JP3411124B2 - Method for manufacturing surface acoustic wave module element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure and manufacturing method of a surface acoustic wave element widely used for mobile communication and the like.

[0002]

2. Description of the Related Art At present, mobile communication systems such as car radios use a frequency band of several tens of MHz to several hundreds of MHz, but in order to meet the rapidly increasing demand for mobile communication equipment,
System operation is becoming mainstream in the quasi-microwave band above 1.5 GHz. Most of these mobile communication devices have surface acoustic waves (Surface Acoustic Waves) generated on a solid surface.
SAW devices using Wave (SAW) are mainly used for filters. Generally, a SAW element is operated by applying a radio wave to a comb-shaped electrode provided on the surface of a piezoelectric substrate to excite a surface acoustic wave on the surface of the substrate. SAW on the market
In the filter, quartz having a high acoustic velocity of surface acoustic waves is used as a substrate, and Al comb electrodes for surface acoustic wave transmission are formed on the quartz substrate and used.

Conventionally, as a frequency adjusting method for a SAW filter, silicon oxide (Si-O) having an unmatched lattice array on a substrate is used.
Some of the present inventors have already proposed a method of forming a thin film and irradiating it with light to change the propagation velocity of a surface acoustic wave (Japanese Patent Publication No. 3-51128).

[0004]

The operating frequency of a surface acoustic wave module element such as a SAW filter is determined by the acoustic velocity of the acoustic wave peculiar to the piezoelectric body and the arrangement period of the comb-shaped electrodes for transmitting and receiving the acoustic wave. . For example, in the case of a cellular phone, the channel interval of the communication line is 12.5 kHz, so S
The operating frequency accuracy of the AW filter is also required to be extremely high, but in the current SAW filter manufacturing process, the electrode film thickness of 500 nm to several μm and submicron to several μm are used.
The processing precision of the array period of m can be suppressed to within 1%,
It is practically difficult to suppress the desired frequency in the 1.5 GHz band to ± 12.5 kHz, and the yield of products that have undergone a manufacturing process that is extremely strictly controlled based on experience is 50 to 70%. It has been strongly desired to establish a method capable of precisely finely adjusting the operating frequency of the SAW filter. In this respect, the method disclosed in Japanese Patent Publication No. 3-51128 is not yet a fully satisfactory method.

Furthermore, in particular LiNbO ₃ , LiTaO ₃ , Li
_{When a} substrate material with strong pyroelectricity such as ₂ B ₄ O ₇ is used for the SAW filter, the operating frequency changes after the temperature reflow test at 200 to 300 ° C., the propagation loss of the element increases, and the element's propagation loss increases. After the electrodes are formed on the substrate wafer, there is a problem that the wafer is charged during dicing and a potential difference is generated between the electrodes to generate a spark, resulting in a short circuit between the electrodes.

In order to solve the above conventional problems, the present invention provides an element structure for expanding the adjustment range of the operating frequency of the SAW filter and stabilizing the operating frequency of the SAW module element, and at the time of dicing (cutting) the wafer. It is an object of the present invention to solve the problem of electrode destruction that occurs and to improve the efficiency of the SAW module device manufacturing process.

[0007]

In order to achieve the above object, the first surface acoustic wave module element of the present invention comprises:
A surface acoustic wave excitation / reception electrode and a surface acoustic wave propagation substrate. A thin film is formed on at least a part of the surface of the substrate, and the propagation velocity of the surface acoustic wave generated in the thin film is the propagation velocity of the substrate. And an oxide thin film containing a group IV- a element is formed.

In the above structure, the oxide thin film containing the IV- a group element preferably has a different crystal arrangement or constituent element from the substrate.

In the above structure, it is preferable that the oxide thin film containing a group IV- a element is at least one thin film selected from Ti-O type and Zr-O type.

In the above structure, it is preferable that the oxide thin film containing a group IV- a element is a thin film deposited or coated on the substrate.

Further, in the above structure, the substrate is a crystal substrate, and the thin film is a microcrystal containing at least a crystal portion and / or
Alternatively, it is preferably an amorphous thin film.

Further, in the above structure, it is preferable that the oxide thin film containing the IV- a group element is an electrical insulator.

In the above structure, it is preferable that the oxide thin film containing the IV- a group element is present on a part of the surface of the substrate.

Further, in the above structure, the thickness of the oxide thin film containing the IV- a group element is 0.001λ to 0.05λ.
(However, λ indicates the wavelength of the surface acoustic wave).

In the above structure, the substrate is a crystal,
LiTaO ₃ , LiNbO ₃ , Li ₂ B ₄ O ₇ , ZnO, AlN,
Ta ₂ O ₅ , Pb-Nd-Ti-Mn-In-O and Pb-Zn-Ti-O
It is preferably at least one piezoelectric substrate selected from

Next, the first method of manufacturing a surface acoustic wave module element according to the present invention comprises:
-A structure in which an oxide thin film containing a group a element is formed, surface acoustic wave excitation and reception electrodes are formed on the surface of the thin film, and a process for changing the crystal atomic arrangement of the thin film is performed in any step. Have.

In the above structure, the surface acoustic wave exciting and receiving electrodes are formed on the surface acoustic wave propagating substrate, and an oxide thin film containing a group IV- a element is formed on the surface of the electrode.
It is preferable to change the crystal atomic arrangement of the thin film.

Further, in the above constitution, the means for changing the crystal arrangement is preferably at least one means selected from light irradiation, heat ray irradiation and electromagnetic wave irradiation.

Further, in the above structure, it is preferable that the treatment for changing the crystal atomic arrangement of the thin film is performed after the packaging of the surface acoustic wave module element.

Next, a second surface acoustic wave module element of the present invention comprises a surface acoustic wave transmitting and receiving electrode and a surface acoustic wave propagating substrate, and at least a part of the surface of the substrate is provided with a high surface acoustic wave. A resistance thin film is formed, and a thin film is formed on the high resistance thin film to make the propagation velocity of the surface acoustic wave different from the propagation velocity of the surface acoustic wave generated on the substrate.

In the above structure, the high resistance thin film is preferably a high resistance thin film having a resistivity of 10 ³ Ωcm or more.

Further, in the above structure, the film thickness of the high resistance thin film is preferably in the range of 1 nm to 100 nm.

Further, in the above structure, the high resistance thin film is preferably a compound thin film containing at least oxygen.

Further, in the above structure, the high resistance thin film is preferably a compound thin film containing at least nitrogen.

Further, in the above structure, it is preferable that the high resistance thin film is one oxide thin film selected from oxides of titanium (Ti), aluminum (Al), silicon (Si) and lithium (Li). Other oxides such as G
a, In, Tl, Ge, Sn, Pb, Zr, Sc, Y,
Oxides of lanthanum elements, elements such as Nb and Ta can also be used.

In the above structure, it is preferable that the high resistance thin film is one nitride thin film selected from nitrides of aluminum (Al), silicon (Si) and boron (B).

Further, in the above structure, it is preferable that the thin film formed on the high resistance thin film for varying the propagation velocity is at least one thin film selected from oxides and nitrides.

In the above structure, the substrate is LiTa.
It is preferably at least one piezoelectric substrate selected from O ₃ , LiNbO ₃ , and Li ₂ B ₄ O ₇ .

Next, a second method of manufacturing a surface acoustic wave module element according to the present invention comprises forming a conductive metal film on a wafer of a surface acoustic wave propagating substrate and then exciting and receiving the surface acoustic wave. After forming electrodes and cutting (dicing) the wafer, a treatment for increasing the resistance of the metal film to a resistivity of 10 ³ Ωcm or more is performed.

Further, in the above structure, the thickness of the metal film is preferably in the range of 1 nm to 100 nm.

Further, in the above structure, it is preferable that the means for increasing the resistance of the metal film is at least one means selected from oxidation and nitridation.

In the above structure, the substrate is LiTa.
It is preferably at least one piezoelectric substrate selected from O ₃ , LiNbO ₃ , and Li ₂ B ₄ O ₇ .

Next, a third method of manufacturing a surface acoustic wave module device according to the present invention comprises forming a surface acoustic wave exciting electrode and a receiving electrode on a wafer of a surface acoustic wave propagating substrate, and then forming a conductive metal film. Is formed, and after the wafer is diced, the metal film is subjected to a treatment for increasing the resistance to 10 ³ Ωcm or more.

