CN112653414B - Lamb wave resonator, and filter and electronic device provided with lamb wave resonator - Google Patents
Lamb wave resonator, and filter and electronic device provided with lamb wave resonator Download PDFInfo
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- 235000019687 Lamb Nutrition 0.000 title claims abstract description 90
- 230000003071 parasitic effect Effects 0.000 claims abstract description 34
- 239000000758 substrate Substances 0.000 claims abstract description 26
- 239000012212 insulator Substances 0.000 claims abstract description 4
- 238000002513 implantation Methods 0.000 claims description 36
- 239000000463 material Substances 0.000 claims description 9
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 229910013641 LiNbO 3 Inorganic materials 0.000 claims description 3
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 3
- 230000008878 coupling Effects 0.000 description 23
- 238000010168 coupling process Methods 0.000 description 23
- 238000005859 coupling reaction Methods 0.000 description 23
- 238000010586 diagram Methods 0.000 description 13
- 230000000694 effects Effects 0.000 description 9
- 238000004088 simulation Methods 0.000 description 6
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 230000001629 suppression Effects 0.000 description 4
- 238000004891 communication Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 244000060701 Kaempferia pandurata Species 0.000 description 1
- 235000016390 Uvaria chamae Nutrition 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000000306 component Substances 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 238000010897 surface acoustic wave method Methods 0.000 description 1
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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
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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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Abstract
The lamb wave resonator of the present invention includes: a substrate as an insulator; a piezoelectric layer disposed on the substrate; a plurality of upper electrodes provided on an upper surface side of the piezoelectric layer; and a plurality of lower electrodes provided on the lower surface side of the piezoelectric layer, wherein each of the upper electrodes is at least partially embedded in the piezoelectric layer, and wherein each of the lower electrodes is not embedded in the piezoelectric layer, and wherein a ratio of a thickness of a portion of the upper electrode in which the piezoelectric layer is embedded to a thickness of the entire upper electrode, that is, an embedding ratio, is set to be an embedding ratio capable of suppressing parasitic modes of lamb waves, based on a thickness of the entire upper electrode.
Description
Technical Field
The present invention relates to a lamb wave resonator, and a filter and an electronic device including the same, which can suppress parasitic modes of lamb waves in the lamb wave resonator and thereby improve an electromechanical coupling coefficient.
Background
With the rapid development of wireless communication technology today, the application of miniaturized portable terminal devices is also becoming increasingly widespread, and thus the demands for high-performance, small-sized radio frequency front end modules and devices are also becoming increasingly urgent. The filter is used as a core component of the radio frequency front end, and the performance of the filter is related to the performance of the whole communication system. The performance of the filter is in turn dependent on the performance of its resonator, and therefore the performance of the resonator is of paramount importance.
Currently widely used resonators are mainly surface acoustic wave resonators (SAW), bulk acoustic wave resonators (BAW), film bulk acoustic wave resonators (FBAR), lamb wave resonators, ultra-high frequency resonators (XBAR), and the like. The most critical properties of the resonator itself are the electromechanical coupling coefficient and the quality factor (Q value). The electromechanical coupling coefficient of the resonator determines the bandwidth of the filter, whose quality factor directly affects its in-band interpolation and the steepness of the filter skirt. Meanwhile, for the multi-band requirement of the 5G radio frequency front end, the adjustable filter is adopted to realize the switching of the multi-band, and the precondition for manufacturing the adjustable filter is to realize a resonator with high frequency, large electromechanical coupling coefficient and high q value.
Among these resonators, the lamb wave resonator is a research hot spot in recent years, has the advantages of both the FBAR and SAW resonators, has the characteristics of higher quality factor, moderate coupling coefficient, low frequency dispersion, high sound speed, low power consumption, small volume and the like, and can realize the design of the multi-frequency resonator on the same wafer, so that the lamb wave resonator is widely applied to multi-frequency band filters, diplexers, antenna transceiving switches, multiplexing filters and the like.
