Bulk acoustic wave resonator and preparation method thereof

Abstract

The invention discloses a bulk acoustic wave resonator and a preparation method thereof. The bulk acoustic wave resonator comprises a substrate, a transducer stacking structure and an interdigital capacitor, the transducer stacking structure comprises a bottom electrode layer, a piezoelectric layer and a top electrode layer which are sequentially arranged on one side of the substrate; the working area is an overlapped area of the bottom electrode layer, the piezoelectric layer and the first branch along the thickness direction of the bulk acoustic wave resonator; the second branch is arranged on one side, far away from the substrate, of the piezoelectric layer; the second part comprises a first conductive part, a second conductive part, a first electrode and a second electrode; the first conductive subsection is connected with the first electrode; the second conductive subsection is connected with the second electrode; the first conductive subsections and the second conductive subsections are arranged in a staggered and interdigital mode in the first direction. And the second branch part and the piezoelectric layer form an interdigital capacitor. Compared with the prior art, the technical scheme has the advantages that the area of the external capacitor is smaller, no extra lead-out path needs to be introduced, corresponding electrical parasitism is avoided, and the performance of the resonator and the filter is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of resonators, and particularly to a bulk acoustic wave resonator and a preparation method thereof. Background Art

[0002] Currently, with the rapid development of wireless communication technologies, there are more and more devices for transmitting and receiving information in higher frequency bands, and the requirements for radio frequency front-end circuits are becoming increasingly stringent. Therefore, the market demand for high-performance filters is increasing. Due to its characteristics such as high quality factor, good out-of-band rejection, and high rectangularity coefficient, bulk acoustic wave filters are gradually becoming the mainstream in the market.

[0003] A bulk acoustic wave filter is composed of multiple resonators cascaded according to a specific circuit. High-performance filters require high-performance resonators. High-performance resonators have a high quality factor, and the high quality factor can enable the filter to have smaller insertion loss and steeper roll-off characteristics, and have more excellent filtering performance. In summary, it is very important to prepare resonators with high stability and excellent performance.

[0004] Due to the limitation of the electromechanical coupling coefficient of the resonator material, the bandwidth of the bulk acoustic wave filter is small. In practical applications, passive devices such as external capacitors or inductors are usually added as matching circuits or to increase the bandwidth of the filter and adjust the filtering characteristics, etc. Surface-mounted capacitor devices are widely used in various electronic products such as mobile phones, computers, tablet computers, televisions, digital cameras, audio equipment, and automotive electronics. However, when used in filters, they need to be connected to the resonator filtering circuit, which requires additional wiring, and their size is relatively large compared to the resonator, resulting in a decrease in filter performance and an inability to reduce the area, which greatly limits the performance of thin film bulk acoustic wave filters. Summary of the Invention

[0005] The present invention provides a bulk acoustic wave resonator and a preparation method thereof to solve the problem in the prior art that adding an external capacitor to the bulk acoustic wave resonator results in a large area and a decrease in performance.

[0006] According to one aspect of the present invention, a bulk acoustic wave resonator is provided, including: a substrate, a transducer stack structure, and an interdigital capacitor;

[0007] The transducer stack structure includes a bottom electrode layer, a piezoelectric layer, and a top electrode layer sequentially disposed on one side of the substrate;

[0008] The top electrode layer includes a first part and a second part; the transducer stack structure includes a working area; the working area is an overlapping area of the bottom electrode layer, the piezoelectric layer, and the first part along the thickness direction of the bulk acoustic wave resonator;

[0009] The second part is disposed on a side of the piezoelectric layer away from the substrate; the second part includes a first conductive part, a second conductive part, a first electrode, and a second electrode; the first conductive part is connected to the first electrode; the second conductive part is connected to the second electrode; the first conductive part and the second conductive part are arranged in an interleaved and interdigital manner along a first direction;

[0010] The second part and the piezoelectric layer form an interdigital capacitor.

[0011] Optionally, the bulk acoustic wave resonator further includes a dielectric layer;

[0012] The dielectric layer is filled between the first conductive part and the second conductive part.

[0013] Optionally, the bulk acoustic wave resonator further includes a connection structure; at least one contact is included on the first conductive part; at least one contact is included on the second conductive part;

[0014] The connection structure is used to connect the contacts on the first conductive part and the contacts on the second conductive part to change the capacitance value of the interdigital capacitor.

