JPH10242795A - Piezoelectric element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element that can suppress the deterioration of its characteristic without deteriorating its miniaturization and mass productivity by preparing a piezoelectric substrate where the electrodes are formed and a holder substrate of the piezoelectric substrate and joining both substrates together by means of both direct junction and junction applying the alloying. SOLUTION: A piezoelectric substrate 1 uses an AT-cut crystal substrate, for example, and a groove 33 is formed on the substrate 1. Then a titanium electrode 12 and a gold electrode 11 are buried into the groove 33 to lead out the end face of each electrode. The electrode 11 is set at the same level as the substrate 1 and then joined to a silicone substrate 2 via the alloying 16 of gold and silicon performed at the junction interface. Meanwhile, both substrates 1 and 2 are held via a direct junction 31 applying mainly the polysiloxane coupling. Accordingly, it's possible to stably hold the substrate 1 with no aging nor deterioration of the element characteristic caused by the remaining stress.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric element and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the recent development of mobile communication, various piezoelectric materials have been used as constituent materials of communication devices.
In particular, quartz, lithium niobate, lithium tantalate, and the like are widely used in bulk wave devices and surface acoustic wave devices such as vibrators and filters.

In general, a piezoelectric element converts a mechanical force into an electric signal, so that the characteristics of the piezoelectric element are greatly affected by residual stress during mounting and changes in the surrounding environment. For example, quartz has been used as a vibrator for temperature-compensated crystal oscillators in mobile phones because of its excellent frequency-temperature characteristics.However, it reduces residual stress after mounting and minimizes variations in residual stress due to elements. There is a need to. Further, in order to prevent the aging of the element due to the surrounding environment, the piezoelectric element must be hermetically sealed in a vacuum or an atmosphere such as nitrogen. The above is indispensable for manufacturing not only quartz but also high-performance piezoelectric elements with good mass productivity.

One of the methods for holding and hermetically sealing a piezoelectric body is a direct bonding technique. Direct bonding is a technique in which two mirror-polished substrates are superimposed and heat-treated to bond the substrates directly by atoms formed from the substrates without an intermediate adhesive layer. For example, iTripley Ultrasonics Symposium Proceedings, p10
45 (1994) (IEEE Ultrasonics)
Symposium Proceeding) reports on direct bonding between a semiconductor and a piezoelectric body, and it is reported that silicon and quartz are bonded between atoms via a silicon dioxide layer. This 2
Silicon oxide is derived from silicon or quartz,
It does not correspond to the intermediate adhesive layer. Direct bonding is a bonding method that is thermally and mechanically stable, and has very small variation in residual stress between elements. In addition, since the bonding is performed at the atomic level, hermetic sealing can be easily performed. The advantages of the piezoelectric element using direct bonding are described in detail in JP-A-4-283957 and JP-A-5-327383.

FIG. 23 shows an example of the structure of a piezoelectric element using direct bonding. FIG. 23A is a perspective view of the piezoelectric element, and FIG. 23B is a top view. In FIG. 23, 41 is a quartz substrate,
Reference numeral 42 denotes a holding substrate directly bonded to a quartz substrate, for example, a glass substrate. Reference numeral 43 denotes an electrode obtained by depositing gold on a chromium base electrode. Reference numeral 49 denotes a through hole provided in the quartz substrate 41, which conducts the back electrode and the front electrode of the quartz substrate 41. Reference numeral 48 denotes a gap portion provided in the holding glass substrate 42, which is provided so as not to contact the quartz substrate 41 and the holding glass substrate 42. With this structure, an electrode can be drawn out to the surface of the quartz substrate 41.

FIG. 24 shows a piezoelectric element having a structure in which an upper lid is attached to the piezoelectric element having the structure shown in FIG. FIG. 24A is a perspective view of a substrate for the upper lid of the piezoelectric element, and FIG. 24B is a perspective view of a glass substrate 42 for holding the piezoelectric element and a quartz substrate 41.
FIG. 11C shows the back surface of FIG.
FIG. 4D is a view showing a surface directly bonded to the holding glass substrate 42, and FIG. 4D is a top view of FIG. FIG.
Reference numeral 44 denotes an upper lid substrate, for example, a glass substrate. 46
Denotes a directly joined portion of the upper lid glass substrate 44 with the holding glass substrate 42. Reference numeral 47 denotes a gap provided in the upper lid glass substrate 44, and the piezoelectric substrate 41 and the upper lid glass substrate 4
4 is provided so as not to make contact. Reference numeral 45 denotes a through hole provided in the upper lid glass substrate 44 for directly connecting the upper lid glass substrate 44 and the holding glass substrate 42 and then taking out the electrodes. 50 is an external electrode.

FIG. 25 shows an example of another piezoelectric element using direct bonding. FIG. 25A is an exploded view of the element, and FIG. 25B is a cross-sectional view taken along the line I-II. A piezoelectric substrate 51 is, for example, a quartz substrate. Reference numeral 54 denotes a substrate for the upper and lower lids, for example, a glass substrate. The electrode 52 is an electrode composed of an excitation electrode 52a formed on the upper and lower surfaces of the quartz substrate and an extraction electrode 52b. However, the electrode 52
Are provided symmetrically on the upper and lower surfaces of the quartz substrate 51, respectively, and a large rectangular portion (excitation electrode 52 a) of the electrode 52 intersects the upper and lower surfaces of the quartz substrate 51. It is provided in the form.

That is, the excitation electrode 52a is an electrode portion of the electrode 52 that intersects the upper and lower surfaces of the quartz substrate 51, and a portion that does not intersect the extraction electrode 52b. That is, it is a thin electrode portion other than the excitation electrode 52a among the electrodes 52 in FIG. Reference numeral 53 denotes an extraction electrode 53 formed on a glass substrate 54. The crystal substrate 51 and the glass substrate 54 are directly joined with the extraction electrodes 52 and 53 provided on the respective substrates. After the direct bonding, if an external electrode is attached to the end face of the piezoelectric element, the end face of the electrode can be pulled out.

[0009]

However, there is the following problem in taking out the electrodes in the piezoelectric element using the direct bonding described above. In the configuration shown in FIG. 23, since the through hole 49 is provided in the quartz substrate 41, the area of the quartz substrate 41 must be increased in order to prevent degradation of element characteristics due to spurious components or the like. Further, since the through holes are provided on the quartz substrate 41, the element strength is reduced.

In the configuration shown in FIG. 24, it is necessary to provide through holes 49 and 45 in both the crystal substrate 41 and the glass substrate 44 for the upper lid, and the element area is further increased. As a method of taking out the external electrode 50 and hermetic sealing, the through hole 4
5, a method of press-fitting a soft metal such as indium into the through hole 4
5 is a method of forming a thick film by a method such as sputtering. The former method uses a very small through hole 4
In this case, the soft metal must be accurately arranged on the substrate 5, which hinders cost reduction and deteriorates mass productivity. Further, when a soft metal is press-fitted into the through-hole 45, the element may be damaged, thereby deteriorating the yield. In order to perform airtight sealing by the latter method, a very thick film must be provided, which hinders cost reduction and deteriorates mass productivity.

FIG. 25 shows one method of extracting electrodes from the end face of the piezoelectric element in order to reduce the size of the piezoelectric element. This configuration has the following problems. (1) Hermetic sealing is difficult. (2) Device characteristics deteriorate due to residual stress. (3) The substrate peels and breaks. (4) The thickness of the embedded electrode is restricted.

(1) will be described. As shown in FIG. 25B, the peripheral portions 55 of the sandwiched lead-out electrodes 52 and 53 are not directly joined to each other, so that a gap is formed, so that hermetic sealing cannot be achieved. For hermetic sealing, a step of filling the gap after the joining step is required. (2) will be described. As shown in FIG. 25B, after the bonding step, distortion remains in the piezoelectric substrate. A description will be given of (3) in which element characteristics are degraded due to residual stress due to this strain. The sandwiched extraction electrodes 52 and 53 and the peripheral portion 55 are not joined, and the holding of the piezoelectric substrate is unstable. Therefore, the substrate is peeled or damaged due to heat shock such as solder reflow or aging. (4) will be described. If the sandwiched extraction electrodes 52 and 53 are too thick, direct joining cannot be achieved. The thickness of the excitation electrode is closely related to the element characteristics, and the thickness of the sandwiching electrode and the thickness of the excitation electrode may need to be different. Therefore, the number of steps increases and the cost increases. However, due to the above problems, it is difficult to obtain a small, high-performance, and highly mass-produced piezoelectric element even with the configuration of FIG.

In the above-described prior art, it is very difficult to obtain a piezoelectric element having good characteristics, small size, good mass productivity, and low cost.

According to the above-described prior art, it is very difficult to obtain a piezoelectric element having good characteristics, small size, good mass productivity, and low cost.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and a piezoelectric element and a method of manufacturing the same without deteriorating the element size and mass productivity and causing less deterioration in element characteristics. The purpose is to provide.

[0016]

According to a first aspect of the present invention, there is provided a piezoelectric substrate on which electrodes are formed, and a holding substrate for holding the piezoelectric substrate, and a joint between the holding substrate and the piezoelectric substrate. This is a piezoelectric element that uses both direct bonding and bonding by alloying.

According to a second aspect of the present invention, there is provided a piezoelectric element wherein the holding substrate is a silicon substrate or a germanium substrate, and the bonding by alloying is a bonding mainly using gold-silicon or gold-germanium. is there.

According to a third aspect of the present invention, there is provided the piezoelectric element, wherein the holding substrate is a silicon substrate on which an integrated circuit is formed.

In the present invention, the direct bonding and the joining by alloying are used together when the holding substrate and the electrode are joined by the alloying. All or some of the joints other than the joints are the piezoelectric elements directly joined.

According to a fifth aspect of the present invention, there is provided a piezoelectric substrate on which a first electrode is formed, and a holding substrate for holding the piezoelectric substrate, on which a second electrode is formed. This is a piezoelectric element in which direct bonding and alloying bonding are used in combination with the piezoelectric substrate.

According to the sixth aspect of the present invention, the simultaneous use of the direct joining and the joining by alloying means that the first electrode and the second electrode are joined by the alloying. The whole or a part of the joining part other than the joining part by the alloying is the piezoelectric element directly joined.

According to a seventh aspect of the present invention, there is provided a piezoelectric substrate on which electrodes are formed, a holding substrate for holding the piezoelectric substrate, and a lid substrate for covering the piezoelectric substrate. At least one of the lid substrates and the piezoelectric substrate are held by direct bonding and bonding by alloying, and the piezoelectric element is hermetically sealed.

The present invention according to claim 8 provides the above-mentioned holding substrate,
In addition, at least one of the lid substrates is a silicon substrate or a germanium substrate, and the bonding by alloying is a piezoelectric element mainly composed of gold-silicon or gold-germanium.

