JP6362741B2 - Electromechanical transducer and method for manufacturing the same - Google Patents

Description

  The present invention relates to an electromechanical transducer and a manufacturing method thereof. In particular, the present invention relates to an electromechanical transducer used as an ultrasonic transducer and a manufacturing method thereof.

  Electromechanical transducers such as CMUTs (Capacitive Micromachined Ultrasonic Transducers) produced by micromachining technology have been studied as alternatives to piezoelectric elements. Such a capacitance-type electromechanical transducer can transmit and receive ultrasonic waves by vibration of the vibrating membrane.

  As a CMUT manufacturing method, Patent Document 1 describes a method of manufacturing a cavity by sacrificial layer etching. In Patent Document 1, in order to prevent the upper electrode from being etched during the sacrifice layer etching, a second electrode is formed between the first membrane and the second membrane, and the sacrifice layer is etched.

US Patent Application Publication No. 2005/0177045

  As in the manufacturing method described in Patent Document 1, in the CMUT, a lower electrode, an insulating film, an upper electrode, and a membrane are sequentially laminated on a substrate. It is conceivable that the thickness of the film varies during the formation of the plurality of films. If the thickness of the film varies from cell to cell and from device to device, the frequency characteristics change from cell to cell and from device to device. Therefore, an object of the present invention is to reduce variation in frequency characteristics for each cell and each element.

  The electromechanical transducer of the present invention includes a substrate, a first electrode formed on the substrate, a membrane formed with a gap from the first electrode, and the first electrode formed on the membrane. An electromechanical transducer including a vibrating membrane having a second electrode facing the electrode, wherein the first electrode has a root mean square value of surface roughness of 6 nm or less.

  The method for producing an electromechanical transducer of the present invention includes a step of forming a first electrode on a substrate, a step of forming a sacrificial layer on the first electrode, and a step of forming a membrane on the sacrificial layer And forming a second electrode on the membrane; and forming an etching hole in the membrane and removing the sacrificial layer through the etching hole; and The first electrode is formed so that the root mean square value of the surface roughness of the electrode is 6 nm or less.

  By optimizing the surface state of the first electrode according to the present invention, it is possible to reduce variation in frequency characteristics for each cell and each element.

It is a schematic diagram for demonstrating the electromechanical converter which can apply Example 1 of this invention. It is process drawing for demonstrating the manufacturing method of the electromechanical converter which can apply Example 1 of this invention. (A) The graph which showed the relationship between the film thickness of 1st electrode, and surface roughness. (B) A graph showing the relationship between the vibration characteristics of the vibrating membrane and the surface roughness of the first electrode. (A) It is a schematic diagram for demonstrating the electromechanical converter which can apply Example 2 of this invention.

  The inventors of the present invention have focused on the fact that the frequency characteristics of the vibration film vary depending on the thickness variation of each layer formed on the substrate. In particular, the focus was on the importance of the first electrode film forming process, which is an initial process for fabricating the device. An electromechanical transducer manufactured by laminating a plurality of films can obtain a film having a surface shape reflecting the surface shape of the first electrode in the steps after the first electrode forming step. From this point, the present inventors have found that the surface roughness of the first electrode and the frequency characteristic of the vibrating membrane have a certain relationship.

  From this relationship, the present invention is characterized in that the root mean square value of the surface roughness of the first electrode is 6 nm or less. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Configuration of electromechanical converter)
FIG. 1A is a top view of one element 1 of the electromechanical transducer of the present invention. FIG. 1B is a cross-sectional view taken along the line AB in the cell structure 2 surrounded by the one-dot chain line in FIG. The element 1 of the present embodiment has a plurality of cell structures 2 that are electrically connected. Although only one element 1 is shown in FIG. 1A, a plurality of elements 1 may be used. Further, in FIG. 1A, the element 1 is configured by arranging nine cell structures 2, but any number may be used. Further, although the cell structures are arranged in a square lattice pattern, they may be arranged in a zigzag manner and may be arranged in any manner. The shape of the cell structure is circular in FIG. 1, but may be a quadrangle or a hexagon.

