A surface acoustic wave resonator and a filter

Abstract

An embodiment of the present invention discloses a surface acoustic wave resonator and a filter. The resonator includes a piezoelectric layer; an electrode layer located on the piezoelectric layer, and the electrode layer includes a plurality of transducers; the piezoelectric layer includes a plurality of hetero-reflection grating structures, the hetero-reflection grating structures extend along a second direction, each hetero-reflection grating structure corresponds to a transducer, and the depth of each hetero-reflection grating structure is greater than the thickness of the transducer; the hetero-reflection grating structure includes a first hetero-reflection grating unit and a second hetero-reflection grating unit, the first hetero-reflection grating unit and the second hetero-reflection grating unit are symmetrically arranged on both sides of the corresponding transducer along a first direction respectively, both the first hetero-reflection grating unit and the second hetero-reflection grating unit include a plurality of reflection gratings, the widths of the plurality of reflection gratings are equal, the lengths of the plurality of reflection gratings are equal, and the plurality of reflection gratings are equally spaced along the first direction. The present invention uses a hetero-reflection grating structure to replace the metal reflection grating of the conventional structure to reflect surface waves, thereby improving the Q value of the resonator.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of semiconductor packaging, and particularly to a surface acoustic wave resonator and a filter. Background Art

[0002] With the development of communication technologies, strict requirements are imposed on the performance of various devices at the product terminals. Filters are key devices in communication systems. As technology develops, there are more and more types of filters, from LCR filters to cavity filters, from LTCC ceramic filters to surface acoustic wave filters, and the technology of filters is constantly evolving. Since entering the LTE era, surface acoustic wave filters have become increasingly important in communication systems. At the same time, with the development of communication technologies, various requirements for filters are also getting higher and higher. Especially with the advent of the fifth-generation mobile communication technology (5G), the filter industry is facing major challenges and opportunities.

[0003] Surface acoustic wave filters are widely used in the radio frequency front end and have the advantages of low insertion loss, wide bandwidth, small volume, etc. However, compared with metal cavity filters and bulk acoustic wave resonators, their Q value is relatively low and they cannot meet the increasingly strict performance requirements. Therefore, it is extremely urgent to improve the Q value of surface acoustic wave resonators. Summary of the Invention

[0004] The present invention provides a surface acoustic wave resonator and a filter to improve the Q value of the surface acoustic wave resonator.

[0005] In a first aspect, an embodiment of the present invention provides a surface acoustic wave resonator, which includes:

[0006] A piezoelectric layer;

[0007] An electrode layer located on the piezoelectric layer, the electrode layer including a plurality of transducers;

[0008] The piezoelectric layer includes a plurality of hetero-reflection grating structures, the propagation speed of the surface acoustic wave in the hetero-reflection grating structure is different from the propagation speed in the piezoelectric layer, the hetero-reflection grating structure extends along a second direction, each hetero-reflection grating structure corresponds to one transducer, and the depth of each hetero-reflection grating structure is greater than the thickness of the transducer;

[0009] The heterogeneous reflection grating structure includes a first heterogeneous reflection grating unit and a second heterogeneous reflection grating unit. The first heterogeneous reflection grating unit and the second heterogeneous reflection grating unit are symmetrically arranged on both sides of the corresponding transducer along a first direction respectively. Both the first heterogeneous reflection grating unit and the second heterogeneous reflection grating unit include multiple reflection gratings. The widths of the multiple reflection gratings are equal, the lengths of the multiple reflection gratings are equal, and the multiple reflection gratings are equally spaced along the first direction; wherein, a second direction intersects with the first direction.

[0010] Optionally, a groove is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and a heterogeneous material layer is filled in the groove. The heterogeneous reflection grating structure includes the heterogeneous material layer.

[0011] Optionally, the material used for the heterogeneous material layer includes silicon dioxide or silicon nitride.

[0012] Optionally, a doping region is provided on the surface of the piezoelectric layer adjacent to the electrode layer. The heterogeneous reflection grating structure includes the piezoelectric layer of the doping region after doping with set particles.

