Bulk acoustic wave resonator and filter
The resonator design with a concave substrate and discrete reflection columns addresses the challenge of improving quality factor and reducing parasitic resonances, achieving better performance by enhancing sound wave reflection and dispersing parasitic energy.
Patent Information
- Application Number
- CN202420433144.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-05
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2034-03-05
AI Technical Summary
Existing bulk acoustic wave resonators face challenges in improving the quality factor while minimizing parasitic resonances introduced by frame structures at the low-frequency end.
A bulk acoustic wave resonator design featuring a substrate with a concave upper surface, a cavity, and an acoustic reflection structure comprising multiple reflection columns along the edge of the effective resonance area, forming a discrete reflection ring to enhance sound wave reflection and disperse parasitic resonance energy.
The design improves the quality factor by reducing sound wave leakage and dispersing parasitic resonance, thereby enhancing performance without introducing additional parasitic resonances.
Smart Images
Figure CN222283219U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of semiconductor devices, and in particular to a bulk acoustic wave resonator and a filter. Background Art
[0002] Bulk acoustic wave resonators have attracted a lot of research attention due to their high Q value, small size, and integration. With the rapid development of mobile communication technology, thin film bulk acoustic wave resonators have not only been widely used in RF front-ends, but also have shown great potential in sensor detection applications. There are two main excitation modes for thin film bulk acoustic wave devices. One is the thickness field excitation mode, where the two electrodes are on the two sides of the piezoelectric layer, and the electric field is along the thickness direction of the piezoelectric layer; the other is the transverse field excitation mode, where the two electrodes are on the same side of the piezoelectric layer. In practical applications, both of these excitation modes will cause the particles in the piezoelectric layer to produce thickness shear vibrations, and the sound waves it generates propagate within the layer, which belongs to bulk acoustic waves. Bulk acoustic wave resonators generally form air interfaces on the upper and lower surfaces of the sandwich structure of the upper electrode-piezoelectric layer-lower electrode, and use the huge difference in acoustic impedance between solids and gases to enable the longitudinal wave energy to be reflected and gathered inside the sandwich structure to form resonance.
[0003] Among them, the quality factor, as an important parameter of the BAW resonator, determines important performance indicators such as the insertion loss, out-of-band suppression, and band edge steepness of the BAW resonator. In the prior art, the method usually used to improve the quality factor of the BAW resonator is to design an acoustic reflection structure. Specifically, a ring-shaped frame structure is designed at the edge of the active area of the resonator. This acoustic reflection structure can concentrate the energy of the BAW inside the active area as much as possible, thereby improving the Q value of the resonator. However, the frame structure will also introduce additional parasitic resonances at the low-frequency end of the resonator, which to a certain extent affects the out-of-band suppression of the low-frequency end of the filter. Utility Model Content
[0004] The purpose of the present application is to provide a bulk acoustic wave resonator and a filter, which can improve the quality factor while reducing the intensity of parasitic resonance.
[0005] On the one hand, an embodiment of the present application provides a bulk acoustic wave resonator, including a substrate and a lower electrode, a piezoelectric layer and an upper electrode arranged in sequence on the substrate, the upper surface of the substrate is concave to form a cavity, and the area where the cavity, the lower electrode, the piezoelectric layer and the upper electrode overlap in the hierarchical direction is an effective resonance area, and an acoustic reflection structure is arranged on the upper electrode, and the acoustic reflection structure includes a plurality of reflection columns arranged along the edge of the effective resonance area.
[0006] As an practicable manner, the sound reflection structure includes a plurality of reflection columns along the center to the periphery of the effective resonance area.
[0007] As an implementable manner, the sound reflection structure further includes a plurality of sub-reflection structures protruding into the effective resonance region, and the sub-reflection structures include a plurality of reflection columns arranged in at least two layers.
[0008] As an implementable manner, in a layer of reflective columns close to the center of the effective resonance region, some reflective columns are shifted to a layer closer to the center of the effective resonance region, so that the inner boundary line of the multilayer reflective columns is different from the boundary of the effective resonance region.
[0009] As an implementable manner, the sound reflection structure further includes a plurality of grooves arranged on one side of the reflection column close to the center of the effective resonance area, and the plurality of grooves are arranged along the edge of the effective resonance area.
[0010] As an implementable manner, the length of the groove along the hierarchical direction is smaller than the height of the reflective column along the hierarchical direction.
[0011] As an implementable manner, the shape of the cross section of the reflective column along the direction perpendicular to the level direction is circular or polygonal.
