JP2015118028A - Ultrasonic sensor element, manufacturing method therefor, and ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel ultrasonic sensor element with high resolution.SOLUTION: An ultrasonic sensor element includes: a substrate 12 having an opening 11 formed therethrough; a vibrating plate 13 provided on the substrate 12 to cover the opening 11; and a piezoelectric element 17 comprising a first electrode 14, piezoelectric layer 15, and second electrode 16 laminated on the vibrating plate 13 on a side opposite the opening 11. An area around the piezoelectric element 17 is surrounded by a sealing plate 22 having recesses 23 formed on a surface facing the piezoelectric element 17.

Description

  The present invention relates to an ultrasonic sensor element, a manufacturing method thereof, and an ultrasonic sensor.

  Conventionally, a semiconductor substrate having an opening, a two-layer electrode on an insulating film layer formed on the surface of the semiconductor substrate by closing the opening, and a PZT ceramic thin film layer sandwiched between the two layers, An ultrasonic sensor is known (for example, see Patent Document 1).

  Such an ultrasonic sensor utilizes the time required to receive an ultrasonic wave (echo signal) after transmitting the ultrasonic wave toward the object, the relationship between the speed of sound in the ultrasonic wave passing area, etc. It detects the presence / absence of a measurement object and the distance to the measurement object, and a configuration is appropriately selected according to the purpose and use of the measurement object and is widely used.

JP 2010-164331 A

  However, depending on the configuration of the ultrasonic sensor, another ultrasonic wave transmitted in a direction different from the ultrasonic wave transmitted in the direction of the measurement object (for example, the opposite direction) is reflected, and an echo signal is reflected on the measurement object side. There is a problem that the measurement resolution is lowered due to the generation of noise.

  The present invention has been made in view of the above situation, and an object thereof is to provide a novel ultrasonic sensor element having high resolution, a method for manufacturing the same, and an ultrasonic sensor.

An aspect of the present invention that solves the above problems includes a substrate on which an opening is formed, a diaphragm provided on the substrate so as to close the opening, and a laminate on the opposite side of the opening of the diaphragm. A piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode, wherein a region including the piezoelectric element is surrounded by a sealing plate, and faces the piezoelectric element of the sealing plate. In the ultrasonic sensor element, a concave portion is formed on the surface.
According to this aspect, other ultrasonic waves transmitted in a direction different from the ultrasonic wave transmitted to the measurement object (for example, the opposite direction) can be irregularly reflected on the surface where the recess is formed. For this reason, it can prevent that said other ultrasonic wave interferes with an echo signal by the side of a measuring object, and can provide the ultrasonic sensor element which has high resolution.

  Here, the inner surface of the recess is preferably curved. This makes it easier to diffusely reflect the other ultrasonic waves.

In addition, the radius r of the opening of the concave portion is expressed by the following equation, where c is the velocity of ultrasonic waves in the enclosed region, and f is the frequency of ultrasonic waves oscillated on the opposite side of the piezoelectric element. It is preferable to satisfy (1). According to this, it is possible to reliably diffuse the other ultrasonic waves.
[Formula 1]
r <c / (2πf) (1)

  Moreover, it is preferable that the circumscribed circle of the opening of the said recessed part satisfy | fills said Formula (1). According to this, it is possible to reliably provide irregular reflection of the other ultrasonic waves and to provide an ultrasonic sensor element having a high degree of configuration freedom.

  It is preferable that the piezoelectric element also serves as a transmitting device that transmits the ultrasonic waves and a receiving device that receives reflected echo signals. According to this, it is possible to provide an ultrasonic sensor element that can diffusely reflect the other ultrasonic waves and is advantageous for downsizing.

  According to another aspect of the present invention for solving the above-described problem, the ultrasonic sensor element according to any one of the above is provided, and a matching layer including a resin is formed in a region partitioned by the substrate and the diaphragm. It is in the ultrasonic sensor characterized by having. According to this aspect, since the ultrasonic sensor element is provided, an ultrasonic sensor having high resolution can be provided.

