Filter, filter manufacturing process and electronic equipment

Abstract

The present application discloses a filter, a manufacturing process of the filter and an electronic device, and relates to the field of integrated circuit technology. The filter comprises a piezoelectric substrate having a first surface and a second surface relative to each other, and the piezoelectric substrate comprises a piezoelectric layer, a silicon dioxide layer, a base layer, a silicon dioxide layer and a piezoelectric layer which are stacked in sequence. A first interdigitated electrode and a first conductive sheet group are arranged on the first surface, and a second interdigitated electrode and a second conductive sheet group are arranged on the second surface, and the first conductive sheet group is electrically connected to the second conductive sheet group. A first cover body is also arranged on the first surface, and a first cavity is formed between the first cover body and the piezoelectric substrate, and the first electrode and the first conductive sheet group are located in the first cavity. A second cover body is also arranged on the second surface, and a second cavity is formed between the second cover body and the piezoelectric substrate, and the second electrode and the second conductive sheet group are located in the second cavity.

Description

Technical Field

[0001] The present application relates to the field of integrated circuit technology, and in particular to a filter, a manufacturing process of the filter, and an electronic device. Background Art

[0002] At present, the trend of miniaturization of terminal equipment is becoming more and more obvious, and the printed circuit board (PCB) in the terminal equipment is also gradually required to be miniaturized, and the packaging size requirements of the components on the PCB are also getting higher and higher. With the application of 5G in terminal equipment, the frequency bands that terminal equipment needs to support are gradually increasing, making the proportion of filters in RF devices higher and higher.

[0003] In the prior art, in the RF front-end module, the filter chip usually accounts for 60% or more, and the filter is mainly integrated in the substrate of the corresponding module in a flat manner, which makes the size of the entire module larger and it is difficult to reduce the packaging size of the entire module. Summary of the invention

[0004] The present application provides a filter, a filter manufacturing process and an electronic device. The filter can form the piezoelectric substrate required for two independent filters in the thickness direction by setting a piezoelectric substrate with a symmetrical stacked structure, thereby forming a double-sided filter. Compared with two separate filters, the area occupied on the PCB can be reduced. When it is applied to a radio frequency module, it is beneficial to reduce the packaging size of the entire radio frequency module.

[0005] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0006] In a first aspect, the present application provides a filter, the filter comprising:

[0007] The piezoelectric substrate has a first surface and a second surface opposite to each other, and the piezoelectric substrate includes a first piezoelectric substrate and a second piezoelectric substrate.

[0008] The first interdigital electrode and the second interdigital electrode are arranged on the first surface, and the second interdigital electrode is arranged on the second surface.

[0009] A first conductive sheet group and a second conductive sheet group, the first conductive sheet group is arranged on the first surface, the second conductive sheet group is arranged on the second surface, and the first conductive sheet group is electrically connected to the second conductive sheet group.

[0010] The first cover is arranged on the first surface of the piezoelectric substrate, and a first cavity is formed between the first cover and the piezoelectric substrate. The first electrode and the first conductive sheet group are located in the first cavity.

[0011] The second cover is arranged on the second surface of the piezoelectric substrate, and a second cavity is formed between the second cover and the piezoelectric substrate. The second electrode and the second conductive sheet group are located in the second cavity.

[0012] The first piezoelectric substrate, the first interdigital electrodes, the first conductive sheet group and the first cover form a first filter, and the second piezoelectric substrate, the second interdigital electrodes, the second conductive sheet group and the second cover form a second filter.

[0013] On this basis, by providing a piezoelectric substrate composed of a first piezoelectric substrate and a second piezoelectric substrate, and providing a first interdigital electrode and a second interdigital electrode, a first conductive sheet group and a second conductive sheet group, a first cover and a second cover on both sides of the piezoelectric substrate, the filter can form a double-sided filter. By providing an electrical connection between the first conductive sheet group and the second conductive sheet group, the two independent filters formed on both sides of the filter can be connected to the interface on the PCB.

[0014] In a possible design of the first aspect, the first conductive sheet group includes a plurality of first conductive sheets, and the second conductive sheet group includes a plurality of second conductive sheets; each first conductive sheet corresponds to and is electrically connected to a second conductive sheet. The number of the first conductive sheets is less than or equal to the number of the second conductive sheets,

[0015] On this basis, by setting each first conductive sheet to correspond to and be electrically connected to a second conductive sheet, the first conductive sheet and the second conductive sheet can be connected to the interface on the substrate, ensuring that the first filter and the second filter can be connected to the radio frequency circuit. Among them, when the number of first conductive sheets is less than or equal to the number of second conductive sheets, each first conductive sheet can have a corresponding second conductive sheet, and each first conductive sheet can be connected to its corresponding second conductive sheet. When the number of first conductive sheets is greater than the number of second conductive sheets, the first conductive sheets of the same type can be electrically connected first, and then one of the first conductive sheets can be connected to the second conductive sheet, that is, it is ensured that each first conductive sheet can be electrically connected to a second conductive sheet.

[0016] In a possible design of the first aspect, through holes are provided on the piezoelectric substrate, the number of the through holes is the same as the number of the first conductive sheets, the first conductive sheet and the second conductive sheet are respectively provided at both ends of the through holes, and the first conductive sheet and the second conductive sheet are electrically connected through the conductor in the through hole.

[0017] On this basis, by setting a through hole on the piezoelectric substrate and setting a conductor in the through hole, the electrical connection between the first conductive sheet and the second conductive sheet can be realized inside the piezoelectric substrate. Among them, the second conductive sheet can be connected to the interface on the PCB, and the first conductive sheet is connected to the interface on the PCB by electrically connecting the second conductive sheet, without setting other connection lines. After the double-sided filter is set on the PCB, both the first filter and the second filter can be connected to the radio frequency circuit.

[0018] In a possible design of the first aspect, the piezoelectric substrate includes a first piezoelectric layer, a passivation layer, and a second piezoelectric layer stacked in sequence, the acoustic impedance of the first piezoelectric layer is different from the acoustic impedance of the passivation layer, and the acoustic impedance of the second piezoelectric layer is different from the acoustic impedance of the passivation layer. The first piezoelectric layer and the passivation layer form a first piezoelectric substrate, and the second piezoelectric layer and the passivation layer form a second piezoelectric substrate.

[0019] This design method provides a specific design method for the piezoelectric substrate. By setting the acoustic impedance of two adjacent material layers to be different, it is beneficial to improve the Q value of the first piezoelectric substrate and the second piezoelectric substrate. By setting the piezoelectric substrate to be symmetrical in form, the first piezoelectric substrate and the second piezoelectric substrate have the same material layer and can both become independent piezoelectric substrates. It should be noted that since the thickness of the first piezoelectric layer and the second piezoelectric layer are not necessarily the same, the piezoelectric substrate is not necessarily symmetrical in structure.

[0020] In a possible design of the first aspect, the acoustic impedance of the passivation layer is lower than the acoustic impedance of the first piezoelectric layer, and the temperature drift coefficient of the first piezoelectric substrate is smaller than the temperature drift coefficient of the first piezoelectric layer. Furthermore, the acoustic impedance of the passivation layer is lower than the acoustic impedance of the second piezoelectric layer, and the temperature drift coefficient of the second piezoelectric substrate is smaller than the temperature drift coefficient of the second piezoelectric layer.

[0021] On this basis, by setting the acoustic impedance of the passivation layer to be different from that of the first piezoelectric layer and the second piezoelectric layer, it is beneficial to improve the Q value of the first filter and the second filter. By setting the passivation layer, the temperature drift coefficients of the first piezoelectric substrate and the second piezoelectric substrate are reduced, which is beneficial to improve the temperature drift characteristics of the first filter and the second filter. Among them, the temperature drift coefficient has positive and negative, so the above-mentioned temperature drift coefficient size comparison refers to the size comparison of the absolute value of its temperature drift coefficient, that is, the absolute value of the temperature drift coefficient of the first piezoelectric substrate is smaller than the absolute value of the temperature drift coefficient of the first piezoelectric layer. The absolute value of the temperature drift coefficient of the second piezoelectric substrate is smaller than the absolute value of the temperature drift coefficient of the second piezoelectric layer. The temperature drift coefficient of the first piezoelectric substrate is smaller than the temperature drift coefficient of the first piezoelectric layer, which means that after the passivation layer is added, the piezoelectric substrate has better temperature drift characteristics than when the passivation layer is not added. For example, the piezoelectric substrate formed by the first piezoelectric layer and the passivation layer has better temperature drift characteristics than the piezoelectric substrate formed by only the first piezoelectric layer.

[0022] In a possible design of the first aspect, the piezoelectric substrate includes a first piezoelectric layer, a first passivation layer, a base layer, a second passivation layer, and a second piezoelectric layer stacked in sequence, and the acoustic impedances of two adjacent layers are different. The first piezoelectric layer, the first passivation layer, and the base layer form a first piezoelectric substrate, and the second piezoelectric layer, the second passivation layer, and the base layer form a second piezoelectric substrate.

