JP2014200041A - Electrode structure of vibration piece, method for manufacturing vibration piece, vibrator, oscillator, electronic apparatus, and mobile body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure of a vibration piece that has excellent jointing strength to a jointed object and can precisely adjust a frequency, a vibration piece manufacturing method capable of easily manufacturing a vibration piece having such an electrode structure, a highly reliable vibrator having the electrode structure of the vibration piece, an oscillator, an electronic apparatus, and a mobile body.SOLUTION: An electrode structure of a vibration piece 190 has: a vibration substrate 191; and an electrode layer 193 formed by sequentially laminating a ground layer 196, an intermediate layer 197, and an upper layer 198 on a surface of the vibration substrate 191. The intermediate layer 197 is formed by applying heat treatment to a temporary layer containing a main component of the ground layer 196 in an oxidative atmosphere to oxidize one part of a surface side of the temporary layer. Also, it is preferable that maximum height roughness Rz is 10 nm or less in a roughness curve of a surface of the intermediate layer 197 on the upper layer 198 side obtained from a vertical cross section of the intermediate layer 197.

Description

  The present invention relates to an electrode structure of a resonator element, a method for manufacturing the resonator element, a vibrator, an oscillator, an electronic device, and a moving body.

Piezoelectric devices using piezoelectric materials such as quartz are used in many fields as electronic components such as piezoelectric vibrators, resonators, and filters.
Among them, the piezoelectric vibrator is frequently used in electronic devices as a time source, a timing source such as a control signal, a reference signal source, and the like. The piezoelectric vibrator includes a piezoelectric vibrating piece and excitation electrodes provided on both main surfaces of the vibration region of the piezoelectric vibrating piece. A bump or the like is bonded to the excitation electrode, and a voltage is applied to the excitation electrode via the bump or the like, so that the piezoelectric vibrating piece is excited.

  In Patent Document 1, a base electrode made of chromium or nickel is provided on the surface of a piezoelectric substrate made of quartz, a barrier layer made of silver or titanium is provided thereon, and a main electrode made of gold is further provided thereon 3 An oscillator including a layered electrode is disclosed. By providing such a barrier layer, it is attempted to prevent the material of the base electrode from being deposited on the surface of the main electrode and to stably bond the main electrode and the bump.

JP 2006-101244 A

However, metal elements such as silver and titanium used for the barrier layer may be deposited on the surface of the main electrode by the heat treatment. Since the oxidation reaction occurs with this precipitation, there is a possibility that stable bonding between the main electrode and the bumps may be hindered.
In the manufacture of the piezoelectric vibrator, the resonance frequency of the piezoelectric vibrating piece is changed by performing processing such as removing a part of the excitation electrode. Thereby, the resonance frequency of the piezoelectric vibrating piece can be adjusted to a desired value.

However, if the material for the base electrode is deposited on the surface of the main electrode, the specific gravity of the object to be removed at the time of processing varies, and the intended mass reduction cannot be achieved. As a result, it is difficult to accurately adjust the resonance frequency of the piezoelectric vibrating piece.
An object of the present invention is to provide an electrode structure of a vibrating piece that has an excellent bonding strength with respect to a bonding partner and can accurately adjust the frequency, and a method of manufacturing a vibrating piece that can easily manufacture a vibrating piece having such an electrode structure, An object of the present invention is to provide a highly reliable vibrator, oscillator, electronic device, and moving body having an electrode structure of the resonator element.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples.
[Application Example 1]
The electrode structure of the resonator element according to the invention includes a vibrating substrate,
An electrode layer in which an underlayer, an intermediate layer, and an upper layer are sequentially laminated from the surface of the vibration substrate;
Including
The intermediate layer is a layer formed by oxidizing a part of the surface side of the surface layer by subjecting the main component of the surface layer of the surface layer to heat treatment in an oxidizing atmosphere. Features.
Accordingly, in order to suppress the base layer main component from diffusing to the upper layer side in the intermediate layer, the electrode has excellent bonding strength with respect to the bonding partner and suppresses the base layer main component from diffusing to the upper layer side. Since it becomes possible to strictly control the amount of change in the mass of the layer, an electrode structure of the resonator element capable of accurately adjusting the frequency of the resonator element is obtained.

[Application Example 2]
In the electrode structure of the resonator element according to the aspect of the invention, it is preferable that the intermediate layer is configured such that an oxygen content rate on the upper layer side surface is larger than an oxygen content rate on the base layer side surface.
As a result, the oxygen content on the surface on the upper layer side is relatively large, so that the main component of the base layer is more reliably prevented from diffusing to the upper layer side, while the oxygen content on the surface on the base layer side is relatively Therefore, the adhesion between the intermediate layer and the base layer becomes larger.

[Application Example 3]
In the electrode structure of the resonator element according to the aspect of the invention, it is preferable that the maximum height roughness Rz is 10 nm or less in the roughness curve of the surface on the upper layer side of the intermediate layer, which is obtained from the longitudinal section of the intermediate layer.
Thereby, while having the outstanding joining strength with respect to a joining other party, the effect that the frequency of a vibration piece can be adjusted correctly is strengthened more. Further, since the surface roughness of the upper layer is sufficiently high, the amount to be removed can be controlled more strictly when adjusting the resonance frequency of the resonator element by removing a part of the upper layer. As a result, the resonance frequency can be adjusted more accurately.

[Application Example 4]
In the electrode structure of the resonator element according to the aspect of the invention, it is preferable that the intermediate layer is configured to wrap around the side surface of the base layer.
Thereby, since it can suppress that an oxidation advances from the side surface of an electrode layer, it suppresses that the mass of an electrode layer increases, and suppresses that the resonant frequency of a vibration piece shifts | deviates with time. be able to.

[Application Example 5]
The method for manufacturing a resonator element according to the invention includes a vibrating substrate,
An electrode layer in which an underlayer, an intermediate layer, and an upper layer are sequentially laminated from the surface of the vibration substrate;
A method of manufacturing a resonator element including:
Forming a temporary layer containing the main component of the foundation layer on the surface of the vibration substrate;
Performing a heat treatment in an oxidizing atmosphere to oxidize a part of the surface side of the temporary layer to form the base layer and the intermediate layer;
Forming the upper layer on the surface of the intermediate layer.
Accordingly, it is possible to easily manufacture a resonator element having an electrode structure capable of accurately adjusting the frequency while having excellent bonding strength with respect to a bonding partner.

