CN117335768A - Thin film bulk acoustic resonator and preparation method thereof - Google Patents

Abstract

The present application provides a thin film bulk acoustic wave resonator and a preparation method thereof, and relates to the technical field of resonators. The thin film volume acoustic resonator includes: a base layer and a bottom electrode, a piezoelectric layer and a top electrode that are stacked on the base layer in sequence. The base layer is provided with an acoustic reflection structure, and the bottom electrode, piezoelectric layer and top electrode are arranged on the base layer. The overlapping portion of the orthographic projection on the base layer and the overlapping area of the orthographic projection of the acoustic reflection structure on the base layer are used as the working area; the bottom electrode and the piezoelectric layer are respectively provided with first concave and convex structures, and the first concave and convex structures are used to change the bottom electrode and the piezoelectric layer. The thickness of the local area on the piezoelectric layer, the position of the first concave-convex structure on the piezoelectric layer corresponds to the position of the first concave-convex structure on the bottom electrode, and the first concave-convex structure is arranged around the working area. The film bulk acoustic resonator can effectively reduce energy loss and increase the Q value, thereby improving the steepness and insertion loss of the resonator. It can also effectively suppress spurious waves, making the frequency response smoother.

Description

Thin film bulk acoustic resonator and preparation method thereof

Technical field

The present application relates to the technical field of resonators, specifically, to a thin film bulk acoustic resonator and a preparation method thereof.

Background technique

Currently, with the rapid development of wireless communications, there are more and more devices that send and receive information in higher frequency bands. The requirements for RF front-end circuits are becoming more and more demanding, and the market demand for high-performance filters is growing. BAW filters are gradually becoming the mainstream of the market due to their high quality factor, good out-of-band suppression, and high rectangular coefficient.

The bulk acoustic wave filter is composed of multiple thin-film bulk acoustic wave resonators connected according to a specific circuit. When the thin-film bulk acoustic wave resonator is working, it will produce transverse vibration due to the piezoelectric effect. The transverse vibration will cause the longitudinal sound wave to be transmitted to the transverse sound wave, and at the same time, different sound waves will be generated. Necessary parasitics cause longitudinal energy loss, reduce the Q value of the resonator, affect filter roll-off, increase in-band ripples, and increase insertion loss, which greatly affects the performance of the bulk acoustic wave filter.

Therefore, high-performance bulk acoustic wave filters require high-performance thin film bulk acoustic wave resonators, and high-performance thin film bulk acoustic wave resonators need to have high quality factors. High quality factors can allow bulk acoustic wave filters to have smaller insertion loss and better performance. Steep roll-off characteristics and superior filtering performance. Therefore, how to improve the Q value of thin film bulk acoustic resonators is an urgent problem that needs to be solved.

In the existing technology, Q-enhancing structures are usually made on the edge of the top electrode, such as top electrode boundary ring (Frame), air bridge (Air bridge) or air wing (Air wing) and other structures. These structures limit the leakage of sound waves by introducing an impedance mismatch structure on the top electrode and reflect most of the sound waves back to the resonator. However, there is still transverse sound wave leakage, which will cause the Q value of the thin film bulk acoustic wave resonator to decrease.

Contents of the invention

The purpose of this application is to provide a thin film bulk acoustic resonator and a preparation method thereof in view of the above-mentioned deficiencies in the prior art, which can effectively improve the Q value of the thin film bulk acoustic resonator.

In order to achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

In one aspect of the embodiment of the present application, a thin film bulk acoustic resonator is provided, including: a base layer and a bottom electrode, a piezoelectric layer and a top electrode that are stacked on the base layer in sequence. The base layer is provided with an acoustic reflection structure, and the bottom electrode , the overlapping portion of the orthographic projection of the piezoelectric layer and the top electrode on the base layer and the overlapping area of the orthographic projection of the acoustic reflection structure on the base layer are used as the working area; the bottom electrode and the piezoelectric layer are respectively provided with first concave and convex structures, The first concave-convex structure is used to change the thickness of the local area on the bottom electrode and the piezoelectric layer. The first concave-convex structure on the piezoelectric layer corresponds to the position of the first concave-convex structure on the bottom electrode. The first concave-convex structure is arranged around the working area.

Optionally, the base layer includes a substrate layer and a seed layer disposed on the substrate layer, the bottom electrode is located on the seed layer; the seed layer is provided with a first concave-convex structure, and the first concave-convex structure on the seed layer is connected with the first concave-convex structure on the bottom electrode. The positions of a concave-convex structure correspond to each other; or, the substrate layer and the seed layer are respectively provided with first concave-convex structures, and the first concave-convex structure on the substrate layer and the first concave-convex structure on the seed layer correspond to the positions of the first concave-convex structure on the bottom electrode. .

Optionally, the first concave-convex structure is annular; or, the first concave-convex structure each includes a plurality of sub-protrusions or a plurality of sub-grooves, and the plurality of sub-protrusions or multiple sub-grooves are spaced around the working area.

Optionally, the first concave-convex structure includes at least two layers, and the at least two layers of the first concave-convex structure are concentrically arranged around the working area.

