Bulk acoustic wave filter, communication device, and method of manufacturing a bulk acoustic wave filter

Abstract

The application provides a bulk acoustic wave filter, a communication device and a preparation method of the bulk acoustic wave filter. The bulk acoustic wave filter comprises: a first substrate; a first bulk acoustic wave resonator and a second bulk acoustic wave resonator which are arranged adjacent to each other in a horizontal direction on the first substrate, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator comprising a laminated structure of a bottom electrode, a piezoelectric layer and a top electrode; the first bulk acoustic wave resonator and the second bulk acoustic wave resonator have no overlap in the orthogonal projection on a horizontal plane; the electrodes of the first bulk acoustic wave resonator and the second bulk acoustic wave resonator have no overlap in the orthogonal projection on a vertical plane, the electrodes comprising at least one of the bottom electrode and the top electrode; and the first bulk acoustic wave resonator and the second bulk acoustic wave resonator are located on the same surface of the first substrate. The technical scheme provided by the embodiment of the application avoids the coupling parasitic effect between the bulk acoustic wave resonators and improves the out-of-band rejection of the bulk acoustic wave filter.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a bulk acoustic wave filter, a communication device, and a method for fabricating the bulk acoustic wave filter. Background Technology

[0002] A bulk acoustic wave resonator array consists of several bulk acoustic wave resonators and can form a bulk acoustic wave filter. Due to its high operating frequency, low power consumption, and high quality factor, it has become an important device in the field of communication devices and is widely used.

[0003] Out-of-band rejection is one of the important performance indicators of bulk acoustic wave (BAS) filters. In modern layouts, the parasitic coupling effect between two BAS resonators can negatively impact the out-of-band rejection of BAS filters, such as the degradation of out-of-band zeros.

[0004] Therefore, it is necessary to avoid the parasitic coupling effects between bulk acoustic resonators in order to improve the out-of-band suppression of bulk acoustic filters. Summary of the Invention

[0005] This invention provides a bulk acoustic wave filter, a communication device, and a method for fabricating a bulk acoustic wave filter, thereby improving the out-of-band suppression of the bulk acoustic wave filter by avoiding the coupling parasitic effect between bulk acoustic wave resonators.

[0006] According to one aspect of the present invention, a bulk acoustic wave filter is provided, comprising: a first substrate;

[0007] A first bulk acoustic wave resonator and a second bulk acoustic wave resonator are arranged adjacent to each other in the horizontal direction on the first substrate. The first bulk acoustic wave resonator and the second bulk acoustic wave resonator include a stacked structure of a bottom electrode, a piezoelectric layer and a top electrode.

[0008] The first bulk acoustic resonator and the second bulk acoustic resonator do not overlap in their orthographic projections on the horizontal plane;

[0009] The electrodes of the first bulk acoustic resonator and the second bulk acoustic resonator do not overlap in the orthographic projection of the vertical plane, and the electrodes include at least one of a bottom electrode and a top electrode;

[0010] The first bulk acoustic resonator and the second bulk acoustic resonator are located on the first surface of the first substrate.

[0011] Optionally, the second bulk acoustic resonator is located on the first substrate;

[0012] The first bulk acoustic resonator is located in a first receiving groove on a first substrate.

[0013] Optionally, the first bulk acoustic resonator is located in a second receiving groove on the first substrate;

[0014] The second bulk acoustic resonator is located in the third receiving groove on the first substrate;

[0015] The depth of the third receiving groove is less than the depth of the second receiving groove.

[0016] Optionally, the upper surface of the top electrode of the first bulk acoustic resonator is lower than the lower surface of the bottom electrode of the second bulk acoustic resonator.

[0017] Optionally, the piezoelectric layer of the first bulk acoustic resonator and the bottom electrode of the second bulk acoustic resonator overlap in the orthographic projection of the vertical plane.

[0018] The top electrode of the first bulk acoustic resonator and the piezoelectric layer of the second bulk acoustic resonator overlap in the orthographic projection of the vertical plane;

[0019] The top electrode of the second bulk acoustic resonator and the top electrode of the first bulk acoustic resonator do not overlap in the orthographic projection of the second electrode onto the vertical plane.

[0020] The bottom electrode of the second bulk acoustic resonator does not overlap with the bottom and top electrodes of the first bulk acoustic resonator in the orthographic projection of the first electrode in the vertical plane.

[0021] Optionally, it further includes a second substrate stacked with the first substrate, wherein a third body acoustic resonator is disposed on the surface of the second substrate away from the first substrate.

[0022] Optionally, it further includes a third substrate stacked with the first substrate, wherein a fourth bulk acoustic resonator is disposed on the surface of the third substrate near the surface of the first substrate.

[0023] Optionally, the first bulk acoustic resonator and the fourth bulk acoustic resonator have their orthogonal projections on the horizontal plane coincide.

[0024] Optionally, the surface of the third substrate near the first substrate is provided with a fifth bulk acoustic wave resonator disposed adjacent to the fourth bulk acoustic wave resonator along the horizontal plane, and the orthographic projections of the fifth bulk acoustic wave resonator and the fourth bulk acoustic wave resonator in the horizontal plane do not overlap; the orthographic projections of the electrodes of the fourth bulk acoustic wave resonator and the fifth bulk acoustic wave resonator in the vertical plane do not overlap, and the electrodes include at least one of a bottom electrode and a top electrode.

[0025] Optionally, the first bulk acoustic resonator and the fourth bulk acoustic resonator have their orthogonal projections on the horizontal plane coincide, and the second bulk acoustic resonator and the fifth bulk acoustic resonator have their orthogonal projections on the horizontal plane coincide.

