US20120252319A1

US20120252319A1 - Polishing method, manufacturing method of piezoelectric vibrating piece, piezoelectric vibrator, oscillator, electronic apparatus and radio-controlled timepiece

Info

Publication number: US20120252319A1
Application number: US13/431,301
Authority: US
Inventors: Youichi Fujihira
Original assignee: Seiko Instruments Inc
Current assignee: SII Crystal Technology Inc
Priority date: 2011-03-28
Filing date: 2012-03-27
Publication date: 2012-10-04
Also published as: TW201304404A; CN102723924A; JP2012205258A

Abstract

Provided is a polishing method which can enhance thickness accuracy of a wafer at the time of polishing the wafer. In a polishing method of a crystal wafer (tuning fork substrate) which is held on a carrier between an upper platen and a lower platen, an AT cut wafer for thickness measurement is arranged on the carrier, the AT cut wafer is polished together with the crystal wafer (tuning fork substrate), resonance frequency of the AT cut wafer is detected, and a thickness of the crystal wafer (tuning fork substrate) is controlled based on a detection result.

Description

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2011-070538 filed on Mar. 28, 2011, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a polishing method, a manufacturing method of a piezoelectric vibrating piece, a piezoelectric vibrator having a piezoelectric vibrating piece manufactured by the manufacturing method of a piezoelectric vibrating piece, an oscillator having the piezoelectric vibrator, an electronic apparatus, and a radio-controlled timepiece.
2. Description of the Related Art
Recently, a package product having the following constitution has been popularly used. The package product includes a base substrate and a lid substrate which are bonded to each other by anodic bonding in a laminated state and form a cavity therebetween, and an operating piece which is mounted on a portion of the base substrate positioned inside the cavity.
As this type of package product, for example, there has been known a piezoelectric vibrator which is mounted on a mobile phone or a personal digital assistant and makes use of crystal or the like as a time source, a timing source for a control signal or the like, a reference signal source or the like.
As such a piezoelectric vibrator, there has been known a thickness-shear vibrator formed of an AT vibrating piece which generates thickness shear vibrations and is preferably used as a vibrator in a control using oscillation frequency falling in a MHz band or in a communication device.
The AT vibrating piece is a vibrating piece which is constituted of an AT vibrating plate (crystal vibrating plate) whose profile is formed into a rectangular shape with a predetermined thickness after cutting crystal by AT cutting (the crystal being cut such that front and back main surfaces make an angle of approximately 35 degrees 15 minutes in the counter clockwise direction from a Z axis about an X axis), and an electrode film which is formed on the main surfaces of the AT vibrating plate. In the AT vibrating piece, when a voltage is applied to the electrode film, the AT vibrating plate performs thickness shear vibrations.
In this thickness shear vibrator, resonance frequency is determined based on a thickness of the AT vibrating piece. Accordingly, there has been known a method which adjusts a thickness of the AT vibrating piece corresponding to desired resonance frequency by detecting resonance frequency while performing a polishing operation of an AT cut wafer for manufacturing AT vibrating pieces (see JP-A-3-251365, for example).
The above-mentioned method pertaining to the related art gives rise to a drawback that the method is not applicable to polishing of a tuning fork forming wafer which vibrates in a bending mode.
To cope with the occurrence of such a drawback, there has been known a method where, at the time of polishing the tuning fork forming wafer, a thickness of the tuning fork forming wafer is controlled using a measuring device which measures a moving amount of a suitable part of a polishing device which is displaced corresponding to the thickness of the tuning fork forming wafer.
As such a measurement device, for example, there has been known a measurement device which measures a moving amount of a sintered hard alloy measuring base of a polishing device which is displaced corresponding to a thickness of a tuning fork forming wafer at the time of polishing by bringing a measuring terminal of the measuring device into contact with the sintered hard alloy measuring base.
However, as in the case of this measuring device, when a measuring terminal is brought into contact with a suitable part of the polishing device, the measuring position becomes the same point and hence, wear occurs thus giving rise to a drawback that thickness accuracy of a tuning fork forming wafer cannot be enhanced.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a polishing method which can enhance thickness accuracy of a wafer at the time of polishing the wafer, a manufacturing method of a piezoelectric vibrating piece, a piezoelectric vibrator, an oscillator, an electronic apparatus and a radio-controlled timepiece.
(1) To achieve the above-mentioned object by overcoming the above-mentioned drawbacks, according to one aspect of the present invention, there is provided a polishing method of a tuning fork forming wafer (a crystal wafer (tuning fork substrate) 155 in the embodiment described later, for example) which is held on a carrier (a carrier 157 in the embodiment described later, for example) between an upper platen (an upper platen 151 in the embodiment described later, for example) and a lower platen (a lower platen 152 in the embodiment described later, for example), wherein an AT cut wafer (an AT cut wafer 156 in the embodiment described later, for example) for thickness measurement is arranged on the carrier, the AT cut wafer is polished together with the tuning fork forming wafer, resonance frequency of the AT cut wafer is detected, and a thickness of the tuning fork forming wafer is controlled based on a detection result.
(2) In the above-mentioned polishing method, polishing may preferably be finished when resonance frequency of the AT cut wafer corresponding to a desired thickness of the tuning fork forming wafer is detected predetermined number of times or more within a predetermined time after polishing of the tuning fork forming wafer is started.
(3) In the above-mentioned polishing method, at least one AT cut wafer may preferably be arranged at the center position of the carrier.
(4) In the above-mentioned polishing method, when a plurality of tuning fork forming wafers are held on the carrier, the AT cut wafer may preferably be arranged between the neighboring tuning fork forming wafers.
(5) In the above-mentioned polishing method, the AT cut wafer may preferably have a disc shape.
(6) According to another aspect of the present invention, there is provided a method of manufacturing a piezoelectric vibrating piece (a piezoelectric vibrating piece 5 in the embodiment described later, for example) where an electrode is formed on a surface of a piezoelectric plate which is formed into a profile of the piezoelectric vibrating piece using a photolithography technique, wherein the piezoelectric plate is polished by the above-mentioned polishing method described in any one of (1) to (5).
(7) According to still another aspect of the present invention, there is provided a piezoelectric vibrator (a piezoelectric vibrator 1 in the embodiment described later, for example), wherein the piezoelectric vibrator includes the piezoelectric vibrating piece manufactured by the above-mentioned method of manufacturing a piezoelectric vibrating piece described in (6).
(8) According to still another aspect of the present invention, there is provided an oscillator (an oscillator 100 in the embodiment described later, for example) where the piezoelectric vibrator described in (7) is electrically connected to an integrated circuit as an oscillating element.
(9) According to still another aspect of the present invention, there is provided an electronic apparatus (a portable information device 110 in the embodiment described later, for example) where the piezoelectric vibrator described in (7) is electrically connected to a timer part.
(10) According to still another aspect of the present invention, there is provided a radio-controlled timepiece (a radio-controlled timepiece 130 in the embodiment described later, for example) where the piezoelectric vibrator described in (7) is electrically connected to a filter part.
According to the polishing method of the present invention described in (1), the resonance frequency of the AT cut wafer polished simultaneously with the tuning fork forming wafer is detected and the thickness of the tuning fork forming wafer is controlled based on the detection result and hence, the tuning fork forming wafer can be easily finished to a desired thickness with high accuracy.
According to the polishing method of the present invention described in (2), the thickness accuracy of the tuning fork forming wafer can be enhanced.
Further, the irregularities of thickness among the plurality of tuning fork forming wafers held for each carrier can be decreased, and also irregularities of thickness of the tuning fork forming wafers among a plurality of carriers can be decreased.
According to the polishing method of the present invention described in (3), the rotational balance of the carrier in rotation and revolution can be enhanced for each carrier and hence, parallelism of the tuning fork forming wafer can be enhanced.
According to the polishing method of the present invention described in (4), the thickness accuracy of the tuning fork forming wafer can be enhanced.
According to the polishing method of the present invention described in (5), the rotational balance of the AT cut wafer can be enhanced and hence, the thickness accuracy and parallelism of the tuning fork forming wafer can be enhanced.
According to the manufacturing method of a piezoelectric vibrating piece of the present invention described in (6), thickness accuracy and parallelism of the tuning fork forming wafer can be enhanced and hence, the operational reliability of the piezoelectric vibrating piece can be enhanced.
The piezoelectric vibrator, the oscillator, the electronic apparatus and the radio-controlled timepiece of the present invention can enhance operational reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an appearance perspective view of a piezoelectric vibrator according to an embodiment of the present invention;

FIG. 2 is an internal constitutional view of the piezoelectric vibrator shown in FIG. 1, and is also a view of a piezoelectric vibrating piece as viewed from above in a state where a lid substrate is removed;

