WO2021098322A1

WO2021098322A1 - Bulk acoustic wave filter and manufacturing method therefor, and duplexer

Info

Publication number: WO2021098322A1
Application number: PCT/CN2020/111353
Authority: WO
Inventors: 庞慰; 郑云卓
Original assignee: 天津大学; 诺思(天津)微系统有限责任公司
Priority date: 2019-11-20
Filing date: 2020-08-26
Publication date: 2021-05-27
Also published as: CN111010143A

Abstract

.A bulk acoustic wave filter and a manufacturing method therefor, and a duplexer. The manufacturing method comprises: forming a plurality of parallel resonators on a first surface of an upper wafer (11); forming a plurality of series resonators on a first surface of a lower wafer (12); connecting first pins to a circuit of the parallel resonators, connecting second pins to a circuit of the series resonators, oppositely arranging the first surface of the upper wafer (11) and the first surface of the lower wafer (12) in parallel, bonding the first pins and the second pins to form a multistage series-parallel filter circuit, and forming a distributed capacitor. The parallel resonators and the series resonators forming the distributed capacitor are in the same stage, in adjacent stages or cross a stage in the multi-stage series-parallel filter circuit. The volume of the filter is reduced by changing the structure thereof without losing the performance of the filter.

Description

Bulk acoustic wave filter, manufacturing method thereof, and duplexer

Technical field

The present invention relates to the technical field of filter components for communication, in particular to a bulk acoustic wave filter, a manufacturing method thereof, and a duplexer.

Background technique

In recent years, with the rapid development of the market, wireless communication terminals and equipment have continued to develop in the direction of miniaturization, multimode-multiband, and wireless communication terminals and equipment have continued to develop in the direction of miniaturization, multimode-multiband. The number of duplexers used for FDD (Frequency Division Multiplexing Duplex) in wireless communication terminals has also increased. Five-mode thirteen-band, and even five-mode seventeen-band have gradually become the standard requirements of mainstream mobile phones. Especially with the approaching of 5G commercialization, small-size, high-performance duplexes such as

Band

1, 2, 3, 5, 7, and 8. The demand for the device is also increasing.

Refer to FIG. 1 for a front view of the upper wafer of a conventional filter. As shown in Figure 1, the resonators in the filter are all set on the upper wafer 101. The S1-S6 and P1-P6 in the figure are connected to the through-wafer holes on the lower wafer through the wafer-level bonding area. , And then connected to the pads on the lower surface of the lower wafer, and interconnected with the pads on the upper surface of the package substrate through solder balls. The two wafers are bonded to form a wafer-level packaging protection structure, and the structure and the packaging substrate are covered with a resin compound plastic encapsulant to form a substrate-level packaging protection structure. The two-level package protection structure jointly protects the internal FBAR from the external environment, so as to avoid deterioration of the filter performance.

The area of the wafer-level package protection structure is 1.3mm ² , because the area of the resonator increases greatly with the decrease of frequency, the size of the wafer-level package protection structure is compared with similar filters in the S band (2GHz～4GHz) , Increased by about 1.5 times to about 2 times, plus the size of the substrate-level packaging, the overall size will reach 1.6mmx1.2mm, the area occupied by mobile terminals is too large, the high-density design of the circuit layout, and the device And the heat dissipation of the whole machine is a severe challenge.

From this, it can be seen that providing a filter that can reduce the size of the filter without affecting its performance is a technical problem that needs to be solved urgently.

Summary of the invention

In view of this, the main purpose of the present invention is to provide a bulk acoustic wave filter, a manufacturing method thereof, and a duplexer, which can reduce the size of the filter and reduce its occupied area without affecting the performance of the filter.

To achieve the above objective, according to one aspect of the present invention, a method for manufacturing a bulk acoustic wave filter is provided, which includes the following steps: forming a plurality of parallel resonators on the first surface of the upper wafer; A plurality of series resonators are formed; a first pin is connected to the circuit of the parallel resonator, a second pin is connected to the circuit of the series resonator, and the first surface of the upper wafer is connected to the lower The first surface of the wafer is arranged in parallel and opposed to each other, and the first pin and the second pin are bonded to form a multi-stage series-parallel filter circuit, and form a distributed capacitor; wherein, the distributed capacitor is formed The parallel resonator and the series resonator in the multi-stage series-parallel filter circuit are in a same-stage relationship, an adjacent stage relationship, or a phase-to-stage relationship.

