JP7376376B2 - sonic controller - Google Patents

Description

The present invention relates to a sound wave controller, and more particularly to a sound wave controller capable of controlling the reflectance of sound waves propagating through an object.

BACKGROUND OF THE INVENTION Various acoustic equipment and facilities that utilize sound waves are used, without being limited to the audible or ultrasonic range. Examples of the audio equipment include speakers, microphones, medical ultrasound equipment, nondestructive testing equipment, and marine sonar, and examples of the audio facilities include music halls. In these audio equipment and audio facilities, sound waves are efficiently transmitted or reflected from various objects depending on the purpose.

For example, in marine sonar, the transmitter and receiver may be installed separately, but if the receiver is installed in front of the transmitter, during transmission, the sound waves transmitted from the transmitter can be efficiently It is desirable to transmit the light through the receiver and radiate it to the surroundings. On the other hand, during reception, it is desired to receive only the sound waves transmitted from the front side of the receiver with high sensitivity, and it is desirable to block the sound waves transmitted from the back side of the receiver and reflect the sound waves efficiently. There is a demand.

Furthermore, in music halls, there is a demand for actively controlling the echoes from the walls, ceiling, floor, etc. of the room depending on the content of the performance or the arrangement of the audience in the hall. Furthermore, in the future, technologies are being devised to create acoustic patterns (acoustic displays) or acoustic mimicry by controlling the reflection and transmission of sound waves on a flat surface.

It is a well-known fact from acoustic propagation theory that in the case of a simple homogeneous medium (elastic body), the reflectance and transmittance of sound waves are determined by the acoustic impedance of the elastic body, the thickness of the elastic body, and the wavelength of the sound wave. It is.

In the same audio equipment and audio facility, there are cases where it is desired to change the transmittance and reflectance from time to time. Generally, when a bulk material is used as a uniform elastic body, there is a large difference between the specific acoustic impedance of the bulk material and the specific acoustic impedance of its surroundings, so by interposing a thick bulk material, it becomes difficult for sound waves to pass through. . Conversely, by interposing a thin bulk material, it becomes easier for sound waves to pass through. Therefore, it is difficult to simultaneously optimize the reflection and transmission of sound waves by an elastic body.

A sonic transducer is known as a type of sonic controller that transmits and receives sound waves. Traditionally, sound transducers using piezoelectric ceramics that utilize piezoelectric phenomena were mainstream, but in recent years, acoustic devices called capacitor-type microphones or CMUT (Capacitive Micromachined Ultrasound Transducer) structures that apply semiconductor processes have become popular. It is used.

For example, Patent Document 1 discloses a CMUT structure in which the frequency characteristics of an ultrasonic transducer can be changed by applying a certain voltage to an electrode installed through a cavity. There is.

Special table 2016-533825 publication

As mentioned above, it is difficult in principle to control the reflection and transmission of sound waves using a bulk material that is a uniform elastic body. At a minimum, the bulk material must have a certain specific acoustic impedance and thickness for efficient reflection. Therefore, a problem arises in which it becomes difficult to secure an installation location or the weight increases.

Although there are methods for changing the transmission and reception characteristics of a sound wave transducer, there is a problem in that the reflectance and transmittance of sound waves propagating through an object cannot be actively and efficiently controlled. If it were possible to actively change the reflectance and transmittance of sound waves propagating through an object using a small or thin sound wave controller, applications in a wider range of fields could be expected. Therefore, the development of such a sound wave controller is desired, and the construction of a technology that improves the performance of the sound wave controller so that the reflectance and transmittance of sound waves can be controlled with high precision is desired. It is also desired to improve the performance of audio equipment using sonic controllers.

Other objects and novel features will become apparent from the description herein and the accompanying drawings.

A brief overview of typical embodiments disclosed in this application will be as follows.

In one embodiment, a sonic controller includes a membrane structure having a first electrode, a first substrate having a second electrode, surrounded by the membrane structure and the first substrate, and comprising: a membrane structure having a first electrode; The device includes a gap layer located between the second electrode and a DC power source electrically connected to the first electrode and the second electrode. Here, the voltage applied from the DC power source to the first electrode has a polarity opposite to the voltage applied from the DC power source to the second electrode, and the voltage applied from the DC power source to the first electrode and the second electrode is opposite in polarity to the voltage applied from the DC power source to the second electrode. By adjusting the voltage applied to each of the membrane structures, the reflectance of sound waves in the membrane structure is controlled.

According to one embodiment, a sound wave controller with good performance can be provided. Furthermore, the performance of audio equipment can be improved.

FIG. 3 is a cross-sectional view for explaining a specific problem in the first embodiment. FIG. 3 is an explanatory diagram of basic physical phenomena used in the first embodiment. FIG. 3 is an explanatory diagram of basic physical phenomena used in the first embodiment. FIG. 3 is an explanatory diagram of basic physical phenomena used in the first embodiment. FIG. 3 is an explanatory diagram of basic physical phenomena used in the first embodiment. FIG. 3 is an explanatory diagram of basic physical phenomena used in the first embodiment. FIG. 3 is an explanatory diagram of basic physical phenomena used in the first embodiment. 1 is a sectional view showing a sonic controller in Embodiment 1. FIG. FIG. 2 is a detailed cross-sectional view showing the sonic controller in Embodiment 1. FIG. 7 is a graph showing the relationship between the reflectance and frequency of sound waves in Embodiment 1. FIG. 7 is a graph showing the relationship between the reflectance and frequency of sound waves in Embodiment 1. FIG. 7 is a graph showing the relationship between the reflectance and frequency of sound waves in Embodiment 1. FIG. 7 is a graph showing the relationship between the reflectance and frequency of sound waves in Embodiment 1. FIG. 7 is a cross-sectional view showing a sonic controller in Modification 1. FIG. FIG. 7 is a cross-sectional view showing a sonic controller in Modification 2. FIG. 7 is a cross-sectional view showing a sonic controller in Modification 3. FIG. 3 is a cross-sectional view showing a marine sonar according to a second embodiment. FIG. 3 is a cross-sectional view of a main part of a part of an ocean sonar according to a second embodiment. FIG. 7 is a cross-sectional view showing an acoustic display in Embodiment 3. FIG. 7 is a plan view showing an acoustic display in Embodiment 3. FIG. 7 is a sectional view showing a sonic controller in Embodiment 4. FIG. 7 is a cross-sectional view showing a sonic controller in Modification 4. FIG. 7 is a cross-sectional view showing a sonic controller in modification 5. FIG. 7 is a cross-sectional view showing a sonic controller in Embodiment 5.