FIG. 3 is a cross-sectional view of the piezoelectric vibrator taken along a line A-A in FIG. 2;

FIG. 4 is an exploded perspective view of the piezoelectric vibrator shown in FIG. 1;

FIG. 5 is a perspective view of a metal pin used in manufacturing the piezoelectric vibrator shown in FIG. 1;

FIG. 6 is a flowchart showing the flow of manufacturing the piezoelectric vibrator shown in FIG. 1;

FIG. 7 is a flowchart of manufacturing steps of a piezoelectric vibrating piece;

FIG. 8 is a view showing the overall structure of a polishing device of a crystal wafer (tuning fork substrate) according to the embodiment of the present invention;

FIG. 9 is a schematic view of the polishing device of the crystal wafer (tuning fork substrate) according to the embodiment of the present invention when a lower platen side is observed from an upper platen side;

FIG. 10 is a schematic view of a polishing device of a crystal wafer (tuning fork substrate) according to a modification of the embodiment of the present invention when the lower platen side is observed from the upper platen side;

FIG. 11 is a view showing a step for explaining a manufacturing method of a piezoelectric vibrator, and is also an exploded perspective view of a wafer bonded body;

FIG. 12A to FIG. 12F are views showing steps for forming through electrodes provided to the piezoelectric vibrator shown in FIG. 2;

FIG. 13A and FIG. 13B are views schematically showing a one-side surface polishing device which polishes the metal pin in the step for forming the through electrodes shown in FIG. 2, wherein FIG. 13A is a side view and FIG. 13B is a view when an upper platen side is viewed from a lower platen side;

FIG. 14A and FIG. 14B are views schematically showing a both-surface polishing device which polishes a base substrate forming wafer in a step for forming a through electrodes provided to the piezoelectric vibrator shown in FIG. 2, wherein FIG. 14A is a side view and FIG. 14B is a cross-sectional view taken along a line D-D in FIG. 14A;

FIG. 15 is a constitutional view showing one embodiment of an oscillator according to the present invention;

FIG. 16 is a constitutional view showing one embodiment of an electronic apparatus according to the present invention; and

FIG. 17 is a constitutional view showing one embodiment of a radio-controlled timepiece according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the explanation is made with respect to a polishing method, a manufacturing method of a piezoelectric vibrating piece, a piezoelectric vibrator having a piezoelectric vibrating piece manufactured by the manufacturing method of a piezoelectric vibrating piece, an oscillator having the piezoelectric vibrator, an electronic apparatus, and a radio-controlled timepiece according to one embodiment of the present invention.
Hereinafter, embodiments of the present invention are explained in conjunction with drawings.

(Piezoelectric Vibrator)

FIG. 1 is an appearance perspective view of a piezoelectric vibrator according to this embodiment as viewed from a lid substrate side. FIG. 2 is an internal constitutional view of the piezoelectric vibrator, and is also a view of a piezoelectric vibrating piece as viewed from above in a state where the lid substrate is removed.
Further, FIG. 3 is a cross-sectional view of the piezoelectric vibrator taken along a line A-A in FIG. 2, and FIG. 4 is an exploded perspective view of the piezoelectric vibrator.
As shown in FIG. 1 to FIG. 4, the piezoelectric vibrator 1 of this embodiment is a surface package type piezoelectric vibrator 1 which includes a box-like package 10 where a base substrate (first substrate) 2 and a lid substrate 3 are bonded to each other by anodic bonding by way of a bonding material 23, and a piezoelectric vibrating piece (electronic part) 5 which is housed in a cavity C of the package 10.
The piezoelectric vibrating piece 5 and external electrodes 6, 7 which are mounted on a back surface 2 a (lower surface: first surface in FIG. 3) of the base substrate 2 are electrically connected with each other via a pair of through electrodes 8, 9 which penetrates the base substrate 2.
The base substrate 2 is a transparent insulation substrate made of a glass material such as soda-lime glass, for example, and has a plate shape. A pair of through holes (recessed portions) 21, 22 in which the pair of through electrodes 8, 9 are formed is formed in the base substrate 2.
The through holes 21, 22 have a tapered cross section where a diameter of the through hole 21, 22 is gradually decreased toward a front surface 2 b (upper surface in FIG. 3) from the back surface 2 a of the base substrate 2.
The lid substrate 3 is, in the same manner as the base substrate 2, a transparent insulation substrate made of a glass material such as soda-lime glass, for example, and has a plate shape with a size where the lid substrate 3 can overlap the base substrate 2.
A rectangular recessed portion 3 a in which the piezoelectric vibrating piece 5 is housed is formed on an inner surface 3 b (lower surface in FIG. 3) side of the lid substrate 3.
The recessed portion 3 a forms the cavity C in which the piezoelectric vibrating piece 5 is housed when the base substrate 2 and the lid substrate 3 overlap with each other.
Further, the lid substrate 3 is bonded to the base substrate 2 by anodic bonding by way of the bonding material 23 in a state where the recessed portion 3 a faces the base substrate 2 side in an opposed manner.
That is, the inner surface 3 b side of the lid substrate 3 is constituted of the recessed portion 3 a which is formed in a center portion of the lid substrate 3, and a picture frame region 3 c which is formed around the recessed portion 3 a and forms a bonding surface with the base substrate 2.
The piezoelectric vibrating piece 5 is a tuning-fork-type vibrating piece which is made of a piezoelectric material such as crystal, lithium tantalite or lithium niobate, and the piezoelectric vibrating piece 5 is vibrated when a predetermined voltage is applied to the piezoelectric vibrating piece 5.
The piezoelectric vibrating piece 5 is of a tuning-fork type which includes a pair of vibrating arm portions 24, 25 which is arranged parallel to each other, and a base portion 26 to which proximal end portions of the pair of vibrating arm portions 24, 25 are integrally fixed.
On outer surfaces of the pair of vibrating arm portions 24, 25, an excitation electrode which is constituted of a pair of a first excitation electrode and a second excitation electrode not shown in the drawing for vibrating the pair of vibrating arm portions 24, 25, and a pair of mount electrodes (not shown in the drawing) which electrically connects the first excitation electrode, the second excitation electrode and routing electrodes 27, 28 described later with each other.
The piezoelectric vibrating piece 5 having such a constitution is, as shown in FIG. 2 and FIG. 3, bonded to the routing electrodes 27, 28 formed on the front surface 2 b of the base substrate 2 by bump bonding by making use of bumps B made of gold or the like.
To be more specific, the first excitation electrode of the piezoelectric vibrating piece 5 is bonded to one routing electrode 27 by bump bonding via one mount electrode and the bump B, while the second excitation electrode is bonded to the other routing electrode 28 by bump bonding via the other mount electrode and the bump B.
Accordingly, the piezoelectric vibrating piece 5 is brought into a state where the piezoelectric vibrating piece 5 is supported in a floating state from the front surface 2 b of the base substrate 2, and the respective mount electrodes and the routing electrodes 27, 28 are respectively electrically connected to each other.
External electrodes 6, 7 are arranged on both sides of the back surface 2 a of the base substrate 2 in the longitudinal direction, and the external electrodes 6, 7 are electrically connected to the piezoelectric vibrating piece 5 via the respective through electrodes 8, 9 and the respective routing electrodes 27, 28.
To be more specific, one external electrode 6 is electrically connected to one mount electrode of the piezoelectric vibrating piece 5 via one through electrode 8 and one routing electrode 27.
On the other hand, the other external electrode 7 is electrically connected to the other mount electrode of the piezoelectric vibrating piece 5 via the other through electrode 9 and the other routing electrode 28.
The through electrode 8, 9 is constituted of a core portion 31 which is arranged in the through hole 21, 22, and a cylindrical body 32 which is formed by baking glass frit filled in a gap formed between the core portion 31 and the through hole 21, 22.
The through electrodes 8, 9 completely occupy the through holes 21, 22 thus maintaining the air tightness in the cavity C, and also play a role of making the external electrodes 6, 7 and the routing electrodes 27, 28 conductive with each other.
To be more specific, one through electrode 8 is positioned below the routing electrode 27 between the external electrode 6 and the base portion 26, and the other through electrode 9 is positioned below the routing electrode 28 between the external electrode 7 and the vibrating arm portion 25.
The cylindrical body 32 is formed such that both ends of the cylindrical body 32 are flat and a thickness of the cylindrical body 32 is substantially equal to the thickness of the base substrate 2, and a profile of the cylindrical body 32 is formed into a frusto-conical shape (having a tapered cross section) in conformity with a shape of the through hole 21, 22.
In this embodiment, the cylindrical body 32 is formed of a glass body 32 a.
The glass body 32 a is formed by baking glass frit in a paste form in a state where the glass frit is filled in a gap formed between the through hole 21, 22 and the core portion 31. Accordingly, the glass body 32 a is firmly fixed to the through hole 21, 22.
To be more specific, the glass body 32 a is formed such that the glass body 32 a occupies the through hole 21, 22 over the substantially whole area in the thickness direction of the base substrate 2.
In this case, an end surface of the glass body 32 a on one end side in the thickness direction is formed coplanar with the front surface 2 b of the base substrate 2, and the end surface is exposed in the cavity C together with the core portion 31.
On the other hand, an end surface of the glass body 32 a on the other end side in the thickness direction is formed coplanar with the back surface 2 a of the base substrate 2, and the end surface is exposed to the outside together with the core portion 31.
The core portion 31 is arranged at the center of the cylindrical body 32 (glass body 32 a) in a state where the core portion 31 penetrates a center hole of the cylindrical body 32.
The above-mentioned core portion 31 is a conductive core which is made of a metal material having smaller thermal expansion coefficient α (α=6 to 7 ppm) than glass frit such as a Fe—Ni alloy (42 alloy), for example, and is formed into a columnar shape. The core portion 31 is formed in the same manner as the cylindrical body 32 such that both ends of the core portion 31 are flat, and a thickness of the core portion 31 is approximately equal to a thickness of the base substrate 2.
When the through electrode 8, 9 is formed as a finished product, as described above, the core portion 31 is formed so as to have a cylindrical shape and the same thickness as the base substrate 2. However, in a manufacturing process, for example, as shown in FIG. 5, the core portion 31 forms a bolt-shaped metal pin 37 together with a planar base portion 36 which is connected to one end portion of the core portion 31.
In the manufacturing process, this base portion 36 is removed by polishing (explained later with respect to the manufacturing method).
The through electrode 8, 9 ensure the electric conductance through the conductive core portion 31.
The bonding material 23 for anodic bonding is formed over the whole inner surface 3 b of the lid substrate 3.
To be more specific, the bonding material 23 is formed so as to cover the picture frame region 3 c and the whole inner surface of the recessed portion 3 a.
Although the bonding material 23 used in this embodiment is formed of a Si film, the bonding material 23 may be formed of an Al film.
The bonding material 23 may be also formed of a Si bulk material whose resistance is lowered by doping or the like.
As described later, the bonding material 23 and the base substrate 2 are bonded to each other by anodic bonding so that the cavity C is sealed in a vacuum.
To operate the piezoelectric vibrator 1 having such a constitution, a predetermined drive voltage is applied to the external electrodes 6, 7 formed on the base substrate 2.
Due to such applying of the drive voltage, an electric current flows in the respective excitation electrodes of the piezoelectric vibrating piece 5 so that a pair of vibrating arm portions 24, 25 can be vibrated at predetermined frequency in the direction that the vibrating arm portions 24, 25 approach to each other or are separated from each other with predetermined resonance frequency.
By making use of the vibrations of the pair of vibrating arm portions 24, 25, the piezoelectric vibrating piece 5 can be used as a time source, a timing source of a control signal, a reference signal source or the like.

