JP2018061254A - Elastic wave device and composite substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable elastic wave device.SOLUTION: An elastic wave device 1 comprises: a first substrate 20 that includes a first surface 20a and a second surface 20b facing each other in the thickness direction; a piezoelectric substrate 10 that is joined to the first surface 20a and has a coefficient of linear expansion larger than that of the first substrate 20; and a second substrate 30 that is joined to the second surface 20b and has a coefficient of linear expansion larger than that of the first substrate 20. When the modulus of elasticity and the thickness of the piezoelectric substrate 10 are E1 and T1, respectively, and the modulus of elasticity and the thickness of the first substrate 20 are E2 and T2, respectively, the relationship 1≤(E2×T2)/(E1×T1)≤9 is satisfied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an acoustic wave device and a composite substrate.

  An acoustic wave device using a piezoelectric substrate such as lithium tantalate is known. However, this lithium tantalate substrate has a frequency temperature characteristic of −36 ppm / ° C. For example, in the case of a device of 2 GHz band, ± 4.3 MHz fluctuates in a temperature range of −30 to + 85 ° C. It may be difficult to meet specifications. And since the temperature fluctuation of an elastic wave device affects the apparatus which uses this, the elastic wave device with few frequency fluctuations with respect to temperature, ie, a favorable temperature characteristic, was desired.

  Therefore, bonding a support substrate (Si substrate, etc.) with a different thermal expansion coefficient to the piezoelectric substrate with an adhesive or the like suppresses the thermal expansion / contraction of the piezoelectric substrate and stabilizes the frequency characteristics with respect to the temperature of the piezoelectric substrate. Are known (see, for example, Patent Document 1).

JP 2005-347295 A

  However, in the configuration of Patent Document 1, there is a possibility that the bonded substrates are warped. In general, a manufacturing process and a mounting process for manufacturing an acoustic wave device are accompanied by a thermal history in which the temperature is raised to nearly 300 ° C. Due to this thermal history, warpage of the bonded substrate is further increased, and this warpage causes cracks and cracks, resulting in a problem that productivity is lowered.

  The present application has been considered under such circumstances, and an object thereof is to provide an elastic wave device having good temperature characteristics and high productivity.

  An elastic wave device according to an aspect of the present disclosure includes a first support including a first surface and a second surface that are opposed in the thickness direction, and a wire that is joined to the first surface than the first support. A piezoelectric substrate having a large expansion coefficient, and a second support having a larger linear expansion coefficient than that of the first support, which is bonded to the second surface. When the elastic modulus of the piezoelectric substrate is E1, the thickness is T1, the elastic modulus of the first support is E2, and the thickness is T2, the relationship 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ing.

  A composite substrate according to an aspect of the present disclosure includes a first support having a first surface and a second surface facing each other in the thickness direction, and linear expansion more than the first support bonded to the first surface. A piezoelectric substrate having a large coefficient, and a second support having a larger linear expansion coefficient than that of the first support, which is bonded to the second surface. When the elastic modulus of the piezoelectric substrate is E1, the thickness is T1, the elastic modulus of the first support is E2, and the thickness is T2, the relationship 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ing. And the said 1st support body contains the fiber extended in the surface direction of the said 1st support body in a resin material, and the ratio per unit volume of the said fiber is large in the surface direction at the outer peripheral side from the center.

  According to the present disclosure, it is possible to provide an elastic wave device having favorable temperature characteristics and high productivity. In addition, it is possible to provide a composite substrate that can provide an elastic wave device with favorable temperature characteristics and high productivity.

It is sectional drawing of the elastic wave device which concerns on embodiment of this indication. It is a diagram which shows the correlation with a temperature compensation stress, and the elastic modulus and thickness of a piezoelectric substrate and a 1st support body. It is a diagram which shows the correlation with bending strength and fracture probability. (A), (b) is a diagram which shows the correlation with the residual stress of a piezoelectric substrate, and the elasticity modulus and thickness of a piezoelectric substrate and a 1st support body, respectively. It is sectional drawing which shows the modification of the elastic wave device shown in FIG. (A) is a top view of the composite board | substrate of this indication, (b) is the VI-VI sectional view taken on the line of (a). FIG. 6 is a diagram showing the relationship between the composition in the outer peripheral region of the first support and the amount of deflection of the composite substrate in the acoustic wave device shown in FIG. 5. (A), (b) is a diagram which shows the correlation with a temperature compensation stress, and the thickness of a piezoelectric substrate, a 1st support body, and a 2nd support body, respectively.

