High-Speed Fabrication of Microelectromechanical System Arrays

Abstract

A method, system, and technique for rapidly manufacturing a microelectromechanical systems (MEMS) array, such as an array of polymer capacitive micromachine ultrasonic transducers (CMUTs). A sheet of material for forming cavities for the devices is obtained, and physical projectiles or energy projectiles are projected into the material to form the cavities. The upper and lower surfaces of the material are respectively contacted and bonded to an upper metallization film and a lower metallization film. The metallized portions of the upper metallization film and the lower metallization film can function as electrodes of the CMUT, and the films themselves can become the substrate and membrane of the CMUT.

Description

Technical Field

[0001] The present disclosure relates generally to the mass manufacture of microelectromechanical system (MEMS) devices and arrays, and more specifically to large flexible arrays of capacitive micromachine ultrasonic transducers (CMUTs).

Background Art

[0002] Ultrasonic imaging is the most widely used medical imaging method in the world in terms of the number of images created annually. In ultrasonic imaging, ultrasonic waves emitted by a transducer pass through a material and are reflected at an interface with another material having a different acoustic impedance. The reflected echo returns to the transducer, where it is processed to form an ultrasonic image. An ultrasonic transducer converts electrical energy into acoustic energy and also performs the reverse conversion.

[0003] CMUT is an alternative technology to piezoelectric-based transducers. CMUT is essentially a parallel plate capacitor, with the bottom electrode fixed to the substrate, and a membrane suspended above the cavity and sealed along its edges. A metal electrode is patterned on the top of the suspended membrane. When an electrical signal is applied (applied) between the electrodes, mechanical movement of the membrane is caused, generating acoustic waves in the medium in contact with the membrane. This represents the transfer (conversion) of electrical energy to acoustic energy. Polymer CMUT (poly-CMUT) is, in fact, a CMUT in which the diaphragm is made of a polymer material. The resonant frequency and acoustic output can depend on their diameter and thickness. The manufacture of poly-CMUT is typically performed in a clean room using photolithography to pattern and build multiple layers of the device. U.S. Patent Nos. 10,509,013, 10,564,132, and 10,598,632 by Gerardo, Rohling, and Cretu (all of which are hereby incorporated by reference in their entirety) disclose a microfabrication method for ultrasonic transducers using polymer membranes, which results in a reduction in the required operating voltage of poly-CMUT.

SUMMARY OF THE INVENTION

[0004] This summary is provided to introduce a selection of concepts in a simplified form, which 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 of the present disclosure, a method of manufacturing a MEMS array, the method comprising: providing a sheet of thin film material; contacting the material with a die including protrusions (physical projectiles), wherein the protrusions are capable of puncturing the material to form cavities patterned therein; contacting the material with an upper metallization film and a lower metallization film; and laminating the films by the addition of energy.

[0006] The method can be carried out without generating chemical waste.

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

[0008] The composition of the material can be, or can include, a polymer, a metal, or polyimide.

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

[0010] According to additional aspects, there are provided a MEMS device manufactured by the foregoing method, a CMUT manufactured by the foregoing method, a poly-CMUT manufactured by the foregoing method and completely by mechanical means without sandwich electrodes, and a method of shaping a MEMS device according to the foregoing method.

[0011] According to another aspect, a method of manufacturing an array of microelectromechanical system devices, comprising: obtaining a sheet of material for forming cavities for the devices; projecting a physical projectile or an energy projectile into the material to form the cavities in the material; contacting an upper surface and a lower surface of the material with the cavities with an upper metallization film and a lower metallization film, respectively; and bonding the upper surface and the lower surface of the material to the upper metallization film and the lower metallization film, respectively.

[0012] The physical projectile can be projected into the material to form the cavity.

[0013] The physical projectile may include a punching stamp.

[0014] The physical projectile may include a stamp die.

[0015] The physical projectile may include a rotating cylinder die.

[0016] The energy projectile can be projected into the material to form the cavity.

[0017] The energy projectile may include a laser.

[0018] The energy projectile may include an electric discharge.

[0019] The physical projectile may include a vapor jet.

[0020] The material may be a polymer.

[0021] The material may include a polyimide.

[0022] The material may include polyethylene terephthalate.

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

[0024] The material may be a metal.

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

[0026] The upper surface and the lower surface of the material with the cavity may be contacted with the upper metallization film and the lower metallization film such that the metallized portions of the upper metallization film and the lower metallization film are respectively located within the cavity.

[0027] The step of joining may include a step of laminating.

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

[0029] The step of laminating may be performed at a pressure of at least 1 bar.

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

[0031] The step of joining may include a step of adhering.

[0032] The lower metallization film may constitute the flexible substrate of the device.

[0033] The metallization films may each have a lattice pattern, and the cavity may be located at a place where the lattice patterns overlap.

[0034] According to another aspect, an apparatus for manufacturing an array of microelectromechanical system devices, comprising a pair of stamping rollers, at least one pair of film rollers, and a pair of laminating rollers, wherein the pair of stamping rollers has a cylinder die and is configured to receive a spacer film and stamp a cavity into the spacer film using the cylinder die, the at least one pair of film rollers is configured to receive the stamped spacer film and a plurality of metallized films and compress the stamped spacer film between the metallized films, and the pair of laminating rollers is configured to receive and laminate the compressed spacer and the metallized films. An apparatus is provided which is characterized in this way.

