Bulk acoustic wave resonator capable of reducing energy leakage, preparation method and bulk acoustic wave filter

Abstract

The invention relates to the technical field of bulk acoustic wave resonators, and particularly provides a bulk acoustic wave resonator capable of reducing energy leakage, a preparation method and a bulk acoustic wave filter, and the resonator comprises a supporting substrate, a graphical bonding layer, a graphical bottom electrode, a graphical piezoelectric layer and a graphical top electrode which are sequentially connected from bottom to top. The patterned top electrode is provided with a step-ring-shaped structure part located above the cavity, the step-ring-shaped structure part is sunken in the patterned top electrode, the outer contour of the cross section of the step-ring-shaped structure part is in a step shape, and the inner boundary of the projection of the step-ring-shaped structure part in the overlook direction is located outside the outer boundary of the projection of the cavity in the overlook direction; the graphical load layer is arranged on the top surface of the graphical top electrode and is positioned outside the stepped ring-shaped structure part; the resonator can effectively reduce the leakage amount of the transverse wave component generated by the vibration of the graphical piezoelectric layer, thereby effectively improving the quality factor and the electrical performance of the bulk acoustic wave resonator.

Description

Technical Field

[0001] The present application relates to the technical field of bulk acoustic wave resonators, and in particular to a bulk acoustic wave resonator for reducing energy leakage, a preparation method and a bulk acoustic wave filter. Background Art

[0002] BAW resonators are electrical devices that use the piezoelectric effect of piezoelectric materials to achieve mutual conversion between electrical energy and mechanical energy, and use the special boundary conditions of the device to make mechanical waves resonate. Because BAW resonators can produce resonance peaks with high quality factors, they are widely used in fields such as communication filtering and navigation positioning.

[0003] Specifically, the quality factor of a BAW resonator can reflect the energy storage status of the BAW resonator. The higher the quality factor of the BAW resonator, the better the frequency selectivity of the BAW resonator. In the actual application scenario of the BAW resonator, the patterned piezoelectric layer will vibrate under the action of the piezoelectric effect, and the patterned piezoelectric layer will generate a shear wave component during the vibration process, and the shear wave component will leak out of the BAW resonator. Therefore, the related technology has the problem that the shear wave component will leak out of the BAW resonator, causing partial energy leakage of the BAW resonator and attenuation of the quality factor of the BAW resonator, thereby causing the electrical performance of the BAW resonator to deteriorate.

[0004] There is no effective technical solution to the above problems. It should be noted that the above information disclosed in this section is only used to understand the background of the present invention, and therefore may contain information that does not constitute prior art. Summary of the invention

[0005] The purpose of the present application is to provide a bulk acoustic wave resonator, a preparation method and a bulk acoustic wave filter that reduce energy leakage, which can effectively reduce the leakage of the shear wave component generated by the vibration of the patterned piezoelectric layer, thereby effectively improving the quality factor and electrical performance of the bulk acoustic wave resonator.

[0006] In a first aspect, the present application provides a bulk acoustic wave resonator for reducing energy leakage, comprising: A supporting substrate, a patterned bonding layer, a patterned bottom electrode, a patterned piezoelectric layer and a patterned top electrode are sequentially connected from bottom to top, and a cavity is provided on the supporting substrate; The patterned top electrode has a stepped ring-shaped structure portion located above the cavity, the stepped ring-shaped structure portion is recessed in the patterned top electrode, the outer contour of the cross section of the stepped ring-shaped structure portion is stepped, and the inner boundary of the projection of the stepped ring-shaped structure portion in the top-view direction is located outside the outer boundary of the projection of the cavity in the top-view direction; The patterned load layer is arranged on the top surface of the patterned top electrode and outside the stepped ring structure portion, and the outer boundary of its projection in the top-view direction coincides with the outer boundary of the projection of the patterned top electrode in the top-view direction.

[0007] The present application provides a BAW resonator with reduced energy leakage, which reflects the transverse wave component generated by the vibration of the patterned piezoelectric layer by making the patterned top electrode have a stepped ring structure portion located above the cavity. Therefore, the present application can effectively reduce the leakage of the transverse wave component generated by the vibration of the patterned piezoelectric layer. Since the energy leakage of the BAW resonator is positively correlated with the leakage of the transverse wave component, the present application can effectively reduce the energy leakage of the BAW resonator, thereby effectively improving the quality factor and electrical performance of the BAW resonator.