Further, in the above structure, the thickness of the metal film is preferably in the range of 1 nm to 100 nm.

In the above structure, the metal film is preferably a metal or alloy selected from titanium (Ti), aluminum (Al), silicon (Si), boron (B) and lithium (Li).

In the above structure, it is preferable that the means for increasing the resistance of the metal film is at least one means selected from oxidation and nitridation.

In the above structure, the substrate is LiTa.
It is preferably at least one piezoelectric substrate selected from O ₃ , LiNbO ₃ , and Li ₂ B ₄ O ₇ .

[0038]

According to the first surface acoustic wave module element of the present invention, the surface acoustic wave exciting and receiving electrodes and the surface acoustic wave propagating substrate are provided on at least a part of the substrate surface. A thin film is formed, and an oxide thin film containing an IV- a group element for making the propagation velocity of surface acoustic waves generated in the thin film different from the propagation velocity of the substrate is formed, thereby adjusting the operating frequency of the SAW filter. And the operating frequency of the SAW module element can be stabilized. That is, the propagation velocity of the generated surface acoustic wave is deviated from the value of the substrate itself by forming a portion on the substrate surface of the surface acoustic wave module element whose piezoelectric constant, solid density, etc. are different from those of the substrate. The operating frequency can be changed.

In the above, when the oxide thin film containing the IV- a group element has a different crystal arrangement or constituent elements from the substrate, the operating frequency of the surface acoustic wave module element can be changed more effectively.

Further, in the above, if the oxide thin film containing the IV- a group element is at least one thin film selected from the Ti-O system and the Zr-O system, the operating frequency of the surface acoustic wave module element is more effective. Can be changed to.

Further, in the above description, when the oxide thin film containing the IV- a group element is a thin film deposited or coated on the substrate, it is thin and more effectively changes the operating frequency of the surface acoustic wave module element. You can

In the above, if the substrate is a crystalline substrate and the thin film is a microcrystalline and / or amorphous thin film containing at least a crystalline portion, the operating frequency of the surface acoustic wave module element can be changed more effectively. it can.

In the above, if the oxide thin film containing the IV- a group element is an electrical insulator, the electrode can be formed in direct contact with the thin film.

In the above, if the oxide thin film containing the IV- a group element is present on a part of the substrate surface, a module element integrated with the substrate can be formed. Here, being present on a part of the surface of the substrate means being a part of the surface in a plane, or partially forming a thin film by performing ion implantation or the like on the substrate itself.

In the above description, when the thickness of the oxide thin film containing the IV- a group element is in the range of 0.001λ to 0.05λ (where λ represents the wavelength of the surface acoustic wave), The operating frequency of the surface acoustic wave module element can be changed more effectively. The range of the film thickness is a value determined by the geometrical condition of the SAW element, that is, the sound velocity of the surface acoustic wave, and is 0.001 λ based on the wavelength λ of the surface acoustic wave (same as the spatial period λ of the electrode). The range is preferably 0.05λ. More preferable thickness is 0.002λ
The range is 0.03λ.

In the above, the substrate is quartz, LiTa.
O ₃ , LiNbO ₃ , Li ₂ B ₄ O ₇ , ZnO, AlN, Ta
_At least one piezoelectric substrate selected from ₂ O ₅ , Pb-Nd-Ti-Mn-In-O and Pb-Zn-Ti-O is preferable for the surface acoustic wave module device.

Next, according to the first method of manufacturing a surface acoustic wave module element of the present invention, an oxide thin film containing a group IV- a element is formed on a surface acoustic wave propagation substrate, and the thin film of the thin film is formed. By forming the surface acoustic wave exciting and receiving electrodes on the surface and performing the process of changing the crystal atomic arrangement of the thin film in any step, the manufacturing process of the SAW module element can be made highly efficient.

In the above, a surface acoustic wave excitation and reception electrode is formed on a surface acoustic wave propagation substrate, an oxide thin film containing a group IV- a element is formed on the surface of the electrode, and a crystal of the thin film is formed. By changing the atomic arrangement, more efficient and rational production is possible.

Further, in the above, when the means for changing the crystal arrangement is at least one means selected from light irradiation, heat ray irradiation, and electromagnetic wave irradiation, the production can be performed more efficiently and rationally.

Further, in the above, if the process of changing the crystal atomic arrangement of the thin film is performed after the packaging of the surface acoustic wave module element, it can be manufactured more efficiently and rationally.

According to the second SAW module element of the present invention described above, the surface acoustic wave transmitting and receiving electrodes and the surface acoustic wave propagating substrate are provided, and at least a part of the substrate surface is provided. , A high resistance thin film is formed, and a frequency adjusting thin film is formed on the high resistance thin film to make the propagation velocity of the surface acoustic wave different from the propagation velocity of the surface acoustic wave generated on the substrate. The operating frequency of the module element can be changed, and by interposing a high-resistance thin film between the frequency adjustment thin film and the substrate, the substrate surface is protected from various operating frequency variable processes and the operation of the device is stabilized. Can be made.

In the above, the resistivity of the high resistance thin film is 10
^When the thin film has a high resistance of ³ Ωcm or more, the operation loss of the surface acoustic wave module element is reduced and the operation of the surface acoustic wave module element is more stable.

In the above, the high resistance thin film has a thickness of 1
In the range of nm to 100 nm, the operation of the surface acoustic wave module element is more effectively stabilized.

Further, in the above, if the high resistance thin film is a compound thin film containing at least oxygen, the operation of the surface acoustic wave module element will be more stable.

Further, in the above, when the high resistance thin film is a compound thin film containing at least nitrogen, the operation of the surface acoustic wave module element becomes more stable.

Further, in the above, when the high resistance thin film is one oxide thin film selected from oxides of titanium (Ti), aluminum (Al), silicon (Si) and lithium (Li), the elastic surface can be more effectively used. The operation of the wave module element is stabilized.

Further, in the above, if the high resistance thin film is one nitride thin film selected from the nitrides of aluminum (Al), silicon (Si) and boron (B), the operation of the surface acoustic wave module device can be more effectively performed. Is stable.

In the above, the substrate is LiTaO ₃ ,
When the piezoelectric substrate is at least one selected from LiNbO ₃ and Li ₂ B ₄ O ₇ , the operation of the surface acoustic wave module element is more effectively stabilized.

Next, according to the second method of manufacturing the surface acoustic wave module element of the present invention, a conductive metal film is formed on the wafer of the surface acoustic wave propagation substrate,
Since the surface acoustic wave excitation and reception electrodes are formed and the wafer is diced, the metal film is processed to have a high resistance of 10 ³ Ωcm or more, so that a pyroelectric phenomenon occurs on the substrate during dicing. Also, the potential between the electrodes can be set to the same potential and the electrode breakdown can be suppressed.

In the above, the thickness of the metal film is 1 nm.
Within the range of up to 100 nm, more efficient and rational production can be achieved.

Further, in the above, if the means for increasing the resistance of the metal film is at least one means selected from oxidation or nitriding, it can be manufactured more efficiently and rationally.

In the above structure, the substrate is LiTa.
At least one piezoelectric substrate selected from O ₃ , LiNbO ₃ , and Li ₂ B ₄ O ₇ can be manufactured more efficiently and rationally.

Next, according to the third method of manufacturing a surface acoustic wave module element of the present invention, the surface acoustic wave excitation and reception electrodes are formed on the wafer of the surface acoustic wave propagation substrate. Since a conductive metal film is formed on the substrate and the wafer is diced, the metal film is processed to have a high resistivity of 10 ³ Ωcm or more. Therefore, even if a pyroelectric phenomenon occurs on the substrate during dicing, the interelectrode gap is increased. It is possible to suppress the electrode breakdown by setting the same potential.

In the above, the thickness of the metal film is 1 nm.
Within the range of up to 100 nm, more efficient and rational production can be achieved.

In the above, the metal film is titanium (T
A metal or alloy selected from i), aluminum (Al), silicon (Si), boron (B) and lithium (Li) can be produced more efficiently and rationally.

Further, in the above, if the means for increasing the resistance of the metal film is at least one means selected from oxidation or nitriding, it can be manufactured more efficiently and rationally.

In the above, the substrate is LiTaO ₃ ,
At least one piezoelectric substrate selected from LiNbO ₃ and Li ₂ B ₄ O ₇ can be manufactured more efficiently and rationally.

