CN114301422B - Filter, multiplexer, radio frequency front end and method of manufacturing a filter - Google Patents
Filter, multiplexer, radio frequency front end and method of manufacturing a filter Download PDFInfo
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- CN114301422B CN114301422B CN202111676549.9A CN202111676549A CN114301422B CN 114301422 B CN114301422 B CN 114301422B CN 202111676549 A CN202111676549 A CN 202111676549A CN 114301422 B CN114301422 B CN 114301422B
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
Abstract
The invention relates to the technical field of filters, and particularly provides a filter, a multiplexer, a radio frequency front end and a method for manufacturing the filter. The filter comprises a piezoelectric substrate provided with grooves, a plurality of resonators arranged on the piezoelectric substrate, and bonding pads comprising an input bonding pad, an output bonding pad and a grounding bonding pad and wires between the resonators due to the connection bonding pad and the resonators, wherein at least one of the bonding pads and/or at least one of the wires is arranged on the grooves. The embodiment of the invention can reduce the generation of parasitic capacitance and improve the out-of-band rejection level of the filter, thereby improving the performance of the filter.
Description
Technical Field
The present invention relates to the field of filters, and in particular, to a filter, a multiplexer, a radio frequency front end, and a method of manufacturing a filter.
Background
A filter is typically included in the radio frequency front end of the communication device to filter the radio frequency signal. An acoustic wave filter is one of filters, which includes a surface acoustic wave (Surface Acoustic Wave, SAW) filter and a bulk acoustic wave (Bulk Acoustic Wave, BAW) filter. The surface acoustic wave (Surface Acoustic Wave, SAW) filter has the characteristics of high working frequency, wide passband, good frequency selection characteristic, small volume, light weight and the like, is simple to manufacture, has low cost, and is widely applied to the radio frequency front end at present.
In general, SAW filters include a plurality of resonators, an input pad, an output pad, and a ground pad, which are disposed on a piezoelectric substrate, the resonators being composed of two reflectors and a plurality of interdigital transducers (Interdigital Transducer, IDT) located between the reflectors, and traces on the piezoelectric substrate mainly electrically connecting the pads with the resonators and the resonators.
In the prior art, parasitic capacitance generated between wires on a piezoelectric substrate can reduce the out-of-band rejection level of a filter, thereby affecting the filter performance. Therefore, how to reduce the parasitic capacitance of the filter has become a problem to be solved.
Disclosure of Invention
The embodiment of the invention provides a filter, a multiplexer, a radio frequency front end and a manufacturing method of the filter, so as to reduce parasitic capacitance and improve the out-of-band rejection level of the filter.
A first aspect of an embodiment of the present invention provides a filter, including:
the piezoelectric substrate is provided with a groove;
a plurality of resonators;
the bonding pad comprises an input bonding pad, an output bonding pad and a grounding bonding pad;
a trace for connection between the pad and the plurality of resonators, and connection between the plurality of resonators;
wherein, at least one of the wires is arranged on the groove.
Optionally, the grooves are filled with insulating material or air, and the dielectric constant of the insulating material is smaller than that of the piezoelectric substrate.
Optionally, a supporting layer is disposed between the wires disposed on the grooves and the grooves, and the hardness of the supporting layer is greater than that of the wires disposed on the grooves.
A second aspect of an embodiment of the present invention provides a filter, including:
the piezoelectric substrate is provided with a groove;
a plurality of resonators;
the bonding pad comprises an input bonding pad, an output bonding pad and a grounding bonding pad;
a trace for connection between the pad and the plurality of resonators, and connection between the plurality of resonators;
wherein at least one of the bonding pads is arranged on the groove.
Optionally, the grooves are filled with insulating material or air, and the dielectric constant of the insulating material is smaller than that of the piezoelectric substrate.
Optionally, a supporting layer is disposed between the bonding pad disposed on the groove and the groove, and the hardness of the supporting layer is greater than that of the bonding pad disposed on the groove.
A third aspect of the embodiments of the present invention provides a multiplexer comprising a receive filter and a transmit filter, at least one of the receive filter and the transmit filter comprising any of the filters described above.
A fourth aspect of an embodiment of the present invention provides a radio frequency front end comprising any of the filters described above.