(Manufacturing Method of Package)

Next, the manufacturing method of a package (piezoelectric vibrator) which houses the above-mentioned piezoelectric vibrating piece is explained in conjunction with flowcharts shown in FIG. 6 and FIG. 7.
FIG. 6 and FIG. 7 are flowcharts showing the manufacturing method of the piezoelectric vibrator according to this embodiment.
FIG. 8 to FIG. 10 are views showing a polishing device of the piezoelectric vibrator substrate.
FIG. 11 is an exploded perspective view of a wafer bonded body.
Hereinafter, the explanation is made with respect to a method where a wafer bonded body 60 is formed by sealing a plurality of piezoelectric vibrating pieces 5 between a base substrate forming wafer 40 on which a plurality of base substrates 2 are arranged and a lid substrate forming wafer 50 on which a plurality of lid substrates 3 are arranged, and a plurality of piezoelectric vibrators 1 are simultaneously manufactured by cutting the wafer bonded body 60.
A broken line M shown in FIG. 11 indicates a cutting line along which the wafer bonded body 60 is cut in a cutting step.
As shown in FIG. 6, the manufacturing method of the piezoelectric vibrator according to this embodiment is mainly constituted of a piezoelectric vibrating piece preparing step (S01), a base substrate forming wafer preparing step (S10), a lid substrate forming wafer preparing step (S30), and an assembling step (S50 and succeeding steps).
Among these steps, the piezoelectric vibrating piece preparing step (S01), the lid substrate forming wafer preparing step (S30) and the base substrate forming wafer preparing step (S10) can be carried out in parallel.

(Manufacturing Method of Piezoelectric Vibrating Piece)

Firstly, the piezoelectric vibrating piece 5 is prepared by carrying out the piezoelectric vibrating piece preparing step (S01).
After preparing the piezoelectric vibrating piece 5, the coarse adjustment of resonance frequency is performed.
Fine adjustment where the resonance frequency is adjusted with higher accuracy is performed after mounting the piezoelectric vibrating piece 5.
The manufacturing step of the piezoelectric vibrating piece 5 according to this embodiment is mainly constituted of a profile forming step S210 where a plurality of profile shapes of the piezoelectric vibrating pieces 5 are formed on a crystal wafer (piezoelectric plate), an electrode forming step S220 where respective electrodes are formed on the crystal wafer, a frequency adjusting step S230 where resonance frequency is adjusted, and a small piece forming step S240 where a plurality of piezoelectric vibrating pieces are formed from one sheet of crystal wafer by separation.
Hereinafter, the detail of the respective steps is explained.

(Profile Forming Step S210)

