Bulk acoustic wave resonator, preparation method thereof and filter

Abstract

The invention discloses a bulk acoustic wave resonator, a preparation method thereof and a filter, and relates to the technical field of resonators. The bulk acoustic wave resonator comprises a substrate, a bottom electrode, a piezoelectric layer and a top electrode, the bottom electrode, the piezoelectric layer and the top electrode are sequentially arranged on the substrate, a groove is formed in the substrate, and the overlapping area of the bottom electrode, the piezoelectric layer and the top electrode in the stacking direction serves as a resonance area. The top electrode comprises a first electrode pattern located in the resonance area and a second electrode pattern located outside the resonance area, the second electrode pattern and the first electrode pattern are arranged at an interval, a dielectric layer and a third electrode pattern are sequentially arranged on the second electrode pattern, and the second electrode pattern, the dielectric layer and the third electrode pattern form a capacitor. According to the bulk acoustic wave resonator, the preparation method thereof and the filter, the problems that in the prior art, extra leads are needed and the device area is large due to the fact that an external capacitor of a bulk acoustic wave resonator is additionally arranged can be solved, corresponding electrical parasitism is avoided, and then the device performance can be improved.

Description

Technical Field

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

[0002] At present, with the rapid development of wireless communication technology, there are more and more devices that send and receive information at higher frequency bands, and the requirements for RF front-end circuits are becoming more and more stringent, so the market demand for high-performance filters is increasing. Bulk acoustic wave filters are gradually becoming the mainstream of the market due to their high quality factor, good out-of-band suppression, and high rectangular coefficient.

[0003] BAW filters are composed of multiple resonators cascaded in a specific circuit. High-performance filters require high-performance resonators with high quality factors. High quality factors can make filters have smaller insertion loss and steeper roll-off characteristics, and have better 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 BAW filter is relatively small. In practical applications, passive devices such as capacitors or inductors are usually added as matching circuits or to increase the bandwidth of the filter, adjust the filtering characteristics, etc. Surface mount capacitors are widely used in various electronic products such as mobile phones, computers, tablet computers, televisions, digital cameras, audio equipment, automotive electronics, etc. However, when used in filters, they need to be connected to the resonator filter circuit, which requires additional routing, and their size is larger than that of the resonator, which reduces the filter performance and cannot reduce the area, greatly limiting the performance of the thin film BAW filter. Summary of the invention

[0005] The purpose of the present application is to provide a bulk acoustic wave resonator and a preparation method and a filter, which can solve the problems in the prior art that the external capacitor of the bulk acoustic wave resonator requires additional leads and the device area is large, thereby avoiding corresponding electrical parasitics and improving device performance.

[0006] The embodiment of the present application is implemented as follows:

[0007] According to a first aspect of an embodiment of the present application, a bulk acoustic wave resonator is provided, comprising a substrate and a bottom electrode, a piezoelectric layer and a top electrode sequentially arranged on the substrate, wherein a groove is arranged on the substrate, and an overlapping area of ​​the bottom electrode, the piezoelectric layer and the top electrode in a stacking direction serves as a resonance area, and the top electrode comprises a first electrode pattern located within the resonance area and a second electrode pattern located outside the resonance area and spaced apart from the first electrode pattern, a dielectric layer and a third electrode pattern are sequentially arranged on the second electrode pattern, and the second electrode pattern, the dielectric layer and the third electrode pattern form a capacitor.

[0008] As an implementation method, a seed layer is provided between the substrate and the bottom electrode.

[0009] As an implementation method, the material of the seed layer is the same as that of the piezoelectric layer.

[0010] As an implementation method, a mass loading layer is provided between the piezoelectric layer and the top electrode.

[0011] As an implementation method, a passivation layer is disposed on the top electrode and the third electrode pattern.

[0012] As an implementation method, a metal layer is arranged on the passivation layer, and the metal layer includes a first metal structure, a second metal structure, a third metal structure and a fourth metal structure arranged at intervals, the first metal structure is connected to the bottom electrode, the second metal structure is connected to the first electrode pattern, the third metal structure is connected to the second electrode pattern, and the fourth metal structure is connected to the third electrode pattern.

[0013] As an implementation method, a first step structure is formed on the dielectric layer at a side away from the resonance region, so that the second electrode pattern and the third electrode pattern are separated by the first step structure.

[0014] As an implementation method, a second step structure is formed on the passivation layer at a side away from the resonance region, so that the second electrode pattern and the fourth metal structure are separated by the second step structure.

