Acoustic transducer and microphone assembly

Abstract

The present invention relates to an acoustic transducer and a microphone assembly, and more particularly to an acoustic transducer having a low pressure region and a diaphragm having a pressure sensor. An acoustic transducer for generating an electrical signal in response to an acoustic signal is disclosed. In some embodiments, the acoustic transducer includes an at least partially vacuum-sealed chamber, the chamber being partially defined by a first diaphragm. The acoustic transducer also includes a back plate at least partially disposed within the chamber. The pressure of the chamber is below atmospheric pressure. The acoustic transducer also includes a pressure sensor coupled to the back plate and configured to sense the pressure in the chamber.

Description

Technical Field

[0001] The present invention generally relates to systems and methods for sensing and monitoring pressure in a vacuum chamber in which a transducer element is disposed. Background Art

[0002] Microphone assemblies used in electronic devices like mobile phones, laptops, hearing devices, smart speakers, and other applications typically include an electroacoustic transducer and an integrated circuit disposed in a housing having a surface mount interface for integration with a host device. Such transducers include capacitive sensors fabricated using microelectromechanical systems (MEMS) technology. Efforts to improve the performance of such transducers include forming the transducing element in an at least partially vacuum-sealed chamber. Summary of the invention

[0003] One aspect of the present invention relates to an acoustic transducer, comprising: an at least partially vacuum-sealed chamber, the at least partially vacuum-sealed chamber being partially defined by a first diaphragm; a backplate, the backplate being at least partially disposed within the at least partially vacuum-sealed chamber, wherein the first diaphragm is movable relative to the backplate in response to sound pressure; and a pressure sensor, the pressure sensor being coupled to the backplate or the first diaphragm and being configured to sense the pressure within the at least partially vacuum-sealed chamber.

[0004] Another aspect of the present invention relates to a microphone assembly, which includes: a shell; an acoustic transducer, which is disposed in the shell and includes: an at least partially vacuum-sealed chamber, which is partially defined by a first diaphragm; a backplate, which is at least partially disposed in the at least partially vacuum-sealed chamber, wherein the first diaphragm is capable of moving relative to the backplate in response to sound pressure; and a pressure sensor, which is connected to the backplate and located in the at least partially vacuum-sealed chamber; and an integrated circuit, which is disposed in the shell, the integrated circuit including a pressure sensing circuit, which is connected to the pressure sensor and is configured to process an electrical signal from the pressure sensor to generate output data indicating pressure.

[0005] Yet another aspect of the present invention relates to a microphone assembly, comprising: a shell; an acoustic transducer disposed in the shell, the acoustic transducer comprising: an at least partially vacuum-sealed chamber, the at least partially vacuum-sealed chamber being partially defined by a first diaphragm; and a backplate, the backplate being at least partially disposed in the at least partially vacuum-sealed chamber, the pressure in the at least partially vacuum-sealed chamber being lower than atmospheric pressure, wherein the backplate is configured to sense the pressure in the at least partially vacuum-sealed chamber; and an integrated circuit, the integrated circuit being disposed in the shell, the integrated circuit being connected to the backplate, the integrated circuit comprising a bias circuit, the bias circuit being configured to selectively apply a bias voltage to the backplate or a sensing current to the backplate. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The foregoing and other features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.The present invention will be described with additional specificity and detail through the use of the accompanying drawings.

[0007] Figure 1 is a side cross-sectional view of a microphone assembly in which an electroacoustic transducer having a sealed chamber may be implemented.

[0008] Figure 2 is a side cross-sectional view of an acoustic transducer.

[0009] Figure 3a An isometric view of a Pirani manometer is depicted.

[0010] Figure 3b Depicted Figure 3a Side view of a Pirani manometer.

[0011] FIG. 4 a depicts a top cross-sectional view of an acoustic transducer.

[0012] FIG. 4b depicts an enlarged view of a portion of the transducer of FIG. 4a .

[0013] Figure 5 Depicted is the pressure sensing circuit.

[0014] Figure 6 An integrated resonator is depicted.

[0015] Figure 7 An integrated resonator is depicted.

[0016] Figure 8a An example of a pressure sensing circuit is depicted.

[0017] Figure 8b A second example of a pressure sensing circuit is depicted.

[0018] Figure 8c A third example of a pressure sensing circuit is depicted.

[0019] Figure 8d A graph depicting the resonant response characteristics of the integrated resonator.

[0020] Figure 8e A graph depicting quality factor characteristics of an integrated resonator according to an exemplary embodiment.

[0021] Figure 8f Several examples of possible integrated resonator designs are depicted.

[0022] Figure 8g The corresponding resonant frequency response characteristics and tensile membrane stress are plotted for several examples of possible integrated resonator designs.

[0023] Figure 9a depicts a top cross-sectional view of a transducer.

[0024] FIG. 9b depicts an enlarged view of a portion of the transducer of FIG. 9a .

[0025] Fig.10a Another example of a pressure sensing circuit for a transducer is depicted.

[0026] Fig.10b A top-down cross-sectional view of the transducer is depicted. DETAILED DESCRIPTION

[0027] Embodiments described herein generally relate to systems and methods for determining pressure within a chamber of a transducer. Specifically, some embodiments described herein relate to a dual-diaphragm acoustic transducer that defines a sealed chamber. This application incorporates by reference U.S. Application No. 16 / 593,263, filed on October 4, 2019, entitled “Acoustic Transducers With A LowPressure Zone and Diaphragms Having Enhanced Compliance”.

[0028] In some embodiments, a dual-diaphragm acoustic transducer includes a first (e.g., top) diaphragm and a second (e.g., bottom) diaphragm with a back plate interposed therebetween. The diaphragm can be sealed under reduced pressure to create a low-pressure region (e.g., chamber) between the top diaphragm and the bottom diaphragm, the pressure of which is significantly lower than atmospheric pressure, for example, in many cases, a moderate vacuum in the range of about 100 mTorr to 100 Torr may be sufficient. The low-pressure region (e.g., chamber) significantly reduces the acoustic damping (i.e., squeeze film damping) of the back plate, thereby reducing the self-noise of the sensor, and also reducing the gap between the diaphragm and the back plate, reducing perforations, and allowing very high inductive capacitance. In addition, since the volume between the top diaphragm and the bottom diaphragm is sealed, particles (e.g., dust, water droplets, solder or component debris, etc.) cannot penetrate between the diaphragm and the back plate, which is a common cause of failure of single-diaphragm acoustic transducers. However, the precise sensitivity and self-noise of the sensor may depend on the actual pressure in the chamber (e.g., low-pressure region). In addition, the pressure within the low pressure region may change over time due to leaks, temperature, or altitude, and the specifications of the transducer may change due to pressure changes in the low pressure region (e.g., chamber). If the pressure within the low pressure region (e.g., chamber) can be determined throughout the operating life of the transducer, the precise specifications of the transducer (e.g., the sensitivity of the transducer) can be adjusted continuously or intermittently. The ability to determine the pressure within the chamber also helps designers and technicians analyze the cause of failure of a device that exhibits atypical performance and provides insights that can be used to improve future iterations of the design and / or manufacturing process.

[0029] As described herein, the term "unanchored" when used in conjunction with a terminal refers to a terminal that extends from one diaphragm of a dual-diaphragm acoustic transducer to the other diaphragm such that there is a gap or space between the end of the terminal and the corresponding diaphragm near the end. The end is brought into contact with the corresponding diaphragm only when a sufficiently high force or pressure (e.g., ambient pressure or electrostatic force due to biasing) acts on one or both diaphragms, so that the unanchored terminal can slide and rotate relative to the corresponding diaphragm.

[0030] As described herein, the term "non-rigid connection" when used in conjunction with a terminal refers to a terminal that extends from one diaphragm of a dual-diaphragm acoustic transducer to the other diaphragm so that the end of the terminal is in permanent contact with the opposite diaphragm so as to allow the terminal to bend or rotate near or about the contact point.