Hereinafter, embodiments will be described in detail based on the drawings. In addition, in all the drawings for explaining the embodiment, members having the same function are given the same reference numerals, and repeated explanation thereof will be omitted. Furthermore, in the following embodiments, descriptions of the same or similar parts will not be repeated in principle unless particularly necessary.

Furthermore, in the drawings describing the embodiments, hatching may be added even in plan views, and hatching may be omitted even in cross-sectional views, in order to make the configuration easier to understand.

(Embodiment 1)
First, specific problems in the first embodiment will be explained using FIG. 1. In FIG. 1, a marine sonar 200 is illustrated as an acoustic device that uses sound waves.

As shown in FIG. 1, marine sonar 200 includes a plurality of receivers 1 and transmitters 2. Each of the plurality of receivers 1 has a receiving circuit for receiving sound waves, and the transmitter 2 has a transmitting circuit for transmitting sound waves.

A plurality of receivers 1 are arranged around a transmitter 2 in an array as a plurality of independent channels, with the transmitter 2 at the center. The transmitter 2 transmits sound waves to the surroundings, and the sound waves transmitted from the transmitter 2 are transmitted to a certain object. By receiving the sound waves reflected by the object with the receiver 1, it becomes possible to know the presence of the object.

Among the sound waves transmitted from the transmitter 2, a part becomes a transmitted wave (transmission sound wave) SW1 that passes through the receiver 1, and another part becomes a reflected wave (transmission sound wave) SW2 that is reflected by the receiver 1. During transmission, the transmitted wave SW1 needs to pass through the receiver 1, but in order to transmit the transmitted wave SW1 to the surroundings more efficiently within the limited consumable energy, it is necessary to transmit the reflected wave SW2. It is necessary to suppress the occurrence. Therefore, the receiver 1 is usually thin and has a structure through which sound waves can easily pass through.

On the other hand, during reception, it is efficient to selectively receive only the reception sound waves SW3 propagated from the front side of the receiver 1. However, the sound waves received by the receiver 1 include a back reflected wave (received sound wave) SW4 that passes through the receiver 1, is reflected by the transmitter 2, and reaches the receiver 1, and other waves existing on the back side. This includes backside transmitted waves (received sound waves) SW5 that have passed through the receiver 1.

In this case, a situation occurs in which the received sound wave SW3 from the front side cannot be distinguished from the back reflected wave SW4 and the back transmitted wave SW5 from the back side. Therefore, there is a problem that object information cannot be obtained with high precision. Therefore, a technique is required that efficiently transmits sound waves through the receiver 1 during transmission and efficiently reflects sound waves from the back side of the receiver 1 during reception.

Next, basic physical phenomena used in the first embodiment will be explained using FIGS. 2A, 2B, 3A, 3B, 4A, and 4B.

FIG. 2A is a cross-sectional view showing the reflection and transmission of sound waves in a bulk material that is an elastic body, and FIG. 2B is a graph showing the relationship between reflectance and frequency. In FIG. 2A or 2B, the symbol z ₁ is the characteristic acoustic impedance of the bulk material, the symbol z ₀ and the symbol z ₂ are the characteristic acoustic impedance of the substance external to the bulk material, and the symbol D is the thickness of the bulk material. be. The frequency f is expressed as the division of the phase velocity c of the sound wave and the wavelength λ of the sound wave (f=c/λ).

When the sound wave SW6 is incident on the bulk material, part of the sound wave SW6 becomes a reflected wave SW7, and the other part becomes a transmitted wave SW8. In addition, when the thickness D of the bulk material is infinite (D=∞), that is, when the thickness D is sufficiently thicker than the wavelength λ of the frequency of interest (λ<<D), the reflectance R is as follows: It is expressed by the equation (1). Transmittance T is expressed by the following equation (2). Note that here, assuming a situation like underwater, it is assumed that the characteristic acoustic impedance z ₂ is equal to the characteristic acoustic impedance z ₀ (z ₂ =z ₀ ).

R = (z ₁ - z ₀ )/(z ₁ +z ₀ ) (1)
T=1-R=2z ₁ /(z ₁ +z ₀ ) (2)
As shown in FIG. 2B, when the thickness D of the bulk material is infinite (D=∞), there is no frequency dependence and the reflectance R is a constant value. On the other hand, when the thickness D is finite (D≠∞), that is, when the thickness D is not sufficiently thicker than the wavelength λ of the frequency of interest, the sound wave SW6 is not reflected in the low frequency band, and the transmitted wave SW8 is Becomes transparent through bulk materials. In other words, in a region where the wavelength is long, the reflectance is low, and the transmitted wave SW8 comes to pass through the bulk material. Therefore, when the material of the bulk material is determined, the transmittance T and reflectance R of the sound wave SW6 can only be controlled by the thickness D with respect to the wavelength λ, and are constant values.