[Application Example 6]
In the method for manufacturing a resonator element according to the aspect of the invention, it is preferable that the heat treatment is performed at a temperature of 200 ° C. to 600 ° C. and a time of 10 minutes to 10 hours.
Thereby, it is possible to form a homogeneous intermediate layer while preventing the characteristics of the vibration substrate from being deteriorated by heat. As a result, the action of suppressing the diffusion of the main component of the underlayer by the intermediate layer is enhanced, and the effect of the present invention becomes more remarkable.

[Application Example 7]
The vibrator according to the present invention includes the resonator element having the electrode structure of the resonator element according to the present invention, and a package that houses the resonator element.
Thereby, a highly reliable vibrator is obtained.
[Application Example 8]
An oscillator according to the present invention includes the vibrator according to the present invention and an oscillation circuit that oscillates the resonator element.
Thereby, a highly reliable oscillator can be obtained.

[Application Example 9]
An electronic apparatus according to the present invention includes the vibrator according to the present invention.
As a result, a highly reliable electronic device can be obtained.
[Application Example 10]
The moving body of the present invention includes the vibrator of the present invention.
Thereby, a mobile body with high reliability is obtained.

It is a top view which shows embodiment of the vibrator | oscillator of this invention. It is the sectional view on the AA line in FIG. FIG. 2 is a plan view of a resonator element included in the vibrator illustrated in FIG. 1. It is the elements on larger scale which expand and show a part of FIG. It is sectional drawing which shows embodiment of the oscillator of this invention. 1 is a perspective view illustrating a configuration of a mobile (or notebook) personal computer to which an electronic apparatus of the present invention is applied. It is a perspective view which shows the structure of the mobile telephone (PHS is also included) to which the electronic device of this invention is applied. It is a perspective view which shows the structure of the digital still camera to which the electronic device of this invention is applied. 1 is a perspective view schematically showing an automobile as an example of a moving object of the present invention. 2 is an electron micrograph of a longitudinal section of an electrode layer of a resonator element obtained in Example 1. FIG.

Hereinafter, the electrode structure of the resonator element, the method for manufacturing the resonator element, the vibrator, the oscillator, the electronic device, and the moving body of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
[Vibrator]
First, an embodiment of the vibrator of the present invention and an embodiment of the electrode structure of the resonator element of the present invention will be described.

1 is a plan view showing an embodiment of the vibrator of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a plan view of a resonator element included in the vibrator shown in FIG. is there. In the following description, the upper side in FIG. 2 is described as “upper”, and the lower side is described as “lower”.
As illustrated in FIGS. 1 and 2, the vibrator 1 includes a package 110 and a vibrating piece 190 accommodated in the package 110.

(Vibration piece)
As shown in FIGS. 3A and 3B, the resonator element 190 has a piezoelectric substrate 191 having a rectangular plate shape in plan view, and conductivity formed on the surface of the piezoelectric substrate 191. A pair of electrode layers 193 and 195 (electrode structure of the resonator element according to the invention). 3A is a plan view of the upper surface of the vibrating piece 190 as viewed from above, and FIG. 3B is a transparent view (plan view) of the lower surface of the vibrating piece 190 as viewed from above.
The piezoelectric substrate 191 is a quartz base plate that mainly performs thickness shear vibration.

In the present embodiment, a quartz base plate cut at a cut angle called AT cut is used as the piezoelectric substrate 191. The AT cut is mainly obtained by rotating a plane (Y plane) including the X axis and the Z axis, which are crystal axes of quartz, about 35 degrees and 15 minutes around the X axis from the Z axis in the counterclockwise direction. It is cut out so as to have a surface (a main surface including the X-axis and the Z′-axis).
The longitudinal direction of the piezoelectric substrate 191 coincides with the X axis, which is the crystal axis of quartz.

The electrode layer 193 includes an excitation electrode 193a formed on the upper surface of the piezoelectric substrate 191, a bonding pad 193b formed on the lower surface of the piezoelectric substrate 191, and a wiring 193c that electrically connects the excitation electrode 193a and the bonding pad 193b. ,have.
On the other hand, the electrode layer 195 includes an excitation electrode 195a formed on the lower surface of the piezoelectric substrate 191, a bonding pad 195b formed on the lower surface of the piezoelectric substrate 191, and a wiring 195c that electrically connects the excitation electrode 195a and the bonding pad 195b. And have.

The excitation electrode 193a and the excitation electrode 195a are provided to face each other via the piezoelectric substrate 191 and have substantially the same shape. That is, when the piezoelectric substrate 191 is viewed in plan (when viewed from the thickness direction of the piezoelectric substrate 191), the excitation electrode 193a and the excitation electrode 195a are positioned so as to overlap each other and have the same contour. Has been.
Further, the bonding pads 193b and 195b are formed apart from each other at the right end of the lower surface of the piezoelectric substrate 191 in FIG.

  Such electrode layers 193 and 195 each have a three-layer structure including a base layer, an intermediate layer, and an upper layer. The electrode layers 193 and 195 will be described later in detail. In the above description, an AT-cut quartz base plate is described as an example, but this cut angle is not particularly limited, and may be a Z-cut, a BT-cut, or the like. The shape of the piezoelectric substrate 191 is not particularly limited, and may be a bipod tuning fork, an H-type tuning fork, a tripod tuning fork, a comb tooth shape, an orthogonal shape, a prismatic shape, or the like. That is, the electrode structure of the resonator element according to the invention can be applied to any electrode structure provided with a section that can vibrate and an electrode layer provided thereon.

(package)
As shown in FIGS. 1 and 2, the package 110 includes a base 120 having a recess 121 that opens to the upper surface, and a lid 130 (lid) that closes the opening of the recess 121. In such a package 110, the inside of the recess 121 closed by the lid 130 is used as a storage space S for storing the above-described vibrating piece 190.