Firstly, the profile forming step S210 where the plurality of profile shapes of the piezoelectric vibrating pieces 5 are formed on the crystal wafer is performed.
To be more specific, the crystal wafer which is already subjected to polishing and is finished to a predetermined thickness with high accuracy is prepared.
Next, the crystal wafer is etched by photolithography technique thus forming the plurality of profile shapes of the piezoelectric vibrating pieces 5 on the crystal wafer thus finishing the profile forming step S210.
A polishing device 150 which finishes a tuning fork forming crystal wafer (tuning fork substrate) to a predetermined thickness with high accuracy is substantially constituted of, for example, as shown in FIG. 8 and FIG. 9, an upper platen 151 having a circular shape as viewed in a plan view, a lower platen 152 having the same circular shape as viewed in a plan view as the upper platen 151, a sun gear 153 which is rotatably mounted on a center portion of the lower platen 152, an internal gear 154 which surrounds the outer periphery of the lower platen 152, a plurality of carriers 157 which are meshed with the sun gear 153 and the internal gear 154 between the upper platen 151 and the lower platen 152 so as to rotate and revolve in cooperation with the sun gear 153 and the internal gear 154, and hold a tuning fork forming crystal wafer (tuning fork substrate) 155 and an AT cut wafer 156, a probe 158 which measures a resonance frequency of the AT cut wafer 156, and a rotating means which rotates the upper platen 151, the lower platen 152, the sun gear 153 and the internal gear 154 respectively (for example, a driver head 160 and the like which rotate the upper platen 151).
The upper platen 151 and the lower platen 152 have the structure where the upper platen 151 and the lower platen 152 are rotatable coaxially in the horizontal direction.
Teeth are vertically and annularly arranged on an outer periphery of the sun gear 153 and an inner periphery of the internal gear 154 at a fixed pitch.
The sun gear 153 and the internal gear 154 are rotatable coaxially with the upper platen 151 and the lower platen 152 in the horizontal direction.
In this embodiment, a both-surface polishing device where the internal gear 154 independently rotates is used. However, it may be possible to use a both-surface polishing device having the structure where the internal gear 154 does not independently rotate and, for example, the internal gear 154 is fixed to the lower platen 152 so that the internal gear 154 is rotated together with the lower platen 152.
The carrier 157 has a disc shape, and a plurality of holding holes in which the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 are fitted and held are formed on an inner side of the carrier 157.
A thickness of the carrier 157 is set smaller than a thickness of the crystal wafer (tuning fork substrate) 155 and the thickness of the AT cut wafer 156, and the carrier 157 holds side surfaces of the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 such that the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 project from upper and lower surfaces of the carrier 157.
Teeth are vertically and annularly arranged on an outer periphery of the carrier 157 at a fixed pitch.
The carrier 157 is not fixed and the teeth of the carrier 157 are meshed with the teeth of the rotating sun gear 153 and the internal gear 154 and hence, the carrier 157 can rotate and revolve.
On each carrier 157, one disc-shaped AT cut wafer 156 is arranged at the center position of the carrier 157, and the plurality of (for example, four) disc-shaped crystal wafer (tuning fork substrate) 155, . . . , 155 are arranged so as to surround the AT cut wafer 156.
On the upper platen 151, the probe 158 which measures resonance frequency of the AT cut wafer 156 is arranged at a position where the probe 158 can face the AT cut wafer 156 held on each carrier 157, for example (for example, a position at which the probe 158 faces a rotation trajectory of the center position of each carrier 157 and a position offset from a rotation axis of the upper platen 151).
The probe 158 is mounted in a through hole which penetrates the upper platen 151 in the thickness direction (not shown in the drawing), for example. The probe 158 is constituted of a detection electrode which is insulated from the upper platen 151, a sweeping oscillator which applies a high frequency voltage whose frequency changes with time between the detection electrode and the lower platen 152, and a detection circuit which detects lowering of apparent impedance of the AT cut wafer 156 when resonance frequency of the AT cut wafer 156 and frequency of a high frequency voltage applied to the sweeping oscillator agree with each other. The AT cut wafer 156 is provided immediately below the detection electrode. The detection electrode, the sweeping oscillator and the detection circuit are not shown in the drawing.
In a polishing method of the crystal wafer (tuning fork substrate) 155, firstly, the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 are mounted in the holding holes formed in the carrier 157.
Then, while supplying a polishing agent to upper and lower surfaces of the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156, the upper platen 151, the lower platen 152, the sun gear 153 and the internal gear 154 are respectively rotated thus also making the carrier 157 on which the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 are held rotate and revolve.
Then, the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 which are held on the carrier 157 are polished by a polishing material adhered to the upper platen 151 and the lower platen 152.
Here, the carrier 157 performs the planetary motion and hence, the AT cut wafer 156 is positioned directly below the detection electrode of the probe 158 at suitable time interval.
Accordingly, after polishing of the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 is started, resonance frequency of the AT cut wafer 156 is measured by the probe 158. Then, polishing is finished when the resonance frequency of the AT cut wafer 156 corresponding to a desired thickness of the crystal wafer (tuning fork substrate) 155 (that is, the resonance frequency of the AT cut wafer 156 corresponding to a finish thickness of the AT cut wafer 156 corresponding to a desired finish thickness of the crystal wafer (tuning fork substrate) 155 when the crystal wafer (tuning fork substrate) 155 and the AT cut wafer 156 are simultaneously polished) is detected predetermined number of times (for example, suitable number ranging from 3 to 5 times) or more within a predetermined time (for example, a suitable time ranging from 0.5 s to 1.0 s).
In this manner, the forming step of the crystal wafer (tuning fork substrate) 155 having a predetermined thickness is finished.
When a plurality of (for example, four) disc-shaped crystal wafers (tuning fork substrates) 155, . . . , 155 are arranged on each carrier 157, for example, as shown in FIG. 10, the AT cut wafer 156 may be arranged between the neighboring crystal wafers (tuning fork substrates) 155, 155.

(Electrode Forming Step S220)

Next, the electrode forming step S220 where respective electrodes constituted of excitation electrodes, routing electrodes and mount electrodes (none of these electrodes not shown in the drawing) are formed on a front surface of the crystal wafer where the profiles of the piezoelectric vibrating pieces 5 are formed is performed.
The electrode forming step S220 is constituted of a metal film forming step S221 where the metal film is formed on the surface of the crystal wafer, a photo resist coating step (mask material coating step) S223 where photo resist (mask material) is applied to the metal film in an overlapping manner by coating, an exposure step S225 where the photo resist is exposed, a developing step S227 where a mask pattern is formed by selectively removing the photo resist, and an etching step S229 where the metal film is etched using the mask pattern thus forming the respective electrodes.

(Metal Film Forming Step S221)

In the electrode forming step S220, firstly, the metal film forming step S221 where a metal film from which excitation electrodes are formed later is formed on the crystal wafer is performed.
In this embodiment, a chromium film having a thickness of approximately several μm and possessing favorable adhesiveness with crystal is formed on a surface of the crystal wafer by a sputtering method, a vacuum deposition method or the like.
A thin gold film is formed on the chromium film as a finish layer.
The excitation electrode and the routing electrode are formed of a single-layered film made of only chromium, and the mount electrode is formed of a laminated film consisting of a chromium film and a gold film.

(Photo Resist Coating Step S223)

Subsequently, the photo resist coating step S223 where a photo resist is applied to the metal film in an overlapping manner by coating is performed.
As described previously, the photo resist is classified into a positive type resist where an exposed portion is softened and is removed and a negative type resist where an exposed portion remains. In this embodiment, the positive type resist is applied.
The photo resist is applied to the whole surface of the crystal wafer by coating in a state where the photo resist overlaps the metal film by a spray coating method, a spin coating method or the like.

(Exposure Step S225)

In the exposure step S225, a photo mask having opening portions is set in a state where the photo mask faces the photoresist, and ultraviolet rays are irradiated to the photoresist through the opening portions.
The opening portions of the photo mask are regions where the photoresist is removed, and are formed corresponding to regions where an electrode film is to be removed in the etching step S229 described later. In other words, the opening portions of the photo mask are formed corresponding to regions where the respective electrodes consisting of the excitation electrodes, the routing electrodes and the mount electrodes (none of these electrodes shown in the drawing) are not formed.
After the exposure is finished, the photo mask is removed.
After the exposure step S225, the developing step S227 where a mask pattern is formed by selectively removing the photoresist is performed.
In the developing step S227, the photoresist is selectively removed by immersing the crystal wafer to which the photoresist is applied by coating in a developer stored in a water vessel not shown in the drawing thus forming a resist pattern (mask pattern).
To be more specific, in the developing step S227, the photoresist corresponding to the regions to which ultraviolet rays are exposed through the opening portions formed in the photo mask, that is, the regions where the respective electrodes consisting of the excitation electrodes, the routing electrodes and the mount electrodes are not formed.

(Cleaning Step S228)

Subsequently, the cleaning step S228 where the developer remaining on the crystal wafer in the developing step S227 is washed away is performed.
In this cleaning step S228, the crystal wafer is immersed in pure water stored in a water vessel not shown in the drawing, and the developer remaining on a surface of the crystal wafer is washed away by swinging the crystal wafer in pure water.

(Etching Step S229)

Next, the etching step S229 where the respective electrodes are formed by etching the metal film using the resist pattern as a mask is performed.
In this step, the metal film which is masked by the resist pattern remains and the metal film which is not masked by the resist pattern is selectively removed.
By the etching step S229, the excitation electrodes, the routing electrodes and the mount electrodes of the piezoelectric vibrating piece 5 are formed.

(Frequency Adjusting Step S230)

Next, as shown in FIG. 1, weight metal films (made of silver, gold or the like, for example) constituted of a coarse adjustment film and a fine adjustment film for frequency adjustment are formed on distal ends of a pair of the vibrating arm portions 24, 25.
Then, the frequency adjusting step S230 where the rough adjustment of the resonance frequency is applied to all vibrating arm portions 24, 25 formed on the crystal wafer is performed.
The frequency adjusting step S230 is performed in such a manner that a portion of the coarse adjustment film is evaporated by irradiating a laser beam to the coarse adjustment film formed of the weight metal film so that a weight of the coarse adjustment film is changed.
The fine adjustment of resonance frequency with high accuracy is performed in the form of the piezoelectric vibrator 1.
The frequency adjusting step S230 is finished with such processing.

(Small Piece Forming Step S240)

Finally, the small piece forming step S240 where connection portions which connect the crystal wafer and the piezoelectric vibrating pieces 5 to each other are cut so that a plurality of piezoelectric vibrating pieces 5 are formed from the crystal wafer by separation is performed.
Accordingly, a plurality of tuning-fork-type piezoelectric vibrating pieces 5 can be manufactured from one sheet of crystal wafer at a time.
At this point of time, the manufacturing steps of the piezoelectric vibrating pieces 5 are finished and a plurality of piezoelectric vibrating piece 5 can be acquired.

(Base Substrate Forming Wafer Preparing Step)

Hereinafter, a step where the base substrate forming wafer 40 which becomes the base substrate 2 is prepared is explained.
Firstly, a step where the base substrate forming wafer 40 which becomes the base substrate 2 later is prepared is performed (S10).
Firstly, a disc-shaped base substrate forming wafer 40 shown in FIG. 11 is formed.
To be more specific, soda-lime glass is polished to a predetermined thickness and is cleaned. Thereafter, a layer degenerated by working on an uppermost surface of the soda-lime glass is removed by etching or the like (S11).
A dotted line M in FIG. 11 indicates a cutting line along which the base substrate forming wafer 40 is cut in the cutting step described later.