Furthermore, the "frequency of interest" expressed in this application means the frequency of the sound waves that one wants to use, and the "frequency band of interest" means the range of frequencies of the sound waves that one wants to use. For example, the frequency band of interest used in ocean sonar, which is an acoustic device in the present application, is from several kHz to several hundred kHz. However, since the frequency band of interest differs depending on the application, the frequency band of interest is appropriately designed according to the application.

FIG. 3A is a cross-sectional view showing a structure including a substrate 13 having a bulk material, a thin plate-like film structure 11, and a gap layer 12 surrounded by these. FIG. 3B is a graph showing the relationship between reflectance and frequency. Note that the thickness D in FIG. 3A is the thickness of the above structure, and is equivalent to the thickness D in FIG. 2A. Further, the gap layer 12 includes a cavity and a gas or liquid existing in the cavity.

In the membrane structure 11, a standing wave is excited at a certain frequency, and when the standing wave has a large amplitude, the membrane structure 11 vibrates. This frequency is called the resonant frequency f _res . The resonant frequency f _res is determined by the shape, material, thickness, etc. of the membrane structure 11, and a plurality of resonant frequencies exist depending on various vibration modes.

When the sound wave SW6 is incident on the membrane structure 11, a force is applied to the membrane structure 11 located around the gap layer 12, so that part of the energy is transmitted as a transmitted wave SW8, and the other part of the energy is transmitted as a transmitted wave SW8. It is reflected as a reflected wave SW7. In this case, since the sound wave SW6 becomes a standing wave at the resonance frequency f _res of the membrane structure 11, the energy at that frequency is confined in the membrane structure 11. As a result, in the film structure 11 in contact with the gap layer 12, the transmitted wave SW8 becomes difficult to propagate, and most of its energy is reflected as a reflected wave SW7.

That is, as shown in FIG. 3B, near the resonant frequency f _res of the film structure 11, the reflectance R becomes large regardless of the material and thickness D of the bulk material. In other words, the reflectance R becomes large even when the thickness D is sufficiently smaller than the wavelength λ.

FIG. 4A is a cross-sectional view showing a state in which the membrane structure 11 shown in FIG. 3A is in contact with the substrate 13. FIG. 4B is a graph showing the relationship between reflectance and frequency.

As mentioned above, the resonant frequency f _res of the membrane structure 11 also depends on its shape. As shown in FIG. 4A, when the membrane structure 11 and the substrate 13, which were facing each other with the gap layer 12 in between, come into contact with each other, the overall resonant frequency shifts to the high frequency side. Therefore, when the sound wave SW6 is incident, the resonant frequency exhibiting a high reflectance also moves to the high frequency side. That is, as shown in FIG. 4B, the resonant frequency f _res0 in the state of FIG. 3A moves to the resonant frequency f _res1 in the state of FIG. 4A. Therefore, the reflected wave SW7 generated near the resonant frequency f _res1 before the membrane structure 11 and the substrate 13 come into contact is hardly generated after the contact, and most of the sound wave SW6 is transferred to the membrane structure 11 as a transmitted wave SW8. Transparent.

The first embodiment utilizes the above phenomenon to provide a sound wave controller that can actively control the reflectance and transmittance of sound waves.

FIG. 5 is a sectional view showing the sonic controller 100 in the first embodiment, and shows the states of the sonic controller 100 when the sound wave SW6 is reflected and when it is transmitted. FIG. 6 is a detailed cross-sectional view of the sonic controller 100. FIG. 7 is a graph showing the relationship between reflectance and frequency.

The acoustic wave controller 100 in the first embodiment is used in various acoustic devices such as a speaker, a microphone, a medical ultrasonic device, a non-destructive testing device, a marine sonar, or an acoustic display.

As shown in FIG. 5, the sonic controller 100 includes a membrane structure 11 having an electrode 14, a substrate 13 having an electrode 15, a gap layer 12 located between the membrane structure 11 and the substrate 13, and a direct current A power source 16 is provided. The membrane structure 11, the gap layer 12, and the substrate 13 constitute a CMUT structure. Further, FIG. 5 shows how the sound wave SW6 is incident from the membrane structure 11 side.

As shown in FIG. 6, the substrate 13 is made of a laminated structure including, for example, a semiconductor substrate SUB, an insulating film IF1, an electrode 15, and an insulating film IF2. The semiconductor substrate SUB is made of a semiconductor material such as silicon. The insulating film IF1 is formed on the semiconductor substrate SUB, and is made of silicon oxide, for example. The electrode 15 is formed on the insulating film IF1, and is made of a conductive film such as aluminum, titanium, or tungsten. The insulating film IF2 is formed on the electrode 15 and is made of silicon oxide, for example.

Note that the laminated structure of the substrate 13 is not limited to the above configuration, and may include other insulating films and other conductive films as long as they are made of materials through which sound waves can pass. Further, in the laminated structure of the substrate 13, for example, the formation of the insulating film IF2 may be omitted.

The film structure 11 is, for example, a stacked structure including an insulating film IF3, an electrode 14, and an insulating film IF4. The insulating film IF3 is formed on the insulating film IF2, and is made of silicon oxide, for example. The electrode 14 is formed on the insulating film IF3, and is made of a conductive film such as aluminum, titanium, or tungsten. The insulating film IF4 is formed on the electrode 14 and is made of silicon nitride, for example.

Note that the laminated structure of the membrane structure 11 is not limited to the above configuration, and may include other insulating films and other conductive films as long as they are made of materials through which sound waves can pass. Further, in the stacked structure of the film structure 11, the formation of the insulating film IF3 or the insulating film IF4 may be omitted, for example.

Although the thickness of the semiconductor substrate SUB, each insulating film, and each conductive film is not particularly limited, here, the thickness of the substrate 13 is greater than the thickness of the film structure 11 facing with the gap layer 12 in between. It's also thicker. Note that the thickness referred to here is the thickness in the stacking direction of the film structure 11, the gap layer 12, and the substrate 13.