[0068]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

FIG. 1 shows a schematic diagram of the basic structure of a conventional SAW filter. In FIG. 1, a surface acoustic wave is a piezoelectric substrate 1.
It is excited by providing the transmission electrode 2 processed into a comb shape on the surface. The surface wave is detected by the receiving electrode 3. Band pass of a radio frequency band having various frequency characteristics depending on the spatial period λ of the electrodes 2 and 3 on the substrate 1 (or also referred to as the wavelength of the excited surface acoustic wave), the number of pairs of electrode fingers and the degree of intersection. A filter can be made.
The relationship between the operating frequency (operating frequency) f of the element and the spatial period is basically expressed by the equation v = λ · f. Here, v represents the SAW phase velocity (surface acoustic wave propagation velocity) unique to the substrate 1. That is, in order to increase the operating frequency, it is understood that a piezoelectric material having a large phase velocity is used as the substrate 1, or the spatial period of the electrode fingers of the electrodes 2 and 3 is made small, that is, the pitch is made fine. Quartz crystals are widely used among piezoelectric materials having a high phase velocity because they can be stably supplied. The phase velocity of the crystal is 3158 m / s, and the frequency band used in the current mobile communication equipment is 100 MHz.
From 1 GHz, the spatial period of electrodes 2 and 3 is 3 ~
It turns out that it is necessary to make it 30 μm. Normal electrodes 2, 3
Although vapor-deposited Al is used for the above, the state of the vapor deposition (adhesion interface) between the electrodes 2 and 3 and the substrate 1, the film thickness of the electrodes 2 and 3, and the processing accuracy influence the fluctuation of the operating frequency. Particularly in the current technology, the limit of the electrode processing accuracy is 1%, which explains the low yield of the SAW filter operating at a desired frequency. Further, when the frequency in the quasi-microwave band is used, a comb-shaped electrode having a submicron spatial period is used, but a device yield of 100% is practically impossible.

Therefore, the present inventors examined the control and adjustment of the sound velocity (phase velocity) of the surface acoustic wave generated on the surface of the substrate 1.

The factor that changes the phase velocity is the substrate 1
Although changes in 1) temperature and 2) humidity of the electrodes themselves or electrodes 2 and 3 can be raised, all are reversible and are not suitable for fundamental control and adjustment. As is well known, substrate 1
The velocity of the surface acoustic wave generated at the time depends on the orientation of the cut surface of the substrate 1 and the physical constants related to the piezoelectric phenomenon such as Young's modulus, density, and Poisson's ratio. Further, since the surface acoustic wave propagates in the region where the surface depth of the substrate 1 is several tens nm to several hundreds nm, the propagation velocity of the surface acoustic wave can be changed by modulating the physical constant in the vicinity of the surface of the substrate 1 by some method. Various experimental studies were conducted with the expectation that it could be performed.

In order to change the piezoelectric constant of the surface acoustic wave propagating substrate surface, it is necessary to apply tension or compressive stress to the substrate surface to generate strain. Possible methods include i) modification of the surface of the substrate itself , and ii) deposition of some substance on the substrate.

First, the case where a part of the substrate surface of the SAW filter was modified was examined. The formation of the modified portion on the surface portion of the solid material can be obtained by forming a lattice defect portion, implanting impurities, or the like. Therefore, as the first step of the experiment, a modified portion was formed on the surface of the substrate 1 by using an ion beam. In the vacuum container, using a Kaufman type ion source, argon (Ar) ions, hydrogen (H) ions, oxygen (O) ions, and helium (He) ions are irradiated on the surface of the SAW filter, and before and after the ion irradiation. The operating frequency was measured. As a result, they have found that the operating frequency of the SAW filter changes. This means that a lattice defect layer or a crystal rearrangement layer is formed on the surface of the substrate 1 by the ion irradiation, the crystal arrangement is different near the surface of the substrate 1 from the substrate 1, and the solid density and the piezoelectric constant are different. And the layer whose surface acoustic wave propagation velocity is different from that of the substrate 1 is the substrate 1
It is considered that this is because the propagation velocity of the surface acoustic wave, which is formed thinly above and is excited by the electrode 2, is effectively changed as compared with that before the formation.

Even if a small amount of metal element is injected into the surface of the substrate 1 by using a large ion beam to form a modified portion on the surface of the substrate 1, the operating frequency of the SAW filter changes. The inventors also found out.

However, the above method of modifying the surface of the substrate 1 using the ion beam has an advantage that the operating frequency of the SAW filter can be adjusted, but the electrodes 2 and 3 are not always optimal because they are etched at the same time. Not a method.

Further, the present inventors investigated changes in the propagation velocity of surface acoustic waves due to the formation of a thin film on the substrate 1. As a result, they found that the operating frequency of the SAW filter changed. Hereinafter, a specific example will be described.

Example 1 In this example, a SAW for a frequency of 315 MHz in which a quartz crystal is used as a surface acoustic wave generation and propagation substrate.
The filter was used as a sample. The thin film deposited on the quartz substrate was a Ti—O film deposited by high frequency magnetron sputtering. FIG. 2 shows a schematic view of a high frequency magnetron sputtering apparatus used for thin film deposition in this example. A disk target 5 obtained by molding and firing Ti-O ceramics on the magnetron cathode 4 is installed, 13.56 MHz high frequency power is injected, the target 5 is sputtered, and the SAW filter sample 7 is installed on the substrate holder 6. depositing a TiO thin film (main component TiO _2). At this time, 1 Pa of argon (Ar) was used as the sputtering gas, and the high frequency injection power was 30.
W. Sample 7 is not heated. The deposition rate of the Ti-O thin film was 1 nm / min, and the film thickness was set to 20 nm by a deposition process for 20 minutes, for example. 3 (a) and 3 (b) are schematic views of the sectional structure of the SAW filter after the Ti-O thin film is deposited. Figure 3 (a) (b)
8 is a quartz substrate, 9 is a surface acoustic wave transmitting comb-shaped electrode, 11 is a surface acoustic wave receiving comb-shaped electrode, 10 is a high frequency power injection lead wire, 12 is a high frequency power extraction lead wire, and 13 is Ti- An O thin film is shown. In FIG. 3 (a), Al electrodes 9 and 11 are formed on the surface of the quartz substrate 8, lead wires 10 and 12 are connected to the electrodes 9 and 11 of the SAW filter, respectively, and a Ti-O thin film 13 is deposited on the surface. It is sectional drawing of the structure. FIG. 3B shows the Ti-O thin film 13 on the quartz substrate 8.
2 is a cross-sectional view of a structure in which Al electrodes 9 and 11 are formed after depositing and lead wires 10 and 12 are respectively connected.

Next, the operating frequency of the SAW filter shown in FIG. 3 (a) was measured. Regarding the operating frequency, a resonator is constituted by a SAW filter and an amplifier, and the resonant frequency is measured by a frequency measuring device. Thickness of Ti-O thin film 13 and Ti-O thin film 1
3 Relationship of frequency change from resonance frequency before deposition is shown in FIG. As can be seen from FIG. 4, it was confirmed that the frequency can be varied by depositing the Ti—O film 13 on the substrate 8. The reason why the Ti-O film 13 is deposited on the operating frequency of the SAW filter is considered as follows. Surface acoustic waves propagate to the Ti-O film 13 as well as the substrate 8, but the piezoelectric constant of the Ti-O film 13 is different from that of the substrate 8 and the propagation velocity of surface acoustic waves is also different, and the electrode 9 to the electrode 11 It is considered that the velocity of the surface wave that arrives deviates from the velocity of the substrate 8. Actually, the propagation loss of the SAW filter is gradually increased by depositing the Ti—O film 13 on the substrate 8. However, if the thickness of the Ti—O film 13 is 0.03λ or less, the propagation loss is also 1 dB. Below, it was confirmed that there was no practical problem.

If the thin film 13 is a thin film having a crystal arrangement different from that of the substrate 8, the same effect as in the present embodiment can be obtained by varying the frequency. That is, when the substrate 8 is a crystalline substrate, the effect of the present invention is obtained when the thin film 13 is a microcrystalline-amorphous thin film containing at least a crystalline portion (a polycrystalline thin film containing a crystalline portion). Further, even when the constituent element or the constituent ratio of the thin film 13 is different from that of the substrate 8, the same effect as the present embodiment is obtained. If the thin film 13 is an insulator, the SAW
Low operating loss of the filter.