[0023] On this basis, this design method provides another specific design method for the piezoelectric substrate. By setting multiple material layers to form a piezoelectric substrate, the performance of the piezoelectric substrate can be improved by material selection. By setting the acoustic impedance between two adjacent material layers to be different, the reflectivity of the surface acoustic wave in the piezoelectric substrate can be improved, leakage can be reduced, and the Q value of the first piezoelectric substrate and the second piezoelectric substrate can be improved. The different acoustic impedances between two adjacent layers refer to: the acoustic impedance between the first piezoelectric layer and the first passivation layer is different, the acoustic impedance between the first passivation layer and the base layer is different, the acoustic impedance between the base layer and the second passivation layer is different, and the acoustic impedance between the second passivation layer and the second piezoelectric layer is different.

[0024] In a possible design of the first aspect, the acoustic impedance of the first passivation layer is lower than the acoustic impedance of the first piezoelectric layer, and the acoustic impedance of the substrate layer is higher than the acoustic impedance of the first passivation layer. The acoustic impedance of the second passivation layer is lower than the acoustic impedance of the second piezoelectric layer, and the acoustic impedance of the substrate layer is higher than the acoustic impedance of the second passivation layer.

[0025] On this basis, this example gives the specific size of the acoustic impedance between two adjacent layers. By setting the acoustic impedance between two adjacent material layers to be different, the reflectivity of the surface acoustic wave in the piezoelectric substrate can be improved, leakage can be reduced, and the Q value of the first piezoelectric substrate and the second piezoelectric substrate can be improved.

[0026] In a possible design manner of the first aspect, the material of the first piezoelectric layer and the second piezoelectric layer is lithium tantalate or lithium niobate.

[0027] In a possible design manner of the first aspect, the material of the first passivation layer and the second passivation layer is silicon dioxide.

[0028] In a possible design manner of the first aspect, the material of the base layer is one of silicon, aluminum oxide or silicon carbide.

[0029] In a second aspect, the present application provides a manufacturing process of a filter, wherein the filter includes a substrate layer, and the manufacturing process of the filter includes:

[0030] A piezoelectric substrate is generated on the base layer, and the piezoelectric substrate includes a first piezoelectric layer, a first passivation layer, a base layer, a second passivation layer, and a second piezoelectric layer stacked in sequence. A first conductive sheet group and a first interdigital electrode are arranged on the first piezoelectric layer; and a first cover is bonded to the first piezoelectric layer. Through an etching process, a through hole is opened on the piezoelectric substrate, and a conductor is arranged in the through hole. A second conductive sheet group and a second interdigital electrode are arranged on the second piezoelectric layer; and a second cover is arranged on the second piezoelectric layer.

[0031] This manufacturing process provides a specific implementation method of the filter provided in this application.

[0032] In a possible design of the second aspect, a piezoelectric substrate is generated on a base layer, comprising:

[0033] Passivation layers are deposited on both sides of the substrate layer to generate a first passivation layer and a second passivation layer; a first piezoelectric layer is bonded on the first passivation layer, and a second piezoelectric layer is bonded on the second passivation layer.

[0034] In a possible design of the second aspect, a through hole is formed on the piezoelectric substrate, including:

[0035] A mask layer is provided on the first piezoelectric layer, and an opening is provided on the mask layer, and the size of the opening is the same as the size of the through hole. The first piezoelectric layer is etched through the opening using a first etching gas. The first passivation layer, the base layer, and the second passivation layer are etched through the opening using a second etching gas. The second piezoelectric layer is etched through the opening using the first etching gas to generate a through hole.

[0036] The first etching gas refers to a gas that can etch the first piezoelectric layer and the second piezoelectric layer, such as a gas that can etch lithium tantalate or lithium niobate. The second etching gas refers to a gas that can etch the first passivation layer, the base layer, and the second passivation layer, such as a gas that can etch silicon dioxide and silicon.

[0037] In a possible design of the second aspect, a mask layer is provided on the second piezoelectric layer, and an opening is provided on the mask layer, and the size of the opening is the same as the size of the through hole. The second piezoelectric layer is etched through the opening using a first etching gas. The second passivation layer, the base layer, and the first passivation layer are etched through the opening using a second etching gas. The first piezoelectric layer is etched through the opening using a first etching gas to generate a through hole.

[0038] In a possible design of the second aspect, a conductor is arranged in the through hole, including:

[0039] A magnetron sputtering process is used to form a conductive layer in the through hole, and an electroplating process is used to form a conductor on the conductive layer. Alternatively, a chemical plating process is used to form a conductive layer in the through hole, and an electroplating process is used to form a conductor on the conductive layer.

[0040] In a third aspect, the present application provides a manufacturing process for a filter, the filter comprising a first piezoelectric substrate, the first piezoelectric substrate comprising a first piezoelectric layer, a first passivation layer and a base layer arranged in sequence, the manufacturing process of the filter comprising: arranging a first conductive sheet group and a first interdigitated electrode on the first piezoelectric layer; bonding a first cover body on the first piezoelectric layer. A second passivation layer is deposited on the other side of the base layer, and a second piezoelectric layer is bonded on the second passivation layer to generate a piezoelectric substrate, the piezoelectric substrate comprising a first piezoelectric layer, a first passivation layer, a base layer, a second passivation layer and a second piezoelectric layer. Through an etching process, a through hole is opened on the piezoelectric substrate, and a conductor is arranged in the through hole. A second conductive sheet group and a second interdigitated electrode are arranged on the second piezoelectric layer, and a second cover body is arranged on the second piezoelectric layer.

[0041] In a fourth aspect, the present application provides an electronic device, comprising one or more radio frequency modules, and the filter in the first aspect and any possible design thereof, wherein the filter is arranged in the radio frequency module.

[0042] It can be understood that the beneficial effects that can be achieved by the electronic device provided by the fourth aspect provided above can refer to the beneficial effects in the first aspect and any possible design method thereof, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of the internal structure of a radio frequency module in a terminal device provided in an embodiment of the present application;

[0044] Figure 2 A schematic diagram of the structure of a filter provided in an embodiment of the present application;

[0045] Figure 3 A schematic diagram of the structure of another filter provided in an embodiment of the present application;

[0046] Figure 4 A schematic diagram of the structure of another filter provided in an embodiment of the present application;

[0047] Figure 5 One of the flow charts of a manufacturing process of the filter provided in an embodiment of the present application;

[0048] Figure 6 A second flowchart of a manufacturing process of a filter provided in an embodiment of the present application;

[0049] Figure 7Another manufacturing process flow chart of the filter provided in the embodiment of the present application;

[0050] Figure 8 A process flow chart of providing a through hole on a piezoelectric substrate of a filter provided in an embodiment of the present application.

[0051] 100-filter; 101-first cavity; 102-second cavity;

[0052] 110-piezoelectric substrate; 120-first conductive sheet; 130-second conductive sheet; 140-first interdigital electrode; 150-second interdigital electrode; 160-first cover; 170-second cover; 180-conductor; 190-conductive column;

[0053] 111 - first piezoelectric layer; 112 - second piezoelectric layer; 113 - passivation layer; 114 - first passivation layer; 115 - second passivation layer; 116 - base layer; 117 - through hole; 118 - support layer; 119 - mask layer;

[0054] 161-connection structure; 162-sealing structure. DETAILED DESCRIPTION

[0055] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0056] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0057] In the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0058] It should be understood that the terms used in the description of the various examples herein are only for describing specific examples and are not intended to be limiting. As used in the description of the various examples, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0059] In this application, "at least one" means one, two or more, and "more" means more than two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0060] It should also be understood that the term "and / or" used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term "and / or" is a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0061] It should also be understood that in the present application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a sliding connection, a detachable connection, or an integral connection, etc.; it can be a direct connection or an indirect connection through an intermediate medium.

[0062] It should also be understood that the term “comprise” (also known as “includes,” “including,” “comprises” and / or “comprising”) when used in this specification specifies the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0063] It should be understood that the "one embodiment", "another embodiment", "a possible design" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment or implementation are included in at least one embodiment of the present application. Therefore, "in one embodiment of the present application" or "in another embodiment of the present application", "a possible design" appearing in various places throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner.

[0064] With the development of technology, the trend of miniaturization of terminal equipment is becoming more and more obvious. The PCB in the terminal equipment also needs to be miniaturized, and the packaging size requirements of the components on the PCB are getting higher and higher. With the application of 5G in terminal equipment, the frequency bands that the terminal equipment needs to support are gradually increasing, making the proportion of filters in RF devices higher and higher. That is, in the RF module of the terminal equipment, there are more and more filters on the substrate of the module.