(Through Electrode Forming Step)

Subsequently, the through electrode forming step where the through electrodes 8, 9 are formed on the base substrate forming wafer 40 is performed (S10A).
This through electrode forming step is explained in detail hereinafter.
Firstly, as shown in FIG. 12A, plural pairs of through holes 21, 22 which penetrate the base substrate forming wafer 40 are formed (S12).
The through holes 21, 22 are formed by the sand blast method, the press working method or the like, for example. When the sand blast method or the press working method is adopted, the through holes 21, 22 can be formed into a tapered shape.
Here, the through holes 21, 22 are tapered such that a diameter of the through hole 21, 22 is gradually decreased toward an upper surface (cavity C side) from a lower surface (outside of the base substrate 2) of the base substrate forming wafer 40.
Subsequently, the core portion 31 of the metal pin 37 is inserted into the through hole 21, 22 from above with an axis thereof aligned with an axis of the through hole 21, 22, and the base portion 36 of the metal pin 37 and the base substrate forming wafer 40 are brought into contact with each other, and the base substrate forming wafer 40 is set upside-down (S13).
Here, as shown in FIG. 12B, the through holes 21, 22 are arranged in the direction that a tapered shape gradually narrows a diameter thereof downwardly, and the metal pin 37 is arranged in the direction that the core portion 31 is positioned on an upper side of the base portion 36.
A planar shape of the base portion 36 is set such that the base portion 36 is larger than an opening on a small diameter side 21 a, 22 a of the through hole 21, 22 so that the base portion 36 can close the opening on the small diameter side 21 a, 22 a.
As shown in FIG. 12C, glass frit in a paste form which forms the glass body 32 a is filled in a gap formed between the through hole 21, 22 and the core portion 31 (S14), and the glass frit is baked at a predetermined temperature so that the glass frit is solidified thus forming the glass body 32 a (S15).
In this manner, by bringing the base portion 36 into contact with the surface of the base substrate forming wafer 40, it is possible to surely fill the glass frit in a paste form in the through holes 21, 22.
Further, the base portion 36 is formed into a planar shape and hence, the metal pins 37 and the base substrate forming wafer 40 on which the metal pins 37 are mounted become stable with no play or the like whereby the operability can be enhanced.
The glass frit is solidified by baking thus forming the glass body 32 a and hence, the metal pins 37 can be fixed in a state where the glass frit adheres to the metal pins 37, and the glass frit is fixed to the through holes 21, 22 thus sealing the through holes 21, 22.
Subsequently, the base portion 36 of the metal pin 37 is removed by polishing (S16).
Polishing of the base portion 36 is performed using the one-surface polishing device 51 as shown in FIG. 13A and FIG. 13B.
The one-surface polishing device 51 is substantially constituted of an upper platen 52 having a circular shape as viewed in a plan view, a lower platen 53 having the same circular shape as viewed in a plan view as the upper platen 52, a plurality of carriers 54 having a circular shape as viewed in a plan view which are arranged on a lower side of the upper platen 52 and fix the base substrate forming wafer 40 thereto by suction, a polishing agent charging means 55 which charges a polishing agent 56 into a gap formed between the upper platen 52 and the lower platen 53, and a rotation means not shown in the drawing which rotates the upper platen 52, the lower platen 53 and the carriers 54 respectively.
The lower platen 53 is formed of a solid platen having no grooves, and is configured to rotate in the direction indicated by an arrow A1 in the drawing on the horizontal plane.
The carrier 54 is configured such that the carrier 54 is held on the upper platen 52 rotatably on the horizontal plane, and is rotatable in the direction indicated by an arrow A2 in the drawing. By adopting the structure where the lower platen 53 rotates and the carrier 54 also rotates in this manner, a surface of the base portion 36 can be polished flat by eliminating uneven wear of a polished surface.
In the step where the base portion 36 is polished, a rotational speed of the lower platen 53 is set to 15 rpm, and a rotational speed of the carrier 54 is set to 45 rpm.
The polishing agent charging means 55 includes a storing portion which stores a polishing agent 56 therein and has a motor for agitation, a pump which conveys the polishing agent 56 in the storing portion and charges the polishing agent 56 to the lower platen 53 from charging ports 55 a formed in the upper platen 52 at approximately 6 to 8 positions, and a PH measuring device which measures PH of the polishing agent 56. In the one-surface polishing device 51, polishing is performed while supplying the polishing agent 56, and a flow rate of the polishing agent 56 which is charged to the lower platen 53 from the charging ports 55 a is set to a predetermined flow rate.
In the polishing method of the base portion 36 of the metal pin 37, firstly, the base substrate forming wafer 40 is mounted on the one-surface polishing device 51 by making the base substrate forming wafer 40 fixed to the carrier 54 by suction in a state where the base portion 36 which projects from the base substrate forming wafer 40 forms a lower side.
Here, dummy substrates 57 having a planar shape and made of a glass epoxy resin (FR4), for example, are mounted on a lower side of the upper platen 52 or the carriers 54.
A thickness of the dummy substrate 57 is set such that a lower end portion of the dummy substrate 57 is positioned below a lower end portion of the base portion 36.
Subsequently, polishing is performed by rotating the lower platen 53 and the carriers 54 by a rotation means respectively while supplying the polishing agent 56. Here, the polishing is performed by applying a pressure of 15 to 50 g/cm²in the direction from the upper platen 52 to the lower platen 53.
Then, the dummy substrates 57 are brought into contact with the lower platen 53 prior to the base portions 36 so that the dummy substrates 57 are polished and, thereafter, the base portions 36 are brought into contact with the lower platen 53 so that the base portions 36 are polished together with the dummy substrates 57.
In this manner, the dummy substrates 57 are polished prior to the base portions 36 and, thereafter, the base portions 36 are polished together with the dummy substrate 57 and hence, it is possible to gradually apply a pressure to the base substrate forming wafer 40 from the lower platen 53 whereby it is possible to prevent the base substrate forming wafer 40 from being damaged. By removing the base portion 36 in this manner, as shown in FIG. 12D, only the core portion 31 remains in the cylindrical body 32.
Subsequently, a step where a glass surface 40 a of the base substrate forming wafer 40 from which the base portion 36 is removed is polished is performed (S17).
A step where the glass surface 40 a is polished is provided for making a frit glass on which indentations are formed mainly by baking flat, and the step is performed using a both-surface polishing device which polishes both front and back surfaces of a wafer which is made of glass, ceramic or the like and is formed into a thin plate shape, for example.
As shown in FIG. 14A and FIG. 14B, a both-surface polishing device 71 is substantially constituted of an upper platen 72 having a circular shape as viewed in a plan view, a lower platen 73 having the same circular shape as viewed in a plan view as the upper platen 72, a sun gear 74 which is positioned at the center of the lower platen 73, an internal gear 75 which surrounds the outer periphery of the lower platen 73, a plurality of carriers 76 which are arranged between the sun gear 74 and the internal gear 75 between the upper platen 72 and the lower platen 73, and holds the base substrate forming wafer 40, a polishing agent charging means 78 which charges a polishing agent 77 to both surfaces of the base substrate forming wafer 40, and a rotating means not shown in the drawing which rotates the upper platen 72, the lower platen 73, the sun gear 74 and the internal gear 75 respectively.
The upper platen 72 and the lower platen 73 have the structure where the upper platen 72 and the lower platen 73 are rotatable coaxially in the horizontal direction. In the step where the glass surface 40 a of the base substrate forming wafer 40 is polished, a rotational speed of the upper platen 72 is set to 45 rpm, and a rotational speed of the lower platen 73 is set to 15 rpm.
To front surfaces of the upper platen 72 and the lower platen 73 on a polishing side, polishing pads 79, 80 are adhered. As such polishing pads, a polishing pad made of ceric oxide, for example, is used.
Teeth 74 a, 75 a are vertically and annularly arranged on an outer periphery of the sun gear 74 and an inner periphery of the internal gear 75 at a fixed pitch. The sun gear 74 and the internal gear 75 are rotatable coaxially with the upper platen 72 and the lower platen 73 in the horizontal direction.
In this embodiment, a both-surface polishing device 71 where the internal gear 75 independently rotates is used. However, it may be possible to use a both-surface polishing device having the structure where the internal gear does not independently rotate and, for example, the internal gear is fixed to the lower platen so that the internal gear is rotated together with the lower platen.
The carrier 76 has a disc shape, and a plurality of base substrate forming wafer holding holes 76 b in which the base substrate forming wafer 40 is fitted and held are formed on an inner side of the carrier 76.
A thickness of the carrier 76 is set smaller than a thickness of the base substrate forming wafer 40, and the carrier 76 holds a side surface of the base substrate forming wafer 40 such that the base substrate forming wafer 40 projects from upper and lower surfaces of the carrier 76.
Teeth 76 a are vertically and annularly arranged on an outer periphery of the carrier 76 at a fixed pitch.
The carrier 76 is not fixed and the teeth 76 a of the carrier 76 are meshed with the teeth 74 a, 75 a of the rotating sun gear 74 and the internal gear 75 and hence, the carrier 76 can perform rotation and revolution.
The polishing agent charging means 78 includes a storing portion not shown in the drawing which stores a polishing agent 77 therein and has a motor for agitation, and a pump not shown in the drawing which conveys the polishing agent 77 in the storing portion and charges the polishing agent 77 to upper and lower surfaces of the base substrate forming wafer 40 from charging ports 78 a formed in the upper platen 52 at approximately 8 positions.
The polishing agent charging means 78 includes a polishing agent recovery portion 81 which recovers the polishing agent 77 discharged to the outside from the lower platen 73 so that the recovered polishing agent 77 can be conveyed to the charging ports 78 a again.
In the step where the glass surface 40 a of the base substrate forming wafer 40 is polished, a flow rate at which the polishing agent 77 is charged to the upper and lower surfaces of the base substrate forming wafer 40 from the charging ports 78 a is set to approximately 10 L/min.
As the polishing agent 77, ceric oxide or the like which is used for polishing a glass surface in general is used.
In a polishing method of the glass surface 40 a of the base substrate forming wafer 40, firstly, the base substrate forming wafer 40 from which the base portions 36 are removed is mounted in the base substrate forming wafer holding holes 76 b formed in the carrier 76.
Then, while supplying the polishing agent 77 to the upper and lower surfaces of the base substrate forming wafer 40, the upper platen 72, the lower platen 73, the sun gear 74 and the internal gear 75 are respectively rotated so that the carriers 76 which hold the base substrate forming wafer 40 are also rotated and revolved.
Then, the glass surfaces 40 a of the base substrate forming wafers 40 held on the carriers 76 are polished by the polishing pads 79, 80 which adhere to the upper platen 72 and the lower platen 73.
Here, polishing is performed by applying a pressure of 100 to 500 g/cm²in the direction from the upper platen 72 to the lower platen 73.
Subsequently, a step where the core portions 31 which project from the base substrate forming wafer 40 are polished is performed (S18).
In polishing the core portion 31, the core portion 31 is polished one surface by one surface using the one-surface polishing device 51 in the same manner as the above-mentioned polishing method of the base portion 36 of the metal pin 37.
Here, polishing is performed by bringing the core portion 31 and the lower platen 53 into contact with each other without using the dummy substrate 57 used in the polishing of the base portion 36.
In this manner, by performing the polishing of the core portion 31 one surface by one surface, a polished amount of an upper surface of the core portion 31 and the polished amount of a lower portion of the core portion 31 can be made equal.
The polishing of the core portion 31 may not be applied to both surfaces of the core portion 31, and may be applied only to the surface of the core portion 31 which forms a cavity-C side surface later.
After polishing a projecting portion of the core portion 31, as shown in FIG. 12E and FIG. 12F, the glass surface 40 a of the base substrate forming wafer 40 and surfaces of the through electrodes 8, 9 are brought into an approximately coplanar state.
The through electrodes 8, 9 are formed on the base substrate forming wafer 40 in this manner.
Next, a bonded film forming step where a bonded film is formed (S19) and a routing electrode forming step where a routing electrode is formed (S20) are performed by forming a conductive material on an upper surface of the base substrate forming wafer 40 by patterning thus finishing the base substrate forming wafer 40 preparing step.