[0015] According to a second aspect of an embodiment of the present application, a method for preparing a bulk acoustic wave resonator is provided, which is used to prepare the above-mentioned bulk acoustic wave resonator, and the method comprises:

[0016] Etching a groove on a substrate and depositing a sacrificial layer in the groove;

[0017] A bottom electrode, a piezoelectric layer and a top electrode are sequentially formed on the substrate on which the sacrificial layer is deposited, wherein an overlapping region of the bottom electrode, the piezoelectric layer and the top electrode in a stacking direction serves as a resonance region, and the top electrode comprises a first electrode pattern located in the resonance region and a second electrode pattern located outside the resonance region and spaced apart from the first electrode pattern;

[0018] forming a dielectric layer and a third electrode pattern in sequence on the second electrode pattern, wherein the second electrode pattern, the dielectric layer and the third electrode pattern form a capacitor;

[0019] A release hole is formed by etching on the first electrode pattern, and the sacrificial layer is released through the release hole until the groove is exposed to form a cavity, thereby obtaining a bulk acoustic wave resonator having the cavity.

[0020] According to a third aspect of the embodiments of the present application, a filter is provided, comprising the above-mentioned bulk acoustic wave resonator.

[0021] The beneficial effects of the embodiments of the present application include:

[0022] The BAW resonator includes a substrate and a bottom electrode, a piezoelectric layer and a top electrode sequentially arranged on the substrate, wherein a groove is arranged on the substrate, and the overlapping area of ​​the bottom electrode, the piezoelectric layer and the top electrode in the stacking direction serves as a resonance area, and the top electrode includes a first electrode pattern located in the resonance area and a second electrode pattern located outside the resonance area and spaced apart from the first electrode pattern, and a dielectric layer and a third electrode pattern are sequentially arranged on the second electrode pattern, and the second electrode pattern, the dielectric layer and the third electrode pattern form a capacitor. By adding a capacitor structure during the preparation of the resonator and using a part of the top electrode of the resonator as one of the electrodes of the capacitor structure, compared with the BAW resonator external capacitor device in the prior art, the capacitor structure directly integrated on the resonator provided by the present application can solve the problem that the BAW resonator external capacitor in the prior art requires additional leads and has a large device area, thereby avoiding corresponding electrical parasitics, and thus improving device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 One of the state schematic diagrams of the bulk acoustic wave resonator provided in the first embodiment of the present application;

[0025] Figure 2 The second state schematic diagram of the BAW resonator provided in the first embodiment of the present application;

[0026] Figure 3 The third state schematic diagram of the BAW resonator provided in the first embodiment of the present application;

[0027] Figure 4 The fourth state schematic diagram of the BAW resonator provided in the first embodiment of the present application;

[0028] Figure 5 A fifth state diagram of the bulk acoustic wave resonator provided in the first embodiment of the present application;

[0029] Figure 6 The sixth state diagram of the BAW resonator provided in the first embodiment of the present application;

[0030] Figure 7 The seventh state diagram of the bulk acoustic wave resonator provided in the first embodiment of the present application;

[0031] Figure 8 The eighth state schematic diagram of the BAW resonator provided in the first embodiment of the present application;

[0032] Fig. 9 A ninth state diagram of the bulk acoustic wave resonator provided in the first embodiment of the present application;

[0033] Fig.10 The tenth state schematic diagram of the BAW resonator provided in the first embodiment of the present application;

[0034] Fig.11 The eleventh state diagram of the BAW resonator provided in the first embodiment of the present application;

[0035] Fig.12 A schematic diagram of the structure of a bulk acoustic wave resonator provided in the second embodiment of the present application;

[0036] Fig.13 A schematic structural diagram of a bulk acoustic wave resonator provided in the third embodiment of the present application.

[0037] Icon: 101-substrate; 102-sacrificial layer; 103-seed layer; 104-bottom electrode; 105-piezoelectric layer; 106-mass load layer; 107-top electrode; 107a-first electrode pattern; 107b-second electrode pattern; 108-dielectric layer; 109-third electrode pattern; 110-passivation layer; 111a-first metal structure; 111b-second metal structure; 111c-third metal structure; 111d-fourth metal structure; 112-cavity. DETAILED DESCRIPTION

[0038] The embodiments set forth below represent information necessary to enable those skilled in the art to practice the embodiments, and illustrate the best mode for practicing the embodiments. After reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure, and will recognize the applications of these concepts not specifically proposed herein. It should be understood that these concepts and applications are within the scope of the present disclosure and the appended claims.

