JP2011071467A - Method of manufacturing ferroelectric device - Google Patents

Abstract

A method of manufacturing a ferroelectric device (power generation device or pyroelectric device) capable of improving the crystallinity and performance of a ferroelectric film irrespective of the substrate material of the ferroelectric device is provided.
A piezoelectric layer forming substrate (second substrate) having better lattice matching with a piezoelectric layer (ferroelectric film) 24b than the element forming substrate (first substrate) 20a. After that, the lower electrode 24a is formed on the piezoelectric layer 24b. Subsequently, the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40 and the element forming substrate 20 are bonded to the bonding layer 51. Then, by removing the piezoelectric layer forming substrate 40, the lower electrode 24a and the piezoelectric layer 24b are transferred to the element forming substrate 20a. Thereafter, the upper electrode 24c is formed on the one surface side of the element formation substrate 20a to form the power generation unit 24, and then the element formation substrate 20a is processed to have the frame portion 21, the cantilever portion 22, and the weight portion 23. A cantilever forming substrate 20 is formed.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a ferroelectric device that uses the piezoelectric effect and pyroelectric effect of a ferroelectric film, and in particular, a vibration-type power generation device that converts vibration energy into electrical energy using the piezoelectric effect, The present invention relates to a method for manufacturing a ferroelectric device used as a pyroelectric device utilizing the pyroelectric effect.

  Conventionally, a ferroelectric device utilizing the piezoelectric effect or pyroelectric effect of a ferroelectric film has attracted attention.

As an example of this type of ferroelectric device, conventionally, as a kind of MEMS (micro electro mechanical systems) device, vibration energy caused by any vibration such as car vibration or vibration caused by human movement is converted into electrical energy. The power generation device to be researched and developed in various places (for example, refer nonpatent literature 1). As other examples of ferroelectric devices, pyroelectric devices such as pyroelectric infrared sensors that use the pyroelectric effect of a ferroelectric film have been researched and developed in various places (for example, Patent Document 1). reference). As a ferroelectric material showing the piezoelectric effect and pyroelectric effect, for example, PZT (: Pb (Zr, Ti) O ₃ ), which is a kind of lead-based oxide ferroelectric, is widely known. .

  As shown in FIG. 11, the power generation device disclosed in Non-Patent Document 1 is formed using an element formation substrate (here, Si substrate) 20a ′ and arranged inside the frame portion 21 ′ and the frame portion 21 ′. And a cantilever forming substrate 20 ′ having a weight portion (vibrator) 23 ′ at the tip of a cantilever portion (flexible portion) 22 ′ that is swingably supported by the frame portion 21 ′. The cantilever portion 22 ′ has a cantilever. A power generation unit 24 ′ including a piezoelectric conversion unit (piezoelectric conversion element) that generates an alternating voltage in response to vibration of the unit 22 ′ is formed.

  Further, the above-described power generation device is formed using the first cover forming substrate (here, the glass substrate) 30a ′, and the frame portion 21 ′ on one surface side (the upper surface side in FIG. 11) of the cantilever forming substrate 20 ′. Is attached to the first cover substrate 30 ′ and the second cover forming substrate (here, a glass substrate) 10a ′, and the other surface side of the cantilever forming substrate 20 ′ (the lower surface side in FIG. 11). And a second cover substrate 10 ′ to which a frame portion 21 ′ is fixed.

  In addition, between each cover board | substrate 10 ', 30' and the movable part which consists of the cantilever part 22 'and the weight part 23' of cantilever formation board | substrate 20 ', the displacement space 16', 36 'of the said movable part is provided. Is formed.

  The piezoelectric conversion unit constituting the power generation unit 24 ′ includes a lower electrode 24a ′ made of a Pt film and a piezoelectric layer made of an AlN thin film or a PZT thin film formed on the opposite side of the lower electrode 24a ′ to the bending part 22 side. 24b ′ and an upper electrode 24c ′ made of an Al film formed on the opposite side of the piezoelectric layer 24b ′ from the lower electrode 24a ′ side.

Note that Non-Patent Document 1 proposes to employ a piezoelectric material having a small relative dielectric constant and a large piezoelectric constant e ₃₁ as the material of the piezoelectric layer 24b ′ in order to increase the output of the power generation device.

Patent Document 1 illustrates a pyroelectric infrared sensor as an example of a ferroelectric device, and discloses a ferroelectric device (ferroelectric element) having a configuration shown in FIG. In the ferroelectric device having the configuration shown in FIG. 12, an MgO thin film 102 preferentially oriented in the (100) plane is formed on one surface of a stainless metal substrate 101, and a lower electrode 103 made of a Pt thin film is formed on the MgO thin film 102. The ferroelectric film 104 made of Pb _0.9 La _0.1 Ti _0.975 O _3, which is a lead titanate ferroelectric material, is formed on a specific portion of the lower electrode 103, and Ni is formed on the ferroelectric film 104. An upper electrode 108 made of a -Cr thin film is formed. Further, in this ferroelectric device, a resin layer 106 that protects the lower electrode 103 and the ferroelectric film 104 is formed on the one surface side of the stainless metal substrate 101, and a resin layer 109 that protects the upper electrode 108. The protective resin layer 107 is formed on the other surface side.

  In the ferroelectric device having the configuration shown in FIG. 12, a gap layer 110 for preventing heat from being dispersed from the ferroelectric film 104 during operation is formed on the one surface side of the stainless metal substrate 101. Is formed. Note that the void layer 110 is an etching hole 105 formed in a laminated structure such as the MgO thin film 102, the lower electrode 102, the ferroelectric film 104, the upper electrode 108, and the resin layer 109 on the one surface side of the stainless metal substrate 101. An etchant is introduced through and a part of the stainless metal substrate 101 is etched.

JP-A-8-321640

R. van Schaijk, et al, “Piezoelectric AlN energy harvesters for wireless autonomous transducer solutions”, IEEE SENSORS 2008 Conference, 2008, p.45-48

  By the way, the power generation device having the configuration shown in FIG. 11 uses a Si substrate as the element formation substrate 20a ′, and the lower electrode 24a on the cantilever portion 22 ′ of the cantilever formation substrate 20 ′ formed using the element formation substrate 20a ′. A power generation unit 24 ′ including “, piezoelectric layer 24 b” and upper electrode 24 c ′ is formed by a reactive sputtering method or the like.

However, in general, a PZT thin film formed on one surface side of a single crystal Si substrate by various thin film formation techniques such as sputtering is polycrystalline, and one surface side of a single crystal MgO substrate or single crystal SrTiO _{3 is formed.} Compared with a single crystal PZT thin film formed on one surface side of the substrate, the crystallinity is inferior and the piezoelectric constant e ₃₁ is also low. In addition, research and development have been conducted on various methods for forming a PZT thin film having excellent crystallinity on one surface side of a single crystal Si substrate. However, a PZT thin film having sufficient crystallinity has not been obtained. Currently.

In general, the relative permittivity of a PZT thin film formed on one surface side of a single crystal Si substrate by various thin film forming techniques such as sputtering is as large as about 500 to 1,000. It is known that the relative dielectric constant of a single crystal PZT thin film formed on one surface side of a single crystal MgO substrate or one surface side of a single crystal SrTiO ₃ substrate is about 150 to 300.

Therefore, in order to increase the output of the power generation device, it is necessary to increase the piezoelectric constant e ₃₁ and decrease the relative permittivity. Therefore, the above-described element formation substrate 20a ′ is a single unit having good lattice matching with the PZT thin film. It is conceivable to use a crystalline MgO substrate, a single crystal SrTiO ₃ substrate, or a sapphire substrate, but the single crystal MgO substrate and the single crystal SrTiO ₃ substrate are weaker than the single crystal Si substrate and have a lower mechanical strength. 22 'becomes easy to be damaged, and the reliability is lowered. Further, the sapphire substrate is difficult to process, and it is difficult to manufacture the power generation device itself. Further, in the power generation device, it is necessary to form the cantilever portion 22 ′ having an appropriate vibration characteristic (frequency characteristic, Q value, etc.) according to the purpose and application. However, when a specific substrate material such as a single crystal MgO substrate, a single crystal SrTiO ₃ substrate, or a sapphire substrate must be used as the element formation substrate 20a ′, the element formation substrate 20a ′ Since the material physical properties of the power generation device are limited, the design flexibility of the power generation device is small, and it may be difficult to obtain desired vibration characteristics.

