JP4428020B2 - Piezoelectric vibrating piece, structure of excitation electrode thereof, electrode forming method, mobile phone device using piezoelectric device and piezoelectric device, and electronic equipment using piezoelectric device - Google Patents

Description

  The present invention relates to a piezoelectric vibrating piece, a structure of an excitation electrode thereof, an electrode forming method, a piezoelectric device in which the piezoelectric vibrating piece is accommodated in a package or a case, and a mobile phone and an electronic apparatus using the piezoelectric device.

Piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators in small information devices such as HDDs (hard disk drives), mobile computers, IC cards, and mobile communication devices such as mobile phones, car phones, and paging systems Is widely used.
A conventional piezoelectric device accommodates, for example, a piezoelectric vibrating piece formed of a piezoelectric material in a package.
The piezoelectric vibrating piece is formed, for example, by etching a quartz wafer into a rectangular shape to provide a driving electrode. FIG. 11 is a partial cross-sectional view of such a piezoelectric vibrating piece.
In the figure, the piezoelectric vibrating reed 1 has an excitation electrode 7 as a driving electrode formed on the surface of a crystal material 2. The excitation electrode 7 is formed, for example, by depositing chromium as the underlayer 3 on the surface of the quartz crystal material 2 and depositing silver or gold as the electrode layer 4 on the surface.

Here, regarding the electrode structure of the piezoelectric vibrating piece, various techniques for forming a plurality of metal layers are known. For example, in the first example (Patent Document 1), an electrode layer is formed on a base layer. A structure in which the same metal layer as the underlayer is formed thereon is shown.
The second example (Patent Document 2) discloses a technique of forming a film in a four-layer structure such as a chromium-silver-chromium mixed layer-silver-chromium when forming an electrode film.

JP2002-344281 JP-A-5-335880

In the electrode structure as shown in FIG. 11, before the excitation electrode 7 described above is formed on the surface of the quartz material 2, the material is exposed to the atmosphere or is subjected to an active process to oxidize with SiO2. A film 2a is formed. The O2 component of the oxide film is combined with Cr, and chromium oxide CrO2 is formed to join the interface between the oxide film 2a and the base layer 3.
On the other hand, there is a very small gap between the silver or gold metal particles constituting the electrode layer 4. When the air enters through this gap and reaches the boundary between the base layer 3 and the electrode layer 4 , chromium oxide is formed. It is formed. However, since chromium oxide is difficult to be bonded to a metal such as silver or gold, as shown in FIG. Usually, a quartz crystal material is etched to form a quartz chip, an electrode is formed to complete the piezoelectric vibrating reed 1, and then it is stored in the atmosphere until it is mounted on a package or the like. The above reaction proceeds.

  FIG. 13 is a photomicrograph showing the piezoelectric vibrating piece in which the float 6 is partially generated. Further, FIG. 14 shows the CI (crystal impedance) value of the piezoelectric vibrating reed 1 in which the left half does not generate a float 6 between the electrode layer and the base layer, and the right half is between the electrode layer and the base layer. The CI value of the piezoelectric vibrating piece 1 in which the float 6 is partially generated is shown. That is, when the above-described float 6 is generated in the piezoelectric vibrating piece 1, the CI value changes greatly.

  On the other hand, in the technique of the first example (Patent Document 1) described above, a metal layer is formed on the electrode layer with the same metal as the base layer, so that the electrode portion formed on the package is electrically conductive. In joining the piezoelectric vibrating piece with the adhesive, it is intended to improve the conduction performance with the above-described package electrode portion, and is not intended to solve the above-described problems of the present application.

  The second example (Patent Document 2) discloses a technique of forming a film in a four-layer structure such as a chromium-silver-chromium mixed layer-silver-chromium when forming an electrode film. In this technique, a metal film having such a four-layer structure is formed on the entire piezoelectric vibrating piece. For example, at the location of the extraction electrode (connection electrode land), these layers are partially peeled off. It is intended to improve the conductivity with the conductive adhesive. That is, the entire electrode is formed of a number of layers, and these layers are partially exposed as necessary to improve the characteristics of each part of the electrode film of the piezoelectric vibrating piece. It is intended to solve a problem different from the problem of the present application, and does not solve the partial peeling between the base layer and the electrode layer.

  The present invention has been made to solve the above problems, and prevents partial peeling at the interface between the base layer and the electrode layer, and effectively avoids an increase in CI value after film formation. Exciting Electrode Structure, Method for Forming the Electrode, Electrode Filming Apparatus, Piezoelectric Vibrating Piece Provided with Exciting Electrode, Piezoelectric Device Using the Same, Manufacturing Method Therefor, and Portable Using the Piezoelectric Device The purpose is to provide telephone and electronic equipment.

