Lamb wave resonator and method of manufacturing the same

Abstract

The application provides a Lamb wave resonator and a preparation method thereof, and relates to the technical field of acoustic wave resonators. The Lamb wave resonator comprises a support substrate, a support structure, a piezoelectric film and a top electrode. The support substrate and the piezoelectric film are arranged at intervals, one end of the support structure is arranged on the surface of the support substrate, the other end of the support structure is arranged on the first surface of the piezoelectric film, the top electrode is arranged on the second surface of the piezoelectric film which is away from the support substrate, and the top electrode and the support structure at least partially overlap in the thickness direction of the piezoelectric film. The Lamb wave resonator can improve the mechanical stability of the piezoelectric film, and improve the heat dissipation characteristics and power characteristics of the resonator. Since the main mode energy of the Lamb wave resonator is mainly concentrated in the part between the electrodes, the multiple reflections of the acoustic wave to the electrode area will generate a stray mode, and the provision of the support structure is conducive to the leakage of the stray acoustic wave energy to the support substrate, thereby improving the problem of multiple stray modes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acoustic wave resonators, in particular to a Lamb wave resonator and a preparation method thereof. BACKGROUND

[0002] The piezoelectric thin film used in the mainstream bulk acoustic wave filter on the market is mainly an aluminum nitride thin film material prepared by a magnetron sputtering method. However, the effective electromechanical coupling coefficient of the bulk acoustic wave resonator prepared by using the aluminum nitride material is low, and the frequency is limited by the thickness of the aluminum nitride thin film, which cannot meet the requirements of high frequency, large bandwidth and low loss of the filter for 5G communication.

[0003] The electromechanical coupling coefficient of lithium niobate material is high, and the intrinsic loss of single crystal lithium niobate thin film is low, which is an ideal piezoelectric thin film for preparing bulk acoustic wave resonators. For example, the effective electromechanical coupling coefficient of the anti-symmetry Lamb wave resonator using Z-cut lithium niobate thin film is as high as 30%, which is much higher than 7% of the longitudinal mode based on aluminum nitride thin film.

[0004] However, the Lamb wave resonator based on lithium niobate thin film also has problems, for example: at present, the resonator body is a suspended thin plate structure, which can only be fixed by an anchor point, which will lead to poor mechanical stability of the resonator, and the suspended structure is not conducive to heat dissipation of the resonator body part, so that it cannot be used in high-power occasions, in addition, the resonator has many spurious modes, which easily increases the in-band fluctuation of the filter. SUMMARY

[0005] The present application provides a Lamb wave resonator and a preparation method thereof, which fixes the piezoelectric thin film through the support structure, so that the mechanical stability is improved, the support structure can also enhance the heat dissipation characteristics of the resonator body part, and can improve the problem of many spurious modes.

[0006] In a first aspect, the embodiments of the present application provide a Lamb wave resonator, which comprises a support substrate, a support structure, a piezoelectric thin film and a top electrode. The support substrate and the piezoelectric thin film are arranged at intervals, one end of the support structure is arranged on the surface of the support substrate, the other end of the support structure is arranged on the first surface of the piezoelectric thin film, the top electrode is arranged on the second surface of the piezoelectric thin film away from the support substrate, and the top electrode and the support structure at least partially overlap in the thickness direction of the piezoelectric thin film.

[0007] The gap is between the support substrate and the piezoelectric film, and the surface of the support substrate and the surface of the piezoelectric film are supported and connected by the support structure. On the one hand, the piezoelectric film can be physically supported by the support structure, the mechanical stability of the piezoelectric film can be improved, and the heat dissipation characteristics and power characteristics of the resonator can be improved. On the other hand, since the main mode energy of the Lamb wave resonator is mainly concentrated in the part between the electrodes, and the top electrode and the support structure at least partially overlap in the thickness direction of the piezoelectric film, the multiple reflections of the sound wave to the electrode area will generate a stray mode, and the support structure is provided to facilitate the stray sound wave energy to leak to the support substrate, thereby improving the problem of multiple stray modes.

[0008] In a second aspect, the embodiments of the present application provide a preparation method of a Lamb wave resonator, comprising: providing a support substrate, forming a support structure on the surface of the support substrate. Forming a piezoelectric film, and setting a first surface of the piezoelectric film to an end of the support structure away from the support substrate. Forming a top electrode on a second surface of the piezoelectric film away from the support substrate, so that the top electrode and the support structure at least partially overlap in the thickness direction of the piezoelectric film.

[0009] The Lamb wave resonator prepared by the above method has excellent performance because the support substrate and the piezoelectric film are connected by the support structure. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0011] Figure 1 The first structure diagram of the Lamb wave resonator provided by the embodiments of the present application;

[0012] Figure 2 The first structure diagram of the support substrate and the support body provided by the embodiments of the present application;

[0013] Figure 3 The second structure diagram of the support substrate and the support body provided by the embodiments of the present application;

[0014] Figure 4 The second structure diagram of the Lamb wave resonator provided by the embodiments of the present application;

[0015] Figure 5 The third structure diagram of the Lamb wave resonator provided by the embodiments of the present application;

[0016] Figure 6AA structure diagram after step S110 in the method for manufacturing the Lamb wave resonator;

[0017] Figure 6B A structure diagram after step S120 in the method for manufacturing the Lamb wave resonator;

[0018] Figure 6C A structure diagram after step S130 in the method for manufacturing the Lamb wave resonator;

