Temperature compensation type bulk acoustic wave resonator, preparation method thereof and duplexer

Abstract

The invention relates to the technical field of bulk acoustic wave resonators, and particularly provides a temperature compensation type bulk acoustic wave resonator, a preparation method thereof and a duplexer, the temperature compensation type bulk acoustic wave resonator comprises a substrate, a bottom electrode, a piezoelectric layer, a top electrode and a temperature compensation layer which are sequentially connected from bottom to top, the substrate is provided with an acoustic reflector, and the temperature compensation layer is provided with a dielectric layer. The temperature drift coefficient of the temperature compensation layer is smaller than that of the piezoelectric layer, the temperature compensation layer comprises a first compensation part, and the boundary of the projection of the first compensation part in the overlook direction is located in the boundary of the projection of the acoustic reflector in the overlook direction; the temperature compensation type bulk acoustic wave resonator can effectively solve the problem that the resonant frequency of the bulk acoustic wave resonator is easily influenced by the temperature change due to the fact that the material characteristic of the piezoelectric layer shifts along with the temperature change.

Description

Technical Field

[0001] The present application relates to the technical field of bulk acoustic wave resonators, and more particularly, to a temperature-compensated bulk acoustic wave resonator, a preparation method thereof, and a duplexer. Background Art

[0002] In related technologies, aluminum nitride is usually selected as the material of the piezoelectric layer for bulk acoustic wave resonators. Since the material properties of aluminum nitride shift with temperature changes, and the material properties of the piezoelectric layer are associated with the resonance frequency of the bulk acoustic wave resonator, there is a problem that the resonance frequency of the bulk acoustic wave resonator in related technologies is easily affected by temperature changes, resulting in poor frequency-temperature stability of the bulk acoustic wave resonator.

[0003] In view of the above problems, there is currently no effective technical solution. It should be noted that the above information disclosed in this part is only used to understand the background of the inventive concept of the present invention, and thus may include information that does not constitute the prior art. Summary of the Invention

[0004] The purpose of the present application is to provide a temperature-compensated bulk acoustic wave resonator, a preparation method thereof, and a duplexer, which can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is easily affected by temperature changes due to the shift of the material properties of the piezoelectric layer with temperature changes.

[0005] In a first aspect, the present application provides a temperature-compensated bulk acoustic wave resonator, which includes: A substrate, a bottom electrode, a piezoelectric layer, a top electrode, and a temperature compensation layer connected in sequence from bottom to top. An acoustic mirror is provided on the substrate. The temperature drift coefficient of the temperature compensation layer is less than that of the piezoelectric layer. The temperature compensation layer includes a first compensation portion, and the boundary of the projection of the first compensation portion in the top view direction is located within the boundary of the projection of the acoustic mirror in the top view direction.

[0006] The temperature-compensated bulk acoustic wave resonator provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer by forming a temperature compensation layer on the top electrode. That is, the present application can effectively suppress the influence of temperature changes on the material properties of the piezoelectric layer. Since the present application can suppress the influence of temperature changes on the material properties of the piezoelectric layer, and the material properties of the piezoelectric layer are associated with the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature changes on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is easily affected by temperature changes due to the shift of the material properties of the piezoelectric layer with temperature changes, thereby effectively improving the frequency-temperature stability of the bulk acoustic wave resonator.

[0007] Optionally, the material of the temperature compensation layer is SiO2.

[0008] Since SiO2 has a low temperature drift coefficient, an ultra-wide bandgap width, and a high critical breakdown electric field, the low temperature drift coefficient can further suppress the temperature drift phenomenon of the piezoelectric layer, the ultra-wide bandgap width can suppress the leakage of transverse waves, and the high critical breakdown electric field can enable the bulk acoustic wave filter to maintain a stable frequency under high-power conditions. Therefore, this technical solution can effectively improve the temperature compensation effect of the temperature compensation layer, as well as improve the quality factor and frequency stability of the bulk acoustic wave resonator, thereby effectively improving the performance of the bulk acoustic wave resonator.

[0009] Optionally, the thickness of the temperature compensation layer is 200 - 350 nm.