According to the first aspect of the present invention, there is provided an electrode forming method in which a metal film is formed on a surface of a piezoelectric material by sputtering to form an excitation electrode that is a driving electrode of a piezoelectric vibrating piece. A base layer made of chromium is formed on the surface by sputtering, and either a silver or gold metal and chromium are sequentially formed by sputtering so that a region where no film adheres to the surface of the base layer remains partially. After the film formation of the silver or gold and chromium, further forming an electrode layer of silver or gold on the surface, through the continuous sputtering step, between the base layer and the electrode layer, This is achieved by an electrode forming method in which a diffusion layer in which chromium is diffused in silver or gold is formed, and the thickness of the diffusion layer is 50 to 200 angstroms .

According to the configuration of the first invention, the film is sequentially formed on the surface of the piezoelectric material, on which the electrode is to be formed, by sputtering. In this case, the main feature is that after a base layer made of chromium is formed, a silver or gold metal layer and a chromium layer are formed on the surface with a minimum thickness. That is, when a metal layer of silver or gold is formed, the film is formed while making the film thickness extremely thin, leaving a part of the surface of the underlayer to which no silver or gold adheres. . Further, in the process of forming a very thin chrome layer thereon, a region where chromium is attached and a region where no chromium is attached are formed. In such a state, when silver or gold as an electrode layer is formed by sputtering at a required film thickness, when the formation of a relatively thick electrode layer is completed, a very thin silver film is formed below the electrode layer. Alternatively, a silver chromium diffusion layer in which chromium is diffused in a metal layer made of gold or a gold chromium diffusion layer can be appropriately formed.
As a result, the atmosphere or the oxygen component in the atmosphere that has entered from the minute gaps between the metal particles of the electrode layer can be blocked by the diffusion layer, thereby reacting with the base layer to form chromium oxide. In addition, the interface between the base layer and the diffusion layer can maintain good bonding. For this reason, the electrode which does not become a peeling state partially can be obtained.

According to a second aspect of the present invention, in the configuration of the first aspect, the film thickness of the silver metal layer of the diffusion layer is practically about 150 angstroms, and the film thickness of the chromium layer of the diffusion layer is thickness, wherein the Oh Rukoto in practice generally 20 angstroms.
According to the second aspect of the invention, the silver or gold metal layer and the chromium layer on the surface thereof are formed as thin as possible to form the silver chromium diffusion layer or the gold chromium diffusion layer. Very favorable conditions can be created above.

In the third aspect of the present invention, the above-described object is achieved by a sputter chamber in an airtight state, a transport means for transporting a piezoelectric chip formed by processing a piezoelectric material provided in the sputter chamber, and the transport A first target material made of chromium, a second target material made of silver or gold, a third target material made of chromium, and a fourth target material made of silver or gold, which are sequentially arranged along the conveying direction of the means; Control means for controlling the transport speed of the transport means, and in the region corresponding to the first target material, the control means sets the transport speed to the first speed corresponding to the formation of the underlayer. In the region corresponding to the second and third target materials in order to form a film of either silver or gold metal and chromium on the surface of the base layer, Setting the conveying speed to the second speed than the first speed which is several times the speed, the electrode film forming device is achieved.
According to the configuration of the third invention, after the transport means in the sputtering chamber forms the chromium underlayer on the surface of the piezoelectric chip by the first target material, it is several times the transfer speed when forming this underlayer. By transporting at a speed, a metal of either silver or gold and chromium can be formed on the surface of the underlayer with a minimum thickness. By forming an electrode layer after forming such a metal layer and a chromium layer, when the electrode layer is completed, a silver chromium diffusion layer or a gold chromium diffusion layer can be suitably formed in the lower layer.

According to a fourth aspect of the invention, in the configuration of the third aspect of the invention, the control means is reciprocated by switching the transport direction of the transport device, and the first target material, the third target material, and the second The target material and the fourth target material are both used.
According to the configuration of the fourth invention, the control means is reciprocated by switching the transport direction of the transport device, and the first target material, the third target material, the second target material, and the second By combining the four target materials, the total length of the sputtering chamber can be shortened compared to the case where the first to fourth target materials are sequentially arranged linearly. It can be a membrane device.

According to the fifth aspect of the present invention, there is provided a piezoelectric vibrating piece including an excitation electrode as a drive electrode on a surface of a piezoelectric chip formed by etching a piezoelectric material, wherein the excitation electrode is a piezoelectric material. Formed on the surface of the diffusion layer, a chromium layer as an underlayer formed on the surface of the metal, a diffusion layer formed by diffusing chromium in silver or chromium in gold, and formed on the surface of the chromium underlayer This is achieved by a piezoelectric vibrating reed comprising an electrode layer made of silver or gold.
According to the configuration of the fifth invention, the excitation electrode on the surface of the piezoelectric chip has a diffusion layer formed by diffusing chromium into silver or diffusing chromium into gold under the electrode layer. For this reason, the atmosphere or the oxygen component in the atmosphere that has entered from the minute gaps between the metal particles of the electrode layer can be blocked by the diffusion layer, thereby reacting with the base layer to form chromium oxide. In addition, the interface between the base layer and the diffusion layer can maintain good bonding. For this reason, the piezoelectric vibrating piece according to the present invention is provided with an excitation electrode that does not partially become peeled, and a piezoelectric vibrating piece that does not vary in CI value due to such partial peeling is obtained. be able to.

