Filter and method for manufacturing the same

Abstract

The embodiments of this application disclose a filter and a method for manufacturing the same, and belong to the technical field of RF (Radio Frequency) miniature electromechanical devices. The filter according to the embodiments of this application includes a substrate on which a resonant assembly is mounted. The resonant assembly includes a first lower electrode, a piezoelectric layer, and a first upper electrode, which are installed in order. The upper surface of the piezoelectric layer is recessed downward to form a mounting groove. The first upper electrode includes a conductive plate and an annular vane. The conductive plate is located at the bottom of the mounting groove, and the annular vane is connected to the outer circumference of the conductive plate and extends to the piezoelectric layer adjacent to the mounting groove. The filter according to the embodiments of this application and a method for manufacturing the same can improve the mechanical performance of a sandwich layer structure without impairing the high-frequency performance of the filter.

Description

Technical Field

[0001] This application belongs to the technical field of RF (Radio Frequency) micro electro-mechanical devices, and specifically relates to filters and their manufacturing methods.

[0002] (Cross-reference to related applications) This disclosure claims priority based on a Chinese application filed with the Chinese Patent Office on April 17, 2024, with application number 202410464334.8 and title "Filter and Its Manufacturing Method", and all of its content is incorporated herein by reference.

Background Art

[0003] With the advent of the 5G era, the number of frequency bands has further increased. For the increasingly congested frequency bands, the market has a growing demand for high-frequency and ultra-high-frequency filter frequency bands, and the demand for multi-frequency band high-frequency filters has increased rapidly. Higher performance is required for piezoelectric resonators. The surface acoustic wave resonator was widely used in the RF front end initially, but due to reasons such as low speed and limitations in photolithography, it is mainly used in the low-frequency market and it is difficult to maintain excellent performance in high-frequency bands. Compared with surface acoustic waves, the film bulk acoustic resonator (FBAR) has relatively small insertion loss, better selectivity, a large mechanical quality factor Q, and a steeper skirt in the medium and high-frequency bands above 2.5 GHz, so it can be used in the high-frequency filter market instead of the surface acoustic wave resonator.

[0004] Film bulk acoustic resonators are widely used in high-frequency filters, and their main structure is a layered structure resembling a sandwich of electrodes, a piezoelectric layer, and an upper electrode. When a film bulk acoustic resonator operates, an electric field is formed between the upper and lower electrodes, and due to the piezoelectric effect, the piezoelectric layer vibrates, forming an acoustic wave. The frequency of the acoustic wave is related to the thickness of the piezoelectric layer, the upper electrode, and the lower electrode; in practical applications, the thinner the thickness, the higher the frequency of the high-frequency filter. However, the thinner the piezoelectric layer, the lower the upper electrode, and the lower electrode, the inferior the mechanical performance of the sandwich layered structure, and the relatively high resistance of the upper and lower electrodes. [Overview of the project] [Problems that the invention aims to solve]

[0005] This application aims to provide a filter and a method for manufacturing the same that can improve the mechanical performance of a sandwich layer structure without impairing the high-frequency performance of the filter. [Means for solving the problem]

[0006] One embodiment of the present invention provides a filter. The filter includes a substrate on which a resonant assembly is mounted, the resonant assembly including a first lower electrode, a piezoelectric layer and a first upper electrode, which are mounted in order, the upper surface of the piezoelectric layer being recessed downward to form a mounting groove, the first upper electrode including a conductive plate and an annular vane, the conductive plate being located at the bottom of the mounting groove and the annular vane being connected to the outer circumference of the conductive plate and extending to the piezoelectric layer adjacent to the mounting groove.

[0007] In one feasible embodiment, there is an annular gap between the annular wing portion and the side wall of the arrangement groove.

[0008] In one feasible embodiment, the annular wing portion includes a wing portion located in a conductive layer and a connecting ring, the wing portion and the conductive plate being connected by the connecting ring.

[0009] In one feasible embodiment, the conductive layer and the wing portion have a height difference, and the connecting ring is formed by an inclined or longitudinally extending surface. When the connecting ring is formed by an inclined surface, the cross-section of the annular gap is triangular, and when the connecting ring is formed by a longitudinally extending surface, the cross-section of the annular gap is rectangular.

[0010] In one feasible embodiment, the side of the connection point between the connecting ring and the blade portion that is spaced away from the piezoelectric layer is provided as an arc-shaped surface.

[0011] In one feasible embodiment, the conductive plate is polygonal, and the annular wing portion has sub-wing portions formed corresponding to each side of the polygon, the sub-wing portions protruding outward and forming an arc-shaped or irregularly curved outer edge.

[0012] In one feasible embodiment, an acoustic reflection structure is further formed between the substrate and the lower electrode, and the acoustic reflection structure protrudes upward, causing the first lower electrode, the piezoelectric layer, and the first upper electrode to bend upward.

