Electrode structures, piezoelectric vibrators, piezoelectric devices, and intermediate wafers for piezoelectric device manufacturing.

Abstract

The present invention provides a piezoelectric vibrator 10 comprising a quartz crystal 11, an excitation electrode 13 composed of a molybdenum film 13a as an underlayer provided on the front and back surfaces of the quartz crystal 11, and a gold film 13b laminated on the molybdenum film, wherein the resistivity and stress of the excitation electrode 13 are improved compared to conventional piezoelectric vibrators. [Solution] The molybdenum film thickness is 0.5 nm to 5 nm, preferably 0.5 nm to 3 nm, more preferably 0.5 nm to 1 nm, and the gold film thickness is 10 nm to 100 nm, preferably 30 nm to 70 nm. The quartz piece 11 is an AT-cut quartz piece.

Description

[Technical Field]

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

[0002] As one type of piezoelectric device, there are piezoelectric devices that vibrate in a thickness shear mode. A piezoelectric device that vibrates in a thickness shear mode includes a piezoelectric vibrating piece composed of a piezoelectric piece and excitation electrodes provided on the front and back surfaces of the piezoelectric piece. A typical example of an electrode structure constituting an excitation electrode is a laminated film including a chromium (Cr) film provided on a piezoelectric piece and a gold film provided on the chromium film. The chromium film functions as an adhesion layer between the piezoelectric piece and the gold film (for example, see paragraph 14 of Patent Document 1). [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2015-179958 [Summary of Invention] [Problem to be Solved by the Invention]

[0004] With increasing communication speeds, the demand for higher frequencies in piezoelectric devices, which are the reference signal sources for communication equipment, is growing. To achieve higher frequencies in piezoelectric devices that vibrate in thickness-slip mode and with a fundamental wave, the thickness of the piezoelectric element needs to be increasingly thin. Consequently, the influence of the excitation electrodes placed on the front and back of the piezoelectric element on the characteristics of the piezoelectric device becomes a problem. Specifically, in the case of high-frequency piezoelectric devices, the resistivity and stress of the electrode film have a greater impact on the characteristics of the piezoelectric device compared to low-frequency devices. Therefore, an electrode structure with the smallest possible resistivity and film stress is desired. In response to this demand, an electrode structure composed of a chromium film and a gold film was not necessarily preferable. Patent document 1 describes improving the electrode structure including a chromium film and a gold film by providing a nickel film as an interlayer between the chromium film and the gold film (paragraph 42, etc.), but this is undesirable because it increases manufacturing man-hours and costs due to the addition of the interlayer.

[0005] This application has been made in view of the above points, and therefore, the object of this application is to provide an electrode structure that can be expected to have improved characteristics compared to the conventional one. Furthermore, the object of this application is to provide a piezoelectric vibrator having the above novel electrode structure. Furthermore, the object of this application is to provide a piezoelectric device using the above piezoelectric vibrator. Furthermore, the object of this application is to provide an intermediate wafer that can be manufactured in high mass productivity for the above piezoelectric device. [Means for solving the problem]

[0006] To achieve the above objective, the electrode structure of the first invention of this application is characterized by comprising a molybdenum film and a gold film laminated on the molybdenum film. Here, "including" means that, assuming that the molybdenum film and the gold film are in contact, films of other materials may also be included. In other words, there may be three or more layers. However, typically, the electrode structure of the first invention consists of a molybdenum film as the lower layer and a gold film laminated on top of it.

[0007] Furthermore, the piezoelectric vibrating piece of the second invention of this application is characterized by comprising a piezoelectric substrate and an electrode structure according to the first invention provided on the front and back surfaces of the substrate. Furthermore, the piezoelectric device, which is the third invention of this application, is characterized by comprising a piezoelectric vibrating piece of the second invention and a container enclosing the piezoelectric vibrating piece. Here, piezoelectric devices include piezoelectric resonators, piezoelectric oscillators, piezoelectric resonators with temperature sensors, piezoelectric oscillators with temperature compensation functions, etc. Typical examples include quartz resonators (including those with temperature sensors) and quartz oscillators (including those with temperature compensation functions) that vibrate in thickness-slip mode, such as AT-cut quartz resonators.

