Bulk acoustic wave (BAW) resonator

Abstract

The application provides a bulk acoustic wave (BAW) resonator, comprising: a substrate; a piezoelectric layer arranged above the substrate; a first electrode arranged below the piezoelectric layer; a second electrode arranged above the piezoelectric layer; a first dielectric layer arranged below the piezoelectric layer; a second dielectric layer arranged below the first dielectric layer; a cavity arranged below the first electrode; a first ground via arranged in the first dielectric layer and the second dielectric layer and separated from the cavity; a bonding metal layer arranged between the second dielectric layer and the substrate; a second ground via arranged in the piezoelectric layer and aligned with the first ground via; and a ground pad metal layer arranged above the piezoelectric layer and located in the second ground via, and electrically connected with the bonding metal layer.

Description

Technical Field

[0001] This application relates to the field of semiconductor devices, and more particularly to a bulk acoustic wave (BAW) resonator. Background Technology

[0002] A bulk acoustic wave (BAW) resonator consists of a thin film made of piezoelectric material disposed between two electrodes. BAW resonator devices are typically manufactured using semiconductor micromachining techniques.

[0003] BAW filters can include two or more BAW resonators, and there is an urgent need to manufacture BAW filters and / or BAW resonators with excellent quality and performance. Summary of the Invention

[0004] According to one aspect of this disclosure, a bulk acoustic wave (BAW) resonator is provided, comprising: a substrate; a piezoelectric layer disposed above the substrate; a first electrode disposed below the piezoelectric layer; a second electrode disposed above the piezoelectric layer; a first dielectric layer disposed below the piezoelectric layer; a second dielectric layer disposed below the first dielectric layer; a cavity disposed below the first electrode; a first ground via disposed in the first and second dielectric layers and spaced apart from the cavity; a bonding metal layer disposed between the second dielectric layer and the substrate, a portion of the bonding metal layer being disposed in the first ground via; a second ground via disposed in the piezoelectric layer and aligned with the first ground via; and a ground metal layer disposed above the piezoelectric layer, a portion of the ground metal layer being disposed in the second ground via; wherein the portion of the ground metal layer located in the second ground via is electrically connected to the portion of the bonding metal layer located in the first ground via. Attached Figure Description

[0005] The accompanying drawings, which are included in and form part of this application, illustrate the disclosed embodiments and, together with the description, serve to explain the disclosed embodiments.

[0006] Figure 1A This is a top view provided according to an embodiment of the present disclosure, showing a selected portion of a BAW resonator used in a BAW filter;

[0007] Figure 1B Provided according to an embodiment of this disclosure Figure 1A The edge of the BAW resonator Figure 1A A cross-sectional view of the cross-sectional line A-A' shown in the figure;

[0008] Figure 2 Manufacturing according to an embodiment of this disclosure Figure 1A and Figure 1B A flowchart of the BAW resonator manufacturing process;

[0009] Figure 3A-3S It is provided according to an embodiment of the present disclosure. Figure 2 A cross-sectional view of the structure formed during the process. Detailed Implementation

[0010] The present disclosure is described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present disclosure. The scope of protection of the present invention includes changes to the structure, method, or function made by those skilled in the art based on these embodiments.

[0011] For ease of illustration in the accompanying drawings, the dimensions of some structures or parts may be enlarged relative to other structures or parts. Therefore, the drawings in this disclosure are for the purpose of illustrating the basic structure of the subject matter only. Unless otherwise stated, the same numerals in different drawings represent the same or similar elements.

[0012] Furthermore, terms indicating relative spatial positions, such as “top,” “bottom,” “upper,” “lower,” “above,” “below,” etc., are used for explanatory purposes to describe the relationship between a unit or feature depicted in the figure and another unit or feature therein. Terms indicating relative spatial positions can refer to positions other than those depicted in the figures when using or operating the device. For example, if the device shown in the figure is flipped over, a unit described as being “below” or “below” another unit or feature would be “above” another unit or feature. Therefore, the descriptive term “below” can include both above and below positions. The device may be oriented in other ways (e.g., rotated 90 degrees or facing another direction), and descriptive terms appearing in the text and relating to space should be interpreted accordingly. When a component or layer is referred to as being “above” or “connected to” another component or layer, it may be directly above or directly connected to another component or layer, or there may be intermediate components or layers.