[0013] In one feasible embodiment, the filter further includes a capacitor mounted on a substrate, the capacitor including a second lower electrode, a dielectric layer, and a second upper electrode, the substrate including a capacitor region for mounting the capacitor and a resonant region for mounting a resonant assembly, the resonant region and the capacitor region being adjacent, and the second upper electrode and the first lower electrode being made of the same material on the same layer.

[0014] In one feasible embodiment, the dielectric layer extends to the resonant region and is located between the first lower electrode and the substrate. A portion of the dielectric layer located within the resonant region is missing, forming a chamber between the substrate and the first lower electrode. The orthographic projections of the chamber, the first lower electrode, the piezoelectric layer, and the first upper electrode on the substrate overlap, and this overlap constitutes the effective resonant region of the resonant assembly.

[0015] In one feasible embodiment, the upper surface of the substrate corresponding to the chamber is recessed downward, forming a groove that communicates with the chamber, and the groove and the chamber constitute an acoustic reflection structure of the resonant assembly.

[0016] In one feasible embodiment, the first lower electrode and the second upper electrode are electrically connected.

[0017] In one feasible embodiment, the connection method between the capacitor and the resonant assembly includes series and parallel connections. When the capacitor and the resonant assembly are connected in parallel, the first lower electrode and the second upper electrode are extended to form a common end, and the first upper electrode and the second lower electrode are extended to form two branch connection ends. When the capacitor and the resonant assembly are connected in series, the first upper electrode and the second lower electrode are extended to form extended ends of the series connection structure.

[0018] Another embodiment of the embodiments of this application provides a method for manufacturing a filter. The manufacturing method includes the steps of providing a substrate and sequentially forming a first lower electrode and a piezoelectric layer on the substrate; etching the upper surface of the piezoelectric layer to form a placement groove and forming a sacrificial block on the side wall of the placement groove; forming a first upper electrode in the piezoelectric layer inside the placement groove and at the edge of the placement groove, wherein the first upper electrode includes a conductive plate and an annular vane, the conductive plate is located at the bottom of the placement groove, and the annular vane is connected to the outer circumference of the conductive plate and extends to a piezoelectric layer adjacent to the placement groove; and releasing the sacrificial block to form an annular gap.

[0019] In one implementable embodiment, the steps of providing a substrate and sequentially forming a first lower electrode and a piezoelectric layer on the substrate include: sequentially forming a second lower electrode and a dielectric layer on the substrate, wherein the substrate includes a capacitor region for setting the second lower electrode and a resonant region for setting the first lower electrode; forming the first lower electrode on the substrate, extending the first lower electrode to the dielectric layer to form a second upper electrode, thereby forming a capacitor with the second upper electrode, the dielectric layer and the second lower electrode; and forming a piezoelectric layer on the first lower electrode.

[0020] In one implementable embodiment, the method includes the steps of forming a groove in a resonant region of the substrate and filling the groove with a sacrificial layer such that the upper surface of the sacrificial layer is parallel to or protrudes from the upper surface of the substrate, before sequentially forming a second lower electrode and a dielectric layer on the substrate, and releasing the sacrificial layer after forming the first upper electrode.

[0021] The embodiments of this application have the following beneficial effects.

[0022] The filter according to this application includes a substrate on which a resonant assembly is installed. The resonant assembly includes a first lower electrode, a piezoelectric layer, and a first upper electrode, which are installed in order. The upper surface of the piezoelectric layer is recessed downward to form a groove. The first upper electrode includes a conductive plate and an annular vane. The conductive plate is located at the bottom of the groove, and the annular vane is connected to the outer circumference of the conductive plate and extends to the piezoelectric layer adjacent to the groove. Because the conductive plate is installed at the bottom of the groove, the upper surface of the piezoelectric layer is recessed downward to form the groove, reducing the thickness of the piezoelectric layer at the location of the groove, thereby reducing the thickness of the sandwich structure. When the resonant assembly is operating, the overlapping orthographic projections of the first upper electrode, the piezoelectric layer, and the first upper electrode on the substrate are the effective resonant region, i.e., the work region of the resonant assembly. When the thickness of the sandwich structure is relatively small, the high-frequency performance of the filter is relatively good. In areas of the piezoelectric layer where no groove is provided, the piezoelectric layer is relatively thick, and therefore has relatively high mechanical strength. Furthermore, the first upper electrode includes an annular vane portion installed on the conductive plate, thereby connecting the annular vane portion to areas where there are no arrangement grooves for the piezoelectric layer, and connecting the conductive plate to areas where there are arrangement grooves for the piezoelectric layer. As a result, the first upper electrode is connected to both areas where there are no arrangement grooves for the piezoelectric layer and areas where there are arrangement grooves for the piezoelectric layer, further improving the mechanical strength of the sandwich structure. Therefore, the mechanical performance of the sandwich layered structure can be improved without impairing the high-frequency performance of the filter according to this application. [Brief explanation of the drawing]