[0008] Furthermore, the fourth invention of this application, an intermediate wafer for manufacturing piezoelectric devices, is characterized by being a piezoelectric wafer having a large number of piezoelectric vibrating pieces of the second invention arranged in a matrix. In this fourth invention, the piezoelectric wafer is a wafer made of a piezoelectric material such as quartz, lithium niobate, or lithium tantalate, but is typically a quartz wafer for a quartz resonator that vibrates in a thickness-slip mode, such as an AT-cut quartz wafer. [Effects of the Invention]

[0009] According to the electrode structure of the first invention of this application, since it includes a molybdenum film and a gold film laminated on the molybdenum film, it is possible to realize an electrode structure that exhibits desired resistivity and stress, as will be clear from the experimental results described later. Therefore, it can be expected to be used as an electrode for various electronic components, such as piezoelectric devices. Furthermore, the piezoelectric vibrator, which is the second invention of this application, is expected to realize a piezoelectric vibrator with improved characteristics compared to conventional ones, since it is equipped with the electrode structure of the first invention. Furthermore, the piezoelectric device, which is the third invention of this application, uses the piezoelectric vibrating piece of the second invention, and is therefore expected to enable the realization of a piezoelectric device with improved characteristics compared to conventional devices, such as a high-frequency piezoelectric device with an oscillation frequency on the order of several hundred MHz. Furthermore, according to the fourth invention of this application, an intermediate wafer for manufacturing piezoelectric devices, since it has a large number of piezoelectric vibrating pieces of the second invention arranged in a matrix, the piezoelectric device of the third invention can be mass-produced by mounting the individual piezoelectric vibrating pieces from this wafer into a container. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram illustrating embodiments of each invention of the electrode structure and piezoelectric vibrator. [Figure 2] This diagram illustrates the experiments and results that identified the requirements for each invention of the electrode structure and piezoelectric vibrator. [Figure 3] This is a diagram illustrating an embodiment of the piezoelectric device invention. [Figure 4] This diagram illustrates an example of a piezoelectric vibrator manufacturing method and an intermediate wafer for piezoelectric device manufacturing. [Figure 5] This is a diagram illustrating a modified piezoelectric vibrator. [Modes for carrying out the invention]

[0011] The embodiments of each invention in this application will be described below with reference to the drawings. Note that the drawings used in this description are only schematic representations to the extent necessary to understand these inventions. Furthermore, in the drawings used in this description, similar components are indicated with the same number, and their descriptions may be omitted. Also, the shapes, dimensions, materials, etc., described below are merely preferred examples within the scope of this invention. Therefore, the present invention is not limited to the embodiments described below.