[0012] As an implementable manner, the reflective columns are cylindrical, and the diameters of the multiple reflective columns are the same, and the ratio of the distance between two adjacent reflective columns to the diameter of the reflective columns is between 1:5 and 5:1.
[0013] As an implementable manner, the boundary of the effective resonance area is a circle, a polygon, or a figure formed by connecting any curves end to end.
[0014] Another aspect of an embodiment of the present application provides a filter, comprising a plurality of the above-mentioned BAW resonators, wherein the plurality of BAW resonators are connected in parallel or in series.
[0015] The beneficial effects of the embodiments of the present application include:
[0016] The BAW resonator provided by the present application includes a substrate and a lower electrode, a piezoelectric layer and an upper electrode sequentially arranged on the substrate. The upper surface of the substrate is concave to form a cavity. The area where the cavity, the lower electrode, the piezoelectric layer and the upper electrode overlap in the hierarchical direction is an effective resonance area. An acoustic reflection structure is arranged on the upper electrode. The acoustic reflection structure includes a plurality of reflection columns arranged along the edge of the effective resonance area. The plurality of reflection columns and the air form a reflection ring. The reflection ring is enclosed in the periphery of the effective resonance area, thereby avoiding the leakage of sound waves in the horizontal direction and improving the quality factor of the BAW resonator. The plurality of reflection columns are arranged at intervals, so that the acoustic reflection structure is a discrete structure. The discrete structure makes the parasitic resonance energy distribution generated at the low-frequency end of the BAW resonator more dispersed, thereby reducing the intensity of the parasitic resonance. Therefore, the BAW resonator of the embodiment of the present application can reduce the intensity of the parasitic resonance while improving the quality factor. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.
[0018] Figure 1 One of the structural schematic diagrams of a bulk acoustic wave resonator provided in an embodiment of the present application;
[0019] Figure 2 A second structural schematic diagram of a bulk acoustic wave resonator provided in an embodiment of the present application;
[0020] Figure 3 A third structural schematic diagram of a bulk acoustic wave resonator provided in an embodiment of the present application;
[0021] Figure 4 A fourth structural schematic diagram of a bulk acoustic wave resonator provided in an embodiment of the present application;
[0022] Figure 5 A fifth structural diagram of a bulk acoustic wave resonator provided in an embodiment of the present application;
[0023] Figure 6 A sixth structural schematic diagram of a bulk acoustic wave resonator provided in an embodiment of the present application;
[0024] Figure 7 One of the impedance curves of the BAW resonator provided in the embodiment of the present application and the prior art;
[0025] Figure 8 The second impedance curve diagram of the BAW resonator provided in the embodiment of the present application and the prior art;
[0026] Fig. 9 The third impedance curve diagram of the BAW resonator provided in the embodiment of the present application and the prior art.
[0027] Icon: 100 - bulk acoustic wave resonator; 110 - substrate; 111 - cavity; 120 - seed layer; 130 - lower electrode; 140 - piezoelectric layer; 150 - upper electrode; 160 - acoustic reflection structure; 161 - reflection column; 162 - sub-reflection structure; 163 - groove. DETAILED DESCRIPTION
[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.
[0029] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.
[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.
[0031] In the description of this application, it should be noted that the terms "center", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.
[0032] The present application embodiment provides a bulk acoustic wave resonator 100, such as Figure 1 and Figure 2 As shown, it includes a substrate 110 and a lower electrode 130, a piezoelectric layer 140 and an upper electrode 150 which are sequentially arranged on the substrate 110. The upper surface of the substrate 110 is concave to form a cavity 111. The area where the cavity 111, the lower electrode 130, the piezoelectric layer 140 and the upper electrode 150 overlap in the hierarchical direction is an effective resonance area. An acoustic reflection structure 160 is arranged on the upper electrode 150, and the acoustic reflection structure 160 includes a plurality of reflection columns 161 arranged along the edge of the effective resonance area.
[0033] When the BAW resonator 100 provided in the embodiment of the present application is working, the upper electrode 150 and the lower electrode 130 are respectively connected to the two ends of the external signal to form a voltage difference between the upper electrode 150 and the lower electrode 130, so that the upper and lower surfaces of the two sides of the piezoelectric layer 140 have a voltage difference. According to the inverse piezoelectric effect, when the two side surfaces of the piezoelectric layer 140 have a voltage difference, the piezoelectric layer 140 generates pressure and moves. When the external signal is a high-frequency conversion, the piezoelectric layer 140 generates sound waves. Among the sound waves generated by the piezoelectric layer 140, there are both sound waves propagating in the hierarchical direction and sound waves propagating in the horizontal direction within the piezoelectric layer 140. In the effective resonance region, the upper electrode 150 is in contact with the air, and the lower electrode 130 is in contact with the air in the cavity 111. Since the upper electrode 150 and the air have different acoustic reflection coefficients, and the lower electrode 130 and the air also have different acoustic reflection coefficients, an acoustic reflection surface is formed on the upper surface of the upper electrode 150 and the lower surface of the lower electrode 130, so that the sound waves along the hierarchical direction continue to propagate in the piezoelectric layer 140 after being reflected at the acoustic reflection surface.