Another aspect of the embodiments of the present application provides a method for preparing a thin film bulk acoustic resonator, which includes: providing a base layer, and forming a reflective structure on the base layer; forming a patterned bottom electrode on the base layer, and forming a patterned bottom electrode on the base layer. A first concave-convex structure is formed on the electrode, wherein the bottom electrode covers at least part of the reflective structure, and the orthographic projection of the first concave-convex structure on the base layer is located outside the reflective structure; a piezoelectric layer and a patterned top electrode are sequentially formed on the bottom electrode. , and at least a first concave-convex structure is formed on the piezoelectric layer at a position corresponding to the first concave-convex structure on the bottom electrode, wherein the piezoelectric layer covers the base layer and the bottom electrode, and the top electrode covers at least part of the reflective structure and the bottom electrode .

Optionally, the preparation method of the thin film bulk acoustic resonator includes: providing a base layer, and forming a reflective structure and a first concave-convex structure on the base layer, wherein the first concave-convex structure is located outside the reflective structure; laying evenly on the base layer The bottom electrode material is used to form a first metal layer; the first metal layer is patterned to obtain a bottom electrode, wherein the bottom electrode covers at least part of the reflective structure and the first concave-convex structure; the base layer and the bottom layer exposed by the bottom electrode are The piezoelectric material is evenly laid on the electrode to form a piezoelectric layer; the top electrode material is evenly laid on the piezoelectric layer to form a second metal layer; the second metal layer is patterned to obtain a top electrode, wherein the top electrode Covering at least part of the reflective structure and the bottom electrode.

Optionally, the preparation method of the thin film bulk acoustic resonator includes: providing a substrate layer, and forming a sacrificial layer within the substrate layer, wherein the upper surface of the sacrificial layer is flush with the upper surface of the substrate layer; on the substrate layer and the sacrificial layer Evenly laying the seed material to form a seed layer; patterning the seed layer to form a first concave-convex structure on the seed layer, wherein the first concave-convex structure is located outside the reflective structure; evenly laying the bottom electrode material on the seed layer to form a first metal layer; pattern the first metal layer to obtain a bottom electrode, wherein the bottom electrode covers at least part of the sacrificial layer and the first concave-convex structure; uniformly on the base layer and the bottom electrode exposed by the bottom electrode Laying a piezoelectric material to form a piezoelectric layer; evenly laying a top electrode material on the piezoelectric layer to form a second metal layer; patterning the second metal layer to obtain a top electrode, wherein the top electrode covers at least part of Sacrificial layer and bottom electrode; release the sacrificial layer to form a cavity.

Optionally, providing a base layer, and forming a reflective structure and a first concave-convex structure on the base layer, wherein the first concave-convex structure is located outside the reflective structure includes: providing a base layer, and forming a reflective structure and a groove on the base layer. , wherein the groove is located outside the reflective structure; patterning the first metal layer to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the first concave-convex structure includes: patterning the first metal layer , to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the groove; patterning the second metal layer to obtain a top electrode, wherein the top electrode covers at least part of the reflective structure and the bottom electrode includes: The metal layer is patterned to obtain a top electrode, wherein the top electrode covers at least part of the reflective structure, the bottom electrode and the groove.

Optionally, providing a base layer, and forming a reflective structure and a first concave-convex structure on the base layer, wherein the first concave-convex structure is located outside the reflective structure includes: providing a base layer, and forming the reflective structure and protrusions on the base layer. , wherein the first concave-convex structure is located outside the reflective structure; patterning the first metal layer to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the first concave-convex structure includes: patterning the first metal layer chemical treatment to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the protrusions.

Optionally, providing a base layer, and forming a reflective structure and a first concave-convex structure on the base layer, wherein the first concave-convex structure is located outside the reflective structure includes: providing a base layer, and forming the reflective structure, the first concave-convex structure on the base layer. The concave-convex structure and the second concave-convex structure, wherein the first concave-convex structure is located outside the reflective structure, and the second concave-convex structure is located above the reflective structure.

The beneficial effects of this application include:

This application provides a thin film bulk acoustic resonator, which includes: a base layer and a bottom electrode, a piezoelectric layer and a top electrode that are stacked on the base layer in sequence. The base layer is provided with an acoustic reflection structure, and the bottom electrode, piezoelectric layer and The overlapping portion of the orthographic projection of the top electrode on the base layer and the overlapping area of the orthographic projection of the acoustic reflection structure on the base layer are used as the working area; the bottom electrode and the piezoelectric layer are respectively provided with first concave and convex structures, and the first concave and convex structures are provided with In order to change the thickness of the bottom electrode and the local area on the piezoelectric layer, the first concave-convex structure on the piezoelectric layer corresponds to the position of the first concave-convex structure on the bottom electrode, and the first concave-convex structure is arranged around the working area. The thin film bulk acoustic resonator introduces an acoustic mismatch boundary by adding a first concave-convex structure on the periphery of the working area. Moreover, the first concave-convex structure at least exists on the bottom electrode and the piezoelectric layer at the same time. Therefore, it can effectively reduce energy loss and Increasing the Q value improves the steepness and insertion loss of the resonator, while also effectively suppressing spurious waves, resulting in a smoother frequency response.

