CN118944630A - A surface acoustic wave resonator - Google Patents
A surface acoustic wave resonator Download PDFInfo
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- CN118944630A CN118944630A CN202411419517.4A CN202411419517A CN118944630A CN 118944630 A CN118944630 A CN 118944630A CN 202411419517 A CN202411419517 A CN 202411419517A CN 118944630 A CN118944630 A CN 118944630A
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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 elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02543—Characteristics of substrate, e.g. cutting angles
- H03H9/02551—Characteristics of substrate, e.g. cutting angles of quartz substrates
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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 elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02637—Details concerning reflective or coupling arrays
- H03H9/02653—Grooves or arrays buried in the substrate
- H03H9/02661—Grooves or arrays buried in the substrate being located inside the interdigital transducers
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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 elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
- H03H9/02834—Means for compensation or elimination of undesirable effects of temperature influence
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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 elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/13—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials
- H03H9/131—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials consisting of a multilayered structure
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Abstract
The invention discloses a surface acoustic wave resonator, which comprises: a composite wafer; the composite wafer comprises a support substrate and a piezoelectric layer, wherein the support substrate is arranged in a laminated manner; the interdigital transducer is positioned on one side of the composite wafer; the interdigital transducer comprises a plurality of interdigital electrodes, the plurality of interdigital electrodes comprise a plurality of first electrodes and a plurality of second electrodes, the first electrodes and the second electrodes are sequentially and alternately arranged along a first direction and extend along a second direction, and the extension length of the first electrodes is smaller than that of the second electrodes along the second direction; wherein, the thickness H1 of the support substrate satisfies: h1 is more than or equal to 150 mu m and less than or equal to 2000 mu m; the thickness H2 of the piezoelectric layer satisfies: h2 with the wavelength of 300nm or less less than or equal to 1500nm. By adopting the technical means, the composite wafer comprises the support substrate and the piezoelectric layer which are arranged in a laminated way, so that the surface acoustic wave resonator has a good heat sink effect, can accelerate heat dissipation, and improves the power tolerance, thereby improving the performance of the resonator.
Description
Technical Field
The invention relates to the technical field of filters, in particular to a surface acoustic wave resonator.
Background
In recent years, mobile communication technology has rapidly developed. The rf front end is a key module for mobile communication, and as one of core components of the rf front end, the acoustic filter has received extensive attention from academia and industry.
At present, along with the introduction of the composite wafer, the performance of the acoustic filter is greatly improved, but the composite wafer at the present stage is generally composed of four layers, a transition layer is arranged between a supporting substrate and a piezoelectric layer, and the transition layer can influence the heat dissipation and the power of the surface acoustic wave resonator, so that the performance of the filter is influenced.
Disclosure of Invention
The embodiment of the invention provides a surface acoustic wave resonator, which is used for realizing a better heat sink effect of the surface acoustic wave resonator, accelerating heat dissipation, improving power tolerance and further improving the performance of the resonator.
The embodiment of the invention provides a surface acoustic wave resonator, which comprises:
a composite wafer; the composite wafer comprises a support substrate and a piezoelectric layer which are arranged in a laminated manner;
an interdigital transducer positioned on one side of the composite wafer; the interdigital transducer comprises a plurality of interdigital electrodes, wherein the interdigital electrodes comprise a plurality of first electrodes and a plurality of second electrodes, the first electrodes and the second electrodes are sequentially and alternately arranged along a first direction and extend along a second direction, and the extension length of the first electrodes is smaller than that of the second electrodes along the second direction; the first direction intersects the second direction;
wherein, the thickness H1 of the support substrate satisfies: h1 is more than or equal to 150 mu m and less than or equal to 2000 mu m; the thickness H2 of the piezoelectric layer satisfies: h2 with the wavelength of 300nm or less less than or equal to 1500nm.