The base 120 has a plate-like base 123 and a frame-like side wall 124 provided on the upper surface of the base 123, thereby forming a recess 121 that opens to the center of the upper surface of the base 120.
The constituent material of the base 120 is not particularly limited as long as it has insulating properties. For example, oxide-based ceramics such as alumina, silica, titania and zirconia, and nitride-based materials such as silicon nitride, aluminum nitride and titanium nitride Various ceramics such as ceramics and carbide ceramics such as silicon carbide can be used.

  A pair of connection electrodes 141 and 151 are formed on the upper surface of the base 123. On the other hand, a pair of external mounting electrodes 142 and 152 are formed on the lower surface of the base 123. The base 123 is formed with through electrodes 143 and 153 penetrating in the thickness direction. The connection electrode 141 and the external mounting electrode 142 are electrically connected through the through electrode 143, and the through electrode 153 is connected. The connection electrode 151 and the external mounting electrode 152 are electrically connected via each other.

The constituent materials of the connection electrodes 141 and 151, the external mounting electrodes 142 and 152, and the through electrodes 143 and 153 are not particularly limited. For example, gold (Au), gold alloy, platinum (Pt), aluminum (Al), aluminum Alloy, silver (Ag), silver alloy, chromium (Cr), chromium alloy, nickel (Ni), copper (Cu), molybdenum (Mo), niobium (Nb), tungsten (W), iron (Fe), titanium ( Metal materials such as Ti), cobalt (Co), zinc (Zn), and zirconium (Zr) can be used.
A frame-like metallized layer 170 is provided on the upper surface of the side wall 124. The metallized layer 170 enhances adhesion with a brazing material 180 described later. Thereby, the joining strength of the base 120 and the lid 130 by the brazing material 180 can be increased.

The constituent material of the metallized layer 170 is not particularly limited as long as it can improve the adhesion to the brazing material 180. For example, the metal as exemplified in the constituent materials such as the connection electrodes 141 and 151 described above. Materials can be used.
The lid 130 is obtained by processing a metal flat plate and mainly has a flat plate shape.
The constituent material (metal material) of the lid 130 is not particularly limited, but it is preferable to use a metal material whose linear expansion coefficient approximates that of the constituent material of the base 120. Therefore, for example, when the base 120 is a ceramic substrate, it is preferable to use an alloy such as an Fe—Ni—Co alloy such as Kovar or an Fe—Ni alloy such as 42 alloy as a constituent material of the lid 130. .

The method of joining the lid 130 to the base 120 is not particularly limited. For example, the edge of the lid 130 is irradiated with a laser in a state where the lid 130 is placed on the base 120, so There is a method in which the material 180 is heated and melted, whereby the lid 130 is joined to the base 120.
A brazing material 180 is provided on the lower surface of the lid 130. In the present embodiment, the brazing material 180 is provided over the entire area of the lower surface of the lid 130. The brazing material 180 may be provided only on the outer peripheral portion of the lower surface of the lid 130.

The lid 130 is bonded to the base 120 by welding the brazing material 180 and the metallized layer 170.
The brazing material 180 is not particularly limited. For example, gold brazing, silver brazing, or the like can be used, but it is preferable to use silver brazing. The melting point of the brazing material 180 is not particularly limited, but is preferably about 800 ° C. or higher and 1000 ° C. or lower, for example.
In the storage space S of such a package 110, the above-described vibrating piece 190 is stored. The vibrating piece 190 stored in the storage space S is cantilevered on the base 120 via a pair of conductive adhesives 161 and 162.

The conductive adhesive 161 is provided in contact with the connection electrode 141 and the bonding pad 193b, and thereby electrically connects the connection electrode 141 and the bonding pad 193b. Similarly, the conductive adhesive 162 is provided in contact with the connection electrode 151 and the bonding pad 195b, thereby electrically connecting the connection electrode 151 and the bonding pad 195b.
Note that the conductive adhesives 161 and 162 can be replaced with conductive metal materials, respectively. Although it does not specifically limit as a conductive metal material, For example, the metal material which was mentioned by the constituent materials, such as the connection electrodes 141 and 151 mentioned above, is mentioned. Further, instead of the conductive adhesives 161 and 162, a bonding wire may be used.

(Electrode layer)
FIG. 4 is a partially enlarged view showing a part of FIG. 2 in an enlarged manner. In FIG. 4, the top and bottom are reversed from those in FIG. 2.
The electrode layer 193 of the resonator element 190 shown in FIG. 4A includes an underlayer 196 formed on the surface of the piezoelectric substrate 191, an intermediate layer 197 formed on the surface of the underlayer 196, and an intermediate layer 197, respectively. It has a three-layer structure composed of an upper layer 198 formed on the surface. Further, the electrode layer 195 has the same configuration as the electrode layer 193.

  Among these, the intermediate layer 197 is composed mainly of an oxide of a base layer main component which is a main component of the base layer 196. As a result, the intermediate layer 197 exhibits high adhesion to the base layer 196, and mechanical characteristics of the electrode layers 193 and 195, specifically, when the electrode layers 193 and 195 are bonded to the bonding partner. Bonding strength can be increased. Further, the provision of the intermediate layer 197 prevents the constituent components in the base layer 196 from diffusing into the upper layer 198. Thereby, it is possible to prevent the bonding between the upper layer 198 and the bonding partner from being inhibited by the diffused component, and to further increase the bonding strength.

In addition, since the constituent components of the base layer 196 are difficult to diffuse into the upper layer 198, the resonator element 190 whose resonance frequency is stable over time can be obtained. This is because the masses of the electrode layers 193 and 195 are one of the factors that determine the vibration characteristics of the resonator element 190.
That is, by appropriately changing the mass of the electrode layers 193 and 195, the resonance frequency of the resonator element 190 can be adjusted to a desired value. However, after the frequency adjustment, the chemical composition of the electrode layers 193 and 195 changes with time. If it changes, the resonant frequency of the resonator element 190 also changes over time, and deviates from the target value.