[0019] Figure 6D A structure diagram after step S140 in the method for manufacturing the Lamb wave resonator;

[0020] Figure 6E A structure diagram after step S150 in the method for manufacturing the Lamb wave resonator;

[0021] Figure 7A A structure diagram after step S210 in the method for manufacturing the Lamb wave resonator;

[0022] Figure 7B A structure diagram after step S220 in the method for manufacturing the Lamb wave resonator;

[0023] Figure 7C A structure diagram after step S230 in the method for manufacturing the Lamb wave resonator;

[0024] Figure 7D A structure diagram after step S240 in the method for manufacturing the Lamb wave resonator;

[0025] Figure 7E A structure diagram after step S250 in the method for manufacturing the Lamb wave resonator;

[0026] Figure 8 A fourth structure diagram of the Lamb wave resonator provided by the embodiment of the present application;

[0027] Figure 9 A structure diagram after step S310 in the method for manufacturing the Lamb wave resonator; Figure 8 An enlarged view of the dashed box in FIG. 10;

[0028] Figure 10A A structure diagram after step S310 in the method for manufacturing the Lamb wave resonator;

[0029] Figure 10B A structure diagram after step S320 in the method for manufacturing the Lamb wave resonator;

[0030] Figure 10C A structure diagram after step S330 in the method for manufacturing the Lamb wave resonator;

[0031] Figure 10D Structure diagram after step S340 in the preparation method of the Lamb wave resonator;

[0032] Figure 10E Structure diagram after step S350 in the preparation method of the Lamb wave resonator;

[0033] Figure 10F Structure diagram after step S360 in the preparation method of the Lamb wave resonator;

[0034] Figure 10G Structure diagram after step S370 in the preparation method of the Lamb wave resonator;

[0035] Figure 10H First structure diagram after step S380 in the preparation method of the Lamb wave resonator;

[0036] Figure 10I Second structure diagram after step S380 in the preparation method of the Lamb wave resonator;

[0037] Figure 10J Structure diagram after step S390 in the preparation method of the Lamb wave resonator;

[0038] Figure 11 Frequency impedance curve comparison diagram of the Lamb wave resonator provided for the examples and comparative examples.

[0039] Figure legend: 110 - support substrate; 120 - support structure; 130 - piezoelectric film; 140 - top electrode; 121 - support body; 141 - sub-electrode; 150 - piezoelectric substrate; 151 - first substrate; 152 - defect layer; 153 - second substrate; 161 - support film; 170 - adhesive layer; 181 - sacrificial layer material; 182 - release hole. DETAILED DESCRIPTION

[0040] The prior art Lamb wave resonator includes a support substrate, a piezoelectric film and a top electrode, the piezoelectric film is suspended above the support substrate, and in order to fix the support substrate and the piezoelectric film, a common fixing method is to fix the piezoelectric film together with the support substrate through anchor points on opposite sides of the piezoelectric film, i.e. the anchor points are arranged on the two side surfaces (not the two surfaces) of the piezoelectric film. This method has the following defects: the method of fixing the piezoelectric film through anchor points will make the mechanical stability of the Lamb wave resonator poor, and the heat transfer effect will also be poor, resulting in low power capacity of the Lamb wave resonator; at the same time, the Lamb wave resonator has many stray modes.

[0041] The application improves the structure of a Lamb wave resonator and its preparation method, so that the mechanical stability is improved, the heat transfer characteristics are optimized, and the problem of multiple spurious modes is improved. In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below in combination with the drawings in the embodiments of the application.

[0042] Figure 1 A first structure diagram of a Lamb wave resonator provided by the embodiments of the application is shown in FIG. 1. As shown in FIG. 1, the Lamb wave resonator comprises a support substrate 110, a support structure 120, a piezoelectric thin film 130 and a top electrode 140. The support substrate 110 and the piezoelectric thin film 130 are arranged at intervals, one end of the support structure 120 is arranged on the surface of the support substrate 110 (i.e. the upper surface of the support substrate 110), the other end of the support structure 120 is arranged on the first surface of the piezoelectric thin film 130 (i.e. the lower surface of the piezoelectric thin film 130), the top electrode 140 is arranged on the second surface of the piezoelectric thin film 130 (i.e. the upper surface of the piezoelectric thin film 130) which is away from the support substrate 110, and the top electrode 140 and the support structure 120 at least partially overlap in the thickness direction of the piezoelectric thin film 130. Figure 1 Figure 1 Figure 1 Figure 1

[0043] In the application, the support substrate 110 and the piezoelectric thin film 130 have a gap therebetween, and the surface of the support substrate 110 and the surface of the piezoelectric thin film 130 are connected by the support structure 120. On the one hand, the support structure 120 can provide physical support for the piezoelectric thin film 130, so that the mechanical stability of the piezoelectric thin film 130 is improved, and the heat generated in the piezoelectric thin film 130 can be transmitted to the support substrate 110 through the support structure 120, so as to promote heat dissipation and improve the power capacity of the resonator. On the other hand, since the main mode energy of the Lamb wave resonator is mainly concentrated in the part between the electrodes, and the top electrode 140 and the support structure 120 at least partially overlap in the thickness direction of the piezoelectric thin film 130, the provision of the support structure 120 is conducive to the leakage of spurious acoustic energy to the support substrate 110, so as to improve the problem of multiple spurious modes.

