JP2011091318A - Power generation device - Google Patents

Abstract

A power generation device capable of improving the power generation amount is provided.
A cantilever forming substrate 20 formed using an element forming substrate 120 and having a frame portion (support portion) 21 and a cantilever portion 22, and a piezoelectric conversion portion that generates an alternating voltage in response to vibration of the cantilever portion 22 ( The lower electrode 24a and the upper electrode 24c of the piezoelectric conversion unit 24 are electrically connected to the lower electrode pad 27a and the upper electrode pad 27c. In the piezoelectric conversion portion 24, the end of the piezoelectric conversion region where the piezoelectric layer 24b contacts the lower electrode 24a and the upper electrode 24c on the frame portion 21 side is aligned with the boundary between the frame portion 21 and the cantilever portion 22.
[Selection] Figure 1

Description

  The present invention relates to a vibration power generation device that converts vibration energy into electrical energy.

  In recent years, as one type of MEMS (micro electro mechanical systems) device, a power generation device that converts vibration energy caused by arbitrary vibration such as vibration of a car or vibration of a person into electric energy has been researched and developed in various places.

  Here, as an electromechanical conversion device that can be used as this type of power generation device, as shown in FIG. 6, it is formed by using an element forming substrate (here, Si substrate) 20a ′ and a frame portion (supporting portion). ) 21 ′ and a cantilever forming substrate 20 ′ having a cantilever portion (flexible portion) 22 ′ that is disposed inside the frame portion 21 ′ and is swingably supported by the frame portion 21 ′, and the cantilever portion of the cantilever forming substrate 20 ′ A device including a piezoelectric conversion unit (piezoelectric element) 24 ′ formed on 22 ′ and functioning as a power generation unit that generates an AC voltage in response to vibration of the cantilever unit 22 ′ has been proposed.

The above-described piezoelectric conversion portion 24 ′ is formed on the insulating film 29a ′ made of a silicon oxide film on one surface side of the element formation substrate 20a ′, and the lower electrode 24a ′ made of a laminated film of a Ti film and a Pt film. A piezoelectric layer 24b ′ made of an AlN thin film or a PZT (: Pb (Zr, Ti) O ₃ ) thin film formed on the opposite side of the lower electrode 24a ′ from the cantilever portion 22 ′ side, and a lower portion of the piezoelectric layer 24b ′. The upper electrode 24c ′ made of a Pt film is formed on the opposite side of the electrode 24a ′.

  Further, in the electromechanical transducer described above, the insulating layer 25 ′ made of a resist layer that prevents a short circuit between the upper electrode 24c ′ and the lower electrode 24a ′ is provided at the end of the piezoelectric transducer 24 ′ on the frame portion 21 ′ side. A connection formed by covering the upper electrode 24c ′ and the upper electrode pad 27c ′ formed on the insulating film 29a ′ in the frame portion 21 ′ and integrally formed on the upper electrode pad 27c ′. A lower electrode pad (not shown) electrically connected via the wiring 26c ′ and formed on the insulating film 29a ′ in the frame portion 21 ′ is formed integrally with the lower electrode 24a ′. They are electrically connected via connection wiring (not shown).

JP 2005-331485 A

  By the way, in the electromechanical transducer having the configuration shown in FIG. 6, the side edges of the lower electrode 24a ′, the piezoelectric layer 24b ′, and the upper electrode 24c ′ that are close to the frame portion 21 ′ are covered with the insulating layer 25 ′. The disconnection of the connection wiring 26c ′ caused by the step at the end of the piezoelectric layer 24b ′ is prevented.

  However, in the electromechanical transducer having the configuration shown in FIG. 6, in the piezoelectric transducer 24 ′, a part of the piezoelectric transducer region where the piezoelectric layer 24b ′ and the lower electrode 24a ′ and the upper electrode 24c ′ are in contact with each other is the frame portion 21 ′. When formed as a power generation device, the piezoelectric conversion region has a portion where no stress is applied even if the cantilever portion 22 ′ vibrates, and the portion becomes a parasitic capacitance. There was a problem that would decrease.

  This invention is made | formed in view of the said reason, The objective is to provide the electric power generation device which can aim at the improvement of electric power generation amount.

