JP4591035B2 - Piezoelectric vibrating piece and method for manufacturing piezoelectric device - Google Patents

Description

  The present invention relates to a method of manufacturing a piezoelectric vibrating piece for housing in a package or case and a piezoelectric device having the piezoelectric vibrating piece housed in a package or case.

Packages such as small information devices such as HDDs (hard disk drives), mobile computers, IC cards, mobile communication devices such as mobile phones, car phones, and paging systems, and measuring devices such as gyro sensors Piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators that house a piezoelectric vibrating piece inside are widely used.
FIG. 8 is a schematic plan view schematically showing a known configuration example (see Patent Document 1) of a piezoelectric vibrating piece used in such a piezoelectric device.

In the figure, the piezoelectric vibrating reed 1 is made of, for example, a single crystal of quartz, and includes a wide base 2 and two vibrating arms 3 and 4 extending in parallel in the same direction from the base. FIG. 9 is a cross-sectional end view taken along the line AA of FIG. 8, and the vibrating arms 3 and 4 have long grooves 5 and 6 extending in the length direction on the front and back surfaces, respectively. Excitation electrodes as drive electrodes (not shown) are formed in the long grooves 5 and 6.
As a result, an electric field is efficiently generated in the vibrating arms 3 and 4 by applying a driving voltage to the excitation electrode from the outside, and each of the vibrating arms 3 and 4 has its tip portion as shown in FIG. It bends and vibrates so as to approach and separate from each other. Then, by extracting the vibration frequency based on such vibration, it is used as a reference signal such as a clock signal for control.

The vibrating arms 3 and 4 of the piezoelectric vibrating piece 1 and the long grooves 5 and 6 of the vibrating arms 3 and 4 are formed by etching a wafer made of a piezoelectric material. That is, generally, the wafer substrate is first etched to form a tuning fork-shaped outer shape as shown in FIG. 8, and then the long grooves 5 and 6 described in FIG. 9 are half-etched.
JP2002-76806

However, in such a piezoelectric vibrating piece 1, in the wet etching in the outer shape etching process, there is a difference in the etching progress speed with respect to the electric axis X, the mechanical axis Y, and the optical axis Z shown in FIGS. As can be seen, a flat bottom surface cannot be formed in the long grooves 5 and 6 due to such etching anisotropy.
As a result, for example, when viewing the vibrating arm 3, the thicknesses of the both side walls 5 a and 5 b sandwiching the long groove 5 are different on the left and right. As a result, the vibrating arm 3 is The side wall portions have different rigidity. That is, the left wall portion 5a has high rigidity, and the right wall portion 5b has lower rigidity.

For this reason, in the state in which the vibrating arms 3 and 4 are bent and vibrated as shown in FIG. 8, the degree of deformation at the time of bending left and right in the horizontal direction is different. Will collapse. As a result, the stress transmitted to the base 2 due to the deformation of the vibrating arms 3 and 4 cannot be canceled out because F1 and F2 are not balanced, causing displacement in the Z direction and displacement in the Y direction. It is thought that the crystal impedance) value increases.
Here, when the piezoelectric vibrating piece is formed by etching, wet etching is performed for a long time, so that the left wall portion 5a among the wall portions 5a and 5b on both sides sandwiching the long grooves 5 and 6 in FIG. Can be made sufficiently thin to balance left and right rigidity.
However, in that case, a much longer time than in the past must be spent in the etching process, resulting in lower productivity.
In addition, when the piezoelectric vibrating piece 1 is reduced in size, the width W1 of the long groove 5 is reduced accordingly. When the width W1 is very narrow, the etchant is difficult to go around, and the thickness of the left and right wall portions 5a and 5b cannot be made equal even when wet etching is performed for a long time.

Further, it is conceivable to process and form the outer shape and the long groove of the piezoelectric vibrating piece 1 by dry etching without etching anisotropy when forming the piezoelectric vibrating piece.
However, dry etching requires much longer time than wet etching, and also in this case, there is a problem that productivity is remarkably deteriorated.

  It is an object of the present invention to provide a manufacturing method for manufacturing a piezoelectric vibrating piece and a piezoelectric device that can improve the vibration balance and keep the CI value low.

