JP2015100093A - Ultrasonic device and probe, and electronic apparatus and ultrasonic image device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic device that can accurately achieve acoustic matching for each frequency of ultrasonic sound to be received.SOLUTION: A substrate 55 has a first plane 58, and a second plane 57 that is separated from a reference plane including the first plane 58 by a specific distance in the normal direction of the reference plane. The first plane has first openings 59a, and the second plane 57 has second openings 59b. A coating layer 56 has a first vibration film 31 that closes the first openings 59a and a second vibration film 36 that closes the second openings 59b. First piezoelectric elements 32 are formed on the first vibration film 31, and second piezoelectric elements 37 are formed on the second vibration film 36. An acoustic matching layer 61 coats the first piezoelectric elements 32 and second piezoelectric elements 37 and has a plane 61a parallel to the first plane 58 and second plane 57.

Description

  The present invention relates to an ultrasonic device, and a probe, an electronic apparatus, an ultrasonic imaging apparatus, and the like using the ultrasonic device.

  Ultrasonic devices are generally known. Ultrasonic devices are widely used in forming ultrasonic images. For example, the ultrasonic device described in Patent Document 1 includes two types of piezoelectric ceramic plates for each received frequency. The thickness of the acoustic matching layer is different for each piezoelectric ceramic plate.

JP-A-2-49640

  In Patent Document 1, a step is formed on the surface of the acoustic load member when setting the film thickness of the acoustic matching layer. A piezoelectric ceramic plate is affixed to the acoustic load material for each step. Generally, an adhesive such as an epoxy resin is used for pasting. As a result, the distance from the surface of the acoustic matching layer to the surface of the piezoelectric ceramic plate tends to vary. It was difficult to achieve accurate acoustic matching for each frequency.

  Therefore, an ultrasonic device that achieves accurate acoustic matching for each frequency of received ultrasonic waves has been desired.

  (1) According to one aspect of the present invention, a first plane and a second plane that is separated from the reference plane including the first plane by a specific distance in a normal direction thereof, and the first plane that opens to the first plane are provided. A substrate having an opening and a second opening that opens in the second plane; a first vibrating membrane that closes the first opening; and a second vibrating membrane that closes the second opening; The formed covering layer, the first piezoelectric element formed on the first vibration film, the second piezoelectric element formed on the second vibration film, the first piezoelectric element, and the second piezoelectric element And an acoustic matching layer having a plane parallel to the first plane and the second plane.

  Ultrasonic waves are transmitted from the acoustic matching layer to the first vibration film and the second vibration film. The ultrasonic waves vibrate the first vibrating membrane and the second vibrating membrane. The piezoelectric effect is exhibited by the first piezoelectric element and the second piezoelectric element in accordance with the vibrations of the first vibration film and the second vibration film. Electromotive voltages are taken out from the first piezoelectric element and the second piezoelectric element, respectively. In this way, ultrasonic waves are measured for each vibrating membrane. At this time, the first film thickness of the acoustic matching layer is specified on the first piezoelectric element of the first vibration film, and the second film thickness of the acoustic matching layer is specified on the second piezoelectric element of the second vibration film. The frequency of the ultrasonic wave transmitted to the first vibration film and the second vibration film is adjusted according to the film thickness of the acoustic matching layer. Thus, the first diaphragm and the second diaphragm receive ultrasonic waves having different frequencies. Since the coating film and the piezoelectric element can be processed accurately on the surface of the substrate, the first film thickness and the second film thickness can be ensured with high precision in the first vibration film and the second vibration film. Therefore, acoustic coupling can be realized with high accuracy for each ultrasonic frequency.

  (2) In the ultrasonic device, the first piezoelectric element has a piezoelectric body, the second piezoelectric element has a piezoelectric body, and the piezoelectric body of the first piezoelectric element and the piezoelectric of the second piezoelectric element. The body may be the same material and have the same thickness. The piezoelectric body of the first piezoelectric element and the piezoelectric body of the second piezoelectric element can be formed in the same manufacturing process. Therefore, complication of the manufacturing process can be avoided.

  (3) The first piezoelectric element has a first electrode on the first vibrating membrane side, the second piezoelectric element has a first electrode on the second vibrating membrane side, and the first piezoelectric element The first electrode and the first electrode of the second piezoelectric element may be made of the same material and have the same thickness. The first electrode of the first piezoelectric element and the first electrode of the second piezoelectric element can be formed in the same manufacturing process. Therefore, complication of the manufacturing process can be avoided.

  (4) The first piezoelectric element has a second electrode on the acoustic matching layer side, the second piezoelectric element has a second electrode on the acoustic matching layer side, and the first piezoelectric element has the second electrode. The second electrode and the second electrode of the second piezoelectric element may be made of the same material and have the same thickness. The second electrode of the first piezoelectric element and the second electrode of the second piezoelectric element can be formed in the same manufacturing process. Therefore, complication of the manufacturing process can be avoided.

  (5) The first vibration film and the second vibration film may have the same thickness. The coating film can be uniformly formed when forming the first vibration film and the second vibration film. Therefore, a uniform coating film can be formed relatively easily and accurately.

  (6) The terminal of the first conductive wiring connected to the first piezoelectric element and the terminal of the second conductive wiring connected to the second piezoelectric element may be arranged on the same plane. In using the ultrasonic device, external wiring is generally connected to the terminal of the first conductive wiring and the terminal of the second conductive wiring. Since the terminal of the first conductive wiring and the terminal of the second conductive wiring are arranged in the same plane, the external wiring can receive the terminal of the first conductive wiring and the terminal of the second conductive wiring in the plane. Complicating the shape of the external wiring is avoided and reliable connection is realized.

