Piezoelectric vibration element, piezoelectric vibrator, and piezoelectric oscillator

Abstract

The present invention provides: a piezoelectric vibration element which is capable of suppressing damage to a wiring electrode due to etching; a piezoelectric vibrator; and a piezoelectric oscillator.　A crystal vibration element 10 is provided with: a crystal piece 11 which has a first main surface 12a and a second main surface 12b; a via electrode 17 which is provided so as to penetrate the crystal piece from the first main surface 12a to the second main surface 12b; a conductive etch stop film 18 which covers the via electrode 17 at the second main surface 12b; and a lead-out electrode 15b which covers at least a part of the outer periphery of the etch stop film 18 at the second main surface 12b.

Description

[Technical field]

[0001] The present invention relates to a piezoelectric vibration element, a piezoelectric vibrator, and a piezoelectric oscillator. [Background technology]

[0002] Vibration elements or vibrators including the same are used for various purposes such as timing devices, sensors, oscillators, etc. in various electronic devices such as mobile communication terminals, communication base stations, home appliances, etc. As electronic devices become more sophisticated, there is a demand for small vibration elements.

[0003] For example, Patent Document 1 discloses a piezoelectric bulk wave device comprising a support substrate, an insulating layer, and a piezoelectric thin plate vibration part, the piezoelectric thin plate vibration part including a piezoelectric thin plate, a first electrode formed on the upper surface of the piezoelectric thin plate, and a second electrode formed on the lower surface of the piezoelectric thin plate. In this piezoelectric bulk wave device, a via hole electrode is provided in the piezoelectric thin plate so as to be electrically connected to a wiring electrode connected to the second electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 031747 Summary of the Invention [Problem to be solved by the invention]

[0005] In the piezoelectric bulk wave device disclosed in Patent Document 1, electrode holes for forming via holes are formed in a piezoelectric thin plate by etching, and then via hole electrodes are formed.

[0006] However, when etching the piezoelectric thin plate, the wiring electrodes formed on the piezoelectric thin plate are easily damaged by the chemicals used for etching, and as a result, there is a risk that the performance of providing electrical continuity to the electrodes formed on the vibration part through the via hole electrodes and the wiring connections (hereinafter referred to as "conductivity") may decrease.

[0007] The present invention has been made in consideration of the above circumstances, and one of its objects is to provide a piezoelectric vibration element, a piezoelectric vibrator, and a piezoelectric oscillator that can suppress damage to wiring electrodes due to etching. [Means for solving the problem]

[0008] A piezoelectric vibration element according to one aspect of the present invention comprises a piezoelectric piece having a first main surface and a second main surface, a via electrode extending from the first main surface to the second main surface, a conductive etch stop film covering the via electrode on the second main surface, and a wiring electrode covering at least a portion of the outer edge of the etch stop film on the second main surface.

[0009] A piezoelectric vibrator according to another aspect of the present invention includes the piezoelectric vibration element described above, and a support substrate that supports the piezoelectric vibration element so that it can vibrate.

[0010] A piezoelectric oscillator according to another aspect of the present invention includes the above-described piezoelectric vibrator and a cover. Effect of the Invention

[0011] According to the present invention, damage to the wiring electrodes caused by etching can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic configuration of a crystal oscillator according to an embodiment. [Diagram 2] FIG. 2 is a plan view that illustrates a schematic configuration of a quartz crystal vibrating element according to an embodiment. [Diagram 3] FIG. 3 is a cross-sectional view that illustrates a schematic configuration of a quartz crystal resonator according to an embodiment. [Figure 4] FIG. 4 is a cross-sectional view that illustrates a schematic configuration of a quartz crystal resonator according to an embodiment. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of a main portion, which shows an example of the configuration of the via electrode and its periphery shown in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a main portion, which shows roughly another example of the configuration of the via electrode and its periphery shown in FIG. [Figure 7] FIG. 7 is a plan view that illustrates a schematic configuration of a quartz crystal vibrating element according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described. In the following description of the drawings, the same or similar components are represented by the same or similar reference numerals. The drawings are illustrative, and the dimensions and shapes of each part are schematic, and the technical scope of the present invention should not be interpreted as being limited to the embodiment.

[0014] In order to clarify the mutual relationships between the drawings and to aid in understanding the positional relationships of the various components, an orthogonal coordinate system consisting of an X-axis, a Y'-axis, and a Z'-axis may be conveniently attached to each drawing. The X-axis, the Y'-axis, and the Z'-axis correspond to each other in each drawing. The X-axis, the Y'-axis, and the Z'-axis each correspond to the crystallographic axes of the quartz blank 11, which will be described later. The X-axis corresponds to the electrical axis (polarity axis) of the quartz, the Y-axis corresponds to the mechanical axis of the quartz, and the Z-axis corresponds to the optical axis of the quartz. The Y'-axis and the Z'-axis are respectively axes obtained by rotating the Y-axis and Z-axis around the X-axis by 35 degrees 15 minutes ± 1 minute 30 seconds in the direction from the Y-axis to the Z-axis.

