CN218416337U

CN218416337U - Resonator and filter

Info

Publication number: CN218416337U
Application number: CN202222364032.2U
Authority: CN
Inventors: 王华磊; 刘旻俊; 杜波; 倪建兴
Original assignee: Ruishi Chuangxin Chongqing Technology Co ltd
Current assignee: Ruishi Chuangxin Chongqing Technology Co ltd
Priority date: 2022-09-06
Filing date: 2022-09-06
Publication date: 2023-01-31
Anticipated expiration: 2032-09-06

Abstract

The utility model relates to a resonator and a filter, which comprises a substrate, a piezoelectric layer and IDT electrodes; the substrate is provided with a cavity; the piezoelectric layer is arranged on the upper surface of the substrate; the upper surface of the piezoelectric layer is provided with a groove, the IDT electrode is formed in the groove, and the thickness of the IDT electrode is smaller than or equal to the depth of the groove; the IDT electrode faces the cavity with the piezoelectric layer interposed therebetween. The utility model discloses in, the syntonizer is transverse excitation film bulk acoustic resonator, will and IDT electrode fill in the recess of the upper surface of piezoelectric layer, can reduce the reflection way of sound wave in the propagation, and then reduce the mode coupling between the sound wave (reduce the clutter promptly), improve transverse excitation film bulk acoustic resonator's working property.

Description

Resonator and filter

Technical Field

The utility model belongs to the technical field of radio frequency filtering, a syntonizer and wave filter is related to.

Background

A transverse-excited thin-film bulk acoustic resonator (XBAR) is an acoustic resonator structure for microwave filters, which can provide high electromechanical coupling and high frequency capability, which can be used in various RF filters (radio frequency filters), such as band-stop filters, band-pass filters, duplexers and multiplexers, and which is suitable for use in filters for communication bands with frequencies above 3 GHz.

The XBAR includes a substrate having a cavity, a piezoelectric layer disposed on an upper surface of the substrate, and an interdigital transducer (IDT) electrode disposed on the upper surface of the piezoelectric layer and opposed to the cavity on the substrate via the piezoelectric layer.

However, the structural arrangement of the XBAR also imposes limitations on the performance of the XBAR, so that the performance of the XBAR cannot meet the increasing demand, and therefore, how to further improve the working performance of the XBAR becomes a problem to be faced by the industry.

SUMMERY OF THE UTILITY MODEL

The utility model provides a syntonizer and wave filter aims at further improving the performance of syntonizer.

The embodiment of the utility model provides a resonator, including substrate, piezoelectric layer and IDT electrode; the substrate is provided with a cavity; the piezoelectric layer is arranged on the upper surface of the substrate; the upper surface of the piezoelectric layer is provided with a groove, the IDT electrode is formed in the groove, and the thickness of the IDT electrode is smaller than or equal to the depth of the groove; the IDT electrode faces the cavity with the piezoelectric layer interposed therebetween.

Optionally, the IDT electrode has a thickness H, and the groove has a depth L, wherein (L-H)/H ranges from 0.1 to 1.

Alternatively, the ratio of (L-H)/H is in the range of 0.2 to 0.6.

Optionally, the piezoelectric layer material is lithium niobate.

Optionally, the cut of the piezoelectric layer is a Z-cut, and a cut angle of the Z-cut of the piezoelectric layer is within a preset range, the preset range being [20 ° -40 ° ], [80 ° -100 ° ], [140 ° -160 ° ], [200 ° -220 ° ], [260 ° -280 ° ], or [320 ° -340 ° ].

Optionally, the predetermined range is [25 ° -35 ° ], [85 ° -95 ° ], [145 ° -155 ° ], [205 ° -215 ° ], [265 ° -275 ° ] or [325 ° -335 ° ].

Optionally, the thickness M of the piezoelectric layer and the thickness of the IDT electrode are H, where H < 0.2M.

Optionally, the thickness M of the piezoelectric layer and the thickness of the IDT electrode are H, where H is greater than or equal to 0.2M.

Optionally, the width of the electrode fingers of the IDT electrode is D, and the thickness of the piezoelectric layer is M, where D > 5M.

Optionally, the duty ratio of the IDT electrode ranges from 0.15 to 0.25.

