Method for manufacturing surface acoustic wave filter and surface acoustic wave filter

Abstract

An embodiment of the present invention provides a manufacturing method of a surface acoustic wave filter and a surface acoustic wave filter. The manufacturing method includes the following steps: S1. Obtain a first cavity and a second cavity, and form a first substrate on the first cavity and a second substrate on the second cavity; S2. Grow an insulating layer on a side of the first bus bar away from the first substrate, and the insulating layer is located at the periphery of the first substrate; S3. Form a through hole communicating with the first bus bar on the insulating layer; S4. Fill the through hole with a conductive material by an electroplating process and extend the conductive material to cover a side of the insulating layer away from the first substrate, and the conductive material is electrically connected to the first bus bar; S5. Stack the second bus bar of the second resonant unit on the conductive material so that the first resonant unit and the second resonant unit are bonded to obtain a surface acoustic wave filter. The surface acoustic wave filter of the present invention is convenient to package, the area of the whole device is small, and the voltage withstand mode performance is good.

Description

Technical Field

[0001] The present invention is applicable to the field of wireless communication technologies, and particularly relates to a manufacturing method of a surface acoustic wave filter and a surface acoustic wave filter. Background Art

[0002] A radio frequency filter is an important component of a radio frequency module. Traditional radio frequency filters often adopt the principle of elastic waves and use mechanical resonance for filtering. Traditional mechanical waves include surface acoustic wave (SAW) or bulk acoustic wave (BAW). Currently, a new resonator form, the laterally excited bulk acoustic wave resonator, has received extensive attention. It relies on laterally excited bulk acoustic waves for filtering, and can achieve an electromechanical coupling coefficient of more than 20% and a frequency above 3 GHz, making it possible to manufacture high-roll-off N77 and N79 band filters.

[0003] The laterally excited bulk acoustic wave resonator uses an ultra-thin single-crystal piezoelectric material. By covering interdigital electrodes, bulk acoustic waves in the film are excited, thereby forming a resonance curve with an ultra-high electromechanical coupling coefficient. Different from the surface acoustic wave filter that also uses interdigital electrodes, its resonance frequency is generally not determined by the width or spacing of the interdigital electrodes, but by the thickness of the piezoelectric material.

[0004] In the prior art, the packaging method of the laterally excited bulk acoustic wave filter generally is to first fabricate laterally excited bulk acoustic wave resonators cascaded with each other on a whole piece of piezoelectric material, and then, through flip-chip or face-up mounting, form a cover plate made of an organic material or an organic circuit board above the cascaded laterally excited bulk acoustic wave resonators to complete the entire packaging.

[0005] However, although the above traditional packaging method has a relatively simple process, the resonance frequency of the laterally excited bulk acoustic wave resonator is determined by the thickness of the piezoelectric material due to its special excitation method. Therefore, in a set of cascaded structures, resonators with different thicknesses usually need to be connected together by wire bonding or other means and then covered with a cover plate for packaging. This increases the complexity of the process and also increases the area of the entire device. Summary of the Invention

[0006] Embodiments of the present invention provide a manufacturing method of a surface acoustic wave filter and a surface acoustic wave filter, aiming to solve the problems of troublesome packaging, increased area of the entire device, and poor compressive performance of the laterally excited bulk acoustic wave filter in the prior art.

[0007] In a first aspect, embodiments of the present invention provide a manufacturing method of a surface acoustic wave filter, and the manufacturing method includes the following steps:

[0008] S1. Obtain a first resonant unit and a second resonant unit. The first resonant unit includes a first substrate provided with a plurality of first laterally excited thin film bulk acoustic wave resonators, a first insulating wall supported and fixed on the first substrate, a first bus bar supported and fixed on the first insulating wall and spaced from the first substrate to enclose a first cavity, and a first electrode formed on a side of the first bus bar away from the first substrate. A positive projection of the first electrode onto the first cavity is completely located within the first cavity. The second resonant unit includes a second substrate provided with a plurality of second laterally excited thin film bulk acoustic wave resonators, a second insulating wall supported and fixed on the second substrate, a second bus bar supported and fixed on the second insulating wall and spaced from the second substrate to enclose a second cavity, and a second electrode formed on a side of the second bus bar away from the second substrate. A positive projection of the second electrode onto the second cavity is completely located within the second cavity.

[0009] S2. Grow an insulating layer on a side of the first bus bar away from the first substrate. The insulating layer is located at a periphery of the first substrate.

