JP2013146478A - Ultrasonic probe and ultrasonic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic probe acquiring high receiving sensitivity by highly efficiently exiting vibration in a thickness mode of an organic piezoelectric layer, and to provide an ultrasonic diagnostic apparatus.SOLUTION: An ultrasonic transmission/reception unit 5 in an ultrasonic probe includes a plurality of sheet-like vibrating portions 6a-6d disposed into an array shape. Each vibrating portion 6a-6d is provided with: a membrane 82 formed in a front face side of a substrate 8 and configured that, because of a recessed portion 81a, the thickness becomes thinner than those of other areas in the substrate 8; an inorganic piezoelectric layer 62 having an inorganic piezoelectric material; and an organic piezoelectric layer 72 having an organic piezoelectric material. The inorganic piezoelectric layer 62 is formed on the front face of the membrane 82, and the organic piezoelectric layer 72 is formed on the front face of the inorganic piezoelectric layer 62.

Description

  The present invention relates to an ultrasonic probe capable of transmitting and receiving ultrasonic waves, and an ultrasonic diagnostic apparatus including the ultrasonic probe.

  An ultrasonic diagnostic apparatus is a medical imaging apparatus that obtains a tomographic image of soft tissue in a living body with minimal invasiveness from a body surface by an ultrasonic pulse reflection method. This ultrasonic diagnostic device is smaller and cheaper than other medical imaging devices, has no safety such as X-ray exposure, has high safety, and allows blood flow imaging by applying the Doppler effect. It is widely used in circulatory system (heart coronary artery), digestive system (gastrointestinal), internal medicine system (liver, pancreas, spleen), urology system (kidney, bladder), and obstetrics and gynecology. An ultrasonic probe used in such a medical ultrasonic diagnostic apparatus generally uses an inorganic piezoelectric element called PZT in order to transmit and receive high-sensitivity and high-resolution ultrasonic waves. In this case, a single-type probe or an array-type probe in which a plurality of probes are two-dimensionally arranged is often used as the transmitting piezoelectric element. Since the array type can obtain a fine image, it is widely used as a medical image for a diagnostic examination.

  On the other hand, harmonic imaging diagnosis using harmonic signals is becoming a standard diagnosis modality because a clear diagnosis image that cannot be obtained by conventional B-mode diagnosis is obtained.

  In harmonic imaging, the side lobe level is small compared to the fundamental wave, the S / N ratio is good, the contrast resolution is good, and the frequency is high, so that the beam width is narrowed and the lateral resolution is good. Because the sound pressure is small and the fluctuation in sound pressure is small at short distances, multiple reflections do not occur (artifacts are difficult, speckle noise is reduced), and attenuation beyond the focal point is similar to the fundamental wave. It has many advantages such as a greater depth speed than ultrasonic waves having a harmonic frequency as a fundamental wave.

  As a specific structure of the array-type ultrasonic probe for harmonic imaging, a piezoelectric vibration section in which each vibration section element constituting the array is a broadband integrated type is used. A method is generally used in which fundamental wave transmission is performed in the frequency region on the low frequency side of the broadband characteristics and harmonics are received in the frequency region on the high frequency side.

  As a specific structure of an array-type ultrasonic probe for harmonic imaging, for example, Patent Document 1 proposes a transmission / reception separation type probe in which a transmission piezoelectric vibration part and a reception piezoelectric vibration part are separately arranged. Yes. In Patent Document 1, a piezoelectric layer that transmits and receives ultrasonic waves having a center frequency f1 is formed of a plurality of piezoelectric elements having a first acoustic impedance to transmit fundamental waves and receive ultrasonic waves including harmonics. And a second piezoelectric layer comprising a plurality of second piezoelectric elements having a second acoustic impedance, overlaid on the first piezoelectric layer, and receiving a ultrasonic wave having a center frequency f2 = 2f1. .

  Moreover, there exists what was proposed by patent document 2 as a thing with higher sensitivity. The device described in Patent Document 2 uses a transmitting piezoelectric element having an inorganic piezoelectric material and a receiving piezoelectric element having an organic piezoelectric material.

Japanese Patent Laid-Open No. 11-276478 JP 2008-188415 A

  However, those described in Patent Documents 1 and 2 use a bulk vibration part, and when such a bulk vibration part is used, it is necessary to mechanically process slits for arraying. In addition, since wiring for transmitting signals from the respective elements arranged in an array to the transmission / reception circuit occupies a large space, it is difficult to miniaturize.

  By the way, as an ultrasonic transducer of a probe, for example, a vibrating part of a unimorph structure in which a piezoelectric layer such as PZT is formed on a membrane formed on a substrate is oscillated so as to be deformed in a drum shape to transmit / receive ultrasonic waves. A pMUT (Piezoelectric Micromachined Ultrasonic Transducer) is known. This pMUT is manufactured by a micro electro mechanical system (MEMS) using semiconductor manufacturing technology.

