JP2005065050A - Surface acoustic wave element, manufacturing method of surface acoustic wave element, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element wherein an energy loss caused at the propagation of a surface acoustic wave is small and high input output efficiency can be obtained, a manufacturing method of the surface acoustic wave element, and an electronic apparatus provided with the surface acoustic wave element. <P>SOLUTION: The surface acoustic wave element 11 is provided with: a substrate 12 configured of a piezoelectric material at least around the surface as a principal material; an IDT 13 deposited on the substrate 12 and stimulating a surface acoustic wave to the substrate 12; and an IDT 14 for converting the surface acoustic wave into an electric signal. Insulation protection films 17 are formed at upper sides of the IDTs 13, 14 with patterns nearly equal to the IDTs. The insulation protection film 17 is formed of a principal material such as silicon oxide. Further, the surface acoustic wave element 11 is provided with reflectors 15, 16 and the insulation protection films 17 are also formed at upper sides of the reflectors 15, 16 with pattern nearly equal to the reflectors. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface acoustic wave element, a method for manufacturing a surface acoustic wave element, and an electronic apparatus.

A wave that propagates with energy concentrated near the surface of the propagation medium is known as a surface acoustic wave (SAW).
A surface acoustic wave element is an element that uses such a surface acoustic wave, such as a band-pass filter for a communication device such as a mobile phone, a resonator as a reference clock, a signal processing delay element (in particular, a Fourier transform functional element). ), Various sensors such as pressure sensors and temperature sensors, and optical deflectors.

  For example, a surface acoustic wave element used as a filter includes a piezoelectric body as a propagation medium of surface acoustic waves, an input for applying a voltage that is disposed on the piezoelectric body and excites the surface acoustic wave, and a piezoelectric element. It includes a pair of interdigital electrodes (IDT) for detecting and outputting surface acoustic waves propagating through the body, converting them into electrical signals and outputting them.

In such a surface acoustic wave element, when a foreign substance or the like adheres to the IDT, the electrode fingers of the IDT may be short-circuited through the foreign substance. Therefore, in order to prevent such adhesion of foreign matter, an insulating protective film is provided so as to cover the entire surface of the IDT (see, for example, Patent Document 1).
However, when an insulating protective film is provided so as to cover the entire surface of the IDT, there is a problem that energy loss generated in the process of propagation of the surface acoustic wave is large and sufficient input / output efficiency cannot be obtained.

That is, as shown in FIG. 11, the surface acoustic wave 110 propagates on the surface of the piezoelectric body 130 so as to have one wavelength for every two electrode fingers 120. And when this surface acoustic wave 110 propagates from a specific material to a different material, the propagation speed changes due to the mass effect, and reflection occurs at that time.
Here, as shown in FIG. 12, in the case where the insulating protective film 140 is provided so as to cover the entire surface of the comb electrode, the insulating protective film 140 is formed on the path through which the surface acoustic wave 110 propagates. There are two material changes from the piezoelectric body 130 and the electrode finger 120 to the piezoelectric body 130. Reflection occurs in each of these two portions, and these reflections interfere with each other, so that there is a problem that energy loss increases and sufficient input / output efficiency cannot be obtained.
JP-A-10-256862

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface acoustic wave device that has a small energy loss when a surface acoustic wave propagates and that provides high input / output efficiency, a method for manufacturing such a surface acoustic wave device, and an electron equipped with such a surface acoustic wave device. To provide equipment.

Such an object is achieved by the present invention described below.
The surface acoustic wave device of the present invention includes a substrate having piezoelectricity at least near the surface;
A surface acoustic wave device provided on the substrate and having a comb-tooth electrode having a function of converting an electric signal into a surface acoustic wave and / or a function of converting a surface acoustic wave into an electric signal on the substrate,
An insulating protective film is provided on the upper surface of the comb electrode in a pattern substantially equal to the comb electrode.
Thereby, the energy loss which arises when a surface acoustic wave propagates is suppressed small, and high input / output efficiency is obtained.

In the surface acoustic wave device of the present invention, it is preferable that the insulating protective film does not exist on the side surface of the comb electrode.
Thereby, the energy loss which arises when a surface acoustic wave propagates is suppressed more reliably, and higher input / output efficiency is obtained.
In the surface acoustic wave element of the present invention, the surface acoustic wave element includes a reflector that is provided on the substrate and reflects the surface acoustic wave propagating to the substrate.
It is preferable that an insulating protective film is provided on the upper surface of the reflector in a pattern substantially equal to the reflector.
Thereby, the energy loss which arises when a surface acoustic wave propagates is suppressed small, and high input / output efficiency is obtained.

