JPH08274573A - Micro piezoelectric vibrator, its manufacture and piezoelectric transducer - Google Patents

Abstract

PURPOSE: To eliminate step structure and spurious vibration by using longitudinal vibration by arranging an upper electrode integrally with the upper face of a piezoelectric film element and the surface of an insulating layer. CONSTITUTION: A surface oxide film 2 is formed on the surface of a heat resisting substrate 1, and moreover, a lower electrode 3 consisting of a Pd thin film setting a Ti as a buffer layer is formed on the substrate 1. A piezoelectric thick film element 4 with cross-section of trapezoidal structure and polarized in a direction from an upper face to a lower face or vice versa is arranged on the electrode 3. A cavity part 5 with uniform thickness is formed extending over the entire oblique face of the element 4, and the insulating layer 6 with upper face flush with the one of the thick film is arranged in its periphery. Moreover, the upper electrode 7 made into a pattern so as to cover the entire upper face of the element 4 and to spread over the cavity part 5 is provided. Thereby, piezoelectric film is made by a jet printing method, and since no adhesive layer exists on a boundary with the substrate 1, no spurious vibration occurs, and filming without composition dislocation on piezoelectric fine powder is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-piezoelectric vibrator used in micromachines for medical and industrial purposes, a method for manufacturing the same, and a micro-piezoelectric transducer using the micro-piezoelectric vibrator.

[0002]

2. Description of the Related Art In recent years, much research has been conducted on piezoelectric sensors and transducers using piezoelectric vibrators used in medical and industrial micromachines. In particular, in the micro tactile sensing technology for the purpose of diagnosis and treatment inside the body cavity, the catheter is inserted into the body, and it is placed at the tip or side trunk of the endoscope, and the catheter and endoscope are safely inserted into the body. As described above, there is a need for a sensor and a transducer for detecting the state of pressure contact with the inner wall of the body cavity and for quantitatively detecting the hardness and softness of the inner wall tissue of the body cavity of the affected area after reaching the affected area. To meet these needs, the present applicant has proposed a micro tactile sensor using a piezoelectric vibrator, especially a piezoelectric thick film vibrator (Japanese Patent Application No. 6-235651).

As shown in FIG. 20, this is a silicon substrate 20 in which sensor drive circuits are monolithically integrated.
The lower electrode 202 is applied to 1, the piezoelectric thick film 203 is formed on the lower electrode 202 by the jet printing method, and then the upper electrode 204 is patterned. As a result, an energy trapping oscillator utilizing the thickness longitudinal vibration is realized, and changes in the resonance frequency and the resonance resistance when the piezoelectric vibrator is brought into contact with an object are detected, and the microtactile sensor is obtained. In the figure, reference numeral 205 is an insulating layer, 206a to 206d are through holes for fixing the base, reference numeral 207 is a constant voltage film, and reference numeral 20 is
8 is an electrode (after fitting the conductive protrusions provided on the base,
Conduction to this electrode). However, although the micro tactile sensor having these structures has been earnestly researched and developed, some new technical problems described below have appeared.

The first is a technique for forming a highly reliable upper electrode. In the above-mentioned prior art, the upper electrode 204 has a step structure and the distance between the upper electrode 204 and the lower electrode is partially reduced, and the applied electric field is concentrated there. It became clear that it could have a negative effect on sexuality.

Secondly, since the energy trapping electrode is used as the upper electrode, there is a region of the piezoelectric thick film which is not used as the piezoelectric vibrator, and there is a problem that the size of the piezoelectric sensor and the transducer as a whole becomes large.

On the other hand, when a measure is taken to increase the capacitance and solve the above-mentioned problem by providing an upper electrode on the entire surface, the mechanical quality factor Qm of the piezoelectric vibrator is reduced. Problem occurred. As a result of studying the reason for this, it was found that the cause is that in-plane spreading vibration and its harmonics are superposed in the vicinity of the resonance frequency of the thickness longitudinal vibration in addition to the thickness longitudinal vibration to be originally used.

Prior art related to the above-mentioned technical problems will be described below. For the first technical problem, that is, the flattening of the upper electrode, there are "1994 Micromachine Technology Development Results Presentation Meeting Proceedings" P32 to P33 as prior art. This is because the PZT slurry is poured into the through holes of the polyimide resin film having a plurality of holes penetrating to the substrate by means of the LIGA process, and the heat treatment is performed to remove the polyimide resin film and solidify and sinter the PZT slurry. Do P
A ZT column array is formed, then a resin layer is embedded, the surface is flattened, and an upper electrode is applied to the entire surface to form a composite piezoelectric element of a PZT piezoelectric element and a resin layer.

This prior art was originally intended to form a composite piezoelectric element of a PZT piezoelectric element and a resin layer to obtain a micro ultrasonic sensor for flaw detection having a small average Qm, and is an object of the present invention. This is contrary to the purpose of achieving a large Qm and obtaining a high sensor sensitivity.

As a prior art relating to the second technical problem, that is, the technical problem that the size of the piezoelectric sensor and the transducer as a whole becomes large, JP-A-61-4 is used.
There is 6608.

In this prior art, as shown in FIG. 21, a constant elastic substrate (vibrating substrate) 211, a piezoelectric thin film 212, and a vibrating electrode film 21.
In the piezoelectric vibrator of the spreading vibration mode having the piezoelectric vibrating element 214 formed by 3 and 3, the vibration substrate 211 has a trapezoidal cross-sectional shape, and the apparent thickness of the vibration substrate 211 is reduced to reduce the capacitance ratio and the resonance frequency. The vibration characteristics such as the difference from the anti-resonance frequency are sufficiently improved. There are many prior art piezoelectric vibrators provided with such full-surface electrodes, and many have been commercialized.

However, most of these used the spreading vibration mode as in the prior art. There are relatively few examples of piezoelectric vibrators provided with full-surface electrodes using the thickness longitudinal vibration mode as in the present invention, except for applications such as Langevan vibrators and ultrasonic transducers for medical and nondestructive inspection. One reason is that the resonance frequency of the vibration mode and its harmonics are near the resonance frequency of the thickness extensional vibration mode in order to make the ideal extension of thickness extensional vibration with the entire surface electrode, which can be excited by Poisson's ratio. Specific consideration must be given to the area / thickness ratio so that it will not occur. Therefore, when the thickness cannot be made large, the surface dimension must be made extremely small. For this reason, special measures for wiring are required, resulting in a product with low reliability and high cost.

From the above, there are relatively few examples in which the full length electrode is thick and the longitudinal vibration mode is used, which is the reason why the energy trapping electrode is used frequently. As described above, particularly in the application to the micromachine, it is necessary to obtain the same vibration characteristics as when the energy trapping electrode is used and to reduce the size of the piezoelectric vibrator as much as possible without using the energy trapping electrode.

Actually, there are many cases where the above-mentioned area / thickness ratio condition cannot be satisfied, but in such a case, it is necessary to obtain the same vibration characteristic as that of the energy trapping electrode.

On the other hand, a proposal for eliminating unnecessary vibration without using an energy trapping electrode is disclosed in Japanese Examined Patent Publication No. 60-38893.
It is made in. Here, FIG. 22 (A), (B), and FIG.
As shown in (A) to (C), the pair of opposed side surfaces of the rectangular piezoelectric plate are made to be the back surface and are inclined with a predetermined inclination to have a trapezoidal cross section. Provide a pair of electrodes at both ends to match
It is a proposal to realize a parallel electric field excitation piezoelectric vibrator in which unnecessary vibration of the piezoelectric vibrator is removed by using this electrode as an excitation electrode. In this structure, the inclined surfaces are arranged on the two surfaces of the end portion in the polarization direction.

FIG. 22A is a structural example of a conventionally known parallel electric field excitation thickness sliding oscillator, in which reference numeral 221 is a piezoelectric body and reference numeral is.
222a and 222b indicate side electrodes, and arrows indicate displacement components associated with sliding vibration. 22B is a parallel electric field excited piezoelectric vibrator according to the invention of the above publication, in which the opposite side surfaces are inclined from the back surface as compared with the structure of FIG. 22A, and the electrodes on the side surfaces are the front surface. And the areas of the surface electrodes 227a and 227b substantially coincide with the projected shadows of the inclined side surfaces 224a and 224b on the surface 226. In FIG. 22B, reference numeral 223 indicates a rectangular piezoelectric plate, and reference numeral 225 indicates a back surface.

23 (A) to 23 (C) are sectional views of various vibrators, FIG. 23 (A) shows that the vibrator of the invention of the above publication has a trapezoidal cross section, and FIG. 23 (B) is A vibrator without tilt is shown to explain the tilt effect of the side surface, and FIG. 23C shows a conventional vibrator. In the figure, reference numerals 231a and 231b indicate areas under the electrodes, and reference numeral 232 indicates a piezoelectrically active area under the electrodes.

[0017]

[Problems to be Solved by the Invention]

Claims 1 and 2 As described above, a piezoelectric vibrator that can be used in a tactile sensor having the structure proposed by the present inventors (Japanese Patent Application No. 6-23565).
In 1), since the electrode has a step structure, a partial electric field concentration may occur and good piezoelectric vibration may not be excited, and it has been found that an electrode structure having no step structure is required.

Regarding the electrode structure having no step structure, see “1994
Annual Meeting on Micromachine Technology Development Results Presentation ”P32-
There is P33, but with this structure, the mechanical quality factor Qm, which is strongly related to the sensor sensitivity, becomes small and sufficient sensor sensitivity cannot be obtained. Excited spreading vibration has a similar resonance frequency depending on the surface dimension / thickness ratio,
Since it is excited by Qm, unnecessary vibration appears in the vicinity of the resonance frequency of the intended thickness longitudinal vibration, which causes a problem that the intended vibration mode cannot be excited stably.

As a method of removing such unnecessary vibration,
There is a well-known method of using the energy confining electrode and ideally designing the surface dimension / thickness ratio.
In the case of using a piezoelectric vibrator for a micromachine, since the energy trapping electrode is not a full-face electrode in the former method, the size of the region without the electrode becomes large. Further, since the electrostatic capacity also becomes small, the S / N as a sensor decreases.

In the latter method, a normal cylindrical or prismatic structure may excite an undesired vibration mode depending on the dimensions, and the sensor may not be able to operate stably. Further, as another method of not exciting unnecessary vibration, there is Japanese Patent Publication No. 60-38893 mentioned above, but it is a parallel electric field excited piezoelectric vibrator, and is not a piezoelectric vibrator utilizing thickness longitudinal vibration as in the present invention.

Therefore, an object of the present invention is to provide a piezoelectric vibrator using a thickness longitudinal vibration, in which electrodes do not have a step structure, and which has a large mechanical quality factor Qm without unnecessary vibration, and a manufacturing method thereof. It is what

In a conventional ultrasonic transducer, particularly a medical ultrasonic transducer, ultrasonic energy excited by a piezoelectric vibrator is efficiently transmitted to and received from an object (living body). It has a power control layer. This uses a material and a shape that satisfy the amplitude condition and the phase condition as the matching layer. If it is a single matching layer, the acoustic impedance Zp of the piezoelectric vibrator and the acoustic impedance Z of the target object are used.
If it is o, a material having an acoustic impedance of (Zp · Zo) ^1/2 is made a thickness of ¼ wavelength to form an acoustic matching layer. However, the purpose of the present invention is to provide both the mechanical properties of the surface of the object and the mechanical properties in the depth direction of the object as proposed by the present inventors in Japanese Patent Application No. 6-235651. It is to detect with one transducer.
Therefore, if most of the ultrasonic energy is incident on the object, the mechanical characteristics of the surface of the object cannot be detected. Therefore, a part of the ultrasonic wave excited by the piezoelectric vibrator is incident on the object, and the remaining part remains in the vibrator composed of the piezoelectric element and the substrate, and the resonance frequency of the vibrator composed of them is There is a need for a technique in which the resonance impedance changes with the contact pressure of an object with great sensitivity.

