Bulk acoustic wave resonator with high electrical property, preparation method and bulk acoustic wave filter

Abstract

The invention relates to the technical field of bulk acoustic wave resonators, and particularly provides a high-electrical-property bulk acoustic wave resonator, a preparation method and a bulk acoustic wave filter, and the method comprises the steps: sequentially forming a buffer layer, a piezoelectric layer and a patterned top electrode on a first substrate; forming a blind hole outside the patterned top electrode; forming a first interconnection line on the top surface of the graphical top electrode and forming a second interconnection line on the top surface of the piezoelectric layer by filling the blind hole; bonding a second substrate on the first interconnection line and the second interconnection line; the etching assembly is inverted, and then the first substrate is etched; a patterned bottom electrode is formed in the groove, and then a film coating layer is attached to the first substrate; removing the second substrate, and then fixing the bulk acoustic wave resonator on the packaging substrate through the first interconnection line and the second interconnection line; the method can effectively solve the problems that the film of the bulk acoustic wave resonator is tympanic or cracked in the process of releasing the sacrificial layer and partial energy of the bulk acoustic wave resonator leaks.

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 with high electrical performance, 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] The specific process of the preparation method of the related BAW resonator is: forming a groove on the substrate; filling the groove with a sacrificial layer; forming a bottom electrode, a piezoelectric layer and a top electrode on the substrate in sequence; removing the sacrificial layer to form a BAW resonator whose acoustic reflector is an air cavity. Since the bottom electrode and the top electrode formed on the substrate both span the air cavity, and the top electrode and the bottom electrode spanning the air cavity will inevitably generate noise, and the noise will leak out of the BAW resonator, the related art has the problem of partial energy leakage of the BAW resonator due to the noise generated by the top electrode and the bottom electrode spanning the air cavity, thereby causing the electrical performance of the BAW resonator to deteriorate, and since the BAW resonator film (bottom electrode, piezoelectric layer and top electrode) may be subjected to excessive stress and / or uneven stress distribution in the process of releasing the sacrificial layer, the related art also has the problem of tympanic membrane or cracking of the BAW resonator film in the process of releasing the sacrificial layer.

[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 high electrical performance BAW resonator, a preparation method and a BAW filter, which can effectively solve the problem of tympanic membrane or cracking of the BAW resonator film during the release of the sacrificial layer due to excessive stress or uneven stress distribution during the release of the sacrificial layer, and the problem of partial energy leakage of the BAW resonator due to the generation of noise by the bottom electrode and the top electrode across the air cavity.

[0006] In a first aspect, the present application provides a method for preparing a bulk acoustic wave resonator with high electrical performance, which comprises the following steps: S1, forming a buffer layer, a piezoelectric layer and a patterned top electrode in sequence on a first substrate, wherein the patterned top electrode partially covers the piezoelectric layer; S2, forming a blind hole outside the patterned top electrode, which penetrates the piezoelectric layer and the buffer layer and has a depth greater than 0 on the first substrate; S3, forming a first interconnection line on the top surface of the patterned top electrode and forming a second interconnection line on the top surface of the piezoelectric layer by filling a blind hole, wherein the second interconnection line is located outside the patterned top electrode; S4, bonding a second substrate to the first interconnection line and the second interconnection line to obtain an etching assembly, with a gap between the second substrate and the patterned top electrode; S5, inverting the etching assembly, and then etching the first substrate to form a groove on the first substrate to expose the buffer layer and the second interconnection line; S6, forming a patterned bottom electrode in the groove, which is connected to the second interconnection line and has a top surface height less than a top surface height of the first substrate, and then mounting a cover film layer on the first substrate to form a bulk acoustic wave resonator; S7, removing the second substrate, and then fixing the BAW resonator on the packaging substrate through the first interconnection line and the second interconnection line and plastic-sealing the BAW resonator.

[0007] The present application provides a method for preparing a BAW resonator with high electrical performance. The method can form an acoustic reflector of the BAW resonator by first etching a first substrate, then forming a patterned bottom electrode in a groove, and finally forming a coating layer on the first substrate. That is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate. Therefore, the present application can effectively solve the problem of tympanic membrane or cracking of the BAW resonator film during the process of releasing the sacrificial layer due to excessive stress or uneven stress distribution on the BAW resonator film during the process of releasing the sacrificial layer. Moreover, since the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the BAW resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the BAW resonator.

[0008] Optionally, step S1 includes: S11, forming a buffer layer on a first substrate; S12, depositing single crystal aluminum nitride on the buffer layer based on a deposition process to form a piezoelectric layer on the buffer layer; S13, forming a patterned top electrode on the piezoelectric layer based on a deposition process and a patterning process.

