High speed fabrication of microelectromechanical systems arrays

Abstract

Methods, systems, and techniques for high speed fabrication of microelectromechanical systems (MEMS) arrays, such as arrays of polymer capacitive micromachined ultrasound transducers (CMUTs). A sheet of material from which a cavity for a device is formed is obtained, and physical or energy protrusions are made to protrude into the material to form the cavity. The upper and lower surfaces of the material are in contact with and bonded to the upper and lower metallized films, respectively. The metallized portions of the upper metallized film and the lower metallized film may serve as electrodes for the CMUT, and the film itself may be a substrate and a film of the CMUT.

Description

Technical Field

[0001] The present disclosure relates generally to large-scale fabrication of microelectromechanical systems (MEMS) devices and arrays, and more particularly to large flexible arrays of capacitive micromachined ultrasound transducers (CMUTs). Background Art

[0002] Ultrasound imaging is the most widely used medical imaging modality in the world in terms of images produced each year. In ultrasound imaging, ultrasound waves emitted by a transducer travel through materials and reflect at interfaces with other materials of different acoustic impedance. The reflected echoes travel back to the transducer where they are processed to form an ultrasound image. Ultrasound transducers convert electrical energy into acoustic energy and vice versa.

[0003] CMUT is an alternative technology to piezoelectric-based transducers. A CMUT is essentially a parallel plate capacitor with electrodes fixed to a substrate at the bottom of the parallel plate capacitor, with a membrane suspended above a cavity and sealed along the edges of the cavity. Metal electrodes are patterned on top of the suspended membrane. When an electrical signal is applied across the electrodes, the resulting mechanical movement of the membrane generates acoustic waves in the medium in contact with the membrane; this represents the conversion of electrical energy into acoustic energy. A polymer CMUT (poly-CMUT) is actually a CMUT in which the vibrating membrane is made of a polymer material. The resonant frequency and acoustic power depend on their diameter and thickness. The fabrication of a poly-CMUT is typically done in a clean room using photolithography techniques to pattern and build the layers of the device. US Patent Nos. 10,509,013, 10,564,132, and 10,598,632, all of which are incorporated herein by reference in their entirety, to Gerardo, Rohling, and Cretu disclose methods of microfabrication of ultrasound transducers using polymer films, thereby reducing the required operating voltage of a poly-CMUT. Summary of the invention

[0004] This Summary is provided to introduce some concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0005] According to a first aspect, a method for making a MEMS array is provided, the method comprising: providing a sheet of thin film material; contacting the material with a mold including protrusions, the protrusions being able to pierce the material to form a shaped cavity according to a pattern; contacting the material with an upper metallized film and a lower metallized film; and laminating the films by adding energy.

[0006] The method can be performed without chemical waste.

[0007] The energy can come from heat and / or pressure.

[0008] The composition of the material may be polymeric, metallic, or include polyimide.

[0009] The MEMS device may be a poly-CMUT and / or a CMUT, or other devices having a similar suspended membrane structure (eg, a pressure sensor).

[0010] According to additional aspects, there is provided a MEMS device made by the aforementioned method; a CMUT made by the aforementioned method; a poly-CMUT made by the aforementioned method, the poly-CMUT having no sandwiched electrodes and made by fully mechanical means; and a method for shaping a MEMS device according to the aforementioned method.

[0011] According to another aspect, a method for making an array of MEMS devices is provided, the method comprising: obtaining a piece of material for forming a cavity of the device; causing a physical or energy protrusion to protrude into the material to form a cavity in the material; contacting an upper surface and a lower surface of the material having the cavity with an upper metallized film and a lower metallized film, respectively; and bonding the upper surface and the lower surface of the material to the upper metallized film and the lower metallized film, respectively.

[0012] Physical protrusions may protrude into the material to form cavities.

[0013] The physical protrusion may include a piercing punch.

[0014] The physical protrusion may include a punch die.

[0015] The physical projection may comprise a rotating cylindrical mould.

[0016] Energy protrusions can protrude into the material to form cavities.

[0017] The energy bumps may include lasers.

[0018] The energy bump may include an electrical discharge.

[0019] The physical protrusions may include steam injections.

[0020] The material may be a polymer.

[0021] The material may include polyimide.

[0022] The material may include polyethylene terephthalate.

[0023] The material may be biaxially oriented polyethylene terephthalate and have a thickness between 600 nm and 1.5 μm.

[0024] The material may be metallic.

[0025] The MEMS device may be a capacitive micromachined ultrasound transducer, such as a polymer capacitive micromachined ultrasound transducer.

[0026] The upper surface and the lower surface of the material having the cavity may be in contact with the upper metallized film and the lower metallized film, so that the metallized portions of the upper metallized film and the lower metallized film are respectively located in the cavity.

[0027] Bonding may include lamination.

[0028] Lamination may be performed using a roll laminator at a temperature of at least 230°C.

[0029] Lamination may be performed at a pressure of at least 1 bar.

[0030] Lamination may be performed at a pressure of about 3 bar and a temperature of about 243°C.

[0031] The joining may comprise gluing.

[0032] The lower metallized film may comprise a flexible substrate of the device.

[0033] The metallized films may include lattice patterns, respectively, and the cavity may be located at a position where the lattice patterns overlap.

[0034] According to another aspect, there is provided an apparatus for making an array of micro-electromechanical system devices, the apparatus comprising: a pair of stamping rollers, wherein the pair of stamping rollers comprises a cylindrical mold and is configured to receive a spacer film and to punch out a cavity in the spacer film using the cylindrical mold; at least one pair of film rollers, wherein the at least one pair of film rollers is configured to receive a stamped spacer film and a metallized film and to compress the stamped spacer film between the metallized films; and a pair of laminating rollers, configured to receive a compressed spacer film and a metallized film and to laminate the compressed spacer film and the metallized film.