  According to a first aspect of the present invention, there is provided a cantilever forming substrate that is formed using an element forming substrate and has a cantilever portion that is swingably supported by the support portion, and a cantilever portion that is formed on the cantilever portion according to vibration of the cantilever portion. A power generation unit including a piezoelectric conversion unit that generates an alternating voltage, and the power generation unit is opposite to the cantilever unit side of the lower electrode and the lower electrode formed in a portion overlapping the cantilever unit on one surface side of the cantilever forming substrate A piezoelectric layer formed on the side and an upper electrode formed on the opposite side of the piezoelectric layer from the lower electrode side, each of the lower electrode and the upper electrode serving as a support portion on the one surface side of the cantilever forming substrate A power generation device that is electrically connected to each other pad formed on the overlapping portion, and in the piezoelectric conversion unit, the piezoelectric layer, the lower electrode, and The end of the supporting portion side of the piezoelectric transducer region and each upper electrode is in contact, characterized in that are aligned to the boundary between the supporting portion and the cantilever portion.

  According to the present invention, since the piezoelectric conversion region has a piezoelectric conversion region where the piezoelectric layer, the lower electrode, and the upper electrode are in contact with each other, the support portion side end is aligned with the boundary between the support portion and the cantilever portion. Compared with the case where the end of the support part side is on the support part side at the boundary between the support part and the cantilever part, the power generation efficiency can be improved by improving the power generation efficiency, and the end of the piezoelectric conversion region on the support part side is Compared to the cantilever part side at the boundary between the support part and the cantilever part, it is possible to increase the area of the piezoelectric conversion region existing in the part where the stress increases during vibration of the cantilever part, and to improve the power generation efficiency.

  According to a second aspect of the present invention, in the first aspect of the present invention, an insulating layer that defines an area where the upper electrode and the piezoelectric layer are in contact and prevents a short circuit between the upper electrode and the lower electrode is provided on the cantilever-forming substrate. It is formed on the one surface side, and the insulating layer defines a position where the piezoelectric layer and the upper electrode are in contact with each other and an end position on the support portion side.

  According to the present invention, the insulating layer that defines an area where the upper electrode and the piezoelectric layer are in contact and prevents a short circuit between the upper electrode and the lower electrode is provided at a position where the piezoelectric layer and the upper electrode are in contact with each other. Since the position of the end on the support portion side is defined, the piezoelectric layer can be formed to extend onto the support portion, and the cantilever can be formed regardless of the patterning accuracy of the piezoelectric layer at the time of manufacture. The piezoelectric layer can be formed over the entire length of the part, and a decrease in power generation amount and variation due to the patterning accuracy can be suppressed.

  According to a third aspect of the present invention, in the second aspect of the present invention, the planar shape of the insulating layer is a frame shape along the peripheral portion of the upper electrode.

  According to this invention, compared with the case where the said insulating layer is formed in the shape along only a part of the circumferential direction of the peripheral part of the said upper electrode, electric power generation efficiency can be improved.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the insulating layer is made of SiO ₂ or Si ₃ N ₄ .

  According to this invention, the insulation can be improved as compared with the case where the insulating layer is a resist.

  The invention according to claim 1 has an effect of improving the power generation amount.

The power generation device of embodiment is shown, (a) is a schematic plan view, (b) is A-A 'schematic sectional drawing of (a). It is principal part explanatory drawing of a power generation device same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of an electric power generation device same as the above. It is a general | schematic disassembled perspective view of the other structural example of an electric power generation device same as the above. It is a general | schematic exploded sectional view of the principal part of the other structural example of an electric power generation device same as the above. The power generation device of a prior art example is shown, (a) is a schematic perspective view, (b) is a schematic cross-sectional view along A-A 'in (a), and (c) is a schematic cross-sectional view along B-B' in (a).

