JP2019016912A - Ultrasonic transducer array, ultrasonic probe, and ultrasonic diagnostic apparatus - Google Patents

Abstract

To provide an ultrasonic transducer array, an ultrasonic probe, and an ultrasonic diagnostic apparatus capable of taking out a signal for ultrasonic transmission/reception without using a penetrating electrode.SOLUTION: In an ultrasonic transducer array in which one or more pMUT cells 100 are arranged on a substrate 101, each of the pMUT cells 100 includes a diaphragm 105 including a diaphragm plate 102a provided on the substrate 101 so as to close an opening 101b provided on the substrate 101, an upper electrode 104a provided on a surface of the diaphragm 102a opposite to the opening 101b, a piezoelectric material layer 103, and a lower electrode 104b, and a conductive member 108 provided in the opening 101b to ensure electrode conduction for driving and receiving of the diaphragm 105.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an ultrasonic transducer array, an ultrasonic probe, and an ultrasonic diagnostic apparatus that are created using a microfabrication technique.

  In recent years, MEMS (Micro Electro Mechanical System) devices manufactured using microfabrication technology have become widespread. MEMS devices are used for sensors, transducers, and the like.

  For example, as a transducer that generates ultrasonic waves (ultrasonic transducer), for example, a unimorph diaphragm (movable film) in which a piezoelectric thin film (driving layer) such as PZT is formed on a substrate (base material layer) such as silicon is drum-shaped. There is a pMUT (Piezoelectric Micromachined Ultrasonic Transducer) that transmits and receives ultrasonic waves.

  The pMUT can be further miniaturized compared to a piezoelectric element obtained by dividing bulk PZT by dicing or the like, for example, so that high sensitivity and high image quality can be expected. It has various features such as being suitable for dimensional arraying and being capable of being reduced in size and thickness.

  In such a pMUT array in which a plurality of pMUTs are arranged, for example, a technique for providing a through electrode and taking out a signal is disclosed in Patent Document 1, for example.

Special table 2015-517752 gazette

  In order to increase the sensitivity of the pMUT array, it is desirable to arrange the pMUT cells as densely as possible. However, for example, when a through electrode is provided and a signal for ultrasonic transmission / reception is taken out, it is necessary to prepare a space for providing the through electrode, so that the pMUT cell density decreases. The decrease in pMUT cell density leads to lower sensitivity and lower image quality of the pMUT array. Therefore, there is a demand for a pMUT array that can extract signals for ultrasonic transmission / reception without using through electrodes.

  An object of the present invention is to provide an ultrasonic transducer array, an ultrasonic probe, and an ultrasonic diagnostic apparatus that can extract an ultrasonic wave transmission / reception signal without using a through electrode.

  The ultrasonic transducer array of the present invention is an ultrasonic transducer array in which one or more pMUT cells are arranged on a substrate, and each of the pMUT cells closes an opening provided on the substrate. A diaphragm provided on the substrate, a diaphragm including an electrode and a piezoelectric material layer provided on a surface opposite to the opening of the diaphragm, and provided in the opening, A conducting member for ensuring electrode conduction for driving and receiving the diaphragm.

  The ultrasonic probe of the present invention is an ultrasonic probe provided with the above-described ultrasonic transducer array.

  The ultrasonic diagnostic apparatus of the present invention is an ultrasonic diagnostic apparatus that generates an ultrasonic diagnostic apparatus using an ultrasonic reception signal obtained from an ultrasonic probe including the ultrasonic transducer array.

  According to the present invention, a signal for ultrasonic transmission / reception can be extracted without using a through electrode.