[0023]

A first invention of the present application relates to a micro-piezoelectric vibrator using resonance characteristics of thickness longitudinal vibration, a substrate having a lower electrode on its surface, and a substrate formed on the lower electrode. A piezoelectric thick film element having a trapezoidal cross section and being polarized in the thickness direction, and a piezoelectric thick film element formed so as to surround a side wall of the piezoelectric thick film element with a gap therebetween and have a surface substantially parallel to the substrate. A micro-piezoelectric vibrator, comprising: an insulating layer formed by the above process; and an upper electrode integrally disposed on the upper surface of the piezoelectric thick film element and the surface of the insulating layer.

A second invention of the present application is a step of forming a piezoelectric thick film in a spot shape by using a jet printing method,
A heat treatment step, a sacrifice layer forming step, an insulating layer forming step,
A surface flattening step, an upper electrode forming step, a polarization step,
A method of manufacturing a micro-piezoelectric vibrator, comprising: an upper electrode patterning step and a sacrificial layer removing step.

According to a third aspect of the present invention, in a piezoelectric transducer having an acoustic coupling layer between the micro-piezoelectric vibrator and an object to be measured, the side where the acoustic coupling layer contacts the object is a subject to be measured. 1. Acoustic impedance of the object
The acoustic impedance of the piezoelectric thick film element is approximately equal to the acoustic impedance of the piezoelectric thick film element, the acoustic impedance of the piezoelectric thick film element is approximately equal to that of the piezoelectric thick film element. A piezoelectric transducer characterized by having a value equal to or higher than a mechanical quality factor of an element.

[0026]

In the present invention, since the piezoelectric thick film element has a trapezoidal shape, resonance vibration in the thickness direction resonates at a frequency at which the distance between the upper surface and the lower surface corresponds to the distance. In the spreading vibration, since the cross-sectional dimension of the cross section perpendicular to the thickness direction of the trapezoidal piezoelectric element is not constant over the entire thickness, the resonance frequency is widely distributed, and the sharpness of resonance (= mechanical quality factor Qm) is also small. So
Only the thickness longitudinal vibration can be regarded as being relatively excited, and stable thickness longitudinal vibration occurs. Further, since the cavity formed so as to surround the side wall of the trapezoidal piezoelectric element is formed between the trapezoidal piezoelectric vibrator and the insulating layer, the vibration of the trapezoidal piezoelectric vibrator is not damped.

[0027]

【Example】

(Embodiment 1) FIG. 1 is a sectional view of a micro-piezoelectric vibrator according to Embodiment 1 of the present invention. 2 to 6 show the manufacturing method thereof.

Reference numeral 1 in the figure denotes a surface oxide film (SiO ₂
It is a heat resistant substrate (Si substrate) on which a film 2 is formed. On the substrate 1, a lower electrode 3 made of, for example, a Pd thin film (Pd / Ti) having Ti as a buffer layer is formed. A piezoelectric thick film element 4 made of, for example, lead zirconate titanate (PZT), which has a trapezoidal cross section, for example, a truncated cone shape, and is polarized from the upper surface to the lower surface or in the opposite direction is arranged on the lower electrode 3. It is set up. Then, a void portion 5 having a uniform thickness is formed over the entire circumference of the inclined surface of the piezoelectric thick film element 4, and an insulating layer 6 having an upper surface flush with the upper surface of the piezoelectric thick film is arranged around the void portion 5. . Then, FIG. 1 (B)
As shown in FIG. 5, an upper electrode 7 is provided which covers the entire upper surface of the piezoelectric thick film element 4 and is patterned so as to extend over a part of the upper surface of the insulating layer 6 so as to straddle the void 5. There is.

A portion of the upper electrode 7 which extends over a part of the upper surface of the insulating layer 6 is a wiring portion 7a which acts as an electric wiring. This wiring portion 7a is a specific one in FIG. 1 (B). Although it is provided so as to be drawn out only in the directions, as a modification, it may be provided so as to be drawn out in a plurality of directions. Also,
In the structure of the first embodiment, the cavities 5 having a uniform thickness are formed over the entire circumference of the inclined surface of the piezoelectric thick film element 4, but the cavities 5 are not necessarily uniform in thickness. Also, it is sufficient that the slope of the piezoelectric element and the side wall of the insulating layer are separated from each other so as not to contact each other.

Next, a method of manufacturing the micro-piezoelectric vibrator according to the first embodiment will be described with reference to FIGS. Note that FIG. 2 is reduced for convenience as compared with FIGS. 3 to 6. First, the surface oxide film 2 having a thickness of 500 to 5000 nm is formed on the surface.
A Pd / Ti two-layer electrode (lower electrode) 3 using Ti as a buffer is formed on the 100-faced silicon substrate 1 on which the Ti is formed by thin film forming means such as sputtering, vapor deposition, and ion plating, and if necessary, means such as ion milling. Turn into pattern. Next, this is heat-treated at 500 ° C. to 800 ° C. to improve the adhesion of the electrode to the substrate and to chemically stabilize the subsequent steps. Next, using the jet printing system device shown in FIG. 7 which will be described in detail below, 50 spot-shaped piezoelectric thick films 21 made of PZT material are formed.
The film is formed to have a thickness of about μm.

Here, the film forming principle of the jet printing system apparatus and the jet printing method of FIG. 7 will be described. Reference numeral 71 in the drawing denotes a film forming chamber, in which a substrate heating device 73 for mounting a substrate 72 is arranged. A substrate heating power source 74 is connected to the substrate heating device 73. A vacuum pump 75 is connected to the film forming chamber 71. A nozzle 76 is arranged above the substrate 72, and one end of an ultrafine particle carrying pipe 77 is connected to the nozzle 76. The other end of the carrier tube 77 is communicated with an ultrafine particle stirring container (aerosolization chamber) 79 containing PZT ultrafine particles 78 having an average particle size of about 0.2 μm. In this stirring container 79,
A gas transfer pipe 80 having a valve 80a interposed therein is communicated.
A carrier gas such as pure air is introduced into the carrier pipe 80.

Aerosolization chamber containing PZT ultrafine powder 77
Pure air is introduced into 79 through the gas transfer pipe 80, and the PZT ultrafine powder 78 is scattered and floated. The ultrafine powder 78 that has been scattered and floated moves at high speed in the ultrafine powder transfer pipe 77 at a speed corresponding to the pressure difference between the film forming chamber 71 and the aerosolization chamber 79 and the nozzle shape, and is directly connected to the transfer pipe 77. Nozzle with its exit hole facing the substrate
A jet is jetted from 76 onto the substrate 72. A film is formed on the substrate 72 in a shape corresponding to the shape of the emission hole of the nozzle 76.

In the first embodiment, the emission hole formation is 0.3 mmφ.
Nozzle of was used. This method has a high film-forming speed, the film-forming composition does not deviate from the powder composition, there is no risk of contamination by complete dry film-forming, and the film is formed with the shape of the nozzle exit hole as it is. It has a feature not found in conventional film forming methods, such as obtaining a thick film without etching. Then
Heat treatment is performed at a temperature of 500 ° C. to 800 ° C. in an air or oxygen atmosphere for the purpose of improving the adhesion to the substrate, the bonding force between fine particles, and the crystallinity (see FIG. 2). At this stage, the piezoelectric spot film 21 has a dome shape as shown in FIG. The dome-shaped piezoelectric spot film 21 has a height of 5 mm or less.
At 0 μm, the diameter at half height is 100 μm.

Next, in order to secure a region for forming a void (see FIG. 6) in the piezoelectric spot film 21 formed in a spot shape on the substrate 1, a paraffin resin that melts at about 80 ° C. is melted. The piezoelectric spot film 21
The film-like first sacrificial layer 22 is naturally cooled and formed by allowing the film-like first sacrificial layer 22 to flow down. Further, a room temperature curable resin or a photocurable resin is applied by spin coating, a dropping method or the like, and then room temperature cured or photocured to form the insulating layer 23 (see FIG. 3).

Next, the surface of the piezoelectric spot film 21 is flattened by mechanical polishing or high precision grinding so that the upper surface of the piezoelectric spot film 21, the upper surface of the first sacrificial layer 22 and the upper surface of the insulating layer 23 are flush with each other.
Make the top surface of 21 exposed (see Figure 4).

Next, an upper electrode / polarized electrode 24 made of gold, silver, nickel, aluminum or the like is formed on the entire surface by means of sputtering, vacuum evaporation or the like. Then, a voltage of about 5 kV DC is applied between the lower electrode 3 and the polarized electrode 24 serving also as the upper electrode to perform the polarization process to bring the piezoelectric spot film 21 into the piezoelectrically active state (see FIG. 5).

Next, platinum is patterned in a pattern on the upper electrode / polarized electrode 6 as an etching resist / second upper electrode by means such as sputtering or ion plating, and then aqua regia or nitric acid is used. Then, the portion of the upper electrode / polarized electrode 6 where the platinum film is not applied is patterned to form a patterned electrode 25. Subsequently, the first sacrificial layer 22 is heated and melted and removed at 100 ° C. or higher to form the voids 26 (see FIG. 6).

Next, the operation of this embodiment will be described with reference to FIG. The micro-piezoelectric vibrator as shown in FIG. 1 can be realized by the steps described above. The feature of this structure is that the piezoelectric thick film is formed by using a film forming method called a jet printing method, and therefore an adhesive layer is not interposed at the boundary with the substrate. Therefore, unnecessary vibration unlike in the case of adhesion does not occur. Further, the piezoelectric fine powder used for the film formation can be formed without causing compositional deviation. PZ, which is the most common piezoelectric body and has a large piezoelectric effect
T is a composite oxide, which is usually a composition in which a trace amount of additive is mixed for the purpose of improving aging and temperature characteristics, and further improving piezoelectric characteristics such as increase of mechanical quality factor Qm, which greatly affects the sensitivity as a sensor. Is used. Since the film forming method according to the present embodiment can surely realize a complicated composition even in the state of a thick film, a piezoelectric vibrator excellent in aging change and temperature characteristics can be obtained as compared with other film forming methods. Further, when the injection hole of the nozzle used in the film forming method of the present embodiment is 0.3 mmφ, the dome-shaped piezoelectric spot film having a height of 50 μm and a half value width diameter of 100 to 200 μmφ as shown in FIG. 3 is obtained. When this is heat-treated, it becomes a material that can be piezoelectrically activated by polarization. The characteristics of the piezoelectric vibrator obtained by the subsequent steps described above are, first of all, a piezoelectric thick film element 4 having a truncated cone shape and polarized in a direction perpendicular to the bottom surface of the trapezoid, and secondly arranged around it. The void part 5,
Thirdly, the upper surface of the piezoelectric thick film element 4 and the upper surface of the insulating layer 6 are flush with each other, and the patterned upper electrode 7 is disposed integrally and steplessly over the entire upper surface of the piezoelectric element and a specific region of the insulating layer. It is configured.

