Manufacturing method of piezoelectric vibrating piece

Abstract

To provide a high-quality piezoelectric vibration piece suppressing frequency fluctuation after frequency adjustment and having excellent vibration characteristics.SOLUTION: A piezoelectric vibration piece 3 includes a piezoelectric plate 30 having a pair of vibrating arms 31, an electrode film 40, and a weight metal film 50 for frequency adjustment. The electrode films 40 are arranged on the front and back surfaces of the piezoelectric plate 30. The metal film 50 is arranged on the electrode film 40 on the surface 64 side of the vibrating arm 31. The back surface 63 of the vibrating arm 31 includes a back side exposed portion 61 in which the piezoelectric plate 30 is exposed. The front surface 64 of the vibrating arm 31 includes a front side exposed portion 62 in which the weight metal film 50 and the electrode film 40 are removed and the piezoelectric plate 30 is exposed. The entire front side exposed portion 62 overlaps the back side exposed portion 61 at intervals with respect to the electrode film 40 on the back surface 63 when viewed from the thickness direction of the piezoelectric plate 30.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention , pressure The present invention relates to a method for manufacturing an electric vibrating piece. [Background technology]

[0002] For example, in electronic devices such as mobile phones and personal digital assistants, piezoelectric vibrators using quartz crystals or the like are used as devices used as a time source, a timing source for control signals, a reference signal source, etc. As this type of piezoelectric vibrator, one in which a piezoelectric vibrating piece is hermetically sealed in a package in which a cavity is formed is known.

[0003] The above-mentioned piezoelectric vibrating piece includes a piezoelectric plate having a base and a pair of vibrating arms extending parallel to each other from the base, and an excitation electrode arranged on the outer surface of the vibrating arm. When a voltage is applied to the excitation electrode, the piezoelectric vibrating piece vibrates at a predetermined resonance frequency in a direction in which each vibrating arm approaches or moves away from each other, starting from the base end (the portion connected to the base).

[0004] Here, as a method for adjusting the frequency of a piezoelectric vibrating piece (vibrating arm), there is a method in which a weight metal film is formed in advance on the tip of the vibrating arm, and this weight metal film is partially removed (trimmed) to adjust the mass of the weight metal film so that the frequency of the vibrating arm becomes a target value. For example, the following Patent Document 1 discloses a configuration in which the weight metal film is irradiated with laser light to partially remove the weight metal film to roughly adjust the resonance frequency, and then the weight metal film is irradiated with an ion beam to finely adjust the resonance frequency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-118652 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in addition to the weight metal film, an electrode film having the same film structure as the excitation electrode is arranged on the outer surface of the vibrating arm. Therefore, when trimming the weight metal film using a laser beam as in the above-mentioned Patent Document 1, the weight metal film is removed and the laser beam incident on the piezoelectric plate passes through the piezoelectric plate. As a result, the electrode film arranged on the opposite side to the weight metal film is irradiated with the laser beam, and the irradiated portion of the electrode film is removed and burrs may occur on the edge of the remaining portion of the electrode film. If the above-mentioned burr comes into contact with the package or is deformed, there is a problem that the frequency adjusted by trimming fluctuates.

[0007] Therefore, the present invention provides a high-quality piezoelectric vibrating piece, a piezoelectric vibrator, an oscillator, and a method for manufacturing a piezoelectric vibrating piece that suppresses frequency fluctuations after frequency adjustment and has excellent vibration characteristics. [Means for solving the problem]

[0008] The piezoelectric vibrating piece of the present invention comprises a piezoelectric plate having a pair of vibrating arms, an electrode film disposed on the front and back surfaces of the piezoelectric plate, and a weight metal film for frequency adjustment disposed on the electrode film on the front surface side of the vibrating arms, the back surface of the vibrating arms having a back-side exposed portion where the piezoelectric plate is exposed, the front surface of the vibrating arms having a front-side exposed portion where the weight metal film and the electrode film are removed to expose the piezoelectric plate, The electrode film is further disposed on a tip surface facing the longitudinal direction of the vibrating arm portion, The entirety of the front-side exposed portion overlaps the back-side exposed portion with a gap therebetween when viewed in the thickness direction of the piezoelectric plate.

[0009] According to the present invention, when the front-side exposed portion is formed in the process of removing the weight metal film together with the electrode film underneath using a laser for frequency adjustment, the laser light transmitted through the piezoelectric plate passes through the rear-side exposed portion. Therefore, the laser light is not irradiated onto the electrode film on the rear surface of the piezoelectric plate, so that the formation of burrs on the electrode film on the rear surface side can be suppressed. Therefore, the frequency fluctuation caused by the falling off or deformation of the burrs on the electrode film can be suppressed. Therefore, the frequency fluctuation after frequency adjustment is suppressed, and a high-quality piezoelectric vibrating piece with excellent vibration characteristics can be provided. Furthermore, according to the present invention, when forming the weight metal film, the weight metal film may wrap around the end face of the vibrating arm, but compared to when the end face of the vibrating arm is exposed, the electrode film on the end face of the vibrating arm serves as a base for the weight metal film, and the adhesion of the weight metal film is increased. Therefore, the falling off of the weight metal film can be suppressed. Therefore, the frequency fluctuation caused by the falling off of the weight metal film can be suppressed. Therefore, the frequency fluctuation after the frequency adjustment can be suppressed.

[0012] In the above-mentioned piezoelectric vibrating piece, the back surface of the vibrating arm may have a tip edge on the tip side of the vibrating arm, and a pair of side edges extending from the tip edge to the base end side of the vibrating arm, and the back side exposed portion may include the tip edge and the side edges on the back surface of the vibrating arm.