A fifth aspect of an embodiment of the present invention provides a method of manufacturing a filter, the method including:
forming a recess on a target surface of a piezoelectric substrate, and depositing a target material in the recess;
and forming a conductive pattern on the target surface, wherein the conductive pattern consists of a resonator, wires and bonding pads, and at least one of the wires and/or at least one of the bonding pads is/are positioned on the groove.
Optionally, the target material is a sacrificial material, and after forming a groove on the target surface of the piezoelectric substrate and depositing the target material in the groove, the method further includes:
forming a supporting layer on the groove, wherein the supporting layer comprises a through hole;
after the forming of the conductive pattern on the target surface, the method further includes:
injecting an etching material into the groove through the through hole to etch the sacrificial material;
at least one of the wirings and/or at least one of the bonding pads is/are positioned on the groove specifically:
at least one of the traces and/or at least one of the pads is located on the support layer.
Optionally, the target material is an insulating material, and a dielectric constant of the insulating material is smaller than a dielectric constant of the piezoelectric substrate.
In an embodiment of the invention, the filter comprises a piezoelectric substrate provided with grooves, a plurality of resonators arranged on the piezoelectric substrate, bonding pads and wires, wherein at least one of the bonding pads and/or at least one of the wires is arranged on the grooves. The embodiment of the invention can reduce the generation of parasitic capacitance and improve the out-of-band rejection level of the filter, thereby improving the performance of the filter.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments of the present invention will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1A is a schematic plan view of a filter according to an embodiment of the present invention;
FIG. 1B is a schematic partial cross-sectional view of the filter of FIG. 1A;
FIG. 1C is a schematic plan view of another filter according to an embodiment of the present invention;
FIG. 1D is a schematic partial cross-sectional view of the filter of FIG. 1C;
FIG. 1E is a schematic plan view of yet another filter provided by an embodiment of the present invention;
FIG. 2A is a schematic plan view of yet another filter according to an embodiment of the present invention;
FIG. 2B is a schematic partial cross-sectional view of the filter of FIG. 2A;
FIG. 2C is a schematic plan view of yet another filter according to an embodiment of the present invention;
FIG. 2D is a schematic partial cross-sectional view of the filter of FIG. 2C;
FIG. 2E is a schematic plan view of yet another filter provided by an embodiment of the present invention;
FIG. 3 is a signal simulation diagram of a filter provided by an embodiment of the present invention;
fig. 4 is a schematic diagram of a duplexer provided in an embodiment of the present invention;
fig. 5A is a signal simulation diagram of a duplexer according to an embodiment of the present invention;
fig. 5B is another signal simulation diagram of the duplexer provided in the embodiment of the present invention;
fig. 5C is a signal isolation diagram of a duplexer according to an embodiment of the present invention;
fig. 6 is a flowchart of a method for manufacturing a filter according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be understood that the present invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the dimensions and relative dimensions of layers and regions may be exaggerated for the same elements throughout for clarity.
It will be understood that when an element or layer is referred to as being "on" …, "" adjacent to "…," "connected to" or "coupled to," "connected to" … another element or layer, it can be directly on, adjacent to, connected to or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on" …, "" directly adjacent to "…," "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
Spatially relative terms, such as "under …," "under …," "below," "under …," "above …," "above," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "under …" and "under …" may include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.
In the following description, for the purpose of providing a thorough understanding of the present invention, detailed structures and steps are presented in order to illustrate the technical solution presented by the present invention. Preferred embodiments of the present invention are described in detail below, however, the present invention may have other embodiments in addition to these detailed descriptions.
The invention relates to the technical field of filters, in particular to a filter, a multiplexer, a radio frequency front end and a method for manufacturing the filter. In practice, it has been found that the existing SAW filter not only generates parasitic capacitance between traces due to potential difference, but also generates parasitic capacitance between pads, thereby reducing the out-of-band rejection level of the filter. In order to solve the above-described problems, therefore, the inventive concept of the present application will be specifically described by the following examples:
referring to fig. 1A, fig. 1A is a schematic plan view of a filter according to an embodiment of the invention. The filter 100 described in this embodiment includes a piezoelectric substrate 121, and resonators 101, 103, and 104, a filter 102, an input pad 105, an output pad 106, ground pads 107 and 108, a plurality of traces 109-115 and 118-120, flying lead materials 116 and 117, and a recess 122 disposed on the piezoelectric substrate 121.
