JP2012105170A - Piezoelectric type transducer and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric type transducer having excellent sound pressure characteristics in which an elastic film is not easily peeled from a piezoelectric element.SOLUTION: A piezoelectric type transducer (1) includes an elastic film (13) formed by a cured liquid film, a support part (11) connecting with an external end part of the elastic film (13) and supporting the elastic film (13), a diaphragm connecting with the elastic film (13) without having an adhesive therebetween, and a piezoelectric element (10) deforming with the elastic film (13). The elastic film (13) connects with an outer edge part including an end surface of the diaphragm.

Description

  The present invention relates to a piezoelectric transducer.

  Conventionally, a piezoelectric transducer such as a piezoelectric speaker that generates sound by driving a diaphragm integrated with a vibration film by a piezoelectric effect is known. When a diaphragm including a piezoelectric element is combined with an elastic film made of a resin film to configure a piezoelectric speaker, resonance in a low frequency band is obtained in a plurality of low order modes including the lowest order mode. Sound pressure level increases. Patent Document 1 discloses a piezoelectric transducer in which a piezoelectric element is bonded to an elastic film made of a resin film with a thermosetting adhesive. In Patent Document 2, an adhesive layer made of a pressure-sensitive adhesive is formed in advance on one surface of a resin film serving as an elastic film, and a piezoelectric element is attached to the adhesive layer of the resin film, and the outer peripheral portion of the piezoelectric element is thermosetting. A piezoelectric transducer bonded by an adhesive is disclosed. In the piezoelectric transducer disclosed in Patent Document 2, the thermosetting adhesive that is interposed between the elastic film and the piezoelectric element protrudes, the film thickness varies, and the sound pressure characteristics deteriorate due to the hardening of the adhesive. In addition to solving the problem by the adhesive layer, a small amount of thermosetting adhesive compensates for a lack of bonding force when the resin film and the piezoelectric element are bonded only by the adhesive layer.

JP 2002-112391 A Japanese Patent No. 4203911

  However, as described in Patent Document 2, even if the decrease in sound pressure characteristics can be suppressed by reducing the amount of thermosetting adhesive used, as long as the thermosetting adhesive is applied to the elastic film, A decrease in the sound pressure characteristics cannot be avoided, and it cannot be denied that the sound pressure characteristics vary due to variations in the amount of thermosetting adhesive used. And if the process of apply | coating an adhesive agent is added, manufacturing cost will rise. In addition, there is a problem that the options for the thickness of the resin film distributed as a ready-made product are narrow.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric transducer that is difficult to peel off an elastic membrane and a vibration plate and has excellent vibration characteristics and can be manufactured by a simple process.

(1) A piezoelectric transducer for achieving the object includes an elastic film in which a liquid film is cured, a support part that is coupled to an outer edge part of the elastic film and supports the elastic film, and without an adhesive. A diaphragm that is coupled to the elastic film and has an inclined end surface and a piezoelectric element that is distorted together with the elastic film, and a central portion of the elastic film is coupled to an outer edge including the end surface of the diaphragm.
According to the present invention, since the diaphragm and the elastic film can be directly coupled without using an adhesive by using a liquid resin, it is possible to realize a piezoelectric transducer that has excellent vibration characteristics and can be manufactured by a simple process. Further, by coupling the inclined end face of the diaphragm and the elastic film, it is possible to realize a piezoelectric transducer in which the area of the coupling interface is increased and the diaphragm is difficult to peel off.

(2) A piezoelectric transducer for achieving the object includes an elastic film in which a liquid film is cured, a support part that is coupled to an outer edge of the elastic film and supports the elastic film, and without an adhesive. A vibration plate coupled to the elastic film and having an end surface having a plurality of irregularities, and a piezoelectric element that is distorted together with the elastic film, and the elastic film is coupled to an outer edge including the end surface of the vibration plate.
According to the present invention, since the diaphragm and the elastic film can be directly coupled without using an adhesive by using a liquid resin, it is possible to realize a piezoelectric transducer that has excellent vibration characteristics and can be manufactured by a simple process. Further, by combining the end face having a plurality of irregularities of the diaphragm and the elastic film, it is possible to realize a piezoelectric transducer in which the area of the coupling interface is increased and the diaphragm is difficult to peel off.

(3) A method of manufacturing a piezoelectric transducer for achieving the above object includes a step of preparing a substrate in which an etching stopper layer and a functional layer are sequentially laminated on one main surface, and the functional layer is formed as the etching stopper. Forming an annular groove by etching in an annular manner until the layer is exposed; forming a liquid film covering the annular groove; forming an elastic film by curing the liquid film; and the elastic film And etching from the other main surface of the substrate until the functional layer inside the annular groove is exposed.
According to the present invention, it is possible to manufacture a piezoelectric transducer that is difficult to peel off and has excellent vibration characteristics by a simple process.