[0015] Optionally, the bulk acoustic wave resonator further includes a dielectric layer;

[0016] The dielectric layer is filled between the first conductive part and the second conductive part;

[0017] A through-channel is included in the dielectric layer; the connection structure is disposed in the through-channel.

[0018] Optionally, the bulk acoustic wave resonator further includes a passivation layer;

[0019] The passivation layer is disposed on a side of the first part away from the piezoelectric layer and the passivation layer covers at least the working area.

[0020] Optionally, the bulk acoustic wave resonator further includes a metal layer;

[0021] The metal layer is disposed on a side of the first electrode away from the piezoelectric layer and is also disposed on a side of the second electrode away from the piezoelectric layer for connecting to an external lead.

[0022] According to another aspect of the present invention, a method for manufacturing a bulk acoustic wave resonator is provided, which is used to manufacture a bulk acoustic wave resonator;

[0023] The manufacturing method includes:

[0024] Providing a substrate;

[0025] Sequentially depositing a bottom electrode layer, a piezoelectric layer, and a top electrode layer on one side of the substrate;

[0026] Etch the top electrode layer to form a first part and a second part; wherein, the transducer stack structure includes a working area; the working area is the overlapping area of the bottom electrode layer, the piezoelectric layer and the first part along the thickness direction of the bulk acoustic wave resonator; wherein, the second part includes a first conductive part, a second conductive part, a first electrode and a second electrode; the first conductive part is connected to the first electrode; the second conductive part is connected to the second electrode; the first conductive part and the second conductive part are arranged in an interleaved finger pattern along a first direction; the second part and the piezoelectric layer form an interdigital capacitor.

[0027] Optionally, after etching the top electrode layer to form a first part and a second part, the method further includes:

[0028] Deposit and etch a dielectric layer to fill the dielectric layer between the first conductive part and the second conductive part.

[0029] Optionally, before depositing and etching the dielectric layer, the method further includes:

[0030] Deposit a connection layer;

[0031] Etch the connection layer to form a connection structure; wherein, the connection structure connects the contact on the first conductive part and the contact on the second conductive part.

[0032] Optionally, after etching the top electrode layer to form a first part and a second part, the method further includes:

[0033] Deposit and etch a metal layer to dispose the metal layer on the side of the first electrode away from the piezoelectric layer and also on the side of the second electrode away from the piezoelectric layer.

[0034] The technical solution of the embodiment of the present invention prepares an interdigital capacitor while preparing a bulk acoustic wave resonator. By etching the top electrode layer to form a first part and a second part, the second part combines with the piezoelectric layer to form an interdigital capacitor structure, integrating the capacitor directly on the chip. Compared with the external capacitor in the prior art, the area is smaller, there is no need to introduce an additional lead-out path, avoiding the corresponding electrical parasitics, thereby improving the performance of the resonator and the filter.

[0035] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0037] Figure 1 is a schematic structural diagram of the first bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0038] Figure 2 is a top view structural diagram of the first interdigital capacitor provided according to an embodiment of the present invention;

[0039] Figure 3 is a schematic structural diagram of the second bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0040] Figure 4 is a top view structural diagram of the second interdigital capacitor provided according to an embodiment of the present invention;

[0041] Figure 5 is a top view structural diagram of the third interdigital capacitor provided according to an embodiment of the present invention;

[0042] Figure 6 is a preparation flow chart of the first bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0043] Figure 7 is a corresponding structural diagram for the preparation of the first bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0044] Figure 8 is a preparation flow chart of the second bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0045] Figure 9 is a corresponding structural diagram for the preparation of the second bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0046] Figure 10 is a preparation flow chart of the third bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0047] Figure 11 is a corresponding structural diagram for the preparation of the third bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0048] Figure 12 is a preparation flow chart of the first bulk acoustic wave resonator provided according to an embodiment of the present invention;

[0049] Figure 13 is a corresponding structural diagram for the preparation of the first bulk acoustic wave resonator provided according to an embodiment of the present invention. Detailed implementation manners

[0050] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solution in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0052] Figure 1 is a schematic structural diagram of a first bulk acoustic wave resonator provided according to an embodiment of the present invention, Figure 2 is a top view structural schematic diagram of a first interdigital capacitor provided according to an embodiment of the present invention. Combining Figure 1 and Figure 2 as shown, the bulk acoustic wave resonator includes: a substrate 101, a transducer stack structure, and an interdigital capacitor;

[0053] The transducer stack structure includes a bottom electrode layer 104, a piezoelectric layer 105, and a top electrode layer 106 sequentially disposed on one side of the substrate 101;