Optionally, the tangential direction of the piezoelectric layer is rotated by α in the second direction, and the in-plane edge direction is rotated by β in the first direction, wherein α is 0 ° or more and 90 ° or less, and β is 0 ° or more and 20 ° or less.
Optionally, the wavelength of the surface acoustic wave resonator is λ;
wherein, lambda is more than or equal to 800nm and less than or equal to 4 mu m, and 0.8H2 is less than or equal to lambda is less than or equal to 4H2.
Optionally, the thickness H3 of the interdigital electrode satisfies: h3 with the wavelength of 30nm or less not more than 900nm, and H3 is less than or equal to 0.6H2.
Optionally, the thickness H3 of the interdigital electrode satisfies: h3 is more than or equal to 0.02λ and less than or equal to 0.25λ.
Optionally, along the first direction, the width D1 of the interdigital electrode satisfies: d1 is less than or equal to 150nm less than or equal to 1.5 mu m;
along the first direction, the width D2 of the gap between two adjacent interdigital electrodes satisfies: d2 of 150nm or less less than or equal to 1.5 mu m.
Optionally, along the second direction, the second electrode includes a first electrode subsection and a second electrode subsection;
in the false finger region, the first electrode subsections and the first electrodes are sequentially and alternately arranged along the first direction and extend along the second direction;
In the effective aperture area, a plurality of the second electrode subsections are arranged along the first direction and all extend along the second direction;
wherein, along the second direction, the dimension W of the effective aperture region satisfies: w is more than or equal to 8 μm and less than or equal to 500 μm.
Optionally, the surface acoustic wave resonator further includes: a plurality of reflective gratings;
The reflecting grating is positioned at least at one side of the interdigital transducer; the reflective gratings are arranged along the first direction and extend along the second direction.
Optionally, the support substrate comprises high resistance silicon, sapphire, spinel, silicon carbide, or diamond;
The piezoelectric layer includes lithium tantalate.
Optionally, the interdigital electrode includes at least one of aluminum, copper, gold, silver, platinum, and titanium.
According to the technical scheme provided by the embodiment of the invention, the composite wafer comprises the support substrate and the piezoelectric layer which are arranged in a laminated manner, namely, the composite wafer is formed by only two layers, compared with the scheme that the composite wafer in the prior art comprises the support substrate, the mode control layer, the functional layer and the piezoelectric layer, the preparation process of the composite wafer can be simplified, and the surface acoustic wave resonator is beneficial to having better heat sink effect, accelerating heat dissipation, improving power tolerance and further improving performance of the surface acoustic wave resonator by reducing the transition layer between the support substrate and the piezoelectric layer. Further, the thickness H1 of the support substrate satisfies: h1 is more than or equal to 150 mu m and less than or equal to 2000 mu m; the thickness H2 of the piezoelectric layer satisfies: the H2 is more than or equal to 300nm and less than or equal to 1500nm, so that the thicknesses of the support substrate and the piezoelectric layer are moderate, the bandwidth and the Q value of the surface acoustic wave resonator are improved, and the performance of the surface acoustic wave resonator is further improved.