[0009] This technical solution is equivalent to using single crystal aluminum nitride as the material of the piezoelectric layer. Since the piezoelectric layer made of single crystal aluminum nitride has a low dislocation density and an atomically smooth surface, this technical solution can effectively improve the effective electromechanical coupling coefficient of the BAW resonator and improve the insertion loss of the BAW filter passband, thereby effectively improving the electrical performance of the BAW resonator and the BAW filter.

[0010] Optionally, step S1 further includes the following steps performed before step S11: S14, cleaning the first substrate.

[0011] This technical solution is equivalent to first cleaning the first substrate and then forming a buffer layer on the first substrate. Since this technical solution can remove organic matter on the surface of the first substrate by cleaning the first substrate, this technical solution can effectively improve the growth quality of the buffer layer, the piezoelectric layer and the patterned top electrode.

[0012] Optionally, step S5 includes: S51, turning the etching assembly upside down; S52, thinning the first substrate so that the distance between the top surface of the first substrate and the top surface of the second interconnection line is a preset distance; S53 , etching the first substrate based on a dry etching process to form a groove on the first substrate to expose the buffer layer and the second interconnection line.

[0013] Since the technical solution thins the first substrate before etching it, that is, the technical solution can effectively reduce the thickness of the first substrate, the technical solution can effectively reduce the etching depth, thereby effectively improving the etching efficiency of the first substrate, and the technical solution can reduce the size of the finally formed BAW resonator by reducing the thickness of the first substrate.

[0014] Optionally, the package substrate has a third interconnection line, and step S7 includes: S71, removing the second substrate based on a stripping process; S72, welding the first interconnection line, the second interconnection line and the third interconnection line based on a flip chip process to fix the BAW resonator on the packaging substrate; S73, plastic-sealing the BAW resonator based on a plastic-sealing process.

[0015] In the second aspect, the present application also provides a high electrical performance bulk acoustic wave resonator, which includes a bulk acoustic wave resonator, a packaging substrate and a plastic packaging layer. The bulk acoustic wave resonator includes a first substrate, a buffer layer, a piezoelectric layer, a patterned top electrode, a first interconnection line, a second interconnection line, a patterned bottom electrode, a coating layer and a first air cavity. The two ends of the first interconnection line are respectively connected to the patterned top electrode and the packaging substrate, the second interconnection line is connected to the piezoelectric layer and the packaging substrate, the second interconnection line runs through the piezoelectric layer and the buffer layer and the depth on the first substrate is greater than 0, the patterned bottom electrode is connected to the buffer layer and the second interconnection line, the first substrate is arranged around the patterned bottom electrode, the coating layer is connected to the top surface of the first substrate and there is a gap between the coating layer and the patterned bottom electrode, the first air cavity is surrounded by the first substrate, the second interconnection line, the patterned bottom electrode and the coating layer, and the plastic packaging layer is arranged on the packaging substrate and wraps the outside of the bulk acoustic wave resonator.

[0016] The present application provides a high electrical performance BAW resonator, which utilizes a first substrate, a second interconnection line, a patterned bottom electrode and a coating layer to enclose a first air cavity, that is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate, so the present application can effectively solve the problem of bulging or cracking of the BAW resonator film during the process of releasing the sacrificial layer due to excessive stress or uneven stress distribution on the BAW resonator film during the process of releasing the sacrificial layer, and because the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the BAW resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the BAW resonator.

[0017] Optionally, the patterned bottom electrode and the patterned top electrode are staggered.

[0018] Since the patterned bottom electrode of the technical solution is located in the first air cavity, that is, the patterned bottom electrode is located in the effective area of ​​the BAW resonator, that is, there is only a patterned top electrode outside the effective area of ​​the BAW resonator, the technical solution can effectively avoid the situation where energy leakage occurs due to the piezoelectric effect between the patterned bottom electrode located outside the effective area of ​​the BAW resonator and the top electrode located outside the effective area of ​​the BAW resonator. The prior art can prevent energy leakage by setting an air gap in the interconnection line external area of ​​the top electrode, but setting the air gap will make the processing technology of the BAW resonator complicated. Since there is no patterned bottom electrode in the interconnection line external area of ​​the patterned top electrode of the technical solution, the technical solution does not need to set an air gap in the interconnection line external area of ​​the patterned top electrode to prevent energy leakage, thereby effectively simplifying the processing technology of the BAW resonator.

[0019] Optionally, the second interconnection line is located at an edge of the patterned bottom electrode.

[0020] Since the second interconnection line of the technical solution runs through the piezoelectric layer and the second interconnection line is located at the edge of the patterned bottom electrode, the technical solution can effectively avoid the situation where the piezoelectric layer structure arranged in the central area of ​​the BAW resonator is destroyed due to the second interconnection line being arranged in the central area of ​​the BAW resonator, thereby affecting the electrical performance of the BAW resonator.

