JP7403960B2 - Acoustic wave devices and their manufacturing methods, filters and multiplexers - Google Patents

Description

The present invention relates to an acoustic wave device, a method for manufacturing the same , a filter, and a multiplexer, and for example, an acoustic wave device having comb-shaped electrodes, a method for manufacturing the same, a filter, and a multiplexer.

Surface acoustic wave resonators are known as elastic wave resonators used in communication devices such as smartphones. It is known to bond a piezoelectric substrate forming a surface acoustic wave resonator to a support substrate. It is known that the upper surface of the support substrate is roughened (for example, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2015-115870 US Patent No. 10020796

As in Patent Documents 1 and 2, by roughening the upper surface of the support substrate, spurious waves and the like are suppressed. However, it may be difficult to make an acoustic wave device into a chip.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to appropriately form a chip.

The present invention provides a support substrate that is a polycrystalline substrate or a single crystal substrate, a piezoelectric substrate provided on the support substrate, a pair of comb-shaped electrodes provided on the piezoelectric substrate, and the support substrate and the piezoelectric substrate. a first insulating layer provided between the first insulating layer and the supporting substrate and having a refractive index lower than that of the supporting substrate; The surface roughness of the first surface is greater than the surface roughness of the second surface between the first insulating layer and the second insulating layer, which has a higher refractive index than the first insulating layer and a lower refractive index than the supporting substrate. , a plurality of modified regions which are amorphous or polycrystalline and whose main component is the constituent element of the support substrate are provided in the plane direction on the side surface of the support substrate, and the refractive index of the second insulating layer is the same as that of the second insulating layer. The acoustic wave device is such that the difference between the refractive index of the first insulating layer and the refractive index of the first insulating layer is greater than or equal to the difference between the refractive index of the supporting substrate and the second insulating layer.

In the above structure, the signs of the temperature coefficients of elastic constants of the first insulating layer and the second insulating layer may be opposite to the signs of the temperature coefficients of elastic constants of the piezoelectric substrate.

In the above configuration, the sound velocity of the first insulating layer and the second insulating layer may be slower than the sound velocity of the support substrate.

The present invention provides a support substrate that is a polycrystalline substrate or a single crystal substrate, a piezoelectric substrate provided on the support substrate, a pair of comb-shaped electrodes provided on the piezoelectric substrate, and the support substrate and the piezoelectric substrate. a first insulating layer provided between the first insulating layer and the supporting substrate and having a refractive index lower than that of the supporting substrate; a second insulating layer having a surface roughness greater than that of a second surface between the first insulating layer and the first insulating layer, and a second insulating layer having a higher refractive index than the first insulating layer; A plurality of modified regions which are amorphous or polycrystalline and whose main component is the constituent element of the support substrate are provided in the plane direction, and the main components of the first insulating layer and the second insulating layer are the same. In the acoustic wave device, the second insulating layer includes impurities that are not added to the first insulating layer.

The present invention provides a support substrate that is a polycrystalline substrate or a single crystal substrate, a piezoelectric substrate provided on the support substrate, a pair of comb-shaped electrodes provided on the piezoelectric substrate, and the support substrate and the piezoelectric substrate. a first insulating layer provided between the first insulating layer and the supporting substrate and having a refractive index lower than that of the supporting substrate; a second insulating layer having a surface roughness greater than that of a second surface between the first insulating layer and the first insulating layer, and a second insulating layer having a higher refractive index than the first insulating layer; A plurality of modified regions which are amorphous or polycrystalline and whose main component is the constituent element of the support substrate are provided in the plane direction, and the main component of the first insulating layer and the second insulating layer is silicon oxide. In the acoustic wave device, the concentration of germanium oxide or zirconium oxide in the second insulating layer is higher than the concentration of germanium oxide or zirconium oxide in the first insulating layer.

In the above configuration, the first surface may have an arithmetic mean roughness of 10 nm or more, and the second surface may have an arithmetic mean roughness of 1 nm or less.

In the above structure, the support substrate may be a single crystal substrate.
In the above structure, the modified region may be amorphous.

