Ultrasound apparatus

Abstract

The invention relates to an ultrasonic device having a piezoelectric micromechanical ultrasonic transducer, which comprises at least one piezoelectric element. The ultrasound device also includes a substrate having a first surface and an opposing second surface, and a CMOS control circuit including a CMOS metallization layer on the first surface and a plurality of transistors integrally disposed within the first surface. The piezoelectric element includes a movable piezoelectric diaphragm having a piezoelectric body, a first electrode, and a second electrode, both disposed on the first surface. A cavity is defined in part by the movable piezoelectric diaphragm and in part by the substrate. The movable piezoelectric diaphragm defines at least a portion of a wall of the cavity and is configured to deform into the cavity. The CMOS control circuit is configured to control ultrasound transmission by controlling movement of the movable piezoelectric diaphragm and / or to control ultrasound reception by receiving a signal generated by movement of the movable piezoelectric diaphragm.

Description

Technical Field

[0001] The present invention relates to ultrasonic devices, particularly piezoelectric ultrasonic transducers, and methods for manufacturing such devices. Background Technology

[0002] Ultrasound equipment is used in many different technological fields, including medical imaging, drug delivery devices, non-destructive testing, gesture recognition, and fingerprint sensors. For many applications within these technological fields, miniaturized ultrasound equipment is required.

[0003] More generally, microelectromechanical systems (MEMS) technology can be used to fabricate miniaturized devices with both electrical and mechanical components. A piezoelectric micromechanical ultrasonic transducer (PMUT) is an example of a type of ultrasonic transducer fabricated using MEMS processes. A PMUT typically comprises a thin piezoelectric film sandwiched between two electrodes and disposed above a cavity defined by a substrate. The piezoelectric material can convert electrical energy into mechanical energy and vice versa. Specifically considering PMUT devices, movement of the piezoelectric film can be used to generate and / or sense ultrasonic waves.

[0004] For many applications, it would be advantageous to provide a PMUT that is highly integrated with associated electronics to improve functionality. However, incompatibilities with some components of the desired circuitry and with MEMS processing make providing highly integrated devices challenging.

[0005] Therefore, the present invention seeks to improve the integration of PMUT MEMS components and associated circuitry to provide a compact, highly integrated ultrasound device. Summary of the Invention

[0006] According to one aspect of the present invention, an ultrasonic device is provided, the ultrasonic device comprising: A substrate having a first surface and an opposing second surface; A CMOS control circuit, the CMOS control circuit including a CMOS metallization layer on a first surface and a plurality of transistors integrally disposed within the first surface; A piezoelectric micromechanical ultrasonic transducer includes at least one piezoelectric element, wherein the piezoelectric element includes a movable piezoelectric diaphragm. A cavity, which is partially defined by a movable piezoelectric diaphragm and partially by a substrate; The movable piezoelectric diaphragm includes a piezoelectric body, a first electrode, and a second electrode, both of which are arranged on the first surface. The movable piezoelectric diaphragm defines at least a portion of the cavity wall and is configured to deform into the cavity; and The CMOS control circuit is configured to control ultrasonic emission by controlling the movement of a movable piezoelectric diaphragm and / or to control ultrasonic reception by receiving signals generated by the movement of the movable piezoelectric diaphragm.

[0007] MEMS components and complementary metal-oxide-semiconductor (CMOS) control circuitry are disposed on the same surface of the substrate to provide a highly integrated monolithic ultrasonic device that is relatively simple to manufacture and cost-effective.

[0008] The substrate may include a silicon wafer. The substrate may be a semiconductor substrate. Multiple transistors are integrally disposed within a first surface; that is, multiple transistors may be formed on and extend into the substrate from the first surface. The CMOS control circuitry can be formed using conventional CMOS fabrication techniques. After the multiple transistors are formed, a CMOS metallization layer may be formed on the first surface.

[0009] A cavity is a hole within a substrate into which a movable piezoelectric diaphragm can be deformed; that is, the cavity provides space for the movable piezoelectric diaphragm to flex therein. The movable piezoelectric diaphragm can also deform in the opposite direction (i.e., away from the cavity). Typically, the movable piezoelectric diaphragm defines one wall of the cavity, and the substrate defines any other walls of the cavity. For example, if the cavity is cubic in shape, the substrate may define four walls of the cavity.

[0010] A piezoelectric body may be disposed between a first electrode and a second electrode. An electric field may be applied between the first and second electrodes to cause deflection of the movable piezoelectric diaphragm. In some embodiments, the substrate includes a buried oxide (BOX) layer. By providing a buried oxide layer, CMOS devices can be operated at higher voltages, thereby facilitating greater deflection of the movable piezoelectric diaphragm.

[0011] The piezoelectric substrate may include at least one piezoelectric material that can be processed at temperatures below 450°C. Examples of piezoelectric materials that can be processed at temperatures below 450°C include aluminum nitride (AlN), zinc oxide (ZnO), and / or scandium aluminum nitride (ScAIN). CMOS components may be damaged at temperatures above 450°C. By using piezoelectric materials that can be processed at temperatures below 450°C, MEMS and CMOS components can be integrated without causing degradation of the CMOS components, thereby improving device operation and efficiency.

[0012] In some embodiments, the piezoelectric element may include an internal portion and an external portion. In these embodiments, the internal portion of the piezoelectric element includes an internal piezoelectric body and a pair of internal electrodes; and the external portion of the piezoelectric element includes an external piezoelectric body and a pair of external electrodes. Each of the internal and external portions may emit and / or receive ultrasound. In some embodiments, the ultrasonic device is configured such that a first potential difference can be applied between the pair of internal electrodes to cause deflection of the internal piezoelectric body in a first direction, and a second potential difference can be applied between the pair of external electrodes to cause deflection of the external piezoelectric body in a second direction opposite to the first direction.

[0013] In some implementations, the walls of the cavity defined by the movable piezoelectric diaphragm are continuous. That is, the movable piezoelectric diaphragm extends across the entire side of the cavity.

[0014] In other embodiments, the movable piezoelectric diaphragm may be discontinuous, i.e., it may not extend across the entire side of the cavity. Instead, the movable piezoelectric diaphragm may have channels defined therethrough. For example, the piezoelectric diaphragm may be annular. In some embodiments, each electrode, piezoelectric body, and any other layer that is part of the piezoelectric diaphragm may be annular and concentrically arranged such that channels are defined through the movable piezoelectric diaphragm. The discontinuous arrangement of the movable piezoelectric diaphragm increases the flexibility of the membrane, thereby altering the frequency response of the movable piezoelectric diaphragm. Those skilled in the art will understand that different ultrasonic frequencies are better suited to different ultrasonic applications. In some embodiments, the channels defined through the movable piezoelectric diaphragm may be filled with an additional material (instead of leaving them empty). For example, the channels may be filled with benzocyclobutene (BCB). This modification also affects the frequency response of the ultrasonic device.

[0015] In some embodiments, the CMOS metallization layer includes conductive connections extending from at least one of a plurality of transistors to at least one of a first electrode and a second electrode of the piezoelectric element. These conductive connections may be adapted to conduct digital or analog information. These conductive connections may be adapted to conduct drive waveforms to actuate the piezoelectric element. In some embodiments, the metallization layer includes a planar structure formed by chemical mechanical planarization to facilitate more direct fabrication of the ultrasonic device.