[0021] Optionally, there are multiple second interconnection lines.

[0022] In a third aspect, the present application further provides a bulk acoustic wave filter, which includes a plurality of high electrical performance bulk acoustic wave resonators provided in the second aspect.

[0023] The present application provides a bulk acoustic wave filter, which utilizes a first substrate, a second interconnection line, a patterned bottom electrode and a coating layer to enclose a first air cavity, that is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate, so the present application can effectively solve the problem of tympaning or cracking of the bulk acoustic wave resonator film during the process of releasing the sacrificial layer due to excessive stress or uneven stress distribution on the bulk acoustic wave resonator film during the process of releasing the sacrificial layer, and because the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the bulk acoustic wave resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the bulk acoustic wave resonator.

[0024] As can be seen from the above, the present application provides a high electrical performance BAW resonator, a preparation method and a BAW filter, which can form an acoustic reflector of the BAW resonator by first etching the first substrate, then forming a patterned bottom electrode in the groove, and finally forming a coating layer on the first substrate. That is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate. Therefore, the present application can effectively solve the problem of tympanic membrane or cracking of the BAW resonator film during the release of the sacrificial layer due to excessive stress or uneven stress distribution on the BAW resonator film during the release of the sacrificial layer. Moreover, since the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the BAW resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the BAW resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a method for preparing a bulk acoustic wave resonator with high electrical performance provided in an embodiment of the present application.

[0026] Figure 2 A schematic diagram of a method for preparing a bulk acoustic wave resonator with high electrical performance provided in an embodiment of the present application.

[0027] Figure 3 A schematic diagram of the structure of a high electrical performance bulk acoustic wave resonator provided in an embodiment of the present application.

[0028] Figure 4 A schematic diagram of the top view of the bulk acoustic wave filter provided in an embodiment of the present application without a plastic packaging layer and a coating layer.

[0029] Figure 5 A schematic cross-sectional structure diagram of a bulk acoustic wave filter provided in the first embodiment of the present application.

[0030] Figure 6 A schematic cross-sectional structure diagram of a bulk acoustic wave filter provided in the second embodiment of the present application.

[0031] Figure 7 A schematic cross-sectional structure diagram of a bulk acoustic wave filter provided in the third embodiment of the present application.

[0032] Figure numerals: 1. first substrate; 2. buffer layer; 3. piezoelectric layer; 4. patterned top electrode; 5. blind hole; 6. first interconnection line; 7. second interconnection line; 8. second substrate; 9. groove; 10. patterned bottom electrode; 11. coating layer; 12. packaging substrate; 13. plastic layer; 14. first air cavity; 15. second air cavity; 16. third interconnection line. DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] First, as Figure 1-Figure 2 As shown, the present application provides a method for preparing a bulk acoustic wave resonator with high electrical performance, which comprises the following steps: S1, forming a buffer layer 2, a piezoelectric layer 3 and a patterned top electrode 4 in sequence on a first substrate 1, wherein the patterned top electrode 4 partially covers the piezoelectric layer 3; S2, forming a blind hole 5 outside the patterned top electrode 4, penetrating the piezoelectric layer 3 and the buffer layer 2 and having a depth greater than 0 on the first substrate 1; S3, forming a first interconnection line 6 on the top surface of the patterned top electrode 4 and forming a second interconnection line 7 on the top surface of the piezoelectric layer 3 by filling the blind hole 5, wherein the second interconnection line 7 is located outside the patterned top electrode 4; S4, bonding the second substrate 8 on the first interconnection line 6 and the second interconnection line 7 to obtain an etching assembly, with a gap between the second substrate 8 and the patterned top electrode 4; S5, inverting the etching assembly, and then etching the first substrate 1 to form a groove 9 on the first substrate 1 to expose the buffer layer 2 and the second interconnection line 7; S6, forming a patterned bottom electrode 10 in the groove 9, which is connected to the second interconnection line 7 and has a top surface height less than the top surface height of the first substrate 1, and then mounting a cover layer 11 on the first substrate 1 to form a bulk acoustic wave resonator; S7 , removing the second substrate 8 , and then fixing the BAW resonator on the packaging substrate 12 through the first interconnection line 6 and the second interconnection line 7 , and plastic-sealing the BAW resonator.

