Bulk acoustic wave resonator, filter, and electronic device having multiple bottom electrode layers

Abstract

The present application relates to a bulk acoustic wave resonator and a manufacturing method thereof. The resonator includes a substrate, a bottom electrode, a top electrode, and a piezoelectric layer, wherein: the bottom electrode includes a plurality of electrode layers, the plurality of electrode layers includes at least a first electrode layer and a second electrode layer disposed in a thickness direction of the resonator, the second electrode layer covers at least a portion of an upper side of the first electrode layer; the resonator further includes a cover layer, and an upper surface of the cover layer is offset from an upper surface of the second electrode layer in a height direction of the resonator outside a non-electrode connection end of the bottom electrode. The present application also relates to a filter and an electronic device.

Description

Technical Field

[0001] Embodiments of the present invention relate to the semiconductor field, and more particularly to a bulk acoustic wave resonator and a method for manufacturing the same, a filter having the resonator, and an electronic device. Background Technology

[0002] Electronic components, as fundamental elements of electronic devices, are widely used in mobile phones, automobiles, and home appliances. Furthermore, future world-changing technologies such as artificial intelligence, the Internet of Things, and 5G communications still rely on electronic components as their foundation.

[0003] Film Bulk Acoustic Resonators (FBARs, also known as BAWs) are playing a vital role in the communications field as an important member of piezoelectric devices. In particular, FBAR filters are gaining an increasingly larger market share in the radio frequency (RF) filter sector. FBARs possess excellent characteristics such as small size, high resonant frequency, high quality factor, large power capacity, and good roll-off effect. Their filters are gradually replacing traditional surface acoustic wave (SAW) filters and ceramic filters, playing a significant role in the RF field of wireless communications. Their high sensitivity advantage can also be applied to sensing fields such as biology, physics, and medicine.

[0004] The main structure of a thin-film bulk acoustic resonator (FBAR) is a "sandwich" structure consisting of an electrode-piezoelectric thin film-electrode, that is, a piezoelectric material sandwiched between two layers of metal electrodes. By inputting a sinusoidal signal between the two electrodes, the FBAR uses the inverse piezoelectric effect to convert the input electrical signal into mechanical resonance, and then uses the piezoelectric effect to convert the mechanical resonance into an electrical signal output.

[0005] For bulk acoustic resonators, a bottom electrode is configured to include multiple layers of electrodes. For example... Figure 1 and Figure 2 As shown, the resonator includes a substrate 101, an acoustic mirror or acoustic mirror cavity 102, a bottom electrode layer 103, a bottom electrode layer 104, a piezoelectric layer 105, a top electrode 106, and a passivation layer or process layer 107.

[0006] When forming a bottom electrode, etching or patterning a bottom electrode layer can damage the surface structure of the film layer beneath it. For example, etching two bottom electrode layers can damage areas without bottom electrodes (e.g., areas without bottom electrodes). Figure 1 The substrate 101 in region A of the structure was damaged to some extent, which led to... Figure 1 The piezoelectric layer and top electrode subsequently grown in region A will form severe defects, thus affecting the performance of the resonator.

[0007] Furthermore, because it is difficult to ensure that the materials of the bottom electrode layer 103 and the bottom electrode layer 104 have exactly the same etching rate during patterning, the edge etching angles of the two materials cannot be made the same, resulting in... Figure 2 As shown, a corner structure appears in region B. This corner structure causes severe defects in the subsequent film layers, such as the piezoelectric layer 105 and the top electrode 106, in this region, thus affecting the resonator performance. Summary of the Invention

[0008] The present invention is proposed to alleviate or solve at least one of the above-mentioned problems in the prior art.

[0009] According to one aspect of an embodiment of the present invention, a bulk acoustic resonator is provided, comprising:

[0010] Base;

[0011] Bottom electrode;

[0012] Top electrode; and

[0013] piezoelectric layer

[0014] in:

[0015] The bottom electrode includes multiple electrode layers, including at least a first electrode layer and a second electrode layer disposed in the thickness direction of the resonator, wherein the second electrode layer covers at least a portion of the upper side of the first electrode layer;

[0016] The resonator further includes a cover layer, and outside the non-electrode connection end of the bottom electrode, the upper surface of the cover layer is offset from the upper surface of the second electrode layer in the height direction of the resonator.

[0017] According to another aspect of the present invention, a method for manufacturing a bulk acoustic resonator is provided, the resonator including a bottom electrode and a piezoelectric layer, the bottom electrode including a plurality of electrode layers, the plurality of electrode layers including at least a first electrode layer and a second electrode layer disposed in the thickness direction of the resonator, the second electrode layer covering at least a portion of the upper side of the first electrode layer, the method including the steps of: disposing a cover layer at a non-electrode connection end of the bottom electrode, and on the outside of the non-electrode connection end of the bottom electrode, the upper surface of the cover layer is offset from the upper surface of the second electrode layer in the height direction of the resonator.

[0018] Embodiments of the present invention also relate to a filter, including the aforementioned bulk acoustic resonator.