  Further, the increase in mass due to oxidation of the metal deposited on the surface of the upper layer 198 due to diffusion from the base layer 196 reduces the frequency of the vibrator and leads to fluctuations in the frequency of the vibrator over time. In addition, since the degree of increase in mass varies depending on the degree of precipitation of metal on the surface due to diffusion, the resonance frequency varies among vibrators manufactured in large quantities.

On the other hand, in the electrode layers 193 and 195 having the three-layer structure described above, the provision of the intermediate layer 197 suppresses diffusion of the base layer main component to the upper layer 198 side. Thereby, in the upper layer 198, it is suppressed that the base layer main component oxidizes, and the mass increase accompanying oxidation is suppressed. This is because the base layer main component is relatively easily oxidized compared to the upper layer main component, so that if the base layer main component diffuses to the surface of the upper layer 198, the base layer main component is exposed on the surface of the upper layer 198. As a result, oxidation easily proceeds in the exposed portion, and as a result, there is a risk that the mass of the electrode layer 193 increases with time, but in the intermediate layer 197, by stopping diffusion of the base layer main component, This is because an increase in mass due to such oxidation can be suppressed. As a result, the resonator element 190 that can prevent a change in the resonant frequency over time (frequency drift) can be obtained.
Further, as described above, the vibration characteristics of the resonator element 190 can be adjusted to a desired range by appropriately changing the mass of the electrode layer 193. However, the amount of adjustment of the resonance frequency is adjusted by the electrode layers 193 and 195. Very sensitive to changes in mass. Accordingly, in adjusting the resonance frequency, it is necessary to strictly control the amount of change in the mass of the electrode layers 193 and 195.

  In order to remove a part of the upper layer 198, first, the specific gravity of the material to be removed is grasped in advance, and the volume to be removed is calculated based on the mass to be reduced and the data of this specific gravity. Remove the top layer 198 of the volume. Therefore, in order to strictly control the amount of change in mass, it is important to precisely grasp the specific gravity of the material to be removed. However, when the constituent material of the upper layer 198 is not homogeneous, this grasp becomes difficult. For example, when the base layer main component is diffused in the upper layer 198, the upper layer 198 is in a state where the upper layer main component and the base layer main component are mixed. Since controlling this mixed state involves a great deal of difficulty, it is inevitably difficult to strictly control the amount of mass change.

  On the other hand, according to the electrode layers 193 and 195, the diffusion of the base layer main component into the upper layer 198 can be suppressed. For this reason, the material which comprises the upper layer 198 is homogeneous, and the specific gravity hardly changes from the specific gravity at the time of formation. Therefore, the specific gravity of the material constituting the upper layer 198 can be easily grasped, and when changing the mass of the upper layer 198, the relationship (rate) of the adjustment amount of the resonance frequency with respect to the mass change amount is strictly controlled. It becomes possible. Therefore, according to the present invention, it is possible to easily obtain the resonator element 190 having a target resonance frequency.

As a base layer main component which is a constituent material of the base layer 196, a material having adhesion to the piezoelectric substrate 191 can be cited. Specifically, chromium (Cr), nickel (Ni), titanium (Ti), Examples include tungsten (W), silver (Ag), aluminum (Al), and the like. Therefore, one or a mixture of two or more of these metal elements (including alloys) is used as the constituent material of the base layer 196. As a constituent material of the underlayer 196, chromium or nickel alone or a mixture (including an alloy) containing any of these is preferably used. Note that the constituent material of the base layer 196 may include a metal element and a non-metal element (for example, Si, C, B, etc.) different from the above in addition to the main component of the base layer. The content of the base layer main component in the base layer 196 is preferably 50% by mass or more.
The average thickness of the base layer 196 is not particularly limited, but is preferably about 3 nm to 300 nm and more preferably about 5 nm to 250 nm. By setting the average thickness of the underlayer 196 within the above range, sufficient adhesion to the piezoelectric substrate 191 is ensured.

  On the other hand, the upper layer main component which is a constituent material of the upper layer 198 includes a material having particularly high electrical conductivity, and specifically includes a noble metal element such as gold (Au) or platinum (Pt). Therefore, the constituent material of the upper layer 198 is a mixture (including an alloy) containing one or more of these noble metal elements. The constituent material of the upper layer 198 may contain a metal element and a non-metal element (for example, Si, C, B, etc.) different from the above in addition to the main component of the upper layer. The content of the upper layer main component in is preferably 50% by mass or more.

  The average thickness of the upper layer 198 is not particularly limited, but is preferably about 10 nm to 1000 nm, and more preferably about 20 nm to 800 nm. By setting the average thickness of the upper layer 198 within the above range, the contact resistance between the electrode layers 193 and 195 and the conductive adhesives 161 and 162 can be suppressed, and the electrical conductivity between them can be increased. When a conductive metal material is used instead of the conductive adhesives 161 and 162, the bonding strength between the electrode layers 193 and 195 and the conductive metal material can be further increased.

As described above, the intermediate layer 197 is mainly composed of the oxide of the base layer main component, which is the main component of the base layer 196. The content ratio of the base layer oxide in the intermediate layer 197 is preferably 50% by mass or more, and more preferably 60% by mass or more. Thereby, the intermediate | middle layer 197 can show | play the effect as mentioned above more reliably.
The intermediate layer 197 is preferably configured so that the oxygen content on the surface on the upper layer 198 side is greater than the oxygen content on the surface on the underlayer 196 side. In such an intermediate layer 197, the oxygen content in the surface on the upper layer 198 side is relatively large, so that the main component of the base layer can be more reliably prevented from diffusing to the upper layer 198 side, and the base layer 196 side can be prevented. Since the oxygen content on the surface is relatively small, the adhesion between the intermediate layer 197 and the base layer 196 is further increased.

  In addition, the oxygen content of the intermediate layer 197 is preferably distributed so as to gradually decrease from the upper layer 198 side to the base layer 196 side in the thickness direction of the intermediate layer 197. Since the composition distribution in the intermediate layer 197 is continuous, the structural continuity of the intermediate layer 197 is increased. For this reason, the mechanical characteristics of the intermediate layer 197 itself are enhanced, and as a result, the bonding strength between the electrode layers 193 and 195 and the bonding partner can be further increased.