(Lid Substrate Forming Wafer Preparing Step)

Next, the lid substrate forming wafer preparing step is performed (S30). In this step, at the same timing as the preparation of the base substrate 2 or at the timing before and after the preparation of the base substrate 2, the lid substrate forming wafer 50 which becomes the lid substrate 3 later is prepared up to a state immediately before anodic bonding.
In a step where the lid substrate 3 is prepared, firstly, a disc-shaped lid substrate forming wafer which becomes the lid substrate 3 later is formed.
To be more specific, soda-lime glass is polished to a predetermined thickness and is cleaned. Thereafter, a layer degenerated by working on an uppermost surface of the soda-lime glass is removed by etching or the like (S31).
Subsequently, a recessed portion 3 a for forming the cavity C is formed on the lid substrate forming wafer by etching, press working or the like (S32).
Next, to ensure the air tightness between the lid substrate forming wafer 50 and the base substrate forming wafer 40 described later, the polishing step where at least a first surface 50 a side of the lid substrate forming wafer 50 which becomes a bonding surface with the base substrate forming wafer 40 is polished is performed (S33) thus applying mirror finishing to the first surface 50 a.
Then, a bonding material forming step where a bonding material 23 is formed on the whole first surface 50 a (a bonding surface with the base substrate forming wafer 40 and an inner surface of the recessed portion 3 a) of the lid substrate forming wafer 50 is performed (S34).
By forming the bonding material 23 on the whole first surface 50 a of the lid substrate forming wafer 50 in this manner, patterning of the bonding material 23 becomes unnecessary and hence, a manufacturing cost can be reduced.
The bonding material 23 may be formed by a film forming method such as sputtering or a CVD.
The bonding surface is polished prior to the bonding material forming step (S34) and hence, the flatness of the surface of the bonding material 23 is ensured whereby the stable bonding of the lid substrate forming wafer 50 with the base substrate forming wafer 40 can be realized thus finishing the lid substrate forming wafer preparing step (S30).

(Assembling Step)

Next, on the routing electrode 27 of the base substrate forming wafer 40 prepared by the base substrate forming wafer preparing step (S10), the piezoelectric vibrating piece 5 prepared by the piezoelectric vibrating piece preparing step (S01) is mounted by way of the bump B made of gold or the like (S50).
Then, the overlapping step where the base substrate forming wafer 40 and the lid substrate forming wafer 50 which are prepared by the above-mentioned respective wafer preparing steps are made to overlap each other is performed (S60).
To be more specific, using reference marks not shown in the drawing or the like as indexes, the base substrate forming wafer 40 and the lid substrate forming wafer 50 are aligned at an accurate position.
Accordingly, the piezoelectric vibrating piece 5 mounted on the base substrate forming wafer 40 is brought into a state where the piezoelectric vibrating piece 5 is housed in the cavity C surrounded by the recessed portion 3 a formed on the lid substrate forming wafer 50 and the base substrate forming wafer 40.
After the overlapping step (S60), bonding step is performed (S70). In the bonding step, two overlapped wafers, that is, the base substrate forming wafer 40 and the lid substrate forming wafer 50 are put into an anodic bonding device not shown in the drawing, and both wafers 40, 50 are bonded to each other by anodic bonding such that a predetermined voltage is applied to the wafers 40, 50 in a predetermined temperature atmosphere in a state where outer peripheral portions of the wafers are clamped by a holding mechanism not shown in the drawing (S70).
To be more specific, the predetermined voltage is applied between the bonding material 23 and the lid substrate forming wafer 50.
As a result, an electrochemical reaction is generated on an interface between the bonding material 23 and the lid substrate forming wafer 50 so that the bonding material 23 and the lid substrate forming wafer 50 are strongly adhered to each other by anodic bonding.
Accordingly, it is possible to obtain a wafer bonded body 60 where the base substrate forming wafer 40 and the lid substrate forming wafer 50 are bonded to each other so that the piezoelectric vibrating piece 5 can be sealed in the cavity C.
When the lid substrate forming wafer 50 and the base substrate forming wafer 40 are bonded to each other by anodic bonding as in the case of this embodiment, compared to a case where the lid substrate forming wafer 50 and the base substrate forming wafer 40 are bonded to each other using an adhesive agent or the like, the displacement caused by the degeneration with time, an impact or the like, warping of the wafer bonded body 60 and the like can be prevented so that the lid substrate forming wafer 50 and the base substrate forming wafer 40 can be bonded to each other more firmly.
Thereafter, a pair of external electrodes 6, 7 which is electrically connected to the pair of through electrodes 8, 9 is formed (S80), and the frequency of the piezoelectric vibrator 1 is subjected to the fine adjustment (S90).
Then, the small piece forming step is performed (S100). In this step, by cutting the wafer bonded body 60 which is formed by bonding the lid substrate forming wafer 50 and the base substrate forming wafer 40 along the cutting line M, a plurality of piezoelectric vibrators are formed from the wafer bonded body 60.
Then, in an electric characteristic inspection step (S110), resonance frequency, a resonance resistance value, drive level characteristics (excitation power dependency of resonance frequency and resonance resistance value) and the like of the piezoelectric vibrator 1 are measured and checked. Further, an insulation resistance characteristic and the like of the piezoelectric vibrator 1 are also checked.
Finally, an appearance inspection of the piezoelectric vibrator 1 is performed so as to make a final check of a size, quality and the like of the piezoelectric vibrator 1.
The manufacture of the piezoelectric vibrator 1 is finished with the processing.
According to the polishing method of the above-mentioned embodiment, the resonance frequency of the AT cut wafer 156 polished simultaneously with the crystal wafer (tuning fork substrate) 155 is detected, and the thickness of the crystal wafer (tuning fork substrate) 155 is controlled based on the detection result and hence, the crystal wafer (tuning fork substrate) 155 can be easily finished to a desired thickness with high accuracy.
Further, the irregularities of thickness among the plurality of crystal wafers (tuning fork substrates) 155 held for each carrier 157 can be decreased, and also irregularities of thickness of the crystal wafer (tuning fork substrate) 155 among a plurality of carriers 157 can be decreased.
By arranging the AT cut wafer 156 at the center position of the carrier 157 or by arranging the AT cut wafer 156 between the neighboring crystal wafers (tuning fork substrates) 155, 155 when the plurality of disc-shaped crystal wafers (tuning fork substrates) 155, . . . , 155 are arranged on each carrier 157, the rotational balance of the carrier 157 in rotation and revolution can be enhanced for each carrier 157 and hence, parallelism of the crystal wafer (tuning fork substrate) 155 can be enhanced.
Further, by forming the AT cut wafer 156 into a disc shape, the rotational balance of the AT cut wafer 156 can be enhanced and hence, the thickness accuracy and parallelism of the crystal wafer (tuning fork substrate) 155 can be enhanced.
Still further, according to the above-mentioned manufacturing method of a piezoelectric vibrating piece of the embodiment, thickness accuracy and parallelism of the crystal wafer (tuning fork substrate) 155 can be enhanced and hence, the operational reliability of the piezoelectric vibrating piece 5 can be enhanced.
Still further, according to the above-mentioned piezoelectric vibrator 1 of this embodiment, it is possible to enhance operational reliability of the piezoelectric vibrating piece 5.