This application also provides a method for preparing a thin film bulk acoustic resonator, which includes: providing a base layer, and forming a reflective structure on the base layer; forming a patterned bottom electrode on the base layer, and forming first concavities and convexities on the bottom electrode structure, wherein the bottom electrode covers at least part of the reflective structure, and the orthographic projection of the first concave-convex structure on the base layer is located outside the reflective structure; a piezoelectric layer and a patterned top electrode are formed on the bottom electrode in sequence, and at least the piezoelectric layer is A first concave-convex structure is also formed on the layer at a position corresponding to the first concave-convex structure on the bottom electrode, wherein the piezoelectric layer covers the base layer and the bottom electrode, and the top electrode at least covers the reflective structure. The preparation method of the thin film bulk acoustic resonator is to form a first concave and convex structure on the periphery of the working area of the bottom electrode and the piezoelectric layer and introduce acoustic mismatch boundaries to reduce energy loss and improve the Q value of the thin film bulk acoustic resonator. This improves the steepness and insertion loss of the resonator, and effectively suppresses spurious waves, making the frequency response of the thin film bulk acoustic resonator smoother.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is one of the structural schematic diagrams of a thin film bulk acoustic resonator provided by an embodiment of the present application;

Figure 2 is the second structural schematic diagram of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 3 is the third structural schematic diagram of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 4 is the fourth structural schematic diagram of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 5 is the fifth structural schematic diagram of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 6 is one of the flow charts of the preparation method of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 7 is the second flow chart of the preparation method of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 8 is one of the schematic diagrams of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 9 is a second schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 10 is the third schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 11 is the fourth schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 12 is the third flow chart of the preparation method of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 13 is the fourth flow chart of the preparation method of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 14 is the fifth schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 15 is the sixth schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 16 is the seventh schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 17 is the eighth schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 18 is the fifth flow chart of the preparation method of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 19 is a ninth schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 20 is a schematic view of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 21 is a flow chart 6 of a method for preparing a thin film bulk acoustic resonator provided by an embodiment of the present application;

Figure 22 is an eleventh schematic diagram of the preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present application;

Figure 23 is the seventh flow chart of the method for preparing a thin film bulk acoustic resonator provided by an embodiment of the present application;

Figure 24 is a schematic diagram of the preparation process of the thin film bulk acoustic resonator provided in the embodiment of the present application.

Icon: 100-thin film bulk acoustic resonator; 110-base layer; 111-substrate layer; 112-seed layer; 113-acoustic reflection structure; 114-reflection structure; 120-bottom electrode; 130-piezoelectric layer; 140-top Electrode; 150-first concave-convex structure; 160-working area; 170-second concave-convex structure.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments These are part of the embodiments of this application, but not all of them. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of the disclosure. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood that when an element (such as a layer, region or substrate) is referred to as being "on" or "extending to" another element, it can be directly on the other element or extend directly to the other element. elements, or there may be intervening elements. In contrast, when an element is referred to as being "directly on" or "directly extending from" another element, there are no intervening elements present. Likewise, it will be understood that when an element (such as a layer, region, or substrate) is referred to as being "on" or "extending over" another element, it can be directly on the other element or directly on the other element. extends above another element, or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or "extending directly over" another element, there are no intervening elements present. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It should also be understood that the terms used herein are to be construed to have a meaning consistent with their meaning in the context of this specification and the related art, and not to be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In one aspect of the embodiment of the present application, with reference to FIGS. 1 and 2 , a thin film bulk acoustic resonator 100 is provided, including: a base layer 110 and a bottom electrode 120 , a piezoelectric layer 130 and a top layer sequentially stacked on the base layer 110 . Electrode 140. The base layer 110 is provided with a sound reflection structure 113. The sound reflection structure 113 can be provided on the surface of the base layer 110 or in the middle of the base layer 110; the sound reflection structure 113 can be a cavity or other structure capable of reflecting sound waves. structure. The overlapping portion of the orthographic projection of the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140 on the base layer 110 and the overlapping area of the orthographic projection of the acoustic reflection structure 113 on the base layer 110 serve as the working area 160, that is, the bottom The area where the electrode 120, the piezoelectric layer 130 and the top electrode 140 overlap each other and are located directly above the acoustic reflection structure 113 together constitute the working area 160 of the thin film bulk acoustic resonator 100. The area surrounding the working area 160 is the non-working area 160. The bottom electrode 120 and the piezoelectric layer 130 are respectively provided with first concave and convex structures 150. The first concave and convex structures 150 are protrusions and/or grooves. The first concave and convex structures 150 are used to change parts of the bottom electrode 120 and the piezoelectric layer 130. The thickness of the region, the thickness of the bottom electrode 120 and the piezoelectric layer 130 at the location where the first concave-convex structure 150 is located is greater or smaller than the thickness at surrounding locations. The first concave-convex structure 150 on the piezoelectric layer 130 corresponds to the first concave-convex structure 150 on the bottom electrode 120 in the sequential stacking direction, and the first concave-convex structure 150 is arranged around the working area 160.

