Electrode structure, piezoelectric vibration piece, piezoelectric device, intermediate body wafer for manufacturing piezoelectric device

Abstract

To provide a piezoelectric vibration piece 10 having an excitation electrode 13 formed of a crystal piece 11, a tungsten film 13a as an underlying layer provided in the front surface and the back surface of the crystal piece 11, and a metal film 13b laminated on the cobalt film, the specific resistance and the stress of the excitation electrode 13 being improved than in an existing piezoelectric vibration piece.SOLUTION: A tungsten film has a thickness in the range from 0.5 nm to 5 nm, both inclusive, preferably has a thickness in the range from 0.5 nm to 3 nm, both inclusive, and more preferably has a thickness in the range from 0.5 nm to 1 nm, both inclusive. The metal film has a thickness in the range from 10 nm to 100 nm, both inclusive, and preferably has a thickness in the range from 10 nm to 60 nm, both inclusive. A crystal piece 11 has an AT-cut crystal piece.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrode structure suitable for use as an excitation electrode for a piezoelectric device, for example, a piezoelectric vibrating piece using the electrode structure, a piezoelectric device using the piezoelectric vibrating piece, and an intermediate wafer suitable for use in manufacturing a piezoelectric device. [Background technology]

[0002] One type of piezoelectric device vibrates in thickness shear mode. A piezoelectric device that vibrates in thickness shear mode includes a piezoelectric vibrating piece that is composed of a piezoelectric piece and excitation electrodes provided on its front and back sides. A typical example of an electrode structure that constitutes the excitation electrode is a laminated film that is composed of a chromium (Cr) film provided on the piezoelectric piece and a gold film provided on the chromium film. The chromium film functions as an adhesive layer between the piezoelectric piece and the gold film (for example, paragraph 14 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-179958 A Summary of the Invention [Problem to be solved by the invention]

[0004] As communication speeds increase, there is an increasing demand for higher frequencies in piezoelectric devices, which are the reference signal sources for communication devices. In order to achieve higher frequencies in piezoelectric devices that vibrate in thickness shear mode and at the fundamental wave, the thickness of the piezoelectric piece becomes thinner and thinner. As a result, the influence of the excitation electrodes provided on the front and back of the piezoelectric piece on the characteristics of the piezoelectric device becomes an issue. Specifically, in the case of high-frequency piezoelectric devices, the resistivity and film stress of the electrode structure have a greater effect on the characteristics of the piezoelectric device than those for low frequencies. Therefore, an electrode structure with as small resistivity and film stress as possible is desired. In response to this demand, an electrode structure composed of a chromium film and a gold film is not necessarily preferable. Patent Document 1 describes an improvement to the electrode structure including a chromium film and a gold film by providing a nickel film as an intermediate film between the chromium film and the gold film (paragraph 42, etc.), but providing an intermediate film increases the number of manufacturing steps and increases costs, which is not preferable.

[0005] This application has been made in consideration of the above points, and therefore, an object of this application is to provide an electrode structure that is expected to have improved characteristics compared to conventional ones. Another object of this application is to provide a piezoelectric vibrating reed having the above-mentioned new electrode structure. Another object of this application is to provide a piezoelectric device using the above-mentioned piezoelectric vibrating reed. Another object of this application is to provide an intermediate wafer that can be used to mass-produce the above-mentioned piezoelectric device. [Means for solving the problem]

[0006] In order to achieve the above object, the electrode structure of the first invention of this application is characterized in that it is an electrode structure including a tungsten film and a gold film laminated on the tungsten film. Here, "including" means that the tungsten film and the gold film are in contact with each other, and may include films of other materials. In other words, it means that there may be three or more layers. However, typically, the electrode structure of the first invention is composed of a tungsten film as a lower layer and a gold film laminated thereon.

[0007] Also, a piezoelectric vibrating piece according to a second aspect of the present invention is characterized in that it comprises a substrate having piezoelectricity and the electrode structure according to the first aspect of the present invention provided on the front and back sides of the substrate. A piezoelectric device according to a third aspect of the present invention is characterized in that it includes the piezoelectric vibrating piece according to the second aspect of the invention, and a container that contains the piezoelectric vibrating piece. Here, piezoelectric devices refer to piezoelectric vibrators, piezoelectric oscillators, piezoelectric vibrators with temperature sensors, piezoelectric oscillators with temperature compensation functions, etc. Typical examples include quartz crystal vibrators (including those with temperature sensors) that vibrate in thickness shear mode, such as AT-cut quartz crystal vibrators, and quartz crystal oscillators (including those with temperature compensation functions).