  As shown in FIG. 1, the power generation device according to the present embodiment is formed using an element forming substrate 120 and is disposed inside the frame portion 21 and the frame portion 21 and is swingably supported by the frame portion 21. A cantilever forming substrate 20 having a front surface 22 and a piezoelectric conversion portion (piezoelectric element) 24 that is formed on the cantilever portion 22 on one surface side of the cantilever forming substrate 20 and generates an AC voltage in response to vibration of the cantilever portion 22. Yes. Further, a weight portion 23 for increasing the amount of displacement of the cantilever portion 22 is integrally provided at the tip end portion of the cantilever portion 22 in the cantilever forming substrate 20. In the present embodiment, the frame portion 21 constitutes a support portion, and the piezoelectric conversion portion 24 constitutes a power generation portion.

  The above-described piezoelectric conversion portion 24 is formed on the lower electrode 24a, the piezoelectric layer 24b formed on the opposite side of the lower electrode 24a on the cantilever portion 22 side, and the opposite side of the piezoelectric layer 24b on the lower electrode 24a side. It is comprised with the upper electrode 24c.

  Further, on the one surface side of the cantilever forming substrate 20, there is a lower electrode which is a separate pad electrically connected to each of the lower electrode 24a and the upper electrode 24c via connection wirings 26a and 26c made of metal wiring. A pad 27 a and an upper electrode pad 27 c are formed at portions that overlap the frame portion 21.

  The piezoelectric transducer 24 is designed such that the planar size of the lower electrode 24a is the largest, the planar size of the piezoelectric layer 24b is the second largest, and the planar size of the upper electrode 24c is the smallest. In the converting portion 24, the piezoelectric layer 24b is in contact with each of the lower electrode 24a and the upper electrode 24c, and the end of the piezoelectric converting region on the frame portion 21 side is on the left side in FIGS. 1 (b) and 2 (a). As shown by the alternate long and short dash line, the boundary between the frame part 21 and the cantilever part 22 is aligned (substantially coincides), and the end on the weight part 23 side of the piezoelectric conversion region is shown by the alternate long and short dash line in FIG. Are designed so that they are aligned (substantially coincide) with the ends of the weights 23. Here, in plan view, the piezoelectric conversion unit 24 has the piezoelectric layer 24b positioned inside the outer peripheral line of the lower electrode 24a, and the upper electrode 24c positioned inside the outer peripheral line of the piezoelectric layer 24b.

  Further, on the one surface side of the cantilever forming substrate 20, an area where the upper electrode 24c and the piezoelectric layer 24b are in contact is defined (the above-described piezoelectric conversion region is defined) and electrically connected to the upper electrode 24c. An insulating layer 25 that prevents a short circuit between the upper electrode 24c and the lower electrode 24a by preventing a short circuit between the electrode 26c and the lower electrode 24a is formed so as to cover the peripheral portions of the lower electrode 24a and the piezoelectric layer 24b. . In short, the planar view shape of the insulating layer 25 is a frame shape (in the illustrated example, a trapezoidal frame shape) along the peripheral portion of the upper electrode 24c.

The insulating layer 25 is composed of a silicon oxide film, but is not limited to a silicon oxide film, and may be composed of a silicon nitride film. In short, the insulating layer 25 has been formed by SiO _2, is not limited to SiO _2, it may be formed by _Si 3 _{N 4.} In addition, the cantilever forming substrate 20 has insulating films 29a and 29b made of a silicon oxide film formed on one surface side and the other surface side of the element forming substrate 120, respectively. The insulating film 29a on the one surface side of the formation substrate 120 is electrically insulated.

  In the power generation device described above, the power generation unit is configured by the piezoelectric conversion unit 24 including the lower electrode 24a, the piezoelectric layer 24b, and the upper electrode 24c, and thus the piezoelectric layer of the piezoelectric conversion unit 24 is caused by the vibration of the cantilever unit 22. 24b receives stress, and a bias of electric charge occurs between the upper electrode 24c and the lower electrode 24a, and an AC voltage is generated in the piezoelectric conversion unit 24.

