Bulk acoustic wave resonator

Abstract

The invention discloses a bulk acoustic wave resonator. The bulk acoustic wave resonator comprises a first electrode, a piezoelectric layer and a second electrode which are stacked, the electrode of the bulk acoustic wave resonator further comprises at least one group of irregular edges, each group of irregular edges comprises a first edge and a second edge which are adjacent to each other, an included angle is formed between the extension direction of the first edge and the extension direction of the second edge, and the first edge and the second edge are provided with nonlinear electrode boundaries; wherein the irregular edges of different groups are the edges of different electrodes, and the irregular edges of the same group are the edges of the same electrode. The manufacturing process of the bulk acoustic wave resonator is simplified, the stability and reliability of the bulk acoustic wave resonator are improved, meanwhile, resonance of a transverse mode can be restrained, dense distribution and layout of the resonators are facilitated, the design of the resonators is simplified, and the cost of the resonators is reduced.

Description

Technical Field

[0001] This invention relates to the field of resonator technology, and more particularly to a bulk acoustic resonator. Background Technology

[0002] A bulk acoustic wave (BAS) resonator is an acoustic stack composed of an upper electrode, a piezoelectric layer, and a lower electrode. This resonator offers advantages such as small size, high performance, and suitability for integrated circuits. The BAS resonator actively excites longitudinal modes that vibrate in the thickness direction, and these longitudinal modes determine the resonator's main performance indicators. However, exciting the longitudinal modes can also induce unwanted transverse parasitic modes, and the strong presence of these transverse modes increases the resonator's clutter. In existing technologies, the electrodes of BAS resonators are typically set in irregular shapes, such as irregular polygons, scallop shapes, and ellipses, to suppress transverse parasitic modes. However, this irregular resonator shape is detrimental to the density and layout of the resonators, negatively impacting filter design and cost control. Summary of the Invention

[0003] This invention provides a bulk acoustic wave resonator that improves the performance of the bulk acoustic wave resonator based on the fact that the macroscopic shape of the bulk acoustic wave resonator is regular, especially rectangular.

[0004] In a first aspect, embodiments of the present invention provide a bulk acoustic resonator, comprising a first electrode, a piezoelectric layer, and a second electrode stacked together.

[0005] The electrodes of the bulk acoustic resonator also include at least one set of irregular edges. Each set of irregular edges includes an adjacent first edge and a second edge. The extension directions of the first edge and the second edge have an angle. Both the first edge and the second edge are non-linear electrode boundaries. The irregular edges in different sets are the edges of different electrodes, and the irregular edges in the same set are the edges of the same electrode.

[0006] Optionally, the orthographic projection of the first electrode on the piezoelectric layer has a first sub-edge and a second sub-edge with different extending directions. The first sub-edge and the second sub-edge are located within the orthographic projection of the second electrode on the piezoelectric layer. The first sub-edge and the second sub-edge are respectively the first edge and the second edge in a set of irregular edges.

[0007] Optionally, the orthographic projection of the second electrode on the piezoelectric layer has a third sub-edge and a fourth sub-edge with different extending directions. The third sub-edge and the fourth sub-edge are located within the orthographic projection of the first electrode on the piezoelectric layer. The third sub-edge and the fourth sub-edge are respectively the first edge and the second edge in a set of irregular edges.

[0008] Optionally, the orthographic projection of the first electrode on the piezoelectric layer has a first sub-edge and a second sub-edge with different extension directions, and the orthographic projection of the second electrode on the piezoelectric layer has a third sub-edge and a fourth sub-edge with different extension directions. The first sub-edge and the second sub-edge are located within the orthographic projection of the second electrode on the piezoelectric layer, and the first sub-edge and the second sub-edge are respectively the first edge and the second edge in a set of irregular edges. The third sub-edge and the fourth sub-edge are located within the orthographic projection of the first electrode on the piezoelectric layer, and the third sub-edge and the fourth sub-edge are respectively the first edge and the second edge in another set of irregular edges.

[0009] Optionally, the non-linear electrode boundary includes periodically arranged protrusions, the protrusions being the outermost points of the edge; along the extension direction of the edge, the distance between two adjacent protrusions is a first distance, the length of the first distance ranging from one-seventh to one-fifteenth of the edge length.

[0010] Optionally, the non-linear electrode boundary further includes periodically arranged concave points, which are alternately arranged with the convex points, and the concave points are the innermost points of the edge; along the first direction, the vertical distance between adjacent convex points and concave points is a second distance, and the length of the second distance is one-third to one-fifth of the first distance; wherein, the first direction is perpendicular to the extension direction of the edge.

[0011] Optionally, the first electrode includes a set of irregular edges, and the shape formed by the connecting lines of the protrusions or concave points of the set of irregular edges and the orthogonal projection of the other edges of the first electrode onto the piezoelectric layer is a rectangle; and / or, the second electrode includes another set of irregular edges, and the shape formed by the connecting lines of the protrusions or concave points of the other set of irregular edges and the orthogonal projection of the other edges of the second electrode onto the piezoelectric layer is a rectangle.

[0012] Optionally, the non-linear electrode boundary is serrated or wavy.

[0013] Optionally, the bulk acoustic wave resonator further includes a substrate having a cavity, a piezoelectric layer disposed on the substrate and covering the cavity, a first electrode disposed on the surface of the piezoelectric layer within the cavity, a second electrode disposed on the side of the piezoelectric layer away from the substrate, the orthographic projection of the irregular edge on the piezoelectric layer being located within the orthographic projection of the cavity on the piezoelectric layer, and a through hole disposed on the second electrode, the through hole penetrating the piezoelectric layer and the first electrode and communicating with the cavity.

