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WO2014103334A1 - Cellule de transducteur ultrasonore, sonde ultrasonore et procédé de commande pour cellule de transducteur ultrasonore - Google Patents

Cellule de transducteur ultrasonore, sonde ultrasonore et procédé de commande pour cellule de transducteur ultrasonore Download PDF

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Publication number
WO2014103334A1
WO2014103334A1 PCT/JP2013/007685 JP2013007685W WO2014103334A1 WO 2014103334 A1 WO2014103334 A1 WO 2014103334A1 JP 2013007685 W JP2013007685 W JP 2013007685W WO 2014103334 A1 WO2014103334 A1 WO 2014103334A1
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WIPO (PCT)
Prior art keywords
membrane
ultrasonic
ultrasonic transducer
transducer cell
electrode
Prior art date
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Ceased
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PCT/JP2013/007685
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English (en)
Japanese (ja)
Inventor
貴之 永田
高志 小椋
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Konica Minolta Inc
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Konica Minolta Inc
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Priority to JP2014554160A priority Critical patent/JP6390428B2/ja
Publication of WO2014103334A1 publication Critical patent/WO2014103334A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0292—Electrostatic transducers, e.g. electret-type

Definitions

  • the present invention relates to an ultrasonic probe used for ultrasonic inspection.
  • the ultrasonic probe is attached to the main body of the ultrasonic diagnostic equipment that has the function to send out ultrasonic waves to the inside of the subject, receive ultrasonic signals reflected inside the subject, and acquire information inside the subject.
  • the ultrasonic probe is attached to the main body of the ultrasonic diagnostic equipment that has the function to send out ultrasonic waves to the inside of the subject, receive ultrasonic signals reflected inside the subject, and acquire information inside the subject.
  • Device is attached to the main body of the ultrasonic diagnostic equipment that has the function to send out ultrasonic waves to the inside of the subject, receive ultrasonic signals reflected inside the subject, and acquire information inside the subject.
  • Ultrasonic transducers used for ultrasonic probes are mainly composed of piezoelectric ceramics typified by PZT (lead zirconate titanate) arranged in a row, but in recent years, 3D / 4D ultrasonic imaging has become popular.
  • Two-dimensional transducers have been studied for the purpose of realizing an inexpensive and small probe that can be used, and cMUT (Capacitive Micromachined Ultrasonic Transducer) elements have been widely studied as a method suitable for array structures (for example, Patent Document 1).
  • This cMUT element is composed of a capacitance type MEMS that drives a vibrating membrane (hereinafter referred to as a membrane) with electrostatic force, and has a structure as shown in FIG. 28, for example.
  • FIG. 28A is a perspective view of the cMUT element
  • FIG. 28B is an exploded perspective view of the cMUT element
  • FIG. 28C is a side sectional view of the cMUT element.
  • the cMUT element 50 includes a substrate 51, a lower layer electrode 52 disposed inside the substrate 51, and an insulating film disposed to face the lower layer electrode 52 with a cavity (cavity) 53 interposed therebetween. 55, a membrane 56, and a membrane support 54 are provided.
  • the cavity 53 includes a space surrounded by the membrane 56, the membrane support portion 54, and the lower layer electrode 52, and is configured to be substantially vacuum.
  • the membrane 56 also serves as an electrode, and the lower layer electrode 52 and the membrane 56 are connected to wirings 60a and 60b, respectively.
  • the membrane 56 is vibrated by the received ultrasonic wave (sound pressure), and the received ultrasonic wave is changed based on the capacitance change between the membrane 56 and the lower layer electrode 52 that occurs at this time.
  • the cMUT element 50 can transmit ultrasonic waves by vibrating the membrane 56 by applying DC and AC voltages between the membrane 56 and the lower layer electrode 52.
  • Such a cMUT element has a merit that wiring is easy and suitable for a two-dimensional array of multiple elements, but has a problem that a transmission output is low.
  • 3D / 4D ultrasonic imaging it is necessary to further increase the transmission output in the cMUT element in order to acquire a high-quality ultrasonic image in a wide range from a shallow part to a deep part from the subject surface.
  • the present invention aims to improve the output sensitivity of a cMUT and improve the transmission output while maintaining a low supply voltage equivalent to that of an ultrasonic probe using a conventional piezoelectric element.
  • an ultrasonic transducer cell includes a substrate, a first electrode disposed on or in the substrate, and a direction perpendicular to the upper surface of the first electrode.
  • a first membrane disposed opposite to the first electrode in a state of being separated from the first membrane; a second membrane disposed opposite to the first membrane in a state of being spaced apart from the upper surface of the first membrane;
  • a first membrane supporting portion disposed in a gap between the substrate and the first membrane and surrounding a space in the gap; and a space in the gap between the first membrane and the second membrane.
  • a second membrane supporting portion surrounding the first membrane, a first wiring portion electrically connected to the first membrane, and a second wiring portion electrically connected to the second membrane (a)
  • the first membrane is the first The thickness in the direction perpendicular to the upper surface of the first membrane is larger than the membrane, or (b) the second gap layer surrounded by the first membrane support part is surrounded by the second membrane support part.
  • the space area in the direction parallel to the upper surface of the first membrane is smaller than the space layer, or (c) the second membrane is perpendicular to the upper surface of the first membrane than the first membrane.
  • the second gap layer surrounded by the second membrane support part has a surface above the first membrane than the first gap layer surrounded by the first membrane support part. It has at least one feature that the space area in the parallel direction is small.
  • the first membrane includes a lower membrane part facing the first gap layer surrounded by the first membrane support part, and the second membrane support part positioned above the lower membrane part.
  • An upper membrane portion facing the second void layer and a connection portion connecting the lower layer membrane portion and the upper membrane portion are laminated, and the upper membrane portion and the lower membrane portion Are electrically connected by the connecting portion, and a cross-sectional area of the connecting portion in a direction parallel to the top surface of the first membrane is parallel to a top surface of the first membrane of the lower membrane portion and the upper membrane portion. It is characterized by being smaller than the cross-sectional area.
  • the above-described ultrasonic probe according to one aspect of the present invention adopts the above configuration in a structure having an ultrasonic transducer cell in which cMUTs are stacked, thereby reducing the deflection of the upper surface of the first membrane and causing a larger displacement than the second membrane. Can be generated. Therefore, a larger ultrasonic transmission output can be obtained as compared with the case of a single layer, and the transmission output characteristics of the ultrasonic probe can be improved.
  • FIG. 1 is a schematic diagram illustrating an overall configuration of an ultrasonic probe 102 according to Embodiment 1.
  • FIG. 3 is a top view showing the arrangement of the ultrasonic transducer array 112 of the ultrasonic probe 102 according to Embodiment 1.
  • FIG. (A) A top view showing the basic structure of the ultrasonic transducer 11 according to the first embodiment, and (b) is a cross-sectional view taken along the line AA in FIG. 2 is a functional block diagram of an ultrasonic diagnostic apparatus 100 using the ultrasonic probe 102 according to Embodiment 1.
  • FIG. 2A is a perspective view of an ultrasonic transducer cell 12 according to Embodiment 1
  • FIG. 2B is an exploded perspective view of the ultrasonic transducer cell 12.
