Bulk acoustic wave resonator, filter, and electronic device

Abstract

The present application relates to a bulk acoustic wave resonator, comprising: a substrate; a top electrode; a piezoelectric layer; a bottom electrode; and an acoustic mirror, wherein: a support layer is provided between the substrate and the resonator structure, the piezoelectric layer is a single-crystal piezoelectric layer arranged substantially parallel to the substrate; in a first cross-section parallel to the thickness direction of the resonator, through a non-electrically connected end of the bottom electrode and a non-electrically connected end of the top electrode, a portion of the outer end of the non-electrically connected end of the bottom electrode is covered by the support layer, at least a portion of the piezoelectric layer at the non-electrically connected end of the bottom electrode is removed, and at least a portion of the upper surface of the non-electrically connected end of the bottom electrode is flush with the upper surface of the support layer. 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 resonator, a filter, and an electronic device. Background Technology

[0002] Thin-film bulk acoustic resonators (FBARs), as a type of MEMS device, possess advantages such as small size, light weight, low insertion loss, wide bandwidth, and high quality factor, making them well-suited for the upgrading of wireless communication systems and thus a research hotspot in the field of communications. The main structure of a FBAR is a "sandwich" structure consisting of an electrode-piezoelectric thin film-electrode, where a piezoelectric material is sandwiched between two layers of metal electrodes. By inputting a sinusoidal signal between the two electrodes, the FBAR utilizes the inverse piezoelectric effect to convert the input electrical signal into mechanical resonance, and then uses the piezoelectric effect again to convert the mechanical resonance into an electrical signal output.

[0003] A schematic diagram of the cross-sectional structure of an existing thin-film bulk acoustic resonator is shown below. Figure 1A As shown, Figure 1A The figure shows a partial cross-sectional view of a "sandwich" structure formed by a piezoelectric layer 202, a top electrode 201, and a bottom electrode 203, disposed on a substrate 204. Region A1 represents the effective region of the resonator. Outside the effective region, when the resonator vibrates, acoustic energy is transmitted along the piezoelectric layer 202 to the outside of the effective region, causing energy leakage, as shown in Q1. This reduces the Q value of the resonator. The resonator requires a support structure for mechanical fixation and a substrate for load-bearing. Generally, the acoustic energy loss of the resonator mainly comes from leakage from the effective region through the support structure to the supporting substrate. In traditional structures, the support structure is a combination of piezoelectric layer 202 extensions and bottom electrode extensions (piezoelectric layer 202 + top electrode 201 or piezoelectric layer 202 + bottom electrode 203), such as... Figure 1A As shown, this structure causes sound wave energy leakage, resulting in a lower Q value (especially the Q value at and near the parallel resonant point).

[0004] To address the Q-value reduction caused by the aforementioned energy leakage problem, conventionally known improved structures can etch away part of the piezoelectric layer, such as... Figure 1B As shown, the transverse Lamb wave propagating in the piezoelectric layer 202 is reflected back to the effective region A1 (see Q2). However, the transverse Lamb wave propagating in the bottom electrode region B1 will cause serious parasitic modes during the reflection back to the effective region A1 (see Q3), affecting the performance of the device and urgently needing improvement. Summary of the Invention

[0005] The present invention is proposed to alleviate or solve at least one of the above-mentioned problems in the prior art.

[0006] According to one aspect of an embodiment of the present invention, a bulk acoustic resonator is provided, comprising:

[0007] Base;

[0008] Top electrode;

[0009] piezoelectric layer;

[0010] Bottom electrode; and

[0011] Acoustic mirror,

[0012] in:

[0013] A support layer is provided between the substrate and the resonant structure, and the piezoelectric layer is a single-crystal piezoelectric layer arranged substantially parallel to the substrate;

[0014] In a first cross-section parallel to the thickness direction of the resonator, passing through the non-electrical connection ends of the bottom electrode and the top electrode, a portion of the outer end of the non-electrical connection end of the bottom electrode is covered by a support layer, at least a portion of the piezoelectric layer at the non-electrical connection end of the bottom electrode is removed, and at least a portion of the upper surface of the non-electrical connection end of the bottom electrode is flush with the upper surface of the support layer.

[0015] According to another aspect of the invention, a filter comprising the aforementioned bulk acoustic resonator is also provided.

[0016] According to another aspect of the present invention, an electronic device comprising the aforementioned bulk acoustic resonator or the aforementioned filter is also provided. Attached Figure Description

[0017] 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:

[0018] Figure 1A and Figure 1B A partial cross-sectional view of an existing bulk acoustic resonator;

[0019] Figure 2 A top view schematic diagram of a bulk acoustic resonator;

[0020] Figure 3 For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 2 A schematic diagram of the cross-section of the OC' line in the diagram;

[0021] Figure 4A-4K An example shows the manufacturing process. Figure 3 The process of the bulk acoustic resonator is shown below;

[0022] Figure 5-19For different exemplary embodiments of the bulk acoustic resonator according to the present invention, the following are examples of their functions: Figure 2 A schematic diagram of the cross-section of the OC' line in the diagram;

[0023] Figure 20-22 For different exemplary embodiments of the bulk acoustic resonator according to the present invention, the following are examples of their functions: Figure 2 A schematic diagram of the cross-section of line OB in the diagram;

[0024] Figure 23 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross-section of the OC line. Detailed Implementation

[0025] 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.

