Film bulk acoustic resonator

Abstract

The invention discloses a film bulk acoustic resonator, and relates to the technical field of resonators, the film bulk acoustic resonator comprises a substrate, and a bottom electrode, a piezoelectric layer and a top electrode which are sequentially arranged on the substrate, the substrate is provided with a groove, and an overlapping area of the bottom electrode, the piezoelectric layer and the top electrode in a stacking direction is used as a resonance area. A temperature compensation layer is arranged on the piezoelectric layer, the orthographic projection of the temperature compensation layer on the substrate falls within the orthographic projection range of the resonance area on the substrate, and a concave structure is arranged on the temperature compensation layer. According to the film bulk acoustic resonator, the temperature compensation layer is introduced on the piezoelectric layer, and the sunken structure is prepared on the temperature compensation layer, so that the damage of a frequency repairing process to the sunken structure can be avoided, a relatively large depth range of the sunken structure can be realized, the process difficulty can be reduced, and the frequency-temperature coefficient of the resonator can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of resonators, and in particular to a thin film bulk acoustic wave resonator. Background Art

[0002] Film bulk acoustic resonator (FBAR) is a key filtering element in modern wireless communication systems and is widely used in filtering and selecting high-frequency signals. FBAR selects and processes signals of specific frequencies through the longitudinal acoustic vibrations generated by piezoelectric materials under the action of an electric field. The propagation behavior of acoustic waves in FBAR is affected by materials and structures, especially in the high-frequency band, where the dispersion effect of acoustic waves has a particularly significant impact on the performance of the resonator. According to the type of dispersion, acoustic wave propagation in FBAR can be divided into Type I dispersion and Type II dispersion. Among them, Type II dispersion FBAR exhibits a complex nonlinear relationship between the resonant frequency and the thickness mode, especially on the left side of the series resonant frequency, which is prone to parasitic acoustic modes. These parasitic modes compete with the main mode, causing the frequency response of the FBAR to be disturbed, thereby reducing the quality factor and frequency selectivity of the resonator and affecting the performance of the communication equipment.

[0003] To address this problem, the prior art has proposed a recessed structure for optimizing the parasitic mode suppression in Type II dispersion FBARs. The recessed structure refers to a local recessed or indented structure designed on the electrode layer (especially the upper electrode layer) of the FBAR. Its purpose is to optimize the sound wave propagation path by changing the geometry of the electrode and reduce unnecessary sound wave reflections and interference. The design of the recessed structure directly targets the parasitic modes generated on the left side of the series resonance frequency in the Type II dispersion FBAR. By adjusting the acoustic behavior of the electrode, these parasitic modes are effectively weakened, thereby improving the purity of the main mode and the quality factor of the resonator. Fig.13 and Fig.14 As shown in FIG. 1 , there is no recessed structure on the FBAR, and in the corresponding impedance-frequency curve, there are a large number of parasitic modes on the left side of the series resonant frequency; Fig.15 and Fig.16 As shown in FIG. 1 , a concave structure is provided on the FBAR, and the depth of the concave structure is appropriate. In the corresponding impedance-frequency curve, the area near the series resonant frequency (including the left and right sides) is smooth and free of parasitics; Fig.17 and Fig.18 As shown, although a recessed structure is provided on the FBAR, the recessed structure is too deep, and a parasitic mode appears on the right side of the series resonant frequency in its corresponding impedance-frequency curve.

