JP2015118014A - 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. An area around the piezoelectric element 17 is surrounded by a sealing plate 22, and the area surrounded by the sealing plate 22 is filled with a resin 23 containing ultrasonic diffusion particles 24.

Description

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

  Conventionally, an ultrasonic sensor is known as one of detectors for acquiring various types of information related to a measurement object. The ultrasonic sensor obtains information on the position, shape, speed, etc. of the measurement object based on the time required from transmitting the ultrasonic wave toward the object until receiving the ultrasonic wave (echo signal). is there.

  As such an ultrasonic sensor, for example, based on an ultrasonic wave transmitted from an ultrasonic sensor unit having a diaphragm and a piezoelectric body, and an ultrasonic wave reflected by a detection target and received by the ultrasonic sensor unit. In addition, a control operation unit that calculates the position, shape, and speed of a detection target is provided, and the above-described piezoelectric body is covered with a reflection chamber (see, for example, Patent Document 1).

  Further, as a detector having this type of piezoelectric body, although it is an example of a pressure sensor, a support body having an opening, a support film provided on the support body, and a pressure formed on the support film A detection unit (piezoelectric element), a frame formed on the pressure detection unit, and a sealing film for closing the frame, and a pressure medium (silicone oil) in an internal space surrounded by the frame Has been proposed (for example, see Patent Document 2). In Patent Document 2, the pressure when the measurement object comes into contact with the sealing film is transmitted to the pressure detection unit on the support film by the pressure medium, that is, the pressure detection unit and the pressure medium are provided from the support film to the sealing film side. It has a provided configuration.

JP 2010-164331 A JP 2012-215533 A

  However, in Patent Document 1, measurement is performed by reflecting 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) by a reflection chamber covering the periphery of the piezoelectric body. There is a problem that interference with an echo signal or the like is caused on the object side, resulting in noise and a decrease in measurement resolution.

  Also in Patent Document 2, another ultrasonic wave transmitted in a direction different from the ultrasonic wave transmitted in the direction of the measurement object (for example, the lateral direction) is caused by a frame body or a sealing film that covers the periphery of the piezoelectric body. Reflecting and interfering with an echo signal or the like on the measurement object side, as a result, there is a problem that noise is generated and the measurement resolution is lowered.

  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 for solving the above problems includes a substrate having an opening, a diaphragm provided on the substrate so as to close the opening, a first electrode laminated on the diaphragm, and a piezoelectric body. A piezoelectric element including a layer and a second electrode, and a region including the piezoelectric element is surrounded by a sealing plate, and the region surrounded by the sealing plate includes a resin, and includes ultrasonic diffusion particles. Is held in the ultrasonic sensor element.
According to this aspect, it is possible to cause another ultrasonic wave transmitted in a direction different from the ultrasonic wave transmitted to the measurement object to collide with the ultrasonic diffusion particles and diffuse. 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, it is preferable that the opening is a region through which an ultrasonic wave passes to the measurement object, and the piezoelectric element is formed on the side opposite to the opening of the diaphragm. According to this, it is possible to realize a configuration in which the opposite side of the diaphragm to the piezoelectric element is a region through which the ultrasonic wave passes to the measurement object, and it is easy to prevent leakage current between the piezoelectric element and the measurement object. . Therefore, an ultrasonic sensor element having high resolution and high safety can be provided.

  Moreover, it is preferable that the said ultrasonic diffusion particle is at least one of a bubble or a filler. According to this, it becomes easy to hold | maintain an ultrasonic diffusion particle in resin. Therefore, an ultrasonic sensor element having high resolution can be easily provided.

  Moreover, it is preferable that the said filler consists of nonmetallic materials. According to this, an ultrasonic sensor element having a high resolution can be provided by using a material having low conductivity as the filler.

  Moreover, it is preferable that the particle size of the ultrasonic diffusion particle is in the range of 0.1 μm to 30 μm. According to this, according to the ultrasonic wavelength in resin, based on at least one phenomenon of Rayleigh scattering, Mie scattering, and geometric optical scattering, for example, the other ultrasonic waves can be reliably diffused. Therefore, an ultrasonic sensor element having higher resolution can be provided.

  Moreover, it is preferable that a through portion is formed on a surface of the sealing plate facing the piezoelectric element. According to this, the sealing plate in a portion facing the piezoelectric element can be removed, and the displacement of the piezoelectric element is hardly hindered by the rigidity of the sealing plate. Therefore, an ultrasonic sensor element having higher resolution can be provided. In addition, resin or ultrasonic diffusion particles can be introduced into the region including the piezoelectric element through the penetrating portion facing the piezoelectric element, and the manufacture of the ultrasonic sensor element is facilitated.

