JP2011166632A - Electrostatic capacitive electro-mechanical transducer having sacrifice region - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitive electro-mechanical transducer capable of preventing a cell or an element from being destroyed even when a high voltage is erroneously applied. <P>SOLUTION: An electrostatic capacitive electro-mechanical transducer has at least one cell including: a first electrode 2; and a second electrode 3 disposed while facing the first electrode 2 via a cavity 4. A sacrifice region 7 composed of an insulator is included and the sacrifice region 7 is configured to incur short-circuiting by applying a voltage lower than a short-circuiting voltage that incurs short-circuiting in a driving region 6 including the cell. The first electrode 2 and the second electrode 3 are configured while holding an insulated portion including the sacrifice region 7 therebetween, and electrically connected to each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a capacitance type electromechanical transducer that performs at least one of reception and transmission of elastic waves such as ultrasonic waves.

In recent years, a capacitive electromechanical transducer manufactured using a micromachining process has been actively studied. A typical electrostatic capacitance type electromechanical transducer has a cell including a lower electrode, a vibrating membrane supported with a gap therebetween, and an upper electrode disposed on the surface of the vibrating membrane. This is used as, for example, a capacitive ultrasonic transducer (CMUT: Capacitive-Micromachined-Ultrasonic-Transducer). The CMUT transmits and receives ultrasonic waves using a lightweight vibrating membrane, and can easily obtain a broadband characteristic having excellent broadband characteristics even in liquid or air. When this CMUT is used, it is possible to make a diagnosis with higher accuracy than the conventional medical diagnosis.

In this capacitive electromechanical transducer, a bias voltage is applied between two electrodes having a cavity and an insulating film interposed therebetween, and the electrodes are held so that the distance between the electrodes is close. The electrodes on one side are in contact with the insulating film so that the two electrodes do not short-circuit when in contact. When a vibration signal is applied to the CMUT in which the distance between the electrodes is close, for example, the electrode on one side not fixed to the substrate can vibrate to emit acoustic energy (transmission). Further, when a sound wave is incident, the capacitance of the CMUT changes due to vibration of one electrode not fixed to the substrate, and the change can be detected as a change in voltage (reception). In order to improve the electromechanical conversion performance, it is desirable to reduce the distance between the two electrodes. For this purpose, it is necessary to generate a high potential difference between the two electrodes. That is, high performance can be exhibited as the bias voltage applied increases.

Such a capacitive electromechanical conversion device is often used as one element (pixel) in which a plurality of cells having a size of several tens to several hundreds of μm are connected by an electrode pattern. In Patent Document 1 that discloses this, one element is short-circuited due to an increase in the bias voltage to be applied, so that it becomes impossible to apply a stable bias voltage to other elements that share the same electrode, and electromechanical conversion is performed. It is described that the performance deteriorates. As countermeasures for this, it has also been shown that electromechanical conversion performance is prevented from being lowered by eliminating shorted elements or eliminating elements that have shorted elements and electrodes in common.

JP 2006-343315 A

However, with the configuration described in Patent Document 1, if a high voltage that causes a short circuit is applied by mistake, all elements may be short-circuited. Moreover, if the element is eliminated after the element is short-circuited as in Patent Document 1, the element cannot be reused. That is, the element itself was not provided with a mechanism for preventing a short circuit.

In view of the above problems, a capacitance type electromechanical transducer according to the present invention includes a cell including a first electrode and a second electrode disposed to face the first electrode with a gap interposed therebetween. Have at least one. And a sacrificial region configured to cause a short circuit when a voltage lower than a short circuit voltage causing a short circuit is applied in a drive region including the cell, and the first electrode and the second electrode include an insulating part including the sacrificial region Are electrically connected to each other.

In the present invention, the sacrificial region is configured to be short-circuited before a required cell is short-circuited. For example, even when a high voltage that causes the cell to be short-circuited is mistakenly applied, It becomes possible to prevent destruction.

The figure explaining 1st embodiment of this invention. The figure explaining 2nd embodiment of this invention. The figure explaining the modification of 2nd embodiment of this invention. The figure explaining 3rd embodiment of this invention. The figure explaining the modification of 3rd embodiment of this invention. The figure explaining 4th embodiment of this invention. The figure explaining the modification of 4th embodiment of this invention. The figure explaining the modification of 4th embodiment of this invention. The figure explaining 5th embodiment of this invention. The figure explaining 6th embodiment of this invention. The figure explaining 7th embodiment of this invention. The figure explaining 8th embodiment of this invention. The figure explaining the structure of the barrier around a sacrificial area.

