Filter and manufacturing method therefor

Abstract

Embodiments of the present application relate to the technical field of radio frequency micro-electro-mechanical devices, and disclosed are a filter and a manufacturing method therefor. The filter in the embodiments of the present application comprises a substrate; a resonance assembly is provided on the substrate and comprises a first lower electrode, a piezoelectric layer, and a first upper electrode which are sequentially arranged; the upper surface of the piezoelectric layer is recessed downwards to form a placement recess; the first upper electrode comprises a conductive piece and a ring flange; the conductive piece is located on the bottom of the placement recess; and the ring flange is connected to the periphery of the conductive piece and extends to the piezoelectric layer adjacent to the placement recess. The filter and the manufacturing method therefor provided in the embodiments of the present application can improve the mechanical properties of a sandwich layered structure while not affecting the high-frequency performance of the filter.

Description

A filter and a preparation method thereof

[0001] Cross-reference to related applications

[0002] The present disclosure claims priority to the Chinese patent application No. 202410464334.8, filed on April 17, 2024, and entitled "A filter and a preparation method thereof"; the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the technical field of radio frequency micro-electro-mechanical devices, in particular to a filter and a preparation method thereof. BACKGROUND

[0004] With the advent of the 5G era, the number of frequency bands will continue to increase. In the face of increasingly crowded frequency bands, the market demand for high-frequency and ultra-high-frequency filter frequency bands is growing rapidly, and the demand for multi-band high-frequency filters is increasing dramatically. This puts higher requirements on the performance of piezoelectric resonators. Surface acoustic wave resonators were widely used in the early days of radio frequency front-end, but due to their low phase velocity, limitations in photolithography, and other reasons, they are mainly used in low-frequency markets and it is difficult to maintain excellent performance in high-frequency bands. Compared with surface acoustic waves, bulk acoustic wave resonators (FBAR) have lower insertion loss and better selectivity in the medium and high frequency bands above 2.5 GHz, and they have a high mechanical quality factor Q, which can make the skirt steeper, so they can replace surface acoustic wave resonators and be applied to the high-frequency filter market.

[0005] Bulk acoustic wave resonators are widely used in high-frequency filters, and the main structure of bulk acoustic wave resonators is a sandwiched layered structure of lower electrode-piezoelectric layer-upper electrode. When the bulk acoustic wave resonator is working, an electric field is formed between the upper electrode and the lower electrode, and according to the piezoelectric effect, the piezoelectric layer vibrates to form 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, when the thickness of the piezoelectric layer, the upper electrode and the lower electrode is thinner, the mechanical properties of the sandwiched layered structure are poor, and the resistance of the upper electrode and the lower electrode is large.

[0006] SUMMARY

[0007] The purpose of the present application is to provide a filter and a preparation method thereof, which can improve the mechanical properties of the sandwiched layered structure without affecting the high-frequency performance of the filter.

[0008] The embodiment of the present application provides a filter, which comprises a substrate, and a resonant assembly arranged on the substrate, wherein the resonant assembly comprises a first lower electrode, a piezoelectric layer and a first upper electrode arranged in sequence, the upper surface of the piezoelectric layer is concave downward to form a setting groove, and the first upper electrode comprises a conductive sheet and a ring wing, the conductive sheet is located at the bottom of the setting groove, and the ring wing is connected with the outer periphery of the conductive sheet and extends to the piezoelectric layer adjacent to the setting groove.

[0009] As an implementable mode, the ring wing has an annular gap between the ring wing and the side wall of the setting groove.

[0010] As an implementable mode, the ring wing comprises a wing on the conductive layer and a connecting ring, and the wing and the conductive sheet are connected through the connecting ring.

[0011] As an implementable mode, the conductive layer and the wing have a height difference, and the connecting ring is inclined or vertical, when the connecting ring is inclined, the cross section of the annular gap is triangular, and when the connecting ring is vertical, the cross section of the annular gap is rectangular.

[0012] As an implementable mode, the side of the connecting ring away from the piezoelectric layer is arranged as an arc surface.

[0013] As an implementable mode, the conductive sheet is a polygon, the ring wing forms a sub-wing corresponding to each side of the polygon, the sub-wing protrudes outward to form an arc-shaped or irregular curved outer edge.

[0014] As an implementable mode, a sound reflection structure is further formed between the substrate and the lower electrode, the sound reflection structure protrudes upward to make the first lower electrode, the piezoelectric layer and the first upper electrode bend upward.

