Double-frequency bulk acoustic wave filter structure

Abstract

The invention provides a double-frequency bulk acoustic wave filter structure, which comprises a substrate, a bottom electrode, a piezoelectric layer and a top electrode, and is characterized in that the bottom electrode is located above the substrate and comprises a first bottom electrode and a second bottom electrode which are spaced by a preset distance in the horizontal direction; the piezoelectric layer is located above the bottom electrode, the piezoelectric layer comprises piezoelectric film layers which are stacked from bottom to top, in the horizontal direction, the piezoelectric layer is divided into a first area and a second area, in the first area, the polarities of the adjacent piezoelectric film layers are the same, and in the second area, the polarities of the adjacent piezoelectric film layers are opposite; the top electrode is located above the piezoelectric layer and comprises a first top electrode and a second top electrode which are spaced by a preset distance in the horizontal direction. The piezoelectric layer is divided into two regions, the polarities of the adjacent piezoelectric film layers in the first region are the same, and the polarities of the adjacent piezoelectric film layers in the second region are opposite, so that the bulk acoustic wave filter has two frequencies and can meet the application requirements of different frequency bands.

Description

Technical Field

[0001] This invention belongs to the field of microelectronics and relates to a dual-frequency bulk acoustic wave filter structure. Background Technology

[0002] Currently, wireless data transmission requires radio frequency (RF) filters with operating frequencies of 5 GHz or higher. The filters used in 5G communication are mainly bulk acoustic wave (BAW) filters and surface acoustic wave (SAW) filters. BAW devices have extremely high Q values ​​(above 4000), operate in frequency bands from 100 MHz to 20 GHz, and offer advantages such as high operating frequency, low insertion loss, high frequency selectivity, high power capacity, and strong electrostatic discharge (ESD) immunity, making them the best solution for future RF front-ends.

[0003] Existing bulk acoustic wave filters operate at a single frequency, which can only meet the application requirements of a certain frequency band and has significant limitations. Therefore, how to provide a dual-frequency bulk acoustic wave filter structure that has two operating frequencies has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a dual-frequency bulk acoustic wave filter structure to solve the problem of the single operating frequency of filters in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides a dual-frequency bulk acoustic wave filter structure, comprising:

[0006] Substrate;

[0007] A bottom electrode is located above the substrate. The bottom electrode includes a first bottom electrode and a second bottom electrode, which are spaced apart by a predetermined distance in the horizontal direction.

[0008] A piezoelectric layer is located above the bottom electrode. The piezoelectric layer includes piezoelectric thin film layers stacked from bottom to top. In the horizontal direction, the piezoelectric layer is divided into a first region and a second region. In the first region, adjacent piezoelectric thin film layers have the same polarity, and in the second region, adjacent piezoelectric thin film layers have opposite polarities.

[0009] A top electrode is located above the piezoelectric layer. The top electrode includes a first top electrode and a second top electrode, which are spaced apart by a preset distance in the horizontal direction.

[0010] In the vertical projection, the first bottom electrode, the first region, and the first top electrode overlap, and the second bottom electrode, the second region, and the second top electrode overlap.

[0011] Optionally, the piezoelectric layer includes a first piezoelectric thin film layer and a second piezoelectric thin film layer stacked from bottom to top. In the first region, the first piezoelectric thin film layer and the second piezoelectric thin film layer are in direct contact. In the second region, an interface modulation layer is disposed between the first piezoelectric thin film layer and the second piezoelectric thin film layer.

[0012] Optionally, the material of the interface modulation layer includes one or more of TiN, Ti2O3, SiO2, SiC, SiN, AlN, Al2O3, AlON, SiON, HfO2, Mo, Mg, MgO, W, and Pt, and the thickness of the interface modulation layer ranges from 1 to 100 nm.

[0013] Optionally, the material of the piezoelectric thin film layer includes AlN, Al x Ga 1-x N(0 < x < 1), Al 1-x Sc x The piezoelectric thin film layer is selected from one or more of N (0 < x < 1), LiNbO3, ZnO, PZT, PbTiO3, and Ga2O3, with a thickness of not less than 0.01 μm and a thickness of not more than 2 μm.

[0014] Optionally, the substrate has a first groove and a second groove, at least a portion of the first groove being located below the first bottom electrode, and at least a portion of the second groove being located below the second bottom electrode.

[0015] Optionally, a bonding layer is provided between the substrate and the bottom electrode, and the bonding layer has a first groove and a second groove, wherein at least a portion of the first groove is located below the first bottom electrode and at least a portion of the second groove is located below the second bottom electrode.

[0016] Optionally, a Bragg reflector layer is disposed between the substrate and the bottom electrode.