Further, in the power generation device described above, when the relative 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. From the viewpoint of the general values of the piezoelectric constant e ₃₁ and relative dielectric constant of PZT and AlN, the power generation index P can be increased by adopting PZT that can square the power generation index P and has a large piezoelectric constant e ₃₁ . However, even in a power generation device in which the piezoelectric layer 24b ′ is composed of a PZT thin film, in order to further increase the output, the relative dielectric constant of the piezoelectric layer 24b ′ is reduced and the piezoelectric constant e ₃₁ is increased. Therefore, it is necessary to improve power generation efficiency.

  In the ferroelectric device having the configuration shown in FIG. 12, the MgO thin film 102 is not a single crystal thin film but preferentially oriented in the (100) plane, and the ferroelectric film 104 also has a polarization axis c. It is preferentially oriented in the axial direction. Here, Patent Document 1 describes that the c-axis orientation rate of the above-described ferroelectric film 104 is 94%.

The present invention has been made in view of the above-mentioned reasons, and its object is to produce a ferroelectric device capable of improving the crystallinity and performance of the ferroelectric film regardless of the substrate material of the ferroelectric device. Is to provide. In particular, with respect to a method for manufacturing a ferroelectric device used as a power generation device, the piezoelectric constant e ₃₁ of a piezoelectric layer made of a ferroelectric film can be increased, the relative permittivity can be decreased, and a highly reliable ferroelectric device. It is in providing the manufacturing method of. Also, as a method for manufacturing a ferroelectric device used as a pyroelectric device, a method for manufacturing a ferroelectric device capable of improving the pyroelectric coefficient of a pyroelectric thin film made of a ferroelectric film at low cost is provided. It is in.

  According to the first aspect of the present invention, a cantilever-forming substrate is formed using the first substrate and has a frame portion and a cantilever portion that is swingably supported by the frame portion, and the cantilever portion is formed on the cantilever portion. A power generation unit including a piezoelectric conversion unit that generates an AC voltage in response to vibration, and the power generation unit includes a lower electrode formed on one surface side of the cantilever unit, and the cantilever unit side of the lower electrode. A piezoelectric layer formed on the opposite side; and an upper electrode formed on the piezoelectric layer opposite to the lower electrode side. The piezoelectric layer has a lattice constant difference from the first substrate. A method of manufacturing a ferroelectric device used as a power generation device comprising a ferroelectric film formed of a ferroelectric material, wherein the ferroelectric film is made stronger than the first substrate. Forming a ferroelectric film on one surface side of the second substrate having good lattice matching with the body film, and forming the lower electrode on the ferroelectric film after the ferroelectric film forming process A lower electrode forming step, and after the lower electrode forming step, the lower electrode on the one surface side of the second substrate and the first substrate are bonded via a bonding layer, and then the second electrode is formed. And a transfer step of transferring the lower electrode and the ferroelectric film to the first substrate by removing the substrate.

  According to a second aspect of the present invention, there is provided a lower electrode formed on one surface side of a first substrate, a pyroelectric thin film formed on the opposite side of the lower electrode from the first substrate side, and the pyroelectric And a pyroelectric thin film formed of a ferroelectric material having a lattice constant difference from the first substrate. The upper electrode is formed on the opposite side of the body thin film from the lower electrode side. A method of manufacturing a ferroelectric device used as a pyroelectric device made of a body film, wherein the first substrate has a lattice matching with the ferroelectric film that is better than the first substrate on the surface side of the second substrate. A ferroelectric film forming step for forming a ferroelectric film, and a first metal for forming a first metal layer constituting the lower electrode on the ferroelectric film after the ferroelectric film forming step; A layer forming step; a second metal layer formed on the one surface side of the first substrate; A bonding step of bonding the first metal layer formed in the metal layer forming step by room temperature bonding, and laser light having a wavelength that passes through the second substrate after the bonding step. And a transfer step of transferring the ferroelectric film to the one surface side of the first substrate.

  According to a third aspect of the present invention, there is provided a lower electrode formed on one surface side of a first substrate, a pyroelectric thin film formed on the opposite side of the lower electrode from the first substrate side, and the pyroelectric And a pyroelectric thin film formed of a ferroelectric material having a lattice constant difference from the first substrate. The upper electrode is formed on the opposite side of the body thin film from the lower electrode side. A method of manufacturing a ferroelectric device used as a pyroelectric device made of a body film, wherein the first substrate has a lattice matching with the ferroelectric film that is better than the first substrate on the surface side of the second substrate. A ferroelectric film forming step for forming a ferroelectric film, a lower electrode forming step for forming the lower electrode on the ferroelectric film after the ferroelectric film forming step, and a lower electrode forming step. Later, the lower electrode and the first substrate are made of a room temperature curable resin adhesive. A bonding step of bonding at a normal temperature via a bonding layer; and a laser beam having a wavelength that passes through the second substrate after the bonding step is irradiated from the second substrate side to apply the ferroelectric film to the first film. And a transfer step of transferring to the one surface side of the substrate.

  According to a fourth aspect of the present invention, in the first aspect of the invention, in the transfer step, an Au layer or a resin layer is used as the bonding layer, and the first substrate is etched after the bonding. It is characterized by removing.

According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, the ferroelectric material is a lead-based oxide ferroelectric, and the second substrate is a single crystal MgO substrate or a single crystal SrTiO. _Three substrates or sapphire substrates are used, and the first substrate is one selected from the group consisting of a Si substrate, an SOI (Siliconon Insulator) substrate, a metal substrate, a glass substrate, and a polymer substrate.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, a seed layer that is a base of the ferroelectric film is formed on the one surface side of the second substrate before the ferroelectric film forming step. A seed layer forming step is provided, and in the transferring step, at least a laminated film having a laminated structure of the ferroelectric film and the lower electrode is transferred.

  A seventh aspect of the invention is characterized in that, in the first aspect of the invention, after the transferring step, a bonding step of bonding a weight portion to a tip portion of the cantilever portion in the first substrate is performed.

  The ferroelectric device manufacturing method of the present invention has an effect that the crystallinity and performance of the ferroelectric film can be improved regardless of the substrate material of the ferroelectric device.

Further, the invention of claim 1 has an effect that the piezoelectric constant e ₃₁ of the piezoelectric layer can be increased, the relative permittivity can be decreased, and a ferroelectric device including a highly reliable power generation device can be provided. is there.

  Further, in the inventions of claims 2 and 3, it is possible to provide a ferroelectric device comprising a pyroelectric device capable of improving the pyroelectric coefficient of the pyroelectric thin film comprising a ferroelectric film at low cost. There is.

FIG. 3 is a main process sectional view for explaining the method for manufacturing the ferroelectric device (power generation device) of the first embodiment. It is a schematic exploded perspective view of a power generation device same as the above. It is a schematic plan view of the vibrator forming substrate in the power generation device same as above. It is a general | schematic exploded sectional view of the principal part of an electric power generation device same as the above. It is a general | schematic exploded sectional view of the other structural example of an electric power generation device same as the above. FIG. 10 is a main process sectional view for illustrating the method for manufacturing the ferroelectric device (power generation device) of the second embodiment. FIG. 10 is a main process sectional view for illustrating the method for manufacturing the ferroelectric device (pyroelectric device) of the second embodiment. It is principal process sectional drawing for demonstrating the manufacturing method of a pyroelectric device same as the above. It is a schematic sectional drawing which shows the application example of the pyroelectric device same as the above. It is a spectral characteristic figure of the material used at the time of manufacture of a pyroelectric device same as the above. It is a schematic sectional drawing of the electric power generation device which shows a prior art example. It is a schematic sectional drawing of the ferroelectric device which shows a prior art example.

