A film bulk acoustic resonator and a method of manufacturing the same

Abstract

The application discloses a film bulk acoustic resonator and a preparation method thereof, and relates to the technical field of resonators, and the film bulk acoustic resonator comprises a substrate, a bottom electrode layer, a piezoelectric layer and a top electrode layer which are sequentially arranged on the substrate, wherein the piezoelectric layer is provided with a groove, the bottom electrode layer and the top electrode layer are respectively formed into a bottom electrode pattern and a top electrode pattern through patterning, the overlapping area of the bottom electrode pattern, the piezoelectric layer and the top electrode pattern in the stacking direction serves as a resonant area, and the groove is arranged around the outer edge of the resonant area. The film bulk acoustic resonator and the preparation method thereof can effectively improve the Q value of the resonator under the condition that the machining precision requirement is low.

Description

Technical Field

[0001] This invention relates to the field of resonator technology, and more specifically, to a thin-film bulk acoustic resonator and its fabrication method. Background Technology

[0002] Due to the continuity of the piezoelectric layer material, thin-film bulk acoustic resonators will inevitably generate transverse vibrations in addition to longitudinal vibrations during operation. The transverse vibrations will transfer some energy to the transverse acoustic waves, causing energy loss from the longitudinal vibrations and reducing the performance of the device.

[0003] The current solution is to form a transverse acoustic impedance structure by depositing different materials around the resonator, or to create a transverse acoustic impedance mismatch by setting grooves around the resonator, thereby limiting the leakage of transverse sound waves.

[0004] However, accurately controlling the thickness and width of the transverse acoustic impedance material places high demands on the processing, and the dimensional errors caused by processing will also greatly affect the performance of the transverse acoustic impedance structure. Summary of the Invention

[0005] The purpose of this invention is to provide a thin-film bulk acoustic resonator and its fabrication method, which can effectively improve the Q value of the resonator under conditions where the processing precision requirements are low.

[0006] The embodiments of the present invention are implemented as follows:

[0007] In one aspect of the present invention, a thin-film bulk acoustic resonator is provided, comprising a substrate and a bottom electrode layer, a piezoelectric layer and a top electrode layer sequentially disposed on the substrate, wherein the piezoelectric layer is provided with a groove, the bottom electrode layer and the top electrode layer are respectively patterned to form a bottom electrode pattern and a top electrode pattern, the overlapping area of ​​the bottom electrode pattern, the piezoelectric layer and the top electrode pattern in the stacking direction serves as a resonant region, and the groove surrounds the outer edge of the resonant region.

[0008] As one possible implementation, the groove is an annular groove, and at least one annular groove is provided around the outer edge of the resonant region. When there are multiple annular grooves, the multiple annular grooves are arranged concentrically, and the depth of the annular groove located on the inner side is greater than the depth of the annular groove located on the outer side.

[0009] As one feasible approach, when there are multiple annular grooves, adjacent annular grooves are interconnected to form a stepped groove.

[0010] As one possible implementation, the groove is an arc-shaped groove, with at least two arc-shaped grooves arranged around the outer edge of the resonant region in the same radial direction, the at least two arc-shaped grooves being spaced apart, and the at least two arc-shaped grooves being connected end to end in sequence to form a closed structure; or, the groove is a polygonal groove, with at least two polygonal grooves arranged around the outer edge of the resonant region in the same radial direction, the at least two polygonal grooves being spaced apart, and the at least two polygonal grooves being connected end to end in sequence to form a closed structure.

[0011] As one possible approach, when the groove is an arc-shaped groove and the number of arc-shaped grooves is multiple segments, adjacent segments of the arc-shaped grooves are arranged at unequal intervals; or, when the groove is a polygonal groove and the number of polygonal grooves is multiple segments, adjacent segments of the polygonal grooves are arranged at unequal intervals.

[0012] As one possible approach, at least two grooves arranged in the same radial direction around the outer edge of the resonant region constitute a groove group, and at least one groove group is arranged in different radial directions around the outer edge of the resonant region. When there are multiple groove groups, the multiple groove groups are arranged concentrically, and the depth of the groove in the inner groove group is greater than the depth of the groove in the outer groove group.

[0013] As one possible approach, when there are multiple sets of grooves, the grooves of two adjacent sets of grooves are interconnected to form a stepped groove.

[0014] As one possible implementation, the inner edge of the groove coincides with the outer edge of the resonant region.