[0031] Figure 11 is a side cross-sectional view of a microphone assembly 100 in which an electroacoustic transducer 102 having a sealed chamber is implemented. The microphone assembly 100 generally includes an electroacoustic transducer 102 coupled to a circuit 103 disposed within a housing 110. The transducer 102 is configured to generate an electrical signal in response to sensing acoustic activity. The transducer 102 may be a capacitive transducer device, a piezoelectric transducer device, or other transducer device implemented using microelectromechanical systems (MEMS) manufacturing or other known or future technologies. The transducer may be a dual-diaphragm acoustic transducer including a first (e.g., top) diaphragm 120 and a second (e.g., bottom) diaphragm 121 with a back plate 123 interposed therebetween. In some embodiments, the back plate 123 may have a pressure sensor 159 disposed thereon. In some embodiments, the back plate 123 may be configured to act as a pressure sensor when in a first state. In some embodiments, the back plate 123 may be formed of a single element or a plurality of elements. In some embodiments, the back plate 123 includes one or more holes such that the chamber 168 is connected between the first diaphragm 120 and the second diaphragm 121 .

[0032] The diaphragm 120 and the diaphragm 121 can be sealed under reduced pressure to create a low pressure region (e.g., a chamber) 168 between the top diaphragm 120 and the bottom diaphragm 121, the pressure of which is significantly lower than atmospheric pressure, for example, in many cases, a moderate vacuum in the range of about 100mTorr to 100Torr may be sufficient. In some embodiments, more or fewer diaphragms can be used to define or create the chamber 168. In some embodiments, the first diaphragm 120 and the second diaphragm 121 can include one or more support structures designed to support the respective diaphragm 120 or 121 so that the chamber 168 remains defined (e.g., so that the first diaphragm or the second diaphragm does not collapse under the pressure difference between the chamber 168 and the space outside the diaphragm).

[0033] Circuit 103 may be implemented by one or more integrated circuits (e.g., an application specific integrated circuit (ASIC) having analog circuits and digital circuits and a discrete digital signal processor (DSP) that performs audio processing (e.g., keyword / command detection, noise suppression, authentication, etc.). Circuit 103 may also include a pressure sensing circuit that is connected to backplane 123 and / or pressure sensor 159 and is configured to determine or assist in determining the pressure within chamber 168. Housing 110 may include an acoustic port 180 and an external device interface 113 having contacts (e.g., for power, data, ground, control, external signals, etc.) connected to the circuit. External device interface 113 is configured for surface mounting to or otherwise (e.g., by reflow soldering) mounted to a host device. In some embodiments, the host device may be an amplifying device that is configured to amplify an audio signal using an electrical signal generated by a transducer and to extend the audio signal to a distant location.

[0034] exist Figure 1 , circuit 103 receives an electrical signal generated by an electroacoustic transducer via connection 141. The signal from transducer 102 can be processed by circuit 103 into an output signal representing the sensed acoustic activity. Circuit 103 may include a signal conditioning circuit, a clock circuit, a direct current (DC) bias circuit, one or more low-pass filters, and a controller, examples of which are described below. In some embodiments, the DC bias is applied to the first terminal of the transducer via connection 141. In some embodiments, the signal conditioning circuit is configured to adjust the electrical signal obtained from the transducer when the circuit is connected to the transducer. In some embodiments, the circuit includes one or more processors, the one or more processors being connected to a non-transitory computer-readable medium configured to store executable instructions. The executable instructions are designed to cause the one or more processors to complete or perform any operation, process, or method described herein when executed by the one or more processors.

[0035] Figure 2 is a side cross-sectional view of the acoustic transducer 200. In some embodiments, the acoustic transducer 200 can be similar to or implemented as reference Figure 1 The transducer 102 in question. The acoustic transducer 200 may be implemented as a MEMS acoustic transducer used, for example, in a MEMS microphone assembly, a MEMS pressure sensor, or a combination thereof. The acoustic transducer 200 is configured to generate an electrical signal in response to an acoustic signal or atmospheric pressure changes.

[0036] The acoustic transducer 200 includes a substrate 212 defining a first opening 213. In some embodiments, the first opening 213 may be similar to the Figure 1Port 180 is depicted. In some embodiments, substrate 212 can be formed of silicon, glass, ceramic, or any other suitable material.

[0037] The acoustic transducer 200 includes a bottom diaphragm or first diaphragm 220, a top diaphragm or second diaphragm 230, and a back plate 240 located between the first diaphragm 220 and the second diaphragm 230. In some embodiments, the first diaphragm 220 and the second diaphragm 230 define a chamber 242 (e.g., a low pressure area). In other embodiments, additional or fewer elements (e.g., diaphragms, plates, substrates, etc.) may be used to define the chamber 242. Each of the first diaphragm 220, the second diaphragm 230, and the back plate 240 is disposed on or coupled to the substrate 212. At least a portion of the first diaphragm 120 may be disposed on a support structure (not shown). In some embodiments, a portion of a radial edge of one or more of the first diaphragm 220, the second diaphragm 230, and the back plate 240 may be embedded in a support structure that connects the substrate to one or more corresponding elements during the manufacturing process of the acoustic transducer 200.

[0038] The diaphragm 220 and the diaphragm 230 may be formed of a conductive material or a sandwich of a conductive material and an insulating material. The materials used to form the diaphragm 120 and the diaphragm 130 may include, for example, silicon, silicon oxide, silicon nitride, silicon carbide, gold, aluminum, platinum, etc. The vibration (e.g., out-of-phase vibration) of the diaphragm 220, 230 relative to the substantially fixed (e.g., substantially inflexible relative to the diaphragm 220, 230) back plate 240 in response to an acoustic signal received on one of the first diaphragm 220 or the second diaphragm 230 causes a change in capacitance between the diaphragm 220 and the diaphragm 230 and the back plate 240, and a corresponding change in the generated electrical signal.

[0039] In other embodiments, piezoelectric materials (e.g., quartz, lead titanate, III-V and II-VI semiconductors (e.g., gallium nitride, indium nitride, aluminum nitride, zinc oxide, etc.), graphene, ultra-nano diamond, polymers (e.g., polyvinylidene fluoride), or any other suitable piezoelectric material) may be used to form at least a portion of the first diaphragm 220 and the second diaphragm 230. For example, the piezoelectric material may be deposited in a ring around the periphery of the first diaphragm 220 or the second diaphragm 230 on top of a base material (e.g., silicon nitride or polycrystalline silicon) forming the diaphragm 220 and the diaphragm 230. In such an embodiment, the vibration of the diaphragms 220, 230 in response to the acoustic signal may generate an electrical signal (e.g., a piezoelectric current or voltage) representing the acoustic signal. When operating as a pressure sensor, each of the diaphragms 220 and 230 displaces inward toward each other when the ambient pressure increases or displaces outward away from each other when the ambient pressure decreases, generating an electrical signal corresponding to the atmospheric pressure. In various embodiments, the first diaphragm 220 and the second diaphragm 230 may be formed of low stress silicon nitride (LSN) or any other suitable material (e.g., silicon oxide, silicon, silicon carbide, ceramic, etc.). In addition, the back plate 240 may be formed of polycrystalline silicon (poly) and silicon nitride or any other suitable material (e.g., silicon oxide, silicon, ceramic, etc.).

[0040] The outer surface 223 of the first diaphragm 220 and the outer surface 233 of the second diaphragm 230 are exposed to the atmosphere (e.g., atmospheric air). The second diaphragm 230 is spaced apart from the first diaphragm 220 so that a chamber or volume 242 is formed between the first diaphragm 220 and the second diaphragm 230. The pressure of the chamber 242 is lower than atmospheric pressure, for example, in the range of 100mTorr to 100Torr, but in some embodiments, limiting the pressure to the range of 1mTorr to 10Torr can provide particular benefits in terms of signal-to-noise ratio (SNR). The back plate 240 is disposed in the chamber 221 between the first diaphragm 220 and the second diaphragm 230. In some embodiments, one or more holes 252 can be defined in the back plate 240 so that a portion of the chamber 242 located between the first diaphragm 220 and the back plate 240 is connected to a portion of the chamber 242 located between the second diaphragm 230 and the back plate 240.