The resonators 101, 103, and 104, the filter 102 include reflectors provided at both ends and IDTs located between the reflectors, the resonators 101, 103, and 104 are SAW resonators coupled laterally, and the filter 102 is a Double-Mode SAW (DMS) filter. The input pad 105 is connected to the resonator 101 by a trace 109. One end of the IDT located in the middle of the DMS filter 102 is connected to the resonator 101 through a trace 112, the other end is connected to the ground pad 107 through a trace 115, one end of the IDT located on both sides of the DMS filter 102 is connected to the ground pad 108 through a trace 110 and a trace 111, respectively, and the other end is electrically connected to the resonator 103 through a trace 114 and a trace 113, respectively. The resonator 103 is electrically connected to the output pad 106 by a trace 118. Resonator 104 is located in parallel with resonator 103 between resonator 103 and output pad 106 by trace 119 and is connected to ground pad 107 by trace 120. Because of the overline condition between the traces 110 and 112 and between the traces 114 and 115, overline material 116 and overline material 117 are respectively disposed at overline portions of the traces 110 and 112 and 114 and 115, respectively, and the overline material 116 and overline material 117 can be specifically insulating material such as silicon dioxide SiO 2 Silicon nitride Si 3 N 4 Or polyimide, etc., and embodiments of the present invention are not limited.
Among the traces disposed on the piezoelectric substrate, at least one trace 109 is disposed on the groove 122, specifically, the trace 109 may be partially disposed on the groove 122 or may be disposed entirely on the groove 122, which is not limited in the embodiment of the present invention.
Specifically, the input signal is input to the resonator 101 through the input pad 105 and the trace 109, is output to the DMS filter 102 through the trace 112 after being subjected to electric-acoustic and acoustic-electric conversion by the resonator 101, is output to the resonator 103 through the trace 113 and the trace 114 after being processed by the DMS filter 102, and is output to the output pad 106 through the trace 118 after being processed by the resonator 103, thereby completing the filtering processing of the signal.
It should be noted that fig. 1A is only a preferred embodiment of the present invention, and in practical application, the groove on the piezoelectric substrate may be located below any one of the at least one traces, and in particular, the groove may be located below one of the two oppositely disposed traces having a potential difference. For example, the groove 122 may be located under the trace 118 due to a potential difference between the trace 109 and the trace 118.
Alternatively (not shown in the drawings), the grooves may be located under any one of the traces 114 and 113, and there may be a plurality of grooves on the piezoelectric substrate, which are located under a plurality of traces, respectively, which is not limited in the embodiment of the present invention.
Further, the shape of the groove is not limited to the shape shown in fig. 1A, but may be square, round, oval, polygonal, irregular, or other shapes.
Further, a cross section taken transversely to the trace 109 in fig. 1A results in fig. 1B, and fig. 1B is a schematic partial cross section of the filter shown in fig. 1A. As shown in fig. 1B, the grooves 122 are disposed on the piezoelectric substrate 121, and the traces 109 are disposed on the grooves 122. The cross section of the groove 122 may be configured as a trapezoid or a rectangle, etc., which is not limited in the embodiment of the present invention.
Alternatively, the depth of the groove may range from 50nm to 3um, which is not limited in the embodiment of the present invention.
In an embodiment of the present invention, the material of the piezoelectric substrate 121 may include lithium tantalate LiTaO 3 Lithium niobate LiNbO 3 The embodiment of the present invention is not limited to at least one of these.
In a possible implementation manner, the metal material adopted by the wire in the prior art is generally smaller in hardness, and the embodiment of the invention can be arranged as a metal layer with larger hardness at the bottom layer of the wire, such as molybdenum Mo, tungsten W and the like, and the embodiment of the invention is not limited, so that the mechanical strength of the wire can be increased, and deformation can be prevented.
Specifically, the metal layer may be disposed on all the bottom layers of the traces, or may be disposed on the bottom layers of the traces disposed on the grooves, such as the bottom layer of the trace 109 shown in fig. 1A, which is a metal layer with a higher hardness.