[0012] 1. Embodiments of electrode structure and piezoelectric vibrator 1-1. Composition Figure 1 is an explanatory diagram of the piezoelectric vibrator 10 as an embodiment of the electrode structure of the first invention and the piezoelectric vibrator of the second invention, respectively. In particular, Figure 1(A) is a plan view of the piezoelectric vibrator 10, and Figure 1(B) is a cross-sectional view of the piezoelectric vibrator 10 along the PP line in Figure 1(A). Figure 1(B) also includes an enlarged view of a portion of the excitation electrode. The piezoelectric vibrating piece 10 of the embodiment is an example of applying the present invention to an AT-cut quartz crystal. The coordinate axes X, Y', and Z' in Figure 1(A) are axes derived from the crystal axes of the quartz. However, the dash symbols Y' and Z' indicate that the axes are shifted from the original crystal axes Y and Z of the quartz according to the cutting angle of the AT cut. The piezoelectric vibrator 10 of this embodiment comprises an AT-cut quartz crystal 11 as a piezoelectric substrate, an excitation electrode 13 provided on the front and back main surfaces thereof, each composed of a molybdenum film 13a as an underlayer and a gold film 13b laminated on the molybdenum film, and an extraction electrode 15. The molybdenum film 13a as an underlayer functions as an adhesion layer between the quartz crystal 11 and the gold film 13b. The thickness of the molybdenum film 13a can be any suitable thickness depending on the design of the piezoelectric device. However, if the thickness of the molybdenum film 13a is too thin, it will not function as an adhesion layer, and if it is too thick, it will lead to an increase in the proportion of electrode mass in the high-frequency piezoelectric device and an increase in film stress, which is undesirable. Considering these factors, the thickness of the molybdenum film 13a is preferably 0.5 nm to 5 nm, more preferably 0.5 nm to 3 nm, more preferably 0.5 nm to 2 nm, and even more preferably 0.5 nm to 1 nm. Furthermore, the thickness of the gold film 13b is preferably between 10 nm and 100 nm, and even better between 10 nm and 60 nm in order to reduce the amount of gold used, and between 30 nm and 70 nm in order to reduce the amount of gold used and to lower the resistivity. The reasons why the above values ​​are appropriate for the thickness of the molybdenum film 13a and the gold film 13b will be explained in the experimental section below.

[0013] In the piezoelectric vibrating piece 10 according to the embodiment, the crystal blank 11 has a quadrangular planar shape, and here is a rectangular AT-cut crystal blank. The thickness (dimension in the Y' direction) of the crystal blank 11 is set to a predetermined thickness corresponding to the oscillation frequency required for the piezoelectric vibrating piece 10. Accordingly, as the piezoelectric vibrating piece 10 is intended for higher frequencies, the thickness of the crystal blank 11 becomes thinner. Furthermore, as the piezoelectric vibrating piece 10 is intended for higher frequencies and the thickness of the piezoelectric vibrating piece becomes thinner, the configuration of the molybdenum film 13a and the gold film 13b of the excitation electrode 13 becomes more important, and the numerical values such as the film thickness described above become effective. Further, in this embodiment, the planar shape of the excitation electrode 13 is also a quadrangle similarly to the crystal blank 11. An extraction electrode 15 is drawn out 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 integrally formed film. It should be noted that the planar shape of the crystal blank and the planar shape of the excitation electrode are not limited to quadrangles, and can be changed according to the design of the piezoelectric vibrating piece 10, and may be circular or elliptical. The planar shape of the crystal blank and the planar shape of the excitation electrode may be different from each other.

[0014] 1-2. Experiment The reason why the film thickness of the molybdenum film 13a and the film thickness of the gold film 13b are set to the above values respectively is based on experiments conducted by the inventor of the present application. This will be described below with reference to FIG. 2. 1-2-1. Examination of Specific Resistance The inventor of the present application prepared a large number of substrates, specifically a large number of AT-cut crystal substrates, divided them into groups, and formed molybdenum films on the substrate for each group of substrates with different film thicknesses, specifically, by sputtering such that the film thicknesses were 1 nm, 3 nm, and 5 nm. On the molybdenum film of each group of substrates on which the molybdenum film had been formed, gold films were formed by sputtering at a plurality of levels between 10 nm and 100 nm, specifically 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, and 100 nm. Each substrate on which a gold film has been formed was subjected to heat treatment at a temperature of 300°C in a nitrogen atmosphere, assuming the heat of the curing process performed when fixing a piezoelectric vibrating piece to a container for a piezoelectric device with a conductive adhesive. Further, a sample having only a molybdenum film was produced by the same procedure as described above except that only a molybdenum film was formed on the substrate. Next, the specific resistance of the film was measured for each of the sample on which a molybdenum film and a gold film were formed and the sample on which only a molybdenum film was formed.

