CN116996038B - Filters, multiplexers and RF front-end modules - Google Patents

Abstract

The invention relates to a filter, a multiplexer and a radio frequency front end module, which comprises a capacitor and at least one bulk acoustic wave resonator; the capacitor comprises a first metal layer and a second metal layer, wherein the first metal layer is positioned on the lower surface of a substrate of the at least one bulk acoustic wave resonator, and the second metal layer is positioned on the upper surface of the substrate; the first metal layer, the second metal layer and the substrate form a capacitance area in a mutually overlapped area, and the orthographic projection of the capacitance area on the lower surface of the substrate is not overlapped with the orthographic projection of the resonance area of the at least one bulk acoustic wave resonator on the lower surface of the substrate. Thus, the capacitor is integrated with the bulk acoustic wave resonator, and can replace a capacitive element in the prior art when in use, so that the packaging size of the filter can be reduced.

Description

Filters, multiplexers and RF front-end modules

Technical Field

The invention belongs to the field of radio frequency filtering devices and relates to a filter, a multiplexer and a radio frequency front-end module.

Background technique

A BAW filter generally includes a BAW resonator, a tuning element, and a packaging substrate, wherein the BAW resonator and the tuning element are both connected to the packaging substrate. The tuning element may be a capacitor element, which can reduce the effective electromechanical coupling coefficient of the BAW resonator, improve the proximal suppression of the BAW filter, and improve the filtering performance of the BAW filter.

However, discrete capacitor elements are usually large in size, so using this method to improve the filtering performance of the BAW filter will increase the size of the BAW filter.

Summary of the invention

The filter, multiplexer and radio frequency front-end module provided by the present invention can achieve high performance and small size of the filter.

An embodiment of the present invention provides a filter, comprising a capacitor and at least one bulk acoustic wave resonator; wherein the capacitor comprises a first metal layer and a second metal layer, the first metal layer is located on the lower surface of a substrate of the at least one bulk acoustic wave resonator, and the second metal layer is located on the upper surface of the substrate; an area where the first metal layer, the second metal layer, and the substrate overlap with each other forms a capacitor region, and an orthographic projection of the capacitor region on the lower surface of the substrate does not overlap with an orthographic projection of a resonance region of the at least one bulk acoustic wave resonator on the lower surface of the substrate.

Optionally, the filter further includes a via hole, and the at least one BAW resonator includes a first BAW resonator; the via hole passes through from the lower surface of the substrate to the upper surface of the piezoelectric layer of the at least one BAW resonator, and one end of the first metal layer is passed through the via hole to electrically connect to the upper electrode of the first BAW resonator; or, the via hole passes through from the lower surface of the substrate to the upper surface of the substrate, and one end of the first metal layer is passed through the via hole to electrically connect to the lower electrode of the first BAW resonator.

Optionally, the first BAW resonator is connected in series with the capacitor; one end of the second metal layer is electrically connected to a first conductive structure other than the lower electrode of the first BAW resonator, and the first conductive structure is located between the piezoelectric layer and the substrate; the other end of the first metal layer, the other end of the second metal layer, and the overlapping area of the substrate form the capacitor region.

Optionally, the first BAW resonator is connected in parallel with the capacitor; one end of the first metal layer is passed through the via hole to electrically connect the upper electrode of the first BAW resonator; one end of the second metal layer is electrically connected to the lower electrode of the first BAW resonator; the other end of the first metal layer, the other end of the second metal layer and the overlapping area of the substrate form the capacitor region.

Optionally, the second metal layer and the lower electrode of the first BAW resonator are an integrally formed structure.

Optionally, the second metal layer and the first conductive structure are an integrally formed structure.

Optionally, an orthographic projection of a resonance region of the at least one BAW resonator on the lower surface of the substrate does not overlap with the first metal layer, and does not overlap with an orthographic projection of the second metal layer on the lower surface of the substrate.

