Biometric sensor with force detection and ultrasound imaging capabilities

Abstract

Embodiments of the subject matter described herein relate to sensors comprising piezoelectric micromachined ultrasonic transducer (PMUT) sensor elements and arrays thereof. The PMUT sensor element is switchable between a non-ultrasonic force detection mode and an ultrasonic imaging mode. The PMUT sensor element may include a diaphragm capable of static displacement when an applied force is applied and capable of dynamic displacement when the PMUT sensor element transmits or receives an ultrasonic signal. In some embodiments, the PMUT sensor element includes a two-dimensional electron gas structure on the membrane. The sensor may further include a sensor controller configured to switch between a non-ultrasonic force detection mode in which the applied force is measured and an ultrasonic imaging mode in which the applied force is measured for one or more of the PMUT sensor elements. And wherein an object is ultrasonically imaged during the ultrasound imaging mode.

Description

[0001] This invention patent application is a divisional application of the invention patent application with international application number PCT / US2018 / 034214, international application date of May 23, 2018, and Chinese national phase application number 201880038832.9, entitled "Biometric Sensor with Force Detection and Ultrasonic Imaging Capabilities".

[0002] Priority requirements

[0003] This application claims priority to U.S. Patent Application No. 15 / 633,386, filed June 26, 2017, entitled “Biometric Sensor with Force Detection and Ultrasonic Imaging Capability,” which is incorporated herein by reference. Technical Field

[0004] This disclosure relates to piezoelectric ultrasonic transducers for biometric sensing, imaging, force detection, and touch recognition, and to electronic sensor arrays composed of piezoelectric ultrasonic transducers, particularly to biometric sensors with force detection and ultrasonic imaging capabilities. Background Technology

[0005] An ultrasonic sensor system can use an ultrasonic transmitter to generate ultrasonic waves and transmit them toward an object to be detected via one or more ultrasonic transmission media. The ultrasonic transmitter can be operatively coupled to an ultrasonic sensor array configured to detect portions of the ultrasonic waves reflected from the object. For example, in an ultrasonic fingerprint sensor, ultrasonic waves can be generated by activating and deactivating the transmitter over short time intervals. A portion of the ultrasonic wave may be reflected at each material interface encountered by the ultrasonic wave.

[0006] For example, in the context of an ultrasonic fingerprint sensor, ultrasonic waves can travel through a pressure plate on which an object, such as a human finger, can be placed to obtain fingerprint image information. After passing through the pressure plate, some portions of the ultrasonic waves may encounter the skin in contact with the pressure plate, such as fingerprint ridges, while other portions encounter air, such as valleys between adjacent fingerprint ridges, and may reflect back towards the ultrasonic sensor array with varying intensities. The ultrasonic sensor array can convert the reflected ultrasonic waves into reflected ultrasonic signals indicating the local intensity of the reflected ultrasonic waves. The reflected signals associated with a finger can be processed and converted into digital values ​​representing the signal strength of the reflected signals. When such reflected signals are collected over a distribution area, these digital values ​​can be used to generate fingerprint image information. The fingerprint image information can be used to generate a graphical display of the signal strength over the distribution area, for example, by converting the digital values ​​into an image, thereby generating an image of the fingerprint. Therefore, an ultrasonic sensor system can be used as a fingerprint sensor or other types of biometric scanners.

[0007] Thin-film piezoelectric acoustic transducers are attractive candidates for a wide range of applications, including biometric sensors, ultrasonic imaging devices, and fingerprint sensors. Such transducers can comprise piezoelectric micromechanical ultrasonic transducers (PMUTs) configured as multi-layer stacks comprising a stack of piezoelectric layers and a mechanical layer disposed over a cavity. The piezoelectric layer stack can contain layers of piezoelectric material. In some applications, one-dimensional or two-dimensional arrays of any number of PMUT sensor elements are conceivable.

[0008] Low-cost and low-power authentication wake-up mechanisms are of interest in electronic devices such as smartphones, tablets, and autonomous vehicles, but present significant challenges. Capacitive touch detection mechanisms may fail to distinguish between confirmed and unintentional touches, leading to unwanted wake-up events. Lightly touching a fingerprint sensor can result in poor image quality, making user authentication more difficult. Summary of the Invention

[0009] The systems, methods, and apparatuses disclosed herein each have several innovative aspects, and each of these innovative aspects is not solely responsible for the desired properties disclosed herein.

[0010] One innovative aspect of the subject matter described in this disclosure relates to a device comprising: a substrate; a sensor comprising an array of piezoelectric micromechanical ultrasonic transducer (PMUT) sensor elements on the substrate, wherein each PMUT sensor element comprises a diaphragm having a piezoelectric layer and a mechanical layer, wherein the diaphragm is capable of static displacement upon application of an applied force and dynamic displacement upon receiving or emitting an ultrasonic signal; and a sensor controller configured to switch the sensor between one or more non-ultrasonic force detection modes and ultrasonic imaging modes in the PMUT sensor elements, wherein the applied force is measured in the non-ultrasonic force detection mode, and wherein an object is ultrasonically imaged during the ultrasonic imaging mode. In some embodiments, the device is configured to detect a finger touch based on a force above a threshold measured by the device in the non-ultrasonic force detection mode. In some embodiments, the sensor controller may be configured to provide a wake-up signal to an application processor after detecting the finger touch to activate one or more wake-up operations. In some embodiments, the device is configured to detect a finger lift based on a threshold external force measured by the device in the non-ultrasonic force detection mode after detecting the finger touch. In some embodiments, the threshold external force is less than the threshold force. In some embodiments, the sensor controller is configured to initialize the ultrasound imaging mode after detecting the finger touch.

[0011] In some embodiments, the sensor controller is configured to initialize the ultrasonic imaging mode based on a minimum imaging threshold force measured by the device in the non-ultrasonic force detection mode. In some embodiments, one or more of the PMUT sensor elements include a 2D electron gas structure disposed on the diaphragm. In some embodiments, the sensor controller is configured to switch between the non-ultrasonic force detection mode and the ultrasonic imaging mode for each PMUT sensor element in the PMUT sensor element array. In some embodiments, the sensor controller is configured to switch between the non-ultrasonic force detection mode and the ultrasonic imaging mode for a subset of the PMUT sensor elements in the PMUT sensor element array.

[0012] In some embodiments, PMUT sensor elements in the subset of the PMUT sensor elements are positioned on the periphery of the PMUT sensor element array. In some embodiments, the PMUT sensor elements in the subset of the PMUT sensor elements differ from the rest of the PMUT sensor elements in the PMUT sensor element array in one or more of their shape or size.

[0013] Another innovative aspect of the subject matter described in this disclosure relates to a method of operating a fingerprint sensor, the method comprising: measuring a finger force of a finger positioned on the fingerprint sensor; imaging the finger when the finger force exceeds a pressing finger threshold level; and authenticating the finger based on the imaging of the finger. In some embodiments, imaging the finger comprises acquiring ultrasonic image information of the finger, and wherein the authentication of the finger is based on the ultrasonic image information. In some embodiments, imaging the finger comprises acquiring ultrasonic image information of the finger when the finger force exceeds a minimum imageable finger threshold level. In some embodiments, imaging the finger comprises acquiring ultrasonic image information of the finger when the finger force is less than a maximum imageable finger threshold level. In some embodiments, the method further comprises waking up at least a portion of a mobile device when the finger force exceeds the pressing finger threshold level. In some embodiments, the method further comprises reducing the sampling rate for measuring the finger force when the finger force is less than a lifting finger threshold level.

[0014] Another innovative aspect of the subject matter described in this disclosure relates to a device comprising: a substrate; a diaphragm including a mechanical layer disposed over a cavity positioned between the diaphragm and the substrate; and a 2D electron gas structure disposed on the diaphragm. In some embodiments, the 2D electron gas structure is an aluminum gallium nitride / gallium nitride (AlGaN / GaN) transistor. In some embodiments, the diaphragm and the 2D electron gas structure are part of a sensor element, the diaphragm being capable of static displacement upon application of an applied force, and the 2D electron gas structure being a strain-sensitive structure configured to provide a static displacement signal corresponding to the applied force. In some embodiments, the diaphragm is additionally capable of dynamic displacement upon the sensor element receiving or transmitting an ultrasonic signal. In some embodiments, the device further comprises a sensor controller configured to switch the sensor element between a non-ultrasonic force detection mode and an ultrasonic imaging mode, wherein the applied force is measured in the non-ultrasonic force detection mode, and wherein an object is ultrasonically imaged during the ultrasonic imaging mode.

[0015] In some embodiments, the sensor element is one of an array of sensor elements on the substrate, each sensor element comprising a diaphragm and a mechanical layer disposed over a cavity positioned between the diaphragm and the substrate, and each sensor element comprising a 2D electron gas structure disposed on the diaphragm. In some embodiments, the device further comprises an array of piezoelectric micromechanical ultrasonic transducer (PMUT) sensor elements on the substrate.

[0016] In some embodiments, the device further includes a piezoelectric layer stack disposed on the diaphragm, wherein the piezoelectric layer stack is configured to excite the diaphragm and generate ultrasonic waves. In some embodiments, the 2D electron gas structure is configured to detect static or dynamic displacement of the diaphragm.

[0017] Another innovative aspect of the subject matter described in this disclosure relates to a non-transitory computer-readable medium storing instructions executable by one or more processors coupled to a fingerprint sensor comprising a piezoelectric ultrasonic transducer (PMUT) sensor element array. The instructions include: instructions for operating the PMUT sensor elements in a force detection mode; instructions for measuring an applied force on the fingerprint sensor while operating in the force detection mode; instructions for determining, based on the measured applied force, that a user's finger has contacted the fingerprint sensor; instructions for operating the PMUT sensor elements in an ultrasonic imaging mode to acquire fingerprint image information of the finger; and instructions for authenticating the user based on the fingerprint image information.