In another possible embodiment, the recess 122 may be filled with air or an insulating material having a dielectric constant less than that of the piezoelectric substrate, typically a material having a dielectric constant less than 10, such as silicon dioxide SiO 2 Silicon nitride Si 3 N 4 And the like, the embodiment of the invention is not limited.
When the grooves 122 are filled with air, as shown in the cross-sectional view of fig. 1B, the width of the traces 109 is greater than the width of the grooves 122, i.e., the traces 109 are partially disposed on the grooves 122. Alternatively (not shown in the drawings), the width of the trace 109 may be smaller than or equal to the width of the groove 122, that is, the trace 109 is erected on the groove 122, that is, partially disposed on the air, as shown in fig. 1E, fig. 1E is a schematic plan view of another filter according to an embodiment of the present invention, and specifically, the width of the trace 109 is smaller than the width of the groove 122.
When the grooves 122 are filled with the insulating material, the width of the traces 109 may be greater than, less than or equal to the width of the grooves 122, i.e., the traces 109 may also be disposed on the insulating material, which is not limited in the embodiment of the present invention.
In still another possible implementation manner, please refer to fig. 1C and fig. 1D, fig. 1C is a schematic plan view of another filter provided by an embodiment of the present invention, and fig. 1D is a schematic partial cross-sectional view of the filter shown in fig. 1C, specifically, a cross-section taken transversely to the trace 109 along fig. 1C. As shown in fig. 1C and fig. 1D, a supporting layer 123 may be further disposed between the recess 122 and the trace 109, and the supporting layer 123 is disposed to cover the recess 122. The supporting layer 123 is made of a material having a hardness higher than that of the trace 109, and may include aluminum nitride AlN, silicon nitride Si 3 N 4 The embodiment of the present invention is not limited to at least one of these.
Preferably, when the grooves 122 are filled with air, a supporting layer 123 is disposed between the grooves 122 and the traces 109, so that the traces can be prevented from being deformed and the mechanical strength of the traces can be improved.
It should be noted that, the groove 122 below the trace 109 may be one groove or may be formed by a plurality of grooves with relatively dense openings, in this case, if the grooves are filled with air, no additional supporting layer is required between the trace and the groove, or no metal layer with relatively high hardness is required on the bottom layer of the trace, so that the mechanical strength of the trace may be ensured. In addition, the embodiment of the present invention is described as only one of SAW filters, i.e., a hybrid SAW filter, and the embodiment of the present invention may also be applied to a filter having parasitic capacitance between wires of a DMS filter, a ladder filter, a lateral coupling filter, a balanced-unbalanced filter, and the like, which is not limited.
Fig. 3 is a signal simulation diagram of a filter according to an embodiment of the present invention. In fig. 3, the dashed line represents the passband signal of the filter under conventional design, the solid line represents the passband signal of the filter when the recess 122 is provided under the trace 109 as in fig. 1A, and it can be seen from fig. 3 that the provision of the recess 122 under the trace 109 can improve the out-of-band rejection level of the filter.
In the embodiment of the invention, the grooves are arranged on the piezoelectric substrate of the filter, and at least one of the wirings is arranged on the grooves, so that parasitic capacitance between the wirings can be reduced, the out-of-band suppression level of the filter is improved, and the performance of the filter is improved.
Referring to fig. 2A, fig. 2A is a schematic plan view of another filter according to an embodiment of the invention. The filter 200 described in this embodiment includes a piezoelectric substrate 221, and resonators 201, 203, and 204, a filter 202, an input pad 205, an output pad 206, ground pads 207 and 208, a plurality of traces 209-215 and 218-220, flying lead materials 216 and 217, and a recess 222 disposed on the piezoelectric substrate 221.
Among the pads disposed on the piezoelectric substrate, at least one pad such as the output pad 206 shown in fig. 2A is disposed on the groove 222, specifically, the output pad 206 may be partially disposed on the groove 222 or may be disposed entirely on the groove 222, which is not limited in the embodiment of the present invention.
Specifically, the input signal is input to the resonator 201 through the input pad 205 and the trace 209, is output to the DMS filter 202 through the trace 212 after being subjected to electric-acoustic and acoustic-electric conversion by the resonator 201, is output to the resonator 203 through the trace 213 and the trace 214 after being processed by the DMS filter 202, and is output to the output pad 206 through the trace 218 after being processed by the resonator 203, thereby completing the filtering process of the signal.
