CN110739931A

CN110739931A - filters and preparation method thereof

Info

Publication number: CN110739931A
Application number: CN201910831792.XA
Authority: CN
Inventors: 樊永辉; 张惠婷
Original assignee: Shenzhen Huixin Communication Technology Co Ltd
Current assignee: Shenzhen Huixin Communication Technology Co Ltd
Priority date: 2019-09-04
Filing date: 2019-09-04
Publication date: 2020-01-31

Abstract

The invention relates to the technical field of micro-electromechanical systems and semiconductors, in particular to a filter structure and a preparation method thereof. The preparation method of the filter comprises the following steps: forming a substrate; arranging a bulk acoustic wave resonator on the substrate; forming an electrical connection layer on the piezoelectric layer of the bulk acoustic wave resonator; forming a sealing layer on the electric connection layer; forming a cap layer on the sealing layer; and forming a protective layer on the cap layer, and forming a metal connecting wire through hole on the protective layer on the outer side of the sealing layer. The preparation method of the filter can simplify the existing process flow, shorten the preparation time and reduce the production cost at the same time, and the filter prepared by the preparation method has small thickness and light weight.

Description

filters and preparation method thereof

Technical Field

The invention relates to the technical field of micro-electromechanical systems and semiconductors, in particular to filters and a preparation method thereof.

Background

The continuous development of the 5G communication technology puts higher technical requirements on miniaturization, high frequency, high performance, low power consumption, low cost and the like on radio frequency devices. The bulk acoustic wave filter is used as a core device of a radio frequency front end, has the advantages of high working frequency, small insertion loss, high tolerance power, small size and the like, can meet the urgent requirements of radio frequency transceiving front ends of electronic systems such as communication and radar on high-frequency and miniaturized radio frequency filters, and becomes a hot spot of market attention.

The method for manufacturing the bulk acoustic wave filter mainly comprises the three steps of , manufacturing a device wafer, namely, completing the main structure of the filter on the wafer, manufacturing a cap wafer, namely, manufacturing a sealing gasket for forming a cavity and bonding with the device wafer on the second wafer, and bonding the two wafers to form the complete bulk acoustic wave resonator.

The preparation method in the prior art has the disadvantages of multiple process flow steps and long production process, so that the production cost is high, and in the preparation method, the thickness and the weight of a device are large due to the fact that two wafers are bonded at .

Disclosure of Invention

The present invention solves of technical problems of the related art at least at degree for this reason, of the embodiments of the present invention are to provide filters having small thickness and light weight.

A second object of the embodiments of the present invention is to provide a method for manufacturing filters, which can reduce the manufacturing cost while simplifying the existing process flow and shortening the manufacturing time.

It is a third object of an embodiment of the present invention to provide filters fabricated using the fabrication method.

The technical scheme adopted by the embodiment of the invention is as follows:

, the filter is provided and comprises a substrate, a bulk acoustic wave resonator, a sealing layer and a cap layer, wherein the bulk acoustic wave resonator comprises a lower electrode, a piezoelectric layer and an upper electrode, the piezoelectric layer is located between the lower electrode and the upper electrode, the bulk acoustic wave resonator is arranged on the substrate, the electrical connection layer is formed on the piezoelectric layer and is respectively connected with the lower electrode and the upper electrode, the sealing layer is formed on the electrical connection layer, and the cap layer covers the sealing layer and forms an upper cavity with the sealing layer, the electrical connection layer and the bulk acoustic wave resonator.

, a protection layer is also included and covers the cap layer and extends to cover the electric connection layer and the sealing layer.

, further comprising one or more of mass loading for tuning frequency, thin film layers for filter temperature compensation, passivation layers for protecting resonators, and stray wave suppression structures.

, the sealing layer is made of metal, photosensitive dry film, etc.

Further , the cap layer can be made of a photo-sensitive dry film.

, the protective layer is made of benzocyclobutene material.

In a second aspect, a method for manufacturing filters is provided, which includes the steps of forming a substrate, disposing a bulk acoustic wave resonator on the substrate, forming an electrical connection layer on a piezoelectric layer of the bulk acoustic wave resonator, forming a sealing layer on the electrical connection layer, forming a capping layer on the sealing layer, forming a protection layer on the capping layer, and forming a metal wiring via on the protection layer outside the sealing layer.

Further , the protective layer can be formed by photolithography and etching.

In a third aspect, filters are provided, which are made by the above-mentioned method for making a filter.

The embodiment of the invention has the following beneficial effects:

according to the embodiment of the invention, the cap layer is prepared by using the photosensitive dry film, so that the process flow of the filter preparation is simplified, the preparation time is shortened, the production cost is reduced, the technical problems of large thickness and large weight of a filter device in the prior art are solved, and the filter with small thickness and light weight is realized.