<Structure of elastic wave device>
FIG. 1 is a cross-sectional view of an acoustic wave device 1 according to an embodiment of the present invention. The acoustic wave device 1 includes a piezoelectric substrate 10, a first support body 20, and a second support body 30. Here, for convenience, the D1, D2, and D3 directions are defined, and the D3 direction is the thickness direction. The thickness of the piezoelectric substrate 10 is T1, the linear expansion coefficient is α1, and the elastic modulus (Young's modulus) is E1. Similarly, the thickness of the first support 20 is T2, the linear expansion coefficient is α2, the elastic modulus is E2, the thickness of the second support 30 is T3, the linear expansion coefficient is α3, and the elastic modulus is E3. Hereinafter, unless otherwise specified, the unit of linear expansion coefficient is ppm / ° C., and the unit of elastic modulus is GPa.

The piezoelectric substrate 10 is a substrate having piezoelectricity. For example, the piezoelectric substrate 10 is a rectangular parallelepiped single crystal substrate having piezoelectricity such as a lithium tantalate single crystal (LiTaO ₃ : hereinafter referred to as LT), a lithium niobate single crystal (LiNbO ₃ ), or a crystal. Specifically, for example, the piezoelectric substrate 10 is configured by a 36 ° to 48 ° Y-X cut LT substrate. Α1 of such a piezoelectric substrate 10 is 16.1 and E1 is 213.

  The planar shape of the piezoelectric substrate 10 may be appropriately set. For example, the piezoelectric substrate 10 is a rectangle having a predetermined direction (D2 direction) as a longitudinal direction. The size of the piezoelectric substrate 10 may be appropriately set. For example, the thickness T1 is 0.3 μm to 100 μm, and the length of one side is 0.5 mm to 2 mm.

  The main surface 10a of the piezoelectric substrate 10 is provided with various electrodes and wirings such as excitation electrodes, connection wirings, and pad electrodes (not shown). The excitation electrode is for generating SAW. The excitation electrode may include a plurality of comb-like IDT electrodes having a plurality of electrode fingers and reflector electrodes arranged at both ends of the plurality of IDT electrodes. Such an excitation electrode constitutes, for example, a ladder type filter or a dual mode SAW resonator filter. The excitation electrode, connection line, pad electrode, and the like are formed of an Al alloy such as an Al—Cu alloy.

Then, a signal is input through any of the pad electrodes functioning as these terminals. The input signal is filtered by an excitation electrode or the like. Then, the filtered signal is output via one of the pad electrodes functioning as a terminal.

  The first support 20 has a uniform thickness T2, and the first surface 20a is bonded to the piezoelectric substrate 10 and the second surface 20b is bonded to the second support 30 described later. The thickness T2 is thicker than the thickness T1 in order to support the piezoelectric substrate 10.

  Such a first support 20 is made of a material having a linear expansion coefficient α2 smaller than α1 of the piezoelectric crystal 10 and an elastic modulus E2. (E2 × T2) / (E1 × T1) satisfies the relationship of 1 to 9. Specifically, E2 may be 10 GPa or more and 40 GPa or less. By setting the elastic modulus E2 within this range, it can be made smaller than E1, and as a result, (E2 × T2) / (E1 × T1) can be made smaller. Α2 may be 2 or more and 4 or less. In this case, (E2 × T2) / (E1 × T1) can be reduced. Moreover, if α2 is smaller than 2, the residual stress associated with the thermal history increases, which may cause cracking or peeling. If α2 is larger than 4, temperature compensation may not be performed efficiently.

  In the present disclosure, an example of a configuration in which the first support 20 includes a resin material 21 and fibers 22 as a material satisfying such a relationship is shown. As the resin material 21, for example, various materials such as an epoxy resin, an acrylic resin, and a urethane resin can be used. The resin material 21 also functions as a bonding material that realizes bonding with the piezoelectric substrate 10 and the second support 30. Further, the linear expansion coefficient of the resin material 21 itself is larger than the linear expansion coefficient of the piezoelectric substrate 10.

