JP2018110282A - Capacitance type transducer and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a capacitive transducer which accurately confirms completion of etching of a sacrificial layer to reduce sensitivity and variation.SOLUTION: In a manufacturing method of a capacitive transducer which forms a gap by removing a sacrificial layer, etching is performed until completion of the etching is confirmed accurately.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a capacitive transducer and a method for manufacturing the same.

  Conventionally, a micromechanical member manufactured by a micromachining technique can be processed on the order of a micrometer, and various microfunctional elements are realized using these. A capacitive micromachined ultrasonic transducer (CMUT) that is a capacitive transducer using micromachining technology has been studied as an alternative to a piezoelectric element. CMUT makes it possible to transmit or receive ultrasonic waves using vibration of the vibrating membrane, and to obtain excellent broadband characteristics particularly in liquid.

  An example of the CMUT includes a plurality of elements, and each element includes a plurality of cells. Each cell includes a gap (cavity) that allows vibration, which can be formed by etching the sacrificial layer through an etching hole. After the etching, sealing is performed by filling the etching hole. In order to suppress cell-to-cell variation, it is desirable to sufficiently seal the etching hole in any cell.

  Patent Document 1 discloses a configuration of a CMUT having sensor cells and dummy cells used for transmission / reception of ultrasonic waves on a substrate, and a method of manufacturing a CMUT by forming a gap by etching a sacrificial layer. Further, Patent Document 1 discloses that it is confirmed that etching of the sacrificial layer is completed using a dummy cell. That is, the sensor cell has an upper electrode on the upper side of the gap (cavity) and a lower electrode on the lower side, but the dummy cell has only the lower electrode. Can do.

JP 2008-085246 A

  However, in the method of Patent Document 1, it may be difficult to accurately grasp whether or not the sensor cell has been etched. That is, when the conditions related to the etching rate are different between the dummy cell and the sensor cell, even if the etching of the dummy cell is completed, the sensor cell etching may not be completed.

  If the end of etching cannot be confirmed accurately, the surface roughness inside the cell will increase due to overetching, and the cell diameter, membrane thickness, gap thickness, etc. will change, and the transmission / reception sensitivity (performance) will change. Sometimes.

  Accordingly, an object of the present invention is to provide a method of manufacturing a capacitive transducer that reduces the sensitivity and reduces variations by accurately confirming that the etching of the sacrificial layer has been completed.

  The method of manufacturing a capacitive transducer according to the present invention includes a step of providing a sacrificial layer in a stacking direction on a first electrode, a step of providing an insulating film in the stacking direction on the sacrificial layer, and the insulating film A step of providing a second electrode so as to be a region smaller than a region in which the sacrificial layer is provided in an in-plane direction orthogonal to the stacking direction; and a step of etching the sacrificial layer; The step of etching includes a first of the sacrificial layer provided outside the region where the second electrode is provided in the in-plane direction. Etching is started from the position, and etching is performed until etching of the second position of the sacrificial layer farthest from the first position is completed.

  Another manufacturing method of a capacitive transducer according to the present invention is a manufacturing method of a capacitive transducer including an element including a plurality of cell structures, in the stacking direction on the first electrode. A step of providing a plurality of sacrificial layer regions so as to be independent cavities for each cell structure, a step of providing an insulating film in the stacking direction on the sacrificial layer region, and the stacking direction on the insulating film A step of providing the second electrode so as to be a region smaller than a region where the insulating film is provided in an in-plane direction orthogonal to the stacking direction, removing the sacrificial layer region, Providing the cavity independently for each structure, and the etching step includes the step of etching the sacrificial layer provided outside the region where the second electrode is provided in the in-plane direction. One Start the laid et etching until said second position of the etching of the first farthest the sacrificial layer from the position is completed, it is a step of etching, characterized by.

  Yet another method of manufacturing a capacitive transducer according to the present invention includes a step of providing a sacrificial layer on the first electrode, a step of providing an insulating film on the sacrificial layer, A step of providing a second electrode, a step of providing an etching hole for etching the sacrificial layer in the insulating film, a step of forming a gap by etching the sacrificial layer through the etching hole, A method of manufacturing a capacitance type transducer having an etching confirmation portion for confirming etching is provided in addition to the etching hole.

