CN116470873A

CN116470873A - Elastic wave device and module comprising same

Info

Publication number: CN116470873A
Application number: CN202310072986.2A
Authority: CN
Inventors: 熊四辈; 高冈良知
Original assignee: Sanyan Japan Technology Co ltd
Current assignee: Sanyan Japan Technology Co ltd
Priority date: 2022-01-19
Filing date: 2023-01-16
Publication date: 2023-07-21
Also published as: JP2023105340A

Abstract

An elastic wave device includes a first piezoelectric substrate including a main surface and another main surface; a second piezoelectric substrate including a main surface connected to the other main surface of the first piezoelectric substrate and the other main surface; the resonator comprises an IDT electrode formed on the main surface of the first piezoelectric substrate, wherein the IDT electrode is provided with comb electrodes which are alternately inserted, and the comb electrodes are provided with a plurality of electrode fingers; when power is applied between the electrode finger to which power is applied and the electrode finger adjacent thereto, the displacement amount near the main surface and the other main surface of the first piezoelectric substrate is larger than the displacement amount inside the first piezoelectric substrate, and the displacement amount near the main surface and the other main surface of the second piezoelectric substrate is larger than the displacement amount inside the second piezoelectric substrate. Thereby, an elastic wave device with increased mechanical strength and a module including the elastic wave device can be provided.

Description

Elastic wave device and module comprising same

Technical Field

The present disclosure relates to an elastic wave device and a module including the same. Specifically, the present invention relates to an elastic wave device using a Lamb wave (Lamb wave) or a shear horizontal wave (SH wave) plate wave device. The elastic wave device is, for example, a filter, a Duplexer (Duplexer), or a Multiplexer (Multiplexer).

Background

Patent document 1 (japanese patent laid-open No. 2007-251910) exemplifies a lamb wave type high-frequency device and a method of manufacturing the same, and provides a lamb wave type high-frequency device capable of realizing improvement of structural strength and stable resonance characteristics, and a method of manufacturing the same which is less likely to break during manufacturing and can increase yield.

In patent document 1, the lamb wave type high-frequency device includes a piezoelectric substrate having an IDT electrode on one principal surface thereof, and a reinforcing substrate connected to the other principal surface of the piezoelectric substrate. The piezoelectric substrate or the reinforcing substrate is provided with a space having a larger area than the lamb wave propagation region, and a joint surface formed on the outer edge of the space.

In recent years, the piezoelectric substrate has been required to be thinned due to the trend of high frequency, however, in the lamb wave type high frequency device described in patent document 1, the manufacturing process thereof cannot ensure mechanical strength enough to withstand the thickness of the piezoelectric substrate.

Therefore, an elastic wave device having sufficient mechanical strength cannot be provided.

Disclosure of Invention

[ problem to be solved by the invention ]

The present disclosure is directed to solving the above problems, and an object of the present disclosure is to provide an elastic wave device capable of improving mechanical strength and a module including the elastic wave device.

[ means for solving the problems ]

An elastic wave device of the present disclosure includes a first piezoelectric substrate including a main surface and another main surface;

a second piezoelectric substrate including a main surface connected to the other main surface of the first piezoelectric substrate and the other main surface; a kind of electronic device with high-pressure air-conditioning system

A resonator including an IDT electrode formed on a main surface of the first piezoelectric substrate, wherein the IDT electrode is provided with comb electrodes that are alternately interposed, and the comb electrodes have a plurality of electrode fingers;

when power is applied, the displacement amount near the main surface and the other main surface of the first piezoelectric substrate is larger than the displacement amount inside the first piezoelectric substrate, and the displacement amount near the main surface and the other main surface of the second piezoelectric substrate is larger than the displacement amount inside the second piezoelectric substrate between the electrode fingers to which power is applied and the electrode fingers adjacent to the electrode fingers.

In one embodiment of the present disclosure, the displacement amount of the main surface of the first piezoelectric substrate is larger than the displacement amount of the vicinity of the other main surface of the first piezoelectric substrate and the main surface of the second piezoelectric substrate in the vicinity of the electrode finger to which power is applied when power is applied.