To solve the above technical problems, an embodiment of the present invention provides a filter, comprising a capacitor and at least one BAW resonator; wherein the capacitor comprises a first metal layer and a second metal layer, the first metal layer is located on the lower surface of the substrate of the at least one BAW resonator, and the second metal layer is located on the upper surface of the piezoelectric layer of the at least one BAW resonator; an area where the first metal layer, the second metal layer, the substrate and the piezoelectric layer overlap with each other forms a capacitor area, and an orthographic projection of the capacitor area on the lower surface of the substrate does not overlap with an orthographic projection of a resonance area of the at least one BAW resonator on the lower surface of the substrate.

Optionally, the filter further includes a via hole, and the at least one BAW resonator includes a first BAW resonator; the via hole passes through from the lower surface of the substrate to the upper surface of the piezoelectric layer of the at least one BAW resonator, and one end of the first metal layer is passed through the via hole to electrically connect to the upper electrode of the first BAW resonator; or, the via hole passes through from the lower surface of the substrate to the upper surface of the substrate, and one end of the first metal layer is passed through the via hole to electrically connect to the lower electrode of the first BAW resonator.

Optionally, the first BAW resonator is connected in series with the capacitor; one end of the second metal layer is electrically connected to a second conductive structure other than the upper electrode of the first BAW resonator, and the second conductive structure is located on the upper surface of the piezoelectric layer; the other end of the first metal layer, the other end of the second metal layer, the piezoelectric layer and the area where the substrate overlap to form the capacitor region.

Optionally, the first BAW resonator is connected in parallel with the capacitor; one end of the first metal layer is passed through the via hole to electrically connect the lower electrode of the first BAW resonator; one end of the second metal layer is electrically connected to the upper electrode of the first BAW resonator; the other end of the first metal layer, the other end of the second metal layer, the piezoelectric layer and the overlapping area of the substrate form the capacitor region.

Optionally, the second metal layer and the upper electrode of the first BAW resonator are an integrally formed structure.

Optionally, the second metal layer and the second conductive structure are an integrally formed structure.

Optionally, an orthographic projection of a resonance region of the at least one BAW resonator on the lower surface of the substrate does not overlap with the first metal layer, and does not overlap with an orthographic projection of the second metal layer on the lower surface of the substrate.

In order to solve the above technical problem, an embodiment of the present invention provides a multiplexer, comprising a filter as described in any one of the above items.

In order to solve the above technical problems, an embodiment of the present invention provides a radio frequency front-end module, including a filter as described in any one of the above items.

In the filter, multiplexer and RF front-end module provided by the embodiment of the present invention, the first metal layer of the capacitor is arranged on the lower surface of the substrate, and the second metal layer of the capacitor is arranged on the upper surface of the substrate or the upper surface of the piezoelectric layer, so that the capacitor and the BAW resonator are prepared as one. By integrating the capacitor on the BAW filter chip, the size of the BAW filter or module package can be greatly reduced without significantly increasing the chip area while improving the performance of the BAW filter.

In addition, in this embodiment, the first metal layer is arranged on the lower surface of the substrate, and the capacitance formed by the first metal layer and the second metal layer through the substrate or through the substrate and the piezoelectric layer will not produce parasitic resonance, and will not produce resonance peaks outside the band, thus not deteriorating the out-of-band suppression effect of the specific frequency band of the filter. Moreover, the capacitance value of the capacitor area formed by this arrangement of the embodiment is relatively small, and compared with the existing discrete capacitor elements, the arrangement of the embodiment can better control the accuracy of the capacitance value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a filter provided in Embodiment 1 of the present invention;

FIG. 2 is a schematic diagram of a filter provided in Embodiment 1 of the present invention.

FIG3 is a partial cross-sectional schematic diagram of a filter provided in Embodiment 1 of the present invention;

Fig. 4 is a cross-sectional view taken along the line A1-A1 in Fig. 3;

FIG5 is a cross-sectional view taken along the line B1-B1 in FIG3 ;

FIG6 is a second partial cross-sectional schematic diagram of the filter provided in the first embodiment of the present invention;

FIG7 is a third partial cross-sectional schematic diagram of the filter provided in Embodiment 1 of the present invention;

FIG8 is a partial cross-sectional schematic diagram of a filter provided in Embodiment 2 of the present invention;

FIG9 is a cross-sectional view taken along the line A2-A2 in FIG8 ;

FIG10 is a cross-sectional view taken along the line B2-B2 in FIG8 ;

11 is a second partial cross-sectional schematic diagram of a filter provided in Embodiment 2 of the present invention;

FIG12 is a third partial cross-sectional schematic diagram of the filter provided in the second embodiment of the present invention.