Drawings

FIG. 1 is a schematic diagram of the structure of a BAW filter according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of another embodiment of the BAW filter according to the present invention;

FIG. 3 is a schematic diagram of the structure of a BAW-SMR filter according to an embodiment of the present invention;

FIGS. 4(a) - (e) are schematic diagrams of a sealing layer preparation process according to an embodiment of the present invention;

FIGS. 5(a) - (c) are schematic diagrams illustrating a capping layer fabrication flow according to an embodiment of the present invention;

FIGS. 6(a) - (c) are schematic diagrams illustrating the preparation process of the protective layer according to the embodiment of the present invention.

Detailed Description

This section will describe in detail embodiments of the present invention, which are illustrated in the accompanying drawings, the purpose of which is to supplement the description of the text of the description with figures so that each technical feature and the whole technical solution of the embodiments of the present invention can be intuitively and visually understood, but it should not be construed as limiting the scope of the present invention.

In the description of the present invention, if an orientation description is referred to, for example, "upper", "lower", "front", "rear", "left", "right", etc., indicating an orientation or positional relationship based on that shown in the drawings, it is merely for convenience of description and simplicity of description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus is not to be construed as limiting the present invention, if a certain feature is referred to as "set", "fixed", or "connected" to another features, it may be directly set, fixed, connected to another features, or indirectly set, fixed, connected to another features.

In the description of the embodiments of the present invention, if "several" is referred to, it means or more, if "plural" is referred to, it means two or more, if "more than", "less than" or "more than" is referred to, it is understood that the number is not included, if "more than", "less than" or "more than" is referred to, it is understood that the number is included, if "" or "second" is referred to, it is understood that the numbers are used for distinguishing the technical features, and it is not understood that the numbers indicate or imply relative importance or implicitly indicate the number of the indicated technical features or implicitly indicate the precedence of the indicated technical features.

In addition, unless defined otherwise, technical and scientific terms used in the embodiments of the present invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

Embodiment 1 provides kinds of BAW filters, and referring to fig. 1, fig. 1 shows a BAW filter structure including a substrate 100, bulk acoustic wave resonators (210, 220, 230), an electrical connection layer 300, a sealing layer 400, a cap layer 500, and a shield layer 600.

In this embodiment, the substrate 100 may be made of Si or SiC, the substrate has a lower cavity 110, the lower cavity 110 is disposed on the upper surface of the substrate, a bulk acoustic wave resonator (210, 220, 230) is disposed on the lower cavity, the bulk acoustic wave resonator includes a lower electrode 210, a piezoelectric layer 220 and an upper electrode 230, and the piezoelectric layer 220 is located between the lower electrode 210 and the upper electrode 230.

The electrical connection layer 300 formed on the piezoelectric layer 220 includes a metal wire, both ends of which are connected to the lower electrode 210 and the upper electrode 230, respectively, to achieve electrical connection, in the present embodiment, the sealing layer 400 formed on the electrical connection layer 300 may be made of metal materials such as gold, copper, aluminum, etc., in the present embodiment, the sealing layer is made of gold, the capping layer 500 made of a photosensitive dry film covers the sealing layer 400, and forms an upper cavity 510 together with the sealing layer 400, the electrical connection layer 300, and the bulk acoustic wave resonator, the photosensitive dry film is a polymer compound, which can generate a polymerization reaction after being irradiated by ultraviolet rays, forming stable substances to be attached to the surface, thereby achieving the function of blocking plating and etching, the photosensitive dry film is composed of three layers, the th layer is a supporting layer, the middle layer is a photosensitive layer, the third layer is a protective layer or a polyethylene film, the supporting layer and the protective layer are removed before lamination and development, the middle layer is used as the capping layer, the capping layer having a predetermined viscosity and a good photosensitive layer, the thickness of 0.8mil (20), 1.2 mil) and the protective layer (600) is preferably used for covering the upper protection layer 600 and the upper protection layer, and the upper layer is used for providing different thicknesses of the protective layer, and the protective layer for the filter 600, and the protective layer, and the filter, which is selected for the filter, and.

Example 2

Embodiment 2 provides another BAW filters, and referring to fig. 2, fig. 2 shows another BAW filter structures, which include not only the substrate 100, the bulk acoustic wave resonators (210, 220, 230), the electrical connection layer 300, the sealing layer 400, the cap layer 500, and the protective layer 600 in embodiment 1, but also the mass load 240 for adjusting the frequency, the thin film layer 250 for filter temperature compensation, the passivation layer 260 for protecting the resonators, and the stray wave suppression structure 270.

