Bulk acoustic wave resonator
By setting a non-centrosymmetric curved segment on the side of the cavity of the bulk acoustic wave resonator, the problems of piezoelectric layer dislocation and fracture are solved, and the performance and reliability of the device are improved.
Patent Information
- Application Number
- CN202422568008.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2025-09-09
- Estimated Expiration
- 2034-10-23
AI Technical Summary
The piezoelectric layer is prone to defects such as dislocation and fracture during the growth process, which affects the performance of the bulk acoustic wave resonator, especially in the air-gap resonator with a ground-type cavity.
A bulk acoustic wave resonator is designed. By setting a non-centrosymmetric first curve segment and a second curve segment on the side of a ground-type cavity, the deformation of the piezoelectric layer is controlled, the leakage of acoustic energy and the spurious mode are reduced, and the device performance is improved.
Effectively reduce the probability of dislocation and fracture defects in the piezoelectric layer, reduce acoustic energy leakage, and improve the performance and reliability of the resonator.
Smart Images
Figure CN223322060U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of communication devices, and primarily to a bulk acoustic wave resonator. Background Art
[0002] The basic structure of a bulk acoustic wave resonator is a "sandwich" structure consisting of a stacked bottom electrode, a piezoelectric layer, and a top electrode. When a high-frequency electrical signal is applied between the top and bottom electrodes, the inverse piezoelectric effect of the piezoelectric layer excites a bulk acoustic wave (BAW) within the piezoelectric layer, propagating along the thickness of the piezoelectric layer. The transmission path of the BAW is equal to the sum of the thicknesses of the top and bottom electrodes and the piezoelectric layer. When a certain relationship exists between the BAW wavelength and the propagation path, standing wave oscillations occur. At this point, the signal resonates within the material, and the equivalent impedance of the device reaches an extreme value. To optimize the performance of BAW in the high-frequency band (above 1 GHz), the optimal solution is to miniaturize the "sandwich" structure from a bulk structure to a thin-film structure.
[0003] Resonators are categorized into air-gap resonators (FBARs) and solid-mounted resonators (SMRs) based on their acoustic wave reflection structures. FBARs use a cavity for acoustic wave reflection, while SMRs use a Bragg reflector. The cavity of an air-gap resonator can be located underground within the substrate or above ground, located on the substrate surface.
[0004] As a radio frequency device, FBAR requires an radio frequency voltage applied to two electrodes to act as a power source. Under the action of the radio frequency voltage, the piezoelectric layer will generate an alternating electric field. Due to the inverse piezoelectric effect, the piezoelectric layer will deform, which manifests as the vibration of phonons at the microscopic level and forms sound waves at the macroscopic level. This sound wave is the bulk acoustic wave inside the piezoelectric body. Through this process, electrical energy is converted into mechanical energy.
[0005] Therefore, the growth quality of the piezoelectric layer is crucial to device performance. However, due to the potential for lateral / oblique tensile forces between the crystal pillars during the piezoelectric layer growth process, the piezoelectric layer is prone to defects such as dislocations and fractures in non-horizontal regions, thereby affecting device performance. This is especially true for air-gap resonators with ground-based cavities.
[0006] Therefore, how to reduce the probability of defects such as dislocation and fracture in the piezoelectric layer, reduce the loss of the piezoelectric layer, and thus improve the performance of the device has become an issue that needs to be considered in resonator design. Utility Model Content
[0007] In order to solve the above technical problems existing in the prior art, the present invention proposes a bulk acoustic wave resonator to solve the above problems.