[0023] To more clearly explain the technical solutions of the embodiments of this application, the drawings used in the embodiments are briefly described below. The drawings to be described only show some embodiments of this application and do not limit the scope. Those skilled in the art can obtain other related drawings based on these drawings without using inventive capabilities. [Figure 1] It is a schematic configuration diagram of a filter according to an embodiment of this application. [Figure 2] It is a schematic configuration diagram of a filter according to an embodiment of this application. [Figure 3] It is a schematic diagram of a resonance assembly according to an embodiment of this application. [Figure 4] It is a schematic configuration diagram of a filter according to an embodiment of this application. [Figure 5] It is a schematic configuration diagram of a filter according to an embodiment of this application. [Figure 6] It is a schematic configuration diagram of a filter according to an embodiment of this application. [Figure 7] It is a flowchart of a manufacturing method of a filter according to an embodiment of this application. [Figure 8] It is a drawing showing a certain stage of a manufacturing method of a filter according to an embodiment of this application. [Figure 9] It is a drawing showing a certain stage of a manufacturing method of a filter according to an embodiment of this application. [Figure 10] It is a drawing showing a certain stage of a manufacturing method of a filter according to an embodiment of this application. [Figure 11] It is a drawing showing a certain stage of a manufacturing method of a filter according to an embodiment of this application. [Figure 12] It is a drawing showing a certain stage of a manufacturing method of a filter according to an embodiment of this application. [Figure 13] It is a drawing showing a certain stage of a manufacturing method of a filter according to an embodiment of this application.

Modes for Carrying Out the Invention

[0024] To clarify the purpose, technical proposal, and advantages of the embodiments of this application, the technical proposal in the embodiments of this application will be clearly and completely described below with reference to the drawings used in the embodiments of this application. The embodiments described are only a selection of embodiments of this application, not all embodiments. The components in the embodiments of this application shown herein with reference to the drawings can be arranged and designed in various ways.

[0025] Therefore, the following detailed description of the embodiments of this application shown in the drawings is merely to illustrate selected embodiments of this application and does not limit the scope of the application to be protected. All other embodiments that a person skilled in the art could obtain without using their inventive ability based on the embodiments of this application also fall within the scope of protection of this application.

[0026] Similar symbols indicate the same thing in drawings, so if they are defined in one drawing, it is unnecessary to define or interpret them further in other drawings.

[0027] In the description of this application, directions or positional relationships expressed using terms such as "center," "vertical," "horizontal," "inside," and "outside" are based on the drawings or represent the usual orientation or positional relationship of the product relating to this application, and are merely for the purpose of briefly and concisely describing this application. They do not necessarily express or imply that the device or element in question has a particular orientation or is configured or operated in a particular orientation, and therefore do not limit this application. Furthermore, terms such as "first," "second," and "third" are merely for the purpose of distinguishing between them and do not express or imply relative importance.

[0028] In 4G and earlier communication technologies, the definition of frequency bands was relatively narrow, and selected electromagnetic or acoustic filters could meet performance requirements depending on the RF system's needs. However, with the advent of 5G, 6G, and Wi-Fi 7, the definition criteria for frequency bands have changed significantly. All frequency bands are now defined as broadband exceeding 500 MHz, and the frequency band spacing is gradually narrowing. This necessitates filters that can simultaneously support broadband and high out-of-band suppression.

[0029] Embodiments of this application provide a filter 100. As shown in Figures 1 and 2, the filter 100 includes a substrate 110 on which a resonant assembly 130 is installed. The resonant assembly 130 includes a first lower electrode 131, a piezoelectric layer 132, and a first upper electrode 133, which are installed in order. The upper surface of the piezoelectric layer 132 is recessed downward to form a placement groove 150. The first upper electrode 133 includes a conductive plate 161 and an annular vane portion 162, the conductive plate 161 being located at the bottom of the placement groove 150, and the annular vane portion 162 being connected to the outer circumference of the conductive plate 161 and extending to the piezoelectric layer 132 adjacent to the placement groove 150.

[0030] When the filter 100 according to the embodiment of this application is in operation, the resonant assembly 130 functions as a frequency selector device. Specifically, the resonant assembly 130 includes a first upper electrode 133, a piezoelectric layer 132, and a first lower electrode 131, with the first upper electrode 133, the piezoelectric layer 132, and the first lower electrode 131 forming a sandwich structure. The first upper electrode 133 and the first lower electrode 131 are connected to both ends of an AC electrical signal, respectively, generating an electric field between the first upper electrode 133 and the first lower electrode 131. The piezoelectric layer 132 is located between the first upper electrode 133 and the first lower electrode 131 and has a piezoelectric effect. Under the action of the voltage formed by the first upper electrode 133 and the first lower electrode 131, mechanical deformation occurs in the piezoelectric layer 132, generating an acoustic wave.