  In addition, the capacitive transducer according to the present invention includes an electrostatic cell having a cell on which a vibration film including one electrode of a pair of electrodes provided to sandwich a gap is supported so as to vibrate. In the capacitive transducer, the gap has at least one or more etching confirmation portions, and the distance between the end of the etching hole and the end of the cell to the end of the etching hole and the end of the etching confirmation portion. Is longer, and at least a part of the etching confirmation portion is not sandwiched between the pair of electrodes.

  According to the method for manufacturing a capacitive transducer according to the present invention, it is possible to accurately confirm that the sacrifice layer has been etched.

FIG. 3 is a top perspective view of the CMUT according to the first embodiment of the present invention, and is a cross-sectional view taken along line AB in FIG. 2. It is sectional drawing of CMUT which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the manufacturing method of CMUT which concerns on Embodiment 1 of this invention. It is CMUT which concerns on Embodiment 2 of this invention (AB sectional drawing of FIG. 1). It is a top perspective view of CMUT concerning Embodiment 3 of the present invention. It is a figure explaining a mode that the etching which removes the sacrificial layer of CMUT concerning Embodiment 1 of the present invention advances. It is a figure of another form of the protrusion shape of the etching confirmation part of CMUT which concerns on Embodiment 1 of this invention. It is a figure of another form of CMUT which concerns on Embodiment 1 of this invention. It is a figure of another form of CMUT which concerns on Embodiment 1 of this invention. It is a figure of another form of CMUT which concerns on Embodiment 1 of this invention. It is a figure of another form of CMUT which concerns on Embodiment 1 of this invention. It is a figure of another form of CMUT which concerns on Embodiment 1 of this invention.

  Hereinafter, although the capacitive transducer (CMUT) which concerns on embodiment of this invention is demonstrated, this invention is not limited to these.

The CMUT manufacturing method according to this embodiment includes at least the following steps. This will be described with reference to FIGS.
(1) A step of providing a sacrificial layer in the stacking direction on the first electrode.
(2) A step of providing an insulating film in the stacking direction on the sacrificial layer.
(3) A step of providing the second electrode on the insulating film so as to be a region smaller than a region where the sacrificial layer is provided in the in-plane direction orthogonal to the stacking direction.
(4) A step of etching the sacrificial layer.

  1 and 3, the first electrode is 6, the sacrificial layer is 15, the insulating film is 9, the second electrode is 10, the stacking direction is the vertical direction of the paper, and the in-plane direction is the horizontal direction of the paper. The insulating film 9 can also be called a membrane (the same applies hereinafter).

  In the etching step, etching is started from the first position of the sacrificial layer provided outside the region where the second electrode is provided in the in-plane direction. Then, the etching is performed until the etching of the second position of the sacrificial layer farthest from the first position is completed.

  Here, the first position is a position in the sacrificial layer which appears by forming 16 etching holes, and is a position where etching is started. The second position is a position farthest from the first position among the 14 etching confirmation portions.

  Since the second position is farthest from the first position, when the etching of the second position is completed, the etching of the other sacrificial layer area is also completed, so the etching timing of the sacrificial layer layer can be accurately grasped. it can. As a result, it is possible to reduce the sensitivity and variation of each cell.

  Moreover, you may have the process of providing a 1st insulating film between the process of providing a 1st electrode, and the process of providing a sacrificial layer.

Further, the first insulating film preferably includes a silicon oxide film, and the insulating film preferably includes a silicon nitride film.
The first electrode is provided on a substrate, and a silicon substrate can be used as the substrate.

  Furthermore, the step of providing a third insulating film on the substrate and the step of providing the first electrode may be a step of providing the first electrode on the third insulating film. The third insulating film preferably includes a silicon oxide film.

  The shape in the in-plane direction of the sacrificial layer may be configured by adding a protrusion to the same shape as the second electrode. Further, the shape of the sacrificial layer in the in-plane direction may be configured by adding a protrusion to the same shape as the second electrode. The shape of the projection in the in-plane direction may be a configuration having at least one of a rectangle, a circle, and a triangle.