In the surface acoustic wave device according to the aspect of the invention, it is preferable that the insulating protective film does not exist on a side surface of the reflector.
Thereby, the energy loss which arises when a surface acoustic wave propagates is suppressed more reliably, and higher input / output efficiency is obtained.
In the surface acoustic wave device according to the aspect of the invention, it is preferable that the insulating protective film is composed mainly of at least one of silicon oxide, silicon nitride, and aluminum oxide.
Thereby, while being able to form an insulating protective film easily, an insulating protective film can also be made excellent in insulation.

In the surface acoustic wave device of the present invention, the insulating protective film preferably has a thickness (average) of 10 to 1000 nm.
Thereby, sufficient insulation is exhibited while preventing or suppressing a decrease in the surface acoustic wave transmission frequency accompanying an increase in the mass of the insulating protective film.
In the surface acoustic wave device according to the aspect of the invention, it is preferable that the substrate is a piezoelectric substrate composed mainly of at least one of quartz, lithium tantalate, lithium niobate, and potassium niobate.
By using such a substrate, a surface acoustic wave device having excellent characteristics can be manufactured at low cost.

In the surface acoustic wave device according to the aspect of the invention, it is preferable that the substrate has a multilayer laminated structure, and the layer closest to the comb electrode is a piezoelectric layer composed mainly of a piezoelectric material.
Thereby, the characteristics of the substrate can be easily controlled.
In the surface acoustic wave device of the present invention, it is preferable that the piezoelectric layer is composed mainly of at least one of zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, and potassium niobate.
As a result, a surface acoustic wave element having a high frequency and excellent temperature characteristics can be obtained.

The surface acoustic wave device according to the present invention may include a base layer that is provided on the opposite side of the piezoelectric layer from the comb electrode and has a function of setting characteristics of the surface acoustic wave excited in the piezoelectric layer. preferable.
This makes it possible to set the surface acoustic wave characteristics to a desired one.
In the surface acoustic wave device of the present invention, it is preferable that the base layer is composed mainly of at least one of diamond, sapphire, lithium tantalate, and potassium niobate.
By forming the underlayer with such a material, it is possible to contribute to the increase in the surface acoustic wave frequency required for application to high-speed communication fields such as wireless LAN and optical communication.

A surface acoustic wave element manufacturing method of the present invention is a surface acoustic wave element manufacturing method for manufacturing the surface acoustic wave element of the present invention,
The comb electrode and the insulating protective film are formed using the same mask.
Thereby, the comb-tooth electrode and the insulating protective film can be formed by a simple process.
In the method for manufacturing a surface acoustic wave device of the present invention, it is preferable that the comb electrode, the reflector and the insulating protective film are formed using the same mask.
Thereby, a comb-tooth electrode, a reflector, and an insulating protective film can be formed in a simple process.

A surface acoustic wave element manufacturing method of the present invention is a surface acoustic wave element manufacturing method for manufacturing the surface acoustic wave element of the present invention,
A conductive material layer and an insulating material layer are sequentially formed on the substrate,
Next, the conductive material layer and the insulating material layer are etched using the same mask to form the comb electrode and the insulating protective film.
Thereby, the comb-tooth electrode and the insulating protective film can be formed by a simple process.

In the method for manufacturing a surface acoustic wave device according to the present invention, the conductive material layer and the insulating material layer are etched using the same mask to form the comb electrode, the reflector, and the insulating protective film. It is preferable.
Thereby, a comb-tooth electrode, a reflector, and an insulating protective film can be formed in a simple process.

In the method for manufacturing a surface acoustic wave element of the present invention, it is preferable that the etching of the conductive material layer and the etching of the insulating material layer are performed collectively using the same etching method.
Thereby, simplification of a manufacturing process can be achieved.
An electronic apparatus according to the present invention includes the surface acoustic wave element according to the present invention.
Thereby, an electronic device having high reliability can be obtained.

Hereinafter, preferred embodiments of a surface acoustic wave device, a method of manufacturing a surface acoustic wave device, and an electronic apparatus according to the present invention will be described.
<First Embodiment>
FIG. 1 is a plan view showing a first embodiment of a surface acoustic wave device according to the present invention, FIG. 2 is a sectional view of the surface acoustic wave device shown in FIG. 1, and FIG. 3 is a diagram of the surface acoustic wave device shown in FIG. It is a schematic diagram which shows the mode of reflection of a surface acoustic wave. In the following description, the upper side in FIGS. 2 and 3 is referred to as “upper” and the lower side is referred to as “lower”.

