阅读说明：本技术 体声波谐振器 (Bulk acoustic wave resonator ) 是由 韩源 金泰润 林昶贤 孙尚郁 吉宰亨 丁大勳 于 2020-10-12 设计创作，主要内容包括：本公开提供了一种体声波谐振器,所述体声波谐振器包括：第一电极,设置在基板上方；压电层,设置为覆盖所述第一电极的至少一部分；以及第二电极,设置为覆盖所述压电层的至少一部分。在所述第一电极、所述压电层和所述第二电极全部设置为彼此叠置的有效区域中,在所述第一电极、所述压电层和所述第二电极中的任意一个或者任意两个或更多个的任意组合中形成至少一个台阶。(The present disclosure provides a bulk acoustic wave resonator, including: a first electrode disposed over the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; and a second electrode disposed to cover at least a portion of the piezoelectric layer. At least one step is formed in any one of the first electrode, the piezoelectric layer, and the second electrode or any combination of any two or more thereof in an active region where the first electrode, the piezoelectric layer, and the second electrode are all disposed so as to overlap each other.)

1. A bulk acoustic wave resonator comprising:

a first electrode disposed over the substrate;

a piezoelectric layer disposed to cover at least a portion of the first electrode; and

a second electrode disposed to cover at least a portion of the piezoelectric layer,

wherein at least one step is formed in any one of the first electrode, the piezoelectric layer, and the second electrode or any combination of any two or more thereof in an active area in which all of the first electrode, the piezoelectric layer, and the second electrode are disposed so as to overlap each other.

2. The bulk acoustic wave resonator according to claim 1, wherein a thickness of one of the first electrode, the piezoelectric layer, and the second electrode at an edge of the active area is larger than a thickness of the one of the first electrode, the piezoelectric layer, and the second electrode in a central portion of the active area to form a step among the at least one step.

3. The bulk acoustic wave resonator according to claim 1, further comprising an intervening layer, wherein a portion of the intervening layer is disposed between the first electrode and the piezoelectric layer.

4. The bulk acoustic wave resonator according to claim 3, wherein:

a thickness of the second electrode in a first region of the bulk acoustic wave resonator is smallest compared to a thickness of the second electrode in other regions of the active region;

the thickness of the second electrode in a second region of the bulk acoustic wave resonator is greater than the thickness of the second electrode in the first region, the second region being disposed outside the first region;

a thickness of the second electrode in a third region of the bulk acoustic wave resonator is larger than a thickness of the second electrode in the second region, the third region being disposed outside the second region; and is

The second electrode overlaps with the piezoelectric layer, the first electrode, and the insertion layer in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

5. The bulk acoustic wave resonator according to claim 4, wherein the piezoelectric layer, the insertion layer and the first electrode are stacked on one another in a fifth area of the bulk acoustic wave resonator, or the second electrode, the piezoelectric layer and the insertion layer are stacked on one another in a fifth area of the bulk acoustic wave resonator, and

wherein the fifth region is disposed outside the fourth region.

6. The bulk acoustic wave resonator according to claim 4, wherein a sum of the width of the second region and the width of the third region is 0.6 μm to 1.0 μm.

7. The bulk acoustic wave resonator according to claim 4, wherein a width of a region where the end portion of the second electrode overlaps the insertion layer is 0.4 μm to 0.8 μm.

8. The bulk acoustic wave resonator according to claim 4, wherein a difference between a thickness of the second electrode in the first region and a thickness of the second electrode in the second region isTo

9. The bulk acoustic wave resonator according to claim 3, wherein:

a thickness of the piezoelectric layer in a first region of the bulk acoustic wave resonator is smallest compared to thicknesses of the piezoelectric layer in other regions of the active region;

a thickness of the piezoelectric layer in a second region of the bulk acoustic wave resonator is greater than a thickness of the piezoelectric layer in the first region, the second region being disposed outside the first region;

a thickness of the piezoelectric layer in a third region of the bulk acoustic wave resonator is larger than a thickness of the piezoelectric layer in the second region, the third region being disposed outside the second region; and is

The piezoelectric layer, the first electrode, the second electrode, and the insertion layer are stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

10. The bulk acoustic wave resonator according to claim 9, wherein the piezoelectric layer, the insertion layer and the first electrode are stacked on one another in a fifth area of the bulk acoustic wave resonator or the second electrode, the piezoelectric layer and the insertion layer are stacked on one another in a fifth area of the bulk acoustic wave resonator, and

wherein the fifth region is disposed outside the fourth region.

11. The bulk acoustic wave resonator according to claim 3, wherein:

a thickness of the first electrode in a first region of the bulk acoustic wave resonator is smallest compared to a thickness of the first electrode in other regions of the active region;

the thickness of the first electrode in a second region of the bulk acoustic wave resonator is greater than the thickness of the first electrode in the first region, the second region being disposed outside the first region;

the first electrode is arranged in a third region of the bulk acoustic wave resonator, and the third region is arranged outside the second region; and is

The piezoelectric layer, the first electrode, the second electrode, and the insertion layer are stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

12. The bulk acoustic wave resonator according to claim 11, wherein the piezoelectric layer, the insertion layer and the first electrode are stacked on top of each other in a fifth area of the bulk acoustic wave resonator or the second electrode, the piezoelectric layer and the insertion layer are stacked on top of each other in a fifth area of the bulk acoustic wave resonator, and

wherein the fifth region is disposed outside the fourth region.

13. The bulk acoustic wave resonator of claim 1, wherein an acoustic impedance of the piezoelectric layer is greater than an acoustic impedance of the first electrode and the second electrode.

14. The bulk acoustic wave resonator of claim 1, further comprising:

an etch stop disposed to surround the cavity;

a sacrificial layer disposed to surround the etch stop portion; and

a metal pad connected to the first electrode and the second electrode.

15. A bulk acoustic wave resonator comprising:

a first electrode disposed over the substrate;

a piezoelectric layer disposed to cover at least a portion of the first electrode;

a second electrode disposed to cover at least a portion of the piezoelectric layer; and

an intervening layer partially disposed between the first electrode and the piezoelectric layer,

wherein at least one step is formed by a difference in area thickness of any one of the insertion layer or the first electrode, the piezoelectric layer, and the second electrode in an effective area where all of the first electrode, the piezoelectric layer, and the second electrode are stacked on one another.