Here, the difference from embodiment 1 is that the sealing layer 400 of the BAW filter in this embodiment is made of a photosensitive dry film.

The mass load 240 is used to adjust the frequency of the mass load, i.e., the frequency of the bulk acoustic wave resonators (210, 220, 230) is fine tuned by placing loads on the upper electrode 230 to meet the design requirements of the filter, the mass load is typically metal.

The filter temperature compensation thin film layer 250 disposed on the surface of the upper electrode 230 is typically a silicon oxide material, so that the filter frequency can be kept stable over a wide temperature range.

The passivation layer 260 for protecting the resonators, which is provided on the bulk acoustic wave resonators (210, 220, 230), the mass load 240, and the upper surface of the thin film layer 250, is typically a silicon nitride material, and can protect the resonators to improve the reliability of the device.

The stray wave suppressing structure 270 is formed by providing structures at the edge of the bulk acoustic wave resonator, for example, etching sized holes, so as to achieve the purposes of suppressing stray waves and reducing energy loss.

Example 3

Example 3 kinds of BAW-SMR filters are provided, and referring to fig. 3, fig. 3 shows a schematic structural view of the BAW-SMR filter structure of the present invention includes a substrate 100, a bragg reflector 800, bulk acoustic wave resonators (210, 220, 230), an electrical connection layer 300, a sealing layer 400, a cap layer 500, and an overcoat layer 600.

In particular, the substrate 100 may be made of the material Si or SiC, which in the embodiment depicted in fig. 3 does not have a lower cavity. The bragg reflector 800 alternately composed of two materials having different acoustic wave impedances is disposed on the substrate 100, and the bragg reflector 800 can effectively reduce the acoustic wave propagating to the substrate. The bragg reflector 800 is provided with a bulk acoustic wave resonator (210, 220, 230), the bulk acoustic wave resonator (210, 220, 230) comprises a lower electrode 210, a piezoelectric layer 220 and an upper electrode 230, and the piezoelectric layer 220 is located between the lower electrode 210 and the upper electrode 230. The electrical connection layer 300 formed on the piezoelectric layer includes metal wires, and two ends of the metal wires are respectively used for electrically connecting the lower electrode and the upper electrode. In the present embodiment, the sealing layer 400 formed on the electrical connection layer 300 is made of a photosensitive dry film material. A cap layer 500 made of a photosensitive dry film covers the sealing layer, and forms an upper cavity 510 together with the sealing layer 400, the electrical connection layer 300, and the bulk acoustic wave resonator. The protective layer 600 covers the cap layer and extends to cover the electrical connection layer 300 and the sealing layer 400, so as to reinforce the cap layer and better protect the bulk acoustic wave resonator.

Example 4

The invention also provides a preparation method of filters, which comprises the following specific preparation steps of forming a substrate 100, arranging bulk acoustic wave resonators (210, 220 and 230) on the substrate, forming an electric connection layer 300 on a piezoelectric layer 220 of the bulk acoustic wave resonators, forming a sealing layer 400 on the electric connection layer 300, forming a cap layer 500 on the sealing layer 400, forming an upper cavity 510 by the cap layer 500, the electric connection layer 300, the sealing layer 400 and the bulk acoustic wave resonators (210, 220 and 230), forming a protective layer 600 on the cap layer 500, and forming a metal connecting through hole 310 on the protective layer 600 outside the sealing layer.

Fig. 4(a) - (e) are schematic diagrams of the fabrication process of the sealing layer in another embodiment , copper metal is used to fabricate the sealing layer of BAW filter, and the fabrication process includes glue coating, mask alignment, exposure, development, metal deposition, photoresist stripping, and cleaning.

Fig. 4(a) shows a glue application step, i.e., a uniform glue application on the surfaces of the electrical connection layer and the bulk acoustic wave resonator.

Fig. 4(b) shows the mask calibration and exposure steps, i.e. mask calibration is performed before exposure, preparation of the sealing layer is achieved by shielding the mask at the preset sealing layer position, and exposure is performed after mask calibration.

Fig. 4(c) shows a developing step.

Fig. 4(d) shows a metal deposition step, i.e. forming a metal layer on the device surface by metal deposition, wherein the electrical connection layer surface is masked and positioned as a sealing layer.

Fig. 4(e) shows a photoresist stripping step, i.e. cleaning to remove material outside the sealing layer.

Fig. 5(a) - (c) are schematic diagrams of a cap layer preparation process in , the photosensitive dry film is used to fabricate the cap layer of the BAW filter, and the preparation process specifically includes film pasting, mask alignment, exposure, dry film removal, and cleaning.

