JP5924861B2 - Surface acoustic wave device and magnetic sensor - Google Patents

Description

  The present invention relates to a surface acoustic wave device using SH waves, and more particularly to a surface acoustic wave device configured using a quartz substrate and a magnetic sensor including the surface acoustic wave device.

  Conventionally, various surface acoustic wave devices using a quartz substrate have been disclosed. For example, Patent Document 1 below discloses a surface acoustic wave device in which an IDT electrode made of Ta or W is formed on a quartz substrate. In Patent Document 1, it is said that temperature characteristics can be improved by using Ta or W as the material of the IDT electrode.

  On the other hand, the following Patent Document 2 discloses a surface acoustic wave device shown in FIGS. 19 (a) and 19 (b). The surface acoustic wave device 1001 has a piezoelectric substrate 1002. A groove is formed on the upper surface of the piezoelectric substrate 1002. An IDT electrode 1003 is formed by filling the groove with a metal. Here, the IDT electrode 1003 is thicker than the depth of the groove.

  In Example 5 of Patent Document 2, as the piezoelectric substrate, a quartz substrate having a cut angle of a rotating Y plate in the range of 100 ° to 130 ° and a quartz substrate having zero frequency temperature characteristics are used. In addition, a quartz substrate having a cut angle in the range of 100 ° to 130 ° is expressed as Euler angle (0 °, 10 ° to 40 °, 0 °) or (0 °, 190 ° to 220 °, 0 °). It is. In Example 5 of Patent Document 2, a surface acoustic wave device using the above-mentioned quartz substrate and using a pseudo surface acoustic wave of a branch is disclosed. This pseudo surface acoustic wave is not described as an SH wave in Patent Document 2.

  Moreover, in Example 5 of patent document 2, it does not specify about the metal material which comprises an IDT electrode. Example 7 of Patent Document 2 shows an aluminum thin film, a copper thin film, a tungsten thin film, a titanium thin film, and a laminated metal film composed of a combination of an aluminum thin film and a thin film such as copper, titanium, or chromium.

JP-A-10-233645 JP 2006-270906 A

  Although the surface acoustic wave device described in Patent Document 1 uses SH waves, Ta or W having a high density is used as an IDT electrode constituent material. Therefore, there has been a problem that the electrical resistance loss is larger than that of Al and the phase velocity is greatly reduced. There is also a problem that the frequency fluctuation due to the film thickness fluctuation of the IDT electrode is large.

On the other hand, Example 5 of Patent Document 2 discloses a structure in which a groove is formed on the surface of a piezoelectric substrate 1002 made of a quartz substrate having the specific Euler angle and zero frequency temperature characteristics. An IDT electrode is formed by filling the groove with a metal. Although it has been shown that such a structure can improve the frequency-temperature characteristics and increase the electromechanical coupling coefficient, the surface wave used is a quasi-surface acoustic wave. The pseudo surface acoustic wave is not necessarily an SH wave. Patent Document 2 does not disclose a surface acoustic wave device using SH waves. For this reason, there is a problem that a practical surface acoustic wave device having a sufficiently high reflection coefficient cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is a surface acoustic wave device using SH waves, which has a low electrical resistance loss despite the fact that an IDT electrode is formed using a metal having a density higher than that of aluminum. A surface acoustic wave device capable of obtaining a large electromechanical coupling coefficient k ² even when the film thickness is increased and a reflection coefficient being sufficiently large, and a magnetic field using the surface acoustic wave device It is to provide a sensor.

  The surface acoustic wave device according to the present invention includes a quartz crystal substrate having an upper surface and a lower surface, and a groove formed on the upper surface, and a first metal layer filled in the groove. This is a surface acoustic wave device using an SH wave using an IDT electrode made of a metal having a higher density than aluminum.

In a specific aspect of the surface acoustic wave device according to the present invention, the IDT electrode is stacked on the first metal layer filled in the groove, and is positioned outside the groove. Two metal layers are further provided. In this case, the reflection coefficient can be increased.

  The first metal layer and the second metal layer may be formed of the same metal or different metals.

In the surface acoustic wave device according to the present invention, preferably, the Euler angle of the quartz crystal substrate is in a range of (0 °, 110 ° to 170 °, 90 ° ± 5 °). In this case, it is possible to increase the electromechanical coupling coefficient k ² further.