Another aspect of the present invention that solves the above problem includes the ultrasonic sensor element according to any one of the above, and a matching layer including a resin is formed in a region partitioned by the substrate and the diaphragm. The ultrasonic sensor is characterized by that. According to this aspect, since the ultrasonic sensor is provided, an ultrasonic sensor having high resolution can be provided.
Here, it is preferable that the matching layer includes a silicone resin. According to this, it is possible to easily provide an ultrasonic sensor having a high resolution by using a silicone resin that is relatively excellent in handling properties and easily holds ultrasonic diffusion particles.

  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.

According to still another aspect of the present invention for solving the above-described problems, a substrate in which an opening is formed, a diaphragm provided on the substrate so as to close the opening, and a first electrode laminated on the diaphragm. And a piezoelectric element comprising a piezoelectric layer and a second electrode, the method including a step of surrounding a region including the piezoelectric element with a sealing plate and holding the resin and ultrasonic diffusion particles in the surrounding region. The ultrasonic sensor element manufacturing method is characterized.
According to this aspect, it is possible to cause another ultrasonic wave transmitted in a direction different from the ultrasonic wave transmitted to the measurement object to collide with the ultrasonic diffusion particles and diffuse. 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 manufacturing method of the ultrasonic sensor element which has high resolution.

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 view for explaining ultrasonic diffusion particles of the ultrasonic sensor according to the first embodiment. FIG. 3 is a view for explaining ultrasonic diffusion particles of the ultrasonic sensor according to the first embodiment. FIG. 4 is a diagram for explaining an example of manufacturing the ultrasonic sensor according to the first embodiment. FIG. 4 is a diagram for explaining an example of manufacturing the ultrasonic sensor according to the first embodiment. FIG. 5 is a cross-sectional view of an ultrasonic sensor according to a second embodiment. 1 is a diagram illustrating a schematic configuration of a liquid ejecting apparatus according to an embodiment of the invention.

(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 this embodiment is laminated on a substrate 12 having an opening 11, a diaphragm 13 provided on the substrate 12 so as to close the opening 11, and the diaphragm 13. The ultrasonic sensor element 1 includes the first electrode 14, the piezoelectric layer 15, and the piezoelectric element 17 including the second electrode 16.

  For example, a silicon single crystal substrate can be used as the substrate 12 of the ultrasonic sensor element 1. 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.

  In the present embodiment, the opening 11 is a region through which ultrasonic waves pass to the measurement object, and the piezoelectric element 17 is formed on the side opposite to the opening 11 of the diaphragm 13. That is, in the present embodiment, a configuration is adopted in which the side opposite to the piezoelectric element 17 of the vibration plate 13 becomes a passage region for ultrasonic waves transmitted toward the measurement object and ultrasonic waves (echo signals) reflected from the measurement object. it can. 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 adhesive fixing area of each component from the object to be measured to prevent contamination and leakage current between them and the object to be measured.

  Therefore, this embodiment can be suitably used as a pressure sensor or the like mounted on a printer, as well as medical equipment that particularly dislikes contamination and leakage current from the viewpoint of safety and the like, for example, an ultrasonic diagnostic apparatus, a sphygmomanometer In addition, the ultrasonic sensor element 1 can be suitably used for a tonometer.

  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. Thus, the acoustic matching layer 19 can be formed by filling a predetermined resin into a region defined by the lens member 18, the substrate 12, and the diaphragm 13. According to such an acoustic matching layer 19, an 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.

  That is, when the difference in acoustic impedance between the piezoelectric element 17 and the measurement object is large, the ultrasonic wave is likely to be reflected at the material interface before the arrival of the measurement object. On the other hand, by reducing the acoustic impedance difference between the piezoelectric element 17 and the measurement object by the acoustic matching layer 19, it is possible to prevent the reflection of the ultrasonic wave at the material interface due to the large acoustic impedance difference, and the ultrasonic wave is efficient. It is often transmitted to the measurement object side.

  Therefore, the resin functioning as the acoustic matching layer 19 can be appropriately selected to have an acoustic impedance that can reduce the acoustic impedance difference between the piezoelectric element 17 and the measurement object. Table 1 shows examples of usable resins and typical acoustic impedance values.