[0014] Optionally, the edge of the second electrode has a right-angle chamfer, which is reused as the through hole, penetrating the piezoelectric layer and the first electrode and communicating with the cavity.

[0015] The technical solution of this invention, by setting the orthogonal projections of the first and second electrodes onto the plane of the piezoelectric layer to be located within the piezoelectric layer, defines the shape of the active excitation portion of the bulk acoustic wave resonator by the overlapping area of ​​the first and second electrodes along the thickness direction. This avoids patterning the piezoelectric layer in the active excitation portion, preventing slopes and lateral parasitic resonances on the sides of the piezoelectric layer, and simplifying the fabrication process of the bulk acoustic wave resonator. Simultaneously, it allows the piezoelectric layers of different bulk acoustic wave resonators to be in a continuous state, greatly improving the stability and reliability of the bulk acoustic wave resonator and reducing the excitation of lateral modes of the piezoelectric layer. Furthermore, the electrodes of the bulk acoustic wave resonator include at least one set of irregular edges, which increases the complexity of lateral mode excitation of the bulk acoustic wave resonator without changing the macroscopic shape of the active excitation portion, thereby suppressing lateral mode resonance. Maintaining a macroscopically regular shape for the first and second electrodes facilitates the dense arrangement and layout of the resonators, simplifies the resonator design, and reduces the cost of the resonator. Furthermore, the extension directions of the first edge and the second edge in each group of irregular edges have an angle. Irregular edges in the same group are edges of the same electrode, while irregular edges in different groups are edges of different electrodes. This can prevent the first edge and the second edge in each group of irregular edges from being parallel, and at the same time, it can prevent irregular edges in different groups from being parallel in the same plane. This reduces the probability of transverse modal resonance reflected by the first edge and the second edge, and also reduces the probability of transverse modal resonance reflected by irregular edges in different groups, further suppressing the transverse modal resonance of the bulk acoustic resonator. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of a bulk acoustic resonator provided in an embodiment of the present invention.

[0017] Figure 2 This is a top view schematic diagram of a bulk acoustic resonator provided in an embodiment of the present invention;

[0018] Figure 3 A frequency-impedance curve of a bulk acoustic resonator provided in an embodiment of the present invention;

[0019] Figure 4 A frequency-impedance curve of another bulk acoustic resonator provided in an embodiment of the present invention;

[0020] Figure 5 A frequency-impedance curve of another bulk acoustic resonator provided in an embodiment of the present invention;

[0021] Figure 6 A top view of another bulk acoustic resonator provided in an embodiment of the present invention;

[0022] Figure 7 A top view of another bulk acoustic resonator provided in an embodiment of the present invention;

[0023] Figure 8 This is a top view of a second electrode provided in an embodiment of the present invention;

[0024] Figure 9 A frequency-impedance curve of another bulk acoustic resonator provided in an embodiment of the present invention;

[0025] Figure 10 A schematic diagram of an electrode with a non-linear electrode boundary provided in an embodiment of the present invention;

[0026] Figure 11 A schematic diagram of another electrode structure with a non-linear electrode boundary provided in an embodiment of the present invention;

[0027] Figure 12 A schematic diagram of an electrode boundary where the edge of another electrode is non-linear, provided in an embodiment of the present invention;

[0028] Figure 13 This is a schematic diagram of another electrode structure provided in an embodiment of the present invention, where the edge of the electrode has a non-linear electrode boundary. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0030] Figure 1 This is a schematic cross-sectional view of a bulk acoustic resonator provided in an embodiment of the present invention. Figure 2 This is a top view schematic diagram of a bulk acoustic resonator provided in an embodiment of the present invention. Figure 1 and Figure 2 As shown, the bulk acoustic wave resonator includes a first electrode 10, a piezoelectric layer 20, and a second electrode 30 stacked together. The electrodes of the bulk acoustic wave resonator also include at least one set of irregular edges. Each set of irregular edges includes an adjacent first edge L1 and a second edge L2. The extension direction of the first edge L1 and the extension direction of the second edge L2 have an angle. The first edge L1 and the second edge L2 are both non-linear electrode boundaries. Among them, the irregular edges of different sets are the edges of different electrodes, and the irregular edges of the same set are the edges of the same electrode.

[0031] Specifically, the first electrode 10, the piezoelectric layer 20, and the second electrode 30 are stacked along the thickness direction. The first electrode 10 can be the lower electrode of the bulk acoustic wave resonator, and the second electrode 30 can be the upper electrode of the bulk acoustic wave resonator. The orthogonal projections of the first electrode 10 and the second electrode 30 onto the plane of the piezoelectric layer 20 are located within the piezoelectric layer 20, such that the overlapping area of ​​the first electrode 10 and the second electrode 30 along the thickness direction defines the shape of the active excitation portion of the bulk acoustic wave resonator. This avoids patterning the piezoelectric layer 20 in the active excitation portion, prevents the generation of slopes and lateral parasitic resonances on the sides of the piezoelectric layer 20, and simplifies the fabrication process of the bulk acoustic wave resonator. Simultaneously, it allows the piezoelectric layer 20 of different bulk acoustic wave resonators to be in a continuous state, greatly improving the stability and reliability of the bulk acoustic wave resonator and reducing the excitation of the lateral modes of the piezoelectric layer 20. For example, when the first electrode 10 and the second electrode 30 are of regular shapes, the bulk acoustic wave resonator is of a regular shape.

