the sensor device <NUM> or the component <NUM> receive attributes or stimuli such as acoustic signals from external environment. A connection link <NUM> may be introduced to communicatively couple the sensor device <NUM> to the component <NUM>. The connection link <NUM> may be wire bond, solder-bump, solder microbump, solder ball, or any suitable connectors. In some embodiments, the connection link <NUM> may be a wireless communication link and the sensor device <NUM> is communicatively coupled to the component <NUM> with built-in interfaces formed in both sensor device <NUM> and the component <NUM>. The wireless communicative link, for example, may be WiFi, near field communication (NFC), Zigbee, Smart WiFi, Bluetooth (BT) Qi wireless communication, ultra-wide band (UWB), cellular protocol frequency, radio frequency, or any suitable communication link. Depending on the applications, any number of sensor devices <NUM>, components <NUM>, or connection links <NUM> between the sensor devices and the components may be used. Although side-by-side configuration of the component <NUM> and the sensor device <NUM> is illustrated in <FIG>, any suitable configurations may be possible. For example, the sensor device <NUM> may be placed or mounted on top of the component <NUM> to form a stacked configuration. In another example, the sensor device <NUM> may be mounted in a hole formed within the component <NUM> configured to receive the sensor device to form a surrounded configuration.

<FIG> illustrates a cross-sectional view of an embodiment of a microphone die <NUM> mounted within the microphone system <NUM> of <FIG>. The microphone die <NUM> comprises a substrate <NUM> including a cavity or a substrate hole <NUM> and a first membrane <NUM> is arranged above a substrate <NUM>. In one embodiment, the membrane <NUM> is electrically connected to the substrate <NUM>. In another embodiment, the membrane <NUM> is electrically isolated from the substrate <NUM> by any suitable methods of technology. The microphone die <NUM> further comprises a second membrane <NUM> connected to the substrate <NUM> by any suitable method of attachment. In between the first and second membrane <NUM>, <NUM>, a plurality of connections <NUM> and posts <NUM> are provided. The posts <NUM> coupled the first and second membrane <NUM>, <NUM> by any suitable methods. In one embodiment, the thickness of the posts <NUM> are either slim or thin to limit stiffening of the two membranes <NUM>, <NUM>. Adjacent to a central portion of the microphone is a coupling <NUM> which provide stiffness to the two membranes <NUM>, <NUM>. As illustrated, a movable electrode <NUM> is attached to at least one membrane <NUM>, <NUM>. The movable electrode <NUM> overhangs beyond the membrane <NUM>, <NUM> and overlaps with at least one stationary electrode <NUM> which is attached to the substrate <NUM>. In another embodiment, the moving electrode is arranged between two membranes. The moving electrode is mechanically coupled with a center region of at least one membrane. In some embodiments, the electrode is electrically non-conductively attached to the membrane. The movable electrode protrudes beyond the membranes. The displacement of the movable electrode is measured in a region outside the membranes via counter electrodes which are fixed to the substrate. The area next to the membrane thereby can efficiently be used as detection area. Between the membranes and between the movable and stationary electrodes, for example, a vacuum, a low pressure, or a pressure different from the surrounding is enclosed. Thereby a small damping can be achieved despite the high capacitive signal. Many connecting trusses/beams are foreseen in order to enable the use of very compliant membranes which do not collapse despite the vacuum between the membranes. The connecting trusses/beams are slim such that reduced or minimum stiffening of the two membranes results. Holes are foreseen in the movable electrode through which the connecting beam reach such that the connecting beams and the movable electrode are not coupled to each other. The two membranes can be stiffened in the center which enables the use of lager membranes which bend only in a ringshaped region at the edge. Thereby larger areas can be spanned for the same single membrane thickness and by this the back volume of a microphone can be optimized for example by increasing footprint of the back volume. The openings through which the vacuum between the membranes and the movable and static electrodes is produced are located preferably at the substrate region near to or above the stationary electrodes and are not required to being located in the membrane. The movable electrode is attached to one or to both membranes through an electrically isolating material like an oxide layer. By electrically separating the substrate potential from the potential of the movable electrode simpler circuits can be used for the read out. In addition to that the parasitic capacitance is reduced considerably which facilitates a much more improved read out of the signal. The electrical connection of the movable electrode to the periphery can be carried out by a very compliant/soft spring structure which for example is realized in the layer of the movable membrane. At least one access channel <NUM> is formed on the membrane <NUM>. The access channel <NUM> is configured to either release, encapsulate, or create a defined pressure, preferably a vacuum, formed in the cavity between the two membranes <NUM>, <NUM> and the movable and the stationary electrodes <NUM>, <NUM>. The access channel <NUM> is closed by inserting a plug <NUM> there through. In some embodiments, the access channel <NUM> is located outside the two membranes without interfering with the mechanical properties of the membranes. In order to achieve a pressure equalization during the operation of the microphone between the side facing the sound and the side facing the back volume little through holes or slits <NUM> are provided in the membranes <NUM>, <NUM>. In one embodiment, the stationary electrode <NUM> is formed on the same layer/plane and by using the same material as the lower membrane. In another embodiment, an additional layer can be placed above the stationary electrode <NUM>. This layer is then partially released and is extended into the region of the membrane in order to use at least a portion of the membrane area for signal detection. The isolation of the stationary electrode can be achieved by an Oxide layer, a Nitride layer, or any suitable material. The signal from the different electrodes can be routed to the outside by any suitable methods.