[0065] In some existing terminal devices, in the RF front-end module, the filter chip usually accounts for more than 60%, and the filter is mainly integrated in the substrate of the corresponding module in a flat manner. Figure 1 , Figure 1 The internal structure diagram of a radio frequency module in a terminal device provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, the RF module includes a substrate, a low noise amplifier (LNA), a switch and a plurality of filters arranged on the substrate, wherein the plurality of filters are laid flat on the substrate. When the number of filters is large, the use of such a laid-out design will occupy more substrate area, resulting in a larger size of the entire RF module, making it difficult to reduce the package size of the entire module. In addition, in the filter discrete module, triplexers and quadplexers are also mainly realized by increasing the chip area or the number of chips. Increasing the chip area or increasing the number of chips will cause the package size of the module to become larger.

[0066] In order to solve the above technical problems, an embodiment of the present application provides a filter, which is applied to electronic devices. The filter forms a double-sided filter per unit area by setting the piezoelectric substrate as a stacked structure that is symmetrical up and down, and making electrodes and conductive sheet groups on the upper and lower surfaces of the piezoelectric substrate respectively. Compared with traditional filters, the double-sided filter occupies the same area on the substrate, but can realize the functions of two filters. When the above-mentioned double-sided filter is applied to a radio frequency module, when the radio frequency module has multiple filters, the space occupied by the multiple filters can be reduced, thereby reducing the size of the entire radio frequency module to reduce the packaging size of the entire device.

[0067] Based on the above-mentioned improvement ideas, the embodiments of the present application are described in detail below in combination with the accompanying drawings. Before introducing the embodiments of the present application, the application scenarios of the present application are first introduced.

[0068] The embodiment of the present application provides an electronic device, which includes one or more radio frequency modules, and the radio frequency module includes multiple filters. Specifically, the electronic device can be a user equipment (UE) or a terminal device (terminal), for example, the electronic device can be a mobile phone, a tablet computer (portable android device, PAD), a personal digital assistant (personal digital assistant, PDA), a handheld device with wireless communication function, a computing device, a vehicle-mounted device, a wearable device, a virtual reality (virtual reality, VR) terminal device, an augmented reality (augmented reality, AR) terminal device, a wireless terminal in industrial control (industrial control), a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in smart grid (smart grid), a wireless terminal in transportation safety (transportation safety), a wireless terminal in a smart city (smart city), a wireless terminal in a smart home (smart home), and other mobile terminals or fixed terminals. The form of the electronic device in the embodiment of the present application is not specifically limited.

[0069] Taking a mobile phone as an example of an electronic device, generally speaking, a mobile phone includes multiple RF modules, for example, a mobile phone includes multiple RF front-end modules. The RF front-end module is a device that integrates two or more discrete devices such as RF switches, low-noise amplifiers, filters, duplexers, and power amplifiers into one module, thereby improving integration and RF performance and miniaturizing the size. According to the different types of integrated devices, the main antenna RF link can be divided into: FEMiD (integrated RF switches, filters, and duplexers), PAMiD (integrated multi-mode multi-band power amplifiers and FEMiD), LPAMiD (integrated low-noise amplifiers, multi-mode multi-band power amplifiers and FEMiD), etc.; the diversity antenna RF link can be divided into: DiFEM (integrated RF switches and filters), LFEM (integrated RF switches, low-noise amplifiers and filters), etc.

[0070] The RF front-end module includes a large number of filters. In order to reduce the package size of the RF front-end module, an embodiment of the present application provides a filter. Figure 2 , Figure 2 A schematic diagram of the structure of a filter provided in an embodiment of the present application. Figure 2As shown, the filter includes a piezoelectric substrate 110 and interdigital electrodes (i.e., interdigital transducers (IDT)) and a conductive sheet assembly cover disposed on the piezoelectric substrate 110. Specifically, the piezoelectric substrate 110 has a first surface ( Figure 2 The upper surface shown in ) and the second surface ( Figure 2 The interdigital electrodes include a first interdigital electrode 140 and a second interdigital electrode 150 . The first interdigital electrode 140 is disposed on a first surface of the piezoelectric substrate 110 , and the second interdigital electrode 150 is disposed on a second surface of the piezoelectric substrate 110 .

[0071] The conductive sheet group includes a first conductive sheet group and a second conductive sheet group, wherein the first conductive sheet group is disposed on the first surface of the piezoelectric substrate 110, the second conductive sheet group is disposed on the second surface of the piezoelectric substrate 110, and the first conductive sheet group is electrically connected to the second conductive sheet group. The cover includes a first cover 160 and a second cover 170, the first cover 160 is disposed on the first surface of the piezoelectric substrate 110, and a first cavity 101 is formed between the first cover 160 and the piezoelectric substrate 110, and the first electrode and the first conductive sheet group are located in the first cavity 101. The second cover 170 is disposed on the second surface of the piezoelectric substrate 110, and a second cavity 102 is formed between the second cover 170 and the piezoelectric substrate 110, and the second electrode and the second conductive sheet group are located in the second cavity 102.

[0072] In the embodiment of the present application, by providing interdigitated electrodes and conductive sheet groups on both surfaces of the piezoelectric substrate 110, the first interdigitated electrodes 140, the first conductive sheet group and the piezoelectric substrate 110 on the first surface form a first filter, and the second interdigitated electrodes 150, the second conductive sheet group and the piezoelectric substrate 110 on the second surface form a second filter, that is, the filter provided in the embodiment of the present application is a double-sided filter. In the embodiment of the present application, by making electrodes and conductive sheet groups on the upper and lower surfaces of the piezoelectric substrate 110 respectively, the filter can form a double-sided filter per unit area. Compared with the traditional filter, the double-sided filter occupies the same area on the substrate, but can realize the functions of two filters. The space occupied by the filter in the RF front-end module can be effectively reduced, which is conducive to reducing the overall size of the RF front-end module. Since the filter is generally arranged on the substrate, the first surface and the second surface of the filter are both provided with conductive sheet groups, and the filter usually has only one side that can be connected to the substrate, that is, only the conductive sheet group on one side can be directly connected to the relevant interface on the substrate. By electrically connecting the first conductive sheet group and the second conductive sheet group, the first conductive sheet group and the second conductive sheet group can be electrically connected to the relevant interface on the substrate, so that the first filter and the second filter can be connected to the radio frequency circuit in the electronic device, ensuring that the first filter and the second filter can play related roles.

[0073] By arranging the first cover 160 on the first surface of the piezoelectric substrate 110, the first cover 160 and the first surface of the piezoelectric substrate 110 form a cavity structure, which facilitates the arrangement of devices such as the first interdigital electrode 140 and the first conductive sheet group on the first surface. The first cover 160 can be used as a support structure of the filter during manufacturing, and can also be used to withstand injection molding pressure during packaging to provide protection for the structure in the first filter, or to be connected to the substrate to support the filter and provide protection for the first interdigital electrode 140 and the first conductive sheet group on the first filter.

[0074] By arranging the second cover 170 on the second surface of the piezoelectric substrate 110, the second cover 170 and the second surface of the piezoelectric substrate 110 form a cavity structure, which facilitates the arrangement of devices such as the second interdigital electrodes 150 and the second conductive sheet group on the second surface. The second cover 170 can be used as a supporting structure of the second filter during packaging, and can be used to provide support for the packaging material, or to be connected to the substrate to support the filter, thereby providing protection for the second interdigital electrodes 150 and the second conductive sheet group on the second filter.

[0075] It should be noted that the piezoelectric substrate 110 in the embodiment of the present application is a whole, which can be used as the substrate of the first filter or the substrate of the second filter. For the convenience of understanding, the piezoelectric substrate 110 can be understood as two parts, one part is the piezoelectric substrate 110 part used as the first filter, called the first piezoelectric substrate; the other part is the piezoelectric substrate 110 part used as the second filter, called the second piezoelectric substrate. The first piezoelectric substrate and the second piezoelectric substrate are structurally a whole, and some structures of the first piezoelectric substrate and the second piezoelectric substrate can be shared. Among them, the first piezoelectric substrate and the second piezoelectric substrate can have the same structure. It can also be a different structure. The structure of the piezoelectric substrate 110 will be described in detail below.

[0076] refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of another filter provided in an embodiment of the present application. Figure 3 As shown, the piezoelectric substrate 110 includes a first piezoelectric layer 111, a passivation layer 113, and a second piezoelectric layer 112 which are sequentially stacked. The passivation layer 113 is disposed between the first piezoelectric layer 111 and the second piezoelectric layer 112. The sequentially stacked arrangement in the embodiment of the present application refers to Figure 3 From top to bottom, a first piezoelectric layer 111, a passivation layer 113, and a second piezoelectric layer 112 are sequentially arranged. The first piezoelectric layer 111 and the passivation layer 113 form a first piezoelectric substrate, and the second piezoelectric layer 112 and the passivation layer 113 form a second piezoelectric substrate. The passivation layer 113, as a common material layer of the first piezoelectric substrate and the second piezoelectric substrate, reduces the thickness of the entire filter in the thickness direction while ensuring the functions of the first filter and the second filter, which is conducive to reducing the package size of the entire filter.

