JP2009232283A - Method of manufacturing baw resonator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a bulk acoustic wave (BAW) resonator capable of improving the crystallinity of a piezoelectric layer, recycling a piezoelectric layer formation substrate and simplifying its manufacturing processes. <P>SOLUTION: A disclosed method includes: a piezoelectric layer forming process of forming a piezoelectric layer 32 constituted of PZT on one surface side of a piezoelectric layer formation substrate 10 constituted of a monocrystal MgO substrate having better lattice matching with the relevant piezoelectric layer 32 in comparison with a support substrate 1 constituted of a monocrystal Si substrate; a transfer process of disposing the piezoelectric layer formation substrate 10 on the one surface side of the support substrate 1 so as to position the piezoelectric layer 32 between the one surface of the piezoelectric layer formation substrate 10 and a lower electrode 31 formed on one surface side of the support substrate 1, irradiating the piezoelectric layer formation substrate 10 from another surface side with laser light transmitted through the piezoelectric layer formation substrate 10, absorbing the laser light on an interface between the piezoelectric layer 32 and the piezoelectric layer formation substrate 10 at the side of the piezoelectric layer 32, and transferring the piezoelectric layer 32 to the one surface side of the support substrate 1; and an upper electrode forming process of forming an upper electrode 33 after the transfer process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a BAW (Bulk Acoustic Wave) resonance device having a resonator using a longitudinal vibration mode in the thickness direction of a piezoelectric layer.

Conventionally, it is known that a BAW resonance device is more suitable than a SAW (Surface Acoustic Wave) resonance device as a resonance device used in a high frequency band of 2 GHz or higher. In recent years, a BAW resonance device has been used for UWB (Ultra Wide Band). When applying to a filter, in order to secure a bandwidth (for example, 300 MHz) that can be applied to a UWB filter, a lead-based piezoelectric material having a large electromechanical coupling coefficient (k _eff ) compared to AlN as a piezoelectric material of the piezoelectric layer. It has been proposed to employ a material (for example, PZT) (for example, see Patent Document 1). In Patent Document 1, FBAR (Film Bulk Acoustic Resonator) and SMR (Solidly Mounted Resonator) are described as BAW resonance devices.

  Further, the BAW resonance device called FBAR is not limited to the structure disclosed in the above-mentioned Patent Document 1, and for example, as shown in FIG. 4 (f), a support made of a single crystal MgO substrate or a single crystal STO substrate. On one surface side of the substrate 1 ′, a lower electrode 31 ′ made of a first conductive material (eg, Pt, Ir, etc.), a piezoelectric layer 32 ′ made of a lead-based piezoelectric material (eg, PZT, etc.), and a second conductive material. A cavity 3a having an upper electrode 33 'made of a conductive material (eg, Pt, Ir, Al, Mo, W, etc.) and exposing the lower electrode 31' to the support substrate 1 '. An installed structure is known. Note that the BAW resonator having the configuration shown in FIG. 4F has an opening that defines the contact area between the upper electrode 33 ′ and the piezoelectric layer 32 ′ on the opposite side of the piezoelectric layer 32 ′ from the lower electrode 31 ′ side. An insulating layer 4 ′ made of a silicon oxide film having a portion 4a ′ is formed.

  Hereinafter, a method of manufacturing the BAW resonator having the configuration shown in FIG.

  First, the lower electrode 31 ′ made of the first conductive material is formed on the one surface side of the support substrate 1 ′ made of a single crystal MgO substrate by a sputtering method, a CVD method, or the like, so that FIG. Get the structure shown.

  Thereafter, a piezoelectric layer 32 ′ made of a lead-based piezoelectric material (for example, PZT) is formed on the one surface side of the support substrate 1 ′ by a sputtering method, a CVD method, a sol-gel method, or the like, as shown in FIG. Get the structure.

  Next, the structure shown in FIG. 4C is obtained by patterning the piezoelectric layer 32 'into a predetermined shape using a photolithography technique and an etching technique.