Optionally, a plurality of the parallel resonators are arranged in a row, and a plurality of the series resonators are arranged in a row; the parallel resonators and the series resonators in the same level relationship form the distributed capacitance.

In another aspect of the present invention, a bulk acoustic wave filter includes: an upper wafer, a first surface of the upper wafer is provided with a plurality of parallel resonators and first pins; a lower wafer, the first surface of the lower wafer One surface is provided with a plurality of series resonators and second pins; the upper wafer and the lower wafer are superimposed to form a packaging structure. Inside the packaging structure, the first surface of the upper wafer and the The first surface of the wafer is arranged oppositely in parallel, and the first pin and the second pin are bonded to form a multi-stage series-parallel filter circuit, and form a distributed capacitor; wherein, the distributed capacitor is formed The parallel resonator and the series resonator in the multi-stage series-parallel filter circuit are in a same-stage relationship, an adjacent stage relationship, or a phase-to-stage relationship.

Optionally, the parallel resonator and the series resonator are thin film bulk acoustic wave resonators, solid-state assembly resonators, or surface acoustic wave resonators.

Optionally, the electromechanical coupling coefficients of the parallel resonator and the series resonator are different.

Optionally, the electromechanical coupling coefficient of the series resonator is at least 2% greater than the electromechanical coupling coefficient of the parallel resonator.

Optionally, the material of the piezoelectric layer of the parallel resonator is different from the material of the piezoelectric layer of the series resonator.

Optionally, the vertical interval between the upper electrode of the parallel resonator and the upper electrode of the series resonator is 5um.

Optionally, the capacitance of the distributed capacitor is 0.1 pF.

Another aspect of the present invention also provides a duplexer including two bulk acoustic wave filters described above.

According to the technical solution of the present invention, a parallel resonator is arranged on the upper wafer, and a series resonator is arranged on the lower wafer. The relatively superposed structure is adopted, which can effectively reduce the volume of the filter; wherein, in this structure, Distributed capacitance will be generated between the parallel resonator and the series resonator. If the distributed capacitance exists between the parallel resonator and the series resonator separated by more than 2 levels, it will have a greater impact on the performance of the filter, including the band External restraint deterioration, insertion loss deterioration, etc. Therefore, in the package structure, by adjusting the position of the parallel resonator/series resonator, the distributed capacitance formed does not span more than two levels. It is in the same level relationship and adjacent It is formed by parallel resonators and series resonators in a level relationship or across a level relationship.

The technical solution of the present invention reduces the size of the filter by changing the structure of the filter without losing the performance of the filter, thereby reducing the space occupied by the communication terminal, thereby facilitating the miniaturization of the product.

Description of the drawings

For the purpose of illustration and not limitation, the present invention will now be described according to preferred embodiments of the present invention, particularly with reference to the accompanying drawings, in which:

Fig. 1 is a front view of the upper wafer of a prior art filter;

Fig. 2 is a flow chart of a method for manufacturing a bulk acoustic wave filter according to an embodiment of the present invention;

Figure 3 is a side view of the filter of the embodiment of the present invention;

4A is a front view of the wafer on the embodiment of the present invention;

4B is a front view of the wafer under the embodiment of the present invention;

FIG. 5 is a circuit diagram of a distributed capacitor non-span filter according to an embodiment of the present invention;

FIG. 6A is a comparison diagram of out-of-band suppression curves in an embodiment of the present invention; FIG.

6B is a comparison diagram of insertion loss curves according to the embodiment of the present invention;

FIG. 7 is a circuit diagram of a distributed capacitor step filter according to an embodiment of the present invention;

8A is a comparison diagram of out-of-band suppression curves of cross-level distributed capacitors according to an embodiment of the present invention;

8B is a comparison diagram of insertion loss curves of cross-level distributed capacitors according to an embodiment of the present invention;

Fig. 9 is a circuit diagram of a filter according to an embodiment of the present invention;

FIG. 10A is a comparison diagram of out-of-band suppression curves according to an embodiment of the present invention; FIG.

10B is a comparison diagram of insertion loss curves according to the embodiment of the present invention;

FIG. 10C is a comparison diagram of roll-off curves in the embodiment of the present invention; FIG.

Fig. 11 is a comparison diagram of electromechanical coupling coefficients of resonators in the filter of the embodiment of the present invention;

Fig. 12 is a schematic structural diagram of a duplexer according to an embodiment of the present invention.

