JP2019041275A - Ultrasonic inspection apparatus and capacitive ultrasonic transducer - Google Patents

Abstract

To improve performance of an ultrasonic inspection apparatus including a capacitance detection type ultrasonic sensor which has a hollow portion between electrodes and vibrates a membrane.SOLUTION: Of membranes 7 of respective channels 6 sharing one cavity 5, between the membranes 7 adjacent to each other, the opposing sides of the membranes 7 are connected to form a connection portion 11 supported by a column 12 in the cavity 5. The connection portion 11 has a lower Young's modulus, acoustic impedance, and a smaller spring constant than the membranes 7.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an ultrasonic inspection apparatus and a capacitive ultrasonic transducer, and in particular, to a capacitive ultrasonic transducer manufactured by MEMS (Micro Electro Mechanical System) technology and the capacitive ultrasonic transducer. The present invention relates to a technique effective when applied to an existing ultrasonic inspection apparatus.

  Ultrasonic sensors have been put to practical use in various ultrasonic inspection apparatuses such as medical ultrasonic echo diagnostic apparatuses or nondestructive ultrasonic inspection apparatuses.

  Conventional ultrasonic sensors mainly use the vibration of a piezoelectric material. However, due to recent advances in MEMS technology, capacitive ultrasonic transducers (CMUT: Capacitive Micro-machined Ultrasonic) using MEMS technology. Transducer) is under development.

  The capacitive ultrasonic transducer is obtained by forming a vibrator having a cavity between electrodes facing each other on a semiconductor substrate. In the capacitive ultrasonic transducer, DC and AC voltages are superimposed and applied to each electrode to vibrate the membrane (flexible film) near the resonance frequency, thereby generating ultrasonic waves.

  A technique related to such a capacitive ultrasonic transducer is described in, for example, Patent Document 1 (US Pat. No. 7,800,189), and each of a plurality of channels sharing one cavity portion. Among these membranes, there is disclosed a capacitive ultrasonic transducer in which a plurality of columns supporting the membrane are arranged in the middle between adjacent membranes connected to each other.

US Pat. No. 7,800,189

  In capacitive ultrasonic transducers that detect the capacitance between the upper and lower electrodes of the membrane, from the viewpoint of improving transmission efficiency and reception sensitivity, a channel that can be used as a vibrator by vibrating the upper electrode relative to the area of the semiconductor chip It is important to increase the ratio (fill factor) occupied by the area. In particular, when the frequency of the sound wave to be transmitted / received is increased, the channel width is decreased, and the area occupied by the rim portion between the channels is increased.

  When a plurality of channels share a single cavity, the occupied area of the partition wall between the channels can be reduced, so that an increase in the area occupied by the rim part is suppressed, and a capacitive ultrasonic transducer is provided. It becomes possible to miniaturize. However, as in Patent Document 1, if the membranes of a plurality of channels sharing a single cavity are directly connected to each other, it becomes difficult for each membrane to vibrate individually, and acoustic separation between channels becomes difficult. There is a problem that can not be done. As a countermeasure, when the membranes are completely separated by providing a cut between the membranes, the vacuum state in the cavity cannot be maintained, and gas or acoustic medium (dust) enters the cavity from the outside, and the reliability of the device There is a risk that the performance will be reduced.

  The above object and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  Of the embodiments disclosed in the present application, the outline of typical ones will be briefly described as follows.

  An ultrasonic inspection apparatus according to an embodiment includes a plurality of flexible films and the plurality of flexible films connected between the adjacent flexible films among the plurality of flexible films. A capacitive ultrasonic transducer having a connection portion having lower acoustic impedance than each of the flexible films and a column supporting the connection portion is provided.

  In addition, a capacitive ultrasonic transducer according to another embodiment includes a plurality of flexible films and a connection between adjacent flexible films among the plurality of flexible films. And a connecting portion having an acoustic impedance lower than each of the plurality of flexible films, and a column supporting the connecting portion.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  According to the present invention, the performance of the ultrasonic inspection apparatus can be improved.

  Further, according to the present invention, the performance of the capacitive ultrasonic transducer can be improved.

It is a top view which shows the capacitive ultrasonic transducer which is Embodiment 1 of this invention. It is a top view which shows the principal part of the capacitive ultrasonic transducer which is Embodiment 1 of this invention. It is sectional drawing in the AA of FIG. It is sectional drawing in the BB line of FIG. It is sectional drawing in the CC line of FIG. It is a top view which shows the capacitive ultrasonic transducer which is the modification 1 of Embodiment 1 of this invention. It is a top view which shows the capacitive ultrasonic transducer which is the modification 2 of Embodiment 1 of this invention. It is a top view which shows the principal part of the capacitive ultrasonic transducer which is the modification 3 of Embodiment 1 of this invention. It is sectional drawing in the AA of FIG. It is sectional drawing in the BB line of FIG. It is a top view which shows the principal part of the capacitive ultrasonic transducer which is Embodiment 2 of this invention. It is sectional drawing in the AA of FIG. It is sectional drawing in the BB line of FIG. It is a top view which shows the principal part of the capacitive ultrasonic transducer which is a modification of Embodiment 2 of this invention. It is sectional drawing in the AA of FIG. It is sectional drawing in the BB line of FIG. It is a top view which shows the principal part of the capacitive ultrasonic transducer which is Embodiment 3 of this invention. It is sectional drawing in the AA of FIG. It is sectional drawing in the BB line of FIG. It is a perspective view which shows the ultrasonic inspection apparatus which is Embodiment 4 of this invention. It is a block diagram which shows the structure of the ultrasonic inspection apparatus which is Embodiment 4 of this invention. 6 is a cross-sectional view showing a main part of a capacitive ultrasonic transducer that is Comparative Example 1. FIG. 6 is a cross-sectional view showing a main part of a capacitive ultrasonic transducer that is Comparative Example 2. FIG. 6 is a cross-sectional view showing a main part of a capacitive ultrasonic transducer that is Comparative Example 2. FIG. It is sectional drawing explaining the motion of the membrane which comprises the capacitive ultrasonic transducer which is the comparative example 1. FIG. It is sectional drawing explaining the motion of the membrane which comprises the capacitive ultrasonic transducer which is Embodiment 1 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Also, in the following embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

  The semiconductor substrate in this application refers to a silicon or other semiconductor single crystal substrate, a quartz substrate, a sapphire substrate, a glass substrate, another insulating substrate, a semiconductor substrate, or the like used for manufacturing a semiconductor integrated circuit, and a composite substrate thereof.

(Embodiment 1)
The capacitive ultrasonic transducer of this embodiment is an ultrasonic transmission / reception sensor manufactured using, for example, MEMS (Micro Electro Mechanical System) technology.

<Structure of capacitive ultrasonic transducer>
Hereinafter, the structure of the capacitive ultrasonic transducer according to the present embodiment will be described with reference to FIGS. 1 and 2 are plan views showing a capacitive ultrasonic transducer according to the present embodiment. 2, the principal part of FIG. 1 is expanded and shown. 3 to 5 are cross-sectional views showing the capacitive ultrasonic transducer of this embodiment. 3 is a cross-sectional view taken along line AA in FIG. 2, FIG. 4 is a cross-sectional view taken along line BB in FIG. 2, and FIG. 5 is a cross-sectional view taken along line CC in FIG.

  FIG. 1 is a plan view showing the entirety of a semiconductor chip 1 which is a capacitive ultrasonic transducer according to the present embodiment. The semiconductor chip 1 has a main surface (upper surface, front surface) and a rear surface (lower surface) located on opposite sides along the thickness direction. In FIG. 1, a plan view of the main surface side of the semiconductor chip 1 ( Top view).

  As shown in FIG. 1, the planar shape of the semiconductor chip 1 is, for example, a rectangle, that is, a rectangle. Here, the semiconductor chip 1 extends in the X direction. A plurality of cells 2 arranged in the X direction and a plurality of bonding pads (hereinafter referred to as pads) 3 and 4 are arranged on the main surface of the semiconductor chip 1. In FIG. 1, three cells 2 are shown on the main surface of the semiconductor chip 1, but the number of cells may be less or more than three. Each of the pads 3 and 4 is arranged adjacent to each cell 2 in the Y direction. The X direction and the Y direction are directions orthogonal to each other in plan view, and both are directions along the main surface of the semiconductor chip 1. In plan view, the X direction is the longitudinal direction of the semiconductor chip 1, and the Y direction is the short direction of the semiconductor chip 1. The pads 3 and 4 are input / output terminals of the semiconductor chip 1, and bonding wires and the like are electrically connected to the pads 3 and 4.

  Each cell 2 has one cavity 5. The shape of the cavity 5 in plan view is, for example, a rectangle. Each cell 2 includes three channels 6 arranged in the X direction in a region overlapping the cavity 5 in plan view. The channel 6 has a membrane (flexible membrane) 7 on the cavity 5. Each of the channels 6 is a minimum unit vibrator capable of generating an ultrasonic wave, transmitting the ultrasonic wave, and receiving the ultrasonic wave. The vibrator constitutes, for example, an electrostatic variable capacitance (variable capacitance sensor). Each channel 6 has an upper electrode 8 disposed on the membrane 7 and a lower electrode 9 (see FIG. 3) disposed below the cavity 5. That is, the lower electrode 9, the cavity 5 and the upper electrode 8 overlap in plan view. Each channel 6 includes one membrane 7 and one upper electrode 8, and all the channels 6 in the cell 2 share one lower electrode (back electrode) 9. A plurality of cells 2 may share one lower electrode 9.

