JP6920161B2 - Elastic wave devices and composite substrates - Google Patents

Description

The present invention relates to elastic wave devices and composite substrates.

An elastic 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 in the 2 GHz band, it fluctuates by ± 4.3 MHz in the temperature range of -30 to + 85 ° C., which is severe in recent years. It may be difficult to meet the specifications. Since the temperature fluctuation of the elastic wave device affects the equipment using the elastic wave device, an elastic wave device having a small frequency fluctuation with respect to the temperature, that is, having good temperature characteristics has been desired.

Therefore, by joining a support substrate (Si substrate, etc.) having a different coefficient of thermal expansion to the piezoelectric substrate with an adhesive or the like, the thermal expansion and contraction of the piezoelectric substrate is suppressed, and the frequency characteristics of the piezoelectric substrate with respect to temperature are stabilized. Techniques are known (see, for example, Patent Document 1 and the like).

Japanese Unexamined Patent Publication No. 2005-347295

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

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

The elastic wave device as one 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 a strand of the first support bonded to the first surface. A piezoelectric substrate having a large expansion coefficient and a second support bonded to the second surface and having a linear expansion coefficient larger than that of the first support are provided. Assuming that 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 of 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ing.

The composite substrate as one aspect of the present disclosure has a first support having a first surface and a second surface facing each other in the thickness direction, and a linear expansion than the first support joined to the first surface. A piezoelectric substrate having a large coefficient and a second support bonded to the second surface and having a coefficient of linear expansion larger than that of the first support are provided. Assuming that 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 of 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ing. The first support includes fibers extending in the surface direction of the first support in the resin material, and the ratio of the fibers per unit volume is larger on the outer peripheral side than the center in the surface direction.

According to the present disclosure, it is possible to provide an elastic wave device having good temperature characteristics and high productivity. Further, it is possible to provide a composite substrate capable of providing an elastic wave device having good temperature characteristics and high productivity.

It is sectional drawing of the elastic wave device which concerns on embodiment of this disclosure. It is a diagram which shows the correlation between the temperature compensation stress and the elastic modulus and the thickness of a piezoelectric substrate and a 1st support. It is a diagram which shows the correlation between the bending strength and the fracture probability. (A) and (b) are diagrams showing the correlation between the residual stress of the piezoelectric substrate and the elastic modulus and thickness of the piezoelectric substrate and the first support, 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 substrate of the present disclosure, and (b) is a sectional view taken along line VI-VI of (a). FIG. 5 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 elastic wave device shown in FIG. (A) and (b) are diagrams showing the correlation between the temperature compensating stress and the thickness of the piezoelectric substrate, the first support and the second support, respectively.

<Structure of elastic wave device>
FIG. 1 is a cross-sectional view of an elastic wave device 1 according to an embodiment of the present invention. The elastic wave device 1 includes a piezoelectric substrate 10, a first support 20, and a second support 30. Here, for convenience, the D1 direction, the D2 direction, and the D3 direction are defined, and the D3 direction is the thickness direction. The thickness of 10 of the piezoelectric substrate is T1, the coefficient of linear expansion is α1, and the elastic modulus (Young's modulus) is E1. Similarly, the thickness of the first support 20 is T2, the coefficient of linear expansion is α2, the elastic modulus is E2, the thickness of the second support 30 is T3, the coefficient of linear expansion is α3, and the elastic modulus is E3. Hereinafter, unless otherwise specified, the unit of the coefficient of linear expansion 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 piezoelectric rectangular single crystal substrate such as _{lithium tantalate single crystal (LiTaO 3} : hereinafter referred to as LT), lithium niobate single crystal (LiNbO _{3), and quartz.} Specifically, for example, the piezoelectric substrate 10 is composed of a 36 ° to 48 ° YX cut LT substrate. The α1 of such a piezoelectric substrate 10 is 16.1 and the E1 is 213.

The planar shape of the piezoelectric substrate 10 may be appropriately set, and is, for example, a rectangle whose longitudinal direction is a predetermined direction (D2 direction). The size of the piezoelectric substrate 10 may be appropriately set, and 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-shaped 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, a double mode SAW resonator filter, and the like. The excitation electrode, the connecting wire, the pad electrode, and the like are formed of an Al alloy such as an Al—Cu alloy.

