CN117792331A - Lamb wave resonator and manufacturing method thereof - Google Patents
Lamb wave resonator and manufacturing method thereof Download PDFInfo
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- CN117792331A CN117792331A CN202311844107.XA CN202311844107A CN117792331A CN 117792331 A CN117792331 A CN 117792331A CN 202311844107 A CN202311844107 A CN 202311844107A CN 117792331 A CN117792331 A CN 117792331A
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 9
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Abstract
The invention provides a lamb wave resonator and a manufacturing method thereof, the lamb wave resonator comprises a substrate, an interdigital transducer, a high sound velocity dielectric film and a mass load layer, wherein the piezoelectric film is arranged above the substrate, the interdigital transducer is positioned above the piezoelectric film and comprises a plurality of interdigital electrodes which are arranged at intervals in the horizontal direction in a staggered way, the mass load layer is positioned above one surface of each interdigital electrode far away from the piezoelectric film and comprises a plurality of mass load blocks, at least one mass load block is arranged above each interdigital electrode, and the width of each mass load block is smaller than that of each interdigital electrode. The lamb wave resonator can remarkably increase the capacitance of the unit area of the device by greatly increasing the width of the interdigital electrode, effectively solve the problem of overlarge area when the device is practically applied, effectively improve the system integration level and expand the application scene of the device, and simultaneously add a mass load layer to keep the high working efficiency and the high electromechanical coupling coefficient performance of the device. The manufacturing method has the advantages of simple manufacturing process steps, mature process and low cost.
Description
Technical Field
The invention belongs to the field of wireless communication equipment and semiconductor devices, and relates to a lamb wave resonator and a manufacturing method thereof.
Background
With the rapid development of wireless communication technology, the requirements on frequency selection and the performance of filters in the radio frequency front end are increasing. As a next generation wireless communication standard, 5G communication puts higher demands on radio frequency front end modules, including higher frequencies and greater bandwidths, and highly accurate frequency selection. In order to solve the problems of low sound velocity, low coupling coefficient and the like of the traditional resonator, a suspended transverse excitation resonator (XBAR) technology based on lithium niobate/lithium tantalate is generated. The transverse excitation resonator adopts a transverse excitation mode, namely, the vibration mode of the resonator is driven by excitation of a transverse electric field. Compared with the traditional surface acoustic wave resonator and the like, the transverse excitation resonator has the advantages of high sound velocity, high working frequency, large electromechanical coupling coefficient and the like, well compensates the defect of the traditional surface acoustic wave resonator in a high-frequency range, and has wide application prospect in wireless communication equipment.
Although the XBAR device shows great advantages in terms of large coupling coefficient and high sound speed, due to the characteristics of the device, in order to obtain a larger coupling coefficient and avoid a higher harmonic spurious mode, the XBAR device often adopts a design with large wavelength and low electrode duty ratio, so that the electrode spacing is larger, and the capacitance per unit area of the device is greatly reduced compared with that of the surface acoustic wave resonator. In practical application, in order to consider that the port impedance matching leads to a filter using an XBAR device to have a much larger area, which leads to the reduction of system integration and the increase of production cost, and seriously affects the practical application of XBAR.
Therefore, how to increase the capacitance per unit area of the device without affecting the resonance performance of the device, so as to reduce the area of the device to expand the application scene of the device, becomes an important technical problem to be solved urgently by those skilled in the art.
It should be noted that the foregoing description of the background art is only for the purpose of facilitating a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. The above-described solutions are not considered to be known to the person skilled in the art simply because they are set forth in the background section of the present application.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a lamb wave resonator and a manufacturing method thereof, which are used for solving the problem that the applicability of the device is affected due to the larger occupied area of the device caused by the low capacitance per unit area of the lamb wave resonator in the prior art.
To achieve the above and other related objects, the present invention provides a lamb wave resonator comprising:
a substrate having a piezoelectric film over the substrate;
the interdigital transducer is positioned above the piezoelectric film and comprises a plurality of interdigital electrodes which are spaced in the horizontal direction and are staggered, and the metallization rate of the interdigital electrodes is more than 0.5;
the mass load layer is positioned above one surface, far away from the piezoelectric film, of the interdigital electrode, the mass load layer comprises a plurality of mass load blocks, at least one mass load block is arranged above each interdigital electrode, and the width of each mass load block is smaller than that of each interdigital electrode.
Optionally, the thickness of the interdigital electrode ranges from 10nm to 500nm, the thickness of the mass loading layer ranges from 10nm to 500nm, and the ratio of the width of the mass loading block to the width of the interdigital electrode is less than 0.5.