[0034] In order to avoid the leakage of the sound waves propagating in the horizontal direction in the piezoelectric layer 140, the embodiment of the present application is provided with a sound reflection structure 160 on the upper electrode 150, and the sound reflection structure 160 includes a plurality of reflection columns 161 arranged along the edge of the effective resonance region, and the reflection columns 161 have different sound reflection coefficients from the air, so that the sound reflection structure 160 forms a reflection ring at the periphery of the effective resonance region, thereby realizing the reflection of the horizontally propagating sound waves, avoiding the leakage of the sound waves, and thus improving the quality factor of the bulk acoustic wave resonator 100. In addition, since the sound reflection structure 160 of the embodiment of the present application includes a plurality of reflection columns 161 arranged along the edge of the effective resonance region, and the plurality of reflection columns 161 are arranged at intervals, the sound reflection structure 160 is a discrete structure, and the discrete structure makes the parasitic resonance energy distribution generated at the low-frequency end of the bulk acoustic wave resonator 100 more dispersed, thereby reducing the intensity of the parasitic resonance. Therefore, the bulk acoustic wave resonator 100 of the embodiment of the present application can reduce the intensity of the parasitic resonance while improving the quality factor.
[0035] In order to verify the beneficial effects of the embodiments of the present application, the performance of the BAW resonator 100 without the acoustic reflection structure 160 and the performance of the BAW resonator 100 with the acoustic reflection structure 160 are simulated. Figure 7 and Figure 8 As shown by Figure 7 and Figure 8 It can be seen that the impedance and quality factor of the BAW resonator 100 with the acoustic reflection structure 160 are improved to a certain extent. In addition, the performance of the BAW resonator 100 with the continuous acoustic reflection structure 160 and the discrete acoustic reflection structure 160 are simulated. The results are as follows: Fig. 9As described above, the BAW resonator 100 of the continuous acoustic reflection structure 160 introduces parasitic resonance at the low frequency end, while the parasitic resonance intensity of the embodiment of the present application is relatively small.
[0036] Specifically, in the BAW resonator 100 , the materials of the substrate 110 , the upper electrode 150 , the lower electrode 130 , and the piezoelectric layer 140 are not limited in the embodiment of the present application. For example, the substrate 110 may be a commonly used substrate such as a silicon substrate, a silicon-on-insulator, etc.
[0037] The material of the upper electrode 150 and the lower electrode 130 can be a combination of one or more of molybdenum, copper, aluminum, and gold. The material of the piezoelectric layer 140 can be one of aluminum nitride, zinc oxide, lithium niobate, lead zirconate titanate, lithium carbonate, and sodium barium niobate.
[0038] In addition, in the preparation of the BAW resonator 100, deposition is mostly used layer by layer. In order to improve the film quality and stability of the lower electrode 130 and the piezoelectric layer 140, a seed layer 120 can be provided between the substrate 110 and the lower electrode 130. Figure 1 As shown, the seed layer 120 can compensate for the lattice mismatch and thermal mismatch between the substrate 110 and the lower electrode 130 and the piezoelectric layer 140 , thereby improving the film quality and stability of the lower electrode 130 and the piezoelectric layer 140 .
[0039] The BAW resonator 100 provided in the present application comprises a substrate 110 and a lower electrode 130, a piezoelectric layer 140 and an upper electrode 150 sequentially arranged on the substrate 110. The upper surface of the substrate 110 is concave to form a cavity 111. The region where the cavity 111, the lower electrode 130, the piezoelectric layer 140 and the upper electrode 150 overlap in the hierarchical direction is an effective resonance region. An acoustic reflection structure 160 is arranged on the upper electrode 150. The acoustic reflection structure 160 comprises a plurality of reflection columns 161 arranged along the edge of the effective resonance region. The plurality of reflection columns 161 form a reflection ring with air, and the reflection ring is surrounded by the periphery of the effective resonance region, thereby avoiding the leakage of sound waves in the horizontal direction and improving the quality factor of the BAW resonator 100. The plurality of reflection columns 161 are arranged at intervals, so that the acoustic reflection structure 160 is a discrete structure. The discrete structure makes the parasitic resonance energy generated at the low-frequency end of the BAW resonator 100 more dispersed, thereby reducing the intensity of the parasitic resonance. Therefore, the BAW resonator 100 according to the embodiment of the present application can reduce the intensity of parasitic resonance while improving the quality factor.
