JP2007173906A - Method of manufacturing piezoelectric resonator chip and piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely form an electrode film even when the compact or subminiature piezoelectric resonator chip is formed. <P>SOLUTION: A method of manufacturing the piezoelectric resonator chip includes: an outward form forming step by applying wet etching to a piezoelectric substrate 4 with an etching anisotropy to form an element chip of the piezoelectric resonator chip; and an electrode forming step for forming a required driving electrode after the forming of the outward form. In the method, after the etching, the electrode film acting like the driving electrode is formed to the substrate except anisotropic regions 54-1, 54-2, 54-3 by the etching anisotropy, and the driving electrode is formed by the method of the photolithography. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in a piezoelectric vibrating piece formed by etching a piezoelectric substrate and a method for manufacturing a piezoelectric device formed using the same.

A piezoelectric vibrating piece used for a conventional piezoelectric device is formed by, for example, forming a driving electrode on an element piece (blank) made of a piezoelectric material cut into a rectangular shape, for example, in order to form a quartz vibrating piece. Yes.
FIG. 8 shows a part of a conventional electrode forming process (see Patent Document 1 and FIG. 9).
In the figure, the element piece 1 is shown as a sectional view in the thickness direction. A mask 2 is arranged on the main surface of the element piece 1, that is, the front and back surfaces to cover a portion to be shielded on the main surface. Thereafter, using the targets 3 and 3, a conductive metal film is formed on the main surfaces 4 and 4 exposed from the mask 2 by sputtering.

JP 2002-217675 A

However, such a method has the following problems.
In the structure of Patent Document 1, the support elements 6 and 7 are left in the state as shown in FIG.
FIG. 9 is a schematic plan view of the element piece 1. The element piece 1 is a rectangular plate formed by wet etching a piezoelectric material such as quartz.
Here, when wet etching is performed on crystal, etching anisotropy is observed, and the etching progress speed varies depending on the crystal axis orientation.

FIG. 10 shows a state in which the end face of the element piece 1 is deformed due to the etching anisotropy. FIG. 10A is a schematic end view taken along the line AA of FIG. 9, and FIG. FIG.
As described above, the size of the deformed portion due to the etching anisotropy is relatively large compared to the size of the element piece 1, even though the element piece 1 has conventionally not changed its thickness. It depends on the fact that the external size is getting smaller.
For this reason, if an electrode film is formed by masking and photolithography using the same technique as in the prior art, a shadowed area cannot be exposed due to the influence of the irregular shape as shown in FIG. There was a problem that could not.

  The present invention has been made to solve the above problems, and uses a piezoelectric vibrating piece capable of accurately forming an electrode film even when a small or ultra-small piezoelectric vibrating piece is formed. An object of the present invention is to provide a method for manufacturing a piezoelectric device.

  According to the first aspect of the present invention, in the first invention, the outer shape forming step of forming the element piece of the piezoelectric vibrating piece by wet etching the piezoelectric substrate having etching anisotropy, and the necessary driving after the outer shape is formed. A method of manufacturing a piezoelectric vibrating piece including an electrode forming step of forming an electrode of the electrode, wherein in the electrode forming step, after the etching, the drive is performed in a remaining region except for a portion that is deformed due to etching anisotropy. This is achieved by a method of manufacturing a piezoelectric vibrating piece in which an electrode film to be an electrode for a film is formed and the driving electrode is formed by a photolithography technique.

According to the configuration of the first invention, since the outer shape of the element piece is formed by wet etching in the outer shape forming step, it is easy to form the outer shape. In particular, the outer shape is formed by wet etching instead of dry etching. It is efficient because it is done.
Further, in the electrode forming process, a mask is provided at a portion that is deformed due to the influence of etching anisotropy so that the electrode film is not formed. For this reason, it is possible to form the electrode film more accurately than a technique in which an electrode film is formed over the entire surface and then a mask is provided to expose and etch the electrode film in unnecessary regions.
That is, after forming an electrode film on the whole, arranging a photoresist, exposing and developing it, and removing the exposed electrode film, it becomes abnormal due to the etching anisotropy described above. In some cases, it may not be possible to sufficiently expose. For this reason, when an electrode remains in such a region, electrode separation is not sufficiently performed, and there is a possibility of short-circuiting.
Therefore, it is possible to separate the electrodes precisely by not forming an electrode film from the beginning especially in such a region.

