Surface acoustic wave resonator and surface acoustic wave filter

Abstract

The invention relates to the field of communication devices, and discloses a surface acoustic wave resonator and a surface acoustic wave filter, comprising a composite substrate and an interdigital transducer arranged on the composite substrate; the interdigital transducer comprises a bus bar, and at least two pairs of interdigital electrodes and electrode short fingers which are alternately arranged on the bus bar; wherein a U-shaped speed change part is arranged between the interdigital electrode and the electrode short finger which are arranged opposite to each other, and the electrode short finger is embedded into an opening of the speed change part. Under the condition that the size of the resonator is not increased, the space between the adjacent finger strips and the space between the short finger and the long finger are utilized, the speed change part is added, the transverse mode suppression effect is achieved, and the purposes of small size and cost reduction are achieved.

Description

Technical Field

[0001] The invention relates to the field of communication devices, and in particular to a surface acoustic wave resonator and a surface acoustic wave filter. Background Art

[0002] SAW on POI substrate can replace TC-SAW (temperature compensated SAW) and BAW in 5G architecture with its unique performance advantages. The technical advantage of SAW based on POI substrate is that it has higher energy efficiency and less energy loss than TC-SAW. Therefore, it has achieved higher frequency and wider bandwidth compared to SAW and TC-SAW. Compared with BAW, the SAW process based on POI substrate is simpler and cheaper. From a production perspective, its production process is similar to that of SAW, but much simpler than TC-SAW and BAW. Compared with TC-SAW, which is generally used for filtering technology in low and medium frequency bands, BAW is generally used in medium and high frequency bands. SAW on POI substrate can solve the technical problems of the two frequency bands, medium and high frequency bands, and become a better solution to replace TC-SAW and BAW in 5G filters.

[0003] However, the existing POI process has a large transverse mode of the resonator, and the resonator needs to be tilted at a certain angle to suppress the transverse mode in order to achieve a high Q value and in-band flat filter. Qualcomm and other companies use a dual busbar approach to suppress the transverse mode, and the resonator does not need to be tilted at this time. However, the above solutions all increase the volume of the original resonator. For cost-sensitive integrated circuit devices, it is necessary to find ways to reduce the volume and reduce costs. Therefore, how to ensure performance without increasing the volume of the resonator is a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a surface acoustic wave resonator and a surface acoustic wave filter. Without increasing the volume of the resonator, the space between adjacent fingers and the space between short fingers and long fingers are utilized to add a speed change part to achieve the effect of transverse mode suppression, thereby achieving the purpose of small volume and reduced cost.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: In a first aspect, the present invention provides a surface acoustic wave resonator, comprising: A composite substrate, and an interdigital transducer disposed on the composite substrate; The interdigital transducer includes a bus bar, and at least two pairs of interdigital electrodes and electrode short fingers alternately arranged on the bus bar; a U-shaped speed change part is arranged between the interdigital electrodes and the electrode short fingers arranged opposite to each other, and the electrode short fingers are embedded in the opening of the speed change part.

[0006] Preferably, two opening edges of the speed change portion are parallel to the electrode short fingers, and a bottom edge of the speed change portion is perpendicular to the electrode short fingers.

[0007] Preferably, the line widths of the two opening edges and the bottom edge of the speed change portion are the same.

[0008] Preferably, the line widths of the two opening edges and the bottom edge of the speed change portion are each one-fourth of the line width of the interdigital electrodes.

[0009] Preferably, the lengths of the two opening edges and the bottom edge of the speed change portion are the same.

[0010] Preferably, the lengths of the two opening sides and the bottom side of the speed change portion are both half the wavelength.

[0011] Preferably, a closed edge is provided at the opening position of the speed change portion.

[0012] Preferably, in the reflection gratings on both sides of the IDT, each grating bar faces away from a U-shaped speed change portion.

[0013] Preferably, a closed edge is provided at the opening position of the speed change portion.

[0014] In a second aspect, the present invention provides a surface acoustic wave filter, comprising the surface acoustic wave resonator as described above.

[0015] The present invention has the following beneficial effects: The present invention utilizes the space between adjacent fingers and the space between short fingers and long fingers to add a speed change part without increasing the volume of the resonator, so as to achieve the effect of transverse mode suppression, thereby achieving the purpose of small volume and cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a surface acoustic wave resonator in Example 1; Figure 2 AA' cross-sectional structural diagram of a surface acoustic wave resonator in Example 1; Figure 3 This is a schematic diagram of the sound velocity region structure of a surface acoustic wave resonator in Example 1; Figure 4 is a structural schematic diagram of a comparative surface acoustic wave resonator; Figure 5 It is a schematic diagram of the sound velocity region structure of a comparative surface acoustic wave resonator; Figure 6 This is a comparison diagram of the admittance parameter curves of surface acoustic wave resonators; Figure 7 This is a comparison diagram of the real part curve of the admittance parameter of the surface acoustic wave resonator; Figure 8 is a schematic structural diagram of a surface acoustic wave resonator in Example 2; Fig. 9 is a schematic structural diagram of a surface acoustic wave resonator in Example 3; Fig.10 This is a schematic diagram of the structure of a surface acoustic wave resonator in Example 4.