[0035] At least one pair of film rollers may include a first pair of film rollers and a second pair of film rollers, wherein: the first pair of film rollers is configured to receive and compress a first metallized film among the stamped spacer film and the metallized film; and the second pair of film rollers is configured to receive the first metallized film among the spacer film and the metallized film after passing through the first pair of film rollers, and the second metallized film among the metallized films, and compress the stamped spacer film between the metallized films, wherein the first metallized film among the metallized films is thicker than the second metallized film among the metallized films.

[0036] The device may also include: a pair of punching aid rollers configured to receive and compress the spacer film and the punching aid, wherein the compressed spacer film and the compressed punching aid are fed into the pair of punching rollers and fed into the first pair of film rollers; and a hard edge positioned to peel the punching aid from the spacer film after the punching aid leaves the first pair of film rollers.

[0037] This summary does not necessarily describe the full scope of all aspects. Other aspects, features, and advantages will be apparent to one of ordinary skill in the art after reviewing the following description of specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0039] Figure 1 is a shaded cross-sectional view showing a single poly-CMUT element in cross section showing component layers of membrane, electrodes, polymer layers, insulator and substrate;

[0040] Figure 2A is a shaded diagram of another embodiment of a poly-CMUT according to an exemplary embodiment, which is compared to Figure 1 The poly-CMUT has fewer layers and is Figure 2B The stack-up of the device shown;

[0041] Figure 2B depicts a stack of a four-chamber device and electrodes according to an exemplary embodiment after alignment to a metallized polyamide film and lamination together at 235° C. and pressure applied in a roll laminator;

[0042] Figure 3 are photographic reproductions of two views of an exemplary mask for stamping and metal evaporation according to an exemplary embodiment;

[0043] Figure 4 A is a graphical reproduction of the displacement magnitude of a poly-CMUT membrane at 120V DC and 60V AC measured in a Laser Doppler Vibrometer (LDV) according to an exemplary embodiment, and Figure 4 B is a photographic reproduction of the corresponding poly-CMUT cell at 10× magnification, where the larger outlines of the two electrodes and the cavity are visible;

[0044] Figure 5A is an illustration of one pattern of a shaped poly-CMUT cavity according to an exemplary embodiment;

[0045] FIG. 5B to FIG. 5D is a picture of an exemplary first wafer and an exemplary second wafer of a MEMS device manufactured in a roll-to-roll setting according to an exemplary embodiment;

[0046] Figure 6 depicts a roller pair including a mold for punching a spacer membrane to prepare an array of shaped poly-CMUT cavities according to an exemplary embodiment; and

[0047] Figure 7 Depicted is a roll-to-roll manufacturing apparatus for preparing an array of shaped poly-CMUT cavities according to an exemplary embodiment. DETAILED DESCRIPTION

[0048] It is arduous to manufacture arrays of CMUTs using conventional methods. One current limitation in the state of the art is the limitation on the maximum speed of CMUT production. Another limitation is the need to perform multiple manufacturing steps on multiple pieces of manufacturing equipment, wherein materials are manually transported between these different multiple pieces of equipment. These equipment include wet benches, mask aligners, ion etchers, dryers, furnaces, and evaporators. Another limitation of CMUT manufacturing is the maximum size of the CMUT transducer array that can be made using conventional manufacturing techniques, which is typically a few centimeters in diameter and is not sufficient to meet applications requiring meter-long arrays. Another limitation of conventional manufacturing methods is the type and quantity of required liquid and gas chemicals (such as photoresists, acids, alkalis, and developers), many of which are toxic and difficult to handle. Therefore, a method for manufacturing CMUTs that overcomes one or more of these limitations is desired.

[0049] The present disclosure is directed to new methods, systems and techniques for making CMUTs and other MEMS devices that utilize cavities in layers to accommodate electromechanical coupling. Although CMUTs are the focus of the exemplary embodiments below, the present disclosure also contemplates other types of MEMS devices with these types of cavities, such as accelerometers, pressure sensors, speakers and gyroscopes. In at least some embodiments, cavities are created by mechanically stamping ultrathin films and laminating these ultrathin films between previously metallized films. Ideally, the benefit is to avoid any wet chemical processing and eliminate the maximum size limitations described above regarding traditional microfabrication methods and equipment. At least some embodiments also allow for a variable compromise in which the precision of the stamped structure is inversely proportional to the speed and scale of the fabrication.

[0050] In at least some embodiments, a number of technical problems must be overcome to achieve this. For example, the cavities used are small (on the order of millimeters or less), and the stamping dies are made to stamp these cavities. This means that the accuracy of the tool and tool manufacturing will be in the range of less than 1 / 100 of a millimeter.

[0051] Another factor is the quality and thickness of the spacer film. For example, as mentioned above, it is very thin but still structurally stable enough to be handled during the manufacturing steps. If the film is damaged or the cutting edge of the mold is defective, the film will tear and the manufacturing will fail.

[0052] In this disclosure, the following terms have the following meanings:

[0053] (a) A "polymer-based capacitive micromachined ultrasonic transducer" or "poly-CMUT" is a layered ultrasonic device having a polymer membrane containing an embedded top electrode suspended above a cavity. Examples of poly-CMUTs can be found, for example, in U.S. Patent No. 10,598,632 by Gerardo, Rohling, and Cretu. Compared to conventional non-polymer-based CMUTs, in a poly-CMUT the top electrode can be embedded within two polymer layers, with the bottom layer being thinner than the top layer. Combined with forming a sufficiently thin CMUT cavity, this structure allows the CMUT to reach the MHz operating region without requiring unacceptably high operating voltages. Poly-CMUT elements can be formed, for example, by the method disclosed in U.S. Patent No. 10,598,632 by Cretu et al.

