WO2023202548A9

WO2023202548A9 - Bulk acoustic wave resonator, method for preparing bulk acoustic wave resonator, and electronic device

Info

Publication number: WO2023202548A9
Application number: PCT/CN2023/088850
Authority: WO
Inventors: 焦卓凡
Original assignee: 京东方科技集团股份有限公司
Priority date: 2022-04-20
Filing date: 2023-04-18
Publication date: 2024-01-11
Also published as: WO2023202548A1; CN116961611A

Abstract

The present disclosure belongs to the technical field of bulk acoustic wave resonators. Provided are a bulk acoustic wave resonator, a method for preparing a bulk acoustic wave resonator, and an electronic device. The bulk acoustic wave resonator comprises a first substrate, a first electrode, a piezoelectric layer, a second electrode and a temperature compensation layer, wherein the first substrate is provided with a first groove; the second electrode, the piezoelectric layer and the first electrode are sequentially arranged along a side that faces away from the first substrate; an opening of the first groove faces the second electrode, and an orthographic projection of the first groove on the piezoelectric layer covers an orthographic projection of the second electrode on the piezoelectric layer; orthographic projections of the first electrode and the second electrode on the piezoelectric layer at least partially overlap; the temperature compensation layer is arranged on the side of the first electrode close to the first substrate, and is in contact with the piezoelectric layer; and the side of the first electrode that faces away from the first substrate is provided with at least one stepped structure, the stepped structure comprises a protruding structure and a second groove, which is arranged on the side of the protruding structure close to the central area of the first electrode, and the second groove and the protruding structure are both annular.

Description

Bulk acoustic wave resonator, preparation method of bulk acoustic wave resonator and electronic equipment

Cross-references to related applications

This application claims priority from Chinese Patent Application No. 2022104177556 filed on April 20, 2022, the content of which is hereby incorporated by reference into this application in its entirety.

Technical field

The present disclosure belongs to the technical field of bulk acoustic wave resonators, and specifically relates to a bulk acoustic wave resonator, a preparation method of a bulk acoustic wave resonator, and electronic equipment.

Background technique

The traditional Bulk Acoustic Wave (BAW) resonator is a three-layer composite structure composed of a first electrode, a piezoelectric layer and a second electrode. It has the advantages of small size and good performance.

On the one hand, when radio frequency signals are excited at both ends of the upper and lower electrodes of the BAW resonator, due to the inverse piezoelectric effect of the piezoelectric material of the piezoelectric layer, the electric field forms elastic waves in the thickness direction of the material, and at the same time some lateral vibrations (such as parasitic vibrations) ) will also be excited, affecting the performance of the BAW resonator. On the other hand, since most of the materials used to prepare BAW resonators are negative temperature coefficient materials (for example, the materials of the piezoelectric layer are aluminum nitride AlN, zinc oxide ZnO, etc., and the electrode materials are molybdenum Mo, aluminum Al, etc.), resulting in BAW resonance The resonant frequency of the device is prone to drift with changes in external temperature.

Contents of the invention

The present disclosure provides a bulk acoustic wave resonator, a preparation method of the bulk acoustic wave resonator, and electronic equipment.

In a first aspect, the bulk acoustic wave resonator provided by the present disclosure includes a first substrate, a first electrode, a piezoelectric layer, a second electrode and a temperature compensation layer; the first substrate has a first groove;

The second electrode, the piezoelectric layer and the first electrode are arranged in sequence along a side away from the first substrate; the groove direction of the first groove is toward the second electrode, and the The orthographic projection of the first groove on the piezoelectric layer covers the orthographic projection of the second electrode on the piezoelectric layer; the orthographic projection of the first electrode and the second electrode on the piezoelectric layer Orthographic projections overlap at least partially;

The temperature compensation layer is disposed on a side of the first electrode close to the first substrate, and the temperature compensation layer The degree compensation layer is in contact with the piezoelectric layer;

Wherein, the side of the first electrode facing away from the first substrate has at least one step structure; each step structure in the at least one step structure includes a protruding structure and is disposed close to the protruding structure. A second groove on one side of the central area of the first electrode; both the second groove and the protruding structure are annular.

In some embodiments, the first electrode includes a plurality of the ladder structures, and the plurality of ladder structures are nested.

In some embodiments, the plurality of ladder structures include a first ladder structure and a second ladder structure; the protruding structure of the first ladder structure is an annular edge portion of the first electrode, and the second ladder structure of the first ladder structure is an annular edge portion of the first electrode. The groove is located inside the convex structure of the first ladder structure; the convex structure of the second ladder structure is located inside the second groove of the first ladder structure, and the second groove of the second ladder structure is located inside the convex structure of the first ladder structure. The interior of the raised structure of the second stepped structure; and the raised structure of the first stepped structure is spaced from the second groove of the first stepped structure by a first step, the second groove of the first stepped structure A second step is spaced apart from the convex structure of the second step structure, and both the first step and the second step are annular.

In some embodiments, the convex structure of the first ladder structure and the convex structure of the second ladder structure have the same height in a direction perpendicular to the first substrate; The second groove and the second groove of the second stepped structure have the same height in a direction perpendicular to the first substrate; and/or the first step and the second step have the same height in a direction perpendicular to the first substrate. The heights of the first substrate in the direction are the same.

In some embodiments, orthographic projections of the outline of the second groove and the outline of the protruding structure on the first substrate are both regular polygons.

In some embodiments, the regular polygons include regular quadrilaterals, regular pentagons and regular hexagons.

