POI-SAW resonator structure for suppressing high-order spurious mode

Abstract

The invention belongs to the technical field of resonators, and particularly relates to a POI-SAW resonator structure for suppressing a high-order spurious mode, the POI-SAW resonator structure comprises reflecting gratings and IDT electrodes, the reflecting gratings are located at two sides of an IDT, and the IDT electrodes are excited to generate sound waves; the IDT electrode comprises a substrate layer, and a high sound velocity layer, a temperature compensation layer, a piezoelectric layer and an electrode layer which are sequentially positioned above the substrate layer; the top of the temperature compensation layer and / or the top of the high-sound-velocity layer are / is provided with protrusions. According to the invention, the problems of high cost and complex design of a suppression high-order mode in the prior art can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of resonators, and particularly relates to a POI-SAW resonator structure for suppressing high-order spurious modes. Background Art

[0002] As a key component of the radio frequency front-end, SAW resonators play an important role in the field of mobile communications; with the development of communication technology from 4G to 5G, the signal transmission speed has accelerated, and higher requirements are put forward for the filtering performance of core transceiver devices; the number of radio frequency spectrum bands in 5G has increased significantly, and some frequency bands are close in frequency, but the relative bandwidths are significantly different, which undoubtedly brings new challenges to the design of SAW resonators.

[0003] In 5G communication, with the wide application of carrier aggregation (CA) technology, the use of multiplexers is becoming more and more frequent; the market demand for the out-of-band rejection performance of high-performance resonators is increasing; POI-SAW resonators perform excellently in near-end out-of-band rejection. However, their high-order parasitic modes have become a major obstacle to the application of multiplexers.

[0004] Existing POI-SAW resonators can suppress high-order modes through a high-order mode elimination method based on Si crystal phase optimization; this method carefully selects the crystal plane and propagation angle α of Si to obtain the required shear body acoustic wave velocity, so as to effectively suppress high-order modes. However, this method has obvious drawbacks; on the one hand, it requires specific materials, which not only increases the difficulty and cost of material procurement, but also limits the material selection range; on the other hand, the precise cut angle processing technology has extremely high process requirements, and a slight deviation may affect the performance of the resonator, which undoubtedly increases the design complexity of the resonator. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a POI-SAW resonator structure for suppressing high-order spurious modes, so as to solve the problems of high cost and complex design existing in suppressing high-order modes in the prior art.

[0006] The basic solution provided by the present invention: A POI-SAW resonator structure for suppressing high-order spurious modes, including a reflection grating and an IDT electrode, the reflection grating is located on both sides of the IDT, and the IDT electrode excites acoustic waves.

[0007] The IDT electrode includes a base layer and a high acoustic velocity layer, a temperature compensation layer, a piezoelectric layer, and an electrode layer sequentially located above the base layer.

[0008] Protrusions are arranged on the top of the temperature compensation layer and / or the high acoustic velocity layer.

[0009] Further, on both sides of the top symmetry line of the temperature compensation layer, a first height protrusion is formed respectively by protruding, and the thickness of the first height protrusion is greater than 0.1*λ and less than 0.5 times the thickness of the piezoelectric layer;

[0010] Wherein, the λ represents the wavelength.

[0011] Further, on both sides of the top symmetry line of the high sound velocity layer, two second height protrusions are formed respectively by protruding, and the two second height protrusions on one side of the top symmetry line of the high sound velocity layer are respectively located on the outer side and the symmetry line side;

[0012] The thickness of the second height protrusion is between 0.1λ - 0.2λ and less than 0.5 times the thickness of the temperature compensation layer;

[0013] Wherein, λ represents the wavelength.

[0014] Further, in the middle of both sides of the top symmetry line of the temperature compensation layer, a third height protrusion is formed respectively by protruding, in the middle of both sides of the top symmetry line of the high sound velocity layer, a fourth height protrusion is formed respectively by protruding, the thickness of the third height protrusion is between 0.04λ - 0.07λ and less than 0.5 times the thickness of the piezoelectric layer;

[0015] The thickness of the fourth height protrusion is between 0.04λ - 0.07λ and less than 0.5 times the thickness of the temperature compensation layer;

[0016] Wherein, λ represents the wavelength.

[0017] Further, the material of the protrusion on the top of the temperature compensation layer is silicon dioxide, and the material of the protrusion on the top of the high sound velocity layer is polysilicon.

