Method of manufacturing a resonant filter

Abstract

The application discloses a manufacturing method of a resonant filter. The method comprises the following steps: manufacturing a first substrate and a resonant filter structure, wherein the resonant filter structure is formed on a first side of the first substrate, the resonant filter structure comprises a bulk acoustic wave resonant structure and a Lamb wave resonant structure, the bulk acoustic wave resonant structure and the Lamb wave resonant structure are electrically connected, the bulk acoustic wave resonant structure comprises a first electrode structure, the Lamb wave resonant structure comprises a second electrode structure, the second electrode structure comprises a first interdigital electrode and a second interdigital electrode, the first electrode structure and the second electrode structure share a same first electrode layer, the first interdigital electrode is electrically connected with the outside, and the second interdigital electrode is electrically connected with the first electrode structure.

Description

[0001] This application is a divisional application of application No. 2025102517468, publication No. CN119788016A, application date is March 5, 2025, and the name is a resonant filter and its manufacturing method. TECHNICAL FIELD

[0002] The present application relates to the technical field of semiconductor products and semiconductor processes, in particular to a manufacturing method of a resonant filter. BACKGROUND

[0003] The bulk acoustic wave resonator has good band-pass performance, so the bulk acoustic wave resonator can be used to realize the band-pass performance of the filter. The Lamb wave resonator has good stop-band performance, so the Lamb wave resonator can be used to realize the stop-band performance of the filter. In this case, if the bulk acoustic wave resonator and the Lamb wave resonator can be combined, the resonant filter circuit formed by the combination can flexibly configure the stop-band frequency of the resonant filter circuit on the basis of realizing excellent band-pass performance. At present, the bulk acoustic wave resonator and the Lamb wave resonator are both independent resonant filter devices formed by respective processes, so the bulk acoustic wave resonator and the Lamb wave resonator can only be combined to build a resonant filter circuit.

[0004] Since the bulk acoustic wave resonator and the Lamb wave resonator are both independent resonant filter devices, the integration of the resonant filter circuit is low, and since the bulk acoustic wave resonator and the Lamb wave resonator are formed by respective processes, the process cost of building the resonant filter circuit is also very high.

[0005] In view of the technical problems of low integration and high process cost of the resonant filter circuit composed of the bulk acoustic wave resonator and the Lamb wave resonator in the prior art, no effective solution has been proposed so far. SUMMARY

[0006] The present disclosure provides a manufacturing method of a resonant filter to at least solve the technical problem of low integration and high process cost of the resonant filter circuit composed of the bulk acoustic wave resonator and the Lamb wave resonator in the prior art.

[0007] According to one embodiment of the present application, a resonant filter is provided, comprising: a first substrate; and a resonant filter structure formed on a first side of the first substrate, wherein the resonant filter structure comprises a bulk acoustic wave resonant structure and a Lamb wave resonant structure, and the bulk acoustic wave resonant structure and the Lamb wave resonant structure are electrically connected. Wherein the bulk acoustic wave resonant structure comprises a first electrode structure, and the Lamb wave resonant structure comprises a second electrode structure, wherein the first electrode structure and the second electrode structure share the same first electrode layer; or the bulk acoustic wave resonant structure and the Lamb wave resonant structure share the same piezoelectric layer.

[0008] According to another embodiment of this application, a method for fabricating a resonant filter is provided, comprising: fabricating a first substrate and a resonant filter structure, wherein the resonant filter structure is formed on a first side of the first substrate, the resonant filter structure includes a bulk acoustic wave resonant structure and a Lamb wave resonant structure, and the bulk acoustic wave resonant structure and the Lamb wave resonant structure are electrically connected, wherein the bulk acoustic wave resonant structure includes a first electrode structure, the Lamb wave resonant structure includes a second electrode structure, wherein the second electrode structure includes a first interdigital electrode and a second interdigital electrode, the first electrode structure and the second electrode structure share the same first electrode layer, the first interdigital electrode is electrically connected to the outside, and the second interdigital electrode is electrically connected to the first electrode structure.

[0009] Therefore, according to the embodiments of this application, in the resonant filter, the bulk acoustic wave resonant structure and the Lamb wave resonant structure share the same substrate, and the bulk acoustic wave resonant structure and the Lamb wave resonant structure also share the same electrode layer or piezoelectric layer. In this way, this embodiment integrates the bulk acoustic wave resonant structure and the Lamb wave resonant structure into a single resonant filter structure, and further integrates them into the same resonant filter device, thereby improving the integration density of the resonant filter circuit. Furthermore, the fabrication method of the resonant filter can simultaneously fabricate the bulk acoustic wave resonant structure and the Lamb wave resonant structure in the same set of processing steps, thereby reducing the process cost of constructing the resonant filter circuit. Attached Figure Description

[0010] The following sections will describe some specific embodiments of this application in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0011] Figure 1 This is a schematic diagram of the layer structure of the resonant filter according to Embodiment 1 of this application;

[0012] Figure 2 This is a top view schematic diagram of the resonant filter according to Embodiment 1 of this application;

[0013] Figure 3 This is a circuit diagram of the resonant filter according to Embodiment 1 of this application;

[0014] Figures 4-6 This is a schematic diagram of a resonant filter according to a modified embodiment 1 of this application;

[0015] Figure 7 This is a schematic diagram of a resonant filter according to yet another modification of Embodiment 1 of this application;

[0016] Figure 8This is a schematic diagram of a resonant filter according to yet another modification of Embodiment 1 of this application;