In one embodiment of the present disclosure, the displacement amount of the main surface of the first piezoelectric substrate is larger than the displacement amounts of the other main surface of the first piezoelectric substrate and the vicinity of the main surface of the second piezoelectric substrate in the vicinity of the electrode fingers that obtain kinetic energy by converting electric power into motive power when electric power is applied.

In one embodiment of the present disclosure, the total displacement amount of the first piezoelectric substrate and the second piezoelectric substrate is larger near the electrode finger that obtains kinetic energy by converting electric power into motive power when electric power is applied than the total displacement amount of the first piezoelectric substrate and the second piezoelectric substrate near the electrode finger to which electric power is applied.

In one aspect of the present invention, at least a part of the main surface of the first piezoelectric substrate and the IDT electrode are provided in a hermetically sealed space.

In one aspect of the present disclosure, the elastic wave device further includes a support substrate, and the support substrate and the other main surface of the second piezoelectric substrate form a hollow structure corresponding to a region of the first piezoelectric substrate where the resonator is formed.

In one aspect of the present disclosure, the first piezoelectric substrate and the second piezoelectric substrate are opposite in polarity.

In one aspect of the present disclosure, the first piezoelectric substrate and the second piezoelectric substrate are bonded by van der Wa1ls force.

In one aspect of the present disclosure, the first piezoelectric substrate and the second piezoelectric substrate include at least one of lithium niobate or lithium tantalate single crystal layers.

In one aspect of the present disclosure, a plate wave propagating through the first piezoelectric substrate and the second piezoelectric substrate is excited by the resonator.

In one aspect of the present disclosure, the resonance frequency of the resonator is 3 to 5GHz.

In one embodiment of the present disclosure, the IDT electrode has a duty cycle of 7% to 15%.

The module of the invention comprises the elastic wave device.

[ Effect of the invention ]

According to the present invention, an elastic wave device with increased mechanical strength and a module including the elastic wave device can be provided.

Drawings

Fig. 1 is a cross-sectional view of an elastic wave device of a first embodiment.

Fig. 2 is a schematic view of an elastic wave element of the elastic wave device of the first embodiment.

Fig. 3 is a schematic diagram of a simulated condition of the first embodiment.

Fig. 4 is a schematic diagram of the simulated conditions of comparative example one of the first embodiment.

Fig. 5 is a schematic diagram of the simulated conditions of comparative example two of the first embodiment.

Fig. 6 is a schematic diagram of resonance characteristics of the first embodiment.

Fig. 7 is a schematic diagram of resonance characteristics of the first comparative example.

Fig. 8 is a schematic diagram of resonance characteristics of the second comparative example.

Fig. 9 is a schematic diagram of the displacement amount of the piezoelectric substrate when electric power is applied in the first embodiment.

Fig. 10 is a cross-sectional view of a module using the elastic wave device of the second embodiment.

Detailed Description

Specific embodiments of the present invention will be described below with reference to the accompanying drawings. It is noted that identical or corresponding parts are provided with the same reference numerals in the various figures. The same or equivalent parts will be appropriately simplified or omitted from illustration.

(first embodiment)

Fig. 1 is a cross-sectional view of an elastic wave device 1 of a first embodiment.

As shown in fig. 1, the acoustic wave device 1 includes a wiring substrate 3, a plurality of external connection terminals 31, a device chip 5, a plurality of electrode pads 9, a plurality of bumps 15, and a sealing portion 17.

The wiring board 3 is, for example, a multilayer board formed of resin. The wiring board 3 may be, for example, a low temperature co-fired ceramic (LTCC, low Temperature Co-wireless Ceramics) multilayer board composed of a plurality of dielectric layers.

The external connection terminals 31 are formed on the lower surface of the wiring board 3.

The electrode pads 9 are formed on the main surface of the wiring board 3. The electrode pads 9 are, for example, copper or an alloy containing copper. The thickness of the electrode pad 9 is, for example, 10 μm to 20 μm.

The bumps 15 are formed on the upper surfaces of the electrode pads 9, respectively. The bump 15 is, for example, a gold bump. The height of the bump 15 is, for example, 10 μm to 50 μm.