[0016] Typically, cavities are formed using an etching process. In some embodiments, at least a portion of at least one of the cavity walls is defined by a deep trench isolation structure. The deep trench isolation structure typically comprises a different material that is more resistant to etching processes compared to the rest of the substrate. Therefore, deep trench isolation structures can be used to better define the cavity geometry.

[0017] The ultrasound device may further include a first acoustic matching layer having a first acoustic impedance.

[0018] When ultrasound travels between two media, a mismatch between the corresponding acoustic impedances of these media causes unwanted reflections, resulting in undesirable reverberation, heating, and wave distortion. An acoustic matching layer is a layer with acoustic impedance selected to increase the transmission of ultrasound waves between a part of an ultrasound device and another medium. The other medium can be external to the device, or it can be a medium contained within the cavity (e.g., a fluid such as air).

[0019] The inventors have recognized that by incorporating an acoustic matching layer, unwanted reflections of ultrasound waves at the boundaries of the ultrasound device are avoided. Therefore, greater transmission of ultrasound waves between two different media can be achieved.

[0020] Furthermore, the inventors have recognized that this provides improved bandwidth for the device, i.e., improved performance of the device over a wider frequency range. Advantageously, the axial resolution achievable using the aforementioned ultrasonic device is improved compared to devices with more limited bandwidth.

[0021] In particular, the addition of an acoustic layer can advantageously modify the resonant frequency of the device.

[0022] At least a portion of the piezoelectric micromechanical ultrasonic transducer and CMOS control circuitry may be disposed between the first acoustic matching layer and the cavity. Alternatively, the movable piezoelectric diaphragm may include the first acoustic matching layer, wherein the first acoustic matching layer defines at least a portion of the cavity wall, the at least portion being configured to deform into the cavity.

[0023] The first acoustic matching layer may be one of a plurality of acoustic matching layers. At least a portion of the piezoelectric micromechanical ultrasonic transducer and the CMOS control circuit may be disposed between the first acoustic matching layer and the cavity. A movable piezoelectric diaphragm may include a second acoustic matching layer, wherein the second acoustic matching layer defines at least a portion of the cavity wall.

[0024] An ultrasonic device may be configured to transmit ultrasound to an external medium via a first acoustic matching layer. An ultrasonic device may also be configured to receive ultrasound propagating in the external medium via the first acoustic matching layer.

[0025] An acoustic matching layer can define the outer surface of an ultrasonic device for contact with an external medium (e.g., direct contact).

[0026] The ultrasonic device may include a protective layer to protect the MEMS components. The protective layer may be disposed between the first acoustic matching layer and the piezoelectric micromechanical ultrasonic transducer.

[0027] The first impedance of the acoustic matching layer can be selected based on the impedance of the external medium. The first impedance of the acoustic matching layer can be selected based on the impedance of the MEMS layer. Specifically, the first impedance of the acoustic matching layer can be selected based on the impedance of the piezoelectric micromechanical ultrasonic transducer. The first impedance of the acoustic matching layer can be selected based on the impedance of the protective layer. The value of the first impedance can be between the impedance of the external medium and the impedance of the portion of the ultrasonic device directly adjacent to the acoustic matching layer. The protective layer can be directly adjacent to the acoustic matching layer. At least a portion of the piezoelectric micromechanical ultrasonic transducer can be directly adjacent to the acoustic matching layer.

[0028] The acoustic matching layer, or each acoustic matching layer, may include a material that can be processed at temperatures below 450°C. The acoustic matching layer, or each acoustic matching layer, may include benzocyclobutene (BCB), polydimethylsiloxane (PDMS), polyurethane, high-density polyethylene (HDPE), and / or epoxy-negative photoresist (e.g., Su-8 3025).

[0029] In some implementations, the acoustic matching layer extends across the entire side of the cavity.

[0030] In other embodiments, the first acoustic matching layer may be discontinuous, for example, it may not extend across the entire side of the cavity. Instead, the first acoustic matching layer (typically accompanied by a movable piezoelectric diaphragm) has a channel extending through it. The ultrasound device may be configured to allow fluid to move between the cavity and the external environment via the channel.

[0031] The first acoustic matching layer may be annular. In some embodiments, each acoustic matching layer, each electrode, piezoelectric body, and any other layer that is part of a piezoelectric diaphragm may be annular and concentrically arranged such that it extends through a defined channel. In some embodiments, the channel may be filled with another material (instead of leaving it empty). For example, the channel may be filled with benzocyclobutene (BCB).

[0032] The characteristics of any channel defined within the movable piezoelectric diaphragm and / or acoustic matching layer may be based on the desired frequency response of the movable piezoelectric diaphragm or support requirements (i.e., the structure above the cavity needs to be adequately supported to maintain device integrity and performance). Channel characteristics include the number of channels, the size of the channel openings, the shape of the channels, and the location of the channels.

[0033] The ultrasound device can be configured to operate at a first frequency, and the shape of the cavity is selected depending on the first frequency.

[0034] In practice, ultrasound equipment will be sensitive to frequency range (e.g., frequency bandwidth). The first frequency falls within the frequency bandwidth.

[0035] The inventors have recognized that the frequency response of an ultrasound device can be tuned using the shape of a cavity. Typically, a cavity serves as an acoustic resonator. By shaping the cavity based on a specific frequency, a more customized frequency response can be provided. Therefore, ultrasound devices with improved bandwidth and thus improved resolution can be provided.

[0036] A cavity can be shaped to reduce (e.g., by canceling) certain frequencies. A cavity can be shaped to amplify certain frequencies.

[0037] The cavity can be cylindrical. It can also be shaped as a cuboid. Typically, one of the walls of the cavity is defined by a movable piezoelectric diaphragm. The cavity will also typically have at least one sidewall extending in a direction having a component perpendicular to a plane parallel to the movable piezoelectric diaphragm (when stationary). Typically, the plane parallel to the movable piezoelectric diaphragm (when stationary) is also parallel to a first surface of the substrate.

[0038] The cross-sectional area of ​​the cavity can vary. One or more of the sidewalls of the cavity can be angled relative to a direction perpendicular to a plane parallel to the movable piezoelectric diaphragm (when stationary).

[0039] One or more of the sidewalls of the cavity may be curved. One or more of the sidewalls of the cavity may have convex portions. One or more of the sidewalls of the cavity may have concave portions. One or more of the sidewalls of the cavity may have both concave and convex portions. One or more of the sidewalls of the cavity may smoothly change between concave and convex portions (e.g., the wall may have an undulating profile).

[0040] One or more of these sidewalls of the cavity may include recessed portions (e.g., side chambers).

[0041] The cavity can be configured to contain fluids other than air. The cavity can contain fluids other than air. The cavity can contain liquids. The cavity can be partially closed; for example, one side of the cavity can be open or partially open.

[0042] The inventors have recognized that the frequency response of an ultrasonic device is affected by the medium contained within the cavity. They have further recognized that the frequency response can be controlled by modifying the shape of the cavity based on the medium to be contained therein.

[0043] The ultrasound device may further include a first attenuation layer disposed on at least one wall of the cavity.

[0044] The inventors have recognized that the frequency response of an ultrasound device can be tuned by incorporating an attenuation layer on the wall of the cavity. Typically, the attenuation layer is configured to absorb ultrasound waves of a specific frequency propagating within the cavity. The attenuation layer can be configured to absorb ultrasound waves within a specific frequency range. This allows for further optimization of the frequency response of the ultrasound device.

