Filter, radio frequency chip and electronic device

Abstract

The present application provides a filter, a radio frequency chip and an electronic device. An interdigital electrode of the filter comprises a first bus bar and a second bus bar which are parallel to each other, release holes are distributed in specific areas between the first bus bar and the second bus bar, the release holes pass through a piezoelectric layer and are communicated with an air cavity, and the size of the release holes is smaller than the length of apertures of the interdigital electrode. When an etching material is injected into the release holes in the specific areas to etch a substrate, the substrate below the interdigital electrode area can be effectively released, thereby reducing the volume of the air cavity formed after etching, preventing the substrate below the non-interdigital electrode area from being released, improving the mechanical strength and power tolerance of the filter, reducing the size of the filter, and reducing the subsequent processing difficulty.

Description

Filters, RF chips and electronic devices

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on January 26, 2024, with application number 202410116653.X, and invention name “Filter, RF Chip and Electronic Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of terminal device hardware, and specifically, to a filter, a radio frequency chip, and an electronic device. Background Art

[0003] Acoustic filters are a crucial component of mobile communication devices and also have important applications in sensing, detection, and other fields. As communication technologies use higher-frequency carrier frequencies to achieve wide-bandwidth, low-latency communications, the industry urgently needs surface acoustic wave filters with higher frequencies and higher quality factors.

[0004] During the fabrication process of a cavity-type surface acoustic wave filter, release holes must be etched into the device's top surface. Then, an etchant is injected through the holes to partially etch away the substrate, leaving the interdigital electrode region suspended. Currently, the release holes are often placed between the finger tips and the busbar. However, this placement of the release holes can also etch away the substrate in areas other than the interdigital electrodes, resulting in an excessively large air cavity after release, which reduces the device's mechanical strength. Therefore, a filter with a small release cavity and high mechanical strength is needed.

[0005] Summary of the Invention

[0006] The present application provides a filter, wherein the release holes of the filter are arranged in a partial area between the interdigitated electrode bus bars. After the substrate is etched by injecting an etching material into the release holes, the volume of the air cavity after etching can be effectively reduced.

[0007] In a first aspect, a filter is provided, comprising: a substrate having an air cavity; a piezoelectric layer located above the substrate; interdigital electrodes located above the piezoelectric layer, the interdigital electrodes comprising a first bus bar and a second bus bar parallel to each other, the interdigital electrodes further comprising fingers extending from the first bus bar and the second bus bar in a first direction; release holes are arranged between the first bus bar and the second bus bar, the release holes penetrate the piezoelectric layer and communicate with the air cavity; in the first direction, a distance x between the release holes and a midpoint of an aperture of the interdigital electrodes satisfies the following condition: x ≤ 0.25W; in a second direction, a distance Δy between adjacent release holes satisfies the following condition: Among them, p is half of the period length of the interdigitated electrode, W is the length of the aperture of the interdigitated electrode, the length of the aperture of the interdigitated electrode is the length of the overlapping area between the fingers on the first bus bar and the fingers on the second bus bar in the first direction, the first direction is the extension direction of the fingers of the interdigitated electrode, the second direction is a direction perpendicular to the first direction, and the size of the release hole is smaller than the length of the aperture of the interdigitated electrode.

[0008] Based on the above technical solution, by arranging release holes between the first bus bar and the second bus bar of the interdigitated electrode, injecting etching material into the release holes and then etching the substrate, the volume of the air cavity after etching can be effectively reduced, thereby improving the mechanical strength and power tolerance of the filter, reducing the size of the filter, and reducing the difficulty of subsequent processing.

[0009] In combination with the first aspect, in certain implementations of the first aspect, a size of the release hole is larger than a width of the finger strip.

[0010] In combination with the first aspect, in some implementations of the first aspect, the value of W is greater than or equal to 10 μm and less than or equal to 150 μm.

[0011] In combination with the first aspect, in some implementations of the first aspect, the value of p is greater than or equal to 600 nm and less than or equal to 10 μm.

[0012] In combination with the first aspect, in certain implementations of the first aspect, a width of the finger stripe is greater than or equal to 200 nm and less than or equal to 2 μm.

[0013] In combination with the first aspect, in certain implementations of the first aspect, the area of ​​the release hole is greater than or equal to 9 μm 2 .

[0014] In combination with the first aspect, in some implementations of the first aspect, the release hole includes a first release hole, which is arranged in the area between the fingers of the interdigitated electrode, and the size of the first release hole in the second direction is smaller than the distance between adjacent fingers of the interdigitated electrode.

[0015] Based on the above technical solution, by arranging the first release holes between the fingers of the interdigital electrodes, the fingers can be effectively supported while the substrate below the interdigital electrode area can be released.

[0016] In combination with the first aspect, in some implementations of the first aspect, the value of x is 0, and in the second direction, adjacent first release holes are separated by a finger of the interdigitated electrode, and the value of p is greater than or equal to 3 μm and less than or equal to 10 μm.

[0017] Based on the above technical solution, first release holes are arranged between adjacent fingers of the interdigitated electrode, and the first release holes are arranged at the midpoint of the aperture of the interdigitated electrode in the first direction, so that when the finger spacing is large, the substrate under the interdigitated electrode area can also be fully released, and the substrate under the non-interdigitated electrode area is not released.

[0018] In combination with the first aspect, in certain implementations of the first aspect, in the second direction, adjacent first release holes are spaced apart by at least two fingers of the interdigital electrodes.

[0019] Based on the above technical solution, the first release holes are arranged at intervals of at least two fingers, so that the arrangement of the first release holes is not too dense, further improving the mechanical strength of the filter.

[0020] In combination with the first aspect, in some implementations of the first aspect, the value of x is 0, and in the second direction, three fingers of the interdigitated electrode are spaced between adjacent first release holes.

