Piezoelectric vibration device and manufacturing method of piezoelectric vibration device

Abstract

To provide a piezoelectric vibration device having a high sealing property and a manufacturing method of the piezoelectric vibration device.SOLUTION: A crystal resonator 100 includes a first bonding layer 115 for bonding a first sealing member 20 and a crystal vibrating plate 10, and a second bonding layer 116 for bonding a second sealing member 30 and the crystal vibrating plate 10. The second bonding layer 116 includes a sealing member base metal layer 116a provided on a first main surface 301 of the second sealing member 30, a vibration plate base metal layer 116b provided on a second main surface 102 of the crystal vibrating plate 10, and a bonding metal layer 116c laminated on the vibration plate base metal layer 116b, and a diffusion prevention layer 116d provided between the bonding metal layer 116c and the sealing member base metal layer 116a.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric vibration device and a method for manufacturing the piezoelectric vibration device. [Background technology]

[0002] In recent years, the operating frequencies of various electronic devices have been increasing and their packages have become smaller (especially lower profile). As a result, piezoelectric resonator devices (such as quartz crystal resonators and crystal oscillators) are also being required to accommodate these trends.

[0003] One such piezoelectric device is a laminated piezoelectric vibrator with a sandwich structure. For example, Patent Document 1 discloses a piezoelectric vibrator in which the first sealing member, second sealing member, and quartz crystal vibrating plate have a multilayer structure of Ti and Au for the metal film of the excitation electrode and the metal film for sealing. In such a piezoelectric vibrating device, the first sealing member and the quartz crystal vibrating plate, and the quartz crystal vibrating plate and the second sealing member are bonded by performing a surface treatment on the Au metal film and then pressure-bonding the two together using a diffusion bonding method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2023-42421 Summary of the Invention [Problem to be solved by the invention]

[0005] However, particularly when the metal film of the bonding layer is composed of a base metal layer and a bonding metal layer, and the base metal layer and the bonding metal layer are a predetermined combination, for example, when the base metal layer is Ti and the bonding metal layer is Au, there is a risk that the metal of the base metal layer will diffuse into the metal of the bonding metal layer due to heating during pressure application during bonding, and that the diffusion of the metal of the base metal layer into the surface of the bonding layer will occur. If the metal of the base metal layer diffuses into the surface of the bonding layer, the bonding with the bonding metal layer on the other side will become unreliable, and the sealing performance will deteriorate, which may lead to poor airtightness.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a piezoelectric vibration device with high sealing properties and a method for manufacturing the piezoelectric vibration device. [Means for solving the problem]

[0007] The present invention is a piezoelectric vibration device comprising: a piezoelectric vibration plate having a first excitation electrode formed on a main surface of a substrate and a second excitation electrode that pairs with the first excitation electrode; first and second sealing members covering both main surfaces of the piezoelectric vibration plate; a first bonding layer bonding the first sealing member to the piezoelectric vibration plate; and a second bonding layer bonding the second sealing member to the piezoelectric vibration plate, wherein the first and second bonding layers provide an internal space in which the vibration portion of the piezoelectric vibration plate, including the first excitation electrode and the second excitation electrode, is hermetically sealed; and at least one of the first and second bonding layers is composed of a sealing member base metal layer provided on the main surface of the first sealing member or the second sealing member, a vibration plate base metal layer provided on the main surface of the piezoelectric vibration plate, a bonding metal layer laminated on the vibration plate base metal layer, and a diffusion prevention layer provided between the bonding metal layer and the sealing member base metal layer.

[0008] That is, the piezoelectric vibration device of the present invention includes a first bonding layer that bonds the first sealing member and the piezoelectric diaphragm, and a second bonding layer that bonds the second sealing member and the piezoelectric diaphragm, and at least one of the first bonding layer and the second bonding layer is composed of a sealing member base metal layer provided on the main surface of the first sealing member or the second sealing member, a diaphragm base metal layer provided on the main surface of the piezoelectric diaphragm, a bonding metal layer provided by laminating on the diaphragm base metal layer, and a diffusion prevention layer provided between the bonding metal layer and the sealing member base metal layer. With this configuration, when the sealing member and the piezoelectric diaphragm are bonded, the diffusion prevention layer prevents diffusion of the sealing member base metal layer into the bonding metal layer, resulting in a piezoelectric vibration device with improved sealing properties.

[0009] The first and second excitation electrodes may also be configured to include an excitation electrode base layer and an electrode layer, with the excitation electrode base layer being formed from the same material as the diaphragm base metal layer, and the electrode layer being formed from the same material as the bonding metal layer. With this configuration, the first and second excitation electrodes do not have a metal layer equivalent to a diffusion prevention layer. This allows for a simple configuration consisting only of a base layer and an electrode layer, which stabilizes the characteristics of the piezoelectric vibration device. Furthermore, when forming the first and second excitation electrodes on the piezoelectric vibration plate, the metal layer for bonding and the metal layer for the excitation electrodes can be formed simultaneously. This improves the productivity of piezoelectric vibration devices.

[0010] The sealing member base metal layer and the diaphragm base metal layer may be composed of a Ti metal layer, the bonding metal layer may be composed of an Au metal layer, and the diffusion barrier layer may be composed of a W metal layer, with the diffusion barrier layer having a thickness of 5 to 10 nm. With this configuration, the Ti metal layer and the W metal layer can be simultaneously patterned by etching, thereby improving the productivity of piezoelectric vibration devices. Furthermore, when the Ti metal layer and the W metal layer are simultaneously patterned, a phenomenon occurs in which the W metal layer underlying the Au metal layer is etched from the side (side etching), which deteriorates the sealing performance. However, by setting the thickness of the W metal layer within the range of the present invention, side etching can be suppressed, thereby improving the sealing performance.