  Such an ultrasonic probe of pMUT can widen the frequency band, can be miniaturized to have a high resolution, and can acquire a three-dimensional image as compared with a bulk PZT divided by dicing. For example, it is suitable for two-dimensional arrangement of vibrating parts, and since it can be reduced in size and thickness, it has advantages such as being suitable for application to an ultrasonic endoscope. In such an ultrasonic probe of pMUT, since the image that can be acquired is a tomographic image in the one-dimensional array of vibration units, there is a risk of false negatives due to the operation. Engineers' skill is required. In order to alleviate such problems, there is a high need for a two-dimensional array of ultrasonic probes capable of acquiring a three-dimensional image.

  Therefore, in this pMUT, that is, in a probe of a type that forms a vibration part by forming a piezoelectric layer on a membrane, it is conceivable to form a receiving layer with an organic piezoelectric layer having an organic piezoelectric material.

  For example, as shown in FIG. 9, a membrane 101a formed on one surface in the thickness direction of the substrate 100, an inorganic piezoelectric layer 102 having an inorganic piezoelectric material on both sides of the membrane 101a, and an organic piezoelectric layer having an organic piezoelectric material 103, and by applying a voltage to the inorganic piezoelectric layer 102, ultrasonic waves can be transmitted to the front side (X direction in the drawing).

  However, when the inorganic piezoelectric layer 102 and the organic piezoelectric layer 103 are formed on both sides of the membrane 101a as shown in FIG. 9, the concave portion 101b provided in the substrate 100 to form the membrane 101a becomes the organic piezoelectric layer 103. A space is formed by being arranged so as to be adjacent to the rear surface side. If such a space is formed on the rear surface side of the organic piezoelectric layer 103, it becomes difficult to excite thickness mode vibration (vibration based on a change in thickness) of the organic piezoelectric layer 103, resulting in deterioration of reception sensitivity. Resulting in.

  An object of the present invention is to provide an ultrasonic probe and an ultrasonic diagnostic apparatus in which vibration of an organic piezoelectric layer is efficiently excited and high reception sensitivity is obtained.

  An ultrasonic probe according to an aspect of the present invention is an ultrasonic probe having a plurality of sheet-like vibrating portions that are arranged in an array and transmit and receive ultrasonic waves, and each of the vibrating portions is provided on a substrate. A membrane formed on one side in the thickness direction along the sound axis direction; an inorganic piezoelectric layer having an inorganic piezoelectric material; and an organic piezoelectric layer having an organic piezoelectric material, wherein the membrane has a thickness of the substrate. The membrane, the inorganic piezoelectric layer, and the organic piezoelectric layer are composed of a thin region formed so that the thickness of the substrate is thinner than the other region by a concave portion that is recessed from the other surface to the one surface side. The membrane, the inorganic piezoelectric layer, and the organic piezoelectric layer are arranged in this order on the one surface side of the substrate along the sound axis direction.

  According to this configuration, the membrane, the inorganic piezoelectric layer, and the organic piezoelectric layer are arranged in the order of the membrane, the inorganic piezoelectric layer, and the organic piezoelectric layer along the sound axis direction. It is possible to prevent the formation of a space due to the concave portion of the substrate adjacent to the side, the vibration in the thickness mode of the organic piezoelectric layer is efficiently excited, and high reception sensitivity can be obtained.

  In another aspect, in the ultrasonic probe, the inorganic piezoelectric layer bends and deforms the vibration part in response to application of a voltage to transmit a first ultrasonic signal to a subject, and the organic piezoelectric layer includes The second ultrasonic signal returned from the subject based on the first ultrasonic signal is received.

  According to this configuration, since the first ultrasonic signal is transmitted by the inorganic piezoelectric layer capable of increasing the transmission power, the transmission power can be increased with a relatively simple structure. Therefore, it is suitable for a harmonic imaging technique that requires transmission of fundamental ultrasonic waves with a relatively large power in order to obtain harmonic echoes, and it is possible to provide ultrasonic images with higher accuracy.

  In addition, since the second ultrasonic signal is received by the organic piezoelectric layer having a characteristic capable of receiving ultrasonic waves over a relatively wide frequency, the frequency band can be widened with a relatively simple structure. . Therefore, it is suitable for harmonic imaging technology that requires receiving harmonic ultrasonic waves, and it is possible to provide more accurate ultrasonic images.

  In another aspect, in the ultrasonic probe, the inorganic piezoelectric layer bends and deforms the vibrating portion in response to application of a voltage, and a first ultrasonic signal is transmitted from the other surface in the thickness direction of the substrate. Transmitting in the direction of one surface, the organic piezoelectric layer is arranged to be in front of the inorganic piezoelectric layer in the transmission direction of the first ultrasonic signal, that is, ultrasonic waves from the membrane. An inorganic piezoelectric layer and an organic piezoelectric layer are arranged in this order toward the transmission / reception surface.

  According to this configuration, it is necessary to efficiently receive the harmonic wave returning from the subject based on the first ultrasonic signal without being obstructed by the inorganic piezoelectric layer, and to receive the harmonic ultrasonic wave. It is possible to make it even more suitable for a harmonic imaging technique.