[0015] In another aspect of the present invention, a method for fabricating a thin-film bulk acoustic resonator is provided, comprising: forming a bottom electrode layer on a substrate, and patterning the bottom electrode layer to form a bottom electrode pattern; forming a piezoelectric layer on the substrate on which the bottom electrode pattern is formed; covering the piezoelectric layer with photoresist, and etching the area of ​​the piezoelectric layer not covered by the photoresist by an ion beam to form a groove, depositing a sacrificial layer in the groove, and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer; forming a top electrode layer on the piezoelectric layer on which the sacrificial layer is deposited, and patterning the top electrode layer to form a top electrode pattern, wherein the overlapping area of ​​the bottom electrode pattern, the piezoelectric layer, and the top electrode pattern in the stacking direction serves as a resonant region; and releasing the sacrificial layer to form a cavity in the groove, wherein the groove surrounds the resonant region.

[0016] As one possible implementation, the step of covering the piezoelectric layer with photoresist and etching the area of ​​the piezoelectric layer not covered by the photoresist with an ion beam to form a groove, depositing a sacrificial layer in the groove, and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer includes: covering the piezoelectric layer with photoresist and etching the area of ​​the piezoelectric layer not covered by the photoresist with an ion beam to form a first sub-groove; covering the piezoelectric layer with photoresist formed on the piezoelectric layer and etching the area of ​​the piezoelectric layer not covered by the photoresist with an ion beam to form a second sub-groove, wherein the first sub-groove and the second sub-groove are concentrically arranged, the depth of the first sub-groove located on the inner side is greater than the depth of the second sub-groove located on the outer side, and the first sub-groove and the second sub-groove are interconnected to form a groove; depositing a sacrificial layer in the groove and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer.

[0017] The beneficial effects of the embodiments of the present invention include:

[0018] This thin-film bulk acoustic wave resonator includes a substrate and a bottom electrode layer, a piezoelectric layer, and a top electrode layer sequentially disposed on the substrate. The piezoelectric layer has a groove. The bottom electrode layer and the top electrode layer are patterned to form bottom electrode patterns and top electrode patterns, respectively. The overlapping area of ​​the bottom electrode pattern, the piezoelectric layer, and the top electrode pattern in the stacking direction serves as the resonant region. The groove surrounds the outer edge of the resonant region. Compared to placing the groove around the resonator or on other layer structures, such as placing the groove on the bottom electrode, which requires additional processing steps and creates boundary acoustic impedance mismatch conditions, thus affecting the quality of the piezoelectric layer film growth, the thin-film bulk acoustic wave resonator provided in this application, because the groove is directly disposed on the piezoelectric layer, does not affect the quality of the piezoelectric layer film growth. Furthermore, when the acoustic signal propagates along the surface of the piezoelectric layer, it can effectively reflect the acoustic signal, thereby significantly suppressing the lateral propagation of the acoustic signal and improving the Q value of the thin-film bulk acoustic wave resonator. Furthermore, the thickness of the groove can be designed and processed according to the thickness of the piezoelectric layer, and the width of the groove can be designed and processed according to the outer edge of the resonant region. It has the advantages of hierarchical structure and simple preparation method, which makes it easy to achieve under the current conditions where the processing accuracy requirements are low. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1This is one of the structural schematic diagrams of a thin-film bulk acoustic resonator provided in an embodiment of the present invention;

[0021] Figure 2 This is a second schematic diagram of the structure of a thin-film bulk acoustic resonator provided in an embodiment of the present invention;

[0022] Figure 3 One of the structural schematic diagrams of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0023] Figure 4 This is a second schematic diagram of the structure of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0024] Figure 5 This is one of the fabrication state diagrams of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0025] Figure 6 The second fabrication state diagram of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0026] Figure 7 The third fabrication state diagram of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0027] Figure 8 Figure 4 shows the fabrication state of a thin-film bulk acoustic resonator provided in another embodiment of the present invention.

[0028] Figure 9 Fifth diagram showing the fabrication state of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0029] Figure 10 Sixth diagram showing the fabrication state of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0030] Figure 11 This is a schematic diagram of the structure of a thin-film bulk acoustic resonator provided in another embodiment of the present invention;

[0031] Figure 12 This is a schematic diagram of the structure of a thin-film bulk acoustic resonator provided in another embodiment of the present invention.

[0032] Icons: 100 - Thin-film bulk acoustic resonator; 10 - Substrate; 11 - Acoustic reflection cavity; 20 - Seed layer; 30 - Bottom electrode layer; 40 - Piezoelectric layer; 41 - Groove; 50 - Top electrode layer. Detailed Implementation

[0033] The embodiments described below represent the information necessary for those skilled in the art to practice the embodiments and illustrate the best mode for practicing the embodiments. After reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of this disclosure and will recognize the application of these concepts not specifically set forth herein. It should be understood that these concepts and applications fall within the scope of this disclosure and the appended claims.

