A heterogeneous thin film substrate, a preparation method thereof, and a filter

Abstract

This application relates to the technical field of radio frequency device fabrication, and particularly to a heterogeneous thin film substrate, a method for fabricating the same, and a filter. The method includes: providing a support substrate having opposite first and second surfaces, wherein the second surface is a rough surface; depositing a defect layer on the second surface; both the surface of the defect layer facing the support substrate and the surface away from the support substrate are rough surfaces; forming an insulating layer on the surface of the defect layer away from the support substrate; polishing the insulating layer; and forming a piezoelectric layer on the surface of the insulating layer away from the support substrate to obtain the heterogeneous thin film substrate. By setting both the surface of the defect layer facing the support substrate and the surface away from the support substrate to be rough surfaces, the bulk acoustic waves propagating thereto can be scattered by the rough surfaces of the defect layer, thereby solving the problem of interface acoustic wave energy reflection in the filter.

Description

Technical Field

[0001] The present application relates to the technical field of radio frequency device preparation, and particularly to a heterogeneous thin film substrate, a preparation method thereof, and a filter. Background Art

[0002] With the increasing pursuit of data transmission speed, performance, and power consumption of telecommunication devices by people, there is a need to provide acoustic filters that operate at higher frequencies and larger bandwidths to achieve higher data transmission. Currently, integrating piezoelectric materials with silicon provides a wafer substrate for material-level integration and a material platform for preparing monolithic integrated modules; filters prepared from current heterogeneous substrate wafers can effectively increase the center frequency and bandwidth of the filter, reduce power consumption, and reduce heat dissipation. Using the ion beam stripping method to transfer piezoelectric single crystal materials onto the required substrate can already provide the corresponding wafer materials, and the thickness of the piezoelectric thin film is uniform, and the prepared devices have good stability.

[0003] However, in actual operation, due to the presence of many interfaces in the multi-layer film structure of the filter, and the different media of the many interfaces, a large acoustic impedance difference will be generated between the interfaces, which will cause additional acoustic wave energy reflection, resulting in additional signal responses in the frequency band of the acoustic filter. This response will cause spurious responses (as Figure 7 shown), thus affecting data transmission and causing crosstalk, which limits the application scenarios of the filter.

[0004] Therefore, there is a need to provide an improved heterogeneous thin film substrate and its preparation scheme to solve the problem of acoustic wave energy reflection at the interfaces in the filter. Summary of the Invention

[0005] In view of the above problems in the prior art, the present application provides a heterogeneous thin film substrate, a preparation method thereof, and a filter to solve technical problems such as acoustic wave energy reflection at the interfaces in the filter in the prior art. The specific technical solutions are as follows:

[0006] On the one hand, the present application provides a preparation method of a heterogeneous thin film substrate, the method comprising:

[0007] Providing a support substrate, the support substrate having opposite first and second surfaces, and the second surface being a rough surface;

[0008] Depositing a defect layer on the second surface; both the surface of the defect layer facing the support substrate and the surface away from the support substrate are rough surfaces;

[0009] Forming an insulating layer on the surface of the defect layer away from the support substrate;

[0010] Performing a polishing treatment on the insulating layer;

[0011] A piezoelectric layer is formed on a surface of the insulating layer away from the support substrate to obtain the heterogeneous thin film substrate.

[0012] Further, forming the piezoelectric layer on the surface of the insulating layer away from the support substrate includes:

[0013] Providing a piezoelectric substrate having opposite third and fourth surfaces;

[0014] Performing ion implantation on the third surface of the piezoelectric substrate to form an ion implantation layer in the piezoelectric substrate;

[0015] Bonding the third surface of the piezoelectric substrate to the surface of the insulating layer away from the support substrate to obtain a bonded wafer;

[0016] Performing annealing and peeling on the bonded wafer so that the bonded wafer peels along the ion implantation layer to form the piezoelectric layer on the surface of the insulating layer away from the support substrate.

[0017] Further, the roughness of the second surface is 1 to 1000 nm; the roughness of both the surface of the defect layer facing the support substrate and the surface away from the support substrate is 1 to 1000 nm.

[0018] Further, the material of the support substrate includes at least one of silicon, silicon oxide, sapphire, diamond, aluminum nitride, gallium nitride, silicon carbide, and silicon on insulator.