[0013] Typically, film bulk acoustic wave (FBAR) resonators and bulk acoustic wave (BAW) structures are fabricated using bonding processes, most of which are based on SiO2-Si or Si-Si bonding. SiO2-Si or Si-Si bonding usually places strict requirements on the material, roughness, and warpage of the silicon wafer bonding surface, making the bonding process difficult and quality control challenging. On the other hand, metal bonding using eutectic bonding or metal diffusion bonding has less stringent requirements on bonding conditions, is relatively easy to implement, and offers good bonding quality. However, if a bonding metal layer is used in a BAW resonator, the presence of this layer beneath the resonator cavity may negatively impact the resonator's performance.

[0014] In embodiments of the present invention, the bonding metal layer is grounded to reduce or eliminate its influence. The presence of the bonding metal layer also helps dissipate heat from the FBAR filter and / or BAW resonator during operation, which is beneficial to the RF power tolerance of the FBAR filter.

[0015] Figure 1A This is a top view provided according to an embodiment of the present disclosure, showing a selected portion of a BAW resonator used in a BAW filter; Figure 1B This is provided according to an embodiment of the present disclosure. Figure 1A BAW resonator along Figure 1A The cross-sectional view of the cross-sectional line A-A' shown in the figure.

[0016] like Figure 1A and 1B As shown, the BAW resonator 10 includes: a resonator substrate 100; a piezoelectric layer 140 disposed above the resonator substrate 100; a first electrode 500 disposed below the piezoelectric layer 140; a second electrode 700 disposed above the piezoelectric layer 140; a first dielectric layer 210 disposed below the piezoelectric layer 140; a second dielectric layer 220 disposed below the first dielectric layer 210; a cavity 1000 disposed below the first electrode 500; and a bonding metal layer 200 disposed between the second dielectric layer 220 and the resonator substrate 100, including a first adhesion layer 150, a first bonding layer 160, a second adhesion layer 170, and a second bonding layer 180. A first ground via 211 is disposed in the first dielectric layer 210 and the second dielectric layer 220 and is spaced apart from the cavity 1000. A portion of the first adhesion layer 150 and a portion of the first bonding layer 160 are disposed in the first ground via 211. The second grounding via 821 is disposed in the piezoelectric layer 140 and aligned with the first grounding via 211. The mat metal layer 361 is disposed on the piezoelectric layer 140. A portion of the mat metal layer 361 is disposed in the second grounding via 821 and is electrically connected to the portion of the first adhesive layer 150 located in the first grounding via 211.

[0017] like Figure 1A and 1B The BAW resonator 10 shown has a bonding metal layer 200 electrically connected to a ground metal layer 361. During operation of the BAW resonator 10, the ground metal layer 361 is grounded, therefore the bonding metal layer 200 is grounded.

[0018] The first dielectric layer 210 is formed of silicon oxide. The first dielectric layer 210 covers a portion of the first electrode 500 and a portion of the piezoelectric layer 140. The portions of the first electrode 500 and the piezoelectric layer 140 not covered by the first dielectric layer 210 correspond to the cavity 1000 of the BAW resonator 10, which is formed by removing a portion of the first dielectric layer 210 (referred to as a "sacrificial island") surrounded by the double-walled protrusion structure 221 of the second dielectric layer 220.

[0019] A second dielectric layer 220 is disposed between the bonding metal layer 200 and the first dielectric layer 210, covering all surfaces of the first dielectric layer 210 except for the first ground via 211. The second dielectric layer 220 is formed of a non-conductive material that is not corroded by hydrofluoric acid, such as a stack of one or more materials selected from polycrystalline silicon, amorphous silicon, aluminum nitride (AlN), silicon nitride (SiN), tantalum nitride (TaN), and gallium nitride (GaN). The second dielectric layer 220 includes a double-walled protrusion structure 221 that protrudes through the first dielectric layer 210 into the piezoelectric layer 140 and surrounds the cavity 1000. The double-walled protrusion structure 221 forms a double-walled boundary structure 300 surrounding the cavity 1000, which is the operating region of the BAW resonator 10, in which the first electrode 500 and the second electrode 700 partially overlap. The double-walled protrusion structure 221 contacts a portion of the piezoelectric layer 140 and a portion of the first electrode 500. The first adhesive layer 150 covers the sidewalls and bottom of the double-walled protrusion structure 221. The first bonding layer 160 fills the double-walled protrusion structure 221.