[0017] The figures are marked as follows: 1. first interdigitated electrode, 2. first electrode short finger, 3. second interdigitated electrode, 4. second electrode short finger, 5. second bus bar, 6. first bus bar, 7. first reflection grid, 8. second reflection grid, 9. first speed change part, 10. second speed change part, 11. silicon, 12. oxide, 13. piezoelectric substrate. DETAILED DESCRIPTION

[0018] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0019] Example 1 like Figure 1 As shown, an embodiment of the present invention provides a surface acoustic wave resonator, comprising: A composite substrate, and an interdigital transducer disposed on the composite substrate; The interdigital transducer includes a bus bar, and at least two pairs of interdigital electrodes and electrode short fingers alternately arranged on the bus bar; a U-shaped speed change part is arranged between the interdigital electrodes and the electrode short fingers arranged opposite to each other, and the electrode short fingers are embedded in the opening of the speed change part.

[0020] like Figure 1 , Figure 2 and Figure 3 As shown, the surface acoustic wave resonator in this embodiment includes a composite substrate, and the composite substrate consists of silicon 11, oxide 12 and piezoelectric substrate 13 in sequence. In the present invention, the silicon 11 is made of polycrystalline silicon, and the top of the polycrystalline silicon is oxide 12. In the present invention, the oxide 12 is made of silicon dioxide, and the top of the silicon dioxide is piezoelectric substrate 13. In the present invention, the piezoelectric substrate 13 is made of lithium tantalate, and the top of the lithium tantalate is covered with an interdigital transducer. In the present invention, the material of the interdigital transducer is aluminum-copper alloy, and the interdigital transducer includes a first interdigital electrode 1, a first electrode short finger 2, a second interdigital electrode 3 and a second electrode short finger 4.

[0021] One end of the first interdigitated electrode 1 is connected to the first bus bar 6, the first electrode short finger 2 is arranged opposite to the first interdigitated electrode 1, the interval between them is a quarter wavelength, and the end of the first electrode short finger 2 away from the first interdigitated electrode 1 is connected to the second bus bar 5. One end of the second interdigitated electrode 3 is connected to the second bus bar 5, the second electrode short finger 4 is arranged opposite to the second interdigitated electrode 3, the interval between them is a quarter wavelength, and the end of the second electrode short finger 4 away from the second interdigitated electrode 3 is connected to the first bus bar 6.

[0022] In this embodiment, the two opening edges of the speed change portion are parallel to the electrode short fingers, and the bottom edge of the speed change portion is perpendicular to the electrode short fingers.

[0023] The line widths of the two opening edges and the bottom edge of the speed change portion are the same.

[0024] The line widths of the two opening edges and the bottom edge of the speed change portion are each one-fourth of the line width of the interdigital electrodes.

[0025] The lengths of the two opening sides and the bottom side of the speed change part are the same.

[0026] The lengths of the two opening sides and the bottom side of the speed change portion are both half the wavelength.

[0027] The speed change part of the present invention is in the same layer as the interdigital electrode, and the material is the same as the interdigital electrode. The shape of the embodiment is U-shaped, and its line width is one-quarter of the line width of the interdigital electrode, and the lengths of the three sides are the same, all of which are half the wavelength. The first speed change part 9 is located between the first interdigital electrode 1 and the first electrode short finger 2, and the U-shaped opening faces the first electrode short finger 2. The second speed change part 10 is located between the second interdigital electrode 3 and the second electrode short finger 4, and the U-shaped opening faces the second electrode short finger 4.

[0028] This embodiment improves the structure of the surface acoustic wave resonator and adds a speed change part structure. There is a gap between the speed change part and the interdigitated electrodes and the electrode short fingers, so that the transmission speed of the surface acoustic wave in the interdigitated electrodes, the electrode short fingers and the bus bar is different, forming different sound speed areas. The surface acoustic wave forms a large sound speed difference from the interdigitated electrodes to the bus bar, which can significantly reduce the generation of secondary harmonics of the resonator and has a good inhibitory effect on the secondary harmonics of the resonator.

[0029] The propagation speed of the surface acoustic wave resonator is the lowest at the busbar, forming a sound speed difference with the electrode short finger. The end of the electrode short finger is wrapped by the speed change part, which reduces its propagation speed. Therefore, the end of the electrode short finger and the electrode short finger form a sound speed difference. There is a gap between the speed change part and the interdigital electrode, and the propagation speed is the fastest in the gap. Figure 4 and Figure 5As shown, it is a surface wave resonator structure of a comparative example, in which only the gap between the forked electrode and the electrode short finger is the sound velocity change zone, and the transverse mode of the resonator cannot be well suppressed, resulting in deterioration of the filter performance. However, the present invention increases the speed change part, divides the space between the forked electrode and the electrode short finger into multiple sound velocity zones, and the surface acoustic wave is scattered multiple times therein, further suppressing the transverse mode of the resonator and improving the device performance.

