Bulk acoustic wave resonator, filter, and electronic device in which piezoelectric layer is provided on both sides of acoustic structure

Abstract

This invention relates to a bulk acoustic resonator and its manufacturing method. The resonator includes: a substrate; an acoustic mirror; a bottom electrode; a top electrode; and a piezoelectric layer, wherein the overlapping region of the top electrode, bottom electrode, piezoelectric layer, and acoustic mirror forms the effective region of the resonator; the top electrode has a first acoustic structure disposed along the effective region; the edge of the non-connected end of the bottom electrode is located outside the edge of the acoustic mirror; and the bottom electrode has a second acoustic structure corresponding to the first acoustic structure disposed along the effective region. This invention 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 layer sandwiched between two metal electrode layers. 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] Thin-film bulk acoustic resonators primarily utilize the longitudinal piezoelectric coefficient of the piezoelectric thin film to generate the piezoelectric effect. Therefore, their main operating mode is the longitudinal wave mode in the thickness direction, meaning the acoustic waves of the bulk acoustic resonator are mainly contained within the thin film of the resonator, and the main vibration direction is longitudinal. However, due to the existence of boundaries, Lamb waves that are not perpendicular to the piezoelectric film layer can exist at the boundaries. In this case, transverse Lamb waves can leak out from the transverse side of the piezoelectric film layer, resulting in acoustic loss and thus reducing the Q value of the resonator.

[0006] In the prior art, the top electrode is provided with acoustic structures such as cantilever, bridge, protrusion and recess to limit the leakage of transverse acoustic wave energy of the resonator, thereby improving the Q value of the resonator.

[0007] However, when the top electrode has an acoustic structure, it can lead to a significant asymmetry between the structure of the bottom electrode and the top electrode, thus affecting the performance of the resonator. 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] Acoustic mirror;

[0012] Bottom electrode;

[0013] Top electrode; and

[0014] piezoelectric layer

[0015] in:

[0016] The overlapping area of ​​the top electrode, bottom electrode, piezoelectric layer, and acoustic mirror forms the effective region of the resonator;

[0017] The top electrode is provided with a first acoustic structure along the effective region;

[0018] The edge of the non-connecting end of the bottom electrode is located outside the edge of the acoustic mirror; and

[0019] The bottom electrode is provided with a second acoustic structure corresponding to the first acoustic structure along the effective region.

[0020] Embodiments of the present invention also relate to a method for manufacturing a bulk acoustic resonator, comprising the steps of:

[0021] Provide a substrate, on which an acoustic mirror is mounted;

[0022] A bottom electrode is formed on the substrate, and the edge of the non-electrode connection portion of the bottom electrode is located outside the edge of the acoustic mirror;

[0023] A void is formed on the upper surface of the bottom electrode;

[0024] The voids are filled with a sacrificial material, which is flush with the upper surface of the bottom electrode.

[0025] A piezoelectric layer is formed, which covers the upper surface of the bottom electrode;

[0026] A top electrode is formed on the piezoelectric layer, and the top electrode is provided with a cantilever or a bridge portion, the gap corresponding to the cantilever or bridge portion;

[0027] Release the sacrificial material.

[0028] Embodiments of the present invention also relate to a filter, including the aforementioned bulk acoustic resonator.

[0029] Embodiments of the present invention also relate to an electronic device, including the filter or the resonator described above. Attached Figure Description

[0030] 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:

[0031] Figure 1A , 1B - Figure 5 A schematic cross-sectional view of a bulk acoustic resonator according to different exemplary embodiments of the present invention;

[0032] Figure 6-11 This is a schematic diagram illustrating the fabrication process of a bulk acoustic resonator according to an embodiment of the present invention.

[0033] Figure 12-20 This is a schematic diagram illustrating the fabrication process of a bulk acoustic resonator according to another embodiment of the present invention. Detailed Implementation

[0034] 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.

[0035] In this invention, when an acoustic structure is provided on the top electrode, the structural symmetry of the resonator can be improved by arranging a corresponding acoustic structure on the bottom electrode, while further limiting the leakage of transverse acoustic wave energy of the resonator, thereby improving the Q value of the resonator.

[0036] Figure 1A This is a schematic cross-sectional view of a bulk acoustic resonator according to an exemplary embodiment of the present invention, the cross-section passing through the non-electrode connection terminals of the top and bottom electrodes. Figure 1B This is a cross-sectional schematic diagram of a bulk acoustic resonator according to an exemplary embodiment of the present invention, the cross-section of which passes through the non-electrode connection terminal of the top electrode and the electrode connection terminal of the bottom electrode.