  FIG. 1B shows a cross-sectional view of the cell structure 2. The cell structure 2 includes a substrate 11, a first insulating film 12 formed on the substrate 11, a first electrode 13, and a second insulating film 14. Further, the cell structure 2 has a vibration film composed of a first membrane 16, a second electrode 17, and a second membrane 18. The first membrane 16 is a gap side (cavity 15 side) membrane and is supported by a membrane support portion 19. The second membrane 18 is a membrane on the side opposite to the cavity 15. The vibration film is disposed so as to be separated from the second insulating film by a cavity 15 that is a gap. The first electrode 13 and the second electrode 17 are opposed to each other with a cavity therebetween, and a voltage is applied between the first electrode 13 and the second electrode 17 by a voltage application unit (not shown). The

  In addition, the electromechanical conversion device can extract an electrical signal from the second electrode 17 for each element by using the lead wiring 6. However, in the present embodiment, an electrical signal is drawn out by the lead-out wiring 6, but a through wiring or the like may be used. In the present embodiment, both the first electrode 13 and the second electrode 17 are arranged for each element, but either the first electrode 13 or the second electrode 17 may be a common electrode. . The common electrode refers to an electrode that is electrically connected to all of the plurality of elements when the plurality of elements are included. Even in this case, if one of the first electrode 13 and the second electrode 17 is separated for each element, an electrical signal for each element can be extracted.

(Driving principle of electromechanical converter)
The driving principle of the present invention will be described. When receiving an ultrasonic wave by the electromechanical transducer, a direct current voltage is applied to the first electrode 13 by a voltage application unit (not shown) so that a potential difference is generated between the first electrode and the second electrode. deep. When the ultrasonic wave is received, the vibration film having the second electrode 17 is bent, so that the distance between the second electrode 17 and the first electrode 13 (distance in the depth direction of the cavity 15) is changed, and the capacitance is changed. Changes. Due to this change in capacitance, a current flows through the lead-out wiring 6. 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 DC voltage may be applied to the second electrode 17 by changing the configuration of the lead wiring, and an electrical signal may be drawn from the first electrode 13 for each element.

  Moreover, when transmitting an ultrasonic wave, a DC voltage can be applied to the 1st electrode 13, an AC voltage can be applied to the 2nd electrode 17, and a vibrating membrane can be vibrated by an electrostatic force. Ultrasound can be transmitted by this vibration. Also in the case of transmitting ultrasonic waves, the vibrating membrane may be vibrated by applying a DC voltage to the second electrode 17 and an AC voltage to the first electrode 13 by changing the configuration of the lead wiring. Further, it is possible to apply a DC voltage and an AC voltage to the first electrode or the second electrode, and to vibrate the vibrating membrane by electrostatic force.

(Relationship between frequency characteristics of diaphragm and surface roughness of first electrode)
As described above, the present invention is characterized in that the root mean square value of the surface roughness of the first electrode is 6 nm or less. Hereinafter, the relationship between the frequency characteristics of the vibrating membrane and the surface roughness of the first electrode will be described with reference to FIG. The surface roughness referred to here is measured using an AFM (Atomic Force Microscope), and the value is represented by Rms (Roughness Root Mean Square). The measurement area of Rms is 5 μm × 5 μm. The AFM used for the measurement is Nanoscope Dimension 3000 manufactured by VEECO Instruments. The electromechanical transducer to be measured has the same configuration as the electromechanical transducer of Example 1 described later except that the thickness of the first electrode 13 is changed.

  FIG. 3A is a graph showing the relationship between the film thickness of the first electrode 13 and the surface roughness, using titanium as the electrode of the first electrode 13. The results of measuring Rms with the RF power fixed at 550 W and the titanium film thickness increased from 50 nm to 200 nm are shown. FIG. 3B is a graph showing the relationship between the frequency characteristics of the diaphragm and the surface roughness of the first electrode 13. The result when the film thickness of titanium was increased from 50 nm to 200 nm as in FIG.

  FIG. 3B shows the relationship with the Q value in evaluating the variation in frequency characteristics. The Q value is a dimensionless number that represents the state of vibration. The value obtained by dividing the resonance frequency of the diaphragm by the half width, and the higher the value, the more the frequency characteristics of the individual diaphragms of the cell structure 2 arrayed. That is, there is little variation in the shape of the diaphragm of the cell structure 2 and the distance between the electrodes.

