BAW resonator

Abstract

This application provides a bulk acoustic wave (BAW) resonator, comprising: a substrate; a piezoelectric layer disposed above the substrate; a first electrode disposed below the piezoelectric layer, including a first portion and a second portion spaced apart from each other; a second electrode disposed above the piezoelectric layer; a first dielectric layer, a second dielectric layer, and a third dielectric layer disposed sequentially between the substrate and the piezoelectric layer in order from the piezoelectric layer to the substrate; a cavity located below the first portion of the first electrode; a bonding metal layer disposed between the third dielectric layer and the substrate; and a ground metal layer disposed above the piezoelectric layer and electrically connected to 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 and including a first portion and a second portion spaced apart from each other; a second electrode disposed above the piezoelectric layer; a first dielectric layer, a second dielectric layer, and a third dielectric layer disposed sequentially between the substrate and the piezoelectric layer in order from the piezoelectric layer to the substrate; a cavity disposed below the first portion of the first electrode; a first ground via disposed in the second and third dielectric layers and exposing a first surface of the second portion of the first electrode; a bonding metal layer disposed between the third dielectric layer and the substrate, and a portion of the bonding metal layer being disposed in the first ground via; a second ground via disposed in the piezoelectric layer and exposing a second surface of the second portion of the first electrode; and a ground metal layer disposed above the piezoelectric layer, and 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 and the portion of the bonding metal layer located in the first ground via are electrically connected through the second portion of the first electrode.

[0005] According to another 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, a second dielectric layer, and a third dielectric layer disposed sequentially between the substrate and the piezoelectric layer in order from the piezoelectric layer to the substrate; a cavity disposed below the first electrode; a bonding metal layer disposed between the third dielectric layer and the substrate; a ground via disposed in the piezoelectric layer, the second dielectric layer, and the third dielectric layer, and exposing the bonding metal layer; and a ground metal layer disposed above the piezoelectric layer and located in the ground via, and electrically connected to the bonding metal layer. Attached Figure Description

[0006] 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.

[0007] 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;

[0008] Figure 1B This is provided according to an embodiment of the present disclosure. Figure 1A The edge of the BAW resonator Figure 1A The cross-sectional view of the cross-sectional line A-A' shown in the figure;

[0009] Figure 2 Manufacturing according to an embodiment of this disclosure Figure 1A and Figure 1B A flowchart of the BAW resonator manufacturing process;

[0010] Figure 3A -3S is provided according to an embodiment of this disclosure. Figure 2 A cross-sectional view of the structure formed during the process;

[0011] Figure 4A 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;

[0012] Figure 4B This is provided according to an embodiment of the present disclosure. Figure 4A The edge of the BAW resonator Figure 4A The cross-sectional view of the cross-sectional line B-B' shown in the figure;

[0013] Figure 5 Manufacturing according to an embodiment of this disclosure Figure 4A and Figure 4B A flowchart of the BAW resonator manufacturing process;

[0014] Figure 6A -6F is provided according to an embodiment of the present disclosure. Figure 5 A cross-sectional view of the structure formed during the process. Detailed Implementation

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 1AThe edge of the BAW resonator Figure 1A The cross-sectional view of the cross-sectional line A-A' shown.

[0021] 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, with a first portion 501 and a second portion 502 of the first electrode 500 spaced apart from each other; a second electrode 700 disposed above the piezoelectric layer 140; a first dielectric layer 210, a second dielectric layer 220, and a third dielectric layer 230 disposed sequentially between the resonator substrate 100 and the piezoelectric layer 240 in the order from the piezoelectric layer 140 to the resonator substrate 100; a cavity 1000 disposed below the first portion 501 of the first electrode 500; and a bonding metal layer 200 disposed between the third dielectric layer 230 and the resonator substrate 100, and including a first adhesion layer 150, a first bonding layer 160, a second adhesion layer 170, and a second bonding layer 180.