Since the piezoelectric vibrator has a trapezoidal cross section according to the first configuration, it does not have a specific diameter. Therefore, even if both the thickness and the diameter are close to each other, the force of the thickness spreading vibration that resonates at the resonance frequency corresponding to the diameter is extremely smaller than that of the cylindrical shape. Therefore, only the intended thickness longitudinal vibration has high vibration efficiency. That is, it becomes possible to have a high Qm.
This means, for example, that a self-excited oscillation circuit having a piezoelectric oscillator as a circuit element is formed, and changes in the resonance frequency and resonance impedance of the piezoelectric oscillator are replaced with changes in the output frequency and output amplitude of the self-excited oscillation circuit. When a sensor that detects the mechanical characteristics of the load is constructed, the vibration mode jump phenomenon does not occur, and stable sensor operation can be expected. The vibration mode jump phenomenon is that self-excited oscillation is likely to occur in the vibration mode with the lower resonance resistance.For example, when an object to be detected is brought into contact with a piezoelectric vibrator and its mechanical characteristics are detected, the contact The operation increases the resonance resistance of the vibration mode of the piezoelectric vibrator that has been used until then. As a result, the resonance resistance of the vibration mode, which happened to be slightly higher than that of the self-excited oscillation, becomes relatively lower, causing oscillation in a new vibration mode, and the displacement direction of vibration suddenly changes. Or the oscillation frequency suddenly changes. Such a thing significantly reduces the reliability of the sensor, and the vibration mode jump phenomenon is a phenomenon that must be completely suppressed. It is clear that this problem can be solved by adopting the first configuration of the present embodiment, and the effect of this configuration becomes more remarkable as the size becomes extremely small as in the case of application to a micromachine. Is an easy guess. Furthermore, since the shortest distance between the upper and lower electrode ends is larger than the thickness between both electrodes by the first configuration, edge discharge is less likely to occur, and the additional effect of improving reliability can be obtained.

Next, the second structure, that is, the presence of the void portion, realizes a completely non-contact state with the insulating layer disposed around the second portion, and the Qm of the piezoelectric vibrator can be maintained in a high state. A vibrator sensor can be realized. Further, the thickness spreading vibration excited from the thickness longitudinal vibration through the Poisson's ratio is so small that the resonance sharpness Qm is negligible as described above, but it is not completely eliminated.

Therefore, if the insulating layer is in contact with the side wall of the piezoelectric vibrator, vibration leaks to the insulating layer, and the mechanical load against the thickness spreading vibration is increased by the Poisson's ratio. It becomes a load of vibration and becomes noise for sensing using the essential thickness longitudinal vibration.
Further, when an array type piezoelectric vibrator in which a large number of the single piezoelectric vibrators shown in FIG. 1 are arrayed is formed as shown in the following embodiment, leakage of vibration to the insulating layer is caused by another adjacent piezoelectric vibrator. This adversely affects the crosstalk characteristics between elements and significantly deteriorates the lateral resolution of the sensor. In the present embodiment, by implementing this second configuration, the lateral resolution of the sensor does not become worse.

In the third structure, that is, the patterned upper electrode having no step has no local deviation between the upper and lower electrodes, no electric field concentration occurs during polarization. Further, since the electric field concentration of the driving electric field does not occur, piezoelectric driving can be performed with a uniform polarization distribution with a uniform driving electric field, and vibration with high efficiency without unnecessary vibration can be excited. This makes it possible to realize highly reliable piezoelectric vibrator operation. In addition, in the third configuration, the patterned upper electrode is provided on the entire upper surface of the piezoelectric element, so that the area can be made larger than that of the energy trapping electrode. As a result, the electrostatic capacity of the piezoelectric vibrator can be made relatively large, and the S
/ N leads to improvement. Furthermore, when the capacitance of the energy trapping electrode is sufficient, no area other than the energy trapping electrode is required, and therefore the overall size of the piezoelectric vibrator can be reduced.

As described above, by including the three characteristic structures, unnecessary vibration, jumping of vibration modes, non-uniform piezoelectric operation due to electric field concentration, etc. do not occur, and thickness longitudinal vibration with large vibration efficiency Qm is highly reliable. It can be realized and can be applied to high-sensitivity micro piezoelectric sensors and micro piezoelectric transducers. In addition, by forming an array, it becomes possible to detect the linear distribution and surface distribution of the mechanical characteristics of the object with high resolution.

Naturally, various modifications and changes can be made to each structure of this embodiment. For example, the heat resistant substrate does not necessarily have to be silicon, and may be alumina or MgO.
Such a substrate may be used as long as it has heat resistance. Also,
The lower electrode is not necessarily limited to Pd / Ti, but Pt / Ti, Ag / Cu, Ir / Ti or Au / Cr.
Such a metal film having high adhesion may be used, or a single layer film of baked silver or baked platinum may be used as long as the adhesion is compensated. Further, the material of the piezoelectric thick film does not necessarily have to be PZT, and for example, a piezoelectric substance having a bismuth layer structure perovskite structure or a tungsten bronze structure may be used. Further, the patterning of the upper electrode is not limited to the method of etching using the platinum electrode as a mask, and a usual photolithography method or ion milling method may be used. The shape of the piezoelectric thick film is not necessarily limited to the truncated cone shape, and may be a truncated pyramid shape or an elliptical truncated cone shape.

Next, FIG. 8 shows a modification of the first embodiment.
A description will be given using (A) to (C). In this modification, the structure of the piezoelectric thick film having the frustum-shaped structure is elliptical (see FIG. 8).
(See (B)) and rectangular (see FIG. 8C). Generally, the electromechanical coupling coefficient of thickness spreading vibration is smaller in an ellipse or a prism than in a circle. Even if the shape of the circle is frustum-shaped, the efficiency of generating the thickness spreading vibration is considerably lowered, but if there is a part of the shape with good symmetry, such as a circle, the thickness spreading vibration is slightly excited by the ratio. On the other hand, if the elliptical shape or the rectangular shape, which is less symmetrical than the circular shape, is used as in this modified example, the local spreading vibration on the surface is less likely to occur. As described above, according to this modification, the vibration is further concentrated on the thickness longitudinal vibration, and the vibration efficiency is improved.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIG. 9 and its manufacturing method with reference to FIGS. The same members as those in FIGS. 1 to 6 are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, a pressure receiving portion 91 made of, for example, polyurethane, silicone resin or epoxy resin is arranged around the upper surface of the piezoelectric film thickness element on the upper surface of the micro-piezoelectric vibrator having the structure of the first embodiment (FIG. 1). It is a micro-piezoelectric sensor with the structure provided. In FIG. 9, reference numeral 92 is a second void portion,
Reference numeral 93 indicates a closed fine hole.

A method of manufacturing the micro-piezoelectric sensor having the structure of the second embodiment will be described below with reference to FIGS. Micro-piezoelectric vibrator according to Example 1 (FIG. 1)
Along the circumference of the upper surface of the piezoelectric thick film element 4 of No. 8 as in Example 1.
A resin material that melts at about 0 ° C. is applied in a molten state so as to be trimmed along the circumference of the upper surface of the piezoelectric thick film element 4 by using a microdispenser or the like, and is naturally cooled and allowed to cool.
The sacrificial layer 94 is formed (see FIG. 10A). The molten resin for the second sacrificial layer was hardened immediately after coating, so that it did not penetrate deep into the void. Next, the second sacrificial layer 94 is completely covered, and polyurethane, silicone, epoxy resin or the like is spotted around the upper surface of the piezoelectric element to the extent that the thickness of the second sacrificial layer covering portion on the void is not too thick. And then semi-cured at room temperature or about 50 ° C. to form the pressure receiving portion 91 (see FIG. 10B). Then, fine holes 93 are made with a needle at several places on the periphery of the pressure receiving portion 91 in the semi-cured state, and finally, the second sacrificial layer 94 is scattered through the fine holes 93 by heating to a temperature of 100 ° C. to 150 ° C. At this time, at the same time, the pressure receiving portion resin, which was in the semi-cured state, is completely cured and becomes chemically stable (see FIG. 10C). The operation of having such a configuration will be described below.

Even in the structure of the first embodiment (FIG. 1), there is no problem if the object to be detected is relatively soft or has a convex shape.
When the object is relatively hard and has a flat or concave shape, the vibrating end of the piezoelectric vibrator may not normally contact the object, and accurate detection may not be possible. Therefore, in the second embodiment, a convex pressure receiving portion as shown in FIGS. 9 and 10 is provided,
This is to always achieve a normal contact state with the object. The second sacrificial layer 94 is scattered and the second void 92 is
The reason for providing is that firstly, the peripheral portion of the pressure receiving portion 91 is provided on the insulating layer to provide a resistance against peeling or deformation due to the rubbing frictional force from the object on the pressure receiving portion 91, and secondly the piezoelectric thickness. This is because the pressure-receiving portion 91 on the membrane element and the pressure-receiving portion 91 on the insulating layer weaken the acoustic coupling and prevent the Qm of the piezoelectric vibrator from decreasing. Thirdly, the contamination of the body fluid or the like existing in the vicinity of the target object This is to prevent the substance from entering the void 5.

The third effect is due to the following reason. Second
The material of the sacrificial layer passes through the fine holes 93 provided in the pressure receiving portion 91 in a semi-cured state in advance by heating, and escapes to the outside of the hole. When the fine holes 93 cannot be escaped from the holes 93 and remain in the fine holes 93, the fine holes 93 are closed and solidified. Since the second embodiment can exert the above-described effects, a micro-piezoelectric sensor having high sensitivity and good chemical resistance with respect to detection of mechanical characteristics of an object such as a living body can be obtained.

Next, a modification of the second embodiment will be described with reference to FIG. In this modification, the pressure receiving portion 111 is arranged via an elastic member 112 joined to the piezoelectric thick film element 4. In addition,
In the figure, reference numeral 113 is a fine hole provided in the pressure receiving portion 111, and reference numeral 114
Indicates the second void portion. The micro-piezoelectric sensor having such a structure is manufactured as shown in FIGS.

That is, first, a crystallized glass such as ceramics of alumina or zirconia or a crystallized glass such as macol is finely processed and joined by a means such as adhesion, and the elastic member 112 is formed.
Is formed at a predetermined position on the patterned upper electrode 7 (see FIG. 12A). Then, the second sacrificial layer 94 made of a low melting point resin is applied to the lower outer peripheral portion of the elastic member 112 by a micro dispenser, and then a semi-cured resin film 115 made of polyurethane, silicone, epoxy resin or the like is formed as a pressure receiving portion ( See FIG. 12 (B). Furthermore, the second sacrificial layer is heated and heated.
The semi-cured resin film 115 is completely cured and the pressure receiving portion 111 is obtained (see FIG. 12C).

With such a structure, the pressure receiving portion 11
The volume ratio of a substance having a good vibration efficiency Qm in 1 is large, the Qm of the entire piezoelectric vibrator is larger than that of the case where the entire pressure receiving portion 111 is resin, and the sensitivity when used as a sensor is improved. Further, since the structure of the pressure receiving portion 111 is constant, the reproducibility of the structure and dimensions is enhanced, and the reproducibility of the piezoelectric vibrator characteristics is increased accordingly, and the matching with the operating circuit is improved.

Example 3 FIG. 1 shows Example 3 according to the present invention.
3 (A) to (D) will be described. Where Figure 13
13A is a top view of the linear array type micro-piezoelectric transducer according to the present invention, FIG. 13B is an enlarged top view of the unit piezoelectric vibrator P of FIG. 13A, and FIG.
(B) A sectional view of the unit piezoelectric vibrator 130 taken along line XX,
FIG. 13D is a sectional view taken along the line YY of FIG. Here, the plurality of unit piezoelectric vibrators 130 are arranged linearly on the substrate.

Reference numeral 131 in the figure indicates a surface oxide film 132 on the surface.
Is a Si substrate on which is formed. A two-layer lower stripe electrode (lower electrode) 133 made of, for example, Pd / Ti is formed on the substrate 131. On this lower electrode 133,
A piezoelectric thick film element 134 made of, for example, lead zirconate titanate (PZT) having a trapezoidal cross section, for example, a frustoconical structure, and polarized in the upper surface to the lower surface or in the opposite direction is provided. Then, a void 135 having a uniform thickness is formed along the entire circumference of the inclined surface of the piezoelectric thick film element 134, and an insulating layer 136 having an upper surface flush with the upper surface of the piezoelectric thick film is arranged around the void 135. . The patterned upper electrode 137 that integrally acts as an electric wiring is provided so as to straddle the void 135 over the entire upper surface of the piezoelectric thick film element 134 and a part of the upper surface of the insulating layer 136. There is. Here, the upper electrode 137 is electrically connected by the common ground electrode 138 and is connected to all unit piezoelectric vibrators.
130 is grounded. In addition, a metal such as gold, silver, platinum, or palladium, which is stable against heat, is formed in a projection shape by a jet printing method on the end portion in the length direction of the lower electrode 133, and the height is about 50 μm. Lower electrode protrusions 139 are formed. Reference numeral 140 in the figure denotes a lower electrode projection coating electrode.