[0008] Optionally, the material of the patterned piezoelectric layer is single crystal aluminum nitride, and the C-axis polarization direction of the single crystal aluminum nitride is perpendicular to the top surface of the patterned piezoelectric layer.

[0009] Optionally, the thickness of the patterned bottom electrode is 100-400 nm.

[0010] This technical solution can make the BAW resonator have a good electromechanical coupling coefficient by setting the thickness of the patterned bottom electrode to 100-400 nm, so this technical solution can effectively improve the piezoelectric performance of the BAW resonator.

[0011] Optionally, the stepped ring structure portion is a multi-step structure, the height of each step of the stepped ring structure portion is 2-20 nm, and the width of each step of the stepped ring structure portion is 1-7 nm.

[0012] In a second aspect, the present application further provides a method for preparing a bulk acoustic wave resonator with reduced energy leakage, which is used to prepare the bulk acoustic wave resonator with reduced energy leakage provided in the first aspect above. The method for preparing a bulk acoustic wave resonator with reduced energy leakage comprises the following steps: S1, sequentially forming a patterned piezoelectric layer, a patterned bottom electrode and a first patterned bonding film on the prepared substrate; S2, forming a second patterned bonding film on the supporting substrate, and etching the supporting substrate to form a cavity on the supporting substrate; S3, inverting the support substrate, and bonding the support substrate above the patterned bottom electrode through the first patterned bonding film and the second patterned bonding film, wherein the first patterned bonding film and the second patterned bonding film form a patterned bonding layer after bonding; S4, removing the prepared substrate, and sequentially forming a patterned top electrode and a patterned load layer on the patterned piezoelectric layer; S5. Etching the patterned top electrode to form a stepped ring structure portion on the patterned top electrode.

[0013] The present application provides a method for preparing a bulk acoustic wave resonator with reduced energy leakage, which is used to prepare a bulk acoustic wave resonator with reduced energy leakage. The resonator reflects the transverse wave component generated by the vibration of the patterned piezoelectric layer by making the patterned top electrode have a stepped ring structure portion located above the cavity. Therefore, the present application can effectively reduce the leakage of the transverse wave component generated by the vibration of the patterned piezoelectric layer. Since the energy leakage of the bulk acoustic wave resonator is positively correlated with the leakage of the transverse wave component, the present application can effectively reduce the energy leakage of the bulk acoustic wave resonator, thereby effectively improving the quality factor and electrical performance of the bulk acoustic wave resonator.

[0014] Optionally, step S1 includes: S11, sequentially depositing a nucleation layer and a single crystal aluminum nitride layer on the prepared substrate based on a chemical vapor deposition process to form a patterned piezoelectric layer on the prepared substrate; S12, forming a patterned bottom electrode on the patterned piezoelectric layer based on a magnetron sputtering process; S13, forming a first patterned bonding film on the patterned bottom electrode.

[0015] Since the technical solution first deposits a nucleation layer on the preparation substrate and then deposits a single-crystalline aluminum nitride layer on the nucleation layer, the technical solution can effectively avoid the situation in which the single-crystalline aluminum nitride layer directly deposited on the preparation substrate is subjected to excessive stress and cracks are generated in the single-crystalline aluminum nitride layer due to the large difference in lattice constants between the single-crystalline aluminum nitride layer and the preparation substrate. That is, the technical solution can effectively improve the growth quality of the single-crystalline aluminum nitride layer, thereby effectively improving the growth quality of the patterned bottom electrode and the first patterned bonding film.

[0016] Optionally, step S11 includes: S111, performing wet chemical cleaning and drying on the prepared substrate, and then performing annealing treatment on the cleaned prepared substrate in a nitrogen atmosphere; S112. Depositing a nucleation layer and a single-crystal aluminum nitride layer in sequence on the annealed prepared substrate based on a chemical vapor deposition process to form a patterned piezoelectric layer on the prepared substrate.

[0017] This technical solution is equivalent to first removing dust and other impurities on the prepared substrate by wet chemical cleaning, drying and annealing the prepared substrate, and then sequentially forming a patterned piezoelectric layer, a patterned bottom electrode and a first patterned bonding film on the prepared substrate. Therefore, this technical solution can effectively avoid the situation where defects in the patterned piezoelectric layer, the patterned bottom electrode and the first patterned bonding film deposited on the prepared substrate occur due to the presence of dust and other impurities on the prepared substrate.