The method for manufacturing a capacitive transducer according to the present embodiment is a method for manufacturing a capacitive transducer including an element including a plurality of cell structures, and includes at least the following steps.
(1) A step of providing a plurality of sacrificial layer regions in the stacking direction on the first electrode so as to be independent cavities for each cell structure.
(2) A step of providing an insulating film in the stacking direction on the sacrificial layer region.
(3) A step of providing the second electrode in the stacking direction on the insulating film so as to be a region smaller than the region in which the insulating film is provided in the in-plane direction orthogonal to the stacking direction.
(4) A step of removing the sacrificial layer region and providing an independent cavity for each cell structure.

  In the etching step, the etching is started from the first position of the sacrificial layer provided outside the region where the second electrode is provided in the in-plane direction. Then, the etching is performed until the etching of the second position of the sacrificial layer farthest from the first position is completed.

  The first position is preferably configured to be shared by a plurality of cells.

(Embodiment 1)
(Composition of CMUT)
The configuration of the CMUT according to the present embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 2 shows a cross-sectional view of the CMUT. The cell 2 includes a substrate 4, a third insulating film 5 provided on the substrate 4, a first electrode 6 formed on the third insulating film 5, and a first insulating film 7 on the first electrode 6. Have Further, the vibration film 12 is formed by the second insulating film 9, the second electrode 10 and the sealing film 11, and the vibration film support portion 13 that supports the vibration film 12 so as to vibrate, the gap 8, the etching confirmation portion 14, have. The vibration film support portion 13 includes a portion including the second electrode 10 and a portion not including the second electrode 10 for wiring extraction. When the substrate 4 is an insulating substrate such as a glass substrate, the third insulating film 5 may not be provided. The shape of the gap 8 as viewed from the top is a circle, and the shape of the vibrating portion is a circle, but it may be a square, a rectangle or the like.

  FIG. 2 is a cross-sectional view taken along the line AB of FIG. Only the main part is shown for clarity. One element 3 is provided on a substrate 4, and the element 3 includes a plurality of cells 2 arranged in an array (cell group). The cell 2 includes a later-described film (plural) and electrodes (a pair), and has an etching confirmation portion 14 and a gap 8. Each gap 8 in the cell 2 is formed by etching through one etching hole 16 for etching a sacrificial layer described later. Each etching confirmation portion 14 is arranged such that the distance D between the end of the etching hole 16 and the end of the etching confirmation portion 14 is longer than the distance C between the end of the etching hole 16 and the end of the gap 8. . In addition to the etching hole, an etching confirmation portion for confirming the etching is provided by making a region where no gap is interposed between the first electrode and the second electrode.

  Further, the etching confirmation portion 14 has a protruding shape with respect to the gap 8 in the in-plane direction of the substrate 4. The protrusion shape is easier to visually recognize the etching, as will be described later. Of the etching confirmation unit 14, the one that communicates with the cell 2 is preferably elongated or tapered. Otherwise, the strength of the vibration film support portion 13 described later is affected, and the vibration characteristics of the vibration film change, which may lead to a decrease in transmission / reception sensitivity. The protrusion shape of the etching confirmation unit 14 may be, for example, a shape as illustrated in FIGS. If the visibility is improved, FIGS. 7B and 7C are desirable. The size of the etching confirmation portion 14 is desirably about 1/100 or less of the size of the cell 2. Therefore, the size of the etching confirmation unit 14 is desirably a size that does not lead to a decrease in transmission / reception sensitivity.

  In FIG. 1, the etching holes are provided at positions equidistant from the center of the gap between the cells, and the etching holes are formed in the gap so that the etching holes for individual etching are not provided.

  In FIG. 2, the first electrode and the gap are formed so that the area of the first electrode is larger than the area of the gap.

(CMUT drive principle)
Here, the driving principle of the CMUT 1 will be described with reference to FIG. When the ultrasonic wave is received by the CMUT 1, a direct current voltage (bias voltage) is supplied from the first voltage application unit 17 so that a potential difference is generated between the first electrode 6 and the second electrode 10. To the state of being applied. When the ultrasonic wave is received in this state, the vibration film 12 having the second electrode 10 vibrates, so that the distance between the second electrode 10 and the first electrode 6 changes, and the capacitance changes. Due to this change in capacitance, a signal (current) is output from the second electrode 10 and a current flows through an unillustrated lead-out wiring. This current is converted into a voltage by a current-voltage conversion element (not shown) to obtain an ultrasonic reception signal. As described above, a signal may be extracted from the first electrode 6 by applying a DC voltage to the second electrode 10 by changing the configuration of the extraction wiring.