  Subsequently, the structure shown in FIG. 4D is obtained by forming the insulating layer 4 ′ having the above-described opening 4 a ′ on the one surface side of the support substrate 1 ′. Here, in forming the insulating layer 4 ′, for example, a resist layer covering a portion other than the region where the insulating layer 4 ′ is to be formed is formed on the one surface side of the support substrate 1 ′, and then a sputtering method or a CVD method is used. For example, an insulating layer 4 ′ may be formed on the entire surface of the one surface side of the support substrate 1 ′, and then the resist layer and the insulating layer 4 ′ on the resist layer may be lifted off.

  After forming the insulating layer 4 ′ having the opening 4 a ′, the upper electrode 33 ′ is formed on the one surface side of the support substrate 1 ′, thereby obtaining the structure shown in FIG. In forming the upper electrode 33 ′, the upper electrode 33 ′ may be formed by sputtering, EB vapor deposition, CVD, or the like, and then patterned into a predetermined shape using a photolithography technique and an etching technique.

  After the upper electrode 33 ′ is formed, a cavity 1a ′ penetrating in the thickness direction is formed in the support substrate 1 ′ by using a photolithography technique and an etching technique, whereby the structure shown in FIG. A BAW resonance device can be obtained. Note that phosphoric acid or the like may be used as an etchant for forming the cavity 1a 'in the support substrate 1' made of a single crystal MgO substrate.

  By the way, when a BAW resonance device using a lead-based piezoelectric material such as PZT as a material of the piezoelectric layer 32 ′ is manufactured by the above-described manufacturing method, a lattice constant difference from the lead-based piezoelectric material as the support substrate 1 ′ is increased. By using a single crystal MgO substrate or a single crystal STO substrate that is smaller than a single crystal Si substrate and has good lattice matching, the crystallinity of the piezoelectric layer 32 'can be improved, and the mechanical quality factor, electromechanical coupling coefficient, etc. can be improved. I can plan. However, the single crystal MgO substrate and the single crystal STO substrate are very expensive as compared with the single crystal Si substrate. When the single crystal Si substrate is used as the support substrate like the BAW resonator disclosed in Patent Document 1 above. Compared with the cost.

On the other hand, as a method of manufacturing a MEMS device having a piezoelectric layer between a pair of electrodes, a piezoelectric layer made of a lead-based piezoelectric material (for example, PZT) on one surface side of a piezoelectric layer forming substrate made of a single crystal MgO substrate. Subsequently, a first bonding metal layer is formed on the piezoelectric layer, and then the first bonding metal layer on the one surface side of the piezoelectric layer forming substrate and a single crystal Si substrate are used. The second bonding metal layer formed on one surface side of the piezoelectric layer forming substrate is bonded, and then the laser beam transmitted through the piezoelectric layer forming substrate is irradiated from the other surface side of the piezoelectric layer forming substrate to thereby piezoelectrically apply the piezoelectric layer forming substrate. A manufacturing method has been proposed in which the piezoelectric layer is transferred to the one surface side of the support substrate by peeling from the layer (for example, Patent Document 2). According to this manufacturing method, the crystallinity of the piezoelectric layer is improved. And re-use of single crystal MgO substrate It is possible. In the manufacturing method described in Patent Document 2, since the first bonding metal layer and the second bonding metal layer constitute one electrode of the pair of electrodes, the piezoelectric layer is formed on the support substrate. After the transfer to the one surface side, the other electrode may be formed.
JP 2007-295025 A JP 2003-309303 A

  However, in the manufacturing method described in Patent Document 2, in order to transfer the piezoelectric layer formed on the piezoelectric layer forming substrate to the supporting substrate side, the first bonding metal layer of the piezoelectric layer forming substrate and the first of the supporting substrate are transferred. Two steps, a joining step for joining the two joining metal layers, and a peeling step for peeling the piezoelectric layer forming substrate by irradiating laser light after the joining step are required.

  The present invention has been made in view of the above-mentioned reasons, and the object of the present invention is to improve the crystallinity of the piezoelectric layer, to enable reuse of the piezoelectric layer forming substrate, and to simplify the manufacturing process. It is to provide a manufacturing method.