[0034] It should be understood that while the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0035] It should be understood that when an element (such as a layer, region, or substrate) is referred to as "on another element" or "extending to another element," it may be directly on or directly extended to the other element, or there may be an intermediate element. Conversely, when an element is referred to as "directly on another element" or "directly extending to another element," there is no intermediate element. Similarly, it should be understood that when an element (such as a layer, region, or substrate) is referred to as "above another element" or "extending above another element," it may be directly on or directly extended to the other element, or there may be an intermediate element. Conversely, when an element is referred to as "directly on another element" or "extending directly to another element," there is no intermediate element. It should also be understood that when an element is referred to as "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be an intermediate element. Conversely, when an element is referred to as "directly connected" or "directly coupled" to another element, there is no intermediate element.

[0036] Related terms such as “below”, “above”, “upper”, “lower”, “horizontal”, or “vertical” are used in this document to describe the relationship between one element, layer, or region and another element, layer, or region, as shown in the figure.

[0037] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that, when used herein, the term “comprising” indicates the presence of the stated feature, integer, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups of the foregoing.

[0038] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that the terms used herein should be interpreted as having the same meaning as they would in the context of this specification and the relevant field, and not in an idealized or overly formal sense, unless expressly defined herein.

[0039] In the prior art, in order to limit the leakage of transverse acoustic waves, a transverse acoustic impedance structure is generally formed around the resonator by depositing different materials, or a transverse acoustic impedance mismatch is formed around the resonator by setting grooves. However, accurately controlling the thickness and width of the transverse acoustic impedance material places high demands on the processing, and the dimensional errors caused by the processing will also greatly affect the effect of the transverse acoustic impedance structure.

[0040] To address the aforementioned issues, this application provides a thin-film bulk acoustic resonator 100 and its fabrication method, which can effectively improve the Q value of the resonator even with low requirements for processing precision.

[0041] Please refer to the reference. Figures 1 to 4 In one aspect of this application, a thin-film bulk acoustic resonator 100 is provided, including a substrate 10 and a bottom electrode layer 30, a piezoelectric layer 40 and a top electrode layer 50 sequentially disposed on the substrate 10. The piezoelectric layer 40 is provided with a groove 41. The bottom electrode layer 30 and the top electrode layer 50 are respectively patterned to form a bottom electrode pattern and a top electrode pattern. The overlapping area of ​​the bottom electrode pattern, the piezoelectric layer 40 and the top electrode pattern in the stacking direction serves as the resonant area. The groove 41 surrounds the outer edge of the resonant area.

[0042] Among them, such as Figure 1 and Figure 3As shown, an acoustic reflection cavity 11 should be provided on the substrate 10 to allow acoustic wave signals to propagate along the surface of the piezoelectric layer 40 and achieve the conversion between mechanical energy and electrical energy based on the piezoelectric effect. Regarding the actual shape of the acoustic reflection cavity 11, those skilled in the art should be able to make reasonable selections and designs according to actual conditions; no specific limitations are made here. For example, the cross-sectional shape of the acoustic reflection cavity 11 can be a regular shape such as rectangular, circular, or elliptical. Figure 2 and Figure 4 As shown, it can also be other irregular shapes.

[0043] like Figures 1 to 4 As shown, a bottom electrode layer 30, a piezoelectric layer 40, and a top electrode layer 50 are sequentially disposed on the substrate 10. The piezoelectric layer 40 has a groove 41 surrounding the outer edge of the resonant region. Compared to placing the groove 41 around the resonator or on other layer structures, such as on the bottom electrode, which requires additional processing steps and creates boundary acoustic impedance mismatch, thus affecting the quality of the piezoelectric layer 40 film growth, the thin-film bulk acoustic resonator 100 provided in this application, because the groove 41 is directly disposed on the piezoelectric layer 40, does not affect the quality of the piezoelectric layer 40 film growth. Furthermore, when the acoustic signal propagates along the surface of the piezoelectric layer 40, it can effectively reflect the acoustic signal, thereby significantly suppressing the lateral propagation of the acoustic signal and improving the Q value of the thin-film bulk acoustic resonator 100. Furthermore, the thickness of the groove 41 can be designed and processed according to the thickness of the piezoelectric layer 40, and the width of the groove 41 can be designed and processed according to the outer edge of the resonant region. It has the advantages of hierarchical structure and simple preparation method, which makes it easy to achieve under the current conditions where the processing accuracy requirements are low.

[0044] For example, in one possible implementation of this embodiment, an acoustic reflection cavity 11 can be formed on a substrate 10 first, then a bottom electrode layer 30 can be formed on the substrate 10 with the acoustic reflection cavity 11, and the bottom electrode layer 30 can be patterned to form a bottom electrode pattern. Next, a piezoelectric layer 40 can be formed on the substrate 10 with the bottom electrode pattern, then a groove 41 can be formed on the piezoelectric layer 40 by etching, a sacrificial layer can be deposited in the groove 41, and the sacrificial layer can be ground until it is flush with the surface of the piezoelectric layer 40. Then, a top electrode layer 50 can be formed on the piezoelectric layer 40 with the deposited sacrificial layer, and the top electrode layer 50 can be patterned to form a top electrode pattern. Finally, the sacrificial layer can be released to form a cavity in the groove 41. In this way, the air in the groove 41 can form an air wall structure. When an acoustic signal propagates along the surface of the piezoelectric layer 40 to the air wall structure, the air wall structure can reflect the acoustic signal, allowing the acoustic signal to be received by the output electrode, thereby increasing the acoustic signal received by the output electrode and thus improving the Q value of the thin-film bulk acoustic resonator 100.

