CN116208112A - Surface acoustic wave device - Google Patents
Surface acoustic wave device Download PDFInfo
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- CN116208112A CN116208112A CN202310077930.6A CN202310077930A CN116208112A CN 116208112 A CN116208112 A CN 116208112A CN 202310077930 A CN202310077930 A CN 202310077930A CN 116208112 A CN116208112 A CN 116208112A
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- electrode finger
- acoustic wave
- surface acoustic
- wave device
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
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- Acoustics & Sound (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
The present invention provides a surface acoustic wave device comprising: a pair of bus bars formed on the piezoelectric substrate; and a plurality of electrode fingers extending in a comb-tooth shape from each of the bus bars toward the bus bar facing each other, the electrode fingers including a first electrode finger film and a second electrode finger film, a base end portion of the first electrode finger film being connected to the bus bar, a base end portion of the second electrode finger film being laminated with the first electrode finger film to form a low sound velocity region; and the bus bar opposite to the front end part of the second electrode finger film is connected with a virtual finger film far away from the front end part of the second electrode finger film. In this surface acoustic wave device, a low acoustic velocity region is formed by laminating the first electrode finger film and the second electrode finger film, so that the loss of scattering of the surface acoustic wave is reduced, and a favorable characteristic in which the scattering is suppressed is obtained as compared with a SAW element having a conventional structure.
Description
Technical Field
The present invention relates to a surface acoustic wave device based on a multilayer film substrate.
Background
With the advancement of thin film technology, devices developed under a multilayer film are increasingly developed, and in the prior art, a surface acoustic wave device is regulated by using a piston method so as to change the speed to improve the generation of ripples, but in products under a multilayer film substrate such as a piezoelectric substrate, a functional layer thin film, a substrate and the like, the product of the multilayer film can have higher Q value compared with the prior art due to the thinning of the piezoelectric layer and the addition of the functional layer, so that better electromechanical performance is obtained, but different amplitudes are generated due to different sound speeds of different areas, and the problem of generating higher harmonics is more serious and complicated due to different received amplitudes of working areas (including C1, C2 and M areas).
Disclosure of Invention
The invention aims to solve the technical problems that: in order to solve the problem that the prior art lacks an improvement scheme for generating ripples of the surface acoustic wave device under the multilayer film substrate, the invention provides a surface acoustic wave device for solving the problem.
The technical scheme adopted for solving the technical problems is as follows: a surface acoustic wave device comprising:
a substrate;
a functional layer film formed on the substrate;
a piezoelectric substrate formed on the functional layer film;
a pair of interdigital transducer electrodes comprising:
a pair of bus bars formed on the piezoelectric substrate; a kind of electronic device with high-pressure air-conditioning system
A plurality of electrode fingers extending from each of the bus bars toward the bus bar in the opposite direction in a comb-tooth shape,
the electrode finger comprises a first electrode finger film and a second electrode finger film, wherein the base end part of the first electrode finger film is connected with the bus bar, and the base end part of the second electrode finger film is laminated with the first electrode finger film to form a low sound velocity region;
and the bus bar opposite to the front end part of the second electrode finger film is connected with a virtual finger film far away from the front end part of the second electrode finger film.
Preferably, the dummy finger membrane comprises a plurality of dummy finger membrane unit blocks which are arranged at intervals.
Preferably, the thickness of the dummy finger film is smaller than that of the second electrode finger film.
Preferably, the film thickness of the first electrode finger is 2% -4% lambda, and the film thickness of the second electrode finger is more than 5% -12% lambda.
Preferably, the material of the piezoelectric substrate is Y-X cut LiTaO 3 The cutting angle in the expression of Euler angles (phi, theta, phi) is phi=0 degree+/-10 degrees, theta=30-60 degrees, and the thickness of the piezoelectric substrate is 0.2lambda-0.5lambda.