In another specific aspect of the surface acoustic wave device according to the present invention, the first metal layer is at least one metal selected from the group consisting of Ni, Ag, Pt, Au, Ta, and Mo, or the metal It consists of an alloy mainly composed of or a layer in which a plurality of these metals are laminated. In this case, the electromechanical coupling coefficient k ² can be reliably enhanced, and it is possible to reduce the electric resistance loss effectively.

In still another specific aspect of the surface acoustic wave device according to the present invention, the first metal layer is made of Cu, W, an alloy mainly containing these, or a layer in which a plurality of these metals are laminated. In this case, the electromechanical coupling coefficient k ² it is possible to effectively improve, and the electrical resistance loss can be reliably reduced.

  The magnetic sensor according to the present invention is composed of a surface acoustic wave device constructed according to the present invention, and the metal constituting the IDT electrode is composed of Ni or an alloy mainly composed of Ni. Since the surface acoustic wave device of the present invention is used, the sensitivity can be effectively increased in the magnetic sensor of the present invention.

  In a specific aspect of the magnetic sensor according to the present invention, the magnetic sensor further includes a pair of reflectors disposed on both sides of the surface acoustic wave propagation direction of the IDT electrode.

According to the present invention, since the first metal layer having a density higher than that of aluminum is formed in the groove on the upper surface of the quartz substrate, and the IDT electrode has the first metal layer, the SH wave is used. when the electromechanical coefficient k ² can be increased, it is possible to further reflection coefficient obtaining sufficient size. In addition, even though a metal having a higher density than aluminum is used, the electrical resistance loss can be reduced.

(A) is a typical front sectional view of a surface acoustic wave device concerning one embodiment of the present invention, and (b) is a top view showing typically an electrode structure of the surface acoustic wave device. It is a figure which shows the relationship between the electrode film thickness and the electromechanical coupling coefficient in the 1st and 2nd structural examples as an embodiment and an comparative example whose IDT electrode consists of Ni. It is a figure which shows the relationship between the electrode film thickness and reflection coefficient in the 1st and 2nd structural example as embodiment whose IDT electrode consists of Ni. It is a figure which shows the relationship between the electrode film thickness of the surface acoustic wave apparatus of the 1st and 2nd structural example which an IDT electrode consists of Ag, and a comparative example, and an electromechanical coupling coefficient. It is a figure which shows the relationship between the electrode film thickness of the surface acoustic wave apparatus of the 1st and 2nd structural example which IDT electrode consists of Ag, and a reflection coefficient. It is a figure which shows the relationship between the electrode film thickness and the electromechanical coupling coefficient of the surface acoustic wave apparatus of the 1st and 2nd structural example whose IDT electrode consists of Cu, and a comparative example. It is a figure which shows the relationship between the electrode film thickness of the surface acoustic wave apparatus of the 1st and 2nd structural example whose IDT electrode consists of Cu, and a reflection coefficient. It is a figure which shows the relationship between the electrode film thickness and the electromechanical coupling coefficient of the surface acoustic wave apparatus of the 1st and 2nd structural example and ID which a IDT electrode consists of Pt. It is a figure which shows the relationship between the electrode film thickness of the surface acoustic wave apparatus of the 1st and 2nd structural example whose IDT electrode consists of Pt, and a reflection coefficient. It is a figure which shows the relationship between the electrode film thickness of the surface acoustic wave apparatus of the 1st and 2nd structural example and ID which a IDT electrode consists of Au, and an electromechanical coupling coefficient. It is a figure which shows the relationship between the electrode film thickness of the surface acoustic wave apparatus of the 1st and 2nd structural example which IDT electrode consists of Au, and a reflection coefficient. It is a figure which shows the relationship between the film thickness of the Al film | membrane in the surface acoustic wave apparatus of embodiment which a 1st metal layer consists of Ni, and a 2nd metal layer consists of Al, and an electromechanical coupling coefficient. It is a figure which shows the relationship between the film thickness of the Al film | membrane in the surface acoustic wave apparatus of embodiment which a 1st metal layer consists of Ni, and a 2nd metal layer consists of Al, and a reflection coefficient. It is a figure which shows the relationship between (theta) of Euler angles in a quartz substrate of Euler angles (0 degree, (theta), 90 degrees), and an electromechanical coupling coefficient. It is a figure which shows the relationship between (theta) of Euler angles in the quartz substrate of Euler angles (0 degree, (theta), 90 degrees), and frequency temperature coefficient TCF. (A) is a figure which shows the relationship between the intensity | strength of an external magnetic field, and the amount of frequency changes in the magnetic sensor of embodiment which the 1st and 2nd metal layer which comprises an IDT electrode consists of 0.03 (lambda) Ni. (B) is a typical perspective view for demonstrating the X-axis, Y-axis, and Z-axis in (a). It is a figure which shows the relationship between the intensity | strength of the magnetic field applied in the magnetic sensor of the comparative example which has the IDT electrode which consists of Ni on the quartz substrate upper surface, and the amount of frequency changes. It is a figure which shows the relationship between the intensity | strength of the magnetic field applied in the magnetic sensor of embodiment which has a 1st metal layer which consists of 0.04 (lambda) Ni, and a frequency variation. (A) And (b) is a typical top view and typical front sectional view for explaining an example of the conventional surface acoustic wave device.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