[0045] For example, in another possible implementation of the present invention, an acoustic reflection cavity 11 can be formed on a substrate 10 first, then a bottom electrode layer 30 can be formed on the substrate 10 with the acoustic reflection cavity 11, and the bottom electrode layer 30 can be patterned to form a bottom electrode pattern. A piezoelectric layer 40 can then be formed on the substrate 10 with the bottom electrode pattern, and a groove 41 can be formed on the piezoelectric layer 40 by etching. An acoustic impedance material is deposited in the groove 41 and ground until it is flush with the surface of the piezoelectric layer 40. Then, a top electrode layer 50 is formed on the piezoelectric layer 40 with the deposited acoustic impedance material, and the top electrode layer 50 can be patterned to form a top electrode pattern. In this way, the acoustic impedance material in the groove 41 can form an acoustic impedance structure. When an acoustic wave signal propagates along the surface of the piezoelectric layer 40 to the acoustic impedance structure, the acoustic impedance structure can reflect the acoustic wave signal so that the acoustic wave signal can be received by the output electrode, thereby increasing the acoustic wave signal received by the output electrode and thus improving the Q value of the thin-film bulk acoustic resonator 100.

[0046] Of the two methods described above, the method of reflecting sound waves using an air wall structure is easier to implement than the method of reflecting sound waves using an acoustic impedance structure, as it eliminates the need to consider the specific selection and deposition process of the acoustic impedance material. Regarding the fabrication method of the thin-film bulk acoustic resonator 100 provided in this application, those skilled in the art should be able to make reasonable selections and designs based on actual circumstances; no specific limitations are imposed here. In some embodiments below, the method of reflecting sound waves using an air wall structure will be used for further explanation and illustration, but this is not intended to be limiting.

[0047] For example, such as Figures 1 to 4 As shown, in one possible embodiment of the present invention, the groove 41 is an annular groove, and at least one annular groove is provided around the outer edge of the resonant region, such as... Figure 3 and Figure 4 As shown, when there are multiple annular grooves, the multiple annular grooves are arranged concentrically, and the depth of the annular groove located on the inner side is greater than the depth of the annular groove located on the outer side.

[0048] It should be noted that the groove 41 can be an annular groove. Since an annular groove itself has a closed structure, it can be directly and entirely surrounded around the outer edge of the resonant region, depending on the shape and size of the outer edge. The actual shape of the annular groove can be any closed structure, such as rectangular, circular, or elliptical, as long as the shape of the annular groove matches the shape of the outer edge of the resonant region. There should be at least one annular groove. The more annular grooves there are, the better the reflection effect on the lateral propagation of the acoustic signal. However, the number of annular grooves should not be too large to avoid making the thin-film bulk acoustic resonator 100 too large. Those skilled in the art should be able to make a reasonable selection and design based on the actual situation regarding the actual number of annular grooves; no specific restrictions are imposed here.

[0049] When there are multiple annular grooves, they are arranged concentrically, and the circumference of the inner annular groove should be smaller than that of the outer annular groove to avoid mutual interference between the multiple annular grooves. Since when the sound wave signal propagates along the surface of the piezoelectric layer 40, it will first propagate to the air wall structure formed by the air in the inner annular groove, and then propagate to the air wall structure formed by the air in the outer annular groove, the depth of the inner annular groove should be greater than that of the outer annular groove, so that the sound wave signal is reflected as completely as possible when it propagates to the air wall structure formed by the air in the inner annular groove.

[0050] In one possible implementation of this invention, such as Figure 3 and Figure 4 As shown, when there are multiple annular grooves, adjacent annular grooves are interconnected to form stepped grooves. Of course, in other possible implementations of this invention, adjacent annular grooves may not be interconnected. Those skilled in the art should be able to make reasonable choices and designs based on actual circumstances, and no specific limitations are imposed here.

[0051] For example, such as Figure 11 and Figure 12 As shown, in another possible embodiment of the present invention, the groove 41 is an arc-shaped groove, and at least two arc-shaped grooves are arranged around the outer edge of the resonant region in the same radial direction. The at least two arc-shaped grooves are arranged at intervals, and the at least two arc-shaped grooves can be connected end to end in sequence to form a closed structure.