[0018] In some embodiments, the instruction for determining that a finger has contacted the fingerprint sensor based on the applied force includes instructions for comparing the applied force with a threshold force. In some embodiments, the instruction further includes instructions for determining that the finger has been removed from the fingerprint sensor based on a threshold external force measured by the device in the non-ultrasonic force detection mode after detecting that the finger has contacted the fingerprint sensor. In some such embodiments, the threshold external force is less than the threshold force. In some embodiments, the device further includes instructions for determining that the applied force is greater than or equal to a minimum imaging threshold force. In some embodiments, the device further includes instructions for initializing the ultrasonic imaging mode after determining that the applied force is greater than or equal to the minimum imaging threshold force.

[0019] Another innovative aspect of the subject matter described in this disclosure relates to a device comprising: a substrate; a sensor comprising an array of piezoelectric micromechanical ultrasonic transducer (PMUT) sensor elements on the substrate, wherein each PMUT sensor element comprises a diaphragm having a piezoelectric layer and a mechanical layer, wherein the diaphragm is capable of static displacement when an applied force is applied and dynamic displacement when the PMUT sensor element receives or transmits an ultrasonic signal; and means electrically coupled to the sensor to switch the sensor between a non-ultrasonic force detection mode and an ultrasonic imaging mode in one or more of the PMUT sensor elements, wherein the applied force is measured in the non-ultrasonic force detection mode, and wherein an object is ultrasonically imaged during the ultrasonic imaging mode. In some embodiments, the device further comprises means for determining that a finger has contacted the sensor. In some embodiments, the device further comprises means for determining that the finger has been removed from the sensor. Attached Figure Description

[0020] Details of one or more embodiments of the subject matter described herein are set forth in this disclosure and in the accompanying drawings. Other features, aspects, and advantages will become apparent upon reading this disclosure. Note that the relative dimensions of the drawings and other simplified diagrams in this disclosure may not be drawn to scale. The sizes, thicknesses, arrangements, materials, etc., shown and described in this disclosure are by way of example only and should not be construed as limiting. Similar reference numerals and names in the drawings indicate similar elements.

[0021] Figure 1A and 1B Side and top views of an example of a piezoelectric micromechanical ultrasonic transducer (PMUT) sensor element with switchable non-ultrasonic force / touch detection and ultrasonic imaging capabilities are shown, respectively.

[0022] Figure 1C Demonstrates operation in non-ultrasonic force / touch detection mode Figure 1A and 1B A side view of an example of a PMUT sensor element shown in the figure.

[0023] Figure 1D Demonstrates operation in ultrasound imaging mode Figure 1A and 1B A side view of an example of a PMUT sensor element shown in the figure.

[0024] Figure 1E yes Figure 1C and 1D An example of a schematic diagram of the equivalent circuit of the PMUT sensor element 100 shown in the figure.

[0025] Figure 2A side view shows an example configuration of a PMUT ultrasound sensor array capable of performing ultrasound imaging.

[0026] Figure 3A A block diagram representation of the components of an example sensing system 300 according to some implementation schemes is shown.

[0027] Figure 3B It shows that it contains Figure 3A A block diagram representation of the components of an example mobile device with a sensing system.

[0028] Figure 4A An example of a flowchart is shown, illustrating a process for force / touch detection, fingerprint imaging, and authentication using a sensor system comprising an array of ultrasonic sensors, according to certain embodiments.

[0029] Figure 4B An example of a flowchart is shown, illustrating the process for force / touch detection, finger lift detection, fingerprint imaging, and authentication using a sensor system comprising an array of ultrasonic sensors.

[0030] Figure 5A This is an example of a simplified graph showing the applied finger force versus time for finger touch detection and finger lift detection events of a fingerprint sensor operating in non-ultrasonic force detection mode.

[0031] Figure 5B This is an example illustrating a simplified graph of the applied finger force versus time for imaging performed by a fingerprint sensor operating in ultrasonic imaging mode.

[0032] Figure 6 This is an example of a simplified diagram illustrating the non-ultrasonic force / touch detection mode and ultrasonic imaging mode of a fingerprint sensor in response to the applied finger force.

[0033] Figure 7A –7C shows an example of a PMUT sensor element that includes a 2D electronic gas structure.

[0034] Figure 7D A side view shows an example of a 2D electronic gas structure that can be implemented with or without the PMUT sensor elements described herein.

[0035] Figure 8-13 Examples of various configurations of an ultrasonic sensor array configured to switch between a non-ultrasonic force detection mode and an ultrasonic imaging mode are shown.

[0036] Figure 14A –17D shows examples of PMUT sensor elements that can be implemented in an ultrasonic sensor array according to various implementation schemes.

[0037] Figure 18A–18D illustrates an example of a process flow for manufacturing sensor elements that include a substrate, a diaphragm, and a 2D electron gas structure disposed on the diaphragm. Detailed Implementation

[0038] The following description relates to certain embodiments in order to achieve the purpose of describing the innovative aspects of this disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in a variety of different ways. The described embodiments can be implemented in any device, apparatus, or system used for ultrasonic sensing. Furthermore, it is contemplated that the described embodiments can be incorporated into or associated with a variety of electronic devices, including but not limited to: mobile phones, multimedia internet-enabled cellular phones, mobile TV receivers, wireless devices, smartphones, smart cards, wearable devices (such as bracelets, armbands, wristbands, rings, hairbands, patches, etc.), Bluetooth® devices, personal data assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, laptop computers, smartbooks, tablet computers, printers, copiers, scanners, fax devices, GPS receivers / navigators, cameras, digital media players (such as MP3 players), camcorders, game consoles, watches, clocks, calculators, television monitors, etc. Flat panel displays, electronic reading devices (e.g., e-readers), mobile health devices, computer monitors, automatic displays (including odometer and speedometer displays, etc.), cockpit controls and / or displays, camera view displays (such as displays for rearview cameras in vehicles), electronic photographs, electronic billboards or signs, projectors, building structures, microwaves, refrigerators, stereo systems, cassette recorders or displays, DVD players, CD players, VCRs, radios, portable memory chips, washing machines, dryers, washer-dryers, ATMs, parking timers, packages (such as in electromechanical systems (EMS) applications that include both microelectromechanical systems (MEMS) and non-EMS applications), aesthetic structures (such as displays of images on jewelry or clothing), and various EMS devices. The teachings herein can also be used in applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion sensing devices, magnetometers, inertial components of consumer electronics, parts of consumer electronics, automotive doors, steering wheels or other automotive parts, varactor tubes, liquid crystal devices, electrophoresis apparatus, drive systems, manufacturing processes, and electronic test equipment. Therefore, the teachings are not intended to be limited to the embodiments depicted in the accompanying drawings, but have broad applicability that will be apparent to those skilled in the art.

[0039] The embodiments of the subject matter described herein relate to piezoelectric micromechanical ultrasonic transducer (PMUT) sensor elements and arrays thereof. The PMUT sensor element can switch between a non-ultrasonic force detection mode and an ultrasonic imaging mode. The PMUT sensor element may include a diaphragm capable of static displacement when force is applied from an object such as a finger and dynamic displacement when the PMUT sensor element emits or receives ultrasonic signals. In some embodiments, the PMUT sensor element may include a two-dimensional electron gas structure on the diaphragm.

[0040] Implementations of the subject matter described herein also relate to sensors comprising an array of PMUT sensor elements. The sensor may further include a sensor controller configured to switch between a non-ultrasonic force detection mode and an ultrasonic imaging mode of one or more of the PMUT sensor elements, wherein the applied force is measured in the non-ultrasonic force detection mode, and wherein the object is ultrasonically imaged during the ultrasonic imaging mode. Forces exceeding threshold force levels for wake-up and imaging can be detected and responded to.

[0041] Specific embodiments of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages: In non-ultrasonic force detection mode, the sensor allows for low-power wake-up of the device. By detecting forces exceeding a threshold force level, the sensor can be made insensitive to light, unintentional touches, thereby reducing unintentional wake-ups. Image quality control for fingerprint imaging can be improved by using a threshold force level for imaging.

[0042] Various aspects of PMUTS have been described in the following patent applications: U.S. Patent Application No. 14 / 569,280, filed December 12, 2014, entitled “MICROMECHANICAL ULTRASONIC TRANSDUCERS AND DISPLAY”; U.S. Patent Application No. 14 / 569,256, filed December 12, 2014, entitled “PIEZOELECTRIC ULTRASONIC TRANSDUCER AND PROCESS”; U.S. Patent Application No. 14 / 883,583, filed October 14, 2015, entitled “THREE-PORT PIEZOELECTRIC ULTRASONIC TRANSDUCER”; and U.S. Patent Application No. 14 / 883,583, filed October 14, 2015, entitled “ACTIVE BEAM-FORMING TECHNIQUE FOR…”. U.S. Patent Application No. 14 / 883,585, entitled "Active Beamforming Technology for Piezoelectric Ultrasonic Transducer Arrays," filed October 14, 2015; U.S. Patent Application No. 14 / 883,586, entitled "Superpixel Array of Piezoelectric Ultrasonic Transducers for 2-D Beamforming," filed October 12, 2016; and U.S. Patent Application No. 14 / 883,586, entitled "Integrated Piezoelectric Ultrasonic Transducer PIXEL," filed October 12, 2016. U.S. Patent Application No. 15 / 292,057, entitled “ANDARRAY (Integrated Piezoelectric Micromechanical Ultrasonic Transducer Pixels and Arrays),” is owned by each of the assignees of this invention and is hereby incorporated herein by reference in its entirety for all purposes.

