A bulk acoustic resonator and its fabrication method

Abstract

This disclosure provides a bulk acoustic wave resonator and its fabrication method. The bulk acoustic wave resonator includes: a substrate comprising a cavity; a bottom electrode formed on the substrate and covering the cavity; a piezoelectric functional layer formed on the bottom electrode; a frame structure formed on the piezoelectric functional layer; and a top electrode formed on the frame structure, wherein the thickness of the frame structure is non-uniform. The processing method of this disclosure improves the reliability of the resonator at the connection edge while limiting lateral energy leakage.

Description

Technical Field

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

[0002] FBAR filters (film bulk acoustic resonators) are receiving increasing attention as a core component of RF (Radio Frequency) front-ends, primarily due to their high power, high bandwidth, and excellent roll-off performance, which effectively meet current RF performance requirements. In particular, compared to SAW (surface acoustic wave) filters, FBAR filters offer significant advantages in high power because they utilize the longitudinal wave propagation mode of bulk acoustic waves, taking advantage of the excellent e33 properties of AlN material for better energy conversion.

[0003] However, for FBAR filters, the piezoelectric layer and electrode materials are not perfectly oriented along the Z-axis, resulting in certain defects. This causes transverse waves to couple out during longitudinal wave propagation. If this energy is not confined, it will leak out laterally, thus reducing the Q value (quality factor) of the FBAR filter. To limit this lateral energy leakage, current techniques typically involve fabricating a frame structure on the top electrode to limit the vibration intensity at the filter edges, thereby reducing edge energy leakage and improving the Q value.

[0004] Furthermore, the following issues arise at the junction edges of FBAR filters: 1. Because the bottom electrode is etched at the junction edge, it creates a significant step difference at the etching boundary for subsequent film layers; 2. The junction edge contains multiple film layers, including a PZ layer, top electrode layer, air ring layer, frame structure layer, and protective layer. This multi-layer structure, coupled with the high step difference, introduces significant stress into the film layers at the junction edge, causing considerable problems in high power and reliability, and making the film layers prone to fracture at the junction edge. Therefore, improving the reliability of the device at the junction edge while limiting lateral energy leakage will further drive the development of FBAR filters. Summary of the Invention

[0005] In view of this, the present disclosure provides a bulk acoustic resonator and a method for its fabrication, which at least partially solves the problems existing in the prior art.

[0006] In a first aspect, embodiments of this disclosure provide a bulk acoustic resonator, comprising:

[0007] Substrate (10), said substrate (10) includes a cavity (19);

[0008] A bottom electrode (12) is formed above the substrate (10) and covers the cavity (19).

[0009] A piezoelectric functional layer (13) is formed above the bottom electrode (12);

[0010] A frame structure is formed above the piezoelectric functional layer (13); and

[0011] The top electrode (16) is formed above the frame structure.

[0012] The thickness of the frame structure is non-uniform.

[0013] According to a specific implementation of this disclosure, an air ring structure (11) is further included between the piezoelectric functional layer (13) and the frame structure. The air ring structure is a bridge structure on the connecting side of the bulk acoustic resonator and a cantilever structure on the non-connecting side of the bulk acoustic resonator.

[0014] According to one specific implementation of this disclosure, the thickness of the frame structure on the connecting side of the bulk acoustic resonator is smaller than the thickness of the frame structure on the non-connecting side of the bulk acoustic resonator.

[0015] According to a specific implementation of this disclosure, the frame structure is a single-layer thickness frame structure on the connecting side of the bulk acoustic resonator, and the frame structure is a double-layer thickness frame structure on the non-connecting side of the bulk acoustic resonator.

[0016] According to a specific implementation of an embodiment of this disclosure, the double-layer thickness frame structure includes a stacked first frame structure (14) and a second frame structure (15), wherein the first frame structure (14) is a frame structure close to the piezoelectric functional layer (13), and the second frame structure (15) is a frame structure far away from the piezoelectric functional layer (13).

[0017] According to a specific implementation of this disclosure, the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting edge is different from the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting edge; or

[0018] The effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting edge is the same as the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting edge.

[0019] According to a specific implementation of this disclosure, the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting edge and the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting edge are both in the range of 0.1μm-10μm.

[0020] According to one specific implementation of this disclosure, the bulk acoustic resonator is a convex polygonal structure, and the thickness of the frame structure at the intersection of the edges of the convex polygonal structure is smaller than the thickness of the frame structure in other parts.

[0021] According to one specific implementation of this disclosure, the intersection points of the edges of the convex polygon structure are set as a single-layer thickness frame structure.

[0022] According to one specific implementation of this disclosure, the bulk acoustic resonator has a convex pentagonal structure.

[0023] According to a specific implementation of this disclosure, the width of the single-layer thickness frame structure at the intersection point of the edges of the convex polygonal structure is greater than 0.1 μm.

[0024] According to one specific implementation of this disclosure, the bulk acoustic resonator further includes an upwardly convex structure (18) disposed above the top electrode (16).