[0045] In some embodiments, the movable piezoelectric diaphragm includes at least a portion of a CMOS metallization layer, and optionally, the CMOS metallization layer includes conductive connectors extending from at least one crystal of a plurality of transistors to at least one of a first electrode and a second electrode of the piezoelectric element.

[0046] In an embodiment where the movable piezoelectric diaphragm includes at least a portion of a CMOS metallization layer, at least a portion of the movable piezoelectric diaphragm deformed into the cavity includes at least a portion of the CMOS metallization layer. This cavity is necessary to allow oscillation of the movable piezoelectric diaphragm. However, the presence of the cavity reduces the space available for electrical wiring. By providing at least a portion of the CMOS metallization layer in the movable piezoelectric diaphragm, more space is available for metal wiring, thereby contributing to device miniaturization.

[0047] At least one of the plurality of transistors can be directly connected (i.e., without an intermediate transistor) to at least one of the first or second electrodes via one of the conductive connectors.

[0048] In some embodiments, the ultrasonic device further includes an additional layer on a first surface of the substrate, wherein a movable piezoelectric diaphragm includes at least a portion of the additional layer, wherein the additional layer defines at least a portion of the wall of the cavity defined by the movable piezoelectric diaphragm, and optionally, wherein at least a portion of a CMOS metallization layer is integrally disposed within the additional layer, and / or optionally, wherein the additional layer includes a CMOS oxide.

[0049] In an embodiment where the movable piezoelectric diaphragm includes at least a portion of an additional layer, at least a portion of the movable piezoelectric diaphragm deformed into the cavity includes at least a portion of the additional layer.

[0050] An additional layer may be disposed directly on a first surface of the substrate. The additional layer may be disposed directly on the first surface of the substrate, and one of the first and second electrodes may be disposed between the additional layer and the piezoelectric body. The additional layer may define at least a portion of the wall of the cavity defined by the movable piezoelectric film. The presence of this additional layer facilitates more controlled oscillations of the piezoelectric film (i.e., oscillations with better defined characteristics). In some embodiments, at least a portion of the CMOS metallization layer may be integrally disposed within the additional layer. The additional layer may include oxides, nitrides, oxide oxynitrides, or a stack.

[0051] In some embodiments, an additional layer defines a notch in the movable piezoelectric region. The walls of the notch may be at least partially defined by a CMOS metallization layer. The presence of the notch in the film affects the frequency response of the movable piezoelectric film.

[0052] Adding an additional layer including a CMOS oxide layer is particularly advantageous because it requires fewer MEMS fabrication steps. Therefore, devices with movable piezoelectric films including CMOS oxide layers are relatively simple to manufacture.

[0053] In some implementations, the additional layer may be composed of CMOS oxide.

[0054] In some implementations, the metallization layer is one of a plurality of metallization layers integrally disposed within an additional layer. The combination of an additional layer comprising a CMOS oxide and a plurality of metallization layers integrally formed therein allows for multilayer conductive interconnects, thereby providing a high level of functionality.

[0055] In some embodiments, the at least one piezoelectric element is one of a plurality of piezoelectric elements arranged in an array. Each piezoelectric element includes a movable piezoelectric diaphragm, and each movable piezoelectric diaphragm includes a piezoelectric body, a first electrode, and a second electrode, which are arranged on a first surface. The cavity is one of a plurality of cavities, wherein each movable piezoelectric diaphragm defines at least a portion of the wall of the respective cavity among the plurality of cavities.

[0056] The ultrasound device may further include a first acoustic matching layer having a first acoustic impedance. The ultrasound device may further include a first attenuation layer disposed on at least one wall of at least one of a plurality of cavities (e.g., each cavity or subset, or one or more cavities). The ultrasound device may be configured to operate at a first frequency, and the shape of at least one of the plurality of cavities (e.g., each cavity, subset, or one or more cavities) is selected according to the first frequency.

[0057] An array of piezoelectric elements may be arranged between a first acoustic matching layer and each of the plurality of cavities. The acoustic impedance of the acoustic matching layer may vary within the acoustic matching layer. For example, the acoustic matching layer may have a first acoustic impedance toward its edge and a second acoustic impedance toward the center of the acoustic matching layer (different from the first acoustic impedance).

[0058] Each movable piezoelectric diaphragm may include an acoustic matching layer, wherein each acoustic matching layer defines at least a portion of the wall of a corresponding cavity. At least one acoustic matching layer defining at least a portion of the wall of a corresponding cavity may have a different acoustic impedance compared to another acoustic matching layer defining at least a portion of the wall of another cavity.

[0059] The shape of one cavity in a plurality of cavities may differ from the shape of another cavity in the plurality of cavities.

[0060] In some implementations, each movable piezoelectric diaphragm includes at least a portion of a CMOS metallization layer.

[0061] For some applications, it is helpful to provide an integrated PMUT device with multiple piezoelectric elements arranged in an array, where each piezoelectric element is connected to a corresponding wiring. For crosstalk considerations, it may be desirable to provide an array with a high element density. However, providing a high element density and the required wiring can be technically challenging. Providing a high element density is particularly challenging when the substrate space is limited by the presence of cavities to allow the deflection of corresponding movable piezoelectric diaphragms.

[0062] By providing at least a portion of the CMOS metallization layer in each movable piezoelectric diaphragm, more space is available for metal wiring, thereby contributing to device miniaturization. Furthermore, the inventors have recognized that providing at least a portion of the CMOS metallization layer in each movable piezoelectric diaphragm also helps to avoid electrical crosstalk.

[0063] In some implementations, the CMOS metallization layer includes a conductive connector extending from at least one of a plurality of transistors to at least one of a first electrode and a second electrode of each respective piezoelectric element.

[0064] In some embodiments, the ultrasonic device further includes an additional layer on a first surface of the substrate, wherein each movable piezoelectric diaphragm includes at least a portion of the additional layer, wherein the additional layer defines at least a portion of the wall of each cavity defined by the respective movable piezoelectric diaphragm, and optionally, wherein at least a portion of the CMOS metallization layer is integrally disposed within the additional layer, and / or optionally, wherein the additional layer includes CMOS oxide.

[0065] In some implementations, the CMOS metallization layer includes conductive connectors extending from at least one of a plurality of transistors to at least one of a first electrode and a second electrode of a respective piezoelectric element, and optionally, the lengths of the conductive connectors are uniform.

[0066] It is advantageous for the conductive connectors to be uniform (i.e., having similar length, thickness, and width) so that they are affected by voltage drop, parasitic capacitance, antenna effects, etc., to a similar degree. In some embodiments, the length variation of the conductive connectors does not exceed 1 cm, preferably not more than 0.1 cm. Typically, the length variation of the conductive connectors does not exceed 10 times the spacing between adjacent piezoelectric elements in the array (i.e., piezoelectric elements adjacent to each other along a row of the array).

[0067] In some embodiments, the array includes a first region having a first side and a second side opposite to the first side, wherein a plurality of piezoelectric elements are arranged in rows, wherein conductive connectors extend into the array from one or both of the first and second sides between rows of piezoelectric elements, and optionally, wherein the first region is elongated, and the first and second sides correspond to the long side along the length of the first region.