Drawings
Fig. 1 is a schematic structural diagram of a surface acoustic wave resonator according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of the SAW filter of FIG. 1 along section line A-A';
FIG. 3 is a schematic diagram of a simulated admittance curve of a first SAW resonator provided by an embodiment of the present invention;
fig. 4 is a schematic view of a main wave shape of an acoustic wave of a first surface acoustic wave resonator according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a slowness curve of a first SAW resonator provided in an embodiment of the present invention;
FIG. 6 is a schematic diagram of a simulated admittance curve of a second surface acoustic wave resonator according to an embodiment of the present invention;
Fig. 7 is a schematic view of a main wave shape of an acoustic surface wave resonator according to a second embodiment of the present invention;
fig. 8 is a schematic diagram of a slowness curve of a second saw resonator according to an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
Fig. 1 is a schematic structural diagram of a surface acoustic wave resonator according to an embodiment of the present invention, and fig. 2 is a schematic structural diagram of a cross section of a surface acoustic wave filter along a section line A-A' corresponding to fig. 1, where the surface acoustic wave resonator includes a composite wafer 10 as shown in fig. 1 and 2; the composite wafer 10 includes a support substrate 101 and a piezoelectric layer 102 stacked; an interdigital transducer 20 located on one side of the composite wafer 10; the interdigital transducer 20 includes a plurality of interdigital electrodes 201, the plurality of interdigital electrodes 201 including a plurality of first electrodes 2011 and a plurality of second electrodes 2012, the first electrodes 2011 and the second electrodes 2012 being alternately arranged in sequence along a first direction (X direction as shown in fig. 1) and each extending along a second direction (Y direction as shown in fig. 1), along the second direction Y, an extension length of the first electrodes 2011 being smaller than an extension length of the second electrodes 2012; the first direction X intersects the second direction Y; wherein the thickness H1 of the support substrate 101 satisfies: h1 is more than or equal to 150 mu m and less than or equal to 2000 mu m; the thickness H2 of the piezoelectric layer 102 satisfies: h2 with the wavelength of 300nm or less less than or equal to 1500nm.
Specifically, the interdigital transducer 20 further includes a bus bar 1013, and the interdigital electrode 201 is electrically connected to the bus bar 1013, and when an alternating current signal of a certain frequency is applied to the bus bar 1013, a surface acoustic wave can be generated. The surface acoustic wave is mainly concentrated in the effective aperture area aa. I.e. the active region, and propagates mainly in the first direction X, but there is also a part of the surface acoustic wave, i.e. the transverse wave, propagating and leaking in the second direction Y to the bus bar side.
Specifically, the interdigital electrode 201 is located above the piezoelectric layer 102 in the composite wafer 10. The interdigital electrode 201 includes a first electrode 2011 and a second electrode 2012, and the first electrode 2011 and the second electrode 2012 form a comb-like structure. Along the second direction Y, the extension length of the first electrode 2011 is smaller than the extension length of the second electrode 2012, that is, the first electrode 2011 is a short finger electrode, that is, a dummy finger electrode, and the second electrode 2012 is a long finger electrode, that is, a real finger electrode.
Specifically, the composite wafer 10 includes a support substrate 101 and a piezoelectric layer 102 that are stacked, i.e., no intermediate transition layer is included between the support substrate 101 and the film layer of the piezoelectric layer 102. As a comparative example, a composite wafer in the prior art includes a support substrate, a mode control layer, a functional layer, and a piezoelectric layer, i.e., a film layer consisting of four stacked layers. Therefore, the composite wafer 10 provided in the embodiment of the invention only includes the film layer provided by the two laminated layers, so that the preparation method of the composite wafer 10 is simple. The intermediate transition layer is not included between the film layers of the support substrate 101 and the piezoelectric layer 102, so that the surface acoustic wave resonator has better heat sink effect, heat dissipation can be quickened, power tolerance is improved, and further performance of the surface acoustic wave resonator is improved.
It should be noted that the preparation method of the composite wafer 10 includes:
And step 1, providing a supporting substrate and a piezoelectric layer, and cleaning the surfaces of the supporting substrate and the piezoelectric layer. Wherein at least one of the support substrate and the piezoelectric layer is a polished surface, which may be defined as a first surface. Preferably, the support substrate comprises a polished face and the piezoelectric layer comprises a polished face.
And 2, aligning and bonding the polished surface of the support substrate and the polished surface of the piezoelectric layer by adopting a direct bonding method to obtain a bonding structure.
And 3, grinding and thinning the piezoelectric layer in the bonding structure until the thickness of the piezoelectric layer meets the application requirement.
And 4, polishing the surface of the thinned piezoelectric layer to make the surface smooth and the thickness of the piezoelectric layer identical to the required thickness, thereby completing the preparation of the composite wafer.
