JPH06132777A - Surface acoustic wave device and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an aluminum electrode that makes the frequency change of a surface acoustic wave element extremely small, and to provide a method for easily manufacturing the surface acoustic wave element. [Structure] An electrode made of an aluminum single crystal film is provided on an LST-cut quartz substrate. In addition, a film is formed on the single crystal piezoelectric substrate at a low film forming speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device used in mobile communication devices such as paging systems and cordless phones, general wireless communication systems, and devices such as TVs and VTRs, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An electrode of a conventional surface acoustic wave element has a polycrystalline structure of a metal such as aluminum or gold. In particular, when an aluminum film was used, a trace amount of copper, titanium, palladium, etc. was added, but it was still a polycrystalline structure. In addition, JP-A-3-14305 and JP-A-3-14305
-14307, JP-A-3-14308, JP-A-3-14
As described in Japanese Patent Publication No. 309, there has been proposed a method of using an aluminum film by orienting it in a constant crystallographic direction. Further, as described in Japanese Patent Laid-Open No. 55-49014, a method has been proposed in which an electrode is formed into a substantially single crystal.

These conventional techniques have been developed in order to reduce the frequency change in the surface acoustic wave element and to improve the power withstanding performance of the surface acoustic wave element. By the way, the frequency change of the surface acoustic wave element and the deterioration of the electric power performance are caused by the migration of the aluminum electrode generated during the operation of the element. This fact was already reported at the Ultrasonic Symposium in 1981.

Further, in semiconductors as well, disconnection caused by aluminum migration has been studied for a long time as electromigration. 1970
It was reported that a single crystal film of aluminum was very excellent for electromigration in 2010.

Therefore, the authors have proposed a Japanese Patent Application No. 4-1 in order to improve the migration resistance of the surface acoustic wave device.
In Japanese Patent Publication No. 84979, it was proposed that an aluminum electrode be a single crystal film in a surface acoustic wave device formed on a quartz substrate, and a manufacturing method thereof was also proposed. Japanese Patent Application 4-18
According to Japanese Patent No. 4979, an aluminum single crystal film can be easily manufactured by forming a minute island structure on the surface of a piezoelectric body.

[0006]

The problems of the prior art will be described below. First, in a polycrystalline aluminum film, stress is generated on the substrate surface due to surface acoustic waves during operation as a surface acoustic wave element, and the generated stress causes crystals such as aluminum to move, resulting in changes in the stress of the electrodes. There is a problem that the frequency of the element changes greatly.
There is a method of adding a trace amount of copper or another metal to reduce this change, but it has the same problem that the frequency changes in the long term. Further, the addition of a trace amount of metal has a problem that it is difficult to keep the composition ratio stable in the manufacturing process.

In the case of a more oriented aluminum electrode, according to the experiments by the authors, when a particular crystal plane is oriented in a certain direction but the orientation of the other plane is disturbed, the crystal is caused by stress during operation. There is a problem that grain boundary movement occurs and frequency changes over time. For example, when the (200) plane, (220) plane, and (311) plane of aluminum are not oriented and only the (111) plane is oriented in a certain direction, or the (200) plane, (111) plane, etc. Is oriented in a certain direction, but the orientation of the (220) plane is disturbed. That is, there is a problem that it is difficult to suppress the change in frequency simply by orienting a certain crystal plane in a certain direction.

In order to reduce the time-dependent change in frequency due to the stress during operation, it is beneficial to use a single crystal film for the electrodes. However, in the prior art, JP-A-55-4
As described in Japanese Patent Publication No. 9014, only almost monocrystalline film is obtained, and in order to obtain this almost monocrystalline film, it is necessary to use the molecular beam epitaxy method, and the apparatus is very expensive. Further, there is a problem that the single crystal electrode film cannot be easily obtained due to the problem that the production amount by this device is very small.