[0044] Optionally, the thickness of the support substrate 110 is 200-500 μm, the thickness of the support structure 120 is 0.05-5 μm, the thickness of the piezoelectric thin film 130 is 0.1-2 μm, and the thickness of the top electrode 140 is 0.05-1 μm. It should be noted that the thicknesses herein refer to the distance between the upper end surface and the lower end surface of each component. Figure 1

[0045] Please continue to refer to FIG. 2. Figure 1 ​​​​​The support structure 120 includes a plurality of supports 121. One end of each support 121 is spaced apart from the surface of the support substrate 110. Figure 1 The upper surface of the supporting substrate 110), and the other ends of the plurality of supports 121 are spaced apart on the first surface of the piezoelectric thin film 130. Figure 1 (Lower surface of the piezoelectric thin film 130). Gaps are provided between the multiple supports 121, which can support the piezoelectric thin film 130 from multiple points, further improving the mechanical stability of the Lamb wave resonator, and at the same time, further improving the problem of multiple stray modes.

[0046] The top electrode 140 includes a plurality of sub-electrodes 141, each sub-electrode 141 being disposed on the second surface of the piezoelectric thin film 130. Figure 1 The upper surface of the piezoelectric thin film 130; a sub-electrode 141 corresponds one-to-one with a support 121 and at least partially overlaps with it in the thickness direction of the piezoelectric thin film 130. In the Lamb wave resonator, the acoustic wave energy is mainly concentrated in the region between adjacent sub-electrodes 141. The acoustic wave energy transmitted to the electrode region (the region where the sub-electrodes 141 are set) will cause stray waves. The one-to-one correspondence between the sub-electrodes 141 and the support 121 and the at least partial overlap in the thickness direction of the piezoelectric thin film 130 is conducive to the leakage of stray wave energy to the support substrate 110, reducing stray waves and thus better improving the problem of multiple stray modes.

[0047] In this application, the sum of the contact areas between the plurality of sub-electrodes 141 and the piezoelectric film 130 is not less than the sum of the contact areas between the plurality of supports 121 and the piezoelectric film 130. That is, the sum of the contact areas between the plurality of sub-electrodes 141 and the piezoelectric film 130 is greater than or equal to the sum of the contact areas between the plurality of supports 121 and the piezoelectric film 130. Since the acoustic wave energy is mainly concentrated in the region between the sub-electrodes 141, this arrangement allows less dominant mode acoustic wave energy to leak to the support substrate 110 while removing stray modes, thereby preventing a decrease in the resonator's quality factor.

[0048] The following explains the "sum of the areas in contact between the multiple sub-electrodes 141 and the piezoelectric film 130": The end of each sub-electrode 141 is disposed on the second surface of the piezoelectric film 130 (e.g., Figure 1 The upper surface of the piezoelectric film 130), one end of the sub-electrode 141 has a contact area with the second surface of the piezoelectric film 130, and the contact area between the multiple sub-electrodes 141 and the second surface of the piezoelectric film 130 has a sum of areas. The following explains "the sum of the contact areas between the multiple supports 121 and the piezoelectric film 130": the end of each support 121 is disposed on the first surface of the piezoelectric film 130 (e.g., the upper surface of the piezoelectric film 130), and the sub-electrode 141 has a contact area with the second surface of the piezoelectric film 130. Figure 1The contact area between one end of the support body 121 and the first surface of the piezoelectric thin film 130 is not less than the contact area between the piezoelectric thin film 130 and the support body 121 corresponding to the sub-electrode 141.

[0049] Optionally, one sub-electrode 141 and one support body 121 correspond to each other and at least partially overlap in the thickness direction of the piezoelectric thin film 130. The contact area between one sub-electrode 141 and the piezoelectric thin film 130 is not less than the contact area between the piezoelectric thin film 130 and the support body 121 corresponding to the sub-electrode 141, which can further prevent sound wave leakage.

[0050] Figure 2 The first structural diagram of the support substrate 110 and the support body 121 provided by the embodiment of the present application; Figure 3 The second structural diagram of the support substrate 110 and the support body 121 provided by the embodiment of the present application. Please refer to Figure 2 and Figure 3 The shape of each support body 121 is a long strip (please refer to Figure 2 ), a prism (please refer to Figure 3 ), a cylinder (not shown in the figure), a prism platform (not shown in the figure) or a circular platform (not shown in the figure). The present application does not make any limitation as long as the support structure 120 can support the support substrate 110 and the piezoelectric thin film 130.

[0051] Please continue to refer to Figure 2 If the shape of each support body 121 is a long strip, each support body 121 is basically parallel; optionally, the distance between two adjacent long strip-shaped support bodies 121 is 0.1-200 μm.

[0052] Please continue to refer to Figure 3 If the shape of each support body 121 is a prism, a cylinder, a prism platform or a circular platform, a plurality of support bodies 121 can be arranged in an array on the support substrate 110. For example, Figure 3 from left to right is a row, and the distance between two adjacent rows of support bodies is 0.1-200 μm; for example, Figure 3 from front to back is a column, and the distance between two adjacent columns of support bodies is 0.1-200 μm.

[0053] It should be noted that the structures of the plurality of support bodies 121 are not limited to be the same, and can be different. For example, the structures of some of the support bodies 121 are long strips, and the structures of some of the support bodies 121 are prisms. For another example, the structures of some of the support bodies 121 are prisms, and the structures of some of the support bodies 121 are cylinders. For yet another example, the structures of some of the support bodies 121 are long strips, the structures of some of the support bodies 121 are prisms, and the structures of some of the support bodies 121 are cylinders.