[0041] In some embodiments, the back plate 240 or a portion of the back plate 240 has a pressure sensor 295 disposed thereon. The pressure sensor 295 can be configured to be connected to a circuit (e.g., such as in Figure 1In some embodiments, the pressure sensor 295 includes an electrical terminal formed in the back plate, the first diaphragm 220, or the second diaphragm 230 or designed to extend through the back plate, the first diaphragm 220, or the second diaphragm 230, and electrically connected to the circuit. In some embodiments, the back plate 240 is configured to act as a pressure sensor itself. That is, in some embodiments and as described below with reference to Figure 10a to Figure 10b As explained, backing plate 240 may include two or more electrical contacts such that current may flow through the backing plate and the backing plate may act as a resonator to determine the pressure within chamber 242 .

[0042] In some embodiments, the large pressure difference between the atmospheric pressure acting on each of the first diaphragm 220 and the second diaphragm 230 and the low pressure in the chamber 242 put the first diaphragm 220 and the second diaphragm 230 in a state of continuous stretching. Therefore, in some embodiments, this significantly reduces the compliance of the diaphragms 220, 230. In order to increase the compliance, in some example embodiments, the first corrugation 222 and the second corrugation 132 are formed on the first diaphragm 120 and the second diaphragm 230, respectively. The first corrugation 222 and the second corrugation 232 protrude outward from the diaphragm 220 and the diaphragm 230, respectively, in a direction away from the back plate 240. In some embodiments, each diaphragm may include additional or fewer corrugations 222 or corrugations 232.

[0043] For example, the diaphragms 220, 230 may include one or more circumferential corrugations for reducing tension and increasing compliance in the first diaphragm 220 and the second diaphragm 230, respectively. In some embodiments, any number of corrugations (e.g., 2, 3, or even more corrugations positioned circumferentially around the longitudinal axis of the sound transducer 200) may be formed in the first diaphragm 220 and the second diaphragm 230. In various embodiments, the height of the corrugations 222 and 232 may be in the range of 0.5 microns to 5 microns (e.g., 0.5 microns, 1 micron, 2 microns, 3 microns, 4 microns, or 5 microns, including all ranges and values ​​therebetween), and the spacing between the diaphragms 220 and 230 may be in the range of 1 micron to 15 microns (e.g., 1 micron, 3 microns, 5 microns, 7 microns, 9 microns, 12 microns, 14 microns, or 15 microns, including all ranges and values ​​therebetween).

[0044] Atmospheric air exerts a force on each of the first diaphragm 220 and the second diaphragm 230 in a direction toward the back plate 240. Because the corrugations 122 and 132 protrude outward from the diaphragms 220 and 230, the atmospheric pressure acting on the corrugations 222 and 232 causes the corrugations to bend axially inward toward the back plate 240 and radially outward. This results in a decrease in diaphragm tension and an increase in compliance, with the compliance increasing in proportion to the relative increase in atmospheric pressure. For example, in some implementations, the acoustic transducer 210 can have an acoustic compliance in the region of the diaphragm 220 and the diaphragm 330 that is approximately twice the acoustic compliance of a similar baseline acoustic transducer that does not include the outwardly protruding corrugations 222 and 232, when the pressure differential between atmospheric pressure and the pressure in the chamber 242 is approximately zero. At a pressure difference of about 100 kPa, the compliance of the acoustic transducer 200 can be increased to more than 8 times the acoustic compliance of the reference acoustic transducer, which corresponds to an increase in acoustic compliance of more than 13 dB. In this way, the transducer 200 has a significantly higher sensitivity to acoustic signals or to measuring pressure changes relative to the reference acoustic transducer.

[0045] In some embodiments, a large pressure differential between the atmospheric pressure acting on each of the first diaphragm 220 and the second diaphragm 230 and the low pressure in the chamber 242 can become large enough to cause the first diaphragm 220 and the second diaphragm 230 to collapse. To prevent this from happening, the second diaphragm 230 (or the first diaphragm 240) can include one or more terminals 259 extending toward the other diaphragm (e.g., through corresponding holes 252 of the back plate 240) to prevent the two diaphragms from collapsing or deforming in a manner that prevents one or more of the diaphragms from functioning as an acoustic sensor (e.g., in its intended manner).

[0046] In some embodiments, the acoustic transducer 200 or any other acoustic transducer described herein can work as a microphone and / or pressure sensing component. In such an embodiment, atmospheric pressure acts on the diaphragm 220 and the diaphragm 230, and the sound pressure acts on one of the diaphragms (e.g., on either the diaphragm 220 or the diaphragm 230). Changes in atmospheric pressure can cause the capacitance value of each of the diaphragms 220 and 230 to change in the same direction that creates a common mode signal (the common mode signal is used for pressure sensing). In some embodiments, the pressure sensor 295 can be used to determine the actual pressure in the chamber 242. This is useful because the pressure in the chamber 242 can change over time (e.g., due to leaks, altitude changes, temperature changes, etc.). In some embodiments, the pressure difference may become too large (e.g., so large that the first diaphragm and the second diaphragm are pushed relative to one or more terminals 259), and the pressure sensor 295 can be used to provide a reference for estimating the acoustic intensity of the sensed acoustic activity. In some embodiments, pressure sensor 295 can be utilized to detect leaks within chamber 242. In some embodiments, pressure sensor 295 can be utilized to detect pressure within chamber 242 in order to determine that transducer 200 is properly manufactured to specific specifications. In some embodiments, pressure sensor 295 can be utilized to detect pressure within chamber 242 and, based on the determined pressure, to adjust or calibrate corresponding circuitry to maximize the quality of the electrical signal created from the sensed acoustic energy.

[0047] Figure 3a An isometric view of a Pirani manometer 300 is depicted in accordance with an exemplary embodiment. Figure 3b A side view of a Pirani pressure gauge 300 according to an exemplary embodiment is depicted. In some embodiments, the Pirani pressure gauge 300 can be used or implemented as Figure 2295. In some embodiments, the Pirani gauge 300 can be mounted to the back plate 240 or a portion of the back plate 240. The Pirani gauge 300 can be electrically connected or electrically coupled to the pressure sensing circuit of the circuit 103. The Pirani gauge 300 includes a first pad 301, a second pad 302, and a micro-beam 303. The first pad 301 is fixed to, coupled to, or disposed on a rigid substrate 350 at a first position. The second pad 302 is fixed to, coupled to, or disposed on the rigid substrate 350 at a second position. The micro-beam 303 has a first end fixed to or connected to the first pad 301 and a second end fixed to or connected to the second pad 302, such that the micro-beam is suspended a distance 330 above the rigid substrate 350. In some embodiments, the rigid substrate 350 is an element capable of and designed to act as a heat sink. In some embodiments, the rigid substrate 350 can be configured to be disposed on a portion of the backplate 240 or coupled to a portion of the backplate 240. In some embodiments, the rigid substrate 350 can be the backplate 240 (e.g., or a portion of the backplate 240). The interior of the first pad 301 (e.g., the portion connected to the microbeam 303) is separated from the interior of the second pad 302 (e.g., the portion connected to the microbeam 303) by a length l. The length l is also the length of the microbeam 303. In some embodiments, the width w and thickness t of the microbeam 303 are constant throughout the microbeam 303.

[0048] It will be understood that although the first pad 301 and the second pad 302 are shown as three-dimensional rectangles, in other embodiments, the first pad 301 and the second pad 302 can have any shape that allows the pad 301 and the pad 302 to be connected to the rigid substrate 350 and also connected to the microbeam 303 so that the microbeam 303 is suspended a distance 330 above the rigid substrate 350. In some embodiments, the distance 330 that the microbeam 303 is suspended above the rigid substrate 350 can be varied and designed for a particular application. In some embodiments, the first pad 301, the second pad 302, and the microbeam 303 are composed of conductive elements. In some embodiments, the first pad 301 is electrically connected to the circuit 103, and the second pad 302 is also electrically connected to the circuit 103.