[0052] It should be noted that the groove 41 can be an arc-shaped groove. Since the arc-shaped groove itself does not have the characteristic of a closed structure, the number of arc-shaped grooves on the same radial direction of the outer edge of the resonant region should be at least two segments. The at least two segments of arc-shaped grooves are arranged at intervals, and the at least two segments of arc-shaped grooves are respectively arranged around the outer edge of the resonant region. The at least two segments of arc-shaped grooves can be connected end to end in sequence to form a closed structure, so as to cooperate with each other to reflect and suppress the lateral propagation of the sound wave signal.

[0053] Similar to the arc-shaped groove, in other possible embodiments of the present invention, the groove 41 is a polygonal groove, with at least two polygonal grooves arranged around the outer edge of the resonant region in the same radial (or circumferential) direction. The at least two polygonal grooves are spaced apart, and the at least two polygonal grooves can be connected end to end in sequence to form a closed structure.

[0054] It should be noted that the groove 41 can also be a polygonal groove. Here, a polygonal groove refers to a polygonal groove that does not have a closed structure. Therefore, on the same circumference of the outer edge of the resonant region, there should be at least two polygonal grooves. The at least two polygonal grooves are arranged at intervals. The at least two polygonal grooves are arranged around the outer edge of the resonant region. The at least two polygonal grooves can be connected end to end in sequence to form a closed structure, so as to cooperate with each other to reflect and suppress the lateral propagation of the sound wave signal.

[0055] Of the three possible implementation methods described above, when the outer edge of the resonant region has a relatively regular shape, the groove 41 can be designed as an annular groove to improve the reflection effect of the groove 41 on the lateral propagation of the sound wave signal. When the outer edge of the resonant region has an overly irregular shape, the groove 41 can be designed as an arc-shaped groove or a polygonal groove to reduce the processing difficulty of the groove 41. Regarding the actual selection of the groove 41, those skilled in the art should be able to make a reasonable selection and design based on the actual situation, and no specific restrictions are imposed here.

[0056] In another possible implementation of the present invention, such as Figure 11 and Figure 12 As shown, when the groove 41 is an arc-shaped groove and there are multiple segments of arc-shaped grooves, adjacent segments of arc-shaped grooves are arranged at unequal intervals; when the groove 41 is a polygonal groove and there are multiple segments of polygonal grooves, adjacent segments of polygonal grooves are arranged at unequal intervals. For example, they can be arranged more densely in the direction where the sound wave signal propagates laterally, and more sparsely in the direction where the sound wave signal propagates laterally. Of course, in other possible implementations of this invention, the actual spacing between adjacent segments of arc-shaped grooves and adjacent segments of polygonal grooves can also be equal. Those skilled in the art should be able to make reasonable selections and designs according to actual conditions, and no specific limitations are made here.

[0057] In another possible implementation of the present invention, such as Figure 11 and Figure 12 As shown, at least two grooves 41 arranged in the same radial direction around the outer edge of the resonant region constitute a groove group, and at least one groove group is arranged in different radial directions around the outer edge of the resonant region, such as... Figure 12 As shown, when there are multiple sets of grooves, the multiple sets of grooves are arranged concentrically, and the depth of the groove 41 in the inner groove set is greater than the depth of the groove 41 in the outer groove set.

[0058] Similar to the annular groove, the number of groove groups should be at least one. The more groove groups there are, the better the reflection effect on the lateral propagation of the sound wave signal. However, the number of groove groups should not be too large to avoid the volume of the thin-film bulk acoustic resonator 100 being too large. Regarding the actual number of groove groups, those skilled in the art should be able to make reasonable selections and designs based on the actual situation, and no specific restrictions are made here. When there are multiple groove groups, the multiple groove groups are arranged concentrically, and the perimeter of the closed structure formed by the inner groove group should be smaller than the perimeter of the closed structure formed by the outer groove group to avoid mutual interference between multiple groove groups. Since when the sound wave signal propagates along the surface of the piezoelectric layer 40, it will first propagate to the air wall structure formed by the air in the inner groove group, and then propagate to the air wall structure formed by the air in the outer groove group, the depth of the groove 41 in the inner groove group is greater than the depth of the groove 41 in the outer groove group, so as to reflect the sound wave signal completely as much as possible when it propagates to the air wall structure formed by the air in the inner groove group.

[0059] In another possible implementation of the present invention, such as Figure 12 As shown, when there are multiple sets of grooves, the grooves 41 of two adjacent sets of grooves are interconnected to form a stepped groove. Of course, in other possible embodiments of the present invention, the grooves 41 of two adjacent sets of grooves may not be interconnected. Those skilled in the art should be able to make reasonable selections and designs according to actual conditions, and no specific limitations are made here.

[0060] In addition, it should be noted that when there are multiple sets of grooves, the grooves 41 of two adjacent sets of grooves can correspond to each other or be staggered. Compared with the corresponding arrangement, in the staggered arrangement, the grooves 41 of one set of grooves can reflect the sound wave signal leaking between the two adjacent grooves of another set of grooves, so as to improve the reflection effect of the grooves 41 on the lateral propagation of the sound wave signal when the grooves 41 are arc-shaped grooves or polygonal grooves.