[0054] Figure 4 A second structural schematic diagram of a Lamb wave resonator provided by an embodiment of the present application; Figure 5 A third structural schematic diagram of a Lamb wave resonator provided by an embodiment of the present application. Please refer to Figure 4 and Figure 5 Each of the sub-electrodes 141 is a long strip (please refer to Figure 1 and Figure 4 ), a prism, or a cylinder (please refer to Figure 5 ). Among them, please refer to Figure 1 , the support body 121 and the sub-electrode 141 are both long strips, and the extending directions of the support body 121 and the sub-electrode 141 are basically consistent. One long strip-shaped support body 121 corresponds to one long strip-shaped sub-electrode 141. The projection of the support body 121 on the piezoelectric film 130 and the projection of the sub-electrode 141 on the piezoelectric film 130 basically overlap. The Lamb wave resonator has good effect of preventing main mode acoustic wave leakage.

[0055] Among them, the structures of the plurality of sub-electrodes 141 can also be interdigital long strips. It should be noted that the structures of the plurality of sub-electrodes 141 are not limited to be the same, and can be different. For example, the structures of some of the sub-electrodes 141 are long strips, and the structures of some of the sub-electrodes 141 are prisms. For another example, the structures of some of the sub-electrodes 141 are prisms, and the structures of some of the sub-electrodes 141 are cylinders. For yet another example, the structures of some of the sub-electrodes 141 are long strips, the structures of some of the sub-electrodes 141 are prisms, and the structures of some of the sub-electrodes 141 are cylinders.

[0056] Please refer to Figure 4 , the structures of the support body 121 and the sub-electrode 141 can be different. For example, the support body 121 is a prism, and the sub-electrode 141 is a long strip. One row of prism-shaped support bodies 121 corresponds to one long strip-shaped sub-electrode 141. Please refer to Figure 5 , the support body 121 is a prism, and the sub-electrode 141 is a cylinder. One prism-shaped support body 121 corresponds to one cylinder-shaped sub-electrode 141.

[0057] In other embodiments, the support structure 120 can also be one, which has a hollow structure, for example: Figure 2The support structure 120 is connected from left to right by one or more long strip structures to form an integral support structure 120 with a hollow structure. The top electrode 140 and the support structure 120 overlap at least partially in the thickness direction of the piezoelectric film 130. The corresponding hollow part of the piezoelectric film 130, that is, between the electrodes, can generate acoustic wave energy. Stray waves can also leak to the support substrate 110 through the support structure 120, reducing stray waves and thus better improving the problem of multiple stray modes.

[0058] In this application, the material of the support structure 120 is SiO2, SiC, SiN or diamond. Choosing this material as the material of the support structure 120 can not only support the piezoelectric film 130, but also facilitate the heat dissipation of the resonator pillar (piezoelectric film 130 and top electrode 140), thereby improving the problem of low power capacity of Lamb wave resonator.

[0059] Optionally, the material of the support substrate 110 may be Si, SOI, SiC, sapphire, or diamond. If the materials of the support structure 120 and the support substrate 110 are the same, heat dissipation is easier, and stray waves can be more easily transmitted to the support substrate 110. Of course, the materials of the support structure 120 and the support substrate 110 may also be different, and this application does not impose any limitations.

[0060] The piezoelectric thin film 130 of the Lamb wave resonator is made of lithium niobate or lithium tantalate, which has a high electromechanical coupling coefficient and low inherent loss, making it suitable for fabricating the Lamb wave resonator and giving it excellent performance. The top electrode 140 of the Lamb wave resonator is made of Al, Mo, Au, Ag, Ni, Pt, or Cu, which facilitates energization to enable the Lamb wave resonator to operate.

[0061] Please see Figures 6A-7E To obtain the aforementioned Lamb wave resonator, its fabrication method includes: providing a support substrate 110, forming a support structure 120 on the surface of the support substrate 110, forming a piezoelectric thin film 130, and placing the first surface of the piezoelectric thin film 130 (… Figure 1 The lower surface of the piezoelectric thin film 130 is disposed at one end of the support structure 120 away from the support substrate 110. On the second surface of the piezoelectric thin film 130... Figure 1 A top electrode 140 is formed on the upper surface of the piezoelectric thin film 130, such that the top electrode 140 and the support structure 120 at least partially overlap in the thickness direction of the piezoelectric thin film 130.

[0062] In one embodiment, the Lamb wave resonator is fabricated as follows:

[0063] S110, a support substrate 110 is provided, and a support structure 120 is formed on the upper part of the support substrate 110 by etching; wherein, Figure 6AThe structure diagram after step S110 in the preparation method of the Lamb wave resonator. Please refer to Figure 6A The support structure 120 is directly formed on the original support substrate 110, and the materials of the support substrate 110 and the support structure 120 are consistent. For example, the materials of the support substrate 110 and the support structure 120 are SiO2, SiC, SiN or diamond.

[0064] The support structure 120 can include a plurality of support bodies 121, which can form support body 121 structures with different structures by etching the support substrate 110 in a patterned manner according to the specific shape of the support body 121. Alternatively, the etching manner of the upper part of the support substrate is specifically ICP-RIE dry etching.