It should be noted that fig. 2A is only a preferred embodiment of the present invention, and in practical application, the groove on the piezoelectric substrate may be located below any at least one pad, specifically, the groove may be located below any two pads with potential differences. For example, the recess 222 may also be located below the input pad 205, since parasitic capacitance generated by a potential difference between the output pad 205 and the output pad 206 has a large influence on the filter 200.
Alternatively (not shown in the drawings), the grooves may be located below any one of the ground pads 207 and 208, and a plurality of grooves may be present on the piezoelectric substrate and located below the plurality of pads, respectively, which is not limited in the embodiment of the present invention.
Further, the shape of the groove is not limited to the shape shown in fig. 2A, but may be other shapes such as rectangle, circle, ellipse, polygon, irregular pattern, etc., and the embodiment of the present invention is not limited thereto.
Further, a section taken along the longitudinal direction of fig. 2A perpendicular to the output pad 206 results in fig. 2B, and fig. 2B is a schematic partial section of the filter shown in fig. 2A. As shown in fig. 2B, the grooves 222 are provided on the piezoelectric substrate 221, and the output pads 206 are located on the grooves 222. The cross section of the groove 222 may be configured as a trapezoid or a rectangle, etc., which is not limited in the embodiment of the present invention.
Alternatively, the depth of the groove may range from 50nm to 3um, which is not limited in the embodiment of the present invention.
In an embodiment of the present invention, the material of the piezoelectric substrate 221 may include lithium tantalate LiTaO 3 Lithium niobate LiNbO 3 The embodiment of the present invention is not limited to at least one of these.
In a possible implementation manner, the bonding pad in the prior art generally adopts a metal material with smaller hardness, and the embodiment of the invention can be arranged as a metal layer with larger hardness, such as molybdenum Mo, tungsten W and the like, at the bottom layer of the bonding pad, and the embodiment of the invention is not limited, so that the mechanical strength of the bonding pad can be increased, and deformation can be prevented.
Specifically, the metal layer may be disposed on all of the pad bottom layers, or may be disposed on the pad bottom layer disposed on the groove, and the bottom layer of the output pad 206 shown in fig. 2A may be disposed as a metal layer having a higher hardness.
In another possible embodiment, the recess 222 may be filled with air or an insulating material having a dielectric constant less than that of the piezoelectric substrateIs typically a material having a dielectric constant of less than 10, for example, silicon dioxide SiO 2 Silicon nitride Si 3 N 4 And the like, the embodiment of the invention is not limited.
When the recess 222 is filled with air, as shown in fig. 2A and 2B, the output pad 206 may be disposed to cover the recess 222, i.e. the pad 206 is partially disposed on the recess 222, or may be disposed on the recess 222, i.e. partially disposed on the air, as shown in fig. 2E, and fig. 2E is a schematic plan view of another filter according to an embodiment of the present invention.
When the grooves 222 are filled with an insulating material, the output pads 206 may be disposed over the grooves 222 or may be disposed on the insulating material, which is not limited by the embodiment of the present invention.
In yet another possible implementation, please refer to fig. 2C and 2D, fig. 2C is a schematic plan view of yet another filter provided by an embodiment of the present invention, and fig. 2D is a schematic partial cross-sectional view of the filter shown in fig. 2C, specifically, a cross-section taken along the longitudinal direction of fig. 2C and perpendicular to the output pad 206. As shown in fig. 2C and 2D, a supporting layer 223 may be further disposed between the recess 222 and the output pad 206, and the supporting layer 223 is disposed to cover the recess 222. The supporting layer 223 is made of a material having a hardness greater than that of the output pad 206, and may include aluminum nitride AlN, silicon nitride Si, for example 3 N 4 The embodiment of the present invention is not limited to at least one of these.
Preferably, when the grooves 222 are filled with air, a supporting layer 223 is provided between the grooves 222 and the output pads 206, so that the pads can be prevented from being deformed, and the mechanical strength of the pads can be improved.
