Semiconductor structure for improving sideband steepness of surface acoustic wave filter
By using the reflective gate structure to form a capacitor in the surface acoustic wave filter and adjusting the anti-resonance point of the resonator, the problem of size increase in the prior art is solved, and a steeper transition zone and smaller size are achieved, which improves the product's Flexibility and power tolerance.
Patent Information
- Application Number
- CN202411370884.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-29
- Publication Date
- 2025-01-17
AI Technical Summary
When existing surface acoustic filters increase the steepness of the transition zone, the direct parallel capacitor scheme will lead to an increase in device size, which violates the trend of miniaturization.
By using the existing reflective gate structure in a cascading surface acoustic wave filter to form a capacitive structure, adjust the anti-resonance point of the resonator, achieving a steeper transition zone without adding additional capacitor devices.
A steeper transition zone is achieved, avoiding additional capacitance devices and improving product size, flexibility and power tolerance.
Smart Images
Figure CN119324689A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of radio frequency filters, and in particular relates to a semiconductor structure for improving the steepness of sidebands of surface acoustic wave filters. Background Art
[0002] With the continuous development of communication technology, the requirements for surface acoustic wave filters are getting higher and higher, and the overall trend is towards smaller size, higher power capacity, smaller insertion loss and steeper transition band. Among them, a steeper transition band means better frequency selectivity. For filters, multiplexers or multi-band synthetic filters, the suppression of adjacent frequency bands or WIFI bands must be considered.
[0003] For surface acoustic wave duplex filters, there are two ways to improve the steepness: one is to improve its piezoelectric structure, such as using multilayer piezoelectric materials with a thin film structure to improve the Q value and energy conversion efficiency of the resonator by optimizing the electromechanical coupling coefficient, acoustic impedance and surface acoustic wave propagation speed; the other is to improve the circuit structure.
[0004] This application mainly considers improving the circuit structure. Taking the four-stage cascade as an example, the existing circuit structure is as follows Figure 1 As shown, four resonators (resonator a, resonator b, resonator c, resonator d) are included. The structure of each resonator is the same. Taking resonator a as an example, it includes a pair of resonant bus bars a1, a plurality of interdigital transducers a2 staggeredly distributed between the resonant bus bars a1, a plurality of reflection gratings a3 distributed on the upper and lower sides of the interdigital transducers a2, and a reflection grating bus bar a4 connected to both ends of the reflection grating a3, and two adjacent resonators are connected to two resonant bus bars in adjacent areas, as shown in FIG. Figure 1 In the figure, the resonance bus bar b1 of resonator b is connected to the right resonance bus bar a1 of resonator a.
[0005] For the improvement of circuit structure, the existing solutions mainly include: 1. Adopting DMS structure or hybrid structure of DMS and single-port resonator is conducive to improving the steepness of low-frequency end of passband, which is often used in RX filter; 2. Directly connect capacitors in parallel at the series resonator to increase the steepness of transition band by adjusting the position of anti-resonance point; 3. Add ground inductance to parallel resonator to increase the steepness of transition band by introducing notch point. Although the second solution increases the steepness of transition band, the parallel capacitor will increase the size of device, which is not in line with the development trend of surface acoustic wave filter. Summary of the invention
[0006] In order to solve the above problems, the present invention provides a semiconductor structure for improving the steepness of the sideband of a surface acoustic wave filter, which improves the steepness of the transition band while avoiding the problem of additional increase in device size caused by the direct parallel capacitor solution.
[0007] The technical solution adopted by the present invention is:
[0008] In the first aspect, the present application discloses a semiconductor structure for improving the steepness of the sideband of a surface acoustic wave filter, comprising at least two resonators, each of the resonators comprising a pair of resonant bus bars, an interdigital transducer distributed between the pair of resonant bus bars, and a reflection grating structure distributed on both sides of the interdigital transducer, the reflection grating structure comprising a pair of reflection grating bus bars and a plurality of reflection gratings distributed between the pair of reflection grating bus bars, wherein the resonant bus bars in adjacent areas of two adjacent resonators are connected; and among the at least two resonators, at least one pair of adjacent reflection grating bus bars forms a capacitor structure.
[0009] As an optional technical solution, the capacitor structure is a single-layer capacitor structure or a multi-layer capacitor structure.
[0010] As an optional technical solution, the capacitor gap of the capacitor structure is 0.2-2 um.
[0011] As an optional technical solution, the number of resonator cascades is set to two, namely a first resonator and a second resonator, the outer resonant bus bar of the first resonator is connected to the outer reflection grating bus bar; the outer resonant bus bar of the second resonator is connected to the outer reflection grating bus bar; the inner reflection grating bus bar of the first resonator and the inner reflection grating bus bar of the second resonator form a capacitor structure.