[0068] By incorporating elongated regions and conductive connectors extending into an array between rows of piezoelectric elements, each piezoelectric element can receive signals (e.g., drive waveforms) transmitted through the conductive connectors at very similar times. This improves the uniformity of the ultrasonic response when using an array of elements.

[0069] In some embodiments, the first region includes at least a first row of piezoelectric elements, a second row of piezoelectric elements, and a third row of piezoelectric elements, wherein a first subset of the conductive connectors extends along the length of the second row between different corresponding piezoelectric elements in the first and second rows, and optionally, The second subset of conductive connectors extends along the length of the second row between the piezoelectric elements in the second row and the piezoelectric elements in the third row, to different corresponding piezoelectric elements.

[0070] A compact wiring arrangement that facilitates device miniaturization is possible by providing a wiring arrangement in which a first region includes at least a first row of piezoelectric elements, a second row of piezoelectric elements, and a third row of piezoelectric elements (typically without other rows in between), wherein multiple (and typically at least four) conductive connectors extend along the length of the second row between the first row of piezoelectric elements and the second row of piezoelectric elements to different corresponding piezoelectric elements, typically wherein multiple (and typically at least four) conductive connectors extend along the length of the second row between the second row of piezoelectric elements and the third row of piezoelectric elements.

[0071] In some implementations, at least a portion of the CMOS control circuitry is arranged in a column adjacent to at least one of the first and second sides of the first region.

[0072] By providing at least a portion of a CMOS control circuit in a column adjacent to at least one of the first and second sides of the first region, and combining it with conductive connectors extending between piezoelectric elements from the CMOS circuit, it is easier to manufacture an ultrasonic device with a small form factor.

[0073] In some implementations, the CMOS control circuitry includes a drive circuit configured to actuate each movable piezoelectric diaphragm in at least a subset of a plurality of piezoelectric elements, such that an ultrasonic signal is emitted. The CMOS control circuit includes a receiving circuit for receiving ultrasonic signals; Optionally, at least a portion of the driving circuit and / or at least a portion of the receiving circuit are arranged in a column adjacent to at least one of the first side and the second side of the first region.

[0074] A highly integrated and compact ultrasonic device can be provided by incorporating CMOS control circuitry that includes drive and receiver circuitry on the same surface as the MEMS device. The size of the ultrasonic device can be further reduced by arranging these circuits in columns adjacent to at least one of the first and second sides of the first region.

[0075] In some implementations, the CMOS control circuitry includes a delay circuitry and / or apodization circuitry; The delay circuit is configured to delay the actuator waveform transmitted to the other piezoelectric element relative to the actuator waveform transmitted to one of the piezoelectric elements, and optionally, at least a portion of the delay circuit is arranged in a column adjacent to at least one of the first side and the second side of the first region. The apodized circuit is configured to increase the amplitude of the actuator waveform transmitted to the other piezoelectric element relative to the actuator waveform transmitted to one of the piezoelectric elements, and optionally, at least a portion of the apodized circuit is arranged in a column adjacent to at least one of the first and second sides of the first region.

[0076] By incorporating a delay circuit, the ultrasound beam emitted from the ultrasound device can be focused. This provides improved resolution for imaging applications and improved energy deposition for therapeutic applications. By incorporating an apodization circuit, the frequency content of the emitted pulses can be better controlled, thereby providing improved signal quality for imaging applications. It is particularly advantageous to arrange this circuit in a column adjacent to at least one of the first and second sides of the first region, as this allows for a particularly compact ultrasound device.

[0077] In some implementations, the CMOS control circuitry includes an amplifier circuit for amplifying the received ultrasonic signal. Optionally, the amplification circuit is configured to amplify the received signal based on the depth to which the received signal has been reflected. Optionally, at least a portion of the amplifier circuit is arranged in a column adjacent to at least one of the first side and the second side of the first region.

[0078] By incorporating an amplification circuit, the received ultrasonic signal is less affected by noise. This amplification can be based on the depth of the received signal (e.g., time-gain amplification). Signal quality is further improved by arranging the amplification circuit in a column adjacent to at least one of the first and second sides of the first region.

[0079] According to another aspect of the invention, a wearable device is provided, which includes any of the ultrasound devices described herein.

[0080] In some implementations, the wearable device is a patch. For example, a patch that can be worn on a user's arm.

[0081] According to another aspect of the invention, a method for forming any of the ultrasonic devices described herein is provided.

[0082] The ultrasonic equipment includes a piezoelectric micromechanical ultrasonic transducer, which comprises n piezoelectric elements. n cavities are formed within a substrate, wherein the substrate has a first surface and an opposing second surface; Multiple transistors are formed within the first surface; A CMOS metallization layer is formed on the first surface; as well as Form n movable piezoelectric films; Each cavity is partially defined by a substrate and partially by one of the n movable piezoelectric films.

[0083] In some embodiments, the method may include forming the cavity using a deep reactive ion etching (DRIE) process. DRIE etching may be performed from the back side of the substrate, and optionally also from the front side of the substrate. In some embodiments, deep trench isolation structures are formed in the substrate to define the walls of the cavity.

[0084] According to another aspect of the present invention, a method for using any of the above-described ultrasonic devices is provided, the method comprising: Transmitting and / or receiving ultrasonic signals; The emission of ultrasonic signals includes using at least a subset of multiple transistors to control the movement of a movable piezoelectric diaphragm; and Receiving ultrasonic signals includes receiving signals generated by the movement of a movable piezoelectric membrane.

[0085] In some implementations, the CMOS control circuitry includes an amplifier circuit, and the method includes using the amplifier circuitry to amplify the received signal.

[0086] In some embodiments, the ultrasonic device includes multiple piezoelectric elements, and the CMOS control circuit includes a beamforming circuit, and the method includes beamforming the received signal using the beamforming circuit.

[0087] In some embodiments, the ultrasonic device includes multiple piezoelectric elements, and the CMOS control circuit includes an apodization circuit, wherein the method includes emitting a first ultrasonic signal from one piezoelectric element and emitting a second ultrasonic signal from a second piezoelectric element, wherein the amplitude of the first ultrasonic signal is different from the amplitude of the second ultrasonic signal.

[0088] In some embodiments, the ultrasonic device includes a plurality of piezoelectric elements, and the CMOS control circuit includes a delay circuit, wherein the method includes emitting a first ultrasonic signal from one piezoelectric element and emitting a second ultrasonic signal from a second piezoelectric element, wherein the first ultrasonic signal is delayed relative to the second ultrasonic signal. Attached Figure Description

[0089] Example embodiments of the present invention will now be illustrated with reference to the following figures, wherein: Figures 1 to 8 These are schematic representations of ultrasonic devices, each representing a corresponding embodiment of the invention.