(Embodiment 1)
In this embodiment, a power generation device is illustrated as a ferroelectric device.

  First, the power generation device in the present embodiment will be described with reference to FIGS. 2 to 4, and then the manufacturing method will be described with reference to FIG. 1.

  The power generation device according to the present embodiment is formed using the element forming substrate 20a, and has a cantilever forming substrate 20 having a frame portion 21 and a cantilever portion 22 that is disposed inside the frame portion 21 and is swingably supported by the frame portion 21. The cantilever portion 22 of the cantilever forming substrate 20 is formed with a power generation portion 24 including a piezoelectric conversion portion (piezoelectric conversion element) that generates an AC voltage in response to vibration of the cantilever portion 22. In the present embodiment, the element formation substrate 20a constitutes the first substrate.

  The power generation device includes a first cover substrate 30 formed using the first cover forming substrate 30a and fixed to the frame portion 21 on one surface side (upper surface side in FIG. 4) of the cantilever forming substrate 20. And a second cover substrate 10 formed using the second cover forming substrate 10a and fixed to the frame portion 21 on the other surface side (lower surface side in FIG. 4) of the cantilever forming substrate 20. 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.

  The piezoelectric conversion part constituting the above-described power generation part 24 includes the lower electrode 24a, the piezoelectric layer 24b formed on the opposite side of the lower electrode 24a to the bending part 22 side, and the lower side of the piezoelectric layer 24b opposite to the lower electrode 24a side. The upper electrode 24c is formed on the side.

  Further, on one surface side of the cantilever forming substrate 20, pads 27 a and 27 b electrically connected to the lower electrode 24 a and the upper electrode 24 c through the metal wirings 26 a and 26 c respectively correspond to the frame portion 21. It is formed with. Here, the power generation unit 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. The layer 24b is designed so that the end of the piezoelectric conversion region in contact with the lower electrode 24a and the upper electrode 24c on the frame portion 21 side substantially coincides with the boundary between the frame portion 21 and the bent portion 22.

  Also, on the one surface side of the cantilever forming substrate 20, an insulating layer 25 for preventing a short circuit between the metal wiring 26c electrically connected to the upper electrode 24c and the lower electrode 24a is provided for each of the lower electrode 24a and the piezoelectric layer 24b. Is formed so as to cover the end on the frame part 21 side. 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 addition, the cantilever forming substrate 20 is formed with insulating films 29a and 29b made of a silicon oxide film on each of the one surface side and the other surface side of the element forming substrate 20a, and the power generation unit 24 and the element forming substrate 20a are insulating films. 29 is electrically insulated.

  The first cover substrate 30 uses a first silicon substrate as the first cover forming substrate 30a, and the cantilever portion 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 22 and the weight part 23 between the cantilever forming substrate 20.

  The first cover substrate 30 has output electrodes 35 and 35 for supplying the AC voltage generated by the power generation unit 24 to the outside on the other surface side of the first cover forming substrate 30a. The output electrodes 35 and 35 are provided so as to penetrate the connecting electrodes 34 and 34 formed on the one surface side of the first cover forming substrate 30a and the thickness direction of the first cover forming substrate 30a. They are electrically connected through the through-hole wirings 33 and 33. Here, the first cover substrate 30 is electrically connected with the connection electrodes 34 and 34 joined to the pads 27 a and 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.

  Further, a first bonding metal layer 28 for bonding to the first cover substrate 30 is formed on the one surface side of the cantilever forming substrate 20 described above, and the first cover substrate 30 includes: A second bonding metal layer (not shown) bonded to the first bonding metal layer 28 is formed. Here, as the material of the first bonding metal layer 28, the same material as that of the pad 27c is adopted, and the first bonding metal layer 28 is formed on the one surface of the cantilever forming substrate 20 (here, The insulating film 29a is formed to have the same thickness as the pad 27.

  The cantilever forming substrate 20 and the cover substrates 10 and 30 are bonded by a room temperature bonding method. May be. In the resin bonding method, if a room temperature curable resin adhesive (for example, a two-part room temperature curable epoxy resin adhesive, a one part room temperature curable epoxy resin adhesive) is used, a thermosetting resin adhesive is used. Compared to the case of using a thermosetting epoxy resin adhesive (for example), the bonding temperature can be lowered.

  In the power generation device described above, since the power generation unit 24 is configured by a piezoelectric conversion unit including the lower electrode 24a, the piezoelectric layer 24b, and the upper electrode 24c, the piezoelectric layer 24b of the power generation unit 24 is caused by the vibration of the cantilever unit 22. As a result, stress is biased between the upper electrode 24 c and the lower electrode 24 a, and an AC voltage is generated in the power generation 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, and the element forming substrate 20a is a single crystal having the (100) plane on the one surface. However, the lead-based piezoelectric material is not limited to PZT. For example, PZT-PMN (: Pb (Mn, Nb) O ₃ ) or PZT added with other impurities may be used. Good. In any case, the piezoelectric material of the piezoelectric layer 24b is a ferroelectric material (PZT, PZT-PMN, lead-based material such as PZT to which impurities are added) having a lattice constant difference from the element forming substrate 20a as the first substrate. The piezoelectric layer 24b is composed of a ferroelectric film formed of the ferroelectric material. The Si substrate used as the element formation substrate 20a is not limited to a single crystal Si substrate (hereinafter referred to as a single crystal Si substrate), and may be a polycrystalline Si substrate.

  In this embodiment, Au is used as the material of the lower electrode 24a, and Pt is used as the material of the upper electrode 24c. However, these materials are not particularly limited, and examples of the material of the lower electrode 24a include: Al may be employed, and as the material of the upper electrode 24c, for example, Mo, Al, Au, or the like may be employed.

In the power generation device according to the present embodiment, the thickness of the lower electrode 24a is set to 500 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. Further, if the relative 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.

  Hereinafter, the manufacturing method of the electric power generation device of this embodiment is demonstrated, referring FIG.

First, a piezoelectric layer 24b made of a piezoelectric material (for example, PZT) is made of a single crystal MgO substrate having a small lattice constant difference from the piezoelectric layer 24b and having good lattice matching as compared with the element forming substrate 20a made of a single crystal Si substrate. A piezoelectric layer forming step is performed on one surface side (upper surface side in FIG. 1A) of the piezoelectric layer forming substrate 40 (see FIG. 1A), and then the lower electrode 24a is formed on the piezoelectric layer 24b. A lower electrode forming step to be formed is performed, and subsequently, the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40 and the element forming substrate 20 are arranged to face each other as shown in FIG. In the above-described piezoelectric layer forming step, the piezoelectric layer 24b may be formed by sputtering, CVD, sol-gel, or the like, and in the lower electrode forming step, the lower electrode 24a may be formed by sputtering, CVD, or the like. As the piezoelectric layer forming substrate 40 used in the piezoelectric layer forming step, a single crystal MgO substrate having a (001) surface and a thickness of 300 μm is used as the piezoelectric layer forming substrate. However, the piezoelectric layer forming substrate 40 is not limited to the single crystal MgO substrate. A single crystal SrTiO ₃ substrate having one surface of (001) plane or a sapphire substrate having one surface having a (0001) plane may be employed. Further, the thickness of the piezoelectric layer forming substrate 10 is not particularly limited. Further, in the present embodiment, the piezoelectric layer forming substrate 40 constitutes a second substrate having better lattice matching with the ferroelectric film than the first substrate, and the piezoelectric layer forming step is performed by the ferroelectric film. Is formed on the one surface side of the second substrate having good lattice matching with the ferroelectric film as compared with the first substrate.

  As described above, after the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40 and the element forming substrate 20 are disposed to face each other, the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40, the element forming substrate 20 and the like. A structure shown in FIG. 1B is obtained by performing a bonding process in which the bonding is performed through the bonding layer 51 formed on the one surface side of the element forming substrate 20. Here, in this embodiment, the bonding layer 51 is composed of an Au layer, and is composed of a Ti layer for improving adhesion between the bonding layer 51 and the insulating film 29a on the one surface side of the element formation substrate 20. An adhesion layer 52 is interposed. In this embodiment, the insulating films 29a and 29b are formed by a thermal oxidation method, the film thickness of the adhesion layer 52 is set to 15 to 50 nm, and the film thickness of the bonding layer 51 is set to 500 nm. The numerical value is an example and is not particularly limited. The material of the adhesion layer 52 is not limited to Ti, and may be, for example, Cr, Nb, Zr, TiN, TaN, or the like. The Au layer constituting the bonding layer 51 is not limited to the Au thin film but may be an Au fine particle layer in which a large number of Au fine particles are deposited.