[0011] The method may also include a sealing member-side bonding layer forming step of forming a sealing member-side bonding layer on one main surface of at least one of the first sealing member and the second sealing member, a piezoelectric vibration plate-side bonding layer forming step of forming a piezoelectric vibration plate-side bonding layer on one main surface of the piezoelectric vibration plate, and a bonding step of diffusion-bonding the sealing member-side bonding layer and the piezoelectric vibration plate-side bonding layer, wherein the sealing member-side bonding layer forming step includes a base metal layer forming step of forming a Ti metal layer as a sealing member base metal layer on one main surface of at least one of the first sealing member and the second sealing member, a diffusion prevention layer forming step of forming a W metal layer as a diffusion prevention layer on the sealing member base metal layer, a bonding metal layer forming step of forming an Au metal layer as a bonding metal layer on the diffusion prevention layer, a first etching step of forming a mask resist on a portion of the Au metal layer and removing by etching the Au metal layer on which the mask resist is not formed, and a second etching step of removing the mask resist and etching away the W metal layer and the Ti metal layer using the Au metal layer as a resist. With this configuration, while it would normally be necessary to perform etching steps for patterning the sealing member base metal layer, the diffusion prevention layer, and the bonding metal layer, respectively, the etching steps for patterning the diffusion prevention layer and the bonding metal layer can be performed simultaneously. In other words, what would normally require three etching steps can be reduced to two, thereby improving the productivity of piezoelectric vibration devices. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a piezoelectric vibration device with high sealing properties and a method for manufacturing the piezoelectric vibration device. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a side view of the crystal resonator according to the embodiment. [Figure 2] FIG. 4 is a cross-sectional side view of a second bonding layer according to the embodiment. [Figure 3] FIG. 2 is a schematic plan view of a first main surface side of a first sealing member of the crystal resonator according to the present embodiment. [Figure 4] FIG. 3 is a schematic plan view of the second principal surface side of the first sealing member of the crystal resonator according to the present embodiment. [Figure 5] 1 is a schematic plan view of a first main surface side of a quartz crystal plate of a quartz crystal resonator according to an embodiment of the present invention. [Figure 6] 3 is a schematic plan view of a second main surface side of a quartz crystal plate of the quartz crystal resonator according to the present embodiment. FIG. [Figure 7] FIG. 3 is a schematic plan view of the first principal surface side of the second sealing member of the quartz crystal resonator according to the present embodiment. [Figure 8] FIG. 3 is a schematic plan view of a second principal surface side of a second sealing member of the crystal resonator according to the present embodiment. [Figure 9] FIG. 10 is a schematic explanatory view illustrating a sealing member-side bonding layer forming step for the second sealing member. [Figure 10] 5A to 5C are schematic explanatory views for explaining the state of a bonding layer in a bonding step. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following preferred embodiments, a piezoelectric resonator device to which the present invention is applied is a quartz resonator.

[0015] First, the basic structure of a quartz crystal resonator 100 according to this embodiment (first embodiment) will be described. As shown in FIG. 1, the quartz crystal resonator 100 is configured to include a quartz crystal vibrating plate (piezoelectric vibrating plate) 10, a first sealing member 20, and a second sealing member 30. In this quartz crystal resonator 100, the quartz crystal vibrating plate 10 and the first sealing member 20 are bonded together with a first bonding layer 115, and the quartz crystal vibrating plate 10 and the second sealing member 30 are bonded together with a second bonding layer 116, thereby forming a package with a substantially rectangular parallelepiped sandwich structure. That is, in the quartz crystal resonator 100, the first sealing member 20 and the second sealing member 30 are bonded to both main surfaces of the quartz crystal vibrating plate 10, respectively, to form an internal space (cavity) of the package, and a vibrating unit 11 (see FIGS. 4 and 5) is hermetically sealed in this internal space.

[0016] FIG. 2 is a cross-sectional side view of the second bonding layer 116 according to this embodiment. In this embodiment, the second bonding layer 116 is composed of a sealing member base metal layer 116a provided on the first main surface 301 of the second sealing member 30, a vibration plate base metal layer 116b provided on the second main surface 102 of the quartz crystal vibration plate 10, a bonding metal layer 116c provided by stacking on the vibration plate base metal layer 116b, and a diffusion prevention layer 116d provided between the bonding metal layer 116c and the sealing member base metal layer 116a.

[0017] The diffusion prevention layer 116d in this embodiment is a W metal layer made of W (tungsten). The W metal layer preferably has a thickness of 5 to 10 nm. Note that, instead of W (tungsten), Mo (molybdenum) may also be used as the diffusion prevention layer 116d.

[0018] In this embodiment, the sealing member base metal layer 116a and the diaphragm base metal layer 116b are Ti (titanium) metal layers. The Ti metal layer preferably has a thickness of 5 to 200 nm, more preferably 100 to 180 nm. The Ti metal layer preferably has a thickness 0.5 to 40 times, more preferably 10 to 30 times, that of the W metal layer that is the diffusion prevention layer 116d.

[0019] In this embodiment, the bonding metal layer 116c is an Au metal layer made of Au (gold), and the Au metal layer preferably has a thickness of 200 to 600 nm.

[0020] Although the second bonding layer 116 has been described in detail in this embodiment, it is preferable that the first bonding layer 115 has a similar configuration to the second bonding layer 116. That is, it is preferable that the first bonding layer 115 is composed of a sealing member base metal layer (not shown) provided on the second main surface 202 of the first sealing member 20, a diaphragm base metal layer (not shown) provided on the first main surface 101 of the quartz crystal vibrating plate 10, a bonding metal layer (not shown) laminated on the diaphragm base metal layer, and a diffusion prevention layer (not shown) provided between the bonding metal layer and the sealing member base metal layer.