[0015] As an implementable mode, the filter further comprises a capacitor arranged on the substrate, the capacitor comprises a second lower electrode, a dielectric layer and a second upper electrode, the substrate comprises a capacitor region for arranging the capacitor and a resonant region for arranging the resonant assembly, the resonant region and the capacitor region are adjacent, and the second upper electrode and the first lower electrode are of the same layer and the same material.

[0016] As an implementable mode, the dielectric layer extends to the resonant region, is located between the first lower electrode and the substrate, and a part of the dielectric layer in the resonant region is missing to form a cavity between the substrate and the first lower electrode, the orthographic projection of the cavity, the first lower electrode, the piezoelectric layer and the first upper electrode on the substrate has an overlapping part, and the overlapping part is an effective resonant region of the resonant assembly.

[0017] As an implementable mode, the upper surface of the substrate corresponding to the cavity is concave downward to form a groove in communication with the cavity, and the groove and the cavity serve as a sound reflection structure of the resonant assembly.

[0018] As an implementable mode, the first lower electrode is electrically connected with the second upper electrode.

[0019] As an implementable manner, the capacitor and resonance assembly includes series and parallel, when the capacitor and resonance assembly is in parallel, the first lower electrode and the second upper electrode are led out as a common terminal, and the first upper electrode and the second lower electrode are respectively led out as two branch connection terminals; when the capacitor and resonance assembly is in series, the first upper electrode and the second lower electrode are respectively led out as a series structure.

[0020] Another aspect of the embodiments of the present application provides a preparation method of a filter, comprising: providing a substrate, and sequentially forming a first lower electrode and a piezoelectric layer on the substrate; etching an upper surface of the piezoelectric layer to form a placement groove and a sacrifice block at a side wall of the placement groove; forming a first upper electrode on the piezoelectric layer in the placement groove and at an edge of the placement groove, the first upper electrode including a conductive sheet and a ring wing, the conductive sheet being located at a groove bottom of the placement groove, and the ring wing being connected with an outer periphery of the conductive sheet and extending to the piezoelectric layer adjacent to the placement groove; and releasing the sacrifice block to form a ring-shaped gap.

[0021] As an implementable manner, the providing a substrate and sequentially forming a first lower electrode and a piezoelectric layer on the substrate includes: sequentially forming a second lower electrode and a dielectric layer on the substrate, the substrate including a capacitor region in which the second lower electrode is arranged and a resonance region in which the first lower electrode is arranged; forming the first lower electrode on the substrate, the first lower electrode extending to the dielectric layer as a second upper electrode, the second upper electrode, the dielectric layer and the second lower electrode forming a capacitor; and forming the piezoelectric layer on the first lower electrode.

[0022] As an implementable manner, before sequentially forming a second lower electrode and a dielectric layer on the substrate, the method includes: forming a groove on the resonance region of the substrate and filling a sacrifice layer in the groove, an upper surface of the sacrifice layer being parallel to or protruding from an upper surface of the substrate; and after forming the first upper electrode, releasing the sacrifice layer.

[0023] The beneficial effects of the embodiments of the present application include:

[0024] The filter provided by the application comprises a substrate, a resonant assembly is arranged on the substrate, the resonant assembly comprises a first lower electrode, a piezoelectric layer and a first upper electrode which are arranged in sequence, the upper surface of the piezoelectric layer is concave downward to form a mounting groove, the first upper electrode comprises a conductive sheet and a ring wing, the conductive sheet is located at the groove bottom of the mounting groove, and the ring wing is connected with the outer periphery of the conductive sheet and extends to the piezoelectric layer adjacent to the mounting groove. Since the conductive sheet is arranged at the groove bottom of the mounting groove, the upper surface of the piezoelectric layer is concave downward to form the mounting groove, the thickness of the piezoelectric layer at the position of the mounting groove is reduced, so as to reduce the thickness of the sandwich structure. When the resonant assembly works, the overlapping part of the first upper electrode, the piezoelectric layer and the normal projection of the first upper electrode on the substrate is the effective resonant area, that is, the working area of the resonant assembly. When the thickness of the sandwich structure is small, the high-frequency performance of the filter is better. At the position where the piezoelectric layer is not provided with the mounting groove, the piezoelectric layer has a relatively thick thickness, so that it has a relatively high mechanical strength. In addition, the first upper electrode comprises the ring wing arranged on the conductive sheet. In this way, the ring wing is connected with the piezoelectric layer at the position where the mounting groove is not arranged, and the conductive sheet is connected with the piezoelectric layer at the position where the mounting groove is arranged. The first upper electrode is connected with the piezoelectric layer at the position where the mounting groove is not arranged and the piezoelectric layer at the position where the mounting groove is arranged, so as to further improve the mechanical strength of the sandwich structure. Therefore, the filter of the application can improve the mechanical performance of the sandwich structure without affecting the high-frequency performance of the filter. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Fig. 1 is a structural schematic diagram of a filter provided by an embodiment of the application;