  According to a second aspect of the invention, in the configuration of the first aspect of the invention, a quartz wafer is used as the piezoelectric substrate. The quartz wafer is related to the crystal axis of the quartz, the X axis being the electrical axis, the Y axis being the mechanical axis, and the Z axis. Is a thin frame that is cut out by a plane inclined at a predetermined angle from the Z-axis in the Cartesian coordinate system with the optical axis, and in the outer shape forming process, the crystal wafer is etched and becomes a folded portion in a later process. A plurality of element pieces are simultaneously formed from a single crystal wafer in a state of an element piece assembly integrally connected to the element pieces, and the folded portion is formed after the electrode forming step is performed. The element piece is folded from the quartz wafer.

  According to the configuration of the second aspect of the invention, in the piezoelectric vibrating piece using quartz having etching anisotropy due to wet etching, not only the influence of the etching anisotropy is particularly eliminated, but precise electrode formation is possible. A large number of element pieces can be formed simultaneously from the quartz wafer.

According to a third 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 a case, wherein the piezoelectric vibrating piece includes a piezoelectric substrate having etching anisotropy. It is formed through a process including an outer shape forming step for forming an element piece of a piezoelectric vibrating piece by etching, and an electrode forming step for forming a necessary driving electrode after the outer shape is formed. After the etching, except for portions that are deformed due to etching anisotropy, an electrode film to be the driving electrode is formed in the remaining region, the driving electrode is formed by a photolithography technique, and the electrode After execution of the forming process, the piezoelectric vibrating piece is separated from the quartz wafer, and the piezoelectric vibrating piece is connected to an electrode part for connection formed in a package or a plug to be attached to the case. The manufacturing method of a piezoelectric device including a bonding step of bonding to the electrode is achieved.
According to the configuration of the third invention, a small piezoelectric vibrating piece is precisely formed on the same principle as that of the first invention, so that a piezoelectric device using this is accurately manufactured.

1 and 2 show an embodiment of a piezoelectric device of the present invention, FIG. 1 is a schematic plan view of the piezoelectric device, and FIG. 2 is a schematic cross-sectional view of a piezoelectric vibrating piece housed in the piezoelectric device of FIG. is there.
In FIG. 1, the piezoelectric device 30 shows an example in which a piezoelectric vibrator is configured, and a piezoelectric vibrating piece 40 is accommodated in a package 31 of the piezoelectric device 30.
As will be described later, the package 31 can be formed by stacking and sintering green sheets formed into the shape of FIG. In this case, the electrode part 33 is formed on the substrate constituting the bottom part of the package 31.
The package 31 is a box-shaped container having an internal space S. Using this internal space S, the piezoelectric vibrating piece 40 is accommodated. A lid 35 made of a metal such as ceramic, glass, or kovar is joined to the package 31 via low-melting glass, nickel, or the like. Thereby, the package 31 is hermetically sealed.

As shown in FIG. 1, electrode portions 33, 33 are formed near both ends in the width direction at end portions in the length direction of the inner surface of the package 31.
The electrode portion 33 is connected to mounting terminals 32 and 32 exposed on the bottom surface of the package 31 by a conductive pattern (not shown).