[0036] Among them, the material of the first substrate 1 in step S1 can be sapphire, spinel, silicon carbide or silicon, and step S1 can form a buffer layer 2, a piezoelectric layer 3 and a patterned top electrode 4 on the first substrate 1 in sequence based on the existing thin film formation process. Since the embodiment first forms the buffer layer 2 on the first substrate 1, and then forms the piezoelectric layer 3 and the patterned top electrode 4 on the buffer layer 2 in sequence, and the lattice mismatch rate between the first substrate 1 and the piezoelectric layer 3 is greater than the lattice mismatch rate between the buffer layer 2 and the first substrate 1, the embodiment can effectively avoid the situation where the piezoelectric layer 3 directly grown on the first substrate 1 and the patterned top electrode 4 grown on the piezoelectric layer 3 have lattice defects due to the excessive lattice mismatch rate between the first substrate 1 and the piezoelectric layer 3. The material of the buffer layer 2 of the embodiment is preferably aluminum nitride, and the thickness of the buffer layer 2 of the embodiment is preferably 10-50nm. The material of the top electrode of this embodiment is a metal material with high electrical conductivity, large acoustic impedance and large Young's modulus. The material of the top electrode is preferably any one or more of aluminum, copper, gold, molybdenum, titanium, tungsten, ruthenium and platinum.

[0037] In step S2 , a blind hole 5 with a depth greater than 0 and penetrating through the piezoelectric layer 3 and the buffer layer 2 and on the first substrate 1 can be formed outside the patterned top electrode 4 by etching the area outside the patterned top electrode 4 based on an etching process.

[0038] Step S3 can form a first interconnection line 6 on the top surface of the patterned top electrode 4 and a second interconnection line 7 on the top surface of the piezoelectric layer 3 based on the existing thin film growth process and photolithography process, that is, the first interconnection line 6 of this embodiment is only connected to the patterned top electrode 4, and the second interconnection line 7 of this embodiment is connected to the first substrate 1, the piezoelectric layer 3 and the buffer layer 2. Since step S6 will form a patterned bottom electrode 10 connected to the second interconnection line 7, in order to avoid the situation where the resonant frequency and quality factor of the bulk acoustic wave resonator are affected due to the interconnection between the patterned top electrode 4 and the patterned bottom electrode 10, the second interconnection line 7 formed in step S3 is located outside the patterned top electrode 4, that is, the second interconnection line 7 is not connected to the patterned top electrode 4. Preferably, the height of the top surface of the first interconnection line 6 of this embodiment is the same as the height of the top surface of the second interconnection line 7. The material of the first interconnection line 6 and the second interconnection line 7 of this embodiment is preferably any one or more of conductive metal materials such as titanium, copper, aluminum, gold and tungsten, and the material of the first interconnection line 6 of this embodiment is preferably the same as the material of the second interconnection line 7.

[0039] In step S4, the second substrate 8 can be bonded on the first interconnection line 6 and the second interconnection line 7 based on the existing bonding process. The second substrate 8 is preferably a silicon substrate. In step S5 and step S6, the second substrate 8 can protect the patterned top electrode 4 and the piezoelectric layer 3 and support the structure located above them. Since the depth of the second interconnection line 7 on the first substrate 1 is greater than 0, that is, part of the second interconnection line 7 is located in the first substrate 1, step S5 can form a groove 9 on the first substrate 1 to expose the buffer layer 2 and the second interconnection line 7 by etching the first substrate 1. It should be understood that since step S6 forms a patterned bottom electrode 10 connected to the second interconnection line 7 in the groove 9, and the contact area between the patterned bottom electrode 10 and the second interconnection line 7 is related to the exposed area of ​​the second interconnection line 7, the electrical connection effect of the patterned bottom electrode 10 and the second interconnection line 7 is positively correlated with the contact area between the patterned bottom electrode 10 and the second interconnection line 7, after the etching of the first substrate 1 is completed, the side and partial top surface of the second interconnection line 7 are preferably exposed in this embodiment.

[0040] The process of forming the patterned bottom electrode 10 in the groove 9 in step S6 is preferably the same as the process of forming the patterned top electrode 4 on the piezoelectric layer 3 in step S1. The material of the patterned bottom electrode 10 in this embodiment is preferably the same as the material of the patterned top electrode 4. The patterned bottom electrode 10 in step S6 is connected to the second interconnection line 7 by contacting the side of the second interconnection line 7. After the patterned bottom electrode 10 is formed, step S6 can mount a coating layer 11 on the first substrate 1 based on the existing coating process. The coating layer 11 is preferably a blue film or a UV film. The material of the coating layer 11 is preferably polyvinyl chloride (PVC), polypropylene (BO Any one or more of PP) and polyester (PET), since the top surface height of the patterned bottom electrode 10 is smaller than the top surface height of the first substrate 1, and the coating layer 11 of this embodiment is mounted on the first substrate 1, after the coating layer 11 is formed, the coating layer 11 of this embodiment, the first substrate 1, the second interconnection line 7 and the patterned bottom electrode 10 are surrounded to form a first air cavity 14, and the first air cavity 14 and the patterned bottom electrode 10, the buffer layer 2, the piezoelectric layer 3, the first interconnection line 6, the second interconnection line 7 and the patterned top electrode 4 form a bulk acoustic wave resonator, that is, the first air cavity 14 of this embodiment is an acoustic reflector of the bulk acoustic wave resonator. It should be understood that, since the first air cavity 14 of this embodiment is formed by enclosing the coating layer 11, the first substrate 1, the second interconnection line 7 and the patterned bottom electrode 10, and the second interconnection line 7 of this embodiment is located outside the patterned top electrode 4, this embodiment is equivalent to making the bottom electrode not span the air cavity, and since when the patterned bottom electrode 10 partially spans the air cavity, even if the patterned top electrode 4 spans the air cavity, the patterned top electrode 4 spanning the cavity will not generate noise with the patterned bottom electrode 10, so this embodiment can effectively avoid the situation where noise is generated due to both the bottom electrode and the top electrode spanning the air cavity.