[0019] Embodiments of the present invention also relate to an electronic device, including the filter or the resonator described above. Attached Figure Description

[0020] The following description and accompanying drawings will better aid in understanding these and other features and advantages of the various embodiments disclosed herein, wherein the same reference numerals in the drawings always denote the same parts, wherein:

[0021] Figures 1-2 A schematic diagram of the cross-section of a known bulk acoustic resonator;

[0022] Figure 3 A schematic cross-sectional view of a bulk acoustic resonator according to an exemplary embodiment of the present invention;

[0023] Figures 4A-4F To illustrate an exemplary embodiment of the present invention Figure 3 A cross-sectional schematic diagram of the manufacturing process of a bulk acoustic resonator;

[0024] Figure 5-8 A schematic cross-sectional view of a bulk acoustic resonator according to different exemplary embodiments of the present invention;

[0025] Figure 9 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to an exemplary embodiment of the present invention, wherein a void layer is provided in the bottom electrode. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation thereof. These are only some embodiments of the invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0027] For bulk acoustic resonators with multiple bottom electrode layers, the present invention provides a covering layer at the non-electrode connection end of the bottom electrode to avoid or reduce the appearance of edges at the non-electrode connection ends of each bottom electrode layer. Figure 2 The defects caused by region B shown, and / or further avoidance or reduction of defects at the non-electrode connection end of the bottom electrode. Figure 1 The defect that appears in region A.

[0028] The reference numerals in the drawings of this invention are explained as follows:

[0029] 101: Substrate, with optional materials including single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0030] 102: Acoustic mirror, which can be a cavity, or it can be a Bragg reflector layer or other equivalent forms.

[0031] 103: Bottom electrode layer, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals.

[0032] 104: Bottom electrode layer, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys, etc. The materials of bottom electrode layer 103 and bottom electrode layer 104 can be different.

[0033] 105: Piezoelectric layer. The material can be aluminum nitride, gallium nitride, lithium niobate, lead zirconate titanate (PZT), potassium niobate, quartz film, zinc oxide, etc. It can also be a rare earth element doped material containing a certain atomic ratio of the above materials. For example, it can be doped aluminum nitride, which 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.

[0034] 106: Top electrode or top electrode layer. Materials may include molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or composites or alloys of these metals. The top and bottom electrodes are generally made of the same material, but they can also be different.

[0035] 107: Dielectric layer or process layer, which is generally made of dielectric material, such as aluminum nitride, silicon dioxide, silicon nitride, etc. If understood, a dielectric layer or process layer may not be provided.

[0036] 108: Seed layer or barrier layer, materials can include AlN, SiN, etc.

[0037] 109: Seed layer or barrier layer, materials can include AlN, SiN, etc.

[0038] 110: Acoustic impedance mismatch structure: This can be made of air, SiO2, SiN, etc., as mentioned later. Alternatively, an acoustic impedance mismatch structure may not be required. An acoustic impedance mismatch structure is one type of acoustic mismatch structure.

[0039] 111: Protruding structure. Materials can include molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a combination of these metals or their alloys. A protruding structure is optional. The protruding structure is a type of acoustic mismatch structure. Although not shown in the figure, other acoustic mismatch structures such as recessed structures, bridge structures, and cantilever structures can also be used.

[0040] 112: Bottom electrode layer, the material of which may be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys, etc. In optional embodiments, the material of bottom electrode layer 112 may be the same as that of bottom electrode layer 104.

[0041] 113: The capping layer can be made of metal, which is advantageous, or it can be a dielectric material such as AlN, SiN, or SiO2.

[0042] 115: Sacrificial layer, the material can be AlN, SiN, SiO2, etc.

[0043] Figure 3 This is a schematic cross-sectional view of a bulk acoustic resonator according to an exemplary embodiment of the present invention. Figure 3 As shown, the bulk acoustic resonator includes:

[0044] Substrate 101;

[0045] Acoustic mirror 102, in Figure 3 It is in the form of a cavity;

[0046] The bottom electrode includes a bottom electrode layer 103 and a bottom electrode layer 104 disposed in the thickness direction of the resonator. Optionally, the materials of the bottom electrode layer 103 and the bottom electrode layer 104 are different from each other.

[0047] Top electrode 106; and

[0048] A piezoelectric layer 105 is disposed between the bottom electrode and the top electrode 106.

[0049] exist Figure 3 In the resonator, a dielectric layer or process layer 107 is also included. As mentioned above, the dielectric layer or process layer 107 may not be provided.

[0050] exist Figure 3 In the embodiments shown, as will be understood, the bottom electrode may not only include bottom electrode layers 103 and 104, but may also include more bottom electrode layers.

[0051] like Figure 3 As shown, the acoustic mirror 102 is disposed in the substrate 101, and the bottom electrode layer 103 covers the upper side of the acoustic mirror 102. The bottom electrode layer 104 covers the upper side of the bottom electrode layer 103 and is located between the piezoelectric layer 105 and the bottom electrode layer 103 in the thickness direction of the resonator.

