Single crystal bulk acoustic resonator and method of manufacturing the same, filter, and electronic device

Abstract

The present application relates to a bulk acoustic wave resonator and a manufacturing method thereof. The resonator comprises: a substrate; an acoustic mirror cavity; a laminated structure comprising a piezoelectric layer, a top electrode and a bottom electrode; a bonding structure arranged between the laminated structure and the substrate, wherein: the bonding structure comprises a first metal bonding layer arranged on one side of the substrate, and a second metal bonding layer arranged on one side of the laminated structure, the first metal bonding layer and the second metal bonding layer are bonded to each other; the second metal bonding layer is electrically connected with the bottom electrode and is arranged in a circumferential direction, and the second metal bonding layer defines at least part of the boundary of the acoustic mirror cavity in the horizontal direction. 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 single-crystal acoustic 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 a bottom electrode and a piezoelectric thin film or a piezoelectric layer and a top electrode, i.e., a piezoelectric material 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 back into an electrical signal output.

[0005] In known technologies, when the acoustic mirror of a resonator is in the form of a cavity, the cavity is typically formed by etching the substrate. This requires several steps, including forming the cavity on the substrate, filling the cavity, planarizing it, forming a release hole, and performing a release process to form the acoustic mirror cavity. These steps are relatively complex, and it is difficult to make the piezoelectric layer into a planar film. In reality, there is a need to propose alternative process steps for forming the acoustic mirror cavity.

[0006] Furthermore, as bulk acoustic wave resonators are miniaturized and applied to high-frequency fields, the thickness of their electrode films is gradually decreasing, which directly increases electrical connection losses. Summary of the Invention

[0007] The present invention is proposed to alleviate or solve at least one of the above-mentioned problems in the prior art.

[0008] According to one aspect of an embodiment of the present invention, a bulk acoustic resonator is provided, comprising:

[0009] Base;

[0010] Acoustic mirror cavity;

[0011] A stacked structure, comprising a piezoelectric layer, a top electrode, and a bottom electrode;

[0012] A bonding structure is positioned between the laminated structure and the substrate.

[0013] in:

[0014] The bonding structure includes a first metal bonding layer disposed on one side of the substrate and a second metal bonding layer disposed on one side of the stacked structure, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other.

[0015] The second metal bonding layer is electrically connected to the bottom electrode and arranged in the circumferential direction, and the second metal bonding layer defines at least a portion of the horizontal boundary of the acoustic mirror cavity.

[0016] This invention also relates to a method for manufacturing a bulk acoustic resonator, comprising:

[0017] Step 1: Deposit a first metal bonding layer on one side of the resonator substrate;

[0018] Step 2: Deposit a second metal bonding layer electrically connected to the bottom electrode on one side of the resonator;

[0019] Step 3: Bond the first metal bonding layer and the second metal bonding layer together to form a bottom electrode power supply path from the first metal bonding layer to the second metal bonding layer and then to the bottom electrode.

[0020] Wherein: the second metal bonding layer is electrically connected to the bottom electrode and arranged in the circumferential direction, and the second metal bonding layer defines at least a portion of the boundary of the acoustic mirror cavity in the horizontal direction.

[0021] Embodiments of the present invention also relate to a filter, including the aforementioned bulk acoustic resonator.

[0022] Embodiments of the present invention also relate to an electronic device, including the filter or the resonator described above. Attached Figure Description

[0023] 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:

[0024] Figure 1 This is a top view schematic diagram of a bulk acoustic resonator according to an exemplary embodiment of the present invention;

[0025] Figure 2For an exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator in the image;

[0026] Figure 3 For another exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator in the image;

[0027] Figure 4-6 For different exemplary embodiments of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator in the image;

[0028] Figure 7 This is a top view schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention;

[0029] Figure 8 For an exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator, showing a through hole on the piezoelectric layer communicating with the cavity of the acoustic mirror;

[0030] Figure 9 For an exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator. Figure 9 The sacrificial layer is shown in the diagram;

[0031] Figure 10 For an exemplary embodiment of the present invention, similar to along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator. Figure 10 It shows Figure 9 A schematic diagram showing that the sacrificial layer inside the cavity of the middle acoustic mirror was not removed;

[0032] Figure 11 For an exemplary embodiment of the present invention, similar to along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator. Figure 11 Compared to Figure 10 The structure also shows a barrier layer;

[0033] Figure 12 According to an exemplary embodiment of the present invention Figure 11 A top view of the barrier layer in the middle;

[0034] Figure 13-19 An example is shown Figure 2 The diagram shows a series of cross-sectional schematics illustrating the fabrication process of the structure shown. Detailed Implementation

[0035] 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.

[0036] In this invention, a bulk acoustic wave resonator is fabricated based on a POI (Piezoelectrics on Insulator) substrate. The POI wafer includes an auxiliary substrate, a single-crystal piezoelectric layer, and an insulating layer disposed between the single-crystal piezoelectric layer and the auxiliary substrate.

[0037] As mentioned later, during the resonator transfer process, the insulating layer can better protect the single-crystal piezoelectric film (i.e., the single-crystal piezoelectric layer), thereby reducing or even avoiding damage to the single-crystal piezoelectric film during the subsequent removal of the auxiliary substrate, reducing or even avoiding surface damage to the piezoelectric film, so as to obtain a high-performance bulk acoustic resonator.

[0038] In addition, the presence of the insulating layer also facilitates the diversification of substrate removal methods and simplifies device fabrication processes.