[0021] Next, the quartz crystal plate 10, the first sealing member 20, and the second sealing member 30 of the quartz crystal unit 100 will be described with reference to Figures 3 to 8. Note that the description here focuses on each component that is configured as a single unit and not bonded together. Figures 3 to 8 merely show one example configuration of the quartz crystal plate 10, the first sealing member 20, and the second sealing member 30, and are not intended to limit the scope of the present invention.

[0022] The quartz crystal plate 10 in this embodiment is an AT-cut quartz crystal plate that vibrates in thickness-shear mode. In the quartz crystal plate 10 shown in FIGS. 5 and 6, both main surfaces 101 and 102 of the quartz crystal plate 10 are in the XZ' plane. In this XZ' plane, the direction parallel to the short side (short edge) of the quartz crystal plate 10 is the X-axis direction, and the direction parallel to the long side (long edge) of the quartz crystal plate 10 is the Z'-axis direction. Note that AT-cut is a processing technique in which a quartz crystal is cut at an angle of 35°15' around the X-axis relative to the Z-axis, one of the three crystal axes of the quartz crystal: the electrical axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). In an AT-cut quartz crystal plate, the X-axis coincides with the crystal axis of the quartz crystal. The Y' and Z' axes are inclined at approximately 35°15° from the Y and Z crystal axes of the quartz crystal (this cutting angle may be changed slightly to adjust the frequency-temperature characteristics of the AT-cut quartz crystal plate). The Y' and Z' axis directions correspond to the cutting direction when the AT-cut quartz crystal plate is cut. Furthermore, both main surfaces of the quartz crystal plate 10 (first main surface 101, second main surface 102) are formed as flat, smooth surfaces that have been polished to a mirror finish, for example.

[0023] The quartz crystal vibration plate 10 has a substantially rectangular vibrating portion 11, an outer frame portion 12 that surrounds the outer periphery of the vibrating portion 11, and a holding portion 13 that connects the vibrating portion 11 and the outer frame portion 12 to hold the vibrating portion 11. That is, the quartz crystal vibration plate 10 is configured such that the vibrating portion 11, the outer frame portion 12, and the holding portion 13 are integrally formed. The holding portion 13 extends (protrudes) from only one corner of the vibrating portion 11 located in the +X direction and the -Z' direction to the outer frame portion 12 in the -Z' direction. A cutout portion 11a is provided between the vibrating portion 11 and the outer frame portion 12 by cutting out the quartz crystal vibration plate 10. In this embodiment, the quartz crystal vibration plate 10 has only one holding portion 13 that connects the vibrating portion 11 and the outer frame portion 12, and the cutout portion 11a is continuously formed to surround the outer periphery of the vibrating portion 11.

[0024] The thickness of the base material of the quartz crystal vibrating plate 10 can be, for example, approximately 40 μm or approximately 60 μm. Furthermore, it is preferable that the vibrating portion 11 of the quartz crystal vibrating plate 10 is formed to be thinner than the outer frame portion 12, and it is more preferable that the thickness of the vibrating portion 11 is about half the thickness of the outer frame portion 12. In this case, it is preferable that the positions of the first main surface 101 of the outer frame portion 12 and the first main surface 101 of the vibrating portion 11 are different in the thickness direction (Y' direction). Note that the thickness of the vibrating portion 11 is related to the vibration characteristics of the quartz crystal resonator 100. Therefore, the thickness of the vibrating portion 11 may be adjusted as appropriate to obtain a quartz crystal resonator 100 with desired characteristics.

[0025] A pair of excitation electrodes (first excitation electrode 111, second excitation electrode 112) are formed on both main surfaces 101, 102 of the quartz crystal vibrating plate 10. The first excitation electrode 111 is provided on the first main surface 101 side of the vibrating part 11, and the second excitation electrode 112 is provided on the second main surface 102 side of the vibrating part 11. Lead wiring (first lead wiring 113, second lead wiring 114) is connected to the first excitation electrode 111 and the second excitation electrode 112 to connect these excitation electrodes to external terminals. The first extraction wiring 113 is extracted from the first excitation electrode 111 and connected to a connection junction pattern 12a formed on the first main surface 101 side of the outer frame portion 12 via the holding portion 13, and the connection junction pattern 12a is further connected to a connection junction pattern 12e formed on the second main surface 102 side of the outer frame portion 12 via a second front / rear extraction wiring 18 formed on the inner wall surface of the outer frame portion 12. The second extraction wiring 114 is extracted from the second excitation electrode 112 and connected to a connection junction pattern 12d formed on the second main surface 102 side of the outer frame portion 12 via the holding portion 13.

[0026] 5 and 6, a first diaphragm-side bonding pattern 121 is formed on the first main surface 101 of the quartz-crystal vibrating plate 10, and a second diaphragm-side bonding pattern 122 is formed on the second main surface 102. The first diaphragm-side bonding pattern 121 and the second diaphragm-side bonding pattern 122 are provided on the outer frame 12 and are formed in an annular shape in a plan view. The outer peripheral edge of the first diaphragm-side bonding pattern 121 is provided adjacent to the outer peripheral edge of the first main surface 101 of the quartz-crystal vibrating plate 10 (outer frame 12). The outer peripheral edge of the second diaphragm-side bonding pattern 122 is provided adjacent to the outer peripheral edge of the second main surface 102 of the quartz-crystal vibrating plate 10 (outer frame 12). In this embodiment, the first diaphragm-side bonding pattern 121 and the second diaphragm-side bonding pattern 122 are connected via first front-to-rear wiring 17 formed on the inner wall surface of the outer frame 12. The first front-to-back wiring 17 is provided on the inner wall surface of the outer frame portion 12 that is along the Z'-axis direction and is on the -X direction side.