  Here, the resin is preferably made of a silicone resin. According to this, an ultrasonic sensor having a high resolution can be easily provided by using a silicone resin that is relatively excellent in handleability.

  Moreover, it is preferable to provide a lens member that closes the opening of the substrate on the side opposite to the diaphragm. According to this, since the matching layer can be easily formed by the lens member, the substrate, and the diaphragm, an ultrasonic sensor having high resolution can be easily provided.

Another aspect of the present invention that solves the above problem is that the substrate on which the opening is formed, the diaphragm provided on the substrate so as to close the opening, and the opening of the diaphragm A piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode laminated on the opposite side, and surrounding a region including the piezoelectric element with a sealing plate; and the piezoelectric element of the sealing plate And a step of forming a concave portion on a surface facing the element.
According to this aspect, other ultrasonic waves transmitted in a direction different from the ultrasonic wave transmitted to the measurement object (for example, the opposite direction) can be irregularly reflected on the surface where the recess is formed. For this reason, other ultrasonic waves can be prevented from interfering with the echo signal on the measurement object side, and a method for manufacturing an ultrasonic sensor element having high resolution can be provided.

1 is an exploded perspective view showing a schematic configuration of an ultrasonic sensor according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view of the ultrasonic sensor according to the first embodiment. FIG. 3 is a diagram illustrating operations of the ultrasonic sensor according to the first embodiment. FIG. 3 is a diagram illustrating operations of the ultrasonic sensor according to the first embodiment. FIG. 3 is a diagram illustrating a configuration example of a concave portion of the ultrasonic sensor according to the first embodiment. FIG. 3 is a diagram illustrating a configuration example of a concave portion of the ultrasonic sensor according to the first embodiment. 5 is a diagram for explaining an example of manufacturing the ultrasonic sensor according to Embodiment 1. FIG. 5 is a diagram for explaining an example of manufacturing the ultrasonic sensor according to Embodiment 1. FIG. The figure which shows schematic structure of the liquid ejecting apparatus which concerns on other embodiment.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing a schematic configuration of an ultrasonic sensor according to Embodiment 1 of the present invention. 2A is a cross-sectional view of FIG. 1, and FIG. 2B is a cross-sectional view taken along line AA ′ of FIG. 2A.

  As shown in the figure, the ultrasonic sensor 10 of the present embodiment includes a substrate 12 in which an opening 11 is formed, a diaphragm 13 provided on the substrate 12 so as to close the opening 11, and an opening in the diaphragm 13. 11 includes an ultrasonic sensor element 1 including a first electrode 14, a piezoelectric layer 15, and a piezoelectric element 17 including a second electrode 16 stacked on the opposite side of the electrode 11.

  As the substrate 12, for example, a silicon single crystal substrate can be used. The diaphragm 13 is configured as an elastic film made of, for example, silicon dioxide, and is elastically deformed by applying a voltage to the piezoelectric element 17. Thereby, an ultrasonic wave will generate | occur | produce.

  That is, in the present embodiment, a configuration is adopted in which the side opposite to the piezoelectric element 17 of the diaphragm 13 is a passage region for ultrasonic waves transmitted toward the measurement object and ultrasonic waves (echo signals) reflected from the measurement object. Has been. According to this, the structure on the opposite side to the piezoelectric element 17 of the diaphragm 13 can be simplified, and a good passing region for ultrasonic waves or the like can be secured. In addition, it is easy to prevent the electrical area such as electrodes and wirings and the adhesion fixing area of each member from the measurement object to prevent contamination and leakage current between these and the measurement object.

  Therefore, this embodiment can be suitably used as a pressure sensor or the like mounted on a printer, and is also suitable for medical devices that particularly dislike contamination and leakage current, such as an ultrasonic diagnostic apparatus, a sphygmomanometer, and a tonometer. It becomes the ultrasonic sensor element 1 which can be used for.