[0013] If the rear exposed portion does not include the tip edge and side edge of the rear surface of the vibrating arm, the entire outer line of the rear exposed portion coincides with the edge of the electrode film on the rear surface. In this case, the weight metal film on the front surface must be removed inside the outer line of the rear exposed portion in a plan view. In the present invention, the edge of the electrode film on the rear surface does not exist in the portion of the outer line of the rear exposed portion that coincides with the tip edge and side edge of the rear surface of the vibrating arm. Therefore, even if the weight metal film on the tip edge and side edge of the front surface of the vibrating arm is removed, it is possible to suppress the transmitted laser light from being irradiated to the electrode film on the rear surface. Therefore, it is possible to increase the ratio of the area of ​​the front exposed portion to the area of ​​the rear exposed portion compared to the case where the rear exposed portion does not include the tip edge and side edge of the rear surface. Therefore, the frequency adjustment range can be set to be wide. In addition, since the weight metal film can be removed in order from the tip of the vibrating arm toward the base end, the frequency adjustment can be performed efficiently.

[0014] In the above-mentioned piezoelectric vibrating piece, a portion of the electrode film arranged on the rear surface of the vibrating arm may straddle an edge of the weight metal film on the base end side of the vibrating arm when viewed from the thickness direction.

[0015] According to the present invention, in a piezoelectric vibrating piece in which an excitation electrode is provided on the base end side of a weight metal film, the wiring connected to the excitation electrode can be formed of an electrode film so as to overlap with the weight metal film in a plan view. Therefore, even if the proportion of the area occupied by the weight metal film increases as the piezoelectric vibrating piece is made smaller, the wiring connected to the excitation electrode can be reliably formed to ensure reliability.

[0016] A piezoelectric vibrator of the present invention includes the above-mentioned piezoelectric vibrating piece and a package that hermetically seals the piezoelectric vibrating piece.

[0017] According to the present invention, since the above-mentioned piezoelectric vibrating piece is included, a high-quality piezoelectric vibrator having excellent operational reliability can be obtained.

[0018] An oscillator of the present invention includes the above-described piezoelectric vibrator, and the piezoelectric vibrator is electrically connected to an integrated circuit as an oscillator.

[0019] According to the present invention, since the above-mentioned piezoelectric vibrating piece is included, a high-quality oscillator having excellent operational reliability can be obtained.

[0020] A method for manufacturing a piezoelectric vibrating piece according to the present invention includes an electrode film forming step of arranging electrode films on the front and back surfaces of a piezoelectric plate having a pair of vibrating arms, and forming a back-side exposed portion on the back surface of the vibrating arms where the piezoelectric plate is exposed; a metal film forming step of forming a weight metal film on the electrode film on the front surface side of the vibrating arms so that at least a portion of the weight metal film overlaps with the back-side exposed portion when viewed in a thickness direction of the piezoelectric plate; and a trimming step of removing the weight metal film and the electrode film on the front surface side of the vibrating arms within a range that overlaps with the back-side exposed portion when viewed in the thickness direction and is spaced from the electrode film on the back surface, by using a laser that is irradiated from the weight metal film side in a direction passing through the back-side exposed portion. In the metal film forming step, the weight metal film is characterized in that, when formed, it wraps around onto the electrode film formed on the tip surface.

[0021] According to the present invention, since the laser light transmitted through the piezoelectric plate in the trimming process passes through the exposed backside portion, it is possible to prevent the electrode film on the backside of the vibrating arm from being irradiated with the laser light and forming burrs. Therefore, it is possible to prevent frequency fluctuations caused by the burrs falling off or deformation of the electrode film. Therefore, it is possible to manufacture a high-quality piezoelectric vibrating piece with excellent vibration characteristics by preventing frequency fluctuations after frequency adjustment. Furthermore, according to the present invention, when forming the weight metal film, the weight metal film may wrap around the end face of the vibrating arm, but compared to when the end face of the vibrating arm is exposed, the electrode film on the end face of the vibrating arm serves as a base for the weight metal film, and the adhesion of the weight metal film is increased. Therefore, the falling off of the weight metal film can be suppressed. Therefore, the frequency fluctuation caused by the falling off of the weight metal film can be suppressed. Therefore, the frequency fluctuation after the frequency adjustment can be suppressed.

[0022] In the above-mentioned method for manufacturing a piezoelectric vibrating reed, a picosecond laser or a femtosecond laser may be used in the trimming step.

[0023] According to the present invention, unlike the case where a nanosecond laser is used, it is possible to suppress the formation of burrs on the electrode film and the weight metal film on the surface side of the vibrating arm portion.

[0024] In the above-mentioned method for manufacturing a piezoelectric vibrating piece, the electrode film forming process may include an electrode film forming process for forming the electrode film, and a patterning process for patterning the electrode film to form an excitation electrode and the back side exposed portion.

[0025] According to the present invention, the rear-side exposed portion can be formed with the same processing accuracy as the excitation electrode. In addition, since no additional process for forming the rear-side exposed portion is required compared to the conventional manufacturing method, an increase in manufacturing costs can be suppressed.

[0026] In the above-described method for manufacturing a piezoelectric vibrating reed, the electrode film forming step may include forming the electrode film in a state where a part of the back surface of the vibrating arm portion is masked, and the part may be the exposed back surface portion.

[0027] According to the present invention, the backside exposed portion can be formed when the electrode film is formed, and therefore, since there is no need to add a step for forming the backside exposed portion to the conventional manufacturing method, an increase in manufacturing costs can be suppressed. Effect of the Invention

[0028] According to the present invention, it is possible to provide a high-quality piezoelectric vibrating piece, a piezoelectric vibrator, an oscillator, and a method for manufacturing a piezoelectric vibrating piece that suppresses frequency fluctuations after frequency adjustment and has excellent vibration characteristics. [Brief description of the drawings]

[0029] [Figure 1] FIG. 2 is a diagram illustrating an oscillator according to an embodiment. [Diagram 2] 1 is an external perspective view of a piezoelectric vibrator according to an embodiment; [Diagram 3] FIG. 4 is a plan view of the piezoelectric vibrator with the sealing plate removed. [Figure 4] 4 is a cross-sectional view corresponding to line IV-IV in FIG. 3. [Diagram 5] FIG. 2 is an exploded perspective view of the piezoelectric vibrator according to the embodiment. [Figure 6] 1 is a plan view of a piezoelectric vibrating piece according to a first embodiment. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 7 is a cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] 4 is a flowchart showing a method for manufacturing the piezoelectric vibrating piece according to the first embodiment. [Figure 10] 9 is a cross-sectional view illustrating a method for manufacturing the piezoelectric vibrating reed according to the first embodiment, which corresponds to FIG. 8. [Figure 11] 9 is a cross-sectional view illustrating a method for manufacturing the piezoelectric vibrating reed according to the first embodiment, which corresponds to FIG. 8. [Figure 12] FIG. 11 is a plan view of a piezoelectric vibrating piece according to a second embodiment. [Figure 13] 13 is a cross-sectional view taken along line XIII-XIII in FIG. 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, components having the same or similar functions are denoted by the same reference numerals. In addition, duplicate descriptions of those components may be omitted.