[0049] The Pirani manometer 300 operates by providing a current or voltage to the first pad 301 or the second pad 302 and determining the amount of resistance present in the microbeam 303. For example, in some embodiments, the microbeam 303 acts as a resistor, and when a current and / or voltage is applied from the circuit 103 via the pads 302 and the pads 301, the microbeam 303 exhibits a resistance that can be determined by the pressure sensing circuit within the circuit 103. The resistance of the microbeam 303 is based on the width w, length l, thickness t, and material of the microbeam 303. However, due to the thermal conduction H of the gas between the microbeam 303 and the rigid substrate (e.g., the rigid substrate acts as a heat sink), the temperature and resistance of the beam vary with pressure. Therefore, since the width w, length l, thickness t, and material of the microbeam 303 are known, the pressure surrounding the Pirani manometer can be estimated based on the sensed resistance and comparing the sensed resistance with its nominal value or initial value at atmospheric pressure. In some embodiments, a Pirani manometer can be provided on the backplate. In some embodiments, as described below with reference to Fig.10a As explained, one or more of the backplate and the diaphragm may function as a Pirani gauge.

[0050] FIG. 4a depicts a top cross-sectional view of transducer 400 according to an exemplary embodiment. FIG. 4b depicts an enlarged view of a portion of the transducer of FIG. 4a. The top cross-sectional view of transducer 400 depicts a back plate 401 of the transducer. That is, for demonstration purposes, the top cross-sectional view of transducer 400 depicts a top view of the transducer without a second or top diaphragm. FIG. 4b depicts an enlarged portion 450 of transducer 400 of FIG. 4a according to an exemplary embodiment. More specifically, the enlarged portion 450 of transducer 400 depicts a Pirani pressure gauge disposed on back plate 401.

[0051] Back plate 401 includes one or more holes 452. In some embodiments, the one or more holes may be similar to Figure 2 In some embodiments, the back plate 401 is similar to one or more holes 252 referred to in the discussion of Figure 2 The transducer 400 includes a Pirani pressure gauge disposed on the back plate 401. In some embodiments, the Pirani pressure gauge may be similar to that described in reference to FIG. Figure 3a and Figure 3bThe Pirani manometer discussed. In some embodiments, the Pirani manometer can be disposed on the backplate at different locations or alternative locations on the backplate 401 and can be formed using the same layers used to form the backplate. The Pirani manometer includes a microbeam resistor 403 (e.g., a conductive strip configured to carry current) electrically connected between a first terminal 402 and a second terminal 404. The first terminal 402 and the second terminal 404 are configured or designed so that the microbeam resistor 403 can be connected to a pressure sensing circuit.

[0052] Figure 5 A pressure sensing circuit 500 is depicted according to an exemplary embodiment. In some embodiments, the pressure sensing circuit 500 can be used with reference to Figure 1 It will be appreciated that the pressure sensing circuit 500 is merely an example of a circuit that can be integrated with a Pirani pressure gauge (such as that described in reference Figure 3a , Figure 3b 4a and 4b). In alternative embodiments, as described above, the pressure sensing circuit 500 can include any type of circuit capable of measuring, determining, or detecting the resistance of a Pirani gauge disposed within the chamber 242 of the transducer.

[0053] The pressure sensing circuit 500 includes a current source 501, a resistance detection circuit 502, and an amplifier circuit (e.g., or a differential circuit) 503. In some embodiments, the current source 501 can be a constant current source. In some embodiments, the current source 501 can include any current source configured to provide current at a set or known rate.

[0054] The resistance detection circuit 502 is configured to receive current from the current source 501 and provide an output indicating the resistance of a particular resistive element (e.g., the resistance of a Pirani manometer). In some embodiments, the resistance detection circuit 502 includes a Wheatstone bridge. Alternatively or additionally, other components or circuits may be included in the resistance detection circuit 502. For example, in some embodiments, the resistance detection circuit 502 may include a voltage divider.

[0055] The current source 501 may have a first terminal connected to ground and an output terminal 510 connected to an input terminal 520 of a Wheatstone bridge. The Wheatstone bridge includes a first resistor R connected between the input terminal 520 and the first output terminal 521 of the Wheatstone bridge 502. 1 The Wheatstone bridge 502 includes a second resistor R connected between a first output terminal 521 of the Wheatstone bridge 502 and ground (eg, or a second known voltage). 2The Wheatstone bridge 502 has a Pirani pressure gauge R connected between an input terminal 520 and a second output terminal 522 of the Wheatstone bridge 502. Pirani (For example, Figure 3a and Figure 3b For example, in some embodiments, the first pad or electrical contact of the Pirani manometer can be connected to the input terminal 520 of the Wheatstone bridge 502, and the second pad or electrical contact of the Pirani manometer can be connected to the second output terminal 522 of the Wheatstone bridge 502. The Wheatstone bridge 502 also includes a third resistor R connected between the second output terminal 522 of the Wheatstone bridge 502 and ground. 3 .

[0056] The first output terminal 521 of the Wheatstone bridge 502 is connected to the first input terminal 531 of the amplifier circuit 503. The second output terminal 522 of the Wheatstone bridge 502 is connected to the second input terminal 532 of the amplifier circuit 503. In some embodiments, the first input terminal 531 of the amplifier circuit 503 is the negative terminal of the operational amplifier 590, and the second input terminal 532 of the amplifier circuit 503 is the positive terminal of the operational amplifier 590. In some embodiments, the polarity of the terminals can be swapped. In some embodiments, the pressure sensing circuit 500 can have a fourth resistor 560 connecting the second input terminal 532 to ground. In some embodiments, the pressure sensing circuit 500 can have a fifth resistor 562 connecting the second input terminal 532 to the second output terminal 522. In some embodiments, the pressure sensing circuit 500 can have a sixth resistor 561 connecting the first input terminal 531 to the second output terminal 521. In some embodiments, the pressure sensing circuit 500 can have a seventh resistor 568 connecting the first input terminal 531 to the output terminal 599 of the amplifier circuit 503. In some embodiments, additional or fewer resistors can be used. In some embodiments, the amplifier circuit 503 can include additional or fewer operational amplifiers, transistors, or transistors that allow the Pirani resistor R to be determined. Pirani Various other components of the resistor. In some embodiments, one or more of the resistors can be formed on a micro-electromechanical system (MEMS) or integrated circuit dye. In some embodiments, the current source outputs a current of + / - 20% of 600 microamps.

[0057] Output terminal 599 may be connected to a processor or ASIC so that the output signal of pressure sensing circuit 500 may be read or detected to determine the Pirani resistor R PiraniThe resistance of the Pirani manometer is determined by the current source 501. For example, as explained above, the current source 501 will provide a current to the Wheatstone bridge 502, thereby providing a current flowing through the Pirani resistor R Pirani The current will affect the Pirani resistor R Pirani The temperature will affect the Pirani resistor R Pirani However, the current affects the Pirani resistor R Pirani The amount of effective resistance will depend on the pressure of the air surrounding the Pirani gauge (e.g., the pressure in the chamber), because the amount of heat that the Pirani resistor can transfer to a heat sink (e.g., or lose in the chamber) depends on the pressure in the chamber. Therefore, by measuring the Pirani resistor R Pirani The amount of resistance change (e.g., via measuring or monitoring the voltage imbalance of the two output terminals 521 and 522 of the Wheatstone bridge 502) will allow the processor or ASIC (e.g., circuit 103) to determine or estimate the pressure within the chamber. In some embodiments, the processor can first determine the Pirani resistor R Pirani resistance, and then based on all other components (e.g., R 1 , R 2 , R 3 The pressure can be calculated, looked up or otherwise estimated from known values ​​of Figure 5 This is shown by way of example only, and other methods or devices may be used to measure the Pirani resistor R Pirani resistance in order to determine or estimate the pressure within chamber 242.