In the structure of the conventional lamb wave resonator, when an excitation voltage is applied to the interdigital electrode, a lamb wave parallel to the width direction of the interdigital electrode is generated in the piezoelectric layer, and when the lamb wave reaches the free boundaries on both sides of the resonator, a standing wave is formed by reflection, so that the strongest electric response mode is called a main mode. However, when the acoustic wave propagates at a non-perpendicular angle, a transverse mode parallel to the length direction of the interdigital electrode is generated, and when the acoustic wave reaches the boundary and is reflected back, a spurious resonance peak burr, i.e. a spurious mode, caused by the transverse mode is generated near the resonance peak of the main mode, which greatly reduces the efficiency of the electronic product for signal transmission and hinders the improvement of the electromechanical coupling coefficient, thereby reducing the quality and efficiency of the resonator.
Although lamb wave resonators have improved operating bandwidth and increased electromechanical coupling coefficient (e.g., from 8% to 17.7%) compared to conventional SAW, BAW, etc., with the development of current 5G handsets, the requirement for resonators for greater bandwidth, i.e., higher electromechanical coupling coefficient, has posed a serious challenge to existing lamb wave resonators.
At present, the research direction of lamb wave resonators is mostly focused on improving the electromechanical coupling coefficient and Q value of the lamb wave resonators, but no good method is available for suppressing and eliminating the parasitic mode of the lamb wave. Patent document 1 discloses a lamb wave resonator in which parasitic modes in the lamb wave resonator are eliminated by providing a plurality of convex structures on the side walls of a piezoelectric layer or on the surfaces of interdigital electrodes, thereby avoiding the occurrence of ripples and burrs in a filter and further improving the quality of the filter. However, this structure is too complex, and for the resonator required in the micrometer scale, the process difficulty is high, and the implementation cost is also high.
Prior art literature
Patent literature
Patent document 1: CN 105337586A
Disclosure of Invention
Technical problem to be solved by the invention
The invention aims to further inhibit or eliminate parasitic modes in a lamb wave resonator, eliminate the stray effect and further improve the electromechanical coupling coefficient of the resonator, and by utilizing a high sound speed structure of POI (piezoelectric insulator) and combining the structural characteristics of an electrode embedded into a piezoelectric layer, the invention realizes that the parasitic modes, namely the stray effect, are inhibited or even eliminated by adjusting the thickness of the electrode and the proportion of the electrode embedded into the piezoelectric layer, and improves the electromechanical coupling coefficient and bandwidth of the lamb wave resonator, and a filter and an electronic device with the lamb wave resonator.
Technical means for solving the technical problems
The present invention provides a lamb wave resonator comprising: a substrate as an insulator; a piezoelectric layer disposed on the substrate; a plurality of upper electrodes provided on an upper surface side of the piezoelectric layer; and a plurality of lower electrodes provided on the lower surface side of the piezoelectric layer, wherein each of the upper electrodes is at least partially embedded in the piezoelectric layer, and wherein each of the lower electrodes is not embedded in the piezoelectric layer, and wherein a ratio of a thickness of a portion of the upper electrode in which the piezoelectric layer is embedded to a thickness of the entire upper electrode, that is, an embedding ratio, is set to be an embedding ratio capable of suppressing parasitic modes of lamb waves, based on a thickness of the entire upper electrode.
In the lamb wave resonator, the embedding ratio is 40% or 80% when the thickness of the whole upper electrode is greater than 100nm and less than 200 nm.
In the lamb wave resonator, the buried ratio is 40% when the thickness of the entire upper electrode is greater than 200nm and less than 400 nm.
In the lamb wave resonator, the embedding ratio is 20% or more and 80% or less, or 80% or more and 100% or less when the thickness of the entire upper electrode is 200 nm.
In the lamb wave resonator, the embedding ratio is 20% when the thickness of the entire upper electrode is 400 nm.
In the lamb wave resonator, the embedding ratio is 100% when the thickness of the entire upper electrode is 500 nm.
In the lamb wave resonator, the substrate is made of any one of 4H-SiC and 6H-SiC high acoustic velocity materials.
In the lamb wave resonator, the piezoelectric layer is 30 YX-LiNbO 3 。
In the lamb wave resonator, the upper electrode and the lower electrode have the same width and thickness, respectively.
In the lamb wave resonator, the upper electrode and the lower electrode are made of any one metal selected from Ti, al, cu, au, pt, ag, pd, ni, an alloy thereof, or a laminate thereof.
In the lamb wave resonator, an intermediate layer made of a low acoustic velocity material having a lower acoustic velocity than that of the substrate is provided between the substrate and the piezoelectric layer, and the lower electrode is buried in the intermediate layer.