[0026] Optionally, the distance between the first substrate and the third substrate is greater than the height of any one bulk acoustic wave resonator located on the substrate, but less than the sum of the heights of two bulk acoustic wave resonators whose orthographic projections on the horizontal plane coincide.

[0027] Optionally, the electrodes of the bulk acoustic resonators located on different substrates and arranged horizontally adjacent to each other do not overlap in the orthographic projection of the vertical plane, and the electrodes include at least one of a bottom electrode and a top electrode.

[0028] Optionally, it also includes an electromagnetic shielding layer located between the first bulk acoustic resonator and the second bulk acoustic resonator.

[0029] According to another aspect of the present invention, a communication device is provided, comprising a bulk acoustic wave filter as described in any embodiment of the present invention;

[0030] The communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0031] According to another aspect of the present invention, a method for fabricating a bulk acoustic wave filter is provided, comprising:

[0032] Provide a first substrate;

[0033] A first bulk acoustic resonator and a second bulk acoustic resonator are formed on the first substrate and arranged adjacent to each other in the horizontal direction.

[0034] The first bulk acoustic wave resonator and the second bulk acoustic wave resonator include a stacked structure of a bottom electrode, a piezoelectric layer and a top electrode; the first bulk acoustic wave resonator and the second bulk acoustic wave resonator do not overlap in their orthographic projections in the horizontal plane; the electrodes of the first bulk acoustic wave resonator and the second bulk acoustic wave resonator do not overlap in their orthographic projections in the vertical plane, and the electrodes include at least one of a bottom electrode and a top electrode; the first bulk acoustic wave resonator and the second bulk acoustic wave resonator are located on the first surface of the first substrate.

[0035] Optionally, forming a first bulk acoustic resonator and a second bulk acoustic resonator arranged adjacent to each other in a horizontal direction on the first substrate includes:

[0036] A first receiving groove is formed on the first substrate;

[0037] The first bulk acoustic resonator is formed within the first receiving groove;

[0038] The second bulk acoustic resonator is formed on the substrate.

[0039] Optionally, forming a first bulk acoustic wave resonator and a second bulk acoustic wave resonator arranged adjacent to each other in a horizontal direction on the first substrate includes:

[0040] A second receiving groove and a third receiving groove are formed on the substrate, wherein the depth of the third receiving groove is less than the depth of the second receiving groove;

[0041] The first bulk acoustic resonator is formed within the second receiving groove;

[0042] The second bulk acoustic resonator is formed within the third receiving groove.

[0043] The bulk acoustic wave filter provided in this embodiment avoids parasitic capacitance in both the horizontal and vertical directions of the electrodes of two adjacent bulk acoustic wave resonators arranged on the same surface of the first substrate by setting the horizontal projections of the first and second bulk acoustic wave resonators arranged adjacent to each other on the first substrate to be non-overlapping, and the horizontal projections of the electrodes of the two adjacent bulk acoustic wave resonators arranged adjacent to each other on the first substrate to be non-overlapping. This avoids the coupling parasitic effect between the bulk acoustic wave resonators and improves the out-of-band rejection of the bulk acoustic wave filter.

[0044] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the structure of a bulk acoustic wave filter according to an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the structure of another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of the structure of another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0050] Figure 5 This is a schematic diagram of the structure of another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0051] Figure 6This is a schematic diagram of the structure of another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0052] Figure 7 This is a schematic diagram of the structure of another bulk acoustic wave filter provided according to an embodiment of the present invention;

[0053] Figure 8 This is a flowchart of a method for fabricating a bulk acoustic wave filter according to an embodiment of the present invention;

[0054] Figure 9 yes Figure 8 A flowchart of the preparation method included in S120;

[0055] Figures 10-16 This is a schematic diagram of the structure corresponding to each step of the fabrication method of a bulk acoustic wave filter provided by an embodiment of the present invention;

[0056] Figure 17 yes Figure 8 A flowchart of another preparation method for S120;

[0057] Figure 18 This is a flowchart of another preparation method including S120, and the corresponding structural schematic diagrams for each step. Detailed Implementation

[0058] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0059] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that includes a series of steps or apparatuses is not necessarily limited to those explicitly listed, but may include other steps or apparatuses not explicitly listed or inherent to such processes, methods, products, or apparatuses.

[0060] To improve the out-of-band rejection of bulk acoustic wave filters by avoiding the parasitic coupling effects between bulk acoustic wave resonators, embodiments of the present invention provide the following technical solutions:

[0061] Figure 1 This is a schematic diagram of a bulk acoustic wave filter according to an embodiment of the present invention. See also... Figure 1 The bulk acoustic wave filter includes: a first substrate 10a; a first bulk acoustic wave resonator 001 and a second bulk acoustic wave resonator 002 disposed horizontally adjacent to each other on the first substrate 10a, the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 including a stacked structure of a bottom electrode 20, a piezoelectric layer 21 and a top electrode 22; the orthographic projections of the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 in the horizontal plane do not overlap; the orthographic projections of the electrodes of the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 in the vertical plane do not overlap, the electrodes including at least one of the bottom electrode 20 and the top electrode 22, and the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 located on the same surface of the first substrate 10a. For example, the first substrate 10a includes a first surface 101 and a second surface 102 disposed opposite to each other. Figure 1 In the first substrate 10a, the first bulk acoustic resonator 001 and the second bulk acoustic resonator 002 are located on the first surface 101 of the first substrate 10a.