[0017] Figure 9 and Figure 10 This is a schematic diagram of a resonant filter according to yet another modification of Embodiment 1 of this application;

[0018] Figure 11 This is a schematic diagram of a resonant filter according to yet another modification of Embodiment 1 of this application;

[0019] Figures 12-31 These are schematic diagrams illustrating the structural steps corresponding to each step of the resonant filter fabrication method according to Embodiment 2 of this application; and

[0020] Figures 32-35 This is a schematic diagram of the structure corresponding to each step of the manufacturing method according to a modified embodiment 2 of this application. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other. This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To enable those skilled in the art to better understand the present disclosure, the technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present disclosure.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] Example 1

[0026] Figure 1 This is a schematic diagram of the layer structure of the resonant filter according to Embodiment 1 of this application; Figure 2 This is a top view schematic diagram of the resonant filter according to Embodiment 1 of this application; Figure 3 This is a circuit diagram of the resonant filter according to Embodiment 1 of this application.

[0027] refer to Figure 1 As shown, the resonant filter according to this embodiment includes: a first substrate 210; and a resonant filter structure formed on a first side of the first substrate 210. Figure 1 In this embodiment, the first side of the first substrate 210 corresponds to the upper side of the first substrate 210, thereby forming the resonant filter structure on the upper side of the first substrate 210. However, the scope of protection of this invention is not limited thereto, for example, when Figure 1 When the device shown is flipped, the first side of the first substrate 210 can also correspond to the lower side of the first substrate 210. Similar situations will not be described again in this specific embodiment.

[0028] refer to Figure 1 and Figure 2 As shown, the resonant filter structure includes a bulk acoustic wave (BAWR) resonant structure and a Lamb wave (LWR) resonant structure, and the BAWR and LWR are electrically connected. The BAWR includes a first electrode structure 131, and the LWR includes a second electrode structure 132. (Reference) Figure 1 As shown, the first electrode structure 131 corresponds to the upper electrode of the bulk acoustic wave resonator structure BAWR, and the second electrode structure 132 corresponds to the upper electrode of the Lamb wave resonator structure LWR. The first electrode structure 131 and the second electrode structure 132 share the same first electrode layer 130. Furthermore, refer to... Figure 2 As shown, the second electrode structure 132 includes interdigitated electrodes 132a and 132b.

[0029] As described in the background section, combining bulk acoustic wave (BAW) resonators and Lamb wave resonators allows for flexible configuration of the stopband frequency while achieving excellent bandpass performance. Currently, BAW and Lamb wave resonators are independently manufactured devices using their respective processes, thus requiring the combination of these independently manufactured devices to construct resonant filter circuits. Because BAW and Lamb wave resonators are independent resonant filter devices, the integration density of the resonant filter circuit is low.

[0030] Therefore, in the resonant filter described in this embodiment, the bulk acoustic wave resonant structure and the Lamb wave resonant structure share the same substrate, and they also share the same electrode layer. In this way, this embodiment integrates the bulk acoustic wave resonant structure and the Lamb wave resonant structure into a single resonant filter structure, and further integrates them into the same resonant filter device, thereby improving the integration density of the resonant filter circuit.

[0031] Furthermore, as another aspect of this embodiment, reference is made to... Figure 1 As shown, the resonant filter structure includes a piezoelectric layer 140, and the bulk acoustic wave resonant structure BAWR and the Lamb wave resonant structure LWR share the piezoelectric layer 140. Therefore, by sharing the same piezoelectric layer 140, the integration density of the resonant filter structure can be improved.

[0032] Optionally, the first electrode structure 131 and the second electrode structure 132 are located on a first side of the piezoelectric layer 140, wherein the first side of the piezoelectric layer 140 is opposite to the first substrate 210. (Reference) Figure 1 As shown, the first side of the piezoelectric layer 140 corresponds to the upper side of the piezoelectric layer 140, so in this embodiment, the first electrode structure 131 and the second electrode structure 132 are located on the upper side of the piezoelectric layer 140.

[0033] Optionally, refer to Figure 1 As shown, the bulk acoustic wave resonator structure BAWR also includes a third electrode structure 150a located on the second side (i.e., the lower side) of the piezoelectric layer 140, wherein the third electrode structure 150a corresponds to the first electrode structure 131. The Lamb wave resonator structure LWR also includes a fourth electrode structure 150b located on the second side of the piezoelectric layer 140, wherein the fourth electrode structure 150b corresponds to the second electrode structure 132. Furthermore, the third electrode structure 150a and the fourth electrode structure 150b share the same second electrode layer 150.

[0034] In this way, the bulk acoustic wave resonant structure BAWR and the Lamb wave resonant structure LWR not only share the same first electrode layer, but also share the same second electrode layer, thereby further improving the integration of the resonant filter structure.

[0035] In addition, further reference Figure 1 As shown, the resonant filter structure further includes: a first resonant cavity 1801, wherein the first resonant cavity 1801 is formed between the bulk acoustic wave resonant structure BAWR and the first substrate 210; and a second resonant cavity 1802, wherein the second resonant cavity 1802 is formed between the Lamb wave resonant structure LWR and the first substrate 210.