  The ultrasonic sensor 10 according to this embodiment includes the ultrasonic sensor element 1 and a matching layer (acoustic matching layer) including a resin is formed in a region partitioned by the substrate 12 and the diaphragm 13. Composed.

  In the ultrasonic sensor 10, a lens member 18 capable of transmitting ultrasonic waves and the like is provided on the opposite side of the substrate 12 from the diaphragm 13. A region defined by the lens member 18, the substrate 12, and the diaphragm 13 is filled with a resin agent 19 that functions as an acoustic matching layer, for example, silicone oil, silicone resin, or silicone rubber. Thereby, the acoustic impedance difference between the piezoelectric element 17 and the measurement object can be reduced, and ultrasonic waves are efficiently transmitted to the measurement object side.

  In the figure, the ultrasonic sensor element 1 and the ultrasonic sensor 10 are realized by the minimum unit configuration in which the substrate 12 has one opening 11, which is an advantageous mode for downsizing. However, it may be arranged one-dimensionally in the width direction or the length direction, or two-dimensionally in the width direction and the length direction, and in this case, the presence or absence of the measurement object based on a large number of signals And the distance to the measurement object can be detected, improving reliability.

  When the ultrasonic sensor element 1 and the ultrasonic sensor 10 are arranged one-dimensionally or two-dimensionally in parallel, the ultrasonic sensor elements 1 and the like may be connected and fixed, and the plurality of openings 11 may be configured. The substrate, the diaphragm, the lens member, and the like may be configured as a common member.

  On the side opposite to the opening 11 of the diaphragm 13, the adhesion between the insulator film 20 made of zirconium oxide or the like and the base of the first electrode 14 made of titanium oxide or the like having a thickness of about 30 to 50 nm is improved. An adhesion layer 21 is provided. The insulator film 20 and the adhesion layer 21 can be omitted as necessary.

  The adhesion layer 21 is formed with a piezoelectric element 17 including a first electrode 14, a piezoelectric layer 15 that is a thin film having a thickness of 3 μm or less, preferably 0.3 to 1.5 μm, and a second electrode 16. Has been. Here, the piezoelectric element 17 refers to a portion including the first electrode 14, the piezoelectric layer 15, and the second electrode 16.

  In general, in the piezoelectric element 17, one of the electrodes is a common electrode, and the other electrode and the piezoelectric layer 15 are configured by patterning for each opening 11. Therefore, when the ultrasonic sensor element 1 and the like are arranged in a one-dimensional or two-dimensional manner, for example, the first electrode 14 is used as the common electrode of the piezoelectric element 17 and the second electrode 16 is used as the piezoelectric element 17. Although it can be an individual electrode, there is no problem even if it is reversed for convenience of a drive circuit and wiring.

  Here, the piezoelectric element 17 and the diaphragm 13 that is displaced by driving the piezoelectric element 17 are collectively referred to as an actuator device. In the above example, the diaphragm 13, the insulator film 20 and the adhesion layer 21 provided as necessary, and the first electrode 14 function as a diaphragm, but the present invention is not limited to this. For example, the diaphragm 13 may not be provided, and the piezoelectric element 17 itself may substantially function as a diaphragm.

The first electrode 14 and the second electrode 16 are not limited as long as they have conductivity. For example, platinum (Pt), iridium (Ir), gold (Au), aluminum (Al), copper (Cu), titanium ( Ti), metal materials such as stainless steel, tin oxide-based conductive materials such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO), zinc oxide-based conductive materials, strontium ruthenate (SrRuO ₃ ), lanthanum nickelate ( An oxide conductive material such as LaNiO ₃ ) or element-doped strontium titanate, a conductive polymer, or the like can be used. However, the material is not limited.