The above-mentioned thin film bulk acoustic resonator 100 introduces an acoustic mismatch boundary by adding the first concave-convex structure 150 on the periphery of the working area 160, and the first concave-convex structure 150 exists at least on the bottom electrode 120 and the piezoelectric layer 130 at the same time. Therefore, It can effectively reduce energy loss and increase the Q value, thereby improving the steepness and insertion loss of the resonator. It can also effectively suppress spurious waves, making the frequency response smoother.

Optionally, in an implementable manner of the embodiment of the present application, please refer to FIG. 1 , the first concave-convex structure 150 is a groove, and the groove is located on the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140, and The grooves on the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140 have corresponding positions along the stacking direction.

The bottom electrode 120, the piezoelectric layer 130 and the top electrode 140 are simultaneously provided with grooves corresponding to each other so that the side surfaces of the working area 160 of the thin film bulk acoustic resonator 100 always have a concave and convex structure along the stacking direction, which can further reduce the acoustic wave energy. The transverse leakage increases the Q value of the thin film bulk acoustic resonator 100 .

More preferably, the base layer 110 is also provided with grooves, and the grooves on the base layer 110 correspond to the grooves on the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140 along the stacking direction. With this arrangement, during the preparation process, grooves can be formed on the base layer 110 first, and then the bottom electrode material, the piezoelectric material and the top electrode material are sequentially laid on the base layer 110, so that the bottom electrode 120, Grooves are formed on the piezoelectric layer 130 and the top electrode 140, making the preparation process simpler.

Optionally, in an implementable manner of the embodiment of the present application, please refer to FIG. 2 , the first concave-convex structure 150 is a protrusion, and the protrusion is located on the bottom electrode 120 and the piezoelectric layer 130 at the same time, and the bottom electrode 120 and The protrusions on the piezoelectric layer 130 have corresponding positions along the stacking direction.

The protrusions on the piezoelectric layer 130 are located on the side of the top electrode 140. When the first concave-convex structure 150 is a protrusion, the protrusions only exist on the bottom electrode 120 and the piezoelectric layer 130, which can also effectively reduce the lateral direction of the sound wave energy. Leakage increases the Q value of the thin film bulk acoustic resonator 100 .

More preferably, the base layer 110 is also provided with protrusions, and the protrusions on the base layer 110 correspond to the protrusions on the bottom electrode 120 and the piezoelectric layer 130 along the stacking direction. Such an arrangement can simplify the preparation process. Moreover, the protrusions on the base layer 110 are located on the side of the working area 160, and cooperate with the protrusions on the bottom electrode 120 and the piezoelectric layer 130 to further improve the Q of the thin film bulk acoustic resonator 100. value.

Optionally, in an implementable manner of the embodiment of the present application, please refer to FIG. 3 , the first concave and convex structure 150 is annular, and the first concave and convex structure 150 is arranged around the working area 160 of the thin film bulk acoustic resonator 100 , so that Can better reflect sound waves back to the working area 160; or, please refer to FIG. 4, the first concave-convex structure 150 includes a plurality of sub-protrusions or a plurality of sub-grooves, and the plurality of sub-protrusions or a plurality of sub-grooves are spaced around the working area 160. , in this way, the sound waves can be better reflected back to the working area 160.

Optionally, in an implementable manner of the embodiment of the present application, please refer to FIG. 5 , the first concave-convex structure 150 includes at least two layers, and the at least two layers of the first concave-convex structure 150 are concentrically arranged around the working area 160 to further improve The Q value of the thin film bulk acoustic resonator 100. At this time, the heights of at least two layers of first concave-convex structures 150 may be equal or unequal.

Preferably, the number of the first concave-convex structures 150 is one to five layers.

Optionally, in an implementable manner of the embodiment of the present application, please refer to FIGS. 1 and 2 . The base layer 110 includes a substrate layer 111 and a seed layer 112 disposed on the substrate layer 111 . The bottom electrode 120 is located on the seed layer. 112; a first concave-convex structure 150 is provided on the seed layer 112, and the first concave-convex structure 150 on the seed layer 112 corresponds to the position of the first concave-convex structure 150 on the bottom electrode 120; or, the substrate layer 111 and the seed layer 112 are respectively A first concave-convex structure 150 is provided. The first concave-convex structure 150 on the substrate layer 111 and the first concave-convex structure 150 on the seed layer 112 correspond to the first concave-convex structure 150 on the bottom electrode 120 .

The arrangement of the seed layer 112 facilitates the subsequent crystal growth of the bottom electrode 120 and the piezoelectric layer 130. The material of the seed layer 112 can be consistent with the material of the piezoelectric layer 130, and the thickness is usually between ten nanometers and several hundred nanometers. The first concave-convex structure 150 is provided on the seed layer 112, or the first concave-convex structure 150 is provided on the substrate layer 111 and the seed layer 112 at the same time. In terms of technology, the first concave-convex structure 150 on the substrate layer 111 or the seed layer 112 can be used. , grooves are naturally formed on the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140, thereby simplifying the preparation process.

This embodiment also provides a method for preparing a thin film bulk acoustic resonator. Please refer to Figure 6 in combination, including:

S100: Provide a base layer and form a reflective structure on the base layer.