[0004] However, although the recessed structure effectively addresses the parasitic mode problem in low-frequency FBAR products, its application in high-frequency products above 5GHz has exposed some significant limitations, especially in terms of process implementation and structural stability. The recessed structure in the prior art is generally made in the upper electrode layer or the passivation layer, but both situations have their own limitations: Fig.19 As shown in the figure, since the electrode material generally has a high acoustic impedance, the thickness requirement for making a recessed structure on the surface of the upper electrode layer is extremely strict. As the application frequency of FBAR increases, the thickness of the upper electrode layer must be extremely thin to adapt to the propagation characteristics of high-frequency sound waves. In high-frequency FBAR products above 5GHz, the thickness of the recessed structure in the upper electrode layer is usually less than 5nm, which has far exceeded the accuracy limit of current thin film deposition and processing technology, making it difficult to achieve a stable and effective structure; while designing a recessed structure on the passivation layer, such as Fig. 20 As shown, although the process limitation caused by the upper electrode layer being too thin can be avoided, in high-frequency applications, since the FBAR usually needs to be precisely adjusted in the subsequent frequency tuning process, and such processes (such as ion beam frequency tuning) are prone to damage the recessed structure on the passivation layer, resulting in increased thickness non-uniformity. Summary of the invention

[0005] The purpose of the present application is to provide a thin film bulk acoustic wave resonator. By introducing a temperature compensation layer on the piezoelectric layer and preparing a recessed structure on the temperature compensation layer, it is possible to avoid damage to the recessed structure by the frequency repair process, achieve a larger depth range of the recessed structure, reduce the process difficulty, and reduce the frequency-temperature coefficient of the resonator.

[0006] The embodiment of the present application is implemented as follows:

[0007] According to a first aspect of an embodiment of the present application, a thin film bulk acoustic wave resonator is provided, comprising a substrate and a bottom electrode, a piezoelectric layer and a top electrode sequentially arranged on the substrate, wherein a groove is arranged on the substrate, and an overlapping area of ​​the bottom electrode, the piezoelectric layer and the top electrode in a stacking direction serves as a resonance area, a temperature compensation layer is arranged on the piezoelectric layer, an orthographic projection of the temperature compensation layer on the substrate falls within the orthographic projection range of the resonance area on the substrate, and a recessed structure is arranged on the temperature compensation layer.

[0008] As an implementation method, the top electrode includes a first top electrode layer and a second top electrode layer which are stacked, and the temperature compensation layer is located between the first top electrode layer and the second top electrode layer.

[0009] As an implementation method, the temperature compensation layer is located between the piezoelectric layer and the top electrode.

[0010] As an implementation method, a thickening layer is further arranged between the piezoelectric layer and the top electrode on the periphery of the temperature compensation layer, and along the direction from the center to the periphery of the temperature compensation layer, the thickening layer includes a connecting portion in contact with the piezoelectric layer and a side wing portion separated from the piezoelectric layer, and an air gap is formed between the side wing portion and the piezoelectric layer.

[0011] As an implementation method, the wing portion extends outside the resonance region, the thickened layer further includes a bonding portion disposed on the piezoelectric layer, and the connecting portion, the wing portion and the bonding portion are connected to form an air bridge.

[0012] As an implementation method, the orthographic projection of the air bridge on the substrate is partially located within the resonance region and partially located outside the resonance region.

[0013] As an implementation method, the air gap and / or the air bridge are filled with a plurality of oxide columns arranged at intervals.

[0014] As an implementation method, oxide is filled between any two adjacent oxide columns.

[0015] As an implementation method, the acoustic impedance of the material of the thickened layer is greater than the acoustic impedance of the material of the piezoelectric layer.

[0016] As an implementation method, the material of the temperature compensation layer is a material with a positive temperature drift coefficient.