A space 16 is formed between the wiring board 3 and the device chip 5.

The device chip 5 is mounted on the wiring substrate 3 by the bump 15 by flip chip bonding technique. The device chip 5 is electrically connected to the electrode pads 9 by means of the bumps 15.

The device chip 5 is a substrate on which functional elements are formed. For example, the main surface of the device chip 5 forms a transmission filter and a reception filter.

The transmission filter is capable of passing an electric signal in a desired frequency band. The transmission filter is, for example, a ladder filter composed of a plurality of series resonators and a plurality of parallel resonators.

The receiving filter is capable of passing an electric signal of a desired frequency band. The receiving filter is, for example, a ladder filter.

The device chip 5 includes a first piezoelectric substrate 11 and a second piezoelectric substrate 21.

For example, the first piezoelectric substrate 11 and the second piezoelectric substrate 21 are substrates formed of at least one piezoelectric single crystal such as lithium tantalate, lithium niobate, or crystal. For example, the first piezoelectric substrate 11 and the second piezoelectric substrate 21 are substrates made of piezoelectric ceramics.

An elastic wave element 52 is formed on the main surface of the first piezoelectric substrate 11. The elastic wave element 52 is, for example, a resonator including IDT electrodes. Plate waves propagating through the first piezoelectric substrate 11 and the second piezoelectric substrate 21 are excited by the resonators. The resonance frequency of the resonator is 3-5 GHz.

The other main surface of the first piezoelectric substrate 11 is bonded to the main surface of the second piezoelectric substrate 21. The first piezoelectric substrate 11 and the second piezoelectric substrate 21 are bonded by, for example, van der waals force (van der Waals force). And may also be connected by an adhesive layer (not shown).

The polarity of the first piezoelectric substrate 11 is opposite to that of the second piezoelectric substrate 21. The first piezoelectric substrate 11 and the second piezoelectric substrate 21 may be substrates that are adjusted to a single polarization state in advance, and may be bonded to each other to have opposite polarities.

For example, before the thinning, a lithium niobate single crystal substrate having a plate thickness of 500 μm is subjected to a heat treatment in air at a temperature lower than the Curie point (Curie point) by about 1100 ℃ for about five hours, whereby a polarization inversion layer can be formed in the center of the plate thickness.

For example, a lithium tantalate single crystal substrate can be subjected to a heat treatment in benzoic acid to replace lithium atoms in the crystal with hydrogen atoms by proton exchange, and then subjected to a heat treatment at a temperature lower than about 590 ℃ than the Curie point (Curie point), thereby forming a polarization-reversal layer.

For example, the device chip 5 is formed by bonding the first piezoelectric substrate 11, the second piezoelectric substrate 21, and a support substrate 22. The support substrate 22 is, for example, a substrate formed of sapphire, silicon, alumina, spinel, crystal, or glass.

As shown in fig. 1, the second piezoelectric substrate 21 is bonded to the support substrate 22 on the other main surface.

The second piezoelectric substrate 21 and the support substrate 22 have a hollow structure in a region corresponding to the elastic wave element 52 formed on the main surface of the first piezoelectric substrate 11 in the other main surface of the second piezoelectric substrate 21, and thus a void 26 is formed.

To form the void 26, the support substrate 22 has a recess, which may be formed, for example, by dry etching or wet etching during wafer processing.

Thereby, the displacement of the other main surface of the second piezoelectric substrate 21 due to the application of electric power can be suppressed.

The sealing portion 17 covers the device chip 5, and the IDT electrode and at least a part of the main surface of the first piezoelectric substrate 11 are provided in the hermetically sealed space. The sealing portion 17 may be formed of an insulator such as a synthetic resin, for example. The seal 17 may be formed of metal, for example.

In the case where the sealing portion 17 is a synthetic resin, the synthetic resin is, for example, an epoxy resin, polyimide, or the like. Preferably, the sealing part 17 may be formed using an epoxy resin through a low temperature hardening process.

Next, the elastic wave element 52 formed on the device chip 5 is described with reference to fig. 2. Fig. 2 is a schematic view of an elastic wave element 52 of the elastic wave device 1 of the first embodiment.