[0018] Optionally, step S4 includes: S41, removing the prepared substrate based on mechanical thinning and dry etching processes to expose the patterned piezoelectric layer; S42, forming a patterned top electrode and a patterned load layer in sequence on the patterned piezoelectric layer based on a sputtering process.

[0019] Optionally, the thickness of the first patterned bonding film and the second patterned bonding film are both 30-200 nm.

[0020] In a third aspect, the present application also provides a bulk acoustic wave filter, which includes a first harmonic signal input terminal, a second harmonic signal input terminal, a first bulk acoustic wave resonator and a second bulk acoustic wave resonator, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator are obtained by equally dividing the bulk acoustic wave resonator for reducing energy leakage provided by the first aspect above, the polarization direction of the patterned piezoelectric layer of the first bulk acoustic wave resonator is opposite to the polarization direction of the patterned piezoelectric layer of the second bulk acoustic wave resonator, the amplitude of the input signal of the first harmonic signal input terminal is equal to the amplitude of the input signal of the second harmonic signal input terminal, and the phase of the input signal of the first harmonic signal input terminal is opposite to the phase of the input signal of the second harmonic signal input terminal.

[0021] The present application provides a bulk acoustic wave filter, comprising a first harmonic signal input terminal, a second harmonic signal input terminal, a first bulk acoustic wave resonator and a second bulk acoustic wave resonator. Since the first bulk acoustic wave resonator and the second bulk acoustic wave resonator of the technical solution are obtained by equally splitting the bulk acoustic wave resonator for reducing energy leakage provided by the first aspect, and the polarization direction of the patterned piezoelectric layer of the first bulk acoustic wave resonator is opposite to the polarization direction of the patterned piezoelectric layer of the second bulk acoustic wave resonator, the technical solution can offset the intermodulation distortion generated by the first bulk acoustic wave resonator and the intermodulation distortion of the second bulk acoustic wave resonator, and since the technical solution The amplitude of the input signal at the first harmonic signal input end of the scheme is equal to the amplitude of the input signal at the second harmonic signal input end, and the phase of the input signal at the first harmonic signal input end is opposite to the phase of the input signal at the second harmonic signal input end, so the technical solution can offset the resonance distortion, thereby effectively avoiding the distortion of the communication signal waveform and the generation of additional power loss due to the generation of harmonic distortion, and reducing the common mode interference and electromagnetic interference caused by nonlinear current and voltage harmonics, thereby effectively reducing the insertion loss and in-band ripple of the bulk acoustic wave filter in the passband and optimizing the out-of-band suppression of the bulk acoustic wave filter. It should be understood that the first bulk acoustic wave resonator of the technical solution can be connected to the second bulk acoustic wave resonator in series or in parallel.

[0022] From the above, it can be seen that the present application provides a bulk acoustic wave resonator, a preparation method and a bulk acoustic wave filter that reduce energy leakage. The transverse wave component generated by the vibration of the patterned piezoelectric layer is reflected by the patterned top electrode having a stepped ring structure portion located above the cavity. Therefore, the present application can effectively reduce the leakage of the transverse wave component generated by the vibration of the patterned piezoelectric layer. Since the energy leakage of the bulk acoustic wave resonator is positively correlated with the leakage of the transverse wave component, the present application can effectively reduce the energy leakage of the bulk acoustic wave resonator, thereby effectively improving the quality factor and electrical performance of the bulk acoustic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a bulk acoustic wave resonator for reducing energy leakage provided in an embodiment of the present application.

[0024] Figure 2 A flow chart of a method for preparing a bulk acoustic wave resonator for reducing energy leakage provided in an embodiment of the present application.

[0025] Figure 3 A schematic diagram of the circuit structure of a bulk acoustic wave filter provided in an embodiment of the present application.

