A surface acoustic wave filter
By setting isolation grooves and adjusting the ramp angle in the surface acoustic wave filter, the contact surface area between the conductive layer and the piezoelectric layer is increased, which solves the problem of insufficient bonding force between the conductive layer and the piezoelectric layer, improves the yield and stability of the surface acoustic wave filter, and protects the interdigital transducer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NINGBO SEMICON INT CORP
- Filing Date
- 2025-05-28
- Publication Date
- 2026-07-03
AI Technical Summary
Insufficient interfacial bonding between the conductive layer and the piezoelectric layer leads to a decrease in the yield rate of surface acoustic wave (SAW) filters.
By setting an isolation groove between the conductive layer and the piezoelectric layer, and forming a first bonding surface with a ramp angle of less than or equal to 60° in the isolation groove, the contact surface area is increased, and the adhesion between the support layer such as polyimide (PI) and the piezoelectric layer is utilized to ensure a stable connection.
It enhances the interfacial bonding between the conductive layer and the piezoelectric layer, improves the yield of the surface acoustic wave filter, avoids the risk of PI loss during the adhesive removal process, and protects the interdigital transducer.
Smart Images
Figure CN224459763U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of filter technology, and more specifically, to a surface acoustic wave filter. Background Technology
[0002] Dividing a wafer can produce multiple surface acoustic wave (SAW) filters. Specifically, the wafer is divided into multiple device regions and segmented regions surrounding the device regions. By forming segmentation grooves in the segmented regions, the device regions are divided into corresponding multiple SAW filter regions.
[0003] However, in related technologies, insufficient interfacial bonding between the conductive layer and the piezoelectric layer leads to unstable connections between them, which in turn reduces the yield of surface acoustic wave filters. Utility Model Content
[0004] The technical problem solved by this invention is that the insufficient interfacial bonding force between the conductive layer and the piezoelectric layer leads to unstable connection between the conductive layer and the piezoelectric layer, thereby reducing the yield of surface acoustic wave filters.
[0005] To address the aforementioned problems, this utility model provides a surface acoustic wave filter, comprising: a substrate with an isolation groove formed thereon; a piezoelectric layer disposed on one side of the substrate, and the piezoelectric layer including a first bonding surface exposed within the isolation groove; and a conductive layer, a portion of which is disposed within the isolation groove and supported by the first bonding surface, the remaining portion of which extends at least to an interdigital transducer disposed on the piezoelectric layer; wherein, a ramp angle is formed between the first bonding surface and the substrate, and the ramp angle is less than or equal to 60°.
[0006] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: To ensure a stable connection between the piezoelectric layer and the conductive layer and to improve the interfacial bonding force between them, the angle between the first bonding surface and the substrate, i.e., the ramp angle, is reduced. By limiting the ramp angle to less than or equal to 60°, the contact surface area between the two layers is increased while maintaining the thickness of the piezoelectric layer and the conductive layer. The increased contact surface area is then used to increase the interfacial bonding force.
[0007] In one embodiment of this utility model, the substrate further forms a second bonding surface connected to the first bonding surface within the isolation groove; the second bonding surface is disposed on the side of the first bonding surface near the bottom of the isolation groove; wherein, the conductive layer is supported by both the first bonding surface and the second bonding surface.
[0008] In one embodiment of this utility model, the first mating surface and the second mating surface are coplanar; or the first mating surface and the second mating surface are at an included angle.
[0009] In one embodiment of this utility model, the surface acoustic wave filter further includes: a support layer, a portion of which is disposed within an isolation groove, and the remaining portion of which extends to the side of the conductive layer away from the substrate; wherein the support layer is disposed between the conductive layer and the piezoelectric layer to support the conductive layer.
