JP7048030B2 - Manufacturing method of ultrasonic oscillator - Google Patents

Description

The present invention relates to a method for manufacturing an ultrasonic vibrator, and particularly to a method for manufacturing an ultrasonic vibrator capable of transmitting and receiving high frequency ultrasonic waves that require high resolution.

Ultrasonic transducers are used in ultrasonic deep tentacles such as medical ultrasonic diagnostic equipment and non-destructive inspection equipment. FIG. 7 shows a schematic view of an ultrasonic deep tentacle using a piezoelectric material. Generally, the ultrasonic deep tentacle includes a piezoelectric element 1 that transmits and receives ultrasonic waves, electrodes 2a and 2b formed on the front and back surfaces of the piezoelectric element 1, and electrode terminals 3a connected to the respective electrodes 2a and 2b. It is equipped with 3b. Further, in order to efficiently transmit and receive ultrasonic waves, an acoustic matching layer 4 is formed on the surface of the piezoelectric element 1. On the other hand, a back load material 5 is formed on the back surface side of the piezoelectric element 1 in order to attenuate unnecessary ultrasonic waves reaching the back surface side. This type of ultrasonic deep tentacle is described in Patent Document 1.

On the other hand, in the medical ultrasonic diagnostic apparatus, when diagnosing the heart or abdomen, ultrasonic waves of about 2.5 MHz to 5 MHz are used, and when diagnosing a region close to the skin (thyroid gland, mammary gland, etc.). In, ultrasonic waves of about 7.5 MHz to 12 MHz are used. However, with such relatively low frequency ultrasonic waves, it is not possible to confirm capillaries with a diameter of 20 μm or less, and an ultrasonic oscillator that radiates ultrasonic waves of 40 MHz to 200 MHz is required (Patent Documents). 2).

Japanese Unexamined Patent Publication No. 2000-184497 Japanese Unexamined Patent Publication No. 2008-10497

The frequency of the ultrasonic waves transmitted and received in the ultrasonic vibrator using the piezoelectric element is determined by the thickness of the piezoelectric element, and in order to transmit and receive high-frequency ultrasonic waves, the thickness of the piezoelectric element 1 shown in FIG. 7 is reduced. There is a need to. As an example, in order to radiate an ultrasonic wave of 80 MHz, it is necessary to make the thickness of the piezoelectric element 1 about 20 μm by using PZT which is a general piezoelectric material. In order to transmit and receive ultrasonic waves having a higher frequency, it is necessary to further reduce the thickness of the piezoelectric element 1.

Generally, the piezoelectric element 1 can be efficiently manufactured by forming a plurality of piezoelectric elements 1 together on a piezoelectric substrate, separating them into individual pieces, and separating them into individual piezoelectric elements. However, when the thickness of the piezoelectric substrate is about 30 μm or less, cracks and cracks occur in the piezoelectric substrate due to insufficient strength, and it becomes difficult to stably manufacture the piezoelectric element. An object of the present invention is to solve such a problem and to provide a manufacturing method capable of stably manufacturing an ultrasonic vibrator capable of emitting high frequency ultrasonic waves.

In order to achieve the above object, the invention according to claim 1 of the present application is a manufacturing method for forming an ultrasonic transducer from a piezoelectric substrate, in which a contact portion abutting with a peripheral edge portion of one surface of the piezoelectric substrate and a corresponding contact portion thereof. A step of preparing a jig having an accommodating portion for accommodating the piezoelectric substrate and an opening for exposing a part of one surface of the piezoelectric substrate surrounded by the contact portion, and a step of preparing the piezoelectric substrate. A step of contacting the peripheral edge portion of the one surface with the abutting portion, accommodating the piezoelectric substrate in the accommodating portion, and exposing a part of the one surface of the piezoelectric substrate from the opening, and the opening . A step of thinning the piezoelectric substrate by removing a part of the exposed one surface of the piezoelectric substrate exposed in the portion to make the piezoelectric substrate a desired thickness, and the one surface of the thinned piezoelectric substrate. A step of forming an electrode film on the other surface and a step of individualizing the piezoelectric substrate on which the electrode film is formed to form an ultrasonic transducer having a desired thickness are included. It is a feature.