Further, the thickness H1 of the support substrate 101 satisfies: the thickness of the supporting substrate 101 is moderate, and H1 is more than or equal to 150 mu m and less than or equal to 2000 mu m, so that the preparation is convenient, and the performance of the resonator can be improved. Illustratively, H1<150 μm, it is difficult to prepare the support substrate 101 with a thin thickness. Preferably, the method comprises the steps of, H1 is more than or equal to 250 mu m and less than or equal to 1000 mu m.
Further, the thickness H2 of the piezoelectric layer 102 satisfies: the thickness of the piezoelectric layer 102 is moderate, so that the preparation is convenient, and the bandwidth and Q value of the surface acoustic wave resonator can be improved. Preferably, H2 is less than or equal to 500nm and less than or equal to 1000nm.
According to the surface acoustic wave resonator provided by the embodiment of the invention, the composite wafer comprises the support substrate and the piezoelectric layer which are arranged in a laminated way, namely, the composite wafer is formed by only two layers, so that on one hand, the preparation process of the composite wafer can be simplified, and the surface acoustic wave resonator is beneficial to having a better heat sink effect, accelerating heat dissipation and improving the power tolerance by reducing the transition layer between the support substrate and the piezoelectric layer, thereby improving the performance of the surface acoustic wave resonator. Further, the thickness H1 of the support substrate satisfies: h1 is more than or equal to 150 mu m and less than or equal to 2000 mu m; the thickness H2 of the piezoelectric layer satisfies: the H2 is more than or equal to 300nm and less than or equal to 1500nm, so that the thicknesses of the support substrate and the piezoelectric layer are moderate, the bandwidth and the Q value of the surface acoustic wave resonator are improved, and the performance of the surface acoustic wave resonator is further improved.
Alternatively, with continued reference to fig. 1 and 2, the tangential direction of the piezoelectric layer 102 is rotated by α in the second direction Y and the in-plane edge direction is rotated by β in the first direction X, wherein 0+.alpha.ltoreq.90°, 0+.beta.ltoreq.20°.
Specifically, since the piezoelectric wafer is a single crystal wafer before the piezoelectric layer is cut, in order to ensure the direction of the piezoelectric layer 102, the direction of the tangential plane is rotated by α ° along the second direction Y, that is, αy, when the piezoelectric wafer is cut. Specifically, the in-plane edge direction of the piezoelectric layer 102 can be understood as the propagation direction of the acoustic surface wave, that is, the in-plane edge direction is βx. By setting alpha to be more than or equal to 0 DEG and less than or equal to 90 DEG and beta to be more than or equal to 0 DEG and less than or equal to 20 DEG, the wave speed of the surface acoustic wave can be improved, the main wave response of the sound wave is enhanced, the rectangular degree of the filter is improved, and the performance of the surface acoustic wave resonator is improved.
Optionally, with continued reference to fig. 1, the saw resonator has a wavelength λ; wherein, lambda is more than or equal to 800nm and less than or equal to 4 mu m, and 0.8H2 is less than or equal to lambda is less than or equal to 4H2.
Specifically, the wavelength λ of the surface acoustic wave resonator can be understood as the sum of the width of the gap between two adjacent interdigital electrodes 201 and the width of a single interdigital electrode 201 in the first direction. For example, the wavelength λ of the surface acoustic wave resonator may be a sum of a gap width between the first electrode 2011 and the second electrode 2012 and a second electrode width.
Preferably, λ=1.4 μm.
Specifically, with continued reference to fig. 1, along the first direction X, the width D1 of the interdigital electrode 201 satisfies: d1 is less than or equal to 150nm less than or equal to 1.5 mu m; in the first direction X, the width D2 of the gap between adjacent two interdigital electrodes 201 satisfies: 150nm is less than or equal to D2 and less than or equal to 1.5 mu m, and lambda=D1+D2, so that the wavelength lambda of the surface acoustic wave resonator is ensured to be moderate, the leakage of the surface acoustic wave is reduced, and the performance of the surface acoustic wave resonator is further improved.