Gap layer 12 is surrounded by membrane structure 11 and substrate 13 . Specifically, the gap layer 12 includes a cavity surrounded by the membrane structure 11 and the substrate 13, and a gas existing in the cavity. The gas is, for example, an inert gas such as nitrogen gas or air. Note that a liquid may exist in the cavity of the gap layer 12 instead of the gas.

Further, in FIG. 6, there are locations where the insulating film IF3 is in contact with the insulating film IF2 and locations where the insulating film IF3 is spaced apart from the insulating film IF2. A portion where the insulating film IF3 and the insulating film IF2 are spaced apart from each other and surrounded by the insulating film IF2 and the insulating film IF3 constitutes the gap layer 12.

Further, the gap layer 12 is provided between the electrode 14 and the electrode 15. Although not shown here, the gap layer 12 is provided at a position overlapping the electrode 14 and the electrode 15 in a plan view perpendicular to the stacking direction of the film structure 11, the gap layer 12, and the substrate 13. Therefore, the electric field generated between the electrode 14 and the electrode 15 is generated inside the gap layer 12.

As shown in FIG. 5, the DC power supply 16 is provided outside the membrane structure 11 and the substrate 13, and is electrically connected to the electrodes 14 and 15. The DC power supply 16 has a terminal 16a and a terminal 16b for supplying a positive voltage or a negative voltage, the terminal 16a is electrically connected to the electrode 14 via a conductive film such as wiring, and the terminal 16b is It is electrically connected to the electrode 15 via a conductive film such as wiring. Therefore, it is possible to apply a positive voltage or a negative voltage to the terminals 16a and 16b.

Note that either the terminal 16a or the terminal 16b may be on the positive voltage side or may be on the negative voltage side. That is, a positive voltage may be applied to the electrode 14 and a negative voltage may be applied to the electrode 15, or a negative voltage may be applied to the electrode 14 and a positive voltage may be applied to the electrode 15.

Further, the DC power supply 16 is a power supply that can change the magnitude of the voltage not only at a constant voltage but also at a desired voltage. Although not shown here, the DC power supply 16 is electrically connected to a control circuit that controls whether voltage can be applied to the electrodes 14 and 15. Furthermore, the magnitude of the voltage applied to the electrodes 14 and 15 is also controlled by the control circuit.

“At the time of reflection” in FIG. 5 indicates the state of the sound wave controller 100 when the sound wave SW6 is reflected in the membrane structure 11, and “at the time of transmission” in FIG. The state of the sonic controller 100 is shown. Note that the thickness of the sound wave controller 100 is designed so that the sound wave SW6 can be sufficiently transmitted. That is, the thickness of the acoustic wave controller 100 corresponds to the thickness D in FIG. 3B, and is preferably smaller than the wavelength λ in the frequency band of interest.

The "reflection" state and the "transmission" state are controlled using a certain threshold potential difference ΔVth as a boundary. Here, the state "at the time of reflection" is a case where the absolute value of the potential difference between the voltage applied to the electrode 14 and the voltage applied to the electrode 15 is smaller than the absolute value of the threshold potential difference ΔVth, and the state "at the time of transmission" The state is a case where the absolute value of the potential difference between the voltage applied to the electrode 14 and the voltage applied to the electrode 15 is greater than or equal to the absolute value of the threshold potential difference ΔVth. Note that when comparing the magnitudes of voltages or potential differences in this application, unless there is a special reason, the magnitudes are compared as absolute values.

When a voltage is applied from the DC power source 16 to the electrodes 14 and 15, the electrostatic force generated between the electrodes 14 and 15 causes the substrate 13 and the membrane structure 11 to attract each other, resulting in a relatively thin layer. The membrane structure 11 is displaced more than the substrate 13 and approaches the surface of the substrate 13. Then, when the potential difference between the voltage applied to the electrode 14 and the voltage applied to the electrode 15 exceeds the threshold potential difference ΔVth, the membrane structure 11 comes into contact with the substrate 13. In this manner, by adjusting the voltage applied from the DC power supply 16, the contact between the membrane structure 11 and the substrate 13 can be controlled, and the reflectance of sound waves in the membrane structure 11 can be controlled.

During "reflection", the voltage applied from the DC power supply 16 to the electrodes 14 and 15 is adjusted so that the film structure 11 and the substrate 13 facing each other with the gap layer 12 in between are separated.

For example, during "reflection", a first voltage with a small absolute value is applied from the DC power supply 16 to the electrode 14, a second voltage with a small absolute value is applied from the DC power supply 16 to the electrode 15, and the first voltage and the second voltage are applied to the electrode 14. The absolute value of the voltage potential difference ΔVdc1a becomes smaller than the absolute value of the threshold potential difference ΔVth. Alternatively, during "reflection", no voltage is applied from the DC power supply 16 to the electrodes 14 and 15. Note that the first voltage applied to the electrode 14 and the second voltage applied to the electrode 15 have opposite polarities. Further, the potential difference ΔVdc1a has a smaller absolute value than the potential difference ΔVdc1b, which will be described later.

Here, as shown in FIG. 7, when the resonant frequency of the membrane structure 11 at this time is f _res0 , the sound wave SW6 is high in the membrane structure 11 because the reflectance is high near the resonant frequency f _res0 . Reflect with efficiency.

During "transmission", the voltage applied from the DC power supply 16 to the electrodes 14 and 15 is adjusted so that the membrane structure 11 and the substrate 13, which were facing each other with the gap layer 12 in between, come into contact with each other.