Preferably, the functional layer film is made of SiO 2 The thickness is 0.2lambda-0.6lambda.
Preferably, the substrate is made of high-resistance silicon, the resistivity of the substrate is larger than 10000 Ω cm, the cutting angle in the expression of Euler angles (phi, theta, phi) is phi=0° ±10°, theta=90 ° -120 °, phi=90 ° -120 °, and the thickness of the substrate is larger than 100um.
Preferably, the high-resistance film is further included, and the high-resistance film is laminated between the substrate and the functional layer film.
Preferably, the material of the high-resistance film is polysilicon, and the thickness of the high-resistance film is 100 nm-1000 nm.
The invention has the beneficial effects that the surface acoustic wave device forms a low sound velocity region through the lamination of the first electrode finger film and the second electrode finger film, the virtual finger region and the GAP region form a high speed region, the speed of the working region is consistent through the adjustment of the high and low speed regions, and further, different amplitudes are not generated, so that the scattering loss of the surface acoustic wave is reduced, and compared with a SAW element with the existing structure, the surface acoustic wave device has the good characteristic of suppressing the stray.
Drawings
The invention will be further described with reference to the drawings and examples.
Fig. 1 is a schematic structural view of embodiment 1 of a surface acoustic wave device of the present invention.
Fig. 2 is a schematic view of a three-substrate laminated structure of embodiment 1 of the surface acoustic wave device of the present invention.
FIG. 3 is a cross-sectional view of P1-P1' of FIG. 1.
Fig. 4 is a schematic structural view of the region F in fig. 3.
Fig. 5 is a schematic diagram of sound velocity and amplitude of embodiment 1 of the surface acoustic wave device of the present invention.
Fig. 6 is a frequency-admittance (admittance) characteristic diagram of a SAW element of a comparative form of example 1 with a conventional structure.
Fig. 7 is a schematic structural view of embodiment 2 of the surface acoustic wave device of the present invention.
Fig. 8 is a schematic diagram of sound velocity and amplitude of embodiment 2 of the surface acoustic wave device of the present invention.
Fig. 9 is a frequency-admittance (admittance) characteristic diagram of the SAW element of example 2.
Fig. 10 is a schematic structural view of embodiment 3 of the surface acoustic wave device of the present invention.
Fig. 11 is a frequency-admittance (admittance) characteristic diagram of the SAW element of example 3.
Fig. 12 is a schematic structural view of embodiment 4 of the surface acoustic wave device of the present invention.
Fig. 13 is a sectional view of P5-P5' in fig. 12.
Fig. 14 is a schematic view of sound velocity and amplitude of embodiment 4 of the surface acoustic wave device of the present invention.
Fig. 15 is a frequency-admittance (admittance) characteristic diagram of a SAW element of comparative form of example 4 with a conventional structure.
Fig. 16 is a schematic structural view of embodiment 5 of the surface acoustic wave device of the present invention.
Fig. 17 is a schematic diagram of sound velocity and amplitude of embodiment 5 of the surface acoustic wave device of the present invention.
Fig. 18 is a frequency-admittance (admittance) characteristic diagram of the SAW element of example 4.
Fig. 19 is a schematic view of a four-substrate laminated structure of another embodiment of the surface acoustic wave device of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "connected," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art. Furthermore, in the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
As shown in fig. 1 to 3, the present invention provides an embodiment 1 of a surface acoustic wave device, including:
the substrate 14 is made of high-resistance silicon, the resistivity of the substrate is larger than 10000 Ω & cm, the chamfer angle in the expression of Euler angles (phi, theta, phi) is phi=0° ±10°, theta=90 ° -120 °, phi=90 ° -120 °, and the thickness of the substrate is larger than 100um.