  The invention of claim 1 is composed of a support substrate, a lower electrode formed on one surface side of the support substrate, and a piezoelectric material formed on the opposite side of the lower electrode from the support substrate side and having a lattice constant difference from the support substrate. A method of manufacturing a BAW resonance device comprising a piezoelectric layer and a resonator having an upper electrode formed on the side opposite to the lower electrode side of the piezoelectric layer, wherein the piezoelectric layer is compared with the piezoelectric layer relative to the support substrate. Piezoelectric layer formed between the one surface of the piezoelectric layer forming substrate and the lower electrode formed on the one surface side of the supporting substrate, and the piezoelectric layer forming step formed on the one surface side of the piezoelectric layer forming substrate with good lattice matching The piezoelectric layer forming substrate is disposed on the one surface side of the support substrate so that the substrate is positioned, and laser light that passes through the piezoelectric layer forming substrate is irradiated from the other surface side of the piezoelectric layer forming substrate. The piezoelectric layer is absorbed by the interface on the piezoelectric layer side. Characterized in that it comprises a transfer step of transferring to the one surface side of the lifting board.

  According to the present invention, the piezoelectric layer forming step of forming the piezoelectric layer on one surface side of the piezoelectric layer forming substrate having better lattice matching with the piezoelectric layer than the supporting substrate, and the one surface of the piezoelectric layer forming substrate A piezoelectric layer forming substrate is disposed on the one surface side of the supporting substrate so that the piezoelectric layer is positioned between the lower electrode formed on the one surface side of the supporting substrate and laser light transmitted through the piezoelectric layer forming substrate. A transfer step of irradiating from the other surface side of the piezoelectric layer forming substrate and absorbing it at the interface between the piezoelectric layer and the piezoelectric layer side of the piezoelectric layer forming substrate and transferring the piezoelectric layer to the one surface side of the supporting substrate. The crystallinity of the piezoelectric layer can be improved and the piezoelectric layer forming substrate can be reused. In addition, the process for transferring the piezoelectric layer formed on the piezoelectric layer forming substrate to the support substrate side is performed by irradiating the piezoelectric layer with laser light. Since only the transfer process to transfer is necessary, Attained to simplify the manufacturing process as compared with the case that requires two steps of the sea urchin bonding step and separation step.

  The invention of claim 2 is the invention of claim 1, wherein the piezoelectric material is a lead-based piezoelectric material, a single crystal MgO substrate or a single crystal STO substrate is used as the piezoelectric layer forming substrate, and a single crystal is used as the support substrate. A Si substrate is used.

  According to this invention, the crystallinity of the piezoelectric layer can be improved and the cost of the support substrate can be reduced.

  According to a third aspect of the present invention, in the second aspect of the invention, the seed layer forming step of forming a seed layer made of PLT, PTO, or SRO on the one surface of the piezoelectric layer forming substrate before the piezoelectric layer forming step. In the transfer step, the laser beam is absorbed at the interface between the piezoelectric layer forming substrate and the seed layer to transfer the laminated film of the piezoelectric layer and the seed layer.

  According to this invention, by providing a seed layer forming step of forming a seed layer made of PLT, PTO or SRO on the one surface of the piezoelectric layer forming substrate before the piezoelectric layer forming step, The crystallinity of the piezoelectric layer can be further improved, and in the transfer step, the laser beam is absorbed at the interface between the piezoelectric layer forming substrate and the seed layer to form a laminated film of the piezoelectric layer and the seed layer. Since the transfer is performed, the piezoelectric layer forming substrate can be reused.

  According to the first aspect of the invention, the crystallinity of the piezoelectric layer can be improved, the piezoelectric layer forming substrate can be reused, and the manufacturing process can be simplified.

  As shown in FIG. 1 (f), the BAW resonance device according to the present embodiment includes a support substrate 1 made of a single crystal Si substrate, a lower electrode 31 formed on one surface side of the support substrate 1, and support on the lower electrode 31. A piezoelectric layer 32 made of a piezoelectric material (for example, PZT) having a lattice constant difference from the support substrate 1 formed on the opposite side of the substrate 1 side, and formed on the opposite side of the piezoelectric layer 32 to the lower electrode 31 side. And a resonator 3 having an upper electrode 33. Here, the lower electrode 31 is made of a first conductive material (for example, In, Pt, Ir, etc.), and the upper electrode 33 is made of a second conductive material (for example, Pt, Ir, Al, Mo, etc.). W etc.).