According to a ninth aspect of the present invention, there is provided the holding substrate,
In addition, at least one of the lid substrates is a piezoelectric element that is a silicon substrate on which an integrated circuit is formed.

According to a tenth aspect of the present invention, at least one of the holding substrate and the lid substrate is joined to the electrode by the alloying, and all the parts other than the joints by the alloying are joined. Alternatively, the piezoelectric element has a part that is directly joined to the piezoelectric element.

According to the present invention, a piezoelectric substrate on which electrodes are formed, a holding substrate for holding the piezoelectric substrate,
A lid substrate for covering the piezoelectric substrate, wherein at least one of the holding substrate and the lid substrate, and the piezoelectric substrate is directly bonded, and held by bonding by alloying, and, The piezoelectric element is hermetically sealed.

According to a twelfth aspect of the present invention, an electrode is formed on at least one of the holding substrate and the lid substrate, and the electrode and the electrode formed on the piezoelectric substrate are connected to each other. Are joined by the alloying,
All or some of the joints other than the joints formed by the alloying are the piezoelectric elements directly joined.

According to a thirteenth aspect of the present invention, a holding substrate comprises:
A lid substrate and a piezoelectric resonator having an electrode formed on the piezoelectric substrate, wherein a node of the vibration of the piezoelectric resonator is held by bonding to one or both of the holding substrate and the lid substrate by alloying The piezoelectric resonator is a piezoelectric element hermetically sealed in a package constituted by at least the holding substrate and the lid substrate.

According to a fourteenth aspect of the present invention, there is provided a piezoelectric element in which the package is hermetically sealed by directly joining the holding substrate and the lid substrate.

According to a fifteenth aspect of the present invention, a spacer substrate is provided between the holding substrate and the lid substrate, and the spacer substrate is directly connected to the holding substrate and the lid substrate. A piezoelectric element hermetically sealed in the package by bonding.

The present invention according to claim 16 is a piezoelectric element wherein the material of the piezoelectric substrate is any one of quartz, lithium niobate, lithium tantalate, and lead zirconate lanthanate titanate. .

According to a seventeenth aspect of the present invention, there is provided the piezoelectric element, wherein the bonding by alloying is a bonding with at least two kinds of metals among gold, silicon, germanium, and tin.

The present invention according to claim 18 is a piezoelectric element in which the vibration mode of the piezoelectric resonator is a long side or short side mode.

According to a nineteenth aspect of the present invention, a step of mirror-polishing at least one principal surface of a holding substrate and at least one principal surface of a piezoelectric substrate, and a step of providing an electrode on the principal surface side of the piezoelectric substrate are provided. A step of overlapping the main surface of the holding substrate and the piezoelectric substrate so that the electrode and the holding substrate are in contact with each other, and directly joining the holding substrate and the piezoelectric substrate,
And a step of alloying the bonding interface between the holding substrate and the electrode and the vicinity thereof.

According to a twentieth aspect of the present invention, there is provided a piezoelectric device including a step of mirror-polishing at least one principal surface of the lid substrate, directly bonding the lid substrate and the holding substrate, and hermetically sealing the piezoelectric substrate. This is a method for manufacturing an element.

According to a twenty-first aspect of the present invention, at least one main surface of a holding substrate and at least one main surface of a piezoelectric substrate are mirror-polished, and a first electrode is provided on the main surface side of the piezoelectric substrate. A step of providing a second electrode on the main surface side of the holding substrate, and a step of overlapping the main surface of the holding substrate and the piezoelectric substrate such that the first electrode and the second electrode are in contact with each other. And directly bonding the holding substrate and the piezoelectric substrate and alloying the first electrode and the second electrode.

According to a twenty-second aspect of the present invention, there is provided a piezoelectric element including a step of mirror-polishing at least one main surface of the lid substrate, directly bonding the lid substrate and the holding substrate, and hermetically sealing the piezoelectric substrate. It is a manufacturing method of.

According to a twenty-third aspect of the present invention, at least one main surface of the holding substrate and the lid substrate, at least one main surface of the piezoelectric substrate is mirror-polished, and at least one main surface of the piezoelectric substrate is provided. Providing an electrode on the side, one or both of the holding substrate and the lid substrate, and at least one main surface of the piezoelectric substrate, and one or both of the holding substrate and the lid substrate and the electrode. Superposing so as to be in contact with each other, directly bonding one or both of the holding substrate and the lid substrate to the piezoelectric substrate, and bonding one or both of the holding substrate and the lid substrate to the electrode And a step of alloying the interface and its vicinity.

According to a twenty-fourth aspect of the present invention, at least one main surface of the holding substrate and the lid substrate, at least one main surface of the piezoelectric substrate is mirror-polished, and at least one main surface of the piezoelectric substrate is provided. Providing a first electrode on the side;
Providing a second electrode on one or both main surfaces of the holding substrate and the lid substrate; and forming one or both of the holding substrate and the lid substrate and the main surface of the piezoelectric substrate on the A step of superposing the first electrode and the second electrode so as to be in contact with each other, and performing a heat treatment to directly join the holding substrate or the lid substrate to the piezoelectric substrate; And a step of alloying the electrodes.

[0040]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) A piezoelectric element according to a first embodiment of the present invention will be described with reference to FIG. 1A to 1D are views showing the structure of a piezoelectric element according to the present embodiment. FIG. 1B is a top view, FIG. 1A is FIG. 1B, and FIG. 1 (c) is a sectional view of FIG.
(B) is a cross-sectional view along III-IV, and FIG. 1 (d) is a cross-sectional view along V-VI in FIG. 1 (b).

In the figure, reference numeral 1 denotes a piezoelectric substrate, for example, A
This is a T-cut quartz substrate. The size is, for example, 3 mm in the vertical direction (width direction), 6 mm in the horizontal direction (longitudinal direction),
The thickness is 50 μm. Reference numeral 2 denotes a silicon substrate having a size of, for example, 3 mm in the vertical direction and 7 mm in the horizontal direction, and having a thickness of 600 mm in a holding portion with quartz, that is, a direct bonding portion.
μm, vibrating part of crystal, that is, 500 μm in concave part 34
m. 11 is a gold electrode and 12 is a titanium electrode.
Numeral 31 is a joint portion by direct joining, and 16 is an alloy layer of silicon and gold, which is a portion joined by alloying.
Reference numeral 33 denotes a groove provided in the AT-cut quartz substrate 1, which has a size of 600 μm in the vertical direction and 2 mm in the horizontal direction, and has a depth of 2000 Å in the depth direction (thickness direction). In the groove 33, a titanium electrode 12, a gold electrode 1
1 is embedded, and the gold electrode 11 in the groove 33 is on the same plane as the AT-cut quartz crystal substrate 1.

The feature of the piezoelectric element of this embodiment is that the grooves 33
The gold electrode 11 and the silicon substrate 2 are bonded by alloying gold and silicon at the bonding interface, and the AT-cut quartz substrate 1 and the silicon substrate 2 are held by direct bonding mainly using a siloxane bond. It is that you are.

In this specification, the term "joining by alloying" refers to a joining form in which two or more metals or semiconductors are fixed by alloying at least in the vicinity of the interface between the metals. An alloy refers to a solid solution, a eutectic, an intermetallic compound, or a mixture thereof.

The term “directly joined” means that the substrates are bonded to each other without interposing an intermediate adhesive layer, such as a bond by an intermolecular force, a hydrogen bond, a covalent bond, or an ion. It refers to the state of being joined by bonding or the like. However, an intermediate layer caused by atoms on the substrate surface generated during a bonding process such as cleaning, overlapping, heat treatment, etc. does not correspond to the above-mentioned intermediate adhesive layer. For example, when silicon and quartz are directly bonded, an amorphous layer is formed at the bonding interface. In this case as well, the substrates are directly bonded. In addition, even when the bonding is performed via a film formed on the substrate surface such as an oxide film or a nitride film, if the bonding is performed by a film formed on the substrate surface or bonding of atoms constituting the substrate itself. Thus, the substrates are directly bonded.

The structure described above has the following effects. The gold electrode in the groove 33 and the AT-cut quartz substrate 1 are joined to the silicon substrate 2 in the same plane, and there is almost no non-joined portion as shown in FIG. Therefore, the AT-cut quartz substrate 1 can be stably held without aging, and there is no deterioration in element characteristics due to residual stress.

With the structure described above, the back electrode of the vibrator can be pulled out from the end face of the piezoelectric body without deteriorating the characteristics, and there is an effect that the size of the piezoelectric element can be reduced.

Note that, even if the gold electrode 11 has a shape protruding from the AT-cut quartz substrate 1 in the sectional view taken along the line I-II in FIG. 1B, the structure is different from that shown in FIG.
The joining portion 33 is fixed by alloying, the proportion of the non-joining portion in the holding portion is small, the holding portion is stably held, and the aging of the holding is small. As a result, FIG.
The conventional problems in the structure shown in FIG. (Embodiment 2) Next, an embodiment of a method for manufacturing a piezoelectric element according to the present invention will be described with reference to FIGS. 2 (a) to 6 (d).

FIGS. 2A to 6D show the second embodiment of the present invention.
It is a figure explaining each process about a manufacturing method of a piezoelectric element of an embodiment. Here, the size and thickness of the AT-cut quartz crystal substrate 1 and the silicon substrate 2 are the same as in the first embodiment. Hereinafter, each of the steps (A) to (E) of the present embodiment will be described with reference to FIG.

Step (A): The AT-cut quartz substrate 1 is mirror-polished to a predetermined thickness, for example, 50 μm. The silicon substrate 2 is mirror-polished (see FIGS. 2A to 2F).
Here, FIGS. 2 (a), (b) and (c) show the AT
FIG. 3 is a view showing a cut quartz substrate 1. Specifically, FIG.
FIG. 2B is a plan view of the AT-cut quartz crystal substrate 1, and FIG.
2 is a cross-sectional view taken along the line I-II in FIG.
FIG. 4C is a cross-sectional view taken along the line III-IV of FIG. FIGS. 2D, 2E, and 2F are diagrams showing the silicon substrate 2, respectively. Specifically, FIG.
2 (e) is a plan view of the silicon 2, FIG. 2 (d) is a cross-sectional view taken along the line I-II of FIG. 2 (e), and FIG.
It is sectional drawing in the III-IV cross section of the same figure (e).

Step (B): After patterning a mask by photolithography on the bonding surface side of the AT-cut quartz substrate 1, a groove 33 is formed by etching with a hydrofluoric acid-based solution. The size of the groove is 600 μm in the vertical direction,
The width was 2 mm and the depth was 2000 Å.
After patterning a mask by photolithography on the bonding surface side of the silicon substrate 2, a concave portion 34 having a depth of 100 μm is provided with a hydrofluoric acid-based liquid (FIG. 3A to FIG. 3A).
(F)). Here, FIGS. 3A to 3F are diagrams showing the substrates 1 and 2 in the step (B).
(A) to (f) respectively.