For example, in the "transmission state", a third voltage with a large absolute value is applied from the DC power supply 16 to the electrode 14, a fourth voltage with a large absolute value is applied from the DC power supply 16 to the electrode 15, and the third voltage and the fourth voltage are applied to the electrode 14. The absolute value of the voltage potential difference ΔVdc1b becomes greater than or equal to the absolute value of the threshold potential difference ΔVth. Note that the third voltage applied to the electrode 14 and the fourth voltage applied to the electrode 15 have opposite polarities. Further, the potential difference ΔVdc1b has a larger absolute value than the above-described potential difference ΔVdc1a.

Here, as shown in FIG. 7, the resonant frequency moves from f _res0 to f _res1 . Since the reflectance is low near the resonance frequency f _res0 , the thinner the sound wave controller 100 is, the more efficiently the sound wave SW6 is transmitted through the membrane structure 11.

As described above, according to the first embodiment, it is possible to provide the sound wave controller 100 that can actively change the reflectance and transmittance of sound waves. Furthermore, as described above, the reflectance and transmittance of the sound wave SW6 are controlled with high accuracy by adjusting the voltage of the DC power supply 16, so that it is possible to provide the sound wave controller 100 with good performance.

Further, the DC power supply 16 in the first embodiment is a power supply whose voltage level can be changed. Therefore, the resonant frequency band can be adjusted.

For example, as described above, the highly efficient reflection band during reflection is determined by the resonant frequency of the membrane structure 11. In a CMUT structure, the resonant frequency depends on the membrane structure 11 and the magnitude of the potential difference between the voltage applied to electrode 14 and the voltage applied to electrode 15. For example, the larger the potential difference, the more the resonance frequency moves to a lower frequency band. FIG. 8 shows this situation.

As shown in FIG. 8, when a voltage larger than that shown in FIG. 7 is applied from the DC power supply 16 to the electrodes 14 and 15 during reflection, the potential difference between these is smaller than the threshold potential difference ΔVth and smaller than the potential difference ΔVdc1a. Also, the potential difference ΔVdc2a becomes large. In this case, the resonant frequency f _res0 moves to the lower frequency side. In this way, since the reflection band can be adjusted relatively freely, the sound wave controller 100 can deal with sound waves having various wavelengths.

Further, the contact area between the membrane structure 11 and the substrate 13 during transmission can be controlled by a DC voltage, and the resonance frequency during contact is also determined according to this contact area. Therefore, by controlling the magnitude of the DC voltage, it is possible to control the reflection band with high efficiency. FIG. 9 shows this situation.

As shown in FIG. 9, when a voltage larger than that shown in FIG. 7 is applied from the DC power supply 16 to the electrodes 14 and 15 during transmission, the potential difference between them is greater than or equal to the threshold potential difference ΔVth, and The potential difference ΔVdc2b is larger than the potential difference ΔVdc1b. In this case, the contact area between the membrane structure 11 and the substrate 13 increases. Then, the resonant frequency f _res1 moves to the high frequency side. In this way, since the transmission band can be adjusted relatively freely, the sound wave controller 100 can handle sound waves having various wavelengths.

In addition, in the frequency characteristics shown in FIGS. 7, 8, and 9, the resonant frequency of the membrane structure 11 is the lowest fundamental mode (low-order exemplified by Maud). However, in reality, the resonant frequency of the membrane structure 11 has vibration modes including a low-order mode and a high-order mode higher than the low-order mode.

FIG. 10 shows a frequency characteristic including a resonant frequency f _res0 of a low-order mode and a resonant frequency f _res2 of the next higher-order mode. In the first embodiment, both a low-order mode and a high-order mode can be used for transmission and reflection of sound waves in the membrane structure 11.

Further, in the above description, only the two-dimensional cross-sectional structure of the acoustic wave controller 100 was shown, but what is important is the resonance frequency of the membrane structure 11. Therefore, as long as the resonance frequency can be controlled, various shapes can be applied to the planar shape of the film structure 11 in a plan view perpendicular to the lamination direction of the film structure 11, gap layer 12, and substrate 13, such as a rectangular shape. shape, circular or close-packed hexagonal.

(Modified example 1, modified example 2)
Modification 1 and Modification 2 of Embodiment 1 will be described below. FIG. 11 is a sectional view showing a sonic controller 100 in a first modification, and FIG. 12 is a sectional view showing a sonic controller 100 in a second modification.

In FIG. 5, an electrode 14 was provided inside the membrane structure 11, and an electrode 15 was provided inside the substrate 13. However, if the membrane structure 11 can be deformed by electrostatic force, the formation positions of the electrodes 14 and 15 can be changed individually.

For example, as shown in FIG. 11, electrode 14 and electrode 15 may be exposed in gap layer 12. More specifically, referring to FIG. 6, electrode 14 may be formed on insulating film IF2, and electrode 15 may be formed under insulating film IF3. Moreover, the electrode exposed in the gap layer 12 may be both the electrode 14 and the electrode 15, or only one of them may be exposed.

Note that during transmission, the electrode 14 and the electrode 15 are in direct contact with each other, but by providing a resistive element on the electrode 14 side, for example, even if these contact, it is possible to suppress the flow of a large current.

Further, as shown in FIG. 12, the electrode 14 may be located at the farthest point from the gap layer 12 so as to be exposed to the outside of the membrane structure 11. More specifically, referring to FIG. 6, the electrode 14 may be formed on the insulating film IF4.

(Modification 3)
Another modification example 3 of the first embodiment will be described below. FIG. 13 is a sectional view showing the sonic controller 100 in Modification 3.

FIG. 5 illustrates a case where the sound wave SW6 is incident from the membrane structure 11 side. As shown in FIG. 13, even when the sound wave SW6 is incident from the substrate 13 side, by applying an appropriate voltage to the electrodes 14 and 15, the reflectance and transmission of the sound wave SW6 can be improved in the membrane structure 11. rate can be controlled.