[0021] Based on the above technical solution, the first release holes are arranged at intervals of three fingers, and the first release holes are arranged at the midpoint of the aperture of the interdigital electrode in the first direction, so that the arrangement of the first release holes is not too dense, further improving the mechanical strength of the filter.

[0022] In conjunction with the first aspect, in certain implementations of the first aspect, in the second direction, a first distance between the fingers adjacent to the first release hole is greater than a second distance between the adjacent fingers when no first release hole is provided. Based on the above technical solution, by appropriately adjusting the distance between some fingers, a larger first release hole can be accommodated, allowing the substrate beneath the interdigital electrode region to be fully released while preventing the substrate beneath the non-interdigital electrode region from being released.

[0023] In combination with the first aspect, in certain implementations of the first aspect, the value of x is 0, and the value of p is greater than or equal to 600 nm and less than 3 μm.

[0024] Based on the above technical solution, when the distance between the fingers of the interdigital electrode is too close to make it difficult to arrange the first release holes, after appropriately adjusting the distance between some of the fingers, large-sized first release holes can be accommodated, and the first release holes are arranged at the midpoint of the aperture of the interdigital electrode in the first direction, so that the substrate under the interdigital electrode area can also be fully released, and the substrate under the non-interdigital electrode area is not released.

[0025] In combination with the first aspect, in some implementations of the first aspect, the release hole further includes a second release hole, and the second release hole is provided through the fingers of the interdigital electrode.

[0026] Based on the above technical solution, when the distance between the fingers of the interdigitated electrodes is close and it is difficult to arrange the first release hole, the second release hole is set through the fingers of the interdigitated electrodes, so that the substrate under the interdigitated electrode area can also be fully released, and the substrate under the non-interdigitated electrode area is not released.

[0027] In combination with the first aspect, in certain implementations of the first aspect, in the second direction, adjacent second release holes are spaced apart by at least two fingers of the interdigital electrodes.

[0028] Based on the above technical solution, the second release holes are arranged at intervals of at least two fingers, so that the arrangement of the second release holes is not too dense, further improving the mechanical strength of the filter.

[0029] In combination with the first aspect, in some implementations of the first aspect, the value of x is 0, and in the second direction, three fingers of the interdigitated electrode are spaced between adjacent second release holes, and the value of p is greater than or equal to 600 nm and less than 3 μm.

[0030] Based on the above technical solution, the second release holes are arranged at intervals of three fingers, and the second release holes are arranged at the midpoint of the aperture of the interdigital electrode in the first direction, so that the arrangement of the second release holes is not too dense, further improving the mechanical strength of the filter.

[0031] In combination with the first aspect, in some implementations of the first aspect, it further includes: a dielectric layer, the dielectric layer is arranged below the piezoelectric layer, the release hole penetrates the dielectric layer, and the thickness of the dielectric layer is greater than or equal to 100 nm and less than or equal to 2 μm.

[0032] In combination with the first aspect, in some implementations of the first aspect, the method further includes: a bottom electrode layer, wherein the bottom electrode layer is arranged above the substrate, and the release hole passes through the bottom electrode layer.

[0033] In combination with the first aspect, in some implementations of the first aspect, the substrate further includes: a release layer, the release layer is disposed above the substrate, and a thickness of the substrate is greater than or equal to 50 μm and less than or equal to 1000 μm.

[0034] In combination with the first aspect, in certain implementations of the first aspect, the release layer is made of polysilicon.

[0035] In combination with the first aspect, in certain implementations of the first aspect, the release hole is a circular release hole, and a diameter of the circular release hole is greater than or equal to 3.4 μm.

[0036] In combination with the first aspect, in certain implementations of the first aspect, the release hole is an elliptical release hole, and a minor axis length of the elliptical release hole is greater than or equal to 3.4 μm.

[0037] In combination with the first aspect, in some implementations of the first aspect, the release hole is a quadrilateral release hole, and the length of a short side of the quadrilateral release hole is greater than or equal to 3 μm.

[0038] In combination with the first aspect, in some implementations of the first aspect, the release hole is a polygonal release hole.

[0039] In combination with the first aspect, in some implementations of the first aspect, the thickness of the piezoelectric layer is greater than or equal to 100 nm and less than or equal to 1 μm.

[0040] In combination with the first aspect, in some implementations of the first aspect, a thickness of the interdigital electrode is greater than or equal to 50 nm and less than or equal to 1 μm.

[0041] In combination with the first aspect, in some implementations of the first aspect, a plurality of the interdigitated electrodes are included, at least one of the first bus bars is connected to the signal input end, and at least one of the second bus bars is connected to the signal output end.

[0042] In a second aspect, a radio frequency chip is provided, comprising a processor and a filter, wherein the processor is coupled to the filter, and the filter is the filter as described in the first aspect and any possible implementation thereof.

[0043] In a third aspect, an electronic device is provided, including a filter and a circuit board, wherein the filter is arranged on the circuit board, and the filter is the filter as described in the first aspect and any possible implementation thereof.

[0044] In a fourth aspect, a method for preparing a filter is provided, wherein the method is used to prepare the filter as described in the first aspect and any possible implementation thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG1 is a schematic diagram of a framework of an electronic device provided in an embodiment of the present application.

[0046] FIG2 is a schematic diagram of the structure of a filter provided in an embodiment of the present application.

[0047] FIG3 is a cross-sectional schematic diagram of a filter provided in an embodiment of the present application.

[0048] FIG4 is a top view of a filter provided in an embodiment of the present application.

[0049] FIG5 is a top view of another filter provided in an embodiment of the present application.

[0050] FIG6 is a top view of another filter provided in an embodiment of the present application.

[0051] FIG7 is a top view of another filter provided in an embodiment of the present application.

[0052] FIG8 is a top view of another filter provided in an embodiment of the present application.

[0053] FIG9 is a cross-sectional schematic diagram of another filter provided in an embodiment of the present application.

[0054] FIG10 is a cross-sectional schematic diagram of another filter provided in an embodiment of the present application.