[0015] In the following description, the direction parallel to the X-axis is referred to as the "X-axis direction", the direction parallel to the Y'-axis is referred to as the "Y'-axis direction", and the direction parallel to the Z'-axis is referred to as the "Z'-axis direction". The directions of the tips of the arrows of the X-axis, Y'-axis, and Z'-axis are referred to as "positive" or "+ (plus)", and the directions opposite to the arrows are referred to as "negative" or "- (minus)". For convenience, the +Y'-axis direction is described as the upward direction, and the -Y'-axis direction is described as the downward direction, but the up-down directions of the crystal resonator element 10, the crystal resonator 1, and the crystal oscillator 100 are not limited to these directions. The plane specified by the X-axis and the Z'-axis is referred to as the Z'X plane, and the same applies to the planes specified by the other axes.

[0016] First, a schematic configuration of a crystal oscillator according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing a schematic configuration of a crystal oscillator 100 according to an embodiment.

[0017] In the following description, a crystal oscillator (XO: Crystal Oscillator) having a crystal resonator (Quartz Crystal Resonator Unit) is taken as an example of the piezoelectric oscillator. A crystal resonator having a crystal vibration element (Quartz Crystal Resonator) is taken as an example of the piezoelectric vibrator. A crystal vibration element having a crystal blank (Quartz Crystal Blank) is taken as an example of the piezoelectric vibration element. A crystal blank is a type of piezoelectric body (piezoelectric piece) that vibrates in response to an applied voltage. Note that the piezoelectric oscillator is not limited to a crystal resonator, and may use other piezoelectric bodies such as ceramics. Similarly, the piezoelectric vibrator is not limited to a crystal resonator, and may use other piezoelectric bodies such as ceramics. Similarly, the piezoelectric vibration element is not limited to a crystal resonator, and may use other piezoelectric bodies such as ceramics.

[0018] 1, the crystal oscillator 100 includes a crystal unit 1, a mounting substrate 130, a lid member 140, and an electronic component 156. The mounting substrate 130 and the lid member 140 of the present embodiment correspond to an example of a "lid body."

[0019] The crystal unit 1 and the electronic component 156 are housed in a space formed between the mounting substrate 130 and the lid member 140. The space formed by the mounting substrate 130 and the lid member 140 is, for example, hermetically sealed. This space may be hermetically sealed in a vacuum state, or may be hermetically sealed in a state filled with a gas such as an inert gas.

[0020] The mounting substrate 130 is a flat circuit board and is configured to include, for example, a glass epoxy plate and a wiring layer patterned on the glass epoxy plate.

[0021] The quartz crystal unit 1 is provided on one surface (the upper surface in FIG. 1) of the mounting substrate 130. More specifically, the quartz crystal unit 1 is electrically connected to the wiring layer of the mounting substrate 130 by a bonding wire 166. The quartz crystal unit 1 and the wiring layer of the mounting substrate 130 are also joined by solder 153. As a result, the quartz crystal unit 1 is sealed in the space formed between the mounting substrate 130 and the lid member 140.

[0022] The lid member 140 includes an opening with a bottom that is open on one side (the lower side in FIG. 1). In other words, the lid member 140 includes a flat top wall portion, a side wall portion that extends from the outer edge of the top wall portion toward the mounting substrate 130, and a flange portion that extends outward from the tip of the side wall portion. The flange portion is disposed in a position close to the mounting substrate 130. of It is bonded to one surface (the upper surface in FIG. 1). As a result, the crystal unit 1 bonded to the mounting substrate 130 is housed inside the lid member 140. The lid member 140 is made of a metal material, and is formed by, for example, drawing a metal plate.

[0023] The electronic component 156 is provided on one surface (the upper surface in FIG. 1) of the mounting board 130. More specifically, the wiring layer of the mounting board 130 and the electronic component 156 are joined by solder 153. In this way, the electronic component 156 is mounted on the mounting board 130.

[0024] The electronic component 156 is electrically connected to the crystal unit 1 through a wiring layer of the mounting substrate 130. The electronic component 156 includes, for example, a capacitor, an IC chip, etc. The electronic component 156 is, for example, a part of an oscillation circuit that causes the crystal unit 1 to oscillate, or a part of a temperature compensation circuit that compensates for the temperature characteristics of the crystal unit 1. When the electronic component 156 includes a temperature compensation circuit, the crystal oscillator 100 is sometimes called a temperature compensated crystal oscillator (TCXO).

[0025] Next, a schematic configuration of a quartz crystal resonator according to an embodiment will be described with reference to Figs. 2 to 4. Fig. 2 is a plan view that shows a schematic configuration of a quartz crystal resonator element 10 according to an embodiment. Fig. 3 is a cross-sectional view that shows a schematic configuration of a quartz crystal resonator 1 according to an embodiment. Fig. 4 is a cross-sectional view that shows a schematic configuration of a quartz crystal resonator 1 according to an embodiment. Fig. 3 shows a cross section parallel to the XY' plane along line III-III shown in Fig. 2. Fig. 4 shows a cross section parallel to the XY' plane along line IV-IV shown in Fig. 2.