[0041] After removing the second substrate 8, in step S7, the BAW resonator can be fixed on the packaging substrate 12 by welding the first interconnection line 6 and the second interconnection line 7 to the packaging substrate 12, and then the BAW resonator is plastic-sealed based on the existing plastic sealing process. The packaging substrate 12 of this embodiment is preferably a ceramic substrate and a resin substrate. After the BAW resonator is fixed on the packaging substrate 12, the packaging substrate 12 and the BAW resonator will enclose a second air cavity 15, and the second air cavity 15 can protect the piezoelectric layer 3 and the patterned top electrode 4. After the plastic sealing is completed, the plastic sealing layer 13 can protect the BAW resonator. The material of the plastic sealing layer 13 of this embodiment is preferably epoxy resin.

[0042] The present application provides a method for preparing a BAW resonator with high electrical performance. The method can form an acoustic reflector of the BAW resonator by first etching the first substrate 1, then forming a patterned bottom electrode 10 in the groove 9, and finally forming a coating layer 11 on the first substrate 1. That is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate. Therefore, the present application can effectively solve the problem of tympanic membrane or cracking of the BAW resonator film during the process of releasing the sacrificial layer due to excessive stress or uneven stress distribution on the BAW resonator film during the process of releasing the sacrificial layer. Moreover, since the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the BAW resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the BAW resonator.

[0043] In some preferred embodiments, step S1 comprises: S11, forming a buffer layer 2 on a first substrate 1; S12, depositing single crystal aluminum nitride on the buffer layer 2 based on a deposition process to form a piezoelectric layer 3 on the buffer layer 2; S13 , forming a patterned top electrode 4 on the piezoelectric layer 3 based on a deposition process and a patterning process.

[0044] Step S12 preferably deposits single-crystalline aluminum nitride on the buffer layer 2 based on a metal organic chemical vapor deposition process, that is, this embodiment is equivalent to using single-crystalline aluminum nitride as the material of the piezoelectric layer 3. Since the piezoelectric layer 3 made of single-crystalline aluminum nitride has a low dislocation density and an atomically smooth surface, this embodiment can effectively improve the effective electromechanical coupling coefficient of the BAW resonator and improve the insertion loss of the BAW filter passband, thereby effectively improving the electrical performance of the BAW resonator and the BAW filter. It should be understood that it is difficult for the prior art to deposit single-crystalline aluminum nitride on a sacrificial layer, that is, it is difficult for the prior art to improve the electrical performance of a bulk acoustic wave resonator by forming a piezoelectric layer 3 whose material is single-crystalline aluminum nitride on a substrate. Since this embodiment does not require the formation of a sacrificial layer on a substrate, and this embodiment can form a piezoelectric layer 3 whose material is single-crystalline aluminum nitride on a first substrate 1 by first forming a buffer layer 2 on the first substrate 1 and then depositing single-crystalline aluminum nitride on the buffer layer 2, this embodiment can improve the electrical performance of a bulk acoustic wave resonator by forming a piezoelectric layer 3 whose material is single-crystalline aluminum nitride on a substrate.

[0045] In some preferred embodiments, step S1 further includes the following steps performed before step S11: S14, cleaning the first substrate 1.

[0046] This embodiment is equivalent to first cleaning the first substrate 1 and then forming a buffer layer 2 on the first substrate 1. Since this embodiment can remove organic matter on the surface of the first substrate 1 by cleaning the first substrate 1, this embodiment can effectively improve the growth quality of the buffer layer 2, the piezoelectric layer 3 and the patterned top electrode 4.