  • FIG. 3 is an explanatory diagram showing the operation of the ultrasonic transducer cell 12 according to the first embodiment, where (a) is a cross-sectional view (b) in a state in which a bias voltage is not applied to the ultrasonic transducer cell 12; It is sectional drawing of the state which applied.
  • 5 is a schematic view showing a method for manufacturing the ultrasonic transducer cell 12 according to Embodiment 1.
  • FIG. 5 is a schematic view showing a method for manufacturing the ultrasonic transducer cell 12 according to Embodiment 1.
  • FIG. FIG. 4 is a diagram illustrating voltages applied to wiring portions 30a, 30b, and 30c and timings in the ultrasonic transducer cell 12.
  • FIG. 6 is a diagram comparing the ultrasonic transmission characteristics of the ultrasonic transducer 11 according to the first embodiment and the ultrasonic transmission characteristics of conventional and comparative capacitive ultrasonic transducers. It is sectional drawing of the ultrasonic transducer
  • FIG. 6 is a diagram comparing the ultrasonic transmission characteristics of the ultrasonic transducer 11 according to the first modification of the first embodiment and the ultrasonic transmission characteristics of a conventional capacitive ultrasonic transducer. It is the chart which showed the conditions at the time of investigating the ultrasonic transmission characteristic shown in FIG. 6 is a cross-sectional view of an ultrasonic transducer cell 12 according to a second modification of the first embodiment.
  • FIG. 6 is a cross-sectional view of an ultrasonic transducer cell 12 according to a third modification of the first embodiment.
  • FIG. 4A is a top view showing a basic structure of an ultrasonic transducer used in an ultrasonic probe 102 according to Embodiment 2, and FIG.
  • FIG. 4B is a cross-sectional view taken along the line AA in FIG. (A) A sectional view in a state where a bias voltage is not applied to the ultrasonic transducer cell 12 according to the second embodiment, and (b) is a sectional view in a state where a bias voltage is applied.
  • 6 is a schematic view showing a method for manufacturing the ultrasonic transducer cell 12 according to Embodiment 2.
  • FIG. 6 is a schematic view showing a method for manufacturing the ultrasonic transducer cell 12 according to Embodiment 2.
  • FIG. 6 is a cross-sectional view of an ultrasonic transducer cell 12 according to a first modification of the second embodiment.
  • FIG. FIG. 10 is a diagram showing ultrasonic transmission characteristics of an ultrasonic transducer 11 according to Modification 1 of Embodiment 2.
  • 6 is a cross-sectional view of an ultrasonic transducer cell 12 according to a second modification of the second embodiment.
  • FIG. FIG. 10 is a diagram comparing the ultrasonic transmission characteristics of the ultrasonic transducer 11 according to the second embodiment and the ultrasonic transmission characteristics of the ultrasonic transducer according to the second modification of the first embodiment.
  • 6 is a cross-sectional view of an ultrasonic transducer cell 12 according to a third modification of the second embodiment.
  • A A perspective view of a conventional capacitive ultrasonic transducer cell, (b) a top view of a conventional capacitive ultrasonic transducer cell, and (c) a conventional capacitive ultrasonic transducer cell. It is sectional drawing. It is the figure which showed the shape of the conventional convex probe.
  • the inventors conducted various studies in order to further improve the ultrasonic transmission / reception sensitivity of the ultrasonic transducer cell using the cMUT element.
  • the conventional cMUT element has the advantage that it is easy to wire and is suitable for a two-dimensional array of multiple elements, while it has a problem that the transmission output is low. Proposals have been made to date.
  • a new operation mode called a collapse mode has been proposed.
  • the collapse mode when a DC voltage is applied to the lower electrode, a specific voltage higher than that in the normal mode is applied to attract the membrane with the DC electrostatic force of the lower electrode, and the membrane is in contact with the lower electrode. This is the operating mode to be activated.
  • this collapse mode it is said that the sensitivity and drive capability are higher than in the normal mode.
  • Patent Document 1 an application structure as shown in Patent Document 1 has been proposed.
  • Patent Document 1 is devised to reduce the necessary DC voltage by fusing the membrane and the substrate in contact with each other, but it can cope with the reliability problem of the collapse mode. Not. That is, in the collapse mode, the membrane and the substrate repeatedly collide around the region where the membrane and the substrate are always in contact with each other, and there is still a problem that the thin insulating film is destroyed.
  • both surfaces sandwiching the cavity function as a membrane, and are configured to bend in the opposite direction when the bias voltage is applied (bend in the direction in which the cavity is contracted).
  • the transmission output characteristics are not improved in a configuration in which both surfaces sandwiching the cavity are bent in opposite directions as a membrane when a bias voltage is applied.
  • the following embodiment solves the problems of the conventional cMUT based on the above findings based on the inventors' investigation, and maintains the same supply voltage as that of an ultrasonic probe using a piezoelectric element that has been conventionally used. However, it is intended to increase transmission / reception sensitivity by structural improvement of cMUT.
  • the ultrasonic transducer cell includes a substrate, a first electrode disposed on or in the substrate, and the first electrode in a state of being vertically separated from the upper surface of the first electrode.
  • a first membrane disposed opposite to the first membrane; a second membrane disposed opposite to the first membrane in a state of being vertically separated from the upper surface of the first membrane; and the substrate and the first membrane A first membrane support portion disposed in the gap and surrounding the space in the gap; and a second membrane support portion disposed in the gap between the first membrane and the second membrane and surrounding the space in the gap.
  • the first membrane support portion when having the feature (b), has a larger cross-sectional area in a direction parallel to the upper surface of the first membrane than the second membrane support portion. May be.
  • the second membrane support portion when having the feature (d), has a larger cross-sectional area in a direction parallel to the upper surface of the first membrane than the first membrane support portion. Also good.
  • the first membrane support portion may have a configuration in which maximum widths in a direction parallel to the second membrane support portion and the upper surface of the first membrane are substantially equal.
  • the substrate, the first electrode disposed on or in the substrate, and the first electrode are arranged opposite to the first electrode in a state of being vertically separated from the upper surface of the first electrode.
  • the upper membrane part and the lower membrane part are electrically connected by the connection part, and the cross-sectional area of the connection part in a direction parallel to the upper surface of the first membrane is
  • the lower layer membrane part and the upper layer membrane part may have a configuration smaller than a cross-sectional area in a direction parallel to the upper surface of the first membrane.
  • the upper membrane portion may have a greater thickness in the direction perpendicular to the upper surface of the first membrane than the second membrane.
  • the lower layer membrane portion may have a greater thickness in a direction perpendicular to the upper surface of the first membrane than the second membrane.
  • the lower membrane portion may have a smaller width in a direction parallel to the upper surface of the first membrane than the second membrane.
  • the lower layer membrane portion, the upper layer membrane portion, and the connection portion may have a configuration in which center positions in a direction parallel to the upper surface of the first membrane coincide with each other.
  • the submembrane electrically connected to the second wiring portion, and the submembrane supporting portion that supports the submembrane and electrically connects the submembrane and the wiring inside the substrate.
  • the structure which has these may be sufficient.
  • first membrane and the second membrane may be conductive.
  • a configuration may be provided that further includes a first insulating membrane made of an insulating material laminated above the first membrane.
  • the configuration may further include a second insulating membrane made of an insulating material stacked above the second membrane.