  As the piezoelectric layer 15, a composite oxide having a perovskite structure based on lead zirconate titanate (PZT) is typically used. According to this, it becomes easy to ensure the displacement amount of the piezoelectric element 17.

  The piezoelectric layer 15 may be made of a compound containing no lead, for example, a composite oxide having a perovskite structure including at least bismuth (Bi), barium (Ba), iron (Fe), and titanium (Ti). According to this, the ultrasonic sensor element 1 can be realized using a lead-free material with a low environmental load.

In such a perovskite structure, that is, the A site of the ABO ₃ type structure, oxygen is 12-coordinated, and the B site is 6-coordinated of oxygen to form an octahedron. In the example of the piezoelectric layer 15 that does not contain lead, Bi, Ba, and Li are located at the A site, and Fe and Ti are located at the B site.

In a composite oxide having a perovskite structure containing Bi, Ba, Fe and Ti, the composition formula is expressed as (Bi, Ba) (Fe, Ti) O ₃ , but a typical composition is bismuth ferrate. And a mixed crystal of barium titanate. Such a mixed crystal is an X-ray diffraction pattern in which bismuth ferrate or barium titanate cannot be detected alone. A composition deviating from the composition of the mixed crystal is also included.

  The composite oxide having a perovskite structure includes those that deviate from the stoichiometric composition due to deficiency / excess, and those in which some of the elements are replaced with other elements. That is, as long as a perovskite structure can be obtained, not only inevitable compositional shift due to lattice mismatch, oxygen deficiency, etc., but also partial substitution of elements is allowed.

  And the structure of the complex oxide of a perovskite structure is not restricted to the said example, You may comprise other elements. For example, the piezoelectric layer 15 preferably further contains manganese (Mn). According to this, it becomes easy to suppress the leakage current, and for example, a highly reliable ultrasonic sensor element 1 can be realized as a lead-free material.

  Bi of the A site of the piezoelectric layer 15 may be replaced with lithium (Li), samarium (Sm), cerium (Ce), etc., and Fe of the B site is replaced with aluminum (Al), cobalt (Co), or the like. You may make it replace. According to this, it is easy to diversify configurations and functions by improving various characteristics. Even in the case of a complex oxide containing these other elements, it is preferably configured to have a perovskite structure.

  The piezoelectric element 17 described above is flexibly deformed by voltage application by a circuit (24 shown in FIG. 3 and the like) and elastically deforms together with the diaphragm 13 to generate ultrasonic waves. The ease of bending deformation of the piezoelectric element 17 varies depending on the constituent material, thickness, arrangement position, and size of the piezoelectric element 17 and the diaphragm 13, and can be adjusted as appropriate according to the application and usage. It is.

  By utilizing the resonance frequency unique to each material, this and the frequency of the charge signal applied to the piezoelectric element 17 are matched or substantially matched, and the piezoelectric element 17 is bent and deformed using resonance. Good.

  Here, in this embodiment, the area including the piezoelectric element 17 is surrounded by the sealing plate 22 (enclosed area). The side opposite to the piezoelectric element 17 of the vibration plate 13 is an ultrasonic wave passing region, and a recess 23 for diffusing the ultrasonic wave is formed on the surface of the sealing plate 22 facing the piezoelectric element 17. In other words, the surface of the sealing plate 22 facing the piezoelectric element 17 is a dimple surface formed by the recess 23. In this way, a plurality of recesses 23 can be formed.

  According to this, other ultrasonic waves transmitted in a direction different from the ultrasonic wave transmitted to the measurement object (for example, in the opposite direction) can be irregularly reflected on the surface where the recess 23 is formed. Diffusely reflected ultrasonic waves are less likely to reach the measurement object side, and are less likely to interfere with ultrasonic waves transmitted in the direction of the measurement object and echo signals reflected from the measurement object. As a result, generation of noise can be prevented, and the ultrasonic sensor element 1 and the ultrasonic sensor 10 having high resolution can be provided.