A surface acoustic wave element 1 shown in each figure is a surface acoustic wave element having a transversal structure, and has a substrate 2 having piezoelectricity at least near the surface, an input IDT 3 provided on the substrate 2, and an output element. It has IDT4 and the insulation protective film 5 provided in the upper surface of each IDT3,4.
The substrate 2 is configured by sequentially laminating a base layer 22 and a piezoelectric layer 23 on a base material layer 21.

Examples of the constituent material of the base material layer 21 include various semiconductor materials such as Si, GaSi, SiGe, GaAs, STC, and InP, various glass materials, various ceramic materials, various resin materials such as polyimide and polycarbonate, and the like. It is done.
Although the thickness (average) of the base material layer 21 is not particularly limited, it is preferably about 0.05 to 1 mm, and more preferably about 0.1 to 0.8 mm.
Moreover, the base material layer 21 may be not only a single layer but also a laminate of a plurality of layers. In this case, each layer uses any combination of the materials as described above. be able to.

The underlayer 22 is provided in contact with the surface of the piezoelectric layer 23 opposite to the IDTs 3 and 4. The underlayer 22 has a function of setting (defining) the characteristics (conditions) of the surface acoustic wave excited in the piezoelectric layer 23.
Examples of this characteristic include oscillation frequency, amplitude, propagation speed, and the like.
By providing the base layer 22 and appropriately setting the constituent materials, it is possible to set the desired surface acoustic wave characteristics. As a constituent material of the underlayer 22, for example, a material mainly containing at least one of diamond, silicon, sapphire, glass, crystal, lithium tantalate, potassium niobate, and lithium niobate is preferable. , Sapphire, lithium tantalate, and potassium niobate are preferred. By forming the underlayer 22 with such a material, it is possible to contribute to the increase in the surface acoustic wave frequency required for the purpose of application to high-speed communication fields such as wireless LAN and optical communication.

The thickness (average) of the underlayer 22 is not particularly limited, but is preferably about 1 to 20 μm, more preferably about 3 to 10 μm, and further preferably about 3 to 5 μm.
The underlayer 22 is not limited to a single layer, but can be composed of a laminate of a plurality of layers according to the target surface acoustic wave characteristics. The underlayer 22 is provided as necessary and can be omitted.

The piezoelectric layer (the layer closest to the IDTs 3 and 4) 23 functions as a surface acoustic wave propagation medium.
As a constituent material of the piezoelectric layer 23, a material mainly composed of at least one of zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, and potassium niobate is preferable. By forming the piezoelectric layer 23 with such a material, the surface acoustic wave element 1 having a high frequency and excellent temperature characteristics can be obtained.

The thickness (average) of the piezoelectric layer 23 is not particularly limited, but is preferably about 0.01 to 5 μm, and more preferably about 0.1 to 2 μm.
The substrate 2 may be a single-layer substrate instead of a multi-layer substrate. Such a substrate 2 can be made of quartz in addition to the materials mentioned for the piezoelectric layer 23. Among these, for the substrate 2, it is particularly preferable to use a piezoelectric substrate composed mainly of at least one of quartz, lithium tantalate, lithium niobate, and potassium niobate. By using such a substrate 2, the surface acoustic wave device 1 having excellent characteristics can be manufactured at low cost.

The IDT (input side electrode) 3 has a function of applying a voltage to the piezoelectric layer 23 to excite the surface acoustic wave in the piezoelectric layer 23, while the IDT (output side electrode) 4 is a piezoelectric layer. It has a function of detecting a surface acoustic wave propagating through the body layer 23, converting the surface acoustic wave into an electric signal, and outputting it to the outside.
Therefore, when a driving voltage is input to the IDT 3, a surface acoustic wave is excited in the piezoelectric layer 23, and an electrical signal in a specific frequency band by the filtering function is output from the IDT 4.

Each IDT 3, 4 is composed of a pair of comb-shaped electrodes having electrode fingers 31, 41, and the width, spacing, thickness, etc. of the electrode fingers 31, 41 of the comb-shaped electrodes are adjusted. By doing so, the characteristic of the oscillation frequency of the surface acoustic wave can be set to a desired one.
Examples of the constituent materials of the IDTs 3 and 4 include Al, Cu, W, Mo, Ti, Au, Y, Pb, Sc, and alloys containing these, and one or two of them are used. A combination of the above can be used.