[0052] from Figure 3 It can be seen that the resonator also includes a capping layer 113. At the non-electrode connection end of the bottom electrode, the end face of the bottom electrode layer 103 and a portion of the bottom electrode layer 104 are covered by the capping layer 113, and the upper surface of the capping layer 113 is lower than the upper surface of the bottom electrode layer 104. Thus, Figure 3 The structure shown is replaced by the upper surface of the cover layer 113. Figure 2 The cornered end face at region B in the diagram. Using... Figure 3 The structure shown facilitates the subsequent deposition of the piezoelectric layer 105 and the top electrode 106, thereby avoiding or reducing [the following]. Figure 2 The defect is caused by the corner structure at point B.

[0053] In addition, such as Figure 3 As shown, on the outside of the non-electrode connection end of the bottom electrode, the capping layer 113 covers at least a portion of the upper surface of the substrate. Alternatively, although not shown, if a seed layer is provided on the upper side of the substrate, the capping layer 113 covers at least a portion of the upper surface of the seed layer provided on the upper surface of the substrate. Thus, the upper surface of the capping layer 113 is used instead of the seed layer. Figure 1 The upper surface of the substrate 101 in region A shown in the diagram, thereby facilitating Figure 1 A piezoelectric layer and top electrode are subsequently grown in region A to reduce defects in the resonator.

[0054] Figure 5 This is a schematic cross-sectional view of a bulk acoustic resonator according to another exemplary embodiment of the present invention, which is consistent with... Figure 3 The difference is that, in Figure 5 In the middle, a barrier layer 109 was added, such as Figure 5 As shown, the bottom electrode layer 103 covers the barrier layer 109 and the barrier layer 109 defines at least a portion of the upper boundary of the acoustic mirror cavity 102.

[0055] exist Figure 1 and Figure 2 In the structure shown, because the acoustic impedance of metallic Al is low, the electrode layer in the multilayer electrode of the bottom electrode that is far from the piezoelectric layer, i.e. Figure 1 and Figure 2 The bottom electrode layer 103 in the structure is often made of metal Al. However, in cases such as Figure 1 and Figure 2 In the resonator structure shown, the acoustic mirror cavity 102 is typically formed by etching sacrificial material SiO2 with HF. During the process of releasing the sacrificial material using HF, HF readily reacts with... Figure 1 The bottom electrode layer 103 located on the upper side of the acoustic mirror cavity 102 is in surface contact, and it is also easy to contact the surface of the bottom electrode layer 103 located on the upper side of the acoustic mirror cavity 102 ... Figure 2 The uneven portion shown in Figure B corrodes the bottom electrode layer 103, leading to the destruction of the resonator structure. Because... Figure 5 The structure shown is relative to Figure 3 The structure shown also includes a barrier layer 109, which, in addition to providing... Figure 3 In addition to the advantages or technical effects of the structure shown, Figure 5The barrier layer 109 in the structure shown can also be designed to resist the release of agents such as HF, thereby avoiding or reducing the release of HF. Figure 1 and Figure 2 The structure shown illustrates the corrosion of the bottom electrode layer 103 during the release of sacrificial material from the acoustic mirror cavity.

[0056] exist Figure 5 In this embodiment, the barrier layer 109 is flush with the non-electrode connection end of the bottom electrode layer 103. In an alternative embodiment, although not shown, the barrier layer 109 may also extend inside the non-electrode connection end of the bottom electrode layer 103.

[0057] In an optional embodiment, although not shown, the barrier layer 109 may also extend outside the non-electrode connection end of the base electrode layer 103 at its non-electrode connection end. In this case, the non-electrode connection end of the cover layer 113 may cover at least a portion of the upper side of the barrier layer 109. In this case, the barrier layer 109 corresponds to the seed layer disposed on the upper side of the substrate mentioned above.

[0058] The following reference Figures 4A-4E Exemplary Description Figure 3 The manufacturing process of the resonator structure shown.

[0059] like Figure 4A As shown, a substrate 101 is provided, and a cavity or groove is formed on the upper side of the substrate 101, the cavity or groove being filled with a sacrificial layer 115. As will be understood, the sacrificial layer 115 may be formed by CMP (Chemical Mechanical Polishing) after a sacrificial material layer (which fills the cavity on the upper side of the substrate) is disposed on the upper side of the substrate 101. Figure 4A In the structure shown, the upper surface of the sacrificial layer 115 is flush with the upper surface of the substrate 101. The sacrificial layer 115 can be released in a subsequent step to form the acoustic mirror structure of the resonator.

[0060] like Figure 4B As shown, in Figure 4A Based on the structure shown, two bottom electrode material layers are deposited and patterned to form bottom electrode layer 103 and bottom electrode layer 104.

[0061] like Figure 4C As shown, in Figure 4B Based on the structure shown, a cover material layer (corresponding to 113) is deposited. The material can be, for example, AlN, SiN, SiO2, etc. The upper surface of this cover material layer is higher than the upper surface of the bottom electrode layer 104 at the non-electrode connection end of the bottom electrode. The thickness of the cover material layer is greater than the sum of the thicknesses of the bottom electrode layer 103 and the bottom electrode layer 104.