[0077] Among them, the acoustic impedance of the passivation layer 113 is different from the acoustic impedance of the first piezoelectric layer 111, and the larger the difference between the two, the better. Moreover, the acoustic impedance of the passivation layer 113 is also different from the acoustic impedance of the second piezoelectric layer 112, and the larger the difference between the two, the better. Specifically, the acoustic impedance of the passivation layer 113 can be set to be greater than the acoustic impedance of the first piezoelectric layer 111, or the acoustic impedance of the passivation layer 113 can be set to be less than the acoustic impedance of the first piezoelectric layer 111. The acoustic impedance of the passivation layer 113 can be set to be greater than the acoustic impedance of the second piezoelectric layer 112, or the acoustic impedance of the passivation layer 113 can be set to be less than the acoustic impedance of the second piezoelectric layer 112. In the embodiment of the present application, the acoustic impedance of the passivation layer 113 is less than the acoustic impedance of the first piezoelectric layer 111, and the acoustic impedance of the passivation layer 113 is less than the acoustic impedance of the second piezoelectric layer 112.

[0078] In the embodiment of the present application, the filter mainly refers to an acoustic filter, which can be divided into a surface acoustic wave (SAW) filter and a bulk acoustic wave (BAW) filter according to different structures. In the process of propagation, the surface acoustic wave will leak in the direction of the substrate (the direction from the first piezoelectric layer 111 to the passivation layer 113, or the direction from the second piezoelectric layer 112 to the passivation layer 113). If there is a material interface on the piezoelectric substrate 110, the wave will be reflected at the interface due to the different acoustic impedances of the two materials; the greater the difference in acoustic impedance between the two materials, the stronger the reflection, so that the energy of the wave will be limited to the vicinity of the first piezoelectric layer 111 or the second piezoelectric layer 112, which is conducive to reducing energy leakage and improving the Q value of the piezoelectric substrate 110. The higher the Q value of the filter, the better the filtering function of the filter can be achieved.

[0079] The basic principle of SAW filter is to convert wireless signal into acoustic signal propagating on the surface of medium by piezoelectric effect at the input end, and convert acoustic signal into wireless signal by inverse piezoelectric effect at the output end. A basic SAW filter is composed of piezoelectric material and two interdigital transducers (IDT). The IDT at the input end converts electrical signal into acoustic wave, and the acoustic wave propagates laterally on the surface of SAW filter substrate in the form of standing wave. The acoustic wave received by IDT at the output end is converted into electrical signal output, thus achieving filtering.

[0080] By arranging different material layers in the piezoelectric substrate 110, since different material layers have different acoustic impedances, the surface acoustic wave will not lose too much energy when propagating between different material layers, which is beneficial to improving the Q value of the filter. Specifically, when the surface acoustic wave propagates in the first piezoelectric layer 111, it will cause leakage in the direction from the first piezoelectric layer 111 to the passivation layer 113, but due to the different acoustic impedances between the first piezoelectric layer 111 and the passivation layer 113, the surface acoustic wave will be reflected at the contact interface between the first piezoelectric layer 111 and the passivation layer 113. The greater the difference in acoustic impedance between the first piezoelectric layer 111 and the passivation layer 113, the stronger the reflection and the less energy leakage generated. Since the first cavity 101 is formed between the first piezoelectric layer 111 and the first cover body 160, the medium contacted by the other side of the first piezoelectric layer 111 is air. Since the acoustic impedance between the first piezoelectric layer 111 and the air is also different, the surface acoustic wave will be reflected on the other side of the first piezoelectric layer 111, that is, on the first surface of the piezoelectric substrate 110, thereby avoiding a large amount of energy leakage.

[0081] Similarly, one side of the second piezoelectric layer 112 is in contact with the passivation layer 113, and the other side is in contact with the air in the second cavity 102, and the acoustic impedance of the second piezoelectric layer 112 is different from the acoustic impedance of the passivation layer 113, and is also different from the acoustic impedance of the air. Therefore, when the surface wave propagates in the second piezoelectric layer 112, the energy loss during the propagation process can be reduced due to the passivation layer 113 and the air on both sides of the second piezoelectric layer 112. The greater the difference between the acoustic impedance of the second piezoelectric layer 112 and the acoustic impedance of the passivation layer 113 and the air, the greater the Q value of the second filter and the smaller the energy loss.

[0082] In one embodiment of the present application, the temperature drift coefficient of the first piezoelectric substrate is smaller than the temperature drift coefficient of the first piezoelectric layer 111, and the temperature drift coefficient of the second piezoelectric substrate is smaller than the temperature drift coefficient of the second piezoelectric layer 112. The temperature drift coefficient has positive and negative sides, so the above-mentioned temperature drift coefficient size comparison refers to the size comparison of the absolute value of the temperature drift coefficient, that is, the absolute value of the temperature drift coefficient of the first piezoelectric substrate is smaller than the absolute value of the temperature drift coefficient of the first piezoelectric layer. The absolute value of the temperature drift coefficient of the second piezoelectric substrate is smaller than the absolute value of the temperature drift coefficient of the second piezoelectric layer. The temperature drift coefficient of the first piezoelectric substrate is smaller than the temperature drift coefficient of the first piezoelectric layer, which means that after the passivation layer is added, the piezoelectric substrate has better temperature drift characteristics than when the passivation layer is not added. For example, the piezoelectric substrate formed by the first piezoelectric layer and the passivation layer has better temperature drift characteristics than the piezoelectric substrate formed by only the first piezoelectric layer.

[0083] The change of semiconductor device parameters caused by temperature change is the main reason for zero drift, so zero drift is also called temperature drift, or temperature drift for short. The temperature drift coefficient can reflect the extent to which the filter is affected by temperature. The temperature characteristics of the filter are an important parameter to measure the performance of the filter. The temperature drift of the filter can affect the insertion loss within the band. The insertion loss and ripple will increase, and the out-of-band suppression will also deteriorate. Extremes may directly affect the performance.

[0084] The first piezoelectric substrate refers to a structure formed by the first piezoelectric layer 111 and the passivation layer 113, and the second piezoelectric layer 112 refers to a structure formed by the second piezoelectric layer 112 and the passivation layer 113. The temperature drift coefficient includes the coefficient of thermal expansion (CTE) and the temperature coefficient of elasticity (TCE), wherein the coefficient of thermal expansion refers to the expansion and contraction of an object due to temperature changes, and its change ability is the change in length value caused by unit temperature change under constant pressure. The temperature coefficient of elasticity can characterize the influence of temperature changes on the propagation of surface waves in the piezoelectric substrate 110. The smaller the temperature coefficient of elasticity, the smaller the influence of temperature changes.

[0085] By providing a passivation layer 113 between the first piezoelectric layer 111 and the second piezoelectric layer 112, the temperature drift coefficient of the first piezoelectric substrate and the second piezoelectric substrate can be adjusted by selecting the material of the passivation layer 113, such as silicon dioxide, so as to improve the temperature drift characteristics of the filter and enhance the performance of the filter.

[0086] In one embodiment of the present application, the first piezoelectric layer 111 can be made of lithium tantalate (LiTaO3, LT for short) or lithium niobate (LiNbO3, LN for short), and the second piezoelectric layer 112 can also be made of lithium tantalate or lithium niobate. Both lithium tantalate crystals and lithium niobate crystals have excellent piezoelectric, thermoelectric, photoelectric and other properties. The passivation layer 113 can be made of silicon dioxide (SiO2). The acoustic impedance difference between silicon dioxide and lithium tantalate or lithium niobate is large, which can reduce the leakage of energy in the filter, improve the Q value of the filter, and thus improve the performance of the filter. In addition, due to the presence of the passivation layer 113 made of silicon dioxide, silicon dioxide has good temperature drift characteristics, which can achieve the reverse superposition of the temperature drift coefficients of the first piezoelectric substrate and the second piezoelectric substrate, thereby improving the temperature drift characteristics of the entire filter.

[0087] In one embodiment of the present application, another piezoelectric substrate 110 is provided. Figure 4 , Figure 4 A schematic diagram of the structure of another filter provided in an embodiment of the present application. Figure 4 As shown, the piezoelectric substrate 110 includes a first piezoelectric layer 111, a first passivation layer 114, a base layer 116, a second passivation layer 115 and a second piezoelectric layer 112 which are stacked in sequence. The first piezoelectric layer 111, the first passivation layer 114 and the base layer 116 form a first piezoelectric substrate, and the second piezoelectric layer 112, the second passivation layer 115 and the base layer 116 form a second piezoelectric substrate.