  The frequency characteristic was measured using an impedance analyzer 4294A manufactured by Agilent. As a result, the Q value shows a high value of 200 or more when the surface roughness of the first electrode is 6 nm or less, and the Q value rapidly decreases in a range larger than 6 nm. The reason why the curve has a partially different slope in the region where the Q value is 200 or more seems to be because the resolution of the impedance analyzer is not sufficient.

  As shown in FIG. 3B, the surface roughness of the first electrode is important for obtaining a diaphragm having a small variation in frequency characteristics. In the range where the surface roughness is 6 nm or less and the range where the surface roughness is larger than 6 nm, It was found that the Q value changed greatly. This relationship does not depend on the material of the first electrode. As described above, when the root mean square value of the surface roughness of the first electrode is 6 nm or less, it is possible to obtain a vibration film with little variation in frequency characteristics for each cell and each element. Further, the smaller the surface roughness of the first electrode, the better.

  When titanium is used as the first electrode, as shown in FIG. 3A, when the film thickness is changed, the titanium thickness shows an inflection point in the vicinity of 100 nm, and the surface roughness suddenly increases. doing. Moreover, even when the titanium thickness is around 200 nm, there is an inflection point, and the increase in surface roughness is slow. This is because, in the film formation mechanism, the film formation surface grows two-dimensionally below a certain film thickness, suddenly shifts to three-dimensional growth, and growth in which two-dimensional and three-dimensional growth are mixed is performed. This tendency shows not only titanium but also titanium-containing alloys such as TiW have similar physical properties. From this result, when titanium or an alloy containing titanium is used as the first electrode of the present invention, the film thickness is preferably 100 nm or less. In addition, when the film is formed, the island shape is changed to a film shape with a film thickness of 10 nm or more. Therefore, the lower limit value of the titanium film thickness is preferably 10 nm or more. Therefore, the thickness of the first electrode of the present invention is preferably 10 nm or more and 100 nm or less.

(Method for producing electromechanical transducer)
Next, a method for manufacturing the electromechanical conversion device of the present invention will be described with reference to FIGS. FIG. 2 is a process diagram for manufacturing the electromechanical transducer shown in FIGS. As shown in FIG. 2A, a first insulating film 12 is formed on the substrate 11. When the substrate 11 is a conductive substrate such as a silicon substrate, the first insulating film 12 is formed for the purpose of insulation between the substrate 11 and the first electrode 13. Therefore, when the substrate 11 is an insulating substrate such as a glass substrate, the insulating film 12 is not necessary. The substrate 11 is desirably a substrate having a surface roughness as small as possible.

  Next, as shown in FIG. 2B, the first electrode 13 is formed on the first insulating film. As described above, the first electrode 13 is formed so that the root mean square value of the surface roughness is 6 nm or less. In the method of manufacturing by stacking, since the surface roughness of the film is reflected in the next film, it is important to suppress the surface roughness in the initial step to be small. In particular, in the metal film forming process in which the surface roughness tends to increase, it is important to suppress variation in characteristics by reducing the surface roughness. In the present invention, by producing the first electrode 13 within the range of the surface roughness, even if the surface roughness is reflected on the laminated film one after another in the steps after this step, the frequency characteristics of the vibrating membrane are improved. An increase in variation can be suppressed. As a material of the first electrode 13, titanium, titanium alloy, or the like having high conductivity, high temperature resistance, and high smoothness is preferable.

  Next, as shown in FIG. 2C, a second insulating film 14 is formed on the first electrode. The second insulating film 14 is for preventing an electrical short circuit or dielectric breakdown between the first electrode and the second electrode when a voltage is applied between the first electrode and the second electrode. Form. In the case of driving at a low voltage, the first membrane is an insulator, so the second insulating film 14 need not be formed. When the surface roughness of the second insulating film 14 is large, the distance between the first electrode and the second electrode due to the surface roughness varies between cells and between elements. However, a material having a small surface roughness is desirable. For example, a silicon nitride film, a silicon oxide film, or the like.

  Next, as shown in FIG. 2D, a sacrificial layer 25 is formed on the second insulating film. Since the sacrificial layer 25 is one that determines the shape (depth) of the cavity, the sacrificial layer 25 is a material that is less affected by grain boundaries and crystal anisotropy at the time of etching, and a material that has high etching selectivity with other constituent materials. Is desirable. In order to shorten the etching time, a material having a high etching rate is desirable. A material having a small surface roughness is desirable. As with the first electrode, when the surface roughness of the sacrificial layer is large, the distance between the first electrode and the second electrode due to the surface roughness varies between cells and between elements. A sacrificial layer with low roughness is desirable. For example, chromium, molybdenum and the like.