The insulating protective film 5 prevents foreign matter from adhering to the surfaces of the IDTs 3 and 4 and prevents a short circuit between the electrode fingers 31 and 41 via the foreign matter.
The insulating protective film 5 is formed on the upper surfaces of IDTs (comb electrodes) 3 and 4 in a pattern substantially equal to these. In the present embodiment, the insulating protective film 5 is formed to have a shape substantially equal to the shape of the IDTs 3 and 4.
With such a configuration, as shown in FIG. 3, there is no material change from the insulating protective film 5 to the substrate 2 on the path through which the surface acoustic wave 6 propagates, and the material change on this path is substantially Only the change from the electrode fingers 31 and 41 to the substrate 2 occurs. Therefore, the reflection of the surface acoustic wave 6 due to the material change and the energy loss due to the reflection can be suppressed, and high input / output efficiency can be obtained.

In particular, since the insulating protective film 5 does not exist on the side surfaces of the IDTs 3 and 4 as in the configuration shown in the drawing, the effect is further improved.
In this case, the insulating protective film 5 is not formed on the side surfaces of the IDTs 3 and 4, but the short circuit between the electrode fingers 31 and 41 due to the foreign matter is mainly caused by the foreign matter adhering to the upper surfaces of the electrode fingers 31 and 41. Therefore, even if the insulating protective film is not formed on the side surface, the short circuit between the electrode fingers 31 and 41 can be suitably prevented by the presence of the insulating protective film 5 on the upper surfaces of the IDTs 3 and 4.

  The constituent material of the insulating protective film 5 is not particularly limited as long as it has insulating properties and can form a film, and examples thereof include silicon oxide, silicon nitride, aluminum oxide, tantalum pentoxide, and molybdenum oxide. However, among these, a material mainly containing at least one of silicon oxide, silicon nitride, and aluminum oxide is preferable. By constituting the insulating protective film 5 with such a material, the insulating protective film 5 can be easily formed, and the insulating protective film 5 can be excellent in insulation.

The thickness (average) of the insulating protective film 5 is not particularly limited, but is preferably about 10 to 1000 nm, and more preferably about 30 to 300 nm. By setting the thickness of the insulating protective film 5 within the above range, sufficient insulation is exhibited while preventing or suppressing a decrease in the surface acoustic wave transmission frequency associated with an increase in mass.
The surface acoustic wave device 1 as described above can be manufactured as follows.
FIG. 4 is a diagram (cross-sectional view) for explaining a method of manufacturing the surface acoustic wave element shown in FIGS. 1 and 2.

[1] Underlayer Formation Step First, as shown in FIG. 4A, the underlayer 22 is formed on the base material layer 21.
For the formation of the underlayer 22, for example, chemical vapor deposition (CVD) such as plasma CVD, thermal CVD, laser CVD, dry plating methods such as vacuum deposition, sputtering, ion plating, electrolytic plating, immersion plating, electroless Wet plating methods such as plating, thermal spraying, and joining of sheet-like members can be used.

[2] Piezoelectric Layer Formation Step Next, as shown in FIG. 4B, a piezoelectric layer 23 is formed on the base layer 22.
Formation of the piezoelectric layer 23 can be performed in the same manner as in the step [1].
[3] Step of Forming Conductive Material Layer and Insulating Material Layer Next, as shown in FIG. 4C, the conductive material layer 7 and the insulating material layer 8 are sequentially formed on the piezoelectric layer 23.

For forming the conductive material layer 7, for example, a dipping method, a printing method, a wet plating method such as electrolytic plating, immersion plating, electroless plating, or a chemical vapor deposition method (CVD) such as plasma CVD, thermal CVD, or laser CVD. ), Vacuum plating, sputtering, dry plating methods such as ion plating, thermal spraying, metal foil bonding, and the like.
The insulating material layer 8 can be formed in the same manner as in the above step [1], but it is particularly preferable to use plasma CVD. According to plasma CVD, the insulating material layer 8 can be formed relatively easily, at high speed and with high accuracy.

[4] IDT and Insulating Protective Film Forming Step Next, as shown in FIG. 4D, a mask 9 having a shape corresponding to IDTs 3 and 4 is formed on the insulating material layer 8, and this mask 9 is used. Etching is performed to obtain IDTs 3 and 4 and an insulating protective film 5 as shown in FIGS.
In this way, by forming the IDTs 3 and 4 and the insulating protective film 5 using the same mask 9, it is possible to simplify the manufacturing process, and to accurately protect the insulation on the upper surfaces of the IDTs 3 and 4. A film 5 can be formed.
Note that a photolithography method is preferably used for forming the mask. Thereby, IDT3 and 4 can be formed in a fine shape.