[0015] Next, the specific resistance of the gold film was calculated from the sample on which a molybdenum film and a gold film were formed and the sample on which only a molybdenum was formed, assuming a parallel resistance model and using the specific resistances of both samples. Here, the reason for calculating the specific resistance of the gold film is to grasp whether diffusion of the molybdenum film or the like occurs into the gold film to change the specific resistance of the gold film, and the degree of influence in the case where the specific resistance is changed. Further, as samples of comparative examples, instead of a molybdenum film, chromium films were formed on substrates with film thicknesses of 3 nm and 5 nm, and other than that, samples of comparative examples were produced by the same procedure as the above-described procedure for producing the sample of the molybdenum film and gold film and the sample of only the molybdenum film. Then, the specific resistance of the gold film of the comparative example samples was also calculated using the same parallel resistance model as described above. Further, as a reference, only gold films were formed on substrates at a plurality of levels from 10 nm to 100 nm, and the specific resistance of each film was measured.

[0016] Fig. 2(A) is a characteristic diagram summarizing the tendency of the specific resistance of the gold film with respect to the thickness of the molybdenum film and the thickness of the gold film, for each of various experimental samples formed as described above using a molybdenum film, the comparative sample formed using a chromium film, and the reference sample using only a gold film. In Fig. 2(A), the broken line (Bulk Au) represents the characteristics of the reference sample. Note that, since the specific resistance of the gold film of the sample with a molybdenum film thickness of 5 nm was substantially the same as that of the sample with a molybdenum film thickness of 3 nm, the plot of the specific resistance of the sample with a molybdenum film thickness of 5 nm is omitted in Fig. 2(A). Figure 2(A) shows that using a molybdenum film as the underlying layer (adhesion layer) results in a lower resistivity of the gold film than using a chromium film. Specifically, in samples using a chromium film as the underlying layer, when the gold film thickness is 50 nm or less, the resistivity of the gold film is at least around 30 μΩcm, and can reach as high as 80 μΩcm. Furthermore, even when the gold film thickness is increased in samples using a chromium film as the underlying layer, the resistivity of the gold film is at least around 15 μΩcm. In contrast, in samples using a molybdenum film as the underlying layer, the resistivity of the gold film is less than 10 μΩcm regardless of the gold film thickness, and can be reduced to less than 5 μΩcm when the gold film thickness is 40 nm or more. The reason why using a molybdenum film as the underlying layer (adhesion layer) results in a lower resistivity of the gold film than using a chromium film is thought to be because there is virtually no diffusion of molybdenum into the gold film, thus suppressing changes in the physical properties of the gold film.

[0017] Here, considering a quartz crystal oscillator as a piezoelectric device, and taking the example of a quartz crystal oscillator with a frequency of, for example, 48 MHz, which is frequently used as a reference clock source, the thickness of the gold film is about 150 nm, and its resistivity is about 20 μΩ cm. Furthermore, it is preferable that the resistivity of the gold film included in the excitation electrode of a high-frequency quartz crystal oscillator be 20 μΩ cm or less. From this perspective, examining the characteristic diagram in Figure 2(A), the following can be said (a) to (d). (a) As mentioned above, using a molybdenum film as the underlayer (adhesion film) results in an electrode film with lower resistivity than using a chromium film. (b) When a molybdenum film is used as the underlying layer, the resistivity of the gold film can be set to 8-3 μΩcm regardless of the thickness of the gold film. Moreover, this tendency can be obtained when the thickness of the molybdenum film is 1 nm, 3 nm, or 5 nm (not shown in the illustration). (c) From the above considerations, it can be said that the thickness of the molybdenum film should be 5 nm or less. However, since the thickness of the molybdenum film should be the minimum necessary to reduce material costs and manufacturing man-hours, the thickness of the molybdenum 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. Furthermore, considering the case in which a laminated film of molybdenum film and gold film is formed by photolithography and metal etching techniques, and considering the reduction of the amount of side etching of the molybdenum film, in other words, the reduction of the gold film on the molybdenum film becoming overhanging, the thickness of the molybdenum film should be the minimum necessary, so for example, it may be 0.5 nm or more and 1 nm or less. The reason for setting the lower limit of the molybdenum film 13a thickness to 0.5 nm is that if the thickness of the molybdenum film 13a is smaller than this, it is considered that the film's structural integrity will be poor, and it will not be able to achieve the adhesion function required for the substrate as an underlying layer. (d) On the other hand, in this experiment, a gold film thickness of 10 nm to 100 nm showed reasonable resistivity. Moreover, if the gold film thickness is 20 nm or more, the resistivity of the gold film can be reduced to less than 5 μΩ cm. Since increasing the thickness of the gold film increases material costs, which is undesirable, we believe that a gold film thickness of 10 to 100 nm, preferably 10 to 70 nm, is good. Considering that the material cost of gold can be reduced, the resistivity of the gold film can be reduced to less than 5 μΩ cm, and that for high-frequency piezoelectric devices, a smaller electrode mass is desirable, we believe that a gold film thickness of 30 to 70 nm is good.