[0032] The overlapping region of the first electrode 10 and the second electrode 30 along the thickness direction constitutes the active excitation portion of the bulk acoustic wave resonator, such that the edges of the active excitation portion of the bulk acoustic wave resonator are the edges of the first electrode 10 and / or the second electrode. When at least one set of edges in the overlapping region of the first electrode 10 and the second electrode 30 along the thickness direction has irregular edges, the active excitation portion of the bulk acoustic wave resonator can include at least one set of irregular edges. Without changing the macroscopic shape of the active excitation portion, the complexity of the transverse modal excitation of the bulk acoustic wave resonator can be increased, thereby suppressing transverse modal resonance. At this time, the macroscopic shape of the first electrode 10 and the second electrode 30 can be a regular shape, which is beneficial for the dense arrangement and layout of the resonator, simplifies the design of the resonator, and reduces the cost of the resonator. Moreover, the extension direction of the first edge L1 and the extension direction of the second edge L2 in each set of irregular edges have an angle, avoiding the parallelism of the first edge L1 and the second edge L2 in each set of irregular edges, reducing the probability of transverse modal resonance reflected by the first edge L1 and the second edge L2, and further suppressing the transverse modal resonance of the bulk acoustic wave resonator. Furthermore, irregular edges in the same group are edges of the same electrode. That is, the first edge L1 and the second edge L2 in the same group can both be edges of the first electrode 10 or edges of the second electrode 30. This increases the complexity of transverse modal excitation of the bulk acoustic resonator by using the edges of the first electrode 10 or the second electrode 30. Irregular edges in different groups are edges of different electrodes. That is, the first edge L1 and the second edge L2 in the first group can both be edges of the first electrode 10, and the first edge L1 and the second edge L2 in the second group can both be edges of the second electrode 30. This avoids parallel irregular edges in different groups on the same plane, reduces the probability of transverse modal resonance reflected from irregular edges in different groups, and further suppresses transverse modal resonance of the bulk acoustic resonator.

[0033] For example, such as Figure 2As shown, the macroscopic shape of the top view of the first electrode 10 can be rectangular. The first sub-side L11 and the second sub-side L12 of the first electrode 10 are two adjacent sides of the rectangle, located within the top view of the second electrode 30. In this case, the first sub-side L11 and the second sub-side L12 serve as the edges of the overlapping region of the first electrode 10 and the second electrode 30 along the thickness direction. By setting the first sub-side L11 and the second sub-side L12 to be the first edge L1 and the second edge L2 in a set of irregular edges, the active excitation part of the bulk acoustic wave resonator can include a set of irregular edges. Without changing the macroscopic shape of the active excitation part, the complexity of the transverse modal excitation of the bulk acoustic wave resonator can be increased, thereby suppressing transverse modal resonance. At this time, the macroscopic shape of the top view of the first electrode 10 and the second electrode 30 can still be rectangular, which is beneficial for the dense arrangement and layout of the resonators, simplifies the resonator design, and reduces the cost of the resonator. Figure 3 This invention provides a frequency-impedance curve diagram of a bulk acoustic wave resonator. The horizontal axis represents frequency, and the vertical axis represents impedance. Curve 1 shows the frequency-impedance curve of the bulk acoustic wave resonator when the first sub-side L11 and the second sub-side L12 are straight edges, and curve 2 shows the frequency-impedance curve of the bulk acoustic wave resonator when the first sub-side L11 and the second sub-side L12 are sawtooth-shaped edges. Figure 3 As shown, curve 2 is smoother at the resonant frequency than curve 1, meaning that when the first sub-side L11 and the second sub-side L12 are sawtooth-shaped edges, the noise of the bulk acoustic resonator is less, suppressing the resonance of the transverse modes of the bulk acoustic resonator.

[0034] It should be noted that, Figure 2 The example shown illustrates that the macroscopic shape of the first electrode 10 projected onto the piezoelectric layer 20 is rectangular. In this case, the extending directions of the first sub-side L11 and the second sub-side L12 are perpendicular. In other embodiments, when the macroscopic shape of the first electrode 10 projected onto the piezoelectric layer 20 is other polygonal shapes, the extending directions of the first sub-side L11 and the second sub-side L12 may not be perpendicular, and this is not limited here.

[0035] The technical solution of this embodiment, by setting the orthogonal projections of the first and second electrodes onto the plane of the piezoelectric layer to be located within the piezoelectric layer, defines the shape of the active excitation portion of the bulk acoustic wave resonator by the overlapping area of ​​the first and second electrodes along the thickness direction. This avoids patterning the piezoelectric layer in the active excitation portion, preventing slopes and lateral parasitic resonances on the sides of the piezoelectric layer, and simplifying the fabrication process of the bulk acoustic wave resonator. Simultaneously, it allows the piezoelectric layers of different bulk acoustic wave resonators to be in a continuous state, greatly improving the stability and reliability of the bulk acoustic wave resonator and reducing the excitation of lateral modes of the piezoelectric layer. Furthermore, the electrodes of the bulk acoustic wave resonator include at least one set of irregular edges, which increases the complexity of lateral mode excitation of the bulk acoustic wave resonator without changing the macroscopic shape of the active excitation portion, thereby suppressing lateral mode resonance. Maintaining a macroscopically regular shape for the first and second electrodes facilitates the dense arrangement and layout of the resonators, simplifies the resonator design, and reduces the cost of the resonator. Furthermore, the extension directions of the first edge and the second edge in each group of irregular edges have an angle. Irregular edges in the same group are edges of the same electrode, while irregular edges in different groups are edges of different electrodes. This can prevent the first edge and the second edge in each group of irregular edges from being parallel, and at the same time, it can prevent irregular edges in different groups from being parallel in the same plane. This reduces the probability of transverse modal resonance reflected by the first edge and the second edge, and also reduces the probability of transverse modal resonance reflected by irregular edges in different groups, further suppressing the transverse modal resonance of the bulk acoustic resonator.