  After the bonding process described above, a substrate removing process for removing the piezoelectric layer forming substrate 40 is performed, thereby obtaining the structure shown in FIG. Here, in the substrate removing step, for example, the piezoelectric layer forming substrate 40 is removed by etching the piezoelectric layer forming substrate 40 using phosphoric acid having a concentration of 30% and a temperature of 90 ° C. The temperature is an example, and is not limited to these values. Alternatively, the piezoelectric layer forming substrate 40 may be removed by etching the piezoelectric layer forming substrate 40 by irradiation with an ion beam using Ar gas. In the present embodiment, the bonding step and the substrate removing step constitute a transfer step for transferring the lower electrode 24a and the piezoelectric layer 24b to the element forming substrate 20a.

  After the above transfer process, a piezoelectric layer patterning process for patterning the piezoelectric layer 24b using a photolithography technique and an etching technique is performed, and then a lower electrode for patterning the lower electrode 24a using a photolithography technique and an etching technique. By performing the patterning process, the lower electrode 24a and the metal wiring 26a and the pad 27a made up of a part of the lower electrode 24a before patterning are formed (the lower electrode 24a, the metal wiring 26a and the pad 27a after patterning form one lower part). Thereafter, an insulating layer forming step of forming the insulating layer 25 on the one surface side of the element forming substrate 20a is performed, and then the upper electrode 24c is formed into a thin film such as a sputtering method or a CVD method. Utilize formation technology, photolithography technology, etching technology At the same time as the upper electrode forming step, the metal wiring 26c and the pad 27c are formed by using a thin film forming technique such as a sputtering method or a CVD method, a photolithography technique, and an etching technique. By performing the substrate processing step of forming the cantilever portion 22 and the weight portion 23 by processing the element forming substrate 20 using the technology and the etching technology, the process shown in FIG. Get the structure shown. In the present embodiment, the metal wiring 26a and the pad 27a are formed by performing the lower electrode patterning process. However, the present invention is not limited to this, and the metal wiring 26a and the pad 27a are formed between the lower electrode patterning process and the insulating layer forming process. A wiring forming process for forming the pad 27a may be provided separately, or a metal wiring forming process for forming the metal wiring 26a and a pad forming process for forming the pad 27a may be provided separately. In the insulating layer forming step, the insulating layer 25 is formed on the entire surface of the element formation substrate 20a by the CVD method and then patterned using the photolithography technique and the etching technique. The insulating layer 25 may be formed using a method.

  After the above-described substrate processing step, a cover joining step for joining the cover substrates 10 and 30 is performed to obtain a power generation device having a structure shown in FIG. Here, after the cover joining process is completed at the wafer level, the dicing process is performed to divide the power generation devices into individual power generation devices. 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.

  The power generation device (ferroelectric device) in the present embodiment described above is formed using the element forming substrate (first substrate) 20a and is supported by the frame portion 21 and the frame portion 21 so as to be swingable. A cantilever forming substrate 20 and a power generation unit 24 that is formed in the cantilever unit 22 and includes a piezoelectric conversion unit that generates an AC voltage in response to vibration of the cantilever unit 22. A lower electrode 24a formed on the surface side, and a piezoelectric layer (a ferroelectric material) formed of a piezoelectric material (ferroelectric material) formed on the opposite side of the lower electrode 24a from the cantilever 22 side and having a lattice constant difference from the element formation substrate 20a Ferroelectric film) 24b and an upper electrode 24c formed on the opposite side of the piezoelectric layer 24b from the lower electrode 24a side. In the manufacturing method, the piezoelectric layer forming step of forming the piezoelectric layer 24b on the one surface side of the piezoelectric layer forming substrate (second substrate) 40 having better lattice matching with the piezoelectric layer 24b than the element forming substrate 20a. (Ferroelectric film forming step), lower electrode forming step of forming the lower electrode 24a on the piezoelectric layer 24b after the piezoelectric layer forming step, and the one surface of the piezoelectric layer forming substrate 40 after the lower electrode forming step. A transfer step of transferring the lower electrode 24a and the piezoelectric layer 24b to the element forming substrate 20a by removing the piezoelectric layer forming substrate 40 after bonding the lower electrode 24a on the side and the element forming substrate 20a through the bonding layer 51; It has.

Therefore, in the manufacturing method of the ferroelectric device (power generation device) of the present embodiment, the ferroelectric material is used regardless of the substrate material of the ferroelectric device (here, the material of the element forming substrate 20a which is the first substrate). The crystallinity and performance (here, piezoelectric constant e ₃₁ ) of the piezoelectric layer 24b that is a film can be improved.

Therefore, according to the method for manufacturing the power generation device of the present embodiment, the piezoelectric layer 24b is placed on the one surface side of the piezoelectric layer forming substrate 40 having a better lattice matching with the piezoelectric layer 24b than the element forming substrate 20a. After the piezoelectric layer forming step to be formed, the lower electrode 24a is formed on the piezoelectric layer 24b, and then the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40 and the element forming substrate 20a are bonded to the bonding layer 51. Since the lower electrode 24a and the piezoelectric layer 24b are transferred to the element forming substrate 20a by removing the piezoelectric layer forming substrate 40 after bonding, the piezoelectric layer 24b is formed on the one surface side of the element forming substrate 20a by a thin film forming technique. The piezoelectric constant e ₃₁ of the piezoelectric layer 24b can be increased and the relative dielectric constant can be reduced as compared with the case where the film is formed, and the element forming substrate 20a is compared with the piezoelectric layer forming substrate 40. In addition, a highly reliable power generation device can be provided by using a device having high mechanical strength. In short, in the power generation device of the present embodiment, the piezoelectric constant e ₃₁ can be increased as compared with the case where the piezoelectric layer 24b is composed of an AlN thin film, and the piezoelectric layer 24b is formed on the one surface side of the element forming substrate 20a. The piezoelectric constant e ₃₁ can be further increased as compared with the case where the polycrystalline PZT thin film is used, and the output can be increased by improving the power generation efficiency. Moreover, the piezoelectric layer 24b is formed of the polycrystalline PZT thin film. Therefore, the relative permittivity can be reduced as compared with the case of the above configuration, and the power generation efficiency can be improved by reducing the parasitic capacitance.

  In addition, according to the method for manufacturing a power generation device of the present embodiment, the choice of material for the cantilever portion 22 is increased, the design freedom of the power generation device is increased, and the generation of a power generation device having desired vibration characteristics is facilitated. Thus, it is possible to realize power generation devices having various vibration characteristics.

  In the power generation device manufacturing method of the present embodiment, an Au layer is used as the bonding layer 51 in the transfer step, and the piezoelectric layer forming substrate 40 is removed by etching the piezoelectric layer forming substrate 40 after bonding. Therefore, by forming the lower electrode 24a with an Au layer, the Au layer of the lower electrode 24a and the Au layer of the bonding layer 51 (that is, the Au layers) are directly bonded at a low temperature by a room temperature bonding method or the like. In addition, since the piezoelectric layer forming substrate 40 is removed by etching after bonding, the process temperature of the transfer process can be lowered, and the characteristics of the piezoelectric layer 24b are deteriorated in the transfer process. Can be prevented. Further, in the transfer process, a resin layer made of an epoxy resin or the like may be used as the bonding layer 51. In this case, bonding can be performed at a lower temperature than in the eutectic bonding method. In addition, when directly bonding Au to each other, not only the room temperature bonding method but also direct bonding by applying appropriate heating (for example, 100 ° C.) and a load may be used.