In some embodiments, the ratio of the thickness of the protruding structure to the thickness of the first electrode is between 9/20 and 11/20; and/or,

The ratio of the thickness of the second groove to the thickness of the first electrode is between 1/5 and 3/10.

In some embodiments, the material of the piezoelectric layer includes single crystal aluminum nitride.

In some embodiments, the material of the temperature compensation layer is a material with a positive temperature coefficient.

In some embodiments, the positive temperature coefficient material includes silicon dioxide.

In some embodiments, the thickness of the temperature compensation layer meets at least one of the following conditions:

The ratio of the thickness of the temperature compensation layer to the thickness of the second electrode is between 19/20 and 21/20;

The ratio of the thickness of the temperature compensation layer to the thickness of the first electrode is between 9/20 and 11/20;

The ratio of the thickness of the temperature compensation layer to the thickness of the piezoelectric layer is between 1/20 and 3/20.

In some embodiments, the temperature compensation layer is disposed between the piezoelectric layer and the first electrode; or, the temperature compensation layer is disposed between the piezoelectric layer and the second electrode.

In some embodiments, an orthographic projection of the temperature compensation layer on the piezoelectric layer at least partially overlaps an orthographic projection of the first electrode and the second electrode on the piezoelectric layer.

In some embodiments, the piezoelectric layer includes an epitaxial growth layer and a seed layer sequentially disposed along a side of the second electrode facing away from the first substrate.

In some embodiments, a passivation layer disposed on a side of the first electrode facing away from the first substrate is further included.

In a second aspect, the present disclosure also provides a method for preparing a bulk acoustic wave resonator, including:

providing a first substrate having a first groove;

forming a piezoelectric layer on the second substrate;

forming a second electrode on a side of the piezoelectric layer facing away from the second substrate;

The second substrate on which the piezoelectric layer and the second electrode are formed is bonded to the first substrate; the groove direction of the first groove is toward the second electrode, and the The orthographic projection of the first groove on the piezoelectric layer covers the orthographic projection of the second electrode on the piezoelectric layer;

The second substrate is removed, and a first electrode is formed on a side of the piezoelectric layer facing away from the first substrate; forming the first electrode includes:

A first electrode material layer is formed, and a first electrode having at least one ladder structure is formed through a patterning process; wherein each of the at least one ladder structure includes a protrusion structure and a second Groove; forming the first electrode with at least one step structure through a patterning process includes: forming the protruding structure on the side of the first electrode facing away from the first substrate; forming the protruding structure close to the first substrate. The second groove is formed on one side of the center area of an electrode; both the second groove and the protruding structure are annular;

The preparation method also includes:

A temperature compensation layer is formed on a side of the first electrode close to the first substrate; the temperature compensation layer is in contact with the piezoelectric layer.

In some embodiments, forming the first electrode having at least one ladder structure through a patterning process includes forming the first electrode having a plurality of ladder structures through a patterning process, such that a plurality of the ladder structures are nested.

In some embodiments, forming the piezoelectric layer includes:

Using a metal organic chemical vapor deposition process, a first material layer is formed on the second substrate, and the first material layer serves as a seed layer;

Using a metal organic chemical vapor deposition process, a second material layer is formed on the side of the seed layer facing away from the second substrate, so that the second material layer grows epitaxially under the action of the first material layer to form The epitaxial growth layer to form the piezoelectric layer stacked by the seed layer and the epitaxial growth layer.

In some embodiments, the formed first material layer and the second material layer are made of single crystal aluminum nitride.

In some embodiments, the step of forming the temperature compensation layer includes any of the following methods:

The temperature compensation layer is formed between the piezoelectric layer and the first electrode; or,

The temperature compensation layer is formed between the piezoelectric layer and the second electrode.

In a third aspect, the present disclosure also provides an electronic device, including the bulk acoustic wave resonator as described in the first aspect.

Description of the drawings

1 and 2 are structural cross-sectional views of a bulk acoustic wave resonator provided by embodiments of the present disclosure;

3a and 3b are structural cross-sectional views of the bulk acoustic wave resonator provided by embodiments of the present disclosure;

4a to 4d are top views of the bulk acoustic wave resonator provided by embodiments of the present disclosure;

Figure 5 is a schematic diagram of a response simulation curve of the real part of the input impedance of the raised structure provided by the embodiment of the present disclosure as the frequency changes;

Figure 6 is a schematic diagram of a response simulation curve of the real part of the input impedance of the second groove as a function of frequency provided by an embodiment of the present disclosure;

Figure 7 is a side view of the specific structure of the piezoelectric layer provided by an embodiment of the present disclosure;

Figure 8 is a flow chart of a method for preparing a bulk acoustic wave resonator provided by an embodiment of the present disclosure;

9a to 9f are schematic diagrams of intermediate structures formed by each step in the preparation method of a bulk acoustic wave resonator provided by embodiments of the present disclosure.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present disclosure are clearly and completely described below in conjunction with the accompanying drawings and specific implementation modes. Obviously, the described embodiments are only some, but not all, of the embodiments of the present disclosure. The following detailed description of the embodiments of the disclosure provided in the appended drawings is not intended to limit the scope of the claimed disclosure, but rather represents only some embodiments of the disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without any creative efforts shall fall within the scope of protection of the present disclosure.