[0047] In some preferred embodiments, step S5 comprises: S51, turning the etching assembly upside down; S52, thinning the first substrate 1 so that the distance between the top surface of the first substrate 1 and the top surface of the second interconnection line 7 is a preset distance; S53 , etching the first substrate 1 based on a dry etching process to form a groove 9 on the first substrate 1 to expose the buffer layer 2 and the second interconnection line 7 .

[0048] Because the first substrate 1 is thinned before being etched in this embodiment, that is, the thickness of the first substrate 1 can be effectively reduced in this embodiment, the etching depth can be effectively reduced in this embodiment, thereby effectively improving the etching efficiency of the first substrate 1, and the size of the finally formed BAW resonator can be reduced by reducing the thickness of the first substrate 1.

[0049] In some preferred embodiments, the package substrate 12 has a third interconnection line 16, and step S7 includes: S71, removing the second substrate 8 based on a stripping process; S72, welding the first interconnection line 6 and the second interconnection line 7 to the third interconnection line 16 based on a flip chip process to fix the BAW resonator on the packaging substrate 12; S73, plastic-sealing the BAW resonator based on a plastic-sealing process.

[0050] Since the packaging substrate 12 of this embodiment has a third interconnection line 16, and step S72 welds the first interconnection line 6 and the second interconnection line 7 to the third interconnection line 16 based on the flip chip process, this embodiment can apply a voltage signal or an electric signal to the patterned top electrode 4 through the third interconnection line 16 and the first interconnection line 6. This embodiment can apply a voltage signal or an electric signal to the patterned bottom electrode 10 through the third interconnection line 16 and the second interconnection line 7. When a voltage signal or an electric signal is applied to the patterned top electrode 4 and the patterned bottom electrode 10, an electric field is formed at both ends of the piezoelectric layer 3 to excite a bulk acoustic wave (equivalent to exciting the piezoelectric layer 3 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.

[0051] As can be seen from the above, the present application provides a method for preparing a high electrical performance bulk acoustic wave resonator, which can form an acoustic reflector of the bulk acoustic wave resonator by first etching the first substrate 1, then forming a patterned bottom electrode 10 in the groove 9, and finally forming a coating layer 11 on the first substrate 1. That is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate. Therefore, the present application can effectively solve the problem of tympanic membrane or cracking of the bulk acoustic wave resonator film during the release of the sacrificial layer due to excessive stress or uneven stress distribution on the film of the bulk acoustic wave resonator during the release of the sacrificial layer. Moreover, since the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the bulk acoustic wave resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the bulk acoustic wave resonator.

[0052] Second, as Figure 3 As shown, the present application also provides a high electrical performance BAW resonator, which includes a BAW resonator, a packaging substrate 12 and a plastic packaging layer 13. The BAW resonator includes a first substrate 1, a buffer layer 2, a piezoelectric layer 3, a patterned top electrode 4, a first interconnection line 6, a second interconnection line 7, a patterned bottom electrode 10, a coating layer 11 and a first air cavity 14. The two ends of the first interconnection line 6 are respectively connected to the patterned top electrode 4 and the packaging substrate 12, and the second interconnection line 7 is connected to the piezoelectric layer 3 and the packaging substrate 12. The second interconnection line 7 penetrates the piezoelectric layer 3 and the buffer layer 2 and has a depth greater than 0 on the first substrate 1. The patterned bottom electrode 10 is connected to the buffer layer 2 and the second interconnection line 7. The first substrate 1 is arranged around the patterned bottom electrode 10. The coating layer 11 is connected to the top surface of the first substrate 1 and there is a gap between the coating layer 11 and the patterned bottom electrode 10. The first air cavity 14 is formed by the first substrate 1, the second interconnection line 7, the patterned bottom electrode 10 and the coating layer 11. The plastic encapsulation layer 13 is arranged on the packaging substrate 12 and wraps the outside of the body acoustic wave resonator.

[0053] The embodiment of the present application provides a high electrical performance BAW resonator. The high electrical performance BAW resonator provided by the embodiment is preferably made by a high electrical performance BAW resonator preparation method provided by the first aspect. The principle of the high electrical performance BAW resonator provided by the embodiment is the same as the principle of the high electrical performance BAW resonator preparation method provided by the first aspect, and will not be discussed in detail here. It should be understood that since the first substrate 1 of the embodiment is arranged around the patterned bottom electrode 10, the outer boundary of the projection of the patterned bottom electrode 10 of the embodiment in the top view direction is located within the inner boundary of the projection of the first substrate 1 in the top view direction.

