WO2009041675A1 - Transducteur électrostatique et procédé de fabrication - Google Patents

Transducteur électrostatique et procédé de fabrication Download PDF

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Publication number
WO2009041675A1
WO2009041675A1 PCT/JP2008/067589 JP2008067589W WO2009041675A1 WO 2009041675 A1 WO2009041675 A1 WO 2009041675A1 JP 2008067589 W JP2008067589 W JP 2008067589W WO 2009041675 A1 WO2009041675 A1 WO 2009041675A1
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WO
WIPO (PCT)
Prior art keywords
vibration membrane
substrate
region
contact
protrusions
Prior art date
Application number
PCT/JP2008/067589
Other languages
English (en)
Inventor
Chienliu Chang
Original Assignee
Canon Kabushiki Kaisha
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP2008236379A external-priority patent/JP5408937B2/ja
Application filed by Canon Kabushiki Kaisha filed Critical Canon Kabushiki Kaisha
Priority to US12/673,232 priority Critical patent/US8410659B2/en
Publication of WO2009041675A1 publication Critical patent/WO2009041675A1/fr

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Classifications

    • 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 electromechanical transducer and a method for manufacturing the same.
  • the electromechanical transducer of the present invention is an acoustic transducer of a capacitive type particularly- suitable for transmission or reception of an ultrasonic wave .
  • CMUT Capacitive Micromachined Ultrasonic Transducer
  • CMUT Capacitive Micromachined Ultrasonic Transducer
  • This CMUT has a construction in which a vibration membrane provided with an upper electrode and a substrate provided with a lower electrode are arranged in opposition to each other, and the vibration membrane is supported by a support member so as to form a gap between the vibration membrane and the substrate (see Japanese patent application laid-open No. 2006-319712).
  • an electrostatic attraction force is first generated between both the electrodes by applying a DC voltage to the lower electrode, so that the vibration membrane is thereby caused to deform.
  • the vibration membrane is vibrated to oscillate an ultrasonic wave.
  • the vibration membrane When the ultrasonic wave is received, the vibration membrane is caused to deform by reception of the ultrasonic wave, whereby the interval or distance between both the electrodes is changed, and a resultant change in the capacitance between both the electrodes is detected as a signal.
  • US Patent No. 6426582 discloses a CMUT which will be described below.
  • a vibration membrane is caused to deform downward, and in such a deformed state, a resist resin is heated and coated " around the vibration membrane. Thereafter, the resist is cooled to harden, and the vibration membrane is fixed in its periphery with its shape being naturally deformed in a .downward direction, whereby an interval between capacitive electrodes is formed to be small.
  • this US Patent No. 6426582 adopts a construction in which the interelectrode interval is controlled by protrusions. That is, the construction adopted is such that the protrusions are formed on a lower side of the vibration membrane, and they alone are in contact with an underlayer substrate, with the central portion of the vibration membrane being not in contact with the underlayer.
  • a collapse mode has being noted as a new operation mode different from a conventional mode that is an ordinary operation mode in a CMUT.
  • This collapse mode means an operation mode in which when a DC voltage is applied to a lower electrode, a vibration membrane is attracted to an underlayer electrode under the action of a DC electrostatic force thereof, so that the vibration membrane is thereby made into a collapsed or crushed state in which it is caused to operate while being in contact with the lower electrode.
  • this specific voltage is called a collapse voltage .
  • the CMUT in order to operate the CMUT in the above-mentioned collapse mode, it is necessary to apply an extremely high DC voltage so as to place the vibration membrane into contact with the lower electrode.
  • the DC voltage (collapse voltage) needed here is in the range of from about 130 to 150 V, and the CMUT can not be kept operating in this mode when such a voltage can not be provided.
  • it is extremely difficult to put a circuit operating with such a high voltage to practical use and in case where the CMUT, being operated with such a high voltage, is used for acoustic diagnostics, unfavorable influences might be exerted on human bodies.
  • the vibration membrane might cause dielectric breakdown, thereby making the lower electrode and the upper electrode be short-circuited to each other.
  • CMUT which is constructed in the following manner so as to decrease a DC voltage in a collapse mode.
  • a construction is used in which a vibration membrane is attracted with the use of a magnet. Specifically, a part of the vibration membrane including a magnetic material is attracted by a magnetic field from the outside, whereby an interval between capacitive electrodes is decreased, as a result of which a high DC voltage (collapse voltage) is made unnecessary, thus lowering a required voltage.
  • the vibration membrane and the substrate are placed in contact with each other as described above in an operating state of the collapse mode, so the variable capacitance between the upper electrode and the lower electrode decreases, resulting in an increase in parasitic capacitance. That is, in a capacitor, which is formed in a region where the vibration membrane and the substrate of both the electrodes are in contact with each other, the distance between the electrodes does not change even at the time when the vibration membrane is caused to vibrate upon transmission and reception of ultrasonic waves, and hence the capacitor does not contribute to the change in capacitance. Due to such an increase in the parasitic capacitance, there arises a problem that the electromechanical transduction efficiency of the CMUT is reduced, and that the signal detection function of the CMUT is lowered.
  • the present invention has an object to provide an electromechanical transducer and a method for manufacturing the same which can decrease the voltage required in a stable manner when the transducer is caused to operate in a collapse mode, without reducing an electromechanical transduction efficiency and without lowering a signal detection function.
  • the present invention provides electromechanical transducers and methods for manufacturing the same which are constructed as follows. [ 0020 ]
  • An electromechanical transducer is characterized by comprising: a vibration membrane provided with a first electrode; a substrate provided with a second electrode; and a support member adapted to support the vibration membrane in such a manner that a gap is formed between the vibration membrane and the substrate with these electrodes being arranged in opposition to each other; wherein a part of the vibration membrane and a region of the substrate are in contact with each other, and a remaining region of the vibration membrane other than the contact region is able to vibrate, and wherein there is an overlap region of the first electrode and second electrode in the contact region, and at least one of these electrodes has a through portion formed therethrough in at least a part of the overlap region.