[0013] Optionally, the set particles include vanadium or the set particles include hydrogen and helium.

[0014] Optionally, the transducer includes: a first bus bar, a first long finger, a first dummy finger, a second bus bar, a second long finger, and a second dummy finger; both the first bus bar and the second bus bar extend along the first direction and are oppositely arranged; the first long finger, the second dummy finger, the second long finger, and the first dummy finger all extend along the second direction and are all located between the first bus bar and the second bus bar; the first long finger and the first dummy finger are alternately arranged along the first direction and are both connected to the first bus bar; the second long finger and the second dummy finger are alternately arranged along the first direction and are both connected to the second bus bar; the first long finger and the second dummy finger are oppositely arranged, there is a first gap between the first long finger and the second dummy finger, the second long finger and the first dummy finger are oppositely arranged, and there is a second gap between the second long finger and the first dummy finger.

[0015] Optionally, the distance between the centers of adjacent reflection gratings includes 0.3λ - 3λ, where λ is the surface acoustic wave wavelength.

[0016] Optionally, the depth of the heterogeneous reflection grating structure along the thickness direction of the surface acoustic wave resonator includes 0.3λ - 3λ, where λ is the surface acoustic wave wavelength, and the length of the heterogeneous reflection grating is greater than the width of the transducer.

[0017] Optionally, it further includes a temperature compensation layer and a substrate. The temperature compensation layer is located on a side of the electrode layer away from the piezoelectric layer, and the substrate is located on a side of the piezoelectric layer away from the electrode layer.

[0018] In a second aspect, an embodiment of the present invention further provides a filter, which includes at least two surface acoustic wave resonators provided in any embodiment of the present invention.

[0019] The technical solution of this embodiment reflects surface waves by using a hetero-reflection grating structure to replace the metal reflection grating in the conventional structure. At the same time, since the hetero-reflection grating structure itself is located inside the piezoelectric layer and its depth far exceeds the thickness of the transducer, it can reflect shallow bulk waves, solving the problem of low Q value of the surface acoustic wave resonator, thereby improving the Q value of the surface acoustic wave resonator. Description of the Drawings

[0020] Figure 1 is a plan view of a conventional surface acoustic wave resonator in the prior art;

[0021] Figure 2 is in the prior art and Figure 1 corresponding conventional surface acoustic wave resonator along the sectional line AA;

[0022] Figure 3 is a structural schematic diagram of a surface acoustic wave resonator provided by an embodiment of the present invention;

[0023] Figure 4 is a partial plan view of a surface acoustic wave resonator provided by an embodiment of the present invention;

[0024] Figure 5 is provided by an embodiment of the present invention and Figure 4 corresponding surface acoustic wave resonator along the sectional line BB;

[0025] Figure 6 is a partial plan view of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0026] Figure 7 is a structural schematic diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0027] Figure 8 is provided by an embodiment of the present invention and Figure 4 corresponding surface acoustic wave resonator with a temperature compensation layer along the sectional line BB;

[0028] Figure 9 is provided by an embodiment of the present invention and Figure 4 corresponding another surface acoustic wave resonator with a temperature compensation layer along the sectional line BB;

[0029] Figure 10 is a cross-sectional view along the section line BB of a surface acoustic wave resonator with a substrate corresponding to Figure 4 provided by an embodiment of the present invention;

[0030] Figure 11 is a cross-sectional view along the section line BB of another surface acoustic wave resonator with a substrate corresponding to Figure 4 provided by an embodiment of the present invention;

[0031] Figure 12 is a cross-sectional view along the section line BB of another surface acoustic wave resonator with a substrate corresponding to Figure 4 provided by an embodiment of the present invention;

[0032] Figure 13 is a cross-sectional view along the section line BB of another surface acoustic wave resonator with a substrate corresponding to Figure 4 provided by an embodiment of the present invention. Detailed implementation manners

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that, for the sake of description, only parts related to the present invention rather than all structures are shown in the drawings.