  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, they may be arranged one-dimensionally in the width direction or the length direction, or two-dimensionally arranged in the width direction and the length direction. In this case, the presence or absence of the measurement object and the distance to the measurement object can be detected based on a large number of signals, and the reliability is improved.

  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 of the ultrasonic sensor element 1, an insulator film 20 made of zirconium oxide or the like and a base of the first electrode 14 made of titanium oxide or the like having a thickness of about 30 to 50 nm. And an adhesion layer 21 that improves the adhesion of the substrate. The insulator film 20 and the adhesion layer 21 can be omitted as necessary.

  On the adhesion layer 21, there is 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. Is formed. 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. Accordingly, when the ultrasonic sensor elements 1 are arranged one-dimensionally or two-dimensionally in parallel, for example, the first electrode 14 is a common electrode of the piezoelectric element 17 and the second electrode 16 is an individual element of the piezoelectric element 17. Although it can be an electrode, there is no problem even if it is reversed for the convenience of the 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-described 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 are not limited thereto. 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 and the ultrasonic sensor 10 can be realized using a lead-free material having a small 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 leak current, and for example, the ultrasonic sensor element 1 and the ultrasonic sensor 10 with high reliability 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 (25 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 the present embodiment, the region including the piezoelectric element 17 is surrounded by the sealing plate 22. Then, an area surrounded by the sealing plate 22 (hereinafter referred to as an “enclosed area”) includes the resin 23 and holds the ultrasonic diffusion particles 24.

  According to this, other ultrasonic waves transmitted in a direction (for example, the opposite direction) different from the ultrasonic waves transmitted to the measurement object can be caused to collide with the ultrasonic diffusion particles 24 and diffused. The diffused ultrasonic wave does not easily reach the measurement object side, and does not easily interfere with the ultrasonic wave transmitted in the direction of the measurement object or the echo signal 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.

  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. By providing the sealing plate 22, an enclosed region including the piezoelectric element 17 can be formed, and the piezoelectric element 17 can be protected. When the piezoelectric element 17 is a thin film (for example, 30 to 200 μm), the handling properties of the ultrasonic sensor element 1 and the ultrasonic sensor 10 including the piezoelectric element 17 can be improved.

  The surrounding region including the piezoelectric element 17 is filled with a resin 23 that functions as an acoustic matching layer. The resin 23 here is not limited to the above example, and the same resin as the resin functioning as the acoustic matching layer 19 filled in the region defined by the lens member 18, the substrate 12, and the diaphragm 13 may be used. Well, different ones may be used.

  That is, the resin functioning as the acoustic matching layer 19 has a function of preventing reflection of ultrasonic waves at the material interface in the previous stage before reaching the measurement target, while the resin 23 filled in the surrounding region is It is not always necessary to have such a function as long as it has a function capable of holding the ultrasonic diffusion particles 24.

  As an example, a silicone resin can be used as the resin 23 filled in the surrounding region. Since such a resin 23 is excellent in handleability and easily holds the ultrasonic diffusion particles 24, the ultrasonic sensor element 1 and the ultrasonic sensor 10 having high resolution can be easily provided.

  Here, it is preferable that the ultrasonic diffusion particle 24 is at least one of a bubble or a filler. According to this, it becomes easy to hold the ultrasonic diffusion particles 24.

  When the ultrasonic diffusing particles 24 are bubbles, the ultrasonic diffusing particles 24 can be configured without adding a new material, which is advantageous in terms of, for example, low cost and ease of manufacture. The bubbles here include not only bubbles that are expected to be filled in the resin 23 but also bubbles that are mixed into the resin 23 during the manufacturing process within a range that does not change the gist of the present invention.

  Bubbles can be held in the resin 23 by bubbling. The bubbling process here refers to a process of blowing an inert gas, for example, nitrogen into the resin 23. Such a bubbling process is provided with a pipe for feeding an inert gas into the resin 23, and a pipe for discharging the fed inert gas from the outside of the resin 23 as necessary, and at a predetermined rate. Is realized by foaming the resin 23. A known apparatus can be used for the bubbling treatment and is not limited as long as it does not adversely affect the characteristics of the resin 23 and the function of the piezoelectric element 17.

  On the other hand, when the ultrasonic diffusion particle 24 is a filler, the ultrasonic diffusion particle 24 can be configured by appropriately selecting various materials, which is advantageous in terms of applicability to various applications, for example. However, bubbles and fillers may be used in combination as the ultrasonic diffusion particles 24.