[0036] In some embodiments, continue to refer to Figure 1 The bulk acoustic wave resonator includes a first pin 40 and a second pin 50, located on the same side of the piezoelectric layer 20. The piezoelectric layer 20 has vias, through which the first electrode 10 can be connected to the first pin 40, and the second electrode 30 can be directly connected to the second pin 50, facilitating the connection of the bulk acoustic wave resonator to other devices.

[0037] Continue to refer to Figure 2 The orthographic projection of the first electrode 10 on the piezoelectric layer 20 has a first sub-edge L11 and a second sub-edge L12 with different extension directions. The first sub-edge L11 and the second sub-edge L12 are located within the orthographic projection of the second electrode 30 on the piezoelectric layer 20. The first sub-edge L11 and the second sub-edge L12 are respectively the first edge L1 and the second edge L2 in a set of irregular edges.

[0038] Specifically, when the first sub-edge L11 and the second sub-edge L12 are located within the orthogonal projection of the second electrode 30 onto the piezoelectric layer 20, the first sub-edge L11 and the second sub-edge L12 serve as two adjacent edges of the overlapping region of the first electrode 10 and the second electrode 30 along the thickness direction. That is, the first sub-edge L11 and the second sub-edge L12 are two adjacent edges of the active excitation portion of the bulk acoustic wave resonator. By setting both the first sub-edge L11 and the second sub-edge L12 to be non-linear electrode boundaries, the active excitation portion of the bulk acoustic wave resonator includes a set of irregular edges. Without changing the macroscopic shape of the first electrode 10, the complexity of the transverse modal excitation of the bulk acoustic wave resonator can be increased, thereby suppressing transverse modal resonance. Simultaneously, this balances the density and layout of the resonators, simplifies the resonator design, and reduces the cost of the resonator.

[0039] It should be noted that the orthogonal projection of the first electrode 10 onto the piezoelectric layer 20 also includes two additional sub-edges, one of which is positioned opposite to the first sub-edge L11, and the other is positioned opposite to the second sub-edge L12. By ensuring that these two additional sub-edges are straight, it avoids the situation where one sub-edge is parallel to the first sub-edge L11 and the other to the second sub-edge L12. This reduces the probability of transverse modal resonance caused by the parallel edges of the first electrode 10, further suppressing the transverse modal resonance of the bulk acoustic resonator. For example, Figure 4 This is a frequency-impedance curve diagram of another bulk acoustic wave resonator provided in an embodiment of the present invention. The horizontal axis represents frequency, and the vertical axis represents impedance. Curve 3 is the frequency-impedance curve of the bulk acoustic wave resonator when the first sub-side L11 and the second sub-side L12 have serrated edges. Curve 4 is the frequency-impedance curve of the bulk acoustic wave resonator when the first sub-side L11, the second sub-side L12, and the sub-side parallel to the second sub-side L12 all have serrated edges. Figure 4 As shown, curve 3 has a sharper peak at the resonant frequency compared to curve 4, meaning that the quality factor Q of the bulk acoustic wave resonator corresponding to curve 3 is greater than that of the bulk acoustic wave resonator corresponding to curve 4. The performance of the bulk acoustic wave resonator when the first sub-side L11 and the second sub-side L12 are sawtooth-shaped edges is better than the performance of the bulk acoustic wave resonator when the first sub-side L11, the second sub-side L12, and the sub-sides parallel to the second sub-side L12 are all sawtooth-shaped edges. Figure 5 This is another frequency-impedance curve diagram of a bulk acoustic wave resonator provided in an embodiment of the present invention. The horizontal axis represents frequency, and the vertical axis represents impedance. Curve 5 shows the frequency-impedance curve of the bulk acoustic wave resonator when the first sub-side L11 and the second sub-side L12 have serrated edges. Curve 6 shows the frequency-impedance curve of the bulk acoustic wave resonator when the first sub-side L11, the second sub-side L12, and the other two sub-sides all have serrated edges. Figure 5As shown, curve 5 has a sharper peak at the resonant frequency compared to curve 6, meaning the quality factor Q of the bulk acoustic wave resonator corresponding to curve 5 is greater than that of the bulk acoustic wave resonator corresponding to curve 6. The performance of the bulk acoustic wave resonator when the first sub-side L11 and the second sub-side L12 are sawtooth-shaped edges is better than the performance of the bulk acoustic wave resonator when the first sub-side L11, the second sub-side L12, and the other two sub-sides are all sawtooth-shaped edges. That is, the performance of the bulk acoustic wave resonator with the first sub-side L11 and the second sub-side L12 of the first electrode 10 being sawtooth-shaped, compared to the performance of the bulk acoustic wave resonator with all four edges of the first electrode 10 being sawtooth-shaped, can achieve a higher Q value. Therefore, it can be seen that setting the first sub-side L11 and the second sub-side L12 of the first electrode 10 to be sawtooth-shaped, while keeping the other two sub-sides straight, further suppresses the resonance of the transverse modes of the bulk acoustic wave resonator.