[0039] The following reference Figure 1-19 Specific embodiments of the present invention will be described.

[0040] The reference numerals in the accompanying drawings of this invention are illustrated as follows:

[0041] 10: Substrate, the specific material can be silicon, silicon carbide, sapphire, silicon dioxide, or other silicon-based materials.

[0042] 20: Acoustic mirror, which can be a cavity, or it can use a Bragg reflector layer or other equivalent forms. The embodiment shown in this invention uses a cavity.

[0043] 30: Bottom electrode (including electrode leads), 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.

[0044] 40: The piezoelectric layer 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. Materials, for example, can be doped aluminum nitride, which contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.

[0045] 50: Top electrode (including electrode leads), material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above metals. The material of the top electrode can be the same as or different from that of the bottom electrode.

[0046] 60: Dielectric layer or process layer, the material can be aluminum nitride, silicon nitride and silicon dioxide, etc.

[0047] 70: Etching barrier layer, which can be made of materials such as aluminum nitride, silicon nitride, and silicon dioxide, mainly protects the parts that do not need to be etched during the etching process.

[0048] 80: Adhesive layer, the material of which can be titanium, titanium nitride, titanium-tungsten alloy, etc.

[0049] 90: Bonding layer, the material of which can be gold, copper or alloy.

[0050] 100: Bonding layer, which can be made of gold, copper or alloy materials.

[0051] 110: Adhesive layer, the material of which can be titanium, titanium nitride, titanium-tungsten alloy, etc.

[0052] 120: A protrusion forming structure is set above the piezoelectric layer. Its material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above metals.

[0053] 130: Electrical connection layer, the material of which may be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals.

[0054] 140: The recessed structure can be made of materials such as molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or composites of the above metals or their alloys, or dielectric or piezoelectric materials such as silicon dioxide, silicon nitride, aluminum nitride, etc.

[0055] 150: Sacrificial layer, the material can be polycrystalline silicon, amorphous silicon, silicon dioxide, phosphorus-doped silicon dioxide (PSG), zinc oxide, magnesium oxide, polymer and similar materials, etc.

[0056] 160: Release hole, which is used to etch the sacrificial layer to form a cavity.

[0057] 170: Barrier layer: Its material can be aluminum nitride, silicon nitride, silicon dioxide, etc.

[0058] 180 / 181: Air gap above the piezoelectric layer.

[0059] 102: POI substrate (Piezoelectrics on Insulator), the POI substrate includes an auxiliary substrate 102, a single-crystal piezoelectric layer 40, and an insulating or dielectric layer 151 disposed between the single-crystal piezoelectric layer 40 and the auxiliary substrate 102. The material of the single-crystal piezoelectric layer corresponds to the material when the piezoelectric layer 40 is a single-crystal piezoelectric layer.

[0060] 102: Optional materials for the auxiliary substrate include single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0061] 151: Insulating layer or dielectric layer, the material can be silicon dioxide, silicon nitride, silicon carbide, sapphire, etc.

[0062] Figure 1 This is a top view schematic diagram of a bulk acoustic resonator according to an exemplary embodiment of the present invention; Figure 2 For an exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator.

[0063] like Figure 1 and 2 The bulk acoustic resonator shown includes:

[0064] Base 10;

[0065] Acoustic mirror cavity 20;

[0066] A stacked structure or sandwich structure, wherein the stacked structure includes a piezoelectric layer 40, a top electrode 50 and a bottom electrode 30;

[0067] A bonding structure is disposed between the stacked structure and the substrate 10. The bonding structure includes a first metal bonding layer 90 disposed on one side of the substrate 10 and a second metal bonding layer 100 disposed on one side of the stacked structure. The first metal bonding layer 90 and the second metal bonding layer 100 are bonded to each other. The first metal bonding layer 90 extends in the horizontal direction. The second metal bonding layer 100 is electrically connected to the bottom electrode 30 and is arranged in the circumferential direction. The second metal bonding layer 100 defines at least a portion of the horizontal boundary of the acoustic mirror cavity 20.

[0068] exist Figure 1-2 In the illustrated embodiment, a metallic bonding connection (bonding layer 90 and bonding layer 100 bonded together) is performed between the formed stacked structure and the substrate 10. Ultimately, the circumferentially arranged bonding layer 100 defines at least a portion of the horizontal boundary of the acoustic mirror cavity 20. Therefore, in this invention, the acoustic mirror cavity is directly formed using metallic bonding.

[0069] In addition, Figure 1-2 In the illustrated embodiment, the bonding layer 100 is electrically connected to the bottom electrode 30. Since the bonding layer 90 participates in electrode conductivity, it helps reduce electrical connection losses. As will be understood, this process can effectively improve insertion loss when fabricating filters.

[0070] like Figure 2 As shown, the bonding layer 90 is a planarization layer, and this planarization layer defines the bottom side of the acoustic mirror 20. In an optional embodiment, the thickness of the bonding layer 90 is in the range of 0.3-5 μm.