In the lamb wave resonator, the intermediate layer uses SiO 2 。
The filter of the present invention includes any of the lamb wave resonators described above.
The electronic device of the invention comprises the filter or any one of the lamb wave resonators described above.
Technical effects
According to the lamb wave resonator of the present invention, the plurality of lower electrodes provided on the lower surface side of the piezoelectric layer are completely embedded in the substrate, the plurality of upper electrodes provided on the upper surface side of the piezoelectric layer are at least partially embedded in the piezoelectric layer, and the embedding ratio of the thickness of the portion of the upper electrode in which the piezoelectric layer is embedded to the thickness of the entire upper electrode is set to be an embedding ratio capable of suppressing parasitic modes according to the thickness of the entire upper electrode. Thus, a lamb wave resonator having suppressed spurious effects, a high electromechanical coupling coefficient, a high Q value, a high frequency, a high sound velocity, and a large bandwidth can be realized.
Drawings
Fig. 1 is a perspective view of a lamb wave resonator 10 according to embodiment 1 of the present invention.
Fig. 2 is a cross-sectional view of lamb wave resonator 10 according to embodiment 1 of the present invention.
Fig. 3 is a diagram showing the dimensional relationship in fig. 2.
Fig. 4 is a graph of total admittance obtained by simulation when the thickness of the upper electrode 3a in the lamb wave resonator 10 according to embodiment 1 of the present invention is 100nm and the upper electrode 3a has different implantation ratios (0%, 20%, 40%, 60%, 80%, 100%).
Fig. 5 (a) to 5 (f) are diagrams showing the admittance diagrams in fig. 4 separately.
Fig. 6 is a graph of total admittance obtained by simulation when the thickness of the upper electrode 3a in the lamb wave resonator 10 according to embodiment 1 of the present invention is 200nm and the upper electrode 3a has different implantation ratios (0%, 20%, 40%, 60%, 80%, 100%).
Fig. 7 (a) to 7 (f) are diagrams showing the admittance diagrams in fig. 6 separately.
Fig. 8 is a graph of total admittance obtained by simulation when the thickness of the upper electrode 3a in the lamb wave resonator 10 according to embodiment 1 of the present invention is 300nm and the upper electrode 3a has different implantation ratios (0%, 20%, 40%, 60%, 80%, 100%).
Fig. 9 (a) to 9 (f) are diagrams showing the admittance diagrams in fig. 8 separately.
Fig. 10 is a graph of total admittance obtained by simulation when the thickness of the upper electrode 3a in the lamb wave resonator 10 according to embodiment 1 of the present invention is 400nm and the upper electrode 3a has different implantation ratios (0%, 20%, 40%, 60%, 80%, 100%).
Fig. 11 (a) to 11 (f) are diagrams showing the admittance diagrams in fig. 10 separately.
Fig. 12 is a graph of total admittance obtained by simulation when the thickness of the upper electrode 3a in the lamb wave resonator 10 according to embodiment 1 of the present invention is 500nm and the upper electrode 3a has different implantation ratios (0%, 20%, 40%, 60%, 80%, 100%).
Fig. 13 (a) to 13 (f) are diagrams showing the admittance diagrams in fig. 12 separately.
Fig. 14 is a cross-sectional view of a lamb wave resonator 10a according to a modification of embodiment 1 of the present invention.
Detailed Description
The technical scheme of the invention is further specifically described below through examples and with reference to the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of embodiments of the present invention with reference to the accompanying drawings is intended to illustrate the general inventive concept and should not be taken as limiting the invention.
Fig. 1 is a perspective view of a lamb wave resonator 10 according to embodiment 1 of the present invention. As shown in fig. 1, the lamb wave resonator 10 includes a substrate 1, a piezoelectric layer 2, interdigital electrodes 3, and a bus bar 4. Wherein the piezoelectric layer 2 is formed on the substrate 1, the interdigital electrode 3 is formed at least on the upper surface of the piezoelectric layer 2, and the bus bar 4 is connected with the finger root parts on both sides of the interdigital electrode 3. In fig. 1, the material of the substrate 1 is a high acoustic speed material having a high acoustic impedance such as 4H-SiC or 6H-SiC, and has a thickness of 5λ (λ is the acoustic wave wavelength excited by the interdigital electrode 3, that is, the lamb wave wavelength) to prevent the energy propagating in the lamb wave resonator 10 from leaking to the outside of the substrate 1, thereby having a high Q value. The piezoelectric layer 2 is 30 degrees YX-LiNbO 3 The piezoelectric material, here the piezoelectric layer 2, has a thickness of 0.8λ. The substrate 1 and the piezoelectric layer 2 constitute the structure of a POI. The interdigital electrode 3 is made of a metal or alloy such as Ti, al, cu, au, pt, ag, pd, ni, or a laminate of these metals or alloys.