[0018] 1-2-2. Stress Analysis Next, we will examine the relationship between the thickness of the molybdenum film in the electrode structure of the present invention and the stress of the electrode structure. Figure 2(B) is a figure summarizing the experimental results of investigating the relationship between the thickness of the molybdenum film and the stress in the electrode structure of the embodiment described above, with the thickness of the gold film on the horizontal axis and the stress of the electrode structure on the vertical axis. Note that the stress of the electrode structure with a molybdenum film thickness of 5 nm was substantially the same as that of the sample with a molybdenum film thickness of 3 nm, so the plot of the stress of the electrode structure with a molybdenum film thickness of 5 nm is omitted in Figure 2(B). Also, as a comparative example, Figure 2(B) shows the results for the stress of a sample prepared in the same manner as the example, except that the lower layer was a chromium film with thicknesses of 3 nm and 5 nm. In Figure 2(B), the positive direction on the vertical axis represents tensile stress, and the negative direction represents compressive stress. In the case of a piezoelectric vibrator, if stress is present in the electrode structure, the oscillation frequency may fluctuate due to stress relaxation over time; therefore, it is preferable to have small stresses in the electrode structure. Considering the characteristic diagram in Figure 2(B) from this perspective, the following can be said. When the lower layer is a molybdenum film, the stress on the electrode structure is within the range of ±50 MPa regardless of whether the molybdenum film thickness is 1 nm, 3 nm, or 5 nm (not shown in the illustration). In contrast, when the lower layer is a chromium film, the stress on the electrode structure is greater than when the lower layer is a molybdenum film, and in particular, when the gold film thickness is 40 nm or less, the stress on the electrode structure increases to 200 MPa to 400 MPa.

[0019] Based on the above stress analysis, it can be said that the thickness of the molybdenum 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. The thickness of the gold film is preferably 10 nm to 100 nm, preferably 10 nm to 70 nm, and more preferably 30 nm to 70 nm. In the electrode structure and piezoelectric vibrator inventions, the molybdenum film thickness is very thin, ranging from a few nanometers to as little as 0.5 nm. Methods for identifying such film thicknesses include, for example, XPS depth profiling, XRR (X-ray reflectivity analysis), and cross-sectional TEM.