[0027] The first extraction wiring 113, the second extraction wiring 114, the connection bonding patterns 12a, 12b, 12c, 12d, 12e, and 12f, the first vibration plate bonding pattern 121, and the second vibration plate bonding pattern 122 formed on the quartz crystal vibration plate 10 are each composed of two layers: a Ti metal layer (vibration plate base metal layer) formed on the corresponding main surface (first main surface 101, second main surface 102) and an Au metal layer (vibration plate bonding metal layer) formed on the Ti metal layer. Also, the first excitation electrode 111 and the second excitation electrode 112 are each composed of two layers: a Ti metal layer (excitation electrode base layer) formed on the corresponding main surface (first main surface 101, second main surface 102) and an Au metal layer (electrode layer) formed on the Ti metal layer. That is, the first excitation electrode 111 and the second excitation electrode 112 are composed of an excitation electrode base layer and an electrode layer, and the excitation electrode base layer is formed of the same Ti metal layer as the diaphragm base metal layer 116b, and the electrode layer is formed of the same Au metal layer as the bonding metal layer 116c.

[0028] The Ti metal layer and the Au metal layer constituting the first excitation electrode 111, the second excitation electrode 112, the first lead wiring 113, the second lead wiring 114, the connection bonding patterns 12a, 12b, 12c, 12d, 12e, and 12f, the diaphragm-side first bonding pattern 121, and the diaphragm-side second bonding pattern 122 of the quartz-crystal vibrating plate 10 can be formed by vapor deposition or sputtering. The various bonding patterns, wiring, and electrodes described above may also be formed by photolithography.

[0029] As shown in FIGS. 3 and 4, the first sealing member 20 is formed as a rectangular parallelepiped substrate made from a single AT-cut quartz crystal plate. The first main surface 201 and second main surface 202 (surfaces bonded to the quartz crystal vibrating plate 10) of this first sealing member 20 are formed as flat, smooth surfaces (mirror-finished). Although the first sealing member 20 does not have a vibrating part, it is preferable to use an AT-cut quartz crystal plate like the quartz crystal vibrating plate 10. In this embodiment, the X-, Y-, and Z'-axes of the first sealing member 20 are oriented in the same directions as the quartz crystal vibrating plate 10. Furthermore, the thickness of the first sealing member 20 is preferably the same as that of the quartz crystal vibrating plate 10.

[0030] Furthermore, the first sealing member 20 does not have any through holes that penetrate between the first main surface 201 and the second main surface 202. Therefore, the first main surface 201 (the upper surface of the quartz crystal unit 100) of the first sealing member 20 in this embodiment is a smooth surface on which the quartz crystal that forms the substrate of the first sealing member 20 is exposed over the entire surface.

[0031] As shown in FIG. 4 , a first sealing member-side bonding pattern 24 is formed on the second main surface 202 of the first sealing member 20. The first sealing member-side bonding pattern 24 is formed in a ring shape in a plan view. The outer peripheral edge of the first sealing member-side bonding pattern 24 is provided close to the outer peripheral edge of the second main surface 202 of the first sealing member 20. In addition, the second main surface 202 of the first sealing member 20 is formed with a connection bonding pattern 22a for bonding to the connection bonding pattern 12a formed on the first main surface 101 of the outer frame portion 12 of the quartz crystal vibrating plate 10, a connection bonding pattern 22b for bonding to the connection bonding pattern 12b formed on the first main surface 101 of the outer frame portion 12 of the quartz crystal vibrating plate 10, and a connection bonding pattern 22c for bonding to the connection bonding pattern 12c formed on the first main surface 101 of the outer frame portion 12 of the quartz crystal vibrating plate 10.

[0032] The connection bonding patterns 22a, 22b, and 22c formed on the first sealing member 20 and the sealing member-side first bonding pattern 24 are each composed of three layers: a Ti metal layer (sealing member base metal layer) formed on the second main surface 202, a W metal layer (diffusion prevention layer) formed on the Ti metal layer, and an Au metal layer (sealing member bonding metal layer) formed on the W metal layer. The various bonding patterns described above can be formed by vapor deposition or sputtering, or may be formed by photolithography.

[0033] As shown in Figures 7 and 8, the second sealing member 30 is formed as a rectangular parallelepiped substrate made from a single AT-cut quartz crystal plate. The first main surface 301 (the surface bonded to the quartz crystal vibrating plate 10) and the second main surface 302 (the bottom surface of the quartz crystal unit 100) of the second sealing member 30 are formed as flat, smooth surfaces (mirror-finished). The second sealing member 30 preferably uses an AT-cut quartz crystal plate, similar to the quartz crystal vibrating plate 10, and the orientations of the X-axis, Y-axis, and Z'-axis are preferably the same as those of the quartz crystal vibrating plate 10. Furthermore, the thickness of the second sealing member 30 is preferably the same as that of the quartz crystal vibrating plate 10 and the first sealing member 20.

[0034] 8, four external terminals 32a, 32b, 32c, and 32d are provided on the second main surface 302 of the second sealing member 30 (the outer main surface that does not face the quartz-crystal vibrating plate 10), which are electrically connected to an external circuit board provided outside the quartz-crystal vibrating device 100. Each of the external terminals 32a, 32b, 32c, and 32d is formed in a substantially rectangular shape and is located at one of the four corners of the second main surface 302 of the second sealing member 30. Each of the external terminals 32a, 32b, 32c, and 32d is located so as to overlap the outer frame 12 of the quartz-crystal vibrating plate 10 in a plan view.