  In the surrounding region, the region including the piezoelectric element 17 does not need to be completely sealed by the sealing plate 22, and the piezoelectric element 17 is substantially sealed within a range that does not change the gist of the present invention. As long as it is surrounded by the sealing plate 22 as described above.

The surrounding region including the piezoelectric element 17 is filled with a resin agent 19 that functions as an acoustic matching layer. Here, the resin agent 19 may be the same as or different from the resin agent 19 filled in the region defined by the lens member 18, the substrate 12, and the diaphragm 13. The acoustic matching layer may be a resin material that can reduce the difference in acoustic impedance between the piezoelectric element and the measurement object, such as acrylic (3.37 × 10 ⁻⁶ ), polycarbonate (2.68 × 10 ^−6). ), Polyethylene terephthalate (2.97 × 10 ⁻⁶ ), polyethylene (2.18 × 10 ⁻⁶ ), polyvinyl chloride (3.20 × 10 ⁻⁶ ), polypropylene (2.43 × 10 ⁻⁶ ), ABS (2.34 × 10 ⁻⁶ ), Duracon (3.35 × 10 ⁻⁶ ), silicone (1.5 × 10 ⁻⁶ ) and the like can be mentioned, and a silicone resin having particularly low acoustic impedance is preferable. In the parentheses, the acoustic impedance value kg / m ² · sec is shown.

  The sealing plate 22 can be made of, for example, a silicon material. If a silicon-based material is also used for the substrate 12 and the diaphragm 13, the bonding properties and manufacturability of each part are facilitated by the same type of material.

  Next, the configurations of the ultrasonic sensor element 1 and the ultrasonic sensor 10 according to the present embodiment described above will be described in more detail with reference to FIGS. 3A to 3C are cross-sectional views illustrating the operation of the ultrasonic sensor 10 and the like.

  First, as shown in FIG. 3A, a circuit 24 for applying a voltage to the piezoelectric element 17 is electrically connected to the ultrasonic sensor 10 of the present embodiment. The circuit 24 can be appropriately configured by combining a known power supply device (not shown), a control means (not shown) mainly composed of a known microcomputer, and the like.

  The circuit 24 can be connected and fixed to the first electrode 14 and the second electrode 16 through the wiring 25, thereby improving the structural stability and electrical reliability. On the other hand, the circuit 24 may be configured to be electrically separable from the first electrode 14 and the second electrode 16 within a range not changing the gist of the present invention, thereby facilitating maintenance and repair replacement. Since the configuration of the ultrasonic sensor element 1 and the ultrasonic sensor 10 itself can be simplified, it can be easily used for various applications.

As shown in FIG. 3B, when a charge signal I _in is applied from the circuit 24 to the piezoelectric element 17, the piezoelectric layer that substantially becomes a drive unit sandwiched between the first electrode 14 and the second electrode 16. The (piezoelectric active part) 15 is flexibly deformed and elastically deformed together with the diaphragm 13 to generate ultrasonic waves. As described above, in the present embodiment, a configuration is adopted in which the opposite side of the vibration plate 13 from the piezoelectric element 17 is a passing region for ultrasonic waves transmitted toward the measurement object, such as ultrasonic waves. A good passing area is secured. In addition, it is easy to prevent electrical currents such as electrodes and wirings and adhesion / fixing regions of the respective members from the object to be measured to prevent contamination and leakage current between them and the object to be measured.

As shown in FIG. 3C, the ultrasonic wave reflected by the measurement object is incident on the diaphragm 13 as an echo signal, whereby the piezoelectric element 17 is elastically deformed together with the diaphragm 13, and the generated charge signal I _{out is} generated. Is measured by the circuit 24. Then, a predetermined calculation is performed by a control means (not shown), and the presence / absence of the measurement object and the distance to the measurement object are detected based on the time difference and the intensity of the charge signal I _in and the charge signal I _out .