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

[0036] The apparatus may further include a pair of stamping auxiliary material rollers configured to receive and compress the spacer film and the stamping auxiliary material. The compressed spacer film and the stamping auxiliary material may be supplied to the pair of stamping rollers and the first pair of film rollers. The apparatus may further include a hard edge positioned to peel the stamping auxiliary material from the spacer film after exiting the first pair of film rollers.

[0037] The abstract does not necessarily describe the entire scope of all aspects. Other aspects, features, and advantages will become apparent to those skilled in the art when referring to the following description of specific embodiments.

[0038] Next, further features and advantages of the present disclosure will become apparent from the following detailed description in combination with the accompanying drawings.

Brief Description of the Drawings

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Figure 1

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Figure 2A

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Figure 2B

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Figure 5A

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Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0048] Manufacturing CMUT arrays using conventional methods is a breakable task. One of the limitations in the prior art is the limit of the maximum speed of CMUT manufacturing. Another limitation is that since multiple manufacturing processes in multiple manufacturing apparatuses are required, it is necessary to manually transport materials between those different apparatuses. Such apparatuses include a wet bench, a mask aligner, an ion etcher, a dryer, a furnace, and an evaporator. Yet another limitation in CMUT manufacturing is the maximum size of CMUT transducer arrays that can be manufactured using conventional manufacturing techniques. This is typically not sufficient for applications that require arrays with a diameter of several centimeters and a length of several meters. Another limitation in traditional manufacturing methods is the type and number of required liquid and gaseous chemical substances such as photoresist, acids, bases, and developers, many of which are toxic and difficult to dispose of. Therefore, a manufacturing method for CMUT that overcomes one or more of these limitations is desired.

[0049] This disclosure is directed to new methods, systems, and technologies for manufacturing CMUTs and other MEMS devices that utilize cavities within layers to accommodate electromechanical coupling. The focus of the following exemplary embodiments is on CMUTs, but this disclosure also contemplates other types of MEMS devices with cavities of those types, such as accelerometers, pressure sensors, speakers, gyroscopes, etc. In at least some embodiments, the cavities are created by mechanically stamping ultrathin films and laminating them between pre-metallized films. The advantages are, ideally, the avoidance of wet chemical processing and the elimination of maximum size limitations with respect to traditional microfabrication methods and apparatuses. At least some embodiments also allow for a variable trade-off since the accuracy of the stamped structures is inversely proportional to the speed and scale of manufacturing.

[0050] In at least some embodiments, to achieve this, a number of technical problems had to be overcome. For example, the cavities used are small (on the order of a few millimeters or less), and stamping dies are manufactured to stamp those cavities. This means that the tool and tool manufacturing precision need to 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, despite being very thin, sufficient structural stability is required to be handled during the manufacturing process. If the film is damaged or the cutting edge of the die has defects, the film will tear and the manufacturing will end in failure.

[0052] In the present disclosure, the following terms have the following meanings. (a) “Polymer-based capacitive micromachine ultrasonic transducer” or “PolyCMUT” is a layered ultrasonic device comprising a polymer film with an embedded top electrode suspended above a cavity. Examples of PolyCMUT can be found, for example, in U.S. Patent No. 10,598,632 by Gerardo, Rohling, and Cretu. In contrast to conventional non-polymer-based CMUTs, in PolyCMUTs, the top electrode can be embedded within two polymer layers, and the lower layer is thinner than the upper layer. This structure, in combination with forming a sufficiently thin CMUT cavity, allows the CMUT to reach the MHz operating region without requiring an unacceptably high operating voltage. PolyCMUT elements can be formed, for example, by the method disclosed in U.S. Patent No. 10,598,632 by Cretu et al. (b) A "microelectromechanical system", i.e., "MEMS", is a small electromechanical device such as a poly-CMUT. In at least some embodiments, these include micro sensors and micro actuators. Piezoelectric materials can be used to form the resonant frequency of MEMS devices. This can affect the performance of those devices. For example, piezoelectric materials can affect the performance of MEMS devices such as accelerometers, energy harvesters, strain gauges, etc. (c) The term "spacer film" means a sheet of material in which a molding cavity is formed for a CMUT or MEMS array and which is stamped / perforated (punched) by hand and / or an automated system. For the manufacture of poly-CMUT, polyimide (e.g., Kapton®), polyethylene terephthalate (PET) (e.g., Mylar®), and gold for electrodes are used. Other spacer films can include, for example, paper, chitosan, polystyrene (PS), or other materials suitable for use as a thin film suitable for adhesion (such as via lamination) to the substrate and film layers of MEMS devices. (d) As used herein, the term "stamping" means removing a portion of the spacer film by pressing (projecting) a die (mold) containing a protrusion (physical projectile) into the spacer film. (e) "Low power" or "passive power" means wireless power transmission using an electromagnetic field, typically operating at a frequency that matches the resonant frequency of a poly-CMUT element. (f) "Array" means a group of poly-CMUT elements arranged side by side in a one-dimensional (1-D) arrangement, a plurality of linear arrays arranged side by side (1.5-D), or a two-dimensional array of poly-CMUT elements (2-D array, also referred to as a "matrix array") that can communicate with each other and communicate with a user interface by either a wired communication signal or a wireless signal (when connected or when activated). (g) The term "forming cavity" refers to perforations that are engraved (e.g., using a laser) or otherwise formed in the spacer film during the manufacture of the poly-CMUT. These can be formed, for example, circularly, as polygons, or as other closed contour shapes, in accordance with the periphery of the desired CMUT or MEMS. (h) A "die having protrusions (physical projectiles)" is a solid material having hard protrusions capable of perforating the spacer film. Examples of dies including protrusions are rotating cylinder dies in a roll-to-roll setup, punching stamps, and manual or automatic leather stamp dies. The protrusions can be metal, mineral, 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 film. Whatever is used to perforate the spacer film, a forming cavity is thereby formed within the spacer film. In still other embodiments, evaporation means or vapor jets (energy projectiles) can be used to form forming cavities in the spacer film. For example, in at least some embodiments, holes can be made in the spacer film via evaporation by an electric discharge or a laser (i.e., via thermal evaporation of a section). More generally, a "die having perforating means" is a solid material having means for selectively perforating the spacer film, and these means include, in various embodiments, protrusions, lasers, evaporation means, vapor jets, etc. (i) "Photoacoustic imaging", i.e., "PA imaging", is a biomedical imaging technique in which non-ionizing laser pulses are delivered into biological tissue. A portion of the delivered energy is absorbed and converted to heat, causing a transient thermoelastic expansion and generating broadband (in MHz) ultrasonic emissions. The typical received frequency response of traditional piezoelectric (PZT) ultrasonic imaging transducers based on PZT technology is not broad enough to fully preserve all the information contained in the photoacoustic signal. CMUTs, when receiving, exhibit higher sensitivity and a significantly broader frequency response, and thus, when combined with PA imaging applications, are more effective than PZT ultrasound.