The linear array type micro-piezoelectric transducer having the above structure is manufactured as follows. First, the lower electrode 133 is formed on the Si substrate 131 on which the surface oxide film 132 is formed.
To form. Next, a metal, such as gold, silver, platinum, or palladium, which is stable against heat, is formed on the end portion in the length direction of the lower electrode 133 in a projection shape by a jet printing method and has a height of 50 μm. The original shape of the lower electrode protrusion 139 is formed. Subsequently, the original shape of the piezoelectric thick film element 134 made of PZT is formed by the jet printing method on the lower electrode 133 avoiding the vicinity of the original shape of the lower electrode protrusion 139. The nozzle used in the jet printing method has a fine powder injection hole having a slit shape, for example, a length of 3 mm,
Those having a width of 0.15 mm are preferable.

Immediately after being formed by this nozzle, the thick film has a ridge shape with a half width of 0.12 mm, a height of 50 μm and a length of about 3 mm, and has no upper surface. Next, heat treatment is performed at 500 ° C. to 800 ° C., adhesion of the PZT film to the substrate, interparticle bonding force,
Modify crystallinity. Then, the molten sacrificial layer material is applied onto the ridge-shaped piezoelectric element original shape after the heat treatment using a microdispenser. The molten sacrificial layer material flows down from the top of the ridge along the slope of the ridge. Then, it is hardened by natural cooling to form a sacrificial layer having a film thickness of about 10 μm.

Next, a resin material for forming an insulating layer, for example, a resin liquid such as epoxy, urethane, or phenol is applied to the substrate 131.
To 50 .mu.m to 80 .mu.m on average, all the ridge-shaped piezoelectric element prototypes and the lower electrode projections 139 prototypes are uniformly applied and coated. As in the third embodiment, the final thickness of the piezoelectric thick film element 134, the lower electrode projection 13
When the height of 9 and the thickness of the insulating layer 136 are both about 40 μm, the minimum thickness of the resin film is 45 μm.
It goes without saying that it may be a roughened state.

Next, the insulating layer prototype is cured at room temperature or light and polished to flatten the entire surface to a thickness of about 40 μm, and thereafter, as shown in FIG. 13B, the exposed piezoelectric thick film is polished. A metal film in which the lower electrode protrusion coating electrode 140 is connected to each of the element 138 and the lower electrode protrusion 139 in a strip shape, a piezoelectric film, an insulating layer sandwiched between them, and a metal film in a strip shape are provided over the surface of the sacrifice layer. , A DC voltage of about 4 kV / mm is applied between the two strip-shaped metal films to polarize the piezoelectric thick film element 138 to a piezoelectrically active state. Then, the upper electrode 137, the lower electrode protruding coating electrode 140, and the common ground electrode 136 for setting all of the upper electrode 137 to the common ground potential are formed by using a normal photolithography process. Finally, above the melting temperature of the sacrificial layer resin,
For example, the sacrificial layer resin is completely scattered and removed by heating at 100 ° C. to 150 ° C. to form the void portion 135. The linear piezoelectric vibrator array 141 having the structure shown in FIG. 12A manufactured by the above manufacturing method has the following actions and effects.

That is, the sectional shape of the piezoelectric vibrator is trapezoidal,
Since there is a void around it, crosstalk between the piezoelectric vibrators becomes extremely small. In addition, since the piezoelectric thick film element has no residual cutting strain or microrack unlike the case of dicing as a method of manufacturing the piezoelectric thick film element, the change over time of a single piezoelectric vibrator is reduced and the reliability is extremely improved. These individual piezoelectric vibrators are arranged in a straight line, and when this linear piezoelectric vibrator array is brought into contact with an object, the vibration frequency and resonance resistance of each of the linearly arranged piezoelectric vibrators become independent. The piezoelectric vibrator has a value according to the elastic property of the object in each part of the object with which it comes into contact, and the mechanical characteristics of the object, such as the linear distribution of elastic modulus and viscosity, can be known by the difference of these values. become. The resonance frequency and resonance resistance of each piezoelectric vibrator are trapezoidal, and since each piezoelectric vibrator is acoustically isolated by the air gap layer, crosstalk between piezoelectric vibrators is extremely small. Therefore, the resolution in the linear direction becomes large, and the linear mechanical characteristic distribution in the minute linear region of the object can be detected with high resolution. Further, by scanning this in the direction perpendicular to the arrangement direction of the piezoelectric vibrators, surface information can be obtained.

Next, FIG. 14 shows a modification of the third embodiment.
Will be explained. However, the same members as those in FIG. 13 are designated by the same reference numerals and the description thereof will be omitted. The basic structure of this modification is exactly the same as that of the third embodiment, except that the pressure receiving portion / acoustic matching layer 145 is additionally provided on the upper surface of the piezoelectric vibrator. FIG. 14 is a diagram comparing with a sectional view of a single piezoelectric vibrator of Example 3 (FIG. 13D). The trapezoidal piezoelectric thick film element 134 in which the first void portion 146 is arranged on the slopes on both sides, the acoustic impedance of the object having the second void portion 147 such as an epoxy resin and the acoustic impedance of the piezoelectric element. The pressure-receiving portion / acoustic matching layer 145 having an acoustic impedance close to the geometric mean extends over the piezoelectric vibrator upper surface portion, the insulating layer 136, and the lower electrode projection covering electrode (not shown) to a specific thickness, that is, a quarter It is arranged with a thickness of one wavelength. With such a configuration, it is possible to realize an array type micro-piezoelectric transducer that detects a tomographic image of an object even when the object has a different acoustic impedance from the piezoelectric thick film element like a living body.

(Fourth Embodiment) A fourth embodiment according to the present invention will be described with reference to FIGS. Where Figure 15
15A is a side view of the array type micro-piezoelectric transducer along the outer peripheral surface of the cylinder according to the fourth embodiment, FIG. 15B is a top view of a single piezoelectric vibrator, and FIG. 15C is FIG. 15B. 15 is a cross-sectional view taken along the line XX of FIG.
It is sectional drawing which follows the Y line.

Reference numeral 151 in the figure denotes a cylindrical insulating substrate (cylindrical substrate) made of, for example, free-cutting ceramics, Macor and having an outer diameter of 5 mm and a length of 5 mm. On this cylindrical substrate 151,
The lower electrode 152 has a width of 80 μm, a length of 5 mm, and a thickness of 10 μ
m gold stripe electrodes are formed at intervals of 120 μm by the jet printing method. A piezoelectric thick film element 153 made of, for example, lead zirconate titanate (PZT), which has a trapezoidal structure in section, for example, a truncated cone shape, and is polarized from the upper surface to the lower surface, or in the opposite direction, is formed on the lower electrode 152.
Is provided. Then, a void 154 having a uniform thickness is formed along the entire circumference of the inclined surface of the piezoelectric thick film element 153, and the insulating layer 15 having the upper surface flush with the upper surface of the piezoelectric thick film is formed around the void portion 154.
5 are arranged. A patterned upper electrode 156 that integrally acts as an electric wiring is provided so as to straddle the void 154 over the entire upper surface of the piezoelectric thick film element 153 and a part of the upper surface of the insulating layer 155. There is. Where the upper electrode 15
6 is electrically connected by a common ground electrode 157, and the upper electrodes of all unit piezoelectric vibrators 158 are grounded. In addition, a metal such as gold, silver, platinum, or palladium, which is stable against heat, is formed in a protrusion shape by a jet printing method on the end portion in the length direction of the lower electrode 152, and the height thereof is about 50 μm. The lower electrode protrusions 159 are formed. Note that reference numeral 16 in the figure
Reference numeral 0 indicates a lower electrode projection coating electrode, reference numeral 161 indicates a ground side wiring, reference numeral 162 indicates a drive signal input / output wiring, and reference numeral 163 indicates a wiring coating code.

The array type micro-piezoelectric transducer having such a structure is manufactured as follows. First, on the cylindrical substrate 151, the lower electrode 152 has a width of 80 μm and a length of 5 m.
Gold stripe electrodes of m and 10 μm in thickness are formed by jet printing at intervals of 120 μm. This forming method is as follows. The cylindrical substrate 151 is rotated by 120 μm at the outer circumference of the cylinder, and the injection hole has a width of 90 μm.
A jet printing film is formed using ultrafine gold powder using a nozzle having a length of 5 mm. Lower electrode protrusions 159 are formed in the film thickness direction at the end portions of each of the striped electrodes, but the method of forming the lower electrode protrusions 159 is the same as that of the third embodiment, so the description thereof is omitted here.

Next, the stripe-shaped P having a trapezoidal cross section is used.
A piezoelectric thick film element 154 made of ZT is formed. That is, jet printing film formation is performed using PZT fine powder using a nozzle having a shape of the injection hole having a width of 100 μm and a length of 5 mm. The full width at half maximum of the thick film immediately after being formed by this nozzle is 1
It has a ridge shape of 00 μm, height 50 μm, and length of about 5 mm, and there is no upper surface. Then, heat treatment is performed at 500 ° C. to 800 ° C. to modify the adhesion of the PZT film to the substrate, the interparticle bonding force, and the crystallinity. Then, the molten sacrificial layer material is applied to the original shape (not shown) of the piezoelectric thick film element 154 in the ridge shape after the heat treatment by using a microdispenser. The molten sacrificial layer material flows down from the top of the ridge along the slope of the ridge. Then, it is hardened by natural cooling to form a sacrificial layer having a film thickness of about 10 μm. Next, a resin material for forming an insulating layer, for example, a resin liquid such as epoxy, urethane, or phenol resin is applied to the cylindrical substrate 151.
All the ridge-shaped piezoelectric element prototypes and the lower electrode protrusions 159 prototypes are evenly dip-coated so that the average height from the surface is 50 μm to 80 μm.

Next, the original shape of the insulating layer is cured at room temperature or light, and the outer periphery is polished to flatten the entire surface to a thickness of about 40 μm.
After that, the piezoelectric thick film element 153 and the lower electrode protrusion 159 exposed by polishing are respectively attached to the lower electrode protrusion coating electrode 160.
A metal film which is connected in a strip shape, a piezoelectric thick film element, an insulating layer sandwiched between them, and a strip-shaped metal film across the surface of the sacrifice layer, and the strip-shaped metal films are arranged at a distance of 4 kV.
A piezoelectric thick film element 15 is polarized by applying a DC voltage of approx.
Set 3 to be piezoelectrically active. Then, a common ground electrode 157 for making all of the upper electrode 156, the lower electrode protruding coating electrode 160, and the upper electrode 156 have a common ground potential is formed by using a curved photolithography process. Finally, the sacrifice layer resin is heated to a melting temperature or higher, for example, 100 ° C. to 150 ° C. to completely scatter and remove the sacrifice layer resin to form the void 35. Finally, the drive signal input / output wiring 162 and the ground side wiring 161 are attached by wire bonding.