[0054] (b) "Microelectromechanical systems" or "MEMS" are microelectromechanical devices, such as poly-CMUTs. In at least some embodiments, these devices include microsensors and microactuators. Piezoelectric materials can be used to adjust the resonant frequency of MEMS devices, which can affect the performance of these devices. For example, piezoelectric materials may affect the performance of MEMS devices such as accelerometers, energy harvesters, or strain gauges.

[0055] (c) The term "spacer" refers to a sheet of material that is used to form the shaped cavity for a CMUT or MEMS array and is punched / perforated manually and / or in an automated system. Polyimide (e.g. Kapton) is used to make poly-CMUTs. TM ), polyethylene terephthalate (PET) (one example is Mylar TM ) and gold for the electrodes. Other spacer films may include, for example, paper, chitosan, polystyrene (PS) or other materials suitable for use as thin films that are suitable for bonding to the substrate and membrane layers of a MEMS device, such as by lamination.

[0056] (d) The term "punching" as used herein refers to removing a portion of a spacer film by pressing a mold including protrusions into the spacer film.

[0057] (e) “Low power” or “passive power” refers to wireless power transfer using electromagnetic fields, which is typically performed at a frequency that matches the resonant frequency of the poly-CMUT element.

[0058] (f) “Array” refers to a group of Poly-CMUT elements aligned side by side in a one-dimensional (1-D) arrangement, a plurality of linear arrays (1.5-D) positioned side by side, or a two-dimensional array of Poly-CMUT elements (2-D array, also referred to as a “matrix array”) that communicate with each other and are capable of communicating with a user interface (once connected or activated) via wired communications or wireless signals.

[0059] (g) The term "shaped cavities" are perforations formed in the spacer membrane during poly-CMUT fabrication by embossing or other means (e.g., using a laser). They can be shaped into circular, polygonal, or other closed contour shapes, for example, to accommodate the desired CMUT or MEMS perimeter.

[0060] (h) A "mold comprising protrusions" is a solid material having hard protrusions capable of perforating the spacer membrane. Examples of molds comprising protrusions are rotating cylindrical molds in a roll-to-roll setting, punching punches, and manual or automatic leather punch molds. The protrusions can be metal, mineral or polymer, or a combination of two or three of these elements. In other embodiments, one or more lasers can be used to perforate the spacer membrane. Regardless of what is used to perforate the spacer membrane, the result is a shaped cavity formed in the spacer membrane. In yet other embodiments, a component for evaporation or steam injection can be used to form a shaped cavity in the spacer membrane. For example, in at least some embodiments, holes can be produced in the spacer membrane via evaporation by electrical discharge or laser (i.e., thermal evaporation by segment). More generally, a "mold comprising perforating components" includes a solid material having components for selectively perforating the spacer membrane, which, in various embodiments, include protrusions, lasers, components for evaporation, steam injection, etc.

[0061] (i) "Photoacoustic imaging" or "PA imaging" is a biomedical imaging modality in which non-ionizing laser pulses are delivered into biological tissue. Some of the delivered energy will be absorbed and converted to heat, causing transient thermoelastic expansion and, therefore, broadband (i.e., MHz) ultrasound emission. The bandwidth of the typical receive frequency response of classical piezoelectric (PZT) ultrasound imaging transducers based on PZT technology is insufficient to fully retain all of the information contained in the photoacoustic signal. CMUTs exhibit both higher sensitivity and significantly wider frequency response on receive, which makes them more effective than PZT ultrasound in connection with PA imaging applications.

[0062] power

[0063] The charges trapped in the membrane of the Poly-CMUT act as a built-in DC bias. Thus, in at least some embodiments, the Poly-CMUT can be used as a passive device (i.e., no external power is applied to the Poly-CMUT) during the reception of an acoustic signal and conversion of the acoustic signal into an electrical signal. Alternatively, excitation voltages of various amplitudes can be applied to the Poly-CMUT. For example, in some embodiments, a relatively low excitation voltage may be sufficient (e.g., 10V DC +12V AC ); while in some other embodiments, a higher voltage may be required, such as when a relatively thick spacing film 130 is used, which will produce a relatively thick cavity 170.

[0064] In some embodiments, wireless communication also includes wireless power transmission, in which a transmitter device driven by power from a power source generates a time-varying electromagnetic field that transmits power through space to a receiver device that extracts power from the field and provides it to a power load. Examples of wireless power transmission include inductive coupling, resonant inductive coupling, capacitive coupling, magnetodynamic coupling, acoustic coupling, and power transmission using microwaves and light waves. The coupling may be near-field coupling or intermediate coupling. In the context of electromagnetic energy, the energy transmitted may be electromagnetic waves, microwaves, X-rays, and light waves with frequencies in the KHz to MHz range, such as solar energy and lasers. These waves may be generated using antennas or other coupling devices. For example, the waves may include electromagnetic energy generated to perform synchronous magnetic resonance imaging or X-ray imaging. Other types of energy that may be transmitted include kinetic energy from acoustic waves and surface waves and thermal energy from heat. The coupler may be externally attached to the poly-CMUT element or embedded directly in the poly-CMUT element. The advantages of using wireless power transmission are increased convenience and safety, and reduced size, weight, cost, and complexity of the poly-CMUT element; this may be particularly beneficial when the poly-CMUT element comprises part of a wearable patch. For example, a lightweight patch may be non-intrusive to the wearer, and the patch may be implanted or embedded in a patient where the use of wires in the patient is contraindicated due to concerns about infection.