[0053] The charge confined within the film of the poly-CMUT functions 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 reception of an acoustic signal and conversion of the acoustic signal to 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 ). In some other embodiments, higher voltages may be required, such as when a relatively thick spacer film 130 is used to provide a relatively thick cavity 170.

[0054] Wireless communication includes, in some embodiments, wireless power transfer. In wireless power transfer, a transmitting device driven by power from a power source generates a time-varying electromagnetic field, the electromagnetic field transmits power across space to a receiving device, and the receiving device extracts power from the electromagnetic field and supplies it to an electrical load. Examples of wireless power transfer include inductive coupling, resonant inductive coupling, capacitive coupling, magnetodynamic coupling, acoustic coupling, and power transfer using microwaves and light waves. The coupling can be near-field coupling or intermediate coupling. In the context of electromagnetic energy, the energy transmitted can be electromagnetic waves at frequencies in the range of KHz to MHz, microwaves, X-rays, light waves such as solar energy and lasers. Such waves can be generated using antennas or other coupling devices. For example, the waves can include electromagnetic energy generated to perform simultaneous magnetic resonance imaging or X-ray imaging. Other types of energy that can be transmitted include kinetic energy from sound waves and surface waves, and thermal energy from heat. The coupler can be externally attached to the poly-CMUT element or can be directly embedded in the poly-CMUT element. The advantages of using wireless power transfer are increased convenience and safety, and reduction in the size, weight, cost, and complexity of the poly-CMUT element. This can be particularly beneficial when the poly-CMUT element forms part of a wearable patch. For example, a lightweight patch may not be obtrusive to the wearer, and the patch can be implanted or embedded in a patient where wires are prohibited due to infection concerns.

[0055] Poly-CMUT can be fabricated on a flexible substrate for wearable applications. This can be difficult for silicon-based CMUTs as they require a rigid substrate. It is not possible to fabricate a flexible substrate when the substrate is made using a ceramic piezoelectric material.

[0056] Previous research has focused on roll-to-roll MEMS processes using photolithography, or the manufacture of solid state devices such as U.S. Patent No. 8,779,650. These references focus on the use of wet or dry etching processes and ultraviolet-sensitive chemicals by selectively curing previously deposited soft layers. In contrast, the methods, systems, and techniques described herein can be completely mechanical and do not require any etching or curing to form the functional shape of a CMUT.

[0057] [Manufacture of Poly CMUT Component Arrays] FIG. 1 shows a MEMS device including an exemplary poly - CMUT 100. The poly - CMUT is composed of four main components: a substrate 160, a spacer film 130 which is PET in FIG. 1, an upper electrode 120 and a bottom electrode 150 which are each made of aluminum in FIG. 1, and a membrane 110. FIG. 1 also shows a cavity 170 within the poly - CMUT 100, although it is shown as part of the poly - CMUT 100 in FIG. 1. In FIG. 1, the spacer film 130 is sandwiched between the upper electrode 120 and the bottom layer of the acrylate insulator 140, and 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 (thickness) polyimide film. In fact, the substrate 160 can be any flexible film such as aluminum foil, paper, or other polymers, etc. Any flexible film can be used as the substrate 160, but in at least some embodiments, the substrate 160 has a thickness equal to or greater than that of the membrane 110, or is mechanically stronger than the membrane 110. The substrate 160 can also adhere to the spacer film 130, or to another layer such as the acrylate insulator 140 if such another layer is present. The adhesion between the flexible film and the spacer film 130 can be achieved by lamination, adhesive bonding, or other suitable methods. To create a functioning device, the substrate 160 can itself be conductive or can be coated with a conductive material. To reduce parasitic capacitance and parasitic resistance, the conductive layer can be patterned through a process such as sputtering on an oil mask. Optionally, the conductive layer can be insulated by one or more other suitable insulators such as acrylate, or silicon dioxide, etc., provided by Steiner GmbH for capacitor foils, for example.