  • the ultrasonic transducer cell includes a plurality of the ultrasonic transducer cells, and at least one of the second membrane or the second wiring portion of the ultrasonic transducer cells adjacent to each other is connected to the plurality of the ultrasonic transducer cells. It may be an ultrasonic transducer in which the second wiring part of the ultrasonic transducer cell is electrically connected.
  • the ultrasonic transducer includes a plurality of ultrasonic transducers, and the plurality of ultrasonic transducers are arranged two-dimensionally in a plane parallel to the upper surface of the second membrane to constitute a transducer array.
  • An ultrasonic probe may be used.
  • a method for controlling the ultrasonic transducer cell wherein a bias voltage is applied to the first electrode and the second wiring part, and a pulse voltage is applied to the first wiring part.
  • a method for controlling an ultrasonic transducer cell that transmits ultrasonic waves may be used.
  • a method for controlling the ultrasonic transducer cell wherein a bias voltage is applied to the first wiring part, and a pulse voltage is applied to the first electrode and the second wiring part.
  • a method for controlling an ultrasonic transducer cell that transmits ultrasonic waves may be used.
  • FIG. 1 is a schematic diagram showing the overall configuration of the ultrasonic probe 102 according to the first embodiment.
  • an ultrasonic probe 102 includes an ultrasonic transducer array 112 (hereinafter referred to as “vibrator array 112”) that transmits and receives ultrasonic waves inside a probe case 111, and an transducer array 112. And a printed circuit board 114 on which a plurality of signal lines for inputting / outputting electric signals independently of the ultrasonic transducer (element) are printed.
  • the ultrasonic probe 102 is connected to the ultrasonic diagnostic apparatus main body 109 via the probe cable 115.
  • FIG. 2 is a top view showing the arrangement of the transducer array 112 of the ultrasonic probe 102 according to the first embodiment.
  • FIG. 3A is a top view showing the basic structure of the ultrasonic transducer 11 according to the first embodiment
  • FIG. 3B is a cross-sectional view taken along the line AA in FIG.
  • the transducer array 112 includes an ultrasonic transducer 11 (hereinafter referred to as “vibrator 11”) composed of a plurality of ultrasonic transducer cells 12 (hereinafter referred to as “vibrator cells 12”). Are two-dimensionally arranged.
  • the transducer 11 is a capacitive ultrasonic transducer (cMUT) manufactured using MEMS (Micro Electro Mechanical System) technology, and is configured to transmit and receive ultrasonic waves three-dimensionally within a subject. ing.
  • Each transducer cell 12 mutually converts electrical energy and mechanical energy due to vibration.
  • the vibrator 11 includes four vibrator cells 12.
  • the diameter of each transducer cell 12 is, for example, 40 to 80 ⁇ m.
  • the number and size of the transducer cells 12 constituting the transducer 11 can be arbitrarily set and are not limited to the above.
  • the transducer cells 12 included in the same transducer 11 are electrically connected and configured to transmit ultrasonic waves in the same phase by applying a pulsed voltage.
  • a driving voltage with a predetermined time difference for each transducer 11, it is possible to focus and deflect the generated ultrasonic waves.
  • the ultrasonic probe 102 is configured to perform sector scanning by transmitting ultrasonic waves in a three-dimensional direction.
  • FIG. 4 is a functional block diagram of the ultrasonic diagnostic apparatus 100 using the ultrasonic probe 102 according to the first embodiment.
  • the ultrasonic diagnostic apparatus 100 transmits an ultrasonic wave to the subject 101, generates an ultrasonic probe 102 that receives an ultrasonic signal reflected inside the subject 101, and a drive signal for transmitting the ultrasonic wave. And transmitting and receiving the signal detected by the ultrasonic element of the ultrasonic probe 102 and amplifying and digitally converting the signal detected by the ultrasonic element of the ultrasonic probe 102 and the signal output from the transmitter and receiver 103.
  • a signal processing unit 104 that performs digital beam forming, an image processing unit 105 that performs rendering processing of a three-dimensional image based on the three-dimensional data generated by the signal processing unit 104, and processed image data
  • the image display unit 106 that displays an image based on the control, and the control that controls the transmission / reception unit 103 to generate a drive signal at a predetermined timing And a 107.
  • the transmission / reception unit 103, the signal processing unit 104, the image processing unit 105, the image display unit 106, and the control unit 107 are stored in the ultrasonic diagnostic apparatus main body 109, and a plurality of signals are exchanged with the ultrasonic probe 102. They are connected by a probe cable that covers the cables of the wires together. Note that some functions of the transmission / reception unit 103 such as detection signal amplification and digital conversion may be realized in the ultrasonic probe 102.
  • FIG. 5A is a perspective view of the transducer cell 12 according to Embodiment 1
  • FIG. 5B is an exploded perspective view of the transducer cell 12.
  • 6A and 6B are explanatory diagrams showing the operation of the transducer cell 12 according to the first embodiment.
  • FIG. 6A is a cross-sectional view of a state in which a bias voltage is not applied to the transducer cell 12
  • FIG. 3 is a cross-sectional view of a state in which a bias voltage is applied to a transducer cell 12.
  • FIG. 6A is a cross-sectional view of a state in which a bias voltage is not applied to the transducer cell 12
  • FIG. 3 is a cross-sectional view of a state in which a bias voltage is applied to a transducer cell 12.
  • the vibrator cell 12 includes a substrate 21 made of an electrically insulating material such as a silicon wafer, glass, quartz, and the like, and the inside of the substrate 21.
  • a conductive lower layer electrode 22, a first membrane 25 disposed to face the lower electrode 22 across the first cavity 23 (first gap layer), and a second cavity 27 (second A second membrane 29, a first membrane support portion 31a, and a second membrane support portion 31b are provided so as to be opposed to the first membrane 25 with a gap layer therebetween.
  • Insulating films 24 and 26 are provided below and above the first membrane 25, respectively, and an insulating film 28 is provided below the second membrane 29.
  • the thickness of the first membrane 25 in the direction perpendicular to the substrate 12 is configured to be larger than the thickness of the second membrane 29.
  • the thickness of the first membrane 25 may be 2 to 4 ⁇ m
  • the thickness of the second membrane 29 may be 1 to 2 ⁇ m.
  • the lower layer electrode 22 can be made of, for example, a conductive metal such as aluminum, silver, copper, or chromium.
  • the film thickness can be about 4 ⁇ m.
  • the first membrane and the second membrane are made of a conductive material.
  • a metal such as aluminum, silver, copper, or chromium, a conductive resin, or the like can be used.
  • the first membrane 25 and the second membrane 29 also serve as electrodes, and the lower layer electrode 22, the first membrane 25, and the second membrane 29 are connected to the wiring portions 30a, 30b, and 30c, respectively.
  • an insulating thin film material can be used for the first membrane support part 31a, the second membrane support part 31b, and the insulating films 24, 26, and 28, an insulating thin film material can be used.
  • SiC, SiO 2 , SiN, or a mixture thereof is used. May be.
  • the thickness of the first membrane support portion 31a and the second membrane support portion 31b in the plane direction parallel to the upper surface of the substrate 21 in FIG. 6A can be configured to be 2 to 4 ⁇ m, for example.
  • the thickness of the one membrane support portion 31a in the planar direction in FIG. 6A is larger than the thickness of the second membrane support portion 31b.
  • the first membrane support 31a can be 3 to 5 ⁇ m
  • the second membrane support 31b can be 2 to 3 ⁇ m.