[0026] The quartz crystal resonator 1 includes a quartz crystal resonator element 10, an upper cover 20, a bonding portion 30, a support substrate 40, and a bonding layer 50.

[0027] The quartz crystal vibrating element 10 is an element that vibrates quartz crystal by the piezoelectric effect and converts electrical energy into mechanical energy. The quartz crystal vibrating element 10 includes an AT-cut quartz crystal piece 11. The AT-cut quartz crystal piece 11 is cut out with the XZ' plane, which is specified by the X-axis and Z-axis, as the main surface, when the Y-axis and Z-axis are respectively rotated around the X-axis by 35 degrees 15 minutes ± 1 minute 30 seconds in the direction from the Y-axis to the Z-axis, out of the X-axis, Y-axis, and Z-axis that are the crystal axes of synthetic quartz crystal.

[0028] The rotation angles of the Y'-axis and Z'-axis in the AT-cut crystal blank 11 may be in the range of -5 degrees to +15 degrees from 35 degrees 15 minutes. The cut angle of the crystal blank 11 may be a cut other than the AT cut, such as a BT cut, a GT cut, or an SC cut.

[0029] A quartz crystal vibration element using an AT-cut quartz crystal piece has high frequency stability over a wide temperature range. In addition, the AT-cut quartz crystal vibration element has excellent aging characteristics and can be manufactured at low cost. Furthermore, the AT-cut quartz crystal vibration element uses the thickness shear vibration mode as the main vibration.

[0030] The quartz crystal vibrating element 10 includes a pair of excitation electrodes. An alternating electric field is applied between the pair of excitation electrodes. This causes the vibrating portion 11A of the quartz crystal blank 11 to vibrate at a predetermined oscillation frequency in a thickness-shear vibration mode, and a resonance characteristic is obtained in association with this vibration.

[0031] The quartz crystal blank 11 has a first main surface 12a and a second main surface 12b which are opposed to each other and are XZ' planes. The quartz crystal blank 11 has a flat plate shape. Therefore, the first main surface 12a and the second main surface 12b of the quartz crystal blank 11 are each a flat surface. Note that the quartz crystal blank 11 is not limited to being a flat plate shape, and may have, for example, a convex or concave central portion.

[0032] The AT-cut crystal blank 11 has a long side direction in which the long side extends parallel to the X-axis direction, a short side direction in which the short side extends parallel to the Z'-axis direction, and a thickness direction in which the thickness extends parallel to the Y'-axis direction. When the first main surface 12a of the crystal blank 11 is viewed in plan, the crystal blank 11 has a rectangular shape. The length of the crystal blank 11 in the direction parallel to the X-axis direction is, for example, about 180 μm, and the length of the crystal blank 11 in the direction parallel to the Z'-axis direction is, for example, about 180 μm. The thickness of the crystal blank 11 is, for example, within a range of 0.5 μm to 3 μm, for example, about 1 μm. For example, when the crystal blank 11 has a larger thickness, it is attached to the support substrate 40 via a bonding layer 50 described later. Canada After thermocompression bonding, the thickness may be reduced to a predetermined thickness by polishing.

[0033] The planar shape of crystal blank 11 is not limited to a rectangular shape, and may be a polygonal shape, a circular shape, an elliptical shape, or a combination thereof.

[0034] The crystal piece 11 includes a vibrating portion 11A, a groove portion 11B, and a holding portion 11C.

[0035] As described above, the vibration part 11A of the crystal blank 11 vibrates at a predetermined oscillation frequency with the thickness-shear vibration mode as the main vibration. The length of the vibration part 11A in the direction parallel to the X-axis direction is, for example, about 80 μm, and the length of the vibration part 11A in the direction parallel to the Z′-axis direction is, for example, about 80 μm.

[0036] The quartz crystal vibrating element 10 includes a first excitation electrode 14a and a second excitation electrode 14b that constitute a pair of excitation electrodes. The first excitation electrode 14a and the second excitation electrode 14b are provided on the vibration part 11A of the quartz crystal blank 11. More specifically, the first excitation electrode 14a is provided on the first main surface 12a, and the second excitation electrode 14b is provided on the second main surface 12b. The first excitation electrode 14a and the second excitation electrode 14b are provided opposite each other with the quartz crystal blank 11 sandwiched therebetween. The first excitation electrode 14a and the second excitation electrode 14b each have a rectangular shape when the first main surface 12a is viewed in plan, and are arranged so that they overlap substantially entirely in the XZ' plane. The first excitation electrode 14a and the second excitation electrode 14b each have a length of, for example, about 50 μm in a direction parallel to the X-axis direction, and a length of, for example, about 50 μm in a direction parallel to the Z'-axis direction.

[0037] It should be noted that the first excitation electrode 14a and the second excitation electrode 14b are not limited to a rectangular shape, and may be a polygonal shape, a circular shape, an elliptical shape, or a combination thereof.

[0038] Groove portion 11B of crystal blank 11 is a groove formed to surround vibrating portion 11A when first main surface 12a is viewed in plan view. The groove penetrates crystal blank 11 in the thickness direction parallel to the Z'-axis direction. Groove portion 11B is formed such that vibrating portion 11A and holding portion 11C are spaced apart by, for example, about 10 μm.