[0058] In FIG. 1, first, a bottom film in the form of a substrate 160 and a top film in the form of a film 110 can be metallized in a pattern necessary for the resulting device. An exemplary use thereof will be described below. This can be carried out by screen printing a mineral oil mask and sputtering a selected electrode material, thereby patterning the electrode material. Thereafter, a spacer film in the form of an ultrathin polymer film or metal film is stamped to create a molding cavity utilized for the electrodes 120, 140 to move or vibrate (the electrodes effectively function as capacitor plates). Each of the molding cavities can be as small as about 200 μm in diameter, and the distance between the cavities can be less than 1 mm. Next, the film is aligned with the substrate 160 and the top film and laminated together by heat and pressure or using an ultrathin polymer adhesive layer.

[0059] The entire process can be performed by stepwise vertical stamping or can be combined with a roll-to-roll stamping and lamination machine. The characteristics of the resulting device are controlled by the film thickness and width of the cavity 170. For example, in order to maintain the operating voltage at a practical level, it is preferable that the spacer film 130 be 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 in order to make the operating voltage of the poly CMUT 100 less than 230 volts. The spacer film 130 also adheres to the layer of the substrate 160 and the layer of the film 110. In FIG. 1, the spacer film 130 is indirectly adhered to the substrate 160 via the insulating layer 140, but as shown in FIG. 2 and described later, the spacer film 130 may be directly bonded to the substrate 160. When adhesive layers are used, it is preferable that they be very thin. In one example, heat and pressure can be used to laminate an ultrathin PET functioning as the spacer film 130 to a polyamide film functioning as the substrate 160 and the film 110.

[0060] To create a functional MEMS device, it is preferable for the device to have space to move. In the case of the poly CMUT 100, the membrane 110 is suspended above the cavity 170. In most MEMS devices, this cavity 170 determines the characteristics of the device, such as the resonance frequency and sensitivity. With respect to Figure 1, the formed cavity is stamped (punched) from the spacer film 130. This can be done entirely by hand using a vertical stamping machine, or, in the case of a large area, it can be done in a roll-to-roll setting. To form the formed cavity, the spacer film can be perforated by a die including protrusions, such as by being stamped by the stamping portion of a roll-to-roll laminating machine, and an array including a plurality of formed cavities for a plurality of MEMS devices can be created at once.

[0061] After creating the formed cavity, three films in the form of the membrane 110, the spacer film 130, and the substrate 160 are aligned and stacked with each other so that conductive layers in the form of the electrodes 120 and 150 are arranged as shown in Figure 1. In at least some embodiments, they are then heated and pressed through two rolls at a pressure of about 3 bar and a temperature of 243 °C. As a result, the films are laminated while the membrane 110 remains suspended above the cavity 170. In at least some embodiments where this process is performed in a roll-to-roll setting, the final device is cut from a continuous film.

[0062] The temperature and pressure during lamination are inversely proportional to each other (that is, as the pressure increases, the required temperature decreases). Generally speaking, lamination (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, and the temperature decreases as the pressure increases. The pressure needs to be kept low enough so that the spacer film 130 is not compressed to the extent that the cavity 170 closes.

[0063] FIG. 5A shows an example of a metal grid pattern 500 that can be formed, for example, on substrate 160 or on film 110.

[0064] A stamped spacer film 130 with a cavity diameter of 0.8 mm and a distance of 5 mm between cavities 170, and a stamping die used in a roll-to-roll machine, are shown in a reproduction (duplication) 600 by the photograph of FIG. 6. The stamping die of FIG. 6 is composed of a rotating cylinder die and can be used in the system described with respect to FIG. 7 below.

[0065] FIGS. 5B through 5D show photographs of an exemplary first sheet 502 and second sheet 504 of a MEMS device that are manufactured in a roll-to-roll setting and include a pair of metal grid patterns 500. FIG. 5B shows a front perspective view of the first sheet 502, FIG. 5C shows a top view of the first sheet 502, and FIG. 5D shows a top view of the second sheet 504. The first sheet 502 of the MEMS device can be cut from the second sheet 504.

[0066] In particular, as is apparent in FIGS. 5B and 5C showing a top view and a bottom view of the first sheet 502 of the device, respectively, the device to be manufactured includes a metallized film 110 for forming a top (upper) electrode 120 and a bond pad electrically coupled to the top electrode 120, and a flexible substrate 160 metallized for forming a bottom (lower) electrode 150 and a bond pad electrically coupled to the bottom electrode 150. The cavity 170 of the device is located at the intersection 506 of the top electrode 120 and the bottom electrode 150 (i.e., the place where the electrodes 120 and 150 overlap) and is not visible in FIGS. 5B and 5C.