  Next, as shown in FIG. 2E, a first membrane 16 is formed on the sacrificial layer. The membrane support portion is formed by the same process as the first membrane 16. The first membrane 16 desirably has a low tensile stress. For example, a tensile stress greater than 0 MPa and less than or equal to 300 MPa is good. The silicon nitride film can be stress-controlled using a PE-CVD (Plasma Enhanced Chemical Vapor Deposition) method, and a low tensile stress can be obtained. When the first membrane 16 has a compressive stress, sticking or buckling is caused, and the vibration film may be greatly deformed. Sticking means that the first membrane 16 adheres to the first electrode side. In addition, in the case of a large tensile stress, the first membrane may be broken. Therefore, the first membrane 16 desirably has a low tensile stress.

  Next, as shown in FIG. 2F, a second electrode 17 is formed, and further an etching hole (not shown) is formed. Thereafter, the sacrificial layer 25 is removed through the etching hole to form a cavity. The second electrode 17 is preferably made of a material having low residual stress, heat resistance, and etching resistance against sacrificial layer etching. In addition, a material that does not cause alteration or increase in stress depending on the temperature at the time of forming the second membrane in the subsequent process is desirable. Further, when the etching selection ratio is small, it is necessary to protect the second electrode 17 when the sacrificial layer is etched, which causes variation. Therefore, a material having resistance to sacrificial layer etching is desirable. For example, titanium or an alloy of titanium.

  Next, as shown in FIG. 2G, the second membrane 18 is formed. In this step, the step of forming the second membrane 18 and the step of sealing the etching hole are performed in the same step. That is, by this process, the second membrane 18 is formed on the second electrode (on the surface opposite to the cavity of the second electrode), thereby forming a vibration film having a desired spring constant. And a sealing portion for sealing the etching hole can be formed.

  When the etching hole is formed after the second membrane 18 is formed and the etching hole is sealed, a film for sealing the etching hole is deposited on the second membrane. When etching is performed to remove the deposited film, variations in the thickness and stress of the vibration film occur. On the other hand, since the process of sealing the etching hole and the process of forming the second membrane 18 are the same as in this process, the vibration film can be formed only by the film forming process.

  The second membrane 18 is preferably made of a material having a low tensile stress. Similar to the first membrane 16, when the second membrane 18 has a compressive stress, the first membrane 16 may cause sticking or buckling, and may be greatly deformed. Further, in the case of a large tensile stress, the second membrane 18 may be broken. Therefore, the second membrane 18 desirably has a low tensile stress. The silicon nitride film can be stress-controlled using PE-CVD, and a low tensile stress can be obtained.

  After this step, a lead-out wiring is formed by a step (not shown) so as to facilitate electrical connection from the first electrode and the second electrode. The wiring material is preferably a highly conductive material suitable for assembly, such as aluminum.

  By producing an electromechanical transducer by this production method, variation in frequency characteristics of the diaphragm can be reduced. In addition, since the electromechanical conversion device manufactured by this manufacturing method can form the vibration film only by the film forming process, the thickness variation of the vibration film can be reduced. Therefore, for each cell and element of the electromechanical conversion device Variations in sensitivity and bandwidth can be reduced.

(Preferred form of the present invention)
In the present invention, any substrate such as a semiconductor substrate, a glass substrate, a ceramic substrate, or a composite substrate thereof may be used as the substrate. When the substrate 11 is an insulator such as a glass substrate, the first insulating film 12 may be omitted. In particular, in the present invention, as described above, it is preferable to use a silicon substrate as the substrate 11 and a thermal oxide film as the first insulating film 12. In particular, a silicon substrate having a thermal oxide film is preferable as a highly smooth substrate.

  The first electrode 13 is preferably made of titanium or a titanium alloy. By controlling the RF power in the sputtering apparatus, the surface roughness of the titanium film used for the first electrode can be accurately controlled. Since titanium has high heat resistance, it can prevent deformation and alteration due to high temperatures in the subsequent steps. Further, since the surface roughness is reflected in the next film by the lamination process, it is important to suppress the surface roughness in the initial process to be small.