[0010] S3. Form a through hole communicating with the first bus bar on the insulating layer.

[0011] S4. Fill the through hole with a conductive material by an electroplating process and extend the conductive material to cover a side of the insulating layer away from the first substrate. The conductive material is electrically connected to the first bus bar.

[0012] S5. Stack the second bus bar of the second resonant unit on the conductive material so that the first resonant unit and the second resonant unit are bonded to obtain the surface acoustic wave filter.

[0013] Preferably, the plurality of first laterally excited thin film bulk acoustic wave resonators are connected in series or in parallel, and the plurality of second laterally excited thin film bulk acoustic wave resonators are connected in the other connection mode of series or parallel.

[0014] Preferably, the plurality of first laterally excited thin film bulk acoustic wave resonators are connected in series in sequence. One end of each second laterally excited thin film bulk acoustic wave resonator is connected between two adjacent first laterally excited thin film bulk acoustic wave resonators, and the other end is grounded.

[0015] Preferably, in step S3, the through hole is formed by an etching process.

[0016] Preferably, in S5, the first substrate and the second substrate are spaced apart and disposed opposite to each other.

[0017] Preferably, the insulating layer is made of a silicon dioxide material.

[0018] Preferably, both the first substrate and the second substrate are made of piezoelectric materials.

[0019] Preferably, the piezoelectric material is any one of lithium niobate, lithium tantalate, piezoelectric ceramics, and piezoelectric quartz.

[0020] In a second aspect, an embodiment of the present invention provides a surface acoustic wave filter, including two mutually stacked first resonant units and second resonant units. The first resonant unit includes a first substrate provided with a plurality of first laterally excited thin film bulk acoustic wave resonators, a first insulating wall supported and fixed on the first substrate, a first bus bar supported and fixed on the first insulating wall and spaced from the first substrate to form a first cavity, and a first electrode formed on a side of the first bus bar away from the first substrate. A positive projection of the first electrode on the first cavity is completely located within the first cavity. The second resonant unit includes a second substrate provided with a plurality of second laterally excited thin film bulk acoustic wave resonators, a second insulating wall supported and fixed on the second substrate, a second bus bar supported and fixed on the second insulating wall and spaced from the second substrate to form a second cavity, and a second electrode formed on a side of the second bus bar away from the second substrate. A positive projection of the second electrode on the second cavity is completely located within the second cavity.

[0021] An insulating layer is fixedly provided on the first bus bar, and the insulating layer is located at the periphery of the first substrate.

[0022] Through holes are formed through the insulating layer, and the through holes are respectively communicated with the first bus bar and the second bus bar.

[0023] The through holes are filled with a conductive layer.

[0024] The surface acoustic wave filter is made by the manufacturing method of the surface acoustic wave filter according to any one of claims 1-8.

[0025] Preferably, the conductive layer includes a first conductive layer and a second conductive layer extending from a direction of the first conductive layer away from the first substrate. The first conductive layer is fixed within the through hole, and the second conductive layer completely covers a surface of the insulating wall away from the first substrate.

[0026] The beneficial effects achieved by the present invention are as follows. Since two substrates with different thicknesses and including laterally excited thin film bulk acoustic wave resonators are used and stacked on each other to complete the entire package. Using this method, one resonator unit serves as the substrate and the other resonator unit serves as the cover plate, making the package cover plate also a functional setting and belonging to a part of the acoustic wave filter, thereby reducing the area of the entire device. At the same time, the piezoelectric substrate used to fabricate the laterally excited thin film bulk acoustic wave filter has high mechanical compressive resistance, providing good protection for the entire filter and improving the die pressing resistance during the subsequent packaging process of the RF module. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flowchart of the steps of a manufacturing method of a surface acoustic wave filter provided by an embodiment of the present invention;

[0028] Figure 2 is a process schematic diagram of a single cavity of a surface acoustic wave filter provided by an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of the cavity structure of a surface acoustic wave filter provided by an embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of the structure of a surface acoustic wave filter provided by an embodiment of the present invention.

[0031] In the figure, 100 is a surface acoustic wave filter, 1 is a first resonator unit, 11 is a first substrate, 12 is a first insulating wall, 13 is a first bus bar, 14 is a first electrode, 15 is a first cavity, 2 is a second resonator unit, 21 is a second substrate, 22 is a second insulating wall, 23 is a second bus bar, 24 is a second electrode, 25 is a second cavity, 3 is an insulating layer, 31 is a through hole, 4 is a conductive layer, 41 is a first conductive layer, and 42 is a second conductive layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to 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 used to limit the present invention.

