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WO2018128072A1 - Transducteur ultrasonore et dispositif d'imagerie ultrasonore - Google Patents

Transducteur ultrasonore et dispositif d'imagerie ultrasonore Download PDF

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Publication number
WO2018128072A1
WO2018128072A1 PCT/JP2017/045408 JP2017045408W WO2018128072A1 WO 2018128072 A1 WO2018128072 A1 WO 2018128072A1 JP 2017045408 W JP2017045408 W JP 2017045408W WO 2018128072 A1 WO2018128072 A1 WO 2018128072A1
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WO
WIPO (PCT)
Prior art keywords
upper electrode
ultrasonic transducer
insulating film
film
cmut
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2017/045408
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English (en)
Japanese (ja)
Inventor
セパラ ゲルド
俊太郎 町田
泰一 竹崎
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Hitachi Ltd
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Hitachi Ltd
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Filing date
Publication date
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Publication of WO2018128072A1 publication Critical patent/WO2018128072A1/fr
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/12—Diagnosis using ultrasonic, sonic or infrasonic waves in body cavities or body tracts, e.g. by using catheters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers

Definitions

  • the present invention relates to an ultrasonic transducer and an ultrasonic imaging apparatus using the ultrasonic transducer.
  • Ultrasonic transducer elements are incorporated in an ultrasonic imaging apparatus, and are used for various applications such as diagnosis of tumors in the human body and inspection of cracks in buildings by transmitting and receiving ultrasonic waves.
  • piezoelectric ceramics represented by PZT (lead zirconate titanate) and the like have been used as an ultrasonic transducer element of an ultrasonic imaging apparatus, but in recent years, a capacitance detection type having a wider band characteristic than piezoelectric ceramics.
  • Ultrasonic transducers Capacitive Micromachined Ultrasonic Transducer; hereinafter abbreviated as CMUT
  • CMUT Capacitive Micromachined Ultrasonic Transducer
  • the basic structure of the CMUT is to provide a cavity (cavity) in the insulating layer between the lower electrode and the upper electrode disposed on the lower electrode, and to form a membrane (also called a diaphragm) between the insulating layer and the upper electrode above the cavity. It is to function as.
  • a DC voltage and an AC voltage are superimposed between the upper electrode and the lower electrode, and the membrane is vibrated at the frequency of the AC voltage by the electrostatic force generated between the electrodes. .
  • the membrane is vibrated by the pressure of the ultrasonic wave reaching the surface of the membrane, and the change in the distance between the two electrodes that occurs at that time is electrically detected as a capacitance change.
  • Patent Document 1 discloses that a concentric convex corrugated region whose center is the same as the center of the membrane is provided on the membrane outside 70% of the radius of the cavity. A technique is disclosed in which the overall rigidity is made smaller than the rigidity of the region other than the outer peripheral portion.
  • CMUT of Patent Document 1 when a voltage is applied between the upper electrode and the lower electrode, a relatively wide region other than the outer peripheral portion of the membrane is attracted while maintaining parallelism on the substrate side. A CMUT having excellent sensitivity and reception sensitivity can be obtained.
  • the above-described ultrasonic imaging apparatus incorporating the CMUT inserts the CMUT built in the tip of the catheter into the body of the subject (patient) and transmits / receives ultrasonic waves, so that it has high sensitivity in a high frequency band. In view of safety, low voltage driving is required.
  • a CMUT includes a lower electrode formed on a substrate via a first insulating film, a second insulating film formed on the lower electrode, and a second electrode formed on the second insulating film.
  • the upper electrode is positioned between the outer edge portion and the center portion having the first film thickness, and between the outer edge portion and the center portion, and is a second film that is thinner than the first film thickness.
  • a groove portion having a thickness of 1 mm.
  • CMUT that achieves both high-frequency vibration of the membrane and low-voltage driving can be realized.
  • FIG. 3 is a plan view of a principal part of the CMUT according to Embodiment 1.
  • FIG. 1A is a cross-sectional view taken along line AA in FIG. 1
  • FIG. 2B is a cross-sectional view taken along line BB in FIG. 1 is a plan view showing an overall configuration of a CMUT according to Embodiment 1.
  • FIG. 3 is a perspective view of an upper electrode of the CMUT according to Embodiment 1.
  • FIG. (A), (b) is principal part sectional drawing which shows an example of the manufacturing method of CMUT which concerns on Embodiment 1.
  • FIG. (A), (b) is principal part sectional drawing which shows the manufacturing method of CMUT following FIG.
  • (A), (b) is principal part sectional drawing which shows the manufacturing method of CMUT following FIG. (A), (b) is principal part sectional drawing which shows the manufacturing method of CMUT following FIG. It is a top view of the upper electrode in a manufacturing process.
  • (A), (b) is principal part sectional drawing which shows the manufacturing method of CMUT following FIG. It is a top view of the upper electrode in a manufacturing process.