16. The bulk acoustic wave resonator of claim 15, wherein:

a thickness of the any one of the first electrode, the piezoelectric layer, and the second electrode in a first region of the bulk acoustic wave resonator is smallest as compared with a thickness of the any one of the first electrode, the piezoelectric layer, and the second electrode in other regions of the active region; and is

A thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in a second region of the bulk acoustic wave resonator is larger than a thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in the first region, the second region being disposed outside the first region; and is

A difference between a thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in the first region and a thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in the second region isTo

17. The bulk acoustic wave resonator of claim 15, wherein:

a thickness of the second electrode in a first region of the bulk acoustic wave resonator is smallest compared to a thickness of the second electrode in other regions of the active region;

the thickness of the second electrode in a second region of the bulk acoustic wave resonator is greater than the thickness of the second electrode in the first region, the second region being disposed outside the first region;

a thickness of the second electrode in a third region of the bulk acoustic wave resonator is larger than a thickness of the second electrode in the second region, the third region being disposed outside the second region; and is

The second electrode overlaps with the piezoelectric layer, the first electrode, and the insertion layer in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

18. The bulk acoustic wave resonator according to claim 17, wherein the piezoelectric layer, the insertion layer and the first electrode are stacked on top of each other in a fifth area of the bulk acoustic wave resonator or the second electrode, the piezoelectric layer and the insertion layer are stacked on top of each other in a fifth area of the bulk acoustic wave resonator, and

wherein the fifth region is disposed outside the fourth region.

19. The bulk acoustic wave resonator according to claim 17, wherein a sum of the width of the second region and the width of the third region is 0.6 μm to 1.0 μm.

20. The bulk acoustic wave resonator according to claim 17, wherein a width of a region where the end portion of the second electrode overlaps the insertion layer is 0.4 μm to 0.8 μm.

21. The bulk acoustic wave resonator according to claim 17, wherein the insertion layer is not provided in the third region.

22. The bulk acoustic wave resonator of claim 15, wherein:

a thickness of the piezoelectric layer in a first region of the bulk acoustic wave resonator is smallest compared to thicknesses of the piezoelectric layer in other regions of the active region;

a thickness of the piezoelectric layer in a second region of the bulk acoustic wave resonator is greater than a thickness of the piezoelectric layer in the first region, the second region being disposed outside the first region;

a thickness of the piezoelectric layer in a third region of the bulk acoustic wave resonator is larger than a thickness of the piezoelectric layer in the second region, the third region being disposed outside the second region; and is

The piezoelectric layer, the first electrode, the second electrode, and the insertion layer are stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

23. The bulk acoustic wave resonator according to claim 22, wherein the piezoelectric layer, the insertion layer and the first electrode are stacked on top of each other in a fifth area of the bulk acoustic wave resonator or the second electrode, the piezoelectric layer and the insertion layer are stacked on top of each other in a fifth area of the bulk acoustic wave resonator, and

wherein the fifth region is disposed outside the fourth region.

24. The bulk acoustic wave resonator of claim 15, wherein:

a thickness of the first electrode in a first region of the bulk acoustic wave resonator is smallest compared to a thickness of the first electrode in other regions of the active region;

the thickness of the first electrode in a second region of the bulk acoustic wave resonator is greater than the thickness of the first electrode in the first region, the second region being disposed outside the first region;

the first electrode is arranged in a third region of the bulk acoustic wave resonator, and the third region is arranged outside the second region; and is

The piezoelectric layer, the first electrode, the second electrode, and the insertion layer are stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

25. The bulk acoustic wave resonator according to claim 24, wherein the piezoelectric layer, the insertion layer and the first electrode are stacked on top of each other in a fifth area of the bulk acoustic wave resonator or the second electrode, the piezoelectric layer and the insertion layer are stacked on top of each other in a fifth area of the bulk acoustic wave resonator, and

wherein the fifth region is disposed outside the fourth region.

26. The bulk acoustic wave resonator of claim 15, wherein an acoustic impedance of the piezoelectric layer is greater than an acoustic impedance of the first electrode and the second electrode.

27. A bulk acoustic wave resonator comprising:

a first electrode disposed over the substrate;

a piezoelectric layer disposed to cover at least a portion of the first electrode; and

a second electrode disposed to cover at least a portion of the piezoelectric layer;

wherein the first electrode, the piezoelectric layer, and the second electrode are all stacked on one another in the entire active area of the bulk acoustic wave resonator,

wherein any one of the first electrode, the piezoelectric layer, and the second electrode has a first thickness in a first region of the active area and a second thickness in a second region of the active area, the second region being disposed outside the first region, and

wherein the second thickness is greater than the first thickness.

28. The bulk acoustic wave resonator according to claim 27, further comprising a step formed in the any one of the first electrode, the piezoelectric layer, and the second electrode by a difference between the first thickness and the second thickness.

29. The bulk acoustic wave resonator according to claim 28, wherein the difference between the first thickness and the second thickness isTo

30. The bulk acoustic wave resonator according to claim 27, wherein any one of the first electrode, the piezoelectric layer, and the second electrode has a third thickness in a third region of the effective area, the third region being provided outside the second region, and

wherein the third thickness is greater than the second thickness.

31. The bulk acoustic wave resonator according to claim 30, further comprising an intervening layer disposed partially between the first electrode and the piezoelectric layer,

wherein the insert layer is disposed entirely outside the third region.

Technical Field

The following description relates to a bulk acoustic wave resonator.

Background

Bulk Acoustic Wave (BAW) filters are constructed using Bulk Acoustic Wave (BAW) resonators. If the quality factor (Q) performance of the BAW resonator is good, the roll-off characteristics that can select only a desired frequency band in the BAW filter are good, and the performance of insertion loss and attenuation is improved. To improve the quality factor (Q) performance of the anti-resonance point in a BAW resonator, a frame may be formed around the resonator to reflect lateral waves generated during resonance into the resonator to collect resonance energy in an active area. Generally, the frame is formed using the same material as that of the upper electrode, and the frame is formed thicker than the remaining portion of the upper electrode disposed in the active area of the BAW resonator. However, when only a single frame is provided, there is a limitation in achieving high quality factor (Q) performance.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one general aspect, a bulk acoustic wave resonator includes: a first electrode disposed over the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; and a second electrode disposed to cover at least a portion of the piezoelectric layer. At least one step is formed in any one of the first electrode, the piezoelectric layer, and the second electrode or any combination of any two or more thereof in an active region where the first electrode, the piezoelectric layer, and the second electrode are all disposed so as to overlap each other.

