JP2006304206A - Surface acoustic wave element, composite piezoelectric chip, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element having high productivity and a high improvement effect of a frequency-temperature characteristic, a composite piezoelectric chip and its manufacturing method. <P>SOLUTION: The surface acoustic wave element with an electrode for exciting and detecting surface acoustic waves formed on a piezoelectric substrate, comprises at least a composite piezoelectric chip obtained by processing a composite piezoelectric substrate with a piezoelectric substrate and a support base stuck together into a chip shape, and a packaging substrate for packaging the composite piezoelectric chip by flip chip bonding across a bump. They are packaged so as to make an expansion coefficient αc (ppm/°C) of the surface of the piezoelectric substrate in a prescribed direction and an expansion coefficient αs (ppm/°C) of the packaging substrate satisfy a relation being αs<αc<αs+6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave element, a composite piezoelectric chip used for a surface acoustic wave element, and the like, and a method for manufacturing the same.

A surface acoustic wave (SAW) element in which a comb-shaped electrode for exciting a surface acoustic wave is formed on a piezoelectric substrate is used as a frequency selection component in high-frequency communication such as a cellular phone. The piezoelectric substrate material used for this has high conversion efficiency (hereinafter referred to as electromechanical coupling coefficient) from electrical signals to mechanical vibrations, and the center frequency of filters, etc., determined by the electrode spacing of the comb electrodes and the acoustic velocity of the elastic waves. Is required not to vary with temperature (hereinafter referred to as frequency-temperature characteristics).
In other words, it is preferable to have a piezoelectric substrate having both a large electromechanical coupling coefficient and a small frequency temperature coefficient.
An example of a piezoelectric substrate that realizes such characteristics is a composite piezoelectric substrate in which a piezoelectric substrate and another substrate are bonded.

As an example of such a composite piezoelectric substrate, an electrode for exciting and detecting an elastic wave is provided on the surface of the piezoelectric material, and the temperature stabilization is characterized in that a composite laminate is joined to the back surface of the piezoelectric material. A surface wave device is disclosed. This surface wave device is such that temperature correction is performed in the piezoelectric material by inducing a controlled stress change in the piezoelectric material (see Patent Document 1).
In this example, “the LiNbO ₃ (lithium niobate) substrate is firmly bonded to the composite laminate to generate a compressive force on the substrate as described above, and this compressive force increases as the temperature increases. It is possible to obtain a means for correcting the influence of temperature on the delay time and the filter center frequency. " This means that the expansion coefficient of the composite laminate as the support substrate is smaller than that of the surface acoustic wave propagation direction of the LiNbO ₃ substrate, which is a piezoelectric material, and stress is generated in the piezoelectric substrate in response to temperature changes. This means that the influence of temperature on the delay time and filter center frequency of the SAW device can be corrected.

Further, an electrical component is disclosed in which a functional element having an electrode provided on the surface of the piezoelectric plate is housed in a package by bonding a rigid plate and a piezoelectric plate using an adhesive (Patent Document). 2).
That is, a surface acoustic wave device using a composite piezoelectric substrate in which a piezoelectric material and a substrate having a smaller expansion coefficient are bonded has improved frequency temperature characteristics, and a rigid plate and a piezoelectric plate are bonded using an adhesive. It is a well-known technique to combine them into an integrated substrate.

Also, a surface acoustic wave device comprising a piezoelectric substrate, an interdigital transducer (IDT) and a bump each having a plurality of electrode fingers and a bus bar that commonly connects these electrode fingers, formed on the piezoelectric substrate. Is a mounting structure of a surface acoustic wave element mounted on a mounting substrate by flip chip bonding via the bump, the mounting substrate having a smaller linear expansion coefficient than the piezoelectric substrate, and A mounting structure of a surface acoustic wave element is disclosed, wherein the bumps are arranged so that thermal expansion and contraction of the piezoelectric substrate due to temperature changes are suppressed by the mounting substrate (Patent) Reference 3).
In the example of this example, LiTaO ₃ (expansion coefficient 16 ppm / ° C.) is used as the piezoelectric body, and alumina (expansion coefficient 7 ppm / ° C.) is used as the mounting base, and the chip is mounted on the mounting substrate by flip chip bonding via bumps. In the surface acoustic wave filter, it is disclosed that the frequency variation due to temperature is improved by −11 kHz / ° C. at an operating frequency of 1.9 GHz.
This improvement effect is preferable because it is improved by about 6 ppm / ° C. in terms of temperature coefficient.

On the other hand, in Non-Patent Document 1, 48 ° rotated Y-cut LiTaO ₃ is used as a piezoelectric body, and an elastic using a composite piezoelectric substrate in which a Si substrate as a supporting substrate is directly bonded to the piezoelectric body via a SiO ₂ layer. A surface wave device is disclosed. The temperature characteristics of the operating frequency of this surface acoustic wave device are as follows. When the composite piezoelectric chip is connected by the bonding wire method, the temperature characteristic of the operating frequency is −12 ppm / ° C., whereas the flip chip bonding method is −22 ppm / ° C. (−35 ppm / ° C.) and temperature characteristics are described as being deteriorated.

JP 51-25951 A Japanese Patent Laid-Open No. 02-62108 JP 2003-324334 A BPAbbot, J. Caron, J. Chocola, K. Lin, S. Malocha, N. Naumenko and P. Welsh, "Advances in Rf SAW Substrates", 2nd International Symposium on Acoustic Wave Devices for Future Mobile Communication Systems, pp. 233-243,2003

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface acoustic wave element, a composite piezoelectric chip, and a method of manufacturing the same, which are highly productive and have a high effect of improving frequency temperature characteristics. It is in.

In order to solve the above problems, the present invention provides a surface acoustic wave element in which an electrode for exciting and detecting surface acoustic waves is formed on a piezoelectric substrate, and is a composite comprising at least a piezoelectric substrate and a support substrate bonded together. A composite piezoelectric chip obtained by processing a piezoelectric substrate into a chip shape, and a mounting substrate on which the composite piezoelectric chip is mounted by flip chip bonding via a bump, and an expansion coefficient αc (ppm / ° C.) in a specific direction on the surface of the piezoelectric substrate. ) And an expansion coefficient αs (ppm / ° C.) of the mounting substrate,
αs <αc <αs + 6
The surface acoustic wave device is provided so as to satisfy the following relationship (claim 1).