[0026] Figure numerals: 1. supporting substrate; 2. patterned bonding layer; 3. patterned bottom electrode; 4. patterned piezoelectric layer; 5. patterned top electrode; 6. stepped ring structure; 7. cavity; 8. patterned load layer; 9. first bulk acoustic wave resonator; 10. second bulk acoustic wave resonator. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the 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 of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0028] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so 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 this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0029] First, as Figure 1As shown, the present application provides a bulk acoustic wave resonator for reducing energy leakage, which includes: A supporting substrate 1, a patterned bonding layer 2, a patterned bottom electrode 3, a patterned piezoelectric layer 4 and a patterned top electrode 5 are sequentially connected from bottom to top, and a cavity 7 is provided on the supporting substrate 1; The patterned top electrode 5 has a stepped ring-shaped structure portion 6 located above the cavity 7, the stepped ring-shaped structure portion 6 is recessed in the patterned top electrode 5, the outer contour of the cross section of the stepped ring-shaped structure portion 6 is stepped, and the inner boundary of the projection of the stepped ring-shaped structure portion 6 in the top view direction is located outside the outer boundary of the projection of the cavity 7 in the top view direction; The patterned load layer 8 is disposed on the top surface of the patterned top electrode 5 and outside the stepped ring structure 6 , and the outer boundary of its projection in the top view direction coincides with the outer boundary of the projection of the patterned top electrode 5 in the top view direction.

[0030] Among them, the material of the support substrate 1 of this embodiment is preferably silicon material, the material of the patterned bonding layer 2 of this embodiment is preferably silicon material, and the patterned bonding layer 2 is used to fix the patterned bottom electrode 3 on the support substrate 1. The material of the patterned bottom electrode 3 and the patterned top electrode 5 of this embodiment is preferably a metal material with high conductivity, large acoustic impedance and large Young's modulus (for example, any one or more of gold, molybdenum, ruthenium and platinum), and the material of the patterned bottom electrode 3 of this embodiment is preferably the same as the material of the patterned top electrode 5 of this embodiment. The material of the patterned piezoelectric layer 4 of this embodiment is preferably aluminum nitride, and an external signal source is provided at the patterned top electrode 5 and the patterned bottom electrode 3 (equivalent to applying a voltage signal or an electric signal to the patterned top electrode 5 and the patterned bottom electrode 3), and an electric field is formed at both ends of the patterned piezoelectric layer 4 to excite a bulk acoustic wave (equivalent to exciting the patterned piezoelectric layer 4 to generate a longitudinal wave), thereby realizing the mutual conversion of electrical energy and mechanical energy and the frequency selection of the bulk acoustic wave resonator. A cavity 7 is provided on the supporting substrate 1 of this embodiment, that is, this embodiment is equivalent to selecting the cavity 7 as an acoustic reflector of the bulk acoustic wave resonator, that is, the resonator of this embodiment belongs to a film bulk acoustic wave resonator (FBAR). Specifically, the inner boundary of the patterned bonding layer 2 of this embodiment in the projection direction coincides with the outer boundary of the cavity 7 in the projection direction, that is, the patterned bonding layer 2 of this embodiment will not cover the cavity 7. The patterned top electrode 5 of this embodiment has a stepped ring-shaped structure portion 6 located above the cavity 7, and the stepped ring-shaped structure portion 6 is recessed in the patterned top electrode 5. The outer contour of the cross section of the stepped ring-shaped structure portion 6 is stepped, and the inner boundary of the projection of the stepped ring-shaped structure portion 6 in the top-view direction is located outside the outer boundary of the projection of the cavity 7 in the top-view direction (that is, the stepped ring-shaped structure portion 6 is located outside the cavity 7), that is, this embodiment is equivalent to forming a stepped ring-shaped recessed structure on the patterned top electrode 5. Since the stepped ring-shaped recessed structure is filled with air, and the two sides of the stepped ring-shaped recessed structure are metal materials, this embodiment is equivalent to setting the patterned top electrode 5 as a metal-air-metal structure. Since there is an obvious acoustic impedance difference between the metal material and the air, the acoustic impedance difference can hinder the propagation of the shear wave component generated by the vibration of the patterned piezoelectric layer 4 and reflect the shear wave component generated by the vibration of the patterned piezoelectric layer 4. Therefore, this embodiment can effectively reduce the leakage of the shear wave component generated by the vibration of the patterned piezoelectric layer 4 by making the patterned top electrode 5 have a stepped ring-shaped structure portion 6 located above the cavity 7. The material of the patterned load layer 8 of this embodiment is preferably molybdenum. The patterned load layer 8 is arranged on the top surface of the patterned top electrode 5 and is located outside the step-ring structure portion 6. The outer boundary of its projection in the top view direction coincides with the outer boundary of the projection of the patterned top electrode 5 in the top view direction. The inner boundary of the projection of the patterned load layer 8 of this embodiment in the top view direction preferably coincides with the outer boundary of the projection of the step-ring structure portion 6 in the top view direction.