Optionally, the material of the mass loading layer includes at least one of a metal material and a dielectric material, wherein the metal material includes at least one of aluminum, copper, gold and platinum, and the dielectric material includes at least one of aluminum nitride, silicon dioxide and silicon carbide.
Optionally, the lamb wave resonator further comprises a high acoustic speed dielectric film, the Gao Shengsu dielectric film is located above and/or below the piezoelectric film, and the propagation speed of the acoustic wave in the Gao Shengsu dielectric film is greater than the propagation speed of the acoustic wave in the piezoelectric film.
Optionally, the center-to-center spacing between two adjacent interdigital electrodes satisfies p>2(h 1 +h 2 ) Wherein p is the center-to-center distance between two adjacent interdigital electrodes, h 1 H is the thickness of the piezoelectric film 2 Is the thickness of the Gao Shengsu dielectric film.
Optionally, the Gao Shengsu dielectric film comprises at least one high-sound-velocity dielectric layer, and the position of the high-sound-velocity dielectric layer comprises at least one of being located between the piezoelectric film and the interdigital electrode, being located between the piezoelectric film and the substrate, being located above the piezoelectric film and at least covering the exposed surface of the interdigital electrode, wherein when the high-sound-velocity dielectric layer is located above the piezoelectric film, the high-sound-velocity dielectric layer only covers the exposed surface of the interdigital electrode or covers both the exposed surface of the interdigital electrode and the mass load layer.
Optionally, the material of the high acoustic velocity dielectric layer includes at least one of aluminum nitride, silicon carbide and diamond, and when the Gao Shengsu dielectric film includes a plurality of high acoustic velocity dielectric layers, the material of each of the high acoustic velocity dielectric layers is the same or different.
Optionally, the lamb wave resonator further comprises an air cavity or a bragg reflection layer, the air cavity is located in the substrate and below the interdigital electrode so that the interdigital electrode is suspended above the air cavity, and the bragg reflection layer is located above the substrate.
Optionally, the material of the piezoelectric film includes at least one of lithium niobate and lithium tantalate.
The invention also provides a manufacturing method of the lamb wave resonator, which comprises the following steps:
providing a substrate, wherein a piezoelectric film is arranged above the substrate;
forming an interdigital transducer above the piezoelectric film, wherein the interdigital transducer comprises a plurality of interdigital electrodes which are spaced in the horizontal direction and are staggered, and the metallization rate of the interdigital electrodes is more than 0.5;
and forming a mass load layer above one surface of the interdigital transducer, which is far away from the piezoelectric film, wherein the mass load layer comprises a plurality of mass load blocks, at least one mass load block is arranged above each interdigital electrode, and the width of the mass load block is smaller than that of each interdigital electrode.
Optionally, the method further comprises the step of forming a high acoustic speed dielectric film, wherein the step of forming the high acoustic speed dielectric film is performed before forming the piezoelectric film and/or after forming the piezoelectric film, and the propagation speed of sound waves in the Gao Shengsu dielectric film is greater than the propagation speed of sound waves in the piezoelectric film.
As described above, the lamb wave resonator of the invention greatly increases the width of the interdigital electrode (namely, the metallization rate of the interdigital electrode is relatively high) on the basis of the conventional resonator structure so as to obviously increase the capacitance per unit area of the device, effectively solve the problem of overlarge area of an XBAR device in practical application, effectively improve the system integration level and expand the application scene of the device, and simultaneously add a mass load layer so as to maintain the performances of high working efficiency, high electromechanical coupling coefficient and the like of the device. And the high sound velocity dielectric film is additionally arranged according to actual needs to inhibit stray modes generated along with the increase of the metallization rate, so that the comprehensive working performance of the device is further improved. The manufacturing method of the lamb wave resonator can be used for manufacturing the lamb wave resonator with high unit area capacitance, and has the advantages of simple manufacturing process steps, mature process, low cost and strong practical applicability.
Drawings
Fig. 1 is a schematic cross-sectional view of a lamb wave resonator according to a comparative example.
Fig. 2 is a graph showing simulated admittance versus metallization ratio for various interdigital electrodes in the lamb wave resonator of fig. 1.
Fig. 3 is a schematic cross-sectional view of a lamb wave resonator according to the present invention.
Fig. 4 is a schematic top view of the lamb wave resonator shown in fig. 3.
Fig. 5 is a schematic diagram showing a second cross-sectional structure of the lamb wave resonator of the present invention.
Fig. 6 is a schematic view showing a third cross-sectional structure of the lamb wave resonator of the present invention.
Fig. 7 is a schematic diagram showing a fourth cross-sectional structure of the lamb wave resonator of the present invention.
Fig. 8 is a schematic cross-sectional view of a lamb wave resonator according to a second embodiment.