[0062] like Figure 4D As shown, in Figure 4C Based on the structure shown, a CMP process is used to smooth the cover material layer (corresponding to 113), ultimately ensuring that a portion of the cover material thickness remains on the bottom electrode layer 104 to prevent damage to the bottom electrode layer 104 during the CMP process. Since the thickness of the bottom electrode layer is crucial to the frequency of the bulk acoustic wave resonator, and the thickness control precision of CMP is far lower than that of the deposition process, it is best to avoid allowing the CMP process to contact the bottom electrode layer 104 to ensure the accuracy of its thickness.

[0063] like Figure 4E As shown, for Figure 4D The structure shown involves removing the cover material layer on the upper surface of the bottom electrode layer 104 and thinning the cover material layer at the non-electrode connection end of the bottom electrode to form a structure as shown. Figure 4E The cover layer 113 is shown. In Figure 4E In the corresponding steps, no photolithography process is required; etching can be performed on the entire wafer. In one embodiment, wet etching is selected to etch the entire wafer, and only the cover material layer is etched, while the thickness of the bottom electrode layer 104 remains essentially unchanged (in this invention, "unchanged thickness" includes not only maintaining the original thickness but also essentially maintaining the thickness, such as when the thickness loss is within the range permitted by the process) to maintain the thickness accuracy of the bottom electrode layer 104, thereby ensuring the thickness accuracy of the bottom electrode layer 104. Simultaneously, to ensure that the cover material on the upper surface of the bottom electrode layer 104 is thoroughly cleaned, a certain amount of over-etching is required in the etching time. Therefore, after etching, the upper surface of the cover layer 113 can be lower than the upper surface of the bottom electrode layer 104. Because the cover layer 113 has undergone CMP processing, the non-electrode connection ends of the bottom electrode can be smooth surfaces, thus not affecting subsequent film growth. Furthermore, the upper surface of the cover layer 113 is advantageously higher than the upper surface of the bottom electrode layer 103, thereby protecting or covering the corner between the bottom electrode layer 103 and the bottom electrode layer 104 at the non-electrode connection end.

[0064] like Figure 4F As shown, in Figure 4E Based on the structure shown, a piezoelectric layer 105 is deposited. For example... Figure 4F As shown, the piezoelectric layer 105 covers the upper surface of the bottom electrode layer 104 and the upper surface of the cover layer 113.

[0065] Although not shown, it can be understood by those skilled in the art that... Figure 4F Based on the structure shown, a bottom electrode 106 and a process layer 107 are formed. The sacrificial layer 115 is selectively etched or released to form the acoustic mirror cavity 102, thereby obtaining... Figure 3 The resonator structure shown is shown.

[0066] In a further optional embodiment, the materials of the bottom electrode layer 103 and the bottom electrode layer 104 are different, which may be Figure 3 The acoustic impedance of the bottom electrode layer 104 is higher than that of the bottom electrode layer 103. Figure 3 The conductivity of the bottom electrode layer 103 is higher than that of the bottom electrode layer 104.

[0067] In one embodiment of the present invention, the resonator may also be provided with an acoustic mismatch structure disposed along the effective region of the resonator. Figure 6 An exemplary structure is shown. Figure 6 In this design, the top electrode has an acoustic impedance mismatch structure 110 and a protrusion structure 111 at both the non-electrode connection end and the electrode connection end. Both the acoustic impedance mismatch structure 110 and the protrusion structure 111 are acoustic mismatch structures. In other specific embodiments, only the acoustic impedance mismatch structure 110 or the protrusion structure 111 may be provided, or other acoustic mismatch structures such as a recessed structure may also be provided. Furthermore, the position of the acoustic mismatch structure in the thickness direction of the resonator is not limited to... Figure 6 The electrode shown is located between the top electrode 106 and the piezoelectric layer 105. It can also be disposed in the piezoelectric layer, or between the piezoelectric layer and the bottom electrode, etc. All of these are within the protection scope of this invention.

[0068] exist Figure 3-6 In the illustrated embodiment, the upper surface of the capping layer 113 is lower than the upper surface of the bottom electrode layer 104, but the invention is not limited thereto. The upper surface of the capping layer 113 may also be higher than the upper surface of the bottom electrode layer 104. Figure 7 Such a structure is illustrated in the example. Figure 7 As shown, the upper surface of the capping layer 113 may also be higher than the upper surface of the bottom electrode layer 104. In addition, a portion of the capping layer 113 also covers a portion of the upper surface of the bottom electrode layer 104. Although not shown, the capping layer 113 may also not cover the upper surface of the bottom electrode layer 104.

[0069] Figure 8 This is a schematic cross-sectional view of a bulk acoustic resonator according to another exemplary embodiment of the present invention. Figure 8 In the structure shown, the capping layer 113 covers a portion of the upper surface of the bottom electrode layer 104, and covers the end faces of the bottom electrode layer 104 and the bottom electrode layer 103. By providing the capping layer 113, even if the end faces of the non-electrode connection ends of the bottom electrode layers 104 and 103 have... Figure 2 The corner structure shown can also be effectively mitigated or reduced by the cover layer 113.