  • the electromechanical transducer according to the present invention is characterized in that the vibration membrane has a region in which the contact state with the substrate is kept with no external force being applied to the vibration membrane.
  • the electromechanical transducer according to the present invention is characterized in that in the region in which the contact state is kept, the vibration membrane is fusion bonded to the substrate.
  • the electromechanical transducer of the present invention is characterized in that in the region in which the contact state is kept, the vibration membrane is brought into contact with, or is fusion bonded to, the substrate through protrusions that are formed on at least one of an upper surface and a lower surface of the vibration membrane.
  • the electromechanical transducer according to the present invention is characterized in that the protrusions have a height in the range of from 10 nm to 200 nm.
  • the electromechanical transducer according to the present invention is characterized in that the protrusions are arranged in a ring shape so as to surround the region in which the contact state is kept.
  • an electromechanical transducer in which the electromechanical transducer includes a vibration membrane provided with a first electrode, a substrate provided with a second electrode, and a support member adapted to support the vibration membrane in such a manner that a gap is formed between the vibration membrane and the substrate with these electrodes being arranged in opposition to each other, wherein a part of the vibration membrane and a region of the substrate are in contact with each other, and a remaining region of the vibration membrane other than the contact region is able to vibrate, and wherein there is an overlap region of the first electrode and second electrode in the contact region, the method comprising: a step of forming a through portion in at least one of the first and second electrodes in at least a part of the overlap region.
  • the method for manufacturing an electromechanical transducer according to the present invention is characterized by comprising a step of forming a structure in which the vibration membrane is caused to plastically deform in such a manner that a part of the vibration membrane is made to operate in a collapse mode while keeping a state of contact thereof with a region of the substrate including the second electrode.
  • the method for manufacturing an electromechanical transducer according to the present invention is characterized by fusion bonding a part of the vibration membrane that has been plastically deformed to the region of the substrate when the structure to keep the contact state is formed.
  • the method for manufacturing an electromechanical transducer according to the present invention is characterized by forming protrusions on at least one of an upper surface and a lower surface of the vibration membrane, wherein when the structure to keep the contact state is formed, the vibration membrane is brought into contact with, or is fusion bonded to, the substrate through the protrusions.
  • the method for manufacturing an electromechanical transducer according to the present invention is characterized in that the protrusions have a height in the range of from 10 nm to 200 nm.
  • the method for manufacturing an electromechanical transducer according to the present invention is characterized in that the protrusions are formed in a ring shape so as to surround the region in which the contact state is kept.
  • Fig. IA is a conceptual cross sectional view illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in a first embodiment of the present invention
  • Fig. IB is a conceptual plan view illustrating the basic construction of the CMUT in the first embodiment.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 2 is a conceptual cross sectional view illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in a second embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 3 is a conceptual cross sectional view illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in a third embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 4 is a conceptual cross sectional view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) in a fourth embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 5 is a conceptual cross sectional view illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in a fifth embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 6 is a conceptual cross sectional view illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in a sixth embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 7 is a conceptual cross sectional view illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in a seventh embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 8A through Fig. 8M are views illustrating the production processes or steps for the capacitive micromachined ultrasonic transducer (CMUT) in an eighth embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 9A is a conceptual cross sectional view illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in a practical example of the present invention
  • Fig. 9B is a conceptual plan view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) .
  • Fig. 1OA is a view illustrating the electrical capacitance characteristic of the capacitive micromachined ultrasonic transducer (CMUT) in the practical example of the present invention
  • Fig. 1OB is a view illustrating the dependency of electrical capacitance vs electrode through-hole internal diameter of a CMUT element
  • Fig. 1OC is a view illustrating the dependency of variable capacitance ratio (active ratio) vs electrode through-hole internal diameter of the CMUT element.
  • Fig. HA through Fig. HM are views illustrating the production processes or steps for the capacitive micromachined ultrasonic transducer (CMUT) in the practical example of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • Electromechanical transducers according to the present invention are suitably used as acoustic transducers that are used in particular for transmission and reception of acoustic waves, and are further suitably used as ultrasonic transducers that are used for transmission and reception of ultrasonic waves.
  • sound or acoustic wave in this specification is not limited to an elastic wave transmitting in air, but is a generic name for all kinds of elastic waves that transmit through elastic bodies irrespective of their states, i.e., gas, liquid or solid. In other words, it is a broad concept even including an ultrasonic wave that is an elastic wave of frequencies exceeding human audio frequencies .
  • the electromechanical transducers according to the present invention can be applied, as ultrasonic probes, to ultrasonic diagnostic apparatuses (echographers) or the like.
  • the present invention will be described as ultrasonic transducers (ultrasonic sensors) that transmit or receive ultrasonic waves, but it is evident that acoustic waves which can be detected are not limited to ultrasonic waves if consideration is given to the principles of the transmission and reception of the acoustic sensors of the present invention.
  • CMUT capacitive micromachined •ultrasonic transducer
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. IA and Fig. IB are views illustrating a basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in the first embodiment of the present invention.
  • Fig. IA is a conceptual cross sectional view of the capacitive micromachined ultrasonic transducer (CMUT)
  • Fig. IB is a conceptual plan view of the capacitive micromachined ultrasonic transducer (CMUT) .
  • Fig. IA and Fig. IB 1 designates an upper electrode which is a first electrode, 2 a vibration membrane support member, 3 a vibration membrane, 4 a substrate, 5 protrusions, 6 an insulation film, 7 an outer peripheral portion of the vibration membrane, 8 a lower electrode which is a second electrode, 9 a contact region (fusion bonded region), 10 a cavity, and 24 an electrode through portion (electrode through hole) .
  • the CMUT of this embodiment includes, as shown in Fig. IA, the vibration membrane 3 provided with the upper •electrode 1, the substrate 4 provided with the lower electrode 8, and the vibration membrane support member 2 that serves to support the vibration membrane so as to form a gap between the vibration membrane and the substrate with these electrodes being arranged in opposition to each other,
  • the vibration membrane 3 is able to vibrate by receiving mechanical energy, such as receiving an ultrasonic wave.