[0010] This technical solution can effectively avoid the situation where the temperature drift suppression effect is limited, the temperature compensation effect is poor due to the too thin temperature compensation layer, and the performance of the bulk acoustic wave resonator is negatively affected due to the too thick temperature compensation layer by setting the thickness of the temperature compensation layer to 200 - 350 nm.

[0011] Optionally, the material of the piezoelectric layer is aluminum nitride or scandium-doped aluminum nitride.

[0012] Optionally, the thickness of the piezoelectric layer is 500 - 1500 nm.

[0013] Optionally, the top electrode has at least one external connection portion, and the temperature compensation layer further includes a second compensation portion provided on the external connection portion.

[0014] In a second aspect, the present application also provides a method for manufacturing a temperature-compensated bulk acoustic wave resonator, the method including the following steps: S1. Form an acoustic mirror on a substrate; S2. Sequentially form a bottom electrode, a piezoelectric layer, and a top electrode on the substrate; S3. Obtain corresponding target compensation layer thickness information based on the target resonance frequency according to a preset conversion relationship; S4. Deposit a material with a temperature drift coefficient smaller than that of the piezoelectric layer on the top electrode to form a low-temperature drift characteristic material layer with a thickness greater than the target compensation layer thickness information, and then etch the low-temperature drift characteristic material layer to obtain a temperature compensation layer including a first compensation portion, and the thickness of the temperature compensation layer is the target compensation layer thickness information.

[0015] A method for manufacturing a temperature-compensated bulk acoustic wave resonator provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer by forming a temperature compensation layer on the top electrode, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer, and the material properties of the piezoelectric layer are associated with the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is vulnerable to temperature change due to the shift of the material properties of the piezoelectric layer with temperature change, thereby effectively improving the frequency temperature stability of the bulk acoustic wave resonator.

[0016] Optionally, step S2 includes: S21. Form a bottom electrode on the substrate by physical sputtering process; S22. Form a piezoelectric layer on the bottom electrode by deposition process, and then repair the piezoelectric layer by an ion beam film repair machine to improve the flatness of the piezoelectric layer; S23. Form a top electrode on the piezoelectric layer by physical sputtering process.

[0017] After forming the piezoelectric layer, the technical solution repairs the piezoelectric layer by an ion beam film repair machine. The ion beam film repair machine uses an ion beam to etch and trim the surface of the piezoelectric layer to improve the flatness of the piezoelectric layer and reduce the surface roughness of the piezoelectric layer. Since the technical solution can remove the surface defects of the piezoelectric layer by repairing the piezoelectric layer with an ion beam film repair machine, the technical solution can effectively improve the piezoelectric effect of the piezoelectric layer, thereby effectively improving the performance of the bulk acoustic wave resonator.

[0018] Optionally, step S4 includes: S41. Form a patterned photoresist layer on the top electrode, and then deposit a material with a temperature drift coefficient smaller than that of the piezoelectric layer on the top electrode based on the patterned photoresist layer to form a low-temperature drift characteristic material layer with a thickness greater than the target compensation layer thickness information; S42. Use the TRIM technology to etch the low-temperature drift characteristic material layer based on the patterned photoresist layer to obtain a temperature compensation layer including a first compensation part, and then remove the patterned photoresist layer.

[0019] The technical solution uses the TRIM technology to etch the low-temperature drift characteristic material layer based on the patterned photoresist layer. Since the TRIM technology has the advantage of high etching accuracy, the technical solution can accurately remove the redundant low-temperature drift characteristic material layer to make the actual thickness of the temperature compensation layer consistent with the target compensation layer thickness and reduce the surface roughness of the temperature compensation layer, thereby effectively improving the temperature compensation effect of the temperature compensation layer.

[0020] In a third aspect, the present application also provides a duplexer, which includes a transmitter and a receiver. Both the transmitter and the receiver include the temperature-compensated bulk acoustic wave resonator provided in the first aspect above, and the transmitter and the receiver share a substrate.