[0036] Specifically, refer to Figure 1 As shown, a first support structure SUP1, a second support structure SUP2, and a third support structure SUP3 are formed on a first side of the first substrate 210. The first support structure SUP1 supports the piezoelectric layer 140, while the second and third support structures SUP2 and SUP3 support the second electrode layer 150. One end of the third electrode structure 150a is supported by the second support structure SUP2, and the other end is a free end. The fourth electrode structure 150b is supported by both the second and third support structures SUP2 and SUP3. This forms a first resonant cavity 1801 between the first and second support structures SUP1 and SUP2, and a second resonant cavity 1802 between the second and third support structures SUP2 and SUP3.

[0037] In this way, this embodiment integrates the bulk acoustic wave resonant structure and the Lamb wave resonant structure into the same resonant filter structure. Based on the structural characteristics of the bulk acoustic wave resonant structure and the Lamb wave resonant structure, electrode support structures and resonant cavities suitable for the bulk acoustic wave resonant structure and the Lamb wave resonant structure, respectively, are constructed. This allows both the bulk acoustic wave resonant structure and the Lamb wave resonant structure integrated into the same resonant filter structure to function normally and to utilize the performance of their respective resonant structures.

[0038] Optionally, refer to Figure 1 As shown, the resonant filter further includes: a second substrate 250, wherein the second substrate 250 includes a central region and an edge region, wherein the central region covers a body acoustic resonant structure BAWR and a Lamb wave resonant structure LWR; and a bonding layer 240, which corresponds to the edge region on the first side of the second substrate 250 and is used to bond the second substrate 250 to the resonant filter structure.

[0039] Therefore, refer to Figure 1As shown, a third resonant cavity 2400 is formed between the resonant filter structure and the second substrate 250. Furthermore, the bulk acoustic wave resonant structure BAWR and the Lamb wave resonant structure LWR share this third resonant cavity 2400.

[0040] Thus, in this embodiment, the resonant filter structure is protected by the second substrate, and the second substrate and bonding layer are used to form a resonant cavity shared by the bulk acoustic wave resonant structure and the Lamb wave resonant structure, thereby further improving the integration of the resonant filter.

[0041] refer to Figure 3 As shown, a conductive electrode is provided on the second side of the second substrate 250, which is electrically connected to the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR. Thus, the resonant filter structure of the resonant filter is electrically connected to the outside through the conductive electrode.

[0042] Furthermore, the conductive electrodes include a first conductive electrode 270a and a second conductive electrode 270b. The first conductive electrode 270a is electrically connected to the second electrode layer 150 via a through-hole; and the second conductive electrode 270b is electrically connected to the first interdigital electrode 132b of the second electrode structure 132 via a through-hole. (See also...) Figures 4-6 As shown, this type of electrical connection realizes the series connection between the bulk acoustic wave resonator BAWR and the Lamb wave resonator LWR.

[0043] also, Figure 4 A schematic diagram illustrating a modification of the resonant filter described in Embodiment 1. (See reference...) Figure 5 and Figure 6 As shown, in this modified example, the conductive electrodes include a first conductive electrode 270a, a second conductive electrode 270b, and a third conductive electrode 260a. Specifically, the first conductive electrode 270a is electrically connected to the second electrode layer 150 via a through-hole; the second conductive electrode 270b is electrically connected to the first interdigital electrode 132b of the second electrode structure 132 via a through-hole; and the third conductive electrode 260a is electrically connected to the second interdigital electrode 132a of the first electrode structure 131 and the second electrode structure 132 via a through-hole.

[0044] Therefore, refer to Figure 7 As shown, this electrical connection method realizes the parallel structure between the bulk acoustic wave resonator BAWR and the Lamb wave resonator LWR.

[0045] also, Figure 8 and Figure 7 A schematic diagram illustrating another modification of the resonant filter described in Embodiment 1. (See reference...) Figure 8 and Figure 7As shown, in this modified example, a conductive electrode electrically connected to the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR is disposed on the second side of the first substrate 210. Wherein... Figure 8 and Figure 7 In this process, the resonant filter is flipped up and down, so that the second side of the first substrate 210 corresponds to the upper side of the first substrate 210.

[0046] Thus, the through-hole conductive structure used to connect the conductive electrode and the bulk acoustic wave resonator structure BAWR and the through-hole conductive structure used to connect the conductive electrode and the bulk acoustic wave resonator structure LWR are formed on the first substrate 210. In addition to penetrating the bonding layer, they also sequentially penetrate the cutoff boundary layer, sacrificial layer, dielectric layer, piezoelectric layer and other solid material layers. Since these layers are mainly composed of solid materials with high mechanical strength and toughness, the risk of fracture caused by weak material connections (such as bonding layers) can be significantly reduced during perforation, the local stress concentration that may be introduced by the perforation operation is reduced, and the fracture caused by perforation during the manufacturing and use of the filter device is greatly reduced, thereby improving the reliability and stability of the filter device.

[0047] Further optional, refer to Figure 3 As shown, the conductive electrodes include a fourth conductive electrode 270c and a fifth conductive electrode 270d. The fourth conductive electrode 270c is electrically connected to the second electrode layer 150 via a through-hole; and the fifth conductive electrode 270d is electrically connected to the first interdigital electrode 132b of the second electrode structure 132 via a through-hole. Thus, through this electrical connection, a series structure between the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR is realized (see reference). Figure 8 (As shown).