  Thus, a composite piezoelectric chip obtained by processing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate into a chip shape, and a mounting substrate on which the composite piezoelectric chip is mounted by flip chip bonding via a bump, If the surface acoustic wave element is mounted so that the expansion coefficient αc in the specific direction of the surface of the piezoelectric substrate and the expansion coefficient αs of the mounting substrate satisfy the above relationship, the surface acoustic wave element has high productivity and high frequency temperature characteristic improvement effect. it can.

In this case, the specific direction is preferably within ± 0.5 degrees from the propagation direction of the surface acoustic wave excited by the electrode.
As described above, if the specific direction is within ± 0.5 degrees from the propagation direction of the surface acoustic wave, the effect of improving the frequency-temperature characteristics can be surely obtained, and the propagation loss of the surface acoustic wave is reduced. Thus, a surface acoustic wave device with little insertion loss can be obtained.

The mounting substrate is preferably made of alumina or a low expansion ceramic.
As described above, if the mounting substrate is made of alumina or low expansion ceramic, the composite piezoelectric chip is mounted so that the expansion coefficients αc and αs satisfy the above relationship by adjusting the thickness of the piezoelectric substrate and the like. It can be a surface acoustic wave element.

The piezoelectric substrate is preferably made of any one of lithium tantalate, lithium niobate, and lithium borate.
Thus, if the piezoelectric substrate is made of a crystal material having a large electromechanical coupling coefficient, a surface acoustic wave element having a wide bandwidth as a frequency selective filter and a small insertion loss is obtained.

Further, the present invention is a composite piezoelectric chip obtained by processing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate into a chip shape, and the composite piezoelectric chip excites and detects surface acoustic waves on the piezoelectric substrate. An electrode is formed and mounted on a mounting board by flip chip bonding via a bump, and an expansion coefficient αc (ppm / ° C.) in a specific direction on the surface of the piezoelectric substrate is an expansion coefficient αs ( ppm / ° C)
αs <αc <αs + 6
Provided is a composite piezoelectric chip that is mounted so as to satisfy the following relationship.

  Thus, a composite piezoelectric chip obtained by processing a composite piezoelectric substrate in which a piezoelectric substrate and a support substrate are bonded into a chip shape, electrodes for exciting and detecting surface acoustic waves are formed on the piezoelectric substrate, and bumps are formed. If it is mounted on the mounting substrate by flip-chip bonding and mounted so that the expansion coefficient αc in the specific direction of the piezoelectric substrate surface satisfies the above relationship with the expansion coefficient αs of the mounting substrate, production It is possible to obtain a composite piezoelectric chip capable of producing a surface acoustic wave device having high performance and high frequency temperature characteristic improvement effect.

In this case, the specific direction is preferably within ± 0.5 degrees from the propagation direction of the surface acoustic wave excited by the electrode.
Thus, if the specific direction is within ± 0.5 degrees from the propagation direction of the surface acoustic wave, the effect of improving the frequency-temperature characteristics can be reliably obtained, and the propagation loss of the surface acoustic wave is reduced. A composite piezoelectric chip capable of producing a surface acoustic wave element with low insertion loss can be obtained.

The mounting board is preferably made of alumina or a low expansion ceramic.
As described above, when the mounting substrate on which the composite piezoelectric substrate is mounted is made of alumina or low expansion ceramic, the expansion coefficient αc and αs satisfy the above relationship by adjusting the thickness of the piezoelectric substrate. A composite piezoelectric chip that can be mounted can be obtained.

The piezoelectric substrate is preferably made of any one of lithium tantalate, lithium niobate, and lithium borate.
Thus, if the piezoelectric substrate is made of a crystal material having a large electromechanical coupling coefficient, a composite piezoelectric chip capable of producing a surface acoustic wave element having a wide bandwidth as a frequency selective filter and a small insertion loss can be obtained. .

The present invention also relates to a method of manufacturing a surface acoustic wave device, wherein at least a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate to a chip shape is processed into a surface acoustic wave on the piezoelectric substrate. When the composite piezoelectric chip is mounted on a mounting substrate by flip chip bonding via a bump, an expansion coefficient αc (ppm / ° C.) in a specific direction of the surface of the piezoelectric substrate, The expansion coefficient αs (ppm / ° C.) of the mounting substrate is
αs <αc <αs + 6
The surface acoustic wave device is manufactured so as to satisfy the following relationship: (Claim 9)

  Thus, an electrode for exciting and detecting surface acoustic waves is formed on a piezoelectric substrate of a composite piezoelectric chip obtained by processing a composite piezoelectric substrate in which a piezoelectric substrate and a support substrate are bonded to a chip shape, and the composite piezoelectric chip is bumped. When mounting on a mounting substrate by flip-chip bonding via the substrate, the expansion coefficient αc (ppm / ° C.) of the piezoelectric substrate surface in a specific direction and the expansion coefficient αs (ppm / ° C.) of the mounting substrate satisfy the above relationship. If mounted in this manner, a surface acoustic wave device having a high frequency temperature characteristic improvement effect can be manufactured with high productivity.

  A surface acoustic wave device according to the present invention, wherein a composite piezoelectric chip obtained by processing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate into a chip shape, and mounting the composite piezoelectric chip via bumps by flip chip bonding If the surface acoustic wave device is mounted so that the expansion coefficient αc in the specific direction of the surface of the piezoelectric substrate and the expansion coefficient αs of the mounting substrate satisfy the relationship of αs <αc <αs + 6, the productivity is improved. A surface acoustic wave device having a high frequency temperature characteristic improvement effect can be obtained.

  Also, a composite piezoelectric chip according to the present invention, in which an electrode for exciting and detecting surface acoustic waves is formed on a piezoelectric substrate, and mounted on a mounting substrate by flip chip bonding via a bump, If it is mounted so that the expansion coefficient αc in a specific direction satisfies the above relationship with the expansion coefficient αs of the mounting substrate, a composite piezoelectric device that can produce a surface acoustic wave device with high productivity and high frequency temperature characteristic improvement effect. Can be a chip.