A functional layer film 12 formed on the substrate, the functional layer film being made of SiO 2 The thickness is 0.2lambda-0.6lambda。
A piezoelectric substrate 11 formed on the functional layer film, the piezoelectric substrate being made of Y-X cut LiTaO 3 The cutting angle of the Euler angles (phi, theta, phi) in the expression is phi=0 degrees+/-10 degrees, theta=30-60 degrees, and the thickness of the piezoelectric substrate is 0.2lambda-0.5lambda.
A pair of interdigital transducer electrodes comprising:
two bus bars 2a, 2b formed on the piezoelectric substrate and connected to the two signal ports, respectively; a kind of electronic device with high-pressure air-conditioning system
The plurality of electrode fingers protrude from the bus bars 2a and 2b in a comb-tooth shape toward the bus bars facing each other.
Two regions where the respective bus bars 2a, 2b are formed will be also referred to as bus bar regions A1 and A2.
The region where the electrode fingers are arranged to intersect corresponds to the intersection region of IDT electrodes composed of C1, C2 and M, and the GAP region 34 is formed in which the tip end portion of the electrode finger connected to one of the bus bars 2a and 2B does not reach the other bus bar 2B and 2a on the bus bar 2a and 2B side, and the two regions B1 and B2 where the electrode fingers do not intersect are formed.
The electrode finger includes a first electrode finger film 31 and a second electrode finger film 32, the base end portion of the first electrode finger film 31 is connected to the bus bar, the base end portion of the second electrode finger film 32 is laminated with the first electrode finger film 31, and the thickness of the laminated portion of the first electrode finger film 31 and the second electrode finger film 32 on the electrode finger is greater than the thickness of the portion of the second electrode finger film 32 in the region M, forming a low sound velocity region, so that the propagation velocity of SAW in the portion of the electrode finger having a greater thickness is lower than that of SAW in the portion of M. The working area (containing C1 and C2 and M areas) is the rate target area for adjustment. As shown in fig. 4, in this example, in the lamination area F, the entire first electrode finger film 31 may be laminated over the base end portion of the second electrode finger film 32, or the base end portion of the second electrode finger film 32 may be laminated over the entire first electrode finger film 31. The film thickness of the first electrode is 2-4% lambda, and the film thickness of the second electrode is more than 5-12%.
The bus bar opposite to the front end portion of the second electrode finger film 32 is connected with a dummy finger film 33 distant from the front end portion of the second electrode finger film. The thickness of the dummy finger film 33 is smaller than that of the second electrode finger film 32, thereby forming a high sound velocity region B1.
In example 1, the film thickness in the different regions was adjusted to adjust the rate, and the film became thicker, the rate became lower, the film became thinner, and the rate became higher. FIG. 5 is a graph showing the rate of the P1-P1 'interface and the P1-P2' interface of example 1.
In the P1-P1' interface: the region B1 is constituted only by the dummy finger film 33 and the blank GAP region 34, forming a high sound velocity region. The rate of the region B1 can be adjusted by adjusting the area of the GAP region 34 or the area of the dummy finger film 33. For example, the area of the dummy finger film 33 becomes larger, the rate decreases, the area of the dummy finger film becomes smaller, the rate increases, the area of the GAP region 34 becomes larger, the rate becomes higher, the area of the GAP becomes smaller, and the rate becomes smaller. The region C1 and the region M are constituted by only the second electric finger film 32, forming a mid-sound velocity region. The region C2 and the region B2 are laminated regions of the first electric finger film 31 and the second electric finger film 32, forming a low sound velocity region. The rate of the low sound velocity region can be adjusted by adjusting the area of the laminated region. The area of the laminated area becomes smaller, the speed becomes higher, the area of the overlapped area becomes larger, and the speed becomes smaller.