Regarding the operation of the cylindrical outer peripheral surface array type array type micro-piezoelectric vibrator array manufactured by the above-mentioned manufacturing method,
This will be described with reference to FIG. The actual number of unit piezoelectric vibrators in the size of this embodiment is 128, but in this model diagram, the number is 64, and 8 units are simultaneously driven. In addition, the driving time is slightly deviated between the eight driving at the same time, and the wave fronts of the vibration waves (ultrasonic waves) emitted from the eight unit piezoelectric vibrators are circled as shown in FIG. Has become. Therefore, these wave fronts are so-called phased array oscillators that are combined to form a convergent oscillatory wave toward the focal point. If the unit piezoelectric vibrators are shifted by one unit as one group of these eight and are sequentially scanned, a vibration wave (ultrasonic wave) beam scanning function equivalent to so-called mechanical sector scanning can be exhibited. Moreover, since it is an electronic scan, there is no concern about uneven rotation like mechanical sector scanning, so a high-resolution rotary encoder is not required, and since there is no shielded piezoelectric vibrator in any direction of 360 degrees, the desired direction is always available. An ultrasonic image of

Next, a modified example of this embodiment will be described with reference to FIG. This modification is the same as the fourth embodiment in that the unit piezoelectric vibrators are arranged along the outer peripheral surface of the cylinder, but is different in that the outer peripheral surface of the cylinder is a curved surface curved with respect to the cylinder axis. There is a difference between the use of an insulating substrate in which the outer peripheral surface of the cylinder is curved as a curved surface with respect to the axis of the cylinder as the substrate, and the surface flattening after curing the insulating layer resin is performed by the outer peripheral curved polishing. Is the same as. This modification has the effect of converging the ultrasonic beam in the cylindrical axis direction by this curved surface and further improving the lateral resolution.

As a further modification, a structure in which an acoustic matching layer is provided as in the modification of the third embodiment (FIG. 14) is naturally conceived, and the same action and effect are not obtained. Needless to say.

(Fifth Embodiment) FIG. 1 shows a fifth embodiment according to the present invention.
This will be described with reference to 8 (A) and (B). Where Figure 18
18A is a top view, and FIG. 18B is a sectional view taken along line XX of FIG.

Reference numeral 181 in the drawing denotes a Si substrate having a surface oxide film 182 formed on its surface. On this board 181, a decoder
Circuits such as 183 and 184 are monolithically integrated.
On the substrate 181, a lower stripe electrode (lower electrode) 185 made of a metal thin film such as palladium whose end is connected to the decoder 184 is formed. This lower electrode 185
A piezoelectric thick film element 186 is formed on the top. This piezoelectric thick film element 186 has voids 18 of uniform thickness over the entire circumference of the inclined surface.
7 is formed, and an insulating layer 188 having an upper surface flush with the upper surface of the piezoelectric thick film element 186 around it is formed. A patterned upper electrode 189 acting integrally as an electric wiring is formed so as to straddle the void 187 over the entire upper surface of the piezoelectric thick film element 186 and a part of the upper surface of the insulating layer 188.

The piezoelectric vibrator two-dimensional array having such a configuration is manufactured as follows. First, circuits such as decoders 183 and 184 are monolithically integrated on a substrate 181 on which a surface oxide film 182 is formed, a lower electrode 185 is formed, and a bottom circle diameter of 120 μmφ is formed on the lower electrode 185 by a jet printing method.
A conical antiferroelectric material having a height of 50 to 100 μm, for example, a lead zirconate spot film is formed. Injection hole diameter 150μmφ
The nozzle is used to jet print fine piezoelectric powder. This is heat-treated at 500 ° C. to 800 ° C. to improve the adhesion between the piezoelectric body and the substrate, the bonding force between the piezoelectric body particles, and the crystallinity. Then, a paraffin resin having a melting point of about 80 ° C. is applied drop-wise onto a conical piezoelectric spot film by a microdispenser.

At this time, the conical PZT spot film is preferably heated to 40 to 60 ° C. for each substrate. The entire surface of this is coated with an epoxy resin or polyurethane resin liquid and cured at room temperature. After curing, the entire surface is flattened by polishing, and then the end portion is connected to the decoder circuit 183 by using a normal photolithography process, and first, the entire surface electrode is applied so as to cover the entire upper surface portion of the piezoelectric thick film element 186 exposed by polishing. To form. And this upper whole surface electrode and each lower electrode
A direct current voltage is applied between the piezoelectric element 185 and the piezoelectric element 185 to polarize all the piezoelectric thick film elements 186 to make them piezoelectrically active. Then, using a normal photolithography process, the upper entire surface electrode is formed into a stripe upper electrode 189.
And Finally, the sacrifice layer is scattered and removed by heating at 100 ° C. to 140 ° C. to form the void layer 187.

The operation of the piezoelectric vibrator two-dimensional array having the simple matrix structure thus configured will be described below.
One of the lower electrodes 185 by the decoder 184, for example, as shown in FIG.
Of a is selected. Similarly the upper electrode by the decoder 183
One of 189, for example, b of FIG. 11 is selected. Then, a pulse voltage of 1/2 of the driving voltage is applied to one of the selected stripe electrodes, and a pulse voltage of -1/2 is applied to the other stripe electrode, and the piezoelectric vibrator c in which both stripe electrodes intersect
A pulse voltage just equal to the drive voltage is applied to.
As a result, the piezoelectric vibrator c resonates and vibrates and radiates ultrasonic waves to the object. Then, the vibration response signal from the object enters the same piezoelectric vibrator c and is output via the stripe electrodes a and b. By inputting a signal to the decoder and sequentially selecting all or part of the piezoelectric vibrators and correlating the signal output between the selected position and the selected pair of stripe electrodes, the mechanical characteristics of the object A two-dimensional distribution image of is obtained.

Although the structure of the present embodiment is shown in FIG. 11, the structure is not limited to this, and a pressure receiving portion / acoustic matching layer is additionally provided on the upper surface of the piezoelectric vibrator as in the modification of the third embodiment. It goes without saying that the same actions and effects can be obtained.

(Embodiment 6) FIG. 1 shows Embodiment 6 according to the present invention.
9 shows. The same members as those in FIG. 18 are designated by the same reference numerals and the description thereof will be omitted. Reference numeral 191 in the figure denotes a silicon substrate, which has an acoustic impedance Zp layer 191a and an acoustic impedance Zm layer 191.
b, acoustic impedance Zi layer (silicon oxide film layer) 191
It consists of c. A lower electrode 192 composed of a Pd / Ti bilayer film is formed on one surface of the substrate 191, and a surface oxide film layer is formed on the other surface as deep as possible, and a part thereof is made convex by chemical etching. Further, on the convex member 193, the convex member
The side that contacts 193 is the acoustic impedance Z1 of the convex member.
And the acoustic impedance Zg on the side in contact with the object 194 is approximately equal to
A pressure receiving member 195 having an acoustic impedance of 1.2 to 5 times o is provided. This becomes the pressure receiving portion 196 that directly contacts the object.

The pressure receiving portion 196 is obtained by the following method. The acoustic impedance of Zl (= 14 × 10 ⁶
20/40% by weight of a low melting glass powder, for example, borosilicate lead glass powder, in a resin solution of epoxy, urethane, silicone or the like, and the degassed slurry of the convex member 193 Apply on top. When this is left to stand for a long time, the low-melting-point glass powder particles settle down, and the glass powder particles in the portion in contact with the convex member 193 have about 10 particles.
0%, and the resin contacting the object 194 is 100%
%, The density of the glass powder particles changes from 0 to 100%. The resin cured in such a state is heat-treated at about 600 ° C. for a short time of 1 minute or less to scatter and remove the resin component. At this time, part of the low-melting glass is melted and sufficient wetting with the surface of the convex member 193 is realized.

Further, as the glass powder particles are separated from the surface of the convex member 193, the glass powder particles are changed from the molten state to the sintered state between the powder particles, and the interparticle voids are increased, but the interparticle bonding force is not lost. To the glass film in such a state, the same resin solution that has been thermally decomposed and removed is applied until the upper surface of the glass film is completely buried. The pressure receiving member 195 thus obtained has a glass melt film in the portion in contact with the surface of the convex member 193 and in the vicinity thereof, and the glass powder particles form pores around the particles in the interparticle sintering state as they are separated from the film. Remaining, the material structure is obtained by filling the void area with resin. The glass powder density decreases with increasing distance, and finally, the vicinity of the surface contacting the object 194 is only resin.

When the member of the resin 100 is exposed on the surface, for example, when the object 194 is a living body, amplitude impedance matching occurs with the acoustic bonding layer, and the vibration response (reaction force) from the surface of the object 194. Cannot be obtained, and the mechanical properties of the surface of the object cannot be detected. Therefore, polishing is continued from the surface, and when the acoustic impedance Zo of the object 194 reaches 1.2 to 3 times, the polishing is stopped. Therefore, the substrate 191 is the Z side on which the lower electrode 192 is formed.
Zi layer 19 having convex member 193 on the surface opposite to p 191a
1c and a Zm layer 191b in the middle thereof.

Therefore, the acoustic impedance also shows different values for each layer. The Zp layer 191c is amorphous and its acoustic impedance is about 15 × 10 ⁶ Kg / s · m. On the other hand, the piezoelectric material is, for example, PZT 35 × 10.
^{It is 6} Kg / s · m. Since silicon is close to the acoustic impedance of the piezoelectric body, the piezoelectric thick film element 186 can be connected to the pressure receiving portion 196.
The acoustic impedance changes almost continuously until. Further, both the silicon and the silicon oxide film have a very high vibration efficiency Qm, and the vibration excited by the piezoelectric thick film element 186 reaches the end surface of the pressure receiving portion with almost no loss. Lower electrode 19
On the second side, a piezoelectric thick film is formed by jet printing, heat treatment, sacrifice layer formation, insulation layer 188 formation, surface flattening by polishing, upper electrode 189 formation, polarization, upper electrode 18
The piezoelectric thick film element 186, the void portion 187, and the insulating layer 188 are formed together by performing the same steps as those in the above-described embodiments of patterning 9 and forming the void portion 187 by removing the sacrificial layer. Next, the operation and effect of the sixth embodiment will be described.

(Operation) The ultrasonic vibration excited in the piezoelectric thick film element is the Zp layer 191a having the same acoustic impedance as the piezoelectric piezoelectric element 186, and the Zm layers 191b and Zm having the average Zm continuously changing from Zp. Pressure receiving part 19 that changes continuously from
The Zi layer 191c having the same acoustic impedance Z1 as that of 6 propagates through the substrate continuously distributed in the thickness direction. Specific examples of these materials include a silicon single crystal part as the Zp layer 191a, an amorphous silicon oxide film as the Zi layer 191c having an acoustic impedance Zl, and a Zm layer having Zm.
The layer 191b impinges on the small, insufficiently oxidized silicon substrate 191 with little loss.

This incident ultrasonic wave propagates through the substrate and reaches the convex member 193. The acoustic impedance changes continuously on the surface of the convex member 193, and the pressure contact surface with the object 194 is 1.2 to 3 times the acoustic impedance of the object 194. Therefore, in a state where the object 194 is not in contact with pressure, ultrasonic waves are reflected on the inner surface of the pressure receiving portion by nearly 100%, and thus resonate at a frequency corresponding to the total thickness of the piezoelectric thick film element 186 and the substrate and the average elastic constant, There is no response signal corresponding to the echo signal. If the acoustic impedance of the object is Zo when the object is in contact with pressure, | Zo-Zc |
The light is reflected at the interface between the object 194 and the pressure receiving portion 196 at a ratio of / | Zo + Zc |. If Zc = 3Zo, the reflectance is 50.
%, And half of the ultrasonic energy propagates in the object. If there is a foreign object with a different acoustic impedance on the fault of the object 194, it will be reflected at the boundary surface and
Half of that is incident on 196. Therefore, if there is no acoustic loss in the object 194, 1/4 of the ultrasonic energy generated by the piezoelectric thick film element 186 enters the piezoelectric vibrator as an echo signal. Actually, since the propagation loss of ultrasonic waves in the object is large, the ultrasonic energy that is incident on the piezoelectric vibrator as an echo signal is extremely small. On the other hand, if an attempt is made to reduce the reflectance and increase the energy of the echo signal, the reaction force from the object received by the pressure receiving section 196 becomes small and the detection sensitivity of the mechanical characteristics of the surface of the object becomes extremely small. .