  The distribution of the oxygen content of the intermediate layer 197 is qualitative quantitative analysis by performing line analysis or surface analysis of qualitative quantitative analysis on the cross section of the electrode layer 193 or removing the electrode layer 193 little by little in the thickness direction. It can be specified by doing. As the qualitative quantitative analysis, for example, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, electron microanalysis, Auger electron spectroscopy, fluorescent X-ray analysis and the like are used.

  The average thickness of the intermediate layer 197 is preferably not less than 0.05 times and not more than 1 time, more preferably not less than 0.1 times and not more than 0.5 times the average thickness of the base layer 196. Such an intermediate layer 197 can ensure sufficient electrical conductivity in the thickness direction of the electrode layers 193 and 195 while sufficiently exhibiting the effects described above. That is, when the average thickness of the intermediate layer 197 is less than the lower limit value, the intermediate layer 197 has an effect of suppressing the diffusion of the main component of the base layer into the upper layer 198 and the bonding strength between the upper layer 198 and the bonding partner. There is a risk that the effect of suppressing the decrease will be lost. On the other hand, when the average thickness of the intermediate layer 197 exceeds the upper limit, the electrical conductivity in the thickness direction of the electrode layers 193 and 195 may be reduced.

  Further, in the roughness curve of the surface on the upper layer 198 side of the intermediate layer 197 obtained from the longitudinal section of the intermediate layer 197, the maximum height roughness Rz is preferably 10 nm or less, and more preferably 5 nm or less. . When the surface roughness on the upper layer 198 side of the intermediate layer 197 is within the above range, the intermediate layer 197 can exhibit the above-described effects more reliably. In addition, since the surface roughness of the upper layer 198 side of the intermediate layer 197 is within the above range, the surface roughness of the upper layer 198 is sufficiently smooth. For this reason, when the resonance frequency of the resonator element 190 is adjusted by removing a part of the upper layer 198, the amount to be removed can be controlled more precisely, so that the resonance frequency can be adjusted more accurately. Can do. This is because, for example, when a part of the upper layer 198 is removed by a method such as ion milling, the surface roughness of the upper layer 198 is sufficiently small, so that the correlation between the processing time and the removal amount becomes strong. This is because it can be controlled accurately.

  The roughness curve of the surface on the upper layer 198 side of the intermediate layer 197 is obtained by removing low frequency components (waviness components) from the cross-sectional curve appearing in the longitudinal section of the intermediate layer 197. The low frequency component can be removed by performing a calculation that filters the cross-sectional curve acquired by the surface roughness measuring instrument. The maximum height roughness Rz of the roughness curve is defined in JIS B 0601-2001.

  Further, by providing the intermediate layer 197, diffusion of the base layer main component to the upper layer 198 can be suppressed, so that the content of the base layer main component can be suppressed to be small on the surface of the upper layer 198. Specifically, when a qualitative quantitative analysis is performed on the upper surface of the upper layer 198, the content of the base layer main component is preferably 8 atomic% or less, and more preferably 5 atomic% or less. Such an upper layer 198 contributes to obtaining a sufficiently high bonding strength when bonding involving metal melting is performed with a bonding partner. For the qualitative quantitative analysis at this time, a surface sensitive analysis method such as X-ray photoelectron spectroscopy or Auger electron spectroscopy is preferably used.

Here, the intermediate layer 197 is formed by subjecting the temporary layer including the main component of the base layer 196 to heat treatment (oxidation treatment) in an oxidizing atmosphere, thereby oxidizing part of the surface side of the temporary layer. It is a layer made to do. By this oxidation treatment, a part of the surface side of the temporary layer becomes the intermediate layer 197 and the remaining part of the temporary layer becomes the underlayer 196.
According to such oxidation treatment, an intermediate layer 197 having a uniform thickness can be formed. For this reason, the obtained intermediate layer 197 is a layer in which the oxide of the base layer main component is formed relatively densely, and has a particularly excellent function of shielding the diffusion of the base layer main component.

  Further, the intermediate layer 197 obtained through such an oxidation treatment tends to make the oxidation state constant when oxidizing the base layer main component. For example, when the base layer main component is Cr, the valence of Cr in the oxide can be made energetically more stable. For this reason, the chemically more stable electrode layers 193 and 195 can be obtained, and the resonator element 190 that can suppress the shift of the resonance frequency with time is obtained.

Further, by subjecting the temporary layer to oxidation treatment, oxidation proceeds not only on the surface of the temporary layer but also on the side surfaces, and the intermediate layer 197 is formed. Therefore, the formed intermediate layer 197 is formed so as to go around not only the surface of the temporary layer but also the side surfaces. According to such an intermediate layer 197, it is possible to suppress the progress of oxidation from the side surfaces of the electrode layers 193 and 195, and thus it is possible to suppress an increase in the mass of the electrode layers 193 and 195, thereby It is possible to suppress the shift of the resonance frequency over time.
If the intermediate layer 197 is not formed as described above, but the intermediate layer 197 is formed by directly supplying an oxide of a main component of the base layer to the surface of the base layer 196, the density of the intermediate layer 197 is increased. In addition to being inferior, the surface smoothness decreases. For this reason, the function of suppressing the diffusion of the main component of the underlying layer is lowered, and the accuracy in adjusting the resonance frequency of the resonator element 190 is lowered.

[Manufacturing method of vibrating piece]
Next, a method for manufacturing the resonator element 190 shown in FIG. 4 (an embodiment of the method for manufacturing the resonator element of the present invention) will be described.
A method of manufacturing the resonator element 190 includes a step of forming a temporary layer 1970 including a main component of an underlayer on the surface of the piezoelectric substrate 191, and a part of the surface side of the temporary layer 1970 by performing heat treatment in an oxidizing atmosphere. The base layer 196 and the intermediate layer 197 are formed, and the upper layer 198 is formed on the surface of the intermediate layer 197. Hereinafter, each process will be described sequentially.