Further, as the substrate 8, other than quartz, LiTaO is used.
Single crystal substrate showing piezoelectricity such as ₃ , LiNbO ₃ , Li ₂ B ₄ O ₇ , ZnO and Al deposited on the surface acoustic wave propagation substrate
N, Ta ₂ O ₅ , Pb-Nd-Ti-Mn-In-O, Pb-Zn-Ti-
It was confirmed that the SAW filter using a piezoelectric thin film such as O also has the frequency changing effect of this embodiment.

As the thin film 13, Zr-O other than Ti-O can be used. Furthermore, in combination with Ti-O or Zr-O, Sr-Ti-O, Ca-Ti-O, Ba-Ti-O, Bi-O,
Tl-O, Pb-O, Si-O, Mn-O, Al-O, Nb-O, T
a-O, Zr-O, Li-O, B-N, Si-N, Al-N, Zr-
Oxides such as N and nitrides, multi-component compounds in which these are combined, polymer materials such as fluorinated polyimide, or monomolecular films composed of polymerizable monomer molecules or laminated films thereof may be used. .

The thin film 13 formed on the substrate 8 may be a continuous film which covers the entire surface of the substrate 8,
Even if it is formed in a discontinuous shape such as an island shape, the operating frequency of the SAW filter can be changed.

(Embodiment 2) The operation frequency of the SAW filter can be effectively changed when light is irradiated to the SAW filter of Embodiment 1 as described below.

In this example, the same 315 MHz SAW filter as in Example 1 was used as a sample, and a krypton fluoride (KrF) excimer laser having a wavelength of 248 nm was used as a light source. FIG. 5 shows a system for measuring the operating frequency of the SAW filter performed in this example. In this example, the laser pulsed light 14 having an energy of 60 mJ was condensed and irradiated on the substrate surface of the SAW filter 15 at 10 Hz for an experiment. The power density of the laser used in this example is 1.2 mW / mm ² per pulse. The operating frequency of the SAW filter 15 was measured by forming a resonator with the amplifier 16 and measuring the frequency of the resonating radio wave with the frequency measuring device 18. FIG. 6 shows the number of shots of the laser pulse light of the SAW filter and the frequency change of the operating frequency of the SAW filter before the laser pulse light irradiation. As shown in FIG. 6, it was found that the operating frequency of the SAW filter can be changed by irradiating the substrate surface with ultraviolet light. In this example, the SAW filter unexpectedly has a propagation loss of about 1.
We also found that we could improve dB. These effects are due to the fact that the surface portion of the quartz substrate is modified by the irradiation of the laser pulse light 14, and a portion having a surface acoustic wave propagation velocity slightly different from that of quartz is formed on the quartz substrate. It is considered that this is because the surface acoustic wave transmitting / receiving comb-shaped electrode of (3) was thermally heated to increase the degree of adhesion to the substrate. It was also confirmed that the same effect can be obtained when the wavelength of the irradiation light is 120 nm or more. That is,
Irradiation of energy rays such as ultraviolet light, infrared light and various electromagnetic waves can be applied to the adjustment of the operating frequency of the SAW filter as in the present embodiment.

In addition to quartz, the present inventors used LiTaO ₃ , LiNbO ₃ , Li ₂ B ₄ O as substrates for surface acoustic wave propagation.
ZnO, AlN, Ta ₂ O ₅ , Pb-Nd-Ti deposited on a single crystal substrate exhibiting piezoelectricity such as ₇ or a surface acoustic wave propagation substrate
It was confirmed that the SAW filter using the Pb-based piezoelectric thin film such as -Mn-In-O and Pb-Zn-Ti-O also has the effect of the frequency change of this embodiment.

In this example, the SAW filter for 315 MHz was used as a sample, but it was also confirmed that SAW filters having different operating frequency bands have the same effect.

The irradiation of energy rays such as light, ultraviolet light, infrared light, various electromagnetic waves, etc. is not limited to the entire surface of the surface acoustic wave propagation substrate constituting the SAW filter. Not limited to the entire surface of the SAW filter including the credit / reception electrodes, but for surface acoustic wave transmission
It may be the entire surface of the SAW filter including the receiving electrode or a part of the substrate.

In the second embodiment, the propagation velocity of the surface acoustic wave is changed in principle, and it does not depend on the materials of the surface acoustic wave transmitting / receiving electrodes and the surface acoustic wave propagating portion.
It was also confirmed that not only the SAW filter but also the module elements using surface acoustic waves such as oscillators, resonators and delay devices have similar effects.

Example 3 Titanium oxide can have various crystal structures such as TiO, Ti ₂ O ₃ and TiO ₂ (rutile type, anatase type).
It is considered that if the thin film is made of Ti-O and the crystal arrangement is changed, the propagation constants of the physical constants related to the piezoelectricity of the thin film and the surface acoustic waves can be changed over a wide range. Therefore, a study was conducted to form a thin film on a surface acoustic wave propagation substrate of a SAW filter and change the crystal arrangement of the thin film.

In this example, a 315 MHz SAW filter was used as a sample as in Examples 1 and 2 above.
On the surface acoustic wave propagating piezoelectric substrate of the SAW filter, the Ti-
An O thin film was deposited, and a SAW filter having the structure shown in FIG. This embodiment will be described with reference to FIG. FIG. 7 shows a schematic diagram of an ion beam sputtering system used for depositing the thin film 13 of this example. The system comprises a SAW filter sample 19 in a vacuum vessel,
A substrate holder 20, an ion gun 21, a sputter target 22, and a crystal vibration type film thickness monitor 23 are included. In this embodiment, the ion gun 21 has a diameter of 30
mm Kaufman type ion gun (Commonwealth, USA), diameter of target 22 after firing after molding
A 75 mm Ti-O ceramic disc was used. For the sputtering, 1.5 SCCM of argon gas was introduced into the ion gun 21, and the sputtering was performed at an acceleration voltage of 500V. The deposition rate of the Ti—O thin film 13 (main component TiO ₂ ) deposited on the substrate 8 can be accurately monitored by the film thickness monitor 23 with an accuracy of 0.01 nm / sec. In this embodiment, the deposition rate is 0.2 nm / min. Met. The Ti-O film having a film thickness of 20 nm was obtained by performing a deposition process for 110 minutes at this speed.

Then, ultraviolet light is applied to the surface of the substrate 8 for Ti-O.
The operating frequency of the SAW filter was measured while irradiating the film 13 using the same measurement system as in Example 2 (FIG. 5).
FIG. 8 shows the Ti-O film 13 when the film thickness of the Ti-O film 13 is 20 nm.
The change in the number of shots of the laser pulsed light irradiated on and the operating frequency of the SAW filter is shown. As shown in FIG.
By irradiating the i-O film 13 with ultraviolet light, the operating frequency of the SAW filter is remarkably changed.

The Ti—O film 1 formed on the surface of the substrate 8
It was also found that when the film thickness of 3 is 1 nm or more, the operating frequency of the SAW filter is changed by ultraviolet irradiation. Actually, the propagation loss of the SAW filter is gradually increased by depositing the Ti—O film 13 on the substrate 8. However, if the thickness of the Ti—O film 13 is 0.03λ or less, the propagation loss is also 1 dB. It was also confirmed below that there is no problem in practical use.

It was also found that the operating frequency of the SAW filter changes even when heat rays or energy rays such as electromagnetic waves are used instead of the above light.

Further, the thin film 13 deposited on the substrate 8 and the wavelength of light, heat rays, and electromagnetic waves to be irradiated were examined.
As a result, it was found that if the light, heat rays, and electromagnetic waves are absorbed by the thin film 13 optically or electromagnetically, the same effect as that of this embodiment is obtained. That is, if the light has a wavelength shorter than the band gap energy of the material of the thin film 13 optically, the energy of the irradiation light is completely absorbed by the thin film 13 and the crystalline state of the thin film 13 changes more efficiently. Can be made. Electromagnetically, if the surface of the thin film 13 is not a mirror surface and has irregularities, the energy of electromagnetic waves is absorbed without being reflected, and it is easy to change the crystalline state of the thin film 13.