[0035] The four external terminals 32a, 32b, 32c, and 32d each have a first region 32a1, 32b1, 32c1, and 32d1 and a second region 32a2, 32b2, 32c2, and 32d2, respectively, in a plan view. The metal material configurations of the first regions 32a1, 32b1, 32c1, and 32d1 are different from the metal material configurations of the second regions 32a2, 32b2, 32c2, and 32d2. Specifically, in the second regions 32a2, 32b2, 32c2, and 32d2, a Ni metal layer primarily composed of Ni (nickel) is laminated on a Ti (titanium) metal layer serving as a base layer. That is, the surface layers of the second regions 32a2, 32b2, 32c2, and 32d2 are Ni metal layers primarily composed of Ni. In this embodiment, the Ni metal layer is a NiTi alloy containing Ni as the main component and Ti as the main component. In the first regions 32a1, 32b1, 32c1, and 32d1, a Ni metal layer containing Ni as the main component is laminated on a Ti metal layer serving as a base layer, and an Au (gold) metal layer is further laminated on the Ni metal layer. That is, the surface layers of the first regions 32a1, 32b1, 32c1, and 32d1 are Au metal layers.

[0036] A sealing member-side second bonding pattern 31 is formed on the first main surface 301 of the second sealing member 30. The sealing member-side second bonding pattern 31 is formed in a ring shape in a plan view. The outer peripheral edge of the sealing member-side second bonding pattern 31 is provided close to the outer peripheral edge of the first main surface 301 of the second sealing member 30. The first main surface 301 of the second sealing member 30 is also formed with a connection bonding pattern 33a for bonding to the connection bonding pattern 12e formed on the second main surface 102 of the quartz-crystal vibrating plate 10, a connection bonding pattern 33b for bonding to the connection bonding pattern 12f formed on the second main surface 102 of the quartz-crystal vibrating plate 10, and a connection bonding pattern 33c for bonding to the connection bonding pattern 12d formed on the second main surface 102 of the quartz-crystal vibrating plate 10. The connection bonding pattern 33b and the connection bonding pattern 33c are connected by a wiring pattern 34.

[0037] The connection bonding patterns 33a, 33b, and 33c, the wiring pattern 34, and the sealing member-side second bonding pattern 31 formed on the first sealing member 20 are each composed of three layers: a Ti metal layer (sealing member base metal layer) formed on the first main surface 301, a W metal layer (diffusion prevention layer) formed on the Ti metal layer, and an Au metal layer (sealing member bonding metal layer) formed on the W metal layer. The various bonding patterns and wiring patterns described above can be formed by vapor deposition or sputtering, or may be formed by photolithography.

[0038] Furthermore, three through holes are formed in the second sealing member 30, penetrating between the first main surface 301 and the second main surface 302. Specifically, a first through hole 161, a second through hole 162, and a third through hole 163 are respectively provided in the second sealing member 30. The first, second, and third through holes 161, 162, and 163 are formed so as to be located within respective regions selected from the second regions 32a2, 32b2, 32c2, and 32d2 in a plan view looking at the second main surface 302 side.

[0039] Conduction electrodes for establishing electrical continuity between the electrodes formed on the first main surface 301 and the second main surface 302 are formed along the inner wall surfaces of the first through hole 161, the second through hole 162, and the third through hole 163. The conduction electrodes of the first through hole 161 are electrically connected to the sealing member-side second bonding pattern 31 formed on the first main surface 301 of the second sealing member 30 and to the second regions 32a2 of the external terminals 32a formed on the second main surface 302. The conduction electrodes of the second through hole 162 are electrically connected to the connection bonding pattern 33a formed on the first main surface 301 of the second sealing member 30 and to the second regions 32b2 of the external terminals 32b formed on the second main surface 302. The conductive electrode of the third through hole 163 is electrically connected to the connection bonding pattern 33b formed on the first main surface 301 of the second sealing member 30 and the second region 32c2 of the external terminal 32c formed on the second main surface 302. That is, the first, second and third through holes 161, 162 and 163 electrically connect the corresponding external terminals 32a, 32b and 32c to the internal electrodes (the sealing member-side second bonding pattern 31, the connection bonding pattern 33a and the connection bonding pattern 33b), respectively.

[0040] In the quartz crystal vibrating device 100 including the quartz crystal vibrating plate 10, first sealing member 20, and second sealing member 30 configured as described above, the quartz crystal vibrating plate 10 and the first sealing member 20 are bonded together. Specifically, the diaphragm-side first bonding pattern 121 and the sealing member-side first bonding pattern 24 are diffusion-bonded (Au-Au bonding) while overlapping each other. The quartz crystal vibrating plate 10 and the second sealing member 30 are also bonded together. Specifically, the diaphragm-side second bonding pattern 122 and the sealing member-side second bonding pattern 31 are diffusion-bonded (Au-Au bonding) while overlapping each other. As a result, the quartz crystal vibrating device 100 is manufactured as a sandwich-structured package, and the internal space of the package, i.e., the space accommodating the vibrating unit 11, is hermetically sealed.

[0041] At this time, the above-mentioned connection bonding patterns are also overlapped and diffusion bonded (Au-Au bonded). More specifically, on the quartz-crystal vibrating plate 10 and the first sealing member 20, the connection bonding patterns 12a and 22a, the connection bonding patterns 12b and 22b, and the connection bonding patterns 12c and 22c are bonded, respectively. The bonding of these corresponding connection bonding patterns and the bonding of the vibration-plate-side first bonding pattern 121 and the sealing member-side first bonding pattern 24 form a first bonding layer 115.

[0042] Furthermore, the connection bonding pattern 12e is bonded to the connection bonding pattern 33a, the connection bonding pattern 12f is bonded to the connection bonding pattern 33b, and the connection bonding pattern 12d is bonded to the connection bonding pattern 33c on the quartz-crystal vibrating plate 10 and the second sealing member 30. The bonding between these corresponding connection bonding patterns and the bonding between the vibration-plate-side second bonding pattern 122 and the sealing member-side second bonding pattern 31 form a second bonding layer 116.