Unless otherwise defined, technical terms or scientific terms used in this disclosure shall have the usual meaning understood by a person with ordinary skill in the art to which this disclosure belongs. "First", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Likewise, similar words such as "a", "an" or "the" do not indicate a quantitative limitation but rather indicate the presence of at least one. Words such as "include" or "include" mean that the elements or things appearing before the word include the elements or things listed after the word and their equivalents, without excluding other elements or things. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", etc. are only used to express relative position relationships. When the absolute position of the described object changes, the relative position Relationships may change accordingly.

It should be noted that in this disclosure, the first direction X, the second direction Y, and the third direction Z intersect each other. In the present disclosure, the first direction X and the third direction X are perpendicular to each other on the plane where the first substrate is located, the first direction direction), and the third direction Z is a vertical direction, which is perpendicular to the plane where the first substrate is located, as an example for illustration. These do not limit the present disclosure.

The present disclosure will be described in more detail below with reference to the accompanying drawings. In the various drawings, identical elements are designated with similar reference numerals. For the sake of clarity, parts of the figures are not drawn to scale. Additionally, some well-known parts may not be shown in the figures.

1 and 2 show structural cross-sectional views of a bulk acoustic wave resonator provided by an embodiment of the present disclosure. The bulk acoustic wave resonator includes a first substrate 10, a first electrode 11, a piezoelectric layer 12, a second electrode 13 and Temperature compensation layer 14. Wherein, the first substrate 10 has a first groove 101 .

The second electrode 13, the piezoelectric layer 12 and the first electrode 11 are arranged in sequence along the side away from the first substrate 10, that is, the first electrode 11, the piezoelectric layer 12 and the second electrode 13 are located in different directions in the second direction Y. layer. The groove direction of the first groove 101 is toward the second electrode 13 , and the orthographic projection of the first groove 101 on the piezoelectric layer 12 covers the orthographic projection of the second electrode 13 on the piezoelectric layer 12 .

For example, the second electrode 13 is not in contact with the first substrate 10 , that is, the length of the second electrode 13 in the first direction X is smaller than the length of the first groove 101 in the first direction X.

Orthographic projections of the first electrode 11 and the second electrode 13 on the piezoelectric layer 12 at least partially overlap. For example, if the dimensions and lengths of the first electrode 11 and the second electrode 13 in the first direction X are the same, the orthographic projections of the first electrode 11 and the second electrode 13 on the piezoelectric layer 12 may be set to completely overlap.

The temperature compensation layer 14 is disposed on the side of the first electrode 11 close to the first substrate 10 , and the temperature compensation layer 14 is in contact with the piezoelectric layer 12 . Specifically, the temperature compensation layer 14 may be disposed between the piezoelectric layer 12 and the first electrode 11, as shown in FIG. 1 . Of course, the temperature compensation layer 14 can also be disposed between the piezoelectric layer 12 and the second electrode 13, as shown in FIG. 2 .

For example, the material of the first substrate 10 may include, but is not limited to, ceramics, glass materials, silicon, gallium arsenide, sapphire and other materials.

In the embodiment of the present disclosure, the material of the piezoelectric layer 12 may include single crystal piezoelectric material, such as single crystal aluminum nitride, and the piezoelectric layer 12 may be a single crystal aluminum nitride film. Among them, single crystal aluminum nitride films have better crystal quality and high voltage electrical properties than polycrystalline aluminum nitride films. Furthermore, BAW resonators composed of single crystal aluminum nitride films have better performance than polycrystalline aluminum nitride films. The BAW resonator composed of polycrystalline aluminum nitride film has lower loss and higher Q value, where the Q value is the quality factor of the BAW resonator; the higher the Q value, the more stable the resonant frequency of the BAW resonator is. The better the performance.

Since single crystal piezoelectric materials have a higher sound speed than polycrystalline piezoelectric materials, it can be seen from the formula f=v/(2t) that at the same resonant frequency, the thickness of single crystal piezoelectric materials is compared with that of polycrystalline piezoelectric materials. Large thickness. Where, f represents the resonant frequency, v represents the sound speed of the single crystal piezoelectric material, and t represents the thickness of the piezoelectric layer 12 . It is known that the crystal quality of the piezoelectric layer 12 decreases as the thickness decreases. Therefore, at the same resonant frequency, the single crystal piezoelectric material provided by the embodiments of the present disclosure has better crystal quality than the polycrystalline piezoelectric material. and piezoelectric properties. In addition, the thermal conductivity of the polycrystalline aluminum nitride film decreases as the thickness decreases, which limits the power processing capability of the BAW resonator. The single crystal aluminum nitride film provided by embodiments of the present disclosure has a better thermal conductivity.

In one embodiment, in order to suppress the parasitic vibration of the BAW resonator, the first electrode 11 adopts the first electrode 11 with a ladder structure 110, as shown in the structural cross-sectional view of the bulk acoustic wave resonator in Figure 3a and Figure 3b, specifically, The side of the first electrode 11 facing away from the first substrate 10 has at least one stepped structure 110; the stepped structure 110 may include a protruding structure 111 and a second recess disposed on the side of the protruding structure 111 close to the central region CR of the first electrode 11. The groove 112; the second groove 112 and the protruding structure 111 are all annular (see the structure shown in Figure 4a below).

Figure 3a takes the first electrode 11 as an example including a ladder structure 110. The outer boundary of the protrusion structure 111 in the ladder structure 110 in the second direction Y is the outer boundary of the first electrode 11 in the second direction Y. The second groove 112 is disposed on a side of the protruding structure 111 close to the central area of the first electrode 11, and the orthographic projection of the outline of the second groove 112 on the piezoelectric layer 12 is consistent with the outline of the protruding structure 111 on the piezoelectric layer. Orthographic projections on 12 do not overlap.