[0027] Fig. 2 is a structural schematic diagram of a filter provided by an embodiment of the application;

[0028] Fig. 3 is a schematic diagram of a resonant assembly provided by an embodiment of the application;

[0029] Fig. 4 is a structural schematic diagram of a filter provided by an embodiment of the application;

[0030] Fig. 5 is a structural schematic diagram of a filter provided by an embodiment of the application;

[0031] Fig. 6 is a structural schematic diagram of a filter provided by an embodiment of the application;

[0032] Fig. 7 is a flow chart of a preparation method of a filter provided by an embodiment of the application;

[0033] Fig. 8 is a state diagram of a method for manufacturing a filter according to an embodiment of the present application;

[0034] Fig. 9 is a state diagram of a method for manufacturing a filter according to an embodiment of the present application;

[0035] Fig. 10 is a state diagram of a method for manufacturing a filter according to an embodiment of the present application;

[0036] Fig. 11 is a state diagram of a method for manufacturing a filter according to an embodiment of the present application;

[0037] Fig. 12 is a state diagram of a method for manufacturing a filter according to an embodiment of the present application;

[0038] Fig. 13 is a state diagram of a method for manufacturing a filter according to an embodiment of the present application.

[0039] Legend: 100 - filter; 110 - substrate; 111 - capacitance region; 112 - resonance region; 120 - capacitor; 121 - second lower electrode; 122 - dielectric layer; 123 - second upper electrode; 130 - resonance assembly; 131 - first lower electrode; 132 - piezoelectric layer; 133 - first upper electrode; 140 - acoustic reflection structure; 141 - cavity; 142 - recess; 150 - seating groove; 161 - conductive tab; 162 - ring wing; 164 - ring-shaped gap; 165 - sub-wing; 171 - sacrificial block. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions, and superiorities of the embodiments of the present application clearer, the following will be a clear and complete description of the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0042] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, thus, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0043] In the description of the present application, it should be noted that the terms "center", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the application is used, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second", "third" and the like are only configured to distinguish the description and cannot be understood as indicating or implying relative importance.

[0044] Before 4G communication technology and 4G communication technology, due to the relatively narrow width of the frequency band definition, according to the requirements of the radio frequency system, the selection of electromagnetic or acoustic filters can meet the performance requirements. But after entering the 5G, 6G and Wi-Fi 7 stage, the frequency band definition specification has undergone major changes, all frequency bands are defined as more than 500MHz of large bandwidth, and the frequency band spacing is gradually narrowed, and it is rigidly required to support filters with large bandwidth and high out-of-band suppression.

[0045] The embodiment of the present application provides a filter 100, as shown in FIG. 1 and FIG. 2, comprising a substrate 110, a resonant assembly 130 is arranged on the substrate 110, the resonant assembly 130 comprises a first lower electrode 131, a piezoelectric layer 132 and a first upper electrode 133 arranged in sequence, the upper surface of the piezoelectric layer 132 is recessed downward to form a mounting groove 150, the first upper electrode 133 comprises a conductive sheet 161 and a ring wing 162, the conductive sheet 161 is located at the groove bottom of the mounting groove 150, and the ring wing 162 is connected with the outer periphery of the conductive sheet 161 and extends to the piezoelectric layer 132 adjacent to the mounting groove 150.

[0046] The filter 100 provided by the embodiment of the present application works, and the resonant assembly 130 serves as a frequency selection device. Specifically, the resonant assembly 130 comprises the first upper electrode 133, the piezoelectric layer 132 and the first lower electrode 131, and the first upper electrode 133, the piezoelectric layer 132 and the first lower electrode 131 form a sandwich structure. The first upper electrode 133 and the first lower electrode 131 are respectively connected with two ends of an alternating current signal to generate an electric field between the first upper electrode 133 and the first lower electrode 131, and 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, the piezoelectric layer 132 produces mechanical deformation and generates a sound wave.