[0034] Figure 1 is a schematic plan view of a conventional surface acoustic wave resonator in the prior art, Figure 2 is a cross-sectional view along the section line AA of a conventional surface acoustic wave resonator corresponding to Figure 1 in the prior art. Referring to Figure 1 and Figure 2 , the conventional surface acoustic wave resonator includes a piezoelectric layer 120 and an electrode layer located on the piezoelectric layer 120. The electrode layer includes a transducer 131 and a metal reflection grating structure 132. The thickness of the transducer 131 is 100 - 500 nm, and the material can be at least one of metals such as Au, Al, Cu, Ti, etc. The transducer 131 is used to generate a surface acoustic wave on the piezoelectric layer 120 and transmit the surface acoustic wave to the metal reflection grating structure 132 respectively. The metal reflection grating structure 132 is an essential structure of the surface acoustic wave resonator. The material and thickness of the metal reflection grating structure 132 are the same as those of the transducer 131. The metal reflection grating structure 132 is used to reflect the surface wave, and the quality of the metal reflection grating structure 132 will directly affect the magnitude of the Q value of the surface acoustic wave resonator.

[0035] Figure 3 is a schematic structural view of a surface acoustic wave resonator provided by an embodiment of the present invention, Figure 4It is a partial plan view of a surface acoustic wave resonator provided by an embodiment of the present invention. Refer to Figure 3 and Figure 4 , an embodiment of the present invention provides a surface acoustic wave resonator, which includes: a piezoelectric layer 120; an electrode layer 130 located on the piezoelectric layer 120, and the electrode layer 130 includes a plurality of transducers 131; the piezoelectric layer 120 includes a plurality of hetero-reflection grating structures 121, the propagation speed of the surface acoustic wave in the hetero-reflection grating structure 121 is different from that in the piezoelectric layer 130, the hetero-reflection grating structures 121 extend along the second direction 2, each hetero-reflection grating structure 121 corresponds to a transducer 131, and the depth of each hetero-reflection grating structure 121 is greater than the thickness of the transducer 131; the hetero-reflection grating structure 121 includes a first hetero-reflection grating unit 1211 and a second hetero-reflection grating unit 1212, the first hetero-reflection grating unit 1211 and the second hetero-reflection grating unit 1212 are symmetrically arranged on both sides of the corresponding transducer 131 along the first direction 1 respectively, the first hetero-reflection grating unit 1211 and the second hetero-reflection grating unit 1212 both include a plurality of reflection gratings 50, the widths of the plurality of reflection gratings 50 are equal, the lengths of the plurality of reflection gratings 50 are equal, and the plurality of reflection gratings 50 are equally spaced along the first direction 1; wherein, the second direction 2 intersects with the first direction 1.

[0036] Specifically, the material of the piezoelectric layer 120 can be lithium niobate or lithium cobaltate, and a metal film is deposited on the surface of the piezoelectric layer 120 by means of electron beam evaporation, plasma, magnetron sputtering, etc. to form the electrode layer 130. Among them, the material for depositing the metal film can be titanium, chromium, copper, silver, aluminum, etc. or a combination thereof.

[0037] There is a sudden change in the sound velocity in the hetero-reflection grating structure 121 and the sound velocity of the piezoelectric layer 120, so as to reflect the surface acoustic wave at the interface. Therefore, this structure can be used as a reflection grating of the surface acoustic resonator; at the same time, because the change in the sound velocity of the hetero-reflection grating structure 121 and the sound velocity of the piezoelectric layer 120 is large and the reflectivity is high, a smaller reflection grating structure can reflect more surface acoustic waves. There is no metal loss in the hetero-reflection grating structure 121; and this structure can reflect the body wave, reducing the loss of the body wave. Therefore, this structure can achieve a high Q value. At the same time, since the depth of the hetero-reflection grating structure 121 exceeds the thickness of the transducer 131, it can reflect the shallow body wave, thereby improving the Q value of the resonator.

[0038] Figure 5 It is a sectional view of the surface acoustic wave resonator provided by an embodiment of the present invention along the section line BB corresponding to Figure 4 . Refer to Figure 5 , the first hetero-reflection grating unit 1211 and the second hetero-reflection grating 1212 are symmetrically arranged on both sides of the transducer 131 respectively, and the plurality of reflection gratings 50 are used to reflect the surface acoustic wave generated by the transducer 131.