A thickness of one of the first electrode, the piezoelectric layer, and the second electrode at an edge of the active area may be greater than a thickness of the one of the first electrode, the piezoelectric layer, and the second electrode in a central portion of the active area to form a step among the at least one step.

The bulk acoustic wave resonator may further include an insertion layer, wherein a portion of the insertion layer is disposed between the first electrode and the piezoelectric layer.

The thickness of the second electrode in the first region of the bulk acoustic wave resonator may be minimized compared to the thickness of the second electrode in other regions of the active region. A thickness of the second electrode in a second region of the bulk acoustic wave resonator, which is disposed outside the first region, may be greater than a thickness of the second electrode in the first region. A thickness of the second electrode in a third region of the bulk acoustic wave resonator, which is disposed outside the second region, may be greater than a thickness of the second electrode in the second region. The second electrode may overlap with the piezoelectric layer, the first electrode, and the insertion layer in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

The piezoelectric layer, the insertion layer, and the first electrode may be stacked on each other in a fifth area of the bulk acoustic wave resonator, or the second electrode, the piezoelectric layer, and the insertion layer may be stacked on each other in a fifth area of the bulk acoustic wave resonator, wherein the fifth area is disposed outside the fourth area.

The sum of the width of the second region and the width of the third region may be 0.6 μm to 1.0 μm.

A width of a region where the end portion of the second electrode overlaps the insertion layer may be 0.4 μm to 0.8 μm.

The difference between the thickness of the second electrode in the first region and the thickness of the second electrode in the second region may beTo

The thickness of the piezoelectric layer in the first region of the bulk acoustic wave resonator may be minimal compared to the thickness of the piezoelectric layer in other regions of the active area. A thickness of the piezoelectric layer in a second region of the bulk acoustic wave resonator, which is disposed outside the first region, may be greater than a thickness of the piezoelectric layer in the first region. A thickness of the piezoelectric layer in a third region of the bulk acoustic wave resonator, which is disposed outside the second region, may be greater than a thickness of the piezoelectric layer in the second region. The piezoelectric layer, the first electrode, the second electrode, and the insertion layer may be stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

The piezoelectric layer, the insertion layer, and the first electrode may be stacked on each other in a fifth area of the bulk acoustic wave resonator, or the second electrode, the piezoelectric layer, and the insertion layer may be stacked on each other in a fifth area of the bulk acoustic wave resonator, wherein the fifth area is disposed outside the fourth area.

The thickness of the first electrode in the first region of the bulk acoustic wave resonator may be minimized compared to the thickness of the first electrode in other regions of the active region. A thickness of the first electrode in a second region of the bulk acoustic wave resonator, which is disposed outside the first region, may be greater than a thickness of the first electrode in the first region. The first electrode may be disposed in a third region of the bulk acoustic wave resonator, the third region being disposed outside the second region. The piezoelectric layer, the first electrode, the second electrode, and the insertion layer may be stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

The piezoelectric layer, the insertion layer, and the first electrode may be stacked on each other in a fifth area of the bulk acoustic wave resonator, or the second electrode, the piezoelectric layer, and the insertion layer may be stacked on each other in a fifth area of the bulk acoustic wave resonator, wherein the fifth area is disposed outside the fourth area.

The acoustic impedance of the piezoelectric layer may be greater than the acoustic impedances of the first and second electrodes.

The bulk acoustic wave resonator may further include: an etch stop disposed to surround the cavity; a sacrificial layer disposed to surround the etch stop portion; and a metal pad connected to the first electrode and the second electrode.

In another general aspect, a bulk acoustic wave resonator includes: a first electrode disposed over the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; a second electrode disposed to cover at least a portion of the piezoelectric layer; and an intervening layer partially disposed between the first electrode and the piezoelectric layer. At least one step is formed by a difference in area thickness of any one of the insertion layer or the first electrode, the piezoelectric layer, and the second electrode in an effective area where all of the first electrode, the piezoelectric layer, and the second electrode are stacked on one another.

The thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in the first region of the bulk acoustic wave resonator may be smallest as compared with the thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in other regions of the active region. A thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in the second region of the bulk acoustic wave resonator may be larger than that of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrodeThe thickness of the arbitrary one in the first region, the second region being disposed outside the first region. A difference between a thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in the first region and a thickness of the arbitrary one of the first electrode, the piezoelectric layer, and the second electrode in the second region may beTo

The thickness of the second electrode in the first region of the bulk acoustic wave resonator may be minimized compared to the thickness of the second electrode in other regions of the active region. A thickness of the second electrode in a second region of the bulk acoustic wave resonator, which is disposed outside the first region, may be greater than a thickness of the second electrode in the first region. A thickness of the second electrode in a third region of the bulk acoustic wave resonator, which is disposed outside the second region, may be greater than a thickness of the second electrode in the second region. The second electrode may overlap with the piezoelectric layer, the first electrode, and the insertion layer in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

The piezoelectric layer, the insertion layer, and the first electrode may be stacked on each other in a fifth area of the bulk acoustic wave resonator, or the second electrode, the piezoelectric layer, and the insertion layer may be stacked on each other in a fifth area of the bulk acoustic wave resonator, wherein the fifth area is disposed outside the fourth area.

The sum of the width of the second region and the width of the third region may be 0.6 μm to 1.0 μm.

A width of a region where the end portion of the second electrode overlaps the insertion layer may be 0.4 μm to 0.8 μm.

The insertion layer may not be disposed in the third region.

The thickness of the piezoelectric layer in the first region of the bulk acoustic wave resonator may be minimal compared to the thickness of the piezoelectric layer in other regions of the active area. A thickness of the piezoelectric layer in a second region of the bulk acoustic wave resonator, which is disposed outside the first region, may be greater than a thickness of the piezoelectric layer in the first region. A thickness of the piezoelectric layer in a third region of the bulk acoustic wave resonator, which is disposed outside the second region, may be greater than a thickness of the piezoelectric layer in the second region. The piezoelectric layer, the first electrode, the second electrode, and the insertion layer may be stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

The piezoelectric layer, the insertion layer, and the first electrode may be stacked on each other in a fifth area of the bulk acoustic wave resonator, or the second electrode, the piezoelectric layer, and the insertion layer may be stacked on each other in a fifth area of the bulk acoustic wave resonator, wherein the fifth area is disposed outside the fourth area.

