Piezoelectric vibration device and frequency adjustment method for piezoelectric vibration device

Abstract

Provided is a method for adjusting the frequency of a quartz oscillator (100), wherein: a metal film (36) for frequency adjustment that comprises a base metal layer (36a) and a metal layer (36b) layered thereon is formed on a first principal surface (301) of a second sealing member (30) facing a second excitation electrode (112); and the second sealing member (30) is formed from quartz. Frequency adjustment is performed by: irradiating the metal film (36) for frequency adjustment with a laser from outside the second sealing member (30); and allowing the laser to pass through the interior of the second sealing member (30) to heat the base metal layer (36a) so that at least part of the metal layer (36b) is caused to vaporize, by melting, and adhere to the second excitation electrode (112). At such time, the melting temperature of the base metal layer (36a) is higher than the melting temperature of the metal layer (36b), and the difference between the melting temperatures of the base metal layer (36a) and the metal layer (36b) is at least 1500K.

Description

[Technical Field]

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

[0002] Conventionally, the manufacturing process of a piezoelectric vibration device such as a quartz crystal unit includes a frequency adjustment process, in which the frequency of the quartz crystal unit is adjusted to fall within a predetermined target frequency range (see, for example, Patent Document 1).

[0003] When performing the frequency adjustment process after sealing the vibration part of the quartz crystal plate with a sealing material, a beam such as a laser is irradiated from outside the quartz crystal unit. In this case, if the beam output is too high, the excitation electrode of the vibration part may be damaged. In addition, debris or gas may be generated in the internal space of the quartz crystal unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5762811 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a piezoelectric vibration device and a frequency adjustment method thereof that allow easy frequency adjustment without degrading the characteristics of the piezoelectric vibration device even after the vibration part of the piezoelectric vibration plate has been sealed with a sealing member. [Means for solving the problem]

[0006] In order to solve the above problems, the first aspect of the piezoelectric vibration device of the present invention is a piezoelectric vibration device in which a vibration part on which an excitation electrode is formed is hermetically sealed by a sealing member, and a frequency-adjusting metal film consisting of a base metal layer and a metal layer laminated on the base metal layer is formed on the main surface of the sealing member facing the excitation electrode, and the melting temperature of the base metal layer is higher than the melting temperature of the metal layer, and the difference in melting temperature between the base metal layer and the metal layer is 1500 K or more.

[0007] In addition, in order to solve the above-mentioned problems, the piezoelectric vibration device of a second aspect of the present invention is a piezoelectric vibration device in which a vibration part on which an excitation electrode is formed is hermetically sealed by a sealing member, and a frequency-adjusting metal film consisting of a base metal layer and a metal layer laminated on the base metal layer is formed on a main surface of the sealing member facing the excitation electrode, and the material of the metal layer is selected from the group consisting of Au (gold), Ag (silver) and Al (aluminum), and the material of the base metal layer is selected from the group consisting of W (tungsten), Mo (molybdenum), Ta (tantalum) and Re (rhenium).

[0008] In addition, in order to solve the above-mentioned problems, a third aspect of the present invention is a method for adjusting the frequency of a piezoelectric vibration device, in which a vibration part on which an excitation electrode is formed is hermetically sealed by a sealing member, wherein the piezoelectric vibration device is the piezoelectric vibration device described above, and the frequency adjustment is performed by irradiating a beam onto the frequency adjustment metal film from outside the sealing member, transmitting the beam through the inside of the sealing member to heat the underlying metal layer, thereby melting and evaporating at least a portion of the metal layer, and attaching it to the excitation electrode.

[0009] According to the above configuration, the metal layer above the base metal layer is melted and evaporated, and the evaporated metal adheres to the excitation electrode, increasing the mass of the excitation electrode and shifting the frequency to a lower side. Since the melting temperature of the base metal layer is sufficiently higher than the melting temperature of the metal layer, it is possible to reliably melt and evaporate only the metal layer. This allows frequency adjustment without significantly degrading the characteristics of the piezoelectric vibration device, even after the vibration section is sealed with a sealing member. [Effects of the Invention]

[0010] The piezoelectric vibrating device and the frequency adjustment method for the piezoelectric vibrating device of the present invention melt and evaporate the metal layer above the base metal layer, and attach the evaporated metal to the excitation electrode, thereby enabling frequency adjustment of the piezoelectric vibrating device even after sealing the vibrating part. In this case, by setting the melting temperature of the base metal layer sufficiently higher than the melting temperature of the metal layer, it is possible to reliably melt and evaporate only the metal layer. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic diagram illustrating each component of a quartz crystal resonator. [Figure 2] 3 is a schematic plan view of a first main surface side of a first sealing member of a quartz crystal resonator. FIG. [Figure 3] 3 is a schematic plan view of the second main surface side of the first sealing member of the quartz crystal resonator. FIG. [Figure 4] FIG. 2 is a schematic plan view of the first main surface side of the quartz crystal plate. [Figure 5] FIG. 2 is a schematic plan view of the second main surface side of the quartz crystal plate. [Figure 6] 3 is a schematic plan view of the first main surface side of the second sealing member of the quartz crystal resonator. FIG. [Figure 7] 4 is a schematic plan view of the second main surface side of the second sealing member of the quartz crystal resonator. FIG. [Figure 8] 1A to 1C are schematic cross-sectional views illustrating a method for adjusting the frequency of a crystal resonator according to a first embodiment. [Figure 9]FIG. 2 is a schematic cross-sectional view showing a metal film for adjusting a frequency of the crystal resonator according to the first embodiment. [Figure 10] 8 and shows a frequency-adjusting metal film of a quartz crystal resonator according to a modified example of the first embodiment. [Figure 11] 3 is a schematic plan view showing a method of irradiating a frequency-adjusting metal film with a laser according to the first embodiment. FIG. [Figure 12] 7 is a view corresponding to FIG. 6 showing a first main surface of a second sealing member of a quartz crystal resonator according to a modified example of the first embodiment. [Figure 13] 8A and 8B are views illustrating a method for adjusting the frequency of a quartz crystal resonator according to a modified example of the first embodiment. [Figure 14] FIG. 10 is a schematic plan view of the first principal surface side of the second sealing member of the quartz crystal resonator according to the second embodiment. [Figure 15] 10A and 10B are schematic cross-sectional views illustrating a method for adjusting the frequency of a crystal resonator according to a second embodiment. [Figure 16] 15A and 15B are views showing a frequency-adjusting metal film of a quartz crystal resonator according to a modified example of the second embodiment. [Figure 17] FIG. 10 is a schematic plan view showing a method of irradiating a frequency-adjusting metal film with a laser according to a second embodiment. [Figure 18] FIG. 10 is a schematic plan view showing a method of irradiating a frequency-adjusting metal film with a laser as a comparative example of the second embodiment. [Figure 19] FIG. 10 is a schematic plan view showing a laser irradiation range on a frequency adjusting metal film according to a second embodiment. [Figure 20] 10A to 10C are schematic cross-sectional views showing a procedure for forming a frequency-adjusting metal film in a quartz crystal resonator according to a second embodiment. [Figure 21] 10A and 10B are enlarged cross-sectional views of a frequency-adjusting metal film according to a second embodiment, in which (a) shows the state before frequency adjustment and (b) shows the state after frequency adjustment. [Figure 22] 14 and shows a first main surface of a second sealing member of a quartz crystal resonator according to a modified example of the second embodiment. [Figure 23]15A and 15B are views illustrating a method for adjusting the frequency of a quartz crystal resonator according to a modified example of the second embodiment. [Figure 24] FIG. 10 is a schematic plan view of a second principal surface side of a second sealing member of a quartz crystal resonator according to a third embodiment. [Figure 25] 10A and 10B are schematic cross-sectional views illustrating a method for adjusting the frequency of a crystal resonator according to a third embodiment. [Figure 26] 25A and 25B are views showing a frequency-adjusting metal film of a quartz crystal resonator according to a modified example of the third embodiment. [Figure 27] 10 is a schematic cross-sectional view showing a method of irradiating a frequency-adjusting metal film with a laser according to a third embodiment. FIG. [Figure 28] 10(a) and 10(b) are schematic cross-sectional views showing a method of irradiating a frequency-adjusting metal film with a laser as a comparative example of the third embodiment. [Figure 29] 10 is a schematic cross-sectional view showing a method of irradiating a frequency-adjusting metal film with a laser according to a third embodiment. FIG. [Figure 30] FIG. 10 is a schematic plan view showing a modified example of the shielding film of the quartz crystal resonator according to the third embodiment. [Figure 31] 25A and 25B are views illustrating a method for adjusting the frequency of a quartz crystal resonator according to a modified example of the third embodiment. [Figure 32] FIG. 10 is a schematic plan view of the first principal surface side of the second sealing member of the quartz crystal resonator according to the fourth embodiment. [Figure 33] 10A and 10B are schematic cross-sectional views illustrating a method for adjusting the frequency of a quartz crystal resonator according to a fourth embodiment. [Figure 34] FIG. 10 is a schematic plan view showing a method of irradiating a frequency adjusting metal film with a laser according to a fourth embodiment. [Figure 35] FIG. 10 is a schematic cross-sectional view showing a metal film for adjusting a frequency of a quartz crystal resonator according to a fourth embodiment. [Figure 36] FIG. 36 is a diagram corresponding to FIG. 35 and schematically showing a frequency-adjusting metal film of a quartz crystal resonator according to a modified example of the fourth embodiment. [Figure 37]FIG. 35 is a diagram corresponding to FIG. 35 and illustrating a method for adjusting the frequency of a quartz crystal resonator according to a modified example of the fourth embodiment. [Figure 38] FIG. 10 is a schematic plan view of a second principal surface side of a first sealing member of a quartz crystal resonator according to a fifth embodiment. [Figure 39] FIG. 10 is a schematic plan view of a first main surface side of a quartz crystal plate according to a fifth embodiment. [Figure 40] FIG. 10 is a schematic plan view of the second main surface side of a quartz crystal vibration plate according to a fifth embodiment. [Figure 41] FIG. 10 is a schematic plan view of the first principal surface side of the second sealing member of the crystal resonator according to the fifth embodiment. [Figure 42] FIG. 10 is a schematic plan view of a second principal surface side of a second sealing member of a quartz crystal resonator according to a fifth embodiment. [Figure 43] FIG. 10 is a schematic diagram showing the configuration of a quartz crystal resonator according to a sixth embodiment. [Figure 44] 13A to 13C are schematic diagrams illustrating the configuration of a quartz crystal resonator according to a modified example of the sixth embodiment. [Figure 45] 13A to 13C are schematic diagrams illustrating the configuration of a quartz crystal resonator according to a modified example of the sixth embodiment. [Figure 46] 13A to 13C are schematic diagrams illustrating the configuration of a quartz crystal resonator according to a modified example of the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First embodiment] 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.

[0013] First, the basic structure of a quartz crystal unit 100 according to this embodiment will be described. As shown in Fig. 1, the quartz crystal unit 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 unit 100, the quartz crystal vibrating plate 10 is bonded to the first sealing member 20, and the quartz crystal vibrating plate 10 is bonded to the second sealing member 30, thereby forming a package with a substantially rectangular parallelepiped sandwich structure. That is, in the quartz crystal unit 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 the vibrating unit 11 (see Figs. 4 and 5) is hermetically sealed in this internal space.