[0020] A first ground via 211 is formed by etching the first dielectric layer 210 and the second dielectric layer 220. The piezoelectric layer 140 is exposed at the bottom of the first ground via 211, and the second dielectric layer 220 is not present in the first ground via 211. A first adhesion layer 150 of the bonding metal layer 200 covers the sidewalls and bottom of the first ground via 211. A first adhesion layer 160 fills the first ground via 212.

[0021] The first adhesion layer 150 and the second adhesion layer 170 are formed by a stack of one or more materials selected from chromium (Cr), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), and tantalum nitride (TaN). The first bonding layer 160 and the second bonding layer 180 are formed by a stack of one or more materials selected from gold (Au), copper (Cu), aluminum (Al), indium (In), nickel (Ni), and tin (Sn).

[0022] A first adhesion layer 150 covers the surface of the second dielectric layer 220, as well as the sidewalls and bottom of the first ground via 211. A first bonding layer 160 covers the first adhesion layer 150 and fills the first ground via 211. A second adhesion layer 170 is disposed on the surface of the resonator substrate 100 facing the piezoelectric layer 140. A second bonding layer 180 is disposed on the second adhesion layer 170 and bonded to the first bonding layer 160 by eutectic bonding or metal diffusion bonding.

[0023] A contact hole 822 is formed in the piezoelectric layer 140 and exposes a portion of the first electrode 500. A first electrode pad metal layer 362 is disposed on the piezoelectric layer 140 and located in the contact hole 822, and is electrically connected to the first electrode 500. A second electrode pad metal layer 363 (as shown) Figure 1A (As shown) is disposed on the piezoelectric layer 140 and electrically connected to a portion of the second electrode 700.

[0024] The resonator substrate 100 is made of silicon, glass (silicon oxide), sapphire (Al₂O₃), gallium nitride (GaN), silicon carbide (SiC), aluminum nitride (AlN), etc. The piezoelectric layer 140 is made of AlN or ScAlN. The piezoelectric layer 140 includes one or more release holes 810 exposing the cavity 1000. One or more release holes are formed in the piezoelectric layer 140 and expose the cavity 1000.

[0025] The first passivation layer 510 is disposed below the first electrode 500. The second passivation layer 710 is disposed above the second electrode 700.

[0026] Figure 2 Manufacturing according to an embodiment of this disclosure Figure 1A and Figure 1B A flowchart of the process of BAW resonator 10; Figure 3A-3S It is provided according to an embodiment of the present disclosure. Figure 2 A cross-sectional view of the structure formed during the process.

[0027] like Figure 3A As shown, in step S0, a temporary substrate 3000 is obtained. The temporary substrate 3000 is formed of silicon.

[0028] like Figure 3BAs shown, in step S1, a buffer layer 3100 is deposited on a temporary substrate 3000. The buffer layer 3100 serves as an etch stop layer for removing the temporary substrate 3000 in subsequent processes. The buffer layer 3100 also serves as a transition layer, which helps improve the quality of the piezoelectric layer 140 subsequently formed on the buffer layer 3100. The buffer layer 3100 is formed from a stack of one or more materials selected from silicon oxide (SiO2), silicon nitride (SiN), aluminum oxide (Al2O3), gallium nitride (GaN), aluminum nitride (AlN), and silicon carbide (SiC).

[0029] In one embodiment, an AlN layer is deposited on a temporary substrate 3000 formed of silicon, and a GaN layer is deposited on top of the AlN layer. The stack of the AlN and GaN layers serves as a buffer layer 3100. In a subsequent process, an AlN or ScAlN piezoelectric layer is deposited on the surface of the GaN layer. Due to the good lattice matching between GaN and AlN / ScAlN, the AlN or ScAlN piezoelectric layer has good crystal quality.