[0018] Further, the shape of the protrusion on the top of the temperature compensation layer and the protrusion on the top of the high sound velocity layer is one of rectangle, trapezoid, and triangle.

[0019] Further, the material of the temperature compensation layer is silicon dioxide, and the material of the high sound velocity layer is polysilicon.

[0020] Further, the material of the electrode layer is one of aluminum, platinum, and copper, the material of the piezoelectric layer is one of lithium tantalate, lithium niobate, and aluminum nitride, and the substrate is single crystal silicon.

[0021] The principle and advantages of the present invention are as follows: First, for the POI-SAW resonator in the prior art when suppressing high-order spurious modes, the technical means adopted is to carefully select the crystal plane of Si and the propagation angle α to obtain the required shear bulk acoustic wave velocity to effectively suppress high-order spurious modes. This kind of method requires specific materials and precise cutting angle processing techniques, which increases the cost and design complexity of the resonator;

[0022] In response to this, a POI-SAW resonator structure for suppressing high-order spurious modes proposed in this solution configures protrusions on the top of the temperature compensation layer and the top of the high acoustic velocity layer, thereby changing the thickness of the piezoelectric layer above the temperature compensation layer and the thickness of the temperature compensation layer above the high acoustic velocity layer. The shape of the protrusions adopts shapes such as rectangles, trapezoids, and triangles, making the thickness of the piezoelectric layer and the temperature compensation layer discontinuous, so as to limit the excitation of the high-order spurious modes of the resonator, thereby suppressing the high-order spurious modes.

[0023] Therefore, the technical means in this solution changes the thickness of the piezoelectric layer and the temperature compensation layer by designing protrusions, effectively suppressing its high-order spurious modes. Compared with the means of carefully selecting the crystal plane of Si and the propagation angle α in the prior art, the design is simple and the cost is low. Brief Description of the Drawings

[0024] Figure 1 It is a top view of the POI-SAW resonator according to an embodiment of the present invention;

[0025] Figure 2 is Figure 1 the dashed cross-sectional view of A-A ′ in;

[0026] Figure 3 It is a schematic diagram of the admittance response curve of the POI-SAW resonator;

[0027] Figure 4 It is a schematic diagram of the comparative example structure of the POI-SAW resonator;

[0028] Figure 5 It is the admittance response curve of the comparative example;

[0029] Figure 6 It is a schematic diagram of the resonator structure of Example 1;

[0030] Figure 7 It is the admittance response curve of Example 1;

[0031] Figure 8 It is a schematic diagram of the resonator structure of Example 2;

[0032] Figure 9 It is the admittance response curve of Example 2;

[0033] Figure 10 It is a schematic diagram of the resonator structure of Example 3;

[0034] Figure 11 It is the admittance response curve of Example 3;

[0035] Figure 12 is Figure 11Schematic diagram of the amplification of the first high-order spurious mode. Detailed implementation manners

[0036] The following is a further detailed description through specific implementation manners:

[0037] The marks in the accompanying drawings of the specification include: reflection grating 1, IDT electrode 2, electrode layer 201, piezoelectric layer 202, temperature compensation layer 203, high acoustic velocity layer 204, and substrate layer 205.

[0038] In the technical solution of this application, it is a POI-SAW resonator structure for suppressing high-order spurious modes. Among them, for a resonator, with the wide application of carrier aggregation technology, the use of multiplexers is becoming more and more frequent. As a result, the market's demand for the out-of-band rejection performance of high-performance resonators is increasing day by day. Among them, the POI-SAW resonator performs well in the near-end out-of-band rejection. However, its high-order parasitic modes have become a major obstacle to the application of multiplexers;

[0039] Based on this, the existing technical solutions adopt a high-order mode elimination method based on Si crystal phase optimization to suppress high-order modes. Specifically, by carefully selecting the crystal plane of Si and the propagation angle α, the required shear bulk acoustic wave velocity is obtained, so as to achieve the purpose of effectively suppressing high-order modes; the disadvantages of this type of method are as follows: one is that specific materials are required, which increases the difficulty and cost of material procurement and limits the selection range of materials; the other is that the precise cut angle processing technology has high requirements for the process, bringing design complexity to the resonator. Therefore, based on the problems existing in the above-mentioned existing technologies, the technical solution of this application is:

[0040] Example 1:

[0041] A POI-SAW resonator structure for suppressing high-order spurious modes. Example 1 is basically as shown in the appendix Figure 1 as follows, Figure 1 This is the top view of the POI-SAW resonator in this application. Its internal structure includes a reflection grating 1 and an IDT electrode 2. In the POI-SAW resonator, both the reflection grating 1 and the IDT electrode 2 play key roles. Among them, the functions of the reflection grating 1 include the following three points:

[0042] First, through a specific period and structure, when the surface acoustic wave propagates to the area of the reflection grating 1, due to the acoustic property difference between the reflection grating 1 and the surrounding medium, the surface acoustic wave will be partially or completely reflected back, thereby changing the propagation direction of the surface acoustic wave and forming specific wave modes such as standing waves in a specific area to meet the working requirements of the resonator;

[0043] Second, the reflection grating 1 can guide the surface acoustic wave to propagate along a specific path, restrict the diffusion and scattering of the surface acoustic wave, enable the surface acoustic wave to propagate inside the resonator along the designed path, thereby improving the utilization efficiency of the surface acoustic wave, reducing energy loss, and enhancing the performance of the resonator;

[0044] Third, the structural parameters of the reflection grating 1, such as the period, width, and height, can be precisely adjusted by reasonable design and adjustment to accurately adjust the resonance frequency of the resonator to meet the requirements of different application scenarios;

[0045] The IDT electrode 2 is a key component for realizing the mutual conversion of electrical energy and mechanical energy in the POI-SAW resonator. At the same time, in this application, the reflection gratings 1 are distributed on both sides of the IDT electrode 2, thereby forming a resonance cavity. Specifically, when the surface acoustic wave excited by the IDT electrode 2 propagates, it will be reflected back when encountering the reflection grating 1, and interfere with the new surface acoustic wave continuously excited by the IDT electrode 2, forming a standing wave in the region between the IDT electrode 2 and the reflection grating 1, thereby constituting a resonance cavity. As Figure 2 shown, for Figure 1 the λ-λ ′ dashed cross-sectional view, it can be clearly obtained from Figure 2 the structure of the IDT electrode 2, including the base layer 205 located at the bottom, and the high sound velocity layer 204, temperature compensation layer 203, piezoelectric layer 202, and electrode layer 201 sequentially arranged above the base layer 205. Among them, the material of the electrode layer 201 is one of aluminum, platinum, and copper. In the technical solution of this application, the material of the electrode layer 201 is set as aluminum, and the material of the piezoelectric layer 202 is one of lithium tantalate, lithium niobate, and aluminum nitride. In the technical solution of this application, the material of the piezoelectric layer 202 is set as lithium tantalate; the material of the temperature compensation layer 203 is silicon dioxide, the material of the high sound velocity layer 204 is polysilicon, and the material of the base layer 205 is single crystal silicon.

[0046] In this embodiment, the structural parameters of the reflection grating 1 of the adopted resonator are the same as those of the IDT electrode 2;

[0047] In this application, the propagation principle of the surface acoustic wave of the resonator IDT electrode 2 is that, taking Figure 2 the direction indicated by the arrow in, the longitudinal acoustic wave is excited from the piezoelectric layer 202 and propagates downward. When reaching the contact boundary of each layer, reflection occurs due to the discontinuous acoustic impedance. At this time, each finger of the electrode layer 201 will excite a certain amount of acoustic wave energy. When the acoustic wave energy excited by multiple fingers is coupled together, one or more stronger spurious modes will be formed. As Figure 3 shown, it is the admittance response curve of the POI-SAW resonator. Among them, the arrow 3 indicates the main mode of the POI-SAW resonator, the arrow 4 is the first higher-order spurious mode, and the arrow 5 is the second higher-order spurious mode.

[0048] In this regard, in order to effectively suppress the high-order spurious modes, in this solution, a first-height protrusion is formed on both sides of the top of the temperature compensation layer 203, protruding respectively. To better demonstrate the effect of the technical solution of this embodiment in suppressing high-order spurious modes, a comparative example is introduced for comparison, as Figure 4 shown. The comparative example is a POI-SAW resonator. The material of the electrode layer 201 is aluminum, the material of the piezoelectric layer 202 is lithium tantalate, the temperature compensation layer 203 is silicon dioxide, the high acoustic velocity layer 204 is polysilicon, and the substrate layer 205 is single-crystalline silicon; as Figure 5 shown, it is the admittance response curve of the comparative example. The first high-order spurious mode appears near 2.6 GHz, and the second high-order spurious mode appears near 3.4 GHz;