  In the BAW resonator according to the present embodiment, the insulating film 20 made of a silicon oxide film is formed on the one surface of the supporting substrate 1, and the lower electrode 31 is formed on the insulating film 20. In the insulating film 20, a cavity 1 a that exposes a portion overlapping the resonance region of the resonator 3 is provided. In short, the BAW resonance apparatus in the present embodiment constitutes an FBAR in which propagation of elastic wave energy to the support substrate 1 side is suppressed by providing the support substrate 1 with a cavity 1a. Note that the cavity 1a of the support substrate 1 is formed in a shape in which the opening area gradually increases as the distance from the insulating film 20 increases in the thickness direction of the support substrate 1 (that is, from the lower electrode 31). When an insulating substrate is used as the support substrate 1, the insulating film 20 does not need to be provided.

Further, the BAW resonance device according to the present embodiment is an insulating film made of a silicon oxide film having an opening 4a that defines the contact area between the upper electrode 33 and the piezoelectric layer 32 on the opposite side of the piezoelectric layer 32 from the lower electrode 31 side. Layer 4 is formed. As the material of the insulating layer 4, is adopted to SiO _2, is not limited to SiO _2, for example, it may be adopted _Si 3 _{N 4.}

  Further, the BAW resonance device in the present embodiment employs PZT, which is a kind of lead-based piezoelectric material, as the piezoelectric material of the piezoelectric layer 32, and the support substrate 1 is a single crystal Si whose one surface is a (100) plane. Although the substrate is used, the lead-based piezoelectric material is not limited to PZT, and for example, PZT-PMT or PZT to which appropriate impurities are added may be employed.

  In the BAW resonator according to the present embodiment, the resonance frequency of the resonator 3 is set to 5 GHz, and the thickness of the piezoelectric layer 32 is set to 600 nm. However, these numerical values are only examples and are particularly limited. It is not a thing. For example, when designing the resonance frequency in the range of 3 GHz to 5 GHz, the thickness of the piezoelectric layer 32 may be appropriately set in the range of 200 nm to 600 nm.

  Hereinafter, a method for manufacturing the BAW resonator according to the present embodiment will be described with reference to FIG.

  First, the piezoelectric layer 32 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 32 and having good lattice matching as compared with the support substrate 1 made of a single crystal Si substrate. A piezoelectric layer forming step is performed on one surface side (the lower surface side in FIG. 1A) of the piezoelectric layer forming substrate 10 (see FIG. 1A), and then, as shown in FIG. The piezoelectric layer 32 on the one surface side of the layer forming substrate 10 and the lower electrode 31 made of an In film having a predetermined thickness (for example, 100 nm) formed on the insulating film 20 on the one surface side of the support substrate 1 are opposed to each other. After that, as shown in FIG. 1C, the support substrate is arranged such that the piezoelectric layer 32 is positioned between the one surface of the piezoelectric layer forming substrate 10 and the lower electrode 31 formed on the one surface side of the support substrate 1. 1. A piezoelectric layer forming substrate is disposed on the one surface side of 1, Laser light that passes through the electrode layer forming substrate 10 is irradiated from the other surface side (the upper surface side in FIG. 1B) of the piezoelectric layer forming substrate 10, and the interface between the piezoelectric layer 32 and the piezoelectric layer 32 side of the piezoelectric layer forming substrate 10 ( Here, a transfer process is performed in which the piezoelectric layer 32 is absorbed at the interface between the piezoelectric layer forming substrate 10 and the piezoelectric layer 32 to transfer the piezoelectric layer 32 to the one surface side of the supporting substrate 1 and separate the piezoelectric layer forming substrate 10 from the supporting substrate 1. As a result, the structure shown in FIG. As the piezoelectric layer forming substrate 10 used in the piezoelectric layer forming step, a single crystal MgO substrate having a surface of (100) and a thickness of 300 μm is used. However, the piezoelectric layer forming substrate 10 is not limited to the single crystal MgO substrate. A single crystal STO substrate having one (100) surface may be employed. Further, the thickness of the piezoelectric layer forming substrate 10 is not particularly limited.