By the way, the power generation device in the present embodiment employs PZT, which is a kind of lead-based piezoelectric material, as the piezoelectric material of the piezoelectric layer 24b. An SOI (Silicon on Insulator) substrate having a single crystal silicon layer (active layer) 120c on a buried oxide film 120b made of a silicon oxide film is used, but the lead-based piezoelectric material is not limited to PZT, for example, PZT-PMN (: Pb (Mn, Nb) O ₃ ) or PZT to which other impurities are added may be employed. Here, in the power generation device of the present embodiment, when the dielectric constant of the piezoelectric layer 24b is ε and the power generation index is P, the relationship P∝e ₃₁ ² / ε is established, and the power generation efficiency increases as the power generation index P increases. made, but which is a typical piezoelectric material PZT and AlN respectively piezoelectric constant e ₃₁ used in the power generation _device, viewed from the common value of the dielectric constant, the square can rather piezoelectric constant e ₃₁ large power generation index P The power generation index P can be increased by adopting PZT. In addition, as the SOI substrate which is the element formation substrate 120, the one surface (the surface of the silicon layer 120c) having a (100) plane is used.

  Further, in the power generation device of the present embodiment, since the above-described SOI substrate is used as the element formation substrate 120, the buried oxide film 120b of the SOI substrate is used as an etching stopper layer when forming the cantilever portion 22 during manufacturing. By using it, the thickness of the cantilever portion 22 can be increased in accuracy, and the reliability can be improved and the cost can be reduced. However, the element formation substrate 120 is not limited to an SOI substrate, and may be a single crystal silicon substrate, for example.

  In the present embodiment, the lower electrode 24a is constituted by a laminated film of a Ti film and a Pt film, and the upper electrode 24c is constituted by a laminated film of a Ti film and an Au film. However, these materials and layer structures are used. Is not particularly limited, and each of the lower electrode 24a and the upper electrode 24c may have a single-layer structure. As a material of the lower electrode 24a, for example, Al may be adopted, and as a material of the upper electrode 24c, For example, Mo, Al, Pt, etc. may be adopted.

  In the power generation device of the present embodiment, the thickness of the lower electrode 24a is set to 100 nm, the thickness of the piezoelectric layer 24b is set to 600 nm, and the thickness of the upper electrode 24c is set to 100 nm. Not what you want.

  Hereinafter, although the manufacturing method of the electric power generating device of this embodiment is demonstrated, referring FIG. 3, the figure (a)-(g) has shown the site | part corresponding to the AB cross section of Fig.1 (a). .

  First, by performing an insulating film forming step of forming insulating films 29a and 29b made of a silicon oxide film on the one surface side and the other surface side of the element forming substrate 120 made of the SOI substrate, respectively, by a thermal oxidation method or the like. The structure shown in FIG.

  Thereafter, a metal layer 240a is formed on the entire surface of the element formation substrate 120 on the one surface side by a sputtering method, a CVD method, or the like, by a sputtering method, a CVD method or the like. Next, a piezoelectric film (for example, PZT film) 240b, which is the basis of the piezoelectric layer 24b made of a piezoelectric material (for example, PZT), is sputtered on the entire surface of the element forming substrate 120 on the one surface side. The structure shown in FIG. 3B is obtained by performing a piezoelectric film forming process formed by the CVD method, the sol-gel method, or the like. The metal layer 240a is not limited to the Au layer, and may be, for example, an Al layer or an Al—Si layer, or an adhesion improving Ti layer interposed between the Au layer and the Au layer and the insulating film 29a. You may comprise. Here, the material of the adhesion layer is not limited to Ti, and may be, for example, Cr, Nb, Zr, TiN, TaN, or the like.

  By performing the piezoelectric film patterning step of forming the piezoelectric layer 24b formed of a part of the piezoelectric film 240b by patterning the piezoelectric film 240b using the photolithography technique and the etching technique after the piezoelectric film forming process described above, The structure shown in FIG.

  Thereafter, the above-described metal layer 240a is patterned using a photolithography technique and an etching technique to form the lower electrode 24a, the connection wiring 26a, and the lower electrode pad 27a, each of which is a part of the metal layer 240a. By performing the process, the structure shown in FIG. In this embodiment, the metal layer 240a is patterned in the metal layer patterning step to form the connection wiring 26a and the lower electrode pad 27a together with the lower electrode 24a. However, the present invention is not limited to this. Only the lower electrode 24a may be formed by patterning the metal layer 240a in the patterning step, and then a wiring formation step for forming the connection wiring 26a and the pad 27a may be provided separately, or the connection wiring 26a is formed. The connection wiring forming step and the lower electrode pad forming step for forming the lower electrode pad 27a may be provided separately. In the etching of the metal layer 240a, for example, an RIE method or an ion milling method may be employed.