The surface acoustic wave device 1 is a surface acoustic wave device using SH waves. The surface acoustic wave device 1 has a quartz substrate 2. A plurality of grooves 2 a are formed on the upper surface of the crystal substrate 2. The groove 2a is filled with a metal layer. In the present embodiment, the metal layer has a first metal layer 3a filled in the groove 2a and a second metal layer 3b stacked on the first metal layer 3a. Thereby, the electrode structure shown in FIG. 1B is formed. This electrode structure includes an IDT electrode 4 and reflectors 5 and 6 disposed on both sides of the IDT electrode 4 in the surface acoustic wave propagation direction.

  In the present embodiment, the first and second metal layers 3a and 3b are stacked, but the second metal layer 3b may not be provided.

  The first metal layer 3a and the second metal layer 3b may be made of the same metal or may be made of another metal. However, the first metal layer 3a is made of a metal having a density higher than that of aluminum.

  As such a metal, Ni, Ag, Pt, Au, Ta, Mo, or an alloy mainly composed of these can be used. A plurality of these metals may be laminated. The main alloy is an alloy having a metal content exceeding 50% by weight. The metal layer 3a may be formed by stacking Cu or W, an alloy mainly composed of these, or these metals.

In the surface acoustic wave device 1, since the IDT electrode 4 is formed by filling the groove 2a of the quartz substrate 2 with a metal, the electrical resistance loss is reduced despite using a metal having a density higher than that of Al. It can be reduced and a large electromechanical coupling coefficient k ² can be obtained. This will be described with reference to FIGS.

FIG. 2 shows the relationship between the electrode film thickness and the electromechanical coupling coefficient k ² when a crystal substrate with Euler angles (0 °, 127 °, 90 °) is used and Ni is used as the material constituting the IDT electrode. FIG. 3 is a diagram showing the relationship between the electrode film thickness and the reflection coefficient. 2 to 13 is a normalized film thickness obtained by normalizing the thickness H by λ, where λ is the wavelength of the surface acoustic wave.

  FIG. 2 shows a first structure example in which the groove 2a is filled with the first metal layer 3a. As shown in FIG. 1A, the second metal layer 3b is formed on the first metal layer 3a. Are stacked, and the electrodes are formed by forming a Ni film on the upper surface of the second structural example, each of which is made of Ni, a quartz substrate prepared for comparison, in particular, a quartz substrate without grooves. The result of the 1st comparative example which formed was shown. The first structure example and the second structure example correspond to embodiments of the present invention.

As is apparent from FIGS. 2 and 3, when a crystal substrate with Euler angles (0 °, 127 °, 90 °) is used, in the first comparative example, the thickness of the electrode made of Ni is 0.022λ. electromechanical coupling coefficient k ² is the largest value. In contrast, in the first structure example, the electromechanical coupling coefficient k ² becomes the maximum value when the electrode thickness is 0.042Ramuda, in the second structure example, the electric machine when the electrode thickness is 0.034λ coupling coefficient k ² is the maximum value. Accordingly, when the surface acoustic wave device having the same electromechanical coupling coefficient k ² is obtained, that is, when obtaining the surface acoustic wave device having the highest electromechanical coupling coefficient, the electrode films according to the first and second structural examples are compared with the first comparative example. It can be seen that the thickness can be 1.5 times to 1.9 times.