[0061] In one possible implementation of this invention, such as Figure 1 and Figure 3As shown, the inner edge of the groove 41 coincides with the outer edge of the resonant region. Of course, in other possible embodiments of the present invention, the inner edge of the groove 41 may not coincide with the outer edge of the resonant region, that is, there may be a certain distance between the inner edge of the groove 41 and the outer edge of the resonant region. Those skilled in the art should be able to make reasonable selections and designs according to actual conditions, and no specific limitations are made here. It is worth noting that when the inner edge of the groove 41 does not coincide with the outer edge of the resonant region, the distance between any point on the inner edge of the groove 41 and the corresponding position on the outer edge of the resonant region may be equal or unequal.

[0062] In one possible embodiment of the present invention, the angle between the extension line of the outer edge of the groove 41 in the stacking direction and the horizontal direction is between 30° and 90°, so as to maximize the propagation effect of the acoustic signal along the surface of the piezoelectric layer 40, thereby effectively improving the Q value of the resonator.

[0063] Please refer to the reference. Figures 5 to 10 In another aspect of this application, a method for fabricating a thin-film bulk acoustic resonator 100 is provided, comprising:

[0064] S110, A bottom electrode layer 30 is formed on the substrate 10, and the bottom electrode layer 30 is patterned to form a bottom electrode pattern;

[0065] It should be noted that in the actual manufacturing process, an acoustic reflection cavity 11 should be provided on the substrate 10 so that the acoustic wave signal can propagate along the surface of the piezoelectric layer 40 and achieve the conversion between mechanical energy and electrical energy based on the piezoelectric effect. This can be achieved by first forming a groove on the substrate 10, then depositing a sacrificial layer in the groove until it is flush with the surface of the substrate 10, and then forming a bottom electrode layer 30 on the substrate 10 with the sacrificial layer deposited.

[0066] In addition, a seed layer 20 may be provided on the substrate 10. This can be achieved by first forming a trench on the substrate 10, then depositing a sacrificial layer in the trench until it is flush with the surface of the substrate 10, and then sequentially forming the seed layer 20 and the bottom electrode layer 30 on the substrate 10 with the sacrificial layer deposited. This provides effective support for the bottom electrode layer 30, the piezoelectric layer 40 and the top electrode layer 50 through the seed layer 20, so that the bottom electrode layer 30, the piezoelectric layer 40 and the top electrode layer 50 can grow better.

[0067] S210. A piezoelectric layer 40 is formed on a substrate 10 on which a bottom electrode pattern is formed;

[0068] S310. Photoresist is covered on the piezoelectric layer 40, and the area of ​​the piezoelectric layer 40 not covered by photoresist is etched by ion beam to form a groove 41. A sacrificial layer is deposited in the groove 41 and the sacrificial layer is polished to be flush with the surface of the piezoelectric layer 40.

[0069] It should be noted that ion beam etching, also known as ion milling, refers to the process where, when directed high-energy ions bombard a solid target, energy is transferred from the incident ions to the atoms on the solid surface. If the binding energy between the atoms on the solid surface is lower than the energy of the incident ions, the atoms on the solid surface will be removed or eliminated from the surface. Typically, the ions used in ion beam etching are derived from inert gases, such as argon. In actual manufacturing processes, argon gas can be ionized into positively charged argon ions (Ar...). + Argon ions (Ar) + After focusing and acceleration, the material impacts the wafer surface, removing atoms from the areas of the piezoelectric layer 40 not covered by photoresist, thus forming grooves 41 on the wafer surface. This process is based on argon ions (Ar... + The etching rate and etching time of the piezoelectric layer 40 can accurately control the etching depth of the groove 41. Unlike traditional etching methods that cannot control the dispersion of the groove depth 41, the ion beam etching method provided in this application can achieve wafer-level precise etching of the groove depth 41, reducing the impact of structural dimensional parameter dispersion on the structural effect of the groove 41. In step S310 above, the area of ​​the piezoelectric layer 40 not covered by photoresist should at least cover the resonant region so that the groove surrounds the outer edge of the resonant region. In actual manufacturing, the sacrificial layer may extend beyond the surface of the piezoelectric layer 40, resulting in an uneven surface of the piezoelectric layer 40. In this case, the sacrificial layer needs to be ground to make its surface flush with the surface of the piezoelectric layer 40, thereby obtaining a piezoelectric layer 40 with a smooth surface and a sacrificial layer deposited thereon.