  • the first cavity 23 is a space surrounded by the first membrane 25, the membrane support portion 31 a, and the substrate 21, and the second cavity 27 is surrounded by the first membrane 25, the membrane support portion 31 b, and the second membrane 29. Space. Both the first cavity 23 and the second cavity 27 are configured to be substantially vacuum.
  • the first cavity 23 is smaller in width in the direction parallel to the upper surface of the substrate 21 in FIG. 6A than the second cavity 27, that is, the cross-sectional area perpendicular to the stacking direction of the membrane is It is configured to be smaller than the second cavity 27.
  • the width of the first cavity 23 and the second cavity 27 in the direction parallel to the upper surface of the substrate 21 in FIG. 6A can be set to 40 to 80 ⁇ m, for example.
  • the height of the first cavity 23 and the second cavity 27 can be set to 200 to 300 nm, for example.
  • the insulating films 24, 26, and 28 are disposed between the first cavity 23 and the second cavity 27 and the first membrane 25 and the second membrane 29, respectively.
  • the thickness of the insulating films 24, 26, and 28 can be set to 200 to 400 nm, for example.
  • the cross-sectional area of the cavity or the membrane support part perpendicular to the stacking direction of the membrane is simply expressed as the cross-sectional area of the cavity or the cross-sectional area of the membrane support part.
  • the first membrane 25 also serving as an electrode
  • an electrode may be formed on or in the first membrane 25.
  • the second membrane 29 also serving as an electrode
  • an electrode may be formed on or in the second membrane 29.
  • the lower layer electrode 22 may be disposed on the substrate 21 instead of being disposed inside the substrate 21.
  • the first membrane 25 has a first insulating membrane made of an insulating material and upper and lower electrode layers arranged so as to sandwich the first insulating membrane, and the upper and lower electrode layers are electrically connected. It is good also as composition which has.
  • the second membrane 29 may include a second insulating membrane made of an insulating material and an electrode layer.
  • transducer cell 12 in the present embodiment has a hexagonal shape as an example, it is not limited to this and may have other shapes.
  • FIG. 7 and 8 are schematic views showing a method for manufacturing the transducer cell 12 according to the first embodiment.
  • an insulating film to be the wiring layer 120 and the substrate 21 is formed on the upper surface of the semiconductor substrate, and a lower layer electrode 22 configured to be connected to the wiring layer 120 is patterned on the upper surface by etching. Further, a thin insulating film 21A is formed thereon (FIG. 7A).
  • the first sacrificial layer 121 for forming the first cavity 23 and the insulating film 24 are formed on the upper surface of the insulating film 21A. Then, a mask corresponding to a portion where the first cavity 23 is formed is two-dimensionally arranged, and a portion not subjected to the mask is removed by an etching process or the like to form a recess 121A reaching the lower layer electrode 22 (FIG. 7). (B)).
  • the first membrane 25 and the insulating film 26 are formed so as to fill the recess 121A and cover the insulating film 24. Then, a hole 25A that penetrates the first membrane 25 and the insulating film 26 and reaches the first sacrificial layer 121 is formed (FIG. 7C).
  • the hole between the cells may have a groove shape that separates the cells.
  • the first sacrificial layer 121 is removed from the hole by etching using a reactive gas or the like to form the first cavity 23 (FIG. 7D).
  • the third sacrificial layer 123 for forming the second cavity 27 and the insulating film 28 are formed on the upper surface of the insulating film 26. Then, a mask corresponding to a portion where the second cavity 27 is to be formed is two-dimensionally arranged, and the third sacrificial layer 123 and the insulating film 28 are partially removed by etching in a portion where the mask is not applied, so as to be insulated. A recess 123A reaching the film 26 is formed (FIG. 8A). At this time, the lateral opening width of the recess 123A is formed smaller than the lateral opening width of the recess 121A. The insulating film 26 is not removed because the second membrane 29 and the first membrane 25 are insulated.
  • a second membrane 29 is formed that fills the portion of the recess 123A removed in the previous step and covers the insulating film 28.
  • the film thickness of the second membrane 29 is formed thinner than the film thickness of the first membrane 25.
  • the hole 29A which penetrates the 2nd membrane 29 and reaches the 3rd sacrificial layer 123 is formed (FIG.8 (b)).
  • the holes between the cells may be groove-shaped, but the cells in the same element are formed so as to be at least partially connected.
  • the third sacrificial layer 123 is removed by etching from the hole 29A formed in the previous step to form the second cavity 27, and the cover layer 124 is formed so that the inside of the second cavity 27 is kept in a vacuum state.
  • the transducer cell 12 is completed by sealing (FIG. 8C).
  • the first cavity 23 and the second cavity 27 are completely sealed and configured to be almost in a vacuum state.
  • These cavities can be formed using a known MEMS technique, for example, SM method (Surface Micromachining method; a method of forming a cavity by removing a sacrificial layer).
  • a sacrificial layer removal hole (not shown) is provided between the second cavity 27 and the first cavity 23 so as to pass through the inside of the second membrane 29 and the insulating film 28. Both cavities can be formed. Further, if the sacrificial layer removal hole on the second membrane 29 is closed, both cavities can be sealed.
  • FIG. 9 is a diagram showing voltages applied to the wiring portions 30a, 30b, and 30c in the transducer cell 12 shown in FIGS. 6A and 6B and timings thereof.
  • 71 indicates a voltage applied to the wiring portions 30a and 30c
  • 72 indicates a voltage applied to the wiring portion 30b.
  • a DC bias voltage for example, ⁇ 100 V
  • the wiring portion 30b is set to 0V.
  • electrostatic attraction acts between the first membrane 25 and the second membrane 29, and the second membrane 29 bends downward.
  • electrostatic attraction acts between the lower layer electrode 22 and the first membrane 25, and the first membrane 25 is slightly bent downward.
  • the first membrane 25 At the moment when the pulse voltage is applied to the wiring portion 30b, the first membrane 25 generates a small acceleration but a large acceleration. This acceleration is transmitted to the second membrane 29, and is also synergistic with the elastic force of the second membrane 29. Since a large displacement is generated in the second membrane 29, an output larger than that of the single layer structure can be obtained.
  • the operation of the transducer cell 12 has been described.
  • the transducer 11 configured by the transducer cell 12 and the transducer array 112 configured by the transducer 11 are described. Is the same operation.
  • the ultrasonic transmission characteristics of the transducer cell 12 will be described.
  • the ultrasonic transmission characteristics of the vibrator according to the first embodiment, the vibrator having the conventional single layer structure, and the vibrator according to the comparative example in which the conventional single layer structure is simply laminated are determined by the finite element method. The analysis results are compared using structural analysis simulation.
  • FIG. 10 is a diagram comparing the ultrasonic transmission characteristics of the vibrator 11 according to the first embodiment and the ultrasonic transmission characteristics of the conventional and comparative capacitive vibrators.
  • FIG. 11 is a cross-sectional view of a transducer cell according to a comparative example in which conventional capacitive transducer structures are simply stacked.
  • FIG. 12 is a chart showing conditions for examining the ultrasonic transmission characteristics shown in FIG.
  • an ultrasonic transmission characteristic 83 represents a simulation result of the ultrasonic transmission characteristic of the transducer 11 in the first embodiment, and the ultrasonic transmission characteristic 81 has the conventional single-layer structure shown in FIG. It is a simulation result of the ultrasonic transmission characteristic of a vibrator.