[0055] FIG11 is a cross-sectional schematic diagram of another filter provided in an embodiment of the present application.

[0056] FIG12 is a flow chart of a method for preparing a filter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0057] The technical solutions in this application will be described below in conjunction with the accompanying drawings. It should be understood that the specific examples in this specification are only intended to help those skilled in the art better understand the embodiments of this application, and are not intended to limit the scope of the embodiments of this application.

[0058] It should also be understood that the various implementation methods described in this specification can be implemented individually or in combination, and the embodiments of the present application are not limited to this.

[0059] Unless otherwise specified, all technical and scientific terms used in the embodiments of the present application have the same meaning as those commonly understood by those skilled in the art in the art of the present application. The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit the scope of this application.

[0060] The terms "include", "comprising", "having" and variations thereof mean "including but not limited to", unless specifically emphasized otherwise.

[0061] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meanings understood by persons having ordinary skills in the technical field to which this application belongs. In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like, indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting this application.

[0062] Before formally introducing the embodiments of the present application, the terms that may be used in the embodiments of the present application are first explained.

[0063] An interdigital transducer (IDT), also known as an interdigital transducer, is a device consisting of two interlocking comb-shaped metal electrode arrays deposited on the surface of a piezoelectric layer (such as quartz or lithium niobate) to form a periodic structure.

[0064] Bus bar: A bus bar electrode used to connect the IDT interdigital electrode fingers to achieve electrical connection between the IDT interdigital electrode functional area and the outside.

[0065] An embodiment of the present application provides an electronic device. The electronic device is, for example, a consumer electronic product, a home electronic product, a vehicle-mounted electronic product, a financial terminal product, or a communication electronic product. Among them, consumer electronic products include mobile phones, tablet computers, laptop computers, e-readers, personal computers (PCs), personal digital assistants (PDAs), desktop displays, smart wearable products (for example, smart watches, smart bracelets), virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, drones, etc. Home electronic products include smart door locks, televisions, remote controls, refrigerators, rechargeable small household appliances (for example, soymilk machines, sweeping robots), etc. Vehicle-mounted electronic products include car navigation systems, car high-density digital video discs (DVDs), etc. Financial terminal products include automated teller machines (ATMs), self-service terminals, etc. Communication electronic products include communication equipment such as servers, storage devices, radars, and base stations.

[0066] For ease of explanation, the following description uses a mobile phone as an example. As shown in Figure 1, electronic device 1 primarily includes a cover plate 11, a display screen 12, a middle frame 13, and a rear housing 14. The rear housing 14 and display screen 12 are located on either side of the middle frame 13, with the middle frame 13 and display screen 12 disposed within the rear housing 14. The cover plate 11 is disposed on the side of the display screen 12 away from the middle frame 13, with the display surface of the display screen 12 facing the cover plate 11.

[0067] The display screen 12 can be a liquid crystal display (LCD). In this case, the LCD includes a liquid crystal display panel and a backlight module. The LCD panel is disposed between the cover plate 11 and the backlight module, and the backlight module is used to provide light for the LCD panel. The display screen 12 can also be an organic light emitting diode (OLED) display. Since OLED displays are self-luminous, a backlight module is not required.

[0068] The middle frame 13 includes a carrier plate 131 and a frame 132 surrounding the carrier plate 131. The electronic device 1 may further include electronic components such as printed circuit boards (PCBs), batteries, and cameras, which may be disposed on the carrier plate 131.

[0069] The electronic device 1 may also include a system-on-chip (SOC), a radio frequency chip, etc., disposed on a PCB. The PCB is used to carry the system-on-chip, the radio frequency chip, etc., and is electrically connected to the system-on-chip, the radio frequency chip, etc. The radio frequency chip may include components such as a filter and a processor. The processor is used to process various signals, and the filter is an important part of radio frequency signal processing, used to pass signals of specific frequencies while blocking signals of other frequencies.

[0070] An embodiment of the present application provides a filter, which can be applied to the above-mentioned electronic device 1, for example, to the radio frequency chip in the electronic device 1. The filter provided in the embodiment of the present application can be, for example, a low-pass filter, a high-pass filter, a band-pass filter, a band-stop filter or an active filter.

[0071] Of course, the filter provided in the embodiment of the present application is not limited to being integrated in the electronic device 1. The filter can also be a separate component, or the filter can be integrated with components such as a power amplifier into a module (such as a radio frequency device, a radio frequency module, a filter module, etc.), and the filter is coupled to the power amplifier for signal processing and transmission.

[0072] As shown in Figure 2, the filter 10 provided in an embodiment of the present application includes multiple cascaded resonators 100. The multiple resonators 100 can have different resonant frequencies and can be cascaded together in series and parallel. Referring to Figure 2, when the multiple resonators 100 are cascaded together in series and parallel, Figure 2 also illustrates the signal input terminal Vi, the signal output terminal Vo, and the ground terminal GND of the filter 10.

[0073] During the fabrication process of a cavity-type surface acoustic wave filter, release holes must be etched into the device's top surface. Then, an etchant is injected through the holes to partially etch away the substrate, leaving the interdigital electrode region suspended. Currently, the release holes are often placed between the finger tips and the busbar. However, this placement of the release holes can also etch away the substrate in areas other than the interdigital electrodes, resulting in an excessively large air cavity after release, which reduces the device's mechanical strength. Therefore, a filter with a small release cavity and high mechanical strength is needed.

[0074] In view of this, an embodiment of the present application provides a filter, the size of the release cavity of which can be effectively limited, thereby improving the mechanical strength and power tolerance of the device, reducing the difficulty of subsequent processing, and reducing the size of the filter.

[0075] FIG3 is a cross-sectional schematic diagram of a filter provided in an embodiment of the present application.