[0048] Further optional, refer to Figure 6 As shown, the conductive electrodes include a fourth conductive electrode 270c, a fifth conductive electrode 270d, and a sixth conductive electrode 260b. Specifically, the fourth conductive electrode 270c is electrically connected to the second electrode layer 150 via a through-hole; the fifth conductive electrode 270d is electrically connected to the first interdigital electrode 132b of the second electrode structure 132 via a through-hole; and the sixth conductive electrode 260b is electrically connected to the second interdigital electrode 132a of the first electrode structure 131 and the second electrode structure 132 via a through-hole. Thus, through this type of electrical connection, a parallel structure between the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR is realized (see reference). Figure 9 (As shown).

[0049] In addition, refer to Figure 10As shown, the resonant filter structure described in this embodiment includes multiple bulk acoustic wave (BAWR) resonant structures and multiple Lamb wave (LWR) resonant structures. Therefore, in this embodiment, not only are one BAWR and one Lamb wave resonant structure integrated into a single resonant filter structure, but multiple BAWR and multiple Lamb wave resonant structures can also be integrated into a single resonant filter structure. This further improves the integration density of the resonant filter. Furthermore, refer to... Figure 11 As shown, optionally, multiple bulk acoustic wave resonator structures (BAWR) and multiple Lamb wave resonator structures (LWR) constitute a trapezoidal filter structure.

[0050] In addition, further reference Figure 11 As shown, the Lamb wave resonant structure LWR can be a dual-mode filter structure. Therefore, the second electrode structure 132 of the Lamb wave resonant structure LWR is... Figures 12-31 The electrode structure shown.

[0051] In summary, in the resonant filter described in this embodiment, the bulk acoustic wave resonant structure and the Lamb wave resonant structure share the same substrate, and they also share the same electrode layer or piezoelectric layer. Thus, in this way, this embodiment integrates the bulk acoustic wave resonant structure and the Lamb wave resonant structure into a single resonant filter structure, and further integrates them into the same resonant filter device, thereby improving the integration density of the resonant filter circuit.

[0052] Example 2

[0053] also, Figure 12 This is a schematic diagram of the layer structure in each fabrication process of the resonant filter according to Embodiment 2 of this application.

[0054] Example 2 provides a method for fabricating a resonant filter. This resonant filter corresponds to the resonant filter described in Example 1. Specifically, the method includes: fabricating a first substrate and a resonant filter structure, wherein the resonant filter structure is formed on a first side of the first substrate, the resonant filter structure includes a bulk acoustic wave (BAW) resonant structure and a Lamb wave resonant structure, and the BAW resonant structure and the Lamb wave resonant structure are electrically connected, wherein the BAW resonant structure includes a first electrode structure, the Lamb wave resonant structure includes a second electrode structure, wherein the second electrode structure includes a first interdigital electrode and a second interdigital electrode, the first electrode structure and the second electrode structure share the same first electrode layer, the first interdigital electrode is electrically connected to the outside, and the second interdigital electrode is electrically connected to the first electrode structure. Specifically, the method for fabricating the resonant filter described in Example 1 includes:

[0055] like Figure 13As shown, a transition layer 110, a seed layer 120, a first electrode layer 130, a piezoelectric layer 140, and a second electrode layer 150 are sequentially fabricated on a temporary substrate 100 used as a temporary substrate. Optionally, the temporary substrate 100 can be a silicon substrate, a silicon-on-insulator substrate, a glass substrate, a silicon carbide substrate, or a gallium arsenide (GaAs) substrate, etc.; the transition layer 110 can be a silicon oxide (SiO2) layer or a silicon nitride (SiNx) layer, etc., and can be formed by thermal oxidation, physical vapor deposition (PVD), or chemical vapor deposition (CVD), etc.; the seed layer 120 can be an aluminum nitride (AlN) layer, formed by physical vapor deposition (PVD), specifically magnetron sputtering; the first electrode layer 130 can be an Al layer, a Cu layer, a Mo layer, etc. The first electrode layer can be an Al layer, an Au layer, or a Pt layer, and can be formed by physical vapor deposition (PVD). Similarly, the second electrode layer 150 can be an Al layer, a Cu layer, a Mo layer, an Au layer, or a Pt layer, and can be formed by physical vapor deposition (PVD). The piezoelectric layer 140 can be an AlN layer, a scandium-doped aluminum nitride (AlxSc1-xN) layer, a lithium niobate (LiNbO3) layer, a lithium tantalate (LiTaO3) layer, or a quartz layer, etc., and can be a polycrystalline layer or a single crystal layer, and can be formed by PVD or metal-organic chemical vapor deposition (MOCVD), etc.

[0056] like Figure 14 As shown, the first region of the second electrode layer 150 is etched to form a stepped structure 151 in the second electrode layer 150 to improve the performance of the resonant filter structure. Specifically, in one embodiment of this application, the etching process for the second electrode layer 150 can be a dry etching process or a wet etching process, but this application does not limit it and it depends on the specific circumstances.

[0057] like Figure 15 As shown, a dielectric layer 160 is formed on the side of the second electrode layer 150 away from the temporary substrate 100. Optionally, the dielectric layer 160 is formed by a deposition process, specifically PVD or CVD, etc. The material of the dielectric layer 160 can be SiO2, SiNx, or AlN, etc., and this application does not limit this; it depends on the specific situation. It should be noted that in the embodiments of this application, the dielectric layer 160 is a protective layer for the second electrode layer 150 to prevent the second electrode layer 150 from being oxidized. Optionally, the dielectric layer 160 also serves as the dielectric layer for the capacitor subsequently formed.