Furthermore, in the sixth invention, the above-mentioned object is a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package or case, and the piezoelectric vibrating piece includes an excitation electrode as a driving electrode. The excitation electrode comprises a chromium layer as an underlayer formed on the surface of the piezoelectric material, and chromium diffused in silver or chromium in the gold formed on the surface of the chromium underlayer. This is achieved by a piezoelectric device comprising a diffused diffusion layer and an electrode layer made of silver or gold formed on the surface of the diffusion layer.
According to the configuration of the sixth invention, the excitation electrode of the piezoelectric vibrating piece housed in the package or case has a diffusion layer formed by diffusing chromium into silver or diffusing chromium into gold under the electrode layer. is doing. For this reason, the atmosphere or the oxygen component in the atmosphere that has entered from the minute gaps between the metal particles of the electrode layer can be blocked by the diffusion layer, thereby reacting with the base layer to form chromium oxide. In addition, the interface between the base layer and the diffusion layer can maintain good bonding. For this reason, the piezoelectric vibrating piece is provided with an excitation electrode that is not partially peeled, and it is possible to obtain a piezoelectric vibrating piece that does not vary in CI value due to such partial peeling. As a result, the reliability of the piezoelectric device is improved.

  According to a seventh aspect of the present invention, there is provided a cellular phone device using a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package or case, wherein the piezoelectric vibrating piece includes a driving device. An excitation electrode is provided as an electrode, and the excitation electrode is formed of a chromium layer as an underlayer formed on the surface of the piezoelectric material, and chromium is diffused in silver formed on the surface of the underlayer of the chromium, Alternatively, it is achieved by a mobile phone device that obtains a clock signal for control by a piezoelectric device including a diffusion layer in which chromium is diffused in gold and an electrode layer made of silver or gold formed on the surface of the diffusion layer. Is done.

  According to an eighth aspect of the present invention, there is provided an electronic apparatus using a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package or case, wherein the piezoelectric vibrating piece includes a driving electrode. As the excitation electrode, a chromium layer as a base layer formed on the surface of the piezoelectric material, and chromium diffused in silver formed on the surface of the chromium base layer, or This is achieved by an electronic device that obtains a clock signal for control by a piezoelectric device having a diffusion layer in which chromium is diffused in gold and an electrode layer made of silver or gold formed on the surface of the diffusion layer. .

1 and 2 show an embodiment of a piezoelectric device of the present invention. FIG. 1 is a schematic perspective view showing a part of the piezoelectric device by cutting a part thereof, and FIG. 2 is a schematic view of the piezoelectric device of FIG. FIG. 3 is a longitudinal sectional view, and FIG. 3 is a schematic perspective view of a piezoelectric vibrating piece used in the piezoelectric device of FIG.
In the figure, the piezoelectric device 30 shows an example in which a piezoelectric vibrator is configured. The piezoelectric device 30 houses a piezoelectric vibrating piece in a package 37.
Specifically, as illustrated in FIG. 2, the piezoelectric device 30 includes a piezoelectric vibrating piece 31 in a package 36 including a first substrate 34 and a second substrate 35 stacked on the first substrate 34. Contained.

The first substrate 34 constituting the package 36 is an insulating base, and the electrode part 32 is formed thereon. In FIG. 1, as indicated by reference numerals 32 and 32, a pair of electrode portions is provided at both end portions in the width direction of the first substrate 34 at the end portion of the package 36.
The first substrate 34 and the second substrate 35 are formed of an insulating material, and ceramic is suitable. In particular, a material having a thermal expansion coefficient that matches or is very close to the thermal expansion coefficient of the piezoelectric vibrating piece 31 or a lid described later is selected as a preferable material. In this embodiment, for example, a ceramic obtained by firing a green sheet is used. It's being used. The green sheet is obtained, for example, by dispersing a ceramic powder in a predetermined solution, forming a kneaded product formed by adding a binder into a sheet-like long tape shape, and cutting it into a predetermined length Is.

  The first substrate 34 and the second substrate 35 can be formed by laminating and sintering green sheets molded into the illustrated shape. In this case, the first substrate 34 is a substrate that constitutes the bottom of the package 36, and the second substrate 35 that is stacked on the first substrate 34 has a frame shape by removing the internal material from the above-described green sheet as a plate shape. As shown in FIG. 2, the internal space S of FIG. 2 is formed, and the piezoelectric vibrating piece 31 is accommodated using the internal space S. The package 36 is hermetically sealed by bonding a lid 37 made of a metal such as ceramic, glass or Kovar to the package 36 via a brazing material 37a.