[0031] The present application provides a BAW resonator with reduced energy leakage, which reflects the transverse wave component generated by the vibration of the patterned piezoelectric layer 4 by making the patterned top electrode 5 have a stepped ring structure portion 6 located above the cavity 7. Therefore, the present application can effectively reduce the leakage of the transverse wave component generated by the vibration of the patterned piezoelectric layer 4. Since the energy leakage of the BAW resonator is positively correlated with the leakage of the transverse wave component, the present application can effectively reduce the energy leakage of the BAW resonator, thereby effectively improving the quality factor and electrical performance of the BAW resonator.

[0032] In some preferred embodiments, the material of the patterned piezoelectric layer 4 is single-crystal aluminum nitride, and the C-axis polarization direction of the single-crystal aluminum nitride is perpendicular to the top surface of the patterned piezoelectric layer 4. This embodiment selects single-crystal aluminum nitride as the material of the patterned piezoelectric layer 4. Since single-crystal aluminum nitride has the advantages of good piezoelectric performance and good stability, this embodiment can effectively improve the electrical performance and reliability of the bulk acoustic wave resonator. In order to enable the patterned piezoelectric layer 4 to generate bulk acoustic waves propagating along the C-axis through the piezoelectric effect, this embodiment needs to make the C-axis polarization direction of the single-crystal aluminum nitride perpendicular to the top surface of the patterned piezoelectric layer 4.

[0033] In some preferred embodiments, the thickness of the patterned bottom electrode 3 is 100-400 nm. This embodiment can make the BAW resonator have a good electromechanical coupling coefficient by setting the thickness of the patterned bottom electrode 3 to 100-400 nm, so this embodiment can effectively improve the piezoelectric performance of the BAW resonator.

[0034] In some preferred embodiments, the stepped ring structure portion 6 is a multi-step structure, the height of each step of the stepped ring structure portion 6 is 2-20nm, and the width of each step of the stepped ring structure portion 6 is 1-7nm. This embodiment enables the BAW resonator with reduced energy leakage to better reflect the shear wave component generated by the vibration of the patterned piezoelectric layer 4 by setting the height of each step of the stepped ring structure portion 6 to 2-20nm and the width of each step of the stepped ring structure portion 6 to 1-7nm, thereby further reducing the leakage of the shear wave component generated by the vibration of the patterned piezoelectric layer 4, and further improving the quality factor and electrical performance of the BAW resonator. Preferably, the number of steps of the stepped ring structure portion 6 of this embodiment is 2-6.

[0035] As can be seen from the above, the present application provides a BAW resonator with reduced energy leakage, which reflects the transverse wave component generated by the vibration of the patterned piezoelectric layer 4 by making the patterned top electrode 5 have a stepped ring structure portion 6 located above the cavity 7. Therefore, the present application can effectively reduce the leakage of the transverse wave component generated by the vibration of the patterned piezoelectric layer 4. Since the energy leakage of the BAW resonator is positively correlated with the leakage of the transverse wave component, the present application can effectively reduce the energy leakage of the BAW resonator, thereby effectively improving the quality factor and electrical performance of the BAW resonator.

[0036] Second, as Figure 2 As shown, the present application also provides a method for preparing a BAW resonator with reduced energy leakage, which is used to prepare the BAW resonator with reduced energy leakage provided in the first aspect above. The method for preparing a BAW resonator with reduced energy leakage comprises the following steps: S1, sequentially forming a patterned piezoelectric layer 4, a patterned bottom electrode 3 and a first patterned bonding film on a prepared substrate; S2, forming a second patterned bonding film on the supporting substrate 1, and etching the supporting substrate 1 to form a cavity 7 on the supporting substrate 1; S3, inverting the support substrate 1, and bonding the support substrate 1 to the top of the patterned bottom electrode 3 through the first patterned bonding film and the second patterned bonding film, wherein the first patterned bonding film and the second patterned bonding film form a patterned bonding layer 2 after bonding; S4, removing the prepared substrate, and sequentially forming a patterned top electrode 5 and a patterned load layer 8 on the patterned piezoelectric layer 4; S5 , etching the patterned top electrode 5 to form a stepped ring structure portion on the patterned top electrode 5 .