  The second insulating film 14 is preferably silicon oxide. A silicon oxide film formed by PE-CVD has high insulation and smoothness, and excellent step coverage. Since a high voltage is applied between the first electrode 13 and the second electrode 17, the silicon oxide film excellent in insulation and step coverage provides a small surface roughness for subsequent processes. This is desirable because it can be used.

  The first membrane 16 and the second membrane 18 are preferably silicon nitride. A silicon nitride film formed using the PE-CVD method can generally obtain tensile stress. In order to prevent large deformation of the vibration film due to the residual stress of the silicon nitride film, a tensile stress and a low stress value are desirable. In the electromechanical transducer of the present invention, the second electrode 17 is formed between the first membrane 16 and the second membrane 18. Compared with the case where the second electrode 17 is formed on the second membrane 18, the distance between the first electrode and the second electrode can be reduced, so that the conversion efficiency can be increased.

  The conversion efficiency here refers to the efficiency of converting the vibration of the diaphragm into an electric signal. The smaller the distance between the first electrode and the second electrode, the higher the conversion efficiency. Further, when the vibration film is composed of a combination of different materials having different thermal expansion coefficients, the vibration film is warped by the bimetal effect. However, by forming the second electrode 17 sandwiched between the same kind of materials between the first membrane 16 and the second membrane 18, it is possible to balance the stress and reduce the warpage of the diaphragm. it can. Therefore, it is desirable because a large deformation of the vibration film can be prevented.

  The second electrode 17 is preferably titanium or a titanium alloy. Titanium or an alloy of titanium can be formed using an electron beam evaporation method, and a titanium film formed under a low vacuum degree using an electron beam evaporation method can obtain tensile stress. When the second electrode 17 is formed with a large compressive stress, the vibration membrane may cause a large deformation due to the stress balance of the second electrode 17 on the first membrane 16, and the deflection variation of the vibration membrane is large. turn into. In order to prevent large deformation of the vibrating membrane, it is desirable that the second electrode 17 has a tensile stress and a low stress value. Moreover, since titanium has high heat resistance, it is possible to prevent alteration due to temperature when the second membrane is formed. Moreover, since titanium can also reduce the surface roughness, it is possible to suppress variations in membrane deflection.

  Hereinafter, the present invention will be described in detail with reference to more specific examples.

  The embodiment of the present invention will be described below with reference to FIG. FIG. 1A is a top view of the electromechanical transducer of the present invention, and FIG. 1B is a cross-sectional view taken along the line AB of FIG. The element 1 of the present invention has nine cell structures 2.

  In FIG. 1B, a substrate 11 which is a 300 μm thick silicon substrate, a first insulating film 12 formed on the silicon substrate, a first electrode 13 formed on the first insulating film 12, A second insulating film 14 on one electrode 13 is provided. In addition, the diaphragm includes a first membrane 16, a second membrane 18, and a second electrode 17. The first membrane 16 is supported by a supporting membrane support portion 19, and the first electrode 13 and the second electrode 17 are disposed to face each other with the cavity 15 therebetween.

  The first insulating film 12 is a 1 μm thick silicon oxide film formed by thermal oxidation. The first electrode 13 is formed using a sputtering apparatus, is titanium having a thickness of 50 nm, and has a surface roughness Rms of 2 nm or less. The second insulating film 14 is a silicon oxide film formed by PE-CVD. Since the second insulating film 14 reflects the surface roughness of the first electrode 13, the second insulating film 14 has a value of Rms comparable to the surface roughness of the first electrode 13. The first electrode 13 of this embodiment is formed on the entire surface of the element 1. When the elements 1 are arranged in a plurality of arrays, the first electrode 13 is a common electrode that is electrically connected to all the elements, and the second electrode 17 is electrically separated for each element. An electric signal can be taken out every time. Alternatively, the second electrode 17 may be a common electrode, and the first electrode 13 may be separated for each element. Furthermore, both the first electrode 13 and the second electrode 17 may be electrodes separated for each element.

  The second electrode 17 forms titanium using an electron beam evaporation apparatus. Titanium has a thickness of 100 nm and is formed with a tensile stress of 200 MPa or less. The first membrane 16 and the second membrane 18 are silicon nitride films produced by PE-CVD, and are formed with a tensile stress of 100 MPa or less. The diameters of the first membrane 16 and the second membrane 18 are 45 μm, the thicknesses are 0.4 μm and 0.7 μm, respectively, and the diameter of the second electrode 17 is 40 μm. The thickness of the cavity is 0.18 μm. The thickness of the second membrane 18 is about three times the thickness of the cavity 15. Thereby, the etching hole can be closed by the insulating film forming the second membrane 18, and the cavity 15 can be satisfactorily sealed.