[0058] like Figure 16As shown, the second region of the second electrode layer 150 and the portion of the dielectric layer 160 located on the surface of the second region of the second electrode layer are etched to obtain the second electrode layer 150. The second electrode layer 150 includes the remaining portion of the second electrode layer 150 and the portion of the dielectric layer 160 located on the surface of the second electrode layer 150. In a plane parallel to the temporary substrate 100, the second region is located on the first side of the stepped structure. Optionally, the etching process for the dielectric layer 160 and the second electrode layer 150 can be a wet etching process or a dry etching process.

[0059] like Figure 17 As shown, a capacitor electrode 170 is formed in a third region on the surface of the dielectric layer 160. Specifically, the capacitor electrode 170 is formed in a third region on the surface of the dielectric layer 160 away from the piezoelectric layer 140. In a plane parallel to the temporary substrate 100, the third region is located on the second side of the stepped structure 151, opposite to the first side. It should be noted that in this embodiment, the capacitor electrode 170, the dielectric layer 160, and the second electrode layer 150 constitute a capacitor. Optionally, the material of the capacitor electrode 170 can be Al, Cu, Mo, Au, or Pt, etc. This application does not limit this; the specific material depends on the circumstances.

[0060] like Figure 18 As shown, a sacrificial layer 180 is formed, which covers the exposed portion of the piezoelectric layer 140, the dielectric layer 160, and the capacitor electrode 170. Optionally, the material of the sacrificial layer 180 can be SiO2, PSG, USG, a-Si, or photoresist, etc.; the formation process of the sacrificial layer 180 can be PVD, CVD, or spin coating, etc.

[0061] like Figure 19 As shown, the sacrificial layer 180 is etched to form vias 181 to 183. Via 181 exposes a portion of the surface of the piezoelectric layer 140, while vias 182 and 183 expose portions of the surface of the dielectric layer 160. Specifically, the etching process for the sacrificial layer 180 can be either dry etching or wet etching.

[0062] like Figure 20 As shown, a cutoff boundary layer 190 is formed on the side of the sacrificial layer 180 away from the dielectric layer 160, and the cutoff boundary layer 190 is also filled with vias 181 to 183. It should be noted that, in this embodiment, the portion of the cutoff boundary layer corresponding to via 181 is in contact with the piezoelectric layer 140, and the portions of the cutoff boundary layer corresponding to vias 182 and 183 are in contact with the dielectric layer 160.

[0063] It should also be noted that in this embodiment, the stop boundary layer 190 and the sacrificial layer 180 are made of different materials so that the chemicals used in etching the sacrificial layer 180 will not damage the stop boundary layer 190. Optionally, the material of the stop boundary layer 190 can be SiO2 or polysilicon (poly-Si), and the formation process can be PVD, CVD, etc.

[0064] like Figure 21 As shown, a bonding layer 200 is formed on the side of the cutoff boundary layer 190 away from the piezoelectric layer 140. The bonding layer 200 covers the surface of the cutoff boundary layer 190 and also fills the vias 181 to 183. Thus, the bonding layer 200 corresponding to the vias 181 to 183 and the cutoff boundary layer 190 form a first support structure SUP1, a second support structure SUP2, and a third support structure SUP3. Optionally, the material of the bonding layer 200 can be SiO2, and the formation process can be PVD or CVD, etc. This application does not limit this, and it depends on the specific circumstances.

[0065] like Figure 22 As shown, a first substrate 210 is bonded as a carrier on the side of the bonding layer 200 away from the cutoff boundary layer 190.

[0066] like Figure 23 As shown, the wafer composed of the above-prepared structures is flipped to remove the temporary substrate 100 and the transition layer 110. Optionally, the removal process of the temporary substrate 100 and the transition layer 110 can be grinding or chemical mechanical polishing (CMP). This application does not limit this process and it depends on the specific circumstances.

[0067] like Figure 24 As shown, the seed layer 120 and the first electrode layer 130 are etched to form a first electrode structure 131 and a second electrode structure 132. The second electrode structure 132 includes interdigitated electrodes 132a and 132b. Optionally, the etching process for the seed layer 120 and the first electrode layer 130 can be wet etching or dry etching. Furthermore, the seed layer 120 is also etched into a first seed layer portion 121 corresponding to the first electrode structure 131 and a second seed layer portion 122 corresponding to the second electrode structure 132.

[0068] like Figure 25As shown, vias 1401 are formed in the exposed portion of the piezoelectric layer 140 and vias 1201 are formed in the seed layer 120. The vias 1401 penetrate the piezoelectric layer 140, exposing a portion of the surface of the second electrode layer 150 to facilitate the extraction of the second electrode layer 150. The vias 1201 penetrate the seed layer 120 (e.g., the second seed layer portion 122), exposing the second electrode structure 132 (e.g., the interdigitated electrode 132b). Optionally, the vias 1201 and 1401 can be formed using either a wet etching process or a dry etching process.

[0069] like Figure 26 As shown, a conductive layer 230 is formed within the through-hole 1201, covering the sidewalls and bottom of the through-hole 1201, and extending to cover a portion of the surface of the seed layer 120; a conductive layer 220 is formed within the through-hole 1401, covering the sidewalls and bottom of the through-hole 1401, and extending to cover a portion of the surface of the piezoelectric layer 140. Optionally, in one embodiment of this application, the materials of the conductive layers 220 and 230 can be Au, Cu, or Al, etc., and the formation method can be PVD or electroplating, etc.