In the first invention, the above object is formed in the length direction of the base, at least a pair of vibrating arms formed integrally with the base, and extending in parallel from the base. A piezoelectric vibrating reed manufacturing method for forming an outer shape of a piezoelectric vibrating piece having a long groove and the long groove by etching, the piezoelectric substrate is prepared, and after forming the outer shape of the piezoelectric vibrating piece,
After forming a groove shallower than the long groove by wet etching at the position of the long groove,
This is achieved by a method for manufacturing a piezoelectric vibrating piece in which a shallow bottom portion of the groove is processed by dry etching .

According to the configuration of the first invention , not only the outer shape processing of the piezoelectric vibrating piece but also the processing of the long groove is performed halfway by the same wet etching as before, and when the long groove is formed to some extent, it is switched to dry etching. Therefore, the time required for the conventional manufacturing can be rapidly processed and formed with the piezoelectric vibrating piece capable of improving the vibration balance and keeping the CI value low without being extremely extended. .

According to a third invention, in the configuration of the first invention, after preparing the piezoelectric substrate, first, the outer shape of the piezoelectric vibrating piece and a part of the processing of the long groove are performed by wet etching. The remaining grooves are processed by dry etching.
According to the configuration of the third invention, not only the outer shape processing of the piezoelectric vibrating piece but also the processing of the long groove is performed halfway by the same wet etching as before, and when the long groove is formed to some extent, it is switched to dry etching. Therefore, the time required for the conventional manufacturing can be rapidly processed and formed with the piezoelectric vibrating piece capable of improving the vibration balance and keeping the CI value low without being extremely extended. .

According to the second aspect of the present invention, there is provided a method of manufacturing a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package or case, wherein the piezoelectric vibrating piece is fixed or bonded to the package or case. And a sealing step for hermetically sealing the package or the case, and the piezoelectric vibrating piece is formed with a base portion, and at least a pair of vibrating arms formed integrally with the base portion and extending in parallel with the base portion. And a tuning-fork type piezoelectric vibrating piece having a long groove formed in the length direction of each vibrating arm, wherein the piezoelectric vibrating piece is formed by the manufacturing method of the first invention. Is achieved.
According to the configuration of the second invention, a piezoelectric device capable of improving the vibration balance and keeping the CI value low can be manufactured in the shortest possible time based on the same principle as the first invention. .

1 and 2 show an embodiment of a piezoelectric device of the present invention. FIG. 1 is a schematic plan view thereof, and FIG. 2 is a schematic cross-sectional view taken along the line BB of FIG.
In the figure, the piezoelectric device 30 shows an example in which a crystal resonator is configured, and the piezoelectric device 30 houses a piezoelectric vibrating piece 32 in a package 36 as a housing container. The package 36 is formed, for example, by laminating a plurality of substrates formed by molding an aluminum oxide ceramic green sheet as an insulating material, and then sintering. Each of the plurality of substrates is formed with a predetermined hole on the inner side thereof, so that a predetermined internal space S2 is formed on the inner side when stacked. The internal space S2 is a housing space for housing the piezoelectric vibrating piece 32.

A piezoelectric vibrating piece 32 is mounted inside the package 36 and hermetically sealed with a lid 39. Here, the lid 39 is formed by selecting a material such as ceramic, metal, or glass.
When the lid 39 is made of metal, for example, there is an advantage that the strength is generally higher than that of other materials. An approximate thermal expansion coefficient with the package 36 is suitable, and for example, Kovar can be used.
Moreover, in order to enable frequency adjustment after sealing the lid, the lid 39 is made of a light transmitting material such as glass, for example. For example, a plate body such as borosilicate glass can be used.

  In the inner space S2 of the package 36, in the vicinity of the left end portion, the laminated substrate that is exposed to the inner space S2 and constitutes the inner bottom portion has, for example, electrode portions 31 and 31 formed by nickel plating and gold plating on tungsten metallization. Is provided. The electrode portions 31 are connected to the outside to supply a driving voltage. Conductive adhesives 43, 43 are applied on the electrode portions 31, 31, and the base 51 of the piezoelectric vibrating piece 32 is placed on the conductive adhesives 43, 43. 43 are hardened. In addition, as the conductive adhesives 43 and 43, a synthetic resin agent as an adhesive component exhibiting bonding strength can be used containing conductive particles such as silver fine particles. A system-based or polyimide-based conductive adhesive or the like can be used.