[0037] The reference numerals in the drawings of this invention are explained as follows:

[0038] 100: Substrate, with optional materials including single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0039] 110: Acoustic mirror, which can be a cavity, or it can be a Bragg reflector layer or other equivalent forms. The embodiment shown in this invention uses a cavity.

[0040] 120: 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.

[0041] 122: A recessed structure or a void structure, which can be an air gap or a dielectric layer, is within the protection scope of this invention.

[0042] 130: Piezoelectric layer. This can be a single-crystal piezoelectric material, such as 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. It can also be a polycrystalline piezoelectric material (as opposed to single-crystal, a non-single-crystal material), such as polycrystalline aluminum nitride, zinc oxide, PZT, etc. It can also be a rare-earth element doped with a certain atomic ratio of the above materials. Mixed materials, such as doped aluminum nitride, contain 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.

[0043] 131: The descending portion of the piezoelectric layer. In the illustrated exemplary embodiment, the descending portion 131 is an inclined descending portion.

[0044] 140: Top electrode, whose material can be the same as the bottom electrode. Materials can include molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or composites or alloys of the above metals. The top and bottom electrodes are generally made of the same material, but they can also be different.

[0045] 141: A cantilever or raised structure is installed at the non-electrode connection end of the top electrode.

[0046] 142: The wing gap is located between the wing of the top electrode and the upper surface of the piezoelectric layer. It can be an air gap or a dielectric layer, both of which are within the protection scope of this invention.

[0047] 150: Process layer. The process layer can cover the top electrode. Its function can be a mass conditioning load or a passivation layer. The passivation layer can be made of dielectric materials such as silicon dioxide, aluminum nitride, or silicon nitride.

[0048] like Figure 1A and 1BAs shown, a gap structure 122 is provided on the upper surface of the bottom electrode 120 near the edge of the acoustic mirror 110. Figure 1A and 1B In the example shown, it constitutes the bridge structure of the bottom electrode.

[0049] exist Figure 1A and 1B In the middle, the portion of the piezoelectric layer 130 that crosses the void structure 122 is not affected by the concave morphology of 122 and remains flat. However, the portion of the piezoelectric layer 130 that crosses the non-electrode connection end of the bottom electrode 120 changes with the morphology of the non-electrode connection end, forming an inclined descending portion 131 at the non-electrode connection end.

[0050] Due to the presence of the void structure 122, the upper surface of the bottom electrode 120 is not in complete contact with the lower surface of the piezoelectric layer 130. Specifically, in Figure 1A and 1B In the illustrated embodiment, the upper surface of the bottom electrode 120, located inside and outside the void structure 122, contacts the horizontal lower surface of the piezoelectric layer 130, while the waist of the trapezoidal cross-section of the non-electrode connection end of the bottom electrode 120 contacts the lower surface of the descending portion 131. In other words, the end face of the non-electrode connection end of the bottom electrode 120 forms surface contact with the descending portion 131 of the piezoelectric layer in the horizontal direction. The portion outside the descending portion 131 of the piezoelectric layer 130 continues to extend outward, and its lower surface contacts the upper surface of the substrate 100.

[0051] exist Figure 1A and 1B In the illustrated embodiment, the resonator's upper and lower structures are more symmetrical relative to the center of the piezoelectric layer due to the recessed portion or void structure 122 provided in the bottom electrode 120. Further, as... Figure 1A and 1B As shown, the inner edge of the void structure 122 is roughly flush with the inner edge of the cantilever void 142, which helps to improve the symmetry of the upper and lower structures of the resonator relative to the center of the piezoelectric layer. Figure 1A and 1B The structure shown is conducive to the resonator's resonance state being close to the ideal main resonance mode. Therefore, the main resonance mode of the resonator is enhanced, while the resonance state of other parasitic modes is weakened, which is manifested as the parasitic thin film of the resonator being suppressed to a certain extent.

[0052] also, Figure 1A and 1B The recessed portion or void structure 122 in the bottom electrode forms an acoustic interference structure at the edge, which can reflect the sound waves propagating from the effective region of the resonator to the ineffective region back to the effective region, confining the sound wave energy within the effective region, thus resulting in an increase in the Q value of the resonator.

[0053] In addition, Figure 1A and1B In the structure shown, the piezoelectric layer between the void structure 122 and the void 142 extends to both sides in the horizontal direction and there is no step-like change in the vertical direction. Therefore, the piezoelectric layer has higher mechanical strength and a more reliable structure, and it does not cause changes in the acoustic wave mode at the step point.

[0054] exist Figure 1A and 1B In the embodiment shown, the non-electrode connection end of the bottom electrode 120 extends horizontally beyond the edge of the acoustic mirror 110 and overlaps the substrate 100. This allows the heat generated during the operation of the resonator to be quickly conducted to the substrate through the metal electrode, thus further increasing the power capacity of the resonator.