[0031] (Oscillator of the embodiment) FIG. 1 is a diagram showing an oscillator according to an embodiment. As shown in FIG. 1, the oscillator 100 includes a substrate 101, an electronic component 102, an integrated circuit 103, and a piezoelectric vibrator 1. The electronic component 102 is, for example, a capacitor, and is mounted on the substrate 101. The integrated circuit 103 is for the oscillator, and is also mounted on the substrate 101. The integrated circuit 103 is electrically connected to the piezoelectric vibrator 1 and the electronic component 102 via wiring (not shown). The piezoelectric vibrator 1 is, for example, mounted on the substrate 101 near the integrated circuit 103. The piezoelectric vibrator 1 functions as an oscillator. The piezoelectric vibrator 1 will be described later. At least a part of the oscillator 100 may be appropriately molded with a resin (not shown).

[0032] In the oscillator 100, when power is supplied to the piezoelectric vibrator 1, a piezoelectric vibrating piece 3 (see FIG. 5) of the piezoelectric vibrator 1 vibrates. The vibration of the piezoelectric vibrating piece 3 is converted into an electric signal by the piezoelectric characteristics of the piezoelectric vibrating piece 3. This electric signal is output from the piezoelectric vibrator 1 to the integrated circuit 103. The integrated circuit 103 executes various processes on the electric signal output from the piezoelectric vibrator 1 to generate a frequency signal.

[0033] The oscillator 100 can be used, for example, as a single-function oscillator for a clock, a timing control device that controls the operation timing of various devices such as a computer, a device that provides time or a calendar, etc. The integrated circuit 103 is configured according to the functions required for the oscillator 100, and may include a so-called RTC (real-time clock) module.

[0034] (Piezoelectric vibrator according to an embodiment) Fig. 2 is an external perspective view of a piezoelectric vibrator according to an embodiment. Fig. 3 is a plan view of the piezoelectric vibrator with a sealing plate removed. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. Fig. 5 is an exploded perspective view of the piezoelectric vibrator according to an embodiment. 2 to 5, the piezoelectric vibrator 1 is a so-called ceramic package type surface mount vibrator. The piezoelectric vibrator 1 includes a package 2 having an airtightly sealed cavity C therein, and a piezoelectric vibrating piece 3 housed in the cavity C. The piezoelectric vibrator 1 has a rectangular parallelepiped shape. In this embodiment, the longitudinal direction of the piezoelectric vibrator 1 in a plan view is referred to as the longitudinal direction L, the lateral direction is referred to as the width direction W, and the direction perpendicular to the longitudinal direction L and the width direction W is referred to as the thickness direction T.

[0035] The package 2 includes a package body 5 and a sealing plate 6 that is joined to the package body 5 and forms a cavity C between the package body 5 and the sealing plate 6. The package body 5 includes a first base substrate 10 and a second base substrate 11 that are bonded together in a stacked state, and a seal ring 12 that is bonded onto the second base substrate 11.

[0036] The first base substrate 10 is a ceramic substrate having a rectangular shape in a plan view seen from the thickness direction T. The upper surface of the first base substrate 10 forms the bottom of a cavity C. A pair of external electrodes 21A, 21B are formed on the lower surface of the first base substrate 10 with a gap therebetween in the longitudinal direction L. The external electrodes 21A, 21B are formed of a single layer film made of a single metal formed by, for example, vapor deposition or sputtering, or a laminated film in which different metals are laminated.

[0037] The second base substrate 11 is a ceramic substrate having the same outer shape as the first base substrate 10 in a plan view, and is integrally bonded to the first base substrate 10 by sintering or the like in a state where it is stacked on the first base substrate 10. Note that the ceramic material used for each of the base substrates 10, 11 can be, for example, HTCC (High Temperature Co-Fired Ceramic) made of alumina, LTCC (Low Temperature Co-Fired Ceramic) made of glass ceramics, or the like.

[0038] As shown in Fig. 3 to Fig. 5, the second base substrate 11 has a through-hole 11a that penetrates the second base substrate 11 in the thickness direction T. The through-hole 11a has a rounded rectangular shape in a plan view. Mounting portions 14A and 14B that protrude inward in the width direction W are formed on the inner surface of the through-hole 11a at portions located on both sides in the width direction W. The mounting portions 14A and 14B are located in the center of the second base substrate 11 in the longitudinal direction L.

[0039] A pair of electrode pads 20A, 20B are formed on the mounting parts 14A, 14B as connection electrodes with the piezoelectric vibrating piece 3. The electrode pads 20A, 20B are formed of a single-layer film of a single metal formed by, for example, vapor deposition or sputtering, or a laminated film in which different metals are laminated, like the external electrodes 21A, 21B described above. The electrode pads 20A, 20B and the external electrodes 21A, 21B are electrically connected to each other via through-wires (not shown) that penetrate each of the base substrates 10, 11 in the thickness direction T.

[0040] At the four corners of each of the base substrates 10, 11, a cutout portion 15 having a 1 / 4 circular arc shape in plan view is formed over the entire thickness direction T of both base substrates 10, 11. Each of the base substrates 10, 11 is produced, for example, by stacking and bonding two wafer-like ceramic substrates, forming a plurality of through holes penetrating both ceramic substrates in a matrix pattern, and cutting both ceramic substrates in a lattice pattern using each through hole as a reference. At this time, the through holes are divided into four to form the above-mentioned cutout portions 15.