  (7) The second diaphragm may have a resonance frequency at a frequency corresponding to a harmonic of the resonance frequency of the first diaphragm. When an ultrasonic wave having a specific frequency is transmitted toward the subject, the reflected ultrasonic wave includes an ultrasonic component of its harmonics in addition to the ultrasonic component of the specific frequency. Therefore, if the ultrasonic wave of the higher harmonic is received in addition to the ultrasonic wave of the specific frequency, the sensitivity of the ultrasonic device is enhanced.

  (8) The film thickness of the acoustic matching layer on the first diaphragm may be an odd multiple of a quarter of the wavelength of the resonance frequency of the first diaphragm, and the acoustic film is formed on the second diaphragm. The thickness of the matching layer may be an odd multiple of one quarter of the wavelength of the resonance frequency of the second vibrating membrane. Such a film thickness reduces the attenuation of the ultrasonic waves. As a result, harmonic components can be transmitted and received with high efficiency.

  (9) The film thickness of the acoustic matching layer on the first vibration film may be an odd multiple of one half of the wavelength of the resonance frequency of the first vibration film, and the acoustic wave is formed on the second vibration film. The thickness of the matching layer may be an odd multiple of one half the wavelength of the resonance frequency of the second vibrating membrane. According to such a film thickness, the pulse width can be shortened and the resolution can be improved by canceling the reverberation part that causes an increase in the pulse width in accordance with the cancellation of the ultrasonic waves.

  (10) The ultrasonic device may be used by being incorporated in a probe. At this time, the probe may include an ultrasonic device and a casing that supports the ultrasonic device.

  (11) The ultrasonic device may be used by being incorporated in an electronic apparatus. At this time, the electronic apparatus may include an ultrasonic device and a processing apparatus that is connected to the ultrasonic device and processes the output of the ultrasonic device.

  (12) The ultrasonic device may be used by being incorporated in an ultrasonic imaging apparatus. At this time, the ultrasonic imaging apparatus may include an ultrasonic device and a display device that displays an image generated from the output of the ultrasonic device.

  (13) According to another aspect of the present invention, there is provided a step of forming a first plane and a second plane having steps on the first surface of the substrate, and the first plane and the second plane on the first surface of the substrate. Forming a coating layer continuously covering the second plane; and opening the substrate from the second surface on the back side of the first surface at a position corresponding to the first plane and the second plane on the substrate. Forming a first vibration film for closing the opening at a position corresponding to the first plane, and forming a second vibration film for closing the opening at a position corresponding to the second plane on the covering layer. Forming a first piezoelectric element on the first vibration film, forming a second piezoelectric element on the second vibration film, and forming the first piezoelectric element on the first surface of the substrate and Forming an acoustic matching layer covering the second piezoelectric element and having a flat upper surface. That process for the preparation of an ultrasound device. Here, the first vibration film and the second vibration film may be formed prior to the formation of the first piezoelectric element and the second piezoelectric element, and the first vibration film and the second vibration film may be formed prior to the formation of the acoustic matching layer. May be formed.

1 is an external view schematically showing a specific example of an electronic apparatus, that is, an ultrasonic diagnostic apparatus. It is an enlarged front view of an ultrasonic probe. 1 is an enlarged plan view of an ultrasonic device according to a first embodiment. It is sectional drawing along the AA line of FIG. It is a manufacturing method of an ultrasonic device, and is an enlarged partial sectional view showing a photoresist on a substrate roughly. It is a manufacturing method of an ultrasonic device, and is an expanded partial sectional view showing roughly the formation process of the upper stage surface and the lower stage surface. It is a manufacturing method of an ultrasonic device, and is an expanded partial sectional view showing a formation process of a silicon oxide layer roughly. It is a manufacturing method of an ultrasonic device, and is an expanded partial sectional view showing a formation process of a zirconium oxide layer roughly. It is a manufacturing method of an ultrasonic device, and is an enlarged partial sectional view showing roughly the formation process of the 1st piezoelectric element and the 2nd piezoelectric element. It is a manufacturing method of an ultrasonic device, and is an expanded partial sectional view showing roughly the formation process of the 1st opening and the 2nd opening. FIG. 5 is an enlarged partial plan view of an ultrasonic device according to a second embodiment. FIG. 6 is an enlarged partial plan view of an ultrasonic device according to a third embodiment. FIG. 10 is an enlarged partial plan view of an ultrasonic device schematically showing another specific example of the arrangement. FIG. 10 is an enlarged partial plan view of an ultrasonic device schematically showing still another specific example of the arrangement.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily.

(1) Overall Configuration of Ultrasonic Diagnostic Device FIG. 1 schematically shows a configuration of an example of an electronic apparatus, that is, an ultrasonic diagnostic device (ultrasonic imaging device) 11. The ultrasonic diagnostic apparatus 11 includes an apparatus terminal (processing apparatus) 12 and an ultrasonic probe (probe) 13. The apparatus terminal 12 and the ultrasonic probe 13 are connected to each other by a cable 14. The apparatus terminal 12 and the ultrasonic probe 13 exchange electric signals through the cable 14. A display panel (display device) 15 is incorporated in the device terminal 12. The screen of the display panel 15 is exposed on the surface of the device terminal 12. In the device terminal 12, an image is generated based on the ultrasonic wave detected by the ultrasonic probe 13. The imaged detection result is displayed on the screen of the display panel 15.