[0070] like Figure 8As shown, the upper surface of the portion of the cover layer 113 located outside the non-electrode connection end of the bottom electrode layer 103 is lower than the upper surface of the bottom electrode layer 104, but the cover layer 113 also includes a portion covering the upper surface of the bottom electrode layer 104.

[0071] The capping layer 113 can be a metallic layer or a non-metallic layer. In an advantageous embodiment, the capping layer 113 is a non-metallic layer. When the capping layer 113 is a non-metallic layer, no patterning is required outside the non-connection terminals of the bottom electrode (because it does not lead to interconnection of bottom electrodes between different resonators), thereby allowing other areas to be flattened; in addition, since the piezoelectric layer is prone to defects at the ramp, adding a non-metallic capping layer can further improve the electrostatic discharge resistance.

[0072] exist Figures 5-8 In the embodiment shown, the upper surface of the cover layer 113 is used instead of Figure 2 The cornered end face at region B in the image facilitates the subsequent deposition of the piezoelectric layer 105 and the top electrode 106, thereby avoiding or reducing [the risk of damage]. Figure 2 The defect is caused by the corner structure at point B. Furthermore, in... Figure 5-8 In the structure shown, on the outer side of the non-electrode connection end of the bottom electrode, the capping layer 113 covers at least a portion of the upper surface of the substrate. Thus, the upper surface of the capping layer 113 replaces... Figure 1 The upper surface of the substrate 101 in region A shown in the diagram, thereby facilitating Figure 1 A piezoelectric layer and top electrode are subsequently grown in region A to reduce defects in the resonator.

[0073] exist Figures 3-8 In the illustrated embodiment, the acoustic mirror 102 is disposed within the substrate 101, but the invention is not limited thereto. The acoustic mirror may also be disposed within the bottom electrode, thus making the bottom electrode a gap electrode; or the acoustic mirror may be disposed between the bottom electrode and the substrate. All of these are within the scope of protection of this invention.

[0074] Figure 9 This is a schematic cross-sectional view of a bulk acoustic resonator according to yet another exemplary embodiment of the present invention. Figure 9 In the structure shown, the acoustic mirror of the resonator is located in the bottom electrode. For example... Figure 9 As shown, a void layer 102 is defined between the bottom electrode layer 112 and the bottom electrode layer 103. Optionally, the material of the bottom electrode layer 112 may be different from the material of the bottom electrode layer 103.

[0075] exist Figure 9 As can be seen, on the outside of the non-electrode connection end of the bottom electrode, the upper surface of the cover layer 113 is lower than the upper surface of the bottom electrode layer 104 within the effective region of the resonator.

[0076] like Figure 9 As shown, at the non-electrode connection end, the bottom electrode layer 104 covers the end face of the bottom electrode layer 103 and the end face of the barrier layer 108, and the end of the bottom electrode layer 112 is located outside the end of the bottom electrode layer 103. In an optional embodiment, as... Figure 9 As shown, the end face of the bottom electrode layer 104 is flush with the end face of the bottom electrode layer 112. The material of the bottom electrode layer 104 and the bottom electrode layer 112 can be the same, which is beneficial to make the end face of the bottom electrode layer 104 flush with the end face of the bottom electrode layer 112 in the subsequent patterning process.

[0077] exist Figure 9 It contains a blocking layer or seed layer 108, but it can also be obtained from... Figure 9 Remove from the structure shown. Figure 9 In this process, the end face of the barrier layer 108 at the non-connected end of the bottom electrode is flush with the end face of the bottom electrode layer 103. However, the end face of the barrier layer 108 may also be located outside or inside the end face of the bottom electrode layer 103.

[0078] Although not shown, in another embodiment, at the non-electrode connection end of the bottom electrode, at Figure 9 The end faces of the bottom electrode layer 103 and the bottom electrode layer 112 can be flush, and the non-electrode connection end of the bottom electrode layer 104 covers the end faces of the bottom electrode layers 103 and 112. In another optional embodiment, Figure 9 The end faces of the bottom electrode layers 103 and 112 may not be flush, but the non-electrode connection end of the bottom electrode layer 104 shall at least cover the end face of the bottom electrode layer 103.

[0079] Although not shown, in Figure 9 In the structure shown, the bottom electrode layer 112 may not be provided separately. Instead, a gap layer 102 is formed between the bottom electrode layer 103 and the bottom electrode layer 104. At the same time, at the non-electrode connection end of the bottom electrode, the end of the bottom electrode layer 104 covers the end face of the bottom electrode layer 103.

[0080] In this invention, although wet etching is used as an example to illustrate the etching of the cover material layer to form the cover layer 113, this invention is not limited to wet etching. Any etching process that can achieve "etching only the cover material layer, but not substantially etching the bottom electrode layer 104, thereby ensuring that the thickness of the bottom electrode layer 104 remains unchanged (in this invention, unchanged thickness includes not only the case where the thickness remains the original thickness, but also the case where the thickness remains substantially unchanged, such as the case where the thickness loss is within the range permitted by the process) and thus maintains thickness accuracy" is included within the scope of "wet etching" in the claims of this invention.