The base layer 110 is used to support the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140. The base layer 110 can be a single-layer structure, or a two-layer or multi-layer structure. For example, the base layer 110 includes a substrate layer 111 and a seed layer 112 covering the substrate layer 111. The substrate layer 111 is made of a silicon wafer, and the seed layer 112 is made of a material that is easy to combine with the bottom electrode 120 and the piezoelectric layer 130. , thereby facilitating crystal growth of the bottom electrode 120 and the piezoelectric layer 130 . A reflective structure 114 is provided on the base layer 110. The reflective structure 114 may be a structure that can directly reflect sound waves, or may be a structure that can reflect sound waves after subsequent processing.

S200: Form a patterned bottom electrode on the base layer, and form a first concave-convex structure on the bottom electrode, wherein the bottom electrode covers at least part of the reflective structure, and the orthographic projection of the first concave-convex structure on the base layer is located outside the reflective structure. .

The patterned bottom electrode 120 covers part of the base layer 110 , and part of the area is located above the reflective structure 114 , thereby forming the working area 160 of the thin film bulk acoustic resonator 100 during subsequent processes. The first concave-convex structure 150 is a groove and/or a protrusion. The first concave-convex structure 150 on the bottom electrode 120 can be directly formed on the bottom electrode 120, or the first concave-convex structure 150 can be formed on the base layer 110, and then through The first concave-convex structure 150 corresponding to the position is also formed on the bottom electrode 120 by evenly spreading the bottom electrode material on the base layer 110 . The orthographic projection of the first concave-convex structure 150 on the base layer 110 is located outside the reflective structure 114, which ensures that the first concave-convex structure 150 is located outside the working area 160, so that the first concave-convex structure 150 can reflect sound waves back to the working area 160.

Please refer to FIG. 2. The first concave-convex structure 150 may be annular, and the first concave-convex structure 150 is arranged around the reflective structure 114; or, please refer to FIG. 4, the first concave-convex structure 150 may include a plurality of sub-protrusions or a plurality of sub-grooves. Sub-protrusions or multiple sub-grooves are spaced around the reflective structure 114 . Referring to FIG. 5 , the first concave-convex structure 150 preferably includes one to five layers. When the number of the first concave-convex structure 150 is at least two layers, at least two layers of the first concave-convex structure 150 are arranged concentrically around the reflective structure 114 .

S300: Form a piezoelectric layer and a patterned top electrode on the bottom electrode in sequence, and at least form a first concave-convex structure on the piezoelectric layer at a position corresponding to the first concave-convex structure on the bottom electrode, wherein the piezoelectric layer The base layer and the bottom electrode are covered, and the top electrode covers at least part of the reflective structure and the bottom electrode.

A piezoelectric layer 130 is formed on the bottom electrode 120, and the piezoelectric layer 130 covers the bottom electrode 120 and the base layer 110 exposed by the bottom electrode 120; then, a patterned top electrode 140 is formed on the piezoelectric layer 130, and the patterned top electrode 140 is formed on the bottom electrode 120. The top electrode 140 covers part of the piezoelectric layer 130 , and part of the area overlaps with the bottom electrode 120 and is located above the reflective structure 114 , thereby forming the working area 160 of the thin film bulk acoustic resonator 100 . The first concave-convex structure 150 on the piezoelectric layer 130 can be formed by utilizing the first concave-convex structure 150 on the bottom electrode 120 by evenly laying the piezoelectric material on the bottom electrode 120 and the base layer 110 exposed by the bottom electrode 120, thereby forming a piezoelectric layer on the piezoelectric layer 130. Corresponding first concave and convex structures 150 are formed on the electrical layer 130 .

The above preparation method of the thin film bulk acoustic resonator introduces acoustic mismatch boundaries by forming the first concave and convex structure 150 on the periphery of the bottom electrode 120 and the working area 160 of the piezoelectric layer 130 to reduce energy loss and improve the thin film bulk acoustic resonator. The Q value is 100, thereby improving the steepness and insertion loss of the resonator, and at the same time, spurious waves can be effectively suppressed, thereby making the frequency response of the thin film bulk acoustic resonator 100 smoother.

Optionally, in an implementable manner of the embodiment of the present application, please refer to Figures 7 to 11. The method for preparing a thin film bulk acoustic resonator includes:

S110: Provide a base layer, and form a reflective structure and a first concave-convex structure on the base layer, where the first concave-convex structure is located outside the reflective structure.

The first concave-convex structure 150 and the reflective structure 114 are located on the base layer 110 at the same time, but the orthographic projections on the base layer 110 do not overlap, so that the first concave-convex structure 150 can be located at the periphery of the working area 160 of the thin film bulk acoustic resonator 100 .

S210: Lay the bottom electrode material evenly on the base layer to form a first metal layer.

Since the first concave-convex structure 150 exists on the base layer 110 and the bottom electrode material is laid evenly, during the laying process, the first concave-convex structure 150 covering the base layer 110 can also be formed on the first metal layer. The first concave-convex structure 150. The laying of the bottom electrode material can be achieved through a metal evaporation or sputtering process; generally speaking, the first metal layer completely or substantially covers the surface of the base layer 110 .

S220: Pattern the first metal layer to obtain a bottom electrode, wherein the bottom electrode covers at least part of the reflective structure and the first concave-convex structure.