[0030] like Figure 6 As shown in FIG. 1 , it is a comparison diagram of the admittance parameter curve of the surface acoustic wave resonator. The solid line is the embodiment, and the dotted line is the comparative example. Figure 7 As shown in FIG. 1 , it is a comparison diagram of the real part curve of the admittance parameter of the surface acoustic wave resonator. The solid line is the embodiment, and the dotted line is the comparative example. It can be seen that the dotted line has more burrs, which causes sharp pits to appear in the filter band composed of the resonator, while the curve of the embodiment is smoother than that of the comparative example, indicating that it has a suppressive effect on the transverse mode, and the filter passband composed of the resonator of the embodiment will be flatter.

[0031] Example 2 like Figure 8 As shown, based on the surface acoustic wave resonator described in Example 1, this embodiment further provides a closed edge at the opening position of the speed change part, and improves the speed change part into a closed U-shape.

[0032] The propagation speed of the surface acoustic wave resonator is the lowest at the bus bar, and a sound speed difference is formed between the electrode short finger. The electrode short finger is divided into two parts by the closed U-shaped speed change part. The propagation speed of the part wrapped by the speed change part is the lowest. Therefore, the part of the electrode short finger close to the bus bar and the part wrapped by the speed change part form a sound speed difference. There is a gap between the speed change part and the interdigital electrode, and the propagation speed is the fastest in the gap. In this embodiment, the interdigital electrode and the electrode short finger are divided into multiple sound speed zones, and the surface acoustic wave is scattered multiple times at this place, which further suppresses the transverse mode of the resonator and makes its resonance curve smoother.

[0033] Example 3 like Fig. 9 As shown, based on the surface acoustic wave resonator described in Example 1, this embodiment further provides a U-shaped speed change portion in the first reflection grating 7 and the second reflection grating 8 on both sides of the interdigital transducer, with each grating bar facing away from the other.

[0034] The acoustic velocity difference of the surface acoustic wave resonator in this embodiment is completely consistent with that in embodiment 1. In addition, this embodiment also adds a speed change part at the position of the reflection grating. After adding the speed change part, the surface acoustic wave can be better confined in the resonator during propagation, and the leakage of the surface acoustic wave through the reflection grating will be less.

[0035] Example 4 like Fig.10As shown, based on the surface acoustic wave resonator described in Example 3, this embodiment further provides a closed edge at the opening position of the speed change part, and improves the speed change part into a closed U-shape.

[0036] The acoustic velocity difference of the surface acoustic wave resonator in this embodiment is completely consistent with that in embodiment 2. In addition, a closed speed change part is added at the position of the reflection grating in this embodiment. After adding the speed change part, the surface acoustic wave can be better confined in the resonator during propagation, and the leakage of the surface acoustic wave through the reflection grating will be less.

[0037] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0038] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A surface acoustic wave resonator, characterized in that: include: A composite substrate, and an interdigital transducer disposed on the composite substrate; The interdigital transducer includes a bus bar, and at least two pairs of interdigital electrodes and electrode short fingers alternately arranged on the bus bar; a U-shaped speed change part is arranged between the interdigital electrodes and the electrode short fingers arranged opposite to each other, and the electrode short fingers are embedded in the opening of the speed change part.

2. A surface acoustic wave resonator according to claim 1, characterized in that: Two opening sides of the speed change portion are parallel to the electrode short fingers, and a bottom side of the speed change portion is perpendicular to the electrode short fingers.

3. A surface acoustic wave resonator according to claim 2, characterized in that: The line widths of the two opening edges and the bottom edge of the speed change portion are the same.

4. A surface acoustic wave resonator according to claim 3, characterized in that: The line widths of the two opening edges and the bottom edge of the speed change portion are each one-fourth of the line width of the interdigital electrodes.

5. A surface acoustic wave resonator according to claim 2, characterized in that: The lengths of the two opening sides and the bottom side of the speed change part are the same.

6. A surface acoustic wave resonator according to claim 5, characterized in that: The lengths of the two opening sides and the bottom side of the speed change portion are both half the wavelength.

7. A surface acoustic wave resonator according to claim 1, characterized in that: A closed edge is provided at the opening position of the speed change portion.

8. A surface acoustic wave resonator according to claim 1, characterized in that: In the reflection grids on both sides of the interdigital transducer, each grid bar faces away from the U-shaped speed change part.

9. A surface acoustic wave resonator according to claim 8, characterized in that: A closed edge is provided at the opening position of the speed change portion.

10. A surface acoustic wave filter, characterized in that: It comprises the surface acoustic wave resonator as claimed in any one of claims 1 to 9.

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