[0037] The embodiment of the present application provides a method for preparing a BAW resonator with reduced energy leakage, and the method for preparing a BAW resonator with reduced energy leakage is used to prepare the BAW resonator with reduced energy leakage provided in the first aspect. The principle of the method for preparing a BAW resonator with reduced energy leakage provided in the embodiment is the same as the principle of the BAW resonator with reduced energy leakage provided in the first aspect, and will not be discussed in detail here. The material for preparing the substrate of the embodiment is preferably sapphire, and the first patterned bonding film and the second patterned bonding film of the embodiment are preferably silicon films, that is, the embodiment is equivalent to bonding the patterned bottom electrode 3 to the supporting substrate 1 using a silicon-silicon bonding process. Since the silicon-silicon bonding process has the advantages of high bonding strength and high bonding efficiency, the embodiment can effectively improve the structural reliability and bonding efficiency of the BAW resonator with reduced energy leakage.

[0038] In some preferred embodiments, step S1 comprises: S11, depositing a nucleation layer and a single-crystal aluminum nitride layer on the prepared substrate in sequence based on a chemical vapor deposition process to form a patterned piezoelectric layer 4 on the prepared substrate; S12, forming a patterned bottom electrode 3 on the patterned piezoelectric layer 4 based on a magnetron sputtering process; S13 , forming a first patterned bonding film on the patterned bottom electrode 3 .

[0039] Since this embodiment first deposits a nucleation layer on the preparation substrate and then deposits a single-crystalline aluminum nitride layer on the nucleation layer, this embodiment can effectively avoid the situation where the single-crystalline aluminum nitride layer directly deposited on the preparation substrate is subjected to excessive stress and cracks are generated in the single-crystalline aluminum nitride layer due to the large difference in lattice constants between the single-crystalline aluminum nitride layer and the preparation substrate. That is, this embodiment can effectively improve the growth quality of the single-crystalline aluminum nitride layer, thereby effectively improving the growth quality of the patterned bottom electrode 3 and the first patterned bonding film.

[0040] In some preferred embodiments, step S11 includes: S111, performing wet chemical cleaning and drying on the prepared substrate, and then performing annealing treatment on the cleaned prepared substrate in a nitrogen atmosphere; S112, depositing a nucleation layer and a single-crystal aluminum nitride layer in sequence on the annealed prepared substrate based on a chemical vapor deposition process to form a patterned piezoelectric layer 4 on the prepared substrate.

[0041] This embodiment is equivalent to first removing dust and other impurities on the prepared substrate by wet chemical cleaning, drying and annealing the prepared substrate, and then sequentially forming a patterned piezoelectric layer 4, a patterned bottom electrode 3 and a first patterned bonding film on the prepared substrate. Therefore, this embodiment can effectively avoid the situation where the patterned piezoelectric layer 4, the patterned bottom electrode 3 and the first patterned bonding film deposited on the prepared substrate have defects due to the presence of dust and other impurities on the prepared substrate.

[0042] In some preferred embodiments, step S4 comprises: S41, removing the prepared substrate based on mechanical thinning and dry etching processes to expose the patterned piezoelectric layer 4; S42 , forming a patterned top electrode 5 and a patterned load layer 8 in sequence on the patterned piezoelectric layer 4 based on a sputtering process.

[0043] Step S1 can form a piezoelectric layer, a bottom electrode and a first patterned bonding film only on the prepared substrate, and step S42 can form a top electrode and a load layer only on the piezoelectric layer. Then, after the load layer is formed, the piezoelectric layer, the bottom electrode, the top electrode and the load layer are patterned based on photolithography and etching processes to obtain a patterned piezoelectric layer 4, a patterned bottom electrode 3, a patterned top electrode 5 and a patterned load layer 8, thereby effectively reducing the number of patterning processes of the bulk acoustic wave resonator.

[0044] In some preferred embodiments, the thickness of the first patterned bonding film and the second patterned bonding film are both 30-200 nm.