[0058] Now, in general, refer to Figure 6 and Figure 7 , Figure 6 An integrated resonator 600 is depicted according to an example embodiment. Figure 7 An integrated resonator 700 is depicted according to an exemplary embodiment. In some embodiments, the integrated resonator 600 or the integrated resonator 700 may be the above Figure 1 and Figure 2, and is disposed on the backplate 240 or a portion of the backplate 240. The integrated resonator 600 includes a plurality of springs 650a to 650e and a surface 690 (e.g., a resonant member), wherein the plurality of springs 650a to 650e are connected to the backplate at a first end and to the outer edge of the surface 690 at a second end, wherein the plurality of springs suspend the surface a distance 681 above or below the counter electrode. The springs 650a to 650e are configured to lift or suspend the surface above the substrate or the counter electrode and provide elasticity to the surface so that the surface 690 can swing, bounce, or otherwise have a resonant frequency. In some embodiments, the springs 650a to 650e (or a single spring) can be configured to suspend the surface within an opening of the substrate or the backplate so that the surface 690 (e.g., the resonant member) can be suspended within the same plane in which the backplate extends. The exact resonant frequency of a particular integrated resonator can depend on the elastic strength of the material of springs 650a-650e, the surface area of ​​surface 690, the number of springs 650a-650e, and the pressure of the air surrounding surface 690. The exact composition of the components of the integrated resonator can depend on the particular application in which the integrated resonator will be deployed (e.g., the set pressure or manufacturing pressure of a particular chamber). In some embodiments, the integrated resonator 600 can be made of silicon nitride.

[0059] Now, in general, refer to Figure 7 , the integrated resonator 700 is similar to the reference Figure 6The integrated resonator 600 described. That is, the integrated resonator 700 includes a plurality of springs 750a to 750c, which are designed to suspend the surface 790 a distance 785 above or below the counter electrode (e.g., or other conductive substrate). For example, the integrated resonator 700 includes a first spring 750a, which is connected to the back plate at a first end 751a and connected to a first portion of the outer edge of the surface 790 at a second end 752a. The integrated resonator 700 also includes a second spring 750b, which is connected to the back plate at a first end 751b and connected to a second portion of the outer edge of the surface 790 at a second end 752b. The integrated resonator 700 also includes a third spring 750c, which is connected to the back plate at a first end 751c and connected to a third portion of the outer edge of the surface 790 at a second end 752c. One or more of the springs 750a-750c can be electrically connected to the circuit 103 (e.g., a pressure sensing circuit) via the end connected to the backplate so that the resonator can receive a drive signal on at least one of the first ends 751a-751c. In some embodiments, the corresponding backplate can have an opening defined in the corresponding backplate so that the first ends 750a-750c can be coupled to or coupled to a corresponding portion of the opening, and the resonant member (surface 790) can be suspended in the same plane that the backplate extends. In some embodiments, the surface 690 or the surface 790 can be suspended in a plane above or below the plane that the backplate extends. In some embodiments, additional or fewer springs 750a-750c can be used or implemented so that the integrated resonator 700 or the integrated resonator 600 is designed to have a specific resonant frequency at an expected pressure or estimated pressure (e.g., an expected pressure or estimated pressure within the chamber 240). In some embodiments, the resonator 700 can be made of silicon nitride, polysilicon, or a multilayer stack of one or more layers including silicon nitride and polysilicon. In some embodiments, the backplate can be made of silicon nitride, polysilicon, or a multilayer stack of one or more layers including silicon nitride and polysilicon. In some embodiments, the resonator is formed within the backplate.

[0060] The integrated resonator 700 may have Figure 6 The integrated resonator 600 has different resonant frequencies. It will be understood that Figure 6 and Figure 7An example of a specific embodiment of an example integrated resonator is shown. The design, shape or composition of the material (e.g., spring or surface) can be changed according to the precise application and the estimated pressure in the chamber. For example, resonator 600 or resonator 700 can be designed to resonate in the range of 20kHz to 150kHz. In some embodiments, each of spring 650 and spring 750 is connected to circuit 103 so that the circuit can provide a signal to integrated resonator 600 or integrated resonator 700 and / or to the electrode. In some embodiments, integrated resonator 700 can have one or more supports extending from one or more portions of surface 690 or surface 790 toward the back plate to provide support for the surface.

[0061] Figure 8a An example of a pressure sensing circuit 800 according to an exemplary embodiment is depicted. In some embodiments, the pressure sensing circuit 800 can be used with reference to Figure 1 The circuit 103 discussed is integrated together. The pressure sensing circuit 800 includes a swept frequency source 801, a resonator circuit 802, and a trans-impedance amplifier circuit (trans-impedance amplifier) ​​803. In some embodiments, the pressure sensing circuit 800 may also include an analog-to-digital converter (ADC) 804 connected to the output of the trans-impedance amplifier circuit 803. In some embodiments, the output of the analog-to-digital converter 804 can be received or accessed or otherwise obtained by a processor or other processing device, and the processor or other processing device is configured to determine the phase or resonant frequency of the resonator circuit 802 (for example, thereby determining the resonant frequency of an integrated resonator that can be used as at least a part of the resonator circuit 802), for example, during operation 865. It should be understood that the pressure sensing circuit 800 is merely a device that can be used with, for example, a reference circuit. Figure 6 and Figure 7 An example of a pressure sensing circuit 800 used in conjunction with the resonators discussed above. In alternative embodiments, as discussed above, the pressure sensing circuit 800 may include any type of circuitry capable of measuring, determining, or detecting the resonant frequency of a resonant device or element.

[0062] The output of the swept frequency source 801 is connected to the resonator circuit 802. In some embodiments, the swept frequency source 801 can include any device configured to generate a swept frequency output signal. In some embodiments, the swept frequency source 801 is configured to generate a signal having a first frequency and sweep the signal to a second frequency in a continuous manner over a period of time. In some embodiments, the continuous manner is linear.

[0063] Resonator circuit 802 is an electrical representation of an integrated resonator that includes, for example, an inductive element 820, a capacitive element 830, and a resistive element 840 wired in series. In some implementations, the represented values ​​of electrical elements 820, 830, or 840, or their wiring configuration, can depend on the precise mechanical or electromechanical configuration of the particular integrated resonator being implemented or applied.

[0064] In some embodiments, the resonator circuit 800 includes a backplate (e.g., 240). That is, in some embodiments, a signal from a swept frequency source 801 can be applied to a first electrode on the backplate so that the backplate resonates at a specific frequency, which can then be monitored and determined. That is, in some embodiments, the backplate 240 or a portion thereof contained in the chamber has its own resonant frequency. A drive signal can be applied to the backplate via an electrical pad or terminal on the backplate and the drive signal can be monitored to determine the resonance of the backplate and thereby the pressure in the chamber. In some embodiments, unlike the resonance of the first diaphragm or the second diaphragm or the transducer, the backplate is independent of the acoustics surrounding the transducer and can therefore be used to accurately measure the pressure in the chamber.

[0065] The output of the resonator circuit 802 (e.g., an integrated resonator) is connected to the input of the transimpedance amplifier 803. In some embodiments, the input of the transimpedance amplifier 803 is the negative terminal of the operational amplifier 835. In some embodiments, the positive terminal of the operational amplifier 835 can be connected to ground. The resistor 831 can be connected between the negative terminal of the operational amplifier 835 and the output terminal of the operational amplifier 835. Additionally or alternatively, the transimpedance amplifier 803 can include additional or fewer resistors, transistors, or operational amplifiers.

[0066] The transimpedance amplifier 803 is configured to receive a signal from the resonator circuit 802 and amplify the signal. The amplified signal may then be processed or otherwise analyzed to determine the resonant frequency of the resonator circuit 802 (e.g., thereby determining the resonant frequency of the integrated resonator 600 or the integrated resonator 700). The processor may then use the determined resonant frequency of the integrated resonator 600 or the integrated resonator 700 to determine the pressure around the integrated resonator 600 or the integrated resonator 700. In some embodiments, the processor (e.g., or ASIC) may use a known or stored frequency response graph or a function of the frequency response of the integrated resonator (e.g., 600 or 700) and the surrounding pressure to determine the pressure within the chamber. For example, the circuit 103 may include a function, lookup table, or graph (e.g., stored in a memory) of the resonant frequency of a particular integrated resonator (e.g., 600 or 700) (or a particular backplate) at different pressures to determine the pressure around the integrated resonator (e.g., 600 or 700) (or backplate) based on the determined resonant frequency determined from the amplified signal. In some embodiments, the processor can determine or estimate the pressure based on the amplified signal by determining the phase or quality factor of the amplified signal. For example, the processor can determine the pressure around the integrated resonator using known or stored phase response or quality factor information at different pressures.