The patterning process of the first metal layer can be completed through a photolithography process and a dry etching process. After partially removing the first metal layer, a bottom electrode 120 is obtained. The bottom electrode 120 covers part of the base layer 110 and covers the first at least Partially reflective structure 114 and first concave-convex structure 150.

S310: Lay the piezoelectric material evenly on the base layer and the bottom electrode exposed by the bottom electrode to form a piezoelectric layer.

Since the first concave-convex structure 150 exists on both the base layer 110 and the bottom electrode 120, and the piezoelectric material is laid evenly, the first concave-convex structure 150 of the base layer 110 can be covered on the piezoelectric layer 130 during the laying process. The first concave-convex structure 150 is also formed at the position. The piezoelectric material can be laid by physical vapor deposition. The thickness of the piezoelectric layer 130 is generally determined by the resonant frequency required by the thin film bulk acoustic resonator 100 . Usually, the resonant frequency is inversely proportional to the thickness of the piezoelectric layer 130 .

S320: Lay the top electrode material evenly on the piezoelectric layer to form a second metal layer.

The laying of the top electrode material can be achieved through a metal evaporation or sputtering process; generally speaking, the second metal layer completely or substantially covers the surface of the piezoelectric layer 130 .

S330: Pattern the second metal layer to obtain a top electrode, where the top electrode covers at least part of the reflective structure and the bottom electrode.

The patterning process of the second metal layer can be completed through a photolithography process and a dry etching process. After partially removing the second metal layer, the top electrode 140 is obtained. If the first concave-convex structure 150 is a groove, preferably, the top electrode 140 also covers the first concave-convex structure 150 on the piezoelectric layer 130, so that the first concave-convex structure 150 is also formed at the corresponding position of the top electrode 140. If the first concave-convex structure 150 is a protrusion, the top electrode 140 may not cover the first concave-convex structure 150 on the piezoelectric layer 130 .

The preparation method of the above-mentioned thin film bulk acoustic resonator is by introducing the first concave and convex structure 150 in the base layer 110 to form a transverse high and low acoustic impedance structure to reflect the transversely leaked sound waves, and then by evenly laying the bottom electrode material, the piezoelectric material and the top electrode material. , thereby forming the first concave-convex structure 150 at least at the corresponding positions of the bottom electrode 120 and the piezoelectric layer 130, the process is simple, and the prepared thin film bulk acoustic resonator 100 can effectively reduce energy loss and have a high Q value, This can improve the steepness and insertion loss of the resonator, while also effectively suppressing spurious waves, resulting in a smoother frequency response.

Optionally, in an implementable manner of the embodiment of the present application, please refer to Figures 8 to 12, a base layer is provided, and a reflective structure and a first concave-convex structure are formed on the base layer, wherein the first concave-convex structure is located The outside of the reflective structure includes:

S111: Provide a base layer, and form a reflective structure and a groove on the base layer, where the groove is located outside the reflective structure.

Grooves can be obtained through standard photolithography processes, that is, coating photoresist, exposing using a mask, dry etching, and removing photoresist.

The first metal layer is patterned to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the first concave-convex structure and includes:

S221: Pattern the first metal layer to obtain a bottom electrode, where the bottom electrode at least covers the reflective structure and the groove.

The second metal layer is patterned to obtain a top electrode 140, wherein the top electrode 140 covers at least part of the reflective structure 114 and the bottom electrode 120 includes:

S331: Pattern the second metal layer to obtain a top electrode, where the top electrode covers at least part of the reflective structure, the bottom electrode and the groove.

In this embodiment, the first concave-convex structure 150 is a groove. By providing grooves on the base layer 110, positions corresponding to the grooves of the base layer 110 are formed on the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140. Grooves are formed everywhere.

Optionally, in an implementable manner of the embodiment of the present application, please refer to FIGS. 13 to 17 to provide a base layer 110 and form a reflective structure 114 and a first concave-convex structure 150 on the base layer 110 , wherein: A concave-convex structure 150 located outside the reflective structure 114 includes:

S112: Provide a base layer, and form a reflective structure and protrusions on the base layer, where the first concave-convex structure is located outside the reflective structure.

The first metal layer is patterned to obtain a bottom electrode 120, wherein the bottom electrode 120 at least covers the reflective structure 114 and the first concave-convex structure 150 and includes:

S222: Pattern the first metal layer to obtain a bottom electrode, where the bottom electrode at least covers the reflective structure and the protrusion.

In this embodiment, the first concave-convex structure 150 is a protrusion. By providing protrusions on the base layer 110, protrusions are formed on the bottom electrode 120 and the piezoelectric layer 130 at positions corresponding to the protrusions of the base layer 110. . The added protruding material may be a material that facilitates the growth of the bottom electrode 120 or the piezoelectric layer 130 , or some highly thermally conductive material to improve the reliability of the thin film bulk acoustic resonator 100 . The added bump material can be dielectric materials such as silicon dioxide and silicon nitride, or other metal materials such as molybdenum and aluminum. The width of the added bumps ranges from 0.5-20um, and the thickness ranges from 20nm-500nm. Since the protrusions on the piezoelectric layer 130 are located on the side surfaces of the top electrode 140, the top electrode 140 may not cover the grooves on the piezoelectric layer 130.