  • the ultrasonic transmission characteristic 82 is a simulation result of the ultrasonic transmission characteristic of the vibrator according to the comparative example shown in FIG. 11 in which the membranes are simply laminated without changing the membrane thickness and the cavity cross-sectional area.
  • the membrane thickness and the cross-sectional area of the cavity are as shown in the table of FIG.
  • the sound pressure at a position separated from the transducer cell 12 by a predetermined distance was obtained by simulation.
  • the ultrasonic transmission characteristic 81 according to the conventional example when the ultrasonic transmission characteristic 81 according to the conventional example is compared with the ultrasonic transmission characteristic 82 according to the comparative example, the ultrasonic transmission characteristic 81 according to the conventional example having a single-layer structure has a greater membrane thickness.
  • the ultrasonic output was higher than the ultrasonic transmission characteristic 82 according to the comparative example in which the layers were simply laminated without changing the cross-sectional area of the cavity.
  • an output twice (6 dB improvement) was obtained as compared with the ultrasonic transmission characteristic 81 according to the conventional example.
  • the ultrasonic output was improved by changing the thickness of the membrane and the cross-sectional area (lateral width) of the cavity.
  • it is set as the structure which changes the cross-sectional area of a cavity by changing the cross-sectional area of a membrane support part.
  • the first membrane 25 In the vibrator cell in which the capacitive vibrator structure shown in the first embodiment or the comparative example is laminated, the first membrane 25 generates a small acceleration but a large acceleration at the moment when the pulse voltage is applied to the wiring portion 30b. The acceleration is transmitted to the second membrane 29, and a displacement is generated in the second membrane 29 by a synergistic effect with the elastic force of the second membrane 29.
  • the frequency of the first membrane 25 is configured to be higher than the frequency of the second membrane 29 by changing the thickness of the membrane and the sectional area (lateral width) of the cavity. Therefore, the phase at the time of displacement of each membrane can be made different between the first membrane 25 and the second membrane 29, and an output larger than that of the single layer structure can be obtained.
  • the first membrane 25 does not bend when the second membrane 29 is displaced.
  • the bending of the first membrane 25 can be reduced by changing the thickness of the membrane and the cross-sectional area (lateral width) of the cavity. As described above, since the first membrane 25 is made difficult to bend, a large displacement can be generated in the second membrane 29, so that it is considered that an improvement in the ultrasonic output was observed.
  • the shape of the membrane or the like is square for simplicity, but it is considered that the same tendency can be obtained even if simulation is performed with other shapes.
  • the bias voltage is applied to the wiring portions 30a and 30c and the pulse voltage is applied to the wiring portion 30b.
  • the bias voltage is applied to the wiring portion 30b and the wiring portions 30a and 30c are applied.
  • a pulse voltage can also be applied.
  • different pulse voltages can be applied to the wiring portions 30a and 30c, it is effective to apply voltages with pulse widths that match the respective resonance frequencies of the first membrane 25 and the second membrane 29.
  • the optimum driving frequency varies depending on the diagnostic purpose of the ultrasonic probe and the location of the subject to be diagnosed. It is preferable to set and drive the resonance frequency of the transducer cell according to the purpose.
  • the driving frequency is preferably selected from a range including 3 MHz to 10 MHz.
  • the timing of applying a voltage to the second membrane 29 is slightly delayed, the reaction force from the subject is reduced and the second membrane can be greatly deformed to the subject side, so that the output can be further improved.
  • the same bias voltage is applied to the wiring portions 30a and 30c.
  • different bias voltages may be applied.
  • the voltage is unbalanced by setting ⁇ 100V to the wiring portion 30a and ⁇ 90V to the wiring portion 30c, and the first membrane 25 is attracted to the substrate 21 side.
  • the stroke of the second membrane 29 can be made larger than the interval (vertical width) of the second cavities 27, and the transmission output can be improved.
  • the vibrator 11 according to the first embodiment can greatly improve the transmission output, which has been a problem with the conventional structure.
  • a two-dimensional array probe capable of transmitting and receiving ultrasonic waves in a wide range from a shallow site to a deep site can be realized, and ultrasonic diagnosis capable of 3D / 4D imaging with a wide range and high image quality is possible.
  • FIG. 13 is a cross-sectional view of the transducer cell 12 according to the first modification of the first embodiment.
  • the first membrane 25 is configured to be thicker than the second membrane 29, and the first cavity 23 has a smaller cross-sectional area (lateral width in the drawing) than the second cavity 27.
  • the second membrane 29 is configured to be thicker than the first membrane 25, and the second cavity 27 has a smaller width than the first cavity 23. It is configured as follows.
  • FIG. 14 is a diagram comparing the ultrasonic transmission characteristics of the vibrator 11 according to the first modification of the first embodiment and the ultrasonic transmission characteristics of a conventional capacitive vibrator.
  • the ultrasonic transmission characteristic 81 is the ultrasonic transmission characteristic of the vibrator having the conventional single layer structure shown in FIG. 10
  • the ultrasonic transmission characteristic 83 is the ultrasonic wave of the vibrator according to the first embodiment.
  • the transmission characteristic, the ultrasonic transmission characteristic 84 shows the simulation result of the ultrasonic transmission characteristic of the vibrator according to the first modification.
  • the membrane thickness and the cross-sectional area of the cavity are as shown in FIG. Modification 1 and Embodiment 1 are simulation results under conditions in which the membrane thickness and the cavity cross-sectional area are reversed.
  • the ultrasonic transmission characteristic 84 according to the first modification is higher than about 12 Mhz in comparison with the ultrasonic transmission characteristic 83 according to the first embodiment and the ultrasonic transmission characteristic 81 according to the conventional example. High sound pressure level at frequency. From the simulation results in the first embodiment and the first modification, it can be seen that stacking the membranes with different membrane thicknesses or cavity cross-sectional areas is effective in improving the ultrasonic transmission characteristics.
  • the membrane thickness or the sectional area of the cavity is equal to the resonance frequency of the membrane. You can see that it has an effect.
  • FIG. 16 is a cross-sectional view of the transducer cell 12 according to the second modification of the first embodiment.
  • the modification 2 has a structure in which the structure is laminated in three stages as shown in FIG.
  • the third membrane 44 disposed so as to face the second membrane 29, and between the second membrane 29 and the third membrane 44.
  • a membrane supporting portion 31c surrounding the third cavity 42 disposed, and insulating films 41 and 43 inserted between the third cavity 42 and the second membrane 29 and the third membrane 44 are provided.
  • the electrodes or membranes of each layer are connected to the wiring portions 30a, 30b, 30c, and 30d, and an ultrasonic wave is transmitted by applying a bias voltage to the wiring portions 30a and 30c and a pulse voltage to the wiring portions 30b and 30d.
  • the thickness of the third membrane 44 is formed thinner than the thickness of the second membrane 29.
  • the lateral width of the third cavity 42 is configured to be larger than the lateral width of the second cavity 27.
  • FIG. 17 is a cross-sectional view of the transducer cell 12 according to the third modification of the first embodiment.
  • the capacitive vibrator has been described with a symmetric structure.
  • the center positions of the first cavity 23 and the second cavity 27 are set as shown in FIG. It has a configuration shifted in the horizontal direction.