[0039] The technical solution of this embodiment reflects surface waves by using a heterogeneous reflection grating structure to replace the metal reflection grating in the conventional structure. At the same time, since the heterogeneous reflection grating structure itself is located inside the piezoelectric layer and its depth exceeds the thickness of the transducer, it can reflect shallow body waves, solving the problem of low Q value of the surface wave resonator, thereby improving the Q value of the surface acoustic wave resonator.

[0040] Optionally, a groove is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the groove is filled with a heterogeneous material layer. The heterogeneous reflection grating structure includes the heterogeneous material layer.

[0041] Specifically, corresponding grooves can be etched at the positions of the heterogeneous reflection grating structure on the piezoelectric layer. Since the material of the heterogeneous material layer is different from that of the piezoelectric layer, the sound velocities of the heterogeneous material layer and the piezoelectric layer are different, and there is a sudden change in the sound velocity between the heterogeneous material layer and the piezoelectric layer in the lateral direction of the resonator, thereby confining the surface acoustic wave in the resonator.

[0042] Optionally, the material used for the heterogeneous material layer includes silicon dioxide or silicon nitride.

[0043] Specifically, after etching, silicon dioxide or silicon nitride is formed in the groove by processes such as plasma chemical vapor deposition, and then the flatness is repaired by etching or chemical mechanical polishing, and then processes such as deposition and etching of the transducer are carried out. The subsequent processes are the same as those of the conventional surface acoustic wave resonator process.

[0044] Optionally, a doped region is provided on the surface of the piezoelectric layer adjacent to the electrode layer. The heterogeneous reflection grating structure includes the piezoelectric layer of the doped region doped with set particles.

[0045] Specifically, ion doping of the corresponding position of the piezoelectric layer needs to be set according to the position and structure of the resonator, and the set ions are injected into the doped region on the surface of the piezoelectric layer adjacent to the electrode layer at a high speed by using an ion implantation process.

[0046] Optionally, the set particles include vanadium or the set particles include hydrogen and helium.

[0047] Specifically, doping vanadium particles can form a sound velocity mutation structure, and doping hydrogen particles and helium particles can form a defect structure. The material of the heterogeneous reflection grating is different from that of the piezoelectric layer, resulting in a sudden change in its sound velocity, thereby reflecting sound waves. The heterogeneous reflection grating structure does not use a metal material as the reflection grating, so there will be no metal loss.

[0048] Figure 6 is a partial plan view of another surface acoustic wave resonator provided by an embodiment of the present invention. Refer to Figure 6, optionally, the transducer 131 includes: a first bus bar 10, a first long finger 11, a first dummy finger 12, a second bus bar 20, a second long finger 21, and a second dummy finger 22; both the first bus bar 10 and the second bus bar 20 extend along a first direction 1 and are oppositely arranged; the first long finger 11, the second dummy finger 22, the second long finger 21, and the first dummy finger 12 all extend along a second direction 2 and are all located between the first bus bar 10 and the second bus bar 20; the first long finger 11 and the first dummy finger 12 are alternately arranged along the first direction 1 and are both connected to the first bus bar 10; the second long finger 21 and the second dummy finger 22 are alternately arranged along the first direction 1 and are both connected to the second bus bar 20; the first long finger 11 and the second dummy finger 22 are oppositely arranged, and there is a first gap 1122 between the first long finger 11 and the second dummy finger 22, the second long finger 21 and the first dummy finger 12 are oppositely arranged, and there is a second gap 2112 between the second long finger 21 and the first dummy finger 12.

[0049] Wherein, the number of the first long finger 11, the second dummy finger 22, the second long finger 21, and the first dummy finger 12 are all equal. The first bus bar 10 and the second bus bar 20 are always parallel to the first direction 1, and the included angle between the second direction 2 and the first direction 1 that intersects each other can be set as required. The exemplary embodiment of the present invention shows the case where the included angle is 90°.