The thickness of the first electrode in the first region of the bulk acoustic wave resonator may be minimized compared to the thickness of the first electrode in other regions of the active region. A thickness of the first electrode in a second region of the bulk acoustic wave resonator, which is disposed outside the first region, may be greater than a thickness of the first electrode in the first region. The first electrode may be disposed in a third region of the bulk acoustic wave resonator, the third region being disposed outside the second region. The piezoelectric layer, the first electrode, the second electrode, and the insertion layer may be stacked on each other in a fourth region of the bulk acoustic wave resonator, the fourth region being disposed outside the third region.

The piezoelectric layer, the insertion layer, and the first electrode may be stacked on each other in a fifth area of the bulk acoustic wave resonator, or the second electrode, the piezoelectric layer, and the insertion layer may be stacked on each other in a fifth area of the bulk acoustic wave resonator, wherein the fifth area is disposed outside the fourth area.

The acoustic impedance of the piezoelectric layer may be greater than the acoustic impedances of the first and second electrodes.

In another general aspect, a bulk acoustic wave resonator includes: a first electrode disposed over the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; and a second electrode disposed to cover at least a portion of the piezoelectric layer. The first electrode, the piezoelectric layer, and the second electrode all overlap each other in the entire active area of the bulk acoustic wave resonator. Any one of the first electrode, the piezoelectric layer, and the second electrode has a first thickness in a first region of the active area and a second thickness in a second region of the active area, the second region being disposed outside the first region. The second thickness is greater than the first thickness.

The bulk acoustic wave resonator may further include a step formed in any one of the first electrode, the piezoelectric layer, and the second electrode by a difference between the first thickness and the second thickness.

The difference between the first thickness and the second thickness may beTo

Any one of the first electrode, the piezoelectric layer, and the second electrode may have a third thickness in a third area of the effective area, the third area being disposed outside the second area. The third thickness may be greater than the second thickness.

The bulk acoustic wave resonator may further include an intervening layer partially disposed between the first electrode and the piezoelectric layer. The insert layer may be disposed entirely outside the third region.

Other features and aspects will be apparent from the following detailed description, the accompanying drawings, and the claims.

Drawings

Fig. 1 is a schematic cross-sectional view illustrating a bulk acoustic wave resonator according to an embodiment.

Fig. 2 is an enlarged view illustrating a portion a of fig. 1.

Fig. 3 is an enlarged view illustrating a portion B of fig. 1.

Fig. 4 is an explanatory diagram showing a conventional bulk acoustic wave resonator.

Fig. 5 is a graph showing attenuation performance according to BR width in a conventional bulk acoustic wave resonator.

Fig. 6 is an explanatory diagram showing the bulk acoustic wave resonator of fig. 1 according to an embodiment.

Fig. 7 is a graph showing attenuation performance according to the sum of widths of the second region and the third region of the second electrode when BR widths are 0.4 μm, 0.6 μm, and 0.8 μm in the bulk acoustic wave resonator of fig. 1.

Fig. 8 is an explanatory diagram showing the bulk acoustic wave resonator of fig. 1 according to an embodiment.

Fig. 9 is a graph showing the damping performance according to BR width when the sum of the widths of the second region and the third region of the second electrode is 0.6 μm, 0.8 μm, or 1.0 μm in the bulk acoustic wave resonator of fig. 1.

Fig. 10 is an explanatory diagram showing the bulk acoustic wave resonator of fig. 1 according to an embodiment.

FIG. 11 is a view showing that in the bulk acoustic wave resonator of FIG. 1, when the difference in thickness between the first region and the second region of the second electrode isAnd the sum of the widths of the second region and the third region of the second electrode is 0.8 μm and 1.0 μm, a graph of the attenuation performance according to the BR width.

Figure 12 is a view showing in the bulk acoustic wave resonator of figure 1,when the thickness difference between the first region and the second region of the second electrode isAnd the sum of the widths of the second region and the third region of the second electrode is 0.8 μm and 1.0 μm, a graph of the attenuation performance according to the BR width.

FIG. 13 is a view showing that in the bulk acoustic wave resonator of FIG. 1, when the difference in thickness between the first region and the second region of the second electrode isAnd the sum of the widths of the second region and the third region of the second electrode is 0.8 μm and 1.0 μm, a graph of the attenuation performance according to the BR width.

Fig. 14 is a schematic cross-sectional view illustrating a bulk acoustic wave resonator according to an embodiment.

Fig. 15 is a schematic cross-sectional view illustrating a bulk acoustic wave resonator according to an embodiment.

Like reference numerals refer to like elements throughout the drawings and the detailed description. The figures may not be drawn to scale and the relative sizes, proportions and depictions of the elements in the figures may be exaggerated for clarity, illustration and convenience.

Detailed Description

The following detailed description is provided to assist the reader in obtaining a thorough understanding of the methods, devices, and/or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and/or systems described herein will be apparent to those skilled in the art in view of the disclosure of the present application. For example, the order of operations described herein is merely an example, and is not limited to the order set forth herein, but rather, variations may be made in addition to the operations which must occur in a particular order, as will be apparent upon an understanding of the present disclosure. Moreover, descriptions of features known in the art may be omitted for the sake of added clarity and conciseness.

The features described herein may be presented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many possible ways to implement the methods, devices, and/or systems described herein that will be apparent after understanding the disclosure of the present application.

Here, it is noted that the use of the term "may" with respect to an example or embodiment (e.g., with respect to what an example or embodiment may include or implement) means that there is at least one example or embodiment that includes or implements such a feature, but all examples and embodiments are not so limited.

Throughout the specification, when an element (such as a layer, region, or substrate) is described as being "on," "connected to," or "coupled to" another element, the element may be directly "on," "connected to," or "coupled to" the other element, or one or more other elements may be present therebetween. In contrast, when an element is referred to as being "directly on," "directly connected to" or "directly coupled to" another element, there may be no intervening elements present.

As used herein, the term "and/or" includes any one of the associated listed items and any combination of any two or more of the items.