Next, in order to clarify the phenomenon that occurs in the thin film 13 deposited on the substrate 8 of the SAW filter when irradiated with energy rays such as light, heat rays and electromagnetic waves, X-ray, electron beam,
It was examined using light. X-ray photoelectron spectroscopy (XPS; X-ray Ph)
It has been found that the crystal state of the Ti—O film 13 approaches the state of TiO ₂ (rutile) by irradiation. According to the spectroscopic measurement, particularly the transmittance measurement, as the irradiation amount increases, the position of the band gap showing the light absorption edge of the Ti—O film 13 approaches 420 nm of the single crystal of TiO ₂ (rutile) from the short wavelength side. It turned out to be steep. Transmission electron microscopy (TEM)
According to e), it was found that the irradiated Ti—O film 13 had grown crystallized portions. Furthermore, Ti-O film 13
As a result of examination of the electron beam diffraction pattern of No. 3, a spot image showing crystallinity was observed from the irradiated Ti—O film 13. According to these analyzes and analyses, in the case of the present embodiment, it was found that the amorphous Ti—O film 13 was crystallized inside the Ti—O film 13 by irradiation with light, heat rays, and electromagnetic waves. . That is, the change in crystallinity of the Ti-O film 13 is
It was found to contribute to the change in the operating frequency of the SAW filter. That is, as shown in the first embodiment, the operating frequency of the SAW filter changes only by depositing the thin film 13 on the substrate 8. This is explained by the fact that the propagation velocity of surface acoustic waves differs between the substrate 8 and the thin film 13, but energy rays such as light, heat rays, and electromagnetic waves excite the atoms and molecules forming the thin film 13 and the energy applied to them. The propagation velocity of the surface acoustic wave in the thin film 13 is further changed by causing the thin film 13 to change the crystal arrangement from the amorphous state to the crystalline state (including the polycrystalline state) or from the single crystal state to the polycrystalline state by the amount. Then, the propagation velocity of the surface acoustic wave generated in the effective SAW filter changes,
It can be said that the operating frequency changes. Then, as shown in FIG. 8, it can be seen that the change of the crystal arrangement in the thin film 13 has an extremely large effect on the change of the operating frequency of the SAW filter.

If the thin film 13 is an insulator, the SAW
We also found that the operating loss of the filter is low.

The thin film 13 formed on the substrate 8 may cover the entire surface of the substrate 8, but even if it is formed in an island shape, it changes the operating frequency of the SAW filter. I confirmed that you can.

Even if the constituent element or constituent element ratio of the thin film 13 is the same as or different from that of the substrate 8, light,
By irradiating the thin film 13 with energy rays such as heat rays and electromagnetic waves, if the crystal arrangement / crystal state of the thin film 13 or the constituent ratio of the constituent elements changes, the effect of varying the operating frequency of the SAW filter of the present embodiment is obtained. I also confirmed that there is.

As the substrate 8, other than quartz, LiTa is used.
Zn deposited on a single crystal substrate showing piezoelectricity such as O ₃ , LiNbO ₃ , Li ₂ B ₄ O ₇ or a substrate for surface acoustic wave propagation.
O, AlN, Ta ₂ O ₅ , Pb-Nd-Ti-Mn-In-O, Pb-Z
It was also confirmed that the SAW filter using the piezoelectric thin film such as a Pb-based piezoelectric material such as n-Ti-O as the substrate 8 also has the effect of changing the frequency.

As the thin film 13 deposited on the substrate 8 of the SAW filter, Zr-O can be used in addition to Ti-O. Furthermore, in combination with Ti-O or Zr-O, Sr-T
i-O, Ca-Ti-O, Ba-Ti-O, Bi-O, Tl-O, Pb-
O, Si-O, Mn-O, Al-O, Nb-O, Ta-O, Zr-
O, Li-O, BN, Si-N, Al-N, Zr-N and other oxides and nitrides, or multi-component compounds combining these, and further polymeric materials such as fluorinated polyimide,
Alternatively, a monomolecular film composed of polymerizable monomer molecules or a laminated film thereof may be used.

In this example, the SAW filter for 315 MHz was used as a sample, but it was also confirmed that SAW filters having different operating frequency bands have the same effect.

The structure shown in this embodiment changes the propagation velocity of surface acoustic waves in principle.
Also, since it does not depend on the material of the substrate 8, it was confirmed that not only the SAW filter but also all the module elements using surface acoustic waves such as oscillators, resonators, and delay devices have similar effects.

Example 4 This example describes the manufacturing process of a suitable device. Figure 9 (a)
(E) shows a standard SAW filter manufacturing process. First, the surface is polished and washed, width 3mm, depth 2
mm on the surface of the crystal substrate 31 of thickness 0.3 mm, thickness 1
The Al electrode thin film 32 having a thickness of μm is formed (a), and the surface acoustic wave transmitting / receiving comb-shaped electrode 33 is formed on the substrate by etching (b), and then the ceramic holder 3
This is fixed inside 4 (c), then the lead wire 35 for high frequency power injection and extraction is connected to the external extraction wire 37 (d), and then sealed with a transparent body such as quartz glass at the final stage. Forming the cutting window 36 and packaging
(e). After that, characteristics such as frequency measurement, loss measurement, and temperature stability are evaluated, and the product is shipped. In the present embodiment, the steps shown in FIGS. 9 (a) to 9 (e), or FIG.
A thin film for changing the propagation velocity of the surface acoustic wave is formed in a step before or after the step.

For example, as shown in FIGS. 10 (a)-(g),
Form the Al electrode thin film 32 on the surface of the crystal substrate 31.
(a) An etching treatment is performed to form a surface acoustic wave transmitting / receiving comb-shaped electrode 33 on the substrate (b), and then this is fixed inside a ceramic holder 34 having a side of 5 mm square (c). ), The high-frequency power injection / extraction lead wire 35 is connected to the external extraction wire 37 (d), and then, for example, the Ti—O-based thin film 38 of Examples 1 to 3 is formed.
(e) Then, a sealing / cutting window 36 is formed by using a transparent body such as quartz glass and packaged (f), and the thin film 38 is modified by using light, heat rays or electromagnetic waves in the final step.
(g). In this example, the thin film 38 is directly deposited on the SAW filter mounted on the holder, which is the simplest method. The thin film 38 may be deposited by using a vacuum device such as the ion beam sputtering method shown in the first to third embodiments, but a method under atmospheric pressure such as spin coating is also effective.

As another example, as shown in FIGS. 11 (a) to 11 (g), the Ti—O type thin film 40 of Examples 1 and 3 is formed on the surface of the quartz substrate 31 (a), A thin film 32 for Al electrode is formed on the surface (b), and a comb-shaped electrode 33 for transmitting / receiving surface acoustic waves is formed on the substrate by etching.
(c) Next, this is fixed inside the ceramic holder 34 (d), then the high-frequency power injection / extraction lead wire 35 is connected to the external extraction wire 37 (e), and then a transparent body such as quartz glass. Is used to form the sealing cutting window 36 for packaging (f), and at the final stage, the thin film 38 is modified using light, heat rays or electromagnetic waves (g).

In this embodiment, the step of forming a thin film on a substrate is step A, and the step of reforming the thin film by using light, heat rays or electromagnetic waves is B. As an application of the process A, as shown in FIG.
There are i) after process d, ii) after process c, and iii) before process a. In the case of i) S mounted on the holder
The simplest method is to deposit a thin film directly on the AW filter. The thin film may be deposited by using a vacuum apparatus such as the ion beam sputtering method shown in this embodiment, but a method under atmospheric pressure such as spin coating is also effective. In the case of ii), the lead wire connecting portion on the electrode is masked to deposit a thin film, or after the thin film is deposited, the lead wire connecting portion is etched to expose the conductive portion of the electrode. In the case of iii), a metal film is deposited after depositing a thin film on the substrate, and the metal film is patterned to form an electrode. As the application of process B,
v) After process d (ie before process e), vi) After process e. In both cases v) and vi), the thin film is modified by laser light irradiation, etc. until the desired characteristics are obtained while connecting to the characteristic measuring device of the SAW filter and measuring its electrical characteristics. When a material that does not transmit light, heat rays or electromagnetic waves is used for the sealing window in step e, step B is applied to step v), but a material that transmits light, heat rays or electromagnetic waves such as a quartz glass material is used for the sealing window. If used for step B, apply step B to vi).

Actually, the required accuracy of the operating frequency of the SAW filter is several tens to several hundreds of ppm, and when the present embodiment is used, the operating frequency can be varied over several thousand ppm, and the variation of the frequency is applied to the thin film. It is simple and highly accurate because it depends on the irradiation amount of light, heat rays or electromagnetic waves and can be performed while measuring the characteristics of the SAW filter.