According to Japanese Patent Application No. 4-184979, an aluminum single crystal film is formed on a 33 ° ST cut quartz substrate and a 9.5 ° LST cut quartz substrate. Furthermore, by forming the surface of the piezoelectric substrate into a fine island structure, an aluminum single crystal is easily formed by the conventional vapor deposition method or sputtering method. However, the island-shaped structure cannot be formed on all piezoelectric substrates, and there is a problem in that a method for stably forming an aluminum film on a substrate having high flatness without the island-shaped structure is not provided. Was there. LS with excellent flatness
A T-cut substrate, a lithium niobate substrate, a lithium tantalate substrate, and the like have a problem that it is difficult to form the island-shaped structure on the surface of the substrate and an aluminum single crystal film cannot be stably formed.

An object of the present invention is to eliminate the stress change inside the metal film for an electrode in the surface acoustic wave element and to reduce the frequency change during the operation of the element. In particular, an LST cut quartz substrate, a lithium niobate substrate, It is to reduce the frequency change of a surface acoustic wave device using a lithium tantalate substrate. Another object is to provide a method for easily manufacturing the surface acoustic wave device.

[0011]

The surface acoustic wave device having a small frequency change as described above is achieved by forming the aluminum electrode constituting the surface acoustic wave device as a single crystal film. The aluminum single crystal film is formed on a single crystal piezoelectric substrate, but by forming the aluminum single crystal film at a low rate of 25 angstroms per second or less, the aluminum single crystal film can be formed by vapor deposition or sputtering. Can be easily manufactured.

[0012]

As described above, the aluminum electrode of the surface acoustic wave device moves aluminum crystals due to the vibration of the surface acoustic wave generated on the substrate surface during operation, resulting in a change in stress inside the electrode and a frequency change. . According to known techniques, it is considered that the movement of the aluminum crystal occurs so that the surface free energy of the crystal grain boundary of the aluminum crystal is minimized. Therefore, basically, in the case of a single crystal film having no grain boundary, this grain boundary movement does not occur, and as a result, the frequency change of the surface acoustic wave element can be made extremely small.

Further, in Japanese Patent Application No. 4-184979, the authors filed an application of forming an island-shaped structure on the surface of a single crystal substrate as a method for obtaining the aluminum single crystal film. After that, the investigation is continued, and in the case of the LST-cut quartz substrate or the like in which the island structure is hard to be obtained, the aluminum single crystal film can be stably formed by slowing down the film formation rate of the aluminum film as shown in the present application. It turned out to be possible.

[0014]

EXAMPLES Example 1 The present invention will be described in detail below with reference to examples. First, the substrate and aluminum for film formation used in this example will be described. Next, the film forming process in this example will be described, and the properties of the metal film produced in this example and the frequency change characteristics of the surface acoustic wave device formed using the metal film will be described.

First, the substrate used in this embodiment is an LST obtained by rotating the Z plate counterclockwise about the X axis by 9.5 degrees.
It is a cut crystal substrate. Hereinafter, this will be simply referred to as an LST cut crystal substrate. The substrate is obtained by cutting an artificially synthesized single-crystal quartz block with a blade saw, a wire saw, or the like, and then polishing both sides. Polishing is performed by lapping to a predetermined thickness, and then the surface is polished. Polishing is a process of completely removing the work-affected layer on the surface of the quartz substrate caused by lapping with cerium oxide abrasive grains or the like to finish it into a mirror surface. Then, finally, the work-affected layer on the surface of the quartz substrate, which is generated by polishing, is removed and stress is released, and etching processing for finishing into an island structure as described later is performed.

In the etching process, the surface of the quartz substrate is etched by about 0.1 to 2 microns by immersing it in an etching solution such as a mixed solution of hydrofluoric acid or ammonium fluoride. As an example, a mixed solution of hydrofluoric acid and ammonium fluoride is used as an etching solution, and the surface of the LST-cut quartz substrate is etched on one side by about 0.2 to 1 micron at a liquid temperature of about 20 to 40 degrees Celsius. The surface roughness of the LST cut quartz crystal substrate in this state is about 0.002 micron or less in terms of root mean square roughness and about 0.02 micron or less in terms of maximum roughness, and a surface having good flatness is obtained.
The surface roughness is measured with a stylus type surface roughness meter. This surface roughness is a very small value as compared with the conventional ST-cut quartz substrate. The surface roughness of the conventional ST-cut quartz substrate was about 0.005 micron in root mean square roughness and about 0.1 micron in maximum roughness.

