Bulk acoustic wave resonator, method of manufacturing the same, and filter

Abstract

The application relates to the technical field of acoustic devices, and discloses a bulk acoustic resonator, a manufacturing method thereof and a filter, wherein the bulk acoustic resonator comprises a piezoelectric material layer, a first electrode layer, a second electrode layer, a pad structure layer, a carrier structure and a cover structure; the piezoelectric material layer comprises a piezoelectric layer, the first electrode layer comprises a first electrode, the second electrode layer comprises a second electrode and an additional electrode, the piezoelectric layer is located between the first electrode and the second electrode, an interconnection pad is connected with the first electrode and connected with the additional electrode through a first connecting via hole penetrating through the piezoelectric material layer; the cover structure has a first cavity between the piezoelectric layer, and the carrier structure has a second cavity between the piezoelectric layer; the bulk acoustic resonator further comprises a first functional groove penetrating through the piezoelectric material layer, and a normal projection of the first functional groove on the piezoelectric material layer is arranged around a normal projection of the first cavity on the piezoelectric material layer. The application can improve product yield and product stability.

Description

[0001] This application claims priority to international patent application No. PCT / CN2026 / 106616, filed on June 26, 2026, entitled "Bulk Acoustic Resonator and Method for Fabrication Thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of acoustic device technology, such as a bulk acoustic resonator and its fabrication method, and a filter. Background Technology

[0003] Currently, with the rapid development of mobile communication technology, filters based on resonators are increasingly widely used in communication devices such as smartphones. A film bulk acoustic resonator (FBAR) typically consists of a piezoelectric material layer, a carrier structure, and a cover structure, with resonator units disposed on the piezoelectric material layer.

[0004] In related technologies, the resonator unit includes a piezoelectric layer located in the piezoelectric material layer, and upper and lower electrodes located on the upper and lower sides of the piezoelectric layer; a first cavity can be formed between the cover structure and the piezoelectric material layer, and a second cavity can be formed between the carrier structure and the piezoelectric material layer, with the resonator unit located between the first cavity and the second cavity.

[0005] In the process of implementing the embodiments of this disclosure, at least the following problems were found in the related art: The related technology causes buckling deformation of the piezoelectric material layer during the formation of the second cavity, affecting product yield and product stability.

[0006] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of protection of these embodiments, but rather as a prelude to the detailed description that follows.

[0008] This disclosure provides a bulk acoustic wave resonator and its manufacturing method, as well as a filter, to avoid buckling deformation of the piezoelectric material layer, thereby improving product yield and product stability.

[0009] In some embodiments, the bulk acoustic wave resonator includes: a piezoelectric material layer having a first side and a second side opposite to each other in a first direction; a first electrode layer disposed on the first side of the piezoelectric material layer; a second electrode layer disposed on the second side of the piezoelectric material layer; a pad structure layer including interconnect pads; a carrier structure located on the side of the piezoelectric material layer and the second electrode layer away from the first electrode layer; and a cover structure located on the side of the piezoelectric material layer and the first electrode layer away from the second electrode layer; wherein the piezoelectric material layer includes a piezoelectric layer, the first electrode layer includes a first electrode, the second electrode layer includes a second electrode and an additional electrode, the piezoelectric layer is located between the first electrode and the second electrode, the interconnect pads are connected to the first electrode and connected to the additional electrode through a first connection via penetrating the piezoelectric material layer; a first cavity is formed between the cover structure and the piezoelectric material layer, at least a portion of the first electrode is located in the first cavity, and a second cavity is formed between the carrier structure and the piezoelectric layer, a portion of the second electrode is located in the second cavity; the bulk acoustic wave resonator further includes a first functional slot penetrating the piezoelectric material layer, the orthographic projection of the first functional slot on the piezoelectric material layer being disposed around the orthographic projection of the first cavity on the piezoelectric material layer.

[0010] Optionally, the bulk acoustic wave resonator further includes: a bonding pad, comprising a first bonding pad portion and a second bonding pad portion, wherein the first bonding pad portion is located in a first functional groove and is in contact with the bottom and sidewall of the first functional groove, and the second bonding pad portion is connected to the first bonding pad portion and is located on the side of the piezoelectric material layer away from the carrier structure.

[0011] Optionally, the second electrode layer further includes a protective electrode located between the first functional groove and the carrier structure, wherein the protective electrode is disposed in contact with the first pad portion, and the orthogonal projection of the protective electrode on the piezoelectric material layer covers the orthogonal projection of the bottom of the first functional groove on the piezoelectric material layer.

[0012] Optionally, the second electrode layer includes: a second electrode body layer located on the side of the piezoelectric material layer away from the first electrode layer; and an edge frame layer located on the side of the second electrode body layer away from the piezoelectric material layer, wherein the second electrode includes a second electrode body and an edge frame located at the edge of the second electrode body, and the protective electrode includes a first sub-protective electrode and a second sub-protective electrode stacked together, the second electrode body and the first sub-protective electrode being located in the second electrode body layer, and the edge frame and the second sub-protective electrode being located in the edge frame layer.

[0013] Optionally, the second electrode further includes a frequency adjustment electrode located on the second electrode body and configured to adjust the frequency.

[0014] Alternatively, the bonding pads can be floated or grounded.

[0015] Optionally, the cover structure includes: a cover plate, a groove located within the cover plate, wherein the cover plate includes a support portion located at the edge of the groove, the support portion being connected to the bonding pads via an adhesive layer, and the groove forming a first cavity.

[0016] Optionally, the thickness of the adhesive layer is less than 3 micrometers.

[0017] Optionally, the thickness of the adhesive layer is less than 1 micrometer.

[0018] Optionally, the cover structure includes: a cover plate, a groove located within the cover plate; and a metal pad, wherein the cover plate includes a support portion located at the edge of the groove, and the metal pad is located on the side of the support portion near the bonding pad and is bonded to the bonding pad, so that the groove forms a first cavity.

[0019] Optionally, the width of the first functional slot can range from 1 micrometer to 20 micrometers.

[0020] Optionally, the width of the first functional slot can range from 3 micrometers to 8 micrometers.

[0021] Optionally, the carrier structure includes: a carrier substrate; and a second functional groove, wherein the second functional groove penetrates at least through the carrier substrate, and the orthographic projection of the second functional groove on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer.

[0022] Optionally, the orthographic projection of the second functional groove on the piezoelectric material layer overlaps with the orthographic projection of the first functional groove on the piezoelectric material layer.

[0023] Optionally, the carrier structure further includes: a carrier bonding layer located on the carrier substrate; a cavity boundary layer located on the side of the carrier bonding layer away from the carrier substrate; and a supporting dielectric layer located between the cavity boundary layer and the piezoelectric material layer, and disposed around the second cavity.

[0024] Optionally, the bulk acoustic wave resonator further includes: a first conductive connection layer; and a first via, wherein the cavity boundary layer includes a first contact opening, the first via penetrates the carrier substrate and the carrier bonding layer, and exposes at least a portion of the additional electrode through the first contact opening, the first conductive connection layer is at least partially located on the side of the carrier structure away from the piezoelectric material layer, and is electrically connected to the additional electrode through the first via.

[0025] Optionally, the second functional slot also penetrates the carrier bonding layer and is positioned in contact with the cavity boundary layer.

[0026] Optionally, the bulk acoustic wave resonator further includes: a first passivation layer located between the second electrode layer and the carrier structure; a first conductive connection layer; and a first via, wherein the first via penetrates the carrier substrate, the carrier bonding layer, the cavity boundary layer and the first passivation layer, and exposes at least a portion of the additional electrode, and the first conductive connection layer is at least partially located on the side of the carrier structure away from the piezoelectric material layer, and is electrically connected to the additional electrode through the first via.

[0027] Optionally, the second functional groove also penetrates the carrier bonding layer, the cavity boundary layer and the supporting dielectric layer, and is disposed in contact with the first passivation layer.

[0028] Optionally, the bulk acoustic resonator further includes: a second conductive connection layer; and a second via located in the carrier structure, wherein the second conductive connection layer is at least partially located on the side of the carrier structure away from the piezoelectric material layer, and is electrically connected to the second electrode through the second via.

[0029] Optionally, the bulk acoustic resonator further includes: an insulating layer located on the side of the first conductive connection layer away from the piezoelectric material layer; and a first conductive bump and a second conductive bump located on the side of the insulating layer away from the piezoelectric material layer, wherein the first conductive bump is electrically connected to the first conductive connection layer through a third via in the insulating layer, and the second conductive bump is electrically connected to the second conductive connection layer through a fourth via in the insulating layer.

[0030] Optionally, the orthographic projection of at least one of the first conductive bump and the second conductive bump on the piezoelectric material layer overlaps with the orthographic projection of the corresponding third or fourth via on the piezoelectric material layer.

[0031] Optionally, the first electrode includes an electrode via communicating with a first connection via to expose at least a portion of the additional electrode, and the interconnect pads are electrically connected to the additional electrode and the first electrode through the electrode via and the first connection via.

[0032] Optionally, the pad structure layer further includes: a first conductive pad located on the surface of a first side of the piezoelectric layer and electrically connected to a second electrode through a second connection via in the piezoelectric layer; and a second conductive pad located on the side of the first electrode away from the piezoelectric layer and electrically connected to the first electrode.

[0033] Optionally, the bulk acoustic resonator includes a plurality of second cavities and a first cavity, wherein the orthographic projection of the plurality of second cavities onto the piezoelectric material layer lies within the orthographic projection of the first cavity onto the piezoelectric material layer.

[0034] Optionally, the bulk acoustic resonator further includes: a first passivation layer located between the second electrode layer and the carrier structure; wherein the first passivation layer includes a passivation layer opening that exposes the portion of the second electrode located in the second cavity.

[0035] In some embodiments, a method for fabricating a bulk acoustic resonator includes: sequentially forming a first electrode layer, a piezoelectric material layer, and a second electrode layer, wherein the first electrode layer and the second electrode layer are respectively located on a first side and a second side opposite to each other in a first direction of the piezoelectric material layer; performing a patterning process on the second electrode layer to form a second electrode and an additional electrode spaced apart from each other; forming a carrier structure on the side of the piezoelectric material layer and the second electrode layer away from the first electrode layer, wherein the carrier structure includes a sacrificial layer covering a portion of the second electrode; performing a patterning process on the first electrode layer to form a first electrode; performing a patterning process on the piezoelectric material layer to form a piezoelectric layer, a release hole, and a first functional groove; and performing a patterning process on the first electrode layer to form a first electrode; and performing a patterning process on the piezoelectric material layer to form a piezoelectric layer, a release hole, and a first functional groove; and performing a patterning process on the first electrode layer to form a first electrode. A pad structure layer is formed on the side, wherein the pad structure layer includes interconnect pads, the interconnect pads are connected to the first electrode, and are connected to an additional electrode through a first connection via penetrating the piezoelectric material layer; the sacrificial layer of the carrier structure is etched and removed through a release hole, and the space occupied by the sacrificial layer forms a second cavity between the piezoelectric material layer and the carrier structure; a cover structure is bonded to the first side of the piezoelectric material layer, and a first cavity is formed between the cover structure and the piezoelectric material layer, at least a portion of the first electrode is located in the first cavity, wherein the piezoelectric layer is located between the first electrode and the second electrode, a first functional groove penetrates the piezoelectric material layer, and the orthographic projection of the first functional groove on the piezoelectric material layer is arranged around the orthographic projection of the first cavity on the piezoelectric material layer.