  Further, according to the present invention, an electrode for exciting and detecting surface acoustic waves is formed on a piezoelectric substrate of a composite piezoelectric chip obtained by processing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate into a chip shape. When mounting on a mounting board by flip chip bonding via a bump, the expansion coefficient αc (ppm / ° C.) of the piezoelectric substrate surface in a specific direction and the expansion coefficient α s (ppm / ° C.) of the mounting board satisfy the above relationship. If it is mounted so as to satisfy, a surface acoustic wave element having a high effect of improving frequency temperature characteristics can be manufactured with high productivity.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.
FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a surface acoustic wave device according to the present invention.
The surface acoustic wave element 10 includes a composite piezoelectric chip 1 obtained by processing at least a composite piezoelectric substrate obtained by bonding a piezoelectric substrate 2 and a support substrate 3 into a chip shape, and flip-chip bonding of the composite piezoelectric chip 1 via bumps 7. And a mounting substrate 8 to be mounted. An electrode 9 for exciting and detecting surface acoustic waves is formed on the piezoelectric substrate 1.
The piezoelectric substrate 1 is mounted so that the expansion coefficient αc (ppm / ° C.) in the specific direction of the surface of the piezoelectric substrate 1 and the expansion coefficient αs (ppm / ° C.) of the mounting substrate satisfy the relationship of αs <αc <αs + 6. It is characterized by being.

By having such a configuration, the surface acoustic wave device 10 has high productivity and high frequency temperature characteristic improvement effect.
That is, the surface acoustic wave device on which the composite piezoelectric substrate is mounted by flip-chip bonding as in the present invention has a frequency temperature coefficient of several ppm / ° C. to several tens ppm / ° C. as compared with the case where it is mounted by, for example, the chip and wire method. Not only the degree of improvement but also mounting by flip-chip bonding can increase productivity.

  Further, when αc is smaller than αs, similarly to Non-Patent Document 1, the result is that the frequency temperature characteristics when mounted by flip-chip bonding are deteriorated compared to when mounted by the chip-and-wire method, Both the frequency temperature characteristic improvement effect and high productivity cannot be achieved. When αc is larger than αs + 6 (ppm / ° C.), the effect of improving the frequency temperature coefficient is small. That is, by mounting so as to satisfy the relationship of αs <αc <αs + 6, both a high frequency improvement effect and high productivity can be achieved. In order to satisfy the above relationship, the expansion coefficient may be mounted by adjusting the thickness of the piezoelectric substrate, the thickness of the adhesive layer that bonds the piezoelectric substrate and the support substrate, the chip size, and the like.

  Also, if the specific direction is within ± 0.5 degrees from the propagation direction of the surface acoustic wave, the effect of the expansion coefficient appears most prominently in the propagation direction of the surface acoustic wave. Can get to. In addition, surface acoustic wave propagation loss is reduced, and a surface acoustic wave device with less insertion loss can be obtained.

Hereinafter, the surface acoustic wave element 10 will be described in detail.
The composite piezoelectric chip 1 is obtained by processing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate 2 and a support substrate 3 into a chip shape, and electrodes 9 for exciting and detecting surface acoustic waves are formed on the piezoelectric substrate 2. In addition, it is mounted on a mounting substrate by flip chip bonding via a bump, and the expansion coefficient αc (ppm / ° C.) in a specific direction on the surface of the piezoelectric substrate is the expansion coefficient αs (ppm / ° C.) and αs of the mounting substrate. It is mounted so as to satisfy the relationship <αc <αs + 6.
By having such a configuration, the composite piezoelectric chip 1 can be a composite piezoelectric chip capable of producing a surface acoustic wave element with high productivity and high frequency temperature characteristic improvement effect.

The composite piezoelectric chip 1 is formed by processing a composite piezoelectric substrate in which a piezoelectric substrate 2 and a support substrate 3 having a smaller expansion coefficient are bonded directly or via an adhesive layer 4 into a chip shape. There may be.
With such a configuration, stress is generated in the piezoelectric substrate 2 in accordance with the temperature change, and in addition to the effect that the expansion coefficients αc and αs satisfy the above relationship, the frequency temperature characteristics can be further improved. . Moreover, if it bonds together through the contact bonding layer 4, it can be made comparatively cheap. Such a composite piezoelectric chip 1 can be manufactured, for example, by applying an adhesive to one or both of the piezoelectric substrate 2 and the support substrate 3 and bonding them firmly under vacuum to bond them firmly. At this time, it is preferable to clean the surface of each substrate before bonding so that no foreign matter is mixed into the adhesive surface, and the surface is subjected to a hydrophilic treatment with an ammonia-hydrogen peroxide aqueous solution or a plasma treatment. Alternatively, the substrate may be heated to 100 ° C. and pretreated with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone to increase the adhesive force.
The size of the composite piezoelectric substrate that is the base material of the composite piezoelectric chip is not particularly limited. For example, the composite piezoelectric substrate may have a diameter of 100 mm, but may be larger or smaller.

  Moreover, it is preferable that the piezoelectric substrate 2 is 5-100 micrometers in thickness, and the adhesion surface 5 of the piezoelectric substrate 2 is processed into the rough surface. If the adhesive surface 5 is processed into a rough surface, the reflection of the back surface of the bulk wave is suppressed, and the adhesive force of the piezoelectric substrate can be further increased. Further, if the thickness of the piezoelectric substrate 2 is 5 to 100 μm, particularly preferably 15 to 30 μm, it is preferable because warpage due to heating is small and there is no crack. If the thickness of the piezoelectric substrate 2 is less than 5 μm, cracks may occur when the piezoelectric substrate 2 is processed to a desired thickness, for example, when processing strain generated by, for example, grinding or lapping process remains inside the piezoelectric substrate. is there. On the other hand, if the thickness is larger than 100 μm, the piezoelectric substrate 2 may be cracked when the composite piezoelectric chip 1 is heated to about 250 ° C. In order to set the thickness of the piezoelectric substrate 2 to a desired value within the above range, for example, after forming the composite piezoelectric substrate, the piezoelectric substrate may be ground, lapped, or polished (polished).