[0040] Optional, such as Figure 3 As shown, the sound reflection structure 160 includes a plurality of reflection columns 161 extending from the center to the periphery of the effective resonance area.
[0041] When the sound reflection structure 160 includes a plurality of layers of reflection columns 161 , the plurality of layers of reflection columns 161 can sequentially reflect sound waves in a horizontal plane, further avoiding leakage of sound waves, thereby further improving the quality factor of the BAW resonator 100 .
[0042] When the sound reflection structure 160 includes multiple layers of reflection columns 161, the reflection columns 161 of two adjacent layers of reflection columns 161 may be staggered, such as Figure 3 As shown, in this way, when the sound wave leaks from between the two reflection columns 161 of the innermost reflection column 161, the reflection columns 161 of the second layer from the inside to the outside are just located between the two reflection columns 161 of the innermost reflection column 161, so that the leaked sound wave can be reflected, further avoiding the leakage of the sound wave, thereby further improving the quality factor of the BAW resonator 100.
[0043] Specifically, the number of layers of the reflective columns 161 is not limited in the present embodiment, and can be, for example, Figure 3 The two layers shown may also be three, four, etc. layers.
[0044] In one possible implementation of the present application, Figure 4 As shown, the sound reflection structure 160 further includes a plurality of sub-reflection structures 162 protruding into the effective resonance region, and the sub-reflection structure 162 includes a plurality of reflection columns 161 arranged in at least two layers.
[0045] A plurality of sub-reflection structures 162 protrude inward from the innermost reflection column 161, so that the inner boundary line of the sound reflection structure 160 bends inward at the sub-reflection structure 162. The inner boundary line of the sound reflection structure 160 is different from the boundary line of the effective resonance area. The sub-reflection mechanism can reflect sound waves while suppressing resonant waves of specific modes, thereby reducing parasitic modes.
[0046] Optional, such as Figure 5 As shown, in a layer of reflection columns 161 near the center of the effective resonance region, some reflection columns 161 are shifted to a layer closer to the center of the effective resonance region, so that the inner boundary line of the multilayer reflection columns 161 is different from the boundary of the effective resonance region.
[0047] In a layer of reflection columns 161 close to the center of the effective resonance area, some of the reflection columns 161 are shifted to a layer closer to the center of the effective resonance area, so that at the innermost reflection column 161, the inner boundary of the sound reflection structure 160 is bent outward; similarly, at the position where the reflection column 161 moves, the inner boundary line of the reflection structure is bent inward, so that the inner boundary line of the sound reflection structure 160 is different from the boundary line of the effective resonance area. The sound reflection structure 160 can reflect sound waves while suppressing resonant waves of specific modes, thereby reducing parasitic modes.
[0048] In one possible implementation of the present application, Figure 6 As shown, the sound reflection structure further includes a plurality of grooves 163 arranged on one side of the reflection column 161 close to the center of the effective resonance area, and the plurality of grooves 163 are arranged along the edge of the effective resonance area.
[0049] A plurality of grooves 163 are arranged along the edge of the effective resonance region, and air is filled inside the grooves 163. The grooves 163 form a reflection structure with the upper electrode 150 in the horizontal direction and a reflection structure with the reflection column 161 in the vertical direction, so that the grooves 163 can reflect sound waves in the horizontal and vertical directions. In addition, while reflecting the sound waves, the grooves 163 can suppress the resonance waves of a specific mode, thereby reducing parasitic modes.
[0050] It can be understood that the reflection column 161 is disposed on the upper electrode 150 , and when the sound reflection structure includes a groove 163 , the groove 163 is a groove 163 opened on the upper electrode 150 .
[0051] In addition, the connecting line of the plurality of grooves 163 and the connecting line of the plurality of reflective columns 161 may be the same or different. Figure 6 As shown, the connection line of the plurality of grooves 163 and the connection line of the plurality of reflection pillars 161 may be the same, and both have the same shape as the edge of the effective resonance region.
[0052] Optionally, the length of the groove 163 along the hierarchical direction is smaller than the height of the reflective column 161 along the hierarchical direction.
[0053] As can be seen from the above, the groove 163 is arranged on the upper electrode 150. In order to prevent the groove 163 from having a larger length along the hierarchical direction and affecting the signal transmission function of the upper electrode 150, the length of the groove 163 along the hierarchical direction is set to be smaller.