As shown in fig. 2, an IDT (Interdigital Transducer ) 52a and a pair of reflectors 52b are formed on the main surface of the device chip 5. The IDT52a and the reflectors 52b excite elastic waves (mainly lamb waves).

For example, the IDT52a and the reflectors 52b are formed of an alloy of aluminum and copper. For example, the IDT52a and the reflectors 52b are formed of a suitable metal such as titanium, palladium, silver, or an alloy thereof.

For example, the IDT52a and the reflectors 52b are formed of a laminated metal film formed by laminating a plurality of metal layers. For example, the thickness of the IDT52a and the reflectors 52b is 150nm to 450nm.

The IDT52a has a pair of interdigitated comb electrodes 52c. The pair of comb electrodes 52c are opposed to each other. Each comb electrode 52c has a plurality of electrode fingers 52d and bus bars 52e.

The electrode fingers 52d extend longitudinally. The bus bar 52e connects the electrode fingers 52d.

Bus bars 52e1 and 52e2 refer to bus bars of the comb-shaped electrode 52c, respectively.

One of the reflectors 52b is adjacent to one side of the IDT52 a. Another one of the reflectors 52b adjoins the other side of the IDT52 a.

Next, the results of the investigation of the elastic wave device 1 in the first embodiment will be described. The inventors made a simulation of the resonators of the device chip 5 and the elastic wave element 52 of the first embodiment according to the following conditions.

Fig. 3 is a schematic diagram of a simulated condition of the first embodiment.

As shown in fig. 3, a lithium niobate piezoelectric single crystal propagating along the X-axis of the Z-axis tangential plane is used, and the crystal orientation (Crystal orientation) of the main surface of the first piezoelectric substrate 11 is (0, 0), and the crystal orientation of the main surface of the second piezoelectric substrate 21 is (0, 180,0).

The thickness of the first piezoelectric substrate 11 is 400nm.

The thickness of the second piezoelectric substrate 21 is 400nm.

The thickness of the IDT is 60nm.

The IDT is formed of aluminum.

The Duty ratio (Duty ratio) is 10%.

The period (Pitch) was 3. Mu.m.

The logarithm of the electrode finger 52d is set to infinity.

As shown in fig. 4, in the first comparative example, a single piezoelectric substrate is provided, which is identical to the first piezoelectric substrate 11 and has a thickness of 400nm. Other conditions are the same as those of the first embodiment.

As shown in fig. 5, the second comparative example is provided with a single piezoelectric substrate, which is the same as the first piezoelectric substrate 11 and has a thickness of 800nm. Other conditions are the same as those of the first embodiment.

The above-described simulation result is described next.

As shown in fig. 6, resonance characteristics were obtained in the range of 4GHz to 6 GHz. In addition, the thickness of the piezoelectric substrate (i.e., the total thickness of the first piezoelectric substrate 11 and the second piezoelectric substrate 21) of the first embodiment is 800nm, compared with the thickness of the piezoelectric substrate of the first comparative example being 400nm, and the mechanical strength can be greatly improved.

As shown in fig. 7, resonance characteristics were obtained in the range of 4GHz to 6 GHz. On the other hand, the piezoelectric substrate of the first comparative example has a thickness of 400nm, and has a lower mechanical strength than the piezoelectric substrate of the first embodiment (i.e., the total thickness of the first piezoelectric substrate 11 and the second piezoelectric substrate 21) (800 nm), and therefore, the resonance characteristics and the mechanical strength cannot be obtained.

As shown in fig. 8, the second comparative example cannot obtain resonance characteristics that can be used as a device. On the other hand, the thickness of the piezoelectric substrate of the second comparative example is the same as the thickness of the piezoelectric substrate of the first embodiment (i.e., the total thickness of the first piezoelectric substrate 11 and the second piezoelectric substrate 21) (800 nm), and the mechanical strength thereof is also the same. However, since the resonance characteristic cannot be obtained, it is said that the resonance characteristic and the mechanical strength cannot be obtained at the same time.