[0039] Holding portion 11C of crystal blank 11 is the portion other than vibrating portion 11A and groove portion 11B of crystal blank 11. Holding portion 11C is connected to the side of vibrating portion 11A on the negative side of the X-axis, and holds vibrating portion 11A.

[0040] The quartz crystal vibrating element 10 further includes lead electrodes 15a, 15b, connection electrodes 16a, 16b, and a via electrode 17. The lead electrodes 15a, 15b, connection electrodes 16a, 16b, and via electrode 17 are provided on a holding portion 11C of the quartz crystal blank 11.

[0041] The extraction electrode 15a is provided on the first main surface 12a of the crystal blank 11, and electrically connects the first excitation electrode 14a and the connection electrode 16a. On the other hand, the extraction electrode 15b is provided on the second main surface 12b of the crystal blank 11, and electrically connects the second excitation electrode 14b and the connection electrode 16b. The extraction electrode 15b and the connection electrode 16b are electrically connected by a via electrode 17 that penetrates the crystal blank 11 in the thickness direction. The via electrode 17 and the configuration around it will be described later. The extraction electrode 15b in this embodiment corresponds to an example of a "wiring electrode".

[0042] The connection electrode 16a is electrically connected to the first excitation electrode 14a through the extraction electrode 15a. The connection electrode 16b is electrically connected to the second excitation electrode 14b through the extraction electrode 15b and the via electrode 17. The connection electrodes 16a and 16b are terminals for electrically connecting to an external electrode (not shown) provided on the upper cover 20. The connection electrodes 16a and 16b are each provided on the first main surface 12a of the crystal piece 11. The connection electrodes 16a and 16b each have a length of, for example, about 15 μm in a direction parallel to the X-axis direction and a length of, for example, about 20 μm in a direction parallel to the Z'-axis direction.

[0043] In this manner, the first excitation electrode 14a is provided on the first principal surface 12a, the second excitation electrode 14b is provided on the second principal surface 12b, and the extraction electrode 15b is electrically connected to the second excitation electrode 14b. As a result, for example, by applying an alternating electric field to the first excitation electrode 14a and the second excitation electrode 14b via the extraction electrodes 15a and 15b, the connection electrodes 16a and 16b, and the via electrode 17, it is possible to realize the vibration section 11A that vibrates in a predetermined vibration mode by the portion of the crystal blank 11 where the first excitation electrode 14a and the second excitation electrode 14b are provided.

[0044] The material of the first excitation electrode 14a, the second excitation electrode 14b, the extraction electrodes 15a, 15b, and the connection electrodes 16a, 16b is preferably, for example, aluminum (Al). In this case, the thickness of the aluminum is, for example, about 0.05 μm. In this way, since the material of the extraction electrode 15b is aluminum, which has high conductivity and low density, unwanted vibration of the vibration part 11A is unlikely to occur, and a piezoelectric vibration element with high frequency vibration can be easily realized.

[0045] The first excitation electrode 14a, the second excitation electrode 14b, the extraction electrodes 15a, 15b, and the connection electrodes 16a, 16b are not limited to being made of aluminum (Al). The material of each electrode may be, for example, molybdenum (Mo) or gold (Au). In this case, the thickness of each electrode is, for example, within a range of 0.03 μm to 0.2 μm. Also, each electrode may be a laminated body made of, for example, a titanium (Ti) layer provided on the crystal blank 11 side and a gold (Au) layer provided on the front side. In this case, the thickness of the titanium layer is, for example, about 0.005 μm, and the thickness of the gold layer is, for example, about 0.05 μm.

[0046] Of the first excitation electrode 14a, the second excitation electrode 14b, the extraction electrodes 15a and 15b, and the connection electrodes 16a and 16b, it is preferable that at least the second excitation electrode 14b and the extraction electrode 15b are integrally formed. This makes it possible to easily form the second excitation electrode 14b and the extraction electrode 15b with the same thickness (thinness). Therefore, it is possible to suppress the generation of unnecessary vibrations when the vibration part 11A is vibrated at high frequency.

[0047] Moreover, it is preferable that the material of the first excitation electrode 14a is the same as the material of the second excitation electrode 14b, which makes it possible to easily realize the vibration part 11A that vibrates with high precision at a predetermined frequency.

[0048] The top cover 20 may be a flat plate-like member, such as a quartz plate, a ceramic plate, or a glass plate. The dimensions of the top cover 20 in a plan view are the same or approximately the same as the dimensions of the quartz vibrating element 10 (quartz blank 11). The length of the top cover 20 in a direction parallel to the X-axis direction is, for example, about 180 μm, and the length of the top cover 20 in a direction parallel to the Z'-axis direction is, for example, about 180 μm. The thickness of the top cover 20 is, for example, in the range of 100 μm to 200 μm.

[0049] The upper cover 20 may be conductive. In this case, the upper cover 20 is made of 42 alloy, which is an alloy containing iron (Fe) and nickel (Ni), or Kovar, which is an alloy containing iron (Fe), nickel (Ni), and cobalt (Co).