  As the filler, a filler made of a metal material, a filler made of a non-metallic material, or a combination thereof can be used, but a filler made of a non-metallic material is preferably used. Since such a filler has low conductivity, it is difficult to cause an adverse electrical effect, and it is easy to avoid the occurrence of leakage current.

  Examples of the filler made of a nonmetallic material include titanium oxide, zirconium oxide, silica, talc, mica, clay, carbon nanotube, carbon fiber, glass bead, glass fiber, or a mixture thereof. Among these, when a silicone resin is used as the resin 23, silica is preferable from the viewpoint of excellent electrical insulation and miscibility with the silicone resin.

  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 25 for applying a voltage to the piezoelectric element 17 is electrically connected to the ultrasonic sensor 10 of the present embodiment. The circuit 25 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 25 can be connected and fixed to the first electrode 14 and the second electrode 16 via the wiring 26, thereby improving the structural stability and electrical reliability. On the other hand, the circuit 25 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 25 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 25. 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, the ultrasonic diffusion particles 24 are held in the resin 23 filled in the surrounding region formed by the sealing plate 22. Therefore, as shown in FIG. 4, ultrasonic waves transmitted in a direction different from the measurement object (for example, the opposite direction) can be scattered by the ultrasonic diffusion particles 24. Scattered 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.

  The configuration of the ultrasonic diffusion particle 24 will be further described in detail. FIGS. 5A to 5C are schematic views showing a state in which ultrasonic waves are diffused by the ultrasonic diffusion particles 24 having different particle sizes, and the directions of the ultrasonic waves are indicated by arrows.

  When the particle size α of the ultrasonic diffusing particle 24 represented by the formula (1) is sufficiently smaller than the wavelength λ of the ultrasonic wave in the resin 23 in the surrounding region, the supersonic wave diffusion particle 24 is supersonic by Rayleigh scattering as shown in FIG. Sound waves can be scattered. In this case, the ultrasonic waves are scattered almost symmetrically with respect to a direction perpendicular to the traveling direction. Therefore, the intensity of the ultrasonic wave can be reduced to about a half with respect to the colliding ultrasonic diffusion particle 24 as a boundary.

[Formula 1]
Ultrasonic diffusion particle diameter α = D × π / λ
(D: Diameter of ultrasonic diffusion particle, λ: Ultrasonic wavelength in resin in surrounding region)

  Further, when the particle diameter α of the ultrasonic diffusion particle 24 represented by the formula (1) is equal to the wavelength λ of the ultrasonic wave in the resin 23 in the surrounding region, the Mie scattering as shown in FIG. Can scatter ultrasonic waves. Even in this case, compared with the case of the Rayleigh scattering described above, the scattering in the traveling direction side of the ultrasonic wave is increased. However, as in the case of the Rayleigh scattering, the intensity of the ultrasonic wave is separated from the colliding ultrasonic diffusion particle 24 as a boundary. Can be reduced.

  Further, when the particle size α of the ultrasonic diffusion particle 24 represented by the formula (1) is sufficiently larger than the wavelength λ of the ultrasonic wave in the resin 23 in the surrounding region, the geometric optical scattering as shown in FIG. Thus, the ultrasonic waves can be scattered. In this case, it is possible to scatter the ultrasonic wave based on the incident angle of the ultrasonic wave to the ultrasonic diffusion particle 24 and reduce the intensity thereof.

  As described above, according to the present embodiment, according to the particle diameter of the ultrasonic diffusion particle 24 and the ultrasonic wavelength in the resin 23, for example, based on at least one phenomenon of Rayleigh scattering, Mie scattering, and geometric optical scattering, the above-mentioned Other ultrasonic waves can be diffused. The particle size of the ultrasonic diffusion particle 24 is preferably in the range of 0.1 μm to 30 μm, and preferably in the range of 0.5 μm to 20 μm.

  As such ultrasonic diffusing particles 24A, spherical particles can be used as shown in FIG. According to such an ultrasonic diffusing particle 24A, the particle size can be accurately calculated, so that the particle size of the ultrasonic diffusing particle 24A can be easily adjusted within the above range.

  Further, when the ultrasonic diffusion particle 24 is a filler, a plate-like one can be used as shown in FIG. According to such an ultrasonic diffusing particle 24B, the ultrasonic wave can collide with a relatively wide side surface portion and can be suitably scattered.

  When the ultrasonic diffusion particle 24 is a filler, a fibrous one can be used as shown in FIG. According to such an ultrasonic diffusion particle 24C, the handleability of the ultrasonic diffusion particle 24C is improved.