  • (A), (b) is principal part sectional drawing which shows the manufacturing method of CMUT following FIG. (A), (b) is principal part sectional drawing which shows the manufacturing method of CMUT following FIG. (A), (b) is principal part sectional drawing which shows the manufacturing method of CMUT following FIG.
  • FIG. 1 is a perspective view illustrating an appearance of an ultrasonic imaging apparatus including a CMUT according to Embodiment 1.
  • FIG. It is a block diagram which shows the function of the ultrasonic imaging device shown in FIG.
  • FIG. 1 is a plan view of a principal part showing a unit cell of a CMUT according to the present embodiment
  • FIG. 2A is a cross-sectional view taken along the line AA in FIG. 1, and
  • FIG. It is B line sectional drawing.
  • FIG. 1 mainly shows a planar layout of upper and lower electrodes and a cavity formed between them, and an insulating film is not shown.
  • the CMUT cell includes an insulating film 11 formed on a substrate 10 made of single crystal silicon, a lower electrode 12 formed on the insulating film 11, and two insulating films 13 and 15 formed on the lower electrode 12.
  • a protective film (not shown) for preventing foreign matter adhesion made of polyimide resin or the like is provided on the uppermost insulating film 19 as necessary.
  • a region that overlaps the cavity 20 in plan view functions as a membrane M that vibrates when transmitting and receiving ultrasonic waves, and a region that functions as the membrane M.
  • a region surrounding the film functions as a fixing portion that supports the membrane M.
  • the insulating films 19, 17 are etched and the external connection pad 21 in which a part of the upper electrode 16 is exposed, and the insulating films 19, 17, 15, 13 are etched.
  • a pad 22 for external connection in which a part of the lower electrode 12 is exposed, is formed.
  • a direct current voltage and an alternating current voltage are applied to CMUT from an external power source through these pads 21 and 22.
  • Reference numeral 18 in the drawing denotes openings formed in the insulating films 15 and 17 in the step of forming the cavity 20 on the substrate 10 (described later).
  • the actual CMUT has a configuration in which a large number of unit cells as described above are arranged on the substrate 10.
  • the CMUT of this embodiment is characterized by the shape of the upper electrode 16. That is, as shown in FIG. 2B, the upper electrode 16 of the CMUT has a relatively thick outer edge portion and central portion of a region overlapping with the cavity 20 (in other words, a region functioning as the membrane M) in plan view. A groove portion 23 having a first film thickness and having a second film thickness smaller than the first film thickness is provided in a region between the outer edge portion and the central portion.
  • one end of the groove portion 23 having the second film thickness is connected to the outer edge portion of the upper electrode 16, and crosses each other at the center portion of the upper electrode 16. It is supported by a plurality of support portions 24. These support portions 24 have the same first film thickness as the outer edge portion of the upper electrode 16.
  • FIG. 4 shows an example in which the three support portions 24 cross each other at the center of the upper electrode 16, but the number of support portions 24 is not limited to three.
  • the adjacent support portions 24 are arranged at equal intervals. That is, it is preferable that the groove portions 23 are evenly supported by the support portion 24.
  • the plurality of groove portions 23 separated by the plurality of support portions 24 have the same area in plan view.
  • FIGS. 5 to 8, 10 and 12 to 14 (a) is a cross-sectional view corresponding to the line AA in FIG. 1 (a), and (b) is a cross-sectional view of FIG. It is sectional drawing corresponding to a B line. 9 and 11 are plan views of the upper electrode during the manufacturing process.
  • an insulating film 11 is formed on a substrate 10, and then a lower electrode 12 is formed on the insulating film 11.
  • the insulating film 11 is made of a silicon oxide film having a thickness of about 500 nm deposited by, for example, a CVD (Chemical Vapor Deposition) method or a thermal oxidation method.
  • the lower electrode 12 is made of, for example, an aluminum alloy film having a thickness of about 100 nm deposited by sputtering.
  • a sacrificial layer (dummy layer) 14 is formed on the insulating film 13.
  • the insulating film 13 is made of, for example, a silicon oxide film having a thickness of about 200 nm deposited by a plasma CVD method.
  • the sacrificial layer 14 is formed, for example, by depositing a polycrystalline silicon film on the insulating film 13 by a CVD method, and then patterning the polycrystalline silicon film using a photolithography technique and a dry etching technique, and a cavity 20 is formed in a later process. It is formed by leaving a polycrystalline silicon film in a region to be formed.
  • the lower metal film 16a is made of, for example, a W (tungsten) film having a thickness of about 50 nm deposited by a sputtering method
  • the upper metal film 16b is made of, for example, a TiN (titanium nitride) film having a thickness of about 50 nm deposited by a sputtering method. Consists of.
  • the metal films 16a and 16b may be composed of two or more kinds of metal films having different etching rates, and are not limited to the combination of the W film and the TiN film.
  • two layers of the metal films 16b and 16a are sequentially patterned by using a photolithography technique and a dry etching technique, and 2 in a region where the upper electrode 16 is formed in a later process.