[0065] Poly-CMUTs can be fabricated on flexible substrates for use in wearable applications. This can be difficult with silicon-based CMUTs, as they require a rigid substrate and it is not possible to fabricate a flexible substrate when the substrate is made using ceramic piezoelectric materials.

[0066] Previous research has focused on either roll-to-roll MEMS processes using photolithography or solid-state device fabrication, such as U.S. Patent No. 8,779,650. These references focus on using wet or dry etching processes and UV-sensitive chemicals by selectively hardening previously deposited soft layers. In contrast, the methods, systems, and techniques described herein can be entirely mechanical and do not involve any etching or curing to form the functional shape of the CMUT.

[0067] Fabrication of poly-CMUT component arrays

[0068] Figure 1 Depicted is a MEMS device including an exemplary poly-CMUT 100. The poly-CMUT includes four main components: a substrate 160; Figure 1 The spacer film 130 includes PET; the top electrode 120 and the bottom electrode 150 are Figure 1 Each of them is made of aluminum; and a membrane 110. Figure 1 Also depicted is the cavity 170 in the poly-CMUT 100; Figure 1 is depicted as part of the poly-CMUT 100. Figure 1 In the embodiment of the present invention, the spacer film 130 is sandwiched between the top electrode 120 and the bottom layer of the acrylate insulator 140, wherein the bottom aluminum electrode 150 is located between the bottom side of the acrylate insulator 140 and above the substrate 160. For example, the substrate 160 can be a 100 μm polyimide film. In fact, the substrate 160 can be any flexible film, such as aluminum foil, paper or other polymers. Any flexible film can be used as the substrate 160, although in at least some embodiments, the substrate 160 has the same or greater thickness as the film 110 or has a stronger mechanical strength than the film 110. The substrate 160 can also be adhered to the spacer film 130, or if there is another layer such as the acrylate insulator 140, it is adhered to the other layer. The adhesion of the flexible film to the spacer film 130 can be achieved by lamination, gluing or other suitable methods. In order to produce a functional device, the substrate 160 can be conductive itself or coated with a conductive material. In order to reduce parasitic capacitance and resistance, the conductive layer can be patterned, for example, by a process similar to sputtering on an oil mask. If desired, the conductive layer may be insulated by, for example, acrylate, a process offered by Steiner GmbH for capacitor foils, or by one or more other suitable insulators, such as silicon dioxide.

[0069] exist Figure 1In the present invention, first, the bottom film in the form of substrate 160 and the top film in the form of membrane 110 can be metallized in the pattern required for the resulting device, an exemplary application of which is described below. This can be done by screen printing a mineral oil mask and sputtering the selected electrode material to pattern it. Thereafter, a spacer film in the form of an ultra-thin polymer or metal film is punched to produce the shaped cavities used by electrodes 120 and 140 (these shaped cavities effectively act as plates of capacitors) to facilitate movement or vibration. The width of each of the shaped cavities can be as small as 200μm, and the distance between each other is less than 1mm. The membrane is then aligned with the substrate 160 and the top film and laminated together, and the lamination is done only by heat and pressure or using an ultra-thin polymer glue layer.

[0070] The entire process can be completed by step-by-step vertical stamping or can be combined in a roll-to-roll stamping and laminating machine. The properties of the resulting device are managed by the film thickness and width of the cavity 170. For example, in order to keep the operating voltage at a practical level, the spacer film 130 is preferably as thin as possible. For example, in at least some embodiments of the poly-CMUT 100, the distance between the two electrodes 120, 150 does not exceed 1 μm, so that the operating voltage of the poly-CMUT 100 is less than 230 volts. The spacer film 130 is also adhered to the substrate 160 and the membrane 110 layer. In Figure 1 In the embodiment of the present invention, the spacer film 130 is indirectly adhered to the substrate 160 via the insulating layer 140; however, as shown in relation to FIG. 2 and discussed below, the spacer film 130 can also be directly bonded to the substrate 160. If glue layers are used, they are preferably extremely thin. In one example, an ultra-thin PET used as the spacer film 130 can be laminated to a polyamide film used as the substrate 160 and the film 110 using heat and pressure.

[0071] In order to create a functional MEMS device, the device preferably has room to move. In the case of the poly-CMUT 100, the membrane 110 is suspended above a cavity 170. For most MEMS devices, this cavity 170 also determines the properties of the device, such as the resonant frequency or sensitivity. Figure 1 In general, the shaped cavities are stamped out of the spacer film 130. This can be done entirely by hand, by a vertical stamping machine, or in a roll-to-roll setup for larger areas. To form the shaped cavities, the spacer film can be perforated by a mold including protrusions, such as by stamping by a stamping section of a roll-to-roll laminator, so as to produce an array including multiple shaped cavities for multiple MEMS devices at one time.

[0072] After the shaped cavity is created, three films in the form of film 110, spacer film 130 and substrate 160 are aligned with each other and stacked so that the conductive layers in the form of electrodes 120 and 150 are aligned with each other. Figure 1As shown. In at least some embodiments, they are then heated and pressed by two rollers at a pressure of about 3 bar and a temperature of 243° C. This laminates the film while still ensuring that the film 110 is suspended above the cavity 170. In at least some embodiments where the process is done in a roll-to-roll setting, the final device is cut from the continuous film.