In this embodiment, the SAW filter for 315 MHz is used as a sample, but SAW filters having different operating frequency bands have the same effect.
The present inventors have also found out.

The structure shown in this embodiment changes the propagation velocity of surface acoustic waves in principle.
Further, since it does not depend on the material of the substrate 8, it was confirmed that not only the SAW filter but also all the module elements using surface acoustic waves such as oscillators, resonators and delay devices have the same effect.

The series of inventions shown in the above Examples 1 to 4 are
It is extremely effective in adjusting the operating frequency of the SAW module element, but the substrate is made of LiTaO ₃ , LiNbO ₃ , L
When a material having strong piezoelectricity and pyroelectricity such as i ₂ B ₄ O ₇ is used, the above-mentioned treatment process using light or heat rays or electromagnetic waves with high intensity for rapid treatment and a sharp temperature gradient are used. When a temperature reflow test of 200 to 300 ° C. was performed, there was a problem that the propagation loss of the device increased or the operating frequency changed. Such a phenomenon cannot be seen when a crystal, which is not so strong in piezoelectricity and pyroelectricity, is used as the substrate. This is considered to be related to the substrate material and the absorption of energy of light, heat rays, or electromagnetic waves, and an experimental study was conducted for the purpose of stabilizing the operation of the SAW module elements having the structures produced in Examples 1 to 4. went. Li
The optical bandgap of TaO ₃ , LiNbO ₃ and Li ₂ B ₄ O ₇ is about 3 eV (up to 400 nm), and the 248 nm light used in Examples 2 to 4 is almost completely absorbed. On the other hand, the band gap of quartz is about 10 eV (up to 120 nm), and 248 nm light is not absorbed but transmitted. Therefore, in the above-mentioned embodiment, the energy of the light that cannot be completely absorbed by the thin film 13 and remains is LiTaO ₃ , LiNb.
It is absorbed by O ₃ and Li ₂ B ₄ O ₇ (substrate 8).
The absorbed energy mainly concentrates in the vicinity of an extremely thin interface between the thin film 13 and the substrate 8, and distortion occurs due to the pyroelectric effect. This strain causes mechanical deterioration in the vicinity of the contact interface between the surface of the substrate 8, the thin film 13, and the electrodes 9 and 11, and the SAW
This is considered to have led to an increase in the propagation loss of the filter and a shift in the operating frequency. Therefore, the present inventors
In the structure in which an extremely thin thin film having a high resistivity is formed on the substrate 8 of the W module element, and the thin film 13 for the purpose of adjusting the operating frequency of the element is formed on the thin film, the thin film is formed on the substrate. I have found that such a problem does not occur, so I will explain.

Example 5 In this example, a SAW filter designed for 900 MHz was used as a sample. 12 (a) and 12 (b) are schematic views of the sectional structure of the SAW filter produced in this example. Figure 1
In 2 (a) and (b), 41 is a 0.3 mm thick 36 ° Y-X cut LiTaO ₃ single crystal substrate, 42 is a surface acoustic wave transmitting comb-shaped electrode, and 44 is a surface acoustic wave receiving comb-shaped electrode. Electrodes, 43 are high frequency power injection lead wires, 45 are high frequency power extraction lead wires, 47 is a Si-O thin film, and 46 is a Ti-O thin film deposited for frequency adjustment. FIG. 12A shows that after forming a high resistance Si—O thin film 47 on the surface of the LiTaO ₃ substrate 41, Al
The electrodes 42 and 44 are formed and the electrode 4 of the SAW filter is formed.
2 is a cross-sectional view of a structure in which lead wires 43 and 45 are connected to 2 and 44, respectively, and a Ti—O thin film 46 is deposited on the surfaces thereof.
FIG. 12B shows an Al electrode 42 on the LiTaO3 substrate 41,
44 is a cross-sectional view of a structure in which a high resistance Si—O thin film 47 is formed and then lead wires 43 and 45 are connected to the electrodes 42 and 44 of the SAW filter, respectively, and a Ti—O thin film 46 is deposited. . 12A and 12B, the thin film 46 was subjected to the step of changing the operating frequency of the SAW filter of the third embodiment. That is, as in the third embodiment, the thin film 46 is formed into a film thickness of 2 by the ion beam sputtering method.
A Ti-O film having a thickness of 0 nm was formed, and a krypton fluoride excimer laser pulse light having a wavelength of 248 nm was irradiated while measuring the operating frequency of the SAW filter. It was confirmed that the operating frequency of the SAW filter changed by about 5 MHz with respect to the number of shots of 300 laser pulse lights, as in FIG.

When a temperature stability test was conducted at 300 ° C. in a nitrogen atmosphere, the high resistance Si—O thin film 47 was found to be the Ti—O thin film 4.
It was found that the fluctuation of the operating frequency of the SAW filter was reduced to 1/2 or less and the propagation loss of the element was reduced by 0.5 dB as compared with the case where it was not between 6 and the substrate 41. It is considered that this is because the high resistance thin film 47 is interposed between the thin film 46 and the substrate 41 to protect the surface of the substrate from various operating frequency variable processes and stabilize the operation of the device.

In the structure of this embodiment, the thin film 47
It was also confirmed that the operation of the surface acoustic wave module device was more stable when the compound was a compound thin film containing at least oxygen.

In the structure of this embodiment, the thin film 47
It was also confirmed that the operation of the surface acoustic wave module device was more stable when the compound film was a compound thin film containing at least nitrogen.

In the structure of this embodiment, the thin film 47
Is a high resistance thin film with a resistivity of 10 3 Ωcm or more,
It was confirmed that the operation loss of the surface acoustic wave module element was reduced and the operation of the surface acoustic wave module element was more stable.

In the structure of this embodiment, the thin film 47
It has been confirmed that when the resistivity of is higher than the resistivity of the thin film 46, the operation loss of the surface acoustic wave module element is reduced and the operation of the surface acoustic wave module element is more stable.

In the structure of this embodiment, the thin film 47
Other than Si-O, IVb group, IIIb group, Vb group, IIIa group, I
It was also confirmed that the operation of the surface acoustic wave module device is more effectively stabilized when the oxide thin film is one oxide selected from the Va group element or the Li oxide.

In the structure of this embodiment, the thin film 47
It was also confirmed that the operation of the surface acoustic wave module device can be more effectively stabilized if the one nitride thin film selected from the nitrides of the IIIa group and the IVa group elements other than Si-O.

In the structure of this embodiment, the thin film 47
It was also confirmed that the operation of the surface acoustic wave module element is more effectively stabilized when the film thickness is in the range of 1 nm to 100 nm.

As the thin film 46, in addition to Ti-O, Zr-
O, Sr-Ti-O, Ca-Ti-O, Ba-Ti-O, Bi-O, T
l-O, Pb-O, Si-O, Mn-O, Al-O, Nb-O, Ta-
O, Zr-O, Li-O, B-N, Si-N, Al-N, Zr-N
It is possible to use oxides and nitrides such as, a multi-component compound in which these are combined, a polymer material such as fluorinated polyimide, or a monomolecular film composed of polymerizable monomer molecules or a laminated film thereof.

In this example, the SAW filter for 900 MHz was used as a sample, but it was also confirmed that SAW filters having different operating frequency bands have the same effect.

It is also confirmed that the structure shown in this embodiment has the same effect not only for the SAW filter but also for all the module elements using surface acoustic waves such as oscillators, resonators and delay devices.

It was also confirmed that the structure shown in this example has the same effect on LiNbO ₃ and Li ₂ B ₄ O _{7 in} addition to LiTaO ₃ as the substrate 41.

Furthermore, the inventors of the present invention, in the case of manufacturing a large number of several hundred SAW module elements from a wafer-like substrate, use a dicing process performed after the formation of the surface acoustic wave transmission / reception electrodes to locally use the dicing. The heat generation is generated on the piezoelectric substrate, a potential difference is generated between the electrodes due to the pyroelectric property of the substrate, and an arc is generated between the electrodes to break down the electrodes. The occurrence of such a problem is caused by LiTaO ₃ , LiNbO ₃ ,
Especially seen in substrate materials with strong piezoelectricity such as Li ₂ B ₄ O ₇ ,
In the high frequency band SAW module element of 1 GHz or more where the electrode interval is narrowed, the strength of the electric field generated between the electrodes is also strong and more serious. Therefore, the present inventors considered that the generation of the arc as described above could be suppressed if the electrodes had the same potential during dicing, and conducted an experimental study. Therefore,
A practical comparative study was carried out when a conductive thin film was formed so as to travel between electrodes.