[0062] In this embodiment of the invention, the horizontal plane is the plane defined by XOZ, and the vertical plane is the plane defined by YOZ.

[0063] Figure 2 This is a schematic diagram of another bulk acoustic wave filter provided according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the structure of another bulk acoustic wave filter provided according to an embodiment of the present invention. Exemplary, Figure 1 and Figure 2 In the first substrate 10a, the first bulk acoustic resonator 001 and the second bulk acoustic resonator 002 are arranged adjacent to each other in the horizontal direction on the first surface 101 of the first substrate 10a. Figure 3 Four bulk acoustic wave resonators are disposed on the first surface 101 of the first substrate 10a, namely a first bulk acoustic wave resonator 001, a second bulk acoustic wave resonator 002, a sixth bulk acoustic wave resonator 003, and a seventh bulk acoustic wave resonator 004. The first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 are arranged adjacent to each other in the horizontal direction. The second bulk acoustic wave resonator 002 and the sixth bulk acoustic wave resonator 003 are arranged adjacent to each other in the horizontal direction. The sixth bulk acoustic wave resonator 003 and the seventh bulk acoustic wave resonator 004 are arranged adjacent to each other in the horizontal direction.

[0064] Figures 1-3The common features of the bulk acoustic wave filters shown are: the orthographic projections of adjacent bulk acoustic wave resonators in the horizontal direction do not overlap in the horizontal plane; and the orthographic projections of the electrodes of adjacent bulk acoustic wave resonators in the horizontal direction do not overlap in the vertical plane, which can avoid the existence of parasitic capacitances in the horizontal and vertical directions of the electrodes of adjacent bulk acoustic wave resonators in the horizontal direction.

[0065] The bulk acoustic wave filter provided in this embodiment avoids parasitic capacitance in both the horizontal and vertical directions of the electrodes of two adjacent bulk acoustic wave resonators arranged on the same surface of the first substrate by setting the horizontal projections of the first and second bulk acoustic wave resonators arranged adjacent to each other on the first substrate to be non-overlapping, and the horizontal projections of the electrodes of the two adjacent bulk acoustic wave resonators arranged adjacent to each other on the first substrate to be non-overlapping. This avoids the coupling parasitic effect between the bulk acoustic wave resonators and improves the out-of-band rejection of the bulk acoustic wave filter.

[0066] Optionally, to reduce the loss of sound waves by the first substrate 10a, an acoustic reflection structure can be formed on or inside the first substrate 10a. For example, in this embodiment, the acoustic reflection structure is a cavity structure 11. It should be noted that in other embodiments, the acoustic reflection structure may also include a Bragg reflective layer formed by alternating stacks of high and low acoustic impedance layers, a groove on the second surface of the first substrate 10a, or a cavity structure formed by the first substrate 10a, the bottom electrode 20, and a support structure located between the first substrate 10a and the bottom electrode 20.

[0067] Regarding the specific location of two horizontally adjacent bulk acoustic resonators on the first substrate, embodiments of the present invention further provide the following technical solution:

[0068] Optionally, the second bulk acoustic resonator is located on the first substrate; the first bulk acoustic resonator is located in the first receiving groove on the first substrate.

[0069] For example, see Figure 1 The second bulk acoustic wave resonator 002 is located on the first substrate 10a; the first bulk acoustic wave resonator 001 is located in the first receiving groove 10A on the first substrate 10a. This ensures that the first bulk acoustic wave resonator 001 in the first receiving groove 10A and the second bulk acoustic wave resonator 002 on the first substrate 10a do not overlap in the horizontal plane, and the electrodes of the two do not overlap in the vertical plane. This avoids the existence of parasitic capacitance in the horizontal and vertical directions of the electrodes of two adjacent bulk acoustic wave resonators, such as the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002, thereby avoiding the coupling parasitic effect between the bulk acoustic wave resonators and improving the out-of-band suppression of the bulk acoustic wave filter.

[0070] Optionally, the first bulk acoustic resonator is located in a second receiving groove on the first substrate; the second bulk acoustic resonator is located in a third receiving groove on the first substrate; the depth of the third receiving groove is less than the depth of the second receiving groove.

[0071] For example, see Figure 2 The first bulk acoustic wave resonator 001 is located in the second receiving groove 10B on the first substrate 10a; the second bulk acoustic wave resonator 002 is located in the third receiving groove 10C on the first substrate 10a; the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 are located in different receiving grooves, so that their orthogonal projections in the horizontal plane do not overlap. Since the depth of the third receiving groove 10C is less than the depth of the second receiving groove 10B, the difference between the depth of the third receiving groove 10C and the depth of the second receiving groove 10B can be set to ensure that the orthogonal projections of the electrodes of the first bulk acoustic wave resonator 001 in the second receiving groove 10B and the second bulk acoustic wave resonator 002 in the third receiving groove 10C do not overlap in the vertical plane. Therefore, the above technical solution can avoid the parasitic capacitance in the horizontal and vertical directions of the electrodes of two adjacent bulk acoustic resonators, such as the first bulk acoustic resonator 001 and the second bulk acoustic resonator 002, thereby avoiding the coupling parasitic effect between bulk acoustic resonators and improving the out-of-band suppression of the bulk acoustic filter.

[0072] When the electrodes of two adjacent bulk acoustic resonators in the horizontal direction do not overlap in the orthographic projection of the vertical plane, the correspondence of the film layers of the two adjacent bulk acoustic resonators in the horizontal direction can include the following two cases.