[0071] like Figure 2 As shown, the bonding layer 90 includes a first portion 91 and a second portion 92, wherein the first portion 91 is in Figure 2 The image shows the left side; the second part 92 is... Figure 2 The image shows the right side, with the first part 91 and the second part 92 connected via... Figure 2 The isolation channel or isolation section shown is electrically separated by 90A. Figure 2 In the middle, the first part is electrically connected to the bottom electrode 30 via the bonding layer 100, and the second part is electrically connected to the top electrode via the bonding layer 100A and the top electrode electrical connection portion 30A. Figure 2 As shown in Figure 30A), it is electrically connected to the electrical connection terminal or electrode pin of the top electrode 50. Since the second portion 92 of the bonding layer 90 is electrically connected to the top electrode 50 via the bonding layer 100A, the bonding layer 90 participates in electrode conductivity, thus also reducing electrical connection losses. See [reference needed] for further understanding. Figure 15 The top electrode electrical connection portion 30A is formed by patterning the electrode film layer of the bottom electrode 30, and it is electrically isolated from the bottom electrode 30.

[0072] exist Figure 2 In the embodiment shown, the piezoelectric layer 40 is provided with a via 42 (see...). Figure 19 The electrode pin portion of the top electrode 50 is electrically connected to the top electrode electrical connection portion 30A via the via 42, thereby being electrically connected to the second portion 92 of the bonding layer 90.

[0073] exist Figure 19 In this embodiment, the angle α formed between the wall of via 42 and the bottom surface of the piezoelectric layer is no greater than 85°, in a further embodiment no greater than 60°, further still no greater than 45°, and even further still no greater than 30°. Using such an angle helps ensure that the top electrode achieves good step coverage.

[0074] Figure 1-2 The bulk acoustic resonator with the structure shown has the following technical advantages:

[0075] 1. The acoustic mirror 20 is formed by bonding between bonding layer 90 and bonding layer 100. The acoustic mirror 20 can be formed without any extra processes in between, and the process is relatively simple.

[0076] 2. During bonding, because the bonding layer 90 has a relatively large area on the side close to the substrate 10 (the bonding layer 90 extends in the horizontal direction), there is no need to consider its alignment accuracy during bonding.

[0077] 3. Because the bonding layer 90 is made of a material with good conductivity and its thickness can be made relatively thick, the electrical connection loss of the bottom electrode 30 can be effectively reduced.

[0078] As will be understood, other embodiments will also employ Figure 2 The structure that achieves the aforementioned technical advantages can also obtain the corresponding technical effects or advantages. In the subsequent descriptions of different embodiments, such technical effects will not be elaborated further.

[0079] like Figure 2 As shown, an etching barrier layer 70 is provided between the adhesive layer 80 and the substrate 10, but the etching barrier layer 70 may not be provided. Figure 2 In the embodiment shown, the isolation channel 90A penetrates the bonding layer 90 and terminates at the etch barrier 70.

[0080] exist Figure 2 In the illustrated embodiment, the electrical connection of the top electrode 30 may not be in this manner. For example, a conventional electrical connection method may be used instead of using the second portion 92 of the bonding layer 90 to form the electrical connection.

[0081] exist Figure 2In the illustrated embodiment, adhesive layers 80 and 110 are provided, with adhesive layer 110 being a conductive adhesive layer. In alternative embodiments, adhesive layers 80 and / or 110 may not be provided.

[0082] Figure 3 For another exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator.

[0083] Figure 3 and Figure 2 The difference is that, in Figure 3 In this configuration, the electrode connection between the top electrode 50 and the bottom electrode 30 is achieved through an opening on the back or bottom side of the substrate. It can be seen that... Figure 3 In the substrate 10, a through hole is provided, and the spaced electrical connection layer 130 passes through the through hole and is electrically connected to the first part 91 and the second part 92 of the bonding layer 90, respectively.

[0084] exist Figure 3 In the structure shown, the area of ​​the resonator can be effectively reduced because the signal can be led out through the opening on the back of the substrate. At the same time, if a reasonable packaging method is adopted, such as flip chip (e.g., packaging the flip chip onto a BGA or PGA substrate), the heat can be quickly dissipated due to the smaller distance between the device and the outside world, and the presence of bonding layers 90, 100, and electrical connection layer 130 with good thermal conductivity. This will effectively improve the power capacity of the resonator.

[0085] Figure 4-6 For different exemplary embodiments of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator.

[0086] like Figure 4 As shown, this structure is different from the structure with the lead-out on the back side, and is similar to... Figure 2 The structure shown is similar. Figure 4 The structure shown does not require an opening at the back, which is a traditional solution for leading out from the front. Figure 4 Since the bonding layer 90 does not need to be etched into the first part and the second part, the etching barrier layer 70 can be omitted from the structure shown. Of course, considering that some processes use etching when etching the bonding layer 80 and the bonding layer 90 structure, the etching barrier layer 70 can also be set. If the liftoff process is used, the etching barrier layer 70 is not required.

[0087] exist Figure 4 In the middle, the top electrode film layer is separated into a top electrode 50 and a bottom electrode electrode lead-out portion 50A. Figure 4The left side of the image is modified to 50A). The bottom electrode film is separated into a bottom electrode 30 and a bottom electrode electrical connection portion 30B. The piezoelectric layer 40 is provided with a through hole, and the electrode lead-out portion 50A of the bottom electrode is electrically connected to the bottom electrode electrical connection portion 30B through this through hole. Figure 4 In this resonator, a bonding layer 100B is also included. The upper end of the bonding layer 100B is electrically connected to the bottom electrode electrical connection portion 30B, and the lower end is electrically connected to the bonding layer 90. This forms a power supply path for the electrode lead-out portion 50A of the bottom electrode 30, the bottom electrode electrical connection portion 30B, the bonding layer 100B, the bonding layer 90, the bonding layer 100, and the bottom electrode 30. Figure 4 As shown.