[0055] In this invention, to help reduce the acoustic wave energy leaked through the bottom electrode overlapping the substrate 100, there may be further requirements regarding the distance from the inner edge of the void structure 122 to the edge of the acoustic mirror. For example... Figure 1A and 1B As shown, this distance is denoted by D1. When this distance D1 is an integer multiple of half the wavelength of the sound wave, it is beneficial to reduce leakage energy and improve the Q value of the resonator. Here, the wavelength is the wavelength of the sound wave corresponding to the resonant frequency of the resonator.

[0056] Due to the inherent properties of the piezoelectric layer, its step transition points are relatively weak, making it prone to cracking and collapse during manufacturing and high-power operation, thus reducing manufacturing yield. Figure 1A and 1B In the embodiment shown, the two beveled ends of the non-electrode connection end of the bottom electrode 120 are in contact with the piezoelectric layer, mechanically supporting the stepped change points of the piezoelectric layer, which improves the mechanical stability and manufacturing yield of the overall structure of the resonator.

[0057] Figure 2 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention, the cross-section of which passes through the non-electrode connection ends of the top electrode and the bottom electrode. Figure 2 Structure and Figure 1A The difference shown is that, in Figure 2In this invention, the top electrode 140 has a recessed structure 144 and a protruding structure 143. Correspondingly, the bottom electrode 120 has a recessed structure 124 on its lower surface. Furthermore, the lower surface of the bottom electrode inside the recessed structure 124 is recessed upward relative to the lower surface of the bottom electrode outside the recessed structure 124. That is, the thickness of the bottom electrode inside the recessed structure 124 is less than the thickness of the bottom electrode outside the recessed structure. This allows the protruding structure of the bottom electrode to be equivalently formed without adding a material layer, avoiding the need to fabricate the protruding structure of the bottom electrode by adding an additional layer, thus reducing manufacturing costs. However, it is also possible to add a protruding structure corresponding to the protruding structure 143 of the top electrode to the bottom electrode, which is also within the scope of protection of this invention.

[0058] Accordingly, in order to effectively create a raised structure of the bottom electrode on the lower surface of the bottom electrode, during the fabrication of the resonator, before forming the bottom electrode on the substrate, a sacrificial material needs to be set and patterned on the upper surface of the substrate to form a sacrificial material layer for the lower side of the bottom electrode. The outer edge of the patterned sacrificial material layer for the lower side of the bottom electrode is inside the inner edge of the gap and is spaced apart in the lateral direction by a distance (to leave space for forming the raised structure). The sacrificial material layer for the lower side of the bottom electrode has a shape with raised edges (corresponding to the gap structure 122) and a flat middle (for thinning the thickness of the middle part of the bottom electrode).

[0059] Because a sacrificial material layer is used on the underside of the bottom electrode, after the metal layer for the bottom electrode is formed, a step is needed to make the upper surface of the bottom electrode flush.

[0060] It should be noted that the bottom electrode may not have a protrusion structure. In this case, the sacrificial material layer on the underside of the bottom electrode may only include a sacrificial layer protrusion for forming the void structure 122, without the flat layer between the protrusions mentioned above.

[0061] and Figure 1A Compared to the structure shown, Figure 2 The structure in the middle, with the addition of raised and recessed structures on both the top and bottom electrodes, can further improve the Q value of the resonator and reduce parasitic modes.

[0062] Figure 3 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention, the cross-section of which passes through the non-electrode connection ends of the top electrode and the bottom electrode. Figure 3 The structure and Figure 1A The difference in the structure shown is that, Figure 3 In this process, the void structure 122 in Figure 1 is extended outward to the lower surface of the descending portion 131 of the piezoelectric layer 130, thus removing the void structure 122. Figure 1AThe portion of the bottom electrode 120 located outside the void structure 122 is such that the outer boundary of the void structure 122 is defined by the descending portion 131. Furthermore, in Figure 3 In the middle, the non-electrode connection end of the bottom electrode 120 is in contact with the descending portion 131 of the piezoelectric layer 130 in the horizontal direction.

[0063] Figure 3 The structure and Figure 1A Compared to the previous model, the symmetry of the top and bottom electrodes is further improved, the resonant mode is closer to the ideal state, and the parasitic mode is further weakened.