[0070] like Figures 12-26 As shown, the portion of the sacrificial layer 180 between the first support structure SUP1 and the second support structure SUP2, and the portion between the second support structure SUP2 and the third support structure SUP3, forms a first resonant cavity 1801 located between the first support structure SUP1 and the second support structure SUP2, and a second resonant cavity 1802 located between the second support structure SUP2 and the third support structure SUP3. Thus, a resonant filter structure is formed, which includes a bulk acoustic wave resonant structure BAWR and a Lamb wave resonant structure LWR.

[0071] As described above, the method described in this embodiment includes fabricating a first substrate 210 serving as a carrier and a resonant filter structure. The resonant filter structure is formed on a first side of the first substrate 210 and includes a bulk acoustic wave resonator (BAWR) and a Lamb wave resonator (LWR), which are electrically connected. The BAWR includes a first electrode structure 131, and the LWR includes a second electrode structure 132. The second electrode structure 132 includes interdigitated electrodes 132a and 132b, and the first electrode structure 131 and the second electrode structure 132 share the same first electrode layer 130.

[0072] As described in the background section, since bulk acoustic wave resonators and Lamb wave resonators are formed using separate processes, the manufacturing cost of constructing resonant filter circuits is also very high. Therefore, the resonant filter fabrication method described in this embodiment can simultaneously fabricate bulk acoustic wave resonant structures and Lamb wave resonant structures in the same set of processing steps, thereby reducing the manufacturing cost of constructing resonant filter circuits.

[0073] Optionally, the bulk acoustic resonant structure and the Lamb wave resonant structure share the same piezoelectric layer 140.

[0074] Alternatively, the second electrode structure 150 may include interdigitated electrodes 132a and 132b. (See also...) Figures 12-26 The process of fabricating the resonant filter structure includes: fabricating a piezoelectric layer 140 shared by the bulk acoustic wave resonant structure BAWR and the Lamb wave resonant structure LWR, wherein the first side of the piezoelectric layer 140 is adjacent to the first electrode layer 130. This allows the piezoelectric layers of both the bulk acoustic wave resonant structure BAWR and the Lamb wave resonant structure LWR to be formed simultaneously in the same process, thereby reducing the manufacturing cost of the resonant filter circuit.

[0075] Alternatively, refer to Figure 26 The process of fabricating the resonant filter structure also includes: fabricating a second electrode layer 150 on the second side of the piezoelectric layer 140; and using the second electrode layer 150 to form a third electrode structure 150a of the bulk acoustic wave resonant structure and a fourth electrode structure 150b of the Lamb wave resonant structure, wherein the third electrode structure 150a corresponds to the first electrode structure 131, and the fourth electrode structure 150b corresponds to the second electrode structure 132. This allows the third electrode structure 150a of the bulk acoustic wave resonant structure BAWR and the fourth electrode structure 150b of the Lamb wave resonant structure LWR to be formed simultaneously in the same process, thereby reducing the manufacturing cost of the resonant filter circuit.

[0076] In addition, refer to Figure 27 The process of fabricating the resonant filter structure also includes: forming a first resonant cavity 1801 between the bulk acoustic wave resonant structure BAWR and the first substrate 210, and forming a second resonant cavity 1802 between the Lamb wave resonant structure LWR and the first substrate 210. This allows the resonant cavity 1801 of the bulk acoustic wave resonant structure BAWR and the resonant cavity 1802 of the Lamb wave resonant structure LWR to be formed simultaneously in the same process, thereby reducing the manufacturing cost of the resonant filter circuit.

[0077] Optionally, the method further includes: bonding a second substrate to a resonant filter structure using a bonding layer, wherein the second substrate includes a central region and an edge region. The central region covers both the acoustic resonant structure and the Lamb wave resonant structure; and the bonding layer corresponds to the edge region on the first side of the second substrate.

[0078] Specifically, such as Figure 28 As shown, the method includes forming a bonding layer 240, which is located on the side of the first electrode layer 130 away from the piezoelectric layer 140, i.e., the bonding layer 240 is located on the side of the seed layer 120 away from the piezoelectric layer 140, and the bonding layer 240 also covers the exposed surface of the piezoelectric layer 140.

[0079] Optionally, the bonding layer 240 is made of SiO2 or SiNx, and the forming process can be PVD or CVD. In another embodiment of this application, the bonding layer 240 is a dry film material similar to photoresist, which is formed by spin coating, photolithography and other processes. This application does not limit this and it depends on the specific circumstances.

[0080] Furthermore, such as Figure 29 As shown, the bonding layer 240 is etched to form a space in the central region for constructing the resonant cavity 2400.

[0081] Then as Figure 30 As shown, a second substrate 250 is bonded to the bonding layer 240. The central region of the second substrate 250 covers the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR, and the bonding layer 240 corresponds to the edge region of the first side of the second substrate 250. A third resonant cavity 2400 is also formed between the resonant filter structure and the second substrate 250. The bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR share this third resonant cavity 2400. Therefore, this embodiment, on the one hand, protects the resonant filter structure through the second substrate, and on the other hand, forms a resonant cavity shared by the bulk acoustic wave resonator structure and the Lamb wave resonator structure in the same process, thereby further reducing the process cost of constructing the resonant filter circuit.

[0082] Optionally, the method further includes forming a conductive electrode on a second side of the second substrate that is electrically connected to the bulk acoustic resonant structure and the Lamb wave resonant structure.

[0083] Specifically, such as Figure 31 As shown, vias 2501 and 2502 are formed through the second substrate 250 and the bonding layer 240. Via 2501 exposes the conductive layer 230, while via 2502 exposes the conductive layer 220.