[0030] In another embodiment, a silicon oxide layer is formed on a silicon temporary substrate 3000. The silicon oxide layer acts as a buffer layer 3100, which also serves as an etch stop layer for subsequent removal of the temporary substrate 3000. A thin AlN seed layer (“first AlN layer”) is then deposited on the silicon oxide buffer layer 3100. This thin AlN seed layer is used to bond the resonator substrate 100 in subsequent processes and can be removed after the temporary substrate 3000 is removed. Therefore, a thicker AlN seed layer can be formed, which is beneficial for improving the quality of the piezoelectric crystal deposited on the AlN seed layer. An AlN layer (“second AlN layer”) or a ScAlN piezoelectric layer is then deposited on the AlN seed layer. The AlN seed layer can be removed after bonding the resonator substrate 100 and removing the temporary substrate 3000.

[0031] In another embodiment, an AlN thin layer (“first AlN layer”) is deposited directly on the silicon temporary substrate 3000 as a buffer layer 3100. The lattice quality of the AlN thin layer deposited directly on the silicon temporary substrate 300 is superior to that of the AlN thin layer deposited on the silicon oxide layer. Furthermore, since the AlN thin layer can be removed in subsequent processes, a thicker AlN layer can be formed. After depositing the AlN thin layer, an AlN layer (“second AlN layer”) or a ScAlN piezoelectric layer is deposited on the AlN thin layer. The AlN thin layer can be removed after bonding the resonator substrate 100 and removing the temporary substrate 3000.

[0032] In another embodiment, when the piezoelectric layer is formed from pure AlN without Sc doping, a silicon oxide layer can be deposited on a temporary substrate 3000 as a buffer layer 3100. The AlN piezoelectric layer can be deposited directly and continuously on the silicon oxide layer in one step. After bonding the resonator substrate 100 and removing the temporary substrate 3000, the lower part (initial deposition portion) of the AlN piezoelectric layer can be removed to leave the remaining portion (upper part) of the well-crystallized AlN piezoelectric layer as the piezoelectric layer 140.

[0033] In another embodiment, when the piezoelectric layer is formed from pure AlN without Sc doping, the AlN piezoelectric layer can be deposited directly and continuously on the temporary substrate 3000. The initial deposition portion of the AlN piezoelectric layer serves as a buffer layer 3100, which can be removed after bonding the resonator substrate 100 and removing the temporary substrate 3000. The subsequent deposition portion of the AlN piezoelectric layer with good crystal quality serves as the piezoelectric layer 140.

[0034] like Figure 3C As shown, in step S2, a piezoelectric layer 140 is deposited on the buffer layer 3100. The piezoelectric layer 140 may be formed of AlN or scandium-doped aluminum nitride (ScAlN). The deposition thickness of the piezoelectric layer 140 is greater than the target thickness of the piezoelectric layer 14 in the BAW resonator 10.

[0035] like Figure 3D As shown, in step S3, a first electrode layer is formed on the piezoelectric layer 140, and a passivation layer is formed on the first electrode layer. Then, the first electrode layer and the passivation layer formed thereon are patterned to form a first electrode 500 and a first passivation layer 510. The first electrode 500 may be formed of a metallic material.

[0036] like Figure 3E As shown, in step S4, the first dielectric layer 210 is deposited on... Figure 3D In the structure shown, the first dielectric layer 210 may be formed of silicon oxide. The first dielectric layer 210 covers the piezoelectric layer 140, the first electrode 500, and the first passivation layer 510.

[0037] like Figure 3F As shown, in step S5, the first dielectric layer 210 is etched to form a first ground via 211 and a trench 212 surrounding the operating region of the BAW resonator 10. A portion of the first dielectric layer 210 surrounded by the trench 212 serves as a sacrificial layer, which will be removed in a subsequent process to form the cavity 1000. A portion of the piezoelectric layer 140 and a portion of the first passivation layer 510 are exposed at the bottom of the trench 212. A portion of the piezoelectric layer 140 is also exposed at the bottom of the first ground via 211.