The figure which shows the external appearance structure of the ultrasonic diagnosing device which has an ultrasonic transducer Block diagram showing an electrical configuration example of an ultrasonic diagnostic apparatus The figure for demonstrating the structure of an ultrasound probe The figure which shows the example which arranged the pMUT cell which comprises an ultrasonic transducer array two-dimensionally The figure which shows the example which arranged the pMUT cell which comprises an ultrasonic transducer array two-dimensionally Cross section of pMUT cell The figure for demonstrating the creation method of a pMUT cell The figure for demonstrating the creation method of a pMUT cell The figure for demonstrating the creation method of a pMUT cell The figure for demonstrating the creation method of a pMUT cell The figure for demonstrating the creation method of a pMUT cell The figure for demonstrating the creation method of a pMUT cell The figure for demonstrating the creation method of a pMUT cell Cross-sectional view of a pMUT cell having a through electrode for extracting signals for ultrasonic transmission / reception FIG. 7A is a plan view showing an example of a channel in which a plurality of cells shown in FIG. 7A are arranged. The top view which shows the example of the channel by which the pMUT cell which concerns on embodiment of this invention was arranged The figure which compared the characteristic of the pMUT array using the pMUT cell which has the penetration electrode for performing the signal extraction for ultrasonic transmission / reception, and the characteristic of the pMUT array using the pMUT cell which concerns on embodiment of this invention The figure for demonstrating the modification 4 which connected the upper electrode of four cells in parallel The figure for demonstrating the modification 4 which connected the upper electrode of four cells in parallel The figure for demonstrating the modification 5 at the time of connecting the upper electrode and lower electrode of 4 cells in parallel The figure for demonstrating the modification 5 at the time of connecting the upper electrode and lower electrode of 4 cells in parallel The top view which illustrated the pMUT array at the time of mixing the pMUT cell which has multiple types of natural frequency The top view which illustrated the pMUT array at the time of mixing the pMUT cell which has multiple types of natural frequency Conceptual diagram showing how the entire array is broadened when narrowband cells are combined

  Embodiments of the present invention will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated example. In addition, in the following description, what has the same function and structure attaches | subjects the same code | symbol, and abbreviate | omits the description.

  FIG. 1 is a diagram showing an external configuration of an ultrasonic diagnostic apparatus. FIG. 2 is a block diagram showing an electrical configuration example of the ultrasonic diagnostic apparatus according to the present embodiment.

  The ultrasonic diagnostic apparatus 1 employs a configuration having an ultrasonic diagnostic apparatus main body 10, an ultrasonic probe 20, and a cable 30.

  The ultrasonic probe 20 transmits an ultrasonic signal to a human body (not shown) that is a subject, and receives an ultrasonic signal reflected by the human body.

  The ultrasonic diagnostic apparatus main body 10 is connected to the ultrasonic probe 20 via a cable 30, and transmits an electric signal transmission signal to the ultrasonic probe 20 via the cable 30, thereby the ultrasonic probe. An ultrasonic signal is transmitted to 20. In addition, the ultrasonic diagnostic apparatus main body 10 uses the electrical signal generated in the ultrasonic probe 20 based on the ultrasonic signal received by the ultrasonic probe 20 as an ultrasonic image of the internal state of the human body. Make an image.

  Specifically, the ultrasonic diagnostic apparatus main body 10 employs a configuration including 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. .

  The operation input unit 11 inputs, for example, a command for instructing the start of diagnosis or information on the subject. The operation input unit 11 is, for example, an operation panel or a keyboard provided with a plurality of input switches.

  The transmission unit 12 transmits a control signal (drive signal) received from the control unit 16 to the ultrasonic probe 20 via the cable 30.

  The receiving unit 13 receives a reception signal transmitted from the ultrasonic probe 20 via the cable 30. Then, the reception unit 13 outputs the received ultrasonic signal to the image processing unit 14.

  The image processing unit 14 generates an ultrasonic diagnostic image (ultrasonic image) representing an internal state in the subject using an ultrasonic signal received from the receiving unit 13 in accordance with an instruction from the control unit 16.

  The display unit 15 displays the ultrasonic image generated in the image processing unit 14 in accordance with an instruction from the control unit 16.

  The control unit 16 performs overall control of the ultrasonic diagnostic apparatus 1 by controlling the operation input unit 11, the transmission unit 12, the reception unit 13, the image processing unit 14, and the display unit 15 according to their functions.

[About Ultrasonic Probe]
FIG. 3 is a diagram for explaining the configuration of the ultrasound probe 20. The ultrasonic probe 20 includes a protective layer 21, a pMUT element 22 as an ultrasonic transmission / reception transducer array, a backing material 23, and a signal processing circuit 24. Details of the pMUT element 22 will be described later.

  The protective layer 21 protects the pMUT element 22. The protective layer 21 is made of a relatively soft silicone rubber or the like that does not give discomfort when being brought into contact with the human body and has an acoustic impedance that is relatively close to that of the human body.