[0033] Please refer to Figures 1 - 4 , an embodiment of the present invention provides a manufacturing method of a surface acoustic wave filter, and the manufacturing method includes the following steps:

[0034] S1. Obtain a first resonant unit 1 and a second resonant unit 2; the first resonant unit 1 includes a first substrate 11 provided with a plurality of first laterally excited thin film bulk acoustic wave resonators, a first insulating wall 12 supported and fixed on the first substrate 11, a first bus bar 13 supported and fixed on the first insulating wall 12 and spaced from the first substrate 11 to enclose a first cavity 15, and a first electrode 14 formed on a side of the first bus bar 13 away from the first substrate 11, and a positive projection of the first electrode 14 onto the first cavity 15 is completely located within the first cavity 15; the second resonant unit 2 includes a second substrate 21 provided with a plurality of second laterally excited thin film bulk acoustic wave resonators, a second insulating wall 22 supported and fixed on the second substrate 21, a second bus bar 23 supported and fixed on the second insulating wall 22 and spaced from the second substrate 21 to enclose a second cavity 25, and a second electrode 24 formed on a side of the second bus bar 23 away from the second substrate 21, and a positive projection of the second electrode 24 onto the second cavity 25 is completely located within the second cavity 25;

[0035] S2. Grow an insulating layer 3 on a side of the first bus bar 13 away from the first substrate 11, and the insulating layer 3 is located at a periphery of the first substrate 11;

[0036] S3. Form a through hole 31 communicating with the first bus bar 13 on the insulating layer 3;

[0037] S4. Fill the through hole 31 with a conductive material by an electroplating process and extend and cover a side of the insulating layer 3 away from the first substrate 11 with the conductive material, and the conductive material is electrically connected to the first bus bar 13; after the conductive material is filled, a conductive layer 4 is formed for electrically connecting the first bus bar and the second bus bar to each other.

[0038] S5. Stack the second bus bar 23 of the second resonant unit 2 on the conductive material so that the first resonant unit 1 and the second resonant unit 2 are bonded to obtain the surface acoustic wave filter.

[0039] Preferably, the thicknesses of the first substrate 11 and the second substrate 21 can be the same or different, effectively saving the device area.

[0040] Wherein, the through hole 31 is filled with the conductive material in sequence by the electroplating process, and the surface of the insulating wall 3 away from the first substrate 11 is continuously electroplated so that the surface of the first substrate 11 is covered with a layer of electroplated layer, facilitating conduction with the bus bar 5 of the first substrate 11.

[0041] Among them, since the through holes 31 and the insulating walls 3 are plated with plating layers, the second substrate 21 of the second resonant unit 22 is bonded to the first substrate 11 of the first resonant unit 11, so that the side of the plating layer away from the first substrate 11 is fixed to the second substrate 21, thereby realizing the conduction of the bus bar 5 between the first substrate 11 and the second substrate 21, and forming a complete packaging of the surface acoustic wave filter 100.

[0042] In some alternative embodiments, bonding the first substrate 11 of the first resonant unit 11 to the second substrate 21 of the second resonant unit 22, the assembled finished product is the same, and the resulting effects are also the same.

[0043] Specifically, through the above steps S1-S5, since two substrates with different thicknesses and including laterally excited thin film bulk acoustic wave resonators are used and stacked on each other to complete the entire packaging. Using this method, the packaging cover plate is also functional and belongs to a part of the acoustic wave filter, thereby reducing the area of the entire device. At the same time, the piezoelectric substrate used to manufacture the laterally excited thin film bulk acoustic wave filter has high mechanical compressive resistance, providing good protection for the entire filter and enhancing the mold pressing resistance during the subsequent packaging process of the RF module.

[0044] In this embodiment, multiple first laterally excited thin film bulk acoustic wave resonators are connected in one of the series or parallel connection methods, and multiple second laterally excited thin film bulk acoustic wave resonators are connected in the other of the series or parallel connection methods.

[0045] In this embodiment, multiple first laterally excited thin film bulk acoustic wave resonators are connected in series in sequence, and one end of each second laterally excited thin film bulk acoustic wave resonator is connected between two adjacent first laterally excited thin film bulk acoustic wave resonators, and the other end is grounded.