[0088] Although not specifically shown, the via through which the electrode lead-out portion 50A passes in the piezoelectric layer 40 can be structured similarly to... Figure 19 The vias 42 shown are the same or similar.

[0089] for Figure 4 The structure shown can be powered by the top electrode 50 in a conventional manner, which will not be described in detail here.

[0090] Figure 5 The structure shown is Figure 2 The difference in the structure shown is that the adhesive layer 110 and the bonding layer 100 are joined to the edge portion of the bottom electrode 30, which can reduce the area of ​​the resonator. Figure 5 Other structures shown and Figure 2 The structures shown are the same, so they will not be described again here.

[0091] Figure 6 The structure shown is Figure 2 The difference in the structure shown is that: Figure 6 In the middle, the top electrode 50 is provided with a cantilever structure, a bridge structure, a protruding structure, and a recessed structure. Figure 6 In the diagram, 180 represents the air gap defined by the cantilever structure, and 181 represents the air gap defined by the bridge structure. Figure 6 In this structure, a protrusion forming structure 120 is specifically provided above the piezoelectric layer 40 to create the protruding structure; a recess forming structure 140 is provided to create the recessed structure. Figure 6 In the middle, the outer edge of the air gap 181 defined by the bridge structure is located outside the non-electrode connection end of the bottom electrode 30 in the horizontal direction, and there is a distance d, where d is greater than 0, such as Figure 6 As shown, this helps to reduce the parasitic capacitance between the bottom electrode and the top electrode, effectively increasing the electromechanical coupling coefficient of the resonator.

[0092] If you can understand, Figure 6 The top electrode 50 may be provided with a cantilever structure, bridge structure, protrusion structure and recessed structure, or only one or more of them may be provided.

[0093] Figure 7 This is a top view schematic diagram of a bulk acoustic resonator according to another exemplary embodiment of the present invention. Figure 7 In the structure shown, the bonding layer 100 is distributed only circumferentially, and it can be a discontinuous structure. Here, the bonding layer 100 mainly serves the functions of electrical connection and support. In an exemplary embodiment of the present invention, the length of the break in the bonding layer 100 in the circumferential direction is no greater than 80% of the annular length in the circumferential direction.

[0094] Figure 7 The other parts of the structure shown are related to Figure 1 and Figure 2 The structures shown are the same, so they will not be described again here.

[0095] If you can understand, Figure 1-6 In the example shown, the bonding layer 100 can be a closed ring structure, or it can be as follows: Figure 7 The discontinuous structure shown.

[0096] Figure 8 For an exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator is shown, illustrating a through-hole 160 on the piezoelectric layer 40 communicating with the acoustic mirror cavity 20. Since the acoustic mirror cavity 20 is a closed annular structure due to the bonding layer 100, it is not connected to the outside, resulting in significant pressure from subsequent manufacturing processes. By providing the through-hole 160, the internal and external pressures of the acoustic mirror cavity 20 can be made uniform, thereby reducing the pressure on the resonator caused by the pressure difference between the inside and outside, and thus reducing the possibility of damage. Figure 8 The other parts of the structure shown are related to Figure 2 The structures shown are the same, so they will not be described again here.

[0097] Figure 9 For an exemplary embodiment of the present invention, along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator. Figure 9 The image shows a sacrificial layer of 150. Figure 10 For an exemplary embodiment of the present invention, similar to along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator. Figure 10 It shows Figure 9 A schematic diagram showing that the sacrificial layer 150 inside the cavity of the middle acoustic mirror was not removed.

[0098] Figure 9 The structure shown is similar to Figure 8 The difference in the structure shown is that, Figure 9In this process, a sacrificial layer 150 is provided on the outside of the closed bonding layer 100.

[0099] like Figure 9 As shown, a sacrificial layer 150 is provided on the outside of the bonding layer 100 that defines the horizontal boundary of the acoustic mirror cavity, and a gap is provided between the lower surface of the sacrificial layer 150 and the upper surface of the bonding layer 90.

[0100] Figure 9 The other parts of the structure shown are related to Figure 8 The structures shown are the same, so they will not be described again here.

[0101] exist Figure 9 and Figure 10 Setting the sacrifice layer to 150 is to solve, for example... Figure 2 and Figure 8 The mechanical problems of the structure shown will be discussed later, for example. Figure 2 During the manufacturing process, it was found that the acoustic mirror 20 or acoustic mirror cavity 20 is formed early in the resonator fabrication process. After this, many steps are required, such as the fabrication of the top electrode 50. Because its interior is hollow, the mechanical strength of the resonator region may be insufficient in subsequent processes, potentially leading to resonator damage. Therefore, it is necessary to increase the mechanical strength of the acoustic mirror cavity. Based on this, a proposed... Figure 9 and Figure 10 The technical solution shown.

[0102] exist Figure 9 and Figure 10 In the middle, the through hole 160 is also a release hole, which can release the sacrificial layer in the acoustic mirror cavity, and at the same time can also play a role in balancing the pressure inside and outside the acoustic mirror cavity 20.

[0103] Figure 11 For an exemplary embodiment of the present invention, similar to along Figure 1 A schematic cross-sectional view of the AA' line of the bulk acoustic resonator. Figure 11 Compared to Figure 10 The structure also shows a barrier layer 170. The barrier layer 170 is disposed on the side closest to the substrate 10, primarily to address the issue of exposed metal bonding layers. This is useful in many factories where exposed metal is not permitted in certain specialized machines. Figure 11 The structure shown protects the interior during bonding by using a barrier layer 170 combined with an outer sacrificial layer 150. Figure 11 The other parts of the structure shown are related to Figure 9 The structures shown are the same, so they will not be described again here.