(4) In the piezoelectric transducer manufacturing method for achieving the above object, the annular film and the liquid film covering the inside of the annular groove may be formed.
By adopting this configuration, it is possible to manufacture a piezoelectric transducer in which the diaphragm is more difficult to peel off by leaving the cured liquid resin film on the diaphragm.

(5) In the method of manufacturing a piezoelectric transducer for achieving the above object, the method further includes the step of removing a part of the elastic film formed inside the annular film by patterning the elastic film. But you can.
When this configuration is adopted, the vibration characteristics of the piezoelectric transducer can be adjusted by adjusting the form in which the cured liquid resin film is left on the vibration plate.

(6) In the piezoelectric transducer manufacturing method for achieving the above object, the diaphragm having an inclined end face may be formed.
When this configuration is adopted, the area of the bonding interface between the diaphragm and the resin film increases, and therefore a piezoelectric transducer that can further prevent the diaphragm from peeling off can be manufactured.

(7) In the method of manufacturing a piezoelectric transducer for achieving the above object, the diaphragm having an end surface having a plurality of irregularities may be formed.
When this configuration is adopted, the area of the bonding interface between the diaphragm and the resin film increases, and therefore a piezoelectric transducer that can further prevent the diaphragm from peeling off can be manufactured.

  In this specification, the terms “main surface” and “end surface” are used in the following meaning. That is, the entire surface of the plate-like object is connected to each other in the form of a ring connecting the two “main surfaces” that are wider than any “end surface” and two “main surfaces” in front and back. The terms “principal surface” and “end surface” are used on the premise that they are composed of a plurality of “end surfaces” narrower than the “main surface”.

1A is a cross-sectional view according to a first embodiment of the present invention, and is a cross-sectional view taken along line 1A-1A shown in FIG. 1B. FIG. 1B is a plan view according to the first embodiment of the present invention. It is sectional drawing concerning the 1st Example of this invention. It is sectional drawing concerning the 1st Example of this invention. It is sectional drawing concerning the 1st Example of this invention. It is sectional drawing concerning the 1st Example of this invention. It is sectional drawing concerning the 1st Example of this invention. It is sectional drawing concerning the 1st Example of this invention. It is sectional drawing concerning the 1st Example of this invention. It is sectional drawing concerning the 1st Example of this invention. 10A is a cross-sectional view according to the second embodiment of the present invention, and is a cross-sectional view taken along the line 10A-10A shown in FIG. 10B. 10B and 10C are plan views according to the second embodiment of the present invention. It is a line graph concerning the 3rd example of the present invention. It is sectional drawing concerning the 3rd Example of this invention. It is sectional drawing concerning a comparative example. It is sectional drawing concerning the other Example of this invention. It is sectional drawing concerning the other Example of this invention. It is sectional drawing concerning the other Example of this invention. It is sectional drawing concerning the other Example of this invention. It is sectional drawing concerning the other Example of this invention. It is sectional drawing concerning the other Example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.

1. First Example (Configuration)
FIG. 1 shows a piezoelectric transducer 1 according to a first embodiment of the present invention. The piezoelectric transducer 1 is a MEMS (Micro Electro Mechanical Systems) manufactured using a semiconductor manufacturing process, and is housed in a case (not shown) and used as a speaker of a portable electronic device. The piezoelectric transducer 1 includes a support portion 11, an elastic film 13, a piezoelectric element 10, and a diaphragm 16.

  The support portion 11 has a rectangular frame shape surrounding the hole 11a. The support part 11 has sufficient rigidity so as not to be deformed by the vibration of the elastic film 13. The support portion 11 includes a substrate layer 101, an insulating layer 102 as an etching stopper layer, and a functional layer 106. The hole 11a may have a circular cross section. As the substrate layer and the functional layer, inorganic materials such as single crystal silicon, polycrystalline silicon, silicon dioxide, ceramics (zirconia, alumina, etc.), glass, glass ceramics, metals (copper, stainless steel), and resins can be used. Silicon oxide or the like can be used as the etching stopper layer.