  Wiring is drawn from the end of each upper electrode 8 in the Y direction, and a pad 3 is formed on the upper surface of the end of the wiring. That is, the pad 3 is electrically connected to the upper electrode 8. A pad 4 electrically connected to the lower electrode 9 is disposed in a region adjacent to the cavity 5 in the Y direction and on the opposite side of the pad 3. Thus, the cavity 5 is disposed between the pad 3 and the pad 4 in plan view, and the three membranes 7 and the three upper electrodes 8 are disposed inside the cavity 5. In other words, the membrane 7 and the upper electrode 8 are located inside the cavity 5 in plan view. The end (side surface) of the cavity 5 in plan view is separated from the membrane 7 and the upper electrode 8, the adjacent membranes 7 are also separated from each other, and the adjacent upper electrodes 8 are also separated from each other. Yes.

  Of the parts constituting the semiconductor chip 1, a frame part (rim part) 10 that is a part adjacent to the cavity part 5 in plan view is made of, for example, an insulating film. A part of the frame portion 10 constitutes a side surface of the cavity portion 5. The frame portion 10 has a role of indirectly supporting the membrane 7 via a connecting portion 11 described later, and a role as a partition between the hollow portions 5 adjacent to each other.

  FIG. 2 is an enlarged plan view of one cell 2 which is a main part of the semiconductor chip 1. As shown in FIG. 2, each of the channel 6, the membrane 7 and the upper electrode 8 has a rectangular layout extending in the Y direction. In a plan view, the membrane 7 and the frame 10 and between the membranes 7 adjacent in the cell 2 are connected by a connecting portion (low Young's modulus portion, low acoustic impedance portion) 11 including a thin insulating film. Has been.

  In the cell 2, a support column 12 is formed in a cavity portion immediately below a region between the membranes 7 adjacent in the X direction. The column 12 is constituted by a columnar insulating film that penetrates the cavity 5 in a direction (vertical direction, vertical direction) perpendicular to the main surface of the semiconductor chip 1. Immediately below the connecting portion 11 extending in the Y direction between the membranes 7 adjacent in the X direction, a plurality of support columns 12 are arranged side by side at a constant interval in the Y direction. That is, the support column 12 supports the connecting portion 11 to indirectly support the membrane 7 and the upper electrode 8 on the membrane 7. In FIG. 2, the outline of the support column 12 is indicated by a broken line.

  3 and 4 are cross sections showing one cell 2 included in the semiconductor chip 1 (see FIG. 1) and showing a cross section along the X direction. FIG. 5 is a cross-section showing one cell 2 included in the semiconductor chip 1 and a cross-section along the Y direction. 3 and 5 show a cross section including the support column 12, and FIG. 4 shows a cross section not including the support column 12.

As shown in FIGS. 3 to 5, the semiconductor chip 1 includes a substrate 13, an insulating film 14, a lower electrode (back electrode) 9, and an insulating film 15 that are sequentially stacked on the substrate 13. The substrate 13 has an upper main surface and a back surface opposite to the main surface. The substrate 13 is made of, for example, silicon (Si) single crystal. The insulating film 14 is made of, for example, silicon oxide (SiO ₂ or the like). Here, the insulating film 14 is made of a TEOS (Tetra Ethyl Ortho Silicate, tetraethoxysilane) film. The lower electrode 9 is made of a conductor film such as a tungsten (W) film or a titanium nitride (TiN) film. Further, the lower electrode 9 may have a laminated structure composed of a plurality of conductor films including a tungsten film or a titanium nitride film. The insulating film 15 is made of, for example, silicon oxide, silicon nitride (Si ₃ N ₄ or the like), silicon carbide (SiC), or silicon carbonitride (SiCN). The insulating film 15 may be made of amorphous silicon which is an intrinsic semiconductor into which no impurity is introduced.

  On the insulating film 15, the frame portion 10 formed in the peripheral portion of the cell 2, the cavity portion 5 surrounded by the frame portion 10 in the direction along the main surface of the substrate 13 (lateral direction), and the cavity portion 5 A plurality of membranes 7 formed immediately above and an upper electrode 8 formed immediately above each of the plurality of membranes 7 are formed. Further, on the hollow portion 5, a connection portion 11 that connects between the membranes 7 adjacent to each other and a connection portion 11 that connects between the frame portion 10 and the membrane 7 adjacent to each other are formed. The cavity 5 exists between the lower electrode 9 and the insulating film 15 and the membrane 7, and the lower electrode 9, the insulating film 15 and the membrane 7 are separated from each other. The bottom surface of the cavity portion 5 is constituted by the insulating film 15, the side surface of the cavity portion 5 is constituted by the frame portion 10, and the upper surface of the cavity portion 5 is constituted by the connection portion 11 and the membrane 7.

  3-5, the connection part 11 is enclosed with the broken line. As shown in FIGS. 3 and 5, a support column 12 is formed immediately below the connecting portion 11 between the membranes 7 adjacent in the X direction. The upper surface of the support column 12 is in contact with the lower surface of the connection portion 11, and the bottom surface of the support column 12 is in contact with the upper surface of the insulating film 15. The side surface of the column 12 constitutes the side surface of the cavity 5. That is, the support column 12 is surrounded by the cavity 5 in plan view, and the support column 12 supports the connection unit 11. That is, the support column 12 supports the membrane 7 and the upper electrode 8 connected to the connection portion 11.

  3 to 5, each of the frame portion 10 and the membrane 7 is shown as one film. However, each of the frame portion 10 and the membrane 7 includes a plurality of insulating films such as a silicon oxide film or a silicon nitride film, for example. Has a laminated structure. Moreover, the support | pillar 12 may have a structure which laminated | stacked the some insulating film. The support column 12 is made of, for example, a silicon oxide film, a silicon nitride film, or a laminated film in which those insulating films are laminated.

  The connection portion 11 is formed by retreating a part of the upper surface of the laminated insulating film including the plurality of membranes 7 by an etching process, thereby forming the groove 16. The groove 16 is formed next to the membrane 7, and the bottom surface of the groove 16 does not reach the height of the bottom surface of the membrane 7. In other words, the bottom surface of the groove 16 is located at an intermediate depth of the laminated insulating film. That is, the groove 16 formed in the etching process does not penetrate the laminated insulating film. A thin film 17 remaining as a result of the upper surface of the laminated insulating film receding is formed at the bottom of the groove 16, and the connection portion 11 is mainly composed of the thin film 17. However, the connection part 11 of this Embodiment shall also include the space in the groove | channel 16 on the thin film 17. FIG. The thin film 17 is an insulating film or a laminated insulating film whose film thickness is smaller than that of the membrane 7. The thin film 17 is made of, for example, a silicon oxide film, a silicon nitride film, or a laminated film in which those insulating films are laminated.

  For example, the thin film 17 is integrated with a part of each of the membrane 7 and the frame part 10. That is, the insulating film constituting the thin film 17 is the same film as a part of the insulating films of the laminated films constituting the membrane 7 and the frame portion 10. In other words, each of the membrane 7, the frame portion 10, and the thin film 17 shares one insulating film. Moreover, the support | pillar 12 may share the same insulating film with the membrane 7 or the thin film 17. FIG.

  In FIG. 3, the groove 16 and the thin film 17 are shown as having the same width as the support 12, but the width of each of the groove 16 and the thin film 17 in the lateral direction is preferably larger than the width of the support 12. That is, it is preferable that the side surfaces on both sides of the groove 16 are located outside the side surfaces of the support column 12 in the lateral direction. In other words, it is desirable that the entire support column 12 is located inside the groove 16 in plan view. As will be described later with reference to FIG. 26, in order to vibrate the membrane 7 and the upper electrode 8 without bending, a connecting portion having a low Young's modulus and a small spring constant is provided between the membrane 7 and the support column 12. 11 is important.

  The membrane here refers to a portion that vibrates during operation of the vibrator. In FIG. 3, the membrane refers to a laminated insulating film positioned immediately above the cavity 5 in each channel 6. Here, the membrane 7 and the upper electrode 8 will be described as separate parts, but the upper electrode 8 may be included in the concept of the membrane.

  As shown in FIGS. 3 to 5, the support column 12 does not extend continuously directly below the connection portion 11 between the membranes 7 adjacent in the X direction, but has a columnar pattern. In addition, a part of the lower surface of the connecting portion 11 is supported in a plurality of locations side by side in the Y direction. The cavities 5 immediately below the membranes 7 of the channels 6 arranged in the X direction in the cell 2 are connected to each other, and the cavities 5 are completely surrounded by the insulating film 15, the frame part 10, the membrane 7 and the connection part 11. Surrounded and sealed. Therefore, it is possible to prevent gas or dust from entering the cavity 5.