  For etching, for example, reactive ion etching (RIE), plasma etching, beam etching, dry etching such as light assisted etching, wet etching, or the like can be used. Etching is preferably used. Thereby, unnecessary portions of the conductive material layer 7 and the insulating material layer 8 can be easily and reliably removed.

Here, the etching of the conductive material layer 7 and the insulating material layer 8 may be performed by different etching methods, but is preferably performed by the same etching method. By using the same etching method for the conductive material layer 7 and the insulating material layer 8 and performing etching in a lump, the manufacturing process can be simplified as compared to using different etching methods.
Through the above-described steps, the surface acoustic wave element 1 of the present invention is manufactured as shown in FIG. The electrical characteristics of the surface acoustic wave element 1 can be confirmed by using, for example, a network analyzer.
Such a surface acoustic wave element 1 can suppress energy loss caused by reflection of surface acoustic waves, and can obtain high input / output efficiency.
In addition, the constituent material of the insulating protective film provided on the upper surfaces of the IDTs 3 and 4 may be the same or different.

Second Embodiment
Next, a second embodiment of the surface acoustic wave device of the present invention will be described.
FIG. 5 is a plan view showing a second embodiment of the surface acoustic wave device of the present invention, and FIG. 6 is a cross-sectional view of the surface acoustic wave device shown in FIG. In the following description, the upper side in FIG. 6 is referred to as “upper” and the lower side is referred to as “lower”.
Hereinafter, the surface acoustic wave element according to the second embodiment will be described. The description will focus on differences from the surface acoustic wave element according to the first embodiment, and description of similar matters will be omitted.

The surface acoustic wave element 11 according to the second embodiment includes a substrate 12, an input IDT 13 and an output IDT 14 provided on the substrate 12, and a pair of reflectors 15 disposed on both sides of the IDTs 13 and 14. 16 and an insulating protective film 17 formed on the upper surfaces of the IDTs 13 and 14 and the reflectors 15 and 16, respectively.
Constituent materials for the base material layer 121, the base layer 122, the piezoelectric layer 123 and the IDTs 13 and 14, and the insulating protective film 17 constituting the substrate 12 are the same as those exemplified in the first embodiment. As a constituent material of the containers 15 and 16, the same constituent materials as those used in the IDTs 13 and 14 can be used.

The IDT (input side electrode) 13 has a function of applying a voltage to the piezoelectric layer 123 to excite a surface acoustic wave in the piezoelectric layer 123, while the IDT (output side electrode) 14 is a piezoelectric layer. It has a function of detecting a surface acoustic wave propagating through the body layer 123, converting the surface acoustic wave into an electric signal, and outputting it to the outside.
Each reflector 15, 16 has a function of reflecting the surface acoustic wave propagating to the piezoelectric layer 123 and confining it between the reflector 15 and the reflector 16.

  Therefore, when a driving voltage is input to the IDT 13, a surface acoustic wave is excited in the piezoelectric layer 123, and an electrical signal having a specific frequency due to resonance is output from the IDT 14.

Each IDT 13 and 14 has a comb-like shape having electrode fingers 131 and 141, respectively, and by adjusting the width, interval, thickness, etc. of the electrode fingers 131 and 141 of the comb-tooth electrode, The oscillation frequency characteristics can be set as desired.
Each of the reflectors 15 and 16 has an interdigital shape, and is configured to efficiently reflect a surface acoustic wave.

The insulating protective film 17 protects the surfaces of the IDTs 13 and 14 and the reflectors 15 and 16 from adhesion of foreign matters, and prevents short-circuiting between electrode fingers via the foreign matters.
The insulating protective film 17 is formed on the upper surfaces of the IDTs 13 and 14 and the reflectors 15 and 16 in a pattern substantially equal to these. In the present embodiment, the insulating protective film 17 is formed to have a shape substantially equal to the shapes of the IDTs 13 and 14 and the reflectors 15 and 16.
With such a configuration, the material change from the insulating protective film 17 to the substrate 12 is eliminated on the path through which the surface acoustic wave propagates, and the material change on this path is substantially the same as the electrode fingers 131 and 141 and the reflector. Only the change from 15 and 16 to the substrate 12 occurs. Therefore, the reflection of the surface acoustic wave caused by the material change and the energy loss due to the reflection can be suppressed, and high input / output efficiency can be obtained.