The reference numerals in the specification are as follows:

100, filter;

1. BAW resonator; 1a. first BAW resonator; 1b. second BAW resonator; 11. substrate; 12. acoustic mirror; 13. piezoelectric layer; 14. upper electrode; 15. lower electrode; 16. resonance region; 17. passivation layer; 18. via hole;

2. Capacitor; 21. First metal layer; 22. Second metal layer; 23. Capacitor region.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

Embodiment 1

As shown in Figures 1 and 2, the filter 100 is a ladder-type structure filter, including a bulk acoustic wave resonator 1 and a capacitor 2. Among them, the bulk acoustic wave resonator 1 includes a plurality of parallel arm resonators and a plurality of series arm resonators, and the capacitor 2 can be connected in series or in parallel with any parallel arm resonator, and can also be connected in series or in parallel with any series arm resonator. In addition, in this embodiment, "plurality" means greater than or equal to two. In some other embodiments, the number of bulk acoustic wave resonators 1 possessed by the filter 100 can also be one (refer to Figure 7) or other numbers. When the number of bulk acoustic wave resonators 1 possessed by the filter 100 is multiple, the connection relationship of these bulk acoustic wave resonators 1 can also be set according to actual needs.

As shown in FIGS. 3 and 4 , the BAW resonator 1 includes a substrate 11, an acoustic mirror 12, a piezoelectric layer 13, an upper electrode 14, and a lower electrode 15. The acoustic mirror 12 is disposed on the substrate 11, the lower electrode 15 is disposed on the upper surface of the acoustic mirror 12, the piezoelectric layer 13 is disposed on the upper surface of the lower electrode 15, and the upper electrode 14 is disposed on the upper surface of the piezoelectric layer 13. In addition, the region where the acoustic mirror 12, the lower electrode 15, the piezoelectric layer 13, and the upper electrode 14 overlap with each other forms a resonance region 16, wherein the region surrounded by the dotted frame Q in FIG. 4 is the resonance region 16. In addition, the region where the four overlap with each other may refer to the region where the orthographic projections of the four on the lower surface of the substrate 11 can overlap.

In a feasible implementation, a seed layer may be further added between the lower electrode 15 and the acoustic mirror 12 , and the material of the seed layer may be aluminum nitride or the like.

In the first embodiment, the material of the substrate 11 can be any one of single crystal silicon, gallium arsenide, gallium nitride, sapphire, quartz and the like. Preferably, the substrate 11 is made of a material with a large dielectric constant to reduce the capacitor area.

In the first embodiment, the acoustic mirror 12 is a cavity embedded in the upper surface of the substrate 11. In other embodiments, the acoustic mirror 12 may be a Bragg reflection layer, or may be formed by a lower electrode to form a cavity.

In the first embodiment, the material of the piezoelectric layer 13 can be aluminum nitride, zinc oxide, lead zirconate titanate (PZT), or rare earth element doped materials of the above materials in a certain atomic ratio. The piezoelectric layer 13 can also be made of single crystal piezoelectric materials, such as single crystal aluminum nitride, lithium niobate, lithium tantalate, quartz, etc.

In the first embodiment, the material of the upper electrode 14 can be a single metal material or a composite or alloy material of different metals. Optionally, the material of the upper electrode 14 can be one of molybdenum, tungsten, ruthenium, gold, magnesium, aluminum, copper, chromium, titanium, osmium, iridium or a composite of the above metals or an alloy thereof. The material of the lower electrode 15 can also be a single metal material or a composite or alloy material of different metals. Optionally, the material of the upper electrode 14 can be one of molybdenum, tungsten, ruthenium, gold, magnesium, aluminum, copper, chromium, titanium, osmium, iridium or a composite of the above metals or an alloy thereof. Among them, the materials of the upper electrode 14 and the lower electrode 15 can be the same or different.