(Oscillator)

Next, one embodiment of the oscillator according to the present invention is explained in conjunction with FIG. 15.
The oscillator 100 of this embodiment is, as shown in FIG. 15, formed as an oscillating element where the piezoelectric vibrator 1 is electrically connected to an integrated circuit 101.
The oscillator 100 includes a substrate 103 on which an electronic part 102 such as a capacitor is mounted.
The above-mentioned integrated circuit 101 for oscillator is mounted on the substrate 103, and the piezoelectric vibrator 1 is mounted on the substrate 103 in the vicinity of the integrated circuit 101.
The electronic part 102, the integrated circuit 101 and the piezoelectric vibrator 1 are electrically connected with each other by a wiring pattern not shown in the drawing.
The respective constitutional parts are molded by a resin not shown in the drawing.
In the oscillator 100 having such a constitution, when a voltage is applied to the piezoelectric vibrator 1, the piezoelectric vibrating piece 5 arranged in the piezoelectric vibrator 1 vibrates.
This vibration is converted into an electric signal due to a piezoelectric characteristic which the piezoelectric vibrating piece 5 possesses, and the electric signal is inputted to the integrated circuit 101.
Various processing are applied to the inputted electric signal by the integrated circuit 101, and a frequency signal is outputted from the integrated circuit 101. Accordingly, the piezoelectric vibrator 1 functions as an oscillating element.
Further, by selectively setting the constitution of the integrated circuit 101, for example, an RTC (real time clock) module or the like corresponding to a request, it is possible to impart, besides a function as a timepiece-use single-function oscillator or the like, a function of controlling an operation date and time of the oscillator or an external device or a function of providing time, calendar and the like to the oscillator 100.
As described above, according to the oscillator 100 of this embodiment, the piezoelectric vibrating piece 5 is formed of the crystal wafer (tuning fork substrate) 155 which exhibits enhanced thickness accuracy and parallelism and hence, the operational reliability of the piezoelectric vibrating piece 5 can be enhanced whereby the oscillator 100 can acquire high quality due to the enhancement of the operational reliability of the oscillator 100.

(Electronic Apparatus)

Next, one embodiment of the electronic apparatus according to the present invention is explained in conjunction with FIG. 16.
The explanation is made with respect to an example where the electronic apparatus is a portable information device 110 which includes the above-mentioned piezoelectric vibrator 1.
Firstly, the portable information device 110 of this embodiment is a device which is represented by a mobile phone, for example, and is a developed or improved form of a wrist watch of the related art.
The portable information device 110 resembles the wrist watch in appearance. A liquid crystal display is arranged on a portion of the portable information device 110 which corresponds to a dial of the wrist watch, and a present time or the like can be displayed on a screen of the liquid crystal display.
Further, when the portable information device 110 is used as a communication device, a user removes the portable information device 110 from his wrist, and performs communication in the same manner as a mobile phone of the related art by a speaker and a microphone incorporated into an inner portion of a band.
However, the portable information device 110 is remarkably miniaturized and light-weighted compared to the conventional mobile phone.
Next, the constitution of the portable information device 110 of this embodiment is explained.
The portable information device 110 includes, as shown in FIG. 16, a piezoelectric vibrator 1 and a power source part 111 for power supply.
The power source part 111 is formed of a lithium secondary battery, for example.
To the power source part 111, a control part 112 which performs various controls, a timer part 113 which counts time or the like, a communication part 114 which performs communication with the outside, a display part 115 which displays various information, and a voltage detection part 116 which detects voltages of the respective functional parts are connected to each other in parallel.
Electricity is supplied to the respective functional parts from the power source part 111.
The control part 112 performs an operational control of the whole system including the transmission and the reception of voice data, the measurement, display of a present time and the like by controlling the respective functional parts.
Further, the control part 112 includes a ROM in which programs are written in advance, a CPU which reads and executes the programs written in the ROM, a RAM which is used as a work area of the CPU and the like.
The timer part 113 includes an integrated circuit which incorporates an oscillation circuit, a register circuit, a counter circuit, an interface circuit and the like therein, and the piezoelectric vibrator 1.
When a voltage is applied to the piezoelectric vibrator 1, the piezoelectric vibrating piece 5 vibrates, the vibrations are converted into an electric signal due to a piezoelectric characteristic which crystal possesses, and the electric signal is inputted to the oscillation circuit.
An output of the oscillation circuit is binalized and the binalized value is counted by the register circuit and the counter circuit.
Then, the transmission/reception of signals is performed between the timer part 113 and the control part 112 via the interface circuit, and a present time, a present date, calendar information and the like are displayed on the display part 115.
The communication part 114 has the substantially same functions as a conventional mobile phone, and includes a wireless part 117, a voice processing part 118, a switching part 119, an amplifying part 120, a voice inputting/outputting part 121, a telephone number inputting part 122, an incoming call sound generation part 123, and a calling-control memory part 124.
The wireless part 117 performs the transmission/reception of various data such as voice data with a base station through an antenna 125.
The voice processing part 118 performs coding and decoding of a voice signal inputted from the wireless part 117 or the amplifying part 120.
The amplifying part 120 amplifies a signal received from the voice processing part 118 or the voice inputting/outputting part 121 to a predetermined level. The voice inputting/outputting part 121 is formed of a speaker, a microphone or the like, and makes an incoming call sound or a received voice loud or collects voice.
Further, the incoming call sound generation part 123 generates an incoming call sound in response to calling from a base station. The switching part 119 switches the amplifying part 120 connected to the voice processing part 118 to the incoming call sound generation part 123 only when a call arrives so that an incoming call sound generated by the incoming call sound generation part 123 is outputted to the voice inputting/outputting part 121 through the amplifying part 120.
Here, the calling control memory part 124 stores a program relating to an incoming/outgoing call control in communication.
Further, the telephone number inputting part 122 includes, for example, numeral keys ranging from 0 to 9 and other keys. By pushing these numeral keys or the like, a user can input the telephone number of the call destination or the like.
The voltage detection part 116, when a voltage applied to the respective functional parts such as the control part 112 from the power source part 111 becomes lower than a predetermined value, detects such lowering of voltage and notifies the lowering of voltage to the control part 112.
The predetermined voltage value at this point of time is a value which is preliminarily set as minimum voltage necessary for stably driving the communication part 114, and is set to approximately 3V, for example.
The control part 112 which receives the notification of the lowering of voltage from the voltage detection part 116 prohibits operations of the wireless part 117, the voice processing part 118, the switching part 119 and the incoming call sound generation part 123.
Particularly, the operation stop of the wireless part 117 which consumes large power is inevitable.
Further, a message that a remaining battery quantity is short so that the communication part 114 is inoperable is displayed on the display part 115.
That is, due to the operation of the voltage detection part 116 and the operation of the control part 112, an operation of the communication part 114 can be prohibited and a message which indicates the prohibition of the operation of the communication part 114 can be displayed on the display part 115.
This display may be formed of a character message. However, as a more intuitive display, a×(bad) mark may be attached to a telephone icon displayed on an upper part of a display screen of the display part 115.
The electronic apparatus is provided with a power source cutting-off part 126 which can selectively cuts off a power source of a portion relating to a function of the communication part 114. In this case, it is possible to stop the function of the communication part 114 more reliably.
As described above, according to the portable information device 110 of this embodiment, the portable information device 110 includes the high-quality piezoelectric vibrator 1 with high operational reliability and hence, the portable information device per se can ensure the stable conductivity in the same manner whereby the portable information device 110 can acquire high quality due to the enhancement of the operational reliability of the portable information device 110.