Optionally, in an implementable manner of the embodiment of the present application, please refer to Figures 18 to 20. The preparation method of the thin film bulk acoustic resonator includes:

S113: Provide a substrate layer and form a sacrificial layer within the substrate layer, where the upper surface of the sacrificial layer is flush with the upper surface of the substrate layer.

S114: Spread the seed material evenly on the substrate layer and the sacrificial layer to form a seed layer.

The seed layer 112 may be formed by one growth, or may be formed by two or more growths.

S115: Pattern the seed layer to form a first concave-convex structure on the seed layer, where the first concave-convex structure is located outside the reflective structure.

Please refer to Figures 8 to 11 in conjunction, S211: evenly lay the bottom electrode material on the seed layer to form a first metal layer.

S223: Pattern the first metal layer to obtain a bottom electrode, where the bottom electrode covers at least part of the sacrificial layer and the first concave-convex structure.

S310: Lay the piezoelectric material evenly on the base layer and the bottom electrode exposed by the bottom electrode to form a piezoelectric layer.

S320: Lay the top electrode material evenly on the piezoelectric layer to form a second metal layer.

S332: Pattern the second metal layer to obtain a top electrode, where the top electrode covers at least part of the sacrificial layer and the bottom electrode.

Please refer to Figure 1 in conjunction with S400: releasing the sacrificial layer to form a cavity.

In this embodiment, the sacrificial layer is the reflective structure 114, but the reflective structure 114 cannot directly reflect sound waves. After forming the bottom electrode 120, the piezoelectric layer 130 and the top electrode 140, the sacrificial layer needs to be released to its position. A cavity is formed where the cavity can reflect sound waves. The first concave-convex structure 150 is initially formed on the seed layer 112, and the first concave-convex structure 150 may be protrusions and/or grooves.

For example, the substrate layer 111 is a silicon wafer, and the thickness of the silicon wafer can be between a few hundred microns to thousands of microns. The surface of the substrate layer 111 is oxidized to grow a layer of silicon dioxide on the surface of the substrate layer 111 The thickness of the silicon dioxide layer can range from hundreds of nanometers to several microns. Through standard photolithography processes, that is, coating photoresist, using a mask to expose, dry etching, and removing the photoresist, the final product is obtained. A specifically shaped pattern of silicon dioxide (i.e. the sacrificial layer). Through the vapor hydrofluoric acid etching method (Vapor HF etching), hydrofluoric acid vapor is introduced into the sacrificial layer, and the hydrofluoric acid vapor chemically reacts with the silicon dioxide to remove the silicon dioxide to form a cavity.

Optionally, in an implementable manner of the embodiment of the present application, please refer to Figure 21, Figure 22 and Figure 14. The preparation method of the thin film bulk acoustic resonator includes:

S113: Provide a substrate layer, and form a sacrificial layer within the substrate layer, wherein the upper surface of the sacrificial layer is flush with the upper surface of the substrate layer.

S116: Pattern the substrate layer to form a first concave-convex structure on the substrate layer, where the first concave-convex structure is located outside the sacrificial layer.

S114: Spread the seed material evenly on the substrate layer and the sacrificial layer to form a seed layer.

In this embodiment, the first concave-convex structure 150 is initially formed on the substrate layer 111, and the first concave-convex structure 150 may be a protrusion and/or a groove.

Optionally, in an implementable manner of the embodiment of the present application, please refer to Figures 23 and 24, a base layer is provided, and a reflective structure and a first concave-convex structure are formed on the base layer, wherein the first concave-convex structure is located The outside of the reflective structure includes:

S117: Provide a base layer, and form a reflective structure, a first concave-convex structure and a second concave-convex structure on the base layer, wherein the first concave-convex structure is located outside the reflective structure, and the second concave-convex structure is located above the reflective structure.

In this embodiment, the concave-convex structure includes a first concave-convex structure 150 and a second concave-convex structure 170. The concave-convex structure is not only located in the non-working area 160 of the thin film bulk acoustic resonator 100, but also located in the working area 160 of the thin film bulk acoustic resonator 100.

The above descriptions are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included in the protection scope of this application.

Claims (10)