[0010] Compared with existing technologies, the technical effects achieved by this solution are as follows: Specifically, the conductive layer achieves cooperation with the piezoelectric layer through a support layer. For example, the support layer can be made of polyimide (PI). Because PI has weak adhesion to the substrate, it is easily eroded by chemical solvents or plasma during subsequent adhesive removal, causing interfacial delamination between PI and the piezoelectric layer. Therefore, by adjusting the ramp angle and increasing the contact surface area between PI and the piezoelectric layer, as mentioned above, the interfacial bonding force between them is improved, achieving stable adhesion of PI to the piezoelectric layer, reducing the occurrence of PI loss, and thus ensuring the support of the conductive layer by PI.
[0011] In one embodiment of this invention, as the ramp angle of the first bonding surface increases, the contact surface area between the support layer and the piezoelectric layer gradually increases.
[0012] Compared with existing technologies, the technical effect achieved by adopting this technical solution is: further improving the interfacial bonding force between the support layer and the piezoelectric layer.
[0013] In one embodiment of this utility model, the climbing angle ranges from 37° to 60°.
[0014] Compared with existing technologies, the technical effect achieved by adopting this technical solution is to ensure the interfacial bonding force between the support layer and the piezoelectric layer.
[0015] In one embodiment of this utility model, the conductive layer is in direct contact with the first bonding surface; wherein, the ramp angle of the first bonding surface is defined as a, where a≤15°.
[0016] Compared with the existing technology, the technical effects achieved by adopting this technical solution are as follows: Specifically, when a≤15°, the contact surface area formed by the first bonding surface and the conductive layer is large enough to ensure that the interfacial bonding force between the conductive layer and the piezoelectric layer is large enough. Compared with the solution of laying PI in the isolation trench, it effectively avoids the risk of PI loss during the subsequent adhesive removal process. In this case, the conductive layer is directly deposited on the surface of the piezoelectric layer.
[0017] In one embodiment of this utility model, a piezoelectric layer is disposed at the upper end of the substrate; an isolation groove extends from the upper end toward the lower end opposite to it, and the isolation groove passes through at least one single layer or multiple layers of material constituting the substrate.
[0018] In one embodiment of this invention, a second protective layer covering the interdigital transducer is also formed on the piezoelectric layer; wherein the material of the second protective layer includes silicon nitride.
[0019] Compared with existing technologies, the technical effect achieved by adopting this technical solution is that the second protective layer effectively protects the interdigital transducer.
[0020] In one embodiment of this utility model, the first mating surface and / or the second mating surface are at least one of a planar surface and an arcuate surface or a combination thereof.
[0021] Compared with the prior art, the technical effect achieved by adopting this technical solution is as follows: by setting the first bonding surface and / or the second bonding surface as an arc-shaped surface, the contact surface area between the conductive layer is further increased, thereby improving the interfacial bonding force between the two.
[0022] By adopting the technical solution of this utility model, the following technical effects can be achieved:
[0023] (1) In order to ensure a stable connection between the piezoelectric layer and the conductive layer and to improve the interfacial bonding force formed between them, the angle between the first bonding surface and the substrate, i.e. the ramp angle, is reduced. By limiting the ramp angle to less than or equal to 60°, the contact surface area between the two is increased while keeping the thickness of the piezoelectric layer and the conductive layer unchanged. The increased contact surface area is used to increase the interfacial bonding force.
[0024] (2) Specifically, when a≤15°, the contact surface area formed by the first bonding surface and the conductive layer is large enough to ensure that the interfacial bonding force between the conductive layer and the piezoelectric layer is large enough. Compared with the scheme of laying PI in the isolation trench, it effectively avoids the risk of PI loss during the subsequent adhesive removal process. In this case, the conductive layer is directly deposited on the surface of the piezoelectric layer. Attached Figure Description
[0025] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 A partial structural schematic diagram of a surface acoustic wave filter provided in an embodiment of this utility model;
[0027] Figure 2 A partial structural schematic diagram of another surface acoustic wave filter provided in an embodiment of this utility model;
[0028] Figure 3 This is a partial structural schematic diagram of another surface acoustic wave filter provided in an embodiment of the present invention.