Fig. 2 is a cross-sectional view of lamb wave resonator 10 according to embodiment 1 of the present invention, specifically, a cross-sectional view taken perpendicular to the extending direction of interdigital electrode 3. As shown in fig. 2, the interdigital electrode 3 is composed of an upper electrode 3a and a lower electrode 3b, wherein the lower electrode 3b is provided on the lower surface side of the piezoelectric layer 2, and the upper surface is in contact with the lower surface of the piezoelectric layer 2 and is entirely buried in the substrate 1. The upper electrode 3a is provided on the upper surface side of the piezoelectric layer 2, and a part of the upper electrode is embedded in the piezoelectric layer 2, and the remaining part is exposed on the upper surface side of the piezoelectric layer 2. Fig. 2 shows that there are two upper and lower electrodes 3a, 3b each, and the upper and lower electrodes 3a, 3b are disposed opposite to each other in the lamination direction of the lamb wave resonator 10, and each upper electrode 3a and each lower electrode 3b have the same thickness and width. In embodiment 1, the widths (widths in the horizontal direction in the drawing) of the upper electrode 3a and the lower electrode 3b are each 0.25λ, the spacing between two adjacent upper electrodes 3a is 0.167 λ, and the spacing between two adjacent lower electrodes 3b is 0.25λ.
In order to make the invention easier to understand, the dimensional relationship in the case of the cross-sectional view of fig. 2 is shown in fig. 3. h is the total thickness of the upper electrode 3a, h1 is the thickness of the upper electrode 3a exposed on the upper surface of the piezoelectric layer 2, i.e., the thickness of the non-embedded piezoelectric layer 2, and h2 is the thickness of the upper electrode 3a embedded in the piezoelectric layer 2, h=h1+h2. t is the thickness of the piezoelectric layer 2. The embedding ratio h2/h, i.e., the ratio of h2 to h, represents the ratio of the thickness of the portion of the upper electrode 3a where the piezoelectric layer 2 is embedded to the total thickness of the upper electrode 3 a.
The inventors have conducted intensive studies on the relationship between the embedding ratio of the upper electrode 3a and the parasitic mode suppressing effect of the lamb wave resonator 10, respectively prepared lamb wave resonators having an electrode thickness h of 100 to 500nm and an embedding ratio of the upper electrode 3a of 0 to 100%, and tested the admittances thereof, and the results are shown in fig. 4 to 13. Fig. 4 is a graph of total admittance of the lamb wave resonator 10 obtained by simulation when the electrode thickness is 100nm and the upper electrode 3a has different implantation ratios (0%, 20%, 40%, 60%, 80%, 100%), and fig. 5 (a) to 5 (f) are graphs showing the respective admittance graphs in fig. 4 separately. Fig. 6 is a graph of total admittance at different implantation ratios for an electrode thickness of 200nm, and fig. 7 (a) to 7 (f) are graphs showing the respective admittances in fig. 6 separately. Fig. 8 is a graph of total admittance at different implantation ratios for an electrode thickness of 300nm, and fig. 9 (a) to 9 (f) are graphs showing the respective admittances in fig. 8 separately. Fig. 10 is a graph of total admittance at different implantation ratios for an electrode thickness of 400nm, and fig. 11 (a) to 11 (f) are graphs showing the respective admittances in fig. 10 separately. Fig. 12 is a graph of total admittance at different implantation ratios for an electrode thickness of 500nm, and fig. 13 (a) to 13 (f) are graphs showing the respective admittances in fig. 12 separately.