In the piezoelectric layer forming step described above, the piezoelectric layer 32 is formed by a sputtering method, a CVD method, a sol-gel method, or the like. Further, the lower electrode 31 on the one surface side of the support substrate 1 may be formed by sputtering, CVD, or the like. Further, in the above-described transfer process, a part of the piezoelectric layer 32 is transferred by controlling the region irradiated with the laser light, so that a separate patterning process for the piezoelectric layer 32 is not necessary. May be transferred. Further, as a laser light source in the transfer process, for example, a KrF excimer laser having a wavelength of 248 nm may be used, and the piezoelectric layer forming substrate 10 is a single crystal MgO substrate, and the piezoelectric material of the piezoelectric layer 32 is PZT. For this, the output density of the KrF excimer laser is preferably set in the range of 0.1 mJ / mm ^{2 to} 1.8 mJ / mm ² . Here, if the output density is less than 0.1 mJ / mm ² , the piezoelectric layer 32 may not be transferred. If the output density is greater than 1.8 mJ / mm ² , the piezoelectric layer forming substrate 10 is cracked and the piezoelectric layer forming substrate 10 is broken. May adhere to the piezoelectric layer 32 side on the support substrate 1 side. Note that the piezoelectric layer 32 remaining on the piezoelectric layer forming substrate 10 peeled off in the transfer process may be selectively etched away with an appropriate etchant (for example, hydrofluoric acid, for example).

  After the above-described transfer step, the structure shown in FIG. 1D is obtained by performing the insulating layer forming step of forming the insulating layer 4 having the above-described opening 4a on the one surface side of the support substrate 1. Here, in the insulating layer forming step, for example, after forming a resist layer covering a portion other than the region where the insulating layer 4 is to be formed on the one surface side of the supporting substrate 1, the supporting substrate 1 is formed by sputtering or CVD. The insulating layer 4 may be formed on the entire surface on the one surface side, and then the resist layer and the insulating layer 4 on the resist layer may be lifted off.

  After the above-described insulating layer forming step, the upper electrode forming step of forming the upper electrode 33 on the one surface side of the support substrate 1 is performed, thereby obtaining the structure shown in FIG. In the upper electrode formation step, the upper electrode 33 may be formed by sputtering, EB vapor deposition, CVD, or the like, and then patterned into a predetermined shape using a photolithography technique and an etching technique.

  After the above-described upper electrode formation step, a cavity portion forming step is performed in which a cavity portion 1a penetrating in the thickness direction is formed in the support substrate 1 by using a photolithography technique and an etching technique, as shown in FIG. A BAW resonance device having a structure can be obtained. Note that phosphoric acid or the like may be used as an etchant when forming the cavity 1a in the support substrate 1 made of a single crystal MgO substrate in the cavity formation process.

  In the manufacture of the above-described BAW resonance device, a large number of BAW resonance devices are formed at the wafer level using the support substrate 1 and the piezoelectric layer-forming substrate 10 described above, respectively. What is necessary is just to divide | segment into a resonance apparatus.

  According to the method for manufacturing the BAW resonance device of the present embodiment described above, the piezoelectric layer 32 is placed on the one surface side of the piezoelectric layer forming substrate 10 having better lattice matching with the piezoelectric layer 32 than the support substrate 1. The piezoelectric layer forming step to be formed, and the piezoelectric layer 32 is positioned between the one surface of the piezoelectric layer forming substrate 10 and the lower electrode 31 formed on the one surface side of the supporting substrate 1. The piezoelectric layer forming substrate 10 is disposed on the front surface side, and laser light transmitted through the piezoelectric layer forming substrate 10 is irradiated from the other surface side of the piezoelectric layer forming substrate 10 to the piezoelectric layer 32 and the piezoelectric layer 32 side of the piezoelectric layer forming substrate 10. And the transfer step of transferring the piezoelectric layer 32 to the one surface side of the support substrate 1 by absorbing the piezoelectric layer 32, so that the crystallinity of the piezoelectric layer 32 can be improved and a high-quality piezoelectric layer 32 can be obtained. Reuse of layered substrate 10 In addition, the process for transferring the piezoelectric layer 32 formed on the piezoelectric layer forming substrate 10 to the support substrate 1 side is only a transfer process for transferring the piezoelectric layer 32 by irradiating the laser beam. As described above, the manufacturing process can be simplified as compared with the case where two processes of the joining process and the peeling process are required.