  Therefore, the electrical resistance loss due to the electrodes can be reduced to 2/3 to 1/2 times according to the first and second structural examples as compared with the first comparative example. Therefore, it can be seen that since the electrical resistance loss can be reduced, a high-Q resonator and a low-loss surface acoustic wave filter can be provided.

In addition, as shown in FIG. 2, in the range of the electrode thickness of 0.027λ or more and 0.16λ, that is, in the wide electrode thickness range, the first and second structural examples have electromechanical coupling compared to the first comparative example. it can be seen that may enhance the coefficient k ^2. In particular, in this wide thickness range, according to the structure of the first and the body 2, the electromechanical coefficient k ² can be seen also be obtained as high as 0.0025 or more. Therefore, even when the lower electrical resistance losses by increasing the electrode thickness, the electromechanical coupling coefficient k ² can be increased as 0.0025 or more. More specifically, in the first structure example, the electrode film thickness, more 0.015Ramuda, within the scope of the following 0.16Ramuda, the electromechanical coupling coefficient ^{k 2} can be 0.0025 or more, the the second structure example, in the range of 0.014Ramuda～0.16Ramuda, the electromechanical coupling coefficient ^{k 2} can be as high as 0.0025 or more.

Moreover, as is clear from FIG. 3, in such electromechanical coupling coefficient k ² of the electrode thickness range that can be 0.0025 or more, in both the first and second structure example, the reflection coefficient 0. It can be seen that it is sufficiently high as 15 or more.

  Therefore, the electrode thickness is preferably in the range of 0.015λ to 0.16λ in the first structural example, and in the range of 0.014λ to 0.16λ in the second structural example.

Therefore, according to the first and second structure example, a wide electrode thickness range, it is possible to obtain a large electromechanical coupling coefficient k ² and a high reflection coefficient.

4 and 5, the electromechanical coefficient k ² and the reflection coefficient of the surface acoustic wave device of the first and second structure example and a first comparative example obtained by changing the metal of Ni to Ag electrode It is a figure which shows film thickness dependence.

As apparent from FIGS. 4 and 5, in the surface acoustic wave device in which the IDT electrode made of Ag is formed, the electrode thickness is in the range of 0.003λ to 0.095λ in the first structural example, and the second structure. if the range of 0.003λ~0.09λ in the example, the electromechanical coefficient ^{k 2} can be increased to about as high as 0.0025 or more. Also in this case, compared to the structure of the first comparative example, a wide thickness range, it can be seen that obtain a large electromechanical coupling coefficient k ^2. Further, when an IDT electrode made of Ag is formed, as shown in FIG. 5, the first structural example has a range of 0.015λ to 0.16λ, and the second structural example has a range of 0.01λ to 0.16λ. In this range, it can be seen that the reflection coefficient is sufficiently high at 0.1 or more.

Therefore, even when an IDT electrode made of Ag is used, according to the first structure example, ie, a structure in which an Ag film is formed as the first metal layer 3a in the groove 2a, the electrode film thickness is increased. However, it can be seen that a large electromechanical coupling coefficient k ² and a sufficiently large reflection coefficient can be realized.

According to the first structure example, as shown in FIG. 4, even when the film thickness of the electrode is 0.02λ or less, that is, when the film thickness is as thin as 0.003λ or more and 0.02λ or less. It can be seen that an extremely high electromechanical coupling coefficient can be realized as compared with the first comparative example. In addition, it can be seen that if the electrode film thickness is 0.035λ or more, the first structural example shows a higher electromechanical coupling coefficient k ² than the first comparative example. Therefore, in the first structural example which is an embodiment of the present invention, the thickness of the IDT electrode made of Ag is within the range of 0.003λ to 0.02λ or 0.03λ to 0.095λ, and the second structural example. Then, if it is in the range of 0.003λ to 0.017λ or 0.032λ to 0.09λ, an electromechanical coupling coefficient larger than that of the first comparative example and higher than 0.0025 can be obtained.