[0067] Further expansion of the size of the array produced is possible by means of an assembly using overlapping tapes / patches. This is a modular assembly method for an array of poly-CMUT cells arranged in a regular pattern (1×2, 2×4, 4×4, etc.) on a flexible substrate 160. In this method, a flexible tape or patch functions as a mechanical substrate 160 for manufacturing an array of transducers on its upper surface, and its bottom side can be specially treated to be adhesive. To ensure electrical interconnectivity between the columns of cells manufactured on the upper surface, each column has associated bond pads (electrical interconnect surfaces) in the margin portions of both the patch / tape. A via mechanism similar to that used in the manufacture of flexible PCBs electrically connects the upper margin bond pads to the patterned margin bond pads on the bottom surface of the tape / patch. The top and bottom sets of margin bond pads are aligned.

[0068] When the tape is made to wrap around a cylindrical surface such as a pipe of a given circumference, the distance between successive columns of transducer cells (arranged in a direction across the margin of the tape (i.e., the successive columns extend axially along the cylindrical surface)) is preferably made such that the diameter of the cylindrical surface corresponds to an integer (number) of the columns arranged around its circumference. The next tape wrap provides an electrical interconnect by aligning the next set (column) of transducer columns with the previous column and overlaying the margin bond pads at the top of the previous tape with the margin bond pads at the bottom of the next tape wrap.

[0069] In at least some embodiments, to ensure better self-alignment, the tape structure has a relief alignment lock-in pattern, such as grooves and wedges, for example, to enhance and stabilize the alignment of the connections between transducers.

[0070] In other embodiments, the aforementioned alignment of the bond pads is also used in flexible patches, bands, foils, fabrics, and the shapes in which the poly-CMUT arrays are formed, of various shapes and sizes.

[0071] Figure 7 shows an exemplary system 700 that can be used to manufacture MEMS devices using a roll-to-roll laminator, according to an exemplary embodiment. The system includes various roller pairs, such as stamping auxiliary material roller pair 702a, stamping roller pair 702b, first film roller pair 702c, second film roller pair 702d, and laminate roller pair 702e. The laminate roller pair 702e forms part of the roll-to-roll laminator.

[0072] In Figure 7, a spacer film 130, which is a PET such as Mylar (registered trademark), is drawn into the stamping auxiliary material roller pair 702a together with the stamping auxiliary material 704. The stamping auxiliary material 704 can be a relatively thick PET layer. For example, after stamping, the stamped portion of the spacer film 130 adheres to it. The spacer film 130 is drawn into the first roller pair 702a and compressed together with the stamping auxiliary material 704. The compressed spacer film 130 and stamping auxiliary material 704 are drawn into the stamping roller pair 702b, and a die having protrusions such as the rotating cylinder die of Figure 6 is used to actually stamp the spacer film 130, creating cavities 170 as described above. In Figure 6, both the spacer film 130 and the stamping auxiliary material 704 are visible, and the stamping auxiliary material 704 is wider than the spacer film 130. The stamped spacer film 130 and stamping auxiliary material 704 are drawn into the first film roller pair 702c and compressed together with the metallized film 706 that functions as the substrate 160 and the bottom electrode 150. The metallized film 706 can be, for example, a layer of polyimide. When exiting the first film roller pair 702c, the stamping auxiliary material 704 is peeled from the spacer film 130 and the metallized film 706 using a hard edge 708 to facilitate the separation (peeling).

[0073] The stamped spacer film 130 and the metallized film 706 are drawn into the second film roller pair 702d, compressed together with another metallized film 710 that functions as the film 110 and the top electrode 120, and the spacer film 130 is sandwiched between the metallized films 706, 710. The metallized film 710 can be, for example, a relatively thin layer of polyimide (e.g., 3 μm to 25 μm (including 25 μm)). If the other metallized film 706 used for the substrate 160 is made of the same material, in at least some embodiments, it has at least about the same thickness as the metallized film 710 used for the film 110 and up to twice the thickness. This ensures that the substrate 160 has at least about the same mechanical strength as the film 110. In embodiments where the film 706 used for the substrate 160 is mechanically stronger than the film 710 used for the film 110, even if the film 706 used for the substrate 160 is thinner than the film 710 used for the film 110, it can result in the substrate 160 being at least as strong as the film 110.

[0074] The three films 706, 130, 710, upon exiting the second film roller pair 702d, are sent to the laminating roller pair 702e and laminated (laminated) together into the finished film 712 of the MEMS device as shown in FIGS. 5B to 5D.

[0075] FIG. 7 shows the first film roller pair 702c and the second film roller pair 702d. In at least some other embodiments, these rollers 702c, 702d can be replaced by a single roller that receives both the metallized films 706, 710 and compresses both 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 supplied via the second film roller pair 702d instead of the first film roller pair 702c as shown in FIG. 7.