  On the first substrate 34, for example, after forming a required conductive pattern using a conductive paste such as silver or palladium or a conductive paste such as tungsten metallization, the first and second substrates are sintered. Thereafter, nickel and gold or silver are sequentially plated to form the electrode portions 32 and 32 described above. As shown in FIG. 2, the electrode portion 32 is connected to mounting terminals 41 and 41 exposed on the bottom surface of the package 36 by a conductive pattern 32a. The conductive pattern for connecting the electrode portion 32 and the mounting terminal 41 may be formed on the surface of a castellation used when forming the package 36, and the outer surface of the package 36 may be routed, or FIG. As indicated by reference numeral 32b, the connection may be made by a conductive through hole penetrating the first substrate 34 or the like.

  As shown in FIG. 2, the piezoelectric vibrating piece 31 is formed by, for example, a so-called AT-cut vibrating piece obtained by processing a wafer formed of a piezoelectric material into a thin rectangular shape, so that a vibrating piece piece that is a piezoelectric chip is formed. Yes. As the piezoelectric material, for example, quartz is used in this embodiment, and other piezoelectric materials such as lithium tantalate and lithium niobate can be used. Further, the piezoelectric chip is not limited to the AT-cut vibrating piece, and a convex type or a reverse mesa type vibrating piece can be used. Further, a wafer made of a crystal Z plate is made of, for example, a hydrofluoric acid solution. Alternatively, a so-called tuning fork type resonator element may be used by wet etching or dry etching.

  In FIG. 3, an excitation electrode 51 is formed as a driving electrode on the surface of a piezoelectric chip which is an individual piece of a vibrating piece. The excitation electrode 51 is formed in a region where the piezoelectric chip is actively vibrated, and is used to efficiently generate an electric field in the material by applying a driving voltage to the piezoelectric material to excite it. The excitation electrode 51 is also formed in the same form on the back surface of a piezoelectric chip (not shown), and is an extraction electrode that is a connection electrode formed at each end in the width direction at the end in the length direction of the piezoelectric vibrating piece 31. 51a and 51a are connected separately.

As shown in FIG. 1, such a piezoelectric vibrating piece 31 is formed by applying conductive adhesives 43 and 43 on the respective electrode portions 32 and 32 on the package 36 side, and then on the piezoelectric vibrating piece 31. The base end portions 31a on which the respective extraction electrodes 51a and 51a described with reference to FIG. 3 are placed are placed, and these conductive adhesives 43 and 43 are cured to be joined in a cantilever manner.
As a result, the drive voltage supplied from the outside of the package 36 via the mounting terminals 41, 41 is transmitted from the electrode portions 32, 32 on the package 36 side to the conductive adhesives 43, 43 and the extraction electrodes 51 a of the piezoelectric vibrating reed 31. It is applied to the excitation electrode 51 via 51a. Accordingly, the distal end side 31b of the piezoelectric vibrating piece 31 is driven by being vibrated by a piezoelectric action.

Here, as the conductive adhesives 43, 43, a binder component made of a predetermined synthetic resin to which conductive particles such as silver particles are added can be used. In addition, the piezoelectric vibrating piece 31 is not necessarily a cantilever type, and a part of the tip end side 31b may be joined to the package 36 side.
In addition, the piezoelectric substrate 31 is hermetically sealed by a shallow box-shaped lid (not shown) without forming the electrode using the first substrate 34 as an insulating base and laminating the second substrate 35. It is also possible to use a package that stops. Alternatively, a plug connected to an external drive voltage source is connected to the piezoelectric vibrating piece 31, the piezoelectric vibrating piece 31 is inserted into a metal cylindrical case with one end closed, and the case is hermetically sealed with this plug. You may make it (not shown).

FIG. 4 shows a cross-sectional structure of the excitation electrode 51 of the piezoelectric vibrating piece 31 of FIG.
In the figure, a base layer 52 of chromium is formed on the surface of the piezoelectric material of the piezoelectric vibrating piece 31, in this case, the crystal 57. A diffusion layer 55 is formed on the surface of the base layer 52, and an electrode layer 56 is formed on the diffusion layer 55. Each of these layers is formed through a step by sputtering described later.

The underlayer 52 is formed with a thickness of 30 to 300 angstroms. In general, since a metal layer serving as an electrode layer cannot be directly bonded to the surface of quartz, a base film having good bondability with the metal constituting the electrode layer is formed. In this embodiment, it is preferable to form the underlying layer of chromium (Cr) as thin as possible from about 30 angstroms. In this embodiment, the base layer 52 is formed with a film thickness of about 70 angstroms, for example. The diffusion layer 55 is a layer having a structure in which one of the base metal, chromium, and the metal constituting the electrode layer is diffused to the other, and preferably has a thickness of about 50 to 200 angstroms. In this embodiment, the diffusion layer 55 is formed to about 170 angstroms. ing. The electrode layer is preferably formed of silver (Ag) or gold (Au) to a film thickness of about 1500 to 3500 angstroms. In this embodiment, the electrode layer is formed of about 2500 angstroms by the process described later .

  The diffusion layer 55 of FIG. 4 is formed by forming a silver or gold metal layer 53 on the surface of the underlayer 52 and a chromium layer 54 on the surface thereof by sputtering with a minimum thickness. The minimum film thickness is, for example, that silver or gold metal particles forming the metal layer 53 and chromium particles forming the chromium layer 54 are formed to a thickness corresponding to the particle diameter. Realized.