The invention according to claim 2 of the present application is the method for manufacturing an ultrasonic vibrator according to claim 1, wherein an acoustic matching film or an acoustic matching film is formed on one surface of the thinned piezoelectric substrate or an electrode film on the other surface. It is characterized in that one or both of the back load materials are formed and then individualized .

The invention according to claim 3 of the present application is the extraction electrode of each electrode on one surface of the thinned piezoelectric substrate or the other surface in the method for manufacturing an ultrasonic vibrator according to claim 1 . A method for manufacturing an ultrasonic vibrator, which comprises a step of forming the ultrasonic vibrator.

The invention according to claim 4 of the present application is the method for manufacturing an ultrasonic vibrator according to claim 3 , after forming either an acoustic matching film or a back load material on the surface of the electrode other than the extraction electrode. A method for manufacturing an ultrasonic vibrator, which is characterized by being separated .

The invention according to claim 5 of the present application is the method for manufacturing an ultrasonic vibrator according to any one of claims 1 to 4 , wherein the jig is separated from the piezoelectric substrate before the individualization. Manufacturing method of oscillator.

In the method for manufacturing an ultrasonic oscillator of the present invention, mechanical strength is maintained by leaving a part of the piezoelectric substrate as a peripheral portion, and the region surrounded by the peripheral portion is thinned to a desired thickness and individualized. As a result, an ultrasonic oscillator is formed. With this configuration, the piezoelectric substrate can be formed very thin so that ultrasonic waves of high frequency can be transmitted and received, while a stable manufacturing method that does not cause defects such as cracks in the piezoelectric substrate can be obtained. It will be possible to make a proposal.

It is also possible to use a jig to increase the mechanical strength, and the use of the jig eliminates distortion of the peripheral portion and makes the manufacturing method more stable. The jig used can be separated from the piezoelectric substrate after the thinning step, but can be configured to be separated from the piezoelectric substrate before the individualization step, which provides a more stable manufacturing method.

According to the method for manufacturing an ultrasonic vibrator of the present invention, it becomes easy to form an acoustic matching film or a back load material on the front surface or the back surface of a piezoelectric substrate before individualization, and the acoustic matching film or the back load material can be formed. It has the advantage that it can be easily formed.

Further, when forming the acoustic matching film or the back loading material, the extraction electrodes formed on both sides of the piezoelectric element are formed on one surface or the other surface, so that the drawing electrodes are covered with the acoustic matching film or the back loading material. It is also easy to form it in a position where it will not be broken. Since the extraction electrode is exposed on one surface, it is easy to assemble when forming a deep tentacle for a medical ultrasonic diagnostic apparatus, and there is an advantage that the size can be further reduced.

It is a figure explaining the manufacturing method of the ultrasonic oscillator of 1st Example of this invention. It is a figure explaining the manufacturing method of the ultrasonic oscillator of 1st Example of this invention. It is a figure explaining the manufacturing method of the ultrasonic oscillator of the 2nd Example of this invention. It is a figure explaining the manufacturing method of the ultrasonic oscillator of the 2nd Example of this invention. It is a figure explaining the manufacturing method of the ultrasonic oscillator of the 3rd Example of this invention. It is a figure explaining the manufacturing method of the ultrasonic oscillator of the 4th Example of this invention. It is explanatory drawing of the conventional ultrasonic oscillator.

In the present invention, in order to manufacture an ultrasonic vibrator capable of transmitting and receiving high-frequency ultrasonic waves used in, for example, a high-resolution medical ultrasonic image pickup device, the peripheral portion of the piezoelectric substrate forming the piezoelectric element is thickened. It is characterized by being manufactured as a state. Hereinafter, examples of the present invention will be described in detail.