Fig. 9 is a schematic cross-sectional structure of a lamb wave resonator in a second comparative example.
Fig. 10 is a schematic diagram showing the displacement of the lamb wave resonator in the first-order anti-symmetric lamb wave mode when the metallization ratio of the lamb wave resonator is 0.2 in the comparative example one.
Fig. 11 is a schematic diagram showing displacement of the lamb wave resonator in the first-order anti-symmetric lamb wave resonance mode in the third embodiment.
Fig. 12 is a graph showing the simulation of admittance characteristics of lamb wave resonators in comparative example one, comparative example two and example three.
Fig. 13 is a graph showing the normalized capacitance per unit area of the lamb wave resonator in the comparative example one, the second example and the third example.
Fig. 14 is a graph showing the simulation of admittance characteristics of lamb wave resonators in the second and third embodiments.
Description of the reference numerals
10. Substrate and method for manufacturing the same
11. Air cavity
20. Piezoelectric film
30. Interdigital transducer
31. Interdigital electrode
32. Bus bar
41. Mass loading block
51. High acoustic velocity dielectric layer
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Please refer to fig. 1 to 14. It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
Comparative example one
After analyzing the technical problems explained in the background section, it is considered that the capacitance per unit area of the device can be improved by increasing the metallization ratio of the interdigital electrode in the lamb wave resonator, and referring to fig. 1, a schematic cross-sectional structure of the lamb wave resonator in this comparative example is shown, where the lamb wave resonator includes a substrate 10, a piezoelectric film 20 located above the substrate 10, and an interdigital transducer 30 located above the piezoelectric film 20, the interdigital transducer 30 includes a plurality of interdigital electrodes 31 arranged at intervals, wherein the substrate 10 is a silicon material, the piezoelectric film 20 is a 128-degree Y-cut lithium niobate film and has a thickness of 300nm, the interdigital electrodes 31 are aluminum materials, the thickness of the interdigital electrodes 31 is 100nm, and the center-to-center spacing of the interdigital electrodes 31 is 2 μm. Referring to fig. 2, the simulation admittance curves of the lamb wave resonator in fig. 1 with different metallization rates of the interdigital electrodes (wherein the solid line, the dotted line and the dash-dot line respectively correspond to the admittance curves of the resonator with the metallization rates of 0.2, 0.4, 0.6 and 0.8) are shown, and after comparing the performances of the devices with different metallization rates of the interdigital electrodes, the performances of the lamb wave resonator are found to correspond to the maximum electromechanical coupling coefficient with respect to the admittance characteristics when the metallization rate is 0.2 (as shown by the solid line in fig. 2), and meanwhile, the simulation admittance curves have the minimum spurious modes, and as the metallization rate of the interdigital electrodes increases, the spurious modes of the devices also increase significantly, and even if the unit area capacitance of the devices is increased, the devices are not practically applicable. Therefore, the simple increase of the metallization rate to increase the capacitance per unit area of the device cannot completely solve the problem of limited practical application scenes of the lamb wave resonator, and a new resonator structure needs to be designed to solve the problem of stray mode increase caused by the increase of the metallization rate. Through multiple experiments, the invention provides the following technical scheme, the metallization rate of the interdigital electrode is increased, the resonator is ensured not to generate more stray modes, the capacitance of the unit area of the device is improved, and the high quality factor of the device is ensured.
Example 1
Referring to fig. 3 and 4, fig. 3 is a schematic cross-sectional view of a first type of a lamb wave resonator, fig. 4 is a schematic top view of the lamb wave resonator shown in fig. 3, and the lamb wave resonator includes a substrate 10, an interdigital transducer 30 and a mass load layer (not shown in fig. 3).
Specifically, as shown in fig. 3, a piezoelectric film 20 is disposed above the substrate 10, the interdigital transducer 30 is disposed above the piezoelectric film 20, as shown in fig. 4, the interdigital transducer 30 includes a plurality of interdigital electrodes 31 spaced and staggered in a horizontal direction, the metallization rate of the interdigital electrodes 31 is greater than 0.5, including but not limited to 0.55, 0.6, 0.65, 0.7, 0.75 and 0.8, the "metallization rate" is the ratio of the width of the interdigital electrode in the interdigital transducer to half the wavelength of a resonator, and the value of the wavelength of the resonator is the same as the distance between two adjacent interdigital electrodes in the plurality of interdigital electrodes connected by the same bus bar; the mass loading layer is located above one surface of the interdigital electrode 31 far away from the piezoelectric film 20, and comprises a plurality of mass loading blocks 41, wherein at least one mass loading block 41 is located above each interdigital electrode 31, and the width of the mass loading block 41 is smaller than that of the interdigital electrode 31.