The present invention is a filter including the above elastic wave device.

The present invention is a multiplexer including the above filter.

The present invention provides a support substrate, a piezoelectric substrate provided on the support substrate, and a first insulator provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate. the first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer and the supporting substrate. a second insulating layer having a larger refractive index than the first insulating layer and a lower refractive index than the supporting substrate , a composite substrate is irradiated with laser light from the piezoelectric substrate side to form a modified region in the supporting substrate. and cutting the composite substrate along the modified region, wherein the difference between the refractive index of the second insulating layer and the refractive index of the first insulating layer is and the refractive index of the second insulating layer.
The present invention provides a support substrate, a piezoelectric substrate provided on the support substrate, and a first insulator provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate. the first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer and the supporting substrate. a second insulating layer that is larger and has a higher refractive index than the first insulating layer; irradiating a composite substrate with a laser beam from the piezoelectric substrate side to form a modified region in the support substrate; cutting the composite substrate along a region, the first insulating layer and the second insulating layer have the same main component, and the second insulating layer is added to the first insulating layer. This is a method for manufacturing an acoustic wave device that contains no impurities.
The present invention provides a support substrate, a piezoelectric substrate provided on the support substrate, and a first insulator provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate. the first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer and the supporting substrate. a second insulating layer that is larger and has a higher refractive index than the first insulating layer; irradiating a composite substrate with a laser beam from the piezoelectric substrate side to form a modified region in the support substrate; cutting the composite substrate along regions, the main component of the first insulating layer and the second insulating layer is silicon oxide, and the concentration of germanium oxide or zirconium oxide in the second insulating layer is This is a method of manufacturing an acoustic wave device in which the concentration of germanium oxide or zirconium oxide is higher than that of the first insulating layer.

According to the present invention, it is possible to appropriately form a chip.

FIG. 1(a) is a plan view of the elastic wave resonator in Example 1, and FIG. 1(b) is a sectional view taken along line AA in FIG. 1(a). FIGS. 2(a) to 2(d) are cross-sectional views (part 1) showing the method for manufacturing the acoustic wave device according to the first embodiment. 3(a) to 3(c) are cross-sectional views (part 2) showing the method for manufacturing the acoustic wave device according to the first embodiment. FIG. 4(a) is a cross-sectional view (Part 3) showing the method for manufacturing the acoustic wave device according to Example 1, and FIG. 4(b) is a side view of the composite substrate in Example 1. FIG. 5 is a diagram showing the admittance of samples A to B in a comparative example. FIG. 6 is a diagram illustrating problems in the comparative example. FIG. 7A is a circuit diagram of a filter according to a second embodiment, and FIG. 7B is a circuit diagram of a duplexer according to a first modification of the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1(a) is a plan view of the elastic wave resonator in Example 1, and FIG. 1(b) is a sectional view taken along line AA in FIG. 1(a). The direction in which the electrode fingers are arranged is the X direction, the extending direction of the electrode fingers is the Y direction, and the direction in which the support substrate and the piezoelectric substrate are laminated is the Z direction. The X direction, Y direction, and Z direction do not necessarily correspond to the X-axis direction and Y-axis direction of the crystal orientation of the piezoelectric substrate. When the piezoelectric substrate is a rotating Y-cut X-propagation substrate, the X direction is the X-axis direction of the crystal orientation.

As shown in FIGS. 1(a) and 1(b), an insulating layer 17 is provided on the support substrate 10. Insulating layer 11 is provided on insulating layer 17 . A piezoelectric substrate 12 is provided on the insulating layer 11. The interface 50 between the support substrate 10 and the insulating layer 17 is a rough surface. An interface 51 between the insulating layers 17 and 11, an interface 52 between the insulating layer 11 and the piezoelectric substrate 12, and an upper surface 53 of the piezoelectric substrate 12 are flat surfaces. The arithmetic mean surface roughness Ra of the interface 50 is larger than the arithmetic surface roughness of the interfaces 51, 52 and the upper surface 53.