[0014] The crystal unit 100 according to this embodiment has a package size of, for example, 1.0 × 0.8 mm, and is designed to be compact and low-profile. To accommodate this compact design, the package does not have castellations, but rather uses through-holes (described below) to ensure electrical continuity between electrodes. The crystal unit 100 is also designed to be electrically connected to an external circuit board (not shown) via solder.

[0015] 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 1 to 7. Note that the description here focuses on the individual components that are not bonded together and are configured as individual components. Figures 2 to 7 merely show one example of the 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.

[0016] As shown in FIGS. 4 and 5, the quartz crystal vibrating plate 10 according to this embodiment is a piezoelectric substrate made of quartz crystal, and both of its main surfaces (first main surface 101 and second main surface 102) are polished (mirror-finished) to form flat, smooth surfaces. In this embodiment, an AT-cut quartz crystal plate that vibrates in thickness-shear mode is used as the quartz crystal vibrating plate 10. In the quartz crystal vibrating plate 10 shown in FIGS. 4 and 5, both main surfaces 101 and 102 of the quartz crystal vibrating plate 10 are in the XZ' plane. In this XZ' plane, the direction parallel to the short side (short side) of the quartz crystal vibrating plate 10 is the X-axis direction, and the direction parallel to the long side (long side) of the quartz crystal vibrating plate 10 is the Z'-axis direction. Note that AT-cut is a processing technique in which artificial quartz crystal is cut at an angle of 35°15' around the X-axis with respect to the Z-axis, one of the three crystal axes of the artificial quartz crystal: the electrical axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). In an AT-cut quartz plate, the X-axis coincides with the crystal axis of the quartz. The Y'-axis and Z'-axis coincide with axes tilted approximately 35°15' from the Y-axis and Z-axis of the quartz crystal (this cutting angle can be changed slightly to adjust the frequency-temperature characteristics of the AT-cut quartz plate). The Y'-axis and Z'-axis directions correspond to the cutting direction when the AT-cut quartz plate is cut.

[0017] A pair of excitation electrodes (first excitation electrode 111 and second excitation electrode 112) are formed on both main surfaces 101, 102 of the quartz crystal vibration plate 10. 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 (connecting portion) 13 that holds the vibrating portion 11 by connecting the vibrating portion 11 and the outer frame portion 12. In other words, 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) in the -Z' direction from only one corner of the vibrating portion 11 located in the +X direction and the -Z' direction to the outer frame portion 12. A through portion (slit) 10a that penetrates the thickness of the quartz crystal vibration plate 10 is provided between the vibrating portion 11 and the outer frame portion 12. In this embodiment, the quartz crystal vibration plate 10 is provided with only one holding portion 13 that connects the vibration portion 11 and the outer frame portion 12, and the through portion 10a is formed continuously so as to surround the outer periphery of the vibration portion 11.

[0018] The first excitation electrode 111 is provided on the first main surface 101 side of the vibrating section 11, and the second excitation electrode 112 is provided on the second main surface 102 side of the vibrating section 11. Input / output lead-out wiring (first lead-out wiring 113, second lead-out wiring 114) is connected to the first excitation electrode 111 and the second excitation electrode 112 to connect these excitation electrodes to external electrode terminals. The first lead-out wiring 113 on the input side is led out from the first excitation electrode 111 and connected to a connection bonding pattern 14 formed on the outer frame section 12 via a holding section 13. The second lead-out wiring 114 on the output side is led out from the second excitation electrode 112 and connected to a connection bonding pattern 15 formed on the outer frame section 12 via a holding section 13.

[0019] Both main surfaces (first main surface 101, second main surface 102) of the quartz crystal vibrating plate 10 are provided with diaphragm-side sealing portions for bonding the quartz crystal vibrating plate 10 to the first sealing member 20 and the second sealing member 30. A diaphragm-side first bonding pattern 121 is formed as the diaphragm-side sealing portion on the first main surface 101, and a diaphragm-side second bonding pattern 122 is formed as the diaphragm-side sealing portion on the second main surface 102. The diaphragm-side first bonding pattern 121 and the diaphragm-side second bonding pattern 122 are provided on the outer frame portion 12 and are formed in an annular shape in a plan view.

[0020] As shown in FIGS. 4 and 5, five through holes are formed in the quartz-crystal vibrating plate 10, penetrating between the first main surface 101 and the second main surface 102. Specifically, the four first through holes 161 are provided in the four corner regions of the outer frame portion 12. The second through hole 162 is provided in the outer frame portion 12 on one side of the vibrating portion 11 in the Z′-axis direction (the −Z′ direction side in FIGS. 4 and 5). A connection bonding pattern 123 is formed around each of the first through holes 161. A connection bonding pattern 124 is formed on the first main surface 101 side of the second through hole 162, and a connection bonding pattern 15 is formed on the second main surface 102 side of the second through hole 162.

[0021] The first through-holes 161 and the second through-holes 162 have through-hole electrodes formed along their inner walls to connect the electrodes formed on the first main surface 101 and the second main surface 102. The central portions of the first through-holes 161 and the second through-holes 162 form hollow through-holes that penetrate between the first main surface 101 and the second main surface 102. The outer peripheral edge of the diaphragm-side first bonding pattern 121 is located close 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 diaphragm-side second bonding pattern 122 is located close to the outer peripheral edge of the second main surface 102 of the quartz-crystal vibrating plate 10 (outer frame 12). In this embodiment, an example has been given in which five through holes are formed between the first main surface 101 and the second main surface 102, but instead of forming through holes, it is also possible to cut out a portion of the side surface of the first sealing member 20 and form a castellation with an electrode coated on the inner wall surface of the cut-out area (the same applies to the second sealing member 30).

[0022] 2 and 3, the first sealing member 20 is a rectangular parallelepiped substrate formed from a single AT-cut quartz crystal plate, which is a translucent material. The second main surface 202 of this first sealing member 20 (the surface that bonds to the quartz crystal vibrating plate 10) is polished (mirror-finished) to a flat, smooth surface. Although the first sealing member 20 does not have a vibrating part, by using an AT-cut quartz crystal plate like the quartz crystal vibrating plate 10, the thermal expansion coefficients of the quartz crystal vibrating plate 10 and the first sealing member 20 can be made the same, thereby suppressing thermal deformation of the quartz crystal unit 100. The X-, Y-, and Z'-axes of the first sealing member 20 are also oriented in the same directions as those of the quartz crystal vibrating plate 10.

[0023] As shown in FIG. 2, first and second wiring terminals 22 and 23 and a metal film 28 for shielding (ground connection) are formed on the first main surface 201 of the first sealing member 20 (the outer main surface not facing the quartz-crystal vibrating plate 10). The first and second wiring terminals 22 and 23 are provided as wiring for electrically connecting the first and second excitation electrodes 111 and 112 of the quartz-crystal vibrating plate 10 to the external electrode terminal 32 of the second sealing member 30. The first and second terminals 22 and 23 are provided at both ends in the Z′-axis direction, with the first terminal 22 on the +Z′-direction side and the second terminal 23 on the −Z′-direction side. The first and second terminals 22 and 23 are formed to extend in the X-axis direction. The first terminal 22 and the second terminal 23 are formed in a substantially rectangular shape.

[0024] The metal film 28 is provided between the first and second terminals 22, 23 and is arranged at a predetermined distance from the first and second terminals 22, 23. The metal film 28 is provided in almost all of the regions of the first main surface 201 of the first sealing member 20 where the first and second terminals 22, 23 are not formed. The metal film 28 is provided from the end of the first main surface 201 of the first sealing member 20 in the +X direction to the end in the −X direction.

[0025] 2 and 3, six through holes are formed in the first sealing member 20, penetrating between the first main surface 201 and the second main surface 202. Specifically, four third through holes 211 are provided in the four corner (corner) regions of the first sealing member 20. Fourth and fifth through holes 212, 213 are provided in the +Z' direction and -Z' direction in FIGS. 2 and 3, respectively.

[0026] In the third through hole 211 and the fourth and fifth through holes 212, 213, through electrodes for establishing electrical continuity between the electrodes formed on the first main surface 201 and the second main surface 202 are formed along the inner wall surfaces of the respective through holes. The central portions of the third through hole 211 and the fourth and fifth through holes 212, 213 form hollow through portions that penetrate between the first main surface 201 and the second main surface 202. The through electrodes of two third through holes 211, 211 located diagonally on the first main surface 201 of the first sealing member 20 (the third through hole 211 located at the corner in the +X direction and the +Z′ direction in FIGS. 2 and 3 , and the third through hole 211 located at the corner in the −X direction and the −Z′ direction) are electrically connected to each other by the metal film 28. Furthermore, the through electrode of the third through hole 211 located at the corner in the −X direction and the +Z′ direction and the through electrode of the fourth through hole 212 are electrically connected by the first terminal 22. The through electrode of the third through hole 211 located at the corner in the +X direction and the −Z′ direction and the through electrode of the fifth through hole 213 are electrically connected by the second terminal 23.

[0027] A sealing member-side first bonding pattern 24 is formed on the second main surface 202 of the first sealing member 20 as a sealing member-side first sealing portion for bonding to the quartz-crystal vibrating plate 10. The sealing member-side first bonding pattern 24 is formed in an annular shape in a plan view. Furthermore, on the second main surface 202 of the first sealing member 20, connection bonding patterns 25 are formed around the third through holes 211. A connection bonding pattern 261 is formed around the fourth through hole 212, and a connection bonding pattern 262 is formed around the fifth through hole 213. Furthermore, a connection bonding pattern 263 is formed on the opposite side of the connection bonding pattern 261 in the longitudinal direction of the first sealing member 20 (the -Z' direction side), and the connection bonding pattern 261 and the connection bonding pattern 263 are connected by a wiring pattern 27. The outer periphery of the sealing member-side first bonding pattern 24 is provided close to the outer periphery of the second main surface 202 of the first sealing member 20.

[0028] 6 and 7, the second sealing member 30 is a rectangular parallelepiped substrate formed from a single AT-cut quartz crystal plate, which is a light-transmitting material, and the first main surface 301 (the surface that bonds to the quartz crystal plate 10) and the second main surface 302 (the outer main surface that does not face the quartz crystal plate 10) of this second sealing member 30 are polished to a flat, smooth surface. Note that the second sealing member 30 also uses an AT-cut quartz crystal plate like the quartz crystal plate 10, and it is desirable that the orientations of the X-axis, Y-axis, and Z'-axis are the same as those of the quartz crystal plate 10.

[0029] A sealing member-side second bonding pattern 31 is formed on the first main surface 301 of the second sealing member 30 as a sealing member-side second sealing portion for bonding to the quartz-crystal vibrating plate 10. The sealing member-side second bonding pattern 31 is formed in an annular shape in a plan view. The outer periphery of the sealing member-side second bonding pattern 31 is provided close to the outer periphery of the first main surface 301 of the second sealing member 30.