Step (C): A titanium electrode 12 and a gold electrode 11 are vacuum-deposited on the upper and lower surfaces of the AT-cut quartz substrate 1. The titanium electrode 12 is 100 angstroms, and the gold electrode 11 is 2 angstroms.
000 angstroms (FIG. 4A)
(F)). Here, FIGS. 4A to 4F are views showing the substrates 1 and 2 in the step (C), and correspond to FIGS. 3A to 3F, respectively.

Step (D): The AT-cut quartz substrate 1 and the silicon substrate 2 are washed with a hydrofluoric acid-based cleaning solution,
After cleaning with a mixed solution of hydrogen peroxide and water, the substrate is rinsed sufficiently with pure water and the two substrates are superposed. Further, heat treatment is performed at 400 ° C. for 2 hours in a hydrogen atmosphere. Reference numeral 16 denotes an alloy layer of gold and silicon (including a eutectic layer). The heat treatment is usually performed at a temperature in the range of 350 ° C. to 573 ° C., which is near the eutectic temperature of silicon and gold, but is preferably performed in a temperature range of 350 ° C. to 450 ° C. in order to avoid the influence of damage to the substrate due to stress. . At the time of the heat treatment, by applying pressure to the joining portion by alloying, that is, the portion of the groove 33, joining by eutectic of gold and silicon further proceeds smoothly (see FIGS. 5A to 5D). Here, FIGS. 5A to 5D are views showing a substrate formed using the AT-cut quartz crystal substrate 1 and the silicon substrate 2 formed in the step (C). More specifically, FIG. 5B is a plan view of a substrate formed using the AT-cut quartz crystal substrate 1 and the silicon substrate 2, and FIG.
(A) is a cross-sectional view taken along the line I-II in (b) of FIG.
FIG. 5C is a cross-sectional view taken along the line III-IV of FIG. FIG. 5D is a cross-sectional view taken along the line V-VI of FIG.

Step (E): A titanium electrode 12 and a gold electrode 11 are vacuum-deposited on the surface of the piezoelectric element. Through the above steps,
The back electrode can be drawn from the end face of the piezoelectric element.

In this embodiment, the bonding portion 31 is fixed by direct bonding mainly using a siloxane bond, and the bonding portion formed by alloying is bonded by the alloy 16 of gold and silicon. Joining by alloying is mainly joining by eutectic of silicon and gold, or a solid solution of silicon and gold, or a mixed alloy thereof (FIG. 6).
(See (a) to (d)). Here, FIGS. 6 (a) to 6 (d)
FIG. 5 is a view showing a substrate formed in the step (E), and FIG.
(A) to (d) respectively.

The following effects are obtained by the manufacturing method described above. That is, in the step (D), since the heat treatment is performed at a temperature higher than the eutectic temperature of gold and silicon, the gold electrode 11 and the silicon substrate 2 are alloyed at the interface. The electrodes 11, 1
Although the thickness of No. 2 is larger than the depth of the groove 33 by about 100 angstroms, during the heat treatment step, silicon and gold at the bonding interface are in a solid solution, and the protruding portion of the gold electrode is eliminated. FIGS. 7A to 7C show this state. Here, FIG.
7A is a cross-sectional view taken along the line I-II of the substrate shown in FIG. 7B and an enlarged view of a portion surrounded by a dotted line in the cross-sectional view, that is, a periphery of the groove 33. FIG. 7 (b)
FIG. 2 is a plan view of the substrate and a portion surrounded by a dotted line in the plan view, that is, an enlarged plan view of the vicinity of the end of the groove 33. or,
FIG. 7C is a diagram showing a state before joining of the portion shown in FIG. In FIG. 7A, reference numeral 16 denotes an alloy made of gold and silicon. As shown in FIG. 7 (c), before bonding, the gold electrode 11 is one step away from the surface of the quartz substrate 1.
It protrudes by 00 angstroms.

As shown in FIGS. 7A and 7B, the solid solution 29 made of excess silicon and gold is formed by the groove 33 and the electrode 11,
It is used to fill a gap 30 between the groove 12 (see FIG. 7A) or discharged outside the groove 33 (see FIG. 7B).
This effect increases as the amount of pressure applied during the heat treatment increases.

When airtight sealing is required as shown in FIGS. 15 (a) to 17 (d), for example, all the gaps 30 shown in FIG. It is desirable to be sealed by 29. At least at the end face of the piezoelectric element, all the gaps 30 need to be sealed by the solid solution 29.

There is also the following operation. That is, since direct bonding is used together, the amount of pressurization can be smaller than that of bonding by ordinary alloying. This is because the pressing force generated at the time of direct joining is added.

The following effects are obtained by the manufacturing method described above. The back electrode can be pulled out at the end face of the piezoelectric substrate,
The size of the element can be reduced. Further, even if the thickness of the gold electrode is not accurately controlled, the gold electrode can be stably held, and there is no characteristic deterioration due to distortion. Further, the amount of pressurization at the time of bonding can be reduced, and the device is not damaged by pressurization, thereby increasing the yield.

(Embodiment 3) Next, a third embodiment of the method of manufacturing a piezoelectric element according to the present invention will be described. Here, the substrate to be used and the shape thereof are the same as those in the second embodiment, and the description will be made with reference to FIGS.

That is, first, the step (A) is performed in the same manner as in the second embodiment.

Next, the step (B) is performed. A resist is applied to the back surface (bonding surface) of the AT-cut quartz substrate 1. Here, the resist used must be resistant to etching in the next step. The resist where the grooves 33 are to be provided is removed by photolithography, and the AT-cut quartz substrate 1 is etched to a depth of 2000 angstroms using a hydrofluoric acid-based etchant.

Next, the step (C) is performed. Electrodes 11 and 12 are vacuum-deposited on the entire back surface of the AT-cut quartz substrate 1. Next, when the resist is removed, the electrodes 11 and 12 deposited on the resist are removed together with the resist, and an electrode pattern is formed only in the groove 33. Furthermore, FIG.
The remaining electrode portion is provided in a shape as shown in FIG.
Here, the thicknesses of the gold electrode 11 and the titanium electrode 12 are the same as in the second embodiment.

Further, similarly to the second embodiment, the step (D),
(E) is performed.

This embodiment is characterized in that steps (B) and (C)
Thus, an extraction electrode is formed in the groove 33. This method is generally called lift-off.

In this embodiment, the AT-cut quartz crystal substrate 1 and the silicon substrate 2 are joined in the same manner as in the second embodiment, and have the same functions and effects as the second embodiment. There are functions and effects as follows. By a very simple method, a lead electrode can be formed in the groove 33 on the AT-cut quartz substrate 1 with high accuracy. This allows
A lead electrode can be provided with high accuracy, and a piezoelectric element can be manufactured with high yield.

The same operation and effect can be obtained by using a germanium substrate instead of the silicon substrate used in the first to third embodiments. When a germanium substrate is used, the bonding layer formed by alloying becomes an alloy of gold and germanium. (Embodiment 4) A fourth embodiment of the piezoelectric element of the present invention will be described with reference to FIGS. In the present embodiment, the size and thickness of the AT-cut quartz crystal substrate 1 and the silicon substrate 2, the electrodes formed on the substrate, the grooves formed on the substrate, the bonding mode, and the like are roughly the same as those in the first embodiment. The difference from the first embodiment is that the integrated circuit 21 is formed on the silicon substrate 2 and the length of the silicon substrate 2 in the horizontal direction is 8 mm. Further, FIG.
In (d), a low-resistance layer 24 is provided on the silicon substrate 2 at a portion joined by the gold-silicon alloy 16.
The connection with the integrated circuit 21 is established. The conduction between the surface electrode on the AT-cut quartz substrate 1 and the integrated circuit 21 is established by a metal film 23 formed by vapor deposition.

According to the configuration of the present embodiment, the same operation and effect as those of the first embodiment are obtained. However, the following operation and effect are further added by the above-described configuration.

The ohmic contact between the gold-silicon alloy 16 and the low resistance layer 24 made of silicon is established, and is directly connected to the circuit. Usually, in such a case, electrical connection between the circuit and the piezoelectric element is established by a method such as wire bonding. However, such a method hinders miniaturization of the element. With the structure of this embodiment mode, the size of the piezoelectric element integrated with the integrated circuit can be easily reduced. (Embodiment 5) A fifth embodiment of the piezoelectric element of the present invention will be described with reference to FIGS. 9 (b) is a top view, FIG. 9 (a) is a cross-sectional view along I-II in FIG. 9 (b), FIG. 9 (c) is a cross-sectional view along III-IV in FIG. 9 (b), and FIG. FIG. 9B is a sectional view taken along line V-VI of FIG. The size of the AT-cut quartz substrate 1 is, for example, 3 mm in the vertical direction (width direction) and 6 mm in the horizontal direction (longitudinal direction).
And the thickness is 50 μm. Reference numeral 33 denotes a groove provided in the AT-cut quartz substrate 1, which has a size of 600 μm in the vertical direction and 2 mm in the horizontal direction, and has a depth of 2000 Å in the depth direction (thickness direction). A chromium electrode 15 and a gold electrode 11 are embedded in the groove 33 for drawing out the end face of the electrode. The gold electrode 11 in the groove 33 is on the same plane as the AT-cut quartz substrate 1. Reference numeral 3 denotes a glass substrate having a size of, for example, 3 mm in the vertical direction and 7 mm in the horizontal direction, and has a thickness of 500 μm in the portion holding the crystal and 450 μm in the vibrating portion of the crystal. 13
Is a tin electrode. The glass substrate 3 has a depth of 500
0 angstrom groove 35 is provided.
Are provided with a chromium electrode 15 and a tin electrode 13.

In the configuration of the present embodiment, the AT-cut quartz crystal substrate 1 and the glass substrate 3 are fixed at the atomic level at the joint portion 31 for direct joining. Gold-tin alloy 19
There exists an alloy mainly composed of a eutectic of gold and tin or a solid solution of tin and gold.

The structure described above has the same functions and effects as those of the first embodiment, but also has the following functions and effects. Since an inexpensive glass substrate is used, a low-cost piezoelectric element can be realized. In addition, the degree of freedom in selecting an alloy is high.

In this embodiment, a gold-tin alloy is used as a bonding layer by alloying, but the same operation and effect can be obtained by using a gold-germanium alloy or a gold-silicon alloy. (Embodiment 6) Next, a method of manufacturing a piezoelectric element according to a sixth embodiment of the present invention will be described with reference to FIGS.