As shown in Figures 3a and 4a, Figure 3a is a cross-sectional view along line EE' of the BAW resonator shown in Figure 4a. The protruding structure 111 is an annular edge portion of the first electrode 11 , and the second groove 112 is formed inside the protruding structure 111 . Between the protruding structure 111 and the second groove 112 is the first step 113 of the first electrode 11 (It is a platform portion whose height in the second direction Y is between the convex surface of the protruding structure 111 and the bottom surface of the second groove 112). A second step 114 (a platform portion whose height in the second direction Y is between the convex surface of the protruding structure 111 and the bottom surface of the second groove 112) is provided inside the second groove 112, which is connected with the second step 114. The height of a step 113 in the second direction Y is the same. Therefore, the second groove 112 can be regarded as a concave structure formed inside the protruding structure 111 of the first electrode 11 and spaced apart from the protruding structure 111 . Both sides of the second groove 112 are first concave structures with the same height in the second direction Y. Platform 113 and second platform 114.

In some embodiments, as shown in Figure 4b, Figure 3b is a cross-sectional view along line EE' of the BAW resonator shown in Figure 4b. The first electrode 11 may include a plurality of ladder structures 110, and the plurality of ladder structures 110 are nested. For example, among the plurality of annular structures of the plurality of ladder structures 110 of the first electrode 11 , one ladder structure 110 of every two adjacent ladder structures 110 is placed inside another ladder structure 110 , that is, every two adjacent ladder structures 110 One of the ladder structures 110 surrounds the other ladder structure 110 .

Figure 4b shows two nested ladder structures 110. Specifically, the first ladder structure 110-1 is disposed on the side of the second ladder structure 110-2 away from the central area of the first electrode 11, and the second groove 112-1 in the first ladder structure 110-1 is disposed on the second The protruding structure 111-2 in the stepped structure 110-2 is away from the central area of the first electrode 11. The outline of the second groove 112-1 in the first stepped structure 110-1 does not overlap with the orthographic projection of the outline of the protruding structure 111 in the second stepped structure 110-2 on the piezoelectric layer 12. The embodiment of the present disclosure does not limit the separation distance between the second groove 112-1 and the protruding structure 111-2, and can be set according to actual conditions and experience.

As shown in Figures 3b and 4b, the protruding structure 111-1 of the first stepped structure 110-1 is an annular edge part of the first electrode 11, and the second groove 112-1 of the first stepped structure 110-1 is formed Inside the protruding structure 111-1 of the first stepped structure 110-1. Between the protruding structure 111-1 of the first stepped structure 110-1 and the second groove 112-1 is the first step 113-1 of the first electrode 11 (which is a platform portion, the height of which in the second direction Y between the convex surface of the convex structure 111-1 of the first stepped structure 110-1 and the bottom surface of the second groove 112-1); provided inside the second groove 112-1 of the first stepped structure 110-1 is the second step 114-1 (which is the platform portion, the height of which in the second direction Y is between the convex surface of the protruding structure 111-1 and the bottom surface of the second groove 112-1), which is different from the first step 113-1 has the same height in the second direction Y. Therefore, the second groove 112-1 can be regarded as a concave structure formed inside the protruding structure 111-1 of the first electrode 11 and spaced apart from the protruding structure 111-1, and its two sides are in the second direction Y. On the first platform 113-1 and the first platform with the same height Two platforms 114-1. Further, the first electrode 11 also includes a second ladder structure 110-2. The protruding structure 111-2 of the second ladder structure 110-2 is an annular protruding part of the first electrode 11, which is different from the first ladder structure 110. The second groove 112-1 of -1 is spaced apart from the second platform 114-1, and the second groove 112-2 of the second stepped structure 110-2 is formed on the protruding structure 111-2 of the second stepped structure 110-2. internal. Between the protruding structure 111-2 of the second stepped structure 110-2 and the second groove 112-2 is the first step 113-2 of the first electrode 11 (which is a platform portion, the height of which is in the second direction Y between the convex surface of the convex structure 111-2 of the second ladder structure 110-2 and the bottom surface of the second groove 112-2); provided inside the second groove 112-2 of the second ladder structure 110-2 is the second step 114-2 (which is the platform portion, the height of which in the second direction Y is between the convex surface of the protruding structure 111-2 and the bottom surface of the second groove 112-2), which is different from the first step 113-2 has the same height in the second direction Y. Therefore, the second groove 112-2 can be regarded as a concave structure formed inside the protruding structure 111-2 of the first electrode 11 and spaced apart from the protruding structure 111-2, and its two sides are in the second direction Y. on the first platform 113-2 and the second platform 114-22 with the same height.

Figure 3b takes the first electrode 11 including two ladder structures 110 as an example, showing the first ladder structure 110-1 and the second ladder structure 110-2; the first ladder structure 110-1 includes a protrusion structure 111-1 and a The second groove 112-1; the stepped structure 111-2 and the second groove 112-2.

The nesting between two or more ladder structures provided by the embodiment of the present disclosure can refer to the nested arrangement of two ladder structures 110 shown in Figure 4b, and the repeated parts will not be described again.