  As shown in FIG. 2, the ultrasonic probe 13 has a housing 16. An ultrasonic device 17 is accommodated in the housing 16. The surface of the ultrasonic device 17 can be exposed on the surface of the housing 16. The ultrasonic device 17 outputs an ultrasonic wave from the surface and receives a reflected wave of the ultrasonic wave. In addition, the ultrasonic probe 13 can include a probe head 13b that is detachably connected to the probe main body 13a. At this time, the ultrasonic device 17 can be incorporated into the housing 16 of the probe head 13b.

(2) Configuration of Ultrasonic Device According to First Embodiment FIG. 3 schematically shows a plan view of the ultrasonic device 17 according to the first embodiment. The ultrasonic device 17 includes a base 21. An element array 22 is formed on the base 21. The element array 22 includes an array of first ultrasonic transducer elements (hereinafter referred to as “first elements”) 23 and second ultrasonic transducer elements (hereinafter referred to as “second elements”) 24. The array is formed of a matrix having a plurality of rows and a plurality of columns. Here, one column of first elements 23 and one column of second elements 24 are alternately arranged in the row direction. One row of the first elements 23 and one row of the second elements 24 form one segment. A plurality of first elements 23 and second elements 24 perform transmission or reception at the same time for each segment. As will be described later, an upper surface 26 and a lower surface 27 having a step 25 are formed on the surface of the base 21, the first element 23 is disposed on the lower surface 27, and the second element 24 is disposed on the upper surface 26. Be placed. The plane including the upper step surface 26 and the plane including the lower step surface 27 spread in parallel to each other. The upper surface 26 is further away from the back surface of the base 21 than the lower surface 27. The lower step surface 27 is continuous around the upper step surface 26. The ultrasonic device 17 is configured as a single ultrasonic transducer element chip.

  Each first element 23 includes a first vibration film 31. Details of the first vibration film 31 will be described later. In FIG. 3, the outline of the first vibration film 31 is drawn with a dotted line in a plan view in a direction orthogonal to the film surface of the first vibration film 31 (a plan view in the thickness direction of the base 21). A first piezoelectric element 32 is formed on the first vibration film 31. In the first piezoelectric element 32, as will be described later, a piezoelectric film 35 is sandwiched between an upper electrode (second electrode) 33 and a lower electrode (first electrode) 34. These are stacked in order. The first vibration film 31 has a resonance frequency at the first frequency.

  Each second element 24 includes a second vibration film 36. Details of the second vibration film 36 will be described later. In FIG. 3, the outline of the second vibration film 36 is drawn with a dotted line in a plan view in a direction orthogonal to the film surface of the second vibration film 36 (a plan view in the thickness direction of the base 21). A second piezoelectric element 37 is formed on the second vibration film 36. In the second piezoelectric element 37, as will be described later, a piezoelectric film 41 is sandwiched between an upper electrode (second electrode) 38 and a lower electrode (first electrode) 39. These are stacked in order. As described above, since the first element 23 is disposed on the lower surface 27 and the second element 24 is disposed on the upper surface 26, the film surface of the second vibration film 36 is the film surface of the first vibration film 31. It arrange | positions in the position higher than the plane containing. The second vibration film 36 has a resonance frequency at the second peripheral edge number. The second frequency corresponds to a harmonic of the first frequency that is the resonance frequency of the first vibrating membrane 31. Therefore, the second vibration film 36 is smaller than the first vibration film 31. The size is compared by the area of the film surface of the first vibration film 31 and the second vibration film 36.

  A plurality of first conductors 42 are formed on the surface of the base 21. The first conductors 42 extend parallel to each other in the column direction of the array. One first conductor 42 is assigned to each row of the first elements 23. One first conductor 42 is disposed in common to the first elements 23 arranged in the column direction of the array. The first conductor 42 forms a lower electrode 34 for each first element 23. For the first conductor 42, for example, a laminated film of titanium (Ti), iridium (Ir), platinum (Pt), and titanium (Ti) can be used. However, other conductive materials may be used for the first conductor 42.

  A plurality of second conductors 43 are formed on the surface of the base 21. The second conductors 43 extend parallel to each other in the column direction of the array. One second conductor 43 is assigned to each row of the second elements 24. One second conductor 43 is disposed in common to the second elements 24 arranged in the column direction of the array. The second conductor 43 forms a lower electrode 39 for each second element 24. For the second conductor 43, for example, a laminated film of titanium (Ti), iridium (Ir), platinum (Pt), and titanium (Ti) can be used. However, other conductive materials may be used for the second conductor 43.

  A plurality of third conductors 44 are further formed on the surface of the base 21. The third conductors 44 extend parallel to each other in the row direction of the array. One third conductor 44 is assigned to the first element 23 and the second element 24 in one row. One third conductor 44 is commonly connected to the first element 23 and the second element 24 arranged in the row direction of the array. The third conductor 44 forms the upper electrodes 33 and 38 for each of the first elements 23 or the second elements 24. Both ends of the third conductor 44 are connected to a pair of lead wires 45, respectively. The lead wires 45 extend in parallel to each other in the column direction of the array. Accordingly, all the third conductors 44 have the same length. Thus, the upper electrodes 33 and 38 are connected in common to the first element 23 and the second element 24 of the entire matrix. The third conductor 44 can be formed of, for example, iridium (Ir). However, other conductive materials may be used for the third conductor 44.

  Energization of the elements 23 and 24 is switched for each segment. Linear scan and sector scan are realized according to such switching of energization. Since the first elements 23 in one column simultaneously output ultrasonic waves, the number of columns, that is, the number of rows in the array, can be determined according to the output level of the ultrasonic waves. For example, the number of lines may be set to about 10 to 15 lines. In the figure, five lines are drawn without illustration. The number of columns in the array can be determined according to the spread of the scanning range. The number of columns may be set to 128 columns or 256 columns, for example. In the figure, there are omitted and 8 columns are drawn. The roles of the upper electrodes 33 and 38 and the lower electrodes 34 and 39 may be interchanged. That is, while the lower electrode is commonly connected to the elements 23 and 24 of the entire matrix, the upper electrode may be commonly connected to each column of the array.