[0038] like Figure 3G As shown, in step S6, the second dielectric layer 220 is deposited on... Figure 3FOn the surface of the structure shown. The second dielectric layer 220 may be formed by a stack of one or more materials selected from polycrystalline silicon, amorphous silicon, silicon nitride, aluminum nitride, gallium nitride, and tantalum nitride. The second dielectric layer 220 completely covers the top surface of the first dielectric layer 210, as well as the sidewalls and bottom of the first ground via 211 and trench 212 formed in the first dielectric layer 210. The second dielectric layer 220 also covers the portion of the piezoelectric layer 140 exposed at the bottom of the first ground via 211, and the portions of the piezoelectric layer 140 and the first passivation layer 510 exposed at the bottom of the trench 212. The portions of the second dielectric layer 220 deposited on the sidewalls and the bottom of the trench 212 form a double-walled protrusion structure 221, which surrounds a portion of the first dielectric layer 210 (referred to as a "sacrificial island") that will be removed to form the cavity 1000.

[0039] like Figure 3H As shown, in step S7, the portion of the second dielectric layer 220 covering the sidewalls and bottom of the first grounding via 211 is removed. This exposes the portion of the piezoelectric layer 140 located at the bottom of the first grounding via 211.

[0040] like Figure 3I As shown, in step S8, the first adhesion layer 150 is deposited on... Figure 3H On the surface of the structure shown, a first adhesion layer 150 covers the entire surface of the second dielectric layer 220, including the sidewalls and bottom of the double-walled protruding structure 221, the sidewalls of the first ground via 211, and the portion of the piezoelectric layer 140 exposed at the bottom of the first ground via 211. The first adhesion layer 150 may be formed of chromium (Cr), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), tantalum nitride (TaN), or other materials, or a combination of two or more materials.

[0041] like Figure 3J As shown, in step S9, in Figure 3IA first bonding layer 160 is electroplated onto the structure shown. The electroplated first bonding layer 160 fills the double-walled protrusion structure 221 of the second dielectric layer 220 and the first ground via 211, and covers all surfaces of the first adhesion layer 150. If necessary, the top surface of the first adhesion layer 130 can be planarized by chemical mechanical polishing (CMP). In subsequent processes, the first bonding layer 160 and the second bonding layer 180 (deposited on the second adhesion layer 170 on the surface of the resonator substrate 100) are bonded by eutectic bonding or metal diffusion bonding. The materials of the first bonding layer 160 and the second bonding layer 180 can be a single type of metal material or a stacked combination of multiple metal materials (e.g., Cu, Au, Al, In, Sn, or Ni) suitable for bonding processes. When the first bonding layer 160 is a stack of multiple metal layers, an electroplating process can be performed to form the first metal layer to fill the double-walled protrusion structure 221 and the first ground via 211 of the second dielectric layer 220 and cover the surface of the second dielectric layer 220. Then, an evaporation, chemical vapor deposition (CVD), or physical vapor deposition (PVD) process can be performed to form other metal layers on the first metal layer.

[0042] like Figure 3K As shown, in step S10, a resonator substrate 100 is obtained, and a second adhesion layer 170 and a second bonding layer 180 are sequentially deposited on the resonator substrate 100. Both the second adhesion layer 170 and the second bonding layer 180 are formed of metallic materials. The resonator substrate 100 can be formed of silicon, glass (silicon oxide), sapphire (Al2O3), gallium nitride (GaN), silicon carbide (SiC), aluminum nitride (AlN). The second adhesion layer 170 adheres the second bonding layer 180 to the surface of the resonator substrate 100. The second adhesion layer 170 can be formed of chromium (Cr), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), tantalum nitride (TaN), or other materials, or a combination of two or more materials. The second bonding layer 180 and the first bonding layer 160 are bonded by eutectic bonding or metal diffusion bonding. The first bonding layer 160 and the second bonding layer 180 can be formed by a combination of a single metal or multiple metal materials suitable for bonding processes.