  • the widths of the membrane support portions on the left and right sides of the first cavity 23 and the widths of the membrane support portions on the left and right sides of the second cavity 27 are different between the first cavity 23 and the second cavity 27.
  • the center position of each cavity can be shifted in the lateral direction. With this configuration, ultrasonic waves can be transmitted in a direction inclined with respect to the vertical direction of the transducer cell.
  • a convex probe as shown in FIG. 29 is used in an application that requires a wide scanning angle with a large ultrasonic transmission range.
  • a wide scanning angle is realized by arranging the piezoelectric element 45 on a curved surface.
  • the piezoelectric element 45 is arranged on a plane.
  • strong ultrasonic waves can be transmitted in a direction inclined from the vertical direction, and can be used for applications that require a wide scanning angle.
  • FIG. 18A is a top view showing the basic structure of the transducer 11 used in the ultrasonic probe 102 according to the second embodiment
  • FIG. 18B is a cross-sectional view taken along the line AA in FIG.
  • FIG. 19A is a cross-sectional view in a state where a bias voltage is not applied to the transducer cell 12 according to the second embodiment
  • FIG. 19B is a cross-sectional view in a state where a bias voltage is applied.
  • the transducer cell 12 includes a substrate 21 made of an electrically insulating material such as a silicon wafer, glass, quartz, and the like.
  • the second membrane 29, the first membrane support portion 31a, and the second membrane support portion 31b are arranged.
  • Insulating films 24 and 26 are provided below and above the first membrane 25, respectively, and an insulating film 28 is provided below the second membrane 29.
  • the first membrane 25 includes a lower layer membrane portion 25a, a connection portion 25b, and an upper layer membrane portion 25c.
  • the connecting portion 25b is configured such that the width in the horizontal direction in FIG. 19A is smaller than the width in the horizontal direction of the lower layer membrane portion 25a and the upper layer membrane portion 25c. Therefore, the lower layer membrane portion 25a and the upper layer membrane portion 25c can reduce the influence of each displacement on the other.
  • the lateral width of the lower layer membrane portion 25a and the upper layer membrane portion 25c may be 40 to 50 ⁇ m
  • the lateral width of the connection portion 25b may be 20 to 40 ⁇ m.
  • the lower layer membrane portion 25a and the upper layer membrane portion 25c are electrically connected to each other by the connection portion 25b.
  • the first membrane 25 and the second membrane 29 also serve as electrodes, and the lower layer electrode 22, the first membrane 25, and the second membrane 29, which will be described later, are connected to the wiring portions 30a, 30b, and 30c, respectively.
  • the thickness of the lower layer membrane portion 25a and the upper layer membrane portion 25c of the first membrane 25 and the thickness of the second membrane 29 can be configured in the range of 1 to 4 ⁇ m.
  • the thickness of the connecting portion 25b can be 2 to 3 ⁇ m.
  • the lower layer electrode 22 can be made of, for example, a conductive metal such as aluminum, silver, copper, or chromium.
  • a conductive metal such as aluminum, silver, copper, or chromium.
  • the film thickness can be about 4 ⁇ m.
  • the first membrane and the second membrane are made of a conductive material.
  • a metal such as aluminum, silver, copper, or chromium, a conductive resin, or the like can be used.
  • an insulating thin film material can be used for the first membrane support part 31a, the second membrane support part 31b, and the insulating films 24, 26, and 28, an insulating thin film material can be used.
  • SiC, SiO 2 , SiN, or a mixture thereof is used. May be.
  • the thickness of the first membrane support portion 31a and the second membrane support portion 31b in the planar direction in FIG. 19A can be configured to be 2 to 4 ⁇ m, for example.
  • the thickness of the planar direction in FIG. 19A of the 1st membrane support part 31a and the 2nd membrane support part 31b is substantially the same.
  • the first cavity 23 (first gap) is a space surrounded by the first membrane 25, the membrane support 31a and the substrate 21, and the second cavity 27 (second gap) is the first membrane 25 and the membrane support. This is a space surrounded by 31b and the second membrane 29. Both the first cavity 23 and the second cavity 27 are configured to be substantially vacuum.
  • the first cavity 23 has substantially the same lateral width in the drawing as the second cavity 27, that is, the cross-sectional area perpendicular to the lamination direction of the membrane is substantially the same in the first cavity 23 and the second cavity 27. It is configured. In other words, the cross-sectional area in the direction perpendicular to the lamination direction of the membrane is the same as that of the membrane support portion 31a and the membrane support portion 31b.
  • the lateral width of the first cavity 23 and the second cavity 27 in FIG. 19A can be set to 40 to 80 ⁇ m, for example.
  • the height of the first cavity 23 and the second cavity 27 can be set to 200 to 300 nm, for example.
  • insulating films 24, 26, and 28 are disposed between the first cavity 23 and the second cavity 27 and the first membrane 25 and the second membrane 29, respectively.
  • the thickness of the insulating films 24, 26, and 28 can be set to 200 to 400 nm, for example.
  • the first membrane 25 also serving as an electrode
  • an electrode may be formed on or in the first membrane 25.
  • the second membrane 29 also serving as an electrode
  • an electrode may be formed on or in the second membrane 29.
  • the lower layer electrode 22 may be disposed on the substrate 21 instead of being disposed inside the substrate 21.
  • the 1st membrane 25 can take the structure which has the 1st insulating membrane which has insulation, and the upper and lower electrode layers arrange
  • the 2nd membrane 29 can take a structure, if it has the 2nd insulating membrane and electrode layer which have insulation. Also in this case, an electrode layer is inserted between the second insulating membrane and the insulating layer 28.
  • the transducer cell 12 in the present embodiment has a hexagonal shape as an example, it is not limited to this and may have other shapes.
  • Method for Manufacturing Vibrator Cell 12 Next, a method for manufacturing the transducer cell 12 will be described. 20 and 21 are schematic diagrams showing a method for manufacturing the transducer cell 12 according to the second embodiment.
  • an insulating film to be the wiring layer 120 and the substrate 21 is formed on the upper surface of the semiconductor substrate, and a lower layer electrode 22 configured to be connected to the wiring layer 120 is patterned on the upper surface by etching. Further, a thin insulating film 21A is formed thereon (FIG. 20A).
  • the first sacrificial layer 121 for forming the first cavity 23 and the insulating film 24 are formed on the upper surface of the insulating film 21A. Then, a mask corresponding to the portion where the first cavity 23 is to be formed is two-dimensionally arranged, and the portion not provided with the mask is removed by etching or the like to form a recess 121A reaching the lower layer electrode 22 (FIG. 20). (B)).
  • a lower layer membrane portion 25a is formed so as to fill the recess 121A and cover the insulating film 24. And the hole 25B which penetrates the lower layer membrane part 25a and reaches the 1st sacrificial layer 121 is formed (FIG.20 (c)).
  • the hole between the cells may have a groove shape that separates the cells.
  • the first sacrificial layer 121 is removed from the hole by etching using a reactive gas or the like to form the first cavity 23, and patterning is newly performed on the lower layer membrane portion 25a by etching or the like.
  • a second sacrificial layer 122 is formed (FIG. 20D).