[0043] Figure 1A and 1B Side and top views are shown, respectively, of an example of a piezoelectric micromechanical ultrasonic transducer (PMUT) sensor element with switchable non-ultrasonic force / touch detection and ultrasonic imaging capabilities. Reference Figure 1AThe PMUT sensor element 100 includes a piezoelectric layer stack 110 and a mechanical layer 130, which are arranged to form a diaphragm (hereinafter referred to as the "PMUT diaphragm" or "deformable diaphragm") supported by an anchoring structure 170 over a cavity 120. The piezoelectric layer stack 110 includes a piezoelectric layer 115, a lower electrode 112, and an upper electrode 114. The upper electrode 114 in the illustrated embodiment can also be referred to as an internal electrode because it is disposed on an inner portion of the deformable diaphragm.

[0044] In the illustrated embodiment, the lower electrode 112 is disposed below the piezoelectric layer 115 and near the cavity 120, while the upper electrode 114 is disposed above the piezoelectric layer 115 and near the surface of the piezoelectric layer 115 opposite to the cavity 120. The cavity 120 may be formed in or on the substrate 160. The cavity 120 is positioned between the diaphragm and the substrate 160. In embodiments where the cavity is formed in the substrate 160 (such as the cavity-silicon-on-insulator embodiment), the anchoring structure 170 may be part of the substrate 160.

[0045] The substrate 160 may be or comprise, for example, a silicon wafer, a silicon-on-insulator (SOI) wafer, a silicon or SOI wafer with an integrated circuit system, a semiconductor substrate, or a glass or polymer substrate with a thin-film transistor (TFT) circuit system. In some embodiments, the substrate 160 may be a flexible substrate, such as a polyimide (PI) thin layer, polyethylene naphthalate (PEN) or polyethylene terephthalate (PET), or a flexible substrate with an InGaZnO (IGZO) circuit system.

[0046] The piezoelectric layer stack may comprise a piezoelectric layer, such as aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), or other suitable piezoelectric materials having one or more electrode layers coupled to the piezoelectric layer. The piezoelectric layer stack may be patterned and etched to form vias, release holes, and other features. The mechanical layer may comprise silicon dioxide (SiO2), silicon oxynitride (SiON), silicon nitride (SiN), other dielectric materials, or combinations of dielectric materials or layers. In some instances, the separator may be configured as an elongated rectangle having a longitudinal dimension of length L and width W, where L is at least twice W. In some instances, the ratio of the width W to the thickness T of the separator may be between 5:1 and 50:1.

[0047] If possible Figure 1B As seen in the image, the PMUT sensor element 100 can have a circular geometry. The PMUT sensor element 100 is an example of a dual-port PMUT, which is a PMUT with two input / output ports, one associated with the lower electrode 112 and the other associated with the upper electrode 114. The lower electrode 112 has a voltage of V.参考 The reference electrode, and the upper electrode 114 is a voltage of V. 内部 The output / drive / sensing electrodes are shown. The transceiver circuitry 180 is schematically shown connected to the lower electrode 112 and the upper electrode 114. The transceiver circuitry 180 can be electrically coupled to the PMUT sensor element 100 through the two input / output ports associated with the transceiver circuitry 180.

[0048] exist Figure 1A and 1B In some examples, the upper electrode 114 may be referred to as the inner electrode. In some embodiments further described below, the three-port PMUT sensor element may have two upper electrodes, such as an inner upper electrode and an outer upper electrode, wherein the outer upper electrode is located near the peripheral region of the deformable diaphragm. The PMUT sensor element described herein is not limited to any particular geometry. References below... Figure 7A –7C and 14A–17D describe further examples of two-port PMUT sensor elements and three-port PMUT sensor elements with various geometries.

[0049] Figure 1C Demonstrates operation in non-ultrasonic force / touch detection mode Figure 1A and 1B A side view of an example of the PMUT sensor element 100 shown in the figure. Figure 1D Demonstrates operation in ultrasound imaging mode Figure 1A and 1B A side view of an example of the PMUT sensor element 100 shown. (Go to...) Figure 1C The PMUT sensor element 100 is shown having a deformable PMUT diaphragm that exhibits static displacement due to an applied force, as indicated by the downward-pointing arrow and the dashed line of the deformed diaphragm. In operation, the piezoelectric layer stack 110 and the mechanical layer 130 are caused to bend in response to an applied force, and the PMUT sensor element converts the applied force into a force that can be generated by… Figure 1B The transceiver circuitry 180 shown reads electrical signals. In the embodiments described herein, force can be applied, for example, by pressing a finger or stylus onto the PMUT sensor element 100 or onto a pressure plate, cover glass, or other device housing located on the PMUT sensor element 100. The output voltage V can be measured. 内部And it is typically proportional to the applied force. It should be understood that while the description herein refers primarily to force detection, sensor elements can also be implemented for pressure detection, where pressure is the ratio of force to the area of ​​force application. Force or pressure detection allows for the detection of finger touch, at least to the extent that a touch (e.g., a light touch) from a user's finger or other object applies a detectable force to one or more of the sensor elements. Figure 1E yes Figure 1C and 1D An example of a schematic diagram of the equivalent circuit of the PMUT sensor element 100 shown in the figure. Figure 1E Electrical connections to the internal and reference electrodes are shown, as well as surface charges formed on the surface of the piezoelectric layer during diaphragm deformation.

[0050] In some implementations, the downward scraping of the PMUT diaphragm caused by the applied force from a finger generates a charge that can be used to power a small front-end portion of the associated controller. For example, the charge generated by the piezoelectric layer during static scraping can be stored in a power supply capacitor, which in turn powers the front-end circuitry of the associated controller. The front-end portion can be used to wake up other parts of the controller or to perform a threshold detection function to prevent the controller and / or associated application processor from waking up unless a minimum threshold force is applied.

[0051] In the following text about Figure 7A In some embodiments further described in –7D, the PMUT sensor element 100 may incorporate a 2D electro-gas structure, such as a 2D gas transistor. Such a 2D electro-gas structure is sensitive to strain caused by applied force and can be used in static displacement non-ultrasonic force detection mode or dynamic displacement mode. A sensor element having a diaphragm and a 2D electro-gas structure disposed on the diaphragm can be used for ultrasonic imaging of an object during ultrasonic imaging mode.

[0052] Figure 1DA side view of a PMUT sensor element 100 with dynamic displacement due to ultrasonic wave generation and detection is shown. During operation, the piezoelectric layer stack 110 and mechanical layer 130 can bend and vibrate in response to a time-varying excitation voltage applied across the upper electrode 114 and lower electrode 112 by the transceiver circuitry 180. Thus, one or more ultrasonic pressure waves with frequencies in the ultrasonic band can propagate into the air, pressure plate, cover glass, or other device housing located on the PMUT sensor element 100. The piezoelectric layer stack 110 can also receive reflected ultrasonic pressure waves from objects in the propagation medium and convert the received ultrasonic pressure waves into electrical signals that can be read by the transceiver circuitry 180. The deformable diaphragm above the cavity 120 can bend and vibrate in response to reflected ultrasonic pressure waves impacting the surface of the PMUT sensor element 100, thereby generating mechanical stress and strain in the PMUT diaphragm and surface charges on the surface of the piezoelectric layer 115 that can be detected by the underlying circuitry. When the PMUT transmits or receives ultrasonic signals, the PMUT diaphragm may experience one or both of dynamic flexure and vibration. Figure 1D The deformable PMUT diaphragm, exhibiting dynamic displacement in transmit or receive modes, is indicated by upward and downward pointing arrows and dashed lines representing the deformed diaphragm. In the depicted embodiment, the lower electrode 112 can be connected to a constant bias voltage V, such as a ground reference potential. 参考 In some implementations, the lower electrode 112 may be grounded or connected to a multi-stage bias signal, such as a receiver bias voltage, that can be provided by the transceiver circuitry 180. The upper electrode 114 is at a drive or sense voltage (V). 内部 ).

[0053] In some implementations, the PMUT sensor element array can be configured as an ultrasonic sensor array, which is configured for ultrasonic fingerprint imaging. Figure 2 A side view shows an example configuration of a PMUT ultrasound sensor array capable of performing ultrasound imaging. Figure 2An ultrasonic sensor array 200 is depicted having a PMUT array with transmitting and receiving elements configured for ultrasonic imaging. PMUT sensor elements 262 on a PMUT sensor array substrate 260 can emit and detect ultrasonic waves. As shown, ultrasonic waves 264 can be emitted from one or more PMUT sensor elements 262. Ultrasonic waves 264 can travel toward an object 202, such as a finger or stylus positioned on the outer surface of a pressure plate 290, through a propagation medium such as an acoustic coupling medium 265 and the pressure plate 290. A portion of the ultrasonic waves 264 can propagate through the pressure plate 290 and into the object 202, while a second portion propagates back from the surface of the pressure plate 290 toward the PMUT sensor elements 262. The amplitude of the reflected waves can depend in part on the acoustic properties of the object 202 and the pressure plate 290. The reflected waves can be detected by the PMUT sensor elements 262, from which an image of the object 202 can be acquired. For example, using a sensor array with a spacing of approximately 50 micrometers (approximately 500 pixels per inch), the ridges and valleys of a fingerprint can be detected. Acoustic coupling media 265, such as adhesives, gels, compliant layers, or other acoustic coupling materials, can be provided to improve the coupling between the PMUT sensor element array 262 mounted on the sensor array substrate 260 and the pressure plate 290. The acoustic coupling media 265 can facilitate the transmission of ultrasonic waves to and from the PMUT sensor elements 262. The pressure plate 290 may comprise, for example, a layer of glass, plastic, sapphire, metal, metal alloy, or other pressure plate material. An acoustic impedance matching layer (not shown) may be disposed on the outer surface of the pressure plate 290. The pressure plate 290 may include a coating (not shown) on its outer surface. In some embodiments, the PMUT sensor elements may be co-fabricated on or within a thin-film transistor (TFT) circuit system or a CMOS circuit system; in some instances, the substrate may be a silicon, SOI, glass, or plastic substrate. The TFT, silicon, or semiconductor substrate may contain row and column addressing electronics, multiplexers, local amplification stages, and control circuit systems.