  The outline of the base body 21 has a first side 21a and a second side 21b that are partitioned by a pair of parallel lines and face each other. One line of the first terminal array 46 a is arranged between the first side 21 a and the outline of the element array 22. One line of the second terminal array 46 b is arranged between the second side 21 b and the outline of the element array 22. The first terminal array 46a can form one line parallel to the first side 21a. The second terminal array 46b can form one line parallel to the second side 21b. The first terminal array 46 a includes a pair of upper electrode terminals 47 and a plurality of lower electrode terminals 48. The upper electrode terminal 47 and the lower electrode terminal 48 are formed on the same plane of the lower step surface 27. Similarly, the second terminal array 46 b includes a pair of upper electrode terminals 49 and a plurality of lower electrode terminals 51. The upper electrode terminal 49 and the lower electrode terminal 51 are formed on the same plane of the lower step surface 27. Upper electrode terminals 47 and 49 are connected to both ends of one lead wire 45, respectively. The lead wiring 45 and the upper electrode terminals 47 and 49 may be formed symmetrically with respect to a vertical plane that bisects the element array 22. Lower electrode terminals 48 and 51 are connected to both ends of the first conductor 42 and the second conductor 43, respectively. The first conductor 42, the second conductor 43, and the lower electrode terminals 48, 51 may be formed in plane symmetry on a vertical plane that bisects the element array 22. Here, the outline of the base 21 is formed in a rectangular shape. The outline of the base 21 may be square or trapezoidal.

  A first flexible printed wiring board (hereinafter referred to as “first wiring board”) 52 a is connected to the base body 21. The first wiring board 52a covers the first terminal array 46a. Conductive lines, that is, first signal lines 53 are formed at one end of the first wiring board 52a corresponding to the upper electrode terminal 47 and the lower electrode terminal 48, respectively. The first signal lines 53 are individually faced and joined to the upper electrode terminal 47 and the lower electrode terminal 48, respectively. Similarly, the base 21 is covered with a second flexible printed wiring board (hereinafter referred to as “second wiring board”) 52b. The second wiring board 52b covers the second terminal array 46b. Conductive lines, that is, second signal lines 54 are formed at one end of the second wiring board 52 b corresponding to the upper electrode terminal 49 and the lower electrode terminal 51 individually. The second signal line 54 is individually faced and joined to the upper electrode terminal 49 and the lower electrode terminal 51.

  As shown in FIG. 4, the base 21 includes a substrate 55 and a coating film 56. The substrate 55 is made of, for example, silicon (Si). An upper step surface (second plane) 57 and a lower step surface (first plane) 58 having steps are formed on the surface of the substrate 55. In the substrate 55, a first opening 59 a is formed for each individual first element 23, and a second opening 59 b is formed for each individual second element 24. The first opening 59 a opens at the lower step surface 58. The second opening 59 b opens at the upper stage surface 57. The first opening 59 a and the second opening 59 b are arranged in an array with respect to the substrate 55. The outline of the region where the first opening 59 a and the second opening 59 b are arranged corresponds to the outline of the element array 22.

A coating film 56 is formed on the entire surface of the substrate 55. The coating film 56 is a uniform continuous film. The coating film 56 is continuous with each other on the upper surface 57 and the lower surface 58. The covering film 56 includes a silicon oxide (SiO ₂ ) layer 56 a stacked on the surface of the substrate 55 and a zirconium oxide (ZrO ₂ ) layer 56 b stacked on the surface of the silicon oxide layer 56 a. The coating film 56 is in contact with the first opening 59a and the second opening 59b. Thus, a part of the coating film 56 forms the first vibration film 31 and the second vibration film 36 corresponding to the contours of the first opening 59a and the second opening 59b, respectively. The first vibration film 31 closes the first opening 59a. The second vibration film 36 closes the second opening 59b. The first vibration film 31 and the second vibration film 36 are portions of the coating film 56 that can vibrate in the thickness direction of the substrate 55 because they face the first opening 59a and the second opening 59b.

  The silicon oxide layer 56 a has a uniform film thickness on the upper step surface 57 and the lower step surface 58. Similarly, the zirconium oxide layer 56 b has a uniform film thickness on the upper step surface 57 and the lower step surface 58. As a result, the upper step surface 26 and the lower step surface 27 appear on the surface of the coating film 56, that is, the surface of the substrate 21, following the upper step surface 57 and the lower step surface 58 of the substrate 55. The film thickness of the silicon oxide layer 56a is about 0.1 to 3.0 μm. The thickness of the zirconium oxide layer 56b is about 0.1 to 1.0 μm.

  A first conductor 42, a piezoelectric film 35, and a third conductor 44 are sequentially stacked on the surface of the first vibration film 31. The piezoelectric film 35 can be formed of, for example, lead zirconate titanate (PZT). Other piezoelectric materials may be used for the piezoelectric film 35. The piezoelectric film 35 covers at least a part of the lower electrode 34 and a part of the first vibration film 31. The upper electrode 33 covers at least a part of the piezoelectric film 35. Here, the piezoelectric film 35 completely covers the surface of the first conductor 42 under the third conductor 44. A short circuit between the first conductor 42 and the third conductor 44 can be avoided by the action of the piezoelectric film 35.