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

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, which will be 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 that of the piezoelectric crystal 10 α1 and an elastic modulus E2. Then, (E2 × T2) / (E1 × T1) satisfies the relationship of 1 or more and 9 or less. Specifically, E2 may be 10 GPa or more and 40 GPa or less. By setting the elastic modulus E2 in this range, it can be made smaller than that of E1, and as a result, (E2 × T2) / (E1 × T1) can be made smaller. Further, α2 may be 2 or more and 4 or less. In this case, (E2 × T2) / (E1 × T1) can be reduced. Further, when 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, there is a risk that temperature compensation cannot be performed efficiently.

In the present disclosure, as a material satisfying such a relationship, the first support 20 shows an example of a configuration including a resin material 21 and fibers 22. As the resin material 21, various materials such as epoxy resin, acrylic resin, and 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 coefficient of linear expansion of the resin material 21 itself is larger than the coefficient of linear expansion of the piezoelectric substrate 10.

The fiber 22 is composed of a large number of elongated linear bodies extending in the plane direction of the first support 20. The coefficient of linear expansion 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, glass fiber may be used as the fiber 22.

With such a configuration, it is possible to suppress the occurrence of cracks while suppressing the deformation caused by the different materials of the piezoelectric substrate 10 and the first support 20. FIG. 2 shows the correlation between the magnitude of (E2 × T2) / (E1 × T1) and the temperature compensating stress (unit: MPa) when the temperature changes by 125 ° C. Here, α1 is fixed at 16.1 and α2 is shown as 2, 3 and 4.

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

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

On the other hand, if (E2 × T2) / (E1 × T1) is too large, the piezoelectric substrate 10 is overstressed and cracks occur. FIG. 3 shows the rate of occurrence of cracks in the piezoelectric substrate 10 with respect to the bending strength (unit: MPa) of the LT substrate. Generally, reliability can be ensured by making the crack occurrence rate 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 (E2 × T2) / (E1 × T1) and the residual stress of the piezoelectric substrate 10 when the temperature is raised to 125 ° C. and then cooled. This diagram shows the case of α2 = 4. As is clear from this figure, (E2 × T2) / (E1 × T1) for setting the stress to 270 GPa is 9. That is, in order to prevent the piezoelectric substrate 10 from cracking, (E2 × T2) / (E1 × T1) may be 9 or less.

That is, the first support 20 needs to have both softness so that the piezoelectric substrate 10 does not crack when stress is applied due to thermal history and hardness that can be restrained so that the piezoelectric substrate 10 is not deformed. The first support 20 realizes such contradictory characteristics with the resin material 21 and the fiber 22. Specifically, the resin material 21 lowers the elastic modulus E to suppress the cracking of the piezoelectric substrate 10, and the fibers 22 reduce the linear expansion coefficient α to suppress the deformation of the resin material 21 and restrain the piezoelectric substrate 10. This has a temperature compensation effect.

When α2 is changed, the inclination of the diagram of FIG. 4A changes. When the temperature compensation capacity is further increased by reducing α2, the upper limit of (E2 × T2) / (E1 × T1) may be lowered. Specifically, when it is set to 2, which is the lower limit of α2, (E2 × T2) / (E1 × T1) is 6 or less, more preferably 3.5, as shown in FIG. 4 (b). It may be 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 the temperature compensation stress is observed. Considering both the temperature compensating stress and ensuring 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, but more preferably 1 or more and 3.5 or less.

A second support 30 is joined to the second surface 20b of the first support 20. The second support 30 is made of a material having a coefficient of linear expansion larger than that of the first support 20. Specifically, various materials such as ceramic substrates, organic substrates, semiconductor substrates such as Si, and single crystal substrates 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 used 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 caused 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, the stress moments on the first surface 20a side and the second surface 20b side of the first support 20 may be set to be balanced. In this example, an LT substrate having the same material and the same thickness as the piezoelectric substrate 10 was used. In this case, it is possible to suppress the warp of the entire elastic wave device 1 when a temperature change occurs.

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

When the linear expansion coefficients α1 and α2 of the piezoelectric substrate 10 and the first support 20 change, the absolute value of the characteristic plot changes in the diagrams shown in FIGS. 2, 3 and 4, but the tendency does not change. Therefore, even if the linear expansion coefficients α1 and α2 change, the elastic wave device 1 can be provided which has a temperature compensation effect while suppressing the occurrence of warpage and cracking by adopting the above configuration.