1. A thin film bulk acoustic resonator, characterized in that it includes: a base layer and a bottom electrode, a piezoelectric layer and a top electrode that are sequentially stacked on the base layer; the base layer is provided with an acoustic reflection structure, so The overlapping portion of the orthographic projection of the bottom electrode, the piezoelectric layer and the top electrode on the base layer and the overlapping area of the orthographic projection of the acoustic reflection structure on the base layer serve as the working area; The bottom electrode and the piezoelectric layer are respectively provided with first concave and convex structures. The first concave and convex structures are used to change the thickness of local areas on the bottom electrode and the piezoelectric layer. All the structures on the piezoelectric layer are The first concave-convex structure corresponds to the position of the first concave-convex structure on the bottom electrode, and the first concave-convex structure is arranged around the working area. 2. The thin film bulk acoustic resonator according to claim 1, wherein the base layer includes a substrate layer and a seed layer disposed on the substrate layer, and the bottom electrode is located on the seed layer; The first concave-convex structure is provided on the seed layer, and the first concave-convex structure on the seed layer corresponds to the position of the first concave-convex structure on the bottom electrode; or, the substrate layer and the The first concave-convex structure is respectively provided on the seed layer, the first concave-convex structure on the substrate layer, the first concave-convex structure on the seed layer and the first concave-convex structure on the bottom electrode. Structural position correspondence. 3. The thin film bulk acoustic resonator according to claim 1, wherein the first concave-convex structure is annular; or the first concave-convex structure includes a plurality of sub-protrusions or a plurality of sub-grooves, and the plurality of first concave-convex structures include a plurality of sub-protrusions or a plurality of sub-grooves. Sub-protrusions or multiple sub-grooves are spaced around the working area. 4. The thin film bulk acoustic resonator according to claim 3, wherein the first concave-convex structure includes at least two layers, and the at least two layers of the first concave-convex structure are arranged concentrically around the working area. 5. A method for preparing a thin film bulk acoustic resonator, which is characterized by comprising: providing a base layer and forming a reflective structure on the base layer; A patterned bottom electrode is formed on the base layer, and a first concave-convex structure is formed on the bottom electrode, wherein the bottom electrode covers at least part of the reflective structure, and the first concave-convex structure is formed on the base layer. An orthographic projection on the ground floor is located outside said reflective structure; A piezoelectric layer and a patterned top electrode are sequentially formed on the bottom electrode, and at least the first uneven structure is also formed on the piezoelectric layer at a position corresponding to the first uneven structure on the bottom electrode. , wherein the piezoelectric layer covers the base layer and the bottom electrode, and the top electrode covers at least part of the reflective structure and the bottom electrode. 6. The preparation method of the thin film bulk acoustic resonator according to claim 5, characterized in that it includes: Provide a base layer, and form a reflective structure and a first concave-convex structure on the base layer, wherein the first concave-convex structure is located outside the reflective structure; Evenly lay a bottom electrode material on the base layer to form a first metal layer; Patterning the first metal layer to obtain a bottom electrode, wherein the bottom electrode covers at least part of the reflective structure and the first concave-convex structure; Evenly lay piezoelectric material on the base layer and the bottom electrode exposed by the bottom electrode to form a piezoelectric layer; Evenly lay a top electrode material on the piezoelectric layer to form a second metal layer; The second metal layer is patterned to obtain a top electrode, wherein the top electrode covers at least part of the reflective structure and the bottom electrode. 7. The preparation method of the thin film bulk acoustic resonator according to claim 6, characterized in that it includes: providing a substrate layer and forming a sacrificial layer within the substrate layer, wherein an upper surface of the sacrificial layer is flush with an upper surface of the substrate layer; Evenly lay seed material on the substrate layer and the sacrificial layer to form a seed layer; Patterning the seed layer to form a first concave-convex structure on the seed layer, wherein the first concave-convex structure is located outside the reflective structure; Evenly lay a bottom electrode material on the seed layer to form a first metal layer; Patterning the first metal layer to obtain a bottom electrode, wherein the bottom electrode covers at least part of the sacrificial layer and the first concave-convex structure; Evenly lay piezoelectric material on the base layer and the bottom electrode exposed by the bottom electrode to form a piezoelectric layer; Evenly lay a top electrode material on the piezoelectric layer to form a second metal layer; Patterning the second metal layer to obtain a top electrode, wherein the top electrode covers at least part of the sacrificial layer and the bottom electrode; The sacrificial layer is released to form a cavity. 8. The method for preparing a thin film bulk acoustic resonator according to claim 6, wherein a base layer is provided, and a reflective structure and a first concave-convex structure are formed on the base layer, wherein the first The concave-convex structure located outside the reflective structure includes: providing a base layer, and forming a reflective structure and a groove on the base layer, wherein the groove is located outside the reflective structure; Patterning the first metal layer to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the first concave-convex structure includes: Patterning the first metal layer to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the groove; Patterning the second metal layer to obtain a top electrode, wherein the top electrode covers at least part of the reflective structure and the bottom electrode includes: The second metal layer is patterned to obtain a top electrode, wherein the top electrode covers at least part of the reflective structure, the bottom electrode and the groove. 9. The method for preparing a thin film bulk acoustic resonator according to claim 6, wherein a base layer is provided, and a reflective structure and a first concave-convex structure are formed on the base layer, wherein the first The concave-convex structure located outside the reflective structure includes: Provide a base layer, and form a reflective structure and protrusions on the base layer, wherein the first concave-convex structure is located outside the reflective structure; Patterning the first metal layer to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the first concave-convex structure includes: The first metal layer is patterned to obtain a bottom electrode, wherein the bottom electrode at least covers the reflective structure and the protrusion. 10. The method for preparing a thin film bulk acoustic resonator according to claim 6, wherein a base layer is provided, and a reflective structure and a first concave-convex structure are formed on the base layer, wherein the first The concave-convex structure located outside the reflective structure includes: A base layer is provided, and a reflective structure, a first concave-convex structure and a second concave-convex structure are formed on the base layer, wherein the first concave-convex structure is located outside the reflective structure, and the second concave-convex structure is located outside the reflective structure. above the reflective structure.