  Similarly, the second conductor 43, the piezoelectric film 41, and the third conductor 44 are sequentially stacked on the surface of the second vibration film 36. The piezoelectric film 41 can be formed of, for example, lead zirconate titanate (PZT). Other piezoelectric materials may be used for the piezoelectric film 41. The piezoelectric film 41 covers at least part of the lower electrode 39 and part of the second vibration film 36. The upper electrode 38 covers at least a part of the piezoelectric film 41. Here, the upper step surface 57 completely covers the surface of the second conductor 43 under the third conductor 44. A short circuit between the second conductor 43 and the third conductor 44 can be avoided by the action of the piezoelectric film 35.

Here, the lower electrode 34 of the first piezoelectric element 32 and the lower electrode 39 of the second piezoelectric element 37 are formed of the same material. Moreover, the thickness t _L1 of the lower electrode 34 of the first piezoelectric element 32 is equal to the thickness t _L2 of the lower electrode 39 of the second piezoelectric element 37. The thicknesses t _L1 and t _L2 are, for example, about 0.1 to 1.0 μm. The piezoelectric film 35 of the first piezoelectric element 32 and the piezoelectric film 41 of the second piezoelectric element 37 are formed from the same material. The thickness t _P1 of the piezoelectric film 35 of the first piezoelectric element 32 and the thickness t _P2 of the piezoelectric film 41 of the second piezoelectric element 37 are equal. The thicknesses t _P1 and t _P2 are on the order of several μm, for example. Further, since the upper electrode 33 of the first piezoelectric element 32 and the upper electrode 38 of the second piezoelectric element 37 are formed in common by the third conductor 44, the upper electrode 33 and the upper electrode 38 are made of the same material. Have the same film thickness. The film thickness of the upper electrodes 33 and 38 is on the order of several tens of nm.

  An acoustic matching layer 61 is laminated on the surface of the base 21. For example, the acoustic matching layer 61 covers the entire surface of the base 21 over the entire surface. As a result, the element array 22, the first terminal array 46a, the second terminal array 46b, the first wiring board 52a, and the second wiring board 52b are covered with the acoustic matching layer 61. The acoustic matching layer 61 covers the first element 23 and the second element 24. The first vibration film 31, the first piezoelectric element 32, the second vibration film 36, and the second piezoelectric element 37 are in close contact with the acoustic matching layer 61 without a gap. For example, a silicone resin film can be used for the acoustic matching layer 61. The acoustic matching layer 61 protects the structure of the element array 22, the bonding between the first terminal array 46a and the first wiring board 52a, and the bonding between the second terminal array 46b and the second wiring board 52b.

  The acoustic matching layer 61 has a flat upper surface (plane). The first upper surface of the first piezoelectric element 32 is separated from the upper surface 61a of the acoustic matching layer 61 by a first distance D1. The film thickness of the acoustic matching layer 61 is set on the first piezoelectric element 32 based on the first distance D1. The first distance D1 is determined according to the first frequency that is the resonance frequency of the first element 23. Here, the first distance D1 is set to an odd multiple of ¼ of the wavelength of the first frequency. The second upper surface of the second piezoelectric element 37 is separated from the upper surface of the acoustic matching layer 61 by a second distance D2. The film thickness of the acoustic matching layer 61 is set on the second element 24 based on the second distance D2. The second distance D2 is determined according to the second frequency that is the resonance frequency of the second element 24. Here, the second distance D2 is set to an odd multiple of ¼ of the wavelength of the second frequency. The second distance D2 is smaller than the first distance D1. Here, the resonance frequency of the second element 24 corresponds to a harmonic of the resonance frequency of the first element 23.

  An acoustic lens 62 is laminated on the acoustic matching layer 61. The acoustic lens 62 is in close contact with the surface of the acoustic matching layer 61. The outer surface of the acoustic lens 62 is formed as a partial cylindrical surface. The partial cylindrical surface has a bus parallel to the first conductor 42 and the second conductor 43. The curvature of the partial cylindrical surface is determined according to the focal position of the ultrasonic wave transmitted from one row of the elements 23 and 24 connected to the first conductor 42 or the second conductor 43 of one line. The acoustic lens 62 is made of, for example, a silicone resin.

  A reinforcing plate 63 is fixed to the back surface of the base 21. The back surface of the base 21 is overlaid on the surface of the reinforcing plate 63. The reinforcing plate 63 closes the first opening 59 a and the second opening 59 b on the back surface of the ultrasonic device 17. The reinforcing plate 63 can include a rigid base material. The reinforcing plate 63 can be formed from, for example, a silicon substrate. The plate thickness of the base 21 is set to about 100 to 300 μm, for example, and the plate thickness of the reinforcing plate 63 is set to about 100 to 150 μm, for example. An adhesive can be used for bonding.

(3) Operation of Ultrasonic Diagnostic Device Next, the operation of the ultrasonic diagnostic device 11 will be briefly described. When transmitting ultrasonic waves, the first piezoelectric element 32 is supplied with a pulse signal having a first frequency. The pulse signal is supplied to the first element 23 for each column through the lower electrode terminals 48 and 51 connected to the first conductor 42 and the upper electrode terminals 47 and 49 connected to the third conductor 44. In each of the first elements 23, an electric field acts on the piezoelectric film 35 between the lower electrode 34 and the upper electrode 33. The piezoelectric film 35 vibrates with ultrasonic waves having the first frequency. The vibration of the piezoelectric film 35 is transmitted to the first vibration film 31. The first vibrating membrane 31 resonates with the first frequency ultrasonic wave. Vibration is enhanced. Thus, the first vibration film 31 vibrates ultrasonically. As a result, a desired ultrasonic beam is emitted toward the subject (for example, inside the human body).