[0030] Furthermore, a frequency-adjusting metal film 36 used to adjust the frequency of the quartz crystal resonator 100 is formed on the first main surface 301 of the second sealing member 30. The frequency-adjusting metal film 36 has a two-layer structure made of two types of metal with different melting temperatures (melting points). As shown in FIG. 8 , the frequency-adjusting metal film 36 includes a base metal layer 36a and a metal layer 36b laminated on the base metal layer 36a. The base metal layer 36a is preferably 50 nm thick, and the metal layer 36b is preferably 100 nm thick. The base metal layer 36a is preferably 50 to 500 nm thick, and the metal layer 36b is preferably 100 to 500 nm thick. A thickness of less than 50 nm for the base metal layer 36a is not preferable because it cannot withstand laser irradiation. A thickness of more than 500 nm for the base metal layer 36a is not preferable because it causes wafer warping and reduces production efficiency due to the thick film. Furthermore, if the thickness of the metal layer 36b is less than 100 nm, it is not preferable because it cannot withstand laser irradiation, and if the thickness of the metal layer 36b is more than 500 nm, it is not preferable because the wafer warps and the thick film reduces production efficiency.

[0031] For reasons that will be described later, it is preferable that the melting temperature of the base metal layer 36a in the frequency-adjusting metal film 36 is higher than that of the metal layer 36b, and that the difference in melting temperature between the base metal layer 36a and the metal layer 36b is 1500 K or more. Furthermore, the metal layer 36b is made of the same material (e.g., Au) as the second excitation electrode 112. In this case, since the melting temperature of Au is 1064 K, the base metal layer 36a can be made of, for example, any of W (tungsten: melting temperature 3387 K), Mo (molybdenum: melting temperature 2623 K), Ta (tantalum: melting temperature 3020 K), and Re (rhenium: melting temperature 3186 K).

[0032] The frequency adjustment metal film 36 is provided at a position facing the second excitation electrode 112 at a predetermined interval. The distance L1 in the vertical direction (Y-axis direction) between the second excitation electrode 112 and the frequency adjustment metal film 36 is 2 to 200 μm.

[0033] The frequency adjustment metal film 36 is formed in a substantially rectangular shape in a plan view. The frequency adjustment metal film 36 is formed slightly smaller than the second excitation electrode 112, and the outer periphery of the frequency adjustment metal film 36 is located inside the outer periphery of the second excitation electrode 112 in a plan view. Furthermore, at least a part of the base metal layer 36a is not covered by the metal layer 36b and is exposed, and a step portion 36c (FIG. 9) is formed inside the frequency adjustment metal film 36. With this configuration, even if the exposed part of the base metal layer 36a of the frequency adjustment metal film 36 comes into contact with the second excitation electrode 112 when the vibrating unit 11 is bent due to an external impact, adhesion (sticking) between the base metal layer 36a and the second excitation electrode 112 can be prevented.

[0034] The first and second main surfaces 301, 302 of the second sealing member 30 are polished to form smooth surfaces, and the arithmetic mean roughness Ra of the first and second main surfaces 301, 302 is 1 nm or less. In addition, the arithmetic mean roughness Ra of the surface of the metal layer 36b of the frequency-adjusting metal film 36 is 3 nm or less.

[0035] Four external electrode terminals 32 are provided on the second main surface 302 of the second sealing member 30. The external electrode terminals 32 are electrically connected to an external circuit board provided outside the quartz crystal unit 100. The external electrode terminals 32 are located at the four corners (corner portions) of the second main surface 302 of the second sealing member 30.

[0036] As shown in FIGS. 6 and 7 , the second sealing member 30 has four through holes formed therein that penetrate between the first main surface 301 and the second main surface 302. Specifically, the four sixth through holes 33 are provided in the four corner regions (corner portions) of the second sealing member 30. In the sixth through holes 33, through electrodes are formed along the inner wall surfaces of the sixth through holes 33 to ensure electrical continuity between the electrodes formed on the first main surface 301 and the second main surface 302. The through electrodes formed on the inner wall surfaces of the sixth through holes 33 in this manner provide electrical continuity between the electrodes formed on the first main surface 301 and the external electrode terminals 32 formed on the second main surface 302. The central portions of the sixth through holes 33 form hollow through portions that penetrate between the first main surface 301 and the second main surface 302. Furthermore, on the first main surface 301 of the second sealing member 30, connection bonding patterns 34 are formed around the sixth through holes 33, respectively.

[0037] In the quartz crystal unit 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 diffusion bonded together with the first vibration plate bonding pattern 121 and the first sealing member bonding pattern 24 overlapping each other, and the quartz crystal vibrating plate 10 and the second sealing member 30 are diffusion bonded together with the second vibration plate bonding pattern 122 and the second sealing member bonding pattern 31 overlapping each other, thereby producing a sandwich-structured package as shown in Fig. 1. This hermetically seals the internal space of the package, i.e., the space housing the vibrating unit 11.

[0038] At this time, the connection bonding patterns are also diffusion bonded while overlapping each other. By bonding the connection bonding patterns together, electrical continuity is achieved among the first excitation electrode 111, the second excitation electrode 112, and the external electrode terminal 32 in the quartz crystal unit 100. Specifically, the first excitation electrode 111 is connected to the external electrode terminal 32 via the first extension wiring 113, the wiring pattern 27, the fourth through-hole 212, the first terminal 22, the third through-hole 211, the first through-hole 161, and the sixth through-hole 33, in that order. The second excitation electrode 112 is connected to the external electrode terminal 32 via the second extension wiring 114, the second through-hole 162, the fifth through-hole 213, the second terminal 23, the third through-hole 211, the first through-hole 161, and the sixth through-hole 33, in that order. Furthermore, the metal film 28 is connected to earth (ground connection, using part of the external electrode terminal 32) via the third through-hole 211, the first through-hole 161, and the sixth through-hole 33 in this order.

[0039] In the quartz crystal unit 100, the various bonding patterns are preferably formed by stacking multiple layers on the quartz crystal plate, with a Ti (titanium) layer and an Au (gold) layer formed from the bottom layer onwards by vapor deposition or sputtering. Furthermore, if the other wiring and electrodes formed on the quartz crystal unit 100 have the same configuration as the bonding patterns, the bonding patterns, wiring and electrodes can be patterned simultaneously, which is also preferable.

[0040] In the quartz crystal resonator 100 configured as described above, the sealing portions (seal paths) 115, 116 that hermetically seal the vibrating portion 11 of the quartz crystal vibrating plate 10 are formed in an annular shape in a plan view. The seal path 115 is formed by diffusion bonding (Au-Au bonding) the above-mentioned diaphragm-side first bonding pattern 121 and the sealing member-side first bonding pattern 24, and the outer and inner edge shapes of the seal path 115 are formed in a substantially octagonal shape. Similarly, the seal path 116 is formed by diffusion bonding (Au-Au bonding) the above-mentioned diaphragm-side second bonding pattern 122 and the sealing member-side second bonding pattern 31, and the outer and inner edge shapes of the seal path 116 are formed in a substantially octagonal shape.

[0041] Next, a frequency adjustment method for the quartz crystal resonator 100 according to this embodiment will be described with reference to Fig. 8. The frequency adjustment in this embodiment is a process of adjusting the mass of the second excitation electrode 112 of the vibration portion 11 of the quartz crystal vibrating plate 10 to adjust the oscillation frequency to a desired value. The frequency adjustment is performed on each of the quartz crystal resonators 100 in a wafer state during the manufacturing process of the quartz crystal resonators 100, but it may also be performed on each of the quartz crystal resonators 100 that have been singulated from the wafer state.

[0042] 8, the frequency is adjusted by irradiating the frequency-adjusting metal film 36 with a laser from outside the second sealing member 30, transmitting the laser through the inside of the second sealing member 30 to heat the base metal layer 36a, thereby melting and evaporating (vaporizing) at least a part of the metal layer 36b, and attaching the evaporated metal to the second excitation electrode 112. In other words, the laser melts and evaporates the metal layer 36b above the base metal layer 36a, and the evaporated metal attaches to the second excitation electrode 112, thereby increasing the mass of the second excitation electrode 112 and shifting the frequency to a lower side.

[0043] The laser is irradiated perpendicularly onto the second sealing member 30. A visible light laser capable of transmitting through the second sealing member 30 made of quartz crystal is used as the laser. Specifically, a green laser with a wavelength of approximately 532 nm can be used (however, the laser wavelength is not limited to 532 nm). The laser output is adjusted to a value that does not penetrate the base metal layer 36a of the frequency adjustment metal film 36. The laser heats the base metal layer 36a, which in turn heats the metal layer 36b above the base metal layer 36a. As described above, the melting temperature of the base metal layer 36a is higher than the melting temperature of the metal layer 36b. Therefore, when the base metal layer 36a is heated to a temperature higher than the melting temperature of the metal layer 36b, the metal layer 36b melts, and a portion of the melted metal layer 36b evaporates. Since the inside of the quartz crystal unit 100 is a vacuum, the evaporated metal moves upward in a substantially straight line, and when it reaches the surface 112a of the second excitation electrode 112, it is cooled and solidified on the surface 112a of the second excitation electrode 112. As a result, the metal evaporated from the frequency-adjusting metal film 36 adheres to the surface 112a of the second excitation electrode 112.

[0044] The metal layer 36b may have a multilayer structure made up of a plurality of metal layers. In this case, Ag (silver: melting temperature 962 K) or Al (aluminum: melting temperature 660 K) can be used for the metal layer 36b in addition to Au. When the metal layer 36b has a multilayer structure, the uppermost metal layer only needs to be made of the same material (e.g., Au) as the second excitation electrode 112. The base metal layer 36a may also have a multilayer structure made up of a plurality of metal layers. In this case, it is preferable that a metal layer with a higher melting temperature (e.g., a W layer) is disposed in a lower layer (closer to the second sealing member 30) and a metal layer with a lower melting temperature (e.g., a Mo layer) is disposed in an upper layer (closer to the metal layer 36b).

[0045] An auxiliary metal layer 36d (see FIG. 10) may be formed between the metal base layer 36a and the second sealing member 30. By using a metal with high adhesion to quartz crystal, such as Ti (titanium), Cr (chromium), or Ni (nickel), for the auxiliary metal layer 36d, the adhesion between the frequency-adjusting metal film 36 and the second sealing member 30 can be improved. The auxiliary metal layer 36d is required to have a melting temperature that is sufficiently higher than that of the metal layer 36b, but unlike the metal base layer 36a, the melting temperature difference between the auxiliary metal layer 36d and the metal layer 36b is not required to be 1500 K or more. For example, if the auxiliary metal layer 36d is made of Ti and the metal layer 36b is made of Au, the melting temperature of Ti is 1672 K, and the melting temperature difference between Ti and Au is approximately 600 K. Even if the auxiliary metal layer 36d is slightly melted by the laser irradiation during frequency adjustment, the presence of the base metal layer 36a on the auxiliary metal layer 36d prevents the molten auxiliary metal layer 36d from scattering onto the second excitation electrode 112.

[0046] Furthermore, there is a risk that the auxiliary metal layer 36d melted by the heat of laser irradiation will diffuse into the upper underlying metal layer 36a, lowering the melting temperature of the underlying metal layer 36a. However, by making the film thickness of the auxiliary metal layer 36d thinner than that of the underlying metal layer 36a, it is possible to irradiate the laser without melting the underlying metal layer 36a (only the metal layer 36b can be evaporated).

[0047] As shown in Fig. 11, the laser irradiation of the base metal layer 36a can be performed in a desired region by arranging irradiation lines LN formed by sweeping the laser spot SP in parallel. At this time, it is preferable that the sweep direction (direction of arrow A) of the laser spot SP is the same for all irradiation lines LN, and that adjacent irradiation lines LN do not partially overlap with each other in the line width direction (direction perpendicular to the sweep direction). Furthermore, it is preferable that the sweep of the laser spot SP is repeated multiple times for each irradiation line LN, and that after multiple laser sweeps are performed for one irradiation line LN, laser sweeps are performed for the adjacent irradiation line LN.