The embodiment of the utility model provides a still provide a wave filter, include above-mentioned arbitrary one the syntonizer.

The embodiment of the utility model provides an among syntonizer and the wave filter, the syntonizer is horizontal excitation film bulk acoustic resonator, fills the IDT electrode of syntonizer in the recess of the upper surface of piezoelectric layer simultaneously, can reduce the reflection way of sound wave in the propagation, and then reduces the modal coupling between the sound wave (reduce the clutter promptly), improves the working property of syntonizer.

Drawings

Fig. 1 is a schematic cross-sectional view of a resonator according to an embodiment of the present invention;

fig. 2 is a schematic cross-sectional view of another resonator provided in an embodiment of the present invention;

fig. 3 is a schematic diagram of an IDT electrode of a surface acoustic wave device according to an embodiment of the present invention;

FIG. 4 is a graph of admittance of a resonator of the prior art;

FIG. 5 is an enlarged view of area A of FIG. 4;

fig. 6 is an admittance graph of a resonator according to an embodiment of the present invention;

FIG. 7 is an enlarged view of area B of FIG. 6;

fig. 8 is another admittance chart provided by an embodiment of the present invention;

FIG. 9 is an enlarged view of area C of FIG. 8;

fig. 10 is a graph of the cut angle of the piezoelectric layer of the resonator according to an embodiment of the present invention;

fig. 11 is a graph of corner cut and electromechanical coupling coefficient of a piezoelectric layer of a resonator according to an embodiment of the present invention;

fig. 12 is a graph illustrating the peak relationship between the chamfer of the piezoelectric layer and the clutter impedance according to an embodiment of the present invention;

fig. 13 is a graph illustrating a relationship between a thickness and a Q value of an IDT electrode of a resonator according to an embodiment of the present invention;

fig. 14 is a graph showing a relationship between the thickness of the IDT electrode and the electromechanical coupling coefficient of the resonator according to an embodiment of the present invention.

The reference numerals in the specification are as follows:

100. a resonator;

1. a substrate; 11. a cavity;

2. a piezoelectric layer; 21. a groove;

3. an IDT electrode; 31. an electrode finger; 32. a bus bar.

Detailed Description

In order to make the technical problem, technical solution and advantageous effects solved by the present invention more clearly understood, the following description is given in conjunction with the accompanying drawings and embodiments to illustrate the present invention in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example one

As shown in fig. 1 to 3, in the first embodiment, a resonator 100 includes a substrate 1, a piezoelectric layer 2, and an IDT electrode 3. Wherein the substrate 1 has a cavity 11, the piezoelectric layer 2 is disposed on the upper surface of the substrate 1, the IDT electrode 3 is disposed on the piezoelectric layer 2, and the IDT electrode 3 is opposite to the cavity 11 across the piezoelectric layer 2, i.e. the resonator 100 is a transverse-excitation thin film bulk acoustic resonator. In addition, the upper surface of the piezoelectric layer 2 is provided with a groove 21, the IDT electrode 3 is formed in the groove 21, and the IDT electrode 3 does not protrude out of the groove 21. This arrangement reduces the reflection path of the sound waves during propagation, thereby reducing modal coupling between the sound waves (i.e., reducing noise) and improving the performance of the resonator 100.

In one implementation of this embodiment (defined as mode one), the thickness of the IDT electrode 3 is equal to the depth of the groove 21, the IDT electrode 3 completely fills the groove 21, and the upper surface of the IDT electrode 3 is flush with the upper surface of the piezoelectric layer 2. Compared with the prior art (i.e., the IDT electrode does not sink, and the IDT electrode is located on the upper surface of the piezoelectric layer), the method can reduce noise waves to some extent, and improve the Q value and the electromechanical coupling coefficient, thereby improving the performance of the resonator 100.

In another implementation manner (defined as manner two) of the present embodiment, the thickness of the IDT electrode 3 is set to be smaller than the depth of the groove 21. At this time, the IDT electrode 3 does not completely fill the groove 21, and there is a certain height difference between the upper surface of the IDT electrode 3 and the upper surface of the piezoelectric layer 2. In this embodiment, the IDT electrode 3 has a different thickness from the depth of the groove 21, and the changed sound velocity is different. Compared with the first mode, the first mode can further solve the problem of overlarge sound velocity offset caused when the IDT electrode 3 completely fills the groove 21, increase the electromechanical coupling coefficient, improve the Q value of the resonator 100, and further enable the resonator 100 to have better working performance.