Specifically, the metallization ratio of the interdigital electrode in the lamb wave resonator of the embodiment is greater than 0.5, and the capacitance per unit area of the lamb wave resonator can be improved, so that the whole volume of equipment or a device with the lamb wave resonator is ensured to be within a preset range, the system integration level is improved, and the application field is expanded. Further, the mass load layer is added, so that a large number of stray modes generated by the first-order antisymmetric lamb wave mode caused by the large metallization rate of the interdigital electrode can be greatly reduced, and the capacitance of the unit area of the resonator is improved while other working performances of the resonator are not influenced.
As an example, the substrate 10 includes a single material layer or a laminated structure formed by two different material layers, and the material of the substrate 10 includes at least one of silicon, silicon dioxide and silicon carbide, such as a silicon substrate, a silicon-silicon dioxide laminated structure, a silicon dioxide-silicon carbide laminated structure, and the like, and the reason for selecting the above materials as the substrate is that the above materials all have the characteristics of easy etching, high resistivity and high sound velocity, and are suitable for being used as the substrate of the resonator of the present embodiment, so that the efficiency and structural stability during manufacturing the resonator can be ensured while the working performance of the resonator is also ensured to a certain extent.
As an example, the lamb wave resonator further comprises an air cavity 11 or a bragg reflection layer, as shown in fig. 3, the air cavity 11 is located in the substrate 10 and below the interdigital electrode 31 such that the interdigital electrode 31 is suspended above the air cavity 11, and the bragg reflection layer (not shown in the drawing) is located above the substrate 10. The air cavity is formed by etching an opening on a structure above the substrate and then performing vapor phase isotropic etching, or alternatively, a sacrificial layer is formed on the substrate in advance and etched to form the air cavity, which can be selected based on actual requirements and is not particularly limited herein.
As an example, as shown in fig. 4, the interdigital ring device 30 further includes two bus bars 32 disposed opposite to each other, a plurality of interdigital electrodes 31 are alternately arranged between the two bus bars 32 and adjacent interdigital electrodes 31 are respectively connected to the two bus bars 32. Further, the number of interdigital transducers is set based on actual needs, preferably in pairs, and is not particularly limited herein.
By way of example, the interdigital electrode 31 has a thickness ranging from 10nm to 500nm, including but not limited to 50nm, 100nm, 250nm and 400nm, preferably from 10nm to 100nm, the thinner the thickness is, the more advantageous the resonator operation performance is.
As an example, the material of the piezoelectric film 20 includes at least one of lithium niobate and lithium tantalate, and the material of the piezoelectric film 20 is preferably Z-tangential or 128-degree Y-tangential, so as to obtain a larger electromechanical coupling coefficient, and of course, other single crystal piezoelectric materials having excellent properties in terms of electromechanical coupling coefficient and quality factor Q are also suitable for manufacturing the piezoelectric film of the present embodiment.
As an example, the lamb wave resonator further includes a high acoustic velocity dielectric film, the Gao Shengsu dielectric film is located above the piezoelectric film 20 and/or below the piezoelectric film 20, and the propagation speed of the acoustic wave in the Gao Shengsu dielectric film is greater than the propagation speed of the acoustic wave in the piezoelectric film 20 (it should be noted that, herein, "the propagation speed of the acoustic wave in the Gao Shengsu dielectric film is greater than the propagation speed of the acoustic wave in the piezoelectric film 20" means a propagation speed relationship of acoustic velocity in the same mode), and the difference therebetween is greater. Under the condition of high-sound-velocity dielectric film, the mass load layer and the Gao Shengsu dielectric film cooperate to ensure that the lamb wave resonator keeps a clear and clean main mode on the premise of greatly expanding the metallization rate, so that the key performances of high working efficiency, high electromechanical coupling coefficient and the like of the device are ensured while the capacitance per unit area of the device is greatly improved.
As an example, the center-to-center spacing between adjacent two of the interdigital electrodes 31 satisfies p>2(h 1 +h 2 ) Wherein p is the center-to-center spacing between two adjacent interdigital electrodes 31, h 1 H is the thickness of the piezoelectric film 20 2 For the thickness of the Gao Shengsu dielectric film, when the center-to-center distance satisfies the above numerical conditions, a relatively large mechanical coupling coefficient can be obtained, and it should be noted that when the Gao Shengsu dielectric film includes a plurality of high acoustic velocity dielectric layers, the overall thickness of the plurality of high acoustic velocity dielectric layers is the thickness of the Gao Shengsu dielectric film.