[0008] According to a fourth aspect of the present invention, there is provided an intermediate wafer for manufacturing a piezoelectric device, which is a wafer having piezoelectricity and which includes a large number of the piezoelectric vibrating pieces according to the second aspect of the present invention in a matrix form. In the fourth aspect of the present invention, the wafer having piezoelectricity is a wafer made of a material having piezoelectricity such as quartz crystal, lithium niobate, or lithium tantalate, and is typically a quartz crystal wafer for quartz crystal resonators that vibrate in a thickness shear mode, such as an AT-cut quartz crystal wafer. Effect of the Invention

[0009] According to the electrode structure of the first invention of this application, since it includes a tungsten film and a gold film laminated on the tungsten film, it is possible to realize an electrode structure exhibiting a desired resistivity and stress, as will be apparent from the experimental results described below. Therefore, it is expected to be used as an electrode for various electronic components, including piezoelectric devices. Furthermore, the piezoelectric vibrating reed that is the second invention of this application is provided with the electrode structure of the first invention, and therefore it is expected to realize a piezoelectric vibrating reed with improved characteristics compared to conventional ones. Furthermore, according to the piezoelectric device, which is the third invention of this application, since it uses the piezoelectric vibrating piece of the second invention, it is expected that a piezoelectric device with improved characteristics compared to conventional devices, for example a high-frequency piezoelectric device with an oscillation frequency on the order of several hundred MHz, can be realized. In addition, the intermediate wafer for manufacturing piezoelectric devices, which is the fourth invention of this application, has a large number of piezoelectric vibrating pieces of the second invention arranged in a matrix, so that the piezoelectric devices of the third invention can be mass-produced by mounting individual piezoelectric vibrating pieces cut from this wafer in a container. [Brief description of the drawings]

[0010] [Figure 1] 1A to 1C are diagrams for explaining an electrode structure and a piezoelectric vibrating reed according to embodiments of the present invention; [Diagram 2] 1A to 1C are diagrams for explaining an experiment for discovering the requirements for each of the electrode structure and the piezoelectric vibrating reed of the present invention and the results thereof. [Diagram 3] 1A to 1C are diagrams illustrating a piezoelectric device according to an embodiment of the present invention. [Figure 4] 1A to 1C are diagrams for explaining an example of a method for manufacturing a piezoelectric vibrating piece and an intermediate wafer for manufacturing a piezoelectric device. [Diagram 5] 13A and 13B are diagrams illustrating a piezoelectric vibrating reed according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the inventions of this application will be described with reference to the drawings. Note that each drawing used in the description is merely a schematic illustration to the extent that these inventions can be understood. In addition, in each drawing used in the description, similar components are indicated by the same numbers, and their description may be omitted. Furthermore, the shapes, dimensions, materials, etc. described in the following description are merely preferred examples within the scope of this invention. Therefore, the present invention is not limited to only the following embodiments.

[0012] 1. Electrode structure and piezoelectric vibrating piece 1-1.Configuration Fig. 1 is an explanatory diagram of a piezoelectric vibrating reed 10 as an embodiment of the electrode structure of the first invention and the piezoelectric vibrating reed of the second invention. In particular, Fig. 1(A) is a plan view of the piezoelectric vibrating reed 10, and Fig. 1(B) is a cross-sectional view of the piezoelectric vibrating reed 10 taken along line PP in Fig. 1(A). Fig. 1(B) also shows an enlarged view of a portion of the excitation electrode. The piezoelectric vibrating piece 10 of the embodiment is an example in which the present invention is applied to an AT-cut quartz crystal piece. The coordinate axes X, Y', and Z' in Fig. 1(A) are axes derived from the crystal axes of quartz crystal. The piezoelectric vibrating piece 10 of the embodiment includes an AT-cut crystal blank 11 as a substrate having piezoelectricity, excitation electrodes 13 provided on the front and back principal surfaces thereof and made up of tungsten films 13a as lower layers and gold films 13b laminated on the tungsten films, and an extraction electrode 15. The tungsten film 13a as the lower layer functions as an adhesive layer between the crystal blank 11 and the gold film 13b. In the present invention, the thickness of the tungsten film 13a is preferably 0.5 nm or more and 5 nm or less, more preferably 0.5 nm or more and 3 nm or less, even more preferably 0.5 nm or more and 2 nm or less, and even more preferably 0.5 nm or more and 1 nm or less. The thickness of the gold film 13b is preferably 10 nm or more and 100 nm or less, more preferably 10 to 60 nm or less in order to reduce the amount of gold used, and even more preferably 10 to 40 nm or less. The reason why it is preferable to set the thickness of tungsten film 13a and the thickness of gold film 13b to the above values ​​will be explained in the experimental section described later.