  The piezoelectric device 30 according to the present embodiment is configured as described above, and the excitation electrode 51 of the piezoelectric vibrating piece 31 housed in the package 36 has chromium diffused in silver under the electrode layer 56 or chromium in gold. Has a diffusion layer 55 formed by diffusion. For this reason, the atmosphere or the oxygen component in the atmosphere that has entered through the minute gaps between the metal particles of the electrode layer 56 is blocked by the diffusion layer 55 below it, thereby reacting with the base layer 52 and being oxidized. Chromium is not formed, and the interface between the base layer 52 and the diffusion layer 55 can maintain good bonding. For this reason, the piezoelectric vibrating piece 31 is provided with the excitation electrode 51 that is not partially peeled, and the CI value variation as described in FIG. 14 is caused by such partial peeling. Therefore, the reliability of the piezoelectric device 30 is improved.

(Piezoelectric device manufacturing method)
Next, an example of a method for manufacturing the piezoelectric device 30 described above will be described.
FIG. 5 is a flowchart showing an example of a method for manufacturing the piezoelectric device 30.
The package 36, the piezoelectric vibrating piece 31, and the lid 37 of the piezoelectric device 30 described with reference to FIGS. 1 and 2 are formed in separate steps.
As described in detail above, the package 36 can be formed using a ceramic obtained by firing a green sheet (ST11). Further, in this embodiment, as described above, the piezoelectric vibrating piece 31 is cut into a rectangular shape (AT vibrating piece) or etched (tuning fork type vibrating piece) to form a quartz chip (ST21) (ST21). After that, it can be manufactured by forming drive electrodes on the surface of the crystal chip (ST22). This electrode forming step will be described in detail later. Further, when the lid body 37 is formed of a transparent glass material, the lid body 37 is formed of a borosilicate glass or Kovar glass having a predetermined size and thickness, or a metal plate such as Kovar. (ST31).

Next, the piezoelectric vibrating reed 31 is joined to the electrode portions 32 and 32 of the completed package 36 (ST12) (joining process).
That is, as described with reference to FIG. 1, the conductive adhesives 43 and 43 are applied on the electrode portions 32 and 32 on the package 36 side, and the lead electrodes described with reference to FIG. The base end portion 31a on which 51a and 51a are formed is placed and the conductive adhesives 43 and 43 are cured.

  Next, in vacuum, a brazing material is applied to the upper end of the package 36 or the joint surface of the lid 37, and the lid 37 is joined to the upper end of the package 36. Alternatively, if the lid 37 is a metal such as Kovar, the package 36 is hermetically sealed by joining the lid to the package 36 by means such as seam welding (ST13). Thereafter, necessary frequency adjustment is performed, the piezoelectric device 30 is driven and a predetermined inspection is performed (ST14), and the piezoelectric device 30 is completed (ST15).

Next, the step of forming the electrode of the piezoelectric vibrating piece 31 (ST22) will be described in detail. Before that, the configuration of the electrode film forming apparatus used for the electrode forming step will be described first.
(Electrode deposition system)
The electrode film forming apparatus of FIG. 6 is an inter-back type sputtering apparatus. The device type is not limited to the inter-back type, and if it is an in-line type, almost the same process as the electrode forming process of the present embodiment can be performed.
In FIG. 6, the electrode film forming apparatus 60 includes a sputter chamber 67 having an airtight structure and a load chamber 61 provided adjacent to the sputter chamber 67.

The load chamber 61 is a space having an airtight structure that serves as both a work preparation chamber and a take-out chamber. The load chamber is provided with an external first gate valve 62 and a second gate valve 65 provided between the load chamber 61 and the sputtering chamber (main chamber).
In the load chamber 61, the piezoelectric vibrating reed 31 described with reference to FIG. 3 and a plurality of resonating reeds before forming an electrode such as the excitation electrode 51, that is, a plurality of piezoelectric chips can be accommodated at the same time. A predetermined number of metal sputtering jigs 66 that can set a mask that exposes only a region where an electrode is to be formed on the chip are stacked.
The load chamber 61 is supplied with a first exhaust means 63 including a vacuum pump for evacuating the inside, and supply of nitrogen gas to introduce nitrogen as an inert gas for vacuum breakage into the load chamber 61. A first nitrogen gas feed means 64 connected to the source.

  The sputter chamber 67 is an airtight chamber connected to the load chamber 61 by a second gate valve 65. In the sputter chamber 67, a transport means 76 such as a transport conveyor for feeding the above-described sputter jig 66 along the film forming process is disposed. The conveying means 76 is configured to convey the sputtering jig 66 along the feeding direction A, and can reverse the conveying motor or the like along the returning direction B by reversing the conveying motor or the like. In the sputtering chamber 67, first, second, third, and fourth target materials are arranged in the order in which the metal layers are formed. In this case, a pair of target materials 68 and 69 made of chromium (Cr) arranged opposite to each other with the conveying means 67 in between are arranged, and these also serve as the first and third target materials. In addition, a pair of silver (Ag) target materials 71 and 72 disposed opposite to each other are disposed downstream of the conveying unit 76 in the conveying direction A, which are the second and fourth targets. Also serves as a material.