As the piezoelectric vibrating piece 40, a so-called AT cut vibrating piece obtained by processing a wafer formed of a piezoelectric material so as to become a thin rectangular substrate is used. That is, as will be described later, an element piece that is a piezoelectric chip is first formed as will be described later, and a piezoelectric vibrating piece 40 that is an AT-cut vibrating piece is formed by forming an excitation electrode 41 for driving on this element piece. .
In the piezoelectric vibrating piece 40, for example, quartz is used as the piezoelectric material. If the piezoelectric anisotropy is observed in other piezoelectric materials such as lithium tantalate and lithium niobate, these may be used. Can be formed. The piezoelectric vibrating piece 40 is not limited to a flat type, and a convex type or an inverted mesa type vibrating piece can be used.

That is, the excitation electrode 41 is formed on the surface of the piezoelectric chip as the element piece 51 as a driving electrode. The excitation electrode 41 is formed in a region where the piezoelectric chip is actively vibrated, and applies a driving voltage to the piezoelectric material, thereby efficiently generating an electric field in the material and exciting the material. The excitation electrode 41 is also formed in the same form on the back surface of the element piece 51.
In addition, as shown in FIG. 2, the excitation electrodes 41 are respectively connected to the extraction electrodes 42, which are connection electrodes respectively formed at both ends in the width direction, at the end portions in the length direction of the piezoelectric vibrating reed 40. Connected separately. Each extraction electrode 42 is also formed on the back surface around the side surface of the piezoelectric chip.

As shown in FIG. 1, such a piezoelectric vibrating piece 40 is joined to the electrode portion 33 on the package 31 side in a cantilever manner.
As a result, the drive voltage supplied from the outside of the package 31 via the mounting terminals 32, 32 is excited from the electrode portion 33 on the package 31 side via the conductive adhesive 43 and the extraction electrode 42 of the piezoelectric vibrating piece 40. Applied to the electrode 41. Therefore, the main surface of the piezoelectric vibrating piece 40 is driven by a thickness-shear vibration caused by a piezoelectric action.

  Note that the package 31 is not a box shape but a simple insulating substrate, electrodes are formed thereon, and the piezoelectric vibrating piece 40 is hermetically sealed by a shallow box-shaped lid (not shown). May be used. Alternatively, a plug connected to an external drive voltage source is connected to the piezoelectric vibrating piece 40, the piezoelectric vibrating piece 40 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).

(Piezoelectric vibrating piece and piezoelectric device manufacturing method)
Next, an embodiment of a method for manufacturing the piezoelectric device 30 will be described.
First, the package for the piezoelectric device and the piezoelectric vibrating piece 40 are formed separately.
The package 31 described with reference to FIGS. 1 and 2 is suitably made of ceramic, and has a thermal expansion coefficient that matches or is very close to the thermal expansion coefficient of the piezoelectric vibrating piece 40 and the lid described later as a preferable material. In this embodiment, for example, a ceramic green sheet is used.

This 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. It is what
That is, the package 31 is formed by laminating and sintering green sheets formed in the shape of FIG.

Here, an electrode portion 33 is formed on the substrate constituting the bottom portion of the package 31.
As shown in FIG. 2, the green sheet stacked on the substrate is a frame shape from which the inner material is removed, and by stacking this on the substrate, the package 31 has a box shape having an internal space S. It is a container.
On the ceramic material forming the package 31, 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, and after sintering, Nickel and gold or silver are sequentially plated to form the electrode portion 33 described above.

The electrode portion 33 is connected to mounting terminals 32 and 32 exposed on the bottom surface of the package 31 by a conductive pattern (not shown). The conductive pattern for connecting the electrode portion 33 and the mounting terminal 32 may be formed on the surface of a castellation (not shown) used when the package 31 is formed, and the outer surface of the package 31 may be drawn around. Alternatively, the connection may be made by a conductive through hole penetrating an insulating substrate constituting the bottom of the package 31.
The piezoelectric vibrating piece 40 is accommodated in the internal space S as will be described later.
A lid 35 made of a metal such as ceramic, glass, or kovar is bonded to the package 31 via a low melting point glass, nickel, or the like in a sealing process described later. Thereby, the package 31 is hermetically sealed.