  Here, in this embodiment, a recess 23 for diffusing ultrasonic waves is formed on the surface of the sealing plate 22 facing the piezoelectric element 17. In other words, the surface of the sealing plate 22 facing the piezoelectric element 17 is a dimple surface formed by the recess 23.

  Therefore, as shown in FIG. 4, ultrasonic waves transmitted in a direction different from the measurement object (for example, the opposite direction) can be irregularly reflected on the surface where the recess 23 is formed. The irregularly reflected ultrasonic wave does not easily reach the measurement object side, and is less likely to interfere with the ultrasonic wave transmitted in the direction of the measurement object or the echo signal reflected from the measurement object.

  A configuration example of such a recess 23 will be described in detail with reference to FIGS. 5A to 5C are enlarged cross-sectional views of the recess 23 (enlarged cross-sectional view along the line BB ′ in FIG. 2).

  As shown in FIG. 5A, the recess 23a can be configured such that the inner surface is curved. According to this, it becomes easy to diffusely reflect the ultrasonic wave transmitted in a direction different from the measurement object. Moreover, the recessed part 23b can be comprised so that it may become a triangular pyramid shape which an inner surface is a taper shape, as shown in FIG.5 (b). According to this, the ultrasonic wave transmitted in the direction different from the measurement object can be irregularly reflected by the tapered surface, and there are relatively few removed portions, and the durability can be easily maintained. Further, as shown in FIG. 5C, the recess 23c can be configured to have a quadrangular prism shape whose inner surface includes a vertical surface and a horizontal surface. According to this, the ultrasonic wave transmitted in a direction different from the measurement object can be irregularly reflected on the vertical plane and the horizontal plane, and the manufacture thereof is facilitated.

  A configuration example of the recess 23 will be described in more detail with reference to FIGS. 6A to 6C are enlarged plan views of the recess 23 as seen from the piezoelectric element 17 side (CC ′ direction in FIG. 5).

When the concave portion 23a having a curved inner surface is employed (see FIG. 5A), the radius r of the opening is set so that the ultrasonic sound velocity in the enclosed region is c and the piezoelectric element 17 is opposite. It is preferable to satisfy the following formula (1), where f is the transmission frequency of the transmitted ultrasonic wave. According to this, the ultrasonic wave transmitted in a direction different from the measurement object can be reliably irregularly reflected.
[Formula 1]
r <c / (2πf) (1)

  Further, when the triangular pyramid-shaped recess 23b is employed (see FIG. 5B) or when the quadrangular prism-shaped recess 23c is employed (see FIG. 5C), the circumscribed circle of the opening is expressed by the above formula. It is preferable to satisfy (1). According to this, the ultrasonic wave transmitted in a direction different from the measurement object can be reliably irregularly reflected.

  In addition, the recessed part 23 is not restrict | limited to these. For example, the concave portions 23 shown in FIGS. 5A to 5C may be combined so that the inner surface has a curved surface shape and a tapered shape, and has a step portion including a vertical surface and a horizontal surface. Even when the recesses other than the modes shown in FIGS. 5A to 5C are employed, it is preferable that the circumscribed circle of the opening satisfies the above formula (1).

  Although it is not necessary to make all of the plurality of recesses 23 the same mode, making all of the plurality of recesses 23 the same mode improves the manufacturability. The shape of the plurality of recesses 23 may be appropriately changed in arrangement to form a dimple surface, and the function of irregularly reflecting ultrasonic waves transmitted in a direction different from the measurement object may be adjusted.

  In such an ultrasonic sensor element 1 or the like, it is preferable that the piezoelectric element 17 also serves as a transmission device that transmits ultrasonic waves and a reception device that receives reflected echo signals. According to this, according to this, the ultrasonic sensor element 1 advantageous for size reduction can be provided. However, you may provide separately the transmission apparatus which transmits an ultrasonic wave, and the receiver which receives the echo signal to reflect.