In the picture:

1. Bulk acoustic wave filter; 11. Upper wafer; 12. Lower wafer.

Detailed ways

As shown in FIG. 2, an embodiment of the present invention provides a method for manufacturing a bulk acoustic wave filter, including:

S1: forming multiple parallel resonators on the first surface of the upper wafer; forming multiple series resonators on the first surface of the lower wafer;

S2: Connect the first pin to the circuit of the parallel resonator, connect the second pin to the circuit of the series resonator, and connect the first surface of the upper wafer to the first surface of the lower wafer. The surfaces are arranged in parallel and oppositely, and the first pin and the second pin are bonded to form a multi-stage series-parallel filter circuit and form a distributed capacitor; wherein, the parallel resonator and the distributed capacitor are formed The series resonator has a same-stage relationship, an adjacent-stage relationship or a phase-cross-stage relationship in the multi-stage series-parallel filter circuit.

Wherein, in step S2, preferably, a plurality of the parallel resonators are arranged in a row, and a plurality of the series resonators are arranged in a row; The distributed capacitance is formed between. When arranging the positions of the parallel resonator and the series resonator, the parallel resonator and the series resonator of the same level are preferentially arranged to form a distributed capacitor. The distributed capacitor and the cross-level distributed capacitor (especially the cross-level distributed capacitor) Compared with the above distributed capacitors, it has a lower impact on the performance of the filter.

As shown in Figures 3-12, the embodiment of the present invention also provides a bulk acoustic wave filter. The upper wafer 11 is provided with a plurality of parallel resonators and first pins on the first surface of the upper wafer 11; The first surface of the wafer 12 is provided with a plurality of series resonators and second pins; the upper wafer 11 and the lower wafer 12 are superimposed to form a package structure. Inside the package structure, the first surface of the upper wafer 11 and the lower crystal The first surface of the circle 12 is arranged in parallel and opposing each other. The first pin and the second pin are bonded to form a multi-stage series-parallel filter circuit and form a distributed capacitor; wherein, the parallel resonator forming the distributed capacitor and the series connection Resonators are in the same-level relationship, adjacent-level relationship, or phase-to-one-level relationship in a multi-stage series-parallel filter circuit.

In the embodiment of the present invention, the parallel resonator and the series resonator are thin film bulk acoustic wave resonators, solid-state assembly resonators, or surface acoustic wave resonators.

The upper wafer 11 and the lower wafer 12 form a superimposed structure, in which a distributed capacitance will be generated between the upper electrodes of the parallel resonator and the series resonator. If the distributed capacitance exists in the parallel resonator and series resonator separated by more than 2 levels Between the devices, the BAW filter will deteriorate out-of-band suppression and insertion loss. Therefore, it is necessary to reasonably arrange the positions of the parallel resonator and the series resonator. In the embodiment of the present invention, the requirements for the positions of the parallel resonator and the series resonator are that the parallel resonator and the series resonator that generate distributed capacitance are at least in the same level relationship, adjacent level relationship, or phase-to-level relationship.

Among them, the bulk acoustic wave filter also includes structures such as solder balls, pads, and packaging substrates. Such structures are similar to existing structures and are not improved in this embodiment, so detailed descriptions are omitted.

As shown in FIG. 3, FBAR resonators are fabricated on the upper wafer 11 and the lower wafer 12 at the same time, wherein all series resonators are fabricated on the lower wafer 12 and all parallel resonators are fabricated on the upper wafer 11. The layout design on the two wafers is shown in Figures 4A and 4B, both of which are viewed from the same direction, so the position of the bonding area is also the same. In the figure, P1-P6 are parallel resonators, S1-S6 are series resonators, VIN is the input pin, VOUT is the output pin, VG1 and VG2 are ground pins, because the series resonator is changed to the lower wafer 12, so it can be visually understood as: for the original wafer containing all the resonators of the filter (similar to the layout in Figure 1, the series resonator and the parallel resonator are distributed separately), along the line between the series resonator and the parallel resonator The dividing line between the two wafers is "folded in half" and "broken" into two wafers. The series resonator and the parallel resonator overlap each other. And at this time, the two wafers are arranged with four bonding areas VIN, VG1, VG2, and VOUT. At the same time, a new bonding area is added at the "folding line" position of the "folding in half" (below the view), namely J1, J2, and J3 in the figure. This new bonding area is only used to connect the upper wafer 11 to the lower wafer. The wafers 12 are connected together, and do not need to be connected to the outside of the chip through vias, so their shapes are all different from the bonding areas of the vias, and the area is only one-half. The dotted circle indicates the position of the chip solder ball connected to the nearby wafer via.