[0076] As shown in Figure 3, the filter 10 is arranged from bottom to top in the following order: a substrate 101 having an air cavity 1011; a piezoelectric layer 102 located above the substrate; and interdigitated electrodes 103 located above the piezoelectric layer 102. The interdigitated electrodes 103 include a first bus bar 1031 and a second bus bar 1032 that are parallel to each other (not shown in Figure 3; see Figure 4). A release hole 104 is arranged between the first bus bar 1031 and the second bus bar 1032. The release hole 104 passes through the piezoelectric layer 102 and communicates with the air cavity 1011.

[0077] In some embodiments provided herein, the air cavity 1011 of the substrate 101 may be formed by injecting etching material into the substrate 101 through the release hole 104 , and the air cavity 1011 may be an overlap of multiple hemispherical cavities.

[0078] An air cavity 1011 is formed in the substrate 101 below the interdigital electrodes 103 , and the interdigital electrodes 103 are suspended in the air, so that the acoustic wave energy is confined in the piezoelectric layer 102 as much as possible, thereby improving the quality factor of the filter 10 .

[0079] In some embodiments, the finger width of the interdigital electrode 103 may be greater than or equal to 200 nm and less than or equal to 2 μm. For example, the finger width of the interdigital electrode 103 may be 300 nm, 500 nm, 800 nm, 1 μm, 1.5 μm or 1.8 μm.

[0080] In some embodiments, the period length of the interdigital electrodes 103 may be greater than or equal to 1.2 μm and less than or equal to 20 μm. For example, the period length of the interdigital electrodes 103 may be 1.4 μm, 1.6 μm, 2 μm, 3 μm, 5 μm, 10 μm or 15 μm.

[0081] In some embodiments, the material of the substrate 101 may include any one of silicon, silicon carbide, quartz, sapphire, diamond, lithium niobate, lithium tantalate, and the like.

[0082] In some embodiments, the material of the piezoelectric layer 102 may include any one of lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, quartz, and the like.

[0083] In some embodiments, the material of the interdigital electrodes 103 may include any one of metal materials such as aluminum, copper, molybdenum, silver, gold, chromium, ruthenium, rhodium, etc., or any one of alloy materials composed of the above metal materials.

[0084] FIG4 is a top view of a filter provided in an embodiment of the present application.

[0085] Release holes 104 are arranged between the fingers of each interdigital electrode 103 of the filter 10. In the figure, the X direction represents the first direction, and the Y direction represents the second direction. In the figure, p represents half the period length of the interdigital electrode 103, and p satisfies the condition: 600nm≤p≤10μm. In the figure, W represents the length of the aperture of the interdigital electrode 103, and W satisfies the condition: 10μm≤W≤150μm.

[0086] In some embodiments, the value of W may be 15 μm, 20 μm, 50 μm, 75 μm, 100 μm, 120 μm or 140 μm.

[0087] In some embodiments, the value of p can be 700 nm, 800 nm, 1 μm, 1.5 μm, 2.5 μm, 5 μm or 7.5 μm.

[0088] The period length of the interdigital electrodes 103 is twice the sum of the width of a single finger and the distance between adjacent fingers. This period length can be a preset period length determined when designing the interdigital electrodes 103. For example, when there are no release holes 104 between adjacent fingers, the value of p is the sum of the distance between the adjacent fingers and the width of a single finger. Twice p is the period length of the interdigital electrodes 103. The period length of the interdigital electrodes 103 is related to the resonant wavelength of the filter 10 during operation. The length of the overlapping region in the first direction between the fingers on the first bus bar 1031 and the fingers on the second bus bar 1032 is called the aperture length of the interdigital electrodes, as shown by W in FIG4 .

[0089] In the first direction, the distance x between the release hole 104 and the midpoint of the aperture of the interdigital electrode 103 satisfies the condition: x≤0.25W. As shown in Figure 4, x represents the distance between the release hole 104a and the midpoint of the aperture of the interdigital electrode 103. For example, the value of x can be 0, 0.05W, 0.1W, 0.15W or 0.2W.

[0090] Δy represents the distance between two adjacent release holes 104 in the second direction, as shown in FIG4 . Δy should satisfy the following conditions:

[0091] In some embodiments, the area of ​​each release hole 104 is greater than or equal to 9 μm 2 ; The size of the release hole 104 is greater than the width of the finger electrode 103.

[0092] In a possible implementation, the shape of the release hole 104 is circular, and the diameter of the circular release hole 104 is greater than or equal to 3.4 μm.

[0093] In a possible implementation, the shape of the release hole 104 is elliptical, and the minor axis length of the elliptical release hole 104 is greater than or equal to 3.4 μm.

[0094] In a possible implementation, the release hole 104 is in the shape of a quadrilateral, and the length of the short side of the quadrilateral release hole 104 is greater than or equal to 3 μm.

[0095] In a possible implementation, the shape of the release hole 104 is a polygon, and the area of ​​the polygonal release hole 104 is greater than or equal to 9 μm. 2 The shape of the release hole 104 can also be an irregular hole, and the area of ​​the irregular hole is greater than or equal to 9μm 2 .

[0096] As shown in FIG. 4 , the release holes 104 may include first release holes 1041 and second release holes 1042 . The first release holes 1041 are arranged between the fingers of the interdigital electrodes 103 , and the second release holes 1042 are provided through the fingers of the interdigital electrodes 103 .

[0097] In one possible implementation, the filter 10 may be provided with only first release holes 1041 arranged in the area between the fingers of the interdigitated electrodes 103, or may be provided with only second release holes 1042 arranged through the fingers of the interdigitated electrodes 103; the filter 10 may also be provided with first release holes 1041 and second release holes 1042 at the same time, and the embodiments of the present application are not limited to this.

[0098] As shown in FIG. 4 , between the fingers of adjacent interdigital electrodes 103 , there may be multiple or only one release hole 104 .

[0099] In some embodiments, only one first release hole 1041 may be arranged between the fingers of adjacent interdigitated electrodes 103, or three first release holes 1041 may be arranged, or a greater number of first release holes 1041 may be arranged. No first release hole 1041 may be arranged between some fingers, and the embodiments of the present application are not limited to this.