  By forming the lower electrode 24a, the connection wiring 26a, and the lower electrode pad 27a by the above-described metal layer patterning step, an insulating layer forming step for forming the insulating layer 25 on the one surface side of the element forming substrate 120 is performed. The structure shown in FIG. 3 (e) is obtained. In the insulating layer forming step, the insulating layer 25 is formed on the entire surface of the element formation substrate 120 on the one surface side by the CVD method and then patterned using the photolithography technique and the etching technique. The insulating layer 25 may be formed using the above.

  After the above-described insulating layer forming process, the connection electrode 26c is formed simultaneously with the upper electrode forming process in which the upper electrode 24c is formed using a thin film forming technique such as EB vapor deposition, sputtering, or CVD, photolithography, or etching. Further, the structure shown in FIG. 3 (f) is obtained by performing a wiring forming process in which the upper electrode pad 27c is formed using a thin film forming technique such as EB vapor deposition, sputtering, or CVD, photolithography, or etching. Get. In other words, in the present embodiment, in the upper electrode formation process, the connection wiring 26c and the upper electrode pad 27c are formed together with the upper electrode 24c, but not limited to this, the upper electrode formation process and the wiring formation process In addition, the wiring forming process may include a connection wiring forming process for forming the connection wiring 26c and an upper electrode pad forming process for forming the upper electrode pad 27c. Also good. The upper electrode 24c may be etched by dry etching such as RIE or wet etching. For example, the Au film may be wet-etched with a potassium iodide aqueous solution and the Ti film may be wet-etched with hydrogen peroxide water.

  After forming the upper electrode 24c, the connection wiring 26c, and the upper electrode pad 27c as described above, the substrate processing for forming the cantilever portion 22, the weight portion 23, and the frame portion 21 using a photolithography technique, an etching technique, and the like. By forming the cantilever forming substrate 20 by performing the steps, the structure shown in FIG. 3G is obtained. Here, in the substrate processing step, parts other than the cantilever part 22, the weight part 23, and the frame part 21 of the element forming substrate 120 from the one surface side of the element forming substrate 120 are utilized by using a photolithography technique, an etching technique, and the like. Etching to a first predetermined depth (here, the silicon layer 120c is etched to a depth reaching the buried oxide film 120b) to perform a surface groove forming step for forming a surface groove, followed by photolithography and etching. Using a technique or the like, the portion other than the weight portion 23 and the frame portion 21 in the element forming substrate 120 is etched from the other surface side of the element forming substrate 120 to the second predetermined depth (here, the buried oxide film 120b is formed). Etching the support substrate 120a to a depth that can be reached) Then, a cantilever portion 22 is formed together with the weight portion 23 and the frame portion 21 by etching away unnecessary portions of the buried oxide film 120b and connecting the front surface groove and the back surface groove. By performing the oxide film etching step, the power generation device having the structure shown in FIG. By the way, in this embodiment, the element forming substrate 120 is etched using an inductively coupled plasma (ICP) type etching apparatus capable of vertical deep digging in the front surface groove forming step and the back surface groove forming step of the substrate processing step. The angle formed between the back surface of the cantilever portion 22 and the inner surface of the rectangular frame-shaped frame portion 120 can be approximately 90 degrees. Thus, as described above, the end of the piezoelectric conversion region on the frame portion 21 side is accurately aligned with the boundary between the frame portion 21 and the cantilever portion 22, and the end of the piezoelectric conversion region on the weight portion 23 side is aligned with the weight portion 23. Can be accurately aligned with the edges of the. Note that the front surface groove forming step and the back surface groove forming step in the substrate processing step are not limited to dry etching using an ICP type dry etching apparatus, but wet etching (crystal difference) using an alkaline solution such as a TMAH aqueous solution or a KOH aqueous solution. (Isotropic etching).

  Here, the power generation device including the cantilever forming substrate 20 and the piezoelectric conversion unit 24 is divided into individual power generation devices by performing the dicing process after performing the substrate processing process at the wafer level. ing.