[0012] As an optional technical solution, the number of resonator cascades is set to four, namely the third resonator, the fourth resonator, the fifth resonator and the sixth resonator; the outer resonant bus bar of the third resonator is connected to the outer reflection grating bus bar, and the outer resonant bus bar of the sixth resonator is connected to the outer reflection grating bus bar; the reflection grating bus bars of the fourth resonator and the fifth resonator in adjacent areas form a capacitor structure.
[0013] In a second aspect, the present application discloses another semiconductor structure for improving the steepness of the sideband of a surface acoustic wave filter, comprising a seventh resonator, an eighth resonator and a ninth resonator, each resonator comprising a pair of resonant bus bars, an interdigital transducer distributed between the pair of resonant bus bars and a reflection grating structure distributed on both sides of the interdigital transducer, the reflection grating structure comprising a pair of reflection grating bus bars and a plurality of reflection gratings distributed between the pair of reflection grating bus bars, wherein the resonant bus bars of two adjacent resonators in adjacent areas are connected; the reflection grating of the seventh resonator is connected to the corresponding reflection grating of the ninth resonator, the upper and lower side reflection gratings of the eighth resonator are respectively connected to the outer resonant bus bar of the ninth resonator and the outer resonant bus bar of the seventh resonator; the outer resonant bus bar of the seventh resonator is connected to the upper reflection grating bus bar, and the outer resonant bus bar of the ninth resonator is connected to the lower reflection grating bus bar.
[0014] As an optional technical solution, the reflection grating of the seventh resonator is connected to the corresponding reflection grating of the ninth resonator through a first bridge layer; the upper reflection grating of the eighth resonator is connected to the outer bus bar of the ninth resonator through a second bridge layer, and the lower reflection grating of the eighth resonator is connected to the outer resonant bus bar of the seventh resonator through a third bridge layer; and a bridge insulation layer is provided between the second bridge layer, the third bridge layer and the first bridge layer.
[0015] In the third aspect, the present application discloses another semiconductor structure for improving the steepness of the sideband of a surface acoustic wave filter, comprising a tenth resonator, an eleventh resonator, a twelfth resonator and a thirteenth resonator; each resonator comprises a pair of resonant bus bars, an interdigital transducer distributed between the pair of resonant bus bars and a reflection grating structure distributed on both sides of the interdigital transducer, the reflection grating structure comprises a pair of reflection grating bus bars and a plurality of reflection gratings distributed between the pair of reflection grating bus bars, wherein the resonant bus bars of two adjacent resonators in adjacent areas are connected; the reflection grating of the tenth resonator is connected to the corresponding reflection grating of the twelfth resonator, and the reflection grating of the eleventh resonator is connected to the corresponding reflection grating of the thirteenth resonator; the outer resonant bus bar of the tenth resonator is connected to the outer reflection grating bus bar, and the outer resonant bus bar of the thirteenth resonator is connected to the outer reflection grating bus bar.
[0016] As an optional technical solution, the reflection grating of the tenth resonator is connected to the corresponding reflection grating of the twelfth resonator through a fourth bridge layer; the reflection grating of the eleventh resonator is connected to the corresponding reflection grating of the thirteenth resonator through a fifth bridge layer; and a bridge insulation layer is provided between the fourth bridge layer and the corresponding fifth bridge layer.
[0017] The beneficial effects of the present invention are as follows: in the present application, a single-port resonator is realized in a cascade manner, wherein the reflective grid is a short-circuit structure, and the capacitive induction between the reflective grid short-circuit connecting lines (i.e., the reflective grid bus bars) is utilized to realize the function of adjusting the anti-resonance point of the resonator, thereby realizing a steeper transition band, and it does not increase the capacitance additionally, but utilizes the reflective grid short-circuit connecting lines in the existing structure to form a capacitance structure, so that the size will not be increased additionally. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a schematic diagram of the semiconductor structure of a four-stage cascade resonator (ie, four surface acoustic wave resonators connected in series) in the prior art.
[0019] Figure 2 Schematic diagram of a semiconductor structure with two cascaded surface acoustic wave resonators, where: Figure 2 -A forms a single-layer capacitor structure, Figure 2 -A multilayer capacitor structure is formed in B.
[0020] Figure 3 Schematic diagram of the admittance curve of a two-stage cascade resonator.
[0021] Figure 4 This is a schematic diagram of a semiconductor structure with four surface acoustic wave resonators cascaded, where: Figure 4 -A forms a single-layer capacitor structure, Figure 4 -A multilayer capacitor structure is formed in B.