When the conductive thin film is deposited on the wafer after forming the electrode, destruction of the electrode due to pyroelectricity of the substrate during dicing can be avoided, but the conductive thin film must be removed later. However, after forming a conductive film on the wafer in advance and forming electrodes on the wafer and dicing, the resistance of the conductive film is increased or the conductive film is formed on the wafer after forming the electrodes. If the resistance of the conductive film is increased after dicing, the destruction of the electrodes due to pyroelectricity can be avoided, and it can be used as a SAW module element as it is. It was found that the inventions shown in Examples 1 to 4 can be applied by forming a thin film, and the substrate surface is protected from the frequency adjustment process to stabilize the operation of the device.

As a method for increasing the resistance of the conductive film, i)
Doping of semiconductors with impurities, or removal of impurities,
ii) Oxidation or nitridation of metals or alloys is possible. However, in the method i), the sample is heated to 300 ° C. or more in order to activate the semiconductor itself , plasma processing is required for impurity doping, and a relatively long vacuum or reduction is performed for impurity removal. It is not optimal because it requires heat treatment in a state and deteriorates the substrate surface and electrodes. On the other hand, the method of ii) is simple because if a metal or alloy that is easily oxidized or nitrided is selected, the oxidation or nitriding treatment may be performed after dicing. Furthermore, since metal has a much higher carrier density than semiconductors and compound conductors, there is an advantage that a very thin thin film can be deposited. In addition, the effect of increasing the resistance is exhibited due to the conductivity in the state where the metal is a very thin film.

Further description will be given below.

Example 6 FIGS. 13 (a) to 13 (g) show a manufacturing process of a SAW filter starting from the preparation of a wafer-shaped substrate according to the present invention. In this embodiment, the wafer 48 has a diameter of 75 mm and a thickness of 0.3 mm and is 36 °.
SA for 900MHz using Y-X cut LiTaO ₃ single crystal
It was applied to the element manufacturing process of the W filter. Wafer 48
After mirror-polishing and cleaning the surface of the Si metal thin film 4 on the wafer 48 by the ion beam sputtering method used in the third embodiment.
9 was deposited (a). In this embodiment, an Si metal disk having a diameter of 75 mm was used as the target 22 in the ion beam sputtering system shown in FIG. Sputtering introduces 2.0 SCCM of argon gas into the ion gun 21,
Sputtering was performed at an acceleration voltage of 1 kV. The deposition rate of the Si thin film 49 deposited on the wafer 48 was 0.3 nm / min. At this speed, for example, a deposition process is performed for 10 minutes, and a Si film having a thickness of 3 nm
A film 49 was obtained. Then, an Al thin film 50 for electrodes having a thickness of 800 nm is formed on the Si thin film 49 (b), and an etching treatment is performed to form comb-shaped electrodes 51 for transmitting and receiving surface acoustic waves on the wafer 48 (c). Then, dicing was performed with a precision cutter to cut the wafer 48 into element units (d).
Then fix it inside the ceramic holder 52
(e), and then lead wire 5 for high frequency power injection and extraction
4 was connected to the external lead wire 54 (f). FIG. 13G shows a step of increasing the resistance of the metal film 49. In this embodiment, S
The i metal thin film 49 was oxidized to oxidize Si to form a high resistance Si—O film 55. The oxidation treatment at this time is
The SAW filter sample placed in the ceramic holder 52 was heated to 100 ° C. and was performed in an oxygen atmosphere for 10 minutes. Then, the electrical characteristics of the SAW filter element were measured. In the conventional SAW filter manufacturing process, as shown in FIG.
There is no step of depositing the metal film 49 of (a), and many arcs are generated on the electrode 51 at the time of dicing of (d), but no arc is observed in this embodiment. Table 1 shows the results of the measurement of the extraction electrical characteristics of 100 SAW filters following the step (g) in comparison with the conventional method.

[0129]

[Table 1] Approximately 60% of the SAW filters produced by the conventional method cannot be used because of a short circuit between the electrodes, whereas the SAW filters produced in this example are 100% usable.
It was proved that the influence of pyroelectricity generated on the wafer 48 during the dicing of (d) could be avoided. The Si-O film 55
Must have a high resistivity of 10 ³ Ωcm or more, and due to insufficient oxidation of the Si metal film 49, Si-O
It was also confirmed that when the resistivity of the film 55 is lower than 10 ³ Ωcm, the propagation loss of the SAW filter also exceeds the practical level of 3 dB.

In this embodiment, for high frequency power injection
After connecting the extraction lead wire 54 to the external extraction wire 54 (f), the Si metal film 49 was oxidized to form the Si—O film 55. The step (g) should be after the dicing step (d). It was also confirmed that the effect of this example can be obtained any time.

Further, it was also confirmed that the effect of this embodiment is obtained when the thickness of the metal film 49 and the SAW filter are in the range of 1 nm to 100 nm. Furthermore, in this film thickness range, S
Since the operating frequency of the AW filter also changes only about several tens of kHz, it was also confirmed that the frequency of the element can be changed by performing the frequency adjustment shown in Examples 1 to 4 as in Examples 1 to 4.

The metal film 49 is made of T instead of Si.
It was also confirmed that the same effect can be obtained by using i, Al, boron (B), Li, or an alloy in which these are combined.

It was also confirmed that, as a means for increasing the resistance of the metal film 49, nitriding other than oxidation has the same effect.

In this example, the SAW filter for 900 MHz was used as a sample, but it was also confirmed that SAW filters having different operating frequency bands have the same effect.

It was also confirmed that the structure shown in this example has the same effect not only for the SAW filter but also for all the module elements using surface acoustic waves such as oscillators, resonators and delay devices.

It was also confirmed that the structure shown in this example has the same effect on LiNbO ₃ and Li ₂ B ₄ O ₇ as the substrate 48, in addition to LiTaO ₃ .

(Example 7) In Example 6, the film thicknesses 1 to 10 deposited on the wafer 48 were measured.
The electrode 51 is formed on the 0 nm metal film 49, but the Al thin film 50 must be etched without removing the Al thin film 50 having a film thickness of 800 nm from the metal film 49. Therefore, even in the case where the metal film 49 is formed after the electrode 51 is formed, it is possible to realize an effective production of the SAW filter while avoiding the effect of pyroelectricity during dicing.

FIGS. 14 (a) to 14 (g) show the manufacturing process of the SAW filter starting from the preparation of the wafer-shaped substrate according to the present invention. Also in this embodiment, the wafer 48 has a diameter of 75 mm and a thickness of
Using 0.3mm 36 ° Y-X cut LiTaO ₃ single crystal, 900
It was applied to the element manufacturing process of the SAW filter for MHz. After the surface of the wafer 48 is mirror-polished and washed, Al with a thickness of 800 nm is used.
The electrode thin film 50 is formed (a), and the surface acoustic wave transmitting / receiving comb-shaped electrode 51 is formed on the wafer 48 by etching (b). Then, the ion beam sputtering used in the third embodiment is performed. A Si metal thin film 49 was deposited on the wafer 48 by the method (c). In this embodiment, in the ion beam sputtering system shown in FIG.
An Si metal disk having a diameter of 75 mm was used as The sputtering was carried out by introducing 2.0 SCCM of argon gas into the ion gun 21 and accelerating the voltage at 1 kV. The deposition rate of the Si thin film 49 deposited on the wafer 48 was 0.3 nm / min. A Si film 49 having a film thickness of 3 nm was obtained by performing a deposition process for 10 minutes at this speed. After that, dicing is performed with a precision cutter on the Si thin film 49, and the wafer 4
8 was cut (d). Next, this was fixed inside the ceramic holder 52 (e), and then the high-frequency power injection / extraction lead wire 54 was connected to the external extraction wire 54.
(f). FIG. 14G shows a step of increasing the resistance of the metal film 49. In this embodiment, the Si metal thin film 49 is oxidized to oxidize Si to form a high resistance Si—O film 55.
The oxidation treatment at this time was performed by heating the SAW filter sample installed in the ceramic holder 52 to 100 ° C. and for 10 minutes in an oxygen atmosphere. Then, the electrical characteristics of the SAW filter element were measured. In the manufacturing process of the conventional SAW filter, there is no step of depositing the metal film 49 of FIG. 14A, and many arcs are generated on the electrode 51 at the time of dicing of FIG. 14D, but in this embodiment, the arc is generated. Could not be seen. After the step (g), 100 SAW filters were sampled and their electrical characteristics were measured. As a result, the SAW filters produced in this example were 100% used, similar to the results shown in Table 1 of Example 6. It was demonstrated that it was possible and that the influence of pyroelectric generated on the wafer 48 during the dicing of (d) could be avoided. The resistivity of the Si-O film 55 needs to be as high as 10 ³ Ωcm or more, and the resistivity of the Si-O film 55 is less than 10 ³ Ωcm due to insufficient oxidation of the Si metal film 49. It was also confirmed that the propagation loss of the SAW filter exceeds a practical level of 3 dB if it is low.