As shown in (a) to (d) in FIG. 5 , the widths of the protruding structures 111 (dimensions along the first direction X shown in FIGS. 3 a and 3 b ) are respectively 2 μm, 4 μm, 6 μm, and 8 μm. The frequency response simulation curve of the real part of the impedance, where the horizontal axis is the frequency (unit: MHz), and the vertical axis represents the gain of the real part of the input impedance. It can be seen from the response simulation curves of the real part of the input impedance of different widths of the protruding structure 111 as a function of frequency that when the width of the protruding structure 111 is set to 6 μm, the parasitic resonance peaks near the series and parallel resonant frequencies are smallest. As shown in (a) to (d) of FIG. 6 , the width of the second groove 112 (the size along the first direction X shown in FIG. 3a and FIG. 3b ) is 2 μm, 3 μm, 4 μm, and 5 μm respectively. The response simulation curve of the real part of the impedance changing with frequency, where the horizontal axis is the frequency (unit: MHz), and the vertical axis represents the gain of the real part of the input impedance. It can be seen from the response simulation curves of the real part of the input impedance of different widths of the second groove 112 as a function of frequency that when the width of the second groove 112 is set to 4 μm, the spurious resonance peaks near the series and parallel resonant frequencies are smallest. Based on the above simulation results, the present disclosure can set the order The width of the protruding structure 111 in the ladder structure 110 is between 5.5 μm and 6.5 μm, for example, 6 μm. The present disclosure may set the width of the second groove 112 in the stepped structure 110 to be between 3.5 μm and 4.5 μm, for example, 4 μm. This ladder structure 110 can effectively suppress the spurious vibration of the BAW resonator and improve the Q value of the BAW resonator.

As shown in Figures 3a and 3b, in the embodiment of the present disclosure, the width w1 of the protruding structure 111 can be between 5.5 μm and 6.5 μm, and the thickness h1 of the protruding structure 111 (along the lines shown in Figures 3a and 3b The size in the second direction Y is the size between the convex surface of the protruding structure 111 (the surface away from the first substrate direction) and the platform portion 113/114 in the direction perpendicular to the first substrate) and the first electrode 11 The thickness ratio may be between 9/20 and 11/20. For example, the thickness h1 of the protruding structure 111 may be half of the thickness of the first electrode 11. Specifically, the thickness of the first electrode 11 may be between 0.3 μm and 0.5 μm. During the period, the thickness of the protruding structure 111 may be between 0.15 μm and 0.25 μm. The width w2 of the second groove 112 may be between 3.5 μm and 4.5 μm. The thickness h2 of the second groove 112 (the size along the second direction Y shown in FIGS. 3a and 3b ) is the second groove. The ratio between the bottom surface of 112 and the platform portion 113/114 in the direction perpendicular to the first substrate) and the thickness of the first electrode 11 can be 1/5 to 3/10, for example, the thickness of the second groove 112 h2 may be one quarter of the thickness of the first electrode 11. Specifically, if the thickness of the first electrode 11 is between 0.3 μm and 0.5 μm, the thickness of the second groove 112 may be between 0.075 μm and 0.175 μm.

For example, the material of the first electrode 11 and the second electrode 13 may include, but are not limited to: platinum, aluminum, molybdenum and other materials.

When the BAW resonator receives elastic waves in the thickness direction of the material, it is often accompanied by some transverse waves. The transverse waves are continuously reflected in the first electrode 11 and produce transverse vibrations (that is, parasitic vibrations). Normally, an acute angle that is too small will cause the transverse wave to continuously reflect in the first electrode 11, and the incident and reflection paths are too short, causing the parasitic frequency of the BAW resonator to be too high, thereby affecting the performance of the BAW resonator. The embodiment of the present disclosure provides the first electrode 11 with a regular polygonal shape, which can avoid excessively small acute angles.

In the embodiment of the present disclosure, the orthographic projections of the outline of the second groove 112 and the outline of the protruding structure 111 on the first substrate 10 are both regular polygons. For example, regular polygons may include, but are not limited to: regular quadrilaterals, regular pentagons, regular hexagons, etc. In this case, the central region CR at least includes the center C of a regular polygon, such as the center of a regular quadrilateral (Fig. 4c), a regular pentagon (Fig. 4b), and a regular hexagon (Fig. 4d). For example, the central area CR is a circle with center C as the center and radius r, as shown in Figure 4a As shown in Figure 4d. Figure 3a is a cross-sectional view of the BAW resonator shown in Figure 4a along line EE'; Figure 3b is a cross-sectional view of the BAW resonator shown in Figures 4b to 4d along line EE', used to illustrate the first electrode 11 away from the surface morphology of the first substrate 10 .

In some embodiments, orthographic projections of the contours of the second groove 112 and the protruding structure 111 on the first substrate 10 may be irregular polygons, but the irregular polygons do not contain acute angles.

The material of the piezoelectric layer 12, the material of the first electrode 11 and the material of the second electrode 13 in the BAW resonator have negative temperature coefficients. When the external operating temperature changes, the operating frequency of the resonator is likely to change with the change of temperature. Therefore, in order to compensate for the frequency shift of the BAW resonator caused by temperature changes, the embodiment of the present disclosure provides a temperature compensation layer 14. The temperature compensation layer 14 is made of a material with a positive temperature coefficient and can compensate for a negative temperature coefficient. The frequency shift of the resonator caused by the temperature change of the material.

By way of example, positive temperature coefficient materials may include, but are not limited to, silicon dioxide.

The thickness of the temperature compensation layer 14 can meet at least one of the following conditions:

The ratio of the thickness of the temperature compensation layer 14 to the thickness of the second electrode 13 is between 19/20 and 21/20;

The ratio of the thickness of the temperature compensation layer 14 to the thickness of the first electrode 11 is between 9/20 and 11/20;

The ratio of the thickness of the temperature compensation layer 14 to the thickness of the piezoelectric layer 12 is between 1/20 and 3/20.