[0046] Among them, the surface acoustic wave filter 100 is composed of multiple resonators (1-6) connected in cascade. The first laterally excited thin film bulk acoustic wave resonators include resonators 1, 2, and 3. Resonators 1, 2, and 3 are series resonators, and their resonant frequencies are similar. The second laterally excited thin film bulk acoustic wave resonators include a parallel resonator composed of 4, 5, and 6. Their resonant frequencies are generally similar and higher than those of resonators 1, 2, and 3. During manufacturing, 1, 2, and 3 can be manufactured through the first substrate 11, and 4, 5, and 6 can be manufactured through the second substrate 21. Installing resonators with different characteristics according to a certain circuit design and cascading them as described in Figure 4 can form the structure of the complete surface acoustic wave filter 100. It should be noted that Figure 4 the connection method described above is only an example of the embodiments of the present invention and is not used to limit the specific structure of the surface acoustic wave filter 100 of the present invention.

[0047] In this embodiment, in step S3, the through hole 31 is formed by an etching process.

[0048] In this embodiment, in S5, the first substrate 11 and the second substrate 21 are arranged at intervals and face each other. It is convenient to manufacture and the overall appearance is beautiful.

[0049] In this embodiment, the insulating layer 3 is made of a silicon dioxide material.

[0050] In this embodiment, both the first substrate 11 and the second substrate 21 are made of a piezoelectric material.

[0051] In this embodiment, the piezoelectric material is any one of lithium niobate, lithium tantalate, piezoelectric ceramics, and piezoelectric quartz.

[0052] An embodiment of the present invention provides a surface acoustic wave filter 100, which includes two mutually stacked first resonance units 1 and second resonance units 2; the first resonance unit 1 includes a first substrate 11 provided with a plurality of first laterally excited thin film bulk acoustic wave resonators, a first insulating wall 12 supported and fixed on the first substrate 11, a first bus bar 13 supported and fixed on the first insulating wall 12 and spaced from the first substrate 11 to enclose a first cavity 15, and a first electrode 14 formed on a side of the first bus bar 13 away from the first substrate 11, and a positive projection of the first electrode 14 onto the first cavity 15 is completely located within the first cavity 15; the second resonance unit 2 includes a second substrate 21 provided with a plurality of second laterally excited thin film bulk acoustic wave resonators, a second insulating wall 22 supported and fixed on the second substrate 21, a second bus bar 23 supported and fixed on the second insulating wall 22 and spaced from the second substrate 21 to enclose a second cavity 25, and a second electrode 24 formed on a side of the second bus bar 23 away from the second substrate 21, and a positive projection of the second electrode 24 onto the second cavity 25 is completely located within the second cavity 25;

[0053] An insulating layer 3 is fixedly provided on the first bus bar 13, and the insulating layer 3 is located at the periphery of the first substrate 11;

[0054] A through hole 31 is formed through the insulating layer 3, and the through hole 31 communicates with the first bus bar 13 and the second bus bar 23 respectively;

[0055] The through hole 31 is filled with a conductive layer 4;

[0056] The surface acoustic wave filter 100 is made by the manufacturing method of the above-mentioned surface acoustic wave filter 100.

[0057] Specifically, since two substrates with different thicknesses and including laterally excited thin film bulk acoustic wave resonators are stacked on top of each other to complete the entire package. Using this method, the package cover plate is also functional and belongs to a part of the acoustic wave filter, thereby reducing the area of the entire device. At the same time, the piezoelectric substrate used to fabricate the laterally excited thin film bulk acoustic wave filter has high mechanical compressive resistance, providing good protection for the entire filter and improving the resistance to molding during the subsequent packaging process of the RF module.

[0058] In this embodiment, the conductive layer 4 includes a first conductive layer 41 and a second conductive layer 42 extending from the first conductive layer 41 in a direction away from the substrate. The first conductive layer 41 is fixed within the through hole 31, and the second conductive layer 42 completely covers the surface of the insulating wall 3 away from the substrate.

[0059] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. What is disclosed is only the preferred embodiments of the present invention. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can make many equivalent changes in form without departing from the spirit and scope of the present invention as protected by the claims, and all of them fall within the protection scope of the present invention.