[0026] First of all, Figure 3-23 The reference numerals in the accompanying drawings of this invention are explained as follows:

[0027] 10: 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.

[0028] 20: Acoustic mirror, which can be a cavity, or a Bragg reflector layer and other equivalent forms. In the embodiment shown in this invention, a cavity is used.

[0029] 20': Release material layer for forming acoustic mirror 20.

[0030] 30: Support layer, the material can be a dielectric material such as SiN or SiO2, and its material is different from that of the release material layer.

[0031] 40: Substrate, with optional materials including single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0032] 41: Bonding layer, such as silicon dioxide, silicon nitride and other materials.

[0033] 50: Top electrode. Materials can 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.

[0034] 60, 61: Bottom electrode lead-out structure, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals, etc.

[0035] 62: Passivation layer, generally a dielectric material, such as silicon dioxide, aluminum nitride, silicon nitride, etc.

[0036] 70: Single-crystal piezoelectric layer, which may be made of single-crystal aluminum nitride, single-crystal gallium nitride, single-crystal lithium niobate, single-crystal lead zirconate titanate, single-crystal potassium niobate, single-crystal quartz film, or single-crystal lithium tantalate, etc. It may also contain rare earth element doping materials of a certain atomic ratio of the above materials, such as 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.

[0037] 81, 84: slots.

[0038] 83: Through hole.

[0039] 85: Long trench or dielectric layer, which can be made of materials such as silicon dioxide, aluminum nitride, or silicon nitride.

[0040] 87, 88: Air gap or dielectric layer, the dielectric layer material can be such as silicon dioxide, aluminum nitride, silicon nitride, etc.

[0041] 89: Filler layer, the material of which can be dielectric material such as SiN, SiO2, etc.

[0042] 91, 92: Air gap.

[0043] 101: Auxiliary substrate, with optional materials including single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0044] 102: Insulating layer, the material can be dielectric materials such as SiN and SiO2.

[0045] Figure 3 This is a cross-sectional schematic diagram of a bulk acoustic resonator according to an exemplary embodiment of the present invention. It is a cross-sectional view parallel to the thickness direction of the resonator through the non-electrical connection ends of the bottom electrode 10 and the top electrode 50.

[0046] like Figure 3As shown in the illustrated embodiment, the bulk acoustic wave resonator mainly includes: a substrate 40, a support layer 30, an acoustic mirror 20, a bottom electrode 10, a piezoelectric layer 70, and a top electrode 50. The support layer 30 is disposed on the substrate 40 and serves to support the resonant structure of the bulk acoustic wave resonator. A cavity is formed in the support layer 30, which constitutes the acoustic mirror 20. The bottom electrode 10 is disposed on the lower surface of the piezoelectric layer 70, and the top electrode 50 is disposed on the upper surface of the piezoelectric layer 40, such that the piezoelectric layer 70 is sandwiched between the bottom electrode 10 and the top electrode 50. Figure 3 As shown, the support layer 30 (i.e., support structure) is disposed between the lower surface of the piezoelectric layer 70 and the upper surface of the substrate 40, and the piezoelectric layer 70 and the substrate 40 are arranged generally parallel.

[0047] It should be noted that in the embodiments shown in this invention, the bottom side of the cavity or acoustic mirror cavity is defined by a support layer; however, this invention is not limited to this, and the bottom side of the cavity may also be defined by a substrate 40. All of these are within the scope of protection of this invention.

[0048] like Figure 3 As shown, in the illustrated embodiment, a portion of the outer end of the non-electrically connected terminal of the bottom electrode 10 is covered by the support layer 30, at least a portion of the piezoelectric layer above the non-electrically connected terminal of the bottom electrode 10 is removed, and at least a portion of the upper surface of the non-electrically connected terminal of the bottom electrode 10 is flush with the upper surface of the support layer 30.

[0049] exist Figure 3 In the diagram, region C1 represents the area on the upper part of the acoustic mirror 20 where only the bottom electrode 10 is covered, or where only the bottom electrode 10 is present. In region C1, the piezoelectric layer is removed. Figure 3 In the illustrated embodiment, at the non-electrically connected end of the bottom electrode 10, the outer end of the piezoelectric layer 70 is located inside the boundary of the acoustic mirror 20. In an optional embodiment, Figure 3 The width of the C1 region, i.e. the horizontal distance between the outer end of the piezoelectric layer 70 at the non-electrical connection end of the bottom electrode 10 and the boundary of the acoustic mirror 20, is greater than one-quarter of the resonator wavelength, or greater than 0.5 μm.

[0050] like Figure 3 As shown, the end face of the piezoelectric layer is beveled. However, the invention is not limited to this; the end face can also be vertical, for example, see [reference needed]. Figure 9 and 10 .