  The backing material 23 attenuates unnecessary vibration generated in the pMUT element 22. The signal processing circuit 24 is a circuit that generates a pulse signal for ultrasonic transmission, processes a received pulse signal, and the like, and is connected to the ultrasonic diagnostic apparatus main body 10 via a cable 30.

[About pMUT element]
The pMUT element 22 is a pMUT array in which a plurality of pMUT cells 100 manufactured using MEMS (Micro Electro Mechanical Systems) technology are arranged one-dimensionally or two-dimensionally. The pMUT element 22 is an example of the ultrasonic transducer array of the present invention.

  4A and 4B are diagrams illustrating an example in which the pMUT cells 100 constituting the pMUT element 22 are two-dimensionally arranged. 4A shows an example in which the pMUT cells 100 are arranged on an orthogonal lattice, and FIG. 4B shows an example in which the pMUT cells 100 are arranged on a triangular lattice.

  4A and 4B, a plurality of adjacent pMUT cells 100 are electrically connected in parallel to form a channel ch. In the example of FIGS. 4A and 4B, one channel is composed of 3 × 11 cells, and FIGS. 4A and 4B show three channels ch_1 to ch_3. 4A and 4B, the pMUT cells 100 are also arranged outside the channels ch_1 to ch_3, but these are cells that do not have an ultrasonic transmission / reception function. In the present embodiment, these cells having no transmission / reception function may be referred to as dummy cells 100D. On the other hand, in FIG. 4A and FIG. 4B, a cell having an ultrasonic transmission / reception function, which is included in channels ch_1 to ch_3, may be referred to as an active cell 100A.

  The dummy cell 100D is installed to maintain the structural boundary symmetry between the cell at the end of the channel ch and the cell inside the channel ch. The dummy cell 100D is provided in an area outside the channel ch and having a width of one wavelength (about 10 cells) at the minimum frequency of the ultrasonic frequency band used in the pMUT element 22. The mechanical structure of the dummy cell 100D is basically the same as that of the active cell 100A. In other words, the pMUT element 22 includes a plurality of cells in a region excluding the dummy cell region corresponding to the width of one wavelength from the end portion of the pMUT cell 100 arranged in a predetermined number on the substrate. It is sufficient that at least one channel ch is configured by electrical connection in parallel.

  The reason why the dummy cell 100D is provided around the active cell 100A is as follows. When a cell is formed by etching, the etching rate may partially increase near the edge of the substrate due to a relatively larger amount of the etchant flowing than near the center. In that case, the shape of the cell formed near the center portion and the vicinity of the end portion of the substrate varies, and thus the cell characteristics may also vary. That is, the first reason for providing the dummy cell 100D is to prevent the cells near the edge of the substrate from being used for ultrasonic transmission / reception, thereby suppressing variation in the shape of the active cell 100A and making the characteristics of the active cell 100A uniform. It is because it can be made.

  The second reason is as follows. When the dummy cell is not provided, other cells exist around the cell at the center of the channel, but no other cell exists outside the cell at the channel end. As a result, the boundary condition of the mechanical vibration is different between the center and the end of the channel, and the resonance frequency and vibration amplitude of the cell fluctuate from cell to cell, resulting in inhomogeneous cell characteristics in the channel. That is, the second reason is that by providing dummy cells, the same mechanical boundary condition as the inside of the channel can be obtained at the end of the channel, and as a result, the vibration characteristics of the entire channel can be homogenized.

  In the following description, as shown in FIG. 4A, a case will be described in which each cell is arranged on an orthogonal lattice. However, from the viewpoint of improving the sensitivity of the pMUT element 22, it is more preferable to arrange cells on a triangular lattice as shown in FIG. 4B because the cell density can be increased.

[Structure of pMUT Cell 100]
Next, the structure of each pMUT cell 100 will be described. FIG. 5 is a cross-sectional view of the pMUT cell 100. The pMUT cell 100 includes a substrate 101 having an opening 101b, a diaphragm 102a, a piezoelectric material layer 103, an upper electrode 104a, and a lower electrode 104b. In the following description, the side on which the upper electrode 104a, the piezoelectric material layer 103, and the lower electrode 104b are provided is the upper side with respect to the substrate 101, and the opposite side (the side on which the opening 101b is provided) is the lower side. Let it be the side.