[0050] The bonding portion 30 bonds the top cover 20 and the quartz crystal vibrating element 10. The space formed by the bonded top cover 20 and the quartz crystal vibrating element 10 forms a part of the vibration space of the vibration portion 11A. The bonding portion 30 is provided around the entire circumference of each of the top cover 20 and the quartz crystal vibrating element 10. Specifically, the bonding portion 30 is provided on the lower surface of the top cover 20 and the first main surface 12a of the quartz crystal blank 11. The bonding portion 30 has a frame shape when the first main surface 12a is viewed in plan. The width of the frame, that is, the difference between the outer circumference and the inner circumference, is, for example, about 20 μm.

[0051] The joint 30 is electrically insulating (non-conductive). The joint 30 is, for example, a glass adhesive made of inorganic glass, which is solidified by heat treatment to exhibit adhesive properties. The inorganic glass is, for example, a low-melting-point glass such as lead borate or tin phosphate.

[0052] When the material of the joint 30 is a low melting point glass adhesive, it may contain lead-free vanadium (V)-based glass that melts at a temperature of 300°C to 410°C. The vanadium-based glass exhibits adhesive properties when a binder and a solvent are added in the form of a paste, melted, and solidified. The vanadium-based glass may contain other metals such as silver (Ag).

[0053] The material of the joint 30 may be, for example, a resin adhesive. The resin adhesive may contain a thermosetting resin or a photocurable resin, and for example, an epoxy-based adhesive containing an epoxy resin as a main component may be used. As the epoxy resin, for example, bifunctional epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin, etc. may be used. In addition, generally known epoxy resins such as multifunctional epoxy resins, glycidylamine type epoxy resins, heterocyclic epoxy resins, and alicyclic epoxy resins may also be applied.

[0054] The support substrate 40 is configured to support the quartz crystal vibrating element 10 so that it can vibrate. The support substrate 40 is, for example, a flat plate-shaped substrate. The dimensions of the support substrate 40 in a plan view are the same or approximately the same as the dimensions of the quartz crystal vibrating element 10 (quartz crystal blank 11). The length of the support substrate 40 in a direction parallel to the X-axis direction is, for example, about 180 μm, and the length of the support substrate 40 in a direction parallel to the Z'-axis direction is, for example, about 180 μm. The thickness of the support substrate 40 is, for example, within a range of 50 μm to 500 μm. The support substrate 40 is, for example, a quartz crystal substrate, but is not limited thereto and may be a silicon substrate.

[0055] The bonding layer 50 bonds the quartz crystal vibrating element 10 to the support substrate 40. More specifically, the bonding layer 50 is provided on the upper surface of the support substrate 40 and bonds the upper surface of the support substrate 40 to the second main surface 12b of the quartz crystal piece 11.

[0056] In this manner, by bonding the quartz crystal vibrating element 10 and the support substrate 40 with the bonding layer 50, it becomes possible to seal the quartz crystal vibrating element 10 between the upper cover 20 and the support substrate 40, for example.

[0057] The bonding layer 50 has a recessed cavity 51 formed in a portion corresponding to the vibration portion 11A of the quartz crystal vibrating element 10. The space formed by the quartz crystal vibrating element 10 and the cavity 51 of the bonding layer 50 forms a part of the vibration space of the vibration portion 11A. The thickness of the cavity 51 is, for example, about 0.2 μm.

[0058] The material of the bonding layer 50 is, for example, a silicon oxide film (silicon dioxide (SiO2)). The thickness of the bonding layer 50 is desirably 0.5 μm or more, for example, about 1 μm. In this way, the material of the bonding layer 50 is silicon dioxide, and the bonding layer 50 bonds the upper surface of the support substrate 40 and the second main surface 12b of the crystal blank 11, so that a protective electrode 19 (described later) is present between the crystal blank 11 and the bonding layer 50 around the via electrode 17, and therefore the stress due to the difference in thermal expansion between the crystal blank 11 and the bonding layer 50 made of silicon dioxide can be alleviated. Therefore, the vibration frequency of the vibrating part 11A can be stabilized.

[0059] The material of the bonding layer 50 is not limited to silicon oxide film, but may be silicon nitride film (silicon nitride (Si3N4)) or various adhesives. Also, the bonding layer 50 may be omitted and the support substrate 40 may be directly bonded to the quartz crystal vibrating element 10.

[0060] Next, a via electrode and its surrounding configuration of a quartz crystal vibrating element according to an embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is an enlarged cross-sectional view of a main part that shows an example of the via electrode 17 and its surrounding configuration shown in Fig. 4. Fig. 6 is an enlarged cross-sectional view of a main part that shows another example of the via electrode 17 and its surrounding configuration shown in Fig. 4.

[0061] 5, the via electrode 17 is provided penetrating from the first main surface 12a to the second main surface 12b of the crystal piece 11. The material of the via electrode 17 is, for example, aluminum (Al), and the thickness of the via electrode 17 is, for example, 1.0 μm. The material of the via electrode 17 may be, for example, copper (Cu). In this case, the thickness of the via electrode 17 is, for example, within the range of 0.5 μm to 3.0 μm.