[0051] Since a portion of the outer end of the non-electrical connection terminal of the bottom electrode 10 is covered by the support layer 30, the Lamb wave transmitted in the bottom electrode 10 can be further diffused outward to the support layer 30, effectively reducing the parasitic modes caused by the return of the Lamb wave from the bottom electrode 10, and effectively improving the performance of the device.

[0052] Figure 5 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 5 The illustrated embodiments and Figure 3 The difference is that, in Figure 5 In this context, the piezoelectric layer outside the effective region is not as... Figure 3 Instead of removing the piezoelectric layer 70, a portion of its thickness is removed from the upper surface of the piezoelectric layer 70, thereby forming a step 71 shape on the upper surface of the piezoelectric layer 70. Figure 5 The structure shown is relative to Figure 3 The structure shown, although it removes less material resulting in more acoustic leakage and a relatively low Q value, offers more robust support and therefore better reliability. Figure 5 The other structures shown, because of their similarity to... Figure 3 The results are basically the same, so I won't repeat them here.

[0053] Figure 6 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 6 The illustrated embodiments and Figure 5 The difference is that, in Figure 6 In this process, a portion of the thickness of the piezoelectric layer outside the effective region is removed from its upper surface, forming multiple steps 71 and 72, rather than as... Figure 5 The image shows only one step. Figure 6 The structure shown is relative to Figure 5 The structure shown, with its stepped structure and greater removal of features, results in less acoustic leakage and a relatively high Q value; compared to Figure 3 As shown, the support is more robust, thus resulting in better reliability. Figure 6 The other structures shown, because of their similarity to... Figure 3 and Figure 5 The results are basically the same, so I won't repeat them here.

[0054] Figure 7 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 7 The illustrated embodiments and Figure 3 The difference is that, in Figure 7 In this context, the piezoelectric layer outside the effective region is not as... Figure 3 The piezoelectric layer 70 was not removed; instead, a portion was removed from its upper surface to form a recess 73. Figure 7 In the middle, the inner edge of the recess 73 is flush with the outer edge of the non-electrical connection end of the top electrode 50. Figure 7 The structure shown is for Figure 5The structure shown provides further enhanced support, resulting in better reliability; at the same time, the concave structure leads to less acoustic leakage and a relatively high Q value. Figure 7 The other structures shown, because of their similarity to... Figure 3 The results are basically the same, so I won't repeat them here.

[0055] Figure 8 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 8 The illustrated embodiments and Figure 7 The difference is that, in Figure 8 In the middle, the recess 73 is filled with 74, and in addition, Figure 8 The outer edge of the non-electrical connection end of the top electrode is located between the inner and outer edges of the groove in the horizontal direction. Figure 8 The structure shown is for Figure 7 The structure shown provides further enhanced support, resulting in improved reliability. Figure 8 The other structures shown, because of their similarity to... Figure 3 and Figure 7 The results are basically the same, so I won't repeat them here.

[0056] Figure 9 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 9 The illustrated embodiments and Figure 3 The difference is that, in Figure 9 In the middle, the end face of the piezoelectric layer is a vertical face of 75 degrees. Figure 9 The other structures shown, because of their similarity to... Figure 3 The results are basically the same, so I won't repeat them here.

[0057] Figure 10 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 10 The illustrated embodiments and Figure 9 The difference is that, in Figure 10 In the middle, a filling layer or support layer 89 is also provided on the outer side of the end face of the piezoelectric layer, which is arranged in the same layer as the piezoelectric layer 70 at the non-electric connection end of the bottom electrode. Figure 10 The other structures shown, because of their similarity to... Figure 3 and Figure 9 The results are basically the same, so I won't repeat them here.

[0058] Figure 11 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 11The illustrated embodiments and Figure 3 The difference is that, in Figure 11 In the middle, the non-electrical connection end of the top electrode 50 extends straight to the outer side of the outer end of the piezoelectric layer, thereby forming an air gap 76 between the non-electrical connection ends of the top electrode 50 and the bottom electrode 10 on the outer side of the piezoelectric layer 70. Figure 11 The structure shown maintains Figure 3 Given the advantages of the structure shown, the resulting air gap 76 can further reduce acoustic leakage and improve the Q value. Figure 11 The other structures shown, because of their similarity to... Figure 3 The results are basically the same, so I won't repeat them here.

[0059] Figure 12 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 12 The illustrated embodiments and Figure 3 The difference is that, in Figure 12 In the middle, the non-electrical connection end of the top electrode 50 is formed with a cantilever structure, thereby forming an air gap 77 between the non-electrical connection end of the top electrode and the upper surface of the piezoelectric layer 70. Figure 12 The structure shown maintains Figure 3 Given the advantages of the structure shown, the resulting air gap 77 can further reduce acoustic leakage and improve the Q value. Figure 12 The other structures shown, because of their similarity to... Figure 3 The results are basically the same, so I won't repeat them here.

[0060] Figure 13 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 13 The illustrated embodiments and Figure 8 The difference is that, in Figure 13 In the piezoelectric layer 70, a recess on the upper surface is horizontally positioned inside the non-point connection end of the top electrode 50. Furthermore, in... Figure 13 In the middle, the concave cross-section is rectangular, while... Figure 8 The middle part is trapezoidal. Figure 13 The depressions are also filled with a medium, such as SiO2, Si3N4, BPSG, etc. Figure 13 The other structures shown, because of their similarity to... Figure 3 and Figure 8 The results are basically the same, so I won't repeat them here.