[1]
First, the temporary layer 1970 is formed on the surface of the piezoelectric substrate 191. The temporary layer 1970 is composed mainly of a base layer main component. At this time, the thickness of the temporary layer 1970 is set to be the sum of the thickness of the base layer 196 to be formed and the thickness of the intermediate layer 197.
A method for forming the temporary layer 1970 is not particularly limited, and examples thereof include various film forming methods such as a vapor deposition method such as a vacuum deposition method, a sputtering method, and a CVD method, a plating method, a coating method, and a printing method. Moreover, after forming into a film by these film-forming methods, you may make it pattern into a desired shape using photolithography and etching as needed.

[2]
Next, the temporary layer 1970 is subjected to heat treatment (oxidation treatment) in an oxidizing atmosphere. Thereby, in the base layer main component included in the temporary layer 1970, oxidation gradually proceeds from the surface side of the temporary layer 1970. As a result, the surface side (surface layer) of the temporary layer 1970 becomes the intermediate layer 197 and the remaining part becomes the underlayer 196.

The conditions for the oxidation treatment are preferably a temperature of 200 ° C. to 600 ° C., a time of 10 minutes to 10 hours, a temperature of 225 ° C. to 500 ° C., and a time of 30 minutes to 4 hours. More preferred. By setting the conditions for the oxidation treatment within the above range, the homogeneous intermediate layer 197 can be formed while preventing the characteristics of the piezoelectric substrate 191 from being deteriorated by heat. Thereby, the effect | action of suppressing the spreading | diffusion of a base layer main component by the intermediate | middle layer 197 is strengthened, and the effect of this invention becomes more remarkable.
The oxidizing atmosphere is not particularly limited as long as it is an oxygen-containing atmosphere, but preferably air is used, and more preferably dry air is used. By using air, the oxidation treatment can be performed without much cost. In addition, since the oxygen concentration is appropriate, there are also advantages that the oxidation reaction can be easily controlled and safety is high.

  Note that by appropriately changing the conditions of the oxidation treatment, it is possible to adjust how much the base layer main component is oxidized in the temporary layer 1970, that is, how much the ratio between the base layer 196 and the intermediate layer 197 is. . For example, the thickness of the intermediate layer 197 can be increased by increasing the heating temperature or increasing the heating time. On the other hand, the thickness of the intermediate layer 197 can be reduced by lowering the heating temperature or shortening the heating time.

[3]
Next, the upper layer 198 is formed on the surface of the intermediate layer 197. Thereby, the electrode layer 193 is formed. The formation method of the upper layer 198 is not particularly limited, and is the same method as the formation method of the base layer 196 described above.

<Oscillator>
Next, an embodiment of the oscillator of the present invention will be described.
FIG. 5 is a cross-sectional view showing an embodiment of the oscillator of the present invention.
Hereinafter, the oscillator will be described. In the following description, differences from the vibrator will be mainly described, and description of similar matters will be omitted.
The oscillator 10 illustrated in FIG. 5 includes a vibrating piece 190 and an IC chip (chip component) 80 for driving the vibrating piece 190. Hereinafter, the oscillator 10 will be described with a focus on differences from the above-described vibrator, and description of similar matters will be omitted. In addition, the same code | symbol is attached | subjected to the structure similar to the vibrator | oscillator mentioned above.

The package 9 includes a box-shaped base 91 having a recess 911 and a plate-shaped lid 92 that closes the opening of the recess 911.
The concave portion 911 of the base 91 opens to the first concave portion 911a that opens to the upper surface of the base 91, the second concave portion 911b that opens to the central portion of the bottom surface of the first concave portion 911a, and the central portion of the bottom surface of the second concave portion 911b. And a third recess 911c.

  A connection terminal 95 is formed on the bottom surface of the first recess 911a. An IC chip 80 is disposed on the bottom surface of the third recess 911c. The IC chip 80 has a drive circuit (oscillation circuit) for controlling the drive of the resonator element 190. By controlling the driving of the vibrating piece 190 by the IC chip 80, a signal having a predetermined frequency can be extracted from the vibrating piece 190.

In addition, a plurality of internal terminals 93 that are electrically connected to the IC chip 80 via wires are formed on the bottom surface of the second recess 911b. The plurality of internal terminals 93 include terminals electrically connected to external terminals (mounting terminals) 94 formed on the bottom surface of the package 9 via vias (not shown) formed on the base 91, vias (not shown), And a terminal electrically connected to the connection terminal 95 through a wire.
In the configuration of FIG. 5, the configuration in which the IC chip 80 is arranged in the storage space has been described. However, the arrangement of the IC chip 80 is not particularly limited, and is arranged, for example, outside the package 9 (the bottom surface of the base). May be.

[Electronics]
Next, the electronic apparatus of the present invention will be described in detail based on FIGS.
FIG. 6 is a perspective view showing a configuration of a mobile (or notebook) personal computer to which the electronic apparatus of the present invention is applied. In this figure, a personal computer 1100 includes a main body portion 1104 provided with a keyboard 1102 and a display unit 1106 provided with a display portion 100. The display unit 1106 is rotated with respect to the main body portion 1104 via a hinge structure portion. It is supported movably. Such a personal computer 1100 has a built-in vibrator 1 that functions as a filter, a resonator, a reference clock, and the like.

  FIG. 7 is a perspective view showing a configuration of a mobile phone (including PHS) to which the electronic apparatus of the present invention is applied. In this figure, a cellular phone 1200 includes a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206, and the display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a cellular phone 1200 incorporates the vibrator 1 that functions as a filter, a resonator, and the like.

  FIG. 8 is a perspective view showing the configuration of a digital still camera to which the electronic apparatus of the present invention is applied. In this figure, connection with an external device is also simply shown. Here, an ordinary camera sensitizes a silver halide photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an imaging device such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.

  A display unit is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to perform display based on an imaging signal from the CCD. The display unit is a finder that displays an object as an electronic image. Function. A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side (the back side in the drawing) of the case 1302.

  When the photographer confirms the subject image displayed on the display unit and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory 1308. In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the input / output terminal 1314 for data communication as necessary. Further, the imaging signal stored in the memory 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation. Such a digital still camera 1300 incorporates a vibrator 1 that functions as a filter, a resonator, or the like.