[0036] Optionally, the pad structure layer further includes: bonding pads, including a first pad portion and a second pad portion, wherein the first pad portion is located in the first functional groove and is in contact with the bottom and sidewall of the first functional groove, and the second pad portion is connected to the first pad portion and is located on the side of the piezoelectric material layer away from the carrier structure.

[0037] Optionally, the patterning process for the second electrode layer further includes: forming a protective electrode located between the first functional groove and the carrier structure, wherein the protective electrode is disposed in contact with the first pad portion, and the orthogonal projection of the protective electrode on the piezoelectric material layer covers the orthogonal projection of the bottom of the first functional groove on the piezoelectric material layer.

[0038] In some embodiments, the filter includes a bulk acoustic resonator as described above, or a bulk acoustic resonator manufactured using the method described above for manufacturing a bulk acoustic resonator.

[0039] The bulk acoustic resonator, its manufacturing method, and the filter provided in this disclosure can achieve the following technical effects: In this embodiment, since the first functional groove penetrates the piezoelectric material layer, and its orthographic projection onto the piezoelectric material layer surrounds the orthographic projection of the first cavity onto the piezoelectric material layer, the first functional groove can separate the portion of the piezoelectric material layer corresponding to the first cavity from the portion of the piezoelectric material layer outside the first functional groove. Therefore, during the formation of the second cavity, because the piezoelectric material layers inside and outside the first functional groove are separated, the first functional groove can be used for stress relief, thereby preventing buckling deformation of the piezoelectric material layer and improving product yield and stability.

[0040] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0041] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein: Figure 1 This is a schematic diagram of the structure of a bulk acoustic resonator provided in an embodiment of the present disclosure; Figure 2 A planar positional relationship diagram of a first functional slot, a first cavity, and a second cavity in a bulk acoustic resonator provided in this embodiment of the present disclosure; Figure 3 A schematic flowchart illustrating a method for fabricating a bulk acoustic resonator according to an embodiment of this disclosure; Figures 4 to 29 A schematic diagram of the structure formed in a method for manufacturing a bulk acoustic resonator according to an embodiment of this disclosure; Figure 30 A schematic diagram of another bulk acoustic resonator provided in this embodiment of the present disclosure; Figure 31 A schematic diagram of another bulk acoustic resonator provided in this embodiment of the present disclosure; Figure 32 A schematic diagram of another bulk acoustic resonator provided in this embodiment of the present disclosure; Figure 33 A schematic diagram of another bulk acoustic resonator provided in an embodiment of this disclosure. Detailed Implementation

[0042] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0043] The terms "first," "second," etc., used in the technical solutions described in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged 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.

[0044] Unless otherwise stated, the term "multiple" means two or more.

[0045] In this embodiment of the disclosure, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0046] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0047] The term "correspondence" can refer to an association or binding relationship. The correspondence between A and B means that there is an association or binding relationship between A and B.

[0048] Thin-film bulk acoustic resonators typically include a first cavity located between a piezoelectric material layer and a cap structure, and a second cavity located between the piezoelectric material layer and a carrier structure. The fabrication of the second cavity usually involves first forming a sacrificial layer, and then etching it away to form the second cavity between the piezoelectric material layer and the carrier structure. During the formation of the second cavity, the removal of the sacrificial layer causes stress release; severe stress release can easily lead to buckling deformation of the structure, resulting in a decrease in product yield.

[0049] This disclosure provides a bulk acoustic wave resonator. The bulk acoustic wave resonator includes a piezoelectric material layer, a first electrode layer, a second electrode layer, a pad structure layer, a carrier structure, and a cover structure. The piezoelectric material layer has a first side and a second side opposite to each other in a first direction. The first electrode layer is disposed on the first side of the piezoelectric material layer. The second electrode layer is disposed on the second side of the piezoelectric material layer. The pad structure layer includes interconnect pads. The carrier structure is located on the side of the piezoelectric material layer and the second electrode layer away from the first electrode layer. The cover structure is located on the side of the piezoelectric material layer and the first electrode layer away from the second electrode layer. The piezoelectric material layer includes a piezoelectric layer, and the first electrode layer includes a first electrode. The second electrode layer includes a second electrode and an additional electrode. The piezoelectric layer is located between the first electrode and the second electrode. The interconnect pad is connected to the first electrode and to the additional electrode through a first connection via penetrating the piezoelectric material layer. The cover structure has a first cavity between itself and the piezoelectric layer, and at least a portion of the first electrode is located in the first cavity. The carrier structure has a second cavity between itself and the piezoelectric layer, and a portion of the second electrode is located in the second cavity. The bulk acoustic resonator also includes a first functional slot penetrating the piezoelectric material layer. The orthographic projection of the first functional slot on the piezoelectric material layer is arranged around the orthographic projection of the first cavity on the piezoelectric material layer.

[0050] In the bulk acoustic resonator provided in this embodiment, since the first functional slot penetrates the piezoelectric material layer, and the orthographic projection of the first functional slot on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer, the first functional slot can separate the portion of the piezoelectric material layer corresponding to the first cavity from the portion of the piezoelectric material layer outside the first functional slot. Therefore, during the formation of the second cavity, since the piezoelectric material layers inside and outside the first functional slot are separated, the first functional slot can be used for stress relief, thereby preventing buckling deformation of the piezoelectric material layer and improving product yield and stability.

[0051] This disclosure also provides a method for fabricating a bulk acoustic wave resonator, comprising: sequentially forming a first electrode layer, a piezoelectric material layer, and a second electrode layer, wherein the first electrode layer and the second electrode layer are respectively located on a first side and a second side opposite to each other in a first direction; performing a patterning process on the second electrode layer to form a second electrode and an additional electrode spaced apart from each other; forming a carrier structure on the side of the piezoelectric material layer and the second electrode layer away from the first electrode layer, the carrier structure including a sacrificial layer covering a portion of the second electrode; performing a patterning process on the first electrode layer to form a first electrode; performing a patterning process on the piezoelectric material layer to form a piezoelectric layer, a release hole, and a first functional groove; and performing a patterning process on the first electrode layer to form a first electrode; and performing a patterning process on the piezoelectric material layer to form a piezoelectric layer, a release hole, and a first functional groove; and performing a patterning process on the first electrode layer to form a first electrode; and performing a patterning process on the piezoelectric material layer to form a piezoelectric layer, a release hole, and a first functional groove; and performing a patterning process on the first electrode layer to form a first electrode; and performing a patterning process on the piezoelectric material layer to form a first electrode; and performing a patterning process on the second electrode ... A pad structure layer is formed on one side, including interconnect pads connected to a first electrode and connected to an additional electrode through a first connection via penetrating the piezoelectric material layer. The sacrificial layer of the carrier structure is etched and removed through a release hole, and the space occupied by the sacrificial layer forms a second cavity between the piezoelectric material layer and the carrier structure. A cover structure is bonded to the first side of the piezoelectric material layer, and a first cavity is formed between the cover structure and the piezoelectric material layer. At least a portion of the first electrode is located in the first cavity. The piezoelectric layer is located between the first electrode and the second electrode. A first functional groove penetrates the piezoelectric material layer, and the orthographic projection of the first functional groove on the piezoelectric material layer is arranged around the orthographic projection of the first cavity on the piezoelectric material layer.

[0052] In the method for fabricating a bulk acoustic resonator provided in the disclosed embodiments, since the first functional slot penetrates the piezoelectric material layer, and the orthographic projection of the first functional slot on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer, the first functional slot can separate the portion of the piezoelectric material layer corresponding to the first cavity from the portion of the piezoelectric material layer outside the first functional slot. Therefore, during the formation of the second cavity, since the piezoelectric material layers inside and outside the first functional slot are separated, the first functional slot can be used for stress relief, thereby preventing buckling deformation of the piezoelectric material layer and improving product yield and product stability.

[0053] The bulk acoustic resonator and its manufacturing method provided in the embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0054] Figure 1 This is a schematic diagram of the structure of a bulk acoustic resonator provided in an embodiment of the present disclosure; Figure 2 A planar positional relationship diagram of a first functional slot, a first cavity, and a second cavity in a bulk acoustic resonator provided in an embodiment of this disclosure.

[0055] like Figure 1As shown, the bulk acoustic wave resonator 500 includes a resonant main body structure 100, a pad structure layer 200, a carrier structure 300, and a cover structure 400. The resonant main body structure 100 includes a piezoelectric material layer 130, a first electrode layer 110, and a second electrode layer 120. The piezoelectric material layer 130 has a first side and a second side opposite to each other in a first direction. The first direction can be the thickness direction of the piezoelectric material layer, that is, the direction perpendicular to the main surface of the piezoelectric material layer. The first electrode layer 110 is disposed on the first side of the piezoelectric material layer 130, and the second electrode layer 120 is disposed on the second side of the piezoelectric material layer 130. That is, the first electrode layer 110, the piezoelectric material layer 130, and the second electrode layer 120 are stacked.

[0056] like Figure 1 As shown, the carrier structure 300 is located on the side of the piezoelectric material layer 130 and the second electrode layer 120 away from the first electrode layer 110; the cover structure 400 is located on the side of the piezoelectric material layer 130 and the first electrode layer 110 away from the second electrode layer 120; the piezoelectric material layer 130 includes a piezoelectric layer 135, the first electrode layer 110 includes a first electrode 115, the second electrode layer 120 includes a second electrode 125 and an additional electrode 126, and the piezoelectric layer 135 is located between the first electrode 115 and the second electrode 125, thereby generating an inverse piezoelectric effect under the drive of the first electrode 115 and the second electrode 125, thus generating vibration. Therefore, the piezoelectric layer 135, the first electrode 115, and the second electrode 125 can form a resonator unit 510. It should be noted that, although... Figure 1 Only one resonator unit 510 is shown, but embodiments of this disclosure include, but are not limited to, the bulk acoustic resonator may also include multiple resonator units.

[0057] like Figure 1 As shown, the pad structure layer 200 includes interconnect pads 210; the interconnect pads 210 are connected to the first electrode 115 and to the additional electrode 126 through a first connection via 131 penetrating the piezoelectric material layer 130; thus, the additional electrode 126 located on the second side of the piezoelectric material layer 130 can be connected to the first electrode 115 located on the piezoelectric material layer 130 through the interconnect pads 210.

[0058] like Figure 1 As shown, a first cavity RC1 exists between the cover structure 400 and the piezoelectric material layer 130, and at least a portion of the first electrode 115 is located in the first cavity RC1. A second cavity RC2 exists between the carrier structure 300 and the piezoelectric layer 135, and a portion of the second electrode 125 is located in the second cavity RC2. That is, the range of the first cavity RC1 corresponds to the cover structure 400 and the piezoelectric material layer 130, while the second cavity RC2 corresponds to the piezoelectric layer 135 or the second electrode 125, which is also corresponding to the resonator unit.

[0059] like Figure 1 and Figure 2 As shown, the bulk acoustic resonator 500 also includes a first functional slot 133, which penetrates the piezoelectric material layer 130. The orthographic projection of the first functional slot 133 on the piezoelectric material layer 130 is arranged around the orthographic projection of the first cavity RC1 on the piezoelectric material layer 130.