[0029] Explanation of reference numerals in the attached figures:
[0030] 10. Substrate; 11. Isolation trench; 12. Second bonding surface; 14. First protective layer; 15. Monosilicon layer; 16. Polysilicon layer; 20. Piezoelectric layer; 21. First bonding surface; 22. Interdigital transducer; 23. Second protective layer; 30. Conductive layer; 40. Support layer. Detailed Implementation
[0031] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.
[0032] See Figure 1 This provides a schematic diagram of the structure of a surface acoustic wave filter according to an embodiment of the present invention. Specifically, in conjunction with... Figures 2-3 The surface acoustic wave filter includes, for example, a substrate 10, a piezoelectric layer 20, and a conductive layer 30. An isolation groove 11 is formed on the substrate 10; the piezoelectric layer 20 is disposed on one side of the substrate 10, and the piezoelectric layer 20 includes a first bonding surface 21 exposed within the isolation groove 11; a portion of the conductive layer 30 is disposed within the isolation groove 11 and supported by the first bonding surface 21, and the remaining portion of the conductive layer 30 extends at least to an interdigital transducer 22 disposed on the piezoelectric layer 20; wherein, a ramp angle is formed between the first bonding surface 21 and the substrate 10, and the ramp angle is less than or equal to 60°.
[0033] Surface Acoustic Wave (SAW) filters have advantages such as small size, suitability for micro-packaging, good consistency, and no need for adjustment, making them widely used in 5G radio frequency. Interdigital transducers 22 (IDTs) are used to convert between electrical and acoustic signals, enabling the SAW filter to filter the signals. In this embodiment, the formed filter is a SAW filter; therefore, the interdigital transducers 22 have a corresponding interdigital electrode structure, comprising multiple electrode fingers. Specifically, the interdigital transducers 22 are metal interdigital transducers.
[0034] In a specific example, for ease of understanding, the wafer is divided into device regions and segmented regions surrounding the device regions. Isolation trenches 11 are formed by etching on the segmented regions to separate the multiple device regions on the wafer. Then, in subsequent processes, the wafer is cut along the segmented regions to obtain multiple surface acoustic wave filters.
[0035] Furthermore, the substrate 10 can be composed of multiple layers of stacked materials. Specifically, the substrate 10 includes a single silicon layer 15 and a polycrystalline silicon layer 16 from bottom to top. During the process of creating the isolation trench 11 on the substrate 10, the corresponding part of the piezoelectric layer 20 disposed on the substrate 10 is also penetrated, so that the piezoelectric layer 20 forms a first bonding surface 21 exposed in the isolation trench 11. Since part of the structure of the conductive layer 30 is disposed in the isolation trench 11, and another part of the structure extends along the side wall of the isolation trench 11 to the interdigital transducer 22 disposed on the piezoelectric layer 20, an electrical connection with the interdigital transducer 22 is achieved. The conductive layer 30 is attached to the first bonding surface 21, and the interfacial bonding force formed between the two ensures a stable connection between the conductive layer 30 and the piezoelectric layer 20.
[0036] In related technologies, the angle between the first bonding surface 21 and the substrate 10 is too large, for example, the angle is 80°, which results in a small contact surface area between the piezoelectric layer 20 and the conductive layer 30. This leads to insufficient interfacial bonding force between the piezoelectric layer 20 and the conductive layer 30, making it difficult to ensure a stable connection between the conductive layer 30 and the piezoelectric layer 20.
[0037] For ease of understanding, the first mating surface 21 mentioned above forms an angle with the base 10. Specifically, it refers to the angle between the first mating surface 21 and the plane on the base 10 that forms the bottom of the isolation groove 11. Of course, it can also refer to the angle between the first mating surface 21 and a plane parallel to the plane on the bottom of the groove, which will not be elaborated here.