[0039] It should be understood that although the terms first, second, etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0040] It should be understood that when an element (such as a layer, region or substrate) is referred to as "on another element" or "extending onto another element", it can be directly on another element or directly extended onto another element, or there can also be an intervening element. On the contrary, when an element is referred to as "directly on another element" or "directly extending onto another element", there is no intervening element. Similarly, it should be understood that when an element (such as a layer, region or substrate) is referred to as "on another element" or "extending onto another element", it can be directly on another element or directly extended onto another element, or there can also be an intervening element. On the contrary, when an element is referred to as "directly on another element" or "extending directly onto another element", there is no intervening element. It should also be understood that when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to another element, or there can be an intervening element. On the contrary, when an element is referred to as "directly connected" or "directly coupled" to another element, there is no intervening element.

[0041] Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe the relationship of one element, layer or region to another element, layer or region as shown in the figures.

[0042] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms as well. It should also be understood that when used herein, the term "comprising" indicates the presence of the features, integers, steps, operations, elements, and / or parts, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups of the above.

[0043] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. It should also be understood that the terms used herein should be interpreted as having the same meaning as they do in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense, unless clearly defined in this article.

[0044] Due to the limitation of the electromechanical coupling coefficient of the resonator material, the bandwidth of the BAW filter is relatively small. Therefore, in practical applications, passive devices such as external capacitors or inductors are currently mainly used as matching circuits or to increase the bandwidth of the filter, adjust the filtering characteristics, etc. Surface mount capacitors are widely used in various electronic products such as mobile phones, computers, tablet computers, televisions, digital cameras, audio equipment, automotive electronics, etc. However, when surface mount capacitors are used in BAW filters, they need to be connected to the resonator filter circuit, which requires additional routing, and their size is larger than that of the resonator, which reduces the filter performance and cannot reduce the area, thus greatly limiting the performance of the thin film BAW filter.

[0045] To solve the above problems, please refer to Figures 1 to 13 The present application provides a bulk acoustic wave resonator and a preparation method thereof, and a filter. By adding a capacitor structure during the preparation process of the resonator and using a portion of the top electrode 107 of the resonator (i.e., the second electrode pattern 107b) as one of the electrodes of the capacitor structure, compared with the bulk acoustic wave resonator with an external capacitor device in the prior art, the capacitor structure directly integrated on the resonator provided by the present application can solve the problem of the bulk acoustic wave resonator with an external capacitor in the prior art requiring additional leads and a large device area, thereby avoiding corresponding electrical parasitics and improving device performance.

[0046] Specifically, Figures 11 to 13As shown, in a first aspect of an embodiment of the present application, a bulk acoustic wave resonator is provided, comprising a substrate 101 and a bottom electrode 104, a piezoelectric layer 105 and a top electrode 107 sequentially arranged on the substrate 101, wherein a groove is arranged on the substrate 101, and an overlapping area of ​​the bottom electrode 104, the piezoelectric layer 105 and the top electrode 107 in the stacking direction serves as a resonance area, and the top electrode 107 comprises a first electrode pattern 107a located in the resonance area and a second electrode pattern 107b located outside the resonance area and spaced apart from the first electrode pattern 107a, a dielectric layer 108 and a third electrode pattern 109 are sequentially arranged on the second electrode pattern 107b, and the second electrode pattern 107b, the dielectric layer 108 and the third electrode pattern 109 form a capacitor, thereby allowing the capacitor structure to be directly integrated on the bulk acoustic wave resonator.

[0047] It should be noted that if Figures 11 to 13 As shown, the BAW resonator includes a substrate 101, on which a bottom electrode 104, a piezoelectric layer 105 and a top electrode 107 are sequentially arranged, so that a sandwich structure is formed by the bottom electrode 104, the piezoelectric layer 105 and the top electrode 107. During the operation of the BAW resonator, the bottom electrode 104 and the top electrode 107 are respectively connected to two ends of an external signal to form an electric field between the bottom electrode 104 and the top electrode 107, so that the piezoelectric layer 105 is located in the electric field and generates vibration to form an acoustic wave under the action of the piezoelectric effect.

[0048] Among them, the overlapping area of ​​the bottom electrode 104, the piezoelectric layer 105 and the top electrode 107 in the stacking direction is used as a resonance area to make the sound waves reflect back and forth in the resonance area; on this basis, a groove is also provided between the upper surface of the substrate 101 and the lower surface of the bottom electrode 104. When the sound wave propagates at both ends of the sandwich structure, the groove is used as a sound reflection cavity, and the air in the groove can be used to reflect the sound wave back into the sandwich structure, so that the energy of the sound wave can be concentrated in the sandwich structure, thereby improving the Q value of the resonator.