[0064] Figure 4 A cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention is shown, the cross-section passing through the non-electrode connection ends of the top electrode and the bottom electrode. Figure 4 The structure shown is similar to Figure 3 The difference in the structure shown is that, Figure 4 In the middle, the non-electrode connection end of the bottom electrode is spaced apart from the descending portion 131 of the piezoelectric layer in the lateral direction, that is, in Figure 4 In the middle, the void structure 122 includes a first void forming a wing of the bottom electrode and a second void between the non-electrode connection end of the bottom electrode and the descending part of the piezoelectric layer, the first void and the second void being in communication.

[0065] Figure 4 The structure shown is similar to Figure 3 Compared to the previous structure, the symmetry of the top and bottom electrodes is further improved, the resonant mode is closer to the ideal state, and the parasitic mode is further weakened. However, since the bottom electrode is not supported at the piezoelectric layer step or the descending part 131, the mechanical stability of the resonator is reduced.

[0066] Figure 5 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention, the cross-section of which passes through the electrode connection end of the top electrode and the non-electrode connection end of the bottom electrode.

[0067] like Figure 5 As shown, the top electrode has a cantilever 141 and a cantilever gap 142 at the non-electrode connection end, and a bridge portion 144 and a bridge gap 143 disposed in the bridge portion at the electrode connection end. The top electrode of the resonator in Figure 1-4 can also have Figure 5 The bridge section and bridge gaps are shown.

[0068] like Figure 5 As shown, at the non-electrode connection end of the bottom electrode, a support structure 120a is provided at the descending portion 131 of the piezoelectric layer 130. The support structure 120a is arranged in the same layer as the bottom electrode 120, and may also be made of the same material as the bottom electrode (in other words, it can be made by etching away material from the bottom electrode 120). Figure 5(The void structure 122 is formed later). For example... Figure 5 As shown, the support structure 120a is disposed between the piezoelectric layer 130 and the substrate 100 in the thickness direction, and the outer edge of the support structure 120a is in contact with the descending portion 131 surface of the piezoelectric layer 130.

[0069] exist Figure 5 In the middle, the support structure 120a is spaced apart from the non-electrode connection end of the bottom electrode 120 in the lateral direction. In addition, the bottom electrode is also provided with a cantilever at the non-electrode connection end, so the void structure 122 includes a first void forming the cantilever and a second void between the non-electrode connection end of the bottom electrode and the support structure 120a. The first void and the second void are connected.

[0070] exist Figure 5 In the middle, the support structure 120a is a trapezoidal support block, which can reinforce the overlap point between the descending part 131 of the piezoelectric layer and the horizontal parts on both sides of the descending part 131, reducing the possibility of cracks. Therefore, with Figure 4 In comparison, Figure 5 In this design, by adding a support structure 120a, the symmetry between the top and bottom electrodes can be further increased, while also providing support for the descending portion 131 of the piezoelectric layer 130, thus enhancing the mechanical stability of the resonator. Figure 5 In this design, the support structure 120a only provides mechanical support and does not participate in the acoustic-electric coupling effect. Therefore, the stability of the resonator can be improved without affecting its electrical performance.

[0071] In addition, such as Figure 5 As shown, the inner side of the bridge gap 142 of the top electrode and the inner side of the gap structure of the bottom electrode can be flush in the lateral direction.

[0072] The following reference Figure 6-11 The fabrication process of the resonator structure shown in Figure 1 is illustrated by way of example. It should be noted that the fabrication process described in this section mainly focuses on the fabrication of the bottom electrode structure, and other traditional structures are not described.

[0073] exist Figure 6 In the steps shown: a cavity (corresponding to the acoustic mirror cavity) is formed on the substrate 100 using an ion etching process, and a sacrificial layer material 110s is filled into the cavity. Then, the upper surface is smoothed using a CMP (chemical mechanical polishing) process to remove excess sacrificial material outside the cavity, forming... Figure 6 The structure shown.

[0074] exist Figure 7 In the steps shown: Figure 6 The upper surface of the structure is deposited with a metal layer of a certain thickness for the bottom electrode 120 by sputtering or vapor deposition processes.

[0075] like Figure 8 In the steps shown: the metal layer for the bottom electrode 120 is patterned using photolithography and etching processes to form... Figure 8 The structure shown is in Figure 8 In the middle, the bottom electrode is an upright trapezoid, and the upper surface of the bottom electrode is provided with a recess corresponding to the void structure 122, and the edge of the bottom electrode is located outside the boundary of the cavity.

[0076] exist Figure 9 In the steps shown: Figure 8 Sacrificial material 122s is deposited on the upper surface of the structure shown, wherein the sacrificial material 122s is carried by Figure 8 The topographic distribution of the upper surface of the structure shown is in Figure 9 In the steps shown, sacrificial material 122s fills the depression.