In particular, since the insulating protective film 17 does not exist on the side surfaces of the IDTs 13 and 14 and the reflectors 15 and 16 as in the configuration shown in the drawing, the above effect is further improved.
Further, in this case, the insulating protective film is not formed on the side surfaces of the IDTs 13 and 14 and the reflectors 15 and 16, but the short circuit between the electrode fingers 131 and 141 due to the foreign matter mainly causes the foreign matter to adhere to the upper surfaces of the IDTs 13 and 14. Therefore, even if an insulating protective film is not formed on the side surface, the presence of the insulating protective film 17 on the upper surfaces of the IDTs 13 and 14 can suitably prevent a short circuit between the electrode fingers 131 and 141. .

In the step [4], such a surface acoustic wave element 11 has a shape corresponding to the IDTs 13 and 14 and the reflectors 15 and 16, as shown in FIG. 7, instead of the shape corresponding to the IDT. By forming 20 on the insulating material layer 19, it can be manufactured in the same manner as in the first embodiment.
Using such a mask 20, the conductive material layer 18 and the insulating material layer 19 are etched together, thereby simplifying the manufacturing process of the surface acoustic wave element 11 as compared to etching each layer separately. Can be achieved.

The constituent materials of the insulating protective film provided on the upper surfaces of the IDTs 13 and 14 and the upper surfaces of the reflectors 15 and 16 may be the same or at least one of them may be different.
The surface acoustic wave elements 1 and 11 as described above can be applied to various electronic devices, and the obtained electronic devices have high reliability.

Hereinafter, an electronic apparatus including the surface acoustic wave element of the present invention will be described in detail based on the embodiments shown in FIGS.
FIG. 8 is a perspective view showing a configuration of a mobile (or notebook) personal computer to which an electronic apparatus including the surface acoustic wave element of the present invention is applied.
In this figure, a personal computer 1100 includes a main body 1104 having an antenna 1101 and a keyboard 1102, and a display unit 1106. The display unit 1106 is rotatable with respect to the main body 1104 via a hinge structure. It is supported.

Such a personal computer 1100 incorporates a surface acoustic wave element 1 (or 11) that functions as a filter, a resonator, a reference clock, or the like.
FIG. 9 is a perspective view showing a configuration of a mobile phone (including PHS) to which an electronic apparatus including the surface acoustic wave element of the present invention is applied.
In this figure, a cellular phone 1200 includes an antenna 1201, a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206, and a display unit is disposed between the operation buttons 1202 and the earpiece 1204.
Such a cellular phone 1200 incorporates a surface acoustic wave element 1 (or 11) that functions as a filter, a resonator, or the like.

FIG. 10 is a perspective view showing a configuration of a digital still camera to which an electronic apparatus including the surface acoustic wave element of the present invention is applied. In this figure, connection with an external device is also simply shown.
Here, an ordinary camera sensitizes a silver halide photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an imaging device such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.

A display unit is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to display based on an imaging signal from the CCD. The display unit is a finder that displays an object as an electronic image. Function.
A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side (the back side in the drawing) of the case 1302.

When the photographer confirms the subject image displayed on the display unit and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory 1308.
In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the input / output terminal 1314 for data communication as necessary. Further, the imaging signal stored in the memory 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation.

Such a digital still camera 1300 incorporates a surface acoustic wave element 1 (or 11) that functions as a filter, a resonator, or the like.
In addition to the personal computer (mobile personal computer) shown in FIG. 8, the mobile phone shown in FIG. 9, and the digital still camera shown in FIG. (For example, inkjet printers), laptop personal computers, televisions, video cameras, video tape recorders, car navigation devices, pagers, electronic notebooks (including those with communication functions), electronic dictionaries, calculators, electronic game machines, word processors, workstations , Video phone, TV monitor for crime prevention, electronic binoculars, POS terminal, medical equipment (for example, electronic thermometer, blood pressure monitor, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices , Instruments (eg, vehicle, aircraft, ship instruments) ), It can be applied to a flight simulator or the like.

The surface acoustic wave element, the method for manufacturing the surface acoustic wave element, and the electronic apparatus of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to these.
For example, in the present invention, any two or more of the configurations of the first and second embodiments can be combined.
The surface acoustic wave device of the present invention may be provided with a temperature compensation film having a function of improving temperature characteristics.