The piezoelectric substrate 2 may be any material as long as it is made of a piezoelectric crystal material such as quartz, but if it is made of any one of lithium tantalate, lithium niobate, and lithium borate, these Is a crystalline material having a large electromechanical coupling coefficient, so that it can be a surface acoustic wave element having a wide bandwidth as a frequency selective filter and a small insertion loss, and a composite piezoelectric chip capable of producing such a surface acoustic wave element. A piezoelectric substrate made of these piezoelectric crystal materials can be obtained with a high quality by growing these single crystal rods by, for example, the Czochralski method and slicing them to a desired thickness.
The substrate orientation is also appropriately selected according to the type of piezoelectric crystal material, the use of the surface acoustic wave element, desired characteristics, such as 36 ° rotation Y-cut, 41 ° rotation Y-cut, 45 ° rotation Y-cut, etc. Can do.

Further, the support substrate 3 may be made of, for example, synthetic quartz, but is made of Si. Preferably, both surface layers of the support substrate 3 are oxidized to a thickness of 0.1 to 20 μm, and an Si oxide film is formed. 6 may be formed.
Thus, if the support substrate 3 is made of Si that is most practically used for semiconductor device fabrication, the surface acoustic wave element and the semiconductor device can be easily combined. Usually, a composite piezoelectric substrate formed by bonding a Si substrate and a piezoelectric substrate has different expansion coefficients, and thus may be warped when heated. Therefore, warping of the composite piezoelectric chip 1 can be reduced by oxidizing both surface layers of the support substrate 3 to a thickness of 0.1 to 20 μm and forming the Si oxide film 6. Further, when the adhesive layer 4 is present, the surface resistance value is 1 × 10 ¹⁵ Ω or more, the resistance value of the Si support substrate 3 is 2000 Ω · cm or more, and the Si oxide film 6 is formed. If so, sufficient insulation can be ensured and electrical characteristics can be improved. Thus, if the resistance of the adhesive layer 4 and the Si support substrate 3 is extremely large, even if the Si oxide films on both surfaces of the support substrate 3 are thin to some extent, the electrical insulation can be dramatically improved.

If the Si oxide film 6 is present only on one surface of the support substrate 3, the composite piezoelectric substrate 1 warps even at room temperature, and the piezoelectric substrate 2 is peeled off from the outer periphery when the piezoelectric substrate 2 is processed to the above thickness. Therefore, it is not preferable because a crack is generated. When the thickness of the Si oxide film 6 is less than 0.1 μm, the effect of reducing the warp of the composite piezoelectric substrate 1 is small. When the thickness is greater than 20 μm, for example, the composite piezoelectric substrate 1 is heated to about 300 ° C. in an N ₂ atmosphere. Since cracks sometimes occur in the piezoelectric substrate 2, it is not preferable.

  It should be noted that the thickness of the Si oxide film 6 is not necessarily the same on both surfaces as long as it is within the above range, but it is preferable that the thickness be the same. In addition, such a support substrate 3 made of Si is produced by growing a single crystal rod of Si by, for example, a floating zone method, and slicing it to a desired thickness, thereby achieving a high quality with an extremely high resistance of 2000 Ω · cm or more. Things are obtained. Moreover, in order to oxidize both surface layers of the support substrate 3, for example, a high pressure oxidation method can be used, and the Si oxide film 6 can be easily made to have the desired thickness with high productivity.

As an adhesive constituting the adhesive layer 4, for example, if it is a photo-curing adhesive mainly composed of epoxy methacrylate, heat resistance of 250 ° C. or more is obtained, and the viscosity before photo-curing is as low as 100 cps or less, A uniform adhesive layer can be easily formed by spin coating or other application methods. If the adhesive layer can be made uniform in this way, the composite piezoelectric chip 1 becomes a high-quality one that is uniformly bonded, and is more difficult to peel off. And since it is photocurable, the piezoelectric substrate 2 and the support substrate 3 can be firmly bonded and bonded by light irradiation at room temperature, and it is not necessary to raise the temperature, so that the piezoelectric substrate 2 is deformed at a high temperature at the time of bonding. It is preferable because it can maintain a flat shape at room temperature. Further, this adhesive has a large surface resistance value of 1 × 10 ¹⁵ Ω, and tan δ at 1 GHz is as small as 0.1 or less, so that the loss in the high frequency region is small. Here, tan δ is a quantity representing the dielectric loss tangent.

  In such a composite piezoelectric chip 1, an electrode 9 for exciting and detecting a surface acoustic wave is formed on a piezoelectric substrate 2. The electrode 9 can be formed by using a conventional photolithography method or the like. For example, a pair of comb-shaped electrodes including a plurality of electrode fingers and a bus bar that commonly connects the electrode fingers are arranged so that the electrode fingers intersect each other. In the IDT, one or a plurality of electrodes are formed according to a desired function / use of the surface acoustic wave element. In addition, reflectors may be formed on both sides of the electrode 9.

  Such a composite piezoelectric chip 1 is mounted on the mounting substrate 8 by conventional flip chip bonding via bumps 7 made of, for example, Au or Sn. If the mounting substrate 8 is made of alumina (expansion coefficient 8 ppm / ° C.) or low expansion ceramic (expansion coefficient 5.5 ppm / ° C.), the expansion coefficient is an appropriate value, and the expansion coefficients αc and αs are the above-mentioned values. It is easy to adjust and mount so as to satisfy the above relationship, but a mounting substrate made of other materials may be used.