The substrate 101 is, for example, a silicon substrate. SiO ₂ layers 101 a are formed on both surfaces of the substrate 101. Further, a highly doped silicon layer (hereinafter referred to as HDSi layer) 102 is joined to the upper side of the upper SiO ₂ layer 101a. The diaphragm 102 a is a part of the HDSi layer 102 and has a thin plate structure that closes the opening 101 b provided in the substrate 101.

  The piezoelectric material layer 103 is made of, for example, a thin film of PZT (lead zirconate titanate), and is opposite to the opening 101b (upper side) with respect to the diaphragm 102a in order to vibrate the diaphragm 102a by applying an electric field. Is formed.

  The upper electrode 104 a is an electrode provided on the upper side of the piezoelectric material layer 103. On the other hand, the lower electrode 104 b is an electrode provided on the lower side of the piezoelectric material layer 103. The lower electrode 104b is electrically connected to a conductive member 108 to be described later via the diaphragm 102a.

  The diaphragm 102a, the piezoelectric material layer 103, the upper electrode 104a, and the lower electrode 104b are formed by patterning, for example, in a circular cross section. Note that the cross-sectional shapes of the diaphragm 102a, the piezoelectric material layer 103, the upper electrode 104a, and the lower electrode 104b may be other than a circular shape, for example, a polygonal shape such as a regular octagon. Further, the shape of the upper electrode 104 a and the lower electrode 104 b may be different from the cross-sectional shape of the piezoelectric material 103. A diaphragm (movable film) 105 serving as a piezoelectric element is configured by the diaphragm 102a thus patterned, the piezoelectric material layer 103, the upper electrode 104a, and the lower electrode 104b.

  The insulating layer 106 is a layer of an insulating material provided so as to cover the patterned piezoelectric material layer 103, the upper electrode 104a, and the lower electrode 104b. As shown in FIG. 5, the upper end portion of the upper electrode 104 a is exposed from the insulating layer 106. An extraction electrode (not shown) for the upper electrode 104a may be further provided on the upper electrode 104a. The insulating layer 106 may be formed of an insulating material having a low dielectric constant, such as polysilicon, epoxy, polyurea, polyimide, polyurea, parylene (registered trademark), or the like.

The insulating layer 107 is a layer of an insulating material formed along the inner wall surface of the opening 101b. The insulating layer 107 is provided so as to cover the structure exposed from the opening 101b of the substrate 101, that is, the HDSi layer 102 (the vibration plate 102a), the SiO ₂ layer 101a, the substrate 101, and the like. The insulating layer 107 is an insulating film formed of, for example, SiO ₂ or the like.

  An opening is provided in a part of the insulating layer 107, and a conductive member 108, which will be described later, is in contact with the HDSi layer 102 (the diaphragm 102a) through the opening. Note that FIG. 5 illustrates the case where an opening is provided in a part of the insulating layer 107, but the opening may be provided in the entire portion of the insulating layer 107 in contact with the diaphragm 102a.

  The conduction member 108 is a member for ensuring conduction with the lower electrode 104b. The conductive member 108 is made of a metal having good conductivity. The conductive member 108 may be composed of a single layer of metal, or may be composed of a plurality of layers of metal (for example, a Cu layer is further plated with a Ni layer as a base).

  At least one pMUT cell 100 having such a configuration is formed on the substrate 101 and connected to an LSI substrate or the like by, for example, ACF pressure bonding. The conduction member 108 is connected to a signal detection circuit that is provided on the LSI substrate and that inputs and outputs signals to the pMUT cell 100. The signal detection circuit is connected to the ultrasonic diagnostic apparatus main body 10 via the cable 30 (or not via the cable wirelessly) via the signal processing circuit 24 (or not via the above-mentioned signal processing circuit 24). Based on the control of the apparatus main body 10, a drive signal is input to the pMUT cell 100, or a reception signal is received from the pMUT cell 100 and output to the ultrasonic diagnostic apparatus main body 10. In the present embodiment, drive signals and reception signals are input / output through the conductive member 108 and the lower electrode 104b.

  Thus, in the pMUT cell 100, the conduction of the lower electrode 104b is ensured by the conduction member 108 via the diaphragm 102a. Therefore, for example, a signal for ultrasonic transmission / reception can be extracted from the lower electrode 104b without providing a through electrode or the like penetrating the substrate 101.