[0022] The second dielectric layer 220 includes a first double-walled protrusion 221 and a second double-walled protrusion 222 protruding into the piezoelectric layer through the first dielectric layer 210. The first double-walled protrusion 221 contacts the first surface (i.e., the bottom surface) of the second portion 502 of the first electrode 500. The third dielectric layer 230 fills the first double-walled protrusion 221 and the second double-walled protrusion 222. A first ground via 400 is disposed in the first double-walled protrusion 221 and exposes the first surface of the second portion 502 of the first electrode 500. A first adhesive layer 150 covers the third dielectric layer 230, covers the sidewalls and bottom of the first ground via 400, and contacts the first surface of the second portion 502 of the first electrode 500 through the first ground via 400. A first bonding layer 160 covers the first adhesive layer 150. A second adhesive layer 170 is disposed on the surface of the resonator substrate 100 facing the piezoelectric layer 140. The second bonding layer 180 is disposed on the second adhesion layer 170 and is bonded to the first bonding layer 160 by eutectic bonding or metal diffusion bonding.

[0023] The second grounding via 821 is disposed in the piezoelectric layer 140 and exposes the second surface (i.e., the top surface) of the second portion 502 of the first electrode 500. The second grounding via 821 is offset from the first grounding via 400, that is, the second grounding via 821 is not perpendicularly aligned with the first grounding via 400. In other words, the exposed portion of the second portion 502 of the first electrode 500 is exposed through the second grounding via 821, but does not overlap with the exposed portion of the second portion 502 of the first electrode 500 exposed by the first grounding via 400.

[0024] A ground pad metal layer 361 is disposed above the piezoelectric layer 140 and located in the second grounding via 821, and contacts the second surface of the second portion 502 of the first electrode 500 through the second grounding via 821. Therefore, the portion of the ground pad metal layer 361 located in the second grounding via 821 and the portion of the bonding metal layer 200 located in the first grounding via 400 are electrically connected through the second portion 502 of the first electrode 500. A contact hole 822 is disposed in the piezoelectric layer 140 and exposes the first portion 501 of the first electrode 500. The first electrode pad metal layer 362 is disposed in the piezoelectric layer 140 and located in the contact hole 822, and contacts the first portion 501 of the first electrode 500 through the contact hole 822. A second electrode pad metal layer 363 (e.g., ...) Figure 1A (As shown) is disposed on the piezoelectric layer 140 and electrically connected to a portion of the second electrode 700.

[0025] In BAW resonator 10, such as Figure 1A and 1B As shown, the bonding metal layer 200 includes a first adhesion layer 150, a first bonding layer 160, a second adhesion layer 170, and a second bonding layer 180. The bonding metal layer 200 is electrically connected to the ground metal layer 361 through the second portion 502 of the first electrode 500. During the operation of the BAW resonator 10, the ground metal layer 361 is grounded, therefore the bonding metal layer 200 is grounded.

[0026] The first adhesion layer 150 and the second adhesion layer 170 are formed by a combination of one or more materials selected from chromium (Cr), titanium (Ti), titanium nitride (TiN), titanium tungsten (TiW), tantalum (Ta), and tantalum nitride (TaN).

[0027] 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). The first bonding layer 160 is bonded to the second bonding layer 180 by eutectic bonding or metal diffusion bonding.

[0028] The first dielectric layer 210 may be formed of silicon oxide. The first dielectric layer 210 covers a portion of the first portion 501 of the first electrode 500, a second portion 502 of the first electrode 500, and a portion of the piezoelectric layer 140. The portion of the first portion 501 of the first electrode 500 and the portion of the piezoelectric layer 140 not covered by the first dielectric layer 210 corresponds 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 second double-walled protrusion structure 222 of the second dielectric layer 220.

[0029] The second dielectric layer 220 may be 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 double-walled protrusion structure 222 surrounds the cavity 1000, which is the operating region of the BAW resonator 10. In the cavity 1000, the first portion 501 of the first electrode 500 and the second electrode 700 partially overlap. The second double-walled protrusion structure 222 is in contact with a portion of the piezoelectric layer 140 and a portion of the first portion 501 of the first electrode 500.

[0030] The third dielectric layer 230 may be formed by a stack of one or more materials selected from silicon oxide, silicon nitride, and aluminum nitride. The third dielectric layer 230 is disposed on the surface of the second dielectric layer 220 on the side away from the piezoelectric layer 140. The third dielectric layer 230 fills between the sidewalls of the first double-wall protrusion structure 221 and the second double-wall protrusion structure 222. The surface of the third dielectric layer 230 away from the second dielectric layer 220 is planarized to serve as a bonding surface for bonding to the resonator substrate 100 via the bonding metal layer 200.

[0031] The resonator substrate 100 is made of silicon, glass (silicon oxide), sapphire (Al2O3), gallium nitride (GaN), silicon carbide (SiC), aluminum nitride (AlN), etc.