  The fiber 22 is composed of a large number of elongated linear bodies extending in the surface direction of the first support 20. The linear expansion coefficient α of the fiber 22 is smaller than that of the resin material 21, and the elastic modulus E is larger than that of the resin material 21. For example, the fiber 22 may be glass fiber.

  By setting it as such a structure, generation | occurrence | production of a crack can also be suppressed, suppressing the deformation | transformation resulting from the material of the piezoelectric substrate 10 and the 1st support body 20 differing. FIG. 2 shows the correlation between the magnitude of (E2 × T2) / (E1 × T1) and the temperature compensation stress (unit: MPa) when the temperature changes by 125 ° C. Here, a diagram in which α1 is constant at 16.1 and α2 is 2, 3, and 4 is shown.

  As is apparent from this figure, when (E2 × T2) / (E1 × T1) is less than 1.0, the temperature compensation stress rapidly deteriorates.

  Therefore, in order to suppress a change in frequency characteristics due to a temperature change, (E2 × T2) / (E1 × T1) may be set to 1 or more.

  On the other hand, if (E2 × T2) / (E1 × T1) is too large, stress is applied to the piezoelectric substrate 10 and cracks are generated. FIG. 3 shows the occurrence rate of cracks in the piezoelectric substrate 10 with respect to the bending strength (unit: MPa) of the LT substrate. Generally, the reliability can be ensured by making the occurrence rate of cracks less than 5%. As is clear from this figure, the bending strength corresponding to 5% is 270 GPa. Here, FIG. 4A shows a diagram showing the relationship between the residual stress of the piezoelectric substrate 10 when it is heated to 125 ° C. and then cooled, and (E2 × T2) / (E1 × T1). This diagram shows the case where α2 = 4. As is apparent from this figure, (E2 × T2) / (E1 × T1) for setting the stress to 270 GPa is 9. That is, in order to prevent cracking of the piezoelectric substrate 10, (E2 × T2) / (E1 × T1) may be set to 9 or less.

In other words, the first support 20 needs to have both a softness that does not cause cracks in the piezoelectric substrate 10 when stress due to thermal history is applied and a hardness that can be restrained so that the piezoelectric substrate 10 does not deform. The first support 20 realizes such conflicting characteristics with the resin material 21 and the fibers 22. Specifically, the elastic modulus E is lowered by the resin material 21 to suppress cracking of the piezoelectric substrate 10, and the linear expansion coefficient α is reduced by the fiber 22 to suppress deformation of the resin material 21 and restrain the piezoelectric substrate 10. This produces a temperature compensation effect.

  When α2 is changed, the slope of the diagram of FIG. 4A changes. When α2 is reduced to further increase the temperature compensation capability, the upper limit value of (E2 × T2) / (E1 × T1) may be lowered. Specifically, when 2 is the lower limit value of α2, as shown in FIG. 4B, (E2 × T2) / (E1 × T1) is 6 or less, more preferably 3.5. What is necessary is as follows.

  Further, it can be seen from FIG. 2 that even if (E2 × T2) / (E1 × T1) is set to 5 or less, no significant improvement in temperature compensation stress is observed. Considering both the temperature compensation stress and the reliability, (E2 × T2) / (E1 × T1) may be 5 or less.

  From the above, (E2 × T2) / (E1 × T1) may be 1 or more and 9 or less, more preferably 1 or more and 3.5 or less.

  The second support 30 is joined to the second surface 20 b of the first support 20. The second support 30 is made of a material having a larger linear expansion coefficient than that of the first support 20. Specifically, various materials such as a ceramic substrate, an organic substrate, a semiconductor substrate such as Si, a single crystal substrate such as sapphire, lithium tantalate, lithium niobate, and quartz can be used.