[0077] exist Figure 10 In the steps shown: smoothing is performed using CMP process. Figure 9 The upper surface of the structure shown is flush with the upper surface of the bottom electrode 120, making the outer side of the bottom electrode and the sacrificial material 122s in the recess flush with the upper surface of the bottom electrode 120, forming... Figure 10 The structure shown.

[0078] exist Figure 11 In the steps shown: the sacrificial material on the outside of the bottom electrode 120 is removed using photolithography and etching processes.

[0079] After that, Figure 11 The structure shown utilizes patterning processes such as deposition, photolithography, and etching to form a piezoelectric layer and a top electrode above the bottom electrode. Finally, a release process is used to remove the sacrificial material, ultimately forming... Figure 1A The resonator structure shown is shown.

[0080] The following reference Figure 12-20 Exemplary Description Figure 2 The fabrication process of the resonator structure shown is illustrated. It should be noted that this section on the fabrication process mainly focuses on the fabrication of the bottom electrode structure; other traditional structures are not described.

[0081] exist Figure 12 In the steps shown: a cavity (corresponding to the acoustic mirror cavity) is formed on the substrate 100 using an ion etching process, and a sacrificial layer material 110s is filled into the cavity. Then, the upper surface is smoothed using a CMP (chemical mechanical polishing) process to remove excess sacrificial material outside the cavity, forming... Figure 6 The structure shown.

[0082] exist Figure 13 In the steps shown: Figure 12The upper surface of the structure is deposited with a metal layer of a certain thickness for the bottom electrode 120 by sputtering or vapor deposition. Optionally, the material of the sacrificial material layer 110s can be made insensitive to the etching environment for the sacrificial material layer 110sa, so that when the etching environment patterns the sacrificial material layer 110sa, the etching of the sacrificial material layer 110s is minimized, thereby ensuring that the surface of the sacrificial material layer 110s is flat.

[0083] exist Figure 14 In the steps shown: the sacrificial material layer 110sa is patterned again to form an inverted trapezoidal depression in the middle, which does not penetrate the sacrificial material layer 110sa.

[0084] like Figure 15 In the steps shown: a metal layer for the bottom electrode 120 is deposited on the surface of the substrate 100, the sacrificial material layer 110s and the sacrificial material layer 110sa, and its upper surface is ground flat using a CMP process.

[0085] In such Figure 16 In the steps shown: the metal layer for the bottom electrode 120 is patterned using photolithography and etching processes to form... Figure 16 The structure shown is in Figure 16 In the middle, the bottom electrode is an upright trapezoid, and the edge of the bottom electrode is located outside the boundary of the cavity.

[0086] In such Figure 17 In the steps shown: a recess corresponding to the void structure 122 is formed on the upper surface of the bottom electrode 120 by photolithography and etching processes.

[0087] exist Figure 18 In the steps shown: Figure 17 Sacrificial material 122a is deposited on the upper surface of the structure shown, wherein the sacrificial material 122a is carried along with Figure 17 The topographic distribution of the upper surface of the structure shown is in Figure 19 In the steps shown, sacrificial material 122a fills the depression.

[0088] exist Figure 19 In the steps shown: smoothing is performed using CMP process. Figure 18 The upper surface of the structure shown is flush with the upper surface of the bottom electrode 120, making the outer side of the bottom electrode and the sacrificial material 122a in the recess flush with the upper surface of the bottom electrode 120, forming... Figure 19 The structure shown.

[0089] exist Figure 20 In the steps shown: the sacrificial material 122a on the outside of the bottom electrode 120 is removed using photolithography and etching processes.

[0090] After that, Figure 20The structure shown utilizes patterning processes such as deposition, photolithography, and etching to form a piezoelectric layer and a top electrode above the bottom electrode. Finally, a release process is used to remove the sacrificial material, ultimately forming... Figure 2 The resonator structure shown is shown.

[0091] In the above embodiments, the non-electrode connection end of the top electrode is provided with a cantilever. However, the present invention is not limited to this; the non-electrode connection end of the top electrode may also be provided with a bridge portion, which is also within the protection scope of the present invention. In the present invention, the top electrode is provided with a wing bridge portion along the effective area, indicating that only a cantilever or only a bridge portion may be provided along the effective area at the non-electrode connection end of the top electrode, and / or, a bridge portion may be provided at the electrode connection end of the top electrode.

[0092] It should be noted that, in this invention, each numerical range, except where explicitly stated not to include endpoint values, can be either an endpoint value or the median of each numerical range, and all of these are within the protection scope of this invention.

[0093] 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.

[0094] 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.

[0095] As those skilled in the art will understand, the bulk acoustic resonator according to the present invention 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.