[0100] In some embodiments, only one second release hole 1042 is arranged on the finger strips of the interdigitated electrode 103, or three second release holes 1042 may be arranged, or a greater number of second release holes 1042 may be arranged, and some finger strips may not be arranged with second release holes 1042. The embodiments of the present application are not limited to this.

[0101] As shown in FIG4 , in the second direction, if the distance Δy between adjacent release holes 104 is too small, the release holes 104 in the filter 10 will be arranged too densely, which will reduce the mechanical strength of the filter 10. Since the area of ​​the substrate 101 that can be released by each release hole 104 is limited after the etching material is injected into the release holes 104, if Δy is too large, the substrate 101 will not be fully released, and a suitable air cavity 1011 cannot be formed, which will affect the performance of the filter 10. Therefore, Δy should meet the following conditions: In this way, the filter 10 can have reliable mechanical strength while completely releasing the area of ​​the substrate 101 that needs to be released, so that the interdigital electrode 103 area is suspended.

[0102] Based on the above technical solution, by setting release holes 104 in the partial area between the fingers of the interdigitated electrodes 103 and / or on the fingers, and injecting etching material into the release holes 104 and then etching the substrate 101, the area where the substrate 101 is released can be effectively limited to below the interdigitated electrodes 103, so that the substrate 101 below the non-interdigitated electrodes 103 area is not etched, thereby improving the mechanical strength of the filter 10.

[0103] In some embodiments, the distance between the fingers of the interdigital electrode 103 may be relatively large. In order to fully release the substrate under the interdigital electrode 103, first release holes 1041 may be provided between adjacent fingers. One first release hole 1041 may be provided between adjacent fingers, or multiple first release holes 1041 may be provided. The embodiments of the present application do not limit this.

[0104] In one possible implementation, the position of each first release hole 1041 in the first direction may satisfy x = 0. In this case, the first release hole 1041 is located at the midpoint of the aperture of the interdigital electrode 103. For example, release hole 104b in FIG4 is located at the midpoint of the aperture of the interdigital electrode 103. Alternatively, the position of some first release holes 1041 satisfies x = 0.25W. In this case, the first release holes 1041 may be located near the first bus bar 1031 or near the second bus bar 1032. For example, in FIG4, release hole 104a is located near the second bus bar 1032 and satisfies x = 0.25W in the first direction. Release hole 104c is located near the first bus bar 1031 and also satisfies x = 0.25W in the first direction. It should be understood that the above x = 0.25W is merely an illustrative description; the value of x can be any value that satisfies x ≤ 0.25W, and this is not limited in the embodiments of the present application.

[0105] FIG5 is a top view of another filter provided in an embodiment of the present application.

[0106] As shown in FIG5 , first release holes 1041 are arranged between each finger of the interdigital electrode 103. There is only one first release hole 1041 between each finger. In the first direction, x = 0. In the second direction, adjacent first release holes 1041 are separated by one finger of the interdigital electrode 103. The value of p is greater than or equal to 3 μm and less than or equal to 10 μm.

[0107] Based on the above technical solution, first release holes 1041 are arranged between adjacent fingers, so that when the period length is long, part of the substrate 101 below the interdigital electrodes 103 can be fully released to ensure that the interdigital electrodes 103 can be suspended.

[0108] In some embodiments, the first release holes 1041 are not arranged between every two fingers of the interdigital electrodes 103, but are arranged at intervals of a certain number of interdigital electrodes. For example, the first release holes 1041 can be arranged at intervals of two fingers, three fingers, or more fingers. In the first direction, the position of the first release holes 1041 only needs to satisfy the condition x ≤ 0.25W. In the second direction, the distance between adjacent first release holes 1041 still satisfies the condition:

[0109] In a possible implementation, one first release hole 1041 may be arranged between adjacent fingers, or a plurality of first release holes 1041 may be arranged, which is not limited in the embodiment of the present application.

[0110] FIG6 is a top view of another filter provided in an embodiment of the present application.

[0111] As shown in FIG. 6 , in the first direction, x=0; in the second direction, three fingers of the interdigital electrodes 103 are spaced between adjacent first release holes 1041 .

[0112] The dotted area 1011a in FIG6 represents the area of ​​the air cavity 1011 formed after the etching material of the filter 10 is etched. It can be seen that the air cavity 1011 is mainly formed below the interdigital electrode 103 area, and does not release the substrate 101 below the non-interdigital electrode area. The filter 10 provided in the embodiment of the present application can effectively reduce the volume of the air cavity 1011, improve the mechanical strength of the filter 10, and reduce the size of the filter 10.

[0113] In some embodiments, the fingers of the interdigitated electrode 103 may be arranged relatively densely, and the distance between the fingers is small. In this case, it is difficult to arrange first release holes 1041 of appropriate sizes between the fingers. In order to accommodate larger-sized first release holes 1041 between the fingers of the interdigitated electrode 103 and increase the speed of releasing the etched material, the distance between adjacent fingers with first release holes 1041 can be increased in the second direction, and the first distance between the fingers adjacent to the first release holes 1041 is greater than the second distance between adjacent fingers when no first release holes 1041 are provided. In the first direction, the position of the first release hole 1041 satisfies the condition x≤0.25W. In the second direction, the distance between adjacent first release holes 1041 still satisfies the condition:

[0114] In a possible implementation, one first release hole 1041 may be arranged between adjacent fingers, or a plurality of first release holes 1041 may be arranged, which is not limited in the embodiment of the present application.

[0115] In a possible implementation, the first release holes 1041 may be arranged at intervals of two fingers, or at intervals of three fingers, or at intervals of more fingers, which is not limited in the embodiments of the present application.

[0116] FIG7 is a top view of another filter provided in an embodiment of the present application.