[0025] According to one specific implementation of this disclosure, the bulk acoustic resonator further includes a protective layer (17) disposed above the top electrode (16) and the convex structure (18).

[0026] According to one specific implementation of the present disclosure, the material of the frame structure is selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above metals.

[0027] Secondly, embodiments of this disclosure provide a method for fabricating a bulk acoustic resonator, comprising:

[0028] A cavity (19) structure is etched on the substrate (10);

[0029] A bottom electrode (12) is formed above the substrate (10), and the bottom electrode (12) covers the cavity (19).

[0030] A piezoelectric functional layer (13) is formed above the bottom electrode (12);

[0031] A frame structure is formed above the piezoelectric functional layer (13); and

[0032] A top electrode (16) is formed above the frame structure.

[0033] The thickness of the frame structure is non-uniform.

[0034] According to a specific implementation of an embodiment of this disclosure, the method further includes: forming an air ring structure (11) between the piezoelectric functional layer (13) and the frame structure.

[0035] Thirdly, embodiments of this disclosure provide a filter, including a bulk acoustic resonator according to the first aspect of the present disclosure or any specific implementation thereof.

[0036] Fourthly, embodiments of this disclosure provide an electronic device, including a bulk acoustic resonator according to the first aspect of this disclosure or any specific implementation thereof, or including a filter according to the third aspect of this disclosure.

[0037] The bulk acoustic wave resonator in this embodiment includes: a substrate comprising a cavity; a bottom electrode formed above the substrate and covering the cavity; a piezoelectric functional layer formed above the bottom electrode; a frame structure formed above the piezoelectric functional layer; and a top electrode formed above the frame structure, wherein the thickness of the frame structure is non-uniform. The processing method of this disclosure improves the reliability of the device at the connection edge while limiting lateral energy leakage. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A structural diagram of a bulk acoustic resonator provided in an embodiment of this disclosure;

[0040] Figure 2 The stress result simulation diagram provided for the embodiment of this disclosure when setting a single-layer thickness frame structure;

[0041] Figure 3 The stress result simulation diagram provided in the embodiments of this disclosure when a double-thickness frame structure is set;

[0042] Figure 4 A structural diagram of another bulk acoustic resonator provided in this disclosure embodiment;

[0043] Figure 5 A schematic diagram illustrating the framework structure provided in this embodiment of the disclosure;

[0044] Figure 6This is a schematic diagram illustrating another framework structure provided in an embodiment of the present disclosure;

[0045] Figures 7-15 A schematic diagram of the process for manufacturing the bulk acoustic resonator according to an embodiment of this disclosure. Detailed Implementation

[0046] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0047] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0048] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0049] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The drawings only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0050] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0051] Traditional bulk acoustic wave (BAS) resonators typically improve their parallel resonant impedance Rp by using a single-layer frame structure. In this embodiment, to further enhance the parallel resonant impedance Rp of the BAS resonator, innovation is made in the frame structure design. Specifically, by using a double-layer frame structure on the non-connecting edges during the fabrication of the BAS resonator, the parallel resonant impedance Rp of the FBAR filter can be further increased by approximately 20-30%.

[0052] Next, with reference to the accompanying drawings, the structure of the bulk acoustic resonator according to an embodiment of the present disclosure will be described in detail.

[0053] First, the reference numerals in the embodiments of this disclosure will be described.

[0054] 10: Substrate, the optional materials are single crystal silicon, gallium arsenide, sapphire, quartz, silicon carbide, SOI, etc., with single crystal silicon being the preferred substrate material.

[0055] 11: An air ring structure, which is a ring-shaped structure formed of air or other low acoustic impedance dielectric material (e.g., SiO) above the piezoelectric functional layer 13 of the bulk acoustic resonator. Specifically, in the embodiments of this disclosure, at the non-connection edge, because the top electrode and the frame structure are etched, the structure formed by the piezoelectric functional layer 13 and the frame structure or the top electrode is a cantilever structure; at the connection edge, the structure formed by the piezoelectric functional layer 13 and the frame structure or the top electrode is a bridge structure.

[0056] 12: Bottom electrode, materials can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites of the above metals or their alloys, etc.

[0057] 13: Piezoelectric functional layer, which can be selected from single crystal piezoelectric materials, polycrystalline piezoelectric materials, or rare earth element doped materials containing a certain atomic ratio of the above materials.

[0058] Specifically, single-crystal piezoelectric materials can be selected from single-crystal aluminum nitride, single-crystal gallium nitride, single-crystal lithium niobate, single-crystal lead zirconate titanate (PZT), single-crystal potassium niobate, single-crystal quartz film, or single-crystal lithium tantalate, etc.; polycrystalline piezoelectric materials (as opposed to single-crystal, non-single-crystal materials) can be selected from polycrystalline aluminum nitride, zinc oxide, PZT, etc.; rare earth element doped materials containing a certain atomic ratio of the above materials, for example, can be Aluminum nitride doping contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.