  • the lower electrode of a low resistance On the substrate 4, there is formed the lower electrode of a low resistance, on which is further disposed the insulation film 6.
  • the insulation film 6 plays the role of preventing the lower electrode 8 and the upper electrode 1 from being short circuited to each other.
  • the vibration membrane support member 2, which serves to support the vibration membrane 3, is fixedly mounted on the substrate 4 through the insulation film 6.
  • the lower electrode 8 itself may be used as a substrate, or the vibration membrane 3 itself may be used as an upper electrode .
  • the vibration membrane is constructed such that a part of the vibration membrane including the upper electrode and a region of the substrate including the lower electrode are kept in contact with each other with no external force being applied to the vibration membrane 3.
  • the vibration membrane being "in contact with the substrate”
  • the insulation film 6 being provided, the whole including not only the substrate 4 but also even the insulation film 6 constitutes a lower substrate.
  • the vibration membrane 3 is constructed in such a manner that a region of the vibration membrane 3 other than that in which the state of contact is kept can vibrate upon reception or transmission of an ultrasonic wave.
  • the vibration membrane 3 in order to form the region in which the state of contact with this substrate is kept, the vibration membrane 3 is deformed into a downwardly concaved shape, thereby forming the contact region 9 which is in contact with the insulation film 6.
  • Such a downwardly concaved deformation can be formed, for instance, by plastic deformation, and the contact region 9 can serve to fusion bond the vibration membrane 3 to the insulation film 6, thereby to form a fusion bonded region.
  • the term "external force” is an external force when attention is focused on the vibration membrane 3, and it means a force acting from the outside of the vibration membrane 3. For instance, as such, there can be exemplified an electrostatic attraction, a magnetic force, etc.
  • the region in which the above-mentioned state of contact is kept is fusion bonded to the substrate through protrusions that are formed on at least one of an upper surface and a lower surface of the vibration membrane.
  • the protrusions 5 are formed on an outer edge or periphery of the contact region (fusion bonded region) 9 prior to the formation of the contact region (fusion bonded region) 9 (see Fig. IB) , so that when the vibration membrane 3 is placed in contact with (fusion bonded to) the insulation film 6, the area of contact (fusion bonding) is controlled by means of the protrusions 5. That is, the area of contact (fusion bonding) or the shape of contact (fusion bonding) is controlled by means of these protrusions 5.
  • the upper electrode 1 is formed on or in at least one of the upper (front) surface, the lower (rear) surface, and the internal portion of the vibration membrane 3, or the main body of the vibration membrane 3 itself is formed by the upper electrode 1.
  • the through portion is formed in at least either one of the electrodes in at least a part of an overlap region in which the above-mentioned contact state is kept to form an overlap of the upper electrode and the lower electrode.
  • the through portion 24 is formed through the upper electrode 1 and is arranged in opposition to the lower electrode 8, whereby a capacitive electrode is formed.
  • This through portion 24 can be formed as a through hole, and it can be formed through the lower electrode 8 instead of the upper electrode 1, or it can be formed in both the upper and lower electrodes.
  • the vibration membrane 3 is supported by the vibration membrane support member 2 lying in an outer edge thereof.
  • the contact region (fusion bonded region) 9 is formed between the vibration membrane 3 and the substrate 4 in the central portion of the vibration membrane 3, and the area or shape of the contact region
  • the upper electrode 1 having the through portion (through hole) 24 formed therein is arranged so as to surround the outer periphery of the contact region 9 in a ring-shaped fashion.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 2 is a conceptual cross sectional view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) in the second embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • the difference thereof from the above-mentioned first embodiment is that the substrate 4 itself is in the form of a low-resistance substrate, or the substrate 4 has a surface highly doped to form the lower electrode 8 by itself.
  • the resistivity of the substrate 4 is preferably equal to or less than 1.0 ⁇ -cm, and more preferably equal to or less than 0.02 ⁇ -cm.
  • the above-mentioned ranges are preferable ranges where Si can be doped in a process.
  • the electrical resistance of the Si substrate be as low as possible, and if the electrical resistance is low, a potential difference due to the resistance becomes small, thus making it possible to reduce capacitance measurement errors between elements in the substrate surface.
  • the transducer can be manufactured in a simpler manner than in the first embodiment 1, and is high in the practical use, so the manufacturing processes to be described later will be explained based on this embodiment.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 3 is a conceptual cross sectional view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) in the third embodiment of the present invention.
  • a second insulation film 19 is provided.
  • this second insulation film 19 it becomes possible to prevent the leakage of an electric current between the electrodes irrespective of the electrical conductivity of the vibration membrane 3.
  • this second insulation film 19 it is preferable to use a high permittivity material (s) such as, for example, one or more kinds of SiO 2 , SiN x , Al 2 O 3 , Y 2 O 3 , HfO 2 , HfSiO x , HfSiON, and HfAlO x .
  • a high permittivity material such as, for example, one or more kinds of SiO 2 , SiN x , Al 2 O 3 , Y 2 O 3 , HfO 2 , HfSiO x , HfSiON, and HfAlO x .
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 4 is a conceptual cross sectional view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) in the fourth embodiment of the present invention.
  • the difference thereof from the first embodiment is that the lower electrode 8 has a through hole 24 formed therein.
  • some methods such as a method for locally doping the substrate 4, or a method for depositing a polycrystalline Si layer that has been locally doped at a high concentration, and patterning the same, or the like.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 5 is a conceptual cross sectional view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) in this embodiment of the present invention.
  • the difference thereof from the fourth embodiment is that the protrusions 5 are formed on the upper portion of the vibration membrane 3. According to the construction of this embodiment, it is possible to decrease alignment errors between the protrusions 5 and the lower electrode 8 and between the upper electrode 1 and the lower electrode 8. In addition, when the vibration membrane 3 is placed in contact with the lower substrate 8, a local flexural boundary condition is provided by the protrusions 5 formed on the upper portion of the vibration membrane 3.