First, a first embodiment of the present invention will be described. FIG. 1 is an explanatory diagram of a method for manufacturing an ultrasonic oscillator according to a first embodiment of the present invention. As shown in FIG. 1, for example, a circular piezoelectric substrate 10 having a thickness of about 30 to 50 μm is prepared, and the photoresist 11 is patterned so as to cover the peripheral portion thereof. When the circular piezoelectric substrate 10 is used, the photoresist 11 has a donut shape (FIG. 1a). The piezoelectric substrate 10 is not limited to inorganic piezoelectric materials such as quartz, lithium niobate, barium titanate, and lead titanate, and may be organic piezoelectric materials or composite materials thereof.

After that, the photoresist 11 is used as an etching mask, and a part of the piezoelectric substrate 10 in the central portion surrounded by the peripheral portion is removed by etching to form the recess 12 (FIG. 1b). At this time, the depth of the recess 12 is such that the thickness of the piezoelectric substrate 10 at the bottom of the recess 12 that remains without being removed is such that the transmitted / received ultrasonic signal has a desired frequency. For the etching for forming the concave portion 12, a dry etching method or a wet etching method may be appropriately selected depending on the piezoelectric substrate to be used. When the wet etching method is adopted, it is necessary to cover the side surface and the back surface side of the piezoelectric substrate 10 with an etching mask in advance so that unnecessary etching is not performed.

When the photoresist 11 is removed, the peripheral portion 13 of the piezoelectric substrate 10 is thick, and the region 14 for forming the piezoelectric element, which is thinned to a desired thickness by forming the concave portion, is formed (FIG. 1c). With such a shape, even if the thickness of the region 14 where the piezoelectric element is planned to be formed is about 20 μm, if the peripheral edge portion 13 retains the shape of the piezoelectric substrate and the peripheral edge portion 13 is handled to proceed with the subsequent process, It is possible to prevent cracks and the like from occurring in the region 14 where the piezoelectric element is planned to be formed.

After that, as shown in FIG. 2A, a metal film is laminated on both sides of the piezoelectric substrate 10 to form an electrode film 15 of the piezoelectric element. Since the surface of the region 14 where the piezoelectric element is planned to be formed, which is the bottom of the recess 12, has a large step on the peripheral edge 13, it is difficult to perform fine processing. Therefore, it is preferable to form only the electrode film 15 on the entire surface. On the other hand, since the back surface of the piezoelectric substrate 10 has a flat shape, it is also possible to laminate the electrode films 15 and then pattern them by a normal photolithography method.

Next, the back surface side of the piezoelectric substrate 10 is attached to the dicing tape 16 for individualization. After that, by forming a grid-shaped cutting groove 18 on the piezoelectric substrate 10 using a dicing saw 17, each piezoelectric element can be individually separated. The grid-shaped cutting groove 18 is also formed in the peripheral edge portion 13 (FIG. 2b).

The piezoelectric element 1 thus formed has a shape in which electrode films 15 are laminated on both sides of the piezoelectric substrate 10, and the thickness of the piezoelectric substrate 10 is set to be thin enough to transmit and receive high-frequency ultrasonic waves. It becomes a sound wave oscillator. In the manufacturing method of the present invention, by leaving a part of the piezoelectric substrate 10 as the peripheral edge portion 13, it is possible to stably form an ultrasonic oscillator from the thin-film piezoelectric substrate 10.

Next, a second embodiment will be described. In the first embodiment, the case where the manufacturing process is carried out while leaving the thick peripheral portion 13 on the piezoelectric substrate 10 has been described. However, when the piezoelectric substrate 10 has a larger diameter or the piezoelectric element formation planned region 14 is further thinned, the piezoelectric substrate 10 may be distorted and the piezoelectric element formation planned region 14 may be damaged. Therefore, in the second embodiment, an example of preventing damage to the piezoelectric element formation planned region 14 by using a jig will be described.

