Cavity type bulk acoustic wave resonator with Bragg reflection layer and preparation method of cavity type bulk acoustic wave resonator

Abstract

The invention provides a cavity type bulk acoustic wave resonator with a Bragg reflection layer and a preparation method of the cavity type bulk acoustic wave resonator, and relates to the technical field of bulk acoustic wave resonator manufacturing. The cavity type bulk acoustic wave resonator comprises a first substrate, a bottom electrode, a piezoelectric layer and a top electrode which are stacked in sequence, a cavity is formed between the first substrate and the bottom electrode, the cavity is provided with a plurality of supporting columns, the supporting columns are used for supporting the first substrate and the bottom electrode, each supporting column comprises at least one group of Bragg reflection layers, and the Bragg reflection layers are arranged in the cavity. The Bragg reflection layer is formed by stacking a first material and a second material, and the acoustic impedance of the first material is higher than that of the second material. The cavity type bulk acoustic wave resonator solves the problem that an existing supporting column increases energy loss, and it is guaranteed that the resonator has more stable performance while the electromechanical coupling coefficient is increased.

Description

Technical Field

[0001] The invention relates to the technical field of bulk acoustic wave resonator manufacturing, and in particular to a cavity type bulk acoustic wave resonator with a Bragg reflection layer and a preparation method thereof. Background Art

[0002] As the research on cavity-type bulk acoustic wave resonators becomes more and more in-depth, researchers have found that the stress on the piezoelectric layer will cause the electromechanical coupling coefficient of the resonator to decrease. Due to the existence of the cavity, the active area is affected by gravity and inevitably causes the piezoelectric layer to be subjected to stress. Therefore, the existing technology proposes to set support columns in the cavity to reduce stress. However, after the support columns are set, the problem of increased energy loss due to sound wave leakage occurs, which causes the stability of the resonator to decrease and the performance of the resonator to be greatly reduced.

[0003] There is currently no effective technical solution to the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a cavity-type bulk acoustic wave resonator with a Bragg reflection layer and a preparation method thereof, which solves the problem of increased energy loss of existing support columns, thereby improving the electromechanical coupling coefficient while ensuring that the resonator has more stable performance.

[0005] In a first aspect, the present invention provides a cavity-type bulk acoustic wave resonator with a Bragg reflection layer, comprising a first substrate, a bottom electrode, a piezoelectric layer and a top electrode stacked in sequence, a cavity is arranged between the first substrate and the bottom electrode, the cavity is provided with a plurality of support columns, the support columns are used to support the first substrate and the bottom electrode, and each of the support columns comprises at least one group of Bragg reflection layers, the Bragg reflection layers are formed by stacking a first material and a second material, and the acoustic impedance of the first material is higher than the acoustic impedance of the second material.

[0006] The cavity-type bulk acoustic wave resonator with a Bragg reflection layer provided by the present invention constructs a support column with the Bragg reflection layer, which not only reduces the stress of the piezoelectric layer, but also avoids the leakage of sound waves, thereby improving the electromechanical coupling coefficient while reducing energy loss, and helping to obtain a more stable and higher performance resonator.

[0007] Furthermore, each of the support columns includes a plurality of groups of the Bragg reflection layers, all of the Bragg reflection layers are stacked, and all of the first materials and the second materials are alternately stacked.

[0008] Furthermore, the first material is made of W and / or Ta; the second material is made of SiO 2 Made of material.

[0009] Furthermore, the thickness of the first material and the second material are both equal to one quarter of the wavelength of the working resonant frequency.

[0010] Furthermore, the height of the support column is 1-4 μm.

[0011] Furthermore, the first substrate is made of any one of sapphire, glass, Si, and SiC.

[0012] Furthermore, the piezoelectric layer is made of AlN, Al x Ga 1-x N, Sc x Al 1-x N、Al x Si 1-x Made of any one of N materials.

[0013] Furthermore, the bottom electrode and the top electrode are both made of any one or more materials selected from the group consisting of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf.

[0014] Furthermore, it also includes a frequency adjustment layer stacked above the top electrode, and the frequency adjustment layer is used to adjust the resonant frequency.

[0015] In a second aspect, the present invention provides a method for preparing the cavity-type bulk acoustic wave resonator with a Bragg reflection layer as described above, comprising the following steps: S1. After cleaning and drying the second substrate, a sacrificial layer is formed on the second substrate; S2. Sequentially fabricating the piezoelectric layer, the bottom electrode and the support column on the sacrificial layer; S3. bonding the first substrate to all the support pillars; S4. removing the second substrate by releasing the sacrificial layer and exposing the side of the piezoelectric layer facing away from the bottom electrode; S5. Fabricate the top electrode on the side of the piezoelectric layer facing away from the bottom electrode.