Hereinafter, embodiments of the present invention will be described. The capacitive electromechanical transducer according to the present invention is characterized in that the sacrificial region is provided and short-circuited in the sacrificial region before the element or cell is short-circuited. Therefore, the sacrificial region is configured to cause a short circuit when a voltage lower than a short circuit voltage causing a short circuit is applied in the drive region including the cell.

Based on this concept, the following embodiments are possible. For example, it may further include a stopping means such as a fuse configured to stop the voltage application to the driving region due to an overcurrent flowing when a short circuit occurs in the sacrificial region. One or more sacrificial regions may be provided for each element or cell comprising one or more cells. In the case where a plurality of sacrificial regions are provided, the sacrificial regions can be configured to have different voltages that cause the short circuit. Further, the second electrode of the driving region can be provided on the insulating film, and the thickness of the insulating film of the driving region can be made thinner than the thickness of the insulating portion of the sacrificial region. In addition, the material and generation method of the insulating film in the driving region and the insulating portion in the sacrificial region can be different. The first electrode used in the capacitive electromechanical transducer of the present invention can be formed of the following material. That is, a conductor selected from Al, Cr, Ti, Au, Pt, Cu, Ag, W, Mo, Ta, Ni, etc., a semiconductor such as Si, AlSi, AlCu, AlTi, MoW, AlCr, TiN, AlSiCu, etc. It can be made of at least one material selected from the alloys In addition, the second electrode is provided on at least one of the top surface, the back surface, and the inside of the vibration film (insulating film), or when the vibration film is formed of a conductor or semiconductor, the vibration film is the second film. The structure can also serve as an electrode. The second electrode can also be formed using the same conductor, semiconductor, or the like as the first electrode. The materials of the first electrode and the second electrode may be different.

Hereinafter, an embodiment of a capacitive electromechanical transducer of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1A is a top view showing the basic structure of the first embodiment of the capacitive electromechanical transducer of the present invention, and FIG. 1B is a cross-sectional view taken along the line AA ′ of FIG. It explains using. In the present embodiment, a first electrode (lower electrode) 2 and a second electrode (upper electrode) 3 are provided on the substrate 1 so as to constitute a cell. The drive region 6 including the cell includes a cavity (gap) 4 and an insulating film 5 between the first electrode 2 and the second electrode 3 facing each other. The second electrode 3 is wired above the insulating film 5. In the portion other than the drive region 6, the second electrode 3 is wired so as to cover the surface of the sacrificial region 7 across the region without the cavity 4. The sacrificial region 7 has an electrode pad above the sacrificial region 7, and this electrode pad is electrically connected to the second electrode 3 by the wiring. In this way, the first electrode 2 and the second electrode 3 are connected to each other with the insulating portion interposed therebetween, and a bias voltage can be applied. . As the substrate 1, various substrates such as a silicon wafer and a glass substrate can be used. In the present embodiment, the first electrode 2 and the second electrode 3 are formed of, for example, at least one material of Al, Cr, Ti, Au, Pt, and Cu, but may be other conductive materials. .