  In another aspect, in the ultrasonic probe, the inorganic piezoelectric layer is provided on a sheet-like inorganic piezoelectric body made of the inorganic piezoelectric material and on one surface side in the thickness direction of the inorganic piezoelectric body. A first electrode and a second electrode disposed between the membrane and the other surface in the thickness direction of the inorganic piezoelectric body, and forming a pair with the first electrode. A sheet-like organic piezoelectric body made of an organic piezoelectric material, a third electrode disposed on one side in the thickness direction of the organic piezoelectric body, the other surface in the thickness direction of the organic piezoelectric body, and the inorganic A fourth electrode disposed between the first electrode of the piezoelectric layer and a pair of the third electrode is provided, and the first electrode and the fourth electrode are common electrodes. And

  According to this configuration, the first electrode of the inorganic piezoelectric layer and the fourth electrode of the organic piezoelectric layer can be used as a common electrode, signal lines can be drawn from the common electrode, signal lines to be drawn can be reduced, and ultrasonic waves can be reduced. The probe can be simplified.

  In another aspect, the ultrasonic probe is characterized in that the first electrode and the fourth electrode are bonded to each other by a conductive adhesive so as to be energized.

  According to this configuration, for example, the inorganic piezoelectric layer including the first electrode and the second electrode and the inorganic piezoelectric layer including the third electrode and the fourth electrode are separately formed, and the first layer is formed using the conductive adhesive. The first electrode and the fourth electrode may be bonded, and the formation can be facilitated.

  An ultrasonic diagnostic apparatus according to an aspect of the present invention includes any one of the above-described ultrasonic probes.

  According to this configuration, vibration in the thickness mode of the organic piezoelectric layer can be efficiently excited and high reception sensitivity can be obtained, which is suitable for harmonic imaging technology and can provide a more accurate ultrasonic image. It becomes.

  In the ultrasonic probe and ultrasonic diagnostic apparatus of the present invention, vibration in the thickness mode of the organic piezoelectric layer is efficiently excited, and high reception sensitivity is obtained.

It is a figure which shows the external appearance structure of the ultrasound diagnosing device which has an ultrasound probe. It is a block diagram which shows the electrical structure of the ultrasonic diagnosing device which has an ultrasonic probe. It is sectional drawing which shows the structure of the ultrasound probe in an ultrasound diagnosing device. It is a rear view of the ultrasonic transmission / reception part in an ultrasonic probe. It is an expanded sectional view of the principal part of the ultrasonic transmission / reception part in an ultrasonic probe. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. It is the VII-VII sectional view taken on the line of FIG. (A) is explanatory drawing of the vibration of the vent mode of a vibration part, (b) is explanatory drawing of the vibration of the thickness mode of a vibration part. It is sectional explanatory drawing at the time of forming an inorganic piezoelectric layer and an organic piezoelectric layer on the both sides across the membrane.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an external configuration of an ultrasonic diagnostic apparatus having an ultrasonic probe according to an embodiment of the present invention. FIG. 2 is a block diagram showing an electrical configuration of an ultrasonic diagnostic apparatus having an ultrasonic probe. FIG. 3 is a cross-sectional view showing the configuration of the ultrasonic probe of FIG.

  As shown in FIG. 1, the ultrasonic diagnostic apparatus S in this embodiment transmits an ultrasonic wave (first ultrasonic signal) to a subject such as a living body (not shown) and transmits the ultrasonic wave to the first ultrasonic signal. The ultrasonic probe 2 that receives the ultrasonic wave (second ultrasonic signal) coming from within the subject is connected, and the ultrasonic probe 2 and the cable 3 are connected to each other, and the cable is connected to the ultrasonic probe 2. By transmitting a transmission signal of an electrical signal via 3, the ultrasonic probe 2 is caused to transmit a first ultrasonic signal to the subject, and from within the subject received by the ultrasonic probe 2. An ultrasonic diagnostic apparatus main body 1 that images an internal state of a subject as an ultrasonic image based on a reception signal of an electric signal generated by the ultrasonic probe 2 in accordance with the second ultrasonic signal that has come. It is prepared for.

  The ultrasonic waves coming from within the subject based on the first ultrasonic signal are not only reflected waves (echoes) reflected from the first ultrasonic signal in the subject due to acoustic impedance mismatches in the subject, for example, When an ultrasonic contrast agent (contrast agent) such as microbubbles is used, there is also an ultrasonic wave generated by the microbubbles of the ultrasonic contrast agent based on the first ultrasonic signal. When an ultrasonic contrast agent is irradiated with ultrasonic waves, the microbubbles of the ultrasonic contrast agent resonate or resonate, and further collapse or disappear at a sound pressure above a certain threshold. In the ultrasonic contrast agent, ultrasonic waves are generated by resonance of microbubbles or by collapse or disappearance of microbubbles.

  For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, an image processing unit 14, a display unit 15, and a control unit 16. Configured.

  The operation input unit 11 is, for example, a device for inputting data such as a command for instructing start of diagnosis and personal information of a subject, and is, for example, an operation panel or a keyboard provided with a plurality of input switches.