Further, FIGS. 2, 3 and 4 show a case where the linear expansion coefficient α3, the thickness T3 and the Young's modulus E3 of the second support 30 are the same as those of the piezoelectric substrate 10. On the other hand, when the coefficient of linear expansion α3, the thickness T3, and Young's modulus E3 of the second support 30 are changed, the absolute value of the characteristic plot changes in the diagrams shown in FIGS. 2, 3, and 4. However, the tendency does not change. Therefore, even when the second support 30 is appropriately changed, it is possible to provide the elastic wave device 1 which has a temperature compensation effect while suppressing the occurrence of warpage and cracks by adopting the above configuration. ..

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

As shown in FIG. 5, in the first support 20 of the elastic wave device 1A, the ratio of the fibers 22 per unit volume is larger in the vicinity of the center of the thickness than in the vicinity of the first surface 20a and the vicinity of the second surface 20b. .. With such a configuration, the vicinity of the first surface 20a and the vicinity of the second surface 20b function as stress relaxation regions, and cracking of the piezoelectric substrate 10 and the second support 30 can be suppressed. Further, it is possible to absorb the warp of the piezoelectric substrate 10 and the second support 30 before the stress due to the temperature history is applied. Further, by increasing the proportion of the resin material 21, the adhesive strength with the piezoelectric substrate 10 and the second support 30 can be increased.

The above-mentioned region near the first surface 20a 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 present. Further, the ratio of the fibers 22 per unit volume may be changed by making the thickness of the fibers 22 in this region thinner than the thickness of the fibers 22 near the center of the thickness. The same applies to the region 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: First support 20>
In the above example, the distribution state of the fibers 22 in the first support 20 in the plane direction is not mentioned, but if the first direction and the second direction intersecting each other in the plane directions are defined, the fibers 22 are defined. May have a mesh shape in which the one extending in the first direction and the one extending in the second direction intersect with each other. With such a configuration, the occurrence of stress distribution in the plane can be suppressed, and the characteristics 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 elastic wave device 1 by setting the grid spacing of the mesh to 500 μm or less.

Further, when the linear expansion coefficient of the piezoelectric substrate 10 has anisotropy in the plane direction, it extends in the mesh shape of the fiber 22 (the angle formed by the first direction and the second direction) or in the first direction. By providing a difference between the number of fibers 22 and the number of fibers 22 extending in the second direction, it is possible to realize the first support 20 having anisotropy similar to the anisotropy of the linear expansion coefficient of the piezoelectric substrate 10. Can be done.

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

With such a configuration, the elastic modulus E2 of the first support 20 can be lowered and the linear expansion coefficient can be reduced, so that the temperature compensation effect can be obtained while suppressing the occurrence of warpage and cracking of the piezoelectric substrate 10. It is possible to provide an elastic wave device 1 capable of providing an elastic wave device 1.

<Other structure of elastic wave device 1: Second support 30>
In the above example, the material and the thickness of the second support 30 can be appropriately selected, and as an example, a configuration in which the same material as the piezoelectric substrate 10 and the same thickness is provided has been described as an example, but the configuration is limited to this configuration. Not done.

For example, the second support 30 may be made of the same material as 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-compensating stress of the elastic wave device, and FIG. 8B shows the relationship between the magnitude of T3 with respect to T2 and the temperature-compensating stress of the elastic wave device. In FIG. 8, the basic model of the 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
Second support 30: α3 ... 16.1 ppm / ° C., E3 ... 213 GPa
As is clear from FIG. 8, the temperature compensation stress increases as T3 / T1 is larger than 1, and when T3 / T2 is larger than 1, the temperature compensation stress becomes smaller than when T1 = T3. That is, the effect of thickening T3 becomes small. From this, 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 to the lower surface of the piezoelectric substrate 10 as a guide. From this, it is possible to realize a reference stress by setting T2 / T1 ≧ 25. Further, when T2 / T1 ≧ 37, a reference stress 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 set. Further, if T2 / T1 ≧ 25 is satisfied, the relationship of 0.3 <T3 / T2 <0.4, in which the compressive stress becomes particularly large, may be satisfied.