6 and 7 show the electromechanical coupling coefficient k ^{2 of} the first and second structural examples and the first comparative example configured in the same manner as described above except that the IDT electrode is changed to Cu. The electrode thickness dependence of the reflection coefficient is shown.

As is apparent from FIGS. 6 and 7, when an electrode made of Cu is formed, the first structural example has a range of 0.015λ to 0.14λ, and the second structural example has a range of 0.012λ to Within the range of 0.125λ, the electromechanical coupling coefficient k ² can be increased to 0.0025 or more. In particular, the first structure example has a higher electromechanical coupling than the first comparative example within the range of 0.034λ or more and 0.16λ, and the second structure example within the range of 0.027λ or more and 0.16λ. it is possible to obtain the coefficients ^{k 2.}

  On the other hand, as is apparent from FIG. 7, the reflection film thickness is 0.02λ or more in the first structure example, 0.01λ or more in the second structure example, and 0.16λ in the second structure example. It can be seen that it is a practical size of 0.07 or more.

Therefore, when a Cu film is used, the electrode thickness is preferably in the range of 0.015λ to 0.14λ, whereby a large electromechanical coupling coefficient k ² and a large reflection coefficient can be obtained.

8 and 9 show the electromechanical coupling coefficient k ^{2 of} the first and second structural examples and the first comparative example configured in the same manner as described above except that the IDT electrode is changed to Pt. The electrode thickness dependence of the reflection coefficient is shown.

As is apparent from FIGS. 8 and 9, when an electrode made of Pt is formed, the first structure example has a wide range of 0.016λ or more, and the second structure example has a range of 0.012λ or more and 0.16λ, An electromechanical coupling coefficient k ² higher than that of the first comparative example can be obtained. In the first structural example, in the range of 0.007Ramuda～0.055Ramuda, in the second structure example, in the range of 0.007Ramuda～0.052Ramuda, the electromechanical coupling coefficient ^{k 2} 0.0025 or more And can be high.

  On the other hand, as can be seen from FIG. 9, the reflection coefficient is 0.07 or more and a practical size within a wide range of 0.005λ or more and 0.16λ.

Therefore, in the case of using a Pt film, electrode thickness is preferably in the range of 0.007Ramuda～0.055Ramuda, it can thereby obtain a large electromechanical coupling coefficient ^{k 2} and large reflection coefficient.

10 and 11 show the electromechanical coupling coefficient k ^{2 of} the first and second structural examples and the first comparative example configured in the same manner as described above except that the IDT electrode is changed to Au. The electrode thickness dependence of the reflection coefficient is shown.

As is apparent from FIGS. 10 and 11, when an electrode made of Au is formed, the first structural example has a range of 0.013λ or more, the second structural example has a range of 0.011λ or more, and 0.16λ, An electromechanical coupling coefficient k ² higher than that of the first comparative example can be obtained. In the first structural example, in the range of 0.0025Ramuda～0.045Ramuda, in the second structure example within the 0.0025Ramuda～0.042Ramuda, the electromechanical coupling coefficient ^{k 2} 0.0025 or more and Can be high.

  On the other hand, as is apparent from FIG. 11, the reflection coefficient is 0.07 or more and a practical size within a wide range of 0.007λ or more and 0.16λ.

Therefore, when an Au film is used, the electrode thickness is preferably in the range of 0.007λ to 0.045λ, whereby a large electromechanical coupling coefficient k ² and a large reflection coefficient can be obtained.

2 to 11, each case of Ni, Ag, Cu, Pt, and Au has been described as the electrode constituent metal. However, in the case of Mo, in the first structure example, the electrode film thickness is the same as Cu. the if 0.012Ramuda～0.14Ramuda, the electromechanical coupling coefficient ^{k 2} is 0.0025 or more, the reflection coefficient can be 0.07 or more. Similarly, in the case of Ta or W, in the first structural example, as in the case of Au, the electromechanical coupling coefficient k ^{2 is set} to 0.0025 or more if the range is 0.0025λ to 0.045λ. It has been confirmed that the reflection coefficient can be 0.07 or more.

FIGS. 12 and 13 show the second structure example described above, that is, the embodiment shown in FIG. 1A, in which the first metal layer 3a is formed of Ni and is located above the groove 2a. the second metal layer 3b is a diagram showing the relationship between the thickness and the reflection coefficient of the relationship and the Al film of the thickness and the electromechanical coupling coefficient k ² of the Al film of the surface acoustic wave device obtained by forming a Al. Here, a 0.04λ Ni film is formed as the first metal layer 3a.