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

[0018] The film bulk acoustic wave resonator includes a substrate and a bottom electrode, a piezoelectric layer and a top electrode sequentially arranged on the substrate, wherein a groove is arranged on the substrate, and the overlapping area of ​​the bottom electrode, the piezoelectric layer and the top electrode in the stacking direction serves as a resonance area, a temperature compensation layer is arranged on the piezoelectric layer, and the orthographic projection of the temperature compensation layer on the substrate falls within the orthographic projection range of the resonance area on the substrate, and a concave structure is arranged on the temperature compensation layer. The present application prepares the concave structure on the temperature compensation layer, so that the concave structure can be transferred to the inside of the top electrode (that is, the side of the top electrode close to the substrate), thereby improving the protection of the concave structure, and thus can avoid the concave structure from being damaged in the subsequent frequency repair process, causing the thickness fluctuation to worsen; it can also make the depth of the concave structure not limited by the thickness of the top electrode, so that the thickness of the concave structure can be increased, which is beneficial to the process processing of the film bulk acoustic wave resonator; in addition, it can also reduce the frequency-temperature coefficient (TCF) of the resonator, achieving a multi-purpose effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 One of the state schematic diagrams of the thin film bulk acoustic resonator provided in the first embodiment of the present application;

[0021] Figure 2 The second state schematic diagram of the thin film bulk acoustic wave resonator provided in the first embodiment of the present application;

[0022] Figure 3 The third state schematic diagram of the thin film bulk acoustic wave resonator provided in the first embodiment of the present application;

[0023] Figure 4 A fourth state schematic diagram of the thin film bulk acoustic wave resonator provided in the first embodiment of the present application;

[0024] Figure 5 A fifth state diagram of the thin film bulk acoustic resonator provided in the first embodiment of the present application;

[0025] Figure 6 The sixth state diagram of the thin film bulk acoustic wave resonator provided in the first embodiment of the present application;

[0026] Figure 7 The seventh state schematic diagram of the thin film bulk acoustic wave resonator provided in the first embodiment of the present application;

[0027] Figure 8 The eighth state schematic diagram of the thin film bulk acoustic wave resonator provided in the first embodiment of the present application;

[0028] Fig. 9 A schematic structural diagram of a thin film bulk acoustic resonator provided in the first embodiment of the present application;

[0029] Fig.10 A schematic structural diagram of a thin film bulk acoustic resonator provided in the second embodiment of the present application;

[0030] Fig.11 A schematic structural diagram of a thin film bulk acoustic resonator provided in the third embodiment of the present application;

[0031] Fig.12 A schematic diagram of the structure of a thin film bulk acoustic resonator provided in a fourth embodiment of the present application;

[0032] Fig.13 One of the structural schematic diagrams of the thin film bulk acoustic resonator provided by the prior art;

[0033] Fig.14 One of the impedance-frequency graphs of the thin film bulk acoustic wave resonator provided by the prior art;

[0034] Fig.15 The second structural schematic diagram of the thin film bulk acoustic wave resonator provided by the prior art;

[0035] Fig.16 The second impedance-frequency curve diagram of the thin film bulk acoustic wave resonator provided by the prior art;

[0036] Fig.17 The third structural schematic diagram of the thin film bulk acoustic resonator provided by the prior art;

[0037] Fig.18 The third impedance-frequency curve diagram of the thin film bulk acoustic wave resonator provided by the prior art;

[0038] Fig.19 The fourth structural diagram of the thin film bulk acoustic wave resonator provided by the prior art;

[0039] Fig. 20 The fifth structural schematic diagram of the thin film bulk acoustic wave resonator provided by the prior art.

[0040] Icon: 101-substrate; 102-sacrificial layer; 102a-groove; 103-seed layer; 104-bottom electrode; 105-piezoelectric layer; 106-sacrificial material; 106a-air gap; 106b-air bridge; 107-thickening layer; 107a-connecting part; 107b-side wing part; 107c-bonding part; 108-top electrode; 108a-first top electrode layer; 108b-second top electrode layer; 109-temperature compensation layer; 110-recessed structure; 111-passivation layer; 112-lead electrode; 113-oxidation column; 114-oxide; 115-release hole. DETAILED DESCRIPTION

[0041] The embodiments set forth below represent information necessary to enable 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 the present disclosure, and will recognize the applications of these concepts not specifically proposed herein. It should be understood that these concepts and applications are within the scope of the present disclosure and the appended claims.