[0043] By bonding the connection bonding patterns together, electrical conduction is established between the first excitation electrode 111 and the external terminal 32c, and electrical conduction is established between the second excitation electrode 112 and the external terminal 32b in the quartz crystal unit 100. Specifically, the first excitation electrode 111 is connected to the external terminal 32c via the first extraction wiring 113, the connection bonding pattern 12a, the second front-rear wiring 18, the connection bonding pattern 12e, the connection bonding pattern 33a, and the conductive electrode of the third through-hole 163, in that order. The second excitation electrode 112 is connected to the external terminal 32b via the second extraction wiring 114, the connection bonding pattern 12d, the connection bonding pattern 33c, the wiring pattern 34, the connection bonding pattern 33b, and the conductive electrode of the second through-hole 162, in that order. The external terminal 32a in this embodiment is connected to the first bonding layer 115, the first front-to-back wiring 17, and the second bonding layer 116 via the conductive electrode of the first through-hole 161, and is connected to earth (ground). That is, the external terminal 32a in this embodiment functions as a ground terminal.

[0044] A manufacturing method for the above-described quartz crystal resonator 100 can include a quartz crystal plate fabrication process for fabricating the quartz crystal plate 10, a sealing member fabrication process for fabricating the first sealing member 20 and the second sealing member 30, and a bonding process for bonding the fabricated quartz crystal plate 10 to the first sealing member 20 and the second sealing member 30. The quartz crystal plate fabrication process includes a quartz crystal plate-side bonding layer formation process for forming a quartz crystal plate-side bonding layer on the first main surface 101 and the second main surface 102 of the quartz crystal plate 10. The quartz crystal plate-side bonding layer corresponds to the piezoelectric diaphragm-side bonding layer of the present invention, and the quartz crystal plate-side bonding layer formation process corresponds to the piezoelectric diaphragm-side bonding layer of the present invention. Furthermore, the sealing member fabrication process includes a sealing member-side bonding layer formation process for forming a sealing member-side bonding layer on one main surface (the second main surface 202 and the first main surface 301) of each of the first sealing member 20 and the second sealing member 30.

[0045] Figure 9 is a schematic explanatory diagram for explaining the sealing member side bonding layer formation process for the second sealing member 30, and Figure 10 is a schematic explanatory diagram for explaining the state of the bonding layer in the bonding process for bonding the second sealing member 30 and the quartz vibration plate 10. As shown in FIG. 9, the sealing member side bonding layer formation process includes (a) a base metal layer formation process for forming a Ti metal layer 30a as a sealing member base metal layer on the first main surface 301 of the second sealing member 30, (b) a diffusion prevention layer formation process for forming a W metal layer 30b on the sealing member base metal layer as a diffusion prevention layer, (c) a bonding metal layer formation process for forming an Au metal layer 30c on the diffusion prevention layer as a bonding metal layer, (d) a mask resist formation process for forming a mask resist 30d on a portion of the Au metal layer 30c, (e) a first etching process for removing the Au metal layer 30c on which the mask resist is not formed using an Au etching solution Eg1, (f) a resist removal process for removing the mask resist, and (g) a second etching process for removing the W metal layer 30b and the Ti metal layer 30a using the Au metal layer 30c as a resist using a TiW etching solution Eg2. Various known etching solutions can be used for the Au etching solution Eg1 and the TiW etching solution Eg2. This manufacturing method allows the second sealing member side bonding layer 303 having a predetermined pattern to be formed on the first main surface 301 of the second sealing member 30. The second sealing member side bonding layer 303 corresponds to the connection bonding patterns 33a, 33b, and 33c and the sealing member side second bonding pattern 31 in this embodiment. Furthermore, by performing the same process as for the second sealing member 30, the first sealing member side bonding layer (not shown) having a predetermined pattern can be formed on the second main surface 202 of the first sealing member 20. The first sealing member side bonding layer corresponds to the connection bonding patterns 22a, 22b, and 22c and the sealing member side first bonding pattern 24 in this embodiment.

[0046] The quartz-crystal vibrating plate-side bonding layer forming process includes a base metal layer forming process for forming a Ti metal layer 10a as a diaphragm base metal layer on both major surfaces (first major surface 101, second major surface 102) of the quartz-crystal vibrating plate 10, a bonding metal layer forming process for forming an Au metal layer 10b as a bonding metal layer by overlaying the diaphragm base metal layer, a mask resist forming process for forming a mask resist with a predetermined shape on the Au metal layer 10b, a first etching process for removing the Au metal layer 10b where the mask resist is not formed using an Au etchant, a resist removal process for removing the mask resist, and a second etching process for removing the Ti metal layer 10a using the Au metal layer 10b as a resist using a Ti etchant. This manufacturing method allows for the formation of a quartz-crystal vibrating plate-side bonding layer 103 with a predetermined pattern on both major surfaces (first major surface 101, second major surface 102) of the quartz-crystal vibrating plate 10. The crystal diaphragm-side bonding layer 103 corresponds to the connection bonding patterns 12a, 12b, 12c, 12d, 12e, and 12f, the diaphragm-side first bonding pattern 121, and the diaphragm-side second bonding pattern 122 in this embodiment.

[0047] 10 , the bonding process involves bonding the quartz-crystal vibrating plate 10 and the second sealing member 30. The Au metal layer 10b of the quartz-crystal vibrating-plate bonding layer 103 and the Au metal layer 30c of the second sealing member bonding layer 303 are brought into contact with each other (a), and then pressure P and heat H are applied (pressure and heat) to perform diffusion bonding (Au-Au bonding). This causes the Au metal layer 10b of the quartz-crystal vibrating-plate bonding layer 103 and the Au metal layer 30c of the second sealing member bonding layer 303 to bond together, forming the bonding metal layer 116c of the second bonding layer 116 (c). Specifically, the Ti metal layer 30a corresponds to the sealing member base metal layer 116a, the W metal layer 30b corresponds to the diffusion barrier layer 116d, and the Ti metal layer 10a corresponds to the vibration plate base metal layer 116b.