[0054] The top electrode layer 106 includes a first part 1061 and a second part 1062; the transducer stack structure includes a working area; the working area is the overlapping area of the bottom electrode layer 104, the piezoelectric layer 105, and the first part 1061 along the thickness direction of the bulk acoustic wave resonator;

[0055] The second part 1062 is disposed on the side of the piezoelectric layer 105 away from the substrate 101; the second part 1062 includes a first conductive part 621, a second conductive part 622, a first electrode 623, and a second electrode 624; the first conductive part 621 is connected to the first electrode 623; the second conductive part 622 is connected to the second electrode 624; the first conductive part 621 and the second conductive part 622 are arranged in an interleaved interdigital pattern along the first direction x;

[0056] The second part 1062 and the piezoelectric layer 105 form an interdigital capacitor.

[0057] Among them, the substrate 101 can be the base of the bulk acoustic wave resonator. The transducer stack structure includes a bottom electrode layer 104, a piezoelectric layer 105, and a top electrode layer 106 sequentially disposed on one side of the substrate 101. The bottom electrode layer 104 is disposed on one side of the substrate 101, the piezoelectric layer 105 is disposed on the side of the bottom electrode layer 104 away from the substrate 101, and the top electrode layer 106 is disposed on the side of the piezoelectric layer 105 away from the substrate 101. The overlapping area of the bottom electrode layer 104, the piezoelectric layer 105, and the top electrode layer 106 is the working area, which can convert electrical energy into sound waves and generate oscillations. During operation, electrical energy is converted into sound waves through the inverse piezoelectric effect in the working area to form resonance.

[0058] In the actual application process, due to the small bandwidth of the bulk acoustic wave resonator, passive devices such as external capacitors or inductors are added as matching circuits or to increase the bandwidth of the filter and adjust the filtering characteristics. In the embodiment of the present invention, while preparing the top electrode layer 106, the top electrode layer 106 is divided into a first part 1061 and a second part 1062 by etching. Among them, the first part 1061 can be used as a part of the bulk acoustic wave resonator, that is, it forms a working area with the bottom electrode layer 104 and the piezoelectric layer 105 to ensure the normal operation of the bulk acoustic wave resonator. The second part 1062 is independent of the first part 1061. The second part 1062 is disposed on the side of the piezoelectric layer 105 away from the substrate 101, and there is no bottom electrode layer 104 between the piezoelectric layer 105 corresponding to the second part 1062 and the substrate 101. The second part 1062 includes a first conductive part 621, a second conductive part 622, a first electrode 623, and a second electrode 624. The first conductive part 621 is arranged at intervals along the first direction x, the second conductive part 622 is arranged at intervals along the first direction x, and the first conductive part 621 and the second conductive part 622 are arranged in an interdigitated manner along the first direction x to form a capacitive structure. The first electrode 623 is connected to the first conductive part 621, and the second electrode 624 is connected to the second conductive part 622. Electrically connecting each conductive part to the electrode ensures that the normal operation of the capacitor is not affected when one conductive part fails, and the stability of the operation of the interdigital capacitor is guaranteed.

[0059] It can be understood that the interdigital capacitor in the embodiment of the present invention is prepared simultaneously with the preparation of the bulk acoustic wave resonator. The capacitor is directly integrated on the basis of the piezoelectric layer 105, which has a smaller area than the external capacitor and has no additional introduction and extraction paths, avoiding the corresponding electrical parasitics, thereby improving the performance of the resonator and the filter. Compared with other types of capacitors, the interdigital capacitor has a simpler structure, simplifies the process while ensuring the performance of the bulk acoustic wave resonator.

[0060] In the technical solution of the embodiment of the present invention, while manufacturing the bulk acoustic wave resonator, an interdigital capacitor is manufactured. By using the etching of the top electrode layer to form a first part and a second part, the second part combines with the piezoelectric layer to form an interdigital capacitor structure, and the capacitor is directly integrated on the chip. Compared with the external capacitor in the prior art, the area is smaller, there is no need to additionally introduce a lead-out path, and the corresponding electrical parasitics are avoided, thereby improving the performance of the resonator and the filter.

[0061] Optionally, Figure 3 FIG. 5 is a schematic structural diagram of a second bulk acoustic wave resonator provided according to an embodiment of the present invention; Figure 4 FIG. 6 is a top view structural schematic diagram of a second interdigital capacitor provided according to an embodiment of the present invention. As shown in combination with Figure 3 and Figure 4 the bulk acoustic wave resonator further includes a dielectric layer 110;

[0062] The dielectric layer 110 is filled between the first conductive part 621 and the second conductive part 622.