[0059] 16: Top electrode, the material of which may be the same as that of bottom electrode 12, and the material may be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys, etc. However, it should be understood that the materials of top electrode 16 and bottom electrode 12 may also be different.

[0060] 17: Protective layer, the material of which is not limited, but the preferred materials are alumina and silicon oxide. Its function is to correct the frequency and protect the top electrode 16.

[0061] 18: The upward convex structure can be made of materials such as molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites of the above metals or their alloys. It can limit the parasitic modes of the bulk acoustic resonator and improve its performance.

[0062] 19: A cavity, a reflective structure composed of air. It should be understood that a Bragg reflector and other equivalent forms may also be used. In this embodiment, a cavity form is used.

[0063] 20, 21: Sacrificial materials can be silicon dioxide and its dopants.

[0064] 14: First frame structure: Materials can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites of the above metals or their alloys, etc.

[0065] 15: Second frame structure: Materials can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites of the above metals or their alloys, etc.

[0066] First Embodiment

[0067] Next, refer to Figure 1 This describes the structure of the bulk acoustic resonator of the present disclosure embodiment. It should be understood that... Figure 1 The bulk acoustic resonator shown can be along... Figure 5 A cross-sectional view of AOA' after cutting.

[0068] In this embodiment of the bulk acoustic wave resonator, the bottom layer is a substrate 10, which can be a single layer made of materials such as single-crystal silicon, gallium arsenide, sapphire, quartz, silicon carbide, SOI, etc.

[0069] A cavity 19 is provided above the substrate 10. The cavity 19 can reflect the sound waves on the lower surface of the bulk acoustic resonator and confine the sound wave energy in the bulk acoustic resonator to form resonance.

[0070] Above the substrate 10 with cavity 19, a bottom electrode 12 and a seed layer (not shown) are deposited. In this embodiment, the seed layer may be aluminum nitride material, the purpose of which is to improve the crystal quality of the bottom electrode 12 and the piezoelectric functional layer 13. In addition, the bottom electrode 12 may be, for example, a composite or alloy of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the above metals, and must at least cover the cavity 19.

[0071] A piezoelectric functional layer 13 is deposited above the bottom electrode 12. The piezoelectric functional layer 13 can be selected from single crystal piezoelectric material, polycrystalline piezoelectric material, or rare earth element doping material containing a certain atomic ratio of the above materials.

[0072] An air ring structure 11 is provided on the piezoelectric functional layer 13. As described above, in this embodiment of the present disclosure, it is a ring structure formed of air or other low acoustic impedance dielectric material (e.g., SiO) above the piezoelectric functional layer 13 of the bulk acoustic wave resonator, and the air ring structure is a bridge structure on the connecting side of the bulk acoustic wave resonator and a cantilever structure on the non-connecting side of the bulk acoustic wave resonator.

[0073] A top electrode 16 and an upper convex structure 18 are disposed on the air ring structure 11 and the piezoelectric functional layer 13. The material of the top electrode 16 may be the same as or different from the material of the bottom electrode 12, and the upper convex structure 18 is a protrusion on the top electrode 16, and may be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals. In the embodiments of this disclosure, the upper convex structure 18 is a region with increased thickness existing at the center of the top electrode 16, and the outer boundary of the region with increased thickness is within the frame structure or the air ring structure.

[0074] To protect the top electrode 16 and the convex structure 18, a protective layer 17 is also provided on the top electrode 16 and the convex structure 18. The structure of the protective layer 17 is not limited.

[0075] In addition, such as Figure 1 As shown in this embodiment, a frame structure is also provided between the piezoelectric functional layer 13 and the top electrode 16. The frame structure can limit the vibration intensity at the edge of the bulk acoustic resonator, thereby reducing energy leakage at the edge and improving the Q value.

[0076] It should be understood that, in Figure 1 In the structure shown, the air ring structure 11, frame structure, convex structure 18 and protective layer 17 can be omitted without affecting the function of the bulk acoustic resonator.

[0077] In this embodiment, to improve the parallel resonant impedance Rp performance of the bulk acoustic wave resonator without reducing reliability at the connection edge and thus reducing stress, the thickness of the frame structure is set to improve the parallel resonant impedance Rp performance of the bulk acoustic wave resonator while reducing stress. Specifically, in this embodiment, the thickness of the frame structure is set to be non-uniform, or the thickness of the frame structure at locations with high stress is set to be smaller than that at other locations, thereby improving the parallel resonant impedance Rp performance of the bulk acoustic wave resonator while reducing stress.

[0078] Specifically, in this embodiment, the thickness of the frame structure at the connecting edge of the bulk acoustic resonator is smaller than the thickness of the frame structure at the non-connecting edge of the bulk acoustic resonator. More specifically, a double-layered frame structure (i.e., a first frame structure 14 and a second frame structure 15) is provided at the non-connecting edge of the bulk acoustic resonator, while only a single-layered frame structure (the first frame structure 14) is provided at the connecting edge. This achieves the effect that the thickness of the frame structure at the connecting edge of the bulk acoustic resonator is smaller than the thickness of the frame structure at the non-connecting edge of the bulk acoustic resonator, thereby improving the parallel resonant point impedance Rp performance of the bulk acoustic resonator while reducing stress.