[0042] It should be understood that although the terms first, second, etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0043] It should be understood that when an element (such as a layer, region or substrate) is referred to as "on another element" or "extending onto another element", it can be directly on another element or directly extended onto another element, or there can also be an intervening element. On the contrary, when an element is referred to as "directly on another element" or "directly extending onto another element", there is no intervening element. Similarly, it should be understood that when an element (such as a layer, region or substrate) is referred to as "on another element" or "extending onto another element", it can be directly on another element or directly extended onto another element, or there can also be an intervening element. On the contrary, when an element is referred to as "directly on another element" or "extending directly onto another element", there is no intervening element. It should also be understood that when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to another element, or there can be an intervening element. On the contrary, when an element is referred to as "directly connected" or "directly coupled" to another element, there is no intervening element.

[0044] Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe the relationship of one element, layer or region to another element, layer or region as shown in the figures.

[0045] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms as well. It should also be understood that when used herein, the term "comprising" indicates the presence of the features, integers, steps, operations, elements, and / or parts, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups of the above.

[0046] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. It should also be understood that the terms used herein should be interpreted as having the same meaning as they do in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense, unless clearly defined in this article.

[0047] As wireless communication technology has increasingly higher requirements for frequency response, quality factor (Q value) and filtering accuracy, the structural design and optimization of FBARs have become particularly important. In order to suppress the parasitic modes in Type II dispersion FBARs, such as Figures 13 to 18 As shown, the prior art proposes a recessed structure, which successfully suppresses the parasitic mode on the left side of the series resonance frequency by optimizing the design of the electrode, improves the frequency stability and signal selectivity of the FBAR device, and meets the high performance requirements of the high-frequency communication system for the filter.

[0048] Therefore, the application of the recessed structure has become a key technology to solve the parasitic mode problem in Type II dispersion FBAR. Although the recessed structure effectively addresses the parasitic mode problem in low-frequency FBAR products, its application in high-frequency products above 5GHz has exposed some significant limitations, especially in terms of process implementation and structural stability. In the prior art, the recessed structure is generally made in the upper electrode layer or the passivation layer, but both situations have their own limitations, such as Fig.19 and Fig. 20 shown.

[0049] To solve the above problems, please refer to Figures 1 to 12 The present application provides a thin film bulk acoustic wave resonator, which introduces a temperature compensation layer 109 on the piezoelectric layer 105 and prepares a recessed structure 110 on the temperature compensation layer 109, thereby avoiding damage to the recessed structure 110 caused by a subsequent frequency correction process, thereby causing worsening thickness fluctuations; and achieving a larger depth range of the recessed structure 110, thereby reducing the difficulty of the process; in addition, the frequency-temperature coefficient of the resonator can also be reduced, thereby achieving a multi-pronged effect.

[0050] Specifically, Figures 9 to 12 As shown, in the first aspect of the present application, a thin film bulk acoustic wave resonator is provided, comprising a substrate 101 and a bottom electrode 104, a piezoelectric layer 105 and a top electrode 108 sequentially arranged on the substrate 101, wherein a groove 102a is arranged on the substrate 101, and the overlapping area of ​​the bottom electrode 104, the piezoelectric layer 105 and the top electrode 108 in the stacking direction serves as a resonance area, a temperature compensation layer 109 is arranged on the piezoelectric layer 105, and the orthographic projection of the temperature compensation layer 109 on the substrate 101 falls within the orthographic projection range of the resonance area on the substrate 101, and a recessed structure 110 is arranged on the temperature compensation layer 109.

[0051] It should be noted that if Figures 9 to 12 As shown, the film bulk acoustic wave resonator includes a substrate 101, on which a bottom electrode 104, a piezoelectric layer 105 and a top electrode 108 are sequentially arranged to form a sandwich structure through the bottom electrode 104, the piezoelectric layer 105 and the top electrode 108. During the operation of the film bulk acoustic wave resonator, the bottom electrode 104 and the top electrode 108 are respectively connected to two ends of an external signal to form an electric field between the bottom electrode 104 and the top electrode 108, so that the piezoelectric layer 105 is located in the electric field and generates vibration to form an acoustic wave under the action of the piezoelectric effect.