  The results when the film thickness of the Al film in FIGS. 12 and 13 is 0 correspond to the case where the film thickness of the Ni film of the first structural example in FIGS. 2 and 3 is 0.04λ. That is, in the first structural example having no second metal layer described above, the numerical value when the thickness of the first metal layer in the groove is made of Ni having a thickness of 0.04λ is Al in FIGS. This corresponds to the result when the film thickness = 0.

As is clear from FIG. 12, in the structure in which the Al film is formed as the second metal layer with various thicknesses on the first metal layer made of Ni, the thickness of the Al film is larger than 0. in 0.098λ within the following range, the electromechanical coupling coefficient ^{k 2} becomes sufficiently large and 0.0025 or more. Further, as apparent from FIG. 13, it can be seen that the reflection coefficient can be further increased as the thickness of the Al film exceeds 0 and the film thickness increases. That is, as apparent from FIG. 13, the reflection coefficient is higher than that in the case where the Al film is not formed, and it can be seen that the reflection coefficient increases as the thickness of the Al film increases. Therefore, a surface acoustic wave device having a larger electromechanical coupling coefficient and a larger reflection coefficient can be obtained.

  As described above, in the structure in which the second metal layer 3b is formed on the first metal layer 3a, the reflection coefficient can be significantly increased due to the presence of the second metal layer 3b. Note that such an increase in the reflection coefficient is provided so that the second metal layer 3b protrudes from the upper surface of the quartz substrate 2, and therefore, not only Al but other metals are used. The same effect can be obtained. That is, even when the second metal layer 3b is formed by using the above-described Ni, Ag, Pt, Au, Ta, Mo, Cu or W or an alloy mainly composed of these, the reflection coefficient can be effectively reduced in the same manner. Can be increased.

Further, in FIGS. 12 and 13, had a 0.04 the thickness of the first metal layer 3a made of Ni, except 0.04, that is, the electromechanical coupling coefficient ^{k 2} shown in FIGS. 2 and 3 0 As long as the film thickness is in the range of 0.015λ to 0.16λ of the first structural example capable of obtaining a value of .0025 or more, the second metal layer 3b is the same as in the case of FIGS. by laminating, an electromechanical coupling coefficient ^{k 2} is 0.0025 or more, and the reflection coefficient can be increased to 0.15 or more.

Furthermore, the first metal layer 3a may be made of the aforementioned metal other than Ni, that is, Ag, Pt, Au, Ta, Mo, Cu, W, or an alloy mainly composed of these metals. Also in this case, as in the case of FIGS. 12 and 13, electromechanical coupling coefficient ^{k 2} 0.0025 or more, it has been verified that the reflection coefficient can be 0.07 or more.

FIG. 14 is a diagram showing the relationship between θ and the electromechanical coupling coefficient k ² in a quartz substrate with Euler angles (0 °, θ, 90 °), and FIG. 15 shows the relationship between θ and the frequency temperature coefficient TCF. FIG.

14 and 15 show characteristics of the Euler angle quartz crystal substrate in which no electrode is formed. As described above, although the electromechanical coupling coefficient k ² by the formation of the IDT electrode is increased, does not so change as 15 even when the frequency temperature coefficient TCF is formed with electrode. As can be seen from FIG. 15, when the Euler angle θ is in the range of 110 ° to 170 °, the absolute value of the frequency temperature coefficient TCF can be reduced to 100 ppm / ° C. or less without lowering the electromechanical coupling coefficient. Recognize. Therefore, in order to obtain a surface acoustic wave device having a large electromechanical coupling coefficient k ² , a large reflection coefficient, and a better frequency temperature characteristic, the Euler angle θ should be in the range of 110 ° to 170 °. I understand that.

  14 and 15, the Euler angle ψ is 90 °. However, if the Euler angle ψ is in the range of 90 ° ± 5 °, that is, in the range of 85 ° to 95 °, FIG. Results similar to those in FIG. 15 are obtained. Accordingly, the Euler angle θ is preferably in the range of (0 °, 110 ° to 170 °, 85 ° to 95 °).