[0032] The portion of the second double-wall protruding structure 222 and the third dielectric layer 230 filled in the second double-wall protruding structure 222 constitutes the double-wall boundary structure 300 surrounding the cavity 1000.

[0033] The piezoelectric layer 140 is made of AlN or ScAlN. The piezoelectric layer 140 includes one or more exposed cavities 1000 and release holes 810.

[0034] 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 is provided according to an embodiment of this disclosure. Figure 2 A cross-sectional view of the structure formed in process 50.

[0035] like Figure 3A As shown, in step S0, a temporary substrate 3000 is obtained. The temporary substrate 3000 is made of silicon.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] like Figure 3D As shown, in step S3, a first electrode 500 is formed on the piezoelectric layer 140. The first electrode 500 is formed of a metallic material. The first electrode 500 includes at least two separate portions. Figure 3D In the illustrated embodiment, the first electrode 500 includes a first portion 501 and a second portion 502 that are separate from each other. The first portion 501 of the first electrode 500 serves as an electrode of the BAW resonator 10, and the second portion 502 of the first electrode 500 serves as an electrical connection portion between the bonding metal layer 200 and an external ground.

[0044] 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 first electrode 500 (including the first portion 501 and the second portion 502) and the piezoelectric layer 140.

[0045] like Figure 3FAs shown, in step S5, the first dielectric layer 210 is etched to form a first trench 211 and a second trench 212 surrounding the operating region of the BAW resonator 10. A portion of the first dielectric layer 210 surrounded by the second trench 212 serves as a sacrificial layer, which will be removed in a subsequent process to form the cavity 1000. A portion of the second portion 502 of the first electrode 500 is exposed at the bottom of the first trench 211. A portion of the piezoelectric layer 140 and a portion of the first portion 501 of the first electrode 500 are exposed at the bottom of the second trench 212.

[0046] like Figure 3G As shown, in step S6, the second dielectric layer 220 is deposited on... Figure 3F On 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 sides and bottom of the first trench 211 and the second trench 212 formed in the first dielectric layer 210. The second dielectric layer 220 also covers the portion of the second portion 502 of the first electrode 500 exposed at the bottom of the first trench 211, and the portion of the piezoelectric layer 140 and the first portion 501 of the first electrode 500 exposed at the bottom of the second trench 212. The portions of the second dielectric layer 220 deposited on the sides and bottom of the first trench 211 form a first double-walled protrusion structure 221, which protrudes toward and contacts the second portion 502 of the first electrode 500. The second dielectric layer 220 deposited on the sides and bottom of the second trench 212 forms a second double-walled protrusion structure 222, 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.

[0047] like Figure 3H As shown, in step S7, the third dielectric layer 230 is deposited on... Figure 3GThe surface of the structure shown is then planarized using a process such as chemical mechanical polishing (CMP). The third dielectric layer 230 may be formed of silicon oxide, silicon nitride, aluminum nitride, or other materials, or a combination of two or more of these materials. The third dielectric layer 230 fills the first trench 211 in the first double-wall protrusion structure 221 and the second trench 212 in the second double-wall protrusion structure 222, forming the first protrusion structure 231 and the second protrusion structure 232 protruding into the piezoelectric layer 140, respectively. The second protrusion structure 232 and the second double-wall protrusion structure 222 together constitute the double-wall boundary structure 300, which surrounds the operating region of the BAW resonator 10 and defines the cavity 1000.

[0048] like Figure 3I As shown, in step S8, in the portion corresponding to the first trench 211 (i.e., the first double-walled protrusion structure 221), the third dielectric layer 230 and the second dielectric layer 220 are etched to expose a portion of the second portion 502 of the first electrode 500, thereby forming a first ground via 400 for grounding the bonding metal layer 200. Figure 1B The opening size of the first grounding through hole 400 is smaller than the opening size of the first trench 211.

[0049] like Figure 3J As shown, in step S9, the first adhesion layer 150 and the first bonding layer 160 are sequentially deposited on... Figure 3I On the surface of the structure shown. Both the first adhesion layer 150 and the first bonding layer 160 are formed of metallic material. Both the first adhesion layer 150 and the first bonding layer 160 cover the entire surface of the third dielectric layer 230, and the sidewall surface of the first ground via 400 and the second portion 502 of the first electrode 500 are exposed at the bottom of the third dielectric layer 230. The first adhesion layer 150 bonds the first bonding layer 160 to the surface of the third dielectric layer 230, and the second portion 502 of the first electrode layer 500 is exposed at the bottom of the first ground via 400. 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. 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.