  • the connecting portion 25b and the upper membrane portion 25a are formed so as to fill the space between the patterned second sacrificial layers 122 and cover the second sacrificial layers 122. Then, a hole 25D that penetrates through the upper membrane portion 25a and reaches the second sacrificial layer 122 is formed (FIG. 21A). Again, the pores between the cells may be in the form of grooves separating the cells.
  • the second sacrificial layer 122 is removed using a reactive gas or the like. Thereafter, as in the second step, the third sacrificial layer 123 and the insulating film 28 for forming the second cavity 27 are formed on the upper surface of the insulating film 26, and the third sacrificial layer 123 and the insulating film 28 are partially formed by etching. To remove. Note that the insulating film 26 is not removed in order to insulate the second membrane 29 and the upper layer membrane portion 25a.
  • a second membrane 29 that is a film that fills the portion removed in the previous process and covers the insulating film 28 is formed.
  • the hole 29A which penetrates the 2nd membrane 29 and reaches the 3rd sacrificial layer 123 is formed (FIG.21 (b)).
  • the holes between the cells may be groove-shaped, but the cells in the same element are formed so as to be at least partially connected.
  • the third sacrificial layer 123 is removed by etching from the hole 29A formed in the previous step to form the second cavity 27, and the cover layer 124 is formed and sealed so that the inside of the second cavity 27 is kept in a vacuum state. Then, the vibrator cell 12 is completed (FIG. 21C).
  • the first cavity 23 and the second cavity 27 are completely sealed and configured to be almost in a vacuum state.
  • These cavities can be formed using a known MEMS technique, for example, SM method (Surface Micromachining method; a method of forming a cavity by removing a sacrificial layer).
  • both cavities can be formed with a single sacrificial layer etch. Further, if the sacrificial layer removal hole on the second membrane 29 is closed, both cavities can be sealed. Therefore, the gap 34 can be sealed in a substantially vacuum state by using such a forming method.
  • a DC bias voltage for example, ⁇ 100 V
  • the wiring portion 30b is set to 0V.
  • an electrostatic attractive force acts between the lower layer electrode 22 and the first membrane 25, and the lower layer membrane portion 25a of the first membrane 25 bends downward. Further, electrostatic attraction also acts between the upper membrane portion 25c of the first membrane 25 and the second membrane 29, and the second membrane 29 bends downward.
  • FIG. 22 is a diagram comparing the ultrasonic transmission characteristics of the transducer 11 according to the second embodiment and the ultrasonic transmission characteristics of a conventional capacitive transducer.
  • an ultrasonic transmission characteristic 81 indicates the ultrasonic transmission characteristic in the conventional example
  • an ultrasonic transmission characteristic 82 indicates the ultrasonic transmission characteristic in the second embodiment.
  • the ultrasonic transmission characteristic 82 As shown in FIG. 22, in the ultrasonic transmission characteristic 82 according to the second embodiment, an output three times or more (an improvement of 10 dB or more) was obtained as compared with the ultrasonic transmission characteristic 81 according to the conventional example.
  • the thickness of the lower layer membrane portion 25a and the upper layer membrane portion 25c is 3 ⁇ m
  • the thickness of the second membrane 29 is 1 ⁇ m
  • the lower layer membrane portion 25a and the upper layer of the first membrane 25 are
  • the membrane portion 25c is configured to be thicker than the second membrane 29.
  • the lower membrane part 25a In the vibrator cell in which the capacitive vibrator structure according to the second embodiment is laminated, at the moment when the pulse voltage is applied to the wiring part 30b, the lower membrane part 25a generates a large acceleration with a small displacement. Is transmitted to the second membrane 29, and the second membrane 29 is displaced due to a synergistic effect with the elastic force of the second membrane 29. At this time, it is desirable that the upper membrane part 25c does not bend, and it is considered that a large displacement can be generated in the second membrane 29 by suppressing the bending of the upper membrane part 25c.
  • the upper layer membrane portion 25c and the lower layer membrane portion 25a are configured to be connected by the narrow connection portion 25b, so that the upper layer membrane portion 25c can reduce bending, and as a result, It is considered that a large displacement can be generated in the second membrane 29 and the ultrasonic output is improved.
  • the shape of the membrane or the like is square for simplicity, but it is considered that the same tendency can be obtained even if simulation is performed with other shapes.
  • the bias voltage is applied to the wiring portions 30a and 30c and the pulse voltage is applied to the wiring portion 30b.
  • the bias voltage is applied to the wiring portion 30b and the wiring portions 30a and 30c are applied.
  • a pulse voltage can also be applied.
  • different pulse voltages can be applied to the wiring portions 30a and 30c, it is effective to apply voltages with pulse widths that match the respective resonance frequencies of the lower layer membrane portion 25a and the second membrane 29. Can be operated automatically.
  • the optimum driving frequency varies depending on the diagnostic purpose of the ultrasonic probe and the location of the subject to be diagnosed. It is preferable to set and drive the resonance frequency of the transducer cell according to the purpose. In the ultrasonic probe, the driving frequency is preferably selected from a range including 3 MHz to 10 MHz.
  • the timing of applying a voltage to the second membrane 29 is slightly delayed, the reaction force from the subject is reduced and the second membrane can be greatly deformed toward the subject, so that the output can be improved.
  • the same bias voltage is applied to the wiring portions 30a and 30c.
  • different bias voltages may be applied.
  • the vibrator 11 according to the first embodiment can greatly improve the transmission output, which has been a problem with the conventional structure.
  • a two-dimensional array probe capable of transmitting and receiving ultrasonic waves in a wide range from a shallow site to a deep site can be realized, and ultrasonic diagnosis capable of 3D / 4D imaging with a wide range and high image quality is possible.
  • FIG. 23 is a cross-sectional view of the transducer cell 12 according to the first modification of the second embodiment.
  • the lateral width of the lower layer membrane portion 25 a is made smaller than the lateral width of the second membrane 29. Since other configurations are the same as those in the second embodiment, description thereof is omitted.
  • FIG. 24 is a diagram illustrating the ultrasonic transmission characteristics of the transducer 11 according to the first modification of the second embodiment.
  • the ultrasonic transmission characteristic 84 of the vibrator according to the modification 1 is superimposed on the simulation result of FIG.
  • the ultrasonic transmission characteristic 81 is the ultrasonic transmission characteristic in the conventional example
  • the ultrasonic transmission characteristic 82 is the ultrasonic transmission characteristic in the second embodiment
  • the ultrasonic transmission characteristic 84 is the ultrasonic transmission characteristic in the first modification. Is shown. As shown in FIG. 24, in the ultrasonic transmission characteristic 84 according to the first modification, an output having a higher sound pressure level near the peak was obtained as compared with the ultrasonic transmission characteristic 82 according to the second embodiment. In addition, an output with a sound pressure level that is at least twice as high as the ultrasonic transmission characteristic 81 of the conventional example is obtained.
  • the ultrasonic transmission characteristic 82 according to the second embodiment is the ultrasonic transmission characteristic according to the first modification, in which the lateral width of the first cavity 23 is 28 um.
  • No. 84 was simulated with the lateral width of the first cavity 23 being 24 um. That is, in the transducer cell 12 of the first modification, the lateral width of the lower layer membrane portion 25 a is configured to be smaller than the lateral width of the second membrane 29. At this time, the thicknesses of the lower layer membrane portion 25a and the second membrane 29 are both 1 um.