[0048] In addition, in the process of bonding the quartz vibration plate 10 and the first sealing member 20, similar to the process of bonding the quartz vibration plate 10 and the second sealing member 30, the bonding metal layer of the first bonding layer 115 is formed by diffusion bonding the first sealing member side bonding layer and the quartz vibration plate side bonding layer.

[0049] The above configuration makes it possible to provide a piezoelectric vibration device with high sealing properties and a method for manufacturing the piezoelectric vibration device. The quartz crystal unit 100 includes a first bonding layer 115 that bonds the first sealing member 20 and the quartz crystal vibration plate 10 together, and a second bonding layer 116 that bonds the second sealing member 30 and the quartz crystal vibration plate 10 together. The second bonding layer 116 is composed of a sealing member base metal layer 116a provided on the first main surface 301 of the second sealing member 30, a vibration plate base metal layer 116b provided on the second main surface 102 of the quartz crystal vibration plate 10, a bonding metal layer 116c that is laminated on the vibration plate base metal layer 116b, and a diffusion prevention layer 116d that is provided between the bonding metal layer 116c and the sealing member base metal layer 116a. With this configuration, when the second sealing member 30 and the quartz crystal vibrating plate 10 are bonded, the diffusion prevention layer 116d prevents the sealing member base metal layer 116a from diffusing into the bonding metal layer 116c, resulting in a quartz crystal vibrating device 100 with improved sealing properties.

[0050] The first excitation electrode 111 and the second excitation electrode 112 are each composed of an excitation electrode base layer and an electrode layer. The excitation electrode base layer is made of the same material as the diaphragm base metal layer 116b, and the electrode layer is made of the same material as the bonding metal layer 116c. This configuration eliminates the need for a metal layer equivalent to the diffusion prevention layer 116d in the first excitation electrode 111 and the second excitation electrode 112. This allows for a simple configuration consisting of only the electrode base layer and the electrode layer, thereby stabilizing the characteristics of the quartz crystal unit 100. Furthermore, when forming the first excitation electrode 111 and the second excitation electrode 112 on the quartz crystal diaphragm 10, the metal layer for bonding and the metal layer for the excitation electrodes can be formed simultaneously. This improves the productivity of the quartz crystal unit 100.

[0051] Furthermore, the sealing member base metal layer 116a and the diaphragm base metal layer 116b are composed of a Ti metal layer, the bonding metal layer 116c is composed of an Au metal layer, and the diffusion prevention layer 116d is composed of a W metal layer, with the diffusion prevention layer 116d having a thickness of 5 to 10 nm. This configuration allows the Ti metal layer and the W metal layer to be simultaneously patterned by etching, improving the productivity of piezoelectric vibration devices. Furthermore, when simultaneously patterning the Ti metal layer and the W metal layer, a phenomenon known as side etching occurs in which the W metal layer underlying the Au metal layer is etched from the sides, deteriorating the sealing performance. However, by setting the thickness of the W metal layer to 10 nm or less, side etching is suppressed, thereby improving the sealing performance. Furthermore, by setting the thickness of the W metal layer to 5 nm or more, the diffusion of the sealing member base metal layer 116a into the bonding metal layer 116c is more effectively prevented.

[0052] The Ti metal layer (sealing member base metal layer 116a and diaphragm base metal layer 116b) has a thickness of 50 to 200 nm, and more preferably 100 to 180 nm. With this configuration, the Au metal layer can be reliably formed on the quartz substrate via the Ti metal layer.

[0053] Furthermore, the Ti metal layer (sealing member underlayer metal layer 116a, 30a) is 5 to 40 times thicker than the W metal layer (diffusion prevention layer 116d, 30b), and more preferably 10 to 30 times thicker. This configuration allows for a thickness relationship that is optimal for balancing the etching rate with the TiW etchant Eg2. Because the etching rate with the TiW etchant Eg2 differs between the Ti metal layer and the W metal layer, if the W metal layer is too thick relative to the Ti metal layer, side etching will result in loss of a portion of the W metal layer, forming a gap between the Au metal layer and the Ti metal layer due to the loss of the W metal layer. The Au metal layer 30c on the sealing member side where the gap is formed will have a weak bond with the Au metal layer 10b on the diaphragm side, which will result in a deterioration of the sealing performance of the quartz crystal unit 100. The above-described configuration of the present invention allows for a thickness relationship that is appropriate for balancing the amount of etching of the Ti metal layer and the W metal layer by the TiW etchant Eg2, and prevents deterioration of the sealing performance of the quartz crystal unit 100 due to side etching of the W metal layer. In other words, the sealing performance of the quartz crystal unit 100 can be improved.

[0054] Furthermore, in the method for manufacturing the quartz crystal unit 100, the sealing member side bonding layer formation process for forming a sealing member side bonding layer on the first main surface 301 of the second sealing member 30 includes a base metal layer formation process for forming a Ti metal layer 30a as a sealing member base metal layer, a diffusion prevention layer formation process for forming a W metal layer 30b as a diffusion prevention layer superimposed on the sealing member base metal layer, a bonding metal layer formation process for forming an Au metal layer 30c as a bonding metal layer superimposed on the diffusion prevention layer, a mask resist formation process for forming a mask resist 30d on a portion of the Au metal layer 30c, a first etching process for removing the Au metal layer 30c on which the mask resist is not formed using an Au etching solution Eg1, a resist removal process for removing the mask resist, and a second etching process for removing the W metal layer 30b and the Ti metal layer 30a using the Au metal layer 30c as a resist using a TiW etching solution Eg2. With this configuration, while it would normally be necessary to perform etching steps for patterning the sealing member base metal layer (Ti metal layer 30a), the diffusion prevention layer (W metal layer 30b), and the bonding metal layer (Au metal layer 30c), respectively, it is possible to simultaneously perform the etching steps for patterning the diffusion prevention layer and the bonding metal layer. In other words, what would normally require three etching steps can be reduced to two etching steps, thereby improving the productivity of the quartz crystal unit 100.