  • the contact region can be controlled according to a region in which the protrusions are arranged.
  • the arrangement region of the protrusions can be controlled in an actual process, and in addition, the area of contact can be effectively controlled by deciding a threshold for the bending moment applied to the vibration membrane.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 6 is a conceptual cross sectional view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) in the sixth embodiment of the present invention.
  • CMUT capacitive micromachined ultrasonic transducer
  • protrusions 5 are formed on an upper portion of the vibration membrane 3. According to this embodiment, it is possible to decrease alignment errors between the protrusions 5 and the lower electrode 8 and between the upper electrode 1 and the lower electrode 8. [0071] [Embodiment 7]
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 7 is a conceptual cross sectional view illustrating the basic construction of the capacitive micromachined ultrasonic transducer (CMUT) in this embodiment .
  • the difference thereof from the third embodiment is that in the form of construction having the second insulation film, the protrusions 5 are formed on the upper portion of the vibration membrane 3. According to this embodiment, it is possible to decrease alignment errors between the protrusions 5 and the lower electrode 8 and between the upper electrode 1 and the lower electrode 8 [0074] [Embodiment 8]
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 8A through Fig. 8M are views illustrating the manufacturing processes or steps for the capacitive micromachined ultrasonic transducer (CMUT) in this embodiment of the present invention.
  • a "patterning process” herein is assumed to include various processes ranging from the processes of photolithography, such as applying a photoresist on the substrate, drying, exposing, developing the photoresist, etc., to other processes such as an etching process, a process of removing the photoresist, a process of washing the substrate, a process of drying the substrate, and so on.
  • a Si substrate 12 is first washed and prepared, as shown in Fig. 8A.
  • the Si substrate 12 is put into a thermal oxidation furnace so that a Si oxide film 11 is formed therein, as shown in Fig. 8B.
  • the thickness of this Si oxide film is in the range of from 10 run to 4, 000 ran, more preferably in the range of from 20 ran to 3,000 nm, and most preferably in the range of from 30 nm to 2,000 nm.
  • a rough or approximate distance between the electrodes is decided according to the above-mentioned thermal oxidation process. If in the above ranges, the thickness is in a feasible or allowable range in actual processes, and a reasonable electric field can be obtained. [0080]
  • the Si oxide film 11 is subjected to patterning, as shown in Fig. 8C.
  • a second thermal oxidation process is performed to form an insulation film 6 in the form of a thin thermal oxide film, as shown in Fig. 8D.
  • the thickness of the insulation film 6 is in the range of from 1 nm to 500 nm, more preferably in the range of from 5 nm to 300 nm, and most preferably in the range of from 10 nm to 200 nm.
  • the insulation film for preventing electrical discharge is decided according to the above-mentioned thermal oxidation process. If the insulation film is too thin, there is obtained no effect of preventing electrical discharge, whereas when it is too thick, the distance between the electrodes becomes too large.
  • the substrate that has been completed in the processes up to the one in Fig. 8D is called an A substrate 16.
  • the thickness of a device layer 15 of this SOI substrate is in the range of from 10 nm to 5,000 run, more preferably in the range of from 20 nm to 3, 000 nm, and most preferably in the range of from 30 nm to 1,000 nm.
  • the above-mentioned ranges of thickness of the device layer 15 can be achieved in the processes.
  • the square of an oscillation frequency is directly proportional to the ratio of spring rigidity to effective mass of the vibration membrane. A spring rigidity and an effective mass are required which correspond to the oscillation frequency at which an ultrasonic wave can be emitted.
  • the spring rigidity and the effective mass of the vibration membrane are both functions of the film thickness of the vibration membrane.
  • the above-mentioned ranges of the film thickness in the device layer 15 are those which can provide an appropriate spring rigidity and an appropriate effective mass as the vibration membrane of the CMUT in this embodiment.
  • the thickness of a BOX (Buried Oxide) layer 14 of the above-mentioned SOI substrate is in the range of from 100 ran to 3,000 run, and more preferably, in the range of from 200 to 1,000 run.
  • the above BOX layer is used as an etching stop layer which is to be described later.
  • the above- mentioned film thickness of the BOX layer is in an appropriate range.
  • a SiN layer 17 is deposited on the device layer 15 according to an LPCVD (Low Pressure Chemical Vapor Deposition) method, and is subjected to patterning.
  • LPCVD Low Pressure Chemical Vapor Deposition
  • the shape into which the above- mentioned SiN layer 17 is patterned is formed of a plurality of circular holes, and these holes are distributed or arranged in a substantially ring shape. It is preferred that the diameter of each of the circular holes be in the range of from 10 run to 3,000 nm.
  • the above range of the circular hole diameter is actually feasible or allowable in actual processes. A process with a circular hole diameter below (smaller than) this range is very difficult. If circular holes of diameters beyond (larger than) this range are formed, protrusions of almost the same shapes as those of the circular holes are then formed, so the larger the protrusions, the more influence is exerted on the mass of the vibration membrane, thus reducing the accuracy of the process.
  • the substrate with the above-mentioned SiN layer is thermally oxidized.
  • a part of the device layer 15 of the SOI substrate exposed from the SiN layer 17 is selectively oxidized, whereby the protrusions 5 are formed.
  • a LOCOS (Local Oxidation of Silicon) process which is a semiconductor process, is generally used for the above selective oxidation process.
  • the protrusions 5 similarly have a granular structure including a lot of substantially hemispheres, and are distributed or arranged in a substantially ring shape.
  • the height of the protrusions is in the range of from 1 nm to 1,000 nm, more preferably in the range of from 5 nm to 500 nm, and most preferably in the range of from 10 nm to 200 nm.
  • the contact region can be controlled according to the height of the protrusions.
  • the range of the height of the protrusions can be controlled in an actual process.
  • the area of contact can be effectively controlled by deciding a threshold for the bending moment applied to the vibration membrane.
  • the external force when the external force is applied to the vibration membrane thereby to place the vibration membrane in contact with the protrusions, the protrusions are forced to form gaps.