[0073] Optionally, the upper surface of the top electrode of the first bulk acoustic resonator is lower than the lower surface of the bottom electrode of the second bulk acoustic resonator.

[0074] For example, see Figure 1 and Figure 2 The upper surface of the top electrode 22 of the first bulk acoustic resonator 001 is lower than the lower surface of the bottom electrode 20 of the second bulk acoustic resonator 002, so as to ensure that the orthographic projections of the electrodes of the two resonators in the vertical plane do not overlap. This avoids the existence of parasitic capacitances in the horizontal and vertical directions of the electrodes of the two adjacent bulk acoustic resonators, thereby avoiding the coupling parasitic effect between the bulk acoustic resonators and improving the out-of-band suppression of the bulk acoustic filter.

[0075] Optionally, the piezoelectric layer of the first bulk acoustic resonator and the bottom electrode of the second bulk acoustic resonator overlap in the orthographic projection in the vertical plane; the top electrode of the first bulk acoustic resonator and the piezoelectric layer of the second bulk acoustic resonator overlap in the orthographic projection in the vertical plane; the top electrode of the second bulk acoustic resonator and the top electrode of the first bulk acoustic resonator do not overlap in the orthographic projection in the vertical plane; the bottom electrode and top electrode of the second bulk acoustic resonator and the bottom electrode of the first bulk acoustic resonator do not overlap in the orthographic projection in the vertical plane.

[0076] For example, see Figure 4 The piezoelectric layer 21 of the first bulk acoustic resonator 001 and the bottom electrode 20 of the second bulk acoustic resonator 002 overlap in the orthographic projection in the vertical plane; the top electrode 22 of the first bulk acoustic resonator 001 and the piezoelectric layer 21 of the second bulk acoustic resonator 002 overlap in the orthographic projection in the vertical plane; the top electrode 22 of the second bulk acoustic resonator 002 and the top electrode 22 of the first bulk acoustic resonator 001 do not overlap in the orthographic projection in the vertical plane; the bottom electrode 20 of the second bulk acoustic resonator 002 and the bottom electrode 20 and top electrode 22 of the first bulk acoustic resonator 001 do not overlap in the orthographic projection in the vertical plane. The above technical solution, on the one hand, ensures that the electrodes of two horizontally adjacent bulk acoustic wave resonators do not overlap in the orthographic projection of the vertical plane, thus avoiding parasitic capacitances in both the horizontal and vertical directions, thereby mitigating the coupling parasitic effects between the bulk acoustic wave resonators and improving the out-of-band suppression of the bulk acoustic wave filter. On the other hand, the above technical solution can reduce the depth of the first receiving groove 10A, improving the structural stability of the mechanical support strength of the substrate 10.

[0077] Optionally, it also includes a second substrate stacked with the first substrate, wherein a third body acoustic resonator is disposed on the surface of the second substrate away from the first substrate.

[0078] Figure 5 This is a schematic diagram of the structure of another bulk acoustic wave filter according to an embodiment of the present invention. For example, see [link to example]. Figure 5 The bulk acoustic wave filter also includes a second substrate 10b stacked with the first substrate 10a, and a third bulk acoustic wave resonator 005 is disposed on the surface of the second substrate 10b away from the first substrate 10a. Optionally, see Figure 5An eighth bulk acoustic wave resonator 006, horizontally adjacent to the third bulk acoustic wave resonator 005, is also disposed on the surface of the second substrate 10b away from the first substrate 10a. Exemplarily, the second substrate 10b includes a first surface 101 and a second surface 102 disposed opposite to each other. It should be noted that the third bulk acoustic wave resonator 005 and the eighth bulk acoustic wave resonator 006 are located on the surface of the second substrate 10b away from the first substrate 10a, and both bulk acoustic wave resonators include a stacked structure of a bottom electrode 20, a piezoelectric layer 21, and a top electrode 22. The electrodes of the third bulk acoustic wave resonator 005 and the eighth bulk acoustic wave resonator 006 do not overlap in the orthographic projection of the vertical plane, which can avoid parasitic capacitance in both the horizontal and vertical directions of the electrodes of the horizontally adjacent bulk acoustic wave resonators. The electrodes include at least one of the bottom electrode 20 and the top electrode 22.

[0079] Specifically, the bulk acoustic wave filter includes at least two substrates stacked vertically. Increasing the number of substrates reduces the horizontal dimension of the bulk acoustic wave filter, thus facilitating miniaturization. It should be noted that when there are at least two substrates, bonding structures can be provided between adjacent substrates for sealing connections between the different substrates.

[0080] Optionally, it also includes a third substrate stacked with the first substrate, wherein a fourth bulk acoustic resonator is disposed on the surface of the third substrate near the surface of the first substrate.

[0081] Figure 6 This is a schematic diagram of the structure of another bulk acoustic wave filter according to an embodiment of the present invention. Figure 7 This is a schematic diagram of the structure of another bulk acoustic wave filter according to an embodiment of the present invention. For example, see [link to example]. Figure 6 and Figure 7 The bulk acoustic wave filter further includes a third substrate 10c stacked with the first substrate 10a, and a fourth bulk acoustic wave resonator 007 is disposed on the surface of the third substrate 10c near the surface of the first substrate 10a. For example, the third substrate 10c includes a first surface 101 and a second surface 102 disposed opposite to each other.

[0082] Specifically, the bulk acoustic wave filter includes at least two substrates stacked vertically. Increasing the number of substrates reduces the horizontal dimension of the bulk acoustic wave filter, thus facilitating miniaturization. Furthermore, based on the above technical solution, bulk acoustic wave resonators are disposed on the opposing surfaces of adjacent substrates, further improving the integration density of the bulk acoustic wave filter.

