CN213484830U - High-power-capacity bulk acoustic wave resonator with embedded reflection layer - Google Patents
High-power-capacity bulk acoustic wave resonator with embedded reflection layer Download PDFInfo
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- CN213484830U CN213484830U CN202022742111.3U CN202022742111U CN213484830U CN 213484830 U CN213484830 U CN 213484830U CN 202022742111 U CN202022742111 U CN 202022742111U CN 213484830 U CN213484830 U CN 213484830U
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Abstract
The utility model provides a high power capacity bulk acoustic wave syntonizer of embedded reflection stratum, include: interdigital electrode systems, thin films; the interdigital electrode system comprises: a positive electrode, a negative electrode; the film is a lithium niobate film; when the interdigital electrode system on the surface of the lithium niobate thin film is loaded with a positive electrode and a negative electrode respectively, a horizontal electric field generated between the adjacent electrodes in an interaction way excites shear wave resonance in the lithium niobate thin film; the shear wave resonates as a primary resonant mode of the resonator, and the resonant wavelength is about twice the thickness of the lithium niobate thin film. The utility model discloses an adopt the interdigital electrode to arouse shear wave resonance on the lithium niobate film for the resonant frequency of this syntonizer mainly is related to with film thickness, thereby can realize the high frequency resonance very easily, has solved the problem that general acoustic resonator hardly produces the high frequency resonance.
Description
Technical Field
The utility model relates to a syntonizer technical field specifically, relates to a high power capacity bulk acoustic wave syntonizer of embedded reflection stratum.
Background
With the rapid development of 5G communication systems, it is difficult for the existing rf front-end resonator to meet the requirement of high-frequency band communication.
Patent document CN110138356A discloses a high-wave-speed supporting substrate to increase the resonance frequency of a surface acoustic wave resonator. The defects of the prior art are as follows: the resonance frequency of the conventional acoustic wave resonator is mainly related to the width and the electrode spacing of the interdigital electrode, and the resonance frequency of the resonator is difficult to improve due to the limitation of processing difficulty and cost; the general piezoelectric material has a very low electromechanical coupling coefficient, so that the performance of the filter based on the resonator is limited, and the lithium niobate thin film adopted by the invention has a very high electromechanical coupling coefficient, so that the lithium niobate thin film can be well used for designing a high-frequency broadband and low-loss filter; many syntonizers based on piezoelectric film because the film suspension produces mechanical strength difference easily, power capacity is low, the radiating effect is poor scheduling problem, and this patent utilizes Bragg reflection stratum fine improvement these not enough under the prerequisite that does not influence the normal work of syntonizer to make the syntonizer that this patent provided have better stability and wider application scope.
SUMMERY OF THE UTILITY MODEL
To the defects in the prior art, the present invention is directed to a high power capacity bulk acoustic wave resonator with an embedded reflective layer.
According to the utility model provides a pair of embedded reflection stratum's high power capacity bulk acoustic wave syntonizer, include: interdigital electrode systems, thin films; the interdigital electrode system comprises: a positive electrode, a negative electrode; the film is a lithium niobate film; when the interdigital electrode system on the surface of the lithium niobate thin film is loaded with a positive electrode and a negative electrode respectively, a horizontal electric field generated between the adjacent electrodes in an interaction way excites shear wave resonance in the lithium niobate thin film; the shear wave resonates as a primary resonant mode of the resonator, and the resonant wavelength is about twice the thickness of the lithium niobate thin film.
Preferably, the positive electrode and the negative electrode adopt top interdigital electrodes; the top interdigital electrode is made of any one of the following materials: -platinum (Pt); aluminum (Al); -molybdenum (Mo); -gold (Au); -silver (Ag); ruthenium (Ru). The top interdigital electrode is mainly used for generating a horizontal electric field. Further comprising: a Bragg reflection layer; the Bragg reflection layer is arranged below the lithium niobate film; the Bragg reflection layer includes: a silicon dioxide layer, a silicon nitride layer; the silicon dioxide layers and the silicon nitride layers which are alternately arranged and have the thickness of a quarter of the resonance wavelength form a Bragg reflection layer.
Compared with the prior art, the utility model discloses following beneficial effect has:
1. the utility model discloses an adopt the lithium niobate film, solved the problem that conventional piezoelectricity material electromechanical coupling coefficient is low, thereby make the utility model provides a syntonizer can be used for designing high frequency broadband, low-loss filter.
2. The utility model discloses an adopt interdigital electrode to arouse shear wave resonance on the lithium niobate film for the resonant frequency of this syntonizer is mainly relevant with film thickness, thereby can realize the high frequency resonance very easily, has solved the problem that general acoustic wave syntonizer hardly produces high frequency resonance.