[0020] 2. Embodiments of Piezoelectric Devices Next, embodiments of the piezoelectric device invention will be described. Here, a quartz crystal oscillator will be described as an example of a piezoelectric device. Figure 3 is an explanatory diagram for this purpose. In particular, Figure 3(A) is a plan view of the piezoelectric device 20 of the embodiment, and Figure 3(B) is a cross-sectional view of the piezoelectric device 20 along the QQ line in Figure 3(A). In Figure 3(A), the cover member 25 provided on the piezoelectric device 20 is not shown. The quartz crystal oscillator 20, which is the piezoelectric device 20 of the embodiment, comprises a piezoelectric vibrating piece 10 according to the first invention and a container 21 that houses the piezoelectric vibrating piece 10. In this example, the container 21 comprises a rectangular recess 21a in plan view for housing the piezoelectric vibrator 10, a bank 21b surrounding the recess 21a, an adhesive pad 21c to which the piezoelectric vibrator 10 is fixedly bonded, and an external connection terminal 21d provided on the outer bottom surface of the container 21 for connecting the piezoelectric device 20 to any electronic device. The adhesive pad 21c and the external connection terminal 21d are electrically connected by via wiring or castellation (not shown). This container 21 can be made of a known ceramic package. In this case, the piezoelectric vibrator 10 has a cantilevered support structure. Therefore, the piezoelectric vibrator 10 is connected and fixed to the adhesive pad 21c of the container 21 by conductive adhesive 23 at the position of the lead electrode 15. A lid member 25 is joined to the top surface of the bank portion 21b of the container 21 in a structure corresponding to the sealing method, and the piezoelectric vibrator 10 is sealed inside the container 21.

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

[0022] 3. Examples of manufacturing methods for piezoelectric vibrating pieces and intermediate wafers for piezoelectric device formation. Next, we will describe an example of a manufacturing method for the electrode structure of the first invention and the piezoelectric vibrator of the second invention, and an embodiment of an intermediate wafer for a piezoelectric device, which is the fourth invention. Figures 4(A) to 4(D) show the main parts of the manufacturing process diagram for this purpose. Figures 4(B) and 4(C) are cross-sectional views of the wafer during the manufacturing process, and are cross-sectional views along the RR line in Figure 4(A). In this example as well, a quartz vibrator will be used as an example of a piezoelectric vibrator. First, an AT-cut quartz wafer 30 is prepared (Figure 4(A)). Next, the quartz wafer 30 is shaped for piezoelectric vibrators using known photolithography and wet etching techniques to form a wafer 30 having a number of quartz pieces 11, each connected to a frame 30a at one end (Figure 4(A)). Next, a molybdenum film 31 is formed on both sides of the quartz wafer 30, from which the quartz fragments 10 have been formed, by an arbitrarily suitable film deposition method, so that the film thickness is within the range required for the first invention, for example, a film thickness of 1 nm (Figure 4(B)). Next, a gold film 33 is formed on the molybdenum film 31 by an arbitrarily suitable film deposition method to a film thickness within the range required for the first invention, for example, a film thickness of 60 nm (Figure 4(C)). Next, the molybdenum film 31 and the gold film 33 are patterned into the shapes of the excitation electrode 13 and the extraction electrode 15 using known photolithography and metal etching techniques (Figure 4(D)). These processes enable the manufacture of piezoelectric vibrating pieces 10, and moreover, an intermediate wafer 30x for piezoelectric device formation (see Figure 4(D)) can be obtained, which has a large number of piezoelectric vibrating pieces 10 arranged in a matrix for piezoelectric device manufacturing.