It should be noted that, the groove 222 below the output pad 206 may be one groove or may be formed by a plurality of grooves with relatively dense openings, in this case, if the grooves are filled with air, no additional supporting layer is required between the pads and the grooves, or no metal layer with relatively high hardness is required on the bottom layer of the pads, so that the mechanical strength of the pads can be ensured. In addition, the embodiment of the present invention is described as only one of SAW filters, i.e., a hybrid SAW filter, and the embodiment of the present invention may also be applied to a filter having parasitic capacitance between pads, such as a ladder filter, a DMS filter, a lateral coupling filter, and a balun filter, which is not limited.
In the embodiment of the invention, the grooves are arranged on the piezoelectric substrate of the filter, and at least one of the bonding pads with potential difference is arranged on the grooves, so that parasitic capacitance between the bonding pads, especially between the input bonding pad and the output bonding pad, can be reduced, the out-of-band inhibition level of the filter is improved, and the performance of the filter is improved.
Referring to fig. 4, fig. 4 is a schematic structural diagram of a duplexer according to an embodiment of the present invention. As shown in fig. 4, the duplexer includes a transmission port TX, a reception port RX, an antenna port ANT, and a transmission filter 401 and a reception filter 402. In the embodiment of the present invention, at least one of the reception filter 401 and the transmission filter 402 is any one of the filters described in the above embodiments.
In fig. 4, a signal is input to a transmission filter 401 by a transmission port TX, and the signal is filtered by the transmission filter 401 and then transmitted through an antenna port ANT; the antenna port ANT receives an external signal, inputs the external signal to the reception filter 402, performs filter processing by the reception filter 402, and outputs the external signal through the reception port RX.
Fig. 5A is a signal simulation diagram of a duplexer provided in an embodiment of the present invention, fig. 5B is another signal simulation diagram of a duplexer provided in an embodiment of the present invention, and fig. 5C is a signal isolation diagram of a duplexer provided in an embodiment of the present invention. Wherein, the dashed line in fig. 5A-5C represents the passband signal of the duplexer in the conventional design, and the solid line represents the passband signal of the duplexer described in the embodiment of the present invention. Fig. 5A is a passband signal between the transmission port TX and the antenna port ANT, fig. 5B is a passband signal between the reception port RX and the antenna port ANT, and fig. 5C is a signal isolation between the transmission port TX and the reception port RX. Therefore, compared with the conventional design of the duplexer, the duplexer provided by the embodiment of the invention has better out-of-band rejection level and better isolation.
It should be noted that, the embodiment of the present invention is just one scheme to which the present invention is applied, and the present invention may also be applied to multiplexers such as triplexer and quad multiplexer, and the embodiment of the present invention is not limited.
The embodiment of the invention also provides a radio frequency front end comprising any one of the filters described above, and the embodiment of the invention will not be described in detail.
In the embodiment of the invention, the filter can reduce parasitic capacitance and improve the out-of-band rejection level, thereby improving the performance of the radio frequency front end,
referring to fig. 6, fig. 6 is a flowchart of a method for manufacturing a filter according to an embodiment of the invention. As shown in fig. 6, the method includes:
601. a recess is formed in a target surface of the piezoelectric substrate, and a target material is deposited in the recess.
In the embodiment of the invention, the filter consists of a piezoelectric substrate, a plurality of resonators, an input pad, an output pad, a grounding pad and a wiring. The traces are used for connection between the pads and the resonators, as well as between the resonators.
The material of the piezoelectric substrate can comprise lithium tantalate LiTaO 3 Lithium niobate LiNbO 3 At least one of them. The target surface represents a certain surface of the piezoelectric substrate, i.e., the upper surface. On the target surface of the piezoelectric substrate, grooves are first formed by etching, then target material is deposited in the grooves, and then a CMP process is used to form a planar surface.
The number of the grooves may be one or more, and the embodiment of the invention is not limited. The shape of the groove can be any shape such as rectangle, square, ellipse, polygon, irregular graph and the like, and the embodiment of the invention is not limited. The depth range of the groove can be 50 nm-3 um, and the embodiment of the invention is not limited.
602. A conductive pattern is formed on the target surface, the conductive pattern being comprised of resonators, traces and pads, wherein at least one of the traces and/or at least one of the pads is located on the recess.