[0054] An ultrasonic sensor array can be part of the sensing system of a device (e.g., a mobile device). Figure 3AA block diagram representation of the components of an example sensing system 300 according to some embodiments is shown. As shown, the sensing system 300 may include a sensor system 302 and a control system 304 electrically coupled to the sensor system 302. The sensor system 302 may be able to detect the presence of an object (e.g., a human finger). The sensor system 302 may be able to scan the object and provide raw measurement image information that can be used to obtain object features (e.g., a fingerprint of a human finger). The control system 304 may be able to control the sensor system 302 and process the raw measurement image information received from the sensor system. In some embodiments, the sensing system 300 may include an interface system 306 that enables communication with various components within or integrated with the sensing system 300, or in some embodiments, with various components, devices, or other systems outside the sensing system to transmit or receive data such as raw or processed measurement image information.

[0055] Figure 3B It shows that it contains Figure 3A A block diagram of the components of an example mobile device 310 of the sensing system 300 is shown. An ultrasonic sensor array 312 (such as...) can be used. Figure 2 The PMUT ultrasonic sensor array 200 shown implements the sensor system 302 of the sensing system 300 of the mobile device 310. A controller 314 electrically coupled to the ultrasonic sensor array 312 can implement the control system 304 of the sensing system 300. Although the controller 314 is shown and described as a single component, in some embodiments, the controller 314 may refer generally to two or more different control units or processing units electrically connected to each other. In some embodiments, the controller 314 may include one or more of the following designed to perform the functions and operations described herein: a general-purpose single-chip or multi-chip processor, a central processing unit (CPU), a digital signal processor (DSP), an application processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof.

[0056] Figure 3BThe sensing system 300 may include an image processing module 318. In some embodiments, raw measurement image information provided by the ultrasonic sensor array 312 may be sent, transmitted, transmitted, or otherwise provided to the image processing module 318. The image processing module 318 may include any suitable combination of hardware, firmware, and software configured, adjusted, or otherwise operable for processing the image information provided by the ultrasonic sensor array 312. In some embodiments, the image processing module 318 may include signal or image processing circuitry or circuit components, including, for example, amplifiers (such as instrumentation amplifiers or buffer amplifiers), analog or digital mixers or multipliers, switches, digital-to-analog converters (ADCs), passive or active analog filters, etc. In some embodiments, one or more of such circuitry or circuit components may be integrated within the controller 314, for example, where the controller 314 is implemented as a system-on-a-chip (SoC) or system-in-package (SIP). In some embodiments, one or more of such circuitry or circuit components may be integrated within the controller 314 or within a DSP coupled to the controller. In some implementations, the image processing module 318 may be implemented at least in part by software. For example, one or more functions of the circuit or circuit components just described, or the operations performed thereby, may instead be performed by one or more software modules, such as those executing in the processing unit of the controller 314 (e.g., in a general-purpose processor or DSP).

[0057] In some embodiments, in addition to the sensing system 300, the mobile device 310 may also include a separate processor 320, such as an application processor, a memory 322, an interface 316, and a power supply 324. In some embodiments, the controller 314 of the sensing system 300 may control the ultrasonic sensor array 312 and the image processing module 318, and the processor 320 of the mobile device 310 may control other components of the mobile device 310. In some embodiments, the processor 320 may transmit data to the controller 314, the data including, for example, instructions or commands. In some such embodiments, the controller 314 may transmit data to the processor 320, the data including, for example, raw image information or processed image information. It should also be understood that in some other embodiments, the controller 314 may be wholly or at least partially implemented by the processor 320. In some such embodiments, a separate controller 314 for the sensing system 300 may not be necessary, as the functions of the controller 314 can be performed by the processor 320 of the mobile device 310.

[0058] According to the implementation, one or both of the controller 314 and the processor 320 may store data in memory 322. For example, the data stored in memory 322 may include raw measurement image information, filtered or otherwise processed image information, estimated PSF or estimated image information, and final refined PSF or final refined image information. Memory 322 may store processor-executable code or other executable computer-readable instructions that can be executed by one or both of the controller 314 and the processor 320 to perform various operations (or cause other components such as the ultrasonic sensor array 312, image processing module 318, or other modules) to perform operations, including calculations, operations, estimations, or any other determinations described herein (including those presented in any of the equations below). It should also be understood that memory 322 may refer to one or more memory devices (or “components”) in general. For example, according to the implementation, the controller 314 may access data in a memory device different from that of the processor 320 and may store data in said memory device. In some embodiments, one or more of the memory components may be implemented as a NOR-based or NAND-based flash memory array. In other embodiments, one or more of the memory components may be implemented as a different type of non-volatile memory. Additionally, in some embodiments, one or more of the memory components may comprise a volatile memory array, such as some type of RAM.

[0059] In some implementations, controller 314 or processor 320 may transmit data stored in memory 322 or data received directly from image processing module 318 via interface 316. For example, such transmitted data may include image information or data obtained or otherwise determined based on image information. Interface 316 may refer to one or more interfaces of one or more types. In some implementations, interface 316 may include a memory interface for receiving data from or storing data in an external memory such as a removable memory device. Additionally or alternatively, interface 316 may include one or more wireless network interfaces or one or more wired network interfaces that enable the transmission and reception of raw or processed data to and from external computing devices, systems, or servers.

[0060] Power source 324 can supply power to some or all of the components in mobile device 310. Power source 324 may include one or more energy storage devices of various kinds. For example, power source 324 may include rechargeable batteries such as nickel-cadmium batteries or lithium-ion batteries. Alternatively or alternatively, power source 324 may include one or more supercapacitors. In some embodiments, power source 324 can be charged (or "recharged") using power obtained from, for example, a wall socket (or "power outlet") or a photovoltaic device (or "solar cell unit" or "solar cell unit array") integrated with mobile device 310. Alternatively or alternatively, power source 324 can be wirelessly charged.

[0061] As used below, the term "processing unit" refers to one or more of the controller of an ultrasound system (e.g., controller 314), the image processing module (e.g., image processing module 318), or a separate processor (e.g., processor 320) of a device containing an ultrasound system. In other words, the operations described below as being performed by or using the processing unit can be performed by one or more of the controller of the ultrasound system, the image processing module, or a separate processor of a device containing a sensing system.

[0062] As described above, the ultrasonic sensor array can be configured to operate in a static, non-ultrasonic mode to detect the force of a finger or other object pressed against the sensor. Once a finger is detected, the fingerprint can be ultrasonically imaged by the sensor, and the user can be authenticated. Figure 4A An example flowchart is shown, illustrating a process 400 for force / touch detection, fingerprint imaging, and authentication using a sensor system comprising an array of ultrasonic sensors, according to certain embodiments. For Figure 4A And for the following text Figure 4B It should be noted that, for clarity, functions that operate independently of force / touch detection (e.g., background routines or applications) are not shown.

[0063] Process 400 at box 402 is used to measure the static force F at the next sampling event. 静态 To begin. Example sampling rates can range from less than approximately 5 events per second to 20 events per second or more. Measurements can be made as described above regarding a single PMUT sensor element. Figure 1C The static force of one or more sensor elements in the described ultrasonic sensor array. Process 400 continues at decision box 404, where the measured static force F is... 静态 Force level F on-threshold 上,最小A comparison is made. In one instance, the threshold level could be 20 grams of force (gf). However, it should be understood that the threshold level can vary depending on the specific sensor, device, and / or user. In some implementations, a user-specific threshold level can be determined during the registration process. If the measured static force is less than the threshold level, process 400 returns to block 402. If the measured static force is greater than or equal to the threshold level, a finger touch is detected, and a finger-pressing state can be entered. A finger-pressing state can be entered when the measured finger force exceeds the threshold level (also known as the finger-pressing threshold level). Process 400 then continues at block 406 with a wake-up operation performed due to the detection of a finger touch. For example, returning to reference... Figure 3B The controller 314 can activate the processor 320 from a sleep mode or disconnected state. In some embodiments, the controller or application processor can also turn on the display. In some embodiments, entering a pressed finger state may include waking up at least a portion of the mobile device (such as a portion of the application processor or a portion of the display) when the measured finger force exceeds a pressed finger threshold. The process then continues at box 420 for ultrasonic imaging of the fingerprint. This can be as described above regarding... Figure 1D and Figure 2 Execute box 420 as described. Then, process 400 continues at box 422 to run the authentication process. Box 422 may involve determining whether the fingerprint imaged in box 420 belongs to a registered user.

[0064] In some implementations, the sensor can detect when a finger is lifted off the sensor and modify the operation of the mobile device accordingly. Figure 4B An example of a flowchart is shown, illustrating process 401 for force / touch detection, finger lift detection, fingerprint imaging, and authentication using a sensor system comprising an array of ultrasonic sensors as described herein.