  When transmitting an ultrasonic wave, an AC voltage is applied to the second electrode 10 by the second voltage applying means 18 while a DC voltage is applied to the first electrode 6. Alternatively, the second voltage applying means 18 applies a voltage (that is, an AC voltage in which positive and negative are not reversed) applied to the second electrode 10 and vibrates the vibrating membrane 12 by electrostatic force. Ultrasound can be transmitted by this vibration. Also in the case of transmitting ultrasonic waves, the vibrating membrane 12 may be vibrated by applying an alternating voltage to the first electrode 6 by changing the configuration of the lead wiring. As described above, the CMUT 1 of the present embodiment can perform at least one of transmission and reception of ultrasonic waves (acoustic waves).

(Manufacturing method of CMUT)
The manufacturing method of CMUT1 based on Embodiment 1 of this invention is shown using FIG. FIG. 3 shows each process through which the CMUT according to this embodiment of FIG. 2 is manufactured. As shown in FIG. 3A, a third insulating film 5 is formed on the substrate 4. The substrate 4 is a silicon substrate, and the third insulating film 5 is provided to electrically insulate between the first electrode 6 and the substrate 4. When the substrate 4 is an insulating substrate such as a glass substrate, the third insulating film 5 may not be formed. The substrate 4 is preferably a substrate having a small surface roughness. When the surface roughness is large, the surface roughness is transferred even in the film-forming process subsequent to this process, and the distance between the first electrode 6 and the second electrode 10 due to the surface roughness is , It varies from cell 2 to cell 2. Since this variation is a variation in conversion efficiency, it is a variation in sensitivity and bandwidth. Therefore, the substrate 4 is preferably a substrate having a small surface roughness.

  Further, the first electrode 6 is formed on the third insulating film 5. The first electrode 6 is preferably a conductive material having a small surface roughness, and a material containing titanium, tungsten, aluminum, or the like can be used as the first electrode 6. Similar to the substrate 4, when the surface roughness of the first electrode 6 is large, the distance between the first electrode 6 and the second electrode 10 depends on the surface roughness for each cell 2, element A conductive material having a small surface roughness is desirable because it varies every three.

  Next, a first insulating film 7 is formed on the first electrode 6. The first insulating film 7 is preferably made of an insulating material having a small surface roughness, and the first electrode 6 and the second electrode 10 when a voltage is applied between the first electrode 6 and a second electrode 10 described later. It is formed to make it difficult for an electrical short circuit or dielectric breakdown between the two electrodes 10. Moreover, it forms in order to suppress the etching of the 1st electrode 6 at the time of the removal of the sacrificial layer 15 implemented by the post process of this process. Similarly to the substrate 4, when the surface roughness of the first insulating film 7 is large, the distance between the first electrode 6 and the second electrode 10 due to the surface roughness varies for each cell 2. It is desirable to use an insulating film having a small surface roughness. As the material of the first insulating film 7, a material including a silicon nitride film, a silicon oxide film, or the like can be used. The first insulating film 7, the second insulating film 9, and the third insulating film 5, which will be described later, have a surface roughness that increases as the thickness increases.