Although terms such as "first", "second", and "third" may be used herein to describe various elements, components, regions, layers or sections, these elements, components, regions, layers or sections are not limited by these terms. Rather, these terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section referred to in the examples described herein could also be termed a second element, component, region, layer or section without departing from the teachings of the examples.

Spatially relative terms, such as "above," "upper," "below," "lower," "front," "rear," and "side," may be used herein for ease of description to describe one element's relationship to another element as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "upper" relative to another element would then be "below" or "lower" relative to the other element. Thus, the term "above" includes both an orientation of above and below, depending on the spatial orientation of the device. For another example, if the device in the figures is turned over, elements described as "in front of" another element would then be "behind" the other element. Thus, the term "front" includes both front and rear orientations, depending on the spatial orientation of the device. The device may also be otherwise positioned (e.g., rotated 90 degrees or at other orientations) and the spatially relative terms used herein are to be interpreted accordingly.

The terminology used herein is for the purpose of describing various examples only and is not intended to be limiting of the disclosure. The singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," and "having" specify the presence of stated features, quantities, operations, elements, components, and/or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and/or combinations thereof.

Variations in the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are possible. Accordingly, the examples described herein are not limited to the particular shapes shown in the drawings, but include changes in shapes that occur during manufacturing.

The features of the examples described herein may be combined in various ways as will be apparent after understanding the disclosure of the present application. Further, while the examples described herein have various configurations, other configurations are possible as will be apparent after understanding the disclosure of the present application.

Fig. 1 is a schematic cross-sectional view illustrating a bulk acoustic wave resonator 100 according to an embodiment. Fig. 2 is an enlarged view illustrating a portion a of fig. 1. Fig. 3 is an enlarged view illustrating a portion B of fig. 1.

Referring to fig. 1 to 3, the bulk acoustic wave resonator 100 may include, for example, a substrate 110, a sacrificial layer 120, an etch stop 130, a film layer 140, a first electrode 150, a piezoelectric layer 160, a second electrode 170, an insertion layer 180, a passivation layer 190, and a metal pad 200.

The substrate 110 may be a silicon substrate. For example, a silicon wafer or a silicon-on-insulator (SOI) type substrate may be used as the substrate 110.

The insulating layer 112 may be disposed on an upper surface of the substrate 110, and may electrically isolate the substrate 110 and structures (e.g., layers and components) disposed thereon from each other. In addition, the insulating layer 112 may prevent the substrate 110 from being etched by the etching gas when the cavity C is formed in the manufacturing process.

In an example, the insulating layer 112 can utilize silicon dioxide (SiO)₂) Silicon nitride (Si)₃N₄) Alumina (Al)₂O₃) And aluminum nitride (AlN), or any combination of any two or more thereof, and may be formed by any one of chemical vapor deposition, RF magnetron sputtering, and evaporation (vacuum evaporation).

The sacrificial layer 120 may be formed on the insulating layer 112, and the cavity C and the etch stop 130 may be disposed in the sacrificial layer 120. The cavity C may be formed by removing a portion of the sacrificial layer 120 during fabrication. As such, since the cavity C is formed in the sacrificial layer 120, the first electrode 150 disposed over the sacrificial layer 120 and the additional layers may be formed to be flat.

The etch stop 130 is disposed along a lateral/side boundary of the chamber C. The etch stop 130 is provided to prevent etching from being performed beyond the cavity region in the process of forming the cavity C. For example, the etch stop 130 may be disposed in the groove 142 of the film layer 140.

The layer 140 forms a cavity C with the substrate 110. In addition, the film layer 140 may be made of a material having low reactivity with an etching gas when removing the sacrificial layer 120. The film 140 may comprise a silicon nitride (Si) containing material₃N₄) Silicon dioxide (SiO)₂) Magnesium oxide (MgO), zirconium oxide (ZrO)₂) Aluminum nitride (AlN), zirconiumLead titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO)₂) Alumina (Al)₂O₃) Titanium oxide (TiO)₂) And zinc oxide (ZnO).

A seed layer (not shown) made of aluminum nitride (AlN) may be formed on the film layer 140. The seed layer may be disposed between the film layer 140 and the first electrode 150. The seed layer may be formed using a dielectric or a metal having an HCP crystal structure, in addition to aluminum nitride (AlN). As an example, the seed layer may be formed using titanium (Ti).

The first electrode 150 is formed on the film layer 140, and a portion of the first electrode 150 is disposed over the cavity C. Further, the first electrode 150 may be configured as any one of an input electrode for inputting an electrical signal such as a Radio Frequency (RF) signal or the like and an output electrode for outputting an electrical signal such as a Radio Frequency (RF) signal or the like.

As an example, the first electrode 150 may be formed using a conductive material such as molybdenum (Mo) or an alloy thereof. However, the first electrode 150 is not limited to these examples, and the first electrode 150 may be made using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or the like, or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

The piezoelectric layer 160 is formed to cover at least a portion of the first electrode 150 disposed over the cavity C. The piezoelectric layer 160 is a portion that generates a piezoelectric effect that converts electric energy into mechanical energy in the form of an elastic wave, and may include, for example, an aluminum nitride (AlN) material.

In addition, dopants such as rare earth metals or transition metals can be doped into the piezoelectric layer 160. As an example, the rare earth metal used as the dopant may include any one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La) or any combination of any two or more thereof. Further, the transition metal used as the dopant may include any one of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), and niobium (Nb) or any combination of any two or more thereof. In addition, the piezoelectric layer 160 may also contain magnesium (Mg) as a divalent metal.

The piezoelectric layer 160 can be made using a material having a low acoustic impedance compared to the acoustic impedance of the first electrode 150 and the second electrode 170.

The value of the acoustic impedance Z as an intrinsic value of the material can be represented by the following formula 1.

Formula (1)

In formula 1 above, ρ is the density and c is the modulus of elasticity.

The second electrode 170 is formed to cover at least a portion of the piezoelectric layer 160 disposed over the cavity C. The second electrode 170 may be configured as any one of an input electrode for inputting an electrical signal, such as a Radio Frequency (RF) signal, and an output electrode for outputting an electrical signal, such as a Radio Frequency (RF) signal. That is, when the first electrode 150 is configured as an input electrode, the second electrode 170 may be configured as an output electrode, and when the first electrode 150 is configured as an output electrode, the second electrode 170 may be configured as an input electrode.