A mixed solution of hydrofluoric acid and ammonium fluoride is
A 47% hydrofluoric acid and 40% ammonium fluoride solution having a volume ratio of 1 to 3 to 3: 1 was used, but the concentration is not particularly limited. Further, these liquids can be used alone or by adding other components.

The aluminum used for film formation has a purity of 99.999% (hereinafter referred to as 5N).

Next, the step of forming the aluminum single crystal film will be described. In this embodiment, film formation is performed by vapor deposition and sputtering. First, the film forming process of the aluminum single crystal film by the vapor deposition method will be described. The LST cut quartz crystal substrate for which the substrate manufacturing process has been completed is attached to a substrate holding jig called a planetary, and the planetary is attached to a vacuum container called a chamber. Then, the chamber is evacuated. Substrate heating is started when the pressure in the chamber becomes small to some extent. The substrate heating temperature in this embodiment is about 140 degrees Celsius.

In this state, the pressure is reduced to 0.5 microtricelli. At this time, the water pressure in the chamber is about 0.03 microtricelli. Then, vapor deposition of aluminum is started at this pressure. The deposition rate is about 15 angstroms per second. The pressure during vapor deposition is about 2 to 4 microtricelli. After vapor deposition of a predetermined film thickness, the vapor deposition is stopped, the chamber is cooled to room temperature, the substrate is taken out, and the vapor deposition step is completed.

The above is the description of the vapor deposition process of the aluminum film on the LST-cut quartz substrate. However, the vapor deposition conditions are not limited to these. The board cutting angle is also 9
The surface acoustic wave element is not limited to a degree, but is commonly used for a surface acoustic wave element at about 7 degrees to 15 degrees. The substrate heating temperature can be from room temperature (about 20 degrees Celsius) to about 200 degrees Celsius. Further, the pressure before vapor deposition may be about 5 microtricelli. Further, in the present embodiment, the vapor deposition was carried out by the electron beam heating method, but the resistance heating method can also be used. In addition to the above, vapor deposition conditions are possible.

Next, the film forming process of the aluminum single crystal film by the sputtering method will be described. The sputtering device is a parallel plate type magnetron system. The sputtering power source is a direct current type. First, the substrate is mounted in a vacuum container called a chamber, and the pressure is reduced to 0.5 microtricelli. Although the substrate is not heated in this embodiment, it may be heated for the purpose of removing substrate contamination. When the pressure is reduced to the above pressure, an inert gas for sputtering is introduced. In this embodiment, argon is used. Then, discharge is started. The pressure of the argon during discharge is about 6 millitrichery. The deposition rate for sputtering is about 5 angstroms per second. The above are the film forming conditions for the aluminum single crystal film by the sputtering method, but the film forming conditions are not limited to these. It is also possible to use a high frequency power supply as the sputtering power supply.

The aluminum single crystal film described above has a very great feature that it can be easily manufactured by the vapor deposition method and the sputtering method. The reason why the aluminum single crystal film can be easily obtained in this way is that the film formation rate is slowed down. In the conventional aluminum film forming method, for example, in the vapor deposition method, the vapor deposition rate is generally 30 angstroms per second or more. Further, as described in JP-A-3-14305, an alignment film is obtained at 20 angstroms per second or more. However, according to the experiments by the authors, it was found that the crystallinity of the aluminum film was disturbed from the single crystal film as the flatness of the substrate was improved. This is because the migration of aluminum particles flying to the surface of the substrate becomes larger as the flatness of the substrate improves, and as a result, the growth of the regular aluminum film is hindered and the crystallinity deteriorates, making it impossible to obtain a single crystal film. Conceivable.
Therefore, in order to obtain a single crystal film, it is considered important to reduce the energy of the aluminum film flying on the substrate surface.

Based on these ideas, the authors have the same LST
Using a cut substrate, an experiment for forming a single crystal aluminum film was performed at four deposition rates of 40 angstroms per second, 25 angstroms per second, 15 angstroms per second, and 7 angstroms per second. As a result 4 per second
Although a single crystal film could not be obtained at 0 Å,
The vapor deposition film of 25, 15, and 7 angstroms per second became a single crystal film. That is, an aluminum single crystal film could be obtained by forming the film at a low speed. Further, the aluminum film formed at a lower speed had better crystallinity.