[0031] Through the specific structural design of the resonant assembly 130, only acoustic waves of a specific frequency can form standing waves in the piezoelectric layer 132. When this frequency is equal to the natural resonant frequency of the piezoelectric layer 132, the resonator exhibits maximum energy absorption and maximum current phase change, thereby achieving frequency selection for the resonant assembly 130.

[0032] In the embodiment of the present application, the upper surface of the piezoelectric layer 132 is recessed downward to form a placement groove 150, and the first upper electrode 133 includes a conductive plate 161 and an annular wing portion 162, the conductive plate 161 is located at the bottom of the placement groove 150, and the annular wing portion 162 is connected to the outer circumference of the conductive plate 161 and extends to the piezoelectric layer 132 adjacent to the placement groove 150. The annular wing portion 162 includes a wing portion located in the conductive layer and a connecting ring connecting the wing portion and the conductive plate 161, and since the upper surface of the piezoelectric layer 132 is recessed downward to form a placement groove 150 and the conductive plate 161 is installed at the bottom of the placement groove 150, the thickness of the piezoelectric layer 132 located in the placement groove 150 is reduced, thereby reducing the thickness of the sandwich structure.

[0033] When the resonant assembly 130 is operating, the overlapping orthographic projection of the first upper electrode 133, the piezoelectric layer 132, and the first upper electrode 133 on the substrate 110 is the effective resonant region 112, which is the work region of the resonant assembly 130. When the thickness of the sandwich structure is relatively small, the high-frequency performance of the filter 100 is relatively good. In areas where there are no placement grooves in the piezoelectric layer 132, the piezoelectric layer 132 has a relatively high thickness and therefore relatively high mechanical strength. Furthermore, the first upper electrode 133 includes an annular vane portion 162 installed on the conductive plate 161. The annular vane portion 162 is connected to areas of the piezoelectric layer 132 where there are no placement grooves, and the conductive plate 161 is connected to areas of the piezoelectric layer 132 where there are placement grooves. As a result, the first upper electrode 133 is connected to both areas of the piezoelectric layer 132 where there are no placement grooves and areas where there are placement grooves, further improving the mechanical strength of the sandwich structure.

[0034] As part of the process of forming the arrangement groove 150, a relatively thick piezoelectric layer 132 is laid, and a predetermined area is etched using ion beam etching to form the arrangement groove 150 by creating a recess. Ion beam etching allows for precise control of the etching depth and good anisotropy, enabling the realization of vertical side walls and a flat bottom wall. As a result, the flatness of the groove bottom of the arrangement groove 150 is relatively high, the thickness of the piezoelectric layer 132 located in the effective resonance region 112 is relatively uniform, and the performance of the resonance assembly 130 can be further improved.

[0035] Specifically, the specific materials of the first upper electrode 133, the piezoelectric layer 132, the second upper electrode 123, and the substrate 110 are not limited in the embodiments of this application. Exemplarily, the substrate 110 may be a silicon substrate 110 and a sapphire substrate 110, etc. The material of the piezoelectric layer 132 may be aluminum nitride or doped aluminum nitride, zinc oxide, lead zirconate titanate, and lithium niobate, etc. The materials of the first upper electrode 133 and the first lower electrode 131 may be the same or different, and both may be metallic materials such as molybdenum Mo, gold Au, aluminum Al, copper Au, titanium Ti, and tungsten Wu.

[0036] Furthermore, the filter 100 according to the embodiment of this application is a type of mixed filter 100, and not only are parts of the resonant assembly 130 present on the substrate 110, but specifically, there may be one resonant assembly 130 or multiple resonant assemblies 130, and it may also include other electronic devices such as capacitors 120 and inductors. Those skilled in the art will know that it is possible to install it according to the actual situation and that it may include at least one of the above resonant assemblies 130.

[0037] When acoustic waves are repeatedly reflected within the sandwich structure, reflective structures are formed on both sides of the sandwich structure to prevent leakage of acoustic waves, and a reflective interface with air is formed at the first upper electrode 133. In practical applications, an acoustic reflective structure 140 is usually formed between the substrate 110 and the first lower electrode 131, for example, the acoustic wave reflective structure shown in Figure 1. The specific acoustic reflective structure 140 is not limited to the embodiments of this application and may, exemplarily, be an air cavity, with a reflective interface formed between the air cavity and the first lower electrode 131.

[0038] The filter 100 according to this application includes a substrate 110, on which a resonant assembly 130 is installed. The resonant assembly 130 includes a first lower electrode 131, a piezoelectric layer 132, and a first upper electrode 133, which are installed in order. The upper surface of the piezoelectric layer 132 is recessed downward to form a placement groove 150. The first upper electrode 133 includes a conductive plate 161 and an annular wing portion 162. The conductive plate 161 is located at the bottom of the placement groove 150, and the annular wing portion 162 is connected to the outer circumference of the conductive plate 161 and extends to the piezoelectric layer 132 adjacent to the placement groove 150.