The insulating film 5 in the drive region 6 and the insulating portion in the sacrificial region 7 are formed of, for example, SiN or SiO _2, but other insulating materials may be used. The cavity 4 may be filled with air or gas, and may be set to a pressure lower than the atmospheric pressure depending on the manufacturing method. The insulating part of the sacrificial region 7 preferably has a lower withstand voltage than the insulating film 5. For example, different insulating materials are used for the insulating portions of the insulating film 5 and the sacrificial region 7. Alternatively, even with the same insulating material, it is possible to lower the withstand voltage of the insulating portion of the sacrificial region 7 with respect to the insulating film 5 of the drive region 6 by changing the method of generating the insulating film. For example, as the type of insulating _{material, SiN, SiO 2, Al 2} O 3, Ta 2 O 5, TiO 2, and the like. Although the withstand voltage of each insulating material varies depending on the generation method, it is 2 to 10 × 10 ⁶ [V / cm], 3 to 11 × 10 ⁶ [V / cm], and 3 to 8 × 10 ⁶ [V]. V / cm], 5 × 10 ⁶ [V / cm], and 0.5 × 10 ⁶ [V / cm]. For example, examples of the method for generating SiO ₂ include thermal oxidation, plasma oxidation, CVD (chemical vapor deposition), and anodization. The dielectric breakdown voltage of the oxide film generated by each method is 5 to 10 × 10 ⁶ [V / cm], 3 to 7 × 10 ⁶ [V / cm], and 4 × 10 ⁶ [V / cm] in the order given above. ], 7 to 11 × 10 ⁶ [V / cm]. In the case of a SiO ₂ film, insulating films having different withstand voltages can be generated by forming respective insulating films by plasma oxidation and anodic oxidation. Further, by generating different types of insulating films using the same generation method, insulating films having different withstand voltages can be generated. For example, if a SiO ₂ film is generated by a plasma CVD method, a film having a withstand voltage of about 8 × 10 ⁶ [V / cm] can be generated, although it varies depending on deposition conditions. Similarly, if a SiN film is generated by the plasma CVD method, a film having a withstand voltage of about 2 × 10 ⁶ [V / cm] can be generated although it varies depending on the deposition conditions. Furthermore, the withstand voltage can be adjusted by changing the thickness of the film formation. Thus, the withstand voltage difference between the insulating film 5 and the insulating portion of the sacrificial region 7 can be adjusted by a combination of the insulating material, the generation method, and the film thickness.

In such a configuration, when a bias voltage is applied between the first electrode 2 and the electrode pad of the sacrificial region 7, the voltage between the first electrode 2 and the second electrode 3 in the drive region 6 is increased according to the magnitude of the bias voltage. The distance changes. In this state, when acoustic energy enters the drive region 6 from the outside, the insulating film 5 in the drive region 6 vibrates. As a result, the capacitance between the first electrode 2 and the second electrode 3 in the drive region 6 changes, and this change in capacitance is detected as a change in voltage via the first electrode 2, for example. Thus, the incident acoustic energy can be detected.

The operation of this embodiment will be described. In the configuration of FIG. 1, by increasing the bias voltage to be applied, the distance between the first electrode 2 and the second electrode 3 in the drive region 6 becomes narrow due to the action of electrostatic attraction. Thereby, the radiation pressure of the acoustic energy to the outside can be increased. Moreover, the detection performance of the incident acoustic energy can be enhanced. However, if the bias voltage to be applied is increased too much, the first electrode 2 and the second electrode 3 are adsorbed via the insulating film 5 at the moment when a certain voltage is reached, and desired vibration characteristics cannot be obtained. This phenomenon is called pull-in, and the voltage at which pull-in occurs is called a pull-in voltage. The insulating film 5 desirably has a withstand voltage that does not short-circuit with the pull-in voltage. When the bias voltage is further increased after the pull-in, the first electrode 2 and the second electrode 3 sandwiching the insulating portion of the sacrificial region 7 with a certain voltage are short-circuited. Due to the short circuit of the sacrificial region 7, the bias voltage applied to the drive region 6 decreases. Thereby, destruction of parts other than the sacrificial region 7 can be prevented. The above is the function that the sacrificial region 7 should perform, and the sacrificial region 7 is configured so that such a function can be completed.

FIG. 1 shows a configuration in which a cavity 4 and an insulating film 5 are interposed between the first electrode 2 and the second electrode 3 in the drive region 6, but a configuration without the insulating film 5 may be used (that is, The second electrode 3 also functions as a vibration film). In that case, by setting the dielectric strength value of the sacrificial region 7 to a value lower than the pull-in voltage, it is possible to prevent the portion other than the sacrificial region 7 from being destroyed. In the configuration of FIG. 1, several insulating films 5 may be interposed between the first electrode 2 and the second electrode 3. Further, in the drive region 6, an insulating film may be provided so as to be in contact with the first electrode 2, and the cavity 4, the insulating film 5, and the second electrode 3 may be provided thereon. The shape of the drive region 6 to the cavity 4 may be circular (indicated by a broken line in FIG. 1A), a quadrangle, a hexagon, or the like, and can be made into a desired shape according to circumstances.