[0008] The utility model proposes a bulk acoustic wave resonator, comprising a substrate, a resonant functional layer arranged on the substrate, and a ground-type cavity located between the substrate and the resonant functional layer; the resonant functional layer comprises a bottom electrode, a piezoelectric layer, and a top electrode that are stacked; the bottom electrode is located between the ground-type cavity and the piezoelectric layer;
[0009] In a cross section perpendicular to the substrate, the above-ground cavity includes a top edge, a bottom edge, and two side edges, both of which are connected to the top edge and the bottom edge; at least one of the side edges includes a first curved segment and a second curved segment;
[0010] The first curved segment is an upward concave curve, while the second curved segment is a downward concave curve. Furthermore, the first and second curved segments on the same side are non-centrosymmetrically arranged. This arrangement of the first and second curved segments in this bulk acoustic wave resonator reduces defects such as misalignment or fracture in the piezoelectric layer. Furthermore, the non-centrosymmetrical arrangement of the first and second curved segments on the same side effectively reduces acoustic energy leakage, thereby improving resonator performance.
[0011] In some embodiments, in any cross section perpendicular to the substrate, the second curved segments on two sides of the above-ground cavity are asymmetrically arranged, thereby effectively reducing spurious modes of acoustic waves.
[0012] In some embodiments, in a cross section perpendicular to the substrate, the curvature change rates between a first curved segment and a second curved segment on the same side, and between two second curved segments on different sides, are different. This configuration can further reduce acoustic energy leakage and lower spurious modes of acoustic waves.
[0013] In some embodiments, the angle α between the tangent line at any point on the first curved segment and the bottom edge is within the range of 0° to 40°. By controlling this angle, the piezoelectric layer is less likely to have defects such as dislocation and fracture at the first curved segment.
[0014] In some embodiments, the angle β between the tangent line at any point on the second curved segment and the top edge is within the range of 140-180°. By controlling this angle, the piezoelectric layer is less likely to have defects such as dislocation and fracture at the second curved segment.
[0015] In some embodiments, the angle α gradually increases from 0° to 40° in a direction in which the first curved segment moves away from the bottom edge.
[0016] In some embodiments, in a direction in which the second curved segment moves away from the top edge, the angle β gradually decreases from 180° to 140°.
[0017] In some embodiments, the external connection end of the bottom electrode extends outward along the side of the above-ground cavity. At this side position of the above-ground cavity, the external connection end of the bottom electrode and the piezoelectric layer thereon have the same shape as the side of the above-ground cavity.
[0018] In some embodiments, on the side of the bottom electrode that is not connected to the outside, the piezoelectric layer extends outward along the side of the above-ground cavity, and at this side position of the above-ground cavity on the side where the bottom electrode is not connected to the outside, the piezoelectric layer has the same shape as the side of the above-ground cavity.
[0019] A bulk acoustic wave resonator of the utility model is provided with a curved segment on the side of a ground-type cavity, so that the piezoelectric layer is less likely to have defects such as dislocation or breakage. The non-center-symmetrical arrangement of the first curved segment and the second curved segment on the same side can effectively reduce the leakage of acoustic energy, thereby improving the performance of the resonator; on any cross-section perpendicular to the substrate, the asymmetric arrangement of the second curved segments on both sides of the ground-type cavity can effectively reduce the stray modes of the acoustic waves. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and, together with the description, serve to explain the principles of the present invention. Other embodiments and many of the expected advantages of the embodiments will be readily apparent as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with respect to each other. Like reference numerals designate corresponding similar parts.
[0021] Figure 1 shows a schematic cross-sectional view of a bulk acoustic wave resonator according to an embodiment of the present utility model;
[0022] Figure 2 A schematic diagram of an above-ground cavity structure according to an embodiment of the present invention is shown;
[0023] Figure 3a-3b A schematic diagram showing the side of an above-ground cavity structure according to a first specific embodiment of the present utility model is shown;
[0024] Figure 4 A schematic diagram of the side of an above-ground cavity structure according to a second specific embodiment of the present utility model is shown. DETAILED DESCRIPTION
[0025] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant utility model and are not intended to limit the utility model. It should also be noted that, for ease of description, only portions relevant to the relevant utility model are shown in the accompanying drawings.