The piezoelectric vibrating piece 32 is formed by etching, for example, quartz as a piezoelectric material by a manufacturing process described later. In the case of the present embodiment, the piezoelectric vibrating piece 32 is formed in a small size to obtain necessary performance. Therefore, in particular, the structure shown in the schematic plan view of FIG. 3 and the C-C line cut end view of FIG. 3 shown in FIG.
That is, the piezoelectric vibrating piece 32 includes a base portion 51 fixed to the package 36 side, and a pair of vibrating arms 34 and 35 extending in parallel in a bifurcated manner upward in the drawing with the base portion 51 as a base end. Thus, a so-called tuning fork type piezoelectric vibrating piece, which is entirely shaped like a tuning fork, is used.

As can be understood with reference to FIGS. 3 and 4, long bottomed long grooves 56 and 57 extending in the length direction are formed in the respective vibrating arms 34 and 35 of the piezoelectric vibrating piece 32. The long grooves 56 and 57 are formed on both front and back surfaces of the vibrating arms 34 and 35 as shown in FIG. 4 which is a cross-sectional end view taken along the line CC of FIG.
In particular, in the piezoelectric vibrating piece 32, the long grooves 56 and 57 have a substantially ideal shape by performing a manufacturing process described later.
4 will be described. As understood from comparison with FIG. 9, the bottom portion 56a of the long groove 56 is horizontal, and both wall portions 56b and 56c sandwiching the long groove 56 have thicknesses KW1 and KW2. Are formed in substantially the same thickness.
For this reason, when bending vibrations of the vibrating arms 34 and 35, the right and left stiffness balance of the individual vibrating arms is improved, and the CI value can be kept low.
Further, in FIG. 3, lead electrodes 52 and 53 are formed near both ends in the width direction of the end portion (lower end portion in FIG. 3) of the base portion 51 of the piezoelectric vibrating piece 32. The lead electrodes 52 and 53 are similarly formed on the back surface (not shown) of the base 51 of the piezoelectric vibrating piece 32.

  These lead electrodes 52 and 53 are portions connected to the package-side electrode portions 31 and 31 shown in FIG. 1 by the conductive adhesives 43 and 43 as described above. As shown in FIGS. 3 and 4, the lead electrodes 52 and 53 are integrally connected to the excitation electrodes 54 and 55 provided in the long grooves 56 and 57 of the vibrating arms 34 and 35, respectively. Yes. Further, as shown in FIG. 4, the excitation electrodes 54 and 55 are also formed on both side surfaces of the vibrating arms 34 and 35. For example, with respect to the vibrating arms 34, the excitation electrodes 54 in the long groove 56. And the excitation electrode 55 of the side part is made to have a different polarity. Further, with respect to the vibrating arm 35, the excitation electrode 55 in the long groove 57 and the excitation electrode 54 on the side surface thereof have different polarities.

Between the base 51 of the piezoelectric vibrating piece 32 and the vibrating arms 34 and 35, a notch portion or a constricted portion (not shown) provided with a reduced width in the width direction of the base 51 may be provided.
Thereby, the leakage of the vibration of the piezoelectric vibrating piece 32 to the base 51 side can be prevented, and the CI (crystal impedance) value can be reduced.
Moreover, the piezoelectric vibrating piece 32 as a whole is extremely small. In FIG. 3, for example, the total length is about 1300 μm, the length of the vibrating arm is about 1040 μm, and the arm width is about 40 μm to 55 μm. It is a very small piezoelectric vibrating piece.

(Piezoelectric device manufacturing method)
Next, a method for manufacturing the above-described piezoelectric device will be described with reference to the flowchart of FIG.
The piezoelectric vibrating piece 32, the package 36, and the lid 39 of the piezoelectric device 30 are manufactured separately.
(Method for manufacturing lid and package)
For example, the lid 39 is prepared as a lid having a size suitable for sealing a package 36 by cutting a glass plate having a predetermined size.
As described above, the package 36 is formed by laminating a plurality of substrates formed by molding an aluminum oxide ceramic green sheet and then sintering. At the time of molding, each of the plurality of substrates forms a predetermined hole on the inside thereof, so that a predetermined internal space S2 is formed on the inner side when stacked.