In addition, the depth of the recess 21 is smaller than the thickness of the piezoelectric layer 2, i.e., the recess 21 does not penetrate to the lower surface of the piezoelectric layer 2.

In this embodiment, the cavity 11 forms a first opening in the upper surface of the substrate 1, and the piezoelectric layer 2 may close the first opening. In addition, "the IDT electrode 3 faces the cavity 11 through the piezoelectric layer 2" means that an orthogonal projection of the IDT electrode 3 on the upper surface of the substrate 1 is located within the first opening.

In an implementable implementation of the present embodiment, as shown in fig. 1, the cavity 11 is open from the upper surface of the substrate 1 and extends towards the lower surface of the substrate 1, but does not penetrate to the lower surface of the substrate 1. Alternatively, as shown in fig. 2, in another embodiment of the present embodiment, the cavity 11 penetrates from the upper surface of the substrate 1 to the lower surface of the substrate 1.

In this embodiment, the recess 21 may be etched in the upper surface of the piezoelectric layer 2 by using a chemical solution, and the idt electrode 3 may be formed in the recess 21 by filling a conductive material, etc., and extend upward from the bottom surface of the recess 21 by a certain thickness.

As shown in fig. 3, the IDT electrode 3 includes a plurality of electrode fingers 31 and bus bars 32, the width of each electrode finger 31 may be the same, one end of each electrode finger 31 is connected to the bus bar 32, the shape of the groove 21 matches the IDT electrode 3, and it has a plurality of first recesses corresponding to the electrode fingers 31 one by one and second recesses corresponding to the bus bars 32, and after the preparation, each electrode finger 31 and the bus bar 32 are respectively embedded in the corresponding recesses.

In this embodiment, the material of the substrate 1 may be silicon, and the material of the piezoelectric layer 2 may be lithium tantalate, lithium niobate, or the like. The material of the IDT electrode 3 may be a single metal material or a composite or alloy material of different metals, and optionally, the material of the IDT electrode 3 may be one of aluminum, copper, or a composite or alloy of the above metals.

In addition, referring to fig. 4 to 9, wherein fig. 4 and 5 show admittance graphs of the prior art scheme, and fig. 5 is an enlarged view of a region a of fig. 4; fig. 6 and 7 are graphs showing admittance curves in a first manner, and fig. 7 is an enlarged view of a region B of fig. 6; fig. 8 and 9 show admittance graphs for the second mode, and fig. 9 is an enlarged view of the area C of fig. 8, in which the abscissa is the frequency value, the unit of frequency is MHZ, the ordinate is the value 20 times the logarithm of the base 10 impedance, and the curves represent the angles of the cut angles of the different piezoelectric layers 2.

As can be seen from fig. 4 and 5, the noise between the resonance point and the anti-resonance point of the prior art becomes significantly larger. As can be seen from fig. 4 to 9, compared with the prior art, the first and second schemes have a small amount of noise between the resonance point and the anti-resonance point, but the noise is small and does not affect the passband. As can be seen from fig. 6 to 9, the noise peak of the mode one is significantly larger than that of the mode two, although the noise between the resonance point and the anti-resonance point is smaller.

Example two

The second embodiment is to further optimize the IDT electrode 3, the piezoelectric layer 2, and the like based on the first embodiment.

In the present embodiment, it is assumed that the thickness M of the piezoelectric layer 2, M being dependent on the wavelength, may range from 350nm to 480nm, for example, M may be 380nm, 400nm, etc. Of course, the value of M may be in other ranges, and this embodiment is not limited. In general, too small value of M may cause too much excited noise, too large value of M may cause too fast decrease of the electromechanical coupling coefficient, and the setting range of the embodiment may avoid too fast decrease of the electromechanical coupling coefficient on the premise of reducing noise, so that the resonator 100 may have better working performance.