[0117] As shown in FIG7 , in the first direction, x=0; the first distance D1 between adjacent fingers to the first release hole 1041 is greater than the second distance D2 between other fingers when no first release hole 1041 is provided. This arrangement facilitates the accommodation of larger first release holes 1041. In the second direction, the distance between adjacent first release holes 1041 still meets the following conditions: The value of p may be greater than or equal to 600 nm and less than 3 μm.

[0118] It should be understood that in the above technical solution, the distance between the fingers of the interdigital electrode 103 is not completely equal, but this does not mean that the period length of the interdigital electrode 103 has changed. The p value shown in the figure still represents half of the period length of the interdigital electrode 103, or in other words, the sum of the second distance D2 between adjacent fingers without release holes 104 and the width of the fingers is half of the period length of the interdigital electrode 103. In other words, when the distance between adjacent fingers of the interdigital electrode 103 is not completely equal, the value of p is the sum of the second distance D2 and the width of the fingers. Increasing the distance between the fingers of some interdigital electrodes 103 is an adaptive adjustment to accommodate larger-sized first release holes 1041 and will not affect the period length of the interdigital electrode 103. The period length of the interdigital electrode 103 can be a fixed value.

[0119] Based on the above technical solution, by increasing the first distance between fingers adjacent to the first release holes 1041 , larger first release holes 1041 can be arranged between the fingers of the interdigital electrodes 103 , effectively increasing the speed of releasing the substrate.

[0120] In some embodiments, the fingers of the interdigitated electrode 103 may be arranged relatively densely, and the distance between the fingers is small, making it difficult to arrange first release holes 1041 of appropriate size between the fingers. In this case, the second release holes 1042 can be set through the fingers of the interdigitated electrode 103. For example, after the fingers of the interdigitated electrode 103 are cut off, the second release holes 1042 are arranged at the position where the fingers of the interdigitated electrode 103 are cut off. The through setting means that the second release hole 1042 is set after the fingers are completely cut off. In the first direction, the position of the second release hole 1042 satisfies the condition x≤0.25W. In the second direction, the distance between adjacent second release holes 1042 still satisfies the condition:

[0121] In a possible implementation, the second release holes 1042 may be arranged at intervals of two fingers, or at intervals of three fingers, or at intervals of more fingers, which is not limited in the embodiments of the present application.

[0122] In a possible implementation, one second release hole 1042 may be provided through the fingers of the interdigital electrode 103 , or a plurality of second release holes 1042 may be provided through the fingers, which is not limited in the embodiment of the present application.

[0123] FIG8 is a top view of another filter provided in an embodiment of the present application.

[0124] As shown in FIG8 , second release holes 1042 are provided through the fingers of the interdigitated electrodes 103 ; in the first direction, x=0, and in the second direction, the distance between adjacent second release holes 1042 still satisfies the condition: Three fingers of the interdigital electrode 103 are spaced between adjacent second release holes 1042. The value of p is greater than or equal to 600 nm and less than 3 μm.

[0125] Based on the above technical solution, when the p value of the interdigital electrode 103 is small, the second release hole 1042 is arranged through the fingers of the interdigital electrode 103, so that the substrate 101 under the interdigital electrode 103 area can be fully released, and the substrate under the non-interdigital electrode 103 area is not released.

[0126] FIG9 is a side view of another filter provided in an embodiment of the present application.

[0127] As shown in FIG9 , the filter 10 is further provided with a dielectric layer 102 a (or referred to as a dielectric material layer). The dielectric layer 102 a is provided below the piezoelectric layer 102 , and the release hole 104 passes through the dielectric layer 102 a .

[0128] In some embodiments, the material of the dielectric layer 102a may include any one of silicon dioxide, silicon nitride, sapphire, and the like.

[0129] In some embodiments, the dielectric layer 102 a may be prepared by physical vapor deposition (PVD) or chemical vapor deposition (CVD), which is not limited in the present embodiment.

[0130] The dielectric layer 102a can provide electrical isolation between different parts of the filter 10 and can also protect the filter 10 from chemical corrosion.

[0131] Silicon dioxide has good electrical insulation, thermal stability and chemical stability; silicon nitride has strong corrosion resistance and can block impurities during diffusion and injection; sapphire, that is, aluminum oxide, has relatively low leakage current and good thermal / electrical stability.

[0132] FIG10 is a side view of another filter provided in an embodiment of the present application.

[0133] As shown in Figure 10, the substrate 101 of the filter 10 is further provided with a release layer 101a, which is provided above the substrate 101. In this case, the air cavity 1011 is formed by injecting an etching material into the release layer 101a through the release hole 104.

[0134] In one possible implementation, the release layer 101a is made of polysilicon. The release layer 101a is provided to more quickly form air cavities 1011 in the release layer 101a when the etching material is injected into the substrate 101 through the release holes 104. The material of the release layer 101a is related to the choice of etching material; the etching material and the material of the release layer 101a should react easily to accelerate the release process.

[0135] It should be understood that when the substrate 101 is not provided with the release layer 101 a , the air cavity 1011 is directly formed in the substrate 101 ; when the release layer 101 a is provided, the air cavity 1011 is formed in the release layer 101 a .

[0136] FIG11 is a side view of another filter provided in an embodiment of the present application.

[0137] As shown in FIG. 11 , the filter 10 is further provided with a bottom electrode layer 105 . The bottom electrode layer 105 is provided above the substrate 101 , and the release hole 104 passes through the bottom electrode layer 105 .

[0138] It should be understood that when the filter 10 is provided with a release layer 101 a , the bottom electrode layer 105 is provided above the release layer 101 a .

[0139] In some embodiments, the material of the bottom electrode layer 105 may include any one of metal materials such as aluminum, copper, molybdenum, silver, gold, chromium, ruthenium, rhodium, etc., or any one of alloy materials composed of the above metal materials.

[0140] FIG12 is a flow chart of a method for preparing a filter 10 provided in an embodiment of the present application.

[0141] The method is used to prepare any filter described in any of the above embodiments.