[0083] Optionally, the orthographic projections of the first-body acoustic resonator and the fourth-body acoustic resonator on the horizontal plane coincide.

[0084] For example, see Figure 6 and Figure 7 The first body acoustic resonator 001 and the fourth body acoustic resonator 007 have their orthogonal projections on the horizontal plane coincide.

[0085] Specifically, the bulk acoustic wave resonators disposed on opposite surfaces of two adjacent substrates have their orthographic projections on the horizontal plane coincide. Furthermore, since the first bulk acoustic wave resonator is recessed into the first substrate, the vertical dimension of the bulk acoustic wave filter can be reduced, thereby helping to form a miniaturized bulk acoustic wave filter.

[0086] Optionally, a fifth bulk acoustic wave resonator is provided on the surface of the third substrate near the first substrate, which is adjacent to the fourth bulk acoustic wave resonator along the horizontal plane. The orthographic projections of the fifth bulk acoustic wave resonator and the fourth bulk acoustic wave resonator in the horizontal plane do not overlap. The orthographic projections of the electrodes of the fourth bulk acoustic wave resonator and the fifth bulk acoustic wave resonator in the vertical plane do not overlap, and the electrodes include at least one of a bottom electrode and a top electrode.

[0087] For example, see Figure 7 A fifth bulk acoustic wave resonator 008 is disposed on the surface of the third substrate 10c near the first substrate 10a, adjacent to the fourth bulk acoustic wave resonator 007. The fifth bulk acoustic wave resonator 008 and the fourth bulk acoustic wave resonator 007 do not overlap in the orthographic projection of their respective electrodes in the horizontal plane. The electrodes include at least one of the bottom electrode 20 and the top electrode 22.

[0088] Specifically, a first bulk acoustic wave (BAS) resonator and a second BAS resonator are arranged adjacently in the horizontal direction on the first substrate. A fifth BAS resonator is arranged adjacent in the horizontal direction to the fourth BAS resonator on the surface of the third substrate near the first substrate. The horizontal projections of the two adjacent BAS resonators on the first and third substrates do not overlap in the horizontal plane, and the vertical projections of the electrodes of the two horizontally adjacent BAS resonators do not overlap. This avoids parasitic capacitance in both the horizontal and vertical directions of the electrodes of the two horizontally adjacent BAS resonators on the same surface of the first and third substrates, thus mitigating the coupling parasitic effect between the BAS resonators and improving the out-of-band rejection of the bulk acoustic wave filter. Furthermore, increasing the number of substrates can reduce the horizontal size of the bulk acoustic wave filter, thereby facilitating the formation of a miniaturized bulk acoustic wave filter.

[0089] Optionally, the orthographic projections of the first body acoustic resonator and the fourth body acoustic resonator on the horizontal plane coincide, and the orthographic projections of the second body acoustic resonator and the fifth body acoustic resonator on the horizontal plane coincide.

[0090] For example, see Figure 7The first bulk acoustic wave resonator 001 and the fourth bulk acoustic wave resonator 007 have their orthographic projections on the horizontal plane coincide. The second bulk acoustic wave resonator 002 and the fifth bulk acoustic wave resonator 008 have their orthographic projections on the horizontal plane coincide. At least one of the two bulk acoustic wave resonators with their orthographic projections on the horizontal surface is recessed into the substrate, which can further reduce the vertical dimension of the bulk acoustic wave filter, thereby helping to form a miniaturized bulk acoustic wave filter.

[0091] Optionally, the distance between the first substrate and the third substrate is greater than the height of any one bulk acoustic wave resonator located on the substrate, but less than the sum of the heights of the two bulk acoustic wave resonators whose orthographic projections on the horizontal plane coincide.

[0092] For example, see Figure 7 The distance between the first substrate 10a and the third substrate 10c is greater than the height of any one of the bulk acoustic wave (BAW) resonators on the first substrate 10a and the third substrate 10c. This prevents the second BAW resonator 002 on the first substrate 10a and the fifth BAW resonator 008 on the third substrate 10c from contacting each other, and also prevents the first BAW resonator 001 on the first substrate 10a and the fourth BAW resonator 007 on the third substrate 10c from contacting each other. Since at least one of the two BAW resonators whose orthographic projections on the horizontal plane coincide is recessed into the substrate, the distance between the first substrate 10a and the third substrate 10c is less than the sum of the heights of the first BAW resonator 001 and the fourth BAW resonator 007 whose orthographic projections on the horizontal plane coincide, and the distance between the first substrate 10a and the third substrate 10c is less than the sum of the heights of the second BAW resonator 002 and the fifth BAW resonator 008 whose orthographic projections on the horizontal plane coincide. This further reduces the vertical dimension of the BAW filter, thereby contributing to the formation of a miniaturized BAW filter.

[0093] Optionally, the electrodes of the bulk acoustic wave resonators located on different substrates and arranged horizontally adjacent to each other do not overlap in the orthographic projection of the vertical plane, and the electrodes include at least one of a bottom electrode and a top electrode.

[0094] For example, Figure 7 The piezoelectric layer of the second bulk acoustic wave resonator 002 on the first substrate 10a and the top electrode of the fourth bulk acoustic wave resonator 007 on the second substrate 10b overlap in the orthographic projection of the piezoelectric layer of the second bulk acoustic wave resonator 002 on the first substrate 10a and the fourth bulk acoustic wave resonator 007 on the second substrate 10b in the orthographic projection of the piezoelectric layer overlap in the vertical plane. This can avoid the existence of parasitic capacitance in the horizontal and vertical directions of the electrodes of two bulk acoustic wave resonators located on different substrates and arranged horizontally adjacent to each other, thereby avoiding the coupling parasitic effect between bulk acoustic wave resonators and improving the out-of-band suppression of the bulk acoustic wave filter.