[0013] In the case of the piezoelectric vibrating piece 10 of the embodiment, the crystal blank 11 has a square planar shape, and in this case, it is rectangular. The thickness (dimension in the Y' direction) of the crystal blank 11 is a predetermined thickness according to the oscillation frequency required of the piezoelectric vibrating piece 10. Therefore, the higher the frequency of the piezoelectric vibrating piece 10, the thinner the crystal blank 11. And, as the piezoelectric vibrating piece 10 becomes higher frequency and the thickness of the piezoelectric vibrating piece becomes thinner, the configuration of the tungsten film 13a and gold film 13b of the excitation electrode 13 becomes more important, and the above-mentioned numerical values ​​of the film thickness, etc. become effective. In this embodiment, the planar shape of the excitation electrode 13 is also rectangular, similar to the crystal blank 11. An extraction electrode 15 is extracted from a part of the excitation electrode 13 to one end of the crystal blank 11. The extraction electrode 15 is made of the same material as the excitation electrode 13 and is formed as an integral film. The planar shapes of the crystal blank and the excitation electrodes are not limited to a rectangle, and may be changed according to the design of the piezoelectric vibrating piece 10, and may be circular or elliptical. The planar shapes of the crystal blank and the excitation electrodes may be different.

[0014] 1-2.Experiment The reason why the thicknesses of the tungsten film 13a and the gold film 13b are set to the above values ​​is based on the experiments conducted by the inventor of this application, which will be described below with reference to FIG. 1-2-1. Study of resistivity The inventors of this application prepared a large number of substrates, specifically AT-cut quartz crystal substrates, divided them into groups, and formed tungsten films on the substrates of each group by evaporation so that the thicknesses were different, specifically 1 nm, 3 nm, 5 nm, and 10 nm. After the tungsten film was formed on the substrate of each group, a gold film was formed by evaporation at multiple levels between 10 nm and 200 nm, specifically at 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 150 nm, and 200 nm. After the gold film had been formed, each substrate was heat-treated at 300°C in a nitrogen atmosphere, simulating the heat of a curing furnace used when fixing the piezoelectric vibrating reed to a piezoelectric device container with a conductive adhesive during the manufacture of the piezoelectric device. Also, a sample having only a tungsten film was prepared in the same manner as in the above sample preparation, except that only a tungsten film was formed on the substrate. Next, the resistivity of the film was measured for each of the sample having the tungsten film and the gold film formed thereon, and the sample having only the tungsten film formed thereon.

[0015] Next, a parallel resistance model was assumed for a sample with a tungsten film and a gold film formed thereon, and a sample with only a tungsten film formed thereon, and the resistivity of the gold film was calculated using the resistivity of both samples. The reason for calculating the resistivity of the gold film here is to grasp whether the resistivity of the gold film has changed due to the diffusion of the tungsten film into the gold film, and the degree of influence if it has changed. In addition, as comparative samples, a chromium film was formed on the substrate instead of the tungsten film, with a film thickness of 3 nm and 5 nm, and the other comparative samples were fabricated in the same manner as the above-mentioned tungsten film and gold film samples and tungsten film only sample. The resistivity of the gold film in the comparative sample was also calculated using the same parallel resistance model as above. Furthermore, as a reference, a gold film alone was formed on the substrate at multiple levels of thickness from 10 nm to 200 nm, and the resistivity of each was measured.

[0016] Figure 2(A) is a characteristic diagram summarizing the tendency of the gold film resistivity with respect to the thickness of the tungsten film and the gold film for each of various experimental samples formed as described above using a tungsten film, a comparative sample formed using a chromium film, and a reference sample using only a gold film. In Figure 2(A), the dashed line (Bulk Au) shows the characteristic of the reference sample. Incidentally, since the resistivity of the gold film of the sample with a tungsten film thickness of 10 nm was substantially the same as that of the sample with a tungsten film thickness of 5 nm, the plot of the resistivity of the sample with a tungsten film thickness of 10 nm is omitted in FIG. 2(A) and FIG. 2(B) described later. From FIG. 2(A), it can be seen that the resistivity of the gold film can be reduced by using a tungsten film as the lower layer (adhesive film) compared to using a chromium film. Specifically, in a sample using a chromium film as the lower layer, when the thickness of the gold film is 50 nm or less, the resistivity of the gold film is at least about 20 μΩcm, and at most about 80 μΩcm. In a sample using a chromium film as the lower layer, even when the gold film is thick, the resistivity of the gold film is at least greater than about 10 μΩcm. In contrast, in the case of a sample using a tungsten film as the lower layer, the resistivity of the gold film is less than 10 μΩcm regardless of the thickness of the gold film, and is reduced to less than 5 μΩcm when the thickness of the gold film is 40 nm or more. The reason why the resistivity of the gold film can be made smaller when a tungsten film is used as the underlayer (adhesion film) than when a chromium film is used is that there is essentially no diffusion of tungsten into the gold film, thereby suppressing changes in the physical properties of the gold film.