[0045] As can be seen from the above, the present application provides a method for preparing a bulk acoustic wave resonator with reduced energy leakage, which is used to prepare a bulk acoustic wave resonator with reduced energy leakage. The resonator reflects the transverse wave component generated by the vibration of the patterned piezoelectric layer 4 by making the patterned top electrode 5 have a stepped ring structure portion 6 located above the cavity 7. Therefore, the present application can effectively reduce the leakage of the transverse wave component generated by the vibration of the patterned piezoelectric layer 4. Since the energy leakage of the bulk acoustic wave resonator is positively correlated with the leakage of the transverse wave component, the present application can effectively reduce the energy leakage of the bulk acoustic wave resonator, thereby effectively improving the quality factor and electrical performance of the bulk acoustic wave resonator.

[0046] Thirdly, Figure 3 As shown, the present application also provides a bulk acoustic wave filter, which includes a first harmonic signal input terminal, a second harmonic signal input terminal, a first bulk acoustic wave resonator 9 and a second bulk acoustic wave resonator 10. The first bulk acoustic wave resonator 9 and the second bulk acoustic wave resonator 10 are obtained by equally dividing the bulk acoustic wave resonator for reducing energy leakage provided by the first aspect above. The polarization direction of the patterned piezoelectric layer 4 of the first bulk acoustic wave resonator 9 is opposite to the polarization direction of the patterned piezoelectric layer 4 of the second bulk acoustic wave resonator 10, the amplitude of the input signal of the first harmonic signal input terminal is equal to the amplitude of the input signal of the second harmonic signal input terminal, and the phase of the input signal of the first harmonic signal input terminal is opposite to the phase of the input signal of the second harmonic signal input terminal.

[0047] The present application embodiment provides a bulk acoustic wave filter, comprising a first harmonic signal input terminal (reference Figure 3 A in), second harmonic signal input terminal (reference Figure 3B), a first BAW resonator 9 and a second BAW resonator 10. Since the first BAW resonator 9 and the second BAW resonator 10 of this embodiment are obtained by equally splitting the BAW resonator for reducing energy leakage provided by the first aspect, and the polarization direction of the patterned piezoelectric layer 4 of the first BAW resonator 9 is opposite to the polarization direction of the patterned piezoelectric layer 4 of the second BAW resonator 10, this embodiment can cancel out the intermodulation distortion generated by the first BAW resonator 9 and the intermodulation distortion generated by the second BAW resonator 10. Since the first harmonic signal input of this embodiment The amplitude of the input signal at the first harmonic signal input terminal is equal to the amplitude of the input signal at the second harmonic signal input terminal, and the phase of the input signal at the first harmonic signal input terminal is opposite to the phase of the input signal at the second harmonic signal input terminal, so this embodiment can offset the resonance distortion, thereby effectively avoiding the distortion of the communication signal waveform and the generation of additional power loss due to the generation of harmonic distortion, and reducing the common mode interference and electromagnetic interference caused by nonlinear current and voltage harmonics, thereby effectively reducing the insertion loss and in-band ripple of the bulk acoustic wave filter in the passband and optimizing the out-of-band suppression of the bulk acoustic wave filter. It should be understood that the first bulk acoustic wave resonator 9 of this embodiment can be connected to the second bulk acoustic wave resonator 10 in series or in parallel.

[0048] As can be seen from the above, the present application provides a BAW resonator, a preparation method and a BAW filter for reducing energy leakage, which reflect the transverse wave component generated by the vibration of the patterned piezoelectric layer 4 by making the patterned top electrode 5 have a stepped ring structure portion 6 located above the cavity 7. Therefore, the present application can effectively reduce the leakage of the transverse wave component generated by the vibration of the patterned piezoelectric layer 4. Since the energy leakage of the BAW resonator is positively correlated with the leakage of the transverse wave component, the present application can effectively reduce the energy leakage of the BAW resonator, thereby effectively improving the quality factor and electrical performance of the BAW resonator.

[0049] In the embodiments provided in the present application, it should be understood that, herein, relational terms such as first and second, etc. are merely 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.

[0050] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. 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 bulk acoustic wave resonator for reducing energy leakage, characterized in that: The BAW resonator for reducing energy leakage comprises: A supporting substrate, a patterned bonding layer, a patterned bottom electrode, a patterned piezoelectric layer and a patterned top electrode are sequentially connected from bottom to top, wherein a cavity is provided on the supporting substrate; The patterned top electrode has a stepped ring-shaped structure portion located above the cavity, the stepped ring-shaped structure portion is recessed in the patterned top electrode, the outer contour of the cross section of the stepped ring-shaped structure portion is stepped, and the inner boundary of the projection of the stepped ring-shaped structure portion in the top view direction is located outside the outer boundary of the projection of the cavity in the top view direction; The patterned load layer is arranged on the top surface of the patterned top electrode and outside the stepped ring structure portion, and the outer boundary of its projection in the top-view direction coincides with the outer boundary of the projection of the patterned top electrode in the top-view direction.