Next, a method of forming the piezoelectric vibrating piece will be described with reference to the flowchart of FIG.
(Outline forming process)
FIG. 4A is a schematic plan view showing a crystal wafer 45 as a piezoelectric substrate for cutting out an element piece for producing the piezoelectric vibrating piece 40.
In this case, the crystal wafer is cut out from the crystal single crystal so that the crystal axis of the crystal is the electric axis, the Y axis is the mechanical axis, and the Z axis is the optical axis. In addition, when cutting from a single crystal of quartz, an AT-cut quartz plate cut out at a predetermined angle, for example, 35.15 degrees from the Z axis in the above-described orthogonal coordinate system consisting of the X, Y, and Z axes. obtain.

Next, the main surface of the AT-cut quartz plate, which is the piezoelectric element piece, is polished to have flatness to form a so-called quartz wafer, which is wet-etched to obtain an element piece assembly to be described later.
That is, by wet-etching the crystal wafer, a large number of element pieces are simultaneously formed in the vertical and horizontal directions of the crystal wafer 45. In this case, the outer periphery of each element piece is separated, and a thin support portion is connected to the frame-shaped quartz material remaining after etching.
4 (b) to 4 (d) and FIG. 5 (e) show DD cross sections in the order of processing in a region where one element piece of the crystal wafer 45 of FIG. 4 (a) is formed.

  As shown in FIG. 4B, the crystal wafer 45 is cleaned with pure water (ST11), and then a base layer 61 is provided on the surface of the crystal wafer 45. This is made up to compensate for the fact that the metal serving as the corrosion-resistant film has a weak adhesion to a piezoelectric material such as quartz, and for example, Cr (chromium) is formed as the underlayer 61 by sputtering or vapor deposition. . On top of this, gold (Au) is formed as a corrosion-resistant layer 62 by sputtering or vapor deposition. In addition, since the same film | membrane is formed in the front and back of the quartz wafer 45, only the upper code | symbol is shown in a cross section.

Next, as shown in FIG. 4C, a resist 63 is applied to the entire surface of the anticorrosion film 62, exposed and developed to form a mask (ST13).
Subsequently, as shown in FIG. 4D, gold, which is the corrosion-resistant layer 62 exposed from the mask opening, is wet-etched using, for example, a potassium iodide solution, and then is etched using a 2 ceric ammonium nitrate solution. The chromium 61 that is the formation is etched (ST14).
Next, the quartz exposed from the mask opening is wet etched using, for example, an ammonium fluoride solution (ST15). Thereby, the element piece 1 is formed as shown in FIG.
Subsequently, the resist 63 is peeled off, and all of the corrosion-resistant layer 62 and the underlying layer 61 are removed using the solution used for each etching (ST16).

(Electrode formation process)
FIG. 5B is a schematic plan view showing the element piece assembly 50 in a state where a large number of element pieces 51 are formed on the crystal wafer 45 through the above-described steps.
A large number of element pieces 51 are formed on the crystal wafer 45 of the element piece assembly 50 in the vertical and horizontal directions. Each element piece 51 is separated in outer shape and surrounded by a crystal wafer 45 in a frame shape. Only the thin frame portions 52 and 52 are integrally connected to the frame-shaped portion.
The frame portions 52 and 52 are folding portions, and the individual piezoelectric vibrating pieces are separated by folding the folding portions in a later step.
The folding part is composed of two frame parts 52, 52 per element piece 51, but may be one, or three or more.

FIG. 5C is a schematic plan view showing an enlarged part of one element piece 51 formed in the element piece assembly 50.
Next, an electrode film-forming mask 53 is placed (ST17). The mask 53 is formed so as to cover the entire element piece assembly 50. With this mask 53, the regions 54-1, 54-1 and 54-2, 54-3, which are deformed due to the etching anisotropy of the element piece 51 and do not require electrode formation, are blocked. Yes.
Among these, in FIG. 5 (c), with respect to the crystal axis of the quartz crystal, there is an orthogonal coordinate system composed of the X axis, the Y axis, and the Z axis where the X axis is the electrical axis, the Y axis is the mechanical axis, and the Z axis is the optical axis. Due to the etching anisotropy of quartz, for example, the region 54-1 has an irregular end surface as shown in FIG. 10A, and the region 54-2 has a shape as shown in FIG. 10A. Corresponds to the location of the irregular end face.