As an example, referring to fig. 3 and fig. 5 to fig. 7, which respectively show four schematic longitudinal sectional structures of the lamb wave resonator, the Gao Shengsu dielectric film includes at least one high-sound-velocity dielectric layer 51, and the position of the high-sound-velocity dielectric layer 51 includes at least one of being located between the piezoelectric film 20 and the interdigital electrode 31 (as shown in fig. 3 and fig. 5 to fig. 7), being located between the piezoelectric film 20 and the substrate 10 (as shown in fig. 5 to fig. 7), being located above the piezoelectric film 20 and at least covering the exposed surface of the interdigital electrode 31 (as shown in fig. 6 and fig. 7), wherein when the high-sound-velocity dielectric layer 51 is located above the piezoelectric film 20, the high-sound-velocity dielectric layer 51 only covers the exposed surface of the interdigital electrode 31 (as shown in fig. 6) or simultaneously covers the exposed surface of the interdigital electrode 31 and the mass load layer (as shown in fig. 7), it is required that, although the situation that the high-sound-velocity dielectric layer is not shown between the piezoelectric film and the substrate or is located above the substrate is only or only in the exposed surface of the substrate, and the situation that the high-sound-velocity dielectric layer is not shown is actually shown, and the situation is not shown, but the situation is that the situation is listed above the high-sound-velocity dielectric layer is only is actually, and the situation is only shown, and the situation is only above the situation.
As an example, the material of the high acoustic velocity dielectric layer 51 includes at least one of aluminum nitride, silicon carbide, and diamond, and when the Gao Shengsu dielectric film includes a plurality of high acoustic velocity dielectric layers 51, the material of each of the high acoustic velocity dielectric layers 51 is the same or different. The reason for selecting the material to manufacture the high sound velocity dielectric layer is that the material has the characteristic of high heat conductivity, can achieve the effect of better eliminating stray modes, and can also play roles of improving the power capacity of the device and enhancing the temperature stability.
By way of example, the mass-loaded layer has a thickness in the range of 10nm to 500nm, including but not limited to 50nm, 100nm, 250nm, and 400nm; the ratio of the width of the mass loading block 41 to the width of the interdigital electrode 31 is less than 0.5, including but not limited to 0.45, 0.4, 0.35 and 0.3, preferably less than 0.2, if the ratio is greater than 0.5, the overall performance of the resonator may be lost, and further, the mass loading block 41 may be centrally disposed on the interdigital electrode 31 or disposed at a position offset from the center of the interdigital electrode 31.
As an example, the material of the mass loading layer includes at least one of a metal material including at least one of aluminum, copper, gold, and platinum, and a dielectric material including at least one of aluminum nitride, silicon dioxide, and silicon carbide.
Referring to fig. 3 to 7, the present embodiment further provides a method for manufacturing a lamb wave resonator, which includes the following steps:
providing a substrate 10, wherein a piezoelectric film 20 is arranged above the substrate 10;
forming an interdigital transducer 30 above the piezoelectric film 20, wherein the interdigital transducer 30 comprises a plurality of interdigital electrodes 31 which are spaced in the horizontal direction and are staggered, and the metallization rate of the interdigital electrodes 31 is greater than 0.5;
a mass loading layer is formed on a side of the interdigital transducer 30 away from the piezoelectric film 20, the mass loading layer comprising a plurality of mass loading blocks 41, each of the mass loading blocks 41 having a width smaller than the width of the interdigital electrode 31 being provided above each of the interdigital electrodes 31.
As an example, the method of manufacturing further comprises the step of forming a high acoustic speed dielectric film, the step of forming a high acoustic speed dielectric film being performed before forming the piezoelectric film and/or after forming the piezoelectric film, the propagation speed of the acoustic wave in the Gao Shengsu dielectric film being greater than the propagation speed of the acoustic wave in the piezoelectric film.
According to the lamb wave resonator, the width of the interdigital electrode is greatly increased (namely, the metallization rate of the interdigital electrode is relatively high) on the basis of a conventional resonator structure, so that the capacitance of a unit area of a device is remarkably increased, the problem that an XBAR device is overlarge in practical application is effectively solved, the system integration level is effectively improved, the application scene of the device is effectively expanded, and meanwhile, a mass load layer is additionally arranged to keep the performances of high working efficiency, high electromechanical coupling coefficient and the like of the device; and the high sound velocity dielectric film is additionally arranged according to actual needs to inhibit stray modes generated along with the increase of the metallization rate, so that the comprehensive working performance of the device is further improved. The manufacturing method of the lamb wave resonator can manufacture the lamb wave resonator with high unit area capacitance, and has the advantages of simple manufacturing process steps, mature process, low cost and strong practical applicability.