[0065] Process 401 is as described above regarding Figure 4A The process begins with blocks 402, 404, and 406, which are executed as described. After a minimum force finger touch is detected and one or more wake-up operations are activated or otherwise performed at block 406, process 401 continues at block 408 to measure the static force. The sampling rate of block 408 may be the same as or different from that of block 402. Process 401 continues at decision block 410, where the measured static force F is... 静态 With respect to the off-threshold force level F 外,最大A comparison is made. The out-of-threshold level is typically less than the over-threshold level. In one instance, the out-of-threshold level could be 10 gf or 10 gf less than the over-threshold level. However, it should be understood that the out-of-threshold level can depend on the specific sensor, device, and / or the registered user. In some implementations, a user-specific out-of-threshold level can be determined during the registration process. If the measured static force is less than the out-of-threshold level, finger lifting is detected, and a finger-lifted state can be entered. A finger-lifted state can be entered when the measured finger force is less than the out-of-threshold level (also known as the finger-lifted threshold level). Process 401 then continues at block 412 with a modification operation due to the detected finger lifting, such as reducing the sampling rate for measuring the static finger force. The process can then return to block 402. If the measured static force is not less than the out-of-threshold level, process 401 continues at block 414 to measure the static force at the next sampling event. The sampling rate of block 414 can be the same as or different from the sampling rate of block 402 or block 408. Process 401 continues at decision box 416, where the measured static force F is... 静态 With minimum imaging threshold force level F 图像,最小 A comparison is made. The minimum imaging threshold level can be the minimum force required to perform ultrasonic imaging of the fingerprint to obtain an image that is accurate and detailed enough for authentication. If the static force is less than the minimum imaging threshold level, the process can return to box 408 to determine whether the finger has been lifted.

[0066] If the static force measured at box 416 is greater than or equal to the minimum imaging threshold level, process 401 continues at decision box 418, where the measured static force F is... 静态 With the maximum imaging threshold level F 图像,最大 A comparison is made. The maximum imaging threshold level can be the maximum force at which ultrasonic imaging of the fingerprint can be performed to obtain an image that is sufficiently accurate and detailed for authentication. If the static force is greater than the maximum imaging threshold level, the process can return to box 414 and can enter the maximum imageable finger state. The maximum imageable finger state can be entered when the measured finger force is greater than the maximum imaging threshold level (also known as the maximum imageable finger threshold level). If the static force is less than or equal to the maximum imaging threshold level and the static force is greater than the minimum imaging threshold level, process 401 can enter the imageable finger state and continue to perform ultrasonic fingerprint imaging at box 420 and run the authentication process at box 422, as described above. Figure 4AAs described above, an imageable finger state can be entered when the measured finger force is greater than a minimum imageable finger threshold level (also known as a minimum imageable finger threshold level). In some embodiments, an imageable finger state can be entered when the measured finger force is greater than the minimum imageable finger threshold level and less than the maximum imageable finger threshold level. In some embodiments, the minimum imageable finger threshold level may be equal to or greater than the pressing finger threshold level.

[0067] In one example, the minimum imaging threshold level can be 40 gf, and the maximum imaging threshold level can be 80 gf. However, it should be understood that these threshold levels can depend on the specific sensor, device, and / or user. In some embodiments, a user-specific imaging threshold level can be determined during the registration process. In some embodiments, a maximum imaging threshold level may not exist, in which case process 401 proceeds directly from block 416 to block 420.

[0068] In some implementations, a registration process is performed in which the applied finger force is measured. A series of images at different forces can be stored as part of the registration process, such as image 1 at 40 gf, image 2 at 50 gf, etc., and the measured finger force can be stored as part of one or more registration templates containing associated fingerprint image information. During the subsequent authentication process, a force ranking comparison method can be used to compare the force of the imaged finger with the stored finger force in the registration template. For example, if the fingerprint is imaged at a finger force of 50 gf, a registration template with a finger force of or close to 50 gf can be used first during the authentication process to attempt to verify that the user is a registered user.

[0069] Figure 5A This is an example of a simplified graph 500 illustrating the applied finger force versus time for finger touch detection and finger lift detection events of a fingerprint sensor operating in non-ultrasonic force detection mode. Ten sampling events t1–t2 are shown. 10 The duration of each event is t. 采样 The y-axis indicates the level F above the threshold. 上,最小 and outside threshold level F 外,最大 At point 502, between sampling events t2 and t3, a finger begins to touch the fingerprint sensor. At point 504, as the finger continues to press, the applied finger force exceeds the threshold level F. 上,最小 Then, at 506, the applied finger force was measured to be greater than the threshold level F. 上,最小This indicates minimum force touch detection, which initializes the wake-up operation and can send a wake-up signal to the application processor to activate one or more wake-up operations. The device's wake-up and continuation operation 520 is executed, which may include performing imaging and authentication operations. Between t6 and t7, the finger begins to lift. At 508, the applied finger force is less than the threshold level F. 外,最大 At point 510, the finger is lifted off the device, which is detected at point 512—the next sampling event. Continued operation 522 can then be performed, such as sampling in non-ultrasonic force detection mode and running a background application. In some implementations, when the measured finger force exceeds a pressing finger threshold level (F... 上,最小 When the applied finger force is less than the finger-lifting threshold level (F) measured and determined at 512, the finger-pressing state can be entered. 外,最大 When you are in a certain position, you can lift your fingers.

[0070] Figure 5B This is an example of a simplified diagram 501 illustrating the applied finger force versus time in an imaging process performed by a fingerprint sensor operating in ultrasonic imaging mode. The simplified diagram 501 shows the relationship between the applied finger force and time as described above. Figure 5A The events described are finger touch detection and finger lift detection 502–512, but it should be noted that some detections are related to... Figure 5A The sampling events in the instance occur when different sampling events occur.

[0071] The minimum imaging threshold level F is indicated on the y-axis. 图像,最小 and maximum imaging threshold level F 图像,最大 .exist Figure 5B In the example, at 514, the applied finger force was measured to be greater than the minimum imaging threshold level F. 图像,最小 This initializes the image acquisition operation 526 performed by the fingerprint sensor operating in ultrasonic imaging mode to acquire or obtain an ultrasonic image and / or fingerprint image information of the finger. Then, the authentication process 528 is performed. Then, a continuation operation 524 can be performed. If the fingerprint is successfully authenticated, the continuation operation 524 can include running various applications on the mobile device. Figure 5B In some instances, continuation operation 522 (e.g., sampling in a non-ultrasonic force detection mode) can continue during continuation operation 524; however, in some embodiments, sampling in a non-ultrasonic force detection mode may not continue if the device is actively used after certification. In some embodiments, when the measured finger force exceeds the minimum imageable finger threshold level (F... 图像,最小 And in some implementations, it is also less than the maximum imageable finger threshold level (F). 图像,最大 When ), the imageable finger state can be entered at 514, where the finger is imaged.

[0072] Figure 6 This is an example of a simplified diagram 600 illustrating the effects of non-ultrasonic force / touch detection mode and ultrasonic imaging mode of a fingerprint sensor on the applied finger force. It indicates the level F above the threshold. 上,最小 , out-of-threshold level F 外,最大 Minimum imaging threshold level F 图像,最小 and the maximum imaging threshold level F 图像,最大 It should be noted that the threshold levels associated with the applied force are illustrative. In the scenario shown, minimum force finger touch detection requires a minimum of 20 gf(F). 上,最小 Furthermore, the finger lift detection requires less than 10 gf(F). 外,最大 Fingerprint imaging requires a minimum of 40 gf (F). 图像,最小 When the applied force (F) 图像,最大 Imaging can be stopped when the image size exceeds 80 gf. However, as mentioned above... Figure 4A and 4B As described, these threshold levels can vary based on one or more of a particular sensor system, device, or user.

[0073] exist Figure 6 In one example, the fingerprint sensor may only be in ultrasonic imaging mode 602 when the applied finger force is between 40 gf and 80 gf (respectively, the minimum and maximum imaging threshold levels). As mentioned above regarding... Figure 4B As indicated, in some implementations, a maximum imaging threshold level may not exist. Similarly, in Figure 6 In this example, a non-ultrasonic force / touch detection mode 604 can be implemented under all applied finger force. It should be noted that between 40 gf and 80 gf, the fingerprint sensor can be in either ultrasonic imaging mode 602 or non-ultrasonic force detection mode 604. For example, if no fingerprint is being imaged or authenticated, the ultrasonic imaging mode can be activated when the applied finger force is measured to be within 40 gf and 80 gf. However, if the fingerprint has been authenticated and the device is in use, the fingerprint sensor can be in a non-ultrasonic detection mode within this range of applied finger force to determine, for example, whether the finger has been lifted. As indicated above, in some embodiments, the non-ultrasonic detection mode can be employed only when the device is in sleep mode or otherwise turned off.

[0074] In some implementations, the PMUT sensor element may include a two-dimensional (2D) electron gas structure, such as a strain-sensitive 2D gas transistor. The 2D electron gas structure may be disposed on or fabricated together with the diaphragm of the PMUT sensor element. Non-ultrasonic force detection modes may employ a static displacement signal from the 2D electron gas structure, which indicates the degree of strain resulting from the static displacement of the diaphragm and corresponds to the applied force. Examples of 2D electron gas (e.g., "two-dimensional electron gas" or "2DEG") structures that can be employed include high electron mobility transistor (HEMT) structures. In a particular example, an aluminum gallium nitride / gallium nitride (AlGaN / GaN) heterostructure may be employed, comprising an AlGaN / GaN transistor and an AlGaN / GaN Schottky diode.