[0060] In the bulk acoustic wave resonator provided in this embodiment, since the first functional slot penetrates the piezoelectric material layer, and the orthographic projection of the first functional slot on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer, the first functional slot can separate the portion of the piezoelectric material layer corresponding to the first cavity from the portion of the piezoelectric material layer outside the first functional slot. Therefore, during the formation of the second cavity, since the piezoelectric material layers inside and outside the first functional slot are separated, the first functional slot can be used for stress relief, thereby preventing buckling deformation of the piezoelectric material layer and improving product yield and stability. It should be noted that in the fabrication of the bulk acoustic wave resonator, multiple bulk acoustic wave resonators are typically fabricated simultaneously on a large-area substrate, and then separated by a cutting process. Therefore, the first functional slot separates the multiple bulk acoustic wave resonators, making them independent and preventing mutual interference, which is beneficial for stress relief. Furthermore, in the reflow soldering and cutting processes of this bulk acoustic wave resonator, the first functional slot can also be used for stress relief, preventing the cover structure or cover plate from collapsing. It should be noted that in the reflow soldering process, the bulk acoustic wave resonator will be heated, which will result in uneven stress.

[0061] In some examples, such as Figure 1 As shown, the first electrode 110 includes an electrode via 112 that penetrates the first electrode 110. The electrode via 112 communicates with the first connection via 131 to expose at least a portion of the additional electrode 126. The interconnect pad 210 is electrically connected to the additional electrode 126 and the first electrode 115 through the electrode via 112 and the first connection via 131. This configuration allows the interconnect pad to be formed on the first electrode, improving the stability of the electrical connection and maximizing the area of ​​the first electrode. It should be noted that the interconnect pad being connected to the additional electrode and the first electrode through the electrode via and the first connection via means that the interconnect pad includes a portion located on the first electrode and a portion extending into the electrode via and the first connection via. The portion on the first electrode forms a stable electrical connection with the first electrode, and the portion extending into the electrode via and the first connection via can form a stable electrical connection with the additional electrode located at the bottom of the first connection via.

[0062] In some examples, such as Figure 1 As shown, the aforementioned pad structure layer 200 further includes a first conductive pad 230 and a second conductive pad 240. The first conductive pad 230 is located on the surface of the first side of the piezoelectric layer 135 and is electrically connected to the second electrode through the second connection via 132 in the piezoelectric layer 135. The second conductive pad 240 is located on the side of the first electrode 115 away from the piezoelectric layer 135 and is electrically connected to the first electrode 115. Therefore, the aforementioned first and second conductive pads can also be used to apply driving signals to the first and second electrodes. For example, the aforementioned first and second conductive pads can be test pads, for instance, used to test the relevant performance of the resonator unit during the manufacturing process of the bulk acoustic wave resonator.

[0063] For example, a second passivation layer 140 is provided on the side of the first electrode 115 away from the piezoelectric layer 135, and a conductive pad 240 is located on the side of the second passivation layer 140 away from the first electrode 115, and is connected to the first electrode 115 through a passivation opening in the second passivation layer 140.

[0064] In some examples, such as Figure 2 As shown, the bulk acoustic resonator 500 includes multiple resonator units 510, each of which includes a second cavity RC2; a first functional slot 133 surrounds a first cavity RC1, and the multiple second cavities RC2 of the multiple resonator units 510 overlap with a first cavity RC1.

[0065] In some examples, such as Figure 2 As shown, the bulk acoustic resonator 500 includes a plurality of second cavities RC2 and a first cavity RC1. The orthogonal projections of the plurality of second cavities RC2 on the piezoelectric material layer 130 are located within the orthogonal projections of the first cavity RC1 on the piezoelectric material layer 130.

[0066] In some examples, such as Figure 1 As shown, the width of the first functional groove 133 ranges from 1 micrometer to 20 micrometers. It should be noted that since the first functional groove has different widths in the thickness direction, the width of the first functional groove described above can be the average width of the first functional groove.

[0067] In some examples, such as Figure 1 As shown, the width of the first functional slot 133 ranges from 3 micrometers to 8 micrometers, for example, 5 micrometers. Therefore, the first functional slot can maintain good stress relief while also having a low width, thus not occupying the device space of the bulk acoustic resonator.

[0068] In some examples, such as Figure 1As shown, the bulk acoustic wave resonator 500 also includes bonding pads 220, which include a first bonding pad portion 221 and a second bonding pad portion 222. The first bonding pad portion 221 is located in the first functional groove 133 and is in contact with the bottom and sidewall of the first functional groove 133. The second bonding pad portion 222 is connected to the first bonding pad portion 221 and is located on the side of the piezoelectric material layer 130 away from the carrier structure 300. Therefore, the bonding pads can prevent etching liquid or etching gas from corroding the carrier structure through the first functional groove during the etching process of the second cavity. Furthermore, the aforementioned bonding pads can also be used for bonding the piezoelectric material layer and the cover structure, thus enabling reuse.

[0069] It should be noted that the bonding pads 220 mentioned above can be located in the pad structure layer 200 mentioned above, that is, the bonding pads 220 and the interconnect pads 210 are disposed on the same layer, that is, they are formed through the same conductive layer and the same patterning process.

[0070] In some examples, such as Figure 1 As shown, the pad structure layer 200 described above may include the interconnect pads 210, bonding pads 220, first conductive pads 230 and second conductive pads 240; that is, the interconnect pads 210, bonding pads 220, first conductive pads 230 and second conductive pads 240 can be fabricated using the same patterning process, thereby saving process steps.

[0071] In some examples, such as Figure 1 As shown, the second electrode layer 120 also includes a protective electrode 122. The protective electrode 122 is located between the first functional groove 133 and the carrier structure 300. The protective electrode 122 is in contact with the first pad portion 220. The orthogonal projection of the protective electrode 122 on the piezoelectric material layer 130 covers the orthogonal projection of the bottom of the first functional groove 133 on the piezoelectric material layer 130. Thus, the protective electrode 122 can cover the bottom of the first functional groove 133, and the protective electrode 122 is in contact with the carrier structure, thereby providing better protection and preventing the etching solution or etching gas from corroding the carrier structure through the first functional groove.

[0072] In some examples, such as Figure 1 As shown, the second electrode layer 120 includes a second electrode body layer 120A and an edge frame layer 120B; the second electrode body layer 120A is located on the side of the piezoelectric material layer 130 away from the first electrode layer 110; the edge frame layer 120B is located on the side of the second electrode body layer 120A away from the piezoelectric material layer 130; the second electrode 125 includes a second electrode body 125A and an edge frame 125B located at the edge of the second electrode body 125A; the edge frame 125B can be used to constrain and limit the acoustic wave energy, and reflect the acoustic wave energy that is easy to leak laterally from the edge back to the central region, thereby significantly improving the performance of the bulk acoustic resonator.

[0073] In some examples, such as Figure 1 As shown, the protective electrode 122 includes a first sub-protective electrode 122A and a second sub-protective electrode 122B stacked together; the second electrode body 125A and the first sub-protective electrode 122A are located in the second electrode body layer 120A, and the edge frame 125B and the second sub-protective electrode 122B are located in the edge frame layer 120B. Therefore, this protective electrode has a better protective effect and can be manufactured using the film layer and patterning process of the second electrode without incurring additional costs.

[0074] In some examples, such as Figure 1 As shown, the second electrode 125 also includes a frequency adjustment electrode 125C, located on the second electrode body 125A, configured to adjust the frequency. This further improves the performance of the bulk acoustic resonator.

[0075] In some examples, such as Figure 1 As shown, the bonding pad 220 is floating, meaning it is not connected to any electrical signal. Therefore, there is no current or voltage flowing through the bonding pad during use, thus avoiding any adverse effects of current or voltage on the bonding effect over long-term use. This extends the lifespan of the bulk acoustic wave resonator.

[0076] In some examples, such as Figure 1 As shown, the bonding pad 220 can also be grounded, thereby achieving electromagnetic shielding and avoiding the generation of parasitic capacitance and parasitic inductance.

[0077] In some examples, such as Figure 1 As shown, the cover structure 400 includes a cover plate 410 and a groove 420 located within the cover plate 410. The cover plate 410 includes a support portion 412 located at the edge of the groove 420. The support portion 412 is connected to the bonding pad 220 via an adhesive layer 430. The groove 420 forms a first cavity RC1. Therefore, the bulk acoustic wave resonator can directly form a groove in the cover plate, and then utilize a portion of the cover plate's thickness to form the first cavity, thereby reducing the adhesive layer thickness and improving sealing performance.

[0078] In typical bulk acoustic wave (SAW) resonators, the cover structure usually consists of only a flat cover plate, which is then bonded to bonding pads on the piezoelectric material layer via a dry film. In this case, to maintain the thickness of the first cavity, the dry film needs to be relatively thick, for example, around 10 micrometers. Since the sealing performance between the piezoelectric material layer and the cover structure mainly depends on the bonding structure between them, a thicker dry film can easily lead to a decrease in sealing performance and reduced airtightness during long-term use. However, in the SAW resonator provided in the example above, a groove can be directly formed in the cover plate, and then a portion of the cover plate's thickness can be used to form the aforementioned first cavity, thereby significantly reducing the thickness of the adhesive layer and thus improving the sealing performance.

[0079] In some examples, such as Figure 1 As shown, the thickness of the adhesive layer 430 can be less than 3 micrometers, or even less than 1 micrometer. Therefore, this adhesive layer can greatly improve the sealing performance.

[0080] In some examples, such as Figure 1 As shown, the carrier structure 300 includes a carrier substrate 310 and a second functional groove 390. The second functional groove 390 penetrates at least through the carrier substrate 310, and its orthographic projection on the piezoelectric material layer 130 surrounds the orthographic projection of the first cavity RC1 on the piezoelectric material layer 130. On one hand, the aforementioned second functional groove can also play a role in stress relief during the formation of the second cavity; on the other hand, in the reflow soldering and cutting processes of this bulk acoustic wave resonator, the second functional groove can also be used for stress relief to prevent the cover structure or cover plate from bursting. It should be noted that in the reflow soldering process, the bulk acoustic wave resonator is heated, resulting in uneven stress distribution; additionally, in the cutting process, there are also issues of uneven stress distribution and stress relief. Therefore, the second functional groove can also be used for stress relief, thereby improving product yield.

[0081] It is worth noting that, in addition to the carrier substrate, the carrier structure described above may also include other film layers, and the second functional groove described above may also penetrate at least a portion of the other film layers, which can be determined according to actual needs and the patterning steps in the manufacturing process.

[0082] In some examples, such as Figure 1 As shown, the orthographic projection of the second functional slot 390 onto the piezoelectric material layer 130 overlaps with the orthographic projection of the first functional slot 133 onto the piezoelectric material layer 130. Therefore, the bulk acoustic resonator can better utilize the first and second functional slots for stress relief. Furthermore, this arrangement also reduces the area occupied by the first and second functional slots.