  In the power generation device of the present embodiment described above, as shown in FIG. 2A, in the piezoelectric conversion portion 24, the piezoelectric layer 24b, the lower electrode 24a, and the upper electrode 24c are in contact with the frame portion 21 side of the piezoelectric conversion region. Since the end (the position of the downward arrow in FIG. 2A) is aligned with the boundary (the position of the upward arrow in FIG. 2A) between the frame portion 21 and the cantilever portion 22, FIG. As shown in b), the end of the piezoelectric conversion region on the frame part 21 side (the position of the downward arrow in FIG. 2B) is the position on the frame part 21 side at the boundary between the frame part 21 and the cantilever part 22 ( Compared to the case of the upward arrow in FIG. 2B, the amount of power generation can be improved by improving the power generation efficiency, and as shown in FIG. 2C, the frame portion of the piezoelectric conversion region 21 side end (in FIG. 2C) Compared with the case where the position of the downward arrow) is at the position on the cantilever part 22 side (position of the upward arrow in FIG. 2C) at the boundary between the frame part 21 and the cantilever part 22, the vibration of the cantilever part 22 It is possible to increase the area of the piezoelectric conversion region existing in a portion where stress sometimes increases (near the boundary between the cantilever portion 22 and the frame portion 21), and to improve power generation efficiency.

  In the power generation device of this embodiment, the insulating layer 25 that defines an area where the upper electrode 24c and the piezoelectric layer 24b are in contact and prevents a short circuit between the upper electrode 24c and the lower electrode 24a is provided on the one surface of the cantilever forming substrate 20. Since the position of the end on the frame portion 21 side is defined by the insulating layer 25 where the piezoelectric layer 24b and the upper electrode 24c are in contact with each other, the piezoelectric layer 24b is extended onto the frame portion 21. Regardless of the patterning accuracy of the piezoelectric layer 24b at the time of manufacture, the piezoelectric layer 24b can be formed over the entire length of the cantilever portion 22, and the power generation amount decreases or varies due to the patterning accuracy. Can be suppressed.

  Further, in the power generation device of the present embodiment, since the planar view shape of the insulating layer 25 is a frame shape along the peripheral portion of the upper electrode 24c, the insulating layer 25 is part of the peripheral direction of the peripheral portion of the upper electrode 24c. The power generation efficiency can be improved as compared with the case where the shape is formed only along the shape.

Further, in the power generation device of the present embodiment, since the insulating layer 25 is formed of SiO ₂ or Si ₃ N ₄ , the insulation and heat resistance can be improved compared to the case where the insulating layer 25 is a resist.

  Further, in the power generation device of the present embodiment, as described above, since the piezoelectric layer 24b is located inside the outer peripheral line of the lower electrode 24a in plan view, as described in the above manufacturing method, element formation is performed. After the metal layer 240a serving as the basis of the lower electrode 24a is formed on the entire surface on the one surface side of the substrate 120, the piezoelectric film 240b serving as the basis of the piezoelectric layer 24b is formed on the entire surface on the one surface side of the element forming substrate 120. After that, by patterning the piezoelectric film 240b, a manufacturing process for forming the piezoelectric layer 24b made of a part of the piezoelectric film 240b can be adopted, and a predetermined shape is formed on the one surface side of the element forming substrate 120. When the manufacturing process of forming the piezoelectric layer 24b by forming the lower electrode 24a, forming the piezoelectric film 240b, and patterning the piezoelectric film 240b is employed. Compared to, it can improve the crystallinity of the piezoelectric layer 24b, thereby improving the power generation efficiency.

  In addition, in this embodiment, the planar view shape of the cantilever part 22 is trapezoidal shape. However, the shape is not limited to this. For example, the cantilever part 22 may be a rectangular shape, and the width dimension becomes closer to the frame part 21 away from the weight part 23. The outer peripheral lines on both sides in the width direction may have a shape defined by an nth-order curve (n ≧ 2) (in this case, both side edges of the cantilever portion 22 are curved surfaces).