In the power generation device manufacturing method of the present embodiment, the piezoelectric material of the piezoelectric layer 24b is a lead-based piezoelectric material, and the piezoelectric layer forming substrate 40 is a single crystal MgO substrate, a single crystal SrTiO ₃ substrate, or a sapphire substrate. Therefore, the piezoelectric layer 24b with good crystallinity can be formed, and since the single crystal Si substrate is used as the element forming substrate 20a, the reliability can be improved and the cost can be reduced.

  Here, as the element formation substrate 20a, for example, as shown in FIG. 5, single crystal silicon is formed on an insulating layer (buried oxide film) 120b made of a silicon oxide film on a support substrate 120a made of a single crystal silicon substrate. The SOI substrate 120 having the layer (active layer) 120c may be used. In this case, the cantilever portion can be obtained by using the insulating layer 120b of the SOI substrate 120 as an etching stopper layer when forming the cantilever portion 22 in manufacturing. The thickness of 22 can be increased, and the reliability can be improved and the cost can be reduced.

  Further, as the element formation substrate 20a, one selected from the group of a metal substrate (for example, a SUS substrate, a Ti substrate, etc.), a glass substrate, and a polymer substrate may be used, and any one of these is used. Even in this case, although the reliability can be improved, it is preferable to use a metal substrate or a glass substrate from the viewpoint of mechanical strength. In addition, what is necessary is just to employ | adopt polyethylene terephthalate etc. as a polymer of a polymer substrate, for example.

  Further, in the transfer step described above, the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40 and the element forming substrate 20a are bonded via the bonding layer 51, and then the wavelength of the wavelength that passes through the piezoelectric layer forming substrate 40 is increased. The piezoelectric layer forming substrate 40 may be peeled off by irradiating laser light from the piezoelectric layer forming substrate 40 side and transferring the lower electrode 24a and the piezoelectric layer 24b to the one surface side of the element forming substrate 20a. When such a transfer process is performed, the expensive piezoelectric layer forming substrate 40 can be reused, and the cost can be reduced.

(Embodiment 2)
The basic configuration of the power generation device, which is a ferroelectric device in the present embodiment, is substantially the same as that of the first embodiment. As shown in FIG. 6E, a piezoelectric layer is interposed between the upper electrode 24c and the piezoelectric layer 24b. The difference is that a seed layer 24d made of SrRuO ₃ , which is a base for the film formation of 24b and is a kind of conductive oxide material, is interposed. Here, the material of the seed layer 24d is not limited to SrRuO _3, and may be (Pb, La) TiO ₃ or PbTiO ₃ . In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  Hereinafter, although the manufacturing method of the electric power generation device of this embodiment is demonstrated, referring FIG. 6, description is abbreviate | omitted suitably about the process similar to Embodiment 1. FIG.

First, the configuration matching with a single crystal MgO substrate having one surface of (001) plane, a single crystal SrTiO ₃ substrate having one surface of (001) plane, or a piezoelectric layer forming substrate 40 made of a sapphire substrate having one surface of (0001) plane. After performing the upper electrode forming step of forming the upper electrode 24c made of a good metal material (for example, Pt) on the one surface side of the piezoelectric layer forming substrate 40, the base layer of the piezoelectric layer 24b is formed on the upper electrode 24c. Then, for example, a seed layer forming step for forming a seed layer 24d made of SrRuO ₃ is performed, and then a piezoelectric layer 24b made of a piezoelectric material (for example, PZT or the like) is formed on the one surface side of the piezoelectric layer forming substrate 40. A piezoelectric layer forming step is performed, and then a lower electrode forming step for forming the lower electrode 24a on the piezoelectric layer 24b is performed, and then the piezoelectric layer is formed as shown in FIG. The lower electrode 24a on the one surface side of the substrate 40 and the element forming substrate 20 are arranged to face each other. In the above-described upper electrode forming step, the upper electrode 24c made of a (001) -oriented Pt thin film is formed as the upper electrode 24c by sputtering or vapor deposition, and in the seed layer forming step, the (110) -oriented SrRuO ₃ thin film is formed. The seed layer 24d may be formed by sputtering or MOCVD.

  As described above, after the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40 and the element forming substrate 20 are disposed to face each other, the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40, the element forming substrate 20 and the like. A structure shown in FIG. 6B is obtained by performing a bonding process in which the bonding is performed through the bonding layer 51 formed on the one surface side of the element formation substrate 20.

  After the bonding step described above, a substrate removing step for removing the piezoelectric layer forming substrate 40 is performed, thereby obtaining the structure shown in FIG. As in the first embodiment, the bonding process and the substrate removing process constitute a transfer process.

  After the above transfer process, an upper electrode patterning process for patterning the upper electrode 24c using a photolithography technique and an etching technique, a seed layer patterning process for patterning a seed layer 24d using a photolithography technique and an etching technique, A lower electrode is formed by performing a piezoelectric layer patterning process for patterning the piezoelectric layer 24b using a lithography technique and an etching technique, and then performing a lower electrode patterning process for patterning the lower electrode 24a using a photolithography technique and an etching technique. 24a and a metal wiring 26a and a pad 27a made up of a part of the lower electrode 24a before patterning (the lower electrode 24a after patterning, the metal wiring 26a and the pad 27a constitute one lower electrode 24a). Thereafter, an insulating layer forming step of forming the insulating layer 25 on the one surface side of the element formation substrate 20a is performed, and then the metal wiring 26c and the pad 27c are formed into a thin film such as a sputtering method or a CVD method. A wiring formation process is performed using technology, photolithography technology, and etching technology, and then the element formation substrate 20 is processed using photolithography technology and etching technology to form the cantilever portion 22 and the weight portion 23. Thus, the substrate processing step for forming the cantilever forming substrate 20 is performed to obtain the structure shown in FIG.

  After the above-described substrate processing process, a cover bonding process for bonding the cover substrates 10 and 30 may be performed. After the cover bonding process is completed at the wafer level, a dicing process is performed. Good. 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.

Thus, according to the method for manufacturing the power generation device of the present embodiment, the SrRuO ₃ or (Pb, La) is the base of the piezoelectric layer 24b on the one surface side of the piezoelectric layer forming substrate 40 before the piezoelectric layer forming step. ) A seed layer forming step of forming a seed layer 24d made of TiO ₃ or PbTiO ₃ is provided. In the transfer step, a laminated film having a laminated structure of the upper electrode 24c, the seed layer 24d, the piezoelectric layer 24b, and the lower electrode 24a is transferred. Therefore, the lattice strain of the piezoelectric layer 24b can be suppressed, and the crystallinity of the piezoelectric layer 24b can be further improved. In the transfer step, at least the laminated film having the laminated structure of the piezoelectric layer 24b and the lower electrode 24a may be transferred, and the laminated film having the laminated structure of the piezoelectric layer 24b and the lower electrode 24a is transferred. The upper electrode 24c may be formed later.

  Further, in the transfer step described above, the lower electrode 24a on the one surface side of the piezoelectric layer forming substrate 40 and the element forming substrate 20a are bonded via the bonding layer 51, and then the wavelength of the wavelength that passes through the piezoelectric layer forming substrate 40 is increased. Laser light is irradiated from the piezoelectric layer forming substrate 40 side, and a laminated film having a laminated structure of the upper electrode 24c, the seed layer 24d, the piezoelectric layer 24b, and the lower electrode 24a is transferred to the one surface side of the element forming substrate 20a. The piezoelectric layer forming substrate 40 may be peeled off. When such a transfer process is performed, the expensive piezoelectric layer forming substrate 40 can be reused, and the cost can be reduced.

  By the way, since the power generation device of Embodiment 1, 2 is provided with the weight part 23 in the front-end | tip part of the cantilever part 22, it can enlarge electric power generation compared with the case where it does not have the weight part 23. However, after the transfer process, an adhesion process may be performed in which the weight part 23 is adhered to the tip of the cantilever part 22 in the element forming substrate 20a with an adhesive or the like. In this case, the cantilever is performed after the transfer process. Since the weight portion 23 is bonded to the tip portion of the portion 22, the design freedom of the shape and material of the weight portion 23 is increased, and a power generation device with a larger power generation amount can be manufactured, and the cantilever portion 22 can be manufactured. In addition, each of the weight portions 23 can be freely formed, and the degree of freedom of the manufacturing process is increased.