[0019] Further, the ions for ion implantation include at least one of hydrogen ions, helium ions, and neon ions;

[0020] The temperature of the ion implantation is -50 to 300 °C;

[0021] The implantation energy of the ion implantation is 1 to 2000 keV;

[0022] The dose of the ion implantation is 1×10 16 ~1×10 18 cm -2 .

[0023] Further, the material of the defect layer includes at least one of polysilicon and polycrystalline germanium, and the thickness of the defect layer is 0.1 - 10 μm.

[0024] Further, the material of the insulating layer includes at least one of silicon oxide and germanium oxide, and the thickness of the insulating layer is 0.1 - 10 μm.

[0025] Further, the material of the piezoelectric substrate includes at least one of lithium niobate, lithium tantalate, lithium borate, lead magnesium niobate-lead titanate, lanthanum gallium silicate, quartz, and sodium potassium tartrate, and the thickness of the piezoelectric substrate is 0.1-10 um.

[0026] On the other hand, the present application also provides a heterogeneous thin film substrate, which is prepared by the preparation method described above, and is characterized by including: a support substrate, a defect layer, an insulating layer, and a piezoelectric layer;

[0027] The support substrate has opposite first and second surfaces, and the second surface is a rough surface;

[0028] The defect layer is deposited on the second surface; both opposite surfaces of the defect layer are rough surfaces;

[0029] The insulating layer is located on the surface of the defect layer away from the support substrate;

[0030] The piezoelectric layer is located on the surface of the insulating layer away from the support substrate.

[0031] On the other hand, the present application also provides a filter, including the heterogeneous thin film substrate structure described above.

[0032] Due to the above technical solutions, the heterogeneous thin film substrate, its preparation method, and the filter provided by the present application have the following beneficial effects:

[0033] By setting the surfaces on one side of the defect layer facing the support substrate and the surface on the side away from the support substrate as rough surfaces, the bulk acoustic wave can be scattered and propagated through the rough surfaces of the defect layer, suppressing the acoustic wave energy reflection at the interface in the device, eliminating the out-of-band response generated by the acoustic wave energy reflection in the filter, reducing the out-of-band frequency response noise, and thus broadening the application range of the filter.

[0034] The rough surface of the defect layer in the present application is also beneficial to releasing the stress between the heterogeneous thin film substrate structures, and thus protecting the overall structure of the heterogeneous thin film substrate. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 It is a schematic flow chart of the method for preparing a heterogeneous thin film substrate provided by an embodiment of the present application;

[0037] Figure 2 It is a schematic structural diagram of the preparation process of the heterogeneous thin film substrate provided by an embodiment of the present application;

[0038] Figure 3 It is another schematic structural diagram of the preparation process of the heterogeneous thin film substrate provided by an embodiment of the present application;

[0039] Figure 4 It is another schematic structural diagram of the preparation process of the heterogeneous thin film substrate provided by an embodiment of the present application;

[0040] Figure 5 It is a frequency response diagram of a resonator applying the heterogeneous thin film substrate of the present application provided by an embodiment of the present application;

[0041] Figure 6 It is a schematic process diagram of forming a piezoelectric layer on an insulating layer provided by an embodiment of the present application;

[0042] Figure 7 It is a frequency response diagram of a resonator in the prior art provided by an embodiment of the present application.

[0043] Among them, the corresponding reference numerals in the figure are: 1 - support substrate; 2 - defect layer; 3 - insulating layer; 4 - piezoelectric substrate; 41 - ion implantation layer; 5 - piezoelectric layer; 6 - metal patterned electrode. Detailed implementation manners

[0044] Next, the technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0045] For the following defined terms, unless a different definition is given elsewhere in the claims or in this specification, these definitions shall apply. All numerical values, whether or not explicitly indicated, are hereby defined as being modified by the term "about". The term "about" generally refers to a numerical range that a person of ordinary skill in the art would consider equivalent to the stated value to produce substantially the same properties, functions, results, etc. A numerical range indicated by a low value and a high value is defined to include all the numerical values included in the numerical range and all the sub-ranges included in the numerical range.