For example, the thickness of the temperature compensation layer 14 may be the same as the thickness of the second electrode 13; for example, the thickness of the temperature compensation layer 14 and the thickness of the second electrode 13 are both between 0.15 μm and 0.25 μm. The ratio of the thickness of the temperature compensation layer 14 to the thickness of the first electrode 11 can be 1/2; if the thickness of the first electrode 11 is between 0.3 μm and 0.5 μm, the thickness of the temperature compensation layer 14 can be set between 0.15 μm and 0.25 μm. between μm. The ratio of the thickness of the temperature compensation layer 14 to the thickness of the piezoelectric layer 12 may be 1/10; for example, if the thickness of the piezoelectric layer 12 is set between 1.5 μm and 2.5 μm, the thickness of the temperature compensation layer 14 may be set to Between 0.15μm～0.25μm.

In one embodiment, the orthographic projection of the temperature compensation layer 14 on the piezoelectric layer 12 at least partially overlaps with the orthographic projection of the first electrode 11 and the second electrode 13 on the piezoelectric layer 12 . For example, if the dimensions and lengths of the first electrode 11 and the second electrode 13 in the first direction It completely overlaps with the orthographic projection of the temperature compensation layer 14 on the piezoelectric layer 12 .

As shown in FIG. 7 , the piezoelectric layer 12 may include an epitaxial growth layer 121 . In order to provide favorable growth conditions for the epitaxial growth layer 121, the piezoelectric layer 12 may further include a seed layer 122. Specifically, the piezoelectric layer 12 includes an epitaxial growth layer 121 and a seed layer 122 sequentially arranged along the side of the second electrode 13 away from the first substrate 10 .

In order to protect the first electrode 11 in this embodiment of the present disclosure, the BAW resonator further includes a passivation layer 15 , and the passivation layer 15 is disposed on the side of the first electrode 11 away from the first substrate 10 , as shown in FIG. 9 f .

The material of the passivation layer 15 may be the same as the material of the piezoelectric layer 12 , for example, the material of the passivation layer 15 is single crystal aluminum nitride. The passivation layer 15 can protect the structure of the BAW resonator and prevent the internal structure of the BAW resonator from being affected by external conditions such as moisture, corrosion, contaminants, and debris.

Based on the same inventive concept, embodiments of the disclosure also provide a method for preparing a bulk acoustic wave resonator. The principle of the problem solved by the bulk acoustic wave resonator in the embodiment of the disclosure is the same as that of the embodiment of the bulk acoustic wave resonator mentioned above. The principles of the problems solved by the disclosed bulk acoustic wave resonators are similar. Therefore, for the specific structure of the bulk acoustic wave resonator in the preparation method of the bulk acoustic wave resonator, please refer to the specific structure of the BAW resonator in the above embodiment of the bulk acoustic wave resonator. The repetitive parts will not be repeated.

The specific preparation process flow of the bulk acoustic wave resonator provided by the embodiment of the present disclosure is as follows, as shown in steps S1 to S5 in Figure 8:

S1. As shown in FIG. 9a, the piezoelectric layer 12 is formed on the second substrate 16.

Here, the thickness of the second substrate 16 may be between 10 μm and 600 μm.

Specifically, a metal organic chemical vapor deposition process may be used to form a piezoelectric layer 12 on the second substrate 16 . The thickness of the piezoelectric layer 12 may be between 1.5 μm and 2.5 μm.

In the case where the piezoelectric layer 12 includes the seed layer 122 and the epitaxial growth layer 121, the step S1 of forming the piezoelectric layer 12 specifically includes S1-1 and S1-2:

S1-1. Use a metal organic chemical vapor deposition process to form a first material layer on the second substrate 16, and the first material layer serves as the seed layer 122.

Here, the thickness of the seed layer 122 may be between 0.5 μm and 1 μm;

S1-2. Use a metal organic chemical vapor deposition process to form a second material layer on the side of the seed layer 122 facing away from the second substrate 16. The second material layer grows epitaxially under the action of the first material layer to form an epitaxial layer. The layer 121 is grown to form the piezoelectric layer 12 which is stacked by the seed layer 122 and the epitaxial growth layer 121 .

The first material layer serving as the seed layer 122 can promote the second material layer to have a good crystal orientation during epitaxial growth. The material of the formed first material layer and the material of the second material layer may be single crystal aluminum nitride.

Here, the thickness of the formed epitaxial growth layer 121 may be between 1 μm and 1.5 μm.

S2. As shown in FIG. 9b, the second electrode 13 is formed on the side of the piezoelectric layer 12 facing away from the second substrate 16.

Here, the thickness of the second electrode 13 may be between 0.15 μm and 0.25 μm.

Specifically, a magnetron sputtering process is used to form the second electrode 13 on the side of the piezoelectric layer 12 facing away from the second substrate 16 .

S3. As shown in Figure 9c, bond the second substrate 16 on which the piezoelectric layer 12 and the second electrode 13 are formed to the first substrate 10. The first substrate 10 has a first groove 101. The groove direction of the groove 101 is toward the second electrode 13 , and the orthographic projection of the first groove 101 on the piezoelectric layer 12 covers the orthographic projection of the second electrode 13 on the piezoelectric layer 12 .

The first substrate 10 has a first groove 101. After the second substrate 16 on which the piezoelectric layer 12 and the second electrode 13 are formed is bonded to the first substrate 10, an air gap is formed. The air gap is used for Confines sound waves within the BAW resonator.