  For example, the transmission unit 12 transmits a control signal from the control unit 16 to the ultrasound probe 2. For example, the receiving unit 13 receives a reception signal transmitted from the ultrasound probe 2 and outputs the received signal to the image processing unit 14.

  The image processing unit 14 controls the inside of the subject based on a predetermined frequency component in the second ultrasound signal received from the inside of the subject based on the first ultrasound signal received by the receiving unit 13 according to the control of the control unit 16. It is a circuit which forms the image (ultrasonic image) showing the internal state of. Examples of the predetermined frequency component include a fundamental wave component and harmonic components such as a second harmonic component, a third harmonic component, and a fourth harmonic component. The image processing unit 14 may be configured to form an ultrasonic image using a plurality of frequency components. The image processing unit 14 performs processing by the DSP (Digital Signal Processor) that generates an ultrasonic image of the subject based on the output of the receiving unit 13 and the DSP to display the ultrasonic image on the display unit 15, for example. And a digital-analog conversion circuit (DAC circuit) for converting the converted signal from a digital signal to an analog signal. The DSP includes, for example, a B-mode processing circuit, a Doppler processing circuit, a color mode processing circuit, and the like, and can generate so-called B-mode images, Doppler images, and color mode images.

  The display unit 15 is a device that displays an ultrasonic image of the subject generated by the image processing unit 14 under the control of the control unit 16. The display unit 15 is, for example, a display device such as a CRT display, LCD (liquid crystal display), organic EL display, or plasma display, or a printing device such as a printer.

  The control unit 16 includes, for example, a microprocessor, a storage element, and peripheral circuits thereof, and the ultrasonic probe 2, the operation input unit 11, the transmission unit 12, the reception unit 13, the image processing unit 14, and a display. It is a circuit that performs overall control of the ultrasound diagnostic apparatus S by controlling the unit 15 according to the function.

  As shown in FIG. 3, the ultrasonic probe (ultrasonic probe, transducer) 2 includes a probe main body 4 and an ultrasonic transmission / reception unit 5 (piezoelectric device) that is provided in the probe main body 4 and transmits / receives ultrasonic waves. ). In the following description, the X direction in FIG. 3 is the front side and the Y direction is the rear side. The same applies to FIGS. 5, 8, and 9 to be described later.

  The probe body 4 includes a coating layer 41 provided at the front end, a signal processing circuit unit 42 provided on the rear end side, and a backing material disposed between the coating layer 41 and the signal processing circuit unit 42. Layer 43.

  For example, the covering layer 41 is in contact with a living body as a subject and does not give unpleasant feeling in contact, and has an acoustic impedance close to that of the human body in order to achieve acoustic matching with the human body. It is formed from rubber or the like.

  The backing material layer 43 plays a role of attenuating unnecessary vibration generated in the ultrasonic transmission / reception unit 5.

  The signal processing circuit unit 42 is connected to the ultrasonic diagnostic apparatus S via the cable 3 and generates a pulse signal for ultrasonic transmission or processes a received pulse signal.

  Specifically, under the control of the control unit 16, the transmission signal of the electrical signal transmitted from the transmission unit 12 is supplied to cause the ultrasonic transmission / reception unit 5 to generate the first ultrasonic signal. For example, a high voltage pulse generator that generates a high voltage pulse is provided. The drive signal generated by the signal processing circuit unit 42 is a plurality of pulse-like signals in which delay times are individually set appropriately for each of a plurality of elements 66 (see FIG. 4) described later. Supplied to each. By the plurality of drive signals, the phases of the ultrasonic waves radiated from the vibrating parts 6a to 6d coincide in a specific direction (specific direction) (or a specific transmission focus point), and a main beam is formed in the specific direction. A first ultrasonic signal of the transmission beam is generated.

  Further, the signal processing circuit unit 42 receives and processes an electric signal received from the ultrasonic transmission / reception unit 5 under the control of the control unit 16. Then, similarly to the formation of a transmission beam at the time of transmission, a reception beam may be formed at the time of reception by so-called phasing addition. That is, by appropriately setting delay times individually for a plurality of output signals output from the vibration units 6a to 6d, and adding the delayed output signals, the phase of each output signal is set to a specific direction. They coincide at (specific azimuth or specific reception focus point), and the main beam is formed in the specific direction. In such a case, for example, a reception beamformer to which each output signal amplified by the amplifier is input may be provided. The signal processing circuit unit 42 may be provided in the ultrasonic diagnostic apparatus main body 1 and can be changed as appropriate.

  The ultrasonic transmission / reception unit 5 is disposed between the covering layer 41 and the backing material layer 43 of the probe body 4. The ultrasonic transmission / reception unit 5 of this embodiment includes a plurality of vibration units 6a to 6d arranged in an array as shown in FIG.

  As shown in FIG. 5, each of the vibrating portions 6a to 6d includes a membrane 82 formed on the front surface (one surface in the thickness direction) of the substrate 8, an inorganic piezoelectric layer 62 having an inorganic piezoelectric material, and an organic piezoelectric material. And an organic piezoelectric layer 72 in the order of the membrane, the inorganic piezoelectric layer, and the organic piezoelectric layer along the sound axis direction (thickness direction of the substrate 8, XY direction in the figure). The inorganic piezoelectric layer 62 and the organic piezoelectric layer 72 are arranged in this order toward the transmission / reception surface.