  The thickness of the second support 30 can be appropriately set according to the piezoelectric substrate 10 and the first support 20. That is, the second support 30 is appropriately set so as to reduce the difference in stress moment between the first surface 20a side and the second surface 20b side of the first support 20 generated by the piezoelectric substrate 1 and the second support 30. The thickness T3, the linear expansion coefficient α3, and the elastic modulus E3 may be set. For example, what is necessary is just to set so that the stress moment of the 1st surface 20a side of the 1st support body 20 and the 2nd surface 20b side may balance. In this example, an LT substrate having the same material and the same thickness as the piezoelectric substrate 10 is used. In this case, the warp of the entire acoustic wave device 1 when a temperature change occurs can be suppressed.

  As described above, the elastic wave device 1 can also exhibit the temperature compensation effect while suppressing the occurrence of warpage and cracking by the first support body 20 and the second support body 30.

  When the linear expansion coefficients α1 and α2 of the piezoelectric substrate 10 and the first support 20 change, the absolute values of the characteristic plots in the diagrams shown in FIGS. 2, 3, and 4 change, but the tendency does not change. For this reason, even if linear expansion coefficients (alpha) 1 and (alpha) 2 change, the elastic wave device 1 which also has a temperature compensation effect can be provided, suppressing generation | occurrence | production of a curvature and a crack by setting it as the above-mentioned structure.

  2, 3, and 4, the linear expansion coefficient α <b> 3, the thickness T <b> 3, and the Young's modulus E <b> 3 of the second support 30 are shown to be equivalent to those of the piezoelectric substrate 10. On the other hand, when the linear expansion coefficient α3, the thickness T3, and the Young's modulus E3 of the second support 30 are changed, the absolute values of the characteristic plots in the diagrams shown in FIGS. However, the trend does not change. For this reason, even if it is a case where the 2nd support body 30 is changed suitably, by setting it as the above-mentioned structure, the elastic wave device 1 which also has a temperature compensation effect can be provided, suppressing generation | occurrence | production of a curvature and a crack. .

<Other structure of elastic wave device 1: 1st support body 10>
In the above example, the distribution state of the fibers 22 in the first support 20 is not mentioned, but a difference in distribution in the thickness direction may be provided as in the elastic wave device 1A shown in FIG.

  As shown in FIG. 5, in the first support 20 of the acoustic wave device 1A, the ratio of the fibers 22 per unit volume is larger near the center of the thickness than near the first surface 20a and near the second surface 20b. . By setting it as such a structure, the 1st surface 20a vicinity and the 2nd surface 20b vicinity function as a stress relaxation area | region, and the crack of the piezoelectric substrate 10 or the 2nd support body 30 can be suppressed. Further, the warp of the piezoelectric substrate 10 and the second support 30 before the stress due to the temperature history is applied can be absorbed. Furthermore, the adhesive strength with the piezoelectric substrate 10 and the 2nd support body 30 can be raised because the ratio of the resin material 21 increases.

  The region in the vicinity of the first surface 20a described above refers to a region of about 1 μm to 10 μm in the thickness direction from the first surface 20a. This region may be composed of only the resin material 21 without the fibers 22. Moreover, you may change the ratio of the fiber 22 per unit volume by making the thickness of the fiber 22 of this area | region thin compared with the thickness of the fiber 22 near the center of thickness. The same applies to the area near the second surface 20b.

  The thickness of the region near the first surface 20a and the region near the second surface 20b may be thicker than that of the piezoelectric substrate 10.

<Other structure of elastic wave device 1: 1st support body 20>
In the above-described example, the distribution state in the surface direction of the fibers 22 in the first support 20 is not mentioned. However, when the first direction and the second direction intersecting each other in the surface direction are defined, the fibers 22 are defined. The one extending in the first direction and the one extending in the second direction may cross each other to form a mesh. By setting it as such a structure, generation | occurrence | production of the stress distribution in a surface can be suppressed and the characteristic of the elastic wave device 1 can be stabilized.

  It has been confirmed that the in-plane stress distribution can be suppressed to a level that does not affect the characteristics of the acoustic wave device 1 by setting the mesh interval of the mesh to 500 μm or less.