[0017] Optionally, the Bragg reflector layer comprises a stacked high acoustic impedance material layer and a low acoustic impedance material layer, wherein the high acoustic impedance material layer is made of one or more of W, Mo, Pt, Au, Ni and Ir, and the low acoustic impedance material layer is made of one or more of AlN, Si3N4 and SiO2.

[0018] Optionally, the bottom electrode is made of one or more of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf; the top electrode is made of one or more of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf.

[0019] Optionally, the substrate includes a Si substrate, a SiC substrate, a Ge substrate, and a sapphire substrate.

[0020] As described above, in the dual-frequency bulk acoustic wave filter structure of the present invention, the piezoelectric layer is divided into two regions. In the first region, adjacent piezoelectric thin film layers have the same polarity, while in the second region, adjacent piezoelectric thin film layers have opposite polarities, so that the bulk acoustic wave filter has two frequencies, which can meet the application requirements of different frequency bands. Attached Figure Description

[0021] Figure 1 The diagram shown is a structural schematic of a dual-frequency bulk acoustic filter in an embodiment of the present invention.

[0022] Figure 2 The figure shown is a simulation result diagram of an embodiment of the present invention.

[0023] Component designation explanation

[0024] 1 Substrate

[0025] 2 Bonding layer

[0026] 20 First Groove

[0027] 21 Second Groove

[0028] 30 First bottom electrode

[0029] 31 Second bottom electrode

[0030] 4 Piezoelectric layer

[0031] 40 First piezoelectric thin film layer

[0032] 41 Second piezoelectric thin film layer

[0033] 5 Interface Modulation Layer

[0034] 60 First top electrode

[0035] 61 Second top electrode

[0036] 70 First bottom electrode pad

[0037] 71 Second bottom electrode pad

[0038] 80 First top electrode pad

[0039] 81 Second top electrode pad Detailed Implementation

[0040] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] Please see Figures 1 to 2 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0042] This embodiment provides a dual-frequency bulk acoustic wave filter structure. Please refer to [link / reference]. Figure 1 The dual-frequency bulk acoustic wave filter structure includes a substrate 1, a bottom electrode, a piezoelectric layer 4, and a top electrode. The bottom electrode is located above the substrate 1 and includes a first bottom electrode 30 and a second bottom electrode 31. In the horizontal direction (X direction), the first bottom electrode 30 and the second bottom electrode 31 are spaced apart by a predetermined distance. The piezoelectric layer 4 is located above the bottom electrode and includes piezoelectric thin film layers stacked from bottom to top. In the horizontal direction, the piezoelectric layer 4 is divided into a first region and a second region. In the first region, adjacent piezoelectric thin film layers have the same polarity (arrows in the figure). The head represents the polarization direction, and the same polarity means the same polarization direction. In the second region, the adjacent piezoelectric thin film layers have opposite polarities. The top electrode is located above the piezoelectric layer 4. The top electrode includes a first top electrode 60 and a second top electrode 61. In the horizontal direction (X direction), the first top electrode 60 and the second top electrode 61 are spaced apart by a preset distance. In the vertical direction (Z direction) projection, the first bottom electrode 30, the first region and the first top electrode 60 overlap, and the second bottom electrode 31, the second region and the second top electrode 61 overlap.

[0043] As an example, the substrate 1 includes a Si substrate, a SiC substrate, a Ge substrate, a sapphire substrate, or any other suitable substrate.

[0044] As an example, a bonding layer 2 is disposed between the substrate 1 and the bottom electrode, and the bonding layer 2 is also located between the adjacent first bottom electrode 30 and second bottom electrode 31. The material of the bonding layer 2 includes dielectric materials such as SiO2 and Si3N4 or polymer materials such as PI (polyimide) and BCB (benzocyclobutene), which are selected according to requirements.

[0045] As an example, the bonding layer 2 is provided with a first groove 20 and a second groove 21. In the horizontal direction (X direction), the first groove 20 and the second groove 21 are spaced apart by a preset distance. At least a portion of the first groove 20 is located below the first bottom electrode 30, and at least a portion of the second groove 21 is located below the second bottom electrode 31. In the vertical direction (Z direction), the first groove 20 covers the overlapping area of ​​the first bottom electrode 30, the first region, and the first top electrode 60, and the second groove 21 covers the overlapping area of ​​the second bottom electrode 31, the second region, and the second top electrode 61.

[0046] It should be noted that in other examples, the bonding layer 2 is not provided between the substrate 1 and the bottom electrode, and the first groove 20 and the second groove 21 are provided in the substrate 1, which also falls within the protection scope of this invention.

[0047] As an example, the material of the bottom electrode includes one or more of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, and the thickness of the bottom electrode does not exceed 0.3 μm.