An elastic wave resonator 20 is provided on the piezoelectric substrate 12. The elastic wave resonator 20 has an IDT 22 and a reflector 24. The reflectors 24 are provided on both sides of the IDT (Inter Digital Transducer) 22 in the X direction. IDT 22 and reflector 24 are formed by metal film 14 on piezoelectric substrate 12 .

The IDT 22 includes a pair of comb-shaped electrodes 18 facing each other. The comb-shaped electrode 18 includes a plurality of electrode fingers 15 and a bus bar 16 to which the plurality of electrode fingers 15 are connected. The area where the electrode fingers 15 of the pair of comb-shaped electrodes 18 intersect is the intersection area 25 . The length of the crossing region 25 is the opening length. The pair of comb-shaped electrodes 18 are provided facing each other so that the electrode fingers 15 are substantially alternated in at least a portion of the crossing region 25. The elastic waves excited by the plurality of electrode fingers 15 in the intersection region 25 mainly propagate in the X direction. The pitch of the electrode fingers 15 of one of the pair of comb-shaped electrodes 18 is approximately equal to the wavelength λ of the elastic wave. The wavelength λ of the elastic wave is approximately the pitch of two electrode fingers 15. The reflector 24 reflects the elastic waves (surface acoustic waves) excited by the electrode fingers 15 of the IDT 22 . As a result, the elastic waves are confined within the intersection area 25 of the IDT 22.

The piezoelectric substrate 12 is a single-crystal lithium tantalate (LiTaO ₃ ) substrate, a single-crystal lithium niobate (LiNbO ₃ ) substrate, or a single-crystal quartz substrate, and is, for example, a rotating Y-cut X-propagating lithium tantalate substrate or a rotating Y-cut It is a lithium niobate substrate. The insulating layer 11 has, for example, silicon oxide (SiO ₂ ) as a main component. The insulating layer 11 is mainly composed of silicon oxide and may contain impurities such as fluorine. The sign of the temperature coefficient of the elastic constant of the insulating layer 11 is opposite to the sign of the temperature coefficient of the elastic constant of the piezoelectric substrate 12. Thereby, the frequency temperature coefficient of the elastic wave resonator can be reduced.

The refractive index of the insulating layer 17 is greater than the refractive index of the insulating layer 11. The insulating layer 17 is mainly composed of silicon oxide and contains germanium oxide (GeO ₂ ) or zirconium oxide (ZrO ₂ ). The weight concentration of Ge or Zr relative to Si is, for example, 10 ppm or more and 10,000 ppm or less, for example, 100 ppm or more and 1,000 ppm or less. Thereby, the refractive index of the silicon oxide film can be increased.

The support substrate 10 has a linear expansion coefficient smaller than that of the piezoelectric substrate 12 in the X direction. Thereby, the frequency temperature coefficient of the elastic wave resonator can be reduced. Support substrate 10 is, for example, a sapphire substrate, an alumina substrate, a spinel substrate, a silicon substrate, or a silicon carbide substrate. The sapphire substrate is a single crystal aluminum oxide (Al ₂ O ₃ ) substrate with an r-plane, c-plane, or a-plane as the upper surface. The alumina substrate is a polycrystalline aluminum oxide (Al ₂ O ₃ ) substrate. The spinel substrate is a single crystal or polycrystalline spinel (MgAl ₂ O ₄ ) substrate. The silicon substrate is a single crystal or polycrystalline silicon (Si) substrate. The silicon carbide substrate is a single crystal or polycrystalline silicon carbide (SiC) substrate.

The metal film 14 is a film whose main component is, for example, aluminum (Al), copper (Cu), or molybdenum (Mo), and is, for example, an aluminum film, a copper film, or a molybdenum film. An adhesive film such as a titanium (Ti) film or a chromium (Cr) film may be provided between the electrode finger 15 and the piezoelectric substrate 12. The adhesive film is thinner than the electrode fingers 15. An insulating film may be provided to cover the electrode fingers 15. The insulating film functions as a protective film or a temperature compensation layer.