[0088] The first passivation layer 114 is disposed between the first piezoelectric layer 111 and the base layer 116, and the second passivation layer 115 is disposed between the second piezoelectric layer 112 and the base layer 116. Figure 4 From top to bottom, the first piezoelectric layer 111, the first passivation layer 114, the base layer 116, the second passivation layer 115 and the second piezoelectric layer 112 are sequentially arranged. The base layer 116 is a common material layer of the first piezoelectric substrate and the second piezoelectric substrate. On the basis of ensuring the functions of the first filter and the second filter, the thickness of the entire filter in the thickness direction is reduced, which is conducive to reducing the packaging size of the entire filter.

[0089] In the embodiment of the present application, the acoustic impedance of the first piezoelectric layer 111 is different from the acoustic impedance of the first passivation layer 114, and the greater the difference between the two, the better. In addition, the acoustic impedance of the base layer 116 is also different from the acoustic impedance of the first passivation layer 114, and the greater the difference between the two, the better. Specifically, in the embodiment of the present application, the acoustic impedance of the first piezoelectric layer 111 is set to be greater than the acoustic impedance of the first passivation layer 114, and the acoustic impedance of the base layer 116 is set to be greater than the acoustic impedance of the first passivation layer 114.

[0090] When the surface acoustic wave propagates on the first piezoelectric layer 111, it will cause leakage in the direction from the first piezoelectric layer 111 to the substrate layer 116. However, due to the different acoustic impedances between the first piezoelectric layer 111 and the first passivation layer 114, the surface acoustic wave will be reflected at the contact interface between the first piezoelectric layer 111 and the first passivation layer 114. The greater the difference in acoustic impedance between the first piezoelectric layer 111 and the first passivation layer 114, the stronger the reflection, and the less energy leakage. When a small part of the leaked surface acoustic wave propagates on the first passivation layer 114, due to the different acoustic impedances between the first passivation layer 114 and the substrate layer 116, the surface acoustic wave will be reflected at the contact interface between the first passivation layer 114 and the substrate layer 116. The greater the difference in acoustic impedance between the first passivation layer 114 and the substrate layer 116, the stronger the reflection, and the less energy leakage to the substrate layer 116.

[0091] Similarly, the acoustic impedance of the second piezoelectric layer 112 is different from the acoustic impedance of the second passivation layer 115, and the greater the difference between the two, the better. Moreover, the acoustic impedance of the base layer 116 is also different from the acoustic impedance of the second passivation layer 115, and the greater the difference between the two, the better. Specifically, in the embodiment of the present application, the acoustic impedance of the second piezoelectric layer 112 is set to be greater than the acoustic impedance of the second passivation layer 115, and the acoustic impedance of the base layer 116 is set to be greater than the acoustic impedance of the second passivation layer 115.

[0092] When the surface acoustic wave propagates on the second piezoelectric layer 112, it will cause leakage in the direction from the second piezoelectric layer 112 to the base layer 116. However, due to the different acoustic impedances between the second piezoelectric layer 112 and the second passivation layer 115, the surface acoustic wave will be reflected at the contact interface between the second piezoelectric layer 112 and the second passivation layer 115. The greater the difference in acoustic impedance between the second piezoelectric layer 112 and the second passivation layer 115, the stronger the reflection and the less energy leakage. When a small part of the leaked surface acoustic wave propagates on the second passivation layer 115, due to the different acoustic impedances between the second passivation layer 115 and the base layer 116, the surface acoustic wave will be reflected at the contact interface between the second passivation layer 115 and the base layer 116. The greater the difference in acoustic impedance between the second passivation layer 115 and the base layer 116, the stronger the reflection and the less energy leakage to the base layer 116.

[0093] In addition, since the other side of the first piezoelectric layer 111 is in contact with the air, the acoustic impedance of the first piezoelectric layer 111 is different from the acoustic impedance of the air. Therefore, when the surface acoustic wave propagating in the first piezoelectric layer 111 propagates to the upper surface of the first piezoelectric layer 111, that is, when it propagates to the first surface of the piezoelectric substrate 110, it will be reflected on the first surface of the piezoelectric substrate 110, thereby avoiding a large amount of energy leakage.

[0094] Similarly, since the other side of the second piezoelectric layer 112 is in contact with the air, the acoustic impedance of the second piezoelectric layer 112 is different from the acoustic impedance of the air. Therefore, when the surface acoustic wave propagating in the second piezoelectric layer 112 propagates to the lower surface of the second piezoelectric layer 112, that is, when it propagates to the second surface of the piezoelectric substrate 110, it will be reflected on the second surface of the piezoelectric substrate 110, thereby avoiding a large amount of energy leakage.

[0095] In the embodiment of the present application, the temperature drift coefficient of the first piezoelectric substrate is smaller than the temperature drift coefficient of the first piezoelectric layer 111, and the temperature drift coefficient of the second piezoelectric substrate is smaller than the temperature drift coefficient of the second piezoelectric layer 112. Among them, the first piezoelectric substrate refers to the structure formed by the first piezoelectric layer 111, the first passivation layer 114 and the base layer 116, and the second piezoelectric layer 112 refers to the structure formed by the second piezoelectric layer 112, the second passivation layer 115 and the base layer 116. Regarding the principle of setting different material layers to reduce the temperature drift coefficients of the first piezoelectric substrate and the second piezoelectric substrate, thereby improving the temperature drift characteristics of the entire filter, please refer to the relevant introduction in the aforementioned embodiment, which will not be repeated here. It should be noted that the materials of the first passivation layer 114 and the second passivation layer 115 can be the same as the passivation layer 113 introduced in the aforementioned embodiment to improve the temperature drift characteristics of the entire piezoelectric substrate 110.

[0096] In the embodiment of the present application, the first piezoelectric layer 111 and the second piezoelectric layer 112 can be made of the same material, and the first passivation layer 114 and the second passivation layer 115 can also be made of the same material, so that the piezoelectric substrate 110 is symmetrical in material composition. Specifically, the first piezoelectric layer 111 can be made of lithium tantalate or lithium niobate, and the second piezoelectric layer 112 can also be made of lithium tantalate or lithium niobate. The first passivation layer 114 and the second passivation layer 115 can both be made of silicon dioxide. The base layer 116 can be a substrate made of silicon, aluminum oxide or silicon carbide.

[0097] In an embodiment of the present application, the first conductive sheet group includes a plurality of first conductive sheets 120, and the second conductive sheet group includes a plurality of second conductive sheets 130, wherein when the number of the first conductive sheets 120 is less than or equal to the number of the second conductive sheets 130, each first conductive sheet 120 may have a corresponding second conductive sheet 130, and each first conductive sheet 120 may be connected to its corresponding second conductive sheet 130. When the number of the first conductive sheets 120 is greater than the number of the second conductive sheets 130, the first conductive sheets 120 of the same type may be electrically connected first, and then one of the first conductive sheets 120 may be connected to the second conductive sheet 130, that is, it is ensured that each first conductive sheet 120 may be electrically connected to one second conductive sheet 130.

[0098] In the embodiment of the present application, the second surface is in contact with the substrate in the RF module, and the number of the first conductive sheets 120 is less than or equal to the number of the second conductive sheets 130 is taken as an example for description.

[0099] Since the first conductive sheet 120 is arranged on the first surface of the piezoelectric substrate 110, and the second conductive sheet 130 is arranged on the second surface of the piezoelectric substrate 110, and the first conductive sheet 120 and the second conductive sheet 130 are used as connection interfaces on the filter, both need to be used to connect with the relevant interfaces in the RF circuit. The filter in the present application is a double-sided filter, and when it is packaged in the RF module, only one side can be in contact with the substrate, and each relevant interface in the RF circuit is arranged on the substrate. Therefore, in order to ensure that the filters on both sides of the double-sided filter can be connected to the interface on the substrate, the first conductive sheet 120 can be connected to the second conductive sheet 130. For example, the second surface of the piezoelectric substrate 110 is set to contact with the substrate, and the second conductive sheet 130 on the second surface can be directly connected to the interface on the substrate, and the first conductive sheet 120 can also be connected to the interface on the substrate by connecting with the second conductive sheet 130, so that both filters can be connected to the interface on the substrate to achieve connection with the RF circuit.