[0017] Here, in the case of a quartz crystal unit as a piezoelectric device, if we consider an example of a quartz crystal unit with a frequency of, for example, 48 MHz, which is often used as a reference clock source, the resistivity of the gold film is about 20 μΩcm. Furthermore, it is preferable that the resistivity of the gold film included in the excitation electrode of a high-frequency quartz crystal unit is 20 μΩcm or less. When considering the characteristics diagram of Figure 2(A) from this perspective, the following points (a) to (d) can be said. (a) As mentioned above, the use of a tungsten film as the lower layer (adhesion film) results in an electrode film with a lower resistivity than the use of a chromium film. (b) When a tungsten film is used as the underlayer, the resistivity of the gold film can be made 10 μΩcm regardless of the thickness of the gold film. Moreover, this tendency is obtained when the thickness of the tungsten film is 1 nm, 3 nm, 5 nm, or 10 nm. (c) From the above points, it can be said that the thickness of the tungsten film should be 10 nm or less. However, since the cost of materials and the number of manufacturing steps can be reduced if the thickness of the tungsten film is kept to a minimum, the thickness of the tungsten film should be 0.5 nm or more and 5 nm or less, more preferably 0.5 nm or more and 3 nm or less, and even more preferably 0.5 nm or more and 2 nm or less or 1 nm or less. The reason why the lower limit of the thickness of tungsten film 13a is set to 0.5 nm is that if tungsten film 13a is thinner than this, it is difficult to function as a film and it is not possible to obtain adhesion to the substrate as an underlying film. (d) On the other hand, in this experiment, a gold film thickness of 10 nm to 200 nm showed a reasonable resistivity. Moreover, if the gold film thickness was 40 nm or more, the resistivity of the gold film was reduced to less than 5 μΩcm. Since a thicker gold film is undesirable because it increases the material cost, it is considered that the gold film thickness should be 10 to 100 nm, preferably 10 to 60 nm. Considering that the gold material cost can be reduced, the resistivity of the gold film can be reduced to less than 5 μΩcm, and that in the case of high-frequency piezoelectric devices, it is preferable that the mass of the electrodes is small, it is considered that the gold film thickness may be 30 to 60 nm.

[0018] 1-2-2. Consideration of stress Next, the relationship between the thickness of the tungsten film in the electrode structure of the present invention and the stress of the electrode structure will be considered. FIG. 2(B) is a diagram summarizing the relationship between the thickness of the tungsten film and the stress in the electrode structure of the above-mentioned embodiment, with the thickness of the gold film on the horizontal axis and the stress of the electrode structure of the embodiment on the vertical axis. In addition, FIG. 2(B) also shows the results of the stress of a sample created in the same manner as the embodiment, except that the lower layer is a chromium film with a thickness of 3 nm and 5 nm, as a comparative example. In FIG. 2(B), the positive direction of the vertical axis is tensile stress, and the negative direction is compressive stress. In the case of a piezoelectric vibrating piece, if stress occurs in the electrode structure, the oscillation frequency may fluctuate due to stress relaxation over time, so it is preferable that the stress in the electrode structure is small. When the characteristic diagram of FIG. 2(B) is examined from this perspective, the following can be said. When the lower layer is a tungsten film, the stress of the electrode film is in the range of ±30 MPa for all thicknesses of 1, 3, 5 nm, and 10 nm (not shown). In contrast, when the lower layer is a chromium film, the stress of the electrode film is generally larger than when the lower layer is a tungsten film, and in particular when the gold film is 40 nm or less in thickness, the stress of the electrode film is as large as 200 MPa to 400 MPa.