(Method for manufacturing piezoelectric vibrating piece)
6 and 7 are process diagrams showing main processes for explaining an example of the method for manufacturing the piezoelectric vibrating piece 32 of the present embodiment.
First, a piezoelectric substrate 71 is prepared, and as shown in FIG. 6A, the outer shape of a predetermined number of piezoelectric vibrating pieces from one piezoelectric substrate 71 is simultaneously formed by etching (outer shape etching). The following steps are illustrated in the order of steps after the cross-sectional view 6 (b) of the vibrating arm 34 of the piezoelectric vibrating piece cut at the position of the CU shown in FIG. 6 (a).

  Here, as the substrate 71, for example, a quartz crystal wafer having a size capable of separating a plurality or a plurality of the piezoelectric vibrating reeds 32 among the piezoelectric materials is used. When the substrate 71 is made into a tuning fork type piezoelectric vibrating piece 32 by the progress of the process, the piezoelectric material, so that the X axis shown in FIG. 3 is the electric axis, the Y axis is the mechanical axis, and the Z axis is the optical axis, For example, it is cut out from a single crystal of quartz. In addition, when cutting out from a single crystal of crystal, the crystal Z cut out by rotating clockwise in the range of 0 degrees to 2 degrees around the Z axis in the orthogonal coordinate system composed of the X axis, Y axis and Z axis described above. It is obtained by cutting and polishing a plate to a predetermined thickness.

  In the outer shape etching, the outer shape of the piezoelectric vibrating piece is etched using, for example, a hydrofluoric acid solution with respect to the substrate 71 exposed as a portion outside the outer shape of the piezoelectric vibrating piece using a mask such as a corrosion-resistant film (not shown). . As the corrosion resistant film, for example, a metal film in which gold is vapor-deposited with chromium as a base can be used. This etching process is wet etching and changes depending on the concentration, type, temperature, and the like of the hydrofluoric acid solution. In this embodiment, the etching process is completed in a predetermined time using hydrofluoric acid and ammonium fluoride as an etching solution (ST11).

(Half etching process for groove formation)
Next, with a groove forming resist (not shown), the corrosion resistance film is left on the portion where the groove is not formed, leaving the walls on both sides sandwiching the long groove described in FIG. As shown in (c), a shallow bottom portion 56-1 corresponding to the long groove is formed by wet etching (ST12).

(Dry etching process)
Subsequently, as shown in FIG. 6D, a metal mask 73 is disposed on the upper side of the portion where the groove is not formed (the wall portions on both sides sandwiching the long groove described in FIG. 4) (ST13). In this state, for example, it is housed in a chamber (not shown), an etching gas is supplied at a predetermined degree of vacuum, etching plasma is generated, and dry etching is performed (ST14). That is, for example, a freon gas cylinder and an oxygen gas cylinder are connected to a vacuum chamber (not shown), and further, an exhaust pipe is provided in the vacuum chamber so that it is evacuated to a predetermined degree of vacuum. Yes.
When a DC voltage is applied in a state where the inside of the vacuum chamber is evacuated to a predetermined degree of vacuum, a freon gas and an oxygen gas are sent, and the mixed gas is filled up to a predetermined atmospheric pressure, plasma is generated. appear. The mixed gas containing ionized particles hits the shallow bottom portion 56-1 of the long groove exposed from the metal mask 73. Due to this impact, the crystal at the shallow bottom is physically scraped and scattered, and etching proceeds as shown in FIG.

Next, as shown in FIG. 7B, the quartz wafer, which is the piezoelectric substrate 72, is inverted and a metal mask 73 is placed (ST15), and as shown in FIG. Etching is performed (ST16).
Thus, as shown in FIG. 7D, the long grooves 56 and 56 can be completed in the vibrating arm 34. In this case, the wall portions 56b and 56c on both sides of the long groove 56 have substantially the same thickness, and the bottom portion 56a of the long groove 56 can realize a substantially horizontal ideal form.
In this state, by forming the necessary driving electrodes described with reference to FIGS. 3 and 4, the piezoelectric vibrating piece 32 can be completed.