  • the external force to be applied should be much greater than that required in the case of no protrusions, and if otherwise, the outer peripheral portion of the vibration membrane is not pressed into a collapsed or crushed state.
  • the distribution or arrangement shape of the protrusions 5 may be a substantially ring shape or a substantially polygonal shape.
  • the area control of the contact region 9 can be made by other methods, too.
  • the protrusions 5 may not be provided if a balance between the cavity 10 and external pressure is controlled in a precise manner.
  • the following materials for the protrusions are suitable in relation to the following fusion bonding process.
  • the materials for the protrusions 5 there can be used at least one of an oxide film, a nitride film, an oxynitride film of Si, Ge, GaAs and so on, or at least one of Cu, W, Sn, Sb, Cd, Mg, In, Al, Cr, Ti, Au and Pt.
  • combinations of the above materials for instance, a multilayered structure, can be used.
  • the SiN layer 17 is etched and removed by the use of a heated liquid containing phosphoric acid.
  • a substrate that has been completed in this manner is called a B substrate 20.
  • An environmental pressure condition in the above bonding process may be one atmospheric pressure, but it is desirable to perform the bonding in vacuum.
  • the pressure is preferably equal to or less than 10 4 Pa, more preferably equal to or less than 10 2 Pa, and most preferably equal to or less than 1 Pa.
  • the above ranges of the degree of vacuum can permit the use of an ordinary vacuum bonding apparatus, and can provide a reasonable convenience of process operation.
  • the temperature in the above bonding process is preferably in the range of from room temperature to 1,200 degrees C, more preferably from 80 degrees C to 1,000 degrees C, and most preferably from 150 degrees C to 800 degrees C.
  • the stress due to the bonding remains, so unfavorable influences might be given to the vibration membrane.
  • the above bonding temperature ranges can provide an appropriate bonding strength and a stable vibration membrane internal stress.
  • LPCVD SiN films are deposited over the entire surfaces of the substrates thus bonded, and an LPCVD SiN film on the B substrate side is removed by means of dry etching.
  • a handling layer 13 is wet etched with a heated alkaline liquid with the use of a single-sided etching jig.
  • the alkaline liquid is very high in the etching selection ratio of Si to SiO (in the range of from about 100 to 10,000), so the wet etching removes the handling layer 13, and stops at the BOX layer 14.
  • the device layer 15 of the B substrate is deformed downwardly into a concave shape under the action of atmospheric pressure. That is, the device layer 15 becomes a concave state without application of external forces other than atmospheric pressure, so it can serve as the vibration membrane 3 of the ultrasonic transducer of this embodiment.
  • the embodiment is not limited to this, and the vibration membrane 3 can be further deformed downwardly by designing the thickness of the oxide film 11 and the size of the vibration membrane 3 in an appropriate manner, and by applying an appropriate external pressure.
  • the central portion of the vibration membrane 3 is brought into contact with the oxide film 11, whereby the contact region 9 can be formed, as shown in Fig. 8K. That is, it is possible to form a shape that can be operated in the above- mentioned collapse mode.
  • the center of the vibration membrane 3 is a maximum point or location of displacement, so the contact region 9 is formed into a substantially concentric circular shape from the center of the vibration membrane 3.
  • the heating temperature capable of plastically deforming the vibration membrane is preferably in the range of from 600 degree C to 1,500 degrees C, more preferably in the range of from 650 degrees C to 1,400 degrees C, and most preferably in the range of from 700 degrees C to 1,300 degrees C.
  • the thin Si film in the form of the vibration membrane 3, when once plastically deformed at high temperature, remains in the collapsed or crushed shape even if its temperature has returned to room temperature, and the shape of the vibration membrane does not restore to its original shape before the plastic deformation.
  • a Si surface and a Si oxide membrane surface at opposite sides of the contact region 9 form chemical bonding in the above-mentioned high temperature range, so that they are bonded or fusion bonded to each other. In that case, the higher the temperature, or the longer the time of contact therebetween, the stronger the strength of the chemical bonding becomes.
  • the strength of the chemical bonding is preferably in the range of from 1 MPa to 22 MPa, more preferably in the range of from 2 MPa to 21 MPa, and most preferably in the range of from 3 MPa to 20 MPa.
  • the crystalline dislocation density is preferably equal to or less than 10 5 /cm 2 , more preferably equal to or less than lOVcm 2 , and most preferably equal to or less than 10 3 /cm 2 .
  • the plastic deformation characteristic of Si depends on an internal initial dislocation density of Si. In case where there is no initial dislocation density, i.e., in the case of substantially perfect single crystal Si and at a temperature of 800 degrees C or above, plastic deformation starts at the instant when an external stress of about 100 MPa is applied. The stress at which such plastic deformation starts is called a plastic deformation starting stress. The more the Si internal initial dislocation density, the smaller the plastic displacement starting stress becomes.
  • the plastic deformation starting stress is about 35 MPa, and is the same value as the above-mentioned flow stress, so the starting point of the plastic deformation becomes difficult to be observed.
  • an external pressure is sometimes applied so as to plastically deform the internal Si of the vibration membrane 3.
  • the Si internal stress generated by the external pressure is preferably in the range of from 10 MPa to 110 MPa, more preferably in the range of from 20 MPa to 110 MPa, and most preferably in the range of from 30 MPa to 90 MPa.
  • This Si internal stress generated by the external pressure is the same meaning as the above-mentioned plastic deformation starting stress.
  • the plastic deformation starting stress be between 100 MPa (substantially perfect single crystal Si) and 35 MPa (flow stress) .
  • the device layer 15 forming the vibration membrane 3 is patterned near the outer edge of the vibration membrane 3 by means of dry etching.
  • the oxide film 11 is directly patterned by means of wet etching without removing a photoresist for the patterning of the device layer 15.
  • An etching hole 21 is formed according to the above-mentioned process, as shown in Fig. 8L. [0111]
  • a metal film for electrodes is deposited and patterned to form the upper electrode 1, an upper electrode pad 23 and a lower electrode pad 22, as shown in Fig. 8M.