Fig. 5 (a) to 5 (f), 7 (a) to 7 (f), 9 (a) to 9 (f), 11 (a) to 11 (f), and 13 (a) to 13 (f) show admittance diagrams of lamb wave resonators with different electrode thicknesses and different embedding ratios, respectively. In these figures, f s Representing the resonant frequency, f, of lamb wave resonator 10 p Is the antiresonant frequency, k, of the lamb wave resonator 10 2 Is the electromechanical coupling coefficient and satisfies k 2 ＝(π 2 /8)(f p 2 -f s 2 )/f s 2 Is a relationship of (3). For example, in FIG. 7 (d), f s ＝2106MHz，f p ＝2323MHz，k 2 =26.71%. Specific examples of admittance maps in the case of other electrode thicknesses and other implantation ratios are also similar to those of fig. 7 (d), and thus a specific explanation is omitted here. In addition, parasitic resonance peaks representing parasitic modes in each admittance diagram are also shown with thin coils.
The data in the admittance graphs are analyzed and arranged to obtain the following working frequency bands (f) with different electrode embedding ratios under different electrode thicknesses s 、f p ) Frequency of working center (f) 0 ＝1/2(f s +f p ) Relative bandwidth ((f) p -f s )÷f 0 ) Coefficient of electromechanical coupling (k) 2 ) And (3) a table.
As can be seen from fig. 4 to 13 (f) and the table above, different upper electrode implantation ratios affect the parasitic mode of the whole lamb wave resonator at different electrode thicknesses. As shown in fig. 4 and 5 (a) to 5 (f), when the upper electrode thickness is 100nm, the parasitic resonance peak is relatively strong near the resonance peak of the main mode when the implantation ratio is 0%, 20%, 100%, and the parasitic resonance peak is relatively weak when the implantation ratio is 40%, 60%, 80%, and particularly when the implantation ratio is 80%, the suppression effect of the parasitic resonance peak is optimal. At the same time, the electromechanical coupling coefficient reaches a high value of 24.5%.
As shown in fig. 6 and 7 (a) to 7 (f), in the case where the upper electrode thickness is 200nm, a strong parasitic resonance peak appears at the implantation ratio of 0%, and the parasitic resonance peaks at other implantation ratios are suppressed or even eliminated, for example, the parasitic resonance peak is not substantially seen in the drawings at the implantation ratios of 20% and 40%, a weak parasitic resonance peak appears at the implantation ratio of 80%, and a weaker parasitic resonance peak appears at the implantation ratio of 60%.
As shown in fig. 8 and 9 (a) to 9 (f), when the upper electrode thickness is 300nm, the parasitic resonance peak is relatively strong near the resonance peak of the main mode when the implantation ratio is 0%, 20%, 60%, 80%, and the parasitic resonance peak is relatively weak when the implantation ratio is 100%, and particularly, when the implantation ratio is 40%, the suppression effect of the parasitic resonance peak is optimal. At the same time, the electromechanical coupling coefficient also reaches a high value of 21.53%.
As shown in fig. 10 and 11 (a) to 11 (f), when the upper electrode thickness is 400nm, the parasitic resonance peak is relatively strong near the resonance peak of the main mode when the implantation ratio is 0%, 60%, 80%, and the parasitic resonance peak is relatively weak when the implantation ratio is 40%, 100%, and particularly, when the implantation ratio is 20%, the suppression effect of the parasitic resonance peak is optimal. At the same time, the electromechanical coupling coefficient reaches a high value of 24.05%.
As shown in fig. 12 and 13 (a) to 13 (f), when the upper electrode thickness is 500nm and the implantation ratio is 100%, the suppression effect of the parasitic resonance peak is optimal, and the parasitic resonance peak is not substantially seen in the figure. The electromechanical coupling coefficient at this time also reaches a high value of 50%.
As is clear from the above analysis, in order to suppress or eliminate the parasitic mode in the lamb wave resonator 10, the embedding ratio of the upper electrode 3a into the piezoelectric layer 2 can be selected and set according to the thickness of the upper electrode 3a, thereby eliminating the spurious effects, specifically as follows:
when the thickness of the upper electrode 3a is greater than 100nm and less than 200nm, the implantation ratio is selected to be 40% or 80%;
when the thickness of the upper electrode 3a is greater than 200nm and less than 400nm, the implantation ratio is selected to be 40%;
when the thickness of the upper electrode 3a is 200nm, the implantation ratio is selected to be 20% or more and 80% or less, or 80% or more and 100% or less;
when the thickness of the upper electrode 3a is 400nm, the implantation ratio is selected to be 20%;
when the thickness of the upper electrode 3a is 500nm, the implantation ratio is selected to be 100%.