[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0027] Figure 1 FIG shows a cross-sectional view of a bulk acoustic wave resonator according to an embodiment of the present invention, which is a schematic cross-sectional view perpendicular to the substrate direction. Figure 1 As shown, the bulk acoustic wave resonator includes a top electrode 1, a piezoelectric layer 2, a bottom electrode 3, a cavity 4 and a substrate 5, wherein the bottom electrode 3, the piezoelectric layer 2 and the top electrode 1 are stacked to form a resonant functional layer; the cavity 4 is located on the substrate 5, which is a ground-type cavity structure; the bottom electrode 3 is between the cavity 4 and the piezoelectric layer 2. Figure 2 The schematic diagram of the cavity structure according to one embodiment of the present invention is shown to explain the cavity structure in detail:
[0028] In a specific embodiment, in the cross section perpendicular to the substrate direction, the cavity 4 specifically includes a top edge 4.1, a bottom edge 4.2 and two side edges 4.3, wherein the two side edges 4.3 are connected to the top edge 4.1 and the bottom edge 4.2. Figure 3a-3b A schematic diagram of the side of the cavity structure according to the first specific embodiment of the present invention is shown. Figure 3a and 3b As shown, at least one side 4.3 specifically includes a first curved segment 4.31 and a second curved segment 4.32, one end of the first curved segment 4.31 is connected to the bottom side 4.2, one end of the second curved segment 4.32 is connected to the top side 4.1, and the other end of the first curved segment 4.31 is connected to the other end of the second curved segment 4.32, and the first curved segment 4.31 and the second curved segment 4.32 on the same side are non-center-symmetrically arranged (that is, the first curved segment 4.31 on the same side does not overlap with the second curved segment 4.32 after being rotated 180° around the connection point between the two curved segments or the midpoint of the connecting line segment).
[0029] In a specific embodiment, first curved segment 4.31 is a curved segment originating from base 4.2 and presenting an overall upward concave state. The angle α between the tangent line at any point on the curved segment and base 4.2 is within a range of 0° to 40°. In this embodiment, first curved segment 4.31 is tangent to base 4.2 at its starting point (i.e., angle α at the connection is 0°). As the concave curve extends away from base 4.2, angle α gradually increases, reaching a maximum of 40° at the other end of first curved segment 4.31. This angle α can be used to control the height of cavity 4 and to reduce the likelihood of defects such as dislocation and fracture in piezoelectric layer 2 at the location of first curved segment 4.31.
[0030] In a specific embodiment, second curved segment 4.32 is a curved segment originating from top edge 4.1 and exhibiting an overall concave shape. The angle β between the tangent line at any point on the curved segment and top edge 4.1 is within a range of 140° to 180°. In this embodiment, second curved segment 4.32 is tangent to top edge 4.1 at its starting point (i.e., the angle β at the connection is 180°). As the concave curve extends away from top edge 4.1, the angle β gradually decreases, reaching a minimum of 140° at the other end of second curved segment 4.32. This angle β can also be used to control the height of cavity 4 and, in addition, to reduce the likelihood of defects such as dislocation and fracture in piezoelectric layer 2 at the location of second curved segment 4.32.
[0031] In a specific embodiment, reference Figure 1 In the view, the external connection end of the bottom electrode 3 extends outward along the side 4.3 of the cavity 4, and in the cross section perpendicular to the substrate, the shape of the external connection end of the bottom electrode 3 on the upper side of the side 4.3 and the piezoelectric layer 2 thereon is the same as the shape of the side 4.3.
[0032] On the non-external connection end side of the bottom electrode 3, the piezoelectric layer 2 extends outward along the side 4.3 of the cavity 4. In the cross section perpendicular to the substrate, the shape of the piezoelectric layer 2 on the upper side of the side 4.3 is the same as that of the side 4.3.
[0033] In a specific embodiment, in any cross-sectional direction perpendicular to the substrate, for example Figure 1 In the view, the second curved segments 4.32 on both sides of the cavity 4 are asymmetrically arranged (i.e., the second curved segment 4.32 on one side is symmetrical about the central axis of the cavity 4 and does not overlap with the second curved segment 4.32 on the other side). This arrangement can effectively reduce the stray modes of the sound waves.