As shown in FIG. 4 , the BAW resonator 1 further comprises a passivation layer 17, which covers the outer surface of the upper electrode 14. The passivation layer 17 may be made of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, or the like.

In addition, in the first embodiment, the BAW resonator 1 may be configured using existing technology, which will not be described in detail in this embodiment.

As shown in FIGS. 3 to 5 , the capacitor 2 includes a first metal layer 21 and a second metal layer 22, wherein the first metal layer 21 is located on the lower surface of the substrate 11, and the second metal layer 22 is located on the upper surface of the substrate 11, and the area where the first metal layer 21, the second metal layer 22 and the substrate 11 overlap each other forms a capacitor area 23, wherein the area surrounded by the dotted frame P in FIG. 5 is the capacitor area 23. The area where the first metal layer 21, the second metal layer 22 and the substrate 11 overlap each other refers to the area where the orthographic projections of the three on the lower surface of the substrate 11 can overlap. In the present embodiment, the capacitor 2 is prepared on the substrate 11, which is equivalent to being prepared as one with the bulk acoustic wave resonator 1. When used, the capacitor 2 can replace the capacitive element in the prior art, thereby reducing the package size of the filter 100.

In addition, in this embodiment, the orthographic projection of the capacitor region 23 on the lower surface of the substrate 11 does not overlap with the orthographic projection of the resonance region 16 of the BAW resonator 1 on the lower surface of the substrate 11, which can effectively avoid interference between the capacitor region 23 and the resonance region 16.

In this embodiment, the first metal layer 21 is arranged on the lower surface of the substrate 11, and the capacitance formed by the first metal layer 21 and the second metal layer 22 across the substrate 11 will not produce parasitic resonance, and will not produce resonance peaks outside the band, thus not deteriorating the out-of-band suppression effect of the specific frequency band of the filter 100. Moreover, the capacitance value of the capacitor area 23 formed by this arrangement of the embodiment is relatively small, and compared with the existing discrete capacitor elements, the arrangement of the embodiment can better control the accuracy of the capacitance value.

In this embodiment, the capacitance C of the capacitor 2 is equal to εS/d, where ε is the dielectric constant of the substrate 11, S is the area of the overlapping region of the first metal layer 21 and the second metal layer 22, and d is the thickness of the substrate 11, where the thickness of the substrate 11 is also the distance between the first metal layer 21 and the second metal layer 22. In general, d>20um, and C is determined according to the design requirements of the filter 100, and the general value is between 0.01pF and 3pF.

As shown in FIG4 , in an achievable implementation of the first embodiment, the filter 100 further includes a through hole 18, which penetrates from the lower surface of the substrate 11 to the upper surface of the piezoelectric layer 13; each BAW resonator 1 of the filter 100 includes a first BAW resonator 1a, and one end of the first metal layer 21 is penetrated through the through hole 18 to electrically connect to the upper electrode 14 of the first BAW resonator 1a. At this time, the first metal layer 21 is equivalent to including two parts, wherein the first part is located on the lower surface of the substrate 11, the second part is electrically connected to the first part, and the second part is penetrated through the through hole 18 to electrically connect to the upper electrode 14 of the first BAW resonator 1a. When preparing the first metal layer 21, some metal will be filled in the through hole 18 to electrically connect the first metal layer 21 to the upper electrode 14 of the first BAW resonator 1a. It should be understood that at this time, the lower electrode 15 of the first BAW resonator 1 a is not electrically connected to the first metal layer 21 , and there is a certain gap between the lower electrode 15 of the first BAW resonator 1 a and the via hole 18 .