Various methods are known for producing a capacitive electromechanical transducer as shown in FIG. For example, it can be produced by a joining type or surface type method. In the bonding type, for example, a cavity structure is formed on a silicon substrate, and an SOI substrate is bonded on the cavity structure. In the surface type, for example, a lower electrode and a sacrificial layer are formed on a silicon substrate. A sacrificial layer pattern to be a cavity is formed, a vibration film (insulating film) and a support portion are formed thereon, and then the sacrificial layer is etched to form a cavity. Among these known manufacturing methods, the withstand voltage difference between the insulating film 5 existing between the two electrodes and the insulating portion constituting the sacrificial region 7 can be adjusted by a combination of an insulating material and a generation method. .

In this embodiment, the sacrificial region insulating portion is short-circuited before the driving region cell is short-circuited. For example, even when a high voltage enough to cause the cell to be short-circuited is applied by mistake, the cell Or it becomes possible to prevent destruction of the element. In addition, before a cell is short-circuited at the time of use, if a voltage is applied to the device so that a cell that is not required in advance is short-circuited, unnecessary cells can be eliminated, so only the desired cell is reused. It becomes possible to do.

(Second embodiment)
FIG. 2 (a) is a top view showing the basic structure of the second embodiment of the capacitive electromechanical transducer of the present invention, and FIG. 2 (b) is a BB ′ sectional view of FIG. 2 (a). It explains using. This embodiment has a voltage application stop means.

The substrate 1, the first electrode 2, the second electrode 3, the cavity 4, the insulating film 5, the drive region 6, and the sacrificial region 7 shown in FIG. 2 are the same as those in the first embodiment. The fuse 9 serving as a voltage application stopping unit electrically couples a part of the second electrode 3 included in the drive region 6 and the electrode pad included in the sacrifice region 7. The fuse 9 is preferably divided by an overcurrent that flows due to a short circuit in the sacrificial region 7. For example, a conductive material having a melting point lower than that of the second electrode 3 or a conductive material having a high resistance value is preferable. Examples include conductive semiconductors, metals, metal alloys, and doped silicon. The fuse 9 may be made of the same material as that of the second electrode 3, but it is preferable to make the resistance value higher than that of the second electrode 3 by adjusting the shape, length, width, thickness, area, and the like.

In the configuration of FIG. 2, when a bias voltage is applied between the first electrode 2 and the electrode pad of the sacrificial region 7 so that the sacrificial region 7 is short-circuited, the sacrificial region 7 is short-circuited and an overcurrent is generated. The fuse 9 is blown by this overcurrent. In this way, destruction of parts other than the sacrificial region 7 and the fuse 9 can be prevented. Further, the second electrode 3 and the sacrificial region 7 can be automatically electrically separated by blowing the fuse 9.

FIG. 3 shows a modification of this embodiment. 3A is a top view, and FIG. 3B is a cross-sectional view taken along the line C-C ′ of FIG. The substrate 1, the first electrode 2, the second electrode 3, the cavity 4, the insulating film 5, the drive region 6, and the sacrificial region 7 shown in FIG. 3 are the same as those in the first embodiment. This modification has a second electrode extraction pad 8 from which the second electrode 3 of the drive region 6 is extracted. The fuse 9 electrically connects a part of the first electrode 2 and an electrode pad (not shown) included in the sacrificial region 7. In this state, a bias voltage can be applied to the drive region 6 by applying a bias voltage between the electrode pad of the sacrificial region 7 and the second electrode 3. When this bias voltage is increased until the sacrificial region 7 is short-circuited, the sacrificial region 7 is short-circuited and an overcurrent is generated. The fuse 9 is blown by this overcurrent. In this way, destruction of parts other than the sacrificial region 7 and the fuse 9 can be prevented. Further, the destroyed sacrificial region 7 and the first electrode 2 can be automatically separated by fusing the fuse 9. The fuse used at this time is preferably a fuse having inductance.

(Third embodiment)
FIG. 4 (a) is a top view showing the basic structure of the third embodiment of the capacitive electromechanical transducer of the present invention, and FIG. 4 (b) is a sectional view taken along the line DD 'in FIG. 4 (a). It explains using. In the present embodiment, the sacrificial region 7 is provided for each element 19 including one or more cells.