  Further, in the power generation device having the configuration shown in FIG. 1, the insulating layer 25 that defines the area where the upper electrode 24c and the piezoelectric layer 24b are in contact and prevents the upper electrode 24c and the lower electrode 24a from being short-circuited is provided on the cantilever-forming substrate 20. All the portions of the connection wiring 26c between the upper electrode 24c and the upper electrode pad 27c electrically connected to the upper electrode 24c are extended to the frame portion 21 on the one surface side of the insulating layer 25. If the upper electrode pad 27c is formed on the flat portion of the insulating layer 25, the level difference in the underlying portion of the connection wiring 26c can be reduced, and the film thickness of the piezoelectric layer 24b is increased. However, it is possible to prevent disconnection of the connection wiring 26c that electrically connects the upper electrode 24c and the upper electrode pad 27c, thereby improving power generation efficiency and reliability. Hakare on, moreover, thereby also improving the power generation efficiency by reducing the parasitic capacitance between the formed element forming substrate 120 by a semiconductor substrate such as a pad 27c and the SOI substrate and a single crystal silicon substrate for the upper electrode. Here, in the power generation device of the present embodiment, as described above, the piezoelectric layer 24b is positioned inside the outer peripheral line of the lower electrode 24a and the upper electrode 24c is positioned inside the outer peripheral line of the piezoelectric layer 24b in plan view. Therefore, compared with the case where the lower electrode 24a, the piezoelectric layer 24b, and the upper electrode 24c have the same planar size, the level difference of the portion serving as the base of the connection wiring 26c can be reduced.

  Incidentally, the power generation device shown in FIG. 1 is composed of the cantilever forming substrate 20 and the piezoelectric conversion portion 24, and is formed using the first cover forming substrate 30a as shown in FIGS. The first cover substrate 30 fixed to the frame portion 21 on the one surface side of the cantilever forming substrate 20 and the second cover forming substrate 10a and the frame portion on the other surface side of the cantilever forming substrate 20 are formed. A second cover substrate 10 fixed to 21 may be provided.

  Hereinafter, the power generation device shown in FIGS. 4 and 5 will be described, but the same components as those in FIG.

  The first cover substrate 30 uses a first silicon substrate as the first cover forming substrate 30a, and a cantilever portion 22 is formed on one surface of the first cover forming substrate 30a on the cantilever forming substrate 20 side. A recess 30 b is formed for forming a displacement space of the movable part composed of the weight part 23 with the cantilever forming substrate 20.

  Further, the first cover substrate 30 is provided with output electrodes 35 and 35 for supplying the AC voltage generated by the piezoelectric conversion unit 24 serving as a power generation unit to the other surface side of the first cover forming substrate 30a. The output electrodes 35 and 35 are connected to the contact electrodes 34 and 34 formed on the one surface side of the first cover forming substrate 30a and the thickness of the first cover forming substrate 30a. They are electrically connected through through-hole wirings 33, 33 penetrating in the direction. Here, the first cover substrate 30 is electrically connected by connecting each of the contact electrodes 34, 34 to the lower electrode pad 27 a and the upper electrode pad 27 c of the cantilever forming substrate 20. In the present embodiment, the output electrodes 35 and 35 and the connection electrodes 34 and 34 are formed of a laminated film of a Ti film and an Au film, but these materials are not particularly limited. Moreover, although Cu is adopted as the material of each through-hole wiring 33, 33, it is not limited thereto, and for example, Ni, Al, etc. may be adopted.

  In the present embodiment, since the first Si substrate is used as the first cover forming substrate 30a, the first cover substrate 30 is silicon for preventing a short circuit between the two output electrodes 35, 35. An insulating film 32 made of an oxide film is formed on the one surface side and the other surface side of the first cover forming substrate 30a and on the inner peripheral surface of the through hole 31 in which the through hole wirings 33 and 33 are formed. It is formed straddling. In the case where an insulating substrate such as a glass substrate is used as the first cover forming substrate 30a, the insulating film 32 need not be provided.

  The second cover substrate 10 uses a second Si substrate as the second cover forming substrate 10a, and a cantilever portion is formed on one surface of the second cover forming substrate 10a on the cantilever forming substrate 20 side. A recess 10 b is formed for forming a displacement space of the movable part composed of 22 and the weight part 23 between the cantilever forming substrate 20. Note that an insulating substrate such as a glass substrate may be used as the second cover forming substrate 10a.