[0054] In one implementable manner of the embodiment of the present application, the shape of the cross section of the reflective column 161 along the direction perpendicular to the level is one of a circle and a polygon.
[0055] The side surface of the reflective column 161 close to the center of the effective resonance area is used as a reflective surface. Those skilled in the art can set the reflective surface to an arc surface, a plane, or a turning surface connecting two planes according to actual conditions. Based on this, the reflective column 161 can be a cylinder or a prism, that is, the shape of the cross section of the reflective column 161 along the direction perpendicular to the level is one of a circle or a polygon. For example, it can be a cylinder, a triangular prism, a quadrangular prism, etc.
[0056] Optionally, the reflective column 161 is a cylinder, and the diameters of the multiple reflective columns 161 are the same, and the ratio of the distance between two adjacent reflective columns 161 to the diameter of the reflective column 161 is between 1:5 and 5:1.
[0057] It can be seen from the above that the closer the distance between two adjacent reflection columns 161 is, the better the reflection effect on the sound waves is. However, when the distance between two adjacent reflection columns 161 is too close, the effect of reducing the intensity of the parasitic resonance is less obvious.
[0058] In one achievable manner of the embodiment of the present application, the boundary of the effective resonance area is a circle, a polygon, or a figure formed by connecting any curves end to end.
[0059] The edge of the effective resonance region is set to be a polygon, a circle or a figure formed by a combination of any curves, so that the shape of the effective resonance region is diversified, thereby making it more convenient to prepare and design.
[0060] In addition, the edge of the effective resonance area can be set as an irregular polygon, or a figure formed by connecting any curves end to end. In this way, the edge of the effective resonance area also has a certain reflection effect on the sound wave, thereby avoiding the leakage of the sound wave.
[0061] The embodiment of the present application also discloses a filter, comprising a plurality of the above-mentioned BAW resonators 100, wherein the plurality of BAW resonators 100 are connected in parallel or in series. The filter comprises the same structure and beneficial effects as the BAW resonator 100 in the aforementioned embodiment. The structure and beneficial effects of the BAW resonator 100 have been described in detail in the aforementioned embodiment, and will not be repeated here.
[0062] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A bulk acoustic wave resonator, characterized in that: The invention comprises a substrate and a lower electrode, a piezoelectric layer and an upper electrode which are sequentially arranged on the substrate, wherein the upper surface of the substrate is concave to form a cavity, and the area where the cavity, the lower electrode, the piezoelectric layer and the upper electrode overlap in the hierarchical direction is an effective resonance area, and an acoustic reflection structure is arranged on the upper electrode, and the acoustic reflection structure comprises a plurality of reflection columns arranged along the edge of the effective resonance area.
2. The bulk acoustic wave resonator according to claim 1, characterized in that The sound reflection structure includes a plurality of reflection columns extending from the center to the periphery of the effective resonance area.
3. The bulk acoustic wave resonator according to claim 1 or 2, characterized in that: The sound reflection structure further includes a plurality of sub-reflection structures protruding into the effective resonance region, and the sub-reflection structures include a plurality of reflection columns arranged in at least two layers.
4. The bulk acoustic wave resonator according to claim 2, characterized in that: In a layer of reflection columns close to the center of the effective resonance region, some reflection columns are shifted to a layer closer to the center of the effective resonance region, so that the inner boundary line of the multilayer reflection columns is different from the boundary of the effective resonance region.
5. The bulk acoustic wave resonator according to claim 1 or 2, characterized in that: The sound reflection structure further includes a plurality of grooves arranged on a side of the reflection column close to the center of the effective resonance area, and the plurality of grooves are arranged along the edge of the effective resonance area.
6. The bulk acoustic wave resonator according to claim 5, characterized in that The length of the groove along the hierarchical direction is smaller than the height of the reflective column along the hierarchical direction.
7. The BAW resonator according to claim 1, characterized in that: The shape of the cross section of the reflective column along the direction perpendicular to the level direction is one of a circle and a polygon.
8. The bulk acoustic wave resonator according to claim 7, characterized in that The reflective columns are cylindrical, and the diameters of the multiple reflective columns are the same, and the ratio of the distance between two adjacent reflective columns to the diameters of the reflective columns is between 1:5 and 5:
1.
9. The BAW resonator according to claim 1, characterized in that: The boundary of the effective resonance region is a figure formed by connecting any curves end to end.
10. A filter, characterized in that: The method comprises a plurality of BAW resonators according to any one of claims 1 to 9, wherein the plurality of BAW resonators are connected in parallel or in series.