  • the metal films 16a and 16b are left as layers.
  • the lower metal film 16a is patterned by changing the etching gas.
  • the metal film 16b is patterned by using a photolithography technique and a dry etching technique to expose a part of the metal film 16a in a region overlapping the cavity 20 in plan view.
  • a groove 23 is formed.
  • the groove 23 is formed by selectively removing only the upper metal film 16b using a predetermined etching gas by utilizing the difference in etching rate between the two metal films 16a and 16b.
  • the region where the upper metal film 16b is left in the region inside the outer edge portion of the region overlapping with the cavity 20 becomes the support portion 24 that supports the groove portion 23 having a thin film thickness.
  • an insulating film 17 made of a silicon oxide film having a thickness of about 200 nm is deposited on the insulating film 15 and the upper electrode 16 by plasma CVD, and then a photolithography technique and a dry etching technique are performed.
  • the openings 18 reaching the sacrificial layer 14 are formed by removing each part of the insulating film 17 and the underlying insulating film 15.
  • a wet etching solution such as an aqueous potassium hydroxide solution is brought into contact with the surface of the sacrificial layer 14 through the opening 18.
  • the substrate 10 in which the openings 18 are formed in the insulating films 17 and 15 is immersed in a wet etching solution.
  • the sacrificial layer 14 is dissolved and disappeared by the wet etching solution, and the cavity 20 is formed in the region where the sacrificial layer 14 was disposed.
  • an insulating film 19 made of a silicon oxide film having a thickness of about 500 nm is deposited on the insulating film 17 by plasma CVD. As a result, the insulating film 19 is buried in the opening 18, and the cavity 20 sealed by the insulating films 13, 15, 19 is completed.
  • a part of the insulating films 19 and 17 is removed by using a photolithography technique and a dry etching technique, and a part of the upper electrode 16 is exposed to form a pad 21. Further, a part of each of the insulating films 19, 17, 15, and 13 is removed, and a part of the lower electrode 12 is exposed to form a pad 22.
  • the CMUT shown in FIGS. 1 and 2 is completed through the steps so far.
  • CMUT electrode material and insulating film material are preferable examples, and are not limited thereto.
  • a metal material other than an aluminum alloy for example, W, Ti, TiN, Al, Cr, Pt, Au, polycrystalline silicon doped with impurities at a high concentration, amorphous silicon, or the like can be used.
  • a silicon oxynitride film, a hafnium oxide film, a silicon-doped hafnium oxide film, or the like can be used instead of the insulating film made of a silicon oxide film.
  • the sacrificial layer 14 is not limited to a polycrystalline silicon film as long as the material has a high etching selectivity with respect to these insulating films.
  • the position where the groove 23 is disposed and the area ratio occupied by the groove 23 can be variously changed. Depending on the position and the area ratio, there is a difference between the magnitude of the drive voltage and the vibration frequency of the membrane M.
  • FIG. 16 is a graph showing a simulation result of the correlation between the area ratio of the groove 23 occupying the upper electrode 16, the resonance frequency of the membrane M, and the drive voltage.
  • the horizontal axis of the graph shown in FIG. 16 indicates the ratio of the area of the groove 23 to the total area of the upper electrode 16 in the region overlapping with the cavity 20, and the vertical axis indicates the resonance frequency and drive voltage of the membrane M.
  • the resonance frequency of the membrane M increases and the drive voltage decreases as the area ratio of the groove 23 occupying the upper electrode 16 increases. This effect becomes remarkable when the area ratio of the groove portion 23 to the upper electrode 16 is 20% or more, particularly 50% or more.
  • FIG. 17 is a graph showing a simulation result of the correlation between the distance from the center of the upper electrode 16 to the outer edge, the resonance frequency of the membrane M, and the drive voltage.
  • the horizontal axis of the graph shown in FIG. 17 indicates the distance from the outer edge of the upper electrode 16 to the groove 23 when the distance from the outer edge to the center of the upper electrode 16 is 1, and the vertical axis indicates the resonance of the membrane M.
  • the frequency and drive voltage are shown.
  • the membrane M can be driven at a low voltage and a high frequency by providing a relatively thin groove 23 in a part of the upper electrode 16. An effect is obtained. Further, it can be seen that the above-described effect can be remarkably obtained by maximizing the area ratio of the groove portion 23 occupying the upper electrode 16 at a position of 75% or more of the distance from the center portion of the upper electrode 16 to the outer edge portion.
  • CMUT capable of low voltage and high frequency driving can be realized.
  • the groove portion 23 of the upper electrode 16 can be provided on the lower surface (bottom surface) of the upper electrode 16 or on both the upper surface and the lower surface (bottom surface) of the upper electrode 16, but as in the present embodiment, the upper surface of the upper electrode 16. It is desirable to provide it on the side.
  • the lower surface of the upper electrode 16 is preferably flat as shown in FIG.