  In this embodiment, the substrate 8 is made of a silicon plate. As shown in FIG. 4, the substrate 8 is provided with a plurality of circular recesses 81a arranged in the left-right direction and the up-down direction. As shown in FIG. 5, each recess 81 a is formed at a predetermined depth from the rear surface to the front surface side of the substrate 8, and is thicker than the other portions on the front surface side of the portion corresponding to the recess 81 a in the substrate 8. A thin thin region is formed.

The membrane 82 is composed of each thin region of the substrate 8. In this embodiment, an insulating material such as silicon dioxide (SiO ₂ ) or silicon nitride (SiN) is used to obtain a good potential distribution in PZT, which will be described later, and in the form of a sheet (in this embodiment, about 2 μm). Thickness).

  The inorganic piezoelectric layer 62 is composed of a plurality of the same number as the membrane 82, each of which includes an inorganic piezoelectric body 61 composed of an inorganic piezoelectric material, and a pair of inorganic piezoelectric layer ground electrodes (first electrodes). 63 and a positive electrode (second electrode) 64 for the inorganic piezoelectric layer.

An example of the inorganic piezoelectric material constituting the inorganic piezoelectric body 61 is PZT. Examples of the inorganic piezoelectric material include quartz, lithium niobate (LiNbO ₃ ), potassium tantalate niobate (K (Ta, Nb) O ₃ ), barium titanate (BaTiO ₃ ), lithium tantalate (LiTaO ₃ ), and titanium. Examples include strontium acid (SrTiO ₃ ), PZN-PT, PMN-PT, and the like, which can be changed as appropriate.

  In addition, the inorganic piezoelectric body 61 of this embodiment is formed of a disk-like one having substantially the same size as the membrane 82 and a thickness of about 2 μm.

  The inorganic piezoelectric layer ground electrode 63 is made of gold or platinum. The inorganic piezoelectric layer ground electrode 63 is disposed on the entire front surface (one surface in the thickness direction) of the inorganic piezoelectric body 61 and has a disk shape. The inorganic piezoelectric layer ground electrode 63 is connected to the signal processing circuit section 42 via an organic piezoelectric layer ground electrode 74 and a through wiring 75 described later.

  The plus electrode 64 for the inorganic piezoelectric layer is made of gold or platinum. The inorganic piezoelectric layer positive electrode 64 is disposed on the entire rear surface of the inorganic piezoelectric body 61 (the other surface in the thickness direction) as shown in FIG. FIG. 7 is a cross-sectional view of the conductive adhesive 9 described later disposed on the front surface of the inorganic piezoelectric layer plus electrode 64 as viewed from the front side.

  The inorganic piezoelectric layer positive electrode 64 is connected to the signal processing circuit section 42 through the through wiring 65.

  And each inorganic piezoelectric layer 62 comprised in this way is arrange | positioned so that the positive electrode 64 for inorganic piezoelectric layers may be joined to the front surface (one side) of each membrane 82. FIG.

  The organic piezoelectric layer 72 includes an organic piezoelectric main body 71 made of an organic piezoelectric material, and a pair of organic piezoelectric layer positive electrodes (third electrode) 73 and an organic piezoelectric layer ground electrode (fourth electrode) 74. Yes.

  As an organic piezoelectric material constituting the organic piezoelectric body 71, for example, a vinylidene fluoride (VDF) copolymer that is a polymer ferroelectric can be used. This vinylidene fluoride copolymer is a copolymer (copolymer) of vinylidene fluoride and other monomers. Examples of the other monomers include ethylene trifluoride, tetrafluoroethylene, perfluoroalkyl vinyl ether ( PFA), perfluoroalkoxyethylene (PAE), perfluorohexaethylene, and the like can be used. In the vinylidene fluoride copolymer, the electromechanical coupling constant (piezoelectric effect) in the thickness direction varies depending on the copolymerization ratio. For example, an appropriate copolymerization ratio is adopted according to the specifications of the ultrasonic probe, etc. . For example, in the case of a vinylidene fluoride / ethylene trifluoride copolymer, the copolymerization ratio of vinylidene fluoride is preferably 60 mol% to 99 mol%, and in the case of a composite element in which an organic piezoelectric element is laminated on an inorganic piezoelectric element. More preferably, the copolymerization ratio of vinylidene fluoride is 85 mol% to 99 mol%. In the case of such a composite element, the other monomers are preferably perfluoroalkyl vinyl ether (PFA), perfluoroalkoxyethylene (PAE), and perfluorohexaethylene. For example, polyurea can be used for the organic piezoelectric material. In the case of this polyurea, it is preferable to produce a piezoelectric body by vapor deposition polymerization. Examples of the monomer for polyurea include a general formula and an H2N-R-NH2 structure. Here, R may include an alkylene group, a phenylene group, a divalent heterocyclic group, or a heterocyclic group which may be substituted with any substituent. The polyurea may be a copolymer of a urea derivative and another monomer. Preferred polyureas include aromatic polyureas using 4,4'-diaminodiphenylmethane (MDA) and 4,4'-diphenylmethane diisocyanate (MDI).