[0100] The second surface of the piezoelectric substrate 110 is set as a surface in contact with / close to the substrate, so that the second conductive sheet 130 can be directly connected to the interface on the substrate. By setting the number of the first conductive sheets 120 to be less than or equal to the number of the second conductive sheets 130, each first conductive sheet 120 can be electrically connected to a second conductive sheet 130, that is, each first conductive sheet 120 has a one-to-one corresponding second conductive sheet 130 for connection. It is ensured that each first conductive sheet 120 can be connected to the interface on the substrate. Of course, the number of the second conductive sheets 130 can also be set to be less than or equal to the number of the first conductive sheets 120. In this case, it is necessary to set the first surface of the piezoelectric substrate 110 to be in contact with / close to the substrate, so that the first conductive sheet 120 can be directly connected to the interface on the substrate. That is, when the number of the first conductive sheets 120 and the second conductive sheets 130 is not equal, the conductive sheets with a larger number are set to be directly connected to the interface on the substrate, and the conductive sheets with a smaller number are electrically connected to the conductive sheets with a larger number through wires or conductive columns 190. This arrangement enables each conductive sheet to be connected to an interface on the substrate.

[0101] Specifically, in one embodiment of the present application, refer to Figure 3 and Figure 4 In order to achieve the connection between the first conductive sheet group and the second conductive sheet group, through holes 117 are provided on the piezoelectric substrate 110, and the number of through holes 117 is equal to the number of the smaller group of conductive sheets in the first conductive sheets 120 and the second conductive sheets 130. Specifically, if the number of the first conductive sheets 120 is less than the number of the second conductive sheets 130, the number of through holes 117 is equal to the number of the first conductive sheets 120, and if the number of the second conductive sheets 130 is less than the number of the first conductive sheets 120, the number of through holes 117 is equal to the number of the second conductive sheets 130. If the number of the first conductive sheets 120 and the number of the second conductive sheets 130 are equal, the number of through holes 117 is equal to the number of the first conductive sheets 120 and the number of the second conductive sheets 130.

[0102] In the embodiment of the present application, the filter is introduced by taking the example that the number of the first conductive sheets 120 is less than the number of the second conductive sheets 130, therefore, the number of the through holes 117 is set to be the same as the number of the first conductive sheets 120. It is ensured that each first conductive sheet 120 can be connected to one second conductive sheet 130.

[0103] The first conductive sheet 120 and the second conductive sheet 130 are respectively disposed at both ends of the through hole 117, and a conductor 180 is disposed in the through hole 117. The first conductive sheet 120 and the second conductive sheet 130 at both ends of the through hole 117 are electrically connected through the conductor 180 in the through hole 117. In the embodiment of the present application, the conductor 180 can be a copper column.

[0104] In addition, in order to facilitate the connection between the second conductive sheet 130 and the interface on the substrate, a conductive column 190 can be provided on the second conductive sheet 130. The conductive column 190 can be a copper column or other conductive materials to achieve the connection between the second conductive sheet 130 and the interface on the substrate.

[0105] In one embodiment of the present application, Figure 4 As shown, the first cover 160 is disposed on the first surface of the piezoelectric substrate 110, and a first cavity 101 is formed between the first cover 160 and the first surface. The second cover 170 is disposed on the second surface of the piezoelectric substrate 110, and the second cover 170 and the second surface form a second cavity 102. The first cover 160 includes a connection structure 161 and a sealing structure 162 that are in contact with the piezoelectric substrate 110. The connection structure 161 is an annular structure. The annular structure is first connected to the first surface of the piezoelectric substrate 110, and then the sealing structure 162 is connected to the annular structure. The first surface of the piezoelectric substrate 110, the connection structure 161, and the sealing structure 162 form a closed cavity, which is the first cavity 101.

[0106] In the embodiment of the present application, the connection structure 161 can be made of silicon dioxide material, and the sealing structure 162 can be made of silicon. Among them, the connection structure 161 can be made on the first surface of the piezoelectric substrate 110 by deposition, and the sealing structure 162 and the connection structure 161 can be connected by bonding. The sealing structure 162 mainly plays a supporting and protective role, and it needs to be able to withstand the injection molding pressure of the filter during packaging. In addition, the sealing structure 162 can also be made of other materials, for example, the sealing structure 162 can be made of glass. The connection structure 161 can also be made of other materials, for example, the connection structure 161 can be organic.

[0107] In the embodiment of the present application, the second cover 170 may have the same structure as the first cover 160, that is, the first cover 160 and the second cover 170 may be symmetrically arranged on the first surface and the second surface of the piezoelectric substrate 110. The second cover 170 may also have a different structure from the first cover 160. For example, Figure 4 As shown, the second cover 170 is an integral body, and the second cover 170 is connected to the second surface of the piezoelectric substrate 110. The second cavity 102 formed by the second cover 170 and the piezoelectric substrate 110 may refer to one cavity or multiple cavities. Figure 4 As shown, the second cover 170 is provided with three supporting structures, so two cavities are formed between the second cover 170 and the piezoelectric substrate 110. The second cover 170 can be made of organic material.

[0108] In the embodiment of the present application, since the filter is a double-layer filter, and the upper and lower filters of the double-layer filter are two separate filters, the upper and lower filters can be applied to different RF circuits, and the upper and lower filters can be independently designed to realize their respective functions.

[0109] Specifically, the specific thickness of each material layer can be set according to the functional requirements of the first filter and the second filter. For example, the thickness, material and tangent of the first piezoelectric layer 111, as well as the thickness of the first passivation layer 114, can be set according to the requirements of the first filter to achieve the performance of the first filter. The thickness, material and tangent of the second piezoelectric layer 112, as well as the thickness of the second passivation layer 115, can also be set according to the requirements of the second filter to achieve the performance of the first filter. That is, in the embodiment of the present application, the first piezoelectric layer 111 and the second piezoelectric layer 112 can be made of the same material, set to the same thickness and tangent, or can be made of different materials, set to different thicknesses and different tangents. The first passivation layer 114 and the second passivation layer 115 can be made of the same material or different materials; they can be set to the same thickness or different thicknesses.

[0110] For example, if the working frequency band of a certain RF circuit is Band 40, the first filter can be applied to the RF circuit; if the working frequency band of another RF circuit is Band 41, the second filter can be applied to the RF circuit. The first filter and the second filter are independent filters, and work in different RF circuits respectively.

[0111] For another example, in FDD mode, the operating frequency band of a certain RF circuit is Band 8. In this mode, the transmitting circuit and receiving circuit of the RF circuit are independent. Therefore, the first filter can be applied to the transmitting circuit of the RF circuit, and the second filter can be applied to the receiving circuit of the RF circuit.

[0112] For another example, a radio frequency circuit with an operating frequency band of Band 40 includes multiple groups of series / parallel resonant cavities. Some of the resonant cavities can be applied to the first filter, and the remaining resonant cavities can be applied to the second filter to form a complete Band 40 filter circuit.

[0113] In an embodiment of the present application, a filter manufacturing process is also provided. Figure 5 , Figure 5 This is one of the flowcharts of a manufacturing process of a filter provided in an embodiment of the present application. The manufacturing process is mainly used to manufacture Figure 4 The filter shown in FIG. 1 is a filter in which the base layer 116 of the filter is a silicon substrate, and the first passivation layer 114 and the second passivation layer 115 of the filter are silicon dioxide layers. Figure 5 As shown in (a), a silicon substrate is manufactured, and the silicon substrate is the base layer 116. Figure 5 As shown in (b), a passivation layer is deposited on both sides of the silicon substrate, that is, a silicon dioxide layer is deposited on the upper surface of the silicon substrate, and the silicon dioxide layer is the first passivation layer 114. A silicon dioxide layer is deposited on the lower surface of the silicon substrate, and the silicon dioxide layer is the second passivation layer 115. The thickness of the two silicon dioxide layers can be determined according to the thickness of the first filter and the second filter. Figure 5 As shown in (c), a lithium tantalate layer (or lithium niobate layer) is bonded on the first passivation layer 114, and the lithium tantalate layer (or lithium niobate layer) is the first piezoelectric layer 111; a lithium tantalate layer (or lithium niobate layer) is bonded on the second passivation layer 115, and the lithium tantalate layer (or lithium niobate layer) is the second piezoelectric layer 112.

[0114] refer to Figure 6 , Figure 6 This is a second flow chart of a manufacturing process of a filter provided in an embodiment of the present application. Figure 6 As shown in (a), after bonding the first piezoelectric layer 111 and the second piezoelectric layer 112, the first piezoelectric layer 111 and the second piezoelectric layer 112 are thinned by a smart peeling (Smut-cut) process or a chemical mechanical polishing (CMP) process. Through the above process, the Figure 4 The piezoelectric substrate 110 is shown in FIG. A support layer 118 is bonded to the piezoelectric layer on one side (eg, the second piezoelectric layer 112 ) and supports the piezoelectric substrate 110 .

[0115] exist Figure 6 Based on the piezoelectric substrate 110 shown in (a), a patterning process is performed on the piezoelectric layer on one side, for example, an interdigital electrode (interdigital transducer) is generated on the first piezoelectric layer 111 and a first conductive sheet 120 is made on the first piezoelectric layer 111, so as to obtain Figure 6 The structure shown in (b).