The elastic film 13 is an elastic film obtained by curing a liquid film. The outer edge portion 13 b of the elastic film 13 is directly coupled to the inner edge portion of the support portion 11. The inner edge 13 a of the elastic film 13 is directly coupled to the outer edge of the diaphragm 16. That is, the elastic film 13 is an elastic film that is supported together with the piezoelectric element 10 by the support portion 11 and whose vibration end shape is determined by the cross-sectional shape of the hole 11a. The elastic film 13 has an annular shape with a thickness of 1 μm to 50 μm and a width of 100 μm to 2000 μm. The elastic film 13 is made of a thermosetting resin such as polyimide, PNB (polynorbornene) or BCB (benzocyclobutene), a thermoplastic elastomer such as silicon elastomer, or an insulating material such as rubber ^1, and has a Young's modulus of 0.01 GPa. A material of 10 GPa or less is preferable.

The piezoelectric element 10 has a structure in which a piezoelectric layer 104 is sandwiched between a lower electrode layer 103 and an upper electrode layer 105 and has a rectangular plate shape on the outer periphery. Wires 15 a and 15 b for applying drive signals are connected to the piezoelectric element 10. In the upper electrode layer 105 and the piezoelectric layer 104, a contact hole 10a for connecting the wire 15a to the lower electrode layer 103 is formed. The side wall of the contact hole 10a is covered with an insulating film 14 of the same quality as the elastic film 13 formed simultaneously with the elastic film 13. By covering the side wall of the contact hole 10a with the insulating film 14, a short circuit can be prevented. Further, by forming the insulating film 14 simultaneously with the elastic film 13, the insulating film 14 can be formed without increasing the manufacturing cost. The piezoelectric layer 104 is made of a piezoelectric material such as lead zirconate titanate (PZT), barium titanate (BaTiO ₃ ), lithium niobate (LiNbO ₃ ), and has a thickness of about 3 μm, for example. Each of the lower electrode layer 103 and the upper electrode layer 105 is made of platinum (Pt), for example, and the thickness is set to about 0.1 μm, for example.
The diaphragm 16 is coupled to the elastic film 13 at the entire outer edge portion formed of an annular end surface. The diaphragm 16 is, for example, a rectangular plate having a length of 8 mm, a width of 13 mm, and a thickness of 10 μm. The end face of the diaphragm 16 is inclined with respect to the interface between the insulating layer 102 and the functional layer 106. For this reason, the coupling interface between the diaphragm 16 and the elastic film 13 is increased as compared with the case where the end face of the diaphragm 16 is perpendicular to the interface between the insulating layer 102 and the functional layer 106. The bond strength with the film 13 is further increased.

(Production method)
Next, a method for manufacturing the piezoelectric transducer 1 will be described with reference to FIGS.
First, as shown in FIG. 2, an SOI (Silicon On Insulator) substrate comprising a thick single crystal silicon layer as the substrate layer 101, a silicon oxide layer as the insulating layer 102, and a thin single crystal silicon layer as the functional layer 106 is prepared. To do. Subsequently, the lower electrode layer 103, the piezoelectric layer 104, and the upper electrode layer 105 are sequentially stacked on the first main surface of the SOI substrate using a sputtering method or the like.

  Next, as shown in FIG. 3, a protective film R 1 having a predetermined pattern made of a photoresist is formed on the upper electrode layer 105. Subsequently, the upper electrode layer 105 and the piezoelectric layer 104 are patterned by etching using the protective film R1.

Next, as shown in FIG. 4, a protective film R2 made of a photoresist covering the contact hole 10a is formed, and the lower electrode layer 103 is patterned by etching using the protective film R2, thereby completing the piezoelectric element 10.
Next, using the lower electrode layer 103 as a protective film, the annular groove T and the diaphragm 16 are formed by annularly etching the functional layer 106 until the etching stopper layer 102 is exposed as shown in FIG. At this time, in order to incline the end face of the diaphragm 16 by etching, an anisotropic wet etching method or a dry etching method using a protective film having an inclined surface may be used.

  Next, as shown in FIG. 6, after the annular groove T, the diaphragm 16 and the piezoelectric element 10 are covered with the liquid film R3, the liquid film R3 is cured to form the elastic film R3. Specifically, for example, after forming a liquid photosensitive polyimide film by coating, spin coating, dipping, spraying, vapor deposition, printing, etc., an elastic film R3 is formed by imidizing and curing the photosensitive polyimide film by heating. To do. At this time, since the side surface of the annular groove T is inclined, a void is hardly formed between the elastic film R3 and the base, and step coverage is improved.

  Next, as shown in FIG. 7, by patterning the elastic film R3, the elastic film R3 which should be left on the inner edge part of the support part 11, the outer edge part of the piezoelectric element 10, and the side wall of the contact hole 10a is left and removed. To do. Specifically, a part of the photosensitive polyimide film is removed by exposing and developing the photosensitive polyimide film.