[0038] Therefore, in order to ensure a stable connection between the piezoelectric layer 20 and the conductive layer 30 and to improve the interfacial bonding force between them, the angle between the first bonding surface 21 and the substrate 10, i.e. the ramp angle, is reduced. By limiting the ramp angle to less than or equal to 60°, the contact surface area between the two is increased while keeping the thickness of the piezoelectric layer 20 and the conductive layer 30 constant. The increased contact surface area is used to increase the interfacial bonding force.
[0039] Combination Figure 1 and Figure 2 Preferably, the substrate 10 further forms a second bonding surface 12 within the isolation groove 11, which is connected to the first bonding surface 21; the second bonding surface 12 is disposed on the side of the first bonding surface 21 near the bottom of the isolation groove 11; wherein, the conductive layer 30 is supported by both the first bonding surface 21 and the second bonding surface 12. Specifically, the second bonding surface 12 is the surface on the substrate 10 where the sidewall of the isolation groove 11 is formed.
[0040] Preferably, the first mating surface 21 and the second mating surface 12 are coplanar; or, the first mating surface 21 and the second mating surface 12 are arranged at an included angle.
[0041] Preferably, the surface acoustic wave filter further includes, for example, a support layer 40, a portion of which is disposed within the isolation groove 11, and the remaining portion of which extends to the side of the conductive layer 30 away from the substrate 10; wherein the support layer 40 is disposed between the conductive layer 30 and the piezoelectric layer 20 to support the conductive layer 30.
[0042] Specifically, the conductive layer 30 is bonded to the piezoelectric layer 20 via the support layer 40. For example, the support layer 40 may be made of polyimide (PI). Since the adhesion between PI and the substrate 10 is weak, it is susceptible to erosion by chemical solvents or plasma during subsequent adhesive removal, causing interfacial delamination between the PI and the piezoelectric layer 20. Therefore, as mentioned above, by adjusting the ramp angle and increasing the contact surface area between the PI and the piezoelectric layer 20, the interfacial bonding force between them is improved, achieving stable adhesion of PI to the piezoelectric layer 20, reducing the possibility of PI loss, and thus ensuring the support of the conductive layer 30 by the PI.
[0043] Preferably, as the slope angle of the first bonding surface 21 increases, the contact surface area between the support layer 40 and the piezoelectric layer 20 gradually increases.
[0044] Preferably, the climbing angle ranges from 37° to 60°. For example, the climbing angle can be any of the following: 37°, 45°, or 60°.
[0045] Combination Figure 3 Preferably, the conductive layer 30 is in direct contact with the first bonding surface 21; wherein, the ramp angle of the first bonding surface 21 is defined as a, and a≤15°.
[0046] Specifically, when a≤15°, the contact surface area formed by the first bonding surface 21 and the conductive layer 30 is large enough to ensure that the interfacial bonding force between the conductive layer 30 and the piezoelectric layer 20 is large enough. Compared with the solution of laying PI in the isolation groove 11, it effectively avoids the risk of PI loss during the subsequent adhesive removal process. In this case, the conductive layer 30 is directly deposited on the surface of the piezoelectric layer 20.
[0047] Furthermore, the substrate 10 also includes a first protective layer 14 deposited beneath the piezoelectric layer 20. The material constituting the first protective layer 14 can specifically be a silicon dioxide layer composed of silicon dioxide, which serves to suppress the piezoelectric layer 20 and prevent it from expanding or contracting during temperature changes, thus affecting the frequency. Below the silicon dioxide layer is a polycrystalline silicon layer 16, which provides high resistivity to reduce losses. Besides the polycrystalline silicon layer 16, materials used to provide high resistivity include polycrystalline alumina, polycrystalline silicon dioxide, or polycrystalline silicon carbide.
[0048] Exemplarily, the piezoelectric layer 20 includes one or more of the following piezoelectric materials: lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz, zinc oxide (ZnO), aluminum nitride (AlN), barium strontium titanate (BST), barium titanate (BT), lead zirconate titanate (PZT), lithium lead barium niobate (PBLN), and lead titanate (PT). It should be noted that the piezoelectric layer 20 may also be doped with rare earth elements, such as any one or a combination of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), to improve the piezoelectric coefficient. The piezoelectric layer 20 is formed by physical vapor deposition, specifically by vacuum evaporation, sputtering, ion plating, etc., and the formed piezoelectric layer 20 is microcrystalline or amorphous.