  Further, in the method of manufacturing the BAW resonator according to this embodiment, the piezoelectric material of the piezoelectric layer 32 is a lead-based piezoelectric material, and a single crystal MgO substrate or a single crystal STO substrate is used as the piezoelectric layer forming substrate 10. Therefore, the crystallinity of the piezoelectric layer 32 can be improved and the cost of the support substrate 1 can be reduced.

  By the way, the piezoelectric material of the piezoelectric layer 32 is not limited to the lead-based piezoelectric material. For example, lead-free KNN (potassium sodium niobate), KN, NN, and KNN have impurities (for example, Li, Nb, Ta, Sb, Cu or the like) may be added. Further, in the above-described method for manufacturing a BAW resonance device, PLT, PTO, or SRO for controlling the crystal orientation of the piezoelectric layer 32 is formed on the one surface of the piezoelectric layer forming substrate 10 before the piezoelectric layer forming step. A seed layer forming step for forming a seed layer is provided, and in the transfer step, laser light is absorbed at the interface between the piezoelectric layer forming substrate 10 and the seed layer to transfer the laminated film of the piezoelectric layer 32 and the seed layer. In addition, by providing the seed layer forming step, the crystallinity of the piezoelectric layer 32 can be further improved, and in the transfer step, the laser light is absorbed at the interface between the piezoelectric layer forming substrate 10 and the seed layer to thereby reduce the piezoelectric layer. Since the laminated film of 32 and the seed layer is transferred, the piezoelectric layer forming substrate 10 can be reused.

  Table 1 below shows the lattice constants and the like of the materials of the piezoelectric layer 32, the seed layer, the lower electrode 31, and the substrate (support substrate 1, piezoelectric layer forming substrate 10).

Note that “a _p ” in Table 1 is a lattice interval in a direction parallel to one surface of the substrate (a direction parallel to the a-axis direction of the substrate material), and the surface at the time of film formation is the (100) plane. In the preferred tetragonal system and cubic system, it is the same as “a”. Further, “c _p ” is a lattice spacing in a direction orthogonal to one surface of the substrate (a direction parallel to the c-axis direction of the substrate material), and the surface at the time of film formation is preferably a (100) plane. For systems and cubic systems, this is the same as “c”. Further, for orthorhombic SRO, the surface during film formation is preferably the (101) plane, but the SRO has the crystal structure shown in FIG. Becomes a two-dimensional lattice as shown in FIG. 2B, so that “a _p ” is not the interval between the lattice points of the adjacent Sr element, but the interval between the pseudo lattice points of the adjacent Ru element and the O element. The same interval is also described for “c _p ”. For “a _p ” and “c _p ” of KNN, KN, and NN, see publication 1 [Takehisa SAITO, et al, “Pulsed Laser Deposition of High-Quality (K, Na) NbO ₃ Thin Films on SrTiO ₃ Substrate Using High-Density Ceramic Targets ”, Japanese Journal of Applied Physics, Vol. 43, No. 9B, 2004, pp. 6627-6631],“ Table II. Lattiice parameters of (K, Na) NbO ₃ films with a The values reported as “a” and “b” in the “psudo-tetoragonal unit cell” are described. Moreover, it is preferable to employ a material having a Young's modulus larger than that of the piezoelectric layer 32 as the material of the piezoelectric layer forming substrate 10.