[0084] Then, as Figure 31 As shown, conductive electrodes 270a and 207b, electrically connected to the conductive layers 220 and 230, are formed on the second side of the second substrate 250. Thus, the conductive electrodes 207a and 207b are electrically connected to the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR. Optionally, the conductive layers 220 and 230 can be made of materials such as Au, Cu, or Al, and can be formed by methods such as PVD or electroplating.

[0085] Optionally, such as Figure 4 As shown, the process of forming conductive electrodes electrically connected to the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR on the second side of the second substrate 250 further includes forming a first conductive electrode 270a and a second conductive electrode 270b on the second side of the second substrate 250. The first conductive electrode 270a is electrically connected to the second electrode layer 150 via a through-hole, and the second conductive electrode is electrically connected to the first interdigitated electrode 132b of the second electrode structure via a through-hole. Thus, a series structure between the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR is realized in this way.

[0086] Furthermore, according to a modification of this embodiment, the process includes: fabricating a first substrate 210 and a resonant filter structure, wherein the resonant filter structure is formed on a first side of the first substrate 210, the resonant filter structure includes a bulk acoustic wave resonant structure and a Lamb wave resonant structure, and the bulk acoustic wave resonant structure and the Lamb wave resonant structure are electrically connected, and wherein the bulk acoustic wave resonant structure and the Lamb wave resonant structure share the same piezoelectric layer 140.

[0087] Furthermore, according to a modification of this embodiment, the process of forming conductive electrodes electrically connected to the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR on the second side of the second substrate 250 further includes: forming a first conductive electrode 270a, a second conductive electrode 270b, and a third conductive electrode 260a on the second side of the second substrate 250. Specifically, the first conductive electrode 270a is electrically connected to the second electrode layer 150 via a via, the second conductive electrode 270b is electrically connected to the first interdigital electrode 132b of the second electrode structure 132 via a via, and the third conductive electrode 260a is electrically connected to the second interdigital electrode 132a of the first electrode structure 131 and the second electrode structure 132 via a via. The resulting resonant filter is as follows: Figure 5 and Figures 24-31 As shown. The specific forming process can be... Figures 32-35 Based on the process shown, adjustments can be made to the third conductive electrode 260a and the corresponding through-hole and conductive layer 230b, which will not be elaborated here. In this way, a parallel structure between the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR is realized.

[0088] Furthermore, according to a modification of this embodiment, the method further includes forming a conductive electrode electrically connected to the bulk acoustic wave resonant structure BAWR and the Lamb wave resonant structure LWR on the second side of the first substrate 210.

[0089] For specific references Figure 32 As shown. Among them Figure 33This is a schematic diagram of the layer structure after bonding the second substrate 250 according to this modification. The second electrode layer 150 is also partially etched at its edge regions, and the etched areas are covered by the sacrificial layer 180, which is used to form vias and conductive electrodes.

[0090] Then refer to Figure 34 As shown, the resonant filter is flipped upside down, so that the first substrate 210 is located on the top side of the device.

[0091] Then refer to Figure 35 As shown, vias 2101 to 2103 are formed from the first substrate 210. Via 2101 penetrates the first substrate 210, bonding layer 200, cutoff boundary layer 190, sacrificial layer 180, and piezoelectric layer 140, thereby exposing the first electrode structure 131. Via 2102 penetrates the first substrate 210, bonding layer 200, cutoff boundary layer 190, sacrificial layer 180, and dielectric layer 160, thereby exposing the second electrode layer 150. Via 2103 penetrates the first substrate 210, bonding layer 200, cutoff boundary layer 190, sacrificial layer 180, and piezoelectric layer 140, thereby exposing the first interdigitated electrode 132b of the second electrode structure.

[0092] Then, refer to Figure 34 As shown, conductive electrodes 260b, 270c and 270d are formed on the second side of the first substrate 210, thereby conducting electrical connections with the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR through through-holes.

[0093] Thus, the through-hole conductive structure used to connect the conductive electrode and the bulk acoustic wave resonator structure BAWR and the through-hole conductive structure used to connect the conductive electrode and the bulk acoustic wave resonator structure LWR are formed on the first substrate 210, and sequentially penetrate the solid material layers such as the cutoff boundary layer, sacrificial layer, dielectric layer, and piezoelectric layer. Since these layers are mainly composed of solid materials with high mechanical strength and toughness, the risk of breakage caused by weak material connections (such as bonding layers) can be significantly reduced during perforation, the local stress concentration that may be introduced by the perforation operation is reduced, and the breakage of the filter device caused by perforation during manufacturing and use is greatly reduced, thereby improving the reliability and stability of the filter device.

[0094] Optionally, refer to Figure 35 and Figure 6As shown, the process of forming conductive electrodes electrically connected to the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR on the second side of the first substrate 210 includes forming a fourth conductive electrode 270c, a fifth conductive electrode 270d, and a sixth conductive electrode 260b on the second side of the first substrate 210. Specifically, the fourth conductive electrode 270c is electrically connected to the second electrode layer 150 via a via; the fifth conductive electrode 270d is electrically connected to the first interdigital electrode 132b of the second electrode structure 132 via a via; and the sixth conductive electrode 260b is electrically connected to the second interdigital electrode 132a of the first electrode structure 131 and the second electrode structure 132 via a via. This electrical connection achieves a parallel structure between the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR (see reference). Figure 7 (As shown).