[0076] [Application to Products] [Remote Control] Many Internet of Things (IoT) devices are battery-powered, but power consumption is a major issue because long life in the field is required. When the device's switch is off, battery consumption is reduced, but sensing cannot be provided when needed. For this reason, there is a need for an energy-efficient way to alert IoT devices to turn their switches on. This means that the device requires a wake-up receiver that can switch the IoT device on and off. In performing this task, ultrasonic waves have several advantages. It can use signals with very short wavelengths, so it is significantly smaller than similar alarm receivers that use wireless signals, and can operate at extremely low power over a wider range (i.e., can receive signals from a wider angular distance). Such an ultrasonic-based receiver can listen for low-amplitude ultrasonic signals that can be uniquely mapped to the device and indicate when the device should be turned on. In at least some embodiments, only nanowatt signal power is required, which only slightly consumes the precious battery energy store. Furthermore, the range of such ultrasonic signals is naturally limited because they cannot propagate through acoustically opaque surfaces such as walls and can be limited, for example, to within a room. This has valuable privacy advantages. This technology can be extended beyond simple wake-up signals and can also include the transmission and reception of other information such as encoded passwords and other information. A further advantage is that ultrasonic frequencies do not interfere with the tightly controlled electromagnetic frequency ranges defined by government regulatory agencies for IoT communications.

[0077] [Polymer CMUT Sleeve] In at least some embodiments, the polymer CMUT array can be fabricated on a stretchable substrate and can behave like an elastic fabric. This is useful when a tight fit is required between the polymer CMUT and the target material, such as when the polymer CMUT forms part of a sleeve that covers a pipe.

[0078] [Structural Integrity Test] In yet other embodiments, a transmissive poly-CMUT array is used for non-destructive testing (NDT) of materials. Typically, X-ray imaging is used for material inspection, but the dose used includes a large amount of ionizing radiation, which in some cases can cause internal damage to the test specimen. The X-ray transmissive poly-CMUT array can be used, additionally or alternatively, to acquire images such as hybrid images obtained from a combination of ultrasonic imaging and X-ray imaging, and can potentially reduce the amount of X-ray energy required.

[0079] [Pipeline Monitoring] In some embodiments, when laying a pipe on-site, a CMUT array can be installed on a part of the pipe. Alternatively, during pipe manufacturing, a CMUT array can be installed on a part of the pipe, enabling better integration with the pipe and protecting against damage to the poly-CMUT array. At least some embodiments are useful for real-time monitoring of underground pipelines in the form of NDT (non-destructive testing).

[0080] [Hydraulic Testing] In some embodiments, the poly-CMUT can be fabricated on an elastic substrate and can deform with the deformation of a hydraulic hose during normal operation. The electrical interconnectivity and flexibility of the substrate can be customized according to the diameter and length of the pipe to be wrapped.

[0081] [Aircraft Wing NDT] In some embodiments, a wrap-around poly-CMUT array that can be installed around the periphery of a wheel is provided. This allows the array to be quickly wrapped around an aircraft wing. The poly-CMUT in contact with the wing can be used to perform ultrasonic imaging. The poly-CMUT can, for example, form part of a flexible fabric.

[0082] For example, when a large-scale poly-CMUT transducer array is needed to inspect an airplane wing or other aircraft, a large film containing the poly-CMUT array can be temporarily attached to the wing being inspected. A permanent monitoring solution can include, for example, incorporating the transducer inside the aircraft body to protect the transducer from physical wear and exposure to the environment.

[0083] [Wearable poly-CMUT array] In another embodiment, a poly-CMUT array fabricated according to the embodiments described herein is used on human or animal tissue. Such flexible or rigid arrays formed for medical or agricultural applications are useful for providing information regarding injuries at the scene when an accident occurs. For example, emergency responders can wrap the injured person in a fabric and image fractures and soft tissue injuries of the injured person before starting transport to a medical facility. This practice can include confirmation of the presence or absence of fractures in the legs, arms, ribs, and spine, as well as confirmation of injuries due to impact on the skull.

[0084] [Bandage for injuries] In at least some embodiments, the poly-CMUT array is manufactured within a bandage used to cover a wound during healing. For this purpose, a flexible substrate is used so that it can better conform to the tissue. This poly-CMUT array bandage can monitor tissue repair and deliver energy to the tissue being repaired to increase the rate of the healing process. In another embodiment, the poly-CMUT array bandage can be used to cavitate fluids within the tissue to assist in debriding.

[0085] [Diagnostic device] In other embodiments, a hybrid integration of a permeable poly-CMUT array combines X-ray, ultrasound, photoacoustics, elastography, and / or combinations thereof, in a single system.

[0086] [Chemical and biological sensing] Wearable poly-CMUT patches can be used for chemical and biological sensing by functionalizing the membranes of the poly-CMUT elements. The functionalized membranes can be sensitive to the presence of chemical or biological substances that change the mass loading of the membranes. For example, the resonant frequency of a poly-CMUT element, like that of a drum, depends on the material properties of the membrane (such as mass, stiffness, viscosity, etc.). When a specific chemical or biological substance intended to be "sensed" is present, the functionalized membrane can absorb a portion of the substance, and its physical properties can be changed accordingly. The change in material properties can be detected, for example, by a change in the frequency, bandwidth, or amplitude of the resonant frequency. In particular, it is known that the change in resonant frequency is proportional to the relative change in the mass of the membrane.

[0087] [Heart monitoring] The patch according to at least some embodiments functions as an emitter that focuses ultrasonic pulses onto the skin towards the heart and as a microphone that records the reflected waves. The patch functions as an air-pulse Doppler ultrasonic system operating in the range of 20 - 60 kHz. The size of an exemplary patch is, for example, in the range of 5×5 cm to 10×10 cm.