[0083] In some examples, such as Figure 1As shown, the carrier structure 300 further includes a carrier bonding layer 320, a cavity boundary layer 330, and a supporting dielectric layer 340; the carrier bonding layer 320 is located on the carrier substrate 310; the cavity boundary layer 330 is located on the side of the carrier bonding layer 320 away from the carrier substrate 310; the supporting dielectric layer 340 is located between the cavity boundary layer 330 and the piezoelectric material layer 130, and is disposed around the second cavity RC2. The cavity boundary layer can be used to define the range of the second cavity, and the supporting dielectric layer can be used to support the formation of the second cavity RC2.

[0084] In some examples, such as Figure 1 As shown, the bulk acoustic resonator 500 also includes a first passivation layer 350 located between the second electrode layer 120 and the carrier structure 300. The first passivation layer 350 includes a passivation layer opening 352, which exposes the portion of the second electrode 125 located in the second cavity RC2. Thus, the passivation layer opening prevents corrosion of the first passivation layer during the formation process of the second cavity, thereby avoiding a large surface roughness on the upper surface of the second cavity and reducing acoustic straying caused by the large surface roughness. Consequently, the amplitude ripple (passband ripple) within the passband of the bulk acoustic resonator is significantly reduced, resulting in a flatter amplitude-frequency response. Simultaneously, the quality factor (Q value) of the bulk acoustic resonator can be improved by more than 10%, indicating lower energy loss and stronger frequency selectivity. It should be noted that although this disclosure describes the first passivation layer and the carrier structure separately, the aforementioned first passivation layer can also be considered part of the carrier structure.

[0085] For example, the material of the first passivation layer described above can be aluminum nitride. Of course, the embodiments disclosed herein include, but are not limited to, other materials that can be used for the first passivation layer.

[0086] In some examples, such as Figure 1 As shown, the bulk acoustic wave resonator 500 further includes a first conductive connection layer L1 and a first via V1. The cavity boundary layer 330 includes a first contact opening 331. The first via V1 penetrates the carrier substrate 310 and the carrier bonding layer 320, and exposes at least a portion of the additional electrode 126 through the first contact opening 331. The first conductive connection layer L1 is at least partially located on the side of the carrier structure 300 away from the piezoelectric material layer 130, and is electrically connected to the additional electrode 126 through the first via V1. Thus, the bulk acoustic wave resonator can utilize the first conductive connection layer for interconnection or for applying a driving signal to the first electrode.

[0087] In some examples, such as Figure 1As shown, the second functional groove 390 can be formed using the patterning process for forming the first via V1. Since the cavity boundary layer 330 includes the first contact opening 331, the patterning process for the first via V1 does not require etching the cavity boundary layer 330. Therefore, the second functional groove 390 can stop at the cavity boundary layer 330. Thus, the second functional groove 390 can penetrate the carrier substrate 310 and the carrier bonding layer 320 and make contact with the cavity boundary layer 330. In this case, the second functional groove has a good stress relief effect without the need for additional processes, thus avoiding increased costs.

[0088] In some examples, such as Figure 1 As shown, the bulk acoustic wave resonator 500 further includes a second conductive connection layer L2 and a second via V2. The second via V2 is located within the carrier structure 300. The second conductive connection layer L2 is at least partially located on the side of the carrier structure 300 away from the piezoelectric material layer 130, and is electrically connected to the second electrode 125 through the second via V2. Thus, the bulk acoustic wave resonator can utilize the second conductive connection layer for interconnection and for applying driving signals to the second electrode. It should be noted that although this disclosure describes and explains the first and second conductive connection layers and the carrier structure separately, the aforementioned first and second conductive connection layers can also be considered as part of the carrier structure.

[0089] It should be noted that the first via and the second via described above can be formed using the same patterning process, and the first conductive connection layer and the second conductive connection layer described above can also be formed using the same patterning process. Furthermore, the first conductive connection layer and the second conductive connection layer described above can serve as redistribution layers.

[0090] In some examples, such as Figure 1 As shown, the bulk acoustic wave resonator 500 further includes an insulating layer 360, a first conductive bump 371, and a second conductive bump 372. The insulating layer 360 is located on the side of the first conductive connection layer L1 and the second conductive connection layer L2 away from the piezoelectric material layer 130. The first conductive bump 371 and the second conductive bump 372 are located on the side of the insulating layer 360 away from the piezoelectric material layer 130. The first conductive bump 371 is electrically connected to the first conductive connection layer L1 through a third via V3 located in the insulating layer 360, and the second conductive bump 372 is electrically connected to the second conductive connection layer L2 through a fourth via V4 located in the insulating layer 360. Thus, the bulk acoustic wave resonator can be connected to a circuit board through the first conductive bump and the second conductive bump. It should be noted that although this disclosure describes and explains the insulating layer and the carrier structure separately, the above-mentioned insulating layer can also be regarded as part of the carrier structure.

[0091] In some examples, the first and second conductive bumps described above may be or include solder bumps. It should be noted that the process of forming the first and second conductive bumps may include: forming a bump material layer; and performing a reflow soldering process on the bump material layer. For example, after patterning the insulating layer to form the third and fourth vias described above, a bump material layer may be formed on the insulating layer, which can be connected to the first and second conductive connection layers through the third and fourth vias respectively, and then the first and second conductive bumps may be formed by a reflow soldering process.

[0092] In the bulk acoustic wave resonator provided in the embodiments of this disclosure, the above-described arrangement of each membrane layer in the carrier structure simplifies the formation process of the second functional groove, the first via, and the second via, and reduces the difficulty of forming the second functional groove, the first via, and the second via. Furthermore, the above-described arrangement of each membrane layer in the carrier structure can also improve the structural strength of the carrier structure and the bulk acoustic wave resonator, thereby improving the reliability and device performance of the bulk acoustic wave resonator.

[0093] At least one embodiment of this disclosure also provides a method for manufacturing a bulk acoustic resonator. Figure 3 This is a schematic flowchart illustrating a method for fabricating a bulk acoustic resonator according to an embodiment of this disclosure.

[0094] like Figure 3 As shown, the fabrication method of this bulk acoustic resonator includes the following steps S301-S308.

[0095] Step S301: A first electrode layer, a piezoelectric material layer, and a second electrode layer are formed sequentially; the first electrode layer and the second electrode layer are respectively located on the first and second opposite sides of the piezoelectric material layer in a first direction.

[0096] For example, the first and second electrode layers described above may each include suitable electrode materials, such as metallic materials including molybdenum (Mo), aluminum (Al), copper (Cu), platinum (Pt), tantalum (Ta), tungsten (W), palladium (Pd), ruthenium (Ru), their analogues, alloys, or combinations thereof. The piezoelectric material layer may include suitable piezoelectric materials, such as aluminum nitride (AlN), scandium-doped aluminum nitride (ScAlN), zinc oxide, lithium niobate, lithium tantalate, and other materials with piezoelectric properties. It should be understood that the above materials are merely illustrative examples, and this disclosure is not limited thereto.

[0097] Step S302: The second electrode layer is patterned to form a second electrode and an additional electrode spaced apart from each other. It should be noted that the second electrode layer can be a multilayer composite structure and is not limited to a single conductive film layer.

[0098] For example, the second electrode layer can be patterned using processes such as exposure, development, and etching to form a second electrode and an additional electrode that are spaced apart from each other and insulated from each other.

[0099] Step S303: A carrier structure is formed on the side of the piezoelectric material layer and the second electrode layer away from the first electrode layer. The carrier structure includes a sacrificial layer that covers a portion of the second electrode. It should be noted that the carrier structure described above can also be a composite film layer and includes materials with different etching selectivity ratios, so that a portion of the film layer can serve as an etching stop layer; the sacrificial layer described above can be removed in subsequent processes to form a cavity.

[0100] Step S304: Perform a patterning process on the first electrode layer to form the first electrode.

[0101] Step S305: Perform a patterning process on the piezoelectric material layer to form a piezoelectric layer, a release hole, and a first functional groove. It should be noted that the difference between the piezoelectric layer and the piezoelectric material layer is that the piezoelectric layer is the portion that vibrates under the drive of the electrodes, while the piezoelectric material layer refers to a film layer formed by a single layer of piezoelectric material. For example, when the bulk acoustic resonator includes multiple resonator units, the piezoelectric material layer may include multiple piezoelectric layers. Furthermore, both the release hole and the first functional groove penetrate the piezoelectric material layer.

[0102] Step S306: A pad structure layer is formed on the first side of the piezoelectric material layer. The pad structure layer includes interconnect pads, which are connected to the first electrode and to an additional electrode through a first connection via penetrating the piezoelectric material layer.

[0103] Step S307: The sacrificial layer of the carrier structure is etched and removed through the release hole, and the space occupied by the sacrificial layer forms a second cavity between the piezoelectric material layer and the carrier structure.

[0104] Step S308: Bond the cover structure to the first side of the piezoelectric material layer and form a first cavity between the cover structure and the piezoelectric material layer. At least a portion of the first electrode is located in the first cavity. The piezoelectric layer is located between the first electrode and the second electrode. The first functional groove penetrates the piezoelectric material layer. The orthographic projection of the first functional groove on the piezoelectric material layer is arranged around the orthographic projection of the first cavity on the piezoelectric material layer.

[0105] In the method for fabricating a bulk acoustic wave resonator provided in this embodiment, since the first functional slot penetrates the piezoelectric material layer, and the orthographic projection of the first functional slot on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer, the first functional slot can separate the portion of the piezoelectric material layer corresponding to the first cavity from the portion of the piezoelectric material layer outside the first functional slot. Therefore, during the process of etching and removing the sacrificial layer of the carrier structure through the release hole, since the piezoelectric material layers inside and outside the first functional slot are separated, the first functional slot can be used for stress release, thereby preventing buckling deformation of the piezoelectric material layer and improving product yield and stability. It should be noted that in the fabrication of a bulk acoustic wave resonator, multiple bulk acoustic wave resonators are usually fabricated simultaneously on a large-area substrate, and then separated by a cutting process. Therefore, the first functional slot separates the multiple bulk acoustic wave resonators, making them independent and preventing them from affecting each other, which is beneficial for stress release. On the other hand, in the reflow and cutting processes of the bulk acoustic wave resonator, the first functional slot can also be used for stress relief to prevent the cover structure or cover plate from cracking. It should be noted that in the reflow process, the bulk acoustic wave resonator will be heated, which will result in uneven stress.

[0106] In some examples, in the fabrication method of this bulk acoustic resonator, the aforementioned pad structure layer further includes a bonding pad, comprising a first pad portion and a second pad portion. The first pad portion is located within a first functional groove and is in contact with the bottom and sidewalls of the first functional groove. The second pad portion is connected to the first pad portion and is located on the side of the piezoelectric material layer away from the carrier structure. That is, during the step of forming the aforementioned interconnecting pads, bonding pads are simultaneously formed at the location of the first functional groove. Therefore, the bonding pads can prevent etching liquid or etching gas from corroding the carrier structure through the first functional groove during the etching process of the second cavity. Furthermore, the aforementioned bonding pads can also be used for bonding the piezoelectric material layer and the cover structure, thereby enabling reuse.