However, even if the deposition rate is controlled, if the surface of the substrate is contaminated, a film having a polycrystalline structure or the like is formed. Therefore, it is important to keep the substrate surface clean.

Next, the evaluation of the aluminum film formed at 15 angstroms per second according to this embodiment and the aluminum film formed at 40 angstroms per second by the conventional technique will be described. The thickness of each aluminum film is about 6000 angstroms. The film was evaluated by a diffraction characteristic diagram by an X-ray diffractometer. The substrate is also an LST cut quartz substrate having the same surface roughness as that of the prior art in this embodiment.

A sample for X-ray diffraction measurement was prepared by cutting an LST cut quartz crystal substrate after film formation into a size of 15 mm square. The measurement was performed by the standard measurement method in which the sample was rotated.

FIG. 1 is a diffraction characteristic diagram of X-ray diffraction by standard measurement of an aluminum single crystal film produced by the vapor deposition method of this embodiment. Further, FIG. 4 is a diffraction characteristic diagram of X-ray diffraction by standard measurement of an aluminum polycrystalline film produced by a conventional technique. The angle of incidence of X-rays in this standard measurement is about 1 degree with respect to the substrate surface. Comparing FIG. 1 with FIG. 4, a peak indicating crystallization is observed in the conventional aluminum film of FIG. 4, whereas no peak is observed in the aluminum film of the present example of FIG.

As described above, in the standard measurement, since the sample is rotated and measured, when the sample is in the polycrystalline state, (1
11) A crystal whose plane is parallel to the sample surface,
Since there are crystals in which the (200) plane is oriented parallel to the sample surface, the peaks of a plurality of crystal planes can be observed. However, when the sample is in a single crystal state, the crystal plane has a certain angle with the sample surface and is oriented in a specific direction, it is impossible to observe the peak. As shown in FIG. 4, the aluminum film according to the prior art has four crystal planes parallel to the sample surface, that is, the (111) plane is parallel to the sample surface and the (200) plane is to the sample surface. It can be seen that the crystal is composed of at least four types of crystals: a parallel crystal, a crystal whose (220) plane is parallel to the sample surface, and a crystal whose (311) plane is parallel to the sample surface. The technology aluminum film is a polycrystalline film.

On the other hand, the aluminum film obtained in this example does not show any peak indicating crystallization as shown in FIG. Usually, when no crystallization peak appears, it is in an amorphous state or a single crystal state. In the amorphous state, the crystallization peak is not sharp and shows a diffractive characteristic with a wide skirt like a hill. Therefore, it differs from the diffraction characteristics of the aluminum film obtained in this example shown in FIG. 1, and it can be said that the aluminum film obtained in this example is not in an amorphous state.

The aluminum film obtained in this example is neither in the polycrystalline state nor in the amorphous state as described above. Generally, as shown in FIG. 1, when no diffraction peak appears between the diffraction angles of 0 to 80 degrees, four planes that should appear for aluminum, that is, (111) plane, (2
It can be judged that the (00) plane, the (220) plane, and the (311) plane all have a certain angle with respect to the sample surface and are extremely correctly oriented in a specific direction. Furthermore, the measurement of FIG. 1 is the same for every part of the sample. As described above, when focusing on an arbitrary crystal plane (crystal axis), a crystalline solid having the same orientation in any part of the sample is defined as a single crystal. It can be judged to be a crystal.

The X-ray diffraction results for the two types of aluminum films have been described above, but it can be concluded from the observation results that the aluminum film according to this example is a single crystal film. However, even in this embodiment, it is difficult to form a completely single crystal film over the entire surface of the LST cut quartz crystal substrate. This is because, if there are fine scratches or holes on the surface of the substrate, the crystallinity will be lost at those portions. However, these should be considered defects of the single crystal film, and do not mean that they are not the single crystal film. Further, there is only one such defect in one surface acoustic wave element or not, and there is almost no effect on reducing the frequency change of the surface acoustic wave element, which is the object of the present invention. is there.