[0043] In one embodiment, both the first bonding layer 160 and the second bonding layer 180 are formed of gold (Au), copper (Cu), or aluminum (Al), and the first bonding layer 160 and the second bonding layer 180 are bonded by metal diffusion bonding. In another embodiment, one of the first bonding layer 160 and the second bonding layer 180 is composed of a stack of gold (Au) and indium (In) (with an indium layer covering a gold layer), while the other of the first bonding layer 160 and the second bonding layer 180 is formed of gold (Au), and the first bonding layer 160 and the second bonding layer 180 are bonded by an Au-In eutectic alloy. In another embodiment, one of the first bonding layer 160 and the second bonding layer 180 is composed of a stack of nickel (Ni), indium (In), and gold (Au), while the other of the first bonding layer 160 and the second bonding layer 180 is composed of a stack of nickel (Ni) and gold (Au), and the first bonding layer 160 and the second bonding layer 180 are bonded by an Au-In eutectic alloy. In another embodiment, one of the first bonding layer 160 and the second bonding layer 180 is composed of a stack of copper (Cu) and tin (Sn) (with a tin layer covering a copper layer), while the other of the first bonding layer 160 and the second bonding layer 180 is formed of copper (Cu), and the first bonding layer 160 and the second bonding layer 180 are bonded by a Cu-Sn eutectic alloy. In another embodiment, one of the first bonding layer 160 and the second bonding layer 180 is composed of a gold (Au) and tin (Sn) stack (a tin layer covering a gold layer), while the other of the first bonding layer 160 and the second bonding layer 180 is formed of gold (Au), and the first bonding layer 160 and the second bonding layer 180 are bonded by an Au-Sn eutectic alloy. In another embodiment, one of the first bonding layer 160 and the second bonding layer 180 is composed of a nickel (Ni) and tin (Sn) stack (a tin layer covering a nickel layer), while the other of the first bonding layer 160 and the second bonding layer 180 is formed of gold (Au), and the first bonding layer 160 and the second bonding layer 180 are bonded by an Au-Sn eutectic alloy.

[0044] like Figure 3L As shown, in step S11, the... Figure 3J The first bonding layer 160 of the structure shown and Figure 3K The second bonding layer 180 of the structure shown is bonded together. Therefore, Figure 3K The structure shown is similar to Figure 3J The structure shown is combined. The first adhesion layer 150, the first bonding layer 160, the second adhesion layer 170, and the second bonding layer 180 together constitute the bonding metal layer 200.

[0045] like Figure 3M As shown, in step S12, the temporary substrate 3000 is removed to expose the buffer layer 3100.

[0046] like Figure 3N As shown, in step S13, the buffer layer 3100 is removed to expose the surface layer of the piezoelectric layer 140.

[0047] like Figure 3O As shown, in step S14, a dry etching or ion beam etching (IBE) process is performed to remove a portion of the exposed surface layer of the piezoelectric layer 140. Therefore, the thickness of the piezoelectric layer 140 can be precisely controlled to be equal to the target thickness required for the BAW resonator 10. The removed portion of the piezoelectric layer 140 is the initial deposition portion of the piezoelectric layer 40, which has relatively low quality and relatively poor piezoelectric performance. Therefore, removing the initial deposition portion of the piezoelectric layer 140 improves the performance of the BAW resonator 10.

[0048] like Figure 3P As shown, in step S15, a second electrode layer and a passivation layer are formed on the piezoelectric layer 140. The second electrode layer and the passivation layer are patterned to form a second electrode 700 and a second passivation layer 710. The second electrode 700 and the second passivation layer 710 partially cover the first electrode 500. A double-walled protrusion structure 221 surrounds the overlapping portion of the first electrode 500 and the second electrode 700. That is, the overlapping portion of the first electrode 500 and the second electrode 700 is aligned with the cavity 1000 to be formed in a subsequent process.

[0049] like Figure 3Q As shown, in step S16, the piezoelectric layer 140 is etched to form one or more release holes 810, a second ground via 821, and a contact hole 822. The release hole 810 exposes a portion of the first dielectric layer 210 surrounded by the double-walled protrusion structure 221 (i.e., the sacrificial island for forming the cavity 1000). The second ground via 821 exposes a portion of the first adhesion layer 150 of the bonding metal layer 200 formed at the bottom of the first ground via 211. The contact hole 822 exposes a portion of the first electrode 500.