FIGS. 10A to 10F are diagrams for explaining each step of the method for manufacturing a piezoelectric element according to the present embodiment. Here, the size and thickness of the AT-cut quartz crystal substrate 1 and the glass substrate 3 are the same as in the fifth embodiment. Hereinafter, each of the steps (A) to (E) of the present embodiment will be described. Step (A): The AT-cut quartz substrate 1 is mirror-polished to a predetermined thickness, for example, 50 μm. The glass substrate 3 is mirror-polished (see FIG. 10). Here, FIG.
(B), (c) is a figure which shows the AT cut crystal substrate 1, respectively. Specifically, FIG. 10B is a plan view of the AT-cut quartz crystal substrate 1, and FIG.
10C is a cross-sectional view taken along the line III-IV in FIG. 10B. or,
FIGS. 10D, 10E, and 10F are diagrams showing the glass substrate 3, respectively. Specifically, FIG. 10E is a plan view of the glass substrate 3, and FIG.
FIG. 10F is a cross-sectional view taken along the line II, and FIG.
It is sectional drawing in the III-IV cross section.

Step (B): After patterning a mask by photolithography on the bonding surface side of the AT-cut quartz substrate 1, grooves 33 are formed by etching with a hydrofluoric acid-based solution. The size of the groove is 600 μm in the vertical direction,
The width was 2 mm and the depth was 2000 Å.
After patterning a mask by photolithography on the bonding surface side of the glass substrate 3, a concave portion 34 is provided with a hydrofluoric acid-based liquid at a depth of 50 μm. Further, a groove 3 is formed on the glass substrate 3 by the same photolithography and etching.
5 is provided. The size of the groove is 600 μm in vertical direction and 3 in horizontal direction.
mm and a depth of 5000 Å (see FIG. 11). Here, FIGS. 11A to 11F are views showing the substrates 1 and 3 in the step (B), and FIGS.
(F) respectively.

Step (C): A titanium electrode 12 and a gold electrode 11 are vacuum-deposited on the upper and lower surfaces of the AT-cut quartz substrate 1. The titanium electrode 12 is 100 angstroms, and the gold electrode 11 is 2 angstroms.
000 angstroms. The chromium electrode 15 and the tin electrode 1 are formed in the groove 35 of the glass substrate 3 by vacuum evaporation.
Form 3 The film thickness was 9700 Å. Next, the gold electrode 11 is vapor-deposited on the tin electrode 13 by 300 angstroms. The gold electrode 11 on the tin electrode 13 functions as a protective film, and prevents the tin electrode from being dissolved in the next step, and also prevents the tin electrode 13 from being oxidized. Gold electrode 13
The thickness of the gold electrode may be enough to fill the groove 35, and the thickness of the gold electrode is controlled in accordance with the thickness of the tin electrode 13 (FIG. 12).
reference). Here, FIGS. 12A to 12F illustrate the step (C).
11 shows the substrates 1 and 3, respectively, and corresponds to (a) to (f) of FIG.

Step (D): The AT-cut quartz substrate 1 and the glass substrate 3 are washed with a neutral detergent or an alkali washing solution, and washed with a mixed solution of ammonia, hydrogen peroxide and water.
Rinse thoroughly with pure water and superimpose the two substrates. Further, heat treatment is performed in a hydrogen atmosphere at 300 ° C. At the time of the heat treatment, by applying pressure to the joining portion by alloying, that is, the portion of the groove 33, the joining by gold and tin eutectic proceeds more smoothly (see FIG. 13). Here, FIG.
(D) is a diagram illustrating a substrate formed using the AT-cut quartz crystal substrate 1 and the glass substrate 3 formed in the step (C). Specifically, FIG. 13B is a plan view of a substrate formed using the AT-cut quartz crystal substrate 1 and the glass substrate 3, and FIG.
FIG. 13C is a cross-sectional view taken along the line II, and FIG.
It is sectional drawing in the III-IV cross section. FIG.
FIG. 4D is a cross-sectional view taken along the line V-VI of FIG.

Step (E): A chromium electrode 15 and a gold electrode 11 are vacuum deposited on the surface of the piezoelectric element.

In this embodiment, the AT-cut quartz substrate 1
(FIG. 14A)
To (d)). Here, FIGS. 14A to 14D are views showing the substrate formed in the step (E), and correspond to FIGS. 13A to 13D, respectively.

According to the above-described manufacturing method, the same operation and effect as those of the second embodiment can be obtained. However, since gold and tin are used as the joining materials by alloying, they are shown in FIG. 3 of the second embodiment. The effect is even greater. Further, since an inexpensive glass substrate is used for holding, the piezoelectric element can be manufactured at low cost. Further, the glass substrate has a high degree of freedom with respect to the coefficient of thermal expansion, so that it is possible to select a coefficient of thermal expansion close to the piezoelectric material used, and damage is reduced by thermal stress at the time of heat treatment. However, the thermal stress referred to here is a thermal stress caused by a difference in thermal expansion coefficient between the glass substrate 3 and the AT-cut quartz substrate 1. Further, the degree of freedom in selecting an alloy used for joining is high.

In this embodiment, the tin electrode is formed on the glass substrate, but the same effect can be obtained by providing silicon or germanium instead of the tin electrode. However, in this case, a low-resistance metal may be provided below silicon and germanium in order to prevent the resistance of the extraction electrode from increasing. For example, chrome, gold,
An extraction electrode laminated in the order of nickel and silicon (or germanium) may be used. (Embodiment 7) Next, a seventh embodiment of the piezoelectric element of the present invention will be described with reference to FIGS.

FIG. 15A is an exploded perspective view of the piezoelectric element according to the present embodiment, which shows, in order from the top, a lid of the piezoelectric element, a piezoelectric vibrator, and a holder for the piezoelectric element. The description of the external electrodes 17 described later is omitted in FIG. FIG. 15B is a cross-sectional view of the piezoelectric element. The lid portion and the holding portion of the piezoelectric element are each formed of a silicon substrate 2. The size is 3 mm long, 6.5 mm wide and 600 μm thick. The central part of the silicon substrate 2 in the upper lid part and the lower lid part is 100
A recess 38 of about μm is provided. The piezoelectric vibrator portion has a groove 33 of 600 μm in the vertical direction, 1.5 mm in the horizontal direction, and 2,000 Å in the depth direction at the electrode lead-out portions on the front and back surfaces of the AT-cut quartz substrate 1.
In the groove 33, a titanium electrode 12 and a gold electrode 11 are stacked. A feature of the present embodiment in which slits are provided at both ends of the excitation electrode of the AT-cut quartz substrate 1 is that the AT-cut quartz substrate 1 includes an upper lid portion and a lower lid portion made of a silicon substrate 2.
The piezoelectric vibrating part made of is directly bonded and bonded by alloying silicon and gold, and the electrodes are drawn out and the vibrator is hermetically sealed.

With the structure described above, the same operation and effect as those of the second embodiment can be obtained. However, when airtight sealing is performed, the effect that there is no non-joining surface is very useful. Therefore,
The end face of the electrode can be completely pulled out and hermetically sealed, so that the size of the element can be reduced and the yield can be improved. (Embodiment 8) A method of manufacturing an eighth piezoelectric element according to the present invention will be described. Since the material and the shape of the substrate are the same as those in the seventh embodiment, the steps (A) to (E) of the present embodiment will be described with reference to FIGS.

Step (A): The AT-cut quartz substrate 1 is mirror-polished to a predetermined thickness, for example, 50 μm. The silicon substrate 2 is mirror-polished.

Step (B): After patterning a mask by photolithography on the front and back surfaces of the AT-cut quartz substrate 1, etching is performed with a hydrofluoric acid-based solution to form grooves 3.
3 is provided.

The size of the groove was 600 μm in the vertical direction, 1.5 mm in the horizontal direction, and 2000 Å in depth. Further, a slit is provided on the AT-cut quartz substrate 1. Next, after patterning a mask by photolithography on the bonding surface side of the upper lid and lower lid silicon substrates 2, a void 38 is provided with a hydrofluoric acid-based liquid at a depth of 100 μm. That is, the AT-cut quartz substrate 1 in this step is:
This corresponds to the AT-cut quartz substrate 1 shown in FIG. 15A in which the electrodes 11 and 12 are not formed.

Step (C): A titanium electrode 12 and a gold electrode 11 are vacuum-deposited on the upper and lower surfaces of the AT-cut quartz substrate 1. However, vapor deposition is performed so that the extraction electrode portion is embedded in the groove 33. The titanium electrode 12 had a thickness of 100 angstroms, and the gold electrode 11 had a thickness of 2000 angstroms (see the AT-cut quartz substrate 1 in FIG. 15A).

Step (D): The AT-cut quartz substrate 1 and the silicon substrate 2 are washed with a hydrofluoric acid-based cleaning solution,
After cleaning with a mixed solution of hydrogen peroxide and water, the substrate is rinsed sufficiently with pure water and the two substrates are superposed. Further, heat treatment is performed at 400 ° C. for 2 hours in a hydrogen atmosphere. At the time of the heat treatment, by applying pressure to the joining portion by alloying, that is, the portion of the groove 33, the joining by eutectic of gold and silicon proceeds more smoothly (see FIG. 15A).

Step (E): External electrode 1 is applied to the end face of the piezoelectric element.
7 is provided by sputtering. The external electrode 17 is provided as a terminal electrode for extracting the extraction electrodes 11 and 12 to the outside. In addition, even when there is a gap between the groove 33 and the extraction electrodes 11 and 12 and it is difficult to hermetically seal it as it is, the provision of the external electrode 17 ensures that hermetic sealing can be reliably performed. There is also an effect.

The feature of this embodiment is that, in the step (D), direct bonding and bonding by alloying are performed to achieve hermetic sealing. Further, the form of bonding is the same as in Embodiment 2 (see FIG. 15B).

The manufacturing method of this embodiment has the same function and effect as those of the second embodiment. However, when airtight sealing is performed, the groove 33 shown in FIGS. 7A to 7C is filled. The effect becomes very useful.

Further, in the material configuration of the present embodiment, direct bonding at the atomic level is started at about 200 ° C.
Up to about 370 ° C., which is the eutectic temperature of silicon and gold, the alloy joint is not completely sealed, and the gas present in the void is removed. There are various possible causes of gas generation, but many are caused by water constituent molecules existing at the bonding interface. In the case where vacuum sealing is performed, the heat treatment atmosphere may be vacuum before sealing.

The same operation and effect can be obtained by using a germanium substrate instead of the silicon substrate used in the seventh to eighth embodiments. When a germanium substrate is used, the bonding layer formed by alloying becomes an alloy of gold and germanium. (Embodiment 9) A ninth embodiment of the piezoelectric element of the present invention will be described with reference to FIGS.

FIG. 16 (a) is an exploded view of the piezoelectric element, which shows, in order from the top, a lid of the piezoelectric element, a piezoelectric vibrator, and a holder for the piezoelectric element. FIG. 16B is a cross-sectional view of the piezoelectric element in the lateral direction. Reference numeral 311 denotes a lid glass substrate, and 312
Is a holding glass substrate. The size is 3mm long and 6mm wide.
5 mm thick and 500 μm thick. Glass substrate for lid 31
1, 1 μm depth on the holding glass substrate 312
Of the lead tin electrode 13
Is provided. The piezoelectric vibrating part of the piezoelectric element is composed of an AT-cut quartz substrate 1 having a size of 3 mm in length, 6 mm in width, and 100 μm in thickness.
5, electrodes made of gold 11 are provided, and slits 321 are provided at both ends of the electrodes so as not to hinder piezoelectric vibration. Reference numeral 19 denotes an alloy made of gold and tin.