[0065] S120, providing a piezoelectric substrate 150, ion implantation is performed on the piezoelectric substrate 150 to form a first substrate 151 and a second substrate 153 connected by a defect layer 152; wherein, Figure 6B The structure diagram after step S120 in the preparation method of the Lamb wave resonator. Please refer to Figure 6B The ion implantation is performed from above the piezoelectric substrate 150. Alternatively, the material of the piezoelectric substrate 150 is lithium niobate or lithium tantalate, and the ion implantation manner is to implant H + or He + ions into the piezoelectric substrate 150 to form the defect layer 152.

[0066] S130, bonding the first substrate 151 to the end of the support structure 120 away from the support substrate 110; wherein, Figure 6C The structure diagram after step S130 in the preparation method of the Lamb wave resonator. Please refer to Figure 6C After bonding, the surface of the first substrate 151 away from the second substrate 153 can be in contact with the upper surface of the support substrate 110 and the upper surface of each support body 121 of the plurality of support bodies 121. Alternatively, the piezoelectric substrate 150 is bonded by direct bonding.

[0067] S140, peeling off the second substrate 153 and thinning the first substrate 151 to form a piezoelectric film 130; wherein, Figure 6D The structure diagram after step S140 in the preparation method of the Lamb wave resonator. Please refer to Figure 6D The second substrate 153 is peeled off from the defect layer 152, and the first substrate 151 is thinned to obtain the piezoelectric film 130, and the thickness of the piezoelectric film 130 after thinning is the thickness of the piezoelectric film 130 in the Lamb wave resonator. Alternatively, the second substrate 153 is peeled off and the first substrate 151 is thinned by heat treatment.

[0068] S150, forming a top electrode 140 on the second surface of the piezoelectric film 130 (the upper surface of the piezoelectric film 130); wherein, Figure 6E Figure 2 is a schematic diagram of the structure after step S150 in the method for preparing the Lamb wave resonator. Please refer to Figure 6E The sub-electrodes 141 of the support 121 and the top electrode 140 correspond to each other and at least partially overlap in the thickness direction of the piezoelectric film 130. Of course, the sub-electrodes 141 of the support 121 and the top electrode 140 can not correspond to each other as long as the top electrode 140 is arranged on the upper surface of the piezoelectric film 130 and the support 121 is arranged on the lower surface of the piezoelectric film 130. Alternatively, the top electrode 140 is formed by depositing a layer of metal on the surface of the piezoelectric film 130 and then etching or using the Lift-off method to form the top electrode 140.

[0069] In another embodiment, the method for preparing the Lamb wave resonator is as follows:

[0070] S210, providing a support substrate 110, forming a support film 161 on the support substrate 110, and etching the support film 161 to form a support structure 120; wherein, Figure 7A Figure 3 is a schematic diagram of the structure after step S210 in the method for preparing the Lamb wave resonator. Please refer to Figure 7A A layer of support film 161 is formed on the support substrate 110. The materials of the support substrate 110 and the support film 161 can be the same or different. For example, the material of the support film 161 is SiO2, SiC, SiN or diamond. After etching the support film 161, the etching depth is less than or equal to the thickness of the support film 161.

[0071] Alternatively, the support film 161 can be formed by thermal oxidation treatment, PECVD, magnetron sputtering or LPCVD deposition. Then the support film 161 can be etched by ICP-RIE dry etching.

[0072] S220, providing a piezoelectric substrate 150, performing ion implantation on the piezoelectric substrate 150 to form a first substrate 151 and a second substrate 153 connected by a defect layer 152; wherein, Figure 7B Figure 4 is a schematic diagram of the structure after step S220 in the method for preparing the Lamb wave resonator. Please refer to Figure 7B The ion implantation is performed from the top of the piezoelectric substrate 150. Alternatively, the material of the piezoelectric substrate 150 is lithium niobate or lithium tantalate. The ion implantation is performed by using an ion implanter to implant H + or He + ions to form the defect layer 152.

[0073] S230, bonding the first substrate 151 to the support structure 120 at an end away from the support substrate 110; wherein, Figure 7C Figure 6 is a schematic diagram of the structure after step S230 in the method of manufacturing a Lamb wave resonator. Please refer to Figure 7C After bonding, the surface of the first substrate 151 facing away from the second substrate 153 can be in contact with the upper surface of the support film 161 and the upper surface of each of the plurality of supports 121. Optionally, the piezoelectric substrate 150 is bonded by direct bonding.

[0074] S240, peeling off the second substrate 153 and thinning the first substrate 151 to form the piezoelectric film 130; wherein, Figure 7D Figure 7 is a schematic diagram of the structure after step S240 in the method of manufacturing a Lamb wave resonator. Please refer to Figure 7D The second substrate 153 is peeled off from the defect layer 152, and the first substrate 151 is thinned to obtain the piezoelectric film 130, and the thickness of the piezoelectric film 130 after thinning is the thickness of the piezoelectric film 130 in the Lamb wave resonator. Optionally, the second substrate 153 is peeled off and the first substrate 151 is thinned by heat treatment.

[0075] S250, forming the top electrode 140 on the second surface of the piezoelectric film 130; wherein, Figure 7E Figure 8 is a schematic diagram of the structure after step S250 in the method of manufacturing a Lamb wave resonator. Please refer to Figure 7E The supports 121 and the sub-electrodes 141 of the top electrode 140 correspond one-to-one and at least partially overlap in the thickness direction of the piezoelectric film 130. Of course, it can not be one-to-one correspondence, as long as the top electrode 140 is disposed on the upper surface of the piezoelectric film 130 and the supports 121 are disposed on the lower surface of the piezoelectric film 130. Optionally, the top electrode 140 is formed by depositing a layer of metal on the surface of the piezoelectric film 130 and then etching or using the Lift-off method to form the top electrode 140.