The thickness of the support substrate 10 is, for example, 50 μm to 500 μm. The thickness of the insulating layer 17 is, for example, 0.5 μm to 5.0 μm. The thickness of the insulating layer 11 is, for example, from 0.5 μm to 10 μm, and is, for example, less than the wavelength λ of the elastic wave. The thickness of the piezoelectric substrate 12 is, for example, from 0.5 μm to 20 μm, and is, for example, less than the wavelength λ of the elastic wave. The wavelength λ of the elastic wave is, for example, 1 μm to 6 μm. The number of pairs of electrode fingers 15 is, for example, 20 to 300 pairs. The duty ratio of the IDT 22 is the thickness of the electrode fingers 15/the pitch of the electrode fingers 15, and is, for example, 30% to 80%. The aperture length of the IDT 22 is, for example, 10λ to 50λ.

[Production method of Example 1]
FIGS. 2(a) to 4(a) are cross-sectional views showing a method for manufacturing an acoustic wave device according to Example 1. FIG. As shown in FIG. 2(a), a support substrate 10 having a rough surface is prepared. As shown in FIG. 2B, an insulating layer 17 is formed on the support substrate 10 using, for example, a CVD (Chemical Vapor Deposition) method, a sputtering method, or a vacuum evaporation method. The interface 50 between the support substrate 10 and the insulating layer 17 is a rough surface. The upper surface of the insulating layer 17 is planarized using, for example, a CMP (Chemical Mechanical Polishing) method.

As shown in FIG. 2C, the insulating layer 11 is formed on the insulating layer 17 using, for example, a CVD method, a sputtering method, or a vacuum evaporation method. The interface 51 between the insulating layers 17 and 11 becomes a flat surface. As shown in FIG. 2D, the bonding layer 13 is, for example, an aluminum oxide layer, an aluminum nitride layer, a diamond-like carbon layer, a silicon carbide layer, a silicon nitride layer, or a silicon layer. The thickness of the bonding layer 13 is, for example, 1 nm to 100 nm. The insulating layer 11 and the piezoelectric substrate 12 may be bonded without using the bonding layer 13. For example, a surface activation method is used for bonding. The interface 52 between the insulating layer 11 and the piezoelectric substrate 12 is a flat surface. Bonding layer 13 is sufficiently thinner than insulating layer 11 and piezoelectric substrate 12 .

As shown in FIG. 3(a), the upper surface of the piezoelectric substrate 12 is planarized using, for example, the CMP method. As a result, a composite substrate 62 (wafer) having the supporting substrate 10, the insulating layers 17 and 11, and the piezoelectric substrate 12 is formed. An elastic wave resonator 20 made of a metal film 14 is formed on the upper surface of the piezoelectric substrate 12. As shown in FIG. 3(b), the cutting area is irradiated with laser light 33 from above the piezoelectric substrate 12. As shown in FIG. Thereby, a modified region 34 is formed within the support substrate 10. The modified region 34 is, for example, a region where the supporting substrate 10 is melted and becomes amorphous and/or polycrystalline. The modified region 34 is made of the constituent elements of the support substrate 10. The laser beam 33 is, for example, the second harmonic of an Nd:YAG laser, and the wavelength of the laser beam 33 is, for example, 532 nm, for example, from 500 nm to 600 nm. The laser light may be visible light, ultraviolet light, or infrared light. The power of the laser beam 33 is, for example, 0.01W. As shown in FIG. 3(c), a dicing film 35 is attached to the lower surface (upper surface in FIG. 3(c)) of the support substrate 10. The break blade is pressed against the support substrate 10 via the dicing film 35.

As shown in FIG. 4A, the support substrate 10 is cut in the modified region 34, and the support substrate 10 is divided into pieces (chips). As a result, the acoustic wave device of Example 1 is formed. FIG. 4(b) is a side view of the composite substrate in Example 1. As shown in FIG. 4B, when the laser beam 33 is pulsed and scanned at a constant speed in FIG. 34 is exposed. The size D1 of the modified region 34 is, for example, 1 μm to 10 μm, and the interval D2 of the modified region 34 in the planar direction is, for example, about 1.5 to 5 times the size of the modified region 34.