  According to the present invention, such a surface acoustic wave element 10 excites surface acoustic waves on the piezoelectric substrate of the composite piezoelectric chip 1 obtained by processing a composite piezoelectric substrate in which the piezoelectric substrate 2 and the support substrate 3 are bonded into a chip shape. When the electrode 9 to be detected is formed and the composite piezoelectric chip 1 is mounted on the mounting substrate 8 via the bump 7 by flip chip bonding, the expansion coefficient αc (ppm / ° C.) in the specific direction of the surface of the piezoelectric substrate 2 is mounted. For example, the thickness of the piezoelectric substrate, the thickness of the adhesive layer that bonds the piezoelectric substrate and the support substrate, and the chip size are set so that the expansion coefficient αs (ppm / ° C.) of the substrate 8 satisfies the relationship of αs <αc <αs + 6. It can be manufactured by adjusting and mounting.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.
Example 1
The surface layers on both sides of the Si substrate having a diameter of 4 inches (100 mm) and a thickness of 200 μm and a resistance value of 5000 Ω · cm were oxidized to a thickness of 6 μm by a high pressure oxidation method. Next, a 36 ° rotated Y-cut lithium tantalate (LiTaO ₃ ) substrate having a diameter of 4 inches (100 mm) has a thickness of 0.2 mm (200 μm) and a surface Ra (average surface roughness) of 0.12 μm by double-sided lapping. It was processed to become.

Next, the surface of the Si substrate with an oxide film is cleaned, and the substrate is pretreated with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone while being heated to 100 ° C., and then ultraviolet light mainly composed of epoxy methacrylate. The cured adhesive was spin coated and applied uniformly on one side surface of the substrate. Next, the back surface of the LiTaO ₃ substrate is washed and the adhesive is applied in the same manner, and the adhesive application surface of the Si substrate with oxide film and the adhesive application surface of the LiTaO ₃ substrate are pressured at 1 × 10 ⁻³ mbar. Were bonded together under vacuum.

Next, the bonded composite piezoelectric substrate was irradiated with ultraviolet rays having an illuminance of 50 mW / cm ² for 10 minutes to cure the adhesive. At this time, the adhesive layer was uniformly 5 μm thick within the substrate surface. After this was a composite piezoelectric substrate chamfered, scraped 160μm by wrap and grinding the surface of the LiTaO ₃ substrate, and as the thickness of the LiTaO ₃ substrate is 15μm by further polishing.

When the composite piezoelectric substrate thus fabricated was heated to 150 ° C., the amount of warpage was as small as 2 mm at the maximum. Next, the composite piezoelectric substrate was cut into 1 × 1.2 mm composite piezoelectric substrate chips, and when the chips were heated to 300 ° C. in an N ₂ atmosphere, the chips were not broken. Further, even when the chip was subjected to a heat cycle of −40 ° C. to 125 ° C. for 1000 cycles, there was no change from before the heat cycle.

  Next, the composite piezoelectric chip is provided with electrodes having an electrode width of about 0.5 microns for exciting and detecting surface acoustic waves so that the operating frequency is about 1.9 GHz, and reflection is performed on both sides thereof. A 1-port surface acoustic wave resonator was fabricated by forming a container.

At this time, the expansion coefficient αc in the X direction ± 0.5 °, which is the leakage acoustic surface wave propagation direction, of the surface on which the electrode of the LiTaO ₃ substrate is formed is heated and cooled to change the temperature change of the electrode width. As a result of in-situ observation, αc = 10 ppm / ° C.

  Next, the composite piezoelectric chip with electrodes formed thereon was flip-chip connected to a mounting substrate made of low expansion ceramic (expansion coefficient αs = 5.5 ppm / ° C.) via solder bumps made of Sn, and packaging was performed. .

  The temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator in which the composite piezoelectric chip is flip-chip connected is examined by changing the ambient temperature from -40 ° C to 85 ° C, and the temperature coefficient of each is investigated. As a result, the temperature coefficient of the resonance frequency was −10 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −20 ppm / ° C.

(Example 2)
A Si substrate having a diameter of 4 inches (100 mm), a thickness of 200 μm, and a resistance value of 5000 Ω · cm was prepared. Next, a 36-degree rotated Y-cut lithium tantalate (LiTaO ₃ ) substrate having a diameter of 4 inches (100 mm) was processed to have a thickness of 0.2 mm (200 μm) and a surface Ra of 0.12 μm by double-sided lapping.

Next, the surface of the Si substrate is cleaned, and the substrate is pretreated with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone while being heated to 100 ° C., and an ultraviolet curable adhesive mainly composed of epoxy methacrylate is spin-coated. Then, it was uniformly applied on one surface of the substrate. Next, the back surface of the LiTaO ₃ substrate is washed, and the adhesive is applied in the same manner. The adhesive application surface of the Si substrate and the adhesive application surface of the LiTaO ₃ substrate are subjected to a vacuum of 1 × 10 ⁻³ mbar. We pasted together.

Next, the bonded composite piezoelectric substrate was irradiated with ultraviolet rays having an illuminance of 50 mW / cm ² for 10 minutes to cure the adhesive. At this time, the adhesive layer was uniformly 5 μm thick within the substrate surface. Then, after chamfering the composite piezoelectric substrate, scraping 155μm the surface of the LiTaO ₃ substrate by grinding and lap, and as the thickness of the LiTaO ₃ substrate is 20μm through further polished.

When the composite piezoelectric substrate thus fabricated was heated to 150 ° C., the amount of warping was as small as 4 mm at the maximum. Further, when this composite piezoelectric substrate was cut into 1 × 1.2 mm composite piezoelectric substrate chips and this chip was heated to 300 ° C. in an N ₂ atmosphere, the chips were not broken. Further, even when the chip was subjected to a heat cycle of −40 ° C. to 125 ° C. for 1000 cycles, there was no change from before the heat cycle.

  Next, the composite piezoelectric chip is provided with electrodes having an electrode width of about 0.5 microns for exciting and detecting surface acoustic waves so that the operating frequency is about 1.9 GHz, and reflection is performed on both sides thereof. A 1-port surface acoustic wave resonator was fabricated by forming a container.

  At this time, the expansion coefficient αc in the X direction ± 0.5 °, which is the leakage acoustic surface wave propagation direction, of the surface on which the electrode of the LiTaO 3 substrate is formed is heated and cooled to change the temperature change of the electrode width. As a result of field observation, αc = 11 ppm / ° C.

  Next, the composite piezoelectric chip with electrodes formed thereon was flip-chip connected to a mounting substrate made of low expansion ceramic (expansion coefficient αs = 5.5 ppm / ° C.) via solder bumps made of Sn, and packaging was performed. .

  The temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator in which the composite piezoelectric chip is flip-chip connected is examined by changing the ambient temperature from -40 ° C to 85 ° C, and the temperature coefficient of each is investigated. As a result, the temperature coefficient of the resonance frequency was −14 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −24 ppm / ° C.