In FIG. 4, a plurality of cells are connected by an electrode pattern to constitute one element (pixel) 19. The drive region 6 is provided in the form of three rows and three columns (example in FIG. 4) or four rows and four columns, and the filling degree of the cells in the element 19 is increased, so that the radiation pressure of acoustic energy is increased and detected. Performance can be increased. The drive region 6 may be arranged in a grid shape as shown in the figure, may be arranged in a staggered manner or randomly, and can be arranged in a desired form. Further, the sacrificial region 7 may be arranged in series with the extracted second electrode 3 as shown in FIG. 4, or in parallel with the extraction pad 8 of the extracted second electrode 3 as shown in FIG. Also good. That is, the sacrificial region 7 can be provided in a desired portion. The substrate 1, the first electrode 2, the second electrode 3, the cavity 4, the insulating film 5, the drive region 6, and the sacrificial region 7 are the same as those in the first embodiment.

4 and 5, when a bias voltage is applied between the first electrode 2 and the electrode pad of the sacrificial region 7 so that the sacrificial region is short-circuited, the first electrode 2 and the sacrificial region 7 is short-circuited. Due to the short circuit of the sacrificial region 7, the bias voltage applied to the element 19, which is an assembly of cells in the drive region 6, decreases. Thereby, destruction of parts other than the sacrificial region 7 can be prevented.

Also, by arranging a plurality of elements as shown in FIGS. 4 and 5, acoustic energy can be emitted and detected over a wide range. In this case, if there is a difference in the response of each element with respect to the bias voltage to be applied, there is a possibility that a malfunction occurs. For example, when radiating acoustic energy, the radiation direction is bent, or when detecting, variations in sensitivity occur between elements, and a true value cannot be detected. Therefore, by providing a sacrificial region 7 for each element and applying a predetermined bias voltage between the first electrode 2 and the electrode pad of the sacrificial region 7 for each element, it is possible to eliminate elements with large variations. become. That is, by applying a predetermined bias voltage in advance, an undesired element connected to the sacrificial region 7 that is short-circuited at the predetermined voltage can be eliminated, and then the same desired element can be reused.

Furthermore, the withstand voltage of the sacrificial region 7 of the element 19 can be changed for each of a plurality of elements arranged. For example, when one of two adjacent elements is used for radiation and the other is used for detection, the withstand voltage of the sacrificial region 7 of the element used for radiation is set high, and the sacrificial region 7 of the element used for detection is set. The withstand voltage can be set low. Thus, by setting the withstand voltage according to the characteristics of each element, it is possible to prevent the element from being destroyed while maximizing the performance of each element.

(Fourth embodiment)
FIG. 6A of the top view showing the basic structure of the fourth embodiment of the capacitive electromechanical transducer of the present invention and FIG. 6B of the EE ′ cross-sectional view of FIG. It explains using. In the present embodiment, a plurality of sacrificial regions 7 are provided.

Also in the configuration of FIG. 6, a plurality of cells are connected by an electrode pattern to constitute one element (pixel) 19. The substrate 1, the first electrode 2, the second electrode 3, the cavity 4, the insulating film 5, the drive region 6, the sacrificial region 7, and the second electrode lead pad 8 are the same as in the third embodiment. In the present embodiment, as shown in FIG. 6, a plurality of sacrificial regions 7 are provided. One of the plurality of sacrificial regions 7 and the second electrode lead pad 8 are electrically connected by a fuse 9. In this state, when a bias voltage is applied between the first electrode 2 and the electrode pad of the sacrificial region 7 so that the sacrificial region is short-circuited, the electrode of the first electrode 2 and the sacrificial region 7 is applied. The pad is short-circuited. Due to the short circuit of the sacrificial region 7, an overcurrent flows and the fuse 9 is divided. As a result, the bias voltage applied to the element 19, which is an assembly of cells in the drive region 6, is lowered, and as a result, it is possible to prevent destruction of portions other than the sacrificial region 7 and the fuse 9.

In the case of the configuration of FIG. 6, since a plurality of sacrificial regions 7 are provided, the electrode pads of the other sacrificial regions 7 that are not destroyed and the second electrode lead pad 8 are newly connected by fuses 9. By connecting the electrode pad and the first electrode 2, the apparatus can be used again in the same manner. FIG. 7A schematically shows a state after the sacrificial region 7 is broken (indicated by reference numeral 14) and the fuse 9 is divided, and FIG. The form after reconnecting the two-electrode lead pad 8 with a new fuse 9 is schematically shown.