  Further, when the linear expansion coefficient of the piezoelectric substrate 10 has anisotropy in the surface direction, the mesh shape of the fibers 22 (an angle formed between the first direction and the second direction) or the first direction extends. Realizing the first support 20 having anisotropy similar to the anisotropy of the linear expansion coefficient of the piezoelectric substrate 10 by providing a difference between the number of the fibers 22 and the number of the fibers 22 extending in the second direction. Can do.

<Other structure of elastic wave device 1: 1st support body 20>
In the above example, the first support 20 has been described in which the fibers 22 are interposed in the resin material 21, but the inorganic fillers 23 may be dispersed and held in the resin material 21 instead of the fibers 22. The inorganic filler 23 is made of a material having a smaller linear expansion coefficient than the resin material 21 and the piezoelectric substrate 10, and for example, a quartz filler can be used. The particle size of the inorganic filler 23 may be about 1 to 10 μm.

  With such a configuration, since the elastic modulus E2 of the first support 20 can be lowered and the linear expansion coefficient can be reduced, the temperature compensation effect is also achieved while suppressing the occurrence of warping and cracking of the piezoelectric substrate 10. The elastic wave device 1 that can be provided can be provided.

<Other structure of elastic wave device 1: 2nd support body 30>
In the above-described example, the material and thickness can be selected as appropriate as the second support 30. As an example, the same material as that of the piezoelectric substrate 10 and the same thickness are described as an example. However, the second support 30 is limited to this configuration. Not.

For example, the second support 30 may be made of the same material as that of the piezoelectric substrate 10 and the thickness T3 may be larger than T1 and smaller than T2. That is, T1 <T3 <T2 may be satisfied.

FIG. 8A shows the relationship between the magnitude of T3 with respect to T1 and the temperature compensation stress of the acoustic wave device, and FIG. 8B shows the relationship between the magnitude of T3 with respect to T2 and the temperature compensation stress of the acoustic wave device. In FIG. 8, the basic model of simulation is as follows.
Piezoelectric substrate 10: α1 16.1 ppm / ° C., E1 213 GPa
First support 20: α2 2.8 ppm / ° C., E2 24 GPa
2nd support body 30: (alpha) 3 ... 16.1ppm / degreeC, E3 ... 213GPa
As is clear from FIG. 8, the temperature compensation stress increases as T3 / T1 increases from 1, and when T3 / T2 exceeds 1, the temperature compensation stress decreases from T1 = T3. That is, the effect of increasing T3 is reduced. Therefore, the temperature compensation stress can be increased by setting T3 / T1> 1 and T3 / T2 <1.

  Further, the temperature compensation stress can be increased by increasing the size of T2 / T1. In order to suppress frequency fluctuations due to temperature changes, it is desirable to apply a compressive stress exceeding 300 MPa as a guide to the lower surface of the piezoelectric substrate 10. For this reason, a standard stress can be realized by setting T2 / T1 ≧ 25. Further, when T2 / T1 ≧ 37, a stress as a guide can be realized regardless of the value of T3.

  Further, when 0.2 <T3 / T2 <0.75, the temperature compensation stress can be further increased. However, in order to reduce the total thickness of the relatively thick first and second supports 20 and 30, T3 / T2 <0.5 may be satisfied. Furthermore, if T2 / T1 ≧ 25 is satisfied, the relationship of 0.3 <T3 / T2 <0.4 where the compressive stress is particularly large may be satisfied.

  It has been confirmed that the above-described relationship shows the same tendency when E1 = E3> E2 and α1 = α3> α2.

<Other structure of elastic wave device 1: 2nd support body 30>
In the above-described example, an example in which the same material as that of the piezoelectric substrate 10 is used as the second support 30 has been described, but quartz may be used as the second support 30.

When quartz is used as the second support 30, the linear expansion coefficient in the planar direction can be adjusted, so that it can be matched with the anisotropy in the planar direction of the linear expansion coefficient of the piezoelectric substrate 10. 1 warpage can be suppressed. Further, when the piezoelectric substrate 10 is a LiTaO ₃ substrate, the second support 30 has a coefficient of linear expansion and a modulus of elasticity between the piezoelectric substrate 10 and the first support 20, and generates an elastic wave. Since it does not adversely affect both the function of the piezoelectric substrate 10 to be propagated and the function of the first support 20 such as the relaxation of the stress caused by the thermal history and the restraint of the piezoelectric substrate 10, the electrical characteristics are excellent and the reliability is high. The acoustic wave device 1 can be provided.