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

<Other structure of elastic wave device 1: Second support 30>
In the above example, an example in which the same material as 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 coefficient of linear expansion in the plane direction can be adjusted, so that the coefficient of linear expansion of the piezoelectric substrate 10 can be matched with the anisotropy in the plane direction. The warp of 1 can be suppressed. Further, when the piezoelectric substrate 10 is a LiTaO ₃ substrate, the second support 30 has a linear expansion coefficient and an elastic modulus between the piezoelectric substrate 10 and the first support 20, and elastic waves are generated. 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 relaxation of stress caused by thermal history and restraint of the piezoelectric substrate 10, it has excellent electrical characteristics and high reliability. An elastic wave device 1 can be provided.

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

The composite substrate 100 of the elastic wave device 1 is divided into a plurality of sections as shown by a broken line in FIG. 6A, and each of the sections is the elastic 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 thereof is cut out and individualized to obtain an elastic wave device 1.

FIG. 6B is a cross-sectional view taken along the line VI-VI of FIG. 6A. As shown in FIG. 6B, the first support 120 includes the resin material 121, and the fibers 122 are provided in the resin material 121. The outer peripheral region 126 has a larger proportion of fibers 122 per unit volume than the central region 125 (also referred to as the surface central region) in the plane direction. When a 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 center region 125. However, with such a configuration, the strength of the outer peripheral region 126 is increased, so that the composite substrate 100 is composited. The warp of the substrate 100 can be suppressed.

It is desirable that such an outer peripheral region 126 is less than 1/3 of the total 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 circumference.

When the piezoelectric substrate 11, the first support 120, and the second support 130 are stacked in this order and pressed and joined to obtain the composite substrate 100, a larger force is applied to the outer peripheral region 126 than to the surface center region 125. As a result, the composite substrate 100 may have a barrel-like shape in which the outer circumference is thinner 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 distribution of the fibers 122 was different in the plane, but instead of the fibers 122, the inorganic filler was dispersed in the resin material 121, and the distribution of the inorganic filler was 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. As long as the strength in the outer peripheral region 126 can be made larger than that in the surface center region 125, the method is not particularly limited.

Further, in the composite substrate 100 described above, the distribution state of the fibers 22 in the plane direction has been described, but in addition to this configuration, as shown in FIG. 5, a distribution in the thickness direction may be provided. That is, the above-mentioned distribution in the plane direction 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 elastic wave device 1 having the configuration shown 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
Electrode finger 32 of IDT electrode:
(Number) 200 (Pitch) 0.791 μm
(Duty) 0.65
(Cross width) 20λ (λ = 2 × pitch)
[First support 20]
Resin material 21: Epoxy resin fiber 22: Glass cloth [2nd support 30]
Material: 42 ° Y-cut X propagation LiTaO ₃ substrate Thickness T3: 10 μm
Elastic modulus E3: 213 GPa
For 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 so that (E2 × T2) / (E1 × T1) was set to 26.5. Specifically, it was made of a sapphire substrate, the elastic modulus of which was 470 GPa, the thickness of which was 300 μm, and the coefficient of linear expansion was 7 ppm / ° C. Other configurations (piezoelectric substrate and second support) were the same as in the examples.

When the temperature compensation stresses of Example 1 and Comparative Example 1 were confirmed, they were both about 210 GPa, but in Example 1, peeling, cracking, cracking, etc. of the piezoelectric substrate 10 did not occur, whereas in Comparative Example. In No. 1, a crack occurred. From the above, it was found that even if the same temperature compensation stress is expressed, the occurrence of cracks and the like can be suppressed only by satisfying (E2 × T2) / (E1 × T1), and a highly reliable elastic wave device can be provided. rice field.

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

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

From the above, it was confirmed that the elastic wave device according to the first embodiment suppresses warpage, suppresses the occurrence of peeling, cracking, cracking, etc. of the piezoelectric substrate 10, and has sufficient temperature compensating stress.

From the above, it has been confirmed that the configuration of the present disclosure can provide a highly reliable elastic wave device having excellent temperature compensation capability and no cracking.

<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
Thermal expansion coefficient α1: 16.1ppm / K
Poisson's ratio: 0.3
First support 120
Resin material 121: Elastic modulus 9 GPa, coefficient of linear expansion 17.5 ppm / K, Poisson's ratio 0.
3
Fiber 122: Elastic modulus 23 GPa, coefficient of linear expansion 2 ppm / K, Poisson's ratio 0.3
Second support 130
Material: 42 ° Y-cut X propagation LiTaO3 substrate Thickness T3: 20 μm
Elastic modulus E3: 213 GPa
Coefficient of thermal expansion α3: 16.1ppm / 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 having 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% and 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 synthetic value thereof. .. Then, a model was produced by making the ratio of the resin material 121 and the fiber 122 in the outer peripheral region 126 different. Specifically, a model in which the ratio of the fibers 122 was changed from 20% to 80% was prepared.