Example two
The present embodiment provides a specific lamb wave resonator, as shown in fig. 8, which includes a substrate 10, an interdigital transducer 30, and a mass load layer, wherein the interdigital transducer 30 includes a plurality of interdigital electrodes 31 arranged at intervals, and the mass load layer includes a plurality of mass load blocks 41.
Specifically, the substrate 10 is a silicon material, the piezoelectric film 20 is a 128-degree Y-cut lithium niobate film, the thickness of the piezoelectric film 20 is 300nm, the interdigital electrode 31 is an aluminum material, the thickness of the interdigital electrode 31 is 50nm, the metallization ratio of the interdigital transducer 30 is 0.8, the center-to-center distance between two adjacent interdigital electrodes 31 is 2 μm, the mass loading layer is an aluminum material, the thickness of the mass loading layer is 50nm, and the ratio of the width of the mass loading block 41 to the width of the interdigital electrode 31 is 0.2.
Example III
The present embodiment provides a specific lamb wave resonator, which is different from the second embodiment in that a high-sound-speed dielectric film is disposed in the present embodiment, and a high-sound-speed dielectric film is not disposed in the second embodiment, as shown in fig. 3, and includes a substrate 10, an interdigital transducer 30, a high-sound-speed dielectric film, and a mass load layer.
Specifically, the substrate 10 is made of a silicon material, the piezoelectric film 20 is a 128-degree Y-cut lithium niobate film, the thickness of the piezoelectric film 20 is 270nm, the Gao Shengsu dielectric film is aluminum nitride, the thickness of the Gao Shengsu dielectric film is 30nm, the interdigital electrode 31 is made of an aluminum material, the thickness of the interdigital electrode 31 is 50nm, the metallization ratio of the interdigital transducer 30 is 0.8, the center-to-center distance between two adjacent interdigital electrodes 31 is 2 μm, the mass loading layer is made of an aluminum material, the thickness of the mass loading layer is 50nm, and the ratio of the width of the mass loading block 41 to the width of the interdigital electrode 31 is 0.2.
Comparative example two
This comparative example provides a specific lamb wave resonator, which is different from the third example in that the present comparative example is provided with only a high acoustic velocity dielectric film without a mass loading layer and the third example is provided with both a high acoustic velocity dielectric film and a mass loading layer, as shown in fig. 9, and includes a substrate 10, an interdigital transducer 30, and a high acoustic velocity dielectric film.
Specifically, the substrate 10 is made of a silicon material, the piezoelectric film 20 is a 128-degree Y-cut lithium niobate film, the thickness of the piezoelectric film 20 is 270nm, the Gao Shengsu dielectric film is aluminum nitride, the thickness of the Gao Shengsu dielectric film is 30nm, the interdigital electrode 31 is made of an aluminum material, the thickness of the interdigital electrode 31 is 100nm, the metallization ratio of the interdigital transducer 30 is 0.8, and the center-to-center distance between two adjacent interdigital electrodes 31 is 2 μm.
Next, the operation performance of the lamb wave resonator according to the first and second comparative examples and the first and second examples will be compared to explain the improvement of the performance and the improvement of the capacitance per unit area of the lamb wave resonator according to the present invention.
Referring to fig. 10 and 11 in comparison, fig. 10 is a schematic displacement diagram of a lamb wave resonator in the first-order anti-symmetric lamb wave resonance mode when the metallization ratio of the lamb wave resonator in the first-order anti-symmetric lamb wave resonance mode in the third embodiment is shown in fig. 10, where in the first-order anti-symmetric lamb wave resonance mode, the interdigital electrode hardly participates in vibration, the displacement under the interdigital electrode is small, the displacement and deformation only occur in the area between the interdigital electrodes, which means that the metallization ratio of the interdigital electrode determines the width of the resonance area in the resonator, the larger the metallization ratio is, the smaller the width of the resonance area is, and the larger the metallization ratio is directly related to the coupling coefficient of the resonator, the smaller the coupling coefficient is, so that the spurious modes are more (as can be known based on fig. 2), while increasing the metallization ratio of the interdigital electrode, the coupling coefficient is kept at a certain level, and the spurious modes are kept as small as possible. Comparing fig. 10 and fig. 11, although the metallization ratio is increased after the mass loading layer is added, it can be seen from fig. 11 that the resonance area of the resonator according to the third embodiment is determined by the width of the mass loading block and not by the metallization ratio of the interdigital electrode, so that the resonance mode is substantially the same as the smaller metallization ratio, and the coupling coefficient is ensured, thereby reducing the spurious mode.