Furthermore, an intermediate layer for any purpose may be provided between the layers constituting the surface acoustic wave device of the present invention.
In addition, the surface acoustic wave device of the present invention may be compounded with semiconductor devices having various functions.
In the method for manufacturing a surface acoustic wave device of the present invention, a comb-shaped electrode and an insulating protective film may be sequentially formed in a through hole using a mask having a through hole having a predetermined shape.

Next, specific examples of the present invention will be described.
(Example 1)
First, a quartz substrate was prepared as a piezoelectric substrate.
Next, aluminum was deposited on the quartz substrate by a vacuum evaporation method to form a conductive material layer (average thickness: 40 nm).

Next, SiO ₂ was deposited on the conductive material layer by plasma CVD to form an insulating material layer (average thickness: 40 nm).
Next, a mask corresponding to the shape of the IDT shown in FIG. 1 was formed on the insulating material layer by photolithography.
Next, the conductive material layer and the insulating material layer were etched by RIE using this mask. As a result, the IDT and the insulating protective film were collectively formed, and the surface acoustic wave device shown in FIG. 1 was obtained.
In the etching by RIE, the reactive gas is mainly composed of BCl ₃ and Cl ₂ for the conductive material layer, and is composed mainly of CF ₄ for the insulating material layer. Was used.

(Example 2)
First, in the same manner as in Example 1, a conductive material layer and an insulating material layer were formed on a quartz substrate (piezoelectric substrate).
Next, a mask corresponding to the shape of the IDT and the reflector shown in FIG. 5 was formed on the insulating material layer by photolithography.
Next, using this mask, etching was performed in the same manner as in Example 1 to form an IDT, a reflector, and an insulating protective film, and the surface acoustic wave device shown in FIG. 5 was produced.

(Example 3)
First, a Si single crystal plate was prepared as a base material layer.
Next, a diamond layer (underlayer) having an average thickness of 3 μm was formed on the Si single crystal plate by vapor phase synthesis.
Next, a zinc oxide layer (piezoelectric layer) having an average thickness of 2 μm was formed on the diamond layer by plasma CVD.
Using such a substrate, a surface acoustic wave device was produced in the same manner as in Example 1.

Example 4
A surface acoustic wave device was manufactured in the same manner as in Example 2 using the same substrate as in Example 3.
(Comparative Examples 1-4)
First, the formation of the insulating material layer was omitted, and an IDT or IDT and a reflector were formed on the substrate in the same manner as in Examples 1 to 4.
Next, SiO ₂ was deposited on the substrate by plasma CVD so as to cover the obtained IDT or the IDT and the reflector, thereby forming an insulating protective film. Thereby, a surface acoustic wave element was obtained.

[Evaluation]
With respect to the surface acoustic wave devices manufactured in each of the examples and the comparative examples, the electrical characteristics were measured using a network analyzer, and the loss (energy loss) of the output power with respect to the input (input) power was examined. The input power was 10W. The energy loss is to be determined by the 10 log ₁₀ (output) / (Input).
The results are shown in Table 1.

As shown in Table 1, in each of the surface acoustic wave devices manufactured in each example, the loss ratio of the output with respect to the input is suppressed smaller than that of the corresponding surface acoustic wave device of the comparative example.
From this, it can be seen that the energy loss can be suppressed by providing the insulating protective film only on the upper surface of the IDT and reflector and exposing the side surface.