<Composite substrate>
Next, the composite substrate 100 for providing the above-described acoustic wave device 1 will be described. FIG. 6A is a top view of the composite substrate 100. In the composite substrate 100, a wafer-like piezoelectric substrate 11, a first support 120, and a second support 130 are laminated in this order. The piezoelectric substrate 110, the first support body 120, and the second support body 130 have the same configurations as the piezoelectric substrate 10, the first support body 20, and the second support body 30, respectively. Hereinafter, only different points will be described, and overlapping descriptions will be omitted.

  The composite substrate 100 of the acoustic wave device 1 is divided into a plurality of sections as indicated by broken lines in FIG. 6A, and each of the sections becomes the acoustic wave device 1. Specifically, an electrode for exciting an elastic wave is formed on the upper surface of the piezoelectric substrate 110 for each section of the composite substrate 100, and one section is cut out and separated into the elastic wave device 1.

  FIG. 6B is a cross-sectional view taken along the line VI-VI in FIG. As shown in FIG. 6B, the first support 120 includes a resin material 121, and includes fibers 122 in the resin material 121. In addition, the outer peripheral region 126 has a higher ratio of the fibers 122 per unit volume than the central region 125 (also referred to as a surface central region) in the surface direction. When thermal stress or the like is applied to the composite substrate 100, the stress in the outer peripheral region 126 becomes larger than that in the surface central region 125. With such a configuration, the strength of the outer peripheral region 126 is increased, so that the composite Warpage of the substrate 100 can be suppressed.

  Note that such an outer peripheral region 126 is preferably less than 1/3 of the entire length. For example, when a 6-inch wafer is used, a ring-shaped outer peripheral region 126 having a width of less than 20 mm may be provided on the outer periphery.

  When the piezoelectric substrate 11, the first support body 120, and the second support body 130 are stacked in this order and pressed and bonded together to obtain the composite substrate 100, a larger force is exerted on the outer peripheral area 126 than the center area 125. As a result, the composite substrate 100 may have a barrel shape with a thinner outer periphery than the center. On the other hand, in the present disclosure, the thickness of the composite substrate 100 can be made constant in the plane by ensuring the strength in the outer peripheral region 126.

  In the above example, the example in which the distribution of the fibers 122 is varied in the plane has been described. However, instead of the fibers 122, an inorganic filler is dispersed in the resin material 121, and the inorganic filler distribution is densely distributed in the outer peripheral region 126. It may be.

  Further, both the fiber 122 and the inorganic filler may be dispersed in the resin material 121. The method is not particularly limited as long as the strength in the outer peripheral region 126 can be increased as compared with the surface central region 125.

  Furthermore, in the above-described composite substrate 100, the distribution state of the fibers 22 in the plane direction has been described, but in addition to this configuration, a distribution in the thickness direction may be provided as shown in FIG. That is, the distribution in the plane direction described above may be provided near the center in the thickness direction.

<Elastic wave device>
Next, in order to verify the effect of the configuration of the present disclosure, the acoustic wave device 1 having the configuration illustrated in FIG. 1 was manufactured. The basic configuration is as follows.
[Basic configuration]
[Piezoelectric substrate 10]
Material: 42 ° Y-cut X-propagation LiTaO ₃ substrate Thickness T1: 10 μm
Elastic modulus E1: 213GPa
[Excitation electrode]
Material: Al—Cu alloy Thickness (Al—Cu alloy layer): 131.5 nm
IDT electrode fingers 32:
(Number) 200 (Pitch) 0.791 μm
(Duty) 0.65
(Intersection width) 20λ (λ = 2 × pitch)
[First support 20]
Resin material 21: Epoxy resin fiber 22: Glass cloth [second support 30]
Material: 42 ° Y-cut X-propagation LiTaO ₃ substrate Thickness T3: 10 μm
Elastic modulus E3: 213GPa
With respect to such a basic configuration, Example 1 was manufactured in which the elastic modulus E2 of the first support 10 was 35 GPa, the thickness T2 was 100 μm, and the linear expansion coefficient α2 was 2.1 ppm / ° C. (E2 × T2) / (E1 × T1) according to Example 1 was 1.60.