Referring to fig. 12, a graph of an admittance characteristic simulation of a lamb wave resonator in the third embodiment, the first comparative embodiment and the second comparative embodiment is shown (wherein, the solid line, the dotted line and the dotted line respectively correspond to the admittance curves of the resonator structures in the third embodiment, the first comparative embodiment and the second comparative embodiment), and the second comparative embodiment has the advantages that, compared with the device structure in the second comparative embodiment, the frequency of the resonator is improved by replacing 10% of the thickness of the piezoelectric film with a high-sound-speed dielectric film, one stray mode is eliminated, the second comparative embodiment is compared with the three phases of the embodiment, and the admittance curves of the resonator are further increased by replacing half of the thickness of the interdigital electrode with a mass load structure, and more importantly, the admittance curves of the resonator are shown as smooth main mode and have no stray mode basically, and the electromechanical coupling coefficient is also greatly improved.
Referring to fig. 13, a comparison diagram of normalized capacitance per unit area of the lamb wave resonators in the first, second and third embodiments is shown (wherein the circles, triangles and squares correspond to the normalized capacitance per unit area of the resonators in the third, second and first embodiments, respectively), and it should be noted that the capacitance of the resonator is normalized for the first embodiment at a metallization rate of 0.2. As can be seen from fig. 13, in the lamb wave resonator structure according to the third embodiment, on the premise of keeping the cleanliness of the main mode, the capacitance per unit area is improved by 50% by greatly increasing the metallization rate, which means that the total area of the device can be reduced by 30% in practical application, the system integration level is greatly improved, the number of devices produced by a single wafer is increased, and the production cost is greatly reduced. In the case where the actual situation allows (without considering the influence caused by more spurious modes or the influence of the spurious modes is negligible, refer to the following for understanding), the lamb wave resonator structure described in the second embodiment is adopted, the capacitance per unit area will be improved by 150%, which will reduce the total area of the device by 60%, but based on the following, it is known that the higher probability will exist at this time that there is a higher spurious mode that affects the working performance of the resonator, so that the specific structure of the resonator can be selected based on the actual requirement.
Referring to fig. 14, which is a graph showing an admittance characteristic simulation comparison of lamb wave resonators in the second embodiment and the third embodiment, compared with the device structure of the third embodiment, the second embodiment is not provided with a high-sound-velocity dielectric film but is only provided with a mass loading layer, and as can be seen from fig. 14, the admittance curve of the resonator in the second embodiment has more spurious modes and smaller electromechanical coupling coefficients, which indicates that only the mass loading layer is provided without the high-sound-velocity dielectric film, and still has the high-frequency spurious modes, which means that only the mass loading layer is provided without the high-sound-velocity dielectric film, and the effect of suppressing the spurious modes cannot be achieved well. It should be noted that, since lithium niobate or lithium tantalate has a relatively large dielectric constant, the dielectric constant of the high acoustic velocity dielectric film is generally smaller than that of the piezoelectric film material used in the third embodiment, which results in a decrease in capacitance per unit area of the resonator described in the third embodiment, and may be selected as needed in practical applications.
In summary, according to the lamb wave resonator disclosed by the invention, the width of the interdigital electrode is greatly increased (namely, the metallization rate of the interdigital electrode is relatively high) on the basis of the conventional resonator structure so as to obviously increase the capacitance of the unit area of the device, the problem that the area of an XBAR device is overlarge in actual application is effectively solved, the system integration level is effectively improved, the application scene of the device is effectively expanded, and meanwhile, a mass load layer is additionally arranged so as to keep the performances of high working efficiency, high electromechanical coupling coefficient and the like of the device; and the high sound velocity dielectric film is additionally arranged according to actual needs to inhibit stray modes generated along with the increase of the metallization rate, so that the comprehensive working performance of the device is further improved. The manufacturing method of the lamb wave resonator can be used for manufacturing the lamb wave resonator with high unit area capacitance, and has the advantages of simple manufacturing process steps, mature process, low cost and strong practical applicability. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (11)
1. A lamb wave resonator, comprising:
a substrate having a piezoelectric film over the substrate;
the interdigital transducer is positioned above the piezoelectric film and comprises a plurality of interdigital electrodes which are spaced in the horizontal direction and are staggered, and the metallization rate of the interdigital electrodes is more than 0.5;
the mass load layer is positioned above one surface, far away from the piezoelectric film, of the interdigital electrode, the mass load layer comprises a plurality of mass load blocks, at least one mass load block is arranged above each interdigital electrode, and the width of each mass load block is smaller than that of each interdigital electrode.
2. The lamb wave resonator of claim 1, wherein: the thickness of the interdigital electrode ranges from 10nm to 500nm, the thickness of the mass load layer ranges from 10nm to 500nm, and the ratio of the width of the mass load block to the width of the interdigital electrode is smaller than 0.5.