  “Ferroelectric material” has spontaneous polarization, and its polarization direction can be artificially changed by an electric field, and artificially changed polarization remains when the electric field is zero (residual). It can be defined as a (polarized) material.

  With regard to the molecular weight of the ferroelectric raw material polymer, in general, with a polymer, a piezoelectric film having flexibility and flexibility specific to the polymer as the molecular weight increases. In VDF-TrFE and / or VDF-TeFE, the melt flow rate at 230 ° C is 0.03 g / min or less, more preferably 0.02 g / min or less, and still more preferably 0.01 g / min. When a polymer piezoelectric body is used, a highly sensitive thin film for a piezoelectric layer can be obtained.

  The above VDF represents vinylidene fluoride, TrFE represents trifluoroethylene, and TeFE represents tetrafluoroethylene. In the field of polymer ferroelectrics, high performance is achieved by various approaches. For example, peptide molecules exhibiting a large dipole moment as a molecule are pyroelectrically controlled by restricting the orientation so as to strengthen the dipole moment. It is said that piezoelectricity can be obtained.

  In addition, the organic piezoelectric body 71 of this embodiment is formed of a disk-shaped body having substantially the same size as the front surface of the substrate 8 and a thickness of about 2 μm.

  The organic piezoelectric layer positive electrode 73 is made of gold or platinum. The organic piezoelectric layer positive electrode 73 is disposed on the entire front surface (one surface in the thickness direction) of the organic piezoelectric body 71. Further, although not shown, the organic piezoelectric layer positive electrode 73 is connected to the signal processing circuit unit 42 through a through wiring.

  The organic piezoelectric layer ground electrode 74 is made of gold or platinum. Then, as shown in FIG. 6, the organic piezoelectric layer ground electrode 74 is positioned at a position corresponding to each inorganic piezoelectric layer ground electrode 63 on the rear surface (the other surface in the thickness direction) of the organic piezoelectric body 71. It has a disk shape that is substantially the same size as the ground electrode 63, and is composed of a plurality of the same number of inorganic piezoelectric layer ground electrodes 63. FIG. 6 is a cross-sectional view of a conductive adhesive 9 (described later) disposed on the rear surface of the organic piezoelectric layer ground electrode 74 as viewed from the rear side.

  The organic piezoelectric layer 72 configured in this manner is configured to adhere the inorganic piezoelectric layer ground electrode 63 and the organic piezoelectric layer ground electrode 74 of each inorganic piezoelectric layer 62 to each other by the conductive adhesive 9 so as to allow current to flow. The inorganic piezoelectric layer 62 is disposed in front of the inorganic piezoelectric layer 62. This conductive adhesive is an adhesive in which conductive materials such as silver powder, copper powder, or carbon fire are mixed.

  In this state, the inorganic piezoelectric layer ground electrode 63 and the organic piezoelectric layer ground electrode 74 are common electrodes. The organic piezoelectric layer ground electrode 74 is connected to the signal processing circuit section 42 through the through wiring 75.

  Moreover, in this embodiment, as shown in FIG. 4, the plurality of vibrating portions 6a to 6d formed as described above surround the four vibrating portions 6a to 6d with one element 66 (two-dot chain lines in FIG. 4). In other words, the plurality of elements 66 are two-dimensionally arranged in the left-right and up-down directions.

  More specifically, the organic piezoelectric layer ground electrode 74 (and the inorganic piezoelectric layer ground electrode 63) are connected to each other so that the four vibrating portions 6a to 6d can be energized with each other.

  Further, the organic piezoelectric layer positive electrode 73 is connected to each of the four vibrating portions 6a to 6d so that they can be energized with each other, and one element 66 comprising the four vibrating portions 6a to 6d. A plurality of elements 66 are connected to each other by element connection wirings (not shown) extending from the respective elements.

  In this embodiment, the ultrasonic transmission / reception unit 5 configured as described above is formed as follows.

As the substrate 8, a Si substrate (thickness: 200 μm) having SiO ₂ oxide film (thickness: 2 μm) on both sides is used.

A resist is applied onto the rear SiO ₂ , and exposure and development are performed to obtain a resist pattern for the recess 81a. Then, using the resist as a mask pattern, the SiO ₂ layer is dry-etched (CHF ₃ gas) with a reactive ion etching (RIE) apparatus, and the SiO ₂ layer not protected by the resist is removed.

Next, titanium (thickness 20 nm) and platinum (thickness 100 nm) are formed by sputtering on the front surface with the SiO ₂ oxide film. Titanium is an adhesion layer, and platinum serves as the positive electrode 64 for the inorganic piezoelectric layer.

  Thereafter, an inorganic piezoelectric body 61 made of PZT (lead zirconate titanate) is formed on the platinum by sputtering at a temperature of 600 degrees (thickness: 2 μm). The formed film is oriented in (111) of the perovskite layer that provides piezoelectric characteristics.