[0050] Continue to refer to Figure 5 , optionally, the distance between the centers of adjacent reflection gratings includes 0.3λ - 3λ, where λ is the surface acoustic wave wavelength.

[0051] Specifically, the reflection grating 50 has periodicity. The period and duty cycle of the reflection grating 50 are related to the materials of the reflection grating 50 and the piezoelectric layer 120 and are related to the wave velocity of the surface wave. The period of the reflection grating 50 refers to the distance d between the centers of adjacent reflection gratings 50. When the distance d between the centers of adjacent reflection gratings 50 is 0.3λ - 3λ, this structure can fully reflect the surface acoustic wave and maintain the phase required for acoustic resonance.

[0052] Optionally, the depth of the heterogeneous reflection grating structure along the thickness direction of the surface acoustic wave resonator includes 0.3λ - 3λ, where λ is the surface acoustic wave wavelength, and the length of the heterogeneous reflection grating is greater than the width of the transducer.

[0053] Specifically, the depth of the heterogeneous reflection grating structure is closely related to the resonator performance. Excessive depth will increase the process difficulty and the spurious body wave peaks on the resonance curve will rise. Considering the materials of the piezoelectric layer, the heterogeneous grating materials, and the resonator performance requirements, when the depth of the heterogeneous reflection grating structure along the thickness direction of the surface acoustic wave resonator is 0.3λ - 3λ, the process difficulty can be reduced, the spurious body wave peaks on the resonance curve will not rise, and the performance is better.

[0054] Figure 7It is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention. Refer to Figure 7 Optionally, it further includes a temperature compensation layer 140 and a substrate 110. The temperature compensation layer 140 is located on the side of the electrode layer 130 away from the piezoelectric layer 120, and the substrate 110 is located on the side of the piezoelectric layer 120 away from the electrode layer 130.

[0055] Specifically, the material of the substrate 110 can be silicon, and the substrate 110 can also be a composite multi-layer substrate, which can enable the surface acoustic wave resonator to achieve characteristics such as low insertion loss, smooth passband, high Q value, and excellent low-frequency temperature. The material of the temperature compensation layer 140 can be silicon dioxide or silicon nitride, and the temperature compensation layer 140 can avoid the influence of temperature change on the resonance frequency of the surface acoustic wave resonator.

[0056] Figure 8 It is a cross-sectional view along the section line BB of a surface acoustic wave resonator with a temperature compensation layer provided by an embodiment of the present invention corresponding to Figure 4 Refer to Figure 9 It is a cross-sectional view along the section line BB of another surface acoustic wave resonator with a temperature compensation layer provided by an embodiment of the present invention corresponding to Figure 4 Refer to Figure 8 and Figure 9 ,

[0057] Figure 8 In Figure 9 , the material of the reflection grating 50 is the same as that of the temperature compensation layer 140, both being silicon dioxide or silicon nitride. In

[0058] Figure 10 Figure 4 It is a cross-sectional view along the section line BB of a surface acoustic wave resonator with a substrate provided by an embodiment of the present invention corresponding to Refer to Figure 11 It is a cross-sectional view along the section line BB of another surface acoustic wave resonator with a substrate provided by an embodiment of the present invention corresponding to Figure 4 Refer to Figure 10 and Figure 11 , Figure 10 and Figure 11 In Figure 10 and Figure 11The cases of reflection gratings 50 with different depths are respectively shown. Since there is a large difference in the sound velocities between the substrate 110 and the piezoelectric layer 120, body waves are reflected at the interface, which can reduce the loss of body waves and thus improve the Q value of the resonator. Compared with the resonator using a metal reflection grating, since the depth of the reflection grating 50 can be adjusted, more body waves can be reflected by the resonator and will not crosstalk to adjacent resonator structures, thereby further improving the Q value of the resonator.