Furthermore, λ is not less than 800nm and not more than 4 μm, and λ is not less than 0.8H2 and not more than 4H2, so that the surface acoustic wave can be limited at a position between the interdigital electrode 201 and the piezoelectric layer 102, leakage of the surface acoustic wave is prevented, and performance of the surface acoustic wave resonator can be improved.
Alternatively, with continued reference to fig. 2, the thickness H3 of the interdigital electrode 201 satisfies: h3 with the wavelength of 30nm or less not more than 900nm, and H3 is less than or equal to 0.6H2.
Specifically, the interdigital electrode 201 includes at least one of aluminum, copper, gold, silver, platinum, and titanium, that is, as a possible embodiment, the material of the interdigital electrode 201 may be a single metal material, that is, the interdigital electrode 201 includes only one layer of metal material. As another possible embodiment, the interdigital electrode 201 is an alloy composed of a plurality of metal materials. When the interdigital electrode 201 is made of multiple metal materials, the interdigital electrode 201 includes multiple metal layers, and at least one of the metal layers is a bulk layer, and at this time, the thickness of the interdigital electrode 201 is the sum of the thicknesses of each metal layer, i.e., the total thickness. The material of the main body layer is aluminum or an alloy taking aluminum as a main element, and the thickness of the main body layer accounts for more than 70% of the total thickness of the interdigital electrode.
Preferably, the thickness H3 of the interdigital electrode 201 is 60 nm.ltoreq.H2.ltoreq.400 nm.
Further, H3 is not more than 0.6H2, so that the surface acoustic wave can be limited at the position between the interdigital electrode 201 and the piezoelectric layer 102, the surface acoustic wave leakage is prevented, and the performance of the surface acoustic wave resonator can be improved.
The thickness of the interdigital electrode 201 may be the thickness of the first electrode 2011 or the thickness of the second electrode 2012. It can be appreciated that in the same resonator, the first electrode 2011 and the second electrode 2012 are completed in one step by using an etching process, so that the thickness of the first electrode 2011 is equal to the thickness of the second electrode 2012.
Alternatively, with continued reference to fig. 2, the thickness H3 of the interdigital electrode 201 satisfies: h3 is more than or equal to 0.02λ and less than or equal to 0.25λ.
Specifically, 0.02λ is less than or equal to h3 and less than or equal to 0.25λ, so that the thickness of the interdigital electrode 201 is moderate, and the surface acoustic wave can be limited between the interdigital electrode 201 and the piezoelectric layer 102, so that acoustic wave leakage can be reduced, and the Q value of the surface acoustic wave resonator is improved.
It should be noted that 0.024 μm is less than or equal to (h3×λ)/h2 is less than or equal to 2.4 μm, so that the performance of the surface acoustic wave resonator can be further ensured.
Optionally, with continued reference to fig. 1, in the second direction Y, the second electrode 2012 includes a first electrode segment 2012-1 and a second electrode segment 2012-2; in the finger prosthesis region bb, the first electrode segments 2012-1 and the first electrodes 2011 are alternately arranged in sequence along the first direction X and each extend along the second direction Y; in the effective aperture area aa, a plurality of second electrode segments 2012-2 are arranged along the first direction X and each extend along the second direction Y; wherein, along the second direction Y, the size W of the effective aperture area aa satisfies: w is more than or equal to 8 μm and less than or equal to 500 μm.
Specifically, the effective aperture area aa includes only the second electrode segment 2012-2 of the second electrode 2012, and the surface acoustic wave is mainly concentrated in the effective aperture area aa. The finger prosthesis area bb includes a first electrode 2012-1 and a first electrode 2011, and by setting the first electrode 2011, the surface acoustic wave leaking along the second direction Y can be reflected back to the effective aperture area aa, so that the leakage of the sound wave can be reduced, and the Q value of the surface acoustic wave resonator can be improved.