[0019] Considering the above stress, it can be said that the thickness of the tungsten film is preferably 0.5 nm or more and 5 nm or less, more preferably 0.5 nm or more and 3 nm or less, and even more preferably 0.5 nm or more and 2 nm or less or 1 nm or less. It can be said that the thickness of the gold film is preferably 10 to 100 nm, preferably 10 to 60 nm, and more preferably 30 to 60 nm. In the electrode structure and the piezoelectric vibrating piece, the thickness of the tungsten film is a thin film, such as a few nm, or 0.5 nm at the minimum. Methods for identifying such a film thickness include, for example, XPS depth profile analysis, XRR (X-ray reflectometry), and cross-sectional TEM.

[0020] 2. Piezoelectric Device Embodiments Next, an embodiment of the piezoelectric device of the present invention will be described. Here, an example of a quartz crystal resonator will be described as the piezoelectric device. Fig. 3 is an explanatory diagram for this purpose. In particular, Fig. 3(A) is a plan view of a piezoelectric device 20 of the embodiment, and Fig. 3(B) is a cross-sectional view of the piezoelectric device 20 taken along line QQ in Fig. 3(A). In Fig. 3(A), the illustration of a cover member 25 provided on the piezoelectric device 20 is omitted. A quartz crystal resonator 20 as a piezoelectric device 20 of the embodiment includes the piezoelectric vibrating piece 10 according to the first aspect of the invention and a container 21 that houses the piezoelectric vibrating piece 10. In this example, the container 21 includes a recess 21a having a rectangular shape in a plan view for accommodating the piezoelectric vibrating piece 10, a bank portion 21b surrounding the recess 21a, an adhesive pad 21c to which the piezoelectric vibrating piece 10 is fixed and bonded, and an external connection terminal 21d provided on the outer bottom surface of the container 21 for connecting the piezoelectric device 20 to an arbitrary electronic device. The adhesive pad 21c and the external connection terminal 21d are electrically connected by via wiring or castellation (not shown). The container 21 can be formed of a known ceramic package. In this case, the piezoelectric vibrating piece 10 has a cantilever support structure. Therefore, the piezoelectric vibrating piece 10 is connected and fixed to the adhesive pad 21c of the container 21 at the position of the extraction electrode 15 by a conductive adhesive 23. A lid member 25 is bonded to the top surface of the bank portion 21b of the container 21 in a structure according to the sealing method, and the piezoelectric vibrating piece 10 is sealed in the container 21.

[0021] In the above embodiment of the piezoelectric device, a quartz crystal resonator is shown as an example of the piezoelectric device, but the electronic device of the present invention also includes a piezoelectric device in which a quartz crystal resonator piece and other electronic components such as a temperature sensor and an oscillation circuit are mounted inside the container 21, that is, a quartz crystal resonator or a quartz crystal oscillator with a temperature sensor (including those having a temperature compensation function). Also, the structure of the container 21 described above is merely one example, and the container may have any other suitable structure.

[0022] 3. Example of manufacturing method for piezoelectric vibrating piece and intermediate wafer for forming piezoelectric device Next, an example of a manufacturing method of the electrode structure of the first invention and the piezoelectric vibrating piece of the second invention, and an embodiment of an intermediate wafer for a piezoelectric device of the fourth invention will be described. Figures 4(A) to (D) are manufacturing process diagrams for this purpose. Figures 4(B) and (C) are cross-sectional views of the wafer during the manufacturing process, and are cross-sectional views taken along line RR in Figure 4(A). In this example, a quartz crystal vibrating piece will be used as the piezoelectric vibrating piece. First, an AT-cut crystal wafer 30 is prepared (FIG. 4(A)). Next, this crystal wafer 30 is processed by known photolithography and wet etching techniques to form the outline of the piezoelectric vibrating pieces, forming a wafer having a large number of crystal pieces 11, each of which is connected at one end to a frame 30a (FIG. 4(A)). Next, tungsten films 31 are formed on the front and back of the quartz crystal wafer 30 on which the quartz crystal piece 10 has been formed, using any suitable film formation method, so as to have a thickness within the range of the first aspect of the invention, for example a thickness of 1 nm (FIG. 4(B)). Next, a gold film 33 is formed on the tungsten film 31 by any suitable film formation method so as to have a thickness within the range of the requirements of the first invention, for example, a thickness of 60 nm (FIG. 4(C)). Next, the tungsten film 31 and the gold film 33 are patterned into the shape of the excitation electrode 13 by known photolithography and metal etching techniques (FIG. 4(D)). By these steps, the piezoelectric vibrating piece 10 can be manufactured, and an intermediate wafer 30x for forming piezoelectric devices (see FIG. 4(D)) can be obtained which has a large number of piezoelectric vibrating pieces 10 for manufacturing piezoelectric devices arranged in a matrix.