  The upper electrode 8 is made of a conductive film such as a tungsten (W) film or a titanium nitride (TiN) film. Further, the upper electrode 8 may have a laminated structure composed of a plurality of conductor films including a tungsten film or a titanium nitride film. The distance between the lower electrode 9 and the upper electrode 8 is, for example, about 500 nm. The upper electrode 8 is not formed immediately above the connection portion 11 and the support column 12.

  A semiconductor chip (capacitive ultrasonic transducer) 1 of the present embodiment shown in FIGS. 1 to 5 is a device having a plurality of vibrators. In the operation (transmission operation) for generating ultrasonic waves using the capacitive ultrasonic transducer, the lower electrode 9 and the upper electrode 8 are applied by superimposing and applying DC and AC voltages to the lower electrode 9 and the upper electrode 8. Electrostatic force works between the two, and the membrane 7 of each vibrator vibrates in the vertical direction near the resonance frequency due to the balance with the spring force of the membrane 7 (see FIG. 26). At this time, the maximum potential difference between the upper electrode 8 and the lower electrode 9 is, for example, 300V. Thereby, an ultrasonic wave (ultrasonic pulse) of several MHz is generated from the vibrator.

  Further, in the reception operation by the capacitive ultrasonic transducer, the membrane 7 vibrates due to the pressure of the ultrasonic waves reaching the membrane 7 of each transducer, and the capacitance between the lower electrode 9 and the upper electrode 8 changes. By doing so, ultrasonic waves can be detected. That is, the displacement of the distance between the lower electrode 9 and the upper electrode 8 due to the reflected wave is detected as a change in electrostatic capacity (capacitance of each vibrator). Thus, by transmitting and receiving ultrasonic waves using a capacitive ultrasonic transducer, for example, a tomographic image of a living tissue can be taken.

  The main feature of the capacitive ultrasonic transducer according to the present embodiment is that when a plurality of channels 6 share the cavity 5 between the upper and lower electrodes, the gap between adjacent membranes 7 is greater than that of the membrane 7. The purpose is to form the connection portion 11 having a soft structure. In the present embodiment, a groove 16 is formed between adjacent membranes 7, and the connecting portion 11 is constituted by a space in the groove 16 and a thin film 17 at the bottom of the groove 16, thereby providing a part of the membrane 7. The Young's modulus and acoustic impedance of the connection part 11 containing the same material are set lower than the Young's modulus and acoustic impedance of the membrane 7, respectively. Since the thin film 17 is thinner than the membrane 7, the spring constant of the thin film 17 is smaller than the spring constant of the membrane 7. Even if the membrane includes the upper electrode, the Young's modulus and acoustic impedance of the connecting portion 11 are lower than the Young's modulus and acoustic impedance of the membrane 7, and the spring constant of the connecting portion 11 is smaller than the spring constant of the membrane 7. small.

  Further, the acoustic impedance of the connecting portion 11 including the thin film 17 having a smaller film thickness than the membrane 7 is lower than the acoustic impedance of the membrane 7. The acoustic impedance represents a resistance value when sound propagates through the medium, and is obtained by the product of the density of the medium through which the sound wave propagates and the sound speed. In the present embodiment, since the connection portion 11 is constituted by the thin film 17 and the space in the groove 16 immediately above the thin film 17, the density of the connection portion 11 is smaller than that of the membrane 7. In addition, the acoustic impedance of a region where a film is not formed, such as a space in the cavity 5 or the groove 16, that is, a region where a gas such as a vacuum region or air exists, is such as a silicon oxide film or a silicon nitride film. Lower than the acoustic impedance of the membrane. Therefore, the acoustic impedance of the connecting portion 11 is lower than the acoustic impedance of the membrane 7.

<Effects of capacitive ultrasonic transducer>
Hereinafter, the effect of the capacitive ultrasonic transducer of the present embodiment will be described with reference to FIG. 26 and FIGS. 22 to 25 showing comparative examples. FIG. 22 is a cross-sectional view showing the main part of a capacitive ultrasonic transducer that is Comparative Example 1. 23 and 24 are cross-sectional views showing the main parts of a capacitive ultrasonic transducer that is Comparative Example 2. FIG. 22 and FIG. 23 are cross sections of the portion corresponding to FIG. 3, that is, a cross section including the column, and FIG. 24 is a cross section of the portion corresponding to FIG. FIG. 25 is a cross-sectional view for explaining the movement of the membrane constituting the capacitive ultrasonic transducer of Comparative Example 1. FIG. 26 is a cross-sectional view for explaining the movement of the membrane constituting the capacitive ultrasonic transducer of this embodiment. In FIGS. 25 and 26, hatching is omitted for some of the upper electrodes.

  Capacitive micro-machined ultrasonic transducers (CMUTs) can expand the application area by increasing the frequency of ultrasonic waves that can be transmitted and received. When a capacitive ultrasonic transducer is applied to a catheter or a microscope, a frequency (20 MHz) higher than an ultrasonic frequency (1 to 10 MHz) transmitted and received by the capacitive ultrasonic transducer used for medical purposes. It is necessary to transmit and receive the above ultrasonic waves.

  When the frequency at which the capacitive ultrasonic transducer can transmit and receive increases, the channel width of the capacitive ultrasonic transducer becomes narrower depending on the wavelength, and as a result, the channel between the device region (sensor region) and the channel is reduced. The proportion of the area of the rim portion increases. This means that the area occupied by the area where the ultrasonic wave is transmitted (generated) and received (channel) is reduced relative to the area of the semiconductor chip which is a capacitive ultrasonic transducer, that is, the fill factor is reduced. . When the fill factor decreases, there arises a problem that the transmission efficiency and reception sensitivity of the capacitive ultrasonic transducer are lowered. In order to avoid deterioration of the characteristics of the capacitive ultrasonic transducer such as transmission efficiency and reception sensitivity, it is conceivable to increase the area of the semiconductor chip, thereby expanding the area of the ultrasonic wave transmission / reception area. However, in this case, there is a problem that it is difficult to miniaturize the capacitive ultrasonic transducer.

  On the other hand, the structure of Comparative Example 1 as shown in FIG. 22 is intended to reduce the area on the semiconductor chip that does not contribute to transmission / reception of sound while preventing an increase in the area of the capacitive ultrasonic transducer. It is conceivable to form a capacitive ultrasonic transducer having That is, instead of enclosing all the channels 6 one by one with the frame portion 10, as shown in FIG. By sharing the plurality of channels 6, it is possible to prevent an increase in the interval between the channels 6. Here, the connecting portion 111 between the membranes 7 adjacent to each other is partially supported by the support column 12.

  The capacitive ultrasonic transducer of Comparative Example 1 has the same structure as the membrane 7 in which the connecting portions 111 provided between the membranes 7 adjacent to each other and between the membrane 7 and the frame portion 10 are the same. And the same film thickness, which is different from the capacitive ultrasonic transducer of this embodiment. That is, the acoustic impedance of the connecting portion 111 is the same value as the acoustic impedance of the membrane 7, and the Young's modulus of the connecting portion 111 is the same value as the Young's modulus of the membrane 7. The spring constant of the connecting portion 111 is the same value as the spring constant of the membrane 7. For this reason, when sound is transmitted / received through a predetermined channel 6, the connection portion connected to the membrane 7 and the other membrane 7 are also vibrated under the influence of the vibration of the membrane 7 of the channel 6. That is, when one membrane 7 vibrates, it cannot prevent other membranes 7 from vibrating. This means that acoustic separation cannot be performed between the channels 6 sharing the same cavity 5.

  When acoustic focusing is performed by arraying cells of the capacitive ultrasonic transducer, each of the plurality of channels 6 in the array transmits and receives at different timings. For this reason, adjacent channels need to be acoustically separated. However, as in Comparative Example 1, when the plurality of channels 6 share the hollow portion 5 and the connecting portion 111 between the membranes 7 has the same structure as the membrane 7, Sound separation is not possible. As a result, there arises a problem that the acoustic resolution between the adjacent channels 6 of the capacitive ultrasonic transducer is lowered.

  When acoustic separation is not possible, the following problems occur. That is, there are problems that noise is generated in sound and signals transmitted and received using the capacitive ultrasonic transducer, and that the membrane 7 is difficult to move when voltage is applied to the upper electrode 8 and the lower electrode 9 during transmission. . That is, it becomes difficult to perform transmission / reception by individually operating the vibrators constituting the adjacent channels 6.

  On the other hand, in order to acoustically separate the channels 6 from each other as in the capacitive ultrasonic transducer of the comparative example 2 shown in FIGS. 23 and 24, the membrane 7 is interposed between the membranes 7 adjacent to each other. It is conceivable to make a notch (through hole 24) penetrating through. That is, the capacitive ultrasonic transducer of Comparative Example 2 does not have a connection portion between the membranes 7 adjacent to each other immediately above the cavity 5, and the adjacent membranes 7 are separated from each other. Yes. The support column 12 supports the lower surface of the end portion of the membrane 7. As shown in FIG. 24, the cavity portion 5 is exposed at a place where the support column 12 is not provided. In this case, gas or an acoustic medium or the like enters the cavity 5 from the outside of the capacitive ultrasonic transducer through the through hole 24 between the membranes 7 adjacent to each other. It is conceivable that the gas or the acoustic medium enters the cavity 5 after the semiconductor chip manufacturing process and the semiconductor chip are completed. As a result, since the vacuum in the cavity 5 cannot be maintained, when a voltage is applied between the upper electrode 8 and the lower electrode 9, discharge easily occurs between the electrodes, and the capacitive ultrasonic transducer Reliability decreases.