[0022] Figure 5 This is a schematic diagram of another semiconductor structure for improving the steepness of the sideband of the surface acoustic wave filter in Example 3.
[0023] Figure 6 This is a schematic diagram of another semiconductor structure for improving the steepness of the sideband of the surface acoustic wave filter in Example 4. DETAILED DESCRIPTION
[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally 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 invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0025] Example 1
[0026] The overall inventive concept of this embodiment is to use the existing reflective grating structure to form a capacitor to adjust the anti-resonance point of the surface acoustic wave resonator, thereby improving the sideband steepness of the surface acoustic wave filter (the surface acoustic wave filter is a series of cascaded surface acoustic wave resonators).
[0027] The present embodiment discloses a semiconductor structure for improving the steepness of the sideband of a surface acoustic wave filter, comprising at least two surface acoustic wave resonators, each of the surface acoustic wave resonators comprising a pair of resonant bus bars, an interdigital transducer distributed between the pair of resonant bus bars, and a reflection grating structure distributed on both sides of the interdigital transducer, the reflection grating structure comprising a pair of reflection grating bus bars and a plurality of reflection gratings distributed between the pair of reflection grating bus bars, wherein the resonant bus bars of two adjacent resonators are connected in adjacent areas; and in the at least two resonators, at least one pair of adjacent reflection grating bus bars forms a capacitor structure.
[0028] As an optional implementation, the capacitor structure is a single-layer capacitor structure or a multi-layer capacitor structure.
[0029] As an optional implementation, the capacitor gap of the capacitor structure is 0.2-2 um.
[0030] The semiconductor structure for improving the steepness of the sideband of the surface acoustic wave filter provided in this embodiment has the following advantages: 1. To achieve the same steepness, the size is smaller than the solution of directly connecting capacitors in parallel in the background technology; 2. The design is flexible, and a steeper transition band can be achieved without changing the layout of the resonator, thereby improving the product yield; 3. Under the same out-of-band suppression conditions, a wider passband bandwidth can be achieved, thereby improving the power tolerance of the device.
[0031] The following is an example of a surface acoustic wave filter including two surface acoustic wave resonators connected in cascade (i.e., in series). The semiconductor structure is as follows: Figure 2 -A, comprising a first resonator 1 and a second resonator 2, the outer resonant bus bar 101 of the first resonator is connected to the outer reflector bus bar 102; the outer resonant bus bar 201 of the second resonator is connected to the outer reflector bus bar 202; the inner resonant bus bar 103 of the first resonator is connected to the inner resonant bus bar 203 of the second resonator; the inner reflector bus bar 104 of the first resonator and the inner reflector bus bar 204 of the second resonator form a capacitor structure C1, and the capacitor structure C1 is a single-layer capacitor structure. Figure 2 As shown in -B, the capacitor structure C2 is a multi-layer capacitor structure. Figure 3As shown, it is the admittance curve of the two-stage cascade resonator, where the solid line is the admittance curve of the two-stage cascade resonator without adding capacitance, and the dotted line is the admittance curve of the two-stage cascade resonator with adding a single-layer capacitor. Figure 3 It can be seen that the anti-resonance point of the admittance curve shifts about 20MHz toward the resonance point. Compared with the single-layer capacitor structure, the multi-layer capacitor structure has the advantage that a larger capacitance can be achieved with the same number of reflection gratings.
[0032] Example 2
[0033] The overall inventive concept of this embodiment is the same as that of the first embodiment, both of which utilize the reflective grid bus bar in the existing reflective grid structure of the cascade resonator to form a capacitor structure, thereby adjusting the anti-resonance point to improve the steepness of the filter transition band. The difference is that the number of cascaded resonators is set differently. In this embodiment, Figure 4 As shown, the number of cascaded surface acoustic wave resonators is set to four, among which, Figure 4 -A forms a single-layer capacitor structure C1, Figure 4 -A can be regarded as Figure 2 -A structure has a resonator connected in series on both the left and right sides; Figure 4 -B forms a multilayer capacitor structure C2, Figure 4 -B can be regarded as Figure 2 -B structure has a resonator connected in series on both the left and right sides.