(Embodiment 2)
In the BAW resonator according to this embodiment, instead of providing the support substrate 1 with the cavity 1a described with reference to FIG. 1 (f) in the first embodiment, as shown in FIG. The difference is that an acoustic mirror (acoustic multilayer film) 2 is formed between the support substrate 1 made of a substrate and the lower electrode 31 of the resonator 3. In short, the BAW resonance device in the present embodiment constitutes an SMR. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  The acoustic mirror 2 is formed by alternately laminating a low acoustic impedance layer 21 made of a material having a relatively low acoustic impedance and a high acoustic impedance layer 22 made of a material having a relatively high acoustic impedance. Is formed on the uppermost low acoustic impedance layer 21. The film thickness of each of the low acoustic impedance layer 21 and the high acoustic impedance layer 22 may be set to a value that is a quarter of the wavelength of the elastic wave (bulk elastic wave) at the resonance frequency of the piezoelectric layer 32.

In this embodiment, SiO ₂ is used as the material of the low acoustic impedance layer 21 and W is used as the material of the high acoustic impedance layer 22. However, these materials are not particularly limited, and the material of the low acoustic impedance layer 21 is used. For example, Si, poly-Si, Al, polymer, or the like may be used. As the material of the high acoustic impedance layer 22, for example, Au, Mo, AlN, ZnO, or the like may be used.

  In the BAW resonance device according to the present embodiment, the resonance frequency of the resonator 3 is set to 4 GHz, the thickness of the lower electrode 31 is 100 nm, the thickness of the piezoelectric layer 32 is 300 nm, the thickness of the upper electrode 33 is 100 nm, and low. Although the thickness of the acoustic impedance layer 21 is set to 400 nm and the thickness of the high acoustic impedance layer 22 is set to 350 nm, these numerical values are merely examples and are not particularly limited. When the resonance frequency is designed in the range of 3 GHz to 5 GHz, the piezoelectric layer 32 has a thickness of 200 nm to 600 nm, the low acoustic impedance layer 21 has a thickness of 250 nm to 550 nm, and the high acoustic impedance layer 22. The thickness of each may be set appropriately in the range of 200 nm to 450 nm.

  Hereinafter, the manufacturing method of the BAW resonator according to the present embodiment will be described with reference to FIG.

First, the piezoelectric layer 32 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 32 and having good lattice matching as compared with the support substrate 1 made of a single crystal Si substrate. A piezoelectric layer forming step is performed on one surface side (the lower surface side in FIG. 3A) of the piezoelectric layer forming substrate 10 (see FIG. 3A), and then, as shown in FIG. The piezoelectric layer 32 on the one surface side of the layer forming substrate 10 and the lower electrode 31 made of an In film having a predetermined film thickness (for example, 100 nm) formed on the acoustic mirror 2 on the one surface side of the support substrate 1 are opposed to each other. After that, as shown in FIG. 3C, the support substrate is arranged such that the piezoelectric layer 32 is located between the one surface of the piezoelectric layer forming substrate 10 and the lower electrode 31 formed on the one surface side of the support substrate 1. 1. A piezoelectric layer forming substrate is arranged on the one surface side of 1 Laser light passing through the piezoelectric layer forming substrate 10 is irradiated from the other surface side (the upper surface side in FIG. 3B) of the piezoelectric layer forming substrate 10 and the interface between the piezoelectric layer 32 and the piezoelectric layer 32 side of the piezoelectric layer forming substrate 10 ( Here, a transfer process is performed in which the piezoelectric layer 32 is absorbed at the interface between the piezoelectric layer forming substrate 10 and the piezoelectric layer 32 to transfer the piezoelectric layer 32 to the one surface side of the supporting substrate 1 and separate the piezoelectric layer forming substrate 10 from the supporting substrate 1. As a result, the structure shown in FIG. The acoustic mirror forming step for forming the acoustic mirror 2 on the one surface side of the support substrate 1 may be performed before the transfer step. In the acoustic mirror forming step, SiO _{2 is} formed on the one surface side of the support substrate 1. The acoustic mirror (acoustic multilayer film) 2 may be formed by alternately forming the low acoustic impedance layer 21 made of a film and the high acoustic impedance layer 22 made of a W film by, for example, a sputtering method or a CVD method.

  After the above-described transfer process, the structure shown in FIG. 3D is obtained by performing an insulating layer forming process for forming the insulating layer 4 having the above-described opening 4a on the one surface side of the support substrate 1.