[0061] Figure 14 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 14 The illustrated embodiments and Figure 8 The difference is that, in Figure 14 In the middle, a recess 81 is provided on the lower surface of the piezoelectric layer 70; in addition, in Figure 14 In the middle, the concave cross-section is rectangular, while... Figure 8 The middle part is trapezoidal. Figure 14 In this context, the depression can be an air gap or filled with a medium, such as SiO2, Si3N4, BPSG, etc. Figure 14 The other structures shown, because of their similarity to... Figure 3 and Figure 8 The results are basically the same, so I won't repeat them here.

[0062] Figure 15 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 15 The illustrated embodiments and Figure 8 The difference is that, in Figure 15 In the piezoelectric layer 70, a through-hole 83 is provided. Figure 15 In this process, the through-hole can be an air gap or filled with a medium, such as SiO2, Si3N4, BPSG, etc. Figure 15 The other structures shown, because of their similarity to... Figure 3 and Figure 8 The results are basically the same, so I won't repeat them here.

[0063] Figure 16 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 16 The illustrated embodiments and Figure 14 The difference is that, in Figure 16 In the middle, the lower surface of the piezoelectric layer 70 has an outwardly extending recess 85, rather than just a... Figure 14 Depression 81 in the middle, Figure 16 The non-electrical connection end of the bottom electrode 10 is a straight portion that extends through the recess 85. The recess 85 can be in the form of an air gap or filled with materials such as SiO2, Si3N4, or BPSG. Figure 16 The recess 85 shown can be extended further outward to further reduce acoustic leakage and improve the Q value. Figure 16 The other structures shown, because of their similarity to... Figure 3 and Figure 14 The results are basically the same, so I won't repeat them here.

[0064] exist Figure 3 , Figure 5-16 In the embodiment shown, the non-electrical connection end of the bottom electrode 10 is a straight portion, and the bottom electrode is a straight electrode; however, the present invention is not limited thereto.

[0065] Figure 17 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 17 The illustrated embodiments and Figure 14 The difference is that, in Figure 17 In the middle, a recess 84 is provided on the lower surface of the piezoelectric layer 70, and the non-electrical connection end of the bottom electrode 10 fills the recess 84. Figure 17 The structure shown is compared to Figure 14 The structure shown has higher mechanical stability and better reliability. Figure 17 The other structures shown, because of their similarity to... Figure 3 and Figure 14 The results are basically the same, so I won't repeat them here.

[0066] Figure 18 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 18 The illustrated embodiments and Figure 17 The difference is that, in Figure 18 In the piezoelectric layer 70, a dielectric layer 87 is provided on the lower surface to fill the depression and cover part of the surface of the piezoelectric layer 70. For example, materials such as SiO2, Si3N4, BPSG, etc. are provided. The non-electrical connection end of the bottom electrode 10 is covered by the dielectric layer 87. Figure 18 The structure shown is compared to Figure 14 The structure shown has higher mechanical stability and better reliability; compared to Figure 17 The structure shown has smaller parasitic modes due to electrode bending, and the electrical response in the parasitic modes is isolated by the dielectric layer. Figure 18 The other structures shown, because of their similarity to... Figure 3 and Figure 17 The results are basically the same, so I won't repeat them here.

[0067] Figure 19 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross section of line OC' in the diagram. Figure 19 The illustrated embodiments and Figure 16 The difference is that, in Figure 19 In the middle, the lower surface of the piezoelectric layer 70 is provided with a filler. Figure 16 The recess in the piezoelectric layer 70 and the dielectric layer 88 covering part of the surface of the piezoelectric layer 70 are made of materials such as SiO2, Si3N4, BPSG, etc. The non-electrical connection end of the bottom electrode 10 is covered by the dielectric layer 88. Figure 19 The structure shown is compared to Figure 16 The structure shown has higher mechanical stability and better reliability. Figure 19 The other structures shown, because of their similarity to... Figure 3 and Figure 16 The results are basically the same, so I won't repeat them here.

[0068] Figure 20 For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 2 A schematic diagram of the cross-section of line OB in the diagram. Figure 20 The diagram shows a cross-sectional view parallel to the thickness direction of the resonator, passing through the non-electrical connection terminal of the bottom electrode 10 and the electrical connection terminal of the top electrode 50. Figure 20 As shown, at the electrical connection end of the top electrode 50, both the upper and lower surfaces of the piezoelectric layer 70 are flat and extend to the outside of the non-electrical connection end of the bottom electrode 10.