Claims

1. A manufacturing method of a surface acoustic wave filter, characterized in that The manufacturing method includes the following steps: S1. Obtain a first resonator unit and a second resonator unit. The first resonator unit includes a first substrate provided with a plurality of first laterally excited thin film bulk acoustic wave resonators, a first insulating wall supported and fixed on the first substrate, a first bus bar supported and fixed on the first insulating wall and spaced from the first substrate to enclose a first cavity, and a first electrode formed on a side of the first bus bar away from the first substrate. A positive projection of the first electrode onto the first cavity is completely located within the first cavity. The second resonator unit includes a second substrate provided with a plurality of second laterally excited thin film bulk acoustic wave resonators, a second insulating wall supported and fixed on the second substrate, a second bus bar supported and fixed on the second insulating wall and spaced from the second substrate to enclose a second cavity, and a second electrode formed on a side of the second bus bar away from the second substrate. A positive projection of the second electrode onto the second cavity is completely located within the second cavity. S2. Grow an insulating layer on a side of the first bus bar away from the first substrate. The insulating layer is located at a periphery of the first substrate. S3. Form a through hole communicating with the first bus bar on the insulating layer. S4. Fill the through hole with a conductive material by an electroplating process and extend and cover a side of the insulating layer away from the first substrate with the conductive material. The conductive material is electrically connected to the first bus bar. S5. Stack the second bus bar of the second resonator unit on the conductive material so that the first resonator unit and the second resonator unit are bonded to obtain the surface acoustic wave filter.

2. The manufacturing method of the surface acoustic wave filter according to claim 1, characterized in that, The plurality of first laterally excited thin film bulk acoustic wave resonators are connected in one of series or parallel connection modes, and the plurality of second laterally excited thin film bulk acoustic wave resonators are connected in the other of series or parallel connection modes.

3. The manufacturing method of the surface acoustic wave filter according to claim 2, characterized in that, The plurality of first laterally excited thin film bulk acoustic wave resonators are connected in series in sequence. One end of each second laterally excited thin film bulk acoustic wave resonator is connected between two adjacent first laterally excited thin film bulk acoustic wave resonators, and the other end is grounded.

4. The manufacturing method of the surface acoustic wave filter according to claim 1, characterized in that, In the step S3, the through hole is formed by an etching process.

5. The manufacturing method of the surface acoustic wave filter according to claim 1, characterized in that, In S5, the first substrate and the second substrate are spaced apart and disposed opposite to each other.

6. The manufacturing method of the surface acoustic wave filter according to claim 1, characterized in that, The insulating layer is made of a silicon dioxide material.

7. The manufacturing method of the surface acoustic wave filter according to claim 1, characterized in that, Both the first substrate and the second substrate are made of a piezoelectric material.

8. The manufacturing method of the surface acoustic wave filter according to claim 7, characterized in that, The piezoelectric material is any one of lithium niobate, lithium tantalate, piezoelectric ceramics, and piezoelectric quartz.

9. A surface acoustic wave filter, characterized in that, It includes a first resonant unit and a second resonant unit which are stacked on each other. The first resonant unit includes a first substrate provided with a plurality of first laterally excited thin film bulk acoustic wave resonators, a first insulating wall supported and fixed on the first substrate, a first bus bar supported and fixed on the first insulating wall and spaced from the first substrate to enclose a first cavity, and a first electrode formed on a side of the first bus bar away from the first substrate. A positive projection of the first electrode onto the first cavity is completely located within the first cavity. The second resonant unit includes a second substrate provided with a plurality of second laterally excited thin film bulk acoustic wave resonators, a second insulating wall supported and fixed on the second substrate, a second bus bar supported and fixed on the second insulating wall and spaced from the second substrate to enclose a second cavity, and a second electrode formed on a side of the second bus bar away from the second substrate. A positive projection of the second electrode onto the second cavity is completely located within the second cavity. An insulating layer is fixedly provided on the first bus bar, and the insulating layer is located at a periphery of the first substrate. Through holes are formed through the insulating layer, and the through holes are respectively communicated with the first bus bar and the second bus bar. The through holes are filled with a conductive layer. The surface acoustic wave filter is made by the manufacturing method of the surface acoustic wave filter according to any one of claims 1-8.

10. The surface acoustic wave filter according to claim 9, wherein The conductive layer includes a first conductive layer and a second conductive layer extending from a direction of the first conductive layer away from the first substrate. The first conductive layer is fixed within the through holes, and the second conductive layer completely covers a surface of the insulating wall away from the first substrate.

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