When Zc = 1.2Zo, the reflectance is 10%, 90% of the ultrasonic energy propagates into the object, and 10% contributes to the formation of standing waves. Even if the reflectance is about 10%, the piezoelectric thick film element 189, Zp layer 191a, Zm
Since both the layer 191b and the convex member 193 have small propagation loss with respect to ultrasonic waves, the function of the piezoelectric thick film element 186 can be exhibited. However, if smaller than this, the piezoelectric thick film element due to the contact pressure of the target object
Changes in the resonant frequency and resonant resistance of the 186 are hardly detected. Therefore, a pressure-receiving member material is selected so that the ultrasonic reflectance at the interface between the pressure-receiving portion 196 and the object 194 is in the range of 0.5 to 0.1, and the acoustic impedance of the intermediate layer is silicon single crystal. A material that continuously changes from the impedance Zp to the acoustic impedance Zl of the pressure receiving member is used.

(Effect) With the above-described structure and operation,
Using the same piezoelectric thick film element, the vibration response of the piezoelectric thick film element on the surface of the object and the echo signal from the discontinuous boundary surface of the acoustic impedance inside the object are detected and analyzed in a time series. It is possible to achieve the purpose of detecting the mechanical properties of the surface and the inside.

Each of the embodiments described above includes the following inventions. 1. [Configuration] In a micro-piezoelectric vibrator using resonance characteristics of thickness longitudinal vibration, a substrate having a lower electrode on its surface and a substrate formed on the lower electrode and having a trapezoidal cross section and being polarized in the thickness direction A piezoelectric thick film element, an insulating layer formed to surround a side wall of the piezoelectric thick film element with a gap therebetween and having a surface substantially parallel to the substrate, and the piezoelectric thick film. A micro-piezoelectric vibrator comprising an upper electrode integrally provided on an upper surface of an element and a surface of the insulating layer.

Example 1 corresponds. The trapezoid used in the present invention is a simplified representation of a trapezoid having a top surface with a plane obtained by slicing a three-dimensional structure such as a cone, an elliptic cone, a quadrangular pyramid, or a triangular pyramid in parallel with the bottom surface thereof. ing.

[Operation] Since the piezoelectric thick film element has a trapezoidal shape, resonant vibration in the thickness direction resonates at a frequency at which the distance between the upper surface and the lower surface corresponds to the distance. In the spreading vibration, since the cross-sectional dimension of the cross section perpendicular to the thickness direction of the piezoelectric thick film element is not constant over the entire thickness, the resonance frequency is widely distributed, and the sharpness of resonance (= mechanical quality factor Qm) is also small. Therefore, it can be considered that only the thickness longitudinal vibration is excited, and stable thickness longitudinal vibration occurs. Further, since the cavity formed so as to surround the side wall of the piezoelectric thick film element is formed between the piezoelectric thick film element and the insulating layer, the vibration of the piezoelectric thick film element is not damped.

[Effect] As described above, since only the thickness vibration is efficiently excited and the resonance sharpness is increased, the sensitivity of the sensor is improved. Further, since the electrodes are formed on the entire surface, there is no useless area, and the electrode area can be made relatively large compared to the energy confining electrode, so that the capacitance can be increased and the S / N of the sensor can be improved. Furthermore, since there is a void, the vibration of the piezoelectric vibrator is not damped, so a large Qm is obtained, and the sensitivity as a sensor is improved.

2. [Structure] In the micro-piezoelectric vibrator according to the first aspect, the upper electrode is integrally formed with a full-surface electrode portion formed on the entire upper surface of the piezoelectric thick film element,
A micro-piezoelectric vibrator, comprising: a patterned wiring that is drawn out from at least one location of the entire surface electrode. Example 1 is applicable.

[Function] Since the electrodes are formed on the entire upper surface of the piezoelectric thick film element, a region where no electrodes are formed unlike the energy confinement oscillator is not required. Moreover, since the wiring is patterned, the degree of freedom in arrangement and shape is increased.

[Effect] The size of the piezoelectric vibrator including the wiring can be reduced. Further, since the wiring has a large degree of freedom in arrangement and shape, it can be applied to various piezoelectric sensors.

3. [Structure] The micro-piezoelectric vibrator according to the above-mentioned item 2, wherein the heights of the entire surface electrode and the patterned wiring from the surface of the substrate are equal to each other. Example 1 is applicable.

[Operation] Since the upper surface of the piezoelectric thick film element and the upper surface of the insulating layer are processed to have the same height, and the upper electrode is integrally arranged, there is no step between the electrodes.

[Effect] Since there is no step, it is possible to prevent electric field concentration between the lower electrode and the step portion of the upper electrode. Therefore, a piezoelectric vibrator having a large mechanical quality factor Qm and a high reliability can be obtained. can get.

4. [Structure] The trapezoidal piezoelectric thick film element described in the above paragraph 1 and polarized in the thickness direction has a circular or elliptical cross section in a direction perpendicular to the thickness direction of the piezoelectric thick film element. A micro piezoelectric vibrator characterized in that Example 1 corresponds.

[Operation] The shape of the upper entire surface electrode is also circular or elliptical. Further, since there is no ridgeline on the slope of the trapezoid, the piezoelectric thick film element has a uniform thickness of the cavity formed so as to surround the side wall. Further, since the radius of the elliptical shape is not determined as compared with the circular shape, the spreading vibration is further suppressed.

[Effect] The structure of the void portion and the structure of the piezoelectric thick film element itself are simplified, and rubbing between the slope of the piezoelectric thick film element and the slope of the insulating layer does not occur, thus improving reliability and facilitating manufacturing. , The manufacturing cost is also reduced. In addition, the vibration efficiency (Qm) of the thickness longitudinal vibration of the piezoelectric vibrator is further improved by making the elliptical shape in which the spreading vibration is less likely to be excited, the sensitivity is improved, and the reliability as a sensor is also improved.

5. [Structure] In the micro-piezoelectric sensor having the micro-piezoelectric vibrator described in the above item 3 as a basic structure, the structure of the micro-piezoelectric sensor is such that a part of the upper surface of the piezoelectric element described in the above item 1 A micro-piezoelectric sensor having an upper electrode disposed so as to extend over both of a part of the upper surface of the layer. Example 1 corresponds.

[Operation] Since the upper surface of the piezoelectric thick film element and the upper surface of the insulating layer have the same height with respect to the substrate by the flattening process, the formed upper electrode has no step and the distance between the upper and lower electrodes is uniform. Since electric field concentration does not occur, the polarization state becomes uniform in the element, and non-uniform piezoelectric operation or dielectric breakdown due to the driving electric field does not occur.

[Effects] Electric field concentration does not occur during the piezoelectric thick film element, polarization, and driving, and uniform piezoelectric characteristics are obtained, and stable and highly reliable piezoelectric vibrator operation can be realized.

6. [Structure] The plurality of micro-piezoelectric vibrators described in the above item 1 are arranged in an array, and each insulating layer, each substrate and each upper electrode are integrally formed with each other, and each lower electrode is separated and insulated from each other. An array-type micro-piezoelectric vibrator, which is characterized in that it is arranged.

The second embodiment corresponds. Array-like means linear (Example 2), planar (Example 3), cylindrical (Example 4)
However, the array shape is not limited to this, but a spherical shape,
The shape is not limited to the above-mentioned array shape even if it is a cross shape or a turret shape, as long as the piezoelectric thick film elements around which voids are arranged can be arranged.

[Operation] It is possible to independently detect a change in resonance frequency and a change in resonance resistance when the piezoelectric vibrators at respective positions arranged in an array contact an object. Correspondence between these signals and the position of the piezoelectric vibrator is established. It is also possible to extract and analyze an echo signal from the vibration response when the object is touched. Further, since the insulating layer is arranged so as to surround the perimeter of each unit, crosstalk is prevented and excessive force is applied to the unit when an object contacts the unit. Is prevented.

[Effect] By detecting changes in the resonance frequency and resonance resistance of the piezoelectric vibrator at each position and correlating these signals with the position of the piezoelectric vibrator, the characteristics of the object corresponding to the array shape can be obtained. The distribution will be understood. Further, it is possible to prevent the cross stroke between the vibrators and prevent the vibrators from being broken by an external force.

7. [Structure] The array-type micro-piezoelectric vibrator according to the sixth aspect, wherein each of the lower-electrodes of the micro-piezoelectric vibrator has a lower electrode protrusion penetrating the insulating layer. Child.

[Operation] The lower electrode is electrically connected through the lower electrode protrusion provided through the insulating layer.

[Effect] Since the lower electrode projection for establishing conduction with the lower electrode is provided so as to be exposed on the surface of the insulating layer in advance, the wiring work is easy and the voltage application to the lower electrode is performed. Can be reliably performed.

8. [Structure] The array-type micro-piezoelectric vibrator according to the sixth aspect, wherein the plurality of array-like arrays are linear.

The second embodiment corresponds. Further, although the shape of each piezoelectric thick film element is a square having a large aspect ratio in the second embodiment, it may be a truncated cone or a square trapezoid. [Operation] The difference between the resonance frequency and the resonance resistance of each of the piezoelectric vibrators arranged in a line corresponds to the linear distribution of the elastic characteristics of the object. The piezoelectric vibrator has a trapezoidal shape, and there are voids around it, and the cross stall between piezoelectric vibrators is small.

[Effect] The linear distribution of the elastic characteristics of the object can be known from the relationship between the vibration frequency of each of the piezoelectric vibrators arranged linearly, the resonance resistance, and the position of the piezoelectric vibrator. Further, by scanning this in the direction perpendicular to the arrangement direction of the piezoelectric vibrators, surface information can be obtained. Since the crosstalk is small, an elastic property distribution image of the object having excellent lateral resolution can be obtained.

9. [Structure] The array-type piezoelectric transducer described in the item 6, wherein the plurality of array-shaped arrays are arranged along the outer peripheral surface of the cylinder. Example 3 corresponds.

[Operation] The vibration direction of the piezoelectric vibrator is the radial direction, and it is possible to make a cylindrical face-to-face contact with an object through an ultrasonic wave propagation medium such as water. A plurality of strip-shaped piezoelectric vibrators are sequentially operated to radially scan the vibration radiation beam, that is, the ultrasonic beam.

[Effect] An ultrasonic tomographic image of the inner wall of the tubular structure such as inside the body cavity can be obtained. Since each transducer has a trapezoidal cross section and a void around it, crosstalk between the transducers is small and a high-resolution tomographic image can be obtained.

10. [Structure] The array-type piezoelectric transducer described in the above item 6, wherein the plurality of array-like arrays are two-dimensional planes. Example 4 corresponds.

The shape of each piezoelectric vibrator may be an ellipse or a square. Both the lower electrode and the upper electrode are stripe-shaped and are arranged orthogonally to each other with a piezoelectric thick film interposed therebetween. Further, both the lower electrode and the upper electrode are connected to the decoder integrally formed on the substrate.

[Operation] A plurality of piezoelectric transducers are arranged in a two-dimensional plane, and one of the plurality of piezoelectric vibrators arranged in the plane can be driven sequentially or simultaneously.

[Effect] Each of the plurality of piezoelectric vibrators arranged in a two-dimensional plane has a trapezoidal sectional structure and a void is arranged around the trapezoidal structure, so that crosstalk between the piezoelectric vibrators is small. It is possible to measure the surface distribution of the elastic properties of the object with excellent surface resolution. It is also possible to obtain a surface distribution tomographic image of an object by injecting an oscillating wave (ultrasonic wave) emitted by a piezoelectric vibrator into the object via an ultrasonic wave propagation medium such as water and analyzing the echo signal. Become.

11. [Structure] The array type piezoelectric transducer described in the above item 8, wherein an outer peripheral surface of the cylinder has a structure curved with respect to a cylinder axis. A modified example of the third embodiment corresponds.

[Operation] The vibration wave (ultrasonic wave) radiated from the piezoelectric vibrator converges according to the curved curvature.

[Effect] Therefore, the resolution in the axial direction of the cylinder is improved. Further, since each piezoelectric vibrator has a trapezoidal trapezoidal shape, the same effect as that of the above item 9 can be obtained.