3. The lamb wave resonator of claim 1, wherein: the material of the mass loading layer comprises at least one of a metal material and a dielectric material, wherein the metal material comprises at least one of aluminum, copper, gold and platinum, and the dielectric material comprises at least one of aluminum nitride, silicon dioxide and silicon carbide.
4. The lamb wave resonator of claim 1, wherein: the lamb wave resonator also comprises a high sound speed dielectric film, wherein the Gao Shengsu dielectric film is positioned above the piezoelectric film and/or below the piezoelectric film, and the propagation speed of sound waves in the Gao Shengsu dielectric film is greater than that of sound waves in the piezoelectric film.
5. The lamb wave resonator of claim 4, wherein: the center-to-center spacing between two adjacent interdigital electrodes satisfies p>2(h 1 +h 2 ) Wherein p is the center-to-center distance between two adjacent interdigital electrodes, h 1 H is the thickness of the piezoelectric film 2 Is the thickness of the Gao Shengsu dielectric film.
6. The lamb wave resonator of claim 4, wherein: the Gao Shengsu dielectric film comprises at least one high-sound-velocity dielectric layer, and the position of the high-sound-velocity dielectric layer comprises at least one of the exposed surface, which is positioned between the piezoelectric film and the interdigital electrode, between the piezoelectric film and the substrate, above the piezoelectric film and at least covers the interdigital electrode, wherein when the high-sound-velocity dielectric layer is positioned above the piezoelectric film, the high-sound-velocity dielectric layer only covers the exposed surface of the interdigital electrode or covers the exposed surface of the interdigital electrode and the mass load layer at the same time.
7. The lamb wave resonator of claim 6, wherein: the high acoustic velocity dielectric layer is made of at least one of aluminum nitride, silicon carbide and diamond, and when the Gao Shengsu dielectric film comprises a plurality of high acoustic velocity dielectric layers, the materials of the high acoustic velocity dielectric layers are the same or different.
8. The lamb wave resonator of claim 1, wherein: the lamb wave resonator also includes an air cavity or a Bragg reflection layer, the air cavity is located in the substrate and below the interdigital electrode so that the interdigital electrode is suspended above the air cavity, and the Bragg reflection layer is located above the substrate.
9. The lamb wave resonator of claim 1, wherein: the material of the piezoelectric film comprises at least one of lithium niobate and lithium tantalate.
10. The manufacturing method of the lamb wave resonator is characterized by comprising the following steps of:
providing a substrate, wherein a piezoelectric film is arranged above the substrate;
forming an interdigital transducer above the piezoelectric film, wherein the interdigital transducer comprises a plurality of interdigital electrodes which are spaced in the horizontal direction and are staggered, and the metallization rate of the interdigital electrodes is more than 0.5;
and forming a mass load layer above one surface of the interdigital transducer, which is far away from the piezoelectric film, wherein the mass load layer comprises a plurality of mass load blocks, at least one mass load block is arranged above each interdigital electrode, and the width of the mass load block is smaller than that of each interdigital electrode.
11. The method of claim 10, further comprising the step of forming a high acoustic speed dielectric film, the step of forming a high acoustic speed dielectric film being performed before and/or after forming the piezoelectric film, the propagation velocity of the acoustic wave in the Gao Shengsu dielectric film being greater than the propagation velocity of the acoustic wave in the piezoelectric film.
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| CN113114158A (en) * | 2021-05-11 | 2021-07-13 | 中国科学院上海微系统与信息技术研究所 | Lamb wave resonator and elastic wave device |
| CN115940869A (en) * | 2023-02-28 | 2023-04-07 | 锐石创芯(深圳)科技股份有限公司 | Surface acoustic wave device, filter, and electronic apparatus |
| CN116318035A (en) * | 2023-04-04 | 2023-06-23 | 天通瑞宏科技有限公司 | Surface acoustic wave resonator and wireless communication device |
| US20230336153A1 (en) * | 2022-03-24 | 2023-10-19 | Skyworks Solutions, Inc. | Multilayer interdigital transducer electrode for surface acoustic wave device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113114158A (en) * | 2021-05-11 | 2021-07-13 | 中国科学院上海微系统与信息技术研究所 | Lamb wave resonator and elastic wave device |
| US20230336153A1 (en) * | 2022-03-24 | 2023-10-19 | Skyworks Solutions, Inc. | Multilayer interdigital transducer electrode for surface acoustic wave device |
| CN115940869A (en) * | 2023-02-28 | 2023-04-07 | 锐石创芯(深圳)科技股份有限公司 | Surface acoustic wave device, filter, and electronic apparatus |
| CN116318035A (en) * | 2023-04-04 | 2023-06-23 | 天通瑞宏科技有限公司 | Surface acoustic wave resonator and wireless communication device |
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