[0076] Figure 9 is a schematic diagram of the structure after step S260 in the method of manufacturing a Lamb wave resonator. Please refer to Figures 10A-10JIn the present application, in order to better control the size and position of the gap between the support bodies 121 and make the preparation of the Lamb wave resonator more successful, the preparation method of the Lamb wave resonator comprises the following steps. A support substrate 110 is provided, and a plurality of support bodies 121 are formed on the surface of the support substrate 110. A sacrificial layer material 181 is deposited to fill the gap between the plurality of support bodies 121, and the upper surface of the sacrificial layer material 181 is flush with the upper surface of the support bodies 121. An adhesive layer 170 is formed on the surface of the sacrificial layer material 181 and the surface of the plurality of support bodies 121. A piezoelectric film 130 is formed, and a first surface of the piezoelectric film 130 is arranged on the surface of the adhesive layer 170 away from the support substrate 110. A top electrode 140 is formed on a second surface of the piezoelectric film 130 away from the adhesive layer 170, so that the top electrode 140 and the plurality of support bodies 121 at least partially overlap in the thickness direction of the piezoelectric film 130. The sacrificial layer material 181 filled between the plurality of support bodies 121 is removed.

[0077] Figure 8 A fourth structural schematic diagram of the Lamb wave resonator provided in the embodiments of the present application is shown in the figure. Figure 9 A fourth structural schematic diagram of the Lamb wave resonator provided in the embodiments of the present application is shown in the figure. Figure 8 An enlarged view of the dashed box in the figure. Please refer to Figure 8 A fourth structural schematic diagram of the Lamb wave resonator provided in the embodiments of the present application is shown in the figure. Figure 9 The adhesive layer 170 is arranged between the support body 121 and the piezoelectric film 130 of the Lamb wave resonator prepared by the above method. The thickness of the adhesive layer 170 can be 50 nm-2 μm. The material of the adhesive layer 170 can be SiO2, SiC, SiN or diamond.

[0078] The preparation method of the Lamb wave resonator is as follows:

[0079] In S310, a support substrate 110 is provided, a support film 161 is formed on the support substrate 110, and the support film 161 is etched to form a plurality of support bodies 121. The material of the support substrate 110 and the material of the support film 161 can be the same or different. For example, the material of the support film 161 can be SiO2, SiC, SiN or diamond. After etching the support film 161, the etching depth is less than the thickness of the support film 161. Figure 10A A fourth structural schematic diagram of the Lamb wave resonator provided in the embodiments of the present application is shown in the figure. Figure 10A A layer of support film 161 is formed on the support substrate 110. The material of the support substrate 110 and the material of the support film 161 can be the same or different. For example, the material of the support film 161 can be SiO2, SiC, SiN or diamond. After etching the support film 161, the etching depth is less than the thickness of the support film 161.

[0080] Optionally, the support film 161 can be formed by thermal oxidation treatment, PECVD, magnetron sputtering or LPCVD deposition. Then the support film 161 can be etched by ICP-RIE dry etching.

[0081] S320, depositing a sacrificial layer material 181 to fill the gaps between the plurality of supports 121 and to level the upper surface of the sacrificial layer material 181 with the upper surface of the supports 121; Figure 10B FIG. 6 is a schematic diagram of a structure after step S320 in the method for manufacturing a Lamb wave resonator. Please refer to Figure 10B The upper surface of the sacrificial layer material 181 is level with the upper surface of the supports 121 and the upper surface of the support film 161.

[0082] Optionally, the sacrificial layer material 181 is polysilicon, and the sacrificial layer material 181 is deposited by PECVD, magnetron sputtering or LPCVD.

[0083] In other embodiments, the sacrificial layer material can also be SiO2, and the sacrificial layer material is deposited by PECVD, magnetron sputtering or LPCVD.

[0084] In the present application, the sacrificial layer material 181 can be deposited to a thickness consistent with the thickness of the supports 121, that is, the sacrificial layer material 181 is deposited to just fill the gaps between the supports 121; or the sacrificial layer material 181 can be deposited to a thickness exceeding the thickness of the supports 121, that is, the sacrificial layer material 181 is deposited to fill the gaps between the supports 121 and to exceed the height of the supports 121, and the sacrificial layer material 181 is also deposited on the upper surface of the support film 161 and the upper surface of the supports 121, and the sacrificial layer material 181 is thinned to expose the supports 121, so that the upper surface of the sacrificial layer material 181 is level with the upper surface of the supports 121.

[0085] It should be noted that, Figure 10A and 10B In the present application, if the plurality of supports 121 are formed on the support film 161, the sacrificial layer material 181 is filled to fill the support film 161 when filling the sacrificial layer material 181; if the plurality of supports are formed by etching the upper part of the support substrate, the sacrificial layer material is filled to fill the support substrate when filling the sacrificial layer material.

[0086] S330, forming an adhesive layer 170 on the surface of the sacrificial layer material 181 and the surface of the plurality of supports 121; Figure 10C FIG. 7 is a schematic diagram of a structure after step S330 in the method for manufacturing a Lamb wave resonator. Please refer to Figure 10C The lower surface of the adhesive layer 170 is in contact with the upper surface of the sacrificial layer material 181 and the upper surface of the supports 121.