[0063] Wherein, after the top electrode layer 106 is manufactured, the dielectric layer 110 can be continuously deposited, and the dielectric layer 110 is only filled between the first conductive part 621 and the second conductive part 622. The existence of the dielectric layer 110 can improve the storage density of the first conductive part 621 and the second conductive part 622, and further improve the capacitance value of the interdigital capacitor.

[0064] It can be understood that only one interdigital capacitor is schematically shown in the figure, and multiple interdigital capacitors can be set according to the requirements of the filter.

[0065] Specifically, in the manufacturing process, a dielectric layer 110 is first deposited, and then the dielectric layer 110 is etched so that the dielectric layer 110 is only filled between the first conductive part 621 and the second conductive part 622.

[0066] In the technical solution of the embodiment of the present invention, by filling a dielectric layer between the first conductive part and the second conductive part, the storage density of the first conductive part and the second conductive part is improved, and further the capacitance value of the interdigital capacitor is improved.

[0067] Optionally, continuing to refer to Figure 4 as shown in FIG. 7, the bulk acoustic wave resonator further includes a connection structure 20; at least one contact 30 is included on the first conductive part 621; at least one contact 30 is included on the second conductive part 622;

[0068] The connection structure 20 is used to connect the contact 30 on the first conductive part 621 and the contact 30 on the second conductive part 622 to change the capacitance value of the interdigital capacitor.

[0069] Among them, the contact 30 can be the connection point of the first conductive branch 621 and the second conductive branch 622. The connection structure 20 can electrically connect the contacts 30 on the first conductive branch 621 and the second conductive branch 622, and the purpose is to adjust the capacitance value of the interdigital capacitor within a small range. Among them, the connection structure 20 can be realized by depositing and etching the connection metal layer 108.

[0070] Exemplarily, as Figure 4 shown, the first conductive branch 621 includes four contacts 30, the second conductive branch 622 includes four contacts 30, and each contact 30 on the first conductive branch 621 can be connected to each contact 30 on the second conductive branch 622 through the connection structure 20. The effect of adjusting the capacitance value after connecting the contacts at different positions is different, thereby realizing the small-range adjustment of the capacitance value of the interdigital capacitor.

[0071] The technical solution of the embodiment of the present invention realizes the small-range adjustment of the capacitance value of the interdigital capacitor by setting a connection structure in the bulk acoustic wave resonator and using the connection structure to connect the contacts on the first conductive branch and the second conductive branch, thereby increasing the matching degree between the interdigital capacitor and the bulk acoustic wave resonator.

[0072] Optionally, continuing to refer to Figure 4 shown, the bulk acoustic wave resonator further includes a dielectric layer 110;

[0073] The dielectric layer 110 is filled between the first conductive branch 621 and the second conductive branch 622;

[0074] The dielectric layer 110 includes a through-channel; the connection structure 20 is arranged in the through-channel.

[0075] Among them, when there is a dielectric layer 110 between the first conductive branch 621 and the second conductive branch 622, the connection structure 20 can be arranged in the through-channel of the dielectric layer 110, so that the connection structure 20 penetrates the dielectric layer 110 to electrically connect the contacts 30 of the first conductive branch 621 and the second conductive branch 622.

[0076] Specifically, when actually preparing the connection structure 20 and the dielectric layer 110, the connection structure 20 can be prepared first. After etching the connection structure 20, the dielectric layer 110 is continuously deposited. The dielectric layer 110 can not only cover the connection structure 20 but also be filled between the first conductive branch 621 and the second conductive branch 622, so as to not only achieve the purpose of increasing the capacitance value but also use the contacts 30 to adjust the capacitance value within a small range.

[0077] In the technical solution of the embodiment of the present invention, by providing a connection structure while providing a dielectric layer, the connection structure is connected to the first conductive part and the second conductive part through the dielectric layer, which can not only achieve the purpose of increasing the capacitance value, but also use the contact 30 to adjust the capacitance value in a small range, improving the matching degree between the bulk acoustic wave resonator and the interdigital capacitor.

[0078] Optionally, continue to refer to Figure 1 As shown, the bulk acoustic wave resonator further includes a passivation layer 107;

[0079] The passivation layer 107 is disposed on the side of the first part 1061 away from the piezoelectric layer 105, and the passivation layer 107 covers at least the working area.