  Next, as shown in FIGS. 1 and 2, the piezoelectric vibrating piece 32 completed as shown in FIG. 3 is joined to the inside of the package 36 using the conductive adhesive 43 (mounting process) (ST17). . Thereafter, a lid 39 is joined to the package 36 using a brazing material (for example, low melting glass) (ST18), whereby the piezoelectric device 30 can be completed (ST19).

According to the above-described embodiment, the outer shape of the piezoelectric vibrating piece 32 can be processed and formed relatively quickly by wet etching as in the past, and the long grooves 56 and 57 can be etched differently by forming them by dry etching. It is possible to prevent defects caused by the directivity.
In addition, in this embodiment, since the outer shape processing by wet etching is preceded, the conventional process can be used as it is, and there is an advantage that can be implemented only by adding the dry etching equipment to the conventional process.
Further, not only the outer shape processing of the piezoelectric vibrating piece 32 but also the processing of the long grooves 56 and 57 are performed halfway by the same wet etching as before, and when the long groove is formed to some extent, switching to dry etching is performed. Without excessively increasing the time required for manufacturing, it is possible to quickly process and form the piezoelectric vibrating piece 32 that can improve the vibration balance and keep the CI value low.

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, as long as the piezoelectric vibrating piece is accommodated in the package, the present invention includes all piezoelectric vibrating pieces and piezoelectric devices using the same regardless of the names of the crystal resonator, the crystal oscillator, the gyroscope, the angle sensor, and the like. Can be applied to.
Moreover, in the above-described embodiment, a box-shaped package using ceramics is used. However, the present invention is not limited to such a form, and a piezoelectric material may be used in a storage container equivalent to a package such as a metal cylindrical case. The present invention can be applied to any package or case that can accommodate a resonator element.

1 is a schematic plan view of a piezoelectric device according to an embodiment of the present invention. The schematic sectional drawing in the BB line of the piezoelectric device of FIG. The schematic plan view which shows an example of the piezoelectric vibrating piece used for the piezoelectric device of FIG. FIG. 4 is a cross-sectional end view of the piezoelectric vibrating piece of FIG. The flowchart which shows embodiment of the manufacturing method of the piezoelectric device of FIG. The figure which shows a process sequentially corresponding to embodiment of the manufacturing method of the piezoelectric vibrating piece of FIG. The figure which shows a process sequentially corresponding to embodiment of the manufacturing method of the piezoelectric vibrating piece of FIG. FIG. 6 is a schematic plan view of a conventional piezoelectric vibrating piece. The AA cut | disconnection end elevation of FIG.

Explanation of symbols

  30 ... Piezoelectric device, 36 ... Package, 32 ... Piezoelectric vibrating piece, 34, 35 ... Vibrating arm, 51 ... Base, 54, 55 ... Excitation electrode, 56, 57 ...・ Long groove

Claims (2)

An outer shape of a piezoelectric vibrating piece including a base, at least a pair of vibrating arms formed integrally with the base and extending in parallel from the base, and a long groove formed in a length direction of each vibrating arm, and the long groove A method of manufacturing a piezoelectric vibrating piece by etching,
After preparing the piezoelectric substrate and forming the outer shape of the piezoelectric vibrating piece,
After forming a groove shallower than the long groove by wet etching at the position of the long groove,
A method of manufacturing a piezoelectric vibrating piece, characterized by processing a shallow bottom portion of the groove by dry etching . A method of manufacturing a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package or case,
A bonding step of fixing or bonding the piezoelectric vibrating piece to the package or case, and a sealing step of hermetically sealing the package or case.
The piezoelectric vibrating piece is
A tuning-fork type piezoelectric vibrating piece including a base, at least a pair of vibrating arms formed integrally with the base and extending in parallel from the base, and a long groove formed in the length direction of each vibrating arm. ,
The method for manufacturing a piezoelectric device, wherein the piezoelectric vibrating piece is formed by the method for manufacturing a piezoelectric vibrating piece according to claim 1 .

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