  • the comparison between the ultrasonic transmission characteristic 84 according to Modification 1 and the ultrasonic transmission characteristic 82 according to Embodiment 2 shows that the lateral width of the lower layer membrane portion 25 a and the second membrane 29 is It can be seen that this affects the resonance frequency.
  • the simulation is performed by changing the horizontal width of the lower membrane portion 25a and the second membrane 29.
  • the horizontal width may be changed and the length in the depth direction of the drawing may be changed.
  • you may change the cross-sectional area of the lower layer membrane part 25a and a 2nd membrane.
  • FIG. 25 is a cross-sectional view of the transducer cell 12 according to the second modification of the second embodiment.
  • the second membrane 29 since the second membrane 29 also serves as an electrode, adjacent cells in the same element are connected by the second membrane 29.
  • a submembrane 32 serving as a path for applying a bias voltage to the second membrane 29 is provided, and the second membrane 29 is pulled out via the submembrane 32.
  • the wiring is configured to be connected to an adjacent cell by wiring in the substrate 21. Except for the point that the sub-membrane 32 is provided, it is the same as the second embodiment, and the description thereof is omitted.
  • the sub-membrane 32 serving as a path for applying a bias voltage to the second membrane 29 may be connected to the first membrane 25 as shown in FIG.
  • this configuration can be adopted by providing the insulating portion 33 between the upper membrane portion 25c and the portion to which the submembrane 32 is connected.
  • FIG. 26 is a diagram comparing the ultrasonic transmission characteristics of the vibrator 11 according to the second modification of the first embodiment and the ultrasonic transmission characteristics of the vibrator according to the comparative example in which the submembrane 32 is removed from the second modification. It is. Here, the simulation is performed assuming that the submembrane 32 is disposed on the first membrane 25.
  • the ultrasonic transmission characteristic 83 indicates the ultrasonic transmission characteristic of the vibrator 11 according to the comparative example
  • the ultrasonic transmission characteristic 85 indicates the ultrasonic transmission characteristic of the vibrator 11 according to the modification 2.
  • the ultrasonic transmission characteristic 83 according to the comparative example shows a frequency characteristic having two peaks, but the ultrasonic transmission characteristic 85 according to the modified example 2 has a wide band characteristic. It is considered that this is because the submembrane 32 seals the gap 34 by providing the submembrane 32. Thus, it is considered that excessive vibration in the lateral direction that occurred in the comparative example was suppressed, and a wide band characteristic was obtained.
  • FIG. 27 is a cross-sectional view of the transducer cell 12 according to the third modification of the second embodiment.
  • the second embodiment, the first modification, and the second modification have been described in the form in which the structure of the capacitive vibrator is stacked in two stages. However, as shown in FIG. 27, a three-stage structure may be used.
  • the additional portion 46 has the same structure as the first membrane 25, the insulating film 26, the second cavity 27, and the insulating film 28, and the third membrane 44 is formed thereon.
  • the electrode or membrane of each layer is connected to the wiring portions 30a, 30b, 30c, and 30d, and an ultrasonic wave is transmitted by applying a bias voltage to the wiring portions 30a and 30c and a pulse voltage to the wiring portions 30b and 30d.
  • the transmission output can be further improved by increasing the number of layers in this way.
  • the ultrasonic probe, ultrasonic transducer, and ultrasonic transducer cell according to each embodiment have been described above.
  • the present invention is not limited to each embodiment.
  • some or all of the processing units included in the ultrasonic diagnostic apparatus in each embodiment may be included in the ultrasonic probe 102.
  • each processing unit included in the ultrasonic diagnostic apparatus is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.
  • circuits are not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor.
  • An FPGA Field Programmable Gate Array
  • reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.
  • ultrasonic diagnostic apparatus may be realized by a processor such as a CPU executing a program.
  • the present invention may be the above program or a non-transitory computer-readable recording medium on which the above program is recorded.
  • the program can be distributed via a transmission medium such as the Internet.
  • division of functional blocks in the block diagram is an example, and a plurality of functional blocks can be realized as one functional block, a single functional block can be divided into a plurality of functions, or some functions can be transferred to other functional blocks. May be.
  • functions of a plurality of functional blocks having similar functions may be processed in parallel or time-division by a single hardware or software.
  • the above-described ultrasonic probe according to one aspect of the present invention adopts the above-described configuration in a structure having an ultrasonic transducer cell in which cMUTs are stacked, thereby reducing the deflection of the upper surface of the first membrane and making the second membrane 29 larger. A displacement can be generated. Thereby, it is possible to obtain a larger ultrasonic transmission output than in the case of a single layer, and to improve the transmission output characteristics of the ultrasonic probe. Thereby, a clear ultrasonic image with less noise can be obtained in 3D / 4D ultrasonic imaging as compared with a conventional cMUT.
  • the ultrasonic transducer cell the ultrasonic transducer, the ultrasonic probe, and the ultrasonic diagnostic apparatus, there are members such as circuit components and lead wires on the substrate.
  • members such as circuit components and lead wires on the substrate.
  • the embodiment it is possible to realize a two-dimensional array probe having high sensitivity up to a deep part.
  • high-quality 3D / 4D imaging can be realized with a small probe in a wide range from a shallow part to a deep part.
  • a clear ultrasonic image with little noise can be obtained.
  • the voltage applied to the ultrasonic transducer can be reduced. Thereby, it can contribute to the power saving of an apparatus. For this reason, it has become a technology that extends to the mobile use of ultrasonic diagnostic equipment by extending battery life, and can be widely used for ultrasonic transducer cells, ultrasonic vibrators, ultrasonic probes, and ultrasonic diagnostic equipment. is there.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Abstract

La présente invention porte sur une cellule de transducteur ultrasonore dans laquelle un élément cMUT est empilé sur un substrat ayant une structure qui est aisée à connecter par fil à chaque électrode, ladite cellule de transducteur ultrasonore ayant au moins l'une des caractéristiques suivantes : (a) l'épaisseur dans une direction qui est perpendiculaire à la surface supérieure d'une première membrane est plus grande dans la première membrane que dans une seconde membrane et/ou (b) la surface spatiale dans une direction qui est parallèle à la surface supérieure de la première membrane est plus petite dans une première couche d'intervalle qui est entourée par une première section de support de membrane que dans une seconde couche d'intervalle qui est entourée par une seconde section de support de membrane ; ou (c) l'épaisseur dans une direction qui est perpendiculaire à la surface supérieure de la première membrane est plus épaisse dans la seconde membrane que dans la première membrane et/ou (d) la surface spatiale dans une direction qui est parallèle à la surface supérieure de la première membrane est plus petite dans la seconde couche d'intervalle qui est entourée par la seconde section de support de membrane que dans la première couche d'intervalle qui est entourée par la première section de support de membrane.
PCT/JP2013/007685 2012-12-28 2013-12-27 Cellule de transducteur ultrasonore, sonde ultrasonore et procédé de commande pour cellule de transducteur ultrasonore Ceased WO2014103334A1 (fr)

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JP2021515887A (ja) * 2018-02-28 2021-06-24 コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． 容量性圧力センサを用いる圧力検出
US20230347381A1 (en) * 2020-02-03 2023-11-02 Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno Ultrasonic transducer with stacked membranes
US12459003B2 (en) * 2020-02-03 2025-11-04 Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno Ultrasonic transducer with stacked membranes

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