[0080] Among them, in order to ensure the reliability of the bulk acoustic wave resonator, the passivation layer 107 can be deposited and patterned above the working area to ensure the reliability of the bulk acoustic wave resonator.

[0081] Specifically, after the top electrode layer 106 is prepared, the passivation layer 107 can be deposited on the side of the top electrode layer 106 away from the substrate 101, so that the passivation layer 107 covers the working area and the interdigital capacitor area, but the passivation layer 107 does not need to be provided in the interdigital capacitor area. Therefore, the passivation layer 107 is etched continuously so that the passivation layer 107 only covers the working area to ensure the reliability of the bulk acoustic wave resonator.

[0082] In the technical solution of the embodiment of the present invention, by further preparing a passivation layer in the bulk acoustic wave resonator, the passivation layer covers the working area of the bulk acoustic wave resonator and does not cover the interdigital capacitor area, ensuring the normal operation of the bulk acoustic wave resonator and improving the reliability of the bulk acoustic wave resonator.

[0083] Optionally, Figure 5 is a top view structural schematic diagram of the third interdigital capacitor provided according to the embodiment of the present invention. Combining Figure 1 and Figure 5 As shown, the bulk acoustic wave resonator further includes a metal layer 108;

[0084] The metal layer 108 is disposed on the side of the first electrode 623 away from the piezoelectric layer 105, and is also disposed on the side of the second electrode 624 away from the piezoelectric layer 105, and is used to connect to an external lead.

[0085] Among them, the metal layer 108 can be electrically connected to the first electrode 623 and the second electrode 624, and is used to lead out the first electrode 623 and the second electrode 624, and further facilitate the electrical connection to the external lead. In the actual preparation process, the material of the metal layer 108 is different from that of the first electrode 623 and the second electrode 624, so as to facilitate the etching of the metal layer 108.

[0086] In some embodiments, a metal layer 108 may also be provided on the first section 1061 as the electrode lead-out end of the first section 1061, which not only reduces the resistance but also facilitates the connection of the bulk acoustic wave resonator and the interdigital capacitor to the external leads.

[0087] In the technical solution of the embodiment of the present invention, after the top electrode layer is prepared, the metal layer is continuously prepared, so that the metal layer is disposed on one side of the first electrode and the second electrode for connecting the external leads, which plays a role in reducing the resistance and facilitating the connection.

[0088] Based on the same inventive concept, Figure 6 FIG. is a flowchart of the preparation of the first bulk acoustic wave resonator provided by the embodiment of the present invention. Figure 7 FIG. is a structural diagram corresponding to the preparation of the first bulk acoustic wave resonator provided by the embodiment of the present invention. As shown in combination with Figure 6 and Figure 7 the embodiment of the present invention provides a method for preparing a bulk acoustic wave resonator, which is used to prepare a bulk acoustic wave resonator.

[0089] The preparation method includes:

[0090] S10. Provide a substrate. As shown in step (a) of Figure 7 .

[0091] Wherein, the substrate 101 may be the base of the bulk acoustic wave resonator.

[0092] S11. Deposit a bottom electrode layer, a piezoelectric layer, and a top electrode layer on one side of the substrate in sequence. As shown in step (b) of Figure 7 .

[0093] Wherein, the bottom electrode layer 104 is disposed on one side of the substrate 101, the piezoelectric layer 105 is disposed on the side of the bottom electrode layer 104 away from the substrate 101, the top electrode layer 106 is disposed on the side of the piezoelectric layer 105 away from the substrate 101, and the overlapping area of the bottom electrode layer 104, the piezoelectric layer 105, and the top electrode layer 106 is the working area, which can convert electrical energy into sound waves and generate oscillations. During the working process, the electrical energy is converted into sound waves through the inverse piezoelectric effect in the working area to form resonance.

[0094] S12. Etch the top electrode layer to form a first section and a second section. As shown in Figure 7As shown in step (c) therein. The transducer stack structure includes a working area; the working area is the overlapping area of the bottom electrode layer 104, the piezoelectric layer 105 and the first sub - part 1061 along the thickness direction of the bulk acoustic wave resonator; wherein, the second sub - part 1062 includes a first conductive sub - part 621, a second conductive sub - part 622, a first electrode 623 and a second electrode 624; the first conductive sub - part 621 is connected to the first electrode 623; the second conductive sub - part 622 is connected to the second electrode 624; the first conductive sub - part 621 and the second conductive sub - part 622 are arranged in an interleaved interdigital pattern along the first direction x; the second sub - part 1062 and the piezoelectric layer 105 form an interdigital capacitor.