[0052] Among them, the overlapping area of ​​the bottom electrode 104, the piezoelectric layer 105 and the top electrode 108 in the stacking direction is used as a resonance area to make the sound waves reflect back and forth in the resonance area; on this basis, a groove 102a is also provided between the upper surface of the substrate 101 and the lower surface of the bottom electrode 104. When the sound wave propagates at both ends of the sandwich structure, the groove 102a is used as a sound reflection cavity, and the air in the groove 102a can be used to reflect the sound wave back into the sandwich structure, so that the energy of the sound wave can be concentrated in the sandwich structure, thereby improving the Q value of the resonator.

[0053] Different from the prior art, in the present application, a temperature compensation layer 109 is introduced on the piezoelectric layer 105, wherein the orthographic projection of the temperature compensation layer 109 on the substrate 101 falls within the orthographic projection range of the resonance region on the substrate 101, so that the temperature compensation layer 109 can be used as a substrate for preparing the recessed structure 110, thereby preparing the recessed structure 110 on the temperature compensation layer 109. Compared with the prior art in which the recessed structure is made on the upper electrode layer (such as Mo) or the passivation layer (such as AlN), the materials of the upper electrode layer and the passivation layer are both materials with large acoustic impedance, so the required depth of the recessed structure is smaller; for example, in the present application, the material of the temperature compensation layer 109 is a material with low acoustic impedance (such as SiO2), so the required depth of the recessed structure 110 is deeper. For process processing, the increase in the depth range is conducive to reducing the process difficulty. Therefore, the present application can provide a larger selection range and degree of freedom for the size of the recessed structure 110, especially the thickness, which is conducive to process processing.

[0054] Table 1 Material properties

[0055]

[0056] In summary, the present application prepares the recessed structure 110 on the temperature compensation layer 109, and can transfer the recessed structure 110 to the inside of the top electrode 108 (that is, the side of the top electrode 108 close to the substrate 101), thereby improving the protection of the recessed structure 110, and thus preventing the recessed structure 110 from being damaged in the subsequent frequency repair process, causing the thickness fluctuation to worsen; it can also make the depth of the recessed structure 110 not limited by the thickness of the top electrode 108, so that the thickness of the recessed structure 110 can be increased, which is beneficial to the process processing of the thin film bulk acoustic wave resonator; in addition, it can also reduce the frequency-temperature coefficient (TCF) of the resonator, achieving multiple effects at one stroke.

[0057] For example, as an implementation method, Fig. 9 As shown, the top electrode 108 includes a first top electrode layer 108a and a second top electrode layer 108b which are stacked, and the temperature compensation layer 109 is located between the first top electrode layer 108a and the second top electrode layer 108b. The materials of the first top electrode layer 108a and the second top electrode layer 108b can be the same or different, which is not limited here. It should be understood by those skilled in the art that the thinner the thickness of the first top electrode layer 108a, the closer the distance between the temperature compensation layer 109 and the piezoelectric layer 105, and the better the temperature compensation effect of the thin film bulk acoustic wave resonator.

[0058] Or, as an implementable embodiment, Fig.10 As shown, the temperature compensating layer 109 is located between the piezoelectric layer 105 and the top electrode 108, so that the temperature compensating layer 109 can offset the temperature coefficient of the piezoelectric layer 105, thereby making the thin film bulk acoustic wave resonator have better temperature stability. It should be understood by those skilled in the art that in order for the temperature compensating layer 109 to offset the temperature coefficient of the piezoelectric layer 105, the temperature coefficient of the temperature compensating layer 109 should be opposite to the temperature coefficient of the piezoelectric layer 105. For example, the material of the temperature compensating layer 109 is a material with a positive temperature drift coefficient.