Next, as shown in FIG. 8, a protective film R4 having a predetermined pattern made of a photoresist is formed on the second main surface of the substrate layer 101 (the main surface on the back side of the first main surface). Subsequently, the hole 11a is formed by wet etching or deep-RIE of the substrate layer 101 using the protective film R4, and the etching stopper layer 102 is exposed.
Next, as shown in FIG. 9, the exposed portion of the etching stopper layer 102 from the hole 11a is removed, and the elastic film 13 and the diaphragm 16 are exposed.
After the removal of the protective film R4, post-processes such as dicing and packaging are performed to complete the piezoelectric transducer 1 shown in FIG.

(Operation)
The piezoelectric transducer 1 manufactured in this way operates as follows. When an audio wave drive signal is applied to the piezoelectric element 10 via the wires 15a and 15b, the piezoelectric element 10 expands and contracts in an in-plane direction (a direction parallel to the paper surface in FIG. 1B). Then, the diaphragm 16 bends and the elastic film 13 vibrates, and sound is transmitted from the elastic film 13.

In the piezoelectric transducer 1, the diaphragm 16 and the elastic film 13 are directly coupled without using an adhesive. Accordingly, it is possible to prevent the vibration characteristics from being lowered due to the use of the adhesive and the vibration characteristics from being varied due to the variation in the amount of the adhesive used, and the bonding strength between the diaphragm 16 and the elastic film 13 can be increased. In addition, since the diaphragm 16 and the elastic film 13 can be coupled simultaneously with the formation of the elastic film 13, the manufacturing cost can be suppressed. Further, since the elastic film 13 is formed by curing the liquid film, the thickness of the elastic film 13 can be freely set and the vibration characteristics can be widely adjusted.
Alternatively, the piezoelectric transducer 1 may be manufactured after forming an insulating layer on the first main surface of the SOI substrate. The functional layer 106 and the lower electrode layer 103 can be electrically separated, and a voltage can be more efficiently applied to the piezoelectric film.

(Second embodiment)
A piezoelectric transducer 2 according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 10C, the elastic film 13 is omitted. The piezoelectric element 10 of the piezoelectric transducer 2 is provided outside the elastic film 13. In the support portion 11, a region 11 b indicated by an arrow illustrated in FIG. 10C of the functional layer 106 protrudes inward from the substrate layer 101. A part of each of the four piezoelectric elements 10 is formed on the region 11b, and the functional layer 106 is thin (thickness 10 μm), so that the piezoelectric element 10 is in the in-plane direction (a direction parallel to the paper surface in FIG. 10B). ), The region 11b bends. Therefore, by driving the four piezoelectric elements 10, it is possible to drive the resin film 13 coupled to the region 11 b and the diaphragm 16 coupled to the resin film 13.
The piezoelectric transducer 2 can be manufactured by a method similar to the method described in the first embodiment because only the pattern of the piezoelectric element 10 and the pattern of the substrate layer 101 are different from those of the piezoelectric transducer 1.

(Third embodiment)
The solid broken line (1) shown in FIG. 11 shows the vibration characteristic of the piezoelectric transducer 3 in which the end face of the diaphragm 16 is directly coupled to the elastic film 13 without an adhesive as shown in FIG. It is. A broken line (2) shown in FIG. 11 is a vibration characteristic of the piezoelectric transducer 9 as a comparative example in which the elastic film 302 and the vibration plate 36 are bonded together by the thermosetting adhesive B as shown in FIG. The diaphragm 36 according to the comparative example 9 is composed of the functional layer 106, and the elastic film 302 according to the comparative example 9 is composed of a ready-made resin film. The dimensions of the piezoelectric transducer 3 as the third embodiment and the piezoelectric transducer 9 as the comparative example are as shown in Table 1 below.

  In the piezoelectric transducer 3 in which the diaphragm 16 is directly coupled to the elastic film 13 and the comparative example 9, the piezoelectric transducer 3 produces a larger sound pressure over almost the entire area as indicated by the broken lines (1) and (2). Obtainable. As described above, the piezoelectric transducer 3 in which the elastic film 13 is thinner than the ready-made elastic film 302 and the elastic film 13 and the diaphragm 16 are directly coupled without using an adhesive is compared with the comparative example 9. Show excellent vibration characteristics.