(Embodiment 2)
Ocean sonar 200 according to the second embodiment will be described below using FIGS. 14 and 15. Note that in the following description, differences from Embodiment 1 will be mainly explained. FIG. 14 is a sectional view showing the ocean sonar 200, and FIG. 15 is an enlarged sectional view of a main part of the area surrounded by a broken line in FIG. In addition, in FIG. 15, illustration of the electrode 14, the electrode 15, and the DC power supply 16 of the sonic controller 100 is omitted in order to make the drawing easier to read.

Marine sonar 200 is an acoustic device using sonic controller 100 in the first embodiment. As shown in FIG. 14, marine sonar 200 includes a plurality of receivers 1 and transmitters 2. Each of the plurality of receivers 1 has a receiving circuit for receiving sound waves, and the transmitter 2 has a transmitting circuit for transmitting sound waves. The acoustic wave controller 100 is provided between the transmitter 2 and each of the plurality of receivers 1.

Please refer to the explanation of FIG. 1 for the functions of each of the plurality of receivers 1 and transmitters 2, and the transmitted and received sound waves handled by these.

As shown in "At the time of transmission" in FIG. 15, at the timing of transmitting the transmission sound wave SW1 from the transmitter 2 to the surroundings, the potential difference between the voltage applied to the electrode 14 and the voltage applied to the electrode 15 is determined as the threshold potential difference ΔVth. By making the above adjustments, the film structure 11 and the substrate 13 are brought into contact. Since the transmitted sound wave SW1 passes through the sound wave controller 100 with high efficiency, loss of the transmitted sound wave SW1 is suppressed.

As shown in "At the time of reception" in FIG. 15, at the timing of receiving the received sound wave SW3 propagated from the front surface of the receiver 1, the potential difference between the voltage applied to the electrode 14 and the voltage applied to the electrode 15 is By adjusting the potential difference to be smaller than the threshold potential difference ΔVth, the membrane structure 11 and the substrate 13 are separated. The back reflected wave SW4 and the back transmitted wave SW5 that enter from the back side of the receiver 1 are reflected with high efficiency on the membrane structure 11, so that the received sound wave SW3, the back reflected wave SW4, and the back transmitted wave SW5 are Problems that make it difficult to distinguish can be suppressed.

As described above, the marine sonar 200 equipped with the sonic wave controller 100 can efficiently transmit the sound waves through the receiver 1 when transmitting, and can efficiently reflect the sound waves from the back side of the receiver 1 when receiving. , the performance of the ocean sonar 200, which is an acoustic device, can be improved.

Further, in FIG. 15, the substrate 13 is located on the receiver 1 side, and the membrane structure 11 is located on the transmitter 2 side. Here, whether a sound wave is incident from the membrane structure 11 side as shown in FIG. 5 or a sound wave is incident from the substrate 13 side as shown in FIG. Reflectance and transmittance can be controlled.

However, in the sound wave controller 100, the reflectance of sound waves is actively controlled by the relatively thin film structure 11. Therefore, by locating the film structure 11 near the back reflected wave SW4 and the back transmitted wave SW5, the back reflected wave SW4 and the back transmitted wave SW5 can be reflected with higher efficiency.

(Embodiment 3)
The acoustic display 300 according to the third embodiment will be described below with reference to FIGS. 16 and 17. Note that in the following description, differences from Embodiment 1 will be mainly explained. FIG. 16 is a cross-sectional view of the acoustic display 300, and FIG. 17 is a plan view of the acoustic display 300 in a plan view perpendicular to the stacking direction of the acoustic wave controller 100 and the attenuation layer 17. In addition, in FIG. 16, in order to make the drawing easier to read, illustrations or symbols of the sonic controller 100 other than the membrane structure 11 are omitted.

Acoustic display 300 is an audio device using sonic controller 100 in the first embodiment. As shown in FIG. 16, the acoustic display 300 includes a plurality of attenuating layers 17 and a plurality of acoustic wave controllers 100. Each of the plurality of damping layers 17 has the property of reducing the amplitude of sound waves propagating therein.

A plurality of sound wave controllers 100 are provided on the surfaces of the plurality of attenuation layers 17, respectively. The reflectance of the sound wave SW9 incident on one attenuation layer 17 is individually controlled by one sound wave controller 100 provided on the surface thereof. Therefore, the plurality of attenuation layers 17 are recognized as a two-dimensional array in plan view, and constitute an acoustic pattern as shown in FIG. 17. In FIG. 17, a pattern similar to the alphabet "H" is illustrated as an acoustic pattern.

As described above, the sound wave controller 100 can actively control the reflectance and transmittance of the sound wave SW9 incident on the attenuation layer 17. Therefore, the performance of the acoustic display 300, which is an audio device, can be improved.

Although the plurality of damping layers 17 are illustrated as separate layers in FIGS. 16 and 17, the plurality of damping layers 17 may be one integrated damping layer. In that case, a set of multiple regions corresponding to multiple acoustic wave controllers 100 can also be recognized as an integrated attenuation layer. That is, the plurality of damping layers 17 in the third embodiment are each an individual damping layer or a plurality of regions of one damping layer.

Moreover, in FIG. 16, the relatively thin film structure 11 is located near the sound wave SW9. That is, each substrate 13 of the plurality of sound wave controllers 100 is located on the attenuation layer 17 side. Therefore, the sound wave SW9 can be reflected with higher efficiency.

(Embodiment 4)
The sonic controller 100 according to the fourth embodiment will be described below using FIG. 18. Note that in the following description, differences between Embodiment 1 and Embodiment 2 will be mainly explained. FIG. 18 is a sectional view showing the sonic controller 100 according to the fourth embodiment.