[0069] Figure 21 For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 2 A schematic diagram of the cross-section of line OB in the diagram. Figure 21 The diagram shows a cross-sectional view parallel to the thickness direction of the resonator, passing through the non-electrical connection terminal of the bottom electrode 10 and the electrical connection terminal of the top electrode 50. Figure 21 As shown, at least a portion of the piezoelectric layer 70 at the electrical connection end of the top electrode 50 is removed, and the outer end of the piezoelectric layer 70 is inside the boundary of the acoustic mirror 20. The electrical connection end of the top electrode 50 extends horizontally across the non-electrical connection end of the bottom electrode 10, and an air gap 91 is defined between the electrical connection end of the top electrode 50, the non-electrical connection end of the bottom electrode 10, and the upper surface of the support layer 30. Figure 21 In this configuration, the electrical connection of the top electrode 50 extends horizontally to the outer side of the piezoelectric layer. In an alternative embodiment, the air gap 91 can be replaced by an insulating medium.

[0070] Figure 22 For a bulk acoustic resonator according to an exemplary embodiment of the present invention, the edge Figure 2 A schematic diagram of the cross-section of line OB in the diagram. Figure 22 The diagram shows a cross-sectional view parallel to the thickness direction of the resonator, passing through the non-electrical connection terminal of the bottom electrode 10 and the electrical connection terminal of the top electrode 50. Figure 22 As shown, at least a portion of the piezoelectric layer 70 at the electrical connection end of the top electrode 50 is removed, and the outer end of the piezoelectric layer 70 is inside the boundary of the acoustic mirror 20. The electrical connection end of the top electrode 50 extends horizontally across the non-electrical connection end of the bottom electrode 10, and an air gap 92 is defined between the electrical connection end of the top electrode 50, the non-electrical connection end of the bottom electrode 10, and the upper surface of the support layer 30. Figure 22 In this embodiment, a portion of the electrical connection terminal of the top electrode 50 forms a gap between it and the upper surface of the piezoelectric layer 70 in the thickness direction of the resonator. In an alternative embodiment, the air gap 92 can be replaced by a filled insulating medium.

[0071] Figure 23 For another exemplary embodiment of the present invention, the bulk acoustic resonator along Figure 2 A schematic diagram of the cross-section of the OC line. Figure 23 The diagram shows a cross-sectional view of the resonator through the electrical connection terminal of the bottom electrode 10 and the non-electrical connection terminal of the top electrode 50, parallel to the thickness direction of the resonator.

[0072] like Figure 23 As shown, a portion of the outer end of the electrical connection terminal of the bottom electrode 10 is covered by the support layer 30. At least a portion of the piezoelectric layer at the electrical connection terminal of the bottom electrode 10 is removed. At least a portion of the upper surface of the electrical connection terminal of the bottom electrode 10 is flush with the upper surface of the support layer 30. At the electrical connection terminal of the bottom electrode 10, the outer end of the piezoelectric layer 70 is inside the boundary of the acoustic mirror 20. The resonator also includes a bottom electrode lead-out portion 61 and a passivation layer 62 that covers at least the top electrode 50. The bottom electrode lead-out portion 61 covers at least a portion of the upper surface of the electrical connection terminal of the bottom electrode 10, and the inner end of the bottom electrode lead-out portion 61 is at least above the piezoelectric layer 70 and outside the outer end of the top electrode 50 in the horizontal direction. Figure 23 In the structure shown, the bottom electrode lead-out portion 61 extends towards the center of the resonator, which helps to address the problem of weakened mechanical support structure caused by etching of the single crystal piezoelectric layer 70.

[0073] The following reference Figure 4A-4K Exemplary description of manufacturing Figure 3 The process of the bulk acoustic resonator is shown.

[0074] Step 1: As Figure 4A As shown, a POI (Piezoelectrics on Insulator) wafer is provided. The POI wafer includes an auxiliary substrate 101, an insulating layer 102 disposed on the auxiliary substrate 101, and a single crystal piezoelectric layer 70 disposed on the insulating layer 102. The side of the piezoelectric layer 70 facing away from the insulating layer 102 is the first side of the piezoelectric layer.

[0075] Step 2: As Figure 4B As shown, a bottom electrode 10 is formed on the first side of the single crystal piezoelectric layer 70.

[0076] Step 3: As Figure 4C As shown, a patterned release material layer 20' is formed on the upper surface of the bottom electrode 10, which is used to form the acoustic mirror 20.

[0077] Step 4: As Figure 4D As shown, in Figure 4CThe structure shown has a support layer 30 covering the release material layer 20', the bottom electrode 10 and the piezoelectric layer 70. The outer surface of the support layer 30 can be planarized by using a CMP (chemical mechanical polishing) process.

[0078] Step 5: As Figure 4E As shown, a substrate 40 is provided, and a bonding layer 41 is provided on one side of the substrate 40.

[0079] Step 6: As Figure 4F As shown, the flat surface of the support layer 30 is bonded to the bonding layer 41. The support layer 30 can be bonded to the substrate 10 by physical or chemical means, or it can be directly bonded without the bonding layer 41. Instead, a chemical bond can be formed between the substrate 40 and the support layer 30, or a physical bond can be formed through intermolecular forces when the surface is polished to a very low surface roughness.