FIG. 5(a) shows the step of laminating films, i.e. laying layers of photosensitive dry films on the sealing layer. specifically, the laminating device can adopt a manual laminating machine or an automatic laminating machine, and the laminating process is optimized according to the following process parameters, namely preheating temperature and time, pressing temperature, rolling temperature, laminating pressure, laminating speed, pressing time and the like.

Fig. 5(b) shows the reticle alignment and exposure step. Specifically, after the film is attached, the mask 700 is aligned, and after the alignment, exposure is prepared. If the dry film before exposure is different from room temperature, the dry film is allowed to stand for about 15-30 minutes and cooled to room temperature. The specific exposure technological parameters are adjusted and optimized according to different types of dry film materials.

Fig. 5(c) shows the development and cleaning steps, i.e. dry film development and cleaning is performed to remove the unexposed dry film, it is left for minutes before development, about 15-30 minutes, the developing solvent and the development parameters such as temperature, pressure, concentration, time, etc. are adjusted according to the dry film type, after cleaning, the remaining dry film forms a cap layer, and forms an upper cavity with the electrical connection layer, the sealing layer, and the bulk acoustic wave resonator.

Fig. 6(a) - (c) are schematic diagrams of a protective layer preparation process, in an embodiment, a benzocyclobutene (BCB) material is used for preparing the protective layer 600, the BCB material is a new active resin monomer of group, can form a thermoplastic polymer and a thermosetting polymer, has excellent electrical insulation performance, and has general application in the field of electronics high technology, and a preparation process flow of the BCB protective layer specifically comprises BCB gluing, calibration, exposure, development, cleaning and curing.

FIG. 6(a) shows the BCB gumming step, i.e., the uniform application of BCB material on the outer surface of the cap layer.

Fig. 6(b) shows a mask alignment and exposure step, i.e., the mask 700 alignment is performed before the BCB material exposure, the metal lead through hole is prepared by shielding the mask at the preset metal lead through hole position, and the exposure is performed after the mask alignment.

Fig. 6(c) shows a develop and clean step, i.e., developing and cleaning is performed to remove the unexposed BCB material, forming metal link via 310.

In yet another embodiment of the present invention, the BCB protective layer is fabricated by a photolithography plus etching method, and the specific fabrication process flow includes BCB coating, photoresist coating, calibration, exposure, photoresist development, BCB etching, photoresist removal, and BCB curing, wherein the BCB etching is used for etching a metal wiring via.

Example 5

This example is a filter prepared using the filter preparation method described above.

The thickness of the cap layer made of the photosensitive dry film is only 20-50 um, while the thickness of the traditional cap wafer is 100-200 um, so that the thickness of the device is smaller, the weight of the device can be reduced by about 30-40%, and meanwhile, the filter structure can be strengthened by using a BCB material to prepare the protective layer of the filter, so that the internal structure of the device can be better protected.

The embodiments of the present invention have been described in detail, but the present invention is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and such equivalent modifications or substitutions are included in the scope of the present invention defined by the claims. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

Claims

A filter of the type , comprising:

a substrate;

the bulk acoustic wave resonator comprises a lower electrode, a piezoelectric layer and an upper electrode; the piezoelectric layer is positioned between the lower electrode and the upper electrode; the bulk acoustic wave resonator is arranged on the substrate; the electric connection layer is formed on the piezoelectric layer and is respectively connected with the lower electrode and the upper electrode;

a sealing layer formed on the electrical connection layer;

and the cover cap layer covers the sealing layer and forms an upper cavity together with the sealing layer, the electric connection layer and the bulk acoustic wave resonator.
2. The filter of claim 1, further comprising a protective layer overlying the capping layer and extending over the electrical connection layer and the sealing layer.
3. The filter of claim 1 or 2, comprising one or more of a mass load for adjusting frequency, a thin film layer for filter temperature compensation, a passivation layer for protecting resonators, and a stray wave suppression structure.
4. A filter according to claim 1 or 2, wherein the sealing layer is made of metal or a photo-sensitive dry film.
5. The filter according to claim 1 or 2, characterized in that the cap layer is made of a photosensitive dry film.
6. The filter of claim 2, wherein the guard layer is made of benzocyclobutene material.
The preparation method of the 7 and filters is characterized by comprising the following steps:

forming a substrate;

arranging a bulk acoustic wave resonator on the substrate;

forming an electrical connection layer on the piezoelectric layer of the bulk acoustic wave resonator;

forming a sealing layer on the electric connection layer;

forming a cap layer on the sealing layer;

and forming a protective layer on the cap layer, and forming a metal connecting wire through hole on the protective layer on the outer side of the sealing layer.
8. The method for manufacturing a filter according to claim 7, wherein the protective layer is formed by photolithography and etching.
A filter of , wherein the filter is made by the method of claim 7 or 8.