  The reflected ultrasonic wave is transmitted through the acoustic matching layer 61 to vibrate the first vibration film 31 and the second vibration film 36. The first vibration film 31 vibrates ultrasonically at a resonance frequency of the first frequency. The second vibration film 36 vibrates ultrasonically at the resonance frequency of the second frequency. The piezoelectric effect is exhibited by the first piezoelectric element 32 and the second piezoelectric element 37 in accordance with the vibration of the first vibration film 31 and the second vibration film 36. In each of the first element 23 and the second element 24, a potential is generated between the upper electrodes 33 and 38 and the lower electrodes 34 and 39. The electromotive voltages are taken out as electrical signals by the first piezoelectric element 32 and the second piezoelectric element 37, respectively. Thus, the first vibrating membrane 31 and the second vibrating membrane 36 receive ultrasonic waves having different frequencies. Since the film thickness of the acoustic matching layer 61 is set for each resonance frequency of the vibration film, acoustic coupling can be realized with high accuracy for each frequency of the ultrasonic wave. In this way, when the first frequency ultrasonic wave is transmitted toward the subject, the reflected ultrasonic wave includes the harmonic component (second frequency) in addition to the first frequency ultrasonic component. Therefore, if the second frequency ultrasonic wave is received in addition to the first frequency ultrasonic wave, the sensitivity of the ultrasonic device 17 is increased.

  Transmission and reception of ultrasonic waves are repeated. As a result, linear scan and sector scan are realized. When the scan is completed, an image is formed based on the digital signal of the output signal. The formed image is displayed on the screen of the display panel 15.

  In the ultrasonic device 17, the first film thickness of the acoustic matching layer 61 is specified on the first piezoelectric element 32 of the first vibration film 31, and the first thickness of the acoustic matching layer 61 is specified on the second piezoelectric element 37 of the second vibration film 36. 2 The film thickness is specified. The frequency of the ultrasonic wave transmitted to the first vibration film 31 and the second vibration film 36 is adjusted according to the film thickness of the acoustic matching layer 61. Thus, the first vibrating membrane 31 and the second vibrating membrane 36 receive ultrasonic waves having different frequencies. Since the coating film 56 and the piezoelectric elements 32 and 37 can be accurately processed on the surface of the substrate 55, the first film thickness and the second film thickness are accurately determined in the first vibration film 31 and the second vibration film 36. Can be secured. Acoustic coupling can be realized with high accuracy for each ultrasonic frequency.

  As described above, the lower electrode 34 of the first piezoelectric element 32 and the lower electrode 39 of the second piezoelectric element 37 are made of the same material and have the same thickness. Therefore, the lower electrode 34 of the first piezoelectric element 32 and the lower electrode 39 of the second piezoelectric element 37 can be formed in the same manufacturing process. Similarly, the upper electrode 33 of the first piezoelectric element 32 and the upper electrode 38 of the second piezoelectric element 37 are made of the same material and have the same thickness. Therefore, the upper electrode 33 of the first piezoelectric element 32 and the upper electrode 38 of the second piezoelectric element 37 can be formed in the same manufacturing process. Further, the piezoelectric film 35 of the first piezoelectric element 32 and the piezoelectric film 41 of the second piezoelectric element 37 are made of the same material and have the same thickness. The piezoelectric film 35 of the first piezoelectric element 32 and the piezoelectric film 41 of the second piezoelectric element 37 can be formed in the same manufacturing process. In any case, complication of the manufacturing process can be avoided. In addition, the coating film 56 has a uniform film thickness in the first vibration film 31 and the second vibration film 36. The coating film 56 can be formed uniformly. The uniform coating film 56 can be formed relatively easily and accurately.

  The lower electrode terminals 48 and 51 of the first conductor 42 connected to the first piezoelectric element 32 and the lower electrode terminals 48 and 51 of the second conductor 43 connected to the second piezoelectric element 37 are arranged on the same plane. Is done. Further, the upper electrode terminals 47 and 49 and the lower electrode terminals 48 and 51 of the third conductor 44 that are commonly connected to the first piezoelectric element 32 and the second piezoelectric element 37 are arranged on the same plane. The first wiring board 52a and the second wiring board 52b can receive the upper electrode terminals 47 and 49 and the lower electrode terminals 48 and 51 in a plane. Compared with the case where the lower electrode terminals 48 and 51 are arranged on the upper surface 26, the shapes of the first wiring board 52a and the second wiring board 52b are prevented from being complicated, and a reliable connection is realized. As described above, since the difference between the first distance D1 and the second distance D2 is an integral multiple of one-fourth the wavelength of the resonance frequency of the second vibration film 36, it is possible to reliably receive harmonic ultrasonic waves. Can be done.

(4) Method for Manufacturing Ultrasonic Device Next, a method for manufacturing the ultrasonic device 17 will be briefly described. A substrate 71 is prepared. The substrate 71 is made of, for example, silicon. As shown in FIG. 5, a pattern of a photoresist 72 is formed on the surface (first surface) 71 a of the substrate 71. The pattern is shaped like the upper surface 57. Etching is performed on the surface 71 a of the substrate 71. As shown in FIG. 6, the surface 71 a of the substrate 71 is engraved to form an upper step surface 73 and a lower step surface 74 having steps. According to the photolithography technique, the upper step surface 73 and the lower step surface 74 can be accurately formed in a plane and parallel to each other.

  As shown in FIG. 7, for example, heat treatment is performed on the surface of the substrate 71 to form an oxide film. The silicon of the substrate 71 is oxidized to form silicon oxide. The oxide film has a uniform film thickness. Thus, the substrate 71 to the substrate 55 and the silicon oxide layer 56a are formed. Since the upper step surface 73 and the lower step surface 74 are oxidized as they are, the surface of the silicon oxide layer 56a can maintain a flat surface and parallelism with high accuracy. Thus, the upper step surface 57 and the lower step surface 58 are established on the surface of the substrate 55.