However, the second electrode 170 is not limited to the above example, and the second electrode 170 may be formed using a conductive material such as molybdenum (Mo) or an alloy thereof. In addition, the second electrode 170 may be made of a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or the like, or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

In an active area where the first electrode 150, the piezoelectric layer 160, and the second electrode 170 are disposed all over one another, at least one step is formed in the second electrode 170. For example, the second electrode 170 may have a region in which at least one step is formed, and the region has a minimum thickness in a central portion of the effective region and a thickness at an edge portion of the effective region different from the thickness at the central portion of the effective region. In more detail, as shown in fig. 2 and 3, for example, the thickness of the second electrode 170 in the first region Z0 (e.g., the effective region) is compared to the thickness of the second electrode 170 in other regions of the effective regionAn inner region in a central portion of the region) can be formed to be minimum. In addition, in the second region Z1 disposed outside the first region Z0, the thickness of the second electrode 170 is formed to be greater than the thickness of the second electrode 170 in the first region Z0. For example, in the second region Z1, the thickness of the second electrode 170 may be greater than the thickness of the second electrode 170 in the first region Z0ToIn addition, the thickness of the second electrode 170 in the third region Z2 disposed outside the second region Z1 is formed to be greater than the thickness of the second electrode 170 in the second region Z1.

As shown in fig. 2 and 3, the first electrode 150, the piezoelectric layer 160, and the second electrode 170 are disposed to overlap each other in the first region Z0, the second region Z1, and the third region Z2.

Further, as shown in fig. 2 and 3, the first electrode 150, the insertion layer 180, the piezoelectric layer 160, and the second electrode 170 are disposed to be superposed in a fourth region Z3 disposed outside the third region Z2. The material of the interposer 180 has an acoustic impedance lower than the acoustic impedance of the materials of the first electrode 150, the piezoelectric layer 160, and the second electrode 170. Therefore, the reflection performance can be improved.

In addition, as shown in fig. 2 and 3, in the fifth area Z4 disposed outside the fourth area Z3, the first electrode 150, the insertion layer 180, and the piezoelectric layer 160 may be disposed to overlap each other, or the insertion layer 180, the piezoelectric layer 160, and the second electrode 170 may be disposed to overlap each other.

Accordingly, as shown in fig. 2 and 3, at least one step is formed on the second electrode 170 and in the first, second, third, fourth, and fifth regions Z0, Z1, Z2, Z3, and Z4.

As described above, the reflection performance can be improved by reflecting lateral waves having various wavelengths at the boundaries of the first, second, third, fourth, and fifth zones Z0, Z1, Z2, Z3, and Z4. Thus, high quality factor (Q) performance can be achieved at the anti-resonance point.

The intervening layer 180 is disposed between the first electrode 150 and the piezoelectric layer 160. The insertion layer 180 may be formed using, for example, a silicon oxide (SiO) containing film₂) Aluminum nitride (AlN), aluminum oxide (Al)₂O₃) Silicon nitride (Si)₃N₄) Magnesium oxide (MgO), zirconium oxide (ZrO)₂) Lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO)₂) Alumina (Al)₂O₃) Titanium oxide (TiO)₂) A dielectric layer of any one of zinc oxide (ZnO), and the like, but may be formed using a material different from that of the piezoelectric layer 160. In addition, if necessary, a region in which the insertion layer 180 is in the form of an air gap may also be formed. The air gap may be achieved by removing the insertion layer 180 during the manufacturing process.

As an example, the insertion layer 180 may be disposed along surfaces of the film layer 140, the first electrode 150, and the etch stop 130. At least a portion of the intervening layer 180 may be disposed between the piezoelectric layer 160 and the first electrode 150. The insertion layer 180 may not be disposed in the third region Z2.

The insertion layer 180 may be made of a material having a lower acoustic impedance than that of the first electrode 150.

The passivation layer 190 is formed in a region except for portions of the first and second electrodes 150 and 170. The passivation layer 190 may prevent the second electrode 170 and the first electrode 150 from being damaged during the manufacturing process.

In addition, a portion of the passivation layer 190 may be removed by etching to adjust frequency characteristics in a final process of manufacturing. That is, the thickness of the passivation layer 190 may be adjusted. As an example, the passivation layer 190 may include silicon nitride (Si) by way of example₃N₄) Silicon dioxide (SiO)₂) Magnesium oxide (MgO), zirconium oxide (ZrO)₂) Aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO)₂) Alumina (Al)₂O₃) Titanium oxide (TiO)₂) And zinc oxide (ZnO).

The metal pad 200 is formed on the first electrode 150 and a portion of the second electrode 170 where the passivation layer 190 is not formed. As an example, the metal pad 200 may be made using a material such as gold (Au), gold-tin (Au-Sn) alloy, copper (Cu), copper-tin (Cu-Sn) alloy, aluminum (Al), or aluminum alloy. For example, the aluminum alloy may be an aluminum-germanium (Al-Ge) alloy.

The metal pad 200 may include a first metal pad 202 connected to the first electrode 150 and a second metal pad 204 connected to the second electrode 170.

As described above, the reflection performance can be improved by reflecting lateral waves having various wavelengths at the boundaries of the first, second, third, fourth, and fifth zones Z0, Z1, Z2, Z3, and Z4. Thus, high quality factor (Q) performance can be achieved at the anti-resonance point.

Hereinafter, the effect of the bulk acoustic wave resonator 100 will be described.

Fig. 4 is an explanatory diagram showing a conventional bulk acoustic wave resonator 10. Fig. 5 is a graph showing attenuation performance according to BR width in a conventional bulk acoustic wave resonator.

Referring to fig. 4, the conventional bulk acoustic wave resonator 10 has 4900 μm²And an aspect ratio (height/width ratio) of 2.4. When the BR width w1 shown in the section A-A 'shown in FIG. 4 was changed, the BE width w2 in the section B-B' shown in FIG. 4 was made constant at 0.4. mu.m. As shown in this experiment in fig. 5, when the BR width is 0.4 μm, the attenuation performance has a maximum of 33.1 dB.

As shown in fig. 4, BR width w1 is the width of a region in which the insertion layer and the second electrode overlap each other, and BE width w2 is the width of a region in which the first electrode and the insertion layer overlap each other.