[0107] In some examples, the patterning process for the second electrode layer in the fabrication method of this bulk acoustic resonator further includes forming a protective electrode located between the first functional groove and the carrier structure. The protective electrode is in contact with the first pad portion, and the orthogonal projection of the protective electrode on the piezoelectric material layer covers the orthogonal projection of the bottom of the first functional groove on the piezoelectric material layer. In other words, the protective electrode is formed simultaneously during the process of patterning the second electrode layer to form the second electrode and the additional electrode. Thus, the protective electrode can cover the bottom of the first functional groove and is in contact with the protective electrode, thereby jointly providing a protective function to prevent etching solution or etching gas from corroding the carrier structure through the first functional groove.

[0108] Figures 4 to 29This is a schematic diagram of the structure formed in a method for manufacturing a bulk acoustic resonator according to an embodiment of the present disclosure.

[0109] like Figure 4 As shown, a substrate 520 is provided. The substrate 520 may be a semiconductor substrate, such as a silicon substrate, but this disclosure is not limited thereto. The substrate 520 may also be made of other suitable materials, such as a glass substrate, as long as it can provide structural support for the subsequently formed overlay layer. The substrate 520 will be removed in a subsequent process and may also be referred to as a sacrificial substrate. In some embodiments, the substrate 520 is a wafer-level substrate.

[0110] like Figure 5 As shown, a dielectric layer 530 is formed on the substrate 520. The dielectric layer 530 may be an oxide layer, for example, the oxide layer includes silicon oxide (SiO2). The dielectric layer 530 may be formed by a deposition process such as chemical vapor deposition or a thermal oxidation process.

[0111] like Figure 6 As shown, a second passivation layer 140, a first electrode layer 110, a piezoelectric material layer 130, and a second electrode layer 120 are sequentially formed on the dielectric layer 530.

[0112] For example, the second passivation layer 140 may include insulating materials such as aluminum nitride, silicon nitride, similar materials, or combinations thereof. For example, the material layer may be formed using a suitable deposition process such as chemical vapor deposition or physical vapor deposition. The second electrode layer 120 may be a composite electrode layer. Figure 6 In the steps shown, the second electrode body layer 120A of the second electrode layer 120 can be formed first.

[0113] For example, the first electrode layer 110 and the second electrode body layer 120A described above may each include suitable electrode materials, such as metallic materials including molybdenum (Mo), aluminum (Al), copper (Cu), platinum (Pt), tantalum (Ta), tungsten (W), palladium (Pd), ruthenium (Ru), their analogues, alloys, or combinations thereof. The piezoelectric material layer 130 may include suitable piezoelectric materials, such as aluminum nitride (AlN), scandium-doped aluminum nitride (ScAlN), zinc oxide, lithium niobate, lithium tantalate, and other materials with piezoelectric properties. It should be understood that the above materials are merely illustrative examples, and this disclosure is not limited thereto.

[0114] like Figure 7 As shown, a frequency adjustment electrode 125C is formed on the second electrode body layer 120A and configured to adjust the frequency. This further improves the performance of the bulk acoustic resonator. It should be noted that the frequency adjustment electrode 125C can be a single-layer or multi-layer structure; additionally, although... Figure 7Only one frequency adjustment electrode 125C is shown, but embodiments of this disclosure include, but are not limited to, a second electrode layer comprising a plurality of second electrodes, each of which may be provided with a corresponding frequency adjustment electrode.

[0115] like Figure 8 As shown, an edge frame layer 120B is formed on the side of the second electrode body layer 120A and the frequency adjustment electrode 125C away from the substrate 520. The edge frame layer 120B can be used to form an edge frame, which is configured to constrain and limit the acoustic wave energy, reflecting the acoustic wave energy that is prone to lateral leakage from the edge back to the central region, thereby significantly improving the performance of the bulk acoustic resonator. At this time, the aforementioned second electrode body layer, frequency adjustment electrode, and edge frame layer form the second electrode layer.

[0116] For example, the aforementioned edge frame layer includes conductive materials, such as metallic materials including molybdenum (Mo), aluminum (Al), copper (Cu), platinum (Pt), tantalum (Ta), tungsten (W), palladium (Pd), ruthenium (Ru), their analogues, their alloys or combinations thereof, etc. The edge frame layer is electrically connected to the second electrode body layer and may have the same or different materials as the second electrode body layer.

[0117] like Figure 9 As shown, the second electrode layer 120 is patterned to form a second electrode 125, an additional electrode 126, and a protective electrode 122. The second electrode 125 includes a second electrode body 125A, a frequency adjustment electrode 125C, and an edge frame 125B located at the edge of the second electrode body 125A. The edge frame 125B can be used to constrain and limit acoustic wave energy, reflecting acoustic wave energy that easily leaks laterally from the edge back to the central region, thereby significantly improving the performance of the bulk acoustic resonator. The protective electrode 122 includes a first sub-protective electrode 122A and a second sub-protective electrode 122B stacked together. The second electrode body 125A and the first sub-protective electrode 122A are located in the second electrode body layer 120A, and the edge frame 125B and the second sub-protective electrode 122B are located in the edge frame layer 120B. Therefore, this protective electrode has a better protective effect and can be fabricated using the film layer and patterning process of the second electrode without incurring additional costs.

[0118] like Figure 10 As shown, a first passivation layer 350 is formed on the side of the piezoelectric material layer 130 and the second electrode layer 120 away from the first electrode layer 110. The first passivation layer 350 extends along the surface of the second electrode layer 120 and the piezoelectric material layer 130 and fills the gap between the second electrode 125, the auxiliary electrode 126 and the protection electrode 122.

[0119] like Figure 11As shown, a supporting dielectric layer 340 and a sacrificial layer 370 are formed on the side of the first passivation layer 350 away from the piezoelectric material layer 130. For example, the supporting dielectric layer can be formed first, and then the supporting dielectric layer 340 and the sacrificial layer 370 can be formed by a patterning process. The supporting dielectric layer 340 is located on a portion of the protection electrode 122, the auxiliary electrode 126, and a portion of the second electrode 125; the sacrificial layer 370 is located on the side of the second electrode 125 away from the piezoelectric material layer 130.

[0120] like Figure 12 As shown, a cavity boundary layer 330 is formed on the side of the first passivation layer 350, the supporting dielectric layer 340, and the sacrificial layer 370 away from the piezoelectric material layer 130. The cavity boundary layer 330 includes a first contact opening 331 and a second contact opening 332; the first contact opening 331 exposes a portion of the first passivation layer 350 on the additional electrode 126, and the second contact opening 332 exposes a portion of the first passivation layer 350 on the second electrode 125.

[0121] For example, the cavity boundary layer 330 covers the sidewalls of the sacrificial layer 370 and the surface away from the piezoelectric material layer 130, the sidewalls of the supporting dielectric layer 340 and the surface of the supporting dielectric layer 340 away from the piezoelectric material layer 130, and a portion of the surface of the first passivation layer 350. The material of the cavity boundary layer 330 is different from that of the sacrificial layer 370, so that the cavity boundary layer can serve as an etching stop layer during the etching process to remove the sacrificial layer.

[0122] For example, the material of the cavity boundary layer 330 may include semiconductor materials, dielectric materials, the like, or combinations thereof. For instance, the cavity boundary layer 330 may include amorphous silicon, polycrystalline silicon, silicon nitride, aluminum nitride, the like, or combinations thereof, and may be formed by suitable deposition processes such as CVD or atomic layer deposition (ALD).

[0123] like Figure 13 As shown, a carrier bonding layer 320 is formed on the side of the cavity boundary layer 330 away from the piezoelectric material layer 130, and the carrier bonding layer 320 extends into the gap between the first electrode 125 and the auxiliary electrode 126.

[0124] For example, the carrier bonding layer 320 has a first filling portion located at the first contact opening 331 and a second filling portion located at the second contact opening 332.

[0125] like Figure 14As shown, a carrier substrate 310 is formed on the side of the carrier bonding layer 320 away from the piezoelectric material layer 130. For example, the carrier substrate 310 is bonded to the carrier bonding layer 320 by a bonding process. The carrier substrate 310, carrier bonding layer 320, cavity boundary layer 330 and supporting dielectric layer 340 described above can form a carrier structure 300.

[0126] For example, the carrier substrate 310 may include semiconductor materials, dielectric materials, the like, or combinations thereof. For instance, the carrier substrate 310 may include a stack of silicon (Si), silicon oxide (SiO2), polycrystalline silicon, silicon carbide, the like, or combinations thereof.

[0127] like Figure 15 and Figure 16 As shown, the substrate 520 and dielectric layer 530 are removed to expose the surface of the second passivation layer 140 on the side away from the piezoelectric material layer 130.

[0128] like Figure 17 As shown, a patterning process (e.g., including photolithography and etching) is performed on the second passivation layer 140 and the first electrode layer 110 to remove portions of the second passivation layer 140 and the first electrode layer 110, forming a first electrode 115 and an electrode via 112 located in the first electrode 115. The second passivation layer 140 covers the surface of the first electrode 115 on the side away from the piezoelectric material layer 130. In addition, the patterning process also forms a portion of a release hole 540 (located in the second passivation layer and the first electrode layer) in the second passivation layer 140 and the first electrode layer 110.

[0129] like Figure 18 As shown, the piezoelectric material layer 130 is patterned to form a piezoelectric layer 135, a first functional groove 133, a first connection via 131, a second connection via 132, and another portion of the release hole 540 (located within the piezoelectric material layer). The first functional groove 133 is located around the piezoelectric layer 135, and the first connection via 131 and the second connection via 132 are located within the piezoelectric layer 135. The first connection via 131 communicates with the electrode via 112.

[0130] like Figure 19 As shown, the second passivation layer 140 is further patterned to remove the portion around the electrode via 112, thereby facilitating connection with subsequent interconnect pads.

[0131] like Figure 20 As shown, a pad structure layer 200 is formed on the second passivation layer 140 and the piezoelectric material layer 130. The pad structure layer 200 includes interconnect pads 210, bonding pads 220, a first conductive pad 230, and a second conductive pad 240.

[0132] For example, the interconnect pad 210 is connected to the first electrode 115 and to the additional electrode 126 through the first connection via 131 penetrating the piezoelectric material layer 130; thus, the additional electrode 126 located on the second side of the piezoelectric material layer 130 can be connected to the first electrode 115 located on the piezoelectric material layer 130 through the interconnect pad 210.

[0133] For example, the bonding pad 220 includes a first pad portion 221 and a second pad portion 222. The first pad portion 221 is located within the first functional groove 133 and is in contact with the bottom and sidewalls of the first functional groove 133. The second pad portion 222 is connected to the first pad portion 221 and is located on the side of the piezoelectric material layer 130 away from the carrier structure 300. Therefore, this bonding pad can prevent the etching solution or etching gas from corroding the carrier structure through the first functional groove during the subsequent etching process to remove the sacrificial layer. On the other hand, the aforementioned bonding pad can also be used for bonding the piezoelectric material layer and the cap structure, thus enabling reuse.

[0134] For example, the first conductive pad 230 is located on the surface of the first side of the piezoelectric layer 135 and is electrically connected to the second electrode through the second connection via 132 in the piezoelectric layer 135; the second conductive pad 240 is located on the side of the first electrode 115 away from the piezoelectric layer 135 and is electrically connected to the first electrode 115. Thus, the first and second conductive pads described above can also be used to apply driving signals to the first and second electrodes. For example, the first and second conductive pads described above can be test pads, for example, used to test the relevant performance of the resonator unit during the manufacturing process of the bulk acoustic resonator.