[0087] Optionally, the material of the adhesive layer 170 is SiO2, SiC, SiN or diamond. The adhesive layer 170 is formed by thermal oxidation, PECVD, magnetron sputtering or LPCVD deposition.

[0088] S340, a piezoelectric substrate 150 is provided, ion implantation is performed on the piezoelectric substrate 150 to form a first substrate 151 and a second substrate 153 connected by a defect layer 152; wherein, Figure 10D Figure 6 is a schematic diagram of a structure after step S340 in the method for manufacturing a Lamb wave resonator. Please refer to Figure 10D The ion implantation is performed from above the piezoelectric substrate 150. Optionally, the material of the piezoelectric substrate 150 is lithium niobate or lithium tantalate, and the ion implantation is performed by using an ion implanter to implant H + or He + ions to form the defect layer 152.

[0089] S350, the first substrate 151 is bonded to the surface of the adhesive layer 170 facing away from the support substrate 110; wherein, Figure 10E Figure 7 is a schematic diagram of a structure after step S350 in the method for manufacturing a Lamb wave resonator. Please refer to Figure 10E After the bonding, the surface of the first substrate 151 facing away from the second substrate 153 can be in contact with the upper surface of the adhesive layer 170. Optionally, the piezoelectric substrate 150 is bonded by direct bonding.

[0090] S360, the second substrate 153 is peeled off and the first substrate 151 is thinned to form a piezoelectric film 130; wherein, Figure 10F Figure 8 is a schematic diagram of a structure after step S360 in the method for manufacturing a Lamb wave resonator. Please refer to Figure 10F The second substrate 153 is peeled off from the defect layer 152, and the first substrate 151 is thinned to obtain the piezoelectric film 130, and the thickness of the piezoelectric film 130 after the thinning is the thickness of the piezoelectric film 130 in the Lamb wave resonator. Optionally, the second substrate 153 is peeled off and the first substrate 151 is thinned by using a thermal treatment method.

[0091] S370, a top electrode 140 is formed on the second surface of the piezoelectric film 130 facing away from the adhesive layer 170; wherein, Figure 10G Figure 9 is a schematic diagram of a structure after step S370 in the method for manufacturing a Lamb wave resonator. Please refer to Figure 10G The support body 121 and the sub-electrode 141 of the top electrode 140 correspond one-to-one and at least partially overlap in the thickness direction of the piezoelectric film 130. Of course, it can not be in a one-to-one correspondence, as long as the top electrode 140 is arranged on the upper surface of the piezoelectric film 130 and the support body 121 is arranged on the lower surface of the piezoelectric film 130.

[0092] S380, forming a release hole 182 on the piezoelectric film 130 and the adhesive layer 170 to expose the sacrificial layer material 181; wherein, Figure 10H Fig. 6 is a first structure diagram after step S380 in the method for manufacturing the Lamb wave resonator; please refer to Figure 10H The release hole 182 penetrates the piezoelectric film 130 and the adhesive layer 170 to expose the sacrificial layer material 181, so as to remove the sacrificial layer material 181 subsequently.

[0093] Optionally, the method for forming the release hole is ICP-RIE dry etching or FIB dry etching.

[0094] Fig. 7 is a second structure diagram after step S380 in the method for manufacturing the Lamb wave resonator; please refer to Figure 10I Fig. 7 is a second structure diagram after step S380 in the method for manufacturing the Lamb wave resonator; please refer to Figure 10I The projection of the release hole 182 on the support substrate 110 is a ring structure, and the plurality of support bodies 121 and the top electrode 140 are located in the ring structure. That is, after the release hole 182 is formed, the circumferential edge of the sacrificial layer material 181 can be exposed, which is beneficial to the etching of the sacrificial layer material 181 subsequently.

[0095] In other embodiments, the release hole 182 can not be a ring structure, and a plurality of release holes 182 can be arranged at intervals to etch the sacrificial layer material 181.

[0096] S390, etching the sacrificial layer material 181 from the release hole 182; wherein, Figure 10J Fig. 8 is a structure diagram after step S390 in the method for manufacturing the Lamb wave resonator; please refer to Figure 10J The space between the plurality of support bodies 121 is fixed in size and position, and the size and position of the space do not change basically during the whole process of manufacturing the Lamb wave resonator due to the filling of the sacrificial layer material 181, so that the success rate of manufacturing the Lamb wave resonator is higher.

[0097] Optionally, the method for etching the sacrificial layer material 181 is XeF2 or HF gas etching.

[0098] Experimental Example

[0099] The Lamb wave resonator provided by the embodiment is Figure 1 The Lamb wave resonator provided by the comparative example is an existing Lamb wave resonator. In the Lamb wave resonator provided by the comparative example, the opposite sides of the piezoelectric film are fixed to the support substrate through anchor points.

[0100] Figure 11 Fig. 9 is a frequency impedance curve comparison diagram of the Lamb wave resonators provided by the embodiment and the comparative example.