In some other embodiments, the via hole 18 may also be formed from the lower surface of the substrate 11 to the upper surface of the substrate 11. In this case, one end of the first metal layer 21 may also be provided through the via hole 18 and electrically connected to the lower electrode 15 of the first BAW resonator 1a. In this manner, the second metal layer 22 may not be electrically connected to the lower electrode 15 of the first BAW resonator 1a. However, the second metal layer 22 may be electrically connected to a conductive structure other than the lower electrode 15 of the first BAW resonator 1a (the conductive structure is defined as the first conductive structure). For the convenience of production, the first conductive structure is located between the piezoelectric layer and the substrate 11, that is, the first conductive structure is also provided on the upper surface of the substrate 11. The first conductive structure may be a pad of the filter 100, a wiring connected to the pad, the lower electrode 15 of another resonator 1, or a wiring connecting the lower electrodes 15 of two resonators 1. Of course, when one end of the first metal layer 21 is electrically connected to the upper electrode 14 of the first BAW resonator 1 a , the second metal layer 22 may also be electrically connected to the first conductive structure.

In a feasible implementation of the first embodiment, the capacitor 2 is connected in series with the first bulk acoustic wave resonator 1a. At this time, one end of the first metal layer 21 of the capacitor 2 is electrically connected to the upper electrode 14 or the lower electrode 15 of the first bulk acoustic wave resonator 1a through the via hole 18, and one end of the second metal layer 22 is electrically connected to the first conductive structure. The other end of the first metal layer 21, the other end of the second metal layer 22 and the overlapping area of the substrate 11 form a capacitor region.

As shown in FIG. 1 , in another feasible implementation, the capacitor 2 and the first BAW resonator 1a may be connected in parallel. In this case, one end of the first metal layer 21 is passed through the wire hole 18 to electrically connect to the upper electrode 14 of the first BAW resonator 1a; one end of the second metal layer 22 is electrically connected to the lower electrode 15 of the first BAW resonator 1a; the other end of the first metal layer 21, the other end of the second metal layer 22 and the overlapping area of the substrate 11 form a capacitor region. Among them, the electrical connection method between the second metal layer 22 and the lower electrode 15 of the first BAW resonator 1a is also diverse: as shown in FIG3 , each BAW resonator 1 also includes a second BAW resonator 1b, and the lower electrode 15 of the first BAW resonator 1a is electrically connected to the lower electrode 15 of the second BAW resonator 1b through a wiring, and the second metal layer 22 is electrically connected to the wiring, thereby realizing electrical connection with the lower electrode 15 of the first BAW resonator 1a; or, as shown in FIG6 , the second metal layer 22 can also be directly electrically connected to the lower electrode 15 of the first BAW resonator 1a.

In addition, the second metal layer 22 and the lower electrode 15 of the first BAW resonator 1a are an integrally formed structure, which is more convenient for production; similarly, the second metal layer 22 and the first conductive structure can also be an integrally formed structure. When the first conductive structure is the lower electrode 15 of the resonator 1 outside the first BAW resonator 1a, or a wiring connecting the lower electrodes 15 of two resonators 1, or a wiring connecting a pad, the second metal layer 22, the lower electrode 15 of the first BAW resonator 1a and the first conductive structure can be integrally formed. For example, during production, a metal conductive layer can be prepared on the lower surface of the piezoelectric layer, and then the metal conductive layer is patterned by processes such as exposure, development, and etching to obtain the lower electrode 15 of the first BAW resonator 1a, the second metal layer 22 and the first conductive structure.

As shown in FIG4 , further, along the direction from the lower surface of the substrate 11 to the upper surface of the piezoelectric layer 13, the aperture of the through hole 18 gradually decreases, which can improve the filling property of the first metal layer 21 in the through hole 18. In other implementations, along the direction from the lower surface of the substrate 11 to the upper surface of the piezoelectric layer 13, the aperture of the through hole 18 can also be set to be consistent, which is not limited in this embodiment.