In the configuration of FIG. 6, the electrode pad of the sacrificial region 7 and the second electrode lead pad 8 are connected by the fuse 9, but the fuse 9 may not be used. In that case, if the sacrificial region 7 is destroyed, the wiring connecting the electrode pad of the sacrificial region 7 and the second electrode lead pad 8 is cut by a cutting means such as a laser, a dicer, or an ultrasonic cutter. can do. And when using again, the electrode pad of another sacrificial area 7 and the 2nd electrode lead pad 8 should just be connected again by wiring. However, considering the disconnection during driving, it is preferable to use the fuse 9.

Further, in the configuration of FIG. 6, a plurality of sacrificial regions 7 are linearly coupled to each other by a fuse 9 in order from the highest withstand voltage, and the sacrificial region 7 having the highest withstand voltage and the second electrode lead pad 8 are fused. The sacrificial region 7 having the lowest withstand voltage may be connected to the first electrode 2. In this case, when one or a plurality of sacrificial regions 7 having a low withstand voltage are short-circuited, the sacrificial region 7 having a higher withstand voltage can be newly connected to the first electrode 2 and used again. In this case, the voltage actually applied to the element 19 can be monitored in a plurality of stages. This monitoring result can be reflected, for example, in voltage control when used again.

Furthermore, it can also be configured as shown in FIG. Here, a plurality of sacrificial regions 7 provided in parallel are connected by fuses 9 to the wiring portion of the second electrode 2 extending to the second electrode lead pad 8. In this case, if the withstand voltage of each sacrificial region 7 is designed to be different, the voltage actually applied to the element 19 can be monitored in a plurality of stages.

Furthermore, it can also be configured as shown in FIG. Here, a plurality of sacrificial regions 7 are provided, and a plurality of sacrificial regions 7 are radially coupled to the central sacrificial region 7. The central sacrificial region 7 and the second electrode lead pad 8 are electrically connected by a fuse 9. The central sacrificial region 7 and the other sacrificial region 7 are connected by the same conductive wiring as that of the second electrode 3. In this state, when a bias voltage is applied between the electrode pad of the central sacrificial region 7 and the first electrode 2, and the applied voltage exceeds the dielectric strength voltage of any one of the five sacrificial regions 7, The electrode 2 and the electrode pad in the sacrificial region 7 are short-circuited. Due to the short circuit of the sacrificial region 7, an overcurrent flows and the fuse 9 is divided. As shown in FIG. 8B, by connecting the plurality of sacrificial regions 7 to each other, the accuracy of causing a short circuit of the sacrificial regions 7 can be improved. Also in the configuration of FIG. 8B, the sacrificial regions 7 having different withstand voltages are radially connected to each other by fuses, and the withstand voltage of the central sacrificial region 7 is set to be the highest so that the second electrode lead pad 8 and the fuse 9 You may connect with. Also with this configuration, the voltage actually applied to the element 19 can be monitored in a plurality of stages.

(Fifth embodiment)
FIG. 9A of the top view showing the basic structure of the fifth embodiment of the capacitive electromechanical transducer of the present invention and FIG. 9B of the FF ′ cross-sectional view of FIG. It explains using. In the configuration of FIG. 9, a plurality of cells are connected by an electrode pattern to constitute one element (pixel) 19. Here, the drive region 6 including the cells is arranged in a matrix form (three rows and two columns in the illustrated example) to increase the filling degree of the cells in the element 19. Thereby, the radiation pressure of acoustic energy can be raised and detection performance can be improved. The substrate 1, the first electrode 2, the second electrode 3, the cavity 4, the insulating film 5, the drive region 6, the sacrificial region 7, and the fuse 9 are the same as in the fourth embodiment.

In this embodiment, as shown in FIG. 9, the sacrificial region 7 is provided for each cell, and the electrode pad of the sacrificial region 7 and the wiring portion extending from the first electrode lead pad 28 are connected by the fuse 9. In this state, when a bias voltage is applied between the first electrode 2 and the first electrode lead pad 28 so that each sacrificial region 7 is short-circuited, the electrode pads of the first electrode 2 and the sacrificial region 7 are applied. And short circuit. Due to the short circuit of the sacrificial region 7, an overcurrent flows and the fuse 9 is divided. As a result, the bias voltage is not applied to the cells in the drive region 6. As a result, it is possible to prevent the portion other than the sacrificial region 7 and the fuse 9 from being destroyed.