  In addition to the personal computer (mobile personal computer) in FIG. 6, the mobile phone in FIG. 7, and the digital still camera in FIG. 8, the electronic apparatus of the present invention includes, for example, an ink jet type ejection device (for example, an ink jet printer), Laptop personal computer, TV, video camera, video tape recorder, car navigation device, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game device, word processor, workstation, video phone, crime prevention TV monitor, electronic binoculars, POS terminal, medical equipment (for example, electronic thermometer, blood pressure monitor, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments (for example, Vehicle, aircraft, ship instrumentation), It can be applied to a site simulator or the like.

[Moving object]
Next, a moving body (the moving body of the present invention) including the vibrator of the present invention will be described.
FIG. 9 is a perspective view schematically showing an automobile as an example of the moving object of the present invention. A vibrator 1500 is mounted on the automobile 1500. The vibrator 1 is a keyless entry, immobilizer, car navigation system, car air conditioner, anti-lock brake system (ABS), air bag, tire pressure monitoring system (TPMS), engine control, hybrid car, The present invention can be widely applied to electronic control units (ECUs) such as battery monitors for electric vehicles and body posture control systems.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to this, The structure of each part can be substituted by the thing of the arbitrary structures which have the same function. .
Moreover, in this invention, arbitrary structures may be added to embodiment mentioned above, and each embodiment may be combined suitably.
In addition, the resonator element including the electrode structure according to the present invention may be a vibrator other than the vibrator described in the embodiment, for example, a surface acoustic wave element.

Next, specific examples of the present invention will be described.
1. Manufacture of vibrating piece (Example 1)
[1] First, an AT-cut quartz substrate was prepared, and a chromium film was formed thereon by vapor deposition. Thereby, a temporary layer was obtained.

[2] Next, the temporary layer was subjected to heat treatment at 275 ° C. for 2 hours in the air. As a result, an underlayer and an intermediate layer were formed.
[3] Next, a gold film was formed on the intermediate layer by vapor deposition. This obtained the upper layer.

In this way, a resonator element including a three-layer electrode layer was manufactured. The structure of the electrode layer is as follows.
<Structure of electrode layer>
・ Underlayer main component: Chromium ・ Average thickness of underlayer: 15 nm
・ Constituent component of intermediate layer: Chromium oxide (Cr ₂ O ₃ )
-Average thickness of the intermediate layer: 3 nm
-Upper layer main component: gold-Average thickness of upper layer: 200 nm

The longitudinal section of the electrode layer was observed with a transmission electron microscope. And the cross-sectional curve of the surface of the upper layer side of the intermediate layer was determined from the observed image.
Subsequently, the roughness curve was calculated | required by removing a low frequency component from the calculated | required cross-sectional curve. And based on JIS B 0601-2001, the maximum height roughness Rz was calculated | required from this roughness curve. The obtained maximum height roughness Rz was 1.2 nm.

(Example 2)
A resonator element was manufactured in the same manner as in Example 1 except that the heat treatment conditions were changed to 450 ° C. × 1 hour. The structure of the obtained electrode layer is as follows.
<Structure of electrode layer>
・ Underlayer main component: Chrome ・ Average thickness of underlayer: 30 nm
・ Constituent component of intermediate layer: Chromium oxide (Cr ₂ O ₃ )
-Average thickness of the intermediate layer: 10 nm
-Upper layer main component: Gold-Average thickness of upper layer: 250 nm
・ Maximum roughness Rz: 2.5 nm

(Example 3)
A resonator element was manufactured in the same manner as in Example 1 except that the heat treatment conditions were changed to 375 ° C. × 0.5 hours. The structure of the obtained electrode layer is as follows.
<Structure of electrode layer>
・ Underlayer main component: Chromium ・ Average thickness of underlayer: 10 nm
・ Constituent component of intermediate layer: Chromium oxide (Cr ₂ O ₃ )
-Average thickness of the intermediate layer: 2 nm
-Upper layer main component: gold-Average thickness of upper layer: 150 nm
-Maximum height roughness Rz: 0.8 nm

Example 4
A resonator element was manufactured in the same manner as in Example 1 except that the upper layer main component was changed to platinum (Pt).
(Example 5)
A resonator element was manufactured in the same manner as in Example 1 except that the base layer main component was changed to nickel (Ni).

(Comparative example)
After the temporary layer was formed on the quartz substrate, the resonator element was manufactured in the same manner as in Example 1 except that the heat treatment was omitted and a two-layered electrode layer was formed. The structure of the obtained electrode layer is as follows.
<Structure of electrode layer>
・ Underlayer main component: Chromium ・ Average thickness of underlayer: 15 nm
-Upper layer main component: gold-Average thickness of upper layer: 200 nm
・ Maximum roughness Rz: 6.3 nm

(Reference example)
A resonator element was manufactured in the same manner as in Example 1 except that an upper layer was formed on the quartz substrate to form an electrode layer having a single layer structure. The structure of the obtained electrode layer is as follows.
<Structure of electrode layer>
-Upper layer main component: gold-Average thickness of upper layer: 200 nm

2. Evaluation of Vibrating Piece The vibrating piece obtained in each example, comparative example, and reference example was subjected to a heat treatment (annealing treatment) at 275 ° C. for 2 hours.
2.1 Qualitative Quantitative Analysis of Electrode Layer Longitudinal Section Next, a qualitative quantitative analysis was performed on the longitudinal section of the electrode layer of the vibrating piece after the heat treatment by energy dispersive X-ray spectroscopy (EDX). As a result, among the electrode layers of the resonator elements obtained in Examples 1 to 3, the analysis results of the base layer indicate that the Cr content is 90 ± 2 atomic% and the O content is 10 ± 4 atomic%. It was within. Further, in the analysis result of the intermediate layer, the Cr content was within 71 ± 3 atomic% and the O content was within 29 ± 6 atomic%.

FIG. 10 is an electron micrograph of the longitudinal section of the electrode layer of the resonator element obtained in Example 1. In the electron micrograph shown in FIG. 10, the presence of each layer is recognized by the difference in the degree of shading.
Also from such an electron micrograph, it is recognized that the electrode layer of the resonator element obtained in Example 1 has a three-layer structure of an underlayer, an intermediate layer, and an upper layer.