[0047] It can be understood that, according to the specific structural arrangement of the resonant assembly 130, only acoustic waves of a specific frequency can form a standing wave in the piezoelectric layer 132, and when the 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 realizing frequency selection of the resonant assembly 130.

[0048] The filter 100 of the embodiment of the present application, the upper surface of the piezoelectric layer 132 is concave downward to form a seating groove 150, and the first upper electrode 133 includes a conductive sheet 161 and a ring wing 162, wherein the conductive sheet 161 is located at the groove bottom of the seating groove 150, and the ring wing 162 is connected with the outer periphery of the conductive sheet 161 and extends to the piezoelectric layer 132 adjacent to the seating groove 150. The ring wing 162 includes a wing located on the conductive layer and a connecting ring connecting the wing and the conductive sheet 161. Since the conductive sheet 161 is arranged at the groove bottom of the seating groove 150, the thickness of the piezoelectric layer 132 at the position of the seating groove 150 is reduced, so as to reduce the thickness of the sandwich structure.

[0049] In operation of the resonant assembly 130, the part where the first upper electrode 133, the piezoelectric layer 132 and the normal projection of the first upper electrode 133 on the substrate 110 overlap is the effective resonant area 112, i.e. the working area of the resonant assembly 130. When the thickness of the sandwich structure is small, the high-frequency performance of the filter 100 is good. At the position where the piezoelectric layer 132 is not provided with the seating groove, the piezoelectric layer 132 has a relatively thick thickness, so as to have a relatively high mechanical strength. In addition, the first upper electrode 133 includes the ring wing 162 arranged on the conductive sheet 161, so that the ring wing 162 connects the piezoelectric layer 132 at the position where the seating groove is not arranged, and the conductive sheet 161 connects the piezoelectric layer 132 at the position where the seating groove is arranged, so that the first upper electrode 133 simultaneously connects the piezoelectric layer 132 at the position where the seating groove is not arranged and the piezoelectric layer 132 at the position where the seating groove is arranged, which can further improve the mechanical strength of the sandwich structure.

[0050] The seating groove 150 is formed by laying a relatively thick piezoelectric layer 132 and etching a preset area by an ion beam, so as to concave the preset area to form the seating groove 150. The ion beam etching can accurately control the etching depth and has good anisotropy, thereby realizing a vertical sidewall and a flat bottom wall, so that the flatness of the groove bottom of the seating groove 150 is high, and the thickness of the piezoelectric layer 132 at the effective resonant area 112 is relatively uniform, which can further improve the performance of the resonant assembly 130.

[0051] 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 the present application, for example, the substrate 110 can be a silicon substrate 110, a sapphire substrate 110, or the like. The material of the piezoelectric layer 132 can be aluminum nitride, or doped aluminum nitride, zinc oxide, lead zirconate titanate, lithium niobate, or the like. The materials of the first upper electrode 133 and the first lower electrode 131 can be the same or different, and both can be molybdenum Mo, gold Au, aluminum Al, copper Au, titanium Ti, tungsten Wu, or the like.

[0052] In addition, it can be understood that the filter 100 of the embodiments of the present application is one of hybrid filters 100, and there is more than one resonant component 130 on the substrate 110. Specifically, the resonant component 130 can include one or more, and can also include other electronic devices, such as a capacitor 120 and an inductor, or the like. Those skilled in the art can set it according to the actual situation, as long as it includes at least one resonant component 130.

[0053] It can also be understood that when the sound wave is reflected back and forth in the sandwich structure, a reflection structure is formed on both sides of the sandwich structure to avoid sound wave leakage, and a reflection interface is formed between the first upper electrode 133 and the air. In practical applications, an acoustic reflection structure 140 is usually formed between the substrate 110 and the first lower electrode 131, as shown in FIG. 1, to reflect the sound wave. The specific acoustic reflection structure 140 is not limited in the embodiments of the present application, for example, it can be an air cavity, and a reflection interface is formed between the air cavity and the first lower electrode 131.

[0054] The filter 100 provided by the present application comprises a substrate 110, the substrate 110 is provided with a resonant component 130, the resonant component 130 comprises a first lower electrode 131, a piezoelectric layer 132 and a first upper electrode 133 arranged in sequence, the upper surface of the piezoelectric layer 132 is downwardly recessed to form a seating groove 150, the first upper electrode 133 comprises a conductive sheet 161 and a ring wing 162, the conductive sheet 161 is located at the groove bottom of the seating groove 150, and the ring wing 162 is connected with the outer periphery of the conductive sheet 161 and extends to the piezoelectric layer 132 adjacent to the seating groove 150.