  Further, as in Comparative Example 1 shown in FIG. 22, when the membrane 7 and the connecting portion 111 have the same structure, the same film thickness, the same Young's modulus, the same spring constant, and the same acoustic impedance, The membrane 7 in the vicinity of the connection portion 111 fixed immediately above hardly moves up and down during the transmission / reception operation. That is, as shown in FIG. 25, the center portion of the membrane 7 vibrates greatly in the vertical direction, but the end portion of the membrane 7 has a small vibration width in the vertical direction. For this reason, the membrane 7 is greatly curved during vibration. In this case, in one channel 6, a region where the distance between the lower electrode 9 and the upper electrode 8 fluctuates when the membrane 7 vibrates, that is, a region where a change in capacitance can be detected is the center of the membrane 7. Therefore, the effective fill factor of the capacitive ultrasonic transducer is reduced.

  FIG. 25 shows only the operation mode of one membrane 7, but as described with reference to FIG. 22, in the capacitive ultrasonic transducer of Comparative Example 1, the sound between adjacent channels 6 is not shown. Since the target separation is insufficient, it is conceivable that when the predetermined membrane 7 vibrates, another membrane 7 adjacent to the membrane 7 also vibrates.

  Therefore, in the capacitive ultrasonic transducer of the present embodiment, Young's modulus and acoustic impedance are lower between the membranes 7 adjacent to each other and between the membrane 7 and the frame portion 10 than the membrane 7, and the spring A connecting portion 11 having a small constant is provided. Here, in one cell 2, a plurality of channels 6 share the cavity portion 5, and the region between the channels 6 is supported by the support column 12 instead of the frame portion 10, whereby the channel 6 in the cell 2. The width between them is reduced. Thereby, since the ratio of the area which a vibrator occupies with respect to the area of a semiconductor chip can be raised, the characteristic (transmission efficiency and reception sensitivity) of a capacitive ultrasonic transducer can be improved.

  Further, in the present embodiment, not only directly above the support column 12, but also in other regions by connecting the membranes 7 with each other by the connecting portion 11, unlike the comparative example 2 shown in FIG. 23 and FIG. The cavity 5 can be sealed. Therefore, since the vacuum in the cavity 5 can be maintained, when a voltage is applied between the upper electrode 8 and the lower electrode 9, it is possible to prevent a discharge from occurring between the electrodes, thereby preventing electrostatic discharge. The reliability of the capacitive ultrasonic transducer can be increased.

  Moreover, in this Embodiment, the Young's modulus and acoustic impedance of the connection part 11 between the membranes 7 are lower than the Young's modulus and acoustic impedance of the membrane 7, respectively. For this reason, when the membrane 7 of the predetermined channel 6 vibrates, other membranes 7 adjacent to the membrane 7 are affected and can be prevented from unintentionally vibrating. Further, when vibrating a predetermined membrane 7 to transmit and receive sound, it is possible to prevent the membrane 7 from being difficult to vibrate due to the membrane 7 being connected to another membrane 7. Therefore, compared with the comparative example 1 shown in FIG. 22, the channels 6 sharing the cavity 5 can be acoustically separated. That is, the channels 6 adjacent to each other are acoustically separated via the connection portion 11 immediately above the support column 12 between them. In addition, the characteristics (transmission efficiency and reception sensitivity) of the capacitive ultrasonic transducer can be improved.

  Further, the Young's modulus and spring constant of the connecting portion 11 are smaller than the Young's modulus and spring constant of the membrane 7, and the connecting portion 11 is softer, lower in rigidity, and easily bent. Therefore, as shown in FIG. 26, when the membrane 7 vibrates, the connecting portion 11 is easily deformed greatly. For this reason, it is possible to prevent the membrane 7 and the upper electrode 8 on the membrane 7 from bending when the membrane 7 vibrates. Therefore, when the membrane 7 vibrates, the membrane 7 and the upper electrode 8 move up and down with almost no curvature, and the distance in the vertical direction between the entire upper electrode 8 and the lower electrode 9 varies uniformly. This means that the entire upper electrode 8 functions as a region where a change in capacitance can be detected.

  In this manner, the upper electrode 8 vibrates while maintaining the positional relationship between the upper electrode 8 and the lower electrode 9 as parallel plates, and therefore, a change in capacitance is detected as compared with the comparative example 1 shown in FIG. It is possible to prevent a reduction in the area that can be used, and to improve the effective fill factor of the capacitive ultrasonic transducer. At this time, in order to vibrate the membrane 7 and the upper electrode 8 without bending, it is important to provide the connection portion 11 having a low Young's modulus between the membrane 7 and the support 12 in a plan view. Therefore, in the lateral direction, the width of the groove 16 and the thin film 17, that is, the width of the connection portion 11 is preferably larger than the width of the support column 12.

  As described above, by providing the connection part 11 having a Young's modulus and acoustic impedance lower than that of the membrane 7 and having a small spring constant, propagation of vibration between the membranes 7 is prevented, and between adjacent channels 6. Thus, the cavity 5 can be sealed to maintain a vacuum state, and the upper electrode 8 can be prevented from bending when the membrane 7 vibrates. In addition, since the channel width can be reduced while preventing the fill factor from decreasing, the frequency of sound waves to be transmitted and received can be increased. Therefore, the frequency band that can be inspected by the capacitive ultrasonic transducer can be expanded.

  1 to 5, the case where the connection portion 11 is formed in the region between the membrane 7 and the frame portion 10 has been described. However, the connection portion 11 is not formed in the region, and the membrane 7 and the frame are formed. The unit 10 may be directly connected. In that case, the effect of vibrating the upper electrode 8 while maintaining the parallel positional relationship between the upper electrode 8 and the lower electrode 9 is difficult to obtain as compared with the case where the connection portion 11 is formed in the region. An acoustic separation effect is obtained.

<Modification 1>
FIG. 6 shows a first modification of the capacitive ultrasonic transducer according to the present embodiment. FIG. 6 is a plan view showing a capacitive ultrasonic transducer that is Modification 1 of the present embodiment.

  In FIG. 1, the case where one cavity 5 has three channels 6 has been described. However, as shown in FIG. 6, one cavity 5 has four or more channels 6 arranged in the X direction. Also good. Even in this case, each of the membranes 7 of the plurality of channels 6 sharing one cavity portion 5 has the connection portion 11 between the other adjacent membranes 7. A plurality of support columns 12 arranged in the Y direction are arranged. Thus, since the area of the frame part 10 can be reduced by increasing the number of channels 6 that share the cavity part 5, the fill factor of the capacitive ultrasonic transducer can be improved.

<Modification 2>
FIG. 7 shows a second modification of the capacitive ultrasonic transducer according to the present embodiment. FIG. 7 is a plan view showing a capacitive ultrasonic transducer that is a second modification of the present embodiment. In FIG. 7, the outline of the lower electrode 9 is indicated by a broken line.

  Although FIG. 1 shows the capacitive ultrasonic transducer when the cells 2 are arranged side by side only in the X direction, a plurality of cells 2 may be arranged in the Y direction in addition to the X direction. That is, the cells 2 may be arranged in an array. In this case, for example, the upper electrodes 8 of the plurality of channels 6 arranged in the Y direction are connected to each other, and the wiring connected to the plurality of upper electrodes 8 arranged in the Y direction is connected to the plurality of upper electrodes 8 with respect to the Y electrodes. The pad 3 is formed at one end outside the direction and at the end of the wiring. For example, the lower electrodes 9 of the plurality of channels 6 arranged in the X direction are connected to each other, and the wiring connected to the lower electrodes 9 of the plurality of cells 2 arranged in the X direction is connected to the plurality of cells 2. On the other hand, the pad 4 is drawn out to the outer side in the X direction, and the pad 4 is formed at the end of the wiring.

  That is, here, one cell 2 is arranged at the intersection of the wiring connected to the predetermined pad 3 and the wiring connected to the predetermined pad 4. Here, in order to supply different potentials to the three upper electrodes 8 in one cell 2, pads 3 connected separately to each of the upper electrodes 8 are formed.

<Modification 3>
In FIGS. 1 to 5, it has been described that a connection portion formed by thinning an insulating film having the same structure as the membrane is provided between the membranes, but in the following, FIGS. 8 to 10 are used. The provision of a connecting portion having a lateral bellows structure between the membranes 7 will be described. FIG. 8 is a plan view of a capacitive ultrasonic transducer that is a third modification of the present embodiment. 9 and 10 are a cross-sectional view taken along line AA in FIG. 8 and a cross-sectional view taken along line BB in FIG. 8, respectively.