In the first embodiment, when the filter 100 has one BAW resonator 1, the orthographic projection of the resonance region 16 of the BAW resonator 1 on the lower surface of the substrate 11 does not overlap with the first metal layer 21, so that the formation of parasitic capacitance between the first metal and the upper electrode 14 or the lower electrode 15 can be avoided, and the leakage of acoustic energy from the region can be avoided, thereby improving the working performance of the filter 100; similarly, the orthographic projection of the resonance region 16 of the BAW resonator 1 on the lower surface of the substrate 11 does not overlap with the orthographic projection of the second metal layer 22 on the lower surface of the substrate 11, so that the formation of parasitic capacitance between the second metal and the upper electrode 14 or the lower electrode 15 can be avoided. When the filter 100 has multiple BAW resonators 1, the orthographic projection of the resonance region 16 of each BAW resonator 1 on the lower surface of the substrate 11 does not overlap with the first metal layer 21, and the orthographic projection of the resonance region 16 of each BAW resonator 1 on the lower surface of the substrate 11 does not overlap with the orthographic projection of the second metal layer 22 on the lower surface of the substrate 11.

It should be noted that the non-overlap mentioned in this embodiment may be incomplete overlap or complete non-overlap, which is not limited in this embodiment.

In addition, in a feasible implementation manner of the first embodiment, the first metal layer 21 and the second metal layer 22 may be two independent pads.

Embodiment 2

As shown in Figures 8 to 12, in the second embodiment, the filter 100 also includes a bulk acoustic wave resonator 1 and a capacitor 2. Among them, the number of bulk acoustic wave resonators 1 in the second embodiment can also be one (refer to Figure 12) or more (refer to Figure 8), and its related settings are the same as those in the first embodiment. The difference between the second embodiment and the first embodiment is that: although the capacitor 2 in the second embodiment also includes a first metal layer 21 and a second metal layer 22, in the second embodiment, the first metal layer 21 is located on the lower surface of the substrate 11 of the bulk acoustic wave resonator 1, and the second metal layer 22 is located on the upper surface of the piezoelectric layer 13 of the bulk acoustic wave resonator 1; the area where the first metal layer 21, the second metal layer 22, the substrate 11 and the piezoelectric layer 13 overlap with each other forms a capacitor area 23, and the orthographic projection of the capacitor area 23 on the lower surface of the substrate 11 does not overlap with the orthographic projection of the resonance area 16 of the bulk acoustic wave resonator 1 on the lower surface of the substrate 11. The area surrounded by the dotted frame Q in FIG. 9 is the resonance region 16, and the area surrounded by the dotted frame P in FIG. 10 is the capacitance region 23.

In the second embodiment, the first metal layer 21 and the second metal layer 22 of the capacitor 2 are respectively arranged on the substrate 11 and the piezoelectric layer 13, so that they are integrated with the bulk acoustic wave resonator 1, which is equivalent to being integrated with the bulk acoustic wave resonator 1. When in use, the capacitor 2 can replace the capacitive element in the prior art, thereby reducing the packaging size of the filter 100.

At this time, the orthographic projection of the resonance region 16 of each BAW resonator 1 on the lower surface of the substrate 11 does not overlap with the first metal layer 21. Similarly, the orthographic projection of the resonance region 16 of each BAW resonator 1 on the lower surface of the substrate 11 does not overlap with the orthographic projection of the second metal layer 22 on the lower surface of the substrate 11.

In addition, the following settings in the second embodiment are different from those in the first embodiment:

As shown in FIG. 9 , in a feasible implementation of the second embodiment, a via hole 18 is also provided on the filter 100, and the via hole 18 passes through the lower surface of the substrate 11 to the upper surface of the substrate 11, and one end of the first metal layer 21 is passed through the via hole 18 to electrically connect the lower electrode 15 of the first bulk acoustic wave resonator 1a.

In another feasible implementation of the second embodiment, the via hole 18 may also pass through the lower surface of the substrate 11 to the upper surface of the piezoelectric layer 13. In this case, one end of the first metal layer 21 is passed through the via hole to electrically connect the upper electrode of the first bulk acoustic wave resonator 1a.