[0095] Wherein, in the embodiment of the present invention, while preparing the top electrode layer 106, it is divided into the first sub - part 1061 and the second sub - part 1062 by etching the top electrode layer 106. Among them, the first sub - part 1061 can be used as a part of the bulk acoustic wave resonator, that is, it forms a working area with the bottom electrode layer 104 and the piezoelectric layer 105 to ensure the normal operation of the bulk acoustic wave resonator. The second sub - part 1062 is independent of the first sub - part 1061. The second sub - part 1062 is disposed on the side of the piezoelectric layer 105 away from the substrate 101, and there is no bottom electrode layer 104 between the piezoelectric layer 105 corresponding to the second sub - part 1062 and the bottom substrate.

[0096] Exemplarily, the specific working process is as follows:

[0097] Provide a substrate 101. Grooves can be etched in the substrate 101 and a sacrificial layer 102 can be filled in the grooves so that a cavity 109 is provided in the subsequent bulk acoustic wave resonator. Deposit the piezoelectric layer 105 and the bottom electrode layer 104 on one side of the substrate 101, and etch the bottom electrode layer 104 to form a corresponding shape. Deposit the piezoelectric layer 105 on the side of the bottom electrode layer 104 away from the substrate 101. After depositing the piezoelectric layer 105, the piezoelectric layer 105 can also be etched to expose the bottom electrode layer 104 for subsequent setting of the lead of the bottom electrode layer 104. After preparing the piezoelectric layer 105, continue to prepare the top electrode layer 106. Pattern the top electrode layer 106 to divide it into the first sub - part 1061 and the second sub - part 1062. The first sub - part 1061 and the bottom electrode layer 104 and the piezoelectric layer 105 are stacked to form the working area of the bulk acoustic wave resonator. The second sub - part 1062 is directly deposited on the piezoelectric layer 105 to form an interdigital electrode with the piezoelectric layer 105, and the shape of the interdigital electrode can be achieved by etching. After preparing the top electrode layer 106, etch the bulk acoustic wave resonator to form a release channel to release the sacrificial layer 102 of the substrate 101, forming a cavity 109 to obtain the final resonator structure.

[0098] In some embodiments, a seed layer 103 can also be provided before depositing the bottom electrode layer 104 to improve the deposition quality of the piezoelectric layer 105.

[0099] In the technical solution of the embodiment of the present invention, while fabricating the bulk acoustic wave resonator, the interdigital capacitor is fabricated. By using the etching of the top electrode layer to form the first part and the second part, the second part combines with the piezoelectric layer to form an interdigital capacitor structure, and the capacitor is directly integrated on the chip. Compared with the external capacitor in the prior art, the area is smaller, there is no need to additionally introduce an extraction path, avoiding the corresponding electrical parasitics, thereby improving the performance of the resonator and the filter.

[0100] Based on the above embodiments, Figure 8 FIG. 5 is a flowchart of fabricating a second bulk acoustic wave resonator according to an embodiment of the present invention, Figure 9 FIG. 6 is a corresponding structural diagram of fabricating a second bulk acoustic wave resonator according to an embodiment of the present invention. As shown in combination with Figure 8 and Figure 9 shown, the fabrication method includes:

[0101] S20. Provide a substrate. As shown in step (d) of Figure 9 .

[0102] S21. Deposit a bottom electrode layer, a piezoelectric layer, and a top electrode layer in sequence on one side of the substrate. As shown in step (e) of Figure 9 .

[0103] S22. Etch the top electrode layer to form a first part and a second part. As shown in step (f) of Figure 9 .

[0104] S23. Deposit and etch a dielectric layer so that the dielectric layer fills between the first conductive part and the second conductive part. As shown in step (g) of Figure 9 .

[0105] Wherein, after the top electrode layer 106 is fabricated, a dielectric layer 110 can be continuously deposited, and the dielectric layer 110 is only filled between the first conductive part 621 and the second conductive part 622. The presence of the dielectric layer 110 can improve the storage density of the first conductive part 621 and the second conductive part 622, and further improve the capacitance value of the interdigital capacitor.

[0106] Specifically, in the fabrication process, a dielectric layer 110 is first deposited, and then the dielectric layer 110 is etched so that the dielectric layer 110 is only filled between the first conductive part 621 and the second conductive part 622.