[0040] Figure 6 This is a top view schematic diagram of another bulk acoustic resonator provided in an embodiment of the present invention. Figure 6 As shown, the orthographic projection of the second electrode 30 onto the piezoelectric layer 20 has a third sub-edge L13 and a fourth sub-edge L14 with different extending directions. The third sub-edge L13 and the fourth sub-edge L14 are located within the orthographic projection of the first electrode 10 onto the piezoelectric layer 20. The third sub-edge L13 and the fourth sub-edge L14 are respectively the first edge L1 and the second edge L2 in a set of irregular edges.

[0041] Specifically, when the third sub-edge L13 and the fourth sub-edge L14 are located within the orthogonal projection of the first electrode 10 onto the piezoelectric layer 20, the third sub-edge L13 and the fourth sub-edge L14 serve as two adjacent edges of the overlapping region of the first electrode 10 and the second electrode 30 along the thickness direction. That is, the third sub-edge L13 and the fourth sub-edge L14 are two adjacent edges of the active excitation portion of the bulk acoustic wave resonator. By setting both the third sub-edge L13 and the fourth sub-edge L14 to be non-linear electrode boundaries, the active excitation portion of the bulk acoustic wave resonator can also include a set of irregular edges. Without changing the macroscopic shape of the second electrode 30, the complexity of the transverse modal excitation of the bulk acoustic wave resonator can be increased, thereby suppressing transverse modal resonance. This also balances the density and layout of the resonators, simplifying the resonator design and reducing the cost of the resonator.

[0042] Continue to refer to Figure 6The orthogonal projection of the second electrode 30 onto the piezoelectric layer 20 also includes two additional sub-edges. One sub-edge is positioned opposite to the third sub-edge L13, and the other sub-edge is positioned opposite to the fourth sub-edge L14. By keeping the other two sub-edges straight, it avoids the situation where one sub-edge is parallel to the third sub-edge L13 and the other sub-edge is parallel to the fourth sub-edge L14. This reduces the probability of transverse modal resonance caused by the parallel edges of the second electrode 30, further suppressing the transverse modal resonance of the bulk acoustic resonator. Figure 6 The example shown illustrates that the macroscopic shape of the second electrode 30 projected onto the piezoelectric layer 20 is rectangular. In this case, the extending directions of the third sub-side L13 and the fourth sub-side L14 are perpendicular. In other embodiments, when the macroscopic shape of the second electrode 30 projected onto the piezoelectric layer 20 is other polygonal shapes, the extending directions of the third sub-side L13 and the fourth sub-side L14 may not be perpendicular, and this is not limited here.

[0043] Figure 7 This is a top view schematic diagram of another bulk acoustic resonator provided in an embodiment of the present invention. Figure 7 As shown, the orthographic projection of the first electrode 10 onto the piezoelectric layer 20 has a first sub-edge L11 and a second sub-edge L12 with different extending directions. The orthographic projection of the second electrode 30 onto the piezoelectric layer 20 has a third sub-edge L13 and a fourth sub-edge L14 with different extending directions. The first sub-edge L11 and the second sub-edge L12 are located within the orthographic projection of the second electrode 30 onto the piezoelectric layer 20. The first sub-edge L11 and the second sub-edge L12 are respectively the first edge L1 and the second edge L2 in a set of irregular edges. The third sub-edge L13 and the fourth sub-edge L14 are located within the orthographic projection of the first electrode 10 onto the piezoelectric layer 20. The third sub-edge L13 and the fourth sub-edge L14 are respectively the first edge L1 and the second edge L2 in another set of irregular edges.

[0044] Specifically, when the first sub-edge L11 and the second sub-edge L12 are located within the orthographic projection of the second electrode 30 onto the piezoelectric layer 20, the first sub-edge L11 and the second sub-edge L12 serve as two adjacent edges of the overlapping region of the first electrode 10 and the second electrode 30 along the thickness direction. That is, the first sub-edge L11 and the second sub-edge L12 are two adjacent edges of the active excitation portion of the bulk acoustic wave resonator. At this time, the first sub-edge L11 and the second sub-edge L12 are both non-linear electrode boundaries, such that the active excitation portion of the bulk acoustic wave resonator includes a set of irregular edges, and this set of irregular edges is a sub-edge of the first electrode 10. When the third sub-edge L13 and the fourth sub-edge L14 are located within the orthographic projection of the first electrode 10 onto the piezoelectric layer 20, the third sub-edge L13 and the fourth sub-edge L14 serve as two other adjacent edges of the overlapping region of the first electrode 10 and the second electrode 30 along the thickness direction. That is, the third sub-edge L13 and the fourth sub-edge L14 are two other adjacent edges of the active excitation portion of the bulk acoustic wave resonator. At this point, both the third sub-edge L13 and the fourth sub-edge L14 are set as non-linear electrode boundaries, so that the active excitation part of the bulk acoustic resonator includes another set of irregular edges, and this set of irregular edges is a sub-edge of the second electrode 30. Without changing the macroscopic shape of the first electrode 10 and the macroscopic shape of the second electrode 30, the resonance of the transverse modes of the first electrode 10 and the second electrode 30 can be suppressed simultaneously. At the same time, it can avoid the irregular edges formed by the sub-edges of the first electrode 10 and the irregular edges formed by the sub-edges of the second electrode 30 being parallel to each other in the same plane, reducing the probability of transverse mode wave resonance reflected from different sets of irregular edges, and further suppressing the resonance of the transverse modes of the bulk acoustic resonator.