[0055] Since the conductive sheet 161 is arranged at the groove bottom of the seating groove 150, the upper surface of the piezoelectric layer 132 is downwardly recessed to form the seating groove 150, so that the thickness of the piezoelectric layer 132 at the position of the seating groove 150 is reduced, thereby reducing the thickness of the sandwich structure.

[0056] When the resonant assembly 130 is working, the first upper electrode 133, the piezoelectric layer 132 and the part of the first upper electrode 133 overlapping the normal projection of the substrate 110 are the effective resonant region 112, i.e. the working region of the resonant assembly 130. When the thickness of the sandwich structure is small, the high frequency performance of the filter 100 is good. At the position where the piezoelectric layer 132 is not provided with the mounting groove, the piezoelectric layer 132 has a relatively thick thickness, so that it has a relatively high mechanical strength.

[0057] In addition, the first upper electrode 133 includes the ring wing 162 provided on the conductive sheet 161, so that the ring wing 162 is connected to the piezoelectric layer 132 at the position where the mounting groove is not provided, and the conductive sheet 161 is connected to the piezoelectric layer 132 at the position where the mounting groove is provided. Thus, the first upper electrode 133 is connected to the piezoelectric layer 132 at the position where the mounting groove is not provided and the piezoelectric layer 132 at the position where the mounting groove is provided, so that the mechanical strength of the sandwich structure can be further improved. Therefore, the filter 100 of the present application can improve the mechanical performance of the sandwich structure without affecting the high frequency performance of the filter 100.

[0058] Optionally, as shown in FIG. 1 and FIG. 2, the ring wing 162 and the sidewall of the mounting groove 150 have a ring-shaped gap 164 therebetween.

[0059] In the actual use of the filter 100, the acoustic waves formed in the piezoelectric layer 132 not only exist in the direction along the layer level, but also exist in the direction along the surface of the piezoelectric layer 132. The ring-shaped gap 164 is formed between the ring wing 162 and the mounting groove 150 in the present application, so that the interface with air is formed at the outer periphery of the conductive sheet 161. The air and the conductive sheet 161 have different acoustic impedances, so that the reflection effect of the acoustic waves can be improved, thereby reducing the energy leakage and improving the Q value of the filter 100.

[0060] As known from the above, the ring wing 162 includes the wing on the conductive layer and the connecting ring connecting the wing and the conductive sheet 161. Since the conductive layer and the wing have a height difference, the connecting ring has a certain distance in height, so that the connecting ring can be vertically or beveled. When the connecting ring is beveled, the cross section of the ring-shaped gap 164 is triangular. When the connecting ring is vertical, the cross section of the ring-shaped gap 164 is rectangular.

[0061] In addition, in order to reduce the sharp discharge caused by the sharp part at the connecting part of the connecting ring and the wing, the side of the connecting part of the connecting ring and the wing away from the piezoelectric layer 132 is provided as an arc surface.

[0062] In an implementable manner of the present application, as shown in FIG. 3, the conductive sheet 161 is a polygon, and the ring wing 162 forms a sub-wing 165 corresponding to each side of the polygon. The sub-wing 165 protrudes outward to form an arc-shaped or irregular curved outer edge.

[0063] The conductive sheet 161 is set as a polygon, so that in the lateral propagation of the sound wave, the reflection direction of the sound wave is different for each side of the polygon, improving the reflection effect, and further improving the Q value of the filter 100. In addition, the sub-wing 165 is outwardly convex to form an arc-shaped or irregular curved outer edge, and the arc-shaped or irregular curved outer edge can improve the reflection effect and further improve the Q value.

[0064] Specifically, the shape of the polygon is not limited in the embodiments of the present application, and for example, can be a pentagon as shown in FIG. 3, or a hexagon or other shapes.

[0065] Optionally, as shown in FIG. 2, the sound reflection structure 140 is further formed between the substrate 110 and the lower electrode, and the sound reflection structure 140 is upwardly convex to make the first lower electrode 131, the piezoelectric layer 132 and the first upper electrode 133 upwardly curved.