  • an electrode through opening 25 is formed as a through portion.
  • the device layer 15 is patterned to complete an element array.
  • a figure for such electrical separation is omitted.
  • the metal film al least one is selected and used from the group comprising Al, Cr, Ti, Au, Pt, Cu, etc.
  • the flexure of the vibration membrane 3 is equal to or less than several hundreds nm, and the size of the transducer (e.g., the diameter of the vibration membrane 3) is in the range of from several tens micrometers to several hundreds micrometers. Therefore, in an exposure process in the patterning process of the metal film, exposure shifts or variations such as optical diffractions can be corrected with the use of an ordinary photolithography or exposure machine .
  • Fig. 8M there is shown an optimal basic form "of capacitive micromachined ultrasonic transducer according to this embodiment, wherein the lower electrode 8 is composed of a main body of the Si substrate 12.
  • the sheet electrical resistance of the Si substrate 12, which forms the lower electrode 8 is preferably equal to or less than l.O ⁇ /sq, more preferably equal to or less than O.l ⁇ /sq, and most preferably equal to or less than 0.02 ⁇ /sq.
  • the substrate 4 itself is shown as the lower electrode, but the region of the lower electrode 8 is not shown.
  • the lower electrode 8 having high electrical conductivity can be embedded or incorporated in the substrate 4, as shown in Fig. IA, Fig. 4, or Fig. 5.
  • the resistivity of the vibration membrane 3 is preferably equal to or higher than lOO ⁇ -cm, more preferably equal to or higher than l,000 ⁇ -cm, and most preferably equal to or higher than 10,000 ⁇ -cm.
  • the vibration membrane 3 is made of Si having low electrical resistance
  • the vibration membrane itself can be used as the upper electrode, and it is not essential to arrange a metal electrode right above the vibration membrane.
  • another or second insulation film can be provided on the vibration membrane 3 of low resistance.
  • this second insulation film for instance, at least one of dielectric materials such as a SiN film, a SiO film, a SiNO film, Y 2 O 3 , HfO, HfAlO and so on can be provided, and in addition, the upper electrode can be arranged on this second insulation film.
  • the insulation film 6 made of a material of high permittivity such as, for example, a SiN film may be omitted. In this case, it is essential to arrange the upper electrode on the vibration membrane.
  • CMUT complementary metal-oxide-semiconductor
  • MEMS MicroElectroMechanical Systems
  • SM Surface Micromachining method; a method of removing a sacrificial layer to form a cavity
  • FIG. 8M shows the optimal basic form in this embodiment.
  • a passivation layer for electrical wiring or the electrical wiring for the upper electrode 1 and the upper electrode pad 23 or the like to be formed thereon are not shown in the figure.
  • the vibration membrane when the vibration membrane is caused to operate in a collapse mode, a part of the vibration membrane can be kept in contact with the substrate without any external force being applied thereto, so it becomes possible to reduce the required voltage in a stable manner.
  • a fixing material such as resin, resist or the like. Accordingly, there is no influence from such a fixing material, so the variation of vibration is limited, thus making it possible to achieve the CMUT that is subjected to little or no change with the lapse of time or the like.
  • the plastically deformed vibration membrane contacts with or is fusion bonded to the underlayer substrate. Therefore, it is possible to greatly-decrease a DC voltage, whereby discharge breakdown of the insulation film can be reduced.
  • parasitic capacitance can be decreased to increase a variable capacitance ratio (active ratio) between the lower electrodes, thereby making it possible to achieve an ultrasonic transducer (CMUT) of high performance with a high electromechanical transduction efficiency.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. 9A and Fig. 9B are views illustrating the basic construction of a capacitive micromachined ultrasonic transducer (CMUT) in this practical example.
  • Fig. 9A is a cross sectional plan view of the capacitive micromachined ultrasonic transducer (CMUT)
  • Fig. 9B is a conceptual plan view thereof.
  • CMUT of this practical example the difference thereof from the CMUT in the embodiment of the present invention as shown in Fig. IA and FIG. IB is that protrusions 5 are formed on an upper portion of a vibration membrane 3 so as to be distributed in a substantially ring- shaped manner, and that a lower electrode 8 is embedded or incorporated in an underlayer substrate.
  • an electrode through hole 24 is formed in an upper electrode 1.
  • Fig. 13A through Fig. 13C show the electrical capacitance characteristics of the capacitive micromachined ultrasonic transducer (CMUT) element of the practical example according to the present invention.
  • Fig. 13A is a cross sectional view explaining a capacitance analysis in the CMUT element of this practical example.
  • the protrusions are not shown, but the radius Rc of a contact region is set to 2 micrometers.
  • the changes of the capacitance and the variable capacitance ratio are calculated in accordance with the change of the radius Rin of the through hole 24 in the upper electrode 1.
  • the area of a circular electrode having a radius of 5 micrometers is taken as a reference for the above-mentioned upper electrode, and the area of a circular electrode having a radius of 2 micrometers is taken as a reference for the contact region.
  • Table 1 below shows detailed items and numerical values for computation.
  • Fig. 1OB is a view illustrating the dependency of electrical capacitance vs electrode through-hole internal diameter of the CMUT element in the practical example. It has been found that the capacitance of the CMUT element dramatically decreases when the radius Rin of the through hole becomes larger than the radius Rc of the contact region. For instance, the capacitance at a through-hole radius of 4 micrometers is about 1/13 of the capacitance at a through-hole radius of 0 micrometers. [0129]
  • Fig. 1OC is a view illustrating the dependency of variable capacitance ratio (active ratio) vs electrode through-hole internal diameter of the CMUT element of this practical example. From Fig. 1OB and Fig. 1OC, it is evident that when the through-hole radius Rin is larger than the contact region radius Rc, the capacitance decreases but the variable capacitance ratio (active ratio) increases. For instance, the variable capacitance ratio at a through-hole radius of 4 micrometers is 1, and the variable capacitance ratio at a through-hole radius of 0 micrometers is as low as about 0.21. That is, the reason why the capacitance is large when the through-hole radius is less than the contact region radius is that the capacitance in the contact region is large.