[0059] Figure 12 is another cross-sectional view along the section line BB of a surface acoustic wave resonator with a substrate provided by an embodiment of the present invention and Figure 4 corresponding thereto, Figure 13 is another cross-sectional view along the section line BB of a surface acoustic wave resonator with a substrate provided by an embodiment of the present invention and Figure 4 corresponding thereto. Referring to Figure 12 and Figure 13 , Figure 12 and Figure 13 the material of the reflection grating 50 in Figure 12 and Figure 13 are doped set particles. The cases of reflection gratings 50 with different depths are respectively shown. The depth of the reflection grating 50 can be adjusted to reflect body waves, reducing the loss of body waves and enabling a high Q value to be achieved.

[0060] An embodiment of the present invention also provides a filter, which includes at least two surface acoustic wave resonators according to any one of the above embodiments.

[0061] Wherein, the filter can be formed by connecting in series and / or in parallel two or more surface acoustic wave resonators according to the above embodiments.

[0062] Note that the above are only the preferred embodiments of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A surface acoustic wave resonator, characterized in that, Comprising: A piezoelectric layer; An electrode layer located on the piezoelectric layer, the electrode layer including a plurality of transducers; The piezoelectric layer includes a plurality of hetero-reflection grating structures, the propagation speed of the surface acoustic wave in the hetero-reflection grating structure is different from that in the piezoelectric layer, the hetero-reflection grating structure extends along a second direction, each hetero-reflection grating structure corresponds to one transducer, and the depth of each hetero-reflection grating structure is greater than the thickness of the transducer; The hetero-reflection grating structure includes a first hetero-reflection grating unit and a second hetero-reflection grating unit, the first hetero-reflection grating unit and the second hetero-reflection grating unit are symmetrically arranged on both sides of the corresponding transducer along a first direction respectively, both the first hetero-reflection grating unit and the second hetero-reflection grating unit include a plurality of reflection gratings, the widths of the plurality of reflection gratings are equal, the lengths of the plurality of reflection gratings are equal, and the plurality of reflection gratings are equally spaced along the first direction; wherein, the second direction intersects with the first direction; A groove is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the groove is filled with a hetero-material layer, and the hetero-reflection grating structure includes the hetero-material layer; The material used for the hetero-material layer includes silicon dioxide or silicon nitride; The transducer includes: a first bus bar, a first long finger, a first dummy finger, a second bus bar, a second long finger and a second dummy finger; both the first bus bar and the second bus bar extend along the first direction and are oppositely arranged; the first long finger, the second dummy finger, the second long finger and the first dummy finger all extend along the second direction and are all located between the first bus bar and the second bus bar; the first long finger and the first dummy finger are arranged alternately along the first direction and are both connected to the first bus bar; the second long finger and the second dummy finger are arranged alternately along the first direction and are both connected to the second bus bar; the first long finger and the second dummy finger are oppositely arranged, there is a first gap between the first long finger and the second dummy finger, the second long finger and the first dummy finger are oppositely arranged, and there is a second gap between the second long finger and the first dummy finger.

2. The surface acoustic wave resonator according to claim 1, characterized in that, A doping region is provided on the surface of the piezoelectric layer adjacent to the electrode layer, and the hetero-reflection grating structure includes the piezoelectric layer of the doping region doped with set particles.

3. The surface acoustic wave resonator according to claim 2, wherein The set particles include vanadium or the set particles include hydrogen and helium.

4. The surface acoustic wave resonator according to claim 1, wherein The distance between the centers of adjacent reflection gratings includes 0.3λ - 3λ, where λ is the surface acoustic wave wavelength.

5. The surface acoustic wave resonator according to claim 1, wherein The depth of the hetero-reflection grating structure along the thickness direction of the surface acoustic wave resonator includes 0.3λ - 3λ, where λ is the surface acoustic wave wavelength, and the length of the hetero-reflection grating is greater than the width of the transducer.

6. The surface acoustic wave resonator according to claim 1, characterized in that, It further includes a temperature compensation layer and a substrate, the temperature compensation layer is located on the side of the electrode layer away from the piezoelectric layer, and the substrate is located on the side of the piezoelectric layer away from the electrode layer.

7. A filter, characterized in that, Including at least two surface acoustic wave resonators according to any one of claims 1 - 6.

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