(Embodiment 3)
In this embodiment, a pyroelectric device is illustrated as a ferroelectric device.

  First, the pyroelectric device in the present embodiment will be described with reference to FIGS. 8C and 9, and then the manufacturing method will be described with reference to FIGS. 7 and 8.

  As shown in FIG. 8C, the pyroelectric device according to the present embodiment has a lower electrode 224a formed on one surface side of the first substrate 220a and the lower electrode 224a opposite to the first substrate 220a side. A pyroelectric thin film 224b formed on the side, and an upper electrode 224c formed on the opposite side of the pyroelectric thin film 224b from the lower electrode 224a side. The pyroelectric thin film 224a is connected to the first substrate 220a. Are formed of pyroelectric materials having a lattice constant difference.

  By the way, the pyroelectric device in this embodiment employs PZT which is a kind of lead-based oxide ferroelectric as the pyroelectric material of the pyroelectric thin film 224b. A (100) -plane single crystal Si substrate is used, but the lead-based oxide ferroelectric is not limited to PZT, for example, PZT-PLT, PLT, PZT-PMN, and other impurities. You may employ | adopt the added PZT type ferroelectric substance. In any case, the pyroelectric material of the pyroelectric thin film 224b is a ferroelectric material having a lattice constant difference from the first substrate 220a (PZT, PZT-PMN, lead-based oxidation such as PZT doped with impurities). The pyroelectric thin film 224b is composed of a ferroelectric film formed of the ferroelectric material. The Si substrate used as the first substrate 220a is not limited to a single crystal Si substrate (hereinafter referred to as a single crystal Si substrate), but may be a polycrystalline Si substrate.

In the present embodiment, Au is used as the material of the lower electrode 224a, and an infrared absorbing material having conductivity such as Ni—Cr, Ni, gold black, etc. is used as the material of the upper electrode 224c. The sensing element 230 is configured by the electrode 224a, the pyroelectric thin film 224b, and the upper electrode 224c. However, these materials are not particularly limited, and examples of the material of the lower electrode 224a include Al and Cu. As the material of the upper electrode 224c, for example, an oxide conductive material having good lattice matching with the above-described ferroelectric material (PZT or the like) such as SrRuO ₃ may be used. Here, when the above-described infrared absorbing material having conductivity is adopted as the material of the upper electrode 224c, the upper electrode 24 also serves as the infrared absorbing film, but an oxide conductive material such as SrRuO ₃ is used. If employed, the sensing element 230, may be provided an infrared absorption film on the upper electrode 24c, as the material of the infrared absorption film, for example, Ni-Cr, Ni, gold black, SiO _2, Si ₃ N ₄ , SiON, etc. may be adopted.

  Further, the first substrate 220a is not limited to a single crystal Si substrate, and may be one selected from the group consisting of a metal substrate (for example, a SUS substrate, a Ti substrate, etc.), a glass substrate, and a polymer substrate. As the polymer for the polymer substrate, for example, polyethylene terephthalate (PET) or polyimide may be employed.

  When the above pyroelectric device is used as a pyroelectric infrared sensor, for example, as shown in FIGS. 9A to 9D, the sensing element 230 is disposed on the other surface side of the first substrate 220a. The support substrate 210 that supports the first substrate 220a provided on the front surface side may be bonded to the first substrate 22a. It is preferable that a thermal insulation gap 211 is formed in the support substrate 210 to thermally insulate the sensing element 230 and the support substrate 210. Here, as the support substrate 210, for example, one selected from the group of a single crystal Si substrate, a glass substrate, and a polymer substrate (for example, a PET substrate) may be used. Without providing the support substrate 210, the thermal insulation gap 211 may be formed in the first substrate 220a. When the gap 211 is provided in the first substrate 220a, the above-described one of the first substrate 220a is provided. It may be formed by etching from the front surface side or by etching from the other surface side of the first substrate 220a.

  The pyroelectric infrared sensor having the configuration shown in FIGS. 9A and 9B includes only one sensing element 230. Also, the pyroelectric infrared sensor having the configuration shown in FIGS. 9C and 9D is an infrared array sensor (infrared image sensor) in which a plurality of sensing elements 230 are arranged in a two-dimensional array. Each element 230 constitutes a pixel.

  In the pyroelectric device according to the present embodiment, the thickness of the lower electrode 224a is set to 100 nm, the thickness of the pyroelectric thin film 224b is set to 1 μm to 3 μm, and the thickness of the upper electrode 224c is set to 50 nm. However, there is no particular limitation.

In the pyroelectric device of this embodiment, the pyroelectric coefficient of the pyroelectric thin film 224b is γ [C / (cm ² · K)], the dielectric constant is ε, and the performance index of the pyroelectric device is F _γ [C / (cm ² · J)], the relationship of F _γ ∝γ / ε is established, and as the pyroelectric coefficient γ of the pyroelectric thin film 224b increases, the performance index F _γ of the pyroelectric device increases.

  Hereinafter, the manufacturing method of the pyroelectric device of this embodiment will be described with reference to FIGS.

First, one of the second substrates 240 (see FIG. 7A) made of a single crystal MgO substrate having a better lattice matching with the pyroelectric thin film 224b than the first substrate 220a made of a single crystal Si substrate. On the surface side (upper surface side in FIG. 7A), a seed layer (buffer) composed of a Pt film as a base of the pyroelectric thin film 224b, or a laminated film of a lower Pt film and an upper SrRuO ₃ film Layer) 224d is formed, and then a pyroelectric thin film 224b made of a pyroelectric material (such as PZT) is formed on the seed layer 224d. By performing the forming step, the structure shown in FIG. 7A is obtained. The seed layer 224d and the pyroelectric thin film 224b are formed by an RF magnetron sputtering method, and the substrate temperature is 600 ° C. to 700 ° C. As the second substrate 240, a single crystal MgO substrate having the above (001) plane and a thickness of 300 μm is adopted as the second substrate 240, but is not limited to a single crystal MgO substrate, and the above one surface has a (001) plane. A single crystal SrTiO ₃ substrate or a sapphire substrate having one surface of the (0001) plane may be employed. Further, the thickness of the second substrate 240 is not particularly limited. In the present embodiment, the pyroelectric thin film forming step is a step in which the ferroelectric film, which is the pyroelectric thin film 224b, is compared with the first substrate 220a, and the second substrate has better lattice matching with the ferroelectric film. A ferroelectric film forming step 240 is formed on the one surface side.

  After the pyroelectric thin film forming step described above, the first Au layer comprising the first Au layer constituting the lower electrode 224a on the pyroelectric thin film 224b (on the opposite side of the pyroelectric thin film 224b from the second substrate 240 side). By performing a first metal layer forming step (lower electrode forming step) for forming one metal layer 251, the structure shown in FIG. 7B is obtained.

  Thereafter, the second metal layer 252 made of the second Au layer formed on the one surface side of the first substrate 220a and the first metal layer 251 formed in the first metal layer forming step are Are arranged opposite to each other (FIG. 7C). Note that each of the first metal layer 251 and the second metal layer 252 may be formed by a sputtering method, an evaporation method, a CVD method, or the like. Moreover, although the film thickness of each of the first metal layer 251 and the second metal layer 252 is set to 100 nm, these numerical values are examples and are not particularly limited.