[0023] This invention can be modified in any suitable manner. In the above embodiment, the planar shape of the quartz crystal wafer is circular, but the planar shape of the quartz crystal wafer may be other shapes, such as a square. Furthermore, the quartz crystal wafer is not limited to an AT cut, and may be a twice-rotated quartz crystal wafer, such as an SC cut. In the above-described embodiment, the piezoelectric vibrating piece uses a flat crystal piece as shown in Fig. 1, but the shape of the piezoelectric vibrating piece is not limited to this. For example, the piezoelectric vibrating piece 40 may be as shown in the plan view and the cross-sectional view along the line SS in Fig. 5(A). That is, the piezoelectric vibrating piece 40 may include a thick portion 41a having a thick portion, a vibrating portion 41b having a predetermined thickness according to the frequency, and excitation electrodes 43 according to the present invention provided on the front and back of the vibrating portion 41b. Also, for example, a piezoelectric vibrating piece 50 as shown in the plan view and the cross-sectional view along the line SS in Fig. 5(B) may be used. That is, the piezoelectric vibrating piece 50 may include a vibrating portion 51a having a predetermined thickness according to the frequency, thick portions 51b surrounding the vibrating portion 51a on all four sides, and excitation electrodes 53 according to the present invention provided on the front and back of the vibrating portion 51a. [Explanation of symbols]

[0024] 10: Piezoelectric vibrating piece (quartz crystal vibrating piece) of embodiment 11: Piezoelectric piece (quartz crystal piece) 13: Electrode structure (excitation electrode) 13a: Tungsten film 13b: Gold film 20: Piezoelectric device (quartz crystal unit) according to an embodiment 21: Container 23: Conductive adhesive 25: Lid component 30: Wafer (quartz crystal wafer) 30a: Frame 31: Tungsten film 33: Gold film 30x: Intermediate wafer for manufacturing piezoelectric vibrating pieces

Claims

1. An electrode structure comprising a tungsten film and a gold film laminated on the tungsten film.

2. 2. The electrode structure according to claim 1, wherein the electrode structure is composed of a tungsten film and a gold film laminated on the tungsten film.

3. 2. The electrode structure according to claim 1, wherein the thickness of the tungsten film is 0.5 nm or more and 5 nm or less.

4. 2. The electrode structure according to claim 1, wherein the gold film has a thickness of 10 nm to 100 nm.

5. The thickness of the tungsten film is set to 0.5 nm or more and 5 nm or less, 2. The electrode structure according to claim 1, wherein the gold film has a thickness of 10 nm to 100 nm.

6. A piezoelectric vibrating piece comprising: a substrate having piezoelectricity; and an excitation electrode including a tungsten film provided on the front and back of the substrate as a lower layer and a gold film laminated on the tungsten film.

7. 7. The piezoelectric vibrating piece according to claim 6, wherein the excitation electrode is made of a tungsten film and a gold film laminated on the tungsten film.

8. 7. The piezoelectric vibrating piece according to claim 6, wherein the thickness of the tungsten film is 0.5 nm or more and 5 nm or less.

9. 7. The piezoelectric vibrating piece according to claim 6, wherein the gold film has a thickness of 10 nm to 100 nm.

10. The thickness of the tungsten film is set to 0.5 nm or more and 5 nm or less, 7. The piezoelectric vibrating piece according to claim 6, wherein the gold film has a thickness of 10 nm to 100 nm.

11. 7. The piezoelectric vibrating piece according to claim 6, wherein the piezoelectric vibrating piece is an AT-cut quartz crystal piece.

12. 12. A piezoelectric device comprising: the piezoelectric vibrating piece according to claim 6; and a container that contains the piezoelectric vibrating piece.

13. 13. The piezoelectric device according to claim 12, wherein the piezoelectric device is a quartz crystal resonator, a quartz crystal resonator with a temperature sensor, a quartz crystal oscillator, or a quartz crystal oscillator with a temperature compensation function.

14. 12. An intermediate wafer for manufacturing a piezoelectric device, comprising a piezoelectric substrate having a large number of the piezoelectric vibrating pieces according to claim 6 in a matrix form.

15. 15. The intermediate wafer for manufacturing a piezoelectric device according to claim 14, wherein the piezoelectric vibrating piece is a quartz vibrating piece, and the intermediate wafer is a quartz wafer.

Images