[0021] The duplexer provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer by forming a temperature compensation layer on the top electrode, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer, and the material properties of the piezoelectric layer are associated with the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is vulnerable to temperature change due to the shift of the material properties of the piezoelectric layer with temperature change, thereby effectively improving the frequency temperature stability of the bulk acoustic wave resonator.

[0022] As can be seen from the above, the temperature-compensated bulk acoustic wave resonator, its manufacturing method and the duplexer provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer by forming a temperature compensation layer on the top electrode, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer, and the material properties of the piezoelectric layer are associated with the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is vulnerable to temperature change due to the shift of the material properties of the piezoelectric layer with temperature change, thereby effectively improving the frequency temperature stability of the bulk acoustic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a temperature-compensated bulk acoustic wave resonator provided by the first embodiment of the present application.

[0024] Figure 2 It is a schematic structural diagram of a temperature-compensated bulk acoustic wave resonator provided by the second embodiment of the present application.

[0025] Figure 3 It is a flowchart of a method for manufacturing a temperature-compensated bulk acoustic wave resonator provided by an embodiment of the present application.

[0026] Figure 4 It is a schematic diagram of a method for manufacturing a temperature-compensated bulk acoustic wave resonator provided by an embodiment of the present application.

[0027] Figure 5 It is a schematic structural diagram of a duplexer provided by an embodiment of the present application.

[0028] Reference numerals: 1, substrate; 2, bottom electrode; 3, piezoelectric layer; 4, top electrode; 5, temperature compensation layer; 51, first compensation portion; 52, second compensation portion; 6, acoustic mirror; 7, transmitter; 8, receiver. Detailed implementation manners

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to 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. The components of the embodiments of the present application described and illustrated herein generally can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0030] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present application, the terms "first", "second" and the like are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0031] In a first aspect, as Figure 1 and Figure 2 shown, the present application provides a temperature-compensated bulk acoustic wave resonator, which includes: A substrate 1, a bottom electrode 2, a piezoelectric layer 3, a top electrode 4 and a temperature compensation layer 5 connected in sequence from bottom to top. An acoustic mirror 6 is provided on the substrate 1. The temperature drift coefficient of the temperature compensation layer 5 is less than that of the piezoelectric layer 3. The temperature compensation layer 5 includes a first compensation portion 51, and the boundary of the projection of the first compensation portion 51 in the top view direction is located within the boundary of the projection of the acoustic mirror 6 in the top view direction.

[0032] Among them, the material of the substrate 1 in this embodiment is preferably any one or more of silicon material, sapphire, spinel, lithium tantalate (LT), lithium niobate (LN), LiGaO2, zinc oxide and zirconia ceramic materials. The materials of the bottom electrode 2 and the top electrode 4 in this embodiment are preferably metal materials with high conductivity, large acoustic impedance and large Young's modulus (such as any one or more of gold, molybdenum, ruthenium and platinum). The material of the bottom electrode 2 in this embodiment is preferably the same as the material of the top electrode 4. Specifically, when a signal source is externally connected to the top electrode 4 and the bottom electrode 2 (equivalent to applying a voltage signal or an electrical signal to the top electrode 4 and the bottom electrode 2), an electric field is formed at both ends of the piezoelectric layer 3 to excite a bulk acoustic wave (equivalent to exciting a longitudinal wave in the piezoelectric layer 3), thereby realizing the mutual conversion of electrical energy and mechanical energy and the frequency selection of the bulk acoustic wave resonator. It should be understood that if it is necessary to increase the effective electromechanical coupling coefficient of the bulk acoustic wave resonator, scandium-doped aluminum nitride can be selected as the material of the piezoelectric layer 3 in this embodiment, and those skilled in the art can determine the specific scandium doping amount based on the actual effective electromechanical coupling coefficient requirements. A sound reflector 6 is provided on the substrate 1 in this embodiment. The sound reflector 6 can be an air cavity or several layers of Bragg reflection layers. Each layer of Bragg reflection layer is composed of a low acoustic impedance layer and a high acoustic impedance layer. In this embodiment, the substrate 1 can be etched first to form a groove on the substrate 1, and then several layers of Bragg reflection layers can be formed in the groove based on the existing Bragg reflection layer forming process. It should be understood that if the sound reflector 6 is an air cavity, the bulk acoustic wave resonator in this embodiment essentially belongs to a Film Bulk Acoustic Resonator (FBAR). If the sound reflector 6 is a Bragg reflection layer, the bulk acoustic wave resonator in this embodiment essentially belongs to a Solid Mounted Resonator (SMR). A temperature compensation layer 5 is provided on the top electrode 4 in this embodiment. The temperature drift coefficient of the temperature compensation layer 5 is smaller than that of the piezoelectric layer 3. The material of the temperature compensation layer 5 is a material with a temperature drift coefficient smaller than that of the piezoelectric layer 3 (such as diamond or silicon carbide). The temperature compensation layer 5 includes a first compensation part 51. The boundary of the projection of the first compensation part 51 in the top view direction is located within the boundary of the projection of the sound reflector 6 in the top view direction, that is, the first compensation part 51 is located within the projection area of the sound reflector 6. It should be understood that since the temperature drift coefficient of the temperature compensation layer 5 in this embodiment is smaller than that of the piezoelectric layer 3, this embodiment can effectively suppress the temperature drift phenomenon of the piezoelectric layer 3 by forming the temperature compensation layer 5 on the top electrode 4 to reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator.