The performance of the conventional resonator 10 is shown in table 1 below.

TABLE 1

Fig. 6 is an explanatory diagram showing the bulk acoustic wave resonator 100 according to the embodiment. Fig. 7 is a graph showing the attenuation performance according to the sum of the widths of the second region Z1 and the third region Z2 of the second electrode 170 when the BR widths are 0.4 μm, 0.6 μm, and 0.8 μm in the bulk acoustic wave resonator 100.

As shown in fig. 7, when the sum of the widths of the second region Z1 and the third region Z2 is 0.8 μm, the attenuation performance has a maximum value of 37.7 dB.

The performance exhibited by the bulk acoustic wave resonator 100 according to the sum of the widths of the second region Z1 and the third region Z2 of the second electrode 170 is shown in table 2 below.

TABLE 2

Fig. 8 is an explanatory diagram showing the bulk acoustic wave resonator 100 according to the embodiment. Fig. 9 is a graph showing the damping performance according to the BR width when the sum of the widths of the second region and the third region of the second electrode 170 is 0.6 μm, 0.8 μm, and 1.0 μm in the bulk acoustic wave resonator 100.

As shown in fig. 9, when the BR width w1 is 0.6 μm, the attenuation performance has a maximum value of 37.7 dB.

The performance exhibited by the bulk acoustic wave resonator 100 according to the BR width is shown in table 3 below.

TABLE 3

Fig. 10 is an explanatory diagram showing the bulk acoustic wave resonator 100 according to the embodiment. FIG. 11 shows that in the bulk acoustic wave resonator 100, when the difference in thickness between the first region Z0 and the second region Z1 of the second electrode 170 isAnd the sum of the widths of the second region Z1 and the third region Z2 of the second electrode 170 is 0.8 μm and 1.0 μm, a graph of attenuation performance according to BR width. Fig. 12 is a view showing that in the bulk acoustic wave resonator 100 according to the embodiment, when the difference in thickness between the first region Z0 and the second region Z1 of the second electrode 170 isAnd the sum of the widths of the second region Z1 and the third region Z2 of the second electrode 170 is 0.8 μm and 1.0 μm, a graph of attenuation performance according to BR width. Fig. 13 is a view showing that in the bulk acoustic wave resonator 100 according to the embodiment, when the difference in thickness between the first region Z0 and the second region Z1 of the second electrode 170 isAnd the sum of the widths of the second region Z1 and the third region Z2 of the second electrode is 0.8 μm and 1.0 μm, a graph of the attenuation performance according to the BR width.

As shown in fig. 11 to 13, when the thickness difference isThe attenuation performance has a maximum of 37.7 dB.

Although in the example, the difference in thickness between the first region Z0 and the second region Z1 of the second electrode 170 is described asToBut when the difference in thickness between the first region and the second region isToWhen this is done, the attenuation performance of the second electrode 170 can be improved.

TABLE 4

Hereinafter, modified embodiments of the bulk acoustic wave resonator 100 described above will be described. However, when fig. 14 and 15 are discussed below, a detailed description of the components shared with the previously described embodiments will not be repeated.

Fig. 14 is a schematic cross-sectional view illustrating a bulk acoustic wave resonator 300 according to an embodiment.

Referring to fig. 14, the bulk acoustic wave resonator 300 may include, for example, a substrate 110, a sacrificial layer 120, an etch stop 130, a film layer 140, a first electrode 150, a piezoelectric layer 360, a second electrode 370, an insertion layer 180, a passivation layer 190, and a metal pad 200. Accordingly, the bulk acoustic wave resonator 300 is different from the bulk acoustic wave resonator 100 in that the bulk acoustic wave resonator 300 includes the piezoelectric layer 360 and the second electrode 370 instead of the piezoelectric layer 160 and the second electrode 170.

The piezoelectric layer 360 is formed to cover at least a portion of the first electrode 150 disposed over the cavity C. The piezoelectric layer 360 is a portion that generates a piezoelectric effect that converts electric energy into mechanical energy in the form of an elastic wave, and may include, for example, an aluminum nitride (AlN) material.

In addition, dopants such as rare earth metals or transition metals can be doped into the piezoelectric layer 360. As an example, the rare earth metal used as the dopant may include any one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La) or any combination of any two or more thereof. Further, the transition metal used as the dopant may include any one of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), and niobium (Nb) or any combination of any two or more thereof. In addition, the piezoelectric layer 360 may also contain magnesium (Mg) as a divalent metal.

Additionally, the piezoelectric layer 360 can be made using a material having a low acoustic impedance compared to the acoustic impedance of the first and second electrodes 150 and 370.

In an active area where the first electrode 150, the piezoelectric layer 360, and the second electrode 370 are all disposed to overlap each other, at least one step is formed in the piezoelectric layer 360. As an example, the piezoelectric layer 360 may have a region in which at least one step is formed, and the region has a minimum thickness in a central portion of the effective region and a thickness different from a thickness at the central portion at edge portions of the effective region. In more detail, for example, the thickness of the piezoelectric layer 360 in the first region is compared to the thickness of the piezoelectric layer 360 in other regions in the active regionThe thickness in a region Z0 (e.g., an inner region in the central portion of the effective region) can be made to be minimum. In addition, in the second region Z1 provided outside the first region Z0, the thickness of the piezoelectric layer 360 is formed to be larger than the thickness of the piezoelectric layer 360 in the first region Z0. In addition, the thickness of the piezoelectric layer 360 in the second region Z1 may be greater than the thickness of the piezoelectric layer 360 in the first region Z0ToIn the third region Z2 provided outside the second region Z1, the thickness of the piezoelectric layer 360 is formed to be larger than the thickness of the piezoelectric layer 360 in the second region Z1.

In the first region Z0, the second region Z1, and the third region Z2, the first electrode 150, the piezoelectric layer 360, and the second electrode 370 are disposed to overlap each other.

In the fourth region Z3 disposed outside the third region Z2, the first electrode 150, the piezoelectric layer 360, and the second electrode 370 are disposed so as to overlap each other. Additionally, the acoustic impedance of the insertion layer 180 may be lower than the acoustic impedance of the first electrode 150, the piezoelectric layer 360, and the second electrode 370. Therefore, the reflection performance can be improved.