In the P2-P2' interface: the region B2 is constituted only by the dummy finger film 33 and the blank GAP region 34, forming a high sound velocity region. The rate of the region B2 can be adjusted by adjusting the area of the GAP region 34 or the area of the dummy finger film 33. For example, the area of the dummy finger film 33 becomes larger, the rate decreases, the area of the dummy finger film becomes smaller, the rate increases, the area of the GAP region 34 becomes larger, the rate becomes higher, the area of the GAP becomes smaller, and the rate becomes smaller. The region C2 and the region M are constituted by only the second electric finger film 32, forming a mid-sound velocity region. The region C1 and the region B1 are laminated regions of the first electric finger film 31 and the second electric finger film 32, forming a low sound velocity region. The rate of the low sound velocity region can be adjusted by adjusting the area of the laminated region. The area of the laminated area becomes smaller, the speed becomes higher, the area of the overlapped area becomes larger, and the speed becomes smaller.
The two areas P1-P1 'and P2-P2' of the surface acoustic wave device integrally form a pair of interdigital, and the pair of interdigital is a period lambda. Fig. 5 also shows the amplitude profile of example 1. It can be seen that in one period, the speed of the working area is adjusted to be consistent, and different amplitudes can not be generated in the case of no different speeds, and finally the same amplitude of the working area is achieved, so that the generation of higher harmonic waves is restrained.
In example 1, the size of the region B1 at the P1-P1' interface is 0.2um to 1.5λ, wherein the Gap region 34 is 0.2um to 1.5λ. The use of the above-sized regions B1 and Gap regions 34 prevents an increase in cost and a decrease in overall electrical performance of the product due to an excessively large B1 region or Gap region.
In this example, the rate can be adjusted by adjusting the thicknesses of the first and second finger films 31 and 32, and the finger film becomes thicker, the rate becomes lower, and the finger film becomes thinner, the rate becomes higher.
Fig. 6 shows a frequency-admittance (admittance) characteristic diagram of a SAW element of a comparative form of example 1 and the conventional structure. As can be seen from the figure, the SAW element of example 1 shows an admittance characteristic substantially equivalent to that of a SAW element of a comparative form of a conventional structure, and has a favorable characteristic in which the spurious emissions are suppressed.
As shown in fig. 7 to 9, embodiment 2 is a surface acoustic wave device of this kind, and unlike embodiment 1, it is: in the region C1 at the interface P3-P3 'and the region C2 at the interface P4-P4', a conditioning film made of the same material as the first electrode finger film 31 is laminated on the tip portion of the second electrode finger film 32. When the high sound velocity region of example 1 fails to meet the velocity adjustment, the scheme of example 2 can be used to further perform the velocity adjustment by adjusting the membrane in the region C1 and the region C2.
As shown in fig. 10 to 11, three schemes of embodiment 3 of this surface acoustic wave device are distinguished in that dummy finger films 33, GAP of different areas and a first electrode finger film in the laminated region are employed. They are different from embodiment 1 in the region C2 and the region B2 in the interface Q-Q', a part of the first electrode finger film 31 being laminated on the base end portion of the second electrode finger film 31, or a base end portion of the second electrode finger film 31 being laminated on a part of the first electrode finger film 31.
In example 3, considering the processing process, the overlap region is completely overlapped on the bus bar region, and the processing conditions are severe, so that example 3 has a higher fault tolerance.
As shown in fig. 12 to 15, which is embodiment 4 of this surface acoustic wave device, the dummy finger film 33 includes a plurality of dummy finger film unit blocks arranged at intervals, and GAP regions 34 are also formed between two dummy finger film unit blocks arranged adjacently. The grid-shaped virtual finger film unit blocks can reflect energy, so that the transverse energy loss is further suppressed. Fig. 15 shows a frequency-admittance (admittance) characteristic diagram of the SAW element of example 4, and it can be seen that the obtained spurious emissions are more suppressed. Embodiment 4 is a modification of embodiment 1, and also when embodiment 1 fails to meet the adjustment rate in the preferable GAP length and B1 length ranges, the rate can be further adjusted by the dummy finger film unit blocks arranged at intervals, as shown in fig. 14, the high sound speed region has a different height from embodiment 1, and at the same time, after the break point, a small reflective grating structure can be formed, and a part of the energy lost from both sides can be reflected back, so that the electrical performance of the product is increased.