After the second metal layer 252 and the first metal layer 251 of the second substrate 240 are arranged to face each other as shown in FIG. 7C, the second metal layer 252 and the first metal layer 251 The structure shown in FIG. 7 (d) is obtained by performing a bonding process for bonding the films by room temperature bonding. By performing this bonding step, the pyroelectric thin film 224 b and the first substrate 220 a are bonded via the lower electrode 224 a made of the first metal layer 251 and the second metal layer 252. Here, both the first metal layer 251 and the second metal layer 252 are composed of Au layers, and the material used when the first metal layer 251 and the second metal layer 252 are bonded at room temperature is used. The combination is an Au-Au combination. In this bonding step, each bonding surface is irradiated with argon plasma, an ion beam, or an atomic beam in vacuum before bonding to the bonding surfaces (the surfaces of the first metal layer 251 and the second metal layer 252). After performing the cleaning and activation, the bonding surfaces are brought into contact with each other and directly bonded by applying an appropriate load at room temperature. An example of process conditions for room-temperature bonding with a combination of Au—Au in this bonding step is, for example, a vacuum degree when irradiating an argon ion beam is 1 × 10 ⁻⁵ Pa or less, an acceleration voltage is 100 V, The irradiation time may be 160 seconds, the bonding load may be 20 kN, and the bonding time may be 300 seconds.

  Note that the combination of materials of the first metal layer 251 and the second metal layer 252 is not limited to the combination of Au—Au, and for example, a combination of Au—AuSn, Al—Al, Cu—Cu, etc. can do. In addition, since the second metal layer 252 is joined and electrically connected to the lower electrode 224a made of the first metal layer 251, as a result, the first metal layer 251 and the second metal layer 252 It can also be regarded as a lower electrode.

  After the above-described bonding step, as shown in FIG. 7E, the pyroelectric thin film 224b is irradiated to the first substrate by irradiating the second substrate 240 with laser light LB having a wavelength that transmits the second substrate 240. A transfer step of transferring to the one surface side of 220a is performed, and the second substrate 240 is peeled off by separating the first substrate 220a and the second substrate 240 as shown in FIG. Perform the process. In the transfer step, not only the pyroelectric thin film 224b but also the seed layer 224d is transferred to the first substrate 220a side. In short, in the transfer step, the laminated film of the seed layer 224d, the pyroelectric thin film 224b, and the lower electrode 224a is transferred to the first substrate 220a side.

By the way, since MgO, PZT, and Pt each have spectral characteristics as shown in FIG. 10, depending on the wavelength of the laser light LB, the pyroelectric thin film is absorbed by the pyroelectric thin film 224b. The physical properties of 224b may change. Therefore, a single crystal MgO substrate is used as the second substrate 240, PZT is adopted as the ferroelectric material that is the pyroelectric material of the pyroelectric thin film 224b, and the material of the seed layer 224d is 400 nm or more like PZT. In the case where SrRuO ₃ , LaNiO ₃ or the like that is an oxide conductive material that absorbs light is employed, the wavelength of the laser beam LB irradiated in the transfer process is determined by the ferroelectric material of the pyroelectric thin film 224b. It is necessary to set the wavelength so that light absorption does not occur (less than 400 nm). In this case, for example, a KrF excimer laser having a wavelength of 248 nm may be used as the laser light source, and laser light LB having an energy density of about 5 to 15 mJ / mm ² may be irradiated at room temperature. The laser light source in this case is not limited to a KrF excimer laser, and for example, an ArF excimer laser having a wavelength of 193 nm, a THG-YAG laser having a wavelength of 355 nm, or the like, and a fundamental wavelength of 750 nm to 1100 nm may be used. The third harmonic of the femtosecond laser (for example, Ti: sapphire laser) may be used as the laser beam LB. On the other hand, when the seed layer 224d is composed of a Pt film or a laminated film of a Pt film and an SrRuO ₃ film, the laser beam LB is reflected by the Pt film, and therefore the laser irradiated in the transfer process The wavelength of the light LB does not necessarily need to be less than 400 nm. The fundamental wave of the femtosecond laser is not limited to the KrF excimer laser having a wavelength of 248 nm, the ArF excimer laser having a wavelength of 193 nm, or the third harmonic of the femtosecond laser. You may irradiate as LB.

After the above-described peeling step, as shown in FIG. 8A, the seed layer 224d opposite to the lower electrode 224a side in the pyroelectric thin film 224b is a Pt film, or a laminated film of a Pt film and a SrRuO ₃ film. In such a case, a structure shown in FIG. 8B is obtained by performing a seed layer removing step of removing the seed layer 224d by ion beam etching or the like. The seed layer 224d is removed because the Pt film has a property of reflecting infrared rays. When the seed layer 224d is a laminated film of a Pt film and an SrRuO ₃ film, only the Pt film is used. It may be removed or the laminated film may be removed.

  After the seed layer removal step described above, the upper electrode 224c made of Ni—Cr, Ni, gold black, or the like is formed by sputtering, vapor deposition, CVD, or the like, so that the pyroelectric structure having the structure shown in FIG. Get the device. In the structure of FIG. 8C, the upper electrode 224c also has a function as an infrared absorption film.

On the other hand, after the above-described peeling step, the SrRuO ₃ film is left as the upper electrode 224c on the opposite side of the pyroelectric thin film 224b from the lower electrode 224a side as shown in FIG. An infrared absorption film made of, for example, Ni—Cr, Ni, gold black, or the like may be formed on 224c.

  After obtaining the pyroelectric device having the structure shown in FIG. 8C, the pyroelectric device is provided with a support substrate 210 provided with a gap 211 for thermal insulation (heat insulation) (see FIGS. 9A to 9D). A pyroelectric infrared sensor is obtained by attaching to the substrate and performing appropriate patterning. Alternatively, after obtaining the pyroelectric device of FIG. 8C, the first substrate 220a may be etched from the one surface side or the other surface side to form a gap for thermal insulation (heat insulation). Good.

In the above-described manufacturing method, PZT is adopted as the pyroelectric material, a 50 nm Pt film and a 50 nm SrRuO ₃ film are sequentially formed on the one surface side of the second substrate 240, and then a PZT thin film is formed by RF magnetron sputtering. As the process conditions for film formation, when the substrate temperature (film formation temperature) that is the temperature of the second substrate 240 is 600 ° C., the RF power density is 4.5 W / cm ² , and the film thickness is 2 μm, the film formation is performed. The formed PZT thin film is a c-axis oriented epitaxial film, and the pyroelectric coefficient γ of the pyroelectric thin film 224b made of the PZT thin film (this pyroelectric thin film 224b is not subjected to polarization treatment) is γ = 4.5 × 10 ⁻⁸ [C / (cm ² · K)], the performance index F _γ of the pyroelectric device was 0.7 × 10 ⁻¹⁰ [C / (cm ² · J)]. The value of pyroelectric coefficient γ of 4.5 × 10 ⁻⁸ [C / (cm ² · K)] is a publication 1 [Ryoichi where a large pyroelectric coefficient γ has been obtained. Takayama and Yoshihiro Tomita, “Preparation of epitaxial Pb (Zr _x Ti _1-x ) O ₃ thin films and their crystallographic, pyroelectric, and ferroelectric properties”, Journal of Applied Physics, Vol.65, 1989, p1666-1670], Publication 2 [Ryoichi Takayama, “Ferroelectric thin film integration technology”, Science Forum, February 1992, p. 47], a PZT thin film with good crystallinity is obtained.

  The ferroelectric device according to the present embodiment described above is formed on the lower electrode 224a formed on the one surface side of the first substrate 220a and on the opposite side of the lower electrode 224a to the first substrate 220a side. A pyroelectric thin film 224b and an upper electrode 224c formed on the opposite side of the pyroelectric thin film 224b from the lower electrode 224a side, and the pyroelectric thin film 224b has a lattice constant difference from the first substrate 220a. It is used as a pyroelectric device composed of a ferroelectric film formed of a certain ferroelectric material. In the method for manufacturing a ferroelectric device according to the present embodiment, the pyroelectric thin film 224b is formed on the one surface side of the second substrate 240, which has better lattice matching with the ferroelectric film than the first substrate 220a. A ferroelectric film forming step for forming the ferroelectric film to be formed, and a first metal layer 251 constituting the lower electrode 224c on the ferroelectric film after the ferroelectric film forming step. The metal layer forming step, the second metal layer 252 formed on the one surface side of the first substrate 220a, and the first metal layer 251 formed in the first metal layer forming step are bonded by room temperature bonding. And a laser beam having a wavelength that passes through the second substrate 240 after the bonding step is irradiated from the second substrate 240 side to transfer the ferroelectric film to the one surface side of the first substrate 220a. Substrate material for ferroelectric devices. Improvement of crystallinity and the performance of the ferroelectric film regardless of the material) of the first substrate 220a is possible.