(Other examples)
As shown in FIG. 14, the elastic film 13 may be directly coupled only to the end face of the diaphragm 16. Even if the elastic film 13 is bonded only to the end face of the diaphragm 16, sufficient coupling strength can be obtained by forming a large number of irregularities on the end face of the diaphragm 16 as shown in FIG. 15.
Moreover, you may laminate | stack the diaphragms 16a and 16b as shown in FIG. In this case, the area of the coupling interface between the diaphragm 16 and the elastic film 13 can be increased by making the outer peripheral dimensions of the diaphragms 16a and 16b different.

As shown in FIG. 17, when the elastic film 13 is constituted by the resin film R108, the resin film R108 formed on the vibration plate 16 may be used as the mass portion 17 for adjusting the vibration characteristics.
Further, as shown in FIG. 18, since stress concentrates on the coupling portion between the vibration plate 16 of the resin film R108 to be the elastic film 13 and the support portion 11, a resin film R109 thicker than the resin film R108 is formed on the resin film R108. You may raise intensity | strength by laminating | stacking on top.
The elastic film is not limited to an annular shape, and may be any form as long as the support part and the diaphragm are connected. For example, four elastic films separated from each other may be coupled to each of the four sides of the diaphragm. .

  Further, as shown in FIG. 19, the bimorph type piezoelectric element 18 itself may be a diaphragm. The bimorph piezoelectric element 18 includes piezoelectric layers 18a and 18b, an electrode layer 19b sandwiched between them, and an electrode layer 19a bonded to the surfaces of the piezoelectric layers 16a and 16b. The electrode layer 19b sandwiched between the piezoelectric layers 18a and 18b is drawn out from the end faces of the piezoelectric layers 18a and 18b, and is bent and bonded to the surface of the piezoelectric layer 18b. A wire 20b is connected to the exposed portion of the electrode layer 19b. The electrode layer 19a is formed so as to cover from the surface of the piezoelectric layer 18a to the surface of the piezoelectric layer 18b. A wire 20a is connected to the electrode layer 19a.

  The technical scope of the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the scope of the present invention. For example, the materials, dimensions, film forming methods, and pattern transfer methods shown in the above-described embodiments are merely examples, and descriptions of addition and deletion of processes and replacement of process orders that are obvious to those skilled in the art are omitted. ing.

DESCRIPTION OF SYMBOLS 1, 2, 3 ... Piezoelectric transducer, 10 ... Piezoelectric element, 10a ... Contact hole, 11 ... Support part, 11a ... Hole, 13 ... Elastic film, 13a ... Inner edge part, 13b ... Outer edge part, 14 ... Insulating film, 15a, 15b ... wire, 16 ... diaphragm, 17 ... mass part, 18 ... piezoelectric element, 19a ... electrode layer, 19b ... electrode layer, 20a ... wire, 20b ... wire, 36 ... diaphragm, 101 ... substrate layer, 102 Insulating layer, 102 Etching stopper layer, 102 Functional layer, 103 Lower electrode layer, 104 Piezoelectric layer, 105 Upper electrode layer, 106 Functional layer

Claims (7)

An elastic film in which the liquid film is cured;
A support portion coupled to an outer edge portion of the elastic membrane and supporting the elastic membrane;
A diaphragm that is coupled to the elastic film without an adhesive and has an inclined end surface;
A piezoelectric element distorted together with the elastic film;
With
A central portion of the elastic membrane is coupled to an outer edge portion including an end face of the diaphragm;
Piezoelectric transducer. An elastic film in which the liquid film is cured;
A support portion coupled to an outer edge portion of the elastic membrane and supporting the elastic membrane;
A diaphragm having a plurality of concavities and convexities on the end face that is coupled to the elastic film without using an adhesive;
A piezoelectric element distorted together with the elastic film;
With
The elastic membrane is bonded to an outer edge including the end face of the diaphragm,
Piezoelectric transducer. Preparing a substrate in which an etching stopper layer and a functional layer are sequentially laminated on one main surface;
Forming an annular groove by etching the functional layer annularly until the etching stopper layer is exposed;
Forming a liquid film covering the annular groove;
Curing the liquid film to form an elastic film;
Etching until the elastic film and the functional layer inside the annular groove are exposed from the other main surface of the substrate;
A method for manufacturing a piezoelectric transducer comprising: Forming the liquid film covering the annular groove and the inside of the annular groove;
A method for manufacturing the piezoelectric transducer according to claim 3. Removing a part of the elastic film formed inside the annular film by patterning the elastic film;
The method for manufacturing a piezoelectric transducer according to claim 4, further comprising: Forming the diaphragm having an inclined end surface;
The method for manufacturing a transducer according to any one of claims 3 to 5. Forming the diaphragm having an end surface having a plurality of irregularities;
The manufacturing method of the transducer as described in any one of Claim 3 to 6.

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