[0033] A temperature-compensated bulk acoustic wave resonator provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer 3 by forming a temperature compensation layer 5 on the top electrode 4, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer 3. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer 3, and the material properties of the piezoelectric layer 3 are related to the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is easily affected by temperature change due to the offset of the material properties of the piezoelectric layer 3 with temperature change, thereby effectively improving the frequency temperature stability of the bulk acoustic wave resonator. In addition, since the temperature compensation layer 5 of the present application is provided on the top electrode 4, the temperature compensation layer 5 can protect the top electrode 4, so this embodiment can effectively reduce the occurrence of oxidation, corrosion or contamination of the top electrode 4 due to contact between the top electrode 4 and the external environment, so that the top electrode 4 can maintain good electrical conductivity and structural integrity.

[0034] In some preferred embodiments, the material of the temperature compensation layer 5 is SiO2. Since SiO2 has a low temperature drift coefficient, an ultra-wide bandgap (bandgap greater than 8 eV) and a high critical breakdown electric field (breakdown field strength greater than 8 MV / cm), the low temperature drift coefficient can further suppress the temperature drift phenomenon of the piezoelectric layer 3, the ultra-wide bandgap can suppress the leakage of transverse waves, and the high critical breakdown electric field can keep the frequency of the bulk acoustic wave filter stable under high power conditions. Therefore, this embodiment can effectively improve the temperature compensation effect of the temperature compensation layer 5 and improve the quality factor and frequency stability of the bulk acoustic wave resonator, thereby effectively improving the performance of the bulk acoustic wave resonator.

[0035] In some preferred embodiments, the thickness of the temperature compensation layer 5 is 200-350 nm. This embodiment can effectively avoid the situation that the temperature drift suppression effect is limited, the temperature compensation effect is poor due to the too thin temperature compensation layer 5, and the performance of the bulk acoustic wave resonator is negatively affected due to the too thick temperature compensation layer 5 by setting the thickness of the temperature compensation layer 5 to 200-350 nm, that is, this embodiment takes into account the overall performance of the bulk acoustic wave resonator while ensuring the temperature compensation effect of the temperature compensation layer 5.

[0036] In some preferred embodiments, the material of the piezoelectric layer 3 is aluminum nitride or scandium-doped aluminum nitride. In this embodiment, aluminum nitride or scandium-doped aluminum nitride is selected as the material of the piezoelectric layer 3. Specifically, aluminum nitride has the advantages of a wide bandgap, high insulation, high longitudinal wave sound velocity, and low loss. Therefore, in this embodiment, the piezoelectric effect and performance of the piezoelectric layer 3 can be improved by selecting aluminum nitride as the material of the piezoelectric layer 3. When it is necessary to increase the effective electromechanical coupling coefficient of the bulk acoustic wave resonator, scandium-doped aluminum nitride can be selected as the material of the piezoelectric layer 3. It should be understood that those skilled in the art can determine the specific amount of scandium doping based on the actual requirement of the effective electromechanical coupling coefficient.