[0039] Since the conductive plate 161 is placed at the bottom of the arrangement groove 150, the upper surface of the piezoelectric layer 132 is recessed downward, forming the arrangement groove 150. This reduces the thickness of the piezoelectric layer 132 in the area of ​​the arrangement groove 150, thereby reducing the thickness of the sandwich structure.

[0040] When the resonant assembly 130 is operating, the overlapping orthographic projection of the first upper electrode 133, the piezoelectric layer 132, and the first upper electrode 133 on the substrate 110 is the effective resonant region 112, which is the work region of the resonant assembly 130. When the thickness of the sandwich structure is relatively small, the high-frequency performance of the filter 100 is relatively good. In areas where there are no placement grooves in the piezoelectric layer 132, the piezoelectric layer 132 has a relatively high thickness and therefore relatively high mechanical strength.

[0041] Furthermore, the first upper electrode 133 includes an annular wing portion 162 installed on the conductive plate 161. As a result, the annular wing portion 162 is connected to areas where there are no arrangement grooves for the piezoelectric layer 132, and the conductive plate 161 is connected to areas where there are arrangement grooves for the piezoelectric layer 132. Thus, the first upper electrode 133 is connected to both areas where there are no arrangement grooves for the piezoelectric layer 132 and areas where there are arrangement grooves for the piezoelectric layer 132, further improving the mechanical strength of the sandwich structure. Therefore, the filter 100 according to this application can improve the mechanical performance of the sandwich layer structure without impairing the high-frequency performance of the filter 100.

[0042] Optionally, as shown in Figures 1 and 2, there is an annular gap 164 between the annular wing portion 162 and the side wall of the arrangement groove 150.

[0043] In the actual use of the filter 100, the acoustic waves formed on the piezoelectric layer 132 include not only waves along the stacking direction, but also acoustic waves that propagate along the surface of the piezoelectric layer 132. In the embodiment of this application, an annular gap 164 is formed between the annular vane portion 162 and the arrangement groove 150, and in this way an interface with air is formed on the outer circumference of the conductive plate 161. Since the air and the conductive plate 161 have different acoustic impedances, the reflection effect on acoustic waves is improved, energy leakage is reduced, and the Q value of the filter 100 can be increased.

[0044] As can be seen from the above, the annular wing portion 162 includes a wing portion located in the conductive layer and a connecting ring connecting the wing portion and the conductive plate 161. There is a height difference between the conductive layer and the wing portion, and as a result, the connecting ring extends for a certain length in the height direction, and in this way the connecting ring can be formed by a longitudinally extending surface or an inclined extending surface. When the connecting ring is formed by an inclined extending surface, the cross-section of the annular gap 164 is triangular, and when the connecting ring is formed by a longitudinally extending surface, the cross-section of the annular gap 164 is rectangular.

[0045] Furthermore, in order to suppress tip discharge caused by the presence of a sharp point at the connection point between the connecting ring and the blade, the side of the connection point between the connecting ring and the blade that is spaced away from the piezoelectric layer 132 is provided as an arc-shaped surface.

[0046] In one feasible embodiment of the present invention, as shown in Figure 3, the conductive plate 161 is polygonal, and the annular wing portion 162 has sub-wing portions 165 formed corresponding to each side of the polygon, the sub-wing portions 165 protruding outward and forming an arc-shaped or irregularly curved outer edge.

[0047] By making the conductive plate 161 polygonal, each side of the polygon reflects the sound waves in a different direction as the sound waves propagate laterally, improving the reflection effect and increasing the Q value of the filter 100. Furthermore, the sub-wing portion 165 protrudes outward, forming an arc-shaped or irregularly curved outer edge, and if the outer edge is arc-shaped or irregularly curved, the reflection effect can be improved and the Q value can be increased.

[0048] Specifically, the shape of the polygon is not limited to the embodiments of this application, and may be, for example, a pentagon as shown in Figure 3, or other shapes such as a hexagon.

[0049] Optionally, as shown in Figure 2, an acoustic reflection structure 140 is further formed between the substrate 110 and the lower electrode, and the acoustic reflection structure 140 protrudes upward, causing the first lower electrode 131, the piezoelectric layer 132, and the first upper electrode 133 to bend upward.

[0050] As the acoustic reflection structure 140 protrudes upward, the first lower electrode 131, the piezoelectric layer 132, and the first upper electrode 133 all bend upward, thus forming a staircase at the edge of the effective resonance region 112. The staircase contributes to the reflection of acoustic waves, preventing acoustic waves from leaking outside the effective resonance region 112 and increasing the Q value of the filter 100.

[0051] In one feasible embodiment of the present invention, as shown in Figures 4, 5, and 6, the filter 100 further includes a capacitor 120 installed on a substrate 110. The capacitor 120 includes a second lower electrode 121, a dielectric layer 122, and a second upper electrode 123. The substrate 110 includes a capacitor region 111 on which the capacitor 120 is installed and a resonant region 112 on which a resonant assembly 130 is installed, wherein the resonant region 112 and the capacitor region 111 are adjacent, and the second upper electrode 123 and the first lower electrode 131 are manufactured from the same material in the same layer.