  As shown in FIGS. 8 to 10, the structure of the capacitive ultrasonic transducer according to this modification is adjacent to the membrane 7 adjacent to the capacitive ultrasonic transducer described with reference to FIGS. 1 to 5. The connection part (low Young's modulus part, low acoustic impedance part) 21 is different in that the cross-sectional structure is bellows-like, and the other structure is the capacitance type described with reference to FIGS. It is the same as an ultrasonic transducer. That is, the connection part 21 is continuously formed between the membranes 7 adjacent to each other in the X direction and between the membrane 7 and the frame part 10 adjacent to each other in the X direction. Here, the connecting portion 11 described with reference to FIGS. 1 to 5 is formed between the membrane 7 and the frame portion 10 adjacent to each other in the Y direction. The cavity 5 is sealed by the insulating film 15, the frame part 10, the connection part 21 and the membrane 7.

  The connection part 21 is made of a part of the insulating films constituting the membrane 7 and the frame part 10. That is, the connection part 21 is connected to the respective side surfaces of the membrane 7 and the frame part 10, and is integrated with each of the membrane 7 and the frame part 10.

  The connecting portion 21 has a bellows-like (wave-like) cross-sectional structure extending in the lateral direction, that is, a zigzag cross-sectional structure. For example, in each of the membranes 7 adjacent to each other in the X direction and between the membrane 7 and the frame portion 10 adjacent to each other in the X direction, the connection portion 21 has an accordion shape (corrugated shape) extending in the X direction. ). That is, the connecting portion 21 has a bellows-like cross-sectional structure extending in the direction in which the membrane 7 is adjacent.

  Here, the connecting portion 11 described with reference to FIGS. 1 to 5 is formed between the membrane 7 and the frame portion 10 adjacent in the Y direction, but the connecting portion 21 is used instead of the connecting portion 11. May be formed. In that case, between the membrane 7 and the frame part 10 adjacent to each other in the Y direction, the connection part 21 has a bellows-like (wave-like) cross-sectional structure extending in the Y direction.

  The position of the lowest surface of the connecting portion 21 and the position of the lowest surface of the membrane 7 are at the same height. Further, the position of the highest surface of the connecting portion 21 and the position of the highest surface of the membrane 7 are at the same height. That is, the total thickness of the connecting portion 21 and the thickness of the membrane 7 are the same. Among the plurality of membranes 7, the connection portion 21 between the first membrane 7 and the second membrane 7 adjacent to each other in the X direction extends in the lateral direction and the first membrane extends in the lateral direction. And a plurality of second films spaced apart from the first film and positioned on the first film, and a plurality of third films extending in the longitudinal direction. The third membrane connects the end of the first membrane on the first membrane 7 side and the end of the second membrane on the second membrane 7 side, or the second membrane 7 of the first membrane. This is an insulating film that connects the end portion on the side and the end portion on the first membrane 7 side of the second film.

  The third film is connected to each of the end of the first film on the first membrane 7 side and the end of the first film on the second membrane 7 side. Similarly, the third film is connected to each of the end of the second film on the first membrane 7 side and the end of the second film on the second membrane 7 side. However, the 3rd film | membrane is not connected to the edge part connected to either the membrane 7 or the frame part 10 among each edge part of a 1st film | membrane and a 2nd film | membrane. 8 to 10 show a structure in the case where the second film is not connected to either the membrane 7 or the frame portion 10. The connecting portion 21 is composed of a continuous insulating film connected in the order of the first film, the third film, the second film, and the third film, and a space between the third films adjacent to each other. Each film thickness of the first film, the second film, and the third film is smaller than the thickness of the membrane 7.

  A first film is formed between the membranes 7 adjacent to each other in the X direction, and a part of the bottom surface of the first film is supported by the support column 12. Of the connection part 21 including the first film, the other first film, the second film, and the third film are not in contact with the support column 12. That is, a connection portion 21 including a third film, a second film, and another first film connected to the first film is formed between the first film immediately above the support column 12 and the membrane 7. Yes.

  In addition, since the 3rd film | membrane (not shown) connected to the edge part of the 2nd film | membrane and the connection part 11 is formed in the edge part of the Y direction of the connection part 21 shown in FIG. Even if the membrane 7 is surrounded by the existing connection portion 21 and the connection portion 11 extending in the X direction, the airtightness of the cavity portion 5 can be maintained. That is, the cavity 5 can be sealed to maintain a vacuum state. Therefore, it is possible to prevent the occurrence of electric discharge due to the invasion of gas or an acoustic medium into the hollow portion 5, thereby improving the reliability of the capacitive ultrasonic transducer.

  Since the connecting portion 21 is a bellows-like insulating film formed with a film thinner than the membrane 7, the Young's modulus and acoustic impedance are lower and the spring constant is smaller than that of the membrane 7. That is, since the connecting portion 21 is softer and less rigid than the membrane 7, it has a property that it is easily deformed and hardly transmits vibration. For this reason, propagation of vibration between the membranes 7 can be prevented, and acoustic separation between the adjacent channels 6 can be realized. Thereby, the performance of the capacitive ultrasonic transducer can be enhanced.

  In addition, the bellows-like connecting portion 21 has a lower Young's modulus and acoustic impedance and a smaller spring constant than the connecting portion 11 described with reference to FIGS. Therefore, as described with reference to FIG. 26, it is possible to prevent the membrane 7 from bending when the membrane 7 vibrates. Therefore, since the upper electrode 8 can be prevented from bending when the membrane 7 vibrates, it is possible to prevent a decrease in a region where a change in capacitance can be detected. The fill factor can be improved.

(Embodiment 2)
Below, providing the connection part which has a flexible material part between adjacent membranes 7 is demonstrated using FIGS. 11-13. FIG. 11 is a plan view of the capacitive ultrasonic transducer according to the second embodiment. 12 and 13 are a cross-sectional view taken along line AA in FIG. 11 and a cross-sectional view taken along line BB in FIG. 11, respectively.

  As shown in FIGS. 11 to 13, the structure of the capacitive ultrasonic transducer according to the present embodiment is adjacent to the capacitive ultrasonic transducer described with reference to FIGS. 1 to 5. The connection part (low Young's modulus part, low acoustic impedance part) 31 between 7 is comprised by the groove | channel 18 which penetrates the membrane 7, and the flexible material part (insulating film) 19 which embedded the groove | channel 18. Is different. Further, the groove 18 is also formed between the membrane 7 and the frame portion 10 adjacent to each other, and the flexible material portion 19 is embedded in the groove 18. Other structures of the capacitive ultrasonic transducer according to the present embodiment are the same as those of the capacitive ultrasonic transducer described with reference to FIGS. Each membrane 7 is surrounded by the connection portion 31 in plan view.

  The flexible material portion 19 is more flexible than the membrane 7, has a property that the Young's modulus and acoustic impedance are low, and the spring constant is small. That is, the material constituting the flexible material portion 19 has a lower Young's modulus and acoustic impedance and a smaller spring constant than both the silicon oxide film and the silicon nitride film constituting the membrane 7. Here, the flexible material portion 19 is made of, for example, a silicon oxide film having a density lower than that of the silicon oxide film constituting the membrane 7, or a resin such as inkjet resin or polyimide. The silicon oxide film constituting the flexible material portion 19 is, for example, SOG (Spin on Glass). Such a low-density silicon oxide film can be formed by, for example, a CVD (Chemical Vapor Deposition) method. The silicon oxide film is an insulating film having a lower dielectric constant than a silicon oxide film formed by an oxidation method, that is, a so-called low-k film.

  The flexible material portion 19 is completely embedded in the groove 18, and a part of the upper portion of the flexible material portion 19 rides on the upper surface of the membrane 7. That is, a part of the flexible material portion 19 covers the upper surface of the membrane 7. The upper surface of the support column 12 is in contact with the lower surface of the flexible material portion 19, and the support column 12 supports the connection portion 31 and the membrane 7 connected to the connection portion 31. Since the groove 18 penetrates the membrane 7, the lower surface of the flexible material portion 19 is exposed in the cavity portion 5 in the region where the support column 12 is not present. Here, when there is no flexible material part 19, since the groove | channel 18 which penetrates the membrane 7 is opened, the airtightness in the cavity part 5 cannot be maintained. However, in the present embodiment, the groove 18 is filled with the flexible material portion 19 so that the cavity portion 5 can be sealed and a vacuum state can be maintained. Therefore, it is possible to prevent the occurrence of discharge due to the intrusion of gas, acoustic medium, or the like into the cavity 5, thereby improving the reliability of the capacitive ultrasonic transducer.

  Here, in FIG. 12 and FIG. 13, the groove 18 and the support 12 having the same width are shown, but as shown in FIG. 11, the width of the groove 18 in the X direction is larger than the width of the support 12 in the X direction. It can be large. Further, the width of the groove 18 in the X direction may be smaller than the width of the support column 12 in the X direction. Since the connection part 31 has a Young's modulus and acoustic impedance lower than those of the membrane 7 and a small spring constant, it has a property that it is difficult to transmit vibration compared to the membrane 7. Further, the membranes 7 adjacent to each other are separated by the groove 18, and a film sharing an insulating film with the membrane 7 is not formed between the membranes 7. For this reason, propagation of vibration between the membranes 7 can be prevented, and acoustic separation between the adjacent channels 6 can be realized. Thereby, the performance of the capacitive ultrasonic transducer can be enhanced.