In addition, in the fifth area Z4 disposed outside the fourth area Z3, the first electrode 150, the insertion layer 180, and the piezoelectric layer 360 are disposed to overlap each other, or the insertion layer 180, the piezoelectric layer 360, and the second electrode 370 are disposed to overlap each other.

Therefore, as shown in fig. 14, at least one step is formed on the piezoelectric layer 360 and in the first region Z0, the second region Z1, the third region Z2, the fourth region Z3, and the fifth region Z4.

As described above, the reflection performance can be improved by reflecting lateral waves having various wavelengths at the boundaries of the first, second, third, fourth, and fifth zones Z0, Z1, Z2, Z3, and Z4. Thus, high quality factor (Q) performance can be achieved at the anti-resonance point.

The second electrode 370 may be formed to cover at least a portion of the piezoelectric layer 360 disposed over the cavity C. The second electrode 370 may be configured as any one of an input electrode for inputting an electrical signal, such as a Radio Frequency (RF) signal, and an output electrode for outputting an electrical signal, such as a Radio Frequency (RF) signal. That is, when the first electrode 150 is configured as an input electrode, the second electrode 370 may be configured as an output electrode, and when the first electrode 150 is configured as an output electrode, the second electrode 370 may be configured as an input electrode.

As an example, the second electrode 370 may be formed using a conductive material such as molybdenum (Mo) or an alloy thereof. However, the second electrode 370 is not limited to these examples, and the second electrode 370 may be made using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or the like, or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

Fig. 15 is a schematic cross-sectional view illustrating a bulk acoustic wave resonator 500 according to an embodiment.

Referring to fig. 15, the bulk acoustic wave resonator 500 may include, for example, a substrate 110, a sacrificial layer 120, an etch stop 130, a film layer 140, a first electrode 550, a piezoelectric layer 160, a second electrode 570, an insertion layer 180, a passivation layer 190, and a metal pad 200. Accordingly, the bulk acoustic wave resonator 500 differs from the bulk acoustic wave resonator 100 in that the bulk acoustic wave resonator 500 includes the first electrode 550 and the second electrode 570 instead of the first electrode 150 and the second electrode 170.

The first electrode 550 is formed on the film layer 140, and a portion of the first electrode 550 is disposed over the cavity C. Further, the first electrode 550 may be configured as any one of an input electrode for inputting an electrical signal such as a Radio Frequency (RF) signal or the like and an output electrode for outputting an electrical signal such as a Radio Frequency (RF) signal or the like.

As an example, the first electrode 550 may be formed using a conductive material such as molybdenum (Mo) or an alloy thereof. However, the first electrode 550 is not limited to these examples, and the first electrode 550 may be made using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or the like, or an alloy of ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

In an active region where the first electrode 550, the piezoelectric layer 160, and the second electrode 570 are all disposed to overlap each other, at least one step is formed in the first electrode 550. As an example, the first electrode 550 may have a region in which at least one step is formed, and the region has a minimum thickness at a central portion of the effective region and a thickness different from a thickness at the central portion at an edge portion of the effective region. For example, the thickness of the first electrode 550 in the first region Z0 (e.g., the inner region in the central portion of the effective region) is formed to be minimum as compared with other regions. In addition, in the second region Z1 disposed outside the first region Z0, the thickness of the first electrode 550 is formed to be greater than the thickness of the first electrode 550 in the first region Z0. In addition, in the second region Z1, the thickness of the first electrode 550 may be greater than that of the first electrode 550 in the first region Z0ToThe third region Z2 is disposed outside the second region Z1.

In the first region Z0, the second region Z1, and the third region Z2, the first electrode 550, the piezoelectric layer 160, and the second electrode 570 are disposed to overlap each other.

In the fourth region Z3 disposed outside the third region Z2, the first electrode 550, the insertion layer 180, the piezoelectric layer 160, and the second electrode 570 are disposed to overlap each other. Additionally, the acoustic impedance of the insertion layer 180 may be lower than the acoustic impedance of the first electrode 550, the piezoelectric layer 160, and the second electrode 570. Therefore, the reflection performance can be improved.

In addition, in the fifth region Z4, the first electrode 550, the insertion layer 180, and the piezoelectric layer 160 are disposed to overlap, or the insertion layer 180, the piezoelectric layer 160, and the second electrode 570 are disposed to overlap.

Therefore, as shown in fig. 15, at least one step is formed on the first electrode 550 in the first region Z0, the second region Z1, the third region Z2, the fourth region Z3, and the fifth region Z4.

As described above, the reflection performance can be improved by reflecting lateral waves having various wavelengths at the boundaries of the first, second, third, fourth, and fifth zones Z0, Z1, Z2, Z3, and Z4. Thus, high quality factor (Q) performance can be achieved at the anti-resonance point.

The second electrode 570 is formed to cover at least a portion of the piezoelectric layer 160 disposed over the cavity C. The second electrode 570 may be configured as any one of an input electrode for inputting an electrical signal such as a Radio Frequency (RF) signal or the like and an output electrode for outputting an electrical signal such as a Radio Frequency (RF) signal or the like. That is, when the first electrode 550 is configured as an input electrode, the second electrode 570 may be configured as an output electrode, and when the first electrode 550 is configured as an output electrode, the second electrode 570 may be configured as an input electrode.

As an example, the second electrode 570 may be formed using a conductive material such as molybdenum (Mo) or an alloy thereof. However, the second electrode is not limited to these examples, and the second electrode 570 may be made using a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), chromium (Cr), or the like, or an alloy of a conductive material such as ruthenium (Ru), tungsten (W), iridium (Ir), platinum (Pt), copper (Cu), titanium (Ti), tantalum (Ta), nickel (Ni), or chromium (Cr).

As described above, according to the disclosure herein, the lateral wave reflection performance of the bulk acoustic wave resonator can be improved.

While the present disclosure includes specific examples, it will be apparent after understanding the disclosure of the present application that various changes in form and detail may be made therein without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered in a descriptive sense only and not for purposes of limitation. The description of features or aspects in each example will be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques were performed in a different order and/or if components in the described systems, architectures, devices, or circuits were combined in a different manner and/or replaced or supplemented by other components or their equivalents. In addition, the various embodiments may be combined with each other. Therefore, the scope of the present disclosure is defined not by the detailed description but by the claims and their equivalents, and all modifications within the scope of the claims and their equivalents are to be construed as being included in the present disclosure.