Specifically, along the second direction Y, the size W of the effective aperture area aa satisfies: w is more than or equal to 8 mu m and less than or equal to 500 mu m, so that the size of an effective aperture area aa is moderate, the acoustic wave leakage is further reduced, and the Q value of the surface acoustic wave resonator is improved.
Optionally, with continued reference to fig. 1, the surface acoustic wave resonator further includes: a plurality of reflective gratings 30; the reflective grating 30 is located at least on one side of the interdigital transducer 20; the plurality of reflective gratings 30 are arranged along the first direction X and each extend along the second direction Y.
Specifically, the reflective grating 30 is at least located at one side of the interdigital transducer 20, that is, the reflective grating 30 may be located only at the left side or the right side of the interdigital transducer 20, and the reflective grating 30 may also be located at the left side and the right side of the interdigital transducer 20, so that the surface acoustic wave to be leaked can be reflected back to the effective aperture area aa, further, the leakage of the acoustic wave can be reduced, and the Q value of the surface acoustic wave resonator is improved.
Specifically, the reflective gratings 30 are mutually communicated, i.e., integrally disposed, so that the arrangement is simple.
It will be appreciated that the saw resonator may further comprise electrode pads, which may serve as signal terminals for connection to an external signal source.
Specifically, the preparation method of the surface acoustic wave resonator comprises the following steps:
Step 1, providing a composite wafer, and cleaning the surface of the composite wafer. The composite wafer may be a two-layer composite wafer provided in any of the above embodiments.
And 2, transferring the designed device pattern to the photoresist above the piezoelectric layer of the compound wafer by utilizing a photoetching process.
And 3, plating electrode materials above the piezoelectric layer and the photoresist by using a coating process.
And 4, removing the photoresist and the redundant electrode material above the photoresist by using a stripping process, and forming the designed device pattern by the electrode material left above the piezoelectric layer.
And step 5, performing overlay or other treatment according to actual needs.
And 6, finishing the preparation of the surface acoustic wave resonator through packaging and other subsequent processes.
Optionally, with continued reference to fig. 2, the support substrate 101 comprises high resistance silicon, sapphire, spinel, silicon carbide, or diamond; the piezoelectric layer 102 comprises lithium tantalate.
As a possible embodiment, the material of the support substrate is sapphire, and the thickness of the support substrate is 600 μm. The piezoelectric layer is made of lithium tantalate, the tangential direction of the piezoelectric layer is 42 DEG Y, the in-plane edge direction of the piezoelectric layer is 0 DEG X, and the thickness of the piezoelectric layer is 800nm. The wavelength λ=1.4 μm of the surface acoustic wave resonator, and the thickness of the interdigital electrode was 128nm. The width of the finger strip of each interdigital electrode and each reflecting grating is 400nm, the width of the gap between every two adjacent interdigital electrodes is 400nm, and the width of the gap between every two adjacent reflecting gratings is 400 nm. The acoustic apertures of the interdigital transducer and the reflective grating are both 40 μm, i.e. the size of the effective aperture area is 40 μm along the second direction. The interdigital electrode comprises a layer of bottom titanium and a layer of main body layer of aluminum, wherein the thickness of the titanium layer can be 2nm, and the thickness of the aluminum layer can be 126nm.
Based on the above parameter design, the preparation steps of the composite wafer in the SAW resonator comprise:
Step 1, providing a single-polished sapphire wafer with the thickness of 600 mu m, obtaining a single-polished lithium tantalate wafer with the tangential direction of 42 DEG Y and the in-plane edge direction of 0 DEG X, and cleaning the surfaces of the two wafers. The polished faces of the two wafers are defined as the first surface.
And 2, aligning and bonding the polished surfaces of the two wafers by adopting a direct bonding method to obtain a bonding structure.
And 3, grinding and thinning the piezoelectric layer in the bonding structure until the thickness of the lithium tantalate is about 1000nm.