[0045] Continue to refer to Figure 1 , Figure 2 , Figure 6 and Figure 7 The bulk acoustic wave resonator also includes a substrate 60, on which a cavity 61 is provided. A piezoelectric layer 20 is disposed on the substrate 60 and covers the cavity 61. A first electrode 10 is disposed on the surface of the piezoelectric layer 20 within the cavity 61. A second electrode 30 is disposed on the side of the piezoelectric layer 20 away from the substrate 60. The orthographic projection of the irregular edge on the piezoelectric layer 20 is located within the orthographic projection of the cavity 61 on the piezoelectric layer 20. A through hole is provided on the second electrode 30, which penetrates the piezoelectric layer 20 and the first electrode 10 and communicates with the cavity 61.

[0046] Figure 8 This is a top view schematic diagram of a second electrode provided in an embodiment of the present invention. Figure 8As shown, the edge of the second electrode 30 has a right-angled chamfer 31, which is reused as a through-hole, penetrating the piezoelectric layer 20 and the first electrode 10 and communicating with the cavity 61. The chamfer 31 serves as a through-hole, allowing the through-hole to occupy the space of the rectangular electrodes when multiple bulk acoustic wave resonators are arranged, avoiding the need for additional space for the through-hole, increasing the arrangement density of the bulk acoustic wave resonators, and significantly saving filter area and reducing filter cost.

[0047] For example, Figure 9 This is a frequency-impedance curve diagram of another bulk acoustic wave resonator provided in an embodiment of the present invention. The horizontal axis represents frequency, and the vertical axis represents impedance. Curve 7 is the frequency-impedance curve of the bulk acoustic wave resonator when the second electrode has no chamfer, and curve 8 is the frequency-impedance curve of the bulk acoustic wave resonator when the second electrode has a right-angle chamfer of 31°. Figure 9 As shown, curves 7 and 8 basically overlap, that is, a right-angled chamfer 31 is provided on the second electrode 30, and the right-angled chamfer penetrates the piezoelectric layer and the first electrode 10 and communicates with the cavity. This will not affect the performance of the bulk acoustic resonator. At the same time, it allows the through hole to occupy the arrangement space of the rectangular electrode, avoiding the need to set up additional space for placing the through hole, thereby increasing the arrangement density of the bulk acoustic resonator, saving the area of ​​the filter to a great extent, and reducing the cost of the filter.

[0048] Figure 10 This is a schematic diagram illustrating the structure of an electrode with a non-linear electrode boundary, provided as an embodiment of the present invention. (See diagram below.) Figure 10 As shown, the non-linear electrode boundary includes periodically arranged protrusions A, where protrusion A is the outermost point of the edge; along the extension direction X of the edge... Figure 10 The example shows the extension direction X of the first sub-edge L11, and the distance between two adjacent protrusions A is the first distance d1. The length of the first distance d1 ranges from one-seventh to one-fifteenth of the edge length D.

[0049] Specifically, the electrode can be either a first electrode 10 or a second electrode 30. When the edge of the electrode has a non-linear electrode boundary, the non-linear electrode boundary can have periodically arranged broken lines or curves, resulting in convex points A and concave points B on the non-linear electrode boundary. Along the extension direction X of the edge, the distance between two adjacent convex points A is the period of the periodically arranged broken lines or curves on the non-linear electrode boundary, which is the first distance d1. The edge length D is the straight-line length required to connect the edge with the two adjacent edges, or it can be the side length of the cavity corresponding to the edge. By setting the length range of the first distance d1 to one-seventh to one-fifteenth of the edge length D, the non-linear electrode boundary can suppress the resonance effect of the transverse mode of the bulk acoustic resonator. At the same time, it can ensure that the overall orthographic projection of the electrode on the piezoelectric layer 20 maintains a regular shape, that is, the macroscopic shape of the orthographic projection of the electrode on the piezoelectric layer 20 is a regular shape, which is beneficial for the dense arrangement and layout of the resonator, simplifies the design of the resonator, and reduces the cost of the resonator.

[0050] For example, such as Figure 10 As shown, when the electrode is the first electrode 10 and the macroscopic shape of its orthographic projection on the piezoelectric layer 20 is rectangular, the first sub-side L11 and the second sub-side L12 are non-linear electrode boundaries. Figure 10The diagram exemplifies electrode boundaries with periodically arranged sawtooth shapes on the first sub-side L11 and the second sub-side L12. The fifth sub-side L15 is parallel to the first sub-side L11, and the sixth sub-side L16 is parallel to the second sub-side L12. In this case, the protrusion A on the first sub-side L11 is the point on the sawtooth-shaped electrode boundary furthest from the fifth sub-side L15, and the protrusion A on the second sub-side L12 is the point on the sawtooth-shaped electrode boundary furthest from the sixth sub-side L16. The length D of the first sub-side L11 is the straight-line distance connecting the first sub-side L11 to the second sub-side L12 and the sixth sub-side L16, and the length D of the second sub-side L12 is the straight-line distance connecting the second sub-side L12 to the first sub-side L11 and the fifth sub-side L15. By setting the distance between two adjacent bumps A on the first sub-side L11 to be between one-seventh and one-fifteenth of the length D of the first sub-side L11, and the distance between two adjacent bumps A on the second sub-side L12 to be between one-seventh and one-fifteenth of the length D of the second sub-side L12, the non-linear electrode boundaries can be used to suppress the resonance of the transverse modes of the bulk acoustic resonator. Simultaneously, the orthographic projection of the electrode onto the piezoelectric layer 20 maintains a regular shape overall; that is, the macroscopic shape of the orthographic projection of the electrode onto the piezoelectric layer 20 is regular. This is beneficial for the density and layout of the resonator, simplifies the resonator design, and reduces the cost of the resonator. For example, when the length D of both the first sub-side L11 and the second sub-side L12 is 100 μm, the distance between two adjacent bumps A can range from 6.67 μm to 14.3 μm. For instance, a densely serrated electrode boundary can be set on the first sub-side L11 and the second sub-side L12, in which case the distance between two adjacent bumps A can be 6.67 μm. Sparse sawtooth-shaped electrode boundaries can also be set on the first sub-side L11 and the second sub-side L12, in which case the distance between two adjacent protrusions A can be 14.3um.