First, as in the first embodiment, for example, a circular piezoelectric substrate 10 having a thickness of about 30 to 50 μm is prepared. Next, the photoresist 11 is applied to the surface of the piezoelectric substrate 10. Unlike the first embodiment, patterning is not performed. This photoresist 11 is used as an adhesive and is adhered to a jig 19 for preventing deformation of the piezoelectric element to be thinned. As shown in FIG. 3A, the jig 19 has a contact portion 19a that abuts on the peripheral edge of the surface of the piezoelectric element 10, an accommodating portion 19b that has a concave shape and houses the piezoelectric substrate 10 inside, and a contact portion. It is provided with an opening 19c that exposes a part of the surface of the piezoelectric substrate 10 surrounded by 19a.

The photoresist 11 exposed in the opening 19c of the jig 19 is exposed and developed (or the jig 19 is used as an etching mask) to expose a part of the piezoelectric substrate 10 in the opening 19c (FIG. 3b). ..

With the piezoelectric element 10 attached to the jig 19, the jig 19 and the photoresist 11 are used as etching masks, and a part of the piezoelectric substrate 10 in the central portion surrounded by the contact portion 19a of the jig 19 is etched. It is removed to form a recess 12 (FIG. 3c). At this time, the depth of the recess 12 is such that the thickness of the bottom of the recess 12 that remains without being removed is such that the transmitted / received ultrasonic signal has a desired frequency. The etching for forming the recess 12 may be performed by a dry etching method or a wet etching method, depending on the piezoelectric substrate used. When the wet etching method is adopted, it is necessary to cover the side surface and the back surface side of the piezoelectric substrate 10 with an etching mask in advance so that unnecessary etching is not performed. As a matter of course, the jig 19 is prevented from being etched, and the jig 19 is prevented from coming into contact with an etching solution or the like to cause abnormal etching.

Here, when the jig 19 is removed together with the photoresist 11, the peripheral edge portion 13 of the piezoelectric substrate 10 is thick as described in the first embodiment, and the piezoelectric element formation planned region is thinned to a desired thickness by forming the concave portion. 14 is formed (FIG. 1c). Hereinafter, the piezoelectric element can be formed by going through the same manufacturing process as in the first embodiment.

By the way, when the thickness of the bottom portion of the recess 12 is made thinner than that described in the first embodiment, it may be preferable to proceed to the subsequent process with the jig 19 attached. In that case, as shown in FIG. 3D, a metal film is laminated on both sides of the piezoelectric substrate 10 to which the jig 19 is attached to form the electrode film 15 of the piezoelectric element. Since the surface of the region 14 where the piezoelectric element is planned to be formed, which is the bottom of the recess 12, has a large step due to the peripheral edge portion 13 and the jig 19, it is difficult to perform fine processing. Therefore, it is preferable to form only the electrode film 15 on the entire surface. .. The electrode film 15 laminated on the jig 19 is also left as it is. On the other hand, the jig 19 does not protrude from the back surface of the piezoelectric substrate 10, and the back surface of the piezoelectric substrate 10 and the back surface of the jig 19 are substantially flush with each other. It is also possible to do.

Next, the back surface side of the piezoelectric substrate 10 is attached to the dicing tape 16 for individualization. If the jig 19 is made of a material that can be separated together with the piezoelectric substrate 10, for example, a silicon substrate, it is not necessary to remove the jig 19, but if the jig 19 is made of metal or the like, it is separated. The jig 19 is removed before the above (FIG. 4b). The jig 19 may be removed by dissolving and removing the photoresist 11 used as an adhesive, and the electrode film 15 laminated on the jig 19 together with the jig 19 is also removed.

As described in the first embodiment, the individualization can be individualized into individual piezoelectric elements by forming a grid-like cutting groove 18 in the piezoelectric substrate 10 using a dicing saw 17. (Fig. 4c).