  Magnets 68a, 69a, 71a, 72a are fixed to the target materials 68, 69, 71, 72, respectively. As shown, these magnets 68a, 69a, 71a, 72a are alternately polarized with N poles and S poles, and the magnets 68a, 69a, 71a, 72a are provided with voltage control means (not shown). Thus, a magnetron cathode is configured by applying a negative voltage as shown. Thereby, the magnetic flux of each magnet forms a magnetic field that passes through each pair of target materials 68 and 69 and target materials 71 and 72.

Further, the sputter chamber 67 is connected to a second exhaust means 73 for evacuating the inside and a nitrogen gas supply source for introducing nitrogen as an inert gas for vacuum breakage into the sputter chamber 67. The second nitrogen gas feed means 74 and an argon gas feed means 75 for introducing argon gas for forming ions are provided.
Further, the electrode film forming apparatus 60 is provided with a control means 81 for controlling each drive part. This control means 81 is incorporated in the electrode film forming apparatus 60 or retrofitted to control the film forming process. For example, a general-purpose personal computer is attached to the electrode film forming apparatus 60 later. It may be provided so as to be driven by predetermined software, or may be configured by incorporating a predetermined sequence circuit in the electrode film forming apparatus 60.

FIG. 7 is a block diagram showing a control structure of the electrode film forming apparatus 60 with the control means 81 as the center. The control means 81 includes a first exhaust means 63, a first nitrogen gas feed means 64, a first gate valve (drive means) 62, and a second gate valve in the load chamber 61 shown in FIG. (Drive means) 65 is connected. Further, a feed motor driving means 82 for driving the conveying means 76 is connected to the control means 81.
The control means 81 is connected to a second exhaust means 73 in the sputtering chamber 67, a second nitrogen gas feed means 74, an argon gas feed means 75, and a voltage control means 83. In addition, as the electrode film-forming apparatus 60, the control means 81 may perform only control of the conveyance speed, and other configurations may be driven manually.
Further, the electrode film forming apparatus 60 may be an in-line type film forming apparatus by forming another load chamber with the sputtering chamber 67 interposed between the load chamber 61 and the load chamber 61. Further, in this case, the first to fourth sputtering materials may be provided separately in the sputtering chamber 67 and sequentially arranged. However, there is an advantage that the apparatus can be formed compactly if the film forming apparatus is an inter-back type as in this embodiment and also functions as a sputtering material.
The electrode film forming apparatus 60 of this embodiment is configured as described above. Next, an electrode forming process of a piezoelectric vibrating piece as an electrode film forming process by the electrode film forming apparatus 60 will be described.

(Electrode formation process)
FIG. 8 is a flowchart for briefly explaining the electrode forming process. The electrode forming process will be described with reference to the configurations of FIGS. 6 and 7 and FIG.
As shown in FIG. 8, the first gate valve 62 is opened by the command of the control means 81 shown in FIGS. Then, a predetermined number of substrate-like jigs 66 on which piezoelectric chips are set are stacked in the load chamber 61 (ST51).
The first gate valve 62 is closed by the control means 81 (ST52), and then the first exhaust means 63 is instructed, whereby the inside of the load chamber 61 has a predetermined degree of vacuum (5 × 10 −3). It is evacuated until it reaches Pa (about Pascal) (ST53).

Next, the control means 81 opens the second gate valve 65, and together with the sputtering jig 66, the piezoelectric chip to be electrode-formed is sent into the sputtering chamber 67 by means not shown, and is placed on the conveying means 76. The gate valve 65 is closed (ST54).
By this time, prior to ST54, the control means 81 issues an instruction to the second exhaust means 73 to evacuate it, and introduces argon gas by the argon gas feed means 75, and the inside of the sputtering chamber 67 is filled. A predetermined degree of vacuum (4 × 10-1 Pa (pascal)) is set (ST55).

  Then, the control means 81 gives an instruction to the feed motor driving means 82 of the transport means 76 and performs film formation by sputtering while feeding the sputtering jig 66 in the direction of arrow A (ST56). In this case, each target is charged to a negative potential by the voltage control means 83, and the above-described magnetic field is formed. Therefore, these magnetic fields, the negative voltage of each target serving as the cathode, and the sputtering functioning as an anode. Due to the action of the jig 66, the argon gas filled in the sputtering chamber 67 is turned into plasma and becomes positive ions. The argon ions that have become positive ions collide with each target, and metal particles according to the type are rebounded and ejected from each target. The metal particles adhere to the exposed surface of the piezoelectric chip held by the sputtering jig 66 to form a metal film.