[0104] Figure 12 According to an exemplary embodiment of the present invention Figure 11A top view of the barrier layer 170. To reduce the area increase caused by the barrier layer 170, it can be designed to have only a ring around the edge of the substrate 10, such as... Figure 12 As shown.

[0105] The following reference Figure 13-19 Exemplary Description Figure 2 The manufacturing process of the structure shown.

[0106] like Figure 13 As shown, an etch barrier layer 70 is grown on the substrate 10.

[0107] like Figure 14 As shown, in Figure 13 The film layers corresponding to the adhesive layer 80 and the bonding layer 90 are grown on the etch barrier layer 70 of the structure shown. Then, through processes such as photolithography and etching, the film is obtained as shown. Figure 14 In the structure shown, the bonding layer 90 is electrically isolated into two parts by the isolation channel 90A. For example... Figure 14 As shown, the isolation channel 90A terminates at the etch barrier layer 70.

[0108] like Figure 15 As shown, a POI wafer or POI substrate is provided. The POI wafer includes an auxiliary substrate 102, an insulating or dielectric layer 151, and a single-crystal piezoelectric layer 40. The single-crystal piezoelectric layer can be a piezoelectric single-crystal thin film such as lithium niobate, lithium tantalate, or quartz. Then, a bottom electrode 30 film is formed on one side of the piezoelectric layer 40 of the POI substrate, and this film is patterned to form a pattern of the bottom electrode 30 and a top electrode electrical connection portion 30A.

[0109] like Figure 16 As shown, in Figure 15 The structure shown has films corresponding to the growing adhesive layer 110, bonding layer 100, and bonding layer 100A. Then, through processes such as photolithography and etching, a film is obtained as shown. Figure 16 The structure shown can also be obtained using a liftoff process. Figure 16 The structure shown.

[0110] like Figure 17 As shown, Figure 14 The structure shown and Figure 16 The structures shown are bonded together.

[0111] like Figure 18 As shown, execution will Figure 17 The process of removing the auxiliary substrate 102 and insulating layer 151 of the device shown.

[0112] The etching processes of the auxiliary substrate 102 and the insulating layer 151 are quite different. For example, the auxiliary substrate 102 is silicon and the insulating layer 151 is silicon dioxide. The insulating layer 151 can act as a termination layer or barrier layer during the removal of the auxiliary substrate 102. The removal process of the insulating layer 151 is gentle, reducing or even avoiding damage to the other surface of the piezoelectric single crystal film during the removal of the auxiliary substrate 102.

[0113] The surface release process of piezoelectric single crystal thin film can be achieved by completely removing the substrate 102 and completely removing the insulating layer 151.

[0114] After the insulating layer 151 is removed, if there is some damage to the surface of the piezoelectric single crystal film, especially to the effective area of ​​the resonator or the filter formed by the resonator, the surface of the piezoelectric film can be polished through a polishing process.

[0115] Next, through photolithography and etching, the following is obtained: Figure 19 The structure, where 'a' is the piezoelectric layer angle, is required to be no greater than 85 degrees in order to facilitate good step coverage of the top electrode. Optionally, it should be no greater than 60 degrees, further no greater than 45 degrees, and even further no greater than 30 degrees.

[0116] Finally, the top electrode 50 and the process layer 60 are patterned to obtain the desired result. Figure 2 The structure shown.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] Based on the above, the present invention proposes the following technical solution:

[0121] 1. A bulk acoustic resonator, comprising:

[0122] Base;

[0123] Acoustic mirror cavity;

[0124] A stacked structure, comprising a piezoelectric layer, a top electrode, and a bottom electrode;

[0125] A bonding structure is positioned between the laminated structure and the substrate.

[0126] in:

[0127] The bonding structure includes a first metal bonding layer disposed on one side of the substrate and a second metal bonding layer disposed on one side of the stacked structure, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other.

[0128] The second metal bonding layer is electrically connected to the bottom electrode and arranged in the circumferential direction, and the second metal bonding layer defines at least a portion of the horizontal boundary of the acoustic mirror cavity.

[0129] 2. The resonator according to 1, wherein:

[0130] The first metal bonding layer includes a flat layer extending in a horizontal direction, and a portion of the first metal bonding layer defines the bottom side of the acoustic mirror cavity.

[0131] 3. The resonator according to 2, wherein:

[0132] The first portion of the first metal bonding layer is a first portion, and the first metal bonding layer further includes a second portion spaced apart from the first portion;

[0133] The resonator further includes a first electrical connection bonding layer, which is arranged in the same layer as the second metal bonding layer and is made of the same material as the second metal bonding layer. The lower end of the first electrical connection bonding layer is bonded to the second part, and the upper end of the first electrical connection bonding layer is electrically connected to the electrical connection end of the top electrode.

[0134] 4. The resonator according to 3, wherein:

[0135] The resonator includes a top electrode electrical connection portion that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material. The electrical connection end of the top electrode is electrically connected to the top electrode electrical connection portion, and the electrical connection bonding layer is electrically connected to the top electrode electrical connection portion.

[0136] 5. The resonator according to 3, wherein:

[0137] The substrate includes a first through-hole and a second through-hole, and the resonator further includes a first electrical connection lead that is electrically connected to the first portion of the first metal bonding layer through the first through-hole, and a second electrical connection lead that is electrically connected to the second portion of the first metal bonding layer through the second through-hole, wherein the first electrical connection lead and the second electrical connection lead are electrically isolated from each other.