[0079] In other words, in this embodiment of the bulk acoustic wave resonator, the non-connected side and the connected side have different structural configurations. The connected side is surrounded by the upper frame structure on both sides, while the non-connected side is surrounded on only one side. Furthermore, the thickness of the frame structure on the non-connected side and the connected side is set differently to reduce stress while improving the parallel resonant point impedance Rp performance of the bulk acoustic wave resonator.

[0080] In this embodiment of the disclosure, the term "connection edge" refers to the edge where the bulk acoustic wave resonator connects to other bulk acoustic wave resonators or test PADs, typically connected via the top electrode 16 or the bottom electrode 12. Therefore, the top or bottom electrode of this edge is not etched (e.g., Figure 1 As shown on the right, its top electrode 16 is not etched); the term "non-connected edge" refers to a bulk acoustic wave resonator where the top electrode 16 or bottom electrode 12 is etched away and not connected to other bulk acoustic wave resonators or pads (e.g., ...). Figure 1 As shown on the left, its top electrode 16 is etched. That is, in Figure 1 In the diagram, the left side is a non-connected edge, and the right side is a connected edge.

[0081] Furthermore, in this embodiment, a double-layer frame structure, namely a first frame structure 14 and a second frame structure 15, is provided on the piezoelectric functional layer 13 on the non-connecting side on the left, while only a single-layer frame structure, namely the first frame structure 14, is provided on the connecting side on the right. That is, in this embodiment, by providing a double-layer thick frame structure on the non-connecting side and only a single-layer frame structure on the connecting side, the thickness of the frame structure on the non-connecting side is made greater than the thickness of the frame structure on the connecting side.

[0082] This frame structure is particularly advantageous because there are multiple film layers such as piezoelectric functional layer 13, top electrode 16, air ring structure 11, frame structure 14 and protective layer 17 at the connection edge. The multi-film layer structure, coupled with the high step difference caused by etching, will bring greater stress to the film layer at the connection edge, making the film layer prone to breakage at the connection edge.

[0083] Compared to a single-layer thick frame structure, a double-layer thick frame structure can further improve the performance of the bulk acoustic wave resonator. While a double-layer structure at the connection edge can also improve Rp, it increases the stress at the connection edge. Therefore, in this embodiment, by setting a double-layer frame structure on the piezoelectric functional layer 13 at the non-connection edge and only a single-layer frame structure at the connection edge, the Q value of the bulk acoustic wave resonator can be improved while preventing breakage at the connection edge. In other words, in this embodiment, the thickness of the frame structure at the non-connection edge can be greater than the thickness of the frame structure at the connection edge.

[0084] Additionally, the effective length of the contact between the frame structure and the piezoelectric functional layer 13 can be set. For example... Figure 1 As shown, in the presence of an air ring, d1+d2 and d3 are the effective lengths of the non-connected side and the connected side, respectively. They are the lengths of the frame structure inside the air ring that are in contact with the piezoelectric functional layer 13, that is, the lengths of the frame structure that are in contact with the piezoelectric functional layer 13 starting from the boundary of the air ring near the center of the bulk acoustic resonator.

[0085] In this embodiment, the first frame structure 14 and the second frame structure 15 in the double-layer thickness frame structure can be a stacked structure, wherein the first frame structure 14 is the frame structure close to the piezoelectric functional layer 13, and the second frame structure 15 is the frame structure away from the piezoelectric functional layer 13. Furthermore, due to the presence of an air ring, the first frame structure 14 can be configured as a "Z" shape, with its bottom edge contacting the piezoelectric functional layer 13 and its top edge contacting the second frame structure 15, the left side being the air ring structure, and the right side being the top electrode 16. In this case, at the non-connected edge of the bulk acoustic resonator, above the piezoelectric functional layer 13, there is a portion of a double-layer thickness frame structure (the portion corresponding to d1) and a portion of a single-layer thickness frame structure (the portion corresponding to d2).

[0086] In this embodiment, the effective length d1+d2 at the non-connecting edge can be equal to or unequal to the effective length d3 at the connecting edge, both ranging from 0.1μm to 10μm. That is, the values ​​of d1+d2 and d3 are both within the range of 0.1μm to 10μm. By allowing the effective length d1+d2 at the non-connecting edge to differ from the effective length d3 at the connecting edge, the influence on sound waves caused by the structural differences between the non-connecting and connecting edges can be offset.

[0087] Furthermore, in this embodiment of the present disclosure, preferably, the effective length d2 is greater than the effective length d1, so as to prevent structural damage caused by vibration of the piezoelectric functional layer 13, since this arrangement of the double-thickness frame structure is equivalent to a cantilever beam structure.

[0088] Next, with other conditions remaining unchanged, simulations were performed on the single-layer and double-layer thick frame structures, yielding the following results. Figure 2 and Figure 3 The results are shown.