For example, the thickness of the first substrate 10 may be between 400 μm and 600 μm. The thickness of the first groove 101 may be between 1/3 and 1/2 of the thickness of the first substrate 10 .

S4. Remove the second substrate 16, and form the first electrode 11 on the side of the piezoelectric layer 12 facing away from the first substrate 10.

As shown in Figure 9d, the second substrate 16 is removed. The specific preparation process is as follows: first, flip the BAW resonator structure shown in Figure 9c; then, use a mechanical grinding process to thin the second substrate 16 to 1/3 to 1/2 of the second substrate 16, and then the remaining second substrate 16 is removed through a patterning process.

As shown in Figure 9e, forming the first electrode 11 may specifically include the following steps S4-1 to S4-2:

S4-1. Use a magnetron sputtering process to form the first electrode 11 material layer on the side of the piezoelectric layer 12 facing away from the first substrate 10.

Here, the thickness of the material layer of the first electrode 11 may be between 0.3 μm and 0.5 μm.

S4-2. Form the first electrode 11 with at least one ladder structure 110 through a patterning process, where the ladder structure 110 includes a protruding structure 111 and a second groove 112; on the side of the first electrode 11 facing away from the first substrate 10 A protruding structure 111 is formed; a second groove 112 is formed on the side of the protruding structure 111 close to the central area of the first electrode 11; both the second groove 112 and the protruding structure 111 are annular.

The thickness of the protruding structure 111 may be half of the thickness of the first electrode 11 ; the thickness of the second groove 112 may be one-quarter of the thickness of the first electrode 11 .

For example, photoresist coating, exposure, development, etching, and photoresist stripping are sequentially performed on the material layer of the first electrode 11 to form the first electrode 11 with at least one ladder structure 110 . The width of the protruding structure 111 may be between 5.5 μm and 6.5 μm, and the thickness may be between 0.15 μm and 0.25 μm; and/or the width of the second groove 112 may be between 3.5 μm and 4.5 μm, and the thickness may be between 3.5 μm and 4.5 μm. Between 0.075μm～0.175μm.

In some embodiments, the formed first electrode 11 may include multiple ladder-like structures, and the multiple ladder-like structures are nested. The specific nested structures can be seen in Figures 4b to 4d, and Figures 4b to 4d. The corresponding explanation content will not be repeated again.

In some embodiments, a temperature compensation layer 14 may be formed on a side of the first electrode 11 close to the first substrate 10; the temperature compensation layer 14 is in contact with the piezoelectric layer 12.

The temperature compensation layer 14 can have a variety of different preparation methods. For S4, in addition to the preparation methods of S4-1 to S4-2, the temperature compensation layer 14 can also be formed between the piezoelectric layer 12 and the first electrode 11. As shown in Figure 1.

Alternatively, in addition to the preparation method of S3, a temperature compensation layer 14 may also be formed between the piezoelectric layer 12 and the second electrode 13, as shown in FIG. 2 .

Here, the thickness of the temperature compensation layer 14 may be between 0.15 μm and 0.25 μm.

S5. As shown in FIG. 9f, based on the structure shown in FIG. 3, a passivation layer 15 is formed on the side of the first electrode 11 away from the first substrate 10.

Based on the same inventive concept, embodiments of the present disclosure also provide an electronic device, which can It includes a bulk acoustic wave resonator disclosed in the above embodiments of the present disclosure, wherein the principle of the problem solved by the bulk acoustic wave resonator in electronic equipment is the same as the bulk acoustic wave resonator disclosed in the above embodiments of the present disclosure. The principles of the problems solved by the acoustic wave resonator are similar. Therefore, for the specific structure of the bulk acoustic wave resonator in the electronic device according to the embodiment of the present disclosure, please refer to the specific structure of the BAW resonator in the above embodiment of the bulk acoustic wave resonator. The repeated details will not be repeated. .

It can be understood that the above embodiments are only exemplary embodiments adopted to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the disclosure, and these modifications and improvements are also regarded as the protection scope of the disclosure.

Claims

A bulk acoustic wave resonator includes a first substrate, a first electrode, a piezoelectric layer, a second electrode and a temperature compensation layer; the first substrate has a first groove;

The second electrode, the piezoelectric layer and the first electrode are arranged in sequence along a side away from the first substrate; the groove direction of the first groove is toward the second electrode, and the The orthographic projection of the first groove on the piezoelectric layer covers the orthographic projection of the second electrode on the piezoelectric layer; the orthographic projection of the first electrode and the second electrode on the piezoelectric layer Orthographic projections overlap at least partially;

The temperature compensation layer is disposed on a side of the first electrode close to the first substrate, and the temperature compensation layer is in contact with the piezoelectric layer;

Wherein, the side of the first electrode facing away from the first substrate has at least one step structure; each step structure in the at least one step structure includes a protruding structure and is disposed close to the protruding structure. A second groove on one side of the central area of the first electrode; both the second groove and the protruding structure are annular.
The bulk acoustic wave resonator according to claim 1, wherein the first electrode includes a plurality of step structures, and a plurality of the step structures are nested.
The bulk acoustic wave resonator according to claim 2, wherein

The plurality of ladder structures include a first ladder structure and a second ladder structure;

The protruding structure of the first stepped structure is the annular edge portion of the first electrode, and the second groove of the first stepped structure is located inside the protruding structure of the first stepped structure;

The raised structure of the second stepped structure is located inside the second groove of the first stepped structure, and the second groove of the second stepped structure is located inside the raised structure of the second stepped structure; and