  After the above-described insulating layer forming step, the upper electrode forming step of forming the upper electrode 33 on the one surface side of the support substrate 1 is performed, whereby the BAW resonance device having the structure shown in FIG. .

  Thus, according to the method of manufacturing the BAW resonator of the present embodiment, the crystallinity of the piezoelectric layer 32 can be improved and a high-quality piezoelectric layer 32 can be obtained as in the first embodiment, and the piezoelectric layer forming substrate 10 can be obtained. In addition, the process for transferring the piezoelectric layer 32 formed on the piezoelectric layer forming substrate 10 to the support substrate 1 side is only a transfer process for transferring the piezoelectric layer 32 by irradiating laser light. Thus, the manufacturing process can be simplified as compared with the conventional case where two processes of the joining process and the peeling process are required.

  By the way, in the transfer process described in the manufacturing method described in the first and second embodiments, the lower electrode 31 made of an In film also serves as a bonding layer, but the bonding layer is configured by at least a part of the lower electrode 31. It only has to be done. Further, the material of the bonding layer is not limited to In, and a conductive epoxy resin may be adopted, and the bonding property and adhesion can be improved. Further, in the transfer step, if pressure is applied from the other surface side of the piezoelectric layer forming substrate 10, the bondability and adhesion can be improved. Moreover, if the support substrate 1 is a flexible substrate, the stress of the piezoelectric layer 32 can be relieved.

  When the BAW resonator described in the first and second embodiments is applied as a filter having a sharp cutoff characteristic and a wide bandwidth in a high frequency band of 3 GHz or more, for example, a UWB filter, a plurality of BAW resonators are used. If (for example, eight) resonators 3 are formed on the one surface side of the support substrate 1 and the plurality of resonators 3 are connected to form a ladder filter, the cost of the UWB filter can be reduced. And downsizing can be achieved.

FIG. 4 is a main process sectional view for explaining the method for manufacturing the BAW resonator according to the first embodiment. It is explanatory drawing of Table 1. FIG. FIG. 10 is a main process sectional view for illustrating the method for manufacturing the BAW resonator according to the second embodiment. It is main process sectional drawing for demonstrating the manufacturing method of the BAW resonance apparatus which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support substrate 1a Cavity part 3 Resonator 4 Insulating layer 10 Substrate for piezoelectric layer formation 20 Insulating film 31 Lower electrode 32 Piezoelectric layer 33 Upper electrode

Claims (3)

  A support substrate, a lower electrode formed on one surface of the support substrate, a piezoelectric layer made of a piezoelectric material formed on the opposite side of the lower electrode from the support substrate side and having a lattice constant difference from the support substrate, and a lower portion of the piezoelectric layer A method of manufacturing a BAW resonance device including a resonator having an upper electrode formed on the side opposite to an electrode side, wherein the piezoelectric layer has a better lattice matching with the piezoelectric layer than the supporting substrate The piezoelectric substrate is formed on one surface side of the forming substrate, and the supporting substrate is positioned so that the piezoelectric layer is positioned between the one surface of the piezoelectric layer forming substrate and the lower electrode formed on the one surface side of the supporting substrate. A piezoelectric layer forming substrate is disposed on the one surface side of the substrate, and laser light transmitted through the piezoelectric layer forming substrate is irradiated from the other surface side of the piezoelectric layer forming substrate and absorbed at the piezoelectric layer side interface between the piezoelectric layer and the piezoelectric layer forming substrate Let the piezoelectric layer on the support substrate Method for manufacturing a BAW resonator, characterized in that it comprises a transfer step of transferring to the side.   The piezoelectric material is a lead-based piezoelectric material, a single crystal MgO substrate or a single crystal STO substrate is used as the piezoelectric layer forming substrate, and a single crystal Si substrate is used as the support substrate. A method of manufacturing a BAW resonance device.   A seed layer forming step of forming a seed layer made of PLT, PTO, or SRO on the one surface of the piezoelectric layer forming substrate prior to the piezoelectric layer forming step; 3. The method of manufacturing a BAW resonance device according to claim 2, wherein the laminated film of the piezoelectric layer and the seed layer is transferred by absorption at an interface between the layer forming substrate and the seed layer.

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