[0073] Lamination temperature and pressure are inversely proportional to each other (i.e., increasing pressure decreases the required temperature). Generally speaking, lamination can be performed at a pressure of 1 bar and a temperature of 243° C. to a pressure of 5 bar and a temperature of 210° C., wherein the temperature decreases as the pressure increases. The pressure should be kept low enough so as not to compress the spacer membrane 130 and seal the cavity 170.

[0074] Figure 5A An example of a metal lattice pattern 500 that may be formed on, for example, the substrate 160 or the film 110 is shown.

[0075] Figure 6 The photographic reproduction 600 of shows a punched spacer film 130 with a cavity diameter of 0.8 mm and a distance between cavities 170 of 5 mm and a punching die for use in a roll-to-roll machine. Figure 6 The stamping dies include rotating cylindrical dies and can be used in the following Figure 7 described in the system.

[0076] FIG. 5B to FIG. 5D A picture is depicted of an exemplary first wafer 502 and a second wafer 504 of a MEMS device manufactured in a roll-to-roll setup, including a pair of metal grid patterns 500 as described above. Figure 5B A front perspective view of the first sheet 502 is depicted; Figure 5C depicts a top plan view of a first sheet 502; and Figure 5D The top side of the second sheet 504 is depicted. The first sheet 502 of MEMS devices may be cut from the second sheet 504.

[0077] Specifically, Figure 5B and Figure 5C , which respectively show a top plan view and a bottom plan view of a first sheet 502 of a device, the device fabricated includes: a film 110, which has been metallized to form a top electrode 120 and a bonding pad electrically coupled to the top electrode 120; and a flexible substrate 160, which has been metallized to form a bottom electrode 150 and a bonding pad electrically coupled to the bottom electrode 150. The cavity 170 for the device is located at the intersection 506 of the top electrode 120 and the bottom electrode 150 (i.e., where the electrodes 120 and 150 overlap) and is therefore Figure 5B and Figure 5C Not visible in.

[0078] The size of the manufactured array can be further expanded by assembling using overlapping tapes / patches. This is a method for modular assembly of a poly-CMUT cell array arranged on a flexible substrate 160 in a regular pattern (one by two, two by four, four by four, etc.). In this method, a flexible tape or patch is used as a mechanical substrate 160 for making a transducer array on its top surface, while the bottom side can be specially treated to be sticky. In order to ensure the electrical interconnectivity between the rows of cells made on the top surface, each row has associated bonding pads (electrical interconnection surfaces) at both edges of the patch / tape. A through-hole mechanism similar to the through-hole mechanism used in making flexible PCBs electrically connects the edge bonding pads on the top surface to the patterned edge bonding pads on the bottom surface of the tape / patch. The top and bottom edge bonding pad groups are aligned.

[0079] When the tape is made for wrapping around a cylindrical surface (such as a pipe of defined circumference), the distance between consecutive rows of transducer elements (arranged in a direction transverse to the edge of the tape [i.e., consecutive rows extending axially along the cylindrical surface]) is preferably such that the diameter of the cylinder corresponds to an integer number of rows arranged around its circumference. The next roll of tape will then align the next set of transducer rows with the previous set and provide electrical interconnection by overlapping the top edge bond pads of the previous tape with the bottom edge bond pads of the next roll of tape.

[0080] In at least some embodiments, to ensure better self-alignment, the tape structure has embossed alignment locking patterns, such as grooves and wedges, for example, to enforce and stabilize the alignment of the connection between transducers.

[0081] In other embodiments, the alignment of bond pads described above is also used for shaped shapes of flexible patches, tapes, foils, fabrics, and poly-CMUT arrays of various shapes and sizes.

[0082] Figure 7 An exemplary system 700 is depicted that can be used to manufacture MEMS devices using a roll-to-roll laminator according to an exemplary embodiment. The system includes multiple pairs of rollers: a stamping assist roller pair 702a, a pair of stamping rollers 702b, a first pair of film rollers 702c, a second pair of film rollers 702d, and a pair of laminating rollers 702e. The pair of laminating rollers 702e comprises a portion of the roll-to-roll laminator.

[0083] Will Figure 7 PET (such as Mylar TM) is pulled into the pair of punching aid rollers 702a together with the punching aid 704. The punching aid 704 may be a relatively thick PET layer, for example, to which the punched-out portion of the spacer film 130 adheres after punching. The spacer film 130 is pulled into the first pair of rollers 702a and compressed together with the punching aid 704. The compressed spacer film 130 and the punching aid 704 are pulled into a pair of punching rollers 702b, in which a convex mold (such as a Figure 6 The rotating cylindrical mold of the present invention is used to actually punch the spacer film 130 to produce the cavity 170 as described above. The spacer film 130 and the punching aid 704 are both in Figure 6 1 and 15 , where the punching aid 704 is wider than the spacer film 130. The punched spacer film 130 and the punching aid 704 are pulled into the first pair of film rollers 702c and compressed with a metallized film 706 to be used as the substrate 160 and the bottom electrode 150. For example, the metallized film 706 can be a polyimide layer. When leaving the first pair of film rollers 702c, the punching aid 704 is peeled off from the spacer film 130 and the metallized film 706 using a hard edge 708 to facilitate separation.

[0084] The stamped spacer film 130 and metallized film 706 are pulled into a second pair of film rollers 702d and compressed with another metallized film 710 to be used as the film 110 and the top electrode 120, so that the spacer film 130 is sandwiched between the metallized films 706, 710. For example, the metallized film 710 can be a relatively thin polyimide layer (e.g., any value from 3 μm to 25 μm (including this value)). When the other metallized film 706 for the substrate 160 is made of the same material, in at least some embodiments, it is at least as thick as the metallized film 710 for the film 110, and up to twice as thick. This is to ensure that the substrate 160 has at least the same mechanical strength as the film 110. In embodiments where film 706 for substrate 160 is mechanically stronger than film 710 for film 110 , film 706 for substrate 160 may be thinner than film 710 for film 110 while still making substrate 160 at least as strong as film 110 .