The piezoelectric element 1 thus formed has a shape in which electrode films 15 are laminated on both sides of the piezoelectric substrate 10, and the thickness of the piezoelectric substrate 10 can be made thinner than in the case of the first embodiment described above. By making it thin enough to transmit and receive high-frequency ultrasonic waves, it becomes an ultrasonic transducer. In the manufacturing method of the present invention, not only a part of the piezoelectric substrate 10 is left as the peripheral edge portion 13, but also the jig 19 is attached and left, so that the thickness can be made thinner than that described in the first embodiment. , It becomes possible to form a piezoelectric element capable of transmitting and receiving ultrasonic waves having a higher frequency.

Next, a third embodiment will be described. As shown in FIG. 7, an ultrasonic deep tentacle such as a medical ultrasonic diagnostic device or a non-destructive inspection device has an acoustic matching layer 4 formed on the front surface of a piezoelectric element 1 that transmits and receives ultrasonic waves, and further on the back surface. Is formed with a back load material 5 that attenuates unnecessary ultrasonic waves. Therefore, one or both of the acoustic matching layer 4 and the back load material 5 may be formed before the individualization, and then the individualization may be performed. For example, in the case of applying to the first embodiment, as shown in FIG. 2A, a metal film is laminated on the front surface and the back surface of the piezoelectric substrate 10, the electrode film 15 of the piezoelectric element is formed, and then the recess 12 is formed. The acoustic matching layer 4 is applied to the surface of the formed piezoelectric element 10. Further, the back load material 5 is applied to the back surface of the piezoelectric substrate 10 (FIG. 5a). After that, the back surface side of the piezoelectric substrate 10 on which the acoustic matching layer 4 and the back load material 5 are formed is attached to the dicing tape 16, and a grid-shaped cutting groove 18 is formed in the piezoelectric substrate 10 using the dicing saw 17. It can be individualized into individual piezoelectric elements (Fig. 5b). The acoustic matching layer 4 and the back load material 5 may be formed by reversing the front and back of the piezoelectric substrate 10. Alternatively, only one of them may be used.

By forming the acoustic matching layer 4 or the back load material 5 on the surface of the piezoelectric substrate 10, the strength of the region 14 where the piezoelectric element is planned to be formed is increased, which is preferable. Further, when either the acoustic matching layer 4 or the back load material 5 is formed on the back surface of the piezoelectric substrate 10, the surface is flat, so it is preferable to form one that requires patterning.

When forming either the acoustic matching layer 4 or the acoustic matching layer 5, the back load material 5 or the acoustic matching layer 4 may be formed after the piezoelectric element after individualization is combined with the ultrasonic deep tentacle. good.

Similarly, in the manufacturing method using the jig 19 described in the second embodiment, it is possible to add the formation of the acoustic matching layer 4 back load material 5.

Next, a fourth embodiment will be described. As described in the third embodiment, in the method of forming the acoustic matching layer 4 or the back load material 5 and then disassembling them, for example, the patterning of the acoustic matching layer 4 in FIG. 5A is difficult, and the acoustic matching is performed. The layer 4 covers the electrode film 15, and it becomes difficult to connect the electrode film 15 to the electrode terminal for pulling out the electrode to the outside. Therefore, the electrode film 15 coated with the acoustic bonding layer 4 may be formed so as to be pulled out on the opposite side of the piezoelectric substrate 10 where patterning is easy.

FIG. 6 shows an enlarged view of a part of the region where the piezoelectric element is planned to be formed after the individualization shown in FIG. 5 described above. In this embodiment, the electrode film 15a formed on the surface of the piezoelectric substrate 10 is connected to the extraction electrode 22a formed on the back surface of the piezoelectric substrate 10 by the through electrode 21. On the other hand, the electrode film 15b formed on the back surface of the piezoelectric substrate 10 is configured to be connected to the electrode film 22b formed on the back surface of the piezoelectric substrate 10. Since the back surface of the piezoelectric substrate 10 is a flat surface, patterning of the extraction electrodes 22a and 22b is easy as shown in FIG.