[0089] Figure 2 This diagram illustrates the stress distribution when a single-layer thickness frame structure (containing only the first frame structure 14) is installed at the connection edge. Figure 3 This diagram illustrates the stress when a double-layered thick frame structure (including the first frame structure 14 and the second frame structure 15) is installed at the connection edge. As can be seen from the diagram, the maximum stress value is 2.23 when a single-layered thick frame structure is installed at the connection edge. The maximum stress value is E7Pa, while when a double-layer thickness frame structure is used at the connection edge, the maximum stress value is 3.27. E7Pa means that, under the same conditions, the maximum stress at the stress concentration point at the connection edge of the double-layer thick frame structure is increased by about 46% compared to the single-layer structure. In other words, compared to the double-layer thick frame structure, the single-layer thick frame structure can reduce the maximum stress by about 31.8%, which reduces the possibility of membrane layer fracture at the connection edge.

[0090] In this invention, the materials of the first and second frame structures can be the same or different.

[0091] In other words, in the first embodiment of this disclosure, the bulk acoustic resonator includes:

[0092] Substrate 10, substrate 10 includes cavity 19;

[0093] Bottom electrode 12 is formed above substrate 10 and covers cavity 19;

[0094] A piezoelectric functional layer 13 is formed above the bottom electrode 12;

[0095] A frame structure is formed above the piezoelectric functional layer 13; and

[0096] Top electrode 16 is formed above the frame structure.

[0097] The frame structure is a single-layer thick frame structure on the connecting side of the bulk acoustic resonator, and a double-layer thick frame structure on the non-connecting side of the bulk acoustic resonator. An air ring structure is also included between the piezoelectric functional layer 13 and the frame structure.

[0098] In this embodiment of the disclosure, by setting a double-thickness frame structure only on the non-connecting side and setting a single-thickness frame structure only on the connecting side, the Q value of the bulk acoustic resonator can be improved, thereby enhancing reliability.

[0099] Second Embodiment

[0100] Next, refer to Figure 4 The second embodiment of this disclosure is described herein, with only the differences from the first embodiment described and the same parts omitted.

[0101] In the second embodiment, the air ring structure 11 may not be provided between the piezoelectric functional layer 13 and the frame structure. In this case, the bulk acoustic resonator includes:

[0102] Substrate 10, substrate 10 includes cavity 19;

[0103] Bottom electrode 12 is formed above substrate 10 and covers cavity 19;

[0104] A piezoelectric functional layer 13 is formed above the bottom electrode 12;

[0105] A frame structure is formed above the piezoelectric functional layer 13; and

[0106] Top electrode 16 is formed above the frame structure.

[0107] The frame structure is a single-layer thickness frame structure on the connecting side of the bulk acoustic resonator, and a double-layer thickness frame structure on the non-connecting side of the bulk acoustic resonator.

[0108] At this time, in the absence of an air ring, the effective length of the connecting edge refers to the length of the frame structure within the cavity 19 that contacts the piezoelectric functional layer 13, that is, the length of the frame structure starting from the boundary of the cavity 19 that contacts the piezoelectric functional layer 13. The effective length of the non-connecting edge refers to the length of the frame structure within the etching boundary of the top electrode 16 that contacts the piezoelectric functional layer 13, that is, the length of the frame structure starting from the etching boundary that contacts the piezoelectric functional layer 13.

[0109] In this embodiment of the disclosure, the first frame structure 14 and the second frame structure 15 in the double-layer thickness frame structure can be a stacked structure, wherein the first frame structure 14 is a frame structure close to the piezoelectric functional layer 13, and the second frame structure 15 is a frame structure far away from the piezoelectric functional layer 13.

[0110] At this time, similar to the first embodiment, the effective length at the non-connected edge can be equal to or unequal to the effective length at the connected edge, and the value range is 0.1μm-10μm.

[0111] Although not specifically described, it should be understood that the bulk acoustic resonator of the present disclosure embodiment may also include a protective layer 17 and an upward convex structure 18, and a seed layer (not shown) is deposited above the substrate 10 where the cavity 19 is provided.

[0112] In this embodiment of the disclosure, by setting a double-thickness frame structure only on the non-connecting side and setting a single-thickness frame structure only on the connecting side, the Q value of the bulk acoustic resonator can be improved, thereby enhancing reliability.

[0113] Third Embodiment

[0114] Next, a third embodiment of this disclosure will be described, in which only the differences from the first and second embodiments will be described and the description of the same parts will be omitted.

[0115] The bulk acoustic resonator in this embodiment of the present disclosure can be, for example, as follows: Figure 5 The pentagonal structure shown, and the first and second embodiments are along... Figure 5 The cross-sectional view after AOA' cutting is shown, where the edges obtained by AO cutting are non-connected edges, and the edges obtained by A'O cutting are connected edges. It can be seen that only the first frame structure 14 is set on the connected edges, and a double-thickness frame structure of the first frame structure 14 and the second frame structure 15 is set on the non-connected edges.