[0049] In the first embodiment, after setting the first-height protrusion on the top of the temperature compensation layer 203, the materials selected for each stacked layer are the same as those of the comparative example, and the structural parameters are also the same as those of the comparative example. The difference is that, as Figure 6 shown in the blue part, the first-height protrusion set on the top of the temperature compensation layer 203 changes the thickness of the piezoelectric layer 202 compared with the comparative document, making the thickness of the piezoelectric layer 202 in the protruding area smaller than that of the non-protruding part of the piezoelectric layer 202. The response of the high-order spurious mode is closely related to the thicknesses of the piezoelectric layer 202 and the temperature compensation layer 203. Since the thicknesses of the piezoelectric layer 202 and the temperature compensation layer 203 are discontinuous under the influence of the first-height protrusion, the excitation of the high-order spurious mode is restricted, thereby achieving the effect of suppressing the high-order spurious mode; as Figure 7 shown, it is the admittance response curve of the first embodiment. It can be observed from the figure that the first and second high-order spurious modes are both effectively suppressed, and different thicknesses of the protruding part bring different suppression effects. When the thickness of the protrusion is 0.1*λ (200 nm), the suppression effect is the best, where λ represents the wavelength, and in this embodiment, λ is 2000 nm. Therefore, the thickness of the first-height protrusion in the first embodiment is greater than 0.1*λ and less than 0.5 times the thickness of the piezoelectric layer 202.

[0050] Embodiment Two:

[0051] The difference between Embodiment Two and Embodiment One is that two second-height protrusions are formed on both sides of the symmetry line at the top of the high acoustic velocity layer 204, and the two second-height protrusions on one side of the symmetry line at the top of the high acoustic velocity layer 204 are located on the outer side and the symmetry line side respectively; in the stacked layer structure of Embodiment Two, the materials selected are the same as those of the comparative example, and the structural parameters are also the same as those of the comparative example. The difference is that there are protrusions configured on the high acoustic velocity layer 204, as Figure 8The blue part shown, compared with the comparative example, in Embodiment 2, the second height protrusion of the high sound velocity layer 204 changes the thickness of the temperature compensation layer 203, making the thickness of the protruding temperature compensation layer 203 greater than that of the non-protruding part of the temperature compensation layer 203. Therefore, due to the discontinuous thickness of the temperature compensation layer 203, the excitation of the high-order spurious modes is restricted, thus achieving the effect of suppressing the high-order spurious modes;

[0052] As Figure 9 shown, it is the admittance response curve of the resonator in Embodiment 2. It can be observed from the figure that both the first and second high-order spurious modes are effectively suppressed, and with different thicknesses of the protruding parts, the suppression effects are different. When the thickness of the protrusion is 0.2λ (400 nm), the suppression effect is the best, where λ represents the wavelength, and in this embodiment, λ is 2000 nm; therefore, according to the simulation results, the thickness of the protruding part in Embodiment 2 should be set between 0.1λ - 0.2λ and less than 0.5 times the thickness of the temperature compensation layer 203.

[0053] Embodiment 3:

[0054] The difference between Embodiment 3 and Embodiment 1 is that in Embodiment 3, in the middle of both sides of the top symmetry line of the temperature compensation layer 203, a third height protrusion is respectively formed, and in the middle of both sides of the top symmetry line of the high sound velocity layer 204, a fourth height protrusion is respectively formed. Specifically, the materials selected for each stack of the resonator in Embodiment 3 are the same as those in the comparative example, and the structural parameters are also the same as those in the comparative example. The difference lies in that a third height protrusion and a fourth height protrusion are respectively provided on the top of the temperature compensation layer 203 and the top of the high sound velocity layer 204. As Figure 10 shown in the blue part, the third height protrusion of the temperature compensation layer 203 changes the thickness of the piezoelectric layer 202, and the fourth height protrusion of the high sound velocity layer 204 changes the thickness of the temperature compensation layer 203. Since the thicknesses of both the temperature compensation layer 203 and the piezoelectric layer 202 are discontinuous, the excitation of the high-order spurious modes is restricted, thus achieving the effect of suppressing the high-order spurious modes.