12. [Structure] The micro-piezoelectric sensor described in the fifth item, wherein the micro-piezoelectric sensor has a structure in which a pressure receiving portion is provided on an upper surface of the piezoelectric element. Example 2 is applicable. The pressure receiving portion is formed on the top surface of the piezoelectric element of the micro-piezoelectric vibrator described in the first embodiment.

[Operation] The pressure receiving portion can accurately contact the object. [Effect] The mechanical characteristics of the object can be detected with high accuracy.

13. [Structure] The micro-piezoelectric sensor according to item 11, wherein the pressure receiving portion has a filling member that fills the surface thereof with a fine hole penetrating in the thickness direction and a substantially fine hole. The second embodiment is applicable.

[Operation] When forming the pressure receiving portion, the sacrificial layer material serves as a path for scattering the sacrificial layer material, and the sacrificial layer material for the final scattering does not pass through the substantially minute holes and remains in the minute holes as a filling member.

[Effect] The fine pores are necessary because they serve as passages when the sacrificial layer scatters, and since the fine pores are closed by the filling material, moisture and the like do not enter the voids and are excellent in environmental resistance. Micro piezoelectric sensor can be realized.

14. [Structure] In the method for manufacturing a micro-piezoelectric vibrator described in the above item 1, the step of forming the piezoelectric thick film element includes a step of forming a piezoelectric thick film pattern on a substrate having the lower electrode on a surface by jet printing. And a step of heat-treating the piezoelectric thick film pattern, an upper surface flattening step of flattening an upper surface of the heat-treated piezoelectric thick film pattern, and an upper electrode formation of forming an upper electrode on an upper surface flattening portion of the piezoelectric thick film pattern. A method of manufacturing a micro-piezoelectric vibrator, comprising:

All examples correspond. [Operation] A piezoelectric thick film pattern formed by jet printing, the cross section has a mountain shape in which the lower part is wider than the upper part as shown in FIG. 2, and the upper surface flattening step is formed on the mountain shape. The cross-sectional shape of the film element is easily formed into a trapezoid as shown in FIG.

[Effect] It is possible to easily form a piezoelectric thick film element having a trapezoidal cross section, which provides stable thickness longitudinal vibration.

15. [Structure] In the method for manufacturing a micro-piezoelectric vibrator described in the paragraph 14, the sacrificial layer forming step of covering the entire surface of the piezoelectric thick film pattern after the heat treatment step with a meltable resin with a predetermined thickness, and the sacrificial layer. And an insulating layer forming step of covering the substrate with an insulating material, and the upper surface flattening step, the insulating layer, the sacrificial layer and the upper portion of the piezoelectric thick film pattern are polished or ground substantially parallel to the substrate to be removed and flattened. Surface forming step, the upper electrode forming step is a step of forming an electrode film across the flat surfaces of the piezoelectric thick film pattern, the sacrificial layer and the insulating layer, and further, the upper electrode and the lower part. A polarization forming step of applying a DC voltage between the electrodes and forming a polarization state in the direction between the electrodes, that is, in the thickness direction of the piezoelectric thick film element; and after the upper electrode is formed, the sacrificial layer is melted and removed to form a gap. Sacrifice forming part Method of manufacturing a micro piezoelectric vibrator and having a layer removing step.

It corresponds to FIGS. 2 to 6 and applies to all the embodiments. [Operation] A flat surface is formed by polishing or grinding and removing the upper portions of the insulating layer, the sacrificial layer and the piezoelectric thick film pattern substantially parallel to the substrate, and a DC voltage is applied between the upper electrode and the lower electrode. After the application, a polarization state in the thickness direction of the piezoelectric thick film element is formed, and then the sacrificial layer made of a meltable resin is melted and removed to form a void portion.

[Effect] It is possible to easily form a piezoelectric thick film element having a trapezoidal section in which stable thickness longitudinal vibration is obtained.
Furthermore, a micro-piezoelectric vibrator in which the upper electrode is formed across the flattened upper surface of the piezoelectric thick film element and the insulating layer via the gap can be easily formed.

16. [Structure] In the method for manufacturing a micro-piezoelectric vibrator according to the fifteenth aspect, the melting temperature of the meltable resin forming the sacrificial layer is higher than the insulating layer forming temperature in the insulating layer forming step. Piezoelectric vibrator manufacturing method.

All examples correspond. [Operation] In the insulating layer forming step, the sacrificial layer is stably held without melting.

[Effect] The formation of the voids of the micro piezoelectric vibrator can be stably realized. 17． [Structure] In the method for manufacturing a micro-piezoelectric vibrator according to the fifteenth aspect, the insulating material in the insulating layer forming step is a photocurable resin, and the photocurable resin is irradiated with an optical image to form an insulating layer. A method of manufacturing a micro-piezoelectric vibrator, comprising:

Example 1 corresponds. [Operation] In the insulating layer forming step, the resin can be cured at a relatively low temperature such as room temperature.

[Effect] Since the insulating layer is cured not by heat but by light, the insulating layer can be formed without affecting the sacrificial layer by heat. As a result, a void layer having a uniform width can be formed, and stable piezoelectric vibration can be used because the slope of the trapezoidal piezoelectric vibrator and the insulating layer do not rub against each other.

18. [Structure] In the method for manufacturing a pressure-receiving portion of a micro-piezoelectric sensor described in the fifth paragraph, the upper electrode forming step described in the fifteenth paragraph is a step of forming the upper electrode into a specific shape, and a peripheral edge portion of the upper electrode. And a second sacrificial layer forming step of forming a sacrificial layer over the void portion, and a resin layer formed over the entire surface of the sacrificial layer, the upper electrode, and a part of the insulating layer to form a pressure receiving portion. And a sacrificial layer removing step of collectively removing the first sacrificial layer and the second sacrificial layer, and a method of manufacturing a micro-piezoelectric sensor.

Example 2 is applicable. This is a manufacturing method in which a second sacrificial layer forming step, a resin pressure-receiving portion layer forming step, and first and second sacrificial layer removing steps are sequentially performed on the upper electrode formed in the specific shape by the upper electrode forming step.

[Operation] A space that will eventually become the second void portion is secured in the second sacrifice layer forming step. In the resin pressure receiving portion layer forming step, the portion that becomes the pressure receiving portion becomes a semi-cured state at room temperature. In the sacrificial layer removal and resin pressure receiving portion curing heating step, both sacrificial layer materials are removed and the semi-cured resin pressure receiving portion is completely cured.

[Effect] A piezoelectric vibrator having a pressure receiving portion can be obtained. 19. [Structure] In the method for manufacturing an array-type piezoelectric transducer described in the above-mentioned item 9, a step of forming a lower electrode on a substrate into a pattern shape separated from each other, and a jet printing system on a portion excluding an end portion on the pattern electrode. A step of forming a piezoelectric thick film in a spot shape using, a heat treatment step, a step of forming a conductive protrusion in the direction perpendicular to the substrate at the end of the separated pattern electrode, a sacrificial layer forming step,
Wiring is connected to each of the insulating layer forming step, the surface flattening step, the upper electrode forming step, the polarization step, the upper electrode patterning step, the sacrificial layer removing step, the upper electrode and the conductive bump electrode. A method of manufacturing an array-type piezoelectric transducer, comprising:

This corresponds to the second embodiment. First, a lower electrode is formed into a separated pattern on a substrate, and then a step of forming a piezoelectric thick film in a spot shape using a jet printing system on a portion excluding an end portion on the pattern electrode, a heat treatment step, A step of forming a conductive protrusion in the vertical direction on the substrate at the end of the separated pattern electrode, a sacrifice layer forming step, an insulating layer forming step, a surface flattening step, an upper electrode forming step, a polarization step, an upper electrode patterning step, A sacrificial layer removing step and a step of connecting wiring to each of the upper electrode and the conductive bump electrode are performed.

[Function] The lower electrode is formed into a separated pattern on the substrate, and then a piezoelectric thick film is formed in a spot shape by using a jet printing system on a portion excluding the end portion on the pattern electrode, followed by heat treatment. In the process, the adhesion between the thick film and the substrate, the inter-particle bonding force forming the piezoelectric thick film, and the crystallinity are improved. Next, a driving voltage input terminal is secured in a process of forming a conductive protrusion in a vertical direction on the substrate at an end of the separated pattern electrode. Since it is a protrusion, an exposed portion can be shown on the surface of the insulating layer in the subsequent surface flattening step. Further, the cavity forming region is secured by the next sacrifice layer forming step. In the insulating layer forming step, the structure on the substrate formed in the previous steps is covered. In the surface flattening process, the piezoelectric thick film with the uneven surface and the extra protruding portions of the protruding lower electrode terminals are removed to flatten the surface, and at the same time, the piezoelectric thick film and the cut surface of the protruding lower electrode terminals are exposed and the insulating layer, It is flush with the sacrificial layer forming resin. Furthermore, the piezoelectric thick film becomes piezoelectrically active in the upper electrode forming step and the polarization step, and the piezoelectric vibrator becomes operable. In the upper electrode patterning step, an upper pattern electrode integrally formed on the upper surface of the piezoelectric vibrator, the sacrificial layer material and the surface of the insulating layer is formed. Further, both sacrificial layers are removed in the sacrificial layer removing step, so that the void portion around the slope of the piezoelectric vibrator and the void portion for the pressure receiving portion are formed. Finally, an array type piezoelectric vibrator transducer is completed by a step of connecting a wiring to each of the upper electrode and the conductive bump electrode.

[Effect] By undergoing the above steps, it is possible to accurately manufacture a trapezoidal piezoelectric vibrator array having a void portion around it and having a pressure receiving portion.

20. [Structure] In the array type piezoelectric transducer described in the above item 8, an insulating cylindrical substrate having a structure in which a lower electrode array is formed, a piezoelectric thick film vibrator array formed on each of the electrodes and polarized, A piezoelectric thick film oscillator array, an insulating layer region formed in a region excluding a portion where wiring is provided in a lower electrode array and a void portion arranged around the piezoelectric thick film oscillator array,
An array-type piezoelectric transducer comprising an upper electrode integrally formed on the upper surface of a piezoelectric thick film oscillator and the surface of the insulating layer. Example 3 is applicable.

An insulating cylindrical substrate having a lower electrode array formed thereon, a polarized piezoelectric thick film oscillator array formed on each of the electrodes, the piezoelectric thick film oscillator array and voids arranged around the piezoelectric thick film oscillator array. And an insulating layer region formed in a region excluding a portion where wiring is attached to the lower electrode array, and an upper electrode integrally formed over the upper surface of the piezoelectric thick film oscillator and the surface of the insulating layer. Become.

[Operation] While the upper electrode is used as the common ground electrode, the lower electrodes are arrayed, so that individual piezoelectric vibrators can be driven at different timings, and one or more piezoelectric vibrators can be driven. Radial scanning is possible even in a lump. Since each piezoelectric vibrator has a trapezoidal cross section and a void is arranged around it, crosstalk between the piezoelectric vibrators can be reduced.

[Effect] Good lateral resolution in the scanning direction can be obtained. 21. [Configuration] In a piezoelectric transducer having an acoustic coupling layer between a piezoelectric vibrator and an object to be measured, the side where the acoustic coupling layer contacts the object is 1.2 of the acoustic impedance of the object. A piezoelectric transducer characterized by having an acoustic impedance of ˜3 times, and a surface in contact with the piezoelectric vibrator side having an acoustic impedance substantially equal to that of the piezoelectric vibrator. It corresponds to Example 6.

The side where the acoustic coupling layer contacts the object has an acoustic impedance that is approximately three times the acoustic impedance of the object, and the surface that contacts the piezoelectric vibrator side is substantially equal to the acoustic impedance of the piezoelectric vibrator. This is a configuration having acoustic impedance.