[0034] On any cross section perpendicular to the substrate, the curvature change rates between the first curve segment 4.31 and the second curve segment 4.32 on the same side and between two first curve segments 4.31 on different sides are different.
[0035] Continue to refer to 4, Figure 4 A schematic diagram of the side of the above-ground cavity structure according to the second specific embodiment of the present invention is shown. Figure 4 As shown, based on the above embodiment, a connecting line segment 4.33 is provided between the first curved segment 4.31 and the second curved segment 4.32. The connecting line segment 4.33 can be a straight line or a curve. In a specific embodiment, the connecting line segment 4.33 is a straight line segment with a slope within the range of 30° to 40°. The connecting line segment 4.33 can transitionally connect the two curved segments to increase the height of the cavity.
[0036] In other embodiments, the connecting line segment 4.33 can be set as a concave upward or concave downward curve segment, and the angle between the tangent of any point on the connecting line segment 4.33 and the bottom edge 4.2 is taken in the range of 30° to 40°, which can also achieve the purpose of increasing the height of the cavity and further reduce defects such as dislocation and fracture of the piezoelectric layer 2 in steep positions.
[0037] The above describes the specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.
[0038] In the description of this application, it should be understood that the terms "upper", "lower", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting this application. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of multiple such elements. The simple fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used for improvement. Any reference signs in the claims should not be interpreted as limiting the scope.
Claims
1. A bulk acoustic wave resonator, characterized in that: The invention comprises a substrate, a resonance function layer provided on the substrate, and a ground-type cavity located between the substrate and the resonance function layer; the resonance function layer comprises a bottom electrode, a piezoelectric layer and a top electrode which are stacked; the bottom electrode is located between the ground-type cavity and the piezoelectric layer; In a cross section perpendicular to the substrate, the above-ground cavity includes a top edge, a bottom edge, and two side edges, wherein the two side edges are connected to the top edge and the bottom edge; at least one of the side edges includes a first curved segment and a second curved segment; The first curved segment is an upward concave curve, the second curved segment is a downward concave curve, and the first curved segment and the second curved segment on the same side are non-centrally symmetrically arranged.
2. The bulk acoustic wave resonator according to claim 1, wherein On any cross section perpendicular to the substrate, the second curved segments on the two side edges of the above-ground cavity are asymmetrically arranged.
3. The bulk acoustic wave resonator according to claim 1 or 2, characterized in that: In a cross section perpendicular to the substrate, the curvature change rates between the first curve segment and the second curve segment on the same side and between two second curve segments on different sides are different.
4. The bulk acoustic wave resonator according to claim 3, characterized in that The included angle α between the tangent line at any point on the first curved segment and the base is within the range of 0° to 40°.
5. The bulk acoustic wave resonator according to claim 3, wherein The included angle β between the tangent line at any point on the second curved segment and the top edge is within the range of 140° to 180°.
6. The bulk acoustic wave resonator according to claim 4, characterized in that In the direction in which the first curved segment moves away from the base, the angle α gradually increases from 0° to 40°.
7. The bulk acoustic wave resonator according to claim 5, characterized in that In a direction in which the second curved segment moves away from the top edge, the angle β gradually decreases from 180° to 140°.
8. The bulk acoustic wave resonator according to claim 1, wherein The external connection end of the bottom electrode extends outward along the side of the above-ground cavity. At this side position of the above-ground cavity, the external connection end of the bottom electrode and the piezoelectric layer thereon have the same shape as the side of the above-ground cavity.
9. The bulk acoustic wave resonator according to claim 1, wherein On the side of the bottom electrode that is not connected to the outside, the piezoelectric layer extends outward along the side of the above-ground cavity. At this side position of the above-ground cavity on the side of the bottom electrode that is not connected to the outside, the piezoelectric layer has the same shape as the side of the above-ground cavity.