[0080] Step 7: As Figure 4G As shown, the auxiliary substrate 101 and the insulating layer 102 are removed to expose the second side of the piezoelectric layer 70. The etching processes of the auxiliary substrate 101 and the insulating layer 102 are quite different. For example, the auxiliary substrate 101 is silicon and the insulating layer 102 is silicon dioxide. The insulating layer 102 can act as a termination layer or barrier layer during the removal of the auxiliary substrate 101. The removal process of the insulating layer 102 is gentle, reducing or even avoiding damage to the other surface of the piezoelectric single crystal film during the removal of the auxiliary substrate 101.

[0081] Step 8: As Figure 4H As shown, a top electrode 50 is formed on the second side of the single-crystal piezoelectric layer 70.

[0082] Step 9: As Figure 4I As shown, for Figure 4H The piezoelectric layer 70 of the structure shown is etched to form Figure 4I The piezoelectric layer 70 is shown. In Figure 4I The release hole for releasing the release material layer 20' is not shown in the figure.

[0083] Step 10: As Figure 4J As shown, in Figure 4I The bottom electrode of the structure shown has a bottom electrode lead-out portion 60 at its electrical connection terminal.

[0084] Step 11: As Figure 4K As shown, the release material layer 20' is released to form the acoustic mirror cavity of the resonator, thereby forming a cavity corresponding to... Figure 3 The structure shown is a bulk acoustic resonator.

[0085] The manufacturing process of the bulk acoustic resonator in other embodiments can be referred to Figure 3 The manufacturing process of the bulk acoustic resonator shown will not be described in detail here for the sake of brevity.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] Based on the above, the present invention proposes the following technical solution:

[0091] 1. A bulk acoustic resonator, comprising:

[0092] Base;

[0093] Top electrode;

[0094] piezoelectric layer;

[0095] Bottom electrode; and

[0096] Acoustic mirror,

[0097] in:

[0098] A support layer is provided between the substrate and the resonant structure, and the piezoelectric layer is a single-crystal piezoelectric layer arranged substantially parallel to the substrate;

[0099] In a first cross-section parallel to the thickness direction of the resonator, passing through the non-electrical connection ends of the bottom electrode and the top electrode, a portion of the outer end of the non-electrical connection end of the bottom electrode is covered by a support layer, at least a portion of the piezoelectric layer at the non-electrical connection end of the bottom electrode is removed, and at least a portion of the upper surface of the non-electrical connection end of the bottom electrode is flush with the upper surface of the support layer.

[0100] 2. The bulk acoustic resonator according to 1, wherein:

[0101] In the first cross-section, at the non-electrically connected end of the bottom electrode, the outer end of the piezoelectric layer is located inside the boundary of the acoustic mirror.

[0102] 3. The bulk acoustic resonator according to 2, wherein:

[0103] In the first cross section, at the non-electrically connected end of the bottom electrode, the horizontal distance between the outer end of the piezoelectric layer and the boundary of the acoustic mirror is greater than one-quarter of the resonator wavelength, or greater than 0.5 μm.

[0104] 4. The bulk acoustic resonator according to claim 2, wherein:

[0105] In the first cross section, at the non-electrically connected end of the bottom electrode, the end face of the outer end of the piezoelectric layer is a vertical surface or an outwardly inclined surface.

[0106] 5. The bulk acoustic resonator according to claim 2, wherein:

[0107] The resonator further includes a filling layer, which is arranged in the same layer as the piezoelectric layer at the non-electrical connection end of the bottom electrode.

[0108] 6. The bulk acoustic resonator according to claim 2, wherein:

[0109] In the first cross-section, at the non-electrically connected end of the bottom electrode, the non-electrically connected end of the top electrode is a straight end and is located outside the end of the piezoelectric layer in the horizontal direction; or

[0110] In the first cross section, the non-electrically connected end of the bottom electrode and the non-electrically connected end of the top electrode have a cantilever structure.

[0111] 7. The bulk acoustic resonator according to claim 1, wherein:

[0112] In the first cross-section, at the non-electrically connected end of the bottom electrode, the upper surface of the piezoelectric layer has one or more stepped portions; or

[0113] In the first cross section, at the non-electrically connected end of the bottom electrode, the lower surface of the piezoelectric layer has one or more stepped portions.

[0114] 8. The bulk acoustic resonator according to claim 1, wherein:

[0115] In the first cross-section, at the non-electrically connected end of the bottom electrode, a recess is formed on the upper or lower surface of the piezoelectric layer; or

[0116] In the first cross section, at the non-electrical connection end of the bottom electrode, the piezoelectric layer is provided with a through hole.

[0117] 9. The bulk acoustic resonator according to 8, wherein:

[0118] The recess or through-hole is filled with a medium material.

[0119] 10. The bulk acoustic resonator according to claim 8, wherein:

[0120] In the first cross-section, the end face of the non-electrically connected end of the top electrode is located between the inner and outer sides of the recess or through hole in the horizontal direction; or

[0121] In the first cross-section, the recess or through-hole is located outside the non-electrode connection end of the top electrode in the horizontal direction; or

[0122] In the first cross-section, the recess or through hole is located inside the non-electrode connection end of the top electrode in the horizontal direction.