  • the vibration membrane in the contact region is unable to vibrate, and provides no variable capacitance, thus resulting in a so-called parasitic capacitance.
  • the parasitic capacitance can be decreased by the provision of the electrode through hole. Further, by setting the through- hole radius to be larger than the contact region radius, the parasitic capacitance substantially disappears or becomes zero, with the result that the variable capacitance ratio reaches a maximum value of 1.
  • CMUT capacitive micromachined ultrasonic transducer
  • Fig. HA through Fig. HM are views illustrating the manufacturing processes or steps for the capacitive micromachined ultrasonic transducer (CMUT) in this example.
  • the Si substrate 12 is washed and prepared. After that, a surface of the Si substrate is made low in resistance by means of a diffusion method or an ion implantation method. Thus, the surface region that has been made low in resistance is incorporated, as the lower electrode 8, into the underlayer substrate, as shown in Fig. 3 described above.
  • the surface resistance value of the Si substrate having been made low in resistance is preferably equal to or less than 10 ⁇ -cm, more preferably equal to or less than 1 ⁇ -cm, most preferably equal to or less than 0.1 ⁇ -cm.
  • the lower electrode 8 is the surface of the substrate 12, and no specific area is illustrated.
  • one SOI substrate e.g., SIMOX SOI substrate or Smart-Cut SOI substrate
  • This substrate is called a C substrate 25.
  • Fig. HF the rear and the front of the C substrate 25 are reversed, and joined or bonded to the A substrate 16, whereby a cavity 10 is formed.
  • the bonding process there is no need for alignment.
  • the surface of a bonding surface is activated at room temperature, and the bonding is performed at a temperature of 150 degrees C or less and at a pressure of 10 "3 Pa (e.g., EVG 810, 520 manufactured by EVG) .
  • the handling layer 13 of the substrate thus joined or bonded as described and shown in Fig. HF is ground in such a manner that the handling layer 13 having a thickness of about several tens micrometers is left and washed.
  • the handling layer 13 is etched by a KOH liquid of 80 degrees C while protecting the rear surface of the ground substrate with the use of a single- sided etching jig (e.g., a wafer holder manufactured by Silicet AG in Germany) .
  • a single- sided etching jig e.g., a wafer holder manufactured by Silicet AG in Germany
  • the BOX layer 14 is etched by means of liquid containing fluorine, so that the device layer 15 is exposed, as shown in Fig. HG.
  • This device layer 15 is used as the vibration membrane 3 of this embodiment.
  • the SiN film 17 is deposited according to the LPCVD method, and is subjected to patterning by means of dry etching. [ 0139 ]
  • the protrusions 5 are caused to grow by means of an epitaxy method.
  • the protrusions 5 grow up from the Si surface of the device layer 15 exposed to the SiN film 17.
  • the height of the protrusions 5 thus grown is preferably in the range of from 1 nm to 1,000 nm, more preferably in the range of from 5 ran to 500 nm, and most preferably in the range of from 10 nm to 200 nm.
  • a method of growing a crystal only from an exposed place as described above is called a selective epitaxy. It is also possible to use a SiO film, a SiON film or the like in place of the patterned SiN film 17 [0140]
  • epitaxy method there can be used one of an MBE (Molecular Beam Epitaxy) method, an LPE (Liquid Phase Epitaxy) method, an SPE (Solid Phase Epitaxy) method and so on.
  • MBE Molecular Beam Epitaxy
  • LPE Liquid Phase Epitaxy
  • SPE Solid Phase Epitaxy
  • the above-mentioned pattering of the protrusions 5 can be performed by the use of a PVD (Physical Vapor Deposition) method or a CVD (Chemical Vapor Deposition) method, and by adding an etching method or a lift-off method.
  • PVD Physical Vapor Deposition
  • CVD Chemical Vapor Deposition
  • the above-mentioned SiN film 17 is removed by etching with the use of a liquid containing phosphoric acid of about 160 degrees C, whereby the vibration membrane 3 provided with the protrusions 5 is completed, as shown in Fig. HJ.
  • the shape of the vibration membrane 3 has a thickness of 340 nm, and is a square having each side of about 40 micrometers. Also, the amount of displacement of the central portion of the vibration membrane 3 by atmospheric pressure is about 360 nm.
  • the above-mentioned substrate is placed in an autoclave, and the central portion of the vibration membrane 3 is brought into contact with the insulation film 6 under the cavity 10 by applying a pressure of about 2.65 atm or higher in case where the height of the cavity 10 is 600 nm.
  • the distribution or arrangement of the protrusions 5 is substantially in the shape of a ring or circle having an internal diameter of 4 micrometers and a width of about 2 micrometers, at the center of the vibration membrane 3 as shown in Fig. 9B.
  • the central portion of the vibration membrane 3 is placed in contact with the insulation film 6, whereby a contact region 9 having a diameter of 4 micrometers, substantially the same as that of the circularly arranged protrusions 5 is formed.
  • the size of the contact region 9 depends strongly on the distribution of the external pressure, minute pressure variation, and the size and the boundary conditions of the vibration membrane 3, so the difference or variation between elements (transducers) becomes great.
  • the protrusions 5 it is possible to form the contact region 9 with substantially the same shape as the distributed or arranged shape of the protrusions 5 even if there is a difference or variation between the elements.
  • the device layer 15 forming the vibration membrane 3 is patterned near the outer edge of the vibration membrane 3 by means of dry etching.
  • an oxide film 11 is directly patterned by means of wet etching without removing a photoresist for the patterning of the device layer 15.