Specifically, a layer of photoresist is filled on the same surface, namely the target surface, of the piezoelectric substrate, a photoresist conductive pattern is determined through an exposure and development process, then a conductive metal layer is deposited on the photoresist, and finally photoresist is dissolved by photoresist stripping solution, so that a non-conductive pattern part in the conductive metal layer is stripped from the piezoelectric substrate, and a conductive pattern is formed.
Furthermore, on the basis of forming the conductive pattern, a lift-off process can be adopted to thicken the metal of the bonding pad part.
In an embodiment of the present invention, the conductive pattern may include a plurality of metal layers, and the conductive pattern includes a resonator, a trace, and a pad, wherein the resonator includes a plurality of IDTs and reflector layers located at both sides of the plurality of IDTs. The two rows of metal bus bars are oppositely arranged, the metal electrode finger group layers with comb teeth are connected with the two rows of bus bars in a staggered mode, and the reflector is also made of metal materials.
In the embodiment of the invention, at least one of the wirings or at least one of the bonding pads is arranged on the groove of the piezoelectric substrate when the conductive pattern is formed. The wires or pads may be partially or entirely located on the grooves.
In one possible embodiment, the target material is a sacrificial material, a recess is formed on the target surface of the piezoelectric substrate by etching, the sacrificial material is deposited in the recess, and after the planar surface is formed by using a CMP process, a support layer is required to be formed on the recess, a support layer pattern is formed by etching, and a through hole is formed between the support layer and the sacrificial layer. After the conductive pattern is formed on the target surface, etching material is injected into the groove through the through hole to etch the sacrificial material, wherein at least one of the traces and/or at least one of the pads is specifically located on the support layer.
The etching material may be etching liquid or etching gas, which is not limited in the embodiment of the present invention. The support layer may be at least one of aluminum nitride AlN, molybdenum Mo, tungsten W, etc., which is not limited in the embodiment of the present invention. The hardness of the supporting layer is greater than that of the metal layer forming the conductive pattern, and is sufficient to support the traces or pads on the grooves without deformation.
In particular, a sacrificial material Si can be sputtered into the recess, the etching gas xenon difluoride XeF 2 And injecting the through hole into the groove to etch the silicon Si. The recess may also be filled with a sacrificial material PSG and an etching liquid HF is injected into the recess through the via to etch the PSG. The embodiment of the invention is not limited. The grooves are filled with air in the mode.
Alternatively, the number of the through holes may be one or more, which is not limited in the embodiment of the present invention.
Alternatively, the bottom layer of the conductive pattern may be a wire and/or a pad above the groove, and the bottom layer of the conductive pattern may be a metal material with higher hardness.
Preferably, when the grooves are filled with air, the bottom layer of the conductive pattern may be a wire located above the grooves and/or the bottom layer of the pad may be a metal material with higher hardness.
In another possible embodiment, the target material is an insulating material, wherein the dielectric constant of the insulating material is smaller than that of the piezoelectric substrate, typically a material with a dielectric constant of less than 10, such as silicon dioxide SiO2, silicon nitride Si 3 N 4 And the like, the embodiment of the invention is not limited. In this embodiment, the grooves are filled with an insulating material, so that the wirings or pads may cover the grooves or may be located on the insulating material, which is not limited in the embodiment of the present invention.
It should be noted that the groove under the trace or the pad may be one groove, or may be formed by a plurality of grooves with relatively dense layout and relatively small openings, which is not limited by the embodiment of the present invention.
According to the embodiment of the invention, the piezoelectric substrate with the grooves can be formed, and at least one of the wirings and/or at least one of the bonding pads are formed on the grooves, so that parasitic capacitance between the wirings or between the bonding pads is reduced, the out-of-band suppression level of the filter is improved, and the performance of the filter is improved.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention.
Claims (11)
1. A surface acoustic wave filter, comprising:
the piezoelectric substrate is provided with a groove;
a plurality of resonators including reflectors provided at both ends and IDTs located between the reflectors;
the bonding pad comprises an input bonding pad, an output bonding pad and a grounding bonding pad;
a trace for connection between the pad and the plurality of resonators, and connection between the plurality of resonators;
wherein, at least one of the wires is arranged on the groove.
2. The filter of claim 1, wherein the recess is filled with an insulating material or air, the insulating material having a dielectric constant less than a dielectric constant of the piezoelectric substrate.