[0066] The upward convexity of the sound reflection structure 140 makes the first lower electrode 131, the piezoelectric layer 132 and the first upper electrode 133 all upwardly curved, so that a step is formed at the edge of the effective resonance area 112, the step helps to reflect the sound wave, avoids the leakage of the sound wave outside the effective resonance area 112, and further improves the Q value of the filter 100.

[0067] In an implementable manner of the embodiments of the present application, as shown in FIGS. 4, 5 and 6, the filter 100 further includes a capacitor 120 disposed on the 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 area 111 for disposing the capacitor 120 and a resonance area 112 for disposing the resonance assembly 130, the resonance area 112 and the capacitor area 111 are adjacent, and the second upper electrode 123 and the first lower electrode 131 are of the same layer and the same material.

[0068] The embodiments of the present application set the first lower electrode 131 and the second upper electrode 123 as the same layer and the same material, that is, the first lower electrode 131 and the second upper electrode 123 are electrically connected, which reduces the connection path compared with the prior art technical solution of separately leading out the two ends of the capacitor 120 and the resonance assembly 130 and then connecting them. In addition, the same layer and the same material can increase the current flow area. The embodiments of the present application reduce the resistance of the capacitor 120 and the resistance connection through the two aspects of reducing the connection path and increasing the flow area, and improve the performance of the filter 100.

[0069] In the filter 100, the capacitor 120 and the resonant assembly 130 are connected in series and in parallel. 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 led out as a common terminal, and then the first upper electrode 133 and the second lower electrode 121 are respectively led out as two branch connection terminals; 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 respectively led out as series connection terminals.

[0070] Optionally, the dielectric layer 122 extends to the resonant region 112, and a portion of the dielectric layer 122 in the resonant region 112 is missing to form a cavity 141 between the substrate 110 and the first lower electrode 131. The cavity 141, the first lower electrode 131, the piezoelectric layer 132, and the conductive sheet 161 have an overlapping part in the orthographic projection on the substrate 110, and the overlapping part is the effective resonant region 112 of the resonant assembly 130.

[0071] In the embodiment of the present application, the dielectric layer 122 extends to the resonant region 112, and a portion of the dielectric layer 122 in the resonant region 112 is missing to form a cavity 141 as the acoustic reflection structure 140. In this way, the cavity 141 can be formed by wet etching after the first upper electrode 133 is prepared, and the size and position of the cavity 141 can be controlled by controlling the time of wet etching. Thus, compared with the cavity 141 formed by filling and releasing the sacrificial layer in the prior art, the process steps are simplified, and the preparation efficiency of the filter 100 is improved.

[0072] Specifically, the material of the dielectric layer is not limited in the embodiment of the present application, and examples can be silicon dioxide, silicon nitride, etc.

[0073] In an implementable manner of the embodiment of the present application, the upper surface of the substrate 110 corresponding to the cavity 141 is recessed downward to form a groove 142 in communication with the cavity 141, and the groove 142 and the cavity 141 serve as the acoustic reflection structure 140 of the resonant assembly 130.

[0074] When the depth of the cavity 141 does not meet the working requirements of the resonant assembly 130, a groove 142 can be formed on the upper surface of the substrate 110 corresponding to the cavity 141, and the groove 142 and the cavity 141 are in communication as the acoustic reflection structure 140 of the resonant assembly 130.

[0075] In another aspect of the embodiment of the present application, a preparation method of the filter 100 is provided, as shown in FIG. 7, comprising:

[0076] S10: as shown in FIGS. 8, 9 and 10, providing a substrate 110, and sequentially forming a first lower electrode 131 and a piezoelectric layer 132 on the substrate 110;

[0077] Specifically, the forming method of the lower electrode and the piezoelectric layer 132 on the substrate 110 is not limited in the embodiments of the present application, and can be physical vapor deposition, chemical vapor deposition, evaporation, or the like. Those skilled in the art can make a specific selection according to actual conditions.

[0078] The specific materials of the substrate 110 and the piezoelectric layer 132 are the same as those of the filter 100, and will not be described herein.

[0079] S20: As shown in FIG. 11, the upper surface of the piezoelectric layer 132 is etched to form a mounting groove 150 and a sacrifice block 171 is formed at the sidewall of the mounting groove 150;

[0080] Specifically, the sacrifice block 171 can be placed in the mounting groove 150 as a finished product, or the sacrifice block 171 can be formed by depositing a sacrifice material and etching.