[Material of diaphragm 102a (HDSi layer 102)]
As described above, the conducting member 108 ensures conduction with the lower electrode 104b via the diaphragm 102a (HDSi layer 102). For this reason, the HDSi layer 102 needs to have a resistivity of, for example, 1 mΩ · cm or less as described above. The Si layer having such a resistivity is obtained, for example, by doping silicon with a dopant such as phosphorus, boron, gallium phosphide, gallium arsenide or the like at a doping concentration of about 10 ¹⁹ cm ⁻³ .

[How to make]
Next, a method for creating the pMUT cell 100 will be described. 6A to 6G are diagrams for explaining a method of creating the pMUT cell 100. FIG.

First, a silicon wafer is prepared as shown in FIG. 6A. This silicon wafer corresponds to the substrate 101 shown in FIG. For example, a SiO ₂ layer (corresponding to the SiO ₂ layer 101a in FIG. 5) is generated on both sides of this silicon wafer by, for example, a thermal oxidation furnace, and a surface activation treatment is performed on one side (HDSi layer 102 in FIG. 5). Are directly joined (FIG. 6B). In the following description, the side on which the highly doped silicon wafer is bonded as viewed from the silicon wafer is described as the upper side.

  Next, as shown in FIG. 6C, a lower electrode layer (corresponding to the lower electrode 104b in FIG. 5), a piezoelectric material layer (corresponding to the piezoelectric material layer 103 in FIG. 5), an upper electrode layer on the highly doped silicon layer. (Corresponding to the upper electrode 104a in FIG. 5) are sequentially formed. The lower electrode layer and the upper electrode layer have a laminated structure of, for example, about 30 nm of titanium and 100 nm of platinum, and are formed by, for example, sputtering or vacuum deposition. The piezoelectric material layer 103 is, for example, a PZT (lead zirconate titanate) layer of about 1 to 3 μm, and is formed by sputtering or a chemical solution method. From the viewpoint of symmetry of the piezoelectric characteristics, it is desirable that the upper electrode layer and the lower electrode layer have the same configuration.

  Next, as shown in FIG. 6D, after patterning the upper electrode layer, the piezoelectric material layer, and the lower electrode layer, an insulating layer (corresponding to the insulating layer 107 in FIG. 5) is formed. Specifically, first, an upper electrode pattern is formed using an etchant (for example, Ar gas, Cl gas, etc.) such that the piezoelectric material layer (PZT) becomes an etching stop layer (high selection ratio). Then, the piezoelectric material layer is patterned using an etchant (for example, a mixed solution of hydrofluoric acid and nitric acid) such that the lower electrode layer becomes an etching stop layer. Further, the lower electrode pattern is formed using an etchant (for example, Ar gas, Cl gas, etc.) such that the silicon layer becomes an etching stop layer. Although illustration is omitted, the highly doped silicon wafer under the lower electrode layer may be further etched for isolation from adjacent cells. Then, an insulating material is formed by depositing an insulating material having a low dielectric constant using sputtering or a vacuum evaporation apparatus. Further, the upper electrode layer is exposed using a CMP (Chemical Mechanical Polishing) process or the like, and an extraction electrode (not shown) for the upper electrode layer is formed.

Then, as shown in FIG. 6E, the SiO ₂ layer and the Si layer are etched from below to form openings (corresponding to the openings 101b in FIG. 5). Specifically, after etching the lower SiO ₂ layer with, for example, hydrofluoric acid or the like, deep RIE (Deep RIE (Reactive Ion Etching)) is performed using an etchant in which the SiO ₂ layer becomes an etching stop layer. Etch the silicon wafer. For example, in the Bosch method, it is desirable to alternately introduce SF ₆ as an etching gas and C ₄ F ₈ as a passivation for protecting the sidewall of the opening. Further, the upper SiO ₂ layer is etched using RIE (reactive ion etching) using an etching gas such as CF ₄ , liquid phase or gas phase hydrofluoric acid, or the like.

Next, as shown in FIG. 6F, an insulating film such as SiO ₂ (corresponding to the insulating layer 107 in FIG. 5) is formed by CVD (chemical vapor deposition) or the like so as to cover the inner wall surface of the opening.

  Thereafter, as shown in FIG. 6G, a part of the insulating film formed in FIG. 6F is removed by etching to expose the surface of the highly doped silicon wafer, and then a conducting member (corresponding to the conducting member 108 in FIG. 5) is removed. A single layer or a plurality of layers are formed by electrolytic plating or the like. The conducting member is a highly conductive metal film having a thickness of, for example, about 0.1 μm.