1 is a plan view showing a first embodiment of a surface acoustic wave element according to the present invention. It is sectional drawing of the surface acoustic wave element shown in FIG. It is a schematic diagram which shows the mode of reflection of the surface acoustic wave in the surface acoustic wave element shown in FIG. It is sectional drawing which shows the manufacturing method of the surface acoustic wave element of this invention. It is a top view which shows 2nd Embodiment of the surface acoustic wave element of this invention. It is sectional drawing of the surface acoustic wave element shown in FIG. It is sectional drawing which shows the manufacturing method of the surface acoustic wave element of this invention. It is an electronic device (notebook type personal computer) provided with the surface acoustic wave element of the present invention. It is an electronic device (cellular phone) provided with the surface acoustic wave element of the present invention. It is an electronic apparatus (digital still camera) provided with the surface acoustic wave element of the present invention. It is a schematic diagram showing how a surface acoustic wave propagates in a surface acoustic wave element. It is a schematic diagram which shows the mode of reflection of the surface acoustic wave in the conventional surface acoustic wave element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 ... Surface acoustic wave element 2 ... Substrate 21 Base material layer 22 ... Underlayer 23 ... Piezoelectric layer 3 ... IDT (input side electrode) 31 ... Electrode finger 4 ... IDT (output side electrode) ) 41 ... Electrode fingers 5 ... Insulating protective film 6 ... Surface acoustic wave 7 ... Conductive material layer 8 ... Insulating material layer 9 ... Mask 12 ... Substrate 121 ... Base material layer 122 ... Bottom Base layer 123 ... Piezoelectric layer 13 ... IDT (input side electrode) 131 ... Electrode finger 14 ... IDT (output side electrode) 141 ... Electrode finger 15, 16 ... Reflector 17 ... Insulating protective film 18 ... ... conductive material layer 19 ... insulating material layer 20 ... mask 1100 ... personal computer 1101 ... antenna 1102 ... keyboard 1104 ... main body 1106 ... display unit 1200 ... mobile phone 1201 ... antenna 120 2 ... Operation buttons 1204 ... Earpiece 1206 ... Mouthpiece 1300 ... Digital still camera 1302 ... Case (body) 1304 ... Light receiving unit 1306 ... Shutter button 1308 ... Memory 1312 ... Video signal output terminal 1314 Input / output terminal for data communication 1430 TV monitor 1440 Personal computer 110 Surface acoustic wave 120 Electrode finger 130 Piezoelectric 140 Insulating protective film

Claims (17)

A substrate having piezoelectricity at least near the surface;
A surface acoustic wave device provided on the substrate and having a comb-tooth electrode having a function of converting an electric signal into a surface acoustic wave and / or a function of converting a surface acoustic wave into an electric signal on the substrate,
A surface acoustic wave device, wherein an insulating protective film is provided on the upper surface of the comb-teeth electrode in a pattern substantially equal to the comb-teeth electrode.   The surface acoustic wave device according to claim 1, wherein the insulating protective film does not exist on a side surface of the comb electrode. A reflector provided on the substrate and reflecting a surface acoustic wave propagating to the substrate;
The surface acoustic wave device according to claim 1, wherein an insulating protective film is provided on the upper surface of the reflector in a pattern substantially equal to the reflector.   The surface acoustic wave device according to claim 3, wherein the insulating protective film does not exist on a side surface of the reflector.   5. The surface acoustic wave device according to claim 1, wherein the insulating protective film is made of at least one of silicon oxide, silicon nitride, and aluminum oxide as a main material.   The surface acoustic wave device according to claim 1, wherein the insulating protective film has a thickness (average) of 10 to 1000 nm.   The surface acoustic wave device according to any one of claims 1 to 6, wherein the substrate is a piezoelectric substrate composed mainly of at least one of quartz, lithium tantalate, lithium niobate, and potassium niobate.   8. The surface acoustic wave device according to claim 1, wherein the substrate has a multilayer laminated structure, and a layer closest to the comb electrode is a piezoelectric layer composed of a piezoelectric material as a main material.   The surface acoustic wave device according to claim 8, wherein the piezoelectric layer is composed mainly of at least one of zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, and potassium niobate.   10. The surface acoustic wave according to claim 8, further comprising a ground layer provided on a side opposite to the comb electrode of the piezoelectric layer and having a function of setting a surface acoustic wave characteristic excited in the piezoelectric layer. 11. element.   The surface acoustic wave device according to claim 10, wherein the underlayer is composed of at least one of diamond, sapphire, lithium tantalate, and potassium niobate as a main material. A method for manufacturing a surface acoustic wave device for manufacturing the surface acoustic wave device according to any one of claims 1 to 11,
The method of manufacturing a surface acoustic wave device, wherein the comb electrode and the insulating protective film are formed using the same mask.   The method for manufacturing a surface acoustic wave device according to claim 12, wherein the comb electrode, the reflector, and the insulating protective film are formed using the same mask. A method for manufacturing a surface acoustic wave device for manufacturing the surface acoustic wave device according to any one of claims 1 to 11,
A conductive material layer and an insulating material layer are sequentially formed on the substrate,
Next, the conductive material layer and the insulating material layer are etched using the same mask to form the comb electrode and the insulating protective film.   The surface acoustic wave device according to claim 14, wherein the conductive material layer and the insulating material layer are etched using the same mask to form the comb electrode, the reflector, and the insulating protective film. Method.   16. The method for manufacturing a surface acoustic wave element according to claim 14, wherein the etching of the conductive material layer and the etching of the insulating material layer are performed collectively using the same etching method. An electronic apparatus comprising the surface acoustic wave element according to claim 1.

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