[0048] As an example, the piezoelectric layer 4 includes a first piezoelectric thin film layer 40 and a second piezoelectric thin film layer 41 stacked from bottom to top. In the first region, the first piezoelectric thin film layer 40 and the second piezoelectric thin film layer 41 are in direct contact and have the same polarity. In the second region, an interface modulation layer 5 is disposed between the first piezoelectric thin film layer 40 and the second piezoelectric thin film layer 41. The interface modulation layer 5 is beneficial to changing the surface chemical bond state of the first piezoelectric thin film layer 40, so that the second piezoelectric thin film layer 41 has the opposite polarity to the first piezoelectric thin film layer 40.

[0049] As an example, the piezoelectric layer 4 is made of AlN, Al x Ga 1-x N(0 < x < 1), Al 1-x Sc x The piezoelectric thin film layer is selected from one or more of N (0 < x < 1), LiNbO3, ZnO, PZT, PbTiO3, and Ga2O3, with a thickness of not less than 0.01 μm and a thickness of not more than 2 μm.

[0050] As an example, the material of the interface modulation layer 5 includes one or more of TiN, Ti2O3, SiO2, SiC, SiN, AlN, Al2O3, AlON, SiON, HfO2, Mo, Mg, MgO, W and Pt, and the thickness of the interface modulation layer 5 ranges from 1 to 100 nm, preferably from 2 to 5 nm.

[0051] As an example, the material of the top electrode includes one or more of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf, and the thickness of the top electrode does not exceed 0.3 μm.

[0052] As an example, the first bottom electrode 30, the first region in the piezoelectric layer 4, and the first top electrode 60 constitute a first resonator. On the projection in the vertical direction (Z direction), the overlapping area of ​​the three is the resonant region of the first resonator. The first groove 20 can be regarded as an air cavity, which is used to confine the sound waves in the piezoelectric layer 4, prevent the sound waves from leaking into the substrate 1, thereby reducing energy loss and helping to achieve a high Q value and low insertion loss.

[0053] As an example, the second bottom electrode 31, the second region in the piezoelectric layer 4, and the second top electrode 61 constitute a second resonator. On the projection in the vertical direction (Z direction), the overlapping area of ​​the three is the resonant region of the second resonator. The second groove 21 can be regarded as an air cavity, which is used to confine the sound waves in the piezoelectric layer 4, prevent the sound waves from leaking into the substrate 1, thereby reducing energy loss and helping to achieve a high Q value and low insertion loss.

[0054] In other examples, a Bragg reflector layer can be disposed between the bottom electrode and the substrate 1 to confine the sound waves in the piezoelectric layer 4, preventing the sound waves from leaking into the substrate 1. The Bragg reflector layer includes a stacked high acoustic impedance material layer and a low acoustic impedance material layer. The high acoustic impedance material layer is made of one or more of W, Mo, Pt, Au, Ni and Ir, and the low acoustic impedance material layer is made of one or more of AlN, Si3N4 and SiO2. The thickness of each layer is 1 / 4 or 3 / 4 of the wavelength of the sound wave corresponding to the resonant frequency of the resonator.

[0055] As an example, it also includes a first bottom electrode pad 70 and a first top electrode pad 80, the first bottom electrode pad 70 being electrically connected through the piezoelectric layer 4 and the first bottom electrode 30 for electrically leading out the first bottom electrode 30, and the first top electrode pad 80 being electrically connected to the first top electrode 60 for electrically leading out the first top electrode 60.

[0056] As an example, it also includes a second bottom electrode pad 71 and a second top electrode pad 81. The second bottom electrode pad 71 is electrically connected through the piezoelectric layer 4 and the second bottom electrode 31 for electrically leading out the second bottom electrode 31. The second top electrode pad 81 is electrically connected to the second top electrode 61 for electrically leading out the second top electrode 61.

[0057] As an example, the dual-frequency bulk acoustic wave filter structure of this embodiment includes a first resonator and a second resonator. The adjacent piezoelectric thin film layers in the piezoelectric layer 4 of the first resonator have the same polarity, which excites a first-order resonance with an operating frequency of f1. The adjacent piezoelectric thin film layers in the piezoelectric layer 4 of the second resonator have opposite polarities, and there is a 180° phase difference in the piezoelectric response to the electrical signal. The inverse piezoelectric effect causes one of the adjacent piezoelectric thin film layers to be subjected to compressive stress and the other to be subjected to tensile stress, which suppresses the first-order resonance and excites a higher-order resonance with an operating frequency of f2. The operating frequency f1 of the first resonator is less than the operating frequency f2 of the second resonator.