In FIG. 9, the electrode pad in the sacrificial region 7 and the wiring portion extending from the first electrode lead pad 28 are connected by the fuse 9, but the fuse 9 may not be used. In that case, as described in the fourth embodiment, the wiring connecting the electrode pad of the sacrificial region 7 and the wiring portion extending from the first electrode lead pad 28 can be cut by the cutting means. it can. Also here, a plurality of sacrificial regions can be provided, and the electrode portion of the sacrificial region 7 and the wiring portion extending from the first electrode lead pad 28 can be connected again and used.

(Sixth embodiment)
A sixth embodiment of the capacitive electromechanical transducer of the present invention will be described with reference to FIG. 10 which is another FF ′ sectional view of FIG. The substrate 1, the first electrode 2, the second electrode 3, the cavity 4, the insulating film 5, the drive region 6, the sacrificial region 7, the first electrode lead pad 28, and the fuse 9 are the same as in the fifth embodiment.

In the present embodiment, as shown in FIG. 10, the thickness of the insulating portion included in the sacrificial region 7 is thinner than the thickness of the insulating film 5 other than the sacrificial region 7. When the insulating portion of the sacrificial region 7 is manufactured by the same method as the method of manufacturing the insulating film 5, the insulating portion of the sacrificial region 7 needs to be thinly processed by an appropriate method. For example, portions other than the sacrificial region 7 are masked with a resist or the like, and only the insulating portion of the sacrificial region 7 is etched to have a desired thickness. Thereafter, the structure shown in FIG. 10 can be realized by removing the resist and the like and providing the second electrode 3 and the fuse 9. Thereby, the thickness of the insulating part of the sacrificial region 7 can be set to a desired withstand voltage.

(Seventh embodiment)
A seventh embodiment of the capacitive electromechanical transducer of the present invention will be described with reference to FIG. The present embodiment is an example of a capacitive electromechanical conversion system having overcurrent detection means and voltage application interruption means. In order to make the figure easy to see, the capacitive electromechanical transducer is shown in a form including one cell. The first electrode 2, the second electrode 3, the insulating film 5, the drive region 6, and the sacrificial region 7 are the same as in the first embodiment. 11 further includes a bias voltage application power source 10, current detection means 11 such as a current detection circuit as overcurrent detection means, a switch 12 for turning on / off electrical connection as voltage application interruption means, and a control signal. A path 13 is provided.

In the present embodiment, when the switch 12 is connected, a bias voltage is applied between the first electrode 2 and the electrode pad of the sacrificial region 7 as in the first embodiment. When the bias voltage exceeds the withstand voltage of the sacrificial region 7, the sacrificial region 7 is short-circuited. At this time, when the current detection means 11 detects the generated overcurrent, a signal for opening the switch 13 is sent through the control signal path 13. Thereby, application of a bias voltage is interrupted | blocked and destruction of parts other than the sacrificial area | region 7 can be prevented. That is, in response to the detection of the overcurrent by the detection means 11, the application of the voltage between the first electrode 2 and the second electrode 3 is interrupted by the interruption means 12, and a desired portion is protected. The current detection means 11 may be of any configuration, but preferably has a configuration that does not generate an extra noise signal when a bias voltage is applied.

In the configuration of FIG. 11, a fuse is not used, but a configuration using a fuse may be used. Further, by providing the current detection means 11 for each element (pixel), it is possible to specify a short-circuited location. By feeding this identified information back to the system, the device can be driven to compensate for the shorted element.

Further, as in the configuration of FIG. 6, a plurality of sacrificial regions 7 are linearly coupled to each other by a fuse 9 in order from the highest withstand voltage, and the sacrificial region 7 having the highest withstand voltage and the second electrode lead pad 8 May be connected by a fuse 9. Further, as in the configuration of FIG. 8A, the sacrificial regions 7 provided in parallel may be connected by fuses 9 to the wiring of the second electrode 2 extending to the second electrode lead pad 8. Thereby, as described in the fourth embodiment, the applied voltage can be monitored in a plurality of stages. 8B, the sacrificial regions 7 having different withstand voltages are radially connected to each other by fuses 9, and the central sacrificial region 7 has the highest withstand voltage, and the second electrode lead pad 8 And a fuse 9.