[0138] 6. The resonator according to 5, wherein:

[0139] The first electrical connection lead-out portion and the second electrical connection lead-out portion include a filling portion that fills the corresponding through-hole and a laterally extending layer that covers a portion of the lower surface of the substrate.

[0140] 7. The resonator according to 3, wherein:

[0141] An etching barrier layer is provided between the substrate and the first metal bonding layer. A first portion and a second portion of the first metal bonding layer are separated by an isolation portion, which penetrates the first metal bonding layer and terminates at the etching barrier portion.

[0142] 8. The resonator according to 2, wherein:

[0143] The resonator includes a bottom electrode electrical connection portion that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material, and the resonator also includes an electrode lead-out portion of the bottom electrode that is electrically connected to the bottom electrode electrical connection portion.

[0144] The resonator further includes a second electrical connection bonding layer, which is arranged in the same layer as the second metal bonding layer and is made of the same material. The lower end of the second electrical connection bonding layer is bonded to the first metal bonding layer, and the upper end of the second electrical connection bonding layer is electrically connected to the bottom electrode electrical connection portion, thereby forming a power supply path including the electrode lead-out portion of the bottom electrode, the bottom electrode electrical connection portion, the second electrical connection bonding layer, the first metal bonding layer, the second metal bonding layer, and the bottom electrode.

[0145] 9. The resonator according to 2, wherein:

[0146] The second metal bonding layer is a continuous ring structure in the circumferential direction.

[0147] 10. The resonator according to 9, wherein:

[0148] The resonator also includes a hole that penetrates the piezoelectric layer and communicates with the cavity of the acoustic mirror.

[0149] 11. The resonator according to 10, wherein:

[0150] A sacrificial layer is provided outside the second metal bonding layer that defines the horizontal boundary of the acoustic mirror cavity, and a gap is provided between the lower surface of the sacrificial layer and the upper surface of the first metal bonding layer.

[0151] The hole that penetrates the piezoelectric layer and communicates with the cavity of the acoustic mirror is a release hole.

[0152] 12. The resonator according to 10, wherein:

[0153] A barrier layer is also provided at the edge of the resonator, and the barrier layer is simultaneously bonded to the lower surface of the sacrificial layer and the upper surface of the first metal bonding layer.

[0154] 13. The resonator according to claim 2, wherein:

[0155] The second metal bonding layer has a discontinuous structure in the circumferential direction.

[0156] 14. The resonator according to 13, wherein:

[0157] In the circumferential direction, the length of the break in the second metal bonding layer is no greater than 80% of the annular length in the circumferential direction.

[0158] 15. The resonator according to any one of 1-14, wherein:

[0159] The second metal bonding layer crosses the end of the bottom electrode in the horizontal direction.

[0160] 16. The resonator according to any one of 1-14, wherein:

[0161] The top electrode is provided with a cantilever structure and / or a bridge structure.

[0162] 17. The resonator according to 16, wherein:

[0163] The top electrode is provided with a bridge structure that defines a bridge gap, the outer edge of which is located outside the end of the bottom electrode in the horizontal direction.

[0164] 18. The resonator according to claim 1, wherein:

[0165] The piezoelectric layer is provided with a through-hole for electrical connection. The angle formed between the wall of the through-hole and the bottom surface of the piezoelectric layer is no greater than 85 degrees, optionally no greater than 60 degrees, further no greater than 45 degrees, and even further no greater than 30 degrees.

[0166] 19. A method for manufacturing a bulk acoustic resonator, comprising:

[0167] Step 1: Deposit a first metal bonding layer on one side of the resonator substrate;

[0168] Step 2: Deposit a second metal bonding layer electrically connected to the bottom electrode on one side of the resonator;

[0169] Step 3: Bond the first metal bonding layer and the second metal bonding layer together to form a bottom electrode power supply path from the first metal bonding layer to the second metal bonding layer and then to the bottom electrode.

[0170] Wherein: the second metal bonding layer is electrically connected to the bottom electrode and arranged in the circumferential direction, and the second metal bonding layer defines at least a portion of the boundary of the acoustic mirror cavity in the horizontal direction.

[0171] 20. According to the method described in 19, wherein:

[0172] The first metal bonding layer includes a flat layer extending in a horizontal direction, and a portion of the first metal bonding layer defines the bottom side of the acoustic mirror cavity.

[0173] 21. The method according to 19 further includes:

[0174] Step 4: Before step 2, a top electrode electrical connection portion is formed that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material. The electrical connection end of the top electrode is electrically connected to the top electrode electrical connection portion.

[0175] Step 5: Simultaneously with Step 2, a first electrical connection bonding layer is formed. The first electrical connection bonding layer is arranged in the same layer as the second metal bonding layer, spaced apart, and is made of the same material as the second metal bonding layer.

[0176] in:

[0177] Step 1 further includes the step of etching the first metal bonding layer into a first part and a second part that are electrically isolated from each other, wherein the first part is electrically connected to the bottom electrode.

[0178] In step 3, the first electrical connection bonding layer is electrically connected to the top electrode electrical connection portion and to the second portion.

[0179] 22. The method according to 19 further includes:

[0180] Step 4: Before step 2, a bottom electrode electrical connection portion is formed that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material. The electrode lead-out portion of the bottom electrode is electrically connected to the bottom electrode electrical connection portion.