[0050] like Figure 3KAs 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.

[0051] 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.

[0052] like Figure 3L As shown, in step S11, the first bonding layer 160 and the second bonding layer 180 are bonded together, such that... Figure 3K The structure shown is Figure 3J The structures shown are bonded together. Thus, the second bonding layer 180 formed on the resonator substrate 100 covers the first ground via 400.

[0053] like Figure 3M As shown, in step S12, the flipping Figure 3L The structure shown is such that the temporary substrate 3000 is removed to expose the buffer layer 3100.

[0054] like Figure 3NAs shown, in step S13, the buffer layer 3100 is removed to expose the surface layer of the piezoelectric layer 140.

[0055] 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.

[0056] like Figure 3P As shown, in step S15, a second electrode 700 is formed on the piezoelectric layer 140. The second electrode 70 partially overlaps with the first portion 501 of the first electrode 500. The overlapping portion of the first portion 501 of the first electrode 500 and the second electrode 700 is surrounded by a second double-walled protruding structure 222. That is, the overlapping portion of the first electrode 500 and the second electrode 700 is provided with a cavity 1000 that will be formed in a subsequent process.

[0057] 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 second double-walled protrusion structure 222 (i.e., the sacrificial island for forming the cavity 1000). The second ground via 821 exposes a portion of the second surface (top surface) of the second portion 502 of the first electrode 500. The contact hole 822 exposes a portion of the first portion 501 of the first electrode 500.

[0058] like Figure 3R As shown, in step S17, in Figure 3Q A 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, and contacts the second surface of the second portion 502 of the first electrode 500 through the second ground via 821. The ground pad metal layer 361 is used to electrically connect 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, and contacts the first portion 501 of the first electrode 500 through the contact hole 822. The first electrode pad metal layer 362 is used for external electrical connection of the BAW resonator 10.

[0059] like Figure 3SAs shown, in step S18, a portion of the first dielectric layer 210 surrounded by the second double-walled protrusion structure 222 is etched and removed to form a 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.

[0060] Figure 4A This is a top view provided according to an embodiment of the present disclosure, showing a selected portion of a BAW resonator 20 used in a BAW filter; Figure 4B This is provided according to an embodiment of the present disclosure. Figure 4A The edge of the BAW resonator 20 Figure 4A The cross-sectional view of the cross-sectional line B-B' shown.

[0061] like Figure 4A and Figure 4B As shown, the BAW resonator 20 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, a second dielectric layer 220, and a third dielectric layer 230 disposed sequentially between the resonator substrate 100 and the piezoelectric layer 240 in the order from the piezoelectric layer 140 to the resonator substrate 100; a cavity 1000 disposed below the first electrode 500; and a bonding metal layer 200 disposed between the third dielectric layer 230 and the resonator substrate 100 and including a first adhesion layer 150, a first bonding layer 160, a second adhesion layer 170, and a second bonding layer 180.

[0062] The second dielectric layer 220 includes a first double-walled protrusion 221 and a second double-walled protrusion 222 protruding into the piezoelectric layer through the first dielectric layer 210. The first double-walled protrusion 221 is spaced apart from the cavity 1000 and contacts a first surface (i.e., bottom surface) of the piezoelectric layer 140. The second double-walled protrusion 222 surrounds the cavity 1000 and contacts a portion of the piezoelectric layer 140 and a portion of the first electrode 500. A third dielectric layer 230 fills the first double-walled protrusion 221 and the second double-walled protrusion 222. A first adhesive layer 150 is disposed below and in contact with the third dielectric layer 230. A first bonding layer 160 is disposed below the first adhesive layer 150. A second adhesive 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 adhesive layer 170 and bonded to the first bonding layer 160 by eutectic bonding or metal diffusion bonding.

[0063] A grounding via 900 is disposed through the piezoelectric layer 140, the second dielectric layer 220, and the third dielectric layer 230 to expose the first adhesive layer 150. The grounding via 900 includes a first grounding via 400 and a second grounding via 821, wherein: the first grounding via 400 is disposed in the first double-walled protrusion structure 221 and exposes the first adhesive layer 150; the second grounding via 821 is disposed in the piezoelectric layer 140 and is aligned with and in contact with the first grounding via 400. A mat metal layer 361 is disposed on the piezoelectric layer 140 and located in the grounding via 900, contacting the first adhesive layer 150 through the grounding via 900.