  Further, by forming the flexible material portion 19 having a lower Young's modulus and acoustic impedance and a smaller spring constant than the membrane 7 at the connection portion 31, as described with reference to FIG. Can be prevented from bending. Therefore, since the upper electrode 8 can be prevented from bending when the membrane 7 vibrates, it is possible to prevent a decrease in a region where a change in capacitance can be detected. The fill factor can be improved. Thus, from the viewpoint of preventing the upper electrode 8 from bending when the membrane 7 vibrates, the width of the groove 18 in the X direction is preferably larger than the width of the support column 12 in the X direction.

  Although the description has been given here of embedding the flexible material portion 19 in the groove 18 penetrating the membrane 7, the thin film 17 is combined with the connection portion 11 (see FIG. 3) of the first embodiment. The flexible material portion 19 may be embedded in the upper groove 16. In this case, the strength of the connection part 11 can be improved. Similarly, in the bellows-like connection portion 21 (see FIG. 9) of the third embodiment, the flexible material portion 19 may be embedded between the third films adjacent to each other.

<Modification>
Hereinafter, using FIG. 14 to FIG. 16, it will be described that the flexible material portion is embedded in a part of the upper portion of the groove between the membranes 7. FIG. 14 is a plan view of a capacitive ultrasonic transducer that is a modification of the present embodiment. 15 and 16 are a cross-sectional view taken along line AA in FIG. 14 and a cross-sectional view taken along line BB in FIG. 14, respectively.

  As shown in FIGS. 14 to 16, the structure of the capacitive ultrasonic transducer of this modification is adjacent to the membrane 7 adjacent to the capacitive ultrasonic transducer described with reference to FIGS. 1 to 5. The connection part (low Young's modulus part, low acoustic impedance part) 41 between them is different by the point comprised by the groove | channel 20 which penetrates the membrane 7, and the flexible material part 25 which embedded the upper part of the groove | channel 20. Yes. Similarly, the groove 20 is also formed between the membrane 7 and the frame portion 10 adjacent to each other, and the flexible material portion 25 is embedded in the groove 20. The other structure of the capacitive ultrasonic transducer of this modification is the same as that of the capacitive ultrasonic transducer described with reference to FIGS. Each membrane 7 is surrounded by the connecting portion 41 in plan view.

  The groove 20 is a slit that penetrates the membrane 7 and is opened between the membranes 7 adjacent to each other and between the membrane 7 and the frame portion 10 adjacent to each other. The width in the short direction of the groove 20 is smaller than the width in the short direction of the groove 18 described with reference to FIGS. 11 to 13 and smaller than the width of the column 12. For this reason, a part of the lower surface of the end portion of the membrane 7 is in contact with the upper surface of the column 12, and the membrane 7 is directly supported by the column 12.

  The upper part in the groove 20 is embedded by the flexible material part 25. However, unlike the flexible material portion 19 described with reference to FIGS. 11 to 13, the flexible material portion 25 does not completely fill the groove 20. That is, the flexible material portion 25 covers only the upper portion (upper end) of the side surface of the groove 20, and the lower portion (lower end) of the side surface is exposed from the flexible material portion 25. For this reason, a part of the groove 20 constitutes the cavity 5. In other words, the flexible material portion 25 is embedded between the upper ends of the membranes 7 adjacent to each other, and a cavity exists between the lower ends of the membranes 7 adjacent to each other.

  The flexible material portion 25 is made of the same material as that of the flexible material portion 19, and has a lower Young's modulus and acoustic impedance than the membrane 7 and a small spring constant. A part of the flexible material portion 25 is located on the membrane 7 and covers an end portion of the upper surface of the membrane 7. As shown in FIGS. 15 and 16, the flexible material portion 25 has a substantially circular cross section. That is, for example, between the membranes 7 adjacent to each other, the flexible material portion 25 has a collapsed columnar structure extending in the Y direction. The upper portions of all the grooves 20 are closed by the flexible material portion 25. Therefore, by embedding the groove 20 with the flexible material portion 25, the cavity portion 5 can be sealed to maintain a vacuum state. For this reason, generation | occurrence | production of the discharge resulting from gas or an acoustic medium infiltrating in the cavity part 5 can be prevented, and, thereby, the reliability of a capacitive ultrasonic transducer can be improved.

  The connecting portion 41 includes the groove 20, a flexible material portion 25 embedded in the upper portion of the groove 20, and a cavity in the groove 20 below the flexible material portion 25. Therefore, the connection portion 41 has a property that the Young's modulus and the acoustic impedance are lower than that of the membrane 7 and the spring constant is small, so that it is difficult to transmit vibration compared to the membrane 7. Further, the membranes 7 adjacent to each other are separated by the groove 20, and a film sharing an insulating film with the membrane 7 is not formed between the membranes 7. For this reason, propagation of vibration between the membranes 7 can be prevented, and acoustic separation between the adjacent channels 6 can be realized. Thereby, the performance of the capacitive ultrasonic transducer can be enhanced.

  In addition, by forming the flexible material portion 25 having a lower Young's modulus and acoustic impedance and a smaller spring constant than the membrane 7 in the connection portion 41, as described with reference to FIG. Can be prevented from bending. That is, as shown in FIG. 22 and FIG. 25, compared with the case where the connecting portion 111 having the same structure as the membrane 7 is formed, the connecting portion 41 of this modification has a low Young's modulus and acoustic impedance and a small spring constant. . Therefore, since the upper electrode 8 can be prevented from bending when the membrane 7 vibrates, it is possible to prevent a decrease in a region where a change in capacitance can be detected. The fill factor can be improved.

  Further, the flexible material portion 25 is not formed in the groove 20, and the flexible material portion 25 covers the upper surface of each end portion of the membrane 7 adjacent to the groove 20 and closes the upper portion of the groove 20. Thus, even when the connecting portion 41 is configured by the flexible material portion 25 on the groove 20 and the space in the groove 20 below the flexible material portion 25, the same effect as described above can be obtained. it can. This is because, also in this case, the cavity 5 is sealed, and the membranes 7 adjacent to each other are connected to each other by the flexible material portion 25 in contact with the end portions of the upper surfaces of the membranes 7. It is.

  Here, the description has been given of embedding the flexible material portion 25 in the groove 20 penetrating the membrane 7, but this modification is combined with the connection portion 11 (see FIG. 3) of the first embodiment to form the thin film 17 on the thin film 17. The flexible material portion 25 may be embedded in the upper portion of the groove 16. In this case, the strength of the connection part 11 can be improved. Similarly, in the bellows-shaped connection portion 21 (see FIG. 9) of the third embodiment, the flexible material portion 25 is provided between the third films adjacent to each other and above the groove just above the first film. May be embedded.

(Embodiment 3)
In the following, using FIGS. 17 to 19, it will be described how to provide a connecting portion having a vertical bellows structure between the membranes 7. FIG. 17 is a plan view of the capacitive ultrasonic transducer according to the third embodiment. 18 and 19 are a sectional view taken along line AA in FIG. 17 and a sectional view taken along line BB in FIG. 17, respectively.

  As shown in FIGS. 17 to 19, the structure of the capacitive ultrasonic transducer of this embodiment is adjacent to the capacitive ultrasonic transducer described with reference to FIGS. The connection part (low Young's modulus part, low acoustic impedance part) 51 between 7 is different in the point that it is a bellows shape of the vertical direction. Other structures of the capacitive ultrasonic transducer according to the present embodiment are the same as those of the capacitive ultrasonic transducer described with reference to FIGS. That is, the connection part 51 is continuously formed between the membranes 7 adjacent to each other in the X direction and between the membrane 7 and the frame part 10.

  The connection part 51 between the membranes 7 adjacent to each other has a plurality of first protrusions protruding laterally from one first side surface to the other second side surface among the opposing side surfaces of the membranes 7. 22 and a plurality of second projecting portions 23 projecting laterally from the second side surface toward the first side surface. That is, the 1st protrusion part 22 is connected to the 1st side surface, and the 2nd protrusion part is connected to the 2nd side surface. The 1st protrusion part 22 and the 2nd protrusion part 23 which comprise the said connection part 51 are mutually spaced apart and arrange | positioned alternately in the vertical direction. Moreover, the 1st side surface and 2nd side surface which are the side surfaces which the membrane 7 opposes are mutually spaced apart. That is, a bellows-like space that penetrates from the upper surface to the lower surface of the membrane 7 is opened between the first side surface and the first protrusion 22 and the second side surface and the second protrusion 23. That is, the space is continuously formed from the upper surface to the lower surface of the membrane 7, and the flexible material portion or the like is not embedded in the space. Therefore, the cavity 5 is not sealed.