[0081] In this invention, "upper" and "lower" are relative to the bottom surface of the resonator's base. For a component, the side closer to the bottom surface is the lower side, and the side farther from the bottom surface is the upper side.

[0082] In this invention, "inner" and "outer" are relative to the center (i.e., the center of the effective region) of the resonator (the overlapping area of ​​the piezoelectric layer, top electrode, bottom electrode, and acoustic mirror in the thickness direction of the resonator constitutes the effective region) in the lateral or radial direction. A component's side or end closer to the center of the effective region is called the inner side or inner end, while the side or end of the component farther from the center of the effective region is called the outer side or outer end. For a reference position, being inside the position means being between that position and the center of the effective region in the lateral or radial direction, while being outside the position means being farther from the center of the effective region in the lateral or radial direction than that position.

[0083] As will be understood by those skilled in the art, the bulk acoustic resonator according to the present invention can be used to form filters or electronic devices.

[0084] Based on the above, the present invention proposes the following technical solution:

[0085] 1. A bulk acoustic resonator, comprising:

[0086] Base;

[0087] Bottom electrode;

[0088] Top electrode; and

[0089] piezoelectric layer

[0090] in:

[0091] The bottom electrode includes multiple electrode layers, including at least a first electrode layer and a second electrode layer disposed in the thickness direction of the resonator, wherein the second electrode layer covers at least a portion of the upper side of the first electrode layer;

[0092] The resonator also includes a cover layer.

[0093] On the outside of the non-electrode connection end of the bottom electrode, the upper surface of the cover layer is offset from the upper surface of the second electrode layer in the height direction of the resonator.

[0094] 2. The resonator according to 1, wherein:

[0095] At the non-electrode connection end of the bottom electrode, the capping layer covers at least a portion of the end face of the second electrode layer.

[0096] 3. The resonator according to 2, wherein:

[0097] At the non-electrode connection end of the bottom electrode, the cover layer also covers the end face of the first electrode layer.

[0098] 4. The resonator according to 3, wherein:

[0099] The acoustic mirror of the resonator is an acoustic mirror cavity;

[0100] The first electrode layer covers the acoustic mirror cavity and defines at least a portion of the upper boundary of the acoustic mirror cavity.

[0101] 5. The resonator according to 3, wherein:

[0102] The acoustic mirror of the resonator is an acoustic mirror cavity;

[0103] The resonator further includes a blocking layer, the first electrode layer covering the blocking layer and the blocking layer defining at least a portion of the upper boundary of the acoustic mirror cavity;

[0104] At the non-electrode connection end of the bottom electrode, the covering layer also covers the end face of the barrier layer.

[0105] 6. The resonator according to 4 or 5, wherein:

[0106] At the non-electrode connection end of the bottom electrode, the upper surface of the cover layer outside the non-electrode connection end of the first electrode layer is lower than the upper surface of the second electrode layer.

[0107] 7. The resonator according to 6, wherein:

[0108] The cover layer also includes a portion covering a portion of the upper side of the second electrode layer.

[0109] 8. The resonator according to 4 or 5, wherein:

[0110] At the non-electrode connection end of the bottom electrode, the upper surface of the cover layer outside the non-electrode connection end of the first electrode layer is higher than the upper surface of the second electrode layer.

[0111] 9. The resonator according to 8, wherein:

[0112] The cover layer also includes a portion covering a portion of the upper side of the second electrode layer.

[0113] 10. The resonator according to claim 1, wherein:

[0114] A void layer is provided in the bottom electrode, and the void layer defines the acoustic mirror cavity of the resonator.

[0115] 11. The resonator according to 10, wherein:

[0116] The upper surface of the cover layer is lower than the upper surface of the second electrode layer within the effective region of the resonator.

[0117] 12. The resonator according to 10, wherein:

[0118] The resonator further includes a third electrode layer, and the gap layer is disposed between the third electrode layer and the first electrode layer, with the third electrode layer located below the gap layer;

[0119] At the non-electrode connection end of the bottom electrode, the end of the third electrode layer is located outside the end of the first electrode layer;

[0120] At the non-electrode connection end of the bottom electrode, the capping layer covers at least a portion of the end face of the third electrode layer.

[0121] 13. The resonator according to 12, wherein:

[0122] The material of the third electrode layer is the same as the material of the second electrode layer;

[0123] At the non-electrode connection end of the bottom electrode, the end face of the third electrode layer is flush with the end face of the second electrode layer.

[0124] 14. The resonator according to 10, wherein:

[0125] The resonator further includes a third electrode layer, and the gap layer is disposed between the third electrode layer and the first electrode layer, with the third electrode layer located below the gap layer;

[0126] At the non-electrode connection end of the bottom electrode, the end of the second electrode layer is located outside the end of the first electrode layer and the end of the third electrode layer to at least cover the end face of the first electrode layer.

[0127] 15. The resonator according to 10, wherein:

[0128] The void layer is provided between the second electrode layer and the first electrode layer.