3. The utility model discloses an adopt the thickness of suitable electrode size, interdigital electrode spacing, lithium niobate film etc. can reduce the interference of transverse vibration mode and higher mode effectively for this syntonizer has more excellent shear wave resonance, makes things convenient for the design of wave filter.
4. The utility model discloses an adopt Bragg reflection stratum, solved the problem that lithium niobate film temperature stability is poor, power capacity is low and mechanical strength nature is low. The Bragg reflection layer can effectively make up for the defects of a single lithium niobate thin-film layer resonator while ensuring the sufficient sound wave reflection coefficient.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic diagram of a high-frequency bulk acoustic wave resonator based on a lithium niobate thin film according to the present invention.
Fig. 2 is a schematic diagram illustrating the principle that a horizontal electric field generated between adjacent electrodes in an embodiment of the present invention will excite a shear wave resonance in a lithium niobate thin film.
Fig. 3a is a schematic view of the general flow of the resonator according to the embodiment of the present invention, which is first processed by using photolithography.
Fig. 3b is a schematic diagram of the general flow of the resonator according to the second embodiment of the present invention, which is processed by using the photolithography technique.
Fig. 4 is a schematic diagram of a shear wave resonator after loading a bragg reflector in an embodiment of the present invention.
In the figure:
1-Positive interdigital electrode System 6-silicon substrate
2-negative interdigital electrode system 7-silicon dioxide
3-lithium niobate thin film 8-electron beam photoresist
4-shear wave resonance 9-ultraviolet photoresist
5-He ion 10-SiN
Detailed Description
The present invention will be described in detail with reference to the following embodiments. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that various changes and modifications can be made by one skilled in the art without departing from the spirit of the invention. These all belong to the protection scope of the present invention.
Fig. 1 shows a high-frequency bulk acoustic wave resonator based on a lithium niobate thin film, which mainly comprises a positive interdigital electrode system 1, a negative interdigital electrode system 2 and a lithium niobate thin film 3. The top interdigital electrode can be platinum (Pt), aluminum (Al), molybdenum (Mo), gold (Au), silver (Ag), ruthenium (Ru), and the like, and is mainly used for generating a horizontal electric field. The lithium niobate thin film tangential to ZY is easy to introduce thickness direction vibration in the ZY direction through lateral field excitation, and the vibration can generate displacement in the Y direction. Thus, when the interdigitated electrode system on the surface of the lithium niobate thin film is loaded with the positive electrode 1 and the negative electrode 2, respectively, as shown in fig. 2, the horizontal electric field generated between the alternating adjacent electrodes will excite a shear wave resonance 4 in the lithium niobate thin film. The shear wave resonates as a primary resonant mode of the resonator, and the resonant wavelength is about twice the thickness of the lithium niobate thin film. This means that the thickness of the lithium niobate thin film will dominate the resonant frequency of the resonator, such as when the lithium niobate thin film is 0.4um thick, the resonator will produce shear wave resonance around 5 GHz. Consequently, compare the ordinary bulk acoustic wave syntonizer that mainly is decided by interdigital electrode width and interdigital electrode spacing in resonant frequency, the utility model provides a shear wave syntonizer will break resonant frequency's bottleneck, the operating frequency of the improvement bulk acoustic wave syntonizer that is showing to the requirement of current 5G communication system to high frequency communication is adapted. In addition, the resonator can derive higher-order resonant modes at higher frequencies, and can be used for designing higher-frequency filters. It is worth mentioning that the resonator of the present invention may have some unnecessary stray modes except the main shear resonant mode, and these stray modes can be avoided by reasonably adjusting the width, thickness and electrode spacing of the interdigital electrodes.
Fig. 3 shows the general flow of processing the resonator proposed by the present invention using photolithographic techniques. As shown in fig. 3a, on the one hand, a defect damaged layer is generated by injecting helium ions (He +)5 into the lithium niobate substrate 3 at a specific depth, and then the damaged layer is used to peel off the lithium niobate thin film. On the other hand, the silicon substrate 6 is surface-oxidized to obtain the silicon dioxide layer 7 and subjected to chemical mechanical polishing. And finally, bonding the treated lithium niobate thin film layer 3 and the silicon dioxide layer 7 to obtain the initial substrate of the resonator. After the initial substrate is obtained, the resonator preparation process is shown in fig. 3 b:
plating an aluminum layer on the surface of the substrate as a protective layer;
etching the silicon layer 6 and the silicon dioxide layer 7 of the region to be determined from the back of the substrate by dry etching, etching the metal protective layer on the upper surface, and only reserving the lithium niobate thin film layer;
plating an electron beam photoresist 8 on the upper surface of the lithium niobate thin film and etching to obtain a specific shape;
etching the required interdigital parts of the positive interdigital electrode system 1 and the negative interdigital electrode system 2 by using electron beams;
coating and etching the ultraviolet photoresist 9;
and etching the thicker interconnection contacts at the two ends of the interdigital electrode.