[0090] Figure 9 This is a schematic representation of an ultrasonic device having multiple piezoelectric elements according to another embodiment of the present invention; Figure 10 This is a schematic representation of an ultrasonic device according to another embodiment of the present invention; Figure 11 This is a schematic representation of a portion of an ultrasonic device according to another embodiment of the present invention; Figure 12 This is a schematic representation of a method for manufacturing an ultrasonic device according to an embodiment of the present invention; Figure 13 This is a schematic representation of a method of using an ultrasonic device according to an embodiment of the present invention; Figure 14 This is a schematic representation of an ultrasonic device according to an embodiment of the present invention; Figure 15 This is a schematic representation of an ultrasonic device with an acoustic matching layer according to an embodiment of the present invention; Figure 16 This is a schematic representation of an ultrasonic device having a cavity shaped based on a desired frequency response according to an embodiment of the present invention; Figure 17 This is a schematic representation of an ultrasonic device having a cavity shaped based on a desired frequency response, according to an embodiment of the present invention; and Figure 18 yes Figure 17 The diagram shows a schematic representation of the plan view of the ultrasonic equipment. Detailed Implementation

[0091] Figure 1This is a schematic representation of an ultrasonic device 100 with piezoelectric elements. The ultrasonic device includes a semiconductor substrate 110 having a first surface 112 opposite to a second surface 114. The ultrasonic device 100 includes a CMOS control circuit including a plurality of transistors 120 integrally disposed within the first surface 112 and a CMOS metallization layer 130 disposed on the first surface 112. The piezoelectric element includes a movable piezoelectric diaphragm including a piezoelectric body 150, a first electrode 152, and a second electrode 154, both disposed on the first surface 112. The movable piezoelectric diaphragm also includes an additional layer 160 (in this embodiment, made of the same material as the remainder of the substrate). A cavity 140 is partially defined by the movable piezoelectric diaphragm and partially by the semiconductor substrate 110. In this embodiment, the CMOS metallization layer 130 includes conductive connections 132, 134 extending from the plurality of transistors 120 to the first electrode 152.

[0092] In use, the movable piezoelectric diaphragm is configured to deform into cavity 140 in response to a control signal from a CMOS control circuit. The movement of the movable piezoelectric diaphragm generates ultrasonic energy, which is emitted from the ultrasonic device 100.

[0093] Figure 2 This is a schematic representation of an ultrasonic device 200 including a substrate 210 having a first surface 212 and an opposing second surface 214. The ultrasonic device 200 includes CMOS control circuitry comprising a plurality of transistors 220 integrally disposed within the first surface 212 and a CMOS metallization layer 230 disposed on the first surface 212. The ultrasonic device 200 includes a piezoelectric element having a movable piezoelectric diaphragm. The movable piezoelectric diaphragm includes a piezoelectric body 250, a first electrode 252, a second electrode 254, and an additional layer 260. The additional layer 260 is a CMOS oxide layer. A cavity 240 is partially defined by the movable piezoelectric diaphragm and partially by the substrate 210. The ultrasonic device includes a protective layer 270 to protect the MEMS components.

[0094] The CMOS metallization layer 230 is integrally disposed with the CMOS oxide layer 260 and includes conductive connectors 232, 234 extending from a plurality of transistors 220 to the first electrode 252. A portion of the metallization layer 230 is disposed within a movable piezoelectric diaphragm, i.e., a portion of the piezoelectric element that deforms into a cavity during use. By disposing a portion of the metallization layer 230 within the movable piezoelectric diaphragm, a particularly compact device can be provided.

[0095] Figure 3This is a schematic representation of an ultrasonic device 300 according to another embodiment of the present invention. The ultrasonic device 300 includes a substrate 310 having a first surface 312 and an opposing second surface 314. The ultrasonic device 300 includes a CMOS control circuit and a piezoelectric element having a movable piezoelectric diaphragm. The CMOS control circuit includes a plurality of transistors 320 integrally disposed within the first surface 312 and a CMOS metallization layer 330. The movable piezoelectric diaphragm includes a piezoelectric body 350, a first electrode 352, a second electrode 354, and an additional layer 360. A cavity 340 is partially defined by the movable piezoelectric diaphragm and partially by the substrate 310. The ultrasonic device also includes a protective layer 270.

[0096] The CMOS metallization layer 330 is integrally disposed with the additional layer 260 and includes conductive connections 332, 334 extending from at least one of the plurality of transistors 320 to the first electrode 352. A portion of the metallization layer 330 is disposed within a movable piezoelectric diaphragm. The metallization layer 330 is only one of a plurality of metallization layers 330, 331, 333 disposed within the additional layer 360. The multiple metallization layers 330, 331, 333 disposed within the movable piezoelectric diaphragm allow for a device with improved functionality while maintaining a small size. Each of these metallization layers 330, 331, 333 is suitable for conducting waveforms between the CMOS control circuitry 320 and the first electrode 352 and / or the second electrode 354.

[0097] Figure 4 This is a schematic representation of an ultrasonic device 400 according to another embodiment of the present invention. The ultrasonic device 400 includes a substrate 410 having a first surface 412 and an opposing second surface 414. The ultrasonic device 400 includes CMOS control circuitry and a piezoelectric element having a movable piezoelectric diaphragm. The movable piezoelectric diaphragm includes a piezoelectric body 450, a first electrode 452, a second electrode 454, and an additional layer 460. The CMOS control circuitry includes a plurality of transistors 420 and a CMOS metallization layer 430. The CMOS metallization layer 430 is disposed on the first surface 412 and includes conductive connectors 432, 434. A cavity 440 is partially defined by the movable piezoelectric diaphragm and partially by the substrate 410. The ultrasonic device also includes a protective layer 470. In this embodiment, the movable piezoelectric diaphragm does not extend across the entire side of the cavity (i.e., it is discontinuous). Each of the first electrode 452, the second electrode 454, and the piezoelectric body 450 is annular and concentrically arranged. The additional layer 460 and the protective layer 470 are also discontinuous, allowing the piezoelectric diaphragm to pass through the defined channel 490, thereby increasing the flexibility of the piezoelectric diaphragm.

[0098] Figure 5 This is a schematic representation of an ultrasonic device 500, which is similar to... Figure 4 The ultrasonic device 400 is shown. Specifically, the ultrasonic device 500 includes a substrate 510 having a first surface 512 and an opposing second surface 514. The ultrasonic device 500 includes CMOS control circuitry and a piezoelectric element having a movable piezoelectric diaphragm. The CMOS control circuitry includes a plurality of transistors 520 and a CMOS metallization layer 530. The movable piezoelectric diaphragm includes a piezoelectric body 550, a first electrode 552, a second electrode 554, and an additional layer 560. The CMOS metallization layer 530 is disposed on the first surface 512 and includes conductive connectors 532, 534. A cavity 540 is partially defined by the movable piezoelectric diaphragm and partially by the substrate 510. The ultrasonic device also includes a protective layer 570. Each of the first electrode 552, the second electrode 554, and the piezoelectric body 550 is annular and concentrically arranged. The additional layer 560 and the protective layer 570 are also discontinuous, such that a channel 590 is defined through the movable piezoelectric diaphragm. Figure 4 Ultrasonic equipment and Figure 5 The main difference between this and other ultrasound devices is that channel 590 is filled with additional material, while channel 490 is empty. In this embodiment, the additional material is benzocyclobutene (BCB).

[0099] Figure 6 This is a schematic representation of an ultrasonic device 600, which is similar to... Figure 1 The ultrasonic device 100 is shown. Specifically, the ultrasonic device 600 includes a substrate 610 having a first surface 612 and a second surface 614. The ultrasonic device 600 includes a protective layer 670 and CMOS control circuitry, which includes a plurality of transistors 620 and a CMOS metallization layer 630. The CMOS metallization layer 630 includes conductive connectors 632, 634. The piezoelectric element includes a movable piezoelectric diaphragm, which includes a piezoelectric body 650, a first electrode 652, a second electrode 654, and an additional layer 660. A cavity 640 is defined by the movable piezoelectric diaphragm and the substrate 610. In this embodiment, the ultrasonic device 600 further includes a buried oxide layer 680. The buried oxide layer 680 allows the CMOS components to be operated at higher voltages, thereby facilitating greater deflection of the movable piezoelectric diaphragm.