2. The BAW resonator for reducing energy leakage according to claim 1, characterized in that: The material of the patterned piezoelectric layer is single-crystal aluminum nitride, and the C-axis polarization direction of the single-crystal aluminum nitride is perpendicular to the top surface of the patterned piezoelectric layer.

3. The BAW resonator for reducing energy leakage according to claim 1, characterized in that: The thickness of the patterned bottom electrode is 100-400nm.

4. The BAW resonator for reducing energy leakage according to claim 1, characterized in that: The stepped ring structure portion is a multi-step structure, the height of each step of the stepped ring structure portion is 2-20 nm, and the width of each step of the stepped ring structure portion is 1-7 nm.

5. A method for preparing a bulk acoustic wave resonator for reducing energy leakage, characterized in that: For preparing a BAW resonator with reduced energy leakage as claimed in any one of claims 1 to 4, the method for preparing the BAW resonator with reduced energy leakage comprises the following steps: S1, sequentially forming a patterned piezoelectric layer, a patterned bottom electrode and a first patterned bonding film on the prepared substrate; S2, forming a second patterned bonding film on a supporting substrate, and etching the supporting substrate to form a cavity on the supporting substrate; S3, inverting the support substrate, and bonding the support substrate above the patterned bottom electrode through the first patterned bonding film and the second patterned bonding film, wherein the first patterned bonding film and the second patterned bonding film form a patterned bonding layer after bonding; S4, removing the prepared substrate, and sequentially forming a patterned top electrode and a patterned load layer on the patterned piezoelectric layer; S5. Etching the patterned top electrode to form a stepped ring structure portion on the patterned top electrode.

6. The method for preparing a bulk acoustic wave resonator with reduced energy leakage according to claim 5, characterized in that: Step S1 includes: S11, sequentially depositing a nucleation layer and a single-crystal aluminum nitride layer on the prepared substrate based on a chemical vapor deposition process to form a patterned piezoelectric layer on the prepared substrate; S12, forming a patterned bottom electrode on the patterned piezoelectric layer based on a magnetron sputtering process; S13, forming the first patterned bonding film on the patterned bottom electrode.

7. The method for preparing a bulk acoustic wave resonator with reduced energy leakage according to claim 6, characterized in that: Step S11 includes: S111, performing wet chemical cleaning and drying on the prepared substrate, and then performing annealing treatment on the cleaned prepared substrate in a nitrogen atmosphere; S112, depositing a nucleation layer and a single-crystal aluminum nitride layer in sequence on the annealed prepared substrate based on a chemical vapor deposition process to form a patterned piezoelectric layer on the prepared substrate.

8. The method for preparing a bulk acoustic wave resonator with reduced energy leakage according to claim 5, characterized in that: Step S4 includes: S41, removing the prepared substrate based on mechanical thinning and dry etching processes to expose the patterned piezoelectric layer; S42, forming a patterned top electrode and a patterned load layer in sequence on the patterned piezoelectric layer based on a sputtering process.

9. The method for preparing a bulk acoustic wave resonator with reduced energy leakage according to claim 5, characterized in that: The thickness of the first patterned bonding film and the second patterned bonding film are both 30-200 nm.

10. A bulk acoustic wave filter, characterized in that: The BAW filter includes a first harmonic signal input terminal, a second harmonic signal input terminal, a first BAW resonator and a second BAW resonator, wherein the first BAW resonator and the second BAW resonator are obtained by equally splitting the BAW resonator for reducing energy leakage as described in any one of claims 1 to 4, the polarization direction of the patterned piezoelectric layer of the first BAW resonator is opposite to the polarization direction of the patterned piezoelectric layer of the second BAW resonator, the amplitude of the input signal of the first harmonic signal input terminal is equal to the amplitude of the input signal of the second harmonic signal input terminal, and the phase of the input signal of the first harmonic signal input terminal is opposite to the phase of the input signal of the second harmonic signal input terminal.

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