[0041] The seal ring 12 is a conductive frame-shaped member that is slightly smaller than the outer shape of each of the base substrates 10, 11, and is joined to the upper surface of the second base substrate 11. Specifically, the seal ring 12 is joined to the second base substrate 11 by baking with a brazing material such as silver brazing or a solder material, or by welding to a metal bonding layer formed on the second base substrate 11. The seal ring 12 constitutes the side wall of the cavity C together with the inner surface of the second base substrate 11 (the through portion 11a). In the illustrated example, the inner surface of the seal ring 12 is disposed flush with the inner surface of the second base substrate 11.

[0042] The material of the seal ring 12 may be, for example, a nickel-based alloy, and specifically may be selected from Kovar, Elinvar, Invar, 42-alloy, etc. In particular, it is preferable to select a material for the seal ring 12 that has a thermal expansion coefficient close to that of the base substrates 10 and 11, which are made of ceramics. For example, the base substrates 10 and 11 may have a thermal expansion coefficient of 6.8×10 -6 When alumina having a thermal expansion coefficient of 5.2×10 / °C is used, the seal ring 12 has a thermal expansion coefficient of 5.2×10 -6 / ℃ Kovar and thermal expansion coefficient 4.5~6.5×10 -6 It is preferable to use 42-alloy with a temperature of 100°C.

[0043] The sealing plate 6 is made of a conductive substrate and is joined onto the seal ring 12 to airtightly seal the inside of the package body 5. The space defined by the seal ring 12, the sealing plate 6, and each of the base substrates 10 and 11 constitutes a hermetically sealed cavity C.

[0044] The piezoelectric vibrating piece 3 is accommodated in a cavity C of a hermetically sealed package 2. The piezoelectric vibrating piece 3 includes a piezoelectric plate 30 formed of a piezoelectric material such as quartz crystal, lithium tantalate, or lithium niobate. The piezoelectric plate 30 has a pair of vibrating arms 31, 32 and a pair of supporting arms 33, 34. The piezoelectric vibrating piece 3 is mounted on the package 2 in the cavity C by supporting the supporting arms 33, 34 on the mounting parts 14A, 14B of the package 2 with a conductive adhesive. As a result, the piezoelectric vibrating piece 3 is supported in the cavity C with the vibrating arms 31, 32 floating above the base substrates 10, 11. Two excitation electrodes 41, 42 (see FIG. 6) are arranged on the outer surfaces of the vibrating arms 31, 32 to vibrate the pair of vibrating arms 31, 32 when a predetermined voltage is applied.

[0045] To operate the piezoelectric vibrator 1, a predetermined voltage is applied to the external electrodes 21A, 21B (see FIG. 2). Then, a current flows through the excitation electrodes 41, 42, and an electric field is generated between the excitation electrodes 41, 42. The vibrating arms 31, 32 vibrate at a predetermined resonance frequency, for example, in a direction approaching or separating from each other (width direction W), due to an inverse piezoelectric effect caused by the electric field generated between the excitation electrodes 41, 42. The vibration of the vibrating arms 31, 32 is used as a time source, a timing source for a control signal, a reference signal source, etc.

[0046] (Piezoelectric vibrating piece according to the first embodiment) The piezoelectric vibrating piece 3 of the first embodiment will be described in detail. FIG. 6 is a plan view of the piezoelectric vibrating reed according to the first embodiment. 6, the piezoelectric vibrating piece 3 includes a piezoelectric plate 30, an electrode film 40 disposed on the outer surface including the front and back surfaces of the piezoelectric plate 30, and a weight metal film 50 for frequency adjustment. In this embodiment, the longitudinal direction L, width direction W, and thickness direction T of the piezoelectric vibrator 1 coincide with the longitudinal direction, width direction, and thickness direction, respectively, of the piezoelectric vibrating piece 3. Therefore, in the following description of the piezoelectric vibrating piece 3, the longitudinal direction L, width direction W, and thickness direction T of the piezoelectric vibrator 1 are used.

[0047] The piezoelectric plate 30 includes a base 35, a pair of vibrating arms 31, 32 (first vibrating arm 31 and second vibrating arm 32) extending from the base 35 in a longitudinal direction L, and a pair of supporting arms 33, 34 (first supporting arm 33 and second supporting arm 34) located on both sides of the base 35 in a width direction W. The piezoelectric plate 30 is formed so that its planar shape as viewed from the thickness direction T is approximately symmetrical with respect to a central axis O along the longitudinal direction L. Note that in this embodiment, quartz crystal will be used as an example of the piezoelectric material forming the piezoelectric plate 30.

[0048] The first vibrating arm 31 and the second vibrating arm 32 are arranged in parallel to each other in the width direction W. Each vibrating arm 31, 32 has a base end on the base portion 35 side as a fixed end and a tip end as a free end, and vibrates in a direction approaching or separating from each other (width direction W). Each vibrating arm 31, 32 has a main body 36 extending from the base end of each vibrating arm 31, 32 to the tip, and a weight 38 located at the tip of each vibrating arm 31, 32.

[0049] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6 and 7, a groove 37 is formed in the main body 36. The groove 37 is recessed in the thickness direction T on both main surfaces of the main body 36 and extends along the longitudinal direction L. The groove 37 is formed from the vicinity of the base end of each of the vibrating arms 31 and 32 to the vicinity of the tip of the main body 36.

[0050] 6, the weights 38 each extend in the longitudinal direction L from the tip of the main body 36. The weights 38 are rectangular in plan view and are formed to be wider in the width direction W than the main body 36. This makes it possible to increase the mass of the tip of each of the vibrating arms 31, 32 and the moment of inertia during vibration, and to reduce the length of each of the vibrating arms 31, 32 compared to a piezoelectric vibrating piece 3 that does not have the weights 38.