[0085] The three films 706, 130 and 710 leaving the second pair of film rollers 702d are fed into a pair of lamination rollers 702e and laminated together to form a finished film 712 of a MEMS device, such as FIG. 5B to FIG. 5D Depicted.

[0086] Figure 7A first pair of film rollers and a second pair of film rollers 702c, 702d are depicted. In at least some other embodiments, these rollers 702c, 702d can be replaced with a single roller that receives both metallized films 706 and 710 and presses them against the stamped spacer film 130. Additionally or alternatively, when two pairs of film rollers 702c, 702d are used, the thicker of the films 706, 710 can be fed through the second pair of film rollers 702d rather than the first pair of film rollers 702c, such as Figure 7 shown.

[0087] Applied to products

[0088] Remote control. Power consumption is a major challenge, as many Internet of Things (IoT) devices are battery powered and need to have a long life in the field. Turning off a device reduces the consumption of battery life, but does not provide sensing when needed, so an energy-efficient way to alert and power on an IoT device is needed. This means that the device needs a wake-up receiver that can turn the IoT device on / off. Ultrasound has several advantages in performing this task. It can use very short wavelength signals and is therefore much smaller than similar alarm receivers using radio signals, while operating at extremely low power and with a wider range (i.e., being able to receive signals from a greater angular distance). Such an ultrasonic-based receiver listens for a low-amplitude ultrasonic signal that can be uniquely mapped to a device, indicating when the device should be turned on. In at least some embodiments, it requires only a nanowatt of signal power, which is a small drain on precious battery energy reserves. In addition, the range of such an ultrasonic signal is naturally limited by its inability to propagate through acoustically opaque surfaces (such as walls), so it can be confined to the interior of a room, for example, which has valuable privacy advantages. The technology can be extended beyond simple wake-up signals and include sending and receiving other information, such as encoded passwords or other information. Another advantage is that ultrasonic frequencies do not interfere with the strictly controlled electromagnetic frequency ranges dictated by government regulators for IoT communications.

[0089] Poly-CMUT sleeve. In at least some embodiments, the Poly-CMUT array can be fabricated on a stretchable substrate so that it behaves like an elastic fabric. This is useful when a tight fit between the Poly-CMUT and the target material is required, such as when the Poly-CMUT comprises part of a sleeve that fits over a pipe.

[0090] Structural integrity testing.In yet other embodiments, transparent poly-CMUT arrays are used for non-destructive testing (NDT) of materials. Typically, X-ray imaging is used for material inspection, but the doses used contain a large proportion of ionizing radiation, which in some cases can cause internal damage to the test sample. X-ray transparent poly-CMUT arrays can additionally or alternatively be used to obtain images, such as hybrid images produced by a combination of ultrasound and X-ray imaging, to potentially reduce the amount of X-ray energy required.

[0091] Pipeline monitoring. In some embodiments, the CMUT array can be mounted on a section of the pipeline when it is placed in the field. Alternatively, it can be mounted on a section of the pipeline when it is manufactured to better integrate with the pipeline and protect the CMUT array from damage. At least some embodiments are useful for real-time monitoring of underground pipelines in the form of NDT.

[0092] Hydraulic testing. The poly-CMUT can in some embodiments be fabricated on an elastic substrate so that it can deform with the deformation of the hydraulic hose during normal operation. The electrical interconnection and flexibility of the substrate can be tailored to the diameter and length of the pipe to be wrapped.

[0093] Aircraft wing NDT. In some embodiments, a rollable poly-CMUT array is provided that can be mounted around the perimeter of a wheel, which enables the array to be quickly rolled onto an aircraft wing. The poly-CMUT in contact with the wing can then be used to perform ultrasound imaging. For example, the poly-CMUT may include a portion of a flexible fabric,

[0094] For example, if a large poly-CMUT transducer array is needed to inspect an aircraft wing or other aircraft, a large membrane including the poly-CMUT array can be temporarily attached to the wing for inspection. Permanent monitoring solutions can include, for example, incorporating the transducer inside the fuselage to protect the transducer from physical wear and environmental exposure.

[0095] Wearable poly-CMUT array. In another embodiment, a poly-CMUT array made according to the embodiments described herein is used on human or animal tissue. The flexible or rigid arrays thus formed for medical or agricultural applications are useful for providing information about injuries at the scene in the event of an accident. For example, emergency responders can wrap the injured in fabric and image the victim's fractures and soft tissue injuries before beginning to transport the victim to a medical facility. This practice can include checking for fractures in the legs, arms, ribs, and spine, as well as checking the skull for impact injuries.

[0096] Bandages for wounds.In at least some embodiments, the poly-CMUT array is made into a bandage for covering a wound during healing. To this end, a flexible substrate is used so that the flexible substrate can better conform to the tissue. This poly-CMUT array bandage can also monitor tissue repair and deliver energy to the tissue below the repair to increase the speed of the healing process. In another embodiment, the poly-CMUT array bandage is used to cavitate fluid in the tissue to support debridement.

[0097] Diagnostic instruments. In other embodiments, hybrid integration of transparent poly-CMUT arrays combines X-ray, ultrasound, photoacoustics, elastography, and / or combinations thereof in a single system.