[Operation] Piezoelectric vibrations (ultrasonic waves) radiated from the surface of the piezoelectric vibrator are incident on this acoustic coupling layer without loss, and the inside of the coupling layer is attenuated as little as the inside of the piezoelectric oscillator. Reaches the target object of the coupling layer, and there is a 1.2 to 3 times difference in acoustic impedance at the interface, so about 1/10 to 10
Half of the vibration energy is reflected at the interface and returns to the piezoelectric vibrator. This reflection is the acoustic impedance of the object,
That is, the resonance frequency and the resonance resistance change corresponding to the values of the real part and the imaginary part of the complex elastic constant. Further, half of the vibration energy is incident on the object and is reflected by the discontinuity surface of the acoustic impedance in the object, and the reflected ultrasonic wave is a boundary with the acoustic coupling layer, and half of it is acoustic. It is incident on the coupling layer side, and is incident on the piezoelectric oscillator without loss at the interface between the piezoelectric oscillator and the acoustic coupling layer. Therefore, this echo signal is converted into an electric signal by the piezoelectric effect of the piezoelectric vibrator.

[Effect] From the resonance frequency and resonance resistance of the piezoelectric vibrator, the real and imaginary parts of the complex elastic modulus near the surface of the object in contact with the acoustic coupling layer, that is, the elastic coefficient (Young's modulus) The viscosity coefficient is known, and the discontinuous state of the elastic constant in the depth direction can be detected from the echo signal.

22. [Structure] In the piezoelectric transducer described in the above paragraph 21, the object is a living body, and the acoustic impedance of the acoustic coupling layer on the side in contact with the living body is 1.8 ×.
10 ⁶ Kg / sec ・ m ² to 4.5 × 10 ⁶ Kg / sec
-A piezoelectric transducer for living body characterized by being in the range of m ² .

This corresponds to the sixth embodiment. The living body here mainly refers to a human body, but any animal or tissue may be used as long as its acoustic impedance has a value in the vicinity of 1.5 × 10 ⁶ Kg / sec · m ² .

[Operation] The acoustic impedance of the living body is approximately 1.5 × 10 ⁶ Kg / sec · m ^2, which is 1.8 × 10 6.
⁶ Kg / sec ・ m ² to 4.5 × 10 ⁶ Kg / sec ・ m
The range of ² is 1.2 to 3 of the acoustic impedance of this living body.
Since it corresponds to a doubled value, piezoelectric vibration (ultrasonic wave) is incident on the acoustic coupling layer without reflection, and ultrasonic energy of about 1/10 to 1/2 is generated at the interface between the living body and the acoustic coupling layer. It reflects and returns to the piezoelectric vibrator. The returned ultrasonic wave contains information about the mechanical properties of the interface, that is, the surface layer of the living body, that is, the elastic coefficient and the viscosity coefficient. on the other hand,
The ultrasonic energy of 9/10 to 1/2 that enters the living body is reflected at the interface with abnormal tissue such as tumor having an acoustic impedance different from that of normal tissue existing in the depth direction, and returns to the piezoelectric transducer as an echo signal. .

[Effect] By having such a binding layer, not only the mechanical properties of the living body surface can be detected, but also
The presence of a foreign substance such as a tumor existing in the depth direction and the location of the foreign substance can be detected.

23. [Structure] The piezoelectric transducer described in the paragraph 21, wherein the acoustic coupling layer has a mechanical quality factor equal to or greater than a mechanical quality factor of the piezoelectric vibrator. . It corresponds to Example 6. The mechanical quality factor of the acoustic coupling layer has a value equal to or higher than the mechanical quality factor of the piezoelectric vibrator.

[Operation] The mechanical quality factor corresponds to the propagation loss of ultrasonic waves, and the larger this value, the smaller the propagation loss of ultrasonic waves. Therefore, if a material with a mechanical quality factor equal to or greater than the mechanical quality factor of the piezoelectric vibrator is used, there is no loss of ultrasonic waves and the resonance resistance of the piezoelectric vibrator increases. There is almost no.

[Effect] The lower the resonance resistance, the larger the change in the resonance resistance when an object is brought into contact with the object. Therefore, the sensitivity and dynamic range of the sensor can be increased.

24. [Structure] The piezoelectric transducer described in the above-mentioned item 21, wherein the piezoelectric element is a piezoelectric vibrator having a trapezoidal cross section with voids arranged around the piezoelectric element. It corresponds to Example 16. The piezoelectric element has a void around it, and its cross section is trapezoidal.

[Action] Since the trapezoidal shape causes the spreading vibration that is likely to occur via the Poisson's ratio to be hardly excited and not to be in contact with the insulating layer, the mechanical quality factor does not decrease. Further, since the spreading vibration does not occur, the bending vibration that is likely to occur in the bonding state with the substrate does not occur.

[Effect] A high mechanical quality factor can be realized,
Further, since only the intended thickness longitudinal vibration can be efficiently excited, the elastic characteristic of the object can be detected with high sensitivity.

[0161]

As described above in detail, according to the present invention, in the piezoelectric vibrator using the thickness extensional vibration, the electrodes do not have a step structure,
It is possible to provide a micro-piezoelectric vibrator having a large mechanical quality factor Qm without unnecessary vibration, a method for manufacturing the same, and a piezoelectric transducer using the micro-piezoelectric vibrator.

[Brief description of drawings]

FIG. 1 is a sectional view of a micro-piezoelectric vibrator according to a first embodiment of the present invention.

FIG. 2 is a process drawing of the method of manufacturing the micro-piezoelectric vibrator according to the first embodiment of the present invention, which is a cross-sectional view showing a state where a piezoelectric spot film is formed.

FIG. 3 is a step diagram of the method of manufacturing the micro-piezoelectric vibrator according to the first embodiment of the present invention, which is a cross-sectional view showing a state in which an insulating layer is formed on the entire surface.

FIG. 4 is a process drawing of the method of manufacturing the micro-piezoelectric vibrator according to the first embodiment of the present invention, which is a cross-sectional view showing a state where the entire surface is flattened.

FIG. 5 is a step diagram of the method of manufacturing the micro-piezoelectric vibrator according to the first embodiment of the present invention, which is a cross-sectional view showing a state in which an upper electrode and a polarized electrode are formed.

FIG. 6 is a step diagram of a method of manufacturing the micro-piezoelectric vibrator according to the first embodiment of the present invention, which is a cross-sectional view showing the final step of forming a patterned upper electrode.

FIG. 7 is an explanatory diagram of a jet printing system device used in the first embodiment of the present invention.

8 is an explanatory diagram of a modified example of Embodiment 1 of the present invention, and FIG.
8A is a cross-sectional view, FIG. 8B is a case where the structure of the piezoelectric thick film having a frustum-shaped structure is elliptical, and FIG. 8C is a case where it is rectangular.

FIG. 9 is a sectional view of a micro-piezoelectric vibrator according to a second embodiment of the present invention.

FIG. 10 is a cross-sectional view showing the method of manufacturing the micro-piezoelectric vibrator according to the second embodiment of the present invention in the order of steps, and FIG.
FIG. 10B is a sectional view showing a state in which a sacrificial layer is formed, FIG. 10B is a state in which fine holes are formed, and FIG. 10C is a state in which a second void portion is formed.

FIG. 11 is a sectional view of a micro-piezoelectric vibrator according to a modified example of Example 2 of the present invention.

12A to 12C are cross-sectional views showing a method of manufacturing the micro-piezoelectric vibrator of FIG. 11 in order of steps, FIG. 12A is a state in which an elastic member is formed, FIG. 12B is a state in which fine holes are formed, and FIG. FIG. 6C is a cross-sectional view showing a state in which a second void portion is formed.

FIG. 13 is an explanatory diagram of a linear array type micro-piezoelectric transducer according to a third embodiment of the present invention, and FIG.
Is a top view, FIG. 13 (B) is a partially enlarged top view of the unit piezoelectric vibrator of FIG. 13 (A), FIG. 13 (C) is a cross-sectional view taken along line XX of FIG. 13 (B), and FIG. 13D is a sectional view taken along the line YY of FIG.

FIG. 14 is a sectional view of an array type micro-piezoelectric transducer according to a modification of Example 3 of the present invention.

15A and 15B are explanatory views of an array type micro-piezoelectric transducer according to a fourth embodiment of the present invention, FIG. 15A is a side view, and FIG. 15B is a single piezoelectric vibrator of FIG. 15A. An enlarged top view, FIG. 15C is a sectional view taken along line XX of FIG. 15B, and FIG. 15D is a sectional view taken along line YY of FIG. 15B.

FIG. 16 is an operation explanatory diagram of an array type micro-piezoelectric transducer according to a modification of Example 4 of the present invention.

FIG. 17 is an explanatory diagram of an array type micro-piezoelectric transducer of a modified example of Example 4 of the present invention.

18A and 18B are explanatory views of a piezoelectric vibrator two-dimensional array according to a fifth embodiment of the invention, FIG. 18A is a plan view, and FIG.
18A is a cross-sectional view taken along line XX of FIG.

FIG. 19 is a sectional view of a piezoelectric vibrator according to Example 6 of the invention.

FIG. 20 is an explanatory diagram of a conventional micro tactile sensor,
20A is a plan view and FIG. 20B is XX of FIG. 20A.
Sectional drawing which follows the line.

FIG. 21 is a sectional view of a conventional piezoelectric vibrator.

FIG. 22 is an explanatory diagram of a conventional parallel electric field excitation piezoelectric vibrator.

FIG. 23 is a cross-sectional view of various vibrators.

[Explanation of symbols]

1,131,181 ... Substrate, 2,132,182 ...
Surface oxide film, 3,133, 152, 185 ... Lower electrode, 4,13
4, 138, 153, 186 ... Piezoelectric thick film element, 5, 92, 146,
147, 154, 187 ... Void, 6,23, 136, 155, 188
... Insulating layer, 7, 137, 156, 189 ... Upper electrode, 21 ... Piezoelectric spot film, 22, 94 ... Sacrificial layer, 24 ... Upper electrode and polarized electrode, 26, 114, 135 ... Void portion, 91, 111 ... Pressure receiving Part, 93, 113 ... Micropores,
112 ... Elastic member, 139, 159 ... Lower electrode protrusion,
140, 160 ... Lower electrode projection coating electrode, 141 ... Linear piezoelectric vibrator array, 145 ... Pressure receiving part and acoustic matching layer, 15
1 ... Cylindrical substrate, 157 ... Common ground electrode, 158 ... Single piezoelectric vibrator, 183, 184 ... Decoder.

Claims (3)

[Claims] 1. A micro-piezoelectric vibrator using resonance characteristics of thickness longitudinal vibration, comprising a substrate having a lower electrode on its surface,
A piezoelectric thick film element formed on the lower electrode and having a trapezoidal cross section and being polarized in the thickness direction, and a piezoelectric thick film element formed so as to surround a side wall of the piezoelectric thick film element with a space therebetween. A micro device comprising an insulating layer having a surface substantially parallel to the substrate, and an upper electrode integrally disposed on the upper surface of the piezoelectric thick film element and the surface of the insulating layer. Piezoelectric vibrator. 2. A step of forming a piezoelectric thick film in a spot shape by using a jet printing method, a heat treatment step, a sacrifice layer forming step, an insulating layer forming step, a surface flattening step, and an upper electrode forming step. A method of manufacturing a micro-piezoelectric vibrator, comprising: a polarization step, an upper electrode patterning step, and a sacrifice layer removal step. 3. A piezoelectric transducer having an acoustic coupling layer between the micro-piezoelectric vibrator and the object to be measured according to claim 1, wherein the side where the acoustic coupling layer contacts the object is the object. 1.2-3 of the acoustic impedance of the object
The acoustic impedance of the piezoelectric thick film element is substantially equal to that of the piezoelectric thick film element on the surface in contact with the piezoelectric thick film element. Piezoelectric transducer characterized by having a value equal to or higher than the dynamic quality factor.