By such setting, parasitic modes and spurious effects of the lamb wave resonator 10 can be suppressed, and a high electromechanical coupling coefficient (both of 18.8% or more) can be achieved. Wherein, when the thickness of the upper electrode 3a is 200nm and the embedded proportion is 100%, the electromechanical coupling coefficient of 33.2% can be achieved without stray. Furthermore, when the thickness of the upper electrode 3a is 500nm and the embedded ratio is 100%, the electromechanical coupling coefficient of 50% can be achieved without the spurious.
Therefore, according to the lamb wave resonator of the present embodiment, the ratio of the thickness of the portion of the upper electrode where the piezoelectric layer is embedded to the thickness of the entire upper electrode, that is, the embedding ratio, is set to be an embedding ratio capable of suppressing the parasitic mode of the lamb wave, so that not only the parasitic mode can be suppressed or even eliminated, but also the spurious effect can be suppressed, and the electromechanical coupling coefficient can be improved, thereby realizing a higher-performance high-frequency resonator, and further realizing a higher-performance sensor, a radio-frequency front end, and other electronic devices, so as to satisfy the current increasingly higher communication demands.
Fig. 14 is a cross-sectional view of a lamb wave resonator 10a according to a modification of embodiment 1 of the present invention. In FIG. 14, an intermediate layer 6 made of a low acoustic velocity material having a lower acoustic velocity than that of the substrate 2 (e.g., 4H-SiC) is interposed between the substrate 1 and the piezoelectric layer 2, and in this modification, siO is used as the intermediate layer 6 2 . Further, unlike the case where the lower electrode 3b is completely buried in the substrate 1 shown in fig. 2, in the modification of fig. 14, the lower electrode 3b is completely buried in the intermediate layer 6. General purpose medicineBy thus providing the intermediate layer 6 of low acoustic velocity, a reflection layer can be formed with the substrate 1 of high acoustic velocity, thereby further preventing leakage of acoustic waves out of the substrate 1, so that the Q value of the lamb wave resonator 10a is higher. Also, the intermediate layer 6, e.g. SiO, due to low sound velocity 2 The layer has a positive temperature coefficient of frequency and the piezoelectric layer 2 has a negative temperature coefficient of frequency by providing SiO 2 The layer serves as an intermediate layer, and the Temperature Coefficient of Frequency (TCF) of the lamb wave resonator 10a can also be reduced, thereby improving the temperature characteristic of frequency thereof.
According to the above embodiment of the present invention, in the lamb wave resonator, the plurality of lower electrodes provided on the lower surface side of the piezoelectric layer are completely embedded in the substrate, the plurality of upper electrodes provided on the upper surface side of the piezoelectric layer are at least partially embedded in the piezoelectric layer, and the embedding ratio of the thickness of the portion of the upper electrode in which the piezoelectric layer is embedded to the entire thickness of the upper electrode is set to be an embedding ratio capable of suppressing the parasitic mode according to the thickness of the entire upper electrode. Thus, a lamb wave resonator having suppressed spurious effects, a high electromechanical coupling coefficient, a high Q value, a high frequency, a high sound velocity, and a large bandwidth can be realized.
In addition, by providing an intermediate layer made of a low acoustic velocity material between the substrate and the piezoelectric layer and embedding the lower electrode in the intermediate layer, the Q value of the lamb wave resonator can be further improved, and the frequency-temperature characteristic thereof can be improved.
The invention also provides a filter which uses the lamb wave resonator with the structure.
The invention also provides electronic equipment comprising the filter or the lamb wave resonator. The electronic equipment comprises, but is not limited to, intermediate products such as a radio frequency front end, a filtering and amplifying module and terminal products such as a mobile phone, a WIFI and an unmanned aerial vehicle.
What has been described above is only a preferred embodiment of the present application, and the present invention is not limited to the above examples. It is to be understood that other modifications and variations which may be directly derived or contemplated by those skilled in the art without departing from the spirit and concepts of the present invention are deemed to be included within the scope of the present invention.