[0046] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present disclosure are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0047] The following introduces the preparation method of the heterogeneous thin film substrate provided by the embodiments of the present application. Please refer to Figure 1 , Figure 1 which is a schematic flowchart of the preparation method of the heterogeneous thin film substrate. Figures 2 - 4 which is a schematic structural diagram of the heterogeneous thin film substrate preparation process. This specification provides method operation steps such as in the embodiments or flowcharts, but based on routine or non-creative labor, it may include more or fewer operation steps. The step sequence listed in the embodiments is only one way among the execution sequences of numerous steps, and does not represent the only execution sequence. When the actual preparation method is executed, it can be executed in the order shown in the embodiments or the drawings or executed in parallel. The method includes:

[0048] S100: Provide a support substrate 1. The support substrate 1 has opposite first and second surfaces, and the second surface is a rough surface.

[0049] In some embodiments, the material of the support substrate 1 includes at least one of silicon, silicon oxide, sapphire, diamond, aluminum nitride, gallium nitride, silicon carbide, and silicon on insulator.

[0050] In some embodiments, the roughness of the second surface is 1 - 1000 nm; the rough surface of the second surface of the support substrate 1 can be obtained by physical or chemical methods, etc. Among them, the physical method can be grinding, and the chemical method can be etching.

[0051] By setting the second surface of the support substrate 1 as a rough surface, it is convenient to prepare the rough surface structure of the surface of the defect layer 2 facing the support substrate side. At the same time, the filter prepared by the heterogeneous thin film substrate of the present application does not contain a smooth multi-layer film, eliminating the phenomenon of out-of-band response introduced after the reflection of acoustic wave energy.

[0052] S200: Deposit a defect layer 2 on the second surface; both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 are rough surfaces; among them, deposit the defect layer 2 on the second surface; the deposition methods include at least one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition. By setting the defect layer 2, the additional loss of the radio frequency device is reduced.

[0053] In some embodiments, the material of the defect layer 2 includes at least one of polysilicon and polycrystalline germanium, and the thickness of the defect layer 2 is 0.1 - 10 um. The roughness of both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 is 1 - 1000 nm. It should be noted that the roughness of the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 can be the same or different.

[0054] In this application, an insulating layer 3 with rough surfaces on both opposite sides is provided. The rough surfaces of the defect layer can scatter the propagation of bulk acoustic waves, inhibit the reflection of acoustic wave energy at the interface in the device, eliminate the out-of-band response generated by the reflection of acoustic wave energy in the filter, reduce the out-of-band frequency response noise, and thus broaden the application range of the filter.

[0055] Meanwhile, the rough surface of the defect layer 2 in this application is also beneficial to releasing the stress between the heterogeneous thin film substrate structures, thereby protecting the overall structure of the heterogeneous thin film substrate.

[0056] S300: Form an insulating layer 3 on the surface of the defect layer 2 away from the support substrate 1.

[0057] In some embodiments, the material of the insulating layer 3 includes at least one of silicon oxide and germanium oxide, and the thickness of the insulating layer 3 is 0.1 - 10 um.

[0058] In some embodiments, the method of forming the insulating layer 3 on the surface of the defect layer 2 away from the support substrate 1 includes at least one of thermal oxidation and chemical vapor deposition. Preferably, when the defect layer 2 is made of polysilicon material, the insulating layer 3 can be formed on the surface of the defect layer 2 away from the support substrate 1 by thermal oxidation. When the defect layer 2 is not made of polysilicon material, the insulating layer 3 can be formed on the surface of the defect layer 2 away from the support substrate 1 by chemical vapor deposition.

[0059] S400: Polish the insulating layer 3.

[0060] S500: Form a piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1 to obtain a heterogeneous thin film substrate. As Figure 6 shown, forming the piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1 includes:

[0061] S501: Provide a piezoelectric substrate 4, and the piezoelectric substrate 4 has opposite third and fourth surfaces.

[0062] In some embodiments, the material of the piezoelectric substrate 4 includes at least one of lithium niobate, lithium tantalate, lithium borate, lead magnesium niobate-lead titanate, lanthanum gallium silicate, quartz, and potassium sodium tartrate, and the thickness of the piezoelectric substrate 4 is 0.1 - 10 um.