[0098] Chemical and biological sensing. By functionalizing the membrane of the poly-CMUT element, wearable poly-CMUT patches can be used for chemical and biological sensing. The functionalized membrane is sensitive to the presence of chemical or biological substances that change the mass loading of the membrane. For example, the resonant frequency of the poly-CMUT element depends on the material properties of the membrane (such as mass, stiffness, and viscosity), which is similar to a drum. In the presence of a specific chemical or biological substance intended to be "sensed", the functionalized membrane can absorb some of the material, and its physical properties change accordingly. Changes in material properties can be detected by changes in the frequency, bandwidth, or amplitude of the resonant frequency, for example. Specifically, it is known that the change in the resonant frequency is proportional to the relative change in the mass of the membrane.

[0099] Heart monitor. According to at least some embodiments, the patch acts as a transmitter to focus ultrasound pulses on the skin toward the heart and a microphone to record reflected waves. The patch acts as an onboard pulsed Doppler ultrasound system operating in the range of 20 to 60 KHz. For example, exemplary patch sizes range from 5 by 5 cm to 10 by 10 cm.

[0100] Blood pressure monitor. In certain embodiments, the poly-CMUT wearable array uses ultrasound Doppler flow measurement to non-invasively determine blood pressure in a patient population. Blood pressure can be measured using the poly-CMUT described below and is comparable to invasive arterial catheters or oscillometric Terumo Elemano TM Blood pressure monitors are compared. To measure blood pressure using poly-CMUTs, blood flow velocity in the radial artery is recorded during cuff deflation by a fabric patch that includes a poly-CMUT array. An S-shaped curve is fit to the preprocessed velocity signal, and systolic and mean arterial pressures are determined. Applications include pre-eclampsia monitoring during pregnancy and ambulatory blood pressure monitoring in cardiac patients.

[0101] Transcranial Focused Ultrasound(FUS) combined with venous circulating microbubbles can temporarily and selectively increase the permeability of the blood-brain barrier to enable targeted drug delivery to the central nervous system. This approach can be used in patients with brain tumors, early Alzheimer's disease, and amyotrophic lateral sclerosis. The challenge addressed by at least some embodiments is that for widespread clinical adoption of FUS-mediated blood-brain barrier permeability, systems and methods for real-time treatment monitoring and control need to be developed to ensure that safe and effective acoustic exposure levels are maintained throughout the process.

[0102] Transmitter and receiver electronics (sometimes referred to as transceivers) that can be incorporated into the above applications are available from, for example, Verasonics TM 、US4US TM 、Interson TM and Texas Instruments TM Commercially acquired.

[0103] At least some embodiments will be more readily understood by reference to the following examples, which are given for the purpose of illustrating various embodiments.

[0104] Example 1

[0105] The working polyCMUT was produced by an all-mechanical process. First, the polyamide was metallized to produce the required electrodes. A thin (900nm thick) Mylar was punched vertically using a 0.5mm leather punch. TM membrane; the membrane acts as Figure 1 A spacer film 130 is provided. A leather stamping die is used to create a shaped cavity in the prototype. More generally, the Mylar film may be any common biaxially oriented polyethylene terephthalate film having a thickness in the range of 600 nm to 1.5 μm.

[0106] Figure 3 A stamped 900 nm Mylar film 130 is shown to show the feasibility of mechanically stamping such a thin film. After being stamped and set up for use, the mask is used as a template for stamping and metal evaporation.

[0107] The stamped film was then aligned with the metallized polyamide film and laminated together in a roll laminator at a temperature of 235°C with pressure. Figure 2B The resulting stack and four-chamber device 300 is shown in FIG.

[0108] Figure 2A The exact stackup of the resulting prototype 200 is shown, where the release film 130 is Mylar TM In this embodiment, the prototype 200 lacks Figure 1However, the prototype includes: a cavity 170 formed by punching the spacer film 130; a film 110 made of Kapton TM The film is metallized and its metallized portion forms the top electrode 120; and a substrate 160, which is made of Kapton TM The substrate is metallized and its metallized portion forms the bottom electrode 150 .

[0109] The layers can then be connected to a bias tee with 120V DC and 60V AC and scanned using LDV to find the resonant frequency and thereby confirm the success of the fabrication.

[0110] exist Figure 4 On the right, a single cavity 170 fabricated in accordance with an embodiment is shown under a 10X microscope. Both electrodes and the larger outline of the cavity 170 are visible, and the resulting left LDV scan 400 reveals a resonant frequency of approximately 230kHz. At 120V DC and 60V AC, the membrane shows a resonant frequency of approximately 230kHz with displacement magnitudes at different frequencies, and demonstrates fabrication of a working prototype. The measurements were done in LDV.

[0111] Example 2

[0112] Should Example A novel MEMS fabrication method is presented that uses a poly-CMUT as an exemplary MEMS device. To use this fully mechanical fabrication method, three main components are used. The first two components are two membranes of equal or different thickness, which can be a homogeneous material or a laminate of several materials obtained; these membranes are used for membrane 110 and substrate 160. To build the poly-CMUT, these membranes are first metallized to form electrodes 120 and 150. For the prototype described, in which the membranes consisted of 25μm and 100μm thick Kapton, respectively. TM , these membranes are metallized with 100nm of gold. The metallization can be conformal or patterned, depending on the architecture of the device. The third component is a very thin spacer membrane 130, which acts as a spacer membrane. In this embodiment of the poly-CMUT, the spacer membrane 130 is Mylar TM The spacer membrane 130 is then punched to create the shaped cavities required to allow the poly-CMUT membrane to move. The resulting membranes are laminated together. In the case of a poly-CMUT, the laminator heats the rollers to 230° and the pressure is 1 bar to achieve permanent lamination. The parameters of this process vary depending on the materials used and the desired characteristics of the resulting device. In one example, the metallized substrate and membrane are formed by adding a very thin layer of acrylate or SiO2 Or similar insulators to insulate. This can be done with one or both of the two metallized films used for the electrodes.