[0088] [Blood pressure monitoring] In certain embodiments, a poly-CMUT wearable array non-invasively measures the blood pressure of a patient population using ultrasonic Doppler flow measurement. The blood pressure can be measured using poly-CMUT as described below and can be compared with an invasive arterial line or an oscillometric Terumo Elemano (registered trademark) blood pressure monitor. To measure blood pressure using poly-CMUT, during the cuff inflation, the blood flow velocity in the radial artery is recorded by a fabric patch containing the poly-CMUT array. A sigmoid curve is fitted to the previously processed velocity signal to determine the systolic blood pressure and the mean arterial pressure. Applications include monitoring preeclampsia during pregnancy and ambulatory blood pressure monitoring in cardiac patients.

[0089] [Transcranial focused ultrasound] Transcranial focused ultrasound (FUS) can be combined with intravenously circulating microbubbles to temporarily and selectively enhance blood-brain barrier permeability, enabling 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 problem addressed by at least some embodiments is to develop systems and methods for real-time monitoring and control of treatment to ensure that a safe and effective acoustic exposure level is maintained throughout the treatment, in order for FUS-mediated blood-brain barrier permeabilization to be widely clinically adopted.

[0090] Transceivers (which may also be referred to as transceivers) of electronic devices that can be incorporated into the above applications are commercially available from, for example, Verasonics®, US4US®, Interson®, and Texas Instruments®.

[0091] At least some embodiments will be more readily understood by reference to the following examples given to illustrate the various embodiments.

[0092] [Example 1] A practical poly-CMUT was fabricated in a completely mechanical process. First, the polyamide was metallized to create the necessary electrodes. A thin (900 nm thick) Mylar® film was stamped vertically using a 0.5 mm leather stamp. This film functions as the spacer film 130 in FIG. 1. A leather stamping die was used to create the prototype molding cavity. More generally, the Mylar® film can be any common biaxially oriented polyethylene terephthalate film having a thickness in the range of 600 nm to 1.5 μm.

[0093] Figure 3 shows a stamped 900 nm thick Mylar® film 130 to demonstrate the feasibility of mechanically stamping such thin films. After stamping and being ready for use, this mask is used as a template for stamping and metal evaporation.

[0094] Next, the stamped film was aligned with the metallized polyamide film and laminated together at a temperature of 235 °C while being combined with pressure by a roll laminator. The resulting layup (layer structure) and the 4 - cavity device 300 are shown in Figure 2B.

[0095] The exact layup of the fabricated prototype 200 is that the spacer film 130 is PET in the form of Mylar®, as shown in Figure 2A. In this embodiment, the prototype 200 lacks the insulating layer 140 of Figure 1. However, it includes a cavity 170 formed by stamping the spacer film 130, a Kapton® film 110 that is metallized and the metallized portion forms the top electrode 120, and a Kapton® substrate 160 that is metallized and the metallized portion forms the bottom electrode 150.

[0096] Next, those layers can be connected to a bias tee of 120 VDC and 60 VAC and scanned with an LDV to find the resonance frequency, thereby confirming the success of the manufacturing.

[0097] On the right side of Figure 4, a single cavity 170 manufactured according to an embodiment is shown with a microscope at a magnification of 10 times. The larger contours of both electrodes and the cavity 170 are visible, and the results of the LDV scan 400 on the left reveal a resonance frequency of approximately 230 kHz. The magnitudes of the displacement of the film at 120 VDC and 60 VAC at various frequencies indicate a resonance frequency of ~230 kHz, proving that a practical prototype has been manufactured. The measurement was performed with an LDV.

[0098] [Embodiment 2] This embodiment is directed to a novel MEMS manufacturing method using a poly-CMUT as an exemplary MEMS device. To use this completely mechanical manufacturing method, three main components are used. The first two components are two films of the same thickness or different thicknesses, which can be of one (the same) homogeneous material or a laminate of multiple materials. These films are used as film 110 and substrate 160. To construct the poly-CMUT, first, these films are metallized for electrodes 120, 150. In the case of the aforementioned prototype where the films are each composed of 25-μm and 100-μm thick Kapton®, those films are metallized with 100-nm (thick) gold. The metallization can be conformal or patterned, depending on the device architecture. The third component is a very thin spacer film 130 that functions as a spacer film. In this embodiment of the poly-CMUT, this spacer film 130 is a thin layer (900 nm) of Mylar®. Next, this spacer film 130 is stamped to create the molding cavities required to allow movement of the poly-CMUT film. The resulting films are laminated together. In the case of the said poly-CMUT, a laminator with a pressure of 1 bar and the roll heated to 230 °C achieved a permanent lamination. The parameters of this process vary depending on the materials used and the desired characteristics of the resulting device. In one embodiment, the metallized substrate and film are insulated by adding a very thin layer of acrylate or SiO2 or a similar insulator. This can be done for either one or both of the two metallized films used for the electrodes.

[0099] In the present disclosure, the term "comprising" is used in a non-limiting sense to mean including the items preceding that term, and items not specifically recited are not excluded. For embodiments that include or may include a particular feature or variable or parameter, it is understood that alternative embodiments may consist of or consist essentially of such feature or variable or parameter(s) only. Reference to an element with the indefinite article "a" does not exclude the possibility that more than one element is present, unless the context clearly requires that there be only one such element.