[0049] Different from the prior art, the top electrode 107 is divided into a first electrode pattern 107a and a second electrode pattern 107b, wherein the first electrode pattern 107a is located in the resonance region, and the second electrode pattern 107b is located outside the resonance region and is spaced apart from the first electrode pattern 107a; on this basis, a dielectric layer 108 and a third electrode pattern 109 are sequentially arranged on the second electrode pattern 107b, and the second electrode pattern 107b, the dielectric layer 108 and the third electrode pattern 109 form a capacitor structure, thereby allowing the capacitor structure to be directly integrated on the BAW resonator.

[0050] The BAW resonator provided in the present application adds a capacitor structure during the preparation process of the resonator and uses a portion of the top electrode 107 of the resonator (i.e., the second electrode pattern 107b) as one of the electrodes of the capacitor structure. Compared with the BAW resonator with an external capacitor device in the prior art, the capacitor structure directly integrated on the resonator provided in the present application can solve the problem of the BAW resonator with an external capacitor in the prior art requiring additional leads and a large device area, thereby avoiding corresponding electrical parasitics and improving device performance.

[0051] As an implementation method, Figure 2 As shown, a seed layer 103 is provided between the substrate 101 and the bottom electrode 104, so as to improve the deposition quality of the bottom electrode 104 through the seed layer 103, thereby improving the deposition quality of the piezoelectric layer 105, and further improving the Q value of the bulk acoustic wave resonator. The material of the seed layer 103 may be the same as or different from that of the piezoelectric layer 105. For example, the material of the seed layer 103 is lithium niobate, lithium tantalate or aluminum nitride.

[0052] As an implementation method, Figure 5 and Figure 6 As shown, a mass load layer 106 is disposed between the piezoelectric layer 105 and the top electrode 107 , so as to adjust the resonant frequency of the resonator through the mass load layer 106 .

[0053] As an implementation method, Fig. 9 As shown, a passivation layer 110 is disposed on the top electrode 107 and the third electrode pattern 109 , so that the passivation layer 110 protects the surface of the BAW resonator away from the substrate 101 .

[0054] As an implementation method, Fig.10 As shown, a metal layer is arranged on the passivation layer 110, and the metal layer includes a first metal structure 111a, a second metal structure 111b, a third metal structure 111c and a fourth metal structure 111d which are arranged at intervals. The first metal structure 111a is connected to the bottom electrode 104, and the second metal structure 111b is connected to the first electrode pattern 107a, so as to be connected to the two ends of the external signal through the first metal structure 111a and the second metal structure 111b respectively, so as to form an electric field between the bottom electrode 104 and the top electrode 107; the third metal structure 111c is connected to the second electrode pattern 107b, and the fourth metal structure 111d is connected to the third electrode pattern 109, so as to use the third metal structure 111c and the fourth metal structure 111d as the connection terminals of the capacitor, and the integrated capacitor is located on the side of the resonance region and is connected in parallel with the resonance region.

[0055] The material of the metal layer may be the same as or different from the material of the top electrode 107 and the bottom electrode 104, and the present application embodiment does not impose any specific limitation. For example, the material of the metal layer may be molybdenum, aluminum or copper.

[0056] As an implementation method, Fig.11 As shown, the dielectric layer 108 is formed with a first step structure on a side away from the resonance region, so that the second electrode pattern 107b and the third electrode pattern 109 are separated by the first step structure, so that the two electrodes of the capacitor structure can be insulated by the first step structure.

[0057] As an implementation method, Fig.12 and 13 As shown, the passivation layer 110 is formed with a second step structure on a side away from the resonance region, so that the second electrode pattern 107b and the fourth metal structure 111d are separated by the second step structure, so that the two electrodes of the capacitor structure are insulated by the second step structure.

[0058] like Figures 1 to 11 As shown, in a second aspect of the embodiment of the present application, a method for preparing a bulk acoustic wave resonator is provided, which is used to prepare the above-mentioned bulk acoustic wave resonator, and the method comprises:

[0059] S001, such as Figure 1 As shown, a groove is formed by etching on the substrate 101, and a sacrificial layer 102 is deposited in the groove;

[0060] S002, such as Figures 2 to 6 As shown, a bottom electrode 104, a piezoelectric layer 105 and a top electrode 107 are sequentially formed on a substrate 101 on which a sacrificial layer 102 is deposited, wherein an overlapping region of the bottom electrode 104, the piezoelectric layer 105 and the top electrode 107 in a stacking direction serves as a resonance region, and the top electrode 107 includes a first electrode pattern 107a located in the resonance region and a second electrode pattern 107b located outside the resonance region and spaced apart from the first electrode pattern 107a;