[0055] The present invention is not limited to the configurations of the above-described embodiments, and many other embodiments can be obtained. For example, in the present embodiment, the vibrating portion 11 is generally rectangular and has a first excitation electrode 111 on the first main surface 101 and a second excitation electrode 112 on the second main surface 102. However, the vibrating portion 11 may also be shaped like a tuning fork, with the first excitation electrode 111 and the second excitation electrode 112 on each main surface of a pair of protruding vibrating arms (corresponding to the vibrating portion in each embodiment). In such a case, the base material of the quartz crystal vibrating plate 10 including the vibrating portion 11 is preferably made of XY-cut quartz crystal. The base materials of the substrates of the first sealing member 20 and the second sealing member 30 are also preferably made of XY-cut quartz crystal.

[0056] In addition, in this embodiment, both first bonding layer 115 and second bonding layer 116 have a diffusion prevention layer, but the diffusion prevention layer may be formed on at least one of first bonding layer 115 and second bonding layer 116. For example, only first bonding layer 115 may have a diffusion prevention layer, or only second bonding layer 116 may have a diffusion prevention layer.

[0057] In this embodiment, the substrates of the first sealing member 20 and the second sealing member 30 are formed from quartz crystal. However, for example, the substrate of at least one of the first sealing member 20 and the second sealing member 30 may be formed from a material selected from glass and silicon. Furthermore, in this embodiment, the base material of the quartz crystal vibration plate 10 is formed from AT-cut quartz crystal. However, it may be formed from quartz crystal obtained in a different cutting direction. In such a case, it is preferable that the substrates of the first sealing member 20 and the second sealing member 30 bonded to the quartz crystal vibration plate 10 are formed from quartz crystal obtained in the same cutting direction as the quartz crystal vibration plate 10.

[0058] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present invention should not be interpreted solely by the above-described embodiments, but should be defined by the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included. [Industrial Applicability]

[0059] The piezoelectric vibration device of the present invention can be used in the industry of manufacturing and selling piezoelectric vibration devices having a sandwich structure. [Explanation of symbols]

[0060] 10...Crystal diaphragm 101...First main surface 102...Second main surface 10a…Ti metal layer 10b…Au metal layer 111...First excitation electrode 112...Second excitation electrode 115...First bonding layer 116…Second bonding layer 116a... Sealing member base metal layer 116b…Diaphragm base metal layer 116c...Joining metal layer 116d... Diffusion prevention layer 20...First sealing member 30...Second sealing member 301...First main surface 302...Second main surface 30a…Ti metal layer 30b…W metal layer 30c…Au metal layer 32a, 32b, 32c, 32d...external terminal 100...Crystal resonator

Claims

1. a piezoelectric diaphragm having a first excitation electrode formed on a main surface of a substrate and a second excitation electrode paired with the first excitation electrode; a first sealing member and a second sealing member covering both main surfaces of the piezoelectric diaphragm; a first bonding layer that bonds the first sealing member and the piezoelectric diaphragm; a second bonding layer that bonds the second sealing member and the piezoelectric diaphragm, a piezoelectric vibration device in which an internal space is provided in which a vibration portion of the piezoelectric vibration plate including the first excitation electrode and the second excitation electrode is hermetically sealed by the first bonding layer and the second bonding layer, At least one of the first bonding layer and the second bonding layer is a sealing member base metal layer provided on a main surface of the first sealing member or the second sealing member; a vibration plate base metal layer provided on a main surface of the piezoelectric vibration plate; a bonding metal layer provided on the diaphragm base metal layer; a diffusion prevention layer provided between the bonding metal layer and the sealing member base metal layer. Piezoelectric vibration device.

2. the first excitation electrode and the second excitation electrode are each composed of an excitation electrode base layer and an electrode layer, the excitation electrode base layer is formed of the same material as the diaphragm base metal layer, The electrode layer is formed of the same material as the bonding metal layer. The piezoelectric vibration device according to claim 1 .

3. the sealing member base metal layer and the diaphragm base metal layer are made of Ti metal layers, the bonding metal layer is composed of an Au metal layer, the diffusion prevention layer is made of a W metal layer, The diffusion prevention layer has a thickness of 5 to 10 nm. The piezoelectric vibration device according to claim 2 .

4. a sealing member side bonding layer forming step of forming a sealing member side bonding layer on one main surface of at least one of the first sealing member and the second sealing member; a piezoelectric vibration plate side bonding layer forming step of forming a piezoelectric vibration plate side bonding layer on one main surface of the piezoelectric vibration plate; a bonding step of diffusion bonding the sealing member side bonding layer and the piezoelectric vibration plate side bonding layer, The sealing member side bonding layer forming step includes: a base metal layer forming step of forming a Ti metal layer as a sealing member base metal layer on one main surface of at least one of the first sealing member and the second sealing member; a diffusion prevention layer forming step of forming a W metal layer as a diffusion prevention layer on the sealing member base metal layer; a bonding metal layer forming step of forming an Au metal layer as a bonding metal layer by overlapping the diffusion prevention layer; a first etching step of forming a mask resist on a portion of the Au metal layer and removing the Au metal layer on which the mask resist is not formed by etching; and a second etching step of removing the mask resist and etching away the W metal layer and the Ti metal layer using the Au metal layer as a resist. A method for manufacturing a piezoelectric vibrating device.

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