In the second embodiment, the first BAW resonator 1a can be connected in series with the capacitor 2; at this time, one end of the first metal layer 21 can be electrically connected to the upper electrode or the lower electrode of the first BAW resonator 1a, and one end of the second metal layer 22 is electrically connected to a conductive structure other than the upper electrode 14 of the first BAW resonator 1a (the conductive structure is defined as the second conductive structure), and the second conductive structure is located on the upper surface of the piezoelectric layer 13; the other end of the first metal layer 21, the other end of the second metal layer 22, the piezoelectric layer 13 and the substrate 11 overlap each other to form a capacitor region 23. In addition, the second conductive structure can be a pad of the filter 100, a wiring connected to the pad, an upper electrode 14 of another resonator 1, or a wiring connecting the upper electrodes 14 of two resonators 1. In addition, at this time, the first metal layer 21 can be electrically connected to the upper electrode 14 of the first BAW resonator 1a or connected to the lower electrode 15 of the first BAW resonator 1a.

In the second embodiment, the first BAW resonator 1a and the capacitor 2 may also be connected in parallel; one end of the first metal layer 21 is passed through the via hole 18 to electrically connect the lower electrode of the first BAW resonator 1a; one end of the second metal layer 22 is electrically connected to the upper electrode 14 of the first BAW resonator 1a; the other end of the first metal layer 21, the other end of the second metal layer 22, the piezoelectric layer 13 and the overlapping area of the substrate 11 form a capacitor region 23. Among them, the electrical connection method between the second metal layer 22 and the upper electrode 14 of the first BAW resonator 1a is also diverse: as shown in FIG8, each BAW resonator 1 also includes a second BAW resonator 1b, and the upper electrode 14 of the first BAW resonator 1a is electrically connected to the upper electrode 14 of the second BAW resonator 1b through a wiring, and the second metal layer 22 is electrically connected to the wiring, thereby achieving electrical connection with the upper electrode 14 of the first BAW resonator 1a; or, as shown in FIG11, the second metal layer 22 can also be directly electrically connected to the upper electrode 14 of the first BAW resonator 1a.

In the second embodiment, the second metal layer 22 is provided on the upper surface of the piezoelectric layer 13, and the second metal layer 22 and the upper electrode 14 of the first BAW resonator 1a can be an integrally formed structure. In addition, the second metal layer 22 and the second conductive structure can also be an integrally formed structure. When the second conductive structure is the upper electrode 14 of the resonator 1 other than the first BAW resonator 1a, or is a trace connecting the upper electrodes 14 of two resonators 1, or is a trace connecting a pad, the second metal layer 22, the upper electrode 14 of the first BAW resonator 1a, and the second conductive structure can be integrally formed.

An embodiment of the present invention further provides a multiplexer, which includes the filter 100 described in any of the above embodiments, wherein the multiplexer can be a duplexer, a triplexer, etc., which is not limited in this embodiment.

In addition, an embodiment of the present invention further provides a radio frequency front-end module, which includes the filter 100 described in any of the above embodiments.

The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (16)

1. A filter comprising a capacitor and at least one bulk acoustic wave resonator; wherein,

The capacitor comprises a first metal layer and a second metal layer, wherein the first metal layer is positioned on the lower surface of a substrate of the at least one bulk acoustic wave resonator, and the second metal layer is positioned on the upper surface of the substrate;

The first metal layer, the second metal layer and the substrate form a capacitance area in a mutually overlapped area, and the orthographic projection of the capacitance area on the lower surface of the substrate is not overlapped with the orthographic projection of the resonance area of the at least one bulk acoustic wave resonator on the lower surface of the substrate.

2. The filter of claim 1, further comprising a via, the at least one bulk acoustic wave resonator comprising a first bulk acoustic wave resonator;

The wire through hole penetrates from the lower surface of the substrate to the upper surface of the piezoelectric layer of the at least one bulk acoustic wave resonator; one end of the first metal layer penetrates through the wire through hole to be electrically connected with the upper electrode of the first bulk acoustic wave resonator; or alternatively

The wire through hole penetrates from the lower surface of the substrate to the upper surface of the substrate, and one end of the first metal layer penetrates through the wire through hole to be electrically connected with the lower electrode of the first bulk acoustic wave resonator.