[0048] By controlling the number of laser pulses irradiated onto the metal base layer 36a, the sweep distance, the number of sweeps, etc., it is possible to control the mass of metal adhering to the second excitation electrode 112, and therefore the amount of frequency adjustment. For example, by continuously irradiating the laser with a low laser output and a narrow pulse interval, it is possible to efficiently heat the metal base layer 36a and evaporate only the metal layer 36b. In this case, it is possible to obtain the amount of frequency adjustment according to the laser sweep distance, enabling highly accurate frequency adjustment.

[0049] According to the frequency adjustment method for the quartz crystal unit 100 of this embodiment, the metal layer 36b above the base metal layer 36a is melted and evaporated, and the evaporated metal adheres to the second excitation electrode 112, thereby increasing the mass of the second excitation electrode 112 and shifting the frequency to a lower value. In this case, the desired frequency adjustment amount can be obtained by controlling the number of laser pulses, sweep distance, etc. Furthermore, by preventing the laser from penetrating the frequency adjustment metal film 36, damage to the second excitation electrode 112 can be suppressed. As a result, frequency adjustment can be performed without significantly degrading the characteristics of the quartz crystal unit 100, even after the vibration portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30.

[0050] In this embodiment, the laser is irradiated so as not to penetrate the base metal layer 36a, and the laser does not penetrate the frequency adjustment metal film 36, which more reliably avoids damaging the second excitation electrode 112. This makes it possible to easily adjust the frequency without degrading the characteristics of the quartz crystal unit 100, even after the vibrating portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30.

[0051] In this embodiment, the difference between the melting temperature of the metal base layer 36a and the melting temperature of the metal layer 36b is 1500 K or more. By irradiating the metal base layer 36a with a laser to a temperature equal to or higher than the melting temperature of the metal layer 36b but lower than the melting temperature of the metal base layer 36a, the metal base layer 36a does not melt, but only the metal layer 36b melts, and some of the molten metal can be evaporated. The evaporated metal adheres to the second excitation electrode 112, increasing the mass of the second excitation electrode 112 and shifting the frequency to a lower level. This allows for easy frequency adjustment without degrading the characteristics of the crystal unit 100, even after the vibration portion 11 of the crystal vibration plate 10 is sealed with the first and second sealing members 20 and 30. Even if the melting temperature of the underlying metal layer 36a is higher than that of the metal layer 36b, if the difference in melting temperatures is small, it is difficult to melt only the metal layer 36b, and melting of the underlying metal layer 36a may occur at the same time.

[0052] In this embodiment, the first main surface 301 of the second sealing member 30 and the second main surface 302 opposite to the first main surface 301 are smooth surfaces, which can suppress reflection and refraction of the laser when the laser is incident on the second main surface 302 of the second sealing member 30 and when the laser is emitted from the first main surface 301 of the second sealing member 30, thereby reducing laser energy loss. As a result, even after the vibrating portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30, high-precision frequency adjustment can be performed according to the number of laser pulses, sweep distance, number of sweeps, etc.

[0053] Furthermore, the metal layer 36b is formed from the same Au (gold) as the second excitation electrode 112, and since the metal layer 36b is made of the same material as the second excitation electrode 112, the characteristics do not change before and after frequency adjustment, and therefore fluctuations in the characteristics of the quartz crystal resonator 100 after sealing can be suppressed.

[0054] Furthermore, the base metal layer 36a is formed of W (tungsten) or the like, and the base metal layer 36a exposed to the internal space of the quartz crystal unit 100 functions as a getter material, thereby enabling the base metal layer 36a to capture gas generated in the internal space of the quartz crystal unit 100. Alternatively, a metal layer (e.g., a W layer) 37 (see FIG. 12) identical to the base metal layer 36a may be formed as a separate layer in a region separate from the base metal layer 36a, and this metal layer 37 may function as a getter material. In this case, the metal layer 37 is preferably formed in a region not facing the second excitation electrode 112.

[0055] Furthermore, by using a visible light laser that has low absorption and high transmittance for the second sealing member 30 made of, for example, quartz or glass, as the laser, it is possible to reduce power loss and damage to the second sealing member 30, making it suitable for frequency adjustment.

[0056] Furthermore, the space sealing the vibration part 11 of the quartz crystal vibration plate 10 is a vacuum, allowing the evaporated metal to move in a substantially linear manner, thereby preventing it from scattering to the surroundings. Furthermore, the evaporated metal can be attached to the second excitation electrode 112 without lowering its temperature.

[0057] In this embodiment, the vertical distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36 is 2 to 200 μm. By minimizing the distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36, the metal evaporated from the frequency adjustment metal film 36 moves in a substantially linear manner, preventing it from scattering to the surroundings. This ensures that the evaporated metal adheres to the second excitation electrode 112, and makes it easy to perform high-precision frequency adjustment even after the vibration portion 11 of the quartz crystal vibration plate 10 is sealed with the first and second sealing members 20 and 30.

[0058] Furthermore, since the outer peripheral edge of the frequency-adjusting metal film 36 is located inside the outer peripheral edge of the second excitation electrode 112 in plan view, even if an exposed portion of the base metal layer 36a of the frequency-adjusting metal film 36 comes into contact with the second excitation electrode 112 when the vibrating portion 11 is bent due to an external impact, adhesion between the base metal layer 36a and the second excitation electrode 112 can be prevented. Furthermore, metal evaporated from the frequency-adjusting metal film 36 can be prevented from scattering outside the second excitation electrode 112, and the evaporated metal can be reliably adhered to the second excitation electrode 112. This makes it easy to perform high-precision frequency adjustment even after the vibrating portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30.

[0059] In this embodiment, the quartz crystal unit 100 includes a first sealing member 20 that covers the first main surface of the vibrating portion 11 of the quartz crystal vibrating plate 10, and a second sealing member 30 that covers the second main surface of the vibrating portion 11 of the quartz crystal vibrating plate 10. The first sealing member 20 and the quartz crystal vibrating plate 10 are bonded together, and the second sealing member 30 is bonded together, thereby hermetically sealing the vibrating portion 11 of the quartz crystal vibrating plate 10. The first sealing member 20 and the second sealing member 30 are made of quartz crystal. Using a three-layer structure like this makes it possible to reduce the size and thickness of the quartz crystal unit 100. Even after sealing the vibrating portion 11 of the quartz crystal vibrating plate 10 with the first and second sealing members 20 and 30, the size and thickness of the reduced-size and reduced-thickness quartz crystal unit 100 can be adjusted with high precision.

[0060] Furthermore, in the quartz crystal resonator 100 of the present embodiment described above, the frequency-adjusting metal film 36 is formed on the first main surface 301 of the second sealing member 30, which faces the second excitation electrode 112, and at least a portion of the base metal layer 36a of the frequency-adjusting metal film 36 is exposed and not covered by the metal layer 36b. This allows the exposed base metal layer 36a to function as a getter material, so that gas generated in the internal space of the quartz crystal resonator 100 can be captured by the base metal layer 36a. This makes it possible to suppress changes in the frequency of the quartz crystal resonator 100 over time that are caused by gas generation.

[0061] Furthermore, since the quartz crystal vibration plate 10 is configured to include a vibration portion 11 and an outer frame portion 12 that surrounds the vibration portion 11, the distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36 can be made very small compared to a configuration in which a sealing member is bonded to a base using adhesive, and as described above, high-precision frequency adjustment can be performed.

[0062] In the above embodiment, the frequency adjustment metal film 36 is provided on the first main surface 301 of the second sealing member 30 facing the second excitation electrode 112. However, the second sealing member 30 may not be provided with a frequency adjustment metal film, and the frequency adjustment metal film may be provided on the second main surface 202 of the first sealing member 20 facing the first excitation electrode 111. Alternatively, as shown in FIG. 13 , the frequency adjustment metal film 26 may be provided on the second main surface 202 of the first sealing member 20, and the frequency adjustment metal film 36 may be provided on the first main surface 301 of the second sealing member 30. The frequency adjustment metal film 26 of the first sealing member 20 has a configuration similar to that of the frequency adjustment metal film 36 of the second sealing member 30 in the above embodiment. The frequency adjustment metal film 26 has a laminated configuration in which a base metal layer 26a made of, for example, W (tungsten) and a metal layer 26b made of the same material as the first excitation electrode 111 (for example, Au) are laminated.

[0063] 13, frequency adjustment can be performed using both the frequency-adjusting metal films 26, 36. By irradiating the frequency-adjusting metal film 26 on the first sealing member 20 side of the quartz crystal resonator 100 with a laser, frequency adjustment can be performed at two locations, on the first sealing member 20 side and the second sealing member 30 side. In this case, frequency adjustment can be performed simultaneously at two locations, on the first sealing member 20 side and the second sealing member 30 side, or can be performed at each location in turn.

[0064] In the above embodiment, the frequency adjustment is performed using a visible light laser, but the frequency adjustment may also be performed using a beam such as an electron beam, etc. In this case, the desired frequency adjustment amount can be obtained by controlling the beam output, irradiation time, etc.

[0065] In the above embodiment, the step portion 36c (FIG. 9) is provided on the central side of the frequency-adjusting metal film 36 to expose the underlying metal layer 36a, but the step portion 36c may be provided on at least a part of the frequency-adjusting metal film 36. Furthermore, the underlying metal layer 36a may be exposed at a location other than the outer periphery as long as it is a location that is not irradiated with a laser.

[0066] In the above embodiment, the internal space of the quartz crystal unit 100 is evacuated, but the internal space of the quartz crystal unit 100 may be filled with low-pressure nitrogen, argon, or the like.

[0067] In the above embodiment, the quartz crystal vibrating plate 10 is an AT-cut quartz crystal plate, but other materials may be used. Also, while the vibrating portion 11 of the quartz crystal vibrating plate 10 is rectangular, the vibrating portion may be shaped like a tuning fork.

[0068] In the above embodiment, the first sealing member 20 and the second sealing member 30 are formed from quartz plates, but the first sealing member 20 and the second sealing member 30 may be formed from, for example, glass. In this case, an infrared laser that can transmit through the first sealing member 20 and the second sealing member 30 may be used. As the infrared laser, for example, a YAG laser with a wavelength of approximately 1064 nm may be used. Note that only a portion of the first sealing member 20 and the second sealing member 30 may be formed from a light-transmitting material such as quartz or glass.

[0069] In the above embodiment, the quartz crystal vibration plate 10 is provided with only one holding portion 13 connecting the vibrating portion 11 and the outer frame portion 12, but two or more holding portions 13 may be provided. Also, a through portion 10a that penetrates the quartz crystal vibration plate 10 in the thickness direction is provided between the vibrating portion 11 and the outer frame portion 12, but a quartz crystal vibration plate configured without a through portion may also be used. Also, in the above embodiment, a framed quartz crystal vibration plate 10 is used that includes the vibrating portion 11 and the outer frame portion 12 that surrounds the vibrating portion 11, but a quartz crystal vibration plate configured without an outer frame portion may also be used.

[0070] Second Embodiment The basic structure of the quartz crystal resonator 100 according to this embodiment is almost the same as that of the first embodiment, except for the shape of the frequency-adjusting metal film 36 formed on the first main surface 301 of the second sealing member 30. Below, a description of the same configuration as the first embodiment will be omitted, and only the characteristic parts of this embodiment will be described.