[0016] As can be seen from the above, the cavity-type bulk acoustic wave resonator with a Bragg reflection layer provided by the present invention uses the first material and the second material stacked alternately to form a Bragg reflection layer and uses the Bragg reflection layer as a basis to make a support column. The stress of the piezoelectric layer is reduced by the support column while the sound waves are confined within the piezoelectric layer by relying on the Bragg reflection layer, thereby avoiding sound wave leakage, achieving the effect of reducing energy loss, and being beneficial to improving the stability of the resonator and ensuring the performance of the resonator.

[0017] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by implementing the embodiments of the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A partial preparation process of a cavity-type bulk acoustic wave resonator with a Bragg reflection layer provided in an embodiment of the present invention.

[0019] Figure 2 A flow chart of a preparation method provided in an embodiment of the present invention.

[0020] Description of labels: 100, first substrate; 200, bottom electrode; 300, piezoelectric layer; 400, top electrode; 500, cavity; 600, support column; 610, Bragg reflection layer; 611, first material; 612, second material; 700, frequency correction layer; 800, sacrificial layer; 900, second substrate. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0025] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0027] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0028] Reference Figure 1 The present invention provides a cavity-type bulk acoustic wave resonator with a Bragg reflection layer, comprising a first substrate 100, a bottom electrode 200, a piezoelectric layer 300 and a top electrode 400 stacked in sequence, a cavity 500 is arranged between the first substrate 100 and the bottom electrode 200, the cavity 500 is provided with a plurality of support columns 600, the support columns 600 are used to support the first substrate 100 and the bottom electrode 200, and each support column 600 includes at least one group of Bragg reflection layers 610, the Bragg reflection layers 610 are formed by stacking a first material 611 and a second material 612, and the acoustic impedance of the first material is higher than the acoustic impedance of the second material.

[0029] In this embodiment, the cavity 500 is constructed by support columns 600, and a plurality of support columns 600 simultaneously support the first substrate 100 and the bottom electrode 200, thereby helping the piezoelectric layer 300 resist gravity in the active area to achieve the purpose of reducing stress. At the same time, the support columns 600 are constructed by the Bragg reflection layer 610. In actual application, due to the difference in acoustic impedance of different material layers in the Bragg reflection layer 610, when the sound wave contacts it, it will be reflected or refracted, thereby forming a standing wave, so that the leakage of the sound wave can be avoided, and the energy loss is effectively reduced, so as to improve the electromechanical coupling coefficient while ensuring that the resonator has a more stable performance.

[0030] In certain embodiments, referring to Figure 2 Each support column 600 includes a plurality of groups of Bragg reflection layers 610 , all the Bragg reflection layers 610 are stacked, and all the first materials 611 and the second materials 612 are alternately stacked.

[0031] In this embodiment, the height of the cavity 500 is adjusted by stacking multiple groups of Bragg reflection layers 610 , and while ensuring that all first materials 611 and second materials 612 are alternately stacked, the difference in acoustic impedance of different material layers is effectively utilized to prevent acoustic wave leakage.

[0032] In some embodiments, the first material 611 is made of W and / or Ta; the second material 612 is made of SiO 2 Made of material.

[0033] In this embodiment, the second material 612 is silicon dioxide, which can also reduce the temperature drift value, which is beneficial to further improve the stability of the resonator.

[0034] In some embodiments, the thickness of the first material 611 and the second material 612 are both equal to one quarter wavelength of the operating resonant frequency.

[0035] In this embodiment, by controlling the thickness of the first material 611 and the second material 612 , it is possible to suppress the parasitic vibration of the support column 600 , thereby ensuring that the resonator has a more stable performance.

[0036] In some embodiments, the height of the support pillars 600 is 1-4 μm.

[0037] In some embodiments, the first substrate 100 is made of any one of sapphire, glass, Si, and SiC.

[0038] In some embodiments, the piezoelectric layer 300 is made of AlN, Al x Ga 1-x N, Sc x Al 1-x N、Al x Si 1-x N. The thickness of the piezoelectric layer 300 may be 0.1-2 μm.

[0039] In some embodiments, the bottom electrode 200 and the top electrode 400 are made of any one or more materials selected from Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, wherein the thickness of the bottom electrode 200 and the top electrode 400 may be 0.05-0.5 μm.