[0181] Step 5: Simultaneously with Step 2, a second electrical connection bonding layer is formed. The second electrical connection bonding layer is arranged in the same layer as the second metal bonding layer, spaced apart, and is made of the same material as the second metal bonding layer.

[0182] in:

[0183] In step 3, the second electrical connection bonding layer is electrically connected to the bottom electrode electrical connection portion and to the first metal bonding layer to form a power supply path from the bottom electrode electrode lead-out portion, the bottom electrode electrical connection portion, the second electrical connection bonding layer, the first metal bonding layer, the second metal bonding layer to the bottom electrode.

[0184] 23. According to the method described in 19, wherein:

[0185] In step 2, the second metal bonding layer is a continuous ring structure in the circumferential direction.

[0186] 24. The method described in 23 further includes:

[0187] Step 6: Form a through hole that penetrates the piezoelectric layer and communicates with the cavity of the acoustic mirror.

[0188] 25. The method according to 24 further includes:

[0189] Step 7: After step 2, a sacrificial layer is provided on one side of the structure in step 2 where the second metal bonding layer is provided. The sacrificial layer includes a portion inside the second metal bonding layer and a portion outside the second metal bonding layer. The lower surface of the sacrificial layer is closer to the bottom electrode in the thickness direction of the resonator than the lower end face of the second metal bonding layer.

[0190] Step 8: Release the portion of the sacrificial layer inside the second metal bonding layer via the via.

[0191] 26. The method according to 25 further includes:

[0192] Step 9: After step 1, a barrier layer of predetermined thickness is disposed at a predetermined position in the first metal bonding layer, the barrier layer being continuously arranged in the circumferential direction.

[0193] in:

[0194] During the bonding process of the first metal bonding layer and the second metal bonding layer, the portions of the barrier layer and the sacrificial layer on the outer side of the second metal bonding layer are in contact with each other.

[0195] 27. According to the method described in 19, wherein:

[0196] In step 2, the second metal bonding layer has a discontinuous structure in the circumferential direction.

[0197] 28. A filter comprising a resonator according to any one of 1-18.

[0198] 29. An electronic device comprising the filter according to claim 28, or the resonator according to any one of claims 1-18.

[0199] 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.

[0200] 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 cavity; A stacked structure, comprising a piezoelectric layer, a top electrode, and a bottom electrode; A bonding structure is positioned between the laminated structure and the substrate. in: The bonding structure includes a first metal bonding layer disposed on one side of the substrate and a second metal bonding layer disposed on one side of the stacked structure, wherein the first metal bonding layer and the second metal bonding layer are bonded to each other. The second metal bonding layer is electrically connected to the bottom electrode and is arranged in the circumferential direction, and the second metal bonding layer defines at least a portion of the boundary of the acoustic mirror cavity in the horizontal direction. The first metal bonding layer includes a flat layer extending in a horizontal direction, and a portion of the first metal bonding layer defines the bottom side of the acoustic mirror cavity.

2. The resonator according to claim 1, wherein: The first portion of the first metal bonding layer is a first portion, and the first metal bonding layer further includes a second portion spaced apart from the first portion; The resonator further includes a first electrical connection bonding layer, which is arranged in the same layer as the second metal bonding layer and is made of the same material as the second metal bonding layer. The lower end of the first electrical connection bonding layer is bonded to the second part, and the upper end of the first electrical connection bonding layer is electrically connected to the electrical connection end of the top electrode.

3. The resonator according to claim 2, wherein: The resonator includes a top electrode electrical connection portion that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material. The electrical connection end of the top electrode is electrically connected to the top electrode electrical connection portion, and the electrical connection bonding layer is electrically connected to the top electrode electrical connection portion.

4. The resonator according to claim 2, wherein: The substrate includes a first through-hole and a second through-hole, and the resonator further includes a first electrical connection lead that is electrically connected to the first portion of the first metal bonding layer through the first through-hole, and a second electrical connection lead that is electrically connected to the second portion of the first metal bonding layer through the second through-hole, wherein the first electrical connection lead and the second electrical connection lead are electrically isolated from each other.

5. The resonator according to claim 4, wherein: The first electrical connection lead-out portion and the second electrical connection lead-out portion include a filling portion that fills the corresponding through-hole and a laterally extending layer that covers a portion of the lower surface of the substrate.

6. The resonator according to claim 2, wherein: An etching barrier layer is provided between the substrate and the first metal bonding layer. A first portion and a second portion of the first metal bonding layer are separated by an isolation portion, which penetrates the first metal bonding layer and terminates at the etching barrier portion.

7. The resonator according to claim 1, wherein: The resonator includes a bottom electrode electrical connection portion that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material, and the resonator also includes an electrode lead-out portion of the bottom electrode that is electrically connected to the bottom electrode electrical connection portion. The resonator further includes a second electrical connection bonding layer, which is arranged in the same layer as the second metal bonding layer and is made of the same material. The lower end of the second electrical connection bonding layer is bonded to the first metal bonding layer, and the upper end of the second electrical connection bonding layer is electrically connected to the bottom electrode electrical connection portion, thereby forming a power supply path including the electrode lead-out portion of the bottom electrode, the bottom electrode electrical connection portion, the second electrical connection bonding layer, the first metal bonding layer, the second metal bonding layer, and the bottom electrode.

8. The resonator according to claim 1, wherein: The second metal bonding layer is a continuous ring structure in the circumferential direction.