In this embodiment, when the material of the piezoelectric layer 2 is lithium niobate, the cut shape of the piezoelectric layer 2 is Z cut, and if the cut angle of the Z cut of the piezoelectric layer 2 is α, α is within a preset range, the resonator 100 can have better performance. In an alternative embodiment, α is preset in the range of [80 ° -100 °, i.e., 80 ° ≦ α ≦ 100 °, which may reduce the noise of the resonator 100 and increase the Q value of the resonator 100, resulting in better performance of the resonator 100. Preferably, the predetermined range of α is [25 ° -35 ° ], to further improve the performance of the resonator 100.

In another alternative embodiment, α is preset in the range of [140 ° -160 ° ] to reduce the spurious and increase the Q of the resonator 100. Preferably, the predetermined range of α is [145 ° -155 ° ]. Wherein each curve represents a cut of the piezoelectric layer 2Z-cut, and wherein the cut of the Z-cut ranges between 148 ° -154 ° in fig. 4-9. In addition, in fig. 4 to 9, the tangent angles of the Z-cuts corresponding to the respective curves are 148 °, 149 °, 150 °, 151 °, 152 °, 153 °, and 154 °, respectively, wherein some of the curves are overlapped with each other.

Further, as shown in fig. 10, this figure shows a comparison graph of the Q values of the conventional proposal and the second mode, and it can be seen from the graph that when the tangential angle of the Z-cut is 148 °, 149 °, 150 °, 151 °, 152 °, 153 °, and 154 °, Q of the second mode is obtained _max Q greater than existing schemes _max 。

As shown in fig. 11, which is a graph comparing electromechanical coupling coefficients of the conventional scheme and the second scheme, it can be seen that, when the tangential angle of the Z-cut is 148 °, 149 °, 150 °, 151 °, 152 °, 153 °, and 154 °, the electromechanical coupling coefficient of the second scheme is significantly greater than that of the conventional scheme.

In some embodiments, the predetermined range of α can also be [80 ° -100 ° ], [200 ° -220 ° ], [260 ° -280 ° ] or [320 ° -340 ° ]. Wherein, when the preset range of α is [80 ° -100 ° ], the preferable range thereof may be [85 ° -95 ° ]; when α is in the preset range of [200 ° -220 ° ], a preferable range thereof may be [205 ° -215 ° ]; when the preset range of α is [260 ° -280 ° ], a preferable range thereof may be [265 ° -275 ° ]; when the preset range of α is [320 ° -340 ° ], a preferable range thereof may be [325 ° -345 ° ]. In addition, the value of α may be in other ranges, and this embodiment is not limited.

As shown in fig. 12, in the figure, the polar coordinate is the cut angle of the piezoelectric layer 2, the passing coordinate is the peak value (unit is dB) of the clutter impedance, each angle corresponds to the size of the peak value of the clutter impedance, and the larger the peak value of the clutter impedance is, the smaller the admittance corresponding to the clutter is, that is, the clutter is. It can be seen from the figure that when α is in a range of [20 ° -40 ° ], [80 ° -100 ° ], [140 ° -160 ° ], [200 ° -220 ° ], [260 ° -280 ° ] or [320 ° -340 ° ], the peak of the clutter impedance is large and the clutter is small. And when the value range of alpha is [ 25-35 ° ], [ 85-95 ° ], [ 145-155 ° ], [ 205-215 ° ], [ 265-275 ° ] or [325 ° -335 ° ], the peak value of the noise impedance may be larger, so that the resonator 100 may have better performance.

In the present embodiment, the IDT electrode 3 has a thickness H, where H < 0.2M in an implementation mode, so as to reduce noise and improve the performance of the resonator 100 while ensuring the Q value and the electromechanical coupling coefficient. In fig. 4 to 9, the thickness of the IDT electrode 3 is 0.12M. Preferably, H is typically 100nm.

As shown in FIG. 13, this figure shows a comparison of Q values of the first and second modes, and it can be seen from the figure that when H is a value smaller than 0.2M, such as 0.1M or 0.15M, Q values of the first and second modes are both obtained _max The values are not very different. As shown in fig. 14, which is a graph comparing the electromechanical coupling coefficients of the first and second modes, it can be seen that the electromechanical coupling systems of both the first and second modes are substantially the same when H is a value less than 0.2M, such as 0.1M, 0.15M, and the like.