[0081] S30: As shown in FIG. 12, a first upper electrode 133 is formed on the piezoelectric layer 132 in the mounting groove 150 and at the edge of the mounting groove 150, and the first upper electrode 133 includes a conductive sheet 161 and a ring wing 162, the conductive sheet 161 is located at the bottom of the mounting groove 150, and the ring wing 162 is connected to the outer periphery of the conductive sheet 161 and extends to the piezoelectric layer 132 adjacent to the mounting groove 150;

[0082] When the first upper electrode 133 is formed, the ring wing 162 covers the upper surface of the sacrifice block 171. The upper electrode is arranged in the mounting groove 150, which reduces the thickness of the sandwich structure and improves the high-frequency performance of the filter 100; at the position where the mounting groove is not arranged on the piezoelectric layer 132, the piezoelectric layer 132 has a relatively thick thickness, so that it has a relatively high mechanical strength.

[0083] In addition, the first upper electrode 133 includes the ring wing 162 arranged on the conductive sheet 161, and the ring wing 162 is connected to the piezoelectric layer 132 at the position where the mounting groove is not arranged, and the conductive sheet 161 is connected to the piezoelectric layer 132 at the position where the mounting groove is arranged, so that the first upper electrode 133 is connected to the piezoelectric layer 132 at the position where the mounting groove is not arranged and the piezoelectric layer 132 at the position where the mounting groove is arranged, which can further improve the mechanical strength of the sandwich structure.

[0084] S40: As shown in FIG. 13, the sacrifice block 171 is released to form a ring-shaped gap 164.

[0085] Optionally, the substrate 110 is provided, and the first lower electrode 131 and the piezoelectric layer 132 are sequentially formed on the substrate 110, which includes:

[0086] S11: As shown in FIG. 9, a second lower electrode 121 and a dielectric layer 122 are sequentially formed on a substrate 110, and the substrate 110 includes a capacitor area 111 where the second lower electrode 121 is arranged and a resonance area 112 where the first lower electrode 131 is arranged;

[0087] S12: As shown in FIG. 9, the first lower electrode 131 is formed on the substrate 110, and the first lower electrode 131 extends onto the dielectric layer 122 as the second upper electrode 123. The second upper electrode 123, the dielectric layer 122 and the second lower electrode 121 form the capacitor 120.

[0088] The first lower electrode 131 extends onto the dielectric layer 122 as the second upper electrode 123, so that the first lower electrode 131 and the second upper electrode 123 are arranged in the same layer and are made of the same material, that is, the first lower electrode 131 and the second upper electrode 123 are electrically connected.

[0089] Compared with the prior art in which the two ends of the capacitor 120 and the resonant assembly 130 are respectively led out and then connected, the connection path is reduced. In addition, the same layer and the same material are arranged, which can increase the current flow area. The present application embodiment reduces the resistance of the capacitor 120 and the resistance connection through the two aspects of reducing the connection path and increasing the flow area, and improves the performance of the filter 100.

[0090] S13: As shown in FIG. 10, the piezoelectric layer 132 is formed on the first lower electrode 131.

[0091] In an implementable manner of the present application, before the second lower electrode 121 and the dielectric layer 122 are sequentially formed on the substrate 110, the method comprises:

[0092] S01: Forming a groove 142 on the resonant region 112 of the substrate 110 and filling a sacrificial layer in the groove 142. 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.

[0093] S02: Releasing the sacrificial layer after forming the first upper electrode 133.

[0094] When the upper surface of the sacrificial layer is parallel to the upper surface of the substrate 110, the sacrificial layer is released, and the structure is as shown in FIG. 6.

[0095] When the upper surface of the sacrificial layer protrudes from the upper surface of the substrate 110, the sacrificial layer is released, and the structure is as shown in FIG. 2. The first lower electrode 131, the piezoelectric layer 132 and the first upper electrode 133 are bent upward, which can avoid the leakage of sound waves outside the effective resonant region 112, and further improve the Q value of the filter 100.

[0096] In the preparation method of the filter 100, the specific structure and beneficial effects are described in the description of the embodiment of the filter 100, and are not described here.

[0097] The above descriptions are merely some embodiments of the present application, but shall not be configured to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. Industrial applicability

[0098] In summary, the present application provides a filter and a preparation method thereof, which can improve the mechanical properties of the sandwich layered structure without affecting the high-frequency performance of the filter.