[0037] In some preferred embodiments, the thickness of the piezoelectric layer 3 is 500 - 1500 nm. By setting the thickness of the piezoelectric layer 3 to 500 - 1500 nm, this embodiment can avoid the reduction in the stability and reliability of the piezoelectric layer 3 caused by the overly thin piezoelectric layer 3, the influence on the stability of the bulk acoustic wave resonator, and the reduction in the resonance frequency of the bulk acoustic wave resonator and the degradation of the performance of the bulk acoustic wave resonator caused by the overly thick piezoelectric layer 3.

[0038] In some preferred embodiments, the top electrode 4 has at least one external connection portion, and the temperature compensation layer 5 further includes a second compensation portion 52 disposed on the external connection portion. The top electrode 4 of this embodiment has at least one external connection portion, which is used to connect to an external circuit to achieve the input and output of electrical signals. To compensate for the temperature drift of the external connection portion, the temperature compensation layer 5 of this embodiment further includes a second compensation portion 52, which is disposed on the external connection portion, that is, the second compensation portion 52 covers the external connection portion area. Therefore, this embodiment is equivalent to using the first compensation portion 51 to compensate for the temperature drift of the area covered by the acoustic mirror 6 and using the second compensation portion 52 to compensate for the temperature drift of the area not covered by the acoustic mirror 6 to perform a more comprehensive temperature compensation for the bulk acoustic wave resonator. Specifically, in the absence of the second compensation portion 52, although the first compensation portion 51 can effectively compensate for the temperature drift of the area covered by the acoustic mirror 6, the external connection portion of the top electrode 4 is exposed to the external environment, and its material properties will be affected by temperature changes, resulting in additional frequency drift. Therefore, this embodiment can compensate for the temperature drift of the external connection portion by setting the second compensation portion 52 to offset or reduce the frequency drift caused by the external connection portion, thereby further improving the frequency-temperature stability of the bulk acoustic wave resonator.

[0039] As described above, a temperature-compensated bulk acoustic wave resonator provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer 3 by forming a temperature compensation layer 5 on the top electrode 4, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer 3. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer 3, and the material properties of the piezoelectric layer 3 are associated with the resonant frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonant frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonant frequency of the bulk acoustic wave resonator is vulnerable to temperature change due to the shift of the material properties of the piezoelectric layer 3 with temperature change, thereby effectively improving the frequency-temperature stability of the bulk acoustic wave resonator.

[0040] In a second aspect, as Figure 3 and Figure 4 shown, the present application also provides a method for manufacturing a temperature-compensated bulk acoustic wave resonator, the method comprising the following steps: S1. Form an acoustic mirror 6 on a substrate 1; S2. Sequentially form a bottom electrode 2, a piezoelectric layer 3, and a top electrode 4 on the substrate 1; S3. Obtain corresponding target compensation layer thickness information based on a preset conversion relationship according to a target resonant frequency; S4. Deposit a material with a temperature drift coefficient smaller than that of the piezoelectric layer 3 on the top electrode 4 to form a low-temperature drift characteristic material layer with a thickness greater than the target compensation layer thickness information, and then etch the low-temperature drift characteristic material layer to obtain a temperature compensation layer 5 including a first compensation portion 51, and the thickness of the temperature compensation layer 5 is the target compensation layer thickness information.

[0041] Among them, a method for manufacturing a temperature-compensated bulk acoustic wave resonator provided by the present application is preferably used to manufacture a temperature-compensated bulk acoustic wave resonator provided in the first aspect above. The acoustic mirror 6 in step S1 can be an air cavity or several layers of Bragg reflection layers. The acoustic mirror 6 can effectively reflect the acoustic wave energy back to the resonant region to reduce energy loss and improve the performance of the bulk acoustic wave resonator. Step S1 can form the acoustic mirror 6 on the substrate 1 by using an existing acoustic mirror 6 forming process. Preferably, after forming the acoustic mirror 6 on the substrate 1, the embodiment uses an existing chemical polishing process to polish the surface of the substrate 1 to improve the flatness of the surface of the substrate 1, thereby effectively improving the quality of the thin film subsequently grown on the substrate 1.