[0096] Based on the above, the present invention proposes the following technical solution:

[0097] 1. A bulk acoustic resonator, comprising:

[0098] Base;

[0099] Acoustic mirror;

[0100] Bottom electrode;

[0101] Top electrode; and

[0102] piezoelectric layer

[0103] in:

[0104] The overlapping area of ​​the top electrode, bottom electrode, piezoelectric layer, and acoustic mirror forms the effective region of the resonator;

[0105] The top electrode is provided with a first acoustic structure along the effective region;

[0106] The edge of the non-connecting end of the bottom electrode is located outside the edge of the acoustic mirror; and

[0107] The bottom electrode is provided with a second acoustic structure corresponding to the first acoustic structure along the effective region.

[0108] 2. The resonator according to 1, wherein:

[0109] The first acoustic structure includes a wing bridge portion, which includes a bridge portion disposed at the non-electrode connection end of the top electrode or a first cantilever and / or a first bridge portion disposed at the electrode connection end of the top electrode;

[0110] The second acoustic structure includes a void structure disposed at the non-electrode connection end of the bottom electrode.

[0111] 3. The resonator according to 2, wherein:

[0112] In the cross-section of the non-electrode connection end that simultaneously passes through the top electrode and the bottom electrode, the void structure is a recessed structure and its inner edge is flush with the inner edge of the corresponding wing bridge in the lateral direction.

[0113] 4. The resonator according to 3, wherein:

[0114] The second acoustic structure includes a void structure disposed at the non-electrode connection end and the electrode connection end of the bottom electrode, wherein the void structure is a recessed structure.

[0115] 5. The resonator according to 2, wherein:

[0116] The void structure is disposed on the upper surface of the bottom electrode, and the outer edge of the void structure is located inside the non-electrode connection end of the bottom electrode.

[0117] 6. The resonator according to 5, wherein:

[0118] The piezoelectric layer has a descending portion located outside the effective region;

[0119] The end face of the non-connected end of the bottom electrode, located outside the void structure, forms a surface contact with the descending portion.

[0120] 7. The resonator according to 2, wherein:

[0121] The piezoelectric layer has a descending portion located outside the effective region;

[0122] The void structure is disposed on the upper surface of the bottom electrode, and the non-electrode connection end of the bottom electrode forms a second cantilever. The end face of the non-electrode connection end of the bottom electrode in the horizontal direction contacts the descending part of the piezoelectric layer, and the outer edge of the void structure is defined by the descending part of the piezoelectric layer.

[0123] 8. The resonator according to 2, wherein:

[0124] The non-electrode connection end of the bottom electrode is spaced apart from the descending part of the piezoelectric layer in the horizontal direction;

[0125] The non-connected end of the bottom electrode forms a second cantilever;

[0126] The void structure includes a first void forming the second cantilever and a second void between the non-electrode connection end of the bottom electrode and the descending portion of the piezoelectric layer, wherein the first void and the second void are connected.

[0127] 9. The resonator according to 2, wherein:

[0128] The resonator also includes a support structure arranged in the same layer as the bottom electrode. The support structure is made of the same material as the bottom electrode. The support structure is disposed between the piezoelectric layer and the substrate in the thickness direction. The outer edge of the support structure is in contact with the descending surface of the piezoelectric layer.

[0129] The non-connected end of the bottom electrode forms a second cantilever;

[0130] The inner edge of the support structure is horizontally spaced from the non-electrode connection end of the bottom electrode.

[0131] The void structure includes a first void forming the second cantilever, and a second void between the non-electrode connection end of the bottom electrode and the support structure, wherein the first void and the second void are connected.

[0132] 10. The resonator according to 9, wherein:

[0133] The supporting structure has a trapezoidal cross-sectional shape.

[0134] 11. The resonator according to 2, wherein:

[0135] The first acoustic structure includes a first bridge portion disposed at the electrode connection end of the top electrode, and the second acoustic structure includes a second bridge portion disposed at the electrode connection end of the bottom electrode.

[0136] In a cross-section that simultaneously passes through the electrode connection end of one of the top and bottom electrodes and the non-electrode connection end of the other, the inner side of the bridge portion of the electrode connection end of one electrode is flush with the inner side of the cantilever of the other electrode in the lateral direction.

[0137] 12. The resonator according to claim 2, wherein:

[0138] The edge of the acoustic mirror is located between the inner and outer edges of the void structure in the horizontal direction.

[0139] 13. The resonator according to 1 or 2, wherein:

[0140] The first acoustic structure includes a first protruding structure and / or a first recessed structure;

[0141] The second acoustic structure includes a second protrusion structure and / or a second recess structure disposed on the lower surface of the bottom electrode.