  Thereafter, as shown in FIG. 8, a zirconium oxide layer 56b is formed on the entire surface of the silicon oxide layer 56a. In forming, a zirconium layer is formed on one side. For example, CVD (Chemical Vapor Deposition) is used. The zirconium layer is formed with a uniform film thickness. An oxidation treatment is performed on the zirconium layer. The coating film 56 is established by stacking the silicon oxide layer 56a and the zirconium oxide layer 56b. The surface of the zirconium oxide layer 56b reflects the surface shape of the planar silicon oxide layer 56a. Thus, the surface of the coating film 56 on the surface of the substrate 55 can be processed with high accuracy.

  Thereafter, as shown in FIG. 9, the first piezoelectric element 32 and the second piezoelectric element 37 are formed on the surface of the coating film 56. For example, a conductive material layer 75 is formed on the entire surface of the zirconium oxide layer 56b. For example, the CVD method is used. The material layer 75 is formed with a uniform film thickness. A pattern of a photoresist 76 is formed on the surface of the material layer 75. The pattern represents the shape of the first conductor 42 and the second conductor 43. Etching is performed from the surface of the material layer 75. As a result, the first conductor 42 and the second conductor 43 are formed from the material layer 75. Since the first conductor 42 and the second conductor 43 are formed of a common material layer, the lower electrode 34 of the first piezoelectric element 32 and the lower electrode 39 of the second piezoelectric element 37 are the same material. Have the same thickness. Thus, the lower electrodes 34 and 39 are formed in the same manufacturing process. The complexity of the manufacturing process is avoided.

  Similarly, piezoelectric films 35 and 41 and upper electrodes 33 and 38 are formed on the surface of the coating film 56. Both are formed from a common material layer. Etching is performed according to the pattern of the photoresist. Therefore, the piezoelectric film 35 and the upper electrode 33 of the first piezoelectric element 32 and the piezoelectric film 41 and the upper electrode 38 of the second piezoelectric element 37 are made of the same material and have the same thickness. Thus, the piezoelectric films 35 and 41 and the upper electrodes 33 and 38 are formed in the same manufacturing process.

  Thereafter, as shown in FIG. 10, a first opening 59 a and a second opening 59 b are formed in the substrate 55 from the back surface (second surface) 71 b of the substrate 71. The first opening 59 a is formed from the back side of the lower step surface 58. The second opening 59 b is formed from the back side of the upper surface 57. In the formation, the substrate 55 is exposed to the etching process from the back surface. At this time, the silicon oxide layer 56a functions as an etching stop layer. As a result, the first vibration film 31 and the second vibration film 36 are established in the coating film 56 through the first opening 59a and the second opening 59b. Thereafter, the reinforcing plate 63 is bonded to the back surface 71b of the substrate 71, for example.

  Thus, in addition to the first piezoelectric element 32 and the second piezoelectric element 37, the first conductor 42, the second conductor 43, the third conductor 44, the upper electrode terminals 47 and 49, and the lower electrode terminals 48 and 51 are formed. Then, the acoustic matching layer 61 is formed on the surface of the coating film 56. For example, spin coating is used for the formation. The fluid material is cured to form the acoustic matching layer 61. Therefore, the surface of the acoustic matching layer 61 is easily planarized. The acoustic matching layer 61 covers the first piezoelectric element 32 and the second piezoelectric element 37. Thereafter, the acoustic lens 62 is formed on the upper surface 61 a of the acoustic matching layer 61. In this way, the ultrasonic device 17 is manufactured.

(5) Configuration of Ultrasonic Device According to Second Embodiment FIG. 11 schematically shows an enlarged partial plan view of an ultrasonic device 17a according to the second embodiment. In the ultrasonic device 17a, the first elements 23 and the second elements 24 are arranged in a staggered arrangement. In the zigzag arrangement, the even-numbered second element group 24 may be staggered with respect to the odd-numbered first element group 23. Here, the third conductors 44 a and 44 b can have a width corresponding to the size of the corresponding first element 23 and second element 24. The width of the third conductor 44b connected to the second element 24 is smaller than the width of the third conductor 44a connected to the first element 23. At this time, the insulating film 81 is sandwiched between the first conductor 42 and the third conductor 44a in the first element group 23 in one row. The insulating film 81 separates the third conductor 44 a from the first conductor 42. Similarly, in the second element 24 group in one row, the insulating film 82 is sandwiched between the second conductor 43 and the third conductor 44b. The insulating film 82 separates the third conductor 44b from the second conductor 43. Thus, a short circuit is avoided. Other configurations are the same as those of the first embodiment.

(6) Configuration of Ultrasonic Device According to Third Embodiment FIG. 12 schematically shows an enlarged partial plan view of an ultrasonic device 17b according to the third embodiment. In the ultrasonic device 17b, the first element 23 and the second element 24 are collected for each row. The first elements 23 and the second elements 24 are alternately arranged in the column direction. The first element 23 and the second element 24 are connected to a common first conductor 42 for each column. In the device terminal 12, the output components of the first frequency and the second frequency are separated from the output signal based on, for example, Fourier transform. Other configurations are the same as those of the first embodiment or the second embodiment.