In FIG. 6A, an electrode film 55 is formed in a region exposed from the mask 53 (ST18).
The electrode film 55 includes, for example, a base layer and an electrode layer, and chromium or nickel is suitable for the base layer, and gold is suitable for the electrode layer. That is, if the base layer and the electrode layer are made the same as the base layer and the corrosion-resistant layer formed in ST14, there is an advantage that they can be formed using, for example, the same sputtering apparatus and target.

In FIG. 6B, the mask 53 is removed (ST19). From here, only the element piece 51 is illustrated and described for convenience of understanding, but the frame portions 52 and 52 which are the folding portions are still connected to the crystal wafer.
Next, as shown in FIG. 6C, a resist 56 is applied over the entire surface (ST20). 6C and FIG. 7, the left side is a plan view, and the right side is a cross-sectional view taken along line EE.

In FIG. 7A, the resist 56 is patterned by exposure and development using a mask (not shown) to expose the unnecessary electrode film 55 (ST21).
Next, as shown in FIG. 7B, the exposed electrode film 55 is removed by etching (ST22), and the resist 56 is removed (ST23). Then, as shown in FIG. The excitation electrode 41 and the extraction electrodes 42 and 42 are formed.
Thus, the piezoelectric vibrating piece 40 described in FIGS. 1 and 2 is completed.

  Thus, in the above manufacturing method, the mask 53 is disposed in a portion that is deformed due to the influence of etching anisotropy so that the electrode film 55 is not formed. For this reason, compared with the conventional method in which an electrode film is formed on the entire surface and then a mask is provided to expose an electrode film in an unnecessary region and etching is performed, an electrode at a location that is deformed due to the influence of etching anisotropy Separation is ensured and the electrode film can be formed more precisely.

(Joining process)
Next, a conductive adhesive 43 is applied on the electrode part 33 on the package 31 side in FIGS. 1 and 2 formed separately from the piezoelectric vibrating piece.
Then, on the conductive adhesive 43, the base end portion or one end portion of the piezoelectric vibrating piece 40 broken from the element piece assembly 50, on which each extraction electrode 42 described in FIG. To do.
The piezoelectric adhesive piece 40 is joined to the inner bottom surface of the package 31 in a cantilever manner by heating and curing the conductive adhesive 43.
Here, as the conductive adhesive 43, a binder component made of a predetermined synthetic resin to which conductive particles such as silver particles are added can be used. Further, the piezoelectric vibrating piece 40 is not necessarily a cantilever type, and may be configured such that a part of the tip side is placed on a convex part (pillow part) formed on the inner bottom surface of the package 31.

Then, a driving voltage is applied to the piezoelectric vibrating piece 40 from the mounting terminal 32 of the package 31, the piezoelectric vibrating piece 40 is driven to measure its frequency, and one of the excitation electrodes 41 is measured based on the measurement result. By reducing the number of parts, the weight is reduced and the frequency is adjusted.
In this frequency adjustment step, the drive voltage is applied by changing the ambient temperature environment, the frequency corresponding to the temperature change is measured, and the temperature-frequency characteristics of the piezoelectric vibrating piece 40 are measured together. Make adjustments accordingly.

Next, the package 31 is moved into a vacuum chamber, and a lid 35 formed of a metal such as ceramic, glass, or kovar is bonded in a vacuum atmosphere via low melting point glass, nickel, or the like. Thereby, the package 31 is hermetically sealed.
Finally, through the necessary inspection, the piezoelectric device 30 is completed.