  Next, an example of the manufacturing method of the ultrasonic sensor of this embodiment is demonstrated with reference to FIGS. 7-8 is sectional drawing which shows the manufacture example of an ultrasonic sensor. Here, an example of a method of manufacturing an ultrasonic sensor having an ultrasonic sensor element and having an acoustic matching layer formed will be described. However, the step of forming the acoustic matching layer is omitted, and the ultrasonic sensor element is manufactured. It can also be a method.

  First, as shown in FIG. 7A, after the diaphragm 13 is formed on the substrate 12 by thermal oxidation or the like, zirconium is formed on the diaphragm 13 and thermally oxidized in a diffusion furnace at 500 to 1200 ° C., for example. An insulator film 20 made of zirconium oxide is formed. Then, the adhesion layer 21 is formed on the insulator film 20 by sputtering or thermal oxidation.

  Thereafter, as shown in FIG. 7B, the first electrode 14 is formed on the adhesion layer 21 by sputtering, vapor deposition, or the like, and the adhesion layer 21 and the first electrode 14 are simultaneously formed in a predetermined shape. Pattern.

  Next, the piezoelectric layer 15 is laminated on the first electrode 14. The piezoelectric layer 15 is formed using, for example, a CSD (Chemical Solution Deposition) method in which a solution in which a metal complex is dissolved / dispersed in a solvent is applied, dried, and then fired at a high temperature to obtain a piezoelectric material made of a metal oxide. it can. The method is not limited to the CSD method, and for example, a sol-gel method, a laser ablation method, a sputtering method, a pulse laser deposition method (PLD method), a CVD method, an aerosol deposition method, or the like may be used. .

  Thereafter, the second electrode 16 is formed on the piezoelectric layer 15 by sputtering or thermal oxidation. As a result, as shown in FIG. 7C, the piezoelectric element 17 including the first electrode 14, the piezoelectric layer 15, and the second electrode 16 is formed in the adhesion layer 21.

  Next, as shown in FIG. 8A, a mask film 26 is formed on the entire periphery of the substrate 12. Then, as shown in FIG. 8B, the substrate 12 is opposed to the piezoelectric element 17 of the substrate 12 by anisotropic etching (wet etching) using an alkaline solution such as KOH through the mask film 26. Remove region.

  Then, as shown in FIG. 8C, the space from which the region facing the piezoelectric element 17 is removed is filled with the resin agent 19, and the lens member 18 is bonded to the opposite side of the substrate 12 from the diaphragm 13. At this time, holes may be formed in necessary portions of the substrate 12 and the lens member 18, the lens member 18 may be joined, and then the resin may be filled from the formed holes. Thereafter, for example, a region surrounding the piezoelectric element 17 and the concave portion 23 are formed by etching or the like on a sealing plate forming substrate made of a silicon material, and the sealing agent 22 is filled with the resin agent 19 and bonded to the vibration plate 13. As described above, the ultrasonic sensor 10 can be manufactured.

(Other embodiments)
As mentioned above, although one Embodiment of this invention was described, the fundamental structure is not limited to what was mentioned above.

  Since the ultrasonic sensor element 1 and the ultrasonic sensor 10 according to an embodiment of the present invention can be used as various pressure sensors, the ultrasonic sensor element 1 and the ultrasonic sensor 10 can also be applied to a liquid ejecting apparatus such as a printer. FIG. 9 is a schematic diagram illustrating an example of an ink jet recording apparatus (liquid ejecting apparatus).

  In the ink jet recording apparatus II shown in FIG. 9, the recording head units IA and IB having the ink jet recording head I are detachably provided with cartridges 2A and 2B constituting the ink supply means. The recording head units IA and IB Is mounted on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction. The recording head units IA and IB are, for example, configured to eject a black ink composition and a color ink composition, respectively.