Here, the thickness of each metal layer to be formed is determined according to the length of time exposed to the flying metal particles. The control means 81 determines the voltage by the voltage control means 83 when the sputtering jig 66 passes through the target materials 68 and 69, and the discharge current is about 0.5 A (ampere), for example. Further, an instruction is given to the feed motor driving means 82 so that the first speed is obtained as the speed at which sputtering is performed corresponding to the film thickness of the underlayer 52 in FIG. Specifically, for example, the motor rotation speed is about 4800 rotations per minute. Thereby, the film thickness of the underlayer 52 is set to about 70 angstroms.
Next, when the control means 81 sends the sputtering jig 66 in the direction of A1 and passes the region of the target materials 71 and 72, for example, the voltage is determined by the voltage control means 83, and the discharge current is, for example, 1A. Further, the feed motor driving means 82 is set to a second speed as a speed at which sputtering is performed corresponding to the film thickness of the metal layer (diffusion layer) 53 of silver in FIG. Give instructions. Specifically, in order to make it several times the first speed, for example, the motor speed is set to about 19500 revolutions per minute. Thereby, the film thickness of the metal layer 53 made of silver is set to about 150 angstroms.

Next, the control means 81 gives an instruction to the feed motor driving means 82, sends the sputter jig 66 in the direction B in an extremely fast reverse direction, returns to the initial position, and performs sputtering again. That is, when the control means 81 sends the sputtering jig 66 in the direction of A2 and passes through the area of the target materials 68 and 69 again, for example, the voltage is determined by the voltage control means 83 and the discharge current is 0, for example. 4A (ampere), and the feed rate is set to be the same as the second rate as the rate at which sputtering is performed corresponding to the film thickness of the chromium layer (diffusion layer) 54 in FIG. An instruction is given to the motor driving means 82. Specifically, for example, the motor rotation speed is about 19,500 rotations per minute. Thereby, the film thickness of the chromium layer 54 is set to about 20 angstroms.
Finally, when the sputter jig 66 passes through the area of the target materials 71 and 72 again, the control means 81 determines the voltage by, for example, the voltage control means 83, and the discharge current is about 1 A (ampere), for example. In addition, the feed motor driving means 82 is instructed to achieve a very slow speed (third speed) as a speed at which sputtering corresponding to the film thickness of the electrode layer 56 of silver in FIG. 4 is performed. Put out. Specifically, in order to make it a fraction of the first speed, for example, the motor rotation speed is set to about 1050 rotations per minute. Thereby, the film thickness of the electrode layer 56 made of silver is set to about 2500 angstroms.

In this way, in the sputtering step of the electrode film forming apparatus 60, after the transport means 76 forms the chromium underlayer 52 on the surface of the piezoelectric chip with the first target materials 68 and 69, the underlayer 52 is formed. A silver metal layer (diffusion layer) 53 and a chrome layer (diffusion layer) 54 are formed on the surface of the underlayer 52 with a minimum film thickness by carrying them at a speed several times the carrying speed at the time. be able to. By forming the electrode layer 56 after forming such a metal layer and a chromium layer, when the electrode layer 56 is completed, the silver chromium diffusion layer 55 can be suitably formed in the lower layer.
That is, first, when the silver metal layer 53 is formed after the chromium underlayer 52 is formed, the film thickness can be made extremely thin. For this reason, film formation is performed while leaving a part of the surface of the underlayer 52 where silver does not adhere. Further, in the process of forming the chrome layer 54 very thin thereon, a region to which chromium is attached and a region to which no chromium is attached are formed. In such a state, when silver as the electrode layer 56 is formed by sputtering with a relatively thick film thickness, when the film formation of the relatively thick electrode layer 56 is completed, a very thin film is formed below the electrode layer 56. Thus, the silver-chromium diffusion layer 55 in which chromium is diffused into the silver can be appropriately formed.

When the film formation of the electrode is completed for the predetermined sputtering jig 66, the second gate valve 65 is opened and pulled into the load chamber 61, and the unprocessed sputtering jig 66 stacked in the load chamber 61 is removed. Then, it is sent to the sputtering chamber 67 in the same manner as described above, and the above film forming process is repeated (ST57).
When the processing of all the sputtering jigs (substrates) 66 stacked in the load chamber 61 is completed, the control unit 81 instructs the first nitrogen gas feeding unit 64 to supply nitrogen, which is an inert gas, into the load chamber 61. Then, the first gate valve 62 is opened and the processed piezoelectric vibrating piece can be taken out (ST58).

  FIG. 9 shows that the conventional piezoelectric vibrating piece and the piezoelectric vibrating piece 31 of FIG. 3 are exposed to the atmosphere for the number of days on the horizontal axis shown in the figure, and the occurrence of floating as described in FIG. It is the graph which recorded the state. As shown by QA in the conventional piezoelectric vibrating piece, partial peeling gradually occurs in the electrode portion after 2 days. However, in the piezoelectric vibrating piece 31 of this embodiment, as shown by reference sign QB, it takes about one week. Even when left untreated, partial peeling of the electrode portion is hardly observed.