[0123] 11. The bulk acoustic resonator according to claim 1, wherein:

[0124] In a second cross section parallel to the thickness direction of the resonator, passing through the electrical connection end of the bottom electrode and the non-electrical connection end of the top electrode, a portion of the outer end of the electrical connection end of the bottom electrode is covered by a support layer, at least a portion of the piezoelectric layer at the electrical connection end of the bottom electrode is removed, and at least a portion of the upper surface of the electrical connection end of the bottom electrode is flush with the upper surface of the support layer.

[0125] At the electrical connection end of the bottom electrode, the outer end of the piezoelectric layer is located inside the boundary of the acoustic mirror;

[0126] The resonator further includes a bottom electrode lead-out portion and a passivation layer that at least covers the top electrode. The bottom electrode lead-out portion covers at least a portion of the upper surface of the electrical connection terminal of the bottom electrode, and the inner end of the bottom electrode lead-out portion is at least above the piezoelectric layer and is located outside the outer end of the top electrode in the horizontal direction.

[0127] 12. The bulk acoustic resonator according to any one of 1-11, wherein:

[0128] The bottom electrode is a straight electrode.

[0129] 13. The bulk acoustic resonator according to claim 1, wherein:

[0130] In the first cross-section, at the non-electrical connection end of the bottom electrode, a recess is formed on the lower surface of the piezoelectric layer, and the non-electrical connection end of the bottom electrode includes a portion located within the recess; or

[0131] In the first cross-section, a recess is formed on the lower surface of the piezoelectric layer at the non-electrical connection end of the bottom electrode. A recess-filling dielectric layer is further included between the non-electrical connection end of the bottom electrode and the piezoelectric layer. The recess-filling dielectric layer fills the recess and covers a portion of the lower surface of the piezoelectric layer. The non-electrical connection end of the bottom electrode covers the filling dielectric layer; or

[0132] In the first cross section, at the non-electrical connection end of the bottom electrode, a step portion is formed on the lower surface of the piezoelectric layer, and a step-filling dielectric layer is further included between the non-electrical connection end of the bottom electrode and the piezoelectric layer. The step-filling dielectric layer fills the step portion and covers a portion of the lower surface of the piezoelectric layer, and the non-electrical connection end of the bottom electrode covers the step-filling dielectric layer.

[0133] 14. The bulk acoustic resonator according to any one of 1-13, wherein:

[0134] In a third section parallel to the thickness direction of the resonator, passing through the non-electrical connection end of the bottom electrode and the electrical connection end of the top electrode, at the electrical connection end of the top electrode, both the upper and lower surfaces of the piezoelectric layer are flat surfaces and extend to the outside of the non-electrical connection end of the bottom electrode.

[0135] 15. The bulk acoustic resonator according to any one of 1-13, wherein:

[0136] In a third section parallel to the thickness direction of the resonator, passing through the non-electrical connection end of the bottom electrode and the electrical connection end of the top electrode, at least a portion of the piezoelectric layer at the electrical connection end of the top electrode is removed and the outer end of the piezoelectric layer is inside the boundary of the acoustic mirror.

[0137] The electrical connection of the top electrode crosses the non-electrical connection of the bottom electrode in the horizontal direction.

[0138] 16. The bulk acoustic resonator according to 15, wherein:

[0139] The electrical connection of the top electrode extends horizontally to the outside of the piezoelectric layer; or

[0140] A portion of the electrical connection terminal of the top electrode forms a gap between the resonator and the upper surface of the piezoelectric layer in the thickness direction.

[0141] 17. A filter comprising a bulk acoustic resonator according to any one of 1-16.

[0142] 18. An electronic device comprising a bulk acoustic resonator according to any one of 1-16, or a filter according to 17.

[0143] 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.