(Example 3)
A synthetic quartz substrate having a diameter of 4 inches (100 mm) and a thickness of 150 μm was prepared. Next, a 36-degree rotated Y-cut lithium tantalate (LiTaO ₃ ) substrate having a diameter of 4 inches (100 mm) was processed to have a thickness of 0.2 mm (200 μm) and a surface Ra of 0.12 μm by double-sided lapping.

Next, the surface of the synthetic quartz substrate is cleaned, and the substrate is pretreated with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone while being heated to 100 ° C., and an ultraviolet curable adhesive mainly composed of epoxy methacrylate is spun. Coated and applied uniformly on one side of the substrate. Next, the back surface of the LiTaO ₃ substrate is washed and the adhesive is applied in the same manner, and the adhesive application surface of the synthetic quartz substrate and the adhesive application surface of the LiTaO ₃ substrate are vacuumed at a pressure of 1 × 10 ⁻³ mbar. Laminated below.

Next, the bonded composite piezoelectric substrate was irradiated with ultraviolet rays having an illuminance of 50 mW / cm ² for 10 minutes to cure the adhesive. At this time, the adhesive layer was uniformly 5 μm thick within the substrate surface. Then, after chamfering the composite piezoelectric substrate, scraping 155μm the surface of the LiTaO ₃ substrate by grinding and lap, and as the thickness of the LiTaO ₃ substrate is 20μm through further polished.

When the composite piezoelectric substrate thus fabricated was heated to 150 ° C., the amount of warping was as small as 4 mm at the maximum. Further, when this composite piezoelectric substrate was cut into 1 × 1.2 mm composite piezoelectric substrate chips and this chip was heated to 300 ° C. in an N ₂ atmosphere, the chips were not broken. Further, even when the chip was subjected to a heat cycle of −40 ° C. to 125 ° C. for 1000 cycles, there was no change from before the heat cycle.

  Next, the composite piezoelectric chip is provided with electrodes having an electrode width of about 0.5 microns for exciting and detecting surface acoustic waves so that the operating frequency is about 1.9 GHz, and reflection is performed on both sides thereof. A 1-port surface acoustic wave resonator was fabricated by forming a container.

At this time, the expansion coefficient αc in the X direction ± 0.5 °, which is the leakage acoustic surface wave propagation direction, of the surface on which the electrode of the LiTaO ₃ substrate is formed is heated and cooled to change the temperature change of the electrode width. As a result of in-situ observation, αc = 8 ppm / ° C.

  Next, the composite piezoelectric chip with electrodes formed thereon was flip-chip connected to a mounting substrate made of low expansion ceramic (expansion coefficient αs = 5.5 ppm / ° C.) via solder bumps made of Sn, and packaging was performed. .

  The temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator in which the composite piezoelectric chip is flip-chip connected is examined by changing the ambient temperature from -40 ° C to 85 ° C, and the temperature coefficient of each is investigated. As a result, the temperature coefficient of the resonance frequency was −13 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −23 ppm / ° C.

Example 4
A Si substrate having a diameter of 4 inches (100 mm), a thickness of 200 μm, and a resistance value of 5000 Ω · cm on which one side was mirror-finished was prepared. Next, a 36-degree rotated Y-cut lithium tantalate (LiTaO ₃ ) substrate having a diameter of 4 inches (100 mm) was finished by double-side polishing so as to have a thickness of 0.15 mm (150 μm). Each of the substrates was pretreated with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone while being heated to 100 ° C.
Then, the LiTaO ₃ substrate and the Si substrate were bonded at room temperature under a vacuum of 1 × 10 ⁻⁴ mbar.

Next, two bonded substrates of a LiTaO ₃ substrate and a Si substrate manufactured by the same method were opposed to each other on the LiTaO ₃ substrate side, bonded through an epoxy adhesive, and heated to 250 ° C.
Then, it cooled to room temperature, peeled off the contact bonding layer with the sulfuric acid, and produced the composite piezoelectric substrate.
Then, after chamfering the composite piezoelectric substrate, scraping 95μm surface side of the LiTaO ₃ substrate by grinding and lap, and as the thickness of the LiTaO ₃ substrate is 30μm by further polishing.

Further, when this composite piezoelectric substrate was cut into 1 × 1.2 mm composite piezoelectric substrate chips and this chip was heated to 300 ° C. in an N ₂ atmosphere, the chips were not broken. Further, even when the chip was subjected to a heat cycle of −40 ° C. to 125 ° C. for 1000 cycles, there was no change from before the heat cycle.

  Next, the composite piezoelectric chip is provided with electrodes having an electrode width of about 0.5 microns for exciting and detecting surface acoustic waves so that the operating frequency is about 1.9 GHz, and reflection is performed on both sides thereof. A 1-port surface acoustic wave resonator was fabricated by forming a container.

At this time, the expansion coefficient αc in the X direction ± 0.5 °, which is the leakage acoustic surface wave propagation direction, of the surface on which the electrode of the LiTaO ₃ substrate is formed is heated and cooled to change the temperature change of the electrode width. As a result of in-situ observation, αc = 7 ppm / ° C.

  Next, the composite piezoelectric chip with electrodes formed thereon was flip-chip connected to a mounting substrate made of low expansion ceramic (expansion coefficient αs = 5.5 ppm / ° C.) via solder bumps made of Sn, and packaging was performed. .

The temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator in which the composite piezoelectric chip is flip-chip connected is examined by changing the ambient temperature from -40 ° C to 85 ° C, and the temperature coefficient of each is investigated. As a result, the temperature coefficient of the resonance frequency was −13 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −23 ppm / ° C.
In any of the above examples, it was confirmed that both the resonance frequency and the antiresonance frequency had a small temperature coefficient, and the effect of improving the frequency temperature characteristic was high.