[0063] S502: Ion implant the third surface of the piezoelectric substrate 4 to form an ion implantation layer 41 within the piezoelectric substrate 4. Among them, the ion implantation layer 41 is a layer that is approximately parallel to the surface of the piezoelectric substrate 4 material and has a uniform thickness.

[0064] In some embodiments, the ions for ion implantation include at least one of hydrogen ions, helium ions, and neon ions.

[0065] In some embodiments, the temperature of the ion implantation is -50 to 300 °C.

[0066] In some embodiments, the implantation energy of the ion implantation is 1 - 2000 keV.

[0067] In some embodiments, the dose of the ion implantation is 1×10 16 ~1×10 18 cm -2 .

[0068] S503: Bond the third surface of the piezoelectric substrate 4 to the surface of the insulating layer 3 away from the support substrate 1 to obtain a bonded wafer.

[0069] In practical applications, the methods and conditions for bonding the piezoelectric substrate 4 and the insulating layer 3 may be the same as those in the prior art, and the present disclosure does not make any limitations.

[0070] S504: Perform annealing and peeling treatment on the bonded wafer so that the bonded wafer peels along the ion implantation layer 41 to form a piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1.

[0071] An embodiment of the present application also provides a heterogeneous thin film substrate prepared by the foregoing preparation method.

[0072] A heterogeneous thin film substrate includes: a support substrate 1, a defect layer 2, an insulating layer 3, and a piezoelectric layer 5; the support substrate 1 has opposite first and second surfaces, and the second surface is a rough surface; the defect layer 2 is deposited on the second surface; both opposite surfaces of the defect layer 2 are rough surfaces; the insulating layer 3 is located on the surface of the defect layer 2 away from the support substrate 1; the piezoelectric layer 5 is located on the surface of the insulating layer 3 away from the support substrate 1.

[0073] In some embodiments, the material of the support substrate 1 includes at least one of silicon, silicon oxide, sapphire, diamond, aluminum nitride, gallium nitride, silicon carbide, and silicon on insulator.

[0074] In some embodiments, the roughness of the second surface may be 1-1000 nm; by setting the second surface of the support substrate 1 as a rough surface, it is convenient to prepare the rough surface structures of the two opposite surfaces of the defect layer 2. At the same time, the filter prepared by the heterogeneous thin film substrate of the present application does not contain a smooth multi-layer film, eliminating the phenomenon of out-of-band response introduced after the reflection of acoustic wave energy.

[0075] In some other embodiments, the roughness of the second surface may be 50-1000 nm;

[0076] In some other embodiments, the roughness of the second surface may be 1-500 nm;

[0077] In some other embodiments, the roughness of the second surface may be 500-800 nm;

[0078] In some embodiments, by setting the defect layer 2, the additional loss of the radio frequency device is reduced. The material of the defect layer 2 includes at least one of polysilicon and polycrystalline germanium, and the thickness of the defect layer 2 is 0.1-10 μm. The roughness of both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 is 1-1000 nm. It should be noted that the roughness of the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 may be the same roughness or different roughnesses.

[0079] In some other embodiments, the roughness of both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 is 1-500 nm.

[0080] In some other embodiments, the roughness of both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 is 80-500 nm.

[0081] The present application provides an insulating layer 3 with rough surfaces on both opposite sides. The rough surface of the defect layer 2 can scatter the bulk acoustic waves propagating thereto, suppressing the reflection of acoustic wave energy at the interface in the device, eliminating the out-of-band response generated by the reflection of acoustic wave energy in the filter, and achieving a 'clean' out-of-band frequency response, thereby enabling the filter to have a wide application range.

[0082] At the same time, the rough surface of the defect layer 2 of the present application is also beneficial to releasing the stress between the heterogeneous thin film substrate structures, thereby protecting the overall structure of the heterogeneous thin film substrate.

[0083] In some embodiments, the material of the insulating layer 3 includes at least one of silicon oxide and germanium oxide, and the thickness of the insulating layer 3 is 0.1-10 μm.

[0084] In some embodiments, the material of the piezoelectric layer 5 includes at least one of lithium niobate, lithium tantalate, lithium borate, lead magnesium niobate-lead titanate, lanthanum gallium silicate, quartz, and sodium potassium tartrate, and the thickness of the piezoelectric layer 5 is 0.1 - 10 μm.