  • the distance between the upper electrode 16 and the lower electrode 12 is uniform in the entire region of the cavity 20, whereas the groove 23 is provided on the lower surface side of the upper electrode 16. In such a case, a region where the distance between the upper electrode 16 and the lower electrode 12 increases locally occurs locally. Accordingly, when the lower surface of the upper electrode 16 is flat, the electrostatic force between the two electrodes generated at a constant drive voltage can be increased compared to when the lower surface of the upper electrode 16 has a step.
  • the material of the support portion 24 that supports the groove portion 23 is not limited to the conductive material, and may be an insulating material. However, when the support portion 24 is made of an insulating material, the electrical resistance of the upper electrode 16 is increased and the manufacturing process of the upper electrode 16 is complicated as compared with the case where the support portion 24 is made of a conductive material.
  • the planar shape of the cavity 20 and the planar shape of the upper electrode 16 in the region overlapping with the cavity 20 are hexagonal, but the planar shape of each of the cavity 20 and the upper electrode 16 is limited to a hexagonal shape.
  • it may be a circle, an ellipse, a quadrangle, an octagon, or the like.
  • the adjacent support portions 24 are arranged at equal intervals as shown in FIG. That is, the groove 23 is preferably divided into equal areas by the support 24.
  • FIG. 19 is a perspective view illustrating an appearance of the ultrasonic imaging apparatus including the CMUT according to the first embodiment
  • FIG. 20 is a block diagram illustrating functions of the ultrasonic imaging apparatus illustrated in FIG.
  • An ultrasonic imaging apparatus 301 includes an ultrasonic transmission / reception circuit that transmits / receives ultrasonic waves, a signal processing circuit that processes an echo signal received by the ultrasonic transmission / reception circuit, and generates an ultrasonic image to be inspected.
  • a display 303 for displaying an ultrasound image and a GUI for interfacing with an operator
  • an input 304 operated by the operator and a catheter connection 306
  • the catheter 302 is provided.
  • the catheter 302 is a device that is inserted into the body of a subject (patient) and transmits / receives ultrasonic waves to / from the subject.
  • a CMUT 307 connected to an ultrasonic transmission / reception circuit in the main body 305 is built in the distal end of the catheter 302. Has been.
  • the CMUT 307 is configured by arranging the unit CMUTs of the first embodiment in a one-dimensional or two-dimensional array within a range of several hundred to 10,000.
  • FIG. 19 shows a movable ultrasonic imaging apparatus provided with a caster 308 at the bottom of the main body 305 as an example.
  • the ultrasonic imaging apparatus 301 of this embodiment is an ultrasonic imaging apparatus fixed to an examination room.
  • the present invention can be applied to an ultrasonic imaging apparatus, a portable ultrasonic imaging apparatus such as a notebook type or a box type, and other known ultrasonic imaging apparatuses.
  • the main body 305 of the ultrasonic imaging apparatus 301 includes an ultrasonic transmission / reception unit 411, a signal processing unit 412, a control unit 413, a memory unit 414, a power supply device 415, and an auxiliary device 416.
  • the ultrasonic transmission / reception unit 411 generates a driving voltage for transmitting ultrasonic waves from the CMUT 307 or receives an echo signal from the CMUT 307, and includes a delay circuit, a filter, a gain adjustment circuit, and the like.
  • the signal processing unit 412 performs processing necessary for correction such as LOG compression and depth correction and image creation on the received echo signal, such as a DSC (digital scan converter), a color Doppler circuit, and an FFT analysis unit May be included.
  • the signal processing by the signal processing unit 412 can be either analog signal processing or digital signal processing, part of which can be realized by software, or by ASIC (application-specific integrated circuit) or FPGA (field-programmable gate array). It can also be realized.
  • the control unit 413 controls each circuit of the main body 305 and devices connected to the main body 305.
  • the memory unit 414 stores information, parameters, and processing results necessary for signal processing and control.
  • the power supply device 415 supplies necessary power to each unit of the ultrasonic imaging apparatus.
  • the auxiliary device 416 is for realizing functions associated with the ultrasonic imaging apparatus 301, such as sound generation, and is added as necessary.
  • the ultrasonic imaging apparatus 301 uses the CMUT according to the first embodiment as the CMUT 307 of the catheter 302, it is possible to perform ultrasonic waves at a low voltage that is safe even when inserted into the body of a subject (patient). Can be transmitted and received with high sensitivity.
  • the CMUT of the present invention can be applied not only to an ultrasonic imaging apparatus but also to various uses such as inspection of cracks in LSI packages and inspection of cracks generated in buildings.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Biomedical Technology (AREA)
  • Molecular Biology (AREA)
  • Biophysics (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Pathology (AREA)
  • Radiology & Medical Imaging (AREA)
  • Acoustics & Sound (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Medical Informatics (AREA)
  • Signal Processing (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)