[0107] In the technical solution of the embodiment of the present invention, by filling a dielectric layer between the first conductive part and the second conductive part, the storage density of the first conductive part and the second conductive part is improved, and further the capacitance value of the interdigital capacitor is improved.

[0108] Based on the above embodiments, Figure 10It is a flowchart for preparing the third bulk acoustic wave resonator according to an embodiment of the present invention. Figure 11 It is a structural diagram corresponding to the preparation of the third bulk acoustic wave resonator according to an embodiment of the present invention. Combining Figure 10 and Figure 11 as shown, the preparation method includes:

[0109] S30. Provide a substrate. Refer to the step (k) shown in Figure 11 .

[0110] S31. Deposit a bottom electrode layer, a piezoelectric layer, and a top electrode layer in sequence on one side of the substrate. Refer to the step (l) shown in Figure 11 .

[0111] S32. Etch the top electrode layer to form a first part and a second part. Refer to the step (m) shown in Figure 11 .

[0112] S33. Deposit a connection layer. Refer to the step (n) shown in Figure 11 . Figure 11 In (n), it is a top view of the interdigital capacitor region.

[0113] Among them, the connection layer may include a metal material and is used to etch and form a connection structure 20.

[0114] S34. Etch the connection layer to form a connection structure. Among them, the connection structure 20 connects the contact 30 on the first conductive part 621 and the contact 30 on the second conductive part 622. Refer to the step (o) shown in Figure 11 . Figure 11 In (o), it is a top view of the interdigital capacitor region.

[0115] Among them, the contact 30 may be the connection point of the first conductive part 621 and the second conductive part 622. Through etching, the connection structure 20 can only electrically connect the contacts 30 on the first conductive part 621 and the second conductive part 622. The purpose is to adjust the capacitance value of the interdigital capacitor in a small range. Among them, the connection structure 20 can be realized by depositing and etching a connection metal layer 108.

[0116] S35. Deposit and etch a dielectric layer so that the dielectric layer fills between the first conductive part and the second conductive part. Refer to the step (p) shown in Figure 11 .

[0117] Among them, after the connection layer is prepared, continue to deposit the dielectric layer 110, so that the dielectric layer 110 can not only cover the connection structure 20 but also fill between the first conductive part 621 and the second conductive part 622, thereby not only achieving the purpose of increasing the capacitance value but also using the contact 30 to adjust the capacitance value in a small range.

[0118] In the technical solution of the embodiment of the present invention, by providing a connection structure while providing a dielectric layer, the connection structure is connected to the first conductive part and the second conductive part through the dielectric layer, which can not only achieve the purpose of increasing the capacitance value, but also can adjust the capacitance value in a small range by using the contacts, improving the matching degree between the bulk acoustic wave resonator and the interdigital capacitor.

[0119] Based on the above embodiment, Figure 12 is the preparation flow chart of the first bulk acoustic wave resonator provided according to the embodiment of the present invention, Figure 13 is the corresponding structural diagram of the preparation of the first bulk acoustic wave resonator provided according to the embodiment of the present invention. As shown in combination with Figure 12 and Figure 13 shown, the preparation method includes:

[0120] S40. Provide a substrate. As shown in step (r) in Figure 13 .

[0121] S41. Deposit a bottom electrode layer, a piezoelectric layer, and a top electrode layer on one side of the substrate in sequence. As shown in step (s) in Figure 13 .

[0122] S42. Etch the top electrode layer to form a first part and a second part. As shown in step (t) in Figure 13 .

[0123] S43. Deposit and etch a metal layer so that the metal layer is disposed on the side of the first electrode away from the piezoelectric layer and also on the side of the second electrode away from the piezoelectric layer. As shown in step (u) in Figure 13 .

[0124] Among them, the metal layer 108 can be used to lead out the first electrode 623 and the second electrode 624, and thus facilitate the electrical connection with the external lead. In the actual preparation process, the material of the metal layer 108 is different from that of the first electrode 623 and the second electrode 624, so as to facilitate the etching of the metal layer 108.

[0125] Exemplarily, after preparing the piezoelectric layer 105, the piezoelectric layer 105 is etched to form a slotted groove, which exposes the bottom electrode layer 104, and then the top electrode layer 106 and the metal layer 108 are continuously prepared, so that part of the metal layer 108 and the top electrode layer 106 are disposed in the slotted groove, used to lead out the bottom electrode layer 104. At the same time, the exposed part of the top electrode layer 106 is also covered by the metal layer 108, used to lead out the top electrode layer 106. At the same time, the electrodes of the interdigital capacitor can also be led out, which not only plays a role in reducing the resistance value, but also facilitates the connection of the bulk acoustic wave resonator and the interdigital capacitor with the external lead.