[0085] On the other hand, the present application also provides a filter, including the heterogeneous thin-film substrate structure as above. The filter includes: depositing a metal patterned electrode 6 (as Figure 4 shown) on the surface of the piezoelectric layer 5 of the heterogeneous thin-film substrate away from the support substrate 1 to obtain the filter.

[0086] Embodiment 1

[0087] Embodiment 1 of the present disclosure discloses a method for preparing a heterogeneous thin-film substrate, and the preparation method includes the following steps:

[0088] S100: Provide a support substrate 1 of a silicon wafer, and the support substrate 1 has opposite first and second surfaces, and the second surface is a rough surface.

[0089] Perform a grinding and thinning treatment on the silicon wafer support substrate 1 so that the roughness of the second surface of the support substrate 1 is 1 - 1000 nm;

[0090] By setting the second surface of the support substrate 1 as a rough surface, it is convenient to prepare the rough surface structures of the two opposite surfaces of the defect layer 2. At the same time, the filter prepared by the heterogeneous thin-film substrate of the present application does not contain a smooth multi-layer film, eliminating the phenomenon of out-of-band response introduced after the reflection of acoustic wave energy.

[0091] S200: Deposit a defect layer 2 on the second surface; both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 are rough surfaces; wherein, deposit the defect layer 2 on the second surface; the deposition method includes at least one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition. By setting the defect layer 2, the additional loss of the radio frequency device is reduced.

[0092] In some embodiments, the material of the defect layer 2 is polysilicon, and the thickness of the defect layer 2 is 1.5 μm. The roughness of both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 is 1 - 1000 nm. It should be noted that the roughness of the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 can be the same roughness or different roughnesses.

[0093] In this application, by setting the surfaces of the defect layer facing the support substrate and away from the support substrate as rough surfaces, the bulk acoustic wave can be scattered and propagated through the rough surfaces of the defect layer, suppressing the reflection of acoustic wave energy at the interface in the device, eliminating the out-of-band response generated by the reflection of acoustic wave energy in the filter, reducing the out-of-band frequency response noise, and thus broadening the application range of the filter.

[0094] Meanwhile, the rough surfaces of the defect layer in this application are also beneficial to releasing the stress between the heterogeneous thin film substrate structures, thereby protecting the overall structure of the heterogeneous thin film substrate.

[0095] S300: Form an insulating layer 3 on the surface of the defect layer 2 away from the support substrate 1 by thermal oxidation.

[0096] In some embodiments, the material of the insulating layer 3 includes at least one of silicon oxide and germanium oxide, and the thickness of the insulating layer 3 is 0.1 - 10 um.

[0097] S400: Polish the insulating layer 3.

[0098] S500: Form a piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1 to obtain a heterogeneous thin film substrate. As Figure 6 shown, forming the piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1 includes:

[0099] S501: Provide a piezoelectric substrate 4 made of lithium tantalate material, and the piezoelectric substrate 4 has opposite third and fourth surfaces.

[0100] In some embodiments, the thickness of the piezoelectric substrate 4 is 0.1 - 10 um.

[0101] S502: Perform ion implantation on the third surface of the piezoelectric substrate 4 to form an ion implantation layer 41 in the piezoelectric substrate 4. Among them, the implanted ions are hydrogen ions, the temperature of ion implantation is 50 - 150 °C, the implantation energy of ion implantation is 200 KeV, and the dose of ion implantation is 1e17 cm -2 .

[0102] S503: Bond the third surface of the piezoelectric substrate 4 to the surface of the insulating layer 3 away from the support substrate 1 to obtain a bonded wafer. Heat the bonded wafer to 200 °C and hold for 100 h.

[0103] In practical applications, the methods and conditions for bonding the piezoelectric substrate 4 and the insulating layer 3 can be the same as those in the prior art, and this disclosure does not make any limitations.

[0104] S504: Perform annealing and peeling treatment on the bonded wafer so that the bonded wafer peels along the ion implantation layer 41 to form a piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1.

[0105] Among them, steps S501 and S502 are as Figure 2 shown, and steps S503 and S504 are as Figure 4 shown.

[0106] Embodiment 2

[0107] Embodiment 2 of the present application discloses a method for preparing a heterogeneous thin film substrate. The preparation method includes the following steps:

[0108] S100: Provide a silicon support substrate 1. The support substrate 1 has opposite first and second surfaces, and the second surface is a rough surface.