[0023] Furthermore, this invention can be modified in any way that suits your needs. In the embodiment described above, the planar shape of the quartz wafer was circular, but the planar shape of the quartz wafer may be other shapes such as a square. Also, the quartz wafer is not limited to AT-cut wafers, but may be a double-rotated quartz wafer such as an SC-cut wafer. Furthermore, in the embodiments described above, the piezoelectric vibrator was a flat quartz crystal as shown in Figure 1, but the shape of the piezoelectric vibrator is not limited to this. For example, it may be a piezoelectric vibrator 40 as shown in the plan view and cross-sectional view along the SS line in Figure 5(A). That is, the piezoelectric vibrator 40 may comprise a thickened portion 41a, a vibrating portion 41b of 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. Alternatively, the piezoelectric vibrating piece 50 may be, for example, as shown in the plan view and cross-sectional view along the SS line in Figure 5(B). That is, it may comprise a vibrating portion 51a of a predetermined thickness according to the frequency, a thickened portion 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 vibrator (quartz vibrator) of the embodiment 11: Piezoelectric vibrator (quartz) 13: Electrode structure (excitation electrode) 13a: Molybdenum film 13b: Gold film 20: Piezoelectric device (quartz oscillator) of an embodiment 21: Container 23: Conductive adhesive 25: Lid component 30: Wafer (quartz wafer) 30a: Frame 31: Molybdenum film 33: Gold film 30x: Intermediate wafer for piezoelectric vibrator manufacturing

Claims

1. An electrode structure characterized by comprising a molybdenum film and a gold film laminated on the molybdenum film.

2. The electrode structure according to claim 1, characterized in that the electrode structure is composed of a molybdenum film and a gold film laminated on the molybdenum film.

3. The electrode structure according to claim 1, characterized in that the thickness of the molybdenum film is 0.5 nm or more and 5 nm or less.

4. The electrode structure according to claim 1, characterized in that the thickness of the gold film is 10 nm or more and 100 nm or less.

5. The thickness of the molybdenum film is set to be 0.5 nm or more and 5 nm or less. The electrode structure according to claim 1, characterized in that the thickness of the gold film is 10 nm or more and 100 nm or less.

6. The thickness of the molybdenum film is set to 0.5 nm or more and 3 nm or less. The electrode structure according to claim 1, characterized in that the thickness of the gold film is 30 nm or more and 70 nm or less.

7. A piezoelectric vibrating piece characterized by comprising a piezoelectric substrate, and excitation electrodes provided on the front and back surfaces of the substrate, including a molybdenum film as a lower layer and a gold film laminated on the molybdenum film.

8. The piezoelectric vibrator according to claim 7, characterized in that the excitation electrode is composed of a molybdenum film and a gold film laminated on the molybdenum film.

9. The piezoelectric vibrator according to claim 7, characterized in that the thickness of the molybdenum film is 0.5 nm or more and 5 nm or less.

10. The piezoelectric vibrating piece according to claim 7, characterized in that the thickness of the gold film is 10 nm or more and 100 nm or less.

11. The thickness of the molybdenum film is set to be 0.5 nm or more and 5 nm or less. The piezoelectric vibrating piece according to claim 7, characterized in that the thickness of the gold film is 10 nm or more and 100 nm or less.

12. The thickness of the molybdenum film is set to 0.5 nm or more and 3 nm or less. The piezoelectric vibrating piece according to claim 7, characterized in that the thickness of the gold film is 30 nm or more and 70 nm or less.

13. The piezoelectric vibrator according to claim 7, characterized in that the piezoelectric vibrator is an AT-cut quartz crystal.

14. A piezoelectric device comprising a piezoelectric vibrating piece according to any one of claims 7 to 13 and a container enclosing the piezoelectric vibrating piece.

15. The piezoelectric device according to claim 14, characterized in that the piezoelectric device is a quartz crystal resonator, a quartz crystal resonator with a temperature sensor, a quartz oscillator, or a quartz oscillator with a temperature compensation function.

16. An intermediate wafer for manufacturing piezoelectric devices, characterized by comprising a piezoelectric substrate having a large number of piezoelectric vibrating pieces arranged in a matrix according to any one of claims 7 to 13.

17. The intermediate wafer for manufacturing a piezoelectric device according to claim 16, characterized in that the piezoelectric vibrator is a quartz vibrator and the intermediate wafer is a quartz wafer.

18. The intermediate wafer for manufacturing a piezoelectric device according to claim 16, characterized in that the piezoelectric vibrator is an AT-cut quartz vibrator and the intermediate wafer is an AT-cut quartz wafer.

Images