[0070] S410. A top electrode layer 50 is formed on a piezoelectric layer 40 on which a sacrificial layer is deposited, and the top electrode layer 50 is patterned to form a top electrode pattern, wherein the overlapping region of the bottom electrode pattern, the piezoelectric layer 40 and the top electrode pattern in the stacking direction is a resonant region.

[0071] S510, Release the sacrificial layer to form a cavity in the groove 41, wherein the groove 41 surrounds the resonant region.

[0072] It should be noted that in the actual manufacturing process, the sacrificial layer in the groove 41 of the piezoelectric layer 40 and the sacrificial layer in the groove of the substrate 10 can be released simultaneously or separately. If released simultaneously, the release hole needs to pass through the sacrificial layer in the groove 41 of the piezoelectric layer 40, the piezoelectric layer 40, and the bottom electrode layer 30 in sequence until the sacrificial layer in the groove of the substrate 10 is exposed. If released separately, if the sacrificial layer in the groove 41 of the piezoelectric layer 40 is not completely covered by the top electrode pattern or the groove 41 is an annular groove, then the sacrificial layer in the groove 41 of the piezoelectric layer 40 can be released directly under the action of the etching medium without being affected by the top electrode pattern. If the sacrificial layer in the groove 41 of the piezoelectric layer 40 is completely covered by the top electrode pattern or the groove 41 is an arc-shaped groove (or a polygonal groove), then a release hole needs to be etched on the top electrode to completely release the sacrificial layer in the groove 41 of the piezoelectric layer 40.

[0073] Regarding the actual material of the sacrificial layer, those skilled in the art should be able to make reasonable selections and designs based on the actual situation, and no specific limitations are imposed here. For example, the material of the sacrificial layer can be silicon dioxide (SiO2), silicon nitride (SiN), phosphoric acid glass (PSG), or borosilicate glass (BPSG), and the etching medium can be a corrosive gas, such as hydrofluoric acid gas (HF) or xenon disulfide (XeF2).

[0074] Regardless of whether the groove 41 is an annular groove, an arc groove, or a polygonal groove, when there are multiple grooves 41, the multiple grooves 41 need to be etched sequentially. The following explanation will be based on the example of two grooves 41 (i.e., the first sub-groove and the second sub-groove), which are interconnected to form a stepped groove.

[0075] In one possible implementation of this invention, S310, covering the piezoelectric layer 40 with photoresist and etching the areas of the piezoelectric layer 40 not covered by photoresist with an ion beam to form a groove 41, depositing a sacrificial layer in the groove 41, and grinding the sacrificial layer until it is flush with the surface of the piezoelectric layer 40 includes:

[0076] S311. Photoresist is applied to the piezoelectric layer 40, and the area of ​​the piezoelectric layer 40 not covered by photoresist is etched by an ion beam to form a first sub-groove.

[0077] S312. Photoresist is applied to the piezoelectric layer 40 on which the first sub-groove is formed, and the area of ​​the piezoelectric layer 40 not covered by photoresist is etched by an ion beam to form a second sub-groove. The first sub-groove and the second sub-groove are concentrically arranged, the depth of the first sub-groove located on the inner side is greater than the depth of the second sub-groove located on the outer side, and the first sub-groove and the second sub-groove are interconnected to form a groove 41.

[0078] S313. Deposit a sacrificial layer in the groove 41 and grind the sacrificial layer until it is flush with the surface of the piezoelectric layer 40.

[0079] It should be noted that the area of ​​the piezoelectric layer 40 not covered by photoresist in steps S311 and S312 above should be determined according to the actual positions of the first sub-groove and the second sub-groove. For example, the area of ​​the piezoelectric layer 40 not covered by photoresist in step S311 should at least cover the resonant region so that the first sub-groove surrounds the outer edge of the resonant region. The area of ​​the piezoelectric layer 40 not covered by photoresist in step S312 should at least cover the first sub-groove to avoid etching the first sub-groove again during the etching process to form the second sub-groove, which would cause the etching depth of the first sub-groove to exceed the preset depth.

[0080] It should also be noted that the fabrication method of the thin-film bulk acoustic wave resonator 100 provided in this embodiment is the same as the specific structure of the thin-film bulk acoustic wave resonator 100 described above. Those skilled in the art can deduce the fabrication method of the thin-film bulk acoustic wave resonator 100 based on the description of the specific structure of the thin-film bulk acoustic wave resonator 100 described above, and this application will not repeat the description. Since the thin-film bulk acoustic wave resonator 100 described above is fabricated using the fabrication method of the thin-film bulk acoustic wave resonator 100 provided in this embodiment, the fabrication method of the thin-film bulk acoustic wave resonator 100 has the same beneficial effects as the thin-film bulk acoustic wave resonator 100 described above, and will not be repeated here.