The thickness of the metal film 49 is 1 nm to 100.
It was also confirmed that the effect of this example was obtained in the range of nm. Furthermore, in this film thickness range, the operating frequency of the SAW filter also changes by only about several tens of kHz, so if the frequency adjustment shown in Examples 1 to 4 is performed following this Example,
It was also confirmed that the frequency of the element can be changed as in Examples 1 to 4.

As the metal film 49, T is used instead of Si.
It was also confirmed that the same effect can be obtained by using i, Al, boron (B), Li, or an alloy in which these are combined.

It was also confirmed that, as a means for increasing the resistance of the metal film 49, nitriding other than oxidation has the same effect.

In this example, the SAW filter for 900 MHz was used as a sample, but it was also confirmed that SAW filters having different operating frequency bands have the same effect.

It was also confirmed that the structure shown in this embodiment has the same effect not only for the SAW filter but also for all the module elements using surface acoustic waves such as oscillators, resonators and delay devices.

It was also confirmed that the structure shown in this example has the same effect on LiNbO ₃ and Li ₂ B ₄ O ₇ as the substrate 48, in addition to LiTaO ₃ .

[0145]

As described above, the present invention can provide an element structure capable of highly accurately varying and stabilizing the operating frequency of a surface acoustic wave module element, which has been a problem in the past. In the manufacturing process of the SAW module element, the operating frequency of the element is measured immediately before packaging, or at the final stage after packaging when a glass material that transmits light and electromagnetic waves is used as a packaging material for element protection. However, the product yield of the device can be significantly increased. In addition, since a thin film is formed on the surface acoustic wave propagation substrate, it protects the element surface from dust and dust generated in the subsequent element manufacturing process. The above utility value is extremely large.

Further, according to the present invention, since the thin film for adjusting the operating frequency of the device is formed on the device, not only can the operating frequency of the device be adjusted to a desired value, but it also occurs in the subsequent manufacturing process of the device. Protects the element surface from dust and dust,
The operating characteristics of the element itself can be stabilized. Also,
When a substrate material with strong pyroelectricity, which has been a problem in the past, is used for the module surface of the elastic element, after the electrodes are formed on the substrate wafer, the wafer is charged during dicing and a potential difference occurs between the electrodes. The industrial value is extremely high in that it is possible to avoid electrode breakage caused by sparking and short-circuiting between electrodes, and to significantly improve the product yield of the device.

[Brief description of drawings]

FIG. 1 is a schematic diagram of the basic structure of a conventional SAW filter.

FIG. 2 is a schematic view of a high frequency magnetron sputtering apparatus used for thin film deposition in Example 1 of the present invention.

FIG. 3 is a schematic sectional view of the SAW filters of Examples 1 and 2 of the present invention.

FIG. 4 is a film pressure and SA of the Ti—O thin film of Example 1 of the present invention.
FIG. 5 is a relational diagram of changes in operating frequency of the W filter.

FIG. 5 is an operating frequency measurement diagram of the SAW filter according to the second embodiment of the present invention.

FIG. 6 is an operating frequency diagram of the SAW filter with respect to the number of laser light shots according to the second embodiment of the present invention.

FIG. 7 is a schematic diagram of an ion beam sputtering system according to a third embodiment of the present invention.

FIG. 8 is a diagram showing operating frequencies of the SAW filter with respect to the number of laser light shots according to the third embodiment of the present invention.

FIG. 9 is a standard schematic view showing the manufacturing process of the SAW filter of Example 4 of the present invention.

FIG. 10 is a schematic view showing a manufacturing process of a SAW filter of Example 4 of the present invention.

FIG. 11 is a schematic view showing a manufacturing process of a SAW filter of Example 4 of the present invention.

FIG. 12 is a schematic cross-sectional structure diagram of a SAW filter of Example 5 of the present invention.

FIG. 13 is a schematic view showing a manufacturing process of a SAW filter of Example 6 of the present invention.

FIG. 14 is a schematic view showing a manufacturing process of a SAW filter of Example 7 of the present invention.

[Explanation of symbols]

1,8 Piezoelectric body 2,9,42 Comb electrode for transmission 3,11,44 Comb electrode for reception 4 Magnetron cathode 5,22 Sputter target 6,20 Substrate holder 7,15,19 SAW filter sample 10,12, 43, 45 Lead wire 13 Deposited thin film 14 Laser light 16 Amplifier 17 Attenuator 18 Frequency measuring instrument 21 Ion gun 23 Crystal vibrating type film thickness monitor 31 Crystal substrate 32, 50 Al electrode thin film 33, 51 Electrode 34, 52 Ceramic holder 35 , 54 Lead wire 36 Window for sealing / cutting 37, 53 External extraction wire 38, 40, 46 Ti-O thin film 39 Light, heat ray or electromagnetic wave 41, 48 LiTaO ₃ substrate 49 Si metal film 47, 55 High resistance Si-O film

Front page continuation (72) Inventor Shunichiro Kawashima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-63103 (JP, A) JP-A-52-16146 (JP) , A) Japanese Unexamined Patent Publication No. 52-63643 (JP, A) Actual Development No. 47-93744 (JP, U) US Patent 4243960 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03H 9/145 H03H 9/25 H03H 3/08

Claims (10)

(57) [Claims] 1. An oxide thin film containing a group IV-a element is formed on a surface acoustic wave propagation substrate, and surface acoustic wave excitation and reception electrodes are formed on the surface of the thin film. A method of manufacturing a surface acoustic wave module element, which comprises a process of changing a crystal atomic arrangement of the thin film. 2. A surface acoustic wave exciting and receiving electrode is formed on a surface acoustic wave propagating substrate, and IV-a is formed on the surface of the electrode.
The method of manufacturing a surface acoustic wave module element according to claim 1 , wherein an oxide thin film containing a group element is formed, and a treatment for changing a crystal atom arrangement of the thin film is performed. 3. The means for changing the crystal arrangement is light irradiation,
The method for manufacturing a surface acoustic wave module element according to claim 1, which is at least one means selected from heat ray irradiation and electromagnetic wave irradiation. 4. The method for manufacturing a surface acoustic wave module element according to claim 1 , wherein the treatment for changing the crystal atom arrangement of the thin film is performed after packaging the surface acoustic wave module element. 5. A conductive metal film is formed on a wafer of a surface acoustic wave propagation substrate, electrodes for surface acoustic wave excitation and reception are formed on the wafer, and the metal film is formed after cutting (dicing) the wafer. A method of manufacturing a surface acoustic wave module element, which comprises a treatment for increasing the resistivity to 10 ³ Ωcm or more. 6. A conductive metal film is formed on a surface acoustic wave propagation substrate and a surface acoustic wave excitation and reception electrode formed on the wafer, and the metal film has a resistivity of 10 ³ after dicing the wafer. A method of manufacturing a surface acoustic wave module element, which comprises a treatment for increasing the resistance to Ωcm or more. 7. The method of manufacturing a surface acoustic wave module element according to claim 5 , wherein the thickness of the metal film is in the range of 1 nm to 100 nm. 8. The metal film is a titanium (Ti), aluminum (Al), silicon (Si), according to claim 5 is boron (B) and metal or alloy selected from lithium (Li)
Alternatively, the method of manufacturing the surface acoustic wave module element according to the sixth aspect . 9. means for increasing the resistance of the metal film is at least one means selected from oxidation and nitriding claims
7. The method for manufacturing the surface acoustic wave module element according to 5 or 6 . 10. The method of manufacturing a surface acoustic wave module element according to claim 5 , wherein the substrate is at least one piezoelectric substrate selected from LiTaO ₃ , LiNbO ₃ , and Li ₂ B ₄ O ₇ .