  Next, as shown in FIG. 3B, the sacrificial layer 15 is formed on the first insulating film 7 in two stages. For example, the sacrificial layer 15 is patterned with a manufactured mask (not shown), and the sacrificial layer 15 is etched with a mask slimmed by side etching. As other methods, a method of controlling the etching directionality, a method of using a two-stage guide, or the like may be used. The thickness of the sacrificial layer 15 that will later become the gap 8 is indicated by a gap 19, and the thickness of the sacrificial layer 15 that becomes the etching confirmation portion 14 is indicated by a gap 20. The sacrificial layer 15 is preferably made of a material having a small surface roughness. Similarly to the substrate 4, when the surface roughness of the sacrificial layer 15 is large, the distance between the first electrode 6 and the second electrode 10 due to the surface roughness varies between the cells 2. A sacrificial layer 15 having a small thickness is desirable. Further, in order to shorten the etching time for removing the sacrificial layer 15, a material having a high etching rate is desirable. Further, it is required to use a material for the sacrificial layer 15 such that the insulating film and the vibration film 12 are hardly etched with respect to the etching solution or etching gas for removing the sacrificial layer 15. When the insulating film and the vibration film 12 are etched with respect to the etching solution or etching gas for removing the sacrificial layer 15, the thickness of the vibration film 12 varies, and the distance between the first electrode 6 and the second electrode 10. Variations are likely to occur. Variations in the thickness of the vibration film 12 and variations in the distance between the first electrode 6 and the second electrode 10 are variations in sensitivity and bandwidth for each cell 2. In the case where the insulating film and the vibration film 12 are a silicon nitride film or a silicon oxide film, the material of the sacrificial layer 15 that can use an etching solution or an etching gas that has a small surface roughness and is difficult to etch the insulating film and the vibration film 12 is used. desirable. For example, amorphous silicon, polyimide, chrome, etc. In particular, when the insulating film and the vibration film 12 are a silicon nitride film or a silicon oxide film, a chromium etching solution is desirable. This is because the chromium etching solution hardly etches the silicon nitride film or the silicon oxide film.

  Next, as shown in FIG. 3C, a second insulating film 9 is formed. The second insulating film 9 desirably has a low tensile stress. For example, a tensile stress of 500 MPa or less is good. The silicon nitride film can be stress-controlled and can have a low tensile stress of 500 MPa or less. When the vibration film 12 has a compressive stress, the vibration film 12 causes sticking or buckling and is greatly deformed. In the case of a large tensile stress, the second insulating film 9 may be broken. Therefore, the second insulating film 9 desirably has a low tensile stress. For example, it is a silicon nitride film capable of controlling the stress and having a low tensile stress. In addition, since the second insulating film 9 is formed on the sacrificial layer 15, it is preferable that the thickness of the second insulating film 9 be such that the coverage of the sacrificial layer 15 can be ensured.

  Next, as shown in FIG. 3D, the second electrode 10 is formed. Therefore, the sacrificial layer 15 to be the gap 8 is sandwiched between a pair of electrodes (the first electrode 6 and the second electrode 10), and the sacrificial layer 15 to be the etching confirmation portion 14 is not sandwiched. The second electrode 10 is preferably made of a material having a small residual stress, such as aluminum. When the removal process or the sealing process of the sacrificial layer 15 is performed after the second electrode 10 is formed, the second electrode 10 is preferably made of a material having etching resistance and heat resistance against etching of the sacrificial layer 15. For example, aluminum silicon alloy or titanium.

  Next, as shown in FIG. 3E, an etching hole 16 is formed in the second insulating film 9. The etching hole 16 is a hole for introducing an etching solution or an etching gas in order to etch and remove the sacrificial layer 15. After the etching, the sacrificial layer 15 is removed to form the gap 8. Therefore, by using the portion of the etching confirmation portion 14 in the sacrificial layer 15, it is possible to confirm the completion of removal of the sacrificial layer 15 that becomes the gap 8. Since the portion of the etching confirmation portion 14 in the sacrificial layer 15 has a projection shape in the in-plane direction of the substrate 4, the etching in the projection direction proceeds quickly, and the etching is easily visible. Furthermore, overetching can be minimized. The manner in which etching proceeds will be described later. The method for removing the sacrificial layer 15 is preferably wet etching or dry etching. When chromium is used as the material of the sacrificial layer 15, wet etching is preferable. When chromium is used as the material of the sacrificial layer 15, the second electrode 10 is preferably made of titanium in order to prevent the second electrode 10 from being etched when the sacrificial layer 15 is etched. In the case where an aluminum silicon alloy or the like is used for the second electrode 10, after forming the second electrode 10, an insulating film is formed on the second electrode 10 with the same material as the second insulating film 9 and then etched. It is preferable to remove the sacrificial layer 15 by forming the holes 16.