[0113] In this disclosure, the word "comprising" is used in a non-limiting sense to mean including the items following the word, but not excluding items not specifically mentioned. It should be understood that in embodiments that include or may include specific features or variables or parameters, alternative embodiments may consist of such features or variables or parameters, or consist essentially of such features or variables or parameters. Reference to an element by the indefinite article "a" does not exclude the possibility that more than one element is present, unless the context clearly requires the presence of one and only one element.

[0114] In this disclosure, the recitation of numerical ranges by endpoints includes all numbers contained within that range, including all whole numbers, all integers, and all decimal intermediate values ​​(e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.). In this disclosure, the singular forms "an" and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to a composition containing "a compound" includes a mixture of two or more compounds.

[0115] In this disclosure, the term "or" is generally employed in its sense including "and / or" unless the content clearly dictates otherwise.

[0116] It is contemplated that any portion of any aspect or implementation discussed in this specification may be implemented or combined with any portion of any other aspect or implementation discussed in this specification, as long as such implementation or combination is not performed using mutually exclusive portions.

[0117] Although exemplary embodiments have been described above and shown in the accompanying drawings, it will be apparent to those skilled in the art that modifications may be made without departing from the present disclosure. These modifications are considered to be possible variations within the scope of the present disclosure.

Claims

1. A method for making an array of micro-electromechanical system devices, the method comprising: (a) obtaining a sheet of material from which a cavity for the device is formed; (b) causing a physical or energetic protrusion to project into said material to form said cavity in said material; (c) contacting the upper surface and the lower surface of the material having the cavity with an upper metallized film and a lower metallized film, respectively; as well as (d) bonding the upper surface and the lower surface of the material to the upper metallized film and the lower metallized film, respectively.

2. The method according to claim 1, wherein: The physical protrusions protrude into the material to form the cavities.

3. The method according to claim 2, wherein: The physical protrusion comprises a piercing punch.

4. The method according to claim 2, wherein: The physical protrusion comprises a punch die.

5. The method according to claim 2, wherein: The physical projection comprises a rotating cylindrical mold.

6. The method according to claim 1, wherein: The energy protrusions protrude into the material to form the cavities.

7. The method according to claim 6, wherein: The energy projections include laser light.

8. The method according to claim 6, wherein: The energy bump includes an electrical discharge.

9. The method according to claim 6, wherein: The physical projections include steam jets.

10. The method according to claim 1, wherein: The material is a polymer.

11. The method according to claim 10, wherein: The material includes polyimide.

12. The method according to claim 1, wherein: The material includes polyethylene terephthalate.

13. The method according to claim 12, wherein: The material is biaxially oriented polyethylene terephthalate and has a thickness between 600 nm and 1.5 μm.

14. The method according to claim 1, wherein: The material is metal.

15. The method according to claim 1, wherein: The MEMS device is a capacitive micromachined ultrasonic transducer.

16. The method according to claim 14, wherein: The MEMS device is a polymer capacitive micromachined ultrasonic transducer.

17. The method according to any one of claims 1 to 16, wherein: The upper surface and the lower surface of the material having the cavity are in contact with the upper metallized film and the lower metallized film, so that metallized portions of the upper metallized film and the lower metallized film are respectively located in the cavity.

18. The method according to any one of claims 1 to 17, wherein: The bonding includes lamination.

19. The method according to claim 18, wherein: The lamination was performed using a roll laminator at a temperature between 210°C and 260°C.

20. The method according to claim 19, wherein: The lamination is performed under pressure conditions between 1 and 5 bars.

21. The method according to any one of claims 1 to 17, wherein: The joining comprises gluing.

22. The method according to any one of claims 1 to 21, wherein: The lower metallized film comprises a flexible substrate of the device.

23. The method according to any one of claims 1 to 22, wherein: The metallized films include lattice patterns, respectively, and wherein the cavity is located at a position where the lattice patterns overlap.

24. An apparatus for making an array of micro-electromechanical system devices, the apparatus comprising: (a) a pair of punching rollers, wherein the pair of punching rollers include a cylindrical die and are configured to receive a spacer film and punch a cavity in the spacer film using the cylindrical die; (b) at least one pair of film rollers, wherein the at least one pair of film rollers is configured to receive the punched spacer film and the metallized film and compress the punched spacer film between the metallized films; and (c) a pair of laminating rollers configured to receive the compressed spacing film and the metallized film and laminate the compressed spacing film and the metallized film.

25. The apparatus of claim 24, wherein: The at least one pair of film rollers comprises a first pair of film rollers and a second pair of film rollers, wherein: (a) the first pair of film rollers is configured to receive and compress the punched spacer film and the first metallized film among the metallized films; and (b) the second pair of film rollers is configured to receive the first metallized film and the second metallized film among the metallized films after passing through the first pair of film rollers, and compress the punched spacer film between the metallized films, The first metallized film in the metallized film is thicker than the second metallized film in the metallized film.

26. The apparatus of claim 25, further comprising: (a) a pair of punching assist rollers configured to receive and compress the spacer film and the punching assist member, wherein the compressed spacer film and the punching assist member are fed into the pair of punching rollers and into the first pair of film rollers; and (b) a hard edge positioned to peel the punch aid from the spacer film after the punch aid leaves the first pair of film rollers.

Images