[0054] In some preferred embodiments, the patterned bottom electrode 10 is staggered with the patterned top electrode 4. Since the patterned bottom electrode 10 of this embodiment is located in the first air cavity 14, that is, the patterned bottom electrode 10 is located in the effective area of ​​the BAW resonator, that is, only the patterned top electrode 4 exists outside the effective area of ​​the BAW resonator, so this embodiment can effectively avoid the situation where energy leakage occurs due to the piezoelectric effect between the patterned bottom electrode 10 located outside the effective area of ​​the BAW resonator and the top electrode located outside the effective area of ​​the BAW resonator. The prior art can prevent energy leakage by setting an air gap in the interconnection line external area of ​​the top electrode, but setting the air gap will make the processing technology of the BAW resonator complicated. Since the patterned bottom electrode 10 does not exist in the interconnection line external area of ​​the patterned top electrode 4 of this embodiment, this embodiment does not need to set an air gap for preventing energy leakage in the interconnection line external area of ​​the patterned top electrode 4, thereby effectively simplifying the processing technology of the BAW resonator.

[0055] In some preferred embodiments, the second interconnection line 7 is located at the edge of the patterned bottom electrode 10. Since the second interconnection line 7 of this embodiment penetrates the piezoelectric layer 3, and the second interconnection line 7 is located at the edge of the patterned bottom electrode 1, this embodiment can effectively avoid the situation where the piezoelectric layer 3 structure arranged in the central area of ​​the BAW resonator is destroyed due to the second interconnection line 7 being arranged in the central area of ​​the BAW resonator, and the electrical performance of the BAW resonator is affected. Preferably, the first interconnection line 6 of this embodiment is arranged at the edge of one side of the patterned top electrode 4 away from the second interconnection line 7.

[0056] In some preferred embodiments, there are multiple second interconnecting lines 7. Since the second interconnecting lines 7 of this embodiment penetrate the piezoelectric layer 3, and the material of the second interconnecting lines 7 is a metal material, that is, the second interconnecting lines 7 can guide the heat generated by the BAW resonator during operation, this embodiment can increase the amount of heat guided out per unit time by setting the number of the second interconnecting lines 7 to multiple, thereby effectively enhancing the heat dissipation effect of the BAW resonator.

[0057] As can be seen from the above, the present application provides a high electrical performance BAW resonator, which utilizes a first substrate 1, a second interconnect line 7, a patterned bottom electrode 10 and a coating layer 11 to enclose a first air cavity 14, that is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate, so the present application can effectively solve the problem of tympaning or cracking of the BAW resonator film during the release of the sacrificial layer due to excessive stress or uneven stress distribution on the BAW resonator film during the release of the sacrificial layer, and because the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the BAW resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the BAW resonator.

[0058] Thirdly, Figure 4-Figure 7 As shown, the present application also provides a bulk acoustic wave filter, which includes a plurality of high electrical performance bulk acoustic wave resonators provided by the second aspect above.

[0059] An embodiment of the present application provides a bulk acoustic wave filter, which includes a plurality of high electrical performance bulk acoustic wave resonators provided by the second aspect above. The principle of the bulk acoustic wave filter provided by this embodiment is the same as the principle of the high electrical performance bulk acoustic wave resonator provided by the second aspect above, and will not be discussed in detail here. It should be understood that the bulk acoustic wave filter of this embodiment includes a plurality of high electrical performance bulk acoustic wave resonators, and this embodiment refers to two adjacent high electrical performance bulk acoustic wave resonators in the bulk acoustic wave filter as a first bulk acoustic wave resonator and a second bulk acoustic wave resonator. This embodiment can connect the patterned top electrode 4 of the first bulk acoustic wave resonator to the patterned bottom electrode 10 of the second bulk acoustic wave resonator by connecting the first interconnect line 6 of the first bulk acoustic wave resonator to the second interconnect line 7 of the second bulk acoustic wave resonator (refer to Figure 5 ), this embodiment can also connect the patterned top electrode 4 of the first BAW resonator to the patterned top electrode 4 of the second BAW resonator by connecting the first interconnection line 6 of the first BAW resonator to the first interconnection line 6 of the second BAW resonator (refer to Figure 6 ), this embodiment can also connect the patterned bottom electrode 10 of the first BAW resonator to the patterned bottom electrode 10 of the second BAW resonator by connecting the second interconnection line 7 of the first BAW resonator to the second interconnection line 7 of the second BAW resonator (refer to Figure 7 ).

[0060] As can be seen from the above, the present application provides a high electrical performance BAW resonator, a preparation method and a BAW filter, which can form an acoustic reflector of the BAW resonator by first etching the first substrate 1, then forming a patterned bottom electrode 10 in the groove 9, and finally forming a coating layer 11 on the first substrate 1. That is, the present application does not need to form a sacrificial layer and release the sacrificial layer on the substrate. Therefore, the present application can effectively solve the problem of tympanic membrane or cracking of the BAW resonator film during the release of the sacrificial layer due to excessive stress or uneven stress distribution on the BAW resonator film during the release of the sacrificial layer. Moreover, since the bottom electrode of the present application does not span the air cavity, the present application can also effectively solve the problem of partial energy leakage of the BAW resonator due to the generation of noise by the bottom electrode and the top electrode spanning the air cavity, thereby effectively improving the electrical performance of the BAW resonator.