Experiments were carried out for the film thickness of aluminum from 500 angstroms to 10000 angstroms, but a single crystal film could be obtained with any film thickness.
It is considered that a film thickness larger than this is possible.

Although aluminum having a purity of 5N is used as the aluminum for vapor deposition in this embodiment, the purity is not limited to this. Further, for example, copper can be added as an impurity. In this case, it is appropriate that the addition amount is about 0.1% to 3% in weight percent, but it is not limited to this ratio.

Next, the surface acoustic wave element formed by using the aluminum single crystal film produced according to this example and the frequency change characteristic of the element will be described.

FIG. 2 shows a surface acoustic wave resonator 1 constructed by using an aluminum single crystal film according to this embodiment. The deposition rate of the aluminum single crystal film is 15 angstroms per second. The element structure is a one-port type resonator in which a pair of comb-teeth shaped electrodes 2 and grid-shaped reflector electrodes 3 are arranged on both sides thereof. However, the number of electrodes is reduced in the drawing. The frequency is 256 MHz and the electrode thickness is about 300
It is 0 angstrom.

The element is formed by forming an aluminum film on the entire surface of an LST-cut quartz crystal substrate, forming a plurality of elements by an etching method, and then cutting and separating with a dicing saw. After that, the element is adhered to a package called a stem using a conductive adhesive, and an aluminum wire is used for connection with an external terminal. Then, the can is sealed by resistance welding in a nitrogen atmosphere. A surface acoustic wave device manufactured by using a conventional aluminum film is also manufactured in the same manner.

Now, FIG. 3 shows the operation of the two elements of the surface acoustic wave resonator of this embodiment and the surface acoustic wave resonator provided with the polycrystalline aluminum electrode manufactured by the conventional technique.
It is a characteristic view which measured the frequency change with time. The input power of this test is about 20 milliwatts. It can be seen from FIG. 3 that the element according to the present embodiment has a very small frequency change and operates very stably. For example, 10
The frequency change after 00 hours was about 2 PPM. As described above, even when the LST-cut quartz crystal substrate is used, the frequency change due to the time-dependent change of the surface acoustic wave element can be made extremely small by forming the aluminum electrode as a single crystal film. On the other hand, it can be seen that the frequency of the element according to the conventional technique is largely shifted downward with the passage of time.

The inclination angle of cutting in the LST-cut quartz crystal substrate was 9.5 degrees in this embodiment, but it is from 7 degrees to 15 degrees.
The degree is suitable. The ratio (D / L) between the surface acoustic wave wavelength L determined by the frequency and the electrode thickness D is 0.02.
About 5 is suitable, and an electrode thickness suitable for the frequency can be selected in addition to the above.

Next, the reason why the frequency stability of the device of this embodiment is excellent will be described. The surface acoustic wave is a wave propagating along the surface of the substrate, and its vibration greatly changes depending on the hardness and viscosity of the electrode. Therefore, when the internal stress of the material forming the electrode changes, the viscosity and the like change, and as a result, the frequency changes. Considering the case where the electrode is in a polycrystalline state, the crystal of the electrode vibrates when the element is operating, and the crystal moves so that the surface free energy of the grain boundary is minimized. This phenomenon is called grain boundary diffusion of aluminum crystals. When this phenomenon occurs, protruding particles called hillocks are generated on the electrode, or conversely, cracks are generated at grain boundaries, resulting in disconnection. Thus, when the electrode film is a polycrystalline aluminum film, the internal stress of the aluminum electrode changes due to vibration during the operation of the element, and the frequency of the element changes.

The above phenomenon is caused by the grain boundaries of the crystal of the aluminum film, and does not occur in the single crystal aluminum film having no grain boundary as in this embodiment. Therefore, the surface acoustic wave resonator according to this embodiment has high frequency stability.

Example 2 Next, an example in which a lithium niobate single crystal substrate is used as a substrate will be described. The lithium niobate single crystal used in this example has a Y-cut of 128 degrees, and its surface roughness has a root mean square roughness of about 0.001 micron or less and a maximum roughness of about 0.005 micron or less.
Very flat.