[0075] Figure 7A –7C shows an example of a PMUT sensor element 700 containing a 2D electronic gas structure. Figure 7A A side view of the PMUT sensor element is shown; Figure 7B A top view of the PMUT sensor element is shown; and Figure 7C yes Figure 7A and 7B The diagram shows a schematic of the equivalent circuit of the PMUT sensor element 700.

[0076] PMUT sensor element 700 and Figure 1A-1D Similar to the PMUT sensor element depicted, a 2D electron gas structure 740 is added, which is formed on the outer region of the mechanical layer 730 of the PMUT diaphragm. Figure 7D An enlarged view of an example of a 2D electron gas structure 740 is shown. The PMUT diaphragm includes a piezoelectric layer stack 710 and a mechanical layer 730 supported on a cavity 720 by an anchoring structure 770. The cavity 720 may be formed in or on a substrate 760.

[0077] The piezoelectric layer stack 710 includes a piezoelectric layer 715, a lower electrode 712, and an upper electrode 714. The upper electrode 714 in the illustrated embodiment may also be referred to as an internal electrode because it is disposed on the inner portion of the deformable diaphragm.

[0078] Figure 7CThe equivalent circuit of PMUT sensor element 700 is shown. Each of the depicted terminals can be connected to a transceiver circuit system where a 2D electro-pneumatic structure is used during non-ultrasonic force detection mode and / or in ultrasonic imaging mode. Instead of detecting static deflection or, in addition to detecting static deflection, the strain-sensitive 2D electro-pneumatic structure can be used to detect vibration or other dynamic deformation. For example, in some embodiments, a piezoelectric layer stack 710 can be configured to excite a diaphragm and generate ultrasonic waves, while the 2D electro-pneumatic structure acts as a receiver element for detecting reflected ultrasonic waves. In such embodiments, an upper electrode 714 can be configured as a driving electrode, while the 2D electro-pneumatic structure 740 can be configured as a sensing electrode. Similarly, in some embodiments, an upper electrode 714 can be configured as a sensing electrode, while the 2D electro-pneumatic structure 740 can be configured as a driving electrode.

[0079] Figure 7D A side view shows an example of a 2D electronic gas structure 740 that can be implemented with or without the PMUT sensor elements described herein. Figure 7D In one example, the 2D electron gas structure 740 is an AlGaN / GaN transistor comprising a GaN buffer layer 782, a GaN body layer 784, an AlGaN gate dielectric layer 786, a source (S) stack 788, a drain (D) stack 790, and a gate (G) stack 792. In one example, the source stack 788 and the drain stack 790 may be titanium / aluminum / nickel / gold (Ti / Al / Ni / Au) stacks, and the gate stack 792 may be a Ni / Au stack. A passivation layer (not shown), such as silicon nitride (SiN) or other suitable dielectric material, may be conformally deposited on the 2D electron gas structure 740. Metal interconnects (not shown) provide connections between the source stack 788, the drain stack 790, the gate stack 792, and a suitable controller circuitry.

[0080] A 2D electron gas structure 740 can be formed on the mechanical layer 730 of the PMUT sensor element 700 using standard thin-film processing techniques such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), photolithographic patterning, and etching. In some embodiments, the 2D electron gas structure can be fabricated during the fabrication of the mechanical layer of the PMUT sensor element, thereby forming an integral part of the mechanical layer.

[0081] In some implementations, a 2D electron gas structure can be formed on or together with a diaphragm that is not an ultrasonic transducer to form a non-ultrasonic sensor element. Structurally, such a sensor element can be combined with... Figure 7AThe sensor element shown is similar, comprising a 2D electron gas structure 740 suspended on a mechanical layer 730 above the cavity 720. A piezoelectric layer stack 710 may or may not be present. As discussed further below, a non-ultrasonic sensor element comprising a 2D electron gas structure on a diaphragm can be incorporated into an ultrasonic sensor array comprising PMUT sensor elements. In some embodiments, a non-ultrasonic sensor element comprising a 2D electron gas structure on a diaphragm or other structures such as a cantilever beam can be incorporated into any suitable sensor array or otherwise used to provide highly sensitive force detection.

[0082] Figure 8-13 Examples of various configurations of an ultrasonic sensor array configured to switch between a non-ultrasonic force detection mode and an ultrasonic imaging mode are shown. In some embodiments, only a subset of the PMUT sensor elements in the PMUT sensor element array is used for force detection in the non-ultrasonic force detection mode. This is because, in some embodiments, accurate force measurements can be obtained using only a subset of the PMUT sensor elements.

[0083] Figure 8 An example of an ultrasonic sensor array 800 comprising PMUT sensor elements 802 and 804 formed on a substrate 860 is shown. PMUT sensor element 802 is shown as a circular PMUT sensor element. (See above reference) Figure 1A-1D And see the following text for reference. Figures 14A-14C Examples of circular PMUT sensor elements are described. It should be understood that these PMUT sensor elements can be of any suitable shape. In some embodiments, PMUT sensor element 802 is not used for force detection in non-ultrasonic force detection modes. PMUT sensor element 804 is larger than PMUT sensor element 802 and is shown as rectangular. The following is combined with... Figures 15A-15C and Figures 16A-16C Examples of rectangular PMUT sensor elements are described. It should be understood that these PMUT sensor elements can be of any suitable shape and size. In some embodiments, the PMUT sensor element 804 for non-ultrasonic force detection can be larger than the PMUT sensor element 802 for ultrasonic imaging only. During non-ultrasonic force detection mode, the PMUT sensor element 804 for detecting the applied force as described above is positioned on the periphery of the ultrasonic sensor array 800. By placing the PMUT sensor element 804 for force detection on the periphery, the ultrasonic sensor array can be used for centering detection. Although only PMUT sensor element 804 is used for non-ultrasonic force detection, both PMUT sensor element 802 and PMUT sensor element 804 can be used as described above regarding... Figure 2The described ultrasound imaging. In other words, in some embodiments, PMUT sensor element 804 may initially be used to statically detect force from finger pressure and then switch to an ultrasound mode for ultrasound imaging. In alternative embodiments, PMUT sensor element 804 may be used only for force detection, with only PMUT sensor element 802 used for ultrasound imaging. In some embodiments, PMUT sensor element 804 near the periphery of ultrasound sensor array 800 may be used for cursor, pointer, or icon control, or for screen navigation on a mobile device's display.

[0084] Figure 9 An example of an ultrasonic sensor array 900 comprising PMUT sensor elements 902 and 904 formed on a substrate 960 is shown. The PMUT sensor element 904, located on the outermost edge of the array periphery, can be used exclusively for non-ultrasonic force detection or for both non-ultrasonic force detection and ultrasonic imaging. In some embodiments, the PMUT sensor element 902, positioned inside the array, can be used for ultrasonic imaging and may or may not be used for non-ultrasonic force detection.

[0085] In some embodiments, the PMUT sensor element 904 includes a 2D electro-gas structure for force detection. In some embodiments, the sensor element 904 may include a piezoelectric layer stack, a 2D electro-gas structure, or both a piezoelectric layer stack and a 2D electro-gas structure. (The above refers to...) Figures 7A-7D And the following text further discusses... Figures 17A-17C Examples of PMUT sensor elements incorporating a 2D electro-pneumatic structure are described. In embodiments where PMUT sensor element 902 is not used for force detection, sensor element 902 may or may not include a 2D electro-pneumatic structure. In embodiments where PMUT sensor element 904 is used for non-ultrasonic force detection, both PMUT sensor element 902 and PMUT sensor element 904 can be used for ultrasonic imaging. In some embodiments, PMUT sensor element 904 can be used for cursor control, screen navigation, and control purposes, with or without a 2D electro-pneumatic structure.

[0086] Figure 10 An example of an ultrasonic sensor array 1000 comprising PMUT sensor elements 1002 and 1004 formed on a substrate 1060 is shown. The PMUT sensor element 1004, positioned at the periphery of the array and forming the outermost edge of the array, can be used for either or both of non-ultrasonic force detection and ultrasonic imaging. In some embodiments, the PMUT sensor element 1002, positioned inside the array, can be used for ultrasonic imaging instead of non-ultrasonic force detection. Figure 8As shown, PMUT sensor element 1004 is rectangular and larger than PMUT sensor element 1002. In some embodiments, PMUT sensor element 1004 can be used for cursor control, screen navigation, and control purposes.

[0087] Figure 11 An example of an ultrasonic sensor array 1100 comprising PMUT sensor elements 1102 and 1104 formed on a substrate 1160 is shown. Sensor element 1104, positioned at the periphery of the array and forming the outermost edge of the array, can be used for non-ultrasonic force detection and may or may not be used for ultrasonic imaging. In some embodiments, PMUT sensor element 1102, positioned inside the array, can be used for ultrasonic imaging and may or may not be used for non-ultrasonic force detection. Figure 8 As shown, PMUT sensor element 1004 is rectangular and larger than PMUT sensor element 1002. Figure 11 In one example, sensor element 1104 can provide x and y cursor or pointer control, sensor element 1110 provides x cursor or x pointer control, and sensor element 1108 provides y cursor or y pointer control.

[0088] Figure 12 An example of an ultrasonic sensor array 1200 comprising PMUT sensor elements 1204 formed on a substrate 1260 is shown. Figure 12 In some instances, a subset or all of the PMUT sensor elements 1204 in the array can be used for both non-ultrasonic force detection and ultrasonic imaging. In some embodiments, the PMUT sensor element 1204 may include, for example, elements related to… Figures 7A-7D The 2D electron gas structure and piezoelectric layer stack described in 17A-17C. In some embodiments, the PMUT sensor element 1204 may not include, for example, the reference 17A-17C. Figure 1A-1E , Figure 14A -C、 Figures 15A-15C and Figures 16A-16C The described 2D electron gas structure.