[0116] Then, the first cover 160 is bonded to the first piezoelectric layer 111, a first cavity 101 is formed between the first cover 160 and the first piezoelectric layer 111, and the support layer 118 on the second piezoelectric layer 112 is peeled off. At this point, the first cover 160 can play a supporting role, that is, play the role of the support layer 118.

[0117] Among them, the first cover body 160 may include a connecting structure 161 and a sealing structure 162. The connecting structure 161 may be an annular silicon dioxide layer. The connecting structure 161 may be disposed on the first piezoelectric layer 111 by deposition, and then the sealing structure 162 is bonded to the connecting structure 161. The sealing structure 162 may be made of silicon.

[0118] Then, etching is used to set a through hole 117 on the piezoelectric substrate 110, and the position of the through hole 117 corresponds to the position of the first conductive sheet 120. Then, magnetron sputtering / chemical plating and electroplating processes are used to set the conductor 180 in the through hole 117. Specifically, magnetron sputtering is used to generate a conductive layer in the through hole 117, and then an electroplating process is used to generate the conductor 180 on the conductive layer. Alternatively, chemical plating is used to generate a conductive layer in the through hole 117, and then an electroplating process is used to generate the conductor 180 on the conductive layer. In addition, interdigitated electrodes and a second conductive chip are set on the second piezoelectric substrate, and a second conductive chip is set at a position corresponding to each through hole 117, so that the first conductive sheet 120 can be electrically connected to the second conductive sheet 130 through the conductor 180 in the through hole 117. Figure 6 The structure shown in (c).

[0119] Then the second cover 170 is bonded to the second piezoelectric layer 112. The second cover 170 can be made by the same process as the first cover 160, or can be made of organic matter. Figure 6 When the second cover 170 is made of organic matter, a support structure of the second cover 170 is firstly made on the second surface ( Figure 6 The connecting portion between the second cover 170 and the second surface is then formed on the structure and an organic film layer is formed to connect with the supporting structure. Figure 6 The second cover 170 shown in FIG. 1 can form a second cavity between the second cover 170 and the second surface. That is, the second cover 170 is a whole in structure, but its manufacturing process is completed in two steps.

[0120] The present application embodiment also provides another filter manufacturing process. Figure 7 , Figure 7 Another manufacturing process flow chart of the filter provided in the embodiment of the present application, the manufacturing process is mainly used to manufacture Figure 4 The filter shown. Figure 7 As shown, a piezoelectric substrate 110 is obtained by deposition, bonding, etc., which is stacked in sequence by a piezoelectric layer, a passivation layer (silicon dioxide layer) and a base layer 116 (silicon substrate), and the piezoelectric layer in the piezoelectric substrate 110 is thinned by a Smut-cut process or a CMP process to obtain Figure 7The piezoelectric substrate 110 is shown in (a). For the convenience of description, the piezoelectric layer is referred to as the first piezoelectric layer 111 and the passivation layer is referred to as the first passivation layer 114.

[0121] Then, a first conductive sheet 120 and interdigital electrodes are arranged on the first piezoelectric layer 111. The first conductive sheet 120 and interdigital electrodes can be arranged by using related processes in the prior art. Figure 7 The structure shown in (b).

[0122] A first cover 160 is disposed on the piezoelectric layer. The first cover 160 can be disposed using the process (including deposition, bonding, etc.) described in the above embodiments. Figure 7 The structure shown in (c).

[0123] Then, the base layer 116 (silicon substrate) is thinned, and a silicon dioxide layer is deposited on the other side of the silicon substrate, the silicon dioxide layer is the second passivation layer 115, and a piezoelectric layer is bonded on the silicon dioxide layer, the piezoelectric layer is the second piezoelectric layer 112. Figure 7 Then, the second piezoelectric layer 112 is thinned by a Smut-cut process or a CMP process. Figure 7 The structure shown in (e).

[0124] Then, a through hole 117 is set on the piezoelectric substrate 110 by etching, and the position of the through hole 117 corresponds to the position of the first conductive sheet 120. Then, a conductor 180 is set in the through hole 117 by magnetron sputtering / chemical plating and electroplating. Specifically, a conductive layer is generated in the through hole 117 by magnetron sputtering, and then the conductor 180 is generated on the conductive layer by electroplating. Alternatively, a conductive layer is generated in the through hole 117 by chemical plating, and then the conductor 180 is generated on the conductive layer by electroplating. In addition, interdigital electrodes and a second conductive chip are set on the second piezoelectric substrate to obtain Figure 7 The structure shown in (f).

[0125] A second conductive chip is disposed at a position corresponding to each through hole 117 , so that the first conductive sheet 120 can be electrically connected to the second conductive sheet 130 through the conductor 180 in the through hole 117 .

[0126] Then the second cover 170 is bonded to the second piezoelectric layer 112. The second cover 170 can be made by the same process as the first cover 160, or can be made of organic matter. Figure 7 The structure shown in (g).

[0127] In one embodiment of the present application, a process for providing a through hole 117 on the piezoelectric substrate 110 of the filter is also provided. Figure 8 , Figure 8 A process flow chart of providing a through hole 117 on a piezoelectric substrate 110 of a filter provided in an embodiment of the present application. Figure 8 As shown in (a), a mask layer 119 is provided on the piezoelectric substrate 110 on one side of the piezoelectric substrate 110, and an opening is provided on the mask layer 119. The opening corresponds to the position where the through hole 117 is required to be provided on the piezoelectric substrate 110, and the size of the opening is the same as the size of the through hole 117 required to be provided. Then, an etching process and a first etching gas are used to etch the second piezoelectric layer 112 in the piezoelectric substrate 110 to obtain Figure 8 After the second piezoelectric layer 112 is etched, the silicon dioxide layer and the silicon substrate (the second passivation layer 115, the base layer 116 and the first passivation layer 114) in the piezoelectric substrate 110 are etched using a second etching gas to obtain Figure 8 Then, the first etching gas is used to etch the first piezoelectric layer 111 in the piezoelectric substrate 110 to obtain Figure 8 The structure shown in (c) can form a through hole 117. After the through hole 117 is formed, a conductor 180 is formed in the through hole 117 by using processes such as magnetron sputtering / chemical plating and electroplating. Specifically, a conductive layer is formed in the through hole 117 by magnetron sputtering, and then the conductor 180 is formed on the conductive layer by electroplating. Alternatively, a conductive layer is formed in the through hole 117 by chemical plating, and then the conductor 180 is formed on the conductive layer by electroplating. Figure 8 The conductor 180 is used to electrically connect the first conductive sheet 120 and the second conductive sheet 130 .

[0128] The first etching gas refers to a gas that can etch the first piezoelectric layer and the second piezoelectric layer, such as a gas that can etch lithium tantalate or lithium niobate. The second etching gas refers to a gas that can etch the first passivation layer, the base layer, and the second passivation layer, such as a gas that can etch silicon dioxide and silicon.

[0129] It should be noted that the present application only describes a method for opening a through hole 117 in the piezoelectric substrate 110. The process for opening multiple through holes 117 is the same as the process for opening one through hole 117. When multiple through holes 117 need to be processed, multiple openings corresponding to the positions of the through holes 117 can be opened on the mask layer 119. According to the above-mentioned hole opening process, multiple through holes 117 can be etched.

[0130] It should be noted that the manufacturing process described in the above embodiment is carried out in the order of manufacturing the first filter first and then manufacturing the second filter. The process of opening the through hole 117 is to set a mask layer 119 on the second piezoelectric layer 112, and then open the through hole 117 in the order of etching the second piezoelectric layer 112, the second passivation layer 115, the base layer 116, the first passivation layer 114 and the first piezoelectric layer 111 in sequence.

[0131] Alternatively, the second filter may be manufactured first and then the first filter, without affecting the double-sided filter generated in the end. Correspondingly, the process of opening the through hole 117 is to set a mask layer 119 on the first piezoelectric layer 111, and then to open the through hole 117 in the order of etching the first piezoelectric layer 111, the first passivation layer 114, the base layer 116, the second passivation layer 115, and the second piezoelectric layer 112 in sequence.

[0132] It should be noted that if both the first cover 160 and the second cover 170 are in the form of a connection structure 161 and a sealing structure 162, then in the manufacturing process of the filter, whether the first filter is manufactured first or the second filter is manufactured first, there is no difference in the process. If the second cover 170 is made of organic matter, the first filter is manufactured first and then the second filter. This is because when manufacturing the second filter, the first cover 160 can play a supporting role in the manufacturing process, while if the second filter is manufactured first, the second cover 170 made of organic matter cannot play a supporting role in the manufacturing process.