Claims (14)
1. A lamb wave resonator, comprising:
a substrate as an insulator;
a piezoelectric layer disposed on the substrate;
a plurality of upper electrodes provided on an upper surface side of the piezoelectric layer; and
a plurality of lower electrodes provided on the lower surface side of the piezoelectric layer,
each of the upper electrodes is at least partially embedded in the piezoelectric layer, each of the lower electrodes is not embedded in the piezoelectric layer,
the ratio of the thickness of the portion of the upper electrode where the piezoelectric layer is embedded to the thickness of the entire upper electrode, that is, the embedding ratio is set to be an embedding ratio capable of suppressing the parasitic mode of lamb waves.
2. A lamb wave resonator according to claim 1, wherein,
when the thickness of the whole upper electrode is greater than 100nm and less than 200nm, the implantation ratio is 40% or 80%.
3. A lamb wave resonator according to claim 1, wherein,
when the thickness of the whole upper electrode is more than 200nm and less than 400nm, the implantation ratio is 40%.
4. A lamb wave resonator according to claim 1, wherein,
when the thickness of the entire upper electrode is 200nm, the implantation ratio is 20% or more and 80% or less, or 80% or more and 100% or less.
5. A lamb wave resonator according to claim 1, wherein,
the buried ratio was 20% when the thickness of the entire upper electrode was 400 nm.
6. A lamb wave resonator according to claim 1, wherein,
when the thickness of the entire upper electrode is 500nm, the implantation ratio is 100%.
7. A lamb wave resonator according to any one of claims 1 to 6,
the substrate uses any one of high sonic velocity materials selected from 4H-SiC and 6H-SiC.
8. A lamb wave resonator according to any one of claims 1 to 6,
the piezoelectric layer uses 30 degrees YX-LiNbO 3 。
9. A lamb wave resonator according to any one of claims 1 to 6,
the upper electrode and the lower electrode have the same width and thickness, respectively.
10. A lamb wave resonator according to any one of claims 1 to 6,
the upper electrode and the lower electrode are made of any one metal selected from Ti, al, cu, au, pt, ag, pd, ni, an alloy thereof, or a laminate thereof.
11. A lamb wave resonator according to any one of claims 1 to 6,
an intermediate layer made of a low acoustic velocity material having a lower acoustic velocity than that of the substrate is provided between the substrate and the piezoelectric layer, and the lower electrode is buried in the intermediate layer.
12. A lamb wave resonator according to claim 11, wherein,
the intermediate layer uses SiO 2 。
13. A filter is characterized in that,
a lamb wave resonator comprising any one of claims 1-12.
14. An electronic device, characterized in that,
comprising a filter according to claim 13 or a lamb wave resonator according to any of claims 1-12.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0983030A (en) * | 1995-09-11 | 1997-03-28 | Matsushita Electric Ind Co Ltd | Surface acoustic wave element and fabrication thereof |
| DE10236003A1 (en) * | 2002-08-06 | 2004-02-19 | Epcos Ag | Acoustic wave component e.g. for use as filter for GHz frequencies, with metallic electrodes embedded in surface of component substrate |
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| KR100506729B1 (en) * | 2002-05-21 | 2005-08-08 | 삼성전기주식회사 | Film bulk acoustic resonator and method for fabrication thereof |
| US9998088B2 (en) * | 2014-05-02 | 2018-06-12 | Qorvo Us, Inc. | Enhanced MEMS vibrating device |
| US10348269B2 (en) * | 2014-12-17 | 2019-07-09 | Qorvo Us, Inc. | Multi-frequency guided wave devices and fabrication methods |
| JP2019062441A (en) * | 2017-09-27 | 2019-04-18 | 株式会社村田製作所 | Elastic wave device |
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| JPH0983030A (en) * | 1995-09-11 | 1997-03-28 | Matsushita Electric Ind Co Ltd | Surface acoustic wave element and fabrication thereof |
| DE10236003A1 (en) * | 2002-08-06 | 2004-02-19 | Epcos Ag | Acoustic wave component e.g. for use as filter for GHz frequencies, with metallic electrodes embedded in surface of component substrate |
| US8456257B1 (en) * | 2009-11-12 | 2013-06-04 | Triquint Semiconductor, Inc. | Bulk acoustic wave devices and method for spurious mode suppression |
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