[0059] In order to improve the film quality of the piezoelectric layer 105, a seed layer 103 is further provided between the substrate 101 and the bottom electrode 104, so that the seed layer 103 provides guidance for the crystal orientation of the piezoelectric layer 105, so that the piezoelectric layer 105 can grow according to a preset crystal orientation, thereby improving the film quality of the piezoelectric layer 105. In addition, a passivation layer 111 can be provided on the side of the top electrode 108 away from the substrate 101, so that the passivation layer 111 can protect the device surface to prevent the device surface from being easily oxidized.

[0060] The material of the substrate 101 can be sapphire, silicon carbide or silicon; the material of the seed layer 103 can be aluminum nitride or titanium nitride; the material of the piezoelectric layer 105 can be one of aluminum nitride, lithium niobate, lithium tantalate, lead zirconate titanate, zinc oxide, scandium-doped aluminum nitride, quartz crystal, lead magnesium niobate, lead fluoride, etc., and their combinations; the material of the bottom electrode 104 and the top electrode 108 can be one of molybdenum, aluminum, copper, tungsten, tantalum, platinum, ruthenium, rhodium, iridium, chromium, titanium, gold, osmium, rhenium, palladium, etc., and their combinations; The material of the filler layer 109 can be one of silicon dioxide, titanium dioxide, tantalum oxide, silicon nitride, aluminum oxide, etc. and their combination; the material of the passivation layer 111 can be silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, polymer materials, etc.; during the preparation process, it is also necessary to deposit a sacrificial layer 102 in the groove 102a, and when the preparation is completed, it is released through the release hole 115 to form an acoustic reflection cavity in the groove 102a. The material of the sacrificial layer 102 can be silicon oxide, silicate glass or silicon nitride, etc. Regarding the materials of each of the above-mentioned layers, those skilled in the art should be able to make reasonable selections and designs according to actual conditions, and no specific restrictions are made here.

[0061] As an implementation method, Fig. 9 and Fig.10 As shown, a thickening layer 107 is also provided between the piezoelectric layer 105 and the top electrode 108 at the periphery of the temperature compensation layer 109. In the direction from the center to the periphery of the temperature compensation layer 109, the thickening layer 107 includes a connecting portion 107a in contact with the piezoelectric layer 105 and a wing portion 107b separated from the piezoelectric layer 105, and an air gap 106a is formed between the wing portion 107b and the piezoelectric layer 105. As an implementable embodiment, the acoustic impedance of the material of the thickening layer 107 can be greater than the acoustic impedance of the material of the piezoelectric layer 105. Those skilled in the art should be able to make reasonable selections and designs according to actual conditions, and no specific restrictions are made here. By way of example, the material of the thickening layer 107 can be a metal material.

[0062] It should be noted that, since the temperature compensation layer 109 itself has a certain thickness, it is easy to cause the slope of the top electrode 108 at the boundary of the temperature compensation layer 109 to be larger, which is not conducive to the deposition of the top electrode 108. In order to solve the above problem, in the present application, a thickening layer 107 is also provided on the periphery of the temperature compensation layer 109. Among them, along the stacking direction, the thickening layer 107 is located between the piezoelectric layer 105 and the top electrode 108, so as to support the top electrode 108 through the thickening layer 107, thereby reducing the processing difficulty of the top electrode 108; along the center to the periphery of the temperature compensation layer 109, the thickening layer 107 includes a connecting portion 107a in contact with the piezoelectric layer 105 and a side wing portion 107b separated from the piezoelectric layer 105, and an air gap 106a is formed between the side wing portion 107b and the piezoelectric layer 105. When the sound wave propagating laterally in the piezoelectric layer 105 propagates to the interface of the air gap 106a, it can be reflected by the air gap 106a, thereby avoiding the leakage of the lateral sound wave, thereby improving the Q value of the thin film bulk acoustic resonator. In addition, along the stacking direction, the air gap 106a has different acoustic reflection coefficients from the piezoelectric layer 105 and the side wing portion 107b, and there is also reflection at the interface between the two. Therefore, the sound waves propagating longitudinally in the piezoelectric layer 105 can also be reflected, thereby further improving the Q value of the thin film bulk acoustic resonator.