[Comparative example]
The reason for providing the insulating layer 17 will be explained using a comparative example. Acoustic wave resonators were manufactured in which the insulating layer 17 was not provided and the surface roughness of the interface between the supporting substrate 10 and the insulating layer 11 was different. The manufacturing conditions are as follows.
Support substrate 10: Sapphire substrate Insulating layer 11: Silicon oxide film with a thickness of 0.4λ Piezoelectric substrate 12: 42° rotated Y-cut lithium tantalate substrate with a thickness of 0.4λ

The arithmetic mean roughness Ra of the interface 50a between the support substrate 10 and the insulating layer 11 of each sample is as follows.
Sample A: about 100nm
Sample B: about 10nm
Sample C: 1 nm or less (almost mirror surface)

FIG. 5 is a diagram showing the admittance of samples A to C in the comparative example. As shown in FIG. 5, spurious waves 59 are generated in a frequency band higher than the resonant frequency fr and the anti-resonant frequency fa. The spurious component 59 is generated when the bulk wave simultaneously excited when the IDT 22 excites the main mode elastic wave is reflected at the interface between the support substrate 10 and the insulating layer 11 . In sample C, a large spurious signal 59 is observed. In sample B, spurious 59 is slightly smaller. In sample A, spurious 59 is considerably smaller. By providing a rough surface between the support substrate 10 and the insulating film in this manner, bulk waves are scattered by the rough surface, and spurious waves caused by bulk waves can be suppressed.

FIG. 6 is a diagram illustrating problems in the comparative example, and is a cross-sectional view illustrating a method of manufacturing an acoustic wave device according to the comparative example. As shown in FIG. 6, when the laser beam 33 is irradiated into the support substrate 10 from the piezoelectric substrate 12 side, the laser beam 33 is scattered on the rough surface of the interface 50a. This makes it difficult for the modified region 34 to be formed within the support substrate 10. The wavelength of the laser beam is several hundred nm, and when the Ra of the interface 50a is 10 nm or more, which is effective in suppressing spurious, the laser beam 33 is easily scattered.

It is also conceivable to irradiate the laser beam 33 from the lower surface of the support substrate 10. However, since the piezoelectric substrate 12, the insulating layer 11, and the support substrate 10 are transparent, in the process of forming an acoustic wave resonator on the piezoelectric substrate 12, the lower surface is made a matte surface (rough surface) so that the wafer can be recognized. Therefore, in order to irradiate the laser beam 33 from the lower surface of the support substrate 10, the lower surface of the support substrate 10 must be made into a mirror surface. If an attempt is made to polish the lower surface of the support substrate 10 after forming the acoustic wave resonator on the piezoelectric substrate 12, the thickness variation of the support substrate 10 will increase. This causes the depth of the modified region 34 to vary. Therefore, it is preferable that the laser beam 33 is irradiated onto the support substrate 10 from the piezoelectric substrate 12 side.

According to Example 1, the refractive index of the support substrate 10 and the insulating layer 17 (second insulating layer) is larger than the refractive index of the insulating layer 11. The surface roughness of the interface 50 (first surface) between the supporting substrate 10 and the insulating layer 17 is greater than the surface roughness of the interface 51 (second surface) between the insulating layers 11 (first insulating layer) and 17. do. In this way, by making the interface 50 a rough surface, spurious waves caused by bulk waves can be suppressed, as shown in FIG. The interface 51 is a flat surface, and the refractive index of the insulating layer 17 is made larger than the refractive index of the insulating layer 11. As a result, as shown in FIG. 3B, when the composite substrate 62 is irradiated with the laser beam 33 from the piezoelectric substrate 12 side to form the modified region 34 in the supporting substrate 10, the laser beam 33 is scattered at the interface 50. become less likely to be By cutting the composite substrate 62 along the modified region 34 as shown in FIG. 3(c), it is possible to appropriately form it into chips.