  Thus, the connection part 51 between the membranes 7 adjacent to each other includes a comb-shaped first protrusion 22 formed in a row in the vertical direction on the first side surface of one membrane 7 and the other membrane. 7 has a shape in which a plurality of comb-shaped second protrusions 23 formed in a row in the vertical direction on the second side surface are alternately combined. That is, the connection part 51 is comprised by the some 1st protrusion part 22, the some 2nd protrusion part 23, and the space between a 1st side surface and a 2nd side surface. The same applies to the connecting portion 51 between the membrane 7 and the frame portion 10 adjacent to each other.

  That is, the connection part 51 between the membrane 7 adjacent to each other and the frame part 10 is directed from one third side surface toward the other fourth side surface among the opposing side surfaces of the membrane 7 and the frame part 10. A plurality of first protrusions 22 protruding in the lateral direction and a plurality of second protrusions 23 protruding in the horizontal direction from the fourth side surface toward the third side surface are provided. That is, the 1st protrusion part 22 is connected to the 3rd side surface, and the 2nd protrusion part is connected to the 4th side surface. The 1st protrusion part 22 and the 2nd protrusion part 23 which comprise the said connection part 51 are mutually spaced apart and arrange | positioned alternately in the vertical direction. Moreover, the 3rd side surface and the 4th side surface which are the side surfaces which mutually oppose are mutually spaced apart. That is, a bellows-like cross section that penetrates from the upper surface of the membrane 7 and the frame portion 10 to the lower surface of the membrane 7 between the third side surface and the first protrusion 22 and the fourth side surface and the second protrusion 23. A space having an opening is opened.

  Thus, the connection part 51 between the membrane 7 adjacent to each other and the frame part 10 includes a plurality of comb-shaped first protrusions 22 formed in the vertical direction on the third side surface, and a fourth side surface. A plurality of comb-shaped second protrusions 23 formed in a row in the vertical direction are alternately combined.

  The overall thickness of the connecting portion 51 and the thickness of the membrane 7 are the same. The 1st protrusion part 22 and the 2nd protrusion part 23 which comprise the connection part 51 have mutually overlapped by planar view. The first projecting portion 22 and the second projecting portion 23 constituting the connecting portion 51 between the membranes 7 adjacent to each other extend in the Y direction along the side surface of the membrane 7. Moreover, the 1st protrusion part 22 and the 2nd protrusion part 23 which comprise the connection part 51 between the membrane 7 and the frame part 10 which adjoin in the X direction are extended in the Y direction along the side surface of the membrane 7. Yes. Moreover, the 1st protrusion part 22 and the 2nd protrusion part 23 which comprise the connection part 51 between the membrane 7 and the frame part 10 which adjoin in the Y direction are extended in the X direction along the side surface of the membrane 7. Yes. The thickness in the vertical direction of each of the first protrusion 22 and the second protrusion 23 is smaller than the thickness of the membrane 7. Further, the vertical distance of the space between the first protrusion 22 and the second protrusion 23 is smaller than the thickness of the membrane 7.

  A part of the lower surface of the connecting portion 51 between the membranes 7 adjacent to each other is supported by the support column 12. That is, the lower surface of either the first protrusion 22 or the second protrusion 23 is in contact with the upper surface of the support column 12. For example, when the lower surface of the first protrusion 22 is in contact with the upper surface of the column 12, the second protrusion 23 is not in contact with the column 12. A part of the upper surface of the support column 12 is in contact with the end portion of the lower surface of the membrane 7 that is separated from the first projecting portion 22 or the second projecting portion 23 in contact with the support column 12. That is, the column 12 directly supports the lower end of one membrane 7 disposed with the space interposed therebetween and the first projecting portion 22 or the second projecting portion 23 connected to the side surface of the other membrane 7.

  As shown in FIG. 19, in the region other than directly above the support column 12 (see FIG. 18), the space constituting the connecting portion 51 penetrates the membrane 7. For this reason, it seems that it becomes a problem that gas or an acoustic catalyst (dust) enters the cavity 5 through the space and discharge occurs between the upper and lower electrodes due to this. However, here, the plurality of first protrusions and the plurality of second protrusions are separated from each other between the adjacent membranes 7 and between the adjacent membranes 7 and the frame portion 10. As a result, the bellows-like space extending in the vertical direction is formed. Thereby, compared with the through-hole 24 of the comparative example 2 shown in FIG.23 and FIG.24, the path | route which gas and refuse penetrate | invade into the cavity part 5 from on the connection part 51 can be lengthened, and the said path | route can be made. Can be complicated.

  Thereby, it is possible to prevent gas and dust from entering the cavity 5. Further, even if gas and dust enter the cavity 5, the probability of gas and dust entering the cavity 5 is reduced as compared with Comparative Example 2 shown in FIGS. 23 and 24. The time required to enter the cavity 5 can be increased. Therefore, since the life of the capacitive ultrasonic transducer can be extended, the reliability of the capacitive ultrasonic transducer can be improved.

  Here, each of the first protrusion 22 and the second protrusion 23 is made of the same insulating film as the insulating film constituting the membrane 7 or the frame 10. That is, each of the first protrusion 22 and the second protrusion 23 is made of, for example, a silicon oxide film or a silicon nitride film. However, the connection part 51 is comprised by the some 1st protrusion part 22, the some 2nd protrusion part 23, and the bellows-like space between the 1st protrusion part 22 and the 2nd protrusion part 23. As shown in FIG. . For this reason, the connection part 51 has a Young's modulus and an acoustic impedance lower than the membrane 7, and a spring constant is small. That is, the connecting portion 51 has a property that it is more easily deformed than the membrane 7 and hardly transmits vibration. For this reason, propagation of vibration between the membranes 7 can be prevented, and acoustic separation between the adjacent channels 6 can be realized. In particular, in the present embodiment, since the membranes 7 adjacent to each other are completely separated, the acoustic separation performance between the channels 6 is excellent. Therefore, the performance of the capacitive ultrasonic transducer can be improved.

  Further, the connecting portion 51 has a lower Young's modulus and acoustic impedance than the membrane 7, and a small spring constant. For this reason, as described with reference to FIG. 26, it is possible to prevent the membrane 7 from bending when the membrane 7 vibrates. Therefore, since the upper electrode 8 can be prevented from bending when the membrane 7 vibrates, it is possible to prevent a decrease in a region where a change in capacitance can be detected. The fill factor can be improved.

(Embodiment 4)
Next, when the ultrasonic transducer (semiconductor chip) according to any one of the first to third embodiments is applied to an ultrasonic inspection apparatus such as an ultrasonic echo diagnostic apparatus (ultrasonic diagnostic apparatus, ultrasonic imaging apparatus), for example. Will be described with reference to FIGS. 20 and 21. FIG. FIG. 20 is a perspective view showing the ultrasonic inspection apparatus of the present embodiment. FIG. 21 is a block diagram illustrating a configuration of the ultrasonic inspection apparatus according to the present embodiment.

  The ultrasonic imaging apparatus is a medical diagnostic apparatus that uses the transmission of sound waves and visualizes the inside of a living body that cannot be seen from the outside by using ultrasonic waves that exceed the audible sound range and can be viewed in real time. . As shown in FIG. 20, the ultrasonic imaging apparatus 30 includes a main body 32, a display unit 33 installed on the upper part of the main body 32, an operation unit 36 attached to the front portion of the main body, and capacitive ultrasonic waves. An ultrasonic probe (probe) 35 including a transducer 34 is provided. A cord extends from the ultrasonic probe 35, and the cord is connected to the main body 32 at the connection portion 37. The capacitive ultrasonic transducer 34 corresponds to, for example, the semiconductor chip 1 shown in FIG.

  As shown in FIG. 21, an ultrasonic imaging apparatus (ultrasonic inspection apparatus) 30 includes an ultrasonic probe 35, a transmission / reception separation unit 40, a transmission unit 42, a bias unit 43, a reception unit 44, a phasing addition unit 45, The image processing unit 46, the display unit 33, the control unit 47, and the operation unit 36 are configured. The ultrasonic probe 35 is connected to the transmission / reception separating unit 40, and the operation unit 36 is connected to the control unit 47. The transmission unit 42 and the bias unit 43 are connected in parallel between the transmission / reception separation unit 40 and the control unit 47. The transmission / reception separation unit 40 is connected to the reception unit 44, the reception unit 44 is connected to the phasing addition unit 45 and the display unit 33, and the image processing unit 46 is a control unit 47, phasing addition unit 45 and display unit. 33.

  The ultrasonic probe 35 is a device that transmits and receives ultrasonic waves to and from a subject by making contact with the subject (living body), and an array of capacitive ultrasonic transducer elements on the contact surface with the subject. It has. As the capacitive ultrasonic transducer, the capacitive ultrasonic transducer according to any one of the first to third embodiments is employed.

  Next, the operation of the ultrasonic imaging apparatus 30 that is the ultrasonic inspection apparatus of the present embodiment will be described. When an inspection is performed using the ultrasonic imaging apparatus 30, an ultrasonic wave is transmitted from the ultrasonic probe 35 to the subject, and a reflected echo signal from the subject is received by the ultrasonic probe 35. The The transmission unit 42 and the bias unit 43 are devices that supply drive signals to the ultrasonic probe 35.