[0116] In addition, although Figure 5 The illustration shows a pentagonal bulk acoustic resonator, but the embodiments disclosed herein are not limited thereto. The structure of the bulk acoustic resonator can be a convex polygon, such as a convex octagon, a convex dodecagon, etc.

[0117] Furthermore, since the intersection of the edges of a convex polygon (e.g., a pentagon) is a place where stress is relatively high, it is also necessary to avoid the appearance of too many layers of film. Therefore, in the embodiments of this disclosure, only one frame structure is provided at the intersection of the edges of the bulk acoustic resonator of the convex polygon, so as to prevent stress concentration at the intersection point.

[0118] Specifically, such as Figure 6 As shown, starting from the intersection point, the structure can extend along the direction of the adjacent side, with only one layer of frame structure on both sides of each intersection point. In this case, in order to alleviate stress concentration, the width of the single-layer frame structure on both sides of the intersection point needs to be greater than 0.1 μm, preferably greater than 1 μm.

[0119] Specifically, such as Figure 6 As shown, within a certain range on both sides of the intersection of adjacent non-connected sides of the bulk acoustic wave resonator, only one layer of frame structure can be provided. Furthermore, on the side of the intersection of the connected and non-connected sides of the bulk acoustic wave resonator closer to the non-connected side, one or two layers of frame structure can be provided. Preferably, a single-layer frame structure is provided on the side of the intersection of the connected and non-connected sides of the bulk acoustic wave resonator closer to the non-connected side. In other words, in this embodiment of the present disclosure, only one layer of frame structure can be provided along a certain range of the non-connected sides at the intersection of the non-connected sides of the bulk acoustic wave resonator, thereby reducing stress concentration.

[0120] Although other structures of the bulk acoustic resonator are not described in the third embodiment, the features described in the first and second embodiments can be arbitrarily combined with the features described in the third embodiment.

[0121] In other words, in this embodiment of the disclosure, the bulk acoustic resonator includes:

[0122] Substrate 10, substrate 10 includes cavity 19;

[0123] Bottom electrode 12 is formed above substrate 10 and covers cavity 19;

[0124] A piezoelectric functional layer 13 is formed above the bottom electrode 12;

[0125] A frame structure is formed above the piezoelectric functional layer 13; and

[0126] Top electrode 16 is formed above the frame structure.

[0127] The frame structure is a single-layer thick frame structure on the connecting side of the bulk acoustic resonator and a double-layer thick frame structure on the non-connecting side of the bulk acoustic resonator. The bulk acoustic resonator can be a convex polygon structure, wherein the intersection point of the edges of the convex polygon structure is set as a single-layer thick frame structure.

[0128] Method Implementation Examples

[0129] Next, refer to Figures 7-15 The fabrication process of the bulk acoustic wave resonator of the first embodiment of the present invention is described, but it should be understood that the bulk acoustic wave resonators of the second and third embodiments can be fabricated similarly.

[0130] Step 1: As Figure 7 As shown, a cavity 19 structure is etched on the substrate 10. The etching process can be dry etching or wet etching. Dry etching can be sputtering and ion beam milling, plasma etching, high-pressure plasma etching, high-density plasma (HDP) etching, or reactive ion etching (RIE).

[0131] Step 2: As Figure 8 As shown, a layer of silicon phosphosilicate glass (PSG) is deposited as a sacrificial material on the etched substrate 10. The upper surface of the sacrificial material layer is larger than the upper surface of the substrate 10, and the thickness of the sacrificial material layer is greater than the depth of the cavity 19 structure. The deposition method can be, for example, chemical vapor deposition (CVD) or PEVCD.

[0132] Step 3: As Figure 9 As shown, the above structure is subjected to chemical mechanical polishing (CMP) to expose the upper surface of the substrate 10 covered by the sacrificial material, and to make the upper surface of the sacrificial material layer flush with the upper surface of the substrate 10, at which point the cavity 19 is filled with the sacrificial material.

[0133] Step 4: As Figure 10 As shown, in Figure 9 The seed layer and bottom electrode 12 material are deposited and etched on the structure shown to obtain the bottom electrode 12 structure. Specifically, a metal layer can be deposited on the surface of the substrate 10 and the sacrificial material by sputtering or evaporation, and the bottom electrode 12 is formed by patterning the metal layer through photolithography and etching processes.

[0134] Step 5: As Figure 11As shown, a piezoelectric functional layer 13 is deposited, and an air ring sacrificial layer 21 is deposited on the piezoelectric functional layer 13, and a first-layer framework structure 14 is patterned and fabricated. Specifically, a piezoelectric material layer is deposited on the surfaces of the substrate 10 and the bottom electrode 12 to form the piezoelectric functional layer 13, and an air ring sacrificial layer 21 is deposited on the piezoelectric functional layer 13, and a first-layer framework structure 14 is patterned and fabricated.

[0135] Step 6: As Figure 12 As shown, a second frame structure 15 is patterned and fabricated on the first frame structure 14. In this embodiment of the disclosure, the second frame structure 15 is fabricated only on the non-connected sides of the bulk acoustic wave resonator, and not on the connected sides of the bulk acoustic wave resonator.