2.2 Element distribution in thickness direction of electrode layer Next, the electrode layer of the resonator element after the heat treatment was subjected to qualitative quantitative analysis by X-ray photoelectron spectroscopy (XPS) while performing sputtering. As a result, it was confirmed that in each of the resonator elements obtained in each example, a concentration distribution was formed in which the oxygen content gradually decreased from the upper layer side of the intermediate layer toward the base layer side.

2.3 Qualitative Quantitative Analysis of Electrode Layer Surface Subsequently, the surface of the electrode layer of the vibrating piece after the heat treatment was subjected to qualitative quantitative analysis by X-ray photoelectron spectroscopy (XPS). As a result, in each of the vibrating bars obtained in each example, the Cr content on the electrode layer surface was below the detection limit, whereas in the vibrating bars obtained in the comparative example and the reference example, both The Cr content was 5 atomic% or more. Therefore, in the electrode layer of the vibrating piece obtained in the example, the diffusion of Cr was suppressed, whereas in the vibrating piece obtained in the comparative example and the reference example, Cr diffused to the surface of the electrode layer. It was recognized that

2.4 Change in Resonant Frequency The resonator element obtained in each example, comparative example, and reference example was subjected to a heat treatment at 290 ° C. for 2 hours, and the frequency change before and after the heat treatment was evaluated.
As a result, in the resonator element obtained in Example 1, the frequency after the heat treatment was 1.7 ppm lower than the frequency before the heat treatment. The standard deviation σ of the frequency after the heat treatment was 1.2 ppm. In addition, the same degree of evaluation was obtained for the vibration pieces obtained in the other examples.
On the other hand, in the resonator element obtained in the comparative example, the frequency after the heat treatment was 24.7 ppm lower than the frequency before the heat treatment. The standard deviation σ of the frequency after the heat treatment was 2.2 ppm.

From the above, it was confirmed that in the resonator element obtained in the comparative example, the frequency was greatly shifted by the heat treatment, and the frequency variation was increased. This is presumably because, in the resonator element obtained in the comparative example, the oxidation of the electrode layer proceeds with heat treatment, and the mass of the electrode layer increases, so that the resonance frequency is greatly reduced. On the other hand, in the resonator element obtained in each example, it is considered that the resonance frequency was hardly changed because the electrode layer was hardly oxidized.
From the above, according to the present invention, it has been clarified that an electrode structure of a resonator element having excellent bonding strength with respect to a bonding partner and capable of accurately adjusting the frequency can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Vibrator 10 ... Oscillator 110 ... Package 120 ... Base 121 ... Recessed part 123 ... Base part 124 ... Side wall 130 ... Lid 141 ... Connection electrode 142 ... External mounting electrode 143 ... Through-hole electrode 151 ...... Connection electrode 152 ...... External mounting electrode 153 ...... Penetration electrode 161 ...... conductive adhesive 162 ...... conductive adhesive 170 ...... metallized layer 180 ...... brazing material 190 …… vibrating piece 191 …… piezoelectric substrate 193 ... Electrode layer 193a ... Excitation electrode 193b ... Bonding pad 193c ... Wiring 195 ... Electrode layer 195a ... Excitation electrode 195b ... Bonding pad 195c ... Wiring 196 ... Underlayer 197 ... Intermediate layer 1970 ... Temporary layer 198 …… Upper layer 80 …… IC chip 9 …… Package 91 …… 911 …… Recess 911a …… First recess 911b …… Second recess 911c …… Third recess 92 …… Lid 93 …… Internal terminal 94 …… External terminal 95 …… Connecting terminal 100 …… Display 1100… ... Personal computer 1102 ... Keyboard 1104 ... Main body 1106 ... Display unit 1200 ... Mobile phone 1202 ... Operation buttons 1204 ... Earpiece 1206 ... Mouthpiece 1300 ... Digital still camera 1302 ... Case 1304 ... Light receiving unit 1306 …… Shutter button 1308 …… Memory 1312 …… Video signal output terminal 1314 …… Input / output terminal 1430 …… TV monitor 1440 …… Personal computer 1500 …… Automobile S …… Storage space

Claims (10)

A vibration substrate;
An electrode layer in which an underlayer, an intermediate layer, and an upper layer are sequentially laminated from the surface of the vibration substrate;
Including
The intermediate layer is a layer formed by oxidizing a part of the surface side of the surface layer by subjecting the main component of the surface layer of the surface layer to heat treatment in an oxidizing atmosphere. The electrode structure of the characteristic vibrating piece.   2. The electrode structure of the resonator element according to claim 1, wherein the intermediate layer is configured such that an oxygen content rate on the surface on the upper layer side is larger than an oxygen content rate on the surface on the base layer side.   3. The electrode structure of the resonator element according to claim 1, wherein a maximum height roughness Rz is 10 nm or less in a roughness curve of the surface on the upper layer side of the intermediate layer, which is obtained from a longitudinal section of the intermediate layer.   4. The electrode structure of the resonator element according to claim 1, wherein the intermediate layer is configured to wrap around a side surface of the base layer. 5. A vibration substrate;
An electrode layer in which an underlayer, an intermediate layer, and an upper layer are sequentially laminated from the surface of the vibration substrate;
A method of manufacturing a resonator element including:
Forming a temporary layer containing the main component of the foundation layer on the surface of the vibration substrate;
Performing a heat treatment in an oxidizing atmosphere to oxidize a part of the surface side of the temporary layer to form the base layer and the intermediate layer;
And a step of forming the upper layer on the surface of the intermediate layer.   The method for manufacturing a resonator element according to claim 5, wherein the conditions for the heat treatment are a temperature of 200 ° C. to 600 ° C. and a time of 10 minutes to 10 hours.   5. A vibrator comprising: a resonator element having the electrode structure of the resonator element according to claim 1; and a package for storing the resonator element.   An oscillator comprising: the vibrator according to claim 7; and an oscillation circuit that oscillates the vibration piece.   An electronic apparatus comprising the vibrator according to claim 7.   A moving body comprising the vibrator according to claim 7.

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