[0144] 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 wave resonator, comprising: a substrate; a top electrode; a piezoelectric layer; a bottom electrode; and an acoustic mirror, wherein: a support layer is provided between the substrate and the piezoelectric layer, and the piezoelectric layer is a single-crystal piezoelectric layer arranged parallel to the substrate; in a first cross section of the non-electrically connected end of the bottom electrode and the non-electrically connected end of the top electrode, which is parallel to the thickness direction of the resonator, a part of the outer end of the non-electrically connected end of the bottom electrode is covered by the support layer, at least a part of the piezoelectric layer at the non-electrically connected end of the bottom electrode is removed, and at least a part of the upper surface of the non-electrically connected end of the bottom electrode is flush with the upper surface of the support layer. 2.The bulk acoustic wave resonator according to claim 1, wherein: in the first cross section, at the non-electrically connected end of the bottom electrode, the outer end of the piezoelectric layer is inside the boundary of the acoustic mirror. 3.The bulk acoustic wave resonator according to claim 2, wherein: in the first cross section, at the non-electrically connected end of the bottom electrode, the distance between the outer end of the piezoelectric layer and the boundary of the acoustic mirror in the horizontal direction is greater than one quarter of the resonator wavelength, or greater than 0.5μm. 4.The bulk acoustic wave resonator according to claim 2, wherein: in the first cross section, at the non-electrically connected end of the bottom electrode, the end surface of the outer end of the piezoelectric layer is a vertical surface or an outwardly inclined inclined surface. 5.The bulk acoustic wave resonator according to claim 2, wherein: the resonator further comprises a filling layer, which is arranged in the same layer as the piezoelectric layer at the non-electrically connected end of the bottom electrode. 6.The bulk acoustic wave resonator according to claim 2, wherein: in the first cross section, at the non-electrically connected end of the bottom electrode, the non-electrically connected end of the top electrode is a flat end and is outside the end of the piezoelectric layer in the horizontal direction; or in the first cross section, at the non-electrically connected end of the bottom electrode, the non-electrically connected end of the top electrode has a cantilever structure. 7.The bulk acoustic wave resonator according to claim 1, wherein: in the first cross section, at the non-electrically connected end of the bottom electrode, the upper surface of the piezoelectric layer is formed with a single or multiple stepped portions; or in the first cross section, at the non-electrically connected end of the bottom electrode, the lower surface of the piezoelectric layer is formed with a single or multiple stepped portions. 8.The bulk acoustic wave resonator according to claim 1, wherein: in the first cross section, at the non-electrically connected end of the bottom electrode, the upper surface or the lower surface of the piezoelectric layer is formed with a recess; or in the first cross section, at the non-electrically connected end of the bottom electrode, the piezoelectric layer is provided with a through hole. 9.The bulk acoustic wave resonator according to claim 8, wherein: the recess or the through hole is filled with a dielectric material. 10.The bulk acoustic wave resonator according to claim 8, wherein: in the first cross section, the end surface of the non-electrically connected end of the top electrode is between the inside and the outside of the recess or the through hole in the horizontal direction; or in the first cross section, the recess or the through hole is outside the non-electrically connected end of the top electrode in the horizontal direction; or in the first cross section, the recess or the through hole is inside the non-electrically connected end of the top electrode in the horizontal direction. ​ ​ 11.The bulk acoustic wave resonator according to claim 1, wherein: in a second cross section parallel to the thickness direction of the resonator, through the electrically connected end of the bottom electrode and the non-electrically connected end of the top electrode, a part of the outer end of the electrically connected end of the bottom electrode is covered by the support layer, at least a part of the piezoelectric layer of the electrically connected end of the bottom electrode is removed, and at least a part of the upper surface of the electrically connected end of the bottom electrode is flush with the upper surface of the support layer; in the electrically connected end of the bottom electrode, the outer end of the piezoelectric layer is inside the boundary of the acoustic mirror; the resonator further comprises a bottom electrode lead-out portion covering at least a part of the upper surface of the electrically connected end of the bottom electrode and an inner end of the bottom electrode lead-out portion at least above the piezoelectric layer and outside the outer end of the top electrode in the horizontal direction, and a passivation layer covering at least the top electrode. 12.The bulk acoustic wave resonator according to any one of claims 1-11, wherein: the bottom electrode is a flat electrode. 13.The bulk acoustic wave resonator according to claim 1, wherein: in the first cross section, in the non-electrically connected end of the bottom electrode, a recess is formed in the lower surface of the piezoelectric layer, and the non-electrically connected end of the bottom electrode comprises a part inside the recess; or in the first cross section, in the non-electrically connected end of the bottom electrode, a recess is formed in the lower surface of the piezoelectric layer, and a recess filling dielectric layer is further comprised between the non-electrically connected end of the bottom electrode and the piezoelectric layer, the recess filling dielectric layer fills the recess and covers a part of the lower surface of the piezoelectric layer, and the non-electrically connected end of the bottom electrode covers the recess filling dielectric layer; or in the first cross section, in the non-electrically connected end of the bottom electrode, a step is formed in the lower surface of the piezoelectric layer, and a step filling dielectric layer is further comprised between the non-electrically connected end of the bottom electrode and the piezoelectric layer, the step filling dielectric layer fills the step and covers a part of the lower surface of the piezoelectric layer, and the non-electrically connected end of the bottom electrode covers the step filling dielectric layer. 14.The bulk acoustic wave resonator according to any one of claims 1-11, wherein: in a third cross section parallel to the thickness direction of the resonator, through the non-electrically connected end of the bottom electrode and the electrically connected end of the top electrode, in the electrically connected end of the top electrode, both the upper and lower surfaces of the piezoelectric layer are flat surfaces and extend outside the non-electrically connected end of the bottom electrode. 15.The bulk acoustic wave resonator according to any one of claims 1-11, wherein: in a third cross section parallel to the thickness direction of the resonator, through the non-electrically connected end of the bottom electrode and the electrically connected end of the top electrode, in the electrically connected end of the top electrode, at least a part of the piezoelectric layer is removed and the outer end of the piezoelectric layer is inside the boundary of the acoustic mirror; the electrically connected end of the top electrode crosses the non-electrically connected end of the bottom electrode in the horizontal direction. 16.The bulk acoustic wave resonator according to claim 15, wherein: the electrically connected end of the top electrode extends horizontally to the outside of the piezoelectric layer; or a part of the electrically connected end of the top electrode forms a gap between the upper surface of the piezoelectric layer in the thickness direction of the resonator.

17. A filter comprising the bulk acoustic resonator of any one of claims 1-16.

18. An electronic device comprising the bulk acoustic resonator of any one of claims 1-16, or the filter of claim 17.

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