For example, if the support substrate 10 is made of sapphire, the refractive index is 1.768. When the insulating layer 11 is made of silicon oxide, the refractive index is 1.457. When the insulating layer 17 is made of silicon oxide doped with iridium oxide or germanium oxide, the refractive index can be set to about 1.7.

When the difference between the refractive index of the supporting substrate 10 and the refractive index of the insulating layer 11 is 0.1 or 0.2 or more, the laser beam 33 is scattered at the interface 50a between the insulating layer 11 and the supporting substrate 10 as shown in FIG. easy to be Therefore, it is preferable to provide the insulating layer 17. Preferably, the refractive index of the insulating layer 17 is smaller than the refractive index of the supporting substrate 10. It is preferable that the difference in refractive index between the insulating layers 17 and 11 is greater than or equal to the difference in refractive index between the insulating layer 17 and the supporting substrate 10. The difference in refractive index between the insulating layers 17 and 11 is preferably at least twice the difference in refractive index between the insulating layer 17 and the supporting substrate 10. Thereby, the laser beam 33 is reflected more easily at the interface 51 than at the interface 50, so that scattering on the rough surface can be suppressed. Note that the refractive index is preferably a refractive index in visible light such as the wavelength of the laser beam 33.

The sign of the temperature coefficient of elastic constant of the insulating layers 11 and 17 is opposite to the sign of the temperature coefficient of elastic constant of the piezoelectric substrate. Thereby, the frequency temperature coefficient of the elastic wave resonator can be reduced.

The acoustic impedance of the insulating layers 11 and 17 is smaller than the acoustic impedance of the support substrate (ie, the sound speed of the insulating layers 11 and 17 is lower than the sound speed of the support substrate 10). Thereby, the bulk wave is hardly reflected at the interface 51 between the insulating layers 11 and 17, and is reflected at the interface between the insulating layer 17 and the support substrate 10. Therefore, bulk waves are scattered and spurious waves can be suppressed.

For example, if the support substrate 10 is made of sapphire, the acoustic impedance is 44.4×10 ⁶ kg/m ² ·s. When the insulating layer 11 is made of silicon oxide, the acoustic impedance is 15.7×10 ⁶ kg/m ² ·s. When the insulating layer 17 is made of silicon oxide added with iridium oxide or germanium oxide, the acoustic impedance can be about 15×10 ⁶ kg/m ² ·s.

The acoustic impedance of the supporting substrate 10 is preferably 1.5 times or more, more preferably 2 times or more, the acoustic impedance of the insulating layers 11 and 17. The difference in acoustic impedance between the insulating layer 17 and the support substrate 10 is preferably greater than the difference in acoustic impedance between the insulating layers 17 and 11. The difference in acoustic impedance between the insulating layer 17 and the support substrate 10 is preferably at least twice the difference in acoustic impedance between the insulating layers 17 and 11. Thereby, the bulk wave is more likely to be reflected at the rough interface 50 than at the flat interface 51, so that spurious waves can be suppressed.

The main components of the insulating layers 11 and 17 are the same, and the insulating layer 17 contains impurities that are not added to the insulating layer 11. Thereby, the acoustic impedance of the insulating layers 11 and 17 can be made almost the same, and the refractive index of the insulating layer 17 can be increased. For example, the main component of the insulating layers 11 and 17 is silicon oxide, and the concentration of germanium oxide or zirconium oxide in the insulating layer 17 is higher than the concentration of germanium oxide or zirconium oxide in the insulating layer 11. Thereby, the acoustic impedance of the insulating layers 11 and 17 can be made almost the same, and the refractive index of the insulating layer 17 can be increased.

In the acoustic wave device cut using the laser dicing method, a plurality of modified regions 34 containing the constituent elements of the support substrate 10 as a main component are provided on the side surface of the support substrate 10 in the planar direction. The modified region 34 is a melting trace that is melted by a laser beam and then becomes solid, and is amorphous and/or polycrystalline having a crystal structure different from that of the supporting substrate 10 . In addition, the piezoelectric substrate 12, the insulating layer 11, and the support substrate 10 are transparent to the laser beam 33.