The feature of the piezoelectric element of this embodiment is that the gold electrode 11 provided on the AT-cut quartz substrate 1 and the tin electrode 13 provided on the lid glass substrate 311 and the holding glass substrate 312 are made of an alloy. 19 and AT
The cut quartz substrate 1 and the glass substrate 3 are held by direct joining, and the quartz oscillator portion is hermetically sealed by two kinds of joining. In the configuration of the present embodiment, the alloy 19, which is a joining portion by alloying, is eutectic of gold and tin or a solid solution containing tin as a main component,
Alternatively, it is based on a hybrid alloy of a eutectic and a solid solution, and is the same as in the fifth embodiment.

Although the piezoelectric element of this embodiment has the same function and effect as the fifth embodiment, the effect that there is no non-joining surface is very useful when airtight sealing is performed.

In the present embodiment, a gold-tin alloy is used as a bonding layer by alloying, but the same operation and effect can be obtained by using a gold-germanium alloy or a gold-silicon alloy. (Embodiment 10) A tenth method for manufacturing a piezoelectric element according to the present invention will be described. Since the material and the shape of the substrate are the same as those in the ninth embodiment, the steps (A) to (E) of the present embodiment will be described with reference to FIGS.

Step (A): The AT-cut quartz substrate 1 is mirror-polished to a predetermined thickness, for example, 50 μm. The lid glass substrate 311 and the holding glass substrate 312 are each mirror-polished.

Step (B): After patterning a mask on the bonding surface side of the holding glass substrate 312 by photolithography, the void 28 is formed with a hydrofluoric acid-based liquid to a depth of 50 μm.
m. Further, a groove 35 is provided on the holding glass substrate 312 by the same photolithography and etching. The chromium and tin electrodes 1 are formed in the grooves 35 in the step (C).
1 and 13 are embedded. Groove size is 600μ in vertical direction
m, 1.5 mm in the horizontal direction, and 1.2 μm in depth. The same process is performed on the lid glass substrate 311 to form the gap 2
8. A groove 35 is provided. However, the groove 35 is provided on the left side of the lid glass substrate 311 opposite to the holding glass substrate 312. The electrodes 11 and 15 provided on the quartz substrate 1
This is for the purpose of overlapping with the extraction electrode portion of FIG.

Step (C): A chromium electrode 15 and a gold electrode 11 are vacuum-deposited on the upper and lower surfaces of the AT-cut quartz substrate 1. The chromium electrode 15 is 100 angstroms, and the gold electrode 11 is 2
000 angstroms. In the groove 35 of the holding glass substrate 312, the chrome electrode 15, the tin electrode 13,
The gold electrode 11 is formed by vacuum evaporation. Chrome electrode is 2
The thickness of the tin electrode was 9500 Å, and that of the gold electrode was 300 Å. The gold electrode 11 on the tin electrode 13 functions as a protective film, and prevents the tin electrode from being dissolved in the next step, and also prevents the tin electrode 13 from being oxidized. Gold electrode 13 on holding glass substrate 312
The thickness of the gold electrode may be enough to fill the groove 35, and the thickness of the gold electrode is controlled according to the thickness of the tin electrode 13. A similar process is performed on the lid glass substrate 311.

Step (D): The AT-cut quartz substrate 1 and the glass substrate 3 are washed with a neutral detergent or an alkali washing solution, and washed with a mixed solution of ammonia, hydrogen peroxide and water.
Rinse thoroughly with pure water and superimpose the two substrates. Here, the same effect can be obtained by performing ashing with oxygen plasma or ozone cleaning instead of cleaning with a mixed solution of ammonia, hydrogen peroxide and water. Further, heat treatment is performed at 300 ° C. for 2 hours in a hydrogen atmosphere. During the heat treatment,
The tin electrode 13 and the gold electrode 11 formed on the lid crow substrate 311 and the holding glass substrate 312 are alloyed. When the heat treatment is further continued, the gold electrode 11 formed on the AT-cut quartz substrate 1 is also alloyed, and the lid glass substrate 31 is formed.
1. The holding glass substrate 312 and the AT-cut quartz substrate 1 are joined by alloying at the electrode portions. or,
Here, portions other than the tin electrode and the gold electrode on the groove 35 are joined by direct joining. At the time of the heat treatment, the bonding part by alloying, that is, the part of the groove 35 is pressed, so that gold,
The eutectic joining of tin proceeds more smoothly.

Step (E): As shown in FIG.
An external electrode 16 is formed on the end face of the piezoelectric element by sputtering.

The feature of the present embodiment is that, in the step (D), direct joining and joining by alloying are performed to achieve hermetic sealing. Regarding the form of bonding, gold,
Embodiment 6 is the same as Embodiment 6 in that a tin alloy is used.

The manufacturing method of this embodiment has the same function and effect as those of the second embodiment, but when airtight sealing is performed, the effect of filling the groove 33 shown in FIG. 7 becomes very useful.
As described above, this effect becomes remarkable when gold or tin is used as a joining material by alloying. Further, in the material configuration of this embodiment, the direct bonding at the atomic level
Starting from about 0 ° C, 232 ° C, the melting point of tin
To a degree, the alloy joints are not completely sealed,
The gas existing in the gap is removed. There are various possible causes of gas generation, but many are caused by water constituent molecules existing at the bonding interface. In the case where vacuum sealing is performed, the heat treatment atmosphere may be vacuum before sealing.

In this embodiment, the tin electrode is formed directly on the holding glass substrate 312 and the lid glass substrate 311. However, in order to enhance the adhesion of the electrodes, a chromium electrode is used as a base electrode. It may be inserted between the glass substrates 311 and 312 and the tin electrode 13.

In this embodiment, the tin electrode is formed on the holding glass substrate 312 and the lid glass substrate 311. However, the same effect can be obtained by providing silicon or germanium instead of the tin electrode. can get. However, in this case, in order to prevent the resistance of the extraction electrode from increasing,
A low-resistance metal may be provided below silicon and germanium. For example, a lead electrode laminated in the order of chromium, gold, nickel, and silicon (or germanium) can be given. (Eleventh Embodiment) Next, an eleventh embodiment of the piezoelectric element of the present invention will be described with reference to FIGS.

In the present embodiment, the size and thickness of the AT-cut quartz substrate 1 and the silicon substrate 2, the electrodes formed on the substrate, the grooves formed on the substrate, the bonding mode, and the like are substantially the same as those of the fourth embodiment. It is. The difference from the fourth embodiment is that a low resistance layer 24 is formed from the integrated circuit portion 21 on the silicon substrate 2 to the end of the silicon substrate 2. This serves as a lead for establishing conduction between the integrated circuit 21 and external elements. The element is hermetically sealed by directly joining the lid made of the glass substrate 3 and the silicon substrate 2 and joining them by alloying.

With the structure of the piezoelectric element of the present embodiment, conduction between the piezoelectric element and the circuit and between the circuit and the external element can be easily achieved, and hermetic sealing can be performed. In addition, the size of the element can be reduced because a normal technique such as wire bonding is not used. (Embodiment 12) Next, a twelfth embodiment of the present invention will be described with reference to FIGS.

FIG. 18A is a top view of the top view of the device when only the holding glass substrate 9 and the device are viewed.
The lid glass substrate 10 is omitted. (B) is sectional drawing in I-II of (a). However, the cover glass substrate 10 is included.

In the same figure, 9 is a holding glass substrate for holding the piezoelectric element, and 10 is a lid glass substrate. Reference numeral 4 denotes a piezoelectric substrate, for example, a 128 ° y-cut lithium niobate substrate. A surface acoustic wave element 22 is formed on the 128 ° y-cut lithium niobate substrate 4, and chromium 15 and gold 11 electrodes are provided as extraction electrodes. The holding glass substrate 9 is provided with a groove, and a chrome electrode 15 for extraction and a tin electrode 13 are provided on the groove. Similarly, a groove is provided in the glass substrate 10 for the lid, and a lead electrode of chromium 15 and gold 11 is provided on the groove. The holding glass substrate 9 and the 128 ° y-cut lithium niobate substrate 4, and the lid glass substrate 10 and the holding glass substrate 9 are each directly bonded and held and hermetically sealed by a tin-gold alloy 19. . The form of bonding is the same as in the sixth embodiment.

The present embodiment has the same effect as the tenth embodiment, except that a lithium niobate substrate is used as a piezoelectric substrate, and a surface acoustic wave element is formed on the substrate. Lithium niobate substrates are characterized by having a larger electromechanical coupling coefficient than quartz, and are widely used for surface acoustic wave devices, vibrators, piezoelectric sensors, and the like. (Embodiment 13) A description will be given using a thirteenth embodiment of the present invention. Since the structure is almost the same as that of the twelfth embodiment, description will be made with reference to FIGS. The difference from the twelfth embodiment is that the 128 ° y-cut lithium niobate 4 and the holding glass substrate 9 are directly bonded and bonded by a gold-germanium alloy, and the holding glass substrate 9 and the lid glass substrate 10 Is that it is directly bonded and bonded and hermetically sealed with a gold-germanium alloy.

This embodiment has the same functions and effects as the twelfth embodiment, but also has the following functions and effects. Gold-germanium alloy has a high eutectic temperature of 356 ° C,
Excellent heat resistance compared to gold and tin alloys. (Embodiment 14) FIG. 19 (a) shows an embodiment of the present invention.
This will be described with reference to (d).

FIG. 19A is a top view when only the holding glass substrate 61 is viewed in the entire device, and FIG.
FIG. 1 is a top view when only the portions of the quartz substrates 5 and 6 are viewed, and FIG.
9 (c) and 9 (d) show I- in FIGS.
It is sectional drawing of the whole element of II, III-IV.

In the figure, reference numeral 5 denotes a quartz substrate, for example, a GT cut quartz substrate. 6 is a quartz substrate,
For example, a GT cut quartz substrate. 61 is a holding glass substrate, and 62 is a lid glass substrate. The size of the quartz substrate 5 is 1.5 × 1.3 mm and the thickness is 55 μm.
It is. Glass substrate 3 is 2 × 2 mm and 150 μm thick
It is. The quartz substrate 5 acting as a GT-cut quartz resonator has a long side and a short side vibrating manner, and the center of the plate is a node of vibration. In other words, holding at the center of the plate enables holding without inhibiting vibration. Here, the long side and short side vibration modes refer to a vibration mode in which long side vibration and short side vibration are combined.
For example, a GT-cut crystal unit is one example.