  Further, as Comparative Example 1, the configuration of the first support was changed, and (E2 × T2) / (E1 × T1) was set to 26.5. Specifically, it consists of a sapphire substrate, the elastic modulus was 470 GPa, the thickness was 300 μm, and the linear expansion coefficient was 7 ppm / ° C. Other configurations (piezoelectric substrate and second support) were the same as in the example.

  The temperature compensation stress of Example 1 and Comparative Example 1 was confirmed to be about 210 GPa, but Example 1 did not cause peeling, cracking, cracking, etc. of the piezoelectric substrate 10, whereas Comparative Example No. 1 was cracked. From the above, it can be seen that even if the equivalent temperature compensation stress is expressed, the occurrence of cracks and the like can be suppressed for the first time by satisfying (E2 × T2) / (E1 × T1), and a highly reliable acoustic wave device can be provided. It was.

  In Comparative Example 2, a configuration in which a sapphire substrate (elastic modulus 470 GP, thickness 300 μm, linear expansion coefficient 7 ppm / ° C.) was used instead of the first support was manufactured. Comparative Example 1 does not include the second support.

  In Comparative Example 2, a large warp occurred as compared with Example 1 due to the thermal history.

  From the above, it was confirmed that the elastic wave device according to Example 1 suppresses warpage, suppresses the occurrence of peeling, cracking, cracking, and the like of the piezoelectric substrate 10 and has sufficient temperature compensation stress.

  From the above, it has been confirmed that the configuration of the present disclosure can provide a highly reliable elastic wave device that has excellent temperature compensation capability and does not crack.

<Composite substrate 100>
Next, the composite substrate 100 having the configuration shown in FIG. 6 was produced. The size of the composite substrate was 3 inches. The basic configurations of the piezoelectric substrate 110, the first support 120, and the second support 130 are as follows.

Piezoelectric substrate 110:
Material: 42 ° Y-cut X-propagation LiTaO3 substrate Thickness T1: 10 μm
Elastic modulus E1: 213GPa
Coefficient of thermal expansion α1: 16.1 ppm / K
Poisson's ratio: 0.3
First support 120
Resin material 121: elastic modulus 9 GPa, linear expansion coefficient 17.5 ppm / K, Poisson's ratio 0.
3
Fiber 122: elastic modulus 23 GPa, linear expansion coefficient 2 ppm / K, Poisson's ratio 0.3
Second support 130
Material: 42 ° Y-cut X-propagation LiTaO 3 substrate Thickness T 3: 20 μm
Elastic modulus E3: 213GPa
Thermal expansion coefficient α3: 16.1 ppm / K
Poisson's ratio: 0.3
Here, the central region 125 is a region having a radius of 63 μm from the center of the composite substrate 100, and the outer peripheral region 126 is located on the outer periphery of the central region 125 and has a ring shape with a width of 14.2 μm. Further, in the central region 125 of the first support 120, the ratio of the resin material 121 is 80%, the ratio of the fibers 122 is 20%, and the Young's modulus (elastic modulus) of the central region 125 is 13 which is a composite value thereof. . And the model was produced by varying the ratio of the resin material 121 and the fiber 122 in the outer peripheral area 126. Specifically, a model in which the ratio of the fibers 122 was changed from 20% to 80% was produced.

  With respect to such a model, the degree of bending of the composite substrate 100 when the temperature was lowered after the temperature was raised by 100 ° C. was simulated. As a result, as shown in FIG. 7, it was confirmed that the amount of bending was reduced as the proportion of the fibers 122 was increased.

<Other Embodiments Extracted from Elastic Wave Device 1A>
In the acoustic wave device 1A, in the first support body 20 satisfying 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9, a region in the vicinity of the first surface 20a and a region in the vicinity of the second surface 20b are provided. As described above, the first support that does not satisfy 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 may be provided with a region near the first surface 20a and a region near the second surface 20b.

  In this case, the resin material in the region in the vicinity of the first surface 20a and the region in the vicinity of the second surface 20b functions as a stress adjustment layer, so that peeling at the bonding interface can be suppressed.