  Next, as shown in FIG. 3F, a sealing film 11 is formed to seal the etching holes 16. The vibration film 12 is formed by the second insulating film 9, the second electrode 10, and the sealing film 11. The sealing film 11 is required to prevent liquid or outside air from entering the gap 8. If the gap 8 is at atmospheric pressure, the gas in the gap 8 expands or contracts due to temperature changes. In addition, since a high electric field is applied to the gap 8, it causes a decrease in the reliability of the element 3 due to ionization of molecules. Therefore, the sealing is required to be performed in a reduced pressure environment. By reducing the pressure inside the gap 8, the air resistance inside the gap 8 can be reduced. As a result, the vibrating membrane 12 can easily vibrate, and the sensitivity of the CMUT 1 can be increased. Moreover, CMUT1 can be used in a liquid by sealing. As the sealing material, the same material as the second insulating film 9 is preferable because of high adhesion. When the second insulating film 9 is silicon nitride, the sealing film 11 is also preferably silicon nitride.

  In FIG. 3, a configuration in which the second electrode 10 is sandwiched between the second insulating film 9 and the sealing film 11 is shown as an example. However, it is also possible to form the etching hole 16 after forming the second insulating film 9 to etch the sacrificial layer 15 and then form the sealing film 11 and then provide the second electrode 10. However, if the second electrode 10 is exposed on the outermost surface, there is a high possibility that the element 3 will be short-circuited by a foreign substance or the like. Therefore, the second electrode 10 is preferably provided on the insulating film.

  The manner in which the etching for removing the sacrificial layer 15 proceeds will be described with reference to FIG. FIG. 6A shows a state before starting etching through the etching hole 16. 6B to 6E show a state after the etching is started. Before the etching of the sacrificial layer 15 is started, as shown in FIG. 6A, the entire sacrificial layer 15 remains, and the gap 8 and the etching confirmation portion 14 are not yet formed. After the etching is started, as shown in FIGS. 6B to 6C, the region of the gap 8 gradually expands from the region close to the etching hole 16. Therefore, as described above, since the sacrificial layer 15 that becomes the gap 8 is sandwiched between the pair of electrodes, the formation of the gap 8 cannot be confirmed. Then, as shown in FIG. 6D, the gap 8 is formed in a complete state, and the etching check portion 14 is formed. Finally, as shown in FIG. 6E, all of the sacrificial layer 15 is etched and completely removed, whereby the etching confirmation portion 14 is formed in a complete state. Therefore, since the etching confirmation portion 14 has a projection shape, it is easy to visually recognize. When the etching confirmation portion 14 is formed, the formation of the gap 8 is completed, so that the completion of the etching of the region of the gap 8 can be confirmed by visually confirming the formation of the etching confirmation portion 14. Note that, without waiting for the completion of the formation of the etching confirmation portion 14, it may be considered that the etching of the region of the gap 8 has been completed when the partial formation of the etching confirmation portion 14 can be visually recognized.

  In FIG. 1, one gap 8 leads to one etching hole 16. However, as shown in FIG. 9, three gaps 8 may lead to one etching hole 16, and as shown in FIG. The gap 8 may lead to one etching hole 16. Further, as shown in FIG. 10, one gap 8 may lead to three etching holes 16, and as shown in FIG. 11, one gap 8 may lead to two etching holes 16. Further, a combination of different patterns through which the gap 8 and the etching hole 16 communicate may be used. For example, as shown in FIG. 12, two gaps 8 combine a pattern that leads to one etching hole 16 and three gaps 8 combine a pattern that leads to one etching hole 16.

  In FIG. 1, one element 3 is shown, but any number of elements 3 may be used. The element 3 is composed of 18 cells 2. However, for example, as shown in FIG. 8 and FIG. 11, the number of cells 2 may be 24 or any number. The arrangement of the cells 2 may be any arrangement such as a lattice arrangement or a staggered arrangement. Furthermore, the rough outer shape of the element 3 may be a rectangle as shown in FIG. 1, a square, or a hexagon.

  Through the above steps, the CMUT 1 as shown in FIGS. 1 and 2 can be manufactured. Since the etching of each cell 2 can be confirmed at the time of manufacturing the CMUT 1 as in the present embodiment, appropriate etching can be performed.

(Embodiment 2)
(The case where the thickness of the etching confirmation part is the same as the gap thickness)
Next, the configuration of the CMUT 1 according to the second embodiment will be described with reference to FIG. 4 is a cross-sectional view taken along the line AB of FIG. The configuration of the CMUT 1 of the second embodiment is different from that of the first embodiment in the thickness of the etching confirmation unit 14.