[0051] It should be noted that the distance between two adjacent bumps A can be greater than or equal to 2µm to meet the process requirements.

[0052] Continue to refer to Figure 10 The non-linear electrode boundary also includes periodically arranged concave points B, which alternate with convex points A, with concave point B being the innermost point of the edge; along the first direction Y ( Figure 10 The example shows a first direction Y that is perpendicular to the extension direction X of the first sub-edge L11, and the vertical distance between adjacent protrusions A and concave points B is a second distance d2, the length of which is one-third to one-fifth of the length of the first distance d1; wherein the first direction Y is perpendicular to the extension direction X of the edge.

[0053] Specifically, the vertical distance between adjacent protrusions A and concave points B is the vertical distance along the first direction Y of the non-linear electrode boundary, which is the second distance d2. By setting the length of the second distance d2 to be between one-third and one-fifth of the first distance d1, it can be ensured that the orthogonal projection of the electrode on the piezoelectric layer 20 maintains a regular shape, which is beneficial for the dense arrangement and layout of the resonator, simplifies the resonator design, and reduces the cost of the resonator. At the same time, it can meet the dimensional requirements of the sawtooth shape in the manufacturing process.

[0054] For example, such as Figure 10 As shown, when the electrode is the first electrode 10 and the macroscopic shape of its orthographic projection on the piezoelectric layer 20 is rectangular, the first sub-side L11 and the second sub-side L12 are non-linear electrode boundaries. Figure 10 The example illustrates periodically arranged sawtooth-shaped electrode boundaries on the first sub-edge L11 and the second sub-edge L12. The fifth sub-edge L15 is parallel to the first sub-edge L11, and the sixth sub-edge L16 is parallel to the second sub-edge L12. In this case, the concave point B on the first sub-edge L11 is the closest point on the sawtooth-shaped electrode boundary to the fifth sub-edge L15, and the concave point B on the second sub-edge L12 is the closest point on the sawtooth-shaped electrode boundary to the sixth sub-edge L16. The first direction Y corresponding to the first sub-edge L11 is perpendicular to the extending direction X of the first sub-edge L11. Along the first direction Y, the vertical distance between adjacent protrusions A and concave points B on the first sub-edge L11 is the second distance d2. By setting the length of the second distance d2 to one-third to one-fifth of the first distance d1, it can be ensured that the orthogonal projection of the electrode on the piezoelectric layer 20 maintains a regular shape, which is beneficial for the dense arrangement and layout of the resonator, simplifies the resonator design, and reduces the cost of the resonator. It can also meet the dimensional requirements of the process for the sawtooth shape.

[0055] Continue to refer to Figure 10 The non-linear electrode boundary is sawtooth-shaped. At this time, the convex point A of the sawtooth shape is located on the midline of the two adjacent concave points B.

[0056] In some embodiments, Figure 11 This is a schematic diagram of another electrode structure provided in an embodiment of the present invention, where the edge of the electrode has a non-linear electrode boundary. (See diagram below.) Figure 11 As shown, the non-linear electrode boundary has another sawtooth shape, in which the convex point A of the sawtooth shape is located on one side of the midline of the adjacent concave points B on both sides.

[0057] In some embodiments, the non-linear electrode boundaries include rounded corners. For example, Figure 12 This is a schematic diagram of another electrode structure provided in an embodiment of the present invention, where the edge of the electrode has a non-linear electrode boundary. (See diagram below.) Figure 12 As shown, the non-linear electrode boundary has a wavy shape. Figure 12The example shows a waveform shape where the wave shape is a trigonometric function. Figure 13 This is a schematic diagram of another electrode structure provided in an embodiment of the present invention, where the edge of the electrode has a non-linear electrode boundary. (See diagram below.) Figure 13 As shown, the non-linear electrode boundary has a serrated convex point A with a rounded corner.

[0058] Continue to refer to Figure 2 , Figure 6 and Figure 7 The first electrode 10 includes a set of irregular edges, and the shape formed by the connecting lines of the protrusions or concave points of the set of irregular edges and the orthogonal projection of the other edges of the first electrode 10 onto the piezoelectric layer 20 is a rectangle; and / or, the second electrode 30 includes another set of irregular edges, and the shape formed by the connecting lines of the protrusions or concave points of the other set of irregular edges and the orthogonal projection of the other edges of the second electrode 30 onto the piezoelectric layer 20 is a rectangle.