  Furthermore, when the ultrasonic diffusion particle 24 is a filler, a rod-shaped one can be used as shown in FIG. According to such an ultrasonic diffusion particle 24D, the characteristics of the spherical ultrasonic diffusion particle 24A shown in FIG. 6A and the plate-like ultrasonic diffusion particle 24B shown in FIG. It is possible to realize the ultrasonic diffusing particle 24D having both.

  Although it is not necessary to make all the ultrasonic diffusing grains 24 the same mode, making all the ultrasonic diffusing grains 24 the same mode improves the manufacturability.

  The density of the ultrasonic diffusion particles 24 with respect to the resin 23 can be appropriately changed depending on the type of the ultrasonic diffusion particles 24. For example, when the ultrasonic diffusion particles 24 are bubbles, the resin 23 can be filled in a range of 30 to 80% by volume. When the ultrasonic diffusion particle 24 is a filler, it can be filled with the same density.

  In such an ultrasonic sensor element 1 and ultrasonic sensor 10, it is preferable that the piezoelectric element 17 also serves as a transmitting device that transmits ultrasonic waves and a receiving device that receives reflected echo signals. According to this, the ultrasonic sensor element 1 etc. advantageous for miniaturization 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, a zirconium film is formed on the diaphragm 13 and then thermally oxidized in a diffusion furnace at 500 to 1200 ° C., for example. Then, the 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 a sputtering method, a vapor deposition method, or the like, so that the adhesion layer 21 and the first electrode 14 have a predetermined shape. Patterning is performed at the same time.

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

  Next, as shown in FIG. 8A, a mask film 27 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 performing anisotropic etching (wet etching) using an alkaline solution such as KOH through the mask film 27. Remove region.

  Then, as shown in FIG. 8C, the space from which the region facing the piezoelectric element 17 is removed is filled with resin, and the lens member 18 is bonded to the side of the substrate 12 opposite to the diaphragm 13. Thereafter, a region surrounding the piezoelectric element 17 is formed by etching or the like on a sealing plate forming substrate made of, for example, a silicon material. Furthermore, a hole is formed in a necessary portion of the sealing plate 22, and the sealing plate 22 is joined to the vibration plate 13. If possible, the hole may be formed after the sealing plate 22 is joined to the diaphragm 13. Further, the sealing plate 22 and the resin 23 do not need to be completely in close contact with each other, and an air layer may enter between them. Thereafter, the resin 23 and the ultrasonic diffusion particles 24 are filled into the surrounding region from the formed holes, and the ultrasonic diffusion particles 24 are held. As described above, the ultrasonic sensor 10 can be manufactured.

(Embodiment 2)
Next, an ultrasonic sensor element, a manufacturing method thereof, and an ultrasonic sensor according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 9 is a cross-sectional view corresponding to FIG. 2 of the first embodiment. Hereinafter, the same reference numerals are assigned to the same members, and repeated description is omitted, and detailed description will be made with a focus on differences from the first embodiment.

  The resin 23 can be easily configured to have low rigidity. In this case, the displacement of the piezoelectric element 17 is not substantially hindered by the resin 23 surrounding the piezoelectric element 17. On the other hand, the rigidity of the sealing plate 22 </ b> A tends to be higher than that of the piezoelectric element 17. Increasing the rigidity of the sealing plate 22A is advantageous in terms of adhesion to the vibration plate 13 and structural stability of the ultrasonic sensor, but may be disadvantageous in terms of the amount of displacement of the piezoelectric element.

  Therefore, the ultrasonic sensor 10A according to the present embodiment includes the ultrasonic sensor element 1A. In the ultrasonic sensor element 1A, a through portion 28 is formed on the surface of the sealing plate 22A facing the piezoelectric element 17. According to this, the part of the sealing plate facing the piezoelectric element 17 can be removed, and the displacement of the piezoelectric element 17 is hardly hindered by the rigidity of the sealing plate 22A. Therefore, the ultrasonic sensor element 1A and the ultrasonic sensor 10A having higher resolution can be provided.

  The shape of the penetrating portion 28 is not particularly limited, but the portion corresponding to the piezoelectric element 17 of the sealing plate 22A can be suitably removed by making it a rectangular shape as illustrated. Therefore, the penetration part 28 is too large with respect to the piezoelectric element 17, and the structural stability of the ultrasonic sensor 10 </ b> A is deteriorated. What cannot be done is prevented.