[0061] S003, such as Figure 7 and Figure 8 As shown, a dielectric layer 108 and a third electrode pattern 109 are sequentially formed on the second electrode pattern 107b, wherein the second electrode pattern 107b, the dielectric layer 108 and the third electrode pattern 109 form a capacitor;

[0062] S004, such as Fig.11 As shown, a release hole is formed by etching on the first electrode pattern 107 a , and the sacrificial layer 102 is released through the release hole until the groove is exposed to form a cavity 112 , thereby obtaining a BAW resonator having the cavity 112 .

[0063] It should be noted that the method for preparing the BAW resonator provided in this embodiment is the same as the specific structure of the BAW resonator in the previous text. A person skilled in the art can infer the method for preparing the BAW resonator based on the description of the specific structure of the BAW resonator in the previous text, and this application will not repeat the description. Since the method for preparing the BAW resonator provided in this embodiment is used to prepare the above-mentioned BAW resonator, the method for preparing the BAW resonator has the same beneficial effects as the above-mentioned BAW resonator, and will not be repeated here.

[0064] According to a third aspect of the embodiments of the present application, a filter is provided, the filter comprising the above-mentioned BAW resonator. Since the structure and beneficial effects of the BAW resonator have been described in detail in the above-mentioned embodiments, they will not be described in detail here.

[0065] The above description is only an optional embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0066] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

Claims

1. A bulk acoustic wave resonator, characterized in that: It includes a substrate and a bottom electrode, a piezoelectric layer and a top electrode arranged in sequence on the substrate, wherein the substrate is provided with a groove, and the overlapping area of ​​the bottom electrode, the piezoelectric layer and the top electrode in the stacking direction serves as a resonance area, the top electrode includes a first electrode pattern located in the resonance area and a second electrode pattern located outside the resonance area and spaced apart from the first electrode pattern, a dielectric layer and a third electrode pattern are arranged in sequence on the second electrode pattern, and the second electrode pattern, the dielectric layer and the third electrode pattern form a capacitor.

2. The bulk acoustic wave resonator according to claim 1, characterized in that A seed layer is disposed between the substrate and the bottom electrode.

3. The bulk acoustic wave resonator according to claim 2, characterized in that: The material of the seed layer is the same as that of the piezoelectric layer.

4. The bulk acoustic wave resonator according to claim 1, characterized in that A mass loading layer is disposed between the piezoelectric layer and the top electrode.

5. The bulk acoustic wave resonator according to claim 1, characterized in that: A passivation layer is disposed on the top electrode and the third electrode pattern.

6. The bulk acoustic wave resonator according to claim 5, characterized in that A metal layer is arranged on the passivation layer, and the metal layer includes a first metal structure, a second metal structure, a third metal structure and a fourth metal structure which are arranged at intervals, the first metal structure is connected to the bottom electrode, the second metal structure is connected to the first electrode pattern, the third metal structure is connected to the second electrode pattern, and the fourth metal structure is connected to the third electrode pattern.

7. The BAW resonator according to claim 1, characterized in that: The dielectric layer is formed with a first step structure at a side away from the resonance region, so that the second electrode pattern and the third electrode pattern are separated by the first step structure.

8. The bulk acoustic wave resonator according to claim 6, characterized in that The passivation layer is formed with a second step structure at a side away from the resonance region, so that the second electrode pattern and the fourth metal structure are separated by the second step structure.

9. 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 to 8, the method comprises: Etching a groove on a substrate and depositing a sacrificial layer in the groove; A bottom electrode, a piezoelectric layer and a top electrode are sequentially formed on the substrate on which the sacrificial layer is deposited, wherein an overlapping region of the bottom electrode, the piezoelectric layer and the top electrode in a stacking direction serves as a resonance region, and the top electrode comprises a first electrode pattern located in the resonance region and a second electrode pattern located outside the resonance region and spaced apart from the first electrode pattern; forming a dielectric layer and a third electrode pattern in sequence on the second electrode pattern, wherein the second electrode pattern, the dielectric layer and the third electrode pattern form a capacitor; A release hole is formed by etching on the first electrode pattern, and the sacrificial layer is released through the release hole until the groove is exposed to form a cavity, thereby obtaining a bulk acoustic wave resonator having the cavity.

10. A filter, characterized in that: A bulk acoustic wave resonator comprising any one of claims 1 to 8.

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