  In the CMUT 1 of the present invention, the thickness of the etching confirmation portion 14 is the same as the thickness of the gap 8. Other configurations and manufacturing methods are substantially the same as those in the first embodiment, and thus description thereof is omitted.

  In the first embodiment, the sacrificial layer 15 has two thicknesses. However, as in this configuration, the sacrificial layer 15 can be reduced in thickness by one, so that the formation process of the sacrificial layer 15 can be reduced. In addition, since the sacrificial layer 15 serving as the gap 8 and the sacrificial layer 15 serving as the etching confirmation portion 14 have the same thickness, it is possible to confirm the etching of the sacrificial layer 15 in the gap 8 in the thickness direction. Etching can be realized.

(Embodiment 3) (Case where there are a plurality of etching confirmation portions in one cell)
Next, the configuration of the CMUT 1 according to the third embodiment will be described with reference to FIG. FIG. 5 is a top perspective view of the CMUT 1 of the present invention. The configuration of the CMUT 1 of the third embodiment is different from that of the first embodiment in the arrangement and number of etching holes 16 and the arrangement and number of etching confirmation portions 14 provided in each gap 8.

  The CMUT 1 of the present invention has a configuration in which an element is formed by a combination of cells 2 in which etching holes 16 are individually provided in each gap 8, and four etching confirmation portions 14 are provided in each gap 8. In FIG. 5, each cell 2 is provided with four etching confirmation portions 14, but may be one to three. Other configurations and manufacturing methods are substantially the same as those in the first embodiment, and thus description thereof is omitted.

  Since each cell 2 has four etching confirmation portions 14 as in this configuration, the etching confirmation of the sacrificial layer 15 that becomes the gap 8 can be confirmed at the four end portions of the gap 8. Therefore, since etching can be confirmed more reliably, more appropriate etching can be realized.

1 Capacitive transducer (CMUT)
2 cells 3 elements
4 substrate 5 third insulating film 6 first electrode 7 first insulating film 8 gap (cavity)
DESCRIPTION OF SYMBOLS 9 2nd insulating film 10 2nd electrode 11 Sealing film 12 Vibration film 13 Vibration film support part 14 Etching confirmation part 15 Sacrificial layer 16 Etching hole 17 1st voltage application means 18 2nd voltage application means 19 of gap | interval Gap 20 Gap of etching confirmation part

Claims (26)