After the extraction electrodes 22a and 22b are formed on the back surface of the piezoelectric substrate 10, the acoustic matching layer 4 is formed on the entire surface of the electrode film 15a, and the back load material 5 is exposed on the electrode film 15b so that the extraction electrodes 22a and 22b are exposed. Form to. The patterning of the back load material 5 can also be performed by a general method because the back surface side of the piezoelectric substrate 10 is a flat surface.

After that, if the pieces are separated by using a dicing saw as described with reference to FIG. 5, the piezoelectric element can be formed. In FIG. 6, the description of the dicing tape 16 and the dicing saw 17 is omitted.

As a method for forming the through electrode 21 shown in FIG. 6, a well-known technique can be applied. For example, a through hole is formed in advance on a thick piezoelectric substrate 10 by using a drill, and then the above-described description is performed. By thinning the region 14 for forming the piezoelectric element to be formed as described above, a thin piezoelectric substrate having through holes can be easily formed.

Further, as a method of forming the through electrode 21, a method of forming the electrode films 15a and 15b from both sides in the through hole to conduct conduction, or a method of forming the electrode films 15a and 15b by a plating method and at the same time forming an electrode film in the through hole. It can be formed by a well-known method such as filling with a metal.

When the extraction electrodes connected to the electrode films formed on both sides of the piezoelectric substrate are formed on one surface in this way, the subsequent assembly of the ultrasonic deep tentacles and the like becomes easy.

Although the examples of the present invention have been described above, the present invention is not limited to the above examples and can be variously modified.

1: Piezoelectric element, 2a, 2b: Electrode, 3a, 3b: Electrode terminal, 4: Acoustic bonding layer, 5: Back load material, 10: Piezoelectric substrate, 11: Photoresist, 12: Recess, 13: Peripheral part, 14 : Piezoelectric element formation planned area, 15: Electrode film, 16: Dicing tape, 17: Dicing saw, 18: Cutting groove, 19: Jig, 20: Storage part, 21: Through electrode, 22a, 22b: Drawer electrode

Claims (5)

In the manufacturing method of forming an ultrasonic vibrator from a piezoelectric substrate,
A contact portion that abuts on the peripheral edge of one surface of the piezoelectric substrate, an accommodating portion that accommodates the piezoelectric substrate together with the corresponding contact portion, and a part of one surface of the piezoelectric substrate surrounded by the contact portion. And the process of preparing a jig with an opening to expose
A step of contacting the peripheral edge of the one surface of the piezoelectric substrate with the abutting portion, accommodating the piezoelectric substrate in the accommodating portion, and exposing a part of the one surface of the piezoelectric substrate from the opening. When,
A step of thinning the piezoelectric substrate by removing a part of the exposed one surface of the piezoelectric substrate exposed in the opening to make the piezoelectric substrate a desired thickness.
A step of forming an electrode film on one surface and the other surface of the thinned piezoelectric substrate, respectively.
A method for manufacturing an ultrasonic vibrator, which comprises a step of disassembling the piezoelectric substrate on which the electrode film is formed to form an ultrasonic vibrator having a desired thickness. In the method for manufacturing an ultrasonic oscillator according to claim 1,
It is characterized in that either or both of an acoustic matching film and a back load material are formed on one surface of the thinned piezoelectric substrate or an electrode film on the other surface, and then individualized . Manufacturing method of ultrasonic transducer. In the method for manufacturing an ultrasonic oscillator according to claim 1 ,
A method for manufacturing an ultrasonic oscillator, which comprises a step of forming an extraction electrode of each electrode on one surface of the thinned piezoelectric substrate or the other surface. In the method for manufacturing an ultrasonic oscillator according to claim 3 ,
A method for manufacturing an ultrasonic oscillator , which comprises forming either an acoustic matching film or a back load material on the surface of the electrode excluding the extraction electrode and then disassembling the material . In the method for manufacturing an ultrasonic oscillator according to any one of claims 1 to 4 .
A method for manufacturing an ultrasonic vibrator , which comprises separating the jig from the piezoelectric substrate before the individualization .

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