3. The filter of claim 2, wherein a support layer is disposed between the traces disposed on the grooves and the grooves, the support layer having a hardness greater than a hardness of the traces disposed on the grooves.
4. A surface acoustic wave filter, comprising:
the piezoelectric substrate is provided with a groove;
a plurality of resonators including reflectors provided at both ends and IDTs located between the reflectors;
the bonding pad comprises an input bonding pad, an output bonding pad and a grounding bonding pad;
a trace for connection between the pad and the plurality of resonators, and connection between the plurality of resonators;
wherein at least one of the bonding pads is arranged on the groove.
5. The filter of claim 4, wherein the recess is filled with an insulating material or air, the insulating material having a dielectric constant less than a dielectric constant of the piezoelectric substrate.
6. The filter of claim 5, wherein a support layer is disposed between the bonding pads disposed on the grooves and the grooves, the support layer having a hardness greater than the hardness of the bonding pads disposed on the grooves.
7. A multiplexer, comprising: a receive filter and a transmit filter, at least one of the receive filter and the transmit filter comprising a filter according to any one of claims 1-6.
8. A radio frequency front end comprising a filter as claimed in any one of claims 1-6.
9. A method of manufacturing a surface acoustic wave filter, the method comprising:
forming a recess on a target surface of a piezoelectric substrate, and depositing a target material in the recess;
forming a conductive pattern on the target surface, wherein the conductive pattern consists of a resonator, wires and bonding pads, and at least one of the wires and/or at least one of the bonding pads is/are positioned on the groove; the resonator includes reflectors provided at both ends and an IDT located between the reflectors.
10. The method of claim 9, wherein the target material is a sacrificial material, wherein the method further comprises, after forming a recess in the target surface of the piezoelectric substrate and depositing the target material in the recess:
forming a supporting layer on the groove, wherein the supporting layer comprises a through hole;
after the forming of the conductive pattern on the target surface, the method further includes:
injecting an etching material into the groove through the through hole to etch the sacrificial material;
at least one of the wirings and/or at least one of the bonding pads is/are positioned on the groove specifically:
at least one of the traces and/or at least one of the pads is located on the support layer.
11. The method of claim 9, wherein the target material is an insulating material having a dielectric constant less than a dielectric constant of the piezoelectric substrate.
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| CN202111676549.9A CN114301422B (en) | 2021-12-31 | 2021-12-31 | Filter, multiplexer, radio frequency front end and method of manufacturing a filter |
| PCT/CN2023/077778 WO2023126020A1 (en) | 2021-12-31 | 2023-02-23 | Filter, multiplexer, radio frequency front end, and method for manufacturing filter |
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| CN117013985A (en) * | 2022-04-29 | 2023-11-07 | 锐石创芯(重庆)科技有限公司 | Filter, multiplexer, radio frequency front end module and preparation method of filter |
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| US6081171A (en) * | 1998-04-08 | 2000-06-27 | Nokia Mobile Phones Limited | Monolithic filters utilizing thin film bulk acoustic wave devices and minimum passive components for controlling the shape and width of a passband response |
| CN102122939B (en) * | 2010-11-01 | 2013-12-04 | 中国电子科技集团公司第二十六研究所 | Preset cavity type SOI (silicon on insulator) substrate film bulk acoustic wave filter and manufacturing method thereof |
| JP5601377B2 (en) * | 2010-11-30 | 2014-10-08 | 株式会社村田製作所 | Elastic wave device and manufacturing method thereof |
| WO2016052129A1 (en) * | 2014-09-30 | 2016-04-07 | 株式会社村田製作所 | Acoustic wave device and method for manufacturing same |
| JP2016195305A (en) * | 2015-03-31 | 2016-11-17 | 太陽誘電株式会社 | Acoustic wave filter, demultiplexer, and module |
| CN113162578B (en) * | 2021-01-13 | 2023-04-07 | 诺思(天津)微系统有限责任公司 | Filter, multiplexer and electronic equipment |
| CN114301422B (en) * | 2021-12-31 | 2023-06-09 | 锐石创芯(重庆)科技有限公司 | Filter, multiplexer, radio frequency front end and method of manufacturing a filter |
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