The raised structure of the first stepped structure is spaced apart from the second groove of the first stepped structure by a first step, and the second groove of the first stepped structure is spaced apart from the raised structure of the second stepped structure. The second step, the first step and the second step are all in the shape of a ring.
The bulk acoustic wave resonator according to claim 3, wherein

The protruding structure of the first stepped structure and the protruding structure of the second stepped structure have the same height in a direction perpendicular to the first substrate;

The second groove of the first stepped structure and the second groove of the second stepped structure have the same height in a direction perpendicular to the first substrate; and/or

The first step and the second step have the same height in a direction perpendicular to the first substrate.
The bulk acoustic wave resonator according to any one of claims 1 to 4, wherein the orthographic projections of the outline of the second groove and the outline of the protruding structure on the first substrate are both regular. polygon.
The bulk acoustic wave resonator according to claim 5, wherein the regular polygon includes a regular quadrilateral, a regular pentagon, and a regular hexagon.
The bulk acoustic wave resonator according to any one of claims 1 to 6, wherein the thickness of the protruding structure in a direction perpendicular to the first substrate is the same as the thickness of the first electrode in a direction perpendicular to the first substrate. The ratio of the thickness in the direction of the first substrate is between 9/20 and 11/20; and/or,

The ratio of the thickness of the second groove in a direction perpendicular to the first substrate to the thickness of the first electrode is between 1/5 and 3/10.
The bulk acoustic wave resonator according to any one of claims 1 to 6, wherein the material of the piezoelectric layer includes single crystal aluminum nitride.
The bulk acoustic wave resonator according to any one of claims 1 to 6, wherein the material of the temperature compensation layer is a material with a positive temperature coefficient.
The bulk acoustic wave resonator according to claim 1, wherein a thickness of the temperature compensation layer in a direction perpendicular to the first substrate satisfies at least one of the following conditions:

The ratio of the thickness of the temperature compensation layer to the thickness of the second electrode in a direction perpendicular to the first substrate is between 19/20 and 21/20;

The ratio of the thickness of the temperature compensation layer to the thickness of the first electrode in a direction perpendicular to the first substrate is between 9/20 and 11/20;

The ratio of the thickness of the temperature compensation layer to the thickness of the piezoelectric layer in a direction perpendicular to the first substrate is between 1/20 and 3/20.
The bulk acoustic wave resonator according to any one of claims 1-0, wherein the temperature compensation layer is provided between the piezoelectric layer and the first electrode; or,

The temperature compensation layer is disposed between the piezoelectric layer and the second electrode.
The bulk acoustic wave resonator according to claim 11, wherein the orthogonal projection of the temperature compensation layer on the piezoelectric layer is the same as the orthogonal projection of the first electrode and the second electrode on the piezoelectric layer. The projections overlap at least partially.
The bulk acoustic wave resonator according to claim 1, wherein the piezoelectric layer includes an epitaxial growth layer and a seed layer sequentially arranged along a side of the second electrode facing away from the first substrate.
The bulk acoustic wave resonator according to claim 1, further comprising a passivation layer disposed on a side of the first electrode facing away from the first substrate.
A method for preparing a bulk acoustic wave resonator, including:

providing a first substrate having a first groove;

forming a piezoelectric layer on the second substrate;

forming a second electrode on a side of the piezoelectric layer facing away from the second substrate;

The second substrate on which the piezoelectric layer and the second electrode are formed is bonded to the first substrate; the groove direction of the first groove is toward the second electrode, and the The orthographic projection of the first groove on the piezoelectric layer covers the orthographic projection of the second electrode on the piezoelectric layer;

The second substrate is removed, and a first electrode is formed on a side of the piezoelectric layer facing away from the first substrate; forming the first electrode includes:

Form a first electrode material layer, and form a first electrode having at least one ladder structure through a patterning process; wherein each of the at least one ladder structure includes a protruding structure and a second groove; formed through a patterning process The first electrode having at least one step structure includes: forming the protruding structure on the side of the first electrode facing away from the first substrate; forming the protruding structure on the side close to the central region of the first electrode. The second groove; both the second groove and the protruding structure are annular;

The preparation method also includes:

A temperature compensation layer is formed on a side of the first electrode close to the first substrate, so that the temperature compensation layer is in contact with the piezoelectric layer.
The method for preparing a bulk acoustic wave resonator according to claim 15, wherein the patterning process The process of forming the first electrode with at least one ladder structure includes forming the first electrode with a plurality of ladder structures through a patterning process, so that a plurality of the ladder structures are nested.
The method of manufacturing a bulk acoustic wave resonator according to claim 16, wherein the step of forming the piezoelectric layer includes:

Using a metal-organic chemical vapor deposition process, a first material layer is formed as a seed layer on the second substrate; and

Using a metal organic chemical vapor deposition process, a second material layer is formed on the side of the seed layer facing away from the second substrate, so that the second material layer grows epitaxially under the action of the first material layer to form The epitaxial growth layer to form the piezoelectric layer stacked by the seed layer and the epitaxial growth layer.
The method of manufacturing a bulk acoustic wave resonator according to claim 17, wherein the formed first material layer and the second material layer are made of single crystal aluminum nitride.
The method for manufacturing a bulk acoustic wave resonator according to any one of claims 15 to 18, wherein the step of forming the temperature compensation layer includes any of the following methods:

The temperature compensation layer is formed between the piezoelectric layer and the first electrode; or,

The temperature compensation layer is formed between the piezoelectric layer and the second electrode.
An electronic device including the bulk acoustic wave resonator according to claims 1 to 14.