[0100] Figure 7 This is a schematic representation of an ultrasonic device 700, which is similar to... Figure 7The ultrasonic device 700 is shown. The ultrasonic device 700 includes a substrate 710 having a first surface 712 and a second surface 714. The ultrasonic device 700 includes a protective layer 770, a plurality of transistors 720, and a CMOS metallization layer 730 including conductive connectors 732, 734. A piezoelectric element includes a movable piezoelectric diaphragm, which includes a piezoelectric body 750, a first electrode 752, a second electrode 754, and an additional layer 760. A cavity 740 is defined by the movable piezoelectric diaphragm and the substrate 710. The ultrasonic device 700 also includes a buried oxide layer 780. In this embodiment, the ultrasonic device 700 further includes a deep trench isolation structure to define the dimensions of the cavity 740. The ultrasonic device 700 also includes a notch 790 in the additional layer 760 and having a CMOS metallization layer 792 as an etch stop. The notch 790, which is at least partially within the movable piezoelectric diaphragm, affects the frequency response of the ultrasonic device 700.

[0101] Figure 8 This is a schematic representation of an ultrasonic device 800 according to an embodiment of the present invention. The ultrasonic device 800 includes a substrate 810 having a first surface 812 and a second surface 814. The ultrasonic device 800 includes a cavity 840, an additional layer 860, a protective layer 870, a plurality of transistors 820, and a CMOS metallization layer 830 including conductive connectors 832, 834. A movable piezoelectric diaphragm includes a piezoelectric element having an inner portion and an outer portion. The inner portion includes an inner piezoelectric body 850b, a first inner electrode 852b, and a second inner electrode 854b. The outer portion includes an outer piezoelectric body 850a, a first outer electrode 852a, and a second outer electrode 854a. In this embodiment, the inner portion is circular, and the outer portion is annular. The inner and outer piezoelectric elements are arranged concentrically.

[0102] In use, each of the internal and external portions can emit and / or receive ultrasound. A first potential difference can be applied between the internal electrode pairs 852b and 854b, and a second potential difference can be applied between the external electrode pairs 852a and 854a, to cause the internal piezoelectric body 850b to deflect in a first direction and to cause the external piezoelectric body 850a to deflect in a second direction opposite to the first direction.

[0103] Figure 9This is a schematic representation of an ultrasonic device 900 comprising multiple piezoelectric elements formed on a semiconductor substrate 910. Each piezoelectric element includes a movable piezoelectric diaphragm, a piezoelectric body 950a-c, a first electrode 952a-c, and a second electrode 954a-c, disposed on a first surface 912 of the substrate 910. Each piezoelectric element is associated with a cavity 940a-c defined by the substrate 910 and each corresponding movable piezoelectric diaphragm. The ultrasonic device 900 includes an additional layer 960, a protective layer 970, multiple transistors 920, and a CMOS metallization layer 930 including conductive connectors 932, 934. The CMOS metallization layer 930 is one of a plurality of CMOS metallization layers 930, 932, 934 integrally disposed in the additional layer 960. In this embodiment, each movable piezoelectric diaphragm includes at least a portion of the CMOS metallization layer. Using the space within the movable piezoelectric diaphragm for the CMOS metallization layer helps to miniaturize the device while avoiding electrical crosstalk between components.

[0104] Figure 10 This is a schematic representation of an ultrasonic device 1000 according to an embodiment of the present invention. The ultrasonic device 1000 includes an array of piezoelectric elements arranged in a row. The array includes an elongated region 1020 having a first side 1022 and a second side 1024. The ultrasonic device includes a plurality of transistors 1010 arranged in a column adjacent to the first side 1022 of the elongated region 1020. Conductive connectors 1030 from the plurality of transistors 1010 extend from the first side 1022 into the array. In use, waveforms can be conducted between the plurality of transistors 1010 and each piezoelectric element.

[0105] Figure 11 This is a schematic representation of a portion of an ultrasonic device 1100 according to an embodiment of the present invention. The ultrasonic device 1100 includes an array of piezoelectric elements 1120 arranged in rows 1110a-c. Conductive connectors 1130 extend from a first side of the array into the array. It should be understood that... Figure 11 Compared to Figure 10 It rotated 90°. (As shown) Figure 11 As shown, a subset of conductive connectors extends along the length of each row 1110a-c between elements in adjacent rows to different corresponding piezoelectric elements.

[0106] Figure 12 This is a schematic representation of a method 1200 for manufacturing an ultrasonic device according to an embodiment of the present invention. The method includes step 1220 of forming n cavities within a substrate. Typically, the cavities are provided from the back side of the substrate (i.e., the opposing second surface) using a DRIE etching process. In other embodiments, the method includes etching from both the front side (i.e., the first surface) and the back side. Buried oxide and deep trench isolation structures can be used to define the cavity dimensions.

[0107] The method includes step 1220 of forming a plurality of transistors within a first surface. The transistors are formed using standard CMOS processing methods, including ion implantation on a p-type or n-type substrate.

[0108] The method also includes step 1230 of forming a CMOS metallization layer on the first surface. The CMOS metallization layer is also formed by standard processes such as ion implantation chemical vapor deposition, physical vapor deposition, etching, chemical mechanical planarization and / or electroplating.

[0109] The method includes step 1240 of forming n movable piezoelectric films (i.e., MEMS components). Forming each movable piezoelectric film includes forming a corresponding electrode and an intermediate piezoelectric body. Typically, this step involves using a continuous thin-film deposition technique. Preferably, each piezoelectric body is formed of a material such as AlN or ScAIN, which can be deposited at a temperature below 450°C by physical vapor deposition (including cryogenic sputtering). The electrodes are formed of, for example, titanium, platinum, aluminum, tungsten, or alloys thereof.

[0110] Figure 13 This is a schematic representation of a method of using an ultrasonic device according to an embodiment of the present invention. Figure 13 A method is shown that includes transmitting and receiving ultrasonic signals (e.g., ultrasonic signals generated by reflection of the transmitted ultrasonic signals from another structure).

[0111] The method includes step 1310 of generating a drive waveform using at least a subset of a plurality of transistors. Typically, one drive waveform is generated for each piezoelectric element of the ultrasonic device. The method also includes step 1320 of introducing a delay into the drive waveform. The drive waveform is delayed based on the relative positions of the piezoelectric elements on the array, such that a focused ultrasonic beam is emitted from the ultrasonic device. In other embodiments, such focusing is not provided, and a plane wave is emitted from the ultrasonic device. The method also includes an apodization step 1330. This step includes weighting the drive waveform such that the amplitude of the ultrasonic signal emitted from piezoelectric elements disposed at the edges of the array is smaller than the amplitude of the ultrasonic signal emitted from piezoelectric elements more centrally. The amplitude variation from the central element to the outer elements is smooth, thereby suppressing unwanted lobes of the emitted ultrasonic pulses, thereby providing improved signal quality (reduced clutter). For example, the variation may be determined based on Hanning, Hamming, or Blackman functions. The method then includes step 1340 of actuating a movable piezoelectric diaphragm. This involves changing the voltage applied to the first and second electrodes of each piezoelectric element based on the driving waveform, so that the movable piezoelectric diaphragm moves into and out of the cavity in a controlled manner.