[0081] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0082] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A film bulk acoustic resonator, characterized by, The piezoelectric layer is provided with a groove, the bottom electrode layer and the top electrode layer are respectively formed into a bottom electrode pattern and a top electrode pattern through patterning, an overlapping area of the bottom electrode pattern, the piezoelectric layer and the top electrode pattern in a stacking direction serves as a resonance area, and the groove is arranged around an outer edge of the resonance area; The groove is an arc-shaped groove, at least two sections of the arc-shaped groove are arranged around the same radial direction of the outer edge of the resonance area, the at least two sections of the arc-shaped groove are arranged at intervals, and the at least two sections of the arc-shaped groove can be sequentially connected in a head-to-tail mode to form a closed structure; or the groove is a polygonal groove, at least two sections of the polygonal groove are arranged around the same radial direction of the outer edge of the resonance area, the at least two sections of the polygonal groove are arranged at intervals, and the at least two sections of the polygonal groove can be sequentially connected in a head-to-tail mode to form a closed structure; The at least two sections of the groove arranged around the same radial direction of the outer edge of the resonance area serve as a groove group, a plurality of groove groups are arranged around different radial directions of the outer edge of the resonance area, the plurality of groove groups are arranged in a concentric mode, and the depth of the groove of the groove group located on the inner side is greater than the depth of the groove of the groove group located on the outer side; The grooves of two adjacent groove groups are arranged in a staggered mode in the circumferential direction.

2. The film bulk acoustic resonator of claim 1, wherein, When the groove is an arc-shaped groove and the number of the arc-shaped grooves is multiple, two adjacent arc-shaped grooves are arranged at unequal intervals. Or, when the groove is a polygonal groove and the number of the polygonal grooves is multiple, two adjacent polygonal grooves are arranged at unequal intervals.

3. The film bulk acoustic resonator of claim 1, wherein, The grooves of two adjacent groove groups are connected to form a stepped groove.

4. The film bulk acoustic resonator of claim 1, wherein, An inner edge of the groove coincides with the outer edge of the resonance area.

5. A method of fabricating a film bulk acoustic resonator, characterized by, The method comprises: forming a bottom electrode layer on a substrate, and patterning the bottom electrode layer to form a bottom electrode pattern; forming a piezoelectric layer on the substrate provided with the bottom electrode pattern; covering photoresist on the piezoelectric layer, etching the piezoelectric layer in an area not covered by the photoresist through an ion beam to form a groove, depositing a sacrificial layer in the groove, and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer; forming a top electrode layer on the piezoelectric layer provided with the sacrificial layer, and patterning the top electrode layer to form a top electrode pattern, wherein an overlapping area of the bottom electrode pattern, the piezoelectric layer and the top electrode pattern in a stacking direction serves as a resonance area; releasing the sacrificial layer to form a cavity in the groove, wherein the groove is arranged around the resonance area; wherein the groove is an arc-shaped groove, at least two sections of the arc-shaped groove are arranged around the same radial direction of the outer edge of the resonance area, the at least two sections of the arc-shaped groove are arranged at intervals, and the at least two sections of the arc-shaped groove can be sequentially connected in a head-to-tail mode to form a closed structure; or the groove is a polygonal groove, at least two sections of the polygonal groove are arranged around the same radial direction of the outer edge of the resonance area, the at least two sections of the polygonal groove are arranged at intervals, and the at least two sections of the polygonal groove can be sequentially connected in a head-to-tail mode to form a closed structure; At least two groups of the grooves are arranged in the same radial direction of the outer edge of the resonance region as a groove group, and multiple groups of the groove groups are arranged in different radial directions of the outer edge of the resonance region, the multiple groups of the groove groups are arranged concentrically, and the depth of the grooves of the groove group on the inner side is greater than the depth of the grooves of the groove group on the outer side; The grooves of the two adjacent groove groups are arranged in a circumferential direction.

6. The method of claim 5, wherein the thin film bulk acoustic resonator is a film bulk acoustic resonator (FBAR). The method for forming the groove in the piezoelectric layer includes: covering photoresist on the piezoelectric layer, and etching the region of the piezoelectric layer which is not covered by the photoresist by ion beam to form a groove, depositing a sacrificial layer in the groove, and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer. The method for forming the groove in the piezoelectric layer includes: covering photoresist on the piezoelectric layer, and etching the region of the piezoelectric layer which is not covered by the photoresist by ion beam to form a groove, depositing a sacrificial layer in the groove, and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer. The method for forming the groove in the piezoelectric layer includes: covering photoresist on the piezoelectric layer, and etching the region of the piezoelectric layer which is not covered by the photoresist by ion beam to form a groove, depositing a sacrificial layer in the groove, and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer. The method for forming the groove in the piezoelectric layer includes: covering photoresist on the piezoelectric layer, and etching the region of the piezoelectric layer which is not covered by the photoresist by ion beam to form a groove, depositing a sacrificial layer in the groove, and grinding the sacrificial layer to be flush with the surface of the piezoelectric layer.

Images