[0040] In some embodiments, the cavity type BAW resonator with a Bragg reflection layer further includes a frequency trimming layer 700 stacked on the top electrode 400. The frequency trimming layer 700 is used to adjust the resonance frequency. The frequency trimming layer 700 is made of AlN material and may be 50-200 nm thick.

[0041] Reference Figure 2 The present invention provides a method for preparing a cavity-type bulk acoustic wave resonator with a Bragg reflection layer in the above embodiment, comprising the following steps: S1. After the second substrate is cleaned and dried, a sacrificial layer is formed on the second substrate; S2. Sequentially forming a piezoelectric layer, a bottom electrode and a support column on the sacrificial layer; S3. Bonding the first substrate to all support pillars; S4. removing the second substrate by releasing the sacrificial layer and exposing the side of the piezoelectric layer facing away from the bottom electrode; S5. Fabricate a top electrode on the side of the piezoelectric layer facing away from the bottom electrode.

[0042] Specifically, for example, the thickness of the bottom electrode 200 and the top electrode 400 are both 500 nm, the thickness of the piezoelectric layer 300 is 2 μm, and the SiO 2 The thickness of the single-layer second material 612 is 540 nm, the thickness of the single-layer first material 611 is 480 nm, and the support column 600 is composed of three layers of alternately grown second material 612 and first material 611, and the total height thereof is 3020 nm.

[0043] Furthermore, the method further includes the step: S6. manufacturing a frequency correction layer 700 on the top electrode.

[0044] In the above embodiment, the second substrate 900 can be cleaned and dried using acetone and hydrofluoric acid; the sacrificial layer 800 is made of AlGaN, NaCl, BaF 2 The piezoelectric layer 300 and the frequency correction layer 700 can be grown by any of PLD, PVD, and MOCVD; the top electrode 400, the bottom electrode 200 and the first material 611 can be grown by PVD; the second material 612 can be grown by any of CVD and MOCVD.

[0045] In addition, the bonding method may be metal bonding, such as Si-Au bonding, Sn-Au bonding or Sn-Si bonding.

[0046] In addition, the sacrificial layer 800 may be released by chemical etching or laser etching.

[0047] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0048] Descriptions with reference to the terms "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" are intended to mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0049] The above description is only an embodiment of the present invention and is not intended to limit the protection scope of the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A cavity-type bulk acoustic wave resonator with a Bragg reflection layer, comprising a first substrate (100), a bottom electrode (200), a piezoelectric layer (300) and a top electrode (400) stacked in sequence, wherein a cavity (500) is provided between the first substrate (100) and the bottom electrode (200), characterized in that: The cavity (500) is provided with a plurality of support columns (600), the support columns (600) being used to support the first substrate (100) and the bottom electrode (200), and each of the support columns (600) comprises at least one group of Bragg reflection layers (610), the Bragg reflection layers (610) being formed by stacking a first material (611) and a second material (612), and the acoustic impedance of the first material is higher than the acoustic impedance of the second material.

2. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: Each of the support columns (600) comprises a plurality of groups of the Bragg reflection layers (610), all of the Bragg reflection layers (610) are stacked, and all of the first materials (611) and the second materials (612) are alternately stacked.

3. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: The first material (611) is made of W and / or Ta material; the second material (612) is made of SiO2 material.

4. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: The thickness of the first material (611) and the second material (612) are both equal to a quarter wavelength of the working resonant frequency.

5. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: The support column (600) has a height of 1-4 μm.

6. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: The first substrate (100) is made of any one of sapphire, glass, Si and SiC.

7. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: The piezoelectric layer (300) is made of AlN, Al x Ga 1-x N, Sc x Al 1-x N、Al x Si 1-x Made of any one of N materials.

8. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: The bottom electrode (200) and the top electrode (400) are both made of any one or more materials selected from the group consisting of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf.

9. The cavity-type bulk acoustic wave resonator with a Bragg reflection layer according to claim 1, characterized in that: It also includes a frequency adjustment layer (700) stacked above the top electrode (400), wherein the frequency adjustment layer (700) is used to adjust the resonance frequency.

10. A method for preparing a cavity-type bulk acoustic wave resonator having a Bragg reflection layer as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: S1. After cleaning and drying the second substrate, a sacrificial layer is formed on the second substrate; S2. Sequentially fabricating the piezoelectric layer, the bottom electrode and the support column on the sacrificial layer; S3. bonding the first substrate to all the support pillars; S4. removing the second substrate by releasing the sacrificial layer and exposing the side of the piezoelectric layer facing away from the bottom electrode; S5. Fabricate the top electrode on the side of the piezoelectric layer facing away from the bottom electrode.

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