[0142] As shown in FIG12 , the preparation method may include:

[0143] S1201: Obtain a substrate.

[0144] In the embodiments provided in the present application, the material used to prepare the substrate 101 may include any one of silicon, silicon carbide, quartz, sapphire, diamond, lithium niobate, lithium tantalate, and the like.

[0145] In some embodiments, the substrate 101 may further include a release layer 101a, and the release layer 101a is located above the substrate 101. The release layer 101a may be made of polysilicon.

[0146] In one possible implementation, a bottom electrode layer 105 may be formed on top of the substrate 101. The material for forming the bottom electrode layer 105 may include any metal material such as aluminum, copper, molybdenum, silver, gold, chromium, ruthenium, rhodium, or any alloy material composed of the above metal materials. It should be understood that when a release layer 101a is formed on top of the substrate 101, the bottom electrode layer 105 is formed on top of the release layer 101a.

[0147] S1202: Prepare a piezoelectric layer above the substrate.

[0148] In some embodiments, a dielectric layer 102 a may be further formed below the piezoelectric layer 102 .

[0149] In some embodiments, the piezoelectric layer 102 and the dielectric layer 102a can be fabricated by PVD or CVD.

[0150] In some embodiments, the material used to prepare the piezoelectric layer 102 may include any one of lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, quartz, etc., and the thickness of the prepared piezoelectric layer 102 is greater than or equal to 100 nm and less than or equal to 1 μm.

[0151] In some embodiments, the material used to prepare the dielectric layer 102a may include any one of silicon dioxide, silicon nitride, sapphire, etc., and the thickness of the prepared dielectric layer 120a is greater than or equal to 100 nm and less than or equal to 2 μm.

[0152] S1203: Prepare a plurality of interdigital electrodes above the piezoelectric layer.

[0153] In some embodiments, the material used to prepare the interdigitated electrode 103 may include any one of metal materials such as aluminum, copper, molybdenum, silver, gold, chromium, ruthenium, rhodium, or any one of alloy materials composed of the above metal materials, and the thickness of the prepared interdigitated electrode 103 is greater than or equal to 50 nm and less than or equal to 1 μm.

[0154] S1204: A release hole is provided between the first bus bar and the second bus bar of the interdigital electrode, and the release hole satisfies the following conditions: in the first direction, the distance x between the release hole and the midpoint of the aperture of the interdigital electrode satisfies the condition: x≤0.25W; in the second direction, the distance Δy between adjacent release holes satisfies the condition: The size of the release hole is smaller than the length of the aperture of the interdigital electrode, and the release hole penetrates the piezoelectric layer.

[0155] Wherein, p is half of the period length of the interdigitated electrode 103, W is the length of the aperture of the interdigitated electrode 103, the length of the aperture of the interdigitated electrode 103 is the length of the overlapping area between the fingers on the first bus bar and the fingers on the second bus bar in the first direction, the first direction is the extension direction of the fingers of the interdigitated electrode 103, and the second direction is a direction perpendicular to the first direction.

[0156] In some embodiments, the release holes 104 may include first release holes 1041 formed between the fingers of the interdigital electrodes 103, or second release holes 1042 formed through the fingers of the interdigital electrodes 103. The first release holes 1041 and the second release holes 1042 may also be provided on the filter 10 at the same time.

[0157] In a possible implementation, the size of the first release hole 1041 opened in this step in the second direction is smaller than the distance between adjacent fingers of the interdigital electrode 103 .

[0158] In a possible implementation, the number of first release holes 1041 opened between adjacent fingers of the interdigital electrode 103 may be one or more; the number of second release holes 1042 opened through the fingers of the interdigital electrode 103 may be one or more.

[0159] In a possible implementation, the area of ​​the release hole 104 opened in this step is greater than or equal to 9 μm 2 .

[0160] In a possible implementation, the release holes 104 opened in this step also meet the following conditions: x=0, in the second direction, adjacent first release holes 1041 are separated by a finger of the interdigital electrode 103 , and the value of p is greater than or equal to 3 μm and less than or equal to 10 μm.

[0161] In a possible implementation, the first release holes 1041 opened in this step further meet the following condition: adjacent first release holes 1041 are spaced apart by at least two fingers of the interdigital electrodes 103 .

[0162] In a possible implementation, the first release holes 1041 opened in this step further meet the following condition: adjacent first release holes 1041 are spaced apart by at least two fingers of the interdigital electrodes 103 .

[0163] In a possible implementation, the first release holes 1041 opened in this step further satisfy the following conditions: the value of x is 0, and three fingers of the interdigital electrodes 103 are spaced between adjacent first release holes 1041 .

[0164] In a possible implementation, the first release holes 1041 opened in this step further meet the following condition: in the second direction, a first distance between fingers adjacent to the first release holes 1041 is greater than a value of p.

[0165] In a possible implementation, the first release hole 1041 opened in this step further satisfies the following conditions: the value of x is 0, and the value of p is greater than or equal to 600 nm and less than 3 μm.

[0166] In a possible implementation, the second release holes 1042 opened in this step further meet the following condition: in the second direction, adjacent second release holes 1042 are spaced apart by at least two fingers of the interdigitated electrode.

[0167] In one possible implementation, the second release holes 1042 opened in this step also meet the following conditions: the value of x is 0, in the second direction, adjacent second release holes 1042 are separated by three fingers of the forked electrode, and the value of p is greater than or equal to 600 nm and less than 3 μm.

[0168] It should be understood that when a dielectric layer 102 a and / or a bottom electrode layer 105 are prepared in the filter 10 , the release hole 104 also penetrates the dielectric layer 102 a and / or the bottom electrode layer 105 .

[0169] S1205: Injecting etching material into the substrate through the release hole, so that an air cavity is formed in the substrate, and the air cavity is connected to the release hole.