[0112] Turning now to receiving, the method includes step 1350 of sensing membrane movement. An ultrasonic signal incident on each movable piezoelectric diaphragm causes the diaphragm to move. An electrical signal is generated based on the movement of the diaphragm. The method further includes an amplification step 1360. This step includes amplifying the electrical signal received from each piezoelectric element. Noise propagation through the circuit is limited by arranging the amplification circuit on the same surface as the MEM component. The method also includes a beamforming step 1370. It will be understood that various beamforming methods can be used. Those beamforming methods may include weighting the received signals based on the position of the piezoelectric element receiving each signal (i.e., receiving the apod) and / or delaying the signals based on the relative position of the signals received from each element. The method also includes an additional filtering step 1380 to reduce noise.

[0113] Figure 14 This is a schematic representation of an ultrasonic device 1400 according to an embodiment of the present invention. Specifically, Figure 14 The diagram includes a highly schematic representation of some control circuitry for the ultrasonic device 1400. In this embodiment, the control circuitry is distributed between the machine controller 1430 and the CMOS control circuitry 1420, with the CMOS control circuitry disposed on and integrally disposed within the surface of the substrate 1410. The circuitry associated with the machine controller 1430 and the CMOS control circuitry 1420 are partially connected by a conductor 1440 extending through a flexible cable 1460.

[0114] Each piezoelectric element 1450 of the ultrasonic device 1400 is connected to a corresponding amplification circuit 1422, drive circuit 1424, and analog-to-digital converter (ADC) 1426. In this embodiment, each piezoelectric element is connected to an additional control circuit 1428. This additional control circuit includes a switching circuit to control which piezoelectric elements can transmit / receive during a given sequence. In alternative embodiments, the switching circuit may be between the piezoelectric element and the amplification / ADC circuitry. In these alternative embodiments, fewer amplification / ADC modules than piezoelectric elements may be present, such that only a subset of the piezoelectric elements can operate simultaneously.

[0115] In use, in transmit mode, the drive waveform generated by drive circuit 1424 is conducted through conductive connectors to at least one electrode of each piezoelectric element 1450 in operation. In receive mode, the ultrasonic energy incident on each piezoelectric element 1450 generates a signal, which is conducted through corresponding conductive connectors, amplified by corresponding amplifier circuit 1422, and converted by corresponding ADC.

[0116] The machine controller 1430 includes at least one waveform generator 1470 and a voltage amplifier 1475, which provides control pulses to the ultrasonic CMOS control circuitry 1420 via a conductor 1440. The machine controller also includes a processor 1480 connected to additional amplification circuitry 1482 for amplifying the received signals. In this embodiment, the processor includes a memory 1484 for storing system settings / received signals. The processor further includes a beamforming module 1486 for beamforming the received signals. The beamforming module 1486 can also perform filtering / other image processing functions.

[0117] In this embodiment, the machine controller is connected to a display device 1490 for displaying beamforming (and / or non-beamforming) data.

[0118] Figure 15 This is a schematic diagram of an ultrasonic device 1500 having an acoustic matching layer 1580. The ultrasonic device 1500 includes a substrate 1510 having a first surface 1512 and a second surface 1514. The ultrasonic device 1500 includes a cavity 1540, an additional layer 1560, a protective layer 1570, a plurality of transistors 1520, and a CMOS metallization layer 1530 including conductive connectors 1532 and 1534. The movable piezoelectric diaphragm includes a piezoelectric element having a piezoelectric body 1550, a first electrode 1552, and a second electrode 1554.

[0119] An acoustic matching layer 1580 is disposed above the protective layer 1570 to reduce acoustic mismatch between the ultrasound device 1500 and another medium. In this embodiment, the ultrasound device is configured to image a patient (not shown). Therefore, the impedance of the acoustic matching layer 1580 is selected to have a value between the impedance of human tissue and the impedance of the protective layer 1570.

[0120] Figure 16 This is a schematic diagram of an ultrasonic device 1600 having an acoustic matching layer 1680 and a cavity 1640 shaped based on a desired frequency response. The ultrasonic device 1600 includes a substrate 1610 having a first surface 1612 and a second surface 1614. The ultrasonic device 1600 includes an additional layer 1660, a protective layer 1670, a plurality of transistors 1620, and a CMOS metallization layer 1630 including conductive connectors 1632, 1634. A movable piezoelectric diaphragm includes a piezoelectric element having a piezoelectric body 1650, a first electrode 1652, and a second electrode 1654.

[0121] Similar to Figure 16 , Figure 17This is also a schematic diagram of an ultrasonic device 1700 having an acoustic matching layer 1780 and a cavity 1740 shaped based on a desired frequency response. The ultrasonic device 1700 includes a substrate 1710 having a first surface 1712 and a second surface 1714. The ultrasonic device 1700 includes an additional layer 1760, a protective layer 1770, a plurality of transistors 1720, and a CMOS metallization layer 1730 including conductive connectors 1732, 1734. The movable piezoelectric diaphragm includes a piezoelectric element having a piezoelectric body 1750, a first electrode 1752, and a second electrode 1754.

[0122] Figure 16 and Figure 17 The cavity shapes of the ultrasound devices shown are all based on the desired operating frequency of the ultrasound device. In both examples, the cavity shape is essentially cylindrical. Figure 16 An example is shown in which cavity 1640 is completely closed, while Figure 17 An alternative embodiment is shown having a channel 1741 extending through a movable piezoelectric diaphragm, a protective layer 1770, and an acoustic matching layer 1780. Figure 17 In the illustrated embodiment, a fluid (not shown) may be contained within cavity 1740. The shape of the cavity is based on the intended fluid, which further improves the frequency response of the ultrasound device 1700. Figure 17 The illustrated embodiment also includes an attenuation layer 1790 surrounding the sidewalls of cavity 1740 for attenuating unwanted frequency components.

[0123] Figure 18 yes Figure 17 The diagram shows a schematic representation of the plan view of the ultrasonic device 1700. In this embodiment, the number and size of the channels 1741 are selected to ensure good support for the layers in both the radial and azimuth directions.

[0124] Throughout this specification and claims, the words “comprising” and “containing” and their variations mean “including, but not limited to,” and they are not intended to exclude, other components, integrals, or steps. Unless the context otherwise requires, the singular encompasses the plural throughout this specification and claims. In particular, where the indefinite article is used, unless the context otherwise requires, this specification should be understood to consider both the plural and the singular.

[0125] Features, integrals, characteristics, or groups described in connection with a particular aspect, embodiment, or example of the invention should be understood to be applicable to any other aspect, embodiment, or example described herein, unless incompatible therewith. All features disclosed in this specification (including any appended claims, abstract, and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except where at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification (including any appended claims, abstract, and drawings), or to any novel step or any novel combination of steps of any method or process so disclosed.