In some embodiments, during fabrication, different layer depositions and structuring of Polysilicon layers and Oxide layers (or additional Nitride layers) may be formed on the Silicon substrate. The Oxide layers used as sacrificial layer can be removed by a HF gas phase etch process, for example. The sacrificial layer is etched to form the access holes for the creation of the vacuum. In order to efficiently remove the sacrificial layer in the membrane region and in order to use only access holes outside the membrane region, etch channels are implemented for the etching of the sacrificial layer in the region between the two membranes to keep the duration of the process step of removing the sacrificial layer within reasonable limits. The etch channels may include optional cavities, depending on a desired application. The microphone <NUM> is provided to allow for an electrode configuration independent from the membrane geometry. The microphone <NUM> is also provided to allow very large and sensitive membrane geometries. A differential read out coupled to the microphone allow for simple static electrode. The microphone <NUM> is provided for the moving electrode to be on a different potential than the substrate in order to enable a simple evaluation of the signal. The membrane operable at substrate potential prevents short circuits between substrate and membrane. Furthermore, a low pressure between the membranes without the need of encapsulation of openings being located in the membrane is provided.

<FIG> illustrates a cross-sectional view of an embodiment of a microphone die <NUM> mounted within the microphone system <NUM> of <FIG>. Unlike from <FIG>, an additional layer which is an upper final layer <NUM> is provided. This layer allows for a more robust microphone. Another stationary counter electrode <NUM> may be formed above the movable electrode. In one embodiment, the upper stationary electrode is formed as the same layer as the upper membrane. The signal may be read out in a fully differential way. In addition to that the center portion of the membrane is stiffened in this example in order to realize a larger membrane with larger back volume and by this gaining more sensitivity.

Claim 1:
A Microelectromechanical System (MEMS) microphone system comprising:
a package housing (<NUM>) having a cavity; and
a MEMS sensor is disposed within the cavity of the package housing (<NUM>), the MEMS sensor comprising:
a substrate (<NUM>);
a first member and a second member spaced apart from the first member are arranged above the substrate (<NUM>);
a plug (<NUM>); and
an access channel (<NUM>) formed on at least one of the first or the second member, the access channel (<NUM>) is configured to receive the plug (<NUM>),
the MEMS sensor further comprising a vacuum formed between the first and second members, the vacuum having a pressure different from the cavity, wherein the MEMS sensor further comprising an electrode assembly having a movable electrode (<NUM>) and a stationary electrode (<NUM>), wherein the movable electrode (<NUM>) is formed between the first and second members, wherein the first and second members comprises a central portion and the movable electrode (<NUM>) is located on the central portion, wherein the movable electrode (<NUM>) is mechanically coupled to at least one of the first or second member and the movable electrode (<NUM>) overlaps with the stationary electrode (<NUM>).