Claims

1. A filter, characterized by, The resonant assembly comprises a first lower electrode, a piezoelectric layer and a first upper electrode arranged in sequence, the upper surface of the piezoelectric layer is concave downward to form a setting groove, the first upper electrode comprises a conductive sheet and a ring wing, the conductive sheet is located at the bottom of the setting groove, and the ring wing is connected with the outer periphery of the conductive sheet and extends to the piezoelectric layer adjacent to the setting groove.

2. The filter of claim 1, wherein, The ring wing and the side wall of the setting groove have an annular gap.

3. The filter according to claim 1 or 2, characterized in that, The ring wing comprises a wing on a conductive layer and a connecting ring, and the wing and the conductive sheet are connected through the connecting ring.

4. The filter of claim 3, wherein, The conductive layer and the wing have a height difference; the connecting ring is inclined or vertical, when the connecting ring is inclined, the cross section of the annular gap is triangular, and when the connecting ring is vertical, the cross section of the annular gap is rectangular.

5. The filter according to claim 3 or 4, characterized in that, The connecting ring is arranged as an arc surface away from one side of the piezoelectric layer.

6. The filter according to any one of claims 1-5, characterized in that, The conductive sheet is polygonal, the ring wing forms a sub wing corresponding to each side of the polygon, the sub wing protrudes outward to form an arc-shaped or irregular curved outer edge.

7. The filter according to any one of claims 1-6, characterized in that, The substrate and the lower electrode further form an acoustic reflection structure, the acoustic reflection structure protrudes upward to make the first lower electrode, the piezoelectric layer and the first upper electrode bend upward.

8. The filter according to any one of claims 1-7, characterized in that, Further comprising a capacitor arranged on the substrate, the capacitor comprises a second lower electrode, a dielectric layer and a second upper electrode, the substrate comprises a capacitor area for arranging the capacitor and a resonant area for arranging the resonant assembly, the resonant area and the capacitor area are adjacent, and the second upper electrode and the first lower electrode are the same layer and the same material.

9. The filter of claim 8, wherein, The dielectric layer extends to the resonant area and is located between the first lower electrode and the substrate, the part of the dielectric layer in the resonant area is missing to form a cavity between the substrate and the first lower electrode, the orthographic projection of the cavity, the first lower electrode, the piezoelectric layer and the conductive sheet on the substrate has an overlapping part, and the overlapping part is the effective resonant area of the resonant assembly.

10. The filter of claim 9, wherein, The upper surface of the substrate corresponding to the cavity is concave downward to form a groove in communication with the cavity, and the groove and the cavity serve as the acoustic reflection structure of the resonant assembly.

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

12. The filter according to any one of claims 8-11, characterized in that, The capacitor and the resonant assembly comprise series and parallel connection, when the capacitor and the resonant assembly are in parallel connection, the first lower electrode and the second upper electrode are led out as a common terminal, and the first upper electrode and the second lower electrode are respectively led out as two branch connection terminals; when the capacitor and the resonant assembly are in series connection, the first upper electrode and the second lower electrode are respectively led out as the leading ends of the series connection structure.

13. A method of making a filter, characterized by, The method comprises: 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 setting groove and forming a sacrifice block at the side wall of the setting groove; A first upper electrode is formed on the piezoelectric layer in the seating groove and on the edge of the seating groove, the first upper electrode comprising a conductive sheet on the bottom of the seating groove and a ring wing connected to the outer periphery of the conductive sheet and extending onto the piezoelectric layer adjacent to the seating groove; The sacrificial layer is released to form an annular gap.

14. The method of claim 13, wherein the filter is prepared by a method comprising: The providing of the substrate and sequentially forming a first lower electrode and a piezoelectric layer on the substrate comprises: Sequentially forming a second lower electrode and a dielectric layer on the substrate, the substrate comprising a capacitive region where the second lower electrode is arranged and a resonant region where the first lower electrode is arranged; A first lower electrode is formed on the substrate, the first lower electrode extending onto the dielectric layer as a second upper electrode, the second upper electrode, the dielectric layer and the second lower electrode forming a capacitor; A piezoelectric layer is formed on the first lower electrode.

15. The method of claim 14, wherein the filter is prepared by a method comprising: The sequentially forming a second lower electrode and a dielectric layer on the substrate comprises: A groove is formed on the resonant region of the substrate and a sacrificial layer is filled in the groove, the upper surface of the sacrificial layer being parallel to or protruding from the upper surface of the substrate; The sacrificial layer is released after the first upper electrode is formed.

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