[0133] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

[0134] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0135] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the protection scope of the present application includes the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0136] The above is a detailed introduction to a filter, a filter manufacturing process and an electronic device provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the transmission circuit of the present application and its core idea; at the same time, for a person skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0137] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application shall be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A filter, characterized in that: include: A piezoelectric substrate having a first surface and a second surface opposite to each other, the piezoelectric substrate comprising a first piezoelectric substrate and a second piezoelectric substrate; a first interdigital electrode and a second interdigital electrode, wherein the first interdigital electrode is disposed on the first surface, and the second interdigital electrode is disposed on the second surface; a first conductive sheet group and a second conductive sheet group, wherein the first conductive sheet group is arranged on the first surface, and the second conductive sheet group is arranged on the second surface, a through hole is arranged on the piezoelectric substrate, a conductor is arranged in the through hole, and the first conductive sheet group and the second conductive sheet group are electrically connected through the conductor in the through hole; A first cover body is disposed on a first surface of the piezoelectric substrate, and a first cavity is formed between the first cover body and the piezoelectric substrate, and the first electrode and the first conductive sheet group are located in the first cavity; A second cover body is disposed on the second surface of the piezoelectric substrate, and a second cavity is formed between the second cover body and the piezoelectric substrate, and the second electrode and the second conductive sheet group are located in the second cavity; The first piezoelectric substrate, the first interdigital electrodes, the first conductive sheet group and the first cover form a first filter, and the second piezoelectric substrate, the second interdigital electrodes, the second conductive sheet group and the second cover form a second filter; The first conductive sheet group includes a plurality of first conductive sheets, the second conductive sheet group includes a plurality of second conductive sheets, and the number of the first conductive sheets is different from the number of the second conductive sheets; The through holes are provided in plurality, wherein: In the case where the number of the first conductive sheets is greater than the number of the second conductive sheets, each of the second conductive sheets is electrically connected to at least one of the first conductive sheets, and the number of the through holes is equal to the number of the second conductive sheets; In the case that the number of the first conductive sheets is less than the number of the second conductive sheets, each of the first conductive sheets is electrically connected to at least one of the second conductive sheets, and the number of the through holes is equal to the number of the first conductive sheets.

2. The filter according to claim 1, characterized in that The piezoelectric substrate comprises a first piezoelectric layer, a passivation layer, and a second piezoelectric layer which are sequentially stacked, the acoustic impedance of the first piezoelectric layer is different from the acoustic impedance of the passivation layer, and the acoustic impedance of the second piezoelectric layer is different from the acoustic impedance of the passivation layer; The first piezoelectric layer and the passivation layer form the first piezoelectric substrate, and the second piezoelectric layer and the passivation layer form the second piezoelectric substrate.

3. The filter according to claim 2, characterized in that The acoustic impedance of the passivation layer is lower than the acoustic impedance of the first piezoelectric layer, and the temperature drift coefficient of the first piezoelectric substrate is smaller than the temperature drift coefficient of the first piezoelectric layer; Moreover, the acoustic impedance of the passivation layer is lower than the acoustic impedance of the second piezoelectric layer, and the temperature drift coefficient of the second piezoelectric substrate is smaller than the temperature drift coefficient of the second piezoelectric layer.

4. The filter according to claim 1, characterized in that The piezoelectric substrate comprises a first piezoelectric layer, a first passivation layer, a base layer, a second passivation layer and a second piezoelectric layer which are stacked in sequence, and the acoustic impedances of two adjacent layers are different; The first piezoelectric layer, the first passivation layer, and the base layer form the first piezoelectric substrate, and the second piezoelectric layer, the second passivation layer, and the base layer form the second piezoelectric substrate.

5. The filter according to claim 4, characterized in that The acoustic impedance of the first passivation layer is lower than the acoustic impedance of the first piezoelectric layer, and the acoustic impedance of the substrate layer is higher than the acoustic impedance of the first passivation layer; The acoustic impedance of the second passivation layer is lower than the acoustic impedance of the second piezoelectric layer, and the acoustic impedance of the substrate layer is higher than the acoustic impedance of the second passivation layer.

6. The filter according to any one of claims 2 to 5, characterized in that: The material of the first piezoelectric layer and the second piezoelectric layer is lithium tantalate or lithium niobate.

7. The filter according to claim 4 or 5, characterized in that The material of the first passivation layer and the second passivation layer is silicon dioxide.

8. The filter according to claim 4 or 5, characterized in that The material of the base layer is one of silicon, aluminum oxide or silicon carbide.

9. A filter manufacturing process, characterized in that: The filter comprises a substrate layer, and the manufacturing process comprises: Generating a piezoelectric substrate on the base layer, the piezoelectric substrate comprising a first piezoelectric layer, a first passivation layer, a base layer, a second passivation layer and a second piezoelectric layer stacked in sequence; Disposing a first conductive sheet group and a first interdigital electrode on the first piezoelectric layer; bonding a first cover body on the first piezoelectric layer; By means of an etching process, a through hole is formed on the piezoelectric substrate, and a conductor is arranged in the through hole; Disposing a second conductive sheet group and a second interdigital electrode on the second piezoelectric layer; Disposing a second cover on the second piezoelectric layer; Wherein, the first conductive sheet group includes a plurality of first conductive sheets, the second conductive sheet group includes a plurality of second conductive sheets, and the number of the first conductive sheets is different from the number of the second conductive sheets; the through hole is provided with a plurality; In the case where the number of the first conductive sheets is greater than the number of the second conductive sheets, each of the second conductive sheets is electrically connected to at least one of the first conductive sheets, and the number of the through holes is equal to the number of the second conductive sheets; In the case that the number of the first conductive sheets is less than the number of the second conductive sheets, each of the first conductive sheets is electrically connected to at least one of the second conductive sheets, and the number of the through holes is equal to the number of the first conductive sheets.

10. The manufacturing process according to claim 9, characterized in that: Generating a piezoelectric substrate on the base layer, comprising: Depositing passivation layers on both sides of the base layer to form the first passivation layer and the second passivation layer; A first piezoelectric layer is bonded on the first passivation layer, and a second piezoelectric layer is bonded on the second passivation layer.

11. The manufacturing process according to claim 9 or 10, characterized in that: Opening a through hole on the piezoelectric substrate comprises: A mask layer is disposed on the first piezoelectric layer, and an opening is disposed on the mask layer, and a size of the opening is the same as a size of the through hole; Using a first etching gas to etch the first piezoelectric layer through the opening; Using a second etching gas to etch the first passivation layer, the base layer and the second passivation layer through the opening; The first etching gas is used to etch the second piezoelectric layer through the opening to generate the through hole.

12. The manufacturing process according to claim 9 or 10, characterized in that: A mask layer is disposed on the second piezoelectric layer, and an opening is disposed on the mask layer, and a size of the opening is the same as a size of the through hole; Using a first etching gas to etch the second piezoelectric layer through the opening; Using a second etching gas, etching the second passivation layer, the base layer and the first passivation layer through the opening; The first etching gas is used to etch the first piezoelectric layer through the opening to generate the through hole.

13. The manufacturing process according to any one of claims 9 to 12, characterized in that: A conductor is arranged in the through hole, comprising: A magnetron sputtering process is used to form a conductive layer in the through hole, and an electroplating process is used to form the conductor on the conductive layer; or a chemical plating process is used to form a conductive layer in the through hole, and an electroplating process is used to form the conductor on the conductive layer.

14. A filter manufacturing process, characterized in that: The filter comprises a first piezoelectric substrate, wherein the first piezoelectric substrate comprises a first piezoelectric layer, a first passivation layer and a base layer arranged in sequence, and the manufacturing process comprises: Disposing a first conductive sheet group and a first interdigital electrode on the first piezoelectric layer; bonding a first cover body on the first piezoelectric layer; Depositing a second passivation layer on the other side of the base layer, bonding a second piezoelectric layer on the second passivation layer to generate a piezoelectric substrate, wherein the piezoelectric substrate includes a first piezoelectric layer, a first passivation layer, a base layer, a second passivation layer and a second piezoelectric layer; By means of an etching process, a through hole is formed on the piezoelectric substrate, and a conductor is arranged in the through hole; Disposing a second conductive sheet group and a second interdigital electrode on the second piezoelectric layer; Disposing a second cover on the second piezoelectric layer; Wherein, the first conductive sheet group includes a plurality of first conductive sheets, the second conductive sheet group includes a plurality of second conductive sheets, and the number of the first conductive sheets is different from the number of the second conductive sheets; the through hole is provided with a plurality; In the case where the number of the first conductive sheets is greater than the number of the second conductive sheets, each of the second conductive sheets is electrically connected to at least one of the first conductive sheets, and the number of the through holes is equal to the number of the second conductive sheets; In the case that the number of the first conductive sheets is less than the number of the second conductive sheets, each of the first conductive sheets is electrically connected to at least one of the second conductive sheets, and the number of the through holes is equal to the number of the first conductive sheets.

15. An electronic device, characterized in that: It comprises one or more radio frequency modules and the filter according to any one of claims 1 to 8, wherein the filter is arranged in the radio frequency module.

Images