The surface acoustic wave device using lithium niobate is mainly used for a broadband filter. It is used as a top filter for high-frequency receivers such as mobile phones and is required to have power resistance. Therefore, conventionally, a trace amount of copper or the like has been added to aluminum. In this example, as described in Example 1, 5N aluminum was used, and the film formation rate was slowed to 10 and 7 angstroms per second instead of the conventional 40 angstroms per second. The film thickness in this embodiment is 2000 angstrom. Further, in this embodiment, a vapor deposition method using electron beam heating is used.

The aluminum film according to the present embodiment is also the first embodiment.
The standard measurement was performed by the thin film X-ray diffraction method in the same manner as above, but the same results as in Example 1 were obtained, and the aluminum film obtained in this example is a single crystal film. Further, the aluminum film formed at a low film formation rate had better crystallinity.

In this example, a resonator type filter was manufactured, electric power of 2 watts was applied, and the state of destruction of the electrode film was investigated. As a result, hillocks and small cracks were observed in the electrode after 1000 hours of observation with the conventional polycrystalline electrode of aluminum-copper alloy, but such a phenomenon did not occur in the example.

A single crystal film is also obtained when the deposition rate is 25 angstroms per second. Further, in this embodiment, 128 degree Y-cut lithium niobate is used, but lithium niobate other than this angle and this cut is also possible. Although the vapor deposition method by the electron beam heating method is used in the present embodiment, the film forming method may be a resistance heating type or laser heating type vapor deposition method, a sputtering method or the like.

Example 3 Next, an example using a lithium tantalate single crystal substrate as a substrate will be shown. The lithium tantalate single crystal used in this example is 112 degrees X-cut,
As for the surface roughness, the root mean square roughness is about 0.001 micron or less and the maximum roughness is about 0.005 micron or less, and the flatness is very excellent.

The surface acoustic wave device using lithium tantalate is mainly used for a wide band filter, like the device using lithium niobate. It is used as a top filter for high-frequency receivers such as mobile phones and is required to have power resistance. Therefore, conventionally, a trace amount of copper or the like has been added to aluminum. 5N in this embodiment
As described in the first embodiment, the aluminum is used to form a film at a slower film forming rate of 10 and 7 angstroms per second, instead of the conventional film forming speed of 40 angstroms per second. The film thickness in this embodiment is 2000 angstrom. Further, in this embodiment, the vapor deposition method by the electron beam heating method is used.

The aluminum film according to the present embodiment is also the first embodiment.
The standard measurement was carried out by the thin film X-ray diffraction method in the same manner as in, but the same results as in Example 1 and Example 2 were obtained, and the aluminum film obtained in this example is a single crystal film. Further, the aluminum film formed at a low film formation rate has better crystallinity.

In this example, a resonator type filter was produced, power of 2 watts was applied, and the state of destruction of the electrode film was investigated. As a result, hillocks and small cracks were observed in the electrode after 1000 hours of observation with the conventional polycrystalline electrode of aluminum-copper alloy, but such a phenomenon did not occur in the example.

A single crystal film is also obtained when the deposition rate is 25 angstroms per second. Further, in this embodiment, 112 ° X-cut lithium tantalate was used, but lithium tantalate other than this angle and this cut is also possible. Although the vapor deposition method by the electron beam heating method is used in the present embodiment, the film forming method may be a resistance heating type or laser heating type vapor deposition method, a sputtering method or the like.

In the above three embodiments, the piezoelectric substrate is a 9.5 ° LST cut quartz substrate, and the 128 ° Y substrate.
Although a cut lithium niobate substrate and a 112 ° X-cut lithium tantalate substrate were used, other cut quartz substrates, such as a 33 ° ST-cut substrate, ST-cut substrates at other angles, and AT-cut substrates are also possible. Is. It is also possible to use an oxide single crystal substrate such as lithium borate. Further, a thin film piezoelectric material such as zinc oxide or aluminum nitride is considered as a substrate and can be applied to these. Further, it can be applied to a semiconductor substrate such as a silicon single crystal substrate or a gallium arsenide single crystal substrate. A sapphire single crystal substrate is also possible.