[0061] 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.

[0062] 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 method for preparing a bulk acoustic wave resonator with high electrical performance, characterized in that: The method for preparing a bulk acoustic wave resonator with high electrical performance comprises: S1. forming a buffer layer, a piezoelectric layer and a patterned top electrode in sequence on a first substrate, wherein the patterned top electrode partially covers the piezoelectric layer; S2, forming a blind hole outside the patterned top electrode, which penetrates the piezoelectric layer and the buffer layer and has a depth greater than 0 on the first substrate; S3, forming a first interconnection line on the top surface of the patterned top electrode and forming a second interconnection line on the top surface of the piezoelectric layer by filling the blind hole, wherein the second interconnection line is located outside the patterned top electrode; S4, bonding a second substrate on the first interconnection line and the second interconnection line to obtain an etching assembly, wherein there is a gap between the second substrate and the patterned top electrode; S5, inverting the etching assembly, and then etching the first substrate to form a groove on the first substrate to expose the buffer layer and the second interconnection line; S6, forming a patterned bottom electrode in the groove, which is connected to the second interconnection line and has a top surface height less than a top surface height of the first substrate, and then mounting a coating layer on the first substrate to form a bulk acoustic wave resonator; S7, removing the second substrate, and then fixing the BAW resonator on a packaging substrate through the first interconnection line and the second interconnection line and plastic-sealing the BAW resonator.

2. The method for preparing a bulk acoustic wave resonator with high electrical performance according to claim 1, characterized in that: Step S1 includes: S11, forming a buffer layer on a first substrate; S12, depositing single crystal aluminum nitride on the buffer layer based on a deposition process to form a piezoelectric layer on the buffer layer; S13, forming a patterned top electrode on the piezoelectric layer based on a deposition process and a patterning process.

3. The method for preparing a bulk acoustic wave resonator with high electrical performance according to claim 2, characterized in that: Step S1 also includes the following steps performed before step S11: S14, cleaning the first substrate.

4. The method for preparing a bulk acoustic wave resonator with high electrical performance according to claim 1, characterized in that: Step S5 includes: S51, turning the etching assembly upside down; S52, thinning the first substrate so that a distance between a top surface of the first substrate and a top surface of the second interconnection line is a preset distance; S53 . Etch the first substrate based on a dry etching process to form a groove on the first substrate to expose the buffer layer and the second interconnection line.

5. The method for preparing a bulk acoustic wave resonator with high electrical performance according to claim 1, characterized in that: The package substrate has a third interconnection line, and step S7 includes: S71, removing the second substrate based on a stripping process; S72, welding the first interconnection line, the second interconnection line and the third interconnection line based on a flip chip process to fix the BAW resonator on the packaging substrate; S73, performing plastic packaging on the BAW resonator based on a plastic packaging process.

6. A high electrical performance bulk acoustic wave resonator, characterized in that: The high electrical performance BAW resonator comprises a BAW resonator, a packaging substrate and a plastic packaging layer. The BAW resonator comprises a first substrate, a buffer layer, a piezoelectric layer, a patterned top electrode, a first interconnection line, a second interconnection line, a patterned bottom electrode, a coating layer and a first air cavity. The two ends of the first interconnection line are respectively connected to the patterned top electrode and the packaging substrate, the second interconnection line is connected to the piezoelectric layer and the packaging substrate, the second interconnection line penetrates the piezoelectric layer and the buffer layer and has a depth greater than 0 on the first substrate, the patterned bottom electrode is connected to the buffer layer and the second interconnection line, the first substrate is arranged around the patterned bottom electrode, the coating layer is connected to the top surface of the first substrate and has a gap with the patterned bottom electrode, the first air cavity is formed by enclosing the first substrate, the second interconnection line, the patterned bottom electrode and the coating layer, and the plastic packaging layer is arranged on the packaging substrate and wraps the outer side of the BAW resonator.

7. The high electrical performance BAW resonator according to claim 6, characterized in that: The patterned bottom electrode and the patterned top electrode are arranged in a staggered manner.

8. The high electrical performance BAW resonator according to claim 6, characterized in that: The second interconnection line is located at the edge of the patterned bottom electrode.

9. The high electrical performance BAW resonator according to claim 6, characterized in that: The number of the second interconnection lines is plural.

10. A bulk acoustic wave filter, characterized in that: The BAW filter comprises a plurality of BAW resonators with high electrical performance as claimed in any one of claims 6 to 9.

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