[0089] As indicated above, in some embodiments, a 2D electron gas structure may be formed on or together with a diaphragm that does not function as an ultrasonic transducer to form a non-ultrasonic sensor element. Figure 13 An example of an ultrasonic sensor array 1300 is shown, comprising a PMUT sensor element 1302 formed on a substrate 1360 and a non-ultrasonic force sensor element 1306 comprising a 2D electron gas structure on a diaphragm. In some embodiments, each PMUT sensor element 1302 in the ultrasonic sensor array 1300 may have a corresponding non-ultrasonic force sensor element 1306 in close proximity. Figure 13 In some of the embodiments shown, each sensor element 1302 may include a piezoelectric layer stack, and each sensor element 1306 may include a 2D electron gas structure.

[0090] Figure 8-13 The ultrasonic sensor array depicted can be configured as a home screen button on a mobile device or as a separate fingerprint sensor. Furthermore, the ultrasonic sensor array can be implemented in a three-dimensional (3D) mouse and a haptic device.

[0091] Figure 14A –17D shows examples of PMUT sensor elements that can be implemented in an ultrasonic sensor array according to various implementation schemes. Figure 14A and 14B A side view shows an example of a three-port PMUT sensor element 1400 operating in non-ultrasonic force detection mode and ultrasonic imaging mode, respectively. Figure 14C It shows Figure 14A and 14B The image shows a top view of the PMUT sensor element 1400. Figure 14D It shows Figure 14A and 14B The equivalent circuit of the PMUT sensor element is shown in the figure. The PMUT sensor element 1400 includes a piezoelectric layer stack 1410 and a mechanical layer 1430, which are arranged to form a deformable diaphragm supported on a cavity 1420 by an anchoring structure 1470. The cavity 1420 may be formed in or on a substrate 1460. The piezoelectric layer stack 1410 includes a piezoelectric layer 1415, a lower electrode 1412, and two upper electrodes: an inner electrode 1414 and an outer electrode 1413.

[0092] In the illustrated embodiment, the internal electrode 1414, external electrode 1413, and lower electrode 1412 can be electrically coupled to the transceiver circuitry and can function as separate electrodes providing signal transmission, signal reception, and a common reference or ground. This arrangement allows the timing of the transmit (Tx) and receive (Rx) signals to be independent of each other. More specifically, the illustrated arrangement enables substantially simultaneous signal transmission and reception between the piezoelectric ultrasonic transducer (PMUT) sensor element 1400 and the transceiver circuitry.

[0093] Figure 14A This is a side view of a PMUT sensor element 1400 exhibiting static displacement due to an applied force. (As mentioned above...) Figure 1C As described, in operation, the piezoelectric layer stack 1410 and mechanical layer 1430 can be bent in response to an applied force, and the PMUT sensor element converts the applied force into an electrical signal that can be read by the transceiver circuitry.

[0094] Figure 14B This is a side view of a PMUT sensor element 1400 exhibiting dynamic displacement due to ultrasonic wave generation and detection. (As described above...) Figure 1D As described, during operation in ultrasonic imaging mode, the piezoelectric layer stack 1410 and mechanical layer 1430 can bend and vibrate in response to a time-varying excitation voltage applied by the transceiver circuitry across the internal electrode 1414 and / or the external electrode 1413. Thus, one or more ultrasonic pressure waves having frequencies in the ultrasonic band can propagate into the air, pressure plate, cover glass, or other device housing located on the PMUT sensor element 1400. The piezoelectric layer stack 140 can also receive reflected ultrasonic pressure waves from objects in the propagation medium and convert the received ultrasonic pressure waves into electrical signals that can be read by the transceiver circuitry.

[0095] PMUT sensor elements can have various geometries, including but not limited to circular and rectangular geometries. In some embodiments, the ultrasonic array can include PMUT sensor elements with different geometries.

[0096] For example, as mentioned above... Figure 10 and 11 The geometry of the PMUT sensor element described for non-ultrasonic force detection and ultrasonic imaging may differ from the geometry of the PMUT sensor element used only for ultrasonic imaging. Figure 15A and 15B A side view shows an example of a rectangular geometry dual-port PMUT sensor element 1500 operating in non-ultrasonic force detection mode and ultrasonic imaging mode, respectively. Figure 15C It shows Figure 15A and 15B The image shows a top view of the PMUT sensor element 1500. Figure 15D It shows Figure 15A and 15B The equivalent circuit of the PMUT sensor element is shown in the figure.

[0097] PMUT sensor element 1500 includes a piezoelectric layer stack 1510 and a mechanical layer 1530, which are arranged to form a deformable diaphragm supported on a cavity 1520 by an anchoring structure 1570. The cavity 1520 may be formed in or on a substrate 1560. The piezoelectric layer stack 1510 includes a piezoelectric layer 1515, a lower electrode 1512, and an upper electrode 1514. The upper electrode 1514 is also referred to as an internal electrode. Figure 15A It is due to the above regarding Figure 1C A side view of the PMUT sensor element 1500, which describes the static displacement caused by the applied force. Figure 15B It is due to the above regarding Figure 1D A side view of the PMUT sensor element 1500, which describes the dynamic displacement generated and detected by ultrasonic waves.

[0098] Figure 16A and 16B A side view shows an example of a rectangular geometry three-port PMUT sensor element 1600 operating in non-ultrasonic force detection mode and ultrasonic imaging mode, respectively. Figure 16C It shows Figure 16A and 16B The image shows a top view of the PMUT sensor element 1600. Figure 16D It shows Figure 16A and 16B The equivalent circuit of the PMUT sensor element is shown in the figure.

[0099] PMUT sensor element 1600 includes a piezoelectric layer stack 1610 and a mechanical layer 1630, which are arranged to form a deformable diaphragm supported on a cavity 1620 by an anchoring structure 1670. The cavity 1620 may be formed in or on a substrate 1660. The piezoelectric layer stack 1610 includes a piezoelectric layer 1615, a lower electrode 1612, and two upper electrodes: an inner electrode 1614 and an outer electrode 1613.

[0100] As described in relation to Figure 14, the internal electrode 1614, the external electrode 1613, and the lower electrode 1612 can be electrically coupled to the transceiver circuitry and can serve as separate electrodes providing signal transmission, signal reception, and a common reference or ground. Figure 16A This is a side view of a PMUT sensor element 1600 exhibiting static displacement due to an applied force. (As mentioned above...) Figure 1C As described, in operation, the piezoelectric layer stack 1610 and mechanical layer 1630 can be bent in response to an applied force, and the PMUT sensor element converts the applied force into an electrical signal that can be read by the transceiver circuitry.

[0101] Figure 16B This is a side view of a PMUT sensor element 1600 exhibiting dynamic displacement due to ultrasonic wave generation and detection. (As described above...) Figure 1D As described, during operation in ultrasonic imaging mode, the piezoelectric layer stack 1610 and mechanical layer 1630 can bend and vibrate in response to the time-varying excitation voltage applied across the transceiver circuitry system via the internal electrode 1614 and / or the external electrode 1613.

[0102] Figure 17A –17D shows an example of the PMUT sensor element 1700, which incorporates a 2D electron gas structure. Figures 17A-17D Examples and the above about Figures 7A-7D The described example is similar, where the upper electrode is an external electrode, not an internal electrode. Figure 17A and 17B A side view shows an example of the PMUT sensor element 1700 operating in non-ultrasonic force detection mode and ultrasonic imaging mode, respectively. Figure 17C It shows Figure 17A and 17B The image shows a top view of the PMUT sensor element 1700. Figure 17D It shows Figure 17A and 17B The equivalent circuit of the PMUT sensor element is shown in the figure.

[0103] PMUT sensor element 1700 includes a 2D electron gas structure 1740 formed on a mechanical layer 1730 of the PMUT diaphragm. Figures 17A-17C In the example, the 2D electron gas structure is placed at the center of the circular diaphragm, while... Figure 7A and 7B The deformable diaphragm is shown disposed on the periphery. It comprises a piezoelectric layer stack 1710 and a mechanical layer 1730 supported on a cavity 1720 by an anchoring structure 1770. The cavity 1720 may be formed in or on a substrate 1760. The piezoelectric layer stack 1710 comprises a piezoelectric layer 1715, a lower electrode 1712, and an upper electrode 1713. The upper electrode 1713 in the illustrated embodiment may also be referred to as an external electrode because it is disposed around the peripheral portion of the diaphragm.

[0104] Figure 17A This is a side view of a PMUT sensor element 1700 exhibiting static displacement due to an applied force. (As mentioned above...) Figure 1C As described, in operation, the piezoelectric layer stack 1710 and mechanical layer 1730 can be bent in response to an applied force, and the PMUT sensor element 1700 converts the applied force into an electrical signal that can be read by the transceiver circuitry.

[0105] Figure 17B This is a side view of a PMUT sensor element 1700 that exhibits dynamic displacement due to the generation and detection of ultrasonic waves. (As described above...) Figure 1D As described, during operation in ultrasonic imaging mode, the piezoelectric layer stack 1710 and mechanical layer 1730 can bend and vibrate in response to a time-varying excitation voltage applied by the transceiver circuitry across the external electrode 1713 and internal electrode 1712. Similarly, the 2D electron gas structure 1740 can exhibit mechanical strain during static displacement of the diaphragm under applied force or during dynamic displacement of the diaphragm in response to reflected ultrasonic waves, which can produce static or time-varying transistor characteristics detectable by the transceiver circuitry.