  Although not shown, the penetrating portion 28 may have a square shape, a circular shape, or an elliptical shape. When a plurality of ultrasonic sensors 10A are arranged, it is not necessary to use the penetrating portions 28 having the same shape for all the ultrasonic sensors 10A, and the penetrating portions 28 may have different shapes.

  Such an ultrasonic sensor 10A can be manufactured as follows, for example. That is, after FIG. 8B of the first embodiment, a region surrounding the piezoelectric element 17 is formed by etching or the like on the sealing plate forming substrate made of, for example, a silicon material, and the surface corresponding to the piezoelectric element 17 is further formed. Is removed to form the penetrating portion 28. After this is bonded to the diaphragm 13 first, the resin 23 and the ultrasonic diffusing particles 24 can be introduced from the penetrating portion 28 to hold the ultrasonic diffusing particles 24. As described above, according to the manufacturing method of the second embodiment, the resin 23 and the ultrasonic diffusing particles 24 can be easily put into the surrounding region, and the resin 23 can be reliably and easily filled in the surrounding region as compared with the first embodiment. it can.

(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 10 according to the embodiment of the present invention can be used as various pressure sensors, it can also be applied to a liquid ejecting apparatus such as a printer. FIG. 10 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. 10, 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.

  Further, since the ultrasonic sensor 10 according to an embodiment of the present invention exhibits excellent displacement characteristics, the ultrasonic sensor 10 is not limited to a liquid ejecting head typified by an ink jet recording head, and includes a piezoelectric motor, an ultrasonic motor, a piezoelectric transformer, The present invention can be suitably applied to a vibration dust removing device, a pressure-electric converter, an ultrasonic transmitter, an acceleration sensor, and the like.

  In addition, as described above, the ultrasonic sensor 10 has a configuration in which the side opposite to the piezoelectric element 17 of the diaphragm 13 is a transmission region for ultrasonic waves transmitted toward the measurement object and echo signals from the measurement object. Thus, it is easy to prevent the electrical area such as electrodes and wirings and the adhesive fixing area of each component from the measurement object, and to prevent contamination and leakage current between these and the measurement object. 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 1,1A ultrasonic sensor element, 10,10A ultrasonic sensor, 11 opening part, 12 board | substrate, 13 diaphragm, 14 1st electrode, 15 piezoelectric material layer, 16 2nd electrode, 17 piezoelectric element, 18 lens member, 19 Acoustic matching layer, 20 insulator film, 21 adhesion layer, 22, 22A sealing plate, 23 resin, 24 ultrasonic diffusion particle, 25 circuit, 26 wiring, 27 mask film, 28 penetration part

Claims (10)

A substrate in which an opening is formed; a diaphragm provided on the substrate so as to close the opening; a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode stacked on the diaphragm; Comprising
A region including the piezoelectric element is surrounded by a sealing plate;
An ultrasonic sensor element characterized in that the region surrounded by the sealing plate contains a resin and holds ultrasonic diffusion particles.   The said opening part is made into the passage area | region of the ultrasonic wave to a measurement object, The said piezoelectric element is formed in the opposite side to the said opening part of the said diaphragm. Ultrasonic sensor element.   The ultrasonic sensor element according to claim 1, wherein the ultrasonic diffusion particles are at least one of bubbles or fillers.   The ultrasonic sensor element according to claim 1, wherein the filler is made of a nonmetallic material.   The ultrasonic sensor element according to any one of claims 1 to 4, wherein a particle diameter of the ultrasonic diffusion particles is in a range of 0.1 µm to 30 µm.   The ultrasonic sensor element according to claim 1, wherein a through portion is formed on a surface of the sealing plate facing the piezoelectric element.   The ultrasonic sensor element according to claim 1 is provided, and a matching layer including a resin is formed in a region partitioned by the substrate and the diaphragm. The ultrasonic sensor as described in any one of 1-6.   The ultrasonic sensor according to claim 7, wherein the matching layer includes a silicone resin.   The ultrasonic sensor according to claim 7, further comprising a lens member that closes the opening of the substrate on a side opposite to the vibration plate. A substrate in which an opening is formed; a diaphragm provided on the substrate so as to close the opening; a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode stacked on the diaphragm; Comprising
A method of manufacturing an ultrasonic sensor element, comprising: enclosing a region including the piezoelectric element with a sealing plate, and holding resin and ultrasonic diffusion particles in the surrounded region.

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