(Radio-Controlled Timepiece)

Next, one embodiment of the radio-controlled timepiece according to the present invention is explained in conjunction with FIG. 17.
The radio-controlled timepiece 130 of this embodiment is a timepiece which includes the piezoelectric vibrator 1 which is electrically connected to a filter part 131, and has a function of receiving a standard electric wave containing timepiece information, automatically correcting time to correct time, and displaying the corrected time.
In Japan, transmission installations (transmission stations) which transmit the standard electric wave are located in Fukushima prefecture (40 kHz) and Saga prefecture (60 kHz) and transmit the standard electric waves respectively.
A long wave having frequency of 40 kHz or 60 kHz has both of property that the wave propagates on a ground and property that the wave propagates while being reflected between an ionosphere and a ground and hence, the long wave has a wide propagation range whereby the standard electric wave can cover all areas of Japan with the above-mentioned two transmission installations.
The functional constitution of the radio-controlled timepiece 130 is explained in detail hereinafter.
The antenna 132 receives the standard electric wave formed of a long wave having frequency of 40 kHz or 60 kHz.
The standard electric wave formed of a long wave is an electric wave which is obtained by AM-modulating a carrier wave having frequency of 40 kHz or 60 kHz by time information called as a time code.
The received standard electric wave formed of a long wave is amplified by an amplifier 133, and is filtered by a filter part 131 having a plurality of piezoelectric vibrators 1, and is tuned.
The piezoelectric vibrators 1 of this embodiment include crystal vibrator parts 138, 139 having resonance frequency of 40 kHz or 60 kHz which is equal to the above-mentioned frequency of the carrier wave respectively.
Further, a filtered signal of predetermined frequency is detected and demodulated by a detection/rectifying circuit 134. Subsequently, the time code is taken out through a waveform shaping circuit 135, and is counted by a CPU 136.
The CPU 136 reads information on present year, cumulative days, day of week, time and the like. The read information is reflected on an RTC 137 so that correct time information is displayed.
The carrier wave has frequency of 40 kHz or 60 kHz and hence, the crystal vibrator parts 138, 139 are preferably formed of a vibrator having the above-mentioned tuning-fork structure.
Although the above-mentioned explanation is made with respect to the radio-controlled timepiece used in Japan, the frequencies of standard electric waves of long wave used overseas differ from the standard electric wave used in Japan.
For example, the standard electric wave having frequency of 77.5 kHz is used in Germany.
Accordingly, in incorporating the radio-controlled timepiece 130 also compatible with the oversea use into a portable device, the piezoelectric vibrator 1 having frequency different from the frequency used in Japan becomes necessary.
As described above, according to the radio-controlled timepiece 130 of this embodiment, the radio-controlled timepiece 130 includes the high-quality piezoelectric vibrator 1 with high operational reliability and hence, the radio-controlled timepiece per se can ensure the stable conductivity in the same manner whereby the radio-controlled timepiece 130 can acquire high quality due to the enhancement of the operational reliability of the radio-controlled timepiece 130.
Although the embodiments of the polishing method according to the present invention have been explained heretofore, the present invention is not limited to the above-mentioned embodiments, and the various modifications and variations are conceivable without departing from the gist of the present invention.
In the above-mentioned embodiment, the polishing is finished when the resonance frequency of the AT cut wafer 156 corresponding to the desired thickness of the crystal wafer (tuning fork substrate) 155 is detected predetermined number of times or more within the predetermined time. However, the present invention is not limited to such a case, and the polishing may be finished when the resonance frequency of the AT cut wafer 156 corresponding to the desired thickness of the crystal wafer (tuning fork substrate) 155 is detected one time.

Claims

1. A method for polishing a wafer mounted on a polishing device that comprises a lower platen, an upper platen above the lower platen, a wafer carrier mounted on the lower platen, a probe mounted on the upper platen, the method comprising:

mounting a first wafer and an AT cut wafer on the wafer carrier;

applying a polishing agent to upper and lower surfaces of the first wafer and the AT cut wafer;

rotating the upper platen and the lower platen while applying the polishing agent, thereby polishing the first wafer and the AT cut wafer by the rotating;

detecting a resonant frequency of the AT cut wafer, wherein the resonant frequency of the AT cut wafer corresponds to a thickness of the first wafer; and

continue rotating the upper and lower platens until a resonant frequency corresponding to a predetermined thickness of the first wafer is detected a predetermined number of times.

2. The method of claim 1, wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected a predetermined number of times within the predetermined period of time.

3. The method of claim 2, wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least three times within the predetermined period of time.

4. The method of claim 2, wherein the predetermined period of time comprises the range of 0.5 seconds to 1.0 seconds.

5. The method of claim 1, wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least once.

6. The method of claim 1, wherein the AT cut wafer is mounted at a center of the carrier.

7. The method of claim 1, further comprising mounting a second wafer on the carrier.

8. The method of claim 7, wherein the AT cut wafer is mounted between the first and second wafers.

9. The method of claim 1, wherein the AT cut wafer is mounted on the carrier at a position such that when the lower and upper platens rotate, the AT cut wafer periodically passes under the probe.

10. The method of claim 1, wherein the upper and lower platens are rotated in opposite directions.

11. A method for polishing a wafer mounted on a polishing device that comprises a lower platen, an upper platen above the lower platen, a wafer carrier mounted on the lower platen, a probe mounted on the upper platen, the method comprising:

mounting a first wafer and an AT cut wafer on the wafer carrier;

rotating the upper platen and the lower platen, thereby polishing the first wafer and the AT cut wafer by the rotating;

continue rotating the upper and lower platens until a resonant frequency corresponding to a predetermined thickness of the first wafer is detected a predetermined number of times within a predetermined period of time.

12. The method of claim 11, further comprising applying a polishing agent to upper and lower surfaces of the first wafer and the AT cut wafer.

13. The method of claim 11, wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least three times within the predetermined period of time.

14. The method of claim 11, wherein the predetermined period of time comprises the range of 0.5 seconds to 1.0 seconds.

15. The method of claim 11, wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least once.

16. The method of claim 11, wherein the AT cut wafer is mounted at a center of the carrier.

17. The method of claim 11, wherein the AT cut wafer is mounted on the carrier at a position such that when the lower and upper platens rotate, the AT cut wafer periodically passes under the probe.

18. The method of claim 11, wherein the upper and lower platens are rotated in opposite directions.

19. A method for polishing a wafer mounted on a polishing device that comprises a lower platen, an upper platen above the lower platen, multiple wafer carriers mounted on the lower platen, a probe mounted on the upper platen, the method comprising:

mounting a first wafer and an AT cut wafer on each of the wafer carriers;

rotating the upper platen and the lower platen, thereby polishing the first wafer and the AT cut wafer mounted on each of the wafer carriers by the rotating;

detecting a resonant frequency of each of the AT cut wafers, wherein the resonant frequency of each AT cut wafer corresponds to a thickness of the corresponding first wafer; and

continue rotating the upper and lower platens until a resonant frequency corresponding to a predetermined thickness of one or more of the first wafers is detected a predetermined number of times within a predetermined period of time.

20. The method of claim 19, wherein the AT cut wafers are each mounted on the corresponding wafer carrier at a position such that when the lower and upper platens rotate, each AT cut wafer periodically passes under the probe.