[Effects of pMUT element 22]
Next, the effect of the pMUT element 22 including one or more pMUT cells 100 according to the embodiment of the present invention will be specifically compared with the case of performing signal extraction for ultrasonic transmission / reception using a through electrode. explain.

  FIG. 7A and FIG. 7B are configuration examples of the pMUT cell when the signal extraction for ultrasonic transmission / reception from the lower electrode is performed using the through electrode. 7A is a cross-sectional view of a pMUT cell having a through electrode, and FIG. 7B is a plan view showing an example in which a plurality of cells shown in FIG. 7A are arranged on a substrate having a predetermined size. On the other hand, FIG. 7C is a plan view showing an example in which the pMUT cells 100 according to the embodiment of the present invention are arranged on a substrate having the same size as FIG. 7B.

  In the example shown in FIG. 7A, a through electrode is provided so as to penetrate from the upper side to the lower side of the substrate (silicon wafer), and a signal for ultrasonic transmission / reception is extracted from the lower electrode by the through electrode. When a through electrode for extracting signals for ultrasonic transmission / reception is provided in this way, a diaphragm (diaphragm, piezoelectric material layer, upper electrode and lower electrode is formed in one cell as shown in FIG. 7B. In addition to the above, a space for providing a through electrode is required.

  On the other hand, in the pMUT cell 100, as described above, the conductive member 108 that secures electrical connection between the lower electrode 104b and the outside is provided in the opening 101b existing on the lower side of the diaphragm. For this reason, as shown in FIG. 7C, it is not necessary to secure a space for providing a through electrode around the diaphragm, as compared with the case where a through electrode for performing signal extraction for ultrasonic transmission / reception is provided. The size of each pMUT cell 100 can be reduced. For this reason, since the pMUT cells 100 can be arranged in the pMUT element 22 with high density, a highly sensitive ultrasonic transducer can be created by the pMUT element 22.

  Further, in the pMUT cell 100, compared with the case where a through electrode for performing signal extraction for ultrasonic transmission / reception is provided, since the size of each cell is small, the structure period is reduced, and the side lobe angle is increased. It is possible to suppress the influence of the virtual image due to the side lobe from the ultrasonic image generated by the ultrasonic diagnostic apparatus main body 10 and improve the image quality.

  Moreover, since the pMUT cell 100 has a highly symmetrical structure as shown in FIG. 7C, the vibration characteristics of the pMUT cells 100 arranged in the pMUT element 22 can be homogenized. Thereby, the sensitivity as an ultrasonic transducer of the pMUT element 22 can be improved.

  Table 1 below shows the characteristics of the pMUT array using the pMUT cell having the through electrode for performing signal extraction for ultrasonic transmission / reception, and the characteristics of the pMUT array using the pMUT cell 100 according to the embodiment of the present invention. It is the table which compared. FIG. 8 shows the characteristics of a pMUT array using a pMUT cell having a through electrode for extracting signals for ultrasonic transmission / reception, and the characteristics of a pMUT array using the pMUT cell 100 according to the embodiment of the present invention. FIG. Table 1 and FIG. 8 show the frequency characteristics calculated by the finite element method when each pMUT array is used as an ultrasonic transducer. Conventional Example 1 has a through electrode diameter of 20 μm and a cell pitch of 110 μm, and Conventional Example 2 has a through electrode diameter of 40 μm and a cell pitch of 150 μm. The cell pitch of the present invention is assumed to be 66 μm.

  As shown in Table 1 and FIG. 8, when the pMUT cell 100 is used, the bandwidth can be expanded without reducing the peak sensitivity. In other words, when the pMUT cell 100 is used, higher transmission sensitivity can be obtained in a wider frequency band than when a through electrode for performing signal extraction for ultrasonic transmission / reception is used. Further, as shown in Table 1, the cell density can be increased.

<Action and effect>
As described above, the ultrasonic transducer array according to the embodiment of the present invention is an ultrasonic transducer array in which one or more pMUT cells 100 are arranged on the substrate 101, and each pMUT cell 100. The diaphragm 102a provided on the substrate 101 so as to close the opening 101b provided on the substrate 101, and the upper electrode 104a provided on the surface opposite to the opening 101b of the diaphragm 102a. And a diaphragm 105 including the piezoelectric material layer 103 and the lower electrode 104b, and a conducting member 108 provided in the opening 101b and ensuring electrode conduction for driving and receiving the diaphragm 105.