Figure 5 is a circuit diagram of an embodiment of the present invention. The upper dashed frame is the circuit in the lower wafer 12, and the lower dashed frame is the circuit in the upper wafer 11. Since the series and parallel resonators are folded and overlapped, Therefore, between the multiple series resonators and the parallel resonators, there are distributed capacitors (shown by the dashed capacitor symbols) formed by the electrodes facing each other; in this embodiment, when the first resonator and the second resonator When the number is different, try to align the series resonators and parallel resonators as much as possible to ensure that the symmetrical arrangement of the resonators is maximized. For example, when the filter includes 5 parallel resonators and 6 series resonators , Then it is necessary to ensure that the 5 parallel resonators and the 5 series resonators are arranged symmetrically; the distributed capacitance formed by the upper electrode of the symmetrical parallel resonator and the upper electrode of the series resonator will not exist between the resonators separated by more than 2 levels. Time, such as between S1 and P3. The "level" here refers to the alignment of the series resonator and the parallel resonator. Refer to Figures 4A and 4B. After the upper wafer 11 and the lower wafer 12 are packaged, the resonator S1 and the resonator P1 are aligned up and down, as Same-level relationship; adjacent resonators of the resonator and the same-level resonator are adjacent-level relationships, such as resonator P1 and resonator S2, resonator S1 and resonator P2, resonator P3 and resonator S4, etc.; resonator The resonator of the same level as the resonator separated by one resonator has a first-order relationship. For example, the resonator P1 and the resonator P3 are separated by a resonator P2, and the resonator S3 is the same level as the resonator P3, then the resonator P1 It straddles the first stage with the resonator S3. In the same way, the resonator S1 and the resonator P3, the resonator P2 and the resonator S4, etc., are also straddling one stage.

As shown in Figures 6A and 6B, the figure shows the comparison of the BAW filter curves with and without distributed capacitors. In the figure, the dashed line is without distributed capacitors, and the solid line is the response curve of the BAW filter with distributed capacitors. It can be seen that the distributed capacitance of this magnitude has almost no effect on the performance of the BAW filter, but the frequency of the roll-off edge on the right side has moved slightly to the inner side by less than 1MHz.

In the embodiment of the present invention, preferably, the distance between the upper electrode of the parallel resonator and the upper electrode of the series resonator is 5um; the capacitance of the distributed capacitor is 0.1pF.

In this embodiment, all/part of the parallel resonators and series resonators are set up with the above-mentioned structure, and the distributed capacitance generated will not have an excessive impact on the performance of the BAW filter. However, if the parallel resonators and series resonators are If the layout of the filter is unreasonable, the distributed capacitor may exist between the resonators of the interval series, as shown in Figure 7. At this time, the distributed capacitor will have a greater impact on the performance of the BAW filter, as shown in the figure. In 8A and 8B, mainly the out-of-band suppression from 925MHz to 960MHz deteriorated by more than 10dB, and the insertion loss on the right side of the passband also deteriorated by 0.1dB.

Due to the technical solution of the embodiment of the present invention, the FBAR resonator, which can only be made on one wafer, can be made on two wafers separately, and finally realizes wafer-level bonding. Compared with the prior art, the size of the filter in the embodiment of the present invention can be significantly reduced. For example, the size of the filter can be reduced from the original 1300um×1000um to 1300um×650um, and the area is reduced from the original 1.3mm ² to 0.845. mm ² . At the same time, because the filter size is reduced, the 1.6mm×1.2mm size duplexer, which was difficult to implement, has also become easier to implement in engineering.