[0071] FIG. 14 is a schematic plan view of the first main surface 301 side of the second sealing member 30 of the quartz crystal unit 100 according to this embodiment. FIG. 15 is a schematic cross-sectional view showing a method for adjusting the frequency of the quartz crystal unit 100 according to this embodiment. As shown in FIGS. 14 and 15, in this embodiment as well, the frequency-adjusting metal film 36 has a two-layer structure made of two types of metal with different melting temperatures (melting points), and includes a base metal layer 36a and a metal layer 36b laminated on this base metal layer 36a. However, the metal layer 36b is not formed so as to cover the entire base metal layer 36a, and at least a portion of the base metal layer 36a is exposed and not covered by the metal layer 36b, forming an exposed portion 361.

[0072] In the example of FIG. 15, the metal layer 36b on the base metal layer 36a is formed in a striped pattern, with an exposed portion 361 between adjacent metal layers 36b. In other words, on the surface of the frequency-adjusting metal film 36, the metal layers 36b and the exposed portions 361 are alternately formed in a striped pattern. The exposed portions 361 may be formed not only between adjacent metal layers 36b, but also on the outer periphery of the frequency-adjusting metal film 36 (see FIG. 14). Other than the shape, the preferred conditions (thickness, material, melting temperature, etc.) of the frequency-adjusting metal film 36 of this embodiment are the same as those of the first embodiment. Similar to the modification of the first embodiment shown in FIG. 10, an auxiliary metal layer 36d (see FIG. 16) may be formed between the base metal layer 36a and the second sealing member 30.

[0073] Next, a frequency adjustment method for the crystal resonator 100 according to this embodiment will be described. Note that since the frequency adjustment method of this embodiment is similar to the frequency adjustment method described in the first embodiment, a description of the same points as in the first embodiment will be omitted, and only the differences will be described.

[0074] In this embodiment, the frequency adjustment metal film 36 is irradiated with a laser by linearly irradiating the laser spot SP while sweeping it, as shown in FIG. 17 . The laser sweeping is performed so that at least a portion of the laser spot SP includes the exposed portion 361. In the example of FIG. 17 , the metal layer 36b and the exposed portion 361 are alternately formed in a striped pattern in the frequency adjustment metal film 36, and the laser sweeping is performed along the longitudinal direction of the linear exposed portion 361 (the direction of arrow A in the figure). At this time, the line width of the exposed portion 361 is set smaller than the diameter (irradiation diameter) of the laser spot SP, so that the metal layer 36b can be heated on both sides of the swept laser spot SP. Furthermore, the laser spot SP is swept multiple times for each irradiation line. After multiple laser sweeps are performed for one irradiation line, laser sweeps are performed for the adjacent irradiation line. At this time, the irradiation lines do not interfere with (overlap with) each other in a planar view.

[0075] The reason why laser sweeping is performed so that at least a portion of the laser spot SP includes the exposed portion 361 during frequency adjustment of the quartz crystal resonator 100 is as follows. Fig. 18 is a schematic diagram showing, as a comparative example, a method of irradiating the frequency-adjusting metal film 36 with a laser. In this comparative example, the metal layer 36b is formed on almost the entire surface of the base metal layer 36a, and the laser spot SP is irradiated onto the frequency-adjusting metal film 36 that does not include the exposed portion 361.

[0076] As described above, when the frequency-adjusting metal film 36 is irradiated with a laser, the underlying metal layer 36a is heated, and the metal layer 36b above the underlying metal layer 36a melts and evaporates. The underlying metal layer 36a is exposed in the area where the metal layer 36b has evaporated. In the comparative example of FIG. 18 , in the irradiation line where a predetermined number of laser sweeps have been completed, Au residues (when the metal layer 36b is made of Au) may be generated, in which small chunks of Au remain on the edge of the metal layer 36b. After the frequency adjustment of the quartz crystal unit 100 is completed, these Au residues may break off from the metal layer 36b and adhere to the second excitation electrode 112, potentially causing an undesired shift in the frequency of the quartz crystal unit 100.

[0077] 18. The Au residue in the comparative example is caused by uneven evaporation of Au in the irradiation line during laser sweep, which causes molten Au to remain in a bridge-like shape (Au bridges). That is, even if the Au bridges themselves that occurred in the irradiation line during laser sweep are eventually eliminated, Au residues tend to remain at the ends of the Au bridges.

[0078] 17, at least a part of the laser spot SP includes the exposed portion 361, and by performing the laser sweep along the exposed portion 361, it is possible to prevent the generation of Au bridges in the irradiation line during the laser sweep, and as a result, it is possible to prevent the generation of Au residues. If the generation of Au residues can be prevented, it is possible to prevent the Au residues from breaking off from the metal layer 36b and adhering to the second excitation electrode 112.

[0079] Furthermore, as described above, when a laser is scanned linearly onto the frequency-adjusting metal film 36, a general property of lasers is that irradiation at the start point of the line becomes unstable. For example, if the laser power becomes too strong at the start point of the line, not only does frequency adjustment become difficult, but melting of the underlying metal layer 36a may also occur. If the overall laser output is weakened to match the power at the start point in order to prevent such melting of the underlying metal layer 36a, the efficiency of frequency adjustment decreases.

[0080] 19, the laser line scan for frequency adjustment may be started from outside the region of the frequency adjustment metal film 36. This stabilizes the power of the laser irradiated onto the frequency adjustment metal film 36, making it possible to suppress melting of the base metal layer 36a without reducing the overall laser output.

[0081] Note that the laser irradiated outside the area of ​​the frequency-adjusting metal film 36 is not blocked by the underlying metal layer 36a. If the unblocked laser reaches the electrodes or wiring (especially the excitation electrodes) of the quartz crystal plate 10, this is undesirable as it could damage the electrodes or wiring. For this reason, when irradiating the laser from outside the area of ​​the frequency-adjusting metal film 36, the laser is irradiated only on the area of ​​the quartz crystal plate 10, not on the areas where the electrodes and wiring are formed. If the laser is irradiated on the quartz crystal area outside the electrodes and wiring, there is no problem as it will pass through.

[0082] In this case, it is preferable to maintain the relationship of "length of the frequency adjustment metal film 36 > length of the excitation electrode (in this case, the second excitation electrode 112)" in the laser scanning direction. However, in this case, the length of the frequency adjustment metal film 36 refers to at least the length of the base metal layer 36a. Furthermore, by making the metal layer 36b shorter than the second excitation electrode 112, it is possible to obtain the effect of allowing the evaporated metal to adhere more reliably to the second excitation electrode 112. Therefore, when laser irradiation is performed from outside the region of the frequency adjustment metal film 36, it is most preferable to maintain the relationship of "length of the base metal layer 36a > length of the second excitation electrode 112 > length of the metal layer 36b" in the laser scanning direction.

[0083] The frequency-adjusting metal film 36 in the crystal resonator 100 configured as described above is formed by the procedure shown in Figure 20. First, a base metal layer 36a and a pre-patterning metal layer 36b' are formed on the second sealing member 30 (see Figure 20(a)). Then, a mask is formed on the metal layer 36b' by photolithography, and the metal layer 36b' is patterned by etching to form the patterned metal layer 36b (see Figure 20(b)).

[0084] 21A and 21B are enlarged cross-sectional views of the frequency-adjusting metal film 36, where (a) shows the state before frequency adjustment and (b) shows the state after frequency adjustment. As shown in Fig. 21A, in the frequency-adjusting metal film 36 before frequency adjustment, the portion where the metal layer 36b' has been removed by etching becomes an exposed portion 361, and the thickness of the underlying metal layer 36a in this exposed portion 361 is smaller than that of the surrounding underlying metal layer 36a due to the effects of etching.

[0085] 21(b), in the frequency-adjusting metal film 36 after frequency adjustment, a portion of the metal layer 36b is removed by evaporation, and the width of the exposed portion 361 becomes wider than before the frequency adjustment. At this time, the portion that was the exposed portion 361 before the frequency adjustment is defined as a first exposed portion 361a, and the portion where the base metal layer 36a is exposed due to the evaporation of the metal layer 36b during frequency adjustment is defined as a second exposed portion 361b.

[0086] The second exposed portion 361b is formed so as to contact both the first exposed portion 361a and the metal layer 36b in a plan view. Furthermore, in the frequency-adjusted quartz-crystal resonator 100, the film thickness of the base metal layer 36a in the first exposed portion 361a is smaller than that in the second exposed portion 361b. In this manner, a structure in which the film thickness of the base metal layer 36a in the first exposed portion 361a is smaller has the advantage of reducing the amount of heat stored in the first exposed portion 361a during laser irradiation for frequency adjustment, allowing the metal layer 36b to be heated efficiently around the first exposed portion 361a.

[0087] In the quartz crystal resonator 100 of this embodiment, similar to the modified example of FIG. 12 in the first embodiment, a metal layer (e.g., a W layer) 37 (see FIG. 22) identical to the base metal layer 36a may be formed as a separate layer in a region separate from the base metal layer 36a, and this metal layer 37 may function as a getter material.

[0088] 23 , the frequency adjustment metal film 26 may be provided on the second main surface 202 of the first sealing member 20, facing the first excitation electrode 111, as in the modified example of the first embodiment. Alternatively, as shown in FIG. 23 , the frequency adjustment metal film 26 may be provided on the second main surface 202 of the first sealing member 20, and the frequency adjustment metal film 36 may be provided on the first main surface 301 of the second sealing member 30. In this case, the frequency adjustment metal film 26 has a configuration in which a base metal layer 26a and a metal layer 26b are stacked, similar to the frequency adjustment metal film 36 of the second sealing member 30.

[0089] Third Embodiment The basic structure of the crystal resonator 100 according to this embodiment is similar to that of the second embodiment, so the following description will omit the description of the same configuration as the second embodiment and will focus only on the distinctive features of this embodiment.

[0090] Fig. 24 is a schematic plan view of the second main surface 302 side of the second sealing member 30 of the quartz crystal resonator 100 according to this embodiment. Fig. 25 is a schematic cross-sectional view that schematically illustrates a method for adjusting the frequency of the quartz crystal resonator 100 according to this embodiment. As shown in Figs. 14 and 25, in this embodiment, a frequency-adjusting metal film 36 similar to that in the second embodiment is formed. That is, the metal layer 36b on the base metal layer 36a is formed in a striped pattern, and an exposed portion 361 is formed between adjacent metal layers 36b.

[0091] Furthermore, in this embodiment, as shown in FIG. 24, a shielding film 38 is formed on the second main surface 302 of the second sealing member 30, which shields a portion of the laser irradiated during frequency adjustment of the quartz crystal resonator 100. A plurality of slits (openings) 381 are formed in the shielding film 38, and the slits 381 are formed in stripes oriented in the same direction as the metal layer 36b of the frequency adjustment metal film 36. Note that the preferred conditions (thickness, material, melting temperature, etc.) of the frequency adjustment metal film 36 and the shielding film 38 of this embodiment other than their shapes are the same as those of the second embodiment. Furthermore, as in the modified example of FIG. 16 in the second embodiment, an auxiliary metal layer 36d (see FIG. 26) may be formed between the base metal layer 36a and the second sealing member 30.