  The first membrane 16 is made thinner than the second membrane 18, and the spring constant of the membrane is adjusted to a desired value depending on the thickness of the second membrane 18. Accordingly, it is possible to form a vibration film having a desired spring constant only by the film forming process without etching the film forming the second membrane 18.

  The electromechanical conversion device of this embodiment can extract an electrical signal for each element from the second electrode 17 by using the lead wiring 6.

  When receiving an ultrasonic wave by the electromechanical transducer, a DC voltage is applied to the first electrode 13 by a voltage applying unit (not shown). When the ultrasonic wave is received, the first membrane 16 and the second membrane 18 having the second electrode 17 are deformed, so that the distance of the cavity 15 between the second electrode 17 and the first electrode 13 changes. A current (electrical signal) flows through the lead-out wiring 6 due to the change in capacitance. This current is converted into a voltage by a current-voltage conversion element (not shown) to obtain an ultrasonic reception signal.

  Moreover, when transmitting an ultrasonic wave, a DC voltage can be applied to the 1st electrode 13, an AC voltage can be applied to the 2nd electrode 17, and a vibrating membrane can be vibrated by an electrostatic force. Thereby, an ultrasonic wave can be transmitted.

  Hereinafter, a second embodiment of the present invention will be described with reference to FIG. FIG. 4A is a top view of the electromechanical transducer according to this embodiment, and FIG. 4B is a cross-sectional view taken along the line C-D in FIG. The configuration of the electromechanical transducer of Example 2 is substantially the same as that of Example 1 except for the shape of the first electrode.

  4B, the silicon substrate 41 having a thickness of 300 μm, the first insulating film 42 formed on the silicon substrate 41, the first electrode 43 formed on the first insulating film 42, the first A second insulating film 44 on the electrode 43 is provided. Further, the diaphragm includes a first membrane 46, a second membrane 48, and a second electrode 47. The first membrane 46 is supported by a membrane support portion 49. The first electrode 43 and the second electrode 47 are disposed to face each other with the cavity 45 therebetween.

  The first insulating film 42 is a silicon oxide film having a thickness of 1 μm formed by thermal oxidation. The first electrode 43 is formed using a sputtering apparatus, is titanium having a thickness of 50 nm, and has a surface roughness of Rms of 2 nm or less. Furthermore, in this embodiment, the first electrode is connected to the second electrode in order to reduce unnecessary parasitic capacitance formed by the first electrode and the second electrode at a position other than the cavity. Patterning is performed so as to minimize the overlapping area.

  By using photolithography and etching, the titanium of the first electrode 43 can be patterned with high accuracy as illustrated. Etching using a solution containing an aqueous hydrogen peroxide solution as an etchant provides a high etching selectivity with the material in which the etchant is constructed, and the surface roughness does not change without damaging the surrounding materials. A first electrode is obtained. In this way, the first electrode 43 is also approximately the same size as the second electrode 47, and the cells are connected by the thin wiring 33. The parasitic capacitance can be reduced by disposing the wiring 33 of the first electrode 43 and the wiring 36 of the second electrode 47 so as not to face each other through the insulating film. The second insulating film 44 is a silicon oxide film formed by PE-CVD.

DESCRIPTION OF SYMBOLS 1 Element 2 Cell structure 5 Etching hole 6 Lead-out wiring 11 Board | substrate 12 1st insulating film 13 1st electrode 14 2nd insulating film 15 Cavity 16 1st membrane 18 2nd membrane 19 Membrane support part

Claims (21)