[0042] In step S2, the bottom electrode 2, the piezoelectric layer 3, and the top electrode 4 can be sequentially formed on the substrate 1 by using existing electrode formation processes and piezoelectric layer 3 formation processes. Specifically, in this embodiment, the bottom electrode 2, the piezoelectric layer 3, and the top electrode 4 can be sequentially formed on the substrate 1 by depositing electrode materials, piezoelectric materials, and electrode materials on the substrate 1 in sequence by using a deposition process.

[0043] The target resonance frequency in step S3 is the resonance frequency of the finally fabricated bulk acoustic wave resonator, and the target compensation layer thickness information in step S3 is the thickness of the temperature compensation layer 5 that finally needs to be formed. Since the resonance frequency of the bulk acoustic wave resonator is associated with the temperature compensation effect of the temperature compensation layer 5, and the temperature compensation effect of the temperature compensation layer 5 is associated with the thickness of the temperature compensation layer 5, in this embodiment, the target compensation layer thickness information can be determined based on the target resonance frequency. The preset conversion relationship in this embodiment is preferably a pre-constructed mapping relationship table regarding the resonance frequency and the compensation layer thickness. In this embodiment, the target compensation layer thickness information can be obtained by querying this mapping relationship table according to the target resonance frequency.

[0044] In step S4, a material with a temperature drift coefficient smaller than that of the material of the piezoelectric layer 3 is first deposited on the top electrode 4. To ensure that there is sufficient material removal amount for subsequent etching, in this embodiment, the thickness of the low-temperature drift characteristic material layer needs to be greater than the target compensation layer thickness information. Since the first compensation part 51 is a structure obtained by etching the low-temperature drift characteristic material layer, the boundary of the projection of the low-temperature drift characteristic material layer of this embodiment in the top view direction is located within the boundary of the projection of the acoustic mirror 6 in the top view direction. It should be understood that if the temperature compensation layer 5 further includes a second compensation part 52, the low-temperature drift characteristic material layer of this embodiment can be divided into a low-temperature drift characteristic material layer located in the area covered by the acoustic mirror 6 and a low-temperature drift characteristic material layer located in the area not covered by the acoustic mirror 6. In this embodiment, an existing etching process (such as a reactive ion etching process (RIE process)) can be used to etch the low-temperature drift characteristic material layer to remove the excess low-temperature drift characteristic material (the material with a temperature drift coefficient smaller than that of the material of the piezoelectric layer 3) and make the final thickness of the temperature compensation layer 5 consistent with the target compensation layer thickness information.

[0045] A method for fabricating a temperature-compensated bulk acoustic wave resonator provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer 3 by forming a temperature compensation layer 5 on the top electrode 4, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer 3. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer 3, and the material properties of the piezoelectric layer 3 are associated with the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is susceptible to temperature change due to the shift of the material properties of the piezoelectric layer 3 with temperature change, thereby effectively improving the frequency temperature stability of the bulk acoustic wave resonator.

[0046] In some preferred embodiments, step S2 includes: S21. Form a bottom electrode 2 on the substrate 1 by using a physical sputtering process; S22. Form a piezoelectric layer 3 on the bottom electrode 2 by using a deposition process, and then repair the piezoelectric layer 3 by using an ion beam film repair machine to improve the flatness of the piezoelectric layer 3; S23. Form a top electrode 4 on the piezoelectric layer 3 by using a physical sputtering process.