[0142] 14. The resonator according to 13, wherein:

[0143] The inner side of the first protrusion is flush with the inner side of the second protrusion in the lateral direction; and / or

[0144] The inner sides of the first recessed structure and the inner sides of the second recessed structure are flush in the lateral direction.

[0145] 15. The resonator according to 13, wherein:

[0146] The thickness of the bottom electrode inside the second recessed structure is less than the thickness of the bottom electrode outside the second recessed structure, so as to form a second protruding structure on the outside of the second recessed structure.

[0147] 16. The resonator according to claim 2, wherein:

[0148] In the horizontal direction, the distance between the inner edge of the void structure and the boundary of the acoustic mirror is an integer multiple of the half wavelength of the acoustic wave of the resonator.

[0149] 17. The resonator according to any one of 1-16, wherein:

[0150] The width of the void structure is in the range of 0.5 μm to 50 μm.

[0151] 18. A method for manufacturing a bulk acoustic resonator, comprising the following steps:

[0152] Provide a substrate, on which an acoustic mirror is mounted;

[0153] A bottom electrode is formed on the substrate, and the edge of the non-electrode connection portion of the bottom electrode is located outside the edge of the acoustic mirror;

[0154] A void is formed on the upper surface of the bottom electrode;

[0155] The voids are filled with a sacrificial material, which is flush with the upper surface of the bottom electrode.

[0156] A piezoelectric layer is formed, which covers the upper surface of the bottom electrode;

[0157] A top electrode is formed on the piezoelectric layer, and the top electrode is provided with a cantilever and / or a bridge portion, the gap corresponding to the cantilever and / or the bridge portion;

[0158] Release the sacrificial material.

[0159] 19. According to the method described in 18, wherein:

[0160] In the step of forming a top electrode on a piezoelectric layer, a protrusion structure and a recess structure are formed on the top electrode;

[0161] Prior to the step of forming the bottom electrode, a patterned sacrificial material is disposed and patterned on the upper surface of the substrate to form a sacrificial material layer on the underside of the bottom electrode, wherein the outer edge of the patterned sacrificial material layer on the underside of the bottom electrode is inside the inner edge of the void and spaced apart by a distance in the lateral direction.

[0162] Before the step of forming a void on the upper surface of the bottom electrode, the upper surface of the bottom electrode is made flush during the step of forming the bottom electrode.

[0163] 20. According to the method described in 19, wherein:

[0164] The bottom electrode has a sacrificial material layer with raised edges and a flat center.

[0165] 21. A filter comprising a bulk acoustic resonator according to any one of 1-17.

[0166] 22. An electronic device comprising the filter according to claim 21, or the bulk acoustic resonator according to any one of claims 1-17.

[0167] 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; Acoustic mirror; Bottom electrode; Top electrode; and piezoelectric layer in: The overlapping area of ​​the top electrode, bottom electrode, piezoelectric layer, and acoustic mirror forms the effective region of the resonator; The top electrode is provided with a first acoustic structure along the effective region; The edge of the non-connecting end of the bottom electrode is located outside the edge of the acoustic mirror; and The bottom electrode is provided with a second acoustic structure corresponding to the first acoustic structure along the effective region; The second acoustic structure avoids the boundary of the acoustic mirror so that the boundary of the acoustic mirror contacts the bottom electrode.

2. The resonator according to claim 1, wherein: The first acoustic structure includes a wing bridge portion, which includes a bridge portion or a first cantilever disposed at the non-electrode connection end of the top electrode, and / or a first bridge portion disposed at the electrode connection end of the top electrode; The second acoustic structure includes a void structure disposed at the non-electrode connection end of the bottom electrode.

3. The resonator according to claim 2, wherein: In the cross-section of the non-electrode connection end that simultaneously passes through the top electrode and the bottom electrode, the void structure is a recessed structure and its inner edge is flush with the inner edge of the corresponding wing bridge in the lateral direction.

4. The resonator according to claim 3, wherein: The second acoustic structure includes a void structure disposed at the non-electrode connection end and the electrode connection end of the bottom electrode, wherein the void structure is a recessed structure.

5. The resonator according to claim 2, wherein: The void structure is disposed on the upper surface of the bottom electrode, and the outer edge of the void structure is located inside the non-electrode connection end of the bottom electrode.

6. The resonator according to claim 5, wherein: The piezoelectric layer has a descending portion located outside the effective region; The end face of the non-connected end of the bottom electrode, located outside the void structure, forms a surface contact with the descending portion.