[0135] like Figure 21 As shown, the sacrificial layer 370 is etched through the release hole 540 and removed. The space occupied by the sacrificial layer 370 forms a second cavity RC2 between the piezoelectric material layer 130 and the carrier structure 300.

[0136] For example, an etchant can be applied to the area where the sacrificial layer 370 is located through the aforementioned release hole 540, thereby removing the sacrificial layer 370 and forming a second cavity RC2 in the location previously occupied by the sacrificial layer 370. The etchant may include, for example, a buffer oxide etching (BOE) or hydrofluoric acid (e.g., diluted hydrofluoric acid (DHF)). The buffer oxide etchant is a mixture of hydrofluoric acid (HF) and NH4F. Because the etching process has a high etching selectivity for the sacrificial layer 370 and the cavity boundary layer 330, the etchant is confined to the area surrounded by the cavity boundary layer 330, and the second cavity RC2 is formed in this area.

[0137] like Figure 22As shown, a cover plate 410 is provided, and the cover plate 410 is ground and etched to form a groove 420 on the cover plate 410. At this time, the cover plate 410 includes a support portion 412 located at the edge of the groove 420, which is configured to form a subsequent first cavity. Thus, the bulk acoustic resonator can directly form a groove in the cover plate, and then utilize a portion of the thickness of the cover plate itself to form the first cavity, thereby allowing for a lower adhesive layer thickness and improved sealing performance.

[0138] For example, the material of the cover plate 410 may be the same as or different from the material of the carrier substrate 310. For instance, the material of the cover plate 410 may be or may include semiconductor materials, insulating materials, piezoelectric materials, etc., such as high-resistivity silicon, low-resistivity silicon, glass, silicon carbide, lithium niobate (LiNbO3), lithium carbonate (LiTaO3), etc. For example, the cover plate 410 may be a wafer, such as a silicon wafer or other semiconductor wafer.

[0139] like Figure 23 As shown, the cover plate 410 and Figure 20 The structure shown is bonded. For example, the support 412 is connected to the bonding pad 220 via an adhesive layer 430, and the aforementioned groove 420 forms the first cavity RC1. In typical bulk acoustic wave resonators, the cover structure usually consists of only a flat cover plate, which is then bonded to the bonding pads on the piezoelectric material layer via a dry film. In this case, to maintain the thickness of the first cavity, the dry film needs to be relatively thick, for example, about 10 micrometers. Since the sealing performance between the piezoelectric material layer and the cover structure mainly depends on the bonding structure between the piezoelectric material layer and the cover structure, a thicker dry film is prone to causing a decrease in sealing performance and reduced airtightness during long-term use. However, in the bulk acoustic wave resonator provided in the above example, the groove can be formed directly in the cover plate, and then a portion of the thickness of the cover plate itself can be used to form the aforementioned first cavity, thereby greatly reducing the thickness of the adhesive layer and thus improving the sealing performance.

[0140] In some examples, such as Figure 23 As shown, the thickness of the adhesive layer 430 can be less than 3 micrometers, or even less than 1 micrometer. Therefore, this adhesive layer can greatly improve the sealing performance. For example, the adhesive layer 340 can be an organic adhesive layer.

[0141] like Figure 24 As shown, the carrier substrate 310 is thinned by a process such as grinding.

[0142] like Figure 25 As shown, the carrier structure 300 is etched to form a second functional groove 390, a first via V1, and a second via V2 in the carrier structure 300.

[0143] For example, the second functional groove 390 penetrates the carrier substrate 310 and the carrier bonding layer 320, and stops at the cavity boundary layer 330. The orthographic projection of the second functional groove 390 on the piezoelectric material layer 130 surrounds the orthographic projection of the first cavity RC1 on the piezoelectric material layer 130. On the one hand, the aforementioned second functional groove can also play a role in stress relief during the formation of the second cavity; on the other hand, in the reflow soldering and cutting processes of this bulk acoustic wave resonator, the second functional groove can also be used for stress relief to prevent the cover structure or cover plate from breaking off. It should be noted that in the reflow soldering process, the bulk acoustic wave resonator will be heated, resulting in uneven stress; in addition, in the cutting process, there will also be problems of uneven stress and stress relief. Therefore, the second functional groove can also be used for stress relief, thereby improving product yield.

[0144] For example, a first via V1 penetrates the carrier substrate 310 and the carrier bonding layer 320 and exposes at least a portion of the additional electrode 126 through a first contact opening 331; a second via V2 penetrates the carrier substrate 310 and the carrier bonding layer 320 and exposes at least a portion of the second electrode 125 through a second contact opening 332.

[0145] like Figure 26 As shown, a first conductive connection layer L1 and a second conductive connection layer L2 are formed on the side of the carrier substrate 310 away from the piezoelectric material layer 130; the first conductive connection layer L1 is at least partially located on the side of the carrier structure 300 away from the piezoelectric material layer 130 and is electrically connected to the additional electrode 126 through a first via V1; the second conductive connection layer L2 is at least partially located on the side of the carrier structure 300 away from the piezoelectric material layer 130 and is electrically connected to the second electrode 125 through a second via V2.

[0146] like Figure 27 As shown, an insulating layer 360 is formed on the side of the carrier substrate 310, the first conductive connection layer L1 and the second conductive connection layer L2 away from the piezoelectric material layer 130, and a third via V3 and a fourth via V4 are formed on the insulating layer 360.

[0147] like Figure 28 and Figure 29 As shown, a first conductive bump 371 and a second conductive bump 372 are formed on the side of the insulating layer 360 away from the carrier substrate 310. The first conductive bump 371 is electrically connected to the first conductive connection layer L1 through a third via V3 located in the insulating layer 360, and the second conductive bump 372 is electrically connected to the second conductive connection layer L2 through a fourth via V4 located in the insulating layer 360. Thus, the bulk acoustic wave resonator can be connected to the circuit board through the first and second conductive bumps.

[0148] For example, the first conductive bump 371 and the second conductive bump 372 described above may be or include solder bumps. For example, forming the first conductive bump 371 and the second conductive bump 372 may include forming bump material and performing a reflow soldering process on the bump material.

[0149] Figure 30 A schematic diagram of another bulk acoustic resonator provided in an embodiment of this disclosure. Figure 30 As shown, the cavity boundary layer 330 may not have the aforementioned first contact opening and second contact opening; then, the aforementioned first via V1, second via V2, and second functional groove 390 can be formed in the carrier substrate, carrier bonding layer, and cavity boundary layer by an etching process. Therefore, this bulk acoustic wave resonator can reduce one masking process, thereby reducing the risk of corrosion of the carrier bonding layer.

[0150] For example, such as Figure 30 As shown, the second functional groove 390 penetrates the carrier substrate 310, the carrier bonding layer 320, the cavity boundary layer 330 and the support dielectric layer 340, and is in contact with the first passivation layer 350.

[0151] Figure 31 This is a schematic diagram of another bulk acoustic resonator provided in an embodiment of this disclosure. The bulk acoustic resonator shown in 31... Figure 1 The first passivation layer of the bulk acoustic resonator shown is improved. Figure 1 The first passivation layer of the bulk acoustic resonator shown has an opening, while Figure 31 The first passivation layer of the bulk acoustic resonator shown does not have an opening.

[0152] like Figure 31 As shown, the bulk acoustic wave resonator 500 includes a resonant main body structure 100, a pad structure layer 200, a carrier structure 300, and a cover structure 400. The resonant main body structure 100 includes a piezoelectric material layer 130, a first electrode layer 110, and a second electrode layer 120. The piezoelectric material layer 130 has a first side and a second side opposite to each other in a first direction, wherein the first direction may be the thickness direction of the piezoelectric material layer. The first electrode layer 110 is disposed on the first side of the piezoelectric material layer 130, and the second electrode layer 120 is disposed on the second side of the piezoelectric material layer 130. That is, the first electrode layer 110, the piezoelectric material layer 130, and the second electrode layer 120 are stacked.

[0153] like Figure 31As shown, the carrier structure 300 is located on the side of the piezoelectric material layer 130 and the second electrode layer 120 away from the first electrode layer 110; the cover structure 400 is located on the side of the piezoelectric material layer 130 and the first electrode layer 110 away from the second electrode layer 120; the piezoelectric material layer 130 includes a piezoelectric layer 135, the first electrode layer 110 includes a first electrode 115, the second electrode layer 120 includes a second electrode 125 and an additional electrode 126, and the piezoelectric layer 135 is located between the first electrode 115 and the second electrode 125, thereby generating an inverse piezoelectric effect under the drive of the first electrode 115 and the second electrode 125, thus generating vibration. Therefore, the piezoelectric layer 135, the first electrode 115, and the second electrode 125 can form a resonator unit 510.

[0154] like Figure 31 As shown, the pad structure layer 200 includes interconnect pads 210; the interconnect pads 210 are connected to the first electrode 115 and to the additional electrode 126 through a first connection via 131 penetrating the piezoelectric material layer 130; thus, the additional electrode 126 located on the second side of the piezoelectric material layer 130 can be connected to the first electrode 115 located on the piezoelectric material layer 130 through the interconnect pads 210.

[0155] like Figure 31 As shown, a first cavity RC1 is provided between the cover structure 400 and the piezoelectric material layer 130, and at least a portion of the first electrode 115 is located in the first cavity RC1. A second cavity RC2 is provided between the carrier structure 300 and the piezoelectric layer 135, and a portion of the second electrode 125 is located in the second cavity RC2.

[0156] like Figure 31 As shown, the bulk acoustic resonator 500 also includes a first passivation layer 350 located between the second electrode layer 120 and the carrier structure 300, and the first passivation layer 350 covers the second electrode 125 located in the second cavity RC2.

[0157] In the bulk acoustic resonator provided in the embodiments of this disclosure, since the first passivation layer covers the second electrode located in the second cavity, the first passivation layer can prevent the etchant from corroding the second electrode and avoid etching damage during the formation of the second cavity.

[0158] For example, the material of the first passivation layer described above can be aluminum nitride. Of course, the embodiments disclosed herein include, but are not limited to, other materials that can be used for the first passivation layer.

[0159] In some examples, such as Figure 31As shown, the cover structure 400 includes a cover plate 410 and a groove 420 located in the cover plate 410; the cover plate 410 includes a support portion 412 located at the edge of the groove 420, the support portion 412 is connected to the bonding pad 220 through an adhesive layer 430, and the groove 420 forms a first cavity RC1.

[0160] In the bulk acoustic wave resonator provided in this example, a groove can be directly formed in the cover plate, and then a portion of the thickness of the cover plate itself is used to form the aforementioned first cavity. The cover structure and the resonant body structure are then bonded together via metal pads and bonding pads. Therefore, this bulk acoustic wave resonator does not require a thick dry film, thus significantly improving sealing performance. It should be noted that in typical bulk acoustic wave resonators, the cover structure usually consists of only a flat cover plate, which is then bonded to bonding pads on the piezoelectric material layer via a dry film. In this case, to maintain the thickness of the first cavity, the dry film needs to be relatively thick, for example, around 10 micrometers. Since the sealing performance between the piezoelectric material layer and the cover structure mainly depends on the bonding structure between them, a thicker dry film can easily lead to a decrease in sealing performance and reduced airtightness during long-term use.