[0106] Figure 18A –18D illustrates an example of a process flow for fabricating a sensor element 1800 comprising a substrate 1860, a diaphragm, and a 2D electron gas structure 1840 disposed on the diaphragm. The diaphragm may include a portion of a mechanical layer 1830 spanning a cavity 1820, wherein the cavity 1820 is positioned between the mechanical layer 1830 and the substrate 1860. The mechanical layer 1830 may be supported on the cavity 1820 by an anchoring structure 1870. The substrate 1860 may include the portion of the mechanical layer 1830 as described above. Figure 7A PMUT sensor element 700 and about Figure 17A The PMUT sensor element 1700 describes and demonstrates one or more piezoelectric layers.

[0107] Substrate 1860 may comprise a glass substrate or a semiconductor substrate, such as a silicon substrate, an SOI substrate, or a cavity SOI substrate. In some embodiments, substrate 1860 may comprise a cavity SOI substrate having one or more cavities 1820 formed between a bonded pair of silicon substrates. In some embodiments, substrate 1860 may comprise one or more sealed cavities formed by a surface micromachining process that allows for the removal of sacrificial material in the cavity regions and subsequent sealing of etched channel regions (not shown) using one or more deposited thin films to establish and maintain a specified vacuum level within the cavities 1820.

[0108] like Figure 18A As shown, a buffer layer 1882, such as a gallium nitride (GaN) buffer layer, can be deposited on the mechanical layer 1830 using processes such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In some embodiments, a seed layer of aluminum nitride (AlN) or a stack of seed layers of aluminum nitride, molybdenum, and aluminum nitride (AlN / Mo / AlN) can serve as the buffer layer 1882. A body layer 1884, such as a GaN body layer, can be epitaxially deposited on the buffer layer 1882 using processes such as MOCVD or MBE. A gate dielectric layer 1886, such as aluminum gallium nitride (AlGaN), can be deposited on the body layer 1884 using processes such as MOCVD or MBE. The gate dielectric layer 1886, body layer 1884 and buffer layer 1882 can be patterned and etched using, for example, photolithography-based photosensitive materials (e.g., photoresist) to form the body of the 2D electron gas structure 1840, the photosensitive material acting as a mask for dry etching (e.g., plasma etching or reactive ion etching) of the AlGaN and GaN layers.

[0109] like Figure 18BAs shown, a source stack 1888 and a drain stack 1890 can be formed on the gate dielectric layer 1886. The source stack 1888 and drain stack 1890 can be formed by depositing a titanium barrier layer 1850 on the gate dielectric layer 1886, followed by depositing an aluminum conductive layer 1852, a nickel second barrier layer 1854, and a gold second conductive layer 1856. The source stack 1888 and drain stack 1890 can be formed using photolithography, with patterning and etching of the conductive layer 1856, barrier layer 1854, conductive layer 1852, and barrier layer 1850 on the gate dielectric layer 1886. Alternatively, a lift-off process can be used to pattern and etch the barrier layer 1850, conductive layer 1852, barrier layer 1854, and conductive layer 1856, in which the layers are deposited on a patterned photoresist layer having openings in the source and drain regions, and in which a wet or dry etching process is subsequently used to remove portions of the photoresist layer and the underlying conductive and barrier layers, thereby leaving the conductive and barrier layers in the source and drain regions intact to form the source stack 1888 and drain stack 1890. An annealing sequence such as a rapid thermal annealing (RTA) sequence can be used to anneal the substrate 1860 and the layers formed thereon containing the source stack 1888 and drain stack 1890, and dopants can be introduced from the source and drain stacks through the gate dielectric layer 1886 and incorporated into the body layer 1884.

[0110] A gate stack 1892 can be formed on the gate dielectric layer 1886, such as Figure 18C As shown. A nickel barrier layer 1864 and a gold conductive layer 1866 can be deposited on the gate dielectric layer 1886 using processes such as sputtering or evaporation, followed by patterning and etching of the conductive layer 1866 and the barrier layer 1864. Alternatively, the gate stack 1892 can be formed using a stripping process with the deposited barrier layer and conductive layer.

[0111] A passivation layer 1868, such as a silicon nitride layer, can be deposited on the exposed portion of the substrate 1860 (including the source stack 1888, gate stack 1892, and drain stack 1890). Figure 18D As shown. The passivation layer 1868 can be patterned and etched to form contact openings and expose the outer portions of the source stack 1888, gate stack 1892, and drain stack 1890. Electrical connections to the source, gate, and drain of the 2D electron gas structure 1840 can be provided using one or more interconnect metal layers (not shown). In some embodiments, MBE and MOCVD deposited materials can be transferred from a carrier substrate (not shown) to the mechanical layer 1830 or substrate 1860 using a transfer process.

[0112] As used in this article, the phrase “at least one of a series of items” refers to any combination of those items containing a single member. For example, “at least one of a, b, or c” is intended to cover: a, b, c, ab, ac, bc, and abc.

[0113] The various illustrative logics, logic blocks, modules, circuits, and algorithmic processes described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. The interchangeability of hardware and software has been demonstrated in terms of overall functionality and in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0114] Hardware and data processing apparatuses for implementing the various illustrative logics, logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented or executed using general-purpose single-chip or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination thereof. A general-purpose processor may be a microprocessor or any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. In some embodiments, specific processes and methods may be performed by a circuit system dedicated to a given function.

[0115] In one or more aspects, the described functionality may be implemented in hardware, digital electronic circuit systems, computer software, firmware (including the structures disclosed in this specification and their structural equivalents), or any combination thereof. Embodiments of the subject matter described in this specification may also be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a computer storage medium for execution by a data processing device or for controlling the operation of a data processing device.

[0116] If implemented in software, functionality can be stored in or transmitted via a computer-readable medium, such as a non-transitory medium, in the form of one or more instructions or codes. The methods or algorithms disclosed herein can be implemented as processor-executable software modules that can reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media, wherein the communication media includes any media enabled to transfer a computer program from one place to another. Storage media can be any available media that can be accessed by a computer. For example, but not limitingly, non-transitory media can include RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, magnetic disk storage devices or other magnetic storage devices, or any other media that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Furthermore, any connection can be appropriately referred to as computer-readable media. The disks or discs used herein include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, wherein disks typically magnetically copy data, while discs optically copy data using lasers. Combinations of the foregoing should also be included within the scope of computer-readable media. Additionally, the operation of a method or algorithm may reside on a machine-readable medium and a computer-readable medium in the form of one or any combination or set of code and instructions, which may be incorporated into a computer program product.

[0117] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of this disclosure. Therefore, the claims are not intended to be limited to the embodiments shown herein, but are accorded the widest scope consistent with this disclosure, the principles disclosed herein, and the novel features. Additionally, as will be readily understood by those skilled in the art, the terms “upper” and “lower,” “top” and “bottom,” “front” and “rear,” and “above,” “overlapping,” “up,” “below,” and “below” are sometimes used for convenience in describing the drawings and indicate relative positions corresponding to the orientation of the figures on a correctly oriented page, and may not reflect the correct orientation of the implemented apparatus.

[0118] Some features described in this specification in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as functioning in certain combinations and even initially required, in some cases one or more features from the required combination may be removed from said combination, and the required combination may involve sub-combinations or variations of sub-combinations.

[0119] Similarly, although operations are described in a specific order in the accompanying drawings, this should not be construed as requiring such operations to be performed in the specific order shown or sequentially, or that all shown operations should be performed to achieve the desired result. Furthermore, the drawings may schematically depict yet another example process in the form of a flowchart. However, other operations not depicted may be incorporated into the illustrated example processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the shown operations. In some cases, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments fall within the scope of the following claims. In some cases, the actions described in the claims may be performed in a different order, and the actions may still achieve the desired result.

Claims

1. An apparatus comprising: Substrate; The sensor comprises an array of piezoelectric micromechanical ultrasonic transducer (PMUT) sensor elements on the substrate, wherein each PMUT sensor element includes a diaphragm having a piezoelectric layer and a mechanical layer, wherein the diaphragm is capable of static displacement when an applied force is applied and dynamic displacement when the PMUT sensor element receives or transmits an ultrasonic signal; and A sensor controller configured to switch the sensor between one or more non-ultrasonic force detection modes and ultrasonic imaging modes in the PMUT sensor elements, wherein the applied force is measured in the non-ultrasonic force detection mode, and wherein the object is ultrasonically imaged during the ultrasonic imaging mode.

2. The device of claim 1, wherein the device is configured to detect finger touch based on force measured above a threshold by the device in the non-ultrasonic force detection mode.

3. The device of claim 2, wherein the sensor controller is configured to provide a wake-up signal to the application processor after detecting the finger touch to activate one or more wake-up operations.

4. The device of claim 2, wherein the device is configured to detect finger lifting based on a threshold external force measured by the device in the non-ultrasonic force detection mode after the finger touch is detected.

5. The device according to claim 4, wherein the threshold external force is less than the threshold upper force.

6. The device of claim 3, wherein the sensor controller is configured to initialize the ultrasound imaging mode after detecting the finger touch.

7. The device of claim 1, wherein the sensor controller is configured to initialize the ultrasonic imaging mode based on the device measuring a minimum imaging threshold force in the non-ultrasonic force detection mode.

8. The device of claim 1, wherein one or more of the PMUT sensor elements comprise a 2D electron gas structure disposed on the diaphragm.

9. The device of claim 1, wherein the sensor controller is configured to switch between a non-ultrasonic force detection mode and an ultrasonic imaging mode for each PMUT sensor element in the PMUT sensor element array.

10. The device of claim 1, wherein the sensor controller is configured to switch between a non-ultrasonic force detection mode and an ultrasonic imaging mode for a subset of the PMUT sensor elements in the PMUT sensor element array.

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