[0058] Specifically, in this embodiment, the first bottom electrode 30 is made of a 100nm thick Mo metal layer, the second bottom electrode 31 is made of a 100nm thick Mo metal layer, the first top electrode 60 is made of a 100nm thick Mo metal layer, and the second top electrode 61 is made of a 100nm thick Mo metal layer. In the first region, the first piezoelectric thin film layer 40 is made of a 192nm thick N-polar AlN layer, and the second piezoelectric thin film layer 41 is made of a 192nm thick N-polar AlN layer. In the second region, the first piezoelectric thin film layer 40 is made of a 192nm thick N-polar AlN layer, and the second piezoelectric thin film layer 41 is made of a 192nm thick Al-polar AlN layer. Please refer to [link / reference]. Figure 2 The figure shown is a simulation result diagram of an embodiment of the present invention. The operating frequency of the first resonator is 6.15 GHz, and the operating frequency of the second resonator is 14.8 GHz. That is, the dual-frequency bulk acoustic wave filter structure of the present invention has two operating frequencies, which can meet the application requirements of different frequency bands.

[0059] In summary, in the dual-frequency bulk acoustic wave filter structure of this invention, the piezoelectric layer is divided into two regions. In the first region, adjacent piezoelectric thin film layers have the same polarity, while in the second region, adjacent piezoelectric thin film layers have opposite polarities. This allows the bulk acoustic wave filter to have two frequencies, meeting the application requirements of different frequency bands. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0060] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A dual-frequency bulk acoustic wave filter structure, characterized in that, include: Substrate; A bottom electrode is located above the substrate. The bottom electrode includes a first bottom electrode and a second bottom electrode, which are spaced apart by a predetermined distance in the horizontal direction. A piezoelectric layer is located above the bottom electrode. The piezoelectric layer includes piezoelectric thin film layers stacked from bottom to top. In the horizontal direction, the piezoelectric layer is divided into a first region and a second region. In the first region, adjacent piezoelectric thin film layers have the same polarity, and in the second region, adjacent piezoelectric thin film layers have opposite polarities. A top electrode is located above the piezoelectric layer. The top electrode includes a first top electrode and a second top electrode, which are spaced apart by a preset distance in the horizontal direction. In the vertical projection, the first bottom electrode, the first region, and the first top electrode overlap, and the second bottom electrode, the second region, and the second top electrode overlap.

2. The dual-frequency bulk acoustic wave filter structure according to claim 1, characterized in that: The piezoelectric layer includes a first piezoelectric thin film layer and a second piezoelectric thin film layer stacked from bottom to top. In the first region, the first piezoelectric thin film layer and the second piezoelectric thin film layer are in direct contact. In the second region, an interface modulation layer is disposed between the first piezoelectric thin film layer and the second piezoelectric thin film layer.

3. The dual-frequency bulk acoustic wave filter structure according to claim 2, characterized in that: The material of the interface modulation layer includes one or more of TiN, Ti2O3, SiO2, SiC, SiN, AlN, Al2O3, AlON, SiON, HfO2, Mo, Mg, MgO, W, and Pt, and the thickness of the interface modulation layer ranges from 1 to 100 nm.

4. The dual-frequency bulk acoustic wave filter structure according to claim 1, characterized in that: The material of the piezoelectric thin film layer includes AlN、Al x Ga 1-x N(0<x<1)、Al 1-x Sc x N(0<x<1)、LiNbO3、ZnO、PZT、PbTiO3、Ga2O3 One or more of the following, wherein the thickness of a single piezoelectric thin film layer is not less than 0.01 μm, and the thickness of the piezoelectric layer does not exceed 2 μm.

5. The dual-frequency bulk acoustic wave filter structure according to claim 1, characterized in that: The substrate has a first groove and a second groove, at least a portion of the first groove is located below the first bottom electrode, and at least a portion of the second groove is located below the second bottom electrode.

6. The dual-frequency bulk acoustic wave filter structure according to claim 1, characterized in that: A bonding layer is provided between the substrate and the bottom electrode. The bonding layer has a first groove and a second groove. At least a portion of the first groove is located below the first bottom electrode, and at least a portion of the second groove is located below the second bottom electrode.

7. The dual-frequency bulk acoustic wave filter structure according to claim 1, characterized in that: A Bragg reflector layer is disposed between the substrate and the bottom electrode.

8. The dual-frequency bulk acoustic wave filter structure according to claim 7, characterized in that: The Bragg reflector layer comprises a stacked high acoustic impedance material layer and a low acoustic impedance material layer. The high acoustic impedance material layer is made of one or more of W, Mo, Pt, Au, Ni, and Ir, and the low acoustic impedance material layer is made of one or more of AlN, Si3N4, and SiO2.

9. The dual-frequency bulk acoustic wave filter structure according to claim 1, characterized in that: The bottom electrode is made of one or more of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf; the top electrode is made of one or more of Au, Ag, Ru, W, Mo, Ir, Al, Pt, Nb, and Hf.

10. The dual-frequency bulk acoustic wave filter structure according to claim 1, characterized in that: The substrates include Si substrates, SiC substrates, Ge substrates, and sapphire substrates.

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