  • An etching hole 21 is formed according to the above-mentioned process, as shown in Fig. HL. [ 0146 ]
  • Al for electrodes is deposited by sputtering, and is then subjected to patterning by means of wet etching, whereby an upper electrode 1, an upper electrode pad 23 and a lower electrode pad 22 are formed, as shown in Fig. HM. [0147]
  • the pattern of the upper electrode 1 is formed into a ring shape, and the internal diameter thereof is made larger than the shape of the protrusions 5. That is, since the through-hole radius of the upper electrode 1 is made larger than the above-mentioned contact region radius, the above-mentioned variable capacitance ratio (active ratio) is a maximum value of 1. [0148]
  • the above-mentioned Al electrodes can thereafter be annealed to form ohmic contact. It is preferred that the temperature of the annealing be in the range of from 200 degrees C to 450 degrees C. This is the temperature range of annealing when ordinary Al electrodes perform ohmic contact.
  • the device layer 15 is patterned to complete an element array. However, it is omitted here to illustrate such electric separation or isolation. Moreover, a passivation layer for electrical wiring or the electrical wiring for the upper electrode 1 and the upper electrode pad 23 or the like to be formed thereon are not shown in the figure. Here, it is preferred that the above-mentioned passivation layer be composed of a SiO film or a SiN film which can be formed at low temperature by means of a PVD method. [0150]

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Abstract

L'invention concerne un transducteur électromécanique comprenant une membrane vibratoire présentant une électrode supérieure, un substrat pourvu d'une électrode inférieure et un élément de support adapté pour supporter la membrane vibratoire de manière à former un espace entre la membrane vibratoire et le substrat, lesdites électrodes étant opposées l'une à l'autre. Ledit transducteur est construit de manière qu'une partie de la membrane vibratoire et une zone du substrat viennent en contact l'une avec l'autre sans application d'une force externe, et qu'une autre zone de la membrane vibratoire, autre que celle où le contact est maintenu, puisse vibrer. La zone de contact présente une zone de chevauchement entre la première électrode et la seconde électrode et au moins une desdites électrodes présente un orifice de passage formé dans au moins une partie de la zone de chevauchement.
PCT/JP2008/067589 2007-09-25 2008-09-19 Transducteur électrostatique et procédé de fabrication WO2009041675A1 (fr)

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US12/673,232 US8410659B2 (en) 2007-09-25 2008-09-19 Electromechanical transducer and manufacturing method therefor

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JP2007246920 2007-09-25
JP2007-246920 2007-09-25
JP2008-236379 2008-09-16
JP2008236379A JP5408937B2 (ja) 2007-09-25 2008-09-16 電気機械変換素子及びその製造方法

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102440005A (zh) * 2009-05-25 2012-05-02 株式会社日立医疗器械 超声波换能器及利用该超声波换能器的超声波诊断装置
US20130087867A1 (en) * 2011-10-11 2013-04-11 The Board Of Trustees Of The Leland Stanford Junio Method for operating CMUTs under high and varying pressure
US20130116568A1 (en) * 2010-07-23 2013-05-09 Universite De Tours Francois Rabelais Method and device for generating ultrasounds implementing cmuts, and method and system for medical imaging
CN103155597A (zh) * 2010-10-15 2013-06-12 株式会社日立医疗器械 超声波转换器以及使用其的超声波诊断装置
US8617078B2 (en) 2010-03-12 2013-12-31 Hitachi Medical Corporation Ultrasonic transducer and ultrasonic diagnostic device using same
CN103917304A (zh) * 2011-10-28 2014-07-09 皇家飞利浦有限公司 具有应力层的预塌陷电容式微加工换能器单元
CN103958079A (zh) * 2011-11-17 2014-07-30 皇家飞利浦有限公司 具有环形塌陷区域的预塌陷电容式微机械换能器元件
WO2020100112A1 (fr) * 2018-11-16 2020-05-22 Vermon S.A. Transducteur à ultrasons micro-usiné capacitif et son procédé de fabrication

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WO2003009319A1 (fr) * 2001-07-17 2003-01-30 Redwood Microsystems, Inc. Capteur micro electromecanique
US20050200241A1 (en) * 2004-02-27 2005-09-15 Georgia Tech Research Corporation Multiple element electrode cMUT devices and fabrication methods

Patent Citations (2)

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WO2003009319A1 (fr) * 2001-07-17 2003-01-30 Redwood Microsystems, Inc. Capteur micro electromecanique
US20050200241A1 (en) * 2004-02-27 2005-09-15 Georgia Tech Research Corporation Multiple element electrode cMUT devices and fabrication methods

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102440005A (zh) * 2009-05-25 2012-05-02 株式会社日立医疗器械 超声波换能器及利用该超声波换能器的超声波诊断装置
CN102440005B (zh) * 2009-05-25 2014-09-24 株式会社日立医疗器械 超声波换能器及利用该超声波换能器的超声波诊断装置
US8617078B2 (en) 2010-03-12 2013-12-31 Hitachi Medical Corporation Ultrasonic transducer and ultrasonic diagnostic device using same
US20130116568A1 (en) * 2010-07-23 2013-05-09 Universite De Tours Francois Rabelais Method and device for generating ultrasounds implementing cmuts, and method and system for medical imaging
CN103155597A (zh) * 2010-10-15 2013-06-12 株式会社日立医疗器械 超声波转换器以及使用其的超声波诊断装置
CN103155597B (zh) * 2010-10-15 2016-06-08 株式会社日立医疗器械 超声波转换器以及使用其的超声波诊断装置
US20130087867A1 (en) * 2011-10-11 2013-04-11 The Board Of Trustees Of The Leland Stanford Junio Method for operating CMUTs under high and varying pressure
US9242273B2 (en) * 2011-10-11 2016-01-26 The Board Of Trustees Of The Leland Stanford Junior University Method for operating CMUTs under high and varying pressure
CN103917304A (zh) * 2011-10-28 2014-07-09 皇家飞利浦有限公司 具有应力层的预塌陷电容式微加工换能器单元
CN103958079A (zh) * 2011-11-17 2014-07-30 皇家飞利浦有限公司 具有环形塌陷区域的预塌陷电容式微机械换能器元件
WO2020100112A1 (fr) * 2018-11-16 2020-05-22 Vermon S.A. Transducteur à ultrasons micro-usiné capacitif et son procédé de fabrication

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