[0034] Specifically, Figure 4 -A, the semiconductor structure includes a third resonator 3, a fourth resonator 4, a fifth resonator 5 and a sixth resonator 6; the outer resonant bus bar 301 of the third resonator is connected to the outer reflector bus bar 302, and the outer resonant bus bar 601 of the sixth resonator is connected to the outer reflector bus bar 602; the adjacent reflector bus bars between the third resonator 3 and the fourth resonator 4 are connected together, the adjacent reflector bus bars between the fifth resonator 5 and the sixth resonator 6 are connected together, and the reflector bus bars (402, 502) of the fourth resonator 4 and the fifth resonator 5 in the adjacent area form a single-layer capacitor structure C1. Figure 4 -B shows the structure Figure 4 -The structure shown in A is basically the same, the difference is: Figure 4 -B forms a multilayer capacitor structure C2 between the fourth resonator 4 and the fifth resonator 5.
[0035] Example 3
[0036] like Figure 5As shown, this embodiment discloses another semiconductor structure for improving the steepness of the sideband of the surface acoustic wave filter. The overall inventive concept is basically the same as that of Example 1, and also uses the reflection grid bus bar in the cascade resonator to form a capacitor structure. The difference is that: this embodiment uses a bridge structure to connect the reflection grid with the corresponding reflection grid, and the reflection grid with the corresponding resonant bus bar. Specifically, the semiconductor structure of this embodiment includes a seventh resonator 7, an eighth resonator 8 and a ninth resonator 9, each resonator including a pair of resonant bus bars, an interdigital transducer distributed between the pair of resonant bus bars, and a reflective grating structure distributed on both sides of the interdigital transducer, the reflective grating structure including a pair of reflective grating bus bars and a plurality of reflective gratings distributed between the pair of reflective grating bus bars, wherein the resonant bus bars of two adjacent resonators in adjacent areas are connected; the reflective grating 703 of the seventh resonator is connected to the corresponding reflective grating 903 of the ninth resonator, and the upper and lower reflective gratings of the eighth resonator are respectively connected to the outer resonant bus bar 901 of the ninth resonator and the outer resonant bus bar 701 of the seventh resonator; the outer resonant bus bar 701 of the seventh resonator is connected to its own upper reflective grating bus bar 702, and the outer resonant bus bar 901 of the ninth resonator is connected to its own lower reflective grating bus bar 902.
[0037] Among them, the reflection grating 703 of the seventh resonator is connected to the corresponding reflection grating 903 of the ninth resonator through the first bridge layer 1401; the upper reflection grating 801 of the eighth resonator is connected to the outer bus bar 901 of the ninth resonator through the second bridge layer 1402, and the lower reflection grating 802 of the eighth resonator is connected to the outer resonant bus bar 701 of the seventh resonator through the third bridge layer 1403; a bridge insulation layer 1404 is provided between the second bridge layer 1402, the third bridge layer 1403 and the first bridge layer 1401.
[0038] Example 4
[0039] This embodiment is basically the same as the third embodiment, and also uses a bridge structure to connect the corresponding reflective grids. Figure 6As shown, the specific structure includes a tenth resonator 10, an eleventh resonator 11, a twelfth resonator 12 and a thirteenth resonator 13; each resonator includes a pair of resonant bus bars, an IDT distributed between the pair of resonant bus bars and a reflection grating structure distributed on both sides of the IDT, the reflection grating structure includes a pair of reflection grating bus bars and a plurality of reflection gratings distributed between the pair of reflection grating bus bars, wherein the resonant bus bars of two adjacent resonators in adjacent areas are connected; the reflection grating 1001 of the tenth resonator is connected to the corresponding reflection grating 1201 of the twelfth resonator, the reflection grating 1101 of the eleventh resonator is connected to the corresponding reflection grating 1301 of the thirteenth resonator; the outer resonant bus bar 1002 of the tenth resonator is connected to its own outer reflection grating bus bar 1003, and the outer resonant bus bar 1302 of the thirteenth resonator is connected to its own outer reflection grating bus bar 1303.
[0040] Among them, the reflection grating 1001 of the tenth resonator is connected to the corresponding reflection grating 1201 of the twelfth resonator through the fourth bridge layer 1405; the reflection grating 1101 of the eleventh resonator is connected to the corresponding reflection grating of the thirteenth resonator through the fifth bridge layer 1406 through 1301; and a bridge insulation layer 1404 is provided between the fourth bridge layer 1405 and the corresponding fifth bridge layer 1406.
[0041] The above description is only a specific implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. All technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.
Claims
1. A semiconductor structure for increasing the steepness of a sideband of a surface acoustic wave filter, characterized in that: The invention comprises at least two resonators, each of which comprises a pair of resonant bus bars, an IDT distributed between the pair of resonant bus bars, and a reflective grating structure distributed on both sides of the IDT, wherein the reflective grating structure comprises a pair of reflective grating bus bars and a plurality of reflective gratings distributed between the pair of reflective grating bus bars, wherein the resonant bus bars in adjacent areas of two adjacent resonators are connected; and among the at least two resonators, at least one pair of adjacent reflective grating bus bars forms a capacitor structure.