  Then, a resist pattern for patterning by wet etching is formed on the front surface of the inorganic piezoelectric body 61. Then, the inorganic piezoelectric body 61 is wet etched with hydrofluoric acid to form a pattern.

  Thereafter, a resist is applied, exposed and developed, and titanium and platinum are etched using the resist as a mask to pattern the positive electrode 64 for the inorganic piezoelectric layer.

  Next, a resin material as an insulating member is uniformly filled and applied by a spray coater so as not to become an uneven surface. Then, the surface of the resin material 91 is removed by the ashing device until the surface of the inorganic piezoelectric body 61 comes out, or masking, exposure and development are performed so that the surface of the inorganic piezoelectric body 61 comes out.

  Next, chromium (Cr) and gold (Au) are formed in a thickness of 0.2 μm on the front surface of the inorganic piezoelectric body 61 by sputtering. Chromium is an adhesion layer, and gold is the inorganic piezoelectric layer ground electrode 63. Then, a resist is applied on the surface, exposure and development are performed, and chromium and gold etching is performed using the resist as a mask to pattern the inorganic piezoelectric layer ground electrode 63.

Next, deep etching is performed by a Bosch process of an ICP etching apparatus using the pattern of the SiO ₂ oxide film on the rear surface of the substrate 8 to form a concave portion 81a having a diameter of 50 μm vertically and horizontally.

  Next, the conductive adhesive 9 is applied on the inorganic piezoelectric layer ground electrode 63 to a thickness of 1 μm by screen printing.

  An organic piezoelectric layer ground electrode 74 formed in the same shape as the inorganic piezoelectric layer ground electrode 63 is formed on the rear surface of the organic piezoelectric body 71 made of VDF-TrFE in advance, and is formed on the entire front surface of the organic piezoelectric body 71. Then, the organic piezoelectric layer 72 formed by vapor deposition of the organic piezoelectric layer positive electrode 73 is positioned, and the organic piezoelectric layer ground electrode 74 is overlaid on the inorganic piezoelectric layer ground electrode 63. Then, the conductive adhesive 9 is cured by heating to 140 ° C.

  In this embodiment, the organic piezoelectric layer 72 having the organic piezoelectric body 71 made of VDF-TrFE prepared in advance is used. However, the present invention is not limited to this. For example, the organic piezoelectric layer 72 is made of VDF-TrFE on the ground electrode 63 for the inorganic piezoelectric layer. The organic piezoelectric body 71 is formed by spin coating and then crystallized by heating at about 150 ° C. for 1.5 hours, and then Au is vapor-deposited on the entire front surface of the organic piezoelectric body 71. May be formed. In this case, the inorganic piezoelectric layer ground electrode 63 also serves as the organic piezoelectric layer ground electrode.

  As described above, it is possible to obtain a plurality of single elements 66 constituted by four vibrating parts 6a to 6d made of a diaphragm having a diameter of 50 μm, two-dimensionally arranged in the left, right, up and down directions.

  Further, a polarization process is performed by applying a voltage so that an electric field of several V / um or more is applied between the inorganic piezoelectric layer positive electrode 64 and the inorganic piezoelectric layer ground electrode 63. Similarly, a polarization process is performed by applying a voltage so that an electric field of several V / um or more is applied between the organic piezoelectric layer positive electrode 73 and the organic piezoelectric layer ground electrode 74.

  When diagnosing with the ultrasound diagnostic apparatus S having the ultrasound probe configured as described above, for example, when an instruction to start diagnosis is input from the operation input unit 11, signal processing is performed according to the control of the control unit 16. The circuit unit 42 generates a pulse signal (first ultrasonic signal) for ultrasonic transmission.

  For this generated pulse signal, for each of the plurality of elements 66 of the ultrasonic transmission / reception unit 5, for example, a pulse voltage is applied at a predetermined delay time so as to sequentially shift the phase, and the inorganic piezoelectric layer plus electrode 64 and the inorganic piezoelectric layer ground Applied between the electrodes 63, an electric field is generated in the thickness direction of the inorganic piezoelectric body 61.

  Due to this electric field, the inorganic piezoelectric body 61 is bent and deformed, and as a result, as shown in FIG. 8A, the vibrating portions 6a to 6d bend like a drum according to the resonance characteristics (resonance frequency fc and attenuation characteristics). The deformed vent mode vibration is vibrated, and pulsed ultrasonic waves are transmitted from the rear surface (other surface) in the thickness direction of the substrate 8 to the front surface (one surface) (X direction) and transmitted into the living body. The By shifting the phase of each element 66 of the array by a predetermined amount, the ultrasonic beam is focused and steered (direction control), and the necessary area is scanned three-dimensionally. In the living body, the ultrasonic wave is transmitted while being attenuated, reflection occurs at a site where the difference in acoustic impedance is generated, and it returns to the ultrasonic probe 2.

  The vibrating portions 6a to 6d vibrate in the vent mode shown in FIG. 8A due to the returned ultrasonic waves (second ultrasonic signals), and electric charges are generated according to the distortion of the inorganic piezoelectric layer 62 associated therewith. The generated charges are processed by the signal processing circuit unit 42 and output to the image processing unit 14. Then, under the control of the control unit 16, the image processing unit 14 determines the distance to the subject based on the time from transmission to reception based on the received reception signal, and the direction of the subject due to the time difference between the elements. Detected.