(Comparative Examples 1-4)
As Comparative Examples 1 to 4, the resonance frequency and anti-resonance of a 1-port surface acoustic wave resonator produced by mounting a composite piezoelectric chip produced by the same method as in Examples 1 to 4 by the chip and wire method, respectively. The temperature dependence of the resonance frequency was manually examined by changing the ambient temperature from −40 ° C. to 85 ° C., and each temperature coefficient was examined. As a result, in Comparative Example 1, the temperature coefficient of the resonance frequency was −20 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −30 ppm / ° C. In Comparative Example 2, the temperature coefficient of the resonance frequency was −24 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −34 ppm / ° C. In Comparative Example 3, the temperature coefficient of the resonance frequency was −23 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −33 ppm / ° C. In Comparative Example 4, the temperature coefficient of the resonance frequency was −19 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −29 ppm / ° C. That is, in Comparative Examples 1 to 4, each temperature coefficient was larger by 6 to 10 ppm / ° C. than Examples 1 to 4.

(Comparative Examples 5 and 6)
A 36-degree rotated Y-cut lithium tantalate (LiTaO ₃ ) substrate with a diameter of 4 inches (100 mm) was processed to a thickness of 0.2 mm (200 μm) with a mirror-finished surface and Ra with a back surface of 0.12 μm by lapping. . Next, this piezoelectric substrate was processed into a 1 × 1.2 mm piezoelectric chip.

  Next, an electrode having an electrode width of about 0.5 microns for exciting and detecting the surface acoustic wave is provided on the piezoelectric chip so that the operating frequency is about 1.9 GHz, and reflectors are provided on both sides thereof. To form a 1-port surface acoustic wave resonator.

  At this time, the expansion coefficient αc of the surface of the LiTaO3 substrate on which the electrode is formed is X-direction ± 0.5 °, which is the direction of propagation of the leaky surface acoustic wave. As a result of observation, αc = 16 ppm / ° C.

  Next, the piezoelectric chip on which the electrode was formed was flip-chip connected to a mounting substrate made of a low expansion ceramic (expansion coefficient αs = 5.5 ppm / ° C.) via a solder bump made of Sn to perform packaging.

  The temperature dependence of the resonance frequency and anti-resonance frequency of the 1-port surface acoustic wave resonator in which the piezoelectric chip is flip-chip connected was examined by changing the ambient temperature from -40 ° C. to 85 ° C., and each temperature coefficient was examined. As a result, the temperature coefficient of the resonance frequency was −26 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −36 ppm / ° C., which was a large value.

  Further, the temperature dependence of the resonance frequency and anti-resonance frequency of a 1-port surface acoustic wave resonator manufactured by mounting the same piezoelectric chip as described above by the chip-and-wire method is from -40 ° C. to 85 ° C. As a result of examining each temperature coefficient, the temperature coefficient of the resonance frequency was −30 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was as large as −40 ppm / ° C.

(Comparative Example 7)
A Si substrate having a diameter of 4 inches (100 mm), a thickness of 200 μm, and a resistance value of 5000 Ω · cm on which one side was mirror-finished was prepared. Then, 6 μm of SiO ₂ was deposited on the mirror-finished Si surface by plasma CVD.
Next, a 36-degree rotated Y-cut lithium tantalate (LiTaO ₃ ) substrate having a diameter of 4 inches (100 mm) was finished by double-side polishing so as to have a thickness of 0.15 mm (150 μm).

It was irradiated with nitrogen plasma to the surface of the side to be bonded of the SiO ₂ with Si side surface of lithium tantalate substrate depositing a SiO ₂ substrate.
Next, the LiTaO ₃ substrate and the Si substrate were bonded together at room temperature under a vacuum of 1 × 10 ⁻⁴ mbar.

Next, two bonded substrates of a LiTaO ₃ substrate and a Si substrate manufactured by the same method were opposed to each other on the LiTaO ₃ substrate side, bonded through an epoxy adhesive, and heated to 250 ° C.
Then, it cooled to room temperature, peeled off the contact bonding layer with the sulfuric acid, and produced the composite piezoelectric substrate.
Then, after chamfering the composite piezoelectric substrate, scraping 110μm the surface of the LiTaO ₃ substrate by grinding and lap, and as the thickness of the LiTaO ₃ substrate is 25μm by further polishing.

  Next, the composite piezoelectric substrate is cut into a 1 × 1.2 mm composite piezoelectric substrate chip, and surface acoustic waves are excited and detected on the composite piezoelectric chip so that the operating frequency is about 1.9 GHz. An electrode having an electrode width of about 0.5 microns was provided, and reflectors were formed on both sides thereof to produce a 1-port surface acoustic wave resonator.

At this time, the expansion coefficient αc in the X direction ± 0.5 °, which is the leakage acoustic surface wave propagation direction, of the surface on which the electrode of the LiTaO ₃ substrate is formed is heated and cooled to change the temperature change of the electrode width. As a result of in-situ observation, αc = 4 ppm / ° C.

  Next, the composite piezoelectric chip on which the electrode was formed was flip-chip connected to a mounting substrate made of alumina ceramic (expansion coefficient αs = 8 ppm / ° C.) via a solder bump made of Sn for packaging.

  The temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator in which the composite piezoelectric chip is flip-chip connected is examined by changing the ambient temperature from -40 ° C to 85 ° C, and the temperature coefficient of each is investigated. As a result, the temperature coefficient of the resonance frequency was −23 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −35 ppm / ° C., so that the effect of improving the temperature characteristics was small.

  Further, the temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator mounted by connecting the composite piezoelectric chip by chip-and-wire connection is investigated by changing the ambient temperature from −40 ° C. to 85 ° C., As a result of examining each temperature coefficient, the temperature coefficient of the resonance frequency was −12 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −22 ppm / ° C., which were good temperature characteristics, but the mounting work was complicated and the productivity was low. Not expensive.

(Comparative Example 8)
A gadolinium gallium garnet (GGG) substrate having a diameter of 4 inches (100 mm) and a thickness of 200 μm was prepared. Next, a 36-degree rotated Y-cut lithium tantalate (LiTaO ₃ ) substrate having a diameter of 4 inches (100 mm) was processed to have a thickness of 0.2 mm (200 μm) and a surface Ra of 0.12 μm by double-sided lapping.