[0170] In some embodiments, a release layer 101a is prepared in the filter 10, and the release layer 101a is located above the substrate 101. At this time, an etching material is injected into the release layer 101a through the release hole 104, so that an air cavity 1011 connected to the release hole 104 is formed in the release layer 101a.

[0171] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0172] In the embodiments of this application, the same reference numerals are used to represent the same components or structural members. For identical structural members in the embodiments of this application, only one structural member may be labeled with a reference numeral in the drawings as an example. It should be understood that the same reference numerals apply to other identical structural members. In addition, the components in the drawings are not drawn to scale, and the dimensions and sizes of the structural members shown in the drawings are for illustrative purposes only and should not be construed as limiting the present application.

[0173] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A filter, characterized in that, Comprising: A substrate having an air cavity; A piezoelectric layer located above the substrate; Interdigitated electrodes located above the piezoelectric layer, the interdigitated electrodes including first and second bus bars parallel to each other, and the interdigitated electrodes further including finger bars extending along a first direction from the first and second bus bars; Release holes are arranged between the first bus bar and the second bus bar, the release holes penetrate the piezoelectric layer and communicate with the air cavity; In the first direction, the distance x between the release hole and the midpoint of the aperture of the interdigitated electrode satisfies the following condition: x ≤ 0.25W; In the second direction, the distance Δy between adjacent ones of the release holes satisfies the following condition: Wherein, p is half of the period length of the interdigitated electrode, W is the length of the aperture of the interdigitated electrode, the length of the aperture of the interdigitated electrode is the length of the overlapping region of the finger bars on the first bus bar and the finger bars on the second bus bar in the first direction, the first direction is the extending direction of the finger bars of the interdigitated electrode, the second direction is the direction perpendicular to the first direction, and the size of the release hole is smaller than the length of the aperture of the interdigitated electrode.

2. The filter according to claim 1, characterized in that, The size of the release hole is larger than the width of the finger bar.

3. The filter according to claim 1 or 2, characterized in that, The value of W is greater than or equal to 10 μm and less than or equal to 150 μm.

4. The filter according to any one of claims 1 to 3, characterized in that The value of p is greater than or equal to 600 nm and less than or equal to 10 μm.

5. The filter according to any one of claims 1-4, characterized in that, The width of the finger bar is greater than or equal to 200 nm and less than or equal to 2 μm.

6. The filter according to any one of claims 1-5, characterized in that, The area of the release hole is greater than or equal to 9 μm 2 .

7. The filter according to any one of claims 1-6, characterized in that, The release hole includes a first release hole arranged in the region between the finger bars of the interdigitated electrode, and the size of the first release hole in the second direction is smaller than the distance between adjacent finger bars of the interdigitated electrode.

8. The filter according to claim 7, characterized in that, The value of x is 0, in the second direction, there is a finger bar of the interdigitated electrode between adjacent first release holes, and the value of p is greater than or equal to 3 μm and less than or equal to 10 μm.

9. The filter according to any one of claims 1-8, characterized in that, In the second direction, there are at least two finger bars of the interdigitated electrode between adjacent first release holes.

10. The filter according to claim 9, characterized in that, The value of x is 0, in the second direction, there are three finger bars of the interdigitated electrode between adjacent first release holes.

11. The filter according to any one of claims 1-7, characterized in that, In the second direction, the first distance between the finger bars adjacent to the first release hole is greater than the second distance between adjacent finger bars when the first release hole is not provided.

12. The filter according to claim 11, wherein, The value of x is 0, and the value of p is greater than or equal to 600 nm and less than 3 μm.

13. The filter according to any one of claims 1-7, characterized in that, The release hole further includes a second release hole penetrating through the finger bars of the interdigitated electrode.

14. The filter according to claim 13, wherein In the second direction, there are at least two finger bars of the interdigitated electrode between adjacent second release holes.

15. The filter according to claim 14, wherein The value of x is 0, in the second direction, there are three finger bars of the interdigitated electrode between adjacent second release holes, and the value of p is greater than or equal to 600 nm and less than 3 μm.

16. The filter according to any one of claims 1-15, characterized in that, Further comprising: A dielectric layer, the dielectric layer being disposed below the piezoelectric layer, the release hole penetrating through the dielectric layer, the thickness of the dielectric layer being greater than or equal to 100 nm and less than or equal to 2 μm.

17. The filter according to any one of claims 1-16, characterized in that, Further comprising: A bottom electrode layer, the bottom electrode layer being disposed above the substrate, the release hole penetrating through the bottom electrode layer.

18. The filter according to any one of claims 1-17, characterized in that, The substrate further comprises: a release layer, the release layer being disposed above the substrate, the thickness of the substrate being greater than or equal to 50 μm and less than or equal to 1000 μm.

19. The filter according to any one of claims 1-18, characterized in that, The release hole is a circular release hole, the diameter of the circular release hole being greater than or equal to 3.4 μm; Or, the release hole is an oval release hole, the length of the minor axis of the oval release hole being greater than or equal to 3.4 μm; Or, the release hole is a quadrilateral release hole, the length of the short side of the quadrilateral release hole being greater than or equal to 3 μm; Or, the release hole is a polygonal release hole.

20. The filter according to any one of claims 1-19, characterized in that, The thickness of the piezoelectric layer is greater than or equal to 100 nm and less than or equal to 1 μm.

21. The filter according to any one of claims 1-20, characterized in that, The thickness of the interdigital electrode is greater than or equal to 50 nm and less than or equal to 1 μm.

22. The filter according to any one of claims 1-21, characterized in that, Comprising a plurality of the interdigital electrodes, at least one of the first busbars being connected to a signal input terminal, and at least one of the second busbars being connected to a signal output terminal.

23. A radio frequency chip, characterized in that, Comprising a processor and a filter, the processor being coupled to the filter, the filter being the filter according to any one of claims 1-22.

24. An electronic device, characterized in that, Comprising a filter and a circuit board, the filter being disposed on the circuit board, the filter being the filter according to any one of claims 1-22.

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