The aluminum used for film formation has a purity of 5
However, the purity is not particularly limited to this. It is also possible to intentionally add impurities,
As impurities, copper, titanium, nickel, palladium,
Tantalum, hafnium, etc. are suitable. The suitable amount of addition is about 0.1% to 3% by weight, but not limited to these.

Further, as the surface acoustic wave element, the one-port type resonator has been described in the two embodiments, but it can be applied to a two-port type resonator, a filter element, a convolver element and the like. It can also be applied to a combination element with an optical element, a magnetic element, a semiconductor element or the like. Further, it can be applied to a crystal bulk type oscillator such as an AT oscillator or a tuning fork type oscillator.

The aluminum single crystal film of this embodiment can be applied to electronic devices other than the surface acoustic wave device, such as sensors and micromachining technology. As the method for forming the aluminum film, the vapor deposition method and the sputtering method have been described in Examples 1, 2, and 3, but the method is not limited to these.

[0056]

As described above, according to the present invention, by performing the aluminum film formation at a low rate of 25 angstroms per second or less, a very flatness can be obtained by a simple method such as vapor deposition and sputtering. It has an effect that an aluminum single crystal film can be easily manufactured even on an excellent single crystal substrate. Further, the surface acoustic wave device including the single crystal aluminum electrode according to the present invention has an effect that a frequency change due to a change with time during operation is extremely small. Further, it has the effect of improving the power resistance.

[Brief description of drawings]

FIG. 1 is a diffraction characteristic diagram of X-ray diffraction by standard measurement of a single crystal aluminum film of a first example according to the present invention.

FIG. 2 is a front view of a surface acoustic wave resonator made of the single crystal aluminum film according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing frequency changes of the surface acoustic wave resonator according to the first embodiment of the present invention and the surface acoustic wave resonator according to the related art.

FIG. 4 is a diffraction characteristic diagram of X-ray diffraction by standard measurement of a polycrystalline aluminum film according to a conventional technique.

[Explanation of symbols]

1 Surface Acoustic Wave Resonator 2 Comb Toothed Electrode 3 Reflector Electrode 4 Characteristics of Surface Acoustic Wave Resonator with Single Crystal Aluminum Electrode 5 Characteristics of Surface Acoustic Wave Resonator with Polycrystalline Aluminum Electrode

Front page continuation (72) Inventor Tomofumi Hama 3-5 Yamato, Suwa City, Nagano Seiko Epson Corporation (72) Inventor Ryuichi Kurosawa 3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation Within

Claims (6)

[Claims] 1. A surface acoustic wave device comprising an aluminum electrode formed on an LST-cut quartz substrate obtained by cutting a Z plate tilted in the counterclockwise direction in the range of 7 ° to 15 ° around the X axis. A surface acoustic wave device, wherein the electrode is a single crystal film. 2. A surface acoustic wave device comprising an aluminum electrode formed on a 128 ° Y-cut lithium niobate single crystal substrate, wherein the aluminum electrode is a single crystal film. 3. A surface acoustic wave device comprising an aluminum electrode formed on a 112 ° X-cut lithium tantalate single crystal substrate, wherein the aluminum electrode is a single crystal film. 4. A surface acoustic wave device comprising an aluminum single crystal film electrode formed on an LST cut quartz substrate obtained by cutting a Z plate tilted counterclockwise in the range of 7 ° to 15 ° about the X axis. A method of manufacturing a surface acoustic wave device, wherein the aluminum single crystal film electrode is formed by a vacuum film forming method, and the film forming rate is 25 angstroms per second or less. 5. A surface acoustic wave device comprising an aluminum single crystal film electrode formed on a 128 ° Y-cut lithium niobate single crystal substrate, wherein the aluminum single crystal film electrode is formed by a vacuum film forming method. A method of manufacturing a surface acoustic wave device, wherein the film velocity is 25 angstroms per second or less. 6. A surface acoustic wave device comprising an aluminum single crystal film electrode formed on a 112 ° X-cut lithium tantalate single crystal substrate, wherein the aluminum single crystal film electrode is formed by a vacuum film forming method. A method of manufacturing a surface acoustic wave device, wherein the film velocity is 25 angstroms per second or less.