[0095] Optionally, such as Figure 3 As shown, the process of forming conductive electrodes electrically connected to the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR on the second side of the first substrate 210 includes forming a fourth conductive electrode 270c and a fifth conductive electrode 270d on the second side of the first substrate 210. The fourth conductive electrode 270c is electrically connected to the second electrode layer 150 via a via; and the fifth conductive electrode 270d is electrically connected to the first interdigital electrode 132b of the second electrode structure 132 via a via. Thus, through this electrical connection, a series structure between the bulk acoustic wave resonator structure BAWR and the Lamb wave resonator structure LWR is realized (see reference). ​ (As shown).

[0096] The method for fabricating the resonant filter described in this embodiment can simultaneously fabricate bulk acoustic resonant structures and Lamb wave resonant structures in the same set of processing steps, thereby reducing the process cost of constructing resonant filter circuits.

[0097] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this disclosure. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0098] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0099] In the description of this disclosure, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of describing this disclosure and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this disclosure; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0100] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for fabricating a resonant filter, characterized in that, include: A first substrate and a resonant filter structure are fabricated, wherein the resonant filter structure is formed on a first side of the first substrate, the resonant filter structure includes a bulk acoustic wave resonant structure and a Lamb wave resonant structure, and the bulk acoustic wave resonant structure and the Lamb wave resonant structure are electrically connected, and wherein... The bulk acoustic resonant structure includes a first electrode structure, and the Lamb wave resonant structure includes a second electrode structure. The second electrode structure includes a first interdigital electrode and a second interdigital electrode. The first electrode structure and the second electrode structure share the same first electrode layer. The first interdigital electrode is electrically connected to the outside, and the second interdigital electrode is electrically connected to the first electrode structure.

2. The method according to claim 1, characterized in that, The bulk acoustic resonant structure and the Lamb wave resonant structure share the same piezoelectric layer.

3. The method according to claim 2, characterized in that, The second electrode structure includes interdigitated electrodes, and a first side of the piezoelectric layer is adjacent to the first electrode layer.

4. The method according to claim 3, characterized in that, The process of fabricating the resonant filter structure also includes: A second electrode layer is fabricated on the second side of the piezoelectric layer; and The second electrode layer is used to form the third electrode structure of the bulk acoustic resonant structure and the fourth electrode structure of the Lamb wave resonant structure, wherein... The third electrode structure corresponds to the first electrode structure, and the fourth electrode structure corresponds to the second electrode structure.

5. The method according to claim 4, characterized in that, The process of fabricating the resonant filter structure also includes: A first resonant cavity is formed between the bulk acoustic resonant structure and the first substrate, and a second resonant cavity is formed between the Lamb wave resonant structure and the first substrate.

6. The method according to claim 5, characterized in that, Also includes: The second substrate is bonded to the resonant filter structure using a bonding layer, wherein The second substrate includes a central region and an edge region, wherein the central region covers the bulk acoustic resonant structure and the Lamb wave resonant structure; and The bonding layer corresponds to the edge region of the first side of the second substrate.

7. The method according to claim 6, characterized in that, It also includes forming a conductive electrode on the second side of the second substrate that is electrically connected to the bulk acoustic resonant structure and the Lamb resonant structure.

8. The method according to claim 7, characterized in that, The process of forming conductive electrodes electrically connected to the bulk acoustic wave resonant structure and the Lamb wave resonant structure on the second side of the second substrate further includes: forming a first conductive electrode and a second conductive electrode on the second side of the second substrate, wherein... The first conductive electrode is electrically connected to the second electrode layer via a through-hole, and the second conductive electrode is electrically connected to the first interdigital electrode of the second electrode structure via a through-hole.

9. The method according to claim 8, characterized in that, The process of forming conductive electrodes electrically connected to the bulk acoustic wave resonant structure and the Lamb wave resonant structure on the second side of the second substrate further includes: forming a first conductive electrode, a second conductive electrode, and a third conductive electrode on the second side of the second substrate, wherein... The first conductive electrode is electrically connected to the second electrode layer via a through-hole, the second conductive electrode is electrically connected to the first interdigital electrode of the second electrode structure via a through-hole, and the third conductive electrode is electrically connected to the second interdigital electrode of the first electrode structure and the second electrode structure via a through-hole.

10. The method according to claim 6, characterized in that, It also includes forming a conductive electrode on the second side of the first substrate that is electrically connected to the bulk acoustic resonant structure and the Lamb resonant structure.

11. The method according to claim 10, characterized in that, The process of forming conductive electrodes electrically connected to the bulk acoustic wave resonant structure and the Lamb wave resonant structure on the second side of the first substrate includes forming a fourth conductive electrode and a fifth conductive electrode on the second side of the first substrate, wherein... The fourth conductive electrode is electrically connected to the second electrode layer via a through-hole; and The fifth conductive electrode is electrically connected to the first interdigital electrode of the second electrode structure via a through hole.

12. The method according to claim 10, characterized in that, The process of forming conductive electrodes electrically connected to the bulk acoustic wave resonant structure and the Lamb wave resonant structure on the second side of the first substrate includes forming a fourth conductive electrode, a fifth conductive electrode, and a sixth conductive electrode on the second side of the first substrate, wherein... The fourth conductive electrode is electrically connected to the second electrode layer via a through-hole; The fifth conductive electrode is electrically connected to the first interdigital electrode of the second electrode structure via a through-hole; and the sixth conductive electrode is electrically connected to the second interdigital electrode of both the first electrode structure and the second electrode structure via a through-hole.

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