9. The resonator according to claim 8, wherein: The resonator also includes a hole that penetrates the piezoelectric layer and communicates with the cavity of the acoustic mirror.

10. The resonator according to claim 9, wherein: A sacrificial layer is provided outside the second metal bonding layer that defines the horizontal boundary of the acoustic mirror cavity, and a gap is provided between the lower surface of the sacrificial layer and the upper surface of the first metal bonding layer. The hole that penetrates the piezoelectric layer and communicates with the cavity of the acoustic mirror is a release hole.

11. The resonator according to claim 10, wherein: A barrier layer is also provided at the edge of the resonator, and the barrier layer is simultaneously bonded to the lower surface of the sacrificial layer and the upper surface of the first metal bonding layer.

12. The resonator according to claim 1, wherein: The second metal bonding layer has a discontinuous structure in the circumferential direction.

13. The resonator according to claim 12, wherein: In the circumferential direction, the length of the break in the second metal bonding layer is no greater than 80% of the annular length in the circumferential direction.

14. The resonator according to any one of claims 1-13, wherein: The second metal bonding layer crosses the end of the bottom electrode in the horizontal direction.

15. The resonator according to any one of claims 1-13, wherein: The top electrode is provided with a cantilever structure and / or a bridge structure.

16. The resonator according to claim 15, wherein: The top electrode is provided with a bridge structure that defines a bridge gap, the outer edge of which is located outside the end of the bottom electrode in the horizontal direction.

17. The resonator according to claim 1, wherein: The piezoelectric layer is provided with a through-hole for electrical connection. The angle formed between the wall of the through-hole and the bottom surface of the piezoelectric layer is no greater than 85 degrees, optionally no greater than 60 degrees, further no greater than 45 degrees, and even further no greater than 30 degrees.

18. A method for manufacturing a bulk acoustic resonator, comprising: Step 1: Deposit a first metal bonding layer on one side of the resonator substrate; Step 2: Deposit a second metal bonding layer electrically connected to the bottom electrode on one side of the resonator; Step 3: Bond the first metal bonding layer and the second metal bonding layer together to form a bottom electrode power supply path from the first metal bonding layer to the second metal bonding layer and then to the bottom electrode. Wherein: the second metal bonding layer is electrically connected to the bottom electrode and is arranged in the circumferential direction, and the second metal bonding layer defines at least a portion of the boundary of the acoustic mirror cavity in the horizontal direction; The first metal bonding layer includes a flat layer extending in a horizontal direction, and a portion of the first metal bonding layer defines the bottom side of the acoustic mirror cavity.

19. The method of claim 18, further comprising: Step 4: Before step 2, a top electrode electrical connection portion is formed that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material. The electrical connection end of the top electrode is electrically connected to the top electrode electrical connection portion. Step 5: Simultaneously with Step 2, a first electrical connection bonding layer is formed. The first electrical connection bonding layer is arranged in the same layer as the second metal bonding layer, spaced apart, and is made of the same material as the second metal bonding layer. in: Step 1 further includes the step of etching the first metal bonding layer into a first part and a second part that are electrically isolated from each other, wherein the first part is electrically connected to the bottom electrode. In step 3, the first electrical connection bonding layer is electrically connected to the top electrode electrical connection portion and to the second portion.

20. The method of claim 18, further comprising: Step 4: Before step 2, a bottom electrode electrical connection portion is formed that is spaced apart from the bottom electrode, arranged in the same layer and made of the same material. The electrode lead-out portion of the bottom electrode is electrically connected to the bottom electrode electrical connection portion. Step 5: Simultaneously with Step 2, a second electrical connection bonding layer is formed. The second electrical connection bonding layer is arranged in the same layer as the second metal bonding layer, spaced apart, and is made of the same material as the second metal bonding layer. in: In step 3, the second electrical connection bonding layer is electrically connected to the bottom electrode electrical connection portion and to the first metal bonding layer to form a power supply path from the bottom electrode electrode lead-out portion, the bottom electrode electrical connection portion, the second electrical connection bonding layer, the first metal bonding layer, the second metal bonding layer to the bottom electrode.

21. The method according to claim 18, wherein: In step 2, the second metal bonding layer is a continuous ring structure in the circumferential direction.

22. The method of claim 21, further comprising: Step 6: Form a through hole that penetrates the piezoelectric layer and communicates with the cavity of the acoustic mirror.

23. The method of claim 22, further comprising: Step 7: After step 2, a sacrificial layer is provided on one side of the structure in step 2 where the second metal bonding layer is provided. The sacrificial layer includes a portion inside the second metal bonding layer and a portion outside the second metal bonding layer. The lower surface of the sacrificial layer is closer to the bottom electrode in the thickness direction of the resonator than the lower end face of the second metal bonding layer. Step 8: Release the portion of the sacrificial layer inside the second metal bonding layer via the via.

24. The method of claim 23, further comprising: Step 9: After step 1, a barrier layer of predetermined thickness is disposed at a predetermined position in the first metal bonding layer, the barrier layer being continuously arranged in the circumferential direction. in: During the bonding process of the first metal bonding layer and the second metal bonding layer, the portions of the barrier layer and the sacrificial layer on the outer side of the second metal bonding layer are in contact with each other.

25. The method according to claim 18, wherein: In step 2, the second metal bonding layer has a discontinuous structure in the circumferential direction.

26. A filter comprising a resonator according to any one of claims 1-17.

27. An electronic device comprising the filter of claim 26, or the resonator of any one of claims 1-17.

Images