[0095] Optionally, it also includes an electromagnetic shielding layer located between the first bulk acoustic resonator and the second bulk acoustic resonator.

[0096] For example, see Figure 4 The electromagnetic shielding layer 30 is located between the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002. The electromagnetic shielding layer 30 is connected to a fixed potential, which is equivalent to an equipotential body. It can shield the transmission and coupling of electromagnetic signals between the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002. It can further avoid the existence of parasitic capacitance in the vertical direction of the electrodes of two horizontally adjacent bulk acoustic wave resonators, thereby avoiding the coupling parasitic effect between bulk acoustic wave resonators and improving the out-of-band suppression of the bulk acoustic wave filter.

[0097] This invention also provides a communication device, including any of the bulk acoustic wave filters described in the above technical solutions; the communication device includes at least one of a filter, a duplexer, and a multiplexer.

[0098] Specifically, a duplexer can be simply understood as the operation of two bulk acoustic wave filters: one is a receiving bulk acoustic wave filter to receive signals, and the other is a transmitting bulk acoustic wave filter to transmit signals. A multiplexer can be simply understood as a communication device composed of at least two duplexers.

[0099] The communication device provided in this embodiment of the invention includes any of the bulk acoustic wave filters described in the above technical solutions, and therefore has the beneficial effects of the bulk acoustic wave filters described above, which will not be repeated here.

[0100] This invention also provides a method for preparing a bulk acoustic wave filter. Figure 8 This is a flowchart illustrating a method for fabricating a bulk acoustic wave filter according to an embodiment of the present invention. See also... Figure 8 The fabrication method of this bulk acoustic wave filter includes the following steps:

[0101] S110 provides a first substrate.

[0102] See Figure 10 A first substrate 10a is provided. Exemplarily, the first substrate 10a may be made of materials such as single-crystal silicon, gallium arsenide, sapphire, and quartz. The first substrate 10a includes a first surface 101 and a second surface 102 disposed opposite to the first surface 101.

[0103] S120, A first bulk acoustic resonator and a second bulk acoustic resonator are formed on a first substrate and arranged adjacent to each other in the horizontal direction.

[0104] See Figure 1A first bulk acoustic resonator 001 and a second bulk acoustic resonator 002 are formed on the first substrate 10a. To reduce the sound wave loss of the first substrate 10a, an acoustic reflection structure can also be formed on or inside the first substrate 10a. For example, in this embodiment, the acoustic reflection structure is a cavity structure 11. It should be noted that in other embodiments, the acoustic reflection structure may also include a Bragg reflector layer formed by alternating stacks of high and low acoustic impedance layers, a groove on the back side of the first substrate 10a, or a cavity structure formed by the first substrate 10a, the bottom electrode 20, and a support structure located between the first substrate 10a and the bottom electrode 20.

[0105] The first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 include a stacked structure of a bottom electrode 20, a piezoelectric layer 21 and a top electrode 22; the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 do not overlap in their orthogonal projections on the horizontal plane; the electrodes of the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 do not overlap in their orthogonal projections on the vertical plane, and the electrodes include at least one of the bottom electrode 20 and the top electrode 22; the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 are located on the same surface of the first substrate 10a.

[0106] The technical solution provided in this embodiment avoids the parasitic coupling effect between bulk acoustic wave resonators by setting the first and second bulk acoustic wave resonators, which are adjacent to each other in the horizontal direction on the first substrate, so that their orthogonal projections in the horizontal plane do not overlap, and the electrodes of the two bulk acoustic wave resonators, which are adjacent to each other in the horizontal direction, do not overlap in the orthogonal projections in the vertical plane. This is to avoid the existence of parasitic capacitance in the horizontal and vertical directions of the electrodes of the two bulk acoustic wave resonators, which are adjacent to each other in the horizontal direction on the same surface of the first substrate, thereby improving the out-of-band suppression of the bulk acoustic wave filter.

[0107] Figure 9 yes Figure 8 A flowchart of a preparation method including S120. Optionally, see... Figure 9 S120, forming a first bulk acoustic wave resonator and a second bulk acoustic wave resonator arranged adjacent to each other in a horizontal direction on the first substrate includes:

[0108] S1201, A first receiving groove is formed on the first substrate.

[0109] For example, see Figure 11 A first receiving groove 10A is formed in the first substrate 10a by a patterning process.

[0110] S1202, A first bulk acoustic resonator is formed in the first receiving groove.

[0111] S1203, A second bulk acoustic resonator is formed on the first substrate.

[0112] See Figure 12 A second groove 11a2 is formed on the first substrate 10a by a patterning process, and a first groove 11a1 is formed in the first receiving groove 10A.

[0113] See Figure 13 A sacrificial layer is formed on a first substrate 10a. Then, a first sacrificial layer 11b1 is formed filling a first groove 11a1, and a second sacrificial layer 11b2 is formed filling a second groove 11a2, using a patterning process such as CMP. The first sacrificial layer 11b1 and the second sacrificial layer 11b2 contain silicon oxide materials such as phosphosilicate glass (PSG). In subsequent steps, the sacrificial layers are etched and removed using an etching solution.