[0052] In the embodiment of this application, the first lower electrode 131 and the second upper electrode 123 are manufactured in the same layer using the same material, that is, the first lower electrode 131 and the second upper electrode 123 are electrically connected, which shortens the connection path compared to the conventional method of extending both ends of the capacitor 120 and the resonant assembly 130 to connect them. Furthermore, by manufacturing them in the same layer using the same material, the current flow area can be increased. The embodiment of this application can reduce the resistance when connecting the capacitor 120 and the resistor, thereby improving the performance of the filter 100, from two aspects: shortening the connection path and increasing the flow area.

[0053] In the filter 100, the connection method between the capacitor 120 and the resonant assembly 130 includes two methods: series connection and parallel connection. Specifically, when the capacitor 120 and the resonant assembly 130 are connected in parallel, the first lower electrode 131 and the second upper electrode 123 are extended to form a common terminal, and the first upper electrode 133 and the second lower electrode 121 are extended to form the connection terminals of the two branches. When the capacitor 120 and the resonant assembly 130 are connected in series, the first upper electrode 133 and the second lower electrode 121 are extended to form the extended terminals of the series connection structure.

[0054] Optionally, the dielectric layer 122 extends to the resonant region 112 and is located between the first lower electrode 131 and the substrate 110. A portion of the dielectric layer 122 located within the resonant region 112 is missing, forming a chamber 141 between the substrate 110 and the first lower electrode 131. The orthographic projections of the chamber 141, the first lower electrode 131, the piezoelectric layer 132, and the conductive plate 161 on the substrate 110 have an overlapping portion, and this overlapping portion is the effective resonant region 112 of the resonant assembly 130.

[0055] In the embodiment of this application, the dielectric layer 122 extends to the resonant region 112, and within the resonant region 112, a portion of the dielectric layer 122 is missing to form a chamber 141 as an acoustic reflection structure 140. After the first upper electrode 133 is manufactured, wet etching is performed, and the size and position of the chamber 141 are controlled by controlling the wet etching time. This simplifies the process steps and improves the manufacturing efficiency of the filter 100 compared to the prior art method of forming the chamber 141 by filling the sacrificial layer and then releasing the sacrificial layer.

[0056] Specifically, the material of the dielectric layer is not limited to the embodiments of this application, but may include, for example, silicon dioxide, silicon nitride, and the like.

[0057] In one feasible embodiment of the present invention, the upper surface of the substrate 110 corresponding to the chamber 141 is recessed downward to form a groove 142 that communicates with the chamber 141, and the groove 142 and the chamber 141 constitute an acoustic reflection structure 140 of the resonant assembly 130.

[0058] If the depth of the chamber 141 does not meet the working requirements of the resonant assembly 130, a groove 142 is formed on the upper surface of the substrate 110 corresponding to the chamber 141, and the groove 142 and the chamber 141 are connected to function as the acoustic reflection structure 140 of the resonant assembly 130.

[0059] In another embodiment of the embodiments of this application, a method for manufacturing the filter 100 is provided. As shown in Figure 7, the manufacturing method includes the following steps.

[0060] Step S10: As shown in Figures 8, 9, and 10, the substrate 110 is provided, and the first lower electrode 131 and the piezoelectric layer 132 are formed sequentially on the substrate 110.

[0061] Specifically, the method for forming the lower electrode and piezoelectric layer 132 on the substrate 110 is not limited to the embodiments of this application, but may include, for example, physical vapor deposition, chemical vapor deposition, or the like. Those skilled in the art can specifically select the appropriate method depending on the actual situation.

[0062] The specific materials of the substrate 110 and the piezoelectric layer 132 are the same as those of the filter 100, so their explanation is omitted here.

[0063] Step S20: As shown in Figure 11, the upper surface of the piezoelectric layer 132 is etched to form an arrangement groove 150, and a sacrificial block 171 is formed on the side wall of the arrangement groove 150.

[0064] Specifically, a pre-made sacrificial block 171 may be placed in the placement groove 150, or the sacrificial block 171 may be formed by depositing and etching sacrificial material.

[0065] Step S30: As shown in Figure 12, a first upper electrode 133 is formed in the piezoelectric layer 132 inside the arrangement groove 150 and at the edge of the arrangement groove 150. The first upper electrode 133 includes a conductive plate 161 and an annular wing portion 162, the conductive plate 161 is located at the bottom of the arrangement groove 150, and the annular wing portion 162 is connected to the outer circumference of the conductive plate 161 and extends to the piezoelectric layer 132 adjacent to the arrangement groove 150.