[0051] Each of the supporting arms 33, 34 has an L-shape in plan view, and surrounds the base 35 and the vibrating arms 31, 32 (main body 36) from the outside in the width direction W. Specifically, each of the supporting arms 33, 34 protrudes from both end faces of the base 35 in the width direction W toward the outside in the width direction W, and then extends parallel to each of the vibrating arms 31, 32 along the longitudinal direction L. The first supporting arm 33 is disposed on the same side of the central axis O as the first vibrating arm 31. The second supporting arm 34 is disposed on the same side of the central axis O as the second vibrating arm 32.

[0052] The electrode film 40 is, for example, a laminated film of chromium (Cr) and gold (Au), which is formed by depositing a thin film of gold on a chromium film that has good adhesion to quartz crystal. However, the film configuration of the electrode film 40 is not limited to this, and for example, a thin film of gold may be further laminated on a laminated film of chromium and nichrome (NiCr), or a single layer film of chromium, nickel, aluminum (Al), titanium (Ti), or the like may be used.

[0053] The electrode film 40 includes excitation electrodes 41 and 42 , mount electrodes 43 and 44 , and a connection wiring 45 . The excitation electrodes 41, 42 are provided in two systems on the outer surface of the main body 36 of the vibrating arms 31, 32. The excitation electrodes 41, 42 are patterned so as to be electrically insulated from each other. The excitation electrodes 41, 42 have a first excitation electrode 41 and a second excitation electrode 42. The first excitation electrode 41 is formed on both side surfaces facing the width direction W of the main body 36 of the first vibrating arm 31 and on the groove 37 of the second vibrating arm 32. The second excitation electrode 42 is formed on the groove 37 of the first vibrating arm 31 and on both side surfaces of the main body 36 of the second vibrating arm 32. The excitation electrodes 41, 42 vibrate the vibrating arms 31, 32 in the width direction W when a predetermined driving voltage is applied between the excitation electrodes 41, 42.

[0054] The mount electrodes 43, 44 are provided as mount parts when mounting the piezoelectric vibrating piece 3 on the package 2. The mount electrodes 43, 44 are provided on the main surfaces (rear surfaces) at the tips of the support arms 33, 34. Specifically, the mount electrodes 43, 44 include a first mount electrode 43 arranged on the first support arm 33 and a second mount electrode 44 arranged on the second support arm 34. The first mount electrode 43 is electrically connected to the first excitation electrode 41. The second mount electrode 44 is electrically connected to the second excitation electrode 42. The mount electrodes 43, 44 are electrically connected to the electrode pads 20A, 20B of the package 2 via a conductive adhesive.

[0055] The connection wiring 45A, 45B connect the excitation electrodes 41, 42 to each other on the tip side of the vibrating arm 31, 32. The connection wiring 45 has a first connection wiring 45A connected to the first excitation electrode 41 and a second connection wiring 45B connected to the second excitation electrode 42. The first connection wiring 45A electrically connects the first excitation electrodes 41 on both side surfaces of the first vibrating arm 31 to each other. The second connection wiring 45B electrically connects the second excitation electrodes 42 on both side surfaces of the second vibrating arm 32 to each other. Since the first connection wiring 45A and the second connection wiring 45B are formed in the same manner, in the following description, when the first connection wiring 45A and the second connection wiring 45B are not to be distinguished from each other, they are simply referred to as the connection wiring 45.

[0056] Each connection wiring 45 has a side portion 46, a front portion 47, and a back portion 48. The side portion 46 is disposed on the entire end surface of the vibrating arms 31, 32 on the tip side of the groove portion 37 in the vibrating arms 31, 32. The end surface is a surface that connects the main surfaces to each other, and includes a tip surface facing the longitudinal direction L and a side surface facing the width direction W. The front portion 47 is disposed on the surface 64 of the vibrating arms 31, 32 on the tip side of the groove portion 37 in the vibrating arms 31, 32. The front portion 47 is disposed at an interval in the longitudinal direction L with respect to the excitation electrodes 41, 42. The front portion 47 extends so as to straddle the boundary between the main body portion 36 and the weight portion 38 in the vibrating arms 31, 32. The side edge of the front portion 47 is connected to the side portion 46. The back portion 48 is disposed on the back surface 63 of the vibrating arms 31, 32, closer to the tip end than the groove portion 37 of the vibrating arms 31, 32. The back portion 48 is disposed at a distance from the excitation electrodes 41, 42 in the longitudinal direction L. The back portion 48 extends so as to straddle the boundary between the main body portion 36 and the weight portion 38 of the vibrating arms 31, 32. The side edges of the back portion 48 are connected to the side portions 46.

[0057] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. As shown in Figs. 6 and 8, the rear part 48 of the connection wiring 45 is arranged so as to expose a part of the rear surface 63 of the vibrating arm parts 31, 32. As a result, the rear surface 63 of the vibrating arm parts 31, 32 has a rear exposed part 61 where the piezoelectric plate 30 is exposed. The rear exposed part 61 is provided only on the rear surface of the weight part 38. The rear exposed part 61 is formed so as to include a tip edge 63t of the rear surface 63 of the vibrating arm parts 31, 32. Furthermore, the rear exposed part 61 is formed so as to include a pair of side edges 63s extending from the tip edge 63t on the rear surface 63 of the vibrating arm parts 31, 32 to the base end side of the vibrating arm parts 31, 32. The rear exposed part 61 is formed in a rectangular shape.

[0058] The weight metal film 50 is disposed on the electrode film 40 on the surface 64 side of the vibrating arms 31, 32. The weight metal film 50 increases the mass at the tip of each vibrating arm 31, 32, and suppresses the increase in frequency associated with the shortening of the length of each vibrating arm 31, 32. The weight metal film 50 is made of, for example, Au or Ag, and has a thickness of about 1 to 10 μm. The weight metal film 50 is disposed on the front portion 47 of the connection wiring 45 of the electrode film 40. The weight metal film 50 is formed so that the side edges on both sides in the width direction W match the side edges of the front portion 47 of the connection wiring 45. The edge of the weight metal film 50 on the base end side of the vibrating arms 31, 32 extends in the width direction W and is located on the tip side of the edge of the front portion 47 of the connection wiring 45 on the base end side of the vibrating arms 31, 32. The rear portion 48 of the connection wiring 45 straddles the edge of the base end side of the weight metal film 50 in a plan view.