  In addition, harmonics (integer multiples of the fundamental wave frequency) generated when the ultrasonic waveform is distorted when the first ultrasonic wave propagates through the tissue are also fed back to the transducer as the second ultrasonic signal. Due to the returned harmonics, the organic piezoelectric layer 72 vibrates in a thickness mode by increasing / decreasing its thickness as shown in FIG. 8B, and the organic piezoelectric layer plus electrode 73 of the organic piezoelectric layer 72 according to its own strain. Electric charge is generated in The center frequency of the thickness mode is determined by the Young's modulus, density, and layer thickness of the material. If a general organic piezoelectric material is used, the center frequency is set to about 2.5 fc by setting the layer thickness to several μm. It is possible.

  Then, the image processing unit 14 generates an ultrasonic image of the internal state of the subject using the harmonic imaging technique based on the harmonic component generated in the organic piezoelectric layer plus electrode 73 of the organic piezoelectric layer 72.

  In the above-described embodiment, the organic piezoelectric body 71 is composed of one. However, the organic piezoelectric body 71 is not limited to this. For example, the organic piezoelectric body 71 includes a plurality of organic piezoelectric bodies 71 having substantially the same size as the inorganic piezoelectric layer 62. It may be configured and arranged on the front side of each inorganic piezoelectric layer 62, and can be changed as appropriate.

  In the above embodiment, the inorganic piezoelectric layer ground electrode 63 (first electrode) and the organic piezoelectric layer ground electrode 74 (fourth electrode) are common electrodes. For example, a dielectric is provided between them. The inorganic piezoelectric layer ground electrode 63 and the organic piezoelectric layer ground electrode 74 may be interposed and connected to the signal processing circuit unit 42 through a through electrode.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 5 Ultrasonic transmission / reception part 6 Vibration part 8 Board | substrate 61 Inorganic piezoelectric main body 62 Inorganic piezoelectric layer 63 Ground electrode (1st electrode) for inorganic piezoelectric layers
64 Positive electrode for inorganic piezoelectric layer (second electrode)
71 Organic Piezoelectric Body 72 Organic Piezoelectric Layer 73 Organic Piezoelectric Layer Positive Electrode (Third Electrode)
74 Ground electrode for inorganic piezoelectric layer (4th electrode)
82 Membrane S Ultrasonic Diagnostic Equipment

Claims (6)

An ultrasonic probe having a plurality of sheet-like vibrating portions arranged in an array to transmit and receive ultrasonic waves,
Each vibrating portion includes a membrane formed on one surface side in the thickness direction along the sound axis direction of the substrate, an inorganic piezoelectric layer having an inorganic piezoelectric material, and an organic piezoelectric layer having an organic piezoelectric material,
The membrane is composed of a thin region formed such that the thickness of the substrate is thinner than the other region by a recess formed on the one surface side from the other surface in the thickness direction of the substrate,
The membrane, the inorganic piezoelectric layer, and the organic piezoelectric layer are disposed on one side of the substrate in the order of the membrane, the inorganic piezoelectric layer, and the organic piezoelectric layer along the sound axis direction. An ultrasonic probe. The inorganic piezoelectric layer is configured to transmit the first ultrasonic signal to the subject by bending and deforming the vibration part with application of a voltage,
The ultrasonic probe according to claim 1, wherein the organic piezoelectric layer is configured to receive a second ultrasonic signal returned from the subject based on the first ultrasonic signal. Child. The inorganic piezoelectric layer is configured to transmit the first ultrasonic signal from the other surface to the one surface in the thickness direction of the substrate by bending and deforming the vibration part with application of a voltage,
3. The ultrasonic probe according to claim 1, wherein the organic piezoelectric layer is disposed on the front side in the transmission direction of the first ultrasonic signal with respect to the inorganic piezoelectric layer. Child. The inorganic piezoelectric layer includes a sheet-like inorganic piezoelectric body made of the inorganic piezoelectric material, a first electrode disposed on one surface side in the thickness direction of the inorganic piezoelectric body, and a thickness direction of the inorganic piezoelectric body. A second electrode disposed between the other surface of the membrane and the membrane and forming a pair with the first electrode,
The organic piezoelectric layer includes a sheet-like organic piezoelectric body made of the organic piezoelectric material, a third electrode disposed on one surface side in the thickness direction of the organic piezoelectric body, and a thickness direction of the organic piezoelectric body. A fourth electrode disposed between the other surface of the inorganic piezoelectric layer and the first electrode of the inorganic piezoelectric layer and forming a pair with the third electrode,
The ultrasonic probe according to claim 1, wherein the first electrode and the fourth electrode are common electrodes.   The ultrasonic probe according to claim 4, wherein the first electrode and the fourth electrode are bonded to each other by a conductive adhesive so as to be energized.   An ultrasonic diagnostic apparatus comprising the ultrasonic probe according to claim 1.

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