[0047] In step S21, a bottom electrode 2 is formed on the substrate 1 by using an existing physical sputtering process, and this physical sputtering process can prepare a uniform and dense thin film to provide a good foundation for the subsequent growth of the piezoelectric layer 3. In step S22, a piezoelectric layer 3 is formed on the bottom electrode 2 by using an existing deposition process (preferably a physical deposition process). After the piezoelectric layer 3 is formed, in this embodiment, the piezoelectric layer 3 is repaired by using an ion beam film repair machine. The ion beam film repair machine uses an ion beam to etch and trim the surface of the piezoelectric layer 3 to improve the flatness of the piezoelectric layer 3 and reduce the surface roughness of the piezoelectric layer 3. Since this embodiment can remove the surface defects of the piezoelectric layer 3 by using the ion beam film repair machine to repair the piezoelectric layer 3, this embodiment can effectively improve the piezoelectric effect of the piezoelectric layer 3, thereby effectively improving the performance of the bulk acoustic wave resonator. In step S23, a top electrode 4 is formed on the piezoelectric layer 3 by using an existing physical sputtering process, and this physical sputtering process can prepare a uniform and dense thin film to provide a good foundation for the subsequent growth of the temperature compensation layer 5.

[0048] In some preferred embodiments, step S4 includes: S41. Form a patterned photoresist layer on the top electrode 4, and then deposit a material with a temperature drift coefficient smaller than that of the piezoelectric layer 3 on the top electrode 4 based on the patterned photoresist layer to form a low-temperature drift characteristic material layer with a thickness greater than the target compensation layer thickness information; S42. Use the TRIM technique to etch the low-temperature drift characteristic material layer based on the patterned photoresist layer to obtain the temperature compensation layer 5 including the first compensation portion 51, and then remove the patterned photoresist layer.

[0049] In step S41, an imaged photoresist layer can be formed on the top electrode 4 by using an existing photoresist layer forming process. Specifically, the patterned photoresist layer has an opening, and the shape of the opening is the same as the shape of the temperature compensation layer 5. After forming the imaged photoresist layer, in step S41, a material with a temperature drift coefficient smaller than that of the piezoelectric layer 3 can be deposited on the top electrode 4 based on the patterned photoresist layer by using an existing deposition process to form a low-temperature drift characteristic material layer with a thickness greater than the target compensation layer thickness information. In step S42, the TRIM technique (ion milling frequency etching technique) is used to etch the low-temperature drift characteristic material layer based on the patterned photoresist layer. Since the TRIM technique has the advantage of high etching accuracy, this embodiment can accurately remove the excess low-temperature drift characteristic material layer, so that the actual thickness of the temperature compensation layer 5 is consistent with the target compensation layer thickness and reduce the surface roughness of the temperature compensation layer 5, thereby effectively improving the temperature compensation effect of the temperature compensation layer 5. Step S42 can remove the patterned photoresist layer by using an existing photoresist layer removal process.

[0050] As can be seen from the above, a method for manufacturing a temperature-compensated bulk acoustic wave resonator provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer 3 by forming the temperature compensation layer 5 on the top electrode 4, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer 3. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer 3, and the material properties of the piezoelectric layer 3 are related to the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is easily affected by temperature change due to the offset of the material properties of the piezoelectric layer 3 with temperature change, thereby effectively improving the frequency temperature stability of the bulk acoustic wave resonator.

[0051] In the third aspect, as Figure 5 shown, the present application also provides a duplexer, which includes a transmitter 7 and a receiver 8. Both the transmitter 7 and the receiver 8 include the temperature-compensated bulk acoustic wave resonator provided in the first aspect above, and the transmitter 7 and the receiver 8 share a substrate 1.

[0052] A duplexer provided by the present application includes a transmitter 7 and a receiver 8. Both the transmitter 7 and the receiver 8 include the temperature-compensated bulk acoustic wave resonator provided in the above first aspect. The principle of the duplexer provided in this embodiment is the same as that of the temperature-compensated bulk acoustic wave resonator provided in the above first aspect, and will not be elaborated here in detail. It should be understood that in this embodiment, a frequency difference between the transmitter 7 and the receiver 8 can be achieved by making the thickness of the top electrode 4 of the transmitter 7 different from that of the top electrode 4 of the receiver 8.