[0059] The front portion 47 of the connection wiring 45 and the weight metal film 50 are arranged so as to expose a part of the surface 64 of the vibrating arms 31, 32. As a result, the surface 64 of the vibrating arms 31, 32 has a front-side exposed portion 62 where the piezoelectric plate 30 is exposed. The edges of the front portion 47 of the connection wiring 45 and the weight metal film 50 coincide with each other on the outline of the front-side exposed portion 62 in a plan view. The front-side exposed portion 62 is formed to include a tip edge 64t of the surface 64 of the vibrating arms 31, 32. Furthermore, the front-side exposed portion 62 is formed to include a pair of side edges 64s extending from the tip edge 64t on the surface 64 of the vibrating arms 31, 32 to the base end side of the vibrating arms 31, 32. The entire front-side exposed portion 62 overlaps the back-side exposed portion 61 in a plan view. The entire front-side exposed portion 62 is disposed at a distance from the electrode film 40 (the rear portion 48 of the connection wiring 45) on the rear surface 63 of the vibrating arm portions 31, 32 in a plan view.

[0060] (Method of manufacturing the piezoelectric vibrating piece according to the first embodiment) A method for manufacturing the piezoelectric vibrating reed 3 of the first embodiment will be described. FIG. 9 is a flowchart showing a method for manufacturing the piezoelectric vibrating reed according to the first embodiment. As shown in FIG. 9, the method for manufacturing the piezoelectric vibrating reed 3 of the first embodiment includes an outer shape forming step S10, an electrode film forming step S20, a metal film forming step S30, and a trimming step S40.

[0061] First, the outer shape forming step S10 is performed. In the outer shape forming step S10, the piezoelectric plate 30 is formed on a wafer of a piezoelectric material. First, a mask having a shape corresponding to the shape of the piezoelectric plate 30 in a planar view is formed on both sides of the wafer by photolithography technology. Next, the wafer is wet-etched. As a result, the unmasked areas of the wafer are selectively removed, and the wafer is shaped into the shape of the piezoelectric plate 30 in a planar view.

[0062] Next, grooves 37 are formed on both main surfaces (front and back) of each of the vibrating arms 31 and 32. Specifically, a mask having a shape corresponding to the shape of the grooves 37 is formed on both main surfaces of the wafer by photolithography. Next, half-etching is performed on the wafer by wet etching to an extent that the grooves 37 do not penetrate the wafer. As a result, a piezoelectric plate 30 having the grooves 37 is formed on the wafer.

[0063] Next, an electrode film forming process S20 is performed. In the electrode film forming process S20, the electrode film 40 is disposed on the front and back surfaces of the piezoelectric plate 30, and a back-side exposed portion 61 is formed on the back surfaces of the vibrating arm portions 31 and 32 of the piezoelectric plate 30. In this embodiment, the electrode film forming process S20 includes an electrode film forming process S21 for forming the electrode film 40, and a patterning process S22 for patterning the electrode film 40 to form the excitation electrodes 41 and 42 and the back-side exposed portion 61.

[0064] In the electrode film forming step S21, an electrode film 40 is formed on the front and rear surfaces and end faces of the wafer by sputtering, deposition, or the like.

[0065] In the patterning step S22, the electrode film 40 is patterned to form two systems of electrodes 41-44 and connection wirings 45A, 45B on the piezoelectric plate 30. First, a mask made of a resist material having a shape corresponding to the outer shape of each of the electrodes 41-44 and the connection wirings 45A, 45B is formed on the outer surface of the electrode film 40 by photolithography. At this time, the mask is formed so as to cover the portion corresponding to the front side exposed portion 62. Next, the electrode film 40 is etched to selectively remove the electrode film 40 in the unmasked region. As a result, the excitation electrodes 41, 42, the mount electrodes 43, 44, and the connection wirings 45A, 45B are formed on the piezoelectric plate 30. In addition, as shown in FIG. 10, a back side exposed portion 61 is formed on the back side 63 of the vibrating arm portions 31, 32 of the piezoelectric plate 30. In this step, the electrode film 40 is arranged on the portion corresponding to the front side exposed portion 62 of the vibrating arm portions 31, 32 of the piezoelectric plate 30.

[0066] Next, a metal film forming step S30 is performed. As shown in Fig. 11, in the metal film forming step S30, a weight metal film 50 for frequency adjustment is formed on the electrode film 40 on the front surface 64 side of each vibrating arm portion 31, 32. At this time, the weight metal film 50 is formed so that at least a part of the weight metal film 50 overlaps the rear exposed portion 61 in a plan view. The weight metal film 50 can be formed by, for example, deposition using a metal mask.

[0067] Next, a trimming process S40 is performed. In the trimming process S40, the resonance frequency of each piezoelectric vibrating piece 3 is roughly adjusted. In the trimming process S40, the weight metal film 50 is partially removed (trimmed) from the surface 64 of the vibrating arm portions 31, 32 together with the electrode film 40 (surface portion 47 of the connection wiring 45) thereunder, depending on the adjustment amount of the resonance frequency. In the trimming process S40, the weight metal film 50 and the electrode film 40 are removed using a pulsed laser. As the pulsed laser, a picosecond laser or a femtosecond laser is preferable, and a picosecond laser is optimal.

[0068] In the trimming process S40, the weight metal film 50 is irradiated with a laser beam from the front side, thereby melting and removing the irradiated portion of the weight metal film 50 together with the electrode film 40 directly below it. At this time, the weight metal film 50 and the electrode film 40 are removed by the laser on the front surface 64 side of the vibrating arms 31, 32 within a range that overlaps with the back side exposed portion 61 in a plan view and is spaced apart from the electrode film 40 on the back surface 63. The above-mentioned back side exposed portion 61 is formed by adjusting the irradiation range of the laser beam according to the adjustment amount of the resonance frequency. Then, the weight metal film 50 is trimmed, and the inertia moment of the vibrating arms 31, 32 changes, thereby changing the frequency of the vibrating arms 31, 32.