[0062] The via electrode 17 is electrically connected to a connection electrode 16b (not shown) on the first main surface 12a, while the via electrode 17 is electrically connected to an etch stop film 18 on the second main surface 12b.

[0063] The etch stop film 18 covers the entire via electrode 17 on the second principal surface 12b of the crystal piece 11. The etch stop film 18 is conductive and is electrically connected to the via electrode 17.

[0064] The aforementioned extraction electrode 15b covers the entire etch stop film 18 on the second main surface 12b. This allows the connection electrode 16b and the second excitation electrode 14b to be electrically connected to each other through the via electrode 17, the etch stop film 18, and the extraction electrode 15b.

[0065] Furthermore, the etch stop film 18 is made of a material that is resistant to chemicals, such as hydrofluoric acid, used when forming the via electrodes 17. Specifically, when forming the via electrodes 17, first, the etch stop film 18 is formed on the second main surface 12b of the crystal blank 11 in correspondence with the position where the via electrodes 17 are to be formed in the holding portion 11C of the crystal blank 11. The etch stop film 18 is formed by, for example, deposition and lift-off, or sputtering and etching. Next, holes with a diameter of about 10 μm are formed through the crystal blank 11 by wet etching or dry etching. The holes are then filled with a conductive material. child Thus, the via electrode 17 is formed.

[0066] As a material having these properties, for example, nickel (Ni) is used for the etch stop film 18. The thickness of the etch stop film 18 is, for example, 0.05 μm. The material of the etch stop film 18 may be, for example, copper (Cu) or platinum (Pt). In this case, the thickness of the etch stop film 18 is, for example, within a range of 0.03 μm to 0.2 μm.

[0067] Here, the etch stop film 18 having a predetermined thickness forms a step at its outer edge. On the other hand, the extraction electrode 15b is patterned (formed) together with the second excitation electrode 14b by, for example, deposition and lift-off method, or sputtering and etching. The first excitation electrode 14a and the second excitation electrode 14b are formed thin to suppress unnecessary vibration of the vibration part 11A, and the thickness of the extraction electrode 15b is about 0.03 μm to 0.2 μm. Therefore, the extraction electrode 15b covering the etch stop film 18 is easily broken at the step at the outer edge of the etch stop film 18.

[0068] The quartz crystal vibrating element 10 of this embodiment further includes a protective electrode 19 that covers the entire portion of the lead electrode 15b covering the etch stop film 18 on the second main surface 12b. The material of the protective electrode 19 is, for example, aluminum (Al). The thickness of the protective electrode 19 is preferably thicker than the thickness of the lead electrode 15b, and is, for example, 0.5 μm. The material of the protective electrode 19 may be, for example, copper (Cu). In this case, the thickness of the protective electrode 19 is, for example, within a range of 0.3 μm to 1.0 μm.

[0069] The protective electrode 19 is formed by, for example, deposition and lift-off, or sputtering and etching, etc. The protective electrode 19 preferably extends to a cavity 51 of the bonding layer 50 that forms the vibration space, and covers the extraction electrode 15b.

[0070] The material of the protective electrode 19 is preferably the same as the material of the lead electrode 15b, so that stress due to a difference in thermal expansion between the lead electrode 15b and the protective electrode 19 does not occur, and the lead electrode 15b and the protective electrode 19 can be easily formed.

[0071] 5 shows an example in which the extraction electrode 15b covers the entire etch stop film 18 on the second main surface 12b, but the present invention is not limited to this. For example, as shown in FIG. 6, the extraction electrode 15b only needs to cover at least a part of the outer edge of the etch stop film 18 on the second main surface 12b. Similarly, the protective electrode 19 is not limited to covering the entire extraction electrode 15b of the part covering the etch stop film 18 on the second main surface 12b. The protective electrode 19 only needs to cover at least the part of the extraction electrode 15b covering the outer edge of the etch stop film 18 on the second main surface 12b.

[0072] In this way, the etch stop film 18 covers the via electrode 17 on the second principal surface 12b of the crystal blank 11, and the extraction electrode 15b covers at least a part of the outer edge of the etch stop film 18 on the second principal surface 12b, so that the conductive etch stop film 18 electrically connects the via electrode 17 and the extraction electrode 15b. Also, for example, when forming a hole penetrating from the first principal surface 12a to the second principal surface 12b to form the via electrode 17, the etch stop film 18 exists between the crystal blank 11 and the extraction electrode 15b on the second principal surface 12b, so that the extraction electrode 15b is not exposed to the etching agent or the like. Therefore, it is possible to suppress damage to the extraction electrode 15b due to etching while maintaining conductivity.

[0073] Moreover, on the second main surface 12b, the protective electrode 19 covers at least a portion of the lead electrode 15b that covers the outer edge of the etch stop film 18. Here, as described above, the lead electrode 15b is prone to disconnection due to a step formed on the outer edge of the etch stop film 18. Therefore, a conduction defect may occur near the outer edge of the etch stop film 18. Therefore, by covering the lead electrode 15b in the portion that covers the outer edge of the etch stop film 18, the protective electrode 19 can increase the strength of the lead electrode 15b in that portion and suppress disconnection of the lead electrode 15b.