[0129] 16. The resonator according to any one of 1-15, wherein:

[0130] The resonator is also provided with an acoustic mismatch structure disposed along the effective region of the resonator.

[0131] 17. The resonator according to any one of 1-16, wherein:

[0132] Outside the non-electrode connection end of the bottom electrode, the covering layer covers at least a portion of the upper surface of the substrate or at least a portion of the upper surface of the seed layer disposed on the upper surface of the substrate.

[0133] 18. A method for manufacturing a bulk acoustic wave resonator, the resonator comprising a bottom electrode and a piezoelectric layer, the bottom electrode comprising a plurality of electrode layers, the plurality of electrode layers including at least a first electrode layer and a second electrode layer disposed in the thickness direction of the resonator, the second electrode layer covering at least a portion of the upper side of the first electrode layer, the method comprising the steps of:

[0134] A cover layer is provided at the non-electrode connection end of the bottom electrode, and the upper surface of the cover layer is offset from the upper surface of the second electrode layer in the height direction of the resonator on the outside of the non-electrode connection end of the bottom electrode.

[0135] 19. According to the method described in 18, wherein:

[0136] The steps of setting the cover layer include: setting a cover material layer covering the bottom electrode and the surface outside the non-electrode connection terminal of the bottom electrode, and forming the cover layer by wet etching of the cover material layer.

[0137] 20. According to the method described in 19, wherein:

[0138] The upper surface of the cover layer is lower than the upper surface of the second electrode layer; and

[0139] The steps to set up an overlay include:

[0140] This makes the upper surface of the covering material layer on the substrate side higher than the upper surface of the second electrode layer;

[0141] This allows the covering material layer to be planarized while retaining the covering material layer on the upper surface of the second electrode layer;

[0142] A cover material layer of a predetermined thickness is removed by wet etching to form the cover layer and expose the upper surface of the second electrode layer, while keeping the thickness of the second electrode layer unchanged, wherein the upper surface of the cover layer is lower than the upper surface of the second electrode layer.

[0143] 21. According to the method described in 19, wherein:

[0144] The upper surface of the cover layer is higher than the upper surface of the second electrode layer; and

[0145] The steps to set up an overlay include:

[0146] This makes the upper surface of the covering material layer on the substrate side higher than the upper surface of the second electrode layer;

[0147] After a mask layer is placed on the cover material layer, the cover material layer of a preset thickness is removed by wet etching to form the cover layer and expose a predetermined position on the upper surface of the second electrode layer, while keeping the thickness of the second electrode layer unchanged. The upper surface of the cover layer is higher than the upper surface of the second electrode layer on the outside of the non-electrode connection end of the bottom electrode.

[0148] 22. The method according to any one of 19-21, wherein:

[0149] The step of setting a covering material layer covering the surface of the bottom electrode and the non-electrode connection end of the bottom electrode includes: such that the covering material layer covers at least a portion of the upper surface of the substrate or covers at least a portion of the upper surface of the seed layer disposed on the upper surface of the substrate.

[0150] 23. According to the method described in 18, wherein:

[0151] In the step of setting the cover layer, the cover layer covers at least a portion of the end face of the second electrode layer.

[0152] 24. A filter comprising a bulk acoustic resonator according to any one of 1-17.

[0153] 25. An electronic device comprising the filter according to claim 24, or the bulk acoustic resonator according to any one of claims 1-17.

[0154] The electronic devices mentioned here include, but are not limited to, intermediate products such as radio frequency front-ends and filtering and amplification modules, as well as terminal products such as mobile phones, WIFI, and drones.

[0155] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that variations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bulk acoustic resonator, comprising: Base; Bottom electrode; Top electrode; and piezoelectric layer in: The bottom electrode includes multiple electrode layers, including at least a first electrode layer and a second electrode layer disposed in the thickness direction of the resonator, wherein the second electrode layer covers at least a portion of the upper side of the first electrode layer; The resonator also includes a cover layer. On the outside of the non-electrode connection end of the bottom electrode, the upper surface of the cover layer is offset from the upper surface of the second electrode layer in the height direction of the resonator.

2. The resonator according to claim 1, wherein: At the non-electrode connection end of the bottom electrode, the capping layer covers at least a portion of the end face of the second electrode layer.

3. The resonator according to claim 2, wherein: At the non-electrode connection end of the bottom electrode, the cover layer also covers the end face of the first electrode layer.

4. The resonator according to claim 3, wherein: The acoustic mirror of the resonator is an acoustic mirror cavity; The first electrode layer covers the acoustic mirror cavity and defines at least a portion of the upper boundary of the acoustic mirror cavity.

5. The resonator according to claim 3, wherein: The acoustic mirror of the resonator is an acoustic mirror cavity; The resonator further includes a blocking layer, the first electrode layer covering the blocking layer and the blocking layer defining at least a portion of the upper boundary of the acoustic mirror cavity; At the non-electrode connection end of the bottom electrode, the covering layer also covers the end face of the barrier layer.