[0069] As described above, the piezoelectric vibrating piece 3 of this embodiment includes the electrode film 40 arranged on the front and back surfaces of the piezoelectric plate 30, and the weight metal film 50 for frequency adjustment arranged on the electrode film 40 on the front surface 64 side of the vibrating arm portions 31 and 32. The back surface 63 of the vibrating arm portions 31 and 32 has a back side exposed portion 61 where the piezoelectric plate 30 is exposed. The front surface 64 of the vibrating arm portions 31 and 32 has a front side exposed portion 62 where the weight metal film 50 and the electrode film 40 are removed to expose the piezoelectric plate 30. The entire front side exposed portion 62 overlaps the back side exposed portion 61 with a gap from the electrode film 40 (back portion 48 of the connection wiring 45) on the back surface 63 of the vibrating arm portions 31 and 32 in a plan view. According to this configuration, when the front side exposed portion 62 is formed in the process of removing the weight metal film 50 together with the electrode film 40 thereunder using a laser for frequency adjustment, the laser light transmitted through the piezoelectric plate 30 passes through the back side exposed portion 61. Therefore, the laser light is not irradiated onto the electrode film 40 on the rear surface 63 of the piezoelectric plate 30, so that it is possible to suppress the formation of burrs on the electrode film 40 on the rear surface 63 side. This makes it possible to suppress frequency fluctuations caused by the falling off or deformation of burrs on the electrode film 40. This makes it possible to provide a high-quality piezoelectric vibrating piece 3 that is excellent in vibration characteristics by suppressing frequency fluctuations after frequency adjustment.

[0070] Moreover, the electrode film 40 has a side portion 46 of the connection wiring 45 arranged on the end faces of the vibrating arms 31, 32 around the front exposed portion 62. According to this configuration, when the weight metal film 50 is formed, the weight metal film 50 may wrap around the end faces of the vibrating arms 31, 32. However, compared to the case where the end faces of the vibrating arms 31, 32 are exposed, the side portion 46 of the connection wiring 45 serves as a base for the weight metal film 50, and the adhesion of the weight metal film 50 is improved. Therefore, the falling off of the weight metal film 50 can be suppressed. Therefore, the frequency fluctuation caused by the falling off of the weight metal film 50 can be suppressed. Therefore, the frequency fluctuation after the frequency adjustment can be suppressed.

[0071] In addition, the rear exposed portion 61 includes the tip edge 63t and the side edge 63s on the rear surface 63 of the vibrating arm portions 31 and 32. If the rear exposed portion 61 does not include the tip edge 63t and the side edge 63s of the rear surface 63, the entire outer shape of the rear exposed portion 61 coincides with the edge of the electrode film 40 on the rear surface 63. In this case, the weight metal film 50 on the front surface 64 side must be removed inside the outer shape of the rear exposed portion 61 in a plan view. In this embodiment, the edge of the electrode film 40 on the rear surface 63 does not exist in the part of the outer shape of the rear exposed portion 61 that coincides with the tip edge 63t and the side edge 63s of the rear surface 63. Therefore, even if the weight metal film 50 on the tip edge 64t and the side edge 64s of the front surface 64 is removed, it is possible to suppress the transmitted laser light from being irradiated to the electrode film 40 on the rear surface 63. Therefore, compared with the case where the rear exposed portion 61 does not include the tip edge 63t and the side edge 63s of the rear surface 63, it is possible to increase the ratio of the area of ​​the front exposed portion 62 to the area of ​​the rear exposed portion 61. Therefore, it is possible to set a wide frequency adjustment range. In addition, since the weight metal film 50 can be removed in order from the tip end of the vibrating arm portions 31 and 32 toward the base end side, it is possible to efficiently adjust the frequency.

[0072] Furthermore, the back portion 48 of the connection wiring 45 straddles the base end side edge of the vibrating arm portions 31, 32 in the weight metal film 50 in a plan view. According to this configuration, in a piezoelectric vibrating piece 3 in which the excitation electrodes 41, 42 are provided on the base end side of the weight metal film 50, the connection wiring 45 connected to the excitation electrodes 41, 42 can be formed in the electrode film 40 so as to overlap with the weight metal film 50 in a plan view. Therefore, even if the proportion of the area occupied by the weight metal film 50 increases as the piezoelectric vibrating piece 3 is miniaturized, the connection wiring 45 can be reliably formed to ensure reliability.

[0073] In the manufacturing method of the piezoelectric vibrating piece 3 of this embodiment, in the trimming process S40, the weight metal film 50 and the electrode film 40 are removed by laser on the front surface 64 side of the vibrating arm parts 31, 32 within a range that overlaps with the back side exposed part 61 in a plan view and is spaced from the electrode film 40 on the back surface 63. As a result, the laser light that has passed through the piezoelectric plate 30 in the trimming process passes through the back side exposed part 61, so that it is possible to prevent the electrode film 40 on the back surface 63 side from being irradiated with the laser light and forming a burr. Therefore, it is possible to suppress the frequency fluctuation caused by the falling off or deformation of the burr of the electrode film 40. Therefore, it is possible to suppress the frequency fluctuation after the frequency adjustment and manufacture a high-quality piezoelectric vibrating piece 3 with excellent vibration characteristics.

[0074] In the trimming process S40, a picosecond laser or a femtosecond laser is used, which, unlike the case where a nanosecond laser is used, makes it possible to suppress the formation of burrs on the electrode film 40 and the weight metal film 50 on the front surface 64 side.

[0075] The electrode film forming process S20 includes an electrode film forming process S21 for forming the electrode film 40, and a patterning process S22 for patterning the electrode film 40 to form the excitation electrodes 41, 42 and the backside exposed portion 61. This allows the backside exposed portion 61 to be formed with the same processing accuracy as the excitation electrodes 41, 42. In addition, since no additional process for forming the backside exposed portion 61 is required compared to the conventional manufacturing method, an increase in manufacturing costs can be suppressed.

[0076] Furthermore, since the piezoelectric vibrator 1 and oscillator 100 of this embodiment have the above-mentioned piezoelectric vibrating piece 3, it is possible to provide a high-quality piezoelectric vibrator 1 and oscillator 100 with excellent operational reliability.