[0101] The frequency impedance curve of the Lamb wave resonator with the support-free suspended plate structure is provided for the comparative example; the frequency impedance curve of the Lamb wave resonator with the support structure is provided for the embodiment. From Figure 11 It can be seen that, since the main resonant mode in the Lamb wave resonator is an anti-symmetrical Lamb wave, the acoustic wave energy is mainly concentrated in the region between the electrodes, and the multiple reflections of the acoustic wave energy transmitted to the electrode region will generate a spurious mode, so the frequency impedance curve in the comparative example contains more spurious waves; in the present application, the support structure 120 (the plurality of supports 121) is added, and the plurality of supports 121 can effectively introduce the spurious mode generated by the multiple reflections of the acoustic wave energy transmitted to the electrode region to the support substrate 110, thereby reducing the spurious waves, so the frequency impedance curve in the embodiment basically does not contain spurious waves. Figure 1

[0102] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. A Lamb wave resonator characterized by, The application relates to a piezoelectric film structure, which comprises a support substrate, a support structure, a piezoelectric film and a top electrode. The support substrate and the piezoelectric film are spaced apart, one end of the support structure is arranged on the surface of the support substrate, the other end of the support structure is arranged on the first surface of the piezoelectric film, the top electrode is arranged on the second surface of the piezoelectric film which is away from the support substrate, and the projection of the top electrode on the piezoelectric film and the projection of the support structure on the piezoelectric film at least partially overlap. The support structure comprises a plurality of support bodies, one end of the plurality of support bodies is spaced apart on the surface of the support substrate, the other end of the plurality of support bodies is spaced apart on the first surface of the piezoelectric film, and the material of the support structure is SiO2, SiC, SiN or diamond; the top electrode comprises a plurality of sub-electrodes, the plurality of sub-electrodes are spaced apart on the second surface of the piezoelectric film; one sub-electrode corresponds to one support body in one-to-one correspondence, and the projection of the support body on the piezoelectric film and the projection of the sub-electrode on the piezoelectric film at least partially overlap. The sum of the areas of the plurality of sub-electrodes in contact with the piezoelectric film is not less than the sum of the contact areas of the plurality of support bodies and the piezoelectric film.

2. The Lamb wave resonator of claim 1, wherein, The shape of each support body is long-strip-shaped, prism-shaped, cylindrical, prismatic or circular.

3. The Lamb wave resonator of claim 1, wherein, Or / and, each sub-electrode is long-strip-shaped, prism-shaped or cylindrical. The material of the support substrate is Si, SOI, SiC, sapphire or diamond.

4. The Lamb wave resonator according to any one of claims 1 to 3, characterized in that, Or / and, the material of the piezoelectric film is lithium niobate or lithium tantalate. Or / and, the material of the top electrode is Al, Mo, Au, Ag, Ni, Pt or Cu. An adhesive layer is arranged between the support body and the piezoelectric film.

5. The Lamb wave resonator of claim 4, wherein, The material of the adhesive layer is SiO2, SiC, SiN or diamond.

6. The Lamb wave resonator of claim 5, wherein, The application relates to a piezoelectric film structure, which comprises a support substrate, a support structure, a piezoelectric film and a top electrode.

7. A method of manufacturing a Lamb wave resonator according to any one of claims 1 to 6, characterized in that, The application provides the support substrate, forms the support structure on the surface of the support substrate; The piezoelectric film is formed, and the first surface of the piezoelectric film is arranged on one end of the support structure which is away from the support substrate; The top electrode is formed on the second surface of the piezoelectric film which is away from the support substrate, so that the projection of the top electrode on the piezoelectric film and the projection of the support structure on the piezoelectric film at least partially overlap. The step of forming the piezoelectric film and bonding the first surface of the piezoelectric film to one end of the support structure which is away from the support substrate comprises the following steps:

8. The method of claim 7, wherein the method further comprises: The piezoelectric substrate is provided, ion implantation is carried out on the piezoelectric substrate, and a first substrate and a second substrate connected by a defect layer are formed; The first substrate is bonded to one end of the support structure which is away from the support substrate; The second substrate is peeled off and the first substrate is thinned to form the piezoelectric film. The step of providing the support substrate and forming the support structure on the surface of the support substrate comprises the following steps:

9. The method of claim 7, wherein the method further comprises: The support substrate is provided, and the upper part of the support substrate is etched to form the support structure; Or, the support substrate is provided, a support film is arranged on the support substrate, and the support film is etched to form the support structure. The application relates to a piezoelectric film structure, which comprises a support substrate, a support structure, a piezoelectric film and a top electrode.

10. The method of claim 7-9, wherein the method further comprises, ​ A support substrate is provided, and a plurality of supports are formed on a surface of the support substrate; A sacrificial layer material is deposited to fill the gaps between the plurality of supports and to make the upper surface of the sacrificial layer material flush with the upper surface of the supports; An adhesive layer is formed on the surface of the sacrificial layer material and the surface of the plurality of supports; A piezoelectric thin film is formed, and a first surface of the piezoelectric thin film is disposed on the surface of the adhesive layer facing away from the support substrate; A top electrode is formed on a second surface of the piezoelectric thin film facing away from the adhesive layer, and the projection of the top electrode on the piezoelectric thin film and the projection of the plurality of supports on the piezoelectric thin film at least partially overlap; The sacrificial layer material filled between the plurality of supports is removed.

11. The method of claim 10, wherein the method further comprises: The sacrificial layer material is polysilicon or silicon dioxide.

12. The method of claim 11, wherein the method further comprises: The step of removing the sacrificial layer material filled between the plurality of supports includes: A release hole is formed on the piezoelectric thin film and the adhesive layer to expose the sacrificial layer material; The sacrificial layer material is etched away from the release hole.

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