[0064] A contact hole 822 is disposed in the piezoelectric layer 140, exposing 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 contacts the first electrode 500 through the contact hole 822.

[0065] In BAW resonator 20, such as Figure 4A and 4B As shown, the bonding metal layer 200 includes a first adhesion layer 150, a first bonding layer 160, a second adhesion layer 170, and a second bonding layer 180. The bonding metal layer 200 is electrically connected to the ground metal layer 361. During operation of the BAW resonator 10, the ground metal layer 361 is grounded, thereby grounding the bonding metal layer 200.

[0066] The other components of BAW resonator 20 are similar to those of BAW resonator 10. Therefore, a detailed description of these components of BAW resonator 20 will not be repeated.

[0067] Figure 5 This is a flowchart of a process 60 for manufacturing a BAW resonator 20 according to an embodiment of the present disclosure; Figure 6A -6F is provided according to an embodiment of the present disclosure. Figure 5 A cross-sectional view of the structure formed in process 60.

[0068] Figure 5 The process 60 shown is... Figure 2 The process 50 shown is similar, except that process 60 omits step S8 for forming the first grounding via 400 and adds step S16a for forming the first grounding via 400 after forming the second grounding via 821 in step S16. The other steps are similar to those in process 50, and their detailed descriptions will not be repeated.

[0069] Specifically, such as Figure 6AAs shown, in step S9, after the third dielectric layer 230 is deposited and planarized in step S7, no vias are formed in the third dielectric layer 230. The first adhesion layer 150 and the first bonding layer 160 are sequentially deposited on the planarized surface of the third dielectric layer 230. The first adhesion layer 150 covers the entire surface of the third dielectric layer 230, and the first bonding layer 160 is adhered to the surface of the third dielectric layer 230.

[0070] like Figure 6B As shown, in step S11, after the second adhesion layer 170 and the second bonding layer 180 are sequentially deposited on the resonator substrate 100 in step S10, the first bonding layer 160 and the second bonding layer 180 are bonded together.

[0071] like Figure 6C As shown, in step S16, after the second electrode 700 is formed on the piezoelectric layer 140 in step S15, the piezoelectric layer 40 is etched to form one or more release holes 810, a second grounding via 821, and a contact hole 822. The release hole 810 exposes the portion of the first dielectric layer 210 surrounded by the second double-walled protrusion structure 222 (i.e., the sacrificial island for forming the cavity 1000). The second grounding via 821 exposes a portion of the top surface of the first double-walled protrusion structure 221. The contact hole 822 exposes a portion of the first portion 501 of the first electrode 500.

[0072] like Figure 6D As shown, in step S16a, the second dielectric layer 220 and the third dielectric layer 230 are etched at the bottom of the second grounding via 821, exposing the first adhesion layer 150 of the bonding metal layer 200, thereby forming the first grounding via 400. The first grounding via 400 is vertically aligned with the second grounding via 821. The first grounding via 400 and the second grounding via 821 together constitute a grounding via 900.

[0073] like Figure 6E As shown, in step S17, in Figure 6D A 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 a ground via 900, and contacts the first adhesion layer 150 through the ground via 900. The ground pad metal layer 361 is used to electrically connect 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, and contacts the first portion 501 of the first electrode 500 through the contact hole 821. The first electrode pad metal layer 362 is used for external electrical connection of the BAW resonator 10.

[0074] like Figure 6FAs shown, in step S18, a portion of the first dielectric layer 210 surrounded by the second double-walled protrusion structure 222 is etched and removed to form a cavity 1000. The etchant and etching products formed during the etching process are released through one or more release holes 810. Thus, Figure 4A and 4B The BAW resonator 20 shown has been manufactured.

[0075] 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 on top of the substrate; The first electrode is disposed below the piezoelectric layer and includes a first portion and a second portion spaced apart from each other. The second electrode is disposed above the piezoelectric layer; The first dielectric layer, the second dielectric layer, and the third dielectric layer are disposed sequentially between the substrate and the piezoelectric layer in the order from the piezoelectric layer to the substrate; A cavity is disposed below the first portion of the first electrode; A first grounding via is disposed in the second dielectric layer and the third dielectric layer, and exposes the first surface of the second portion of the first electrode; A bonding metal layer is disposed between the third dielectric layer and the substrate, and a portion of the bonding metal layer is disposed in the first ground via. A second grounding via is disposed in the piezoelectric layer and exposes the second surface of the second portion of the first electrode; and A ground mat metal layer is disposed above 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 and the portion of the bonding metal layer located in the first grounding through hole are electrically connected through a second portion of the first electrode.