  The receiving unit 44 is a device that receives a reflected echo signal output from the ultrasonic probe 35. The receiving unit 44 further performs processing such as analog-digital conversion on the received reflected echo signal. The transmission / reception separation unit 40 switches between transmission and reception so as to pass a drive signal from the transmission unit 42 to the ultrasonic probe 35 at the time of transmission and to pass a reception signal from the ultrasonic probe 35 to the reception unit 44 at the time of reception. To do.

  The phasing addition unit 45 is a device that performs phasing addition of the received reflected echo signals. The image processing unit 46 is a device that configures a diagnostic image (for example, a tomographic image or a blood flow image) based on the reflected echo signal subjected to phasing addition. The display unit 33 is a display device that displays a diagnostic image subjected to image processing.

  The control unit 47 is a device that controls each component described above. The operation unit 36 is a device that gives an instruction to the control unit 47. The operation unit 36 is, for example, an input device such as a trackball, a keyboard, or a mouse, or a combination thereof.

  An ultrasonic probe 35 shown in FIG. 20 is an ultrasonic transmission / reception unit. A capacitive ultrasonic transducer 34 is attached to the distal end surface of the probe case forming the ultrasonic probe 35 with its main surface (surface on which a plurality of transducers are formed) facing outward. .

  In ultrasonic diagnosis, the tip of the ultrasonic probe 35 is applied to the surface of the subject (living body), and then scanning is performed while gradually shifting the position where the tip of the ultrasonic probe 35 contacts the surface of the subject. At this time, an ultrasonic pulse of several MHz is transmitted from the ultrasonic probe 35 applied to the body surface into the subject, and a reflected wave (an echo or an echo) from a tissue boundary having a different acoustic impedance is received. Thereby, the tomographic image of the living tissue displayed on the display unit 33 can be obtained, and information related to the diagnosis target can be known. The distance information of the reflector can be obtained by the time interval from transmitting the ultrasonic wave to receiving it. Also, information on the presence or quality of the reflector can be obtained from the level or contour of the reflected wave.

  The ultrasonic inspection apparatus according to the present embodiment employs the capacitive ultrasonic transducer described in the first to third embodiments as the capacitive ultrasonic transducer included in the ultrasonic probe. That is, the capacitive ultrasonic transducer is a connection portion supported by the support column 12 between the membranes of a plurality of channels sharing the cavity, and has a Young's modulus and acoustic impedance higher than those of the membrane. It has a connection part that is low and has a small spring constant.

  This prevents the propagation of vibrations between membranes and enables acoustic separation between adjacent channels, improving the characteristics (transmission efficiency and reception sensitivity) of capacitive ultrasonic transducers. Can be made. Further, even if the channel width is reduced, it is possible to prevent the ratio of the area occupied by the frame portion from increasing because the plurality of channels share the cavity portion. Therefore, miniaturization of the capacitive ultrasonic transducer while preventing the reduction of the ratio (fill factor) of the area of the channel that can be used as a vibrator in the main surface of the capacitive ultrasonic transducer. Can do. In addition, by reducing the channel width while preventing the fill factor from decreasing, the frequency of sound waves to be transmitted and received can be increased, so that the frequency band that can be inspected by the ultrasonic inspection apparatus can be expanded. Therefore, the performance of the ultrasonic inspection apparatus can be improved.

  In addition, acoustic separation between the membranes can be realized while enhancing the airtightness of the cavity of the capacitive ultrasonic transducer. Therefore, the reliability of the ultrasonic inspection apparatus can be improved. In addition, since the membrane and upper electrode can be prevented from bending when the membrane vibrates, the ratio of the area of the channel that can be used as a transducer (fill factor) to the main surface of the capacitive ultrasonic transducer Can be improved. Therefore, the performance of the ultrasonic inspection apparatus can be improved.

  Although the invention made by the present inventors has been specifically described based on the embodiment, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the fourth embodiment, the case where a capacitive ultrasonic transducer is used in a medical diagnostic apparatus has been described. However, the capacitive ultrasonic transducer described in the first to third embodiments may be a catheter or It can be used for an ultrasonic inspection apparatus such as a microscope.

5 Cavity 6 Channel 7 Membrane 8 Upper Electrode 9 Lower Electrode 10 Frame 11 Connection (Low Young's Modulus, Low Acoustic Impedance)
12 props

Claims (15)

An ultrasonic inspection apparatus including a capacitive ultrasonic transducer,
The capacitive ultrasonic transducer is
A plurality of flexible membranes;
Of the plurality of flexible membranes, connected between the adjacent flexible membranes, each having a lower acoustic impedance than each of the plurality of flexible membranes;
A column supporting the connecting portion;
A first electrode formed immediately below the plurality of flexible films;
A second electrode formed immediately above each of the plurality of flexible membranes;
A cavity formed between the plurality of flexible membranes and the first electrode;
An ultrasonic inspection apparatus. The ultrasonic inspection apparatus according to claim 1,
The ultrasonic inspection apparatus, wherein a thickness of the first film constituting the connection portion is smaller than a thickness of each of the plurality of flexible films. The ultrasonic inspection apparatus according to claim 1,
The said connection part is an ultrasonic inspection apparatus comprised by the bellows-like 2nd film | membrane where the said some flexible film is extended in the mutually adjacent direction. The ultrasonic inspection apparatus according to claim 1,
The connection portion includes a second film embedded in a through hole between the plurality of adjacent flexible films,
The ultrasonic inspection apparatus, wherein the second film has an acoustic impedance lower than that of each of the plurality of flexible films. The ultrasonic inspection apparatus according to claim 1,
The connecting portion includes a plurality of first protrusions extending from the first side surface to the second side surface between the opposing first and second side surfaces of the plurality of adjacent flexible films. And a plurality of second protrusions extending from the second side surface to the first side surface side,
The plurality of first protrusions and the plurality of second protrusions are alternately stacked in the vertical direction,
The ultrasonic inspection apparatus, wherein the plurality of first protrusions and the first side surface, and the plurality of second protrusions and the second side surface are separated from each other. A plurality of flexible membranes;
Of the plurality of flexible membranes, connected between the adjacent flexible membranes, each having a lower acoustic impedance than each of the plurality of flexible membranes;
A column supporting the connecting portion;
A first electrode formed immediately below the plurality of flexible films;
A second electrode formed immediately above each of the plurality of flexible membranes;
A cavity formed between the plurality of flexible membranes and the first electrode;
A capacitive ultrasonic transducer. The capacitive ultrasonic transducer according to claim 6,
The capacitive ultrasonic transducer, wherein a thickness of the first film constituting the connection portion is smaller than a thickness of each of the plurality of flexible films. The capacitive ultrasonic transducer according to claim 6,
The said connection part is a capacitive ultrasonic transducer comprised by the bellows-like 2nd film | membrane where the said some flexible film is extended in the mutually adjacent direction. The capacitive ultrasonic transducer according to claim 6,
The connection portion includes a second film embedded in a through hole between the plurality of adjacent flexible films,
The second membrane is a capacitive ultrasonic transducer having an acoustic impedance lower than that of each of the plurality of flexible membranes. The capacitive ultrasonic transducer according to claim 6,
The connecting portion includes a plurality of first protrusions extending from the first side surface to the second side surface between the opposing first and second side surfaces of the plurality of adjacent flexible films. And a plurality of second protrusions extending from the second side surface to the first side surface side,
The plurality of first protrusions and the plurality of second protrusions are alternately stacked in the vertical direction,
The plurality of first protrusions and the first side face, and the plurality of second protrusions and the second side face are capacitive ultrasonic transducers that are separated from each other. An ultrasonic inspection apparatus including a capacitive ultrasonic transducer,
The capacitive ultrasonic transducer is
A plurality of flexible membranes;
Of the plurality of flexible films, connected between the adjacent flexible films, each having a lower Young's modulus than each of the plurality of flexible films,
A column supporting the connecting portion;
A first electrode formed immediately below the plurality of flexible films;
A second electrode formed immediately above each of the plurality of flexible membranes;
A cavity formed between the plurality of flexible membranes and the first electrode;
An ultrasonic inspection apparatus. The ultrasonic inspection apparatus according to claim 11,
The ultrasonic inspection apparatus, wherein a thickness of the first film constituting the connection portion is smaller than a thickness of each of the plurality of flexible films. The ultrasonic inspection apparatus according to claim 11,
The said connection part is an ultrasonic inspection apparatus comprised by the bellows-like 2nd film | membrane where the said some flexible film is extended in the mutually adjacent direction. The ultrasonic inspection apparatus according to claim 11,
The connection portion includes a second film embedded in a through hole between the plurality of adjacent flexible films,
The ultrasonic inspection apparatus, wherein the second film has a Young's modulus lower than each of the plurality of flexible films. The ultrasonic inspection apparatus according to claim 11,
The connecting portion includes a plurality of first protrusions extending from the first side surface to the second side surface between the opposing first and second side surfaces of the plurality of adjacent flexible films. And a plurality of second protrusions extending from the second side surface to the first side surface side,
The plurality of first protrusions and the plurality of second protrusions are alternately stacked in the vertical direction,
The ultrasonic inspection apparatus, wherein the plurality of first protrusions and the first side surface, and the plurality of second protrusions and the second side surface are separated from each other.

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