  With such a configuration, since the size of the pMUT cell 100 can be reduced as compared with the case where a through electrode for performing signal extraction for ultrasonic transmission / reception is provided, the cell density can be improved. . For this reason, a wide band and an improvement in reception sensitivity are realized. Further, since the channel pitch is reduced, the side lobe angle is increased and the image quality of the ultrasonic image is expected to be improved. Further, the structural strength of the entire ultrasonic transducer array can be improved by providing the conducting member 108 in the opening 101b constituting the diaphragm 105. Furthermore, since each pMUT cell 100 has a highly symmetric structure, the vibration characteristics of each pMUT cell 100 (or each channel) can be homogenized, and the reception sensitivity of the entire ultrasonic transducer array can be improved.

<Modification example>
As mentioned above, although embodiment of this invention was described referring drawings, this invention is not limited to this example. Various changes or modifications that can be conceived by those skilled in the art within the scope of the claims are also included in the technical scope of the present invention. In addition, the constituent elements in the above embodiments may be arbitrarily combined within the scope not departing from the spirit of the disclosure. Hereinafter, various modified examples will be described in detail.

[Modification Example 1]
In the embodiment described above, the opening 101b is a simple cavity, but the opening 101b may be sealed with, for example, a vacuum or an inert gas. Alternatively, the opening 101b may be filled with liquid, resin, or the like. When these are sealed or filled, a conductive material (metal, conductive resin, conductive oxide) is provided at the inlet portion in the opening 101b (for example, near the lower end of the opening 101b shown in FIG. 5). Also good. By doing in this way, effects, such as protection of conduction member 108, conduction stability, and a broad band, are acquired.

[Modification Example 2]
In the embodiment described above, the conductive member 108 is provided in all the pMUT cells 100. For example, the conductive member 108 is not provided in all the pMUT cells 100, and one or more pMUT cells 100 in the channel ch are provided. Only the conductive member 108 may be provided. That is, in the present invention, one cell may be provided with a conductive member in the channel ch, but it is desirable to provide a conductive member in a plurality of cells in consideration of disconnection of the conductive line.

[Modification Example 3]
In the above-described embodiment, the extraction electrode (not shown) is connected to the upper electrode 104a. However, for example, a through electrode that penetrates the substrate 101 is provided, and a signal is extracted from the upper electrode 104a. You may do it. The upper electrode 104a is an inter-channel common electrode (GND), and even if a through electrode is provided in the upper electrode 104a as in the third modification, the number of the upper electrodes 104a is very small. For this reason, even if a through electrode is provided for the upper electrode 104a, the vibration characteristics in the entire channel are not significantly affected.

[Modification Example 4]
In the case of providing a through electrode for extracting a signal from the upper electrode 104a, the following configuration is suitable. FIG. 9A and FIG. 9B are diagrams for explaining a modification example 4 in which the upper electrodes 104a of four cells are coupled in parallel. 9A is a plan view, and FIG. 9B is a cross-sectional view taken along line AA of FIG. 9A.

  As shown in FIGS. 9A and 9B, in the modified example 4, the upper electrodes 104a of the four cells are coupled in parallel to provide a through electrode 104aT at the center. With such a configuration, it is possible to provide a through electrode that extracts a signal from the upper electrode 104a without increasing the size of the cell. In addition, with such a configuration, the symmetry of the vibration characteristics of each cell can be ensured.

[Modification Example 5]
In the modified example 4, only the upper electrodes of the four cells are coupled in parallel and the lower electrode 104b is independent for each cell, but the lower electrode 104b may also be coupled in parallel. FIG. 10A and FIG. 10B are diagrams for explaining a modification example 5 in which the upper electrode 104a and the lower electrode 104b of four cells are coupled in parallel. 10A is a plan view, and FIG. 10B is a cross-sectional view taken along line BB of FIG. 10A. As shown in FIGS. 10A and 10B, in the modified example 5, the lower electrodes 104b of the four cells are coupled in parallel, and the conductive member 108 is provided in the opening 101b only in one of the four cells.