The structure of the piezoelectric element according to the present embodiment will be described. The crystal substrate 5 is processed so that the central portion has a convex shape, and the size of the central convex portion 39 is 100 μm in diameter.
Circle. On the upper and lower surfaces of the quartz substrate 5, a titanium electrode 12 and a gold electrode 11 are formed with a film thickness of 100 Å and 1500 Å, respectively. Further, the lid glass substrate 62 has a 1.2 μm gap portion 36 provided so as not to come into contact with the quartz substrate 5, and a lead electrode portion including the chromium electrode 15 and the tin electrode 13. The holding glass substrate 61 has a symmetrical structure with respect to the lid glass substrate 62. The crystal substrate 5 is a holding glass substrate 6
1, and gold in the lid glass substrate 62 and the central convex portion 39,
At the same time as being held by eutectic bonding of tin, conduction between the lid glass substrate 62 and the extraction electrode on the holding glass substrate 61 is established. Hermetic sealing is performed by eutectic bonding at the portion of the extraction electrode 18 and by direct bonding at other portions.

With the structure described above, the piezoelectric substrate in a long-side or short-side vibration mode, which is difficult to hold, can be stably held, and electrical conduction with the outside and hermetic sealing can be performed at the same time. In addition, since no wire bonding or conductive adhesive is used, the size and height of the device can be easily reduced.

In this embodiment, the extraction electrode 18
However, the present invention is not limited to this. For example, in the holding glass substrate 61 and the lid glass substrate 62, a through hole is provided at a position corresponding to the convex portion 39, and an electrode is taken out from the through hole. Is also good. In other embodiments described below, a similar through hole may be provided. (Embodiment 15) An embodiment showing a manufacturing method of the present invention will be described with reference to FIGS.

FIGS. 20A to 20F correspond to steps (A) to (F) of this embodiment. Specifically, for example,
FIG. 20A is a top view of each of the holding glass substrate 61, the GT cut quartz substrate 7, and the lid glass substrate 62 in the step (A). FIG. 20D shows a bonding substrate 617 of the holding glass substrate 61 and the GT cut quartz crystal substrates 5, 6, and 7 and a lid glass substrate 6 in the step (D).
2 is a top view of each of FIG. FIG. 20F is a top view of the piezoelectric element 618 of the holding glass substrate 61, the GT cut quartz substrates 5, 6, and 7, and the lid glass substrate 62.

Hereinafter, steps (A) to (F) of this embodiment will be described in order.

Step (A): holding glass substrate 61, GT
At least the surface to which the cut quartz substrate 7 and the lid glass substrate 62 are directly bonded is mirror-polished. As for the size, the lid glass substrate 62 and the holding glass substrate 61 are 2 × 2 mm and 150 μm in thickness, and the quartz substrate 1 is 2 × 2 mm and 50 μm in thickness (see FIG. 20A).

Step (B): The concave portion 3 is formed by etching the holding glass substrate 61 and the lid glass substrate 62.
6 is provided. The depth of the recess 36 was 1.2 μm. GT
The cut quartz substrate 7 is etched by 0.5 μm to provide a recess 37. Each substrate is washed (see FIG. 20B).

Step (C): A chromium electrode 15 and a tin electrode 13 were formed on a holding glass substrate 61 and a lid glass substrate 62.
Is provided. The total thickness of the electrodes is 1.1
μm. 1.3 × 1.5 on GT cut quartz substrate 7
An electrode having a size of mm and a total thickness of 0.1 μm including the titanium electrode 12 and the gold electrode 11 is provided. At this time, a similar electrode is also provided in the extraction electrode portion at the same time (FIG. 20).
(C)).

Step (D): After cleaning the holding glass substrate 61 and the GT cut quartz substrate 7 in the step (C), the holding glass substrate 61 and the GT cut quartz substrate 7 in the step (C) are washed.
Heat treatment is performed by superposing the upper surfaces of
17 is formed.

Here, the term “overlapping the top surfaces” means that the surfaces shown on the paper surface of FIG. 20C are overlaid so as to face each other. That is, in the drawing, the lower left corner G1 of the holding glass substrate 61 and the lower right corner G2 of the GT cut quartz substrate 7 are superimposed so as to face each other. In FIGS. 20D and 20E, G12 is attached to a position corresponding to the position of the lower left corner G1 and the lower right corner G2 superimposed as described above.

The heat treatment is usually performed in a temperature range from 217 ° C., which is the eutectic temperature of gold and tin, to 573 ° C., which is the α-β transition temperature of quartz. However, in consideration of damage to the substrate due to stress, stability of metal bonding, and the like. Preferably, it is performed in a temperature range of about 217 to 350 ° C. In this embodiment, heat treatment is performed at 260 ° C. for 3 hours. Next, a titanium electrode 12 and a gold electrode 11 are provided with a total thickness of 1 μm. This is a mask 619 for etching, which is 1 mm from a region of 1.3 × 1.5 mm.
Provided for etching a region separated by 00 μm, that is, a region of 1.31 × 1.51 mm (FIG. 20D)
reference). That is, portions other than the white band-shaped square frame on the bonding substrate 617 shown in FIG. 20D correspond to the mask 619.

Step (E): The GT cut quartz substrate 7 is etched to separate the GT cut quartz substrate into the vibrator portion 5 and the spacer portion 6. The titanium electrode 12 and the gold electrode 11 on the GT cut quartz substrates 6 and 7 are removed, and the titanium electrode 12 and the gold electrode are further placed on the vibrator portion 5 of the GT cut quartz substrate and the lead electrode portion on the GT cut quartz substrate 6. An electrode having a total thickness of 0.1 μm made of the electrode 11 is provided (FIG. 20E).
reference).

Step (F): After cleaning the bonding substrate 617 and the lid glass substrate 62 formed in the step (E), they are superposed and heat-treated to form a piezoelectric element 618.
The heat treatment conditions are the same as in (D) (see FIG. 20 (F)). That is, in FIG. 20E, the lower right corner G12 of the bonding substrate 617 and the lower left corner G22 of the lid glass substrate 62 are overlapped so as to face each other.

By using the manufacturing method of the present embodiment, the long and short side vibrators holding the center of the substrate can be reduced in size and size.
Can be created low profile. (Embodiment 16) An embodiment of the present invention will be described with reference to FIG. FIGS. 21A to 21D are schematic views, and FIG.
(A) to (d), except that the nickel electrode 14 has a thickness of 500 angstroms and the gold-germanium alloy electrode 20 has a thickness of 1000 on the convex portion 39 at the center of the quartz substrate 5.
Angstrom is provided. The lead electrode of the lid glass substrate 3 and the holding glass substrate 3 is a titanium electrode 12 having a thickness of 100 Å and a thickness of 1 μm.
Gold electrode 11, a nickel electrode 14 having a thickness of 500 angstroms, and a gold-germanium alloy electrode 20 having a thickness of 1000 angstroms. Convex part 39
The layer of the gold-germanium alloy 20 on the quartz substrate 6 is fixed by bonding by alloying.

In this embodiment, the same operation and effect as those of the fourteenth embodiment are obtained. However, since the gold-germanium alloy electrode 14 is used as an adhesive layer for bonding by alloying, the present embodiment is stable and effective. A piezoelectric element with less aging can be realized. (Embodiment 17) An embodiment showing a manufacturing method of the present invention will be described with reference to FIGS.

FIGS. 22A to 22F correspond to steps (A) to (F) of this embodiment.

Hereinafter, steps (A) to (F) of the present embodiment will be described in order.

Step (A): holding glass substrate 61, GT
At least the surface to which the cut quartz substrate 7 and the lid glass substrate 62 are directly bonded is mirror-polished. As for the size, the lid glass substrate 62 and the holding glass substrate 61 are 2 × 2 mm and have a thickness of 150 μm, and the quartz substrate 1 is 2 × 2 mm and have a thickness of 50 μm (see FIG. 22A).

Step (B): The recess 3 is formed by etching the holding glass substrate 61 and the lid glass substrate 62.
6 is provided. The depth of the recess 36 was 1.25 μm. G
The T-cut quartz substrate 7 is etched by 0.55 μm
7 is provided. Each substrate is washed (see FIG. 22B).

Step (C): A titanium electrode 12 having a thickness of 200 Å, a gold electrode 11 having a thickness of 9300 Å, and a nickel electrode 1 having a thickness of 500 Å on a holding glass substrate 61 and a lid glass substrate 62.
4. A lead electrode made of a gold-germanium alloy electrode 20 having a thickness of 1000 angstroms is provided by vacuum evaporation. A titanium electrode 12 having a size of 1.3 × 1.5 mm and a thickness of 200 Å on a GT cut quartz substrate;
A gold electrode 11 having a thickness of 800 Å is provided. Further, a nickel electrode 14 having a thickness of 500 angstroms and a gold-germanium electrode 20 having a thickness of 1000 angstroms are provided on the projection 39 at the center of the GT-cut quartz substrate 7 and on the extraction electrode portion. However, the composition of the gold-germanium alloy 20 is 89:11 by weight ratio of gold: germanium.
To 87:13.

Step (D): After cleaning the holding glass substrate 61 and the GT cut quartz substrate 7 in the step (C), the holding glass substrate 61 and the GT cut quartz substrate 7 in the step (C) are washed.
Heat treatment is performed by superposing the upper surfaces of
17 is formed.

Here, the term “overlapping the top surfaces” means that the surfaces appearing on the surface of the paper surface of FIG. 22 (C) face each other. That is, in the drawing, the lower left corner G1 of the holding glass substrate 61 and the lower right corner G2 of the GT cut quartz substrate 7 are superimposed so as to face each other. In FIGS. 22 (D) and (E), G12 is attached to a position corresponding to the position of the lower left corner G1 and the lower right corner G2 which are superimposed as described above.

The heat treatment is usually performed at a temperature between 356 ° C., which is the eutectic temperature of gold and germanium, and 573 ° C., which is the α-β transition temperature of quartz.
The temperature range is preferably 356 to 450 in consideration of breakage of the substrate due to stress, stability of metal bonding, and the like.
It is preferable to carry out in a temperature range of about ° C. In the present embodiment, 4
Heat treatment was performed at 00 ° C. for 3 hours. Next, the titanium electrode 1
2. The gold electrode 11 is provided with a total thickness of 1 μm. This is an etching mask 619, a region 100 μm away from a 1.3 × 1.5 mm region, that is, 1.31 × 1.
It is provided for etching up to a region of 51 mm (see FIG. 22D). That is, portions other than the white band-shaped square frame on the bonding substrate 617 shown in FIG. 22D correspond to the mask 619.

Step (E): The GT cut quartz substrate 7 is etched to separate the GT cut quartz substrate into the vibrator portion 5 and the spacer portion 6. The titanium electrode 12 and the gold electrode 11 on the GT cut quartz substrates 6 and 7 are removed, and further, a 200 angstrom thick titanium is applied to the vibrator portion 5 of the GT cut quartz substrate and the lead electrode portion on the GT cut quartz substrate 6. An electrode 12 and a gold electrode 11 having a thickness of 800 Å are provided (see FIG. 22E).