Next, the surface of the GGG substrate is cleaned, and the substrate is further pretreated with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone while being heated to 100 ° C., and an ultraviolet curable adhesive mainly composed of epoxy methacrylate is spin-coated. Then, it was uniformly applied on one surface. Next, the back surface of the LiTaO ₃ substrate is washed, and the adhesive is applied in the same manner. The adhesive application surface of the GGG substrate and the adhesive application surface of the LiTaO ₃ substrate are subjected to a vacuum of 1 × 10 ⁻³ mbar. We pasted together.

Next, the bonded composite piezoelectric substrate was irradiated with ultraviolet rays having an illuminance of 50 mW / cm ² for 10 minutes to cure the adhesive. At this time, the adhesive layer was uniformly 5 μm thick within the substrate surface. Then, after chamfering the composite piezoelectric substrate, scraping 155μm the surface of the LiTaO ₃ substrate by grinding and lap, and as the thickness of the LiTaO ₃ substrate is 20μm through further polished.

  Next, the composite piezoelectric substrate is cut into a 1 × 1.2 mm composite piezoelectric substrate chip, and surface acoustic waves are excited and detected on the composite piezoelectric chip so that the operating frequency is about 1.9 GHz. An electrode having an electrode width of 0.5 microns was provided, and reflectors were formed on both sides thereof to produce a 1-port surface acoustic wave resonator.

At this time, the expansion coefficient αc in the X direction ± 0.5 °, which is the leakage acoustic surface wave propagation direction, of the surface on which the electrode of the LiTaO ₃ substrate is formed is heated and cooled to change the temperature change of the electrode width. As a result of in-situ observation, αc = 15 ppm / ° C.

  Next, the composite piezoelectric chip on which the electrode was formed was flip-chip connected to a mounting substrate made of an alumina ceramic substrate (expansion coefficient αs = 8 ppm / ° C.) via a solder bump made of Sn, and packaging was performed.

  The temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator in which the composite piezoelectric chip is flip-chip connected is examined by changing the ambient temperature from -40 ° C to 85 ° C, and the temperature coefficient of each is investigated. As a result, the temperature coefficient of the resonance frequency was −29 ppm / ° C., the temperature coefficient of the anti-resonance frequency was −39 ppm / ° C., and there was almost no improvement in temperature characteristics.

  Further, the temperature dependence of the resonance frequency and antiresonance frequency of the 1-port surface acoustic wave resonator mounted by connecting the composite piezoelectric chip by chip-and-wire connection is investigated by changing the ambient temperature from −40 ° C. to 85 ° C., As a result of examining each temperature coefficient, the temperature coefficient of the resonance frequency was −30 ppm / ° C. and the temperature coefficient of the anti-resonance frequency was −40 ppm / ° C., and there was no effect of improving temperature characteristics.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

For example, in the embodiment, a 36 ° rotated Y-cut LiTaO ₃ substrate is used as the piezoelectric substrate, but a LiNbO ₃ substrate or another piezoelectric substrate may be used. In addition, these piezoelectric substrates may be those in which surface charge accumulation due to pyroelectricity is eliminated.

1 is a schematic cross-sectional view showing an example of an embodiment of a surface acoustic wave element according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Composite piezoelectric chip, 2 ... Piezoelectric substrate, 3 ... Supporting substrate, 4 ... Adhesive layer,
5 ... Bonding surface of piezoelectric substrate, 6 ... Si oxide film, 7 ... Bump, 8 ... Mounting substrate,
9 ... electrode, 10 ... surface acoustic wave element.

Claims (9)

A surface acoustic wave element in which an electrode for exciting and detecting surface acoustic waves is formed on a piezoelectric substrate, and at least a composite piezoelectric chip obtained by processing a composite piezoelectric substrate in which a piezoelectric substrate and a support substrate are bonded together into a chip shape A mounting substrate on which the composite piezoelectric chip is mounted by flip chip bonding via bumps, and an expansion coefficient αc (ppm / ° C.) in a specific direction of the surface of the piezoelectric substrate and an expansion coefficient αs (ppm) of the mounting substrate / ℃)
αs <αc <αs + 6
The surface acoustic wave device is mounted so as to satisfy the following relationship.   2. The surface acoustic wave device according to claim 1, wherein the specific direction is within ± 0.5 degrees from the propagation direction of the surface acoustic wave excited by the electrode.   3. The surface acoustic wave element according to claim 1, wherein the mounting substrate is made of alumina or a low expansion ceramic.   4. The surface acoustic wave device according to claim 1, wherein the piezoelectric substrate is made of any one of lithium tantalate, lithium niobate, and lithium borate. 5. A surface acoustic wave device. A composite piezoelectric chip obtained by processing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate into a chip shape, wherein the composite piezoelectric chip has electrodes for exciting and detecting surface acoustic waves formed on the piezoelectric substrate, and It is mounted on a mounting substrate by flip chip bonding via a bump, and an expansion coefficient αc (ppm / ° C.) in a specific direction of the piezoelectric substrate surface is an expansion coefficient αs (ppm / ° C.) of the mounting substrate.
αs <αc <αs + 6
A composite piezoelectric chip that is mounted so as to satisfy the following relationship.   6. The composite piezoelectric chip according to claim 5, wherein the specific direction is within ± 0.5 degrees from the propagation direction of the surface acoustic wave excited by the electrode.   7. The composite piezoelectric chip according to claim 5, wherein the mounting substrate is made of alumina or a low expansion ceramic.   The composite piezoelectric chip according to any one of claims 5 to 7, wherein the piezoelectric substrate is made of any one of lithium tantalate, lithium niobate, and lithium borate. Composite piezoelectric chip. A method of manufacturing a surface acoustic wave device, wherein at least an electrode for exciting and detecting surface acoustic waves on a piezoelectric substrate of a composite piezoelectric chip obtained by processing a composite piezoelectric substrate in which a piezoelectric substrate and a support substrate are bonded together into a chip shape When the composite piezoelectric chip is mounted on a mounting substrate by flip chip bonding via a bump, an expansion coefficient αc (ppm / ° C.) in a specific direction on the surface of the piezoelectric substrate and an expansion coefficient αs of the mounting substrate (Ppm / ° C)
αs <αc <αs + 6
The surface acoustic wave device is manufactured so as to satisfy the relationship.

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