[0161] In some examples, such as Figure 31 As shown, the bulk acoustic resonator 500 also includes a first functional slot 133, which penetrates the piezoelectric material layer 130. The orthographic projection of the first functional slot 133 on the piezoelectric material layer 130 is arranged around the orthographic projection of the first cavity RC1 on the piezoelectric material layer 130.

[0162] In this bulk acoustic wave resonator, since the first functional slot penetrates the piezoelectric material layer, and the orthographic projection of the first functional slot on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer, the first functional slot can separate the portion of the piezoelectric material layer corresponding to the first cavity from the portion of the piezoelectric material layer outside the first functional slot. Therefore, during the formation of the second cavity, since the piezoelectric material layers inside and outside the first functional slot are separated, the first functional slot can be used for stress relief, thereby preventing buckling deformation of the piezoelectric material layer and improving product yield and stability. It should be noted that in the fabrication of bulk acoustic wave resonators, multiple bulk acoustic wave resonators are typically fabricated simultaneously on a large-area substrate, and then separated through a cutting process. Therefore, the first functional slot separates the multiple bulk acoustic wave resonators, making them independent and preventing mutual interference, which is beneficial for stress relief. Furthermore, in the reflow soldering and cutting processes of this bulk acoustic wave resonator, the first functional slot can also be used for stress relief, preventing the cover structure or cover plate from shattering.

[0163] Figure 32 A schematic diagram of another bulk acoustic resonator provided in an embodiment of this disclosure. Figure 32 The bulk acoustic resonator shown is in Figure 1 The conductive bumps of the bulk acoustic resonator shown are improved.

[0164] like Figure 32 As shown, the bulk acoustic wave resonator 500 includes an insulating layer 360, a first conductive bump 371, and a second conductive bump 372. The insulating layer 360 is located on the side of the first conductive connection layer L1 and the second conductive connection layer L2 away from the piezoelectric material layer 130. The first conductive bump 371 and the second conductive bump 372 are located on the side of the insulating layer 360 away from the piezoelectric material layer 130. The first conductive bump 371 is electrically connected to the first conductive connection layer L1 through a third via V3 located in the insulating layer 360, and the second conductive bump 372 is electrically connected to the second conductive connection layer L2 through a fourth via V4 located in the insulating layer 360. Thus, the bulk acoustic wave resonator can be connected to a circuit board through the first conductive bump and the second conductive bump.

[0165] In some examples, the first and second conductive bumps described above may be or include solder bumps. It should be noted that the process of forming the first and second conductive bumps may include: forming a bump material layer; and performing a reflow soldering process on the bump material layer. For example, after patterning the insulating layer to form the third and fourth vias described above, a bump material layer may be formed on the insulating layer, which can be connected to the first and second conductive connection layers through the third and fourth vias respectively, and then the first and second conductive bumps may be formed by a reflow soldering process.

[0166] In some examples, such as Figure 32 As shown, the orthographic projection of at least one of the first conductive bump 371 and the second conductive bump 372 on the piezoelectric material layer 130 overlaps with the orthographic projection of the corresponding third via V3 or fourth via V4 on the piezoelectric material layer 130, thereby increasing design freedom and reducing bare core size.

[0167] Figure 33 A schematic diagram of another bulk acoustic resonator provided in an embodiment of this disclosure. Figure 33 The bulk acoustic resonator shown is in Figure 1 The bonding structure of the bulk acoustic resonator shown is improved. Figure 1 The bulk acoustic wave resonator shown connects the cover plate and the bonding pads via an adhesive layer, while Figure 33 The bulk acoustic wave resonator shown does not use an adhesive layer, but instead uses metal pads and bonding pads to connect the cover structure to the piezoelectric material layer.

[0168] like Figure 33 As shown, the bulk acoustic wave resonator 500 includes a resonant main body structure 100, a pad structure layer 200, a carrier structure 300, and a cover structure 400. The resonant main body structure 100 includes a piezoelectric material layer 130, a first electrode layer 110, and a second electrode layer 120. The piezoelectric material layer 130 has a first side and a second side opposite to each other in a first direction, wherein the first direction may be the thickness direction of the piezoelectric material layer. The first electrode layer 110 is disposed on the first side of the piezoelectric material layer 130, and the second electrode layer 120 is disposed on the second side of the piezoelectric material layer 130. That is, the first electrode layer 110, the piezoelectric material layer 130, and the second electrode layer 120 are stacked.

[0169] like Figure 33 As shown, the carrier structure 300 is located on the side of the piezoelectric material layer 130 and the second electrode layer 120 away from the first electrode layer 110; the cover structure 400 is located on the side of the piezoelectric material layer 130 and the first electrode layer 110 away from the second electrode layer 120; the piezoelectric material layer 130 includes a piezoelectric layer 135, the first electrode layer 110 includes a first electrode 115, the second electrode layer 120 includes a second electrode 125 and an additional electrode 126, and the piezoelectric layer 135 is located between the first electrode 115 and the second electrode 125, thereby generating an inverse piezoelectric effect under the drive of the first electrode 115 and the second electrode 125, thus generating vibration. Therefore, the piezoelectric layer 135, the first electrode 115, and the second electrode 125 can form a resonator unit 510.

[0170] like Figure 33 As shown, the pad structure layer 200 includes interconnect pads 210; the interconnect pads 210 are connected to the first electrode 115 and to the additional electrode 126 through a first connection via 131 penetrating the piezoelectric material layer 130; thus, the additional electrode 126 located on the second side of the piezoelectric material layer 130 can be connected to the first electrode 115 located on the piezoelectric material layer 130 through the interconnect pads 210.

[0171] like Figure 33 As shown, a first cavity RC1 is provided between the cover structure 400 and the piezoelectric material layer 130, and at least a portion of the first electrode 115 is located in the first cavity RC1. A second cavity RC2 is provided between the carrier structure 300 and the piezoelectric layer 135, and a portion of the second electrode 125 is located in the second cavity RC2.

[0172] like Figure 33As shown, the pad structure layer 200 also includes bonding pads 220, and the cover structure 400 includes a cover plate 410, a groove 420 and a metal pad 440. The groove 420 is located in the cover plate 410, and the cover plate 410 includes a support portion 412 located at the edge of the groove 420. The metal pad 440 is located on the side of the support portion 412 close to the bonding pad 220 and is bonded to the bonding pad 220 so that the groove 420 forms a first cavity RC1.

[0173] In the bulk acoustic wave resonator provided in this embodiment, a groove can be directly formed in the cover plate, and then a portion of the thickness of the cover plate itself is used to form the aforementioned first cavity. The cover structure and the resonant body structure are then bonded together using metal pads and bonding pads. Therefore, this bulk acoustic wave resonator does not require a thick dry film, thus significantly improving sealing performance. It should be noted that in typical bulk acoustic wave resonators, the cover structure usually consists of only a flat cover plate, which is then bonded to bonding pads on the piezoelectric material layer using a dry film. In this case, to maintain the thickness of the first cavity, the dry film needs to be relatively thick, for example, around 10 micrometers. Since the sealing performance between the piezoelectric material layer and the cover structure mainly depends on the bonding structure between them, a thicker dry film can easily lead to a decrease in sealing performance and reduced airtightness during long-term use.

[0174] In some examples, such as Figure 33 As shown, the bulk acoustic resonator 500 also includes a first functional slot 133, which penetrates the piezoelectric material layer 130. The orthographic projection of the first functional slot 133 on the piezoelectric material layer 130 is arranged around the orthographic projection of the first cavity RC1 on the piezoelectric material layer 130.

[0175] In this bulk acoustic wave resonator, since the first functional slot penetrates the piezoelectric material layer, and the orthographic projection of the first functional slot on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer, the first functional slot can separate the portion of the piezoelectric material layer corresponding to the first cavity from the portion of the piezoelectric material layer outside the first functional slot. Therefore, during the formation of the second cavity, since the piezoelectric material layers inside and outside the first functional slot are separated, the first functional slot can be used for stress relief, thereby preventing buckling deformation of the piezoelectric material layer and improving product yield and stability. It should be noted that in the fabrication of bulk acoustic wave resonators, multiple bulk acoustic wave resonators are typically fabricated simultaneously on a large-area substrate, and then separated through a cutting process. Therefore, the first functional slot separates the multiple bulk acoustic wave resonators, making them independent and preventing mutual interference, which is beneficial for stress relief. Furthermore, in the reflow soldering and cutting processes of this bulk acoustic wave resonator, the first functional slot can also be used for stress relief, preventing the cover structure or cover plate from shattering.

[0176] In some examples, such as Figure 33 As shown, the bonding pad 220 includes a first pad portion 221 and a second pad portion 222. The first pad portion 221 is located within the first functional groove 133 and is in contact with the bottom and sidewalls of the first functional groove 133. The second pad portion 222 is connected to the first pad portion 221 and is located on the side of the piezoelectric material layer 130 away from the carrier structure 300. Therefore, this bonding pad can prevent etching liquid or etching gas from corroding the carrier structure through the first functional groove during the etching process of the second cavity. Furthermore, the aforementioned bonding pad can also be used for bonding the piezoelectric material layer and the cap structure, thus enabling reuse.

[0177] In some examples, such as Figure 33 As shown, the second electrode layer 120 also includes a protective electrode 122. The protective electrode 122 is located between the first functional groove 133 and the carrier structure 300. The protective electrode 122 is in contact with the first pad portion 220. The orthogonal projection of the protective electrode 122 on the piezoelectric material layer 130 covers the orthogonal projection of the bottom of the first functional groove 133 on the piezoelectric material layer 130. Thus, the protective electrode 122 can cover the bottom of the first functional groove 133, and the protective electrode 122 is in contact with the carrier structure, thereby providing better protection and preventing the etching solution or etching gas from corroding the carrier structure through the first functional groove.

[0178] In some examples, such as Figure 33As shown, the carrier structure 300 includes a carrier substrate 310 and a second functional groove 390. The second functional groove 390 penetrates at least through the carrier substrate 310, and its orthographic projection on the piezoelectric material layer 130 surrounds the orthographic projection of the first cavity RC1 on the piezoelectric material layer 130. On one hand, the aforementioned second functional groove can also play a role in stress relief during the formation of the second cavity; on the other hand, in the reflow soldering and cutting processes of this bulk acoustic wave resonator, the second functional groove can also be used for stress relief to prevent the cover structure or cover plate from bursting. It should be noted that in the reflow soldering process, the bulk acoustic wave resonator is heated, resulting in uneven stress distribution; additionally, in the cutting process, there are also issues of uneven stress distribution and stress relief. Therefore, the second functional groove can also be used for stress relief, thereby improving product yield.

[0179] In some examples, such as Figure 33 As shown, the orthographic projection of the second functional slot 390 onto the piezoelectric material layer 130 overlaps with the orthographic projection of the first functional slot 133 onto the piezoelectric material layer 130. Therefore, the bulk acoustic resonator can better utilize the first and second functional slots for stress relief. Furthermore, this arrangement also reduces the area occupied by the first and second functional slots.