[0092] Next, a frequency adjustment method for the crystal resonator 100 according to this embodiment will be described. Note that since the frequency adjustment method of this embodiment is similar to the frequency adjustment method described in the second embodiment, a description of the same points as in the second embodiment will be omitted, and only the differences will be described.

[0093] In this embodiment, the laser irradiation to the frequency-adjusting metal film 36 is performed by irradiating the laser in a line shape while sweeping the laser spot SP, as in the second embodiment. The laser sweeping in this case is performed from above the shielding film 38 as shown in FIG. 25 so that at least a part of the laser spot SP includes the exposed portion 361.

[0094] In the quartz crystal resonator 100 of this embodiment, as shown in FIG. 27 , a frequency-adjusting metal film 36 is formed on the first main surface 301 of the second sealing member 30, and a shielding film 38 is formed on the second main surface 302 (the surface on the side irradiated with laser light). The shielding film 38 preferably has a surface made of a metal (such as Au, Ag, or Al) with high reflectivity with respect to the laser (in this embodiment, a green laser with a wavelength of 532 nm) to shield the irradiated laser light by reflection. By using a metal with high reflectivity for the surface of the shielding film 38, it is possible to prevent the temperature of the shielding film 38 itself from increasing due to laser irradiation. Therefore, the shielding film 38 can have a two-layer structure, for example, with a Ti layer 38a on the lower layer side and an Au layer 38b on the upper layer (surface layer) side. The shielding film 38 also has slits 381 formed in a stripe shape oriented in the same direction as the metal layer 36b of the frequency-adjusting metal film 36.

[0095] The slit 381 is formed wider than the exposed portion 361 and is formed to include the exposed portion 361 in a planar view. Therefore, in this example, the line width Lb of the slit 381 is formed wider than the line width La of the exposed portion 361. This allows the metal layer 36b located on both outer sides of the exposed portion 361 to be heated via the base metal layer 36a, thereby enabling efficient frequency adjustment. Furthermore, the exposed portion 361 and the slit 381 are aligned so that their centers in the line width direction coincide in a planar view. Both the shielding film 38 and the metal layer 36b are formed by forming a mask using photolithography and patterning by etching, allowing for highly accurate alignment.

[0096] 27, the frequency-adjusting metal film 36 is irradiated with a laser beam such that the laser spot SP includes the slit 381. Specifically, the line width Lb of the slit 381 is smaller than the irradiation diameter Lc of the laser spot SP, and the laser spot SP is irradiated with the laser beam such that both ends of the slit 381 in the line width direction partially overlap the shielding film 38. In this case, the laser beam that overlaps the shielding film 38 is blocked (reflected) by the shielding film 38 and does not pass through the second sealing member 30. Therefore, only the laser beam irradiated within the slit 381 passes through the second sealing member 30, and the frequency-adjusting metal film 36 can be heated.

[0097] The reason for forming the shielding film 38 on the laser irradiation surface (in this case, the second main surface 302 of the second sealing member 30) in the quartz crystal resonator 100 is as follows. Here, FIG. 28 is a comparative example that schematically illustrates laser irradiation of the frequency-adjusting metal film 36 when the shielding film 38 is not present. In this comparative example, as shown in FIG. 28(a), it is preferable that the center of the laser spot SP is aligned with the center of the exposed portion 361 in the line width direction. However, in reality, the alignment accuracy of the laser spot SP is not very high, and as shown in FIG. 28(b), it is possible that the laser spot SP will be misaligned with respect to the exposed portion 361.

[0098] If the laser spot SP is misaligned with respect to the exposed portion 361, irradiation of an undesired area may destabilize the adjustment amount. Furthermore, in the irradiation line after laser sweeping, Au residue (if the metal layer 36b is made of Au) may be generated at the edge of the metal layer 36b. The Au residue in this case is thought to be caused by a misalignment of the laser spot SP between the irradiation area of ​​the laser spot SP and the applied heat amount relative to the metal layer 36b. For example, if the laser spot SP is misaligned as shown in FIG. 28(b), the applied heat amount is less relative to the irradiation area (line area) of the metal layer 36b on the left side of the laser spot SP. This melts the Au in the metal layer 36b but does not evaporate it, resulting in re-solidification of the Au. The Au residue is thought to be generated when the Au re-solidifies. As explained in the second embodiment, the generation of such Au residues may cause an undesired shift in the frequency of the quartz crystal resonator 100 after the frequency adjustment of the quartz crystal resonator 100 is completed.

[0099] In contrast, in the crystal unit 100 with the shielding film 38 formed thereon, even if the laser spot SP is misaligned, as shown in FIG. 29, the beam can be reliably irradiated onto the region of the metal layer 36b to be heated. In other words, stable frequency adjustment can be performed regardless of the positional accuracy of the laser irradiation device. Furthermore, since the laser irradiation range of the frequency-adjusting metal film 36 is restricted by the shielding film 38, imbalance between the irradiation area of ​​the laser spot SP on the metal layer 36b and the amount of heat applied is significantly suppressed. As a result, the generation of Au residue can be avoided, and undesired frequency shifts can be prevented after frequency adjustment of the crystal unit 100 is completed.

[0100] 24, each slit 381 in the shielding film 38 is a closed area surrounded on all four sides by the shielding film 38. That is, the shielding film 38 in FIG. 24 has a frame that surrounds the entire periphery of the slit 381. However, in order to avoid the generation of Au residues as described above, the shape of the shielding film 38 is not limited to this. For example, as shown in FIG. 30, a configuration may be adopted in which a plurality of shielding films 38 are formed in a stripe pattern, and an open slit 381 is provided between adjacent shielding films 38.

[0101] However, the example of the shielding film 38 shown in FIG. 24 also has the following advantage. That is, as described above, when a laser is scanned linearly onto the frequency-adjustment metal film 36 to irradiate the metal film 36, the general property of the laser is that irradiation at the start point of the line becomes unstable. For example, if the laser power becomes too strong at the start point of the line, not only does frequency adjustment become difficult, but melting of the underlying metal layer 36a may also occur. If the overall laser output is weakened to match the power at the start point in order to prevent such melting of the underlying metal layer 36a, the efficiency of frequency adjustment decreases.

[0102] 24 is employed, and the laser line scanning for frequency adjustment is started outside the area of ​​the slit 381 (outside the longitudinal end of the slit 381) and in the area where the shielding film 38 is present (for example, the frame portion at the upper side of the shielding film 38), the laser with unstable power at the start point of the line can be blocked by the shielding film 38. This stabilizes the power of the laser irradiated onto the frequency adjustment metal film 36, making it possible to suppress melting of the base metal layer 36a without weakening the overall laser output.

[0103] Furthermore, by forming the shielding film 38 in the second sealing member 30 of the quartz crystal unit 100 in correspondence with the frequency-adjusting metal film 36, it is possible to obtain the effect of suppressing warping of the second sealing member 30. Furthermore, in the quartz crystal unit 100, the shielding film 38 may be electrically connected to the external electrode terminal 32 to which a ground (GND) potential is applied when the quartz crystal unit 100 is in operation. In this case, the shielding film 38 can function as a shielding film for the excitation electrode of the quartz crystal unit 100. Furthermore, the frequency-adjusting metal film 36 may also be electrically connected to an electrode or wiring to which a ground potential is applied when the quartz crystal unit 100 is in operation.

[0104] Furthermore, similar to the modified example of the second embodiment, the second sealing member 30 may not be provided with a frequency adjustment metal film, but may instead be provided on the second main surface 202 of the first sealing member 20 that faces the first excitation electrode 111. Alternatively, as shown in FIG. 31 , a frequency adjustment metal film 26 may be provided on the second main surface 202 of the first sealing member 20, and a frequency adjustment metal film 36 may be provided on the first main surface 301 of the second sealing member 30. In this case, the frequency adjustment metal film 26 has a structure in which a base metal layer 26a and a metal layer 26b are laminated, similar to the frequency adjustment metal film 36 of the second sealing member 30. Furthermore, a shielding film 29 is provided on the first main surface 201 of the first sealing member 20 in correspondence with the frequency adjustment metal film 26. The shielding film 29 (and the slits 291) of the first sealing member 20 has a structure similar to the shielding film 38 (and the slits 381) of the second sealing member 30.

[0105] [Fourth embodiment] The basic structure of the crystal resonator 100 according to this embodiment is similar to that of the second embodiment, so the following description will omit the description of the same configuration as the second embodiment and will focus only on the distinctive features of this embodiment.

[0106] FIG. 32 is a schematic plan view of the first main surface 301 of the second sealing member 30 of the crystal unit 100 according to this embodiment. FIG. 33 is a schematic cross-sectional view illustrating a method for adjusting the frequency of the crystal unit 100 according to this embodiment. As shown in FIGS. 32 and 33, in this embodiment, the frequency-adjusting metal film 36 has a multilayer structure made of two or more metals with different melting temperatures (melting points). In the example shown in FIG. 33, the frequency-adjusting metal film 36 has a three-layer structure. Specifically, the frequency-adjusting metal film 36 includes a base metal layer 36a, a first metal layer 36b stacked on the base metal layer 36a, and a second metal layer 36e stacked on the first metal layer 36b. The first metal layer 36b here corresponds to the metal layer 36b in the second and third embodiments.

[0107] The melting temperature of the second metal layer 36e is set higher than that of the first metal layer 36b. The second metal layer 36e may be formed of the same material as the underlying metal layer 36a, or the underlying metal layer 36a and the second metal layer 36e may be formed of, for example, W (tungsten). The second metal layer 36e may be formed of a material different from that of the underlying metal layer 36a, or the underlying metal layer 36a may be formed of, for example, W (tungsten), and the second metal layer 36e may be formed of, for example, Mo (molybdenum), Ta (tantalum), or Re (rhenium).

[0108] An opening is formed in the frequency-adjusting metal film 36, and a portion of the underlying metal layer 36a is exposed and not covered by the first and second metal layers 36b and 36e. As shown in FIGS. 33 to 35, the first and second metal layers 36b and 36e have openings 361a and 361b, respectively, and the openings 361a and 361b of the first and second metal layers 36b and 36e are connected to each other so that the underlying metal layer 36a is exposed. Specifically, the openings 361a and 361b of the first and second metal layers 36b and 36e are connected to each other, forming an exposed underlying metal portion where a portion of the underlying metal layer 36a is exposed and not covered by the first and second metal layers 36b and 36e. Furthermore, the opening 361b in the second metal layer 36e forms a first exposed metal portion where a portion of the first metal layer 36b is exposed and not covered by the second metal layer 36e.

[0109] In a plan view, the exposed base metal portion of the base metal layer 36a and the exposed first metal portion of the first metal layer 36b extend linearly. The exposed first metal portion of the first metal layer 36b is provided between the exposed base metal portion of the base metal layer 36a and the second metal layer 36e. Specifically, the exposed first metal portion of the first metal layer 36b is provided on both sides of the exposed base metal portion of the base metal layer 36a. Furthermore, the second metal layer 36e is provided on both sides of the exposed base metal portion of the base metal layer 36a and the exposed first metal portions of the first metal layer 36b on both sides of the exposed base metal portion of the base metal layer 36a. The exposed base metal portions of the base metal layer 36a and the exposed first metal portions of the first metal layer 36b are formed at multiple locations spaced a predetermined distance apart. The frequency-adjusting metal film 36 is irradiated with laser light along the exposed base metal portions of the base metal layer 36a and the exposed first metal portions of the first metal layer 36b.