  The surface acoustic wave device of the present invention can be suitably used as a magnetic sensor by using Ni, which is a ferromagnetic material, as an electrode material.

  That is, the surface acoustic wave device 1 shown in FIGS. 1A and 1B can be used as it is as a magnetic sensor. When a magnetic field is applied to the surface acoustic wave device 1, the SH wave excited by Ni that is a ferromagnetic material is affected by the magnetic field, and the frequency changes. The magnitude of the magnetic field applied by this amount of frequency change can be measured.

  FIG. 16A is a diagram illustrating characteristics of a magnetic sensor including the surface acoustic wave device of the second structural example described above. That is, in the surface acoustic wave device 1 in which the first metal layer 3a is filled in the groove and the second metal layer 3b is stacked, the first and second metal layers 3a and 3b are Was also formed of Ni. The thickness of the entire electrode was 0.03λ. In addition, the X-axis, Y-axis, and Z-axis in FIG. 16A show the results when a magnetic field is applied in the X-axis, Y-axis, and Z-axis directions schematically shown in FIG.

  For comparison, FIG. 17 shows changes in magnetic field strength and frequency when a surface acoustic wave device in which a Ni film having a thickness of 0.02λ is formed as an electrode in the first comparative example described above is used as a magnetic sensor. The relationship with quantity is shown.

  FIG. 18 shows a magnetic field in the case of a magnetic sensor composed of a surface acoustic wave device in which the thickness of the first metal layer 3a made of Ni is 0.04λ in the surface acoustic wave device of the first structural example described above. The relationship between the intensity and frequency variation is shown.

  Compared to the case of the first comparative example shown in FIG. 17, it can be seen that in both FIGS. 16A and 18, the amount of frequency change when a magnetic field is applied can be increased. In particular, it can be seen that even when the magnetic field strength is as small as 1000 Oe or less, the amount of frequency change can be increased, and thus the sensitivity of the magnetic sensor can be effectively increased.

  When used as a magnetic sensor, the metal constituting the electrode is not limited to Ni, but may be an alloy mainly composed of Ni.

Further, as described above, the present invention uses an IDT electrode made of a metal having a density higher than that of the aluminum, which has a groove formed on the upper surface of the quartz substrate and is filled in the groove, and uses SH waves. Therefore, the structure of the IDT electrode is not limited to the one-port resonator structure shown in FIG.

DESCRIPTION OF SYMBOLS 1 ... Surface acoustic wave apparatus 2 ... Quartz substrate 2a ... Groove 3a ... 1st metal layer 3b ... 2nd metal layer 4 ... IDT electrode 5, 6 ... Reflector

Claims (6)

A quartz substrate having an upper surface and a lower surface, grooves formed on the upper surface, and Euler angles (0 °, 127 °, 90 °) ;
A first metal layer filled in the groove, the first metal layer comprising an IDT electrode made of a metal having a density higher than that of aluminum, and utilizing SH waves;
When the wavelength of the SH wave is λ, the film thickness (λ) of the first metal layer is shown in Table 1 below according to the type of metal constituting the first metal layer. A surface acoustic wave device that is one of the combinations.

A quartz substrate having an upper surface and a lower surface, with grooves formed on the upper surface and having Euler angles of (0 °, 127 °, 90 °) ;
A first metal layer filled in the groove, the first metal layer comprising an IDT electrode made of a metal having a density higher than that of aluminum, and utilizing SH waves;
A second metal layer laminated on the first metal layer and positioned outside the groove;
When the wavelength of the SH wave is λ, the first metal layer and the second metal layer are formed according to the metal constituting the first metal layer and the metal constituting the second metal layer. A surface acoustic wave device in which the film thickness (λ) is one of the combinations shown in Table 2 below.

  The surface acoustic wave device according to claim 2, wherein the first metal layer and the second metal layer are made of the same metal.   The surface acoustic wave device according to claim 2, wherein the first metal layer and the second metal layer are made of different metals.   5. A magnetic sensor comprising the surface acoustic wave device according to claim 1, wherein the metal constituting the IDT electrode is made of Ni or an alloy mainly composed of Ni.   The magnetic sensor according to claim 5, further comprising a pair of reflectors disposed on both sides of the IDT electrode in the surface acoustic wave propagation direction.

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