In order to suppress spurious noise, the arithmetic mean roughness Ra of the interface 51 is preferably 10 nm or more, more preferably 100 nm or more. In order to suppress scattering of the laser beam 33, the arithmetic mean roughness of the interfaces 51 and 52 is preferably 1 nm or less, more preferably 0.5 nm or less.

When the IDT 22 excites SH (Shear Horizontal), bulk waves are likely to be generated. When the piezoelectric substrate 12 is a Y-cut lithium tantalate substrate rotated by 36 degrees or more and 48 degrees or less, SH waves are excited. Therefore, at this time, it is preferable to make the interface 50 a rough surface. When the thickness of the piezoelectric substrate 12 is equal to or less than the wavelength λ of the elastic wave, that is, when the thickness is equal to or less than twice the average pitch of the electrode fingers 15, loss is suppressed. Further, when the distance from the top surface of the support substrate 10 to the top surface of the piezoelectric substrate 12 is four times or less the average value of the pitch of the electrode fingers 15, loss is suppressed.

In order to prevent elastic waves from leaking to the support substrate 10, the acoustic impedance of the support substrate 10 is preferably higher than the acoustic impedance of the piezoelectric substrate 12 (that is, the sound speed of the support substrate 10 is faster than the sound speed of the piezoelectric substrate 12). Furthermore, since elastic waves propagate within the insulating layers 11 and 17, the acoustic impedance of the insulating layers 11 and 17 is lower than the acoustic impedance of the piezoelectric substrate 12 and the supporting substrate 10 (that is, the sound velocity of the insulating layers 11 and 17 is lower than that of the piezoelectric substrate 12 and the supporting substrate 10). (lower than the sound velocity of the support substrate 10) is preferable.

FIG. 7(a) is a circuit diagram of a filter according to the second embodiment. As shown in FIG. 7A, one or more series resonators S1 to S3 are connected in series between the input terminal Tin and the output terminal Tout. One or more parallel resonators P1 and P2 are connected in parallel between the input terminal Tin and the output terminal Tout. The elastic wave resonator of Example 1 can be used as at least one of the one or more series resonators S1 to S3 and the one or more parallel resonators P1 and P2. The number of resonators of the ladder filter can be set as appropriate. The filter may be a multimode filter.

[Modification 1 of Example 2]
FIG. 7(b) is a circuit diagram of a duplexer according to a first modification of the second embodiment. As shown in FIG. 7(b), a transmission filter 40 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 42 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 40 passes a signal in the transmission band among the high frequency signals inputted from the transmission terminal Tx to the common terminal Ant as a transmission signal, and suppresses signals of other frequencies. The reception filter 42 passes a signal in the reception band among the high-frequency signals inputted from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals at other frequencies. At least one of the transmission filter 40 and the reception filter 42 can be the filter of the second embodiment.

Although a duplexer has been described as an example of a multiplexer, a triplexer or a quadplexer may also be used.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention as described in the claims. Changes are possible.

10 Support substrate 11, 17 Insulating layer 12 Piezoelectric substrate 13 Bonding layer 15 Electrode finger 18 Comb-shaped electrode 20 Acoustic wave resonator 22 IDT
33 Laser light 50-52 Interface

Claims (13)