  Specifically, the first support 20 is made of a material having a smaller linear expansion coefficient than that of the piezoelectric substrate 10 such as Si or sapphire substrate at the center of the thickness, and the upper and lower surfaces thereof are arranged in the vicinity of the first surface 20a, the first It may be configured to be sandwiched between separate resin layers as the region in the vicinity of the two surfaces 20b. That is, the first support 20 may have a laminated structure of a central part such as Si or sapphire and resin parts positioned above and below the central part. The thickness of each resin portion is larger than the thickness of the piezoelectric substrate 10. More preferably, the thickness of the piezoelectric substrate 10 may be 3 to 4 times.

  The first support 20 is configured as described above, and the stress is applied to the piezoelectric substrate 10 while adjusting the linear expansion coefficient of the resin portion between the material of the central portion and the linear expansion coefficient of the piezoelectric substrate 10. Is possible. Thereby, compressive stress can be applied to the piezoelectric substrate 10 to adjust the speed of sound, and as a result, temperature compensation can be performed. Furthermore, by making the elastic modulus smaller than that of the central portion and the piezoelectric substrate 10, it is possible to suppress cracking, peeling, and the like of each component.

  As one configuration of the acoustic wave device including the first support substrate 20 described above, for example, the piezoelectric substrate 10 and the second support body 30 are configured by an LT substrate, and the first support body 20 includes a central portion made of Si and its Some have a laminated structure with resin portions located above and below in the thickness direction. In this case, the warp of the laminated structure of the piezoelectric substrate 10, the first support 20, and the second support 30 can be suppressed by the second support 30.

DESCRIPTION OF SYMBOLS 1 ... Elastic wave device 10, 110 ... Piezoelectric substrate 20, 120 ... 1st support body 21 ... Resin material 22 ... Fiber 30, 130 ... 2nd support body 100 ... Composite substrate

Claims (11)

A first support including a first surface and a second surface facing in the thickness direction;
A piezoelectric substrate bonded to the first surface and having a larger linear expansion coefficient than the first support;
A second support joined to the second surface and having a larger linear expansion coefficient than the first support,
When the elastic modulus of the piezoelectric substrate is E1, the thickness is T1, the elastic modulus of the first support is E2, and the thickness is T2, the relationship 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. , Elastic wave device.   The elastic wave device according to claim 1, wherein the elastic modulus E2 of the first support is 10 GPa or more and 40 GPa or less.   The acoustic wave device according to claim 1, wherein the first support includes a resin material.   The said 1st support body is an elastic wave device of Claim 3 provided with the fiber extended in the surface direction of the said 1st support body in the said resin material. The resin material has a larger coefficient of linear expansion than the piezoelectric substrate,
The acoustic wave device according to claim 4, wherein the fiber has a smaller coefficient of linear expansion and a larger elastic modulus than the resin material. The first support is
6. The acoustic wave device according to claim 4, wherein, in the thickness direction, an area between the first surface side and the second surface side has a smaller ratio per unit volume of the fiber than a thickness central region.   The elastic wave device according to claim 3, wherein the first support includes an inorganic filler in the resin material.   The acoustic wave device according to claim 1, wherein the second support is made of the same material as the piezoelectric substrate.   The acoustic wave device according to claim 1, wherein the piezoelectric substrate is made of a lithium tantalate substrate, and the second support is made of quartz.   9. The thickness of the piezoelectric substrate, the first support, and the second support satisfies the relationship of T1 <T3 <T2 when the thickness of the second support is T3. 10. The acoustic wave device according to 9. A first support including a first surface and a second surface facing in the thickness direction;
A piezoelectric substrate bonded to the first surface and having a larger linear expansion coefficient than the first support;
A second support joined to the second surface and having a larger linear expansion coefficient than the first support,
When the elastic modulus of the piezoelectric substrate is E1, the thickness is T1, the elastic modulus of the first support is E2, and the thickness is T2, the relationship 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ,
The first support is a composite substrate that includes fibers extending in a surface direction of the first support in a resin material, and in the surface direction, the ratio per unit volume of the fibers is larger on the outer peripheral side than the center.