6. The resonator according to claim 4 or 5, wherein: At the non-electrode connection end of the bottom electrode, the upper surface of the cover layer outside the non-electrode connection end of the first electrode layer is lower than the upper surface of the second electrode layer.

7. The resonator according to claim 6, wherein: The cover layer also includes a portion covering a portion of the upper side of the second electrode layer.

8. The resonator according to claim 4 or 5, wherein: At the non-electrode connection end of the bottom electrode, the upper surface of the cover layer outside the non-electrode connection end of the first electrode layer is higher than the upper surface of the second electrode layer.

9. The resonator according to claim 8, wherein: The cover layer also includes a portion covering a portion of the upper side of the second electrode layer.

10. The resonator according to claim 1, wherein: A void layer is provided in the bottom electrode, and the void layer defines the acoustic mirror cavity of the resonator.

11. The resonator according to claim 10, wherein: The upper surface of the cover layer is lower than the upper surface of the second electrode layer within the effective region of the resonator.

12. The resonator according to claim 10, wherein: The resonator further includes a third electrode layer, and the gap layer is disposed between the third electrode layer and the first electrode layer, with the third electrode layer located below the gap layer; At the non-electrode connection end of the bottom electrode, the end of the third electrode layer is located outside the end of the first electrode layer; At the non-electrode connection end of the bottom electrode, the capping layer covers at least a portion of the end face of the third electrode layer.

13. The resonator according to claim 12, wherein: The material of the third electrode layer is the same as the material of the second electrode layer; At the non-electrode connection end of the bottom electrode, the end face of the third electrode layer is flush with the end face of the second electrode layer.

14. The resonator according to claim 10, wherein: The resonator further includes a third electrode layer, and the gap layer is disposed between the third electrode layer and the first electrode layer, with the third electrode layer located below the gap layer; At the non-electrode connection end of the bottom electrode, the end of the second electrode layer is located outside the end of the first electrode layer and the end of the third electrode layer to at least cover the end face of the first electrode layer.

15. The resonator according to claim 10, wherein: The void layer is provided between the second electrode layer and the first electrode layer.

16. The resonator according to any one of claims 1-5, 7, 9-15, wherein: The resonator is also provided with an acoustic mismatch structure disposed along the effective region of the resonator.

17. The resonator according to any one of claims 1-5, 7, 9-15, wherein: Outside the non-electrode connection end of the bottom electrode, the covering layer covers at least a portion of the upper surface of the substrate or at least a portion of the upper surface of the seed layer disposed on the upper surface of the substrate.

18. A method for manufacturing a bulk acoustic resonator, the resonator comprising a bottom electrode and a piezoelectric layer, the bottom electrode comprising a plurality of electrode layers, the plurality of electrode layers including at least a first electrode layer and a second electrode layer disposed in the thickness direction of the resonator, the second electrode layer covering at least a portion of the upper side of the first electrode layer, the method comprising the steps of: A cover layer is provided at the non-electrode connection end of the bottom electrode, and the upper surface of the cover layer is offset from the upper surface of the second electrode layer in the height direction of the resonator on the outside of the non-electrode connection end of the bottom electrode.

19. The method of claim 18, wherein: The steps of setting the cover layer include: setting a cover material layer covering the bottom electrode and the surface outside the non-electrode connection terminal of the bottom electrode, and forming the cover layer by wet etching of the cover material layer.

20. The method of claim 19, wherein: The upper surface of the cover layer is lower than the upper surface of the second electrode layer; and The steps to set up an overlay include: This makes the upper surface of the covering material layer on the substrate side higher than the upper surface of the second electrode layer; This allows the covering material layer to be planarized while retaining the covering material layer on the upper surface of the second electrode layer; A cover material layer of a predetermined thickness is removed by wet etching to form the cover layer and expose the upper surface of the second electrode layer, while keeping the thickness of the second electrode layer unchanged, wherein the upper surface of the cover layer is lower than the upper surface of the second electrode layer.

21. The method according to claim 19, wherein: The upper surface of the cover layer is higher than the upper surface of the second electrode layer; and The steps to set up an overlay include: This makes the upper surface of the covering material layer on the substrate side higher than the upper surface of the second electrode layer; After a mask layer is placed on the cover material layer, the cover material layer of a preset thickness is removed by wet etching to form the cover layer and expose a predetermined position on the upper surface of the second electrode layer, while keeping the thickness of the second electrode layer unchanged. The upper surface of the cover layer is higher than the upper surface of the second electrode layer on the outside of the non-electrode connection end of the bottom electrode.

22. The method according to any one of claims 19-21, wherein: The step of setting a covering material layer covering the surface of the bottom electrode and the non-electrode connection end of the bottom electrode includes: such that the covering material layer covers at least a portion of the upper surface of the substrate or covers at least a portion of the upper surface of the seed layer disposed on the upper surface of the substrate.

23. The method of claim 18, wherein: In the step of setting the cover layer, the cover layer covers at least a portion of the end face of the second electrode layer.

24. A filter comprising a bulk acoustic resonator according to any one of claims 1-17.

25. An electronic device comprising the filter of claim 24, or the bulk acoustic resonator of any one of claims 1-17.

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