2. The BAW resonator according to claim 1, characterized in that, The first grounding through hole and the second grounding through hole are offset from each other.

3. The BAW resonator according to claim 2, characterized in that, 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.

4. The BAW resonator according to claim 3, 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).

5. The BAW resonator according to claim 3, 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).

6. The BAW resonator according to claim 3, characterized in that, The second dielectric layer includes a first double-walled protrusion structure that protrudes from the first dielectric layer into the piezoelectric layer, and the first double-walled protrusion structure is in contact with a first surface of a second portion of the first electrode; The third dielectric layer fills the first double-walled protruding structure; The first grounding through hole is disposed in the first double-walled protruding structure; The first adhesion layer covers the third dielectric layer, covers the sidewalls and bottom of the first grounding via, and contacts the first surface of the second portion of the first electrode through the first grounding via; The first bonding layer covers the first adhesion layer; The second adhesion layer is disposed on the surface of the substrate facing the piezoelectric layer.

7. The BAW resonator according to claim 6, characterized in that, The second dielectric layer includes a second double-walled protruding structure that protrudes through the first dielectric layer into the piezoelectric layer and surrounds the cavity; The second double-walled protruding structure is in contact with a portion of the piezoelectric layer and a portion of the first portion of the first electrode; The third dielectric layer fills the second double-walled protrusion structure.

8. The BAW resonator according to claim 6, characterized in that, The first dielectric layer is formed of silicon oxide; and / or 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; and / or The third dielectric layer is formed by a stack of one or more materials selected from silicon oxide, silicon nitride, and aluminum nitride.

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 first 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 contacts the first part of the first electrode through the contact hole.

10. 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; The first dielectric layer, the second dielectric layer, and the third dielectric layer are disposed sequentially between the substrate and the piezoelectric layer in the order from the piezoelectric layer to the substrate; A cavity is located below the first electrode; A bonding metal layer is disposed between the third dielectric layer and the substrate; A grounding via is disposed in the piezoelectric layer, the second dielectric layer and the third dielectric layer, and exposes the bonding metal layer; and A metal layer for the floor mat is disposed on the piezoelectric layer and located in the grounding through hole, and is electrically connected to the bonding metal layer; 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 second dielectric layer includes a first double-walled protrusion structure that protrudes from the first dielectric layer into the piezoelectric layer. The first double-walled protrusion structure is in contact with the first surface of the piezoelectric layer and is separated from the cavity. The third dielectric layer fills the first double-walled protrusion structure. The first adhesion layer is disposed below the third dielectric layer and in contact with the third dielectric layer; The first bonding layer is disposed below the first adhesion layer; 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; The grounding via includes a first grounding via disposed in the first double-walled protruding structure and exposing the first adhesive layer, and a second grounding via disposed in the piezoelectric layer and aligned with the first grounding via.

11. The BAW resonator according to claim 10, 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).

12. The BAW resonator according to claim 10, 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).

13. The BAW resonator according to claim 10, characterized in that, The second dielectric layer includes a second double-walled protruding structure that protrudes through the first dielectric layer into the piezoelectric layer and surrounds the cavity; The second double-walled protruding structure is in contact with a portion of the piezoelectric layer and a portion of the first electrode; The third dielectric layer fills the second double-walled protrusion structure.

14. The BAW resonator according to claim 10, characterized in that, The first dielectric layer is formed of silicon oxide.

15. The BAW resonator according to claim 10, characterized in that, The second dielectric layer is formed by a combination of one or more of the following materials: polycrystalline silicon, amorphous silicon, silicon nitride, aluminum nitride, gallium nitride, and tantalum nitride.

16. The BAW resonator according to claim 10, characterized in that, The third dielectric layer is formed by a stack of one or more materials selected from silicon oxide, silicon nitride, and aluminum nitride.

17. The BAW resonator according to claim 10, characterized in that, Also includes: One or more release holes are formed in the piezoelectric layer and expose the cavity.

18. The BAW resonator according to claim 10, 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 contacts the first electrode through the contact hole.

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