[0063] As an implementation method, Fig. 9 and Fig.10 As shown, the wing portion 107b extends outside the resonance region, the thickened layer 107 further includes a bonding portion 107c disposed on the piezoelectric layer 105, and the connecting portion 107a, the wing portion 107b and the bonding portion 107c are connected to form an air bridge 106b.

[0064] It should be noted that since the side of the wing portion 107b away from the temperature compensation layer 109 is suspended, in the present application, along the center to the periphery of the temperature compensation layer 109, the thickening layer 107 also includes a bonding portion 107c arranged on the piezoelectric layer 105, so that the connecting portion 107a, the wing portion 107b and the bonding portion 107c are connected to form an air bridge 106b, thereby, the bonding portion 107c can support the side of the wing portion 107b away from the temperature compensation layer 109, thereby improving the stability of the wing portion 107b.

[0065] As an implementation method, Fig. 9 and Fig.10 As shown, the orthographic projection of the air bridge 106b on the substrate 101 is partially located in the resonance region and partially located outside the resonance region. Figure 2As shown, during the preparation process, by depositing a sacrificial material 106 on the piezoelectric layer 105 and designing the position and lateral width of the sacrificial material 106, the sacrificial material 106 can be released after the preparation is completed so that the orthographic projection of the formed air bridge 106b on the substrate 101 is partially located within the resonance region and partially located outside the resonance region.

[0066] As an implementation method, Fig.11 As shown, the air gap 106a and / or the air bridge 106b are filled with a plurality of spaced oxide columns 113. Thus, each oxide column 113 and the air in the air gap 106a or the air bridge 106b can form a reflection interface, so that the sound wave can be reflected at the location of each oxide column 113, thereby further improving the Q value of the thin film bulk acoustic wave resonator.

[0067] As an implementation method, Fig.12 As shown, oxide 114 is filled between any two adjacent oxide columns 113. Thus, each oxide 114 can have different acoustic reflection coefficients with the piezoelectric layer 105 and the wing portion 107b, and reflection also exists at the interface between the two, so that the sound waves propagating in the longitudinal direction in the piezoelectric layer 105 can also be reflected, thereby further improving the Q value of the thin film bulk acoustic wave resonator.

[0068] like Figures 1 to 9 As shown, taking the first embodiment of the present application as an example, the second aspect of the present application provides a method for preparing a thin film bulk acoustic wave resonator, which is used to prepare the thin film bulk acoustic wave resonator provided by the first embodiment of the present application, and the method includes:

[0069] S01, etching a groove 102a on the substrate 101, and depositing a sacrificial layer 102 in the groove 102a;

[0070] S02, sequentially forming a seed layer 103 and a bottom electrode 104 on the substrate 101 on which the sacrificial layer 102 is deposited, and patterning the bottom electrode 104;

[0071] S03, forming a piezoelectric layer 105 on the seed layer 103 on which the bottom electrode 104 is deposited;

[0072] S04, depositing a sacrificial material 106 on the piezoelectric layer 105, and patterning the sacrificial material 106;

[0073] S05, forming a thickening layer 107 on the piezoelectric layer 105 on which the sacrificial material 106 is deposited, and patterning the thickening layer 107;

[0074] S06, forming a first top electrode layer 108a on the piezoelectric layer 105 on which the thickening layer 107 is deposited, and patterning the first top electrode layer 108a;

[0075] S07, forming a temperature compensation layer 109 on the first top electrode layer 108a, and patterning the temperature compensation layer 109;

[0076] S08, etching to form a recessed structure 110 on the temperature compensation layer 109;