Abstract

La présente invention concerne un transducteur capacitif ultrasonore micro-usiné (cMUT) permettant d'obtenir à la fois une vibration haute fréquence d'une membrane et un fonctionnement à basse tension. Le cMUT comprend : une électrode inférieure (12) formée sur un substrat (10) ; une cavité (20) formée entre deux couches de films d'isolation (13, 15) disposées sur l'électrode inférieure (12) ; et une électrode supérieure (16) formée sur le film d'isolation (15) et disposée en chevauchement avec la cavité (20) dans une vue en plan, l'électrode supérieure (16) étant pourvue : d'une partie de bord extérieur et d'une partie centrale présentant chacune une première épaisseur de film ; et d'une partie de rainure (23) positionnée entre la partie de bord extérieur et la partie centrale et présentant une deuxième épaisseur de film inférieure à la première épaisseur de film.
PCT/JP2017/045408 2017-01-06 2017-12-19 Transducteur ultrasonore et dispositif d'imagerie ultrasonore Ceased WO2018128072A1 (fr)

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JP2017001198A JP6752727B2 (ja) 2017-01-06 2017-01-06 超音波トランスデューサおよび超音波撮像装置
JP2017-001198 2017-01-25

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Cited By (1)

* Cited by examiner, † Cited by third party
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TWI750862B (zh) * 2020-10-23 2021-12-21 友達光電股份有限公司 電容式超音波換能器及其製造方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102359155B1 (ko) * 2019-12-31 2022-02-08 한국과학기술원 하이브리드 초음파 탐촉자 및 그 제조 방법
CN113926679B (zh) 2020-06-29 2022-09-27 京东方科技集团股份有限公司 声波换能单元及其制备方法和声波换能器

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JP2007074628A (ja) * 2005-09-09 2007-03-22 Hitachi Ltd 超音波探触子およびその製造方法
US7615834B2 (en) * 2006-02-28 2009-11-10 The Board Of Trustees Of The Leland Stanford Junior University Capacitive micromachined ultrasonic transducer(CMUT) with varying thickness membrane
JP2010004199A (ja) * 2008-06-19 2010-01-07 Hitachi Ltd 超音波トランスデューサおよびその製造方法

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Publication number Priority date Publication date Assignee Title
JP2007074628A (ja) * 2005-09-09 2007-03-22 Hitachi Ltd 超音波探触子およびその製造方法
US7615834B2 (en) * 2006-02-28 2009-11-10 The Board Of Trustees Of The Leland Stanford Junior University Capacitive micromachined ultrasonic transducer(CMUT) with varying thickness membrane
JP2010004199A (ja) * 2008-06-19 2010-01-07 Hitachi Ltd 超音波トランスデューサおよびその製造方法

Non-Patent Citations (2)

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Title
HUANG, YONGLI ET AL.: "Capacitive Micromachined Ultrasonic transducers with Piston-Shaped Membranes: Fabrication and Ecperimental Characterization", IEEE TRANSUCTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL, vol. 56, no. 1, January 2009 (2009-01-01), pages 136 - 145, XP011267411 *
YOON, HYO-SEON ET AL.: "Fabrication of CMUT Cells with Gold Center Mass for Higher Output Pressure", AIP CONF. PROC., vol. 1359, 2011, pages 183 - 188, XP055607050 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI750862B (zh) * 2020-10-23 2021-12-21 友達光電股份有限公司 電容式超音波換能器及其製造方法

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