[0109] In some embodiments, the roughness of the second surface is 1 - 1000 nm.

[0110] S200: Deposit a polysilicon defect layer 2 on the second surface; both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 are rough surfaces; wherein, the roughness of both the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 is 140 - 160 nm.

[0111] The present application provides an insulating layer 3 with rough surfaces on both opposite sides. The rough surface of the defect layer 2 can scatter the bulk acoustic waves propagating thereto, suppressing the acoustic wave energy reflection at the interface in the device, eliminating the out-of-band response generated by the acoustic wave energy reflection in the filter, and achieving a 'clean' out-of-band frequency response, thereby enabling the filter to have a wide application range.

[0112] Meanwhile, the rough surface of the defect layer 2 in the present application is also beneficial to releasing the stress between the heterogeneous thin film substrate structures, thereby protecting the overall structure of the heterogeneous thin film substrate.

[0113] S300: Form a silicon dioxide insulating layer 3 on the surface of the defect layer 2 away from the support substrate 1.

[0114] The thickness of the silicon dioxide insulating layer 3 is 0.1 - 10 um.

[0115] S400: Polish the silicon dioxide insulating layer 3.

[0116] S500: Form a lithium tantalate piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1 to obtain a heterogeneous thin film substrate. As Figure 6 shown, forming the piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1 includes:

[0117] S501: Provide a piezoelectric substrate 4. The lithium tantalate piezoelectric substrate 4 includes opposite third and fourth surfaces.

[0118] The thickness of the piezoelectric substrate 4 is 0.1 - 10 um.

[0119] S502: Ion implant the third surface of the piezoelectric substrate 4 to form an ion implantation layer 41 within the piezoelectric substrate 4. Herein, ion implantation means that after an ion beam hits the material of the piezoelectric substrate 4, its speed gradually decreases due to the resistance of the piezoelectric substrate 4 material and finally stops within the piezoelectric substrate 4 material. The ion implantation layer 41 is a layer that is approximately parallel to the surface of the piezoelectric substrate 4 material and has a uniform thickness.

[0120] In some embodiments, the ions for ion implantation include at least one of hydrogen ions, helium ions, and neon ions.

[0121] In some embodiments, the temperature of ion implantation is -50 to 300 °C.

[0122] In some embodiments, the implantation energy of ion implantation is 1 to 2000 keV.

[0123] In some embodiments, the dose of ion implantation is 1×10 16 ~1×10 18 cm -2 .

[0124] S503: Bond the third surface of the piezoelectric substrate 4 to the surface of the insulating layer 3 away from the support substrate 1 to obtain a bonded wafer.

[0125] S504: Perform annealing and peeling treatment on the bonded wafer so that the bonded wafer peels along the ion implantation layer 41 to form a lithium tantalate piezoelectric layer 5 on the surface of the insulating layer 3 away from the support substrate 1.

[0126] Specifically, the resonator is the basic unit of the filter. A resonator is fabricated using the heterogeneous thin film substrate provided by the present application and its frequency response is tested. As shown in Figure 5 and Figure 7 , Figure 5 is the frequency response diagram of the resonator fabricated using the heterogeneous thin film substrate of Embodiment 2 herein; Figure 7 is the frequency response diagram of the resonator in the prior art when the two opposite surfaces of the defect layer in the heterogeneous thin film substrate are smooth; it can be clearly seen that Figure 5 has less clutter response, Figure 7 has more clutter. By setting the surface of the defect layer 2 facing the support substrate 1 and the surface away from the support substrate 1 to be rough surfaces, the present application scatters and propagates the bulk acoustic wave through the rough surfaces of the defect layer, suppresses the acoustic wave energy reflection at the interface in the device, eliminates the out-of-band response generated by the acoustic wave energy reflection in the filter, reduces the out-of-band frequency response noise, thereby broadening the application range of the filter.

[0127] Due to the above technical solution, the heterogeneous thin film substrate, its preparation method and the filter provided by the present application have the following beneficial effects:

[0128] In the present application, by setting the surfaces of the defect layer facing the support substrate and away from the support substrate to be rough surfaces, the bulk acoustic wave can be scattered and propagated through the rough surfaces of the defect layer, suppressing the acoustic wave energy reflection at the interface in the device, eliminating the out-of-band response generated by the acoustic wave energy reflection in the filter, reducing the out-of-band frequency response noise, and thus broadening the application range of the filter.