Since the shear wave resonator described above has its body portion only on the suspended lithium silicate film, this results in a low mechanical strength of the proposed resonator and a relatively small power capacity. In addition, the temperature coefficient of the resonance frequency of the lithium niobate thin film itself is negative, i.e., the resonance frequency thereof decreases with increasing temperature, which also results in the proposed resonator becoming less temperature stable. Therefore, the utility model discloses further provide and place the Bragg reflection stratum below lithium niobate film and remedy above-mentioned not enough. Fig. 4 shows a shear wave resonator according to the present invention after loading the bragg reflector. The bragg reflection layer under the lithium niobate thin film is composed of silicon dioxide (SiO2) layers 7 and silicon nitride (Si3N4) layers 10 of quarter-resonant wavelength thickness alternately arranged, and the total number of layers is N. The thickness of each layer can be adjusted according to actual conditions. Since the silicon dioxide 7 has a positive temperature coefficient of resonance frequency, the temperature coefficient of the lithium niobate thin film layer can be compensated to a certain extent after the silicon dioxide is bonded with the lithium niobate layer, and the temperature stability of the resonator is further improved. In addition, the silicon nitride layer 10 disposed alternately with the silicon dioxide 7 has a higher acoustic wave impedance than the silicon dioxide 7, which enables the entire bragg reflection layer to have a good acoustic wave reflection effect, so that the shear wave resonance of the resonator itself is not affected, and a sufficiently good reflection effect can be obtained when the total number n of layers is generally equal to or greater than 5. The silicon nitride layer 9 having high wave resistance may be replaced with aluminum nitride (AlN) or tungsten (W). In addition, the Bragg reflection layer is arranged under the lithium niobate thin film, so that the heat dissipation of the resonator can be well facilitated, the power capacity can be improved, and the mechanical strength of the resonator can be improved. Therefore, the utility model provides a bragg reflector layer can be fine when not destroying syntonizer resonance characteristic compensate the not enough of suspension lithium niobate film syntonizer.
The shear wave resonator with the Bragg reflection layer can be realized by combining a sputtering process and a photoetching process. A specific number of bragg reflector layers are grown on the silicon substrate by sputtering, and then the etching of the positive interdigital electrode system 1 and the negative interdigital electrode system 2 is realized by the photolithography process shown in fig. 3 b.
In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.
The foregoing description of the specific embodiments of the invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (6)
1. A high power capacity bulk acoustic wave resonator with an embedded reflective layer, comprising: interdigital electrode systems, thin films;
the interdigital electrode system comprises: a positive electrode, a negative electrode;
the film is a lithium niobate film;
when the interdigital electrode system on the surface of the lithium niobate thin film is loaded with a positive electrode and a negative electrode respectively, a horizontal electric field generated between the adjacent electrodes in an interaction way can excite shear wave resonance in the lithium niobate thin film.
2. The reflection layer embedded high power capacity bulk acoustic resonator according to claim 1, wherein top interdigital electrodes are adopted for the positive electrode and the negative electrode.
3. The reflection layer embedded high power bulk acoustic resonator according to claim 2, wherein the top interdigital electrode is made of any one of the following materials:
-platinum;
-aluminium;
-molybdenum;
-gold;
-silver;
-ruthenium.
4. The reflective layer embedded high power capacity bulk acoustic wave resonator of claim 1, further comprising: a Bragg reflection layer;
the Bragg reflection layer is placed under the lithium niobate film.
5. The embedded reflector high power capacity bulk acoustic resonator of claim 4, wherein the Bragg reflector comprises: silicon dioxide layer, silicon nitride layer.
6. The embedded reflector high power bulk acoustic resonator according to claim 5, wherein the alternating layers of silicon dioxide and silicon nitride of quarter-wave resonant wavelength thickness form Bragg reflectors.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113437947A (en) * | 2021-07-06 | 2021-09-24 | 电子科技大学 | Film bulk acoustic resonator for inhibiting side energy radiation based on phononic crystal |
| CN113810014A (en) * | 2021-09-23 | 2021-12-17 | 武汉敏声新技术有限公司 | Interdigital bulk acoustic wave resonator and filter |
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2020
- 2020-11-24 CN CN202022742111.3U patent/CN213484830U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113437947A (en) * | 2021-07-06 | 2021-09-24 | 电子科技大学 | Film bulk acoustic resonator for inhibiting side energy radiation based on phononic crystal |
| CN113810014A (en) * | 2021-09-23 | 2021-12-17 | 武汉敏声新技术有限公司 | Interdigital bulk acoustic wave resonator and filter |
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