[0077] In the above embodiment, the rear exposed portion 61 is formed in the patterning process S22, but the method of forming the rear exposed portion 61 is not limited to this. In the electrode film forming process, the electrode film 40 may be formed in a state where a part of the rear surface 63 of the vibrating arm portions 31 and 32 is masked, and the masked part may be used as the rear exposed portion 61. According to this method, the rear exposed portion 61 can be formed when the electrode film 40 is formed. Therefore, since there is no additional process for forming the rear exposed portion 61 compared to the conventional manufacturing method, an increase in manufacturing costs can be suppressed.

[0078] [Second embodiment] Next, the second embodiment will be described with reference to Fig. 12 and Fig. 13. In the first embodiment, the front side exposed portion 62 is formed to include the tip edge 64t of the surface 64 of the vibrating arm portions 31 and 32. In contrast, the second embodiment differs from the first embodiment in that the front side exposed portion 62A is formed closer to the base end than the tip edge 64t of the surface 64 of the vibrating arm portions 31 and 32. Note that the configuration other than that described below is the same as that of the first embodiment.

[0079] Fig. 12 is a plan view of the piezoelectric vibrating piece according to the second embodiment, Fig. 13 is a cross-sectional view taken along line XIII-XIII in Fig. 12. As shown in FIG. 12 and FIG. 13, the front-side exposed portion 62A is formed to include only the middle portion of each of a pair of side edges 64s on the surface 64 of the vibrating arms 31 and 32. As a result, the front portion 47A of the connection wiring 45 covers the tip edge 64t of the surface 64 of the vibrating arms 31 and 32, and is connected to the side portion 46 on the tip edge 64t of the surface 64. The weight metal film 50A is disposed on the front portion 47A of the connection wiring 45 on both sides of the front-side exposed portion 62A in the longitudinal direction L. The edges of the front portion 47A of the connection wiring 45 and the weight metal film 50A are aligned with each other on the outline of the front-side exposed portion 62A in a plan view. In this embodiment, the entire front-side exposed portion 62A overlaps the back-side exposed portion 61 with a gap from the electrode film 40 on the back surface 63 of the vibrating arms 31 and 32 in a plan view.

[0080] As described above, in this embodiment, the entire front-side exposed portion 62A overlaps the rear-side exposed portion 61 in plan view with a gap between the electrode film 40 on the rear surface 63 of the vibrating arm portions 31 and 32. Therefore, according to the piezoelectric vibrating piece 3A of this embodiment, it is possible to achieve the same effects as those of the first embodiment.

[0081] The present invention is not limited to the above-described embodiment explained with reference to the drawings, and various modifications are possible within the technical scope of the present invention. For example, in the above embodiment, the piezoelectric vibrating piece 3 is a so-called side arm type vibrating piece in which the supporting arms 33, 34 are arranged outside the vibrating arms 31, 32. However, the present invention is not limited to this, and the piezoelectric vibrating piece may be, for example, a so-called center arm type vibrating piece in which one supporting arm is arranged between a pair of vibrating arms, or a vibrating piece that does not have a supporting arm. Also, a configuration in which no groove is formed in each vibrating arm may be used. Also, a configuration in which no weight is formed in each vibrating arm may be used.

[0082] 6 and 12, the edge of the weight metal film 50, 50A along the front-side exposed portion 62, 62A extends linearly in the width direction W, but the shape of the edge is not limited thereto. For example, the edge of the weight metal film along the front-side exposed portion may extend concavely so as to be recessed inward of the weight metal film.

[0083] In the above embodiment, the back portion 48 of the connection wiring 45 straddles the base end side edge of the weight metal film 50 in a plan view. However, the entire back portion of the connection wiring may be disposed on the base end side of the weight metal film 50 in a plan view.

[0084] In addition, the components in the above-described embodiments can be replaced with well-known components as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0085] REFERENCE SIGNS LIST 1...piezoelectric vibrator 2...package 3,3A...piezoelectric vibrating piece 30...piezoelectric plate 31...first vibrating arm (vibrating arm) 32...second vibrating arm (vibrating arm) 40...electrode film 41,42...excitation electrode 50,50A...weight metal film 61...rear exposed portion 62,62A...front exposed portion 63...rear surface 63s...side edge 63t...tip edge 64...surface 100...oscillator 103...integrated circuit S20...electrode film forming process S21...electrode film deposition process S22...patterning process S30...metal film forming process S40...trimming process

Claims

1. an electrode film forming process for disposing an electrode film on the front and rear surfaces and the tip surface of a piezoelectric plate having a pair of vibrating arms, and forming a rear-side exposed portion in which the piezoelectric plate is exposed on the rear surface of the vibrating arms; a metal film forming step of forming a weight metal film on the electrode film on the front surface side of the vibrating arm portion so that at least a portion of the weight metal film overlaps with the rear exposed portion when viewed from a thickness direction of the piezoelectric plate; a trimming process for removing the weight metal film and the electrode film on the front surface side of the vibrating arm portion by a laser irradiated in a direction passing through the back exposed portion from the weight metal film side within a range that overlaps the back exposed portion when viewed from the thickness direction and is spaced from the electrode film on the back surface; Equipped with In the metal film forming step, the weight metal film is formed on the electrode film formed on the tip surface. A method for manufacturing a piezoelectric vibrating piece.

2. In the trimming step, a picosecond laser or a femtosecond laser is used. A method for manufacturing the piezoelectric vibrating piece according to claim 1 .

3. The electrode film forming step includes: an electrode film forming step of forming the electrode film; a patterning step of patterning the electrode film to form an excitation electrode and the rear side exposed portion; Equipped with The method for manufacturing the piezoelectric vibrating piece according to claim 1 or 2.

4. The electrode film forming step includes forming the electrode film in a state where a part of the back surface of the vibrating arm portion is masked, and the part is set as the back surface exposed portion. The method for manufacturing the piezoelectric vibrating piece according to claim 1 or 2.

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