[0050] like Figure 3R As shown, in step S17, in Figure 3QA pad metal layer is formed on the structure shown, and the pad metal layer is patterned to form a ground pad metal layer 361 and a first electrode pad metal layer 362. The ground pad metal layer 361 is disposed on the piezoelectric layer 140 and located in the second ground via 821. The portion of the ground pad metal layer 361 located in the second ground via 821 contacts the portion of the first adhesion layer 150 of the bonding metal layer 200 located in the first ground via 211. Accordingly, the ground pad metal layer 361 electrically connects the bonding metal layer 200 to ground. The first electrode pad metal layer 362 is disposed on the piezoelectric layer 140 and located in a contact hole 822. The portion of the first electrode pad metal layer 362 located in the contact hole 822 contacts and is electrically connected to the first electrode 500. The first electrode pad metal layer 362 is used for external electrical connection of the BAW resonator 10.

[0051] like Figure 3S As shown, in step S18, a portion of the first dielectric layer 210 surrounded by the double-walled protrusion structure 221 is etched and removed to form the cavity 1000. The etchant and etching products formed during the etching process are released through one or more release holes 810. Thus, Figure 1A and 1B The BAW resonator 10 shown has been manufactured.

[0052] Other embodiments of the invention will become apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the appended claims.

Claims

1. A bulk acoustic wave (BAW) resonator, characterized in that, include: substrate; A piezoelectric layer is disposed above the substrate; The first electrode is disposed below the piezoelectric layer; The second electrode is disposed above the piezoelectric layer; A cavity is located below the first electrode; A first dielectric layer is disposed below the piezoelectric layer; A second dielectric layer is disposed below the first dielectric layer; the second dielectric layer includes a double-walled protruding structure that protrudes through the first dielectric layer into the piezoelectric layer and surrounds the cavity; A first grounding via is disposed in the first dielectric layer and the second dielectric layer, and is separated from the cavity; A bonding metal layer is disposed between the second dielectric layer and the substrate, and a portion of the bonding metal layer is disposed in the first ground via; the bonding metal layer includes a first adhesion layer, a first bonding layer, a second adhesion layer, and a second bonding layer; wherein the second bonding layer is bonded to the first bonding layer by eutectic bonding or metal diffusion bonding; the first adhesion layer covers the sidewalls and bottom of the double-wall protrusion structure; the first bonding layer fills the double-wall protrusion structure; A second grounding via is disposed in the piezoelectric layer and aligned with the first grounding via; and A ground mat metal layer is disposed on the piezoelectric layer, and a portion of the ground mat metal layer is disposed in the second grounding through hole; wherein the portion of the ground mat metal layer located in the second grounding through hole is electrically connected to the portion of the bonding metal layer located in the first grounding through hole.

2. The BAW resonator according to claim 1, characterized in that, The first adhesive layer and the second adhesive layer are formed by a combination of one or more of the following materials: chromium (Cr), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), and tantalum nitride (TaN).

3. The BAW resonator according to claim 1, characterized in that, The first bonding layer and the second bonding layer are formed by a combination of one or more materials selected from gold (Au), copper (Cu), aluminum (Al), indium (In), nickel (Ni), and tin (Sn).

4. The BAW resonator according to claim 1, characterized in that, The first adhesive layer covers the sidewalls and bottom of the first grounding via; The first bonding layer covers the first adhesion layer and fills the first ground via; The second adhesion layer is disposed on the surface of the substrate facing the piezoelectric layer; The second bonding layer is disposed on the second adhesion layer and is bonded to the first bonding layer by eutectic bonding or metal diffusion bonding.

5. The BAW resonator according to claim 1, characterized in that, The double-walled protruding structure is in contact with a portion of the piezoelectric layer and a portion of the first electrode.

6. The BAW resonator according to claim 1, characterized in that, The first dielectric layer is formed of silicon oxide.

7. The BAW resonator according to claim 1, characterized in that, The second dielectric layer is formed by a stack of one or more materials selected from polycrystalline silicon, amorphous silicon, silicon nitride, aluminum nitride, gallium nitride, and tantalum nitride.

8. The BAW resonator according to claim 1, characterized in that, Also includes: One or more release holes are formed in the piezoelectric layer and expose the cavity.

9. The BAW resonator according to claim 1, characterized in that, Also includes: A contact hole is provided in the piezoelectric layer and exposes a portion of the first electrode; and A first electrode pad metal layer is disposed on the piezoelectric layer and located in the contact hole, and is in contact with the first electrode.

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