7. The resonator according to claim 2, wherein: The piezoelectric layer has a descending portion located outside the effective region; The void structure is disposed on the upper surface of the bottom electrode, and the non-electrode connection end of the bottom electrode forms a second cantilever. The end face of the non-electrode connection end of the bottom electrode in the horizontal direction contacts the descending part of the piezoelectric layer, and the outer edge of the void structure is defined by the descending part of the piezoelectric layer.

8. The resonator according to claim 2, wherein: The non-electrode connection end of the bottom electrode is spaced apart from the descending part of the piezoelectric layer in the horizontal direction; The non-connected end of the bottom electrode forms a second cantilever; The void structure includes a first void forming the second cantilever and a second void between the non-electrode connection end of the bottom electrode and the descending portion of the piezoelectric layer, wherein the first void and the second void are connected.

9. The resonator according to claim 2, wherein: The resonator also includes a support structure arranged in the same layer as the bottom electrode. The support structure is made of the same material as the bottom electrode. The support structure is disposed between the piezoelectric layer and the substrate in the thickness direction. The outer edge of the support structure is in contact with the descending surface of the piezoelectric layer. The non-connected end of the bottom electrode forms a second cantilever; The inner edge of the support structure is horizontally spaced from the non-electrode connection end of the bottom electrode. The void structure includes a first void forming the second cantilever, and a second void between the non-electrode connection end of the bottom electrode and the support structure, wherein the first void and the second void are connected.

10. The resonator according to claim 9, wherein: The supporting structure has a trapezoidal cross-sectional shape.

11. The resonator according to claim 2, wherein: The first acoustic structure includes a first bridge portion disposed at the electrode connection end of the top electrode, and the second acoustic structure includes a second bridge portion disposed at the electrode connection end of the bottom electrode. In a cross-section that simultaneously passes through the electrode connection end of one of the top and bottom electrodes and the non-electrode connection end of the other, the inner side of the bridge portion of the electrode connection end of one electrode is flush with the inner side of the cantilever of the other electrode in the lateral direction.

12. The resonator according to claim 2, wherein: The edge of the acoustic mirror is located between the inner and outer edges of the void structure in the horizontal direction.

13. The resonator according to claim 1 or 2, wherein: The first acoustic structure includes a first protruding structure and / or a first recessed structure; The second acoustic structure includes a second protrusion structure and / or a second recess structure disposed on the lower surface of the bottom electrode.

14. The resonator according to claim 13, wherein: The inner side of the first protrusion is flush with the inner side of the second protrusion in the lateral direction; and / or The inner sides of the first recessed structure and the inner sides of the second recessed structure are flush in the lateral direction.

15. The resonator according to claim 13, wherein: The thickness of the bottom electrode inside the second recessed structure is less than the thickness of the bottom electrode outside the second recessed structure, so as to form a second protruding structure on the outside of the second recessed structure.

16. The resonator according to claim 2, wherein: In the horizontal direction, the distance between the inner edge of the void structure and the boundary of the acoustic mirror is an integer multiple of the half wavelength of the acoustic wave of the resonator.

17. The resonator according to any one of claims 1-16, wherein: The width of the void structure is in the range of 0.5 μm to 50 μm.

18. A method for manufacturing a bulk acoustic resonator, comprising the steps of: Provide a substrate, on which an acoustic mirror is mounted; A bottom electrode is formed on the substrate, and the edge of the non-electrode connection portion of the bottom electrode is located outside the edge of the acoustic mirror; A gap is formed on the upper surface of the bottom electrode, and the boundary of the acoustic mirror is in contact with the bottom electrode; The voids are filled with a sacrificial material, which is flush with the upper surface of the bottom electrode. A piezoelectric layer is formed, which covers the upper surface of the bottom electrode; A top electrode is formed on the piezoelectric layer, and the top electrode is provided with a cantilever and / or a bridge portion, the gap corresponding to the cantilever and / or the bridge portion; Release the sacrificial material.

19. The method of claim 18, wherein: In the step of forming a top electrode on a piezoelectric layer, a protrusion structure and a recess structure are formed on the top electrode; Prior to the step of forming the bottom electrode, a patterned sacrificial material is disposed and patterned on the upper surface of the substrate to form a sacrificial material layer on the underside of the bottom electrode, wherein the outer edge of the patterned sacrificial material layer on the underside of the bottom electrode is inside the inner edge of the void and spaced apart by a distance in the lateral direction. Before the step of forming a void on the upper surface of the bottom electrode, the upper surface of the bottom electrode is made flush during the step of forming the bottom electrode.

20. The method of claim 19, wherein: The bottom electrode has a sacrificial material layer with raised edges and a flat center.

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

22. An electronic device comprising the filter of claim 21, or the bulk acoustic resonator of any one of claims 1-17.

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