[0049] Continue to combine Figure 3 Preferably, the piezoelectric layer 20 is disposed at the upper end of the substrate 10; the isolation trench 11 extends from the upper end toward the lower end opposite to it, and the isolation trench 11 passes through at least a single layer or multiple layers of material constituting the substrate 10. Specifically, the isolation trench 11 passes through at least the single silicon layer 15, the polysilicon layer 16, the silicon dioxide layer, and the piezoelectric layer 20 as mentioned above.
[0050] Preferably, a second protective layer 23 covering the interdigital transducer 22 is also formed on the piezoelectric layer 20; wherein the material of the second protective layer 23 includes silicon nitride.
[0051] Preferably, the first mating surface 21 and / or the second mating surface 12 are at least one of a planar surface and an arcuate surface or a combination thereof.
[0052] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A surface acoustic wave filter, characterized by, include: A substrate (10) having an isolation groove (11) formed thereon; A piezoelectric layer (20) is disposed on one side of the substrate (10), and the piezoelectric layer (20) includes a first bonding surface (21) exposed in the isolation groove (11); A conductive layer (30) is partially disposed within the isolation groove (11) and supported by the first bonding surface (21). The remaining portion of the conductive layer (30) extends at least to the interdigital transducer (22) disposed on the piezoelectric layer (20). Wherein, a ramp angle is formed between the first bonding surface (21) and the base (10), and the ramp angle is less than or equal to 60°.
2. The surface acoustic wave filter according to claim 1, characterized in that, The substrate (10) also forms a second mating surface (12) within the isolation groove (11) that is connected to the first mating surface (21); The second mating surface (12) is disposed on the side of the first mating surface (21) near the bottom of the isolation groove (11); The conductive layer (30) is supported by the first bonding surface (21) and the second bonding surface (12).
3. The surface acoustic wave filter according to claim 2, characterized in that, The first mating surface (21) and the second mating surface (12) are coplanar; or The first mating surface (21) and the second mating surface (12) are set at an angle.
4. The surface acoustic wave filter according to any one of claims 1 to 3, characterized by, The surface acoustic wave filter further includes: A support layer (40) is provided in part within the isolation groove (11), and the remaining structure of the support layer (40) extends to the side of the conductive layer (30) away from the substrate (10). The support layer (40) is disposed between the conductive layer (30) and the piezoelectric layer (20) to support the conductive layer (30).
5. The surface acoustic wave filter according to claim 4, characterized in that, As the slope angle of the first bonding surface (21) increases, the contact surface area between the support layer (40) and the piezoelectric layer (20) gradually increases.
6. The surface acoustic wave filter according to claim 4, characterized in that, The climbing angle ranges from 37° to 60°.
7. The surface acoustic wave filter according to any one of claims 1-3, characterized in that, The conductive layer (30) is in direct contact with the first bonding surface (21); The climbing angle of the first bonding surface (21) is defined as a, where a ≤ 15°.
8. The surface acoustic wave filter according to claim 7, characterized in that, The piezoelectric layer (20) is disposed at the upper end of the substrate (10); The isolation groove (11) extends from the upper end toward the lower end opposite to it, and the isolation groove (11) passes through at least a single layer or multiple layers of material that make up the substrate (10).
9. The surface acoustic wave filter according to claim 1, characterized in that, A second protective layer (23) covering the interdigital transducer (22) is also formed on the piezoelectric layer (20); The material of the second protective layer (23) includes silicon nitride.
10. The surface acoustic wave filter according to claim 2 or 3, characterized in that, The first mating surface (21) and / or the second mating surface (12) are at least one of a planar surface and an arcuate surface or a combination thereof.