[0114] See Figure 14 Alternatively, a thin film electrode can be deposited on the first sacrificial layer 11b1 and the second sacrificial layer b2, and then a bottom electrode 20 with a predetermined pattern can be formed by etching. Or, a thin film electrode can be deposited on the first sacrificial layer 11b1 and the second sacrificial layer b2, and then a bottom electrode 20 with a predetermined pattern can be formed by lift-off. Specifically, forming the bottom electrode 20 with a predetermined pattern by lift-off includes: first photolithographically etching a specific area corresponding to the pattern of the bottom electrode 20, then depositing a thin film electrode over the entire surface, and then peeling off the photoresist and the thin film electrode thereon, leaving the thin film electrode in the specific area as the bottom electrode 20. For example, the bottom electrode 20 can be selected from at least one of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, and titanium, which have good conductivity.

[0115] See Figure 15 A piezoelectric layer 21 is formed on the bottom electrode 20. For example, the piezoelectric layer 21 can be selected from at least one of single-crystal piezoelectric thin film materials such as aluminum nitride, zinc oxide, lead zirconate titanate piezoelectric ceramics, lithium niobate, lithium tantalate, and potassium niobate, as well as polycrystalline piezoelectric thin film materials. A certain proportion of rare earth elements can also be doped into the piezoelectric layer 21 to improve the performance of the piezoelectric material layer.

[0116] See Figure 16The piezoelectric layer 21 can be pre-deposited with a thin film electrode, and then a top electrode 22 with a predetermined pattern can be formed by etching. Alternatively, a thin film electrode can be pre-deposited with the piezoelectric layer 21, and then a top electrode 22 with a predetermined pattern can be formed by lift-off. Specifically, the lift-off method for forming the top electrode 22 with a predetermined pattern includes: first photolithographically etching a specific area corresponding to the pattern of the top electrode 22, then depositing a thin film electrode over the entire surface, and then peeling off the photoresist and the thin film electrode on it, leaving the thin film electrode in the specific area as the top electrode 22. The bulk acoustic wave resonator includes a stacked structure of a bottom electrode 20, a piezoelectric layer 21, and a top electrode 22. For example, the top electrode 22 can be selected from at least one of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, and titanium, which have good conductivity.

[0117] The above steps form a first bulk acoustic wave resonator 001 within the first receiving groove 10A and a second bulk acoustic wave resonator 002 on the first substrate 10a. The bulk acoustic wave resonator includes a stacked structure of a bottom electrode 20, a piezoelectric layer 21, and a top electrode 22; the orthographic projections of the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 in the horizontal plane do not overlap; the orthographic projections of the electrodes of the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 in the vertical plane do not overlap, and the electrodes include at least one of the bottom electrode 20 and the top electrode 22.

[0118] See Figure 1 The first sacrificial layer 11b1 and the second sacrificial layer 11b2 are released by wet corrosion, forming the cavity structure 11 of the first bulk acoustic resonator 001 and the second bulk acoustic resonator 002.

[0119] Figure 17 yes Figure 8 A flowchart of another preparation method including S120. See also Figure 17 S120, forming a first bulk acoustic wave resonator and a second bulk acoustic wave resonator arranged adjacent to each other in a horizontal direction on the first substrate includes:

[0120] S1204. A second receiving groove and a third receiving groove are formed on the first substrate, wherein the depth of the third receiving groove is less than the depth of the second receiving groove.

[0121] See Figure 18 A second receiving groove 10B and a third receiving groove 10C are formed on a first substrate 10a through a patterning process, wherein the depth of the third receiving groove 10C is less than the depth of the second receiving groove 10B.

[0122] S1205, A first bulk acoustic resonator is formed in the second receiving groove.

[0123] See Figure 2 A first bulk acoustic resonator 001 is formed within the second receiving groove 10B.

[0124] S1206. A second bulk acoustic resonator is formed in the third receiving groove.

[0125] See Figure 2 A second bulk acoustic wave resonator 002 is formed within the third receiving groove 10C. The methods for preparing the internal films of the first bulk acoustic wave resonator 001 and the second bulk acoustic wave resonator 002 can be found in the aforementioned method for preparing a bulk acoustic wave filter.

[0126] The above steps form a first bulk acoustic resonator 001 in the second receiving groove 10B and a second bulk acoustic resonator 002 in the third receiving groove 10C, thus fabricating... Figure 2 The volume acoustic wave filter shown.

[0127] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0128] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A bulk acoustic wave filter, characterized in that, include: First substrate; A first bulk acoustic wave resonator and a second bulk acoustic wave resonator are arranged adjacent to each other in the horizontal direction on the first substrate. The first bulk acoustic wave resonator and the second bulk acoustic wave resonator include a stacked structure of a bottom electrode, a piezoelectric layer and a top electrode. The first bulk acoustic resonator and the second bulk acoustic resonator do not overlap in their orthographic projections on the horizontal plane; The electrodes of the first bulk acoustic resonator and the second bulk acoustic resonator do not overlap in the orthographic projection of the vertical plane, and the electrodes include at least one of a bottom electrode and a top electrode; The first bulk acoustic wave resonator and the second bulk acoustic wave resonator are located on the same surface of the first substrate; The piezoelectric layer of the first bulk acoustic resonator and the bottom electrode of the second bulk acoustic resonator overlap in the orthographic projection of the vertical plane; The top electrode of the first bulk acoustic resonator and the piezoelectric layer of the second bulk acoustic resonator overlap in the orthographic projection of the vertical plane; The top electrode of the second bulk acoustic resonator and the top electrode of the first bulk acoustic resonator do not overlap in the orthographic projection of the second electrode onto the vertical plane. The bottom electrode of the second bulk acoustic resonator does not overlap with the bottom and top electrodes of the first bulk acoustic resonator in the orthographic projection of the first electrode in the vertical plane.