[0066] When forming the first upper electrode 133, the annular wing portion 162 covers the upper surface of the sacrificial block 171. By placing the upper electrode within the arrangement groove 150, the thickness of the sandwich structure is reduced, resulting in relatively good high-frequency performance of the filter 100. In areas of the piezoelectric layer 132 where arrangement grooves are not provided, the piezoelectric layer 132 is relatively thick, and therefore has relatively high mechanical strength.

[0067] Furthermore, the first upper electrode 133 includes an annular wing portion 162 installed on the conductive plate 161, and the annular wing portion 162 is connected to a portion of the piezoelectric layer 132 where there is no arrangement groove, and the conductive plate 161 is connected to a portion of the piezoelectric layer 132 where there is an arrangement groove, so the first upper electrode 133 is connected to both a portion of the piezoelectric layer 132 where there is no arrangement groove and a portion of the piezoelectric layer 132 where there is an arrangement groove, thereby further improving the mechanical strength of the sandwich structure.

[0068] Step S40: As shown in Figure 13, the sacrificial block 171 is released to form an annular gap 164.

[0069] Optionally, providing a substrate 110 and sequentially forming a first lower electrode 131 and a piezoelectric layer 132 on the substrate 110 includes the following steps.

[0070] Step S11: As shown in Figure 9, the second lower electrode 121 and the dielectric layer 122 are formed sequentially on the substrate 110. The substrate 110 includes a capacitor region 111 where the second lower electrode 121 is installed and a resonant region 112 where the first lower electrode 131 is installed.

[0071] Step S12: As shown in Figure 9, a first lower electrode 131 is formed on the substrate 110, and the first lower electrode 131 is extended to the dielectric layer 122 to become a second upper electrode 123, and a capacitor 120 is formed by the second upper electrode 123, the dielectric layer 122 and the second lower electrode 121.

[0072] By extending the first lower electrode 131 to the dielectric layer 122 to form the second upper electrode 123, the first lower electrode 131 and the second upper electrode 123 are manufactured in the same layer using the same material, that is, the first lower electrode 131 and the second upper electrode 123 are electrically connected.

[0073] Compared to the conventional method of extending both ends of the capacitor 120 and the resonant assembly 130 to connect them, the connection path is shortened. Furthermore, by manufacturing them in the same layer using the same material, the current flow area can be increased. The embodiment of this application can reduce the resistance when connecting the capacitor 120 and the resistor, thereby improving the performance of the filter 100, through the two aspects of shortening the connection path and increasing the current flow area.

[0074] Step S13: As shown in Figure 10, a piezoelectric layer 132 is formed on the first lower electrode 131.

[0075] In one feasible embodiment of the present invention, the following steps are taken before sequentially forming the second lower electrode 121 and the dielectric layer 122 on the substrate 110.

[0076] Step S01: A groove 142 is formed in the resonant region 112 of the substrate 110, and a sacrificial layer is filled into the groove 142 such that the upper surface of the sacrificial layer is parallel to the upper surface of the substrate 110 or protrudes from the upper surface of the substrate 110.

[0077] Step S02: After forming the first upper electrode 133, the sacrificial layer is released.

[0078] If the top surface of the sacrificial layer is parallel to the top surface of the substrate 110, the state after releasing the sacrificial layer will be as shown in Figure 6.

[0079] If the upper surface of the sacrificial layer protrudes from the upper surface of the substrate 110, the state after the sacrificial layer is released will be as shown in Figure 2, in which the first lower electrode 131, the piezoelectric layer 132, and the first upper electrode 133 will bend upward, preventing acoustic waves from leaking outside the effective resonance region 112 and increasing the Q value of the filter 100.

[0080] The specific structure and beneficial effects of the manufacturing method of filter 100 can be found in the description of the examples of filter 100, so a detailed explanation is omitted here.

[0081] The foregoing describes only preferred embodiments of this application and does not limit it. Those skilled in the art may have various modifications and changes to this application. All modifications, equivalent substitutions, improvements, etc., that do not deviate from the spirit and principles of this application are all within the scope of protection of this application.

[0082] Industrial applicability As described above, the filter and its manufacturing method according to this application can improve the mechanical performance of the sandwich layer structure without impairing the high-frequency performance of the filter. [Explanation of Symbols]

[0083] 100 filters 110 circuit boards 111 Capacitor region 112 Resonance region 120 Capacitors 121 2nd lower electrode 122 Dielectric layer 123 2nd upper electrode 130 Resonant Assembly 131 1st lower electrode 132 Piezoelectric layer 133 1st upper electrode 140 Acoustic reflective structure Room 141 142 groove 150 Placement groove 161 Conductive plate 162 Annular wing section 163 Connecting ring 164 Annular gap 165 Subwing section 171 Sacrifice Block

Claims

1. The device includes a substrate on which a resonant assembly is installed, the resonant assembly including a first lower electrode, a piezoelectric layer, and a first upper electrode, which are installed in order, the upper surface of the piezoelectric layer being recessed downward to form a placement groove, the first upper electrode including a conductive plate and an annular vane, the conductive plate being located at the bottom of the placement groove, and the annular vane being connected to the outer circumference of the conductive plate and extending to the piezoelectric layer adjacent to the placement groove. A filter characterized by the following features.