  In addition, in the ultrasonic device 17c, as shown in FIG. 13, the first element 23 and the second element 24 may be collectively arranged for each region. As a result, the step difference between the upper step surface 26 and the lower step surface 27 is only one straight line. As shown in FIG. 14, in the ultrasonic device 17d, the first element 23 and the second element 24 may be arranged concentrically. Here, the second element 24 and the first element 23 may be arranged on the inner side and the outer side with a specific circle as a boundary. As a result, the step difference between the upper step surface 26 and the lower step surface 27 is one circle. Other configurations are the same as those of the first embodiment and other embodiments.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Therefore, all such modifications are included in the scope of the present invention. For example, a term described with a different term having a broader meaning or the same meaning at least once in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. Also, the configuration and operation of a wiring structure such as the ultrasonic diagnostic apparatus 11, the apparatus terminal 12, the ultrasonic probe 13, the display panel 15, the elements 23 and 24, the first conductor 42, the second conductor 43, and the third conductor. Also, the present invention is not limited to that described in the present embodiment, and various modifications are possible.

  DESCRIPTION OF SYMBOLS 11 Ultrasonic image apparatus (ultrasonic diagnostic apparatus) as an electronic device, 12 Processing apparatus (apparatus terminal), 13 Probe (ultrasonic probe), 15 Display apparatus (display panel), 17 Ultrasonic device, 17a Ultrasonic device, 17b Ultrasonic device, 31 1st vibrating membrane, 32 1st piezoelectric element, 33 2nd electrode (upper electrode), 34 1st electrode (lower electrode), 35 Piezoelectric membrane, 36 2nd vibrating membrane, 37 1st 2 piezoelectric elements, 38 second electrode (upper electrode), 39 first electrode (lower electrode), 41 piezoelectric film, 42 first conductive wiring (first conductor), 43 second conductive wiring (second conductive) Body), 47 terminal (upper electrode terminal), 48 terminal (lower electrode terminal), 49 terminal (upper electrode terminal), 51 terminal (lower electrode terminal), 55 substrate, 56 coating film, 59a opening (first opening) , 59b opening ( 2 opening), 73 the upper surface 74 lower surface.

Claims (13)

A first plane; a second plane spaced from the reference plane including the first plane by a specific distance in a normal direction thereof; a first opening opening in the first plane; and a second opening opening in the second plane. A substrate having an opening;
A coating layer formed on the substrate, the first vibration film closing the first opening and the second vibration film closing the second opening;
A first piezoelectric element formed on the first vibrating membrane;
A second piezoelectric element formed on the second vibrating membrane;
An acoustic matching layer covering the first piezoelectric element and the second piezoelectric element and having a plane parallel to the first plane and the second plane;
Ultrasonic device having   2. The ultrasonic device according to claim 1, wherein the first piezoelectric element includes a piezoelectric body, the second piezoelectric element includes a piezoelectric body, and the piezoelectric body and the second piezoelectric element of the first piezoelectric element. The ultrasonic device is characterized in that the piezoelectric body is made of the same material and has the same thickness.   3. The ultrasonic device according to claim 1, wherein the first piezoelectric element has a first electrode on the first vibrating membrane side, and the second piezoelectric element has a first electrode on the second vibrating membrane side. An ultrasonic device comprising an electrode, wherein the first electrode of the first piezoelectric element and the first electrode of the second piezoelectric element are made of the same material and have the same thickness.   The ultrasonic device according to claim 1, wherein the first piezoelectric element has a second electrode on the acoustic matching layer side, and the second piezoelectric element is on the acoustic matching layer side. An ultrasonic wave having a second electrode, wherein the second electrode of the first piezoelectric element and the second electrode of the second piezoelectric element are made of the same material and have the same thickness device.   5. The ultrasonic device according to claim 1, wherein the first vibration film and the second vibration film have the same thickness. 6.   The ultrasonic device according to claim 1, wherein a terminal of a first conductive wiring connected to the first piezoelectric element and a terminal of a second conductive wiring connected to the second piezoelectric element. Are arranged in the same plane.   The ultrasonic device according to claim 1, wherein the second vibration film has a resonance frequency at a frequency corresponding to a harmonic of the resonance frequency of the first vibration film. Ultrasonic device.   8. The ultrasonic device according to claim 1, wherein the film thickness of the acoustic matching layer on the first vibration film is an odd number that is a half of a wavelength of a resonance frequency of the first vibration film. 9. The ultrasonic device according to claim 1, wherein the thickness of the acoustic matching layer on the second vibrating membrane is an odd multiple of one half of the wavelength of the resonance frequency of the second vibrating membrane.   The ultrasonic device according to claim 1, wherein the specific distance is an odd multiple of a half of a wavelength of a resonance frequency of the second vibrating membrane. .   A probe comprising: the ultrasonic device according to claim 1; and a housing that supports the ultrasonic device.   An electronic apparatus comprising: the ultrasonic device according to claim 1; and a processing apparatus that is connected to the ultrasonic device and processes an output of the ultrasonic device.   An ultrasonic imaging apparatus comprising: the ultrasonic device according to claim 1; and a display device that displays an image generated from an output of the ultrasonic device. Forming a first plane and a second plane having steps on the first surface of the substrate;
Forming a coating layer continuously covering the first plane and the second plane on the first surface of the substrate;
An opening is formed in the substrate from the second surface on the back side of the first surface at a position corresponding to the first plane and the second plane on the substrate, and the opening at a position corresponding to the first plane is closed. Forming a first vibrating membrane on the covering layer and a second vibrating membrane for closing the opening at a position corresponding to the second plane;
Forming a first piezoelectric element on the first vibrating membrane and forming a second piezoelectric element on the second vibrating membrane;
Forming an acoustic matching layer having a flat upper surface on the first surface of the substrate, covering the first piezoelectric element and the second piezoelectric element;
An ultrasonic device manufacturing method comprising:

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