[0055] Figure 11 It is the admittance response curve of Embodiment 3. It can be observed from the figure that both the first and second high-order spurious modes are effectively suppressed, and with different thicknesses of the protruding parts, the suppression effects are different. As Figure 12 shown in the Figure 11 amplification schematic diagram of the first high-order spurious mode in, when the thickness of the protrusion is 140 nm, the suppression effect is the best. Therefore, according to the simulation results, the thickness of the third height protrusion is between 0.04λ - 0.07λ and less than 0.5 times the thickness of the piezoelectric layer 202; the thickness of the fourth height protrusion is between 0.04λ - 0.07λ and less than 0.5 times the thickness of the temperature compensation layer 203, where λ represents the wavelength, and in this embodiment, λ is 2000 nm.

[0056] In the technical solution of the present application, in Embodiment 1, Embodiment 2, and Embodiment 3, the shape of the protrusion on the top of the temperature compensation layer 203 and the shape of the protrusion on the top of the high sound velocity layer 204 are one of a rectangle, a trapezoid, and a triangle; specifically, it is a rectangle; the material of the protrusion on the top of the temperature compensation layer 203 is silicon dioxide, and the material of the protrusion on the top of the high sound velocity layer 204 is polysilicon.

[0057] The above are only the embodiments of the present invention. Common knowledge such as the specific structures and characteristics known in the art is not described in detail herein. Those of ordinary skill in the art know all the common technical knowledge in the technical field to which the invention belongs before the application date or the priority date, can know all the existing technologies in this field, and have the ability to apply the conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in the present application, combine their own abilities to improve and implement this solution. Some typical well-known structures or well-known methods should not become an obstacle for those of ordinary skill in the art to implement the present application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by the present application should be based on the content of its claims, and the specific implementation manners and the like described in the specification can be used to interpret the content of the claims.

Claims

1. A POI-SAW resonator structure for suppressing high-order spurious modes, characterized in that: It includes a reflection grid and an IDT electrode, wherein the reflection grid is located on both sides of the IDT, and the IDT electrode is excited to generate an acoustic wave; The IDT electrode comprises a substrate layer and a high acoustic velocity layer, a temperature compensation layer, a piezoelectric layer and an electrode layer sequentially located above the substrate layer; The temperature compensation layer and / or the high sound velocity layer is / are / is ...

2. The POI-SAW resonator structure for suppressing high-order spurious modes according to claim 1, characterized in that: Both sides of the top symmetry line of the temperature compensation layer protrude to form a first height protrusion, and the thickness of the first height protrusion is greater than 0.1*λ and less than 0.5 times the thickness of the piezoelectric layer; Here, λ represents the wavelength.

3. The POI-SAW resonator structure for suppressing high-order spurious modes according to claim 1, characterized in that: The two sides of the top symmetry line of the high sound velocity layer are respectively protruded to form two second height protrusions, and the two second height protrusions on one side of the top symmetry line of the high sound velocity layer are respectively located on the outside and the side of the symmetry line; The thickness of the second height protrusion is between 0.1λ and 0.2λ and is less than 0.5 times the thickness of the temperature compensation layer; Here, λ represents the wavelength.

4. The POI-SAW resonator structure for suppressing high-order spurious modes according to claim 1, characterized in that: The middle parts of both sides of the top symmetry line of the temperature compensation layer protrude to form a third height protrusion, and the middle parts of both sides of the top symmetry line of the high sound velocity layer protrude to form a fourth height protrusion, and the thickness of the third height protrusion is between 0.04λ and 0.07λ and less than 0.5 times the thickness of the piezoelectric layer; The thickness of the fourth height protrusion is between 0.04λ and 0.07λ and is less than 0.5 times the thickness of the temperature compensation layer; Here, λ represents the wavelength.

5. The POI-SAW resonator structure for suppressing high-order spurious modes according to claim 1, characterized in that: The material of the protrusion on the top of the temperature compensation layer is silicon dioxide, and the material of the protrusion on the top of the high acoustic velocity layer is polysilicon.

6. The POI-SAW resonator structure for suppressing high-order spurious modes according to claim 5, characterized in that: The shape of the protrusion on the top of the temperature compensation layer and the protrusion on the top of the high sound velocity layer is one of a rectangle, a trapezoid and a triangle.

7. The POI-SAW resonator structure for suppressing high-order spurious modes according to claim 6, characterized in that: The material of the temperature compensation layer is silicon dioxide, and the material of the high acoustic velocity layer is polysilicon.

8. The POI-SAW resonator structure for suppressing high-order spurious modes according to claim 7, characterized in that: The electrode layer material is one of aluminum, platinum, and copper; the piezoelectric layer material is one of lithium tantalate, lithium niobate, and aluminum nitride; and the substrate is single crystal silicon.

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