[0100] In the present disclosure, the recitation of a numerical range by its (two) endpoints includes all numbers within that range, including all integers and all fractions (intermediate values) (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). In the present disclosure, unless the context clearly dictates otherwise, the singular forms "a(n)" and "the" (when accompanied by an object of reference) include plural objects of reference. Thus, for example, a reference to a composition containing "a compound" includes a mixture of two or more compounds.

[0101] In the present disclosure, the term "or" is generally used in the sense of including "and / or" unless the context clearly dictates otherwise.

[0102] Any aspect or any part of any embodiment described herein can be implemented or combined with any other aspect or any part of any other embodiment described herein, provided that the parts used are not mutually exclusive.

[0103] Although exemplary embodiments have been described above and are illustrated in the accompanying drawings, it will be apparent to those skilled in the art that changes can be made without departing from the present disclosure. Such changes are considered to be possible variations included within the scope of the present disclosure.

Claims

1. A method for manufacturing an array of microelectromechanical system devices, (a) A step of obtaining a sheet of material for forming a cavity for the device, (b) A step of projecting a physical projector or an energy projector into the material to form the cavity in the material, (c) A step of bringing the upper surface and lower surface of the material with the cavity into contact with the upper metallized film and the lower metallized film, respectively. (d) A step of joining the upper surface and the lower surface of the material with the upper metallized film and the lower metallized film, respectively. A method characterized by comprising:

2. The physical projectile is projected into the material to form the cavity. The method according to feature 1.

3. The aforementioned physical projectile includes a punching stamp. The method according to feature 2.

4. The aforementioned physical projectile includes a stamp die. The method according to feature 2.

5. The aforementioned physical projectile includes a rotating cylinder die. The method according to feature 2.

6. The energy projector is projected into the material to form the cavity. The method according to feature 1.

7. The energy projector includes a laser. The method according to feature 6.

8. The energy projector includes an electrical discharge. The method according to feature 6.

9. The aforementioned physical projectile includes a vapor jet. The method according to feature 6.

10. The aforementioned material is a polymer. The method according to feature 1.

11. The aforementioned material includes polyimide. The method according to the present invention, characterized by the present invention.

12. The aforementioned material includes polyethylene terephthalate. The method according to feature 1.

13. The material is biaxially oriented polyethylene terephthalate with a thickness of 600 nm to 1.5 μm. The method according to 12, characterized by the features described above.

14. The aforementioned material is a metal. The method according to feature 1.

15. The MEMS device is a capacitive micromachine ultrasonic transducer. The method according to feature 1.

16. The MEMS device is a polymer capacitive micromachine ultrasonic transducer. The method according to the present invention, characterized by the present invention.

17. The upper and lower surfaces of the material with the cavity are in contact with the upper and lower metallized films such that the metallized portions of the upper and lower metallized films are located within the cavity, respectively. The method according to any one of 1 to 16, characterized by the features described herein.

18. The joining step includes a lamination step. The method according to any one of 1 to 16, characterized by the features described herein.

19. The lamination process is carried out using a roll laminator at a temperature between 210°C and 260°C. The method according to the present invention, characterized by the present invention.

20. The aforementioned stacking process is carried out under a pressure between 1 bar and 5 bar. The method according to feature 19.

21. The aforementioned joining step includes a bonding step. The method according to any one of 1 to 16, characterized by the features described herein.

22. The aforementioned metallized film constitutes the flexible substrate of the device. The method according to any one of 1 to 16, characterized by the features described herein.

23. Each of the aforementioned metallized films has a grid pattern, The cavity is located where the grid patterns overlap. The method according to any one of 1 to 16, characterized by the features described herein.

24. Apparatus for manufacturing an array of microelectromechanical system devices, (a) A pair of stamping rollers, (b) at least one pair of film rollers, (c) A pair of laminating rollers, Equipped with, The pair of stamping rollers each have a cylinder die and are configured to receive a spacer film and use the cylinder die to stamp a cavity within the spacer film. The at least one pair of film rollers are configured to receive the stamped spacer film and a plurality of metallized films, and to compress the stamped spacer film between the metallized films. The pair of laminating rollers are configured to receive and laminate the compressed spacer and the metallized film. A device characterized by the following features.

25. The aforementioned at least one pair of film rollers includes a first pair of film rollers and a second pair of film rollers. (a) The first pair of film rollers is configured to receive and compress the first metallized film among the stamped spacer film and the metallized film, (b) The second film roller pair is configured to receive the spacer film and the first metallized film and the second metallized film among the metallized films after they have passed through the first film roller pair, and to compress the stamped spacer film between the metallized films. The first metallized film is thicker than the second metallized film. The apparatus according to feature 24.

26. (a) A pair of stamping aid rollers configured to receive and compress the spacer film and stamping aid. Furthermore, The compressed spacer film and the stamping aid are supplied to the stamping roller pair and the first film roller pair. (b) A hard edge positioned to peel the stamping aid from the spacer film after it has left the first pair of film rollers. The apparatus according to claim 25, further comprising the above.

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