[0129] The rough surfaces of the defect layer of the present application are also beneficial to releasing the stress between the heterogeneous thin film substrate structures, thereby protecting the overall structure of the heterogeneous thin film substrate.

[0130] The above description has fully disclosed the specific implementation manners of the present application. It should be noted that any modification made by those skilled in the art to the specific implementation manners of the present application does not depart from the scope of the claims of the present application. Accordingly, the scope of the claims of the present application is not limited solely to the foregoing specific implementation manners.

Claims

1. A method for preparing a heterogeneous thin film substrate, characterized in that, The method includes: providing a support substrate (1), the support substrate (1) having opposite first and second surfaces, the second surface being a rough surface; depositing a defect layer (2) on the second surface; both a surface of the defect layer (2) facing the support substrate (1) and a surface of the defect layer (2) away from the support substrate (1) are rough surfaces; forming an insulating layer (3) on a surface of the defect layer (2) away from the support substrate (1); performing a polishing treatment on the insulating layer (3); forming a piezoelectric layer (5) on a surface of the insulating layer (3) away from the support substrate (1) to obtain the hetero-film substrate; the roughness of the second surface is 1 to 1000 nm; the roughness of both a surface of the defect layer (2) facing the support substrate (1) and a surface of the defect layer (2) away from the support substrate (1) is 1 to 1000 nm.

2. The method according to claim 1, characterized in that, The forming the piezoelectric layer (5) on a surface of the insulating layer (3) away from the support substrate (1) includes: providing a piezoelectric substrate (4), the piezoelectric substrate (4) having opposite third and fourth surfaces; performing ion implantation on the third surface of the piezoelectric substrate (4) to form an ion implantation layer (41) in the piezoelectric substrate (4); bonding the third surface of the piezoelectric substrate (4) to the surface of the insulating layer (3) away from the support substrate (1) to obtain a bonded wafer; performing an annealing and peeling treatment on the bonded wafer to peel the bonded wafer along the ion implantation layer (41) so as to form the piezoelectric layer (5) on a surface of the insulating layer (3) away from the support substrate (1).

3. The method according to claim 1, wherein The material of the support substrate (1) includes at least one of silicon, silicon oxide, sapphire, diamond, aluminum nitride, gallium nitride, silicon carbide, and silicon on insulator.

4. The method according to claim 2, characterized in that, The ions for the ion implantation include at least one of hydrogen ions, helium ions, and neon ions; the temperature of the ion implantation is -50 to 300 °C; the implantation energy of the ion implantation is 1 to 2000 keV; The dose of the ion implantation is 1×10 16 ~1×10 18 cm -2 .

5. The method according to claim 1, characterized in that The material of the defect layer (2) includes at least one of polysilicon and polycrystalline germanium, and the thickness of the defect layer (2) is 0.1 - 10 μm.

6. The method according to claim 1, wherein The material of the insulating layer (3) includes at least one of silicon oxide and germanium oxide, and the thickness of the insulating layer (3) is 0.1 - 10 μm.

7. The method according to claim 2, wherein The material of the piezoelectric substrate (4) includes at least one of lithium niobate, lithium tantalate, lithium borate, lead magnesium niobate-lead titanate, lanthanum gallium silicate, quartz, and sodium potassium tartrate, and the thickness of the piezoelectric substrate (4) is 0.1 - 10 μm.

8. A heterogeneous thin film substrate prepared by the preparation method according to any one of claims 1-7, characterized in that, including: a support substrate (1), a defect layer (2), an insulating layer (3), and a piezoelectric layer (5); the support substrate (1) has opposite first and second surfaces, the second surface being a rough surface; the defect layer (2) is deposited on the second surface; both opposite surfaces of the defect layer (2) are rough surfaces; the insulating layer (3) is located on a surface of the defect layer (2) away from the support substrate (1); The piezoelectric layer (5) is located on the surface of the insulating layer (3) away from the support substrate (1).

9. A filter, characterized in that, Comprising a heterogeneous thin film substrate according to claim 8.

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