  With such a configuration, it is possible to provide a through electrode that extracts a signal from the upper electrode 104a without increasing the size of the cell. 10A and 10B, the conductive member 108 is provided only in one of the four cells, but the conductive member 108 may be provided in two or more cells.

[Modification Example 6]
In general, the pMUT has a narrow band characteristic. In the ultrasonic transducer array using the pMUT cell 100 described in the above embodiment, since the cell density is improved by the configuration without the through electrode, the bandwidth is increased compared to the configuration with the through electrode. However, in order to further increase the bandwidth, the following configuration 6 may be adopted.

  FIG. 11A and FIG. 11B are plan views illustrating a pMUT array in the case where pMUT cells having a plurality of types of natural frequencies are mixed, and FIG. It is the conceptual diagram which showed a mode that it was performed. FIG. 11A shows a configuration example of a two-channel one-dimensional array, and FIG. 11B shows a configuration example of a two-channel × two-channel two-dimensional array. 11A and 11B, cells having a plurality of types of natural frequencies are mixedly arranged.

  By mixing cells having a plurality of types of natural frequencies in this way, the entire array can be broadened as shown in FIG. 11C.

[Modification Example 7]
In the embodiment described above, the pMUT cell 100 included in all channels is used for ultrasonic wave transmission / reception, but a transmission channel and a reception channel may be provided separately. The pMUT cell included in the transmission channel desirably has a dielectric constant of the piezoelectric material layer 103 larger than that of the pMUT cell included in the reception channel. Specifically, for example, the lower electrode 104b illustrated in FIG. 6C is formed using different materials for the pMUT cell included in the transmission channel and the pMUT cell included in the reception channel, thereby forming a film thereon. Further, the dielectric constant of the piezoelectric material layer 103 can be made different between the transmission channel and the reception channel.

  The present invention can be used for an ultrasonic transducer array that transmits and receives ultrasonic waves using a pMUT.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus 10 Ultrasonic diagnostic apparatus main body 11 Operation input part 12 Transmission part 13 Reception part 14 Image processing part 15 Display part 16 Control part 20 Ultrasonic probe 21 Protective layer 22 pMUT element 23 Backing material 24 Signal processing circuit 30 cable 100 pMUT cell 100A active cell 100D dummy cell 101 substrate 101a SiO ₂ layer 101b opening 102 highly doped silicon (HDSi) layer 102a vibration plate 103 piezoelectric material layer 104a upper electrode 104aT through electrode 104b lower electrode 105 diaphragm 106 insulating layer 107 insulation Layer 108 Conductive member

Claims (10)

An ultrasonic transducer array in which one or more pMUT cells are arranged on a substrate,
Each said pMUT cell is
A diaphragm provided on the substrate so as to close an opening provided on the substrate; and an electrode and a piezoelectric material layer provided on a surface of the diaphragm opposite to the opening. Diaphragm,
A conducting member that is provided in the opening and ensures electrode conduction for driving and receiving the diaphragm;
An ultrasonic transducer array. The electrode and the conducting member are conducted through the diaphragm,
The ultrasonic transducer array according to claim 1. The diaphragm is composed of highly doped silicon having a resistivity of 1 mΩ · cm or less.
The ultrasonic transducer array according to claim 2. A plurality of channels electrically connecting a plurality of the pMUT cells are disposed on the substrate;
The ultrasonic transducer array according to claim 1. The channel vibrates the diaphragm when a driving signal is input to the electrode through the conducting member, and transmits an ultrasonic wave. When the ultrasonic wave is received, the channel outputs the vibration of the diaphragm as a reception signal. Composed of multiple pMUT cells,
The ultrasonic transducer array according to claim 4. Around the channel, a predetermined number or more of pMUT cells that do not transmit and receive ultrasonic waves are disposed.
The ultrasonic transducer array according to claim 5. The channel includes a channel that performs only ultrasonic transmission and a channel that performs only ultrasonic reception.
The ultrasonic transducer array according to claim 5. When the plurality of pMUT cells are arranged on the substrate, the plurality of pMUT cells have two or more types of natural frequencies.
The ultrasonic transducer array according to any one of claims 1 to 7. The ultrasonic transducer array according to any one of claims 1 to 8, comprising:
Ultrasonic probe. An ultrasonic diagnostic image is generated using an ultrasonic reception signal obtained from an ultrasonic probe including the ultrasonic transducer array according to any one of claims 1 to 8.
Ultrasound diagnostic device.

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