Step (F): After cleaning the bonding substrate 617 and the lid glass substrate 62 formed in the step (E), they are superposed and heat-treated to form a piezoelectric element 618.
The heat treatment conditions are the same as in (D) (see FIG. 22 (F)). That is, in FIG. 22E, the lower right corner G12 of the bonding substrate 617 and the lower left corner G22 of the lid glass substrate 62 are overlapped so as to face each other.

By using the manufacturing method of the present embodiment, the same functions and effects as those of the fifteenth embodiment are obtained, but the following functions and effects are further obtained. Since the composition of the gold-germanium alloy is set at a weight ratio of 89:11 to 87:13, at a heat treatment temperature of 400 ° C., it is almost in a liquid layer state, and the joining by alloying proceeds smoothly. As a result, the production yield of the device is increased.

In the embodiments 16 and 17, a gold-germanium alloy is used as the alloy. However, similar effects can be obtained by using an alloy such as a gold-tin alloy or a gold-silicon alloy.

In the fourteenth to seventeenth embodiments, the piezoelectric resonator having the long-side and short-side vibration modes is used.
Similar effects can be obtained. In short, what is necessary is just to join the part which becomes a node of vibration by alloying.

Further, Embodiments 1 to 17 described above are used.
In the above, a quartz substrate was mainly used as the piezoelectric substrate, but the same applies when other mirrors that can be mirror-polished and can be directly bonded, such as lithium niobate, lithium tantalate, and lead lanthanum lanthanum titanate, are used. The effect of is obtained. Similar effects can be obtained even if a quartz substrate other than the AT cut and GT cut is used. By using these piezoelectric bodies, application to various piezoelectric elements becomes possible.

Further, the piezoelectric substrate of the present invention is not limited to the piezoelectric vibrator of the above-described embodiment, but may be, for example, a piezoelectric filter or a piezoelectric sensor. Also in this case, a piezoelectric element having the same effect as described above can be configured.

In the above-described embodiments 14-17,
The case has been described in which electrodes for excitation (titanium electrode 12 and gold electrode 11) are formed on the entire surface of both surfaces of the quartz substrate as the piezoelectric substrate of the present invention, and the entire quartz substrate functions as a piezoelectric vibrator. However, the present invention is not limited to this. For example, an excitation electrode may be formed on a part of each surface, and a part of the piezoelectric substrate may be naturally vibrated.

As described above, the first configuration of the piezoelectric element according to the above-described embodiment is composed of the holding substrate and the piezoelectric substrate on which the electrodes are formed. Characterized by being held by bonding.

In the first configuration, the holding substrate is preferably a silicon or germanium substrate, and the alloy is preferably an alloy mainly composed of gold-silicon or gold-germanium.

Further, the second configuration of the piezoelectric element according to the above embodiment comprises a holding substrate on which electrodes are formed, and a piezoelectric substrate on which electrodes are formed, and the holding substrate and the piezoelectric substrate are directly bonded. And being held by bonding by alloying.

In the second structure, the alloy is preferably made of at least two metals selected from gold, silicon, germanium, and tin.

A third configuration of the piezoelectric element according to the above embodiment comprises a holding substrate, a lid substrate, and a piezoelectric substrate on which electrodes are formed, and the holding substrate and the piezoelectric substrate are directly bonded. And it is characterized by being held and hermetically sealed by joining by alloying.

In the third configuration, the holding substrate and the lid substrate are preferably silicon or germanium substrates, and the alloy is preferably an alloy mainly composed of gold-silicon or gold-germanium. .

A fourth configuration of the piezoelectric element according to the above embodiment comprises a holding substrate, a lid substrate, and a piezoelectric substrate, and is selected from the holding substrate, the lid substrate, and the piezoelectric substrate. Electrodes are formed on at least two substrates to be formed, and the two substrates are held and hermetically sealed by direct bonding and bonding by alloying.

Further, in the fourth configuration, the alloy is at least two selected from gold, silicon, germanium, and tin.
Preferably, it is made of one or more metals.

In the first to fourth configurations,
Preferably, the piezoelectric substrate is selected from quartz, lithium niobate, lithium tantalate, and lead lanthanum titanate zirconate langasite.

A fifth configuration of the piezoelectric element according to the above embodiment comprises a holding substrate, a lid substrate, and a piezoelectric substrate on which electrodes are formed, and a piezoelectric vibrator is formed on the piezoelectric substrate. A portion of a node of vibration of the piezoelectric vibrator is held by bonding to the holding substrate or at least one of the lid substrate by alloying, and the piezoelectric vibrator is directly connected to the holding substrate. , And is hermetically sealed in a package composed of at least two of the piezoelectric substrate and the lid substrate.

In the fifth configuration, it is preferable that the vibration mode of the piezoelectric substrate is a long side and a short side mode. As a piezoelectric substrate in such a vibrating state, for example, a GT cut quartz crystal is used. In the case of GT-cut quartz, the node of vibration is at the center of the GT-cut quartz substrate, but if the holding part is circular, its diameter should be 25% or less with respect to the short side direction of the GT-cut quartz substrate. Is preferred. More preferably, it is preferably 10% or less with respect to the short side direction of the GT cut quartz substrate. When the holding portion is rectangular, it is preferable that the short side direction of the rectangle is 20% or less of the short side direction of the GT cut quartz substrate. More preferably, the short side direction of the rectangle is 8% or less of the short side direction of the GT cut quartz substrate. An increase in the size of the holding portion causes a decrease in the frequency sharpness Q value of the vibrator and a decrease in the vibration level.

In the first method of manufacturing a piezoelectric element according to the above embodiment, at least one main surface of the holding substrate is provided.
A step of mirror-polishing at least one main surface of the piezoelectric substrate, a step of providing an electrode on the main surface side of the piezoelectric substrate, and a step in which the electrode and the holding substrate contact the main surface of the holding substrate and the piezoelectric substrate. And a step of directly joining the holding substrate and the piezoelectric substrate, and alloying atoms and atoms constituting a surface of the holding substrate with the electrodes. Examples of atoms constituting the substrate surface include silicon and germanium,
Examples of the electrode material provided on the piezoelectric substrate include gold. The direct bonding and alloying processes usually involve a heat treatment, but when no pressure is applied, the heat treatment temperature is a combination of silicon and gold, which is a eutectic temperature of 370 ° C.
It is preferable that it is above. The upper limit of the heat treatment temperature is determined by the breakage of the substrate or the transition temperature of the piezoelectric body. The heat treatment temperature determined by the breakage of the substrate varies depending on the thickness and size of the substrate. The upper limit of the heat treatment temperature determined by the transition temperature of the substrate varies depending on the substrate material, and is preferably at least 573 ° C. or less when the piezoelectric substrate is made of quartz. Further, by applying pressure during the heat treatment, the heat treatment temperature can be lowered, for example, 5
When a pressure higher than the atmospheric pressure is applied, the heat treatment temperature is preferably from 250 ° C. to 573 ° C.

In the first method of manufacturing a piezoelectric element according to the above-described embodiment, at least one principal surface of the lid substrate is mirror-polished, and the lid substrate and the holding substrate are directly bonded to each other. It is preferable to include a step of hermetically sealing Further, the second manufacturing method of the piezoelectric element according to the above-described embodiment includes a step of mirror-polishing at least one main surface of the holding substrate and at least one main surface of the piezoelectric substrate; A step of providing a first electrode; a step of providing a second electrode on the main surface side of the holding substrate; and a step in which the first electrode and the second electrode contact the main surface of the holding substrate and the piezoelectric substrate. And a step of directly bonding the holding substrate and the piezoelectric substrate and alloying the first electrode and the second electrode. As the combination of the first electrode and the second electrode, gold-tin, gold-silicon, gold-germanium, an alloy of gold-gold and silicon, an alloy of gold-gold and germanium, and gold Gold-tin alloy and gold-silicon alloy-gold-silicon alloy and gold-germanium alloy-gold-germanium alloy and gold-tin alloy-gold-tin alloy. Direct joining, and
The alloying step usually involves heat treatment, but when no pressure is applied, the heat treatment temperature is preferably 217 ° C. or higher, which is the lowest eutectic temperature in the case of a gold-tin combination.
The upper limit of the heat treatment temperature varies depending on the damage of the substrate or the transition temperature of the piezoelectric body. The upper limit of the heat treatment temperature determined by the transition temperature of the substrate is preferably at least 573 ° C. or less when the piezoelectric substrate material is quartz. In other combinations, the heat treatment temperature is preferably equal to or higher than the eutectic temperature and equal to or lower than the transition temperature of the piezoelectric substrate.

In the second method of manufacturing a piezoelectric element according to the above-described embodiment, at least one principal surface of the lid substrate is mirror-polished, and the lid substrate and the holding substrate are directly bonded to each other. It is preferable to include a step of hermetically sealing

The third method of manufacturing a piezoelectric element according to the above embodiment includes a step of mirror-polishing at least one main surface of the holding substrate and the lid substrate and at least one main surface of the piezoelectric substrate; Providing an electrode on at least one principal surface of the piezoelectric substrate; and attaching the holding substrate, or the lid substrate, or both the holding substrate and the lid substrate, and at least one principal surface of the piezoelectric substrate to the piezoelectric substrate. Superposing the electrode and the holding substrate, or the lid substrate, or both of the holding substrate and the lid substrate so as to be in contact with each other; and holding the electrode with the holding substrate, the lid substrate, or the holding substrate and the lid. Directly bonding both the lid substrate and the piezoelectric substrate, and alloying the electrodes and the atoms constituting the surface of the holding substrate or the lid substrate.

Further, in the fourth method of manufacturing a piezoelectric element according to the above-described embodiment, a step of mirror-polishing at least one main surface of the holding substrate and the lid substrate and at least one main surface of the piezoelectric substrate is provided. Providing a first electrode on at least one principal surface of the piezoelectric substrate; and providing a first electrode on at least one principal surface of the holding substrate, the lid substrate, or both of the holding substrate and the lid substrate. Providing the first electrode and the second electrode on the holding substrate, or the lid substrate, or both the holding substrate and the lid substrate, and the main surface of the piezoelectric substrate. And a step of performing heat treatment to directly join the holding substrate or the lid substrate to the piezoelectric substrate, and alloying the first electrode and the second electrode. Characterized by

As described above, according to the piezoelectric element of the present invention, the element can be stably held, the electrodes can be easily pulled out from the element, and the element can be easily hermetically sealed. Thus, a low-profile piezoelectric element can be realized.

According to the method of manufacturing a piezoelectric element according to the present invention, it is possible to stably hold the element and easily perform electrode extraction and hermetic sealing while being a small and low-profile element with little aging. Is possible, and the production yield is improved.