As shown in fig. 16 to 18, example 5 is a surface acoustic wave device of this kind, and unlike example 4, it is: in the region C1 at the interface between P7 and P7 'and the region C2 at the interface between P8 and P8', a conditioning film made of the same material as the first electrode finger film 31 is laminated on the tip portion of the second electrode finger film 32. When the high sound velocity region of example 1 fails to meet the velocity adjustment, the scheme of example 5 can be used to further perform the velocity adjustment by adjusting the membrane in the region C1 and the region C2.
According to other embodiments, as shown in fig. 19, the surface acoustic wave device further includes a high-resistance film 13, the high-resistance film 13 being laminated between the substrate and the functional layer film. The high-resistance film is made of polysilicon, and the thickness of the high-resistance film is 100 nm-1000 nm.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
With the above-described preferred embodiments according to the present invention as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.
Claims (9)
1. A surface acoustic wave device, comprising:
a substrate;
a functional layer film formed on the substrate;
a piezoelectric substrate formed on the functional layer film;
a pair of interdigital transducer electrodes comprising:
a pair of bus bars formed on the piezoelectric substrate; a kind of electronic device with high-pressure air-conditioning system
A plurality of electrode fingers extending from each of the bus bars toward the bus bar in the opposite direction in a comb-tooth shape,
the electrode finger comprises a first electrode finger film and a second electrode finger film, wherein the base end part of the first electrode finger film is connected with the bus bar, and the base end part of the second electrode finger film is laminated with the first electrode finger film to form a low sound velocity region;
and the bus bar opposite to the front end part of the second electrode finger film is connected with a virtual finger film far away from the front end part of the second electrode finger film.
2. The surface acoustic wave device according to claim 1, wherein: the virtual finger film comprises a plurality of virtual finger film unit blocks which are arranged at intervals.
3. The surface acoustic wave device according to claim 2, wherein: the thickness of the virtual finger film is smaller than that of the second electrode finger film.
4. A surface acoustic wave device according to any one of claims 1 to 3, wherein: the film thickness of the first electrode finger is 2-4% lambda, and the film thickness of the second electrode finger is more than 5-12%.
5. The surface acoustic wave device according to claim 4, wherein: the piezoelectric substrate is made of Y-X cut LiTaO 3 The cutting angle in the expression of Euler angles (phi, theta, phi) is phi=0 degree+/-10 degrees, theta=30-60 degrees, and the thickness of the piezoelectric substrate is 0.2lambda-0.5lambda.
6. The surface acoustic wave device according to claim 5, wherein: the functional layer film is made of SiO 2 The thickness is 0.2lambda-0.6lambda.
7. The surface acoustic wave device according to claim 6, wherein: the substrate is made of high-resistance silicon, the resistivity of the substrate is larger than 10000 Ω & cm, the chamfer angle in the expression of Euler angles (phi, theta, phi) is phi=0 degree+/-10 degrees, theta=90-120 degrees, phi=90-120 degrees, and the thickness of the substrate is larger than 100um.
8. The surface acoustic wave device according to claim 7, wherein: the high-resistance film is laminated between the substrate and the functional layer film.
9. The surface acoustic wave device according to claim 8, wherein: the high-resistance film is made of polysilicon, and the thickness of the high-resistance film is 100 nm-1000 nm.
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| CN202310077930.6A CN116208112A (en) | 2023-02-08 | 2023-02-08 | Surface acoustic wave device |
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| CN113872562A (en) * | 2020-06-30 | 2021-12-31 | Ndk声表滤波器股份有限公司 | Surface acoustic wave device |
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| CN113872562A (en) * | 2020-06-30 | 2021-12-31 | Ndk声表滤波器股份有限公司 | Surface acoustic wave device |
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