  More specifically, according to the method of manufacturing a ferroelectric device of this embodiment, the pyroelectric thin film 224b is placed on the one surface side of the second substrate 240 having better lattice matching than the first substrate 220a. After the formation, it is transferred to the one surface side of the first substrate 220a, so that the crystallinity of the pyroelectric thin film 224b can be improved and the second substrate 240 can be reused. A pyroelectric device capable of improving the pyroelectric coefficient of the pyroelectric thin film 224b made of a ferroelectric film at low cost can be provided. In the joining process, since the first metal layer 251 and the second metal layer 252 are joined by room temperature joining, the process temperature of the joining process can be lowered, and the physical properties of the pyroelectric thin film 224b can be reduced in the joining process. It is possible to prevent the change (the characteristic of the pyroelectric thin film 224b is deteriorated). Here, the process temperature of the bonding process is not limited to room temperature (room temperature), and for example, if the temperature is not more than half of the Curie temperature (about 350 ° C. in PZT) of the pyroelectric thin film 224b, Since the change in physical properties can be surely prevented, the bonding process is not limited to room temperature bonding, and may be direct bonding in which an appropriate load is applied while heating at 150 ° C. or lower.

Here, when the pyroelectric material of the pyroelectric thin film 224b is a lead-based oxide ferroelectric, a single crystal MgO substrate, a single crystal SrTiO ₃ substrate, or a sapphire substrate is used as the second substrate 240. A pyroelectric thin film 224b with good crystallinity can be formed, and a Si substrate (single crystal Si substrate, polycrystalline Si substrate) that is less expensive than the second substrate 240 can be used as the first substrate 220a. The cost can be reduced by using an SOI substrate, a glass substrate, a metal substrate, a polymer substrate, or the like.

  Further, according to the pyroelectric device manufacturing method of the present embodiment, the pyroelectric thin film 224b is formed on the one surface side of the second substrate 240 before the dielectric thin film forming step (ferroelectric film forming step). A seed layer forming step of forming a seed layer 224d as a base is provided, and in the transfer step, a laminated film having a laminated structure of the seed layer 224d, the dielectric thin film 224b, and the lower electrode 224a is transferred. Lattice distortion can be suppressed and the crystallinity of the dielectric thin film 224b can be further improved. In the transfer process, it is sufficient to transfer at least a laminated film having a laminated structure of the dielectric thin film 224b and the lower electrode 224a, and the seed layer forming process is not necessarily provided.

  In the manufacturing method described above, room temperature bonding is performed in the bonding process. However, the present invention is not limited to this. For example, in the bonding process, the lower electrode 224a and the first substrate are bonded after the lower electrode forming process. It may be bonded at room temperature via a bonding layer made of a room temperature curable resin adhesive (for example, a two-component room temperature curable epoxy resin adhesive, a one-component room temperature curable epoxy resin adhesive). In this case as well, the bonding temperature can be lowered similarly to the room temperature bonding. Further, the resin adhesive for the bonding layer is not limited to a room temperature curable type, and for example, if the curing temperature is 150 ° C. or less, a thermosetting resin adhesive (for example, a thermosetting epoxy resin adhesive) ) May be used.

20 Cantilever forming substrate 20a Element forming substrate (first substrate)
21 Frame portion 22 Cantilever portion 23 Weight portion 24 Power generation portion 24a Lower electrode 24b Piezoelectric layer (ferroelectric film)
24c Upper electrode 24d Seed layer 40 Piezoelectric layer forming substrate (second substrate)
51 Bonding layer 220a First substrate 224a Lower electrode 224b Pyroelectric thin film (ferroelectric film)
224c Upper electrode 240 Second substrate 251 First metal layer 252 Second metal layer

Claims (7)

  A cantilever forming substrate formed using a first substrate and having a frame portion and a cantilever portion swingably supported by the frame portion, and an alternating voltage is formed according to the vibration of the cantilever portion formed on the cantilever portion. A power generation unit composed of a piezoelectric conversion unit that is generated, and the power generation unit includes a lower electrode formed on one surface side of the cantilever unit and a piezoelectric formed on the opposite side of the lower electrode to the cantilever unit side. And an upper electrode formed on the opposite side of the piezoelectric layer from the lower electrode side, and the piezoelectric layer is formed of a ferroelectric material having a lattice constant difference from the first substrate. A method for manufacturing a ferroelectric device used as a power generation device comprising a ferroelectric film, wherein the ferroelectric film is lattice-matched with the ferroelectric film as compared with the first substrate. A ferroelectric film forming step formed on one surface side of a good second substrate, and a lower electrode forming step of forming the lower electrode on the ferroelectric film after the ferroelectric film forming step; After the lower electrode forming step, the lower substrate on the one surface side of the second substrate and the first substrate are bonded through a bonding layer, and then the second substrate is removed. And a transfer step of transferring the lower electrode and the ferroelectric film to the first substrate.   A lower electrode formed on one surface side of the first substrate; a pyroelectric thin film formed on the opposite side of the lower electrode from the first substrate; and the lower electrode side of the pyroelectric thin film And a pyroelectric device comprising a ferroelectric film formed of a ferroelectric material having a lattice constant difference from that of the first substrate. A method of manufacturing a ferroelectric device used as a method for forming a ferroelectric film on one surface side of a second substrate having a lattice matching with the ferroelectric film better than that of the first substrate. A ferroelectric film forming step; a first metal layer forming step of forming a first metal layer constituting the lower electrode on the ferroelectric film after the ferroelectric film forming step; The second metal layer formed on the one surface side of the one substrate and the first metal layer forming step A bonding step of bonding the formed first metal layer by room temperature bonding, and a laser beam having a wavelength that passes through the second substrate after the bonding step is irradiated from the second substrate side to increase the intensity. And a transfer step of transferring a dielectric film to the one surface side of the first substrate.   A lower electrode formed on one surface side of the first substrate; a pyroelectric thin film formed on the opposite side of the lower electrode from the first substrate; and the lower electrode side of the pyroelectric thin film And a pyroelectric device comprising a ferroelectric film formed of a ferroelectric material having a lattice constant difference from that of the first substrate. A method of manufacturing a ferroelectric device used as a method for forming a ferroelectric film on one surface side of a second substrate having a lattice matching with the ferroelectric film better than that of the first substrate. A ferroelectric film forming step, a lower electrode forming step for forming the lower electrode on the ferroelectric film after the ferroelectric film forming step, a lower electrode and the lower electrode after the lower electrode forming step The first substrate is always connected via a bonding layer made of a room-temperature curable resin adhesive. A bonding step of bonding the ferroelectric film on the one surface of the first substrate by irradiating a laser beam having a wavelength that transmits the second substrate after the bonding step from the second substrate side. And a transfer step of transferring to the side.   The strong transfer according to claim 1, wherein, in the transfer step, an Au layer or a resin layer is used as the bonding layer, and the first substrate is removed by etching the first substrate after the bonding. A method for manufacturing a dielectric device. The ferroelectric material is a lead-based oxide ferroelectric, and a single crystal MgO substrate, a single crystal SrTiO ₃ substrate, or a sapphire substrate is used as the second substrate, and a Si substrate is used as the first substrate. 5. The method of manufacturing a ferroelectric device according to claim 1, wherein one selected from the group consisting of an SOI substrate, a metal substrate, a glass substrate, and a polymer substrate is used.   A seed layer forming step of forming a seed layer that is a base of the ferroelectric film on the one surface side of the second substrate prior to the ferroelectric film forming step; 6. The method of manufacturing a ferroelectric device according to claim 5, wherein a laminated film having a laminated structure of a ferroelectric film and the lower electrode is transferred.   2. The method of manufacturing a ferroelectric device according to claim 1, wherein after the transferring step, a bonding step of bonding a weight portion to a tip portion of the cantilever portion on the first substrate is performed.

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