(Eighth embodiment)
FIG. 12 (a) is a top view showing the basic structure of the eighth embodiment of the capacitive electromechanical transducer of the present invention, and FIG. 12 (b) is a sectional view taken along the line GG ′ of FIG. 12 (a). It explains using. In the configuration of FIG. 12, the conductive substrate 1 is on the first electrode 2, the insulating film 25 is present thereon, and the cavity 4 is formed in a part of the insulating film 25. A silicon membrane 18 exists on the insulating film 25, and the second electrode 3 is wired thereon. The second electrode 3 is wired to the second electrode lead pad 8 across the area without the cavity 4 except for the drive area 6. The sacrificial region 7 has a silicon membrane 18 on an insulating portion included in the sacrificial region 7 and an electrode pad on the silicon membrane 18. The electrode pad is connected to the second electrode lead pad 8 through a fuse 9. ing.

As shown in FIG. 12B, the first electrode 2 may be taken out using a conductive substrate 1, or when the substrate 1 is an insulator such as glass, the through wiring in the insulator It is preferable to take out to the upper part using. In the configuration of FIG. 12, the first electrode 2 is divided by the groove for each element (pixel) 19, but the electrode may be drawn to the back side for each element 19 using a through wiring. The sacrificial region 7 can be produced in the same manner as in the first embodiment.

In the above embodiment, the first electrode 2 and the second electrode 3 are taken out to the upper part (vibration surface side) of the capacitive electromechanical transducer, but one electrode may be taken out to the back side. Moreover, in the said embodiment, it has mainly demonstrated with the structure which provided the fuse between a part of 2nd electrode and the electrode pad of the sacrificial area | region 7. FIG. However, a configuration in which a part of the first electrode and the electrode pad of the sacrificial region 7 are connected by a fuse can be adopted in all the embodiments.

In the above embodiment, a structure as shown in FIG. 13 can be used. FIG. 13A shows an enlarged view of a structure in which a barrier 16 is provided around the sacrificial region 7 in a region 15 surrounded by a dotted frame in FIG. When the sacrificial region 7 is short-circuited, sparks are generated due to dielectric breakdown, and sparks and electrode fragments in the sacrificial region 7 may be scattered around. In order to prevent scattering of these sparks and debris, a barrier 16 may be provided around or around the sacrificial region 7. Further, as shown in FIG. 13B, these scattering can be suppressed by changing the shape of the electrode pad included in the sacrificial region 7. Here, the electrode pad has a first portion connected to the wiring 17 connected to the sacrificial region 7 and a second portion formed so as to surround the first portion except a portion where the wiring 17 passes.

2 ... First electrode (lower electrode), 3 ... Second electrode (upper electrode), 4 ... Air gap (cavity), 5 ... Insulating film, 6 ... Drive region, 7 ... Sacrificial region, 19 ... Element

Claims (8)

A capacitive electromechanical transducer having at least one cell including a first electrode and a second electrode disposed to face the first electrode with a gap between the first electrode and the second electrode,
An insulating portion including a sacrificial region configured to cause a short circuit by applying a voltage lower than a short circuit voltage causing a short circuit in the drive region including the cell;
The capacitance-type electromechanical transducer according to claim 1, wherein the first electrode and the second electrode are electrically connected to each other with an insulating part including the sacrificial region interposed therebetween. 2. The capacitive electromechanical conversion according to claim 1, further comprising a stop unit configured to stop voltage application to the drive region due to an overcurrent flowing when a short circuit occurs in the sacrificial region. 3. apparatus. The capacitive electromechanical transducer according to claim 2, wherein the stopping means is a fuse. 4. The capacitive electric machine according to claim 1, wherein the one or more sacrificial regions are provided for each element or each cell including one or more cells. 5. Conversion device. The capacitive electromechanical transducer according to claim 4, wherein the plurality of sacrificial regions are configured to have different voltages that cause the short circuit. A second electrode of the drive region is provided on the insulating film;
6. The capacitive electromechanical transducer according to claim 1, wherein a thickness of the insulating film in the driving region is smaller than a thickness of an insulating portion in the sacrificial region. 7. A barrier is provided around the sacrificial region to prevent the possibility of scattering when a short circuit occurs in the sacrificial region. The electrostatic capacity type electromechanical transducer according to claim 1. Detecting means for detecting an overcurrent flowing when the first electrode and the second electrode are short-circuited;
8. A blocking unit that blocks application of voltage between the first electrode and the second electrode in response to detection of overcurrent by the detection unit. The electrostatic capacity type electromechanical transducer according to claim 1.

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