[0163]

As is apparent from the above description, the present invention has the advantage that the aging can be further reduced as compared with the prior art.

[Brief description of the drawings]

FIGS. 1A to 1D are explanatory views of a piezoelectric element according to a first embodiment of the present invention.

FIGS. 2A to 2F are explanatory views of a step A of a method for manufacturing a piezoelectric element according to a second embodiment of the present invention.

FIGS. 3A to 3F are explanatory views of a step B of the method for manufacturing a piezoelectric element according to the second embodiment of the present invention.

FIGS. 4A to 4F are explanatory diagrams of a step C of the method for manufacturing a piezoelectric element according to the second embodiment of the present invention.

FIGS. 5A to 5D are explanatory views of a step D of the method for manufacturing a piezoelectric element according to the second embodiment of the present invention.

FIGS. 6A to 6D are explanatory views of a step E of the method for manufacturing a piezoelectric element according to the second embodiment of the present invention.

FIGS. 7A to 7C are explanatory views of joining by alloying according to the second embodiment of the present invention.

FIGS. 8A to 8D are explanatory views of a piezoelectric element according to a fourth embodiment of the present invention.

FIGS. 9A to 9D are explanatory views of a piezoelectric element according to a fifth embodiment of the present invention.

FIGS. 10A to 10F are explanatory diagrams of a step A of a method for manufacturing a piezoelectric element according to a sixth embodiment of the present invention.

11A to 11F are explanatory views of a step B of the method for manufacturing a piezoelectric element according to the sixth embodiment of the present invention.

FIGS. 12A to 12F are explanatory views of a step C of the method for manufacturing a piezoelectric element according to the sixth embodiment of the present invention.

13A to 13D are explanatory views of a step D of the method for manufacturing a piezoelectric element according to the sixth embodiment of the present invention.

14A to 14D are explanatory views of a step E of the method for manufacturing a piezoelectric element according to the sixth embodiment of the present invention.

15A and 15B are explanatory diagrams of a piezoelectric element according to a seventh embodiment of the present invention.

16A and 16B are explanatory diagrams of a piezoelectric element according to a ninth embodiment of the present invention.

17A to 17D are explanatory diagrams of a piezoelectric element according to an eleventh embodiment of the present invention.

FIGS. 18A and 18B are explanatory diagrams of a piezoelectric element according to a twelfth embodiment of the present invention.

19A to 19D are explanatory diagrams of a piezoelectric element according to a fourteenth embodiment of the present invention.

FIGS. 20A to 20F are explanatory views of a method for manufacturing a piezoelectric element according to a fifteenth embodiment of the present invention.

FIGS. 21A to 21D are explanatory diagrams of a piezoelectric element according to a sixteenth embodiment of the present invention.

22A to 22F are explanatory diagrams of a method for manufacturing a piezoelectric element according to a seventeenth embodiment of the present invention.

FIGS. 23A and 23B are explanatory diagrams of a conventional piezoelectric element.

24A to 24D are explanatory diagrams of a conventional piezoelectric element.

25A and 25B are explanatory views of a conventional piezoelectric element.

[Explanation of symbols]

 1. 1. AT-cut quartz substrate 2. Silicon substrate 4. Glass substrate 4. 128 ° y-cut lithium niobate substrate 5. GT cut quartz substrate (vibrating part) 6. GT cut quartz substrate (spacer part) GT cut quartz substrate 11. Gold electrode 12. Titanium electrode 13. Tin electrode 14. Nickel electrode 15. Chrome electrode 16. Alloy made of gold and silicon 17. External electrode 18. Lead electrode 19. Alloy made of gold and tin 20. Alloy made of gold and germanium 21. Integrated circuit 22. Surface acoustic wave device 23. Metal film 24. Low resistance layer 29. Solid solution 30. Gap 31. Joint part by direct joining 33. Groove provided on crystal substrate 34. Recess provided on silicon substrate 35. Groove provided on glass substrate 36. Depressed portion provided on glass substrate 37. Depressed portion provided on quartz substrate 39. recess provided in silicon substrate Projection provided at the center of GT cut quartz substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H03H 9/10 H03H 9/10

Claims (24)

[Claims] 1. A piezoelectric substrate having electrodes formed thereon, and a holding substrate for holding the piezoelectric substrate, wherein the holding substrate and the piezoelectric substrate are joined together by direct joining and joining by alloying. A piezoelectric element, characterized in that: 2. The method according to claim 1, wherein the holding substrate is a silicon substrate or a germanium substrate, and the joining by alloying is a joining mainly using gold-silicon or gold-germanium. Piezoelectric element. 3. The piezoelectric element according to claim 1, wherein the holding substrate is a silicon substrate on which an integrated circuit is formed. 4. The phrase that the direct joining and the joining by alloying are used in combination means that the holding substrate and the electrode are joined by the alloying, and all or one of the joints other than the joining part by the alloying is used. The piezoelectric element according to claim 1, wherein a joining portion of the portions is directly joined. 5. A piezoelectric substrate having a first electrode formed thereon, and a holding substrate holding the piezoelectric substrate having a second electrode formed thereon, wherein the piezoelectric substrate is directly connected to the holding substrate and the piezoelectric substrate. A piezoelectric element comprising a combination of joining and joining by alloying. 6. The combination of the direct joining and the joining by alloying means that the first electrode and the second electrode are joined by the alloying, and the joining part by the alloying is used. The piezoelectric element according to claim 5, wherein all or a part of the joint other than the above is directly joined. 7. A piezoelectric substrate having electrodes formed thereon, a holding substrate for holding the piezoelectric substrate, and a lid substrate for covering the piezoelectric substrate, wherein at least one of the holding substrate and the lid substrate A piezoelectric element, wherein one substrate and the piezoelectric substrate are held by direct bonding and bonding by alloying, and hermetically sealed. 8. The holding substrate and at least one of the lid substrates is a silicon substrate or a germanium substrate, and the bonding by alloying is mainly made of gold-silicon or gold-germanium. The piezoelectric element according to claim 7, wherein the piezoelectric element is a joint. 9. The piezoelectric element according to claim 7, wherein at least one of the holding substrate and the lid substrate is a silicon substrate on which an integrated circuit is formed. 10. The electrode is bonded to at least one of the holding substrate and the lid substrate by the alloying, and all or a part of the bonding part other than the bonding part by the alloying is formed. The piezoelectric element according to claim 7, wherein the piezoelectric element is directly joined. 11. A piezoelectric substrate having electrodes formed thereon, a holding substrate for holding the piezoelectric substrate, and a lid substrate for covering the piezoelectric substrate, wherein at least one of the holding substrate and the lid substrate is provided. A piezoelectric element, wherein one substrate and the piezoelectric substrate are held and hermetically sealed by direct bonding and bonding by alloying. 12. An electrode is formed on at least one of the holding substrate and the lid substrate, and the electrode and the electrode formed on the piezoelectric substrate are joined by the alloying. 12. The piezoelectric element according to claim 11, wherein all or a part of the joint other than the joint formed by alloying is directly joined. 13. A piezoelectric device comprising a holding substrate, a lid substrate, and a piezoelectric resonator having electrodes formed on a piezoelectric substrate, and a node of vibration of the piezoelectric resonator is one of the holding substrate and the lid substrate. Or it is held by joining by alloying with both,
The piezoelectric element is characterized in that the piezoelectric resonator is hermetically sealed in a package constituted by at least the holding substrate and the lid substrate. 14. The piezoelectric element according to claim 13, wherein the package is hermetically sealed by directly joining the holding substrate and the lid substrate. 15. A spacer substrate is provided between the holding substrate and the lid substrate, and air in the package is formed by directly joining the spacer substrate with the holding substrate and the lid substrate. 14. The piezoelectric element according to claim 13, wherein hermetic sealing is performed. 16. The piezoelectric substrate according to claim 1, wherein the material of the piezoelectric substrate is any one of quartz, lithium niobate, lithium tantalate, and lanthanum lanthanum titanate. 14. The piezoelectric element according to 7, 11, or 13. 17. The bonding according to claim 5, wherein the bonding by alloying is bonding of at least two kinds of metals among gold, silicon, germanium, and tin.
The piezoelectric element according to 1, 13, 14, or 15. 18. The piezoelectric element according to claim 13, wherein the vibration mode of the piezoelectric resonator is a long side and a short side vibration mode. 19. At least one main surface of a holding substrate,
A step of mirror-polishing at least one main surface of the piezoelectric substrate; a step of providing an electrode on the main surface side of the piezoelectric substrate; and the electrode and the holding substrate contacting the main surface of the holding substrate and the piezoelectric substrate. A step of directly bonding the holding substrate and the piezoelectric substrate, and alloying a bonding interface between the holding substrate and the electrode and its vicinity. Production method. 20. The method according to claim 19, further comprising: mirror-polishing at least one principal surface of the lid substrate, directly bonding the lid substrate and a holding substrate, and hermetically sealing the piezoelectric substrate. The manufacturing method of the piezoelectric element according to the above. 21. Mirror-polishing at least one main surface of the holding substrate and at least one main surface of the piezoelectric substrate; providing a first electrode on the main surface side of the piezoelectric substrate; Providing a second electrode on the main surface side; overlapping the main surfaces of the holding substrate and the piezoelectric substrate such that the first electrode and the second electrode are in contact with each other; Bonding the piezoelectric substrate directly and alloying the first electrode and the second electrode. A method for manufacturing a piezoelectric element, comprising: 22. The method according to claim 21, further comprising a step of mirror-polishing at least one principal surface of the lid substrate, directly joining the lid substrate and the holding substrate, and hermetically sealing the piezoelectric substrate. Method for manufacturing a piezoelectric element. 23. A step of mirror-polishing at least one principal surface of the holding substrate and the lid substrate and at least one principal surface of the piezoelectric substrate; and a step of providing an electrode on at least one principal surface side of the piezoelectric substrate. Superposing one or both of the holding substrate and the lid substrate and at least one main surface of the piezoelectric substrate such that one or both of the holding substrate and the lid substrate and the electrode are in contact with each other. And directly bonding one or both of the holding substrate and the lid substrate to the piezoelectric substrate, and alloying a bonding interface between the one or both of the holding substrate and the lid substrate and the electrode and the vicinity thereof. And a method of manufacturing a piezoelectric element. 24. A step of mirror-polishing at least one principal surface of the holding substrate and the lid substrate and at least one principal surface of the piezoelectric substrate, and forming a first electrode on at least one principal surface of the piezoelectric substrate. Providing, a step of providing a second electrode on one or both main surfaces of the holding substrate and the lid substrate; and one or both of the holding substrate and the lid substrate and a main surface of the piezoelectric substrate Overlapping the first electrode and the second electrode so that the first electrode and the second electrode are in contact with each other; and performing a heat treatment to directly bond the piezoelectric substrate to the holding substrate or the lid substrate, and the first electrode And a step of alloying the second electrode with the second electrode.