3. The filter of claim 2, wherein the first bulk acoustic wave resonator is connected in series with the capacitor;

One end of the second metal layer is electrically connected with a first conductive structure except for a lower electrode of the first bulk acoustic wave resonator, and the first conductive structure is positioned between the piezoelectric layer and the substrate;

The other end of the first metal layer, the other end of the second metal layer and the area where the substrates overlap each other form the capacitance area.

4. The filter of claim 2, wherein the first bulk acoustic wave resonator is connected in parallel with the capacitor;

one end of the first metal layer penetrates through the wire through hole to be electrically connected with the upper electrode of the first bulk acoustic wave resonator;

one end of the second metal layer is electrically connected with the lower electrode of the first bulk acoustic wave resonator;

The other end of the first metal layer, the other end of the second metal layer and the area where the substrates overlap each other form the capacitance area.

5. The filter of claim 4, wherein the second metal layer is of unitary construction with the lower electrode of the first bulk acoustic resonator.

6. A filter according to claim 3, wherein the second metal layer is of unitary construction with the first conductive structure.

7. The filter of claim 1, wherein an orthographic projection of the resonating region of the at least one bulk acoustic wave resonator on the lower surface of the substrate does not overlap the first metal layer and does not overlap an orthographic projection of the second metal layer on the lower surface of the substrate.

8. A filter comprising a capacitor and at least one bulk acoustic wave resonator; wherein,

The capacitor comprises a first metal layer and a second metal layer, wherein the first metal layer is positioned on the lower surface of the substrate of the at least one bulk acoustic wave resonator, and the second metal layer is positioned on the upper surface of the piezoelectric layer of the at least one bulk acoustic wave resonator;

The first metal layer, the second metal layer, the substrate and the piezoelectric layer form a capacitance region in a mutually overlapped region, and the orthographic projection of the capacitance region on the lower surface of the substrate is not overlapped with the orthographic projection of the resonance region of the at least one bulk acoustic wave resonator on the lower surface of the substrate.

9. The filter of claim 8, further comprising a via, the at least one bulk acoustic wave resonator comprising a first bulk acoustic wave resonator;

The wire through hole penetrates through the lower surface of the substrate to the upper surface of the piezoelectric layer of the at least one bulk acoustic wave resonator, and one end of the first metal layer penetrates through the wire through hole to be electrically connected with the upper electrode of the first bulk acoustic wave resonator; or alternatively

The wire through hole penetrates from the lower surface of the substrate to the upper surface of the substrate; one end of the first metal layer penetrates through the wire through hole to be electrically connected with the lower electrode of the first bulk acoustic wave resonator.

10. The filter of claim 9, wherein the first bulk acoustic wave resonator is connected in series with the capacitor;

one end of the second metal layer is electrically connected with a second conductive structure except for an upper electrode of the first bulk acoustic wave resonator, and the second conductive structure is positioned on the upper surface of the piezoelectric layer;

The other end of the first metal layer, the other end of the second metal layer, the piezoelectric layer and the region where the substrate overlaps each other form the capacitance region.

11. The filter of claim 9, wherein the first bulk acoustic wave resonator is connected in parallel with the capacitor;

one end of the first metal layer penetrates through the wire through hole to be electrically connected with the lower electrode of the first bulk acoustic wave resonator;

One end of the second metal layer is electrically connected with the upper electrode of the first bulk acoustic wave resonator;

The other end of the first metal layer, the other end of the second metal layer, the piezoelectric layer and the region where the substrate overlaps each other form the capacitance region.

12. The filter of claim 10, wherein the second metal layer is of unitary construction with the upper electrode of the first bulk acoustic resonator.

13. The filter of claim 10, wherein the second metal layer is an integral structure with the second conductive structure.

14. The filter of claim 8, wherein an orthographic projection of the resonating region of the at least one bulk acoustic wave resonator on the lower surface of the substrate does not overlap the first metal layer and does not overlap an orthographic projection of the second metal layer on the lower surface of the substrate.

15. A multiplexer comprising the filter of any one of claims 1-14.

16. A radio frequency front end module comprising the filter of any of claims 1-14.