As shown in fig. 9, the displacement amount between the electrode finger 52dIN to which power is applied and the electrode finger 52dOUT adjacent thereto in the vicinity of the main surface1 and the other main surface2 of the first piezoelectric substrate 11 is larger than the displacement amount of the internal1 of the first piezoelectric substrate 11 when power is applied.

Between the electrode fingers 52dIN and their adjacent electrode fingers 52dOUT, displacement amounts of about 14 to 18 are observed in the vicinity of the principal surface1 and the other principal surface2 of the first piezoelectric substrate 11. A displacement of about 0 to 8 is observed in the internal portion 1 of the first piezoelectric substrate 11.

The unit of displacement is μm. The ratio was 100 times. In order to improve the recognition of the deformation of the piezoelectric substrate, the deformation is shown in the figure at a scale of 100 times.

The displacement amount in the vicinity of the main surface2 and the other main surface3 of the second piezoelectric substrate 21 is larger than the displacement amount of the internal surface2 of the second piezoelectric substrate 21. Between the electrode finger 52dIN to which electric power is applied and the electrode finger 52dOUT adjacent thereto, a displacement amount of about 14 to 18 is observed in the vicinity of the main surface2 and the other main surface3 of the second piezoelectric substrate 21. A displacement of about 0 to 8 is observed in the internal portion 2 of the second piezoelectric substrate 21.

In addition, since the other main surface2 of the first piezoelectric substrate 11 is bonded to the main surface2 of the second piezoelectric substrate 21, the same reference numerals are used for convenience of explanation.

As shown in fig. 9, the displacement amount of the surface1 of the first piezoelectric substrate 11 in the vicinity of the electrode finger 52dIN to which power is applied is larger than the displacement amounts of the other surface2 of the first piezoelectric substrate 11 and the vicinity of the surface2 of the second piezoelectric substrate 21.

When power is applied, a displacement of about 8 is observed in the surface1 of the first piezoelectric substrate 11 in the vicinity of the electrode finger 52dIN to which power is applied. A displacement of about 2 is observed near the other main surface2 of the first piezoelectric substrate 11 and the main surface2 of the second piezoelectric substrate 21.

As shown in fig. 9, the displacement amount of the main surface1 of the first piezoelectric substrate 11 in the vicinity of the electrode finger 52dOUT which obtains kinetic energy by converting electric power into motive power is larger than the displacement amounts of the other main surface2 of the first piezoelectric substrate 11 and the vicinity of the main surface2 of the second piezoelectric substrate 21 when electric power is applied.

When electric power is applied, a displacement of about 14 is observed on the main surface1 of the first piezoelectric substrate 11 in the vicinity of the electrode finger 52dOUT which obtains kinetic energy by converting electric power into motive power. A displacement of about 2 is observed near the other main surface2 of the first piezoelectric substrate 11 and the main surface2 of the second piezoelectric substrate 21.

As shown in fig. 9, the total displacement amount of the first piezoelectric substrate 11 and the second piezoelectric substrate 21 in the vicinity of the electrode finger 52dOUT, which is converted into power by the power, is larger than the total displacement amount of the first piezoelectric substrate 11 and the second piezoelectric substrate 21 in the vicinity of the electrode finger 52dIN, which is applied with the power, when the power is applied.

According to the first embodiment described above, an elastic wave device with increased mechanical strength can be provided.

(second embodiment)

Fig. 10 is a cross-sectional view of a module using the elastic wave device of the second embodiment. It should be understood that the same or equivalent parts as those of the first embodiment are given the same reference numerals. The same or equivalent parts will be omitted from the description.

As shown in fig. 10, the module 100 includes a wiring board 130, a plurality of external connection terminals 131, an integrated circuit module IC, the elastic wave device 1, an inductor 111, and a sealing portion 117.

The external connection terminal 131 is formed on the lower surface of the wiring substrate 130. The external connection terminal 131 is mounted on a predetermined motherboard of the mobile communication terminal.

For example, the integrated circuit assembly IC is mounted inside the wiring substrate 130. The integrated circuit component IC includes a switching circuit and a low noise amplifier.

The acoustic wave device 1 is mounted on the main surface of the wiring board 130.