[0067] In some embodiments, the pressure sensing circuit 800 can include an analog-to-digital converter configured to convert the amplified signal received from the transimpedance amplifier 803 into a digital format before the processor or other processing device determines the resonant frequency of the resonator circuit 802. In some embodiments, the resonant frequency of the resonator circuit 802 can be determined in the analog domain or the digital domain.

[0068] Figure 8b Another example of a pressure sensing circuit 1200 according to an exemplary embodiment is depicted. In some embodiments, the pressure sensing circuit 1200 can be used with reference to Figure 1 The pressure sensing circuit 1000 includes an oscillator circuit 1201, a resonator circuit 802, a current amplitude detection circuit 1203, a differentiator circuit 1204, and a comparator circuit 1205. In some embodiments, the resonator circuit 802 is integrated with a reference circuit 1205. Figure 8a The resonator circuit 802 described is similar or identical.

[0069] The resonator circuit 802 is coupled between the oscillating circuit 1201 and the current amplitude detection circuit 1202. In some embodiments, the oscillating circuit 1201 is a voltage-controlled oscillator. In some embodiments, the oscillating circuit 1201 may include any circuit or element configured to selectively generate an oscillating electrical signal at various frequencies. The output of the current amplitude detection circuit 1202 is coupled to the input of the differentiator circuit 1204, and the output of the differentiator circuit 1204 is coupled to the input of the comparator circuit 1205. The output of the comparator circuit 1205 is connected to the output terminal 1299 of the pressure sensing circuit 1200 and the input of the oscillating circuit 1201. In some embodiments, the differentiator circuit 1204 may be or may include any circuit configured to generate an output signal that is a first-order derivative of an input signal. In some embodiments, the differentiator circuit 1204 may be implemented via hardware, via software of a processor executing specific instructions, or a combination thereof. In some embodiments, the comparator circuit 1205 can be any circuit configured to compare two voltages or currents and output a digital signal indicating which of the two voltages or currents is larger. In some embodiments, the comparator circuit 1205 can be implemented via hardware, software via a processor executing specific instructions, or a combination thereof. In some embodiments, the current amplitude detection circuit 1202 can be any circuit configured to detect the current flowing through the resonator circuit 802 when driven by the oscillator 1201. In some embodiments, when the oscillator is started at a certain (e.g., predetermined) initial frequency (which is determined by the initial value of the output voltage at the terminal 1299), the current amplitude detection circuit 1202 detects the initial current amplitude. The differentiator circuit 1204 determines the time derivative of the detected current amplitude and outputs the value to the logic comparator circuit 1205. Initially, since there is no previous value, the time derivative of the current amplitude can be positive. Receiving a positive value at the input of the logic comparator circuit 1205 can cause the logic comparator circuit 1205 to increase the voltage at its output by a predetermined increment. The increased voltage at output terminal 1299 and the input of oscillator 1201 causes oscillator 1201 to increase its frequency by a predetermined amount. At this point, the circuit loop completes another cycle to determine whether the current amplitude in the resonator is higher or lower than the previous value. If the current amplitude is higher, the circuit responds by further increasing the voltage at output terminal 1299 and thus increasing the oscillator frequency. If the current amplitude is lower, the circuit responds by decreasing the voltage at output terminal 1299 and thus decreasing the oscillator frequency. The operation of circuit 1200 is that of a hill-climbing algorithm to find and maintain an oscillator frequency at which the current amplitude in resonator circuit 802 is maximum.The oscillator frequency coincides with the resonant frequency of the resonator circuit 802, and the voltage on the output terminal 1299 can be used as an indirect measure of the resonator frequency.

[0070] The pressure sensing circuit 1200 determines the pressure within a chamber (e.g., around a resonator of the resonator circuit 802 disposed within the chamber) by determining the resonant frequency of the resonator circuit 802 and providing an electrical output representative of the resonant frequency. The electrical output may be compared to a previously determined stored or known value that relates the electrical output level at the output terminal 1299 to the pressure around the integrated resonator.

[0071] Figure 8c Another example of a pressure sensing circuit 1100 according to an exemplary embodiment is depicted. In some embodiments, the pressure sensing circuit 1100 can be used with reference to Figure 1 The pressure sensing circuit 1100 includes a voltage source 1101, an amplifier circuit 1102, a resonator circuit 802, and a phase-locked loop (PLL) circuit 1103. In some embodiments, the resonator circuit 802 is integrated with a reference Figure 8a The resonator circuit 802 described is similar or identical.

[0072] In some embodiments, the voltage source 1101 is coupled to an input of the amplifier circuit 1102. In some embodiments, the amplifier circuit 1102 includes an operational amplifier. In some embodiments, the output of the voltage source 1101 is coupled to a first (e.g., positive or negative) input terminal of the operational amplifier. The resonator circuit 802 is coupled between a second input terminal of the operational amplifier and the output of the operational amplifier. The output of the operational amplifier is also coupled to an input of the PLL circuit 1103.

[0073] In some embodiments, the PLL circuit 1103 includes a phase comparator circuit 1130, a filter circuit 1131 connected to an output of the phase comparator circuit 1130, and an oscillator circuit 1132. The phase comparator circuit 1130 has an input that is also an input of the PLL circuit 1103, and an output connected to an input of the filter circuit 1131. The oscillator circuit 1132 may have an output connected to an output terminal 1199 of the pressure sensing circuit 1110 and an input connected to an output of the filter circuit 1131. In some embodiments, the oscillator circuit 1132 is similar to the oscillator circuit 1132 described above with reference to FIG. Figure 8bThe oscillator circuit 1201 described above is similar or identical to the oscillator circuit 1201 described above. It should be understood that the PLL circuit 1103 is only one example of a phase-locked loop circuit, and in other embodiments, other forms of PLL circuits may be deployed or used. In some embodiments, the PLL circuit 1103 may be an analog or digital circuit provided on the circuit 103 (e.g., an ASIC). In some embodiments, the PLL circuit 1103 may be implemented using software running on a processor (e.g., a processor of an ASIC).

[0074] The pressure sensing circuit 1100 determines the pressure within the chamber (e.g., around the resonator of the resonator circuit 802 disposed within the chamber) by matching the frequency of the voltage controlled oscillator 1132 to the frequency of a free running oscillator formed by the operational amplifier 1102 and the resonator. For the pressure sensing circuit 1200, the control voltage of the voltage controlled oscillator 1132 can be an indirect measure of the resonant frequency of the resonator circuit 802, and an electrical output representative of the resonant frequency can be provided at the output terminal 1199. The electrical output can be compared to a previously determined stored or known value that relates the electrical output level at the output terminal 1199 to the pressure around the integrated resonator.

[0075] Figure 8d A graph depicting a resonant response characteristic of an integrated resonator according to an exemplary embodiment is depicted. The graph includes a y-axis representing the resonant frequency of a particular integrated resonator and an x-axis representing the pressure surrounding the integrated resonator (e.g., the pressure within a chamber). The graph includes a signal profile 892 of a particular resonant frequency response characteristic of a particular integrated resonator. In this manner, once the resonant frequency of an integrated resonator within a chamber is determined using a pressure sensing circuit, the graph or a function of the signal profile 892 may then be used to determine or interpolate the pressure of the chamber.

[0076] Figure 8e A graph depicting a quality factor characteristic of an integrated resonator according to an exemplary embodiment is depicted. The graph includes a y-axis representing the quality factor of a particular integrated resonator and an x-axis representing the pressure surrounding the integrated resonator (e.g., the pressure within a chamber). The graph includes a signal profile 894 of a particular resonant frequency response characteristic of the particular integrated resonator. In this manner, once the quality factor of an integrated resonator within a chamber is determined using a pressure sensing circuit, the graph or a function of the signal profile 894 may then be used to determine or interpolate the pressure of the chamber.