And step 4, polishing the surface of the thinned piezoelectric layer to make the surface smooth and the thickness of the lithium tantalate be 800nm, thereby completing the preparation of the composite wafer.
Based on the above parameter design, the preparation steps of the surface acoustic wave resonator comprise:
And step 1, carrying out surface cleaning on the prepared composite wafer.
And 2, transferring the designed device pattern to the photoresist above the piezoelectric layer of the compound wafer by utilizing a photoetching process.
And 3, sequentially plating the piezoelectric layer and the photoresist with 2nm titanium and 126nm aluminum by using a coating process.
And 4, removing the photoresist and the redundant electrode material above the photoresist by using a stripping process, and forming the designed device pattern by the electrode material left above the piezoelectric layer.
And step 5, performing overlay or other treatment according to actual needs.
And 6, finishing the preparation of the surface acoustic wave resonator through packaging and other subsequent processes.
Fig. 3 is a schematic diagram of a simulated admittance curve of a first surface acoustic wave resonator according to an embodiment of the present invention, fig. 4 is a schematic diagram of a main wave shape of a sound wave of the first surface acoustic wave resonator according to an embodiment of the present invention, and fig. 5 is a schematic diagram of a slowness curve of the first surface acoustic wave resonator according to an embodiment of the present invention, as shown in fig. 3, in a range of 2.5GHz-2.6GHz, that is, in a range of a resonance point and an anti-resonance point, an admittance curve is smoother and has no burrs, which means that the main wave response of the surface acoustic wave resonator is strong, no obvious clutter response in a band, no obvious high-order modal clutter out of a band, and excellent performance. As shown in fig. 4, the acoustic vibration position is basically concentrated between the interdigital electrode and the lithium tantalate film layer, and less energy is leaked downwards, so that the quality factor of the device is higher, and the rectangular degree is better. As shown in FIG. 5, the abscissas each represent slowness, i.e., the reciprocal of velocity. Wherein the abscissa Sx represents slowness in a first direction and the ordinate Sy represents slowness in a second direction. In the region near sy=0, the slowness curve is concave, that is, the slowness curve of the saw resonator is not convex but is nearly straight concave, so that the transverse mode clutter will not be generated, that is, the embodiment of the invention can fundamentally solve the problem of the transverse mode clutter. Overall, the acoustic wave resonator has excellent overall performance.
As another possible embodiment, the material of the support substrate is high-resistance silicon, and the thickness of the support substrate is 525 μm. The piezoelectric layer is made of lithium tantalate, the tangential direction of the piezoelectric layer is 36 DEG Y, the in-plane edge direction of the piezoelectric layer is 0 DEG X, and the thickness of the piezoelectric layer is 500nm. The wavelength λ=1.2 μm of the surface acoustic wave resonator, and the thickness of the interdigital electrode was 96nm. The width of the finger strip of each interdigital electrode and each reflecting grating is 300nm, the width of the gap between every two adjacent interdigital electrodes is 400nm, and the width of the gap between every two adjacent reflecting gratings is 300nm. The acoustic apertures of the interdigital transducer and the reflective grating are both 25 μm, i.e. the size of the effective aperture area is 25 μm along the second direction. The interdigital electrode comprises a layer of bottom titanium and a layer of main body layer of aluminum, wherein the thickness of the titanium aluminum can be 3nm, and the thickness of the aluminum can be 93nm.
Based on the above parameter design, the preparation steps of the composite wafer in the SAW resonator comprise:
Step 1, providing a single-throw high-resistance silicon wafer with the thickness of 525 mu m, obtaining a single-throw lithium tantalate wafer with the tangential direction of 36 DEG Y and the in-plane edge direction of 0 DEG X, and cleaning the surfaces of the two wafers. The polished faces of the two wafers are defined as the first surface.
And 2, aligning and bonding the polished surfaces of the two wafers by adopting a direct bonding method to obtain a bonding structure.