The inductor 111 is mounted on a main surface of the wiring board 130. An inductor 111 is provided for impedance matching. For example, the inductor 111 may be an integrated passive device (Integrated Passive Device, IPD).

The sealing portion 117 seals a plurality of electronic components including the elastic wave device 1.

According to the second embodiment described above, the module 100 contains the elastic wave device 1. Thus, a module including an elastic wave device with increased mechanical strength can be provided.

While at least one embodiment has been described above, it is to be appreciated various alterations, modifications, or improvements will readily occur to those skilled in the art. Such alterations, modifications, or improvements are intended to be part of this disclosure, and are intended to be within the scope of the invention.

It is to be understood that the aspects of the method or apparatus described herein are not limited in their implementation to the constructions and arrangements of parts described in the foregoing description or shown in the drawings. The methods and apparatus may be practiced or carried out in other embodiments.

The examples are given for illustration only and are not intended to be limiting.

Further, the descriptions or words used herein are merely for illustration, and are not necessarily limiting. The use of "including," "comprising," "having," "containing," and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

The use of the word "or any use of the word" or "described may be interpreted as one, more than one, or all of the words described.

Any terms such as front, back, left, right, top, bottom, upper, lower, longitudinal, and transverse are used for convenience of description and do not limit the position or spatial arrangement of any one of the constituent elements of the present invention. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. An elastic wave device comprising:

a first piezoelectric substrate including a main surface and another main surface;

the method is characterized in that: when power is applied, the displacement amount near the main surface and the other main surface of the first piezoelectric substrate is larger than the displacement amount inside the first piezoelectric substrate, and the displacement amount near the main surface and the other main surface of the second piezoelectric substrate is larger than the displacement amount inside the second piezoelectric substrate between the electrode fingers to which power is applied and the electrode fingers adjacent to the electrode fingers.

2. The elastic wave device according to claim 1, wherein: when power is applied, the displacement amount of the main surface of the first piezoelectric substrate is larger than the displacement amount of the vicinity of the other main surface of the first piezoelectric substrate and the main surface of the second piezoelectric substrate in the vicinity of the electrode finger to which power is applied.

3. The elastic wave device according to claim 1 or 2, wherein: when electric power is applied, the displacement amount of the main surface of the first piezoelectric substrate is larger than the displacement amount of the vicinity of the other main surface of the first piezoelectric substrate and the main surface of the second piezoelectric substrate in the vicinity of the electrode finger which obtains kinetic energy by converting electric power into motive power.

4. The elastic wave device according to claim 1, wherein: when power is applied, the total displacement amount of the first piezoelectric substrate and the second piezoelectric substrate is larger than the total displacement amount of the first piezoelectric substrate and the second piezoelectric substrate in the vicinity of the electrode finger to which power is applied, in the vicinity of the electrode finger to which power is converted into power to obtain kinetic energy.

5. The elastic wave device according to claim 1, wherein: the IDT electrode is provided in a hermetically sealed space on at least a part of the main surface of the first piezoelectric substrate.

6. The elastic wave device according to claim 1, wherein: the elastic wave device further includes a support substrate, and hollow structures are formed in the support substrate and the other main surface of the second piezoelectric substrate, the hollow structures corresponding to regions where the first piezoelectric substrate forms the resonators.

7. The elastic wave device according to claim 1, wherein: the polarities of the first piezoelectric substrate and the second piezoelectric substrate are opposite.

8. The elastic wave device according to claim 1, wherein: the first piezoelectric substrate and the second piezoelectric substrate are bonded by van der Waals force.

9. The elastic wave device according to claim 1, wherein: the first piezoelectric substrate and the second piezoelectric substrate include at least one of lithium niobate or a single crystal layer of lithium tantalate.

10. The elastic wave device according to claim 1, wherein: plate waves propagating through the first piezoelectric substrate and the second piezoelectric substrate are excited by the resonator.

11. The elastic wave device according to claim 1, wherein: the resonance frequency of the resonator is 3-5 GHz.

12. The elastic wave device according to claim 1, wherein: the duty ratio of the IDT electrode is 7% -15%.

13. A module comprising the elastic wave device of any one of claims 1 to 12.