FIG. 10 is a diagram showing a schematic configuration of a digital mobile phone device as an example of an electronic apparatus using the piezoelectric device according to the above-described embodiment of the present invention.
In the figure, a microphone 308 for receiving the voice of the sender and a speaker 309 for outputting the received content as a voice output are provided, and further, an integrated circuit or the like as a control unit connected to the modulation and demodulation unit of the transmission / reception signal. The CPU (Central Processing Unit) 301 is provided.
In addition to modulation and demodulation of transmission / reception signals, the CPU 301 includes an information input / output unit 302 including an LCD as an image display unit and operation keys for inputting information, and an information storage unit (memory) 303 including a RAM, a ROM, and the like. Control is to be performed. For this reason, the piezoelectric device 30 is attached to the CPU 301, and its output frequency is used as a clock signal suitable for the control content by a predetermined frequency dividing circuit (not shown) incorporated in the CPU 301. ing. The piezoelectric device 30 attached to the CPU 301 is not limited to a piezoelectric vibrator but may be an oscillator combined with a predetermined frequency dividing circuit or the like.

  The CPU 301 is further connected to a temperature compensated crystal oscillator (TCXO) 305, and the temperature compensated crystal oscillator 305 is connected to the transmitter 307 and the receiver 306. Thus, even if the basic clock from the CPU 301 fluctuates when the environmental temperature changes, it is corrected by the temperature compensated crystal oscillator 305 and supplied to the transmission unit 307 and the reception unit 306.

  As described above, the piezoelectric device according to each of the above-described embodiments can be used for an electronic apparatus such as the digital cellular phone device 300 including the control unit. In this case, since the piezoelectric vibrating reed 31 accommodated therein does not cause partial peeling at the electrode portion and has excellent CI value performance, the reliability of the product is improved.

The present invention is not limited to the above-described embodiment. Each configuration of each embodiment can be appropriately combined or omitted, and can be combined with other configurations not shown.
In addition, the present invention can be applied to all piezoelectric devices regardless of the names of piezoelectric vibrators, piezoelectric oscillators, etc., as long as they are covered with a package and accommodate a piezoelectric vibrating piece inside. .

1 is a schematic perspective view showing an internal structure by cutting a part of a piezoelectric device according to an embodiment of the present invention. FIG. 2 is a schematic sectional view of the piezoelectric device of FIG. 1. The schematic perspective view which shows embodiment of the piezoelectric vibrating piece accommodated in the piezoelectric device of FIG. FIG. 4 is a partial schematic cross-sectional view showing an electrode structure of the piezoelectric vibrating piece in FIG. 3. The flowchart which shows an example of the manufacturing method of the piezoelectric device of FIG. The schematic block diagram of embodiment of the electrode film-forming apparatus for forming the electrode structure of FIG. The block diagram which shows an example of the control structure of the electrode film-forming apparatus of FIG. The flowchart which shows an example of the film-forming process of the electrode film-forming apparatus of FIG. The graph which shows the state of the partial peeling of the electrode part about the piezoelectric vibrating piece which concerns on embodiment of this invention, and the conventional piezoelectric vibrating piece. 1 is a diagram showing a schematic configuration of a digital mobile phone device as an example of an electronic apparatus using a piezoelectric device according to an embodiment of the present invention. The fragmentary sectional view of the electrode part of the piezoelectric vibrating piece utilized for the conventional piezoelectric device. FIG. 12 is a cross-sectional view illustrating a state where partial peeling occurs in the electrode portion of the piezoelectric vibrating piece in FIG. 11. FIG. 12 is a photomicrograph showing a state where partial peeling occurs in the electrode portion of the piezoelectric vibrating piece of FIG. 11. The graph which compared the CI value performance about what the partial peeling has produced in the electrode part of the piezoelectric vibrating piece, and the thing which has not occurred.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Piezoelectric device, 31 ... Piezoelectric vibrating piece, 36 ... Package, 51 ... Excitation electrode, 52 ... Underlayer, 53 ... Metal layer, 54 ... Chrome layer, 56 ... Electrode layer, 60 ... Electrode film forming apparatus, 61 ... Load chamber, 67 ... Sputter chamber.

Claims (2)

In an electrode forming method of forming an excitation electrode that is a drive electrode of a piezoelectric vibrating piece by forming a metal film on the surface of a piezoelectric material by sputtering,
Forming a base layer of chromium on the surface of the piezoelectric material by sputtering;
A metal, either silver or gold, and chromium are sequentially formed by sputtering so that a region where the film does not adhere to the surface of the base layer remains partially ,
After the formation of the silver or gold and chromium, further forming an electrode layer of silver or gold on the surface,
By passing through the continuous sputtering step, a diffusion layer in which chromium is diffused in silver or gold is formed between the base layer and the electrode layer,
The electrode formation method, wherein the diffusion layer has a thickness of 50 to 200 angstroms . Thickness at the time of deposition of the metal layer of silver of the diffusion layer is a practically generally 150 Å, and the film thickness during film formation of the chromium layer of the diffusion layer, Oh with a practically generally 20 Å Rukoto The electrode forming method according to claim 1.

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