[0110] Next, a frequency adjustment method for the crystal resonator 100 according to this embodiment will be described. Note that since the frequency adjustment method of this embodiment is similar to the frequency adjustment method described in the second embodiment, a description of the same points as in the second embodiment will be omitted, and only the differences will be described.

[0111] 33, in this embodiment, a laser is irradiated onto the frequency-adjusting metal film 36 from outside the second sealing member 30, and the laser passes through the inside of the second sealing member 30 to heat the base metal layer 36a, thereby melting and evaporating (vaporizing) at least a portion of the first metal layer 36b, and the evaporated metal is then attached to the second excitation electrode 112, thereby performing frequency adjustment. That is, the laser melts the first metal layer 36b above the base metal layer 36a and evaporates it from the opening 361b. That is, the metal evaporated from the first metal layer 36b attaches to the second excitation electrode 112. On the other hand, the second metal layer 36e above the first metal layer 36b has a higher melting temperature than the first metal layer 36b, and therefore remains in a solid state without being melted.

[0112] Laser irradiation of the metal film 36 for frequency adjustment is performed by linearly irradiating while sweeping the laser spot SP. As shown in FIG. 34, by arranging the irradiation lines LN formed by sweeping the laser spot SP in parallel, laser irradiation is performed on a desired region of the metal film 36 for frequency adjustment. At this time, the sweeping direction of the laser spot SP (direction of arrow A) is the same for all the irradiation lines LN, and each irradiation line LN is set along the base metal exposed portion of the base metal layer 36a and the first metal exposed portion of the first metal layer 36b. Specifically, the irradiation line LN is a line along the approximate center of the base metal exposed portion of the base metal layer 36a (approximate center of the line width W1), and is also a line along the approximate center of the first metal exposed portion of the first metal layer 36b (approximate center of the line width W2).

[0113] The sweeping of the laser spot SP is repeated a plurality of times for each irradiation line LN. After performing laser sweeping a plurality of times for one irradiation line LN, laser sweeping for the adjacent irradiation line LN is performed. The pitch P1 of the laser sweeping (interval in the direction orthogonal to the sweeping direction) is set to be larger than the diameter (irradiation diameter) D1 of the laser spot SP (P1 > D1), and the adjacent irradiation lines LN in the direction orthogonal to the sweeping direction do not interfere with each other (do not overlap) in a plan view. Also, the line width W1 of the base metal exposed portion of the base metal layer 36a and the line width W2 of the first metal exposed portion of the first metal layer 36b are set to be smaller than the irradiation diameter D1 of the laser spot SP (W1 < D1 and W2 < D), and the first metal layer 36b is heated on both sides of the laser spot SP to be swept.

[0114] By irradiating the frequency-adjusting metal film 36 with a laser beam, the base metal layer 36a is heated, and the first metal layer 36b above the base metal layer 36a melts and evaporates. At this time, a portion of the melted first metal layer 36b may flow outside the laser irradiation range. However, in this embodiment, as shown in FIG. 35 , even if a portion of the melted first metal layer 36b flows outside the laser irradiation range, it adheres to the side surfaces of the unmelted first metal layer 36b and the end of the second metal layer 36e, becoming solidified metal 36f. Specifically, the first metal layer 36b with the second metal layer 36e on its upper side is heated more slowly than the first metal layer 36b without the second metal layer 36e on its upper side, making it less likely to melt. The second metal layer 36e acts as a stopper to prevent the melted first metal layer 36b from flowing out of the laser irradiation range, and the melted first metal layer 36b can be kept within the laser irradiation range (within the laser spot SP). This allows the heat of the laser irradiation to be efficiently transferred to the melted first metal layer 36b that remains within the laser irradiation range, and prevents a decrease in the frequency adjustment amount caused by part of the melted first metal layer 36b flowing out of the laser irradiation range.

[0115] Furthermore, the metal 36f attached to the side surfaces of the first metal layer 36b and the ends of the second metal layer 36e solidifies in a relatively stable shape, which prevents the metal 36f from scattering to the outside as foreign matter after frequency adjustment.

[0116] As shown in FIG. 36 , the frequency-adjusting metal film 36 may have an opening 361b formed only in the second metal layer 36e, but no opening in the first metal layer 36b. That is, the opening 361b in the second metal layer 36e defines the exposed first metal portion of the first metal layer 36b in the frequency-adjusting metal film 36, but does not define the exposed base metal portion of the base metal layer 36a. In this case, laser irradiation of the frequency-adjusting metal film 36 heats the base metal layer 36a, melting and vaporizing the first metal layer 36b in the exposed first metal portion. The melted first metal layer 36b, which tends to flow outside the laser irradiation range, can be prevented from flowing outside the laser irradiation range by adhering it to the unmelted first metal layer 36b and the second metal layer 36e. This prevents the melted first metal layer 36b from flowing outside the laser irradiation range, and keeps the melted first metal layer 36b within the laser irradiation range (within the laser spot SP). Also, the processing step of forming an opening in the first metal layer 36b is not required, which simplifies the process of forming the frequency-adjusting metal film 36. Furthermore, a large area of ​​the first metal layer 36b that can be used for frequency adjustment can be secured.

[0117] When the second metal layer 36e is made of a metal different from that of the underlying metal layer 36a, the heat absorption effect of the second metal layer 36e can be improved by forming the second metal layer 36e from a material with a high specific heat or a high thermal conductivity. For example, the heat absorption effect of the second metal layer 36e can be improved by forming the second metal layer 36e from Mo (molybdenum) and the underlying metal layer 36a from W (tungsten).

[0118] On the other hand, if the second metal layer 36e is formed from the same metal as the underlying metal layer 36a, the process of forming the frequency-adjusting metal film 36 can be simplified, and productivity can be improved. For example, by forming both the second metal layer 36e and the underlying metal layer 36a from W (tungsten), there is no need to consider melting of the second metal layer 36e, and stable frequency adjustment can be performed.

[0119] Furthermore, similar to the modified example of the second embodiment, the second sealing member 30 may not be provided with a frequency adjustment metal film, but may instead be provided on the second main surface 202 of the first sealing member 20 that faces the first excitation electrode 111. Alternatively, as shown in Fig. 37, the frequency adjustment metal film 26 may be provided on the second main surface 202 of the first sealing member 20, and the frequency adjustment metal film 36 may be provided on the first main surface 301 of the second sealing member 30. The frequency adjustment metal film 26 of the first sealing member 20 has a configuration in which a base metal layer 26a, a first metal layer 26b, and a second metal layer 26e are stacked, similar to the frequency adjustment metal film 36 of the second sealing member 30 of this embodiment.

[0120] Fifth Embodiment The frequency adjustment metal films 26, 36 described in the first to fourth embodiments may be electrically connected to electrodes or wiring to which a ground potential (GND) is applied during operation of the crystal unit. An example configuration of a crystal unit 100 in which the frequency adjustment metal films 26, 36 can be connected to GND will be described with reference to FIGS. 38 to 42. FIG. 38 is a schematic plan view of the second main surface 202 side of the first sealing member 20 of the crystal unit 100. FIG. 39 is a schematic plan view of the first main surface 101 side of the crystal vibrating plate 10 of the crystal unit 100. FIG. 40 is a schematic plan view of the second main surface 102 side of the crystal vibrating plate 10 of the crystal unit 100. FIG. 41 is a schematic plan view of the first main surface 301 side of the second sealing member 30 of the crystal unit 100. FIG. 42 is a schematic plan view of the second main surface 302 side of the second sealing member 30 of the crystal unit 100.

[0121] The crystal resonators 100 described in the first to fourth embodiments have wiring and electrodes designed on the assumption that an IC chip for constituting a crystal oscillator together with the crystal resonator 100 will be mounted on the first sealing member 20. In contrast, the crystal resonators 100 shown in FIGS. 38 to 42 are not designed on the assumption that an IC chip will be mounted on the first sealing member 20, and the wiring and electrodes are designed differently from those of the first to fourth embodiments. However, in the following description, components having the same functions as those of the crystal resonators 100 described in the first to fourth embodiments will be described using the same component numbers.

[0122] In the quartz-crystal resonator 100 of this embodiment, the external electrode terminal 32A located on the upper right of the second main surface 302 of the second sealing member 30 in FIG. 42 is an electrode connected to GND. This external electrode terminal 32A is connected to a second sealing member bonding pattern 31 formed on the first main surface 301 of the second sealing member 30 via a through-hole 33A (see FIGS. 41 and 42). Furthermore, by bonding the second sealing member 30 to the quartz-crystal vibrating plate 10, the second sealing member bonding pattern 31 is integrated with a second vibration plate bonding pattern 122 formed on the second main surface 102 of the quartz-crystal vibrating plate 10.

[0123] In the quartz-crystal vibrating plate 10, the second diaphragm-side bonding pattern 122 formed on the second principal surface 102 is electrically connected to the first diaphragm-side bonding pattern 121 formed on the first principal surface 101. The electrical connection between the second diaphragm-side bonding pattern 122 and the first diaphragm-side bonding pattern 121 can be achieved, for example, by forming a metal film on the inner wall surface of the quartz-crystal vibrating plate 10 (for example, the inner wall surface in area A in FIGS. 39 and 40). Furthermore, by bonding the quartz-crystal vibrating plate 10 to the first sealing member 20, the first diaphragm-side bonding pattern 121 is integrated with the first sealing member-side bonding pattern 24 formed on the second principal surface 202 of the first sealing member 20.

[0124] As described above, in the quartz crystal resonator 100 of this embodiment, an electrical path is formed in the following order from the external electrode terminal 32A to the through-hole 33A, the sealing member-side second bonding pattern 31, the diaphragm-side second bonding pattern 122, the diaphragm-side first bonding pattern 121, and the sealing member-side first bonding pattern 24, and a ground potential can be applied to this electrical path.

[0125] When the frequency adjustment metal film 26 is formed on the second main surface 202 of the first sealing member 20, the frequency adjustment metal film 26 and the sealing member-side first bonding pattern 24 are connected by connection wiring 26c as shown in Fig. 38. In this case, the connection wiring 26c can be formed, for example, simultaneously with the base metal layer 26a of the frequency adjustment metal film 26. When the frequency adjustment metal film 36 is formed on the first main surface 301 of the second sealing member 30, the frequency adjustment metal film 36 and the sealing member-side second bonding pattern 31 are connected by connection wiring 36c as shown in Fig. 41. In this case, the connection wiring 36c can be formed, for example, simultaneously with the base metal layer 36a of the frequency adjustment metal film 36.

[0126] In this way, by connecting the frequency adjustment metal films 26 and 36 to GND, it becomes possible to use the frequency adjustment metal films 26 and 36 as a shield for ESD (high frequency noise) countermeasures.

[0127] Sixth Embodiment In the first to fifth embodiments, a three-layer structure crystal unit 100 is used in which the crystal vibrating plate 10 is sandwiched between the first sealing member 20 and the second sealing member 30. However, crystal units with other structures may also be used. For example, a crystal unit may be used in which the crystal vibrating plate is housed inside a base having a recess and made of an insulating material such as ceramic, glass, or crystal, and a lid is bonded to the base.