The present invention is not limited to the above-described embodiment. In the above embodiment, each region of 54-1, 54-2, and 54-3 in FIG. 5C is shown as a region covered with a mask because it becomes irregular due to etching anisotropy. It is not necessary to cover all of these regions with a mask, and if etching anisotropy occurs in addition to these due to etching conditions, etc., an electrode film may be formed by covering such regions with a mask. Of course.
Furthermore, each configuration of the above-described embodiment can be appropriately combined or omitted, and can be combined with other configurations not shown.
The present invention can be applied to all piezoelectric devices regardless of the names of piezoelectric vibrators, piezoelectric oscillators, etc., as long as they use a package or a case and accommodate a piezoelectric vibrating piece therein.

1 is a schematic plan view of a piezoelectric device according to an embodiment of the present invention. CC schematic sectional drawing of FIG. The flowchart which shows an example of the manufacturing method of the piezoelectric vibrating piece accommodated in the piezoelectric device of FIG. FIG. 2 is a process diagram sequentially illustrating an example of a manufacturing process of the piezoelectric vibrating piece of FIG. 1. FIG. 2 is a process diagram sequentially illustrating an example of a manufacturing process of the piezoelectric vibrating piece of FIG. 1. FIG. 2 is a process diagram sequentially illustrating an example of a manufacturing process of the piezoelectric vibrating piece of FIG. 1. FIG. 2 is a process diagram sequentially illustrating an example of a manufacturing process of the piezoelectric vibrating piece of FIG. 1. The figure which shows a part of manufacturing process of the conventional piezoelectric vibrating piece. The schematic plan view of the element piece before forming a drive electrode in a piezoelectric vibrating piece. FIG. 10 is a partial cross-sectional view of FIG. 9.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Piezoelectric device, 31 ... Package, 40 ... Piezoelectric vibrating piece, 41 ... Excitation electrode, 50 ... Element piece assembly, 51 ... Element piece, 53 ... Mask

Claims (3)

Piezoelectric vibrating piece including an outer shape forming step of wet etching a piezoelectric substrate having etching anisotropy to form an element piece of a piezoelectric vibrating piece, and an electrode forming step of forming a necessary driving electrode after the outer shape is formed A manufacturing method of
In the electrode forming step, after the etching, an electrode film to be the driving electrode is formed in the remaining region except for a portion that is deformed due to etching anisotropy,
A method of manufacturing a piezoelectric vibrating piece, wherein the driving electrode is formed by a photolithography technique. As the piezoelectric substrate, a quartz wafer is used, and the quartz wafer is a predetermined angle with respect to the crystal axis of the quartz in a rectangular coordinate system in which the X axis is an electric axis, the Y axis is a mechanical axis, and the Z axis is an optical axis. It is cut out on a tilted surface,
In the outer shape forming step, the crystal wafer is wet-etched, and a thin frame portion that becomes a break-off portion in a later step is in a state of an element piece assembly integrally connected to the element piece. A plurality of the element pieces are simultaneously formed from the quartz wafer,
2. The method for manufacturing a piezoelectric vibrating piece according to claim 1, wherein the element piece is folded from the crystal wafer in the folding portion after the electrode forming step is performed. A method of manufacturing a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package or case,
The piezoelectric vibrating piece is
Through a process including an outer shape forming step of wet etching a piezoelectric substrate having etching anisotropy to form an element piece of a piezoelectric vibrating piece, and an electrode forming step of forming a necessary driving electrode after the outer shape is formed. Formed,
In the electrode forming step, after the etching, an electrode film to be the driving electrode is formed in the remaining region except for a portion that is deformed due to etching anisotropy,
The driving electrode is formed by a photolithography technique,
After execution of the electrode forming step, the piezoelectric vibrating piece is separated from the quartz wafer,
A method for manufacturing a piezoelectric device, comprising: a step of bonding the piezoelectric vibrating piece to a connecting electrode portion formed on a package or an electrode of a plug attached to the case.

Images