2. The bulk acoustic wave filter according to claim 1, characterized in that, The second bulk acoustic resonator is located on the first substrate; The first bulk acoustic resonator is located in a first receiving groove on a first substrate.

3. The bulk acoustic wave filter according to claim 1, characterized in that, The first bulk acoustic resonator is located in a second receiving groove on the first substrate; The second bulk acoustic resonator is located in the third receiving groove on the first substrate; The depth of the third receiving groove is less than the depth of the second receiving groove.

4. The bulk acoustic wave filter according to any one of claims 1-3, characterized in that, The upper surface of the top electrode of the first bulk acoustic resonator is lower than the lower surface of the bottom electrode of the second bulk acoustic resonator.

5. The bulk acoustic wave filter according to claim 1, characterized in that, It also includes a second substrate stacked with the first substrate, wherein a third body acoustic resonator is disposed on the surface of the second substrate away from the first substrate.

6. The bulk acoustic wave filter according to claim 1, characterized in that, It also includes a third substrate stacked with the first substrate, and a fourth bulk acoustic resonator is disposed on the surface of the third substrate near the surface of the first substrate.

7. The bulk acoustic wave filter according to claim 6, characterized in that, The first body acoustic resonator and the fourth body acoustic resonator have their orthogonal projections on the horizontal plane coincide.

8. The bulk acoustic wave filter according to claim 6, characterized in that, The surface of the third substrate near the first substrate is provided with a fifth body acoustic resonator that is adjacent to the fourth body acoustic resonator along the horizontal plane, and the orthographic projections of the fifth body acoustic resonator and the fourth body acoustic resonator on the horizontal plane do not overlap. The electrodes of the fourth and fifth body acoustic resonators do not overlap in their orthographic projections in the vertical plane, and the electrodes include at least one of a bottom electrode and a top electrode.

9. The bulk acoustic wave filter according to claim 8, characterized in that, The first bulk acoustic resonator and the fourth bulk acoustic resonator have their orthogonal projections on the horizontal plane coincide, and the second bulk acoustic resonator and the fifth bulk acoustic resonator have their orthogonal projections on the horizontal plane coincide.

10. The bulk acoustic wave filter according to claim 7, characterized in that, The distance between the first substrate and the third substrate is greater than the height of any one bulk acoustic wave resonator located on the substrate, but less than the sum of the heights of two bulk acoustic wave resonators whose orthographic projections on the horizontal plane coincide.

11. The bulk acoustic wave filter according to claim 6, characterized in that, The electrodes of the bulk acoustic wave resonators located on different substrates and arranged horizontally adjacent to each other have no overlap in their orthogonal projections in a vertical plane, and the electrodes include at least one of a bottom electrode and a top electrode.

12. The bulk acoustic wave filter according to claim 1, characterized in that, It also includes an electromagnetic shielding layer, which is located between the first bulk acoustic resonator and the second bulk acoustic resonator.

13. A communication device, characterized in that, Includes the bulk acoustic wave filter according to any one of claims 1-12; The communication device includes at least one of a filter, a duplexer, and a multiplexer.

14. A method for fabricating a bulk acoustic wave filter, characterized in that, include: Provide a first substrate; A first bulk acoustic resonator and a second bulk acoustic resonator are formed on the first substrate and arranged adjacent to each other in the horizontal direction. The first and second bulk acoustic wave resonators each have a stacked structure comprising a bottom electrode, a piezoelectric layer, and a top electrode. The first and second bulk acoustic wave resonators do not overlap in their orthographic projections onto a horizontal plane. The electrodes of the first and second bulk acoustic wave resonators do not overlap in their orthographic projections onto a vertical plane, and each electrode includes at least one of a bottom electrode and a top electrode. The first and second bulk acoustic wave resonators are located on a first surface of the first substrate. The piezoelectric layer of the first bulk acoustic resonator and the bottom electrode of the second bulk acoustic resonator overlap in the orthographic projection of the vertical plane; The top electrode of the first bulk acoustic resonator and the piezoelectric layer of the second bulk acoustic resonator overlap in the orthographic projection of the vertical plane; The top electrode of the second bulk acoustic resonator and the top electrode of the first bulk acoustic resonator do not overlap in the orthographic projection of the second electrode onto the vertical plane. The bottom electrode of the second bulk acoustic resonator does not overlap with the bottom and top electrodes of the first bulk acoustic resonator in the orthographic projection of the first electrode in the vertical plane.

15. The method for fabricating a bulk acoustic wave filter according to claim 14, characterized in that, Forming a first bulk acoustic wave resonator and a second bulk acoustic wave resonator arranged adjacent to each other in a horizontal direction on the first substrate includes: A first receiving groove is formed on the first substrate; The first bulk acoustic resonator is formed within the first receiving groove; The second bulk acoustic resonator is formed on the first substrate.

16. The method for fabricating a bulk acoustic wave filter according to claim 14, characterized in that, Forming a first bulk acoustic wave resonator and a second bulk acoustic wave resonator arranged adjacent to each other in a horizontal direction on the first substrate includes: A second receiving groove and a third receiving groove are formed on the first substrate, wherein the depth of the third receiving groove is less than the depth of the second receiving groove; The first bulk acoustic resonator is formed within the second receiving groove; The second bulk acoustic resonator is formed within the third receiving groove.

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