Providing a sacrificial layer in the stacking direction on the first electrode;
Providing an insulating film in the stacking direction on the sacrificial layer;
A step of providing a second electrode on the insulating film so as to be a region smaller than a region in which the sacrificial layer is provided in an in-plane direction orthogonal to the stacking direction;
Etching the sacrificial layer, and a method of manufacturing a capacitive transducer comprising:
The etching step starts etching from the first position of the sacrificial layer provided outside the region where the second electrode is provided in the in-plane direction, and starts from the first position. The method of manufacturing a capacitive transducer according to claim 1, wherein the etching is performed until etching of the second position of the farthest sacrificial layer is completed. A method of manufacturing a capacitive transducer characterized by the above.   The method of manufacturing a capacitive transducer according to claim 1, further comprising a step of providing a first insulating film between the step of providing the first electrode and the step of providing the sacrificial layer. .   The method for manufacturing a capacitive transducer according to claim 1, wherein the first insulating film includes a silicon oxide film.   The method of manufacturing a capacitive transducer according to claim 1, wherein the insulating film includes a silicon nitride film.   The method of manufacturing a capacitive transducer according to claim 1, wherein the first electrode is provided on a substrate.   The method for manufacturing a capacitive transducer according to claim 1, wherein the substrate includes a silicon substrate.   A step of providing a third insulating film on the substrate, wherein the step of providing the first electrode is a step of providing the first electrode on the third insulating film. Item 7. A method for manufacturing a capacitive transducer according to any one of Items 1 to 6.   The method of manufacturing a capacitive transducer according to claim 1, wherein the third insulating film includes a silicon oxide film.   9. The shape of the sacrificial layer in the in-plane direction is formed by adding a protrusion to the same shape as the second electrode. 9. Manufacturing method of capacitance type transducer.   The method of manufacturing a capacitive transducer according to claim 9, wherein a shape of the protrusion in the in-plane direction is at least one of a rectangle, a circle, and a triangle. A method of manufacturing a capacitive transducer having an element including a plurality of cell structures,
Providing a plurality of sacrificial layer regions in the stacking direction on the first electrode so as to be independent cavities for each of the cell structures;
Providing an insulating film in the stacking direction on the sacrificial layer region;
Providing the second electrode in the stacking direction on the insulating film so as to be a region smaller than a region in which the insulating film is provided in an in-plane direction orthogonal to the stacking direction;
Removing the sacrificial layer region and providing independent cavities for each cell structure;
Have
The etching step starts etching from the first position of the sacrificial layer provided outside the region where the second electrode is provided in the in-plane direction, and starts from the first position. Etching is performed until etching of the second position of the farthest sacrificial layer is completed. A method for manufacturing a capacitive transducer, comprising:   The method of manufacturing a capacitive transducer, wherein the first position is configured to be shared by the plurality of cells. A capacitive transducer comprising a plurality of cells having a plurality of cells each including a first electrode and a membrane including a second electrode provided with a gap from the first electrode on a substrate. A manufacturing method of
Forming a sacrificial layer on the first electrode; forming a membrane on the sacrificial layer; forming an etching hole in the membrane; and etching the sacrificial layer through the etching hole. A step of forming the gap and the etching confirmation portion by
Each gap communicates with at least one or more etching holes, and the gap includes at least one or more etching confirmation portions, and the distance between the edge of the etching hole and the edge of the gap, The distance to the end of the etching confirmation part is longer,
The method of manufacturing a capacitive transducer, wherein the etching confirmation portion is formed so that at least a part thereof is not sandwiched between the first electrode and the second electrode.   The etching confirmation portion is formed such that a distance between the end of the etching hole and the end of the etching confirmation portion is longer than a distance between the end of the etching hole and the end of the gap. A method for manufacturing the capacitive transducer according to claim 13. Providing a plurality of the cells;
15. The capacitive transducer according to claim 13, wherein the etching hole is formed so that each of the plurality of cells is provided with the etching hole for performing individual etching. Method. The etching hole is provided at a position equidistant from the center of the gap of the cell, and the etching hole for individual etching is not provided in the gap.
The method for manufacturing a capacitive transducer according to claim 13, wherein the etching hole is formed.   14. The gap between the first electrode and the first electrode is formed on the substrate, and the area of the first electrode is larger than the area of the gap. The manufacturing method of the capacitive transducer as described in any one of thru | or 16. In the thickness direction of the substrate, so that the thickness of the etching confirmation portion is equal to or less than the thickness of the gap,
The method of manufacturing a capacitive transducer according to claim 13, wherein the etching confirmation portion is formed.   The method of manufacturing a capacitive transducer according to claim 13, wherein the cells are formed so as to be arranged in an array. A capacitive transducer including a cell on which a vibration film is supported so as to be able to vibrate includes one electrode of a pair of electrodes provided so as to sandwich a gap on a substrate, wherein the gap is at least one It has the above etching confirmation part,
The distance between the end of the etching hole and the end of the etching confirmation portion is longer than the distance between the end of the etching hole and the end of the cell, and at least a part of the etching confirmation portion is sandwiched between the pair of electrodes. Capacitive transducer characterized in that it does not.   The capacitance type transducer according to claim 20, wherein the shape of the etching confirmation portion is a protrusion shape. The capacitive transducer has a plurality of cells,
The capacitive transducer according to claim 20 or 21, wherein the cell is provided with the etching hole for individual etching.   23. The etching hole is provided at a position equidistant from the center of each gap constituting each cell group, and an etching hole for individual etching is provided in each gap. The capacitive transducer according to any one of the above.   24. One of the pair of electrodes is formed on a substrate, and the area of the one electrode formed on the substrate is larger than the area of the gap. The capacitive transducer according to Item.   The capacitive transducer according to any one of claims 20 to 24, wherein a thickness of the etching confirmation portion is equal to or less than a thickness of the gap in a thickness direction of the substrate.   26. The capacitive transducer according to any one of claims 20 to 25, wherein the cells are arranged in an array.

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