[0074] Moreover, the thickness of the protective electrode 19 is preferably at least twice the thickness of the lead electrode 15b, which makes it possible to easily increase the strength of the lead electrode 15b in the portion covering the outer edge of the etch stop film 18.

[0075] Next, a modified example of the embodiment described above will be described. The same or similar components as those shown in Figures 1 to 6 will be denoted by the same or similar reference numerals, and the description thereof will be omitted as appropriate. Also, the same effects and advantages due to the same components will not be mentioned one by one.

[0076] (Modification) FIG. 7 is a plan view that illustrates a schematic configuration of a quartz crystal vibrating element 10A according to a modified example of the embodiment.

[0077] As shown in FIG. 7, a quartz crystal piece 11' of a quartz crystal vibrating element 10A includes connecting portions 11D and 11E in addition to a vibrating portion 11A, a groove portion 11B, and a holding portion 11C.

[0078] The connecting portions 11D and 11E connect the vibrating portion 11A and the holding portion 11C, respectively. More specifically, the connecting portion 11D connects the vibrating portion 11A and the holding portion 11C on one side (lower side in FIG. 7) of the vibrating portion 11A when the first main surface 12a of the crystal piece 11' is viewed in plan. The connecting portion 11E connects the vibrating portion 11A and the holding portion 11C on the other side (upper side in FIG. 7) of the vibrating portion 11A when the first main surface 12a is viewed in plan. The connecting portions 11D and 11E each have a length parallel to the X-axis direction of, for example, about 10 μm, and a length parallel to the Z'-axis direction of, for example, about 16 μm.

[0079] The extraction electrode 15a is disposed on one side of the first main surface 12a with respect to the vibration portion 11A (in FIG. 7 ). under On the other hand, the extraction electrode 15b is provided on the second main surface 12b on the other side (in FIG. 7) of the vibration portion 11A. above Side) connection part 11 E and is provided on the holding portion 11C.

[0080] The connection electrode 16a is disposed on one side of the first main surface 12a with respect to the vibrating portion 11A (in FIG. 7 under On the other hand, the connection electrode 16 b In the first main surface 12a, the other side (in FIG. 7) of the vibration portion 11A is above The retaining portion 11C is provided on the retaining portion 11C (side).

[0081] The via electrode 17 is disposed on the other side (in FIG. 7) of the vibrating portion 11A. above side) to the holding part 11C oh The hole penetrates crystal blank 11' in the thickness direction.

[0082] The configurations of the via electrode 17, the etch stop film 18, the extraction electrode 15b, and the protective electrode 19 are similar to those in the example shown in FIGS.

[0083] An exemplary embodiment of the present invention has been described above. In a quartz crystal vibrating element according to one embodiment, the etch stop film covers the via electrode on the second main surface of the quartz crystal piece, and the extraction electrode covers at least a part of the outer edge of the etch stop film on the second main surface. This allows the conductive etch stop film to electrically connect the via electrode and the extraction electrode. In addition, for example, when forming a hole penetrating from the first main surface to the second main surface to form a via electrode, since the etch stop film exists between the quartz crystal piece and the extraction electrode on the second main surface, the extraction electrode is not exposed to an etching agent or the like. Therefore, it is possible to suppress damage to the extraction electrode caused by etching while maintaining conductivity.

[0084] In the above-mentioned quartz crystal vibration element, the protective electrode covers at least a portion of the lead electrode that covers the outer edge of the etch stop film on the second main surface. Here, as described above, the step formed on the outer edge of the etch stop film makes the lead electrode prone to disconnection. Therefore, a conduction defect may occur near the outer edge of the etch stop film. Therefore, by covering the lead electrode in the portion that covers the outer edge of the etch stop film, the protective electrode increases the strength of the lead electrode in that portion and can suppress disconnection of the lead electrode.

[0085] In the above-described quartz crystal resonator element, the material of the protective electrode is the same as the material of the lead electrode, which prevents stress caused by a difference in thermal expansion between the protective electrode and the lead electrode, and makes it easy to form the protective electrode and the lead electrode.

[0086] In the above-described quartz crystal vibrating element, the thickness of the protective electrode is at least twice as thick as the lead electrode, which makes it possible to easily increase the strength of the lead electrode in the portion covering the outer edge of the etch stop film.

[0087] In addition, in the above-mentioned quartz crystal vibration element, the material of the extraction electrodes is aluminum, which has high conductivity and low density. This makes it difficult for unwanted vibrations to occur in the vibration part, making it easy to realize a piezoelectric vibration element that vibrates at high frequencies.

[0088] In the above-mentioned quartz crystal vibrating element, the first excitation electrode is provided on the first main surface, the second excitation electrode is provided on the second main surface, and the extraction electrode is electrically connected to the second excitation electrode. As a result, for example, by applying an alternating electric field to the first excitation electrode and the second excitation electrode through the extraction electrode, the connection electrode, and the via electrode, a vibration part that vibrates in a predetermined vibration mode can be realized by the part of the quartz crystal blank where the first excitation electrode and the second excitation electrode are provided.