Claims

1. An ultrasound device, comprising: a substrate having a first surface and an opposite second surface; a CMOS control circuit comprising a CMOS metallization layer on the first surface and a plurality of transistors integrally provided within the first surface; a piezoelectric micromechanical ultrasound transducer comprising at least one piezoelectric element, wherein the piezoelectric element comprises a movable piezoelectric diaphragm; a cavity partly defined by the movable piezoelectric diaphragm and partly defined by the substrate; wherein the movable piezoelectric diaphragm comprises a piezoelectric body, a first electrode and a second electrode, all arranged on the first surface; wherein the movable piezoelectric diaphragm defines at least part of a wall of the cavity and is configured to deform into the cavity; and wherein the CMOS control circuit is configured to control ultrasound emission by controlling movement of the movable piezoelectric diaphragm and / or to control ultrasound reception by receiving signals resulting from movement of the movable piezoelectric diaphragm.

2. The ultrasound device according to claim 1, further comprising a first acoustic matching layer having a first acoustic impedance.

3. The ultrasound device according to claim 1 or claim 2, wherein the ultrasound device is configured to operate at a first frequency, and wherein a shape of the cavity is selected in dependence on the first frequency.

4. The ultrasound device according to any preceding claim, further comprising a first attenuation layer provided on at least one wall of the cavity.

5. The ultrasound device according to any preceding claim, wherein the movable piezoelectric diaphragm comprises at least part of the CMOS metallization layer, and optionally wherein the CMOS metallization layer comprises an electrically conductive connection extending from at least one transistor of the plurality of transistors to at least one of the first electrode and the second electrode of the piezoelectric element.

6. The ultrasound device according to any preceding claim, further comprising an additional layer on the first surface of the substrate, wherein the movable piezoelectric diaphragm comprises at least part of the additional layer, wherein the additional layer defines the at least part of the wall of the cavity defined by the movable piezoelectric diaphragm, and optionally wherein at least part of the CMOS metallization layer is integrally provided within the additional layer, and / or optionally wherein the additional layer comprises CMOS oxide.

7. The ultrasound device according to claim 1, wherein the at least one piezoelectric element is one of a plurality of piezoelectric elements arranged in an array, wherein each piezoelectric element comprises a movable piezoelectric diaphragm, wherein each movable piezoelectric diaphragm comprises a piezoelectric body, a first electrode, and a second electrode, arranged on the first surface, wherein the cavity is one of a plurality of cavities, wherein each movable piezoelectric diaphragm defines at least part of a wall of a respective cavity of the plurality of cavities.

8. The ultrasound device according to claim 7, further comprising: a first acoustic matching layer having a first acoustic impedance, and / or a first attenuating layer disposed on at least one wall of at least one of the plurality of cavities, and / or wherein the ultrasound device is configured to operate at a first frequency, and wherein a shape of at least one of the plurality of cavities is selected dependent on the first frequency.

9. The ultrasound device of claim 7 or 8, wherein each movable piezoelectric diaphragm comprises at least part of the CMOS metallization layer.

10. The ultrasound device of any one of claims 7 to 9, further comprising an additional layer on the first surface of the substrate, wherein each movable piezoelectric diaphragm comprises at least part of the additional layer, wherein the additional layer defines the at least part of the wall of each cavity defined by the respective movable piezoelectric diaphragm, and optionally wherein at least part of the CMOS metallization layer is integrally disposed within the additional layer, and / or optionally wherein the additional layer comprises CMOS oxide.

11. The ultrasound device of any one of claims 7 to 10, wherein the CMOS metallization layer comprises electrically conductive connections extending from at least one of the plurality of transistors to at least one of the first and second electrodes of a respective piezoelectric element, and optionally wherein lengths of the electrically conductive connections are uniform.

12. The ultrasound device of claim 11, wherein the array comprises a first region having a first side and a second side opposite the first side, wherein the plurality of piezoelectric elements are arranged in rows, wherein the electrically conductive connections extend into the array from one or both of the first and second sides between the rows of piezoelectric elements, and optionally wherein the first region is elongate and the first and second sides correspond to long sides along a length of the first region.

13. The ultrasound device of claim 12, wherein the first region comprises at least a first row of piezoelectric elements, a second row of piezoelectric elements, and a third row of piezoelectric elements, wherein a first subset of the electrically conductive connections extend to different respective piezoelectric elements between the first and second rows of piezoelectric elements along a length of the second row, and optionally, wherein a second subset of the electrically conductive connections extend to different respective piezoelectric elements between the second and third rows of piezoelectric elements along the length of the second row.

14. The ultrasound device of claim 12 or claim 13, wherein at least part of the CMOS control circuitry is arranged in a column adjacent at least one of the first and second sides of the first region.

15. The ultrasound device of any preceding claim, wherein the CMOS control circuitry comprises a drive circuit configured to actuate each movable piezoelectric diaphragm in at least a subset of the plurality of piezoelectric elements such that an ultrasound signal is emitted; and wherein the CMOS control circuit comprises a receive circuit for receiving ultrasound signals.

16. The ultrasound device of claim 14, wherein the CMOS control circuit comprises a drive circuit configured to actuate each moveable piezoelectric diaphragm in at least a subset of the plurality of piezoelectric elements such that an ultrasound signal is emitted; wherein the CMOS control circuit comprises a receive circuit for receiving ultrasound signals. and wherein at least part of the drive circuit and / or at least part of the receive circuit is arranged in the column adjacent to at least one of the first side and the second side of the first area.

17. The ultrasound device of any preceding claim, wherein the CMOS control circuit comprises a delay circuit and / or a apodization circuit; wherein the delay circuit is configured to delay an actuator waveform conducted to one of the piezoelectric elements relative to an actuator waveform conducted to another piezoelectric element; wherein the apodization circuit is configured to increase an amplitude of the actuator waveform conducted to one of the piezoelectric elements relative to the actuator waveform conducted to another piezoelectric element.

18. The ultrasound device of claim 14 or claim 16, wherein the CMOS control circuit comprises a delay circuit and / or a apodization circuit; wherein the delay circuit is configured to delay an actuator waveform conducted to one of the piezoelectric elements relative to an actuator waveform conducted to another piezoelectric element, and wherein at least part of the delay circuit is arranged in the column adjacent to at least one of the first side and the second side of the first area; wherein the apodization circuit is configured to increase an amplitude of the actuator waveform conducted to one of the piezoelectric elements relative to the actuator waveform conducted to another piezoelectric element, and wherein at least part of the apodization circuit is arranged in the column adjacent to at least one of the first side and the second side of the first area.

19. The ultrasound device of any preceding claim, wherein the CMOS control circuit comprises an amplification circuit for amplifying received ultrasound signals, and optionally wherein the amplification circuit is configured to amplify received signals based on a depth at which the received signals have been reflected.

20. The ultrasound device of claim 14, claim 16, or claim 18, wherein the CMOS control circuit comprises an amplification circuit for amplifying received ultrasound signals. wherein at least part of the amplification circuit is arranged in the column adjacent to at least one of the first side and the second side, and optionally wherein the amplification circuit is configured to amplify received signals based on a depth at whic the received signals have been reflected.

21. A wearable device comprising the ultrasound device of any preceding claim.

22. A method of forming an ultrasonic device according to any of the preceding claims, wherein the ultrasonic device comprises a piezoelectric micromechanical ultrasonic transducer, the piezoelectric micromechanical ultrasonic transducer comprising n piezoelectric elements; n cavities are formed within a substrate, wherein the substrate has a first surface and an opposing second surface; Multiple transistors are formed within the first surface; A CMOS metallization layer is formed on the first surface; as well as Form n movable piezoelectric films; Each cavity is partially defined by the substrate and partially by one of the n movable piezoelectric films.

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