A capacitance type electromechanical transducer,
A substrate,
A first electrode, an insulating film, and a vibrating film are arranged in this order from the substrate side in the stacking direction on the substrate, and in this order, with a gap between the insulating film and the vibrating film. And
The vibrating membrane includes a first membrane and the second electrode are configured to membrane of the first is positioned at the gap side,
The insulating film has a root mean square value of surface roughness of 6 nm or less,
The capacitance-type electromechanical transducer according to claim 1, wherein the first electrode includes tungsten and titanium. 2. The capacitance type electromechanical transducer according to claim 1, further comprising a cell configured to include the first electrode, the insulating film, and the vibration film on the substrate. A capacitance type electromechanical transducer,
A substrate,
A first electrode, an insulating film, and a vibrating film are arranged in this order from the substrate side in the stacking direction on the substrate, and in this order, with a gap between the insulating film and the vibrating film. And
The vibrating membrane includes a first membrane and the second electrode are configured to membrane of the first is positioned at the gap side,
The insulating film has a root mean square value of surface roughness of 6 nm or less,
A cell including the first electrode, the insulating film, and the vibration film;
The capacitance type electromechanical transducer is characterized in that the cell has a quadrangular shape. A capacitance type electromechanical transducer,
A substrate,
A first electrode, an insulating film, and a vibrating film are arranged in this order from the substrate side in the stacking direction on the substrate, and in this order, with a gap between the insulating film and the vibrating film. And
The vibrating membrane includes a first membrane and a second electrode, and is configured such that the first membrane is located on the gap side,
The insulating film has a root mean square value of surface roughness of 6 nm or less,
A cell including the first electrode, the insulating film, and the vibration film;
The capacitance type electromechanical transducer is characterized in that the cell has a hexagonal shape. A capacitance type electromechanical transducer,
A substrate,
A first electrode, an insulating film, and a vibrating film are arranged in this order from the substrate side in the stacking direction on the substrate, and in this order, with a gap between the insulating film and the vibrating film. And
The vibrating membrane includes a first membrane and a second electrode, and is configured such that the first membrane is located on the gap side,
The insulating film has a root mean square value of surface roughness of 6 nm or less,
A cell including the first electrode, the insulating film, and the vibration film;
The capacitance type electromechanical transducer is characterized in that the cell has a circular shape. A plurality of the cells on the substrate;
Wherein at least one of the first electrode and the second electrode, according to any one of claims 2 to 5, characterized in that a common electrode is used in common among the plurality of cells Capacitance type electromechanical transducer. The capacitance-type electromechanical transducer according to claim 6 , comprising a plurality of elements including the plurality of cells. The capacitance type electromechanical conversion according to claim 7 , wherein any one of the first electrode and the second electrode is a common electrode used in common among the plurality of the elements. apparatus. The insulating layer, the surface roughness capacitive electromechanical transducer according to any one of claims 1 to 8 the root mean square value is equal to or is 2nm following. Wherein the first electrode has a surface roughness capacitive electromechanical transducer according to any one of claims 1 to 9 root mean square value is equal to or is 6nm following. Wherein the first electrode has a surface roughness capacitive electromechanical transducer according to any one of claims 1 to 10 root mean square value is equal to or is 2nm following. The capacitance type electromechanical transducer according to any one of claims 1 to 11 , wherein the first electrode has a thickness in the stacking direction of 10 nm or more and 100 nm or less. Capacitive electromechanical transducer according to any one of claims 1 to 12, characterized by having a thermal oxide film between the substrate and the first electrode. Capacitive electromechanical transducer according to any one of claims 1 to 13, wherein said insulating film comprises silicon oxide film. It said first membrane capacitive electromechanical transducer according to any one of claims 1 to 14, characterized in that it has a silicon nitride film. The vibration film, the in the stacking direction, said first membrane, said a second electrode, wherein a second membrane to any one of claims 1 to 15, characterized in that it comprises in this order Capacitance type electromechanical transducer. The electrostatic electromechanical transducer according to claim 16 , wherein the second membrane includes a silicon nitride film. 18. The root mean square value of the surface roughness is a value when the measurement area of the surface roughness of the insulating film is 5 μm × 5 μm. 18. Capacitance type electromechanical transducer. Root mean square value of the surface roughness, electromechanical transducer of the electrostatic capacitance type according to any one of claims 1 to 18, characterized in that a measured value with an atomic force microscope apparatus. The resonance frequency of the vibrating membrane, capacitive electric according to any one of claims 1 to 19 Q value is a value obtained by dividing the half-width of the resonance curve and wherein the at least 200 Mechanical conversion device. The current caused by the change in the distance between the second electrode and the first electrode, current is converted into a voltage - to any one of claims 1 to 20, characterized in that it comprises a voltage conversion device The capacitance-type electromechanical transducer described.

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