[0077] Figure 8f depicts several examples A to D of possible integrated resonator designs, and Figure 8gCorresponding resonant frequency response characteristics (without air loading) versus tensile membrane stress 898 are shown for several examples of possible integrated resonator designs.

[0078] FIG. 9a depicts a top cross-sectional view of transducer 900 in accordance with an exemplary embodiment. The top cross-sectional view of transducer 900 depicts a backplate 901 of the transducer. That is, the top cross-sectional view of transducer 900 depicts a top view of the transducer without a second or top diaphragm. FIG. 9b depicts an enlarged portion 950 of transducer 900 of FIG. 9a in accordance with an exemplary embodiment. More specifically, enlarged portion 950 of transducer 900 depicts an integrated resonator disposed on backplate 901. In some embodiments, the integrated resonator can be similar to one or more of the integrated resonators described herein.

[0079] The back plate 901 includes one or more holes 952. In some embodiments, the one or more holes may be similar to Figure 2 In some embodiments, the back plate 901 is similar to the one or more holes 252 referenced in the discussion of Figure 2 9b . The transducer 900 includes an integrated resonator disposed on the backplate 901 , as depicted in FIG. 9b . In some embodiments, the integrated resonator can be disposed on the backplate at different or alternative locations on the backplate 901 . The integrated resonator includes one or more springs 920 and a surface 909 . In some embodiments, the surface 909 can include a hole 922 that allows the top diaphragm to have a post or support extending therethrough so as to prevent the top diaphragm from collapsing onto the surface 909 or otherwise contacting the surface 909 . In some embodiments, the hole 922 is located at the center of the surface 909 . In some embodiments, the surface 909 can also have a plurality of release holes 921 that are configured to allow for proper removal of a sacrificial layer around the integrated resonator during manufacturing. The integrated resonator can be electrically connected between a first terminal 902 and a second terminal 904 of the transducer 900 . The first terminal 902 and the second terminal 904 are designed so that the integrated resonator 900 can be connected to a pressure sensing circuit. In some embodiments, the first terminal 902 can be electrically connected to one or more electrodes on the surface 909 (or the surface 909 itself), and the second terminal 904 can be connected to one or more counter electrodes formed above or below the surface 909. In some embodiments, the surface 909 can be made of the same material or layer as the back plate, so that the surface 909 extends along the same plane as the back plate. In some embodiments, the electrode layer of the top diaphragm and / or the bottom diaphragm of the microphone can be used to form one or more counter electrodes above and / or below the surface 909.

[0080] Now, in general, refer to Fig.10a , Fig.10a 1 is another example of a pressure sensing circuit 1000 of a transducer according to an exemplary embodiment. The pressure sensing circuit 1000 is configured to use the backplate 1002 of the transducer 1001 to sense or determine the pressure within the chamber 1003. In some embodiments, the backplate 1002 can be used as a Pirani pressure gauge. That is, in some embodiments, the bottom (e.g., first) diaphragm 1050 can be used as a heat sink that allows the electrodes of the backplate to be used as a Pirani pressure gauge.

[0081] In some embodiments, pressure sensing circuit 1000 includes bias circuit 1090 configured to selectively apply (e.g., via switch 1050) a voltage bias 1040 or a current source 1041 to an electrode on backplate 1002 via first connection 1021. In some embodiments, switch includes one or more transistors or other static or dynamic electronic components configured to selectively switch between voltage bias 1040 and current source 1041. In some embodiments, voltage bias 1040 is applied to backplate 1002 when transducer 1001 is in an operating mode for sensing acoustic signals. That is, in the operating mode, a DC bias voltage is applied to backplate 1002, and the first capacitance and the second capacitance can be monitored via first amplifier 1078 and second amplifier 1088, respectively, to generate an electrical signal indicative of acoustic energy sensed via transducer 1001.

[0082] In some embodiments, during a test mode, current source 1041 is selectively applied to backplate 1002. The test mode can be configured to determine or measure the pressure within chamber 1003. Current source 1041 can be similar to Figure 5 The current source referred to in , and can be configured to apply a current (e.g., a constant current) to the back plate. As the current passes through the first electrode 1021 of the back plate 1002 to the second electrode or contact 1022, the back plate 1002 may begin to heat up. Similar to the reference Figure 5 As discussed, the heat causes the effective resistance of the backplate 1002 to change via thermal conduction between the backplate 1002 (e.g., acting as a microbeam) and the first diaphragm 1050 (e.g., acting as a heat sink). The resistance detection circuit 1099 can then be used to monitor the effective resistance of the backplate 1002 (e.g., the actual resistance at a set time) to indicate the pressure in the chamber 1003. In some embodiments, the resistance detection circuit 1099 can include a Wheatstone bridge (similar to Figure 5 Referenced Wheatstone bridge), voltage divider, or other circuit configured to indicate the measured resistance of a resistor.

[0083] Fig.10b A top cross-sectional view of a transducer 1051 according to an exemplary embodiment is depicted. The top cross-sectional view of the transducer 1051 depicts a backplate 1052 of the transducer 1051. That is, the top cross-sectional view of the transducer 1051 depicts a top view of the transducer without a second or top diaphragm. The backplate 1052 can be electrically connected between a first terminal 1053 and a second terminal 1054 of the transducer 1051. The first terminal 1053 and the second terminal 1054 are designed so that the backplate can be connected to a pressure sensing circuit. In some embodiments, similar to the reference Fig.10a As depicted, backplate 1052 is electrically connected to the pressure sensing circuitry.

[0084] In some embodiments, the Pirani gauge and / or resonator can be formed in, on, or as part of a back plate and / or one of the diaphragms. In some embodiments, the Pirani gauge and / or resonator can be formed with the back plate and / or the top diaphragm layer or the bottom diaphragm layer as a single element or a combination of multiple different elements.

[0085] Embodiments described herein generally relate to systems and methods for detecting and / or monitoring pressure within a sealed chamber of an acoustic transducer. Specifically, some embodiments described herein relate to detecting pressure within a sealed chamber defined by at least a first diaphragm and provided with at least a portion of a backplate in order to monitor the sensitivity and accuracy or noise of a microphone assembly. In one implementation, an acoustic transducer includes a microelectromechanical system (MEMS) die, the microelectromechanical system die including: an at least partially vacuum sealed chamber, which is partially defined by a first diaphragm; a backplate, the backplate being disposed within the chamber, wherein the first diaphragm is movable relative to the backplate in response to acoustic pressure; and a pressure sensor, the pressure sensor being coupled to the backplate and configured to sense pressure within the chamber.

[0086] In some embodiments, at least a portion of the vacuum sealed chamber is also defined by a second diaphragm spaced apart from the first diaphragm. In some embodiments, the backplate defines at least one hole passing through the backplate. In some embodiments, the acoustic transducer further comprises a first terminal electrically coupled to a first portion of the backplate and a second terminal electrically coupled to a second portion of the backplate. In some embodiments, the pressure sensor comprises a Pirani pressure gauge formed on the backplate. In some embodiments, the Pirani pressure gauge comprises a microbeam resistor, a first pad formed on the backplate, and a second pad formed on the backplate, wherein the microbeam resistor is connected to the first pad and the second pad and is suspended above or below the heat sink. In some embodiments, the first pad is electrically coupled to the first terminal, and the second pad is electrically coupled to the second terminal. In some embodiments, wherein, the microbeam resistor is configured to transmit a bias current from the first terminal to the second terminal.

[0087] In some embodiments, the pressure sensor includes an integrated resonator coupled to a backplate. In some embodiments, the integrated resonator includes a spring and a resonant member, wherein the spring is coupled to the backplate and to an outer edge of the resonant member, wherein the spring suspends the surface relative to the backplate. In some embodiments, the integrated resonator further includes: a first spring coupled to the backplate at a first end and to a first portion of the outer edge of the surface; a second spring coupled to the backplate at a first end and to a second portion of the outer edge of the surface; and a third spring coupled to the backplate at a first end and to a third portion of the outer edge of the surface.