[0136] Step 7: As Figure 13 As shown, in Figure 12 A metal layer is deposited on the upper surface of the structure shown, and the metal layer is patterned into a top electrode 16 and an upper convex structure 18.

[0137] Step 8: As Figure 14 As shown, in Figure 13 A protective layer 17 is formed by applying a patterned passivation layer material to the upper surface of the structure shown.

[0138] Step 9: Remove the materials from sacrificial layer 20 and sacrificial layer 21 to obtain the final device.

[0139] It should be understood that the method for preparing the bulk acoustic resonator in the second embodiment is similar to that in the fourth embodiment, except that in step 5, after depositing the piezoelectric functional layer 13, an air ring sacrificial layer 21 is not deposited on the piezoelectric functional layer 13, but only the first frame structure 14 is patterned and prepared.

[0140] It should be understood that the method for preparing the bulk acoustic resonator in the third embodiment is similar to that in the fourth embodiment, except that in step 6, not only is the second frame structure 15 not prepared on the connecting edge of the bulk acoustic resonator, but the second frame structure 15 is also not prepared on both sides of the intersection of the non-connecting edge of the bulk acoustic resonator.

[0141] Furthermore, as those skilled in the art will understand, the bulk acoustic resonator according to this disclosure can be used to form filters or electronic devices. These electronic devices include, but are not limited to, intermediate products such as RF front-ends and filtering / amplifying modules, as well as terminal products such as mobile phones, Wi-Fi devices, and drones.

[0142] Based on the above, the present disclosure proposes the following solutions:

[0143] 1. A bulk acoustic resonator, comprising:

[0144] Substrate (10), said substrate (10) includes a cavity (19);

[0145] A bottom electrode (12) is formed above the substrate (10) and covers the cavity (19).

[0146] A piezoelectric functional layer (13) is formed above the bottom electrode (12);

[0147] A frame structure is formed above the piezoelectric functional layer (13); and

[0148] The top electrode (16) is formed above the frame structure.

[0149] The thickness of the frame structure is non-uniform.

[0150] 2. The bulk acoustic resonator according to 1, characterized in that an air ring structure (11) is further included between the piezoelectric functional layer (13) and the frame structure, wherein the air ring structure is a bridge structure on the connecting side of the bulk acoustic resonator and a cantilever structure on the non-connecting side of the bulk acoustic resonator.

[0151] 3. In the bulk acoustic resonator according to 1 or 2, the thickness of the frame structure on the connecting side of the bulk acoustic resonator is smaller than the thickness of the frame structure on the non-connecting side of the bulk acoustic resonator.

[0152] 4. According to the bulk acoustic resonator described in 3, the frame structure is a single-layer thickness frame structure on the connecting side of the bulk acoustic resonator, and the frame structure is a double-layer thickness frame structure on the non-connecting side of the bulk acoustic resonator.

[0153] 5. According to the bulk acoustic resonator of 4, the double-layer thickness frame structure includes a stacked first frame structure (14) and a second frame structure (15), wherein the first frame structure (14) is a frame structure close to the piezoelectric functional layer (13), and the second frame structure (15) is a frame structure far away from the piezoelectric functional layer (13).

[0154] 6. According to 1 or 2, the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting side is different from the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting side; or

[0155] The effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting edge is the same as the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting edge.

[0156] 7. According to the bulk acoustic resonator of 1 or 2, the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting side and the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting side are both in the range of 0.1μm-10μm.

[0157] 8. The bulk acoustic resonator according to 1 or 2, wherein the bulk acoustic resonator is a convex polygonal structure, and the thickness of the frame structure at the intersection of the edges of the convex polygonal structure is smaller than the thickness of the frame structure in other parts.

[0158] 9. According to the bulk acoustic resonator described in 8, the intersection points of the edges of the convex polygonal structure are configured as a single-layer thickness frame structure, and the other parts are configured as a double-layer thickness frame structure.

[0159] 10. The bulk acoustic resonator according to 8, wherein the bulk acoustic resonator has a convex pentagonal structure.

[0160] 11. According to the bulk acoustic resonator of 9, the width of the single-layer thickness frame structure at the intersection of the edges of the convex polygonal structure is greater than 1 μm.

[0161] 12. The bulk acoustic resonator according to 1 or 2, wherein the bulk acoustic resonator further includes an upper convex structure (18) disposed above the top electrode (16).

[0162] 13. The bulk acoustic resonator according to 1 or 2, the bulk acoustic resonator further includes a protective layer (17) disposed above the top electrode (16) and the convex structure (18).

[0163] 14. The bulk acoustic resonator according to 1 or 2, wherein the material of the frame structure is selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or alloys thereof.

[0164] 15. A method for fabricating a bulk acoustic resonator, comprising:

[0165] A cavity (19) structure is etched on the substrate (10);

[0166] A bottom electrode (12) is formed above the substrate (10), and the bottom electrode (12) covers the cavity (19).