In the second embodiment, the sonic wave controller 100 in the first embodiment is provided as a separate structure from the receiver 1 and the transmitter 2, and is provided between the transmitter 2 and the receiver 1. The sonic controller 100 in the fourth embodiment includes a receiver 1 and is integrated with the receiver 1.

As shown in FIG. 18, the receiver 1 according to the fourth embodiment includes a membrane structure 21 having an electrode 24, a substrate 23 having an electrode 25, and a gap layer 22 located between the membrane structure 21 and the substrate 23. , a DC power supply 26 and a receiving circuit 27. The receiver 1 has a CMUT structure substantially similar to that of the sonic controller 100, and the receiver 1 and the sonic controller 100 are individually controlled by different DC power supplies 16 and 26, respectively.

The membrane structure 21 and the substrate 23 are made of a laminated structure in which the insulating films and conductive films used in the membrane structure 11 and the substrate 13 are applied and laminated as appropriate. The gap layer 22 is surrounded by the membrane structure 21 and the substrate 23, and, like the gap layer 12, is composed of a cavity and a gas or liquid existing in the cavity.

Further, the substrate 23 includes a semiconductor substrate similar to the semiconductor substrate SUB of the substrate 13. In the fourth embodiment, the sonic controller 100 and the receiver 1 are integrated by bonding the substrate 13 and the substrate 23. Specifically, the semiconductor substrate SUB of the substrate 13 and the semiconductor substrate of the substrate 23 are bonded.

Further, the receiver 1 is formed on the substrate 23 and includes a receiving circuit 27 for receiving the sound wave SW3. Receiving circuit 27 is electrically connected to electrode 24 and DC power supply 26 . Specifically, the receiving circuit 27 includes a semiconductor element formed on the semiconductor substrate of the substrate 23 and a wiring layer electrically connected to the semiconductor element, and the wiring layer is connected to the semiconductor element through the electrode 24. and is electrically connected to a DC power source 26.

Even in the sound wave controller 100 integrated with the receiver 1, the reflectance and transmittance of sound waves can be actively controlled. Therefore, during transmission, the transmitted sound wave SW1 can be transmitted, and during reception, the back reflected wave SW4 and the back transmitted wave SW5 can be efficiently reflected, and the received sound wave SW3 can be received.

In addition, although the receiver 1 of CMUT structure was illustrated in Embodiment 4, the receiver 1 may be comprised from a well-known piezoelectric element, for example instead of a CMUT structure.

Furthermore, in Embodiment 4, the structure in FIG. 18 is described as the sonic controller 100 including the receiver 1, but the structure in FIG. It can also be said that it is 1.

(Modification 4)
A fourth modification of the fourth embodiment will be described below. FIG. 19 is a cross-sectional view showing the sonic controller 100 in Modified Example 4.

As shown in FIG. 19, the sonic wave controller 100 in Modification 4 includes not only a receiving circuit 27 but also a transmitting circuit 28. That is, the sonic controller 100 is integrated with the transceiver 3 that includes the receiving circuit 27 and the transmitting circuit 28 .

The structure of the transceiver 3 in Modification 4 is almost the same as the structure in FIG. 18 except that a transmitting circuit 28 is formed.

Further, the transceiver 3 is formed on the substrate 23 and includes a transmitting circuit 28 for transmitting the sound wave SW1. Transmission circuit 28 is electrically connected to DC power supply 26 via electrode 24 and electrode 25 . Specifically, the transmitting circuit 28 includes a semiconductor element formed on the semiconductor substrate of the substrate 23 and a wiring layer electrically connected to the semiconductor element, and the wiring layer includes the electrode 24 and the electrode. It is electrically connected to a DC power supply 26 via 25.

During transmission, a sound wave SW1 is transmitted from the front side of the transceiver 3, but a sound wave with a certain amount of energy is also emitted from the back side of the transceiver 3, and a reflected wave SW10 of the sound wave is returned. Furthermore, during reception, there are a back reflected wave SW4 and a back transmitted wave SW5, as in the previous explanation.

Even in the sound wave controller 100 integrated with such a transceiver 3, the reflectance and transmittance of sound waves can be actively controlled. Therefore, at the time of transmission, the reflected wave SW10 can be reflected efficiently, so that it is possible to suppress the reflected wave SW10 from being mixed with the sound wave SW1. At the time of reception, the back reflected wave SW4 and the back transmitted wave SW5 are efficiently reflected, and the received sound wave SW3 can be received.

Furthermore, in Modification 4, it is explained that the structure in FIG. It can also be rephrased as .

(Modification 5)
Another modification example 5 of the fourth embodiment will be described below. FIG. 20 is a sectional view showing a sonic controller 100 in Modification 5.

In FIGS. 18 and 19, the substrate 13 and the substrate 23 are bonded, and specifically, the semiconductor substrate SUB of the substrate 13 and the semiconductor substrate of the substrate 23, which are made of the same semiconductor material, are bonded.

As shown in FIG. 20, in modification 5, an intervening layer 18 is provided between the substrate 13 and the substrate 23, and the substrate 13 and the substrate 23 are bonded via the intervening layer 18. The intervening layer 18 is provided to more stably bring the semiconductor substrate SUB of the substrate 13 and the semiconductor substrate of the substrate 23 into close contact. The intervening layer 18 only needs to be made of a material through which sound waves can pass, and is made of, for example, a conductive film such as an aluminum film, or an insulating film such as a silicon oxide film or a resin film.

Further, in the above-mentioned modification 4 as well, the intervening layer 18 may be provided between the substrate 13 and the substrate 23.

(Embodiment 5)
The sonic wave controller 100 according to the fifth embodiment will be described below using FIG. 21. Note that in the following description, differences from Embodiment 1 will be mainly explained. FIG. 21 is a cross-sectional view showing the sonic controller 100 according to the fifth embodiment. In addition, in FIG. 21, illustration of the electrode 14, the electrode 15, and the DC power supply 16 of the sonic controller 100 is omitted in order to make the drawing easier to read.