[0128] 43 is a schematic diagram showing the components of a quartz crystal resonator (piezoelectric resonator device) 400 according to this embodiment. As shown in Fig. 43, the quartz crystal resonator 400 has a structure in which a quartz crystal vibrating plate (vibration portion) 60 is housed inside a base 40 having a recess 401, and a lid 50 is bonded to the base 40. A first excitation electrode 601 and a second excitation electrode 602 are formed on each of the two main surfaces of the quartz crystal vibrating plate 60.

[0129] In the quartz crystal unit 400, a frequency-adjusting metal film 51 is formed on the back surface (the surface facing the base 40) of the lid 50, which serves as a sealing member. Similar to the frequency-adjusting metal film 36 of the first embodiment, the frequency-adjusting metal film 51 is configured to include a base metal layer 51a and a metal layer 51b. The lid 50 is formed from a material (such as quartz or glass) that has high laser transmittance, and after the lid 50 is bonded to the base 40 and the quartz crystal vibrating plate 60 is sealed in the package, the base metal layer 51a can be heated by laser irradiation from the front surface of the lid 50 (the surface not facing the base 40).

[0130] As a result, even in the quartz crystal oscillator 400, a laser is irradiated onto the frequency-adjusting metal film 51 from outside the base 40, and the laser passes through the inside of the base 40 to heat the underlying metal layer 51a, thereby melting and evaporating (vaporizing) at least a portion of the metal layer 51b, and the evaporated metal is then attached to the excitation electrode (in this example, the first excitation electrode 601), thereby enabling frequency adjustment.

[0131] 43, the frequency-adjusting metal film 51 has the same configuration as the frequency-adjusting metal film 36 of the first embodiment, but as shown in FIGS. 44 and 46, the frequency-adjusting metal film 51 may have the same configuration as the frequency-adjusting metal film 36 of the second or fourth embodiment. Also, as shown in FIG. 45, a shielding film 52 may be formed on the surface of the lid 50, as in the third embodiment.

[0132] 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.

[0133] This application claims priority based on Japanese Patent Application No. 2022-008170 filed in Japan on January 21, 2022, Japanese Patent Application No. 2022-009290 filed in Japan on January 25, 2022, and Japanese Patent Application No. 2022-013237 filed in Japan on January 31, 2022, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0134] 10 Crystal diaphragm 11 Vibration unit 20 First sealing member (sealing member) 30 Second sealing member (sealing member) 36,51 Frequency adjustment metal film 36a,51a Base metal layer 36b,51b Metal layer 361 Exposed part 361a 1st exposed part 361b 2nd exposed part 38,29,52 Shielding membrane 381,291 Slit (opening) 100,400 Quartz crystal unit (piezoelectric vibration device) 111,601 1st excitation electrode 112,602 2nd excitation electrode 301 First main surface 40 base 50 Lid (sealing member) 60 Crystal diaphragm (vibrating part)

Claims

1. A piezoelectric vibration device in which a vibration section in which an excitation electrode is formed on a piezoelectric vibration plate is airtightly sealed by a sealing member, a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, the frequency adjustment metal film is disposed opposite the excitation electrode such that an outer periphery of the frequency adjustment metal film is located inside an outer periphery of the excitation electrode in a plan view, the melting temperature of the metal base layer is higher than the melting temperature of the metal layer, and the difference in melting temperature between the metal base layer and the metal layer is 1500 K or more; the frequency-adjusting metal film has an exposed portion in which a part of the underlying metal layer is not covered with the metal layer and is exposed; the exposed portion includes a first exposed portion and a second exposed portion in which the film thickness of the underlying metal layer is larger than that of the first exposed portion, The second exposed portion is in contact with both the first exposed portion and the metal layer in a plan view. A piezoelectric vibration device characterized by:

2. A piezoelectric vibration device in which a vibration section on which an excitation electrode is formed is airtightly sealed by a sealing member, a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, the frequency adjustment metal film is disposed opposite the excitation electrode such that an outer periphery of the frequency adjustment metal film is located inside an outer periphery of the excitation electrode in a plan view, the material of the metal layer is selected from the group consisting of Au (gold), Ag (silver) and Al (aluminum); the material of the underlayer metal layer is selected from the group consisting of W (tungsten), Mo (molybdenum), Ta (tantalum), and Re (rhenium); the frequency-adjusting metal film has an exposed portion in which a part of the underlying metal layer is not covered with the metal layer and is exposed; the exposed portion includes a first exposed portion and a second exposed portion in which the film thickness of the underlying metal layer is larger than that of the first exposed portion, A piezoelectric vibration device characterized in that the second exposed portion is in contact with both the first exposed portion and the metal layer in a planar view.

3. 3. The piezoelectric vibration device according to claim 1, A piezoelectric vibration device, characterized in that the first exposed portion and the second exposed portion are formed in a linear shape.

4. 3. The piezoelectric vibration device according to claim 1, the thickness of the underlying metal layer is 50 to 500 nm; A piezoelectric vibration device characterized in that the thickness of the metal layer is 100 to 500 nm.

5. A method for adjusting the frequency of a piezoelectric vibration device in which a vibration section in which an excitation electrode is formed on a piezoelectric vibration plate is airtightly sealed by a sealing member, comprising: In the piezoelectric vibration device, a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, the frequency adjustment metal film is disposed opposite the excitation electrode such that an outer periphery of the frequency adjustment metal film is located inside an outer periphery of the excitation electrode in a plan view, the melting temperature of the metal base layer is higher than the melting temperature of the metal layer, and the difference in melting temperature between the metal base layer and the metal layer is 1500 K or more; the frequency-adjusting metal film has an exposed portion in which a part of the underlying metal layer is not covered with the metal layer and is exposed; A method for adjusting the frequency of a piezoelectric vibration device, characterized in that a beam is irradiated from outside the sealing member onto the frequency adjustment metal film from the side of the base metal layer so as to include at least the exposed portion in a planar view, and the beam is passed through the inside of the sealing member to heat the base metal layer, thereby melting and evaporating at least a portion of the metal layer, and adhering it to the excitation electrode, thereby adjusting the frequency.

6. A method for adjusting the frequency of a piezoelectric vibration device in which a vibration section in which an excitation electrode is formed on a piezoelectric vibration plate is airtightly sealed by a sealing member, comprising: In the piezoelectric vibration device, a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, the frequency adjustment metal film is disposed opposite the excitation electrode such that an outer periphery of the frequency adjustment metal film is located inside an outer periphery of the excitation electrode in a plan view, the material of the metal layer is selected from the group consisting of Au (gold), Ag (silver) and Al (aluminum); the material of the underlayer metal layer is selected from the group consisting of W (tungsten), Mo (molybdenum), Ta (tantalum), and Re (rhenium); the frequency-adjusting metal film has an exposed portion in which a part of the underlying metal layer is not covered with the metal layer and is exposed; A method for adjusting the frequency of a piezoelectric vibration device, characterized in that a beam is irradiated from outside the sealing member onto the frequency adjustment metal film from the side of the base metal layer so as to include at least the exposed portion in a planar view, and the beam is passed through the inside of the sealing member to heat the base metal layer, thereby melting and evaporating at least a portion of the metal layer, and adhering it to the excitation electrode, thereby adjusting the frequency.

7. 7. A method for adjusting the frequency of a piezoelectric vibration device according to claim 5, comprising: A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the exposed portions are formed at multiple locations at predetermined intervals.

8. 7. A method for adjusting the frequency of a piezoelectric vibration device according to claim 5, comprising: A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the exposed portion is formed in a linear shape, and the beam is irradiated along the line of the exposed portion.

9. 9. A method for adjusting a frequency of a piezoelectric vibration device according to claim 8, comprising: A method for adjusting the frequency of a piezoelectric vibration device, wherein the line width of the exposed portion is smaller than the irradiation diameter of the beam.

10. 9. A method for adjusting a frequency of a piezoelectric vibration device according to claim 8, comprising: A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the beam is irradiated so that the beam spot includes the exposed portion and two of the metal layers adjacent to the exposed portion.

11. A method for adjusting the frequency of a piezoelectric vibration device in which a vibration section in which an excitation electrode is formed on a piezoelectric vibration plate is airtightly sealed by a sealing member, comprising: In the piezoelectric vibration device, a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, the frequency adjustment metal film is disposed opposite the excitation electrode such that an outer periphery of the frequency adjustment metal film is located inside an outer periphery of the excitation electrode in a plan view, the melting temperature of the metal base layer is higher than the melting temperature of the metal layer, and the difference in melting temperature between the metal base layer and the metal layer is 1500 K or more; the frequency-adjusting metal film has an exposed portion in which a part of the underlying metal layer is not covered with the metal layer and is exposed; a shielding film corresponding to the frequency-adjusting metal film is formed on a main surface of the sealing member opposite to a main surface facing the excitation electrode, The shielding film has an opening formed to include the exposed portion in a plan view. A method for adjusting the frequency of a piezoelectric vibration device, characterized in that a beam is irradiated from outside the sealing member onto the frequency adjustment metal film from the side of the base metal layer through the shielding film so as to include at least the opening in a planar view, and the beam is transmitted through the inside of the sealing member within the area of ​​the opening to heat the base metal layer, thereby melting and evaporating at least a portion of the metal layer, and adhering it to the excitation electrode, thereby adjusting the frequency.

12. A method for adjusting the frequency of a piezoelectric vibration device in which a vibration section in which an excitation electrode is formed on a piezoelectric vibration plate is airtightly sealed by a sealing member, comprising: In the piezoelectric vibration device, a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, the frequency adjustment metal film is disposed opposite the excitation electrode such that an outer periphery of the frequency adjustment metal film is located inside an outer periphery of the excitation electrode in a plan view, the material of the metal layer is selected from the group consisting of Au (gold), Ag (silver) and Al (aluminum); the material of the underlayer metal layer is selected from the group consisting of W (tungsten), Mo (molybdenum), Ta (tantalum), and Re (rhenium); the frequency-adjusting metal film has an exposed portion in which a part of the underlying metal layer is not covered with the metal layer and is exposed; a shielding film corresponding to the frequency-adjusting metal film is formed on a main surface of the sealing member opposite to a main surface facing the excitation electrode, The shielding film has an opening formed to include the exposed portion in a plan view. A method for adjusting the frequency of a piezoelectric vibration device, characterized in that a beam is irradiated from outside the sealing member onto the frequency adjustment metal film from the side of the base metal layer through the shielding film so as to include at least the opening in a planar view, and the beam is transmitted through the inside of the sealing member within the area of ​​the opening to heat the base metal layer, thereby melting and evaporating at least a portion of the metal layer, and adhering it to the excitation electrode, thereby adjusting the frequency.

13. 13. A method for adjusting the frequency of a piezoelectric vibration device according to claim 11, comprising: A method for adjusting the frequency of a piezoelectric vibration device, wherein the opening width of the opening in the shielding film is smaller than the irradiation diameter of the beam.

14. 13. A method for adjusting the frequency of a piezoelectric vibration device according to claim 11, comprising: the exposed portion is formed in a line shape, and the opening is formed in a line shape corresponding to the exposed portion, A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the beam is irradiated along a line of the exposed portion.

15. 13. A method for adjusting the frequency of a piezoelectric vibration device according to claim 11, comprising: A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the exposed portions and the openings are formed at a plurality of locations spaced apart by a predetermined distance.

16. 13. A method for adjusting the frequency of a piezoelectric vibration device according to claim 11, comprising: A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the shielding film has a frame portion around the opening, and the beam irradiation start position is within the area of ​​the frame portion in a planar view.

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