a supporting substrate that is a polycrystalline substrate or a single crystalline substrate;
a piezoelectric substrate provided on the support substrate;
a pair of comb-shaped electrodes provided on the piezoelectric substrate;
a first insulating layer provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate;
provided between the first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer; a second insulating layer having a higher refractive index than the first insulating layer and a lower refractive index than the supporting substrate ;
Equipped with
A plurality of modified regions which are amorphous or polycrystalline and whose main component is the constituent element of the support substrate are provided in a planar direction on the side surface of the support substrate,
The acoustic wave device wherein the difference between the refractive index of the second insulating layer and the refractive index of the first insulating layer is greater than or equal to the difference between the refractive index of the support substrate and the second insulating layer. a supporting substrate that is a polycrystalline substrate or a single crystalline substrate;
a piezoelectric substrate provided on the support substrate;
a pair of comb-shaped electrodes provided on the piezoelectric substrate;
a first insulating layer provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate;
provided between the first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer; a second insulating layer having a higher refractive index than the first insulating layer;
Equipped with
A plurality of modified regions which are amorphous or polycrystalline and whose main component is the constituent element of the support substrate are provided in a planar direction on the side surface of the support substrate,
The first insulating layer and the second insulating layer have the same main components, and the second insulating layer contains impurities that are not added to the first insulating layer. a supporting substrate that is a polycrystalline substrate or a single crystalline substrate;
a piezoelectric substrate provided on the support substrate;
a pair of comb-shaped electrodes provided on the piezoelectric substrate;
a first insulating layer provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate;
provided between the first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer; a second insulating layer having a higher refractive index than the first insulating layer;
Equipped with
A plurality of modified regions which are amorphous or polycrystalline and whose main component is the constituent element of the support substrate are provided in a planar direction on the side surface of the support substrate,
The main component of the first insulating layer and the second insulating layer is silicon oxide, and the concentration of germanium oxide or zirconium oxide in the second insulating layer has higher elasticity than the concentration of germanium oxide or zirconium oxide in the first insulating layer. wave device. The elastic wave according to any one of claims 1 to 3, wherein the signs of the temperature coefficients of elastic constants of the first insulating layer and the second insulating layer are opposite to the signs of the temperature coefficients of elastic constants of the piezoelectric substrate. device. The acoustic wave device according to claim 4, wherein the sound velocity of the first insulating layer and the second insulating layer is lower than the sound velocity of the support substrate. The acoustic wave device according to any one of claims 1 to 5, wherein the first surface has an arithmetic mean roughness of 10 nm or more, and the second surface has an arithmetic mean roughness of 1 nm or less. The acoustic wave device according to any one of claims 1 to 6, wherein the support substrate is a single crystal substrate. The acoustic wave device according to any one of claims 1 to 7, wherein the modified region is amorphous. A filter comprising the elastic wave device according to any one of claims 1 to 8. A multiplexer comprising a filter according to claim 9. a support substrate, a piezoelectric substrate provided on the support substrate, a first insulating layer provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate; provided between a first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer and the first insulating layer; a second insulating layer having a higher refractive index than the first insulating layer and a second insulating layer having a lower refractive index than the supporting substrate; irradiating a composite substrate with laser light from the piezoelectric substrate side to form a modified region in the supporting substrate; and,
cutting the composite substrate along the modified region;
including;
The method for manufacturing an acoustic wave device, wherein the difference between the refractive index of the second insulating layer and the refractive index of the first insulating layer is greater than or equal to the difference between the refractive index of the support substrate and the second insulating layer. a support substrate, a piezoelectric substrate provided on the support substrate, a first insulating layer provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate; provided between a first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer and the first insulating layer; a second insulating layer having a higher refractive index than the first insulating layer; irradiating a composite substrate with a laser beam from the piezoelectric substrate side to form a modified region in the supporting substrate;
cutting the composite substrate along the modified region;
including;
The first insulating layer and the second insulating layer have the same main components, and the second insulating layer contains impurities that are not added to the first insulating layer. a support substrate, a piezoelectric substrate provided on the support substrate, a first insulating layer provided between the support substrate and the piezoelectric substrate and having a refractive index lower than the refractive index of the support substrate; provided between a first insulating layer and the supporting substrate, the surface roughness of the first surface between the first insulating layer and the supporting substrate is greater than the surface roughness of the second surface between the first insulating layer and the first insulating layer; a second insulating layer having a higher refractive index than the first insulating layer; irradiating a composite substrate with laser light from the piezoelectric substrate side to form a modified region in the supporting substrate;
cutting the composite substrate along the modified region;
including;
The main component of the first insulating layer and the second insulating layer is silicon oxide, and the concentration of germanium oxide or zirconium oxide in the second insulating layer is higher than the concentration of germanium oxide or zirconium oxide in the first insulating layer. Method of manufacturing wave devices.

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