[0077] S09, forming a second top electrode layer 108b on the temperature compensation layer 109, and patterning the second top electrode layer 108b;

[0078] S10, forming a passivation layer 111 on the second top electrode layer 108b, and patterning the passivation layer 111;

[0079] S11, etching the piezoelectric layer 105 and the passivation layer 111 to form extraction holes, and depositing metal materials in the extraction holes to form extraction electrodes 112 connected to the bottom electrode 104 and the second top electrode layer 108b;

[0080] S12, etching a release hole 115 on the piezoelectric layer 105, and introducing an etching medium into the groove 102a through the release hole 115 to release the sacrificial layer 102 in the groove 102a to form an acoustic reflection cavity.

[0081] It should be noted that the method for preparing the thin film bulk acoustic wave resonator provided in this embodiment is the same as the specific structure of the thin film bulk acoustic wave resonator in the previous text. Those skilled in the art can infer the method for preparing the thin film bulk acoustic wave resonator based on the description of the specific structure of the thin film bulk acoustic wave resonator in the previous text, and this application will not repeat the description. Since the method for preparing the thin film bulk acoustic wave resonator provided in this embodiment is used to prepare the above-mentioned thin film bulk acoustic wave resonator, the method for preparing the thin film bulk acoustic wave resonator has the same beneficial effects as the above-mentioned thin film bulk acoustic wave resonator, and will not be repeated here.

[0082] The above description is only an optional embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0083] 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, this application will not further describe various possible combinations.

Claims

1. A thin film bulk acoustic resonator, characterized in that: It includes a substrate and a bottom electrode, a piezoelectric layer and a top electrode which are sequentially arranged on the substrate, wherein a groove is arranged on the substrate, and the overlapping area of ​​the bottom electrode, the piezoelectric layer and the top electrode in the stacking direction serves as a resonance area, a temperature compensation layer is arranged on the piezoelectric layer, the orthographic projection of the temperature compensation layer on the substrate falls within the orthographic projection range of the resonance area on the substrate, and a concave structure is arranged on the temperature compensation layer.

2. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: The top electrode comprises a first top electrode layer and a second top electrode layer which are stacked, and the temperature compensation layer is located between the first top electrode layer and the second top electrode layer.

3. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: The temperature compensation layer is located between the piezoelectric layer and the top electrode.

4. The thin film bulk acoustic wave resonator according to claim 1, characterized in that: A thickening layer is also arranged between the piezoelectric layer and the top electrode on the periphery of the temperature compensation layer. Along the direction from the center to the periphery of the temperature compensation layer, the thickening layer includes a connecting portion in contact with the piezoelectric layer and a side wing portion separated from the piezoelectric layer, and an air gap is formed between the side wing portion and the piezoelectric layer.

5. The thin film bulk acoustic resonator according to claim 4, characterized in that: The side wing portion extends outside the resonance region, the thickened layer further includes a bonding portion arranged on the piezoelectric layer, and the connecting portion, the side wing portion and the bonding portion are connected to form an air bridge.

6. The thin film bulk acoustic wave resonator according to claim 5, characterized in that: The orthographic projection of the air bridge on the substrate is partially located within the resonance region and partially located outside the resonance region.

7. The thin film bulk acoustic resonator according to claim 5, characterized in that: The air gap and / or the air bridge are filled with a plurality of oxide columns arranged at intervals.

8. The thin film bulk acoustic wave resonator according to claim 7, characterized in that: Oxide is filled between any two adjacent oxide columns.

9. The thin film bulk acoustic wave resonator according to claim 4, characterized in that: The acoustic impedance of the material of the thickened layer is greater than the acoustic impedance of the material of the piezoelectric layer.

10. The thin film bulk acoustic wave resonator according to any one of claims 1 to 9, characterized in that: The material of the temperature compensation layer is a material with a positive temperature drift coefficient.

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