  Then, the driving force of the driving motor 6 is transmitted to the carriage 3 through a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 on which the recording head units IA and IB are mounted is moved along the carriage shaft 5. The On the other hand, the apparatus main body 4 is provided with a conveyance roller 8 as a conveyance means, and a recording sheet S which is a recording medium such as paper is conveyed by the conveyance roller 8. Note that the conveyance means for conveying the recording sheet S is not limited to the conveyance roller, and may be a belt, a drum, or the like.

  In addition, since the ultrasonic sensor element 1 and the ultrasonic sensor 10 according to an embodiment of the present invention exhibit excellent displacement characteristics, the ultrasonic sensor element 1 and the ultrasonic sensor 10 are not limited to a liquid ejecting head typified by an ink jet recording head. It can be suitably applied to a sonic motor, a piezoelectric transformer, a vibratory dust removing device, a pressure-electric converter, an ultrasonic transmitter, an acceleration sensor, and the like.

  In addition, in the ultrasonic sensor element 1 and the ultrasonic sensor 10 as described above, the ultrasonic wave transmitted toward the measurement object and the echo signal from the measurement object pass on the opposite side of the diaphragm 13 from the piezoelectric element 17. The area configuration is adopted, and the electrical area such as electrodes and wiring and the adhesive fixing area of each member are kept away from the measurement object to prevent contamination and leakage current between them and the measurement object. It becomes easy. Accordingly, the present invention can be suitably applied to medical devices that particularly dislike contamination and leakage current, such as ultrasonic diagnostic apparatuses, blood pressure monitors, and tonometers.

  DESCRIPTION OF SYMBOLS 1 Ultrasonic sensor element, 10 Ultrasonic sensor, 11 Opening part, 12 Substrate, 13 Diaphragm, 14 1st electrode, 15 Piezoelectric layer, 16 2nd electrode, 17 Piezoelectric element, 18 Lens member, 19 Resin agent, 20 Insulator film, 21 adhesion layer, 22 sealing plate, 23 recess, 24 circuit, 25 wiring, 26 mask film

Claims (9)

A substrate in which an opening is formed; a diaphragm provided on the substrate so as to close the opening; a first electrode, a piezoelectric layer, and a first layer stacked on a side of the diaphragm opposite to the opening. A piezoelectric element composed of two electrodes,
A region including the piezoelectric element is surrounded by a sealing plate;
An ultrasonic sensor element, wherein a concave portion is formed on a surface of the sealing plate facing the piezoelectric element.   The ultrasonic sensor element according to claim 1, wherein an inner surface of the recess is curved. The radius r of the opening of the recess is expressed by the following formula (1) where c is the speed of ultrasonic waves in the enclosed region and f is the frequency of ultrasonic waves transmitted to the opposite side of the piezoelectric element. 3) The ultrasonic sensor element according to claim 1 or 2, wherein:
[Formula 1]
r <c / (2πf) (1)   The ultrasonic sensor element according to claim 3, wherein a circumscribed circle of the opening of the recess satisfies the formula (1).   5. The ultrasonic sensor element according to claim 1, wherein the piezoelectric element also serves as a transmitting device that transmits the ultrasonic waves and a receiving device that receives reflected echo signals. 6. It comprises the ultrasonic sensor element according to any one of claims 1 to 7,
An ultrasonic sensor, wherein a matching layer containing a resin is formed in a region partitioned by the substrate and the diaphragm.   The ultrasonic sensor according to claim 6, wherein the resin is made of a silicone resin.   The ultrasonic sensor according to claim 6, further comprising a lens member that closes the opening of the substrate on the side opposite to the diaphragm. A substrate in which an opening is formed; a diaphragm provided on the substrate so as to close the opening; a first electrode, a piezoelectric layer, and a first layer stacked on a side of the diaphragm opposite to the opening. A piezoelectric element composed of two electrodes,
Surrounding the region containing the piezoelectric element with a sealing plate;
Forming a recess on a surface of the sealing plate facing the piezoelectric element. A method for manufacturing an ultrasonic sensor element, comprising:

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