[0053] As can be seen from the above, a temperature-compensated bulk acoustic wave resonator, a preparation method thereof, and a duplexer provided by the present application can effectively suppress the temperature drift phenomenon of the piezoelectric layer 3 by forming a temperature compensation layer 5 on the top electrode 4, that is, the present application can effectively suppress the influence of temperature change on the material properties of the piezoelectric layer 3. Since the present application can suppress the influence of temperature change on the material properties of the piezoelectric layer 3, and the material properties of the piezoelectric layer 3 are related to the resonance frequency of the bulk acoustic wave resonator, the present application can effectively reduce the influence of temperature change on the resonance frequency of the bulk acoustic wave resonator. Therefore, the present application can effectively solve the problem that the resonance frequency of the bulk acoustic wave resonator is easily affected by temperature change due to the offset of the material properties of the piezoelectric layer 3 with temperature change, thereby effectively improving the frequency temperature stability of the bulk acoustic wave resonator.

[0054] In the embodiments provided by the present application, it should be understood that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0055] The above are only the embodiments of the present application and are not intended to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A temperature-compensated bulk acoustic wave resonator, characterized in that The temperature-compensated bulk acoustic wave resonator includes: A substrate, a bottom electrode, a piezoelectric layer, a top electrode, and a temperature compensation layer connected in sequence from bottom to top. An acoustic mirror is provided on the substrate. The temperature drift coefficient of the temperature compensation layer is less than that of the piezoelectric layer. The temperature compensation layer includes a first compensation portion, and the boundary of the projection of the first compensation portion in the top view direction is located within the boundary of the projection of the acoustic mirror in the top view direction.

2. The temperature-compensated bulk acoustic wave resonator according to claim 1, wherein The material of the temperature compensation layer is SiO2.

3. The temperature-compensated bulk acoustic wave resonator according to claim 1, wherein The thickness of the temperature compensation layer is 200 - 350 nm.

4. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that The material of the piezoelectric layer is aluminum nitride or scandium-doped aluminum nitride.

5. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that, The thickness of the piezoelectric layer is 500 - 1500 nm.

6. The temperature-compensated bulk acoustic wave resonator according to claim 1, wherein The top electrode has at least one external connection portion, and the temperature compensation layer further includes a second compensation portion provided on the external connection portion.

7. A preparation method of a temperature-compensated bulk acoustic wave resonator, characterized in that, The method for manufacturing the temperature-compensated bulk acoustic wave resonator includes the following steps: S1. Form an acoustic mirror on the substrate; S2. Sequentially form a bottom electrode, a piezoelectric layer, and a top electrode on the substrate; S3. Obtain the corresponding target compensation layer thickness information based on the target resonance frequency according to a preset conversion relationship; S4. Deposit a material with a temperature drift coefficient less than that of the piezoelectric layer on the top electrode to form a low-temperature-drift characteristic material layer with a thickness greater than the target compensation layer thickness information, and then etch the low-temperature-drift characteristic material layer to obtain a temperature compensation layer including a first compensation portion, and the thickness of the temperature compensation layer is the target compensation layer thickness information.

8. The method for preparing a temperature-compensated bulk acoustic wave resonator according to claim 7, characterized in that, Step S2 includes: S21. Form a bottom electrode on the substrate by using a physical sputtering process; S22. Form a piezoelectric layer on the bottom electrode by using a deposition process, and then repair the piezoelectric layer by using an ion beam film repair machine to improve the flatness of the piezoelectric layer; S23. Form a top electrode on the piezoelectric layer by using a physical sputtering process.

9. The method for manufacturing a temperature-compensated bulk acoustic wave resonator according to claim 7, characterized in that, Step S4 includes: S41. Form a patterned photoresist layer on the top electrode, and then deposit a material with a temperature drift coefficient less than that of the piezoelectric layer on the top electrode based on the patterned photoresist layer to form a low-temperature-drift characteristic material layer with a thickness greater than the target compensation layer thickness information; S42. Etch the low-temperature-drift characteristic material layer based on the patterned photoresist layer by using the TRIM technology to obtain a temperature compensation layer including a first compensation portion, and then remove the patterned photoresist layer.

10. A duplexer, characterized in that, The duplexer includes a transmitter and a receiver. Both the transmitter and the receiver include the temperature-compensated bulk acoustic wave resonator according to any one of claims 1 - 6, and the transmitter and the receiver share a substrate.

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