2. There is an annular gap between the annular wing portion and the side wall of the arrangement groove. The filter according to feature 1.

3. The annular wing portion includes a wing portion located in the conductive layer and a connecting ring, and the wing portion and the conductive plate are connected by the connecting ring. The filter according to claim 1 or 2, characterized by the features described above.

4. The conductive layer and the wing portion have a height difference, and the connecting ring is formed by a surface that extends inclined or a surface that extends vertically. If the connecting ring is formed by a surface that extends inclined, the cross-section of the annular gap is triangular, and if the connecting ring is formed by a surface that extends vertically, the cross-section of the annular gap is rectangular. The filter according to claim 3.

5. The side of the connection point between the connecting ring and the blade portion that is spaced apart from the piezoelectric layer is provided as an arc-shaped surface. The filter according to claim 3 or 4, characterized by the features described above.

6. The conductive plate is polygonal, and the annular wing portion has sub-wing portions formed corresponding to each side of the polygon, and the sub-wing portions protrude outward, forming an arc-shaped or irregularly curved outer edge. The filter according to any one of claims 1 to 5.

7. An acoustic reflection structure is further formed between the substrate and the lower electrode, and the acoustic reflection structure protrudes upward, causing the first lower electrode, the piezoelectric layer and the first upper electrode to bend upward. The filter according to any one of claims 1 to 6.

8. The substrate further includes a capacitor, the capacitor comprising a second lower electrode, a dielectric layer, and a second upper electrode; the substrate comprises a capacitor region for mounting the capacitor and a resonant region for mounting the resonant assembly, the resonant region and the capacitor region being adjacent, and the second upper electrode and the first lower electrode being made of the same material from the same layer. The filter according to any one of claims 1 to 7.

9. The dielectric layer extends to the resonance region and is located between the first lower electrode and the substrate. A portion of the dielectric layer located within the resonance region is missing, forming a chamber between the substrate and the first lower electrode. The orthographic projections of the chamber, the first lower electrode, the piezoelectric layer, and the conductive plate on the substrate overlap, and the overlapping portion is the effective resonance region of the resonance assembly. The filter according to feature 8.

10. The upper surface of the substrate corresponding to the chamber is recessed downward, forming a groove that communicates with the chamber, and the groove and the chamber are configured as an acoustic reflection structure for the resonant assembly. The filter according to feature 9.

11. The first lower electrode and the second upper electrode are electrically connected. The filter according to any one of claims 8 to 10, characterized by the above.

12. The connection method between the capacitor and the resonant assembly includes series connection and parallel connection. When the capacitor and the resonant assembly are connected in parallel, the first lower electrode and the second upper electrode are extended to form a common end, and the first upper electrode and the second lower electrode are extended to form two branch connection ends. When the capacitor and the resonant assembly are connected in series, the first upper electrode and the second lower electrode are extended to form extended ends of the series connection structure. The filter according to any one of claims 8 to 11, characterized by the features described above.

13. The steps include providing a substrate and sequentially forming a first lower electrode and a piezoelectric layer on the substrate, The steps include etching the upper surface of the piezoelectric layer to form an arrangement groove, and forming a sacrificial block on the side wall of the arrangement groove, A first upper electrode is formed in the piezoelectric layer inside the arrangement groove and at the edge of the arrangement groove, the first upper electrode includes a conductive plate and an annular vane, the conductive plate is located at the bottom of the arrangement groove, and the annular vane is connected to the outer circumference of the conductive plate and extends to the piezoelectric layer adjacent to the arrangement groove, The step includes releasing the sacrificial block to form an annular gap. A method for manufacturing a filter characterized by the above.

14. The steps of providing a substrate and sequentially forming a first lower electrode and a piezoelectric layer on the substrate are: The steps include: sequentially forming a second lower electrode and a dielectric layer on the substrate, wherein the substrate includes a capacitor region for installing the second lower electrode and a resonant region for installing the first lower electrode; The steps include forming a first lower electrode on the substrate, extending the first lower electrode to the dielectric layer to form a second upper electrode, and forming a capacitor with the second upper electrode, the dielectric layer and the second lower electrode, The step of forming a piezoelectric layer on the first lower electrode includes A method for manufacturing a filter according to claim 13, characterized in that it is a product of the present invention.

15. Before sequentially forming the second lower electrode and the dielectric layer on the substrate, The steps include forming a groove in the resonant region of the substrate, and filling the groove with a sacrificial layer such that the upper surface of the sacrificial layer is parallel to the upper surface of the substrate or protrudes from the upper surface of the substrate, The step includes releasing the sacrificial layer after forming the first upper electrode. A method for manufacturing a filter according to claim 14, characterized by the features described above.

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