[0126] In the technical solution of the embodiment of the present invention, after the top electrode layer is prepared, a metal layer is further prepared, so that the metal layer is disposed on one side of the first electrode and the second electrode and is used to connect an external lead, which plays a role in reducing the resistance and facilitating the connection.

[0127] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0128] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bulk acoustic wave resonator, characterized in that, Comprising: A substrate, a transducer stack structure, and an interdigital capacitor; The transducer stack structure includes a bottom electrode layer, a piezoelectric layer, and a top electrode layer sequentially disposed on one side of the substrate; The top electrode layer includes a first portion and a second portion; the transducer stack structure includes a working area; the working area is the overlapping area of the bottom electrode layer, the piezoelectric layer, and the first portion along the thickness direction of the bulk acoustic wave resonator; The second portion is disposed on the side of the piezoelectric layer away from the substrate; the second portion includes a first conductive portion, a second conductive portion, a first electrode, and a second electrode; the first conductive portion is connected to the first electrode; the second conductive portion is connected to the second electrode; the first conductive portion and the second conductive portion are arranged in an interdigitated manner along a first direction; The second portion and the piezoelectric layer form the interdigital capacitor.

2. The bulk acoustic wave resonator according to claim 1, characterized in that, The bulk acoustic wave resonator further includes a dielectric layer; The dielectric layer is filled between the first conductive portion and the second conductive portion.

3. The bulk acoustic wave resonator according to claim 1, wherein The bulk acoustic wave resonator further includes a connection structure; at least one contact is included on the first conductive portion; at least one contact is included on the second conductive portion; The connection structure is used to connect the contacts on the first conductive portion and the contacts on the second conductive portion to change the capacitance value of the interdigital capacitor.

4. The bulk acoustic wave resonator according to claim 3, wherein The bulk acoustic wave resonator further includes a dielectric layer; The dielectric layer is filled between the first conductive portion and the second conductive portion; A through-channel is included in the dielectric layer; the connection structure is disposed in the through-channel.

5. The bulk acoustic wave resonator according to claim 1, characterized in that, The bulk acoustic wave resonator further includes a passivation layer; The passivation layer is disposed on the side of the first portion away from the piezoelectric layer and the passivation layer at least covers the working area.

6. The bulk acoustic wave resonator according to claim 1, wherein The bulk acoustic wave resonator further includes a metal layer; The metal layer is disposed on the side of the first electrode away from the piezoelectric layer and is also disposed on the side of the second electrode away from the piezoelectric layer for connecting an external lead.

7. A method for preparing a bulk acoustic wave resonator, characterized in that, For preparing the bulk acoustic wave resonator according to any one of claims 1-6; The preparation method includes: Providing a substrate; Sequentially depositing a bottom electrode layer, a piezoelectric layer, and a top electrode layer on one side of the substrate; Etching the top electrode layer to form a first portion and a second portion; wherein, the transducer stack structure includes a working area; the working area is the overlapping area of the bottom electrode layer, the piezoelectric layer, and the first portion along the thickness direction of the bulk acoustic wave resonator; wherein, the second portion includes a first conductive portion, a second conductive portion, a first electrode, and a second electrode; the first conductive portion is connected to the first electrode; the second conductive portion is connected to the second electrode; the first conductive portion and the second conductive portion are arranged in an interdigitated manner along a first direction; the second portion and the piezoelectric layer form the interdigital capacitor.

8. The preparation method according to claim 7, wherein, After etching the top electrode layer to form a first portion and a second portion, it further includes: Depositing and etching a dielectric layer so that the dielectric layer is filled between the first conductive portion and the second conductive portion.

9. The preparation method according to claim 8, characterized in that, Before depositing and etching the dielectric layer, it further includes: Depositing a connection layer; Etch the connection layer to form a connection structure; wherein the connection structure connects the contacts on the first conductive part and the contacts on the second conductive part.

10. The preparation method according to claim 7, characterized in that, Etch the top electrode layer to form a first part and a second part, and then further include: Deposit and etch a metal layer so that the metal layer is disposed on a side of the first electrode away from the piezoelectric layer and is also disposed on a side of the second electrode away from the piezoelectric layer.

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