In addition, in order to achieve faster roll-off characteristics, it is generally necessary to reduce the electromechanical coupling coefficient of the resonator in the bulk acoustic wave filter. In the prior art, since the series and parallel resonators are all arranged on the same wafer, the electromechanical coupling coefficient is different. It will be too different. In this embodiment, since the parallel resonator and the series resonator are distributed on the upper and lower wafers, the electromechanical coupling coefficients of the parallel resonator and the parallel resonator can be set to be different. As shown in Figures 9 and 11, the resonant frequency of the series resonator in the circuit diagram is around 896MHz. The resonant frequency of each series resonator can be the same or different, but has almost the same electromechanical coupling coefficient, about 7.5%. The resonant frequency of the parallel resonator is near 858MHz. The resonant frequency of each parallel resonator can be the same or different, but has almost the same electromechanical coupling coefficient, which is about 9.5%. It can be seen that the electromechanical coupling coefficient ratio of the series resonator The electromechanical coupling coefficient of the parallel resonator is at least 2% larger; the types of mass loads are increased, and more resonance frequencies can be realized.

A specific way to achieve different electromechanical coupling coefficients between a parallel resonator and a series resonator is to set the piezoelectric layer of the parallel resonator and the piezoelectric layer of the series resonator as different materials.

As shown in Figure 10A to Figure C, the dotted line in the figure is the performance parameter curve of the existing bulk acoustic wave filter, and the solid line is the performance parameter curve of the bulk acoustic wave filter according to the embodiment of the present invention; it can be seen that the passband insertion loss is not sacrificed. Under the premise of, roll off the right side to the frequency position of 50dB, which is reduced from the original 924MHz by 1.5MHz to 922.5MHz, which greatly improves the roll-off characteristics of the filter.

In another aspect of the embodiment of the present invention, a duplexer is provided, as shown in FIG. 12, which includes two bulk acoustic wave filters 1 described above. Since the volume of the bulk acoustic wave filter 1 is reduced, the volume of the duplexer can also be reduced, and the product can be miniaturized.

The foregoing specific implementations do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that, depending on design requirements and other factors, various modifications, combinations, sub-combinations, and substitutions can occur. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

A method for manufacturing a bulk acoustic wave filter is characterized in that it comprises the following steps:

Forming a plurality of parallel resonators on the first surface of the upper wafer; forming a plurality of series resonators on the first surface of the lower wafer;

Connect the first pin to the circuit of the parallel resonator, and connect the second pin to the circuit of the series resonator to parallel the first surface of the upper wafer and the first surface of the lower wafer Relative arrangement, and bonding the first pin and the second pin to form a multi-stage series-parallel filter circuit, and form a distributed capacitor;

Wherein, the parallel resonator and the series resonator forming the distributed capacitor are in the same-stage relationship, adjacent-stage relationship, or inter-stage relationship in the multi-stage series-parallel filter circuit.
The method of manufacturing a bulk acoustic wave filter according to claim 1, wherein a plurality of the parallel resonators are arranged in a line, and a plurality of the series resonators are arranged in a line;

The distributed capacitance is formed between the parallel resonator and the series resonator in the same order relationship.
A bulk acoustic wave filter is characterized in that it comprises:

An upper wafer, a first surface of the upper wafer is provided with a plurality of parallel resonators and first pins;

A lower wafer, a first surface of the lower wafer is provided with a plurality of series resonators and second pins;

The upper wafer and the lower wafer are superimposed to form a packaging structure. Inside the packaging structure, the first surface of the upper wafer and the first surface of the lower wafer are arranged opposite to each other in parallel. One pin and the second pin are bonded to form a multi-stage series-parallel filter circuit, and form a distributed capacitor;

Wherein, the parallel resonator and the series resonator forming the distributed capacitor are in the same-level relationship, adjacent-level relationship, or phase-to-level relationship in the multi-stage series-parallel filter circuit.
The bulk acoustic wave filter according to claim 3, wherein the parallel resonator and the series resonator are thin film bulk acoustic wave resonators, solid-state assembly resonators, or surface acoustic wave resonators.
The bulk acoustic wave filter according to claim 3, wherein the electromechanical coupling coefficients of the parallel resonator and the series resonator are different.
The bulk acoustic wave filter according to claim 3, wherein the electromechanical coupling coefficient of the series resonator is at least 2% greater than the electromechanical coupling coefficient of the parallel resonator.
The bulk acoustic wave filter according to claim 3, wherein the material of the piezoelectric layer of the parallel resonator is different from the material of the piezoelectric layer of the series resonator.
The bulk acoustic wave filter according to claim 3, wherein the vertical interval between the upper electrode of the parallel resonator and the upper electrode of the series resonator is 5um.
The bulk acoustic wave filter of claim 3, wherein the capacitance of the distributed capacitor is 0.1 pF.
A duplexer, characterized by comprising two bulk acoustic wave filters according to any one of claims 3-9.