[0059] Specifically, when the shape formed by the orthogonal projection of a set of irregularly shaped protrusions or concave points onto the piezoelectric layer 20, along with the other edges of the first electrode 10, is rectangular, the macroscopic shape of the orthogonal projection of the first electrode 10 onto the piezoelectric layer 20 is also rectangular. Arranging multiple bulk acoustic wave resonators on the filter simplifies the layout of the bulk acoustic wave resonators, simplifies the filter design, and simultaneously increases the density of the bulk acoustic wave resonators, reducing the cost of the resonators. Similarly, when the shape formed by the orthogonal projection of another set of irregularly shaped protrusions or concave points onto the piezoelectric layer 20, along with the other edges of the second electrode 30, is rectangular, the macroscopic shape of the orthogonal projection of the second electrode 30 onto the piezoelectric layer 20 is also rectangular. Arranging multiple bulk acoustic wave resonators on the filter simplifies the layout of the bulk acoustic wave resonators, simplifies the filter design, and simultaneously increases the density of the bulk acoustic wave resonators, reducing the cost of the resonators.

[0060] It should be noted that, in other embodiments, the macroscopic shape of the first electrode 10 projected onto the piezoelectric layer 20 and the macroscopic shape of the second electrode 30 projected onto the piezoelectric layer 20 can also be a square. This can also simplify the layout of the bulk acoustic wave resonator, simplify the filter design, and increase the arrangement density of the bulk acoustic wave resonator, thereby reducing the cost of the resonator. Alternatively, the macroscopic shape of the first electrode 10 projected onto the piezoelectric layer 20 and the macroscopic shape of the second electrode 30 projected onto the piezoelectric layer 20 can also be regular polygons, such as regular pentagons, regular hexagons, etc., and are not limited here.

[0061] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A bulk acoustic resonator, characterized in that, It includes a first electrode, a piezoelectric layer, and a second electrode stacked together. The electrodes of the bulk acoustic resonator also include at least one set of irregular edges. Each set of irregular edges includes an adjacent first edge and a second edge. The extension directions of the first edge and the second edge have an angle. Both the first edge and the second edge are non-linear electrode boundaries. The irregular edges in different sets are the edges of different electrodes, and the irregular edges in the same set are the edges of the same electrode.

2. The bulk acoustic resonator according to claim 1, characterized in that, The orthographic projection of the first electrode on the piezoelectric layer has a first sub-edge and a second sub-edge with different extension directions. The first sub-edge and the second sub-edge are located within the orthographic projection of the second electrode on the piezoelectric layer. The first sub-edge and the second sub-edge are respectively the first edge and the second edge in a set of irregular edges.

3. The bulk acoustic resonator according to claim 1, characterized in that, The second electrode has a third sub-edge and a fourth sub-edge with different extending directions in its orthogonal projection onto the piezoelectric layer. The third sub-edge and the fourth sub-edge are located within the orthogonal projection of the first electrode onto the piezoelectric layer. The third sub-edge and the fourth sub-edge are respectively the first edge and the second edge in a set of irregular edges.

4. The bulk acoustic resonator according to claim 1, characterized in that, The first electrode has a first sub-edge and a second sub-edge with different extending directions in its orthogonal projection onto the piezoelectric layer. The second electrode has a third sub-edge and a fourth sub-edge with different extending directions in its orthogonal projection onto the piezoelectric layer. The first sub-edge and the second sub-edge are located within the orthogonal projection of the second electrode onto the piezoelectric layer. The first sub-edge and the second sub-edge are respectively the first edge and the second edge in a set of irregular edges. The third sub-edge and the fourth sub-edge are located within the orthogonal projection of the first electrode onto the piezoelectric layer. The third sub-edge and the fourth sub-edge are respectively the first edge and the second edge in another set of irregular edges.

5. The bulk acoustic resonator according to any one of claims 1-4, characterized in that, The non-linear electrode boundary includes periodically arranged protrusions, each protrusion being the outermost point of the edge. Along the extension direction of the edge, the distance between two adjacent protrusions is a first distance, the length of which ranges from one-seventh to one-fifteenth of the edge length.

6. The bulk acoustic resonator according to claim 5, characterized in that, The non-linear electrode boundary also includes periodically arranged concave points, which are alternately arranged with the convex points, and the concave points are the innermost points of the edge; along the first direction, the vertical distance between adjacent convex points and concave points is the second distance, and the length of the second distance is one-third to one-fifth of the first distance; wherein, the first direction is perpendicular to the extension direction of the edge.

7. The bulk acoustic resonator according to claim 6, characterized in that, The first electrode includes a set of irregular edges, and the shape formed by the connecting lines of the protrusions or concave points of the set of irregular edges and the orthogonal projection of the other edges of the first electrode onto the piezoelectric layer is a rectangle; and / or, the second electrode includes another set of irregular edges, and the shape formed by the connecting lines of the protrusions or concave points of the other set of irregular edges and the orthogonal projection of the other edges of the second electrode onto the piezoelectric layer is a rectangle.

8. The bulk acoustic resonator according to claim 5, characterized in that, The non-linear electrode boundary is serrated or wavy.

9. The bulk acoustic resonator according to claim 1, characterized in that, It also includes a substrate having a cavity, a piezoelectric layer disposed on the substrate and covering the cavity, a first electrode disposed on the surface of the piezoelectric layer within the cavity, a second electrode disposed on the side of the piezoelectric layer away from the substrate, the orthographic projection of the irregular edge on the piezoelectric layer being located within the orthographic projection of the cavity on the piezoelectric layer, and a through hole disposed on the second electrode, the through hole penetrating the piezoelectric layer and the first electrode and communicating with the cavity.

10. The bulk acoustic resonator according to claim 9, characterized in that, The edge of the second electrode has a right-angle chamfer, which is reused as the through hole, penetrating the piezoelectric layer and the first electrode and communicating with the cavity.

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