As shown in FIG. 21, the sonic controller 100 according to the fifth embodiment has a plurality of CMUT structures including a membrane structure 11, a gap layer 12, and a substrate 13. Each of the plurality of CMUT structures is provided with a plurality of gap layers 12 in the left and right direction, and the CMUT structure including the plurality of gap layers 12 is vertically arranged by joining the film structures 11 and substrates 13 to each other. Laminated in the direction.

Further, the upper gap layer 12 having a CMUT structure and the lower gap layer 12 having a CMUT structure are arranged with a wide interval in the left-right direction. That is, in the vertical and horizontal directions, the position of the upper gap layer 12 is shifted from the position of the lower gap layer 12.

Note that the above-mentioned vertical direction is the lamination direction of the film structure 11, the gap layer 12, and the substrate 13, and the above-mentioned left-right direction is a direction perpendicular to the lamination direction.

By shifting the positions of the plurality of gap layers 12, some of the back reflected waves SW4 are reflected at the film structure 11 in contact with the lower gap layer 12, while other back reflected waves SW4 are reflected by the upper gap layer 12. It is reflected at the membrane structure 11 that is in contact with. Therefore, the back reflected wave SW4 can be reflected in stages. In other words, the back reflected wave SW4 can be attenuated in stages. Further, the same effect can be obtained even when the back surface transmitted wave SW5 is used instead of the back surface reflected wave SW4.

In this way, in the fifth embodiment, the sonic wave controller 100 can also function as an attenuator.

Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist thereof.

For example, in the above embodiment, the film structure 11 and the substrate 13 formed of a plurality of insulating films and a plurality of conductive films are illustrated, but the structure of each of the film structure 11 and the substrate 13 is limited to these. Not done. The membrane structure 11 and the substrate 13 may be formed using a plastic or resin film, and may be formed, for example, by joining a plate-shaped plastic plate and a bent plastic plate.

1 Receiver 2 Transmitter 3 Transmitter/receiver 11 Membrane structure 12 Gap layer 13 Substrate 14 Electrode 15 Electrode 16 DC power supply 16a, 16b Terminal 17 Attenuation layer 18 Intervening layer 21 Membrane structure 22 Gap layer 23 Substrate 24 Electrode 25 Electrode 26 DC Power supply 27 Receiving circuit 28 Transmitting circuit 100 Sound wave controller 200 Marine sonar 300 Acoustic display SW1 Transmitted wave (transmitted sound wave)
SW2 Reflected wave (transmitted sound wave)
SW3 Front transmitted wave (received sound wave)
SW4 Back reflected wave (received sound wave)
SW5 Back transmitted wave (received sound wave)
SW6 Sound wave SW7 Reflected wave SW8 Transmitted wave SW9 Sound wave SW10 Reflected wave

Claims (8)

a membrane structure having a first electrode;
a first substrate having a second electrode;
a gap layer surrounded by the membrane structure and the first substrate and located between the first electrode and the second electrode;
a DC power supply electrically connected to the first electrode and the second electrode;
a second substrate bonded to the first substrate;
a receiving circuit formed on the second substrate;
Equipped with
The voltage applied from the DC power source to the first electrode has a polarity opposite to the voltage applied from the DC power source to the second electrode,
By adjusting the voltages applied from the DC power supply to the first electrode and the second electrode, the reflectance of the sound wave in the membrane structure is controlled,
When reflecting a first sound wave in the membrane structure having a first resonant frequency, the membrane structure and the first substrate facing each other with the gap layer in between are separated;
When transmitting the first sound wave through the membrane structure, the first resonance frequency of the membrane structure is increased by bringing the membrane structure and the first substrate, which were facing each other through the gap layer, into contact with each other. , to a second resonant frequency different from the first resonant frequency ;
The receiving circuit is a sound wave controller that receives the first sound wave . The sonic controller according to claim 1,
When reflecting the first sound wave in the membrane structure, a first voltage is applied from the DC power source to the first electrode, and a second voltage having a polarity opposite to the first voltage is applied from the DC power source to the second electrode. is applied, and the absolute value of the potential difference between the first voltage and the second voltage is smaller than the absolute value of a threshold potential difference, or no voltage is applied from the DC power supply to the first electrode and the second electrode. ,
When the first sound wave is transmitted through the membrane structure, a third voltage having an absolute value larger than the first voltage is applied from the DC power source to the first electrode, and a third voltage whose absolute value is larger than the first voltage is applied from the DC power source to the second electrode. A fourth voltage having a polarity opposite to that of the third voltage and having a larger absolute value than the second voltage is applied, and the absolute value of the potential difference between the third voltage and the fourth voltage is equal to or greater than the absolute value of the threshold potential difference. A sonic controller. The sonic controller according to claim 1,
The DC power source is a sonic controller in which the voltage level can be changed. The sonic controller according to claim 1,
The first resonant frequency and the second resonant frequency of the membrane structure have vibration modes including a low-order mode and a high-order mode, and the transmission or reflection of the first sound wave in the membrane structure has a low A sonic controller that can be used in both next-order and higher-order modes. The sonic controller according to claim 1 ,
A sound wave controller, further comprising a transmission circuit formed on the second substrate and configured to transmit the first sound wave. The sonic controller according to claim 1 ,
further comprising an intervening layer provided between the first substrate and the second substrate,
The first substrate and the second substrate are bonded to each other via the intervening layer. The sonic controller according to claim 1,
The gap layer is configured by a cavity surrounded by the membrane structure and the first substrate, and a gas existing in the cavity. The sonic controller according to claim 1,
The gap layer is a sound wave controller including a cavity surrounded by the membrane structure and the first substrate, and a liquid existing in the cavity.

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