[0088] In another implementation, a microphone assembly includes a housing, an acoustic transducer disposed within the housing, and an integrated circuit disposed within the housing. The acoustic transducer includes: an at least partially vacuum-sealed chamber, the chamber being partially defined by a first diaphragm; a backplate disposed within the chamber, wherein the first diaphragm is movable relative to the backplate in response to acoustic pressure; and a pressure sensor coupled to the diaphragm and configured to sense pressure within the chamber. The integrated circuit includes a pressure sensing circuit connected to the pressure sensor and configured to process an electrical signal from the pressure sensor to generate output data indicative of pressure.

[0089] In some embodiments, the at least partially vacuum sealed chamber is further defined by a second diaphragm spaced apart from the first diaphragm. In some embodiments, the backplate defines at least one hole through the backplate. In some embodiments, the pressure sensor comprises a Pirani pressure gauge coupled to the backplate, the Pirani pressure gauge comprising a microbeam resistor, a first pad formed on the backplate, and a second pad formed on the backplate, wherein the microbeam resistor is connected to the first pad and the second pad and is suspended relative to the backplate. In some embodiments, the pressure sensing circuit comprises a Wheatstone bridge and a differential amplifier, the microbeam resistor being connected in a first branch of the Wheatstone bridge. In some embodiments, the pressure sensor comprises an integrated resonator coupled to the backplate, the integrated resonator comprising a spring and a resonant member, wherein the spring is connected to the backplate and to an outer edge of the resonant member, wherein the spring suspends the resonant member relative to the backplate. In some embodiments, the pressure sensing circuit comprises a swept frequency generator and a transimpedance amplifier, the output of the swept frequency generator being connected to the input of the integrated resonator, and the transimpedance amplifier being connected to the output of the integrated resonator. In some embodiments, the pressure sensing circuit further comprises an analog-to-digital converter connected to the output of the transimpedance amplifier, and the integrated circuit further comprises a processor configured to receive a signal from the analog-to-digital converter and detect a phase of the signal and a frequency indicative of a resonant frequency of the integrated resonator. In some embodiments, the integrated resonator has a resonant frequency that depends on the pressure in the chamber. In some embodiments, the resonant frequency of the integrated resonator ranges between 50 kilohertz (kHz) and 100 kHz.

[0090] In another implementation, a microphone assembly includes a housing, an acoustic transducer disposed within the housing, and an integrated circuit disposed within the housing. The acoustic transducer includes: an at least partially vacuum-sealed chamber, the chamber being partially defined by a first diaphragm; a backplate disposed within the chamber, wherein the first diaphragm is movable relative to the backplate in response to acoustic pressure. The backplate is configured to sense pressure within the chamber. The integrated circuit is connected to the backplate and includes a bias circuit configured to selectively apply a bias voltage to the backplate or to apply a sensing circuit to the backplate.

Claims

1. An acoustic transducer, comprising: an at least partially vacuum sealed chamber, the at least partially vacuum sealed chamber being defined in part by a first diaphragm; a back plate disposed at least partially within the at least partially vacuum sealed chamber, wherein the first diaphragm is movable relative to the back plate in response to acoustic pressure; as well as A pressure sensor is coupled to the back plate or the first diaphragm and is configured to sense pressure within the at least partially vacuum sealed chamber.

2. The acoustic transducer according to claim 1, wherein: The at least partially vacuum sealed chamber is also defined by a second diaphragm spaced apart from the first diaphragm.

3. The acoustic transducer according to claim 2, wherein: The acoustic transducer further includes a first terminal and a second terminal, wherein the first terminal is electrically coupled to the back plate or a first portion of the first diaphragm, and the second terminal is electrically coupled to the back plate or a second portion of the first diaphragm.

4. The acoustic transducer according to claim 3, wherein: The pressure sensor includes a Pirani pressure gauge formed on the back plate or the first diaphragm.

5. The acoustic transducer according to claim 4, wherein: The Pirani gauge includes a microbeam resistor electrically coupled to the first terminal and the second terminal, wherein the microbeam resistor is suspended relative to the backplate or the first diaphragm.

6. The acoustic transducer according to claim 5, wherein: The microbeam resistor is configured to transmit a bias current from the first terminal to the second terminal.

7. The acoustic transducer according to claim 3, wherein: The pressure sensor includes an integrated resonator coupled to the backplate or the first diaphragm.

8. The acoustic transducer according to claim 7, wherein: The integrated resonator includes a spring and a resonant member, wherein the spring is connected to the backplate or the first diaphragm and to an edge of the resonant member, wherein the spring suspends the resonant member relative to the backplate or the first diaphragm.

9. The acoustic transducer according to claim 8, wherein: The spring comprises: a first spring interconnecting the backplate or the first diaphragm with a first portion of the resonant member; a second spring interconnecting the backplate or the first diaphragm with a second portion of the resonant member; and A third spring interconnects the back plate or the first diaphragm with a third portion of the resonant member.

10. The acoustic transducer according to claim 9, wherein: The back plate defines an opening, wherein the resonating member is suspended within the opening.

11. A microphone assembly, comprising: case; An acoustic transducer, the acoustic transducer being disposed in the housing and comprising: an at least partially vacuum sealed chamber, the at least partially vacuum sealed chamber being defined in part by a first diaphragm; a back plate disposed at least partially within the at least partially vacuum sealed chamber, wherein the first diaphragm is movable relative to the back plate in response to acoustic pressure; and a pressure sensor coupled to the backing plate and located within the at least partially vacuum sealed chamber; and An integrated circuit is disposed within the housing, the integrated circuit including a pressure sensing circuit connected to the pressure sensor and configured to process an electrical signal from the pressure sensor to generate output data indicative of pressure.

12. The microphone assembly of claim 11, wherein: The at least partially vacuum sealed chamber is further defined by a second diaphragm spaced apart from the first diaphragm, wherein the back plate defines at least one aperture therethrough.

13. The microphone assembly of claim 12, wherein: The pressure sensor includes a Pirani pressure gauge connected to the back plate, the Pirani pressure gauge including a microbeam resistor, a first pad formed on the back plate, and a second pad formed on the back plate, wherein the microbeam resistor is connected to the first pad and the second pad and is suspended relative to the back plate.

14. The microphone assembly of claim 13, wherein: The pressure sensing circuit includes a Wheatstone bridge and a differential amplifier, and the micro-beam resistor is connected in a first branch of the Wheatstone bridge.

15. The microphone assembly of claim 12, wherein: The pressure sensor includes an integrated resonator coupled to the backplate, the integrated resonator including a spring and a resonant member, wherein the spring is connected to the backplate and to an outer edge of the resonant member, and wherein the spring suspends the resonant member relative to the backplate.

16. The microphone assembly of claim 15, wherein: The pressure sensing circuit includes a swept frequency generator and a transimpedance amplifier, wherein an output terminal of the swept frequency generator is connected to an input terminal of the integrated resonator, and the transimpedance amplifier is connected to an output terminal of the integrated resonator.

17. The microphone assembly of claim 16, wherein: The pressure sensing circuit also includes an analog-to-digital converter connected to the output of the transimpedance amplifier, and the integrated circuit also includes a processor, which is configured to receive a signal from the analog-to-digital converter and detect a phase of the signal and a frequency indicating a resonant frequency of the integrated resonator.

18. The microphone assembly of claim 17, wherein: The resonant frequency of the integrated resonator depends on the pressure in the at least partially vacuum-sealed chamber.

19. The microphone assembly of claim 18, wherein: The resonant frequency of the integrated resonator ranges from 50 kHz to 150 kHz.

20. A microphone assembly, comprising: case; An acoustic transducer, wherein the acoustic transducer is disposed in the housing, and the acoustic transducer comprises: an at least partially vacuum sealed chamber defined in part by the first diaphragm; and a backing plate disposed at least partially within the at least partially vacuum sealed chamber, the at least partially vacuum sealed chamber having a pressure below atmospheric pressure, wherein the backing plate is configured to sense the pressure within the at least partially vacuum sealed chamber; and An integrated circuit is disposed in the housing, the integrated circuit is connected to the backplate, and the integrated circuit includes a bias circuit configured to selectively apply a bias voltage to the backplate or a sensing current to the backplate.

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