In another practical embodiment, H ≧ 0.2M, such as H of 0.25M, 0.3M, 0.35M, 0.4M, 0.45M, 0.5M, or the like. As shown in FIGS. 13 and 14, when H.gtoreq.0.2M, the difference in Q between the first and second modes is not large, and the noise in the first and second modes is a little more than that in the case where H < 0.2M; however, both mode one and mode two can have higher electromechanical coupling systems at H ≧ 0.2M. It will be appreciated that H is always less than M, since H is less than or equal to the depth L of the recess, which in turn is less than the thickness M of the piezoelectric layer.

In the present embodiment, the width of the electrode finger 31 of the IDT electrode 3 is D, where D > M, which can provide the resonator 100 with better operation performance. Preferably, D > 5M. In addition, the value of D may be in other ranges, and this embodiment is not limited.

In the present embodiment, the duty ratio is set in the range of 0.15-0.25, where the duty ratio =2D/λ, λ being the electrode period of the IDT electrode 3. As shown in fig. 3, in the front projection of the IDT electrode 3 on a plane, in the arrangement direction of the electrode fingers 31 of the IDT electrode 3, the distance between the central lines of the projections of two adjacent electrode fingers 31 is the electrode period. In fig. 4 to 9, the duty ratio is 0.2. In addition, the value of the duty ratio may also be other values, and this embodiment is not limited.

In the present embodiment, the depth of the groove 21 is L, L is smaller than the thickness of the piezoelectric layer, the spacing between the upper surface of the IDT electrode 3 and the upper surface of the piezoelectric layer 2 is N, N = L-H, and N/H ranges from 0.1 to 1. This can avoid the problem of insufficient driving force of the IDT electrode 3 while providing the resonator 100 with a higher Q value. The value of N/H can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc. Preferably, N/H is in the range of 0.2 to 0.6. In addition, the value of N/H may also be in other ranges, and this embodiment is not limited.

In this embodiment, the resonator 100 further comprises a dielectric layer disposed between the piezoelectric layer 2 and the substrate 1, and the dielectric constant of the dielectric layer is smaller than the dielectric constant of the piezoelectric layer 2. The material of the dielectric layer may be silicon dioxide, etc.

The embodiment of the utility model provides a still provide a filter, this filter includes any one of the above-mentioned embodiment syntonizer 100 to improve the working property of filter.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A resonator includes a substrate, a piezoelectric layer, and an IDT electrode;

the substrate is provided with a cavity;

the piezoelectric layer is arranged on the upper surface of the substrate;

the upper surface of the piezoelectric layer is provided with a groove, the IDT electrode is formed in the groove, and the thickness of the IDT electrode is smaller than or equal to the depth of the groove;

the IDT electrode faces the cavity with the piezoelectric layer interposed therebetween.

2. The resonator of claim 1, wherein the IDT electrode has a thickness H and the groove has a depth L, and wherein (L-H)/H ranges from 0.1 to 1.

3. The resonator of claim 2, wherein (L-H)/H is in the range of 0.2-0.6.

4. The resonator of claim 1, wherein the piezoelectric layer material is lithium niobate.

5. The resonator of claim 1 or 4, wherein the cut of the piezoelectric layer is Z-cut, and wherein a cut angle of the Z-cut of the piezoelectric layer is within a predetermined range, the predetermined range being [20 ° -40 ° ], [80 ° -100 ° ], [140 ° -160 ° ], [200 ° -220 ° ], [260 ° -280 ° ] or [320 ° -340 ° ].

6. The resonator according to claim 5, characterized in that the predetermined range is [25 ° -35 ° ], [85 ° -95 ° ], [145 ° -155 ° ], [205 ° -215 ° ], [265 ° -275 ° ] or [325 ° -335 ° ].

7. The resonator of claim 1, wherein a thickness M of the piezoelectric layer and a thickness H of the IDT electrode, wherein H < 0.2M.

8. The resonator of claim 1, wherein the thickness of the piezoelectric layer M and the thickness of the IDT electrode H, wherein H ≧ 0.2M.

9. The resonator of claim 1, wherein the IDT electrodes have electrode fingers having a width D and the piezoelectric layer has a thickness M, wherein D > 5M.

10. The resonator of claim 1, wherein a duty cycle of the IDT electrode is in a range of 0.15-0.25.

11. A filter comprising a resonator according to any of claims 1-10.