2. The semiconductor structure for improving the sideband steepness of a surface acoustic wave filter according to claim 1, characterized in that: The capacitor structure is a single-layer capacitor structure or a multi-layer capacitor structure.
3. The semiconductor structure for improving the sideband steepness of a surface acoustic wave filter according to claim 1, characterized in that: The capacitance gap of the capacitance structure is 0.2-2 um.
4. The semiconductor structure for improving the sideband steepness of a surface acoustic wave filter according to any one of claims 1 to 3, characterized in that: The number of resonator cascades is set to two, namely the first resonator and the second resonator. The outer resonant bus bar of the first resonator is connected to the outer reflection grid bus bar; the outer resonant bus bar of the second resonator is connected to the outer reflection grid bus bar; the inner reflection grid bus bar of the first resonator and the inner reflection grid bus bar of the second resonator form a capacitor structure.
5. The semiconductor structure for improving the sideband steepness of a surface acoustic wave filter according to any one of claims 1 to 3, characterized in that: The number of resonator cascades is set to four, namely the third resonator, the fourth resonator, the fifth resonator and the sixth resonator; the outer resonant bus bar of the third resonator is connected to the outer reflection grid bus bar, and the outer resonant bus bar of the sixth resonator is connected to the outer reflection grid bus bar; the reflection grid bus bars of the fourth resonator and the fifth resonator in adjacent areas form a capacitor structure.
6. A semiconductor structure for increasing the steepness of a sideband of a surface acoustic wave filter, characterized in that: The invention comprises a seventh resonator, an eighth resonator and a ninth resonator, each of which comprises a pair of resonant bus bars, an interdigital transducer distributed between the pair of resonant bus bars and a reflective grating structure distributed on both sides of the interdigital transducer, the reflective grating structure comprises a pair of reflective grating bus bars and a plurality of reflective gratings distributed between the pair of reflective grating bus bars, wherein the resonant bus bars of two adjacent resonators in adjacent areas are connected; the reflective grating of the seventh resonator is connected to the corresponding reflective grating of the ninth resonator, the upper and lower reflective gratings of the eighth resonator are respectively connected to the outer resonant bus bar of the ninth resonator and the outer resonant bus bar of the seventh resonator; the outer resonant bus bar of the seventh resonator is connected to the upper reflective grating bus bar, and the outer resonant bus bar of the ninth resonator is connected to the lower reflective grating bus bar.
7. The semiconductor structure for improving the sideband steepness of a surface acoustic wave filter according to claim 6, characterized in that: The reflection grating of the seventh resonator is connected to the corresponding reflection grating of the ninth resonator through a first bridge layer; the upper reflection grating of the eighth resonator is connected to the outer bus bar of the ninth resonator through a second bridge layer, and the lower reflection grating of the eighth resonator is connected to the outer resonant bus bar of the seventh resonator through a third bridge layer; a bridge insulation layer is provided between the second bridge layer, the third bridge layer and the first bridge layer.
8. A semiconductor structure for increasing the steepness of a sideband of a surface acoustic wave filter, characterized in that: The invention comprises a tenth resonator, an eleventh resonator, a twelfth resonator and a thirteenth resonator; each resonator comprises a pair of resonant bus bars, an IDT distributed between the pair of resonant bus bars and a reflection grating structure distributed on both sides of the IDT, the reflection grating structure comprises a pair of reflection grating bus bars and a plurality of reflection gratings distributed between the pair of reflection grating bus bars, wherein the resonant bus bars of two adjacent resonators in adjacent areas are connected; the reflection grating of the tenth resonator is connected to the corresponding reflection grating of the twelfth resonator, the reflection grating of the eleventh resonator is connected to the corresponding reflection grating of the thirteenth resonator; the outer resonant bus bar of the tenth resonator is connected to the outer reflection grating bus bar, and the outer resonant bus bar of the thirteenth resonator is connected to the outer reflection grating bus bar.
9. The semiconductor structure for improving the sideband steepness of a surface acoustic wave filter according to claim 8, characterized in that: The reflection grating of the tenth resonator is connected to the corresponding reflection grating of the twelfth resonator through a fourth bridge layer; the reflection grating of the eleventh resonator is connected to the corresponding reflection grating of the thirteenth resonator through a fifth bridge layer; a bridge insulation layer is provided between the fourth bridge layer and the corresponding fifth bridge layer.