[0089] In addition, in the above-mentioned quartz crystal vibration element, the second excitation electrode and the extraction electrode are integrally formed. This makes it possible to easily form the second excitation electrode and the extraction electrode with the same thickness (thinness). Therefore, it is possible to suppress the generation of unnecessary vibrations when the vibration part is vibrated at a high frequency.

[0090] In the above-described quartz crystal vibrating element, the material of the first excitation electrode is the same as the material of the second excitation electrode, which makes it possible to easily realize a vibrating part that vibrates at a predetermined frequency with high accuracy.

[0091] In addition, a quartz crystal resonator according to an embodiment includes the above-described quartz crystal resonator element and a support substrate that supports the quartz crystal resonator element so that the quartz crystal resonator element can vibrate. This makes it possible to easily realize a quartz crystal resonator that maintains electrical conductivity while suppressing damage to the extraction electrodes due to etching.

[0092] In the above-described crystal unit, the bonding layer bonds the crystal unit to the support substrate, which makes it possible to seal the crystal unit between the upper cover and the support substrate.

[0093] In addition, in the above-mentioned quartz crystal unit, the material of the bonding layer is silicon dioxide, and the bonding layer bonds the upper surface of the support substrate and the second main surface of the quartz crystal piece. As a result, a protective electrode is present between the quartz crystal piece and the bonding layer around the via electrode, so that the stress caused by the difference in thermal expansion between the quartz crystal piece and the bonding layer made of silicon dioxide can be alleviated. Therefore, the vibration frequency of the vibration part can be stabilized.

[0094] In addition, a crystal oscillator according to an embodiment includes the above-described crystal unit, a mounting substrate, and a cover member, which makes it possible to easily realize a crystal oscillator that maintains electrical conductivity while suppressing damage to the extraction electrodes due to etching.

[0095] The above-described embodiments are provided to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention may be modified / improved without departing from the spirit thereof, and equivalents are also included in the present invention. In other words, the embodiment and / or modification may be modified by a person skilled in the art as long as it has the characteristics of the present invention. For example, the elements and their arrangements, materials, conditions, shapes, sizes, etc. of the embodiment and / or modification are not limited to those shown as examples, and may be modified as appropriate. In addition, the embodiment and modification are illustrative, and it goes without saying that partial replacement or combination of the configurations shown in different embodiments and / or modifications is possible, and these are also included in the scope of the present invention as long as they include the characteristics of the present invention. [Explanation of symbols]

[0096] 1...quartz crystal resonator, 10, 10A...quartz crystal resonator element, 11, 11'...quartz crystal blank, 11A...vibrating portion, 11B...groove portion, 11C...holding portion, 11D, 11E...connecting portion, 12a...first main surface, 12b...second main surface, 14a...first excitation electrode, 14b...second excitation electrode, 15a, 15b...drawing electrode, 16a, 16b...connecting electrode, 17...via electrode, 18...etch stop film, 19...protective electrode, 20...upper cover, 30...joint portion, 40...support substrate, 50...joint layer, 51...cavity, 100...quartz crystal oscillator, 130...mounting substrate, 140...cover member, 153...solder, 156...electronic component, 166...bonding wire.

Claims

1. a piezoelectric piece having a first principal surface and a second principal surface; a via electrode provided penetrating from the first main surface to the second main surface; a conductive etch stop film covering the via electrode on the second main surface; a wiring electrode covering at least a portion of an outer edge of the etch stop film on the second main surface; a protection electrode covering at least a portion of the wiring electrode that covers an outer edge of the etch stop film on the second main surface; Equipped with Piezoelectric vibration element.

2. The material of the protective electrode is the same as the material of the wiring electrode. The piezoelectric vibration element according to claim 1 .

3. The thickness of the protective electrode is at least twice the thickness of the wiring electrode. The piezoelectric vibration element according to claim 1 .

4. The material of the wiring electrode is aluminum. The piezoelectric vibration element according to claim 1 .

5. a first excitation electrode provided on the first main surface; A second excitation electrode provided on the second main surface, The wiring electrode is electrically connected to the second excitation electrode. The piezoelectric vibration element according to claim 1 .

6. The wiring electrode and the second excitation electrode are integrally formed. The piezoelectric vibration element according to claim 5 .

7. The material of the first excitation electrode is the same as the material of the second excitation electrode. The piezoelectric vibration element according to claim 5 or 6.

8. The piezoelectric vibration element according to claim 1 , A support substrate that supports the piezoelectric vibration element so that the piezoelectric vibration element can vibrate. Piezoelectric vibrator.

9. Further comprising a bonding layer that bonds the piezoelectric vibration element and the support substrate. The piezoelectric vibrator according to claim 8 .

10. the material of the bonding layer is silicon dioxide; The bonding layer bonds the second main surface and the support substrate. The piezoelectric vibrator according to claim 9 .

11. A piezoelectric vibrator according to any one of claims 8 to 10, A lid body, Piezoelectric oscillator.

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