[0180] The foregoing description and accompanying drawings fully illustrate embodiments of this disclosure to enable those skilled in the art to practice them. Other embodiments may include structural, logical, electrical, procedural, and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. Moreover, the terminology used in this application is for describing embodiments only and is not intended to limit the technical solutions described herein. As used in the technical solutions described herein, the singular forms “a,” “an,” and “the” are intended to equally include the plural forms unless the context clearly indicates otherwise. Similarly, the term “and / or” as used herein refers to any and all possible combinations of one or more of the associated listed elements. Additionally, when used in this application, the term "comprise" and its variations "comprises" and / or "comprising" refer to the presence of stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof. Without further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the process, method, or apparatus that includes said element. In this document, each embodiment may focus on the differences from other embodiments, and similar or identical parts between embodiments can be referred to mutually. For methods, products, etc., disclosed in the embodiments, if they correspond to the method section disclosed in the embodiments, the relevant parts can be referred to the description of the method section.

Claims

1. A bulk acoustic resonator, characterized in that, include: A piezoelectric material layer having a first side and a second side opposite to each other in a first direction; The first electrode layer is disposed on the first side of the piezoelectric material layer; The second electrode layer is disposed on the second side of the piezoelectric material layer; Pad structure layer, including interconnect pads; The carrier structure is located on the side of the piezoelectric material layer and the second electrode layer that is away from the first electrode layer; The cover structure is located on the side of the piezoelectric material layer and the first electrode layer that is far from the second electrode layer; The piezoelectric material layer includes a piezoelectric layer, the first electrode layer includes a first electrode, the second electrode layer includes a second electrode and an additional electrode, the piezoelectric layer is located between the first electrode and the second electrode, the interconnect pad is connected to the first electrode and is connected to the additional electrode through a first connection via penetrating the piezoelectric material layer; There is a first cavity between the cover structure and the piezoelectric material layer, at least a portion of the first electrode is located in the first cavity, and there is a second cavity between the carrier structure and the piezoelectric layer, a portion of the second electrode is located in the second cavity; The bulk acoustic resonator also includes a first functional slot that penetrates the piezoelectric material layer, and the orthographic projection of the first functional slot on the piezoelectric material layer is arranged around the orthographic projection of the first cavity on the piezoelectric material layer.

2. The bulk acoustic resonator according to claim 1, characterized in that, Also includes: Bonding pads, including a first pad portion and a second pad portion, The first pad portion is located in the first functional groove and is in contact with the bottom and sidewall of the first functional groove. The second pad portion is connected to the first pad portion and is located on the side of the piezoelectric material layer away from the carrier structure.

3. The bulk acoustic resonator according to claim 2, characterized in that, The second electrode layer also includes: The protective electrode is located between the first functional groove and the carrier structure. The protective electrode is positioned in contact with the first pad, and the orthographic projection of the protective electrode on the piezoelectric material layer covers the orthographic projection of the bottom of the first functional groove on the piezoelectric material layer.

4. The bulk acoustic resonator according to claim 3, characterized in that, The second electrode layer includes: The second electrode body layer is located on the side of the piezoelectric material layer away from the first electrode layer; and The edge frame layer is located on the side of the second electrode body layer away from the piezoelectric material layer. The second electrode includes a second electrode body and an edge frame located at the edge of the second electrode body, and the protective electrode includes a first sub-protective electrode and a second sub-protective electrode stacked together. The second electrode body and the first sub-protective electrode are located in the second electrode body layer, while the edge frame and the second sub-protective electrode are located in the edge frame layer.

5. The bulk acoustic resonator according to claim 4, characterized in that, The second electrode also includes a frequency adjustment electrode, located on the second electrode body, configured to adjust the frequency.

6. The bulk acoustic resonator according to claim 2, characterized in that, Bonding pads are either floating or grounded.

7. The bulk acoustic resonator according to claim 2, characterized in that, The cover structure includes: Cover plate, The groove is located within the cover plate. The cover plate includes a support portion located at the edge of the groove, the support portion being connected to the bonding pad via an adhesive layer, and the groove forming a first cavity.

8. The bulk acoustic resonator according to claim 7, characterized in that, The thickness of the adhesive layer is less than 3 micrometers.

9. The bulk acoustic resonator according to claim 8, characterized in that, The thickness of the adhesive layer is less than 1 micrometer.

10. The bulk acoustic resonator according to claim 2, characterized in that, The cover structure includes: Cover plate, The groove is located within the cover plate; and Metal pads, The cover plate includes a support portion located at the edge of the groove, and a metal pad located on the side of the support portion close to the bonding pad and bonded to the bonding pad, so that the groove forms a first cavity.

11. The bulk acoustic resonator according to claim 1, characterized in that, The width of the first functional slot ranges from 1 micrometer to 20 micrometers.

12. The bulk acoustic resonator according to claim 11, characterized in that, The width of the first functional slot ranges from 3 micrometers to 8 micrometers.

13. The bulk acoustic resonator according to claim 1, characterized in that, The carrier structure includes: carrier substrate; and Second function slot, The second functional groove extends at least through the carrier substrate, and the orthographic projection of the second functional groove on the piezoelectric material layer surrounds the orthographic projection of the first cavity on the piezoelectric material layer.

14. The bulk acoustic resonator according to claim 13, characterized in that, The orthographic projection of the second functional groove on the piezoelectric material layer overlaps with the orthographic projection of the first functional groove on the piezoelectric material layer.

15. The bulk acoustic resonator according to claim 13, characterized in that, The carrier structure also includes: The carrier bonding layer is located on the carrier substrate; The cavity boundary layer is located on the side of the carrier bonding layer away from the carrier substrate; and A supporting dielectric layer is located between the cavity boundary layer and the piezoelectric material layer, and is disposed around the second cavity.

16. The bulk acoustic resonator according to claim 15, characterized in that, Also includes: First conductive connection layer; as well as First through hole, The cavity boundary layer includes a first contact opening, a first via penetrating the carrier substrate and the carrier bonding layer, and exposing at least a portion of the additional electrode through the first contact opening. The first conductive connection layer is located at least a portion on the side of the carrier structure away from the piezoelectric material layer, and is electrically connected to the additional electrode through the first via.

17. The bulk acoustic resonator according to claim 16, characterized in that, The second functional slot also penetrates the carrier bonding layer and is positioned in contact with the cavity boundary layer.

18. The bulk acoustic resonator according to claim 15, characterized in that, Also includes: The first passivation layer is located between the second electrode layer and the carrier structure; First conductive connection layer; as well as First through hole, The first via penetrates the carrier substrate, the carrier bonding layer, the cavity boundary layer and the first passivation layer, and exposes at least a portion of the additional electrode. The first conductive connection layer is located at least a portion on the side of the carrier structure away from the piezoelectric material layer, and is electrically connected to the additional electrode through the first via.

19. The bulk acoustic resonator according to claim 18, characterized in that, The second functional groove also penetrates the carrier bonding layer, the cavity boundary layer and the supporting dielectric layer, and is in contact with the first passivation layer.

20. The bulk acoustic resonator according to any one of claims 16 to 19, characterized in that, Also includes: Second conductive connection layer; as well as The second via is located within the carrier structure. The second conductive connection layer is located at least partially on the side of the carrier structure away from the piezoelectric material layer, and is electrically connected to the second electrode through the second via.

21. The bulk acoustic resonator according to claim 20, characterized in that, Also includes: An insulating layer is located on the side of the first conductive connection layer away from the piezoelectric material layer; as well as The first and second conductive bumps are located on the side of the insulating layer away from the piezoelectric material layer. The first conductive bump is electrically connected to the first conductive connection layer through a third via located in the insulating layer, and the second conductive bump is electrically connected to the second conductive connection layer through a fourth via located in the insulating layer.

22. The bulk acoustic resonator according to claim 21, characterized in that, The orthographic projection of at least one of the first and second conductive bumps on the piezoelectric material layer overlaps with the orthographic projection of the corresponding third or fourth via on the piezoelectric material layer.

23. The bulk acoustic resonator according to any one of claims 1 to 19, characterized in that, The first electrode includes an electrode via that communicates with a first connection via to expose at least a portion of an additional electrode, and an interconnect pad is electrically connected to the additional electrode and the first electrode through the electrode via and the first connection via.

24. The bulk acoustic resonator according to any one of claims 1 to 19, characterized in that, The pad structure layer also includes: A first conductive pad is located on the surface of a first side of the piezoelectric layer and is electrically connected to a second electrode through a second connection via in the piezoelectric layer; and The second conductive pad is located on the side of the first electrode away from the piezoelectric layer and is electrically connected to the first electrode.

25. The bulk acoustic resonator according to any one of claims 1 to 19, characterized in that, The bulk acoustic resonator includes multiple second cavities and a first cavity, with the orthographic projections of the multiple second cavities onto the piezoelectric material layer located within the orthographic projections of the first cavity onto the piezoelectric material layer.

26. The bulk acoustic resonator according to any one of claims 1 to 17, characterized in that, Also includes: The first passivation layer is located between the second electrode layer and the carrier structure; The first passivation layer includes a passivation layer opening that exposes the portion of the second electrode located in the second cavity.

27. A method for manufacturing a bulk acoustic resonator, characterized in that, include: A first electrode layer, a piezoelectric material layer, and a second electrode layer are formed sequentially, wherein the first electrode layer and the second electrode layer are located on a first side and a second side opposite to each other in a first direction, respectively. The second electrode layer is patterned to form second electrodes and additional electrodes spaced apart from each other; A carrier structure is formed on the side of the piezoelectric material layer and the second electrode layer away from the first electrode layer, wherein the carrier structure includes a sacrificial layer that covers a portion of the second electrode; The first electrode layer is patterned to form the first electrode; A patterning process is performed on the piezoelectric material layer to form a piezoelectric layer, release holes, and a first functional groove; A pad structure layer is formed on the first side of the piezoelectric material layer, wherein the pad structure layer includes interconnect pads, the interconnect pads are connected to the first electrode, and are connected to an additional electrode through a first connection via penetrating the piezoelectric material layer. The sacrificial layer of the carrier structure is etched and removed by releasing the hole, and the space occupied by the sacrificial layer forms a second cavity between the piezoelectric material layer and the carrier structure. The cover structure is bonded to the first side of the piezoelectric material layer, and a first cavity is formed between the cover structure and the piezoelectric material layer, with at least a portion of the first electrode located within the first cavity. The piezoelectric layer is located between the first electrode and the second electrode, the first functional groove penetrates the piezoelectric material layer, and the orthographic projection of the first functional groove on the piezoelectric material layer is arranged around the orthographic projection of the first cavity on the piezoelectric material layer.

28. The manufacturing method according to claim 27, characterized in that, The pad structure layer also includes: Bonding pads, including a first pad portion and a second pad portion, The first pad portion is located in the first functional groove and is in contact with the bottom and sidewall of the first functional groove. The second pad portion is connected to the first pad portion and is located on the side of the piezoelectric material layer away from the carrier structure.

29. The manufacturing method according to claim 28, characterized in that, The patterning process for the second electrode layer also includes: A protective electrode is formed, located between the first functional groove and the carrier structure. The protective electrode is positioned in contact with the first pad, and the orthographic projection of the protective electrode on the piezoelectric material layer covers the orthographic projection of the bottom of the first functional groove on the piezoelectric material layer.

30. A filter, characterized in that, Includes a bulk acoustic resonator as described in any one of claims 1 to 26, or a bulk acoustic resonator manufactured using the method for manufacturing a bulk acoustic resonator as described in any one of claims 27 to 29.

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