For such a model, the magnitude of deflection of the composite substrate 100 when the temperature was raised by 100 ° C. and then lowered was simulated. As a result, as shown in FIG. 7, it was confirmed that the amount of bending decreased as the proportion of the fibers 122 was increased.

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

In this case, since the resin material in the region near the first surface 20a and the region near the second surface 20b functions as the stress adjusting layer, peeling at the bonding interface can be suppressed.

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

The first support 20 has the above-described configuration, and the coefficient of linear expansion of the resin portion is set to a value between the material in the central portion and the coefficient of linear expansion of the piezoelectric substrate 10, so that the stress is applied to the piezoelectric substrate 10 while adjusting. Is possible. As a result, 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. Further, by making the elastic modulus smaller than that of the central portion and the piezoelectric substrate 10, cracking, peeling, etc. of each component can be suppressed.

As one configuration of the elastic wave device provided with the first support substrate 20 described above, for example, the piezoelectric substrate 10 and the second support 30 are composed of an LT substrate, and the first support 20 is a central portion made of Si and a central portion thereof. Some have a laminated structure with resin portions located above and below in the thickness direction. In this case, the second support 30 can suppress the warp of the laminated structure of the piezoelectric substrate 10, the first support 20, and the second support 30.

1 ... Elastic wave device 10, 110 ... Piezoelectric substrate 20, 120 ... First support 21 ... Resin material 22 ... Fiber 30, 130 ... Second support 100 ... Composite substrate

Claims (8)

A first support having a first surface and a second surface facing each other in the thickness direction,
A piezoelectric substrate bonded to the first surface and having a coefficient of linear expansion larger than that of the first support.
A second support having a coefficient of linear expansion larger than that of the first support, which is joined to the second surface, is provided.
Assuming that 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 of 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ,
The first support contains a resin material and contains
The first support includes fibers extending in the plane direction of the first support in the resin material.
The resin material has a larger coefficient of linear expansion than the piezoelectric substrate.
The fiber has a smaller coefficient of linear expansion and a higher elastic modulus than the resin material.
Elastic wave device. A first support having a first surface and a second surface facing each other in the thickness direction,
A piezoelectric substrate bonded to the first surface and having a coefficient of linear expansion larger than that of the first support.
A second support having a coefficient of linear expansion larger than that of the first support, which is joined to the second surface, is provided.
Assuming that 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 of 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ,
The first support contains a resin material and contains
The first support includes fibers extending in the plane direction of the first support in the resin material.
The first support is
In the thickness direction, the region between the first surface side and the second surface side has a smaller ratio per unit volume of the fiber than the central thickness region.
Elastic wave device. The elastic wave device according to claim 1 or 2 , wherein the elastic modulus E2 of the first support is 10 GPa or more and 40 GPa or less. The elastic wave device according to claim 1 or 2 , wherein the first support includes an inorganic filler in the resin material. The elastic wave device according to any one of claims 1 to 4 , wherein the second support is made of the same material as the piezoelectric substrate. The elastic wave device according to any one of claims 1 to 5 , wherein the piezoelectric substrate is made of a lithium tantalate substrate, and the second support is made of quartz. According to claim 5 or 6 , when the thickness of the second support is T3, the thickness of the piezoelectric substrate, the first support, and the second support satisfies the relationship of T1 <T3 <T2. The described elastic wave device. A first support having a first surface and a second surface facing each other in the thickness direction,
A piezoelectric substrate bonded to the first surface and having a coefficient of linear expansion larger than that of the first support.
A second support having a coefficient of linear expansion larger than that of the first support, which is joined to the second surface, is provided.
Assuming that 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 of 1 ≦ (E2 × T2) / (E1 × T1) ≦ 9 is satisfied. ,
The first support is a composite substrate containing fibers extending in the surface direction of the first support in a resin material, and having a large proportion of the fibers per unit volume on the outer peripheral side from the center in the surface direction.

Images