[0167] A piezoelectric functional layer (13) is formed above the bottom electrode (12);

[0168] A frame structure is formed above the piezoelectric functional layer (13); and

[0169] A top electrode (16) is formed above the frame structure.

[0170] The thickness of the frame structure is non-uniform.

[0171] 16. The method for preparing a bulk acoustic resonator according to 15 further includes: forming an air ring structure (11) between the piezoelectric functional layer (13) and the frame structure.

[0172] 17. A filter comprising a bulk acoustic resonator according to any one of 1-14.

[0173] 18. An electronic device comprising a bulk acoustic resonator according to any one of 1-14 or comprising a filter according to 17.

[0174] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A bulk acoustic wave resonator, characterized by, include: A substrate (10) comprising a cavity (19); A bottom electrode (12) is formed above the substrate (10) and covers the cavity (19); A piezoelectric functional layer (13) is formed above the bottom electrode (12); A frame structure is formed above the piezoelectric functional layer (13); and Top electrode (16) is formed above the frame structure. The thickness of the frame structure is non-uniform; Wherein, the thickness of the frame structure on the connecting side of the bulk acoustic resonator is smaller than the thickness of the frame structure on the non-connecting side of the bulk acoustic resonator. The frame structure is a single-layer thickness frame structure on the connecting side of the bulk acoustic resonator, and the frame structure is a double-layer thickness frame structure on the non-connecting side of the bulk acoustic resonator. The double-layer thickness frame structure includes a stacked first frame structure (14) and a second frame structure (15), wherein the first frame structure (14) is a frame structure close to the piezoelectric functional layer (13), and the second frame structure (15) is a frame structure away from the piezoelectric functional layer (13).

2. The bulk acoustic resonator of claim 1, wherein, An air ring structure (11) is also included between the piezoelectric functional layer (13) and the frame structure. The air ring structure is a bridge structure on the connecting side of the bulk acoustic resonator and a cantilever structure on the non-connecting side of the bulk acoustic resonator.

3. The bulk acoustic resonator of claim 1 or 2, wherein, The effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting edge is different from the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting edge; or The effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting edge is the same as the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting edge.

4. The bulk acoustic resonator of claim 1 or 2, wherein, The effective length of the frame structure in contact with the piezoelectric functional layer (13) at the non-connecting edge and the effective length of the frame structure in contact with the piezoelectric functional layer (13) at the connecting edge are both in the range of 0.1μm-10μm.

5. The bulk acoustic resonator of claim 1 or 2, wherein, The bulk acoustic resonator has a convex polygonal structure, and the thickness of the frame structure at the intersection of the edges of the convex polygonal structure is smaller than the thickness of the frame structure in other parts.

6. The bulk acoustic resonator according to claim 5, characterized in that, The intersection points of the edges of the convex polygon structure are set as single-layer thickness frame structures.

7. The bulk acoustic resonator according to claim 5, characterized in that, The bulk acoustic resonator has a convex pentagonal structure.

8. The bulk acoustic resonator according to claim 5, characterized in that, The width of the single-layer thickness frame structure at the intersection of the edges of the convex polygon structure is greater than 0.1 μm.

9. The bulk acoustic resonator according to claim 1 or 2, characterized in that, The bulk acoustic resonator also includes an upward convex structure (18) disposed above the top electrode (16).

10. The bulk acoustic resonator according to claim 9, characterized in that, The bulk acoustic resonator also includes a protective layer (17) disposed above the top electrode (16) and the convex structure (18).

11. The bulk acoustic resonator according to claim 1 or 2, characterized in that, The material of the frame structure is selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above metals.

12. A method for fabricating a bulk acoustic resonator, characterized in that, include: A cavity (19) structure is etched on the substrate (10); A bottom electrode (12) is formed above the substrate (10), and the bottom electrode (12) covers the cavity (19); A piezoelectric functional layer (13) is formed above the bottom electrode (12); A frame structure is formed above the piezoelectric functional layer (13); and A top electrode (16) is formed above the frame structure; The thickness of the frame structure is non-uniform; Wherein, the thickness of the frame structure on the connecting side of the bulk acoustic resonator is smaller than the thickness of the frame structure on the non-connecting side of the bulk acoustic resonator. The frame structure is a single-layer thickness frame structure on the connecting side of the bulk acoustic resonator, and the frame structure is a double-layer thickness frame structure on the non-connecting side of the bulk acoustic resonator. The double-layer thickness frame structure includes a stacked first frame structure (14) and a second frame structure (15), wherein the first frame structure (14) is a frame structure close to the piezoelectric functional layer (13), and the second frame structure (15) is a frame structure away from the piezoelectric functional layer (13).

13. The method for preparing a bulk acoustic resonator according to claim 12, characterized in that, Also includes: An air ring structure (11) is formed between the piezoelectric functional layer (13) and the frame structure.

14. A filter, characterized in that, Includes a bulk acoustic resonator according to any one of claims 1-11.

15. An electronic device, characterized in that, It includes a bulk acoustic resonator according to any one of claims 1-11 or a filter according to claim 14.

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