And 3, grinding and thinning the piezoelectric layer in the bonding structure until the thickness of the lithium tantalate is about 700nm.
And step 4, polishing the surface of the thinned piezoelectric layer to make the surface smooth and the thickness of lithium tantalate be 500nm, thereby completing the preparation of the composite wafer.
Based on the above parameter design, the preparation steps of the surface acoustic wave resonator comprise:
And step 1, carrying out surface cleaning on the prepared composite wafer.
And 2, transferring the designed device pattern to the photoresist above the piezoelectric layer of the compound wafer by utilizing a photoetching process.
And 3, sequentially plating 3nm titanium and 93nm aluminum on the piezoelectric layer and the photoresist by using a coating process.
And 4, removing the photoresist and the redundant electrode material above the photoresist by using a stripping process, and forming the designed device pattern by the electrode material left above the piezoelectric layer.
And step 5, performing overlay or other treatment according to actual needs.
And 6, finishing the preparation of the surface acoustic wave resonator through packaging and other subsequent processes.
Fig. 6 is a schematic diagram of a simulated admittance curve of a second surface acoustic wave resonator according to an embodiment of the present invention, fig. 7 is a schematic diagram of a main wave shape of an acoustic wave of the second surface acoustic wave resonator according to an embodiment of the present invention, and fig. 8 is a schematic diagram of a slowness curve of the second surface acoustic wave resonator according to an embodiment of the present invention, as shown in fig. 6, in a range of 3.3GHz-3.5GHz, that is, in a range of a resonance point and an anti-resonance point, an admittance curve is smoother and free of burrs, which indicates that the main wave response of the surface acoustic wave resonator is strong, no obvious clutter response in a band, no obvious high-order modal clutter out of a band, and excellent performance. As shown in fig. 7, the acoustic vibration position is basically concentrated between the interdigital electrode and the lithium tantalate film layer, and less energy leaks downwards, so that the quality factor of the device is higher, and the rectangular degree is better. As shown in FIG. 8, the abscissas each represent slowness, i.e., the reciprocal of velocity. Wherein the abscissa Sx represents slowness in a first direction and the ordinate Sy represents slowness in a second direction. In the region near sy=0, the slowness curve is concave, that is, the slowness curve of the saw resonator is not convex but is nearly straight concave, so that the transverse mode clutter will not be generated, that is, the embodiment of the invention can fundamentally solve the problem of the transverse mode clutter. Overall, the acoustic wave resonator has excellent overall performance.
In summary, the surface acoustic wave resonator provided by the embodiment of the invention has better heat sink effect when being applied to an acoustic wave device by designing the integral structure of the composite wafer and the material, tangential direction and thickness of the piezoelectric layer, and the two layers of composite wafers without the intermediate transition layer, thereby accelerating heat dissipation and improving power tolerance. The accurate design of the material, tangential direction and thickness of the piezoelectric layer can strengthen the main wave response of sound waves, so that the rectangular degree of the filter is improved, and the thermal expansion inhibition effect of the supporting substrate can also be strengthened, so that the temperature stability of the device is improved. In addition, by setting the wavelength of the SAW resonator, the material and thickness of the interdigital electrode and combining with the design of the composite wafer, the intensity, frequency and bandwidth of the main wave response of the acoustic wave can be ensured to meet the expectations, and the enhancement of high-order modal clutter can be prevented. Meanwhile, due to the linkage design, the slowness curve of the sound wave in the device can be enabled to be in a flat or nearly flat concave slowness characteristic, and therefore the occurrence of transverse mode clutter is avoided. In addition, from the material design point of view, the embodiment of the invention avoids the occurrence of the transverse mode clutter from the source, solves the transverse mode clutter, avoids the complex interdigital transducer structural design, and further ensures the overall quality and yield of the device.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, and that various obvious changes, rearrangements, combinations, and substitutions can be made by those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.
Claims (10)
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