  A plurality (four in the illustrated example) of first bonding metal layers 28 for bonding to the first cover substrate 30 are formed on the one surface side of the cantilever forming substrate 20 described above. The first cover substrate 30 is formed with a plurality of second bonding metal layers (not shown) bonded to the first bonding metal layer 28.

  Here, the cantilever forming substrate 20 and the cover substrates 10 and 30 are bonded by a room temperature bonding method (in the case where the upper electrode pad 27c is formed on the insulating layer 25, the insulating layer 25 described above is used. Are extended to a wider range, and not only the upper electrode pad 27c but also the lower electrode pad 27a and the first bonding metal layer 28 are formed on the insulating layer 25 with the same material and thickness as the upper electrode pad 27c. It is preferable to form it. However, the bonding method between the cantilever-forming substrate 20 and the cover substrates 10 and 30 is not limited to the room temperature bonding method, and for example, a resin bonding method using an epoxy resin or the like, an anodic bonding method, or the like may be employed.

  In manufacturing the power generation device shown in FIGS. 4 and 5, after forming the cantilever forming substrate 20, a cover joining step for joining the cover substrates 10 and 30 may be performed. What is necessary is just to divide | segment into each electric power generation device by performing a dicing process after performing until completion | finish at a wafer level. Here, the cover substrates 10 and 30 may be formed by appropriately applying known processes such as a photolithography process, an etching process, a thin film forming process, and a plating process.

By the way, in the electric power generation device of the above-mentioned embodiment, the piezoelectric layer 24b is formed on the lower electrode 24a. However, a seed serving as a base when the piezoelectric layer 24b is formed between the piezoelectric layer 24b and the lower electrode 24a. Of course, the crystallinity of the piezoelectric layer 24b may be further improved by interposing a layer. Here, as the material of the seed layer, for example, SrRuO ₃ , (Pb, La) TiO ₃ , PbTiO ₃ or the like, which is a kind of conductive oxide material, may be employed.

  Moreover, since the power generation device of the above-mentioned embodiment is provided with the weight part 23 at the tip part of the cantilever part 22, the power generation amount can be increased as compared with the case where the weight part 23 is not provided.

20 Cantilever forming substrate 21 Frame part (support part)
22 Cantilever part 23 Weight part 24 Piezoelectric conversion part (power generation part)
24a Lower electrode 24b Piezoelectric layer 24c Upper electrode 25 Insulating layer 26a Connection wiring 26c Connection wiring 27a Lower electrode pad (pad)
27c Pad for upper electrode (pad)
120 element forming substrate

Claims (4)

  A cantilever forming substrate that is formed using an element forming substrate and has a cantilever portion that is swingably supported by the support portion, and a piezoelectric conversion that generates an AC voltage in response to the vibration of the cantilever portion formed on the cantilever portion. And a piezoelectric layer formed on the opposite side of the lower electrode from the cantilever part side, the lower electrode formed on the surface of the cantilever forming substrate on the surface overlapping the cantilever part. And an upper electrode formed on the opposite side of the piezoelectric layer from the lower electrode side, and each of the lower electrode and the upper electrode is formed in a portion overlapping the support portion on the one surface side of the cantilever forming substrate. A power generation device electrically connected to another pad, wherein each of the piezoelectric layer, the lower electrode and the upper electrode in the piezoelectric conversion unit Power generation device, wherein a contact end of the supporting portion side of the piezoelectric transducer region, are aligned to the boundary between the supporting portion and the cantilever portion.   An insulating layer that defines an area where the upper electrode and the piezoelectric layer are in contact and prevents a short circuit between the upper electrode and the lower electrode is formed on the one surface side of the cantilever forming substrate, and the piezoelectric layer is used to form the piezoelectric layer. The power generation device according to claim 1, wherein a position where the layer and the upper electrode are in contact with each other and a position of an end on the support portion side is defined.   The power generation device according to claim 2, wherein a shape of the insulating layer in a plan view is a frame shape along a peripheral portion of the upper electrode. The power generation device according to claim ₂ , wherein the insulating layer is made of SiO ₂ or Si ₃ N ₄ .

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